It wasn't so long ago that nitric oxide (NO) was eschewed as a noxious gas associated with auto exhaust, smog, acid rain and destruction of the ozone layer.

But in 1987, it was discovered that NO is produced in humans. Research with the NO molecule has shown that it is a gaseous free radical that acts as both an intra- and intercellular messenger, as well as a potent vasodilator. However, abnormally elevated levels of NO - created when inflammatory cytokines and endotoxins induce the transcription of the iNOS gene (the gene for inducible nitric-oxide synthase, which produces nitric oxide) - have been linked to the pathology of conditions such as stroke, autoimmune disease, allograft rejection and diabetes.