Prevention and reversal of cardiac hypertrophy by soluble epoxide hydrolase inhibitors

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.

Soft robotic platform for progressive and reversible aortic constriction in a small-animal model

Our understanding of cardiac remodeling processes due to left ventricular pressure overload derives largely from animal models of aortic banding. However, these studies fail to enable control over both disease progression and reversal, hindering their clinical relevance. Here, we describe a method for progressive and reversible aortic banding based on an implantable expandable actuator that can be finely tuned to modulate aortic banding and debanding in a rat model. Through catheterization, imaging, and histologic studies, we demonstrate that our platform can recapitulate the hemodynamic and structural changes associated with pressure overload in a controllable manner. We leveraged soft robotics to enable noninvasive aortic debanding, demonstrating that these changes can be partly reversed because of cessation of the biomechanical stimulus. By recapitulating longitudinal disease progression and reversibility, this animal model could elucidate fundamental mechanisms of cardiac remodeling and optimize timing of intervention for pressure overload.

CYP2J2-mediated metabolism of arachidonic acid in heart: A review of its kinetics, inhibition and role in heart rhythm control

Cytochrome P450 2 J2 (CYP2J2) is primarily expressed extrahepatically and is the predominant epoxygenase in human cardiac tissues. This highlights its key role in the metabolism of endogenous substrates. Significant scientific interest lies in cardiac CYP2J2 metabolism of arachidonic acid (AA), an omega-6 polyunsaturated fatty acid, to regioisomeric bioactive epoxyeicosatrienoic acid (EET) metabolites that show cardioprotective effects including regulation of cardiac electrophysiology. From an in vitro perspective, the accurate characterization of the kinetics of CYP2J2 metabolism of AA including its inhibition and inactivation by drugs could be useful in facilitating in vitro-in vivo extrapolations to predict drug-AA interactions in drug discovery and development. In this review, background information on the structure, regulation and expression of CYP2J2 in human heart is presented alongside AA and EETs as its endogenous substrate and metabolites. The in vitro and in vivo implications of the kinetics of this endogenous metabolic pathway as well as its perturbation via inhibition and inactivation by drugs are elaborated. Additionally, the role of CYP2J2-mediated metabolism of AA to EETs in cardiac electrophysiology will be expounded.

Role of soluble epoxide hydrolase in pain and depression comorbidity

The coexistence of chronic pain and depression in clinical practice places a substantial social burden and profoundly impacts in patients. Although a clear correlation exists, the underlying mechanism of comorbidity between chronic pain and depression remains elusive. Research conducted in recent decades has uncovered that soluble epoxide hydrolase, a pivotal enzyme in the metabolism of polyunsaturated fatty acids, plays a crucial role in inflammation. Interestingly, this enzyme is intricately linked to the development of both pain and depression. With this understanding, this review aims to summarize the roles of soluble epoxide hydrolase in pain, depression, and their comorbidity. Simultaneously, we will also explore the underlying mechanisms, providing guidance for future research and drug development.

Design and Synthesis of Dual-Targeting Inhibitors of sEH and HDAC6 for the Treatment of Neuropathic Pain and Lipopolysaccharide-Induced Mortality

Epoxyeicosatrienoic acids with anti-inflammatory effects are inactivated by soluble epoxide hydrolase (sEH). Both sEH and histone deacetylase 6 (HDAC6) inhibitors are being developed as neuropathic pain relieving agents. Based on the structural similarity, we designed a new group of compounds with inhibition of both HDAC6 and sEH and obtained compound M9. M9 exhibits selective inhibition of HDAC6 over class I HDACs in cells. M9 shows good microsomal stability, moderate plasma protein binding rate, and oral bioavailability. M9 exhibited a strong analgesic effect in vivo, and its analgesic tolerance was better than gabapentin. M9 improved the survival time of mice treated with lipopolysaccharide (LPS) and reversed the levels of inflammatory factors induced by LPS in mouse plasma. M9 represents the first sEH/HDAC6 dual inhibitors with in vivo antineuropathic pain and anti-inflammation.

Glimepiride, a novel soluble epoxide hydrolase inhibitor, protects against heart failure via increasing epoxyeicosatrienoic acids

BACKGROUND

Epoxyeicosatrienoic acids (EETs), which exert multiple endogenous protective effects, are hydrolyzed into less active dihydroxyeicosatrienoic acids (DHETs) by soluble epoxide hydrolase (sEH). However, commercial drugs related to EETs or sEH are not yet in clinical use.

METHODS

Firstly, the plasma concentration of EETs and DHETs of 316 patients with heart failure (HF) were detected and quantitated by liquid chromatography-tandem mass spectrometry. Then, transverse aortic constriction (TAC)-induced HF was introduced in cardiomyocyte-specific Ephx2-/- mice. Moreover, Western blot, real-time PCR, luciferase reporter, ChIP assays were employed to explore the underlying mechanism. Finally, multiple sEH inhibitors were designed, synthesized, and validated in vitro and in vivo.

RESULTS

The ratios of DHETs/EETs were increased in the plasma from patients with HF. Meanwhile, the expression of sEH was upregulated in the heart of patients and mice with HF, especially in cardiomyocytes. Cardiomyocyte-specific Ephx2-/- mice ameliorated cardiac dysfunction induced by TAC. Consistently, Ephx2 knockdown protected Angiotensin II (AngII)-treated cardiomyocytes via increasing EETs in vitro. Mechanistically, AngII could enhance the expression of transcript factor Krüppel-like factor 15 (KLF15), which in turn upregulated sEH. Importantly, glimepiride was identified as a novel sEH inhibitor, which benefited from the elevated EETs during HF.

CONCLUSIONS

Glimepiride attenuates HF in mice in part by increasing EETs.

CLINICAL TRIAL IDENTIFIER

NCT03461107 (https://clinicaltrials.gov).

Future treatments in hypertension: Can we meet the unmet needs of patients?

The prevalence of arterial hypertension is approximately 47% in the United States and 55% in Europe. Multiple different medical therapies are used to treat hypertension including diuretics, beta blockers, calcium channel blockers, angiotensin receptor blockers, angiotensin converting enzyme inhibitors, alpha blockers, central acting alpha receptor agonists, neprilysin inhibitors and vasodilators. However, despite the numerous number of medications, the prevalence of hypertension is on the rise, a considerable proportion of the hypertensive population is resistant to these therapeutic modalities and a definitive cure is not possible with the current treatment approaches. Therefore, there is a need for novel therapeutic strategies to provide better treatment and control of hypertension. In this review, our aim is to describe the latest developments in the treatment of hypertension including novel medication classes, gene therapies and RNA-based modalities.

Quantification of soluble epoxide hydrolase inhibitors in experimental and clinical samples using the nanobody-based ELISA

To ensure proper dosage of a drug, analytical quantification of it in biofluid is necessary. Liquid chromatography mass spectrometry (LC-MS) is the conventional method of choice as it permits accurate identification and quantification. However, it requires expensive instrumentation and is not appropriate for bedside use. Using soluble epoxide hydrolase (sEH) inhibitors (EC5026 and TPPU) as examples, we report development of a nanobody-based enzyme-linked immunosorbent assay (ELISA) for such small molecules and its use to accurately quantify the drug chemicals in human samples. Under optimized conditions, two nanobody-based ELISAs were successfully established for EC5026 and TPPU with low limits of detection of 0.085 ng/mL and 0.31 ng/mL, respectively, and two order of magnitude linear ranges with high precision and accuracy. The assay was designed to detect parent and two biologically active metabolites in the investigation of a new drug candidate EC5026. In addition, the ELISAs displayed excellent correlation with LC-MS analysis and evaluation of inhibitory potency. The results indicate that nanobody-based ELISA methods can efficiently analyze drug like compounds. These methods could be easily implemented by the bedside, in the field in remote areas or in veterinary practice. This work illustrates that nanobody based assays offer alternative and supplementary analytical tools to mass spectrometry for monitoring small molecule medicines during clinical development and therapy. Attributes of nanobody based pharmaceutical assays are discussed.

Regulatory lipid vicinal diols counteract the biological activity of epoxy fatty acids and can act as biomarkers and mechanisms for disease progression

Polyunsaturated fatty acids (PUFAs) are essential fatty acids required for human health and are obtained primarily from food or synthesized in the body by highly regulated processes. The metabolites of these lipids, formed largely through the action of cyclooxygenase, lipoxygenase, or cytochrome P450 (CYP450) enzymes, are responsible for multiple biological functions including inflammation, tissue repair, cell proliferation, blood vessel permeability, and immune cell behavior. The role of these regulatory lipids in disease has been well studied since their discovery as druggable targets; however, the metabolites generated downstream of these pathways have only recently gained attention for regulating biology. Specifically, the biological activity of lipid vicinal diols formed from the metabolism of CYP450-generated epoxy fatty acids (EpFA) by epoxide hydrolases were previously thought to have little biological activity but increasingly are recognized as promoting inflammation and brown fat adipogenesis, and exciting neurons through the regulation of ion channel activity at low concentrations. These metabolites also appear to balance the action of the EpFA precursor. For example, EpFA demonstrate the ability to resolve inflammation and reduce pain, while some lipid diols, through opposing mechanisms, promote inflammation and pain. This review describes recent studies that highlight the role of regulatory lipids, focusing on the balance between EpFA and their diol metabolites in promoting or resolving disease.

Effects of Individual Circulating FFAs on Plasma and Hepatic FFA Epoxides, Diols, and Epoxide-Diol Ratios as Indices of Soluble Epoxide Hydrolase Activity

Oxylipins, oxidation products of unsaturated free fatty acids (FFAs), are involved in various cellular signaling systems. Among these oxylipins, FFA epoxides are associated with beneficial effects in metabolic and cardiovascular health. FFA epoxides are metabolized to diols, which are usually biologically less active, by soluble epoxide hydrolase (sEH). Plasma epoxide-diol ratios have been used as indirect measures of sEH activity. This study was designed to examine the effects of acute elevation of individual plasma FFAs on a variety of oxylipins, particularly epoxides, diols, and their ratios. We tested if FFA epoxide-diol ratios are altered by circulating FFA levels (i.e., substrate availability) independent of sEH activity. Wistar rats received a constant intravenous infusion of olive (70% oleic acid (OA)), safflower seed (72% linoleic acid (LA)), and fish oils (rich in ω-3 FFAs) as emulsions to selectively raise OA, LA, and ω-3 FFAs (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)), respectively. As expected, olive, safflower seed, and fish oil infusions selectively raised plasma OA (57%), LA (87%), EPA (70%), and DHA (54%), respectively (p < 0.05 for all). Raising plasma FFAs exerted substrate effects to increase hepatic and plasma epoxide and diol levels. These increases in epoxides and diols occurred to similar extents, resulting in no significant changes in epoxide-diol ratios. These data suggest that epoxide-diol ratios, often used as indices of sEH activity, are not affected by substrate availability or altered plasma FFA levels and that epoxide-diol ratios may be used to compare sEH activity between conditions of different circulating FFA levels.

Enhancement of the liver's neuroprotective role ameliorates traumatic brain injury pathology

Traumatic brain injury (TBI) is a pervasive problem worldwide for which no effective treatment is currently available. Although most studies have focused on the pathology of the injured brain, we have noted that the liver plays an important role in TBI. Using two mouse models of TBI, we found that the enzymatic activity of hepatic soluble epoxide hydrolase (sEH) was rapidly decreased and then returned to normal levels following TBI, whereas such changes were not observed in the kidney, heart, spleen, or lung. Interestingly, genetic downregulation of hepatic Ephx2 (which encodes sEH) ameliorates TBI-induced neurological deficits and promotes neurological function recovery, whereas overexpression of hepatic sEH exacerbates TBI-associated neurological impairments. Furthermore, hepatic sEH ablation was found to promote the generation of A2 phenotype astrocytes and facilitate the production of various neuroprotective factors associated with astrocytes following TBI. We also observed an inverted V-shaped alteration in the plasma levels of four EET (epoxyeicosatrienoic acid) isoforms (5,6-, 8,9-,11,12-, and 14,15-EET) following TBI which were negatively correlated with hepatic sEH activity. However, hepatic sEH manipulation bidirectionally regulates the plasma levels of 14,15-EET, which rapidly crosses the blood-brain barrier. Additionally, we found that the application of 14,15-EET mimicked the neuroprotective effect of hepatic sEH ablation, while 14,15-epoxyeicosa-5(Z)-enoic acid blocked this effect, indicating that the increased plasma levels of 14,15-EET mediated the neuroprotective effect observed after hepatic sEH ablation. These results highlight the neuroprotective role of the liver in TBI and suggest that targeting hepatic EET signaling could represent a promising therapeutic strategy for treating TBI.

Classes of Lipid Mediators and Their Effects on Vascular Inflammation in Atherosclerosis

It is commonly believed that the inactivation of inflammation is mainly due to the decay or cessation of inducers. In reality, in connection with the development of atherosclerosis, spontaneous decay of inducers is not observed. It is now known that lipid mediators originating from polyunsaturated fatty acids (PUFAs), which are important constituents of all cell membranes, can act in the inflamed tissue and bring it to resolution. In fact, PUFAs, such as arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), are precursors to both pro-inflammatory and anti-inflammatory compounds. In this review, we describe the lipid mediators of vascular inflammation and resolution, and their biochemical activity. In addition, we highlight data from the literature that often show a worsening of atherosclerotic disease in subjects deficient in lipid mediators of inflammation resolution, and we also report on the anti-proteasic and anti-thrombotic properties of these same lipid mediators. It should be noted that despite promising data observed in both animal and in vitro studies, contradictory clinical results have been observed for omega-3 PUFAs. Many further studies will be required in order to clarify the observed conflicts, although lifestyle habits such as smoking or other biochemical factors may often influence the normal synthesis of lipid mediators of inflammation resolution.

