NF-kappaB-dependency and consequent regulation of IL-8 in echinomycin-induced apoptosis of HT-29 colon cancer cells

The present study was to see whether echinomycin-induced apoptosis would be NF-kappaB-dependent and if so, whether echinomycin would activate or inhibit NF-kappaB as well as resultant chemokine IL-8 expression. In HT-29 cells echinomycin activated NF-kappaB in time-dependent manner. EMSA in the presence of antibodies specific for p50 and p65 subunits indicated that echinomycin-induces the translocation of p50-p65 heterodimeric subunits of NF-kappaB. Levels of IkappaB were detected at initial echinomycin treatment and thereafter decreased, faintly seen after a 6h treatment. In contrast p-IkappaB levels were clearly detected throughout 6-24h of echinomycin treatment, albeit initially fainted. To clarify the role of NF-kappaB on IL-8 expression in echinomycin-mediated apoptosis of HT-29 cells, ELISA plus RT-PCR clearly showed that IL-8 production is inducible by echinomycin treatment. Using a specific inhibitor, IL-8 regulation at echinomycin treatment in HT-29 cells occurred via both caspase-3 and NF-kappaB-dependent signal pathway. To confirm whether two different pathways (NF-kappaB and caspase) would be coupled, only NF-kappaB inhibitor (PDTC) and caspase-3 specific inhibitor (Z-DEVD-FMK) together significantly attenuated echinomycin-initiated apoptosis of HT-29 cells, pretreatment of HT-29 cells with PDTC rarely affected echinomycin-induced caspase-3 activation. So echinomycin-induced apoptosis in HT-29 cells occurs via NF-kappaB activation independent of caspase-3 activation modulating the resultant-linked key chemokine IL-8 expression and echinomycin-induced apoptosis is NF-kappaB-dependant and directly related to NF-kappaB activation, consequently regulating IL-8 expression.     

Epigallocatechin-3-gallate, constituent of green tea, suppresses the LPS-induced phenotypic and functional maturation of murine dendritic cells through inhibition of mitogen-activated protein kinases and NF-kappaB

The effects of epigallocatechin-3-gallate (EGCG) on dendritic cells (DC) maturation were investigated. EGCG, in a dose-dependent manner, profoundly inhibited CD80, CD86, and MHC class I and II expression on bone marrow-derived murine myeloid DC. EGCG restored the decreased dextran-FITC uptake and inhibited enhanced IL-12 production by LPS-treated DC. EGCG-treated DC were poor stimulators of nai;ve allogeneic T-cell proliferation and reduced levels of IL-2 production in responding T cells. EGCG-pretreated DC inhibited LPS-induced MAPKs, such as ERK1/2, p38, JNK, and NF-kappaB p65 translocation. Therefore, the molecular mechanisms by which EGCG antagonized LPS-induced DC maturation appeared to involve the inhibition of MAPK and NF-kappaB activation. These novel findings provide new insight into the immunopharmacological role of EGCG and suggest a novel approach to the manipulation of DC for therapeutic application of autoimmune and allergic diseases.