Roles Of LOX-1 And CD147 In Monocrotaline-induced Vascular Remodeling Of Pulmonary Arterial Hypertension In Rats

BACKGROUNDPulmonary arterial hypertension (PAH) is a fatal syndrome characterized by an elevated blood pressure in the pulmonary circulation, due to increased resistance of pulmonary arterioles.PAH includes idiopathic("primary") form and "secondary" forms.Despite the diverse etiologic differences, there are many similarities in the pathological alterations in pulmonary arteries among the various forms of pulmonary hypertension, ie,endothelial dysfunction/increased vasoconstriction; activation of inflammatory processes; and vascular remodeling. Pulmonary vascular remodeling is a distinctive feature of PAH, which includes vascular smooth cells proliferation and extracellular matrix remodeling. MMPs/TIMPs system plays an important role in vascular remodeling. Endothelial dysfunction in PAH is related to various pathophysiological processes, vascular endothelial injury caused by oxidative stress can activate MMPs, which led to MMPs/TIMPs imbalance and then leading to vascular remodeling. Many studies have found that the expression and the activity of MMPs increase, while CD 147 as the extracellular matrix metalloproteinase inducer is involved in the process of induction of MMPs production and secretion, suggesting that CD147 may play an important role in the process of PAH. LOX-1 is a typeⅡmembrane protein that structurally belongs to the C-type lectin family.As a new type of ox-LDL scavenger receptor, LOX-1 can specifically bind and internalize OX-LDL Many pro-inflammatory cytokines, growth factors and oxidative stress can promote the expression of LOX-1. LOX-1 binding to ligands may induce the expression and the activity of NADPH oxidase subunits,and then generating ROS, in turn, can cause corresponding damage and pathological changes. Using LOX-1 neutralizing antibody and the NADPH oxidase inhibitors, researchers have found there are a positive feedback loop between LOX-1 and NADPH oxidase-mediated oxidative stress.In addition, LOX-1 can activate MMPs, oxidative stress is also involved in the process.Therefore, the aim of present study was to investigate the role of LOX-1 and CD147 in the pulmonary vascular remodeling and the potential relationship between LOX-1 and CD 147.METHODSMale Sprague-Dawley rats (180-220g body weight) were received a single subcutaneous injection of 2% monocrotaline (MCT,60mg/kg), which has been well documented to cause PAH in rats. The group of control was injected with saline (3 ml /kg, s.c). We performed all experiments on day 21 after MCT injection. After the rats were anesthetized with pentobarbital sodium (45 mg/kg, ip), right ventricle systolic pressures (RVSP), mean pulmonary arterial pressure and carotid artery pressure evaluations were performed. Then blood was obtained from common carotid artery, heart and lung were collected.. The right ventricle (RV) was dissected from the left ventricle(LV) and interventricular scptum(IS) and weighed for evaluating the extent of RV hypertrophy as the weight ratio of RV/(LV+IS). Also, the ratio of the RV free wall weight divided by the length of the tibia was calculated as an index of RV hypertrophy. Pulmonary artery was frozen in liquid nitrogen for mRNA analysis. The mRNA expression of LOX-1, CD 147, collagen I, collagenⅢand TIMP-2 was measured by RT-PCR. The mRNA expression ofTGFβ1,Nox2,p47phox,MMP-2,MMP-9 and CD 147 was measured by Real-time PCR. Right lung was fixed in 4% formaldehyde for slicing and histological staining. The extent of pulmonary vascular remodeling and right wentricular hypertrophy was investigated by hematoxylin-eosin staining. The percentage of pulmonary arterial forbrosis was detected by Masson staining. The protein expression of LOX-1 and CD 147 was examined by immunohistochemistry.RESULTS1. Compared with control group, mean pulmonary artery pressure was elevated and obvious ventricular hypertrophy was observed in MCT-treated rats, the pulmonary artery was thickened and fibrotic.2. The levels of TGF-β1, Nox2, LOX-1 mRNA and LOX-1 protein expression weresignificantly increased in pulmonary arteries of MCT group, especially in endothelial cell.3. The gene expression of MMP-2 and CD147, the protein expression of CD147 especially in endothelial cell were increased in pulmonary arteries of MCT group.CONCLUSIONIn the chronic inflammatory pulmonary arterial hypertension model in rat induced by monocrotaline, LOX-1 and CD 147 increased while pulmonary vascular remodeling happened,suggesting that LOX-1/CD 147 pathyway may be crucial for vascular remodeling in PAH.