Soluble epoxide hydrolase inhibition alleviates chemotherapy induced neuropathic pain

Chemotherapy induced peripheral neuropathy (CIPN) is a particularly pernicious form of neuropathy and the associated pain is the primary dose-limiting factor of life-prolonging chemotherapy treatment. The prevalence of CIPN is high and can last long after treatment has been stopped. Currently, late in the COVID-19 pandemic, there are still increased psychological pressures on cancer patients as well as additional challenges in providing analgesia for them. These include the risks of nonsteroidal anti-inflammatory drug (NSAID) analgesics potentially masking early infection symptoms and the immunosuppression of steroidal and opiate based approaches. Even without these concerns, CIPN is often inadequately treated with few therapies that offer significant pain relief. The experiments we report use soluble epoxide hydrolase inhibitors (sEHI) which relieved this intractable pain in preclinical models. Doses of EC5026, an IND candidate intended to treat neuropathic pain, elicited dose dependent analgesic responses in multiple models including platinum-based, taxane, and vinca alkaloid-based CIPN pain in Sprague Dawley rats. At the same time as a class, the sEHI are known to result in fewer debilitating side effects of other analgesics, likely due to their novel mechanism of action. Overall, the observed dose-dependent analgesia in both male and female rats across multiple models of chemotherapy induced neuropathic pain holds promise as a useful tool when translated to the clinic.

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.

Crosstalk between adenosine receptors and CYP450-derived oxylipins in the modulation of cardiovascular, including coronary reactive hyperemic response

Adenosine is a ubiquitous endogenous nucleoside or autacoid that affects the cardiovascular system through the activation of four G-protein coupled receptors: adenosine A₁ receptor (A₁AR), adenosine A_2A receptor (A_2AAR), adenosine A_2B receptor (A_2BAR), and adenosine A₃ receptor (A₃AR). With the rapid generation of this nucleoside from cellular metabolism and the widespread distribution of its four G-protein coupled receptors in almost all organs and tissues of the body, this autacoid induces multiple physiological as well as pathological effects, not only regulating the cardiovascular system but also the central nervous system, peripheral vascular system, and immune system. Mounting evidence shows the role of CYP450-enzymes in cardiovascular physiology and pathology, and the genetic polymorphisms in CYP450s can increase susceptibility to cardiovascular diseases (CVDs). One of the most important physiological roles of CYP450-epoxygenases (CYP450-2C & CYP2J2) is the metabolism of arachidonic acid (AA) and linoleic acid (LA) into epoxyeicosatrienoic acids (EETs) and epoxyoctadecaenoic acid (EpOMEs) which generally involve in vasodilation. Like an increase in coronary reactive hyperemia (CRH), an increase in anti-inflammation, and cardioprotective effects. Moreover, the genetic polymorphisms in CYP450-epoxygenases will change the beneficial cardiovascular effects of metabolites or oxylipins into detrimental effects. The soluble epoxide hydrolase (sEH) is another crucial enzyme ubiquitously expressed in all living organisms and almost all organs and tissues. However, in contrast to CYP450-epoxygenases, sEH converts EETs into dihydroxyeicosatrienoic acid (DHETs), EpOMEs into dihydroxyoctadecaenoic acid (DiHOMEs), and others and reverses the beneficial effects of epoxy-fatty acids leading to vasoconstriction, reducing CRH, increase in pro-inflammation, increase in pro-thrombotic and become less cardioprotective. Therefore, polymorphisms in the sEH gene (Ephx2) cause the enzyme to become overactive, making it more vulnerable to CVDs, including hypertension. Besides the sEH, ω-hydroxylases (CYP450-4A11 & CYP450-4F2) derived metabolites from AA, ω terminal-hydroxyeicosatetraenoic acids (19-, 20-HETE), lipoxygenase-derived mid-chain hydroxyeicosatetraenoic acids (5-, 11-, 12-, 15-HETEs), and the cyclooxygenase-derived prostanoids (prostaglandins: PGD₂, PGF_2α; thromboxane: Txs, oxylipins) are involved in vasoconstriction, hypertension, reduction in CRH, pro-inflammation and cardiac toxicity. Interestingly, the interactions of adenosine receptors (A_2AAR, A₁AR) with CYP450-epoxygenases, ω-hydroxylases, sEH, and their derived metabolites or oxygenated polyunsaturated fatty acids (PUFAs or oxylipins) is shown in the regulation of the cardiovascular functions. In addition, much evidence demonstrates polymorphisms in CYP450-epoxygenases, ω-hydroxylases, and sEH genes (Ephx2) and adenosine receptor genes (ADORA1 & ADORA2) in the human population with the susceptibility to CVDs, including hypertension. CVDs are the number one cause of death globally, coronary artery disease (CAD) was the leading cause of death in the US in 2019, and hypertension is one of the most potent causes of CVDs. This review summarizes the articles related to the crosstalk between adenosine receptors and CYP450-derived oxylipins in vascular, including the CRH response in regular salt-diet fed and high salt-diet fed mice with the correlation of heart perfusate/plasma oxylipins. By using A_2AAR^-/-, A₁AR^-/-, eNOS^-/-, sEH^-/- or Ephx2^-/-, vascular sEH-overexpressed (Tie2-sEH Tr), vascular CYP2J2-overexpressed (Tie2-CYP2J2 Tr), and wild-type (WT) mice. This review article also summarizes the role of pro-and anti-inflammatory oxylipins in cardiovascular function/dysfunction in mice and humans. Therefore, more studies are needed better to understand the crosstalk between the adenosine receptors and eicosanoids to develop diagnostic and therapeutic tools by using plasma oxylipins profiles in CVDs, including hypertensive cases in the future.

Exploration of the Mechanism of Linoleic Acid Metabolism Dysregulation in Metabolic Syndrome

We aimed to explore the mechanism of the linoleic acid metabolism in metabolic syndrome (MetS). RNA-seq data for 16 samples with or without MetS from the GSE145412 dataset were collected. Gene set variation analysis (GSVA), gene set enrichment analysis (GSEA), and gene differential expression analysis were performed. Expression data of differentially expressed genes (DEGs) involved in the linoleic acid metabolism pathway were mapped to the pathway by using Pathview for visualization. There were 19 and 10 differentially expressed biological processes in the disease group and healthy group, respectively. 9 KEGG pathways were differentially expressed in the disease group. Linoleic acid metabolism was the only differentially expressed pathway in the healthy group. The GSVA enrichment score of the linoleic acid metabolism pathway in the disease group was markedly lower than that in the healthy group. The GSEA result showed that the linoleic acid metabolism pathway was significantly downregulated in the disease group. JMJD7-PLA2G4B, PLA2G1B, PLA2G2D, CYP2C8, and CYP2J2 involved in the pathway were significantly downregulated in the disease group. This study may provide novel insight into MetS from the point of linoleic acid metabolism dysregulation.

The juvenile hormone epoxide hydrolase homolog in Penaeus vannamei plays immune-related functions

Juvenile hormone epoxide hydrolase (JHEH) participates in the degradation of juvenile hormone and also involved in the development and molting process in insects. Here, the JHEH homolog in Pennaus vannamei was cloned and found to consist of a full-length cDNA of 2543 bp and an open reading frame (ORF) of 1386 bp. Transcripts of PvJHEH1 were expressed in most tissues of healthy shrimp with the highest found in the hepatopancreas and lowest in hemocytes. Both Gram-negative (Vibrio parahaemolyticus) and Gram-positive (Streptococcus iniae) bacteria induced PvJHEH1 expression in shrimp hemocytes and hepatopancreas, suggesting the involvement of PvJHEH1 in P. vannamei immune responses. Moreover, the mRNA levels of ecdysone inducible nuclear transcription factor PvE75 and crustacean hyperglycemic hormone (PvCHH), two endocrine-related genes with roles in shrimp innate immune response, decreased significantly in shrimp hemocytes after PvJHEH1 knockdown. Shrimp survival was also affected after PvJHEH1 knockdown followed by V. parahaemolyticus challenge, indicating that JHEH1 plays an essential role in shrimp survival during bacterial infection.

