Hypoxia-inducible factor 2α (HIF-2α) heterozygousnull mice exhibit exaggerated carotid body sensitivity to hypoxia, breathing instability, and hypertension

Cardiorespiratory functions in mammals are exquisitely sensitive to changes in arterial O-2 levels. Hypoxia-inducible factors (e.g., HIF-1 and HIF-2) mediate transcriptional responses to reduced oxygen availability. We demonstrate that haploinsufficiency for the O-2-regulated HIF-2 alpha subunit results in augmented carotid body sensitivity to hypoxia, irregular breathing, apneas, hypertension, and elevated plasma norepinephrine levels in adult Hif-2 alpha(+/-) mice. These dysregulated autonomic responses were associated with increased oxidative stress and decreased mitochondrial electron transport chain complex I activity in adrenal medullae as a result of decreased expression of major cytosolic and mitochondrial antioxidant enzymes. Systemic administration of a membrane-permeable antioxidant prevented oxidative stress, normalized hypoxic sensitivity of the carotid body, and restored autonomic functions in Hif-2 alpha(+/-) mice. Thus, HIF-2 alpha-dependent redox regulation is required for maintenance of carotid body function and cardiorespiratory homeostasis.