title: Arsenite induces endothelial cytotoxicity by down-regulation of vascular endothelial nitric oxide synthase.
abstract: Epidemiological studies have demonstrated a high association of inorganic arsenic exposure with vascular diseases. Recent research has also linked this vascular damage to impairment of endothelial nitric oxide synthase (eNOS) function by arsenic exposure. However, the role of eNOS in regulating the arsenite-induced vascular dysfunction still remains to be clarified. In our present study, we investigated the effect of arsenite on Akt1 and eNOS and its involvement in cytotoxicity of vascular endothelial cells. Our study demonstrated that arsenite decreased the protein levels of both Akt1 and eNOS accompanied with increased levels of ubiquitination of total cell lysates. We found that inhibition of the ubiquitin-proteasome pathway by MG-132 could partially protect Akt1 and eNOS from degradation by arsenite together with a proportional protection from the arsenite-induced cytoxicity. Moreover, up-regulation of eNOS protein expression significantly attenuated the arsenite-induced cytotoxicity and eNOS activity could be significantly inhibited after incubation with arsenite for 24 h in a cell-free system. Our study indicated that endothelial eNOS activity could be attenuated by arsenite via the ubiquitin-proteasome-mediated degradation of Akt1/eNOS as well as via direct inhibition of eNOS activity. Our study also demonstrated that eNOS actually played a protective role in arsenite-induced cytoxicity. These observations supported the hypothesis that the impairment of eNOS function by arsenite is one of the mechanisms leading to vascular changes and diseases.
authors.affiliation: Division of Environmental Health and Occupational Medicine, National Health Research Institutes, 100 Shih-Chuan 1st Road, Kaohsiung 807, Taiwan, ROC. tctsou@nhri.org.tw
authors.forename: Tsui-Chun
authors.initials: TC
authors.lastname: Tsou
authors.forename: Feng-Yuan
authors.initials: FY
authors.lastname: Tsai
authors.forename: Yao-Wen
authors.initials: YW
authors.lastname: Hsieh
authors.forename: Lih-Ann
authors.initials: LA
authors.lastname: Li
authors.forename: Szu Ching
authors.initials: SC
authors.lastname: Yeh
authors.forename: Louis W
authors.initials: LW
authors.lastname: Chang
mesh_terms: D000730:Androstadienes / Q000008:administration & dosage; D000818:Animals; D001013:Aorta, Thoracic / Q000473:pathology; D018053:Arsenites / Q000037:antagonists & inhibitors / Q000633:toxicity*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects*; D002867:Chromones / Q000008:administration & dosage; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D042783:Endothelial Cells / Q000737:chemistry / Q000187:drug effects / Q000473:pathology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D007976:Leupeptins / Q000494:pharmacology; D009025:Morpholines / Q000008:administration & dosage; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000008:administration & dosage; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D017670:Sodium Compounds / Q000037:antagonists & inhibitors / Q000633:toxicity*; D013552:Swine; D013997:Time Factors; D015854:Up-Regulation; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D018053:Arsenites; D002867:Chromones; D007976:Leupeptins; D009025:Morpholines; D017670:Sodium Compounds; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C017947:sodium arsenite; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; D000077191:Wortmannin