NOS2 and gastritis: However, chronic inflammation, including inflammatory bowel disease and Helicobacter pylori-induced gastritis induce inducible NOS (iNOS) and generate large quantities of NO [22,146,147], forming nitrosating and oxidant species such as N2O3 and peroxynitrite, which might cause mutagenesis through deamination, nitration of DNA, or inhibition of the DNA repair system [148,149].