Confirmatory platelet-activating factor receptor antagonist trial in patients with severe gram-negative bacterial sepsis: a phase III, randomized, double-blind, placebo-controlled, multicenter trial. BN 52021 Sepsis Investigator Group

The End of “One Size Fits All” Sepsis Therapies: Toward an Individualized Approach

Sepsis, defined as life-threatening organ dysfunction caused by a dysregulated host response to an infection, remains a major challenge for clinicians and trialists. Despite decades of research and multiple randomized clinical trials, a specific therapeutic for sepsis is not available. The evaluation of therapeutics targeting components of host response anomalies in patients with sepsis has been complicated by the inability to identify those in this very heterogeneous population who are more likely to benefit from a specific intervention. Additionally, multiple and diverse host response aberrations often co-exist in sepsis, and knowledge of which dysregulated biological organ system or pathway drives sepsis-induced pathology in an individual patient is limited, further complicating the development of effective therapies. Here, we discuss the drawbacks of previous attempts to develop sepsis therapeutics and delineate a future wherein interventions will be based on the host response profile of a patient.

Chasing the Ghost: Hyperinflammation Does Not Cause Sepsis

Sepsis is infection sufficient to cause illness in the infected host, and more severe forms of sepsis can result in organ malfunction or death. Severe forms of Coronavirus disease-2019 (COVID-19), or disease following infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are examples of sepsis. Following infection, sepsis is thought to result from excessive inflammation generated in the infected host, also referred to as a cytokine storm. Sepsis can result in organ malfunction or death. Since COVID-19 is an example of sepsis, the hyperinflammation concept has influenced scientific investigation and treatment approaches to COVID-19. However, decades of laboratory study and more than 100 clinical trials designed to quell inflammation have failed to reduce sepsis mortality. We examine theoretical support underlying widespread belief that hyperinflammation or cytokine storm causes sepsis. Our analysis shows substantial weakness of the hyperinflammation approach to sepsis that includes conceptual confusion and failure to establish a cause-and-effect relationship between hyperinflammation and sepsis. We conclude that anti-inflammation approaches to sepsis therapy have little chance of future success. Therefore, anti-inflammation approaches to treat COVID-19 are likewise at high risk for failure. We find persistence of the cytokine storm concept in sepsis perplexing. Although treatment approaches based on the hyperinflammation concept of pathogenesis have failed, the concept has shown remarkable resilience and appears to be unfalsifiable. An approach to understanding this resilience is to consider the hyperinflammation or cytokine storm concept an example of a scientific paradigm. Thomas Kuhn developed the idea that paradigms generate rules of investigation that both shape and restrict scientific progress. Intrinsic features of scientific paradigms include resistance to falsification in the face of contradictory data and inability of experimentation to generate alternatives to a failing paradigm. We call for rejection of the concept that hyperinflammation or cytokine storm causes sepsis. Using the hyperinflammation or cytokine storm paradigm to guide COVID-19 treatments is likewise unlikely to provide progress. Resources should be redirected to more promising avenues of investigation and treatment.

Activation of Neutrophil Granulocytes by Platelet-Activating Factor Is Impaired During Experimental Sepsis

Platelet-activating factor (PAF) is an important mediator of the systemic inflammatory response. In the case of sepsis, proper activation and function of neutrophils as the first line of cellular defense are based on a well-balanced physiological response. However, little is known about the role of PAF in cellular changes of neutrophils during sepsis. Therefore, this study investigates the reaction patterns of neutrophils induced by PAF with a focus on membrane potential (MP), intracellular pH, and cellular swelling under physiological and pathophysiological conditions and hypothesizes that the PAF-mediated response of granulocytes is altered during sepsis. The cellular response of granulocytes including MP, intracellular pH, cellular swelling, and other activation markers were analyzed by multiparametric flow cytometry. In addition, the chemotactic activity and the formation of platelet-neutrophil complexes after exposure to PAF were investigated. The changes of the (electro-)physiological response features were translationally verified in a human ex vivo whole blood model of endotoxemia as well as during polymicrobial porcine sepsis. In neutrophils from healthy human donors, PAF elicited a rapid depolarization, an intracellular alkalization, and an increase in cell size in a time- and dose-dependent manner. Mechanistically, the alkalization was dependent on sodium-proton exchanger 1 (NHE1) activity, while the change in cellular shape was sodium flux- but only partially NHE1-dependent. In a pathophysiological altered environment, the PAF-induced response of neutrophils was modulated. Acidifying the extracellular pH in vitro enhanced PAF-mediated depolarization, whereas the increases in cell size and intracellular pH were largely unaffected. Ex vivo exposure of human whole blood to lipopolysaccharide diminished the PAF-induced intracellular alkalization and the change in neutrophil size. During experimental porcine sepsis, depolarization of the MP was significantly impaired. Additionally, there was a trend for increased cellular swelling, whereas intracellular alkalization remained stable. Overall, an impaired (electro-)physiological response of neutrophils to PAF stimulation represents a cellular hallmark of those cells challenged during systemic inflammation. Furthermore, this altered response may be indicative of and causative for the development of neutrophil dysfunction during sepsis.

Targeting of G-protein coupled receptors in sepsis

The Third International Consensus Definitions (Sepsis-3) define sepsis as life-threatening multi-organ dysfunction caused by a dysregulated host response to infection. Sepsis can progress to septic shock-an even more lethal condition associated with profound circulatory, cellular and metabolic abnormalities. Septic shock remains a leading cause of death in intensive care units and carries a mortality of almost 25%. Despite significant advances in our understanding of the pathobiology of sepsis, therapeutic interventions have not translated into tangible differences in the overall outcome for patients. Clinical trials of antagonists of various pro-inflammatory mediators in sepsis have been largely unsuccessful in the past. Given the diverse physiologic roles played by G-protein coupled receptors (GPCR), modulation of GPCR signaling for the treatment of sepsis has also been explored. Traditional pharmacologic approaches have mainly focused on ligands targeting the extracellular domains of GPCR. However, novel techniques aimed at modulating GPCR intracellularly through aptamers, pepducins and intrabodies have opened a fresh avenue of therapeutic possibilities. In this review, we summarize the diverse roles played by various subfamilies of GPCR in the pathogenesis of sepsis and identify potential targets for pharmacotherapy through these novel approaches.

