Relationship between plasma levels of lipopolysaccharide (LPS) and LPS-binding protein in patients with severe sepsis and septic shock

Platelets protect from septic shock by inhibiting macrophage-dependent inflammation via the cyclooxygenase 1 signalling pathway

Although it has long been known that patients with sepsis often have thrombocytopenia and that septic patients with severe thrombocytopenia have a poor prognosis and higher mortality, the role of platelets in the pathogenesis of sepsis is poorly understood. Here we report a protective role of platelets in septic shock. We show that experimental thrombocytopenia induced by intraperitoneal injection of an anti-glycoprotein Ibα monoclonal antibody increases mortality and aggravates organ failure, whereas transfusion of platelets reduces mortality in lipopolysaccharide-induced endotoxemia and a bacterial infusion mouse sepsis model. Plasma concentrations of proinflammatory cytokines TNF-α and IL-6 are elevated by thrombocytopenia and decreased by platelet transfusion in septic mice. Furthermore, we identify that platelets protect from septic shock by inhibiting macrophage-dependent inflammation via the COX1/PGE₂/EP4-dependent pathway. Thus, these findings demonstrate a previously unappreciated role for platelets in septic shock and suggest that platelet transfusion may be effective in treating severely septic patients.

Laboratory detection of sepsis: biomarkers and molecular approaches

Sepsis, severe sepsis, and septic shock cause significant morbidity and mortality worldwide. Rapid diagnosis and therapeutic interventions are desirable to improve the overall mortality in patients with sepsis. However, gold standard laboratory diagnostic methods for sepsis, pose a significant challenge to rapid diagnosis of sepsis by physicians and laboratories. This article discusses the usefulness and potential of biomarkers and molecular test methods for a more rapid clinical and laboratory diagnosis of sepsis. Because new technologies are quickly emerging, physicians and laboratories must appreciate the key factors and characteristics that affect the clinical usefulness and diagnostic accuracy of these test methodologies.

Biomarkers of sepsis

Sepsis remains a leading cause of death in critically ill patients, despite efforts to improve patient outcome. Thus far, no magic drugs exist for severe sepsis and septic shock. Instead, early diagnosis and prompt initial management such as early goal-directed therapy are key to improve sepsis outcome. For early detection of sepsis, biological markers (biomarkers) can help clinicians to distinguish infection from host response to inflammation. Ideally, biomarkers can be used for risk stratification, diagnosis, monitoring of treatment responses, and outcome prediction. More than 170 biomarkers have been identified as useful for evaluating sepsis, including C-reactive protein, procalcitonin, various cytokines, and cell surface markers. Recently, studies have reported on the usefulness of biomarker-guided antibiotic stewardships. However, the other side of these numerous biomarkers is that no novel single laboratory marker can diagnose, predict, and track the treatment of sepsis. The purpose of this review is to summarize several key biomarkers from recent sepsis studies.

Bactericidal/permeability-increasing protein in host defense and its efficacy in the treatment of bacterial sepsis

The 55-kD bactericidal/permeability-increasing protein (BPI) is a neutrophil-derived polypeptide belonging to a family of lipid and endotoxin binding proteins. BPI is composed of two functionally distinct structural domains: a potently antibacterial and antiendotoxin ∼ 20-kD aminoterminal half, and an opsonic carboxy-terminal portion. In multiple animal models, a recombinant amino-terminal fragment of BPI (rBPI21) is nontoxic and protects against gram-negative bacteria and endotoxin. In humans, rBPI21 is also nontoxic and nonimmunogenic and has undergone phase II/III clinical trials with apparent therapeutic benefit.

CD14 mediates binding of high doses of LPS but is dispensable for TNF-α production

Activation of macrophages with lipopolysaccharide (LPS) involves a sequential engagement of serum LPS-binding protein (LBP), plasma membrane CD14, and TLR4/MD-2 signaling complex. We analyzed participation of CD14 in TNF-α production stimulated with 1-1000 ng/mL of smooth or rough LPS (sLPS or rLPS) and in sLPS binding to RAW264 and J744 cells. CD14 was indispensable for TNF-α generation induced by a low concentration, 1 ng/mL, of sLPS and rLPS. At higher doses of both LPS forms (100-1000 ng/mL), TNF-α release required CD14 to much lower extent. Among the two forms of LPS, rLPS-induced TNF-α production was less CD14-dependent and could proceed in the absence of serum as an LBP source. On the other hand, the involvement of CD14 was crucial for the binding of 1000 ng/mL of sLPS judging from an inhibitory effect of the anti-CD14 antibody. The binding of sLPS was also strongly inhibited by dextran sulfate, a competitive ligand of scavenger receptors (SR). In the presence of dextran sulfate, sLPS-induced production of TNF-α was upregulated about 1.6-fold. The data indicate that CD14 together with SR participates in the binding of high doses of sLPS. However, CD14 contribution to TNF α production induced by high concentrations of sLPS and rLPS can be limited.

Towards clinical applications of anti-endotoxin antibodies; a re-appraisal of the disconnect

Endotoxin is a potent mediator of a broad range of patho-physiological effects in humans. It is present in all Gram negative (GN) bacteria. It would be expected that anti-endotoxin therapies, whether antibody based or not, would have an important adjuvant therapeutic role along with antibiotics and other supportive therapies for GN infections. Indeed there is an extensive literature relating to both pre-clinical and clinical studies of anti-endotoxin antibodies. However, the extent of disconnect between the generally successful pre-clinical studies versus the failures of the numerous large clinical trials of antibody based and other anti-endotoxin therapies is under-appreciated and unexplained. Seeking a reconciliation of this disconnect is not an abstract academic question as clinical trials of interventions to reduce levels of endotoxemia levels are ongoing. The aim of this review is to examine new insights into the complex relationship between endotoxemia and sepsis in an attempt to bridge this disconnect. Several new factors to consider in this reappraisal include the frequency and types of GN bacteremia and the underlying mortality risk in the various study populations. For a range of reasons, endotoxemia can no longer be considered as a single entity. There are old clinical trials which warrant a re-appraisal in light of these recent advances in the understanding of the structure-function relationship of endotoxin. Fundamentally however, the disconnect not only remains, it has enlarged.

Rapid diagnosis of sepsis

Fast and appropriate therapy is the cornerstone in the therapy of sepsis. However, the discrimination of sepsis from non-infectious causes of inflammation may be difficult. Biomarkers have been suggested to aid physicians in this decision. There is currently no biochemical technique available which alone allows a rapid and reliable discrimination between sepsis and non-infectious inflammation. Procalcitonin (PCT) is currently the most investigated biomarker for this purpose. C-reactive protein and interleukin 6 perform inferior to PCT in most studies and their value in diagnosing sepsis is not defined. All biomarkers including PCT are also released after various non-infectious inflammatory impacts. This shortcoming needs to be taken into account when biomarkers are used to aid the physician in the diagnosis of sepsis. Polymerase chain reaction (PCR) based pathogen detection may improve time to adequate therapy but cannot rule out the presence of infection when negative.

