The Role And Mechanism Of Histone Methylase SETDB1 In Pulmonary Vascular Remodeling Accompanied By Hypoxic Pulmonary Hypertension

【Objective】To clarify the expression of histone methylase SETDB1（SET Domain Bifurcated Histone Lysine Methyltransferase 1,SETDB1）in pulmonary hypertension disease models.To study the regulation of HIF2（Hypoxia inducible factor-2,HIF-2）on the SETDB1/K3K9me3signaling pathway,and the mechanism of SETDB1 affecting endothelial apoptosis and senescence by using rat microvascular endothelial cells.【Methods】1.The degree of co-localization of SETDB1 with pulmonary vascular intima was high.Compared with the respective control group,the expression level of SETDB1 protein in pulmonary artery endothelial cells of IPAH patients（P<0.05）and lung tissue of SUHX rat model（P<0.01）was increased.2.Hypoxia（1%O₂）and Cobalt Chiloride（Co Cl₂）was used to stmulate rat pulmonary microvascular endothelial cells（RPMVECs）and rat pulmonary arterial smooth muscle cells（RPASMCs）,Expression of SETDB1,HIF2α,H3K9me3 is detected by western blotting,immunofluorescence and quantitative real-time PCR（q RT-PCR）.3.After the up-regulation of HIF2α,western blotting is taken to observe the changes of SETDB1.After the down-regulation of HIF2α,western blotting and immunofluorescence is taken to observe the changes of SETDB1 and H3K9me3.4.After the down-regulation of HIF2αor SETDB1,western blotting and flow cytometry is taken to observe the level of apoptosis to observe the effect of（1%O₂）and Co Cl₂on PMVECs apoptosis,Confocal Microscope andβ-Galactosidase is to detect the cell senescence of PMVECs.【Results】1.The degree of co-localization of SETDB1 with pulmonary vascular intima is high,and the level of SETDB1 protein in the lung tissue of Su Hx pulmonary hypertension rat model is increased and in the endothelial cells of IPAH patients compared with the control group.2.The transcription and expression of SETDB1 in rat microvascular endothelial cells were increased after hypoxia and cobalt chloride stimulation,and the modification degree of H3K9me3 was increased.Overexpression of HIF2αresulted in an increase in the level of SETDB1 protein,and HIF2αknockdown inhibited the SETDB1/H3K9Me3 signaling axis.3.After hypoxia stimulation,apoptosis of microvascular endothelial cells increased compared with the control group,and apoptosis decreased after SETDB1 knockdown.After the stimulation of cobalt chloride,the apoptosis of microvascular endothelial cells increased,the senescence of cell senescence related heterochromatin increased,and the senescence level ofβ-gal stained cells increased.After SETDB1 down-regulation,the apoptosis level decreased,the senescence level of cell senescence related heterochromatin decreased,and the senescence level ofβ-gal stained cells decreased.【Conclusions】SETDB1 protein level is increased in models of pulmonary hypertension.The SETDB1/H3K9me3 signaling pathway is activated by hypoxia and cobalt chloride,and is regulated by HIF2α.Knocking down HIF2αor SETDB1 can reduce cell apoptosis and delay cell senescence.