Vascular smooth muscle cell contractile machinery (NO–cGMP pathway)

The vascular smooth muscle cell contractile machinery via the nitric oxide-mediated cGMP pathway is not a single molecular target but rather describes an integrated signaling cascade that regulates the contraction state of vascular smooth muscle cells. The process begins with the production of nitric oxide (NO) by endothelial cells. NO diffuses into adjacent vascular smooth muscle cells where it activates its main receptor, soluble guanylyl cyclase. This enzyme catalyzes the conversion of GTP to cyclic GMP (cGMP), which acts as a second messenger. Elevated intracellular cGMP leads to several downstream effects that promote smooth muscle relaxation, including: - Activation of cGMP-dependent protein kinase I (PKGI) which phosphorylates targets such as myosin light chain phosphatase, increasing its activity and promoting dephosphorylation—and thus inactivation—of myosin light chains required for contraction[4][5]. - Inhibition of calcium entry into the cell and reduction in cytosolic calcium concentration. - Opening potassium channels causing hyperpolarization. These mechanisms collectively result in vasodilation—the widening or relaxation of blood vessels—which is critical for regulating blood pressure and tissue perfusion[1][2][3]. Pharmacologically, this pathway is targeted by drugs such as nitrodilators/nitrovasodilators that release NO directly or indirectly mimic its effects; also by phosphodiesterase type 5 inhibitors like sildenafil that prevent breakdown of cGMP thereby enhancing vasorelaxation responses[1][2]. Disruption or dysfunction within this system contributes significantly to cardiovascular diseases such as hypertension and atherosclerosis. This entry does not represent a canonical molecular target but rather an entire physiological mechanism; therefore it should be considered incorrect if used where specific drug targets are required. The actual druggable entities within this system include soluble guanylyl cyclase itself or downstream effectors like PKGI or specific ion channels modulated by these signals[6].

Other names

Nitric oxide–mediated cGMP signaling in vascular smooth muscleNO/cGMP pathway in VSMCNitric oxide–guanylyl cyclase pathwaySoluble guanylate cyclase (sGC) signaling axis

Activation of soluble guanylyl cyclase by nitric oxide to increase cGMP[2][6]; Activation of cGMP-dependent protein kinase leading to myosin light chain phosphatase activation and smooth muscle relaxation[4][5][6]