Abstract: Proliferation suppression and apoptosis are the prominent characteristics induced by heat stress (HS) in cells, whereas the effects of HS on cell growth (mass accumulation) are unknown. In this study, Lantang swine (an indigenous breed of China) skeletal muscle satellite cells (SCs) were pre-cultured at 37 °C for 24 h. The HS group was subjected to HS at 41 °C, while the control group was maintained at 37 °C. Heat shock protein 70 (HSP70) expression and SC size are significantly increased (P<0.05) by HS, but cell proliferation is suppressed (P<0.05) and apoptosis is induced (P<0.05). HS led to a lower percentage of SCs in the G0/G1 phase (P<0.05) together with a higher percentage of SCs in the S phase (P<0.05). However, the percentage of SCs in the G2/M phase was decreased (P<0.05) at 48 h but then increased (P<0.05) at 72 h with HS. In addition, the phosphorylation ratios of protein kinase b (Akt), ribosomal protein S6 kinase (S6K), and ribosomal protein S6 were increased (P<0.05) by HS. Nevertheless, the phosphorylation ratios of the 4E binding protein 1 and the eukaryotic initiation factor-4E were indistinguishable (P>0.05) from those of the control group. The phosphorylation ratio of the mammalian target of rapamycin (mTOR) (Ser²⁴⁴⁸) increased (P<0.05) within 48 h, and apparent differences were abrogated at 72 h (P>0.05). Moreover, cleaved caspase-3 expression was increased at 72 h (P<0.05). These findings indicate that HS induces apoptosis and disrupts cell cycle distribution to decrease the number of cells. Additionally, HS can promote SC growth via an activated Akt/mTOR/S6K signaling pathway.

热应激对猪骨骼肌卫星细胞增殖和生长的影响

[1]Bang, O.S., Ha, B.G., Park, E.K., et al., 2000. Activation of Akt is induced by heat shock and involved in suppression of heat-shock-induced apoptosis of NIH3T3 cells. Biochem. Biophys. Res. Commun., 278(2):306-311.

[2]Costa, M.R., Ortega, F., Brill, M.S., et al., 2011. Continuous live imaging of adult neural stem cell division and lineage progression in vitro. Development, 138(6):1057-1068.

[3]Dowling, R.J., Topisirovic, I., Alain, T., et al., 2010. mTORC1-mediated cell proliferation, but not cell growth, controlled by the 4E-BPs. Science, 328(5982):1172-1176.

[4]Furusawa, Y., Iizumi, T., Fujiwara, Y., et al., 2012. Inhibition of checkpoint kinase 1 abrogates G₂/M checkpoint activation and promotes apoptosis under heat stress. Apoptosis, 17(1):102-122.

[5]Gao, C.Q., Zhi, R., Yang, Z., et al., 2015. Low dose of IGF-I increases cell size of skeletal muscle satellite cells via Akt/S6K signaling pathway. J. Cell Biochem., in press.

[6]Kamanga-Sollo, E., Pampusch, M.S., White, M.E., et al., 2011. Effects of heat stress on proliferation, protein turnover, and abundance of heat shock protein messenger ribonucleic acid in cultured porcine muscle satellite cells. J. Anim. Sci., 89(11):3473-3480.

[7]Kühl, N.M., Rensing, L., 2000. Heat shock effects on cell cycle progression. Cell Mol. Life Sci., 57(3):450-463.

[8]Li, C.M., Yan, H.C., Fu, H.L., et al., 2014. Molecular cloning, sequence analysis, and function of the intestinal epithelial stem cell marker Bmi1 in pig intestinal epithelial cells. J. Anim. Sci., 92(1):85-94.

[9]Li, S.Q., Li, R.F., Xi, S.M., et al., 2012. Systematical analysis of impacts of heat stress on the proliferation, apoptosis and metabolism of mouse hepatocyte. J. Physiol. Sci., 62(1):29-43.

[10]Li, Y., Zhang, P., Qiu, F., et al., 2012. Inactivation of PI3K/ Akt signaling mediates proliferation inhibition and G2/M phase arrest induced by andrographolide in human glioblastoma cells. Life Sci., 90(25-26):962-967.

