Altered endothelial mitochondrial Opa1-related fusion in mouse amplifies age-associated vascular and kidney damages

Abstract

Background: Cardiovascular diseases are the major cause of death worldwide and their frequency increases with age in association with progressive kidney damages. Endothelial cells (ECs) are early affected in cardiovascular diseases. Although energy production in ECs involves glycolysis, endothelial mitochondria play a role in modulating cellular signalling. A reduction in fusion protein Opa1 level in ECs decreases the vascular response to flow and increased oxidative stress in perfused kidneys. Thus, we hypothesized that reduced Opa1 expression contributes to vascular aging. Methods: We used male and female mice with ECs specific Opa1 knock-out (EC-Opa1), and littermate wild-type (EC-WT) mice aged 6 (young) and 20 months (old). Mesenteric resistance arteries (MRA) and kidneys were collected for vascular reactivity and Western-blot analysis. Results: In old EC-Opa1 mice blood urea was greater than in age-matched EC-WT mice and MRA showed hypercontractilty and reduced endothelium-dependent relaxation. In kidneys, the mitochondria fission protein Fis-1 and the peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1) were increase in old EC-Opa1 mice. The level of eNOS expression was greater in young EC-Opa1 mice and caveolin-1 expression greater in old EC-Opa1 mice. Moreover, in kidneys from EC-Opa1 old mice, NADPH-oxidase subunits gp91, p47 and p67 expression was greater than in age-matched EC-WT mice. No difference was observed between old and young EC-WT mice. Conclusion: Reduced mitochondrial fusion in mouse ECs altered mesenteric vascular reactivity and increased oxidative stress in aging kidneys. Thus, Opa1 might protect the vascular tree in target organs such as the kidney during aging