THE ENTEROGLIAL-DERIVED S100B PROTEIN CONTROLSHUMAN INTESTINAL EPITHELIAL CELLS DIFFERENTIATION ANDPROLIFERATION VIA RAGE INTERACTION

INTRODUCTION: In the human gut, S100B protein is specifically expressed by enteroglial cells (EGCs) and, in response to various stimuli, it is released in the extracellular space where it is suggested to participate to intestinal homeostasis. Most of its effects are mediated by the interaction with the receptor for advanced glycation endproducts (RAGE), which is expressed also by intestinal epithelial cells (IECs). AIMS & METHODS: We aimed to study the effects of different concentrations of S100B on viability, proliferation and differentiation of the human IECs. To achieve this goal, Caco-2 cells were exposed to nanomolar or micromolar concentrations of S100B (0.005 and 5 uM, respectively), for 24h, in presence or absence of a specific anti- RAGE neutralizing antibody (1/1000 v/v) added 2h before S100B stimulation. Cells viability, proliferation and differentiation were respectively studied by MTT vitality test, Bromodeoxyuridine incorporation assay, lactase/sucrase enzymes activity tests. Cells with medium alone were used as control. Data are expressed as mean±SD. RESULTS: Both S100B 0.005 uM and S100B 5 uM, compared to control, did not affect cell viability (0.8±0.3 and 0.7±0.3 vs 0.7±0.1 l540−630; p=ns). Both concentrations of S100B significantly decreased proliferation respect to control (0.17±0.01 and 0.18±0.01 vs 0.23±0.01 l450−540; p<0.05). This antiproliferative effect was not observed when cells were pre-treated with anti-RAGE. Compared to control, S100B 0.005 uM, but not S100B 5 uM, significantly increased lactase activity (+7.5±0.9, p<0.05 and +1.9±0.5 fold increase vs control; p=ns) and sucrase activity (+2.6±0.3, p<0.05 and +0.7±0.4, p=ns fold increase vs control). The increase in lactase/sucrase activity was not observed when cells were pre-treated with anti-RAGE. CONCLUSION: Nanomolar concentration of S100B significantly reduces IECs proliferation and stimulates cells differentiation, without cytotoxic effects. Very intriguingly, these effects were abolished in the presence of a specific anti-RAGE antibody. Our findings further support the role of EGCs in the regulation of intestinal mucosal barrier functions.