Cytochrome P450 metabolites of arachidonic acid play a role in the enhanced cardiac dysfunction in diabetic rats following ischaemic reperfusion injury

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.

Multi-omics insights into potential mechanism of SGLT2 inhibitors cardiovascular benefit in diabetic cardiomyopathy

Background

Metabolic and energy disorders are considered central to the etiology of diabetic cardiomyopathy (DCM). Sodium-glucose cotransporter-2 inhibitors (SGLT2i) can effectively reduce the risk of cardiovascular death and heart failure in patients with DCM. However, the underlying mechanism has not been elucidated.

Methods

We established a DCM rat model followed by treatment with empagliflozin (EMPA) for 12 weeks. Echocardiography, blood tests, histopathology, and transmission electron microscopy (TEM) were used to evaluate the phenotypic characteristics of the rats. The proteomics and metabolomics of the myocardium in the rat model were performed to identify the potential targets and signaling pathways associated with the cardiovascular benefit of SGLT2i.

Results

The diabetic rat showed pronounced DCM characterized by mitochondrial pleomorphic, impaired lipid metabolism, myocardial fibrosis, and associated diastolic and systolic functional impairments in the heart. To some extent, these changes were ameliorated after treatment with EMPA. A total of 43 proteins and 34 metabolites were identified as targets in the myocardium of diabetic rats treated with EMPA. The KEGG analysis showed that arachidonic acid is associated with the maximum number of related pathways and may be a potential target of EMPA treatment. Fatty acid (FA) metabolism was enhanced in diabetic hearts, and the perturbation of biosynthesis of unsaturated FAs and arachidonic acid metabolism was a potential enabler for the cardiovascular benefit of EMPA.

Conclusion

SGLT2i ameliorated lipid accumulation and mitochondrial damage in the myocardium of diabetic rats. The metabolomic and proteomic data revealed the potential targets and signaling pathways associated with the cardiovascular benefit of SGLT2i, which provides a valuable resource for the mechanism of SGLT2i.

The multifaceted role of cytochrome P450-Derived arachidonic acid metabolites in diabetes and diabetic cardiomyopathy

Understanding lipid metabolism is a critical key to understanding the pathogenesis of Diabetes Mellitus (DM). It is known that 60-90% of DM patients are obese or used to be obese. The incidence of obesity is rising owing to the modern sedentary lifestyle that leads to insulin resistance and increased levels of free fatty acids, predisposing tissues to utilize more lipids with less glucose uptake. However, the exact mechanism is not yet fully elucidated. Diabetic cardiomyopathy seems to be associated with these alterations in lipid metabolism. Arachidonic acid (AA) is an important fatty acid that is metabolized to several bioactive compounds by cyclooxygenases, lipoxygenases, and the more recently discovered, cytochrome P450 (P450) enzymes. P450 metabolizes AA to either epoxy-AA (EETs) or hydroxy-AA (HETEs). Studies showed that EETs could have cardioprotective effects and beneficial effects in reversing abnormalities in glucose and insulin homeostasis. Conversely, HETEs, most importantly 12-HETE and 20-HETE, were found to interfere with normal glucose and insulin homeostasis and thus, might be involved in diabetic cardiomyopathy. In this review, we highlight the role of P450-derived AA metabolites in the context of DM and diabetic cardiomyopathy and their potential use as a target for developing new treatments for DM and diabetic cardiomyopathy.

The CYP/20-HETE/GPR75 axis in hypertension

20-Hydroxyeicosatetraenoic acid (20-HETE) is a bioactive lipid generated from the ω-hydroxylation of arachidonic acid (AA) by enzymes of the cytochrome P450 (CYP) family, primarily the CYP4A and CYP4F subfamilies. 20-HETE is most notably identified as a modulator of vascular tone, regulator of renal function, and a contributor to the onset and development of hypertension and cardiovascular disease. 20-HETE-mediated signaling promotes hypertension by sensitizing the vasculature to constrictor stimuli, inducing endothelial dysfunction, and potentiating vascular inflammation. These bioactions are driven by the activation of the G-protein coupled receptor 75 (GPR75), a 20-HETE receptor (20HR). Given the capacity of 20-HETE signaling to drive pro-hypertensive mechanisms, the CYP/20-HETE/GPR75 axis has the potential to be a significant therapeutic target for the treatment of hypertension and cardiovascular diseases associated with increases in blood pressure. In this chapter, we review 20-HETE-mediated cellular mechanisms that promote hypertension, highlight important data in humans such as genetic variants in the CYP genes that potentiate 20-HETE production and describe recent findings in humans with 20HR/GPR75 mutations. Special emphasis is given to the 20HR and respective receptor blockers that have the potential to pave a path to translational and clinical studies for the treatment of 20-HETE-driven hypertension, and obesity/metabolic syndrome.

Effects of Arachidonic Acid Metabolites on Cardiovascular Health and Disease

Arachidonic acid (AA) is an essential fatty acid that is released by phospholipids in cell membranes and metabolized by cyclooxygenase (COX), cytochrome P450 (CYP) enzymes, and lipid oxygenase (LOX) pathways to regulate complex cardiovascular function under physiological and pathological conditions. Various AA metabolites include prostaglandins, prostacyclin, thromboxanes, hydroxyeicosatetraenoic acids, leukotrienes, lipoxins, and epoxyeicosatrienoic acids. The AA metabolites play important and differential roles in the modulation of vascular tone, and cardiovascular complications including atherosclerosis, hypertension, and myocardial infarction upon actions to different receptors and vascular beds. This article reviews the roles of AA metabolism in cardiovascular health and disease as well as their potential therapeutic implication.

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.

