NOS2 and inflammation: Nitric oxide (NO) is a free radical signaling molecule, but its excessive production can increase the generation of IL-1, TNF-α, and IFN-γ while exacerbating immune responses; inducible nitric oxide synthase (iNOS) is generally not expressed under resting conditions but can be cytokine-induced and highly expressed during intestinal inflammation, which catalyzes the high-yield production of NO from L-arginine through oxidation of the terminal nitrogen in the guanidino group [48,49,50,51,52,53,54].