Abstract P440: Renin-angiotensin Signal Develops Arterial Senescence and Atherosclerosis via Modulation of Mitochondrial Dynamics

Abstract

Introduction: Mitochondria are dynamic organelles that undergo fusion and fission. It is reported that renin-angiotensin signal (RAS) inhibition retards arterial senescence and development of arteriosclerosis. This study aims to clarify whether mitochondrial dynamics is involved in the effects of RAS-inhibition on arterial senescence and atherosclerosis. Methods and Results: Vascular smooth muscle cells (VSMC) were used in in vitro experiments. Administration of Angiotensin II to VSMCs increased p53 and p21 protein expressions and senescence associated beta galactosidase (SA-beta Gal) positive cells, indicating that angiotensin II induces cellular senescence. Administration of oxidized low-density lipoprotein (ox-LDL) to VSMC also facilitated cellular senescence through RAS stimulation. Dynamin-related protein 1 (Drp1), which mediates mitochondrial fission, was activated with phosphorylation at serine 616 and mitochondrial fission assessed by electron microscopy increased in VSMC with either angiotensin II or ox-LDL administration. Administration of pharmacological Drp1 inhibitor, mdivi1, to VSMC with either angiotensin II or ox-LDL stimulation decreased mitochondrial fission, increased fused mitochondria and retarded cellular senescence. These results suggest that mitochondrial fission is crucial to develop stress induced cellular senescence. We also conducted in vivo experiments using C57BL6, apolipoprotein E knockout (ApoE KO) and double KO mice (DKO) of angiotensin II type Ia receptor KO and ApoE KO. Ser616p-Drp1 and mitochondrial fission increased in the artery of ApoE KO compared to age-matched C57BL6. The degree of arterial senescence and atherosclerosis are greater in ApoE KO than in C57BL6 assessed by SA-beta Gal and oil red o staining and immunoblot of p53 and p21. ATP production was lower and reactive oxygen species (ROS) production was higher in ApoE KO. DKO showed lower degrees of arterial senescence, ROS generation and atherosclerosis compared to AopE KO. Expression of arterial Ser616 p-Drp1 was lower and the number of fused mitochondria and ATP production were higher in DKO than ApoE KO. Conclusion: Mitochondrial fusion plays a crucial role to retard arterial senescence and atherosclerosis by RAS-inhibition.