Kaempferol, a Tea Flavonol, Effect on Interleukin-2 Signal Transduction of Human T Cell Leukemia

CCRF-CEM and Jurkat E6-1, human T cell leukemia, produced interleukin (IL)-2 stimulated with phorbol myristate acetate (PMA) and pokeweed mitogen (PWM). IL-2 cytokine production and mRNA expression of CCRF-CEM were increased by treatment with kaempferol, a tea (Camellia sinensis L.) flavonol, while those of Jurkat E6-1 were decreased by kaempferol treatment. We therefore investigated the nuclear factor expression of activated T cell (NFAT), a critical regulator of IL-2 gene transcription during T cell activation. In CCRF-CEM, NFAT induction of cytoplasmic extract and NFAT translocation to the nucleus were increased by kaempferol, demonstrating that kaempferol might affect the upstream cascade of T cell signaling. However, in Jurkat E6-1, NFAT induction of cytoplasmic extract was normal, but NFAT translocation to the nucleus was decreased by kaempferol treatment. In this report, it is demonstrated that kaempferol has different effects in the T cell signaling cascade. Discipline: Tea industry / Animal industry Additional key words: cytokine, tea (Camellia sinensis L.), NFAT (nuclear factor expression of activated T cell) when they are stimulated. IL-2 is an immune modulator Introduction It has been reported that tea has various bioregulatory activities and immuno-regulatory functions. Flavonols, kaempferol, myricetin and quercetin are components of tea belonging to a group of polyphenolic compounds found in fruit, vegetables and tea. Previous studies of the biological functions of kaempferol have focused on its anti-inflammatory effects and antioxidative activities in macrophages and neurons. The immunoregulatory effects of kaempferol have weak inhibitory interleukin (IL)-5 bioactivity and inhibit histamine release in basophils and mast cells. Recently, some reports showed that kaempferol suppressed interferon-γ and IL-2 production of T cells in in vivo experiments. However, we have reported that IL-2 production in T cell leukemia CCRF-CEM was increased by kaempferol. These results differ between in vivo and in vitro, and we therefore analyzed additional in vitro experiments using T cell leukemia, Jurkat E6-1. Human T cell leukemia, Jurkat, was used as a model to examine the requirements of T cell activation. T cells, a type of lymphocyte, are very important in the immune system, and produce IL-2 and a major autocrine growth factor, and contributes to immune responses in part by promoting the rapid proliferation of activated T cells. In order to clarify the effect of kaempferol on IL-2 production in vitro, we used two forms of T cell leukemia, CCRF-CEM and Jurkat E6-1. We analyzed IL-2 production, mRNA expression and transcriptional factor NFAT, to clarify the in vitro mechanism of kaempferol effect on IL-2 production. Materials and methods 1. Cells and culture CCRF-CEM (CCL-1199) and Jurkat E6-1 (TIB-152) were purchased from the American Type Culture Collection (ATCC). Cells were cultured in RPMI 1640 supplemented with 10% fetal bovine serum in the presence or the absence of 10 μg/mL of tea flavonols (kaempferol, myricetin) for 48 h, which time was the best among our testing culture times (4, 12, 24, 48, 72 or 96 h). The cells were washed and then stimulated with 5 μg/mL of pokeweed mitogen (PWM) and 10 ng/mL of phorbol myristate acetate (PMA) for 24 h. Kaempferol and *Corresponding author: fax +81–547–46–2169; e-mail [email protected] Received 15 October 2004; accepted 17 January 2005.