乙酰半胱氨酸对香烟烟雾暴露大鼠 Clara 细胞的影响。

Effects of N-acetylcysteine on Clara cells in rats with cigarette smoke exposure.

机构信息

Department of Respiratory Medicine, Peking University First Hospital, Beijing 100034, China.

出版信息

Chin Med J (Engl). 2010 Feb 20;123(4):412-7.

DOI:

PMID:20193479

Abstract

BACKGROUND

The number of Clara cells and the Clara cell 16-kDa protein (CC16) levels of the lung decrease in patients with chronic obstructive pulmonary disease (COPD). N-acetylcysteine (NAC) is a powerful antioxidant and can reduce the frequency of acute exacerbations of COPD. But the exact mechanism is unclear. The present study was designed to investigate the effects of NAC on Clara cells in rats with cigarette smoke exposure.

METHODS

Eighteen adult male Wistar rats were randomly divided into 3 groups, 12 exposed to cigarette smoke (CS) thrice a day, 10 cigarettes for 30 minutes each time for 1 week, without (CS group) or with (CS + NAC group) oral intake of NAC 80 mg x kg(-1) x d(-1), and another 6 rats exposed to fresh air (control group). Clara cells were observed by an electron microscope. The mRNA expression of CC16 and CC16 protein in lungs were determined by reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry respectively. The glutathion (GSH) level in plasma and lung tissue were tested by fluorimetry assay.

RESULTS

Compared with the controls, the pathologic score of small airways significantly increased in the CS exposed rats (20.3 +/- 14.7 vs. 53.7 +/- 11.5, P < 0.05). The Clara cell particles in cytoplasm decreased in the CS group (P < 0.05). The percentage of CC16-positive cells in bronchioles in the CS group (27.8 +/- 4.3 and 29.5 +/- 2.4 in terminal bronchioles and respiratory bronchioles, respectively) significantly decreased as compared with the control group (37.1 +/- 3.8 and 43.8 +/- 5.8 in terminal bronchioles and respiratory bronchioles, respectively) (P < 0.05). No significant difference was observed in GSH level ((181 +/- 26) nmol/L in the control group vs. (170 +/- 18) nmol/L in the CS group) between the two groups. After treatment with NAC, the pathologic score of small airways (24.1 +/- 17.5) decreased (P < 0.05). Clara cell particles in cytoplasm of Clara cells increased and GSH level in plasma ((213 +/- 40) nmol/L vs. (170 +/- 18) nmol/L in the CS group) increased too (P < 0.05), while the increase in the proportions of CC16 positive cells in bronchioles (30.1 +/- 6.4 and 34.3 +/- 6.3 in terminal bronchioles and respiratory bronchioles, respectively) did not reach the statistical significance (P > 0.05). No significant difference was found in the expression of CC16 mRNA among the three groups. Correlation analysis indicated that the percentage of CC16-positive cells in bronchioles negatively correlated with the pathologic score of small airways (r = -0.592, P < 0.05), but not with GSH level.

CONCLUSIONS

One-week CS exposure decreased the number of Clara cells and the expression of CC16 in bronchioles in rats. NAC might provide protection of the Clara cells from oxidative damage and possibly through the elevation of the synthesis and secretion of CC16. These data indicate that NAC decreases airway inflammation induced by CS via induction of CC16.

摘要

背景

在慢性阻塞性肺疾病（COPD）患者中，肺内的 Clara 细胞数量和 Clara 细胞 16kDa 蛋白（CC16）水平下降。N-乙酰半胱氨酸（NAC）是一种强大的抗氧化剂，可减少 COPD 急性加重的频率。但确切机制尚不清楚。本研究旨在探讨 NAC 对吸烟暴露大鼠 Clara 细胞的影响。

方法

将 18 只成年雄性 Wistar 大鼠随机分为 3 组，12 只大鼠每天接受 3 次香烟烟雾暴露（CS），每次 10 支香烟，每次 30 分钟，共 1 周，无（CS 组）或有（CS+NAC 组）口服 NAC 80mg·kg(-1)·d(-1)，另外 6 只大鼠暴露于新鲜空气中（对照组）。用电子显微镜观察 Clara 细胞。通过逆转录聚合酶链反应（RT-PCR）和免疫组织化学分别测定 CC16 和 CC16 蛋白在肺中的 mRNA 表达。用荧光法测定血浆和肺组织中的谷胱甘肽（GSH）水平。

结果

与对照组相比，CS 暴露大鼠的小气道病理评分显著升高（20.3±14.7 vs. 53.7±11.5，P<0.05）。CS 组细胞浆中的 Clara 细胞颗粒减少（P<0.05）。CS 组终末细支气管和呼吸性细支气管中 CC16 阳性细胞的比例（分别为 27.8±4.3 和 29.5±2.4）明显低于对照组（分别为 37.1±3.8 和 43.8±5.8）（P<0.05）。两组间 GSH 水平无显著差异（对照组为（181±26）nmol/L，CS 组为（170±18）nmol/L）。用 NAC 治疗后，小气道病理评分（24.1±17.5）降低（P<0.05）。Clara 细胞浆中的 Clara 细胞颗粒增多，血浆中 GSH 水平升高（（213±40）nmol/L vs. （170±18）nmol/L 在 CS 组）（P<0.05），而支气管中 CC16 阳性细胞的比例增加（终末细支气管和呼吸性细支气管分别为 30.1±6.4 和 34.3±6.3）没有达到统计学意义（P>0.05）。三组间 CC16 mRNA 的表达无显著差异。相关性分析表明，支气管中 CC16 阳性细胞的比例与小气道病理评分呈负相关（r=-0.592，P<0.05），但与 GSH 水平无关。