Endogenous monocyte chemoattractant protein-1 (MCP-1) protects mice in a model of acute septic peritonitis: cross-talk between MCP-1 and leukotriene B4

We investigated the involvement of monocyte chemoattractant protein (MCP)-1 in a murine model of septic peritonitis induced by cecal ligation and puncture (CLP). Initial studies demonstrated that CLP induced a dramatic increase in MCP-1 production in the peritoneum, followed by an increase in the recruitment of leukocytes. MCP-1 blockade with anti-MCP-1 antiserum significantly decreased the survival rate following CLP, which was accompanied by an enhanced recovery of viable bacteria from the peritoneum. This was likely due to the reduction in the recruitment and activation of both macrophages and neutrophils. To understand the mechanisms whereby MCP-1 may influence neutrophil infiltration, levels of chemokines known to attract neutrophils were monitored, which showed that peritoneal levels of macrophage-inflammatory protein (MIP)-2, KC, and MIP-1alpha were not altered with anti-MCP-1 Abs. However, anti-MCP-1 Abs reduced the peritoneal levels of leukotriene B4 (LTB4) by 59%. The i.p. injection of MCP-1 into normal mice resulted in elevated levels of LTB4 in the peritoneum. In vitro, MCP-1 stimulated the production of LTB4 from peritoneal macrophages, in a dose-dependent manner. A specific LTB4 receptor antagonist (CP-105, 696) inhibited CLP-induced recruitment of both neutrophils and macrophages, which was accompanied by a reduced level of MCP-1 in the peritoneum. Finally, administration of CP-105,696 was extremely detrimental to the survival of mice following CLP. These experiments demonstrate that endogenous MCP-1 serves as an indirect mediator to attract neutrophils via the production of LTB4, and suggest the cross-talk can occur between MCP-1 and the lipid mediator LTB4 during septic peritonitis.     

C1 inhibitor-mediated protection from sepsis

C1 inhibitor (C1INH) protects mice from lethal Gram-negative bacterial LPS-induced endotoxin shock and blocks the binding of LPS to the murine macrophage cell line, RAW 264.7, via an interaction with lipid A. Using the cecal ligation and puncture (CLP) model for sepsis in mice, treatment with C1INH improved survival in comparison with untreated controls. The effect was not solely the result of inhibition of complement and contact system activation because reactive center-cleaved, inactive C1INH (iC1INH) also was effective. In vivo, C1INH and iC1INH both reduced the number of viable bacteria in the blood and peritoneal fluid and accelerated killing of bacteria by blood neutrophils and peritoneal macrophages. In vitro, C1INH bound to bacteria cultured from blood or peritoneal fluid of mice with CLP-induced sepsis, but had no direct effect on bacterial growth. However, both C1INH and iC1INH enhanced the bactericidal activity of blood neutrophils and peritoneal exudate leukocytes. C1INH-deficient mice (C1INH-/- mice) subjected to CLP had a higher mortality than did wild-type littermate mice. Survival of C1INH-/- mice was significantly increased with two doses of C1INH, one given immediately following CLP, and the second at 6 h post-CLP. C1INH may be important in protection from sepsis through enhancement of bacterial uptake by, and/or bactericidal capacity of, phagocytes. Treatment with C1INH may provide a useful additional therapeutic approach in some patients with peritonitis and/or sepsis.     

Cystathionine-γ-lyase gene silencing with siRNA in monocytes/macrophages attenuates inflammation in cecal ligation and puncture-induced sepsis in the mouse

Hydrogen sulphide is an endogenous inflammatory mediator produced by cystathionine-γ-lyase (CSE) in macrophages. To determine the role of H₂S and macrophages in sepsis, we used small interference RNA (siRNA) to target the CSE gene and investigated its effect in a mouse model of sepsis. Cecal ligation puncture (CLP)-induced sepsis is characterized by increased levels of myeloperoxidase (MPO) activity, morphological changes in liver and pro-inflammatory cytokines and chemokines in the liver and lung. SiRNA treatment attenuated inflammation in the liver and lungs of mice following CLP-induced sepsis. Liver MPO activity increased in CLP-induced sepsis and treatment with siRNA significantly reduced this. Similarly, lung MPO activity increased following induction of sepsis with CLP while siRNA treatment significantly reduced MPO activity. Liver and lung cytokine and chemokine levels in CLP-induced sepsis reduced following treatment with siRNA. These findings show a crucial pro-inflammatory role for H₂S synthesized by CSE in macrophages in sepsis and suggest CSE gene silencing with siRNA as a potential therapeutic approach for this condition.     

