TRPC1 protects dopaminergic SH-SY5Y cells from MPP⁺, salsolinol, and N-methyl-(R)-salsolinol-induced cytotoxicity

Neurotoxins and alterations in Ca²⁺ homeostasis have been associated with Parkinson's disease (PD), but the role of store-operated Ca ²⁺ entry channels is not well understood. Previous studies have shown the neurotoxicity of salsolinol and 1-methyl-4-phenylpyridinium ion on SH-SY5Y cells and cytoprotection induced by transient receptor potential protein 1 (TRPC1). In the present study, N-methyl-(R)-salsolinol was tested for its cellular toxicity and effects on TRPC1 expression. MTT (3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide) assays, DAPI (4′,6-diamidino-2- phenylindole), fluorescein isothiocyanate-Annexin-V/propidium iodide, western blot analysis, and JC-1 labeling revealed that the three indicated drugs could induce caspase-dependent, mitochondrial-mediated apoptosis. Exposure of SH-SY5Y cells to the indicated drugs resulted in a significant decrease in thapsigargin-mediated Ca²⁺ influx and TRPC1 expression. Immunocytochemistry experiments revealed that neurotoxins treatment induced TRPC1 translocation to the cytoplasm. Taken together, our results indicate that treatment with neurotoxins may alter Ca²⁺ homeostasis and induce mitochondrial-mediated caspase-dependent cytotoxicity, an important characteristic of PD.