Gene_locus Report for: mouse-hyes

This study investigated changes in neuroinflammation and cognitive function in adult zebrafish exposed to acute hypoxia and protective effects of glucosamine (GlcN) against hypoxia-induced brain damage. The survival rate of zebrafish following exposure to hypoxia was improved by GlcN pretreatment. Moreover, hypoxia-induced upregulation of neuroglobin, NOS2alpha, glial fibrillary acidic protein, and S100beta in zebrafish was suppressed by GlcN. Hypoxia stimulated cell proliferation in the telencephalic ventral domain and in cerebellum subregions. GlcN decreased the number of bromodeoxyuridine (BrdU)-positive cells in the telencephalon region, but not in cerebellum regions. Transient motor neuron defects, assessed by measuring the locomotor and exploratory activity of zebrafish exposed to hypoxia recovered quickly. GlcN did not affect hypoxia-induced motor activity changes. In passive avoidance tests, hypoxia impaired learning and memory ability, deficits that were rescued by GlcN. A learning stimulus increased the nuclear translocation of phosphorylated cAMP response element binding protein (p-CREB), an effect that was greatly inhibited by hypoxia. GlcN restored nuclear p-CREB after a learning trial in hypoxia-exposed zebrafish. The neurotransmitters, gamma-aminobutyric acid and glutamate, were increased after hypoxia in the zebrafish brain, and GlcN further increased their levels. In contrast, acetylcholine levels were reduced by hypoxia and restored by GlcN. Acetylcholinesterase inhibitor physostigmine partially reversed the impaired learning and memory of hypoxic zebrafish. This study represents the first examination of the molecular mechanisms underlying hypoxia-induced memory and learning defects in a zebrafish model. Our results further suggest that GlcN-associated hexosamine metabolic pathway could be an important therapeutic target for hypoxic brain damage.

Depression is a severe and chronic psychiatric disease, affecting 350 million subjects worldwide. Although multiple antidepressants have been used in the treatment of depressive symptoms, their beneficial effects are limited. The soluble epoxide hydrolase (sEH) plays a key role in the inflammation that is involved in depression. Thus, we examined here the role of sEH in depression. In both inflammation and social defeat stress models of depression, a potent sEH inhibitor, TPPU, displayed rapid antidepressant effects. Expression of sEH protein in the brain from chronically stressed (susceptible) mice was higher than of control mice. Furthermore, expression of sEH protein in postmortem brain samples of patients with psychiatric diseases, including depression, bipolar disorder, and schizophrenia, was higher than controls. This finding suggests that increased sEH levels might be involved in the pathogenesis of certain psychiatric diseases. In support of this hypothesis, pretreatment with TPPU prevented the onset of depression-like behaviors after inflammation or repeated social defeat stress. Moreover, sEH KO mice did not show depression-like behavior after repeated social defeat stress, suggesting stress resilience. The sEH KO mice showed increased brain-derived neurotrophic factor (BDNF) and phosphorylation of its receptor TrkB in the prefrontal cortex, hippocampus, but not nucleus accumbens, suggesting that increased BDNF-TrkB signaling in the prefrontal cortex and hippocampus confer stress resilience. All of these findings suggest that sEH plays a key role in the pathophysiology of depression, and that epoxy fatty acids, their mimics, as well as sEH inhibitors could be potential therapeutic or prophylactic drugs for depression.

The crystal structure of recombinant murine liver cytosolic epoxide hydrolase (EC 3.3.2.3) has been determined at 2.8-A resolution. The binding of a nanomolar affinity inhibitor confirms the active site location in the C-terminal domain; this domain is similar to that of haloalkane dehalogenase and shares the alpha/beta hydrolase fold. A structure-based mechanism is proposed that illuminates the unique chemical strategy for the activation of endogenous and man-made epoxide substrates for hydrolysis and detoxification. Surprisingly, a vestigial active site is found in the N-terminal domain similar to that of another enzyme of halocarbon metabolism, haloacid dehalogenase. Although the vestigial active site does not participate in epoxide hydrolysis, the vestigial domain plays a critical structural role by stabilizing the dimer in a distinctive domain-swapped architecture. Given the genetic and structural relationships among these enzymes of xenobiotic metabolism, a structure-based evolutionary sequence is postulated.

