Hormone deprivation induces an increase in oxidative damage to mitocondrial DNA in the hippocampus

AVACA, MICAELA; GREDILLA RICARDO; VILLA IVANA; REINÉS ANALÍA; STEVNSNER TINNA; ZÁRATE SANDRA

Congreso; Reunión Anual de Sociedades de Biociencias; 2023

Ovarian hormone loss is related to brain mitochondrial dysfunction and oxidative stress. Base excision repair (BER) is the main mechanism to repair mitochondrial DNA (mtDNA) and is critical to avoid accumulation of mutations in this organelle. It comprises several steps involving lesion-specific glycosylases and endonucleases.We previously showed that the activity of glycosylases that repair oxidative lesions and APEendonuclease was decreased in mitochondria from the hippocampus of hormone-deprived rats. Conversely, the activity of those enzymes in cortical mitochondria was increased, suggesting a putative compensatory mechanism to avoid accumulation of oxidative lesions in this brain area. The aim of this work was to determine the level of mtDNA damage in the hippocampus (Hp) and cerebral cortex (Cc) of animals subjected to chronic deprivation of ovarian hormones induced by ovariectomy. For this purpose, adult rats were ovariectomized (OVX) or sham operated (SHAM). After 12 weeks, total DNA from the Hp and Cc was purified and subjected to long-amplicon PCR for a 13.4kb-fragment of mtDNA, which allows estimation of DNA polymerase blocking lesions. To estimate oxidized base lesions, DNA was pre-incubated with Fpg enzyme. The ratio of amplification of a short mtDNA fragment/nuclear DNA amplicon was used as an estimation of mtDNA copy number. In the Hp, Fpg-treated mtDNA from OVX rats showed a lower relative amplification than SHAM (p