Mechanistic insights into the protective impact of zinc on sepsis - Cytokines and grow factors 2017 (1)

Prévia do material em texto

Contents lists available at ScienceDirect
Cytokine and Growth Factor Reviews
journal homepage: www.elsevier.com/locate/cytogfr
Mechanistic insights into the protective impact of zinc on sepsis
Jolien Souffriaua,b, Claude Liberta,b,⁎
a Center for Inflammation Research, VIB, Ghent, Belgium
bDepartment of Biomedical Molecular Biology, Ghent University, Ghent, Belgium
A R T I C L E I N F O
Keywords:
Sepsis
Cytokines
Immunity
Microbiome
Therapy
A B S T R A C T
Sepsis, a systemic inflammation as a response to a bacterial infection, is a huge unmet medical need. Data
accumulated over the last decade suggest that the nutritional status of patients as well as composition of their gut
microbiome, are strongly linked with the risk to develop sepsis, the severity of the disease and prognosis. In
particular, the essential micronutrient zinc is essential in the resistance against sepsis and has shown to be
protective in animal models as well as in human patients. The potential mechanisms by which zinc protects in
sepsis are discussed in this review paper: we will focus on the inflammatory response, chemotaxis, phagocytosis,
immune response, oxidative stress and modulation of the microbiome. A full understanding of the mechanism of
action of zinc may open new preventive and therapeutic interventions in sepsis.
1. General introduction and basic aspects of the physiology of zinc
Most living organisms on Earth need zinc to sustain growth and
differentiation and to maintain homeostasis. Zinc is an essential trace
ion needed for the proper function of numerous proteins and pathways
[1]. After iron, Zn is the most abundant trace element in the human
body. Mammals have to retrieve Zn from the food on a regular basis,
since they have no significant Zn storage capacity [2]. Based on the
unequal amounts of zinc in the soil and the unequal availabilities of
different food components (such as red meat) in the world and the
changing feeding behaviors in human populations, the Zn amounts in
blood and tissues, in big proportions of the human population, are
found to be significantly lower than recommended [3–7]. Severe Zn-
deficiency in human beings was first described in 1963 and associated
with anemia and parasite infections in a group of Iranian children [8].
This phenotype, apparently reversible by simple Zn-supplementation,
has been observed ever since in developing countries where Zn defi-
ciencies form a very common consequence of malnutrition and is as-
sociated with death. In these countries, Zn deficiency is the 5th leading
cause of mortality [9]. No less than 2 billion people in developing
countries thus display Zn deficiency. However, also in the Western
world, Zn deficiencies are common. Young children, diabetics and el-
derly people are particularly at risk. A recent study concluded that over
half of the +71y old people in the USA display mild Zn deficiency [10].
In total, up to almost 30% of the world population is supposed to have a
mild to moderate Zn deficiency [10]. Based on studies in human pa-
tients and in animal models, Zn deficiency may be cause of many health
problems, including increased sensitivity for infection and sepsis [7].
Zinc is distributed in all mammalian organs, but skeletal muscle and
bone are compartments with most Zn reserve [11]. The fraction of zinc
in the blood is only 0.1% and most blood zinc is bound on proteins such
as albumin, alpha-2-macroglobulin, transferrin and ceruloplasmin
[12,13]. Although the blood zinc levels are indicative of the total zinc
load in an individual, there is also active transport of zinc between
organs and blood. For example, during inflammation and sepsis, the
blood zinc levels decline, probably because zinc is required to support
the transcription and translation of novel genes and proteins, e.g. the
acute phase proteins in hepatocytes [14,15].
Transport of zinc is a complex phenomenon (see Fig. 1). In general,
zinc can be transported from the extracellular compartment and cell
organelles into the cell cytoplasm via a family of “Zrt/Irt-like proteins
(ZIPs)”, of which 14 have been identified so far. They are encoded by 14
different genes, named SLC39A1 until SLC39A14. The proteins are 8-
transmembrane-spanning glycosylated proteins. These proteins are ex-
pressed in a cell-specific and organelle-specific way [18–20],16]. De-
ficiencies of some of these proteins can have drastic effects. For ex-
ample, in humans, a rare zinc-deficiency syndrome (acrodermatitis
enterohepatica) results from a mutation in the human SLC39A4 gene
[17]. Zinc from the food is primarily taken up by enterocytes of the
small intestine via ZIP4 [18–20]. Zinc in the cytoplasm can be stored in
specific Zn-containing organelles (“zincosomes”) and can have many
different functions (see further). Besides these classical ZIPs, a number
of other zinc transporters have been identified, e.g. ZnR/GPR39, a
multi-ligand G-protein-coupled receptor, expressed in the intestinal
track, including colon intestinal epithelium [21,22].
Excess zinc can be dealt with in several ways, including excretion of
https://doi.org/10.1016/j.cytogfr.2017.12.002
Received 20 November 2017; Accepted 19 December 2017
⁎ Corresponding author at: Center for Inflammation Research, VIB, Ghent, Belgium.
E-mail address: Claude.Libert@IRC.VIB-UGent.be (C. Libert).
Cytokine and Growth Factor Reviews xxx (xxxx) xxx–xxx
1359-6101/ © 2017 Elsevier Ltd. All rights reserved.
Please cite this article as: Souffriau, J., Cytokine and Growth Factor Reviews (2017), https://doi.org/10.1016/j.cytogfr.2017.12.002
http://www.sciencedirect.com/science/journal/13596101
https://www.elsevier.com/locate/cytogfr
https://doi.org/10.1016/j.cytogfr.2017.12.002
https://doi.org/10.1016/j.cytogfr.2017.12.002
mailto:Claude.Libert@IRC.VIB-UGent.be
https://doi.org/10.1016/j.cytogfr.2017.12.002
zinc out of the cytoplasm in the extracellular space using “zinc trans-
porters (ZnTs)”. Mammals encode 10 such (6-transmembrane spanning)
transporters, named ZnT1 to ZnT10, encoded by genes called SLC30A1
to SLC30A10. Again, the genes are expressed in tissue specific ways
[23],16]. From the cytoplasm, zinc can also be transported to orga-
nelles via ZnTs, e.g. into the secretory granules of Paneth cells (see Box
1) in the intestinal crypts of Lieberkühn via ZnT2 [23], or into granules
in beta cells in the pancreas (ZnT8) [24] as well as in synaptic vesicles
in neurons (ZnT3) [25]. Molecularly, zinc binds on histidines in the
cytoplasmic C-terminal part of a ZnT protein, and is then transported
out of the cytoplasm in exchange of a proton. How the cellular dis-
tribution of zinc is sensed and organized is still unclear, but a role of the
major Zn-responsive transcription factor Metal Transcription Factor-1
(MTF-1) has been shown [2].
Fig. 1. Cellular Zn homeostasis.
Zinc homeostasis is regulated by Zrt/Irt-like proteins (ZIP, green) and Zinc Transporter Proteins (ZnT, red) by transporting zinc in and out of the cell and its organelles. In the cytoplasm
free zinc concentration is regulated by metallothioneins (MT). Metal Transcription Factor-1 (MTF-1) is activated by zinc, regulates the expression of several genes, coding for proteins
involved in zinc homeostasis, such as Slc30a1, Slc30a2 and metallothionein-coding genes Mt1, Mt2, Mt3, Mt4. In case of heavy metal stress zinc will be released (by displacement) from
the metallothionein zinc fingers and activate MTF-1 to induce an anti-heavy metal response.
Box 1
Paneth cells
Paneth cells are found in the crypts of Lieberkühn of the small intestine. They are called after a 19th century Austrian scientist. They are
very distinct cells with specific features. For example, they stain very eosinophilic in a classical H&E stain, and they are located just below
the stem cells. In terms of function, they are the main cells that produce antimicrobial proteins and peptides and other proteins involved in
inflammation and immunity. Most of these proteins and peptides are stored in the eosinophylic, secretorygranules that are typical for these
cells. Many antimicrobial peptides have been identified. The principle defense proteins are lysozyme and phospholipase A2, Reg-IIIγ and
Lypd8, and the major defense peptides are called alpha-defensins. These cysteine rich-peptides are hydrophobic as well as positively
charged, and are able to disrupt bacterial membranes, while preserving the eukaryotic own membranes. The defensins are generated by
proteolytic cleavage from pre-defensins, and in mice, the major defensing cleaving protease was found to be matrix metalloproteinsase-7
[138].
J. Souffriau, C. Libert Cytokine and Growth Factor Reviews xxx (xxxx) xxx–xxx
2
As a positively charged bivalent cation, zinc is bound by a great
number of proteins on negatively charged amino acid residues, and
some proteins have evolved into a role in Zn- (and other heavy metals)
homeostasis, e.g. metallothioneins (MTs). Over 300 enzymes are
thought to bind zinc in the active center and depend on zinc for bio-
logical activity [1]. Examples are DNA polymerase and RNA poly-
merase-II, but also several histone deacetylases [26], meaning that zinc
plays an important role in regulation of gene expression. Also super-
oxide dismutase depends on zinc for its anti-oxidant function [27,28].
