2010 Progress Report: Novel Markers of Air Pollution-induced Vascular Toxicity

EPA Grant Number: R833990
Title: Novel Markers of Air Pollution-induced Vascular Toxicity
Investigators: Campen, Matthew J. , Lund, Amie K.
Institution: Lovelace Biomedical & Environmental Research Institute
Current Institution: University of New Mexico
EPA Project Officer: Nolt-Helms, Cynthia
Project Period: November 1, 2008 through October 31, 2011 (Extended to October 31, 2012)
Project Period Covered by this Report: November 1, 2009 through October 31,2010
Project Amount: $500,000
RFA: Development of Environmental Health Outcome Indicators (2007) RFA Text |  Recipients Lists
Research Category: Health Effects , Health

Objective:

Efforts to reduce the burden of heart disease and stroke have been hampered by a lack of knowledge in key areas including, but not limited to, environmental factors that may predispose susceptible individuals to plaque rupture as well as detrimental pathological effects associated with already increased levels of factors in the circulation or tissue. The objective of the present project is to characterize the role of known factors associated with progression of atherosclerosis associated with exposure to ubiquitous environmental air pollutants, such as diesel and gasoline engine exhaust. Furthermore, we have examined the role of oxidized low density lipoprotein (oxLDL) acting through the LOX-1 receptor as a mediator of the induction of vascular proteinases associated with plaque instability.

Because we have seen very clearly two predominant outcomes in our toxicological assays (vascular lipid peroxidation and inflammation), we wished to examine:  (1) whether specific receptors, such as LOX-1, might link these outcomes; and (2) whether other biomarkers might arise from within these pathways that may represent more robust indicators of exposure.

Progress Summary:

In Specific Aim 1, we proposed to assay hypothesized markers in plasma and aortic tissue from mice exposed to various pollutant atmospheres. These studies will link the plasma markers with their mechanistic origins.

Mouse plasma from 7- and 50-day exposures to diesel emissions, coal combustion, and woodsmoke combustion have been transferred from LRRI to UNM for analysis. We have completed most proposed assays on the 50-day samples. Examples of findings for LOX-1 and osteopontin (OPN) are presented below. Interestingly, the responses of LOX-1 are quite different compared to what we have seen acutely, with a significant downregulation in the diesel exposed mice. OPN showed minimal changes, possibly a reduction in the medium concentration of diesel. We are continuing to analyze the 7-day samples and also are investigating related markers. Over the coming year, data will be finalized and we will integrate our findings with respect to the relative pollutant concentrations within each of the combustion mixtures. Much of the chemistry of the exposure atmospheres has been characterized and reported within the framework of the National Environmental Respiratory Center, and we will be able to consider multivariate analysis of the observed changes in biomarkers.

Because of the striking findings from Aims 2 and 3 earlier, we followed up with plasma assays on mice exposed to ozone with or without the antibody against LOX-1. These assays will include the endothelial cell activation model developed in Aim 3 over the past year. 

In Specific Aim 2, we proposed to test the role of LOX-1 scavenger receptors in mediating the vascular effects of inhaled pollutants. We hypothesize that oxidatively modified phospholipids may be a link between the lung and systemic circulation; scavenger receptors are the likely mediating intermediary.

We have completed Aim 2, treating mice with an antibody to LOX-1, to selectively block the function of this pathway during mixed vehicular emissions (gasoline and diesel engine exhausts) exposures. We observed a complete blockade of the systemic vascular lipid peroxidation caused by exposure to vehicular emissions. Similarly, reductions in intravascular accumulation of macrophages, along with mRNA induction of a number of markers, were observed due to the LOX-1 blockade. Thus, Aim 2 confirms the importance of the LOX-1 pathway in driving the systemic vascular effects of inhaled emissions.

This study has been published in the American Journal of Respiratory and Critical Care Medicine. A second manuscript, detailing the changes in LOX-1 in a more chronic rat model exposed to ozone with/without diesel particles, also hasbeen published in the past year (Kodavanti et al., 2010).

In Specific Aim 3, we proposed to use the information obtained in Specific Aims 1 and 2 to develop hypotheses for protein or biochemical markers to test in human plasma. We have confirmed that relative levels of soluble LOX-1 in the plasma of human subjects become elevated following controlled exposure to diesel exhaust. We followed up on these studies with plasma from human volunteers exposed to nitrogen dioxide and/or particulate matter, in collaboration with the EPA Human Studies Division. Interestingly, particulate matter did not induce a significant elevation in LOX-1, but NO2 did. 

