OBJECTIVETo investigate the role of calcium dyshomeostasis in 1-methyl-4-phenylpyridinium ion (MPP⁺)-induced apoptosis of human neuroblastoma SH-SY5Y cells.

METHODSThe viability of SH-SY5Y cells exposed to varying concentrations of MPP⁺ was assessed using MTT colorimetric assay, and MPP⁺-induced cell apoptosis was detected with hoechst 33342 staining and Annexin V+PI assay. Western blotting and rhodamine 123 staining were employed to examine the changes in cellular poly(ADP-ribose) polymerase (PARP) protein expression and mitochondrial membrane potential in response to MPP⁺ exposure. The effects of ruthenium red and/or MPP⁺ on calcium concentration in the cytoplasm, mitochondria and endoplasmic reticulum were evaluated using confocal microscopy.

RESULTSMPP⁺ induced apoptosis and caused reduced cell viability and mitochondrial membrane potential in SH-SY5Y cells. The cells exposed to MPP⁺ showed a lowered calcium concentration in the cytoplasm and endoplasmic reticulum and an increased mitochondrial Ca²⁺ uptake. Ruthenium red rescued MPP⁺-induced apoptosis and mitochondrial membrane potential reduction, reduced PARP cleavage, and inhibited the increase of mitochondrial matrix free Ca²⁺ in the cells exposed to MPP⁺.

CONCLUSIONMitochondrial calcium overload plays an important role in MPP⁺-induced apoptosis of SH-SY5Y cells, which is closely associated with dysregulation of intracellular Ca²⁺ homeostasis.