Retinoic acid induces corneal epithelial CYP4B1 gene expression and stimulates the synthesis of inflammatory 12-hydroxyeicosanoids.
Injury to the ocular surface provokes an inflammatory response that is mediated, at least in part, by corneal epithelial derived 12-hydroxyeicosanoids (HETEs) including 12-HETE and 12-HETrE; both metabolites exhibit potent inflammatory and angiogenic properties and are formed by a cytochrome P450 (CYP) 4B1. Retinoids are known to mediate wound-healing processes in many tissues and, as such, are integral components of the inflammatory response. We studied the effect of various retinoids on corneal synthesis of 12-hydroxyeicosanoids and on activation of CYP4B1 gene expression. Corneal organ cultures were used to assess the effect of retinoic acid on epithelial metabolism of arachidonic acid to 12-hydroxyeicosanoids. Luciferase reporter vectors containing different lengths of the CYP4B1 3.4 kb-5'-untranslated region were used to examine the effect of vitamin D and retinoids (9-cis-retinoic acid and all-trans retinoic acid) on transcriptional activation of CYP4B1 in transient transfection experiments with HepG2 cells. Vitamin D had no effect on CYP4B1 promoter activity, but 9-cis and all-trans retinoic acids increased promoter activity by up to 70% over control. Addition of both 9-cis and all-trans retinoic acids resulted in an additive effect increasing promoter activity by 2-fold. The increased promoter activity correlated with the presence of RAR/RXR binding motifs. Incubation of corneal organ culture for 24 hours in the presence of 9-cis and all-trans retinoic acids increased the synthesis of 12-HETE and 12-HETrE by 2-fold. The finding that retinoic acid increases the expression of the CYP4B1 gene and enhances production of the inflammatory 12-hydroxyeicosanoids in the corneal epithelium may provide a linkage between wound healing and inflammation in the ocular surface.
Ashkar
Silvia
S
Department of Pharmacology and Ophthalmology, New York Medical College, Valhalla, NY 10595, USA.
Mesentsev
Alexandre
A
Zhang
Wen-Xiang
WX
Mastyugin
Vladimir
V
Dunn
Michael W
MW
Laniado-Schwartzman
Michal
M
D000077556:Alitretinoin; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D045744:Cell Line, Tumor; D019573:Epithelium, Corneal / Q000187:drug effects* / Q000201:enzymology; D005260:Female; D015870:Gene Expression / Q000187:drug effects*; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000096:biosynthesis*; D008156:Luciferases / Q000235:genetics; D008297:Male; D009924:Organ Culture Techniques; D010100:Oxygen / Q000378:metabolism; D010957:Plasmids; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011817:Rabbits; D015533:Transcriptional Activation / Q000235:genetics; D014212:Tretinoin / Q000494:pharmacology*; D014807:Vitamin D / Q000494:pharmacology
D006893:Hydroxyeicosatetraenoic Acids; D014807:Vitamin D; D000077556:Alitretinoin; D014212:Tretinoin; D008156:Luciferases; D001189:Aryl Hydrocarbon Hydroxylases; C095029:cytochrome P-450 CYP4B1; D010100:Oxygen