Bidirectional Regulation of Nitric Oxide and Endothelin-1 in Cerebral Vasospasm: Mechanisms and Therapeutic Perspectives

Cerebral vasospasm (CVS) following a subarachnoid hemorrhage (SAH) is a critical complication driven by imbalances between vasodilators and vasoconstrictors. This review explores the bidirectional interplay between nitric oxide (NO) and endothelin-1 (ET-1) in CVS pathogenesis. NO, a potent vasodilator mainly produced by endothelial and neuronal nitric oxide synthase (eNOS/nNOS) under normal physiological conditions, is scavenged early after SAH by hemoglobin derivatives, leading to microcirculatory dysfunction, pericyte constriction, and impaired neurovascular coupling. Conversely, ET-1 exacerbates vasoconstriction by suppressing NO synthesis via ROS-dependent eNOS uncoupling and Rho-kinase activation. The NO/ET-1 axis further influences delayed cerebral ischemia (DCI) through mechanisms like 20-HETE-mediated cGMP suppression and oxidative stress. Emerging therapies—including NO donors, NOS gene therapy, and ET-1 receptor antagonists—aim to restore this balance. Understanding these pathways offers translational potential for mitigating CVS and improving outcomes post-SAH.