Physiological and clinical importance of nitric oxide

Nitric oxide is an unusual messenger molecule with many physiologic roles, in the cardiovascular, neurologic and immune systems. It mediates blood vessel relaxation, neurotransmission and pathogen suppression. Two major categories of nitric oxide synthase enzyme produce nitric oxide. The constituent isoforms present in the endothelial cell and neurons release small amounts of nitric oxide intermittently to signal adjacent cells. The inducible isoforms found in macrophages release large amounts of nitric oxide continuously eliminating bacteria and parasites. Nitric oxide regulates blood pressure, transmits signals between neurons and suppresses pathogens. Excess amounts of nitric oxide may damage host cells causing neurotoxicity during strokes, and causing hypotension associated with sepsis. Further research is needed to understand the role of nitric oxide in the treatment of disease.