PMID- 31401143 OWN - NLM STAT- MEDLINE DCOM- 20191219 LR - 20201101 IS - 1528-0012 (Electronic) IS - 0016-5085 (Print) IS - 0016-5085 (Linking) VI - 157 IP - 5 DP - 2019 Nov TI - Inflammation-induced Occludin Downregulation Limits Epithelial Apoptosis by Suppressing Caspase-3 Expression. PG - 1323-1337 LID - S0016-5085(19)41200-6 [pii] LID - 10.1053/j.gastro.2019.07.058 [doi] AB - BACKGROUND & AIMS: Epithelial tight junctions are compromised in gastrointestinal disease. Processes that contribute to the resulting barrier loss include endocytic occludin removal from the tight junction and reduced occludin expression. Nevertheless, the relatively-normal basal phenotype of occludin knockout (KO) mice has been taken as evidence that occludin does not contribute to gastrointestinal barrier function. We asked whether stress could unmask occludin functions within intestinal epithelia. METHODS: Wildtype (WT), universal and intestinal epithelial-specific occludin KO, and villin-EGFP-occludin transgenic mice as well as WT and occludin knockdown (KD) Caco-2(BBe) cell monolayers were challenged with DSS, TNBS, staurosporine, 5-FU, or TNF. Occludin and caspase-3 expression were assessed in patient biopsies. RESULTS: Intestinal epithelial occludin loss limited severity of DSS- and TNBS-induced colitis due to epithelial resistance to apoptosis; activation of both intrinsic and extrinsic apoptotic pathways was blocked in occludin KO epithelia. Promoter analysis revealed that occludin enhances CASP3 transcription and, conversely, that occludin downregulation reduces caspase-3 expression. Analysis of biopsies from Crohn's disease and ulcerative colitis patients and normal controls demonstrated that disease-associated occludin downregulation was accompanied by and correlated with reduced caspase-3 expression. In vitro, cytokine-induced occludin downregulation resulted in reduced caspase-3 expression and resistance to intrinsic and extrinsic pathway apoptosis, demonstrating an overall protective effect of inflammation-induced occludin loss. CONCLUSIONS: The tight junction protein occludin regulates apoptosis by enhancing caspase-3 transcription. These data suggest that reduced epithelial caspase-3 expression downstream of occludin downregulation is a previously-unappreciated anti-apoptotic process that contributes to mucosal homeostasis in inflammatory conditions. CI - Copyright (c) 2019 AGA Institute. Published by Elsevier Inc. All rights reserved. FAU - Kuo, Wei-Ting AU - Kuo WT AD - Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts. FAU - Shen, Le AU - Shen L AD - Department of Pathology, The University of Chicago, Chicago, Illinois. FAU - Zuo, Li AU - Zuo L AD - Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts; Anhui Medical University, Hefei, Anhui, China. FAU - Shashikanth, Nitesh AU - Shashikanth N AD - Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts. FAU - Ong, Ma Lora Drizella M AU - Ong MLDM AD - Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts. FAU - Wu, Licheng AU - Wu L AD - Department of Pathology, The University of Chicago, Chicago, Illinois. FAU - Zha, Juanmin AU - Zha J AD - Department of Pathology, The University of Chicago, Chicago, Illinois; Soochow University and Department of Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China. FAU - Edelblum, Karen L AU - Edelblum KL AD - Department of Pathology, The University of Chicago, Chicago, Illinois; Department of Pathology and Laboratory Medicine, Center for Inflammation and Immunity, Rutgers New Jersey Medical School, Newark, New Jersey. FAU - Wang, Yitang AU - Wang Y AD - Department of Pathology, The University of Chicago, Chicago, Illinois. FAU - Wang, Yingmin AU - Wang Y AD - Department of Pathology, The University of Chicago, Chicago, Illinois. FAU - Nilsen, Steven P AU - Nilsen SP AD - Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts. FAU - Turner, Jerrold R AU - Turner JR AD - Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts; Department of Pathology, The University of Chicago, Chicago, Illinois. Electronic address: jrturner@bwh.harvard.edu. LA - eng GR - R24 DK099803/DK/NIDDK NIH HHS/United States GR - K01 DK092381/DK/NIDDK NIH HHS/United States GR - R01 DK061931/DK/NIDDK NIH HHS/United States GR - P30 DK034854/DK/NIDDK NIH HHS/United States GR - R01 DK068271/DK/NIDDK NIH HHS/United States PT - Journal Article PT - Research Support, N.I.H., Extramural PT - Research Support, Non-U.S. Gov't DEP - 20190808 PL - United States TA - Gastroenterology JT - Gastroenterology JID - 0374630 RN - 0 (OCLN protein, human) RN - 0 (Occludin) RN - 0 (Ocln protein, mouse) RN - 0 (Tjp1 protein, mouse) RN - 0 (Zonula Occludens-1 Protein) RN - 8T3HQG2ZC4 (Trinitrobenzenesulfonic Acid) RN - 9042-14-2 (Dextran Sulfate) RN - EC 3.4.22.- (CASP3 protein, human) RN - EC 3.4.22.- (Casp3 protein, mouse) RN - EC 3.4.22.- (Caspase 3) SB - IM MH - Animals MH - *Apoptosis MH - Caco-2 Cells MH - Case-Control Studies MH - Caspase 3/deficiency/genetics/*metabolism MH - Colitis/chemically induced/*enzymology/genetics/pathology MH - Colitis, Ulcerative/enzymology/pathology MH - Colon/*enzymology/pathology MH - Crohn Disease/enzymology/pathology MH - Dextran Sulfate MH - Disease Models, Animal MH - Epithelial Cells/*enzymology/pathology MH - Humans MH - Intestinal Mucosa/*enzymology/pathology MH - Mice, Inbred C57BL MH - Mice, Knockout MH - Occludin/deficiency/genetics/*metabolism MH - Signal Transduction MH - Trinitrobenzenesulfonic Acid MH - Zonula Occludens-1 Protein/genetics/metabolism PMC - PMC6815722 MID - NIHMS1536914 OTO - NOTNLM OT - Cell Death OT - Gene Regulation OT - IBD OT - Permeability COIS- The authors have declared that no conflicts of interest exist. EDAT- 2019/08/12 06:00 MHDA- 2019/12/20 06:00 PMCR- 2020/11/01 CRDT- 2019/08/12 06:00 PHST- 2019/01/03 00:00 [received] PHST- 2019/07/15 00:00 [revised] PHST- 2019/07/22 00:00 [accepted] PHST- 2019/08/12 06:00 [pubmed] PHST- 2019/12/20 06:00 [medline] PHST- 2019/08/12 06:00 [entrez] PHST- 2020/11/01 00:00 [pmc-release] AID - S0016-5085(19)41200-6 [pii] AID - 10.1053/j.gastro.2019.07.058 [doi] PST - ppublish SO - Gastroenterology. 2019 Nov;157(5):1323-1337. doi: 10.1053/j.gastro.2019.07.058. Epub 2019 Aug 8.