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P008. The pro-apoptotic galectin-1 is functionally inhibited in inflamed intestinal areas of IBD patients

R. Papa Goby1, A. Rocca2, A. Sambuelli3, G. Ravinovich4, M. Toscano4, A. Gil5, S. Negreira6, S. Huernos5, S. Goncalves5, M. Bellicoso5, S. Goncalves5, P. Tirado5, R. Curciarello7, A. Irigoyen6, C. Muglia8, M. Yantorno9, G. Docena7, 1Fac. de Ciencias Exactas Universidad Nacional del Comahue (Laboratorio de Investigacione, LISINs del Sistema Inmune), La Plata, Argentina, 2Bonorino Udaondo Gastroenterology Hopital, Endoscopy Service, Buenos Aires, Argentina, 3Institute, Medicine, IBD Section, Gastroenterology, Buenos Aires, Argentina, 4IBYME, Laboratorio de Inmunopatologia, Buenos Aires, Argentina, 5Bonorino Udaondo Gastroenterology Hopital, IBD Section, Buenos Aires, Argentina, 6Bonorino Udaondo Gastroenterology Hopital, Buenos Aires, Buenos Aires, Argentina, 7LISIN (Laboratorio de Investigaciones del Sistema Inmune), Laboratorio de Investigaciones del Sistema Inmune, La Plata, Argentina, 8UNLP, Servicio de Gastroenterologia, La Plata, Argentina, 9Hospital Interzonal de Agudos, Gastroenterologia, La Plata, Argentina

Background

Inflammatory bowel diseases (IBD) are multifactorial disorders characterized by a chronic and relapsing intestinal inflammation. Galectin-1, a ubiquitous endogenous lectin, has been implicated in several chronic inflammatory disorders. We aimed to analyze its role in the colonic mucosa of patients with Crohn's disease (CD) and Ulcerative colitis (UC).

Methods

Gal-1 expression was studied by qPCR, immunoblotting and histology in biopsies and resected tissues of patients with IBD (n = 26) and control patients (n = 20). Gal-1-specific binding ligands were also analyzed by flow cytometry in lamina propria and its physiologycal role in the induction of cell death was evaluated by flow cytometry.

Results

We found in 21 biopsies of CD and 22 biopsies of CU that Gal-1 mRNA expression was increased in colonic inflamed areas (p < 0.01). However Gal-1 protein expression was lower as compared to non-inflamed areas. To clarify this controversial finding we cultured control biopsies with TNF-α (1, 5 and 10 ng/mL) and observed a dose-response increase in the expression and secretion of Gal-1 (p < 0.05). Additionally, fibroblast supernatants from IBD patients show the ability to cleave Gal-1 protein. Both findings could explain the dissociation between mRNA expression and protein secretion. Gal-1-specific binding sites were considerably reduced in isolated lamina propria CD4 or CD8 lymphocytes from inflamed areas (n = 11), as compared to non-inflamed areas (n = 10) or control samples (n = 8) (p < 0.05). A consistent lower binding of PNA and C2GnT-1 expression was found in IBD samples, suggesting lower levels of asialo-core 1-O-glycans. When apoptosis was analyzed we found that 10 ng Gal-1 increased the frequency of annexin-1-positive cells in control patients (n = 6) (17.94% with medium and 32.94% with 10 ng Gal-1. p < 0.05). Nevertheless no increased in the frequency of annexin-1-positive cells was observed in inflamed areas of IBD patients (n = 5, p = 0.9647).

Conclusion

In conclusion, we found a differential expression of Gal-1 and Gal-1-specific glycosylated ligands in biological samples of IBD. We also found that Gal-1 exerts a pro-apoptotic effect in T lymphocytes from non-inflamed areas, whereas T cells from inflamed areas are refractory to cell death. The reduced expression of this protein in inflamed areas and the absence of Gal-1-specific sites may have relevant implications in the survival vs cell death of mucosal T lymphocytes. This might impact in the persistency of the inflammatory process in the affected colon.