Sepsis-induced Changes Research Articles

Human Leukocyte Antigen-DR Isotype Expression in Monocytes and T Cells Interferon-Gamma Release Assay in Septic Patients and Correlation With Clinical Outcome.

BackgroundSepsis is a life-threatening dysregulated host response to infection responsible of multiple organs dysfunction (Sepsis-3 International Consensus Definition), during which clinical outcome is a balance between inflammation and immune suppression. Monocytes and lymphocytes may play an important role in immune paralysis, and their impaired functional activity can decrease overall immune system efficiency. We evaluated sepsis-induced changes in monocytes human leukocyte antigen-DR isotype (HLA-DR) expression and T cell capacity of interferon (IFN)-γ production in relation with patient’s clinical outcome.MethodsAnalysis of HLA-DR expression on blood monocytes (mHLA-DR) was performed in 55 patients with high procalcitonin (hPCT, > 0.5 ng/mL,) and suspected/confirmed sepsis, and 20 controls. HLA-DR absolute quantification and IFN-γ release assay were monitored in 16 septic patients for 4 weeks following sepsis confirmation.ResultsCytofluorimetric analysis revealed a significant decrease of mHLA-DR percentage in septic patients with adverse outcome compared to patients with better clinical outcome (88.4% vs. 98.6% with P < 0.05), in combination with a significant decrease of absolute number of HLA-DR molecules per monocyte (P < 0.05, starting at 1 week of follow-up). Lymphocytes stimulation with phytohemagglutinin (PHA), Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans) showed a severe declining of IFN-γ release related to fatal clinical outcome of patients.ConclusionsThis immunologic anergy of innate and adaptative immunity showed an early immune paralysis during sepsis which appears correlated with the impairment of clinical outcome.

Wnt/β-Catenin Antagonist Pyrvinium Exerts Cardioprotective Effects in Polymicrobial Sepsis Model by Attenuating Calcium Dyshomeostasis and Mitochondrial Dysfunction.

Calcium dysregulation and mitochondrial dysfunction are key elements in the development of sepsis-induced cardiac dysfunction. Evidences have suggested that inhibition of Wnt/β-Catenin signalling prevents cardiac dysfunction and remodelling in surgical, hypertension and pressure overload models. The present study investigated the effects of Wnt/β-Catenin inhibitor on calcium overload and mitochondrial dysfunction in rat sepsis model of cardiomyopathy. Induction of sepsis by cecal ligation puncture (CLP) resulted in the up-regulation of cardiac β-catenin transcriptional levels and cardiac dysfunction depicted by increased serum lactate dehydrogenase, CK-MB levels reduced maximum (dp/dt max.) and minimum developed pressure (dp/dt min.), increased LVEsDP and relaxation constant tau values. Moreover, oxidative and inflammatory stress, immune cell infiltration, increased myeloperoxidase activity, enhanced caspase-3 activity and fibronectin protein levels were observed in septic rat's heart. Also, septic rat's heart displayed mitochondrial dysfunction due to mPTP opening, increased calcium up-regulation in left ventricular apex tissues and whole heart, increased collagen staining, necrosis and structural damage. Pre-treatment with Wnt/β-Catenin antagonist attenuated sepsis-induced serum and tissue biochemical changes, cardiac dysfunction and structural alterations by inhibiting mitochondrial mPTP opening and restricting calcium overloading in cardiac tissue.

