Ag. Estevez et al., Liposome-delivered superoxide dismutase prevents nitric oxide-dependent motor neuron death induced by trophic factor withdrawal, FREE RAD B, 28(3), 2000, pp. 437-446
Inhibition of nitric oxide synthesis prevents rat embryonic motor neurons f
rom undergoing apoptosis when initially cultured without brain-derived neur
otrophic factor. Using an improved cell culture medium, we found that the p
artial withdrawal of trophic support even weeks after motor neurons had dif
ferentiated into a mature phenotype still induced apoptosis through a proce
ss dependent upon nitric oxide. However, nitric oxide itself was not direct
ly toxic to motor neurons. To investigate whether intracellular superoxide
contributed to nitric oxide-dependent apoptosis. we developed a novel metho
d using pH-sensitive liposomes to deliver Cu, Zn superoxide dismutase intra
cellularly into developed a novel method using pH-sensitive liposomes to de
liver Cu, Zn superoxide dismutase intracellularly into motor neurons, Intra
cellular superoxide dismutase prevented motor neuron apoptosis from trophic
factor withdrawal, whereas empty liposomes, inactivated superoxide dismuta
se in liposomes or extracellular superoxide dismutase did not. Neither hydr
ogen peroxide nor nitrite added separately or in combination affected motor
neuron survival. Our results suggest that a partial reduction in trophic s
upport induced motor neuron apoptosis by a process requiring the endogenous
a process requiring the endogenous production of both nitric oxide and sup
eroxide, irrespective of the extent of motor neuron maturation in culture.
(C) 2000 Elsevier Science Inc.