Klotho alleviates chronic intermittent hypoxia-induced genioglossus myocyte apoptosis by inhibiting endoplasmic reticulum stress

Chronic intermittent hypoxia (CIH) has been shown to induce cell apoptosis in multiple organs of the human body. The present study aimed to assess the effects of exogenous klotho on CIH-induced genioglossus muscle injury, as well as the involvement of endoplasmic reticulum stress (ERS) in this process. A total of 36 adult C57BL/6 male mice were assigned to normoxia control (NC), CIH and CIH + klotho groups (n=12 mice/group). ELISA was performed to detect the level of klotho protein in the serum and in the genioglossus muscle tissue samples. Apoptosis was evaluated using the TUNEL assay. Reactive oxygen species (ROS) levels were quantified using a dihydroethidium assay kit, and the protein and mRNA levels of ERS-associated proteins (namely, glucoseregulated protein 78, C/EBP homologous protein, cleaved caspase-12 and cleaved caspase-3) in genioglossus samples were assessed using immunoblot assay and reverse transcription-quantitative PCR, respectively. Compared with the NC group, the quantities of klotho protein in the serum and genioglossus muscle tissue samples in the CIH group were significantly decreased, whereas the apoptotic rate, ROS levels and protein and mRNA levels of the ERS-associated proteins in the genioglossus muscle were significantly increased. Following supplementation with exogenous klotho protein, the klotho protein levels in the serum and genioglossus muscle tissue of mice were found to be markedly increased, and the apoptotic rate, ROS levels and protein and mRNA levels of the ERS-associated proteins in the genioglossus muscle were decreased compared with those in the CIH group. Taken together, the results of the present study have demonstrated that exogenous klotho may inhibit apoptosis of genioglossus myocytes in mice by inhibiting ROS-associated ERS.