Interactions among nitric oxide and Bcl-family proteins after MPP+ exposure of SH-SY5Y neural cells I: MPP+ increases mitochondrial NO and Bax protein

✍ Scribed by Jameel Dennis; James P. Bennett Jr.

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 745 KB
• Volume: 72
• Category: Article
• ISSN: 0360-4012
• DOI: 10.1002/jnr.10539

✦ Synopsis

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 ρ^0^ 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‐X~L~ proteins ∼2‐fold over 24 hr, with Bax increases occurring first; Bax did not increase in ρ^0^ cells. The Bax increase, but not that of Bcl‐2 or Bcl‐X~L~, 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. © 2003 Wiley‐Liss, Inc.