Characterization of four new mouse cytochrome P450 enzymes of the CYP2J subfamily

A Narrative Review of the Published Pre-Clinical Evaluations: Multiple Effects of Arachidonic Acid, its Metabolic Enzymes and Metabolites in Epilepsy

Arachidonic acid (AA), an important polyunsaturated fatty acid in the brain, is hydrolyzed by a direct action of phospholipase A2 (PLA2) or through the combined action of phospholipase C and diacylglycerol lipase, and released into the cytoplasm. Various derivatives of AA can be synthesized mainly through the cyclooxygenase (COX), lipoxygenase (LOX) and cytochrome P450 (P450) enzyme pathways. AA and its metabolic enzymes and metabolites play important roles in a variety of neurophysiological activities. The abnormal metabolites and their catalytic enzymes in the AA cascade are related to the pathogenesis of various central nervous system (CNS) diseases, including epilepsy. Here, we systematically reviewed literatures in PubMed about the latest randomized controlled trials, animal studies and clinical studies concerning the known features of AA, its metabolic enzymes and metabolites, and their roles in epilepsy. The exclusion criteria include non-original studies and articles not in English.

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.

Effects of sEH inhibition on the eicosanoid and cytokine storms in SARS-CoV-2-infected mice

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection involves an initial viral infection phase followed by a host-response phase that includes an eicosanoid and cytokine storm, lung inflammation and respiratory failure. While vaccination and early anti-viral therapies are effective in preventing or limiting the pathogenic host response, this latter phase is poorly understood with no highly effective treatment options. Inhibitors of soluble epoxide hydrolase (sEH) increase levels of anti-inflammatory molecules called epoxyeicosatrienoic acids (EETs). This study aimed to investigate the impact of sEH inhibition on the host response to SARS-CoV-2 infection in a mouse model with human angiotensin-converting enzyme 2 (ACE2) expression. Mice were infected with SARS-CoV-2 and treated with either vehicle or the sEH inhibitor 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU). At day 5 post-infection, SARS-CoV-2 induced weight loss, clinical signs, a cytokine storm, an eicosanoid storm, and severe lung inflammation with ~50% mortality on days 6-8 post-infection. SARS-CoV-2 infection induced lung expression of phospholipase A2 (PLA2), cyclooxygenase (COX) and lipoxygenase (LOX) pathway genes, while suppressing expression of most cytochrome P450 genes. Treatment with the sEH inhibitor TPPU delayed weight loss but did not alter clinical signs, lung cytokine expression or overall survival of infected mice. Interestingly, TPPU treatment significantly reversed the eicosanoid storm and attenuated viral-induced elevation of 39 fatty acids and oxylipins from COX, LOX and P450 pathways, which suggests the effects at the level of PLA2 activation. The suppression of the eicosanoid storm by TPPU without corresponding changes in lung cytokines, lung inflammation or mortality reveals a surprising dissociation between systemic oxylipin and cytokine signaling pathways during SARS-CoV-2 infection and suggests that the cytokine storm is primarily responsible for morbidity and mortality in this animal model.

Direct androgen receptor control of sexually dimorphic gene expression in the mammalian kidney

Mammalian organs exhibit distinct physiology, disease susceptibility, and injury responses between the sexes. In the mouse kidney, sexually dimorphic gene activity maps predominantly to proximal tubule (PT) segments. Bulk RNA sequencing (RNA-seq) data demonstrated that sex differences were established from 4 and 8 weeks after birth under gonadal control. Hormone injection studies and genetic removal of androgen and estrogen receptors demonstrated androgen receptor (AR)-mediated regulation of gene activity in PT cells as the regulatory mechanism. Interestingly, caloric restriction feminizes the male kidney. Single-nuclear multiomic analysis identified putative cis-regulatory regions and cooperating factors mediating PT responses to AR activity in the mouse kidney. In the human kidney, a limited set of genes showed conserved sex-linked regulation, whereas analysis of the mouse liver underscored organ-specific differences in the regulation of sexually dimorphic gene expression. These findings raise interesting questions on the evolution, physiological significance, disease, and metabolic linkage of sexually dimorphic gene activity.

