[Nitric oxide produced by pulmonary leukocytes in bronchial asthma].

Nitric oxide (NO) is a multifunctional particle and may play diverse roles in physiological and pathological processes. Depending on its concentration, NO can be involved in neurotransmission, the regulation of smooth muscle and vascular tone, vascular permeability, as well as in immune response. NO is produced by a wide variety of cell types and is generated via oxidation of L-arginine, catalyzed by the enzyme NO synthase (NOS). Elevated concentrations of NO were observed in the exhaled air of asthmatics. Recently, the level of this mediator in exhaled air was considered a useful marker in monitoring inflammation as well as disease severity and exacerbation in asthma patients. However, the role NO in asthma is still unclear. The cellular source of the high concentration of nitric oxide in asthma is also not yet certain. Nitric oxide synthases (NOS) were localized in a variety of cells of the respiratory tract, including epithelial cells, smooth muscle cells, and also pulmonary leukocytes such as macrophages, eosinophils, and neutrophils. Most investigators concentrate on epithelial cells as a major source of nitric oxide in airways. There is a limited number of studies on the production of NO by pulmonary leukocytes. The review presents current knowledge on the role of nitric oxide in the process of asthma.