Epoxides and diols of polyunsaturated fatty acids (PUFAs) are bioactive and can influence processes such as tumor cell proliferation and angiogenesis. Studies with inhibitors of the soluble epoxide hydrolase (sEH) in animals overexpressing cytochrome P450 enzymes or following the systemic administration of specific epoxides revealed a markedly increased incidence of tumor metastases. To determine whether PUFA epoxides increased metastases in a model of spontaneous breast cancer, sEH(-/-) mice were crossed onto the polyoma middle T oncogene (PyMT) background. We found that the deletion of the sEH accelerated the growth of primary tumors and increased both the tumor macrophage count and angiogenesis. There were small differences in the epoxide/diol content of tumors, particularly in epoxyoctadecamonoenic acid versus dihydroxyoctadecenoic acid, and marked changes in the expression of proteins linked with cell proliferation and metabolism. However, there was no consequence of sEH inhibition on the formation of metastases in the lymph node or lung. Taken together, our results confirm previous reports of increased tumor growth in animals lacking sEH but fail to substantiate reports of enhanced lymph node or pulmonary metastases.

The soluble epoxide hydrolase (sEH) enzyme is a major regulator of bioactive lipids. The enzyme is highly expressed in liver and kidney and modulates levels of endogenous epoxy-fatty acids, which have pleiotropic biological effects including limiting inflammation, neuroinflammation, and hypertension. It has been hypothesized that inhibiting sEH has beneficial effects on limiting obesity and metabolic disease as well. There is a body of literature published on these effects, but typically only male subjects have been included. Here, we investigate the role of sEH in both male and female mice and use a global sEH knockout mouse model to compare the effects of diet and diet-induced obesity. The results demonstrate that sEH activity in the liver is modulated by high-fat diets more in male than in female mice. In addition, we characterized the sEH activity in high fat content tissues and demonstrated the influence of diet on levels of bioactive epoxy-fatty acids. The sEH KO animals had generally increased epoxy-fatty acids compared to wild-type mice but gained less body weight on higher-fat diets. Generally, proinflammatory prostaglandins and triglycerides were also lower in livers of sEH KO mice fed HFD. Thus, sEH activity, prostaglandins, and triglycerides increase in male mice on high-fat diet but are all limited by sEH ablation. Additionally, these changes also occur in female mice though at a different magnitude and are also improved by knockout of the sEH enzyme.

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

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.

This study investigated changes in neuroinflammation and cognitive function in adult zebrafish exposed to acute hypoxia and protective effects of glucosamine (GlcN) against hypoxia-induced brain damage. The survival rate of zebrafish following exposure to hypoxia was improved by GlcN pretreatment. Moreover, hypoxia-induced upregulation of neuroglobin, NOS2alpha, glial fibrillary acidic protein, and S100beta in zebrafish was suppressed by GlcN. Hypoxia stimulated cell proliferation in the telencephalic ventral domain and in cerebellum subregions. GlcN decreased the number of bromodeoxyuridine (BrdU)-positive cells in the telencephalon region, but not in cerebellum regions. Transient motor neuron defects, assessed by measuring the locomotor and exploratory activity of zebrafish exposed to hypoxia recovered quickly. GlcN did not affect hypoxia-induced motor activity changes. In passive avoidance tests, hypoxia impaired learning and memory ability, deficits that were rescued by GlcN. A learning stimulus increased the nuclear translocation of phosphorylated cAMP response element binding protein (p-CREB), an effect that was greatly inhibited by hypoxia. GlcN restored nuclear p-CREB after a learning trial in hypoxia-exposed zebrafish. The neurotransmitters, gamma-aminobutyric acid and glutamate, were increased after hypoxia in the zebrafish brain, and GlcN further increased their levels. In contrast, acetylcholine levels were reduced by hypoxia and restored by GlcN. Acetylcholinesterase inhibitor physostigmine partially reversed the impaired learning and memory of hypoxic zebrafish. This study represents the first examination of the molecular mechanisms underlying hypoxia-induced memory and learning defects in a zebrafish model. Our results further suggest that GlcN-associated hexosamine metabolic pathway could be an important therapeutic target for hypoxic brain damage.