Redox Regulation of Soluble Epoxide Hydrolase-Implications for Cardiovascular Health and Disease

Cell responses to changes in their redox state are significantly mediated by reversible oxido-reductive post-translational modifications of proteins, potentially altering their activities or interactions. These modifications are important for the homeostatic responses of cells to environmental changes that alter their redox state. Such redox regulatory mechanisms not only operate to maintain health, but can become dysregulated and contribute to pathophysiology. In this review, we focus on the redox control of soluble epoxide hydrolase (sEH), which is widely expressed, including in blood vessels and cardiomyocytes. We review the different types of oxidative modifications that regulate sEH and how they may alter cardiovascular physiology and affect disease progression during stress.

A novel soluble epoxide hydrolase vaccine protects murine cardiac muscle against myocardial infarction

Myocardial infarction is still a life-threatening disease, even though its prognosis has been improved through the development of percutaneous coronary intervention and pharmacotherapy. In addition, heart failure due to remodeling after myocardial infarction requires lifelong management. The aim of this study was to develop a novel treatment suppressing the myocardial damage done by myocardial infarction. We focused on inhibition of soluble epoxide hydrolase to prolong the activation of epoxyeicosatrienoic acids, which have vasodilatory and anti-inflammatory properties. We successfully made a new vaccine to inactivate soluble epoxide hydrolase, and we have evaluated the effect of the vaccine in a rat myocardial infarction model. In the vaccinated group, the ischemic area was significantly reduced, and cardiac function was significantly preserved. Vaccine treatment clearly increased microvessels in the border area and suppressed fibrosis secondary to myocardial infarction. This soluble epoxide hydrolase vaccine is a novel treatment for improving cardiac function following myocardial infarction.

The Critical Roles of Proteostasis and Endoplasmic Reticulum Stress in Atrial Fibrillation

Atrial fibrillation (AF) remains the most common arrhythmia seen clinically. The incidence of AF is increasing due to the aging population. AF is associated with a significant increase in morbidity and mortality, yet current treatment paradigms have proven largely inadequate. Therefore, there is an urgent need to develop new effective therapeutic strategies for AF. The endoplasmic reticulum (ER) in the heart plays critical roles in the regulation of excitation-contraction coupling and cardiac function. Perturbation in the ER homeostasis due to intrinsic and extrinsic factors, such as inflammation, oxidative stress, and ischemia, leads to ER stress that has been linked to multiple conditions including diabetes mellitus, neurodegeneration, cancer, heart disease, and cardiac arrhythmias. Recent studies have documented the critical roles of ER stress in the pathophysiological basis of AF. Using an animal model of chronic pressure overload, we demonstrate a significant increase in ER stress in atrial tissues. Moreover, we demonstrate that treatment with a small molecule inhibitor to inhibit the soluble epoxide hydrolase enzyme in the arachidonic acid metabolism significantly reduces ER stress as well as atrial electrical and structural remodeling. The current review article will attempt to provide a perspective on our recent understandings and current knowledge gaps on the critical roles of proteostasis and ER stress in AF progression.

Epoxylipids and soluble epoxide hydrolase in heart diseases

Cardiovascular and heart diseases are leading causes of morbidity and mortality. Coronary artery endothelial and vascular dysfunction, inflammation, and mitochondrial dysfunction contribute to progression of heart diseases such as arrhythmias, congestive heart failure, and heart attacks. Classes of fatty acid epoxylipids and their enzymatic regulation by soluble epoxide hydrolase (sEH) have been implicated in coronary artery dysfunction, inflammation, and mitochondrial dysfunction in heart diseases. Likewise, genetic and pharmacological manipulations of epoxylipids have been demonstrated to have therapeutic benefits for heart diseases. Increasing epoxylipids reduce cardiac hypertrophy and fibrosis and improve cardiac function. Beneficial actions for epoxylipids have been demonstrated in cardiac ischemia reperfusion injury, electrical conductance abnormalities and arrhythmias, and ventricular tachycardia. This review discusses past and recent findings on the contribution of epoxylipids in heart diseases and the potential for their manipulation to treat heart attacks, arrhythmias, ventricular tachycardia, and heart failure.

Soluble Epoxide Hydrolase Inhibitors Regulate Ischemic Arrhythmia by Targeting MicroRNA-1

Background: Soluble epoxide hydrolase inhibitors (sEHis) inhibit the degradation of epoxyeicosatrienoic acids (EETs) in cells, and EETs have antiarrhythmic effects. Our previous experiments confirmed that t-AUCB, a preparation of sEHis, inhibited ischemic arrhythmia by negatively regulating microRNA-1 (miR-1), but its specific mechanism remained unclear. Aim: This study aimed to examine the role of serum response factor (SRF) and the PI3K/Akt/GSK3β pathway in t-AUCB-mediated regulation of miR-1 and the interaction between them. Methods/Results: We used SRF small interfering RNA (siSRF), SRF small hairpin (shSRF) RNA sequence adenovirus, PI3K/Akt/GSK3β pathway inhibitors, t-AUCB, and 14,15-EEZE (a preparation of EETs antagonists) to treat mouse cardiomyocytes overexpressing miR-1 and mice with myocardial infarction (MI). We found that silencing SRF attenuated the effects on miR-1 and its target genes KCNJ2 and GJA1 in the presence of t-AUCB, and inhibition of the PI3K/Akt/GSK3β pathway antagonized the effects of t-AUCB on miR-1, KCNJ2, and GJA1, which were associated with PI3Kα, Akt, and Gsk3β but not PI3Kβ or PI3Kγ. Moreover, the PI3K/Akt/GSK3β pathway was involved in the regulation of SRF by t-AUCB, and silencing SRF inhibited the t-AUCB-induced increases in Akt and Gsk3β phosphorylation. Conclusions: Both the SRF and the PI3K/Akt/GSK3β pathway are involved in the t-AUCB-mediated regulation of miR-1, and these factors interact with each other.

Epoxyeicosatrienoic acids prevent cardiomyocytes against sepsis by A2AR-induced activation of PI3K and PPARγ

Although epoxyeicosatrienoic acids (EETs) have multiple protective effects against different diseases, whether they can improve the pathogenesis of lipopolysaccharide (LPS)-induced septic cardiac dysfunction remains unknown. We investigated the effects of EETs on the LPS-induced inflammatory response in myocardial dysfunction mice and H9c2 cardiac myocytes. Cardiac-specific CYP2J2 transgenic mice (Tr) showed improved cardiac function and reduced inflammation response after administration with LPS, while the protective effects were not observed in A_2A adenosine receptor (A_2AR/ADORA2A)-deficient mice (knockout/KO). In vitro, EETs prevented LPS-induced inflammation and apoptosis in the cardiomyocytes via A_2AR activation. Moreover, ZM241385 (A_2AR inhibitor) attenuated the cardioprotective properties of EETs. Further investigation demonstrated that A_2AR signal pathway activation partly regulated phosphatidylinositol 3-kinase (PI3K) and peroxisome proliferator-activated receptor-γ (PPARγ) expression. This is the first report on EETs exerting cardioprotective effects against LPS-induced cardiomyocyte injury via A_2AR activation.