The Role of Epidermal Growth Factor Receptor Family of Receptor Tyrosine Kinases in Mediating Diabetes-Induced Cardiovascular Complications

Diabetes mellitus is a major debilitating disease whose global incidence is progressively increasing with currently over 463 million adult sufferers and this figure will likely reach over 700 million by the year 2045. It is the complications of diabetes such as cardiovascular, renal, neuronal and ocular dysfunction that lead to increased patient morbidity and mortality. Of these, cardiovascular complications that can result in stroke and cardiomyopathies are 2- to 5-fold more likely in diabetes but the underlying mechanisms involved in their development are not fully understood. Emerging research suggests that members of the Epidermal Growth Factor Receptor (EGFR/ErbB/HER) family of tyrosine kinases can have a dual role in that they are beneficially required for normal development and physiological functioning of the cardiovascular system (CVS) as well as in salvage pathways following acute cardiac ischemia/reperfusion injury but their chronic dysregulation may also be intricately involved in mediating diabetes-induced cardiovascular pathologies. Here we review the evidence for EGFR/ErbB/HER receptors in mediating these dual roles in the CVS and also discuss their potential interplay with the Renin-Angiotensin-Aldosterone System heptapeptide, Angiotensin-(1-7), as well the arachidonic acid metabolite, 20-HETE (20-hydroxy-5, 8, 11, 14-eicosatetraenoic acid). A greater understanding of the multi-faceted roles of EGFR/ErbB/HER family of tyrosine kinases and their interplay with other key modulators of cardiovascular function could facilitate the development of novel therapeutic strategies for treating diabetes-induced cardiovascular complications.

Unraveling the Role of 12- and 20- HETE in Cardiac Pathophysiology: G-Protein-Coupled Receptors, Pharmacological Inhibitors, and Transgenic Approaches

ABSTRACT

Arachidonic acid-derived lipid mediators play crucial roles in the development and progression of cardiovascular diseases. Eicosanoid metabolites generated by lipoxygenases and cytochrome P450 enzymes produce several classes of molecules, including the epoxyeicosatrienoic acid (EET) and hydroxyeicosatetraenoic acids (HETE) family of bioactive lipids. In general, the cardioprotective effects of EETs have been documented across a number of cardiac diseases. In contrast, members of the HETE family have been shown to contribute to the pathogenesis of ischemic cardiac disease, maladaptive cardiac hypertrophy, and heart failure. The net effect of 12(S)- and 20-HETE depends upon the relative amounts generated, ratio of HETEs:EETs produced, timing of synthesis, as well as cellular and subcellular mechanisms activated by each respective metabolite. HETEs are synthesized by and affect multiple cell types within the myocardium. Moreover, cytochrome P450-derived and lipoxygenase- derived metabolites have been shown to directly influence cardiac myocyte growth and the regulation of cardiac fibroblasts. The mechanistic data uncovered thus far have employed the use of enzyme inhibitors, HETE antagonists, and the genetic manipulation of lipid-producing enzymes and their respective receptors, all of which influence a complex network of outcomes that complicate data interpretation. This review will summarize and integrate recent findings on the role of 12(S)-/20-HETE in cardiac diseases.

A new trick for an old dog? Myocardial-specific roles for prostaglandins as mediators of ischemic injury and repair

The small lipid-derived paracrine signaling molecules known as prostaglandins have been recognized for their ability to modulate many facets of cardiovascular physiology since their initial discovery more than 85 years ago. Although the role of prostaglandins in the vasculature has gained significant attention across time, a handful of historical studies have also directly implicated the cardiomyocyte in both prostaglandin synthesis and release. Recently, our understanding of how prostaglandin receptor modulation impacts and contributes to myocardial structure and function has gained attention while leaving most other components of myocardial prostaglandin metabolism and signaling unexplored. This mini-review highlights both the key historical studies that underpin modern prostaglandin research in the heart, while concurrently presenting the latest findings related to how prostaglandin metabolism and signaling impact myocardial injury and repair.

Peripheral soluble epoxide hydrolase inhibition reduces hypernociception and inflammation in albumin-induced arthritis in temporomandibular joint of rats

Rheumatoid arthritis (RA) is characterized by chronic inflammation of the synovial tissue, joint dysfunction, and damage. Epoxyeicosatrienoic acids (EETs) are endogenous anti-inflammatory compounds, which are quickly converted by the soluble epoxide hydrolase (sEH) enzyme into a less active form with decreased biological effects. The inhibition of the sEH enzyme has been used as a strategy to lower nociception and inflammation. The goal of this study was to investigate whether the peripheral treatment with the sEH enzyme inhibitor 1- trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) could prevent the hypernociception and inflammation in the albumin-induced arthritis model in rats' temporomandibular joint (TMJ). After the induction of experimental arthritis, animals were assessed for nociceptive behavior test, leukocyte infiltration counts and histologic analysis, ELISA to quantify several cytokines and Western blotting. The peripheral pretreatment with TPPU inhibited the arthritis-induced TMJ hypernociception and leukocyte migration. Moreover, the local concentrations of proinflammatory cytokines were diminished by TPPU, while the anti-inflammatory cytokine interleukin-10 was up-regulated in the TMJ tissue. Finally, TPPU significantly decreased protein expression of iNOS, while did not alter the expression of MRC1. This study provides evidence that the peripheral administration of TPPU reduces hypernociception and inflammation in TMJ experimental arthritis.

20-HETE in the regulation of vascular and cardiac function

20-HETE, the ω-hydroxylation product of arachidonic acid catalyzed by enzymes of the cytochrome P450 (CYP) 4A and 4F gene families, is a bioactive lipid mediator with potent effects on the vasculature including stimulation of smooth muscle cell contractility, migration and proliferation as well as activation of endothelial cell dysfunction and inflammation. Clinical studies have shown elevated levels of plasma and urinary 20-HETE in human diseases and conditions such as hypertension, obesity and metabolic syndrome, myocardial infarction, stroke, and chronic kidney diseases. Studies of polymorphic associations also suggest an important role for 20-HETE in hypertension, stroke and myocardial infarction. Animal models of increased 20-HETE production are hypertensive and are more susceptible to cardiovascular injury. The current review summarizes recent findings that focus on the role of 20-HETE in the regulation of vascular and cardiac function and its contribution to the pathology of vascular and cardiac diseases.

