Mitofusin 2 Triggers Vascular Smooth Muscle Cell Apoptosis via Mitochondrial Death Pathway

Previous studies have shown that mitofusin 2 (Mfn-2) (or hyperplasia suppressor gene [HSG]) inhibits vascular smooth muscle cell (VSMC) proliferation. Here, we demonstrate that Mfn-2 is a primary determinant of VSMC apoptosis. First, oxidative stress with H2O2, inhibition of protein kinase C with staurosporine, activation of protein kinase A with forskolin, and serum deprivation concurrently elevate Mfn-2 expression and induce VSMC apoptosis. Second, overexpression of Mfn-2 also triggers apoptosis of VSMCs in culture and in balloon-injured rat carotid arteries, thus contributing to Mfn-2–mediated prevention of neointima formation after angioplasty. Third, Mfn-2 silencing protects VSMCs against H2O2 or Mfn-2 overexpression–induced apoptosis, indicating that upregulation of Mfn-2 is necessary and sufficient for oxidative stress–mediated VSMC apoptosis. The Mfn-2 proapoptotic effect is independent of its role in mitochondrial fusion but mainly mediated by inhibition of Akt signaling and the resultant activat...