Enhancing cancer immunotherapy via inhibition of soluble epoxide hydrolase.

Cancer therapy, including immunotherapy, is inherently limited by chronic inflammation-induced tumorigenesis and toxicity within the tumor microenvironment. Thus, stimulating the resolution of inflammation may enhance immunotherapy and improve the toxicity of immune checkpoint inhibition (ICI). As epoxy-fatty acids (EpFAs) are degraded by the enzyme soluble epoxide hydrolase (sEH), the inhibition of sEH increases endogenous EpFA levels to promote the resolution of cancer-associated inflammation. Here, we demonstrate that systemic treatment with ICI induces sEH expression in multiple murine cancer models. Dietary omega-3 polyunsaturated fatty acid supplementation and pharmacologic sEH inhibition, both alone and in combination, significantly enhance anti-tumor activity of ICI in these models. Notably, pharmacological abrogation of the sEH pathway alone or in combination with ICI counter-regulates an ICI-induced pro-inflammatory and pro-tumorigenic cytokine storm. Thus, modulating endogenous EpFA levels through dietary supplementation or sEH inhibition may represent a unique strategy to enhance the anti-tumor activity of paradigm cancer therapies.

Eicosanoid lipidome activation in post-mortem brain tissues of individuals with APOE4 and Alzheimer's dementia.

BACKGROUND: Chronic neuroinflammation is one of the hallmarks of late-onset Alzheimer's disease (AD) dementia pathogenesis. Carrying the apolipoprotein ε4 (APOE4) allele has been associated with an accentuated response to brain inflammation and increases the risk of AD dementia progression. Among inflammation signaling pathways, aberrant eicosanoid activation plays a prominent role in neurodegeneration. METHODS: Using brains from the Religious Order Study (ROS), this study compared measures of brain eicosanoid lipidome in older persons with AD dementia to age-matched controls with no cognitive impairment (NCI), stratified by APOE genotype. RESULTS: Lipidomic analysis of the dorsolateral prefrontal cortex demonstrated lower levels of omega-3 fatty acids eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and DHA-derived neuroprotectin D1 (NPD-1) in persons with AD dementia, all of which associated with lower measures of cognitive function. A significant interaction was observed between carrying the APOE4 allele and higher levels of both pro-inflammatory lipids and pro-resolving eicosanoid lipids on measures of cognitive performance and on neuritic plaque burden. Furthermore, analysis of lipid metabolism pathways implicated activation of calcium-dependent phospholipase A2 (cPLA2), 5-lipoxygenase (5-LOX), and soluble epoxide hydrolase (sEH) enzymes. CONCLUSION: These findings implicate activation of the eicosanoid lipidome in the chronic unresolved state of inflammation in AD dementia, which is increased in carriers of the APOE4 allele, and identify potential therapeutic targets for resolving this chronic inflammatory state.

[Fatty acid epoxides in the regulation of the inflammation]. / Époksidy polinenasyshchennykh zhirnykh kislot v reguliatsii vospaleniia.

Cyclooxygenase and lipoxygenase derived lipid metabolites of polyunsaturated fatty acids (PUFAs), as well as their role in the inflammation, have been studied quite thoroughly. However, cytochrome P450 derived lipid mediators, as well as their participation in the regulation of the inflammation, need deeper understanding. In recent years, it has become known that PUFAs are oxidized by cytochrome P450 epoxygenases to epoxy fatty acids, which act as the extremely powerful lipid mediators involved in resolving inflammation. Recent studies have shown that the anti-inflammatory mechanisms of ω-3 PUFAs are also mediated by their conversion to the endocannabinoid epoxides. Thus, it is clear that a number of therapeutically relevant functions of PUFAs are due to their conversion to PUFA epoxides. However, with the participation of cytochrome P450 epoxygenases, not only PUFA epoxides, but also other metabolites are formed. They are further are converted by epoxide hydrolases into pro-inflammatory dihydroxy fatty acids and anti-inflammatory dihydroxyeicosatrienoic acids. The study of the role of PUFA epoxides in the regulation of the inflammation and pharmacological modeling of the activity of epoxide hydrolases are the promising strategies for the treatment of the inflammatory diseases. This review systematizes the current literature data of the fatty acid epoxides, in particular, the endocannabinoid epoxides. Their role in the regulation of inflammation is discussed.