Immunomodulation in sepsis: the role of endotoxin removal by polymyxin B-immobilized cartridge

Severe sepsis results in high morbidity and mortality. Immunomodulation strategies could be an adjunctive therapy to treat sepsis. Endotoxin is a component of gram-negative bacteria and plays an important role in the pathogenesis of septic shock when it is recognized by immune cells. Removal of endotoxin could be an effective adjunctive approach to the management of sepsis. Devices to adsorb endotoxin or inflammatory cytokines have been designed as a strategy to treat severe sepsis, especially sepsis caused by gram-negative bacteria. Polymyxin B-immobilized cartridge has been successfully used to treat patients with sepsis of abdominal origin. Although this cartridge was conceived to adsorb endotoxin, several other immunological mechanisms have been elucidated, and this device has also yielded promising results in patients with nonseptic respiratory failure. In this paper, we summarize the immune modulation actions of Polymyxin B-immobilized cartridge to explore its potential usefulness beyond endotoxin elimination.

Frequency and severity of cirrhotic cardiomyopathy and its possible relationship with bacterial endotoxemia

BACKGROUND

The cardiac dysfunction presented in cirrhotic patients is already known as cirrhotic cardiomyopathy. The pathogenesis of this entity is not fully understood.

AIMS

The aim of this study was to evaluate the frequency and characteristics of cirrhotic cardiomyopathy and to investigate the possible role of bacterial endotoxemia on its aggravation.

METHODS

Forty-five cirrhotics were studied by a tissue Doppler imaging echocardiography at rest and after stress. The diagnosis of left ventricular diastolic dysfunction was based on the latest guidelines of the American Society of Echocardiography, whereas its severity was defined by the E/e'av ratio. Endotoxemia was estimated by measuring the serum levels of lipopolysaccharide-binding protein (LBP) and cytokines.

RESULTS

None of the patients had systolic dysfunction, but 17/45 (37.8 %) had a diastolic one. Patients with grade II diastolic dysfunction had significantly longer QTc (p = 0.049), larger left atrium volume (p = 0.013), higher Brain Natriuretic Peptide levels (p = 0.007) and higher LBP levels (p = 0.02), compared to those with normal cardiac function, without differences in the systemic hemodynamics and the cytokines' levels. Moreover, the severity of diastolic dysfunction as reflected by the E/e'av. was significantly correlated with the LBP levels (p = 0.002). On the multivariate analysis, the LBP was independently associated with the presence of diastolic dysfunction.

CONCLUSIONS

Cirrhosis is commonly complicated by cardiac dysfunction. Patients with severe cirrhotic cardiomyopathy have higher LBP levels, which are significantly correlated with the degree of diastolic dysfunction. Our findings support a potential role of bacterial endotoxemia on the aggravation of cardiomyopathy in cirrhotic patients.

Risk factors for sepsis after percutaneous renal stone surgery

Since its introduction into the endourologist's armamentarium almost 40 years ago, percutaneous nephrolithotomy (PCNL) has become the standard of care for patients with large-volume nephrolithiasis. Postoperative infection is one of the most common complications of the procedure, and postoperative sepsis is one of the most detrimental. A number of factors have been found to increase the risk of postoperative sepsis. These include patient characteristics that are known preoperatively, such as urine culture obtained from the bladder or from the renal pelvis if percutaneous access to the renal pelvis is obtained in advance to the procedure. Neurogenic bladder dysfunction secondary to spinal cord injury and anatomical renal abnormalities, such as pelvicalyceal dilatation, have also been associated with increased incidence of fever and sepsis after the procedure. Several intraoperative factors, such as the average renal pressure sustained during PCNL and the operative time, also seem to increase the risk of sepsis. Finally, the contribution of postoperative factors, such as presence of a nephrostomy tube or a urethral catheter, has also been investigated. A short preoperative course of antibiotics has been found to significantly decrease the rate of postoperative fever and sepsis. Novel agents targeted at sepsis prevention and treatment, such as anti-endotoxin antibodies and cholesterol-lowering drugs statins, are currently under investigation.

CRISPLD2 is expressed at low levels during septic shock and is associated with procalcitonin

Introduction

Previous studies have shown that cysteine-rich secretory protein containing LCCL domain 2 (CRISPLD2) is a novel lipopolysaccharide (LPS)-binding protein, and the upregulation of CRISPLD2 expression protects mice against LPS-induced lethality. The aim of this study was to examine the expression of CRISPLD2 in patients with sepsis and characterize the association of this protein with procalcitonin.

Methods

The expression of CRISPLD2 was determined in100 healthy volunteers and 119 septic patients. According to the definition of sepsis, patients were divided into three groups sepsis, severe sepsis, and septic shock. The relationship between CRISPLD2 levels and procalcitonin was also examined and statistically analyzed.

Results

The CRISPLD2 levels in healthy individuals were 219.3±69.1 µg/ml. Patients with sepsis exhibited higher CRISPLD2 levels than observed in healthy individuals (p = 0.001), but CRISPLD2 expression was not upregulated in patients with septic shock. No significant differences were observed between the levels of CRISPLD2 in surviving and non-surviving spesis patients. CRISPLD2 levels were negatively correlated with procalcitonin levels(r = −0.334, p<0.001).

Conclusions

The present study is the first to demonstrate the decreased expression of CRISPLD2 in septic shock and its association with PCT in sepsis. Further studies are needed to clarify the potential association between CRISPLD2 expression and clinical outcomes to determine if it could be used as a novel sepsis biomarker.

Infection-associated platelet dysfunction of canine platelets detected in a flow chamber model

BACKGROUND

In the present study, the influence of bacterial infection, lipopolysacharides (LPS) and hydroxyethyl starch (HES) on platelet function in a parallel plate flow chamber were measured. Experiments were performed with non-activated and protease-activating-receptor (PAR) 4 agonist activated platelets. Comparative measurements were in vivo capillary bleeding time, platelet function analyzer and impedance aggregometry.

RESULTS

PAR 4 agonist did not increase platelet adhesion of platelets from dogs with bacterial inflammation in the flow chamber in contrast to platelets of healthy dogs. Except from impedance aggregometry with lower sensitivity and specificity, PFA did not detect platelet dysfunctions in dogs with infection. In vitro addition of LPS or HES significantly reduced platelet covered area after PAR-activation.

CONCLUSIONS

The flow chamber detects platelet dysfunctions in dogs with inflammatory diseases. In vitro addition of LPS highlights the inhibiting effect of bacterial wall components on platelet function. Platelet dysfunction induced by infection could possibly also be diagnosed after treatment of sepsis with colloids has commenced. The flow chamber could be a useful tool to detect sepsis associated platelet dysfunction given that larger prospective trials confirm these findings from a proof of concept study.