GYY4137 alleviates sepsis-induced acute lung injury in mice by inhibiting the PDGFRβ/Akt/NF-κB/NLRP3 pathway

AimsGYY4137 [GYY, morpholin-4-ium-4-methoxyphenyl (morpholino) phosphinodithioate] is a novel and perfect hydrogen sulfide (H2S) donor that is stable in vivo and in vitro. H2S, along with CO and NO, has been recognized as the third physiological gas signaling molecule that plays an active role in fighting various lung infections. However, the mechanism by which GYY4137 affects cecal ligation and puncture (CLP)-induced acute lung injury (ALI) is not understood. This study aimed to investigate whether GYY4137 inhibits the activation of the pyrin domain-containing protein 3 (NLRP3) inflammasome by inhibiting the PDGFRβ/Akt/NF-κB pathway. Main methodsThe model of CLP-induced ALI was established in vivo. The mice were subsequently treated with GYY4137 (25 μg/g and 50 μg/g) to simulate the realistic conditions of pathogenesis. Western blotting and immunohistochemical staining were used to examine protein expression, hematoxylin and eosin staining was used for the histopathological analysis, and the levels of inflammatory factors were determined using enzyme-linked immunosorbent assays (ELISAs). Key findingsGYY4137 significantly increased the 7-day survival of mice with septic peritonitis and protected against CLP-induced ALI, including decreasing neutrophil infiltration, improving sepsis-induced lung histopathological changes, diminishing lung tissue damage, and attenuating the severity of lung injury in mice. The protective effect of GYY4137 was undoubtedly dose-dependent. We discovered that GYY4137 reduced the levels of the p-PDGFRβ, p-NF-κB, ASC, NLRP3, caspase-1, and p-Akt proteins in septic mouse lung tissue. Akt regulates the generation of proinflammatory cytokines in endotoxemia-associated ALI by enhancing the nuclear translocation of NF-κB. SignificanceThese results indicate a new molecular mechanism explaining the effect of GYY4137 on the treatment of CLP-induced ALI in mice.

Inducing Experimental Polymicrobial Sepsis by Cecal Ligation and Puncture.

Numerous models are available for the preclinical study of sepsis, and they fall into one of three general categories: (1) administration of exogenous toxins (e.g., lipopolysaccharide, zymosan), (2) virulent bacterial or viral challenge, and (3) host barrier disruption, e.g., cecal ligation and puncture (CLP) or colon ascendens stent peritonitis (CASP). Of the murine models used to study the pathophysiology of sepsis, CLP combines tissue necrosis and polymicrobial sepsis secondary to autologous fecal leakage, as well as hemodynamic and biochemical responses similar to those seen in septic humans. Further, a transient numerical reduction of multiple immune cell types, followed by development of prolonged immunoparalysis, occurs in CLP-induced sepsis just as in humans. Use of the CLP model has led to a vast expansion in knowledge regarding the intricate physiological and cellular changes that occur during and after a septic event. This updated article details the steps necessary to perform this survival surgical technique, as well as some of the obstacles that may arise when evaluating the sepsis-induced changes within the immune system. It also provides representative monoclonal antibody (mAb) panels for multiparameter flow cytometric analysis of the murine immune system in the septic host. © 2020 Wiley Periodicals LLC. Basic Protocol: Cecal ligation and puncture in the mouse.

Adipose-derived mesenchymal stem cells attenuate acute lung injury and improve the gut microbiota in septic rats