To expand this Aim, we developed a novel model for assessing the in vitro inflammatory potential of the plasma in endothelial cells. Quite simply, we treated confluent primary human coronary artery endothelial cells (hCAECs) with a 10% or 30% dilution of plasma in media for 24 hours, then harvested the mRNA from the hCAECs to examine transcriptional responses to the contents of the plasma. What we observed were significant elevations in adhesion molecules ICAM-1 and VCAM-1, both of which are vital players in early atherosclerosis initiation. The trends followed a dose-response pattern (in terms of dilution in media) and temporal effects also could be determined, based on the time of plasma collection post-exposure. This manuscript has been submitted for publication. We believe that future studies will be able to build off of this model to better explore the causative components in exhaust, the intermediates in the plasma/serum, and the biological mechanisms underlying the inflammatory responses of the hCAECs.

As a further bridge to translational applications with the LOX-1 and oxidized LDL markers, we have obtained plasma from one clinical and one community population. The clinical population, collected by our colleague Akshay Sood, M.D., consisted of women described as healthy, asthmatic, obese, or asthmatic and obese. Although minimal information exists in the literature regarding the impact of asthma on coronary artery disease, we observed a clear interaction between obesity and asthma in driving elevations in oxLDL. In the community population, we are examining the potential impact of uranium mine legacy waste on cardiovascular biomarkers in the Navajo Nation, in association with Johnnye Lewis, Ph.D. Here, we have determined in preliminary statistical models that past occupational exposure to uranium mining and levels of arsenic in the available water sources may both have an important contribution to oxLDL levels. 

Future Activities:

Thus, over the final year of this project we will round out the assays and integration of data for Aims 1 and 3.  We hope to complete the studies of the clinical and community populations with regard to the biomarkers oxLDL and LOX-1 and publish those findings. Although certain follow-up activities are planned related to the mechanistic findings of a role for LOX-1 in lipid peroxidation, those will be outside the scope of the current project.


Journal Articles on this Report : 4 Displayed | Download in RIS Format

Other project views: All 9 publications 6 publications in selected types All 6 journal articles
Type Citation Project Document Sources
Journal Article Campen MJ, Lund A, Rosenfeld M. Mechanisms linking traffic-related air pollution and atherosclerosis. Current Opinion in Pulmonary Medicine 2012;18(2):155-160. R833990 (2010)
R833990 (2011)
R834796 (2012)
R834796 (2013)
R834796 (2015)
R834796 (Final)
R834796C003 (2012)
R834796C003 (2013)
R834796C003 (Final)
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  • Journal Article Channell MM, Paffett ML, Devlin RB, Madden MC, Campen MJ. Circulating factors induce coronary endothelial cell activation following exposure to inhaled diesel exhaust and nitrogen dioxide in humans: evidence from a novel translational in vitro model. Toxicological Sciences 2012;127(1):179-186. R833990 (2010)
    R833990 (2011)
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  • Abstract: Oxford Journals-Abstract
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  • Journal Article Kodavanti UP, Thomas R, Ledbetter AD, Schladweiler MC, Shannahan JH, Wallenborn JG, Lund AK, Campen MJ, Butler EO, Gottipolu RR, Nyska A, Richards JE, Andrews D, Jaskot RH, McKee J, Kotha SR, Patel RB, Parinandi NL. Vascular and cardiac Impairments in rats inhaling ozone and diesel exhaust particles. Environmental Health Perspectives 2011;119(3):312-318. R833990 (2009)
    R833990 (2010)
    R833990 (2011)
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  • Abstract: EHP - Abstract & Full Text HTML
  • Journal Article Lund AK, Lucero J, Harman M, Madden MC, McDonald JD, Seagrave JC, Campen MJ. The oxidized low-density lipoprotein receptor mediates vascular effects of inhaled vehicle emissions. American Journal of Respiratory and Critical Care Medicine 2011;184(1):82-91. R833990 (2009)
    R833990 (2010)
    R833990 (2011)
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  • Supplemental Keywords:

    RFA, Health, Scientific Discipline, Air, particulate matter, Health Risk Assessment, Risk Assessments, ambient air quality, atmospheric particulate matter, chemical characteristics, human health effects, cardiovascular vulnerability, biological mechanisms, chemical composition, biological mechanism , human exposure, ambient particle health effects, autonomic dysfunction, oxidative stress

    Progress and Final Reports:

    Original Abstract
  • 2009 Progress Report
  • 2011 Progress Report
  • Final