Acid-sensing ion channels in the vasculature: emerging roles in systemic and pulmonary circulations

Acid-sensing ion channels (ASICs) are proton-gated members of the degenerin/epithelial sodium channel family that are emerging as multifaceted regulators of cardiovascular function. ASICs expressed in baroreceptor, cardiac, and skeletal muscle afferents contribute to reflex control of blood pressure, cardiac function, and sympathetic outflow. In vascular smooth muscle and endothelial cells, ASICs integrate mechanical, metabolic, and humoral signals to regulate vascular tone. In the systemic circulation, ASIC2 contributes to pressure-dependent vasoconstriction of renal and cerebral arteries, supporting blood flow autoregulation and protection against organ injury. In contrast, ASIC1a promotes vasodilation, contributing to nitric oxide-dependent dilation in the cerebral arteries and to endothelium-dependent hyperpolarization and vasodilation in mesenteric arteries. In the pulmonary vascular smooth muscle cells, ASIC1a plays a central role in acute hypoxic- and receptor-mediated vasoconstriction, a role that becomes increasingly important in chronic hypoxia-induced pulmonary hypertension. Under these conditions, metabolic reprogramming drives extracellular acidification and enhances ASIC1a trafficking to the plasma membrane, promoting sustained depolarization, augmented store-operated calcium entry, and a hyperproliferative, apoptosis-resistant smooth muscle phenotype. ASIC1a additionally regulates mitochondrial homeostasis by modulating mitochondrial membrane potential, redox balance, and apoptotic susceptibility. Chronic hypoxia redistributes ASIC1a from mitochondria to the plasma membrane, leading to mitochondrial dysfunction and cell survival signaling, key features of pulmonary vascular disease. This review summarizes current understanding of ASIC function in the systemic and pulmonary vasculature and highlights non-proton-mediated signaling mechanisms, emerging mitochondria-specific mechanisms, sex-related differences, and therapeutic opportunities and challenges in targeting ASIC-dependent signaling pathways in vascular disease.