BackgroundWe hypothesized that adipose-derived mesenchymal stem cells (ADMSCs) may ameliorate sepsis-induced acute lung injury (ALI) and change microorganism populations in the gut microbiota, such as that of Firmicutes and Bacteroidetes.MethodsA total of 60 male adult Sprague-Dawley (SD) rats were separated into three groups: the sham control (SC) group, the sepsis induced by cecal ligation and puncture (CLP) group, and the ADMSC treatment (CLP-ADMSCs) group, in which rats underwent the CLP procedure and then received 1 × 106 ADMSCs. Rats were sacrificed 24 h after the SC or CLP procedures. To study the role of ADMSCs during ALI caused by sepsis and examine the impact of ADMSCs on the gut microbiome composition, rat lungs were histologically evaluated using hematoxylin and eosin (H&E) staining, serum levels of pro-inflammatory factors were detected using enzyme-linked immunosorbent assay (ELISA), and fecal samples were collected and analyzed using 16S rDNA sequencing.ResultsThe serum levels of inflammatory cytokines, tumor necrosis factor (TNF)-α and interleukin (IL)-6, were significantly increased in rats after the CLP procedure, but were significantly decreased in rats treated with ADMSCs. Histological evaluation of the rat lungs yielded results consistent with the changes in IL-6 levels among all groups. Treatment with ADMSCs significantly increased the diversity of the gut microbiota in rats with sepsis. The principal coordinates analysis (PCoA) results showed that there was a significant difference between the gut microbiota of the CLP-ADMSCs group and that of the CLP group. In rats with sepsis, the proportion of Escherichia–Shigella (P = 0.01) related to lipopolysaccharide production increased, and the proportion of Akkermansia (P = 0.02) related to the regulation of intestinal mucosal thickness and the maintenance of intestinal barrier function decreased. These changes in the gut microbiota break the energy balance, aggravate inflammatory reactions, reduce intestinal barrier functions, and promote the translocation of intestinal bacteria. Intervention with ADMSCs increased the proportion of beneficial bacteria, reduced the proportion of harmful bacteria, and normalized the gut microbiota.ConclusionsTherapeutically administered ADMSCs ameliorate CLP-induced ALI and improves gut microbiota, which provides a potential therapeutic mechanism for ADMSCs in the treatment of sepsis.

NMR-based metabolomics approach reveals effects of antioxidant nutrients in sepsis-induced changes in rat liver injury

Oxidative stress and the production of intracellular reactive oxygen species (ROS) have been implicated in the pathogenesis of sepsis. In excess, oxidative stress is not deemed an unbalanced biochemical reaction in the critically ill rats, but it is a key pathological factor in driving systemic inflammatory response that can result in multiple organ failure in sepsis. Thus, we aimed to explore whether antioxidant nutrients could reduce or delay the oxidative stress condition of sepsis rats, and then play a prospective role in the oxidative stress condition of critical disease. In this investigation, the ability of exogenous and endogenous antioxidant nutrients (ascorbate, taurine and glutathione) to prevent sepsis-induced changes in liver injury was examined using a rat model of sepsis induced by cecal ligation and puncture (CLP), and the underlying mechanisms were also investigated. The effects of three antioxidants on sepsis were assessed based on biochemical assays in combination with an NMR-based metabolomics approach and correlation network analysis. Our results suggested that ascorbate, taurine and glutathione had broadly similar protective effects on reducing oxidative stress. Compared with CLP rats, antioxidant-treated rats exhibited alleviated (P<.05) organ dysfunction and improved liver pathology. Moreover, taurine showed a better efficacy compared with ascorbate and glutathione, evidenced by significantly reversed metabolomics profiles toward normal state. Under conditions of sepsis, antioxidants suppressed inflammatory responses by restraining key signaling pathways, including the redox-sensitive transcription factor pathways of NF-κB and MAPK. Collectively, our findings suggested that antioxidant nutrients exerted beneficial effects on septic rats via protecting mitochondrial.

Emodin attenuates acute lung injury in Cecal-ligation and puncture rats

Acute lung injury (ALI) is a major cause of sepsis-induced acute respiratory failure. Emodin has been considered to play a protective role for acute lung edema in cecal ligation and puncture (CLP)-induced sepsis model. In this study we aimed to investigate whether emodin could improve CLP-induced lung sepsis via regulating aquaporin (AQP) and tight junction (TJ), inflammatory factors, and pulmonary apoptosis. The results showed that sepsis-induced pulmonary pathological changes were significantly improved after emodin treatment. Emodin was found to upregulate AQP and TJ expression in the CLP model. Meanwhile, inflammatory cytokine release and pulmonary apoptosis was remarkably reduced after emodin treatment in lung sepsis. Our data demonstrated that emodin could suppresse inflammation, restore pulmonary epithelial barrier and reduce mortality in CLP-induced ALI, suggesting the potential therapeutic application of emodin in sepsis.

The Acute Phase Response Is a Prominent Renal Proteome Change in Sepsis in Mice.

