title: Dexamethasone increases expression of 5-lipoxygenase and its activating protein in human monocytes and THP-1 cells.
abstract: The aim of this study was to assess the effect of dexamethasone on 5-lipoxygenase pathway expression in human peripheral blood monocytes and the acute monocytic leukemia cell line, THP-1. Cells were conditioned over a period of days with dexamethasone, at concentrations relevant in vivo, to study the effect of the glucocorticoid on calcium-ionophore-stimulated 5-lipoxygenase product and arachidonic acid release. The effect of dexamethasone on levels of immunoreactive protein and steady-state messenger RNA encoding for 5-lipoxygenase and its activating protein (5-LAP) was also assessed. Dexamethasone increased the stimulated release of 5-lipoxygenase products from both monocytes and THP-1 cells in a dose-dependent fashion. The increase in product generation was not due to changes in the availability of arachidonic acid. However, immunoreactive protein and steady-state messenger RNA encoding for 5-lipoxygenase and 5-LAP were increased by conditioning with dexamethasone. There was no apparent effect of the glucocorticoid on LTA4-hydrolase-immunoreactive protein levels or specific activity. We conclude that dexamethasone increases 5-lipoxygenase pathway expression in both monocytes and in THP-1 cells. This effect is due, at least in part, to increases in immunoreactive protein and steady-state messenger RNA encoding for 5-lipoxygenase and 5-LAP. These results suggest a role for glucocorticoids in the regulation of 5-lipoxygenase pathway expression in mononuclear phagocytes.
authors.affiliation: Department of Veteran Affairs Medical Center, San Diego, CA 92161, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Riddick
authors.forename: W L
authors.initials: WL
authors.lastname: Ring
authors.forename: J R
authors.initials: JR
authors.lastname: Baker
authors.forename: C R
authors.initials: CR
authors.lastname: Hodulik
authors.forename: T D
authors.initials: TD
authors.lastname: Bigby
mesh_terms: D058927:5-Lipoxygenase-Activating Proteins; D001094:Arachidonate 5-Lipoxygenase / Q000235:genetics / Q000378:metabolism*; D016718:Arachidonic Acid / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004851:Epoxide Hydrolases / Q000378:metabolism; D005786:Gene Expression Regulation / Q000235:genetics; D006801:Humans; D015151:Immunoblotting; D007213:Indomethacin / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D058927:5-Lipoxygenase-Activating Proteins; C548592:ALOX5AP protein, human; D002352:Carrier Proteins; D008565:Membrane Proteins; D012333:RNA, Messenger; D016718:Arachidonic Acid; D003907:Dexamethasone; D001094:Arachidonate 5-Lipoxygenase; D004851:Epoxide Hydrolases; C043134:leukotriene A4 hydrolase; D007213:Indomethacin