The HIF2α-dependent upregulation of SETDB1 facilitates hypoxia-induced functional and phenotypical changes of pulmonary microvascular endothelial cells.

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. 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. 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 patients with idiopathic pulmonary arterial hypertension (IPAH), comparing with their respective controls. In primarily cultured rat PMVECs, treatment of hypoxia or CoCl₂ induces significant upregulation of HIF2α, SETDB1, and H3K9me3. Specific knockdown and overexpression strategies indicate that the hypoxia- or CoCl₂-induced upregulation of SETDB1 is mediated through a HIF2α-dependent mechanism. Knockdown of SETDB1 significantly inhibits the hypoxia- or CoCl₂-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. 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.NEW & NOTEWORTHY Abnormal histone modification plays vital role in pulmonary hypertension (PH). This study reports the regulation and role of a histone 3 lysine 9 (H3K9) methyltransferase, SETDB1, in primarily cultured rat pulmonary microvascular endothelial cells (PMVECs). Hypoxia induces significant upregulation of SETDB1 at both mRNA and protein levels, in a HIF2α-dependent manner. The hypoxic upregulation of SETDB1 leads to significant apoptosis, senescence, and endothelial-to-mesenchymal transition in PMVECs. Treatment of a specific inhibitor of histone methyltransferase, Chaetocin, effectively attenuates the disease pathogenesis of PH rat model induced by SU5416/hypoxia.