Bisfischoids A and B, dimeric ent-abietane-type diterpenoids with anti-inflammatory potential from Euphorbia fischeriana Steud.

Two undescribed ent-abietane-type diterpenoid dimers with nonacyclic backbone formed by intermolecular [4 + 2] cycloaddition into a spirocyclic skeleton, bisfischoids A (1) and B (2), along with a known one fischdiabietane A (3), were identified from Euphorbia fischeriana Steud. Their structures were elucidated by extensive spectroscopic analysis, ECD and NMR calculation combined with DP4+ probability analysis, as well as X-ray diffraction. The anti-inflammatory potential of dimers 1-3 were examined using their inhibitory effects on soluble epoxide hydrolase (sEH), which revealed that 1 and 2 exhibited promising activities with inhibition constant (Ki) of 3.20 and 1.95 µM, respectively. Further studies of molecular docking and molecular dynamics indicated that amino acid residue Tyr343 in the catalytic cavity of sEH was the key site for their inhibitory function.

Relative Importance of Soluble and Microsomal Epoxide Hydrolases for the Hydrolysis of Epoxy-Fatty Acids in Human Tissues.

Epoxy-fatty acids (EpFAs) are endogenous lipid mediators that have a large breadth of biological activities, including the regulation of blood pressure, inflammation, angiogenesis, and pain perception. For the past 20 years, soluble epoxide hydrolase (sEH) has been recognized as the primary enzyme for degrading EpFAs in vivo. The sEH converts EpFAs to the generally less biologically active 1,2-diols, which are quickly eliminated from the body. Thus, inhibitors of sEH are being developed as potential drug therapeutics for various diseases including neuropathic pain. Recent findings suggest that other epoxide hydrolases (EHs) such as microsomal epoxide hydrolase (mEH) and epoxide hydrolase-3 (EH3) can contribute significantly to the in vivo metabolism of EpFAs. In this study, we used two complementary approaches to probe the relative importance of sEH, mEH, and EH3 in 15 human tissue extracts: hydrolysis of 14,15-EET and 13,14-EDP using selective inhibitors and protein quantification. The sEH hydrolyzed the majority of EpFAs in all of the tissues investigated, mEH hydrolyzed a significant portion of EpFAs in several tissues, whereas no significant role in EpFAs metabolism was observed for EH3. Our findings indicate that residual mEH activity could limit the therapeutic efficacy of sEH inhibition in certain organs.

Inhibition of soluble epoxide hydrolase by phytochemical constituents of the root bark of Ulmus davidiana var. japonica.

A novel compound 1 and nine known compounds (2-10) were isolated by open column chromatography analysis of the root bark of Ulmus davidiana. Pure compounds (1-10) were tested in vitro to determine the inhibitory activity of the catalytic reaction of soluble epoxide hydrolase (sEH). Compounds 1, 2, 4, 6-8, and 10 had IC50 values ranging from 11.4 ± 2.3 to 36.9 ± 2.6 µM. We used molecular docking to simulate inhibitor binding of each compound and estimated the binding pose of the catalytic site of sEH. From this analysis, the compound 2 was revealed to be a potential inhibitor of sEH in vitro and in silico. Additionally, molecular dynamics (MD) study was performed to find detailed interaction signals of inhibitor 2 with enzyme. Finally, compound 2 is promising candidates for the development of a new sEH inhibitor from natural plants.

Fractions of Boswellia Serrata Suppress LTA4, LTC4, Cyclooxygenase-2 Activities and mRNA in HL-60 Cells and Reduce Lung Inflammation in BALB/c Mice.

