The Peroxisome Proliferator-Activated Receptor Gamma System Regulates Ultraviolet B-Induced Prostaglandin Production in Human Epidermal Keratinocytes
agonists, but not or agonists, induce PGE2 production in PHKs; agonist-induced PGE2 production and COX-2 mRNA expression are inhibited by GW9662. (a) PPAR agonists, but not PPAR or agonists, induce PGE2 production in PHKs. PHKs were treated for 24 hours with vehicle (CONT), 5 M of the PPAR agonist, ciglitazone (CIG), 1 M of the endogenous PPAR agonist, azPC, a PPAR agonist (WY-14,643, 1 M), or a PPAR agonist (GW501516, 500 nM). The media were then removed and PGE2 was quantitated in the culture media using a commercial PGE2 EIA kit. Values represent the mean SEM of PGE2 levels as a percent of control levels ( experiments done in triplicate). , one sample t-test. (b) GW9662 inhibits PPAR agonist-induced PGE2 production in PHKs but has no significant effect on vehicle-treated cells. PHKs were pretreated for 1 hour with 1 M GW9662 prior to addition of vehicle (VEH), ciglitazone (5 M), or azPC (1 M) for 24 hours. PGE2 was then quantitated in tissue culture supernatants. The results shown represent the percent inhibition of vehicle or agonist-induced PGE2 formation by GW9662. Mean and SEM. , one-sample t-test. (c) GW9662 treatment inhibits ciglitazone-induced COX-2 mRNA expression. PHKs were treated with vehicle and ciglitazone, with and without GW9662, as detailed in Figure 2(b) above. At 2, 4, 8, and 24 hours, total RNA was isolated and quantitative RT-PCR was performed for COX-2 mRNA and 18S rRNA expression. The results are shown as COX-2 expression normalized to 18S and expressed as a fold change relative to VEH control (assigned a value of 1 for all time points). When data for all time points was analyzed, only ciglitazone-treated cells exhibited a significant induction in COX-2 expression (one-sample t-test, ).