Oxysterol and 9-cis-retinoic acid stimulate the group IIA secretory phospholipase A2 gene in rat smooth-muscle cells.
The inflammation that occurs during rheumatoid arthritis or atherosclerosis is characterized by the release of large amounts of sPLA(2) (group IIA secretory phospholipase A(2)). We have shown previously that the sPLA(2) promoter in SMC (smooth-muscle cells) is activated by interleukin-1beta and cAMP-signalling pathways, through the interplay of multiple transcription factors [Antonio, Brouillet, Janvier, Monne, Bereziat, Andreani, and Raymondjean (2002) Biochem. J. 368, 415-424]. In the present study, we have investigated the regulation of sPLA(2) gene expression in rat aortic SMCs by oxysterols. We found that oxysterol ligands that bind to the LXR (liver X receptor), including 25-HC (25-hydroxycholesterol) and 22( R )-HC, cause the accumulation of sPLA(2) mRNA and an increased enzyme activity. Transient transfection experiments demonstrated that the sPLA(2) promoter is synergistically activated by 22( R )-HC in combination with 9- cis -retinoic acid, a ligand for the LXR heterodimeric partner RXR (retinoid X receptor). Promoter activity was also increased in a sterol-responsive fashion when cells were co-transfected with LXRalpha/RXRalpha or LXRbeta/RXRalpha. Mutagenesis studies and gel mobility-shift assays revealed that LXR/RXR heterodimers regulate sPLA(2) transcription directly, by interacting with a degenerated LXRE (LXR response element) at position [-421/-406] of the sPLA(2) promoter. Chromatin immunoprecipitation revealed the in vivo occupancy of LXR on the sPLA(2) promoter. In addition, the orphan nuclear receptor LRH-1 (liver receptor homologue-1) potentiated the sterol-dependent regulation of the sPLA(2) promoter by binding to an identified promoter element (TCAAGGCTG). Finally, we have demonstrated that oxysterols act independent of interleukin-1beta and cAMP pathways to activate the sPLA(2) promoter. In the present study, we have identified a new pathway activating sPLA(2) gene expression in SMCs.
Antonio
Valérie
V
UMR (Unité Mixte de Recherche 7079) Physiologie et Physiopathologie, Université Pierre et Marie Curie, Case courrier 256, Bâtiment A, 5èmeétage, 7 quai St Bernard, 75252 Paris cedex 05, France.
Janvier
Brigitte
B
Brouillet
Arthur
A
Andreani
Marise
M
Raymondjean
Michel
M
D000077556:Alitretinoin; D000818:Animals; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D004268:DNA-Binding Proteins; D004790:Enzyme Induction; D054501:Group II Phospholipases A2; D006888:Hydroxycholesterols / Q000494:pharmacology*; D007375:Interleukin-1 / Q000494:pharmacology; D000071518:Liver X Receptors; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D057093:Orphan Nuclear Receptors; D010741:Phospholipases A / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D054467:Phospholipases A2; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D020218:Response Elements; D047488:Retinoid X Receptors; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation; D014212:Tretinoin / Q000494:pharmacology*
D004268:DNA-Binding Proteins; D006888:Hydroxycholesterols; D007375:Interleukin-1; D000071518:Liver X Receptors; C000605214:Nr1h3 protein, mouse; C000605215:Nr1h3 protein, rat; C431936:Nr5a2 protein, mouse; D057093:Orphan Nuclear Receptors; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D014157:Transcription Factors; C003585:22-hydroxycholesterol; D000077556:Alitretinoin; D014212:Tretinoin; C007997:25-hydroxycholesterol; D000242:Cyclic AMP; D010741:Phospholipases A; D054501:Group II Phospholipases A2; D054467:Phospholipases A2