Inhibition of Src activation reverses pulmonary vascular remodeling in experimental pulmonary arterial hypertension via Akt/mTOR/HIF-1 < alpha > signaling pathway

Pulmonary arterial hypertension (PAH) is a diffuse pulmonary microvascular remodeling disease accompanied by malignant proliferation of pulmonary artery smooth muscle cells (PASMCs), which causes persistent pulmonary artery pressure elevation, right ventricular hypertrophy (RVH) and death. However, current therapies targeting pulmonary vascular remodeling and RVH remain poorly effective in reversing PAH. Overactivation of the protein tyrosine kinase Src plays an important role in tumor cell growth, proliferation and invasion; we thus hypothesized that inhibitors targeting Src activation could reverse experimental PAH. We demonstrated that Src was markedly activated in hypoxia-stimulated PASMCs from donors and PASMCs isolated from PAH patients. We investigated the effects of the Src-selective inhibitor 1-(1,1-dimethylethyl)-1-(4-methylpheny1)-1H-pyrazolo [3,4d]pyrimidin-4-amine (PP1) and berberine (BBR) on PAH-PASMC proliferation and migration by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), 5-ethynyl-2'-deoxyuridine (EdU) and wound healing assays. Our in vitro results showed that inhibition of Src (Tyr416) phosphorylation repressed PAH-PASMC proliferation and migration by inhibiting hypoxia-inducible factor-1 alpha (HIF-1 alpha) expression through Akt/mTOR signal pathway. In vivo, PP1 and BBR significantly alleviated distal pulmonary vascular remodeling and decreased right ventricular systolic pressure (RVSP) and RVH in Sugen (SU) 5416/hypoxia (SU-PAH) mice. These findings demonstrate that pharmacological (PP1 or BBR) inhibition of Src activation could be a novel means of treating severe pulmonary vascular remodeling and RVH in PAH patients.