Epoxyeicosatrienoic acids protect rat hearts against tumor necrosis factor-α-induced injury

Emerging Roles and Therapeutic Applications of Arachidonic Acid Pathways in Cardiometabolic Diseases

Cardiometabolic disease has become a major health burden worldwide, with sharply increasing prevalence but highly limited therapeutic interventions. Emerging evidence has revealed that arachidonic acid derivatives and pathway factors link metabolic disorders to cardiovascular risks and intimately participate in the progression and severity of cardiometabolic diseases. In this review, we systemically summarized and updated the biological functions of arachidonic acid pathways in cardiometabolic diseases, mainly focusing on heart failure, hypertension, atherosclerosis, nonalcoholic fatty liver disease, obesity, and diabetes. We further discussed the cellular and molecular mechanisms of arachidonic acid pathway-mediated regulation of cardiometabolic diseases and highlighted the emerging clinical advances to improve these pathological conditions by targeting arachidonic acid metabolites and pathway factors.

Cardioprotective properties of OMT-28, a synthetic analog of omega-3 epoxyeicosanoids

OMT-28 is a metabolically robust small molecule developed to mimic the structure and function of omega-3 epoxyeicosanoids. However, it remained unknown to what extent OMT-28 also shares the cardioprotective and anti-inflammatory properties of its natural counterparts. To address this question, we analyzed the ability of OMT-28 to ameliorate hypoxia/reoxygenation (HR)-injury and lipopolysaccharide (LPS)-induced endotoxemia in cultured cardiomyocytes. Moreover, we investigated the potential of OMT-28 to limit functional damage and inflammasome activation in isolated perfused mouse hearts subjected to ischemia/reperfusion (IR) injury. In the HR model, OMT-28 (1 μM) treatment largely preserved cell viability (about 75 versus 40% with the vehicle) and mitochondrial function as indicated by the maintenance of NAD+/NADH-, ADP/ATP-, and respiratory control ratios. Moreover, OMT-28 blocked the HR-induced production of mitochondrial reactive oxygen species. Pharmacological inhibition experiments suggested that Gαi, PI3K, PPARα, and Sirt1 are essential components of the OMT-28-mediated pro-survival pathway. Counteracting inflammatory injury of cardiomyocytes, OMT-28 (1 μM) reduced LPS-induced increases in TNFα protein (by about 85% versus vehicle) and NF-κB DNA binding (by about 70% versus vehicle). In the ex vivo model, OMT-28 improved post-IR myocardial function recovery to reach about 40% of the baseline value compared to less than 20% with the vehicle. Furthermore, OMT-28 (1 μM) limited IR-induced NLRP3 inflammasome activation similarly to a direct NLRP3 inhibitor (MCC950). Overall, this study demonstrates that OMT-28 possesses potent cardio-protective and anti-inflammatory properties supporting the hypothesis that extending the bioavailability of omega-3 epoxyeicosanoids may improve their prospects as therapeutic agents.

Arachidonic acid metabolism in health and disease

Arachidonic acid (AA), an n-6 essential fatty acid, is a major component of mammalian cells and can be released by phospholipase A2. Accumulating evidence indicates that AA plays essential biochemical roles, as it is the direct precursor of bioactive lipid metabolites of eicosanoids such as prostaglandins, leukotrienes, and epoxyeicosatrienoic acid obtained from three distinct enzymatic metabolic pathways: the cyclooxygenase pathway, lipoxygenase pathway, and cytochrome P450 pathway. AA metabolism is involved not only in cell differentiation, tissue development, and organ function but also in the progression of diseases, such as hepatic fibrosis, neurodegeneration, obesity, diabetes, and cancers. These eicosanoids are generally considered proinflammatory molecules, as they can trigger oxidative stress and stimulate the immune response. Therefore, interventions in AA metabolic pathways are effective ways to manage inflammatory-related diseases in the clinic. Currently, inhibitors targeting enzymes related to AA metabolic pathways are an important area of drug discovery. Moreover, many advances have also been made in clinical studies of AA metabolic inhibitors in combination with chemotherapy and immunotherapy. Herein, we review the discovery of AA and focus on AA metabolism in relation to health and diseases. Furthermore, inhibitors targeting AA metabolism are summarized, and potential clinical applications are discussed.

Effect of inflammation on cytochrome P450-mediated arachidonic acid metabolism and the consequences on cardiac hypertrophy

The incidence of heart failure (HF) is generally preceded by cardiac hypertrophy (CH), which is the enlargement of cardiac myocytes in response to stress. During CH, the metabolism of arachidonic acid (AA), which is present in the cell membrane phospholipids, is modulated. Metabolism of AA gives rise to hydroxyeicosatetraenoic acids (HETEs) and epoxyeicosatrienoic acids (EETs) via cytochrome P450 (CYP) ω-hydroxylases and CYP epoxygenases, respectively. A plethora of studies demonstrated the involvement of CYP-mediated AA metabolites in the pathogenesis of CH. Also, inflammation is known to be a characteristic hallmark of CH. In this review, our aim is to highlight the impact of inflammation on CYP-derived AA metabolites and CH. Inflammation is shown to modulate the expression of various CYP ω-hydroxylases and CYP epoxygenases and their respective metabolites in the heart. In general, HETEs such as 20-HETE and mid-chain HETEs are pro-inflammatory, while EETs are characterized by their anti-inflammatory and cardioprotective properties. Several mechanisms are implicated in inflammation-induced CH, including the modulation of NF-κB and MAPK. This review demonstrated the inflammatory modulation of cardiac CYPs and their metabolites in the context of CH and the anti-inflammatory strategies that can be employed in the treatment of CH and HF.

Topical Aspirin Administration Improves Cutaneous Wound Healing in Diabetic Mice Through a Phenotypic Switch of Wound Macrophages Toward an Anti-inflammatory and Proresolutive Profile Characterized by LXA4 Release

Patients with diabetes present a persistent inflammatory process, leading to impaired wound healing. Since nonhealing diabetic wound management shows limited results, the introduction of advanced therapies targeting and correcting the inflammatory status of macrophages in chronic wounds could be an effective therapeutic strategy to stop the sustained inflammation and to return to a healing state. In an excisional skin injury in a diet-induced diabetic murine model, we demonstrate that topical administration of low-dose aspirin (36 μg/wound/day) improves cutaneous wound healing by increasing wound closure through the promotion of the inflammation resolution program of macrophages. This treatment increased efferocytosis of wound macrophages from aspirin-treated diabetic mice compared with untreated diabetic mice. We also show that aspirin treatment of high-fat-fed mice oriented the phenotype of wound macrophages toward an anti-inflammatory and proresolutive profile characterized by a decrease of LTB4 production. The use of diabetic mice deficient for 5-LOX or 12/15-LOX demonstrated that these two enzymes of acid arachidonic metabolism are essential for the beneficial effect of aspirin on wound healing. Thus, aspirin treatment modified the balance between pro- and anti-inflammatory eicosanoids by promoting the synthesis of proresolving LXA4 through 5-LOX, LTA4, 12/15-LOX signaling. In conclusion, the restoration of an anti-inflammatory and proresolutive phenotype of wound macrophages by the topical administration of low-dose aspirin represents a promising therapeutic approach in chronic wounds.

Cardiomyocyte-specific CYP2J2 and its therapeutic implications

INTRODUCTION

Cytochrome P450s (CYPs) are a superfamily of monooxygenases with diverse biological roles. CYP2J2 is an isozyme highly expressed in the heart where it metabolizes endogenous substrates such as N-3/N-6 polyunsaturated fatty acids (PUFA) to produce lipid mediators involved in homeostasis and cardioprotective responses. Expanding our knowledge of the role CYP2J2 has within the heart is important for understanding its impact on cardiac health and disease.

AREAS COVERED

The objective of this review was to assess the state of knowledge regarding cardiac CYP2J2. A literature search was conducted using PubMed-MEDLINE (from 2022 and earlier) to evaluate relevant studies regarding CYP2J2 mediated cardioprotection, small molecule modulators, effects of CYP2J2 substrates toward biologically relevant effects and implications of CYP2J2 polymorphisms and sexual dimorphism in the heart.

