Objective To investigate the effects and mechanism of mitochondrial transcription factor A (TFAM) and cytochrome c oxidase (COX) pathway in the energy production of hypoxic cardiomyocytes of rats regulated by tumor necrosis factor receptor associated protein 1 (TRAP1).
Methods The cardiomyocytes were isolated from 135 neonatal Sprague-Dawley rats (aged 1-3 d) and cultured for the following experiments. (1) Cells were collected and divided into normoxia blank control (NBC) group, hypoxia blank control (HBC) group, hypoxia+ TRAP1 over-expression control (HTOC) group, and hypoxia+ TRAP1 over-expression (HTO) group according to the random number table (the same grouping method below), with 1 bottle in each group. Cells in NBC group were cultured routinely, cells in HBC group were cultured in hypoxic condition for 6 hours after routine culture, cells in HTOC and HTO groups were respectively added with TRAP1 over-expression empty virus vector and TRAP1 over-expression adenovirus vector virus suspension for transfection for 48 hours after routine culture and then cultured in hypoxic condition for 6 hours. The protein expression of TFAM of cells in each group was detected by Western blotting. (2) Cells were collected and divided into NBC, HBC, HTOC, HTO, HTO+ TFAM interference control (HTOTIC), and HTO+ TFAM interference (HTOTI) groups, with 1 well in each group. Cells in the former 4 groups were dealt with the same methods as the corresponding groups in experiment (1). Cells in HTOTIC and HTOTI groups were respectively added with TFAM interference empty virus vector and TFAM interference adenovirus vector virus suspension for transfection for 48 hours, and the other processing methods were the same as those in HTO group. The content of ATP of cells in each group was determined by ATP determination kit and microplate reader, and the COX activity of cells in each group was determined by COX activity assay kit and microplate reader. (3) Cells were collected and divided into NBC group, normoxia+ sodium azide (NSA) group, HBC group, and hypoxia+ sodium azide (HSA) group, with 1 well in each group. Cells in NBC and HBC groups were respectively dealt with the same methods as the corresponding groups in experiment (1). Cells in NSA and HSA groups were respectively added with 32 nmol sodium azide at 30 min before experiment or hypoxia, and then cells in HSA group were cultured in hypoxic condition for 6 hours. The content of ATP was determined by the same method as above. The above three experiments were repeated for three times. Data were statistically analyzed with one-way analysis of variance and least significant difference test.
Results (1) Compared with that in NBC group, the protein expression of TFAM of cells in HBC group was significantly decreased (
P<0.01). Compared with that in HBC group or HTOC group, the protein expression of TFAM of cells in HTO group was significantly increased (
P<0.01). (2) Compared with 0.552±0.041 and 1.99±0.15 in NBC group, the COX activity (0.270±0.044) and ATP content (1.09±0.11) of cells in HBC group were significantly decreased (
P<0.01). Compared with 0.269±0.042 and 1.17±0.12 in HBC group and those in HTOC group, the COX activity (0.412±0.032 and 0.404±0.016) and ATP content (1.75±0.06 and 1.69±0.07) of cells in HTO and HTOTIC groups were significantly increased (
P<0.01). Compared with those in HTO and HTOTIC groups, the COX activity (0.261±0.036) and ATP content (1.23±0.07) of cells in HTOTI group were significantly decreased (
P<0.01). (3) Compared with that in NBC group, the ATP content of cells in NSA and NBC groups was significantly decreased (
P<0.01). Compared with that in HBC group, the ATP content of cells in HSA group was significantly decreased (
P<0.01).
Conclusions TRAP1 can increase the COX activity of cardiomyocytes by raising the expression of TFAM, and finally alleviate the impairment in energy production of cardiomyocytes caused by hypoxia.
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