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.. CONCLUSION: 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."