Direct androgen receptor regulation of sexually dimorphic gene expression in the mammalian kidney

Mammalian organs exhibit distinct physiology, disease susceptibility and injury responses between the sexes. In the mouse kidney, sexually dimorphic gene activity maps predominantly to proximal tubule (PT) segments. Bulk RNA-seq data demonstrated sex differences were established from 4 and 8 weeks after birth under gonadal control. Hormone injection studies and genetic removal of androgen and estrogen receptors demonstrated androgen receptor (AR) mediated regulation of gene activity in PT cells as the regulatory mechanism. Interestingly, caloric restriction feminizes the male kidney. Single-nuclear multiomic analysis identified putative cis-regulatory regions and cooperating factors mediating PT responses to AR activity in the mouse kidney. In the human kidney, a limited set of genes showed conserved sex-linked regulation while analysis of the mouse liver underscored organ-specific differences in the regulation of sexually dimorphic gene expression. These findings raise interesting questions on the evolution, physiological significance, and disease and metabolic linkage, of sexually dimorphic gene activity.

Monolayer autoxidation of arachidonic acid to epoxyeicosatrienoic acids as a model of their potential formation in cell membranes

In light of the importance of epoxyeicosatrienoic acids (EETs) in mammalian pathophysiology, a nonenzymatic route that might form these monoepoxides in cells is of significant interest. In the late 1970s, a simple system of arranging linoleic acid molecules on a monolayer on silica was devised and shown to yield monoepoxides as the main autoxidation products. Here, we investigated this system with arachidonic acid and characterized the primary products. By the early stages of autoxidation (∼10% conversion of arachidonic acid), the major products detected by LC-MS and HPLC-UV were the 14,15-, 11,12-, and 8,9-EETs, with the 5,6-EET mainly represented as the 5-δ-lactone-6-hydroxyeicosatrienoate as established by 1H-NMR. The EETs were mainly the cis epoxides as expected, with minor trans configuration EETs among the products. 1H-NMR analysis in four deuterated solvents helped clarify the epoxide configurations. EET formation in monolayers involves intermolecular reaction with a fatty acid peroxyl radical, producing the EET and leaving an incipient and more reactive alkoxyl radical, which in turn gives rise to epoxy-hydro(pero)xides and other polar products. The monolayer alignment of fatty acid molecules resembles the arrangements of fatty acids in cell membranes and, under conditions of lipid peroxidation, this intermolecular mechanism might contribute to EET formation in biological membranes.

Application of carbon monoxide in kidney and heart transplantation: A novel pharmacological strategy for a broader use of suboptimal renal and cardiac grafts

Carbon monoxide (CO) was historically regarded solely as a poisonous gas that binds to hemoglobin and reduces oxygen-carrying capacity of blood at high concentrations. However, recent findings show that it is endogenously produced in mammalian cells as a by-product of heme degradation by heme oxygenase, and has received a significant attention as a medical gas that influences a myriad of physiological and pathological processes. At low physiological concentrations, CO exhibits several therapeutic properties including antioxidant, anti-inflammatory, anti-apoptotic, anti-fibrotic, anti-thrombotic, anti-proliferative and vasodilatory properties, making it a candidate molecule that could protect organs in various pathological conditions including cold ischemia-reperfusion injury (IRI) in kidney and heart transplantation. Cold IRI is a well-recognized and complicated cascade of interconnected pathological pathways that poses a significant barrier to successful outcomes after kidney and heart transplantation. A substantial body of preclinical evidence demonstrates that CO gas and CO-releasing molecules (CO-RMs) prevent cold IRI in renal and cardiac grafts through several molecular and cellular mechanisms. In this review, we discuss recent advances in research involving the use of CO as a novel pharmacological strategy to attenuate cold IRI in preclinical models of kidney and heart transplantation through its administration to the organ donor prior to organ procurement or delivery into organ preservation solution during cold storage and to the organ recipient during reperfusion and after transplantation. We also discuss the underlying molecular mechanisms of cyto- and organ protection by CO during transplantation, and suggest its clinical use in the near future to improve long-term transplantation outcomes.