Pharmacological regulation of cytochrome P450 metabolites of arachidonic acid attenuates cardiac injury in diabetic rats

Diabetic cardiomyopathy (DCM) is a well-established complication of type 1 and type 2 diabetes associated with a high rate of morbidity and mortality. DCM is diagnosed at advanced and irreversible stages. Therefore, it is of utmost need to identify novel mechanistic pathways involved at early stages to prevent or reverse the development of DCM. In vivo experiments were performed on type 1 diabetic rats (T1DM). Functional and structural studies of the heart were executed and correlated with mechanistic assessments exploring the role of cytochromes P450 metabolites, the 20-hydroxyeicosatetraenoic acids (20-HETEs) and epoxyeicosatrienoic acids (EETs), and their crosstalk with other homeostatic signaling molecules. Our data displays that hyperglycemia results in CYP4A upregulation and CYP2C11 downregulation in the left ventricles (LV) of T1DM rats, paralleled by a differential alteration in their metabolites 20-HETEs (increased) and EETs (decreased). These changes are concomitant with reductions in cardiac outputs, LV hypertrophy, fibrosis, and increased activation of cardiac fetal and hypertrophic genes. Besides, pro-fibrotic cytokine TGF-ß overexpression and NADPH (Nox4) dependent-ROS overproduction are also correlated with the observed cardiac functional and structural modifications. Of interest, these observations are attenuated when T1DM rats are treated with 12-(3-adamantan-1-yl-ureido) dodecanoic acid (AUDA), which blocks EETs metabolism, or N-hydroxy-N'-(4-butyl-2-methylphenol)Formamidine (HET0016), which inhibits 20-HETEs formation. Taken together, our findings confer pioneering evidence about a potential interplay between CYP450-derived metabolites and Nox4/TGF-β axis leading to DCM. Pharmacologic interventions targeting the inhibition of 20-HETEs synthesis or the activation of EETs synthesis may offer novel therapeutic approaches to treat DCM.

Targeting Soluble Epoxide Hydrolase and Cyclooxygenases Enhance Joint Pain Control, Stimulate Collagen Synthesis, and Protect Chondrocytes From Cytokine-Induced Apoptosis

Objective: To determine the symptomatic and disease-modifying capabilities of sEH and COX inhibitors during joint inflammation. Methods: Using a blinded, randomized, crossover experimental design, 6 adult healthy horses were injected with lipopolysaccharide (LPS; 3 μg) from E. coli in a radiocarpal joint and concurrently received the non-selective cyclooxygenase (COX) inhibitor phenylbutazone (2 mg/kg), the sEH inhibitor t-TUCB (1 mg/kg) or both (2 mg/kg phenylbutazone and 0.1, 0.3, and 1 mg/kg t-TUCB) intravenously. There were at least 30 days washout between treatments. Joint pain (assessed via inertial sensors and peak vertical forces), synovial fluid concentrations of prostanoids (PGE₂, TxB₂), cytokines (IL-1β, IL-6, TNF-α) and biomarkers of collagen synthesis (CPII) and degradation (C2C) were measured at pre-determined intervals over a 48-h period. The anti-apoptotic effect of COX and sEH inhibitors was determined via ELISA technique in primary equine chondrocytes incubated with TNF-α (10 ng/ml) for 24 h. Apoptosis was also determined in chondrocytes incubated with sEH-generated metabolites. Results: Combined COX and sEH inhibition produced significantly better control of joint pain, prostanoid responses, and collagen synthesis-degradation balance compared to each compound separately. When administered separately, pain control was superior with COX vs. sEH inhibition. Cytokine responses were not different during COX and/or sEH inhibition. In cultured chondrocytes, sEH inhibition alone or combined with COX inhibition, but not COX inhibition alone had significant anti-apoptotic effects. However, sEH-generated metabolites caused concentration-dependent apoptosis. Conclusions: Combined COX and sEH inhibition optimize pain control, attenuate loss of articular cartilage matrix during joint inflammation and cytokine-induced chondrocyte apoptosis.

An Optimized Model of Hypertrophic Preconditioning Confers Cardioprotection in the Mouse

BACKGROUND

Conventional models of hypertrophic preconditioning (C-HP) can be established surgically through transverse aortic constriction (TAC) → deconstriction (De-TAC) → reconstriction (Re-TAC) characterized by dynamic afterload while it exerts technical difficulty on operators and poses high mortality during perioperative period in mice. We aimed to introduce an optimized method for obtaining a hypertrophic preconditioning (O-HP) model for further study on cardiac hypertrophy.

METHODS

Ninety mice were divided into four groups: sham, TAC, C-HP, and O-HP. The sham group was exerted on three-time thoracotomies. The TAC group experienced twice thoracotomies and one TAC operation. C-HP and O-HP groups were given TAC, De-TAC, and Re-TAC operation at day 0, day 3, and day 7 in conventional and optimized method, respectively. We optimized the operating procedure in O-HP mice compared with the C-HP group by (1) leaving a ∼3-cm suture fixed in the subcutaneous layer after aortic constriction in TAC surgery (2) using two small forceps to untie the constriction knot instead of cutting it in the De-TAC operation. Ultrasound biomicroscopy was used for hemodynamics and cardiac function detection. Four weeks after the third surgery, all mice were sacrificed and pathology was analyzed among four groups.

RESULTS

Four weeks after Re-TAC, the survival of O-HP mice was 63.3% while that of C-HP was 26.7%. Ultrasound biomicroscopy showed a successful establishment of HP models. C-HP and O-HP mice had improved cardiac structure and function indicated by left ventricular end-systolic diameter, left ventricular end-systolic posterior wall thickness, left ventricular ejection fraction, and left ventricular fractional shortening than the TAC group. Pathological analysis showed O-HP as well as C-HP had less hypertrophy than the TAC mice.

CONCLUSIONS

Our results provide a rapid, safe, efficient, and reproducible method for optimized establishment of the HP model, which will facilitate studies for early intervention and prevention of left ventricular hypertrophy and heart failure.

The Role of Epoxyeicosatrienoic Acids in Cardiac Remodeling

Epoxyeicosatrienoic acids (EETs) are metabolites of arachidonic acid by cytochrome P450 (CYP) epoxygenases, which include four regioisomers: 5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET. Each of them possesses beneficial effects against inflammation, fibrosis, and apoptosis, which could combat cardiovascular diseases. Numerous studies have demonstrated that elevation of EETs by overexpression of CYP2J2, inhibition of sEH, or treatment with EET analogs showed protective effects in various cardiovascular diseases, including hypertension, myocardial infarction, and heart failure. As is known to all, cardiac remodeling is the major pathogenesis of cardiovascular diseases. This review will begin with the introduction of EETs and their protective effects in cardiovascular diseases. In the following, the roles of EETs in cardiac remodeling, with a particular emphasis on myocardial hypertrophy, apoptosis, fibrosis, inflammation, and angiogenesis, will be summarized. Finally, it is suggested that upregulation of EETs is a potential therapeutic strategy for cardiovascular diseases. The EET-related drug development against cardiac remodeling is also discussed, including the overexpression of CYP2J2, inhibition of sEH, and the analogs of EET.