Risk factors for systemic inflammatory response syndrome following percutaneous nephrolithotomy

The aim of this study was to analyze the pre- and intraoperative risk factors that affect the development of postoperative systemic inflammatory response syndrome (SIRS) after percutaneous nephrolithotomy (PCNL). Medical records on 317 adult patients with the complete data who underwent single-stage PCNL and followed at our center were retrospectively studied. Patients' data were collected through a database which was collected prospectively. All patients' vital signs were recorded hourly in the postoperative period and were divided into two groups as patients developing SIRS and not developing SIRS. There were 202 men and 115 women with a mean age of 48 ± 13.7 (range 19-82) years. There were 53 (16.7 %) in the SIRS and 264 (83.3 %) patients in the non-SIRS group. Preoperative positive urine cultures (UCs), intraoperative positive renal pelvic urine cultures (RPUCs), and stone cultures (SCs) were strongly correlated with the development of SIRS (p = 0.001). In the SIRS developers' group, preoperative UCs, intraoperative RPUCs, and SCs were positive in 33.9, 22.5, and 28.6 % of patients, respectively, but only 9.8, 3.3, and 4.2 % for the corresponding specimens in non-SIRS group. Positive preoperative UCs, intraoperative RPUCs, and SCs are important factors indicating the development of postoperative SIRS. Appropriately treated preoperative urinary infections may not prevent infected urine at PCNL. RPUCs and SCs may be the only way to identify the causative organism and direct antimicrobial therapy, so we recommend collecting RPUCs and SCs routinely to identify the offending organism and guide treatment.

Microbial translocation is associated with extensive immune activation in dengue virus infected patients with severe disease

Background

Severe dengue virus (DENV) disease is associated with extensive immune activation, characterized by a cytokine storm. Previously, elevated lipopolysaccharide (LPS) levels in dengue were found to correlate with clinical disease severity. In the present cross-sectional study we identified markers of microbial translocation and immune activation, which are associated with severe manifestations of DENV infection.

Methods

Serum samples from DENV-infected patients were collected during the outbreak in 2010 in the State of São Paulo, Brazil. Levels of LPS, lipopolysaccharide binding protein (LBP), soluble CD14 (sCD14) and IgM and IgG endotoxin core antibodies were determined by ELISA. Thirty cytokines were quantified using a multiplex luminex system. Patients were classified according to the 2009 WHO classification and the occurrence of plasma leakage/shock and hemorrhage. Moreover, a (non-supervised) cluster analysis based on the expression of the quantified cytokines was applied to identify groups of patients with similar cytokine profiles. Markers of microbial translocation were linked to groups with similar clinical disease severity and clusters with similar cytokine profiles.

Results

Cluster analysis indicated that LPS levels were significantly increased in patients with a profound pro-inflammatory cytokine profile. LBP and sCD14 showed significantly increased levels in patients with severe disease in the clinical classification and in patients with severe inflammation in the cluster analysis. With both the clinical classification and the cluster analysis, levels of IL-6, IL-8, sIL-2R, MCP-1, RANTES, HGF, G-CSF and EGF were associated with severe disease.

Conclusions

The present study provides evidence that both microbial translocation and extensive immune activation occur during severe DENV infection and may play an important role in the pathogenesis.

The pathogenesis of severe dengue virus (DENV) infection is still not fully understood. It is hypothesized that it is caused by a cytokine storm as is described in severe sepsis. In the sepsis field, the potent immunostimulator lipopolysaccharide (LPS) is proposed to play an important role in the development of a cytokine storm. In a previous study we have found elevated levels of LPS in children with severe DENV infection. In this study we have investigated if we could confirm that microbial translocation occurs in DENV-infected patients. Moreover, we have determined the levels of thirty cytokines to get more insight in the cytokine storm during DENV infections and we have investigated whether microbial translocation is associated with immune activation. The patients in this cohort were classified according to their clinical presentation. Furthermore, a cluster analysis based on the expression of the determined cytokines was applied to identify patients with similar cytokine profiles. With these two techniques, we identified cytokines that may contribute significantly to the cytokine storm, and we could relate elevated levels of LPS to patients with a pro-inflammatory cytokine profile.

Direct effects of locally administered lipopolysaccharide on glucose, lipid, and protein metabolism in the placebo-controlled, bilaterally infused human leg

CONTEXT

Accumulating evidence suggests that chronic exposure to lipopolysaccharide (LPS, endotoxin) may create a constant low-grade inflammation, leading to insulin resistance and diabetes. All previous human studies assessing the metabolic actions of LPS have used systemic administration, making discrimination between direct and indirect effects impossible.

OBJECTIVE

We sought to define the direct, placebo-controlled effects of LPS on insulin resistance and protein and lipid metabolism in the infused human leg without systemic interference from cytokines and stress hormones.

DESIGN

This was a randomized, placebo-controlled, single-blinded study.

PARTICIPANTS AND INTERVENTION

We studied 8 healthy volunteers with bilateral femoral vein and artery catheters during a 3-hour basal and 3-hour hyperinsulinemic-euglycemic clamp period with bilateral muscle biopsies in each period during infusion with saline and LPS.

RESULTS

Overall, LPS perfusion significantly decreased leg glucose uptake, and during the clamp LPS decreased glucose arteriovenous differences (0.65 ± 0.07 mmol/L vs 0.73 ± 0.08 mmol/L). Net palmitate release was increased by LPS, and secondary post hoc testing indicated increased palmitate isotopic dilution, although primary ANOVA tests did not reveal significant dilution. Leg blood flows, phenylalanine, lactate kinetics, cytokines, and intramyocellular insulin signaling were not affected by LPS. LPS thus directly inhibits insulin-stimulated glucose uptake and increases palmitate release in the perfused human leg without detectable effects on amino acid metabolism.

CONCLUSIONS

These data strongly suggest that the primary metabolic effect of LPS is increased lipolysis and muscle insulin resistance, which, together with secondary insulin resistance, caused by systemic cytokine and stress hormone release may lead to overt glucose intolerance and diabetes.

