糖皮质激素对哮喘豚鼠血浆、肺组织中神经激肽A含量的影响及其分子机制

Effect of glucocorticoid on neurokinin A in plasma and lungs of guinea pigs with asthma and molecular mechanism of the effect

目的研究糖皮质激素(地塞米松)对哮喘豚鼠血浆、肺组织中神经激肽A(NKA)含量的影响及其分子机制。方法用吸入卵蛋白致敏及激发诱喘方法制作豚鼠哮喘模型30例,随机分成地塞米松腹腔注射治疗组及非地塞米松治疗组,各15例;正常对照组15例,以生理盐水替代卵蛋白雾化溶液吸入及地塞米松腹腔注射;用ELISA方法检测各组血浆及肺组织中NKA含量;用反转录多聚酶链式反应检测肺组织中NKAmRNA相对含量。结果(1)非地塞米松治疗组哮喘豚鼠血浆NKA含量为[(2·20±0·46)ng/ml],肺组织中NKA含量为[(5·02±2·11)ng/g蛋白],肺组织中NKAmRNA表达为(1·10±0·06),均高于正常对照组豚鼠[(0·84±0·33)ng/ml,(2·56±0·80)ng/g蛋白,(0·30±0·04)],差异有统计学意义(P均<0·001);(2)地塞米松治疗组哮喘豚鼠血浆NKA含量为[(0·98±0·23)ng/ml],肺组织中NKA含量为[(2·71±0·50)ng/g蛋白],肺组织中NKAmRNA表达为(0·35±0·07),均低于非地塞米松治疗组哮喘豚鼠,差异有统计学意义(P均<0·001);地塞米松治疗组与正常对照组比较,各指标差异无统计学意义(P均>0·05)。结论(1)哮喘豚鼠肺组织中NKAmRNA表达上调,血浆及肺组织中NKA含量明显增高;(2)糖皮质激素具有显著降低哮喘豚鼠血浆、肺组织中NKA含量的作用,其机制与糖皮质激素下调肺组织中NKAmRNA的表达有关。

Objective Bronchial asthma is a chronic inflammatory disorder of the airways caused by many complicated elements. Recently, a close attention has been paid to the neurogenic inflammation in airways, which is mediated by sensory neuropeptides secreted by sensory nerve. Neurokinin A (NKA) is an important transmitter of non-cholinergic excitatory nerves in the lung which is an important sensory neuropeptide causing airway neurogenic inflammation. The purpose of this study was to investigate the effect of glucocorticoid (dexamethasone) on neurokinin A in plasma and lungs of guinea pigs with asthma and to explore its molecular mechanism. Methods Thirty guinea pigs (1.5 months old and weighed 200-225 g ) were sensitized by exposure to aerosolized ovalbumin and challenged with the same antigen to establish asthma model. These animals were divided randomly into dexamethasone-treatment group and non-dexamethasone-treatment group (15 guinea pigs in each group). Normal control group animals ( n =15) were treated with normal saline (NS) instead of aerosolized ovalbumin. The guinea pigs in the dexamethasone-treatment group were treated with dexamethasone (5.0 mg/kg, intraperitoneal injection) one day before asthma-inducement, on the day of inducement and 24 h after inducement. The non-dexamethasone-treatment group animals were treated with NS (5.0 mg/kg, intraperitoneal injection) on the same days as the dexamethasone-treatment group was treated. The normal control group animals were treated with NS (5.0 mg/kg, intraperitoneal injection). The contents of NKA in the plasma and lung tissues were detected by ELISA; the expression of NKA mRNA in lung tissues was examined by RT-PCR. Results (1) The contents of NKA in the plasma (2.20±0.46 ng/ml), lung tissues (5.02±2.11 ng/g·protein) and the NKA mRNA expression in the lung tissues (1.10±0.06)of guinea pigs with induced asthma were significantly higher than those of the normal control group(plasma 0.84±0.33 ng/ml,lung tissues 2.56±0.80 ng/g·protein,mRNA 0.30±0.04; P <0.001, respectively). (2) The contents of NKA in the plasma, lung tissues and the NKA mRNA expression in the lung tissues of guinea pigs with induced asthma were significantly lower in dexamethasone-treatment group (plasma 0.98±0.23 ng/ml,lung tissues 2.71±0.50 ng/g·protein,mRNA 0.35±0.07)than those in the non-dexamethasone-treatment group (plasma 2.20±0.46 ng/ml,lung tissues 5.02±2.11 ng/g·protein,mRNA 1.10±0.06; P <0.001, respectively). No significant difference was found between the dexamethasone-treatment group and the normal control group ( P >0.05, respectively). Conclusions (1) NKA mRNA expression in the lungs of guinea pigs with asthma was up-regulated and NKA contents were higher in plasma and lungs;(2) Glucocorticoid could significantly decrease the contents of NKA in plasma, lung tissues of guinea pigs with induced asthma;the mechanism of the effect may be related to down-regulation of NKA mRNA expression in lung tissues caused by glucocorticoid.