Biology subjects

Overstreet, A.-M. C.

Publications and source records attributed to Overstreet, A.-M. C..

3 recordsLinked to original sources

bioRxiv2026

CFTR dysfunction in the intestinal epithelium is sufficient to promote pathogenic expansion of E. coli and enhanced barrier permeability in cystic fibrosis

Changes in the gut microbiome in cystic fibrosis (CF) are well characterized, yet their causes and downstream effects remain largely unknown. Well-documented alterations include reduced overall complexity (i.e. alpha diversity) of the gut microbiota and increased relative abundance of E. coli, which are associated with greater inflammation and shorter stature in infants. Previous results from our laboratory using a germ-free cystic fibrosis transmembrane conductance regulator (Cftr) mutant mouse model (CF mouse) demonstrated that the observed fecal microbiome dysbiosis is driven by mutated Cftr independent of factors such as diet or antibiotic treatment. We expand on these results in this report by using the defined 8-member community Altered Schaedler Flora (ASF) with and without E. coli, to show that E. coli is pathogenic in the context of the CF gut microbiome, resulting in increased intestinal permeability. We also show that Cftr deletion in intestinal epithelial cells alone, using a Villin-Cre targeted model, is sufficient to raise E. coli abundance in the fecal microbiome, increase intestinal permeability, and amplify the number of TH17 cells in the mesenteric lymph nodes. Together, our results demonstrate that the intestinal epithelium plays a dominant role in fecal microbiome alterations in CF and that the resultant dysbiosis contributes to CF pathogenesis.

microbiology↗

bioRxiv2026

A preliminary study of HMGB1 defense in Crohn's disease

IntroductionIntestinal barrier failure is a key characteristic of both kinds of inflammatory bowel disease (IBD), ulcerative colitis (UC) and Crohns disease (CD). The intestinal barrier, or gut mucosal barrier, is composed of mucus and a tightly interconnected single layer of intestinal epithelial cells (IEC) that line the gut. Together, these components work to contain the gut microbiota within the gut lumen and when they fail, microbes, microbial products, or microbial components cause damage, inflammation, and immune activation in host tissue. We previously reported that High mobility group box 1 (HMGB1) in colonic mucus aggregates bacteria, limits bacterial invasion through mucus, and prevents bacteria from adhering to host tissue. Epithelial surface-associated HMGB1 is decreased in active UC lesions and low levels of HMGB1 are associated with high levels of tissue-adherent bacteria expressing adhesins carrying the molecular target of HMGB1 (ToH1). The study reported here was designed to determine whether HMGB1 defense is also compromised in active lesions from CD patients. MethodsImmunofluorescence microscopy was used to visualize mucus and HMGB1 in tissue from colonic resections performed in CD and non-IBD control patients. ResultsActive CD lesions had areas where the IEC were absent or pulling away from underlying tissue along with areas of increased mucus thickness and goblet cells full of mucus highly positive for alpha-linked-fucose residues. The surface associated HMGB1 was also decreased in active CD lesions. ConclusionTissue from CD patients exhibited cellular and acellular intestinal barrier defects in comparison to control patients. We observed the previously reported loss of IEC barrier integrity and abnormalities in the amount and distribution of mucus in CD lesions. We also report for the first time that CD is associated with decreased HMGB1 defense at the colon surface.

immunology↗

bioRxiv2023

HMGB1 acts as an agent of host defense at the gut mucosal barrier

Mucosal barriers provide the first line of defense between internal body surfaces and microbial threats from the outside world.1 In the colon, the barrier consists of two layers of mucus and a single layer of tightly interconnected epithelial cells supported by connective tissue and immune cells.2 Microbes colonize the loose, outer layer of colonic mucus, but are essentially excluded from the tight, epithelial-associated layer by host defenses.3 The amount and composition of the mucus is calibrated based on microbial signals and loss of even a single component of this mixture can destabilize microbial biogeography and increase the risk of disease.4-7 However, the specific components of mucus, their molecular microbial targets, and how they work to contain the gut microbiota are still largely unknown. Here we show that high mobility group box 1 (HMGB1), the prototypical damage-associated molecular pattern molecule (DAMP), acts as an agent of host mucosal defense in the colon. HMGB1 in colonic mucus targets an evolutionarily conserved amino acid sequence found in bacterial adhesins, including the well-characterized Enterobacteriaceae adhesin FimH. HMGB1 aggregates bacteria and blocks adhesin-carbohydrate interactions, inhibiting invasion through colonic mucus and adhesion to host cells. Exposure to HMGB1 also suppresses bacterial expression of FimH. In ulcerative colitis, HMGB1 mucosal defense is compromised, leading to tissue-adherent bacteria expressing FimH. Our results demonstrate a new, physiologic role for extracellular HMGB1 that refines its functions as a DAMP to include direct, virulence limiting effects on bacteria. The amino acid sequence targeted by HMGB1 appears to be broadly utilized by bacterial adhesins, critical for virulence, and differentially expressed by bacteria in commensal versus pathogenic states. These characteristics suggest that this amino acid sequence is a novel microbial virulence determinant and could be used to develop new approaches to diagnosis and treatment of bacterial disease that precisely identify and target virulent microbes.

microbiology↗