(1) Background: Sepsis-induced acute kidney injury (AKI) is the most common form of acute kidney injury (AKI). We studied the temporal profile of the sepsis-induced renal proteome changes. (2) Methods: Male mice were injected intraperitoneally with bacterial lipopolysaccharide (LPS) or saline (control). Renal proteome was studied by LC-MS/MS (ProteomeXchange: PXD014664) at the early phase (EP, 1.5 and 6 h after 40 mg/kg LPS) and the late phase (LP, 24 and 48 h after 10 mg/kg LPS) of LPS-induced AKI. Renal mRNA expression of acute phase proteins (APP) was assessed by qPCR. (3) Results: Renal proteome change was milder in EP vs. LP. APPs dominated the proteome in LP (proteins upregulated at least 4-fold (APPs/all): EP, 1.5 h: 0/10, 6 h: 1/10; LP, 24 h: 22/47, 48 h: 17/44). Lipocalin-2, complement C3, fibrinogen, haptoglobin and hemopexin were the most upregulated APPs. Renal mRNA expression preceded the APP changes with peak effects at 24 h, and indicated renal production of the majority of APPs. (4) Conclusions: Gene expression analysis revealed local production of APPs that commenced a few hours post injection and peaked at 24 h. This is the first demonstration of a massive, complex and coordinated acute phase response of the kidney involving several proteins not identified previously.

Marker Of Sepsis Severity Is Associated With The Variation In Cardio-Ankle Vascular Index (CAVI) During Sepsis Treatment.

IntroductionThe main pathophysiology of sepsis is considered to be circulation crisis with an imbalance of vasodilation and vasoconstriction mechanisms, which contributes to multiple organ failure. However, sepsis-induced hemodynamic changes have not been fully validated by novel arterial stiffness parameter. The aim of this study was to clarify the acute vascular alteration and hemodynamic change in sepsis using cardio-ankle-vascular index (CAVI).MethodsTwenty-one Japanese patients (14 males and 7 females, age 62.8 ± 19.0 years) with sepsis were recruited. CAVI was measured before and 1-week after sepsis treatment.ResultsThe leading underlying cause of sepsis was pyelonephritis, followed by pneumonia, lung abscess, hepatic abscess and cholecystitis. All subjects recovered from sepsis. Analysis of all subjects showed a significant increase in CAVI after 1-week treatment (7.9 ± 2.4 to 9.6 ± 1.8, P < 0.001), but no significant change in blood pressure (BP) was observed. Significant correlations were observed for all combinations among the change in CAVI, systolic BP and ln[procalcitonin (PCT)], respectively. Additionally, in subjects with PCT at presentation ≥2.0 ng/mL, the increase in CAVI after treatment was significantly greater compared to those with PCT < 2.0 ng/mL (2.4 ± 1.6 vs 1.1 ± 0.9, P = 0.037).DiscussionCAVI may reflect sepsis-induced vascular alteration which is not indicated by BP change, and is associated with sepsis severity. These findings suggest the usefulness of CAVI in the management of circulatory failure in sepsis patients.

Sepsis alters the transcriptional and translational landscape of human and murine platelets

