Increased inducible apoptosis in CD4+ T lymphocytes during polymicrobial sepsis is mediated by Fas ligand and not endotoxin

Fentanyl alleviates intestinal mucosal barrier damage in rats with severe acute pancreatitis by inhibiting the MMP-9/FasL/Fas pathway

BACKGROUND

Fentanyl is an analgesic used against pancreatitis-related pain, while whether it ameliorates severe acute pancreatitis (SAP) has yet to be checked. The present study aims to determine fentanyl-delivered effect on SAP and the mechanism underlying this effect.

METHODS

Rat SAP models were established, following fentanyl treatment. The serum activity of amylase (AMY), lipase (LIP) and diamine oxidase (DAO) was detected by enzyme-linked immunosorbent assay. Histological examination was performed in the pancreatic and intestinal tissues with hematoxylin-eosin staining. After transfection with matrix metalloproteinase (MMP)9 overexpression plasmids, Caco-2 monolayers were treated with fentanyl and subsequently exposed to lipopolysaccharide (LPS). The transepithelial electrical resistance (TEER) value was determined in rat intestinal mucosa through an Ussing chamber assisted by Analyze & Acquire, and in Caco-2 cell monolayers through a voltohmmeter. Intestinal mucosa and paracellular permeabilities were determined by fluorescein isothiocyanate (FITC)-labeled dextran assay. The expressions of ZO-1, Occludin, MMP9, Fas and Fas ligand (FasL) in rat intestinal mucosa and/or Caco-2 monolayers were analyzed by qRT-PCR or/and western blot.

RESULTS

Fentanyl alleviated SAP-related histological alterations in the pancreas and intestines, reduced the elevated levels of SAP-related AMY, LIP and DAO, but promoted the levels of ZO-1 and Occludin. In SAP rats and Caco-2 monolayers, SAP-related or LPS-induced TEER value decreases, permeability increases, and increases in the expressions of MMP9, Fas and FasL were reversed partly by fentanyl. Notably, MMP9 overexpression could reverse the above fentanyl-delivered in vitro effects.

CONCLUSION

Fentanyl alleviates intestinal mucosal barrier damage in rats with SAP by inhibiting the MMP9/FasL/Fas pathway.

The protective role of human ghrelin in sepsis: Restoration of CD4 T cell proliferation

Decrease of CD4 T cell numbers causes immunosuppression in sepsis. We previously showed the beneficial role of ghrelin in sepsis. We hypothesize that the protective outcome of ghrelin in sepsis is mediated partially through the restoration of CD4 T cells’ proliferation. Sepsis was induced in mice by cecal ligation and puncture (CLP). The percentage of CD4 T cells in spleen was assessed by flow cytometry and their proliferation was determined by carboxyfluorescein succinimidyl ester (CSFE). Compared to sham mice, the percentages of splenic CD4 T cells were reduced by 20%, 21%, and 29% at day 1, 2 and 3 after CLP, respectively. Human ghrelin was given to 3 day septic mice by s.c. injection at 5 and 24 h after CLP. Treatment with ghrelin restored the loss of CD4 T cells by increasing their proliferation in septic mice. The expression of cyclin D1 and B1 was significantly increased, while the expression of p57 was decreased in ghrelin-treated mice compared to vehicle-treated mice in sepsis. Treatment with human ghrelin significantly increased the p-AKT levels in the spleen compared to vehicle-treated septic mice. Human ghrelin plays an important role in reestablishing the proliferation of CD4 T cells and serves as a promising therapeutic agent in sepsis.

Effects of simvastatin on the function of splenic CD4+ and CD8+ T cells in sepsis mice

Simvastatin may be beneficial for treating sepsis due to its immune-regulating properties, although the mechanisms remain elusive. Herein, we hypothesized simvastatin may attenuate T cell dysfunction induced by sepsis. To test this hypothesis, we used a model based on cecal ligation and puncture (CLP) to induce sepsis in mice. Male C57BL/6 mice were pre-treated with simvastatin (0.2 μg/g of body weight) before CLP. The expression of B and T lymphocyte attenuator (BTLA) on splenic CD4⁺ T cells and T cell apoptosis, CD4⁺ and CD8⁺ T cells were quantified by flow cytometry. Immunohistochemical staining was performed to evaluate the loss of immune effector cells. Formation of TNF-α and interleukin 10 (IL-10) in the spleen and plasma levels of presepsin, IL-1β, and IL-6 were determined using enzyme-linked immunosorbent assay. Simvastatin markedly inhibited the reduction in cytokine secretion from lipopolysaccharide (LPS)-stimulated splenocytes. Simvastatin-treated mice had significantly decreased the percentages of negative costimulatory receptor BTLA on CD4 T cell expression. Simvastatin markedly reduced T cell apoptosis through downregulating the Fas/FasL expression and decrease the percentage of caspase-3 activity in spleen tissue. There was significantly less depletion of splenic CD4⁺ and CD8⁺ T cells in simvastatin-treated mice. Simvastatin reduced plasma levels of presepsin, IL-1β, and IL-6. Simvastatin can be a powerful regulator of immune function under sepsis conditions by improving T cell function in sepsis.

Ursodeoxycholyl Lysophosphatidylethanolamide Protects Against CD95/FAS-Induced Fulminant Hepatitis

Increased activation of CD95/Fas by Fas ligand in viral hepatitis and autoimmunity is involved in pathogenesis of fulminant hepatitis and liver failure. We designed a bile-acid phospholipid conjugate ursodeoxycholyl lysophosphatidylethanolamide (UDCA-LPE with LPE containing oleate at the sn-1) as a hepatoprotectant that was shown to protect against fulminant hepatitis induced by endotoxin. We herein further assessed the ability of UDCA-LPE to prevent death receptor CD95/Fas-induced fulminant hepatitis. C57BL/6 mice were intravenously administered with CD95/Fas agonistic monoclonal antibody (Jo-2) with or without 1 h pretreatment with 50 mg/kg UDCA-LPE. Jo-2 administration caused massive hepatocyte damage as seen by histology, and this was associated with a significant decrease in hepatic phosphatidylcholine (PC), lysoPC, and lysophosphatidylethanolamine levels. By histology, UDCA-LPE pretreatment improved hepatocyte damage and restored the loss of these phospholipids in part by a mechanism involving an inhibition of cytosolic phospholipaseA2 expression. Accordingly, Jo-2 treatment increased hepatic expression of cleaved caspase 8, caspase 3, and poly (ADP-Ribose) polymerase-1, and on the other hand decreased that of anti-apoptotic cellular FLICE-inhibitory protein. UDCA-LPE pretreatment was able to reverse all these changes. Moreover, UDCA-LPE attenuated inflammatory response by lowering the levels of Jo-2-induced proinflammatory cytokines TNF-α, IL-6, and IL-1β in liver and serum. UDCA-LPE was also able to decrease the levels of stimulated Th1/Th17 cytokines in Jo-2-primed isolated splenocytes. Taken together, UDCA-LPE exhibited potent anti-inflammatory effects against CD95/Fas-induced fulminant hepatitis.

A new mass spectrometry-based method for the quantification of histones in plasma from septic shock patients

The aim of this study was to develop a novel method to detect circulating histones H3 and H2B in plasma based on multiple reaction monitoring targeted mass spectrometry and a multiple reaction monitoring approach (MRM-MS) for its clinical application in critical bacteriaemic septic shock patients. Plasma samples from 17 septic shock patients with confirmed bacteraemia and 10 healthy controls were analysed by an MRM-MS method, which specifically detects presence of histones H3 and H2B. By an internal standard, it was possible to quantify the concentration of circulating histones in plasma, which were significantly higher in patients, and thus confirmed their potential as biomarkers for diagnosing septic shock. After comparing surviving patients and non-survivors, a correlation was found between higher levels of circulating histones and unfavourable outcome. Indeed, histone H3 proved a more efficient and sensitive biomarker for septic shock prognosis. In conclusion, these findings suggest the accuracy of the MRM-MS technique and stable isotope labelled peptides to detect and quantify circulating plasma histones H2B and H3. This method may be used for early septic shock diagnoses and for the prognosis of fatal outcomes.

Role of Mitochondrial DNA in Septic AKI via Toll-Like Receptor 9

Toll-like receptor 9 (TLR9) contributes to the development of polymicrobial septic AKI. However, the mechanisms that activate the TLR9 pathway and cause kidney injury during sepsis remain unknown. To determine the role of mitochondrial DNA (mtDNA) in TLR9-associated septic AKI, we established a cecal ligation and puncture (CLP) model of sepsis in wild-type (WT) and Tlr9-knockout (Tlr9KO) mice. We evaluated systemic circulation and peritoneal cavity dynamics and immune response and tubular mitochondrial dysfunction to determine upstream and downstream effects on the TLR9 pathway, respectively. CLP increased mtDNA levels in the plasma and peritoneal cavity of WT and Tlr9KO mice in the early phase, but the increase in the peritoneal cavity was significantly higher in Tlr9KO mice than in WT mice. Concomitantly, leukocyte migration to the peritoneal cavity increased, and plasma cytokine production and splenic apoptosis decreased in Tlr9KO mice compared with WT mice. Furthermore, CLP-generated renal mitochondrial oxidative stress and mitochondrial vacuolization in the proximal tubules in the early phase were reversed in Tlr9KO mice. To elucidate the effects of mtDNA on immune response and kidney injury, we intravenously injected mice with mitochondrial debris (MTD), including substantial amounts of mtDNA. MTD caused an immune response similar to that induced by CLP, including upregulated levels of plasma IL-12, splenic apoptosis, and mitochondrial injury, but this effect was attenuated by Tlr9KO. Moreover, MTD-induced renal mitochondrial injury was abolished by DNase pretreatment. These findings suggest that mtDNA activates TLR9 and contributes to cytokine production, splenic apoptosis, and kidney injury during polymicrobial sepsis.

