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Experimental Biology and Medicine 230:645-651 (2005)
© 2005 Society for Experimental Biology and Medicine

ORIGINAL RESEARCH ARTICLE

Epigallocatechin Gallate Modulates Cytokine Production by Bone Marrow–Derived Dendritic Cells Stimulated with Lipopolysaccharide or Muramyldipeptide, or Infected with Legionella pneumophila

James Rogers, Izabella Perkins, Alberto van Olphen, Nicholas Burdash, Thomas W. Klein and Herman Friedman1

Department of Medical Microbiology and Immunology, University of South Florida, Tampa, Florida 33612

To whom requests for reprints should be addressed at 1 Department of Medical Microbiology and Immunology, University of South Florida, 12901 Bruce B. Downs Boulevard, Tampa, FL 33612. E-mail: hfriedma{at}hsc.usf.edu

The primary polyphenol in green tea extract is the catechin epigallocatechin gallate (EGCG). Various studies have shown significant suppressive effects of catechin on mammalian cells, either tumor or normal cells, including lymphoid cells. Previous studies from this laboratory reported that EGCG has marked suppressive activity on murine macrophages infected with the intracellular bacterium Legionella pneumophila (Lp), an effect mediated by enhanced production of both tumor necrosis factor-{alpha} (TNF-{alpha}) and {gamma}-interferon (IFN-{gamma}). In the present study, primary murine bone marrow (BM)–derived dendritic cells (DCs), a phagocytic monocytic cell essential for innate immunity to intracellular microorganisms, such as Lp, were stimulated in vitro with the microbial stimulant lipopolysaccharide (LPS) from gram-negative bacteria, the cell wall component from gram-positive bacteria muramyldipeptide (MDP) or infected with Lp. Production of the T helper cell (Th1)-activating cytokine, interleukin-12 (IL-12) and the proinflammatory cytokine, tumor necrosis factor-{alpha} (TNF-{alpha}),produced mainly by phagocytic cells and important for antimicrobial immunity, was determined in cell culture supernatants by enzyme-linked immunosorbent assay (ELISA). Treatment of the cells with EGCG inhibited, in a dose-dependent manner, production of IL-12. In contrast, enhanced production of TNF-{alpha} occurred in a dose-dependent manner in the DC cultures stimulated with either soluble bacterial product or infected with Lp. Thus, the results of this study show that the EGCG catechin has a marked effect in modulating production of these immunoregulatory cytokines in stimulated DCs, which are important for antimicrobial immunity, especially innate immunity. Further studies are necessary to characterize the physiologic function of the effect of EGCG on TNF-{alpha} and IL-12 during Lp infection, and the mechanisms involved.

Key Words: catechin • cytokines • dendritic cells • Legionella pneumophilia






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