Francesca Palone

Role of HMGB1 as a suitable biomarker of subclinical intestinal inflammation and mucosal healing in patients with inflammatory bowel disease.

Background:Noninvasive biomarkers of high- and low-grade intestinal inflammation and of mucosal healing (MH) in patients with inflammatory bowel disease are currently lacking. We have recently shown that fecal high mobility group box 1 (HMGB1) protein is a novel biomarker of gut inflammation. We aimed at investigating in a mouse model if HMGB1 was able to foresee both a clinically evident and a subclinical gut inflammation and if its normalization indicated MH. We also aimed at confirming the results in patients with Crohns disease (CD) and ulcerative colitis. Methods:C57BL6/J mice were treated with increasing doses of dextran sodium sulphate to induce colitis of different severity degrees; 28 with CD, 23 with ulcerative colitis, and 17 controls were also enrolled. Fecal HMGB1 was analyzed by enzyme-linked immunosorbent assay and immunoblotting. Results:Fecal HMGB1 increased by 5-, 11-, 18-, and 24-folds with dextran sodium sulphate doses of 0.25%, 0.50%, 1%, and 4%, respectively, showing that the protein detected a high-grade and a subclinical inflammation. After a recovery time of 4-week posttreatment, HMGB1 returned to control levels, paralleling MH. In patients, fecal HMGB1 significantly correlated with endoscopic indexes (Simple Endoscopic Score for Crohns Disease [SES-CD], endoscopic Mayo subscore), but not with the disease activity indexes (Crohns disease Activity Index, partial Mayo score). Conclusions:Fecal HMGB1 is a robust noninvasive biomarker of clinically overt and subclinical gut inflammation; it can also be a surrogate marker of MH. We suggest the use of fecal HMGB1 to monitor the disease course and assess therapy outcomes in inflammatory bowel disease.

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

Background High 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. Aim This study is aimed at verifying whether the inhibition of HMGB1 through dipotassium glycyrrhizate (DPG) is a good strategy to reduce intestinal inflammation. Methods Human 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. Results DPG 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. Conclusions HMGB1 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.

NOD2 induces autophagy to control AIEC bacteria infectiveness in intestinal epithelial cells

ObjectiveThe importance of autophagy in mechanisms underlying inflammation has been highlighted. Downstream effects of the bacterial sensor NOD2 include autophagy induction. Recently, a relationship between defects in autophagy and adherent/invasive Escherichia coli (AIEC) persistence has emerged. The present study aims at investigating the interplay between autophagy, NOD2 and AIEC bacteria and assessing the expression level of autophagic proteins in intestinal biopsies of pediatric patients with inflammatory bowel disease (IBD).MethodsA human epithelial colorectal adenocarcinoma (Caco2) cell line stably over-expressing NOD2 was produced (Caco2NOD2). ATG16L1, LC3 and NOD2 levels were analysed in the Caco2 cell line and Caco2NOD2 after exposure to AIEC strains, by western blot and immunofluorescence. AIEC survival inside cells and TNFα, IL-8 and IL-1βmRNA expression were analysed by gentamicin protection assay and real time PCR. ATG16L1 and LC3 expression was analyzed in the inflamed ileum and colon of 28 patients with Crohn’s disease (CD), 14 with ulcerative colitis (UC) and 23 controls by western blot.ResultsAIEC infection increased ATG16L1 and LC3 in Caco2 cells. Exposure to AIEC strains increased LC3 and ATG16L1 in Caco2 overexpressing NOD2, more than in Caco2 wild type, while a decrease of AIEC survival rate and cytokine expression was observed in the same cell line. LC3 expression was increased in the inflamed colon of CD and UC children.ConclusionsThe NOD2-mediated autophagy induction is crucial to hold the intramucosal bacterial burden, especially towards AIEC, and to limit the resulting inflammatory response. Autophagy is active in inflamed colonic tissues of IBD pediatric patients.

