Sepsis: Still Going Strong

A highly efficient hybrid peptide ameliorates intestinal inflammation and mucosal barrier damage by neutralizing lipopolysaccharides and antagonizing the lipopolysaccharide-receptor interaction

Intestinal inflammatory disorders, such as inflammatory bowel disease, are major contributors to mortality and morbidity in humans and animals worldwide. While some native peptides have great potential as therapeutic agents against intestinal inflammation, potential cytotoxicity, anti-inciting action, and suppression of anti-inflammatory activity may limit their development as anti-inflammatory agents. Peptide hybridization is an effective approach for the design and engineering of novel functional peptides because hybrid peptides combine the advantages and benefits of various native peptides. In the present study, a novel hybrid anti-inflammatory peptide that combines the active center of Cecropin A (C) and the core functional region of LL-37 (L) was designed [C-L peptide; C (1-8)-L (17-30)] through in silico analysis to reduce cytotoxicity and improve the anti-inflammatory activity of the parental peptides. The resulting C-L peptide exhibited lower cytotoxicity than either C or L peptides alone. C-L also exerted a protective effect against lipopolysaccharide (LPS)-induced inflammatory responses in RAW264.7 macrophages and in the intestines of a mouse model. The hybrid peptide exhibited increased anti-inflammatory activity compared to the parental peptides. C-L plays a role in protecting intestinal tissue from damage, LPS-induced weight loss, and leukocyte infiltration. In addition, C-L reduces the expression levels of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), IL-1β, and interferon-gamma (IFN-γ), as well as reduces cell apoptosis. It also reduced mucosal barrier damage caused by LPS. The anti-inflammatory effects of the hybrid peptide were mainly attributed to its LPS-neutralizing activity and antagonizing the activation of LPS-induced Toll-like receptor 4-myeloid differentiation factor 2 (TLR4/MD2). The peptide also affected the TLR4-(nuclear factor κB) signaling pathway, modulating the inflammatory response upon LPS stimulation. Collectively, these findings suggest that the newly designed peptide, C-L, could be developed into a novel anti-inflammatory agent for animals or humans.

Structure-Activity Relationship in TLR4 Mutations: Atomistic Molecular Dynamics Simulations and Residue Interaction Network Analysis

Toll-like receptor 4 (TLR4), a vital innate immune receptor present on cell surfaces, initiates a signaling cascade during danger and bacterial intrusion. TLR4 needs to form a stable hexamer complex, which is necessary to dimerize the cytoplasmic domain. However, D299G and T399I polymorphism may abrogate the stability of the complex, leading to compromised TLR4 signaling. Crystallography provides valuable insights into the structural aspects of the TLR4 ectodomain; however, the dynamic behavior of polymorphic TLR4 is still unclear. Here, we employed molecular dynamics simulations (MDS), as well as principal component and residue network analyses, to decipher the structural aspects and signaling propagation associated with mutations in TLR4. The mutated complexes were less cohesive, displayed local and global variation in the secondary structure, and anomalous decay in rotational correlation function. Principal component analysis indicated that the mutated complexes also exhibited distinct low-frequency motions, which may be correlated to the differential behaviors of these TLR4 variants. Moreover, residue interaction networks (RIN) revealed that the mutated TLR4/myeloid differentiation factor (MD) 2 complex may perpetuate abnormal signaling pathways. Cumulatively, the MDS and RIN analyses elucidated the mutant-specific conformational alterations, which may help in deciphering the mechanism of loss-of-function mutations.

Toll-like receptor 4 gene is associated with recurrent spontaneous miscarriage in Uygur and Han women in Xinjiang

