Deng Yan, Wu Weifeng, Guo Shenglan, Chen Yuming, Liu Chang, Gao Xingcui, Wei Bin
Department of Ultrasound, First Affiliated Hospital of Guangxi Medical University, Nanning, People's Republic of China.
Department of Cardiology, First Affiliated Hospital of Guangxi Medical University, 6 Shuangyong Road, Nanning, 530021, People's Republic of China.
Respir Res. 2017 Mar 24;18(1):53. doi: 10.1186/s12931-017-0536-7.
Right ventricular structure and function is a major predictor of outcomes in pulmonary hypertension (PH), yet the underlying mechanisms remain poorly understood. Growing evidence suggests the importance of autophagy in cardiac remodeling; however, its dynamics in the process of right ventricle(RV) remodeling in PH has not been fully explored. We sought to study the time course of cardiomyocyte autophagy in the RV in PH and determine whether mammalian target of rapamycin (mTOR) and Beclin-1 hypoxia-related pro-autophagic pathways are underlying mechanisms.
Rats were studied at 2, 4, and 6 weeks after subcutaneous injection of 60 mg/kg monocrotaline (MCT) (MCT-2 W, 4 W, 6 W) or vehicle (CON-2 W, 4 W, 6 W). Cardiac hemodynamics and RV function were assessed in rats. Autophagy structures and markers were assessed using transmission electron microscope, RT-qPCR, immunohistochemistry staining, and western blot analyses. Western blot was also used to quantify the expression of mTOR and Beclin-1 mediated pro-autophagy signalings in the RV.
Two weeks after MCT injection, pulmonary artery systolic pressure increased and mild RV hypertrophy without RV dilation was observed. RV enlargement presented at 4 weeks with moderately decreased function, whereas typical characteristics of RV decompensation and failure occurred at 6 weeks thus demonstrating the progression of RV remodeling in the MCT model. A higher LC3 (microtubule- associated protein light chain 3) II/I ratio, upregulated LC3 mRNA and protein levels, as well as accumulation of autophagosomes in RV of MCT rats indicated autophagy induction. Autophagy activation was coincident with increased pulmonary artery systolic pressure. Pro-autophagy signaling pathways were activated in a RV remodeling stage-dependent manner since phospho-AMPK (adenosine monophosphate-activated protein kinase)-α were primarily upregulated and phospho-mTOR suppressed in the RV at 2 and 4 weeks post-MCT injection, whearas, BNIP3 (Bcl2-interacting protein 3) and beclin-1 expression were relatively low during these stages, they were significantly upregulated after 6 weeks in this model.
Our findings provide evidence of sustained activation of autophagy in RV remodeling of MCT induced PH model, while pro-autophagic signaling pathways varied depending on the phase.
右心室结构和功能是肺动脉高压（PH）患者预后的主要预测指标，但其潜在机制仍知之甚少。越来越多的证据表明自噬在心脏重塑中具有重要作用；然而，其在PH患者右心室（RV）重塑过程中的动态变化尚未得到充分研究。我们旨在研究PH患者RV中心肌细胞自噬的时间进程，并确定雷帕霉素靶蛋白（mTOR）和Beclin-1缺氧相关的促自噬途径是否为潜在机制。
对皮下注射60mg/kg野百合碱（MCT）的大鼠（MCT-2W、4W、6W）或注射赋形剂的大鼠（CON-2W、4W、6W）在2、4和6周时进行研究。评估大鼠的心脏血流动力学和RV功能。使用透射电子显微镜、RT-qPCR、免疫组织化学染色和蛋白质印迹分析评估自噬结构和标志物。蛋白质印迹还用于定量RV中mTOR和Beclin-1介导的促自噬信号的表达。
MCT注射后2周，肺动脉收缩压升高，观察到轻度RV肥大但无RV扩张。4周时出现RV扩大，功能中度下降，而6周时出现RV失代偿和衰竭的典型特征，从而证明了MCT模型中RV重塑的进展。MCT大鼠RV中较高的LC3（微管相关蛋白轻链3）II/I比值、上调的LC3 mRNA和蛋白水平以及自噬体的积累表明自噬被诱导。自噬激活与肺动脉收缩压升高同时发生。促自噬信号通路以RV重塑阶段依赖性方式被激活，因为MCT注射后2周和4周时，RV中磷酸化AMPK（单磷酸腺苷激活蛋白激酶）-α主要上调，磷酸化mTOR被抑制，而在此阶段BNIP3（Bcl2相互作用蛋白3）和Beclin-1表达相对较低，在该模型中6周后它们显著上调。
我们的研究结果提供了证据，表明在MCT诱导的PH模型的RV重塑中自噬持续激活，而促自噬信号通路因阶段而异。