A2B adenosine receptor blockade enhances macrophage-mediated bacterial phagocytosis and improves polymicrobial sepsis survival in mice

Antimicrobial treatment strategies must improve to reduce the high mortality rates in septic patients. In noninfectious models of acute inflammation, activation of A2B adenosine receptors (A2BR) in extracellular adenosine-rich microenvironments causes immunosuppression. We examined A2BR in antibacterial responses in the cecal ligation and puncture (CLP) model of sepsis. Antagonism of A2BR significantly increased survival, enhanced bacterial phagocytosis, and decreased IL-6 and MIP-2 (a CXC chemokine) levels after CLP in outbred (ICR/CD-1) mice. During the CLP-induced septic response in A2BR knockout mice, hemodynamic parameters were improved compared with wild-type mice in addition to better survival and decreased plasma IL-6 levels. A2BR deficiency resulted in a dramatic 4-log reduction in peritoneal bacteria. The mechanism of these improvements was due to enhanced macrophage phagocytic activity without augmenting neutrophil phagocytosis of bacteria. Following ex vivo LPS stimulation, septic macrophages from A2BR knockout mice had increased IL-6 and TNF-α secretion compared with wild-type mice. A therapeutic intervention with A2BR blockade was studied by using a plasma biomarker to direct therapy to those mice predicted to die. Pharmacological blockade of A2BR even 32 h after the onset of sepsis increased survival by 65% in those mice predicted to die. Thus, even the late treatment with an A2BR antagonist significantly improved survival of mice (ICR/CD-1) that were otherwise determined to die according to plasma IL-6 levels. Our findings of enhanced bacterial clearance and host survival suggest that antagonism of A2BRs offers a therapeutic target to improve macrophage function in a late treatment protocol that improves sepsis survival.     

Immunomodulatory role of CXCR2 during experimental septic peritonitis

The loss of CXCR2 expression by neutrophils is a well-described, but poorly understood, consequence of clinical sepsis. To address the potential impact of this CXCR2 deficit during the septic response, we examined the role of CXCR2 in a murine model of septic peritonitis provoked by cecal ligation and puncture (CLP). CLP-induced mouse mortality was significantly attenuated with i.v. or i.p. administration of an affinity-purified murine CXCR2-specific polyclonal Ab. Mouse survival required Ab administration before and every 2 days following CLP. Furthermore, mice deficient in CXCR2 (CXCR2(-/-)) were significantly protected against CLP-induced mortality compared with control (CXCR2(+/+)) mice. The anti-CXCR2 Ab treatment delayed, but did not completely inhibit, the recruitment of leukocytes, specifically neutrophils, into the peritoneal cavity. Peritoneal macrophages from anti-CXCR2 Ab-treated mice exhibited markedly increased RNA and protein levels of several key proinflammatory cytokines and chemokines. Specifically, isolated preparations of these cells released approximately 11-fold more CXCL10 protein compared with peritoneal macrophages from control-treated or naive mice. CXCR2(-/-) mice had higher resting and CLP-induced levels of peritoneal CXCL10 compared with CXCR2(+/+) mice. Administration of a neutralizing, affinity-purified, murine CXCL10-specific polyclonal Ab before CLP in wild-type mice and every 2 days after surgery significantly increased mortality compared with control Ab-treated mice. Anti-CXCL10 treatment in CXCR2(-/-) mice negated the protective effect associated with the absence of CXCR2. In summary, these data demonstrate that the absence of CXCR2 protects mice from septic injury potentially by delaying inflammatory cell recruitment and enhancing CXCL10 expression in the peritoneum.     