Toll-like receptor 4 (TLR4), a recently identified vertebrate receptor, serves a pivotal role in immune responses. The aim of the present study was to investigate the association between the human TLR4 gene and recurrent spontaneous miscarriage (RSM). A total of 306 RSM patents and 306 age-matched controls were genotyped for four single-nucleotide polymorphisms (SNPs) of the human TLR4 gene (rs1927914, rs1927911, rs4986790 and rs4986791). Data were analyzed for Uygur and Han women separately using a haplotype-based case-control study. There were significant differences between the distributions of rs1927914, rs1927911 and rs4986790 SNPs between RSM patients and the controls (P=0.001, P<0.001 and P=0.015, respectively) were identified in Uygur women, and significant differences between the distributions of the rs1927914 and rs1927911 SNPs between RSM patients and the controls (P<0.001 and P<0.001, respectively) were identified in Han women. Results of the logistic regression analysis indicated that rs1927914, rs1927911 and rs4986790 SNPs were significantly higher in the RSM patients compared with the control individuals (P=0.012, P=0.024 and P=0.035, respectively) in Uygur women. Furthermore, significantly higher frequency was noted for the A-G-G haplotype (SNP1-SNP2-SNP3) (P=0.016) in RSM patients compared with the controls in Uygur women. The results indicate that rs1927914, rs1927911, rs4986790 and the A-G-G haplotype (SNP1-SNP2-SNP3) of the human TLR4 gene may be genetic markers for RSM in Uygur women, while rs1927914 and rs1927911 SNPs of the human TLR4 gene are most likely associated with RSM in Han women in Xinjiang.

Activation of Human Toll-like Receptor 4 (TLR4)·Myeloid Differentiation Factor 2 (MD-2) by Hypoacylated Lipopolysaccharide from a Clinical Isolate of Burkholderia cenocepacia

Lung infection by Burkholderia species, in particular Burkholderia cenocepacia, accelerates tissue damage and increases post-lung transplant mortality in cystic fibrosis patients. Host-microbe interplay largely depends on interactions between pathogen-specific molecules and innate immune receptors such as Toll-like receptor 4 (TLR4), which recognizes the lipid A moiety of the bacterial lipopolysaccharide (LPS). The human TLR4·myeloid differentiation factor 2 (MD-2) LPS receptor complex is strongly activated by hexa-acylated lipid A and poorly activated by underacylated lipid A. Here, we report that B. cenocepacia LPS strongly activates human TLR4·MD-2 despite its lipid A having only five acyl chains. Furthermore, we show that aminoarabinose residues in lipid A contribute to TLR4-lipid A interactions, and experiments in a mouse model of LPS-induced endotoxic shock confirmed the proinflammatory potential of B. cenocepacia penta-acylated lipid A. Molecular modeling combined with mutagenesis of TLR4-MD-2 interactive surfaces suggests that longer acyl chains and the aminoarabinose residues in the B. cenocepacia lipid A allow exposure of the fifth acyl chain on the surface of MD-2 enabling interactions with TLR4 and its dimerization. Our results provide a molecular model for activation of the human TLR4·MD-2 complex by penta-acylated lipid A explaining the ability of hypoacylated B. cenocepacia LPS to promote proinflammatory responses associated with the severe pathogenicity of this opportunistic bacterium.

Vizantin inhibits endotoxin-mediated immune responses via the TLR 4/MD-2 complex

Vizantin has immunostimulating properties and anticancer activity. In this study, we investigated the molecular mechanism of immune activation by vizantin. THP-1 cells treated with small interfering RNA for TLR-4 abolished vizantin-induced macrophage activation processes such as chemokine release. In addition, compared with wild-type mice, the release of MIP-1β induced by vizantin in vivo was significantly decreased in TLR-4 knockout mice, but not in TLR-2 knockout mice. Vizantin induced the release of IL-8 when HEK293T cells were transiently cotransfected with TLR-4 and MD-2, but not when they were transfected with TLR-4 or MD-2 alone or with TLR-2 or TLR-2/MD-2. A dipyrromethene boron difluoride-conjugated vizantin colocalized with TLR-4/MD-2, but not with TLR-4 or MD-2 alone. A pull-down assay with vizantin-coated magnetic beads showed that vizantin bound to TLR-4/MD-2 in extracts from HEK293T cells expressing both TLR-4 and MD-2. Furthermore, vizantin blocked the LPS-induced release of TNF-α and IL-1β and inhibited death in mice. We also performed in silico docking simulation analysis of vizantin and MD-2 based on the structure of MD-2 complexed with the LPS antagonist E5564; the results suggested that vizantin could bind to the active pocket of MD-2. Our observations show that vizantin specifically binds to the TLR-4/MD-2 complex and that the vizantin receptor is identical to the LPS receptor. We conclude that vizantin could be an effective adjuvant and a therapeutic agent in the treatment of infectious diseases and the endotoxin shock caused by LPS.

