Burge, M. | Search bioRxiv

bioRxiv2026

Extracellular HSPB1 protects intestinal epithelial cells against ethanol-activated ferroptosis

Alcohol consumption damages the gastrointestinal tract, the initial site of contact for ingested ethanol. Intestinal epithelial cells (IEC) lining the small intestine are at particular risk of ethanol toxicity since they are largely responsible for ethanol absorption and metabolize ethanol into toxic metabolites. These toxic metabolites generate oxidative stress that damages cellular components and leads to programmed cell death. The small heat shock protein HSPB1 regulates oxidative stress and provides cytoprotection in cells exposed to ethanol, but its specific role in intestinal ethanol toxicity is still unclear. Therefore, the goal of this study was to understand the role of HSPB1 in IEC stress response pathways during ethanol exposure. Here we utilized in vitro models to demonstrate that IEC rapidly upregulate and release HSPB1 in response to ethanol. HSPB1 expression in IEC mitigated oxidative stress, oxidative damage, and iron uptake, the hallmarks of ferroptosis, during ethanol stress. Interestingly, recombinant HSPB1 rescued cells, suggesting that extracellular HSPB1 is responsible for its protective effect. Our findings establish extracellular HSPB1 as a previously unrecognized mediator of IEC cytoprotection during acute ethanol exposure. However, HSPB1 functions as a "double-edged sword" along the gut-liver axis. While transient extracellular HSPB1 protects the gut epithelium from acute oxidative damage, sustained levels driven by chronic alcohol consumption lead to HSPB1 release from hepatocytes that activates macrophages and contributes to driving self-damaging inflammation in conditions like alcohol-associated hepatitis. Therefore, targeting extracellular HSPB1 levels along the gut-liver axis offers a promising diagnostic and therapeutic avenue to mitigate severe alcohol-induced organ injury.

pharmacology and toxicology↗

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↗