Rutin Reverses Abnormal Autophagy in Hypoxic Pulmonary Arterial Hypertension via Regulation of Mitofusin 1

Abstract Background:Recently, rutin, a citrus flavonoid occurring in many plants, has been found to be beneficial in preventing hypoxia-induced pulmonary arterial smooth muscle cells (PASMCs) from proliferating via scavenged reactive oxygen species (ROS). However, rutin’s underlying mechanism of action against PASMCs in the context of hypoxia is still unclear. Autophagy, the main intracellular degradation and recycling process, exerts a critical adaptive effect on the pathological angiogenesis associated with hypoxic pulmonary arterial hypertension (HPAH) by removing damaged mitochondria and regulating ROS production and cell proliferation. It would be useful to identify the role of rutin and its interaction with autophagy in exerting protective effects against HPAH.Methods:We chose 21 SD rats and randomly and equally divided them into three groups of normoxia, hypoxia, and hypoxia + rutin. At the end of the exposure period, we measured the right ventricular systolic pressure (RVSP), the weight of right ventricle (RV), and the ratio of RV weight to left ventricular (LV) weight plus septum (RV/LV+S) of each rat. PASMCs of the three groups of rats were isolated and cultured, and the effect of rutin on autophagy-related protein expression under hypoxia was analyzed using immunofluorescence analysis, transmission electron microscopy, western blot (WB) analysis, and siRNA design and transfection.Results:We found RVSP, RV/LV+S, and pulmonary artery wall thickness were reduced by rutin in the pulmonary arterial hypertension (PAH) animal model. WB results showed that rutin regulated expression of autophagy-related proteins. Moreover, rutin downregulated Mitofusin 1 (Mfn1) over-expression induced by hypoxia. But when Mfn1 was silenced, there was little difference in the expressions of beclin-1 (BECN-1), and other marker proteins with or without rutin.Conclusions:Rutin suppressed the abnormal autophagy of hypoxia-induced PASMCs via the regulation of the target, Mfn1. This revealed the protective effect of rutin on vascular remodeling caused by hypoxia and demonstrated how rutin could slow down the development of HPAH.