Exposure to automobile exhaust and wastes generated by industrial combustion through contaminated air is one of the most common environmental exposures among the general public, and long-term exposure to such polluted air and its main constituent, fine and ultrafine particulate matter (PM), has long been recognized as a major risk factor for cardiovascular morbidity and mortality. Notably, recent population-based epidemiological studies identify PM's significant influence on cognitive function in humans, and indicate it as an increased risk for developing Alzheimer's disease (AD). These findings suggest that exposure to PM causes lifelong impact on the central nervous system and substantial neurotoxicity, giving rise to accelerated cognitive decline and possibly the development of AD neuropathology. However, research has yet to fully elucidate the biological mechanisms of PM-induced neurotoxicity, at the molecular and cellular levels, or to elucidate functional, morphological, anatomical, and/or pathological changes leading to cognitive decline and increased risk for AD. Given our expertise and recently emerging evidence in the field, we hypothesize that the exposure to PM perturbs dendritic spines and promotes the buildup of toxic amyloid-beta (A?) species by aggravated microglial activation and neuroinflammation. The proposed research will rigorously assess the changes in dendritic spine morphology, A? buildup, microglial activation, and inflammatory profiles in mice exposed to environmentally- relevant PM and determine the microglia's prime role in PM-induced neurotoxicity by ablating them. The proposed project is significant as we aim to identify microglia as a key mediator of inhaled PM-induced neurotoxicity and reveal inhaled PM's biological impact on cognitive decline and the risk for AD. Deciphering cellular cascades triggered by exposure to environmental PM will exhibit highly intrinsic merit toward understanding the environmental impact on brain health and will contribute to improving public awareness of the risk of exposure to environmental contaminants. This project has significant translational value, as an improved understanding of the biological mechanisms by which exposure to PM influences cognitive decline will pave the way for more effective preventive and therapeutic measures.

Public Health Relevance

As air quality deteriorates in rapidly developing countries and major cities in the U.S., more individuals are at risk of increasing exposure to highly contaminated urban air pollution containing fine and ultrafine particulate matter (PM) generated from industrial combustion and automobile exhaust. While the impact of PM exposure on cardiovascular mortality and morbidity has been extensively studied and well recognized, its neurotoxic effects leading to accelerated cognitive decline and the increased risk for Alzheimer's disease (AD) remain largely unknown. This proposal aims to determine how exposure to fine and ultrafine PM affects brain function by destroying functional synapses. Understanding PM neurotoxicity may help improve public awareness of air pollution and its impact on health and lead to more effective preventive and therapeutic measures.

National Institute of Health (NIH)
National Institute of Environmental Health Sciences (NIEHS)
Exploratory/Developmental Grants (R21)
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Neurotoxicology and Alcohol Study Section (NAL)
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Hollander, Jonathan
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University of California Irvine
Internal Medicine/Medicine
Schools of Medicine
United States
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