β-adrenergic Receptor-stimulated Cardiac Myocyte Apoptosis: Role of Cytochrome P450 ω-hydroxylase

Prolonged or excessive β-adrenergic activation leads to cardiac myocyte loss and heart dysfunction; however, the underlying cellular mechanisms are still unclear. Therefore, we first confirmed the effect of isoproterenol (ISO), a β-adrenergic receptor agonist, on cardiac toxicity using TUNEL and caspase activity assays in cultured rat cardiomyocytes. ISO treatment significantly increased cardiomyocyte apoptosis. Persistent ISO stimulation of cardiomyocytes also increased the expression of CYP4A3, a major CYP450 ω-hydroxylase that produces 20-hydroxyeicosatetraenoic acid (20-HETE) in a time-dependent manner. Next, we examined the effect of ISO and 20-HETE on cardiomyocyte apoptosis using annexin V and propidium iodide staining. Treatment with either 20-HETE or ISO significantly increased cardiomyocyte apoptosis, and inhibition of 20-HETE production using 17-ODYA, a CYP450 ω-hydroxylase inhibitor, dramatically attenuated ISO-induced cardiomyocyte apoptosis. To determine the apoptotic pathway involved, the mitochondrial membrane potential (ΔΨm) was measured by detecting the ratio of JC-1 green/red emission intensity. The results demonstrated that 17-ODYA significantly abolished ISO-induced disruption of ΔΨm and that 20-HETE alone induced a marked disruptive effect on ΔΨm in cardiomyocytes. In addition, 20-HETE-induced disruption of ΔΨm and apoptosis was significantly attenuated by KN93, a CaMKII inhibitor. Taken together, these results demonstrate that 20-HETE treatment induces significant apoptosis via mitochondrial-dependent pathways, and that inhibition of 20-HETE production using 17-ODYA attenuates ISO-induced cardiomyocyte apoptosis.

Altered Protein Expression of Cardiac CYP2J and Hepatic CYP2C, CYP4A, and CYP4F in a Mouse Model of Type II Diabetes-A Link in the Onset and Development of Cardiovascular Disease?

Arachidonic acid can be metabolized by cytochrome P450 (CYP450) enzymes in a tissue- and cell-specific manner to generate vasoactive products such as epoxyeicosatrienoic acids (EETs-cardioprotective) and hydroxyeicosatetraenoic acids (HETEs-cardiotoxic). Type II diabetes is a well-recognized risk factor for developing cardiovascular disease. A mouse model of Type II diabetes (C57BLKS/J-db/db) was used. After sacrifice, livers and hearts were collected, washed, and snap frozen. Total proteins were extracted. Western blots were performed to assess cardiac CYP2J and hepatic CYP2C, CYP4A, and CYP4F protein expression, respectively. Significant decreases in relative protein expression of cardiac CYP2J and hepatic CYP2C were observed in Type II diabetes animals compared to controls (CYP2J: 0.80 ± 0.03 vs. 1.05 ± 0.06, n = 20, p < 0.001); (CYP2C: 1.56 ± 0.17 vs. 2.21 ± 0.19, n = 19, p < 0.01). In contrast, significant increases in relative protein expression of both hepatic CYP4A and CYP4F were noted in Type II diabetes mice compared to controls (CYP4A: 1.06 ± 0.09 vs. 0.18 ± 0.01, n = 19, p < 0.001); (CYP4F: 2.53 ± 0.22 vs. 1.10 ± 0.07, n = 19, p < 0.001). These alterations induced by Type II diabetes in the endogenous pathway (CYP450) of arachidonic acid metabolism may increase the risk for cardiovascular disease by disrupting the fine equilibrium between cardioprotective (CYP2J/CYP2C-generated) and cardiotoxic (CYP4A/CYP4F-generated) metabolites of arachidonic acid.

The Role of Cytochrome P450 Epoxygenases, Soluble Epoxide Hydrolase, and Epoxyeicosatrienoic Acids in Metabolic Diseases

Metabolic diseases are associated with an increased risk of developing cardiovascular disease. The features comprising metabolic diseases include obesity, insulin resistance, hyperglycemia, hyperlipidemia, and hypertension. Recent evidence has emerged showcasing a role for cytochrome P450 epoxygenases, soluble epoxide hydrolase, and epoxyeicosatrienoic acids (EETs) in the development and progression of metabolic diseases. This review discusses the current knowledge related to the modulation of cytochrome P450 epoxygenases and soluble epoxide hydrolase to alter concentrations of biologically active EETs, resulting in effects on insulin resistance, lipid metabolism, obesity, and diabetes. Future areas of research to address current deficiencies in the understanding of these enzymes and their eicosanoid metabolites in various aspects of metabolic diseases are also discussed.

Development of cellular hypertrophy by 8-hydroxyeicosatetraenoic acid in the human ventricular cardiomyocyte, RL-14 cell line, is implicated by MAPK and NF-κB

Recent studies have established the role of mid-chain hydroxyeicosatetraenoic acids (mid-chain HETEs) in the development of cardiovascular disease. Among these mid-chains, 8-HETE has been reported to have a proliferator and proinflammatory action. However, whether 8-HETE can induce cardiac hypertrophy has never been investigated before. Therefore, the overall objectives of the present study are to elucidate the potential hypertrophic effect of 8-HETE in the human ventricular cardiomyocytes, RL-14 cells, and to explore the mechanism(s) involved. Our results showed that 8-HETE induced cellular hypertrophy in RL-14 cells as evidenced by the induction of cardiac hypertrophy markers ANP, BNP, α-MHC, and β-MHC in a concentration- and time-dependent manner as well as the increase in cell surface area. Mechanistically, 8-HETE was able to induce the NF-κB activity as well as it significantly induced the phosphorylation of ERK1/2. The induction of cellular hypertrophy was associated with a proportional increase in the formation of dihydroxyeicosatrienoic acids (DHETs) parallel to the increase of soluble epoxide hydrolase (sEH) enzyme activity. Blocking the induction of NF-κB, ERK1/2, and sEH signaling pathways significantly inhibited 8-HETE-induced cellular hypertrophy. Our study provides the first evidence that 8-HETE induces cellular hypertrophy in RL-14 cells through MAPK- and NF-κB-dependent mechanism

