Breakdown of mucin as barrier to digestive enzymes in the ischemic rat small intestine.
Breakdown of mucin as barrier to digestive enzymes in the ischemic rat small intestine.
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DOI：
10.1371/journal.pone.0040087
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
Schmid-Schönbein GW
中科院分区：
文献类型：
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作者：
Chang M;Alsaigh T;Kistler EB;Schmid-Schönbein GW
小肠中上皮/粘膜屏障完整性的丧失与胃肠道中起源和/或发展的不同病理学相关。我们最近发现，粘液层中的主要蛋白粘蛋白在肠缺血的早期被破坏。该事件伴随胰腺消化酶进入肠壁。我们推测含粘蛋白的粘液层是阻止消化酶接触上皮的主要屏障。粘蛋白分解可能使上皮细胞接近胰腺酶，导致其破坏和渗透性增加。本研究的目的是探讨粘蛋白作为保护上皮完整性和功能的作用。采用大鼠内脏动脉闭塞（SAO）模型，研究了两种粘蛋白亚型（粘蛋白2和粘蛋白13）和两种上皮细胞膜蛋白（E-钙粘蛋白和Toll样受体4，TLR 4）的降解。此外，在该模型中，通过阿卡波糖、氨甲环酸或甲磺酸萘莫司他的管腔抑制来评估消化酶在粘蛋白分解中的作用。此外，在体外研究了粘蛋白层对胰蛋白酶介导的肠上皮破坏的保护作用。SAO后的大鼠表现出粘蛋白2的降解和粘蛋白13的片段化，这不能被蛋白酶抑制所阻止。粘蛋白分解伴随着增加的肠道通透性FITC-葡聚糖以及降解E-钙粘蛋白和TLR 4。此外，在体外肠上皮细胞的粘蛋白对胰蛋白酶介导的E-钙粘蛋白和TLR 4的降解和降低的渗透性的FITC-葡聚糖通过单层保护。这些结果表明，粘蛋白在粘膜屏障的保护中起着重要的作用，并且局部缺血而不是消化酶干扰粘蛋白的完整性，而消化酶积极介导上皮细胞破坏。
Loss of integrity of the epithelial/mucosal barrier in the small intestine has been associated with different pathologies that originate and/or develop in the gastrointestinal tract. We showed recently that mucin, the main protein in the mucus layer, is disrupted during early periods of intestinal ischemia. This event is accompanied by entry of pancreatic digestive enzymes into the intestinal wall. We hypothesize that the mucin-containing mucus layer is the main barrier preventing digestive enzymes from contacting the epithelium. Mucin breakdown may render the epithelium accessible to pancreatic enzymes, causing its disruption and increased permeability. The objective of this study was to investigate the role of mucin as a protection for epithelial integrity and function. A rat model of 30 min splanchnic arterial occlusion (SAO) was used to study the degradation of two mucin isoforms (mucin 2 and 13) and two epithelial membrane proteins (E-cadherin and toll-like receptor 4, TLR4). In addition, the role of digestive enzymes in mucin breakdown was assessed in this model by luminal inhibition with acarbose, tranexamic acid, or nafamostat mesilate. Furthermore, the protective effect of the mucin layer against trypsin-mediated disruption of the intestinal epithelium was studied in vitro. Rats after SAO showed degradation of mucin 2 and fragmentation of mucin 13, which was not prevented by protease inhibition. Mucin breakdown was accompanied by increased intestinal permeability to FITC-dextran as well as degradation of E-cadherin and TLR4. Addition of mucin to intestinal epithelial cells in vitro protected against trypsin-mediated degradation of E-cadherin and TLR4 and reduced permeability of FITC-dextran across the monolayer. These results indicate that mucin plays an important role in the preservation of the mucosal barrier and that ischemia but not digestive enzymes disturbs mucin integrity, while digestive enzymes actively mediate epithelial cell disruption.