Mitochondrial mutagenesis in the brain in forensic and pathological research

Mitochondrial-nuclear epistasis: implications for human aging and longevity

There is substantial evidence that mitochondria are involved in the aging process. Mitochondrial function requires the coordinated expression of hundreds of nuclear genes and a few dozen mitochondrial genes, many of which have been associated with either extended or shortened life span. Impaired mitochondrial function resulting from mtDNA and nuclear DNA variation is likely to contribute to an imbalance in cellular energy homeostasis, increased vulnerability to oxidative stress, and an increased rate of cellular senescence and aging. The complex genetic architecture of mitochondria suggests that there may be an equally complex set of gene interactions (epistases) involving genetic variation in the nuclear and mitochondrial genomes. Results from Drosophila suggest that the effects of mtDNA haplotypes on longevity vary among different nuclear allelic backgrounds, which could account for the inconsistent associations that have been observed between mitochondrial DNA (mtDNA) haplogroups and survival in humans. A diversity of pathways may influence the way mitochondria and nuclear-mitochondrial interactions modulate longevity, including: oxidative phosphorylation; mitochondrial uncoupling; antioxidant defenses; mitochondrial fission and fusion; and sirtuin regulation of mitochondrial genes. We hypothesize that aging and longevity, as complex traits having a significant genetic component, are likely to be controlled by nuclear gene variants interacting with both inherited and somatic mtDNA variability.

Histopathological Changed of the Hypophysis in Malnutrition in Elderly Subjects

Major objectives in forensic gerontology are physical and mental disorders during aging, which can be caused by various factors involving nutrition and stress, often accompanied by dysfunction in the neuroendocrine systems including the hypophysis. The objective of the present study was to investigate the histopathological changes in the adenohypophysis in elderly subjects using autopsy materials. Hypophyses with a scaphoid shape (group S: 16 males and 4 females; mean age, 78.6 years) and a normal one (group C: 30 males and 20 females; mean age, 65.2 years) were compared. Incidence of the scaphoid-shaped hypophysis mildly increased with age, being 17% in the elderly over 65 years of age. The weight of the pituitary gland in group S (0.42 +/- 0.1 g) was lower than that of group C (0.65 +/- 0.2 g). The degree of fibrosis was higher in group S (31.6% +/- 5.4%) than in group C (18.3% +/- 6.3%). Immunohistochemical staining showed no significant differences in the proportion of the ACTH cells and the TSH cells between the two groups (p > 0.05). However, there was an increase in the proportion of gonadotrophs, prolactin cells, and S-100-containing cells in group S and a decrease in that of GH cells (p < 0.05). These findings may be associated with reduced anabolic, gonadal and hepatic functions due to malnutrition.

A low dose of ethidium bromide leads to an increase of total mitochondrial DNA while higher concentrations induce the mtDNA 4997 deletion in a human neuronal cell line

Ethidium bromide (EtBr) is widely used to deplete mitochondrial DNA (mtDNA) and produce mitochondrial DNA-less cell lines. However, it frequently fails to deplete mtDNA in mouse cells. In this study we show by using a highly sensitive real-time PCR, that low doses of EtBr (10 microM) did lead to a three-fold increase of the total amount of mitochondrial DNA in a human neuronal cell line (Ntera 2). A higher dose of EtBr (25 microM) led to the expected decrease of mtDNA until day 22 when the cells almost died. Cell growth and mtDNA content could be restored after additional 22 days of non-EtBr treatment. The highest concentration of 50 microM also led to a significant increase of mtDNA. The cells died when they had only about 10% of mtDNA left, indicating a mtDNA threshold for cell survival. Additionally, the so-called common 4977 bp deletion could be induced by prolonged exposure to ethidium bromide. Whereas the higher doses led to significant higher amounts of deleted mtDNA.