Department of Oral Pathology, School of Dentistry, Morioka, Japan.
J Periodontal Res. 2010 Apr;45(2):207-15. doi: 10.1111/j.1600-0765.2009.01219.x. Epub 2009 Sep 23.
It has been reported that retinoic acid disintegrates the desmosome formation of squamous epithelium, resulting in inhibition of stratification. In contrast, it is not known whether retinoic acid influences the integration of tight junctions. Therefore, our objective of this study is to disclose effects of retinoic acid on the formation and maintenance of tight junction.
In the present study, the alteration of expression of tight junction constituent proteins and keratin peptides in immortalized oral mucosal epithelial cells (GE1) induced by 1 microm retinoic acid was analyzed by immunofluorescence, electron microscopy and reverse transcription-polymerase chain reaction (RT-PCR).
The stratifying GE1 cells expressed claudin-1, claudin-4, claudin-5, occludin and zonula occludens 1 in the control culture. The RT-PCR showed that retinoic acid significantly reduced the expression of claudin-1 mRNA, whereas it dramatically enhanced expression of claudin-4 mRNA. Immunofluorescence showed that claudin-1 was present at cell-to-cell contact sites in the flattened uppermost layers of the control culture. In the culture with retinoic acid, the flattened uppermost cells were absent and there claudin-1 was less present, but claudin-4 was prominently present in all layers. Claudin-5 was present in a variety of patterns, regardless of the presence of retinoic acid. Along with the change of claudin species, the expressions of keratin 7, keratin 8 and keratin 18, as markers for the simple epithelium, were clearly stimulated by retinoic acid.
Retinoic acid changed the expression of tight junction constituent molecules, such as claudin-1 and claudin-4, in oral keratinocytes. These findings suggest that long-term application of retinoids in clinical therapy should be carefully performed.
已有报道称，维 A 酸可破坏鳞状上皮的桥粒形成，从而抑制其分层。相反，维 A 酸是否影响紧密连接的整合尚不清楚。因此，本研究旨在揭示维 A 酸对紧密连接形成和维持的影响。
本研究通过免疫荧光、电子显微镜和反转录-聚合酶链反应（RT-PCR）分析了 1 μm 维 A 酸诱导的永生化口腔黏膜上皮细胞（GE1）中紧密连接组成蛋白和角蛋白肽的表达变化。
在对照培养中，分层的 GE1 细胞表达 Claudin-1、Claudin-4、Claudin-5、Occludin 和 Zonula Occludens 1。RT-PCR 显示维 A 酸显著降低 Claudin-1 mRNA 的表达，而显著增强 Claudin-4 mRNA 的表达。免疫荧光显示 Claudin-1 存在于对照培养物扁平最上层的细胞间接触部位。在含有维 A 酸的培养物中，扁平的最上层细胞不存在，Claudin-1 表达减少，但 Claudin-4 在所有层中均明显存在。Claudin-5 以多种形式存在，与维 A 酸的存在无关。随着 Claudin 种类的变化，作为简单上皮标志物的角蛋白 7、角蛋白 8 和角蛋白 18 的表达也被维 A 酸明显刺激。
维 A 酸改变了口腔角质形成细胞中紧密连接组成分子如 Claudin-1 和 Claudin-4 的表达。这些发现表明，在临床治疗中长期应用维 A 酸应谨慎进行。
