Interactions among nitric oxide and Bcl‐family proteins after MPP+ exposure of SH‐SY5Y neural cells I: MPP+ increases mitochondrial NO and Bax protein
- 19 February 2003
- journal article
- research article
- Published by Wiley in Journal of Neuroscience Research
- Vol. 72 (1) , 76-88
Abstract
We studied effects of methylpyridinium ion (MPP+) on apoptosis, cell death and regulation of Bcl‐2‐family proteins in SH‐SY5Y neuroblastoma cells. MPP+ increased intracellular accumulation of DNA‐histone complexes as a measure of apoptosis and decreased intracellular calcein fluorescence as a measure of cell death. If ATP synthesis was supported, MPP+ caused apoptosis in ρ0 cells devoid of electron transport function. Caspase inhibition blocked apoptosis but not cell death caused by MPP+. MPP+ increased levels of Bax, Bcl‐2 and Bcl‐XL proteins ∼2‐fold over 24 hr, with Bax increases occurring first; Bax did not increase in ρ0 cells. The Bax increase, but not that of Bcl‐2 or Bcl‐XL, was dependent on nitric oxide (NO) and seemed post‐transcriptional. DAF‐FM imaging revealed increased mitochondrial NO within hours of exposure to MPP+. Western blots showed a constitutive ∼130 kD protein that stained for NOS‐2, consistent with reports of mitochondrial nitric oxide synthase (mtNOS). MPP+ caused a NO‐dependent release of cytochrome C into cytoplasm. MPP+ increases mitochondrial NO levels and causes a NO‐dependent increase in Bax protein, providing a mechanism for NOS‐and Bax‐dependency of MPTP neurotoxicity in vivo and implicating locally produced NO as a signaling molecule used by mitochondria to manipulate cell death cascades.Keywords
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