Early enhanced local neutrophil recruitment in peritonitis-induced sepsis improves bacterial clearance and survival

Neutrophils are critical for the rapid eradication of bacterial pathogens, but they also contribute to the development of multiple organ failure in sepsis. We hypothesized that increasing early recruitment of neutrophils to the focus of infection will increase bacterial clearance and improve survival. Sepsis was induced in mice, using cecal ligation and puncture (CLP); blood samples were collected at 6 and 24 h; and survival was followed for 28 d. In separate experiments, peritoneal bacteria and inflammatory cells were measured. Septic mice predicted to die based on IL-6 levels (Die-P) had higher concentrations of CXCL1 and CXCL2 in the peritoneum and plasma compared with those predicted to live (Live-P). At 6 h, Live-P and Die-P had equivalent numbers of peritoneal neutrophils and bacteria. In Die-P mice the number of peritoneal bacteria increased between 6 and 24 h post-CLP, whereas in Live-P it decreased. The i.p. injection of CXCL1 and CXCL2 in naive mice resulted in local neutrophil recruitment. When given immediately after CLP, CXC chemokines increased peritoneal neutrophil recruitment at 6 h after CLP. This early increase in neutrophils induced by exogenous chemokines resulted in significantly fewer peritoneal bacteria by 24 h [CFU (log) = 6.04 versus 4.99 for vehicle versus chemokine treatment; p < 0.05]. Chemokine treatment significantly improved survival at both 5 d (40 versus 72%) and 28 d (27 versus 52%; p < 0.02 vehicle versus chemokines). These data demonstrate that early, local treatment with CXC chemokines enhances neutrophil recruitment and clearance of bacteria as well as improves survival in the CLP model of sepsis.     

NK but not CD1-restricted NKT cells facilitate systemic inflammation during polymicrobial intra-abdominal sepsis

Evidence suggests that NK and NKT cells contribute to inflammation and mortality during septic shock caused by cecal ligation and puncture (CLP). However, the specific contributions of these cell types to the pathogenesis of CLP-induced septic shock have not been fully defined. The goal of the present study was to determine the mechanisms by which NK and NKT cells mediate the host response to CLP. Control, NK cell-deficient, and NKT cell-deficient mice underwent CLP. Survival, cytokine production, and bacterial clearance were measured. NK cell trafficking and interaction with myeloid cells was also studied. Results show that mice treated with anti-asialoGM1 (NK cell deficient) or anti-NK1.1 (NK/NKT cell deficient) show less systemic inflammation and have improved survival compared with IgG-treated controls. CD1 knockout mice (NKT cell deficient) did not demonstrate decreased cytokine production or improved survival compared with wild type mice. Trafficking studies show migration of NK cells from blood and spleen into the inflamed peritoneal cavity where they appear to facilitate the activation of peritoneal macrophages (F4-80(+)GR-1(-)) and F4-80(+)Gr-1(+) myeloid cells. These findings indicate that NK but not CD1-restricted NKT cells contribute to acute CLP-induced inflammation. NK cells appear to mediate their proinflammatory functions during septic shock, in part, by migration into the peritoneal cavity and amplification of the proinflammatory activities of specific myeloid cell populations. These findings provide new insights into the mechanisms used by NK cells to facilitate acute inflammation during septic shock.     

Role of CC chemokine CCL6/C10 as a monocyte chemoattractant in a murine acute peritonitis

The aim of this study was to determine the role of CC chemokine CCL6/C10 in acute inflammation. Intraperitoneal injection of thioglycollate increased peritoneal CCL6, which peaked at 4 h and remained elevated at 48 h. Neutralization of CCL6 significantly inhibited the macrophage infiltration (34-48% reduction), but not other cell types, without decreasing the other CC chemokines known to attract monocytes/macrophages. CCL6 was expressed in peripheral eosinophils and elicited macrophages, but not in elicited neutrophils. Peritoneal CCL6 level was not decreased in granulocyte-depleted mice where eosinophil influx was significantly impaired. Thus, CCL6 appears to contribute to the macrophage infiltration that is independent of other CC chemokines. Eosinophils pre-store CCL6, but do not release CCL6 in the peritoneum in this model of inflammation.     