Finally, a large group of metalloproteases, including the family of ma-
trix metalloproteinases (MMPs) with over 20 members, strictly depend
on zinc for their important biological functions. MMPs have been im-
plicated in development, cancer progression, inflammation and anti-
bactericidal functions [29].
Many transcription factors depend on zinc-finger structures for
proper protein–protein interaction and/or DNA binding. GATA3 for
example contains two (Cys)4 zinc fingers which are essential for GATA3
DNA binding, and which therefore help to determining T-cell lineage
differentiation and activity [30–32]. The PPAR transcription factors,
which bind lipid-like ligands, undergo hetero-dimerization with other
proteins, such as the RXR, via their zinc-fingers [33]. Once these het-
erodimers are formed, they bind DNA and regulate transcription of
genes involved in metabolism of fatty acids [34,35]. As has been shown
for the Estrogen Receptor [36] and Glucocorticoid Receptor [37] the
thiol groups of cysteins in such zinc fingers are kept in a reduced status
(e.g. by thioredoxin), but under oxidative stress conditions in cells
oxidation of these thiol groups (loss of H+ ) leads to destabilization of
zinc fingers and to loss of zinc and loss of function of these nuclear
receptors [38].
In addition, a specific transcription factor, MTF-1, recognizes and
binds zinc and performs functions based on the amounts of available
zinc [39–42]. MTF-1 is an ubiquitously expressed protein, containing
six (Cys)2(His)2 zinc fingers. It is a very conserved transcription factor,
already found in insects. The major function is thought to be the reg-
ulation of normal physiological cation biology, as well as the detection
and management of increased heavy metal concentrations. When cells
are confronted with high levels of zinc or other heavy metals, or when
cells are undergoing oxidative stress leading to release of zinc from
redox sensitive proteins, free zinc ions are binding to the MTF-1 zinc
fingers, which leads to homo-dimerization of MTF-1, DNA binding,
recruitment of nuclear co-regulators and regulation of processes that
aim to normalize zinc levels or protect the cell from the high zinc
concentration [43–45]. Hence, MTF-1 induces the expression of several
proteins, e.g. ZnT1 [46], ZnT2 [47], as well as MTs [44,45], the latter
ones binding and sequestering zinc and other heavy metal ions. Zinc-
induced MT also plays other biological roles, such as regulating au-
tophagy and bacterial clearance [48].
2. The relation between zinc levels and sepsis sensitivity
Sepsis is currently defined as a condition of organ failure based on
an over-reactive host response to infection [49]. Sepsis can also be
considered as a form of systemic inflammatory response syndrome
(SIRS) associated with infection. SIRS is a critical condition leading to
the admission of patients in the Intensive Care Unit. SIRS can result
from severe burns, ischemia/reperfusion, severe bleeding and certain
surgical interventions [50]. The numbers of patients suffering from
sepsis or septic shock (sepsis involving decreased blood pressure)
amounts to more than 30 million per year, and with a mortality of
about 30% sepsis is undoubtedly one of the most urgent unmet medical
needs of today [51]. There is considerable controversy about the un-
derlying reasons of the many failing clinical trials in sepsis. In the sepsis
field, it is accepted that patients first develop an acute inflammatory
phase (as part of innate immunity), followed by an immune suppressive
phase [52]. Patients can die during the first phase, but also long after
the onset of sepsis, i.e. during the immune-suppressive phase. This late
lethality is supposedly due to secondary infections caused by a mal-
functioning of the innate and adaptive immune response [53,54]. Many
failed clinical trials have focused on the initial inflammation, or the so
called “cytokine storm” [55], but without much success. In fact, the
most help in sepsis has come from better clinical management strategies
instead [56].
Some of the most applied models of SIRS and sepsis relevant for this
review paper are the following: (1) animals (mice) can be injected with
cell-wall components of gram-negative bacteria, lipopolysaccharide
(LPS) or endotoxins, leading to SIRS, i.e. endotoxemia, (2) animals can
also be infected with specific bacteria, for example Salmonella typhi-
murium, Eschericchia coli or Pseudomonas aeruginosa or (3) they can be
subjected to cecal ligation and puncture (CLP). The latter model is more
and more used as a polymicrobial peritoneal sepsis model [57]. In these
SIRS and sepsis models, as well as in sepsis patients, the intestinal
epithelium is considered a key barrier that must remain intact to pre-
vent intestinal flora from entering the system. Some authors therefore
have launched the idea that “the gut is the motor in sepsis” [58]. In this
chapter, we will illustrate that there is an intricate relation between Zn
levels and sensitivity to sepsis, in animal models as well as in human
patients.
In human sepsis patients and in pre-clinical models, a clear direct
link between low zinc levels and sensitivity to SIRS and sepsis has been
found [14,59–63]. As discussed, a large portion of the human popula-
tion has low to very low blood zinc levels, based on dietary conditions,
or based on reduced uptake or increased excretion (e.g. diabetics). Low
blood serum levels are thus typically found in young children, older
people and diabetics. Whether this Zn deficiency of these people forms
the basis of their risk to develop sepsis is not known. Not only blood
zinc is low in SIRS patients, but also selenium, copper and iron blood
values are lower than normal [64]. A correlation with SIRS mortality
was specifically significant with zinc and selenium. In mice, it was re-
ported that a low zinc diet sensitized the animals drastically in models
of SIRS and sepsis and led to more lethality in these models. Liu [65]
described an extreme sensitivity for LPS induced endotoxemia under
zinc-deficient conditions, while Knoell [66] described a similar sensi-
tivity in the mouse polymicrobial CLP sepsis model. Zinc depletion in
mice also leads to increased sensitivity to infections, e.g. with Strepto-
coccus pneumonia [67]. When mice are subjected to CLP, blood zinc
levels sharply decrease to a significantly low level, some 9h–24 h after
onset of CLP, and zinc levels in liver increase, in response to upregu-
lation of Zip14 (Slc39a14) expression [14]. This redistribution of zinc
during the acute phase of sepsis may be essential to ensure transcription
and translation of the acute phase proteins, to provide zinc-containing
proteins with zinc and to protect hepatocytesfrom oxidative stress and
inflammation. Whether the low levels of blood zinc in human blood
reflect an ongoing sepsis rather than a causative factor still needs to be
studied. The sensitizing effects of low zinc food to endotoxemia and CLP
were found to be associated with increased inflammation (IL6, TNF),
reduced neutrophil chemotaxis, reduced phagocytosis, increased cell
death in liver and lung and increased protein oxidation [66,68,69]. Zinc
deficiency clearly leads to a decreased protective response at multiple
levels. Zinc is important for the intestinal epithelial cell (IEC) barrier
(Fig. 2) and Zn deficiency has been found to lead specifically to a failure
of the IEC barrier [70], which can be responsible for numerous down-
stream effects (food allergies, diarrhea, mal-absorption), but also to gut
flora translocation and so sensitization to SIRS and sepsis. Based on in
vitro studies, the underlying mechanism of this barrier failure may be
based on decreased expression of tight junction proteins (occludin and
claudin-3) [71]. Low zinc, high intestinal permeability and diarrhea
have been found to be closely linked in African children [65],72].
Interestingly, increasing the blood zinc levels has been shown to
lead to protection in mouse SIRS and sepsis models [14,73–76] as well
as in limited clinical trials in human patients [77,78]. When mice are
injected with recombinant TNF, they develop a lethal, acute SIRS,
characterized by hypothermia, induction of blood cytokines and
J. Souffriau, C. Libert Cytokine and Growth Factor Reviews xxx (xxxx) xxx–xxx
3
damage to different tissues. Especially the intestinal epithelium is
particularly sensitive to cell death and tissue damage caused by TNF.
Permeability of the intestinal epithelium, followed by gut flora leakage
into the system is a key event in this model [79,80]. We described that
simple addition of zinc (ZnSO4) in the drinking water of mice during 1
week completely protects them against this lethal SIRS TNF model,
especially at the level of the IECs [74,75]. Also in the LPS model [81],
as well as the CLP model, addition of zinc to animals has proven to
protect significantly against lethal outcome. In the latter model, zinc led
to reduced inflammation [14,66] and reduced systemic bacterial load
[73]. In mice, zinc treatment also protected against two very acute
bacterial septic peritonitis models, i.e. after injection of fecal slurry [73]
or cecal slurry [76], the latter effect of zinc being linked to better acute
antibacterial effects of polymorphonuclear leucocytes (PMNs).
In humans, zinc treatment strongly reverts intestinal permeability
and diarrhea in developing countries [85],82,83] and reduces the in-
fection risk in elderly people [84]. Furthermore, babies suffering from
“small for gestational age” are typically more sensitive for infections
and are protected by zinc [85]. Based on these encouraging data, recent
trials confirmed the preventive effects of zinc treatment in neonatal
sepsis in babies, whereby reduced expression of TNF, IL6, calprotectin
and mortality were observed [77,78].
