Toll-like receptors 4 contribute to endothelial injury and inflammation in hemorrhagic shock in mice

Objective: Hemorrhagic shock followed by resuscitation (HS/R) promotes organ injury by priming cells of the innate immune system for inflammatory response. Toll-like receptors (TLRs) play an important role in signal transduction in shock/resuscitation conditions. Because proinflammatory mediators are a critical event in mesenteric endothelial injury induced by HS/R, we assessed the role of TLR4 or TLR2 in this setting. Design: Laboratory investigation. Setting: Research laboratory at Rouen University Medical School. Subjects: Male wild-type, TLR4(-/-) and TLR2(-/-) mice with the same C57BL/6 background. Interventions: Mice were submitted to 30 minutes hemorrhagic shock followed by 1 hour resuscitation, after which mesenteric endothelial dysfunction, microvascular injury, and TNF alpha production were assessed. Measurements and Main Results: HS/R markedly decreased nitric oxide-mediated mesenteric relaxations induced by acetylcholine, assessed ex vivo on a myograph. By contrast, in TLR4-deficient mice, HS/R did not impair the nitric oxide-mediated responses to acetylcholine. No protection was observed in TLR2-deficient mice. TLR4-deficient mice also displayed a significant reduction in fluid resuscitation and TNF alpha systemic production. Conclusions: TLR4 contributes to mesenteric endothelial dysfunction after hemorrhagic shock. This early TLR4-induced vascular injury, may be an important trigger of the systemic inflammatory response occurring in this disease. (Crit Care Med 2009; 37:1724-1728)