Crohn’s disease proteolytic microbiota enhances inflammation through PAR2 pathway in gnotobiotic mice

ABSTRACT

Emerging evidence implicates microbial proteolytic activity in ulcerative colitis (UC), but whether it also plays a role in Crohn’s disease (CD) remains unclear. We investigated the effects of colonizing adult and neonatal germ-free C57BL/6 mice with CD microbiota, selected based on high (CD-HPA) or low fecal proteolytic activity (CD-LPA), or microbiota from healthy controls with LPA (HC-LPA) or HPA (HC-HPA). We then investigated colitogenic mechanisms in gnotobiotic C57BL/6, and in mice with impaired Nucleotide-binding Oligomerization Domain-2 (NOD2) and Protease-Activated Receptor 2 (PAR2) cleavage resistant mice (Nod2^−/−; R38E-PAR2 respectively). At sacrifice, total fecal proteolytic, elastolytic, and mucolytic activity were analyzed. Microbial community and predicted function were assessed by 16S rRNA gene sequencing and PICRUSt2. Immune function and colonic injury were investigated by inflammatory gene expression (NanoString) and histology. Colonization with HC-LPA or CD-LPA lowered baseline fecal proteolytic activity in germ-free mice, which was paralleled by lower acute inflammatory cell infiltrate. CD-HPA further increased proteolytic activity compared with germ-free mice. CD-HPA mice had lower alpha diversity, distinct microbial profiles and higher fecal proteolytic activity compared with CD-LPA. C57BL/6 and Nod2^−/− mice, but not R38E-PAR2, colonized with CD-HPA had higher colitis severity than those colonized with CD-LPA. Our results indicate that CD proteolytic microbiota is proinflammatory, increasing colitis severity through a PAR2 pathway.

KEYWORDS:

• Crohn’s disease
• proteolytic activity
• inflammation
• DSS-induced colitis
• Proteinase-activated receptor 2 (PAR2)
• gnotobiotic mice

Acknowledgments

The authors thank the staff at the Axenic Gnotobiotic Unit in McMaster University, Joe Notarangelo, Michael Rosati, and Sarah Armstrong for their assistance in mouse care. The authors thank the clinical team at McMaster University, Pedro Miranda, Andrea Nardelli, and Rajka Borojevic. We also thank the McMaster Genome Facility for technical support with 16S rRNA gene sequencing and NanoString assays.

Disclosure statement

EFV is Member of the Biocodex International and National (Canada) Scientific Review Boards, Member of the Center for Gut Microbiome Research and Education Scientific Advisory Board of the AGA, Secretary of the International Society of the Study of Celiac Disease, and holds grants from Kallyope and Codexis, unrelated to this study.

Data availability statement

All sequencing data have been deposited in the Sequence Read Archive (SRA). 16S rRNA gene sequencing data used in this study can be accessed under BioProject ID PRJNA861238 at https://www.ncbi.nlm.nih.gov/bioproject/PRJNA861238.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/19490976.2023.2205425

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This study was funded by a CIHR Project Grant (PJT-478700) and by a Weston Family Foundation Proof-of-Principle grant to EFV and HJG and a CCC-GIA to EFV who also holds a Tier 1 Canada Research Chair in Microbial Therapeutics and Nutrition in Gastroenterology. AS received a Farncombe Postdoctoral Fellowship Award from McMaster University and an Elevate Postdoctoral Fellowship Award. AH received an Elevate Masters research scholarship. JL received an IMAGINE-CIHR-CAG postdoctoral research fellowship. KJ holds a Vanier Canada Graduate Scholarship. WR is supported by the German Research Foundation (Project Number 318346496, SFB1292/2 TP02). AC holds a Paul Douglas Chair in Intestinal Research. PB holds the Richard Hunt-AstraZeneca Chair in Gastroenterology. RR is supported by a CIHR grant (376560).