The role of 20-HETE in cardiovascular diseases and its risk factors

Arachidonic acid (AA) is metabolized in mammals by enzymes of the CYP4A and 4F families to 20-hydroxyeicosatetraeonic acid (20-HETE) which plays an important role in the regulation of renal function, vascular tone and arterial pressure. In the vasculature, 20-HETE is a potent vasoconstrictor, the up-regulation of which contributes to inflammation, oxidative stress, endothelial dysfunction and an increase in peripheral vascular resistance in models of obesity, diabetes, ischemia/reperfusion, and vascular oxidative stress. Recent studies have established a role for 20-HETE in normal and pathological angiogenic conditions. We discuss in this review the synthesis of 20-HETE and how it and various autacoids, especially the renin-angiotensin system, interact to promote hypertension, vasoconstriction, and vascular dysfunction. In addition, we examine the molecular mechanisms through which 20-HETE induces these actions and the clinical implication of inhibiting 20-HETE production and activity.

Molecular mechanisms and cell signaling of 20-hydroxyeicosatetraenoic acid in vascular pathophysiology

Cytochrome P450s enzymes catalyze the metabolism of arachidonic acid to epoxyeicosatrienoic acids (EETs), dihydroxyeicosatetraenoic acid and hydroxyeicosatetraeonic acid (HETEs). 20-HETE is a vasoconstrictor that depolarizes vascular smooth muscle cells by blocking K+ channels. EETs serve as endothelial derived hyperpolarizing factors. Inhibition of the formation of 20-HETE impairs the myogenic response and autoregulation of renal and cerebral blood flow. Changes in the formation of EETs and 20-HETE have been reported in hypertension and drugs that target these pathways alter blood pressure in animal models. Sequence variants in CYP4A11 and CYP4F2 that produce 20-HETE, UDP-glucuronosyl transferase involved in the biotransformation of 20-HETE and soluble epoxide hydrolase that inactivates EETs are associated with hypertension in human studies. 20-HETE contributes to the regulation of vascular hypertrophy, restenosis, angiogenesis and inflammation. It also promotes endothelial dysfunction and contributes to cerebral vasospasm and ischemia-reperfusion injury in the brain, kidney and heart. This review will focus on the role of 20-HETE in vascular dysfunction, inflammation, ischemic and hemorrhagic stroke and cardiac and renal ischemia reperfusion injury.

20-Hydroxyeicosatetraenoic Acid Is a Key Mediator of Angiotensin II-induced Apoptosis in Cardiac Myocytes

Cardiomyocyte apoptosis is involved in a variety of cardiac stresses, including ischemia-reperfusion injury, heart failure, and cardiomyopathy. Both Angiotensin II (Ang II) and 20-hydroxyeicosatetraenoic acid (20-HETE) induce apoptosis in cardiomyocytes. Here, we examined the relationship between 20-HETE and Ang II in cardiomyocyte apoptosis. Apoptosis was examined using flow cytometry in primary cultured rat cardiomyocytes treated with control, Ang II, and Ang II plus HET0016 (a 20-HETE formation inhibitor). The results demonstrated that the treatment of cardiomyocytes with Ang II or 20-HETE significantly increased the percentage of apoptotic cells and that Ang II-induced apoptosis was markedly attenuated by HET0016 or losartan (an AT1 receptor antagonist). In apoptotic mechanism experiments, Ang II or 20-HETE treatment significantly reduced mitochondrial membrane potential, indicating that a mitochondria-dependent mechanism is involved. Ang II-induced alteration in mitochondrial membrane potential was significantly attenuated by HET0016. Treatment of cardiomyocytes with Ang II also increased superoxide production, and this effect of Ang II was attenuated by HET0016. Treatment of cardiomyocytes with Ang II significantly increased CYP4A1 expression and 20-HETE production, as measured by Western blot, real-time RT-PCR, and mass spectrometric analysis. All results suggest that 20-HETE may play a key role in Ang II-induced apoptosis in cardiomyocytes by a mitochondrial superoxide-dependent pathway.

Pretreatment with low-dose gadolinium chloride attenuates myocardial ischemia/reperfusion injury in rats

AIM

We have shown that low-dose gadolinium chloride (GdCl3) abolishes arachidonic acid (AA)-induced increase of cytoplasmic Ca(2+), which is known to play a crucial role in myocardial ischemia/reperfusion (I/R) injury. The present study sought to determine whether low-dose GdCl3 pretreatment protected rat myocardium against I/R injury in vitro and in vivo.

METHODS

Cultured neonatal rat ventricular myocytes (NRVMs) were treated with GdCl3 or nifedipine, followed by exposure to anoxia/reoxygenation (A/R). Cell apoptosis was detected; the levels of related signaling molecules were assessed. SD rats were intravenously injected with GdCl3 or nifedipine. Thirty min after the administration the rats were subjected to LAD coronary artery ligation followed by reperfusion. Infarction size, the release of serum myocardial injury markers and AA were measured; cell apoptosis and related molecules were assessed.

