Differential Roles of Peroxisome Proliferator-Activated Receptor-α and Receptor-γ on Renal Crystal Formation in Hyperoxaluric Rodents

Peroxisome proliferator-activated receptors (PPARs) and related inflammatory and oxidative molecule expression were investigated in a hyperoxaluric rodent model to evaluate the in vivo efficacy of PPAR agonists in preventing renal crystal formation. PPAR expression was examined in a mouse hyperoxaluria kidney stone model induced by daily intra-abdominal glyoxylate injection. Therapeutic effects of the PPARα agonist fenofibrate and PPARγ agonist pioglitazone were also assessed in a 1% ethylene glycol-induced rat model of hyperoxaluria. Crystal formation, inflammation, cell injury, apoptosis, and oxidative stress were compared to those of vehicle-treated controls. Quantitative reverse transcription-polymerase chain reaction revealed that PPARα and PPARγ expression decrease and increase, respectively, during crystal formation in hyperoxaluric kidneys. In addition, PPARα localized to the cytoplasm of both proximal and distal tubular cells, whereas PPARγ accumulated in the nucleus of proximal tubular cells. Furthermore, renal crystal formation was significantly less prevalent in pioglitazone-treated rats but higher in the fenofibrate-treated and fenofibrate/pioglitazone-cotreated groups compared to controls, thus indicating that pioglitazone, but not fenofibrate, markedly decreased cell inflammation, oxidative stress, and apoptosis. Collectively, the results demonstrated that PPARγ suppressed renal crystal formation via its antioxidative and anti-inflammatory effects; however, the renotoxicity of PPARα may elicit the opposite effect.