Forty Years Since the Structural Elucidation of Platelet-Activating Factor (PAF): Historical, Current, and Future Research Perspectives

In the late 1960s, Barbaro and Zvaifler described a substance that caused antigen induced histamine release from rabbit platelets producing antibodies in passive cutaneous anaphylaxis. Henson described a ‘soluble factor’ released from leukocytes that induced vasoactive amine release in platelets. Later observations by Siraganuan and Osler observed the existence of a diluted substance that had the capacity to cause platelet activation. In 1972, the term platelet-activating factor (PAF) was coined by Benveniste, Henson, and Cochrane. The structure of PAF was later elucidated by Demopoulos, Pinckard, and Hanahan in 1979. These studies introduced the research world to PAF, which is now recognised as a potent phospholipid mediator. Since its introduction to the literature, research on PAF has grown due to interest in its vital cell signalling functions and more sinisterly its role as a pro-inflammatory molecule in several chronic diseases including cardiovascular disease and cancer. As it is forty years since the structural elucidation of PAF, the aim of this review is to provide a historical account of the discovery of PAF and to provide a general overview of current and future perspectives on PAF research in physiology and pathophysiology.

Platelet-activating factor (PAF) mediates NLRP3-NEK7 inflammasome induction independently of PAFR

Platelet-activating factor (PAF) can drive pathophysiological inflammation, but the mechanism remains incompletely understood. Here, Deng et al. report that PAF activates the canonical NLRP3 inflammasome independently of its receptor PAFR.

The role of lipids in inflammasome activation remains underappreciated. The phospholipid, platelet-activating factor (PAF), exerts multiple physiological functions by binding to a G protein–coupled seven-transmembrane receptor (PAFR). PAF is associated with a number of inflammatory disorders, yet the molecular mechanism underlying its proinflammatory function remains to be fully elucidated. We show that multiple PAF isoforms and PAF-like lipids can activate the inflammasome, resulting in IL-1β and IL-18 maturation. This is dependent on NLRP3, ASC, caspase-1, and NEK7, but not on NLRC4, NLRP1, NLRP6, AIM2, caspase-11, or GSDMD. Inflammasome activation by PAF also requires potassium efflux and calcium influx but not lysosomal cathepsin or mitochondrial reactive oxygen species. PAF exacerbates peritonitis partly through inflammasome activation, but PAFR is dispensable for PAF-induced inflammasome activation in vivo or in vitro. These findings reveal that PAF represents a damage-associated signal that activates the canonical inflammasome independently of PAFR and provides an explanation for the ineffectiveness of PAFR antagonist in blocking PAF-mediated inflammation in the clinic.

Anti-inflammatory Effects of Oct4/Sox2-overexpressing Human Adipose Tissue-derived Mesenchymal Stem Cells

BACKGROUND/AIM

The transcription factors Oct4 and Sox2 enhance the proliferation and pluripotency of human adipose tissue-derived mesenchymal stem cells (hAT-MSCs); however, the anti-inflammatory effects of Oct4- and Sox2-overexpressing hAT-MSCs (Oct4/Sox2-hAT-MSCs) are unclear. Here, we evaluated the anti-inflammatory effects of Oct4/Sox2-hAT-MSCs in vitro and in vivo.

MATERIALS AND METHODS

Supernatants from green-fluorescent protein (GFP)- and Oct4/Sox2-hAT-MSCs were used to treat lipopolysaccharide (LPS)-stimulated RAW264.7 cells and inflammatory cytokine expression was determined. In LPS-induced mice, GFP- and Oct4/Sox2-hAT-MSCs were injected intraperitoneally and survival rates, as well as sickness scores of mice, were monitored.

RESULTS

Decreased expression of pro-inflammatory cytokines was observed in Oct4/Sox2-hAT-MSC supernatant-exposed RAW264.7 cells compared to that in GFP-hAT-MSC supernatant-exposed RAW264.7 cells. The sickness score was reduced to 34.9% and the survival rate was increased by 11.1% in Oct4/Sox2-hAT-MSC-injected mice compared to that in GFP-hAT-MSC-injected mice.

CONCLUSION

Our findings provide important insights into the development of therapies utilizing Oct4/Sox2-hAT-MSCs in inflammatory diseases.

Clinically-oriented therapies in sepsis: a review

Our insight of the sepsis response has evolved to encompass not only the pro-inflammatory but also an anti-inflammatory reaction following infection. Clinical trials have been designed to target either bacterial products, endotoxin in particular, or mediators involved in the sepsis response, but until recently the majority of them have given unfavorable results. In this article, we provide a scope of clinical trials that have been done in immunomodulation during sepsis whether or not they provide positive results. We will also discuss some of the reasons why those studies have been disappointing. Current and future trials with a better assessment of inflammatory status of patients and better-defined outcomes such as organ dysfunction are now underway.

Biosynthesis of oxidized lipid mediators via lipoprotein-associated phospholipase A2 hydrolysis of extracellular cardiolipin induces endothelial toxicity

We (66) have previously described an NSAID-insensitive intramitochondrial biosynthetic pathway involving oxidation of the polyunsaturated mitochondrial phospholipid, cardiolipin (CL), followed by hydrolysis [by calcium-independent mitochondrial calcium-independent phospholipase A2-γ (iPLA2γ)] of oxidized CL (CLox), leading to the formation of lysoCL and oxygenated octadecadienoic metabolites. We now describe a model system utilizing oxidative lipidomics/mass spectrometry and bioassays on cultured bovine pulmonary artery endothelial cells (BPAECs) to assess the impact of CLox that we show, in vivo, can be released to the extracellular space and may be hydrolyzed by lipoprotein-associated PLA2 (Lp-PLA2). Chemically oxidized liposomes containing bovine heart CL produced multiple oxygenated species. Addition of Lp-PLA2 hydrolyzed CLox and produced (oxygenated) monolysoCL and dilysoCL and oxidized octadecadienoic metabolites including 9- and 13-hydroxyoctadecadienoic (HODE) acids. CLox caused BPAEC necrosis that was exacerbated by Lp-PLA2 Lower doses of nonlethal CLox increased permeability of BPAEC monolayers. This effect was exacerbated by Lp-PLA2 and partially mimicked by authentic monolysoCL or 9- or 13-HODE. Control mice plasma contained virtually no detectable CLox; in contrast, 4 h after Pseudomonas aeruginosa (P. aeruginosa) infection, 34 ± 8 mol% (n = 6; P < 0.02) of circulating CL was oxidized. In addition, molar percentage of monolysoCL increased twofold after P. aeruginosa in a subgroup analyzed for these changes. Collectively, these studies suggest an important role for 1) oxidation of CL in proinflammatory environments and 2) possible hydrolysis of CLox in extracellular spaces producing lysoCL and oxidized octadecadienoic acid metabolites that may lead to impairment of pulmonary endothelial barrier function and necrosis.

