Relative ability of dietary compounds to modulate nuclear factor-kappaB activity as assessed in a cell-based reporter system.

The ability of various dietary compounds to modulate the activity of the transcription factor nuclear factor kappaB (NF-kappaB) was examined using a cell-based reporter system. NF-kappaB is central to the response of cells to stress and has been linked to cancer. HCT 116 (human colon carcinoma) and HepG2 (human liver carcinoma) cell lines were stably transfected with a NF-kappaB luciferase reporter vector. The reporter cell lines were preincubated with different concentrations (0-50 microM) of ascorbic acid, epigallocatechin gallate, genistein, quercetin, naringenin, and resveratrol for varying periods of times (1-12 hours), after which the NF-kappaB inducer tumor necrosis factor-alpha (TNF-alpha) was added (4-8 ng/mL) for 4 hours. Compound alone, without TNF-alpha, did not alter luciferase activity. Levels of TNF-alpha-induced luciferase (NF-kappaB) activity varied depending on compound type and concentration, whereas preincubation time and cell type contributed less. Significant changes in luciferase (NF-kappaB) activity were detected for some of the compounds at more physiological concentrations (1-10 microM). Our data suggest that dietary modulation of NF-kappaB activity involves distinct mechanisms, depending on compound type and concentration. More generally, this approach can be utilized for analyzing dietary compounds for effects on specific cellular factors over a range of concentrations and incubation times, in combination, and in different cell types.