Severe sepsis and Toll-like receptors

Special Issue "The Role of Toll-Like Receptors (TLRs) in Infection and Inflammation 2.0"

Toll-like receptors (TLRs) are key players in the innate immune system, in host' first-line defense against pathogens [...].

Quantification of NETs formation in neutrophil and its correlation with the severity of sepsis and organ dysfunction

BACKGROUND

Previous study from this lab has discerned oxidative, nitrosative stress and their relationship with cytokines contributing to the severity of sepsis and organ dysfunction. Cytokines are known to induce neutrophil extracellular traps (NETs) formation via free radicals generation. Hyper-activation of neutrophil leads to the increased NETs formation or ineffective clearance of NETs would likely increase the risk of auto-antibody generation against NETs components and being partly responsible for the sepsis severity and organ dysfunction. The present study was undertaken to further assess the status of NETs formation and their correlation with severity of sepsis, with the cytokines and organ dysfunction.

METHODS

The level of NETs formation, DNA release, elastase release, and inflammatory cytokines was determined in 80 sepsis patients and 45 healthy volunteers. Their linearity with organ parameters and associations with sepsis severity were also assessed.

RESULTS

NETs formation experiment was carried out and it was significantly higher in sepsis (70%) compared to control (30%). NETs % were positively correlated with severity of sepsis and organ dysfunction. Pearson's correlation coefficient demonstrated a direct relation between NETs components and organ parameters with Sepsis severity scores.

CONCLUSION

NETs formation is significantly higher due to which it is contributing to the sepsis severity and organ failure.

Cytokine storm and sepsis disease pathogenesis

Infectious diseases are a leading cause of death worldwide. Sepsis is a severe clinical syndrome related to the host response to infection. The severity of infections is due to an activation cascade that will lead to an autoamplifying cytokine production: the cytokine storm. Cytokines are a broad category of relatively small proteins (<40 kDa) that are produced and released with the aim of cell signaling. Our understanding of the processes that trigger this tremendous amount of cytokine production has made dramatic progress over the last decades, but unfortunately, these findings could not translate yet into effective treatments; so far, all clinical trials targeting cytokine production or effects failed. This review aims to summarize the pathophysiology of the cytokine storm; to describe the type, effects, and kinetics of cytokine production; and to discuss the therapeutic challenges of targeting cytokines. New promising therapeutic strategies focusing on the endothelium, as a source and a target of cytokines, are described.

Is there any relationship between Toll-like receptor 3 c.1377C/T and -7C/A polymorphisms and susceptibility to Crimean Congo hemorrhagic fever?

Crimean-Congo hemorrhagic fever (CCHF) is an infectious disease that is caused by CCHF virus. A family of transmembrane receptors called as Toll-like receptors (TLRs) selectively acts in recognizing a wide range of microbial components and endogenous molecules released by damaged tissue and have been preserved throughout evolution. TLRs initiate some signaling cascades which activate the innate immune system. Mainly four TLRs act in protection against viral infections; TLR3 is one of them. TLR3 identifies dsRNA. By producing inflammatory cytokines and type I interferons, it generates an antiviral immune response. Proper response to TLR ligands may be impaired by single nucleotide polymorphisms (SNPs) within TLR genes in some indviduals, and this can cause varied susceptibility to infections. In the present work, polymerase chain reaction-based restriction fragment length polymorphism is used to analyze the frequencies of TLR3 (c.1377C/T and -7C/A) polymorphisms in 149 CCHF patients and 171 healthy adults as controls, in Cumhuriyet University, Sivas/Turkey. We also investigated the relation between these polymorphisms and severity or mortality of CCHF disease. This is the first study investigating the TLR3 SNPs in patients with CCHF. In the present study, the frequency of the TLR3 (c.1377C/T and -7A/C) genotypes in fatal and non-fatal cases were comparable, however, the homozygous mutant (TT) genotype frequency of TLR3 c.1377C/T in CCHF patients was significantly higher than that of the healthy controls. In conclusion, presence of TLR3 c.1377 TT genotype may have a role in the susceptibility to CCHF. J. Med. Virol. 88:1690-1696, 2016. © 2016 Wiley Periodicals, Inc.