RESULTS

In A/R-treated NRVMs, pretreatment with GdCl3 (2.5, 5, 10 μmol/L) dose-dependently inhibited caspase-3 activation, death receptor-related molecules DR5/Fas/FADD/caspase-8 expression, cytochrome c release, AA release and sustained cytoplasmic Ca(2+) increases induced by exogenous AA. In I/R-treated rats, pre-administration of GdCl3 (10 mg/kg) significantly reduced the infarct size, and the serum levels of CK-MB, cardiac troponin-I, LDH and AA. Pre-administration of GdCl3 also significantly decreased the number of apoptotic cells, caspase-3 activity, death receptor-related molecules (DR5/Fas/FADD) expression and cytochrome c release in heart tissues. The positive control drug nifedipine produced comparable cardioprotective effects in vitro and in vivo.

CONCLUSION

Pretreatment with low-dose GdCl3 significantly attenuates I/R-induced myocardial apoptosis in rats by suppressing activation of both death receptor and mitochondria-mediated pathways.

The role of mid-chain hydroxyeicosatetraenoic acids in the pathogenesis of hypertension and cardiac hypertrophy

The incidence, prevalence, and hospitalization rates associated with cardiovascular diseases (CVDs) are projected to increase substantially in the world. Understanding of the biological and pathophysiological mechanisms of survival can help the researchers to develop new management modalities. Numerous experimental studies have demonstrated that mid-chain HETEs are strongly involved in the pathogenesis of the CVDs. Mid-chain HETEs are biologically active eicosanoids that result from the metabolism of arachidonic acid (AA) by both lipoxygenase and CYP1B1 (lipoxygenase-like reaction). Therefore, identifying the localizations and expressions of the lipoxygenase and CYP1B1 and their associated AA metabolites in the cardiovascular system is of major importance in understanding their pathological roles. Generally, the expression of these enzymes is shown to be induced during several CVDs, including hypertension and cardiac hypertrophy. The induction of these enzymes is associated with the generation of mid-chain HETEs and subsequently causation of cardiovascular events. Of interest, inhibiting the formation of mid-chain HETEs has been reported to confer a protection against different cardiac hypertrophy and hypertension models such as angiotensin II, Goldblatt, spontaneously hypertensive rat and deoxycorticosterone acetate (DOCA)-salt-induced models. Although the exact mechanisms of mid-chain HETEs-mediated cardiovascular dysfunction are not fully understood, the present review proposes several mechanisms which include activating G-protein-coupled receptor, protein kinase C, mitogen-activated protein kinases, and nuclear factor kappa B. This review provides a clear understanding of the role of mid-chain HETEs in the pathogenesis of cardiovascular diseases and their importance as novel targets in the treatment for hypertension and cardiac hypertrophy.

Hyperbaric oxygenation modulates vascular reactivity to angiotensin-(1-7) in diabetic rats: potential role of epoxyeicosatrienoic acids

Previously, a facilitating effect of hyperbaric oxygenation (HBO₂) on aortic ring responses to angiotensin-(1-7) in healthy rats was reported, with epoxyeicosatrienoic acids (EETs) possibly playing an important role. The aim of this study was to assess whether HBO₂ exerts similar effects in diabetic rats and to further explore the role of specific cytochrome P450 (CYP) enzymes in changes induced by HBO₂. Aortic relaxation to angiotensin-(1-7) was significantly higher in HBO₂ diabetic rats compared to control diabetic rats, while HBO₂ had no effect on angiotensin II contraction. N-methylsulphonyl-6-(2-propargyloxyphenyl/hexanamide inhibited the facilitation of angiotensin-(1-7) responses in HBO₂ rats, suggesting an important role of EETs in this modulation. mRNA expression of CYP2J3 and protein expression of CYP2C11 were significantly upregulated in HBO₂ diabetic rats, whereas CYP4A1, CYP4A2 and CYP4A3 mRNA and CYP2J3 protein expression was similar between groups. Mean arterial pressure, ferric reducing ability of plasma and Thiobarbituric Acid Reactive Substances levels and serum angiotensin-(1-7) concentrations were not significantly changed.

Human fetal ventricular cardiomyocyte, RL-14 cell line, is a promising model to study drug metabolizing enzymes and their associated arachidonic acid metabolites

INTRODUCTION

RL-14 cells, human fetal ventricular cardiomyocytes, are a commercially available cell line that has been established from non-proliferating primary cultures derived from human fetal heart tissue. However, the expression of different drug metabolizing enzymes (DMEs) in RL-14 cells has not been elucidated yet. Therefore, the main objectives of the current work were to investigate the capacity of RL-14 cells to express different cytochrome P450 (CYP) isoenzymes and correlate this expression to primary cardiomyocytes.

METHODS

The expression of CYP isoenzymes was determined at mRNA, protein and catalytic activity levels using real time-PCR, Western blot analysis and liquid chromatography-electron spray ionization-mass spectrometry (LC-ESI-MS), respectively.

RESULTS

Our results showed that RL-14 cells constitutively express CYP ω-hydroxylases, CYP1A, 1B, 4A and 4F; CYP epoxygenases, CYP2B, 2C and 2J; in addition to soluble epoxide hydrolayse (EPHX2) at mRNA and protein levels. The basal expression of CYP ω-hydroxylases, epoxygenases and EPHX2 was supported by the ability of RL-14 cells to convert arachidonic acid to its biologically active metabolites, 20-hydroxyeicosatetraenoic acids (20-HETEs), 14,15-epoxyeicosatrienoic acids (14,15-EET), 11,12-EET, 8,9-EET, 5,6-EET, 14,15-dihydroxyeicosatrienoic acid (14,15-DHET), 11,12-DHET, 8,9-DHET and 5,6-DHET. Furthermore, RL-14 cells express CYP epoxygenases and ω-hydroxylase at comparable levels to those expressed in adult and fetal human primary cardiomyocytes cells implying the importance of RL-14 cells as a model for studying DMEs in vitro. Lastly, different CYP families were induced in RL-14 cells using 2,3,7,8-tetrachlorodibenzo-p-dioxin and fenofibrate at mRNA and protein levels.