EXPERT OPINION

Cardiac CYP2J2-mediated metabolism of endogenous and exogenous substrates have been shown to impact cardiac function. Identifying individual factors, like sex and age, that affect CYP2J2 require further elucidation to better understand CYP2J2's clinical relevance. Resolving the biological targets and activities of CYP2J2-derived PUFA metabolites will be necessary to safely target CYP2J2 and design novel analogues. Targeting CYP2J2 for therapeutic aims offers a potential novel approach to regulating cardiac homeostasis, drug metabolism and cardioprotection.

CYP450 Epoxygenase Metabolites, Epoxyeicosatrienoic Acids, as Novel Anti-Inflammatory Mediators

Inflammation plays a crucial role in the initiation and development of a wide range of systemic illnesses. Epoxyeicosatrienoic acids (EETs) are derived from arachidonic acid (AA) metabolized by CYP450 epoxygenase (CYP450) and are subsequently hydrolyzed by soluble epoxide hydrolase (sEH) to dihydroxyeicosatrienoic acids (DHETs), which are merely biologically active. EETs possess a wide range of established protective effects on many systems of which anti-inflammatory actions have gained great interest. EETs attenuate vascular inflammation and remodeling by inhibiting activation of endothelial cells and reducing cross-talk between inflammatory cells and blood vessels. EETs also process direct and indirect anti-inflammatory properties in the myocardium and therefore alleviate inflammatory cardiomyopathy and cardiac remodeling. Moreover, emerging studies show the substantial roles of EETs in relieving inflammation under other pathophysiological environments, such as diabetes, sepsis, lung injuries, neurodegenerative disease, hepatic diseases, kidney injury, and arthritis. Furthermore, pharmacological manipulations of the AA-CYP450-EETs-sEH pathway have demonstrated a contribution to the alleviation of numerous inflammatory diseases, which highlight a therapeutic potential of drugs targeting this pathway. This review summarizes the progress of AA-CYP450-EETs-sEH pathway in regulation of inflammation under different pathological conditions and discusses the existing challenges and future direction of this research field.

ROS-responsive nanoparticle-mediated delivery of CYP2J2 gene for therapeutic angiogenesis in severe hindlimb ischemia

With critical limb ischemia (CLI) being a multi-factorial disease, it is becoming evident that gene therapy with a multiple bio-functional growth factor could achieve better therapeutic outcomes. Cytochrome P450 epoxygenase-2J2 (CYP2J2) and its catalytic products epoxyeicosatrienoic acids (EETs) exhibit pleiotropic biological activities, including pro-angiogenic, anti-inflammatory and cardiovascular protective effects, which are considerably beneficial for reversing ischemia and restoring local blood flow in CLI. Here, we designed a nanoparticle-based pcDNA3.1-CYP2J2 plasmid DNA (pDNA) delivery system (nanoparticle/pDNA complex) composed of a novel three-arm star block copolymer (3S-PLGA-po-PEG), which was achieved by conjugating three-armed PLGA to PEG via the peroxalate ester bond. Considering the multiple bio-functions of CYP2J2-EETs and the sensitivity of the peroxalate ester bond to H₂O₂, this nanoparticle-based gene delivery system is expected to exhibit excellent pro-angiogenic effects while improving the high oxidative stress and inflammatory micro-environment in ischemic hindlimb. Our study reports the first application of CYP2J2 in the field of therapeutic angiogenesis for CLI treatment and our findings demonstrated good biocompatibility, stability and sustained release properties of the CYP2J2 nano-delivery system. In addition, this nanoparticle-based gene delivery system showed high transfection efficiency and efficient VEGF expression in vitro and in vivo. Intramuscular injection of nanoparticle/pDNA complexes into mice with hindlimb ischemia resulted in significant rapid blood flow recovery and improved muscle repair compared to mice treated with naked pDNA. In summary, 3S-PLGA-po-PEG/CYP2J2-pDNA complexes have tremendous potential and provide a practical strategy for the treatment of limb ischemia. Moreover, 3S-PLGA-po-PEG nanoparticles might be useful as a potential non-viral carrier for other gene delivery applications.

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Cytochrome P450 epoxygenase-2J2 (CYP2J2) was first applied in the field of therapeutic angiogenesis for critical limb ischemia treatment.

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The ROS-responsive three-arm star block copolymer (3S-PLGA-po-PEG) was synthesized with peroxalate ester as H₂O₂-responsive linkages through the esterification reaction of oxalyl chloride and hydroxyl group.

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The CYP2J2 nano-delivery system achieved high transfection efficiency and significant therapeutic angiogenesis effect.

GSK2256294 Decreases sEH (Soluble Epoxide Hydrolase) Activity in Plasma, Muscle, and Adipose and Reduces F2-Isoprostanes but Does Not Alter Insulin Sensitivity in Humans

[Figure: see text].

Metabolism pathways of arachidonic acids: mechanisms and potential therapeutic targets

The arachidonic acid (AA) pathway plays a key role in cardiovascular biology, carcinogenesis, and many inflammatory diseases, such as asthma, arthritis, etc. Esterified AA on the inner surface of the cell membrane is hydrolyzed to its free form by phospholipase A2 (PLA2), which is in turn further metabolized by cyclooxygenases (COXs) and lipoxygenases (LOXs) and cytochrome P450 (CYP) enzymes to a spectrum of bioactive mediators that includes prostanoids, leukotrienes (LTs), epoxyeicosatrienoic acids (EETs), dihydroxyeicosatetraenoic acid (diHETEs), eicosatetraenoic acids (ETEs), and lipoxins (LXs). Many of the latter mediators are considered to be novel preventive and therapeutic targets for cardiovascular diseases (CVD), cancers, and inflammatory diseases. This review sets out to summarize the physiological and pathophysiological importance of the AA metabolizing pathways and outline the molecular mechanisms underlying the actions of AA related to its three main metabolic pathways in CVD and cancer progression will provide valuable insight for developing new therapeutic drugs for CVD and anti-cancer agents such as inhibitors of EETs or 2J2. Thus, we herein present a synopsis of AA metabolism in human health, cardiovascular and cancer biology, and the signaling pathways involved in these processes. To explore the role of the AA metabolism and potential therapies, we also introduce the current newly clinical studies targeting AA metabolisms in the different disease conditions.

CYP2J2 Molecular Recognition: A New Axis for Therapeutic Design

Cytochrome P450 (CYP) epoxygenases are a special subset of heme-containing CYP enzymes capable of performing the epoxidation of polyunsaturated fatty acids (PUFA) and the metabolism of xenobiotics. This dual functionality positions epoxygenases along a metabolic crossroad. Therefore, structure-function studies are critical for understanding their role in bioactive oxy-lipid synthesis, drug-PUFA interactions, and for designing therapeutics that directly target the epoxygenases. To better exploit CYP epoxygenases as therapeutic targets, there is a need for improved understanding of epoxygenase structure-function. Of the characterized epoxygenases, human CYP2J2 stands out as a potential target because of its role in cardiovascular physiology. In this review, the early research on the discovery and activity of epoxygenases is contextualized to more recent advances in CYP epoxygenase enzymology with respect to PUFA and drug metabolism. Additionally, this review employs CYP2J2 epoxygenase as a model system to highlight both the seminal works and recent advances in epoxygenase enzymology. Herein we cover CYP2J2's interactions with PUFAs and xenobiotics, its tissue-specific physiological roles in diseased states, and its structural features that enable epoxygenase function. Additionally, the enumeration of research on CYP2J2 identifies the future needs for the molecular characterization of CYP2J2 to enable a new axis of therapeutic design.

