Nitric oxide synthase 3 and Nitric oxide synthase 2 (NOS3 and NOS2)

Nitric oxide synthase 3 (NOS3), also known as endothelial NOS (eNOS), and inducible nitric oxide synthase (NOS2 or iNOS) are enzymes responsible for the endogenous production of nitric oxide (NO) from L-arginine [1, 3]. NOS3 is constitutively expressed in the vascular endothelium, where it plays a vital role in maintaining vascular tone, inhibiting platelet aggregation, and protecting against atherosclerosis [3, 10]. In contrast, NOS2 is typically induced by pro-inflammatory cytokines and bacterial products, producing high levels of NO as a defense mechanism during immune responses [7, 16]. Dysregulation of these isoforms is central to various diseases: a deficiency in NOS3-derived NO is linked to hypertension and cardiovascular dysfunction, while excessive NOS2 activity contributes to chronic inflammation, septic shock, and neurodegeneration [3, 13, 23]. Therapeutic interventions target these enzymes through either the use of NOS inhibitors to reduce pathological NO levels or the use of modulators like statins to enhance protective NO production [3, 18]. Achieving high isoform selectivity is a primary challenge in drug development to avoid off-target effects such as systemic hypertension or compromised immunity [7, 19].

Other names

Endothelial nitric oxide synthaseInducible nitric oxide synthaseeNOSiNOSNOS3NOS2NOS-IIINOS-IIcNOS

Competitive inhibition of L-arginine binding at the enzyme's oxygenase domain to prevent nitric oxide synthesis; or transcriptional and post-translational modulation (e.g., via Akt phosphorylation or cofactor availability) to increase enzyme activity or expression [3, 7, 15, 18].