A SNP of bacterial blc disturbs gut lysophospholipid homeostasis and induces inflammation through epithelial barrier disruption

Dayuan Zou; Jingwen Pei; Jianfeng Lan; Hong Sang; Hongjuan Chen; Haoliang Yuan; Di Wu; Yuanyuan Zhang; Yufang Wang; Dingyu Wang; Yujie Zou; Di Chen; Jianan Ren; Xiang Gao; Zhaoyu Lin

doi:10.1016/j.ebiom.2020.102652

A SNP of bacterial blc disturbs gut lysophospholipid homeostasis and induces inflammation through epithelial barrier disruption

EBioMedicine. 2020 Feb:52:102652. doi: 10.1016/j.ebiom.2020.102652. Epub 2020 Feb 12.

Authors

Dayuan Zou¹, Jingwen Pei¹, Jianfeng Lan¹, Hong Sang², Hongjuan Chen¹, Haoliang Yuan³, Di Wu¹, Yuanyuan Zhang¹, Yufang Wang¹, Dingyu Wang¹, Yujie Zou¹, Di Chen¹, Jianan Ren⁴, Xiang Gao⁵, Zhaoyu Lin⁶

Affiliations

¹ State Key Laboratory of Pharmaceutical Biotechnology, Nanjing Drum Tower Hospital, MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing 210061, China.
² Department of Dermatology, Jinling Hospital, Medical School of Nanjing University, Nanjing 210002, China.
³ State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, Center of Drug Discovery, China Pharmaceutical University, Nanjing 210009, China.
⁴ Department of General Surgery, Jinling Hospital, Medical School of Nanjing University, Nanjing 210002, China. Electronic address: jiananr@nju.edu.cn.
⁵ State Key Laboratory of Pharmaceutical Biotechnology, Nanjing Drum Tower Hospital, MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing 210061, China. Electronic address: gaoxiang@nju.edu.cn.
⁶ State Key Laboratory of Pharmaceutical Biotechnology, Nanjing Drum Tower Hospital, MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing University, Nanjing 210061, China. Electronic address: Linzy@nju.edu.cn.

Abstract

Background: Alteration of commensal bacterial composition is associated with many inflammatory diseases. However, few studies have pinpointed the specific bacterial genes that may suppress host immune responses against microbes and maintain homeostasis in the host intestine.

Methods: High-throughput screening was performed in Caenorhabditis elegans with a single gene knockout ut screening was performed in Caenorhabditis elegans with a single gene knockout Escherichia coli (E. coli) library and identified the immune suppression gene blc. The coding sequences of blc among different kinds of E. coli strains were aligned to identify the single nucleotide polymorphisms (SNPs). Physiological and biochemical experiments were performed in C. elegans and mice to explore the function of the blc variant.

Findings: By screening 3983 E. coli mutants, we discovered that 9 bacterial genes, when deleted, activate innate immunity in the host C. elegans. Among these 9 genes, the gene encoding blc showed a distinctive SNP in many clinically pathogenic bacteria. We found that bacteria with this SNP, which converts Blc ^G84 to Blc ^E84, are highly enriched in the faeces of patients with inflammatory bowel disease (IBD). Exposure to Blc^E84-encoding bacteria resulted in epithelial barrier disruption and immune activation in both worms and mice. Detailed analysis indicated that infection with Blc^E84-encoding bacteria causes a significant decrease in LPE levels in the intestine and subsequently disrupts gut epithelial integrity in mice. Consistently, the levels of LPE in patients with IBD are significantly lower than those in healthy people. Finally, supplementation with LPE, which activates LPA₁/PLCβ/PKC signaling, reversed the defects induced by Blc^E84-encoding bacteria.

Interpretation: Our results identified a novel bacterial gene, blc, in E. coli that regulates host gut integrity and immunity. FUND: The Ministry of Science and Technology of China; the National Natural Science Foundation of China; and the Natural Science Foundation of Jiangsu Province.

Keywords: Bacterial lipocalin; Epithelial barrier; Gut homeostasis; Keio collection; lysophosphatidylethanolamine (LPE).

MeSH terms

Animals
Bacteria / genetics*
Bacteria / metabolism*
Bacterial Outer Membrane Proteins / genetics*
Base Sequence
Biomarkers
Cell Line
Disease Models, Animal
Disease Susceptibility
Escherichia coli Proteins / genetics
Homeostasis
Host-Pathogen Interactions / immunology
Humans
Inflammatory Bowel Diseases / etiology
Inflammatory Bowel Diseases / metabolism
Inflammatory Bowel Diseases / pathology
Intestinal Mucosa / metabolism*
Intestinal Mucosa / microbiology*
Intestinal Mucosa / pathology
Lipocalins / genetics*
Lysophospholipids / chemistry
Lysophospholipids / metabolism*
Male
Mice
Mutation
Permeability
Polymorphism, Single Nucleotide*

Substances

Bacterial Outer Membrane Proteins
Biomarkers
Escherichia coli Proteins
Lipocalins
Lysophospholipids
blc protein, E coli