Prognostic value of endotoxemia in patients with Gram-negative bacteremia is bacterial species dependent

The prognostic impact of endotoxemia detection in sepsis is unclear. Endotoxemia is detectable in <70% of patients with Gram-negative (GN) bacteremias. Mortality proportion data were available from 27 published studies of patients with GN bacteremia in various settings. Among ten studies restricted to specific types of GN bacteremia, endotoxemia was associated with significantly increased mortality risk for Neisseria meningitidis (4 studies; 138 bacteremias; OR 26.0; 95% CI, 1.6-321) but not for Salmonella enterica serovar Typhi (3 studies; 36 bacteremias; OR 0.89; 95% CI, 0.01-74.1). For 17 unrestricted studies (319 GN bacteremic patients), endotoxemia was associated with an increased mortality risk with non-Escherichia coli Enterobacteriaceae such as Klebsiella and Enterobacter species (97 bacteremias; OR 3.7; 95% CI, 1.3-10.3). By contrast, E. coli (144 bacteremias; OR 0.78; 95% CI, 0.36-1.7), and non-Enterobacteriaceae species such as Pseudomonas species (78 bacteremias; OR 1.7; 95% CI, 0.7-4.6) had no increased mortality risk. That endotoxemia detection is predictive of mortality among patients bacteremic with non-E. coli Enterobacteriaceae but not E. coli is surprising given the presumed commonality of the hexa-acyl lipid A structure among Enterobacteriaceae species.

Glutamine and alanine-induced differential expression of intracellular IL-6, IL-8, and TNF-α in LPS-stimulated monocytes in human whole-blood

To investigate the effects of the commonly-used immunomodulators l-glutamine, l-alanine, and the combination of both l-alanyl-l-glutamine (Dipeptamin(®)) on intracellular expression of IL-6, IL-8, and TNF-α during endotoxemia, lipopolysaccharide (LPS)-stimulated human monocytes in a whole blood system were investigated by flow cytometry. Whole blood of twenty-seven healthy volunteers was stimulated with LPS and incubated with three different amino acid solutions (1. l-glutamine, 2. l-alanine, 3. l-alanyl-l-glutamine, each concentration 2 mM, 5 mM, incubation time 3 h). CD14(+) monocytes were phenotyped in whole-blood and intracellular expression of cytokines was assessed by flow cytometry. Our investigations showed for the first time in whole blood probes, imitating best physiologically present cellular interactions, that l-glutamine caused a dose-independent inhibitory effect on IL-6 and TNF-α production in human monocytes stimulated with LPS. However, l-alanine had contrary effects on IL-6 expression, significantly upregulating expression of IL-6 in LPS-treated monocytes. The impact of l-alanine on the expression of TNF-α was comparable with glutamine. Neither amino acid was able to affect IL-8 production in LPS-stimulated monocytes. The combination of both did not influence significantly IL-6 and IL-8 expression in monocytes during endotoxemia, however strongly reduced TNF-α production. For the regulation of TNF-α, l-glutamine, l-alanine and the combination of both show a congruent and exponentiated downregulating effect during endotoxemia, for the modulation of IL-6, l-glutamine and l-alanine featured opposite regulation leading to a canceling impact of each other when recombining both amino acids.

The importance of biomarkers in neonatology

Despite a 35% decline in the mortality rate for infants aged <5 years over the past two decades, every year nearly 40% of all deaths in this age group occur in the neonatal period, defined as the first 28 days of life. New knowledge on molecular and biochemical pathways in neonatal diseases will lead to the discovery of new candidate biomarkers potentially useful in clinical practice. In the era of personalized medicine, biomarkers may play a strategic role in accelerating the decline in neonatal mortality by assessing the risk of developing neonatal diseases, by implementing tailored therapeutic treatment, and by predicting the clinical outcome. However, there is an urgent need to reduce the gap in translating newly acquired knowledge from bench to bedside. Traditional and candidate biomarkers for neonatal sepsis and necrotizing enterocolitis will be discussed in this review, such as C-reactive protein (CRP), procalcitonin (PCT), serum amyloid A (SAA), soluble form of CD14 subtype presepsin (sCD14-ST), lipolysaccharide binding protein (LBP), angiopoietins (Ang)-1 and -2, soluble form of triggering receptor expressed on myeloid cells (sTREM-1), soluble form of urokinase-type plasminogen activator receptor (suPAR), platelet-activating factor (PAF) and calprotectin. New frontiers in managing critically ill newborns may be opened by metabolomics, a diagnostic tool based on the recognition of metabolites contained in biological fluids. Metabolomics represents the passage from a descriptive science to a predictive science, having the potential to translate benchtop research to real clinical benefits.

An agent-based model of cellular dynamics and circadian variability in human endotoxemia

As cellular variability and circadian rhythmicity play critical roles in immune and inflammatory responses, we present in this study an agent-based model of human endotoxemia to examine the interplay between circadian controls, cellular variability and stochastic dynamics of inflammatory cytokines. The model is qualitatively validated by its ability to reproduce circadian dynamics of inflammatory mediators and critical inflammatory responses after endotoxin administration in vivo. Novel computational concepts are proposed to characterize the cellular variability and synchronization of inflammatory cytokines in a population of heterogeneous leukocytes. Our results suggest that there is a decrease in cell-to-cell variability of inflammatory cytokines while their synchronization is increased after endotoxin challenge. Model parameters that are responsible for IκB production stimulated by NFκB activation and for the production of anti-inflammatory cytokines have large impacts on system behaviors. Additionally, examining time-dependent systemic responses revealed that the system is least vulnerable to endotoxin in the early morning and most vulnerable around midnight. Although much remains to be explored, proposed computational concepts and the model we have pioneered will provide important insights for future investigations and extensions, especially for single-cell studies to discover how cellular variability contributes to clinical implications.

New approaches to sepsis: molecular diagnostics and biomarkers

Sepsis is among the most common causes of death in hospitals. It arises from the host response to infection. Currently, diagnosis relies on nonspecific physiological criteria and culture-based pathogen detection. This results in diagnostic uncertainty, therapeutic delays, the mis- and overuse of antibiotics, and the failure to identify patients who might benefit from immunomodulatory therapies. There is a need for new sepsis biomarkers that can aid in therapeutic decision making and add information about screening, diagnosis, risk stratification, and monitoring of the response to therapy. The host response involves hundreds of mediators and single molecules, many of which have been proposed as biomarkers. It is, however, unlikely that one single biomarker is able to satisfy all the needs and expectations for sepsis research and management. Among biomarkers that are measurable by assays approved for clinical use, procalcitonin (PCT) has shown some usefulness as an infection marker and for antibiotic stewardship. Other possible new approaches consist of molecular strategies to improve pathogen detection and molecular diagnostics and prognostics based on transcriptomic, proteomic, or metabolic profiling. Novel approaches to sepsis promise to transform sepsis from a physiologic syndrome into a group of distinct biochemical disorders and help in the development of better diagnostic tools and effective adjunctive sepsis therapies.

Determinants of serum concentrations of lipopolysaccharide-binding protein (LBP) in the adult population: the role of obesity

Background and Aim

Assessment of serum concentration of lipopolysaccharide (LPS)-binding protein (LBP) has been suggested as a useful biomarker to indicate activation of innate immune responses to microbial products. We investigated LBP concentrations and associations with demographics, lifestyle factors, and common metabolic abnormalities in adults. We also examined if LBP concentrations were associated with common polymorphisms in genes coding for LBP (rs2232618), CD14 (rs2569190), and TLR4 (rs4986790), the molecules responsible for the innate immune response to LPS, or serum levels of soluble CD14 (sCD14) and proinflammatory cytokines.

