Epigallocatechin-3-gallate (EGCG), a green tea polyphenol suppresses bacilli-induced augmented expression of Mycobacterium tuberculosis 85B and proinflammatory TNF-α in human monocytes

Reactive oxygen species (ROS) and tumor necrosis factor (TNF-α), the hallmarks of tuberculosis, are directly induced in human monocytes by Mycobacterium tuberculosis (MTB). We have previously shown that the expression of 85B in MTB infected monocytes correlates positively with both the amount of secreted TNF-α and subsequent mycobacterial growth. In this study, we show the augmented expression of 85B in MTB and TNF-α at both the gene and protein levels in MTB-infected monocytes were suppressed by EGCG, a green tea polyphenol, in dose-dependent manner. Of notable importance, the antiinflammatory mechanism of EGCG was mediated by inhibition of NF-κB pathway. Moreover, EGCG enhances the antioxidant potential of monocytes by ameliorating the intramonocyte sIFN-γ levels, glutathione levels and glutathione peroxidase activity, which correlates with the down regulation of TNF-α in MTBinfected monocytes. Taken together, this study provides the first novel insight into the possible anti-inflammatory and antioxidant role of EGCG that can be exploited in tuberculosis management.