The Role Of Calcium Activated Potassium Channel KCa In The Effect Of Quercetin On Hypoxia-induced Pulmonary Hypertension In Rats And Its Possible Mechanism

Objective: This article aims to explore the effect of quercetin on hypoxia-induced pulmonary hypertension in rats,and the role and mechanism of calcium-activated potassium channel KCa in the occurrence and development of hypoxic pulmonary hypertension.Methods: 1.Animal level:SD rats were randomly divided into normoxic group(N group),normoxic quercetin gavage group(NQ group),hypoxic group(H group)and normoxic quercetin gavage group(HQ group).A self-made normal pressure hypoxia chamber was used to construct a rat model of pulmonary hypertension.Among them,the NQ group and the HQ group were given quercetin(150 mg/kg)by gavage every day.After 4 weeks,the pulmonary artery acceleration time(PAT)and pulmonary artery ejection time(PET)of each group were analyzed using small animal ultrasound recordings,mean pulmonary arterial pressure(m PAP)was measured by the right cardiac catheterization method.The free wall of the right ventricle(RV)of rats was measured.The left ventricular and ventricular septum(LV+S)were cut completely and dried on a filter paper,then weighed,and the Right ventricular hypertrophy index(RVHI)was calculated.The complete right lower lung with abundant blood flow was taken for pathological section to observe the pulmonary arteriolar vessel remodeling.Total protein was extracted from rat lung tissue and blood serum to observe the expression of KCa proteins.2.Cell level:Pulmonary artery was acutely isolated from SD rats,and Pulmonary artery smooth muscle cells(PASMC)were cultured using modified enzyme digestion method,and immunofluorescence identification was performed.PASMC was divided into normoxic group(N group),normoxic quercetin(100umol/L)intervention group (NQ group),hypoxic group(H group)and hypoxic quercetin(100umol/L)intervention group(HQ group).CCK-8 and flow cytometry were used to detect the proliferation and apoptosis of cells in each group.Total cell proteins were extracted to detect the expression of KCa proteins.Results: 1.General conditions of rats:Rats in H group had negative intake of food and water,decreased activity,listless spirit,unsatisfactory weight gain,relatively thin body,dull and rough hair,dark red conjunctiva,and blue mucosa in outer ears and extremities;General condition of rats in HQ group was improved.N Group and NQ group were agile,with normal weight growth,smooth hair color,light red mucosa color and no blue.2.Hemodynamic indicators:Compared with N group,PAT and PET in H group were significantly shortened.Compared with group H,PAT and PET in HQ group were significantly prolonged.Compared with group N,m PAP and RVHI in H and HQ groups were significantly higher than those in N group.Compared with the H group,the levels of m PAP and RVHI were significantly decreased in the HQ group.3.Remodeling of pulmonary arterioles:The N and NQ groups had thinner vessel walls,no obvious thickening,and no lumen stenosis.In H group,the vascular wall was thickened,the lumen was narrowed and the cells in the vascular wall were disordered.After quercetin intervention,vascular wall thickening,lumen stenosis and disorder of cell arrangement were alleviated.Compared with N group,WA% in NQ group decreased,and WA% in H and HQ group increased.Compared with H group,the degree of vascular remodeling in HQ group was reduced.4.Proliferation of pulmonary artery smooth muscle cells:Primary pulmonary artery smooth muscle cells can be successfully isolated and cultured by the improved enzyme digestion method.Compared with C group,apoptosis increased and proliferation decreased in CQ group.Apoptosis decreased and proliferation increased in A and AQ groups.Compared with A group,apoptosis was increased and proliferation was decreased in AQ group.5.Expression of KCa protein in lung tissue and pulmonary artery smooth muscle cells:Compared with the normal group,the expression of KCa protein in the lung tissue and cells of ratsin the hypoxia group was significantly decreased,and the expression of KCa protein was significantly increased after the intervention of quercetin.Conclusion: 1.Quercetin can significantly prolong PAT and PET,reduce m PAP and RVHI,and improve pulmonary arteriolar remodeling in rats with pulmonary hypertension.2.Quercetin can reduce the resistance to apoptosis of pulmonary artery smooth muscle cells and effectively inhibit the abnormal proliferation of cells.3.Quercetin has a protective effect on hypoxia-induced pulmonary hypertension,and the realization of this effect may be related to the regulation of KCa protein expression.