Effects of imiquimod on airway inflammation and STAT6 expression in mouse models of asthma

    JIN Shuª²Xian, YIN Kaiª²Sheng, BIAN Tao, CHEN Ziª²Qing

    1Department of Respiratory Medicine, 2Central Laboratory, First Affiliated Hospital, Nanjing Medical University, Nanjing 210029, China

    ¡¾Abstract¡¿ AIM: To observe the effects of aerosol imiquimod on the antigenª²induced airway inflammation and the expressions of Th2ª²type chemokines Eotaxin, macrophageª²derived chemokine (MDC) and thymus and activation regulated chemokine (TARC) in mouse models of asthma. METHODS: Imiquimod and dexamethasone were administered to immunized mice before antigen challenge. At 24 h after the final OVA inhalation, the left superior lung tissue was taken, HE stained and the changes of inflammation were observed. Bronchial alveolar lavage fluid (BALF) was collected to count the number of cells and classify them. The expressions of signal transducers and activators of transcription 1(STAT1) and signal transducers and activators of transcription 6(STAT6) in lungs were detected by immunohistochemistry and western blot. The mRNA expressions of STAT1, STAT6, ILª²4, eotaxin and IFNª²¦Ã in lungs were examined by reverse transcriptaseª²polymerase chain reaction. RESULTS: ¢Ù Imiquimod and dexamethasone attenuated the airway inflammation of asthmatic mice. ¢Ú Imiquimod decreased the totol cell counts, EOS and lymphocyte counts in BALf. ¢Û The expressions of STAT1 and STAT6 were mainly on the bronchial epithelium. STAT1 and STAT6 proteins and mRNA levels increased in lung tissues in asthma group. Imiquimod significantly reduced STAT1 and STAT6 protein and mRNA expression. Dexamethasone significantly reduced the levels of STAT6 protein and mRNA, but failed to inhibit the expression of STAT1. ¢Ü Imiquimod modulated the Th1/Th2 response by enhancing Th1 cytokine IFNª²¦Ã mRNA and inhibiting the Th2 cytokine ILª²4 mRNA expression in lung tissues. CONCLUSION: Imiquimod aerosol inhalation may inhibit antigenª²induced airway inflammation and decrease the over expression of STAT6 protein and mRNA in asthmatic mouse but has no influence on STAT1 expression. ......