Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A previously validated small mammal trauma model, hindlimb ischemia secondary to infrarenal aortic ligation in the rat, was utilized to investigate the effects of traumatic injury on two of the major hepatic enzymes of detoxification, glutathione S-transferase and epoxide hydrolase. Hepatic cytosolic glutathione S-transferase activity toward a variety of substrates showed a 26-34% decrease at 24 hr after model injury. Hepatic microsomal epoxide hydrolase activity toward 1,2-epoxy-3-(p-nitrophenoxy)propane was diminished by 53% after model trauma. Both enzymatic activities toward styrene oxide were similarly depressed. The toxicological sequelae of these derangements were illustrated by administering a dose of styrene oxide (300 mg/kg, ip) which was below the threshold dose (350 mg/kg, ip) necessary to produce hepatotoxicity in control animals. Model trauma dramatically enhanced the hepatotoxic effects of the subthreshold dose, as well as the covalent binding of labeled styrene oxide to liver proteins. These findings indicate that traumatic injury renders the animal more susceptible to agents which are detoxified by glutathione S-transferase and epoxide hydrolase. Conversely, model trauma provided almost complete protection from the hepatotoxic effects of a standard dose (200 mg/kg, ip) of bromobenzene. This protection appeared to derive from a post-traumatic alteration of cytochrome P-450 subpopulations that decreased the formation of the potentially toxic 3,4-epoxide metabolite, despite an increase in the cytochrome P-448-mediated generation of the nontoxic 2,3-epoxide. For bromobenzene, the change in cytochrome P-450-mediated activation appeared quantitatively more significant in overall toxicity than the post-traumatic depression of detoxification pathways described above, leading to decreased toxicity in vivo. For other compounds, the combination of post-traumatic influences on cytochrome P-450/P-448 activity and epoxide hydrolase/glutathione S-transferase activities could lead to markedly enhanced toxicity.
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PMID:Effects of model traumatic injury on hepatic drug metabolism in the rat. VI. Major detoxification/toxification pathways. 289 98

Epoxide hydrolases comprise a family of enzymes important in detoxification and conversion of lipid signaling molecules, namely epoxyeicosatrienoic acids (EETs), to their supposedly less active form, dihydroxyeicosatrienoic acids (DHETs). EETs control cerebral blood flow, exert analgesic, anti-inflammatory and angiogenic effects and protect against ischemia. Although the role of soluble epoxide hydrolase (sEH) in EET metabolism is well established, knowledge on its detailed distribution in rodent brain is rather limited. Here, we analyzed the expression pattern of sEH and of another important member of the EH family, microsomal epoxide hydrolase (mEH), in mouse brain by immunohistochemistry. To investigate the functional relevance of these enzymes in brain, we explored their individual contribution to EET metabolism in acutely isolated brain cells from respective EH -/- mice and wild type littermates by mass spectrometry. We find sEH immunoreactivity almost exclusively in astrocytes throughout the brain, except in the central amygdala, where neurons are also positive for sEH. mEH immunoreactivity is abundant in brain vascular cells (endothelial and smooth muscle cells) and in choroid plexus epithelial cells. In addition, mEH immunoreactivity is present in specific neuronal populations of the hippocampus, striatum, amygdala, and cerebellum, as well as in a fraction of astrocytes. In freshly isolated cells from hippocampus, where both enzymes are expressed, sEH mediates the bulk of EET metabolism. Yet we observe a significant contribution of mEH, pointing to a novel role of this enzyme in the regulation of physiological processes. Furthermore, our findings indicate the presence of additional, hitherto unknown cerebral epoxide hydrolases. Taken together, cerebral EET metabolism is driven by several epoxide hydrolases, a fact important in view of the present targeting of sEH as a potential therapeutic target. Our findings suggest that these different enzymes have individual, possibly quite distinct roles in brain function and cerebral EET metabolism.
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PMID:Distribution of soluble and microsomal epoxide hydrolase in the mouse brain and its contribution to cerebral epoxyeicosatrienoic acid metabolism. 1954 Mar 14

Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid into epoxyeicosatrienoic acids (EETs), which play an important role in blood pressure regulation, protection against ischemia-reperfusion injury, angiogenesis, and inflammation. Epoxide hydrolases metabolize EETs to their corresponding diols (dihydroxyeicosatrienoic acids; DHETs) which are biologically less active. Microsomal epoxide hydrolase (EPHX1, mEH) and soluble epoxide hydrolase (EPHX2, sEH) were identified >30 years ago and are capable of hydrolyzing EETs to DHETs. A novel epoxide hydrolase, EPHX3, was recently identified by sequence homology and also exhibits epoxide hydrolase activity in vitro with a substrate preference for 9,10-epoxyoctadecamonoenoic acid (EpOME) and 11,12-EET. EPHX3 is highly expressed in the skin, lung, stomach, esophagus, and tongue; however, its endogenous function is unknown. Therefore, we investigated the impact of genetic disruption of Ephx3 on fatty acid epoxide hydrolysis and EET-related physiology in mice. Ephx3-/- mice were generated by excising the promoter and first four exons of the Ephx3 gene using Cre-LoxP methodology. LC-MS/MS analysis of Ephx3-/- heart, lung, and skin lysates revealed no differences in endogenous epoxide:diol ratios compared to wild type (WT). Ephx3-/- mice also exhibited no change in plasma levels of fatty acid epoxides and diols relative to WT. Incubations of cytosolic and microsomal fractions prepared from Ephx3-/- and WT stomach, lung, and skin with synthetic 8,9-EET, 11,12-EET, and 9,10-EpOME revealed no significant differences in rates of fatty acid diol formation between the genotypes. Ephx3-/- hearts had similar functional recovery compared to WT hearts following ischemia/reperfusion injury. Following intranasal lipopolysaccharide (LPS) exposure, Ephx3-/- mice were not different from WT in terms of lung histology, bronchoalveolar lavage fluid cell counts, or fatty acid epoxide and diol levels. We conclude that genetic disruption of Ephx3 does not result in an overt phenotype and has no significant effects on the metabolism of EETs or EpOMEs in vivo.
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PMID:Generation and characterization of epoxide hydrolase 3 (EPHX3)-deficient mice. 2838 53