Integrin β3 Modulates TLR4-Mediated Inflammation by Regulation Of CD14 Expression In Macrophages In Septic Condition.

Sepsis is a major challenge in clinical practice and responsible for high mortality. Recent studies indicated that integrins participated in toll-like-receptor (TLR)-mediated innate immunity. In the present study, we investigated the mechanism of integrin beta 3 and TLR4 signaling using a cecal ligation and puncture (CLP)-induced sepsis and lipopolysaccharide (LPS)-treated macrophage cell model. In a lethal CLP model, the survival rate of integrin beta 3(-/-)mice was higher than that of wild-type mice. The levels of alanine aminotransferase, aspartate transaminase, creatinine, blood urea nitrogen , and lactate dehydrogenase in the serum and cluster of differentiation 14 (CD14) protein expression in the tissues were significantly decreased in integrin beta 3(-/-)mice. A similar effect with regard to CD14 down-regulation was observed in septic TLR4(-/-)mice. In wild-type macrophages, the inhibition of integrin beta 3 by P11 or with a specific antibody, inhibited TNF-alpha, and IL-6 release at the early time period of LPS stimulation. However, during the late periods of LPS stimulation this effect was not noted. CD14 expression levels had no change in such treatment. In contract, LPS-induced TNF-alpha and IL-6 release and LPS-induced CD14 expression were significantly decreased in integrin beta 3(-/-)macrophages. The inhibition of the TLR4 pathway by TAK-242, or in TLR4 mutant macrophages abolished LPS-induced CD14 expression. Integrin beta 3 pathway activation by vitronectin exhibited no effect in CD14 expression. Furthermore, recombinant CD14 protein stimulation reversed integrin beta 3 deficiency and caused lower TNF-alpha and IL-6 release. Moreover, the molecular interaction of TLR4 and integrin beta 3 was significantly increased following LPS stimulation. In conclusion, integrin beta 3 positively regulated TLR4-mediated inflammatory responses via CD14 expression in macrophages in septic condition. Specifically targeting integrin beta 3/TLR4-CD14 signaling pathway may be a potential treatment strategy for polymicrobial sepsis.