DOP49 Context-dependent roles of High-mobility group box 1 (HMGB1) during intestinal inflammation and carcinogenesis
Zierz, E.(1);Foelsch, K.(1);Pelczar, P.(1);Qi, M.(2);Alawi, M.(2);Clauditz, T.(3);Gagliani, N.(4);Huber, S.(1);Huebener, P.(1);
(1)University Medical Center Hamburg-Eppendorf, I. Department of Medicine, Hamburg, Germany;(2)University Medical Center Hamburg-Eppendorf, Bioinformatics Core Facility, Hamburg, Germany;(3)University Medical Center Hamburg-Eppendorf, Institute of Pathology, Hamburg, Germany;(4)University Medical Center Hamburg-Eppendorf, Department of General- Visceral and Thoracic Surgery, Hamburg, Germany; Huebener
Background
HMGB1 is a ubiquitously expressed nucleoprotein with proinflammatory functions following cellular release. The protein is passively released during tissue necrosis, acting as a damage-associated molecular pattern, but can also be actively secreted by immune cells. Stool and serum HMGB1 levels have been suggested as markers of both inflammatory bowel disease (IBD) activity and colorectal cancer (CRC) invasiveness, and antibody-mediated HMGB1 neutralization was beneficial in animal models of IBD. We explored context-dependent functions of HMGB1 in the injured intestine using novel experimental mice with cell-specific genetic HMGB1 deficiency.
Methods
To circumvent the postnatal lethality of global HMGB1 deficiency in animals, we used the Cre-lox system to generate enterocyte-specific (Hmgb1ΔIEC, Villin-Cre) and myeloid cell-specific (Hmgb1ΔLysM, LysM-Cre) HMGB1-knockout mice. Animals were subjected to well-established models of acute (DSS, Citrobacter rodentium) and chronic (AOM+DSS, CD45RBhigh T cell transfer colitis, Apc+/min) intestinal injury, followed by clinical, endoscopic, histological and molecular analysis. HMGB1 expression was assessed in human IBD and CRC specimens.
Results
IBD and CRC biopsies exhibited high levels of HMGB1 expression in epithelia, immune cells, tumor cells and the peritumoral stroma. HMGB1 deficiency from enterocytes and myeloid cells did not alter Citrobacter- or T cell transfer-induced enterocolitis, when epithelial injury was comparably low. In contrast, Hmgb1ΔIEC mice exhibited aggravated DSS-induced colitis, as evidenced by severe weight loss as well as exacerbated neutrophil- and monocyte-driven mucosal inflammation compared to Hmgb1f/f. Whole tissue RNA sequencing indicated defective cellular proliferation in injured Hmgb1ΔIEC intestines. In the AOM+DSS-model, Hmgb1ΔIEC had a comparable tumor burden to Hmgb1f/f, whereas Hmgb1ΔLysM had significantly fewer and smaller tumors, potentially linked to metabolic alterations in the tumor micromilieu. In the Apc+/min model, enterocyte HMGB1 deficiency effectuated more and larger tumors, whereas leukocyte HMGB1 did not affect tumor load.
Conclusion
Contrasting antibody-mediated HMGB1 neutralization in animal models of IBD, our findings from genetic HMGB1 deletion studies reveal a critical role of enterocyte HMGB1 in the maintenance of the intestinal barrier during severe colitis. Impaired epithelial regeneration or inefficient local immune cell expansion in Hmgb1ΔIEC may account for the aggravated phenotype. HMGB1 from enterocytes and immune cells context-dependently affect maladaptive intestinal would healing, potentially mediated by cell-intrinsic and -extrinsic mechanisms that warrant further investigation.