Modulation of CD14 and TLR4·MD-2 activities by a synthetic lipid A mimetic

Monosaccharide lipid A mimetics based on a glucosamine core linked to two fatty acid chains and bearing one or two phosphate groups have been synthesized. Compounds 1 and 2, each with one phosphate group, were practically inactive in inhibiting LPS-induced TLR4 signaling and cytokine production in HEK-blue cells and murine macrophages, but compound 3, with two phosphate groups, was found to be active in efficiently inhibiting TLR4 signal in both cell types. The direct interaction between compound 3 and the MD-2 coreceptor was investigated by NMR spectroscopy and molecular modeling/docking analysis. This compound also interacts directly with the CD14 receptor, stimulating its internalization by endocytosis. Experiments on macrophages show that the effect on CD14 reinforces the activity on MD-2·TLR4 because compound 3's activity is higher when CD14 is important for TLR4 signaling (i.e., at low LPS concentration). The dual targeting of MD-2 and CD14, accompanied by good solubility in water and lack of toxicity, suggests the use of monosaccharide 3 as a lead compound for the development of drugs directed against TLR4-related syndromes.

The crystal structure of human soluble CD14 reveals a bent solenoid with a hydrophobic amino-terminal pocket

Human monocyte differentiation Ag CD14 is a pattern recognition receptor that enhances innate immune responses to infection by sensitizing host cells to bacterial LPS (endotoxin), lipoproteins, lipoteichoic acid, and other acylated microbial products. CD14 physically delivers these lipidated microbial products to various TLR signaling complexes that subsequently induce intracellular proinflammatory signaling cascades upon ligand binding. The ensuing cellular responses are usually protective to the host but can also result in host fatality through sepsis. In this work, we have determined the x-ray crystal structure of human CD14. The structure reveals a bent solenoid typical of leucine-rich repeat proteins with an amino-terminal pocket that presumably binds acylated ligands including LPS. Comparison of human and mouse CD14 structures shows great similarity in overall protein fold. However, compared with mouse CD14, human CD14 contains an expanded pocket and alternative rim residues that are likely to be important for LPS binding and cell activation. The x-ray crystal structure of human CD14 presented in this article may foster additional ligand-bound structural studies, virtual docking studies, and drug design efforts to mitigate LPS-induced sepsis and other inflammatory diseases.

Structural analyses of human Toll-like receptor 4 polymorphisms D299G and T399I

BACKGROUND

TLR4 polymorphism replacing Asp-299 with Gly and Thr-399 with Ile (D299G/T399I) causes LPS hyporesponsiveness.

RESULTS

TLR4(SNPs)·MD-2·LPS exhibits an agonistic 2:2:2 architecture. Local structural differences were observed around D299G, but not around T399I, SNP site.

CONCLUSION

These local differences cause the modulation of surface properties of TLR4, which may affect ligand binding.

SIGNIFICANCE

This study provides structural evidence of the functionality of the mutant TLR4 carrying the SNPs. Toll-like receptor 4 (TLR4) and its coreceptor MD-2 recognize bacterial lipopolysaccharide (LPS) and signal the innate immune response. Two single nucleotide polymorphisms (SNPs) of human TLR4, D299G and T399I, have been identified and suggested to be associated with LPS hyporesponsiveness. Moreover, the SNPs have been proposed to be associated with a variety of infectious and noninfectious diseases. However, how the SNPs affect the function of TLR4 remains largely unknown. Here, we report the crystal structure of the human TLR4 (D299G/T399I)·MD-2·LPS complex at 2.4 Å resolution. The ternary complex exhibited an agonistic "m"-shaped 2:2:2 architecture that was similar to that of the human wild type TLR4·MD-2·LPS complex. Local structural differences that might affect the binding of the ligands were observed around D299G, but not around T399I, SNP site.

Effects of low-dose acetylsalicylic acid and atherosclerotic vascular diseases on the outcome in patients with severe sepsis or septic shock

