title: AMP-18 protects barrier function of colonic epithelial cells: role of tight junction proteins.
abstract: Antrum mucosal protein (AMP)-18 and a synthetic peptide of amino acids 77-97 have mitogenic and motogenic properties for epithelial cells. The possibility that AMP-18 is also protective was evaluated in the colonic mucosa of mice and monolayer cultures of human colonic epithelial Caco-2/bbe (C2) cells. Administration of AMP peptide to mice with dextran sulfate sodium (DSS)-induced colonic injury delayed the onset of bloody diarrhea and reduced weight loss. Treatment of C2 cells with AMP peptide protected monolayers against decreases in transepithelial electrical resistance induced by the oxidant monochloramine, indomethacin, or DSS. A molecular mechanism for these barrier-protective effects was sought by asking whether AMP peptide acted on specific tight junction (TJ) proteins. Immunoblots of detergent-insoluble fractions of C2 cells treated with AMP peptide exhibited increased accumulation of specific TJ proteins. Occludin immunoreactivity was also increased in detergent-insoluble fractions obtained from colonic mucosal cells of mice injected with AMP peptide. Observations using laser scanning confocal (CF) microscopy supported the capacity of AMP peptide to enhance accumulation of occludin and zonula occludens-1 in TJ domains of C2 cell monolayers and together with immunoblot analysis showed that the peptide protected against loss of these TJ proteins following oxidant injury. AMP peptide also protected against a fall in TER during disruption of actin filaments by cytochalasin D and stabilized perijunctional actin during oxidant injury when assessed by CF. These findings suggest that AMP-18 could protect the intestinal mucosal barrier by acting on specific TJ proteins and stabilizing perijunctional actin.
authors.affiliation: Department of Medicine, The University of Chicago, Chicago, IL 60637, USA.
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Walsh-Reitz
authors.forename: Erick F
authors.initials: EF
authors.lastname: Huang
authors.forename: Mark W
authors.initials: MW
authors.lastname: Musch
authors.forename: Eugene B
authors.initials: EB
authors.lastname: Chang
authors.forename: Terence E
authors.initials: TE
authors.lastname: Martin
authors.forename: Sreedharan
authors.initials: S
authors.lastname: Kartha
authors.forename: F Gary
authors.initials: FG
authors.lastname: Toback
mesh_terms: D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D018938:Caco-2 Cells; D002478:Cells, Cultured; D003106:Colon / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004285:Dogs; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007668:Kidney / Q000166:cytology; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008934:Mitogens / Q000138:chemical synthesis / Q000494:pharmacology*; D008969:Molecular Sequence Data; D062793:Occludin; D036361:Peptide Hormones; D010455:Peptides; D010750:Phosphoproteins / Q000378:metabolism; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism*; D062826:Zonula Occludens-1 Protein
chemical_list: D000199:Actins; C477000:GKN1 protein, human; D008565:Membrane Proteins; D008934:Mitogens; C568985:OCLN protein, human; D062793:Occludin; C568986:Ocln protein, mouse; D036361:Peptide Hormones; D010455:Peptides; D010750:Phosphoproteins; C569042:TJP1 protein, human; C569043:Tjp1 protein, mouse; D062826:Zonula Occludens-1 Protein