关键词: 心肌肥大, 环状RNA, CHACR, 血管紧张素Ⅱ, 横向主动脉缩窄手术, 氧化应激损伤

Abstract: BACKGROUND: Pathological cardiac hypertrophy is a risk factor for various heart diseases, but its pathogenesis remains unclear. Circular RNAs are strongly associated with cardiac hypertrophy. However, the role of circular RNA CHACR in cardiac hypertrophy and its regulatory mechanisms have not been clarified. 
OBJECTIVE: To investigate the role of circular RNA CHACR in pressure overload-induced cardiac hypertrophy and the underlying mechanisms.  
METHODS: (1) Transverse aortic constriction was used to induce cardiac hypertrophy in vivo after in situ injection of cyclic RNA CHACR overexpressing lentivirus into the heart for 1 week. Heart mass/tibia length ratio and lung mass/tibia length ratio were calculated; cardiomyocyte surface area was measured; hypertrophic marker gene expression levels were detected; myocardial fibrosis degree was detected, and cardiac function was assessed. (2) H9c2 cardiomyocytes were treated with circular RNA CHACR overexpressing lentivirus for 72 hours, and then treated with 1 µmol/L angiotensin II for 24 hours to induce hypertrophy of cardiomyocytes. The hypertrophy was assessed by measuring the surface area of cardiomyocytes, the expression level of hypertrophic marker genes, and the protein /DNA ratio. Oxidative stress damage was assessed by detecting reactive oxygen species levels and mitochondrial membrane potential. 
RESULTS AND CONCLUSION: (1) The expression level of circular RNA CHACR was significantly decreased in both in vivo and in vitro myocardial hypertrophy models (P < 0.01). (2) The overexpression of circular RNA CHACR significantly inhibited the cardiac hypertrophy induced by transverse aortic constriction, including reducing the enlarged heart volume, significantly decreasing the increased heart mass/tibia length ratio (P < 0.05), lung mass/tibia length ratio (P < 0.05), and cardiomyocyte surface area (P < 0.05), and decreasing the upregulated expression levels of hypertrophic markers atrial natriuretic peptide (P < 0.05) and brain natriuretic peptide (P < 0.05). (3) Cardiac fibrosis induced by transverse aortic constriction in mice was significantly inhibited by enforcing expression of circular RNA CHACR, as evidenced by reduced fibrotic area (P < 0.01) and decreased expression levels of the fibrosis marker gene Acta1 (P < 0.05). (4) Overexpression of circular RNA CHACR significantly improved cardiac function in mice, including significantly increased ejection fraction (P < 0.05) and fractional shortening (P < 0.01). (5) Enforced expression of circular RNA CHACR significantly inhibited angiotensin II-induced cardiomyocyte hypertrophy, including a significant reduction in cardiomyocyte surface area (P < 0.05), downregulation of atrial natriuretic peptide (P < 0.05), and brain natriuretic peptide (P < 0.05) expression levels, and a significant decrease in protein/DNA ratio (P < 0.05). (6) Overexpression of circular RNA CHACR significantly inhibited the elevation of reactive oxygen species levels (P < 0.001) and the decrease in mitochondrial membrane potential (P < 0.05) induced by angiotensin II. These results confirm that the expression level of circular RNA CHACR is significantly decreased in cardiac hypertrophy at both in vivo and in vitro myocardial hypertrophy models, and overexpression of circular RNA CHACR significantly inhibits cardiac hypertrophy, alleviates cardiac fibrosis, improves cardiac function, and significantly attenuates angiotensin II-induced oxidative stress damage.

Key words: cardicac, circular RNA, CHACR, angiotensin II, transverse aortic constriction, oxidative stress damage