AbstractThere is increasing recognition that platelets have a functional role in the pathophysiology of sepsis, though this role has not been precisely defined. Whether sepsis alters the human platelet transcriptome and translational landscape has never been established. We used parallel techniques of RNA sequencing and ribosome footprint profiling to interrogate the platelet transcriptome and translatome in septic patients and healthy donors. We identified 1806 significantly differentially expressed (false discovery rate <0.05) transcripts in platelets from septic patients. Platelet translational events during sepsis were also upregulated. To explore the relevance of a murine model of sepsis, cecal ligation and puncture (CLP), we compared sepsis-induced changes in platelet gene expression between septic patients and mice subjected to CLP. Platelet transcriptional (ρ = 0.42, P = 3.2 × 10−285) and translational (ρ = 0.65, P = 1.09 × 10−56) changes were significantly correlated between septic patients and mice. We focused on ITGA2B, tracking and validating the expression, regulation, and functional impact of changes in ITGA2B during sepsis. Increased ITGA2B was identified in bone marrow megakaryocytes within 24 hours of sepsis onset. Subsequent increases in ITGA2B were seen in circulating platelets, suggesting dynamic trafficking of the messenger RNA. Transcriptional changes in ITGA2B were accompanied by de novo protein synthesis of αIIb and integrin αIIbβ3 activation. Increased αIIb was associated with mortality in humans and mice. These findings provide previously unrecognized evidence that human and murine sepsis similarly alters the platelet transcriptional and translational landscape. Moreover, ITGA2B is upregulated and functional in sepsis due to trafficking from megakaryocytes and de novo synthesis in platelets and is associated with increased mortality.

MCP-induced protein 1 attenuates sepsis-induced acute lung injury by modulating macrophage polarization via the JNK/c-Myc pathway

Sepsis is a potentially fatal systemic inflammatory response syndrome caused by infection. In this study, we evaluated the effects of MCP-induced protein 1 (MCPIP1), a recently discovered inflammation-related ribonuclease, on sepsis-induced acute lung injury (ALI) and investigated the underlying mechanisms. Cecal ligation puncture and lipopolysaccharide induction were performed on Sprague-Dawley rats and RAW264.7 cells, respectively, to establish sepsis-induced ALI models. The proteasome inhibitor MG132 used as an activator of MCPIP1 overexpression, and we showed that MG132 can indeed increase the expression of MCPIP1. MCPIP1 overexpression induced by MG132 alleviated sepsis-induced pathologic changes, water content and protein leakage in the lungs, and induction of systemic inflammatory mediators, and improved the 7-day mortality rate in the model rats. We also showed that MCPIP1 p showed romoted macrophage polarization from the M1 to the M2 type in sepsis-induced ALI. Furthermore, MCPIP1-enhanced M2 polarization was inhibited by an MCPIP1-targeting small interfering RNA (siMCPIP1) in RAW264.7 cells. Further mechanistic studies showed that the promotive effect of MCPIP1 on M2 polarization was related to the inhibition of c-Jun N-terminal kinase (JNK) and its downstream transcription factor c-Myc in the in vitro model. Conversely, siMCPIP1 transfection resulted in the recovery of JNK and c-Myc expression in LPS-treated cells. Taken together, these findings indicate that MCPIP1 plays a protective role in sepsis-induced ALI by modulating macrophage polarization through inhibition of the JNK/c-Myc signaling pathway. Our study presents a potentially novel therapeutic strategy for the treatment of lung injury involving the inflammatory cascade.

A novel role for programmed cell death receptor ligand 2 in sepsis-induced hepatic dysfunction.

The liver is an organ that, when dysfunctional in a septic patient, is strongly associated with morbidity and mortality. Understanding the pathophysiology of liver failure during sepsis may lead to improved diagnostics and potential therapeutic targets. Historically, programmed cell death receptor (PD) ligand 1 (PD-L1) has been considered the primary ligand for its checkpoint molecule counterpart, PD-1, with PD-L2 rarely in the immunopathological spotlight. PD-1 and PD-L1 contribute to liver dysfunction in a murine cecal ligation and puncture (CLP) model of sepsis, but virtually nothing is known about PD-L2's role in sepsis. Therefore, our central hypothesis was that sepsis-induced changes in hepatic PD-L2 expression contributed to worsened liver function and, subsequently, more pronounced morbidity and mortality. We found that although PD-L1 gene deficiency attenuated the hepatic dysfunction seen in wild-type mice after CLP, the loss of PD-L2 appeared to actually worsen indices of liver function along with a trend toward higher liver tissue vascular permeability. Conversely, some protective effects of PD-L2 gene deletion were noted, such as reduced liver/peritoneal bacterial load and reduced IL-6, IL-10, and macrophage inflammatory protein 2 levels following CLP. These diverse actions, as well as the unique expression pattern of PD-L2, may explain why no overt survival advantage could be witnessed in the septic PD-L2-/- mice. Taken together, these data suggest that although PD-L2 has some selective effects on the hepatic response seen in the septic mouse, these factors are not sufficient to alter septic mortality in this adult murine model. NEW & NOTEWORTHY Our study shows not only that ligands of the checkpoint protein PD-1 respond inversely to a stressor such as septic challenge (PD-L2 declines, whereas PD-L1 rises) but also that aspects of liver dysfunction increase in septic mice lacking the PD-L2 gene. Furthermore, these differences in PD-L2 gene-deficient animals culminated in the abrogation of the survival advantage seen in the septic PD-L1-knockout mice, suggesting that PD-L2 may have roles beyond a simple immune tolerogen.

