Endogenous nitric oxide inhibits leukotriene B4 release from rat alveolar macrophages.
Effects of endogenous nitric oxide (NO) on the release of mediators of the lipoxygenase and cyclo-oxygenase pathway from rat alveolar macrophages were studied. Alveolar macrophages, freshly isolated or after 18-h culture, were incubated in (amino acid-free) Krebs medium and labelled with [3H]arachidonic acid. The release of [3H]leukotriene B4 and [3H]prostanoids (separated by high performance liquid chromatography) was determined. A 23187 was used as stimulus, as rising intracellular Ca2+ activates directly the phospholipase A2 and lipoxygenase pathway. A 23187 (10 microM) enhanced [3H]leukotriene B4 release from freshly prepared alveolar macrophages about 65-fold, but only 5- to 6-fold from cultured alveolar macrophages. Evoked [3H]leukotriene B4 release and spontaneous [3H]prostanoid release were inhibited when L-arginine (300 microM) was added to the Krebs incubation medium of alveolar macrophages, in which marked NO synthase had been induced by culture with lipopolysaccharides (10 microg/ml). Inhibitory effects of L-arginine were prevented by N(G)-monomethyl-L-arginine (L-NMMA, 100 microM). Inhibition of NO synthase during the culture period by L-NMMA (culture medium, in contrast to Krebs medium, already contains the substrate of NO synthase, L-arginine), resulted in attenuation of the 'culture-dependent' decline of the evoked release of [3H]leukotriene B4 and allowed lipopolysaccharides to cause an increase in spontaneous [3H]prostanoid release (i.e., to induce cyclo-oxygenase activity). In conclusion, in rat alveolar macrophages, endogenous NO appears to inhibit the release of mediators of the cyclo-oxygenase and lipoxygenase pathway through multiple sites of action.
Brunn
G
G
Department of Pharmacology, University of Frankfurt, Germany.
Hey
C
C
Wessler
I
I
Racké
K
K
D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism; D000001:Calcimycin / Q000494:pharmacology; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007975:Leukotriene B4 / Q000378:metabolism*; D008084:Lipoxygenase / Q000378:metabolism; D016676:Macrophages, Alveolar / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism*; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D019323:omega-N-Methylarginine / Q000494:pharmacology
D001095:Arachidonic Acids; D004791:Enzyme Inhibitors; D007975:Leukotriene B4; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D000001:Calcimycin; D008084:Lipoxygenase; D019001:Nitric Oxide Synthase; D011451:Prostaglandin-Endoperoxide Synthases