15-hydroxy-5-8-11-13-eicosatetraenoic-acid and Respiratory-Tract-Diseases

Pulmonary epithelial cells may be primarily responsible for initiating or regulating inflammatory responses in the airways, in part by releasing chemical mediators. Among the most potent mediators of inflammation are the lipoxygenase metabolites of arachidonic acid, including the leukotrienes and the other mono- and dihydroxyeicosatetraenoic acids (HETEs). The human airway epithelium contains significant 15-lipoxygenase activity. Although some biologic functions of 15-lipoxygenase metabolites are known, further understanding of the role of this enzyme in the airway requires localization in tissue and studies of expression, regulation, and biologic activity. Towards these aims, we purified and characterized 15-lipoxygenase from eosinophil-enriched leukocytes. First, we studied cofactors that may be involved in regulating enzymatic activity. We discovered that calcium and phosphatidylcholine both enhanced, but ATP inhibited, the 15-lipoxygenase activity of highly enriched enzyme. Second, we isolated to homeogeneity, for the first time, human 15-lipoxygenase. This led to the determination of the N-terminal amino acid sequence and the discovery of homology among various mammalian lipoxygenases. Further research using purified lipoxygenase is expected to increase our understanding of the biologic roles and biochemical features of 15-lipoxygenation of arachidonic acid.

Topics: Arachidonate 15-Lipoxygenase; Arachidonate Lipoxygenases; Epithelium; Humans; Hydroxyeicosatetraenoic Acids; Inflammation; Respiratory Tract Diseases

It was shown that 15-hydroxyeicosatetraenoic acid (15-HETE) but not 15-H(P)ETE or 5-HETE is a potent agonist for secretion of glycoprotein-containing mucus from the in vivo canine trachea. Given by aerosol into the lungs or by intra-arterial injection into the trachea, 15 HETE also caused the chemotaxis of inflammatory cells into the lumen of the airways. Accompanying this inflammatory cell infiltrate was an increase (183%, p less than 0.05) of expiration of fluid in the partially saturated air coming from the lung. The levels of 15-HETE extracted from tracheal mucus correlated well with hillocks and weight of secreted mucus found in the mucus after hypoxia or after arachidonic acid loading. Indomethacin and atropine blocked the mucus secretagogue effect of 15-HETE in the trachea. Indomethacin and U-52, 412 (a 15-lipoxygenase inhibitor) pretreatment abolished a portion of the 15-HETE-induced enhancement of mucus weight and 15-HETE level in the secretion.

Topics: Aerosols; Animals; Arachidonic Acid; Arachidonic Acids; Body Fluids; Cell Movement; Chemotaxis; Dogs; Hydroxyeicosatetraenoic Acids; Hypoxia; Inflammation; Leukotrienes; Lipid Peroxides; Lipoxygenase Inhibitors; Mucus; Respiration; Respiratory System; Respiratory Tract Diseases; Trachea