Methods

Serum LBP was measured with a commercial immunoassay in a random sample of the adult population (n = 420, 45% males, age 18–92 years) from a single municipality.

Results

Serum LBP concentrations increased with age (P<0.001) and were higher in individuals who were overweight or obese than in normal-weight individuals (P<0.001). Similarly, LBP concentrations were higher in individuals with metabolic syndrome than in individuals without it (P<0.001). Among metabolic syndrome components, LBP concentrations were independently associated with abdominal obesity (P = 0.002) and low concentrations of HDL-cholesterol (P<0.001). Serum LBP concentrations tended to be independently associated with smoking (P = 0.05), but not with alcohol consumption. Likewise, there was not significant association between LBP concentrations and gene polymorphisms. Concentrations of LBP significantly correlated with serum levels of proinflammatory cytokines (IL-6 and IL-8), sCD14, and with liver enzymes.

Conclusions

Serum LBP concentrations increased with age. Overweight, obesity, and having metabolic syndrome (particularly, low HDL cholesterol levels) were associated with higher LBP concentrations. These findings are consistent with microbial exposure playing a role in these inflammatory, metabolic abnormalities.

TAK-242, a small-molecule inhibitor of Toll-like receptor 4 signalling, unveils similarities and differences in lipopolysaccharide- and lipid-induced inflammation and insulin resistance in muscle cells

Emerging evidence suggests that TLR (Toll-like receptor) 4 and downstream pathways [MAPKs (mitogen-activated protein kinases) and NF-κB (nuclear factor κB)] play an important role in the pathogenesis of insulin resistance. LPS (lipopolysaccharide) and saturated NEFA (non-esterified fatty acids) activate TLR4, and plasma concentrations of these TLR4 ligands are elevated in obesity and Type 2 diabetes. Our goals were to define the role of TLR4 on the insulin resistance caused by LPS and saturated NEFA, and to dissect the independent contribution of LPS and NEFA to the activation of TLR4-driven pathways by employing TAK-242, a specific inhibitor of TLR4. LPS caused robust activation of the MAPK and NF-κB pathways in L6 myotubes, along with impaired insulin signalling and glucose transport. TAK-242 completely prevented the inflammatory response (MAPK and NF-κB activation) caused by LPS, and, in turn, improved LPS-induced insulin resistance. Similar to LPS, stearate strongly activated MAPKs, although stimulation of the NF-κB axis was modest. As seen with LPS, the inflammatory response caused by stearate was accompanied by impaired insulin action. TAK-242 also blunted stearate-induced inflammation; yet, the protective effect conferred by TAK-242 was partial and observed only on MAPKs. Consequently, the insulin resistance caused by stearate was only partially improved by TAK-242. In summary, TAK-242 provides complete and partial protection against LPS- and NEFA-induced inflammation and insulin resistance, respectively. Thus, LPS-induced insulin resistance depends entirely on TLR4, whereas NEFA works through TLR4-dependent and -independent mechanisms to impair insulin action.

Serum adenosine deaminase and total immunoglobulin G correlate with markers of immune activation and inversely with CD4 counts in asymptomatic, treatment-naive HIV infection

PURPOSE

HIV-infection is characterized by aberrant immune activation and ongoing inflammation. Markers of inflammation are now recognized to have prognostic value for adverse events, independent of viral loads and CD4 counts. This study aimed to delineate a panel of affordable markers of immune activation in untreated HIV-infection that may have an impact on the management of HIV in resource-limited settings.

METHODS

This was a cross-sectional study of 86 untreated newly diagnosed HIV-infected patients and 54 matched controls attending a voluntary testing clinic in Cape Town, South Africa. Serum levels of adenosine deaminase (ADA), total immunoglobulin G (IgG), soluble CD14 and lipopolysaccharide-binding protein (LBP) were measured and correlated with CD4 counts, viral loads and expression of CD38 on CD8+ T cells.

RESULTS

ADA, IgG and LBP were all significantly increased in the HIV infected group (p < 0.0001) compared with uninfected controls. Soluble CD14 was also significantly increased (p = 0.0187). Furthermore, all these parameters correlated inversely with CD4 counts (r = -0.481 p < 0.0001; r = -0.561; p < 0.0001; r = -0.387 p = 0.0007 and r = -0.254 p = 0.0240, respectively). Only ADA correlated with viral load (r = 0.260 p = 0.0172). Importantly, ADA, IgG and LBP correlated directly with %CD38 on CD8+ T cells (r = 0.369 p < 0.0001; r = 0.284 p = 0.001; r = 0.408 p = 0.0006, respectively).

CONCLUSION

Affordable parameters such as serum ADA and IgG correlated significantly with immune activation levels and markers of disease progression in untreated HIV-infection and therefore may add value to the management of these patients in resource-limited settings.

Preclinical sepsis models

BACKGROUND

A variety of sepsis models have been used to unravel pathophysiologic processes and to examine the effects of novel therapeutic interventions. The lack of therapeutic efficacy of numerous compounds in clinical sepsis trials, despite glorious results in animal models of sepsis, has raised doubt and debate about the usefulness of such models.

METHODS

Review of the pertinent literature.

RESULTS

Many sepsis models have been described, none of which is ideal. Clinical sepsis can originate from different sources, can be accompanied by many complicating conditions, and strikes human beings with strongly variable genetic backgrounds, co-morbidities, and drug usages. To provide answers to the three main objectives of research-insight into the regulation of normal host defense mechanisms in the early stages of infection; the mechanisms underlying dysregulation of the host response; and proof of principle for the mechanism of action of novel therapeutic agents and to establish their efficacy and potential harm-diverse models are required. The future of sepsis research lies in the systematic combination of models, together with in vitro studies and carefully designed and monitored Phase I/II clinical studies.

CONCLUSION

This review discusses the nature of various animal sepsis models and the way their results should be interpreted.

RETRACTED: Cardiac-specific overexpression of catalase attenuates lipopolysaccharide-induced myocardial contractile dysfunction: Role of autophagy

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. After an institutional investigation into the work of Dr. Jun Ren, University of Wyoming subsequently conducted an examination of other selected publications of Dr. Ren's under the direction of the HHS Office of Research Integrity. Based on the findings of this examination, the University of Wyoming recommended this article be retracted due to concerns regarding data irregularities inconsistent with published conclusions. Specifically, University of Wyoming found evidence of data irregularities and image reuse in Figure 2 that significantly affect the results and conclusions reported in the manuscript.

