Secreted microbial metabolites modulate gut immunity and inflammatory tone

Abstract

Bioactive 15Running title: Production of NF-κB suppressive bioactives by the human gut microbiota 16 Abstract 20Evidence is emerging that microbiome-immune system crosstalk regulates the tenor of host 21 intestinal immunity and predisposition to inflammatory bowel disease (IBD). We identified 22five NF-B suppressive strains affiliated with Clostridium clusters IV, XIVa and XV that 23 independently suppressed secretion of the chemokine IL-8 by peripheral blood mononuclear 24 cells and gut epithelial organoids from healthy human subjects, as well as patients with the 25 predominant IBD subtypes, Crohn's disease and ulcerative colitis. The NF-B suppressive 26Clostridium bolteae AHG0001, but not C. bolteae BAA-613, suppressed cytokine-driven 27 inflammatory responses and endoplasmic reticulum stress in gut epithelial organoids derived 28 from Winnie mice that develop spontaneous colitis. This predicted in vivo responses thereby 29 validating a precision medicine approach to treat Winnie colitis and suggesting the microbiome 30 may function as an extrinsic regulator of host immunity. Finally, we identified a novel 31 molecule associated with NF-B suppression indicating gut bacteria could be harnessed to 32 develop new therapeutics. 33Inflammatory bowel disease (IBD) is comprised of two predominant subtypes, termed Crohn's 41 disease (CD) and ulcerative colitis (UC), that are characterised by relapsing and remitting gut 42 3 inflammation. The Nuclear factor-B (NF-B) family of transcription factors are master 43 regulators of gut epithelial integrity and inflammation, activation of antigen presenting cells 44 and effector leukocytes, and are important contributors to the pathogenesis of IBD. Upon 45 activation, NF-B dimers translocate to the nucleus where they regulate transcription of a wide 46 range of genes including those involved in immune and inflammatory responses 6 . In the 47 healthy gut, NF-B activation is tightly regulated 7 however several IBD genetic risk alleles 48 including nod2, TOLLIP and A20 exert their pathogenic effects at least in part through 49 dysregulated NF-B signalling 8 . Additionally, CD disease phenotype correlates with NF-B 50 activation 9 , and macrophages and epithelial cells isolated from inflamed intestine of CD and 51 UC subjects show increased activation of nuclear NF-B-p65 10 . As such, NF-B signalling 52 contributes significantly to the cascade of host-responses underlying the pathogenesis of IBD. 53The gut microbiota is increasingly recognised as an important contributory risk factor for IBD. 54Underlying this, the healthy and IBD gut microbiota differ and are characterised by structure-55 function alterations to the microbiota 11 12 , and faecal transplantation has proven effective in 56 some patients with UC 13, 14 . Such findings suggest that key members of the microbiota regulate 57 host inflammatory responses. Indeed, several bacterial taxa are not only more abundant in the 58 healthy gut but can also suppress inflammatory responses and alleviate inflammation in an...

Development of Next-Generation Probiotics by Investigating the Interrelationships between Gastrointestinal Microbiota and Diarrhea in Preruminant Holstein Calves

“…The cell-free supernatant of Pseudoflavonifractor sp. AHG0008 showed the ability to suppress IL-8 secretion by peripheral blood mononuclear cells [43,44]. However, little was known about the role of Pseudoflavonifractor in the gastrointestinal sites.…”

Microbial Metabolites, Postbiotics, and Intestinal Epithelial Function

“…A recent study from the same group showed similar results using 5 different human gut bacterial strains from the Clostridia genus, also isolated by metaparental mating. [ 21 ] Postbiotics derived from the isolated bacteria were able to suppress NF‐κB activation in a strain‐specific manner: they compared the suppressive capacity of bacterial isolates assigned to the same operational taxonomic units (≥97% 16S rRNA sequence identity) and found differences between species in their ability to repress NF‐κB activation—as also showed by others. [ 131 ] Going one step further, they also determined that the suppressive capacity of almost all the examined strains corresponded to the <3 kDa fraction of the postbiotics.…”

“…demonstrated the usefulness of organoid culture for studying the anti‐inflammatory effects derived from bacterial postbiotics. [ 21 ]…”

“…also studied the anti‐diarrheal properties of two postbiotics derived from Clostridium bolteae in Winnie mice. [ 21 ] One of the tested postbiotics not only reduced diarrhea scores, but it also significantly diminished colonic inflammation. Moreover, goblet cells (a population of mucus secreting epithelial cells) were recovered and their mucin production increased.…”

“…In fact, most of the published studies about postbiotics have not provided a description of the molecular composition underlying this “metabolite‐cocktail”. [ 19–23 ]…”