S100b protects IMR-32 cells against Ab(1-42) induced neurotoxicity via modulation of apoptotic genes expression

Amyloid beta (1-42) peptide is considered responsible for the formation of senile plaques that accumulate in the brain of patients with Alzheimer's disease (AD). In the last years considerable attention has been focused on identifying new protective substances that prevent or almost retard the appearance of amyloid beta (1-42)-related neurotoxic effects. In this study, human neuroblastoma cells (IMR-32) was used as system model to evaluate the protective role of S100b, a neurotrophic factor and neuronal survival protein, that is highly expressed by reactive astrocytes in close vicinity of beta-amyloid deposits, against amyloid beta (1-42)-dependent toxicity. Our results show that at nanomolar concentrations, S100b protects cells against Ab mediated cytotoxicity, as assessed by MTS vitality test. The protective mechanism seems be related to the effect on bcl-2 (an anti-apoptotic gene) expression, which is highly down-regulated by amyloid beta (1-42) treatment, while resulted more expressed in the presence of S100b. On the contrary, Bax, a pro-apoptotic gene, resulted down-regulated by the treatment with S100 compared with the results obtained in the presence of amyloid beta (1-42) peptide. However, at micromolar doses, S100b is toxic for IMR-32 cells and its toxicity adds to that of the Ab peptide, suggesting that additional molecular mechanisms may be involved in the neurotoxic process.