Robert N. Schuck

Endothelial CYP epoxygenase overexpression and soluble epoxide hydrolase disruption attenuate acute vascular inflammatory responses in mice

Cytochrome P‐450 (CYP)‐derived epoxyei‐cosatrienoic acids (EETs) possess potent anti‐inflammatory effects in vitro. However, the effect of increased CYP‐mediated EET biosynthesis and decreased soluble epoxide hydrolase (sEH, Ephx2)‐mediated EET hydrolysis on vascular inflammation in vivo has not been rigorously investigated. Consequently, we characterized acute vascular inflammatory responses to endotoxin in transgenic mice with endothelial expression of the human CYP2J2 and CYP2C8 epoxygenases and mice with targeted disruption of Ephx2. Compared to wild‐type controls, CYP2J2 transgenic, CYP2C8 transgenic, and Ephx2−/− mice each exhibited a significant attenuation of endotoxin‐induced activation of nuclear factor (NF)‐κB signaling, cellular adhesion molecule, chemokine and cytokine expression, and neutrophil infiltration in lung in vivo. Furthermore, attenuation of endotoxin‐induced NF‐κB activation and cellular adhesion molecule and chemokine expression was observed in primary pulmonary endothelial cells isolated from CYP2J2 and CYP2C8 transgenic mice. This attenuationwas inhibited bya putative EET receptor antagonist and CYP epoxygenase inhibitor, directly implicating CYP epoxygenase‐derived EETs with the observed anti‐inflammatory phenotype. Collectively, these data demonstrate that potentiation of the CYP epoxygenase pathway by either increased endothelial EET biosynthesis or globally decreased EET hydrolysis attenuates NF‐κB‐dependent vascular inflammatory responses in vivo and may serve as a viable anti‐inflammatory therapeutic strategy.—Deng, Y., Edin, M. L., Theken, K N., Schuck, R N., Flake, G. P., Kannon, M. A., DeGraff, L. M., Lih, F. B., Foley, J., Bradbury, J. A., Graves, J. P., Tomer, K. B., Falck, J. R., Zeldin, D. C., Lee, C. R. Endothelial CYP epoxygenase overexpression and soluble epoxide hydrolase disruption attenuate acute vascular inflammatory responses in mice. FASEB J. 25, 703–713 (2011). www.fasebj.org

Evaluation of cytochrome P450-derived eicosanoids in humans with stable atherosclerotic cardiovascular disease

OBJECTIVE Preclinical and genetic epidemiologic studies suggest that modulating cytochrome P450 (CYP)-mediated arachidonic acid metabolism may have therapeutic utility in the management of coronary artery disease (CAD). However, predictors of inter-individual variation in CYP-derived eicosanoid metabolites in CAD patients have not been evaluated to date. Therefore, the primary objective was to identify clinical factors that influence CYP epoxygenase, soluble epoxide hydrolase (sEH), and CYP ω-hydroxylase metabolism in patients with established CAD. METHODS Plasma levels of epoxyeicosatrienoic acids (EETs), dihydroxyeicosatrienoic acids (DHETs), and 20-hydroxyeicosatetraenoic acid (20-HETE) were quantified by HPLC-MS/MS in a population of patients with stable, angiographically confirmed CAD (N=82) and healthy volunteers from the local community (N=36). Predictors of CYP epoxygenase, sEH, and CYP ω-hydroxylase metabolic function were evaluated by regression. RESULTS Obesity was significantly associated with low plasma EET levels and 14,15-EET:14,15-DHET ratios. Age, diabetes, and cigarette smoking also were significantly associated with CYP epoxygenase and sEH metabolic activity, while only renin-angiotensin system inhibitor use was associated with CYP ω-hydroxylase metabolic activity. Compared to healthy volunteers, both obese and non-obese CAD patients had significantly higher plasma EETs (P<0.01) and epoxide:diol ratios (P<0.01), whereas no difference in 20-HETE levels was observed (P=NS). CONCLUSIONS Collectively, these findings suggest that CYP-mediated eicosanoid metabolism is dysregulated in certain subsets of CAD patients, and demonstrate that biomarkers of CYP epoxygenase and sEH, but not CYP ω-hydroxylase, metabolism are altered in stable CAD patients relative to healthy individuals. Future studies are necessary to determine the therapeutic utility of modulating these pathways in patients with CAD.