Overexpression of Fas and FasL is associated with infectious complications and severity of experimental severe acute pancreatitis by promoting apoptosis of lymphocytes

This study investigated the relationship of Fas and Fas ligand (FasL) expression and apoptosis of lymphocytes in relation to the pathogenic immune response and infectious complications observed in experimental severe acute pancreatitis in mice. Forty male Balb/c mice were randomly divided into control, mild (MAP), and severe acute pancreatitis (SAP) groups. Overexpression of Fas/FasL messenger ribonucleic acid (mRNA) and protein was observed in spleen-derived lymphocytes in SAP (p < 0.01). Apoptosis of these resulted in a depletion of circulating lymphocytes in this group (p < 0.05). A further significant change in the SAP group with infectious complications was observed. A positive relationship was found between the Fas/FasL expression and lymphocyte apoptosis, and negative relationships were observed between Fas/FasL expression and CD4⁺ and CD19⁺ lymphocytes and the CD4⁺/CD8⁺ ratio in SAP mice (p < 0.01). The results suggest that the overexpression of Fas/FasL is associated with infectious complications and severity of experimental severe acute pancreatitis by promoting apoptosis of lymphocytes.

Alterations of dendritic cells in sepsis: featured role in immunoparalysis

Sepsis, the leading cause of mortality in intensive care unit, is characterized by hyperinflammatory response in the early stage and followed by a period of immunosuppression. This immune disorder is believed to be the potent factor that is tightly associated with high mortality in sepsis. Dendritic cells (DCs) serve as professional antigen-presenting cells that play a vital role in immune response by activating T lymphocytes. During the progression of sepsis, DCs have been reported to take part in the aberrant immune response and be necessary for survival. Therefore, a better understanding of the DCs pathology will be undoubtedly beneficial for resolving the problems occurring in sepsis. This review discusses effects of sepsis on DCs number and function, including surface molecules expression, cytokines secretion, and T cell activation, and the underlying mechanism as well as some potential therapeutic strategies.

Revisiting caspases in sepsis

Sepsis is a life-threatening illness that occurs due to an abnormal host immune network which extends through the initial widespread and overwhelming inflammation, and culminates at the late stage of immunosupression. Recently, interest has been shifted toward therapies aimed at reversing the accompanying periods of immune suppression. Studies in experimental animals and critically ill patients have demonstrated that increased apoptosis of lymphoid organs and some parenchymal tissues contributes to this immune suppression, anergy and organ dysfunction. Immediate to the discoveries of the intracellular proteases, caspases for the induction of apoptosis and inflammation, and their striking roles in sepsis have been focused elaborately in a number of original and review articles. Here we revisited the different aspects of caspases in terms of apoptosis, pyroptosis, necroptosis and inflammation and focused their links in sepsis by reviewing several recent findings. In addition, we have documented striking perspectives which not only rewrite the pathophysiology, but also modernize our understanding for developing novel therapeutics against sepsis.

The role of Fas expression on the occurrence of immunosuppression in severe acute pancreatitis

BACKGROUND

Severe acute pancreatitis (SAP) is a dangerous illness with high mortality where most patients do not die of excessive inflammation, but die of immunosuppression and multiple infections at a later stage. The mechanism of immunosuppression in SAP is unknown.

AIM

The purpose of this study was to analyze the role of Fas expression on the occurrence of immunosuppression in patients with SAP.

METHODS

Forty-eight patients with pancreatitis were divided into two groups: 20 cases with SAP (7 cases with sepsis, 13 cases without sepsis) and 28 cases with mild acute pancreatitis (MAP). Twenty-eight healthy volunteers were selected as controls. Fas mRNA expression in peripheral blood was detected by qPCR and Fas protein of lymphocyte membranes; T lymphocyte subsets and expression of monocyte Human leukocyte antigen DR (HLA-DR) in peripheral blood were detected by flow cytometry.

RESULTS

Compared with MAP and control groups, expression level of Fas mRNA and lymphocyte Fas protein in peripheral blood were significantly increased in the SAP group (all P < 0.01). There was a further significant increase in the SAP group with sepsis compared to those without sepsis (all P < 0.01). The CD4(+) T cell ratio, CD4(+)/CD8(+) ratio and monocyte HLA-DR expression in the SAP group were decreased significantly compared with MAP and control groups (all P < 0.01). Significant negative relationships were observed between Fas mRNA expression and CD4(+) T-cell ratio, CD4(+)/CD8(+) ratio, and monocyte HLA-DR expression in SAP patients with sepsis (all P < 0.05).

CONCLUSIONS

The results suggest that expression level of Fas is related to severity and immune status of pancreatitis. Overexpression of Fas may lead to the occurrence of immunosuppression and sepsis.

Dehydroepiandrosterone and metyrapone partially restore the adaptive humoral and cellular immune response in endotoxin immunosuppressed mice

Prior exposure to endotoxins renders the host temporarily refractory to subsequent endotoxin challenge (endotoxin tolerance). Clinically, this state has also been pointed out as the initial cause of the non-specific humoral and cellular immunosuppression described in these patients. We recently demonstrated the restoration of immune response with mifepristone (RU486), a receptor antagonist of glucocorticoids. Here we report the treatment with other modulators of glucocorticoids, i.e. dehydroepiandrosterone (DHEA), a hormone with anti-glucocorticoid properties, or metyrapone (MET) an inhibitor of corticosterone synthesis. These drugs were able to partially, but significantly, restore the humoral immune response in immunosuppressed mice. A significant recovery of proliferative responsiveness was also observed when splenocytes were obtained from DHEA- or MET-treated immunosuppressed mice. In addition, these treatments restored the hypersensitivity response in immunosuppressed mice. Finally, although neither DHEA nor MET improved the reduced CD4 lymphocyte count in spleen from immunosuppressed mice, both treatments promoted spleen architecture reorganization, partially restoring the distinct cellular components and their localization in the spleen. The results from this study indicate that DHEA and MET could play an important role in the restoration of both adaptive humoral and cellular immune response in LPS-immunosuppressed mice, reinforcing the concept of a central involvement of endogenous glucocorticoids on this phenomenon.

Burn-injury affects gut-associated lymphoid tissues derived CD4+ T cells

After scald burn-injury, the intestinal immune system responds to maintain immune balance. In this regard CD4+T cells in Gut-Associated Lymphoid Tissues (GALT), like mesenteric lymph nodes (MLN) and Peyer's patches (PP) respond to avoid immune suppression following major injury such as burn. Therefore, we hypothesized that the gut CD4+T cells become dysfunctional and turn the immune homeostasis towards depression of CD4+ T cell-mediated adaptive immune responses. In the current study we show down regulation of mucosal CD4+ T cell proliferation, IL-2 production and cell surface marker expression of mucosal CD4+ T cells moving towards suppressive-type. Acute burn-injury lead to up-regulation of regulatory marker (CD25+), down regulation of adhesion (CD62L, CD11a) and homing receptor (CD49d) expression, and up-regulation of negative co-stimulatory (CTLA-4) molecule. Moreover, CD4+CD25+ T cells of intestinal origin showed resistance to spontaneous as well as induced apoptosis that may contribute to suppression of effector CD4+ T cells. Furthermore, gut CD4+CD25+ T cells obtained from burn-injured animals were able to down-regulate naïve CD4+ T cell proliferation following adoptive transfer of burn-injured CD4+CD25+ T cells into sham control animals, without any significant effect on cell surface activation markers. Together, these data demonstrate that the intestinal CD4+ T cells evolve a strategy to promote suppressive CD4+ T cell effector responses, as evidenced by enhanced CD4+CD25+ T cells, up-regulated CTLA-4 expression, reduced IL-2 production, tendency towards diminished apoptosis of suppressive CD4+ T cells, and thus lose their natural ability to regulate immune homeostasis following acute burn-injury and prevent immune paralysis.

Correlation of Fas expression and apoptosis of lymphocytes with occurrence of sepsis in patients with severe acute pancreatitis

AIM: To investigate Fas expression and apoptosis of lymphocytes in severe acute pancreatitis (SAP) patients with and without sepsis.

METHODS: Fas expression and apoptosis of lymphocytes were examined by flow cytometry. Serum soluble Fas (sFas) levels were measured by enzyme-linked immunosorbent assay (ELISA) in 18 SAP patients (10 cases with sepsis, 8 cases without sepsis), 20 patients with mild acute pancreatitis (MAP), and 20 healthy volunteers (control).

