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Right ventricular remodeling and its function are closely related to the symptom severity and survival of hypoxia pulmonary hypertension, but molecular mechanisms of cardiomyocyte hypertrophy and myocardial injury remain unclear. It evaluated the cardiac function (by right cardiac catheterization to measure right ventricular systolic pressure and mean pulmonary artery pressure), myocardial tissue morphology（Haematoxylin and Eosin）, myocardial hypertrophy (Wheat Germ Agglutinin Staining), then RNA sequencing was applied to explore the mechanism, which results were verified by western blot in final. Hypoxia developed pulmonary hypertension, right ventricular diastolic and systolic functions were enhanced in rats, such as the mean pulmonary artery pressure, systolic pressure of pulmonary artery, the max pressure of right ventricular, the mean right ventricular pressure, and the heart rate was significantly higher than that in control. We found that Hif-1 signaling pathway and p38-MAPK signaling pathway have been activated by hypoxia, and cardiomyocyte apoptosis also aggravated in the right ventricular, which might be one cause of cardiomyocyte hypertrophy and myocardial injury, and targeted intervention might be one potential prevention for cardiomyocyte hypertrophy and myocardial injury induced by hypoxia.

Mitochondria-associated membranes (MAM) are a well-recognized contact link between the mitochondria and endoplasmic reticulum that affects mitochondrial biology and vascular smooth muscle cells (VSMCs) proliferation via the regulation of mitochondrial Ca2+(Ca2+m) influx. Nogo-B receptor (NgBR) plays a vital role in proliferation, epithelial-mesenchymal transition, and chemoresistance of some tumors. Recent studies have revealed that downregulation of NgBR, which stimulates the proliferation of VSMCs, but the underlying mechanism remains unclear. Here, we investigated the role of NgBR in MAM and VSMC proliferation. We analyzed the expression of NgBR in pulmonary arteries using a rat model of hypoxic pulmonary hypertension (HPH), in which rats were subjected to normoxic recovery after hypoxia. VSMCs exposed to hypoxia and renormoxia were used to assess the alterations in NgBR expression in vitro. The effect of NgBR downregulation and overexpression on VSMC proliferation was explored. The results revealed that NgBR expression was negatively related with VSMCs proliferation. Then, MAM formation and the phosphorylation of inositol 1,4,5-trisphosphate receptor type 3 (IP3R3) was detected. We found that knockdown of NgBR resulted in MAM disruption and augmented the phosphorylation of IP3R3 through pAkt, accompanied by mitochondrial dysfunction including decreased Ca2+m, respiration and mitochondrial superoxide, increased mitochondrial membrane potential and HIF-1&alpha, nuclear localization, which were determined by confocal microscopy and Seahorse XF-96 analyzer. By contrast, NgBR overexpression attenuated IP3R3 phosphorylation and HIF-1&alpha, nuclear localization under hypoxia. These results reveal that dysregulation of NgBR promotes VSMC proliferation via MAM disruption and increased IP3R3 phosphorylation, which contribute to the decrease of Ca2+m and mitochondrial impairment.