title: 20-Hydroxyeicosatetraenoic acid inhibits ATP-induced COX-2 expression via peroxisome proliferator activator receptor-α in vascular smooth muscle cells.
abstract: OBJECTIVE
  20-Hydroxyeicosatetraenoic acid (20-HETE), formed from arachidonate by cytochrome P450, regulates vascular smooth muscle cell (VSMC) function. Because 20-HETE may activate peroxisome proliferator activator receptors (PPARs) and may participate in inflammatory responses, we asked whether 20-HETE may inhibit cyclooxygenase 2 (COX-2) expression by activating PPARs in VSMC.
  
  
  METHODS
  Quiescent neonatal VSMC (R22D cell line), were incubated with 20-HETE, synthetic ligands of PPARs, or inhibitors of the extracellular signal regulated kinase (ERK1/2), c-jun N-terminal kinase and the transcription factor activated protein-1 before adding ATPγS. mRNA and protein expression of COX-2 and the promoter luciferase activity of COX-2 and PPAR response element were determined.
  
  
  RESULTS
  Pretreatment with 20-HETE (5-10 µM) significantly inhibited ATPγS-induced COX-2 mRNA and protein expression in VSMC. The inhibitory effect of 20-HETE on COX-2 expression was mimicked by WY14643, a PPARα ligand and inhibited by MK886, a PPARα inhibitor or by transfection of shRNA for PPARα. Both 20-HETE and WY14643 significantly increased the PPAR-response element luciferase activity. Furthermore, ATPγS-induced activation of the COX-2 promoter containing the activated protein-1 site was also inhibited by pretreatment with 20-HETE, which was reversed by MK886 or by transfection with shRNA for PPARα.
  
  
  CONCLUSIONS
  The PPARα may mediate the inhibitory effects of 20-HETE on COX-2 expression through a negative cross-talk between PPARα and the COX-2 promoter.
authors.affiliation: Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, Kuei-Shan, Tao-Yuan, Taiwan.
authors.forename: Chan-Jung
authors.initials: CJ
authors.lastname: Liang
authors.forename: Ching-Ping
authors.initials: CP
authors.lastname: Tseng
authors.forename: Chuen-Mao
authors.initials: CM
authors.lastname: Yang
authors.forename: Yunn-Hwa
authors.initials: YH
authors.lastname: Ma
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D006893:Hydroxyeicosatetraenoic Acids / Q000494:pharmacology*; D007211:Indoles / Q000494:pharmacology; D008156:Luciferases / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000201:enzymology*; D047493:PPAR alpha / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011743:Pyrimidines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D051381:Rats; D018808:Transcription Factor AP-1 / Q000378:metabolism; D002722:Chlorobenzenes
chemical_list: D000255:Adenosine Triphosphate; D051546:Cyclooxygenase 2; D006893:Hydroxyeicosatetraenoic Acids; D007211:Indoles; D008156:Luciferases; D020929:Mitogen-Activated Protein Kinase Kinases; D047493:PPAR alpha; D011743:Pyrimidines; D034741:RNA, Small Interfering; D018808:Transcription Factor AP-1; C060893:MK-886; D002722:Chlorobenzenes; C022571:adenosine 5'-O-(3-thiotriphosphate); C055987:20-hydroxy-5,8,11,14-eicosatetraenoic acid; C006253:pirinixic acid