RAGE-DEPENDENT S100B PROTEIN MODULATION OF PERIPHERAL AND MUCOSAL IMMUNE CELLS' FUNCTIONS IN PATIENTS WITH ULCERATIVE COLITIS (UC)

Background and aim: Glial cells (EGC) in the gut participate to local inflammatory responses triggered by various insults. Whether EGC directly affect the responses of immune cells during intestinal inflammatory diseases is unknown. We aimed to investigate the ability of glial S100B protein to mediate immune cells’ functions in UC patients. Material and methods: Mucosal immune cells (MIC) were isolated from rectal mucosal biopsies of 10 patients with UC (mean age 47; 6 male) and characterized by FACS. In the same subjects, peripheral blood mononuclear cells (PBMC) were isolated. Both MIC and PBMC were stimulated with exogenous S100B protein (0.05-5 μ M) to evaluate cells’ proliferation (by MTT assay after 72h) and responses [by measuring interferon gamma levels (IFN-g), inducibile nitric oxide synthase (iNOS) and tumor necrosis factor- alpha (TNF-a) proteins expression, each after 24h]. In the same experimental conditions we evaluated expression of receptor for advanced glycation end- products (RAGE) both in PBMC and MIC to evaluate if its expression can modulate S100B-mediated effects on immune cells. Results: In PBMC, S100B protein 5 μ M did not significantly affect cells’ proliferation, but it induced a significant and concentration-dependent increase of IFN-g level (89 ± 5vs75 ± 6 ng/mL, p < 0.05), and of both iNOS and TNF-a protein expression (+32 ± 4% and +41 ± 9% vs. unstimulated, p < 0.05 and p < 0.01respectively). This was associated with a significant increase of RAGE expression after S100B addition (+52 ± 10% vs unstimulated, p < 0.01). In MIC, similar concentrations of S100B protein did not affect cells’ prolifera- tion, but, unlikely PBMC, induced a significant and concentration-dependent decrease of IFN-g level (42 ± 7vs61 ± 4 ng/mL, p < 0.01), and of both iNOS and TNF-a protein expression (-34 ± 13 and -70 ± 2% vs unstimulated, p < 0.05 and p < 0.01). This finding was associated with a significant decrease of RAGE expression after S100B challenge (-52 ± 14% vs unstimulated, p < 0.05). Conclusions: Although further studies are needed, we show that EGC par- ticipate to the immune responses in the inflamed gut. We suggest that S100B-RAGE interaction represents a crucial mechanism involved in the modulation, either positive or negative, of immune cells’ functions in UC.