3. Mechanistic impact of zinc on SIRS and sepsis
From the previous chapter, it is clear that there is a link between the
nutritional zinc status and resistance against SIRS and sepsis and that
zinc might have preventive therapeutic power. But what is the me-
chanism of this effect of zinc? To answer this question we must un-
derstand which are the biological pathways of relevance in SIRS and
sepsis. If we consider the mouse CLP model as an example, sepsis is
initiated by the infection of the peritoneal cavity with cecum-located
bacteria. The composition of the intestinal flora, the microbiome, is
expected to have a huge impact on the severity of the sequences that
follow. Local inflammation in the peritoneum leads to activation of
phagocytosis and chemotaxis of phagocytes (macrophages, PMNs, DCs)
from the system to the peritoneal cavity [86]. This local inflammation
and phagocytosis are needed to clear the infection. The puncture is
closed by a process of wound healing. The local inflammation becomes
a systemic inflammation and leads to extravasation of white blood cells,
edema, blood clotting, complement activation, oxidative stress, cell
death and loss of barrier function, a.o. in the gut [87], which leads to
transport of gut flora and microbial molecules (PAMPs) into the
draining lymph nodes, system, organs and peritoneum [88]. This
leakage of gut flora has also been observed in models of septic pneu-
monia [89] and after LPS injection [90] or TNF injection [80]. When
SIRS or sepsis pertains after several days, also the adaptive immune
response is activated as well as the acute phase response. This latter
response is considered as an evolutionary ancient, a-specific and slow
response [91]. These two last responses are slow and take several days
to be established, and are antigen specific and a-specific respectively.
3.1. Zinc and the microbiome
In human patients, sepsis is typically resulting from infection. This
can be community or hospital acquired on the one hand, or originating
from the own microflora on the other hand, or a combination of both.
The major routes of infection are the lungs, peritoneum, urogenital
route and the brain [92,93]. In animal models, infection with specific
bacterial strains (incl. human isolates) are used to induce sepsis, while
in the CLP model, cecal flora leads to sepsis in the peritoneal cavity.
Also in pneumonia models and in pneumonia patients gut flora is de-
tected in the lungs, suggesting that permeability of the gut epithelium
followed by spreading of gut flora are common essential contributing
factors in sepsis [88,94]. Also in the SIRS models where mice are in-
jected with TNF or with LPS gut permeability also leads to influx of gut
flora bacteria into the system [80].
A healthy gut microbiome is a diverse microbiome which provides
resistance against colonization of pathogenic bacteria [95,96]. To
maintain homeostasis, the gut microbiome outcompetes pathogens by
consuming nutrients, by binding to mucosal binding sites, by regulating
the immune response, by producing antimicrobial substances such as
bacteriocins and by stimulating host cells, e.g. Paneth cells (see Box 1),
to produce antimicrobial peptides [97,98].
Septic patients are characterized by a dysbiotic microbiome, with a
decrease in diversity, lower abundances of key commensal bacteria and
overgrowth of pathogenic bacteria. In general, the shifts in the com-
position of the gut microbiome are caused by extrinsic factors (e.g.
Fig. 2. Zn deficiency and susceptibility for disease.
Humans deficient in zinc are more prone for infec-
tions and sepsis. Zn deficiency might result from low
dietary zinc intake (because of a diet consisting of
high cereal food, high phytate and low animal food
content, or because of consumption of plants grown
on Zn deficient soils and of meat lower in zinc than
normal); high losses (e.g. via feces in case of diar-
rhea) or impaired uptake (genetic disorders, such as
acrodermatitis enterohepatica, caused by mutations
in SLC39A4). Increasing zinc levels e.g. by bio-for-
tification in agriculture or by direct zinc supple-
mentation strengthens the defense against infection.
J. Souffriau, C. Libert Cytokine and Growth Factor Reviews xxx (xxxx) xxx–xxx
4
antibiotics, nutrition, medication) and intrinsic factors (e.g. systemic
inflammation). It is believed that a healthy gut microbiome might en-
hance the host defense and that a dysbiotic microbiome, as is seen in
sepsis patients, might contribute to a poor host defense, and hence poor
outcome in inflammation and infection [95–97]. Targeting the gut
microbiome in sepsis by augmenting beneficial bacteria (with probio-
tics, prebiotics and synbiotics) and decreasing harmful bacteria, or by
using fecal transplants could potentially improve outcomes in critically
ill patients [99]. Furthermore, modulating the microbiome of patients
at risk to develop sepsis (prematurelyborn children, elderly, diabetics)
for example by specific diets is currently under investigation [100].
Several data from the literature have suggested that zinc is an im-
portant regulator of the gut flora microbiome communities. Both in
poultry and pig industry, zinc has been used extensively since decades
to reduce gastrointestinal (GI) infections, diarrhea and deaths and as a
growth-stimulating agent [3]. Weaned piglets encounter several stres-
sors shortly after weaning from the mother (diet, social, environmental)
which lead to anorexia, intestinal inflammation and diarrhea [101].
The changes in the GI tract, such as overgrowth of pathogenic bacteria
and increased permeability to antigens and toxins, have been linked to
changes in the gut microbiota [102,103]. At weaning phase microbial
dysbiosis is seen marked by a loss of diversity [104], a generally ob-
served decrease in health promoting Lactobacillus species [105,106] and
an increased relative abundance of facultative anaerobic bacteria such
as enterobacteriaceae [107] and E. coli [108]. Classical antibiotics have
been used to decrease GI infections and to overcome this sensitive
phase, but the increased risk for antimicrobial resistance urged to look
for alternatives [109]. Zn oxide (ZnO) is a highly effective and abun-
dantly used replacement for antibiotics and has been shown to have
antimicrobial activities itself [110]. The effect of ZnO on the micro-
biome and its composition is however controversial. Most studies
showed a decrease in microbial diversity when administering high Zn
doses. Despite the fact that results are conflicting, most studies show a
decline in the health associated Lactobacillus species [111–113]. Lac-
tobacillus bacteria are a part of the GI and vaginal flora. They are used
as probiotics and have been shown protective against sepsis
[100,114–116]. However, caution has to be taken and occasionally they
can be pathogenic and have been seen to cause bacteremia and sepsis in
patients at risk [117–120]. In conclusion, zinc addition appears to de-
crease the microbiome diversity, however because of its excessive
health improving use it might reduce its virulence. Caution is necessary,
because the decrease in microbial diversity by excess zinc was recently
associated with an increased susceptibility to Clostridium difficile in-
fection when mice were also co-treated with antibiotics [121].
Recently, several studies have shown that deficiency of zinc in
chickens (induced by low zinc containing food) leads to a significant
shift in gut microbiome composition [122]. The microbial shift ob-
served resembled those seen in different pathological states, such as
Fig. 3. Zinc and the intestinal mucosal barrier function.
The physical barrier of the intestine is formed by a single layer of epithelial cells, superposed with mucus, which is produced by Goblet cells (GC). These cells and the mucus form a barrier
(together with a chemical and immunological barrier not (fully) depicted in the figure) for the intestinal microbes residing in the gut lumen. Zinc modulates the barrier function by
strengthening the cell-to-cell contacts via upregulation of tight junctions and by increasing GC numbers and influencing mucin composition in the bowel. Furthermore, zinc is also
necessary for a proper anti-microbial activity of Paneth cells. The latter is related to a ZnT2-mediated zinc uptake mechanism in the secretory granules of the Paneth cells, probably
influencing anti-microbial peptide (AMP) function. Zinc is also able to modulate the microbiome directly by promoting growth of certain microbes and inhibiting growth of others.
J. Souffriau, C. Libert Cytokine and Growth Factor Reviews xxx (xxxx) xxx–xxx
5
diabetes [123] and Crohn Disease [124]. The study in chickens also
found that zinc shortage led to reduced levels of short chain fatty acids
(SCFAs) in the stool of these animals. By a number of mechanisms,
SCFAs (acetate, butyrate, propionate), which are produced by bacteria
from fiber-rich food, have anti-inflammatory activities and tighten the
intestinal barrier and protect in models of SIRS and sepsis [125–127].
Also, SCFAs are very low in feces of sepsis patients, and point to dys-
biosis in these people [128,129].
Disturbances in zinc uptake or proper zinc biodistribution are also
shown to impact the microbiome. A missense mutations in the Zn
transporter coding gene Slc39a8 (encoding ZIP8) has been shown to
lead to a human gut microbiome shift strongly resembling the microbial
changes seen in Crohn’s disease (CD) and obesity patients [130]. Fur-
thermore, Podany et al. [23] showed that Slc30a2 (coding for ZnT2) KO
mice, suffer from reduced zinc accumulation in Paneth cell granules
and displayed decreased in Ruminococcaceae, Clostrideacea and Methy-
lobacterium in the gut microbiome. These families are representative for
a healthy microbiome. ZnT2 KO mice further showed an enrichment in
the Bacteroidales family S24-7, which has been identified as a possible
indicator of disease onset in colitis models [131]. Finally, zinc is critical
for Paneth cell survival. Acute zinc depletion eradicates Paneth cells,
rendering animals extremely sensitive for certain infections, e.g. with
Klebsiella pneumonia [132].