Endotoxemia and mortality prediction in ICU and other settings: underlying risk and co-detection of gram negative bacteremia are confounders

INTRODUCTION

The interdependence between endotoxemia, gram negative (GN) bacteremia and mortality has been extensively studied. Underlying patient risk and GN bacteremia types are possible confounders of the relationship.

METHODS

Published studies with ≥ 10 patients in either ICU or non-ICU settings, endotoxemia detection by limulus assay, reporting mortality proportions and ≥ 1 GN bacteremia were included. Summary odds ratios (OR) for mortality were derived across all studies by meta-analysis for the following contrasts: sub-groups with either endotoxemia (group three), GN bacteremia (group two) or both (group one) each versus the group with neither detected (group four; reference group). The mortality proportion for group four is the proxy measure of study level risk within L'Abbé plots.

RESULTS

Thirty-five studies were found. Among nine studies in an ICU setting, the OR for mortality was borderline (OR <2) or non-significantly increased for groups two (GN bacteremia alone) and three (endotoxemia alone) and patient group one (GN bacteremia and endotoxemia co-detected) each versus patient group four (neither endotoxemia nor GN bacteremia detected). The ORs were markedly higher for group one versus group four (OR 6.9; 95% confidence interval (CI), 4.4 -to 11.0 when derived from non-ICU studies. The distributions of Pseudomonas aeruginosa and Escherichia coli bacteremias among groups one versus two are significantly unequal.

CONCLUSIONS

The co-detection of GN bacteremia and endotoxemia is predictive of increased mortality risk versus the detection of neither but only in studies undertaken in a non-ICU setting. Variation in GN bacteremia species types and underlying risk are likely unrecognized confounders in the individual studies.

Characterization of lipopolysaccharide-stimulated cytokine expression in macrophages and monocytes

OBJECTIVE

In vitro cell culture models are widely used in inflammation research; however, information regarding the time- and dose-dependency of inflammatory responses toward LPS in these cell lines is scattered in the literature.

MATERIAL

J774A.1 mouse macrophage and THP-1 human monocyte cell lines.

TREATMENT

J774A.1 and THP-1 cells were treated with 0-500 ng/mL lipopolysaccharide for 0-24 h.

METHODS

SRB and BCA tests were used to measure total protein. Real-time PCR was used to determine gene expression levels, and ELISA was used to assess the protein levels. One-way ANOVA and Tukey's Honestly Significant Difference test were used to test the significance levels.

RESULTS

In J774A.1 and THP-1 cells, cytokines responded in distinct patterns upon LPS stimulation in a time- and dose-dependent manner, and the differential regulation of the response to LPS between J774A.1 and THP-1 cells appeared to correlate with the differential regulation of TLR4 at the mRNA level.

CONCLUSION

In summary, this study indicated that temporal and dose-dependent responses to LPS need to be controlled for and that extrapolation of data on mechanisms may differ between cell lines of different origin.

Sepsis-associated changes of the arachidonic acid metabolism and their diagnostic potential in septic patients

OBJECTIVES

Sepsis-associated changes of the arachidonic acid metabolism and the utility of arachidonic acid metabolites for the diagnosis of sepsis have been poorly investigated so far. Therefore, the primary objective of our study was to screen for differentially regulated arachidonic acid metabolites in septic patients using a lipopolysaccharide whole-blood model and to investigate their diagnostic potential.

DESIGN

Prospective, observational, single-center, clinical study.

SETTING

Intensive care unit at University Hospital Leipzig.

PATIENTS

Thirty-five patients (first cohort 25 patients, second cohort 10 patients) meeting the criteria for severe sepsis or septic shock were enrolled. Eighteen healthy volunteers (first cohort 15 subjects, second cohort 3 subjects) were enrolled as controls.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Arachidonic acid and its metabolites were investigated in supernatants of nonactivated (baseline) and lipopolysaccharide-activated heparinized whole blood of healthy subjects (n=15) and septic patients (n=25) by solid phase extraction and subsequent liquid chromatography-tandem mass spectrometry. Arachidonic acid, arachidonic acid analogues, and the cyclooxygenase-associated metabolites prostaglandin E2, 11-hydroxyeicosatetraenoic acid, and thromboxane B2 were identified as differentiating metabolites between septic patients and healthy subjects. Some of these compounds, including arachidonic acid, its analogues, and the cyclooxygenase metabolites prostaglandin E2 and thromboxane B2 differed at baseline. The inducibility of arachidonic acid and the cyclooxygenase metabolites 11-hydroxyeicosatetraenoic and prostaglandin E2 were reduced by 80% to 90% in septic patients. The degree of the inducibility was associated with severity of sepsis and clinical outcome. A reduced inducibility of COX-2 but preserved inducibility of mPGES-1 on gene expression level were confirmed in an independent cohort of septic patients (n=10) by quantitative reverse-transcription polymerase chain reaction compared to healthy controls (n=3).

CONCLUSIONS

Arachidonic acid metabolism is markedly affected in patients with sepsis. Our data suggest that the analysis of arachidonic acid metabolites in an in vitro whole blood activation model may be a promising approach for risk estimation in septic patients that has to be further evaluated in subsequent large-scale clinical studies.

[Host inflammatory and anti-inflammatory response during sepsis]

Sepsis still remains the major complication for patients admitted in intensive care units (ICU), and is responsible for numerous deaths. ICU patients admitted after sepsis, hemorrhagic shock, severe trauma, severe burns or major surgery show a systemic inflammatory response syndrome (SIRS). This syndrome is characterized by an exacerbation of inflammation, with increased levels of pro- (IL-1β, TNFα, IL-6, IL-8) as well as anti-inflammatory (IL-10, IL-1Ra, TGFβ) cytokines into their bloodstream. During sepsis, the bacteria release microbial motifs such as peptidoglycan, lipopolysaccharide (LPS) and DNA that initiate the inflammatory response, and are involved in the onset of multiple organ failure. The same microbial motifs can also be found in patients with a SIRS of non-infectious origin, following the translocation of bacteria from their digestive tract. This translocation is certainly contributing to the difficulty of discriminating between septic and SIRS patients using biological markers. Furthermore, the host response is accompanied by an alteration of the ex vivo response of circulating leukocytes, particularly monocytes. This hyporesponsiveness to LPS is associated with a decreased activation of the transcription factor NF-κB (required for the expression of pro-inflammatory cytokines) and an increased expression of negative regulators of the NF-κB pathway. However, the leukocyte hyporesponsiveness is not a global phenomenon, it depends on the type of patient, on the receptor-activator pair, on the timing, and on the cytokine.

Lipopolysaccharide binding protein is down-regulated during acute liver failure

BACKGROUND AND AIMS

Lipopolysaccharide binding protein (LBP) is involved in the modulation of acute liver injury and failure caused by acetaminophen (APAP). Although the biological activity of LBP is concentration dependent, little is known about its levels in acute liver failure.

