Pan-capase inhibitor treatment reduces the effect of SB on apoptosis but not α-Syn oligomer accumulation. 3D5 cells with 10 ds of differentiation and induced α-Syn expression were treated with 10 mM SB in the presence or absence of 50 μM z-VAD (OMe)-fmk, a pan caspase inhibitor (CI), for 24 hs. Cultures without any drug treatment or treated with CI only were included as controls. (A) Calcein AM cell viability assay. The SB-treated cultures displayed a significant decrease of cell viability when compared to untreated counterparts (**P < 0.01, n = 3). The extent of cell death is significantly reduced (#P < 0.05, n = 3) in cultures treated with SB plus CI. (B) Western blotting of cell lysates. Antibodies to α-Syn, caspase 9, active Caspase 3, PARP and GAPDH were used. The SB and CI co-treated or the SB-treated cultures displayed similar levels and profiles of α-Syn oligomers and contained more α-Syn oligomers than non-treated (Con) or CI-treated control. In contrast, the SB and CI co-treated cultures displayed more full-length and less cleaved caspases 3 and 9 or PARP than the SB-treated. Molecular weight markers were included as references.