In terms of the mechanism by which zinc modulates the micro-
biome, two major possibilities can be identified (Fig. 3). First, zinc has
direct activating and inhibiting effects on growth and pathogenicity of
certain species [133]. As discussed earlier, in sepsis patients, blood
levels of zinc are usually low. This has been explained by a redis-
tribution of the available zinc to the liver, by means of ZIP14 induction
in hepatocytes. One of the interpretations of this finding is that thereby
zinc is less available as a growth stimulating factor for bacteria that
have contaminated the blood. Some bacteria have evolved strategies to
overcome extreme zinc conditions by use of Zn efflux and influx
transporters such as the ZnuABC transporter which makes certain
bacteria capable of surviving in Zn limited conditions [125]. By use of
these Zn transporters they have survival benefits towards other bacteria
in extreme Zn conditions. A therapeutic advantage of this mechanism is
that disruption or blocking of this ZnuABC transporter for example can
be a new therapeutic strategy to block bacterial growth and patho-
genicity [134–136]. Second and next to a direct effect of zinc on bac-
teria, zinc can stimulate certain cells of the host to modulate the mi-
crobiome. It was found that zinc leads to increased production of
antimicrobial peptides (AMPs) by IECs, e.g. LL-37 in Caco2 cell cultures
[137], and elegant work by Podany [23] links zinc to microbiome
changes via Paneth cells. Paneth cells produce a variety of AMPs, in-
cluding Reg-IIIγ, Lypd8, lysozyme and alpha-defensins [138,139].
Identification of zinc-stimulated AMPs that mediate microbiome re-
shaping and resistance to SIRS and sepsis would be a great step forward
in zinc research. Paneth cells secrete AMPs from their secretory gran-
ules into the lumen, have been shown to take up zinc, and by ZnT2
expression, put this zinc into the granules [23]. How zinc is able to
influence the AMP production or stability is not known. Release of zinc
via Paneth cell granules may lead to high zinc concentrations in the
crypth [140], and thus local changes in microbiome in the crypth and
mucus layer. Finally, some AMPs, e.g. the PGLYRP peptidoglycan re-
cognition proteins, are also depending on Zn for their stability and
biological activity [141].
3.2. Zinc and inflammatory signal transduction
In sepsis, inflammation is activated in numerous cells, including
white blood cells, endothelial cells and epithelial cells. In bacterial
sepsis, the major triggers of inflammation are cell wall components of
bacteria, e.g. lipopolysaccharides. These and other components are
recognized by Patter Recognition Receptors of the host, such as Toll-like
receptors, NLRs and others [142]. As a result,a number of transcription
factors are activated. The major inflammatory transcription factor is
NFΚB, which is involved in different signaling pathways of the host
response. NFΚB is necessary to induce cytokines, which activate the
immune response and coordinate, along with chemokines, chemotaxis
and phagocytosis. Its activity is increased in sepsis patients and is as-
sociated with higher mortality rates [143–145].
Contradictory results have been found on the effect of Zn on NFΚB.
Zn has been shown to induce NFΚB [146], but it is generally accepted
that zinc inhibits NFΚB activation. Different mechanisms of Zn induced
NFΚB inhibition have been shown. (1) Zn inhibits cyclic nucleotide
phosphodiesterase (PDE), leading to an increase of cGMP, activation of
protein kinase A (PKA) and Raf phosphorylation, which inhibits NFΚB
activation [147]. (2) Zn can also directly inhibit the IΚB kinase (IKK)
complex, by inhibiting the IKKβ subunit which ubiquitinates IΚB
leading to its proteasomal degradation [148]. (3) Zn also exerts a major
effect on the protein TNFAIP3, better known as A20. This protein is a
de-ubiquitinase and is the main regulator of NFΚB activation [149].
Prasad et al. [150,151] showed that Zn is able to induce A20 mRNA and
protein levels. Zn has also been shown to induce epigenetic modifica-
tions of the A20 promoter [152]. (4) Next to A20, peroxisome-pro-
liferator activated receptor (PPAR) −α is also induced by Zn. This is
another important anti-inflammatory protein blocking NFΚB by com-
peting with NFΚB for binding to certain DNA sequences in the genome
[153].
3.3. Zinc and chemotaxis and phagocytosis
After infection, the activation of the innate immune system leads to
recruitment of specific white blood cells to the primary site of infection.
PMNs (mainly neutrophils), macrophages and Natural Killer (NK) cells
are the first recruited cells to the place of infection and are necessary for
effective pathogen eradication [154]. However, in sepsis decreased
neutrophil chemotaxis and impaired phagocytosis are often observed
[155,156]. This defect in first line defense is also observed in Zn defi-
ciency [157,158]. Chelation of free zinc in vitro is shown to impair
neutrophil chemotaxis and phagocytosis [159], confirming the essential
role of zinc in these processes. Increased neutrophil chemotaxis by Zn
supplementation was shown in studies of Hujanen [160] and Ganatra
[76], in vitro and in vivo. After infection, macrophages are attracted to
the site of infection, where they clear infectious agents and produce
high amounts of pro-inflammatory cytokines. However, during sepsis,
decreased expression of HLA-DR on monocytes and a polarisation of
macrophages into so called M2 macrophages, incl. an anti-in-
flammatory phenotype, have been observed, characterized by de-
creased cytokine expression [161–163]. Zinc is important for phago-
cytic activity [164] and cytokine expression in macrophages [165] and
increased macrophage phagocytosis by Zn has been shown in a CLP
[76] and fecal slurry mouse model of sepsis [73]. Third, NK cells are
another important defense line of the innate immune response. Like
neutrophils and macrophages these cells are also seen to be affected in
sepsis patients [166–168] and during Zn deficiency. NK cell cytotoxic
functions are decreased with consequently less IFNγ production and
this can be restored by Zn treatment [169], Zn also improves the de-
velopment of CD34+ cell progenitors towards NK cells [170].
3.4. Sepsis, anti-oxidative stress and the protective role of zinc
A critical role for oxidative stress in sepsis patients is known since
many years and has been reviewed extensively [38,171,172]. This
oxidative stress, characterized by an imbalance between oxidants and
antioxidants, results from the characteristic inflammatory response of
sepsis and may lead to organ damage. There is intracellular oxidative
stress as well as extracellular. During infection phagocytes produce
reactive oxygen species (ROS) via the so called respiratory burst, which
is necessary for eradication of micro-organisms [173]. However, ex-
cessive oxidative stress in sepsis patients (which is associated with bad
J. Souffriau, C. Libert Cytokine and Growth Factor Reviews xxx (xxxx) xxx–xxx
6
outcomes in sepsis [174,175]) has been shown to lead to lipid perox-
idation of cell membranes, protein oxidation [176], DNA damage
[177,178], mitochondrial damage [172] and to apoptosis and necrosis
[179–181]. Furthermore, NFκB leads to induction of inducible nitric
oxide synthetase (iNOS), but is itself also activated by ROS, showing a
close interrelationship between oxidative stress and inflammation.
iNOS-induced NO% overproduction has been seen to cause a decreased
vascular tonus and hypotension in sepsis patients [182–184]. Together,
these mechanisms lead to cytotoxicity and multi-organ system dys-
function in sepsis patients. Several preclinical studies have shown a
potential benefit for antioxidant therapy in sepsis [171,185].
Zn deficiency is also associated with increased levels of oxidative
stress and Zn supplementation has been shown to decrease plasma
markers of oxidative stress in elderly people [84,150,153]. Different
anti-oxidant mechanisms of Zn have been identified. (1) Zn can po-
tentiate the activity of anti-oxidant enzymes. Zn is a structural com-
ponent of the Cu/Zn superoxide dismutase (SOD) which converts su-
peroxide (O2%−) to hydrogen peroxide (H2O2) and oxygen (O2), which
are less toxic [28]. Thus, Zn deficiency negatively affects the Cu/Zn
SOD function. By producing H2O2 SOD also helps in removing neu-
trophils by means of apoptosis in a caspase-3 dependent manner, itself
also dependent of Zn [186]. By this, SOD protects against neutrophil
mediated tissue injury. (2) Other anti-oxidant enzymes shown to be
induced by Zn are heme-oxygenase (HO-1) [187], catalase and glu-
tathione-S-transferase (GST)[188]. (3) Zn activates Nrf2, an essential
transcription factor involved in regulating oxidative stress. NRF2 reg-
ulates glutathione, SOD, GST and HO-1 by binding to anti-oxidant re-
sponsive elements in the promoter region of these genes [189–192].
