Inducible nitric oxide synthase (iNOS) (iNOS)

Inducible nitric oxide synthase (iNOS), also known as NOS2, is a key enzyme in the nitric oxide synthase family that catalyzes the production of nitric oxide (NO) from L-arginine [1, 14]. Unlike the constitutive isoforms (nNOS and eNOS), iNOS is typically expressed in response to inflammatory stimuli such as cytokines (e.g., TNF-alpha, IL-1beta) and bacterial lipopolysaccharides [1, 13, 21]. Once induced, iNOS produces high, sustained levels of NO that are independent of intracellular calcium levels [4, 12, 18]. This high-output NO production is essential for the innate immune response, providing antimicrobial and antitumor activity through the generation of reactive nitrogen species [1, 2, 5, 16]. However, dysregulated or excessive iNOS activity is a major driver of tissue damage and chronic inflammation in diseases such as sepsis, rheumatoid arthritis, and various cancers [1, 4, 6, 9, 19]. Therapeutic development focuses on selective iNOS inhibitors to mitigate pathological NO levels while sparing the homeostatic functions of other NOS isoforms [6, 9, 16]. Despite numerous candidates in clinical trials, achieving sufficient selectivity and balancing the enzyme's protective versus harmful roles remains a significant challenge [6, 9, 16].

Other names

NOS2NOS-IIHepatocyte NOSMacrophage NOSNitric oxide synthase 2

Inhibition of enzyme activity through competitive binding at the L-arginine substrate site or by preventing enzyme dimerization, thereby reducing the production of nitric oxide [6, 9, 16].