Yde Jonathan, Keely Stephen, Wu Qi, Borg Johan F, Lajczak Natalia, O'Dwyer Aoife, Dalsgaard Peter, Fenton Robert A, Moeller Hanne B
Department of Biomedicine, InterPrET Center, Aarhus University , Aarhus , Denmark.
RCSI Education and Research Centre, Royal College of Surgeons in Ireland, Beaumont Hospital , Dublin , Ireland.
Front Nutr. 2016 Oct 10;3:46. doi: 10.3389/fnut.2016.00046. eCollection 2016.
In normal individuals, the epithelium of the colon absorbs 1.5-2 l of water a day to generate dehydrated feces. However, in the condition of bile acid malabsorption (BAM), an excess of bile acids in the colon results in diarrhea. Several studies have attempted to address the mechanisms contributing to BAM induced by various bile acids. However, none have addressed a potential dysregulation of aquaporin (AQP) water channels, which are responsible for the majority of transcellular water transport in epithelial cells, as a contributing factor to the onset of diarrhea and the pathogenesis of BAM. In this study, we aimed to systematically analyze the expression of AQPs in colonic epithelia from rat, mouse, and human and determine whether their expression is altered in a rat model of BAM. Mass spectrometry-based proteomics, RT-PCR, and western blotting identified various AQPs in isolated colonic epithelial cells from rats (AQP1, 3, 4, 7, 8) and mice (AQP1, 4, 8). Several AQPs were also detected in human colon (AQP1, 3, 4, 7-9). Immunohistochemistry localized AQP1 to the apical plasma membrane of epithelial cells in the bottom of the crypts, whereas AQP3 (rat, human) and AQP4 (mice, human) were localized predominantly in the basolateral plasma membrane. AQP8 was localized intracellularly and at the apical plasma membrane of epithelial cells. Rats fed sodium cholate for 72 h had significantly increased fecal water content, suggesting development of BAM-associated diarrhea. Colonic epithelial cells isolated from this model had significantly altered levels of AQP3, 7, and 8, suggesting that these AQPs may be involved in the pathogenesis of bile acid-induced diarrhea.
在正常个体中，结肠上皮每天吸收1.5 - 2升水以产生脱水粪便。然而，在胆汁酸吸收不良（BAM）的情况下，结肠中过量的胆汁酸会导致腹泻。多项研究试图阐明各种胆汁酸诱导BAM的机制。然而，尚无研究探讨水通道蛋白（AQP）水通道的潜在失调，而水通道蛋白负责上皮细胞中大部分跨细胞水转运，是导致腹泻发作和BAM发病机制的一个因素。在本研究中，我们旨在系统分析大鼠、小鼠和人类结肠上皮中AQP的表达，并确定其在BAM大鼠模型中的表达是否发生改变。基于质谱的蛋白质组学、RT-PCR和蛋白质免疫印迹法在大鼠（AQP1、3、4、7、8）和小鼠（AQP1、4、8）分离的结肠上皮细胞中鉴定出各种AQP。在人类结肠中也检测到了几种AQP（AQP1、3、4、7 - 9）。免疫组织化学将AQP1定位于隐窝底部上皮细胞的顶端质膜，而AQP3（大鼠、人类）和AQP4（小鼠、人类）主要定位于基底外侧质膜。AQP8定位于细胞内以及上皮细胞的顶端质膜。用胆酸钠喂养72小时的大鼠粪便含水量显著增加，提示发生了与BAM相关的腹泻。从该模型分离的结肠上皮细胞中AQP3、7和8的水平发生了显著改变，表明这些AQP可能参与了胆汁酸诱导的腹泻的发病机制。
