title: Modulation of cytosolic phospholipase A(2) by PPAR activators in human preadipocytes.
abstract: Cytosolic phospholipase A(2) (cPLA(2)) is responsible for the release of arachidonic acid, a precursor for eicosanoid biosynthesis, from cellular phospholipids. The objective of this study is to examine the regulation of cPLA(2) by peroxisome proliferator-activated receptor (PPAR) activators in preadipocyte SW872 (SW) cells. PPAR belong to the superfamily of nuclear hormone receptors that heterodimerize with the retinoid X receptor. In this study, the presence of both PPARalpha and PPARgamma was confirmed in SW cells by positive identification of their mRNA in the cellular homogenate. Clofibrate, a PPARalpha activator, caused an enhancement of ionophore A-23187-induced arachidonate release in SW cells. This increase resulted from an enhancement of cPLA(2) activity, which was caused by an increase in enzyme protein. Clofibrate at lower concentrations (10-200 microM) produced increases in the mRNA levels of cPLA(2) in a dose-response manner. At higher concentrations (>400 microM), clofibrate treatment resulted in the attenuation of the cPLA(2) mRNA level and protein expression. We postulate that clofibrate, acting through the PPARalpha, caused an induction in the transcription of cPLA(2) gene, which led to an increase in the cPLA(2) protein. The observed increase in arachidonate release in SW cells appeared to be a direct result of the enhanced cPLA(2) activity.
authors.affiliation: The Lipid Research Group, Department of Biochemistry and Medical Genetics, Faculty of Medicine, 770 Bannatyne Avenue, University of Manitoba, Winnipeg, Manitoba, Canada R3E 0W3.
authors.forename: Y J
authors.initials: YJ
authors.lastname: Jiang
authors.forename: G M
authors.initials: GM
authors.lastname: Hatch
authors.forename: D
authors.initials: D
authors.lastname: Mymin
authors.forename: T
authors.initials: T
authors.lastname: Dembinski
authors.forename: E A
authors.initials: EA
authors.lastname: Kroeger
authors.forename: P C
authors.initials: PC
authors.lastname: Choy
mesh_terms: D042962:Acyl-CoA Oxidase; D017667:Adipocytes / Q000187:drug effects* / Q000201:enzymology; D016718:Arachidonic Acid / Q000096:biosynthesis / Q000378:metabolism; D000001:Calcimycin / Q000494:pharmacology; D002994:Clofibrate / Q000494:pharmacology*; D051546:Cyclooxygenase 2; D004789:Enzyme Activation; D006801:Humans; D000960:Hypolipidemic Agents / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008080:Liposarcoma; D008565:Membrane Proteins; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010741:Phospholipases A / Q000235:genetics / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
chemical_list: D000960:Hypolipidemic Agents; D007476:Ionophores; D007527:Isoenzymes; D008565:Membrane Proteins; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D016718:Arachidonic Acid; D000001:Calcimycin; D010088:Oxidoreductases; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D042962:Acyl-CoA Oxidase; D010741:Phospholipases A; D002994:Clofibrate