Ricanek Petr, Lunde Lisa K, Frye Stephan A, Støen Mari, Nygård Ståle, Morth Jens P, Rydning Andreas, Vatn Morten H, Amiry-Moghaddam Mahmood, Tønjum Tone
Department of Microbiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway ; Department of Gastroenterology, Akershus University Hospital, Lørenskog and Campus Ahus, Institute of Clinical Medicine, University of Oslo, Lørenskog, Norway.
Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, Norway.
Clin Exp Gastroenterol. 2015 Jan 9;8:49-67. doi: 10.2147/CEG.S70119. eCollection 2015.
The aim of this study was to investigate the relationship between aquaporin (AQP) water channel expression and the pathological features of early untreated inflammatory bowel disease (IBD) in humans.
Patients suspected to have IBD on the basis of predefined symptoms, including abdominal pain, diarrhea, and/or blood in stool for more than 10 days, were examined at the local hospital. Colonoscopy with biopsies was performed and blood samples were taken. Patients who did not meet the diagnostic criteria for IBD and who displayed no evidence of infection or other pathology in the gut were included as symptomatic non-IBD controls. AQP1, 3, 4, 5, 7, 8, and 9 messenger RNA (mRNA) levels were quantified in biopsies from the distal ileum and colon by quantitative real-time polymerase chain reaction. Protein expression of selected AQPs was assessed by confocal microscopy. Through multiple alignments of the deduced amino acid sequences, the putative three-dimensional structures of AQP1, 3, 7, and 8 were modeled.
AQP1, 3, 7, and 8 mRNAs were detected in all parts of the intestinal mucosa. Notably, AQP1 and AQP3 mRNA levels were reduced in the ileum of patients with Crohn's disease, and AQP7 and AQP8 mRNA levels were reduced in the ileum and the colon of patients with ulcerative colitis. Immunofluorescence confocal microscopy showed localization of AQP3, 7, and 8 at the mucosal epithelium, whereas the expression of AQP1 was mainly confined to the endothelial cells and erythrocytes. The reduction in the level of AQP3, 7, and 8 mRNA was confirmed by immunofluorescence, which also indicated a reduction of apical immunolabeling for AQP8 in the colonic surface epithelium and crypts of the IBD samples. This could indicate loss of epithelial polarity in IBD, leading to disrupted barrier function.
AQPs 1 and 8 and the aquaglyceroporins AQPs 3 and 7 are the AQPs predominantly expressed in the lower intestinal tract of humans. Their expression is significantly reduced in patients with IBD, and they are differentially expressed in specific bowel segments in patients with Crohn's disease and ulcerative colitis. The data present a link between gut inflammation and water/solute homeostasis, suggesting that AQPs may play a significant role in IBD pathophysiology.
本研究旨在调查水通道蛋白（AQP）水通道表达与人类未经治疗的早期炎症性肠病（IBD）病理特征之间的关系。
对因出现预先定义的症状（包括腹痛、腹泻和/或便血超过10天）而疑似患有IBD的患者在当地医院进行检查。进行结肠镜检查并取活检组织，同时采集血样。未符合IBD诊断标准且肠道无感染或其他病理迹象的患者被纳入有症状的非IBD对照组。通过定量实时聚合酶链反应对回肠末端和结肠活检组织中的AQP1、3、4、5、7、8和9信使核糖核酸（mRNA）水平进行定量。通过共聚焦显微镜评估所选AQP的蛋白表达。通过推导氨基酸序列的多重比对，对AQP1、3、7和8的假定三维结构进行建模。
在肠黏膜的所有部位均检测到AQP1、3、7和8的mRNA。值得注意的是，克罗恩病患者回肠中的AQP1和AQP3 mRNA水平降低，溃疡性结肠炎患者回肠和结肠中的AQP7和AQP8 mRNA水平降低。免疫荧光共聚焦显微镜显示AQP3、7和8定位于黏膜上皮，而AQP1的表达主要局限于内皮细胞和红细胞。免疫荧光证实了AQP3、7和8 mRNA水平的降低，这也表明IBD样本结肠表面上皮和隐窝中AQP8的顶端免疫标记减少。这可能表明IBD中上皮极性丧失，导致屏障功能破坏。
AQP1和8以及水甘油通道蛋白AQP3和7是主要在人类下肠道表达的AQP。它们在IBD患者中的表达显著降低，并且在克罗恩病和溃疡性结肠炎患者的特定肠段中差异表达。这些数据揭示了肠道炎症与水/溶质稳态之间的联系，表明AQP可能在IBD病理生理学中发挥重要作用。
