Melanocortin System Activates Carotid Body Arterial Chemoreceptors in Hypertension

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Abstract
BACKGROUND: The internal milieu of the body is controlled by a system of interoceptors coupled to motor outflows that drive compensatory adaptive responses. These include the arterial chemoreceptors, best known for sensing arterial oxygen. In cardiometabolic diseases, such as essential hypertension, the carotid bodies (CB) exhibit heightened reflex sensitivity and tonic activity without an apparent stimulus. The mechanisms behind CB sensitization in these conditions are not well understood. METHODS: Guided by functional genomics, a range of functional assays is used to interrogate downstream intracellular and interorgan signaling pathways involved in arterial chemosensory function. RESULTS: Here, we report the presence of the MC4R (melanocortin 4 receptor) in the mammalian CB and show its elevated expression in experimental hypertension. We demonstrate that melanocortin agonists activate arterial chemosensory cells, modulating CB chemosensory afferent drive to influence chemoreflex-evoked sympathetic and ventilatory activity. Transcriptional analysis of hypertensive CB implicates the activation of the Mash1 (mammalian achaete-scute homolog 1; Ascl1 ) regulatory network in driving elevated Mc4r expression. CONCLUSIONS: Collectively, our data indicate a primarily pathophysiological role of melanocortin signaling in arterial chemosensation, contributing to excess sympathetic activity in cardiometabolic disease.
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