Tea has been around for centuries, and its medicinal properties have been purported in the literature but never fully confirmed. Interleukin-8 is a principle neutrophil chemoattractant and activator in humans. We determined the effects of theaflavin, a black tea-derived polyphenol, on tumor necrosis factor-α-mediated expression of the interleukin-8 gene in A549 cells.
Prospective laboratory study.
A549 cells were exposed to varying concentrations of theaflavin and analyzed for tumor necrosis factor-α-mediated interleukin-8 gene expression.
Measurements and Main Results:
Theaflavin inhibited tumor necrosis factor-α-mediated interleukin-8 gene expression, as measured by luciferase assay and Northern blot analysis, at concentrations of 10 and 30 μg/mL. This effect appears to primarily involve inhibition of interleukin-8 transcription because theaflavin inhibited tumor necrosis factor-α-mediated activation of the interleukin-8 promoter in cells transiently transfected with an interleukin-8 promoter-luciferase reporter plasmid. In addition, theaflavin inhibited tumor necrosis factor-α-mediated activation of IκB kinase and subsequent activation of the IκB-α/nuclear factor-κB pathway. Theaflavin also significantly reduced tumor necrosis factor-α-mediated DNA binding of activator protein-1.
We conclude that theaflavin is a potent inhibitor of interleukin-8 gene expression in vitro. The proximal mechanism of this effect involves, in part, inhibition of IκB kinase activation and activator protein-1 pathway.