Genetic Variation in Soluble Epoxide Hydrolase (EPHX2) Is Associated With Forearm Vasodilator Responses in Humans

Cytochrome P450-derived epoxyeicosatrienoic acids are potent vasodilators in preclinical models and are hydrolyzed by soluble epoxide hydrolase (EPHX2). Associations between the EPHX2 Lys55Arg and Arg287Gln polymorphisms and cardiovascular disease risk have been reported; however, their impact on vascular function in humans has not been investigated. In 265 volunteers (198 white, 67 black American), forearm blood flow was measured by strain-gauge venous occlusion plethysmography at baseline and in response to bradykinin, methacholine, and sodium nitroprusside. Forearm vascular resistance was calculated as mean arterial pressure/forearm blood flow. In white Americans, Lys55Arg genotype was associated with vasodilator response to bradykinin, such that forearm blood flow was significantly lower (P=0.043) and forearm vascular resistance was significantly higher (P=0.013) in Arg55 variant allele carriers compared to wild-type individuals. Significant associations were also observed with methacholine and sodium nitroprusside. In contrast, no relationship was observed in black Americans. In black Americans, Arg287Gln genotype was associated with vasodilator response to bradykinin. Although the difference in forearm blood flow did not reach statistical significance (P=0.058), forearm vascular resistance was significantly lower (P=0.037) in Gln287 variant allele carriers compared to wild-type individuals. Significant associations were also observed with methacholine and sodium nitroprusside. In white Americans, Gln287 variant allele carriers did not exhibit significantly higher forearm blood flow (P=0.128) or lower forearm vascular resistance (P=0.080). Genetic variation in EPHX2 is associated with forearm vasodilator responses in a bradykinin receptor- and endothelium-independent manner, suggesting an important role for soluble epoxide hydrolase in the regulation of vascular function in humans.

Functional characterization of cytochrome P450-derived epoxyeicosatrienoic acids in adipogenesis and obesity

Adipogenesis plays a critical role in the initiation and progression of obesity. Although cytochrome P450 (CYP)-derived epoxyeicosatrienoic acids (EETs) have emerged as a potential therapeutic target for cardiometabolic disease, the functional contribution of EETs to adipogenesis and the pathogenesis of obesity remain poorly understood. Our studies demonstrated that induction of adipogenesis in differentiated 3T3-L1 cells (in vitro) and obesity-associated adipose expansion in high-fat diet (HFD)-fed mice (in vivo) significantly dysregulate the CYP epoxygenase pathway and evoke a marked suppression of adipose-derived EET levels. Subsequent in vitro experiments demonstrated that exogenous EET analog administration elicits potent anti-adipogenic effects via inhibition of the early phase of adipogenesis. Furthermore, EET analog administration to mice significantly mitigated HFD-induced weight gain, adipose tissue expansion, pro-adipogenic gene expression, and glucose intolerance. Collectively, these findings suggest that suppression of EET bioavailability in adipose tissue is a key pathological consequence of obesity, and strategies that promote the protective effects of EETs in adipose tissue offer enormous therapeutic potential for obesity and its downstream pathological consequences.

The Cytochrome P450 Epoxygenase Pathway Regulates the Hepatic Inflammatory Response in Fatty Liver Disease

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.

Enalapril reverses high-fat diet-induced alterations in cytochrome P450-mediated eicosanoid metabolism.

Metabolism of arachidonic acid by cytochrome P450 (CYP) to biologically active eicosanoids has been recognized increasingly as an integral mediator in the pathogenesis of cardiovascular and metabolic disease. CYP epoxygenase-derived epoxyeicosatrienoic and dihydroxyeicosatrienoic acids (EET + DHET) and CYP ω-hydroxylase-derived 20-hydroxyeicosatetraenoic acid (20-HETE) exhibit divergent effects in the regulation of vascular tone and inflammation; thus, alterations in the functional balance between these parallel pathways in liver and kidney may contribute to the pathogenesis and progression of metabolic syndrome. However, the impact of metabolic dysfunction on CYP-mediated formation of endogenous eicosanoids has not been well characterized. Therefore, we evaluated CYP epoxygenase (EET + DHET) and ω-hydroxylase (20-HETE) metabolic activity in liver and kidney in apoE(-/-) and wild-type mice fed a high-fat diet, which promoted weight gain and increased plasma insulin levels significantly. Hepatic CYP epoxygenase metabolic activity was significantly suppressed, whereas renal CYP ω-hydroxylase metabolic activity was induced significantly in high-fat diet-fed mice regardless of genotype, resulting in a significantly higher 20-HETE/EET + DHET formation rate ratio in both tissues. Treatment with enalapril, but not metformin or losartan, reversed the suppression of hepatic CYP epoxygenase metabolic activity and induction of renal CYP ω-hydroxylase metabolic activity, thereby restoring the functional balance between the pathways. Collectively, these findings suggest that the kinin-kallikrein system and angiotensin II type 2 receptor are key regulators of hepatic and renal CYP-mediated eicosanoid metabolism in the presence of metabolic syndrome. Future studies delineating the underlying mechanisms and evaluating the therapeutic potential of modulating CYP-derived EETs and 20-HETE in metabolic diseases are warranted.

Beyond statins: lipid management to reduce cardiovascular risk.