Cytochrome P450 2A6 is associated with macrophage polarization and is a potential biomarker for hepatocellular carcinoma

Cytochrome P450 2A6 (CYP2A6) is an important metabolic enzyme and is involved in the progression of hepatocellular carcinoma (HCC). However, its specific function and the mechanism of modulation remain to be elucidated. In this study, we found that CYP2A6 is dramatically downregulated in HCC. CYP2A6 expression is closely associated with pathological grading, histologic grade, hepatitis, vascular metastasis, liver inflammation, and worse prognosis. Reduced expression of CYP2A6 contributes to alternative activation of macrophage polarization and impairs macrophage maturation and phagocytosis. Mechanistically, CYP2A6 participates in arachidonic acid metabolism, initiates 20‐hydroxyeicosatetraenoic acid (HETE) generation, and inhibits epoxyeicosatrienoic acid (EET) generation. Disruption of the equilibrium between 20‐HETE and EETs can induce macrophage polarization, thereby modulating antitumor immunity.

CYP2J2 Molecular Recognition: A New Axis for Therapeutic Design

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

Cytochrome P450 epoxygenase-derived 5,6-epoxyeicosatrienoic acid relaxes pulmonary arteries in normoxia but promotes sustained pulmonary vasoconstriction in hypoxia

AIMS

The aim of the study was to investigate the role of cytochrome P450 (CYP) epoxygenase-derived epoxyeicosatrienoic acids (EETs) in sustained hypoxic pulmonary vasoconstriction (HPV).

METHODS

Vasomotor responses of isolated mouse intrapulmonary arteries (IPAs) were assessed using wire myography. Key findings were verified by haemodynamic measurements in isolated perfused and ventilated mouse lungs.

RESULTS

Pharmacological inhibition of EET synthesis with MS-PPOH, application of the EET antagonist 14,15-EEZE or deficiency of CYP2J isoforms suppressed sustained HPV. In contrast, knockdown of EET-degrading soluble epoxide hydrolase or its inhibition with TPPU augmented sustained HPV almost twofold. All EET regioisomers elicited relaxation in IPAs pre-contracted with thromboxane mimetic U46619. However, in the presence of KCl-induced depolarization, 5,6-EET caused biphasic contraction in IPAs and elevation of pulmonary vascular tone in isolated lungs, whereas other regioisomers had no effect. In patch-clamp experiments, hypoxia elicited depolarization in pulmonary artery smooth muscle cells (PASMCs), and 5,6-EET evoked inward whole cell currents in PASMCs depolarized to the hypoxic level, but not at their resting membrane potential.

CONCLUSIONS

The EET pathway substantially contributes to sustained HPV in mouse pulmonary arteries. 5,6-EET specifically appears to be involved in HPV, as it is the only EET regioisomer able to elicit not only relaxation, but also sustained contraction in these vessels. 5,6-EET-induced pulmonary vasoconstriction is enabled by PASMC depolarization, which occurs in hypoxia. The discovery of the dual role of 5,6-EET in the regulation of pulmonary vascular tone may provide a basis for the development of novel therapeutic strategies for treatment of HPV-related diseases.

