[The role of expression of Toll-like receptor 2 and Toll-like receptor 4 in hyperoxia-induced acute lung injury in rat].

OBJECTIVE

To investigate the role of Toll-like receptors (TLRs) in pathogenesis of hyperoxia- induced acute lung injury (ALI).

METHODS

Thirty-two Sprague-Dawley (SD) rats were randomly divided into air control group, hyperoxia for 24 hours group, hyperoxia for 48 hours group, and hyperoxia for 72 hours group, with 8 rats in each group. At corresponding exposure time points the animals were sacrificed, then the left lung was removed and measured the wet/dry weight (W/D) ratio. The severity of lung injury was assessed by lung histopathology scores, the expression of TLR2 mRNA and TLR4 mRNA in lung tissue was assessed by real-time reverse transcription-polymerase chain reaction (RT-PCR), the expression of TLR2 and TLR4 protein in lung tissue was measured by Western blotting, the amount of interleukin-6 (IL-6) in lung tissue was measured by enzyme linked immunosorbent assay (ELISA).

RESULTS

After hyperoxia exposure, an increase in lung W/D ratio was noted compared with that of the air control group (all P<0.01). Lung injury scores in hyperoxia for 48 hours (2.69+/-0.52) and 72 hours group (3.94+/-0.62) were significantly higher than that of the air control group (0.41+/-0.38, both P<0.01). Real-time RT-PCR results showed that TLR2 mRNA and TLR4 mRNA expression in lung tissue in hyperoxia exposure groups was significantly higher than that of the air control group (0.67+/-0.15, 0.63+/-0.19), and it reached the peak at 24 hours (1.82+/-0.33, 1.35+/-0.26, both P<0.05). Western blotting study showed increased protein expression of TLR2 and TLR4 in lung tissues of the hyperoxia groups compared with the air control group [(7.20+/-0.51)%, (14.26+/-0.19)%], and it peaked at 48 hours and 72 hours [(28.12+/-0.24)%, (81.35+/-0.82)%, both P<0.05]. ELISA assay also demonstrated upregulation of IL-6 levels in lung tissue of hyperoxia groups compared with the air control group [(639.38+/-95.24) pg/L], and it reached the peak at 72 hours [(1 300.58+/-442.24) pg/L, P<0.05].

CONCLUSION

The prolonged exposure to hyperoxia may cause ALI in rat, and TLR2 and TLR4 plays an important role in the development of hyperoxia-induced ALI in rat.