Abstract
Alzheimer’s disease (AD) is an age-dependent neurodegenerative disease that degrades cognitive function resulting in memory loss, difficulty in completing daily tasks and dementia. Both endogenous and external factors can significantly impact risk, such that development of AD has become one of the most common progressive diseases in the United States. Unfortunately, the causal mechanism of this complex disease is still unknown. One hypothesis, the amyloid cascade hypothesis, posits that AD is caused by accumulation of Aβ plaques due to misfolded proteins. The proteostasis network works to maintain protein folding and a healthy proteome through regulating protein synthesis, degradation, and folding. As AD progresses, amyloid beta (Aβ) and tau proteins aggregate and misfold exemplifying proteostasis collapse. In mice, exposure to nano-particulate matter (nPM) from traffic-derived air pollution increases Aβ aggregation. The mechanism by which this occurs is also still unknown, but we hypothesize that it does so by contributing to proteostasis collapse. To test this hypothesis, we used the model organism Caenorhabditis elegans expressing the neurodegenerative disease-associated proteins polyglutamine (polyQ) and Aβ as aggregation-prone sensors of proteostasis decline. In animals expressing polyQ in body wall muscle cells, protein aggregation increased and mobility decreased upon exposure to nPM compared to control animals which were not exposed to nPM. Similarly, animals expressing polyQ in intestinal cells showed increased aggregation upon nPM exposure compared to controls. In animals expressing Aβ in body wall muscle cells, Aβ protein aggregate formation into large visible proteins increased upon exposure to nPM when compared to controls. Protein aggregation and decreased mobility signify proteostasis decline. Together, these findings support our hypothesis that nPM acts, at least in part, by disrupting proteostasis.
