Sulforaphane induces glutathione S-transferase isozymes which detoxify aflatoxin B(1)-8,9-epoxide in AML 12 cells.
The aflatoxin B(1)-8,9-epoxide (AFBO) is hepatocarcinogenic intermediate of aflatoxin B(1) (AFB(1)) and is detoxified by glutathione S-transferases (GSTs). In this study, we investigated whether sulforaphane (SFN) could increase the rate of conjugation between AFBO and glutathione (GSH) as well as which of the GST isozymes were involved in the conjugation reaction. The conjugation potential was inhibited dose dependently with curcumin, an inhibitor of GSTs. SFN induced the expression of GST A3, GST A4, GST M1, GST P1, and GST T1 in alpha mouse line (AML) 12 cells. The cells treated with SFN (10 microM) for 12 h showed a 35-fold increase in conjugation potential of AFBO with GSH compared with the vehicle-treated cell. The conjugation potential was blocked partially by transfection of cells with siRNAs against each of the GST isozymes. The activity of GST A3 had the strongest effect on the conjugation potential. SFN treatment also increased total GST activity detected with 1-chloro-2,4-dinitrobenzene (CDNB) up to 4.3-fold. The induction fold was much lower than that detected with AFBO. These results suggest that the chemopreventive effect of SFN on the decomposition of AFBO is related to the upregulation of several GST isozymes genes. The increase of GST activity by SFN was extremely specific toward the conjugation reaction of AFBO compared with CDNB. Therefore, this system for detecting GST activity seems to be an excellent method for screening chemopreventive compounds toward AFB(1) toxicity.
Gao
Shang Shang
SS
Vestibulocochlear Research Center and Department of Biochemistry, Wonkwang University, Chollabuk-Do, Republic of Korea.
Chen
Xiao Yan
XY
Zhu
Ri Zhe
RZ
Choi
Byung-Min
BM
Kim
Bok-Ryang
BR
D016604:Aflatoxin B1 / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D018890:Chemoprevention; D004137:Dinitrochlorobenzene / Q000737:chemistry; D005982:Glutathione Transferase / Q000378:metabolism*; D008658:Inactivation, Metabolic; D007527:Isoenzymes / Q000378:metabolism; D017879:Isothiocyanates; D051379:Mice; D013454:Sulfoxides; D013861:Thiocyanates / Q000494:pharmacology*; D014162:Transfection
D016588:Anticarcinogenic Agents; D004137:Dinitrochlorobenzene; D007527:Isoenzymes; D017879:Isothiocyanates; D013454:Sulfoxides; D013861:Thiocyanates; C006426:aflatoxin B1-2,3-oxide; D016604:Aflatoxin B1; D005982:Glutathione Transferase; C016766:sulforaphane