Higher Epoxyeicosatrienoic Acids in Cardiomyocytes-Specific CYP2J2 Transgenic Mice Are Associated with Improved Myocardial Remodeling

Elevated cis-epoxyeicosatrienoic acids (EETs) are known to be cardioprotective during ischemia-reperfusion injury in cardiomyocyte-specific overexpressing cytochrome P450 2J2 (CYP2J2) transgenic (Tr) mice. Using the same Tr mice, we measured changes in cardiac and erythrocyte membranes EETs following myocardial infarction (MI) to determine if they can serve as reporters for cardiac events. Cardiac function was also assessed in Tr vs. wild-type (WT) mice in correlation with EET changes two weeks following MI. Tr mice (N = 25, 16 female, nine male) had significantly higher cardiac cis- and trans-EETs compared to their WT counterparts (N = 25, 18 female, seven male). Total cardiac cis-EETs in Tr mice were positively correlated with total cis-EETs in erythrocyte membrane, but there was no correlation with trans-EETs or in WT mice. Following MI, cis- and trans-EETs were elevated in the erythrocyte membrane and cardiac tissue in Tr mice, accounting for the improved cardiac outcomes observed. Tr mice showed significantly better myocardial remodeling following MI, evidenced by higher % fractional shortening, smaller infarct size, lower reactive oxygen species (ROS) formation, reduced fibrosis and apoptosis, and lower pulmonary edema. A positive correlation between total cardiac cis-EETs and total erythrocyte membrane cis-EETs in a Tr mouse model suggests that erythrocyte cis-EETs may be used as predictive markers for cardiac events. All cis-EET regioisomers displayed similar trends following acute MI; however, the magnitude of change for each regioisomer was markedly different, warranting measurement of each individually.

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.

Comprehensive analysis of the mouse cytochrome P450 family responsible for omega-3 epoxidation of eicosapentaenoic acid

Metabolites generated via oxygenation of the omega-3 double bond (omega-3 oxygenation) in eicosapentaenoic acid (EPA) have recently been identified as novel anti-inflammatory lipid mediators. Therefore, oxygenase(s) responsible for this metabolic pathway are of particular interest. We performed genome-wide screening of mouse cytochrome P450 (CYP) isoforms to explore enzymes involved in omega-3 oxygenation of EPA. As a result, 5 CYP isoforms (mouse Cyp1a2, 2c50, 4a12a, 4a12b, and 4f18) were selected and identified to confer omega-3 epoxidation of EPA to yield 17,18-epoxyeicosatetraenoic acid (17,18-EpETE). Stereoselective production of 17,18-EpETE by each CYP isoform was confirmed, and molecular modeling indicated that chiral differences stem from different EPA binding conformations in the catalytic domains of respective CYP enzymes.

Epoxide hydrolase 1 (EPHX1) hydrolyzes epoxyeicosanoids and impairs cardiac recovery after ischemia

Stimuli such as inflammation or hypoxia induce cytochrome P450 epoxygenase-mediated production of arachidonic acid-derived epoxyeicosatrienoic acids (EETs). EETs have cardioprotective, vasodilatory, angiogenic, anti-inflammatory, and analgesic effects, which are diminished by EET hydrolysis yielding biologically less active dihydroxyeicosatrienoic acids (DHETs). Previous in vitro assays have suggested that epoxide hydrolase 2 (EPHX2) is responsible for nearly all EET hydrolysis. EPHX1, which exhibits slow EET hydrolysis in vitro, is thought to contribute only marginally to EET hydrolysis. Using Ephx1^-/-, Ephx2^-/-, and Ephx1^-/-Ephx2^-/- mice, we show here that EPHX1 significantly contributes to EET hydrolysis in vivo Disruption of Ephx1 and/or Ephx2 genes did not induce compensatory changes in expression of other Ephx genes or CYP2 family epoxygenases. Plasma levels of 8,9-, 11,12-, and 14,15-DHET were reduced by 38, 44, and 67% in Ephx2^-/- mice compared with wildtype (WT) mice, respectively; however, plasma from Ephx1^-/-Ephx2^-/- mice exhibited significantly greater reduction (100, 99, and 96%) of those respective DHETs. Kinetic assays and FRET experiments indicated that EPHX1 is a slow EET scavenger, but hydrolyzes EETs in a coupled reaction with cytochrome P450 to limit basal EET levels. Moreover, we also found that EPHX1 activities are biologically relevant, as Ephx1^-/-Ephx2^-/- hearts had significantly better postischemic functional recovery (71%) than both WT (31%) and Ephx2^-/- (51%) hearts. These findings indicate that Ephx1^-/-Ephx2^-/- mice are a valuable model for assessing EET-mediated effects, uncover a new paradigm for EET metabolism, and suggest that dual EPHX1 and EPHX2 inhibition may represent a therapeutic approach to manage human pathologies such as myocardial infarction.

