Soluble ST2 plasma concentrations predict mortality in severe sepsis

Patients with sepsis-after surviving the initial hyperinflammatory phase-display features consistent with immunosuppression, including hyporesponsiveness of immunocompetent cells to bacterial agents. Immunosuppression is thought to be facilitated by negative regulators of toll-like receptors, including membrane-bound ST2. We investigated the release of soluble ST2 (sST2), a decoy receptor that inhibits membrane-bound ST2 signaling, during sepsis. The study population comprised 95 patients with severe sepsis admitted to one of two intensive care units (ICUs) at the day the diagnosis of severe sepsis was made. Blood was obtained daily from admission (day 0) until day 7 and finally at day 14. Twenty-four healthy subjects served as controls. sST2 and cytokines were measured in serum. Mortality among patients was 34% in the ICU and 45% in the hospital. On admission, sepsis patients had higher sST2 levels [10,989 (7,871-15,342) pg/ml, geometric mean (95% confidence interval, CI)] than controls [55 (20-145) pg/ml, P < 0.0001]. Serum sST2 remained elevated in patients from day 0 to 14 and correlated with disease severity scores (P < 0.001) and cytokine levels on day 0 and during course of disease (P < 0.0001). Nonsurvivors displayed elevated sST2 levels compared with survivors of the intensive care unit (P < 0.0001). Sepsis results in sustained elevation of serum sST2 levels, which correlates with disease severity and mortalit

Differential dose-dependent effects of prednisolone on shedding of endothelial adhesion molecules during human endotoxemia

Low dose prednisolone was shown to be beneficial in the treatment of the Acute respiratory distress syndrome (ARDS) and septic shock. One corticosteroid-induced effect, postulated to mediate corticosteroid-induced anti-inflammatory effects, is decreased expression of adhesion molecules on endothelial cells, thereby preventing leukocyte recruitment at inflammatory sites. The current study aimed to investigate the effect of increasing doses of prednisolone on the release of soluble adhesion molecules in healthy volunteers challenged with endotoxin. Therefore, 32 healthy, male volunteers received prednisolone orally at doses of 0mg, 3mg, 10mg or 30mg at 2h before injection of endotoxin prepared from Escherichia coli (4ng/kg) and levels of soluble E-selectin (sE-selectin), soluble VCAM-1 (sVCAM-1) and soluble ICAM-1 (sICAM-1) were measured. Levels of all markers were increased after induction of endotoxemia. Levels of sE-selectin were inhibited by a dose of 3mg prednisolone and levels of sVCAM-1 were decreased after a dose of 10mg. Maximal inhibition of both sE-selectin and sVCAM-1 levels was achieved by the highest dose of prednisolone 30mg. Remarkably, prednisolone 3mg potentiated endotoxin-induced sVCAM-1 release. Levels of sICAM-1 were not affected by prednisolone. Together, the data suggest that prednisolone differentially and dose-dependently influences the release of soluble endothelial adhesion molecules during human endotoxemi

Intrapulmonary delivery of ethyl pyruvate attenuates lipopolysaccharide- and lipoteichoic acid-induced lung inflammation in vivo

Ethyl pyruvate (EP) is a stable pyruvate derivative that has been shown to exert anti-inflammatory effects in various models of systemic inflammation including endotoxemia. We here sought to determine the local effects of EP, after intrapulmonary delivery, in models of lung inflammation induced by instillation via the airways of either lipopolysaccharide (LPS, a constituent of the gram-negative bacterial cell wall) or lipoteichoic acid (LTA, a component of the gram-positive bacterial cell wall). For this, we first established that EP dose dependently reduced the responsiveness of mouse MH-S alveolar macrophages and mouse MLE-15 and MLE-12 respiratory epithelial cells to stimulation with LPS or LTA in vitro. We then showed that intranasal administration of EP dose dependently inhibited tumor necrosis factor alpha release in bronchoalveolar lavage fluid of mice challenged with either LPS or LTA via the airways. Moreover, EP reduced the recruitment of neutrophils into the bronchoalveolar space after either LPS or LTA administration. These data suggest that intrapulmonary delivery of EP diminishes lung inflammation induced by LPS or LTA, at least in part by targeting alveolar macrophages and respiratory epithelial cell

Neutrophil-derived S100A12 in acute lung injury and respiratory distress syndrome

