Effects of 6-formylpterin as an internal source of hydrogen peroxide on cell death of human peripheral blood leukocytes.
The intracellular generation of hydrogen peroxide (H(2)O(2)) by 6-formylpterin and its effects on the cell surface exposure of phosphatidylserine (PS) as a marker of cell death were examined in human peripheral blood leukocytes, and the effects were compared with those of exogenously administered H(2)O(2). Neutrophils, monocytes and lymphocytes were isolated from fresh blood, and cultured for 24 h in vitro. In neutrophils, the intracellular H(2)O(2) generation was observed when the cells were incubated with 100-500 microM 6-formylpterin, and the PS exposure due to spontaneous apoptosis was inhibited. The underlying mechanism of the inhibition was attributed to the suppression of both activation and activity of caspase-3. On the other hand, exogenously administered 100 microM H(2)O(2) did not affect the PS exposure. The intracellular H(2)O(2) generation was also observed in monocytes and lymphocytes. In monocytes, 500 microM 6-formylpterin induced more PS exposure than 100 microM H(2)O(2) did. In lymphocytes, up to 500 microM 6-formylpterin did not induce conspicuous PS exposure, while 100 microM H(2)O(2) induced severe PS exposure. These findings indicated that the resistance against an internal and external source of H(2)O(2) are different among leukocytes, for example, lymphocytes are poorly resistant against external H(2)O(2) but highly resistant against internal one.
Kyoto Institute of Technology, Japan.
Maiko
M
Nishioka
Toshiyuki
T
Arai
Kouhei
K
Yamashita
Masataka
M
Sasada
Hiroko
H
Mori
Hisanari
H
Ishii
Kunihiko
K
Tajima
Keisuke
K
Makino
Kazuhiko
K
Fukuda
D000328:Adult; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D016923:Cell Death; D004578:Electron Spin Resonance Spectroscopy; D004789:Enzyme Activation; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007962:Leukocytes / Q000187:drug effects / Q000378:metabolism*; D010718:Phosphatidylserines / Q000494:pharmacology; D011621:Pteridines / Q000494:pharmacology*; D011622:Pterins
D010718:Phosphatidylserines; D011621:Pteridines; D011622:Pterins; C005926:2-amino-4-hydroxy-6-formylpteridine; D006861:Hydrogen Peroxide; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases