ABSTRACT: Among the eight stereoisomers of phytanic acid (PA), the 3RS, 7R, 11R-isomer is naturally occurring and is present in foods and the human body. PA is considered to have possible health benefits in the immune system. However, it remains undetermined whether these effects are elicited by the 3RS, 7R, 11R-PA isomer, because previous studies used a commercially available PA whose isomer configuration is unknown. In this study, we synthesized a preparation of 3RS, 7R, 11R-PA, and investigated its in vitro immunomodulatory effects, especially the T-cell production of interferon (IFN)-?, which is associated with various autoimmune diseases. This study also investigated the effects of 3RS, 7R, 11R-PA on NF-?B activity in order to address the mechanism of its immunomodulatory effects.Mouse splenocytes and purified T-cells were stimulated with T-cell mitogens and incubated with 3RS, 7R, 11R-PA, followed by evaluation of IFN-? production. The effect of 3RS, 7R, 11R-PA on NF-?B activity was also investigated using an A549 cell line with stable expression of an NF-?B-dependent luciferase reporter gene.3RS, 7R, 11R-PA significantly reduced in vitro IFN-? production at both the protein and mRNA levels, and was accompanied by decreased expression of T-bet, a key regulator of Th1 cell differentiation. The results indicated that NF-?B-mediated transcriptional activity was significantly decreased by 3RS, 7R, 11R-PA and that GW6471, an antagonist of peroxisome proliferator activated receptor ? (PPAR?), abrogated the inhibitory effect of 3RS, 7R, 11R-PA on NF-?B activity.The present study suggests that 3RS, 7R, 11R-PA is a functional and bioactive fatty acid, and has a potentially beneficial effect for amelioration of T-cell mediated autoimmune diseases. This study also indicates that interference in the NF-?B pathway via PPAR? activation is a potential mechanism of the immunomodulatory effects of 3RS, 7R, 11R-PA.
