SUMMARY Through this RIVER proposal, I seek support to characterize and understand early biological responses that anticipate age-related disease, which typically develops from exposures that occurred much earlier in life. My primary focus will be on the effects of air pollution on accelerated brain aging, a major interest of my lab. Ambient air particulate pollution has been shown to hasten cognitive aging by as much as 5 years. Because of the strong age dependence of dementia, merely delaying its onset could have a dramatic impact. For effectively preventing such effects, we need to develop biomarkers that reflect not only adverse exposures, but also preclinical effects on cognitive function and brain health deterioration. That is, we need to find easy-to-use tools to detect the impact of air pollution and the beginnings of cognitive decline before they manifest fully. To address this urgent clinical and public health need, I propose a series of coordinated human and in vitro studies of an underappreciated cellular communication system enabled by extracellular vesicles (EVs). EVs are nano-sized (0.05–1 μm) membrane-bound vesicles released by human cells into the bloodstream that contain cargo, such as microRNAs, that can be integrated into recipient cells and modify their biology. We have built capacity to isolate circulating EVs based on their source cell type (SCT) using surface markers that EVs derive from the cells that released them. These new methods will enable my lab to identify signals from the precise cell types and organs affected by the exposures. We will apply these new methods to large cohort studies with existing blood samples and clinical data collected longitudinally at multiple time points over decades of follow-up to identify specific communication routes mediating the adverse effects of air pollution on the brain. Based on preliminary evidence and pilot data, my hypothesis is that circulating EVs released by the lung in response to air pollution carry signals, including microRNAs, that can that reach the brain and accelerate brain aging. In parallel, we will conduct in vitro studies investigating how EVs released by the lung in response to air pollution affect brain function using human bronchial epithelial cell cultures and cultured 3D brain organoids—a novel model that can be used to study the neurodegenerative processes underlying age- related brain health deterioration. Further, I will apply current data science techniques to identify patterns activated by environmental exposures and predictive of future health outcomes. I am confident that I can successfully lead this program. Over the last 10 years, I served as (M)PI on 16 NIH- funded awards. My work has produced >450 publications, and I was recently recognized as one of the highest cited, most influential investigators of the past decade. I have demonstrated a broad vision and made seminal contributions to the understanding of molecular mechanisms, including EVs, that are part of homeostatic alterations caused by environmental exposures. The flexible and sustained RIVER support will help continue a highly successful record of innovation and leadership in environmental health sciences.

PROJECT NARRATIVE While the human body is composed of ~200 different cell types and chronic diseases stem from dysfunction of multiple cells types in specific organs, most human environmental studies have overlooked such complexity. By capturing cell type-specific signals in easily obtainable biospecimens (i.e., standard blood draw) I propose to identify early biological responses to environmental exposures that are predictive of future health-related conditions, specifically of the effects of air pollution on accelerated brain aging—a primary focus of my laboratory. Due to the central roles that extracellular vesicles have in aging and chronic disease, this work will provide a model that can be applied to many other types of exposures and various chronic diseases.