Nrf2 deficient mice are more sensitive to sepsis, supporting its im-
portant function [193]. (4) Furthermore, Zn functions as an inhibitor of
oxidative enzymes such as NADPH oxidase [194], which is expressed on
phagocyte membranes and which produces O2%−, and iNOS. (5) During
oxidative stress, zinc will be released from MTs and other proteins,
because of the oxidation of the sulfhydryl groups of cysteine and his-
tidine residues. Zn itself will induce an anti-oxidative response as dis-
cussed, but when released from oxidized proteins such as MT, it will
also activate MTF-1, and by this it will induce different anti-oxidant
systems via new transcription [195,196]. MTs, which are induced by
MTF-1, are known for their anti-oxidative functions, since they are able
to bind ROS. MTF-1 also induces expression of the glutathione-binding
protein Selenoprotein 1 (Sepw1) which binds free radicals [197].
3.5. Zinc and the adaptive immune response
Next to the innate immune response, also the adaptive immune
response is impaired during sepsis. Reduced lymphocyte numbers are a
hallmark of sepsis [198–200]. Lymphocyte apoptosis leads to immune
suppression and therapies boosting adaptive immunity, e.g. via inter-
ferons, are currently evaluated in clinical trials in sepsis patients [201].
Similar, in zinc deficiency, thymic atrophy is observed causing lym-
phopenia [202]. Immature T cells are the most sensitive cells to apop-
tosis due to Zn shortage. Thymulin, a protein which is necessary for T
cell differentiation and function depends on Zn and is decreased during
Zn deficiency [203]. Furthermore, a Th1/Th2 shift is observed in Zn
deficiency together with decreased IL2, IFNγ and TNFα levels (Th1
cytokines) and unaffected IL4, IL6 and IL10 (Th2 cytokines) levels
[204,205]. The same shift is also observed in sepsis patients, which
leads to the typicalanti-inflammatory state in the later phases of sepsis
[198]. Zn supplementation has been shown to restore this balance in
zinc deficient subjects [206]. Although T-lymphocytes are the most
effected during zinc deficiency, B cell numbers are also reduced ac-
companied by lower antibody production [207,208]. All together these
data may suggest that (part of) the immune suppression observed in the
later phase of sepsis might be due to acute zinc deficiency and the key
to understand the therapeutic role of zinc in sepsis may be found here.
On the other hand, excess levels of zinc have also been shown to inhibit
T cells, for example TH17 cells, which are decreased in sepsis [209]. Zn
is also shown to induce Treg cells, which remain [210] elevated in pa-
tients who die of sepsis [211,212].
4. Concluding remarks
The direct association between blood zinc levels and sepsis re-
sistance and survival has formed the motivation to identify the poten-
tial protective mechanism of zinc in this disease. Although there are
many questions that remain unanswered, the therapeutic impact of zinc
in sepsis and other forms of SIRS becomes generally accepted. More
elaborate clinical trials are needed to strengthen the findings and dis-
cover the potentials and limits of zinc-based therapies in sepsis.
Acknowledgements
Research in the laboratory of the authors was funded by the Agency
for Innovation of Science and Technology in Flanders (IWT), the
Research Council of Ghent University (GOA program), the Research
Foundation Flanders (FWO Vlaanderen) and the Interuniversity
Attraction Poles Program of the Belgian Science Policy (IAP-VI-18).
References
[1] W. Maret, Zinc biochemistry: from a single zinc enzyme to a key element of life,
Adv. Nutr. 4 (1) (2013) 82–91.
[2] T. Kambe, et al., The physiological: biochemical, and molecular roles of zinc
transporters in zinc homeostasis and metabolism, Physiol. Rev. 95 (3) (2015)
749–784.
[3] F.H. Nielsen, History of zinc in agriculture, Adv. Nutr. 3 (6) (2012) 783–789.
[4] N. Roohani, et al., Zinc and its importance for human health: an integrative re-
view, J. Res. Med. Sci. 18 (2) (2013) 144–157.
[5] K.R. Wessells, K.H. Brown, Estimating the global prevalence of zinc deficiency:
results based on zinc availability in national food supplies and the prevalence of
stunting, PLoS One 7 (11) (2012) pe50568.
[6] M. Sillanpää, Micronutrients and the Nutrient Status of Soils, A Global Study, FAO
Soil Bulletin, Rome, 1982.
[7] R. Gibson, Zinc deficiency and human health: etiology, health consequences, and
future solutions, Plant Soil (2012) 291–299.
[8] A.S. Prasad, Discovery of human zinc deficiency: its impact on human health and
disease, Adv. Nutr. 4 (2) (2013) 176–190.
[9] N.Z. Gammoh, L. Rink, Zinc in infection and inflammation, Nutrients 9 (6) (2017).
[10] L.M. Plum, L. Rink, H. Haase, The essential toxin: impact of zinc on human health,
Int. J. Environ. Res. Public Health 7 (4) (2010) 1342–1365.
[11] M.E. Wastney, et al., Kinetic analysis of zinc metabolism and its regulation in
normal humans, Am. J. Physiol. 251 (2 Pt 2) (1986) R398–408.
[12] J.K. Chesters, M. Will, Zinc transport proteins in plasma, Br. J. Nutr. 46 (1) (1981)
111–118.
[13] A.S. Prasad, D. Oberleas, Binding of zinc to amino acids and serum proteins in
vitro, J. Lab. Clin. Med. 76 (3) (1970) 416–425.
[14] I. Wessels, R.J. Cousins, Zinc dyshomeostasis during polymicrobial sepsis in mice
involves zinc transporter Zip14 and can be overcome by zinc supplementation,
Am. J. Physiol. Gastrointest. Liver Physiol. 309 (9) (2015) G768–78.
[15] J.P. Liuzzi, et al., Interleukin-6 regulates the zinc transporter Zip14 in liver and
contributes to the hypozincemia of the acute-phase response, Proc. Natl. Acad. Sci.
U. S. A. 102 (19) (2005) 6843–6848.
[16] T. Hara, et al., Physiological roles of zinc transporters: molecular and genetic
importance in zinc homeostasis, J. Physiol. Sci. 67 (2) (2017) 283–301.
[17] K. Wang, et al., A novel member of a zinc transporter family is defective in ac-
rodermatitis enteropathica, Am. J. Hum. Genet. 71 (1) (2002) 66–73.
[18] X. Wang, Dietary zinc absorption: a play of Zips and ZnTs in the gut, IUBMB Life
(2010) 176–182.
[19] R.J. Cousins, Gastrointestinal factors influencing zinc absorption and homeostasis,
Int. J. Vitam. Nutr. Res. 80 (4–5) (2010) 243–248.
[20] D. Ford, Intestinal and placental zinc transport pathways, Proc. Nutr. Soc. 63 (1)
(2004) 21–29.
[21] L. Cohen, I. Sekler, M. Hershfinkel, The zinc sensing receptor ZnR/GPR39, controls
proliferation and differentiation of colonocytes and thereby tight junction for-
mation in the colon, Cell. Death. Dis. 5 (2014) pe1307.
[22] L. Sunuwar, et al., The zinc sensing receptor ZnR/GPR39, triggers metabotropic
calcium signalling in colonocytes and regulates occludin recovery in experimental
colitis, Philos. Trans. R Soc. Lond. B Biol. Sci. 2016 (371) (1700).
[23] A.B. Podany, et al., ZnT2-Mediated zinc import into paneth cell granules is ne-
cessary for coordinated secretion and paneth cell function in mice, Cell Mol.
Gastroenterol. Hepatol. 2 (3) (2016) 369–383.
[24] F. Chimienti, et al., Identification and cloning of a beta-cell-specific zinc trans-
porter: znT-8, localized into insulin secretory granules, Diabetes 53 (9) (2004)
2330–2337.
J. Souffriau, C. Libert Cytokine and Growth Factor Reviews xxx (xxxx) xxx–xxx
7
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0005
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0005
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0010
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0010
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0010
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0015
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0020
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0020
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0025
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0025
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0025
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0030
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0030
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0035
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0035
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0040
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0040
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0045
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0050
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0050
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0055
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0055
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0060
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0060
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0065
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0065
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0070
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0070
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0070
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0075
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0075
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0075
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0080
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0080
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0085
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0085
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0090
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0090
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0095
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0095
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0100
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0100
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0105
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0105
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0105http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0110
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0110
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0110
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0115
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0115
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0115
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0120
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0120
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0120
[25] T.B. Cole, et al., Elimination of zinc from synaptic vesicles in the intact mouse
brain by disruption of the ZnT3 gene, Proc. Natl. Acad. Sci. U. S. A. 96 (4) (1999)
1716–1721.
[26] E. Seto, M. Yoshida, Erasers of histone acetylation: the histone deacetylase en-
zymes, Cold Spring Harb. Perspect. Biol. 6 (4) (2014) a018713.