Inflammation-Induced Changes in Circulating T-Cell Subsets and Cytokine Production During Human Endotoxemia

Observational clinical studies suggest the initial phase of sepsis may involve impaired cellular immunity. In the present study, we investigated temporal changes in T-cell subsets and T-cell cytokine production during human endotoxemia. Endotoxin (Escherichia coli lipopolysaccharide 4 ng/kg) was administered intravenously in 15 healthy volunteers. Peripheral blood and bronchoalveolar lavage fluid (BALF) were collected at baseline and after 2, 4, 6, 8, and 24 hours for flow cytometry. CD4⁺CD25⁺CD127lowFoxp3⁺ regulatory T cells (Tregs), CD4⁺CD161⁺ cells, and activated Human leukocyte antigen, HLA-DR⁺CD38⁺ T cells were determined. Ex vivo whole-blood cytokine production and Toll-like receptor (TLR)-4 expression on Tregs were measured. Absolute number of CD3⁺CD4⁺ (P = .026), CD3⁺CD8⁺ (P = .046), Tregs (P = .023), and CD4⁺CD161⁺ cells (P = .042) decreased after endotoxin administration. The frequency of anti-inflammatory Tregs increased (P = .033), whereas the frequency of proinflammatory CD4⁺CD161⁺ cells decreased (P = .034). Endotoxemia was associated with impaired whole-blood production of tumor necrosis factor-α, interleukin-10, IL-6, IL-17, IL-2, and interferon-γ in response to phytohaemagglutinin but did not affect TLR4 expression on Tregs. No changes in the absolute count or frequency of BALF T cells were observed. Systemic inflammation is associated with lymphopenia, a relative increase in the frequency of anti-inflammatory Tregs, and a functional impairment of T-cell cytokine production.

Anti-inflammatory effects of benzenediamine derivate FC-98 on sepsis injury in mice via suppression of JNK, NF-κB and IRF3 signaling pathways

FC-98, a synthesized benzenediamine derivate, was reported to regulate Toll-like receptor 9-induced activation of dendritic cells in our previous study. In this study, we evaluated the anti-inflammatory properties of FC-98 both in macrophages and in septic mouse models. By using enzyme-linked immunosorbent assay and real-time quantitative PCR, we found that FC-98 (6.25, 25 and 100μM) dose-dependently attenuated lipopolysaccharide (LPS)-induced tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and monocyte chemoattractant protein (MCP-1) productions in RAW264.7 and primary mouse peritoneal macrophages. These inhibitory effects were not due to inducing cell cytotoxicity or altering LPS binding or TLR4 expression. Subsequently, western blot, immunofluorescence and luciferase reporter assays were used to investigate the underlying mechanisms of its anti-inflammatory activities. Results showed that FC-98 blocked activation of the c-Jun N-terminal kinase (JNK), nuclear factor-κB (NF-κB) and interferon regulatory factor 3 (IRF3) signaling pathways. In vivo, FC-98 (30 or 100mg/kg) was intraperitoneally administrated into LPS-induced or CLP-induced sepsis mice. It was observed to enhance the survival rate, inhibit pro-inflammatory mediator production, improve organ injuries and suppress bacterial propagation. In conclusion, FC-98 effectively inhibited macrophage inflammatory responses and ameliorated sepsis in mice through down-regulation of both MyD88 and TRIF-dependent pathways. These results suggest that FC-98 could be a promising therapeutic agent for inflammatory diseases.

