Debilitating age-related neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease, are characterized by progressive neuronal loss. Although a percentage of these cases can be attributed to genetic mutations, the majority arise from unknown causes. Exposure to environmental toxicants, such as pesticides, heavy metals, and industrial solvents, is strongly associated with an increased risk of developing neurodegenerative diseases. Despite this growing body of epidemiologic evidence, the molecular basis for this increased risk resulting from environmental exposure remains poorly characterized. Delineating the molecular mechanisms by which environmental toxicant exposure translates to neuronal cell death is anticipated to improve our understanding of the initiation and progression of neurologic disorders and inform the development of new treatments. Chlorpyrifos (CPF) is a widely-used, commercially available blood-brain- barrier permeant organophosphate pesticide that is widely-accepted to act through inhibition of acetylcholinesterase (AChE). Exposure to CPF is associated with increased risk of developing multiple age- related neurodegenerative diseases but discrepancies exist related to mechanisms of toxicity underlying CPF exposure. For example, experimental evidence suggests that AChE inhibition is neuroprotective; and moreover, CPF toxicity is readily observed in cells that are not known to express AChE. This disconnect underscores the importance of characterizing alternative mechanisms of CPF-induced neuronal cell death. We have characterized CPF-induced neuronal cell death utilizing cultured primary neurons. Transcriptomic and ontologic analyses identified the pro-apoptotic mediator Bbc3 (aka Puma) and the p53 pathway as significantly enriched following CPF exposure compared to controls. Several studies have identified CPF-induced neuronal stress and programmed cell death in cell and animal models, but it is unknown whether activation of the p53- Bbc3 signaling axis is required for programmed cell death in neurons or if inhibition of Bbc3 activity is neuroprotective in CPF-exposed neurons. Here we describe a rigorous research and training plan designed to test the hypothesis that CPF exposure leads to the activation of a Bbc3-dependent cellular death program, an induction of molecular machinery independent of CPF's inhibitory action on AChE. These mechanistic studies will provide experimental evidence to support epidemiologic findings related to CPF and prevalent neurologic disorders as well as a platform for further analysis of the impact of disease-associated pesticides on the brain.
Neuronal cell death is characteristic of neurodegenerative diseases associated with exposure to environmental pollutants. We propose to characterize neuronal cell death associated with exposure to the widely-used pesticide chlorpyrifos at the molecular level. These experiments are expected to provide a new understanding of how environmental toxicant exposure contributes to common diseases of the elderly, thus informing public health and the development of new approaches to diagnose, monitor, and treat those at risk of developing age- related neurologic disorders.
