Differential modulation of PPARα and γ target gene expression in the liver and kidney of rats treated with aspirin

Aspirin modified peroxisomal enzymatic activities both in the liver and renal cortex of rats, producing typical effects of peroxisomal proliferators (PPs). Although similar increments in β-oxidation system and catalase activities were observed in both organs, induction of mRNA-Cyp4a10 and mRNA-FAT/CD36, target genes for peroxisome proliferator-activated receptors α (PPARα) and γ (PPARγ), respectively, was only present in the liver. There was no effect on liver mRNA-PPARα, while mRNA-PPARγ was down-regulated, probably as a result of enzymatic inhibition of cyclooxygenases (COXs) by aspirin which has been shown to decrease the levels of PGJ2 and its metabolites, known as strong endogenous ligands for PPARγ. Typical PP alterations in cell replication and apoptosis were not found during aspirin treatment or after withdrawal, suggesting that peroxisome proliferation occurs without inducing cell cycle alterations. Probably, the synergic action of both PPARα and PPARγ receptors might reduce the impact on cell proliferation and apoptosis.