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Age-related alteration of poly(ADP-ribose) polymerase activity in different parts of the brain.

100%
Strosznajder J. B., Jęśko H., Strosznajder R. P.
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2000
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vol. 47
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issue 2
331-337
EN
Poly(ADP-ribose) polymerase (PARP) is a conserved enzyme involved in the regulation of DNA repair and genome stability. The role of PARP during aging is not well known. In this study PARP activity was investigated in nuclear fractions from hippocampus, cerebellum, and cerebral cortex of adult (4 months), old adult (14 months) and aged (24-27 months) rats. Concomitantly, the free radical evoked lipid peroxidation was estimated as thiobarbituric acid reactive substances (TBARS). The specific activity of PARP in adult brain was about 25, 21 and 16 pmol/mg protein per min in hippocampus, cerebellum and cerebral cortex, respectively. The enzyme activity was higher in all investigated parts of the brain of old adults. In aged animals PARP activity was lower in hippocampus by about 50%, and was unchanged in cerebral cortex and in cerebellum comparing to adult rats. The concentration of TBARS was the same in all parts of the brain and remained unchanged during aging. There is no direct correlation between PARP activity and free radical evoked lipid peroxidation during brain aging. The lowered enzyme activity in aged hippocampus may decrease DNA repair capacity which subsequently may be responsible for the higher vulnerability of hippocampal neurons to different toxic insults.
2
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Effect of amyloid beta peptide on poly(ADP-ribose) polymerase activity in adult and aged rat hippocampus.

100%
Strosznajder J. B., Jęśko H., Strosznajder R. P.
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2000
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vol. 47
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issue 3
847-854
EN
It is suggested that the fibrillar amyloid beta peptide (Aβ) in brain plays a direct role in neurodegeneration in Alzheimer's disease, probably through activation of reactive oxygen species formation. Free radicals and numerous neurotoxins elicit DNA damage that subsequently activates poly(ADP-ribose) polymerase (PARP, EC 2.4.2.30). In this study the effect of neurotoxic fragment (25-35) of full length Aβ peptide on PARP activity in adult and aged rat hippocampus was investigated. In adult (4 month old) rat hippocampus the Aβ 25-35 peptide significantly enhanced PARP activity by about 80% but had no effect on PARP activity in cerebral cortex and in hippocampus from aged (24-27 month old) rats. The effect of Aβ peptide was reduced by half by the nitric oxide synthase inhibitor N-nitro-L-arginine. Stimulation of glutamate receptor(s) itself enhanced PARP activity by about 80% in adult hippocampus. However, Aβ 25-35 did not exert any additional stimulatory effect. These results indicate that Aβ, through NO and probably other free radicals, induces activation of DNA bound PARP activity exclusively in adult but not in aged hippocampus.
3
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Amyloid beta enhances cytosolic phospholipase A2 level and arachidonic acid release via nitric oxide in APP-transfected PC12 cells

64%
Chalimoniuk M., Stolecka A., Cąkała M., Hauptmann S., Schulz K., Lipka U., Leuner K., Eckert A., Muller W. E., Strosznajder J. B.
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EN
Cytosolic phospholipase A2 (cPLA2) preferentially liberates arachidonic acid (AA), which is known to be elevated in Alzheimer's disease (AD). The aim of this study was to investigate the possible relationship between enhanced nitric oxide (NO) generation observed in AD and cPLA2 protein level, phosphorylation, and AA release in rat pheochromocytoma cell lines (PC12) differing in amyloid beta secretion. PC12 control cells, PC12 cells bearing the Swedish double mutation in amyloid beta precursor protein (APPsw), and PC12 cells transfected with human APP (APPwt) were used. The transfected APPwt and APPsw PC12 cells showed an about 2.8- and 4.8-fold increase of amyloid β (Aβ) secretion comparing to control PC12 cells. An increase of NO synthase activity, cGMP and free radical levels in APPsw and APPwt PC12 cells was observed. cPLA2 protein level was higher in APPsw and APPwt PC12 cells comparing to PC12 cells. Moreover, phosphorylated cPLA2 protein level and [3H]AA release were also higher in APP-transfected PC12 cells than in the control PC12 cells. An NO donor, sodium nitroprusside, stimulated [3H]AA release from prelabeled cells. The highest NO-induced AA release was observed in control PC12 cells, the effect in the other cell lines being statistically insignificant. Inhibition of cPLA2 by AACOCF3 significantly decreased the AA release. Inhibitors of nNOS and γ-secretase reduced AA release in APPsw and APPwt PC12 cells. The basal cytosolic [Ca2+]i and mitochondrial Ca2+ concentration was not changed in all investigated cell lines. Stimulation with thapsigargin increased the cytosolic and mitochondrial Ca2+ level, activated NOS and stimulated AA release in APP-transfected PC12 cells. These results indicate that Aβ peptides enhance the protein level and phosphorylation of cPLA2 and AA release by the NO signaling pathway.
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