The HIF2α-dependent Upregulation of SETDB1 Facilitates Hypoxia-induced Functional and Phenotypical Changes of Pulmonary Microvascular Endothelial Cells

Background: Emerging studies have reported the vital role of histone modification in the dysfunction of pulmonary vascular endothelial cells, which acts as the key reason to drive the hypoxia-induced pulmonary vascular remodeling and pulmonary hypertension (PH). This study aims to investigate the role of a histone 3 lysine 9 (H3K9) methyltransferase, SET domain bifurcated 1 (SETDB1), in hypoxia-induced functional and phenotypical changes of pulmonary vascular endothelial cells. Methods: Primarily cultured rat pulmonary microvascular endothelial cells (PMVECs) were used as cell model. Specific knockdown and overexpression strategies were used to systematically determine the molecular regulation and function of SETDB1 in PMVECs. Results: SETDB1 is highly expressed and significantly upregulated in the pulmonary vascular endothelium of lung tissue isolated from SU5416/hypoxia-induced PH (SuHx-PH) rats, and also in pulmonary arterial endothelial cells (PAECs) from idiopathic pulmonary arterial hypertension (IPAH) patients, comparing to their respective controls. In primarily cultured rat PMVECs, treatment of hypoxia or CoCl 2 induces significant upregulation of HIF2α, SETDB1 and H3K9me3. Specific knockdown and overexpression strategies indicate the hypoxia- or CoCl 2 -induced upregulation of SETDB1 is mediated through a HIF2α-dependent mechanism. Knockdown of SETDB1 significantly inhibits the hypoxia- or CoCl 2 -induced apoptosis, senescence and endothelial to mesenchymal transition (EndoMT) in rat PMVECs. Moreover, treatment of the specific inhibitor of histone methyltransferase, Chaetocin, effectively attenuates the disease pathogenesis of SuHx-PH in rat. Conclusions: Our results suggest that the HIF2α-dependent upregulation of SETDB1 facilitates hypoxia-induced functional and phenotypical changes of PMVECs, potentially contributing to the hypoxia-induced pulmonary vascular remodeling and PH.