Expression and contribution of endogenous IL-13 in an experimental model of sepsis

IL-13 has been shown to exert potent anti-inflammatory properties. In this study, we elucidated the functional role of endogenous IL-13 in a murine model of septic peritonitis induced by cecal ligation and puncture (CLP). Initial studies demonstrated that the level of IL-13 increased in tissues including liver, lung, and kidney, whereas no considerable increase was found in either peritoneal fluid or serum after CLP. Immunohistochemically, IL-13-positive cells were Kupffer cells in liver, alveolar macrophages in lung, and epithelial cells of urinary tubules in kidney. IL-13 blockade with anti-IL-13 Abs significantly decreased the survival rate of mice after CLP from 53% to 14% on day 7 compared with control. To determine the potential mechanisms whereby IL-13 exerted a protective role in this model, the effects of anti-IL-13 Abs on both local and systemic inflammation were investigated. Administration of anti-IL-13 Abs did not alter the leukocyte infiltration and bacterial load in the peritoneum after CLP but dramatically increased the neutrophil influx in tissues after CLP, an effect that was accompanied by significant increases in the serum levels of aspartate transaminase, alanine transaminase, blood urea nitrogen, and creatinine. Tissue injury caused by IL-13 blockade was associated with increases in mRNA and the protein levels of CXC chemokines macrophage inflammatory protein-2 and KC as well as the CC chemokine macrophage inflammatory protein-1alpha and the proinflammatory cytokine TNF-alpha. Collectively, these results suggest that endogenous IL-13 protected mice from CLP-induced lethality by modulating inflammatory responses via suppression of overzealous production of inflammatory cytokines/chemokines in tissues.     

Contributory Role of BLT2 in the Production of Proinflammatory Cytokines in Cecal Ligation and Puncture-Induced Sepsis

BLT2 is a low-affinity receptor for leukotriene B₄, a potent lipid mediator of inflammation generated from arachidonic acid via the 5-lipoxygenase pathway. The aim of this study was to investigate whether BLT2 plays any role in sepsis, a systemic inflammatory response syndrome caused by infection. A murine model of cecal ligation and puncture (CLP)-induced sepsis was used to evaluate the role of BLT2 in septic inflammation. In the present study, we observed that the levels of ligands for BLT2 (LTB₄ [leukotriene B₄] and 12(S)-HETE [12(S)-hydroxyeicosatetraenoic acid]) were significantly increased in the peritoneal lavage fluid and serum from mice with CLP-induced sepsis. We also observed that the levels of BLT2 as well as 5-lipoxygenase (5-LO) and 12-LO, which are synthesizing enzymes for LTB₄ and 12(S)-HETE, were significantly increased in lung and liver tissues in the CLP mouse model. Blockade of BLT2 markedly suppressed the production of sepsis-associated cytokines (IL-6 [interleukin-6], TNF-α[[tumor necrosis factor alpha], and IL-1β [interleukin-1β] as well as IL-17 [interleukin-17]) and alleviated lung inflammation in the CLP group. Taken together, our results suggest that BLT2 cascade contributes to lung inflammation in CLP-induced sepsis by mediating the production of inflammatory cytokines. These findings suggest that BLT2 may be a potential therapeutic target for sepsis patients.     

