Activation of Poly(ADP-Ribose)Polymerase in rat hepatocytes does not contribute to their cell death by oxidative stress.
Latour I, Leunda-Casi A, Denef JF, Buc Calderon P
Departement des Sciences Pharmaceutiques, Universite Catholique de Louvain, Brussels, 1200, Belgium.
Oxidative stress induced by tert-butyl hydroperoxide (tBOOH) in freshly
isolated rat hepatocytes caused DNA damage and loss of membrane integrity.
Such DNA lesions are likely to be single strand breaks since neither caryolysis
nor chromatine condensation was seen in electron micrographs from tBOOH-treated
cells. In addition, pulsed field gel electrophoresis of genomic DNA from
both control and tBOOH-treated hepatocytes showed similar profiles, indicating
the absence of internucleosomal DNA cleavage, a classical reflection of
apoptotic endonuclease activity. The activation of the repair enzyme poly(ADP-ribose)polymerase
(PARP) following DNA damage by tBOOH induced a dramatic drop in both NAD(+)
and ATP. The inhibition of PARP by 3-aminobenzamide enhanced DNA damage
by tBOOH, restored NAD(+) and ATP levels, but did not result in better
survival against cell killing by tBOOH. The lack of the protective effect
of PARP inhibitor, therefore, does not implicate PARP in the mechanism
of tBOOH-induced cytotoxicity. Electron micrographs also show no mitochondrial
swelling in cells under oxidative stress, but such organelles were mainly
located around the nucleus, a picture already observed in autoschizis,
a new suggested kind of cell death which shows both apoptotic and necrotic
morphological characteristics. Copyright 2000 Academic Press.
PMID: 10623477, UI: 20090800