Group 2 Innate Lymphoid Cells (ILC2s) Are Key Mediators of the Inflammatory Response in Polymicrobial Sepsis

Sepsis remains a major public health concern, characterized by marked immune dysfunction. Innate lymphoid cells develop from a common lymphoid precursor but have a role in orchestrating inflammation during innate response to infection. Here, we investigate the pathologic contribution of the group 2 innate lymphoid cells (ILC2s) in a murine model of acute septic shock (cecal ligation and puncture). Flow cytometric data revealed that ILC2s increase in number and percentage in the small intestine and in the peritoneal cells and inversely decline in the liver at 24 hours after septic insult. Sepsis also resulted in changes in ILC2 effector cytokine (IL-13) and activating cytokine (IL-33) in the plasma of mice and human patients in septic shock. Of interest, the sepsis-induced changes in cytokines were abrogated in mice deficient in functionally invariant natural killer T cells. Mice deficient in IL-13-producing cells, including ILC2s, had a survival advantage after sepsis along with decreased morphologic evidence of tissue injury and reduced IL-10 levels in the peritoneal fluid. Administration of a suppressor of tumorigenicity 2 (IL-33R) receptor-blocking antibody led to a transient survival advantage. Taken together, these findings suggest that ILC2s may play an unappreciated role in mediating the inflammatory response in both mice and humans; further, modulating ILC2 response invivo may allow development of immunomodulatory strategies directed against sepsis.

Adequate anti-infective treatment : Importance of individual dosing and application

Sepsis-induced changes in pharmacokinetic parameters are a well-known problem in intensive care medicine. Dosing of antibiotics in this setting is therefore challenging. Alterations to the substance-specific kinetics of anti-infective substances have an effect on the distribution and excretion processes in the body. Increased clearance and an increased distribution volume (Vd) and particularly compromized organ function with reduced antibiotic elimination are often encountered in patients with sepsis. Renal replacement treatment, which is frequently used in intensive care medicine, represents a substantial intervention in this system. Current international guidelines recommend individualized dosing strategies and adaptation of doses according to measured serum levels and pharmacokinetic/pharmacodynamic (PK/PD) parameters as concepts to optimize anti-infective therapy in the critically ill. Likewise, the recommendation to adjust the administration form of beta-lactam antibiotics to prolonged or continuous infusion can be found increasingly more often in the literature. This article reviews the background of the individual dosing in intensive care patients and their applicability to the clinical routine.

Lipidomic analysis of plasma lipids composition changes in septic mice.

A lipidomic study on extensive plasma lipids in bacterial peritonitis (cecal ligation and puncture, CLP)-induced sepsis in mice was done at 24 h post-CLP. The effects of administration of lysophosphatidylcholine (LPC) and lysophosphatidic acid (LPA), compounds known to have beneficial effects in CLP, on the sepsis-induced plasma lipid changes were also examined. Among the 147 plasma lipid species from 13 lipid subgroups (fatty acid [FA], LPA, LPC, lysophosphatidylethanolamine [LPE], phosphatidic acid [PA], phosphatidylcholine [PC], phosphatidylethanolamine [PE], phosphatidylinositol [PI], monoacylglyceride [MG], diacylglyceride [DG], triacylglyceride [TG], sphingomyelin [SM], and ceramide [Cer]) analyzed in this study, 40 and 70 species were increased, and decreased, respectively, in the CLP mice. Treatments with LPC and LPA affected 14 species from 7 subgroups, and 25 species from 9 subgroups, respectively. These results could contribute to finding the much needed reliable biomarkers of sepsis.