Sepsis: in search of cure

INTRODUCTION

Sepsis is a complex inflammatory disorder believed to originate from an infection by any types of microbes and/or their products. It is the leading cause of death in intensive care units (ICUs) throughout the globe. The mortality rates depend both on the severity of infection and the host's response to infection.

METHODS

Literature survey on pathobiology of sepsis in general and failure of more than hundred clinical trials conducted so far in search of a possible cure for sepsis resulted in the preparation of this manuscript.

FINDINGS

Sepsis lacks a suitable animal model that mimics human sepsis. However, based on the results obtained in animal models of sepsis, clinical trials conducted so far have been disappointing. Although involvement of multiple mediators and pathways in sepsis has been recognized, only few components are being targeted and this could be the major reason behind the failure of clinical trials.

CONCLUSION

Inability to recognize a single critical mediator of sepsis may be the underlying cause for the poor therapeutic intervention of sepsis. Therefore, sepsis is still considered as a disease-in search of cure.

Non-cultured dermal-derived mesenchymal cells attenuate sepsis induced by cecal ligation and puncture in mice

Sepsis remains a threat to critically ill patients and carries a high morbidity and mortality. Cell-based therapies have risen in prominence in recent years. Dermal-derived mesenchymal cells (DMCs) are attractive as one of the abundant sources from which to isolate mesenchymal cells for therapeutic applications and can be easily accessed with minimal harm to the donor. In this study, we described for the first time the use of non-cultured DMCs for treating sepsis in a cecal ligation and puncture (CLP) mouse model and investigated their immunomodulatory effects. We found that non-cultured DMCs administration provides a beneficial effect to improve survival in CLP-induced sepsis. This effect is partly mediated by the ability of DMCs to home to sites of injury, to reduce the inflammatory response, to inhibit apoptosis, and to stimulate macrophage migration and phagocytosis. Our further findings suggest that DMCs treatment modulates the beneficial cytoprotective effects exhibited during sepsis, at least in part, by altering miRNA expression. These discoveries provide important evidence that non-cultured DMCs therapy has a specific anti-inflammatory effect on sepsis, and provide the basis for the development of a new therapeutic strategy for managing clinical sepsis.

Current Perspectives on the Beneficial Role of Ginkgo biloba in Neurological and Cerebrovascular Disorders

Ginkgo biloba extract is an alternative medicine available as a standardized formulation, EGb 761^®, which consists of ginkgolides, bilobalide, and flavonoids. The individual constituents have varying therapeutic mechanisms that contribute to the pharmacological activity of the extract as a whole. Recent studies show anxiolytic properties of ginkgolide A, migraine with aura treatment by ginkgolide B, a reduction in ischemia-induced glutamate excitotoxicity by bilobalide, and an alternative antihypertensive property of quercetin, among others. These findings have been observed in EGb 761 as well and have led to clinical investigation into its use as a therapeutic for conditions such as cognition, dementia, cardiovascular, and cerebrovascular diseases. This review explores the therapeutic mechanisms of the individual EGb 761 constituents to explain the pharmacology as a whole and its clinical application to cardiovascular and neurological disorders, in particular ischemic stroke.

Platelets in the immune response: Revisiting platelet-activating factor in anaphylaxis

Anaphylaxis is an acute, severe, life-threatening multisystem allergic reaction resulting from the sudden systemic release of biochemical mediators and chemotactic substances. Release of both preformed granule-associated mediators and newly generated lipid-derived mediators contributes to the amplification and prolongation of anaphylaxis. Platelet-activating factor (PAF) is a potent phospholipid-derived mediator the central role of which has been well established in experimental models of both immune-mediated and non-immune mediated anaphylaxis. It is produced and secreted by several types of cells, including mast cells, monocytes, tissue macrophages, platelets, eosinophils, endothelial cells, and neutrophils. PAF is implicated in platelet aggregation and activation through release of vasoactive amines in the inflammatory response, resulting in increased vascular permeability, circulatory collapse, decreased cardiac output, and various other biological effects. PAF is rapidly hydrolyzed and degraded to an inactive metabolite, lysoPAF, by the enzyme PAF acetylhydrolase, the activity of which has shown to correlate inversely with PAF levels and predispose to severe anaphylaxis. In addition to its role in anaphylaxis, PAF has also been implicated as a mediator in both allergic and nonallergic inflammatory diseases, including allergic rhinitis, sepsis, atherosclerotic disease, and malignancy, in which PAF signaling has an established role. The therapeutic role of PAF antagonism has been investigated for several diseases, with variable results thus far. Further investigation of its role in pathology and therapeutic modulation is highly anticipated because of the pressing need for more selective and targeted therapy for the management of severe anaphylaxis.

Strategies to improve drug development for sepsis

Sepsis, a common and potentially fatal systemic illness, is triggered by microbial infection and often leads to impaired function of the lungs, kidneys or other vital organs. Since the early 1980s, a large number of therapeutic agents for the treatment of sepsis have been evaluated in randomized controlled clinical trials. With few exceptions, the results from these trials have been disappointing, and no specific therapeutic agent is currently approved for the treatment of sepsis. To improve upon this dismal record, investigators will need to identify more suitable therapeutic targets, improve their approaches for selecting candidate compounds for clinical development and adopt better designs for clinical trials.

