Exposure to 3-Nitropropionic Acid Mitochondrial Toxin Induces Tau Pathology in Tangle-Mouse Model and in Wild Type-Mice.

Oxidative stress, particularly of mitochondrial origin, plays an important role in the pathogenesis of neurodegenerative disorders, including Alzheimer's disease (AD) and other tauopathies. Controversies regarding the responses of tau phosphorylation state to various stimuli causing oxidative stress have been reported. Here we investigated the effect of 3-nitropropionic acid (3NP), a mitochondrial toxin which induces oxidative stress, on the tangle-pathology in our previously generated double mutant (E257T/P301S, DM) -Tau-tg mice and in WT-mice. We detected an increase in tangle pathology in the hippocampus and cortex of the DM-Tau-tg mice following exposure of the mice to the toxin, as well as generation of tangles in WT-mice. This increase was accompanied with alterations in the level of the glycogen synthase kinase 3ß (GSK3ß), the kinase which phosphorylates the tau protein, and in the phosphorylation state of this kinase. A response of microglial cells was noticed. These results point to the involvement of mitochondrial dysfunction in the development of the tangle-pathology and may suggest that interfering with mitochondrial dysfunction may have an anti-tangle therapeutic potential.

Moderate environmental enrichment mitigates tauopathy in a neurofibrillary tangle mouse model.

Epidemiological studies show that stimulating activities reduce the risk of dementia. In animal models of Alzheimer disease, there have been conflicting results of the effects of environmental enrichment (EE) on disease-related amyloid pathology. Here, we tested the direct effect of EE, independently of amyloid pathology, on brain neurofibrillary tangles (NFTs), which best correlate with dementia. We exposed transgenic mice (E257K/P301S-Tau-Tg driven by the natural tau promoter) to moderate nonstrained EE or regular environment. Concomitant with neurogenesis, we detected a decrease in NFT burden and a decrease in the activation of microglia in EE versus regular-environment mice. There was also a trend toward improvement in cognitive tasks in the EE mice. Increased immunoreactivity of brain-derived neurotrophic factor, which is involved in the regulation of tau phosphorylation, was detected in the EE mice, suggesting its possible involvement in the beneficial effects on NFTs and other parameters in the EE mice. These results suggest that NFTs may be directly responsive to environmental stimulating activities and that even nonstrained activities may mitigate tauopathies independent of the involvement of amyloid.