Dipotassium Glycyrrhizate Inhibits HMGB1-Dependent Inflammation and Ameliorates Colitis in Mice

Roberta Vitali,Manuela Costanzo,Francesca Palone,Laura Stronati,Leonardo Cavone,Marina Aloi,Anna Dilillo,Salvatore Cucchiara,Anna Negroni,Ivan J Fuss

doi:10.1371/journal.pone.0066527

Abstract

BackgroundHigh mobility group box-1 (HMGB1) is a DNA-binding protein that is released from injured cells during inflammation. Advances in targeting HMGB1 represent a major challenge to improve the treatment of acute/chronic inflammation.AimThis study is aimed at verifying whether the inhibition of HMGB1 through dipotassium glycyrrhizate (DPG) is a good strategy to reduce intestinal inflammation.MethodsHuman colon adenocarcinoma cell line, HT29, human epithelial colorectal adenocarcinoma, Caco2, and murine macrophage cell line, RAW 264.7, were cultured to investigate the effect of DPG on the secretion of HMGB1. Acute colitis was induced in C57BL/6 mice through administration of 3% dextran sodium sulphate (DSS); a combined treatment with DSS and 3 or 8 mg/kg/day DPG was used to investigate the effects of DPG on intestinal inflammation. Animals were euthanized at seventh day and colonic samples underwent molecular and histological analyses.ResultsDPG significantly reduces in vitro the release of HMGB1 in the extracellular matrix as well as expression levels of pro-inflammatory cytokines, TNF-alpha, IL-1beta and IL-6, by inhibiting HMGB1. Moreover, DPG significantly decreases the severity of DSS-induced colitis in mice. Murine colonic samples show decreased mRNA levels of pro-inflammatory cytokines TNF-alpha, IL-1beta and IL-6, as well as HMGB1 receptors, RAGE and TLR4. Finally, HMGB1, abundantly present in the feces of mice with DSS-induced colitis, is strongly reduced by DPG.ConclusionsHMGB1 is an early pro-inflammatory cytokine and an active protagonist of mucosal gut inflammation. DPG exerts inhibitory effects against HMGB1 activity, significantly reducing intestinal inflammation. Thus, we reason that DPG could represent an innovative tool for the management of human intestinal inflammation.

Highlights

High mobility group box 1 (HMGB1) is a DNA-binding nuclear protein that, like other endogenous molecules termed alarmins or DAMPs (Damage Associated Molecular Patterns), can be released into the extracellular milieu during states of cellular stress or damage and subsequently activate the immune system and promote inflammation [1,2]
High mobility group box-1 (HMGB1) carries out primary functions in the nucleus, where it is abundantly expressed in almost all eukaryotic cells
First we evaluated the effect of dipotassium glycyrrhizate (DPG) on HMGB1 gene/protein expression

Summary

Introduction

High mobility group box 1 (HMGB1) is a DNA-binding nuclear protein that, like other endogenous molecules termed alarmins or DAMPs (Damage Associated Molecular Patterns), can be released into the extracellular milieu during states of cellular stress or damage and subsequently activate the immune system and promote inflammation [1,2]. To exert these activities, HMGB1 must transit from the nucleus, through the cytoplasm, to the outside of the cell. Advances in targeting HMGB1 represent a major challenge to improve the treatment of acute/chronic inflammation

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