[11]Lindquist, S., 1986. The heat-shock response. Annu. Rev. Biochem., 55:1151-1191.

[12]Liu, F., Yin, J., Du, M., et al., 2009. Heat-stress-induced damage to porcine small intestinal epithelium associated with down regulation of epithelial growth factor signaling. J. Anim. Sci., 87(6):1941-1949.

[13]Lloyd, A.C., 2013. The regulation of cell size. Cell, 154(6):1194-1205.

[14]Locke, M., Celotti, C., 2014. The effect of heat stress on skeletal muscle contractile properties. Cell Stress Chaperones, 19(4):519-527.

[15]Millward, D., Garlick, P., Nnanyelugo, D., et al., 1976. The relative importance of muscle protein synthesis and breakdown in the regulation of muscle mass. Biochem. J., 156(1):185-188.

[16]Morales, A., Grageola, F., Garcia, H., et al., 2014. Performance, serum amino acid concentrations and expression of selected genes in pair-fed growing pigs exposed to high ambient temperatures. J. Anim. Physiol. Anim. Nutr., 98(5):928-935.

[17]Pearce, S.C., Gabler, N.K., Ross, J.W., et al., 2013. The effects of heat stress and plane of nutrition on metabolism in growing pigs, J. Anim. Sci., 91(5):2108-2118.

[18]Pende, M., Um, S.H., Mieulet, V., et al., 2004. S6K1^(−/−)/ S6K2^(−/−) mice exhibit perinatal lethality and rapamycin-sensitive 5'-terminal oligopyrimidine mRNA translation and reveal a mitogen-activated protein kinase-dependent S6 kinase pathway. Mol. Cell Biol., 24(8):3112-3124.

[19]Rezai Rad, M., Wise, G.E., Brooks, H., et al., 2013. Activation of proliferation and differentiation of dental follicle stem cells (DFSCs) by heat stress. Cell Prolif., 46(1):58-66.

[20]Shelton, S.N., Dillard, C.D., Robertson, J.D., 2010. Activation of caspase-9, but not caspase-2 or caspase-8, is essential for heat-induced apoptosis in Jurkat cells. J. Biol. Chem., 285(52):40525-40533.

[21]Sirotkin, A.V., Bauer, M., 2011. Heat shock proteins in porcine ovary: synthesis, accumulation and regulation by stress and hormones. Cell Stress Chaperones, 16(4):379-387.

[22]Taheri-Araghi, S., Bradde, S., Sauls, J.T., et al., 2015. Cell-size control and homeostasis in bacteria. Curr. Biol., 25(3):385-391.

[23]Tumaneng, K., Russell, R.C., Guan, K.L., 2012. Organ size control by hippo and tor pathways. Curr. Biol., 22(9):R368-R379.

[24]Uehara, K., Goto, K., Kobayashi, T., et al., 2004. Heat-stress enhances proliferative potential in rat soleus muscle. Jpn. J. Physiol., 54(3):263-271.

[25]Velichko, A.K., Markova, E.N., Petrova, N.V., et al., 2013. Mechanisms of heat shock response in mammals. Cell Mol. Life Sci., 70(22):4229-4241.

[26]Wang, X.Q., Yang, W.J., Yang, Z., et al., 2012. The differential proliferative ability of satellite cells in Lantang and landrace pigs. PLoS ONE, 7(3):e32537.

[27]Welch, W.J., 1992. Mammalian stress response: cell physiology, structure/function of stress proteins, and implications for medicine and disease. Physiol. Rev., 72(4):1063-1081.

[28]Yoshihara, T., Naito, H., Kakigi, R., et al., 2013. Heat stress activates the Akt/mTOR signalling pathway in rat skeletal muscle. Acta Physiol., 207(2):416-426.

[29]Zhang, M., Jiang, M., Bi, Y., et al., 2012. Autophagy and apoptosis act as partners to induce germ cell death after heat stress in mice. PLoS ONE, 7(7):e41412.