Dipotassium glycyrrhizate via HMGB1 or AMPK signaling suppresses oxidative stress during intestinal inflammation

AIMS Oxidative stress and inflammation are always associated. Appropriate management of oxidative mediators may represent a therapeutic strategy to reduce inflammation, and use of antioxidant can be protective against inflammatory diseases. Glycyrrhizin (GL) plays an anti-inflammatory and antioxidant effect by inhibiting high mobility group box 1 (HMGB1) or 11-β-hydroxysteroid dehydrogenase type II (11βHSD2) enzyme. In this study, the potential role of dipotassium glycyrrhizate (DPG), a salt of GL, to reduce oxidative stress in intestinal inflammatory condition was investigated in vivo and the mechanism of action of DPG was studied in vitro. RESULTS In a colitis mouse model DPG affected oxidative stress reducing iNOS and COX-2 expression, as well as NO and PGE2 levels. By means of LPS-stimulated macrophages we found that DPG inhibited the expression of pro-inflammatory cytokines and reduced iNOS and COX-2 expression in a time dependent manner, through two different ways of signal. DPG reduced, at a later time, both iNOS and COX-2, through a mechanism HMGB1-dependent, and at an earlier time only COX-2, through a mechanism AMP-activated kinase (AMPK)-phosphorylation-mediated. CONCLUSION DPG has a protective effect on colitis and inflammation through the inhibition of oxidative stress. This study clarifies the two-ways mechanism by which DPG inhibits iNOS and COX-2 during inflammation and demonstrates for the first time that AMPK is a target of DPG. Uncovering this mechanism is significant to clarify the relationship between energy homeostasis and anti-oxidative responses and suggests that DPG could play a relevant role in the development of new therapy against inflammatory diseases associated to oxidative stress.

Krill oil reduces intestinal inflammation by improving epithelial integrity and impairing adherent-invasive Escherichia coli pathogenicity

BACKGROUND Krill oil is a marine derived oil rich in phospholipids, astaxanthin and omega-3 fatty acids. Several studies have found benefits of krill oil against oxidative and inflammatory damage. AIMS We aimed at assessing the ability of krill oil to reduce intestinal inflammation by improving epithelial barrier integrity, increasing cell survival and reducing pathogenicity of adherent-invasive Escherichia coli. METHODS CACO2 and HT29 cells were exposed to cytomix (TNFα and IFNγ) to induce inflammation and co-exposed to cytomix and krill oil. E-cadherin, ZO-1 and F-actin levels were analyzed by immunofluorescence to assess barrier integrity. Scratch test was performed to measure wound healing. Cell survival was analyzed by flow cytometry. Adherent-invasive Escherichia coli LF82 was used for adhesion/invasion assay. RESULTS In inflamed cells E-cadherin and ZO-1 decreased, with loss of cell-cell adhesion, and F-actin polymerization increased stress fibres; krill oil restored initial conditions and improved wound healing, reduced bacterial adhesion/invasion in epithelial cells and survival within macrophages; krill oil reduced LF82-induced mRNA expression of pro-inflammatory cytokines. CONCLUSIONS Krill oil improves intestinal barrier integrity and epithelial restitution during inflammation and controls bacterial adhesion and invasion to epithelial cells. Thus, krill oil may represent an innovative tool to reduce intestinal inflammation.

Fecal HMGB1 Reveals Microscopic Inflammation in Adult and Pediatric Patients with Inflammatory Bowel Disease in Clinical and Endoscopic Remission.

