Local increase in the number of mast cells and expression of nerve growth factor in the bronchus of asthmatic patients after repeated inhalation of allergen at low-dose
Local increase in the number of mast cells and expression of nerve growth factor in the bronchus of asthmatic patients after repeated inhalation of allergen at low-dose
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DOI：
10.1046/j.1365-2222.2001.01177.x
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发表时间：
2001-09-01
影响因子：
6.1
通讯作者：
Frossard, N
中科院分区：
文献类型：
--
作者：
Kassel, O;De Blay, F;Frossard, N
背景反复吸入低剂量过敏原可引起支气管高反应性增加，但无任何相关症状。目的研究轻度哮喘患者反复吸入低剂量变应原前后气道肥大细胞数量的动态变化及神经生长因子（NGF）的表达，方法将12例过敏性哮喘患者随机分为对照组和安慰剂组，每组12例。对照研究，并提交重复低剂量过敏原暴露（激发剂量的1/5）。使用针对肥大细胞类胰蛋白酶的抗体对肥大细胞进行免疫定位。分别使用抗NGF和抗TrkA抗体对NGF及其高亲和力受体TrkA进行免疫定位。从支气管活检组织中提取总RNA，逆转录后通过竞争性聚合酶链反应（PCR）定量NGF mRNA。结果过敏原暴露后支气管肺泡灌洗液（BAL）中的肥大细胞数量较暴露前明显增多，且与对照组比较差异有统计学意义（P < 0. 05）。支气管中的NGF表达主要免疫定位于上皮细胞，但也存在于成纤维细胞、血管和少数浸润细胞。支气管活检组织中的NGF mRNA水平在变应原暴露后显著增加。高亲和力的神经生长因子受体，TrkA，免疫定位于浸润的肥大细胞membrane.Conclusion我们的研究表明，肥大细胞的数量和在支气管哮喘患者的过敏原暴露诱导的神经生长因子的表达增加发生在症状发作之前。此外，我们发现原位浸润的肥大细胞膜上存在TrkA受体，这为肥大细胞作为哮喘气道中NGF生长因子活性的靶细胞提供了证据。
Background Repeated inhalation of allergen at low-dose induces an increase in bronchial hyper-responsiveness, without any associated symptom. The concomitant events in the bronchus have not been described.Objective We have studied the dynamic number of mast cells in the airways of patients with mild asthma before and after repeated inhalation of allergen at low-dose and the expression of nerve growth factor (NGF), which is reported to promote growth and survival of mast cells.Methods Twelve patients with mild asthma to cat allergen were enrolled at random in a blind placebo-controlled study, and submitted to repeated low-dose allergen exposure (1/5 of the provocative dose). Mast cells were immunolocalized using an antibody against mast cell tryptase. NGF and its high affinity receptor, TrkA, were immunolocalized using anti-NGF and anti-TrkA antibodies, respectively. NGF mRNA was quantified by competitive polymerase chain reaction (PCR) after reverse transcription of total RNA extracted from bronchial biopsy. NGF protein levels were measured by ELISA in bronchoalveolar lavage (BAL) fluid.Results Bronchial mast cell number was increased significantly after allergen exposure as compared with before. NGF expression in the bronchus was immunolocalized mainly to epithelial cells, but also to fibroblasts, blood vessels, and a few infiltrated cells. NGF mRNA levels in bronchial biopsies were increased significantly after allergen exposure. The high affinity receptor for NGF, TrkA, was immunolocalized to the infiltrated mast cell membrane.Conclusion Our study shows that the increase in the number of mast cells and in the expression of NGF induced by allergen exposure in the bronchus of asthmatic patients is occurring before the onset of symptoms. In addition, our finding of the presence of the TrkA receptor on the membrane of the infiltrated mast cell in situ brings evidence of the mast cell as a target cell for the growth factor activity of NGF in the airways in asthma.