Cytochrome P450 Eicosanoids are Activators of Peroxisome Proliferator-Activated Receptor

Cytochrome P450 (P450) eicosanoids regulate vascular tone, renal tubular transport, cellular proliferation, and inflammation. Both the CYP4A -hydroxylases, which catalyze 20-hydroxyeicosatetraenoic acid (20-HETE) formation, and soluble epoxide hydrolase (sEH), which catalyzes epoxyeicosatrienoic acid (EET) degradation to the dihydroxyeicosatrienoic acids (DHETs), are induced upon activation of peroxisome proliferator-activated receptor (PPAR ) by fatty acids and fibrates. In contrast, the CYP2C epoxygenases, which are responsible for EET formation, are repressed after fibrate treatment. We show here that P450 eicosanoids can bind to and activate PPAR and result in the modulation of PPAR target gene expression. In transactivation assays, 14,15-DHET, 11,2-EET, and 20-HETE were potent activators of PPAR . Gel shift assays showed that EETs, DHETs, and 20-HETE induced PPAR -specific binding to its cognate response element. Expression of apolipoprotein A-I was decreased 70% by 20-HETE, whereas apolipoprotein A-II expression was increased up to 3-fold by 11,12-EET, 14,15-DHET, and 20-HETE. In addition, P450 eicosanoids induced CYP4A1, sEH, and CYP2C11 expression, suggesting that they can regulate their own levels. Given that P450 eicosanoids have multiple cardiovascular effects, pharmacological modulation of their formation and/or degradation may yield therapeutic benefits. Eicosanoids generated from arachidonic acid metabolism by cytochrome P450 (P450) enzymes are important autocrine and paracrine factors that have diverse biological functions. P450 eicosanoids are involved in the regulation of vascular tone, renal tubular transport, cardiac contractility, cellular proliferation, and inflammation (Roman, 2002). The major products of P450-catalyzed arachidonic acid metabolism are 19and 20-hydroxyeicosatetraenoic acid (19and 20HETE), and the regioand stereoisomeric epoxyeicosatrienoic acids (EETs) (Roman, 2002). 20-HETE formation is catalyzed by the CYP4A (Nguyen et al., 1999; Wang et al., 1999) and CYP4F (Powell et al., 1998; Xu et al., 2004) family of enzymes, whereas the EETs are products of arachidonic acid metabolism by the CYP2C and CYP2J enzymes (Karara et al., 1993; Wu et al., 1996, 1997). EETs are subsequently metabolized by the soluble epoxide hydrolase (sEH) into dihydroxyeicosatrienoic acids (DHETs) (Zeldin et al., 1993; Yu et al.,