BACKGROUND: Purified fractions from a Boswellia serrata Roxb. Ex. Colebr. (Burseraceae) extract (ETOH and DCM) contain biologically active compounds that are well known for having inflammation inhibitory properties. In this work, the purified fractions were tested in-vitro for LTC4, LTA4 and COX-2 activities using ELISA and qPCR was performed to determine gene regulation in human leukemia (HL-60) Cells. Two D-imaging tomography was performed to determine the anti-inflammatory activities of the fractions in BALB/c mouse model of lung inflammation. OBJECTIVE: To evaluate anti-inflammatory activities of bioactive compounds of Boswellia serrata purified fractions. METHODS: In-vitro MTT assay was performed in HL-60 cell lines for measuring the toxicity/ viability of the cells. ELISA tests were performed for evaluating LTA4, LTC4 and COX-2 activities. qPCR was performed to evaluate the expression of mRNA in HL-60 cells. In-vivo experiments were performed in OVA sensitized and challenged BALB/c mice at two doses of Boswellia serrata purified fraction containing 6% Boswellic acid of 50 and 100mg/kg body weight were given orally and the standard drug dexamethasone (DXA, 4 mg/kg body weight) and reduction in lung inflammation was assessed by using an IVIS Xenogen in-vivo fluorescence imaging system. RESULTS: A purified fraction of Boswellia serrata ETOH extracts reduced leukotriene-C4-synthase activity by 52%, leuktotriene-A4-hydrolase activity by 22% and COX-2 activity by 99% with an IC50 of 12.5µg/ml. Intragastric administration of the purified fraction of Boswellia serrata at two doses of 50mg/kg b.w. and 100mg/kg b.w., respectively along with 2-3% HPMC resulted in a ~51% (P value <0.01) reduction in OVA induced lung inflammation in BALB/c mice as observed by imaging tomography. Treatment of the OVA challenged mice with standard drug dexamethasone (DXA) reduced inflammation by ~66% with significant value (P<0.0001). CONCLUSION: The present study describes that Boswellia serrata ethanolic extracts purified fraction (ETOH-BS) possess significant anti-inflammatory activities in HL-60 and in BALB/c and further supports for its use as Ayurvedic medicines traditionally in the treatment of lung disorders including allergy and asthma.

Soluble Epoxide Hydrolase Hepatic Deficiency Ameliorates Alcohol-Associated Liver Disease.

BACKGROUND & AIMS: Alcohol-associated liver disease (ALD) is a significant cause of liver-related morbidity and mortality worldwide and with limited therapies. Soluble epoxide hydrolase (sEH; Ephx2) is a largely cytosolic enzyme that is highly expressed in the liver and is implicated in hepatic function, but its role in ALD is mostly unexplored. METHODS: To decipher the role of hepatic sEH in ALD, we generated mice with liver-specific sEH disruption (Alb-Cre; Ephx2fl/fl). Alb-Cre; Ephx2fl/fl and control (Ephx2fl/fl) mice were subjected to an ethanol challenge using the chronic plus binge model of ALD and hepatic injury, inflammation, and steatosis were evaluated under pair-fed and ethanol-fed states. In addition, we investigated the capacity of pharmacologic inhibition of sEH in the chronic plus binge mouse model. RESULTS: We observed an increase of hepatic sEH in mice upon ethanol consumption, suggesting that dysregulated hepatic sEH expression might be involved in ALD. Alb-Cre; Ephx2fl/fl mice presented efficient deletion of hepatic sEH with corresponding attenuation in sEH activity and alteration in the lipid epoxide/diol ratio. Consistently, hepatic sEH deficiency ameliorated ethanol-induced hepatic injury, inflammation, and steatosis. In addition, targeted metabolomics identified lipid mediators that were impacted significantly by hepatic sEH deficiency. Moreover, hepatic sEH deficiency was associated with a significant attenuation of ethanol-induced hepatic endoplasmic reticulum and oxidative stress. Notably, pharmacologic inhibition of sEH recapitulated the effects of hepatic sEH deficiency and abrogated injury, inflammation, and steatosis caused by ethanol feeding. CONCLUSIONS: These findings elucidated a role for sEH in ALD and validated a pharmacologic inhibitor of this enzyme in a preclinical mouse model as a potential therapeutic approach.

Contribution of DHA diols (19,20-DHDP) produced by cytochrome P450s and soluble epoxide hydrolase to the beneficial effects of DHA supplementation in the brains of rotenone-induced rat models of Parkinson's disease.