Soluble Epoxide Hydrolase Inhibition Prevents Experimental Type 4 Cardiorenal Syndrome

Objectives: Cardiovascular diseases (CVD) remain the leading cause of morbimortality in patients with chronic kidney disease (CKD). The aim of this study was to assess the cardiovascular impact of the pharmacological inhibition of soluble epoxide hydrolase (sEH), which metabolizes the endothelium-derived vasodilatory and anti-inflammatory epoxyeicosatrienoic acids (EETs) to dihydroxyeicosatrienoic acid (DHETs), in the 5/6 nephrectomy (Nx) mouse model.

Methods and Results: Compared to sham-operated mice, there was decrease in EET-to-DHET ratio 3 months after surgery in vehicle-treated Nx mice but not in mice treated with the sEH inhibitor t-AUCB. Nx induced an increase in plasma creatinine and in urine albumin-to-creatinine ratio as well as the development of kidney histological lesions, all of which were not modified by t-AUCB. In addition, t-AUCB did not oppose Nx-induced blood pressure increase. However, t-AUCB prevented the development of cardiac hypertrophy and fibrosis induced by Nx, as well as normalized the echocardiographic indices of diastolic and systolic function. Moreover, the reduction in endothelium-dependent flow-mediated dilatation of isolated mesenteric arteries induced by Nx was blunted by t-AUCB without change in endothelium-independent dilatation to sodium nitroprusside.

Conclusion: Inhibition of sEH reduces the cardiac remodelling, and the diastolic and systolic dysfunctions associated with CKD. These beneficial effects may be mediated by the prevention of endothelial dysfunction, independent from kidney preservation and antihypertensor effect. Thus, inhibition of sEH holds a therapeutic potential in preventing type 4 cardiorenal syndrome.

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.

Movement to the Clinic of Soluble Epoxide Hydrolase Inhibitor EC5026 as an Analgesic for Neuropathic Pain and for Use as a Nonaddictive Opioid Alternative

This report describes the development of an orally active analgesic that resolves inflammation and neuropathic pain without the addictive potential of opioids. EC5026 acts on the cytochrome P450 branch of the arachidonate cascade to stabilize epoxides of polyunsaturated fatty acids (EpFA), which are natural mediators that reduce pain, resolve inflammation, and maintain normal blood pressure. EC5026 is a slow-tight binding transition-state mimic that inhibits the soluble epoxide hydrolase (sEH) at picomolar concentrations. The sEH rapidly degrades EpFA; thus, inhibiting sEH increases EpFA in vivo and confers beneficial effects. This mechanism addresses disease states by shifting endoplasmic reticulum stress from promoting cellular senescence and inflammation toward cell survival and homeostasis. We describe the synthesis and optimization of EC5026 and its development through human Phase 1a trials with no drug-related adverse events. Additionally, we outline fundamental work leading to discovery of the analgesic and inflammation-resolving CYP450 branch of the arachidonate cascade.

Soluble Epoxide Hydrolase as an Important Player in Intestinal Cell Differentiation

There is growing evidence that soluble epoxide hydrolase (sEH) may play a role in cell differentiation. sEH metabolizes biologically highly active and generally cytoprotective epoxyeicosatrienoic acids (EETs), generated from arachidonic acid metabolism by CYP epoxygenases (CYP2C and CYP2J subfamilies), to less active corresponding diols. We investigated the effect of sEH inhibitor (TPPU) on the expression of villin, CYP2C8, CYP2C9, CYP2J2, and sEH in undifferentiated and in vitro differentiated HT-29 and Caco2 cell lines. The administration of 10 μM TPPU on differentiated HT-29 and Caco2 cells resulted in a significant decrease in expression of villin, a marker for intestinal cell differentiation. It was accompanied by a disruption of the brush border when microvilli appeared sparse and short in atomic force microscope scans of HT-29 cells. Although inhibition of sEH in differentiated HT-29 and Caco2 cells led to an increase in sEH expression in both cell lines, this treatment had an opposite effect on CYP2J2 expression in HT-29 and Caco2 cells. In addition, tissue samples of colorectal carcinoma and adjacent normal tissues from 45 patients were immunostained for sEH and villin. We detected a significant decrease in the expression of both proteins in colorectal carcinoma in comparison to adjacent normal tissue, and the decrease in both sEH and villin expression revealed a moderate positive association. Taken together, our results showed that sEH is an important player in intestinal cell differentiation.

Cytochrome P450-derived linoleic acid metabolites EpOMEs and DiHOMEs: a review of recent studies

Linoleic acid (LA) is the most abundant polyunsaturated fatty acid found in the Western diet. Cytochrome P450-derived LA metabolites 9,10-epoxyoctadecenoic acid (9,10-EpOME), 12,13-epoxyoctadecenoic acid (12,13-EpOME), 9,10-dihydroxy-12Z-octadecenoic acid (9,10-DiHOME) and 12,13-dihydroxy-9Z-octadecenoic acid (12,13-DiHOME) have been studied for their association with various disease states and biological functions. Previous studies of the EpOMEs and DiHOMEs have focused on their roles in cytotoxic processes, primarily in the inhibition of the neutrophil respiratory burst. More recent research has suggested the DiHOMEs may be important lipid mediators in pain perception, altered immune response and brown adipose tissue activation by cold and exercise. The purpose of this review is to summarize the current understanding of the physiological and pathophysiological roles and modes of action of the EpOMEs and DiHOMEs in health and disease.

Suppression of inflammation and fibrosis using soluble epoxide hydrolase inhibitors enhances cardiac stem cell-based therapy

Stem cell replacement offers a great potential for cardiac regenerative therapy. However, one of the critical barriers to stem cell therapy is a significant loss of transplanted stem cells from ischemia and inflammation in the host environment. Here, we tested the hypothesis that inhibition of the soluble epoxide hydrolase (sEH) enzyme using sEH inhibitors (sEHIs) to decrease inflammation and fibrosis in the host myocardium may increase the survival of the transplanted human induced pluripotent stem cell derived-cardiomyocytes (hiPSC-CMs) in a murine postmyocardial infarction model. A specific sEHI (1-trifluoromethoxyphenyl-3-(1-propionylpiperidine-4-yl)urea [TPPU]) and CRISPR/Cas9 gene editing were used to test the hypothesis. TPPU results in a significant increase in the retention of transplanted cells compared with cell treatment alone. The increase in the retention of hiPSC-CMs translates into an improvement in the fractional shortening and a decrease in adverse remodeling. Mechanistically, we demonstrate a significant decrease in oxidative stress and apoptosis not only in transplanted hiPSC-CMs but also in the host environment. CRISPR/Cas9-mediated gene silencing of the sEH enzyme reduces cleaved caspase-3 in hiPSC-CMs challenged with angiotensin II, suggesting that knockdown of the sEH enzyme protects the hiPSC-CMs from undergoing apoptosis. Our findings demonstrate that suppression of inflammation and fibrosis using an sEHI represents a promising adjuvant to cardiac stem cell-based therapy. Very little is known regarding the role of this class of compounds in stem cell-based therapy. There is consequently an enormous opportunity to uncover a potentially powerful class of compounds, which may be used effectively in the clinical setting.