Background:Fecal high mobility group box 1 (HMGB1) has been suggested to be a novel noninvasive biomarker of gut inflammation. We aimed to assess the reliability of fecal HMGB1, compared with fecal calprotectin (FC), in detecting intestinal inflammation in pediatric and adult patients with inflammatory bowel disease (IBD) and to evaluate the accuracy of HMGB1 in identifying patients with IBD in clinical and endoscopic remission who still have histologic features of inflammation. Methods:Stool samples from 85 children with IBD (49 Crohns disease [CD] and 36 ulcerative colitis [UC] and 119 adults [57 Crohns disease and 62 ulcerative colitis]) were analyzed for the study. Age-matched healthy subjects were used as controls. Fecal HMGB1 and fecal calprotectin were detected through western blot and ELISA, respectively. Results:Fecal HMGB1 expression was significantly increased in pediatric and adult patients with Crohns disease and ulcerative colitis and strongly correlated with the disease severity. Fecal calprotectin and HMGB1 significantly correlated in pediatric (r: 0.60, P < 0.001) and adult (r: 0.72, P < 0.001) IBD patients. Moreover, in patients with clinical and endoscopic remission only fecal HMGB1 showed a strong match with the degree of histological scores of inflammation (CGHAS/IGHAS for Crohns disease and Geboes Score for ulcerative colitis). Conclusions:Fecal HMGB1 is confirmed to be a reliable biomarker of intestinal inflammation; indeed, it significantly correlates with fecal calprotectin in pediatric and adult IBD patients. Moreover, only fecal HMGB1 identifies histologic inflammation in subjects with IBD in clinical and endoscopic remission.

RIP3 AND pMLKL promote necroptosis-induced inflammation and alter membrane permeability in intestinal epithelial cells

BACKGROUND Necroptosis is an inflammatory form of programmed cell death requiring receptor-interacting protein kinase 3 (RIP3) and mixed lineage kinase domain-like protein (MLKL). AIMS The aim of this study is to examine in depth in vitro and ex vivo the contribution of necroptosis to intestinal inflammation. METHODS In vitro: we used an intestinal cell line, HCT116RIP3, produced in our laboratory and overexpressing RIP3. Ex vivo: intestinal mucosal biopsies were taken from patients with inflammatory bowel disease (IBD) (20 with Crohns disease; 20 with ulcerative colitis) and from 20 controls. RESULTS RIP3-induced necroptosis triggers MLKL activation, increases cytokine/alarmin expression (IL-8, IL-1β, IL-33, HMGB1), NF-kBp65 translocation and NALP3 inflammasome assembly. It also affects membrane permeability by altering cell-cell junctional proteins (E-cadherin, Occludin, Zonulin-1). Targeting necroptosis through Necrostatin-1 significantly reduces intestinal inflammation in vitro and in cultured intestinal explants from IBD. CONCLUSION We show for the first time in vitro and ex vivo that RIP3-driven necroptosis seriously affects intestinal inflammation by increasing pMLKL, activating different cytokines and alarmins, and altering epithelial permeability. The inhibition of necroptosis causes a significant decrease of all these effects. These data strongly support the view that targeting necroptosis may represent a promising new option for the treatment of inflammatory enteropathies.

Faecal high mobility group box 1 in children with celiac disease: A pilot study

BACKGROUND Celiac disease (CD) is a gluten-related immunological disorder resulting in inflammatory enteropathy. AIMS We assessed a stool marker of intestinal inflammation, the HMGB1 protein, in children with CD on a gluten free diet (GFD) at baseline and at follow up (FU). METHODS Thirty-nine children were investigated at diagnosis and at FU. Traditional serum markers of CD (anti-transglutaminase and anti-endomysial antibodies) and faecal HMGB1 (by enzyme-linked immunosorbent assay and immunoblotting) were tested. RESULTS There was a marked increase at baseline in both serum anti-transglutaminase IgA (anti-tTGAs) and faecal HMGB1; the latter being undetectable in controls. A strong correlation occurred between the two markers. At 12-month FU in 24 patients on GFD, HMGB1 decreased in all subjects, yet still being detectable in six children: high anti-tTGAs where evident in three, while the three with normal anti-tTGAs were complaining of intestinal symptoms and reported a low GFD adherence. CONCLUSIONS Faecal HMGB1 is a valuable marker of intestinal inflammation and may have a role in complementing serology in the management of CD children. Future studies including larger patient cohorts and small bowel mucosa histology will be designed to assess the relationship between faecal HMGB1 levels and duodeno-jejunal histopathology.