RESULTS: Compared to the MAP and control groups, Fas expression, apoptosis of lymphocytes, and serum sFas levels increased significantly in the SAP group (all P < 0.01), and these changes were more significant in SAP patients with sepsis than in those without sepsis (38.37% ± 4.33% vs 26.34% ± 2.65%, 13.45% ± 2.99% vs 6.33% ± 2.05%, 9.89 ng/mL ± 1.25 ng/mL vs 7.36 ng/mL ± 0.95 ng/mL, all P < 0.01). There was no significant difference in Fas expression, apoptosis of lymphocytes, and serum sFas levels between the normal control group and MAP group. A significant positive relationship was observed between Fas expression and apoptosis of lymphocytes in SAP patients with sepsis (r = 0.988, P < 0.01).

CONCLUSION: The Fas signaling pathway may be involved in apoptosis of lymphocytes and is closely related to the severity of pancreatitis. Excessive apoptosis of lymphocytes appears to be related to immunosuppression and thereby results in the occurrence and development of sepsis in SAP patients.

Prevention of lymphocyte apoptosis in septic mice with cancer increases mortality

Lymphocyte apoptosis is thought to have a major role in the pathophysiology of sepsis. However, there is a disconnect between animal models of sepsis and patients with the disease, because the former use subjects that were healthy prior to the onset of infection while most patients have underlying comorbidities. The purpose of this study was to determine whether lymphocyte apoptosis prevention is effective in preventing mortality in septic mice with preexisting cancer. Mice with lymphocyte Bcl-2 overexpression (Bcl-2-Ig) and wild type (WT) mice were injected with a transplantable pancreatic adenocarcinoma cell line. Three weeks later, after development of palpable tumors, all animals received an intratracheal injection of Pseudomonas aeruginosa. Despite having decreased sepsis-induced T and B lymphocyte apoptosis, Bcl-2-Ig mice had markedly increased mortality compared with WT mice following P. aeruginosa pneumonia (85 versus 44% 7-d mortality; p = 0.004). The worsened survival in Bcl-2-Ig mice was associated with increases in Th1 cytokines TNF-α and IFN-γ in bronchoalveolar lavage fluid and decreased production of the Th2 cytokine IL-10 in stimulated splenocytes. There were no differences in tumor size or pulmonary pathology between Bcl-2-Ig and WT mice. To verify that the mortality difference was not specific to Bcl-2 overexpression, similar experiments were performed in Bim(-/-) mice. Septic Bim(-/-) mice with cancer also had increased mortality compared with septic WT mice with cancer. These data demonstrate that, despite overwhelming evidence that prevention of lymphocyte apoptosis is beneficial in septic hosts without comorbidities, the same strategy worsens survival in mice with cancer that are given pneumonia.

Dysregulated cytokine expression by CD4+ T cells from post-septic mice modulates both Th1 and Th2-mediated granulomatous lung inflammation

Previous epidemiological studies in humans and experimental studies in animals indicate that survivors of severe sepsis exhibit deficiencies in the activation and effector function of immune cells. In particular, CD4+ T lymphocytes can exhibit reduced proliferative capacity and improper cytokine responses following sepsis. To further investigate the cell-intrinsic defects of CD4+ T cells following sepsis, splenic CD4+ T cells from sham surgery and post-septic mice were transferred into lymphopenic mice. These recipient mice were then subjected to both TH1-(purified protein derivative) and TH2-(Schistosoma mansoni egg antigen) driven models of granulomatous lung inflammation. Post-septic CD4+ T cells mediated smaller TH1 and larger TH2 lung granulomas as compared to mice receiving CD4+ T cells from sham surgery donors. However, cytokine production by lymph node cells in antigen restimulation assays indicated increased pan-specific cytokine expression by post-septic CD4+ T cell recipient mice in both TH1 and TH2 granuloma models. These include increased production of T_H2 cytokines in TH1 inflammation, and increased production of T_H1 cytokines in TH2 inflammation. These results suggest that cell-intrinsic defects in CD4+ T cell effector function can have deleterious effects on inflammatory processes post-sepsis, due to a defect in the proper regulation of TH-specific cytokine expression.

Epigenetic regulation of immune cell functions during post-septic immunosuppression

Studies in humans and animal models indicate that profound immunosuppression is one of the chronic consequences of severe sepsis. This immune dysfunction encompasses deficiencies in activation of cells in both the myeloid and lymphoid cell lineages. As a result, survivors of severe sepsis are at risk of succumbing to infections perpetrated by opportunistic pathogens that are normally controlled by a fully functioning immune system. Recent studies have indicated that epigenetic mechanisms may be one driving force behind this immunosuppression, through suppression of proinflammatory gene production and subsequent immune cell activation, proliferation and effector function. A better understanding of epigenetics and post-septic immunosuppression can improve our diagnostic tools and may be an important potential source of novel molecular targets for new therapies. This review will discuss important pathways of immune cell activation affected by severe sepsis, and highlight pathways of epigenetic regulation that may be involved in post-septic immunosuppression.

Insights into sepsis therapeutic design based on the apoptotic death pathway

Sepsis remains the leading cause of death in critically ill patients. A major problem contributing to sepsis-related high mortality is the lack of effective medical treatment. Thus, the key goal in critical care medicine is to develop novel therapeutic strategies that will impact favorably on septic patient outcome. While it is generally accepted that sepsis is an inflammatory state resulting from the systemic response to infection, apoptosis is implicated to be an important mechanism of the death of lymphocytes, gastrointestinal and lung epithelial cells, and vascular endothelial cells associated with the development of multiple organ failure in sepsis. The pivotal role of cell apoptosis is now highlighted by multiple studies demonstrating that prevention of cell apoptosis can improve survival in clinically relevant animal models of sepsis. In this review article, we address the scientific rationale for remedying apoptotic cell death in sepsis and propose that therapeutic efforts aimed at blocking cell signaling pathways leading to apoptosis may represent an attractive target for sepsis therapy.

Impaired CD4+ T-cell proliferation and effector function correlates with repressive histone methylation events in a mouse model of severe sepsis

Immunosuppression following severe sepsis remains a significant human health concern, as long-term morbidity and mortality rates of patients who have recovered from life-threatening septic shock remain poor. Mouse models of severe sepsis indicate this immunosuppression may be partly due to alterations in myeloid cell function; however, the effect of severe sepsis on subsequent CD4(+) T-cell responses remains unclear. In the present study, CD4(+) T cells from mice subjected to an experimental model of severe sepsis (cecal ligation and puncture (CLP)) were analyzed in vitro. CD4(+)CD62L(+) T cells from CLP mice exhibited reduced proliferative capacity and altered gene expression. Additionally, CD4(+)CD62L(+) T cells from CLP mice exhibit dysregulated cytokine production after in vitro skewing with exogenous cytokines, indicating a decreased capability of these cells to commit to either the T(H)1 or T(H)2 lineage. Repressive histone methylation marks were also evident at promoter regions for the T(H)1 cytokine IFN-gamma and the T(H)2 transcription factor GATA-3 in naïve CD4(+) T cells from CLP mice. These results provide evidence that CD4(+) T-cell subsets from post-septic mice exhibit defects in activation and effector function, possibly due to chromatin remodeling proximal to genes involved in cytokine production or gene transcription.

Immature dendritic cell-derived exosomes rescue septic animals via milk fat globule epidermal growth factor-factor VIII [corrected]

Sepsis, a highly lethal systemic inflammatory syndrome, is associated with increases of proinflammatory cytokines (e.g., TNF-alpha, HMGB1) and the accumulation of apoptotic cells that have the potential to be detrimental. Depending on the timing and tissue, prevention of apoptosis in sepsis is beneficial; however, thwarting the development of secondary necrosis through the active removal of apoptotic cells by phagocytosis may offer a novel anti-sepsis therapy. Immature dendritic cells (IDCs) release exosomes that contain milk fat globule EGF factor VIII (MFGE8), a protein required to opsonize apoptotic cells for phagocytosis. In an experimental sepsis model using cecal ligation and puncture, we found that MFGE8 levels decreased in the spleen and blood, which was associated with impaired apoptotic cell clearance. Administration of IDC-derived exosomes promoted phagocytosis of apoptotic cells and significantly reduced mortality. Treatment with recombinant MFGE8 was equally protective, whereas MFGE8-deficient mice suffered from increased mortality. IDC exosomes also attenuated the release of proinflammatory cytokines in septic rats. Liberation of HMGB1, a nuclear protein that contributes to inflammation upon release from unengulfed apoptotic cells, was prevented by MFGE8-mediated phagocytosis in vitro. We conclude that IDC-derived exosomes attenuate the acute systemic inflammatory response in sepsis by enhancing apoptotic cell clearance via MFGE8.

VX-166: a novel potent small molecule caspase inhibitor as a potential therapy for sepsis

Introduction

Prevention of lymphocyte apoptosis by caspase inhibition has been proposed as a novel treatment approach in sepsis. However, it has not been clearly demonstrated that caspase inhibitors improve survival in sepsis models when dosed post-insult. Also, there are concerns that caspase inhibitors might suppress the immune response. Here we characterize VX-166, a broad caspase inhibitor, as a novel potential treatment for sepsis.

Methods

VX-166 was studied in a number of enzymatic and cellular assays. The compound was then tested in a murine model of endotoxic shock (lipopolysaccharide (LPS), 20 mg/kg IV) and a 10 d rat model of polymicrobial sepsis by caecal ligation and puncture (CLP).

