Exogenous platelet-activating factor acetylhydrolase reduces mortality in mice with systemic inflammatory response syndrome and sepsis.

Current evidence indicates that dysregulation of the host inflammatory response to infectious agents is central to the mortality of patients with sepsis and in those with systemic inflammatory response syndrome. Strategies to block inflammatory mediators, often with complicated outcomes, are currently being investigated as new adjuvant therapies for sepsis. Here, we determined if administration of recombinant platelet-activating factor (rPAF)-acetylhydrolase (rPAF-AH), an enzyme that inactivates PAF and PAF-like lipids, protects mice from inflammatory injury and death after administration of lipopolysaccharide (LPS) or cecal ligation and puncture (CLP). Administration of rPAF-AH increased plasma PAF-AH activity and reduced mortality in both models. Treatment with rPAF-AH increased peritoneal fluid levels of monocyte chemoattractant protein 1/CCL-2 and decreased interleukin 6 and migration inhibitory factor levels after LPS administration or CLP. Administration of a broad-spectrum antibiotic together with rPAF-AH was more protective than single treatment with either of these agents. The combined treatment was associated with reduced interleukin 6 levels in mice subjected to CLP. We observed acute decreases in plasma PAF-AH activity in mice subjected to CLP or challenged with LPS and in human patients with sepsis. We conclude that alterations in the endogenous PAF-AH contribute to the pathophysiology of sepsis and that administration of exogenous rPAF-AH reduces inflammatory injury and mortality in models relevant to the clinical syndrome. Variations in endogenous PAF-AH activity may potentially account for variable responses to exogenous rPAF-AH in previous clinical trials. Serial measurements of plasma PAF-AH activity in murine models demonstrate dynamic regulation of the endogenous enzyme, potentially explaining the variations in human subjects.

Antibiotic treatment in a murine model of sepsis: impact on cytokines and endotoxin release.

Experimental and clinical studies in sepsis indicate that antibiotic therapy may induce the release of endotoxin (LPS) from the outer membrane of gram-negative bacteria and therefore may affect the physiologic response and survival. The aim of this study was to evaluate if antibiotics commonly used to treat secondary peritonitis are capable of changing survival rates, proinflammatory and anti-inflammatory cytokine concentrations, and the release of endotoxin in a murine model of sepsis. Sepsis was induced by cecal ligation and puncture (CLP) in Swiss mice using an 18-gauge needle. The animals received injections of saline solution or imipenem or a combination of ciprofloxacin plus clindamycin every 8 h for 3 days. Antibiotic treatment induced an increase in survival rate and decreased plasma and peritoneal fluid levels of TNF-alpha and IL-6 at 6 and 24 h after CLP as compared with saline-treated animals. Antibiotic-treated animals also showed an early (6 h) decrease and a late (24 h) increase in IL-10 concentration in the peritoneal fluid. LPS concentrations were elevated in all groups, but imipenem-treated animals showed higher levels (2.2 EU/mL) than ciprofloxacin plus clindamycin (1.3 EU/mL) and saline-treated (1.5 EU/mL) groups. We conclude that antibiotic-induced endotoxin release is not a major determinant in the inflammatory response and prognosis in murine models of sepsis.