Genetic polymorphisms of innate and adaptive immunity as predictors of outcome in critically ill patients

Sepsis and septic shock frequently cause the admission or complicate the clinical course of critically ill patients admitted in the intensive care units (ICU). Genetic variations disrupting the immune sensing of infectious organisms, could affect the ability of the immune system to respond to infection, and may influence both the genetic predisposition to infection and the diversity of the clinical presentation of sepsis. The aim of this study was to uncover possible associations between common functional immune gene polymorphisms (of both innate and adaptive immunity) and ICU-acquired sepsis and mortality. The TLR4-D299G (rs4986790), TLR4-T399I (rs4986791), C2-c.841_849+19del28 (rs9332736), TACI-C104R (rs34557412), BAFFR-P21R (rs77874543), and BAFFR-H159Y (rs61756766) polymorphisms were detected in a cohort of 215 critically ill patients, admitted in an 8-bed medical/surgical ICU. Interestingly, TLR4-D299G, TLR4-T399I and BAFFR-P21R carriage was associated with a lower risk of ICU-acquired sepsis. This association applied particularly in medical patients, while in trauma and surgical patients no significant associations were observed. Moreover, carriers of TACI-C104R displayed an undiagnosed mild to moderate hypogammaglobulinemia along with a significantly lower survival rate in the ICU, although lethal events were not attributed to sepsis. These findings further elucidate the role that host immune genetic variations may play in the susceptibility to ICU-acquired sepsis and ICU mortality.

Sustained expression of lipocalin-2 during polymicrobial sepsis

Sepsis is a major healthcare problem and a leading cause of death worldwide. There is no dependable diagnosis, and treatment for this condition remains mainly supportive. The etiology of sepsis is related to an overwhelming inflammatory response. In this regard, the antimicrobial protein lipocalin-2 (Lcn2) has been associated with several inflammatory conditions, but its contribution to polymicrobial sepsis is unclear. Polymicrobial sepsis was induced by cecal ligation and puncture (CLP), and Lcn2 mRNA levels and protein expression were measured in liver and lung tissues. We observed that Lcn2 expression was robustly induced in liver and lung of C57BL/6 J (B6) mice, and remained elevated during the stage of innate immune dysfunction observed in sepsis. This response was different in A/J mice, suggesting a contribution of the genetic background, probably due to differences in IL-10 expression between these two mouse strains. Indeed, IL-10 was found to regulate Lcn2 expression in both primary and J774A.1 macrophages. Thus, Lcn2 expression is highly regulated during CLP-induced sepsis, suggesting that this antimicrobial protein could have a role as a potential biomarker for the diagnosis of sepsis.

Effect of transforming growth factor-β1 on monocyte Toll-like receptor 4 expression in septic rats

BACKGROUND

Sepsis is a tough problem in critical ill patients. This study aimed to investigate the dynamic changes of monocyte Toll-like receptor (TLR) 4 expression in peripheral blood of septic rats and to determine the effects of transforming growth factor (TGF)-β1 on TLR4 expression.

METHODS

Altogether 132 clean level SD rats were randomly divided into a control group (n=12), a sepsis model group (n=60), and a TGF-β1 intervention group (n=60). In the sepsis model group and TGF-β1 intervention group, the rats were subdivided into five groups (2-hour group, 6-hour group, 12-hour group, 24-hour group, and 48-hour group), with 12 rats in each group. Cecal ligation puncture (CLP) was performed in the sepsis model group and TGF-β1 intervention group to establish models of sepsis. The rats in the sepsis model group were injected with 1 mL normal saline at the caudal vein 0.5 hour after the model establishment; the rats in the TGF-β1 intervention group were injected with 20 ng/mL or 250 g TGF-β1 0.5 hour after the model establishment. Flow cytometry was used to detect the change of monocyte TLR4 in peripheral blood, and enzyme-linked immunosorbent assay (ELISA) was used to detect the change of TNF-α level in peripheral blood.

