Basic Study
Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Aug 28, 2020; 26(32): 4763-4785
Published online Aug 28, 2020. doi: 10.3748/wjg.v26.i32.4763
Immune and microRNA responses to Helicobacter muridarum infection and indole-3-carbinol during colitis
Rasha Raheem Alkarkoushi, Yvonne Hui, Abbas S Tavakoli, Udai Singh, Prakash Nagarkatti, Mitzi Nagarkatti, Ioulia Chatzistamou, Marpe Bam, Traci L Testerman
Rasha Raheem Alkarkoushi, Yvonne Hui, Prakash Nagarkatti, Mitzi Nagarkatti, Ioulia Chatzistamou, Marpe Bam, Traci L Testerman, Department of Pathology, Microbiology and Immunology, University of South Carolina School of Medicine, Columbia, SC 29209, United States
Abbas S Tavakoli, College of Nursing, University of South Carolina, University of South Carolina, Columbia, SC 29208, United States
Udai Singh, Department of Medicine, Hematology and Oncology, University of Virginia School of Medicine, Charlottesville, VA 22908, United States
Author contributions: Alkarkoushi RR, Hui Y, Tavakoli AS, Testerman TL and Singh U assisted with conceptualization, performed experiments, analyzed data, and drafted the manuscript; Nagarkatti P and Nagarkatti M assisted with conceptualization and funding acquisition; Chatzistamou I performed histopathological analysis; Bam M analyzed microRNA data; Testerman TL conceptualized assisted with funding acquisition, and wrote and edited the manuscript.
Supported by the National Institutes of Health, No. P20GM103641.
Institutional review board statement: This study did not involve human subjects.
Institutional animal care and use committee statement: All experimental procedures were conducted in accordance with the guidelines for the use of experimental animals and were approved by the Institutional Review Committee on Animal Care and Use at the University of South Carolina.
Conflict-of-interest statement: The authors have nothing to disclose.
Data sharing statement: Raw data have been provided as supplemental material.
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 that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (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:
Corresponding author: Traci L Testerman, PhD, Assistant Professor, Department of Pathology, Microbiology and Immunology, University of South Carolina School of Medicine, 6439 Garners Ferry Road, Columbia, SC 29209, United States.
Received: March 19, 2020
Peer-review started: March 20, 2020
First decision: April 8, 2020
Revised: July 16, 2020
Accepted: August 12, 2020
Article in press: August 12, 2020
Published online: August 28, 2020

Indole-3-carbinol (I3C) and other aryl hydrocarbon receptor agonists are known to modulate the immune system and ameliorate various inflammatory and autoimmune diseases in animal models, including colitis induced by dextran sulfate sodium (DSS). MicroRNAs (miRNAs) are also gaining traction as potential therapeutic agents or diagnostic elements. Enterohepatic Helicobacter (EHH) species are associated with an increased risk of inflammatory bowel disease, but little is known about how these species affect the immune system or response to treatment.


To determine whether infection with an EHH species alters the response to I3C and how the immune and miRNA responses of an EHH species compare with responses to DSS and inflammatory bowel disease.


We infected C57BL/6 mice with Helicobacter muridarum (H. muridarum), with and without DSS and I3C treatment. Pathological responses were evaluated by histological examination, symptom scores, and cytokine responses. MiRNAs analysis was performed on mesenteric lymph nodes to further evaluate the regional immune response.


H. muridarum infection alone caused colonic inflammation and upregulated proinflammatory, macrophage-associated cytokines in the colon similar to changes seen in DSS-treated mice. Further upregulation occurred upon treatment with DSS. H. muridarum infection caused broad changes in mesenteric lymph node miRNA expression, but colitis-associated miRNAs were regulated similarly in H. muridarum-infected and uninfected, DSS-treated mice. In spite of causing colitis exacerbation, H. muridarum infection did not prevent disease amelioration by I3C. I3C normalized both macrophage- and T cell-associated cytokines.


Thus, I3C may be useful for inflammatory bowel disease patients regardless of EHH infection. The miRNA changes associated with I3C treatment are likely the result of, rather than the cause of immune response changes.

Keywords: Helicobacter muridarum, MicroRNA, Immune, T regulatory cell, T helper 17 cell, Colitis, Cytokine

Core tip: The immune response to Helicobacter muridarum (H. muridarum), an enterohepatic Helicobacter species, mimics responses seen during chemically induced colitis and human inflammatory bowel disease (IBD) in terms of local and systemic cytokine responses and microRNA changes. Most microRNAs that are altered in IBD are also altered by H. muridarum infection with or without dextran sodium sulfate treatment. Furthermore, H. muridarum does not alter activity of an aryl hydrocarbon receptor agonist, indole-3-carbinol, a natural compound being explored as a treatment for IBD. Therefore, H. muridarum infection provides a viable model for predicting the effects of enterohepatic Helicobacter species on IBD.