[Study on the effects of telomerase reverse transcriptase in alleviating doxorubicin induced cardiotoxicity].

Objective: To investigate the role of telomerase reverse transcriptase (TERT) in alleviating doxorubicin (DOX)-induced cardiotoxicity.

Methods: (1) Cell experiments: rat H9c2 cardiomyocytes were divided into control group (CON group), null adenovirus transfection group (NC group), TERT overexpression adenovirus transfection group (TERT group), DOX group (treated with 1 μmol/L DOX for 12 hours), DOX+NC group, and DOX+TERT group (null adenovirus or TERT overexpression adenovirus were transfected for 24 hours and then treated with 1 μmol/L DOX for 12 hours). The mRNA expression of TERT in cardiomyocytes was detected by real-time fluorescence quantitative polymerase chain reaction (RT-qPCR). The level of mitochondrial membrane potential was detected by immunofluorescence. The expression levels of intracellular Bax, Bcl-2, microtubule-associated protein 1 light chain 3 (LC3) and p62 were detected by Western blotting. (2) Animal experiments: male C57BL/6 mice were randomly divided into a sham operation group (Sham group), DOX group (acute cardiotoxicity model was constructed by intraperitoneal injection of DOX 15 mg/kg), DOX+NC group and DOX+TERT group (modeled after transfection with airborne adenovirus or TERT overexpression adenovirus for 7 days). After 7 days of modeling, the area of myocardial fibrosis was detected by Sirius scarlet staining, and cardiac function was detected by echocardiography.

Results: (1) Cellular experiments: the mRNA expression level of TERT was significantly higher in the TERT group compared with the CON and NC groups. Compared with the CON group, the TERT mRNA expression level of cardiomyocytes in the DOX group and the DOX+NC group were significantly lower, the level of mitochondrial membrane potential was significantly lower, the protein expressions of Bax and LC3 were significantly increased, and the protein expressions of Bcl-2 and p62 were significantly decreased. No significant differences were found between the DOX group and DOX+NC group. Compared with the DOX group and DOX+NC group, the TERT mRNA expression level was increased in the DOX+TERT group (relative expression: 1.02±0.10 vs. 0.61±0.05, 0.54±0.03, both P < 0.05), the level of mitochondrial membrane potential was significantly increased (1.14±0.05 vs. 0.96±0.01, 0.96±0.01, both P < 0.05), the protein expressions of Bax and LC3 were significantly decreased, and the protein expressions of Bcl-2 and p62 were significantly increased (Bax/β-actin: 0.88±0.01 vs. 1.31±0.02, 1.26±0.01; LC3-II/I: 2.16±0.05 vs. 2.64±0.06, 2.58±0.02; Bcl-2/β-actin: 0.65±0.01 vs. 0.40±0.01, 0.41±0.01; p62/β-actin: 0.45±0.01 vs. 0.23±0.02, 0.29±0.01; all P < 0.05). (2) Animal experiments: compared with the Sham group, the percentage of myocardial fibrosis area was significantly increased and left ventricular ejection fraction (LVEF) and fractional shortening (FS) were significantly decreased in the DOX group and DOX+NC group. Compared with the DOX group and DOX+NC group, the percentage of myocardial fibrotic area was significantly decreased in the DOX+TERT group (%: 2.33±0.06 vs. 3.76±0.07, 3.87±0.06, both P < 0.05), and the LVEF and FS were significantly increased [LVEF (%): 67.00±1.14 vs. 54.60±1.57, 53.40±2.18; FS (%): 38.60±0.51 vs. 30.60±1.10, 30.00±0.71; all P < 0.05].

Conclusion: Up-regulation of TERT expression can inhibit DOX-induced cardiomyocyte autophagy and apoptosis, attenuate DOX-induced myocardial fibrosis in mice, improve cardiac function, and thus alleviate DOX-induced cardiotoxicity.