The discovery that elevated total cholesterol levels and the subsequent understanding that low‐density lipoprotein cholesterol levels are associated with higher risk for cardiovascular disease (CVD) has led to the development of lipid management strategies that seek to reduce the burden of CVD. Although substantive progress has been made in reducing death and cardiovascular events, questions remain regarding the optimal approach to further reduce CVD‐associated death and disability. Based on current evidence, statins are the clear first‐line agents for the management of hyperlipidemia in patients at high risk for cardiovascular events. However, due to the failure of recent clinical trials evaluating antihyperlipidemic drugs, the most appropriate lipid management strategy in patients who cannot tolerate statin therapy or who warrant antihyperlipidemic therapies in addition to statins is a major therapeutic controversy. In this review, we summarize the clinical trial evidence evaluating the efficacy of second‐line antihyperlipidemic drug classes for reducing cardiovascular risk, provide recommendations for appropriate use of nonstatin lipid‐altering drugs, and identify key areas of future research to support evidence‐based lipid management. Given the complexity, magnitude, and burden of CVD, opportunities to improve processes of care and identify new therapeutic options clearly exist.

Dual modulation of cyclooxygenase and CYP epoxygenase metabolism and acute vascular inflammation in mice

Cyclooxygenase (COX)-derived prostaglandins and cytochrome P450 (CYP) epoxygenase-derived epoxyeicosatrienoic acids are important regulators of inflammation; however, functional interactions between these pathways in the regulation of vascular inflammation in vivo have not been studied. We investigated the relative and additive effects of endothelial CYP2J2 overexpression (Tie2-CYP2J2-Tr), global sEH disruption (Ephx2(-/-)), and pharmacologic COX inhibition with indomethacin on the acute vascular inflammatory response to endotoxin in mice. Compared to vehicle-treated wild-type C57BL/6 controls, induction of myeloperoxidase (MPO) activity in lung and liver was similarly attenuated in Tie2-CYP2J2-Tr mice, Ephx2(-/-) mice and wild-type mice treated with moderate dose indomethacin. Dual modulation of both pathways, however, did not produce an additive anti-inflammatory effect. These findings demonstrate that both COX and CYP epoxygenase-mediated eicosanoid metabolism are important regulators of the acute vascular inflammatory response in vivo, and suggest that the anti-inflammatory effects of modulating each pathway may be mediated, at least in part, by overlapping mechanisms.

Urinary 11-dehydro-thromboxane B2 Levels are Associated with Vascular Inflammation and Prognosis in Atherosclerotic Cardiovascular Disease

Cyclooxygenase-derived thromboxane (TxA2) and prostacyclin (PGI2) regulate atherogenesis in preclinical models. However, the relationship between TxA2 and PGI2 biosynthesis, vascular inflammation, and atherosclerotic cardiovascular disease (ASCVD) progression in humans remains unclear. The association between stable urine metabolites of thromboxane (TxA2-M) and prostacyclin (PGI2-M), circulating levels of cellular adhesion molecules (CAMs: E-selectin, P-selectin), chemokines and C-reactive protein, and the incidence of major adverse cardiovascular events (MACE) were evaluated in 120 patients with stable ASCVD on aspirin therapy. Urinary TxA2-M levels were significantly correlated with circulating P-selectin (r=0.319, p<0.001) and E-selectin (r=0.245, p=0.007) levels, and associated with higher risk of MACE (p=0.043). In contrast, PGI2-M levels were not significantly associated with CAM levels or MACE. These results provide insight into the contribution of TxA2 biosynthesis to ASCVD progression in humans, and suggest that patients with elevated TxA2-M levels may be predisposed to advanced platelet and endothelial activation and higher risk of adverse cardiovascular outcomes.

Clinical Evidence Supports a Protective Role for CXCL5 in Coronary Artery Disease

Our goal was to measure the association of CXCL5 and molecular phenotypes associated with coronary atherosclerosis severity in patients at least 65 years old. CXCL5 is classically defined as a proinflammatory chemokine, but its role in chronic inflammatory diseases, such as coronary atherosclerosis, is not well defined. We enrolled individuals who were at least 65 years old and undergoing diagnostic cardiac catheterization. Coronary artery disease (CAD) severity was quantified in each subject via coronary angiography by calculating a CAD score. Circulating CXCL5 levels were measured from plasma, and both DNA genotyping and mRNA expression levels in peripheral blood mononuclear cells were quantified via microarray gene chips. We observed a negative association of CXCL5 levels with CAD at an odds ratio (OR) of 0.46 (95% CI, 0.27-0.75). Controlling for covariates, including sex, statin use, hypertension, hyperlipidemia, obesity, self-reported race, smoking, and diabetes, the OR was not significantly affected [OR, 0.54 (95% CI, 0.31-0.96)], consistent with a protective role for CXCL5 in coronary atherosclerosis. We also identified 18 genomic regions with expression quantitative trait loci of genes correlated with both CAD severity and circulating CXCL5 levels. Our clinical findings are consistent with the emerging link between chemokines and atherosclerosis and suggest new therapeutic targets for CAD.