NLRX1 knockout aggravates lipopolysaccharide (LPS)-induced heart injury and attenuates the anti-LPS cardioprotective effect of CYP2J2/11,12-EET by enhancing activation of NF-κB and NLRP3 inflammasome

NLRX1 weakens lipopolysaccharide (LPS)-induced NF-κB activation on immune cells. Cytochrome P450 epoxygenase 2J2 (CYP2J2) attenuates LPS-induced cardiac injury by inhibiting NF-κB activation. However, it is still unclear whether NLRX1 could reduce LPS-induced heart damage and whether it is involved in the anti-LPS cardioprotective effect of CYP2J2. In this study, we found that NLRX1 knockout further exacerbated LPS-induced heart injury and up-regulated the proinflammatory cytokines in serum and heart tissue, and weakened the inhibitory effect of CYP2J2 on the harmful effects caused by LPS. We also found that LPS treatment induced ubiquitination of NLRX1 and promoted its binding to IKKα/β in myocardial tissue, which should theoretically inhibit NF-κB activation. However, LPS eventually leads to activation of NF-κB and NLRP3 inflammasome. Under the action of LPS, CYP2J2 further promoted the ubiquitination of NLRX1 and its binding to IKKα/β, impaired NF-κB activation and NLRP3 inflammasome activation. NLRX1 knockout notably aggravated LPS-induced NF-κB activation and NLRP3 inflammasome activation, and attenuated the inhibitory effects of CYP2J2 on NF-κB signal and NLRP3 inflammasome. More, CYP2J2 reduced LPS-induced reactive oxygen species (ROS) production and mitochondrial depolarization in heart cells, thereby inhibiting NLRP3 inflammasome activation. NLRX1 knockdown aggravated mitochondrial depolarization induced by LPS and weakened the protective effect of CYP2J2 on mitochondrial potential, although it had no significant effect on reactive oxygen species production. Together, these findings demonstrated that NLRX1 knockout aggravated LPS-induced heart injury and weakened the anti-LPS cardioprotective effect of CYP2J2 by enhancing activation of NF-κB and NLRP3 inflammasome.

Dietary n-6 and n-3 PUFA alter the free oxylipin profile differently in male and female rat hearts

Oxylipins are bioactive lipid mediators synthesised from PUFA. The most well-known oxylipins are the eicosanoids derived from arachidonic acid (ARA), and many of them influence cardiac physiology in health and disease. Oxylipins are also formed from other n-3 and n-6 PUFA such as α-linolenic acid (ALA), EPA, DHA and linoleic acid (LA), but fundamental data on the heart oxylipin profile, and the effect of diet and sex on this profile, are lacking. Therefore, weanling female and male Sprague-Dawley rats were given American Institute of Nutrition (AIN)-93G-based diets modified in oil composition to provide higher levels of ALA, EPA, DHA, LA and LA + ALA, compared with control diets. After 6 weeks, free oxylipins in rat hearts were increased primarily by their precursor PUFA, except for EPA oxylipins, which were increased not only by dietary EPA but also by dietary ALA or DHA. Dietary DHA had a greater effect than ALA or EPA on reducing ARA oxylipins. An exception to the dietary n-3 PUFA-lowering effects on ARA oxylipins was observed for several ARA-derived PG metabolites that were higher in rats given EPA diets. Higher dietary LA increased LA oxylipins, but it had no effect on ARA oxylipins. Overall, heart oxylipins were higher in female rats, but this depended on dietary treatment: the female oxylipin:male oxylipin ratio was higher in rats provided the ALA compared with the DHA diet, with other diet groups having ratios in between. In conclusion, individual PUFA and sex have unique and interactive effects on the rat heart free oxylipin profile.

Cytochrome P450 Epoxygenase 2J2 Protects Against Lung Ischemia/Reperfusion Injury by Activating the P13K/Akt/GSK-3-β/NF-kB Signaling Pathway During Deep Hypothermic Low Flow in Mice

BACKGROUND

Cytochrome P450 epoxygenase 2J2 (CYP2J2) metabolizes arachidonic acid to epoxyeicosatrienoic acids, which exert anti-inflammatory effects and alleviate oxidative stress in the cardiovascular system. Our previous work revealed that CYP2J2 is expressed in pulmonary artery endothelial cells. It was therefore hypothesized that CYP2J2 overexpression may prevent lung ischemia/reperfusion injury (LIRI) in 3-week-old C57BL/6 mice during deep hypothermic low flow (DHLF). This study aimed to establish whether CYP2J2 protects against LIRI and the mechanisms of CYP2J2 overexpression during DHLF in mice. The aim of this study was to explore the effects of DHLF on lung tissue in mice and to find out the regularity of this process, so as to provide theoretical data for lung tissue protection in children undergoing this process in clinic.

METHODS

A 3-week-old C57BL/6 mouse model was used to mimic LIRI conditions during DHLF by clamping the left pulmonary artery and left main bronchus for 120 min, followed by reperfusion for 2 h. The body temperature of the mice was maintained between 18°C and 19°C to induce DHLF.

RESULTS

During DHLF, lung ischemia/reperfusion increased the left lung wet/dry weight, the left lung weight/body weight ratio, the protein concentration in bronchoalveolar lavage fluid, and the concentration of proinflammatory mediators in the lungs, including interleukin (IL)-1, IL-8, and necrosis factor (NF)-α, and decreased the concentration of the anti-inflammatory mediator IL-10. Furthermore, activation of NF-κB p65 and degradation of IKBα were remarkably increased in lung tissues after ischemia/reperfusion. The CYP2J2 overexpression group showed the opposite results (P < 0.05), and p-Akt1 and p-GSK-3β expression were significantly higher in the CYP2J2 overexpression group (P < 0.05). Moreover, the changes in IL-1, IL-8, tumor necrosis factor-α, IL-10, p-Akt1, p-GSK-3β, NF-κB p65, and IKBα were reversed in the Akt1 gene heterozygous knockout group, and lung damage was significantly higher in the Akt1 gene heterozygous knockout group than in the CYP2J2 overexpression group. CYP2J2 overexpression can protect against LIRI, whereas Akt1 gene heterozygous knockout in mice can abolish this protective effect.

CONCLUSIONS

CYP2J2 overexpression can protect against LIRI by activating the P13K/Akt/GSK-3β/NF-kB signaling pathway during DHLF. Thus, changing CYP2J2 expression can be a novel strategy for the prevention and treatment of LIRI during DHLF.

PPAR-Mediated Toxicology and Applied Pharmacology

Peroxisome proliferator-activated receptors (PPARs), members of the nuclear hormone receptor family, attract wide attention as promising therapeutic targets for the treatment of multiple diseases, and their target selective ligands were also intensively developed for pharmacological agents such as the approved drugs fibrates and thiazolidinediones (TZDs). Despite their potent pharmacological activities, PPARs are reported to be involved in agent- and pollutant-induced multiple organ toxicity or protective effects against toxicity. A better understanding of the protective and the detrimental role of PPARs will help to preserve efficacy of the PPAR modulators but diminish adverse effects. The present review summarizes and critiques current findings related to PPAR-mediated types of toxicity and protective effects against toxicity for a systematic understanding of PPARs in toxicology and applied pharmacology.

CYP2J2/EET reduces vulnerability to atrial fibrillation in chronic pressure overload mice

Growing evidence has well established the protective effects of CYP2J2/EET on the cardiovascular system. The aim of the present study was to determine whether CYP2J2/EET has a preventive effect on atrial fibrillation (AF) and to investigate the underlying mechanisms. Wild‐type mice were injected with or without AAV9‐CYP2J2 before abdominal aortic constriction (AAC) operation. After 8 weeks, compared with wild‐type mice, AAC mice display higher AF inducibility and longer AF durations, which were remarkably attenuated with AAV9‐CYP2J2. Also, AAV9‐CYP2J2 reduced atrial fibrosis area and the deposit of collagen‐I/III in AAC mice, accompanied by the blockade of TGF‐β/Smad‐2/3 signalling pathways, as well as the recovery in Smad‐7 expression. In vitro, isolated atrial fibroblasts were administrated with TGF‐β1, EET, EEZE, GW9662, SiRNA Smad‐7 and pre‐MiR‐21, and EET was demonstrated to restrain the differentiation of atrial fibroblasts largely dependent on Smad‐7, due to the inhibition of EET on MiR‐21. In addition, increased inflammatory cytokines, as well as activated NF‐κB pathways induced by AAC surgery, were also significantly blunted by AAV9‐CYP2J2 treatment. These effects of CYP2J2/EET were partially blocked by GW9662, the antagonist of PPAR‐γ. In conclusion, this study revealed that CYP2J2/EET ameliorates atrial fibrosis through modulating atrial fibroblasts activation by disinhibition of MiR‐21 on Smad‐7, and attenuates atrial inflammatory response by repressing NF‐κB pathways, reducing the vulnerability to AF, and CYP2J2/EET exerts its role at least partially through PPAR‐γ activation. Our findings might provide a novel upstream therapeutic strategy for AF.

