title: Mechanism of enhanced fibroblast arachidonic acid metabolism by mononuclear cell factor.
abstract: Chronic inflammation is associated with an infiltration of mononuclear cells, fibroblast proliferation, and elevated levels of prostaglandin (PG) E2. Mononuclear cell conditioned factor (MNCF) medium (5%) stimulated a 100-fold increase in basal human dermal fibroblast PGE2 release over 48 h as compared with fibroblasts that were incubated with control medium (conditioned medium prepared without cells). The MNCF-induced PGE2 production was suppressed by protein synthesis inhibitors. Fibroblasts pretreated with control medium released PGE2 only modestly in response to 1 nM bradykinin for 1 h (basal, 50 +/- 7 pg PGE2/micrograms protein; stimulated, 104 +/- 12 pg PGE2/micrograms protein), whereas cells that had been pretreated with MNCF showed a greatly facilitated bradykinin-induced release of PGE2. (basal, 297 +/- 59 pg PGE2/micrograms protein; stimulated, 866 +/- 85 pg PGE2/micrograms protein). The exaggerated agonist response is not specific for bradykinin because platelet-derived growth factor elicits a similar response. Exogenous arachidonic acid conversion to PGE2 was also facilitated (two- to threefold) by MNCF pretreatment as compared with control. Both the enhanced agonist-stimulated and exogenous arachidonic acid-induced PGE2 release from the MNCF pretreated cells were inhibited by actinomyin D or cycloheximide. A kinetic study of microsomal cyclooxygenase prepared from fibroblasts pretreated with MNCF showed a threefold increase in the maximum velocity (Vmax) but the same Michaelis constant (Km) as control-treated cells. This augmented arachidonic acid metabolism and subsequent enhanced PGE2 production may play an important role in macrophage-fibroblast interactions at sites of inflammation.
mesh_terms: D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D001920:Bradykinin / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D015232:Dinoprostone; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology; D015846:Monokines; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D011458:Prostaglandins E / Q000378:metabolism; D011506:Proteins / Q000494:pharmacology*
chemical_list: D001095:Arachidonic Acids; D015846:Monokines; D011458:Prostaglandins E; D011506:Proteins; D003609:Dactinomycin; D016718:Arachidonic Acid; D003513:Cycloheximide; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone; D001920:Bradykinin