Results

VX-166 showed potent anti-apoptotic activity in vitro and inhibited the release of interleukin (IL)-1beta and IL-18. In the LPS model, VX-166 administered 0, 4, 8 and 12 h post-LPS significantly improved survival in a dose-dependent fashion (P < 0.0028). In the CLP model, VX-166 continuously administered by mini-osmotic pump significantly improved survival when dosed 3 h after insult, (40% to 92%, P = 0.009). When dosed 8 h post-CLP, VX-166 improved survival from 40% to 66% (P = 0.19). Mode of action studies in the CLP model confirmed that VX-166 significantly inhibited thymic atrophy and lymphocyte apoptosis as determined by flow cytometry (P < 0.01). VX-166 reduced plasma endotoxin levels (P < 0.05), suggesting an improved clearance of bacteria from the bloodstream. Release of IL-1beta in vivo or T-cell activation in vitro were moderately affected.

Conclusions

Our studies enhance the case for the use of caspase inhibitors in sepsis. VX-166 itself has promise as a therapy for the treatment of sepsis in man.

The potential role of T-cells and their interaction with antigen-presenting cells in mediating immunosuppression following trauma-hemorrhage

OBJECTIVE

Trauma-hemorrhage results in depressed immune responses of antigen-presenting cells (APCs) and T-cells. Recent studies suggest a key role of depressed T-cell derived interferon (IFN)-g in this complex immune cell interaction. The aim of this study was to elucidate further the underlying mechanisms responsible for dysfunctional T-cells and their interaction with APCs following trauma-hemorrhage.

DESIGN

Adult C3H/HeN male mice were subjected to trauma-hemorrhage (3-cm midline laparotomy) followed by hemorrhage (blood pressure of 35 +/- 5 mmHg for 90 min and resuscitation) or sham operation. At 24 h thereafter, spleens were harvested and T-cells (by Microbeads) and APCs (via adherence) were Isolated. Co-cultures of T-cells and APCs were established for 48 h and stimulated with concanavalin A and lipopolysaccharide. T-Cell specific cytokines known to affect APC function (i.e. interleukin(IL)-2, IL-4 and granulocyte-macrophage colony-stimulating factor (GM-CSF)) were measured in culture supernatants by Multiplex assay. The expression of MHC class II as well as co-stimulatory surface molecules on T-cells and APCs was determined by flow cytometry.

RESULTS

The release of IL-4 and GM-CSF by T-cells was suppressed following trauma-hemorrhage, irrespective of whether sham or trauma-hemorrhage APCs were present. Antigen-presenting cells from animals subjected to trauma-hemorrhage did not affect T-cell derived cytokine release by sham T-cells. In contrast, T-cells from trauma-hemorrhage animals depressed MHC class II expression of CD11c(+) cells, irrespective of whether APCs underwent sham or trauma-hemorrhage procedure. Surprisingly, co-stimulatory molecules on APCs (CD80, CD86) were not affected by trauma-hemorrhage.

CONCLUSIONS

These results suggest that beside IFN-g other T-cell derived cytokines contribute to immunosuppression following trauma-hemorrhage causing diminished MHC II expression on APCs. Thus, T-cells appear to play an important role in this interaction at the time-point examined. Therapeutic approaches should aim at maintenance of T-cell function and their interaction with APCs to prevent extended immunosuppression following trauma-hemorrhage.

Enhanced T-cell apoptosis in human septic shock is associated with alteration of the costimulatory pathway

T-cell apoptosis during septic shock (SS) has been associated with deleterious outcome, but the mechanisms of apoptosis are not well understood. As T-cells are not infected in bacterial infection, our hypothesis was that deleterious interactions between lymphocytes and monocytes could be involved. This is a cross-sectional study of 27 patients presenting with community-acquired SS, 23 infected patients without SS and 18 controls. Cytofluorometric techniques were used to study apoptosis, the costimulatory pathway and cytokine synthesis. Apoptosis was increased in SS compared to infected patients without SS and controls: the median values were 18, 2 and 3%, respectively, for CD4(+) T-cells (P < 0.001), and 12, 5 and 2%, respectively, for CD8(+) T-cells (P < 0.001). Patients with SS exhibited significant CD152 over-expression on T-cells, while CD86 expression was decreased on monocytes (P = 0.004). The synthesis of interleukin-2 was decreased in patients with SS compared to the other groups, while secretions of interferon-gamma and TNF-alpha were not altered. Ten surviving patients with SS showed a trend towards the normalisation of these parameters on day 7. In SS, T-cell apoptosis is related, at least in part, to the alteration of the costimulatory pathway, which, in turn, leads to significant modification of the cytokine network.

Second hit post burn increased proximal gut mucosa epithelial cells damage

Secondary infections after burn are common and are a major contributor to morbidity and mortality. We previously showed that burn disrupted proximal gut mucosal homeostasis through increased epithelial cell apoptosis. In the present study, we sought to determine whether proximal gut mucosal disruption is additively affected by secondary endotoxemia after a severe burn. C57BL/6 mice received 30% total body surface area full-thickness scald burns and were randomized to receive saline or LPS 1 mg/kg body weight given intraperitoneally 72 h after burn. Proximal small bowel was harvested 12 h after LPS injection. Mucosal height and epithelial cell number were assessed on hematoxylin-eosin sections, intestinal epithelial cell apoptosis was identified by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, and cell proliferation by immunohistochemical staining for proliferating cell nuclear antigen. Results showed that proximal gut mucosa impairment occurred 12 h after injury, including significantly decreased proximal gut wet weight, gut mucosal height, and epithelial cell number associated with increased proximal gut epithelial apoptosis (P < 0.05). This impairment diminished 72 h after burn. Second-hit endotoxemia caused additional proximal gut mucosa damage with decreased proximal gut weight, cell number, and mucosal height (P < 0.05) and significantly increased small intestinal epithelial apoptosis and mucosal atrophy, even after the first event, indicating a second detrimental effect of endotoxemia after the initial injury.

Regulatory roles of CD1d-restricted NKT cells in the induction of toxic shock-like syndrome in an animal model of fatal ehrlichiosis

CD1d-restricted NKT cells are key players in host defense against various microbial infections. Using a murine model of fatal ehrlichiosis, we investigated the role of CD1d-restricted NKT cells in induction of toxic shock-like syndrome caused by gram-negative, lipopolysaccharide-lacking, monocytotropic Ehrlichia. Our previous studies showed that intraperitoneal infection of wild-type (WT) mice with virulent Ehrlichia (Ixodes ovatus Ehrlichia [IOE]) results in CD8+ T-cell-mediated fatal toxic shock-like syndrome marked by apoptosis of CD4+ T cells, a weak CD4+ Th1 response, overproduction of tumor necrosis factor alpha and interleukin-10, and severe liver injury. Although CD1d-/- mice succumbed to high-dose IOE infection similar to WT mice, they did not develop signs of toxic shock, as shown by elevated bacterial burdens, low serum levels of tumor necrosis factor, normal serum levels of liver enzymes, and the presence of few apoptotic hepatic cells. An absence of NKT cells restored the percentages and absolute numbers of CD4+ and CD8+ T cells and CD11b+ cells in the spleen compared to WT mice and was also associated with decreased expression of Fas on splenic CD4+ lymphocytes and granzyme B in hepatic CD8+ lymphocytes. Furthermore, our data show that NKT cells promote apoptosis of macrophages and up-regulation of the costimulatory molecule CD40 on antigen-presenting cells, including dendritic cells, B cells, and macrophages, which may contribute to the induction of pathogenic T-cell responses. In conclusion, our data suggest that NKT cells mediate Ehrlichia-induced T-cell-mediated toxic shock-like syndrome, most likely via cognate and noncognate interactions with antigen-presenting cells.

Role of Programmed Cell Death in the Immunopathogenesis of Sepsis

Apoptosis is an important mechanism during the immunopathogenesis of sepsis. Early programmed cell death of lymphocytes substantially impairs innate and adaptive immunity reducing the capacity to ward off the invading pathogen. Apoptosis of parenchymal cells (e.g. in the lung, liver and gut) may also promote organ failure and death. Several experimental therapeutic strategies have now been developed to beneficially influence these mechanisms; however, their potential clinical benefit is yet to be evaluated.

Mice depleted of alphabeta but not gammadelta T cells are resistant to mortality caused by cecal ligation and puncture

The present study was undertaken to determine whether the mice depleted of alphabeta or gammadelta T cells show resistance to acute polymicrobial sepsis caused by cecal ligation and puncture (CLP). T-cell receptor beta knockout (betaTCRKO) and T-cell receptor delta knockout (deltaTCRKO) mice were used. An additional group of mice was treated with an antibody against the alphabeta T-cell receptor to induce alphabeta T-cell depletion; a subset of alphabeta T cell-deficient mice was also treated with anti-asialoGM1 to deplete natural killer (NK) cells. The mice underwent CLP and were monitored for survival, temperature, acid-base balance, bacterial counts, and cytokine production. The betaTCRKO mice and the wild-type mice treated with anti-beta T-cell receptor (anti-TCRbeta) antibody showed improved survival after CLP compared with wild-type mice. The treatment of alphabeta T cell-deficient mice with anti-asialoGM1further improved survival after CLP, especially when the mice were treated with imipenem. The improved survival observed in alphabeta T cell-deficient mice was associated with less hypothermia, improved acid-base balance, and decreased production of the proinflammatory cytokines interleukin (IL) 6 and macrophage inflammatory protein (MIP) 2. Compared with wild-type controls, the overall survival was not improved in deltaTCRKO mice. The concentrations of IL-6 and MIP-2 in plasma and cytokine mRNA expression in tissues were not significantly different between wild-type and deltaTCRKO mice. These studies indicate that mice depleted of alphabeta but not of gammadelta T cells are resistant to mortality in an acutely lethal model of CLP. The depletion of NK cells caused further survival benefit in alphabeta T cell-deficient mice. These findings suggest that alphabeta T and NK cells mediate or facilitate CLP-induced inflammatory injury.

