[Effects of change in the activity of vacuolar adenosine triphosphatase of myocardial lysosome on myocardial damage in rats after severe burn and its mechanism].

Objective: To explore the effects of change of activity of vacuolar adenosine triphosphatase (V-ATPase) of myocardial lysosome on myocardial damage in rats after severe burn and its mechanism. Methods: The myocardial lysosomes were extracted from the hearts of 12 SD rats with ultra-high speed gradient density centrifugation, then Western blotting and transmission electron microscope observation were conducted for identification. One hundred and twenty rats were divided into pure burn group, ATP group, normal control group, and bafilomycin group according to the random number table, with 30 rats in each group. Rats in pure burn group and ATP group were inflicted with 40% TBSA full-thickness scald on the back. Immediately after injury, rats in pure burn group were intraperitoneally injected with lactated Ringer's solution in 4 mL·%TBSA(-1)·kg(-1,) and rats in ATP group were intraperitoneally injected with ATP in 0.4 mg/kg at 12 h before burn, immediately after burn, and 12 h after burn. Rats in normal control group did not receive any treatment, and rats in bafilomycin group were intraperitoneally injected with bafilomycin A1 in 0.3 mg/kg at the same time points as those of ATP group. At 24 h after burn, 30 rats from each group were collected for determining activity of V-ATPase of myocardial lysosome with coupled-enzyme assay and the expression of myocardium autophagy-related proteins microtubule-associated protein 1 light chain 3 (LC3) and P62 by Western blotting. Left ventricular arterial blood was collected to detect the content of 5 items of myocardial enzyme spectrum and cardiac troponin T (cTnT). Data were processed with one-way analysis of variance and t test. Results: (1) After identification, both the expression level of lysosome-related membrane protein 1 and purity of lysosome in the sample were high, and the structure of lysosome was intact. (2) At 24 h after burn, the activity values of V-ATPase of myocardial lysosome in rats of pure burn group, ATP group, normal control group, and bafilomycin group were (2.03±0.67), (3.01±0.58), (4.29±0.26), and (1.83±0.52) μmol·mg(-1)·h(-1,) respectively. The activity value of V-ATPase of myocardial lysosome in rats of pure burn group was significantly lower than the values in ATP group and normal control group (with t values respectively 3.14 and 8.87, P values below 0.01). The activity values of V-ATPase of rats in normal control group were significantly higher than those in bafilomycin group (t=11.87, P<0.01). At 24 h after burn, the expressions of myocardial LC3 and P62 in pure burn group were significantly higher than those in ATP group and normal control group (with t values from 3.73 to 5.88, P values below 0.01). The expressions of myocardial LC3 and P62 in normal control group were significantly lower than those in bafilomycin group (with t values respectively 2.64 and 3.07, P<0.05 or P<0.01). At 24 h after burn, the content of 5 items of myocardial enzyme spectrum and cTnT in pure burn group was significantly higher than that in ATP group and normal control group (with t values from 3.24 to 16.72, P values below 0.01). The content of 5 items of myocardial enzyme spectrum and cTnT in normal control group was significantly lower than that in bafilomycin group (with t values from 2.39 to 10. 70, P values below 0.01). Conclusions: The activity of V-ATPase of myocardial lysosome decreased in rats after severe burn, which can result in myocardial damage by inhibiting myocardial autophagy flux.