DISCUSSION

The current study provides the first evidence that RL-14 cells express CYP isoenzymes at comparable levels to those expressed in the primary cells and thus offers a unique in vitro model to study DMEs in the heart.

Diplotypes of CYP2C9 gene is associated with coronary artery disease in the Xinjiang Han population for women in China

Background

Cytochrome P450 (CYP) 2C9 is expressed in the vascular endothelium and metabolizes arachidonic acid to biologically active epoxyeicosatrienoic acids (EETs), which have the crucial role in the modulation of cardiovascular homeostasis. We sought to assess the association between the human CYP2C9 gene and coronary artery disease (CAD) in Xinjiang Han Population of China.

Methods

301 CAD patients and 220 control subjects were genotyped for 4 single-nucleotide polymorphisms (SNPs) of the human CYP2C9 gene (rs4086116, rs2475376, rs1057910, and rs1934967) by a Real-Time PCR instrument. The datas were assessed for 3 groups: total, men, and women via diplotype-based case–control study.

Results

For women, the distribution of genotypes, dominant model and alleles of SNP2 (rs2475376) showed significant difference between the CAD patients and control participants (p = 0.033, P = 0.010 and p = 0.038, respectively). The significant difference of the dominant model (CC vs CT + TT) was retained after adjustment for covariates in women (OR: 2.427, 95% confidence interval [CI]: 1.305-4.510, p = 0.005). The haplotype (C-T-A-C) and the diplotypes (CTAC/CTAC) in CYP2C9 gene were lower in CAD patients than in control subjects (p* = 0.0016, and p* = 0.036 respectively). The haplotype (C-C-A-T) was higher in the CAD patients than in the control subjects in women (p* = 0.016).

Conclusions

CC genotype of rs2475376 and C-C-A-T haplotype in CYP2C9 may be a risk genetic marker of CAD in women. T allele of rs2475376, the haplotype (C-T-A-C) and the diplotype (CTAC/CTAC) could be protective genetic markers of CAD for women in Han population of China.

Chronic treatment with Ang-(1-7) reverses abnormal reactivity in the corpus cavernosum and normalizes diabetes-induced changes in the protein levels of ACE, ACE2, ROCK1, ROCK2 and omega-hydroxylase in a rat model of type 1 diabetes

Angiotensin-(1-7) [Ang-(1-7)] may have beneficial effects in diabetes mellitus-induced erectile dysfunction (DMIED) but its molecular actions in the diabetic corpus cavernosum (CC) are not known. We characterized the effects of diabetes and/or chronic in vivo administration of Ang-(1-7) on vascular reactivity in the rat corpus cavernosum (CC) and on protein expression levels of potential downstream effectors of the renin-angiotensin-aldosterone system (RAAS) such as angiotensin-converting enzyme (ACE), ACE2, Rho kinases 1 and 2 (ROCK1 and ROCK2), and omega-hydroxylase, the cytochrome-P450 enzyme that metabolizes arachidonic acid to form the vasoconstrictor, 20-hydroxyeicosatetraenoic acid. Streptozotocin-treated rats were chronicically administered Ang-(1-7) with or without A779, a Mas receptor antagonist, during weeks 4 to 6 of diabetes. Ang-(1-7) reversed diabetes-induced abnormal reactivity to vasoactive agents (endothelin-1, phenylepherine, and carbachol) in the CC without correcting hyperglycemia. Six weeks of diabetes led to elevated ACE, ROCK1, ROCK 2, and omega-hydroxylase and a concomitant decrease in ACE2 protein expression levels that were normalized by Ang-(1-7) treatment but not upon coadministration of A779. These data are supportive of the notion that the beneficial effects of Ang-(1-7) in DMIED involve counterregulation of diabetes-induced changes in ACE, ACE2, Rho kinases, and omega-hydroxylase proteins in the diabetic CC via a Mas receptor-dependent mechanism.

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.

Elevated level of pro-inflammatory eicosanoids and EPC dysfunction in diabetic patients with cardiac ischemia

BACKGROUND

Circulating endothelial progenitor cells (EPCs) are recruited from the blood system to sites of ischemia and endothelial damage, where they contribute to the repair and development of blood vessels. Since numerous eicosanoids including leukotrienes (LTs) and hydroxyeicosatetraenoic acids (HETEs) have been shown to exert potent pro-inflammatory activities, we examined their levels in chronic diabetic patients with severe cardiac ischemia in conjunction with the level and function of EPCs.

RESULTS

Lipidomic analysis revealed a diabetes-specific increase (p<0.05) in inflammatory and angiogenic eicosanoids including the 5-lipoxygenase-derived LTB (4.11±1.17 vs. 0.96±0.27 ng/ml), the lipoxygenase/CYP-derived 12-HETE (117.08±35.05 vs. 24.34±10.03 ng/ml), 12-HETrE (17.56±4.43 vs. 4.15±2.07 ng/ml), and the CYP-derived 20-HETE (0.32±0.04 vs. 0.06±0.05 ng/ml) the level of which correlated with BMI (p=0.0027). In contrast, levels of the CYP-derived EETs were not significantly (p=0.36) different between these two groups. EPC levels and their colony-forming units were lower (p<0.05) with a reduced viability in diabetic patients compared with non-diabetics. EPC function (colony-forming units (CFUs) and MTT assay) also negatively correlated with the circulating levels of HgA1C.

CONCLUSION

This study demonstrates a close association between elevated levels of highly pro-inflammatory eicosonoids, diabetes and EPC dysfunction in patients with cardiac ischemia, indicating that chronic inflammation impact negatively on EPC function and angiogenic capacity in diabetes.

