Shekels L L, Lyftogt C T, Ho S B
Department of Internal Medicine, University of Minnesota, Minneapolis 55417, USA.
Int J Biochem Cell Biol. 1996 Feb;28(2):193-201. doi: 10.1016/1357-2725(95)00125-5.
Damage to the gastrointestinal tract mucous layer may render underlying cells susceptible to intraluminal toxins or carcinogens. Our aim was to determine the effect of bile acids on mucin, the primary constituent of mucous. Differentiated Caco-2 and HT29 cells were used as models of human colonic epithelial cells. Mucin was measured by [3H]-glucosamine labeling. Short term (30 min) incubations with 1-5 mM unconjugated bile acids or taurodeoxycholic acid induced mucin release relative to bile acid hydrophobicity. Longer incubations were cytotoxic. Long term (7 days) incubation at nontoxic concentrations (0.1 mM) of deoxycholic acid (DC) decreased total mucin by 36 +/- 2% (SEM, P = 0.0003) in differentiated HT29 cells and by 57.2 +/- 2% (P < 0.05) in Caco-2 cells. Tauroursodeoxycholic acid (TUDC) or ursodeoxycholic acid (0.1-0.5 mM) did not alter mucin levels. Simultaneous incubation of 0.1 mM DC and 0.1-0.5 mM TUDC or 2.5 mM TDC and TUDC did not change mucin levels. Differentiated HT29 and Caco-2 cells contained high levels of intestinal mucin MUC3 mRNA while undifferentiated HT29 cells did not possess a MUC3 message. Deoxycholic acid (0.1 mM) did not alter the MUC3 mRNA level. Neither cell type showed detectable expression of intestinal MUC2 or gastric MUC6. Thus, cytotoxic concentrations of bile acids induce mucin release, presumably due to detergent effects. Nontoxic concentrations of DC reduce mucin levels in differentiated enterocyte-like cells, which can be prevented by coincubation with TUDC. The bile acid-induced alterations in mucin production by enterocytes observed in vitro may influence intestinal cytoprotection in vivo.
胃肠道黏膜层受损可能会使下层细胞易受管腔内毒素或致癌物的影响。我们的目的是确定胆汁酸对黏液的主要成分黏蛋白的影响。分化的Caco-2和HT29细胞被用作人类结肠上皮细胞的模型。通过[3H]-葡糖胺标记法测量黏蛋白。与胆汁酸的疏水性相关，用1-5 mM未结合的胆汁酸或牛磺去氧胆酸进行短期（30分钟）孵育可诱导黏蛋白释放。较长时间的孵育具有细胞毒性。在无毒浓度（0.1 mM）的脱氧胆酸（DC）下进行长期（7天）孵育，可使分化的HT29细胞中的总黏蛋白减少36±2%（SEM，P = 0.0003），在Caco-2细胞中减少57.2±2%（P < 0.05）。牛磺熊去氧胆酸（TUDC）或熊去氧胆酸（0.1-0.5 mM）不会改变黏蛋白水平。同时孵育0.1 mM DC和0.1-0.5 mM TUDC或2.5 mM TDC和TUDC不会改变黏蛋白水平。分化的HT29和Caco-2细胞含有高水平的肠道黏蛋白MUC3 mRNA，而未分化的HT29细胞则没有MUC3信息。脱氧胆酸（0.1 mM）不会改变MUC3 mRNA水平。两种细胞类型均未显示出肠道MUC2或胃MUC6的可检测表达。因此，细胞毒性浓度的胆汁酸会诱导黏蛋白释放，可能是由于去污剂效应。无毒浓度的DC可降低分化的肠上皮样细胞中的黏蛋白水平，与TUDC共同孵育可预防这种情况。体外观察到的胆汁酸诱导的肠上皮细胞黏蛋白产生变化可能会影响体内的肠道细胞保护作用。
