The Epoxygenases CYP2J2 Activates the Nuclear Receptor PPARα In Vitro and In Vivo

Abstract

BackgroundPeroxisome proliferator-activated receptors (PPARs) are a family of three (PPARα, -β/δ, and -γ) nuclear receptors. In particular, PPARα is involved in regulation of fatty acid metabolism, cell growth and inflammation. PPARα mediates the cardiac fasting response, increasing fatty acid metabolism, decreasing glucose utilisation, and is the target for the fibrate lipid-lowering class of drugs. However, little is known regarding the endogenous generation of PPAR ligands. CYP2J2 is a lipid metabolising cytochrome P450, which produces anti-inflammatory mediators, and is considered the major epoxygenase in the human heart.Methodology/Principal FindingsExpression of CYP2J2 in vitro results in an activation of PPAR responses with a particular preference for PPARα. The CYP2J2 products 8,9- and 11-12-EET also activate PPARα. In vitro, PPARα activation by its selective ligand induces the PPARα target gene pyruvate dehydrogenase kinase (PDK)4 in cardiac tissue. In vivo, in cardiac-specific CYP2J2 transgenic mice, fasting selectively augments the expression of PDK4.Conclusions/SignificanceOur results establish that CYP2J2 produces PPARα ligands in vitro and in vivo, and suggests that lipid metabolising CYPs are prime candidates for the integration of global lipid changes to transcriptional signalling events.

CYP450-derived oxylipins mediate inflammatory resolution

“…Rodents have expanded CYP2J and CYP2C subfamilies compared with humans, and we found the epoxygenase CYP2C44 (40) along with CYP2J6 and CYP2J9 to be present in all inflammatory exudates tested, although these findings do not rule out contributions from other local stromal or vascular cells. To test the role of epoxygenases, we used the epoxI SKF525A, which we routinely use in our in vitro assays (18)(19)(20)(21)41) and found to have an IC 50 for human CYP2J2 of 1 μM (20). SKF525A is routinely used in vivo within the range of 5-50 mg/kg (42-45) and, although reported as a selective epoxygenase inhibitor, SKF525A had not been examined in the in vivo setting followed by lipidomic analysis to confirm this.…”

“…vascular tone, smooth muscle cell mitogenesis, platelet aggregation, steroidogenesis, and endothelial and vascular smooth muscle cell activation (4,5,7,(17)(18)(19). We recently published that in human monocytes and macrophages, epoxygenases and some of their arachidonic acid products were antiinflammatory through their ability to activate the peroxisome proliferator-activated receptor (PPAR), in particular PPARα (20,21). Overexpression of epoxygenase enzymes CYP2J2 and CYP2C8 or genetic disruption of sEH (sEH −/− ) inhibits LPS-induced pulmonary inflammation (22,23), and sEH −/− mice or treatment with sEH inhibitors is highly effective against inflammatory and neuropathic pain (24)(25)(26)(27).…”

Endogenous Ligands for Nuclear Receptors: Digging Deeper

“…ACOX1 (acyl-CoA oxidase 1) and several dehydrogenases have been implicated in the inactivation of putative PPAR␣ ligands, whereas fatty acid synthase (FAS), 8-, 12-, 15-, and 5-lipoxygenases, and the P450 cytochrome Cyp2J2 have been associated with their synthesis (37)(38)(39)(40).…”

Cytochrome P450-CYP2 Family-Epoxygenase Role in Inflammation and Cancer

“…EETs or CYP2J2 overexpression can prevent TNF-α-induced cardiac cell injury and cardiac dysfunction by inhibiting apoptosis, reducing inflammation, and enhancing PPARγ expression (Zhao, Wang, et al, 2012b). Overexpression of human CYP2J2 in HEK293 cells resulted in a synergistic activation of PPARα, -β/δ, and -γ reporter gene activity, and EETs were able to induce PPARα reporter activity (Wray et al, 2009). In diabetic mice, CYP2J2 expression attenuated the diabetic phenotype and insulin resistance via inhibition of NF-κB and mitogenactivated protein kinase signaling pathways and activation of PPARγ (Li et al, 2015).…”