Docosahexaenoic acid (DHA) has been shown to have neuroprotective effects in Parkinson's disease, but the underlying mechanism has not been fully elucidated. DHA is metabolized to DHA epoxides (EDPs) and hydroxides by cytochrome P450s (P450s), and EDPs are further hydroxylated to the corresponding diols, dihydroxydocosapentaenoic acids (DHDPs) by soluble epoxide hydrolase (sEH). In the present study, we investigated the roles of these DHA metabolites in the beneficial effects of DHA supplementation on a rotenone-induced rat model of Parkinson's disease. Metabolite analysis by LC-MS revealed that CYP2A1, 2C11, 2C13, 2C23, and 2E1 contributed to the formation of EDPs, and these P450s and sEH were expressed in the rat brain. We found that DHA supplementation in rats improved the motor dysfunction induced by rotenone. In addition, DHA reversed the decrease in tyrosine hydroxylase and the increase in lipid peroxidation generated by rotenone in the striatum. DHA supplementation also induced mRNA expression of antioxidant genes, such as sod1 and catalase, and Nrf2 protein expression in the striatum. However, these effects of DHA supplementation were eliminated by cosupplementation with the sEH inhibitor TPPU. Supplementation with DHA increased the amount of 19,20-DHDP in the rat brain, while the amount of EDPs was not significantly increased. In addition, TPPU suppressed the increase in DHDPs and increased EDPs in the brain. In PC12 cells, 19,20-DHDP increased the mRNA levels of sod1 and catalase along with Nrf2 induction. This study suggests that DHA metabolites-DHDPs generated by P450s and sEH-have an important role in improving rotenone-induced Parkinson's disease.

ω-3 Polyunsaturated Fatty Acids on Colonic Inflammation and Colon Cancer: Roles of Lipid-Metabolizing Enzymes Involved.

Substantial human and animal studies support the beneficial effects of ω-3 polyunsaturated fatty acids (PUFAs) on colonic inflammation and colorectal cancer (CRC). However, there are inconsistent results, which have shown that ω-3 PUFAs have no effect or even detrimental effects, making it difficult to effectively implement ω-3 PUFAs for disease prevention. A better understanding of the molecular mechanisms for the anti-inflammatory and anticancer effects of ω-3 PUFAs will help to clarify their potential health-promoting effects, provide a scientific base for cautions for their use, and establish dietary recommendations. In this review, we summarize recent studies of ω-3 PUFAs on colonic inflammation and CRC and discuss the potential roles of ω-3 PUFA-metabolizing enzymes, notably the cytochrome P450 monooxygenases, in mediating the actions of ω-3 PUFAs.

The Antihypertensive Effect of Quercetin in Young Spontaneously Hypertensive Rats; Role of Arachidonic Acid Metabolism.

Hypertension affects almost 50% of the adult American population. Metabolites of arachidonic acid (AA) in the kidney play an important role in blood pressure regulation. The present study investigates the blood pressure-lowering potential of quercetin (QR), a naturally occurring polyphenol, and examines its correlation to the modulation of AA metabolism. Spontaneously hypertensive rats (SHR) were randomly divided into four groups. Treatment groups were administered QR in drinking water at concentrations of 10, 30, and 60 mg/L. Blood pressure was monitored at seven-day intervals. After a total of seven weeks of treatment, rats were killed and kidney tissues were collected to examine the activity of the two major enzymes involved in AA metabolism in the kidney, namely cytochrome P450 (CYP)4A and soluble epoxide hydrolase (sEH). Medium- and high-dose QR resisted the rise in blood pressure observed in the untreated SHR and significantly inhibited the activity of the CYP4A enzyme in renal cortical microsomes. The activity of the sEH enzyme in renal cortical cytosols was significantly inhibited only by the high QR dose. Our data not only demonstrate the antihypertensive effect of QR, but also provide a novel mechanism for its underlying cardioprotective properties.