Dronedarone-Induced Cardiac Mitochondrial Dysfunction and Its Mitigation by Epoxyeicosatrienoic Acids

Dronedarone and amiodarone are structurally similar antiarrhythmic drugs. Dronedarone worsens cardiac adverse effects with unknown causes while amiodarone has no cardiac adversity. Dronedarone induces preclinical mitochondrial toxicity in rat liver and exhibits clinical hepatotoxicity. Here, we further investigated the relative potential of the antiarrhythmic drugs in causing mitochondrial injury in cardiomyocytes. Differentiated rat H9c2 cardiomyocytes were treated with dronedarone, amiodarone, and their respective metabolites namely N-desbutyldronedarone (NDBD) and N-desethylamiodarone (NDEA). Intracellular ATP content, mitochondrial membrane potential (Δψm), and inhibition of carnitine palmitoyltransferase I (CPT1) activity and arachidonic acid (AA) metabolism were measured in H9c2 cells. Inhibition of electron transport chain (ETC) activities and uncoupling of ETC were further studied in isolated rat heart mitochondria. Dronedarone, amiodarone, NDBD and NDEA decreased intracellular ATP content significantly (IC50 = 0.49, 1.84, 1.07, and 0.63 µM, respectively) and dissipated Δψm potently (IC50 = 0.5, 2.94, 12.8, and 7.38 µM, respectively). Dronedarone, NDBD, and NDEA weakly inhibited CPT1 activity while amiodarone (IC50 > 100 µM) yielded negligible inhibition. Only dronedarone inhibited AA metabolism to its regioisomeric epoxyeicosatrienoic acids (EETs) consistently and potently. NADH-supplemented ETC activity was inhibited by dronedarone, amiodarone, NDBD and NDEA (IC50 = 3.07, 5.24, 11.94, and 16.16 µM, respectively). Cytotoxicity, ATP decrease and Δψm disruption were ameliorated via exogenous pre-treatment of H9c2 cells with 11, 12-EET and 14, 15-EET. Our study confirmed that dronedarone causes mitochondrial injury in cardiomyocytes by perturbing Δψm, inhibiting mitochondrial complex I, uncoupling ETC and dysregulating AA-EET metabolism. We postulate that cardiac mitochondrial injury is one potential contributing factor to dronedarone-induced cardiac failure exacerbation.

Vascular repair and anti-inflammatory effects of soluble epoxide hydrolase inhibitor

Kawasaki disease (KD) is the leading cause of acquired heart disease in pediatric patients in developed countries. Coronary artery aneurysms and myocardial infarction may occur if the disease remains untreated. An estimated 10-20% of KD patients do not respond to intravenous gamma globulin (IVIG), and thus, alternative treatments are currently being investigated. Epoxyeicosatrienoic acids (EETs) are natural anti-inflammatory factors and angiogenic mediators degraded by soluble epoxide hydrolase (sEH). sEH inhibitory factors have been demonstrated to stabilize EET levels, inhibit inflammation and promote vascular repair in vivo. The present study aimed to determine whether an increase in EET levels induced by treatment with the sEH inhibitor 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA) promotes vascular repair in human coronary arterial endothelial cells (HCAECs) and reduces inflammation in a mouse model of KD induced by Lactobacillus casei cell wall extract. The effect of AUDA on vascular repair in HCAECs was assessed by using cell proliferation, migration, adhesion and tube formation assays, and the anti-inflammatory effect of AUDA in the mouse model of KD was determined by detecting the expression of matrix metalloproteinase (MMP)-9, tumor necrosis factor (TNF)-α and interleukin (IL)-1β at the protein level via ELISA. The results demonstrated that AUDA increased the proliferation, migration, adhesion and tube formation ability of HCAECs in a dose-dependent manner. Furthermore, in the mouse model of KD, AUDA reduced the protein expression of MMP-9, IL-1β and TNF-α, indicating that AUDA may alleviate inflammatory reactions in the coronary arteries of KD model mice. The present results also indicate that these effects may be exerted through the peroxisome proliferator activated receptor γ signaling pathway. Taken together, the present study supports the potential utility of AUDA in the treatment of KD.

Deficiency of Soluble Epoxide Hydrolase Protects Cardiac Function Impaired by LPS-Induced Acute Inflammation

Lipopolysaccharide (LPS) is a bacterial wall endotoxin producing many pathophysiological conditions including myocardial inflammation leading to cardiotoxicity. Linoleic acid (18:2n6, LA) is an essential n-6 PUFA which is converted to arachidonic acid (20:4n6, AA) by desaturation and elongation via enzyme systems within the body. Biological transformation of PUFA through CYP-mediated hydroxylation, epoxidation, and allylic oxidation produces lipid mediators, which may be subsequently hydrolyzed to corresponding diol metabolites by soluble epoxide hydrolase (sEH). In the current study, we investigate whether inhibition of sEH, which alters the PUFA metabolite profile, can influence LPS induced cardiotoxicity and mitochondrial function. Our data demonstrate that deletion of soluble epoxide hydrolase provides protective effects against LPS-induced cardiotoxicity by maintaining mitochondrial function. There was a marked alteration in the cardiac metabolite profile with notable increases in sEH-derived vicinal diols, 9,10- and 12,13-dihydroxyoctadecenoic acid (DiHOME) in WT hearts following LPS administration, which was absent in sEH null mice. We found that DiHOMEs triggered pronounced mitochondrial structural abnormalities, which also contributed to the development of extensive mitochondrial dysfunction in cardiac cells. Accumulation of DiHOMEs may represent an intermediate mechanism through which LPS-induced acute inflammation triggers deleterious alterations in the myocardium in vivo and cardiac cells in vitro. This study reveals novel research exploring the contribution of DiHOMEs in the progression of adverse inflammatory responses toward cardiac function in vitro and in vivo.

Soluble epoxide hydrolase inhibition alleviated cognitive impairments via NRG1/ErbB4 signaling after chronic cerebral hypoperfusion induced by bilateral carotid artery stenosis in mice

Cerebral ischemic stroke is associated with a high rate of incidence, prevalence and mortality globally. Carotid artery stenosis, which is mainly caused by atherosclerosis plaque, results in chronic cerebral hypoperfusion and predominantly increases the risk of ischemic stroke. In the present study, we used bilateral common carotid artery stenosis (BCAS) model by placing microcoils of 0.18 mm diameter encompassing both common carotid arteries respectively, to mimic the pathogenesis of carotid artery atherosclerosis and intensively explore the pathology. We found that BCAS injury for 1 month impaired spatial cognitive functions significantly, and inhibited synaptic plasticity, including hippocampal long-term potentiation (LTP) inhibition, dendritic spine density reduction and synaptic associative proteins disorder. BCAS-induced cerebral hypoperfused mice treated with 1-(1-propanoylpiperidin-4-yl)-3-[4-(trifluoromethoxy)phenyl]urea (TPPU), a potent soluble epoxide hydrolase (sEH) inhibitor, exhibited amelioration of cognitive dysfunction and improved synaptic plasticity. The neural protective effects of TPPU on BCAS-induced cerebral hypoperfusion might due to activation of neuregulin-1 (NRG1)/ErbB4 signaling, and triggered PI3K-Akt pathways subsequently. Our results suggested that sEH inhibition could exert multi-target protective effects and alleviate spatial cognitive dysfunctions after chronic cerebral hypoperfusion in mice.

Formation of Both Heme and Apoprotein Adducts Contributes to the Mechanism-Based Inactivation of Human CYP2J2 by 17α-Ethynylestradiol

17α-Ethynylestradiol (EE), a major component of many oral contraceptives, affects the activities of a number of the human cytochrome P450 (P450) enzymes. Here, we characterized the effect of EE on CYP2J2, a major human P450 isoform that participates in metabolism of arachidonic acid. EE inactivated the hydroxyebastine carboxylation activity of CYP2J2 in a reconstituted system. The loss of activity is time and concentration dependent and requires NADPH. The KI and kinact values for the inactivation were 3.6 μM and 0.08 minute-1, respectively. Inactivation of CYP2J2 by EE was due to formation of a heme adduct as well as an apoprotein adduct. Mass spectral analysis of CYP2J2 partially inactivated by EE showed two distinct protein masses in the deconvoluted spectrum that exhibited a mass difference of approximately 312 Da, which is equivalent to the sum of the mass of EE and one oxygen atom. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis revealed a heme adduct with MH+ ion at m/z 875.5, corresponding to alkylation of an iron-depleted prosthetic heme by EE plus one oxygen atom. The reactive intermediate responsible for covalently modifying both the prosthetic heme and apoprotein was characterized by trapping with glutathione (GSH). LC-MS/MS analysis revealed two GSH conjugate isomers with MH+ ions at m/z 620, which were formed by reaction between GSH and EE with the oxygen being added to either the internal or terminal carbon of the ethynyl moiety. High-pressure liquid chromatography analysis revealed that three other major metabolites were formed during EE metabolism by CYP2J2.

