Ra. Gottlieb et al., APOPTOSIS INDUCED IN JURKAT CELLS BY SEVERAL AGENTS IS PRECEDED BY INTRACELLULAR ACIDIFICATION, Proceedings of the National Academy of Sciences of the United Statesof America, 93(2), 1996, pp. 654-658
We have previously shown that in neutrophils deprived of granulocyte c
olony-stimulating factor, apoptosis is preceded by acidification and t
hat the protection against apoptosis conferred on neutrophils by granu
locyte colony-stimulating factor is dependent upon delay of this acidi
fication, To test the hypothesis that acidification could be a general
feature of apoptosis, we examined intracellular pH changes in another
cell line, Jurkat cells, a T-lymphoblastoid line, were induced to und
ergo apoptosis with anti-Fas IgM, cycloheximide, or exposure to short-
wavelength UV light, We found that acidification occurred in response
to treatment with these agents and that acidification preceded DNA fra
gmentation, Jurkat cells were also found to possess an acid endonuclea
se that is active below pH 6.8, compatible with a possible role for th
is enzyme in chromatin digestion during apoptosis, Incubation of the c
ells with the bases imidazole or chloroquine during treatment with ant
i Fas antibody or cycloheximide or after UV exposure decreased apoptos
is as assessed by nuclear morphology and DNA content, The alkalinizing
effect of imidazole and chloroquine was shown by the demonstration th
at the percentage of cells with an intracellular pH below 6.8 after tr
eatment with anti-Fas antibody, cycloheximide, or UV was diminished in
the presence of base as compared with similarly treated cells incubat
ed in the absence of base, We conclude that acidification is an early
event in programmed cell death and may be essential for genome destruc
tion.