Disease relevance of Ephx2

• Isolation and characterization of a cDNA encoding rat liver cytosolic epoxide hydrolase and its functional expression in Escherichia coli [1].
• Renal cortical sEH protein expression was significantly higher in Ang II hypertension compared with normotensive animals [2].
• Attenuation of tobacco smoke-induced lung inflammation by treatment with a soluble epoxide hydrolase inhibitor [3].
• The rat hepatoma cell line Fu5AH, which lacks this particular CEH activity, was stably transfected with the cDNA of rat pancreatic CEH, and the effects on cholesterol and cholesteryl ester metabolism in clones with varying levels of CEH expression determined [4].
• CEH activity, in contrast, increases during endotoxic shock; it shows a maximum (twofold the activity seen in control rats) at 6 h after lipopolysaccharide injection [5].

High impact information on Ephx2

• Epoxyeicosatrienoic acids (EETs) have demonstrated antiinflammatory properties, and hydrolysis of these epoxides by sEH is known to diminish this activity [3].
• The sEH inhibitor significantly decreased total bronchoalveolar lavage cell number by 37% in tobacco smoke-exposed rats with significant reductions noted in neutrophils, alveolar macrophages, and lymphocytes [3].
• The mammalian soluble epoxide hydrolase (sEH) is an enzyme with multiple functions, being implicated in detoxification of xenobiotic epoxides as well as in regulation of physiological processes such as blood pressure [6].
• Subsequently, we found rat sEH hydrolyzed 4-nitrophenyl phosphate with a rate constant of 0.8 s(-1) and a K(m) of 0.24 mM [6].
• The expressed CEH activity was highly dependent on the presence of trihydroxy bile salts (cholate or one of its conjugates); maximum hydrolytic activity was observed in the presence of 10 mM sodium cholate [7].

Chemical compound and disease context of Ephx2

• Soluble epoxide hydrolase inhibition lowers arterial blood pressure in angiotensin II hypertension [2].
• With advancing age a feminization of male glutathione S-transferase and cytosolic epoxide hydrolase activities was found, as well as a significant decline of the female microsomal epoxide hydrolase activity and an increase of the cytochrome P-450 content in the oldest female rats [8].

Biological context of Ephx2

• A cDNA of 1992 base pairs encoding the complete rat liver cytosolic epoxide hydrolase has been isolated using a polymerase chain reaction-derived DNA fragment (Arand, M., Knehr, M., Thomas, H., Zeller, H. D., and Oesch, F. (1991) FEBS Lett. 294, 19-22) known to represent the 3'-end of the cytosolic epoxide hydrolase mRNA [1].
• Sequence analysis of one of the differentially expressed genes, cytosolic epoxide hydrolase, revealed that two haplotypes could in part explain the expression level [9].
• We measured soluble epoxide hydrolase (sEH) renal gene expression in prehypertensive (4 to 5 weeks old) spontaneously hypertensive rats of the Heidelberg SP substrain (SHR [Heid]) and when blood pressure levels entered the hypertensive plateau (17 to 18 weeks old) and compared expression with matched Wistar-Kyoto (WKY [Heid]) rats [10].
• Increase in cytosolic epoxide hydrolase activity was not due to enzyme activation as demonstrated by in vitro studies [11].
• The present studies identify the putative hormone response elements in the CEH promoter [12].

Anatomical context of Ephx2

• The most significant structure of the deduced protein is a modified peroxisomal targeting signal (Ser-Lys-Ile) at the carboxyl terminus that is regarded to be responsible for the unusual dual localization of the cytosolic epoxide hydrolase in peroxisomes as well as in the cytosol [1].
• A catalytically active bile salt-dependent cholesteryl ester hydrolase (CEH) was expressed when Xenopus oocytes were injected with rat liver mRNA [7].
• Polyclonal antibodies raised to TLCEH exhibited no cross-immunoreactivity with cytosolic proteins from other rat tissues and inhibited 70% of testis cytosolic CEH [13].
• Radiation inactivation by high energy electrons, a method for determining the size of a protein without prior purification, was used to study the acid and neutral cholesteryl ester hydrolase (CEH) activities of rat liver microsomes [14].
• In spite of significant amounts of intracellular enzyme protein demonstrated by Western blotting, in cell lysates there was a consistently low level of catalytic activity, and in cultured cells there was no evidence that CEH served as an effective intracellular cholesteryl ester hydrolase or synthase [4].

