Abstract: Objective To evaluate the effect of rosmarinic acid (RA) on mitophagy and hypertrophy of cardiomyocytes exposed to high glucose (HG). Methods Rat cardiomyocytes (H9c2) exposed to HG (25 mmol/L) were treated with 50 μmol/L RA or with both RA treatment and Parkin siRNA transfection, with the cells cultured in normal glucose (5.5 mmol/L) and HG as the controls. The expressions of PINK1, Parkin and LC3II/LC3I in the cells were detected by Western blotting. The formation of mitochondrial autophagosomes was observed by transmission electron microscope. Flow cytometry was employed to detect the level of reactive oxygen species (ROS) and apoptotic rate of the cells. The activities of respiratory chain complex enzymes were measured by spectrophotometry. Fluorescence enzyme labeling and 3H-leucine labeling were used for determining the level of membrane potential and protein synthesis rate, respectively. The cell surface area was observed by light microscopy. Results RA treatment significantly increased the expression levels of PINK1, Parkin and LC3-II/I (P<0.05), promoted the formation of mitochondrail autophagosome, inhibited the production of reactive oxygen species (P<0.05), restored the activities of mitochondrial respiratory chain complex enzymes and mitochondrial membrane potential (P<0.05), inhibited apoptosis (P<0.05), and reduced the cell surface area and protein synthesis rate of H9c2 cells induced by HG exposure (P<0.05). The protective effects of RA against HG-induced oxidative stress and cardiomyocyte hypertrophy was obviously blocked by inhibition of mitophagy mediated by transfection with Parkin siRNA (P<0.05). Conclusion RA can protect rat cardiomyocytes against oxidative stress injury and cardiomyocyte hypertrophy induced by HG by activating Parkin-mediated mitophagy.

Key words: rosmarinic acid, Parkin, mitophagy, oxidative stress, cardiomyocyte hypertrophy