Abstract:Objective：To explore the mechanism of the activation of Toll-like receptor 2 in alveolar macrophage and its significances in hepatic ischemia/reperfusion(HIR) associated lung injury in mice. Methods：Wild type mice（C3h/Heouj）and TLR4-deficient mice(C3h/HeJ) were used in a model of hepatic ischemia/reperfusion. Alveolar macrophages were collected at the time point of 1h, 6h and 12h after HIR by means of bronchoalveolar lavage (BAL),and the expression of TLR2/4 mRNA was detected with Real-Time PCR. The level of endotoxin and TNF-α in BAL fluid were measured. The concentration of MPO, the ratio of wet/dry weight of lung tissue, and lung histological scores were used to assess the degrees of lung injuries. Results：The expressions of TLR2/4 mRNA in HIR group of C3h/Heouj mice were up-regulated at the all three time points after HIR. The level of TLR2mRNA was increased sustainedly and TLR4 markedly increased at 6h(P<0.01). At the same time TNF-α concentrations in BALF were increased(P<0.01) and lung injuries were aggravated which was indicated by the level of MPO, the ratio of wet/dry weight of lung and lung histological scores. But in TLR4-deficient(C3h/Hej) animals, the activations of TLR2 after HIR were only slight increased. TNF-α levels were significantly decreased compared to wild type mice at three time points after reperfusion(P<0.01), and lung injuries were milder than that in wild typy mice(P<0.05). Conclusions：Toll-like receptor 2 on alveolar macrophage can up-regulate TLR4 expression after HIR, which can aggravated the injury of the lung.