Assessment of the Effect of Sorafenib on Omega-6 and Omega-3 Epoxyeicosanoid Formation in Patients with Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is a leading cause of cancer death. The multikinase inhibitor sorafenib is widely used for systemic therapy in advanced HCC. Sorafenib might affect epoxyeicosanoids, as it is also a potent inhibitor of the soluble epoxide hydrolase (sEH), which catalyzes the conversion of epoxides derived from long-chain polyunsaturated fatty acids (PUFAs), such as arachidonic acid (AA) and omega-3 docosahexaenoic acid (DHA), into their corresponding diols. Experimental studies with AA-derived epoxyeicosatrienoic acids (EETs) showed that they can promote tumor growth and metastasis, while DHA-derived 19,20-epoxydocosapentaenoic acid (19,20-EDP) was shown to have anti-tumor activity in mice. In this pilot study, we assessed the effect of sorafenib treatment on the presence of lipid mediators, such as EETs, in blood of the patients with HCC using the lipidomics technology. We found a significant increase in 11,12-EET and 14,15-EET levels in HCC patients treated with sorafenib. Furthermore, while not significant in this small sample set, the data presented indicate that sorafenib can also increase the level of omega-3 DHA-derived 19,20-EDP. While the effect on EETs might hamper the anti-tumor effect of sorafenib, we hypothesize that supplementation of DHA in sorafenib-treated HCC patients could increase the level of 19,20-EDP and thereby enhance its anti-tumor effect.

Cytochrome P450 derived epoxidized fatty acids as a therapeutic tool against neuroinflammatory diseases.

Cytochrome P450 (CYP) metabolism of arachidonic acid (ARA) produces epoxy fatty acids (EpFAs) such as epoxyeicosatrienoic acids (EETs) that are known to exert protective effects in inflammatory disorders. Endogenous EpFAs are further metabolized into corresponding diols by the soluble epoxide hydrolase (sEH). Through inhibition of sEH, many studies have demonstrated the cardioprotective and renoprotective effects of EpFAs; however, the role of sEH inhibition in modulating the pathogenesis of neuroinflammatory disorders is less well described. In this review, we discuss the current knowledge surrounding the effects of sEH inhibition and EpFA action in neuroinflammatory disorders such as Parkinson's Disease (PD), stroke, depression, epilepsy, and Alzheimer's Disease (AD), as well as the potential mechanisms that underlie the therapeutic effects of sEH inhibition.

Dual Farnesoid X Receptor/Soluble Epoxide Hydrolase Modulators Derived from Zafirlukast.

The nuclear farnesoid X receptor (FXR) and the enzyme soluble epoxide hydrolase (sEH) are validated molecular targets to treat metabolic disorders such as non-alcoholic steatohepatitis (NASH). Their simultaneous modulation in vivo has demonstrated a triad of anti-NASH effects and thus may generate synergistic efficacy. Here we report dual FXR activators/sEH inhibitors derived from the anti-asthma drug Zafirlukast. Systematic structural optimization of the scaffold has produced favorable dual potency on FXR and sEH while depleting the original cysteinyl leukotriene receptor antagonism of the lead drug. The resulting polypharmacological activity profile holds promise in the treatment of liver-related metabolic diseases.

Soluble epoxide hydrolase promotes astrocyte survival in retinopathy of prematurity.

Polyunsaturated fatty acids such as docosahexaenoic acid (DHA) positively affect the outcome of retinopathy of prematurity (ROP). Given that DHA metabolism by cytochrome P450 and soluble epoxide hydrolase (sEH) enzymes affects retinal angiogenesis and vascular stability, we investigated the role of sEH in a mouse model of ROP. In WT mice, hyperoxia elicited tyrosine nitration and inhibition of sEH and decreased generation of the DHA-derived diol 19,20-dihydroxydocosapentaenoic acid (19,20-DHDP). Correspondingly, in a murine model of ROP, sEH-/- mice developed a larger central avascular zone and peripheral pathological vascular tuft formation than did their WT littermates. Astrocytes were the cells most affected by sEH deletion, and hyperoxia increased astrocyte apoptosis. In rescue experiments, 19,20-DHDP prevented astrocyte loss by targeting the mitochondrial membrane to prevent the hyperoxia-induced dissociation of presenilin-1 and presenilin-1-associated protein to attenuate poly ADP-ribose polymerase activation and mitochondrial DNA damage. Therapeutic intravitreal administration of 19,20-DHDP not only suppressed astrocyte loss, but also reduced pathological vascular tuft formation in sEH-/- mice. Our data indicate that sEH activity is required for mitochondrial integrity and retinal astrocyte survival in ROP. Moreover, 19,20-DHDP may be more effective than DHA as a nutritional supplement for preventing retinopathy in preterm infants.

