title: Homocysteine upregulates soluble epoxide hydrolase in vascular endothelium in vitro and in vivo.
abstract: BACKGROUND
  Hyperhomocysteinemia is a risk factor of atherogenesis. Soluble epoxide hydrolase (sEH) is a major enzyme that hydrolyzes epoxyeicosatrienoic acids and attenuates their cardiovascular protective effects. Whether homocysteine (Hcy) regulates sEH and the underlying mechanism remains elusive.
  
  
  OBJECTIVE
  To elucidate the mechanism by which Hcy regulates sEH expression and endothelial activation in vitro and in vivo.
  
  
  RESULTS
  Hcy treatment in cultured human endothelial cells dose-dependently and time-dependently upregulated sEH mRNA and protein. Hcy increased the expression of adhesion molecules, which was markedly reversed by inhibiting sEH activity. Hcy-induced sEH upregulation is associated with activation of activating transcription factor-6 (ATF6). Bioinformatics analysis revealed a putative ATF6-binding motif in the promoter region of the sEH gene, which was found at a methylation site. Site-directed mutagenesis and chromatin immunoprecipitation assays demonstrated that Hcy treatment or ATF6 overexpression promoted ATF6 binding to the promoter of sEH and increased its activity. Results of methylation-specific polymerase chain reaction revealed that the ATF6 binding site on the sEH promoter was partially methylated and was demethylated with Hcy. SiRNA knockdown of ATF6α or SP1 blocked and ATF6 overexpression and DNA methyltransferase inhibitor mimicked the effect of homocysteine on sEH upregulation. In vivo, immunofluorescence assay revealed elevated expression of sEH and adhesion molecules in the aortic intima of mice with mild hyperhomocysteinemia, which was attenuated by sEH deletion or inhibition.
  
  
  CONCLUSIONS
  ATF6 activation and DNA demethylation may coordinately contribute to Hcy-induced sEH expression and endothelial activation. Inhibition of sEH may be a therapeutic approach for treating Hcy-induced cardiovascular diseases.
authors.affiliation: Cardiovascular Research Center, Shantou University Medical College, Guangdong, China.
authors.forename: Donghong
authors.initials: D
authors.lastname: Zhang
authors.forename: Xina
authors.initials: X
authors.lastname: Xie
authors.forename: Yequn
authors.initials: Y
authors.lastname: Chen
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Hammock
authors.forename: Wei
authors.initials: W
authors.lastname: Kong
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhu
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000378:metabolism; D051702:Activating Transcription Factor 6 / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001011:Aorta / Q000166:cytology; D001483:Base Sequence; D019175:DNA Methylation / Q000502:physiology; D042783:Endothelial Cells / Q000166:cytology / Q000201:enzymology*; D004851:Epoxide Hydrolases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D006710:Homocysteine / Q000378:metabolism* / Q000494:pharmacology; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D020138:Hyperhomocysteinemia / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D011401:Promoter Regions, Genetic / Q000502:physiology; D011721:Pyrenes / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000494:pharmacology; D012995:Solubility; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
chemical_list: C497111:ATF6 protein, human; D051702:Activating Transcription Factor 6; C497112:Atf6 protein, mouse; D011721:Pyrenes; D034741:RNA, Small Interfering; C121436:thiouredopyrenetrisulfonate; D006710:Homocysteine; C046782:14,15-epoxy-5,8,11-eicosatrienoic acid; D004851:Epoxide Hydrolases; C506428:EPHX2 protein, human; C518648:Ephx2 protein, mouse; D015126:8,11,14-Eicosatrienoic Acid