Thermal injury-plus-sepsis contributes to a substantial deletion of intestinal mesenteric lymph node CD4 T cell via apoptosis

Thermal injury (TI) with septic complications continues to be a serious clinical problem. One of the main concerns in such patients is immunosuppression related to functional derangements in intestinal CD4⁺ T lymphocytes. Extensive previous studies in thermal injury/septic patients and animal models of thermal injury/sepsis have shown decreased responsiveness of intestinal CD4⁺ T cells to antigen/mitogen. This hyporesponsiveness could significantly contribute to increase injured host susceptibility to pathogens including those translocating from host's gut lumen. Our previous studies indicated that while thermal injury or sepsis alone lead to suppressed proliferation and IL-2 production of intestinal CD4⁺ T cells, this study showed a substantial deletion via apoptosis of the Mesenteric Lymph Nodes (MLN) CD4⁺ T cells. Hence, thermal injury-plus-sepsis contributes not only to suppressed CD4⁺ T proliferation/IL-2 production but also to a substantial modulation of CD4⁺ T cell survivability. These findings allow us to conclude that while thermal injury alone can produce attenuated cell mediated responses without an overt change in CD4⁺ T cell survival, thermal injury with septic complications causes CD4⁺ T cell death and an irreversible loss of cell-mediated responses. The latter happening could be responsible for high morbidity and mortality in the injured host afflicted with thermal injury plus a critical infection.

Prophylaxis with lactoferrin, a novel antimicrobial agent, in a neonatal rat model of coinfection

Lactoferrin has broad-spectrum antimicrobial activity, and the authors hypothesized that recombinant human lactoferrin (Talactoferrin alfa [TLF]) would reduce mortality and morbidity in a coinfection model. The MIC 50 (minimum inhibitory concentration required to inhibit the growth of 50% of organisms) of TLF against Candida albicans and Staphylococcus epidermidis was determined. Neonatal Wistar rats were infected with C albicans or S epidermidis or both, at doses of 2 x10(8) colony-forming units (CFUs) given subcutaneously. Rat pups in each group were randomly given TLF intraperitoneally at 40 mg/kg/dose or 300 mg/kg/dose, or saline in 0.2 mL, once a day for 4 d and were monitored for mortality, weight gain, and blood culture positivity. Trough serum levels of TLF were measured at 24, 48, 72, 96, and 144 h. MIC 50 of TLF was 30 microg/mL and 500 microg/mL for C albicans and S epidermidis, respectively. TLF prophylaxis significantly improved survival in the coinfection group at 40 mg/kg/dose (by 16.1%; P=.019) and at 300 mg/kg/dose (by 15.1%; P=.027) and in the S epidermidis group at a dose of 40 mg/kg/dose (by 18.6%; P=.04). Weight gain was not affected by TLF prophylaxis. Serum trough levels of TLF were 1000-fold lower than in vitro MIC 50. The authors conclude that lactoferrin prophylaxis significantly enhanced survival in coinfection and in the subgroup of S epidermidis infection (40 mg/kg/dose) through indirect mechanisms.

Depressed T cell-derived IFN-gamma following trauma-hemorrhage: a potential mechanism for diminished APC responses

INTRODUCTION

Prolonged immunosuppression has been demonstrated after trauma-hemorrhage resulting in an increased susceptibility to sepsis. The contribution of antigen-presenting cells (APC) vs T cells to this diminished immune response, however, remains unknown.

MATERIALS AND METHODS

To study this, male mice were trauma-hemorrhaged (35 +/- 5 mmHg for 90 min and resuscitation) or sham operated. At 24 h thereafter, spleens were harvested and T cells (via Microbeads) and APC (via adherence) were isolated. Cocultures of combined T cells and APC were established for 48 h, stimulated with ConA and LPS. The T cell-derived cytokine IFN-gamma and IL-12 for APC responses were measured in the supernatants by the multiplex assay.

RESULTS

The release of IFN-gamma was suppressed by T cells after trauma-hemorrhage irrespective of whether sham or trauma-hemorrhage APC were added. Trauma-hemorrhaged APC did not affect T cells-derived IFN-gamma release by sham T cells. In contrast, trauma-hemorrhaged T cells depressed the release of IL-12 by APC. The release of IL-12 by trauma-hemorrhaged APC was not altered when sham T cells were cocultured.

CONCLUSION

Prolonged immunosuppression after trauma-hemorrhage appears to be predominantly due to diminished T cell function. Thus, attempts to prevent immunodysfunction should be directed towards T cells.

Neonatal coinfection model of coagulase-negative Staphylococcus (Staphylococcus epidermidis) and Candida albicans: fluconazole prophylaxis enhances survival and growth

Coagulase-negative staphylococci (CoNS) and Candida are among the most common causes of single infections and coinfections in neonates after 72 h of age. In neonates, coinfection increases the rate of mortality threefold and results in significantly greater morbidity compared to those that result from single infections. In an effort to better understand this phenomenon, we developed the first neonatal animal model of coinfection (with CoNS and Candida) and evaluated its effects on mortality and morbidity and the impact of antifungal prophylaxis with fluconazole. Neonatal Wistar rats were infected with Candida albicans and/or Staphylococcus epidermidis with doses of 2x10(8) and 2x10(6) CFU subcutaneously in different combinations and were monitored for mortality, weight gain, and bacteremia. The in vitro sensitivity of C. albicans to fluconazole was evaluated and the MIC was determined. A subset of rats in these experiments received fluconazole at 10 mg/kg of body weight/dose intraperitoneally starting 24 h before infection for 4 days, and the serum trough levels of fluconazole were measured. Coinfection in the suckling rat significantly increased the rate of mortality compared to that after infection with a single species (P<0.001) and resulted in deaths even at sublethal doses. Coinfection also impaired weight gain significantly in severely infected pups compared to that achieved after infection with a single species (P<0.001). Fluconazole prophylaxis significantly reduced mortality by 30% in the Candida group and 36% in the coinfection group and improved weight gain in this neonatal model of coinfection (P<0.001). We developed a neonatal model of coinfection with Candida and CoNS, observed significantly greater mortality and morbidity with coinfection, and found that fluconazole prophylaxis significantly reduced the rates of both mortality and morbidity. Further research on neonatal coinfection is urgently needed to improve clinical outcomes.

INFLUENCE OF CYCLOOXYGENASE INHIBITORS ON GUT IMMUNE CELL DISTRIBUTION AND APOPTOSIS RATE IN EXPERIMENTAL SEPSIS

The aim of this study was to determine if cyclooxygenase (COX) inhibitors influence immune cell distribution in the small intestinal mucosa and mesenteric lymph nodes (MLNs), the grade of mucosal damage, and the rate of apoptosis in septic rats. The effects induced by a selective COX-2 inhibitor (SC-236) were compared with those of a nonselective COX-1 and -2 inhibitor (indomethacin). Cecal ligation and puncture (CLP), CLP + SC-236 p.o, and CLP + indomethacin p.o, were evaluated. Animals were harvested 6 and 24 h after CLP, respectively. The concentration of proinflammatory cytokines was higher in ascitic fluid than in blood. CLP + SC-236 attenuated IL-6 in plasma and in ascitic fluid and CLP + indomethacin augmented TNF-alpha in ascitic fluid compared with CLP at 6 h. CLP + SC-236 gave a lesser degree of mucosal damage compared with CLP alone or with indomethacin at 6 and 24 h (P < 0.05). Untreated CLP had significant reductions in the number of T lymphocytes in the villi and increases of macrophages in the mucosa and MLNs compared with controls (P < 0.05). CLP + indomethacin decreased T lymphocytes in the villi and MLNs. CLP caused an enhanced apoptosis in the mucosa compared with controls (P < 0.05), pretreatment with COX inhibitors did not significantly change this. Both COX inhibitors enhanced apoptosis in MLNs and attenuated the increase of macrophages in mucosa and MLNs (P < 0.05). It is proposed that the increased apoptosis and the decrease in T cells in the mucosa may be causally related. Apoptosis of lymphocytes may impair the immunologic defense in sepsis. Furthermore, loss of intestinal epithelial cells may compromise bowel wall integrity and facilitate translocation.