The TFPI-2 derived peptide EDC34 improves outcome of gram-negative sepsis

Sepsis is characterized by a dysregulated host-pathogen response, leading to high cytokine levels, excessive coagulation and failure to eradicate invasive bacteria. Novel therapeutic strategies that address crucial pathogenetic steps during infection are urgently needed. Here, we describe novel bioactive roles and therapeutic anti-infective potential of the peptide EDC34, derived from the C-terminus of tissue factor pathway inhibitor-2 (TFPI-2). This peptide exerted direct bactericidal effects and boosted activation of the classical complement pathway including formation of antimicrobial C3a, but inhibited bacteria-induced activation of the contact system. Correspondingly, in mouse models of severe Escherichia coli and Pseudomonas aeruginosa infection, treatment with EDC34 reduced bacterial levels and lung damage. In combination with the antibiotic ceftazidime, the peptide significantly prolonged survival and reduced mortality in mice. The peptide's boosting effect on bacterial clearance paired with its inhibiting effect on excessive coagulation makes it a promising therapeutic candidate for invasive Gram-negative infections.

Bacterial infections, especially sepsis, are worldwide a major cause of morbidity and mortality. Sepsis is characterized by an excessive and uncontrolled immune and coagulation response caused by bacteria and bacterial products, which eventually leads to multiple organ failure. Despite supportive treatments and administration of antibiotics, the incidence of sepsis is rising. Development of antibiotic resistance among bacteria, and the inability of antibiotics to target dysregulated host responses during severe infections and sepsis, motivates the search for novel anti-infective treatment modalities. Here, we describe a therapeutic potential of the peptide EDC34, derived from the C-terminus of tissue factor pathway inhibitor-2 (TFPI-2). The peptide's boosting effect on bacterial clearance paired with its inhibiting effect on excessive coagulation makes it a promising therapeutic candidate for invasive Gram-negative infections.

Protective Effects of Huang-Lian-Jie-Du-Tang against Polymicrobial Sepsis Induced by Cecal Ligation and Puncture in Rats

Huang-Lian-Jie-Du-Tang (HLJDT) is a traditional formula that has long been used for treatment of inflammatory diseases in Traditional Chinese Medicine. In this study, we examined its protective effect against sepsis in an experimental septic model induced by cecal ligation and puncture (CLP) in rats. The results demonstrated that prophylactic administration of HLJDT protected rats from CLP-induced lethality and ameliorated CLP-induced liver and lung injury. HLJDT treatment suppressed the production of proinflammatory cytokines, including TNF-α, IL-1, IL-6, and IL-17A, indicating HLJDT could limit excessive inflammatory responses in septic condition. In addition, HLJDT facilitated bacterial clearance by increasing phagocytic activities of peritoneal macrophages. Furthermore, HLJDT treatment reversed CLP-induced suppression of IFN-γ expression and blocked CLP-induced increase in IL-4 expression in spleens of rats at 24 h after CLP, indicating that HLJDT could reverse the shift from Th1 to Th2 response and promote Th1/Th2 balance toward Th1 predominance in septic rats. Moreover, HLJDT also inhibited the expression of IL-17A and ROR-γt in spleens of septic rats, indicating HLJDT is able to inhibit Th17 activation in septic condition. In conclusion, the present study demonstrated the protective effects of HLJDT against sepsis and highlighted the potential of HLJDT as a medication for septic patients.

The regulatory role of immunosuppressants on immune abnormalities in acute pancreatitis

The uncontrolled progression of the inflammatory cascade is the main cause underlying the development of multiple organ dysfunction syndrome (MODS) in acute pancreatitis. In this study, we investigated the effects of several immunosuppressants on mitigating the systemic inflammatory reaction syndrome (SIRS) and the compensatory anti-inflammatory response syndrome (CARS) associated with acute pancreatitis. A total of 93 male Sprague Dawley rats were divided into 5 groups: group 1 was the sham group and group 2 underwent laparoscopic intrapancreatic duct injection of sodium taurocholate to induce pancreatitis. The remaining 3 groups were the same as group 2, with the addition of methylprednisolone, cyclophosphamide or methotrexate treatment (metastab, CTX or MTX groups, respectively). Following establishment of the acute pancreatitis model, the serum levels of inflammatory and anti-inflammatory cytokines in groups 2, 3, 4 and 5 were found to be significantly elevated. Following immunosuppressant administration, the levels of all inflammatory and anti-inflammatory cytokines investigated in groups 3, 4 and 5 were decreased compared to those in group 2. The pancreatic amylase levels and pancreatic wet weight (PWW) were also decreased in groups 3, 4 and 5 compared to those in group 2. Therefore, immunosuppressants may reduce inflammation-related cytokine levels in acute pancreatitis and relieve disease progression.

Animal models of sepsis

Sepsis remains a common, serious, and heterogeneous clinical entity that is difficult to define adequately. Despite its importance as a public health problem, efforts to develop and gain regulatory approval for a specific therapeutic agent for the adjuvant treatment of sepsis have been remarkably unsuccessful. One step in the critical pathway for the development of a new agent for adjuvant treatment of sepsis is evaluation in an appropriate animal model of the human condition. Unfortunately, the animal models that have been used for this purpose have often yielded misleading findings. It is likely that there are multiple reasons for the discrepancies between the results obtained in tests of pharmacological agents in animal models of sepsis and the outcomes of human clinical trials. One of important reason may be that the changes in gene expression, which are triggered by trauma or infection, are different in mice, a commonly used species for preclinical testing, and humans. Additionally, many species, including mice and baboons, are remarkably resistant to the toxic effects of bacterial lipopolysaccharide, whereas humans are exquisitely sensitive. New approaches toward the use of animals for sepsis research are being investigated. But, at present, results from preclinical studies of new therapeutic agents for sepsis must be viewed with a degree of skepticism.

Immune-modulating interventions in critically ill septic patients: pharmacological options

Critically ill patients with severe sepsis and septic shock are characterized by a systemic inflammatory response consisting of pro- and anti-inflammatory mediators. Owing to the high mortality of severe sepsis, great efforts have been undertaken within the last 30 years to develop an immune-modulating therapy to improve survival. Relatively few pharmacological immune-modulating interventions have demonstrated a beneficial impact on survival, while other studies have shown a detrimental effect of such interventions. Among the immune-modulating interventions tested, activated protein C and intensive insulin therapy have been shown to improve survival in septic patients. However, in later studies, it has been difficult to reproduce these beneficial effects. There appears to be a discrepancy between the promising effects of immune-modulating interventions in animal studies and the effects seen in the clinical setting. In the future, the onset of the proinflammatory versus the anti-inflammatory response must be better defined and the timing of treatment with immune-modulating agents should be better managed.