RESULTS

At 6-12 hours after CLP, the monocyte TLR4 in peripheral blood started to decrease, and reached the lowest level at 12 hours. Compared to the control group, the monocyte TLR4 expression at 6 and 12 hours was lowered significantly (P<0.05). Compared to the sepsis model group at 2, 24 and 48 hours after CLP, the monocyte TLR4 expression in the TGF-β1 intervention group decreased dramatically (P<0.05), but there were no differences between the two groups at 6 and 12 hours respectively. Compared to the control group, the concentration of NF-κ in liver tissue increased significantly 6 hours after CLP (P<0.05). After use of TGF-β1, the concentration of NF-κ was decreased significantly but still higher than that of the control group. Compared to the control group, the concentration of TNF-α in peripheral blood was increased significantly at 2-48 hours after CLP (P<0.05). After use of TGF-β1, TNF-α was further increased.

CONCLUSION

During sepsis, TGF-β1 can decrease the monocyte TLR4 expression and NF-κ in liver tissue, but facilitate the formation of proinflammatory mediator TNF-α. This finding indicates that TGF-β1 may play a role in promoting inflammatory response during sepsis, but this regulation is not via direct regulation of monocyte TLR4 in peripheral blood.

Transcompartmental inflammatory responses in humans: IV versus endobronchial administration of endotoxin*

OBJECTIVES

Transcompartmental signaling during early inflammation may lead to propagation of disease to other organs. The time course and the mechanisms involved are still poorly understood. We aimed at comparing acute transcompartmental inflammatory responses in humans following lipopolysaccharide-induced pulmonary and systemic inflammation.

DESIGN

Randomized, double-blind, placebo-controlled, crossover study.

SETTING ICU SUBJECTS

Healthy male volunteers.

INTERVENTIONS

Fifteen volunteers (mean age, 23; SD, 2 yr) received Escherichia coli endotoxin (lipopolysaccharide, 4 ng/kg) IV or endobronchially on two different study days. Groups were evaluated by bronchoalveolar lavage at baseline (0 hr) and 2, 4, 6, 8, or 24 hours postchallenge. Cardiorespiratory variables were continuously recorded throughout the study day, and plasma and bronchoalveolar lavage fluid markers of inflammation were measured.

MEASUREMENTS AND MAIN RESULTS

IV endotoxin elicited a systemic inflammatory response with a time-dependent increase and peak in tumor necrosis factor-α, interleukin-6, and leukocyte counts (all p < 0.001). Furthermore, a delayed (6-8 hr) increase in bronchoalveolar lavage fluid interleukin-6 concentration (p < 0.001) and alveolar leukocyte count (p = 0.03) and a minor increase in bronchoalveolar lavage fluid tumor necrosis factor-α were observed (p = 0.06). Endobronchial endotoxin was followed by progressive alveolar neutrocytosis and increased bronchoalveolar lavage fluid tumor necrosis factor-α, interleukin-6, and albumin (all p < 0.001); a systemic inflammatory response was observed after 2-4 hours, with no change in plasma tumor necrosis factor-α.

CONCLUSIONS

Acute lung or systemic inflammation in humans is followed by a transcompartmental proinflammatory response, the degree and differential kinetics of which suggests that the propagation of inflammation may depend on the primary site of injury.

5-Lipoxygenase activating protein (FLAP) dependent leukotriene biosynthesis inhibition (MK591) attenuates Lipid A endotoxin-induced inflammation

