Brain aging and testosterone-induced neuroprotection: studies on cultured sheep cortical neurons.
OBJECTIVE
This research reports the expression of topoisomerase βII in fetal sheep neuronal cells. The β isoform of DNA topoisomerase II plays a role in DNA repair process in non proliferating cells as neurons and its expression tends to be downregulated with senescence.


METHODS
Cortical neurons from 60-day-old sheep embryos underwent two protocols: the former based on rising time of culture (10, 20 and 30 days); the latter based on the 72hrs exposure to 3-nitro-L-tyrosine (oxidative/nitrosative stressor) and/or testosterone.


RESULTS
Our results showed an increase in β-galactosidase activity and, in contrast, a reduction in topoisomerase βII expression with time (first protocol). The exposure of sheep primary neurons to 3-nitro-L-tyrosine led to an upregulation of βII topoisomerase expression to be likely seen as a reaction to nitrosative stress. Testosterone addition to 3-nitro-L-tyrosine-exposed cells results in topoisomerase βII decrease possibly due to the neuroprotective properties of testosterone (second protocol). No significant variations in the marker of aging β-galactosidase were observed in the cells exposed to 3-nitro-L-tyrosine and testosterone.


CONCLUSIONS
The protocol based on time could be of some interest as a model of neuronal senescence in vitro. Topoisomerase βII decrease with aging likely indicates a reduced ability to repair DNA during neuronal senescence. In contrast, the second protocol may not be seen as a reliable model of aging since 3-nitro-L-tyrosine does not lead to a topoisomerase βII decrease. Testosterone was able to cope with oxidative/nitrosative damage, allowing cells to reduce their needs in DNA repair which in turn leads to a downregulation of topoisomerase IIβ expression.
Department of Veterinary Medicine, University of Sassari, Italy. lepore@uniss.it.
Gianluca
G
Lepore
Marco
M
Zedda
Emilio
E
Mura
Stefano
S
Giua
Gian Luca
GL
Dedola
Vittorio
V
Farina
D000375:Aging / Q000378:metabolism*; D000818:Animals; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology*; D012756:Sheep; D013739:Testosterone / Q000494:pharmacology*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects
D004268:DNA-Binding Proteins; D018696:Neuroprotective Agents; C002744:3-nitrotyrosine; D013739:Testosterone; D014443:Tyrosine; D004250:DNA Topoisomerases, Type II