Epigallocatechin gallate induces apoptosis of monocytes.
BACKGROUND
Monocytes are the main effector cells of the immune system, and the regulation of their survival and apoptosis is essential for monocyte-involved immune responses. Green tea polyphenol catechin has been reported to have antiallergic and anti-inflammatory activities, but its effect on monocytes has not yet been explored.


OBJECTIVE
To elucidate the mechanisms of the anti-inflammatory effect of catechin, we studied the effect of catechin, especially epigallocatechin gallate (EGCG), on the apoptosis of monocytes.


METHODS
Isolated peripheral blood monocytes were incubated without or with catechin, and apoptosis was evaluated by annexin V and propidium iodide double-staining or terminal deoxynucleotidyl assay. The activation of caspases 3, 8, and 9 was also evaluated by flow cytometry. The influence of GM-CSF or LPS, the known monocyte survival factors, on the EGCG-induced apoptosis of monocytes was investigated.


RESULTS
Among the 4 catechin derivatives tested, EGCG and epicatechin gallate induced apoptosis of monocytes. Caspases 3, 8, and 9, which play a central role in the apoptotic cascade, were dose-dependently activated by EGCG treatment. The EGCG-induced apoptosis of monocytes was not affected by GM-CSF or LPS.


CONCLUSIONS
Catechin, especially EGCG, by promoting monocytic apoptosis, may be a new promising anti-inflammatory agent, and should be tested in clinical trials.
Kawai
Kazushige
K
Department of Surgical Oncology, Faculty of Medicine, University of Tokyo, Japan. kz-kawai@mvd.biglobe.ne.jp
Tsuno
Nelson H
NH
Kitayama
Joji
J
Okaji
Yurai
Y
Yazawa
Kentaro
K
Asakage
Masahiro
M
Sasaki
Shin
S
Watanabe
Toshiaki
T
Takahashi
Koki
K
Nagawa
Hirokazu
H
D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006801:Humans; D009000:Monocytes / Q000187:drug effects* / Q000276:immunology / Q000502:physiology; D013662:Tea
D000893:Anti-Inflammatory Agents; D013662:Tea; D002392:Catechin; C045651:epigallocatechin gallate; D020169:Caspases