Orally Active Epoxyeicosatrienoic Acid Analogs

Biologically active epoxyeicosatrienoic acid (EET) regioisomers are synthesized from arachidonic acid by cytochrome P450 epoxygenases of endothelial, myocardial, and renal tubular cells. EETs relax vascular smooth muscle and decrease inflammatory cell adhesion and cytokine release. Renal EETs promote sodium excretion and vasodilation to decrease hypertension. Cardiac EETs reduce infarct size after ischemia-reperfusion injury and decrease fibrosis and inflammation in heart failure. In diabetes, EETs improve insulin sensitivity, increase glucose tolerance, and reduce the renal injury. These actions of EETs emphasize their therapeutic potential. To minimize metabolic inactivation, 14,15-EET agonist analogs with stable epoxide bioisosteres and carboxyl surrogates were developed. In preclinical rat models, a subset of agonist analogs, termed EET-A, EET-B, and EET-C22, are orally active with good pharmacokinetic properties. These orally active EET agonists lower blood pressure and reduce cardiac and renal injury in spontaneous and angiotensin hypertension. Other beneficial cardiovascular actions include improved endothelial function and cardiac antiremodeling actions. In rats, EET analogs effectively combat acute and chronic kidney disease including drug- and radiation-induced kidney damage, hypertension and cardiorenal syndrome kidney damage, and metabolic syndrome and diabetes nephropathy. The compelling preclinical efficacy supports the prospect of advancing EET analogs to human clinical trials for kidney and cardiovascular diseases.

Heme Modification Contributes to the Mechanism-Based Inactivation of Human Cytochrome P450 2J2 by Two Terminal Acetylenic Compounds

The mechanism-based inactivation of human CYP2J2 by three terminal acetylenic compounds: N-(methylsulfonyl)-6-(2-propargyloxyphenyl)hexanamide (MS), 17-octadecynoic acid (OD), and danazol (DZ) was investigated. The loss of hydroxyebastine (OHEB) carboxylation activity in a reconstituted system was time- and concentration-dependent and required NADPH for MS and OD, but not DZ. The kinetic constants for the mechanism-based inactivation of OHEB carboxylation activity were: KI of 6.1 μM and kinact of 0.22 min-1 for MS and KI of 2.5 μM and kinact of 0.05 min-1 for OD. The partition ratios for MS and OD were ∼10 and ∼20, respectively. Inactivation of CYP2J2 by MS or OD resulted in a loss of the native heme spectrum and a similar decrease in the reduced CO difference spectrum. A heme adduct was observed in the MS-inactivated CYP2J2. The possible reactive metabolite which covalently modified the prosthetic heme was characterized by analysis of the glutathione conjugates formed by MS or OD following oxygenation of the ethynyl moiety. Liquid chromatography-mass spectrometry showed that inactivation by MS or OD did not lead to modification of apoprotein. Interaction of CYP2J2 with DZ produced a type II binding spectrum with a Ks of 2.8 μM and the IC50 for loss of OHEB carboxylation activity was 0.18 μM. In conclusion, heme modification by MS and OD was responsible for the mechanism-based inactivation of CYP2J2. The results suggest that the ethynyl moiety of MS and OD faces the heme iron, whereas the isoxazole ring of DZ is preferentially oriented toward the heme iron of CYP2J2.

Epoxyeicosatrienoic acids regulate macrophage polarization and prevent LPS-induced cardiac dysfunction

Macrophages, owning tremendous phenotypic plasticity and diverse functions, were becoming the target cells in various inflammatory, metabolic and immune diseases. Cytochrome P450 epoxygenase 2J2 (CYP2J2) metabolizes arachidonic acid to form epoxyeicosatrienoic acids (EETs), which possess various beneficial effects on cardiovascular system. In the present study, we evaluated the effects of EETs treatment on macrophage polarization and recombinant adeno-associated virus (rAAV)-mediated CYP2J2 expression on lipopolysaccharide (LPS)-induced cardiac dysfunction, and sought to investigate the underlying mechanisms. In vitro studies showed that EETs (1µmol/L) significantly inhibited LPS-induced M1 macrophage polarization and diminished the proinflammatory cytokines at transcriptional and post-transcriptional level; meanwhile it preserved M2 macrophage related molecules expression and upregulated anti-inflammatory cytokine IL-10. Furthermore, EETs down-regulated NF-κB activation and up-regulated peroxisome proliferator-activated receptors (PPARα/γ) and heme oxygenase 1 (HO-1) expression, which play important roles in regulating M1 and M2 polarization. In addition, LPS treatment in mice induced cardiac dysfunction, heart tissue damage and infiltration of M1 macrophages, as well as the increase of inflammatory cytokines in serum and heart tissue, but rAAV-mediated CYP2J2 expression increased EETs generation in heart and significantly attenuated the LPS-induced harmful effects, which mechanisms were similar as the in vitro study. Taken together, the results indicate that CYP2J2/EETs regulates macrophage polarization by attenuating NF-κB signaling pathway via PPARα/γ and HO-1 activation and its potential use in treatment of inflammatory diseases.

Whatever happened to the epoxyeicosatrienoic Acid-like endothelium-derived hyperpolarizing factor? The identification of novel classes of lipid mediators and their role in vascular homeostasis

SIGNIFICANCE

Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid (AA) to generate epoxyeicosatrienoic acids (EETs). The latter are biologically active and reported to act as an endothelium-derived hyperpolarizing factor as well as to affect angiogenic and inflammatory signaling pathways.

RECENT ADVANCES

In addition to AA, the CYP enzymes also metabolize the ω-3 polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid and docosahexaenoic acid to generate bioactive lipid epoxide mediators. The latter can be more potent than the EETs, but their actions are under investigated. The ω3-epoxides, like the EETs, are metabolized by the soluble epoxide hydrolase (sEH) to corresponding diols, and epoxide hydrolase inhibition increases epoxide levels and demonstrates anti-hypertensive as well as anti-inflammatory effects.

CRITICAL ISSUES

It seems that the overall consequences of CYP activation largely depend on enzyme substrate preference and the endogenous ω-3/ω-6 PUFA ratio.

FUTURE DIRECTIONS

More studies combining PUFA profiling with cell signaling and disease studies are required to determine the spectrum of molecular pathways affected by the different ω-6 and ω-3 PUFA epoxides and diols. Such information may help improve dietary studies aimed at promoting health via ω-3 PUFA supplementation and/or sEH inhibition.

LRH-1 mediates anti-inflammatory and antifungal phenotype of IL-13-activated macrophages through the PPARγ ligand synthesis

Liver receptor homologue-1 (LRH-1) is a nuclear receptor involved in the repression of inflammatory processes in the hepatointestinal tract. Here we report that LRH-1 is expressed in macrophages and induced by the Th2 cytokine IL-13 via a mechanism involving STAT6. We show that loss-of-function of LRH-1 in macrophages impedes IL-13-induced macrophage polarization due to impaired generation of 15-HETE PPARγ ligands. The incapacity to generate 15-HETE metabolites is at least partially caused by the compromised regulation of CYP1A1 and CYP1B1. Mice with LRH-1-deficient macrophages are, furthermore, highly susceptible to gastrointestinal and systemic Candida albicans infection. Altogether, these results identify LRH-1 as a critical component of the anti-inflammatory and fungicidal response of alternatively activated macrophages that acts upstream from the IL-13-induced 15-HETE/PPARγ axis.

