Salsolinol, an endogenous
neurotoxin, may be involved in the pathogenesis of
Parkinson's disease. In this study, we sought to determine whether
salsolinol-induced cytotoxicity in SH-SY5Y human
neuroblastoma cells, a cloned cell line which expresses dopaminergic activity, could be prevented by overexpressing a Ca(2+) channel, transient receptor potential (TRPC1)
protein. Exposure of SH-SY5Y cells to 500 microM
salsolinol for 12 h resulted in a significant decrease in
thapsigargin or
carbachol-mediated Ca(2+) influx. Consistent with these results, SH-SY5Y cells treated with
salsolinol showed approximately 60% reduction in TRPC1
protein levels. Confocal microscopy also showed that SH-SY5Y cells treated with
salsolinol had a significant decrease in the plasma membrane staining of the TRPC1
protein. Interestingly, overexpression of TRPC1 increases TRPC1
protein levels and also protected SH-SY5Y
neuroblastoma cells against
salsolinol-mediated cytotoxicity as determined by 3,[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium
bromide (MTT) assay. The protective effect of TRPC1 was blocked by the addition of TRPC1 blockers
lanthanum, or
2APB. Activation of TRPC1
protein by either
thapsigargin or
carbachol further protected SH-SY5Y cells from
salsolinol treatments. Staining of SH-SY5Y cells with an apoptotic marker (YO-PRO-1) showed that TRPC1
protein protects against apoptosis. Furthermore, TRPC1 overexpression also inhibited
cytochrome c release and decreased
BAX protein levels required for apoptosis. Taken together, these findings suggest that the reduction in cell surface TRPC1
protein expression in response to
salsolinol may be a contributory factor in cellular toxicity of the dopaminergic neurons. Furthermore, overexpression of TRPC1 could inhibit apoptotic complex thereby increasing neuronal cell survivability in
Parkinson's disease.