Porphyromonas gingivalis Impairs Oral Epithelial Barrier through Targeting GRHL2
Porphyromonas gingivalis Impairs Oral Epithelial Barrier through Targeting GRHL2
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DOI：
10.1177/0022034519865184
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发表时间：
2019-07-24
影响因子：
7.6
通讯作者：
Kang, M. K.
中科院分区：
文献类型：
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作者：
Chen, W.;Alshaikh, A.;Kang, M. K.
口腔粘膜通过形成由多蛋白紧密连接(TJ)、黏附连接、桥粒和缝隙连接复合体相互连接的上皮细胞屏障，提供了抵御各种环境和微生物刺激的第一道防线。颗粒头样转录因子2(GRHL2)是一种上皮特异性转录因子，通过调节连接蛋白的表达，可能在粘膜上皮屏障的形成中发挥作用。本研究探讨了GRHL2在牙龈卟啉单胞菌(PG)诱导的上皮屏障功能损伤中的作用。人口腔角质形成细胞(HOK-16B和OKF6细胞)暴露于PG或PG衍生的脂多糖(PG LPS)后，内源性GRHL2和连接蛋白(如闭锁小带、E-钙粘附素、Claudins和闭锁蛋白)迅速丧失。Grhl2直接调节连接蛋白的表达水平和小分子(如葡聚糖细菌和PG细菌)的上皮通透性。为了探索GRHL2在口腔黏膜屏障中的功能作用，我们使用了Grhl2条件性基因敲除(KO)小鼠模型，该模型允许以诱导的方式产生上皮组织特异性的GRHL2 KO。Grhl2KO可抑制结扎牙周炎模型牙周交界上皮细胞连接蛋白的表达，增加牙槽骨的丢失。荧光原位杂交显示，与野生型小鼠相比，Grhl2KO小鼠口腔细菌对上皮的穿透性增加。此外，与野生型小鼠相比，Grhl2KO小鼠的口腔细菌(如类杆菌、芽孢杆菌、细菌、β-蛋白细菌和螺旋体)的血液负荷显著增加。这些数据表明，PG细菌可能部分通过靶向GRHL2在口腔上皮细胞中的表达而促进细胞旁穿透口腔黏膜，从而通过抑制连接蛋白的表达而损害上皮屏障，导致肺泡组织破坏和全身性菌血症的增加。
Oral mucosa provides the first line of defense against a diverse array of environmental and microbial irritants by forming the barrier of epithelial cells interconnected by multiprotein tight junctions (TJ), adherens junctions, desmosomes, and gap junction complexes. Grainyhead-like 2 (GRHL2), an epithelial-specific transcription factor, may play a role in the formation of the mucosal epithelial barrier, as it regulates the expression of the junction proteins. The current study investigated the role of GRHL2 in the Porphyromonas gingivalis (Pg)-induced impairment of epithelial barrier functions. Exposure of human oral keratinocytes (HOK-16B and OKF6 cells) to Pg or Pg-derived lipopolysaccharides (Pg LPSs) led to rapid loss of endogenous GRHL2 and the junction proteins (e.g., zonula occludens, E-cadherin, claudins, and occludin). GRHL2 directly regulated the expression levels of the junction proteins and the epithelial permeability for small molecules (e.g., dextrans and Pg bacteria). To explore the functional role of GRHL2 in oral mucosal barrier, we used a Grhl2 conditional knockout (KO) mouse model, which allows for epithelial tissue-specific Grhl2 KO in an inducible manner. Grhl2 KO impaired the expression of the junction proteins at the junctional epithelium and increased the alveolar bone loss in the ligature-induced periodontitis model. Fluorescence in situ hybridization revealed increased epithelial penetration of oral bacteria in Grhl2 KO mice compared with the wild-type mice. Also, blood loadings of oral bacteria (e.g., Bacteroides, Bacillus, Firmicutes, beta-proteobacteria, and Spirochetes) were significantly elevated in Grhl2 KO mice compared to the wild-type littermates. These data indicate that Pg bacteria may enhance paracellular penetration through oral mucosa in part by targeting the expression of GRHL2 in the oral epithelial cells, which then impairs the epithelial barrier by inhibition of junction protein expression, resulting in increased alveolar tissue destruction and systemic bacteremia.