title: TPN-associated intestinal epithelial cell atrophy is modulated by TLR4/EGF signaling pathways.
abstract: Recent studies suggest a close interaction between epidermal growth factor (EGF) and TLR signaling in the modulation of intestinal epithelial cell (IEC) proliferation; however, how these signaling pathways adjust IEC proliferation is poorly understood. We utilized a model of total parenteral nutrition (TPN), or enteral nutrient deprivation, to study this interaction as TPN results in mucosal atrophy due to decreased IEC proliferation and increased apoptosis. We identified the novel finding of decreased mucosal atrophy in TLR4 knockout (TLR4KO) mice receiving TPN. We hypothesized that EGF signaling is preserved in TLR4KO-TPN mice and prevents mucosal atrophy. C57Bl/6 and strain-matched TLR4KO mice were provided either enteral feeding or TPN. IEC proliferation and apoptosis were measured. Cytokine and growth factor abundances were detected in both groups. To examine interdependence of these pathways, ErbB1 pharmacologic blockade was used. The marked decline in IEC proliferation with TPN was nearly prevented in TLR4KO mice, and intestinal length was partially preserved. EGF was significantly increased, and TNF-α decreased in TLR4KO-TPN versus wild-type (WT)-TPN mice. Apoptotic positive crypt cells were 15-fold higher in WT-TPN versus TLR4KO-TPN mice. Bcl-2 was significantly increased in TLR4KO-TPN mice, while Bax decreased 10-fold. ErbB1 blockade prevented this otherwise protective effect in TLR4KO-sTPN mice. TLR4 blockade significantly prevented TPN-associated atrophy by preserving proliferation and preventing apoptosis. This is driven by a reduction in TNF-α abundance and increased EGF. Potential manipulation of this regulatory pathway may have significant clinical potential to prevent TPN-associated atrophy.
authors.affiliation: *Department of Surgery, Section of Pediatric Surgery, and Center for Organogenesis, University of Michigan, Ann Arbor, Michigan, USA; and School of Medicine, Department of Pediatrics, University of Colorado, Denver, Anschutz Medical Campus, Denver, Colorado, USA.
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Freeman
authors.affiliation: *Department of Surgery, Section of Pediatric Surgery, and Center for Organogenesis, University of Michigan, Ann Arbor, Michigan, USA; and School of Medicine, Department of Pediatrics, University of Colorado, Denver, Anschutz Medical Campus, Denver, Colorado, USA.
authors.forename: Yongjia
authors.initials: Y
authors.lastname: Feng
authors.affiliation: *Department of Surgery, Section of Pediatric Surgery, and Center for Organogenesis, University of Michigan, Ann Arbor, Michigan, USA; and School of Medicine, Department of Pediatrics, University of Colorado, Denver, Anschutz Medical Campus, Denver, Colorado, USA.
authors.forename: Farokh R
authors.initials: FR
authors.lastname: Demehri
authors.affiliation: *Department of Surgery, Section of Pediatric Surgery, and Center for Organogenesis, University of Michigan, Ann Arbor, Michigan, USA; and School of Medicine, Department of Pediatrics, University of Colorado, Denver, Anschutz Medical Campus, Denver, Colorado, USA.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Dempsey
authors.affiliation: *Department of Surgery, Section of Pediatric Surgery, and Center for Organogenesis, University of Michigan, Ann Arbor, Michigan, USA; and School of Medicine, Department of Pediatrics, University of Colorado, Denver, Anschutz Medical Campus, Denver, Colorado, USA dttlbm@umich.edu.
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Teitelbaum
mesh_terms: D000818:Animals; D017209:Apoptosis; D001284:Atrophy; D049109:Cell Proliferation; D004815:Epidermal Growth Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D066246:ErbB Receptors / Q000037:antagonists & inhibitors; D000077156:Gefitinib; D007371:Interferon-gamma / Q000378:metabolism; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010289:Parenteral Nutrition, Total / Q000009:adverse effects*; D011799:Quinazolines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D011799:Quinazolines; D012333:RNA, Messenger; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D004815:Epidermal Growth Factor; D007371:Interferon-gamma; D066246:ErbB Receptors; D000077156:Gefitinib
keywords: apoptosis; epidermal growth factor; epithelial cell proliferation; mucosal atrophy; total parenteral nutrition