In Vivo Toll-Like Receptor 4 Antagonism Restores Cardiac Function During Endotoxemia

Abstract

Severe sepsis and septic shock are often accompanied by acute cardiovascular depression. Lipopolysaccharide (LPS) signaling via Toll-like receptor 4 (TLR4) can induce septic organ dysfunction. The aim of this study was to elucidate the in vivo impact of pharmacological TLR4 antagonism on LPS-induced cardiovascular depression using eritoran tetrasodium (E5564). To simulate sepsis, C3H/HeN mice were challenged i.p. with 2 mg/kg body weight LPS. With the intent to antagonize the LPS effects, eritoran was administered i.v. (4 mg/kg body weight). Physical activity, peripheral blood pressure, and heart frequency were recorded before and after LPS and eritoran injection. In addition, intracardiac hemodynamic parameters were analyzed with a pressure conductance catheter. After 2 and 6 h of LPS stimulation ± eritoran treatment, the hearts and aortae were harvested, and TLR as well as inflammatory mediator expression was measured using reverse transcription-quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. Lipopolysaccharide significantly decreased arterial blood pressure over time. Administration of eritoran partially prevented the LPS-dependent reduction in blood pressure and preserved cardiac function. In addition, LPS increased the expression of CD14 and TLR2 in cardiac and aortic tissue. In aortic tissue, eritoran attenuated this increase, whereas no significant reduction was observed in the heart. Furthermore, cardiac and aortic inducible nitric oxide synthetase mRNA levels were significantly increased 6 h after LPS application. This effect was reduced in the presence of eritoran. In summary, the beneficial influence of eritoran on cardiovascular function in vivo seems to rely mainly on reduction of LPS-induced inducible nitric oxide synthetase expression as well as on attenuated cytokine expression in the vascular wall.