Liposome-delivered superoxide dismutase prevents nitric oxide-dependent motor neuron death induced by trophic factor withdrawal.
Inhibition of nitric oxide synthesis prevents rat embryonic motor neurons from undergoing apoptosis when initially cultured without brain-derived neurotrophic factor. Using an improved cell culture medium, we found that the partial withdrawal of trophic support even weeks after motor neurons had differentiated into a mature phenotype still induced apoptosis through a process dependent upon nitric oxide. However, nitric oxide itself was not directly toxic to motor neurons. To investigate whether intracellular superoxide contributed to nitric oxide-dependent apoptosis, we developed a novel method using pH-sensitive liposomes to deliver Cu, Zn superoxide dismutase intracellularly into motor neurons. Intracellular superoxide dismutase prevented motor neuron apoptosis from trophic factor withdrawal, whereas empty liposomes, inactivated superoxide dismutase in liposomes or extracellular superoxide dismutase did not. Neither hydrogen peroxide nor nitrite added separately or in combination affected motor neuron survival. Our results suggest that a partial reduction in trophic support induced motor neuron apoptosis by a process requiring the endogenous production of both nitric oxide and superoxide, irrespective of the extent of motor neuron maturation in culture.
Estévez
A G
AG
Departments of Anesthesiology, Biochemistry, and Molecular Genetics and Neurobiology, The UAB Center for Free Radical Biology, University of Alabama at Birmingham, Birmingham, AL 35294-0006, USA.
Sampson
J B
JB
Zhuang
Y X
YX
Spear
N
N
Richardson
G J
GJ
Crow
J P
JP
Tarpey
M M
MM
Barbeito
L
L
Beckman
J S
JS
D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects*; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004337:Drug Carriers; D004622:Embryo, Mammalian; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008081:Liposomes; D009046:Motor Neurons / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009410:Nerve Degeneration / Q000517:prevention & control; D009569:Nitric Oxide / Q000494:pharmacology*; D051381:Rats; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology; D013116:Spinal Cord / Q000166:cytology*; D013482:Superoxide Dismutase / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D013997:Time Factors; D019323:omega-N-Methylarginine / Q000494:pharmacology
D019208:Brain-Derived Neurotrophic Factor; D015853:Cysteine Proteinase Inhibitors; D004337:Drug Carriers; D008081:Liposomes; D011994:Recombinant Proteins; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase; D020169:Caspases; D019331:NG-Nitroarginine Methyl Ester