NOS3 and endothelial dysfunction: In aging, greater endothelial oxidative stress is a result of increased production of uncoupled endothelial nitric oxide synthase (eNOS) and intracellular enzyme nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) oxidase as well as from mitochondrial respiration, leading to endothelial dysfunction (Donato et al., 2015).