Sepsis and its sequelae of multiple organ failure is one of the leading causes of death in the industrial countries. Several studies have shown that patients who are treated with low-dose acetyl salicylic acid (ASA) for secondary prevention of atherothrombosis may have a lower risk to develop organ failure in the case of critical illness. The benefit of ASA is probably due to an inhibition of platelet activation as well as an increase in the formation of anti-inflammatory lipoxin A4. On the other hand, the effect of ASA could be - at least partially - an indirect one, caused by atherosclerotic vascular diseases as the cause of ASA treatment. Atherosclerosis is considered as a moderate systemic inflammation and we hypothesise that this chronic condition could have an impact on the outcome in sepsis. To get more information on the benefit of ASA in critically ill patients and on possible interference with atherosclerotic vascular diseases, we analysed the medical records of 886 septic patients who were admitted to the surgical intensive care unit (ICU) of a university hospital. Logistic regression analysis indicated that patients who were treated during the ICU stay with ASA (100 mg/d) had a significantly lower mortality. Odds ratios (ORs; with 95% confidential intervals) of 0.56 (0.37-0.84) and 0.57 (0.39-0.83) were calculated for ICU and hospital mortality, respectively. In contrast, statin treatment did not have significant effect on mortality. Diagnosis of atherosclerotic vascular diseases according to ICD classification did not influence ICU mortality but lowered hospital mortality (OR = 0.71 (0.52-0.99)). Subgroup analysis provided preliminary evidence that clopidogrel when given as only anti-platelet drug may have a similar benefit as ASA, but the combination of ASA and clopidogrel failed to improve the outcome. The time course of plasma fibrinogen and procalcitonin levels indicate that ASA seems to reduce the activation of haemostasis and increase the resolution of inflammation. It is concluded that prospective interventional studies should be done to test the use of ASA as novel therapeutic approach in critically ill patients.

Alcohol acute intoxication before sepsis impairs the wound healing of intestinal anastomosis: rat model of the abdominal trauma patient

Introduction

Most trauma patients are drunk at the time of injury. Up to 2% of traumatized patients develop sepsis, which considerably increases their mortality. Inadequate wound healing of the colonic repair can lead to postoperative complications such as leakage and sepsis.

Objective

To assess the effects of acute alcohol intoxication on colonic anastomosis wound healing in septic rats.

Methods

Thirty six Wistar rats were allocated into two groups: S (induction of sepsis) and AS (alcohol intake before sepsis induction). A colonic anastomosis was performed in all groups. After 1, 3 or 7 days the animals were killed. Weight variations, mortality rate, histopathology and tensile breaking strength of the colonic anastomosis were evaluated.

Results

There was an overall mortality of 4 animals (11.1%), three in the group AS (16.6%) and one in the S group (5.5%). Weight loss occurred in all groups. The colon anastomosis of the AS group didn’t gain strength from the first to the seventh postoperative day. On the histopathological analysis there were no differences in the deposition of collagen or fibroblasts between the groups AS and S.

Conclusion

Alcohol intake increased the mortality rate three times in septic animals. Acute alcohol intoxication delays the acquisition of tensile strength of colonic anastomosis in septic rats. Therefore, acute alcohol intoxication before sepsis leads to worse prognosis in animal models of the abdominal trauma patients.

Increased NTPDase activity in lymphocytes during experimental sepsis

We investigated in rats induced to sepsis the activity of ectonucleoside triphosphate diphosphohydrolase (NTPDase; CD39; E.C. 3.6.1.5), an enzyme involved in the modulation of immune responses. After 12 hours of surgery, lymphocytes were isolated from blood and NTPDase activity was determined. It was also performed the histology of kidney, liver, and lung. The results demonstrated an increase in the hydrolysis of adenosine-5′-triphosphate (ATP) (P < 0.01), but no changes regarding adenosine-5′-monophosphate (ADP) hydrolysis (P > 0.05). Histological analysis showed several morphological changes in the septic group, such as vascular congestion, necrosis, and infiltration of mononuclear cells. It is known that the intracellular milieu contains much more ATP nucleotides than the extracellular. In this context, the increased ATPasic activity was probably induced as a dynamic response to clean up the elevated ATP levels resulting from cellular death.

Structural basis of species-specific endotoxin sensing by innate immune receptor TLR4/MD-2

Lipopolysaccharide (LPS), also known as endotoxin, activates the innate immune response through toll-like receptor 4 (TLR4) and its coreceptor, MD-2. MD-2 has a unique hydrophobic cavity that directly binds to lipid A, the active center of LPS. Tetraacylated lipid IVa, a synthetic lipid A precursor, acts as a weak agonist to mouse TLR4/MD-2, but as an antagonist to human TLR4/MD-2. However, it remains unclear as to how LPS and lipid IVa show agonistic or antagonistic activities in a species-specific manner. The present study reports the crystal structures of mouse TLR4/MD-2/LPS and TLR4/MD-2/lipid IVa complexes at 2.5 and 2.7 Å resolutions, respectively. Mouse TLR4/MD-2/LPS exhibited an agonistic "m"-shaped 2:2:2 complex similar to the human TLR4/MD-2/LPS complex. Mouse TLR4/MD-2/lipid IVa complex also showed an agonistic structural feature, exhibiting architecture similar to the 2:2:2 complex. Remarkably, lipid IVa in the mouse TLR4/MD-2 complex occupied nearly the same space as LPS, although lipid IVa lacked the two acyl chains. Human MD-2 binds lipid IVa in an antagonistic manner completely differently from the way mouse MD-2 does. Together, the results provide structural evidence of the agonistic property of lipid IVa on mouse TLR4/MD-2 and deepen understanding of the ligand binding and dimerization mechanism by the structurally diverse LPS variants.

Vibrio vulnificus IlpA induces MAPK-mediated cytokine production via TLR1/2 activation in THP-1 cells, a human monocytic cell line

Vibrio vulnificus is a pathogenic bacterium causing primary septicemia, which is followed by a classical septic shock pathway including an overwhelming inflammatory cytokine response. V. vulnificus IlpA is a potent immunogenic lipoprotein that triggers cytokine production in human monocytes by activating the toll-like receptor 2 (TLR2). In this study, we further defined the IlpA signaling pathways involved in cytokine production in the human monocytic cell line, THP-1. TLR2 was involved in cytokine production by complexing with TLR1, but not with TLR6. MyD88 was necessary for IlpA-induced cytokine expression through TLR1/TLR2. Three mitogen activated protein kinases (MAPK), p38, ERK1/2, and JNK, were activated in THP-1 cells stimulated with recombinant IlpA (rIlpA). Selective inhibition of each MAPK resulted in significant decrease of rIlpA-induced cytokine production. Especially, functional TLR2 was necessary for IlpA-induced activation of p38 and JNK. IlpA augmented the DNA-binding activity of nuclear factor-kappaB (NF-κB) and activator protein-1 (AP-1) transcriptional factors to their recognition sites in THP-1 cells. These results suggest that serial activation of TLR1/TLR2, MyD88, the three MAPKs, and NF-κB/AP-1 comprises the signaling pathway responsible for proinflammatory cytokine production by V. vulnificus IlpA.

Genome-wide expression profiling and mutagenesis studies reveal that lipopolysaccharide responsiveness appears to be absolutely dependent on TLR4 and MD-2 expression and is dependent upon intermolecular ionic interactions

Lipid A (a hexaacylated 1,4' bisphosphate) is a potent immune stimulant for TLR4/MD-2. Upon lipid A ligation, the TLR4/MD-2 complex dimerizes and initiates signal transduction. Historically, studies also suggested the existence of TLR4/MD-2-independent LPS signaling. In this article, we define the role of TLR4 and MD-2 in LPS signaling by using genome-wide expression profiling in TLR4- and MD-2-deficient macrophages after stimulation with peptidoglycan-free LPS and synthetic Escherichia coli lipid A. Of the 1396 genes significantly induced or repressed by any one of the treatments in the wild-type macrophages, none was present in the TLR4- or MD-2-deficient macrophages, confirming that the TLR4/MD-2 complex is the only receptor for endotoxin and that both are required for responses to LPS. Using a molecular genetics approach, we investigated the mechanism of TLR4/MD-2 activation by combining the known crystal structure of TLR4/MD-2 with computer modeling. According to our murine TLR4/MD-2-activation model, the two phosphates on lipid A were predicted to interact extensively with the two positively charged patches on mouse TLR4. When either positive patch was abolished by mutagenesis into Ala, the responses to LPS and lipid A were nearly abrogated. However, the MyD88-dependent and -independent pathways were impaired to the same extent, indicating that the adjuvant activity of monophosphorylated lipid A most likely arises from its decreased potential to induce an active receptor complex and not more downstream signaling events. Hence, we concluded that ionic interactions between lipid A and TLR4 are essential for optimal LPS receptor activation.

