The Expression Of Galectin-3in Pulmonary Arterial Hypertension

ObjectivePulmonary arterial hypertension (PAH) is a syndrome resulting from restricted flow through the pulmonary arterial circulation resulting in increased pulmonary vascular resistance and ultimately in right heart failure. Multiple pathogenic pathways have been implicated in the development of PAH, including those at the molecular and genetic levels and in the smooth muscle and endothelial cells and adventitia. Increasingly it is recognized that PAH also involves an imbalance of proliferation and apoptosis. Previous reports have suggested that Galectin-3(Gal-3) induces endothelial cell morphogenesis and regulates myofibroblast activation. Here we hypothesized that Gal-3might be involved in the pathogenesis of PAH. Gal-3expression was investigated in both a cohort of IPAH patients as well as in the hypoxia-induced PAH rats model.Methods1) Plasma Gal-1and Gal-3levels were determined by ELISA in31PAH patients, diagnosed from right heart catheterization, as well as18healthy controls.2) Animals experiments were performed on Sprague-Dawley Rats PAH models after21days exposure to chronic hypoxia (10%O2). RVSP and mPAP were measured by right external jugular vein cannula. Hearts were removed and dissected to isolate the free wall of RV from LV+S. RV/(LV+S) was used as an index of RV hypertrophy generated as a result of hypoxia-induced PAH. Blood samples were taken from heart.3) Lung tissues were collected for histological analysis including Gal-3lung qualitative localization by HE, Masson staining and immunohistochemistry. The freshly isolated lung tissue samples were used for measurement of Gal-3and Tenascin-C expression. Total mRNA was extracted from pulmonary artery, then quantitative PCR was performed with total cellular mRNA to measure Gal-1, Gal-3and Tenascin-C expression. Western blot analysis was performed to detect and quantitate Gal-3level in lung tissues. Plasma level of Gal-3was determined by ELISA.Results1) Plasma level of Gal-1showed no change between PAH patients and healthy controls.2) Plasma level of Gal-3was significantly decreased in PAH patients compared with healthy controls (P<0.001). For the comparison among subgroups, only IPAH patients statistically expressed the lower level of Gal-3(P<0.001). Gal-3levels inversely correlated with mPAP (r=-0.57, P=0.021) and PVR (r=-0.55, P＝0.027), and correlated with cardiac output(r=0.530, P=0.035) in IPAH patients.3) As a biomarker, decreased Gal-3levels detected IPAH with93%sensitivity and88%specificity, with the cut-off value of1.765ng/ml (area under the curve=0.95).4) The hemodynamic parameters showed RVSP and mPAP significantly increased in PAH rats (P<0.001). Plasma level of TGF-β1was elevated in PAH group compared to the control group (P<0.01).5) According to Quantitative PCR assay, the expression of Gal-3mRNA was significantly down-regulated in the pulmonary artery from lung tissue samples in PAH rats. Gal-1was also noted to be down-regulated in these samples.6) Plasma level of Gal-3was also lower in PAH rats by ELISA, consisting with the expression in lung tissues through western blots assay (P<0.05).7) Immunohistochemistry method identified Gal-3and Tenascin-C were both distributed throughout the adventitia of the pulmonary arterioles, however, they presented in the opposite way and confirmed by quantitative PCR assay.ConclusionOur results show that plasma Gal-3levels are decreased in PAH patients as compared to healthy controls, especially for IPAH. Our findings suggest that circulating Gal-3levels in patients may be an effective biomarker for the diagnosis of IPAH, and that levels may negatively correlate with disease severity.In the model of hypoxia-induced PAH rats, Gal-1and Gal-3expression were both shown to be decreased compared to healthy controls. It is possible that Gal-3may be involved in the pathogenesis of PAH, however further studies are needed to elucidate disease etiology.