ABSTRACT:Cytochrome P450 (P450)-mediated metabolism of arachidonic acid regulates inflammation in hepatic and extrahepatic tissue. CYP2C/ CYP2J-derived epoxyeicosatrienoic and dihydroxyeicosatrienoic acids (EET؉DHET) elicit anti-inflammatory effects, whereas CYP4A/ CYP4F-derived 20-hydroxyeicosatetraenoic acid (20-HETE) is proinflammatory. Because the impact of inflammation on P450-mediated formation of endogenous eicosanoids is unclear, we evaluated P450 mRNA levels and P450 epoxygenase (EET؉DHET) and -hydroxylase (20-HETE) metabolic activity in liver, kidney, lung, and heart in mice 3, 6, 24, and 48 h after intraperitoneal lipopolysaccharide (LPS) (1 mg/kg) or saline administration. Hepatic Cyp2c29, Cyp2c44, and Cyp2j5 mRNA levels and EET؉DHET formation were significantly lower 24 and 48 h after LPS administration. Hepatic Cyp4a12a, Cyp4a12b, and Cyp4f13 mRNA levels and 20-HETE formation were also significantly lower at 24 h, but recovered to baseline at 48 h, resulting in a significantly higher 20-HETE/EET؉DHET formation rate ratio compared with that for saline-treated mice. Renal P450 mRNA levels and P450-mediated eicosanoid metabolism were similarly suppressed 24 h after LPS treatment. Pulmonary EET؉DHET formation was lower at all time points after LPS administration, whereas 20-HETE formation was suppressed in a time-dependent manner, with the lowest formation rate observed at 24 h. No differences in EET؉DHET or 20-HETE formation were observed in heart. Collectively, these data demonstrate that acute activation of the innate immune response alters P450 expression and eicosanoid metabolism in mice in an isoform-, tissue-, and time-dependent manner. Further study is necessary to determine whether therapeutic restoration of the functional balance between the P450 epoxygenase and -hydroxylase pathways is an effective anti-inflammatory strategy.

Cyclopentenone prostaglandins (CyPGs), such as 15-deoxy-Δ 12,14 -prostaglandin J 2 (15d-PGJ 2 ), are active prostaglandin metabolites exerting a variety of biological effects that may be important in the pathogenesis of neurological diseases. Ubiquitin-C-terminal hydrolase L1 (UCH-L1) is a brain specific deubiquitinating enzyme whose aberrant function has been linked to neurodegenerative disorders. We report that [15d-PGJ 2 ] detected by quadrapole mass spectrometry (MS) increases in rat brain after temporary focal ischemia, and that treatment with 15d-PGJ 2 induces accumulation of ubiquitinated proteins and exacerbates cell death in normoxic and hypoxic primary neurons. 15d-PGJ 2 covalently modifies UCH-L1 and inhibits its hydrolase activity. Pharmacologic inhibition of UCH-L1 exacerbates hypoxic neuronal death while transduction with a TAT-UCH-L1 fusion protein protects neurons from hypoxia. These studies indicate UCH-L1 function is important in hypoxic neuronal death and excessive production of CyPGs after stroke may exacerbate ischemic injury by modification and inhibition of UCH-L1.

Fatty liver disease is an emerging public health problem without effective therapies, and chronic hepatic inflammation is a key pathologic mediator in its progression. Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid to biologically active epoxyeicosatrienoic acids (EETs), which have potent anti-inflammatory effects. Although promoting the effects of EETs elicits anti-inflammatory and protective effects in the cardiovascular system, the contribution of CYP-derived EETs to the regulation of fatty liver disease-associated inflammation and injury is unknown. Using the atherogenic diet model of non-alcoholic fatty liver disease/non-alcoholic steatohepatitis (NAFLD/NASH), our studies demonstrated that induction of fatty liver disease significantly and preferentially suppresses hepatic CYP epoxygenase expression and activity, and both hepatic and circulating levels of EETs in mice. Furthermore, mice with targeted disruption of Ephx2 (the gene encoding soluble epoxide hydrolase) exhibited restored hepatic and circulating EET levels and a significantly attenuated induction of hepatic inflammation and injury. Collectively, these data suggest that suppression of hepatic CYP-mediated EET biosynthesis is an important pathological consequence of fatty liver disease-associated inflammation, and that the CYP epoxygenase pathway is a central regulator of the hepatic inflammatory response in NAFLD/NASH. Future studies investigating the utility of therapeutic strategies that promote the effects of CYP-derived EETs in NAFLD/NASH are warranted.

The cyclopentenone prostaglandin (CyPG) J2 series, including prostaglandin J2 (PGJ2), Δ12-PGJ2 and 15-deoxy-Δ12, 14 -prostaglandin J2 (15d-PGJ2), are active metabolites of PGD2, exerting multiple effects on neuronal function. However, the physiologic relevance of these effects remains uncertain as brain concentrations of CyPGs have not been precisely determined. In this study, we found that free PGD2 and the J2 series CyPGs (PGJ2, Δ12-PGJ2 and 15d-PGJ2) were increased in post-ischemic rat brain as detected by UPLC-MS/MS with 15d-PGJ2 being the most abundant CyPG. These increases were attenuated by pre-treating with the cyclooxygenase inhibitor piroxicam. Next, effects of chronic exposure to 15d-PGJ2 were examined by treating primary neurons with 15d-PGJ2, CAY10410 (a 15d-PGJ2 analog lacking the cyclopentenone ring structure), or vehicle for 24 h to 96 h. Because we found that the concentration of free 15d-PGJ2 decreased rapidly in cell culture medium, freshly prepared medium containing 15d-PGJ2, CAY10410 or vehicle was changed twice daily to maintain steady extracellular concentrations. Incubation with 2.5 μM 15d-PGJ2, but not CAY10410, increased neuronal cell death without induction of caspase-3 or PARP cleavage, consistent with a primarily necrotic mechanism for 15d-PGJ2-induced cell death which was further supported by TUNEL assay results. Ubiquitinated protein accumulation and aggregation was observed after 96 h 15d-PGJ2 incubation, accompanied by compromised 20S proteasome activity. Unlike another proteasome inhibitor, MG132, 15d-PGJ2 treatment did not activate autophagy or induce aggresome formation. Therefore, the cumulative cytotoxic effects of increased generation of CyPGs after stroke may contribute to delayed post-ischemic neuronal injury.