Abstract

2-Arachidonyl glycerol (2-AG) is an endogenous arachidonic acid derivative capable of suppressing interleukin (IL)-2 production by activated T cells. 2-AG-mediated IL-2 suppression is dependent on cyclooxygenase-2 (COX-2) metabolism and peroxisome proliferator activated receptor γ (PPARγ) activation. The objective of the present studies was to examine whether 15-deoxy-Δ^12,14-PGJ₂-glycerol ester (15d-PGJ₂-G), a putative metabolite of 2-AG, can mimic the actions of 2-AG on IL-2 regulation through PPARγ activation. 15d-PGJ₂-G bound PPARγ-ligand binding domain in a PPARγ competitive binding assay. 15d-PGJ₂-G treatment activated PPARγ in a reporter assay, and PPARγ activation was attenuated when a PPARγ antagonist, 2-chloro-5-nitro-N-4-pyridinylbenzamide (T0070907), was present. 15d-PGJ₂-G treatment suppressed IL-2 production by activated Jurkat cells, which was partially attenuated when pretreated with T0070907. Moreover, IL-2 suppression was pronounced when 15d-PGJ₂-G was present 30 min before or after T-cell activation. Concordant with IL-2 suppression, 15d-PGJ₂-G treatment decreased nuclear factor of activated T cells (NFAT) transcriptional activity in transiently transfected Jurkat cells. It is noteworthy that T0070907 alone markedly increased NFAT reporter activity, suggesting the existence of endogenous PPARγ activation and modulation of NFAT. Because COX-2 metabolism of 2-AG is important for IL-2 suppression, the effect of 2-AG on COX-2 and PPARγ mRNA expression was investigated. 2-AG treatment decreased the up-regulation of COX-2 mRNA after T-cell activation, which suggests negative feedback limiting COX-2-mediated metabolism of 2-AG. PPARγ mRNA expression was increased upon activation, and 2-AG treatment produced a modest decrease in PPARγ mRNA expression. Collectively, our findings suggest that 15d-PGJ₂-G activates PPARγ to decrease NFAT transcriptional activity and IL-2 expression in activated T cells.