Endogenous Epoxygenases Are Modulators of Monocyte/Macrophage Activity

Abstract

BackgroundArachidonic acid is metabolized through three major metabolic pathways, the cyclooxygenase, lipoxygenase and CYP450 enzyme systems. Unlike cyclooxygenase and lipoxygenases, the role of CYP450 epoxygenases in monocyte/macrophage-mediated responses is not known.Methodology/Principal FindingsWhen transfected in vitro, CYP2J2 is an efficient activator of anti-inflammatory pathways through the nuclear receptor peroxisome proliferator-activated receptor (PPAR) α. Human monocytes and macrophages contain PPARα and here we show they express the epoxygenases CYP2J2 and CYP2C8. Inhibition of constitutive monocyte epoxygenases using the epoxygenase inhibitor SKF525A induces cyclooxygenase (COX)-2 expression and activity, and the release of TNFα, and can be reversed by either add back of the endogenous epoxygenase products and PPARα ligand 11,12- epoxyeicosatrienoic acid (EET) or the addition of the selective synthetic PPARα ligand GW7647. In alternatively activated (IL-4-treated) monocytes, in contrast to classically activated cells, epoxygenase inhibition decreased TNFα release. Epoxygenases can be pro-inflammatory via superoxide anion production. The suppression of TNFα by SKF525A in the presence of IL-4 was associated with a reduction in superoxide anion generation and reproduced by the superoxide dismutase MnCl2. Similar to these acute activation studies, in monocyte derived macrophages, epoxygenase inhibition elevates M1 macrophage TNFα mRNA and further decreases M2 macrophage TNFα.Conclusions/SignificanceIn conclusion, epoxygenase activity represents an important endogenous pathway which limits monocyte activation. Moreover endogenous epoxygenases are immuno-modulators regulating monocyte/macrophage activation depending on the underlying activation state.

CYP2J2 overexpression increases EETs and protects against angiotensin II-induced abdominal aortic aneurysm in mice

“…Recent studies have demonstrated that EETs suppress the infl ammatory response in vitro and in vivo ( 5,40,41 ), and we recently reported that CYP2J2 overexpression reduced infl ammatory responses and protected against heart and renal injury ( 12,19 ). Consistent with a previous study of the s-EH inhibitor ( 14 ), our work demonstrates that CYP2J2 overexpression has a substantial inhibitory effect on vascular infl ammation, which is considered to be the major mechanism of Ang II-induced AAA development ( 4,20 ).…”

CYP450-derived oxylipins mediate inflammatory resolution

“…3H). These results are consistent with our previous findings, which reported an antiinflammatory role of epoxygenases in classically activated human monocytes and macrophages in vitro (21). (31).…”

“…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).…”

The Pharmacology of the Cytochrome P450 Epoxygenase/Soluble Epoxide Hydrolase Axis in the Vasculature and Cardiovascular Disease

“…Despite the fact that monocytes are an integral part of the inflammatory response and the COX and LOX pathways have been extensively studied in these cells, little is known about the ability of monocytederived macrophages to generate fatty acid epoxides. CYP2J2 and CYP2C8 were identified as EET-generating P450 enzymes in monocytes/macrophages (Nakayama et al, 2008;Bystrom et al, 2011), but whether these are the most relevant enzymes remains unclear, as does the biologic consequences of P450 activation. Certainly, the characteristics of the two enzymes are such that different biologic reactions would be expected after activation.…”