Translational research in sepsis - an ultimate challenge?

In the era of evidence-based medicine, large, randomized, controlled, multicenter studies represent the "summit of evidence". In contrast to specialties like cardiology, the majority of randomized, controlled trials in critical care medicine, however, have failed to demonstrate a survival benefit; notably, despite encouraging results from experimental and phase-II clinical studies. The difficulty in translating our theoretical knowledge into successful multicenter randomized, controlled trials and subsequent treatment recommendations may represent one reason, why the mortality of septic shock still averages between 40-60%, although our knowledge about the underlying pathophysiology has considerably increased and international guidelines have widely been implemented. The present article elucidates some of the difficulties in translating research from bench to bedside.

Critical care trial design and interpretation: a primer

OBJECTIVE

Better understanding of the pathophysiology of critical illness has led to an increase in clinical trials designed to improve the clinical care and outcomes of patients with life-threatening illness. Knowledge of basic principles of clinical trial design and interpretation will assist the clinician in better applying the results of these studies into clinical practice.

DATA SOURCES

We review selected clinical trials to highlight important design features that will improve understanding of the results of critical care clinical trials designed to improve clinical care of the critically ill.

RESULTS

Trial design features such as patient selection, bias, sample size calculation, selection of subjects and controls, and primary outcome measure may influence the results of a critical care clinical trial designed to test a therapy targeting improved clinical care. In conjunction with trial design knowledge, understanding the size of the anticipated treatment effect, the importance of any clinical end point achieved, and whether patients in the trial are representative of typical patients with the illness will assist the reader in determining whether the results should be applied to specific patients or usual clinical practice.

CONCLUSIONS

Better understanding of important aspects of trial design and interpretation, such as whether patients enrolled in both intervention arms were comparable and whether the primary outcome of the trial is clinically important, will assist the bedside clinician in determining whether to apply the findings from the clinical study into clinical practice.

The agonists of formyl peptide receptors prevent development of severe sepsis after microbial infection

Severe sepsis, a principal cause of death in intensive care units, occurs when host immune defenses fail to combat invading microbes. In this paper, we report that the administration of peptide agonists of formyl peptide receptors, including Trp-Lys-Tyr-Met-Val-D-Met (WKYMVm), protected against death by enhanced bactericidal activity and inhibition of vital organ inflammation and immune cell apoptosis in a cecal ligation and puncture (CLP) sepsis mouse model. The administration of WKYMVm also enhanced the production of type 1 (IFN-γ and IL-12) and type 17 (IL-17 and TGF-β) cytokines in CLP mice. In contrast, the administration of WKYMVm inhibited the production of proinflammatory cytokines (TNF-α, IL-1β, and IL-6) in the CLP mice. The therapeutic and bactericidal effects of WKYMVm were partly reversed in IFN-γ-deficient mice, whereas target organ inflammation was not. Meanwhile, the therapeutic and anti-inflammatory effects of WKYMVm were partly reversed in IL-17-deficient mice. In addition, the administration of WKYMVm also enhanced type 1 and type 17 Th cell responses in mice sensitized with LPS plus Ags. These results suggest that the agonists of formyl peptide receptors effectively prevent development of severe sepsis following microbial infection partly via augmentation of type 1 and type 17 immune responses.

The platelet activating factor (PAF) signaling cascade in systemic inflammatory responses

The platelet-activating factor (PAF) signaling cascade evolved as a component of the repertoire of innate host defenses, but is also an effector pathway in inflammatory and thrombotic diseases. This review focuses on the PAF signaling cascade in systemic inflammatory responses and, specifically, explores its activities in experimental and clinical sepsis and anaphylaxis in the context of the basic biochemistry and biology of signaling via this lipid mediator system.

Harvesting, identification and barrier function of human lung microvascular endothelial cells

Endothelial barrier dysfunction is an important contributor to the pathogenesis of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Even though approaches that target the prevention and repair of endothelial barrier dysfunction are clearly needed, our understanding of the molecular regulation of pulmonary microvascular endothelial permeability remains incomplete. Cultured pulmonary microvascular endothelial cells represent an attractive paradigm for the study of barrier function. Here, we describe a method for the harvest, identification and culture of human lung microvascular endothelial cells (HLMVEC). HLMVEC thus obtained, grow as a monolayer, exhibit contact inhibition and have the typical cobblestone appearance. They express endothelial proteins, such as von Willebrand factor and endothelial nitric oxide synthase and take up an acetylated LDL. Furthermore, HLMVEC respond predictably and with superior sensitivity to the barrier disruptive effects of Gram positive and Gram negative bacterial products, thrombin, vascular endothelial growth factor and microtubule disrupting agents. These HLMVEC present an in-house-derived alternative to commercially available human cells for the study of mechanisms contributing to ALI and ARDS.

Has mortality from sepsis improved and what to expect from new treatment modalities: review of current insights

BACKGROUND

The incidence of sepsis is increasing continuously, making mortality rate reduction through improved intensive care unit (ICU) care and new treatment modalities a pressing issue. This study aimed to provide insight into the effects of modern ICU care on mortality trends from severe sepsis and to provide a quantitative review of the relative effectiveness of new treatment modalities in reducing deaths.

METHODS

Mortality data from severe sepsis were extracted from the control arms of several large randomized trials of sepsis treatment published within the last two decades. The effectiveness of recent treatment strategies was expressed as the number of patients it is necessary to treat by that method to save one life (number needed to treat: NNT).

RESULTS

Death from severe sepsis showed a decline from 44% to 35% between 1990 and 2000. The two most effective strategies in critically ill patients are early appropriate antibiotics (NNT 3; 95% confidence interval [CI] 2, 4) and early goal-directed therapy (NNT 6; 95% CI 4, 24). Infusion of recombinant human activated protein C is the most effective anticoagulant therapy (NNT 15; 95% CI 10, 27). Intensive insulin therapy is only moderately effective (NNT 27; 95% CI 15, 124).