Depression is a severe and chronic psychiatric disease, affecting 350 million subjects worldwide. Although multiple antidepressants have been used in the treatment of depressive symptoms, their beneficial effects are limited. The soluble epoxide hydrolase (sEH) plays a key role in the inflammation that is involved in depression. Thus, we examined here the role of sEH in depression. In both inflammation and social defeat stress models of depression, a potent sEH inhibitor, TPPU, displayed rapid antidepressant effects. Expression of sEH protein in the brain from chronically stressed (susceptible) mice was higher than of control mice. Furthermore, expression of sEH protein in postmortem brain samples of patients with psychiatric diseases, including depression, bipolar disorder, and schizophrenia, was higher than controls. This finding suggests that increased sEH levels might be involved in the pathogenesis of certain psychiatric diseases. In support of this hypothesis, pretreatment with TPPU prevented the onset of depression-like behaviors after inflammation or repeated social defeat stress. Moreover, sEH KO mice did not show depression-like behavior after repeated social defeat stress, suggesting stress resilience. The sEH KO mice showed increased brain-derived neurotrophic factor (BDNF) and phosphorylation of its receptor TrkB in the prefrontal cortex, hippocampus, but not nucleus accumbens, suggesting that increased BDNF-TrkB signaling in the prefrontal cortex and hippocampus confer stress resilience. All of these findings suggest that sEH plays a key role in the pathophysiology of depression, and that epoxy fatty acids, their mimics, as well as sEH inhibitors could be potential therapeutic or prophylactic drugs for depression.

Ovulation is a complex process initiated by the surge of the pituitary luteinizing hormone (LH) that provokes the expression of specific genes. We report herein the isolation and characterization of an ovulation-associated, ovary-specific novel isoform of epoxide hydrolase 2 (Ephx2), Ephx2C. This variant is exclusively expressed in the granulosa cells of preovulatory mouse ovarian follicles. The LH-induced expression of Ephx2C is mediated by the protein kinase A and partially by the protein kinase C signaling pathways. The involvement of p38 kinase has also been demonstrated.

Only a small proportion of the mouse genome is transcribed into mature messenger RNA transcripts. There is an international collaborative effort to identify all full-length mRNA transcripts from the mouse, and to ensure that each is represented in a physical collection of clones. Here we report the manual annotation of 60,770 full-length mouse complementary DNA sequences. These are clustered into 33,409 'transcriptional units', contributing 90.1% of a newly established mouse transcriptome database. Of these transcriptional units, 4,258 are new protein-coding and 11,665 are new non-coding messages, indicating that non-coding RNA is a major component of the transcriptome. 41% of all transcriptional units showed evidence of alternative splicing. In protein-coding transcripts, 79% of splice variations altered the protein product. Whole-transcriptome analyses resulted in the identification of 2,431 sense-antisense pairs. The present work, completely supported by physical clones, provides the most comprehensive survey of a mammalian transcriptome so far, and is a valuable resource for functional genomics.

The RIKEN Mouse Gene Encyclopaedia Project, a systematic approach to determining the full coding potential of the mouse genome, involves collection and sequencing of full-length complementary DNAs and physical mapping of the corresponding genes to the mouse genome. We organized an international functional annotation meeting (FANTOM) to annotate the first 21,076 cDNAs to be analysed in this project. Here we describe the first RIKEN clone collection, which is one of the largest described for any organism. Analysis of these cDNAs extends known gene families and identifies new ones.

In the effort to prepare the mouse full-length cDNA encyclopedia, we previously developed several techniques to prepare and select full-length cDNAs. To increase the number of different cDNAs, we introduce here a strategy to prepare normalized and subtracted cDNA libraries in a single step. The method is based on hybridization of the first-strand, full-length cDNA with several RNA drivers, including starting mRNA as the normalizing driver and run-off transcripts from minilibraries containing highly expressed genes, rearrayed clones, and previously sequenced cDNAs as subtracting drivers. Our method keeps the proportion of full-length cDNAs in the subtracted/normalized library high. Moreover, our method dramatically enhances the discovery of new genes as compared to results obtained by using standard, full-length cDNA libraries. This procedure can be extended to the preparation of full-length cDNA encyclopedias from other organisms.

