Microglial activation by α-synuclein and inhibition by galectin-3 inhibitor. We measured iNOS expression by western blot in microglial cells after 12 h incubation with α-synuclein monomers (A) and α-synuclein aggregates (B) using different concentrations, 5 μm, 10 μm and 20 μm. iNOS was significantly up regulated with both protein preparations of α-synuclein. α-synuclein aggregates (B) induced a 3-fold higher activation compared to monomers (A). To determine the role of galectin-3 we used a pre-treatment, incubating the galectin-3 inhibitor for 30 min and then we incubated for 12 h the cells with α-synuclein, monomers or aggregates, using the highest concentration, 20 μm. The lower iNOS expression induced by α-synuclein monomers was not significantly inhibited by pharmacological inhibition of galectin-3 (C). iNOS expression induced by α-synuclein aggregates (D) was inhibited by more than 50% using 100 μm of the inhibitor. We use the highest iNOS response in each experiment as an internal control to evaluate the response to the other concentrations. Western blot analysis displays iNOS and β-actin protein levels. One-way ANOVA, *P < 0.05, **P < 0.01, n = 3, mean ± S.E.M.