CONCLUSIONS

The mortality rate from severe sepsis has decreased significantly with modernization of ICU care. New therapeutic strategies may reduce further the mortality rate. However, focused implementation of these new strategies in accordance with their relative effectiveness is needed before we can expect to see their true effect on mortality rates.

Improving clinical trials in the critically ill: unique challenge--sepsis

OBJECTIVE

This article aimed at providing suggestions to improve the success rate of future sepsis trials.

DESIGN

Systematic review.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

CENTRAL (The Cochrane Library Issue 2, 2007) was searched using "sepsis" OR "severe sepsis" OR "septic shock" as search terms. The search was restricted to studies designed and conducted in adults with severe sepsis or septic shock after June 1992, published before September 2007, and powered for survival analysis. Twenty-seven trials were included and analyzed. The author suggested six key points for the design and conduct of future sepsis trials: 1) avoid mixing patients with severe sepsis and septic shock; 2) restrict time window to less than 24 hrs from onset of the first organ dysfunction or shock; 3) include only undisputable sepsis; 4) use the Sepsis-related Organ Failure Assessment score for eligibility; 5) include a first interim analysis after enrollment of 25% of the planned sample size to check the actual basal risk of death and to recalculate the number of patients needed; 6) strictly control for concomitant treatments on the basis of the Surviving Sepsis Campaign.

CONCLUSIONS

There is a need to limit the sources of heterogeneity in sepsis trials by a better definition of target populations, by a better estimation of basal risk of death, and by controlling cointerventions.

Multicenter, randomized, controlled trials evaluating mortality in intensive care: doomed to fail?

OBJECTIVES

To determine how many multicenter, randomized controlled trials have been published that assess mortality as a primary outcome in the adult intensive care unit population, and to evaluate their methodologic quality.

DATA SOURCE

A sensitive search strategy for randomized controlled trials was conducted in the Cochrane Central Register of Controlled Trials and in MedLine using the PubMed interface.

STUDY SELECTION

All publications of adult, multicenter randomized controlled trials carried out in the intensive care unit, with mortality as a primary outcome, and including >50 patients were selected.

DATA EXTRACTION

Seventy-two randomized controlled trials were retrieved and were classified according to their effect on mortality: beneficial, detrimental, or neutral.

DATA SYNTHESIS

Ten of the studies reported a positive impact of the studied intervention on mortality, seven studies reported a detrimental effect of the intervention, and 55 studies showed no effect on mortality.

CONCLUSIONS

This literature search demonstrates that relatively few of the randomized controlled trials conducted in intensive care units and using mortality as a primary outcome show a beneficial impact of the intervention on the survival of critically ill patients. Methodological limitations of some of the randomized controlled trials may have prevented positive results. Other forms of evidence and end points other than mortality need to be considered when evaluating interventions in critically ill patients.

Understanding the inflammatory cytokine response in pneumonia and sepsis: results of the Genetic and Inflammatory Markers of Sepsis (GenIMS) Study

BACKGROUND

Severe sepsis is common and frequently fatal, and community-acquired pneumonia (CAP) is the leading cause. Although severe sepsis is often attributed to uncontrolled and unbalanced inflammation, evidence from humans with infection syndromes across the breadth of disease is lacking. In this study we describe the systemic cytokine response to pneumonia and determine if specific patterns, including the balance of proinflammatory and anti-inflammatory markers, are associated with severe sepsis and death.

METHODS

This is a cohort study of 1886 subjects hospitalized with CAP through the emergency departments in 28 US academic and community hospitals. We defined severe sepsis as CAP complicated by new-onset organ dysfunction, following international consensus conference criteria. We measured plasma tumor necrosis factor, IL-6 (interleukin 6), and IL-10 levels daily for the first week and weekly thereafter. Our main outcome measures were severe sepsis and 90-day mortality.

RESULTS

A total of 583 patients developed severe sepsis (31%), of whom 149 died (26%). Systemic cytokine level elevation occurred in 82% of all subjects with CAP. Mean cytokine concentrations were highest at presentation, declined rapidly over the first few days, but remained elevated throughout the first week, beyond resolution of clinical signs of infection. Cytokine levels were highest in fatal severe sepsis and lowest in CAP with no severe sepsis. Unbalanced (high/low) cytokine patterns were unusual (4.6%) and not associated with decreased survival. Highest risk of death was with combined high levels of the proinflammatory IL-6 and anti-inflammatory IL-10 cytokine activity (hazard ratio, 20.5; 95% confidence interval, 10.8-39.0) (P<.001).

CONCLUSIONS

The circulating cytokine response to pneumonia is heterogeneous and continues for more than a week after presentation, with considerable overlap between those who do and do not develop severe sepsis. Unbalanced activation is uncommon, and mortality is highest when both proinflammatory and anti-inflammatory cytokine levels are high.

New evaluation therapies for sepsis

This article presents an analysis of the literature of the last 2 years on the treatment of sepsis and septic shock. It appears that most of the antimediator therapies applied in phase II or III clinical trials yielded disappointing results. But, many other therapeutic approaches are proposed or are ongoing, and many papers report critical analysis of the reasons for the lack of success of past clinical trials.

Clinical trials in sepsis: an update

In this article, we place clinical sepsis trials from the past year in the context of similar sepsis trials run over the past three decades. These recent clinical sepsis trials include studies of agents administered to limit the effects of specific host proinflammatory mediators (tumor necrosis factor, platelet-activating factor and prostaglandins), studies of use of corticosteroids at low doses late in sepsis, and studies of administration of high doses of a nonspecific nitric oxide synthase inhibitor to decrease nitric oxide production in septic shock. The three trials of agents designed to limit host proinflammatory mediators showed minimal beneficial effects, results that are similar to those of the approximately 20 previous trials of similar agents. Low-dose corticosteroid therapy reversed shock and showed nonsignificant trends towards improvements in survival rates. In contrast, high doses of corticosteroids given early in sepsis have shown harmful effects in clinical sepsis trials. Finally, inhibition of nitric oxide production was lethal, indicating that high doses of nonspecific inhibitors of nitric oxide production are contraindicated in septic shock.

