Skeletal muscle-derived musclin attenuates glycolysis, oxidative stress, and pulmonary hypertension through the NPR3/AKT/mTORC1 pathway

Abstract

Exercise ameliorates pulmonary hypertension (PH) progression. However, the underlying mechanisms are largely unclear. Musclin is an exercise-responsive myokine that exerts protective effects on cardiovascular diseases. The current study aims to explore the role of musclin in the development of PH. A monocrotaline (MCT)-induced mouse PH model is established. Adeno-associated virus serotype 6 (AAV6)-mediated gene transfer is used to induce musclin overexpression in skeletal muscle. Ultrasound and morphological analyses are utilized to assess the severity of PH. Cell viability assay, Ki-67 immunofluorescence staining, wound healing assay, and transwell assay are used to evaluate the proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs). We find that the musclin levels in both plasma and skeletal muscle are decreased in MCT-treated mice. The external expression of musclin in skeletal muscle ameliorates pulmonary arterial remodeling and right ventricular dysfunction. In vitro, musclin treatment suppresses hypoxia-induced glycolysis, oxidative stress, proliferation, and migration. Further experiments reveal that musclin inhibits mechanistic target of rapamycin complex 1 (mTORC1) activity in hypoxia-stimulated PASMCs and pulmonary arteries of MCT-treated mice. Reactivating mTORC1 abolishes the protective role of musclin against PH. Additionally, musclin enhances its interaction with natriuretic peptide receptor 3 (NPR3) in PASMCs. Silencing of NPR3 reverses the inhibitory effects of musclin on AKT phosphorylation, mTORC1 activity, glycolysis, oxidative stress, proliferation, and migration in hypoxia-challenged PASMCs. In conclusion, our study highlights the inhibitory role of musclin in the proliferation and migration of PASMCs and PH progression, thereby providing a novel potent therapeutic strategy for treating PH and partly clarifying the mechanism of exercise-mediated protection against PH.

1. Introduction

Vascular remodeling of the pulmonary artery (PA) is considered a critical part of PH progression [1]. Current treatments focus mainly on reducing the resistance of PAs by inducing pulmonary vascular dilation. However, the therapeutic effects are not satisfactory, as PA remodeling is not ameliorated [2]. After endothelial dysfunction caused by adverse stress, such as hypoxia, growth and inflammatory factors, pulmonary arterial smooth muscle cells (PASMCs) migrate from the media to the intima, rapidly proliferate, and ultimately result in PA remodeling [3]. As the major component of the vascular wall, the reprogramming of PASMCs, which is characterized by excessive proliferation and migration, plays a critical role in the development of PH. Therefore, focusing on the mechanisms underlying PASMC reprogramming is highly important.

Accumulating evidence has demonstrated that exercise may reduce the mean pulmonary arterial pressure and morbidity of adverse events in PH patients [4,5]. The beneficial effects of exercise on PH partly rely on skeletal muscle-secreted myokines [6,7]. Musclin, also known as osteocrin, is an exercise-responsive myokine that is highly homologous to natriuretic peptides [8]. The protective roles of musclin in the cardiovascular system have been well investigated. Musclin is essential for exercise-induced cardiac protection and can prevent heart failure [9,10]. The circulating musclin level is decreased in patients with hypertension and transcatheter aortic valve implantation [11,12], suggesting that musclin may play a protective role in vascular events. Additionally, Musclin has been confirmed to suppress the attachment of vascular endothelial cells to monocytes, which serves as a critical event during atherosclerosis [13]. However, little is known about the regulatory effect of musclin on pulmonary hypertension.