Therapeutic effects of lysophosphatidylcholine in experimental sepsis

Sepsis represents a major cause of death in intensive care units. Here we show that administration of lysophosphatidylcholine (LPC), an endogenous lysophospholipid, protected mice against lethality after cecal ligation and puncture (CLP) or intraperitoneal injection of Escherichia coli. In vivo treatment with LPC markedly enhanced clearance of intraperitoneal bacteria and blocked CLP-induced deactivation of neutrophils. In vitro, LPC increased bactericidal activity of neutrophils, but not macrophages, by enhancing H(2)O(2) production in neutrophils that ingested E. coli. Incubation with an antibody to the LPC receptor, G2A, inhibited LPC-induced protection from CLP lethality and inhibited the effects of LPC in neutrophils. G2A-specific antibody also blocked the inhibitory effects of LPC on certain actions of lipopolysaccharides (LPS), including lethality and the release of tumor necrosis factor-alpha (TNF-alpha) from neutrophils. These results suggest that LPC can effectively prevent and treat sepsis and microbial infections.     

Role of A2A adenosine receptors in regulation of opsonized E. coli-induced macrophage function

Adenosine is a biologically active molecule that is formed at sites of metabolic stress associated with trauma and inflammation, and its systemic level reaches high concentrations in sepsis. We have recently shown that inactivation of A_2A adenosine receptors decreases bacterial burden as well as IL-10, IL-6, and MIP-2 production in mice that were made septic by cecal ligation and puncture (CLP). Macrophages are important in both elimination of pathogens and cytokine production in sepsis. Therefore, in the present study, we questioned whether macrophages are responsible for the decreased bacterial load and cytokine production in A_2A receptor-inactivated septic mice. We showed that A_2A KO and WT peritoneal macrophages obtained from septic animals were equally effective in phagocytosing opsonized E. coli. IL-10 production induced by opsonized E. coli was decreased in macrophages obtained from septic A_2A KO mice as compared to WT counterparts. In contrast, the release of IL-6 and MIP-2 induced by opsonized E. coli was higher in septic A_2A KO macrophages than WT macrophages. These results suggest that peritoneal macrophages are not responsible for the decreased bacterial load and diminished MIP-2 and IL-6 production that are observed in septic A_2A KO mice. In contrast, peritoneal macrophages may contribute to the suppressive effect of A_2A receptor inactivation on IL-10 production during sepsis.     

Role of alveolar macrophage and migrating neutrophils in hemorrhage-induced priming for ALI subsequent to septic challenge

Acute lung injury (ALI) is identified with the targeting/sequestration of polymorphonuclear leukocytes (PMN) to the lung. Instrumental to PMN targeting are chemokines [e.g., macrophage inflammatory protein-2 (MIP-2), keratinocyte-derived chemokine (KC), etc.] produced by macrophage, PMN, and other resident pulmonary cells. However, the relative contribution of resident pulmonary macrophages as opposed to PMN in inducing ALI is poorly understood. We therefore hypothesize that depletion of peripheral blood PMN and/or the oblation of a macrophage-mediated PMN chemokine signal (via macrophage deficiency) will reduce the inflammation and ALI observed in mice following hemorrhage (Hem) and subsequent sepsis (CLP) in our murine model of ALI. To examine this we pretreated mice with either 500 microg anti-mouse Gr1 antibody/animal (to deplete PMN) or subjected mice deficient in mature macrophage (B6C3Fe-a/a-CsF1op) to Hem (90 min at 35 +/- 5 mmHg) followed by resuscitation. Twenty-four hours post-Hem, mice were subjected to CLP and killed 24 h later, and lung tissue samples were collected. Our data showed that in the absence of either peripheral blood PMN or mature tissue macrophages there was a suppression of IL-6, KC, and MIP-2 levels in lung tissue from Hem/CLP mice as well as a reduction in PMN influx to the lung and lung injury (bronchoalveolar lavage fluid protein). In contrast, lung tissue IL-10 and TNF-alpha levels were suppressed in the macrophage-deficient Hem/CLP mice compared with PMN-depleted Hem/CLP mice. Together, these data suggest that both the PMN and the macrophage are required to induce inflammation seen here, however, macrophage not PMN regulate the release of IL-10, independent of local changes in TNF.     