Program Cell Death Receptor-1-Mediated Invariant Natural Killer T-Cell Control of Peritoneal Macrophage Modulates Survival in Neonatal Sepsis.

We have shown that invariant natural killer T (iNKT) cells mediate sepsis-induced end-organ changes and immune responses, including macrophage bacterial phagocytosis, a finding regulated by the check point protein program cell death receptor-1 (PD-1). Furthermore, PD-1 mediates mortality in both adult and neonatal murine sepsis as well as in surgical patients. Given our previous findings, we hypothesize that iNKT cells will also modulate neonatal sepsis survival, and that this effect is regulated in part through PD-1. We utilized a polymicrobial intra-peritoneal cecal slurry (CS) sepsis model in wild type (WT), iNKT−/− or PD-1−/− 5–7 day old neonatal pups. Typically, tissues were harvested at 24 h for various bioassays/histology and, in some cases, survival was assessed for up to 7 days. Interestingly, similar to what we recently reported for PD-1−/− mice following CS, iNKT−/−-deficient animals exhibit a markedly improved survival vs. WT. Histologically, minor alterations in liver architectural, which were noted in WT pups, were attenuated in both iNKT−/− and PD-1−/− pups. Following CS, PECAM-1 expression was unchanged in the WT pups but increased in both iNKT−/− and PD-1−/− pups. In WT, following CS the emergence of a Ly6Clow subpopulation was noted among the influxed peritoneal macrophage population. Conversely, within iNKT−/− pups, there were fewer peritoneal macrophages and a greater percentage of Ly6Chigh macrophages. We show not only a key role for iNKT cells in affecting end-organ damage as well as alterations in phagocytes phenotypes in neonatal sepsis but that this iNKT cell mediated effect is driven by the central checkpoint protein PD-1.

Polymicrobial Sepsis Diminishes Dendritic Cell Numbers and Function Directly Contributing to Impaired Primary CD8 T Cell Responses In Vivo.

Patients surviving acute stages of sepsis often display impaired adaptive-immune responses. Using the cecal ligation and puncture model, we demonstrated that sepsis leads to substantial and long-lasting changes in the naive CD8 T cell repertoire, affecting the capacity of the host to respond to new infections. However, the identity of CD8 T cell-extrinsic factor(s) and mechanism(s) that contribute to impaired CD8 T cell responses after sepsis is unknown. Priming of naive CD8 T cells is critically dependent on the ability of dendritic cells (DCs) to provide Ag, costimulation, and inflammatory signal 3 cytokines; therefore, the sepsis-induced changes in the DC compartment might represent a contributing factor leading to diminished CD8 T cell immunity in septic hosts. In a direct test of this hypothesis, we show that, in addition to numerical decline, sepsis leads to functional impairments in DCs, diminishing their capacity to produce cytokines upon TLR stimulation in vitro or postinfection in vivo. Importantly, we demonstrated a direct link between DC dysfunction and impairments in CD8 T cell immunity after sepsis by directly targeting Ag to DCs. Finally, postsepsis Flt3 ligand treatment increased the number of DCs and improved DC function, including the ability to sense inflammation and produce IL-12, leading to improved primary CD8 T cell responses to newly encountered Ags. Thus, sepsis-induced numerical and functional loss of DCs contributes to the observed defects in CD8 T cell immunity, and therapeutic approaches designed to improve the status of the DC compartment after sepsis might facilitate the recovery of CD8 T cell immunity.

