The Molecular Mechanism For ET-1 Expression Regulated By TGF-β1 And PPAR-γ In Pulmonary Hypertension

Background: Pulmonary hypertension(PH)as a group of diseases characterized by a progressive increase of pulmonary vascular resistance(PVR)leading to right ventricular failure and death.The pathogenesis of PH involves multiple and complex mechanisms including vasoconstriction,cell proliferation,vascular remodeling,thrombosis and endothelial injury,which contribute to the progressive increasing of PVR.There is no effective treatment and the prognosis of these patients is extremely poor.Endothelin-1(ET-1)is involved in pulmonary vascular remodeling and corelated with increased PVR,but the molecular mechanism for that remains unclear.Previous studies have shown that ET-1,TGF-β1 and PPAR-γ were involved in the pathogenesis of PH,and the molecular mechanisms and signal transduction pathways are still unclear which worthy of further study.Objective: The aim of this study was to test the expression of serum ET-1 and TGF-β1,detect the localization and expression of PPAR-γ in lung tissue of patients with PH,investigate the biochemical interactions between PPAR-γ,TGF-β1 and ET-1 expression to reveal the molecular mechanisms for the regulation of ET-1 in vitro.Methods:Part 1 :Detection the expression of serum ET-1 and TGF-β1 by ELISA in patients with PH;determination the localization and expression of PPAR-γ in lung tissue in patients with PH by immunohistochemistry.Part 2 : A549 cells were pre-treated with S2505(10 μM),S2871(10 μM)with/without SB203580(10 μM)for 60 min following 2 h treatment with 10 ng/m L TGF-β1.A549 cells were also transfected with positive or negative PPAR-γ plasmids for comparison.q RT-PCR,ELISA, western blotting and confocal laser scanning microscopy(CLSM)were used to measure the relevant expression of m RNA,protein,mediators of pathways and nuclear factor translocation.Results:Part 1 :The expression of serum ET-1 and TGF-β1 in patients with PH were significantly higher than those in control group.While the pulmonary arterial systolic pressure got higher,the expression of ET-1 and TGF-β1 protein were the higher.There was a positive correlation between ET-1 and TGF-β1.PPAR-γ was mainly expressed in nucleus of alveolar epithelial cells and vascular endothelial cells in lung tissues,and the expression of PPAR-γ in lung tissues of PH patients was significantly reduced while compared with the control group.Part 2 :SB203580 inhibited TGF-β1 induced ET-1 expression in A549 cells.S2871 decreased PPAR-γ m RNA and increase TGF-β1-induced ET-1 expression.S2871 increased phosphorylation of p38 MAPK and Smad2.Cells transfected with PPAR-γ negative plasmid increased TGF-β1 induced ET-1 expression,and increased the expression of phospho-p38 MAPK and phospho-Smad2.S2505 increased PPAR-γ m RNA expression,suppressed the increased TGF-β1-induced expression of ET-1.S2505 inhibited TGF-β1 induced phosphorylation of p38 MAPK and Smad2,also the nuclear translocation of Smad2.Cells transfected with PPAR-γ positive plasmid reduced TGF-β1-induced ET-1 expression,and inhibited the expression of phospho-p38 MAPK and phospho-Smad2.Conclusions: The expression of serum ET-1 and TGF-β1 was increased and there was a positive correlation with pulmonary arterial systolic pressure.The expression of PPAR-γ in lung tissues was decreased in patients with PH.TGF-β1 induced release of ET-1 is PPAR-γ dependent in cultured A549 cells.