Inducible nitric oxide synthase and inflammatory diseases.

Nitric oxide (NO) is a colorless gas at room temperature and one of the simplest molecules known, yet it has been implicated in a wide variety of regulatory mechanisms ranging from vasodilatation and blood pressure control to neurotransmission. It is also involved in nonspecific immunity and participates in the complex mechanism of tissue injury as a major mediator of inflammatory processes and apoptosis (1). This work focuses on the complex role of NO produced by the inducible form of nitric oxide synthase (iNOS) in inflammatory and autoimmune diseases. Although the earliest studies in the field suggested that NO is a strictly pro-inflammatory macrophage product, it is clear from the current literature that, in fact, NO is made by numerous cell types and is often anti-inflammatory. Much of this dichotomy can be explained by the particular responses of given cells involved in the inflammatory response, but another variable involves the complex chemistry in which NO can participate. As we outline below, various facets of the immune response can be examined from these perspectives.