地塞米松对哮喘豚鼠嗜酸细胞中白细胞介素3、5及粒-巨噬细胞集落刺激因子受体表达的影响

目的观察地塞米松(DM)对嗜酸细胞(EOS)上白细胞介素5受体α(IL-5Rα)、白细胞介素3受体α(IL-3Rα)、粒-巨噬细胞集落刺激因子受体α(GM-CSFRα)及共同β链(βcR)mRNA表达的影响,探讨糖皮质激素促进哮喘EOS凋亡的机制.方法18只健康豚鼠随机分为正常组、哮喘组、地塞米松组,每组6只,以卵蛋白致敏激发制作哮喘豚鼠模型,密度梯度分离法分离支气管肺泡灌洗液(BALF)中的低密度EOS(HEOS)及正常密度EOS(NEOS),以末端脱氧核糖核苷酸转移酶介导的dUTP缺口末端标记法(TUNEL)法检测细胞凋亡,原位杂交检测各受体mRNA表达,逆转录-多聚酶链式反应(RT-PCR)法检测EOSIL-5Rα、IL-3Rα相对含量.结果HEOS及NEOS凋亡,哮喘组(4.0±2.0、3.0±2.0)与正常组(8.0±2.0、7.0±2.0)比较差异有显著性(P＜0.01),而细胞数哮喘组(75.2±12.6、50.7±11.2)与正常组(4.8±1.5、9.5±2.6)比较差异也有显著性(P＜0.01).用DM2h后不同密度EOS数量(14.8±8.3、20.0±7.0)与哮喘组比较差异有显著性(P＜0.01),DM组以HEOS下降为明显(P＜0.05),BALF中EOS以NE0S为主,EOS凋亡DM组(24.0±5.0、22.0±4.0)与哮喘组比较差异有显著性(P＜0.01);EOS表达IL-5、IL-3及GM-CSFα受体mRNA,哮喘组与正常组比较差异有显著性(P＜0.01,0.05),DM组与哮喘组比较差异有显著性(P＜0.05或0.01);而βcR表达哮喘组(41±6、39±7)与正常组(28±5、26±5)比较差异有显著性(P＜0.01);DM组(32±8、30±5)与哮喘组比较差异有显著性(P＜0.05).HEOS表达各受体与NEOS比较差异无显著性(P＞0.05);RT-PCR检测显示,DM组IL-5Rα、IL-3RαmRNA与哮喘组比较差异均有显著性(P＜0.01,0.05).结论DM可促进哮喘豚鼠肺内EOS凋亡,减少肺内EOS浸润,DM可通过促进IL-5、IL-3、GM-CSF受体各自α链表达,抑制这三种受体的共同β链表达,减少其生物学功能,促进EOS凋亡.

The influence of dexamethasone on mRNA expression of interleukin-5, interleukin-3 and granulocyte macrophage colony-stimulating factor receptors in eosinophils of guinea pig asthma model

OBJECTIVE: To investigate the iufluence of dexamethasone (DM) on expression of interleukin-5 receptor alpha(IL-5R alpha), interleukin-3 receptor alpha (IL-3R alpha), granulocyte-macrophage-colony-stimulating factor receptor alpha(GM-CSFR alpha) and common beta receptor (beta cR) in bronchalveolar lavage fluid (BALF) eosinophils in guinea pig asthma model, and to study the mechanism of promotion effect of steroid on eosinophil apoptosis. METHODS: 18 guinea pigs were divided into three groups randomly, normal control group, asthma group and DM-treated group. Asthma models of guinea pig were sensitized by ovalbumin(OVA). Hypodense EOS (HEOS) and normodense EOS (NEOS) were purified from BALF by gradients of percoll. Apoptosis was detected by method of TdT-mediated dUTP nick end labeling. The mRNA expression of IL-5R alpha, IL-3R alpha, GM-CSFR alpha and common beta receptor (beta cR) in eosinophils were measured by RT-PCR and in situ hybridization. RESULTS: Apoptosis of HEOS and NEOS in asthma group(4.0 +/- 2.0 and 3.0 +/- 2.0, respectively) were significanteylower than normal group(8.0 +/- 2.0 and, 7.0 +/- 2.0 respectively, P < 0.01), while the numbers of EOS cells (75.2 +/- 12.6 and 50.7 +/- 11.2, respectively) were significantly higher than normal group (4.8 +/- 1.5 and 9.5 +/- 2.6, respectively, P < 0.01). The BALF HEOS and NEOS of asthma group were remarkably reduced after DM treatment (14.8 +/- 8.0 and 20.0 +/- 7.0, respectively, P < 0.01), Eosinophils apoptosis in DM-treated group (24.0 +/- 5.0 and 22.0 +/- 4.0, respectively) was remarkably higher than those in asthma group (P < 0.01); The expressions of IL-5R alpha, IL-3R alpha, GM-CSFR alpha mRNA of BALF EOS of asthma group were significantly lower, but the expression of beta cR mRNA was significantly higher than those of normal group(P < 0.01, 0.05). The expressions of IL-5R alpha, IL-3R alpha, GM-CSFR alpha mRNA in EOS of DM-treated group were significantly higher, while the expression of beta cR mRNA were significantly lower than those of asthma group (P < 0.01, 0.05). CONCLUSIONS: DM promote the apoptosis of BALF EOS of guinea pigs asthma models. and reduce EOS infiltration in lung of guinea pigs asthma models. It also decreased the effect of IL-5, IL-3 and GM-CSF and promoted the apoptosis of lung EOS through inducing the mRNA expression of their specific alpha chain and reducing the mRNA expression of the common beta chain.