Determination of the dominant arachidonic acid cytochrome p450 monooxygenases in rat heart, lung, kidney, and liver: protein expression and metabolite kinetics

Cytochrome P450 (P450)-derived arachidonic acid (AA) metabolites serve pivotal physiological roles. Therefore, it is important to determine the dominant P450 AA monooxygenases in different organs. We investigated the P450 AA monooxygenases protein expression as well as regioselectivity, immunoinhibition, and kinetic profile of AA epoxygenation and hydroxylation in rat heart, lung, kidney, and liver. Thereafter, the predominant P450 epoxygenases and P450 hydroxylases in these organs were characterized. Microsomes from heart, lung, kidney, and liver were incubated with AA. The protein expression of CYP2B1/2, CYP2C11, CYP2C23, CYP2J3, CYP4A1/2/3, and CYP4Fs in the heart, lung, kidney, and liver were determined by Western blot analysis. The levels of AA metabolites were determined by liquid chromatography-electrospray ionization mass spectroscopy. This was followed by determination of regioselectivity, immunoinhibition effect, and the kinetic profile of AA metabolism. AA was metabolized to epoxyeicosatrienoic acids and 19- and 20-hydroxyeicosatetraenoic acid in the heart, lung, kidney, and liver but with varying metabolic activities and regioselectivity. Anti-P450 antibodies were found to differentially inhibit AA epoxygenation and hydroxylation in these organs. Our data suggest that the predominant epoxygenases are CYP2C11, CYP2B1, CYP2C23, and CYP2C11/CYP2C23 for the heart, lung, kidney, and liver, respectively. On the other hand, CYP4A1 is the major ω-hydroxylase in the heart and kidney; whereas CYP4A2 and/or CYP4F1/4 are probably the major hydroxlases in the lung and liver. These results provide important insights into the activities of P450 epoxygenases and P450 hydroxylases-mediated AA metabolism in different organs and their associated P450 protein levels.

Acute arsenic toxicity alters cytochrome P450 and soluble epoxide hydrolase and their associated arachidonic acid metabolism in C57Bl/6 mouse heart

Acute arsenic (As(III)) exposure has been reported to cause cardiac toxicity, however this toxicity was never linked to the disturbance in cytochrome P450 (P450)-mediated arachidonic acid metabolism. Therefore, we investigated the effect of acute As(III) toxicity on the expression of P450 and soluble epoxide hydrolase (sEH) and their associated arachidonic acid metabolism in mice hearts. As(III) toxicity was induced by a single intraperitoneal injection of 12.5 mg/kg of As(III). Our results showed that As(III) treatment caused a significant induction of the cardiac hypertrophic markers in addition to Cyp1b1, Cyp2b, Cyp2c, Cyp4f, and sEH gene expression in mice hearts. Furthermore, As(III) increased sEH protein expression and activity in hearts with a consequent decrease in 11,12-, and 14,15-epoxyeicosatrienoic acids (EETs) formation. Whereas the formation of 8,9-, 11,12-, 14,15-dihydroxyeicosatrienoic acids (DHETs) was significantly increased. As(III) also increased sEH mRNA and protein expression levels in addition to the hypertrophic markers which was reversed by knockdown of sEH in H9c2 cells. In conclusion, acute As(III) toxicity alters the expression of several P450s and sEH enzymes with a consequent decrease in the cardioprotective EETs which may represent a novel mechanism by which As(III) causes progressive cardiotoxicity. Furthermore, inhibiting sEH might represent a novel therapeutic approach to prevent As(III)-induced hypertrophy.

20-Hydroxyeicosatetraenoic acid induces apoptosis in neonatal rat cardiomyocytes through mitochondrial-dependent pathways

OBJECTIVE

20-Hydroxyeicosatetraenoic acid (20-HETE), a [omega]-hydroxylation product of arachidonic acid catalyzed by cytochrome P450 4A, may play a role in the cardiovascular system. It is well known that cytochrome P450 [omega]-hydroxylase inhibitors markedly reduced the cardiac ischemia reperfusion injury. However, the direct effect of 20-HETE on cardiomyocytes is still poorly investigated. Here, we studied the effect of 20-HETE on cardiomyocyte apoptosis and the apoptosis-associated signaling pathways.

METHODS AND RESULTS

The cardiomyocyte apoptosis was measured by fluorescein isothiocyanate conjugated annexin V/propidium iodide double staining cytometry, indicating that the percentage of early apoptotic cells increased from 15.6% +/- 2.6% to 25.5% +/- 2.5% in control and 20-HETE-treated cells, respectively. The mitochondrial membrane potential ([DELTA][PSI]m) was measured by detecting the ratio of JC-1 green/red emission intensity. A significant decrease in the ratio was observed after treatment with 20-HETE for 24 hours in comparison with control group, suggesting the disruptive effect of 20-HETE on mitochondrial [DELTA][PSI]m. In addition, 20-HETE stimulated caspase-3 activity and Bax mRNA expression in cardiomyocytes. In contrast, the Bcl-2 mRNA levels were significantly decreased by 20-HETE treatment.

CONCLUSION

These results demonstrate that 20-HETE induces cardiomyocyte apoptosis by activation of several intrinsic apoptotic pathways. The 20-HETE-induced apoptosis could contribute to the cytochrome P450 [omega]-hydroxylase-dependent cardiac injure during cardiac ischemia-reperfusion.

CYP-eicosanoids--a new link between omega-3 fatty acids and cardiac disease?

Fish oil omega-3 fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) protect against arrhythmia and sudden cardiac death by largely unknown mechanisms. Recent in vitro and in vivo studies demonstrate that arachidonic acid (AA) metabolizing cytochrome P450-(CYP) enzymes accept EPA and DHA as efficient alternative substrates. Dietary EPA/DHA supplementation causes a profound shift of the cardiac CYP-eicosanoid profile from AA- to EPA- and DHA-derived epoxy- and hydroxy-metabolites. CYP2J2 and other CYP epoxygenases preferentially epoxidize the ω-3 double bond of EPA and DHA. The corresponding metabolites, 17,18-epoxy-EPA and 19,20-epoxy-DHA, dominate the CYP-eicosanoid profile of the rat heart after EPA/DHA supplementation. The (ω-3)-epoxyeicosanoids show highly potent antiarrhythmic properties in neonatal cardiomyocytes, suggesting that these metabolites may specifically contribute to the cardioprotective effects of omega-3 fatty acids. This hypothesis is discussed in the context of recent findings that revealed CYP-eicosanoid mediated mechanisms in cardiac ischemia-reperfusion injury and maladaptive cardiac hypertrophy.

