Faculty Bibliography

INTRODUCTION: Intestinal fibrosis is a common and severe complication of inflammatory bowel disease (IBD) characterized by excessive deposition of extracellular matrix components (ECM) and for which efficient and well-tolerated therapies are currently lacking. Inflamed colonic mucosa of patients with active IBD show a significant increase in expression of the receptor for advanced glycation end products (RAGE), a member of the immunoglobulin superfamily of cell surface receptors, able to regulate chronic inflammation by activating the NF-kB pathway and inducing inflammatory and oxidative stress. In addition, a growing body of evidences in kidney, liver and lung fibrosis shows how the increased myofibroblast activation and numbers and the consequent ECM accumulation are regulated by RAGE. All these data may place this receptor among the most innovative and promising targets for new antifibrotic therapies in IBD AIMS & METHODS: We propose to investigate the involvement of RAGE in the development of the DSS-induced intestinal fibrosis in mice. Chronic colitis and fibrosis were induced in C57BL/6 wild type (WT) and RAGE null mice by administration of 2.5% (w/v) dextran sulfate sodium (DSS) in drinking water for 5 days followed by 7 days of water, for three cycles. Three days after the last cycle of treatment, the entire colon was rapidly excised and scored for the assessment of macroscopic lesion, including dilation, thickness and adhesion, on a 0-3 scale by an investigator naive to the experimental conditions. The sum of the scores of colonic lesions was expressed as total macroscopic score. Tissue specimens, collected from distal colon, were subject to Hematoxylin/Eosin staining, to assess the degree of inflammation, and Picrosirius red staining was performed to assess collagen deposition. Thus, a total microscopic score was calculated evaluating presence of ulceration, inflammatory degree, depth of lesions and fibrotic degree. mRNA expression of the main profibrotic mediator, Tgf-beta1, and the expression of ECM components, mainly collagen types I-III (Col1A1 gene) and fibronectin (Fn-1 gene), were evaluated by quantitative RT-PCR RESULTS: Compared to WT mice, DSS-treated C57/Bl6 RAGE null mice showed a significant 29% decrease of the colon weight/length ratio (p<0.0001), an indicator of wall thickening. A total macroscopic score of 6 +/- 0.92 was assessed in colons recovered from DSS-treated WT mice, but in mice devoid of RAGE, the appearance of the macroscopic lesions was significantly reduced, 1.43 +/- 0.54 (p<0.0001, n=15). DSS-treated RAGE null mice showed also a significant 49% decrease of total microscopic score compared to WT mice. mRNA Tgf-beta1 expression was significantly increased 3.4 fold by the DSS administration in WT mice colon, whereas it was unchanged in RAGE null mice compared to mice receiving only tap water. Col1A1 and Fn-1 genes were upregulated in DSS-treated WT mice (5.52 folds, p= 0.137 and 53 folds, p= 0.0016, respectively). Lack of RAGE decreased 3.17 folds (p= 0.0341) Col1A1 expression and totally prevents the Fn-1 upregulation induced by DSS treatment CONCLUSION: The potential profibrotic role of RAGE in IBD could both shed light into the complex and dynamic fibrogenic processes in IBD and pave the way for new anti-fibrotic agents and approaches in this disease

