NADPH oxidase mediates hypersomnolence and brain oxidative injury in a murine model of sleep apnea

Rationale: Persons with obstructive sleep apnea may have significant residual hypersomnolence, despite therapy. Long-term hypoxia/ reoxygenation events in adult mice, simulating oxygenation patterns of moderate-severe sleep apnea, result in lasting hypersomnolence, oxidative injury, and proinflammatory responses in wake active brain regions. We hypothesized that long-term intermittent hypoxia activates brain NADPH oxidase and that this enzyme serves as a critical source of superoxide in the oxidation injury and in hypersomnolence. Objectives: We sought to determine whether long-term hypoxia/ reoxygenation events in mice result in NADPH oxidase activation and whether NADPH oxidase is essential for the proinflammatory response and hypersomnolence. Methods: NADPH oxidase gene and protein responses were measured in wake-active brain regions in wild-type mice exposed to long-term hypoxia/reoxygenation. Sleep and oxidative and proinflammatory responses were measured in adult mice either devoid of NADPH oxidase activity (gp91(phox)-null mice) or in which NADPH oxidase activity was systemically inhibited with apocynin osmotic pumps throughout hypoxia/reoxygenation. Main Results: Long-term intermittent hypoxia increased NADPH oxidase gene and protein responses in wake-active brain regions. Both transgenic absence and pharmacologic inhibition of NADPH oxidase activity throughout long-term hypoxia/reoxygenation conferred resistance to not only long-term hypoxia/reoxygenation hypersomnolence but also to carbonylation, lipid peroxidation injury, and the proinflammatory response, including inducible nitric oxide synthase activity in wake-active brain regions. Conclusions: Collectively, these findings strongly support a critical role for NADPH oxidase in the lasting hypersomnolence and oxidative and proinflammatory responses after hypoxia/reoxygenation patterns simulating severe obstructive sleep apnea oxygenation, highlighting the potential of inhibiting NADPH oxidase to prevent oxidation-mediated morbidities in obstructive sleep apnea.