Oral Presentation 14th Lorne Infection and Immunity 2024

Specific gut microbiota modulates intestinal epithelial cell signalling and inflammation (#58)

Michelle Chonwerawong 1 2 , Gemma DAdamo 1 2 , Linden J Gearing 1 2 , Vanessa Rossetto Marcelino 3 4 , Jodee A Gould 1 5 , Emily L Rutten 1 2 , Trevor J Wilson 5 , Tamblyn Thomason 1 2 , Emily L Gulliver 1 2 , Kitty McCaffrey 1 2 , Eva Chan 1 2 , Garrett Ng 1 2 , Paul J Hertzog 1 2 , Edward M Giles 1 6 , Samuel C Forster 1 2
  1. Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, VIC, Australia
  2. Department of Molecular and Translational Sciences, Monash University, Clayton, VIC, Australia
  3. Melbourne Integrative Genomics, The Univerity of Melbourne, Melbourne, VIC, Australia
  4. Department of Microbiology and Immunology, Peter Doherty Institute, Melbourne, VIC, Australia
  5. MHTP Medical Genomics Facility, Hudson Institute of Medical Research, Clayton, VIC, Australia
  6. Department of Paediatrics, Monash Health, Clayton, VIC, Australia

The gastrointestinal microbiome plays key roles in the development and modulation of innate immune responses. Despite these known associations, mechanistic understanding of the host-microbiota interactions in the gut remains poorly understood. This greatly limits our ability to functionally define the role of the microbiome in heterogenous diseases associated with the gut such as inflammatory bowel disease (IBD). We performed site-specific bacterial culturing on patient intestinal biopsies (IBD and control) and integrated this culture-dependent approach with bacterial metagenomic and host transcriptional analysis. We found that specific bacterial clades that were closely related phylogenetically, were associated with distinct host inflammatory signatures. Co-culturing these bacteria with Caco2 epithelial cells and colonic organoid monolayers demonstrated a clade-specific cell death phenotype associated with the unfolded protein response (UPR) and endoplasmic reticulum (ER) stress pathways which are signalling processes known to be associated with regulation of epithelial cells and intestinal immunity implicated in IBD. This phenotype was dependent on direct bacterial-cell contact with Caco2 cells; however, the response was abrogated upon treatment of cells with heat-killed bacteria. In addition, we demonstrated that the cytokine IL-6, was induced following stimulation of Caco2 cells with clade-specific bacteria. Cell-free conditioned media from bacterial-stimulated epithelial cells also resulted in transcriptional modulation of ER stress pathways in Caco2 cells suggesting that there may be microbial and host mediators previously unknown that act to regulate epithelial cell death and stress signalling associated with intestinal inflammatory responses. Given that there are significant knowledge gaps in the pathophysiology of IBD and the microbiome, a comprehensive understanding of how specific bacteria modulate host cell responses will provide insight into the development of targeted microbial-based treatments for IBD and for microbiome-related diseases beyond the gut.