METHODS

Serum and hepatic LBP were measured in acute APAP-induced liver injury in mice. Serum LBP was measured in patients with acute liver failure from APAP and non-APAP causes.

RESULTS

Interestingly, contrary to other diseases, serum and hepatic LBP levels decreased significantly in mice within 24 h after being subjected to APAP-induced injury compared to the control (1.6 ± 0.1 vs. 3.5 ± 1.6 μg/ml, respectively; P < 0.05). Similar decreases were noted in another mouse model of acute liver injury due to carbon tetrachloride. Among patients with acute liver failure due to APAP (n = 5) and non-APAP (n = 5) causes, admission LBP levels were decreased compared to those of healthy controls (5.4 ± 1.4 vs. 3.2 ± 0.2 μg/ml, normal vs. acute liver failure; P = 0.07). However, the levels were not associated with the etiology of acute liver failure or 3-week outcome.

CONCLUSIONS

Serum and hepatic LBP levels are significantly reduced early after the induction of severe acute liver injury/failure due to acetaminophen and other liver injuries. This reduction in LBP production is specific to acute liver failure and may be important in developing future diagnostic and therapeutic approaches for patients with acute liver failure.

Interleukin 6, lipopolysaccharide-binding protein and interleukin 10 in the prediction of risk and etiologic patterns in patients with community-acquired pneumonia: results from the German competence network CAPNETZ

Background

The aim of our study was to investigate the predictive value of the biomarkers interleukin 6 (IL-6), interleukin 10 (IL-10) and lipopolysaccharide-binding protein (LBP) compared with clinical CRB and CRB-65 severity scores in patients with community-acquired pneumonia (CAP).

Methods

Samples and data were obtained from patients enrolled into the German CAPNETZ study group. Samples (blood, sputum and urine) were collected within 24 h of first presentation and inclusion in the CAPNETZ study, and CRB and CRB-65 scores were determined for all patients at the time of enrollment. The combined end point representative of a severe course of CAP was defined as mechanical ventilation, intensive care unit treatment and/or death within 30 days. Overall, a total of 1,000 patients were enrolled in the study. A severe course of CAP was observed in 105 (10.5%) patients.

Results

The highest IL-6, IL-10 and LBP concentrations were found in patients with CRB-65 scores of 3-4 or CRB scores of 2-3. IL-6 and LBP levels on enrollment in the study were significantly higher for patients with a severe course of CAP than for those who did not have severe CAP. In receiver operating characteristic analyses, the area under the curve values for of IL-6 (0.689), IL-10 (0.665) and LPB (0.624) in a severe course of CAP were lower than that of CRB-65 (0.764) and similar to that of CRB (0.69). The accuracy of both CRB and CRB-65 was increased significantly by including IL-6 measurements. In addition, higher cytokine concentrations were found in patients with typical bacterial infections compared with patients with atypical or viral infections and those with infection of unknown etiology. LBP showed the highest discriminatory power with respect to the etiology of infection.

Conclusions

IL-6, IL-10 and LBP concentrations were increased in patients with a CRB-65 score of 3-4 and a severe course of CAP. The concentrations of IL-6 and IL-10 reflected the severity of disease in patients with CAP. The predictive power of IL-6, IL-10 and LBP for a severe course of pneumonia was lower than that of CRB-65. Typical bacterial pathogens induced the highest LBP, IL-6 and IL-10 concentrations.

Complement takes its Toll: an inflammatory crosstalk between Toll-like receptors and the receptors for the complement anaphylatoxin C5a

The innate immune system is responsible for a rapid inflammatory response to pathogens that is essential for the clearance of infections. Although this response is vital, it is nonetheless potentially harmful, and dysregulated inflammation is a feature of many disease states. Thus, the mechanisms that regulate the release of soluble mediators of inflammation are an active focus of investigation. The activation by infections of two key components of the innate immune system, the Toll-like receptors (TLRs) and complement, leading to the release of soluble mediators of inflammation, is critical to microbial killing and clearance. Both TLRs and complement are independently capable of triggering pro-inflammatory responses, but their synergistic interaction resulting from a substantial crosstalk markedly amplifies those responses and may contribute to the pathophysiology of diseases such as sepsis.

Old and new findings on lipopolysaccharide-binding protein: a soluble pattern-recognition molecule

LBP [LPS (lipopolysaccharide)-binding protein] was discovered approximately 25 years ago. Since then, substantial progress has been made towards our understanding of its function in health and disease. Furthermore, the discovery of a large protein family sharing functional and structural attributes has helped in our knowledge. Still, key questions are unresolved, and here an overview on the old and new findings on LBP is given. LBP is an acute-phase protein of the liver, but is also synthesized in other cells of the organism. While LBP is named after the ability to bind to LPS of Gram-negative bacteria, it also can recognize other bacterial compounds, such as lipopeptides. It has been shown that LBP is needed to combat infections; however, the main mechanism of action is still not clear. New findings on natural genetic variations of LBP leading to functional consequences may help in further elucidating the mechanism of LBP and its role in innate immunity and disease.

Lipopolysaccharide levels are elevated in dengue virus infected patients and correlate with disease severity

BACKGROUND

Although in the majority of cases dengue virus (DENV) infection results in a self-limiting febrile disease, it can cause severe plasma leakage in a minority of patients. The appearance of plasma leakage indicates an increased permeability of the vascular wall. In this study we investigated if DENV infection can lead to leakage of lipopolysaccharide (LPS) from the intestine into the blood of the patient, indicative of an increased permeability of the intestinal mucosal barrier.

OBJECTIVES

The aim of this study was to investigate if LPS levels were elevated in DENV infected patients and if these levels correlated with disease severity.

STUDY DESIGN

LPS levels in the blood of DENV infected children were determined using the Limulus Amebocyte Lysate assay. To determine disease severity we used the 1997-WHO criteria, the expert physician's judgement and a score that focused on plasma leakage in particular. Furthermore, the modulatory factors LPS binding protein (LBP) and sCD14, as well as the immune activation marker neopterin were determined.

RESULTS

We showed significantly elevated LPS levels in plasma of DENV infected children compared to healthy controls. The plasma leakage severity score had the strongest correlation with levels of LPS. LBP, sCD14 and neopterin were elevated compared to healthy controls.

CONCLUSION

In this study we show evidence of elevated LPS levels during DENV infection. Moreover, a correlation between LPS levels and disease severity was found, especially when disease severity was determined in terms of plasma leakage.

