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Objectives: Annexin A5 is a 35-kDa protein with high affinity binding to negatively charged phospholipids. However, its effects on sepsis are not known. Our aim was to study the effects of annexin A5 on myocardial tumor necrosis factor-α expression, cardiac function, and animal survival in endotoxemia. Design: Prospective experimental study. Setting: University laboratory. Subjects: Adult male C57BL/6 mice. Interventions: Mice were challenged with lipopolysaccharide (4 or 20 mg/kg, i.p.) to induce endotoxemia with and without recombinant human annexin A5 treatment (5 or 10 μg/kg, IV). Cytokine expression and cardiac function were assessed, and animal survival was monitored. Measurements and Main Results: Treatment with annexin A5 inhibited myocardial mitogen-activated protein kinase, and nuclear factor-κB activation in mice with endotoxemia. Furthermore, annexin A5-treated animals showed significant reductions in myocardial and plasma levels of tumor necrosis factor-α and interleukin-1β while cardiac function was significantly improved during endotoxemia. Additionally, 5-day animal survival was significantly improved by either an immediate or a 4-hour delayed annexin A5 treatment after lipopolysaccharide challenge. Importantly, annexin A5 dose-dependently inhibited lipopolysaccharide binding to a toll-like receptor-4/myeloid differentiation factor 2 fusion protein. Conclusions: Annexin A5 treatment decreases cytokine expression and improves cardiac function and survival during endotoxemia. These effects of annexin A5 are mediated by its ability to inhibit lipopolysaccharide binding to toll-like receptor-4, leading to reductions in mitogen-activated protein kinase and Akt signaling. Our study suggests that annexin A5 may have therapeutic potential in the treatment of sepsis.

Background. Lipopolysaccharide (LPS), the major glycolipid component of Gram-negative bacterial outer membranes, is a potent endotoxin responsible for many of the directly or indirectly induced symptoms of infection. Lipoproteins (in particular, high-density lipoproteins) sequester LPS, thereby acting as a humoral detoxification mechanism. Patients. Differences in the lipoprotein composition in human plasma and lymph of a control patient group (n = 5) without systemic inflammatory response syndrome (non-SIRS/MOF) and patients with SIRS and multiple organ failure (MOF, n = 9) were studied. The LPS binding capacity of the lipoproteins in SIRS/MOF and non-SIRS/MOF patients was investigated by rechallenge of the plasma and lymph with fluorescently labeled LIPS ex vivo. The lipoprotein composition was analyzed using immunochemical techniques and high-performance gel permeation chromatography. Results: In the non-SIRS/MOF patient group, plasma and lymph levels of apolipoprotein A-1 (600 and 450 mg/L, respectively), apolipoprotein B (440 and 280 mg/L, respectively), total cholesterol (2.88 and 1.05 mM, respectively), and total triglycerides (0.67 and 0.97 mM, respectively) were observed. In the SIRS/MOF group, a decrease of apolipoprotein A-1 (-55% in plasma and lymph), a decrease of apolipoprotein B (-43% in plasma and -38% in lymph), and a decrease of total cholesterol levels (-54% in plasma and -37% in lymph) were demonstrated. However, the triglyceride levels in the SIRS/MOF group showed a 30% increase in plasma and a 47% decrease in lymph compared with the non-SIRS/MOF patients. In SIRS/MOF patients, a 2.8-fold increase in plasma and a 1.8-fold increase in lymph of the LPS low-density lipoprotein/high-density lipoprotein ratio was observed, indicating that the relative LPS binding capacity of the lipoproteins in the SIRS/MOF patient group showed a trend to be shifted mainly toward low-density lipoproteins. Furthermore, in plasma and lymph of four SIRS/MOF patients, a novel cholesterol-containing high-density lipoprotein-like particle was found that barely had LPS binding capacity (