[27] I.N. Zelko, T.J. Mariani, R.J. Folz, Superoxide dismutase multigene family: a
comparison of the CuZn-SOD (SOD1), Mn-SOD (SOD2), and EC-SOD (SOD3) gene
structures, evolution, and expression, Free Radic. Biol. Med. 33 (3) (2002)
337–349.
[28] E. Mariani, et al., Effects of zinc supplementation on antioxidant enzyme activities
in healthy old subjects, Exp. Gerontol. 43 (5) (2008) 445–451.
[29] R.E. Vandenbroucke, C. Libert, Is there new hope for therapeutic matrix me-
talloproteinase inhibition? Nat. Rev. Drug Discov. 13 (12) (2014) 904–927.
[30] A.H. Fox, et al., Key residues characteristic of GATA N-fingers are recognized by
FOG, J. Biol. Chem. 273 (50) (1998) 33595–33603.
[31] M.C. Labastie, et al., Structure and expression of the human GATA3 gene,
Genomics 21 (1) (1994) 1–6.
[32] M.C. Nawijn, et al., Enforced expression of GATA-3 during T cell development
inhibits maturation of CD8 single-positive cells and induces thymic lymphoma in
transgenic mice, J. Immunol. 167 (2) (2001) 715–723.
[33] V. Chandra, et al., Structure of the intact PPAR-gamma-RXR- nuclear receptor
complex on DNA, Nature 456 (7220) (2008) 350–356.
[34] K. Schoonjans, B. Staels, J. Auwerx, The peroxisome proliferator activated re-
ceptors (PPARS) and their effects on lipid metabolism and adipocyte differentia-
tion, Biochim. Biophys. Acta 1302 (2) (1996) 93–109.
[35] A. Chawla, et al., Nuclear receptors and lipid physiology: opening the X-files,
Science 294 (5548) (2001) 1866–1870.
[36] R.M. Whittal, et al., Preferential oxidation of zinc finger 2 in estrogen receptor
DNA-binding domain prevents dimerization and: hence, DNA binding,
Biochemistry 39 (29) (2000) 8406–8417.
[37] K.A. Hutchison, et al., Redox manipulation of DNA binding activity and BuGR
epitope reactivity of the glucocorticoid receptor, J. Biol. Chem. 266 (16) (1991)
10505–10509.
[38] J. Macdonald, H.F. Galley, N.R. Webster, Oxidative stress and gene expression in
sepsis, Br. J. Anaesth. 90 (2) (2003) 221–232.
[39] R. Heuchel, et al., The transcription factor MTF-1 is essential for basal and heavy
metal-induced metallothionein gene expression, EMBO J. 13 (12) (1994)
2870–2875.
[40] A.L. Guerrerio, J.M. Berg, Metal ion affinities of the zinc finger domains of the
metal responsive element-binding transcription factor-1 (MTF1), Biochemistry 43
(18) (2004) 5437–5444.
[41] X. Chen, M. Chu, D.P. Giedroc, MRE-Binding transcription factor-1: weak zinc-
binding finger domains 5 and 6 modulate the structure, affinity, and specificity of
the metal-response element complex, Biochemistry 38 (39) (1999) 12915–12925.
[42] D.C. Bittel, I.V. Smirnova, G.K. Andrews, Functional heterogeneity in the zinc
fingers of metalloregulatory protein metal response element-binding transcription
factor-1, J. Biol. Chem. 275 (47) (2000) 37194–37201.
[43] V. Günther, et al., A conserved cysteine cluster: essential for transcriptional ac-
tivity, mediates homodimerization of human metal-responsive transcription
factor-1 (MTF-1), Biochim. Biophys. Acta 1823 (2) (2012) 476–483.
[44] V. Günther, U. Lindert, W. Schaffner, The taste of heavy metals: gene regulation by
MTF-1, Biochim. Biophys. Acta 1823 (9) (2012) 1416–1425.
[45] A. Grzywacz, et al., Metal responsive transcription factor 1 (MTF-1) regulates zinc
dependent cellular processes at the molecular level, Acta Biochim. Pol. 62 (3)
(2015) 491–498.
[46] S.J. Langmade, et al., The transcription factor MTF-1 mediates metal regulation of
the mouse ZnT1 gene, J. Biol. Chem. 275 (44) (2000) 34803–34809.
[47] L. Guo, et al., STAT5-glucocorticoid receptor interaction and MTF-1 regulate the
expression of ZnT2 (Slc30a2) in pancreatic acinar cells, Proc. Natl. Acad. Sci. U. S.
A. 107 (7) (2010) 2818–2823.
[48] A. Lahiri, C. Abraham, Activation of pattern recognition receptors up-regulates
metallothioneins, thereby increasing intracellular accumulation of zinc, autop-
hagy, and bacterial clearance by macrophages, Gastroenterology 147 (4) (2014)
835–846.
[49] M. Singer, et al., The third international consensus definitions for sepsis and septic
shock (Sepsis-3), JAMA 315 (8) (2016) 801–810.
[50] R.A. Balk, Systemic inflammatory response syndrome (SIRS): where did it come
from and is it still relevant today? Virulence 5 (1) (2014) 20–26.
[51] C. Fleischmann, et al., Assessment of global incidence and mortality of hospital-
treated sepsis: current estimates and limitations, Am. J. Respir. Crit. Care Med.
193 (3) (2016) 259–272.
[52] J.S. Boomer, et al., Immunosuppression in patients who die of sepsis and multiple
organ failure, JAMA 306 (23) (2011) 2594–2605.
[53] B.D. Winters, et al., Long-term mortality and quality of life in sepsis: a systematic
review, Crit. Care Med. 38 (5) (2010) 1276–1283.
[54] T. Wang, et al., Subsequent infections in survivors of sepsis: epidemiology and
outcomes, J. Intensive Care Med. 29 (2) (2014) 87–95.
[55] K.A. Brown, et al., Targeting cytokines as a treatment for patients with sepsis: a
lost cause or a strategy still worthy of pursuit? Int. Immunopharmacol. 36 (2016)
291–299.
[56] C.A. Schorr, R.P. Dellinger, The surviving sepsis campaign: past, present and fu-
ture, Trends Mol. Med. 20 (4) (2014) 192–194.
[57] L. Dejager, et al., Cecal ligation and puncture: the gold standard model for poly-
microbial sepsis? Trends Microbiol. 19 (4) (2011) 198–208.
[58] N.J. Klingensmith, C.M. Coopersmith, The gut as the motor of multiple organ
dysfunction in critical illness, Crit. Care Clin. 32 (2) (2016) 203–212.
[59] J. Hoeger, et al., Persistent low serum zinc is associated with recurrent sepsis in
critically ill patients – a pilot study, PLoS One 12 (5) (2017) p. e0176069.
[60] B.Y. Besecker, et al., A comparison of zinc metabolism: inflammation, and disease
severity in critically ill infected and noninfected adults early after intensive care
unit admission, Am. J. Clin. Nutr. 93 (6) (2011) 1356–1364.
[61] N.Z. Cvijanovich, et al., Zinc homeostasis in pediatric critical illness, Pediatr. Crit.
Care Med. 10 (1) (2009) 29–34.
[62] L.M. Gaetke, et al., Effects of endotoxin on zinc metabolism in human volunteers,
Am. J. Physiol. 272 (6 Pt 1) (1997) E952–6.
[63] K. Mertens, et al., Low zinc and selenium concentrations in sepsis are associated
with oxidative damage and inflammation, Br. J. Anaesth. 114 (6) (2015) 990–999.
[64] M. Rech, et al., Heavy metal in the intensive care unit: a review of current lit-
erature on trace element supplementation in critically ill patients, Nutr. Clin.
Pract. 29 (1) (2014) 78–89.
[65] M.J. Liu, et al., Zinc regulates the acute phase response and serum amyloid A
production in response to sepsis through JAK-STAT3 signaling, PLoS One 9 (4)
(2014) e94934.
[66] D.L. Knoell, et al., Zinc deficiency increases organ damage and mortality in a
murine model of polymicrobial sepsis, Crit. Care Med. 37 (4) (2009) 1380–1388.
[67] T.A. Strand, et al., Pneumococcal pulmonary infection: septicaemia and survival in
young zinc-depleted mice, Br. J. Nutr. 86 (2) (2001) 301–306.
[68] M. Shea-Budgell, et al., Marginal zinc deficiency increased the susceptibility to
acute lipopolysaccharide-induced liver injury in rats, Exp. Biol. Med.(Maywood)
231 (5) (2006) 553–558.
[69] K.T. Crowell, et al., Marginal dietary zinc deprivation augments sepsis-induced
alterations in skeletal muscle TNF-α but not protein synthesis, Physiol. Rep. 4 (21)
(2016).
[70] S. Skrovanek, et al., Zinc and gastrointestinal disease, World J. Gastrointest.
Pathophysiol. 5 (4) (2014) 496–513.
[71] Y. Miyoshi, S. Tanabe, T. Suzuki, Cellular zinc is required for intestinal epithelial
barrier maintenance via the regulation of claudin-3 and occludin expression, Am.
