title: Dimethyldiselenide and methylseleninic acid generate superoxide in an in vitro chemiluminescence assay in the presence of glutathione: implications for the anticarcinogenic activity of L-selenomethionine and L-Se-methylselenocysteine.
abstract: The reduction of cancer incidence by dietary supplementation with L-selenomethionine, L-Se-methylselenocysteine, and other methylated selenium compounds and metabolites is believed to be due to the metabolic generation of the monomethylated selenium species methylselenol. Dimethyldiselenide and methylseleninic acid were reduced by glutathione in an in vitro chemiluminescent assay in the presence of lucigenin for the detection of superoxide (O2-.). The methylselenol produced on reduction of dimethyldiselenide and methylseleninic acid was found to be highly catalytic, continuously generating a steady state of O2-. The O2-. detected by the chemiluminescence generated by methylselenol was fully quenched by superoxide dismutase, causing a complete cessation of chemiluminescence. In contrast, dimethyldisulfide in the presence of glutathione was not catalytic to any measurable extent and did not generate any superoxide. These in vitro results suggest that methylselenol catalysis is possible in vivo, and if metabolism generates sufficient concentrations of methlylselenol from L-selenomethionine or L-Se-methylselenocysteine in vivo, it could change the redox status of cells and oxidatively induce cellular apoptosis.
authors.affiliation: Department of Ophthalmology, Texas Tech University Health Sciences Center, Selenium Technologies, Inc., Lubbock, TX, USA. jspallholz@hs.ttu.edu
authors.forename: J E
authors.initials: JE
authors.lastname: Spallholz
authors.forename: B J
authors.initials: BJ
authors.lastname: Shriver
authors.forename: T W
authors.initials: TW
authors.lastname: Reid
mesh_terms: D016588:Anticarcinogenic Agents / Q000378:metabolism* / Q000627:therapeutic use; D003545:Cysteine / Q000031:analogs & derivatives* / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D007700:Kinetics; D008163:Luminescent Measurements; D016566:Organoselenium Compounds / Q000378:metabolism* / Q000627:therapeutic use; D017279:Selenocysteine / Q000031:analogs & derivatives; D012645:Selenomethionine / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*
chemical_list: D016588:Anticarcinogenic Agents; D016566:Organoselenium Compounds; D017279:Selenocysteine; D013481:Superoxides; C037445:dimethyldiselenide; D012645:Selenomethionine; C008493:methylselenic acid; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D005978:Glutathione; D003545:Cysteine; C002979:selenomethylselenocysteine