DMCA
Differential Effects of a Toll-Like Receptor Antagonist on Mycobacterium tuberculosis-Induced Macrophage Responses 1
BibTeX
@MISC{Keane_differentialeffects,
author = {Joseph Keane and Douglas T. Golenbock and Stefanie N. Vogel and Matthew J. Fenton},
title = {Differential Effects of a Toll-Like Receptor Antagonist on Mycobacterium tuberculosis-Induced Macrophage Responses 1},
year = {}
}
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Abstract
We previously showed that viable Mycobacterium tuberculosis (Mtb) bacilli contain distinct ligands that activate cells via the mammalian Toll-like receptor (TLR) proteins TLR2 and TLR4. We now demonstrate that expression of a dominant negative TLR2 or TLR4 proteins in RAW 264.7 macrophages partially blocked Mtb-induced NF-�B activation. Coexpression of both dominant negative proteins blocked virtually all Mtb-induced NF-�B activation. The role of the TLR4 coreceptor MD-2 was also examined. Unlike LPS, Mtb-induced macrophage activation was not augmented by overexpression of ectopic MD-2. Moreover, cells expressing an LPS-unresponsive MD-2 mutant responded normally to Mtb. We also observed that the lipid A-like antagonist E5531 specifically inhibited TLR4-dependent Mtb-induced cellular responses. E5531 could substantially block LPS- and Mtbinduced TNF- � production in both RAW 264.7 cells and primary human alveolar macrophages (AM�). E5531 inhibited Mtbinduced AM � apoptosis in vitro, an effect that was a consequence of the inhibition of TNF- � production by E5531. In contrast, E5531 did not inhibit Mtb-induced NO production in RAW 264.7 cells and AM�. Mtb-stimulated peritoneal macrophages from TLR2- and TLR4-deficient animals produced similar amounts of NO compared with control animals, demonstrating that these TLR proteins are not required for Mtb-induced NO production. Lastly, we demonstrated that a dominant negative MyD88 mutant could block Mtb-induced activation of the TNF- � promoter, but not the inducible NO synthase promoter, in murine macrophages. Together, these data suggest that Mtb-induced TNF- � production is largely dependent on TLR signaling. In contrast, Mtb-induced NO production may be either TLR independent or mediated by TLR proteins in a MyD88-independent manner. The Journal of
Keyphrases
mycobacterium tuberculosis-induced macrophage toll-like receptor antagonist differential effect mtb-induced nf activation tlr protein tlr4-dependent mtb-induced cellular response activate cell viable mycobacterium tuberculosis mtb-stimulated peritoneal macrophage mtbinduced apoptosis myd88-independent manner dominant negative tlr2 mtb-induced production ectopic md-2 mtb-induced tnf production murine macrophage bacillus contain dominant negative protein mtbinduced tnf production inducible synthase promoter mtb-induced macrophage activation primary human alveolar macrophage tlr4 coreceptor md-2 lps-unresponsive md-2 mutant lipid a-like antagonist e5531 tlr4-deficient animal mtb-induced activation tnf promoter tnf production control animal similar amount mammalian toll-like receptor dominant negative myd88 mutant tlr4 protein