Diversity and distribution of CYP gene family in Bactrian camel

Cytochrome P450 (CYP) enzymes belong to a superfamily of monooxygenases which are phase I enzymes responsible for the first pass metabolism of about 90% of drugs in animals. However, these enzymes are often polymorphic and metabolism of the same drug in different species or different individuals is influenced by genetic and non-genetic factors. Bactrian camels are capable of survival in harsh living environments, being able to consume diets that are often toxic to other mammals and can tolerate extreme water and food deprivation. The aim of this study was to investigate whether the Bactrian camel's special metabolic pathways and unique detoxification capabilities are attributable to particularities of the CYP gene family. The Bactrian camel's whole genome sequencing data were systemically analyzed and annotated, and then, CYP gene family was searched from the whole protein database and compared with CYP gene families of cattle, horse, chicken, and human. The total of 63 CYP gene copies were found in Bactrian camel's whole genome and were classified into 17 families and 38 subfamilies. Among them, 9 multi-gene families were found, and CYP2, CYP3, and CPY4 have 27, 6, and 7 subfamilies, accounting for 43, 10, and 11% in camel CYP gene, respectively. In comparison with cattle, chicken, horse, and human, the distribution of CYP gene subfamilies in camel is different, with more CYP2J and CYP3A copies in the Bactrian camel, which may contribute to the Bactrian camel's specific biological characteristics and metabolic pathways. Comparing to the cow, horse, chicken, and human CYP genes, the distribution of CYP gene subfamilies is distinct in the Bactrian camel. The higher copy number of CYP2J gene and CYP3A gene in Bactrian camel may be the important factors contributing to the distinct biological characteristics and metabolic pathways of Bactrian camels for adaptation to the harsh environments.

Transcriptomic analysis and plasma metabolomics in Aldh16a1-null mice reveals a potential role of ALDH16A1 in renal function

ALDH16A1 is a novel member of the ALDH superfamily that is enzymatically-inactive and highly expressed in the kidney. Recent studies identified an association between a rare missense single nucleotide variant (SNV) in the ALDH16A1 gene and elevated serum uric acid levels and gout. The present study explores the mechanisms by which ALDH16A1 influences uric acid homeostasis in the kidney. We generated and validated a mouse line with global disruption of the Aldh16a1 gene through gene targeting and performed RNA-seq analyses in the kidney of wild-type (WT) and Aldh16a1 knockout (KO) mice, along with plasma metabolomics. We found that ALDH16A1 is expressed in proximal and distal convoluted tubule cells in the cortex of the kidney and in zone 3 hepatocytes. RNA-seq and gene ontology enrichment analyses showed that cellular lipid and lipid metabolic processes are up-regulated. Three transporters localized in the apical membrane of the proximal convoluted tubule of the kidney known to influence urate/uric acid homeostasis were found to be up-regulated (Abcc4, Slc16a9) or down-regulated (Slc17a3). An initial metabolomics analysis in plasma revealed an altered lipid profile in KO mice that is in agreement with our RNA-seq analysis. This is the first study demonstrating a functional role of ALDH16A1 in the kidney.

