adenosine-5--o-(3-thiotriphosphate) and 20-hydroxy-5-8-11-14-eicosatetraenoic-acid

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.. 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.. 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.. 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.

Topics: Adenosine Triphosphate; Animals; Cell Line; Cyclooxygenase 2; Hydroxyeicosatetraenoic Acids; Indoles; Luciferases; Mitogen-Activated Protein Kinase Kinases; Muscle, Smooth, Vascular; PPAR alpha; Promoter Regions, Genetic; Pyrimidines; Rats; RNA, Small Interfering; Transcription Factor AP-1