Saeedi Bejan J, Kao Daniel J, Kitzenberg David A, Dobrinskikh Evgenia, Schwisow Kayla D, Masterson Joanne C, Kendrick Agnieszka A, Kelly Caleb J, Bayless Amanda J, Kominsky Douglas J, Campbell Eric L, Kuhn Kristine A, Furuta Glenn T, Colgan Sean P, Glover Louise E
Mucosal Inflammation Program, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045.
Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus, Aurora, CO 80045.
Mol Biol Cell. 2015 Jun 15;26(12):2252-62. doi: 10.1091/mbc.E14-07-1194. Epub 2015 Apr 22.
Intestinal epithelial cells (IECs) are exposed to profound fluctuations in oxygen tension and have evolved adaptive transcriptional responses to a low-oxygen environment. These adaptations are mediated primarily through the hypoxia-inducible factor (HIF) complex. Given the central role of the IEC in barrier function, we sought to determine whether HIF influenced epithelial tight junction (TJ) structure and function. Initial studies revealed that short hairpin RNA-mediated depletion of the HIF1β in T84 cells resulted in profound defects in barrier and nonuniform, undulating TJ morphology. Global HIF1α chromatin immunoprecipitation (ChIP) analysis identified claudin-1 (CLDN1) as a prominent HIF target gene. Analysis of HIF1β-deficient IEC revealed significantly reduced levels of CLDN1. Overexpression of CLDN1 in HIF1β-deficient cells resulted in resolution of morphological abnormalities and restoration of barrier function. ChIP and site-directed mutagenesis revealed prominent hypoxia response elements in the CLDN1 promoter region. Subsequent in vivo analysis revealed the importance of HIF-mediated CLDN1 expression during experimental colitis. These results identify a critical link between HIF and specific tight junction function, providing important insight into mechanisms of HIF-regulated epithelial homeostasis.
肠上皮细胞（IECs）暴露于氧张力的剧烈波动中，并已进化出对低氧环境的适应性转录反应。这些适应主要通过缺氧诱导因子（HIF）复合体介导。鉴于IEC在屏障功能中的核心作用，我们试图确定HIF是否影响上皮紧密连接（TJ）的结构和功能。初步研究表明，短发夹RNA介导的T84细胞中HIF1β缺失导致屏障功能严重缺陷以及TJ形态不均匀、起伏不平。全局HIF1α染色质免疫沉淀（ChIP）分析确定闭合蛋白-1（CLDN1）是一个重要的HIF靶基因。对HIF1β缺陷型IEC的分析显示CLDN1水平显著降低。在HIF1β缺陷型细胞中过表达CLDN1可导致形态异常的消退和屏障功能的恢复。ChIP和定点诱变揭示了CLDN1启动子区域存在显著的缺氧反应元件。随后的体内分析揭示了HIF介导的CLDN1表达在实验性结肠炎中的重要性。这些结果确定了HIF与特定紧密连接功能之间的关键联系，为深入了解HIF调节上皮内环境稳定的机制提供了重要线索。
