OBJECTIVETo investigate the effects of lipopolysaccharide (LPS) on airway inflammation, airway remodeling and the expression of Toll-like receptor 4 (TLR4) mRNA in asthmatic rats.

METHODSTwenty-four SPF level SD rats were randomly divided into four groups (n = 6): control group, low dose of LPS group, high dose of LPS group and asthma group. Using ovalbumin (OVA) to sensitize and challenge to establish asthmatic rat model. Observed pathological changes of lung tissue by HE staining, inflammatory cell infiltration was observed by airway wall eosinophils (EOS) counts; airway resistance was determined; image analysis software was used to determine the thickness of airway wall, detected airway smooth muscle TLR4 expression levels by RT-PCR.

RESULTSThe rat airway resistance and the EOS number of airway wall and the thickness of airway wall in asthma group, low dose of LPS group and high dose of LPS group were significantly higher than those in control group (P < 0.01). The above-mentioned parameters of high dose of LPS group showed significantly lower than those in asthma group and low dose of LPS group (P < 0.05). The expression of rat airway smooth muscle TLR4 mRNA in low dose of LPS group and high dose of LPS group were significantly higher than those in asthma group (P < 0.01). And the expression of rat airway smooth muscle TLR4 mRNA in high dose of LPS group was significantly higher than that in low dose of LPS group (P < 0.05).

CONCLUSIONTLR4 plays an important role in asthmatic airway inflammation and airway remodeling, LPS may play double-sided regulation in asthmatic airway inflammation and airway remodeling by activated TLR4.