The Study Of Effect And Mechanism Of SB203580on Glucocorticoid Sensitivity

Objective To establish model of cigarette smoke exposure to asthmatic rats and glucocorticoid resistance induced by nicotine in alveolar epithelioid cells A549cells. Investigate the effect of a p38MAPK inhibitor SB203580on the cigarette smoke exposure to asthmatic rats and study the mechanism to the change of glucocorticoid sensitivity induced by p38MAPK inhibitor SB203580.Method Wistar rats were randomly divided into four groups:normal group, asthmatic group, cigarette smoke exposure to asthmatic group and SB203580group. Rat lung function was measured by animal pulmonary function meter. ELISA was used to detect the level of cytokines in homogenate of rats'lungs. GR,HSP90and p38MAPK mRNA expression was detected by RT-PCR, and GR,HSP90and p38MAPK protein expression was detected by western blot. A549cells were randomly divided into four groups:group A:normal group, group B:1umol/L dexamethasone (DEX), group C lumol/L DEX+1umol/L nicotine, group D:lumol/L DEX+1umol/L nicotine+lumol/L SB203580.Immunofluorescence staining was used to study the colocalization of glucocorticoid receptor(GR) in A549cells.Results Compared to the cigarette smoke exposure to asthmatic group, the rats of SB203580group had a lower airway resistance and a higher pulmonary compliance, the difference was statistically significant (P<0.05). SB203580treatment attenuated airway inflammation. The results of ELISA showed the level of IL-4, IL-5and IL-8was lower in SB203580group than cigarette smoke exposure to asthmatic group. In RT-PCR experiment, the mRNA expression of HSP90and p38MAPK was significantly lower in SB203580group than cigarette smoke exposure to asthmatic group (P<0.05). However, the difference of GR mRNA expression between SB203580group and cigarette smoke exposure to asthmatic group wasn't statistically significant. Western blot detecting protein expression found the GR,HSP90and p38MAPK protein expression was the same as mRNA expression. The ratio of the GR amount within A549nucleus versus that in cytoplasm was0.08±0.05in group C and0.59±0.25in group D. The difference was statistically significant (P<0.05).Conclusion It is suggested that p38MAPK inhibitor SB203580may be effective on reducing airway inflammation and bronchial contractile response in cigarette smoke exposure to asthmatic rats. The mechanism of SB203580improving the glucocorticoid sensitivity may be improving nuclear translocation of GR to elevate glucocorticoid sensitivity.