The crystal structure of recombinant murine liver cytosolic epoxide hydrolase (EC 3.3.2.3) has been determined at 2.8-A resolution. The binding of a nanomolar affinity inhibitor confirms the active site location in the C-terminal domain; this domain is similar to that of haloalkane dehalogenase and shares the alpha/beta hydrolase fold. A structure-based mechanism is proposed that illuminates the unique chemical strategy for the activation of endogenous and man-made epoxide substrates for hydrolysis and detoxification. Surprisingly, a vestigial active site is found in the N-terminal domain similar to that of another enzyme of halocarbon metabolism, haloacid dehalogenase. Although the vestigial active site does not participate in epoxide hydrolysis, the vestigial domain plays a critical structural role by stabilizing the dimer in a distinctive domain-swapped architecture. Given the genetic and structural relationships among these enzymes of xenobiotic metabolism, a structure-based evolutionary sequence is postulated.

The soluble epoxide hydrolase (sEH) plays a significant role in the biosynthesis of inflammation mediators as well as xenobiotic transformations. Herein, we report the discovery of substituted ureas and carbamates as potent inhibitors of sEH. Some of these selective, competitive tight-binding inhibitors with nanomolar K(i) values interacted stoichiometrically with the homogenous recombinant murine and human sEHs. These inhibitors enhance cytotoxicity of trans-stilbene oxide, which is active as the epoxide, but reduce cytotoxicity of leukotoxin, which is activated by epoxide hydrolase to its toxic diol. They also reduce toxicity of leukotoxin in vivo in mice and prevent symptoms suggestive of acute respiratory distress syndrome. These potent inhibitors may be valuable tools for testing hypotheses of involvement of diol and epoxide lipids in chemical mediation in vitro or in vivo systems.

We have analyzed amino acid sequence relationships among soluble and microsomal epoxide hydrolases, haloacid dehalogenases, and a haloalkane dehalogenase. The amino-terminal residues (1-229) of mammalian soluble epoxide hydrolase are homologous to a haloacid dehalogenase. The carboxy-terminal residues (230-554) of mammalian soluble epoxide hydrolase are homologous to haloalkane dehalogenase, to plant soluble epoxide hydrolase, and to microsomal epoxide hydrolase. The shared identity between the haloacid and haloalkane dehalogenases does not indicate relatedness between these two types of dehalogenases. The amino-terminal and carboxy-terminal homologies of mammalian soluble epoxide hydrolase to the respective dehalogenases suggests that this epoxide hydrolase, but not the soluble epoxide hydrolase of plant or the microsomal epoxide hydrolase, derives from a gene fusion. The homology of microsomal to soluble epoxide hydrolase suggests they derive from a gene duplication, probably of an ancestral bacterial (epoxide) hydrolase gene. Based on homology to haloalkane dehalogenase, the catalytic residues for the soluble and microsomal epoxide hydrolases are predicted. A nomenclature system based on divergent molecular evolution is proposed for these epoxide hydrolases.

The soluble epoxide hydrolase mRNA level in liver was increased eight-fold upon administration of the hypolipidemic drug and peroxisome proliferator clofibrate for 7 days to mice. The soluble epoxide hydrolase mRNA was back at control levels within 1-2 days after clofibrate withdrawal. The highest expression was in liver, intestine and kidney. Lower levels were found in heart and muscle and very low levels were found in testes, lung, brain and spleen. The mRNA levels were increased in liver, kidney and heart by clofibrate.

A clofibrate-induced mouse liver cDNA library was prepared and used to isolate the coding sequence for soluble epoxide hydrolase. A 1668-base pair (bp) clone was isolated and found to contain a 1269-bp open reading frame coding for 423 amino acids. Subsequent RNA polymerase chain reaction resulted in the isolation of 396 bp of additional 5'-sequence. Translation of the resulting 1659-bp open reading frame produced a 553-residue protein (62,527 Da) containing deduced peptide segments that matched the amino acid sequences of six peptide fragments isolated previously from CNBr digests of pure murine soluble epoxide hydrolase. Neither the DNA nor the protein sequence showed significant similarity to other currently published sequences. Structural analysis of the soluble epoxide hydrolase coding region suggested at least one potential regulatory motif. Expression of the composite cDNA in COS-7 cells resulted in a 5-10-fold increase in soluble epoxide hydrolase activity and a similar increase in soluble epoxide hydrolase protein amount compared to mock-transfected or vector control-transfected cells. Treatment of C57BL/6J mice with clofibrate led to an approximately 4-fold increase in both soluble epoxide hydrolase enzyme activity and steady-state mRNA levels.