The Lipid A moiety of endotoxin potently activates TLR-4 dependent host innate immune responses. We demonstrate that Lipid-A mediated leukotriene biosynthesis regulates pathogen-associated molecular patterns (PAMP)-dependent macrophage activation. Stimulation of murine macrophages (RAW264.7) with E. coli 0111:B4 endotoxin (LPS) or Kdo2-lipid A (Lipid A) induced inflammation and Lipid A was sufficient to induce TLR-4 mediated macrophage inflammation and rapid ERK activation. The contribution of leukotriene biosynthesis was evaluated with a 5-lipoxygenase activating protein (FLAP) inhibitor, MK591. MK591 pre-treatment not only enhanced but also sustained ERK activation for up to 4 hours after LPS and Lipid A stimulation while inhibiting cell proliferation and enhancing cellular apoptosis. Leukotriene biosynthesis inhibition attenuated inflammation induced by either whole LPS or the Lipid A fraction. These responses were regulated by inhibition of the key biosynthesis enzymes for the proinflammatory eicosanoids, 5-lipoxygenase (5-LO), and cyclooxygenase-2 (COX-2) quantified by immunoblotting. Inhibition of leukotriene biosynthesis differentially regulated TLR-2 and TLR-4 cell surface expression assessed by flow cytometry, suggesting a close mechanistic association between TLR expression and 5-LO associated eicosanoid activity in activated macrophages. Furthermore, MK591 pre-treatment enhanced ERK activation and inhibited cell proliferation after LPS or Lipid A stimulation. These effects were regulated in part by increased apoptosis and modulation of cell surface TLR expression. Together, these data clarify the mechanistic association between 5-lipoxygenase activating protein-mediated leukotriene biosynthesis and 5-LO dependent eicosanoid metabolites in mediating the TLR-dependent inflammatory response after endotoxin exposure typical of bacterial sepsis.

Severe pneumonia mortality in elderly patients is associated with downregulation of Toll-like receptors 2 and 4 on monocytes

BACKGROUND

Elderly patients with pneumonia have a high mortality rate. Since Toll-like receptor (TLR) signaling is involved in the inflammatory response, we conducted a prospective observational case-control study to assess the relationships of TLR2 and TLR4 mortality with elderly patients with pneumonia.

METHODS

Clinical and laboratory data were collected from these elderly patients with pneumonia (patient group; n = 40) and healthy age-matched subjects (control 1; n = 20). TLR2 and TLR4 expression levels on blood monocytes were examined, and inflammatory cytokine tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1) and interleukin-6 (IL-6) plasma concentrations were analyzed.

RESULTS

Increased TLR2 and TLR4 expression levels were detected in elderly patients with severe pneumonia compared with healthy subjects. Furthermore, we observed a positive correlation between TLR2 and TLR4 expression levels and IL-1 and IL-6 levels, and TLR2- and TLR4-positive cell percent expressions correlated with TNF-α levels. By day 28 of observation, the mortality rate of the patient group was 30%. Decreased TLR2 and TLR4 expression was observed in deceased patients compared with survivors. APACHE (Acute Physiology and Chronic Health Evaluation) II scores and CURB-65 scores (Confusion, blood Urea nitrogen, Respiratory rate and low Blood pressure scores) were lower in survivors.

CONCLUSIONS

These findings demonstrate a previously undocumented association between mortality in elderly patients with severe pneumonia and decreased TLR2 and TLR4 expression. Our results highlight that TLRs can be targeted in the development of improved immune modulation therapies for these patients.

The contribution of group A streptococcal virulence determinants to the pathogenesis of sepsis

Streptococcus pyogenes (group A streptococcus, GAS) is responsible for a wide range of pathologies ranging from mild pharyngitis and impetigo to severe invasive soft tissue infections. Despite the continuing susceptibility of the bacterium to β-lactam antibiotics there has been an unexplained resurgence in the prevalence of invasive GAS infection over the past 30 years. Of particular importance was the emergence of a GAS-associated sepsis syndrome that is analogous to the systemic toxicosis associated with TSST-1 producing strains of Staphylococcus aureus. Despite being recognized for over 20 years, the etiology of GAS associated sepsis and the streptococcal toxic shock syndrome remains poorly understood. Here we review the virulence factors that contribute to the etiology of GAS associated sepsis with a particular focus on coagulation system interactions and the role of the superantigens in the development of streptococcal toxic shock syndrome.