CYP epoxygenase 2J2 prevents cardiac fibrosis by suppression of transmission of pro-inflammation from cardiomyocytes to macrophages

Cytochrome P450 epoxygenase (CYP450)-derived epoxyeicosatrienoic acids (EETs) are important regulators of cardiac remodeling; but the underlying mechanism remains unclear. The present study aimed to elucidate how EETs regulated cardiac fibrosis in response to isoprenaline (Iso) or angiotensin (Ang) II. Cardiac-specific human CYP2J2 transgenic mice (Tr) and wild-type (WT) C57BL/6 littermates were infused with Iso- or Ang II. Two weeks after infusion, Tr mice showed more alleviative cardiac fibrosis and inflammation compared with WT mice. In vitro, we found Iso or Ang II induced nuclear transfer of NF-κB p65 and inflammatory cytokines expression in cardiomyocytes. Furthermore, inflammation response emerged in macrophages cultured in cardiomyocytes-conditioned medium. When pretreatment with 14,15-EET in cardiomyocytes, the inflammatory response was markedly suppressed and the transmission of inflammation from cardiomyocytes to macrophages was reduced. In conclusion, CYP2J2 and EETs prevent cardiac fibrosis and cardiac dysfunction by suppressing transmission of pro-inflammation from cardiomyocytes to macrophages in heart, suggesting that elevation of EETs level could be a potential strategy to prevent cardiac fibrosis.

Cardiomyocyte-specific expression of CYP2J2 prevents development of cardiac remodelling induced by angiotensin II

AIMS

Cardiac remodelling is one of the key pathological changes that occur with cardiovascular disease. Previous studies have demonstrated the beneficial effects of CYP2J2 expression on cardiac injury. In the present study, we investigated the effects of cardiomyocyte-specific CYP2J2 expression and EET treatment on angiotensin II-induced cardiac remodelling and sought to determine the underlying molecular mechanisms involved in this process.

METHODS AND RESULTS

Eight-week-old mice with cardiomyocyte-specific CYP2J2 expression (αMHC-CYP2J2-Tr) and wild-type (WT) control mice were treated with Ang-II. Ang-II treatment of WT mice induced changes in heart morphology, cardiac hypertrophy and dysfunction, as well as collagen accumulation; however, cardiomyocyte-specific expression of CYP2J2 attenuated these effects. The cardioprotective effects observed in α-MHC-CYP2J2-Tr mice were associated with peroxisome proliferator-activated receptor (PPAR)-γ activation, reduced oxidative stress, reduced NF-κB p65 nuclear translocation, and inhibition of TGF-β1/smad pathway. The effects seen with cardiomyocyte-specific expression of CYP2J2 were partially blocked by treatment with PPAR-γ antagonist GW9662. In in vitro studies, 11,12-EET(1 μmol/L) treatment attenuated cardiomyocyte hypertrophy and remodelling-related protein (collagen I, TGF-β1, TIMP1) expression by inhibiting the oxidative stress-mediated NF-κB pathway via PPAR-γ activation. Furthermore, conditioned media from neonatal cardiomyocytes treated with 11,12-EET inhibited activation of cardiac fibroblasts and TGF-β1/smad pathway.

CONCLUSION

Cardiomyocyte-specific expression of CYP2J2 or treatment with EETs protects against cardiac remodelling by attenuating oxidative stress-mediated NF-κBp65 nuclear translocation via PPAR-γ activation.

CYP2J2 overexpression attenuates nonalcoholic fatty liver disease induced by high-fat diet in mice

Cytochrome P-450 epoxygenase-derived epoxyeicosatrienoic acids (EETs) exert diverse biological activities, which include potent vasodilatory, anti-inflammatory, antiapoptotic, and antioxidatant effects, and cardiovascular protection. Liver has abundant epoxygenase expression and high levels of EET production; however, the roles of epoxygenases in liver diseases remain to be elucidated. In this study, we investigated the protection against high-fat diet-induced nonalcoholic fatty liver disease (NAFLD) in mice with endothelial-specific CYP2J2 overexpression (Tie2-CYP2J2-Tr). After 24 wk of high-fat diet, Tie2-CYP2J2-Tr mice displayed attenuated NAFLD compared with controls. Tie2-CYP2J2-Tr mice showed significantly decreased plasma triglyceride levels and liver lipid accumulation, improved liver function, reduced inflammatory responses, and less increase in hepatic oxidative stress than wild-type control mice. These effects were associated with inhibition of NF-κB/JNK signaling pathway activation and enhancement of the antioxidant defense system in Tie2-CYP2J2-Tr mice in vivo. We also demonstrated that 14,15-EET treatment protected HepG2 cells against palmitic acid-induced inflammation and oxidative stress. 14,15-EET attenuated palmitic acid-induced changes in NF-κB/JNK signaling pathways, malondialdehyde generation, glutathione levels, reactive oxygen species production, and NADPH oxidase and antioxidant enzyme expression in HepG2 cells in vitro. Together, these results highlight a new role for CYP epoxygenase-derived EETs in lipotoxicity-related inflammation and oxidative stress and reveal a new molecular mechanism underlying EETs-mediated anti-inflammatory and antioxidant effects that could aid in the design of new therapies for the prevention and treatment of NAFLD.

PPARγ signaling is required for mediating EETs protective effects in neonatal cardiomyocytes exposed to LPS

Lipopolysaccharide (LPS) is a bacterial wall endotoxin producing many pathophysiological conditions including myocardial inflammation leading to cardiotoxicity. Epoxyeicosatrienoic acids (EETs) are biologically active metabolites of arachidonic acids capable of activating protective cellular pathways in response to stress stimuli. EETs evoke a plethora of pathways limiting impairments of cellular structures, reducing cell death, and promoting anti-inflammatory reactions in various cell types. Considering EETs are capable of producing various biological protective effects, we hypothesized that EETs would protect rat neonatal cardiomyocytes (NCM) against LPS-induced cytotoxicity. In this study, we used a dual-acting, synthetic analog of EETs, UA-8 [13-(3-propylureido)tridec-8-enoic acid], possessing both EET-mimetic and soluble epoxide hydrolase selective inhibitory properties and 14,15-EET as a model of canonical EET molecules. We found that both UA-8 and 14,15-EET significantly improved cell viability and mitochondrial function of cardiomyocytes exposed to LPS. Furthermore, treatment with UA-8 or 14,15-EET resulted in significant attenuation of LPS-triggered pro-inflammatory response, caspase-3 activation and reduction in the total antioxidant capacity in cardiomyocytes. Importantly, EET-mediated effects were significantly reduced by pharmacological inhibition of peroxisome proliferator-activated receptors γ (PPARγ) suggesting that PPARγ signaling was required for EETs exerted protective effects. Data presented in the current study demonstrate that activation of PPARγ signaling plays a crucial role in EET-mediated protection against LPS-cytotoxicity in cardiomyocytes.

The pharmacology of the cytochrome P450 epoxygenase/soluble epoxide hydrolase axis in the vasculature and cardiovascular disease

Over the last 20 years, it has become clear that cytochrome P450 (P450) enzymes generate a spectrum of bioactive lipid mediators from endogenous substrates. However, studies focused on the determining biologic activity of the P450 system have focused largely on the metabolites generated by one substrate (i.e., arachidonic acid). However, epoxides and diols derived from other endogenous substrates, such as linoleic acid, eicosapentaenoic acid, and docosahexaenoic acid, may be generated in higher concentrations and may potentially be of more physiologic relevance. Recent studies that used a combination of phenotyping and lipid array analyses revealed that rather than being inactive products, fatty acid diols play important roles in a number of biologic processes including inflammation, angiogenesis, and metabolic regulation. Moreover, inhibitors of the soluble epoxide hydrolase that increase epoxide but decrease diol levels have potential for the treatment of the metabolic syndrome.

Cytochrome P450 epoxygenase pathway of polyunsaturated fatty acid metabolism

Polyunsaturated fatty acids (PUFA) are oxidized by cytochrome P450 epoxygenases to PUFA epoxides which function as potent lipid mediators. The major metabolic pathways of PUFA epoxides are incorporation into phospholipids and hydrolysis to the corresponding PUFA diols by soluble epoxide hydrolase. Inhibitors of soluble epoxide hydrolase stabilize PUFA epoxides and potentiate their functional effects. The epoxyeicosatrienoic acids (EETs) synthesized from arachidonic acid produce vasodilation, stimulate angiogenesis, have anti-inflammatory actions, and protect the heart against ischemia-reperfusion injury. EETs produce these functional effects by activating receptor-mediated signaling pathways and ion channels. The epoxyeicosatetraenoic acids synthesized from eicosapentaenoic acid and epoxydocosapentaenoic acids synthesized from docosahexaenoic acid are potent inhibitors of cardiac arrhythmias. Epoxydocosapentaenoic acids also inhibit angiogenesis, decrease inflammatory and neuropathic pain, and reduce tumor metastasis. These findings indicate that a number of the beneficial functions of PUFA may be due to their conversion to PUFA epoxides. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance".

