NADPH oxidase 4 mediates the protective effects of physical activity against obesity-induced vascular dysfunction

Abstract

Aims Physical activity is one of the most potent strategies to prevent endothelial dysfunction. Recent evidence suggests vaso-protective properties of hydrogen peroxide (H2O2) produced by main endothelial NADPH oxidase isoform 4 (Nox4) in the vasculature. Therefore, we hypothesized that Nox4 connects physical activity with vaso-protective effects. Methods and results Analysis of the endothelial function using Mulvany Myograph showed endothelial dysfunction in wild-type (WT) as well as in C57BL/6J/ Nox4−/− (Nox4−/−) mice after 20 weeks on high-fat diet (HFD). Access to running wheels during the HFD prevented endothelial dysfunction in WT but not in Nox4−/− mice. Mechanistically, exercise led to an increased H2O2 release in the aorta of WT mice with increased phosphorylation of eNOS pathway member AKT serine/threonine kinase 1 (AKT1). Both H2O2 release and phosphorylation of AKT1 were diminished in aortas of Nox4−/− mice. Deletion of Nox4 also resulted in lower intracellular calcium release proven by reduced phenylephrine-mediated contraction, whilst potassium-induced contraction was not affected. H2O2 scavenger catalase reduced phenylephrine-induced contraction in WT mice. Supplementing H2O2 increased phenylephrine-induced contraction in Nox4−/− mice. Exercise-induced peroxisome proliferative-activated receptor gamma, coactivator 1 alpha (Ppargc1a), as key regulator of mitochondria biogenesis in WT but not Nox4−/− mice. Furthermore, exercise-induced citrate synthase activity and mitochondria mass were reduced in the absence of Nox4. Thus, Nox4−/− mice became less active and ran less compared with WT mice. Conclusions Nox4 derived H2O2 plays a key role in exercise-induced adaptations of eNOS and Ppargc1a pathway and intracellular calcium release. Hence, loss of Nox4 diminished physical activity performance and vascular protective effects of exercise.

Regulation of Nrf2 by Mitochondrial Reactive Oxygen Species in Physiology and Pathology

“…Although different NOX4 subcellular localization has been reported, including in the nucleus and endoplasmic reticulum [76,77], NOX4 has been shown to mainly localize in mitochondria, especially in the heart [78][79][80]. Indeed, several beneficial effects of exercise in the vasculature and skeletal muscle, such as increased physical activity, are diminished in NOX4-knockout mice [81]. Furthermore, Hancock et al conclusively demonstrated that Nrf2 activation by AES is mediated by NOX4 and contributes to mitochondrial quality control using cardiomyocyte-specific knockout of NOX4 and Nrf2 (csNrf2 KO) [73].…”

Nicotinamide Adenine Dinucleotide Phosphate Oxidases in Glucose Homeostasis and Diabetes-Related Endothelial Cell Dysfunction

“…Physiologically, Nox4 appears to play a significant role in regulating the metabolic and vascular adaptions needed during exercise [ 151 , 152 ]. Nox4-deficient mice had impaired glucose and fatty acid oxidation in response to acute exercise.…”

“…Furthermore, following a chronic exercise regime, NOX4 -deficient mice had worse exercise capacity (measured by a reduced time to exhaustion) and reduced activity of skeletal muscle citrate synthase and beta-hydroxyacyl-coA dehydrogrenase (important enzymes involved in mitochondrial metabolism) compared to their wild-type litter mates [ 151 ]. Access to an exercise wheel prevented endothelial dysfunction in wild-type, but not Nox4 −/− deficient mice fed a high fat diet [ 152 ]. Exercise of wild type mice resulted in increased H 2 O 2 release in the aorta with increased phosphorylation of Akt and activation of eNOS, whereas both H 2 O 2 release and phosphorylation of Akt were reduced in aortas of Nox4 −/− mice.…”

Reflections of an aging free radical

“… Footnotes. a Exercise has benefits other than weight loss, some of them may be “antioxidant” by upregulating endogenous antioxidant defences [ 82 , 84 , 85 ]. b May depend on how well glucose and lipids have been normalized in the diabetic cohorts studied.…”

“… a Exercise has benefits other than weight loss, some of them may be “antioxidant” by upregulating endogenous antioxidant defences [ 82 , 84 , 85 ]. …”