Toll-like Receptor 4 Relates to Lipopolysaccharide-induced Mucus Hypersecretion in Rat Airway

Background. Toll-like receptor 4 (TLR4) is a transmembrane protein that participates in the recognition of lipopolysaccharide (LPS), a potentially important source of inflammation. To investigate the role of TLR4 in LPS-induced airway Mucus hypersecretion (AMH), we used a LPS-induced rat model treated with dexamethasone (DEX). Methods. Rats were randomly divided into four experimental groups: 1) saline (SA)treated with distilled water (DW) (control group); 2) LPS-treated with DW (LPS group); 3) LPS-treated with DEX (LPS plus DEX group); 4) SA-treated with DEX (DEX group). DEX (5 mg/kg) was intraperitoneally injected I h before being administered intratracheally with LPS. Expressions of TLR4 and MUC5AC were evaluated with RT-PCR, in situ hybridization, immunohistochemistry and Alcian blue/Periodic acid-schiff (AB/PAS) staining. Results. Increased expressions of TLR4 protein and mRNA were found in rat airway treated with LPS and peaked on day 2 after LPS administration. Following this, LPS increased MUC5AC expression and AB/PAS-stained goblet cells in rat airway. Correlation analysis showed TLR4 correlated well with the expression of MUC5AC (r = 0.684, p < 0.0 1) and AB/PAS-stained area(r = 0.781, p < 0.0 1). In addition, DEX pretreatment significantly reduced LPS-induced overexpression of TLR4 (p < 0.05) in rat airway. Conclusions. These results suggest TLR4 relates to LPS-induced AMH and support a role of TLR4 in DEX inhibition of LPS-induced AMH. (C) 2009 IMSS. Published by Elsevier Inc.