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Background & aims: We previously demonstrated the efficacy of garlic extract (GE) in the prevention of rat liver fibrosis by inhibiting tissue transglutaminase (tTG) activity. In the present study we aimed to evaluate the potential of GE in the regression of liver fibrosis and the underlining mechanism. Methods: Male Wistar rats were i.p. injected, twice a week, for 7 weeks, with CCl4 to develop liver fibrosis. Successively, a group was immediately sacrificed, while the remaining two groups received the GE or the vehicle, respectively, over the following 2 wks. A group of normal rats was also included in the study. Liver function, histology, and collagen deposition in parallel with gene and protein expression of α-SMA, tTG, TGF-β1, SEMA-7A, and metalloproteinase inhibitor 1 (TIMP1) as well as measure of active by total TGF-β1 were assessed. Results: CCl4 administration increased alanine-aminotransferase (ALT) activity, hepatic collagen deposition and gene and protein expression of all monitored markers. GE, but not the sole vehicle, restored liver histology and function by decreasing fibrogenesis markers (α-SMA, tTG, TGF-β1, SEMA-7A and TIMP1). Active by total TGF-β1 was significantly reduced (p < 0.05) in GE treated rats compared to the CCl4 at 7 weeks, and vehicle rats. Conclusions: These findings concurrently suggested that GE elicited therapeutic effect against liver fibrosis. Regression of liver fibrosis occurred by reducing myofibroblasts (through modulation of HSCs activation mechanisms), remodelling extracellular matrix (through increase of its degradation) and regenerating liver tissue and functions: three processes regulated by fine mechanisms where active TGF-β1 and tTG play a central role.

Background and aim: Searching for alternative therapies that are effective, safe and less expensive of those currently used for ulcerative colitis, we investigated the efficacy of a polyphenol extract from apple in rat colitis. Methods: Rats with trinitrobenzensulphonic acid-induced colitis were treated daily with rectal administration of apple polyphenols 10(-4) M for 14 days. COX-2, TNF-alpha, tissue transglutaminase and calpain in colon mucosa samples were assessed by reverse transcription-polymerase chain reaction and western blot analyses. To ascertain the role of tissue transglutaminase in mucosal healing, wounded rat fibroblasts were incubated with cystamine (a tissue transglutaminase activity inhibitor). Results: Colitis was associated with increased COX-2, TNF-alpha, calpain, and tissue transglutaminase mRNA. The protein expression of COX-2, TNF-alpha and calpain was increased whilst tissue transglutaminase was decreased. Apple extract treatment reduced the severity of colitis (p < 0.05) and restored all the considered biomarkers at the baseline level. Apple polyphenols reduced the degradation of tissue transglutaminase protein occurring through calpain action. Apple polyphenols-treated wounded fibroblast recovered within 24 h showing intense immunoreactivity for tissue transglutaminase. Conclusion: The efficacy of apple extract is mediated by its effects on COX-2 and TNF-alpha. The unbalance between calpain and tissue transglutaminase may play a role in colonic damage and future therapeutic interventions in ulcerative colitis can target this mechanisms. (C) 2012 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

BACKGROUND: Celiac Disease (CD) is both a frequent disease (1:100) and an interesting model of a disease induced by food. It consists in an immunogenic reaction to wheat gluten and glutenins that has been found to arise in a specific genetic background; however, this reaction is still only partially understood. Activation of innate immunity by gliadin peptides is an important component of the early events of the disease. In particular the so-called "toxic" A-gliadin peptide P31-43 induces several pleiotropic effects including Epidermal Growth Factor Receptor (EGFR)-dependent actin remodelling and proliferation in cultured cell lines and in enterocytes from CD patients. These effects are mediated by delayed EGFR degradation and prolonged EGFR activation in endocytic vesicles. In the present study we investigated the effects of gliadin peptides on the trafficking and maturation of endocytic vesicles. METHODS/PRINCIPAL FINDINGS: Both P31-43 and the control P57-68 peptide labelled with fluorochromes were found to enter CaCo-2 cells and interact with the endocytic compartment in pulse and chase, time-lapse, experiments. P31-43 was localised to vesicles carrying early endocytic markers at time points when P57-68-carrying vesicles mature into late endosomes. In time-lapse experiments the trafficking of P31-43-labelled vesicles was delayed, regardless of the cargo they were carrying. Furthermore in celiac enterocytes, from cultured duodenal biopsies, P31-43 trafficking is delayed in early endocytic vesicles. A sequence similarity search revealed that P31-43 is strikingly similar to Hrs, a key molecule regulating endocytic maturation. A-gliadin peptide P31-43 interfered with Hrs correct localisation to early endosomes as revealed by western blot and immunofluorescence microscopy. CONCLUSIONS: P31-43 and P57-68 enter cells by endocytosis. Only P31-43 localises at the endocytic membranes and delays vesicle trafficking by interfering with Hrs-mediated maturation to late endosomes in cells and intestinal biopsies. Consequently, in P31-43-treated cells, Receptor Tyrosine Kinase (RTK) activation is extended. This finding may explain the role played by gliadin peptides in inducing proliferation and other effects in enterocytes from CD biopsies.

Background & Aims: Tissue transglutaminase (tTG) autoantibodies are markers of celiac disease, and the enzyme is required for several crucial biological processes. The aim of this study was to determine whether these autoantibodies are involved in the pathogenesis of the mucosal lesion typical of celiac disease. Methods: Using rhodamine-conjugated phalloidin staining, we evaluated whether tTG antibodies, both commercially available and cloned from patients with celiac disease, cause cytoskeletal changes in Caco-2, MCF7, and NIH 3T3 cells. We monitored cell levels of bromodeoxyuridine incorporation to determine whether tTG autoantibodies are able to induce NIH 3T3 fibroblasts and epithelial mucosal cells into S phase. Results: Treatment with tTG antibodies caused a dose-dependent increase of membrane ruffling in Caco-2, MCF7, and NIH 3T3 cells. It also dose-dependently induced G0-synchronized NIH 3T3 fibroblasts into S phase but did not affect the rate of apoptosis. Similarly, tTG antibodies induced S-phase entry of epithelial cells in cultured intestinal biopsy specimens from patients with celiac disease. They did not affect biopsy specimens from patients without celiac disease. Conclusions: Our results suggest that tTG autoantibodies per se, by interacting with the extracellular membrane–bound transglutaminase, may play an important role in epithelial cell proliferation in celiac disease.