Associations of Ephx2 with chemical compounds

• These studies demonstrate that increased sEH expression in the Ang II hypertensive kidney leads to increased EET hydration [2].
• In additional experiments, the sEH inhibitor N-cyclohexyl-N-dodecyl urea (NCND; 3 mg/d) or vehicle (corn oil, 0.5 mL) was administered daily by intraperitoneal injection starting on day 10 [2].
• In the presence of 10 mM sodium cholate, the CEH activity was maximal near pH 7 but was significant between pH 6 and 8 [7].
• The expressed CEH was not activated by dihydroxy bile salts (deoxycholate and its conjugates) [7].
• Phenylmethylsulfonyl fluoride, a serine enzyme inhibitor, was inhibitory to the expressed CEH activity, whereas p-chloromercuribenzoate (up to 5 mM), a potent thiol-blocking agent, did not significantly inhibit the expressed activity [7].

Other interactions of Ephx2

• Only a single functional epoxide hydrolase gene was identified and no evidence of hybridization to the genes for the microsomal cholesterol epoxide hydrolase or the cytosolic epoxide hydrolase was observed [15].
• The induction of catalase (2-3-fold) and cytosolic epoxide hydrolase (3-5-fold) was also observed in Kupffer and endothelial cells; furthermore, a low peroxisomal fatty acid beta-oxidation activity was detected in endothelial cells [16].
• The following phase II enzyme activities were also well maintained after cryopreservation: Phenol sulfotransferase (92%), 1-naphthol UDP-glucuronosyl transferase (95%), soluble epoxide hydrolase (87%), and glutathione S-transferase (88%), determined with broad spectrum substrate 1-chloro-2,4-dinitrobenzene [17].
• The activity of UDP-glucuronosyltransferase and cytosolic epoxide hydrolase were not detectable [18].
• There was limited overlap in observed protein abundance changes between the three groups, and where this was the case (cytosolic epoxide hydrolase, peroxisomal bifunctional enzyme, hydroxymethyl glutaryl CoA, synthase, long chain acyl-CoA thioesterase), expression of these proteins had previously been shown to be under the control of PPAR activity [19].

Analytical, diagnostic and therapeutic context of Ephx2

• The obtained sequence information was used to perform PCR experiments resulting in the isolation of a 680 bp cDNA clone encoding the carboxy terminus of cEH [20].
• The unique cDNA was sequenced and found to be similar to hepatic CEH, pI 6.1 esterase, and hydrolase A. In Northern blot analysis, the cDNA hybridized with a single band from lung messenger RNA (mRNA) [21].
• The 1,839-base pair complementary DNA (cDNA) for rat lung carboxylesterase was cloned by reverse transcriptase polymerase chain reaction from total rat lung RNA using specific primers derived from the 5' and 3' untranslated regions of rat hepatic cholesteryl ester hydrolase (CEH) [21].
• Gel mobility shift assays further demonstrated that NF-Y binds to the inverted CCAAT box motif and is required for the sterol-mediated regulation.These results indicate that multiple cis-elements regulate transcription of the cholesteryl ester hydrolase (CEH) gene, consistent with the reported regulation of CEH expression.-Natarajan, R., S [12].
• A rat liver cytosolic cholesteryl ester hydrolase (CEH) was purified 12,600-fold by ammonium sulfate precipitation, cation exchange chromatography and gel permeation high-performance liquid chromatography, with an overall yield of 20% [22].

References