Gene-metabolite network analysis in different nonalcoholic fatty liver disease phenotypes

We sought to identify common key regulators and build a gene-metabolite network in different nonalcoholic fatty liver disease (NAFLD) phenotypes. We used a high-fat diet (HFD), a methionine-choline-deficient diet (MCDD) and streptozocin (STZ) to establish nonalcoholic fatty liver (NAFL), nonalcoholic steatohepatitis (NASH) and NAFL+type 2 diabetes mellitus (T2DM) in rat models, respectively. Transcriptomics and metabolomics analyses were performed in rat livers and serum. A functional network-based regulation model was constructed using Cytoscape with information derived from transcriptomics and metabolomics. The results revealed that 96 genes, 17 liver metabolites and 4 serum metabolites consistently changed in different NAFLD phenotypes (>2-fold, P<0.05). Gene-metabolite network analysis identified ccl2 and jun as hubs with the largest connections to other genes, which were mainly involved in tumor necrosis factor, P53, nuclear factor-kappa B, chemokine, peroxisome proliferator activated receptor and Toll-like receptor signaling pathways. The specifically regulated genes and metabolites in different NAFLD phenotypes constructed their own networks, which were mainly involved in the lipid and fatty acid metabolism in HFD models, the inflammatory and immune response in MCDD models, and the AMPK signaling pathway and response to insulin in HFD+STZ models. Our study identified networks showing the general and specific characteristics in different NAFLD phenotypes, complementing the genetic and metabolic features in NAFLD with hepatic and extra-hepatic manifestations.

Beyond the classic eicosanoids: Peripherally-acting oxygenated metabolites of polyunsaturated fatty acids mediate pain associated with tissue injury and inflammation

Pain is a complex sensation that may be protective or cause undue suffering and loss of function, depending on the circumstances. Peripheral nociceptor neurons (PNs) innervate most tissues, and express ion channels, nocisensors, which depolarize the cell in response to intense stimuli and numerous substances. Inflamed tissues manifest inflammatory hyperalgesia in which the threshold for pain and the response to painful stimuli are decreased and increased, respectively. Constituents of the inflammatory milieu sensitize PNs, thereby contributing to hyperalgesia. Polyunsaturated fatty acids undergo enzymatic and free radical-mediated oxygenation into an array of bioactive metabolites, oxygenated polyunsaturated fatty acids (oxy-PUFAs), including the classic eicosanoids. Oxy-PUFA production is enhanced during inflammation. Pioneering studies by Vane and colleagues from the early 1970s first implicated classic eicosanoids in the pain associated with inflammation. Here, we review the production and action of oxy-PUFAs that are not classic eicosanoids, but nevertheless are produced in injured/ inflamed tissues and activate or sensitize PNs. In general, oxy-PUFAs that sensitize PNs may do so directly, by activation of nocisensors, ion channels or GPCRs expressed on the surface of PNs, or indirectly, by increasing the production of inflammatory mediators that activate or sensitize PNs. We focus on oxy-PUFAs that act directly on PNs. Specifically, we discuss the role of arachidonic acid-derived 12S-HpETE, HNE, ONE, PGA2, iso-PGA2 and 15d-PGJ2, 5,6-and 8,9-EET, PGE2-G and 8R,15S-diHETE, as well as the linoleic acid-derived 9-and 13-HODE in inducing acute nocifensive behavior and/or inflammatory hyperalgesia in rodents. The nocisensors TRPV1, TRPV4 and TRPA1, and putative Gαs-type GPCRs are the PN targets of these oxy-PUFAs.

Marmoset cytochrome P450 2J2 mainly expressed in small intestines and livers effectively metabolizes human P450 2J2 probe substrates, astemizole and terfenadine

