Glucocorticoids regulate barrier function and claudin expression in intestinal epithelial cells via MKP-1
Glucocorticoids regulate barrier function and claudin expression in intestinal epithelial cells via MKP-1
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DOI：
10.1152/ajpgi.00095.2013
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发表时间：
2014-02-01
影响因子：
4.5
通讯作者：
Theuring, Franz
中科院分区：
文献类型：
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作者：
Fischer, Andreas;Gluth, Markus;Theuring, Franz
屏障功能障碍在炎症性肠病(IBD)和胶原性结肠炎的发病机制中起关键作用。糖皮质激素可恢复克罗恩病的屏障功能，但这是否反映了炎症的减轻或上皮细胞的特异性作用尚未得到解决。使用滤膜生长的Caco-2单层作为肠上皮屏障的体外模型，我们观察到糖皮质激素以糖皮质激素受体依赖的方式诱导跨皮细胞电阻(TEER)的时间和剂量依赖性增加，而不改变较大的溶质流量或主要紧密连接结构。伴随而来的是细胞旁阳离子流量的减少，致孔紧密连接成分claudin-2的表达减少，以及封闭紧密连接蛋白claudin-4的上调。相反，occludin、claudin-1、-7或-8的表达没有改变。地塞米松增加MAPK磷酸酶-1的表达和活性，抑制该磷酸酶可阻止糖皮质激素诱导的TEER和claudin表达的改变，但抑制p38或MEK1/2不足以复制糖皮质激素的作用。在暴露于干扰素-γ、肿瘤坏死因子-α或白介素1-β的情况下，地塞米松处理的细胞中的TERS下降，但始终高于未接受糖皮质激素治疗的细胞。用干扰素/肿瘤坏死因子处理后，Claudin-2的表达上调，地塞米松可显著减弱Claudin-2的表达，而IL-1β刺激下Claudin-2的表达不受糖皮质激素的影响。综上所述，屏障增强可能代表了一种以前未知的作用机制，可能有助于糖皮质激素治疗IBD和胶原性结肠炎的疗效。
Barrier dysfunction is pivotal to the pathogenesis of inflammatory bowel diseases (IBD) and collagenous colitis. Glucocorticoids restore barrier function in Crohn's disease, but whether this reflects attenuated inflammation or an epithelial-specific action has not yet been addressed. Using filter-grown Caco-2 monolayers as an in vitro model of the intestinal epithelial barrier, we observed that glucocorticoids induced a time-and dose-dependent increase in transepithelial electrical resistance (TEER) in a glucocorticoid receptor-dependent manner without altering flux of larger solutes or changing principal tight junction architecture. This was accompanied by reduced paracellular cation flux, reduced expression of the pore-forming tight junction component claudin-2, and upregulation of the sealing tight junction protein claudin-4. In contrast, expression of occludin, claudin-1, -7, or -8 was not altered. Dexamethasone increased expression and activity of MAPK phosphatase-1 and inhibition of this phosphatase prevented the glucocorticoid-induced changes in TEER and claudin expression, whereas inhibiting p38 or MEK1/2 was not sufficient to replicate the glucocorticoid effects. Upon exposure to IFN-gamma, TNF-alpha, or IL-1 beta, TEERs declined in dexamethasone-treated cells but remained consistently higher than in cells not receiving glucocorticoids. Treatment with IFN/TNF resulted in an upregulation of claudin-2 that was significantly attenuated by dexamethasone, whereas increased claudin- 2 expression upon IL-1 beta stimulation was not affected by glucocorticoids. Taken together, barrier augmentation might represent a previously unrecognized mechanism of action, potentially contributing to the therapeutic efficacy of glucocorticoids in IBD and collagenous colitis.