神经生长因子对支气管哮喘大鼠肾上腺素释放障碍的机制研究

目的探讨支气管哮喘(简称哮喘)状态下肾上腺髓质嗜铬细胞释放肾上腺素不足的可能原因,明确神经生长因子(NGF)在哮喘发病机制中的作用。方法雄性SD大鼠32只,按随机数字表法分为对照组、哮喘组、NGF干预组、抗NGF组,每组8只。对照组以生理盐水代替抗原行致敏和激发,NGF干预组、抗NGF抗体干预组建立哮喘模型后分别用NGF和抗NGF抗体干预哮喘大鼠。电镜观察肾上腺髓质嗜铬细胞超微结构的改变,免疫组织化学结合显微图像分析各组大鼠髓质嗜铬细胞中苯乙醇胺N-甲基转移酶(PNMT)的表达变化,用酶联免疫吸附试验(ELISA)法检测各组大鼠血清中肾上腺素和去甲肾上腺素的变化。结果电镜观察可见:(1)哮喘组、NGF组和抗NGF抗体干预组大鼠肾上腺髓质细胞线粒体增多,嗜铬颗粒减少;(2)NGF组肾上腺髓质嗜铬细胞膜可见杵状和绒毛状突起。图像分析结果显示NGF组PNMT平均灰度(A)值为218±38,与对照组(182±25)、哮喘组(198±33)和抗NGF组(195±41)比较差异有统计学意义(t值分别为23.42、19.76、17.93,P均<0.05);ELISA结果显示NGF组血清肾上腺素浓度为(2.9±0.5)ng/ml、与对照组(7.1±0.4)ng/ml]、哮喘组(5.9±1.7)ng/ml]、抗NGF组(5.7±0.6)ng/ml]比较差异均有统计学意义(t值分别为7.64、5.41、4.96,P均<0.01),哮喘组与对照组比较差异也有统计学意义(t=5.64,P<0.01),哮喘组和抗NGF组肾上腺素水平比较差异无统计学意义(t=0.87,P>0.05)。结论NGF通过启动肾上腺髓质嗜铬细胞的功能冗余性使其表型和功能发生转化,导致肾上腺素水平下降而参与哮喘的发生与发展。

Dysfunction of releasing adrenaline in asthmatic adrenaline medullary chromaffin cells due to functional redundancy primed by nerve growth factor

OBJECTIVE: To investigate the possible causes of the dysfunction of adrenaline release in asthma rats and to identify the role of nerve growth factor (NGF) in this process. METHODS: Thirty-two SD rats were randomly divided into four groups: control group (n = 8), asthma group (n = 8), NGF group (n = 8) and anti-NGF group (n = 8). The rats of asthma group, NGF group and anti-NGF group were sensitized and challenged with ovalbumin (OVA), and then NGF group and anti-NGF group were treated with NGF and anti-NGF, respectively. Adrenal glands were obtained for electron microscopic examination. The expression of phenylethanola-mine N-methyltransferase (PNMT) was analyzed by immunohistochemistry combined with the micro-image analysis. The concentrations of adrenaline and noradrenaline in serum were measured by enzyme-linked-immunosorbent assay (ELISA). RESULTS: The data from the electron microscopy showed: (1) Compared with the control group, the number of mitochondria increased, while the concentration of the chromaffin granula decreased in asthma, NGF and anti-NGF groups. (2) There were some drumstick-like and villiform processes in the adrenaline medullary chromaffin cells (AMCC) membrane of the NGF group. The results of immunohistochemistry showed that the average gray value of PNMT of the NGF group was 218 +/- 38, which was significantly higher than those in the control group (182 +/- 25), asthma group (198 +/- 33) and anti-NGF group (195 +/- 41, t = 23.42, 19.76, 17.93, all P < 0.05). Serum levels of adrenaline in the NGF group were (2.9 +/- 0.5) ng/ml. They were significantly lower than those in the control group (7.1 +/- 0.4) ng/ml, asthma group (5.9 +/- 1.7) ng/ml and anti-NGF group (5.7 +/- 0.6) ng/ml (t = 7.64, 5.41, 4.96, all P < 0.01). Serum levels of adrenaline in the asthma group were significantly lower than those in the control group (t = 5.64, P < 0.01). However, no difference was found between the asthma group and the anti-NGF group (t = 0.87, P > 0.05). CONCLUSIONS: NGF can prime the functional redundancy of the adrenaline medullary chromaffin cells, which leads to the dysfunction of adrenaline release and hence the pathogenesis of asthma.