Basic Study
Copyright ©The Author(s) 2018. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Oct 14, 2018; 24(38): 4341-4355
Published online Oct 14, 2018. doi: 10.3748/wjg.v24.i38.4341
Temporal clinical, proteomic, histological and cellular immune responses of dextran sulfate sodium-induced acute colitis
Natalia Schneider Nunes, Saejeong Kim, Maggie Sundby, Parwathy Chandran, Scott Robert Burks, Ana Helena Paz, Joseph Alan Frank
Natalia Schneider Nunes, Saejeong Kim, Maggie Sundby, Parwathy Chandran, Scott Robert Burks, Joseph Alan Frank, Frank Laboratory, Radiology and Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, MD 20892, United States
Natalia Schneider Nunes, Ana Helena Paz, Gastroenterology and Hepatology Sciences Graduate Program, Universidade Federal do Rio Grande do Sul, Porto Alegre 90035-093, Brazil
Joseph Alan Frank, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, United States
Author contributions: Nunes NS, Paz AH and Frank JA assisted in research design; Nunes NS carried out the research; Nunes NS and Frank JA analyzed data and wrote manuscript; Sundby M and Paz AH assisted with histological analysis; Kim S and Chandran P assisted with flow cytometry analysis; Burks SR assisted with proteomic analysis; all authors reviewed and approved manuscript.
Institutional animal care and use committee statement: All procedures involving animal subjects were reviewed and approved by the Animal Care and Use Committee of the Clinical Center at the National Institutes of Health (ACUC protocol number: LDRR16-02).
Conflict-of-interest statement: The authors declare that they have no conflict-of-interests.
Data sharing statement: Materials used for the current study are available from the corresponding author on reasonable request.
ARRIVE guidelines statement: The authors have read the ARRIVE guidelines, and the manuscript was prepared and revised according to the ARRIVE guidelines.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Natalia S Nunes, PhD, Frank Laboratory, Radiology and Imaging Sciences, Clinical Center, National Institutes of Health, Bldg 10 Room B1N256, 10 Center Drive, Bethesda, MD 20892, United States. natalia.schneidernunes@nih.gov
Telephone: +1-301-9063353
Received: June 21, 2018
Peer-review started: June 21, 2018
First decision: August 1, 2018
Revised: August 6, 2018
Accepted: August 24, 2018
Article in press: August 24, 2018
Published online: October 14, 2018
ARTICLE HIGHLIGHTS
Research background

Ulcerative colitis (UC) is an inflammatory bowel disease that affects the colon and the rectum, being characterized by uncontrolled immune response and inflammation. There is no specific cause for this disease and no current treatment that provides sustained remission. The animal model of colitis induced by dextran sulfate sodium (DSS) is largely used as a tool to better investigate human UC. Although not completely understood, DSS induces an uncontrolled immune response through disruption of the epithelial layer, providing a higher access of antigens to the colonic mucosa, this way perpetuating inflammation and tissue destruction.

Research motivation

There is no current study providing a detailed integrative temporal analysis of DSS-induced acute colitis regarding clinical symptoms, proteomics, immune cell profile and histology. Understanding the interaction of these factors may contribute to the research of novel UC therapies.

Research objectives

The aim of this study was to compare different concentrations of DSS in the induction of acute colitis, followed by a temporal analysis of clinical symptoms, colon proteomics, immune cell profile and histology of the most characteristic presentation of colitis amongst the different DSS concentrations. The changes seen throughout the 8 d may provide a clearer understanding of the DSS model mechanisms.

Research methods

1%, 2% and 3% DSS in drinking water was used for the induction of acute colitis. Clinical symptoms were daily scored for weight loss, stool consistency and blood in the stool. After 8 d, colon, spleen and mesenteric lymph nodes (MLN) were collected. Histological scores were evaluated through HE staining and grading of colonic samples for inflammation, extent, regeneration, crypt damage and percent of involvement. Colon proteomics was analyzed through multiplex ELISA for 3% DSS at different time points, in addition to immune cell profiling of the colon, spleen and MLN through immunohistochemistry and flow cytometry for B220+, CD4+, CD8+, CD25+ and F4/80+ cells.

Research results

Severity of colitis is related to the increase in DSS concentration. When analyzing 3% DSS-induced colitis, worsening of histological inflammation agrees with an increase of immune cells’ influx to the colon and changes in the pro- and anti-inflammatory cytokines colonic profile. Macrophages are the first ones to respond to the damage caused by DSS, followed by changes in the colonic cytokine profile and influx of CD25+ T cells. Next, there is an increase in colonic CD4+ and CD8+ T cells and the highest level of pro-inflammatory cytokines is seen at day 8. Levels of T cells are progressively decreased in the spleen and MLN, while worsening of clinical symptoms corresponds with the progressive increase in histological inflammation, with exception of day 8.

Research conclusions

Our study demonstrates the correlated temporal changes of clinical, proteomic, immunological and histological characteristics of DSS-induced acute colitis. There is an important initial response by the innate immune system, mainly coordinated by macrophages, followed by increasing inflammation, further tissue damage and influx of T cells. T cells may be leaving the secondary lymphoid organs progressively towards the gut, as a response to the changes in colonic cytokine levels. There is a mixed response of pro- and anti-inflammatory cytokines in the colon, with the highest increase occurring after DSS withdrawal. Interestingly, amelioration of clinical symptoms is seen on day 8, demonstrating a mismatch to the histological/immunological/proteomic worsening of the disease. Since histological inflammation is seen in UC patients with endoscopic and clinical remission, this model could be used as a tool for the development of novel therapies targeting complete remission and prevention of disease relapse.

Research perspectives

Our study demonstrates that no individual factor develops this disease model, but rather a coordination between anti- and pro-inflammatory cytokines. Therefore, researchers should seriously consider a temporal analysis before investigating new therapies. The disease course here described would be highly recommended for the study of novel treatments aiming resolution of histological inflammation during disease remission. Further temporal analysis of DSS-induced chronic colitis would add to a better understanding of this animal model.