Transgenic expression of proximal tubule peroxisome proliferator-activated receptor-alpha in mice confers protection during acute kidney injury

Abstract

Our previous studies suggest that peroxisome proliferator-activated receptor-alpha (PPAR alpha) plays a critical role in regulating fatty acid beta-oxidation in kidney tissue and this directly correlated with preservation of kidney morphology and function during acute kidney injury. To further study this, we generated transgenic mice expressing PPAR alpha in the proximal tubule under the control of the promoter of KAP2 (kidney androgen-regulated protein 2). Segment-specific upregulation of PPAR alpha expression by testosterone treatment of female transgenic mice improved kidney function during cisplatin or ischemia-reperfusion-induced acute kidney injury. Ischemia-reperfusion injury or treatment with cisplatin in wild-type mice caused inhibition of fatty-acid oxidation, reduction of mitochondrial genes of oxidative phosphorylation, mitochondrial DNA, fatty-acid metabolism, and the tricarboxylic acid cycle. Similar injury in testosterone-treated transgenic mice resulted in amelioration of these effects. Similarly, there were increases in the levels of 4-hydroxy-2-hexenal-derived lipid peroxidation products in wild-type mice, which were also reduced in the transgenic mice. Similarly, necrosis of the S3 segment was reduced in the two injury models in transgenic mice compared to wild type. Our results suggest proximal tubule PPAR alpha activity serves as a metabolic sensor. Its increased expression without the use of an exogenous PPA R alpha ligand in the transgenic mice is sufficient to protect kidney function and morphology, and to prevent abnormalities in lipid metabolism associated with acute kidney injury. Kidney International (2009) 76, 1049-1062; doi:10.1038/ki.2009.330; published online 26 August 2009