Abstract 15506: Inhibition of Angiotensin II Type I Receptor Induces Dual Modification of Mitochondrial Dynamics and Mitophagy via Inactivation of Ras/raf/mek Pathway and Contributes Vascular Anti-senescence

Abstract

Introduction: Angiotensin II (Ang II) causes vascular senescence by damaging mitochondria that undergo quality control by mitochondrial dynamics and mitophagy. We examined whether and how AngII type I receptor (AT1R) signal regulates mitochondrial dynamics and mitophagy in the etiology of vascular senescence. Methods: We used vascular smooth muscle cells (VSMC) and C57BL6 (WT), apolipoprotein E deficient (ApoE KO) and the double knockout of ApoE and AT1R mice. Results: Administration of Ang II to VSMC forced mitochondria to fission and induced cellular senescence and mitochondrial dysfunction, which were restored by inhibition of fission by use of Mdivi-1. Treatment of ox-LDL also induced cellular senescence accompanied by excessive mitochondrial fission through phosphorylation of Drp1 at Ser616 and mitochondrial dysfunction. These alterations were ameliorated by inhibition of AT1R signal, suggesting that AT1R signal inhibition may contribute anti-cellular senescence by modification of mitochondrial dynamics. AT1R signal inhibition also induced mitophagy assessed by electron microscopy and immunohistochemistry of LAMP2 and TOMM20. AT1R inhibition-induced mitophagy was not affected by Atg7 Knockdown, whereas it was diminished by Rab9 knockdown. Immunohistochemistry showed TOMM20 dots were co-localized to LAMP2 and Rab9 but not LC3. These results suggest that AT1R signal induces mitophagy derived from Rab9-dependent alternative autophagy. Treatment of ox-LDL activated Ras, Raf and MEK, and AT1R inhibition inactivated them. Inhibition of Ras/Raf/MEK decreased excessive mitochondrial fission and induced mitophagy, suggesting that AT1R signal followed by Ras/Raf/MEK pathway modulates both mitochondrial dynamics and mitophagy. The degree of arterial senescence and atherosclerosis, Drp1 expression in mitochondrial fraction and oxidative stress in artery were higher and the number of mitophagy, fused mitochondria and its function were lower in ApoE KO than those of WT mice. AT1R KO to ApoE KO attenuated these adverse effects of ApoE KO. Conclusions: Inhibition of AT1R signal contributes vascular senescence through modification of mitochondrial dynamics and mitophagy by inactivation of Ras/Raf/MEK pathway.