title: Selenite negatively regulates caspase-3 through a redox mechanism.
abstract: Selenium, an essential biological trace element, exerts its modulatory effects in a variety of cellular events including cell survival and death. In our study we observed that selenite protects HEK293 cells from cell death induced by ultraviolet B radiation (UVB). Exposure of HEK293 cells to UVB radiation resulted in the activation of caspase-3-like protease activity, and pretreatment of the cells with z-DEVD-fmk (N-benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethylketone), a caspase-3 inhibitor, prevented UVB-induced cell death. Interestingly, enzymatic activity of caspase-3-like protease in cell lysates of UVB-exposed cells was repressed in vitro by the presence of selenite. Selenite also inhibited the in vitro activity of purified recombinant caspase-3 in cleaving Ac-DEVD-pNA (N-acetyl-Asp-Glu-Asp-p-nitroanilide) or ICAD(L) (inhibitor of a caspase-activated deoxyribonuclease) and in the induction of DNA fragmentation. The inhibitory action of selenite on a recombinant active caspase-3 could be reversed by sulfhydryl reducing agents, such as dithiothreitol and beta-mercaptoethanol. Furthermore, pretreatment of cells with selenite suppressed the stimulation of the caspase-3-like protease activity in UVB-exposed cells, whereas dithiothreitol and beta-mercaptoethanol reversed this suppression of the enzymatic activity. Taken together, our data suggest that selenite inhibits caspase-3-like protease activity through a redox mechanism and that inhibition of caspase-3-like protease activity may be the mechanism by which selenite exerts its protective effect against UVB-induced cell death.
authors.affiliation: National Creative Research Initiative Center for Cell Death, Korea University, Anam-dong, Sungbuk-ku, Seoul 136-701, Korea.
authors.forename: H S
authors.initials: HS
authors.lastname: Park
authors.forename: S H
authors.initials: SH
authors.lastname: Huh
authors.forename: Y
authors.initials: Y
authors.lastname: Kim
authors.forename: J
authors.initials: J
authors.lastname: Shim
authors.forename: S H
authors.initials: SH
authors.lastname: Lee
authors.forename: I S
authors.initials: IS
authors.lastname: Park
authors.forename: Y K
authors.initials: YK
authors.lastname: Jung
authors.forename: I Y
authors.initials: IY
authors.lastname: Kim
authors.forename: E J
authors.initials: EJ
authors.lastname: Choi
mesh_terms: D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000187:drug effects*; D016923:Cell Death / Q000187:drug effects*; D002478:Cells, Cultured; D053938:DNA Fragmentation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D009842:Oligopeptides / Q000494:pharmacology; D010084:Oxidation-Reduction; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology; D012643:Selenium / Q000494:pharmacology*; D018038:Sodium Selenite / Q000494:pharmacology*; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D061945:Caspase Inhibitors; D009842:Oligopeptides; D011480:Protease Inhibitors; D013438:Sulfhydryl Compounds; C110772:benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D012643:Selenium; D018038:Sodium Selenite