Effects of intracellular reactive oxygen species generated by 6-formylpterin on T cell functions.
The intracellular generation of reactive oxygen species (ROS) by 6-formylpterin and its effects on the human T cell functions were examined in vitro. When T cells isolated from fresh blood were incubated with 6-formylpterin for 1hr, the oxygen consumption and concomitant ROS generation were observed. The incubation of T cells with 50-500microM 6-formylpterin for 24hr brought about the elevation of intracellular ROS without inducing cell death. In contrast, the incubation of T cells with exogenously administered hydrogen peroxide (H(2)O(2)) or other pterin derivatives (6-hydroxymethylpterin, pterin-6-carboxylic acid, pterin, neopterin, biopterin and folic acid) for 24hr did not cause the intracellular ROS elevation. In the T cells stimulated with mitogenic lectin phytohemagglutinin (PHA) in conjunction with phorbol myristate acetate (PMA), 6-formylpterin suppressed the NF-kappaB-dependent transcription, the production of cytokines (IFN-gamma and IL-2) and the cell proliferation. These suppressive effects of 6-formylpterin were all reversed by N-acetyl-l-cystein (NAC). However, 6-formylpterin did not inhibit the NF-kappaB-DNA binding of the nuclear extracts obtained from the PHA/PMA-stimulated T cells. Since the NF-kappaB-DNA binding assay performed in vitro merely shows the presence or absence of NF-kappaB subunit in the nuclear extracts but not guarantees the actual binding of NF-kappaB with DNA in the nucleus, these findings suggest that intracellular ROS generated by 6-formylpterin does not affect the translocation of NF-kappaB to the nucleus but that it inhibits the NF-kappaB-dependent transcription in the nucleus, resulting in the suppression of cytokine production and cell proliferation in the activated T cells.
Arai
Toshiyuki
T
Department of Anesthesia, Kyoto University Hospital, Kyoto 606-8507, Japan. arai@kuhp.kyoto-u.ac.jp
Yamada
Hiroko
H
Namba
Tsunehisa
T
Mori
Hiroko
H
Ishii
Hisanari
H
Yamashita
Kouhei
K
Sasada
Masataka
M
Makino
Keisuke
K
Fukuda
Kazuhiko
K
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000328:Adult; D002455:Cell Division / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007963:Leukocytes, Mononuclear / Q000187:drug effects* / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects; D011622:Pterins / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013601:T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D014158:Transcription, Genetic
D016207:Cytokines; D016328:NF-kappa B; D011622:Pterins; D017382:Reactive Oxygen Species; C005926:2-amino-4-hydroxy-6-formylpteridine