[Septic vasculopathy]

Sepsis is one of the commonest causes of death around the world. The real frequency of cutaneous lesions in the setting of sepsis is unknown, but when they appear, they are usually one of the earliest signs of sepsis, thus allowing a rapid diagnosis of this potentially life-threatening condition. Four are the main physiopathologic mechanisms that can induce cutaneous lesions in sepsis: a) disseminated intravascular coagulation; b) direct vessel wall invasion by the microorganism; c) immune-mediated vasculitis, and d) septic embolism. We know that more than one of these mechanisms can appear in one single patient. In this review, we analyse these four mechanisms, their clinical presentation, and the histological findings that can be found in the cutaneous biopsy.

Outer membrane vesicles derived from Escherichia coli induce systemic inflammatory response syndrome

Sepsis, characterized by a systemic inflammatory state that is usually related to Gram-negative bacterial infection, is a leading cause of death worldwide. Although the annual incidence of sepsis is still rising, the exact cause of Gram-negative bacteria-associated sepsis is not clear. Outer membrane vesicles (OMVs), constitutively secreted from Gram-negative bacteria, are nano-sized spherical bilayered proteolipids. Using a mouse model, we showed that intraperitoneal injection of OMVs derived from intestinal Escherichia coli induced lethality. Furthermore, OMVs induced host responses which resemble a clinically relevant condition like sepsis that was characterized by piloerection, eye exudates, hypothermia, tachypnea, leukopenia, disseminated intravascular coagulation, dysfunction of the lungs, hypotension, and systemic induction of tumor necrosis factor-alpha and interleukin-6. Our study revealed a previously unidentified causative microbial signal in the pathogenesis of sepsis, suggesting OMVs as a new therapeutic target to prevent and/or treat severe sepsis caused by Gram-negative bacterial infection.

MD-2-mediated ionic interactions between lipid A and TLR4 are essential for receptor activation

Lipopolysaccharide (LPS) activates innate immune responses through TLR4.MD-2. LPS binds to the MD-2 hydrophobic pocket and bridges the dimerization of two TLR4.MD-2 complexes to activate intracellular signaling. However, exactly how lipid A, the endotoxic moiety of LPS, activates myeloid lineage cells remains unknown. Lipid IV(A), a tetra-acylated lipid A precursor, has been used widely as a model for lipid A activation. For unknown reasons, lipid IV(A) activates proinflammatory responses in rodent cells but inhibits the activity of LPS in human cells. Using stable TLR4-expressing cell lines and purified monomeric MD-2, as well as MD-2-deficient bone marrow-derived macrophages, we found that both mouse TLR4 and mouse MD-2 are required for lipid IV(A) activation. Computational studies suggested that unique ionic interactions exist between lipid IV(A) and TLR4 at the dimerization interface in the mouse complex only. The negatively charged 4'-phosphate on lipid IV(A) interacts with two positively charged residues on the opposing mouse, but not human, TLR4 (Lys(367) and Arg(434)) at the dimerization interface. When replaced with their negatively charged human counterparts Glu(369) and Gln(436), mouse TLR4 was no longer responsive to lipid IV(A). In contrast, human TLR4 gained lipid IV(A) responsiveness when ionic interactions were enabled by charge reversal at the dimerization interface, defining the basis of lipid IV(A) species specificity. Thus, using lipid IV(A) as a selective lipid A agonist, we successfully decoupled and coupled two sequential events required for intracellular signaling: receptor engagement and dimerization, underscoring the functional role of ionic interactions in receptor activation.

Tissue factor pathway inhibitor and P-selectin as markers of sepsis-induced non-overt disseminated intravascular coagulopathy

Inflammation and coagulation occur concomitantly in sepsis. Thrombin activates platelet that leads to P-selectin translocation, which upregulate tissue factor (TF) generation. Tissue factor pathway inhibitor (TFPI) is an anticoagulant that modulates coagulation induced by TF. The term non-overt disseminated intravascular coagulation (DIC) refers to a state of affairs prevalent before the occurrence of overt DIC. It was suggested that an initiation of treatment in non-overt DIC has better outcome than overt DIC. This study investigated the role of TFPI level, P-selectin, and thrombin activation markers in non-overt and overt DIC induced by sepsis and its relationship to outcome and organ dysfunction as measured by the Sequential Organ Failure Assessment (SOFA) score. It included 176 patients with sepsis. They were admitted to the pediatric intensive care unit (ICU).They included 144 cases of non-overt DIC and 32 cases of overt DIC. There was a significant difference in hemostatic markers, platelet count, partial thromboplastin time (PTT), P-selectin, thrombin activation markers, TFPI, and DIC score between overt and non-overt DIC in both groups. It was noticed that P-selectin was positively correlated with DIC score, fibrinogen consumption, fibrinolysis (D-dimer), thrombin activation markers, and TFPI. Tissue factor pathway inhibitor was significantly correlated with fibrinolysis, DIC score, and prothrombin fragment 1+2. Sequential Organ Failure Assessment score was correlated with DIC score and other hemostatic markers in patients with overt DIC. To improve the outcome of patients with DIC, there is a need to establish more diagnostic criteria for non-overt-DIC. Plasma levels of TFPI and P-selectin may be helpful in this respect.