TRPV1 deletion enhances local inflammation and accelerates the onset of systemic inflammatory response syndrome

The transient receptor potential vanilloid 1 (TRPV1) is primarily localized to sensory nerve fibers and is associated with the stimulation of pain and inflammation. TRPV1 knockout (TRPV1KO) mice show enhanced LPS-induced sepsis compared with wild type (WT). This implies that TRPV1 may have a key modulatory role in increasing the beneficial and reducing the harmful components in sepsis. We investigated immune and inflammatory mechanisms in a cecal ligation and puncture (CLP) model of sepsis over 24 h. CLP TRPV1KO mice exhibited significant hypothermia, hypotension, and organ dysfunction compared with CLP WT mice. Analysis of the inflammatory responses at the site of initial infection (peritoneal cavity) revealed that CLP TRPV1KO mice exhibited: 1) decreased mononuclear cell integrity associated with apoptosis, 2) decreased macrophage tachykinin NK(1)-dependent phagocytosis, 3) substantially decreased levels of nitrite (indicative of NO) and reactive oxygen species, 4) increased cytokine levels, and 5) decreased bacteria clearance when compared with CLP WT mice. Therefore, TRPV1 deletion is associated with impaired macrophage-associated defense mechanisms. Thus, TRPV1 acts to protect against the damaging impact of sepsis and may influence the transition from local to a systemic inflammatory state.     

Neutralisation of Peritoneal IL-17A Markedly Improves the Prognosis of Severe Septic Mice by Decreasing Neutrophil Infiltration and Proinflammatory Cytokines

Purpose

The current study aimed to elucidate the role of peritoneal fluid IL-17A in septic mice, and the effects of intraperitoneal or intravenous blockade of the IL-17A pathway by anti-IL17A antibody on survival, plasma, and peritoneal cavity cytokine profile in a murine caecal ligation and puncture (CLP) sepsis model. The main source of peritoneal fluid IL-17A in septic mice was identified.

Methods

Male C57BL/6 mice that underwent severe CLP or sham surgery were intraperitoneally or intravenously administered anti-IL17A antibodies or isotype antibodies. The survival rates were observed. IL-17A, TNF-α, and IL-6 cytokine levels were measured by ELISA. Surface and intracellular IL-17A immunofluorescence stains were detected by flow cytometry to identify the IL-17A–producing cells.

Results

The IL-17A level was elevated much higher and earlier in peritoneal fluid than in the blood of the CLP mice. The intraperitoneal IL-17A blockade more significantly protects against CLP-induced mortality than intravenous blockade because of decreased TNF-α and IL-6 levels both in peritoneal fluid and blood, neutrophil infiltration in the peritoneal cavity, and lung injury. γδ T lymphocytes were identified to be the main source of IL-17A in the peritoneal fluid of septic mice.

Conclusions

The earlier and higher elevated IL-17A derived from γδ T cells in peritoneal fluid plays a critical role during polymicrobial severe sepsis and effect of intraperitoneal IL-17A antibody administration superior to intravenous administration on survival of severe CLP-induced septic mice. The intraperitoneal blockade of IL-17A decreases proinflammatory cytokine production, neutrophil infiltration, and lung injury, thereby improving septic mice survival, which provides a new potential therapy target for sepsis.     

Glucan phosphate attenuates cardiac dysfunction and inhibits cardiac MIF expression and apoptosis in septic mice

Myocardial dysfunction is a major consequence of septic shock and contributes to the high mortality of sepsis. We have previously reported that glucan phosphate (GP) significantly increased survival in a murine model of cecal ligation and puncture (CLP)-induced sepsis. In the present study, we examined the effect of GP on cardiac dysfunction in CLP-induced septic mice. GP was administered to ICR/HSD mice 1 h before induction of CLP. Sham surgically operated mice served as control. Cardiac function was significantly decreased 6 h after CLP-induced sepsis compared with sham control. In contrast, GP administration prevented CLP-induced cardiac dysfunction. Macrophage migration inhibitory factor (MIF) has been implicated as a major factor in cardiomyocyte apoptosis and cardiac dysfunction during septic shock. CLP increased myocardial MIF expression by 88.3% (P < 0.05) and cardiomyocyte apoptosis by 7.8-fold (P < 0.05) compared with sham control. GP administration, however, prevented CLP-increased MIF expression and decreased cardiomyocyte apoptosis by 51.2% (P < 0.05) compared with untreated CLP mice. GP also prevented sepsis-caused decreases in phospho-Akt, phospho-GSK-3beta, and Bcl-2 levels in the myocardium of septic mice. These data suggest that GP treatment attenuates cardiovascular dysfunction in fulminating sepsis. GP administration also activates the phosphoinositide 3-kinase/Akt pathway, decreases myocardial MIF expression, and reduces cardiomyocyte apoptosis.     

