Epigallocatechin Gallate, a Potential Immunomodulatory Agent of Tea Components by Kazuto Matsunaga, Thomas W. Klein, Herman Friedman, and Yoshimasa Yamamoto
Epigallocatechin Gallate, a Potential
Immunomodulatory Agent of Tea Components, Diminishes Cigarette
Smoke Condensate-Induced Suppression of Anti-Legionella pneumophila
Activity and Cytokine Responses of Alveolar
Macrophages.
Even though cigarette smoking has been shown to suppress immune
responses in the lungs, little is known about the effect of
cigarette smoke components on respiratory infections. In the
present study, the effects of cigarette smoke condensate (CSC) on
bacterial replication in alveolar macrophages and the immune
responses of macrophages to infection were examined. Furthermore, a
possible immunotherapeutic effect of epigallocatechin gallate
(EGCg), a major form of tea catechins, on the CSC-induced
suppression of antimicrobial activity and immune responses of
alveolar macrophages was also determined. The treatment of murine
alveolar macrophage cell line (MH-S) cells with CSC significantly
enhanced the replication of Legionella pneumophila in
macrophages and selectively down-regulated the production of
interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-) induced
by bacterial infection. The treatment of macrophages with EGCg not
only overcame the CSC-induced suppression of antimicrobial activity
but also strengthened the resistance of macrophages to infection.
EGCg also markedly up-regulated the CSC-suppressed IL-6 and TNF-
production by macrophages in response to infection. The results of
exogenous TNF- treatment and neutralization treatment with
anti-TNF- and anti-gamma-interferon (IFN-) antibodies and the
determination of IFN- mRNA levels indicate that CSC-suppressed
macrophages can be activated by EGCg to inhibit L.
pneumophila growth by up-regulation of TNF- and IFN-
production. Thus, this study revealed that CSC selectively alters
the immune responses of macrophages to L. pneumophila
infection and leads to an enhancement of bacterial replication in
macrophages. In addition, the tea catechin EGCg can diminish such
suppressive effects of CSC on alveolar macrophages.
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