Long-term supranutritional supplementation with selenate decreases hyperglycemia and promotes fatty liver degeneration by inducing hyperinsulinemia in diabetic db/db mice

There are conflicting reports on the link between the micronutrient selenium and the prevalence of diabetes. To investigate the possibility that selenium acts as a "double-edged sword" in diabetes, cDNA microarray profiling and two-dimensional differential gel electrophoresis coupled with mass spectrometry were used to determine changes in mRNA and protein expression in pancreatic and liver tissues of diabetic db/db mice in response to dietary selenate supplementation. Fasting blood glucose levels increased continuously in db/db mice administered placebo (DMCtrl), but decreased gradually in selenate-supplemented db/db mice (DMSe) and approached normal levels after termination of the experiment. Pancreatic islet size was increased in DMSe mice compared with DMCtrl mice, resulting in a clear increase in insulin production and a doubling of plasma insulin concentration. Genes that encode proteins involved in key pancreatic β-cell functions, including regulation of β-cell proliferation and differentiation and insulin synthesis, were found to be specifically upregulated in DMSe mice. In contrast, apoptosis-associated genes were downregulated, indicating that islet function was protected by selenate treatment. Conversely, liver fat accumulation increased in DMSe mice together with significant upregulation of lipogenic and inflammatory genes. Genes related to detoxification were downregulated and antioxidant enzymatic activity was reduced, indicating an unexpected reduction in antioxidant defense capacity and exacerbation of fatty liver degeneration. Moreover, proteomic analysis of the liver showed differential expression of proteins involved in glucolipid metabolism and the endoplasmic reticulum assembly pathway. Taken together, these results suggest that dietary selenate supplementation in db/db mice decreased hyperglycemia by increasing insulin production and secretion; however, long-term hyperinsulinemia eventually led to reduced antioxidant defense capacity, which exacerbated fatty liver degeneration.

Epoxyeicosatrienoic acids and cardioprotection: the road to translation

Cardiovascular disease, including acute myocardial infarction (AMI), is the leading cause of morbidity and mortality globally, despite well-established treatments. The discovery and development of novel therapeutics that prevent the progression of devastating consequences following AMI are thus important in reducing the global burden of this devastating disease. Scientific evidence for the protective effects of epoxyeicosatrienoic acids (EETs) in the cardiovascular system is rapidly emerging and suggests that promoting the effects of these cytochrome P450-derived epoxyeicosanoids is a potentially viable clinical therapeutic strategy. Through a translational lens, this review will provide insight into the potential clinical utility of this therapeutic strategy for AMI by 1) outlining the known cardioprotective effects of EETs and underlying mechanisms demonstrated in preclinical models of AMI with a particular focus on myocardial ischemia-reperfusion injury, 2) describing studies in human cohorts that demonstrate a relationship between EETs and associated pathways with coronary artery disease risk, and 3) discussing preclinical and clinical areas that require further investigation in order to increase the probability of successfully translating this rapidly emerging body of evidence into a clinically applicable therapeutic strategy for AMI.

Soluble epoxide hydrolase inhibitor, t-TUCB, protects against myocardial ischaemic injury in rats

OBJECTIVES

To determine the protective role of a soluble epoxide hydrolase(sEH) inhibitor, trans-4-{4-[3-(4-trifluoromethoxyphenyl)-ureido] cyclohexyloxy} benzoic acid (t-TUCB), in isoproterenol (ISO)-induced myocardial ischaemic injury in vivo.

METHODS

Cardioprotective activity of t-TUCB was studied against ISO-induced myocardial ischaemic injury in male Wistar rats. Cardioprotection was assessed by measuring elecrocardiographic (EKG), serum lactate dehydrogenase (LDH) and creatine kinase (CK-MB) levels, cardiac calcium and antioxidant levels, and also by measuring infarct size in the cardiac tissue.

KEY FINDINGS

Pretreatment with t-TUCB at 3, 10 and 30 mg/kg orally for a period of 14 days significantly prevented the changes in EKG parameters (QTc interval prolongation, ST height depression, pathological Q waves formation and T-wave inversion), serum cardiac biomarkers (CK-MB and LDH), relative heart weight, myocardial calcium levels, infarct size and the oxidative status in the cardiac tissue (lipid peroxidation, catalase and superoxide dismutase levels) when compared with the untreated control animals (P < 0.05).

CONCLUSION

The sEH inhibitor t-TUCB significantly prevents ISO-induced myocardial ischaemic injury in rats. This study provides a preliminary confirmation of the efficacy of t-TUCB by oral administration in rats.

Modulation of cardiac cytochrome P450 in patients with heart failure

INTRODUCTION

There is increasing evidence that cytochrome P450 (CYP) plays a role in the onset, progression and prognosis of cardiovascular disease (CVD), in particular, heart failure (HF). The importance of CYP enzymes in cardiovascular physiology derives from their ability to metabolize arachidonic acid to epoxyeicosatrienoic and hydroxyeicosatetraenoic acids, which are involved in the maintenance of cardiovascular health, including the regulation of vascular tone, cardiac ion channels and heart contractility. Moreover, CYP plays a central role in the Phase I metabolism of drugs and other xenobiotics. Inter-individual variability in expression and function of CYP enzymes is a major factor accounting for individual susceptibility to drug response.

AREAS COVERED

This review focuses on current knowledge of the role of CYP enzymes and their metabolites in the pathogenesis of CVD, in particular, HF. The role of CYP enzymes in affecting individual response to cardiovascular drugs is also discussed. The literature search was performed using the PubMed database.

EXPERT OPINION

More research is needed to elucidate the mechanisms by which CYP affects the pathophysiology of HF and also the mechanism by which HF alters cardiac and hepatic CYP enzymes.

CYP2J2-derived epoxyeicosatrienoic acids suppress endoplasmic reticulum stress in heart failure

Prolonged endoplasmic reticulum (ER) stress causes apoptosis and is associated with heart failure. Whether CYP2J2 and its arachidonic acid metabolites [epoxyeicosatrienoic acids (EETs)] have a protective influence on ER stress and heart failure has not been studied. Assays of myocardial samples from patients with end-stage heart failure showed evidence of ER stress. Chronic infusion of isoproterenol (ISO) or angiotensin II (AngII) by osmotic mini-pump induced cardiac hypertrophy and heart failure in mice as evaluated by hemodynamic measurements and echocardiography. Interestingly, transgenic (Tr) mice with cardiomyocyte-specific CYP2J2 expression were protected against heart failure compared with wild-type mice. ISO or AngII administration induced ER stress and apoptosis, and increased levels of intracellular Ca(2+). These phenotypes were abolished by CYP2J2 overexpression in vivo or exogenous EETs treatment of cardiomyocytes in vitro. ISO or AngII reduced sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA2a) expression in hearts or isolated cardiomyocytes; however, loss of SERCA2a expression was prevented in CYP2J2 Tr hearts in vivo or in cardiomyocytes treated with EETs in vitro. The reduction of SERCA2a activity was concomitant with increased oxidation of SERCA2a. EETs reversed SERCA2a oxidation through increased expression of antioxidant enzymes and reduced reactive oxygen species levels. Tempol, a membrane-permeable radical scavenger, similarly decreased oxidized SERCA2a levels, restored SERCA2a activity, and markedly reduced ER stress response in the mice treated with ISO. In conclusion, CYP2J2-derived EETs suppress ER stress response in the heart and protect against cardiac failure by maintaining intracellular Ca(2+) homeostasis and SERCA2a expression and activity.

Role of cytochrome P450-mediated arachidonic acid metabolites in the pathogenesis of cardiac hypertrophy

A plethora of studies have demonstrated the expression of cytochrome P450 (CYP) and soluble epoxide hydrolase (sEH) enzymes in the heart and other cardiovascular tissues. In addition, the expression of these enzymes is altered during several cardiovascular diseases (CVDs), including cardiac hypertrophy (CH). The alteration in CYP and sEH expression results in derailed CYP-mediated arachidonic acid (AA) metabolism. In animal models of CH, it has been reported that there is an increase in 20-hydroxyeicosatetraenoic acid (20-HETE) and a decrease in epoxyeicosatrienoic acids (EETs). Further, inhibiting 20-HETE production by CYP ω-hydroxylase inhibitors and increasing EET stability by sEH inhibitors have been proven to protect against CH as well as other CVDs. Therefore, CYP-mediated AA metabolites 20-HETE and EETs are potential key players in the pathogenesis of CH. Some studies have investigated the molecular mechanisms by which these metabolites mediate their effects on cardiomyocytes and vasculature leading to pathological CH. Activation of several intracellular signaling cascades, such as nuclear factor of activated T cells, nuclear factor kappa B, mitogen-activated protein kinases, Rho-kinases, Gp130/signal transducer and activator of transcription, extracellular matrix degradation, apoptotic cascades, inflammatory cytokines, and oxidative stress, has been linked to the pathogenesis of CH. In this review, we discuss how 20-HETE and EETs can affect these signaling pathways to result in, or protect from, CH, respectively. However, further understanding of these metabolites and their effects on intracellular cascades will be required to assess their potential translation to therapeutic approaches for the prevention and/or treatment of CH and heart failure.

