Nitric oxide (EDRF [endothelium-derived relaxing factor])
Chapter: 2
This is a potent regulatory and cytotoxic molecule. In inflammation, its production is catalyzed by inducible nitric oxide synthase, which is the product of an inducible gene that is selectively expressed under inflammatory conditions. It allows leukocytes, especially macrophages and neutrophils, to produce large amounts of a reactive nitrogen intermediate, NO (nitric oxide), during inflammatory responses. NO, like its reactive oxygen counterparts (see also reactive oxygen intermediates), can kill microorganisms, tumor cells, and damage tissues. The earlier name, EDRF, comes from the fact that a second gene, which encodes a constitutively expressed isoform of nitric oxide synthase, produces small amounts of NO that is involved in the regulation of vascular smooth muscle tone. Nitric oxide is also preduced in the brain by a neuronal isoform of nitric oxide synthase, where it functions in intercellular signaling between nerve cells.