title: Intestinal NHE8 is highly expressed in goblet cells and its expression is subject to TNF-α regulation.
abstract: While the intestine plays an important role in digestion and absorption, the mucus lining the epithelium represents a pivotal function in mucosal protection. Goblet cells are scattered in both the crypts and among enterocytes, and they secrete an important component of mucus, mucin. We have reported that sodium/hydrogen exchanger (NHE) 8 is a novel player in mucosal protection, since loss of NHE8 function resulted in reduced mucin production and increased bacterial adhesion. While NHE8 has been shown to be expressed in enterocytes and its expression is reduced during intestinal inflammation, nothing is known about the role of NHE8 in goblet cells. This current study is designed to define the expression of NHE8 and the role of TNF-α in the regulation of NHE8 in goblet cells. Using HT29-MTX cells as an in vitro model, we detected abundant NHE8 mRNA in goblet cells. Immunohistochemical staining localized NHE8 protein on the plasma membrane and in the intracellular compartments in goblet cells. Furthermore, NHE8 expression in goblet cells is regulated by the proinflammatory cytokine TNF-α. The expression of NHE8 in HT29-MTX cells was significantly reduced at both mRNA and protein levels in the presence of TNF-α. This inhibition of NHE8 mRNA expression could be blocked by the transcriptional inhibitor actinomycin D. Promoter reporter assay showed that NHE8 promoter activity was indeed reduced by TNF-α. Mechanistically, TNF-α reduced Sp3 protein binding to the human NHE8 basal promoter region. Therefore, NHE8 is expressed in goblet cells, and the inflammatory cytokine TNF-α downregulates NHE8 expression by a transcriptional mechanism.
authors.affiliation: University of Arizona Health Sciences Center, Tucson, Arizona.
authors.forename: Hua
authors.initials: H
authors.lastname: Xu
authors.affiliation: University of Arizona Health Sciences Center, Tucson, Arizona.
authors.forename: Qingtian
authors.initials: Q
authors.lastname: Li
authors.affiliation: University of Arizona Health Sciences Center, Tucson, Arizona.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: University of Arizona Health Sciences Center, Tucson, Arizona.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.affiliation: University of Arizona Health Sciences Center, Tucson, Arizona fghishan@peds.arizona.edu.
authors.forename: Fayez K
authors.initials: FK
authors.lastname: Ghishan
mesh_terms: D002460:Cell Line; D003609:Dactinomycin / Q000494:pharmacology; D020397:Goblet Cells / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D051705:Sp3 Transcription Factor / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D011500:Protein Synthesis Inhibitors; C486775:SLC9A8 protein, human; C497121:SP3 protein, human; D017923:Sodium-Hydrogen Exchangers; D014409:Tumor Necrosis Factor-alpha; D051705:Sp3 Transcription Factor; D003609:Dactinomycin
keywords: sodium/hydrogen exchanger; tumor necrosis factor-α