Bacterial components regulate the expression of Toll-like receptor 4 on human mast cells

Abstract.

Objectives and design:

The aim of this study was to investigate whether the exposure of mast cells (MCs) to bacterial components affects the expression of Toll-like receptor (TLR) 4, and to elucidate the behavior of MCs during the early response to infection.

Materials:

Two human MC lines, HMC-1 and LAD2, were employed. Messenger RNA expression was observed by RT and real-time PCR. TLR4 expression was determined by Western blotting. TNF-α secretion was analyzed with ELISA. The degranulation ratio was measured with betahexosaminidase assay.

Results:

Although bacterial components increased TLR4 mRNA, only lipopolysaccharide (LPS) augmented the TLR4 protein expression. LAD2 pre-treated with LPS for 8 h resulted in 2-fold increased TNF-α secretion on LPS restimulation.

Conclusion:

These results suggest that the exposure of MCs to LPS may reinforce the innate immune system due to up-regulation of MC TLR4, followed by increased TNF-α release.