Su1190 Effect of Gastrointestinal Barrier Protection on Sepsis-Induced Changes of Intestinal Motility, Inflammation and Colonic Permeability

Su1190 Effect of Gastrointestinal Barrier Protection on Sepsis-Induced Changes of Intestinal Motility, Inflammation and Colonic Permeability

Carbon Monoxide-Releasing Molecule-2 Reduces Intestinal Epithelial Tight-Junction Damage and Mortality in Septic Rats.

ObjectiveDamage to intestinal epithelial tight junctions plays an important role in sepsis. Recently we found that Carbon Monoxide-Releasing Molecule-2 (CORM-2) is able to protect LPS-induced intestinal epithelial tight junction damage and in this study we will investigate if CORM-2 could protect intestinal epithelial tight junctions in the rat cecal ligation and puncture (CLP) model.Materials and MethodsThe CLP model was generated using male Sprague-Dawley (SD) rats according to standard procedure and treated with CORM-2 or inactive CORM-2 (iCORM-2), 8 mg/kg, i.v. immediately after CLP induction and euthanized after 24h or 72h (for mortality rate only). Morphological changes were investigated using both transmission electron and confocal microscopy. The levels of important TJ proteins and phosphorylation of myosin light chain (MLC) were examined using Western blotting. Cytokines, IL-1β and TNF-α were measured using ELISA kits. The overall intestinal epithelial permeability was evaluated using FD-4 as a marker.ResultsCORM-2, but not iCORM-2, significantly reduced sepsis-induced damage of intestinal mucosa (including TJ disruption), TJ protein reduction (including zonula occludens-l (ZO-1), claudin-1 and occludin), MLC phosphorylation and proinflammatory cytokine release. The overall outcomes showed that CORM-2 suppressed sepsis-induced intestinal epithelial permeability changes and reduced mortality rate of those septic rats.ConclusionsOur data strongly suggest that CORM-2 could be a potential therapeutic reagent for sepsis by suppressing inflammation, restoring intestinal epithelial barrier and reducing mortality.

Disruption of REDD1 gene ameliorates sepsis-induced decrease in mTORC1 signaling but has divergent effects on proteolytic signaling in skeletal muscle.

Sepsis-induced skeletal muscle atrophy and weakness are due in part to decreased mTORC1-mediated protein synthesis and increased proteolysis via the autophagy-lysosomal system and ubiquitin-proteasome pathway. The REDD1 (regulated in development and DNA damage-1) protein is increased in sepsis and can negatively regulate mTORC1 activity. However, the contribution of REDD1 to the sepsis-induced change in muscle protein synthesis and degradation has not been determined. Sepsis was produced by cecal ligation and puncture in female REDD1(-/-) or wild-type (WT) mice, and end points were assessed 24 h later in gastrocnemius; time-matched, pair-fed controls of each genotype were included. Sepsis increased REDD1 protein 300% in WT mice, whereas REDD1 was absent in REDD1(-/-) muscle. Sepsis decreased protein synthesis and phosphorylation of downstream targets of mTORC1 (S6K1 Thr(389), rpS6 Ser(240/244), 4E-BP1 Ser(65)) in WT but not REDD1(-/-) mice. However, Akt and PRAS40 phosphorylation was suppressed in both sham and septic muscle from REDD1(-/-) mice despite unaltered PDK1, PP2A, or TSC2 expression. Sepsis increased autophagy as indicated by decreased ULK1 Ser(757) phosphorylation and p62 abundance and increased LC3B-II/I in WT mice, whereas these changes were absent in septic REDD1(-/-) mice. Conversely, REDD1 deletion did not prevent the sepsis-induced decrease in IGF-I mRNA or the concomitant increase in IL-6, TNFα, MuRF1, and atrogin1 mRNA expression. Lastly, 5-day survival in a separate set of septic mice did not differ between WT and REDD1(-/-) mice. These data highlight the central role of REDD1 in regulating both protein synthesis and autophagy in skeletal muscle during sepsis.