Basic Study
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World J Gastroenterol. Sep 21, 2021; 27(35): 5946-5957
Published online Sep 21, 2021. doi: 10.3748/wjg.v27.i35.5946
Proteomics identifies a novel role of fibrinogen-like protein 1 in Crohn’s disease
Xue-Liang Sun, Li-Chao Qiao, Jing Gong, Ke Wen, Zhi-Zhong Xu, Bo-Lin Yang
Xue-Liang Sun, Li-Chao Qiao, Jing Gong, Bo-Lin Yang, First Clinical Medical College, The Affiliated Hospital of Nanjing University of Chinese Medicine, Nanjing 210029, Jiangsu Province, China
Xue-Liang Sun, Ke Wen, Zhi-Zhong Xu, Department of Colorectal Surgery, Suzhou TCM Hospital Affiliated to Nanjing University of Chinese Medicine, Suzhou 215000, Jiangsu Province, China
Bo-Lin Yang, Department of Colorectal Surgery, Jiangsu Province Hospital of Chinese Medicine, Nanjing 210029, Jiangsu Province, China
Author contributions: Sun XL and Yang BL contributed to designing the study; Sun XL, Qiao LC and Gong J contributed to performing the experiments; Wen K and Xu ZZ contributed to sample collection and statistical analysis; Sun XL and Qiao LC contributed to manuscript drafting; all authors made critical revisions to the manuscript and approved the final version of the article to be published.
Supported by National Natural Science Foundation of China, No. 82074431; The Open Projects of the Discipline of Chinese Medicine of Nanjing University of Chinese Medicine Supported by the Subject of Academic Priority Discipline of Jiangsu Higher Education Institutions, No. ZYX03KF034; and Suzhou Municipal Science and Technology Bureau, No. SYSD2020253 and No. SS202085.
Institutional review board statement: The study was approved by the Ethics Committee of the Affiliated Hospital of Nanjing University of Chinese Medicine (2018NL-171-02).
Conflict-of-interest statement: To the best of our knowledge, no conflict of interest exists.
Data sharing statement: No additional data are available.
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: http://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Bo-Lin Yang, MD, Chief Doctor, First Clinical Medical College, The Affiliated Hospital of Nanjing University of Chinese Medicine, No. 155 Hanzhong Road, Nanjing 210029, Jiangsu Province, China. yfy0051@njucm.edu.cn
Received: March 5, 2021
Peer-review started: March 5, 2021
First decision: April 5, 2021
Revised: April 7, 2021
Accepted: August 10, 2021
Article in press: August 10, 2021
Published online: September 21, 2021
Processing time: 194 Days and 4 Hours
Abstract
BACKGROUND

Crohn’s disease (CD) is an incurable intestinal disorder with unclear etiology and pathogenesis. Currently, there is a lack of specific biomarkers and drug targets for CD in clinical practice. It is essential to identify the precise pathophysiological mechanism of CD and investigate new therapeutic targets.

AIM

To explore a new biomarker and therapeutic target for CD and verify its role in the CD pathological mechanism.

METHODS

Proteomics was performed to quantify the protein profile in the plasma of 20 CD patients and 20 matched healthy controls. Hub genes among the selected differentially expressed proteins (DEPs) were detected via the MCODE plugin in Cytoscape software. The expression level of one hub gene with an immunoregulatory role that interested us was verified in the inflamed intestinal tissues of 20 CD patients by immunohistochemical analysis. After that, the effects of the selected hub gene on the intestinal inflammation of CD were identified in a CD cell model by examining the levels of proinflammatory cytokines by enzyme-linked immunosorbent assays and the expression of the NF-κB signalling pathway by quantitative real-time PCR analysis and Western blot assays.

RESULTS

Thirty-five DEPs were selected from 393 credible proteins identified by proteomic analysis. Among the DEPs, fibrinogen-like protein 1 (FGL1), which attracted our attention due to its function in the regulation of the immune response, had 1.722-fold higher expression in the plasma of CD patients and was identified as a hub gene by MCODE. Furthermore, the expression of FGL1 in the intestinal mucosal and epithelial tissues of CD patients was also upregulated (P < 0.05). In vitro, the mRNA levels of FGL1 and NF-κB; the protein expression levels of FGL1, IKKα, IKKβ, p-IKKα/β, p-IκBα, and p-p65; and the concentrations of the proinflammatory cytokines IL-1β, IL-6, IL-17, and TNF-α were increased (P < 0.05) after stimulation with lipopolysaccharide, which were reversed by knockdown of FGL1 with siRNA transfection (P < 0.05). Conversely, FGL1 overexpression enhanced the abovementioned results (P < 0.05).

CONCLUSION

FGL1 can induce intestinal inflammation by activating the canonical NF-κB signalling pathway, and it may be considered a potential biomarker and therapeutic target for CD.

Keywords: Crohn’s disease; Fibrinogen-like protein 1; Proteomics; NF-κB pathway

Core Tip: In this study, fibrinogen-like protein 1 (FGL1) was identified to be significantly upregulated in the plasma and intestinal mucosa of Crohn’s disease (CD) patients. In vitro, silencing FGL1 downregulated the levels of the proinflammatory cytokines IL-1β, IL-6, IL-17, and TNF-α. Furthermore, FGL1 knockdown suppressed the mRNA expression of NF-κB and the protein levels of IKKα, IKKβ, p-IKKα/β, p-IκBα, and p-p65. These results could be reversed by the overexpression of FGL1. Taken together, these data suggest that FGL1 may induce intestinal inflammation by activating the canonical NF-κB signalling pathway and has the potential to be a therapeutic target for CD.