Hif1α-dependent mitochondrial acute O2 sensing and signaling to myocyte Ca2+ channels mediate arterial hypoxic vasodilation

Vasodilation in response to low oxygen (O₂) tension (hypoxic vasodilation) is an essential homeostatic response of systemic arteries that facilitates O₂ supply to tissues according to demand. However, how blood vessels react to O₂ deficiency is not well understood. A common belief is that arterial myocytes are O₂-sensitive. Supporting this concept, it has been shown that the activity of myocyte L-type Ca²⁺channels, the main ion channels responsible for vascular contractility, is reversibly inhibited by hypoxia, although the underlying molecular mechanisms have remained elusive. Here, we show that genetic or pharmacological disruption of mitochondrial electron transport selectively abolishes O₂ modulation of Ca²⁺ channels and hypoxic vasodilation. Mitochondria function as O₂ sensors and effectors that signal myocyte Ca²⁺ channels due to constitutive Hif1α-mediated expression of specific electron transport subunit isoforms. These findings reveal the acute O₂-sensing mechanisms of vascular cells and may guide new developments in vascular pharmacology.