Treatment with anti-inflammatory drugs in community-acquired pneumonia

Pneumonia exhibits a broad range of severity, from mildly symptomatic at one end to fulminant septic shock and death at the other. Although an adequate inflammatory response is necessary for the clearance of microorganisms, excessive inflammation can lead to ongoing local and systemic damage. Because of this extended inflammatory response despite appropriate antibiotic therapy, as well as increasing antibiotic resistance, adjuvant therapy for pneumonia that can favourably modify the immune response has become an increasingly relevant approach to improve prognosis. Different adjuvant treatment options for pneumonia have recently been proposed. Promising treatment options include corticosteroids, statins, macrolides and Toll-like receptor antagonists. The aim of this review is to summarize the inflammatory response during pneumonia and discuss the current knowledge and future perspectives regarding the anti-inflammatory treatment options for patients with pneumonia.

Analysis of membrane antigens on neutrophils from patients with sepsis

The aim of the present study was to assess changes of cell membrane antigens on neutrophils in septic patients. Expression levels of neutrophil membrane antigens were measured employing a FACS calibur flow cytometer with several fluorescence-labeled monoclonal antibodies. Expression levels of the CD14 antigen were higher in patients with sepsis than in healthy individuals. In particular, the expression levels of CD14 increased in patients complicated by septic shock. Expression levels of TLR-4 were higher in patients with sepsis or septic shock than in healthy individuals. Expression levels of CD11b and CD16 were lower in patients with sepsis or septic shock than in healthy individuals and were even lower in those complicated by septic shock. Expression levels of neutrophil membrane antigens in patients with sepsis markedly changed in the acute phase. However, these levels tended to return to those of healthy individuals in the convalescing phase. Analyses of the surface antigens on neutrophils strongly involved in biological defense or tissue injury are informative for understanding the pathology of sepsis and for conducting therapy targeting neutrophils in the future.

LOX-1 deletion improves neutrophil responses, enhances bacterial clearance, and reduces lung injury in a murine polymicrobial sepsis model

Inflammatory tissue injury and immunosuppression are the major causes of death in sepsis. Novel therapeutic targets that can prevent excessive inflammation and improve immune responses during sepsis could be critical for treatment of this devastating disease. LOX-1 (lectin-like oxidized low-density lipoprotein receptor-1), a membrane protein expressed in endothelial cells, has been known to mediate vascular inflammation. In the present study, we demonstrated that LOX-1 deletion markedly improved the survival rate in a murine model of polymicrobial sepsis. Wild-type (LOX-1(+/+)) and LOX-1 knockout (LOX-1(-/-)) mice were subjected to cecal ligation and puncture (CLP) to induce sepsis. LOX-1 deletion significantly reduced systemic inflammation and inflammatory lung injury during sepsis, together with decreased production of proinflammatory cytokines and reduced lung edema formation. Furthermore, LOX-1 deletion improved host immune responses after the induction of sepsis, as indicated by enhanced bacterial clearance. Interestingly, we were able to demonstrate that LOX-1 is expressed in neutrophils. LOX-1 deletion prevented neutrophil overreaction and increased neutrophil recruitment to infection sites after sepsis induction, contributing at least partly to increased immune responses in LOX-1 knockout mice. Our study results indicate that LOX-1 is an important mediator of inflammation and neutrophil dysfunction in sepsis.

Alarmin HMGB1 is released in the small intestine of gnotobiotic piglets infected with enteric pathogens and its level in plasma reflects severity of sepsis

OBJECTIVES

Alarmin high mobility group box 1 (HMGB1) is essential for correct DNA folding and transcription. It can be released from damaged cells or secreted by stimulated cells. HMGB1 has been detected in serum or plasma as a late marker of sepsis, but its suitability as a marker of sepsis has been disputed.

METHODS

One-week-old germ-free piglets were orally infected/colonized with enteric bacterial pathogens (Salmonella Typhimurium or Escherichia coli O55) or with probiotic bacteria (E. coli Nissle 1917) for 24 h. The transcriptions of HMGB1, interleukin (IL)-8, tumor necrosis factor (TNF)-α, and IL-10 (quantitative reverse transcription and polymerase chain reaction), their protein levels (ELISA), and clinical state of the piglets (somnolence, anorexia, diarrhea, tachycardia, tachypnea, and tremor) were estimated.