[Critical analysis of noninflammatory treatments of sepsis: lessons learned from previous trials]

A large number of immunomodulatory therapies has been evaluated in patients with severe sepsis and septic shock. Until recently, none of these treatments has ever demonstrated any benefit in terms of decreased mortality. Many biases could interfere with the results of these clinical trials linked to poor comprehension of immune response, pharmacological errors, selection bias, and mistakes in the evaluation of the patients and in the interpretation of the results. Based on these methodological flaws, the authors try to define directions for future clinical trials.

Immunomodulation by n-3- versus n-6-rich lipid emulsions in murine acute lung injury--role of platelet-activating factor receptor

OBJECTIVE

Cytokines, platelet-activating factor (PAF), and eicosanoids control local and systemic inflammation. Conventional soybean oil-based lipid emulsions used for parenteral nutrition may aggravate the leukocyte inflammatory response or adhesion to the vessel wall. Fish oil-based lipid emulsions, in contrast, may exert an anti-inflammatory effect.

DESIGN

We investigated the impact of lipid emulsions on leukocyte invasion, protein leakage, and cytokines in two murine models of acute inflammation.

SETTING

Research laboratory of a university hospital.

SUBJECTS

Wild-type mice and PAF-receptor knockout mice.

INTERVENTIONS

Mice received an infusion of normal saline, fish oil- or soybean oil-based lipid emulsions before lipopolysaccharide challenge.

MEASUREMENTS AND MAIN RESULTS

Preinfusion with soybean oil resulted in increased leukocyte invasion, myeloperoxidase activity, and protein leakage and exaggerated release of tumor necrosis factor (TNF)-alpha as well as macrophage inflammatory protein (MIP)-2 into the alveolar space after intratracheal lipopolysaccharide challenge. In contrast, preinfusion with fish oil reduced leukocyte invasion, myeloperoxidase activity, protein leakage, and TNF-alpha as well as MIP-2 generation. Corresponding profiles were found in plasma following intraperitoneal lipopolysaccharide application: Soybean oil increased but fish oil decreased the TNF-alpha and MIP-2 formation. When PAF-receptor-deficient mice were challenged with lipopolysaccharide, leukocyte invasion, lung tissue myeloperoxidase, cytokine generation, and alveolar protein leakage corresponded to those observed in wild-type animals. Fish oil and soybean oil lost their diverging effects on leukocyte transmigration, myeloperoxidase activity, leakage response, and cytokine generation in these knockout mice. Similarly, the differential impact of both lipid emulsions on these lipopolysaccharide-provoked changes was suppressed after pretreating animals with a PAF-receptor antagonist.

CONCLUSIONS

Fish oil- vs. soybean oil-based lipid infusions exert anti- vs. proinflammatory effects in murine models of acute inflammation. The PAF/PAF-receptor-linked signaling appears to be a prerequisite for this differential profile.

Leptin: at the crossroads of energy balance and systemic inflammation

In addition to playing a central role in energy homeostasis, leptin is also an important player in the inflammatory response. Systemic inflammation is accompanied by fever (less severe cases) or hypothermia (more severe cases). In leptin-irresponsive mutants, the hypothermia of systemic inflammation is exaggerated, presumably due to the enhanced production and cryogenic action of tumor necrosis factor (TNF)-alpha. Mechanisms that exaggerate hypothermia can also attenuate fever, particularly in a cool environment. Another common manifestation of systemic inflammation is behavioral depression. Along with the production of interleukin (IL)-1beta, this manifestation is exaggerated in leptin-irresponsive mutants. The enhanced production of TNF-alpha and IL-1beta may be due, at least in part, to insufficient activation of the anti-inflammatory hypothalamo-pituitary-adrenal axis by immune stimuli in the absence of leptin signaling. In experimental animals and humans that are responsive to leptin, suppression of leptin production under conditions of negative energy balance (e.g., fasting) can exaggerate both hypothermia and behavioral depression. Since these manifestations aid energy conservation, exaggeration of these manifestations under conditions of negative energy balance is likely to be beneficial.

Drotrecogin alfa (activated) in the treatment of severe sepsis

Severe sepsis is a common and frequently fatal condition. Evidence showing a link between the coagulation system and the inflammatory response to sepsis led to the development of drotrecogin alfa (activated) as an agent in the treatment of severe sepsis. Recent studies have shown that the mode of action is actually more complex than initially thought. This recombinant form of the natural anticoagulant, activated protein C, has been demonstrated to reduce mortality in a large randomized controlled, Phase III study involving 1690 patients, even though the results of this and subsequent studies and the licensing of drotrecogin alfa (activated) have generated considerable debate. Administration of drotrecogin alfa (activated) is associated with an increased risk of bleeding and its use is contraindicated in patients with a high risk of bleeding or recent hemorrhagic events.

Modifications of cellular responses to lysophosphatidic acid and platelet-activating factor by plasma gelsolin

Gelsolin is a highly conserved intracellular actin-binding protein with an extracellular isoform, plasma gelsolin (pGSN). Blood concentrations of pGSN decrease in response to diverse tissue injuries. Depletion of pGSN to critical levels precedes and often predicts complications of injuries such as lung permeability changes and death. Administration of recombinant pGSN ameliorates such complications and reduces mortality in animal models. One proposed mechanism for pGSN's protective effects is that it inhibits inflammatory mediators generated during primary injuries, since pGSN binds bioactive mediators, including lysophospatidic acid (LPA) and endotoxin in vitro. However, no direct evidence in support of this hypothesis has been available. Here we show that recombinant pGSN modestly inhibited LPA-induced P-selectin upregulation by human platelets in the presence of albumin (P < 0.0001). However, physiologically relevant pGSN concentrations inhibit platelet-activating factor (PAF)-mediated P-selectin expression by up to 77% (P < 0.0001). pGSN also markedly inhibited PAF-induced superoxide anion (O(2)(-)) production of human peripheral neutrophils (PMN) in a concentration-dependent manner (P < 0.0001). A phospholipid-binding peptide derived from pGSN (QRLFQVKGRR) also inhibited PAF-mediated O(2)(-) generation (P = 0.024). Therefore, pGSN interferes with PAF- and LPA-induced cellular activation in vitro, suggesting a mechanism for the protective role of pGSN in vivo.

