Koo J S, Yoon J H, Gray T, Norford D, Jetten A M, Nettesheim P
Laboratory of Pulmonary Pathobiology, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA.
Am J Respir Cell Mol Biol. 1999 Jan;20(1):43-52. doi: 10.1165/ajrcmb.20.1.3310.
Retinoid-deficient cultures of airway epithelial cells undergo squamous differentiation. Treatment of such cultures with retinoic acid (RA) leads to restoration of the mucous phenotype. The purpose of our study was to characterize the cellular and molecular changes following RA treatment of retinoid-deficient human tracheobronchial epithelial cell cultures. Of particular interest was to determine when during the conversion of the squamous to the mucous phenotype the mucin genes MUC2, MUC5AC, and MUC5B were expressed. We used cornifin alpha and secreted mucin as markers to monitor the squamous and mucous phenotypes, respectively. Our studies showed that the RA responsiveness of the cultures progressively decreased with protracted retinoid deficiency, requiring higher RA concentrations to restore the mucous phenotype. Within 12 h after the start of RA treatment, cornifin alpha expression decreased, signaling the beginning of a change in cellular phenotype. At 24 h after addition of RA to the cultures, a significant number of mucous cells appeared, and at 72 h mucin was secreted in measurable amounts. Induction of mucin gene expression occurred sequentially: MUC2, MUC5AC, and MUC5B mRNAs were upregulated at 24, 48, and 72 h, respectively. When cultures maintained in 10(-8) M RA were treated with 10(-6) M RA, MUC2 but not MUC5AC and MUC5B mRNA levels were upregulated within 6 h. Our study indicates that MUC2 mRNA is an early marker of mucous differentiation, whereas MUC5AC and MUC5B mRNAs are expressed during more advanced stages of mucous differentiation. Our studies further suggest that each of the mucin genes is regulated by distinct mechanisms.
维甲酸缺乏的气道上皮细胞培养物会发生鳞状分化。用视黄酸（RA）处理这种培养物可导致黏液表型的恢复。我们研究目的是描述RA处理维甲酸缺乏的人气管支气管上皮细胞培养物后细胞和分子水平的变化。特别感兴趣的是确定在从鳞状表型转变为黏液表型的过程中，黏蛋白基因MUC2、MUC5AC和MUC5B何时表达。我们分别使用角质化包膜蛋白α和分泌型黏蛋白作为标志物来监测鳞状和黏液表型。我们的研究表明，随着维甲酸缺乏时间的延长，培养物对RA的反应性逐渐降低，需要更高浓度的RA才能恢复黏液表型。在开始RA处理后的12小时内，角质化包膜蛋白α表达下降，表明细胞表型开始发生变化。在向培养物中添加RA后的24小时，出现了大量黏液细胞，在72小时时可检测到有黏液分泌。黏蛋白基因表达的诱导是依次发生的：MUC2、MUC5AC和MUC5B的mRNA分别在24、48和72小时上调。当维持在10^(-8) M RA中的培养物用10^(-6) M RA处理时，MUC2的mRNA水平在6小时内上调，而MUC5AC和MUC5B的mRNA水平未上调。我们的研究表明，MUC2 mRNA是黏液分化的早期标志物，而MUC5AC和MUC5B的mRNA在黏液分化的更晚期阶段表达。我们的研究进一步表明，每个黏蛋白基因都受不同机制的调控。
