Nitric oxide signaling pathway components (NO signaling pathway)

The nitric oxide (NO) signaling pathway is a fundamental biological cascade responsible for regulating vascular tone, immune response, and neuronal communication. The pathway is initiated by the synthesis of NO from L-arginine by nitric oxide synthase (NOS) enzymes, including neuronal (nNOS/NOS1), inducible (iNOS/NOS2), and endothelial (eNOS/NOS3) isoforms [1][2]. Once produced, NO diffuses into target cells where it binds to and activates soluble guanylate cyclase (sGC), leading to the conversion of GTP to cyclic guanosine monophosphate (cGMP) [2][3]. cGMP acts as a second messenger that triggers downstream effectors like protein kinase G (PKG) to induce smooth muscle relaxation and inhibit platelet aggregation [3][4]. Impairment of this pathway is a hallmark of endothelial dysfunction and contributes to diseases such as pulmonary arterial hypertension (PAH), heart failure, and erectile dysfunction [1][5]. Therapeutic strategies include the use of NO donors (e.g., nitroglycerin), sGC stimulators (e.g., riociguat), and PDE5 inhibitors (e.g., sildenafil) to restore or enhance cGMP signaling [4][6]. This entry describes the collective components of the pathway rather than a single molecular target. (Sources: [1] StatPearls: NBK499831; [2] Nature Reviews Drug Discovery: 10.1038/nrd.2017.243; [3] UniProt: P14678, P33523; [4] Circulation: 10.1161/CIRCULATIONAHA.111.081943; [5] JCI: 10.1172/JCI63912; [6] FDA Drug Labels for Adempas and Revatio).

Other names

NO/cGMP signaling pathwayNitric oxide-guanylate cyclase-cGMP pathwayEndothelium-derived relaxing factor (EDRF) pathwayNitric oxide synthase (NOS)Soluble guanylate cyclase (sGC)Phosphodiesterase 5 (PDE5)

Pharmacological agents modulate this pathway by providing exogenous nitric oxide (NO donors), directly stimulating or activating soluble guanylate cyclase (sGC) to increase cGMP production, or inhibiting phosphodiesterase 5 (PDE5) to prevent the breakdown of cGMP, ultimately promoting vasodilation and reducing vascular resistance [1][2][4].