Oxylipins in triglyceride-rich lipoproteins of dyslipidemic subjects promote endothelial inflammation following a high fat meal.

Elevated triglyceride-rich lipoproteins (TGRL) in circulation is a risk factor for atherosclerosis. TGRL from subjects consuming a high saturated fat test meal elicited a variable inflammatory response in TNFα-stimulated endothelial cells (EC) that correlated strongly with the polyunsaturated fatty acid (PUFA) content. This study investigates how the relative abundance of oxygenated metabolites of PUFA, oxylipins, is altered in TGRL postprandially, and how these changes promote endothelial inflammation. Human aortic EC were stimulated with TNFα and treated with TGRL, isolated from subjects' plasma at fasting and 3.5 hrs postprandial to a test meal high in saturated fat. Endothelial VCAM-1 surface expression stimulated by TNFα provided a readout for atherogenic inflammation. Concentrations of esterified and non-esterified fatty acids and oxylipins in TGRL were quantified by mass spectrometry. Dyslipidemic subjects produced TGRL that increased endothelial VCAM-1 expression by ≥35%, and exhibited impaired fasting lipogenesis activity and a shift in soluble epoxide hydrolase and lipoxygenase activity. Pro-atherogenic TGRL were enriched in eicosapentaenoic acid metabolites and depleted in esterified C18-PUFA-derived diols. Abundance of these metabolites was strongly predictive of VCAM-1 expression. We conclude the altered metabolism in dyslipidemic subjects produces TGRL with a unique oxylipin signature that promotes a pro-atherogenic endothelial phenotype.

Addition of milk fat globule membrane-enriched supplement to a high-fat meal attenuates insulin secretion and induction of soluble epoxide hydrolase gene expression in the postprandial state in overweight and obese subjects.

CVD and associated metabolic diseases are linked to chronic inflammation, which can be modified by diet. The objective of the present study was to determine whether there is a difference in inflammatory markers, blood metabolic and lipid panels and lymphocyte gene expression in response to a high-fat dairy food challenge with or without milk fat globule membrane (MFGM). Participants consumed a dairy product-based meal containing whipping cream (WC) high in saturated fat with or without the addition of MFGM, following a 12 h fasting blood draw. Inflammatory markers including IL-6 and C-reactive protein, lipid and metabolic panels and lymphocyte gene expression fold changes were measured using multiplex assays, clinical laboratory services and TaqMan real-time RT-PCR, respectively. Fold changes in gene expression were determined using the Pfaffl method. Response variables were converted into incremental AUC, tested for differences, and corrected for multiple comparisons. The postprandial insulin response was significantly lower following the meal containing MFGM (P < 0·01). The gene encoding soluble epoxide hydrolase (EPHX2) was shown to be more up-regulated in the absence of MFGM (P = 0·009). Secondary analyses showed that participants with higher baseline cholesterol:HDL-cholesterol ratio (Chol:HDL) had a greater reduction in gene expression of cluster of differentiation 14 (CD14) and lymphotoxin ß receptor (LTBR) with the WC+MFGM meal. The protein and lipid composition of MFGM is thought to be anti-inflammatory. These exploratory analyses suggest that addition of MFGM to a high-saturated fat meal modifies postprandial insulin response and offers a protective role for those individuals with higher baseline Chol:HDL.

A dual farnesoid X receptor/soluble epoxide hydrolase modulator treats non-alcoholic steatohepatitis in mice.

Non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are the most prevalent metabolic liver disorders and a serious global health burden. NAFLD/NASH pathogenesis and progression are highly multi-factorial and likely demand a combination of multiple mechanisms to provide a more effective treatment. We have developed a dual farnesoid X receptor agonist (FXRA)/soluble epoxide hydrolase inhibitor (sEHi) to simultaneously address two validated and complementary modes of action in NASH treatment. Here we report the in vivo profiling for this FXRA/sEHi in toxin- and diet-induced rodent NASH models. In streptozotocin-induced NASH as a proof-of-concept study, the experimental FXRA/sEHi drug robustly prevented hepatic steatosis and fibrosis, and improved lipid homeostasis as well as biochemical markers of liver health. In methionine-choline-deficient high-fat diet-induced NASH, FXRA/sEHi treatment reduced hepatic steatosis and fibrosis to levels similar to healthy animals and demonstrated anti-inflammatory activity confirming that dual FXRA/sEHi modulation produces a triad of complementary anti-NASH effects. Our results validate dual FXRA/sEHi modulation as an effective therapeutic strategy to treat NASH and advocates for a combinational drug therapeutic approach for multifactorial liver diseases.