Update on the management of infection in patients with severe sepsis

Morbidity and mortality associated with the development of severe sepsis remain unacceptably high. However, with the introduction of a protocol called early goal-directed therapy, significant benefits in terms of patient's outcome have been demonstrated. In an aim to improve outcome and to increase awareness, practical evidence-based guidelines for the management of severe sepsis and septic shock were developed under the auspices of the Sepsis Surviving Campaign, easy to apply by the bedside medical and nursing staff. The treatment of severe sepsis includes 3 main essentials: (1) eradication of the inciting infection using source control measures and empiric antimicrobials, (2) hemodynamic resuscitation of tissue hypoperfusion using fluids and inotropic drugs to prevent life-threatening organ damage, and (3) sustained organ support using mechanical interventions to diminish organ injury. This review article highlights the anti-infective approach of the management of sepsis.

Bench-to-bedside review: Developmental influences on the mechanisms, treatment and outcomes of cardiovascular dysfunction in neonatal versus adult sepsis

Sepsis is a significant cause of morbidity and mortality in neonates and adults, and the mortality rate doubles in patients who develop cardiovascular dysfunction and septic shock. Sepsis is especially devastating in the neonatal population, as it is one of the leading causes of death for hospitalized infants. In the neonate, there are multiple developmental alterations in both the response to pathogens and the response to treatment that distinguish this age group from adults. Differences in innate immunity and cytokine response may predispose neonates to the harmful effects of pro-inflammatory cytokines and oxidative stress, leading to severe organ dysfunction and sequelae during infection and inflammation. Underlying differences in cardiovascular anatomy, function and response to treatment may further alter the neonate's response to pathogen exposure. Unlike adults, little is known about the cardiovascular response to sepsis in the neonate. In addition, recent research has demonstrated that the mechanisms, inflammatory response, response to treatment and outcome of neonatal sepsis vary not only from that of adults, but vary among neonates based on gestational age. The goal of the present article is to review key pathophysiologic aspects of sepsis-related cardiovascular dysfunction, with an emphasis on defining known differences between adult and neonatal populations. Investigations of these relationships may ultimately lead to 'neonate-specific' therapeutic strategies for this devastating and costly medical problem.

Early effects of lipopolysaccharide on cytokine release, hemodynamic and renal function in newborn piglets

BACKGROUND

Gram-negative sepsis in newborns is associated with high mortality and morbidity. Lipopolysaccharide (LPS) and cytokines released upon exposure to gram-negative sepsis are well known to be involved in the pathophysiology.

OBJECTIVE

In this report we investigate cytokine release, hemodynamic, and renal function induced by LPS in a newborn animal model with the intention to further examine early changes in gram-negative sepsis.

METHODS

Five 7- to 10-day-old domestic piglets were anesthetized and catheters placed in the jugular veins, left ventricle, and femoral artery. Urine output was monitored via suprapubic cystostomy. Mean arterial pressure, heart rate, and arterial blood gases were continuously monitored. Thirty minutes after line placement and obtaining baseline values, 0.06 mug/kg LPS were administered intravenously. One, 2, and 3 h later samples were taken to monitor tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, endothelin, and nitric oxide (NO)/nitrate via ELISA. In addition, blood flow was assessed by the microsphere method.

RESULTS

Our data show an initial surge of TNF-alpha and IL-1beta at 1 h after exposure to LPS. NO/nitrate, endothelin, and hemodynamic as well as metabolic changes became apparent mostly 3 h after exposure, by which time TNF-alpha and IL-1beta fell back to baseline.

CONCLUSIONS

Our sepsis model suggests a brief initial TNF-alpha and IL-1beta surge following LPS challenge; however, their effects become apparent by the time the levels are already subsiding. The emergence of vasoactive substances, NO and endothelin, precedes the first substantial clinical symptoms.

