The Cyclopentenone-Type Prostaglandin 15-Deoxy-Δ12,14-Prostaglandin J2 Inhibits CD95 Ligand Gene Expression in T Lymphocytes: Interference with Promoter Activation Via Peroxisome Proliferator-Activated Receptor-γ-Independent Mechanisms

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Abstract
15-Deoxy-Δ12,14-PGJ2 (15d-PGJ2) is a cyclopentenone-type PG endowed with anti-inflammatory properties and produced by different cells, including those of the immune system. 15d-PGJ2 is a natural ligand of the peroxisome proliferator-activated receptor (PPAR)-γ nuclear receptor, but relevant PPARγ-independent actions mediated by this prostanoid have been described. Fas (APO-1/CD95) and its ligand (Fas-L) are cell surface proteins whose interaction activates apoptosis of Fas-expressing targets. In T cells, the Fas-Fas-L system regulates activation-induced cell death and has been implicated in diseases in which lymphocyte homeostasis is compromised. Moreover, several studies have described the pathogenic functions of Fas and Fas-L in vivo, particularly in the induction-progression of organ-specific autoimmune diseases. In this study we describe the effect of 15d-PGJ2 on the activation of the fas-L gene in T lymphocytes. We show that 15d-PGJ2 inhibits fas-L mRNA expression, activation-induced cell death, and fas-L promoter activity by mechanisms independent of PPARγ and mediated by its chemically reactive cyclopentenone moiety. Our data indicate that 15d-PGJ2 may repress fas-L activation by interfering with the expression and/or transcriptional activity of different transcription factors (early growth response types 3 and 1, NF-κB, AP-1, c-Myc, Nur77) whose altered balancing and transactivation may contribute for overall repression of this gene. In addition, the activation/expression of the heat shock response genes HSF-1 and HSP70 is not directly involved in the repression, and the electrophilic molecule cyclopentenone (2-cyclopenten-1-one) may reproduce the effects mediated by 15d-PGJ2. These results suggest that modulation of Fas-L by 15d-PGJ2 in T cells may represent an additional tool to consider for treatment of specific autoimmune and inflammatory disorders.