J. Physiol. Gastrointest. Liver Physiol. 311 (1) (2016) G105–16.
[72] G.W. Lindenmayer, R.J. Stoltzfus, A.J. Prendergast, Interactions between zinc
deficiency and environmental enteropathy in developing countries, Adv. Nutr. 5
(1) (2014) 1–6.
[73] J.E. Nowak, et al., Prophylactic zinc supplementation reduces bacterial load and
improves survival in a murine model of sepsis, Pediatr. Crit. Care Med. 13 (5)
(2012) e323–9.
[74] W. Waelput, et al., A mediator role for metallothionein in tumor necrosis factor-
induced lethal shock, J. Exp. Med. 194 (11) (2001) 1617–1624.
[75] W. Van Molle, et al., Protection of zinc against tumor necrosis factor induced lethal
inflammation depends on heat shock protein 70 and allows safe antitumor
therapy, Cancer Res. 67 (15) (2007) 7301–7307.
[76] H.A. Ganatra, et al., Zinc supplementation leads to immune modulation and im-
proved survival in a juvenile model of murine sepsis, Innate Immun 23 (1) (2017)
67–76.
[77] N. Banupriya, et al., Efficacy of zinc supplementation on serum calprotectin: in-
flammatory cytokines and outcome in neonatal sepsis – a randomized controlled
trial, J. Matern. Fetal Neonatal Med. 30 (13) (2017) 1627–1631.
[78] N. Banupriya, et al., Short term oral zinc supplementation among babies with
neonatal sepsis for reducing mortality and improving outcome – a double-blind
randomized controlled trial, Indian J. Pediatr. 85 (1) (2017) 5–9.
[79] F. Van Hauwermeiren, et al., Safe TNF-based antitumor therapy following
p55TNFR reduction in intestinal epithelium, J. Clin. Invest. 123 (6) (2013)
2590–2603.
[80] F. Van Hauwermeiren, et al., TNFR1-induced lethal inflammation is mediated by
goblet and Paneth cell dysfunction, Mucosal Immunol. 8 (4) (2015) 828–840.
[81] S.L. Snyder, R.I. Walker, Inhibition of lethality in endotoxin-challenged mice
treated with zinc chloride, Infect. Immun. 13 (3) (1976) 998–1000.
[82] Z.A. Bhutta, et al., Therapeutic effects of oral zinc in acute and persistent diarrhea
in children in developing countries: pooled analysis of randomized controlled
trials, Am. J. Clin. Nutr. 72 (6) (2000) 1516–1522.
[83] S.K. Roy, et al., Impact of zinc supplementation on intestinal permeability in
Bangladeshi children with acute diarrhoea and persistent diarrhoea syndrome, J.
Pediatr. Gastroenterol. Nutr. 15 (3) (1992) 289–296.
[84] A.S. Prasad, et al., Zinc supplementation decreases incidence of infections in the
elderly: effect of zinc on generation of cytokines and oxidative stress, Am. J. Clin.
Nutr. 85 (3) (2007) 837–844.
[85] S. Sazawal, et al., Zinc supplementation in infants born small for gestational age
reduces mortality: a prospective, randomized, controlled trial, Pediatrics 108 (6)
(2001) 1280–1286.
[86] L. Dejager, et al., Cecal ligation and puncture: the gold standard model for poly-
microbial sepsis? Trends Microbiol. 19 (4) (2011) 198–208.
[87] L.Y. Jiang, et al., Changes of the immunological barrier of intestinal mucosa in rats
with sepsis, World J. Emerg. Med. 1 (2) (2010) 138–143.
[88] B.P. Yoseph, et al., Mechanisms of intestinal barrier dysfunction in sepsis, Shock
46 (1) (2016) 52–59.
[89] P. Yu, C.M. Martin, Increased gut permeability and bacterial translocation in
Pseudomonas pneumonia-induced sepsis, Crit. Care Med. 28 (7) (2000)
2573–2577.
[90] A.B. Ribeiro, et al., Dexamethasone prevents lipopolysaccharide-Induced epithe-
lial barrier dysfunction in rat ileum, Shock (2017).
[91] S. Vandevyver, et al., An acute phase protein ready to go therapeutic for sepsis,
EMBO Mol. Med. 6 (1) (2014) 2–3.
[92] D.B. Page, J.P. Donnelly, H.E. Wang, Community-, healthcare-, and hospital-ac-
quired severe sepsis hospitalizations in the university health system consortium,
J. Souffriau, C. Libert Cytokine and Growth Factor Reviews xxx (xxxx) xxx–xxx
8
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0125
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0125
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0125
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0130
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0130
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0135
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0135
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0135
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0135
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0140
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0140
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0145
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0145
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0150
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0150
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0155
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0155
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0160
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0160
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0160
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0165
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0165
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0170
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0170
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0170
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0175
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0175
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0180
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0180
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0180
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0185
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0185
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0185
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0190
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0190
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0195
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0195
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0195
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0200
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0200
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0200
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0205
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0205
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0205
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0210
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0210
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0210
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0215
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0215
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0215
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0220
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0220
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0225
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0225
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0225
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0230
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0230
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0235
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0235
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0235
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0240
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0240
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0240
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0240http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0245
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0245
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0250
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0250
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0255
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0255
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0255
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0260
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0260
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0265
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0265
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0270
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0270
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0275
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0275
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0275
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0280
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0280
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0285
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0285
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0290
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0290
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0295
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0295
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0300
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0300
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0300
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0305
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0305
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0310
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0310
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0315
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0315
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0320
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0320
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0320
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0325
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0325
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0325
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0330
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0330
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0335
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0335
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0340
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0340
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0340
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0345
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0345
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0345
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0350
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0350
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0355
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0355
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0355
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0360
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0360
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0360
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0365
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0365
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0365
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0370
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0370
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0375
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0375
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0375
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0380
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0380
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0380
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0385
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0385
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0385
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0390
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0390
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0390
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0395
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0395
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0395
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0400
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0400
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0405
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0405
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0410
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0410
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0410
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0415
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0415
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0415
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0420
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0420
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0420
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0425
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0425
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0425
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0430
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0430
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0435
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0435
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0440
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0440
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0445
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0445
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0445
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0450
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0450
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0455
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0455
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0460
http://refhub.elsevier.com/S1359-6101(17)30188-0/sbref0460
Crit. Care Med. 43 (9) (2015) 1945–1951.
[93] F.B. Mayr, S. Yende, D.C. Angus, Epidemiology of severe sepsis, Virulence 5 (1)
(2014) 4–11.
[94] L.F. Huang, et al., Association between regulatory T cell activity and sepsis and
outcome of severely burned patients: a prospective, observational study, Crit. Care
14 (1) (2010) p. R3.
[95] D. McDonald, et al., Extreme dysbiosis of the microbiome in critical illness,
mSphere 1 (4) (2016).
[96] R.P. Dickson, The microbiome and critical illness, Lancet Respir. Med. 4 (1) (2016)
59–72.
[97] M.C. Jacobs, et al., Gut microbiota and host defense in critical illness, Curr. Opin.
Crit. Care 23 (4) (2017) 257–263.
[98] L.A. Lobo, C.F. Benjamim, A.C. Oliveira, The interplay between microbiota and
inflammation: lessons from peritonitis and sepsis, Clin. Transl. Immunol. 5 (7)
(2016) e90.
[99] P.E. Wischmeyer, D. McDonald, R. Knight, Role of the microbiome: probiotics, and
‘dysbiosis therapy' in critical illness, Curr. Opin. Crit. Care 22 (4) (2016) 347–353.
[100] P. Panigrahi, et al., A randomized synbiotic trial to prevent sepsis among infants in
rural India, Nature 548 (7668) (2017) 407–412.
[101] R. Gresse, et al., Gut microbiota dysbiosis in postweaning piglets: understanding
the keys to health, Trends Microbiol. 25 (10) (2017) 851–873.
[102] V.T. Rist, et al., Impact of dietary protein on microbiota composition and activity
in the gastrointestinal tract of piglets in relation to gut health: a review, Animal 7
(7) (2013) 1067–1078.
[103] J. Lallès, et al., Weaning – a challenge to gut physiologists, Livestock Sci. 108
(1–3) (2007) 82–93.
[104] X. Tao, Z. Xu, J. Wan, Intestinal microbiota diversityand expression of pattern
recognition receptors in newly weaned piglets, Anaerobe 32 (2015) 51–56.
[105] Y. Su, et al., Changes in abundance of Lactobacillus spp. and Streptococcus suis in
the stomach: jejunum and ileum of piglets after weaning, FEMS Microbiol. Ecol. 66
(3) (2008) 546–555.
[106] S.R. Konstantinov, et al., Post-natal development of the porcine microbiota com-
position and activities, Environ. Microbiol. 8 (7) (2006) 1191–1199.
[107] S. Dou, et al., Characterisation of early-life fecal microbiota in susceptible and
healthy pigs to post-weaning diarrhoea, PLoS One 12 (1) (2017) e0169851.