Krill oil, vitamin D and Lactobacillus reuteri cooperate to reduce gut inflammation

Current research into original therapies to treat intestinal inflammation is focusing on no-drug therapies. KLD is a mixture of krill oil (KO), probiotic Lactobacillus reuteri (LR), and vitamin D (VitD3). The aim of this study was to assess in vitro and in vivo the potential cooperative effects of KLD in reducing gut inflammation. Colorectal adenocarcinoma cell lines, CACO2 and HT29, and C57BL/6 mice were used for in vitro and in vivo analyses, respectively. Cells were exposed to cytomix (interferon gamma + tumour necrosis factor alpha (TNF-α)) to induce inflammation or co-exposed to cytomix and KO, LR and VitD3 alone or to cytomix and KLD. Animals were treated for 7 days with dextran sodium sulphate (DSS) to induce colitis or with DSS and KLD. In vitro assays: F-actin expression was analysed by immunofluorescence; scratch test and trans-epithelial electric resistance test were performed to measure wound healing; adhesion/invasion assays of adhesive and invasive Escherichia coli (AIEC) bacteria were made; mRNA expression of TNF-α, interleukin (IL)-8 and vitamin D receptor (VDR) was detected by quantitative PCR. In vivo assays: body weight, clinical score, histological score and large intestine weight and length were estimated; mRNA expression of TNF-α, IL-1β, IL-6, IL-10 by quantitative PCR; VDR expression was detected by quantitative PCR and immunohistochemistry. In vitro: KLD restores epithelial cell-cell adhesion and mucosal healing during inflammation, while decreases the adhesiveness and invasiveness of AIEC bacteria and TNF-α and IL-8 mRNA expression and increases VDR expression. In vivo: KLD significantly improves body weight, clinical score, histological score and large intestine length of mice with DSS-induced colitis and reduces TNF-α, IL-1β and IL-6 mRNA levels, while increases IL-10 mRNA and VDR levels. KLD has significant effects on the intestinal mucosa, strongly decreasing inflammation, increasing epithelial restitution and reducing pathogenicity of harmful commensal bacteria.

Tu1833 Dipotassium Glycyrrhizate Affects Oxidative Stress to Reduce Inflammation

Background and aim: High mobility group box 1 (HMGB1) protein is a highly conserved nuclear protein with important functions in the regulation of transcription. In inflammatory conditions, HMGB1 is actively secreted from immune cells in the extracellular matrix, where it behaviors as a pro-inflammatory cytokine. Dipotassium glycyrrhizate (DPG) is a glycyrrhizin-derived compound that is known to inhibit the pro-inflammatory activity of extracellular HMGB1. We previously showed that DPG significantly reduces, without adverse side effects, the DSS induced colitis in mice. Since a known relationship exists between HMGB1 and oxidative stress as well as between the latter and inflammation, the aim of the present study is to investigate whether DPG acts on the oxidative stress mechanisms to reduce inflammation Methods: In vivo: DPG (8mg/Kg) was administered to DSS-treated C57BL/6 mice. After 7 days, mice were sacrificed and inflamed colon removed. Expression levels of iNOS and COX2, involved in oxidative stress, were analysed by RT-PCR. In vitro: RAW267.4 cells were treated with LPS, DPG, LPS+DPG, HMGB1-B-Box, HMGB1-BBox+DPG at a earlier (4-8h) or later (24-48h) time. Expression levels of iNOS and COX2 were analysed by RT-PCR and AMPK phosphorylation was analysed by western blot. Results: In vivo: mice treated with DPG+DSS showed a significant decrease of iNOS and COX2 mRNA expression, compared to DSS-treated mice. In vitro: DPG reduced iNOS and COX2 expression induced by LPS at the later time and COX2 expression at the earlier time. Besides, HMGB1-B-Box increased iNOS expression at the earlier time, but this effect was counteracted by DPG. Finally, DPG induced AMPK phosphorylation, that is known to inhibit COX2, after LPS treatment. Conclusion: Our data show that DPG affects oxidative stress reducing iNOS and COX2 expression during inflammation. It is likely that DPG reduces iNOS through a mechanism HMGB1-dependent and COX2 through a mechanism AMK phosphorylation-mediated.