OBJECTIVE: Both persistent accumulation and activation of neutrophils may contribute to the most severe form of acute lung injury, acute respiratory distress syndrome. We analyzed the expression of neutrophil-derived S100A12 and the proinflammatory receptor for advanced glycation end products (RAGE) in patients with acute respiratory distress syndrome. Additional in vivo and in vitro experiments were performed to further analyze the contribution of S100A12 to pulmonary inflammation. SUBJECTS: We included 14 patients with acute respiratory distress syndrome and eight controls. In addition, 16 healthy subjects were included in an experimental lipopolysaccharide challenge model. INTERVENTIONS: Concentrations of S100A12 and soluble RAGE were analyzed in bronchoalveolar lavage fluid. The expression of S100A12 and RAGE in lung biopsies from patients was analyzed by immunohistochemistry. S100A12 was also analyzed in bronchoalveolar lavage fluid from eight healthy subjects after challenge with lipopolysaccharide and compared with eight controls who received placebo inhalation. Effects of S100A12 on endothelial cells were analyzed in vitro. MAIN RESULTS: Patients with acute respiratory distress syndrome had significantly enhanced pulmonary S100A12 expression and higher S100A12 protein concentrations in bronchoalveolar lavage fluid than controls. Levels of soluble RAGE were not significantly elevated in acute respiratory distress syndrome. S100A12 concentrations decreased with time from disease onset. In healthy volunteers, S100A12 was elevated in bronchoalveolar lavage fluid after lipopolysaccharide inhalation. In vitro experiments confirmed strong proinflammatory effects of human S100A12. CONCLUSIONS: S100A12 and its receptor RAGE are found at high concentrations in pulmonary tissue and bronchoalveolar lavage fluid in acute lung injury. S100A12 expression may reflect neutrophil activation during lung inflammation and contribute to pulmonary inflammation and endothelial activation via binding to RAG

Mrp8 and Mrp14 are endogenous activators of Toll-like receptor 4, promoting lethal, endotoxin-induced shock

To identify new components that regulate the inflammatory cascade during sepsis, we characterized the functions of myeloid-related protein-8 (Mrp8, S100A8) and myeloid-related protein-14 (Mrp14, S100A9), two abundant cytoplasmic proteins of phagocytes. We now demonstrate that mice lacking Mrp8-Mrp14 complexes are protected from endotoxin-induced lethal shock and Escherichia coli-induced abdominal sepsis. Both proteins are released during activation of phagocytes, and Mrp8-Mrp14 complexes amplify the endotoxin-triggered inflammatory responses of phagocytes. Mrp8 is the active component that induces intracellular translocation of myeloid differentiation primary response protein 88 and activation of interleukin-1 receptor-associated kinase-1 and nuclear factor-kappaB, resulting in elevated expression of tumor necrosis factor-alpha (TNF-alpha). Using phagocytes expressing a nonfunctional Toll-like receptor 4 (TLR4), HEK293 cells transfected with TLR4, CD14 and MD2, and by surface plasmon resonance studies in vitro, we demonstrate that Mrp8 specifically interacts with the TLR4-MD2 complex, thus representing an endogenous ligand of TLR4. Therefore Mrp8-Mrp14 complexes are new inflammatory components that amplify phagocyte activation during sepsis upstream of TNFalpha-dependent effect

Receptor for Advanced Glycation End Products (RAGE) Serves a Protective Role during Klebsiella pneumoniae - Induced Pneumonia

Klebsiella species is the second most commonly isolated gram-negative organism in sepsis and a frequent causative pathogen in pneumonia. The receptor for advanced glycation end products (RAGE) is expressed on different cell types and plays a key role in diverse inflammatory responses. We here aimed to investigate the role of RAGE in the host response to Klebsiella (K.) pneumoniae pneumonia and intransally inoculated rage gene deficient (RAGE-/-) and normal wild-type (Wt) mice with K. pneumoniae. Klebsiella pneumonia resulted in an increased pulmonary expression of RAGE. Furthermore, the high-affinity RAGE ligand high mobility group box-1 was upregulated during K. pneumoniae pneumonia. RAGE deficiency impaired host defense as reflected by a worsened survival, increased bacterial outgrowth and dissemination in RAGE-/- mice. RAGE-/- neutrophils showed a diminished phagocytosing capacity of live K. pneumoniae in vitro. Relative to Wt mice, RAGE-/- mice demonstrated similar lung inflammation, and slightly elevated-if any-cytokine and chemokine levels and unchanged hepatocellular injury. In addition, RAGE-/- mice displayed an unaltered response to intranasally instilled Klebsiella lipopolysaccharide (LPS) with respect to pulmonary cell recruitment and local release of cytokines and chemokines. These data suggest that (endogenous) RAGE protects against K. pneumoniae pneumonia. Also, they demonstrate that RAGE contributes to an effective antibacterial defense during K. pneumoniae pneumonia, at least partly via its participation in the phagocytic properties of professional granulocytes. Additionally, our results indicate that RAGE is not essential for the induction of a local and systemic inflammatory response to either intact Klebsiella or Klebsiella LP

S100A12 and soluble receptor for advanced glycation end products levels during human severe sepsis

