Projects per year
Regulation of breathing is critical to our capacity to accommodate deficits in oxygen availability and demand during, for example, sleep and ascent to altitude. Key to this are two reflex responses, hypoxic pulmonary vasoconstriction (HPV), which aids ventilation-perfusion matching at the lungs, and the hypoxic ventilatory response (HVR) which accelerates ventilation. In 2004 I proposed that HPV might be mediated by the AMP-activated protein kinase, which governs cell autonomous metabolic homeostasis. Pharmacological evidence was presented in support of this view, and the hypothesis extended to incorporate a role for AMPK in regulating carotid body afferent input responses during hypoxia and thus the HVR. The present article reviews our subsequent findings on these matters and those of others, which provide strong support for the view that AMPK mediates HPV. AMPK is also critical to the HVR, but against our expectations it is not required for carotid body activation during hypoxia. Contrary to current consensus in this respect, our findings suggest that AMPK deficiency blocks the HVR at the level of the brainstem, even when afferent input responses from the carotid body are normal. We have therefore revised our hypothesis on the HVR, now proposing that AMPK integrates local hypoxic stress at defined loci within the brainstem respiratory network with an index of peripheral hypoxic status, namely afferent chemosensory inputs. Nevertheless, in general outcomes are consistent with the original hypothesis, that the role of AMPK has evolved, through natural selection, to extend to the regulation of breathing, and thus oxygen and energy (ATP) supply to the whole body.
1/06/13 → 31/05/18