The transcriptional response to a peroxisome proliferator-activated receptor α agonist includes increased expression of proteome maintenance genes

The nuclear receptor peroxisome proliferator-activated receptor α (PPARα), in addition to regulating lipid homeostasis, controls the level of tissue damage after chemical or physical stress. To determine the role of PPARα in oxidative stress responses, we examined damage after exposure to chemicals that increase oxidative stress in wild-type or PPARα-null mice. Primary hepatocytes from wild-type but not PPARα-null mice pretreated with the PPAR pan-agonist WY-14,643 (WY) were protected from damage to cadmium and paraquat. The livers from intact wild-type but not PPARα-null mice were more resistant to damage after carbon tetrachloride treatment. To determine the molecular basis of the protection by PPARα, we identified by transcript profiling genes whose expression was altered by a 7-day exposure to WY in wild-type and PPARα-null mice. Of the 815 genes regulated by WY in wild-type mice (p ≤ 0.001; ≥1.5-fold or ≤-1.5-fold), only two genes were regulated similarly by WY in PPARα-null mice. WY increased expression of stress modifier genes that maintain the health of the proteome, including those that prevent protein aggregation (heat stress-inducible chaperones) and eliminate damaged proteins (proteasome components). Although the induction of proteasomal genes significantly overlapped with those regulated by 1,2-dithiole-3-thione, an activator of oxidant-inducible Nrf2, WY increased expression of proteasomal genes independently of Nrf2. Thus, PPARα controls the vast majority of gene expression changes after exposure to WY in the mouse liver and protects the liver from oxidant-induced damage, possibly through regulation of a distinct set of proteome maintenance genes.