15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) signals through retinoic acid receptor-related orphan receptor-alpha but not peroxisome proliferator-activated receptor-gamma in human vascular endothelial cells: the effect of 15d-PGJ2 on tumor necrosis factor-alpha-induced gene expression.
OBJECTIVE
15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2), a natural ligand of the peroxisome proliferator-activated receptor-gamma (PPARgamma), has been shown to inhibit proinflammatory gene expression, but the signaling mechanisms involved remain unclear. Because retinoic acid receptor-related orphan receptor-alpha (RORalpha) has been reported to suppress tumor necrosis factor-alpha (TNF-alpha)-induced expression of proinflammatory genes, we hypothesized that 15d-PGJ2 may induce RORalpha expression resulting in inhibition of proinflammatory gene expression.


RESULTS
We demonstrate that 15d-PGJ2 induced RORalpha1 and RORalpha4 expression and inhibited TNF-alpha-induced vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) expression in human umbilical vein endothelial cells (HUVECs). In contrast, the synthetic PPARgamma ligand pioglitazone weakly induced RORalpha4 expression but did not affect RORalpha1 expression or TNF-alpha-induced gene expression. Biphenol A diglycidyl ether, a PPARgamma antagonist, did not block the effect of 15d-PGJ2 on RORalpha expression. Adenovirus-mediated overexpression of RORalpha1 inhibited TNF-alpha-induced VCAM-1 and ICAM-1 expression, and overexpression of a mutant form of RORalpha1 (RORalpha1Delta), which inhibited transcriptional activity of RORalpha1 and RORalpha4, attenuated its inhibition. Furthermore, we found that RORalpha1Delta attenuated the inhibitory actions of 15d-PGJ2 on TNF-alpha-induced VCAM-1 and ICAM-1 expression.


CONCLUSIONS
These results suggest that 15d-PGJ2 inhibits TNF-alpha-induced expression of proinflammatory genes mediated in part via induction of RORalpha in HUVECs. This mechanism provides a novel insight into PPARgamma-independent actions of 15d-PGJ2.
Migita
Hideyuki
H
Department of Pharmacology, Berlex Biosciences, Richmond, CA 94806, USA. hideyuki_migita@berlex.com
Morser
John
J
D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000276:immunology*; D015870:Gene Expression / Q000187:drug effects / Q000276:immunology; D005799:Genes, Dominant; D006801:Humans; D007155:Immunologic Factors / Q000494:pharmacology*; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics; D047495:PPAR gamma / Q000378:metabolism*; D015230:Prostaglandin D2 / Q000031:analogs & derivatives* / Q000494:pharmacology; D018168:Receptors, Retinoic Acid / Q000378:metabolism*; D000072482:Retinoic Acid Receptor alpha; D015398:Signal Transduction / Q000187:drug effects*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics*; D014471:Umbilical Veins / Q000166:cytology; D019010:Vascular Cell Adhesion Molecule-1 / Q000235:genetics
C097240:15-deoxy-delta(12,14)-prostaglandin J2; D007155:Immunologic Factors; D047495:PPAR gamma; C000607071:RARA protein, human; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D014409:Tumor Necrosis Factor-alpha; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1; D015230:Prostaglandin D2