1. Common marmoset (Callithrix jacchus), a New World Monkey, has potential to be a useful animal model in preclinical studies. However, drug metabolizing properties have not been fully understood due to insufficient information on cytochrome P450 (P450), major drug metabolizing enzymes. 2. Marmoset P450 2J2 cDNA was isolated from marmoset livers. The deduced amino acid sequence showed a high-sequence identity (91%) with cynomolgus monkey and human P450 2J2 enzymes. A phylogenetic tree revealed that marmoset P450 2J2 was evolutionarily closer to cynomolgus monkey and human P450 2J2 enzymes, than P450 2J forms in pigs, rabbits, rats or mice. 3. Marmoset P450 2J2 mRNA was abundantly expressed in the small intestine and liver, and to a lesser extent in the brain, lung and kidney. Immunoblot analysis also showed expression of marmoset P450 2J2 protein in the small intestine and liver. 4. Enzyme assays using marmoset P450 2J2 protein heterologously expressed in Escherichia coli indicated that marmoset P450 2J2 effectively catalyzed astemizole O-demethylation and terfenadine t-butyl hydroxylation, similar to human and cynomolgus monkey P450 2J2 enzymes. 5. These results suggest the functional characteristics of P450 2J2 enzymes are similar among marmosets, cynomolgus monkeys and humans.

Opioid Analgesia in P450 Gene Cluster Knockout Mice: A Search for Analgesia-Relevant Isoforms

Cytochrome P450 monooxygenases (P450s), which are well-known drug-metabolizing enzymes, are thought to play a signal transduction role in µ opioid analgesia and may serve as high-affinity (3)H-cimetidine ((3)HCIM) binding sites in the brain. (3)HCIM binding sites may also be related to opioid or nonopioid analgesia. However, of the more than 100 murine P450 enzymes, the specific isoform(s) responsible for either function have not been identified. Presently, three lines of constitutive P450 gene cluster knockout (KO) mice with full-length deletions of 14 Cyp2c, 9 Cyp2d, and 7 Cyp3a genes were studied for deficiencies in (3)HCIM binding and for opioid analgesia. Liver and brain homogenates from all three genotypes showed normal (3)HCIM binding values, indicating that gene products of Cyp2d, Cyp3a, and Cyp2c are not (3)HCIM-binding proteins. Cyp2d KO and Cyp3a KO mice showed normal antinociceptive responses to a moderate systemic dose of morphine (20 mg/kg, s.c.), thereby excluding 16 P450 isoforms as mediators of opioid analgesia. In contrast, Cyp2c KO mice showed a 41% reduction in analgesic responses following systemically (s.c.) administered morphine. However, the significance of brain Cyp2c gene products in opioid analgesia is uncertain because little or no analgesic deficits were noted in Cyp2c KO mice following intracerebroventricular or intrathecalmorphine administration, respectively. These results show that the gene products of Cyp2d and Cyp3a do not contribute to µ opioid analgesia in the central nervous system. A possible role for Cyp2c gene products in opioid analgesia requires further consideration.

Quantitative Polymerase Chain Reaction Analysis of the Mouse Cyp2j Subfamily: Tissue Distribution and Regulation

Members of the cytochrome P450 CYP2J subfamily are expressed in multiple tissues in mice and humans. These enzymes are active in the metabolism of fatty acids to generate bioactive compounds. Herein we report new methods and results for quantitative polymerase chain reaction (qPCR) analysis for the seven genes (Cyp2j5, Cyp2j6, Cyp2j8, Cyp2j9, Cyp2j11, Cyp2j12, and Cyp2j13) of the mouse Cyp2j subfamily. SYBR Green primer sets were developed and compared with commercially available TaqMan primer/probe assays for specificity toward mouse Cyp2j cDNA, and analysis of tissue distribution and regulation of Cyp2j genes. Each TaqMan primer/probe set and SYBR Green primer set were shown to be specific for their intended mouse Cyp2j cDNA. Tissue distribution of the mouse Cyp2j isoforms confirmed similar patterns of expression between the two qPCR methods. Cyp2j5 and Cyp2j13 were highly expressed in male kidneys, and Cyp2j11 was highly expressed in both male and female kidneys. Cyp2j6 was expressed in multiple tissues, with the highest expression in the small intestine and duodenum. Cyp2j8 was detected in various tissues, with highest expression found in the skin. Cyp2j9 was highly expressed in the brain, liver, and lung. Cyp2j12 was predominately expressed in the brain. We also determined the Cyp2j isoform expression in Cyp2j5 knockout mice to determine whether there was compensatory regulation of other Cyp2j isoforms, and we assessed Cyp2j isoform regulation during various inflammatory models, including influenza A, bacterial lipopolysaccharide, house dust mite allergen, and corn pollen. Both qPCR methods detected similar suppression of Cyp2j6 and Cyp2j9 during inflammation in the lung.