RESULTS

The piglets infected with enteric pathogens suffered from infections. HMGB1 was transcribed in the terminal ileum constitutively, regardless of any bacterial presence. In contrast, the transcription of cytokines was upregulated by virulent bacteria. HMGB1, IL-8, and TNF-α levels in the ileum were increased by both enteric pathogens, while IL-10 levels increased in E. coli O55-infected piglets only. HMGB1 significantly increased in the plasma of piglets infected with virulent E. coli only, but cytokine levels were in most cases increased by both virulent bacteria. HMGB1 and cytokine levels in ileum lavages and plasma of piglets colonized with probiotic E. coli remained comparable to those of the non-stimulated germ-free piglets.

CONCLUSION

The local and systemic expression of HMGB1, its relationship to the inflammatory cytokines, and clinical findings showed HMGB1 as a suitable marker of severity of sepsis in the gnotobiotic piglet infection model.

Sepsis and septic shock: pathophysiological and cardiovascular background as basis for therapy

INTRODUCTION

Sepsis and septic shock are common causes for admission to intensive care units. The morbidity and mortality remain unacceptably high despite the advanced treatments.

OBJECTIVES

To review the most commonly reported underlying mechanisms of sepsis and septic shock, besides discussion of sepsis-induced cardiovascular dysfunction. Therapeutic strategies for sepsis-induced myocardial depression are briefly discussed.

DATA SYNTHESIS

The development of sepsis and septic shock is multifactorial. Two major mechanisms contribute to the haemodynamic collapse. The extrinsic and intrinsic mechanisms induce a complex cascade which results in the release of pro- and anti-inflammatory mediators. Sepsis develops when the initial, appropriate host response to an infection becomes amplified and then dysregulated leading to haemodynamic and circulatory changes. The pro-inflammatory mediators tumour necrosis factor alpha, interleukin-beta and nitric oxide play a significant role in sepsis-related hypotension, shock and depression of cardiomyocyte contractility. Septic cardiac dysfunction can be explained by various mechanisms: changes in circulating volume, down-regulation of beta-adrenergic receptors, depressed post-receptor signalling pathways, reduced calcium release from the sarcoplasmic reticulum and impaired electromechanical coupling and reduced calcium sensibility at the myofibrillar level. Mitochondrial derangement seems to be of great importance in tissue injury and sepsis-associated multi organ failure. There is no consistent protocol for treating sepsis and septic shock. Guidelines include early goal-directed therapy, source control and haemodynamic supportive measures.

CONCLUSION

Further studies are needed to distinguish the importance of these various mechanisms. We recommend that further investigational work should focus on the recovery of the mitochondria-related bio-energetic shut down as the mitochondria could play a key role in the understanding of apoptosis and protective measures. Understanding the pathophysiology of sepsis and septic shock will inevitably lead to a more accurate treatment of these still too often fatal syndromes.

Toll-like receptor 8 and 9 polymorphisms in Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever (CCHF) is an acute viral hemorrhagic fever. The clinical course and outcome of the CCHF infection are different in humans. Toll-like receptors (TLRs) are a family of pathogen recognition receptors. TLR8 and TLR9 contribute to the recognition of viruses. We investigated frequency of TLR8 Met1Val, TLR8 -129C/G, TLR9 -1486T/C and TLR9 2458G/A polymorphisms in CCHF patients and healthy controls. Our study was conducted between June 1 and August 31, 2007 in Cumhuriyet University Hospital, Turkey. TLR genotypes were detected using the PCR-RFLP assay in 85 CCHF patients and 171 healthy controls. We found that heterozygous plus homozygous mutant genotypes frequency for TLR8 Met1Val and for TLR9 -1486T/C were significantly higher in CCHF patients than controls (p = 0.038 and p = 0.009, respectively). The frequency of TLR8 -129G/G genotype in the fatal CCHF patients was significantly higher than that of the non-fatal patients (p = 0.026). The frequency of TLR9 -1486C/C genotype was significantly higher in fatal CCHF patients than in healthy controls (p = 0.009) and in patients with severe disease compared to non-severe disease (p = 0.044). Our findings suggest that TLR8 Met1Val, TLR8 -129C/G, and TLR9 -1486T/C polymorphisms are important on clinical course of CCHF disease.

