MD1 deletion exaggerates cardiomyocyte autophagy induced by heart failure with preserved ejection fraction through ROS/MAPK signalling pathway

In our previous studies, we reported that myeloid differentiation protein 1 (MD1) serves as a negative regulator in several cardiovascular diseases. However, the role of MD1 in heart failure with preserved ejection fraction (HFpEF) and the underlying mechanisms of its action remain unclear. Eight-week-old MD1-knockout (MD1-KO) and wild-type (WT) mice served as models of HFpEF induced by uninephrectomy, continuous saline or d-aldosterone infusion and a 1.0% sodium chloride treatment in drinking water for 4 weeks to investigate the effect of MD1 on HFpEF in vivo. H9C2 cells were treated with aldosterone to evaluate the role of MD1 KO in vitro. MD1 expression was down-regulated in the HFpEF mice; HFpEF significantly increased the levels of intracellular reactive oxygen species (ROS) and promoted autophagy; and in the MD1-KO mice, the HFpEF-induced intracellular ROS and autophagy effects were significantly exacerbated. Moreover, MD1 loss activated the p38-MAPK pathway both in vivo and in vitro. Aldosterone-mediated cardiomyocyte autophagy was significantly inhibited in cells pre-treated with the ROS scavenger N-acetylcysteine (NAC) or p38 inhibitor SB203580. Furthermore, inhibition with the autophagy inhibitor 3-methyladenine (3-MA) offset the aggravating effect of aldosterone-induced autophagy in the MD1-KO mice and cells both in vivo and in vitro. Our results validate a critical role of MD1 in the pathogenesis of HFpEF. MD1 deletion exaggerates cardiomyocyte autophagy in HFpEF via the activation of the ROS-mediated MAPK signalling pathway.