Optimized inhibitors of soluble epoxide hydrolase improve in vitro target residence time and in vivo efficacy

Diabetes is affecting the life of millions of people. A large proportion of diabetic patients suffer from severe complications such as neuropathic pain, and current treatments for these complications have deleterious side effects. Thus, alternate therapeutic strategies are needed. Recently, the elevation of epoxy-fatty acids through inhibition of soluble epoxide hydrolase (sEH) was shown to reduce diabetic neuropathic pain in rodents. In this report, we describe a series of newly synthesized sEH inhibitors with at least 5-fold higher potency and doubled residence time inside both the human and rodent sEH enzyme than previously reported inhibitors. These inhibitors also have better physical properties and optimized pharmacokinetic profiles. The optimized inhibitor selected from this new series displayed improved efficacy of almost 10-fold in relieving pain perception in diabetic neuropathic rats as compared to the approved drug, gabapentin, and previously published sEH inhibitors. Therefore, these new sEH inhibitors could be an attractive alternative to treat diabetic neuropathy in humans.

Deletion of the murine cytochrome P450 Cyp2j locus by fused BAC-mediated recombination identifies a role for Cyp2j in the pulmonary vascular response to hypoxia

Epoxyeicosatrienoic acids (EETs) confer vasoactive and cardioprotective functions. Genetic analysis of the contributions of these short-lived mediators to pathophysiology has been confounded to date by the allelic expansion in rodents of the portion of the genome syntenic to human CYP2J2, a gene encoding one of the principle cytochrome P450 epoxygenases responsible for the formation of EETs in humans. Mice have eight potentially functional genes that could direct the synthesis of epoxygenases with properties similar to those of CYP2J2. As an initial step towards understanding the role of the murine Cyp2j locus, we have created mice bearing a 626-kb deletion spanning the entire region syntenic to CYP2J2, using a combination of homologous and site-directed recombination strategies. A mouse strain in which the locus deletion was complemented by transgenic delivery of BAC sequences encoding human CYP2J2 was also created. Systemic and pulmonary hemodynamic measurements did not differ in wild-type, null, and complemented mice at baseline. However, hypoxic pulmonary vasoconstriction (HPV) during left mainstem bronchus occlusion was impaired and associated with reduced systemic oxygenation in null mice, but not in null mice bearing the human transgene. Administration of an epoxygenase inhibitor to wild-type mice also impaired HPV. These findings demonstrate that Cyp2j gene products regulate the pulmonary vascular response to hypoxia.

In mice and humans, the CYP2J class of cytochrome P450 epoxygenases metabolizes arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs), short-lived mediators with effects on both the pulmonary and systemic vasculature. Genetic dissection of CYP2J function to date has been complicated by allelic expansion in the rodent genome. In this study, the mouse chromosomal locus syntenic to human CYP2J2, containing eight presumed genes and two pseudogenes, was deleted via generation of a recombinant template created by homologous and site-specific recombination steps that joined two precursor bacterial artificial chromosomes (BACs). The Cyp2j null mice were subsequently complemented by transgenic delivery of BAC sequences encoding human CYP2J2. Hypoxic pulmonary vasoconstriction (HPV) and systemic oxygenation during regional alveolar hypoxia were unexpectedly found to be impaired in null mice, but not in null mice bearing the transgenic human allele, suggesting that Cyp2j products contribute to the pulmonary vascular response to hypoxia.