The effects of postconditioning with propofol on Toll-like receptor 4 expression in the lung tissue of rat with acute lung injury

Abstract

To investigate the effect of postconditioning with propofol on Toll-like receptor 4 (TLR4) expression in the lung tissue in lipopolysaccharide (LPS)-induced acute lung injury (ALI) rats. Thirty Sprague-Dawley (SD) rats were randomly assigned to control group, ALI group, and propofol postcondition group (each n=10). The model of ALI was reproduced by intravenous injection of LPS (8 mg/kg for 30 minutes) into the rats, equivalent normal saline was injected into the rats of control group. The rats were postconditioned with propofol injected intravenously by 20 mg/kg bolus dose and then continuously by 40 mg×kg(-1)×h(-1) with a constant speed for 1 hour. The rats were sacrificed 6 hours after drug injection. Lung wet/dry weight (W/D) ratio and lung permeability index (LPI) was taken. Tumor necrosis factor-α (TNF-α) level in bronchoalveolar lavage fluid (BALF) was detected using enzyme linked immunosorbent assay (ELISA) method and TLR4 mRNA expression in lung tissue was assessed by reverse transcription-polymerase chain reaction (RT-PCR). The lung W/D ratio, LPI, TLR4 mRNA and TNF-α in BALF were all increased in ALI group compared with control group [lung W/D ratio: 5.30±0.28 vs. 4.21±0.14, LPI (×10(-3)): 8.7±2.2 vs. 3.3±2.0, TLR4 mRNA: 2.451±0.028 vs. 0.998±0.021, TNF-α: 643.46±62.31 ng/L vs. 120.43±12.65 ng/L, all P<0.05]. The above indexes were significantly reduced in the propofol group than those in the ALI group [lung W/D ratio: 4.68±0.19 vs. 5.30±0.28, LPI (×10(-3)): 5.8±2.0 vs. 8.7±2.2, TLR4 mRNA: 1.126±0.025 vs. 2.451±0.028, TNF-α: 290.53±32.01 ng/L vs. 643.46±62.31 ng/L, all P<0.05], but still higher than those in control group (all P<0.05). Postconditioning with propofol may alleviate ALI via reducing TLR4 mRNA expression, and inhibit the waterfall-like inflammatory reaction.