Study On The Mechanism Of Gp130 In The Pathogenesis Of Pulmonary Hypertension

Part I:The changes of Gp130 and its upstream and downstream signaling pathways in pulmonary arterial hypertensionBackground:Pulmonary arterial hypertension (PAH) is a progressive disease caused by multiple factors, and its pathophysiologic mechanisms have not been fully understood. Interleukin-6 (IL-6) is a pleiotropic cytokine, which is produced by fibroblasts, monocytes, macrophages, T lymphocytes, B lymphocytes and a variety of tumor cells. IL-6 is a potent mitogen for a number of cell types. Glycoprotein 130 (Gp130) is the most critical intracellular signaling molecule in the course of IL-6 signal transduction. This study aimed to investigate the changes of Gp130 and its upstream and downstream signaling pathways in monocrotaline-induced pulmonary hypertension.Methods:Sprague-Dawley rats (n=64, weight,240-250 g) were randomly divided into eight groups:control(Con)1 wee、Con 2 weeks、Con 3 weeks and Con 4 weeks and monocrotaline-exposed (MCT) 1 week、MCT 2 weeks、MCT 3 weeks and MCT 4 weeks. MCT-exposed rats received a single intraperitoneal injection of 60 mg/kg MCT. Rats in the control group received the same vehicle solution. Eight rats were sacrificed in each group at weeks 1,2,3, and 4. Pulmonary hemodynamics were measured by the right heart catheterization and pulmonary arteriole morphological changes were analyzed by staining with hematoxylin-eosin (HE) and elastic Van Gieson (VG). The changes of IL-6, Gp130, signal transducer and activator of transcription 3 (STAT3) and its upstream and downstream signaling pathways in lung tissues were evaluated by immunohistochemical staining and Western blot.Results:Compared with the controls, the mean pulmonary arterial pressure (mPAP) and right ventricular systolic pressure (RVSP) slight increased at 2 weeks and significantly increased at 4 weeks after injection of MCT. The morphological analysis of pulmonary arteries indicated that a slight increase in proliferation of PASMCs and an obvious infiltration of inflammatory cells in the perivascular space were founded at 14 days. And a further increase in proliferation of PASMCs but a reduced infiltration of inflammatory cells were detected at 28 days after MCT injection. The expressions of IL-6, STAT3, proliferating cell nuclear antigen (PCNA), a-Smooth muscle actin (a-SMA), vascular endothelial growth factor (VEGF) and Survivin were significantly increased at 4 weeks post-MCT. The levels of Bax and cleaved Caspase-3 also apparently elevated. But the expressions of bone morphogenetic protein type II receptor (BMPRII) and p-Smad 1/5/8 were significantly decreased at 4 weeks after MCT injection.Conclusions:The increased proliferation of pulmonary arterial smooth cells and apoptosis of endothelial cells were founded in MCT-exposed rats. IL-6/Gp130/STAT3 signaling pathway was involved in the pathogenesis of MCT-induced pulmonary hypertension. Gp130 may be a therapeutic target in pulmonary arterial hypertension.Part Ⅱ:Glycoprotein 130 inhibitor ameliorates monocrotaline-induced pulmonary hypertension in ratsBackground:Pulmonary arterial hypertension (PAH) is characterized by vasoconstriction, vascular remodeling, and micro-thrombotic events. Inflammatory cytokine interleukin 6 (IL-6) may be a key factor in PAH development, and glycoprotein 130 (Gp130) is an important signal-transducing subunit of IL-6. The aim of our study was to evaluate the effectiveness of Gp130 inhibitor in reducing inflammation and ameliorating PAH-related vascular remodeling in MCT-exposed rats.Methods:Sprague-Dawley rats (n=96, weight,240-250 g) were randomly divided into three groups:control, monocrotaline-exposed (MCT), and MCT-exposed plus Gp130 inhibitor (MCT-Gp) administered daily (5mg/kg) from day 14 to 28. Eight rats were sacrificed in each group at weeks 1 through 4, with the following measured variables compared across groups at day 28:hemodynamics, right ventricular hypertrophy, morphometry, immunohistochemistry, IL-6, phosphorylated signal transducer and activator of transcription 3, proliferating cell nuclear antigen (PCNA), bone morphogenetic protein receptor Ⅱ (BMPRⅡ), proangiogenic factor, vascular endothelial growth factor (VEGF), proproliferative kinase extracellular signal-regulated kinase (ERK), survivin, Bcl-2, and Bax. Pulmonary arteriole morphological changes were analyzed by staining with hematoxylin-eosin (HE) and elastic van Gieson (VG).Results:Compared to the MCT group, Gp130 inhibitor, following MCT-exposure, reduced the mean pulmonary arterial pressure (mPAP), right ventricular systolic pressure (RVSP), severity of inflammation, and pulmonary arterial remodeling assessed by medial wall thickness at 4 weeks. Also, Gp130 inhibitor significantly decreased the expression of IL-6, IL-1β, TNFα, CX3CL1, PCNA, VEGF, ERK, and surviving. And Gp130 inhibitor upregulated BMPRII expression in MCT-exposed lungs, but the BMPRII level was lower than that in the control group.Conclusions:Gp130 inhibitor upregulated BMPR2 expression in MCT-exposed lungs, restored the BMPRII-to IL-6 balance, reduced IL-6-associated inflammation, inhibited pulmonary arterial smooth muscle cell proliferation, and ameliorated pulmonary vascular remodeling in MCT-induced PH in rats. Therefore, Gp130 inhibitors may become a new drug in the treatment of PAH.