Interactions among nitric oxide and Bcl-family proteins after MPP+ exposure of SH-SY5Y neural cells II: exogenous NO replicates MPP+ actions.
In the preceding companion article, we showed that the neurotoxin methylpyridinium (MPP(+)) increases mitochondrial nitric oxide (NO), causes a post-transcriptional, NO-dependent increase in Bax protein and produces caspase-dependent apoptosis and caspase-independent cell death. In the present study, we show that exogenous NO replicates these findings. The long-term NO generator diethylenetriamine-NO (DETA-NO) reproduced the post-transcriptional Bax protein increase, but did not increase Bcl-2 or Bcl-X(L) proteins. Like MPP(+), DETA-NO caused an early decrease in Bcl-2 mRNA, did not increase Bax protein in rho(0) cells and caused caspase- and cycloheximide-dependent apoptosis and caspase-independent cell death. We developed cell lines with inducible overexpression of Bcl proteins, at levels relevant to those we found in cells exposed to MPP(+) or DETA-NO. Inducible overexpression ( approximately 2-fold) of Bcl-2 or Bcl-X(L) proteins reduced MPP(+) or NO-induced apoptosis but did not affect cell death. Inducible Bax overexpression ( approximately 5-fold) slightly increased cell death. Our results show that exogenous NO mimics actions of MPP(+) on SH-SY5Y neuroblastoma cells and supports the mediation of MPP(+) neurotoxicity by NO generated intracellularly in mitochondria.
Dennis
Jameel
J
Neuroscience Graduate Program, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
Bennett
James P
JP
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D006801:Humans; D009447:Neuroblastoma / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism* / Q000494:pharmacology*; D011518:Proto-Oncogene Proteins / Q000032:analysis / Q000096:biosynthesis*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D011726:Pyridinium Compounds / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011726:Pyridinium Compounds; D051028:bcl-2-Associated X Protein; D009569:Nitric Oxide; C014677:1-methylpyridinium