Transport stress induces apoptosis in rat myocardial tissue via activation of the mitogen-activated protein kinase signaling pathways

The present study aimed to elucidate the mechanism of myocardial damage induced by simulated transport stress. Sprague-Dawley rats were subjected to 35 degrees C and 60 rpm (0.1xg rcf) on a constant temperature shaker. The blood samples were prepared for detection of epinephrine (E), norepinephrine (NE), atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and serum cardiac troponin T (cTNT); myocardium samples were prepared for morphological examination and signaling protein quantitative. The result showed that plasma norepinephrine (NE) and epinephrine (E) concentrations increased in all stressed groups (P < 0.01). Levels of serum cardiac troponin T (cTNT) were elevated in both the S2d (P < 0.05) and S3d groups (P < 0.01). The concentration of plasma BNP was increased significantly in S3d group (P < 0.05); the difference in ANP was not remarkable. Morphological observation demonstrated obvious microstructure and ultrastructure damage after simulated transport stress. There was also a significant increase in the number of TUNEL-positive cardiomyocytes in stressed hearts. Western blot analysis found that the mitogen-activated protein kinase (MAPK) pathways were activated by strengthening phosphorylation of ASK-1, JNK, P38 and ERK in rat myocardial tissue after simulated transport stress (P < 0.05, P < 0.01). In addition, the ratio of pro-apoptotic Bax and anti-apoptotic Bcl-2 proteins was increased in stressed rats (P < 0.01), and the amount of cleaved-caspase3 increased in all stressed rats (P < 0.01). The expression of cleaved-caspase9 protein was also elevated in S2d and S3d groups (P < 0.01). Consequently simulated transport stress induced obvious myocardial damage, which may be attributed to the activation of caspase 9-mediated mitochondrial apoptotic pathway and MAPK pathways.