Transient elevation of intracellular calcium ion levels as an early event in T-2 toxin-induced apoptosis in human promyelotic cell line HL-60.
Recently we have reported that T-2 toxin, a trichothecene mycotoxin produced by Fusarium species, is a potent inducer of apoptosis in the human promyelotic cell line HL-60. To clarify the signal transduction pathway of apoptosis primed by T-2 toxin, T-2 toxin-induced apoptosis was investigated in detail using confocal laser microscopy and flow cytometry. Apoptosis in HL-60 cells induced by T-2 toxin was dose dependent when the cells were treated with concentrations of 5-100 ng/ml for more than 2 hr. The apoptosis proceeds through various cell cycle stages of HL-60 cells. Prior to apoptosis, the intracellular calcium ion (Ca+2i) level was markedly elevated within 3-5 min after exposure to T-2 toxin and returned to normal level thereafter. A well-known chelator for Ca+2i, ethylene-N,N,N', N'-tetraacetic acid 4K acetoxymethyl ester (BAPTA-AM), a Ca+2-dependent endonuclease inhibitor ZnCl2, and calpain inhibitor 1 sharply blocked T-2 toxin-induced apoptosis. These results strongly suggest that the Ca+2 signal triggered by T-2 toxin is transduced by the activation of endonuclease and protease, and ultimately evokes apoptosis.
Yoshino
N
N
Faculty of Pharmaceutical Sciences, Science University of Tokyo, Japan.
Takizawa
M
M
Akiba
H
H
Okumura
H
H
Tashiro
F
F
Honda
M
M
Ueno
Y
Y
D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism*; D005434:Flow Cytometry; D018922:HL-60 Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D018613:Microscopy, Confocal; D013605:T-2 Toxin / Q000633:toxicity*
D013605:T-2 Toxin; D002118:Calcium