Ag. Estevez et al., PEROXYNITRITE-INDUCED CYTOTOXICITY IN PC12 CELLS - EVIDENCE FOR AN APOPTOTIC MECHANISM DIFFERENTIALLY MODULATED BY NEUROTROPHIC FACTORS, Journal of neurochemistry, 65(4), 1995, pp. 1543-1550
Peroxynitrite is a powerful oxidant formed by the near-diffusion-limit
ed reaction of nitric oxide with superoxide, Large doses of peroxynitr
ite (> 2 mM) resulted in rapid cell swelling and necrosis of undiffere
ntiated PC12 cells, However, brief exposure to lower concentrations of
peroxynitrite (EC(50) = 850 mu M) initially (3-4 h) caused minimal da
mage to low-density cultures. By 8 h, cytoplasmic shrinkage with nucle
ar condensation and fragmentation became increasingly evident, After 2
4 h, 36% of peroxynitrite-treated cells demonstrated these features as
sociated with apoptosis, In addition, 46% of peroxynitrite-treated cel
ls demonstrated DNA fragmentation (by terminal-deoxynucleotide transfe
rase-mediated dUTP-digoxigenin nick end-labeling) after 7 h, which was
inhibited by posttreatment with the endonuclease inhibitor aurintrica
rboxylic acid, Serum starvation also resulted in apoptosis in control
cells (23%), the percentage of which was not altered significantly by
peroxynitrite treatment, Although peroxynitrite is known to be toxic t
o cells, the present study provides a first indication that peroxynitr
ite induces apoptosis, Furthermore, pretreatment of cells with nerve g
rowth factor or insulin, but not epidermal growth factor, was protecti
ve against peroxynitrite-induced apoptosis, However, both acidic and b
asic fibroblast growth factors greatly increased peroxynitrite-initiat
ed apoptosis, to 63 and 70%, respectively, Thus, specific trophic fact
ors demonstrate differential regulation of peroxynitrite-induced apopt
osis in vitro.