OBJECTIVE: To compare bariatric surgery versus intensive medical weight management (MWM) in patients with type 2 diabetes mellitus (T2DM) who do not meet current National Institutes of Health criteria for bariatric surgery and to assess whether the soluble form of receptor for advanced glycation end products (sRAGE) is a biomarker to identify patients most likely to benefit from surgery. BACKGROUND: There are few studies comparing surgery to MWM for patients with T2DM and BMI less than 35. METHODS: Fifty-seven patients with T2DM and BMI 30 to 35, who otherwise met the criteria for bariatric surgery were randomized to MWM versus surgery (bypass, sleeve or band, based on patient preference). The primary outcomes assessed at 6 months were change in homeostatic model of insulin resistance (HOMA-IR) and diabetes remission. Secondary outcomes included changes in HbA1c, weight, and sRAGE. RESULTS: The surgery group had improved HOMA-IR (-4.6 vs +1.6; P = 0.0004) and higher diabetes remission (65% vs 0%, P < 0.0001) than the MWM group at 6 months. Compared to MWM, the surgery group had lower HbA1c (6.2 vs 7.8, P = 0.002), lower fasting glucose (99.5 vs 157; P = 0.0068), and fewer T2DM medication requirements (20% vs 88%; P < 0.0001) at 6 months. The surgery group lost more weight (7. vs 1.0 BMI decrease, P < 0.0001). Higher baseline sRAGE was associated with better weight loss outcomes (r = -0.641; P = 0.046). There were no mortalities. CONCLUSIONS: Surgery was very effective short-term in patients with T2DM and BMI 30 to 35. Baseline sRAGE may predict patients most likely to benefit from surgery. These findings need to be confirmed with larger studies.ClinicalTrials.gov ID: NCT01423877.

BACKGROUND: The receptor for advanced glycation end products (RAGE) shares common ligands and signaling pathways with TLR4, a key mediator of house dust mite (Dermatophagoides pteronyssinus) (HDM) sensitization. We hypothesized that RAGE and its ligand high-mobility group box-1 (HMGB1) cooperate with TLR4 to mediate HDM sensitization. OBJECTIVES: To determine the requirement for HMGB1 and RAGE, and their relationship with TLR4, in airway sensitization. METHODS: TLR4(-/-), RAGE(-/-), and RAGE-TLR4(-/-) mice were intranasally exposed to HDM or cockroach (Blatella germanica) extracts, and features of allergic inflammation were measured during the sensitization or challenge phase. Anti-HMGB1 antibody and the IL-1 receptor antagonist Anakinra were used to inhibit HMGB1 and the IL-1 receptor, respectively. RESULTS: The magnitude of allergic airway inflammation in response to either HDM or cockroach sensitization and/or challenge was significantly reduced in the absence of RAGE but not further diminished in the absence of both RAGE and TLR4. HDM sensitization induced the release of HMGB1 from the airway epithelium in a biphasic manner, which corresponded to the sequential activation of TLR4 then RAGE. Release of HMGB1 in response to cockroach sensitization also was RAGE dependent. Significantly, HMGB1 release occurred downstream of TLR4-induced IL-1alpha, and upstream of IL-25 and IL-33 production. Adoptive transfer of HDM-pulsed RAGE(+/+)dendritic cells to RAGE(-/-) mice recapitulated the allergic responses after HDM challenge. Immunoneutralization of HMGB1 attenuated HDM-induced allergic airway inflammation. CONCLUSION: The HMGB1-RAGE axis mediates allergic airway sensitization and airway inflammation. Activation of this axis in response to different allergens acts to amplify the allergic inflammatory response, which exposes it as an attractive target for therapeutic intervention.

In mammals, changes in the metabolic state, including obesity, fasting, cold challenge and high fat diets activate complex immune responses. In many strains of rodents, high fat diets induce a rapid systemic inflammatory response and lead to obesity. Little is known about the molecular signals required for high fat diet (HFD)-induced phenotypes. Here we studied the function of the receptor for advanced glycation products (RAGE) in the development of phenotypes associated with high fat feeding in mice. RAGE is highly expressed on immune cells, including macrophages. High fat feeding induced expression of RAGE ligand HMGB1 and carboxy methyl lysine (CML)-advanced glycation endproducts (AGE) epitopes in liver and adipose tissue. Genetic deficiency of RAGE prevented the effects of HFD on energy expenditure, weight gain, adipose tissue inflammation, and insulin resistance. RAGE deficiency had no effect on genetic forms of obesity caused by impaired melanocortin signaling. Hematopoietic deficiency of RAGE or treatment with soluble RAGE partially protected against peripheral HFD-induced inflammation and weight gain. These data argue that high fat feeding induces peripheral inflammation and weight gain in a RAGE-dependent manner, providing a foothold in the pathways that regulate diet-induced obesity and offering the potential for therapeutic intervention.