Peroxisome proliferator-activated receptor γ contributes to T lymphocyte apoptosis during sepsis

In the last two decades, extensive research failed to significantly improve the outcome of patients with sepsis. In part, this drawback is based on a gap in our knowledge about molecular mechanisms understanding the pathogenesis of sepsis. During sepsis, T cells are usually depleted. Recent studies in mice and human cells suggested a role of the peroxisome proliferator-activated receptor gamma (PPARgamma) in provoking apoptosis in activated T lymphocytes. Therefore, we studied whether expression/activation of PPARgamma might contribute to T cell death during sepsis. We observed PPARgamma up-regulation in T cells of septic patients. In contrast to controls, PPARgamma expressing cells from septic patients responded with apoptosis when exposed to PPARgamma agonists. Cell demise was attenuated by SR-202, a synthetic PPARgamma antagonist, and specificity was further verified by excluding a proapoptotic response to a PPARalpha agonist. We propose that up-regulation of PPARgamma sensitizes T cells of septic patients to undergo apoptosis. PPARgamma activation in T cells requires an exogenous PPARgamma agonist, which we identified in sera of septic patients. Septic sera were used to study reporter gene expression containing a PPAR-responsive element. We conclude that PPARgamma plays a significant role in T cell apoptosis, contributing to lymphocyte loss in sepsis. Thus, inhibition of PPARgamma may turn out to be beneficial for patients suffering from lymphopenia during sepsis.

Major upper gastrointestinal surgery is associated with an antigen-dependent proinflammatory T cell response

BACKGROUND

T cells play a central role in the immune response to injury. Oesophageal and pancreatic resections are associated with significant risk of systemic inflammatory response syndrome and sepsis. This study involved a detailed analysis of T cell function in a consecutive cohort of patients undergoing such surgery.

METHODS

Twenty-five patients undergoing major oncological upper gastrointestinal surgery were investigated for T cell expression of Fas and the activation markers CD69 and CD25, as well as interleukin (IL) 2, IL-10 and interferon (IFN) gamma responses to stimulation with staphylococcal enterotoxin B (SEB). T cell activation in healthy volunteer peripheral blood mononuclear cells was studied in co-culture with patients' serum, either alone or with cytotoxic T lymphocyte-associated antigen (CTLA) 4, an inhibitor of antigen presentation.

RESULTS

T cells expressed significantly raised levels of CD69 and CD25 after surgery, but no change in Fas expression was evident. There was a significant increase in the production of IL-2 after surgery without a concomitant increase in IFN-gamma or IL-10 in response to SEB. Postoperative serum activated healthy volunteer T cells, a response that was inhibited (P = 0.053) by co-incubation with CTLA-4.

CONCLUSION

Major surgery results in pan-T cell activation via a serum-mediated antigenic mechanism that is independent of Fas expression. Postoperative T cells are primed for an augmented proinflammatory response to superantigen, sustained for at least 1 week, implicating the adaptive immune system in the development of the postoperative systemic immunoinflammatory state.

Age disproportionately increases sepsis-induced apoptosis in the spleen and gut epithelium

Both aging and sepsis independently increase splenic and gut epithelial apoptosis. Sepsis-induced apoptosis in either cell type is also associated with increased mortality in young mice. We sought to determine whether age alters sepsis-induced splenic and gut epithelial cell death. Young (2 months) and aged (22 months) male ND4 mice were subjected to either single-puncture cecal ligation and puncture (CLP) with a 23-gauge needle or sham laparotomy. Apoptosis was assessed 24 hours later in the spleen and gut epithelium by active caspase 3 and hematoxylin and eosin staining. Aged septic mice had increased splenic apoptosis compared with either young septic animals or aged sham animals (15 vs. 7 vs. 5 apoptotic cells/high-powered field, P < 0.05). Similarly, aged septic animals had an elevation in gut epithelial cell death compared with either young septic or aged sham mice (33 vs. 16 vs. 6 apoptotic cells/100 contiguous crypts, P < 0.05). Elevated intestinal cell death was not associated with changes in either gut proliferation or cell division. To verify that the increase in splenic apoptosis seen in septic aged animals was not strain specific, double-puncture CLP with a 25-gauge needle or sham laparotomy was performed on young (4 months) or aged (24 months) C57BL/6 male mice. Similar to results seen in outbred animals, aged septic animals in this inbred strain had increased splenic apoptosis compared with either young septic animals or aged sham animals (23 vs. 7 vs. 4 apoptotic cells/ high powered field, P < 0.05). These results indicate that although infection and aging each independently cause an increase in splenic and gut epithelial apoptosis, their combination leads to a disproportionate increase in cell death in these rapidly dividing cell populations,and potentially plays a role in the marked increase in mortality seen with aging in sepsis.

Are alterations of lymphocyte subpopulations in polymicrobial sepsis and DHEA treatment mediated by the tumour necrosis factor (TNF)-alpha receptor (TNF-RI)? A study in TNF-RI (TNF-RI(-/-)) knock-out rodents

Sepsis is associated with depression of T cell-dependent immune reactivity with proinflammatory cytokines, such as tumour necrosis factor (TNF)-alpha, playing an important role. Recent investigations describe an association between these immunological alterations and disturbances of the endocrine system, related most frequently to sex steroid hormones. Dehydroepiandrosterone (DHEA), one of the most abundant adrenal sex steroid precursors, seems to have a protective immunological effect towards septic insults. In this study, both the role of TNF-receptor I (RI) and possible interactions in the protective role of DHEA were investigated in a murine model of polymicrobial sepsis. Polymicrobial sepsis was induced by caecal ligation and puncture (CLP) in a murine model. The effects of DHEA on survival, clinical parameters and cellular immunity (T lymphocytes and natural killer (NK) cells) were investigated. CLP was performed in genetically modified TNF-RI knock-out (TNF-RI(-/-)) and genetically unmodified (wild-type, WT) mice. DHEA application was associated with a decrease in the mortality rate in WT animals. A mortality rate of 91.7% was observed in TNF-RI(-/-) mice after CLP. This mortality rate was reduced to 37.5% by the application of DHEA. In sham-operated TNF-RI(-/-) animals, a significantly higher proportion of NK cells within the lymphocyte population was measured compared with the corresponding WT group. After CLP, a significant increase in the percentage cell count of NK cells was recorded in WT mice. Overall, following DHEA application in WT mice, an alteration in the cellular immune response was characterized by a reduction in the percentage counts of CD4(+), CD8(+) and NK cells. In the group of TNF-RI(-/-) mice treated with DHEA, no increase in the percentage cell count of NK cells was observed after CLP. No data for cell analysis were available from the CLP-TNF-RI(-/-) mice treated with saline, due to the high mortality rate in these animals. DHEA reduces the complications of sepsis in a TNF-RI-independent manner. Our study suggests that NK cells are involved in the protective mechanism of DHEA in WT mice. It would therefore seem that DHEA represents a feasible alternative therapy for the dysregulated immune system in sepsis.

Burn injury induces a change in T cell homeostasis affecting preferentially CD4+T cells

Burn injuries are known to be associated with altered immune functions, resulting in decreased resistance to subsequent infection. In the present study, we determined the in vivo changes in T cell homeostasis following burn injury. Two groups of mice were used: a sham-burn group receiving buprenorphine as an analgesic and a burn group receiving buprenorphine and subjected to burn injury on 20% of the total body surface area. Results showed an important decrease in splenocytes following burn injury. This decrease persisted for 5 days and was followed, at day 10, by a 63% increase in number of cells. In vivo cell proliferation, as determined by the incorporation of 5-bromo-2'-dexoxyuridine, showed a significant increase of cycling splenocytes between days 2 and 10 after burn injury. The percentage of CD4+ and CD8+ T cells in the spleen was altered for 10 days after thermal injury. Analysis of naive (CD62Lhigh CD44low) and effector/memory (CD62Llow CD44high) T cells showed a percent decrease, independent of the expression of CD4 or CD8 molecules. However, early activation markers, such as CD69+, were expressed only on CD4+ T cells after a number of days following injury. Even with an activated phenotype, 10 days post-burn injury, CD4+ naive T cells significantly increased spontaneous apoptosis, detected by using a fluorescent DNA-binding agent 7-amino-actinomycin D. CD8+ T lymphocytes did not express early activation markers and were more resistant to apoptosis. Using purified T cells, we have shown unresponsiveness at day 10. Overall, these results demonstrate that mechanisms of T cell homeostasis were perturbed following burn injury. However, after 10 days, this perturbation persisted only in CD4+ T cells.

Akt decreases lymphocyte apoptosis and improves survival in sepsis

Sepsis induces extensive death of lymphocytes that may contribute to the immunosuppression and mortality of the disorder. The serine/threonine kinase Akt is a key regulator of cell proliferation and death. The purpose of this study was to determine whether overexpression of Akt would prevent lymphocyte apoptosis and improve survival in sepsis. In addition, given the important role of Akt in cell signaling, T cell Th1 and Th2 cytokine production was determined. Mice that overexpress a constitutively active Akt in lymphocytes were made septic, and survival was recorded. Lymphocyte apoptosis and cytokine production were determined at 24 h after surgery. Mice with overexpression of Akt had a marked improvement in survival compared with wild-type littermates, i.e., 94 and 47% survival, respectively, p < 0.01. In wild-type littermates, sepsis caused a marked decrease in IFN-gamma production, while increasing IL-4 production >2-fold. In contrast, T cells from Akt transgenic mice had an elevated production of IFN-gamma at baseline that was maintained during sepsis, while IL-4 had little change. Akt overexpression also decreased sepsis-induced lymphocyte apoptosis via a non-Bcl-2 mechanism. In conclusion, Akt overexpression in lymphocytes prevents sepsis-induced apoptosis, causes a Th1 cytokine propensity, and improves survival. Findings from this study strengthen the concept that a major defect in sepsis is impairment of the adaptive immune system, and suggest that strategies to prevent lymphocyte apoptosis represent a potential important new therapy.

