Ro5‐4864, a ligand of the mitochondrial translocator protein, protects against heart failure in mice via regulation of the p62‐Keap1‐Nrf2 axis

Abstract The 18‐kDa mitochondrial translocator protein (TSPO) has been shown to modulate mitochondrial function and the cardiac response to pressure overload. We have previously shown that conditional knockout of TSPO limited the development of heart failure in the murine model of transverse aortic constriction (TAC). In this study, we hypothesized that similar protection could be achieved by a ligand of TSPO, Ro5‐4864 (Ro5), in an in‐vivo model of pressure‐overload induced heart failure. To test this hypothesis, C57/BL6J mice had TAC or sham surgery, with daily 0.1 mg/kg Ro5 or saline intra‐peritoneal injection for 8 weeks, with echocardiographic measurement of left ventricular (LV) size and function. Cardiac tissue protein expression was then analyzed by LC/MS. Markers of inflammation were quantified via western blot. Isolated murine cardiomyocytes were co‐treated with 25 µM H 2 O 2 and 2.5 µg Ro5 to investigate oxidative stress. The results of these experiments showed that Ro5‐4864 significantly prevented the TAC‐induced decline in LV function, as well as the associated increases in natriuretic peptide A and collagen alpha‐1 (XII) expression observed in saline‐treated animals. Ro5‐4864 also reduced oxidative stress and activated the Nrf2 pathway, likely due to decreased p62 accumulation secondary to enhanced mitophagy and restoration of autophagic flux. These in vivo findings were supported by complementary in vitro experiments in cardiomyocytes, where Ro5 attenuated oxidative stress induced by exogenous H 2 O 2 . In conclusion, these results indicate that Ro5‐4864 mitigates the development of pressure overload induced heart failure in mice, suggesting that pharmacologic modulation of the TSPO represents a promising therapeutic strategy for the prevention or treatment of heart failure. image Key points This study employed Ro5‐4864, a ligand of the mitochondrial translocator protein (TSPO), to test the hypothesis that pharmacologic inhibition of TSPO could limit the development of heart failure in a murine model of transverse aortic constriction (TAC). Ro5‐4864 preserved left ventricular function after TAC and limited the biochemical markers of heart failure and fibrosis. Proteomic analysis showed a significant effect of Ro5 on markers of immune activation, oxidative stress and inflammation. Ro5‐4864 increased the expression of Nrf2, a transcription factor that induces cytoprotective proteins such as NQO1 and SOD2, coupled with regulators of Nrf2 such as p62 and Keap1. These data establish a foundation for further development of anti‐inflammatory interventions in heart failure.