[Dexmedetomidine prevents inflammatory responses in injured rat lung tissues induced by ischemia/reperfusion through inhibition of TLR4 expression].

Objective: To investigate the effect of Dexmedetomidine (Dex) on Toll-like receptor 4(TLR4) expression in lung during lung ischemia/reperfusion(I/R) in rats and its possible protecting mechanisms.

Methods: In vivo I/R model in left lung of SD rats was estab-lished. Fifty adult healthy male SD rats were randomly divided into five groups (=10):control group (Sham group), I/R group, Dex group, atipamezole group (Atip group) and Dex+Atip group. After the I/R experiment,rats were killed and the left lung tissues were harvest-ed to get the lung wet/dry weight(W/D); Ultrastructure of lung tissue were observed under light microscopy; The mRNA expression of TLR4 in lung tissues were determined by RT-PCR; The protein level of TLR4 in lung tissues was detected by Western blot.

Results: ①Compared with those in the Sham group, W/D and total lung water content (TLW) in other groups increased significantly (<0.05), the mRNA and protein expression levels of TLR4 in lung tissues increased too. The structure damages of lung tissues observed under light microscopy in other groups were more than that of Sham group. ②Compared with those in the I/R group, W/D and TLW in the Dex group were lower (<0.05, <0.01), the mRNA and protein expression levels of TLR4 in lung tissues decreased (<0.01), and reduced structure damages of lung tissues were observed under light microscopy in Dex group. ③Compared with those in the Dex group, W/D and TLW in the Dex+Atip group were higher (<0.01), the mRNA and protein expression levels of TLR4 in lung tissues increased (<0.01), and the structure damages of lung tissues observed under light microscopy were more serious. There was no significant difference of the above parameters among I/R、Atip、Dex+Atip groups.

Conclusions: Lung ischemia/reperfusion caused high expression of TLR4 and finally induced damages of the lung. Dexmedetomidine could inhibit TLR4 expression and alleviate the lung ischemia/reperfusion injury, which was related to activation of α2-adreno receptor.