Nitric Oxide

Nitric oxide (NO) is involved in numerous physiologic functions ranging from regulation of cardiovascular functions to participating in memory (1–4). In the immune system, this diatomic radical is involved in host defense and has tumoricidal functions (5,6) However, despite these properties, which are critical in maintaining homeostasis, NO has been implicated as a participant or causative agent in a variety of pathophysiologic conditions (7,8). Defining the exact role of NO under pathophysiologic conditions is further complicated by the fact that it has been shown to be both protective as well as deleterious even in the context of the same biologic setting. Therefore, the search for mechanistic explanations to account for these differing effects is ongoing. Unlike other biologic mediators, the main determinants of the biologic effects of NO are its chemical and physical properties. In addition to the numerous potential reactions of NO in biologic systems, many of its effects can be attributed to additional reactive nitrogen oxide species (RNOS) that are formed and that have their own selective reactivity. Although a large variety of chemical reactions relate to NO in biologic systems, it is difficult to determine which ones are pertinent. In an attempt to sort out the diverse chemical reactions and their importance, we have developed the concept of the “chemical biology of nitric oxide” (9–11). The chemical biology of NO sepa2