Mortality in human sepsis is associated with downregulation of Toll-like receptor 2 and CD14 expression on blood monocytes

Pattern recognition receptors are a key component of the first line host defense against infection, recognizing specific microbial products. We hypothesize that monocyte hyporesponsiveness in human sepsis is associated with a downregulation of the pattern recognition receptors Toll-like receptor (TLR)-2 and TLR4.Protein expression of CD14, TLR2 and TLR4 on blood monocytes was examined using flow cytometry from 29 patients with sepsis and 14 healthy controls. In addition LPS stimulated TNF-alpha and IL-10 production was studied in a 24 hour whole blood assay.We found an increased expression of CD14, TLR2 and TLR4 in patients with sepsis compared to controls (p < 0.01). In patients with sepsis, death was associated with significant lower CD14 and TLR2 expression at admission (CD14: 25.7 +- 19.1 vs 39.1 +- 17.3 mean fluorescence intensity [MFI], p = 0.02; TLR2: 21.8 +- 9.4 vs. 30.9 +- 9.6, p = 0.01). At 72 hours the TLR2 expression on monocytes was associated with the IL-10 inducibility after LPS stimulation (r = 0.52, p = 0.02) and the CD14 expression with the IL-6, IL-10 and TNF inducibility.We conclude that septic patients are characterized by an increased expression of CD14, TLR2 and TLR4 on monocytes compared to controls. Death is associated with downregulation of TLR2 and CD14 expression on monocytes correlating with reduced cytokine inducibility. We suggest that CD14 and TLR2 are a key factor in monocyte hyporesponsibility during severe sepsis.

Role of pulmonary intravascular macrophages in endotoxin-induced lung inflammation and mortality in a rat model

Background

Bile-duct ligated (BDL) rats recruit pulmonary intravascular macrophages (PIMs) and are highly susceptible to endotoxin-induced mortality. The mechanisms of this enhanced susceptibility and mortality in BDL rats, which are used as a model of hepato-pulmonary syndrome, remain unknown. We tested a hypothesis that recruited PIMs promote endotoxin-induced mortality in a rat model.

Methods

Rats were subjected to BDL to induce PIM recruitment followed by treatment with gadolinium chloride (GC) to deplete PIMs. Normal and BDL rats were treated intravenously with E. coli lipopolysaccharide (LPS) with or without GC pre-treatment followed by collection and analyses of lungs for histopathology, electron microscopy and cytokine quantification.

Results

BDL rats recruited PIMs without any change in the expression of IL-1β, TNF-α and IL-10. GC caused reduction in PIMs at 48 hours post-treatment (P < 0.05). BDL rats treated intravenously with E. coli LPS died within 3 hours of the challenge while the normal LPS-treated rats were euthanized at 6 hours after the LPS treatment. GC treatment of rats 6 hours or 48 hours before LPS challenge resulted in 80% (1/5) and 100% (0/5) survival, respectively, at 6 hours post-LPS treatment. Lungs from BDL+LPS rats showed large areas of perivascular hemorrhages compared to those pre-treated with GC. Concentrations of IL-1β, TNF-α and IL-10 were increased in lungs of BDL+LPS rats compared to BDL rats treated with GC 48 hours but not 6 hours before LPS (P < 0.05).

Conclusion

We conclude that PIMs increase susceptibility for LPS-induced lung injury and mortality in this model, which is blocked by a reduction in their numbers or their inactivation.