Characterisation of a new bacterial ligand for PPARy
(2019) United European Gastroenterology Week — Location: Barcelona, Spain
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- Abstract
- Data from clinical research suggest that certain probiotic bacterial strains have the potential to modulate colonic inflammation in patients with inflammatory bowel diseases. Nonetheless, this data differs considerably among studies due to the probiotic bacterial strains used and the poor knowledge of their mechanisms of action. The aim of our study was to better characterize the mechanisms of the anti-inflammatory activity of Escherichia coli Nissle 1917 (EcN), a probiotic used for the treatment of multiple intestinal disorders Lipids were extracted from pathogenic Escherichia coli (E. coli) strains UTI, Nu14, SP15, CFT, NC101, from an asymptomatic E. coli ABU, from a commensal E. coli M1/5 and from the probiotic EcN. For identification, lipid extracts were analyzed by liquid chromatography coupled to high resolution mass spectrometry and by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) for quantification. To assess the passage of 3-hydroxyoctadecaenoic acid (C18-3OH) across the intestinal barrier, we used caco2 cells differentiated in transwell and colon biopsies in Ussing chambers. Time-resolved fluorescence resonance energy transfer (TR-FRET)-based competitive binding assay was performed to assess the C18-3OH peroxisome proliferator activated receptor gamma (PPARy-agonist properties. Mice received an oral administration of C18-3OH and were injected with a PPARy antagonist (GW9662, IP). Concentration of C18-3OH and mRNA expression of genes dependent on PPARy activation (Fiaf and Lfabp) were quantified in mice colons. In order to test the impact of the C18-3OH on colitis, mice have been submitted to a DSS-induced colitis model and to oral administration of C18-3OH. Intensity of colitis was determined by the quantification macroscopic and microscopic scores, paracellular permeability, pro-inflammatory and pro-resolving lipids and mRNA expression of protein implicated in barrier functions (Zo1, Occludin, Muc2, …), chemokines (Cxcl1, Cxcl2,…) and cytokines (IL6, IL1b, …). In EcN we identified and quantified free long chain fatty acids (LCFA) from 8 to 18 carbons hydroxylated on the 3rd carbon. The concentration of C18-3OH was increased in EcN compared to other E. coli strains. This bacterial lipid was not able to cross caco2 cells in transwell or tissue in Ussing chambers but penetrated the cells. The C18-3OH bonded the receptor-binding site of PPARy. Oral administration of C18-3OH increased its concentration at the colonic level and increased Fiaf and Lfabp mRNA expression; treatment with a PPAR antagonist inhibited these effects. C18-3OH treatment to mice with DSS-induced colitis significantly decreased paracellular permeability, colon thickness, macroscopic and microscopic scores and pro inflammatory lipid concentration compared to DSS-treated mice. In addition, the C18-3OH decreased Reg3y, Zo1, Cxcl1 and Cxcl2 mRNA expression. The C18-3OH could therefore represent a new endogenous PPAR agonist produced by bacteria with an anti-inflammatory activity.
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Petitfils, C., & et al. (2019). Characterisation of a new bacterial ligand for PPARy. United European Gastroenterology Week, Barcelona, Spain.