Abstract: Objective To explore the role and mechanism of demedetomidine in mitigation of lipopolysaccharide(LPS) induced acute lung injury(ALI) in rats. Methods SD rats were randomly divided: control group, lipopolysaccharide group (LPS group, intraperitoneal injection LPS 5 mg/kg), dexmedetomidine+LPS group (LD group, intraperitoneal injection demedetomidine 25 μg/kg and LPS 5 mg/kg). After LPS injection 6h later, broncho-alveolar lavage fluid (BALF) in left lung was collected for determination of concentrations of interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor (TNF-α) by enzyme linked immunosorbent assay (ELISA). And the right lung was removed to observe the pathological changes by HE staining and measure the lung injury score(LIS). The wet to dry lung weight (W/D) ration was calculated. The expression of HGMB1, TLR4 and TLR2 were detected by western blot. Results Compared with control group, the ALI, W/D ration, IL-1β, IL-6 and TNF-α in BALF, and the expression of HMGB1, TLR4 and TLR2 were significantly increased in LPS group (P<0.05). Compared with LPS group, the changes of each index in LD group were significantly relieved (P<0.05). Conclusion Dexmedetomidine relieves LPS-induced ALI in rats through inhibiting the expression of HGMB1 and TLRs.

Key words: Keywords: Acute lung injury, Dexmedetomidine, Lipopolysaccharide, High mobility group box 1 protein, Toll-like receptors.