Dissemination of bacteria in multiple organs associated with apoptosis and macrophage activity in different stages of experimental sepsis

BACKGROUND

Gram negative sepsis is reported to induce massive translocation of bacteria into tissues, which associates with decreased macrophage function and increased macrophage apoptosis.

AIMS

The objective of this study was to detect the translocation of bacteria into different organs and to evaluate macrophage activity and the apoptosis of macrophages in the liver during different stages of sepsis and to correlate these parameters.

MATERIAL

Wistar rats (n = 43) were inoculated intraperitoneally with an E. coli and divided into 5 groups, which were killed at different times.

METHODS

Counts of translocated bacteria in tissues were evaluated by using morphological and bacteriological methods. Macrophage activity and apoptotic cells in the liver were studied by applying immunohistochemical methods.

RESULTS

The counts of E. coli were the highest in the organs and blood 6 h after the onset of sepsis, being in correlation with the highest counts of apoptotic cells in the liver and the falling counts of activated macrophages. The counts of microbes show a new wave of elevation in tissues by 120th h.

CONCLUSIONS

The massive penetration of bacteria, the depressed macrophage response in early sepsis following the increased rate of apoptotic macrophages, the different rate of bacterial multiplication in tissues and blood and the second wave of the multiplication of bacteria in tissues in late sepsis all refer to the significance of developing immune dysfunction.

Sepsis induces apoptosis and profound depletion of splenic interdigitating and follicular dendritic cells

Dendritic cells are a phenotypically diverse group of APC that have unique capabilities to regulate the activity and survival of B and T cells. Although proper function of dendritic cells is essential to host control of invading pathogens, few studies have examined the impact of sepsis on dendritic cells. The purpose of this study was to determine the effect of sepsis on splenic interdigitating dendritic cells (IDCs) and follicular dendritic cells (FDCs) using a clinically relevant animal model. Immunohistochemical staining for FDCs showed that sepsis induced an initial marked expansion in FDCs that peaked at 36 h after onset. The FDCs expanded to fill the entire lymphoid zone otherwise occupied by B cells. Between 36 and 48 h after sepsis, there was a profound caspase 3 mediated apoptosis induced depletion of FDCs such that only a small contingent of cells remained. In contrast to the initial increase in FDCs, IDC numbers were decreased to approximately 50% of control by 12 h after onset of sepsis. IDC death occurred by caspase 3-mediated apoptosis. Such profound apoptosis induced loss of FDCs and IDCs may significantly compromise B and T cell function and impair the ability of the host to survive sepsis.

Early circulating lymphocyte apoptosis in human septic shock is associated with poor outcome

The role of lymphocyte apoptosis in septic shock remains a controversial issue. Using Annexin V and flow cytometry analysis on freshly isolated cells, we evaluated circulating lymphocyte apoptosis in 23 septic shock, 25 sepsis without shock, 7 nonseptic critically ill, and 25 control patients. In patients with sepsis, we compared day 1 lymphocyte apoptosis (i.e., within 3 days of the onset of infection) with that observed 5-7 days after (day 6) according to shock state, mortality, and seventy factors. At day 1, patients in septic shock exhibited higher lymphocyte apoptosis than that present in controls (16.5% +/- 3.5% vs. 3% +/- 0.5%, respectively, P = 0.0001). At day 6, patients with sepsis without shock restored undamaged CD4+ T and CD8+ T lymphocyte counts, whereas patients in septic shock increased only CD4+ T cells. Similarly, survivors restored undamaged lymphocyte count at day 6 (+70%, P < 0.001), whereas nonsurvivors did not. Day 6 undamaged lymphocyte count negatively correlated with day 1 SAPS II, day 6 LOD score, mechanical ventilation, and ICU stay duration. We observed no apoptotic effect of septic shock plasma or septic shock circulating mononuclear cells on target lymphoid cell lines. We found no alteration in any death receptors Fas, TRAIL-R1, TRAIL-R2, or in their ligands on circulating blood cells. Catecholamines and interleukin 10 levels significantly increased in patients with septic shock, but did not correlate with apoptosis levels. We conclude that lymphocyte apoptosis is rapidly increased in blood of patients in septic shock and that lymphocyte apoptosis leads to a profound and persistent lymphopenia associated with poor outcome. These results suggest that lymphocyte apoptosis is one of the main components of human septic shock immune dysfunction and could be related more to microcirculatory disturbance than to circulating factors.

Dehydroepiandrosterone (DHEA) modulates the activity and the expression of lymphocyte subpopulations induced by cecal ligation and puncture

Dehydroepiandrosterone (DHEA) exerts a variety of positive effects on the immunologic alterations after trauma and sepsis. We therefore measured the therapeutic efficacy of DHEA after cecal ligation and puncture (CLP) on the expression of lymphocyte subpopulations and on the delayed type hypersensitivity (DTH) reaction. Male NMRI-mice were randomly assigned to four different treatment groups. Treatment consisted of DHEA or saline (S) administration after CLP or laparotomy only. Flow cytometry was performed (CD4+, CD8+, and CD56 lymphocytes) after 96 hours. DTH-reaction, activity and mortality rate were documented. The CLP-induced reduction in activity and survival (mortality: 34/40) was significantly (p < 0.03) less sustained in CLP-DHEA (mortality: 22/40). The DTH-ratio (before vs. after secondary challenge) was significantly lowered in CLP-S (1.01 +/- 0.15) compared to CLP-DHEA (1.35 +/- 0.1) after 48 hours (p < 0.01). CLP-DHEA (22.2 +/- 7.9%) was associated with a statistically significant less sustained increase of CD56+ cells (p < 0.01) compared with CLP-S (49.0 +/- 6.9%). DHEA-treatment after CLP was associated with less reduction in the CD8+ T-lymphocyte subsets (p < 0.01 vs. all other groups). DHEA treatment after CLP was associated with fewer alterations in the changes of CD8+ and CD56, cells, and the DTH reaction compared with animals submitted to CLP without any treatment. This difference was associated with improved outcome (reactivity, mortality). These results suggest a modulation at specific immune reactions by DHEA treatment.

Infection in the chronically critically ill: unique risk profile in a newly defined population

Although CCI is defined as prolonged ventilatory failure with tracheotomy stemming from preceding critical illness, the contention that multisystem debilities impact on most CCI patients' care and recovery is a central thesis of this volume. Perhaps reflecting the combined debilities inherent in CCI, infectious complications take their toll in morbidity, mortality, and persistent ventilatory insufficiency. Enhanced susceptibility to infection results from a potent admixture of barrier breakdown, exposure to virulent and resistant nosocomial pathogens, and postulated "immune exhaustion" that stems from the combined impact of comorbidities and the sequellae of critical illness. Strategies to improve outcome in CCI-related infection include standard measures of support especially nutrition, reducing environmental inoculum through pulmonary hygiene measures, skin care, and limiting barrier breaches, and appropriate antimicrobials directed at likely pathogens. Future stratification of patient risk on the basis of immune phenotype or genotype and potential immunomodulatory prophylaxis may be around the corner, as new prospects in the pharmaceutical armamentarium are presently undergoing testing.

C5a receptor and thymocyte apoptosis in sepsis

In sepsis, apoptosis occurs in many different organs. The mediators responsible for induction of apoptosis are not clearly known, although there are some suggestions that C5a and the C5a receptor (C5aR) might be directly linked to apoptosis. In the cecal ligation/puncture (CLP) model of sepsis in rats, apoptosis occurs early in a variety of organs, especially in the thymus. We demonstrate that thymocytes from normal rats show specific, saturable, and high affinity binding of 125I-labeled recombinant rat C5a. C5a binding to thymocytes was significantly increased 3 h after CLP and also when thymocytes from normal rats were first incubated in vitro with lipopolysaccharide (LPS) or IL-6. The expression of C5aR mRNA in thymocytes was markedly increased 3, 6, and 12 h after CLP and increased similarly when normal thymocytes were first exposed to LPS or IL-6 in vitro. Thymocytes obtained 2 or 3 h after CLP and exposed in vitro to C5a, but not normal thymocytes, underwent increased apoptosis, as demonstrated by annexin-V binding, coinciding with increased activation of caspases 3, 6, and 8. These data provide the first direct evidence that in the early onset of sepsis, increased expression of C5aR occurs in thymocytes, which increases their susceptibility to C5a-induced apoptosis.

