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Accumulation of DNA Damage in Aging Neurons Occurs Through a Mechanism Other than Apoptosis
Author(s) -
Mandavilli Bhaskar S.,
Rao Kalluri Subba
Publication year - 1996
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1996.67041559.x
Subject(s) - biology , programmed cell death , apoptosis , acridine orange , dna damage , dna fragmentation , microbiology and biotechnology , glutamate receptor , aurintricarboxylic acid , cycloheximide , neuron , dna , fragmentation (computing) , agarose gel electrophoresis , senescence , biochemistry , protein biosynthesis , neuroscience , ecology , receptor
Two biochemical strategies using nick translation‐type of incubation and terminal transferase‐catalyzed reaction were used to assess single‐ (SSB) and double‐strand (DSB) breaks in DNA of permeabilized neurons isolated from young, adult, and old rat cerebral cortex. Both SSBs and DSBs accumulate with age. On prior treatment of neuronal cells with 1 m M glutamate or 50 µ M N ‐methyl‐ N′ ‐nitro‐ N ‐nitrosoguanidine (MNNG), more extensive damage was seen at all ages, with the old neurons suffering maximal damage. When neuronal DNA was subjected to agarose electrophoresis, increasingly diffused bands were seen with age in normally aging neurons. However, a typical nucleosomal ladder, characteristic of apoptosis, was seen only when the cells were exposed to either glutamate or MNNG irrespective of the age of the neurons. Furthermore, this apoptotic fragmentation of DNA was prevented by prior treatment of the cells with either cycloheximide or aurintricarboxylic acid, indicating that both glutamate and MNNG induce programmed cell death. Fluorescence microscopic observation of glutamate‐ and MNNG‐treated neurons after acridine orange staining revealed a high degree of staining and marked condensation of nuclear DNA. On the other hand, no such phenomenon was observed in normally aging neurons either histologically or in biochemical assays of damage. It is concluded that both glutamate and MNNG induce programmed cell death in neurons independent of age and that accumulation of DNA damage in naturally aging neurons occurs through a process other than that of apoptosis.