Voluntary wheel running prevents salt-induced endothelial dysfunction: role of oxidative stress

Diets high in salt can lead to endothelial dysfunction, a nontraditional risk factor for cardiovascular disease (CVD). Exercise is known to reduce CVD risk; however, it remains unknown whether chronic physical activity can attenuate salt-induced endothelial dysfunction independent of blood pressure (BP) and whether these changes are due to an upregulation in endogenous antioxidants. Eight-week-old Sprague-Dawley rats were fed either a normal (NS; 0.49%)- or a high (HS; 4.0%)-salt diet and further divided into voluntary wheel running (NS-VWR, HS-VWR) and sedentary (NS, HS) groups for 6 wk. BP was measured weekly and remained unchanged within groups ( P = 0.373). Endothelium-dependent relaxation (EDR) was impaired in the femoral artery of HS compared with NS (38.6 ± 4.0% vs. 65.0 ± 3.6%; P = 0.013) animals, whereas it was not different between NS and HS-VWR (73.4 ± 6.4%; P = 0.273) animals. Incubation with the antioxidants TEMPOL ( P = 0.024) and apocynin ( P = 0.013) improved EDR in HS animals, indicating a role for reactive oxygen species (ROS). Wheel running upregulated the antioxidant superoxide dismutase-2 (SOD-2) ( P = 0.011) under HS conditions and lowered NOX4 and Gp91-phox, two subunits of NADPH oxidase. Wheel running elevated phosphorylated endothelial nitric oxide synthase (eNOS) ( P = 0.014) in HS-fed rats, demonstrating a role for physical activity and eNOS activity under HS conditions. Finally, there was a reduction in EDR ( P = 0.038) when femoral arteries from NS-VWR animals were incubated with TEMPOL or apocynin, suggesting there may be a critical level of ROS needed to maintain endothelial function. In summary, physical activity protected HS-fed rats from reductions in endothelial function, likely through increased SOD-2 levels and reduced oxidative stress. NEW & NOTEWORTHY Our data suggest that voluntary wheel running can prevent impairments in endothelium-dependent relaxation in the femoral artery of rats fed a high-salt diet. This appears to be independent of blood pressure and mediated through a decrease in expression of NADPH oxidases as a result of physical activity. These data suggest that increased chronic physical activity can protect the vasculature from a diet high in salt, likely through a reduction in oxidative stress.