CD4+ lymphocyte responses to pulmonary infection with Mycobacterium tuberculosis in naïve and vaccinated BALB/c mice

The Biostack experiments I and II were flown on board the Apollo 16 and 17 command modules in order to obtain information on the biological damage produced by the bombardment of heavy high-energy (HZE) particles of cosmic radiation during spaceflight. Such data are required for estimating radiation hazards in manned spaceflight. Seven biological systems in resting state (Bacillus subtilis spores, Colpoda cucullus cysts, Arabidopsis thaliana seeds, and eggs of Artemia salina, Tribolium castaneum and of Carausius morosus) were accommodated in the two Biostacks. By using a special sandwich construction of visual track detectors and layers of biological objects, identification of each hit biological object was achieved and the possible biological damage correlated with the physical features of the responsible HZE-particle. In the different systems the degree of damage depended on whether the hit cell was replaceable or not. A high sensitivity to HZE-particle bombardment was observed on Artemia salina eggs; 90% of the embryos, which were induced to develop from hit eggs, died at different developmental stages. Malformations of the abdomen or the extremities of the nauplius were frequently induced. In contrast, the growth of hit Vicia faba radiculae and the germination of hit Arabidopsis thaliana seeds and hit Bacillus subtilis spores were not influenced remarkably. But there was an increase in multicaulous plants and a reduction in the outgrowth of the bacteria] spores. In addition, information was obtained on the fluence of the HZE-particles, on their spectrum of charge and energy loss, and on the absorption by the Apollo spacecraft and the Biostack material itself. This will help to improve knowledge concerning radiation conditions inside of spacecrafts, necessary to secure a The Biostack experiments I and II were flown on board the Apollo 16 and 17 command modules in order to obtain information on the biological damage produced by the bombardment of heavy high-energy (HZE) particles of cosmic radiation during spaceflight. Such data are required for estimating radiation hazards in manned spaceflight. Seven biological systems in resting state (Bacillus subtilis spores, Colpoda cucullus cysts, Arabidopsis thaliana seeds, and eggs of Artemia salina, Tribolium castaneum and of Carausius morosus) were accommodated in the two Biostacks. By using a special sandwich construction of visual track detectors and layers of biological objects, identification of each hit biological object was achieved and the possible biological damage correlated with the physical features of the responsible HZE-particle. In the different systems the degree of damage depended on whether the hit cell was replaceable or not. A high sensitivity to HZE-particle bombardment was observed on Artemia salina eggs; 90% of the embryos, which were induced to develop from hit eggs, died at different developmental stages. Malformations of the abdomen or the extremities of the nauplius were frequently induced. In contrast, the growth of hit Vicia faba radiculae and the germination of hit Arabidopsis thaliana seeds and hit Bacillus subtilis spores were not influenced remarkably. But there was an increase in multicaulous plants and a reduction in the outgrowth of the bacteria] spores. In addition, information was obtained on the fluence of the HZE-particles, on their spectrum of charge and energy loss, and on the absorption by the Apollo spacecraft and the Biostack material itself. This will help to improve knowledge concerning radiation conditions inside of spacecrafts, necessary to secure a The Biostack experiments I and II were flown on board the Apollo 16 and 17 command modules in order to obtain information on the biological damage produced by the bombardment of heavy high-energy (HZE) particles of cosmic radiation during spaceflight. Such data are required for estimating radiation hazards in manned spaceflight. Seven biological systems in resting state (Bacillus subtilis spores, Colpoda cucullus cysts, Arabidopsis thaliana seeds, and eggs of Artemia salina, Tribolium castaneum and of Carausius morosus) were accommodated in the two Biostacks. By using a special sandwich construction of visual track detectors and layers of biological objects, identification of each hit biological object was achieved and the possible biological damage correlated with the physical features of the responsible HZE-particle. In the different systems the degree of damage depended on whether the hit cell was replaceable or not. A high sensitivity to HZE-particle bombardment was observed on Artemia salina eggs; 90% of the embryos, which were induced to develop from hit eggs, died at different developmental stages. Malformations of the abdomen or the extremities of the nauplius were frequently induced. In contrast, the growth of hit Vicia faba radiculae and the germination of hit Arabidopsis thaliana seeds and hit Bacillus subtilis spores were not influenced remarkably. But there was an increase in multicaulous plants and a reduction in the outgrowth of the bacteria] spores. In addition, information was obtained on the fluence of the HZE-particles, on their spectrum of charge and energy loss, and on the absorption by the Apollo spacecraft and the Biostack material itself. This will help to improve knowledge concerning radiation conditions inside of spacecrafts, necessary to secure a maximum possible protection to the astronauts.

IFN-gamma overproduction and high level apoptosis are associated with high but not low virulence Toxoplasma gondii infection

Toxoplasma gondii is an opportunistic intracellular parasite which induces a highly strong type 1 cytokine response. The present study focuses on defining the factors influencing the outcome of infection with tachyzoites of the type I, highly lethal RH strain, relative to the type II, low virulence strain ME49. Infection with the RH strain led to widespread parasite dissemination and rapid death of mice; in contrast, mice survived low virulence strain ME49 infection, and tachyzoite dissemination was much less extensive. Furthermore, massive apoptosis and disintegration of the splenic architecture was characteristic of RH, but not ME49, infection. In addition, hyperinduction of IFN-gamma and lack of NO production were found during RH, in contrast to ME49 infection. These data demonstrate that Toxoplasma strain characteristics exert a profound effect on the host immune response and that the latter itself is a crucial determinant in parasite virulence.

Increased apoptosis in lamina propria B cells during polymicrobial sepsis is FasL but not endotoxin mediated

Recent studies from our laboratory demonstrated that mucosal lymphoid tissue such as Peyer's patch cells and lamina propria (LP) B lymphocytes from mice shows evidence of increased apoptosis after sepsis that is associated with localized inflammation/activation. The mechanism for this is poorly understood. Endotoxin as well as Fas/Fas ligand (FasL) have been shown to augment lymphocyte apoptosis; however, their contribution to the increase of apoptosis in LP B-cells during sepsis is not known. To study this, sepsis was induced by cecal ligation and puncture (CLP) in endotoxin-tolerant C3H/HeJ or FasL-deficient C3H/HeJ-FasL(gld) (FasL(-)) mice and LP lymphocytes were isolated 24 h later. Phenotypic, apoptotic, and functional indexes were assessed. The number of LP B cells decreased markedly in C3H/HeJ mice but not in FasL-deficient animals at 24 h after CLP. This was associated with comparable alteration in apoptosis and Fas antigen expression in the B cells of these mice. Septic LP lymphocytes also showed increased IgA production, which was absent in the FasL-deficient CLP mice. Furthermore, Fas ligand deficiency appeared to improve survival of septic challenge. These data suggest that the increase in B cell apoptosis in septic animals is partially due to a Fas/FasL-mediated process but not endotoxin.

IL-10 mediation of activation-induced TH1 cell apoptosis and lymphoid dysfunction in polymicrobial sepsis

Recent studies suggest that increased activation-induced lymphocyte apoptosis (AICD) is detected in mouse splenocytes during polymicrobial sepsis which may contribute to lymphocyte immune dysfunction [i.e., decreased interleukin (IL-)2 and interferon-gamma (IFN-gamma) production] leading to the associated morbidity seen in those animals. Thus, we wanted to examine the hypothesis that immune suppressive agents, such as IL-4, IL-10 or prostaglandin E2(PGE2), known to be elevated in septic animals, also contribute to this increase in AICD. Here we demonstrate that the inclusion of monoclonal antibody (mAb) to IL-10, but not anti-IL-4 or ibuprofen (IBU), blunted this sepsis induced increase in splenocyte AICD. Additionally, septic mice deficient in the IL-10 gene product (-/-) showed neither an increase in AICD nor a loss of IL-2/IFN-gamma release capacity. Interestingly, mAb to IL-10 did not altered the extent of AICD in a Th2-cell line, but exogenous IL-10 did potentiate Th1-like cell line AICD. This was consistent with the finding that the increased AICD seen in septic mouse splenocytes was restricted largely to the CD4+ cells producing IL-2 (Th1-cells) and that mAb to IL-10 treatment suppressed this change. Furthermore, IL-10 appears to mediate its AICD effect by upregulation of the Fas receptor and Fas receptor signaling protein components, but not by altered expression of Bcl/Bax/Bad family members, in septic mouse splenocytes. To the extent that these processes contribute in a pathological fashion to the animal's capacity to survive sepsis we have previously observed that in vivo post-treatment of mice with mAb IL-10 markedly attenuated septic mortality. Collectively, these data indicate that in the septic mouse the Th2 cytokine IL-10 not only serves to actively induce Th1 lymphocyte immune dysfunction but also plays a role in their apoptotic depletion. These processes in turn appear to contribute to the animal's inability to ward off lethal septic challenge.

Apoptosis in sepsis: a new target for therapeutic exploration

The treatment of sepsis and septic shock remains a clinical conundrum, and recent prospective trials with biological response modifiers aimed at the inflammatory response have shown only modest clinical benefit. Recently, interest has shifted toward therapies aimed at reversing the accompanying periods of immune suppression. Studies in experimental animals and critically ill patients have demonstrated that increased apoptosis of lymphoid organs and some parenchymal tissues contributes to this immune suppression, anergy, and organ system dysfunction. During sepsis syndromes, lymphocyte apoptosis can be triggered by the absence of IL-2 or by the release of glucocorticoids, granzymes, or the so-called 'death' cytokines: tumor necrosis factor alpha or Fas ligand. Apoptosis proceeds via auto-activation of cytosolic and/or mitochondrial caspases, which can be influenced by the pro- and anti-apoptotic members of the Bcl-2 family. In experimental animals, not only can treatment with inhibitors of apoptosis prevent lymphoid cell apoptosis; it may also improve outcome. Although clinical trials with anti-apoptotic agents remain distant due in large part to technical difficulties associated with their administration and tissue targeting, inhibition of lymphocyte apoptosis represents an attractive therapeutic target for the septic patient.