Role of hydrogen sulfide in cecal ligation and puncture-induced sepsis in the mouse

Endogenous hydrogen sulfide (H(2)S) is naturally synthesized in various types of mammalian cells from l-cysteine in a reaction catalyzed by two enzymes, cystathionine-gamma-lyase (CSE) and/or cystathionine-beta-synthase. The latest studies have implied that H(2)S functions as a vasodilator and neurotransmitter. However, so far there is little information about the role played by H(2)S in systemic inflammation such as sepsis. Thus the aim of this study was to investigate the potential role of endogenous H(2)S in cecal ligation and puncture (CLP)-induced sepsis. Male Swiss mice were subjected to CLP-induced sepsis and treated with saline (ip), dl-propargylglycine (PAG, 50 mg/kg ip), a CSE inhibitor, or sodium hydrosulfide (NaHS; 10 mg/kg ip). PAG was administered either 1 h before or 1 h after the induction of sepsis, whereas NaHS was given at the same time of CLP. CLP-induced sepsis significantly increased the plasma H(2)S level and the liver H(2)S synthesis 8 h after CLP compared with sham operation. Induction of sepsis also resulted in a significant upregulation of CSE mRNA in liver. On the other hand, prophylactic as well as therapeutic administration of PAG significantly reduced sepsis-associated systemic inflammation, as evidenced by myeloperoxidase activity and histological changes in lung and liver, and attenuated the mortality of CLP-induced sepsis. Injection of NaHS significantly aggravated sepsis-associated systemic inflammation. Therefore, the effect of inhibition of H(2)S formation and administration of NaHS suggests that H(2)S plays a proinflammatory role in regulating the severity of sepsis and associated organ injury.     

Overexpression of suppressor of cytokine signaling-5 in T cells augments innate immunity during septic peritonitis

Suppressors of cytokine signaling (SOCS) proteins are negative regulators of cytokine signaling by inhibiting the JAK-STAT signal transduction pathway, but their role in innate immunity remains to be investigated. In the present study, we demonstrate that overexpression of SOCS5 in T cells augments innate immunity during septic peritonitis induced by cecal ligation and puncture (CLP). Mice with a cell-specific overexpression of SOCS5 in T cells (SOCS5 transgenic (Tg)) were resistant to the lethality relative to the wild-type (WT) mice. This was most likely due to the enhanced innate immunity in SOCS5Tg mice, as bacterial burden in SOCS5Tg mice was significantly lower than WT mice. Accumulation of neutrophils and macrophages was augmented in SOCS5Tg mice, an event that was accompanied by increased peritoneal levels of IL-12, IFN-gamma, and TNF-alpha. In vitro bactericidal activities of macrophages and neutrophils were enhanced in SOCS5Tg mice. Both neutrophils and macrophages from WT mice adopted enhanced bacterial killing activity when cocultured with CD4+ T cells from SOCS5Tg mice, relative to CD4+ T cells from WT mice. Adoptive transfer of SOCS5Tg-CD4+ T cells into T- and B cell-deficient RAG-2(-/-) mice resulted in augmented leukocyte infiltration and increased peritoneal levels of IL-12, IFN-gamma, and TNF-alpha after CLP, as compared with the controls. Furthermore, CLP-induced bacterial burden in RAG-2(-/-) mice harboring SOCS5Tg-CD4+ T cells was significantly reduced relative to the controls. These findings provide evidence that intervention of SOCS5 expression in T cells affects innate immunity, which highlight a novel role of T cells during sepsis.