Neutrophils in development of multiple organ failure in sepsis

Multiple organ failure is a major threat to the survival of patients with sepsis and systemic inflammation. In the UK and in the USA, mortality rates are currently comparable with and projected to exceed those from myocardial infarction. The immune system combats microbial infections but, in severe sepsis, its untoward activity seems to contribute to organ dysfunction. In this Review we propose that an inappropriate activation and positioning of neutrophils within the microvasculature contributes to the pathological manifestations of multiple organ failure. We further suggest that targeting neutrophils and their interactions with blood vessel walls could be a worthwhile therapeutic strategy for sepsis.

Effect of intraperitoneal application of an endotoxin inhibitor on survival time in a laparoscopic model of peritonitis in rats

Gram-negative sepsis due to fecal peritonitis is a hazardous disease with a high percentage having a lethal course. The inflammatory effects are induced by endotoxin release. We performed this study to evaluate the potential of direct intraperitoneal application of an endotoxin inhibitor in a laparoscopic peritonitis model in rats. The human feces specimen was prepared, and a standard fecal specimen (0.5 ml/kg b.w.) was applied via minilaparotomy. The rats were randomized to two studies. First, rats were randomized to three groups to define the survival time: (1) rats without further manipulation; (2) rats with laparoscopic lavage using NaCl; (3) rats with laparoscopic lavage using endotoxin inhibitor. Second, rats underwent the same procedure used in the first part of the study and an additional group with only NaCl lavage without peritonitis was randomized. To evaluate the immunologic or biochemical effects, animals were killed at a standard time of 20 hours until the postmortem examination was established. Interleukins 6 and 10 (IL-6, IL-10), malondialdehyde, and protein carbonyl group levels in plasma and particularly in peritoneal fluid were assayed. The first part of the experiment showed significantly increased survival after endotoxin inhibitor lavage. In the second part, administration of endotoxin inhibitor intraperitoneally caused a significant reduction of IL-6 in the peritoneal fluid, in contrast to that in the other groups. Laparoscopic application of endotoxin inhibitor intraperitoneally thus produced a beneficial effect on survival and reduction of IL-6 in peritoneal fluid. Hence, it is possible to influence the inflammation cascade by causing intraperitoneal endotoxin inhibition.

Ginkgolide B stimulates signaling events in neutrophils and primes defense activities

Ginkgolide B (GKB) is a bioactive component of the standardized extract from the leaves of the Ginkgo biloba tree (EGb 761), which is used in Chinese and in occidental medicine. GKB is known as a platelet-activating factor receptor antagonist. Here, we provide evidence that GKB per se (0.25-5 microM) stimulated tyrosine phosphorylation of proteins, phospholipase D activation, calcium transients, and activation of p38 but not p44/42 Map kinases in human polymorphonuclear leukocytes (PMN). These stimulatory effects remained relatively weak and primed PMN for subsequent stimulation of respiratory burst (RB) or directed locomotion by the chemoattractant fMet-Leu-Phe (fMLP) or complement-derived factor C5a. A similar RB priming was observed with rat exudate PMN after in vivo administration of EGb 761 (25 and 50 mg/kg) to rats before pleurisy induction. Thus, GKB primarily induces activation of intracellular signaling events and has the potential to prime cellular functions such as PMN defense activities.

Lack of evidence for qualitative treatment by disease severity interactions in clinical studies of severe sepsis

INTRODUCTION

The design of clinical trials of interventions aimed at reducing mortality in patients with severe sepsis assumes that the relative treatment effect of the intervention is independent of the patients' risk for death. We reviewed published data from phase III clinical studies of severe sepsis to determine whether a relationship exists between risk for death and the relative benefit of the investigational agent. Such an interaction might warrant a change in the assumptions that underlie current trial designs.

METHODS

We conducted a systematic review of published phase III, randomized, placebo-controlled trials in adult patients with sepsis, severe sepsis, or septic shock up to November 2004. All studies enrolled patients with known or suspected infection, evidence of a systemic response to the infection, and one or more organ dysfunctions resulting from the systemic response.

RESULTS

Twenty-two publications, investigating 17 molecular entities, fulfilled criteria for phase III or equivalent studies aimed at reducing mortality in adult patients with severe sepsis or septic shock. Three studies achieved the prospectively defined primary end-point of a statistically significant reduction in 28-day all-cause mortality. The control group mortality rates for these studies were 31%, 43% and 61%, indicating that the beneficial effects of adjunct therapies could be demonstrated over a wide range of illness severity. Analysis of subgroup data from failed studies provided no evidence that the efficacy of the therapeutics being investigated varied by baseline placebo mortality rates. Among all studies, interventions with anticoagulant activity or anti-inflammatory activity did not appear to be harmful in patients with evidence of less coagulopathy or less inflammation.

CONCLUSION

Our review of published clinical data does not support the hypothesis that mortality risk of the population studied alters the relative treatment effect associated with anti-inflammatory or other agents used to treat severe sepsis. Clinical studies in severe sepsis should continue to enroll patients over a wide range of disease severity, as long as patients enrolled have evidence of sepsis-induced organ dysfunction(s), patients are at an appreciable risk for death (e.g. as evidenced by admission to an intensive care unit), and the potential for benefit outweighs the potential for harm.

Estimating sample size in critical care clinical trials

Estimating the required sample size for a study is necessary during the design phase to ensure that it will have maximal efficiency to answer the primary question of interest. Clinicians require a basic understanding of the principles underlying sample size calculation to interpret and apply research findings. This article reviews the critical components of sample size calculation, including the selection of a primary outcome, specification of the acceptable types I and II error rates, identification of the minimal clinically important difference, and estimation of the error associated with measuring the primary outcome. The relationship among confidence intervals, precision, and study power is also discussed.

Sepsis and coagulation

The host response to infection is a highly complex yet well-orchestrated process that involves an elaborate array of soluble mediators and cells. Normally, the host response prevails in containing and eliminating the pathogenic threat. When excessive or sustained, however, the host response may "turn on its bearer" and lead to organ dysfunction. Severe sepsis is invariably associated with activation of primary and secondary hemostasis. This article describes sepsis-associated changes in coagulation, discusses the putative role for these changes in pathogenesis of the sepsis syndrome, and outlines current diagnostic and therapeutic strategies.