S100A12 is highly expressed, and serum levels correlate with individual disease activity in patients with inflammatory diseases. We here sought to determine the extent of S100A12 release and its soluble high-affinity receptor for advanced glycation end products (sRAGE) in patients with severe sepsis stratified to the three most common infectious sources (lungs, abdomen, and urinary tract) and to determine S100A12 and sRAGE concentrations at the site of infection during peritonitis. Two patient populations were studied: (a) 51 patients with sepsis due to (i) peritonitis (n = 12), (ii) pneumonia (n = 29), or (iii) urinary tract infection (n = 10); and (b) 17 patients with peritonitis. In addition, eight healthy humans were studied after intravenous injection of lipopolysaccharide (4 ng/kg). Compared with healthy volunteers, patients with severe sepsis displayed increased circulating S100A12 concentrations at day 0 (591.2 ± 101.0 vs. 106.2 ± 15.6 ng/mL [control subjects], P < 0.0001) and at day 3 (637.2 ± 111.2 vs. 106.2 ± 15.6 ng/mL [control subjects], P < 0.0001). All three severe sepsis subgroups had elevated serum S100A12 concentrations at both time points (sepsis due to [i] peritonitis [393.5 ± 89.9 at day 0 and 337.9 ± 97.2 at day 3 vs. 106.2 ± 15.6 ng/mL, control subjects, P < 0.005 and P < 0.05, respectively]; [ii] pneumonia [716.9 ± 167.0 at day 0 and 787.5 ± 164.7 at day 3 vs. 106.2 ± 15.6 ng/mL, control subjects, both P < 0.0001]; and [iii] urinary tract infection [464.2 ± 115.6 at day 0 and 545.6 ± 254.9 at day 3 vs. 106.2 ± 15.6 ng/mL, control subjects, P < 0.0001 and P < 0.05, respectively]). Remarkably, patients with sepsis due to pneumonia had the highest S100A12 levels (716.9 ± 167.0 and 787.5 ± 164.7 ng/mL at days 0 and 3, respectively). S100A12 levels were not correlated to either Acute Physiology and Chronic Health Evaluation II scores (r = -0.185, P = 0.19) or Sepsis-Related Organ Failure Assessment scores (r = -0.194, P = 0.17). Intravenous lipopolysaccharide injection in healthy humans elevated systemic S100A12 levels (peak levels at 3 h of 59.6 ± 22.0 vs. 12.4 ± 3.6 ng/mL; t = 0 h, P < 0.005). In contrast to S100A12, sRAGE concentrations did not change during severe sepsis or human endotoxemia. During peritonitis, S100A12 concentrations in abdominal fluid (12945.8 ± 4142.1 ng/mL) were more than 100-fold higher than in concurrently obtained plasma (121.2 ± 80.4 ng/mL, P < 0.0005), whereas sRAGE levels in abdominal fluid (148.8 ± 36.0 pg/mL) were lower than those in plasma (648.7 ± 145.6 pg/mL, P < 0.005) and did not increase. In conclusion, in severe sepsis, S100A12 is released systemically irrespective of the primary source of infection. During abdominal sepsis, S100A12 release likely predominantly occurs at the site of infection. Concentrations of its high-affinity sRAGE do not change during infection or human endotoxemia

Induction of IRAK-M is associated with lipopolysaccharide tolerance in a human endotoxemia model

Recent in vitro and murine in vivo studies have identified several potential LPS tolerance factors. In this study, we describe the expression kinetics of these LPS tolerance factors in standardized human endotoxemia models using i.v. LPS bolus administration. Responsiveness to LPS as well as the expression of potential regulators of LPS signaling were determined in peripheral whole blood. Intravenous LPS administration (4 ng/kg) resulted in peak plasma levels of TNF-alpha at 1.5 h followed by subsequent peaks of the classic negative feedback inhibitors A20 and IL-10 at 2 and 3 h, respectively. Circulating blood monocyte counts decimated during the initial inflammatory response, but normalized in the period between 4 and 8 h post-LPS. The LPS response as determined by ex vivo TNF release per monocyte in whole blood was profoundly decreased at 6-8 h post-LPS injection despite cessation of A20 and IL-10 expression after 4 h. Analysis of MyD88short, IL-1R-associated kinase (IRAK)-1, IRAK-M, ST2, suppressor of cytokine signaling-1 and -3, SHIP-1, and MAP kinase phosphatase-1 expression indicated that the observed LPS tolerance was associated with decreased IRAK-1 and elevated IRAK-M expression in this human model. Interestingly, a lower dose of LPS (1 ng/kg) induced LPS tolerance accompanied with IRAK-M up-regulation but without depletion of IRAK-1. In vitro studies in whole blood showed that IRAK-M up-regulation by LPS is largely dependent on TNF-alpha. The observed rise of IRAK-M transcription in the human endotoxemia model appeared much greater compared with in vitro-stimulated whole blood. In conclusion, LPS tolerance in human endotoxemia models is associated with IRAK-M up-regulatio