Nitric oxide synthase 3 (NOS3) and the NO–cGMP–PKG signaling pathway (eNOS/NO–cGMP–PKG)

Endothelial nitric oxide synthase (eNOS), also known as NOS3, is the primary enzyme responsible for generating nitric oxide (NO) in the vascular endothelium (UniProt: P29474). NO acts as a potent signaling molecule that diffuses into vascular smooth muscle cells to activate soluble guanylate cyclase (sGC), which catalyzes the production of cyclic guanosine monophosphate (cGMP) (StatPearls: Physiology, Nitric Oxide). This increase in cGMP activates protein kinase G (PKG), leading to reduced intracellular calcium and subsequent vasodilation, as well as the inhibition of platelet aggregation and leukocyte adhesion (PubMed: PMC2806714). Impairment of this pathway is a central feature of endothelial dysfunction, contributing significantly to the pathogenesis of hypertension, atherosclerosis, and heart failure (PubMed: PMC4521546). Therapeutic strategies targeting this axis include NO donors (e.g., nitroglycerin), sGC stimulators (e.g., riociguat), and PDE5 inhibitors (e.g., sildenafil), which collectively aim to restore or enhance NO-mediated signaling (PubMed: PMC3130714). Additionally, statins and ACE inhibitors are known to indirectly upregulate eNOS expression and activity, further supporting vascular health (PubMed: PMC1906511). Safety concerns for drugs targeting this pathway primarily involve excessive vasodilation, leading to hypotension and syncope, particularly when multiple agents are used concurrently (PubMed: PMC3130714).

Other names

Endothelial nitric oxide synthaseNOS3eNOSNitric oxide–cyclic guanosine monophosphate–protein kinase G pathwayConstitutive nitric oxide synthasec-NOS

The pathway is targeted via nitric oxide donation to increase NO bioavailability, stimulation or activation of soluble guanylate cyclase (sGC) to increase cGMP production, and inhibition of phosphodiesterase 5 (PDE5) to prevent cGMP degradation, ultimately enhancing PKG-mediated signaling.