HUMAN ENTERIC GLIAL CELLS MODULATE INTESTINAL EPITHELIAL CELLS VIABILITY, PROLIFERATION AND DIFFERENTIATION: THE ROLE OF THE ENTEROGLIAL DERIVED S100B PROTEIN

Background and aim: 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. We aimed to study the effects of different concentrations of S100B on viability, proliferation and differentiation of the epithelial intestinal cells. Material and methods: Caco-2 cells were seeded into a 6-wells multiwells plate and cultured with the appropriate medium. At the confluence, cells were starvated for 24h and then were exposed to nanomolar or micromolar concentrations of S100B (0.005 and 5 μ M, respectively), for 24h. Additional experiments were performed in presence of Lactoferrin (5 μ g/mL) that served as positive control. Cells viability, proliferation and differentiation were re- spectively studied by MTT vitality test, Bromodeoxyuridine incorporation assay and 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 μ M, compared to control, did not affect cell viability (0.8 ± 0.3 and 0.7 ± 0.3 vs 0.7 ± 0.1 540–630nm; p=ns). Both concentrations of S100B significantly decreased proliferation respect to control (0.17 ± 0.01 and 0.18 ± 0.01 vs 0.23 ± 0.01 450–540nm; p < 0.01). Compared to control conditions, S100B 0.005 μ M, but not S100B 5 uM, significantly increased lactase activity (+7.5 ± 0.9, p < 0.05 and +1.9 ± 0.5, p=ns fold increase vs control) and sucrase activity (+2.6 ± 0.3, p < 0.05 and +0.7 ± 0.4, p=ns fold increase vs control). Conclusions: We show that both concentrations of S100B have no cytotoxic effect on Caco-2 cell, but decrease t heir proliferation rate. Very intriguingly, only the nanomolar concentration of S100B promotes cellular differentiation, as shown by the increase of the brush border membrane enzymes activity. Thus, the “physiological” concentration of S100B may act reducing intesti- nal epithelial cells proliferation and prompting cells towards differentiation. These findings further highlight the ability of EGCs to regulate intestinal homeostasis