Divergent role of calcium on Aβ- and MPTP-induced cell death in SK-N-SH neuroblastoma

We attempted to clarify the role of Ca2+ in cell death caused by β-amyloid protein (Aβ) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in SK-N-SH neuroblastoma, respectively. Two insults both reduced cell viability in a concentration-dependent manner and induced equal cytotoxicity in the presence of 20 μM Aβ and 0.4 mM MPTP for 72 h, respectively (68 ± 7 vs. 64 ± 6% viability). Time-related study showed that Aβ evoked cell death occurred quickly at 24 h. Relatively, MPTP exhibited a delayed cell death significantly after 72 h of culture. Pretreating the cells with nimodipine and chelating of Ca2+ by EGTA plus 1,2-bis-(O-aminophenoxy)-ethane-N,N,N′,N′-tetraacetic acid acetoxymethyl ester (BAPTA-AM) successfully rescued Aβ-induced cell death but failed to prevent MPTP toxicity. ELISA determination of mono/oligonucleosomes accumulation showed the mode of cell death evoked by MPTP was presumably apoptosis while by Aβ was necrosis. SK-N-SH cells constitutively expressed the α1C subunit of L-type Ca2+ channel and exposure to Aβ or MPTP for 96 h did not further modify its expression. By contrast, α1D subunit was undetectable or low level expressed in basal condition, but was induced to express after Aβ and MPTP stimulation in a time-dependent manner. Functional assay revealed that KCl-evoked [Ca2+]i rise was significantly greater in Aβ-, but not in MPTP-treated cells when compared with control. Taken together, these results showed that Aβ and MPTP elicited different mode of cell death in SK-N-SH. Nevertheless, Ca2+ overload seems to solely display a crucial role in Aβ-induced cytotoxicity and over-expressed α1D may contribute to the disruption of cellular Ca2+ homeostasis.