title: Tight Junction Ultrastructure Alterations in a Mouse Model of Enteral Nutrient Deprivation.
abstract: Total parenteral nutrition (TPN), a necessary treatment for patients who cannot receive enteral nutrition, is associated with infectious complications due in part to a loss of intestinal epithelial barrier function (EBF). Using a mouse model of TPN, with enteral nutrient deprivation, we previously demonstrated an increase in mucosal interferon-γ and tumor necrosis factor-α; these cytokine changes are a major mediator driving a reduction in epithelial tight junction (TJ) protein expression. However, the exact ultrastructural changes to the intestinal epithelial barrier have not been previously described.
  
  
  
  We hypothesized that TPN dependence results in ultrastructural changes in the intestinal epithelial TJ meshwork.
  
  
  
  C57BL/6 mice underwent internal jugular venous cannulation and were given enteral nutrition or TPN with enteral nutrient deprivation for 7 days. Freeze-fracture electron microscopy was performed on ileal tissue to characterize changes in TJ ultrastructure. EBF was measured using transepithelial resistance and tracer permeability, while TJ expression was measured via Western immunoblotting and immunofluorescence staining.
  
  
  
  While strand density, linearity, and appearance were unchanged, TPN dependence led to a mean reduction in one horizontal strand out of the TJ compact meshwork to a more basal region, resulting in a reduction in meshwork depth. These findings were correlated with the loss of TJ localization of claudin-4 and tricellulin, reduced expression of claudin-5 and claudin-8, and reduced ex vivo EBF.
  
  
  
  Tight junction ultrastructural changes may contribute to reduced EBF in the setting of TPN dependence.
authors.affiliation: Section of Pediatric Surgery, Department of Surgery, Mott Children's Hospital, University of Michigan Health System, 1540 E. Hospital Dr., SPC 4211, Ann Arbor, MI, 48109-4211, USA. fdemehri@med.umich.edu.
authors.forename: Farokh R
authors.identifier: 0000-0002-9662-8470
authors.initials: FR
authors.lastname: Demehri
authors.affiliation: Institute of Clinical Physiology, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Susanne M
authors.initials: SM
authors.lastname: Krug
authors.affiliation: Section of Pediatric Surgery, Department of Surgery, Mott Children's Hospital, University of Michigan Health System, 1540 E. Hospital Dr., SPC 4211, Ann Arbor, MI, 48109-4211, USA.
authors.forename: Yongjia
authors.initials: Y
authors.lastname: Feng
authors.affiliation: Institute of Clinical Physiology, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: In-Fah M
authors.initials: IF
authors.lastname: Lee
authors.affiliation: Institute of Clinical Physiology, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Joerg D
authors.initials: JD
authors.lastname: Schulzke
authors.affiliation: Section of Pediatric Surgery, Department of Surgery, Mott Children's Hospital, University of Michigan Health System, 1540 E. Hospital Dr., SPC 4211, Ann Arbor, MI, 48109-4211, USA.
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Teitelbaum
mesh_terms: D000818:Animals; D005614:Freeze Fracturing; D007413:Intestinal Mucosa / Q000166:cytology* / Q000187:drug effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008854:Microscopy, Electron / Q000379:methods; D010289:Parenteral Nutrition, Total / Q000009:adverse effects*; D019108:Tight Junctions / Q000187:drug effects / Q000648:ultrastructure*
keywords: Epithelial barrier function; Freeze-fracture electron microscopy; Parenteral nutrition; Small intestine; Tight junction