Selenite negatively regulates caspase-3 through a redox mechanism.
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.
Park
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HS
National Creative Research Initiative Center for Cell Death, Korea University, Anam-dong, Sungbuk-ku, Seoul 136-701, Korea.
Huh
S H
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Kim
Y
Y
Shim
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Lee
S H
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Park
I S
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Jung
Y K
YK
Kim
I Y
IY
Choi
E J
EJ
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*
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