Nickan Research Institute Immunopathologia Persa 2423-8015 5 1 2019 01 01 The role of nitric oxide in inflammation and oxidative stress e08 e08 10.15171/ipp.2019.08 EN Sajad Papi Fariba Ahmadizar Amin Hasanvand https://orcid.org/0000-0003-0837-7542 Journal Article 10.15171/ipp.2019.08 2019 01 09 2019 03 20 Nitric oxide (NO) is one of the most important components of blood vessels’ health. NO is a gas compound with different physiological and biochemical effects on the body. It is a free radical, which plays as an endogenous and endothelium relaxing factor. NO has a protective role in digestive system which also plays different roles in the immune system as a mediator of immunity; e.g. regulating immune response, and stimulation and suppression of the immune system. NO has three isoforms each of which is expressed by a special gene. These isoforms include neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS) which both are depending on calcium and calmodulin. The third isoform, independent on calcium and calmodulin, is inducible nitric oxide synthase (iNOS). Even in special conditions such as renal ischemia-reperfusion, it has been shown that high iNOS and low eNOS levels are involved in increased inflammation and connective tissue damage.