Effect Of Caveolin-1 On Contact Inhibition Of Rats Pulmonary Microvascular Endothelial Cells In Hepatopulmonary Syndrome

Implications and objective:Hepatopulmonary syndrome(HPS) is a clinical complication of advanced liver disease, which exhibits hypoxemia and intrapulmonary vascular dilatation(IPVD). This condition occurs in up to 32% of patients with cirrhosis, which markedly increases mortality. There is currently no effective medical treatment for HPS. Liver transplantation is considered the only dependable mode of therapy for HPS. The main reason for the absence of effective therapeutic measures is that the pathophysiological mechanisms associated with HPS have not been identified. Multiple factors are involved in the pathogenesis of HPS. Among these factors, IPVD contributes to pulmonary microvascular remodeling and hypoxemia. And the proliferation and the contact inhibition weakening of pulmonary microvascular endothelial cells(PMVECs) play an important role in the IPVD of HPS. In the setting of liver disease, large number of cytokines including ET-1, TNF-α are released into circulation, which activates and increases related proteins expression of many signaling pathways triggering the proliferation of PMVECs. However, the pathogenesis of contact inhibition remains unclear.Caveolin-1, a membrane protein, which is the major structural and functional protein of caveolae. Structurely, caveolin-1 is composed of two domains including Ntermin and c-termin.at the N-termin, there is a special construction- CSD(Caveolin Scaffolding domain), and it can bind multiple signaling proteins and regulate adhesion, proliferation, migration and apoptosis on PMVECs. However the effects of caveolin-1 on common bile duct ligation(CBDL)-rat-serum induced PMVECs contact inhibition weakening and proliferation remains eclusive. Therefore we sought to make the underlying mechanism clear. We hypothesized that down-regulation of caveolin-1 participating in contact inhibition weaken and proliferation of PMVECs induced by HPS rat-serum may play an important role in the development of HPS.The aim of this study was to describle the mechanism of contact inhibition weakness in PMVECs induced by HPS rat serum and to explore the role of caveolin-1 in regulation contact inhibition weakness of PMVECS under HPS rat serum condition. A wellestablished experimental model for hepatopulmonary syndrome is biliary cirrhosis and portal hypertension in rats induced by CBDL [8] and is the only recognized model for the study of HPS. We detected the expression of caveolin-1 and ve-cadherin proteins in PMVBECs and the contact inhibition of PMVECs after treatment with HPS serum. Our data showed that the expression of caveolin-1, ve-cadherin proteins and the contact inhibition decreased dramatically, while the proliferation increased significantly following stimulation with HPS rat serum. In conclusion, caveolin-1 may play an essential roles in HPS-associated pulmonary microvascular remodeling and could became an effective therapeutic target of HPS.MethodsTotal three parts:1. HPS model establishment and serum collectionThe HPS rat model was constructed by chronic bile duct ligation(CBDL).The serum was collected at 2-weeks after CBDL.2. Primary culture of PMVECs and contact inhibition detectingPrimary PMVECs of normal SD-rats was established. Then the PMVECs were randomly divided into two groups: group HPS and group C. Group HPS was treated with serum of HPS and group C was treated with serum of normal rats for various time periods:12h, 24 h, 36 h. the adhesion assay were detected by CCK-8.3. Then caveolin-1 and ve-cadherin protein expression of Group HPS and group C, treated with serum of HPS and group C was treated with serum of normal rats for various time periods:12h, 24 h,36 h Respectively, were determined by Western blot.Results:1. The HPS rat model was established successfully in our study, conforming to a combination of gas exchange abnormalities(Pa O2 > 85 mm Hg and P(A–a)O2 < 18mmHg) and intrapulmonary vascular dilation confirmed by histopathological analyses. And HPS rat serum was collected.2. Primary PMVECs were cultivated successfully. HPS rat serum reduce the adhesion rate of PMVECs and suppressed PMVECs contact inhibition, while greatly stimulated the proliferation of PMVECs.3. HPS rat serum decreased the expression of caveolin-1 and ve-cadherin in PMVECs. Conclusions:Our result showed the contact inhibition weaken of PMVECs might be relevant to the change of caveolin-1 and ve-cadherin protein. caveolin-1 may play an important role in contact inhibition of PMVECs induced by HPS rats serum.