Cardiac-specific overexpression of CYP2J2 attenuates diabetic cardiomyopathy in male streptozotocin-induced diabetic mice

Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid to biologically active cis-epoxyeicosatrienoic acids, which have potent vasodilatory, antiinflammatory, antiapoptotic, and antidiabetes properties. Here, we showed the effects of cardiac-specific overexpression of CYP epoxygenase 2J2 (CYP2J2) on diabetic cardiomyopathy and insulin resistance in high-fat (HF) diet fed, low-dose streptozotocin-treated mice. Diabetic cardiomyopathy was induced by HF and streptozotocin in cardiac-specific CYP2J2 transgenic mice. Physiological parameters and systemic metabolic parameters were monitored using ELISA kits. Intraperitoneal injection glucose tolerance test and hyperinsulinemic-euglycemic clamp study were implied to indicate insulin resistance. Cardiac function was assessed by echocardiography and Millar catheter system. Real-time PCR and Western blotting were used in signal pathway detection. αMHC-CYP2J2 transgenic mice showed significantly lower plasma glucose and insulin levels, improved glucose tolerance, and increased cardiac glucose uptake. Furthermore, αMHC-CYP2J2 transgenic mice were significantly protected from HF-streptozotocin-induced diabetic cardiomyopathy. Strikingly, CYP2J2 overexpression attenuated myocardial hypertrophy induced by diabetes. We conclude that cardiac-specific overexpression of CYP2J2 significantly protects against diabetic cardiomyopathy, which may be due to improved cardiac insulin resistance, glucose uptake, and reversal of cardiac hypertrophy. Relevant mechanisms may include up-regulation of peroxisome proliferator-activated receptor γ, activation of insulin receptor and AMP-activated protein kinase signaling pathways, and inhibition of nuclear factor of activated T cells c3 signal by enhanced atrial natriuretic peptide production. These results suggest that CYP2J2 epoxygenase metabolites likely play an important role in plasma glucose homeostasis, and enhancement of epoxyeicosatrienoic acids activation may serve as an effective therapeutic strategy to prevent diabetic cardiomyopathy.

CYP2J3 gene delivery up-regulated adiponectin expression via reduced endoplasmic reticulum stress in adipocytes

Ample evidences demonstrate that cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid into epoxyeicosatrienoic acids (EETs), which play crucial and diverse roles in cardiovascular homeostasis. We and others have identified that EETs exert a beneficial role on insulin resistance and diabetes. This study investigated the effects of CYP2J3 epoxygenase gene delivery on adiponectin expression in rats treated with high-fat (HF) diet. CYP2J3 gene delivery in vivo increased EET generation, enhanced adiponectin expression and secretion and accompanied by activation of adiponectin downstream signaling, and decreased insulin resistance as determined by plasma insulin levels, insulin resistance index and glucose tolerance test, as well as phosphorylation of protein kinase B in both liver and muscle. Furthermore, CYP2J3 overexpression prevented HF diet-induced endoplasmic reticulum (ER) stress in adipose tissue of rats. Also, CYP2J3 gene transfection and exogenous administration of EETs inhibited thapsigargin-induced ER stress with increased adiponectin expression and secretion in differentiated 3T3-L1 adipocytes. Thus, CYP2J3 gene delivery up-regulated adiponectin expression and excretion in adipose tissue of rats treated with HF diet through inhibition of ER stress, which can decrease adiponectin expression. These results further highlight the beneficial roles of the CYP epoxygenase 2J3 and its metabolites EETs on adiponectin expression and secretion.

Novel orally active epoxyeicosatrienoic acid (EET) analogs attenuate cisplatin nephrotoxicity

Nephrotoxicity severely limits the use of the anticancer drug cisplatin. Oxidative stress, inflammation, and endoplasmic reticulum (ER) stress contribute to cisplatin-induced nephrotoxicity. We developed novel orally active epoxyeicosatrienoic acid (EET) analogs and investigated their prophylactic effect in cisplatin-induced nephrotoxicity in rats. Cisplatin-induced nephrotoxicity was manifested by increases in blood urea nitrogen, plasma creatinine, urinary N-acetyl-β-(d)-glucosaminidase activity, kidney injury molecule 1, and histopathology. EET analogs (10 mg/kg/d) attenuated cisplatin-induced nephrotoxicity by reducing these renal injury markers by 40-80% along with a 50-70% reduction in renal tubular cast formation. This attenuated renal injury is associated with reduced oxidative stress, inflammation, and ER stress evident from reduction in related biomarkers and in the renal expression of genes involved in these pathways. Moreover, we demonstrated that the attenuated nephrotoxicity correlated with decreased apoptosis that is associated with 50-90% reduction in Bcl-2 protein family mediated proapoptotic signaling, reduced renal caspase-12 expression, and a 50% reduction in renal caspase-3 activity. We further demonstrated in vitro that the protective activity of EET analogs does not compromise the anticancer effects of cisplatin. Collectively, our data provide evidence that EET analogs attenuate cisplatin-induced nephrotoxicity by reducing oxidative stress, inflammation, ER stress, and apoptosis without affecting the chemotherapeutic effects of cisplatin.

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

Cytochrome P450 epoxygenase 2J2 (CYP2J2) metabolizes arachidonic acids to form epoxyeicosatrienoic acids (EETs), which possess various beneficial effects on the cardiovascular system. However, whether increasing EETs production by CYP2J2 overexpression in vivo could prevent abdominal aortic aneurysm (AAA) remains unknown. Here we investigated the effects of recombinant adeno-associated virus (rAAV)-mediated CYP2J2 overexpression on angiotensin (Ang) II-induced AAA in apoE-deficient mice. rAAV-CYP2J2 delivery led to an abundant aortic CYP2J2 expression and increased EETs generation. It was shown that CYP2J2 overexpression attenuated matrix metalloproteinase expression and activity, elastin degradation, and AAA formation, which was associated with reduced aortic inflammation and macrophage infiltration. In cultured vascular smooth muscle cells (VSMCs), rAAV-mediated CYP2J2 overexpression and EETs markedly suppressed Ang II-induced inflammatory cytokine expression. Moreover, overexpressed CYP2J2 and EETs inhibited Ang II-induced macrophage migration in a VSMC-macrophage coculture system. We further indicated that these protective effects were mediated by peroxisome proliferator-activated receptor (PPAR)γ activation. Taken together, these results provide evidence that rAAV-mediated CYP2J2 overexpression prevents AAA development which is likely via PPARγ activation and anti-inflammatory action, suggesting that increasing EETs levels could be considered as a potential strategy to prevent and treat AAA.

Mechanisms of epoxyeicosatrienoic acids to improve cardiac remodeling in chronic renal failure disease

Both clinical and basic science studies have demonstrated that cardiac remodeling in patients with chronic renal failure (CRF) is very common. It is a key feature during the course of heart failure and an important risk factor for subsequent cardiac mortality. Traditional drugs or therapies rarely have effects on cardiac regression of CRF and cardiovascular events are still the first cause of death. Epoxyeicosatrienoic acids (EETs) are the products of arachidonic acids metabolized by cytochrome P450 epoxygenases. It has been found that EETs have important biological effects including anti-hypertension and anti-inflammation. Recent data suggest that EETs are involved in regulating cardiomyocyte injury, renal dysfunction, chronic kidney disease (CKD)-related risk factors and signaling pathways, all of which play key roles in cardiac remodeling induced by CRF. This review analyzes the literature to identify the possible mechanisms for EETs to improve cardiac remodeling induced by CRF and indicates the therapeutic potential of EETs in it.