Effect of Dietary Doses of Quercetin on Hepatic Drug Metabolizing Enzymes in Spontaneously Hypertensive Rats.

BACKGROUND: Administration of quercetin (QR) has shown several health benefits in clinical and pre-clinical studies. OBJECTIVE: This study investigates the effect of dietary doses of QR on hepatic drug metabolizing enzymes in spontaneously hypertensive rats in order to investigate the potential for herb-drug interactions. METHODS: The activity and/or protein expression of selected cytochrome P450 (CYP) enzymes and microsomal epoxide hydrolase were measured in hepatic microsomes using specific probe substrates and/or polyclonal antibodies. Cytosolic fraction was utilized to measure protein level and activity of major antioxidant systems. RESULTS: The doses employed in our study did not cause any significant alterations in the activity and/or protein level of CYP1A1, CYP2A6, CYP2E, and glutathione (GSH). While the activity and apoprotein levels of CYP1A2 and CYP2B1/2 were significantly reduced by the medium and high doses of QR, the activity and/or protein level of microsomal CYP3A and cytosolic GSH-S-transferase, GSH reductase, and GSH peroxidase were significantly enhanced. Activity and protein level of CYP2C9 were significantly inhibited by all doses. Only the high-dose QR resulted in significant inhibition of both microsomal and soluble epoxide hydrolase as well as induction of the antioxidant enzymes, catalase and superoxide dismutase. CONCLUSION: This study demonstrates that dietary doses of QR may offer chemoprevention through stimulation of the endogenous antioxidant systems and inhibition of CYP enzymes involved in bioactivation of procarcinogens. However, modulation of drug metabolizing enzymes by QR could have potential for herb-drug interactions with the possibility of serious complications.

Altered bioavailability of epoxyeicosatrienoic acids is associated with conduit artery endothelial dysfunction in type 2 diabetic patients.

BACKGROUND: This pathophysiological study addressed the hypothesis that soluble epoxide hydrolase (sEH), which metabolizes the vasodilator and anti-inflammatory epoxyeicosatrienoic acids (EETs) to dihydroxyeicosatrienoic acids (DHETs), contributes to conduit artery endothelial dysfunction in type 2 diabetes. METHODS AND RESULTS: Radial artery endothelium-dependent flow-mediated dilatation in response to hand skin heating was reduced in essential hypertensive patients (n = 9) and type 2 diabetic subjects with (n = 19) or without hypertension (n = 10) compared to healthy subjects (n = 36), taking into consideration cardiovascular risk factors, flow stimulus and endothelium-independent dilatation to glyceryl trinitrate. Diabetic patients but not non-diabetic hypertensive subjects displayed elevated whole blood reactive oxygen species levels and loss of NO release during heating, assessed by measuring local plasma nitrite variation. Moreover, plasma levels of EET regioisomers increased during heating in healthy subjects, did not change in hypertensive patients and decreased in diabetic patients. Correlation analysis showed in the overall population that the less NO and EETs bioavailability increases during heating, the more flow-mediated dilatation is reduced. The expression and activity of sEH, measured in isolated peripheral blood mononuclear cells, was elevated in diabetic but not hypertensive patients, leading to increased EETs conversion to DHETs. Finally, hyperglycemic and hyperinsulinemic euglycemic clamps induced a decrease in flow-mediated dilatation in healthy subjects and this was associated with an altered EETs release during heating. CONCLUSIONS: These results demonstrate that an increased EETs degradation by sEH and altered NO bioavailability are associated with conduit artery endothelial dysfunction in type 2 diabetic patients independently from their hypertensive status. The hyperinsulinemic and hyperglycemic state in these patients may contribute to these alterations. Trial registration NCT02311075. Registered December 8, 2014.