Assessment of OMT-28, a synthetic analog of omega-3 epoxyeicosanoids, in patients with persistent atrial fibrillation: Rationale and design of the PROMISE-AF phase II study

We designed a placebo controlled, double-blind, randomized, dose-finding phase II study on OMT-28 in the maintenance of sinus rhythm after electrical cardioversion (DCC) in patients with persistent atrial fibrillation (PROMISE-AF). OMT-28 is a first-in-class, synthetic analog of 17,18-epoxyeicosatetetraenoic acid, a bioactive lipid mediator generated by cytochrome P450 enzymes from the omega-3 fatty acid eicosapentaenoic acid. OMT-28 improves Ca²⁺-handling and mitochondrial function in cardiomyocytes and reduces pro-inflammatory signaling. This unique mode of action may provide a novel approach to target key mechanism contributing to AF pathophysiology. In a recent phase I study, OMT-28 was safe and well tolerated and showed favorable pharmacokinetics. The PROMISE-AF study (NCT03906799) is designed to assess the efficacy (primary objective), safety, and population pharmacokinetics (secondary objectives) of three different doses of OMT-28, administered once daily, versus placebo until the end of the follow-up period. Recruitment started in March 2019 and the study will include a total of 120 patients. The primary efficacy endpoint is the AF burden (% time with any AF), evaluated over a 13-week treatment period after DCC. AF burden is calculated based on continuous ECG monitoring using an insertable cardiac monitor (ICM). The primary efficacy analysis will be conducted on the modified intention-to-treat (mITT) population, whereas the safety analysis will be done on the safety population. Although ICMs have been used in other interventional studies to assess arrhythmia, PROMISE-AF will be the first study to assess antiarrhythmic efficacy and safety of a novel rhythm-stabilizing drug after DCC by using ICMs.

Soluble Epoxide Hydrolase Regulation of Lipid Mediators Limits Pain

The role of lipids in pain signaling is well established and built on decades of knowledge about the pain and inflammation produced by prostaglandin and leukotriene metabolites of cyclooxygenase and lipoxygenase metabolism, respectively. The analgesic properties of other lipid metabolites are more recently coming to light. Lipid metabolites have been observed to act directly at ion channels and G protein-coupled receptors on nociceptive neurons as well as act indirectly at cellular membranes. Cytochrome P450 metabolism of specifically long-chain fatty acids forms epoxide metabolites, the epoxy-fatty acids (EpFA). The biological role of these metabolites has been found to mediate analgesia in several types of pain pathology. EpFA act through a variety of direct and indirect mechanisms to limit pain and inflammation including nuclear receptor agonism, limiting endoplasmic reticulum stress and blocking mitochondrial dysfunction. Small molecule inhibitors of the soluble epoxide hydrolase can stabilize the EpFA in vivo, and this approach has demonstrated relief in preclinical modeled pain pathology. Moreover, the ability to block neuroinflammation extends the potential benefit of targeting soluble epoxide hydrolase to maintain EpFA for neuroprotection in neurodegenerative disease.

Epoxy Fatty Acids: From Salt Regulation to Kidney and Cardiovascular Therapeutics: 2019 Lewis K. Dahl Memorial Lecture

Epoxyeicosatrienoic acids (EETs) are epoxy fatty acids that have biological actions that are essential for maintaining water and electrolyte homeostasis. An inability to increase EETs in response to a high-salt diet results in salt-sensitive hypertension. Vasodilation, inhibition of epithelial sodium channel, and inhibition of inflammation are the major EET actions that are beneficial to the heart, resistance arteries, and kidneys. Genetic and pharmacological means to elevate EETs demonstrated antihypertensive, anti-inflammatory, and organ protective actions. Therapeutic approaches to increase EETs were then developed for cardiovascular diseases. sEH (soluble epoxide hydrolase) inhibitors were developed and progressed to clinical trials for hypertension, diabetes mellitus, and other diseases. EET analogs were another therapeutic approach taken and these drugs are entering the early phases of clinical development. Even with the promise for these therapeutic approaches, there are still several challenges, unexplored areas, and opportunities for epoxy fatty acids.

Mitochondrial Dysfunction and Inflammaging in Heart Failure: Novel Roles of CYP-Derived Epoxylipids

Age-associated changes leading to a decline in cardiac structure and function contribute to the increased susceptibility and incidence of cardiovascular diseases (CVD) in elderly individuals. Indeed, age is considered a risk factor for heart failure and serves as an important predictor for poor prognosis in elderly individuals. Effects stemming from chronic, low-grade inflammation, inflammaging, are considered important determinants in cardiac health; however, our understanding of the mechanisms involved remains unresolved. A steady decline in mitochondrial function is recognized as an important biological consequence found in the aging heart which contributes to the development of heart failure. Dysfunctional mitochondria contribute to increased cellular stress and an innate immune response by activating the NLRP-3 inflammasomes, which have a role in inflammaging and age-related CVD pathogenesis. Emerging evidence suggests a protective role for CYP450 epoxygenase metabolites of N-3 and N-6 polyunsaturated fatty acids (PUFA), epoxylipids, which modulate various aspects of the immune system and protect mitochondria. In this article, we provide insight into the potential roles N-3 and N-6 PUFA have modulating mitochondria, inflammaging and heart failure.

Cardiac Damage in Anthracyclines Therapy: Focus on Oxidative Stress and Inflammation

Significance: Despite their serious side effects, anthracyclines (ANTs) are the most prescribed chemotherapeutic drugs because of their strong efficacy in both solid and hematological tumors. A major limitation to ANTs clinical application is the severe cardiotoxicity observed both acutely and chronically. The mechanism underlying cardiac dysfunction under chemotherapy is mainly dependent on the generation of oxidative stress and systemic inflammation, both of which lead to progressive cardiomyopathy and heart failure. Recent Advances: Over the years, the iatrogenic ANTs-induced cardiotoxicity was believed to be simply given by iron metabolism and reactive oxygen species production; however, several experimental data indicate that ANTs may use alternative damaging mechanisms, such as topoisomerase 2β inhibition, inflammation, pyroptosis, immunometabolism, and autophagy. Critical Issues: In this review, we aimed at discussing ANTs-induced cardiac injury from different points of view, updating and focusing on oxidative stress and inflammation, since these pathways are not exclusive or independent from each other but they together importantly contribute to the complexity of ANTs-induced multifactorial cardiotoxicity. Future Directions: A deeper understanding of the mechanistic signaling leading to ANTs side effects could reveal crucial targeting molecules, thus representing strategic knowledge to promote better therapeutic efficacy and lower cardiotoxicity during clinical application.

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.

Assessment of soluble epoxide hydrolase activity in vivo: A metabolomic approach

Soluble epoxide hydrolase (sEH) converts several FFA epoxides to corresponding diols. As many as 15 FFA epoxide-diol ratios are measured to infer sEH activity from their ratios. Using previous data, we assessed if individual epoxide-diol ratios all behave similarly to reflect changes in sEH activity, and whether analyzing these ratios together increases the power to detect changes in in-vivo sEH activity. We demonstrated that epoxide-diol ratios correlated strongly with each other (P < 0.05), suggesting these ratios all reflect changes in sEH activity. Furthermore, we developed a modeling approach to analyze all epoxide-diol ratios simultaneously to infer global sEH activity, named SAMI (Simultaneous Analysis of Multiple Indices). SAMI improved power in detecting changes in sEH activity in animals and humans when compared to individual ratio estimates. Thus, we introduce a new powerful method to infer sEH activity by combining metabolomic determination and simultaneous analysis of all measurable epoxide-diol pairs.