20-hydroxyeicosatetraeonic acid: a new target for the treatment of hypertension

Arachidonic acid is metabolized by enzymes of the CYP4A and 4F families to 20-hydroxyeicosatetraeonic acid (20-HETE), which plays an important role in the regulation of renal function, vascular tone, and the long-term control of arterial pressure. In the vasculature, 20-HETE is a potent vasoconstrictor, and upregulation of the production of this compound contributes to the elevation in oxidative stress and endothelial dysfunction and the increase in peripheral vascular resistance associated with some forms of hypertension. In kidney, 20-HETE inhibits Na transport in the proximal tubule and thick ascending loop of Henle, and deficiencies in the renal formation of 20-HETE contributes to sodium retention and development of some salt-sensitive forms of hypertension. 20-HETE also has renoprotective actions and opposes the effects of transforming growth factor β to promote proteinuria and renal end organ damage in hypertension. Several new inhibitors of the synthesis of 20-HETE and 20-HETE agonists and antagonists have recently been developed. These compounds along with peroxisome proliferator-activated receptor-α agonists that induce the renal formation of 20-HETE seem to have promise as antihypertensive agents. This review summarizes the rationale for the development of drugs that target the 20-HETE pathway for the treatment of hypertension and associated cardiovascular complications.

1-Aryl-3-(1-acylpiperidin-4-yl)urea inhibitors of human and murine soluble epoxide hydrolase: structure-activity relationships, pharmacokinetics, and reduction of inflammatory pain

1,3-Disubstituted ureas possessing a piperidyl moiety have been synthesized to investigate their structure-activity relationships as inhibitors of the human and murine soluble epoxide hydrolase (sEH). Oral administration of 13 1-aryl-3-(1-acylpiperidin-4-yl)urea inhibitors in mice revealed substantial improvements in pharmacokinetic parameters over previously reported 1-adamantylurea based inhibitors. For example, 1-(1-(cyclopropanecarbonyl)piperidin-4-yl)-3-(4-(trifluoromethoxy)phenyl)urea (52) showed a 7-fold increase in potency, a 65-fold increase in C(max), and a 3300-fold increase in AUC over its adamantane analogue 1-(1-adamantyl)-3-(1-propionylpiperidin-4-yl)urea (2). This novel sEH inhibitor showed a 1000-fold increase in potency when compared to morphine by reducing hyperalgesia as measured by mechanical withdrawal threshold using the in vivo carrageenan induced inflammatory pain model.

Effect of cytochrome P450 polymorphism on arachidonic acid metabolism and their impact on cardiovascular diseases

Cardiovascular diseases (CVDs) remain the leading cause of death in the developed countries. Taking into account the mounting evidence about the role of cytochrome P450 (CYP) enzymes in cardiovascular physiology, CYP polymorphisms can be considered one of the major determinants of individual susceptibility to CVDs. One of the important physiological roles of CYP enzymes is the metabolism of arachidonic acid. CYP epoxygenases such as CYP1A2, CYP2C, and CYP2J2 metabolize arachidonic acid to epoxyeicosatrienoic acids (EETs) which generally possess vasodilating, anti-inflammatory, anti-apoptotic, anti-thrombotic, natriuretic, and cardioprotective effects. Therefore, genetic polymorphisms causing lower activity of these enzymes are generally associated with an increased risk of several CVDs such as hypertension and coronary artery disease. EETs are further metabolized by soluble epoxide hydrolase (sEH) to the less biologically active dihydroxyeicosatrienoic acids (DHETs). Therefore, sEH polymorphism has also been shown to affect arachidonic acid metabolism and to be associated with CVDs. On the other hand, CYP omega-hydroxylases such as CYP4A11 and CYP4F2 metabolize arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE) which has both vasoconstricting and natriuretic effects. Genetic polymorphisms causing lower activity of these enzymes are generally associated with higher risk of hypertension. Nevertheless, some studies have denied the association between polymorphisms in the arachidonic acid pathway and CVDs. Therefore, more research is needed to confirm this association and to better understand the pathophysiologic mechanisms behind it.

Cytochrome P450 enzymes and the heart

The cytochrome P450 monooxygenase system (CYP) is a multigene superfamily of heme-thiolate enzymes, which are important in the metabolism of foreign and endogenous compounds. Genetic variations, drug interactions, or pathophysiological factors can lead to reduced, absent, or increased enzymatic activity. This altered CYP activity greatly influences an individual's response to therapeutic treatment. What is not known is the impact of these changes on the many functional roles of CYP in physiological and pathophysiological processes of the heart. Many extrahepatic tissues, like heart, contain active P450 enzymes but lack information regarding their role in cellular injury or homeostasis. Much of our current knowledge about cardiac CYP has been limited to studies investigating the role of fatty acid metabolites in heart. Traditional risk factors including diabetes, smoking, and hypertension have well established links to cardiovascular disease. And new evidence strongly suggests exposure to chemicals and other environmental agents has a profound impact on the cardiovascular system. These risk factors can independently affect the expression and activity of CYP enzymes. Therefore, altered CYP activity is important from a detoxification as well as a bioactivation perspective. Considering CYP, interactions are greatly dependent on inherited differences or acquired changes in enzyme activity further research into their potential impact on pathogenesis, risk assessment, and therapy of heart disease is warranted. This review explores the expression of CYP isoforms, their functional roles, and the effects of genetic variation in the heart.