Biophysical mechanisms of endotoxin neutralization by cationic amphiphilic peptides

Bacterial endotoxins (lipopolysaccharides (LPS)) are strong elicitors of the human immune system by interacting with serum and membrane proteins such as lipopolysaccharide-binding protein (LBP) and CD14 with high specificity. At LPS concentrations as low as 0.3 ng/ml, such interactions may lead to severe pathophysiological effects, including sepsis and septic shock. One approach to inhibit an uncontrolled inflammatory reaction is the use of appropriate polycationic and amphiphilic antimicrobial peptides, here called synthetic anti-LPS peptides (SALPs). We designed various SALP structures and investigated their ability to inhibit LPS-induced cytokine secretion in vitro, their protective effect in a mouse model of sepsis, and their cytotoxicity in physiological human cells. Using a variety of biophysical techniques, we investigated selected SALPs with considerable differences in their biological responses to characterize and understand the mechanism of LPS inactivation by SALPs. Our investigations show that neutralization of LPS by peptides is associated with a fluidization of the LPS acyl chains, a strong exothermic Coulomb interaction between the two compounds, and a drastic change of the LPS aggregate type from cubic into multilamellar, with an increase in the aggregate sizes, inhibiting the binding of LBP and other mammalian proteins to the endotoxin. At the same time, peptide binding to phospholipids of human origin (e.g., phosphatidylcholine) does not cause essential structural changes, such as changes in membrane fluidity and bilayer structure. The absence of cytotoxicity is explained by the high specificity of the interaction of the peptides with LPS.

Toll-like receptor-4 antagonist eritoran tetrasodium for severe sepsis

The human innate immune system initiates inflammation in response to bacterial molecules, particularly Gram-negative bacterial endotoxin. The steps by which endotoxin exposure leads to systemic inflammation include binding to Toll-like receptor-4 that specifically recognizes endotoxin and subsequently triggers cellular and molecular inflammatory responses. Severe sepsis is a systemic inflammatory response to infection that induces organ dysfunction and threatens a person's survival. Severe sepsis is frequently associated with increased blood levels of endotoxin. It is a significant medical problem that effects approximately 700,000 patients every year in the USA, resulting in 250,000 deaths. Eritoran tetrasodium is a nonpathogenic analog of bacterial endotoxin that antagonizes inflammatory signaling by the immune receptor Toll-like receptor-4. Eritoran is being evaluated for the treatment of patients with severe sepsis.

Biomarkers of immune dysfunction following combination antiretroviral therapy for HIV infection

Combination antiretroviral therapy (cART) has significantly reduced morbidity and mortality of HIV-infected patients, yet their life expectancy remains reduced compared with the general population. Most HIV-infected patients receiving cART have some persistent immune dysfunction characterized by chronic immune activation and premature aging of the immune system. Here we review biomarkers of T-cell activation (CD69, -25 and -38, HLA-DR, and soluble CD26 and -30); generalized immune activation (C-reactive protein, IL-6 and D-dimer); microbial translocation (lipopolysaccharide, 16S rDNA, lipopolysaccharide-binding protein and soluble CD14); and immune dysfunction of specific cellular subsets (T cells, natural killer cells and monocytes) in HIV-infected patients on cART and their relationship to adverse clinical outcomes including impaired CD4 T-cell recovery, as well as non-AIDS clinical events, such as cardiovascular disease.

Lipopolysaccharide-binding protein for monitoring of postoperative sepsis: complemental to C-reactive protein or redundant?

INTRODUCTION

To prospectively evaluate the performance of Lipopolysaccharide-Binding Protein (LBP) in prediction of hospital mortality and its correlation to C-reactive Protein (CRP), we studied sixty consecutive, postoperative patients with sepsis admitted to the university hospital intensive care unit.

MEASUREMENTS AND METHODS

Plasma LBP and CRP were serially measured from day(d)1 (onset of sepsis) to d14 in parallel with clinical data until d28. Predictive value and correlation of LBP and CRP were analyzed by Receiver Operating Characteristic (ROC) curve analysis and Pearson's test, respectively.

MAIN RESULTS

LBP and CRP showed the highest levels on d2 or d3 after the onset of sepsis with no significant difference between survivors and nonsurvivors. Only at d7, nonsurvivors had significantly (p = .03) higher levels of CRP than survivors. Accordingly, in ROC analysis, concentration of CRP and LBP on d7 poorly discriminated survivors from nonsurvivors (area under curve = .62 and .55, respectively) without significant difference between LBP- and CRP-ROC curves for paired comparison. LBP and CRP plasma levels allocated to quartiles correlated well with each other (r(2) = .95; p = .02). Likewise, changes in plasma concentrations of LBP and CRP from one observation to the next showed a marked concordance as both parameters concomitantly increased or decreased in 76% of all cases.

CONCLUSIONS

During the first 14 days of postoperative sepsis, LBP plasma concentrations showed a time course that was very similar to CRP with a high concordance in the pattern of day-to-day changes. Furthermore, like CRP, LBP does not provide a reliable clue for outcome in this setting.

Biomarkers: the future

The future application of biomarkers in critical illness will be to select and guide therapy. Specific biomarkers could identify a pathophysiologic perturbation or noxious mediator to counteract or the need to replete a deficient protective protein. Functional genomics could identify patients at risk for illness or at risk for a poor outcome in critical illness. Genetic expression studies could help differentiate patients with sepsis from those with noninfectious inflammation and could also help to monitor illnesses over time. Expressional and functional proteomics could lead to the identification of new biomarkers and organ-specific therapies.

TLR activation enhances C5a-induced pro-inflammatory responses by negatively modulating the second C5a receptor, C5L2

TLR and complement activation ensures efficient clearance of infection. Previous studies documented synergism between TLRs and the receptor for the pro-inflammatory complement peptide C5a (C5aR/CD88), and regulation of TLR-induced pro-inflammatory responses by C5aR, suggesting crosstalk between TLRs and C5aR. However, it is unclear whether and how TLRs modulate C5a-induced pro-inflammatory responses. We demonstrate a marked positive modulatory effect of TLR activation on cell sensitivity to C5a in vitro and ex vivo and identify an underlying mechanistic target. Pre-exposure of PBMCs and whole blood to diverse TLR ligands or bacteria enhanced C5a-induced pro-inflammatory responses. This effect was not observed in TLR4 signalling-deficient mice. TLR-induced hypersensitivity to C5a did not result from C5aR upregulation or modulation of C5a-induced Ca²⁺ mobilization. Rather, TLRs targeted another C5a receptor, C5L2 (acting as a negative modulator of C5aR), by reducing C5L2 activity. TLR-induced hypersensitivity to C5a was mimicked by blocking C5L2 and was not observed in C5L2KO mice. Furthermore, TLR activation inhibited C5L2 expression upon C5a stimulation. These findings identify a novel pathway of crosstalk within the innate immune system that amplifies innate host defense at the TLR-complement interface. Unravelling the mutually regulated activities of TLRs and complement may reveal new therapeutic avenues to control inflammation.