초록/요약

Endothelial oxidative stress develops with aging and reactive oxygen species impair endothelium-dependent relaxation (EDR) by decreasing nitric oxide (NO) availability. Endothelial KCa3.1, which contributes to EDR, is upregulated by H2O2. We investigated whether KCa3.1 upregulation compensates for diminished EDR to NO during aging-related oxidative stress. Previous studies identified that the levels of ceramide synthase 5 (CerS5), sphingosine, and sphingosine 1-phosphate were increased in aged wild-type and CerS2 mice. In primary mouse aortic endothelial cells (MAECs) from aged wild-type and CerS2 null mice, superoxide dismutase (SOD) was upregulated, and catalase and glutathione peroxidase 1 (GPX1) were downregulated, when compared to MAECs from young and age-matched wild-type mice. Increased H2O2 levels induced Fyn and extracellular signal-regulated kinases (ERKs) phosphorylation and KCa3.1 upregulation. Catalase/GPX1 double knockout (catalase-/-/GPX1-/-) upregulated KCa3.1 in MAECs. NO production was decreased in aged wild-type, CerS2 null, and catalase-/-/GPX1-/- MAECs. However, KCa3.1 activation-induced, NG-nitro-l-arginine-, and indomethacin-resistant EDR was increased without a change in acetylcholine-induced EDR in aortic rings from aged wild-type, CerS2 null, and catalase-/-/GPX1-/- mice. CerS5 transfection or exogenous application of sphingosine or sphingosine 1-phosphate induced similar changes in levels of the antioxidant enzymes and upregulated KCa3.1. Our findings suggest that, during aging-related oxidative stress, SOD upregulation and downregulation of catalase and GPX1, which occur upon altering the sphingolipid composition or acyl chain length, generate H2O2 and thereby upregulate KCa3.1 expression and function via a H2O2/Fyn-mediated pathway. Altogether, enhanced KCa3.1 activity may compensate for decreased NO signaling during vascular aging. © 2016 The Anatomical Society and John Wiley & Sons Ltd.