Mechanism of cell autophagy for regulating skeletal muscle wasting of rats after severe burns

Abstract

Objective: To investigate the mechanism of cell autophagy for regulating skeletal muscle wasting of rats after severe burns. Methods: Seventy-two Sprague-Dawley rats were collected and divided into sham injury group, simple burn group, burn+ phosphate buffer solution (PBS) group, and burn+ 3-methyladenine (3-MA) group according to the random number table, with 18 rats in each group. Rats in simple burn group, burn+ PBS group, and burn+ 3-MA group were inflicted with 30% total body surface area full-thickness scald (hereinafter referred to as burns). Rats in sham injury group were sham injured. Immediately after burns and fluid resuscitation, rats in burn+ PBS group were intraperitoneally injected with 1 mL PBS, and rats in burn+ 3-MA group were intraperitoneally injected with 1 mL 3-MA (125 g/L). On post injury day 3 and 7, the weights of anterior tibial muscle of right hind limbs and body of rats were measured to calculate percentage of anterior tibial muscle of right hind limbs weight. Protein expressions of microtubule related protein 1 light chain 3A (LC3A) and Beclin-1 of anterior tibial muscle were observed by immunofluorescence method and detected by Western blotting, and ratio of microtubule related protein 1 LC3A-Ⅱ to LC3A-Ⅰ was calculated. Data were processed with analysis of variance of factorial design, one-way analysis of variance, t-test and Bonferroni correction. Results: On post injury day 3 and 7, percentages of anterior tibial muscle of right hind limbs weight of rats in simple burn group were (0.148±0.009)% and (0.134±0.018)%, respectively, which were significantly lower than those in sham injury group [(0.203±0.009)%, (0.181±0.015)%, t=10.585, 4.913, P<0.01]. Percentages of anterior tibial muscle of right hind limbs weight of rats in burn+ 3-MA group were (0.187±0.004)% and (0.192±0.009)%, respectively, which were obviously higher than those in burn+ PBS group [(0.162±0.005)%, (0.167±0.005)%, t=9.564, 5.948, P<0.01]. On post injury day 3 and 7, protein expressions of Beclin-1 and microtubule related protein 1 LC3A of anterior tibial muscle of rats in simple burn group were significantly higher than those in sham injury group, while protein expressions of Beclin-1 and microtubule related protein 1 LC3A of anterior tibial muscle of rats in burn+ 3-MA group were significantly lower than those in burn+ PBS group. Ratios of microtubule related protein 1 LC3A-Ⅱ to LC3A-Ⅰ of anterior tibial muscle of rats in simple burn group were significantly higher than those in sham injury group (t=3.461, 3.353, P<0.05), while ratios of microtubule related protein 1 LC3A-Ⅱ to LC3A-Ⅰ of anterior tibial muscle of rats in burn+ 3-MA group were significantly lower than those in burn+ PBS group (t=3.129, 3.977, P<0.05). Conclusions: Cell autophagy induced by severe burns is involved in the process of skeletal muscle wasting of rats, and inhibition of cell autophagy may contribute to the remission of skeletal muscle wasting of rats induced by burns.