Cathelicidins and functional analogues as antisepsis molecules

The emergence of antibiotic-resistant bacteria together with the limited success of sepsis therapeutics has lead to an urgent need for the development of alternative strategies for the treatment of systemic inflammatory response syndrome and related disorders. Immunomodulatory compounds that do not target the pathogen directly (therefore limiting the development of pathogen resistance), and target multiple inflammatory mediators, are attractive candidates as novel therapeutics. Cationic host defence peptides such as cathelicidins have been demonstrated to be selectively immunomodulatory in that they can confer anti-infective immunity and modulate the inflammatory cascade through multiple points of intervention. The human cathelicidin LL-37, for example, has modest direct antimicrobial activity under physiological conditions, but has been demonstrated to have potent antiendotoxin activity in animal models, as well as the ability to resolve certain bacterial infections. A novel synthetic immunomodulatory peptide, IDR-1, built on this same theme has no direct antimicrobial activity, but is effective in restricting many types of infection, while limiting pro-inflammatory responses. The ability of these peptides to selectively suppress harmful pro-inflammatory responses, while maintaining beneficial infection-fighting components of host innate defences makes them a good model for antisepsis therapies that merit further investigation.

Vibrio vulnificus IlpA-induced cytokine production is mediated by Toll-like receptor 2

Vibrio vulnificus is a pathogenic bacterium causing primary septicemia, which follows a classical septic shock pathway, including an overwhelming inflammatory cytokine response. In this study, we identified a putative lipoprotein of V. vulnificus, encoded by the ilpA gene, as one of the surface proteins that specifically reacted with the antibodies raised against outer membrane proteins of V. vulnificus. Using a mutant V. vulnificus in which its ilpA gene was knocked out, we found that IlpA is important in the production of interferon-gamma in human peripheral blood mononuclear cells. Production of tumor necrosis factor-alpha and interleukin-6 is also induced by the recombinant IlpA (rIlpA) in human monocytes. Lipidation of the rIlpA was observed by in vivo labeling in Escherichia coli. Experiments using the mutant IlpA, which is unable to be modified by lipidation, indicate that the lipid moiety of this protein has an essential property for cytokine production in human cells. Pretreatment of monocytes with antibodies against Toll-like receptor 2 (TLR2) inhibited production of both tumor necrosis factor-alpha and interleukin-6. The role of TLR2 in IlpA-induced cytokine production was confirmed by an in vitro assay, in which only the TLR2-expressing cells showed a dramatic induction of nuclear factor-kappaB activity by rIlpA. In addition, rIlpA treatment resulted in induction of TLR2 transcription in human cells. In comparison with the wild type V. vulnificus, the ilpA mutant showed a reduced mortality in mice. These results demonstrate that IlpA of V. vulnificus functions as an immunostimulant to human cells via TLR2.

Modification of the structure of peptidoglycan is a strategy to avoid detection by nucleotide-binding oligomerization domain protein 1

Nucleotide-binding oligomerization domain (NOD) protein 1 (NOD1) and NOD2 are pathogen recognition receptors that sense breakdown products of peptidoglycan (PGN) (muropeptides). It is shown that a number of these muropeptides can induce tumor necrosis factor alpha (TNF-alpha) gene expression without significant TNF-alpha translation. This translation block is lifted when the muropeptides are coincubated with lipopolysaccharide (LPS), thereby accounting for an apparently synergistic effect of the muropeptides with LPS on TNF-alpha protein production. The compounds that induced synergistic effects were also able to activate NF-kappaB in a NOD1- or NOD2-dependent manner, implicating these proteins in synergistic TNF-alpha secretion. It was found that a diaminopimelic acid (DAP)-containing muramyl tetrapeptide could activate NF-kappaB in a NOD1-dependent manner, demonstrating that an exposed DAP is not essential for NOD1 sensing. The activity was lost when the alpha-carboxylic acid of iso-glutamic acid was modified as an amide. However, agonists of NOD2, such as muramyl dipeptide and lysine-containing muramyl tripeptides, were not affected by amidation of the alpha-carboxylic acid of iso-glutamic acid. Many pathogens modify the alpha-carboxylic acid of iso-glutamic acid of PGN, and thus it appears this is a strategy to avoid recognition by the host innate immune system. This type of immune evasion is in particular relevant for NOD1.