Epoxy Fatty Acids Are Promising Targets for Treatment of Pain, Cardiovascular Disease and Other Indications Characterized by Mitochondrial Dysfunction, Endoplasmic Stress and Inflammation

Bioactive lipid mediators resulting from the metabolism of polyunsaturated fatty acids (PUFA) are controlled by many pathways that regulate the levels of these mediators and maintain homeostasis to prevent disease. PUFA metabolism is driven primarily through three pathways. Two pathways, the cyclooxygenase (COX) and lipoxygenase (LO) enzymatic pathways, form metabolites that are mostly inflammatory, while the third route of metabolism results from the oxidation by the cytochrome P450 enzymes to form hydroxylated PUFA and epoxide metabolites. These epoxygenated fatty acids (EpFA) demonstrate largely anti-inflammatory and beneficial properties, in contrast to the other metabolites formed from the degradation of PUFA. Dysregulation of these systems often leads to chronic disease. Pharmaceutical targets of disease focus on preventing the formation of inflammatory metabolites from the COX and LO pathways, while maintaining the EpFA and increasing their concentration in the body is seen as beneficial to treating and preventing disease. The soluble epoxide hydrolase (sEH) is the major route of metabolism of EpFA. Inhibiting its activity increases concentrations of beneficial EpFA, and often disease states correlate to mutations in the sEH enzyme that increase its activity and decrease the concentrations of EpFA in the body. Recent approaches to increasing EpFA include synthetic mimics that replicate biological activity of EpFA while preventing their metabolism, while other approaches focus on developing small molecule inhibitors to the sEH. Increasing EpFA concentrations in the body has demonstrated multiple beneficial effects in treating many diseases, including inflammatory and painful conditions, cardiovascular disease, neurological and disease of the central nervous system. Demonstration of efficacy in so many disease states can be explained by the fundamental mechanism that EpFA have of maintaining healthy microvasculature and preventing mitochondrial and endoplasmic reticulum stress. While there are no FDA approved methods that target the sEH or other enzymes responsible for metabolizing EpFA, current clinical efforts to test for efficacy by increasing EpFA that include inhibiting the sEH or administration of EpFA mimics that block metabolism are in progress.

Role of cytochrome P450-derived, polyunsaturated fatty acid mediators in diabetes and the metabolic syndrome

Over the last decade, cases of metabolic syndrome and type II diabetes have increased exponentially. Exercise and ω-3 polyunsaturated fatty acid (PUFA)-enriched diets are usually prescribed but no therapy is effectively able to restore the impaired glucose metabolism, hypertension, and atherogenic dyslipidemia encountered by diabetic patients. PUFAs are metabolized by different enzymes into bioactive metabolites with anti- or pro-inflammatory activity. One important class of PUFA metabolizing enzymes are the cytochrome P450 (CYP) enzymes that can generate a series of bioactive products, many of which have been attributed protective/anti-inflammatory and insulin-sensitizing effects in animal models. PUFA epoxides are, however, further metabolized by the soluble epoxide hydrolase (sEH) to fatty acid diols. The biological actions of the latter are less well understood but while low concentrations may be biologically important, higher concentrations of diols derived from linoleic acid and docosahexaenoic acid have been linked with inflammation. One potential application for sEH inhibitors is in the treatment of diabetic retinopathy where sEH expression and activity is elevated as are levels of a diol of docosahexaenoic acid that can induce the destabilization of the retina vasculature.

Complex interrelationships between nitro-alkene-dependent inhibition of soluble epoxide hydrolase, inflammation and tumor growth

Nitro-oleate (10-nitro-octadec-9-enoic acid), which inhibits soluble epoxide hydrolase (sEH) by covalently adducting to C521, increases the abundance of epoxyeicosatrienoic acids (EETs) that can be health promoting, for example by lowering blood pressure or their anti-inflammatory actions. However, perhaps consistent with their impact on angiogenesis, increases in EETs may exacerbate progression of some cancers. To assess this, Lewis lung carcinoma (LLc1) cells were exposed to oleate or nitro-oleate, with the latter inhibiting the hydrolase and increasing their proliferation and migration in vitro. The enhanced proliferation induced by nitro-oleate was EET-dependent, being attenuated by the ETT-receptor antagonist 14,15-EE-5(Z)-E. LLc1 cells were engineered to stably overexpress wild-type or C521S sEH, with the latter exhibiting resistance to nitro-oleate-dependent hydrolase inhibition and the associated stimulation of tumor growth in vitro or in vivo. Nitro-oleate also increased migration in endothelial cells isolated from wild-type (WT) mice, but not those from C521S sEH knock-in (KI) transgenic mice genetically modified to render the hydrolase electrophile-resistant. These observations were consistent with nitro-oleate promoting cancer progression, and so the impact of this electrophile was examined in vivo again, but this time comparing growth of LLc1 cells expressing constitutive levels of wild-type hydrolase when implanted into WT or KI mice. Nitro-oleate inhibited tumor sEH (P < 0.05), with a trend for elevated plasma 11(12)-EET/DHET and 8(9)EET/DHET (dihydroxyeicosatrienoic acid) ratios when administered to WT, but not KI, mice. Although in vitro studies with LLc1 cells supported a role for nitro-oleate in cancer cell proliferation, it failed to significantly stimulate tumor growth in WT mice implanted with the same LLc1 cells in vivo, perhaps due to its well-established anti-inflammatory actions. Indeed, pro-inflammatory cytokines were significantly down-regulated in nitro-oleate treated WT mice, potentially countering any impact of the concomitant inhibition of sEH.

CYP-derived eicosanoids: Implications for rheumatoid arthritis

Today the role of cytochrome P450 metabolites in inflammatory rheumatic disease, such as rheumatoid arthritis (RA) is still poorly understood. In this review we survey the current knowledge on cytochrome P450 metabolites in rheumatoid arthritis. The balance between CYP epoxygenase- and CYP ω- hydroxylase is correlated to the regulation of NF-κB. In RA patients synovial fluid there are higher levels of IL-6, which suppresses activities of CYP enzymes, such as CYP3A, CYP2C19, CYP2C9, and CYP1A2. EETs have anti-inflammatory effects, probably attributed to the PPARγ activation. EETs inhibit bone resorption and osteoclastogenesis, and can be considered as an innovative therapeutic strategy for rheumatoid arthritis. In reference to the CYP ɷ-hydroxylase pathway, 20-HETE is a pro-inflammatory mediator. While there is scarce information on the role of 20-HETE inhibitors and its antagonists in rheumatoid arthritis, the elevation of EETs levels by sEH inhibitors is a promising therapeutic strategy for rheumatoid arthritis patients. In addition, hybrid compounds, such as sEH inhibitors/FLAP inhibitors, or sEHI combined with NSAIDs/COXIBs are also important therapeutic target. However, studies investigating the effects of inflammation and rheumatic disease on CYP-mediated eicosanoid metabolism are necessary. Obtaining a better understanding of the complex role of CYP-derived eicosanoids in inflammatory rheumatic disease, such as rheumatoid arthritis will provide valuable insight for basic and clinical researchers investigation.