[108] H.K. Wei, et al., A carvacrol-thymol blend decreased intestinal oxidative stress and
influenced selected microbes without changing the messenger RNA levels of tight
junction proteins in jejunal mucosa of weaning piglets, Animal 11 (2) (2017)
193–201.
[109] M.D. Barton, Impact of antibiotic use in the swine industry, Curr. Opin. Microbiol.
19 (2014) 9–15.
[110] J. Liedtke, W. Vahjen, In vitro antibacterial activity of zinc oxide on a broad range
of reference strains of intestinal origin, Vet. Microbiol. 160 (1–2) (2012) 251–255.
[111] Y. Feng, et al., Zinc oxide nanoparticles influence microflora in ileal digesta and
correlate well with blood metabolites, Front. Microbiol. 8 (2017) 992.
[112] J. Shen, et al., Coated zinc oxide improves intestinal immunity function and reg-
ulates microbiota composition in weaned piglets, Br. J. Nutr. 111 (12) (2014)
2123–2134.
[113] T. Yu, et al., Dietary high zinc oxide modulates the microbiome of ileum and colon
in weaned piglets, Front. Microbiol. 8 (2017) 825.
[114] W. Panpetch, et al., Lactobacillus rhamnosus L34 attenuates gut translocation
induced bacterial sepsis in murine models of leaky gut, Infect. Immun. 19 (86(1))
(2017).
[115] L. Chen, et al., Probiotic pre-administration reduces mortality in a mouse model of
cecal ligation and puncture-induced sepsis, Exp. Ther. Med. 12 (3) (2016)
1836–1842.
[116] G. Athalye-Jape, S. Rao, S. Patole, Lactobacillus reuteri DSM 17938 as a probiotic
for preterm neonates: a strain-specific systematic review, JPEN. J. Parenter.
Enteral Nutr. 40 (6) (2016) 783–794.
[117] A. Pararajasingam, J. Uwagwu, Lactobacillus: the not so friendly bacteria, BMJ
Case Rep. 2017 (2017).
[118] M. Sherid, et al., Liver abscess and bacteremia caused by lactobacillus: role of
probiotics? Case report and review of the literature, BMC Gastroenterol. 16 (1)
(2016) 138.
[119] M. Molinaro, et al., Lactobacillus Rhamnosus sepsis in a preterm infant associated
with probiotic integrator use: a case report, Recenti Prog. Med. 107 (9) (2016)
485–486.
[120] H.S. Kulkarni, C.C. Khoury, Sepsis associated with Lactobacillus bacteremia in a
patient with ischemic colitis, Indian J. Crit. Care Med. 18 (9) (2014) 606–608.
[121] J.P. Zackular, et al., Dietary zinc alters the microbiota and decreases resistance to
Clostridium difficile infection, Nat. Med. 22 (11) (2016) 1330–1334.
[122] S. Reed, et al., Chronic zinc deficiency alters chick gut microbiota composition and
function, Nutrients 7 (12) (2015) 9768–9784.
[123] A. Giongo, et al., Toward defining the autoimmune microbiome for type 1 dia-
betes, ISME J. 5 (1) (2011) 82–91.
[124] C. Manichanh, et al., Reduced diversity of faecal microbiota in Crohn's disease
revealed by a metagenomic approach, Gut 55 (2) (2006) 205–211.
[125] D.A. Capdevila, J. Wang, D.P. Giedroc, Bacterial strategies to maintain zinc me-
tallostasis at the host-Pathogen interface, J. Biol. Chem. 291 (40) (2016)
20858–20868.
[126] F. Wang, et al., Butyrate pretreatment attenuates heart depression in a mice model
of endotoxin-induced sepsis via anti-inflammation and anti-oxidation, Am. J.
Emerg. Med. 35 (3) (2017) 402–409.
[127] F. Wang, et al., The inflammation induced by lipopolysaccharide can be mitigated
by short-chain fatty acid: butyrate, through upregulation of IL-10 in septic shock,
Scand. J. Immunol. 85 (4) (2017) 258–263.
[128] T. Yamada, et al., Rapid and sustained long-Term decrease of fecal short-chain
fatty acids in critically ill patients with systemic inflammatory response syndrome,
JPEN. J. Parenter. Enteral Nutr. 39 (5) (2015) 569–577.
[129] G.D. Kitsios, et al., Dysbiosis in the intensive care unit: microbiome science coming
to the bedside, J. Crit. Care 38 (2017) 84–91.
[130] D. Li, et al., A pleiotropic missense variant in SLC39A8 is associated with crohn's
disease and human gut microbiome composition, Gastroenterology 151 (4) (2016)
724–732.
[131] K.L. Ormerod, et al., Genomic characterization of the uncultured Bacteroidales
family S24-7 inhabiting the guts of homeothermic animals, Microbiome 4 (1)
(2016) 36.
[132] C. Zhang, et al., Paneth cell ablation in the presence of Klebsiella pneumoniae
induces necrotizing enterocolitis (NEC)-like injury in the small intestine of im-
mature mice, Dis. Model Mech. 5 (4) (2012) 522–532.
[133] M. Cerasi, S. Ammendola, A. Battistoni, Competition for zinc binding in the host-
pathogen interaction, Front. Cell. Infect. Microbiol. 3 (2013) 108.
[134] H.S. Garmory, R.W. Titball, ATP-binding cassette transporters are targets for the
development of antibacterial vaccines and therapies, Infect. Immun. 72 (12)
(2004) 6757–6763.
[135] L.M. Gielda, V.J. DiRita, Zinc competition among the intestinal microbiota, MBio 3
(4) (2012) pe00171–12.
[136] M. Pesciaroli, et al., Salmonella Typhimurium lacking the Znuabc transporter is
attenuated and immunogenic in pigs, Vaccine 31 (27) (2013) 2868–2873.
[137] P. Talukder, et al., Trace metal zinc stimulates secretion of antimicrobial peptide
LL-37 from Caco-2 cells through ERK and p38 MAP kinase, Int.
Immunopharmacol. 11 (1) (2011) 141–144.
[138] H.C. Clevers, C.L. Bevins, Paneth cells: maestros of the small intestinal crypts,
Annu. Rev. Physiol. 75 (2013) 289–311.
[139] R. Okumura, et al., Lypd8 promotes the segregation of flagellated microbiota and
colonic epithelia, Nature 532 (7597) (2016) 117–121.
[140] L.J. Giblin, et al., Zinc-secreting paneth cells studied by ZP fluorescence, J.
Histochem. Cytochem. 54 (3) (2006) 311–316.
[141] M. Wang, et al., Human peptidoglycan recognition proteins require zinc to kill
both gram-positive and gram-negative bacteria and are synergistic with anti-
bacterial peptides, J. Immunol. 178 (5) (2007) 3116–3125.
[142] E. Crouser, et al., Sepsis: links between pathogen sensing and organ damage, Curr.
Pharm. Des. 14 (19) (2008) 1840–1852.
[143] E. Abraham, Nuclear factor-kappaB and its role in sepsis-associated organ failure,
J. Infect. Dis. 187 (Suppl 2) (2003) S364–9.
[144] F. Arnalich, et al., Predictive value of nuclear factor kappaB activity and plasma
cytokine levels in patients with sepsis, Infect Immun. 68 (4) (2000) 1942–1945.
[145] H. Böhrer, et al., Role of NFkappaB in the mortality of sepsis, J. Clin. Invest. 100
(5) (1997) 972–985.
[146] A.S. Prasad, et al., Zinc activates NF-kappaB in HUT-78 cells, J. Lab. Clin. Med.
138 (4) (2001) 250–256.
[147] V. von Bülow, et al., Zinc-dependent suppression of TNF-alpha production is
mediated by protein kinase A-induced inhibition of Raf-1: I kappa B kinase beta,
and NF-kappa B, J. Immunol. 179 (6) (2007) 4180–4186.
[148] M.J. Liu, et al., ZIP8 regulates host defense through zinc-mediated inhibition of
NF-κB, Cell Rep. 3 (2) (2013) 386–400.
[149] M. Lork, K. Verhelst, R. Beyaert, CYLD, A20 and OTULIN deubiquitinases in NF-κB
signaling and cell death: so similar, yet so different, Cell Death Differ. 24 (7)
(2017) 1172–1183.
[150] A.S. Prasad, et al., Antioxidant effect of zinc in humans, Free Radic. Biol. Med. 37
(8) (2004) 1182–1190.
[151] A.S. Prasad, et al., Zinc-suppressed inflammatory cytokines by induction of A20-
mediated inhibition of nuclear factor-κB, Nutrition 27 (7–8) (2011) 816–823.
[152] C. Li, et al., Maternal high-zinc diet attenuates intestinal inflammation by reducing
DNA methylation and elevating H3K9 acetylation in the A20 promoter of offspring
chicks, J. Nutr. Biochem. 26 (2) (2015) 173–183.
[153]