Increased Epithelial Permeability Is the Primary Cause for Bicarbonate Loss in Inflamed Murine Colon
Increased Epithelial Permeability Is the Primary Cause for Bicarbonate Loss in Inflamed Murine Colon
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DOI：
10.1097/mib.0b013e3182813322
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发表时间：
2013-04-01
影响因子：
4.9
通讯作者：
Bachmann, Oliver
中科院分区：
文献类型：
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作者：
Juric, Marina;Xiao, Fang;Bachmann, Oliver
背景：在不同物种的肠道炎症过程中，Biclitazone会丢失到管腔中。然而，候选途径如CFTR或CFTR在发炎的肠道中被抑制。这项研究解决了这个问题是否以及如何炎症相关的肠通透性增加可能会导致上皮HCO 3- loss.Methods：小鼠近端结肠进行了研究，因为它不表达功能性结肠炎，但发炎的肿瘤坏死因子α过表达小鼠模型（TNF Δ ARE）。管腔碱化，H-3-甘露醇通量，阻抗谱，稀释电位进行了测量，而紧密连接相关蛋白的表达和定位进行了分析，通过Western印迹和免疫组化。结果：管腔碱化率和H-3-甘露醇通量增加TNF+/Δ ARE近端结肠，而毛喉素刺激的I-SC没有改变。上皮电阻降低，但上皮下电阻增加。上皮衬里是完整的，肠上皮细胞凋亡率没有增加，尽管大量增加的Th 1细胞因子水平和淋巴浆细胞浸润。稀释电位的测量表明，随着阴离子渗透性的增加，阳离子选择性损失。Western分析显示封闭蛋白表达下调，封闭蛋白2和封闭蛋白5上调，ZO-1、E-钙粘蛋白、封闭蛋白4和封闭蛋白8无变化。免疫组化表明正确occludin定位，但减少紧密连接密度在TNF+/Δ ARE表面epithelium.Conclusions：炎症过程中TNF-α过度表达导致增加上皮通透性在小鼠近端结肠，减少紧密连接阳离子的选择性，并增加HCO 3-损失到管腔。炎症相关的结肠HCO 3损失可能通过渗漏的紧密连接而不是通过HCO 3分泌离子转运蛋白发生。
Background: Bicarbonate loss into the lumen occurs during intestinal inflammation in different species. However, candidate pathways like CFTR or DRA are inhibited in the inflamed gut. This study addressed the question whether and how inflammation-associated increased intestinal permeability may result in epithelial HCO3- loss.Methods: Murine proximal colon was studied because it does not express functional DRA but is inflamed in the tumor necrosis factor alpha overexpressing mouse model (TNF Delta ARE). Luminal alkalization, H-3-mannitol fluxes, impedance spectroscopy, and dilution potentials were measured in Ussing chambers, whereas expression and localization of tight junction-associated proteins were analyzed by Western blots and immunohistochemistry.Results: Luminal alkalization rates and H-3-mannitol fluxes were increased in TNF+/Delta ARE proximal colon, whereas forskolin-stimulated I-sc was not altered. Epithelial resistance was reduced, but subepithelial resistance increased. The epithelial lining was intact, and enterocyte apoptosis rate was not increased despite massively increased Th1 cytokine levels and lymphoplasmacellular infiltration. Measurement of dilution potentials suggested a loss of cation selectivity with increased anion permeability. Western analysis revealed a downregulation of occludin expression and an upregulation of both claudin-2 and claudin-5, with no change in ZO-1, E-cadherin, claudin-4, and claudin-8. Immunohistochemistry suggested correct occludin localization but reduced tight junction density in TNF+/Delta ARE surface epithelium.Conclusions: Inflammation during TNF-alpha overexpression leads to increased epithelial permeability in murine proximal colon, decreased tight junctional cation selectivity, and increased HCO3- loss into the lumen. Inflammation-associated colonic HCO3- loss may occur through leaky tight junctions rather than through HCO3- secreting ion transporters.