Increased sensitivity to oxidative injury in chinese hamster ovary cells stably transfected with rat liver S-adenosylmethionine synthetase cDNA

Sánchez-Góngora, E.; Pastorino, J.G.; Alvarez, L.; Pajares, M.A.; García, C.; Viña, J.R.; Mato, J.M.; Farber, J.L.

Biochemical Journal 319: 767-773

1996


ISSN/ISBN: 0264-6021
PMID: 8920979
DOI: 10.1042/bj3190767
Accession: 008851517

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Abstract
Chinese hamster ovary cells were stably transfected with rat liver S-adenosylmethionine synthetase cDNA. As a result, S-adenosylmethionine synthetase activity increased 2.3-fold, an effect that was accompanied by increased S-adenosylmethionine, a depletion of ATP and NAD levels, elevation of the S-adenosylmethionine/S-adenosylhomocysteine ratio (the methylation ratio), increased DNA methylation and polyamine levels (spermidine and spermine), and normal GSH levels. By contrast, the transfected cells showed normal growth curves and morphology. Exposure to an oxidative stress by the addition of H-2O-2 resulted in a greater consumption of ATP and NAD in the transfected cells than in the wild-type cells. In turn, cell killing by H-2O-2 was greater in the transfected cells than in the wild-type cells. This killing of Chinese hamster ovary cells by H-2O-2 involved the activation of poly(ADP-ribose) polymerase with the resultant loss of NAD and ATP. 3-Aminobenzamide, an inhibitor of poly(ADP-ribose) polymerase, but not the antioxidant N,N'-diphenylphenylenediamine, prevented the killing of Chinese hamster ovary cells by H-2O-2 and maintained the contents of NAD and ATP. The results of this study indicate that a moderate activation of the synthesis of S-adenosylmethionine leads to ATP and NAD depletion and to a greater sensitivity to cell killing by oxidative stress.