Exercise training upregulates Nrf2 protein in the rostral ventrolateral medulla of mice with heart failure

Abstract

Chronic heart failure (CHF) is associated with global oxidative stress, which contributes to sympathoexcitation. Increased reactive oxygen species in the brain accumulate within neurons and lead to enhanced neuronal excitability. Exercise training (ExT) is associated with a reduction of oxidative stress by upregulation of antioxidant enzymes. The link between ExT and antioxidant enzyme expression in the brain of animals with CHF is not clear. We hypothesized that ExT enhances transcription and translation of the nuclear factor erythroid 2-related factor 2 (Nrf2) gene, a master transcription factor that modulates antioxidant enzyme gene expression, in the rostral ventrolateral medulla (RVLM) of mice with CHF. Mice were divided into the following groups: Sham sedentary (Sham-Sed), Sham-ExT, CHF-Sed, and CHF-ExT. After 8 wk of ExT, we measured Nrf2 and NAD(P)H dehydrogenase [quinone] 1 (NQO-1) message and protein expression along with maximal exercise tolerance and urinary norepinephrine (NE) excretion. We found that Nrf2 and NQO-1 mRNA and protein expression in the RVLM were lower in CHF-Sed mice compared with Sham-Sed. ExT attenuated the CHF-induced reduction of Nrf2 and NQO-1 mRNA and protein expression in the RVLM. NE excretion was higher in CHF-Sed mice compared with Sham-Sed (666.8 ± 79.3 ng/24 h, n = 6 vs. 397.8 ± 43.7 ng/24 h, P = 0.04). CHF-ExT mice exhibited reduced urinary NE excretion compared with CHF-Sed (360.7 ± 41.7 ng, n = 4 vs. 666.8 ± 79.3 ng, n = 6; P = 0.03). We conclude that ExT-induced upregulation of Nrf2 in the RVLM contributes to the beneficial effects of ExT on sympathetic function in the heart failure state. NEW & NOTEWORTHY This study provide evidence for an important role for exercise training in the modulation of antioxidant enzyme production in the rostral ventrolateral medulla (RVLM) in the heart failure state. We show here a correlation between exercise training and the expression of the antioxidant transcription factor Nrf2 in the RVLM. Exercise training reduced sympathetic function (norepinephrine excretion) and upregulated both Nrf2 and the antioxidant enzyme NQO-1. We conclude that Nrf2 in the RVLM may be an important target for controlling sympathetic outflow in heart failure.