Enteroglial derived S100B protein modulates differentiation, proliferation and nitrosative stress of human intestinal epithelial cells in a rage-dependent manner

Objective: 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). We aimed to study the effects of different concentrations of S100B on viability, proliferation, differentiation and nitric oxide (NO) release of the epithelial intestinal cells (IECs). Methods: Caco-2 cells were exposed to nanomolar or micromolar concentrations of S100B (0.005 and 5 l mol L)1, respectively), for 24 h, in presence or absence of a specific anti-RAGE neutralizing antibody (1/1000 v/v) added 2 h before S100B stimulation. Cells viability, proliferation, differentiation and NO release were respectively studied by MTT vitality test, Bromodeoxyuridine incorporation assay, lactase/sucrase enzymes activity tests and with nitrite assay test. Cells with medium alone were used as control. Data are expressed as mean ± SD. Results: Both S100B 0.005 l mol L)1 and S100B 5 l mol L)1, compared to control, did not affect cell viability (0.8 ± 0.3 and 0.7 ± 0.3 vs 0.7 ± 0.1 k540–630; 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 k450–540; P < 0.05). This antiproliferative effect was not observed when cells were pre-treated with anti-RAGE. Compared to control, S100B 0.005 l mol L)1, but not S100B 5 l mol L)1, significantly increased lactase activity (+7.5 ± 0.9, P < 0.05 and +1.9 ± 0.5 fold increase versus control; P = ns) and sucrase activity (+2.6 ± 0.3, P < 0.05 and +0.7 ± 0.4, P = ns fold increase versus control). The increase in lactase/sucrase activity was not observed when cells were pre-treated with anti-RAGE. Both S100B 0.005 l mol L)1 and S100B 5 l mol L)1 increased NO release (+2.5 ± 0.3 and +3.4 ± 0.5 fold increase versus control; P < 0.05) from Caco-2 but not from cells pre-treated with anti-RAGE. Conclusion: Nanomolar, but not micromolar, concentration of S100B seems to act reducing IECs proliferation and prompting cells towards differentiation, without cytotixic effects. Conversely, both concentrations of S100B increased nitrosative stress in IECs. Very intriguingly, these effects were abolished in the presence of a specific anti-RAGE antibody. Our findings further highlight the ability of EGCs to regulate intestinal homeostasis.