Differential Potencies of Naturally Occurring Regioisomers of Nitrolinoleic Acid in PPARγ Activation

详细信息    查看全文

• 作者：Richard L. Alexander ; Marcus W. Wright ; Michael J. Gorczynski ; Pamela K. Smitherman ; Taro E. Akiyama ; Harold B. Wood ; Joel P. Berger ; S. Bruce King ; Charles S. Morrow
• 刊名：Biochemistry
• 出版年：2009
• 出版时间：January 20, 2009
• 年：2009
• 卷：48
• 期：2
• 页码：492-498
• 全文大小：200K
• 年卷期：v.48,no.2(January 20, 2009)
• ISSN：1520-4995

文摘

Previous studies demonstrated that the naturally occurring electrophile and PPARγ ligand, nitrolinoleic acid (NOb>2b>-LA), exists as a mixture of four regioisomers [Alexander, R. L., et al. (2006) Biochemistry 45, 7889−7896]. We hypothesized that these alternative isomers have distinct bioactivities; therefore, to determine if the regioisomers are quantitatively or qualitatively different with respect to PPARγ activation, NOb>2b>-LA was separated into three fractions which were identified by NMR (13-NOb>2b>-LA, 12-NOb>2b>-LA, and a mixture of 9- and 10-NOb>2b>-LA) and characterized for PPARγ interactions. A competition radioligand binding assay showed that all three NOb>2b>-LA fractions had similar binding affinities for PPARγ (ICb>50b> = 0.41−0.60 μM) that were comparable to that of the pharmaceutical ligand, rosiglitazone (ICb>50b> = 0.25 μM). However, when PPARγ-dependent transcription activation was examined, there were significant differences observed among the NOb>2b>-LA fractions. Each isomer behaved as a partial agonist in this reporter gene assay; however, the 12-NOb>2b> derivative was the most potent with respect to maximum activation of PPARγ and an ECb>50b> of 0.045 μM (compare with the rosiglitazone ECb>50b> of 0.067 μM), while the 13-NOb>2b> and 9- and 10-NOb>2b> derivatives were considerably less effective with ECb>50b> values of 0.41−0.62 μM. We conclude that the regioisomers of NOb>2b>-LA are not functionally equivalent. The 12-NOb>2b> derivative appears to be the most potent in PPARγ-dependent transcription activation, whereas the weaker PPARγ agonists, 13-NOb>2b> and 9- and 10-NOb>2b>, may be relatively more important in signaling via other, PPARγ-independent pathways in which this family of nitrolipid electrophiles is implicated.