地塞米松对变应性哮喘小鼠胸腺活化调节趋化因子及mRNA表达的影响

Effects of Dexamethasone on the Expression of Thymus and Activation- Regulated Chemokine and Its mRNA in Murine Model with Allergic Asthma

目的探讨地塞米松对哮喘小鼠胸腺活化调节趋化因子(TARC)及其mRNA表达的影响。方法30只清洁级雄性BALB/C小鼠分为3组:正常对照组、哮喘组和地塞米松组。以卵清白蛋白(OVA)致敏激发法制备小鼠哮喘模型,末次激发24h后留取支气管肺泡灌洗液(BALF)及肺组织。BALF行嗜酸性粒细胞(EOS)计数及分类;采用酶联免疫吸附法(ELISA)测BALF中TARC和IL-4水平;免疫组化法和逆转录-聚合酶链反应(RT-PCR)法分别检测TARC蛋白和TARC mRNA在肺组织中的表达。结果①哮喘组BALF中细胞总数,EOS绝对数和EOS占细胞总数的百分数(EOS%)均显著高于正常对照组,地塞米松组上述指标均显著低于哮喘组(均P<0.01);②哮喘组BALF中TARC,IL-4浓度均显著高于对照组,地塞米松干预后BALF中TARC,IL-4浓度均显著低于哮喘组(均P<0.01)。③免疫组化及RT-PCR结果显示,肺组织中TARC蛋白及其mR-NA的表达,哮喘组显著高于对照组,地塞米松组较哮喘组显著减弱(均P<0.01),免疫组化显示,TARC蛋白主要表达于支气管上皮细胞。④相关性分析显示,小鼠BALF中TARC浓度与EOS绝对值、IL-4浓度均呈显著正相关(均P<0.01)。结论糖皮质激素(地塞米松)可抑制TARC在哮喘小鼠气道上皮中的表达,可能是其治疗哮喘气道炎症的部分作用机制。

OBJECTIVE To study the effects of dexamethasone on the expression of thymus and activation-regulated chemokine （TARC） and its mRNA in asthmatic mice. METHODS Thirty male Balb/C mice were randomly divided into three groups ： the control group, asthma group and dexamethasone （ DXM ） treated group. In the experiment , the mice models of asthma were established by sensitization and challenge with ovalbumin （OVA）. Bronchoalveolar lavage fluid （BALF） and lung tissues were collected from mice 24 h after the last challenge . The total cell numbers, Eosinophils （EOS） numbers and the cell differentials of BALF cells were counted. The levels of TARC and IL-4 in BALF were measured by enzyme-linked immunosorbent assay （ELISA）. The expression of TARC protein and mRNA were detected by immunohistochemistry and reverse transcription polymerase chain reaction （RT-PCR）, respectively. RESULTS The total cell numbers in BALF,the absolute numbers of EOS, the ratios of EOS to the total cell numbers（EOS% ） of asthma group were all significantly higher than those of the control group（ P 〈 0. 01, respectively）. Compared with asthma group, those were all markedly decreased in DXM group（P 〈0.01, respectively）. The levels of TARC and IL-4 in BALF of asthma group were markedly higher than those in control group and DXM group（ P 〈 0. 01, respectively）. Immunohistochemistry and RT-PCR showed that the protein and mRNA expression of TARC in asthma group were significantly higher than that of control group （P 〈 0. 01, respectively）. While that of DXM group were significantly lower than that of asthma group （ P 〈0. 01 ,respectively）. Immunohistochemistry also showed that the predominant cells in lung tissues that expressed TARC were epithelial cells. Strong positive correlations were found between TARC and absolute numbers of EOS and IL-4 in BALF. CONCLUSION The beneficial effect of glucocorticoid （dexamethasone） on airway inflammation may be at least in part due to their direct inhibitory effect on TARC generation by the bronchial epithelium.