2015 Progress Report: Cardiovascular Consequences of Immune Modification by Traffic-Related Emissions

EPA Grant Number: R834796C003
Subproject: this is subproject number 003 , established and managed by the Center Director under grant R834796
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: University of Washington Center for Clean Air Research
Center Director: Vedal, Sverre
Title: Cardiovascular Consequences of Immune Modification by Traffic-Related Emissions
Investigators: Campen, Matthew J. , McDonald, Jacob D. , Rosenfeld, Michael
Institution: Lovelace Respiratory Research Institute , University of New Mexico , University of Washington
Current Institution: University of New Mexico , Lovelace Respiratory Research Institute , University of Washington , Washington State University
EPA Project Officer: Callan, Richard
Project Period: December 1, 2010 through November 30, 2015 (Extended to November 30, 2017)
Project Period Covered by this Report: August 1, 2014 through July 31,2015
RFA: Clean Air Research Centers (2009) RFA Text |  Recipients Lists
Research Category: Health Effects , Air

Objective:

Objectives/Hypothesis: Traffic-related emissions are associated with the incidence and progression of acute and chronic cardiovascular sequelae in human population studies. Such phenomena of near-roadway health effects have yet to be characterized toxicologically. Because of overlapping issues related to noise, socioeconomic status, ethnicity, etc., there is a need to better understand the biological plausibility that fresh mixtures of vehicular emissions have a more potent than expected impact on human health. We hypothesize that the complex mixtures produced by traffic are inherently more toxic due to the combined presence of both particulates and volatile organic emissions. Furthermore, we hypothesize that emissions-induced oxidation of certain endogenous phospholipids, presumably from the pulmonary surfactant, can stimulate the activity of immune cells through such receptors and in turn promote the invasion of existing vascular lesions.

Approach: This project uses complex roadway mixtures as generated and characterized in the laboratory. In Aim 1, we will ascertain (1) the potentiating effects of physical and photochemical aging on fresh emissions and (2) interactions of vehicular emissions with pertinent copollutants (ozone, road dust), both in terms of driving systemic vascular oxidative stress. In Aim 2, we will examine effects of the emissions-induced oxidative modifications to endogenous phospholipids, in terms of activating immune-modulating receptors such as LOX-1, CD-36, TLR-2, and TLR-4. This Aim will utilize transgenic models to examine the roles of these receptors, as well as characterize the lipidomic alterations in various tissues. Lastly, in Aim 3, we will further explore the role of specific immune cell populations as participants in the innate and adaptive responses to emissions-induced phospholipid modifications. In this Aim, we will utilize mouse models of immunodeficiency, including SCID and B-Cell deficient models. Additionally, we will pursue bone-marrow transplants from mice lacking those receptors described in Aim 2 to mechanistically establish the involvement of the oxidatively-modified phospholipids.

Based on suggestions from the Advisory Committee, we have focused on the nature and bioactivity of circulating factors induced by pollutant exposures, as these appear to be ligands that interact with the scavenger receptors of interest in Aims 2 and 3. This has been an area of significant progress for the past year.

Expected Results: Findings will (1) indicate the most potent combinations of urban roadway and background copollutants in terms of vascular toxicity and (2) detail the role of the immune system in mechanistically driving the systemic effects of inhaled pollutants.

Progress Summary:

Following up on the previous year's observation of the role of blood-borne ligands and bioactivity in terms of driving endothelial cell activation or dysfunction following ozone exposure, we identified a potential for altered serum biochemicals to scavenge nitric oxide, which was associated with lower levels of circulating nitrites/nitrates and also elevated nitrosothiols (Paffett, et al., Toxicol Sci 2015). This finding offers a complementary mechanism to previous observations of ligand-receptor dependent alterations impacting vasodilation (Robertson, et al., Toxicol Sci 2013). Ongoing research into the chemical changes in the blood has offered paradigm-shifting insights. For one, we typically see minimal, if any, changes in cytokine levels following even moderately high levels of pollutants. However, we routinely observe increases in fragmented and adducted proteins, and metabolomics studies suggest small molecule changes also may be numerous and contributory. A recent observation with serum from woodsmoke-exposed mice suggests that it is in fact a loss of some factor, rather than induction of higher levels of some mediator or mediators, that leads to indirect vascular pathology.

In the first study, we examined further the bioactivity of O3 on coronary arteries from rats. Following inhalation of 1 ppm O3, we found that coronaries harvested from exposed rats had a greater propensity to constrict to serotonin and a dramatically reduced ability to dilate to acetylcholine (Figure 1A, B). The impairment in dilation related to intracellular oxidative stress, as full dilation could be recovered with co-treatment with apocynin (Figure 1C) or superoxide dismutase and catalase (not shown). Most importantly, coronary vessels from unexposed (naïve) rats lost dilatory capacity when perfused intraluminally with serum from O3-exposed rats, as compared to the serum from air-exposed rats (Figure 1D). Thus, the serum components alone could approximate the impairments seen in vivo. These effects were not likely due to cytokines in the serum, as concentrations of nine measured cytokines did not differ between exposure groups (Figure 2). However, working with a proteomics group at Virginia Commonwealth University, we have identified classes of fragmented peptides induced in the serum following O3 exposure that may drive a systemic inflammatory response consistent with our observations.

To test the degree of bioactivity conferred to serum following complex mixtures exposures, wildtype (C57BL/6) mice were exposed to woodsmoke, mixed vehicle emissions (MVE), or road dust for a single 6-hour period (Aragon, et al., 2015). Serum obtained from mice 24 hours after these exposures was used as a stimulus to assess inflammatory potential in two assays: incubated with primary murine cerebrovascular endothelial cells for 4 hours to measure inflammatory gene expression or applied to naïve aortic rings in an ex vivo myographic preparation. Road dust and wood smoke exposures were most potent at inducing inflammatory gene expression, while MVE atmospheres and wood smoke were most potent at impairing vasorelaxation to acetylcholine. Responses are consistent with recent reports on MVE toxicity, but reveal novel serum bioactivity related to wood smoke and road dust. Ongoing work with serum from wood smoke exposed mice suggests that bioactivity changes in the serum, at 10% dilution in media, can impair regrowth in a wound healing assay (Figure 1A). Follow-up studies with different concentrations of serum show that the regrowth is normalized at higher concentration (30%) and potentially even worse at 2.5 percent (Figure 1B–E), suggesting that the adverse effects are not caused by an induced factor, but rather one that is reduced in concentration.


Figure 1. Bioactivity changes in serum from wood smoke exposed mice. A. 10% dilution. B. 2.5% dilution. C. 5% dilution. D. 10% dilution. E. 20% dilution.

Serum from MVE-exposed mice remained the most potent at inhibiting endothelium-dependent vasodilation (Figure 2). This effect seemed to be largely driven by gaseous components, as serum from mice exposed to the MVE-filtered atmosphere (with PM removed) was the most potent inhibition of dilation, while the road dust exposures had only limited impact. While we had previously demonstrated a receptor-ligand linkage to explain this effect with ozone, the recent data suggest that scavenging nitric oxide by novel serum components also may be a concern (Paffett, et al., 2015). Further research on this will be conducted in the coming year.

Ongoing studies to delineate the role of PM surface-adsorbed semivolatile organic compounds (SVOCs) are underway. These employ a catalytic stripper in addition to denuder to more completely remove adsorbed SVOCs. Serum samples have been found to induce endothelial VCAM and cause small impairments in endothelial regrowth, but studies remain in process.


Figure 2. Endothelium-dependent vasodilation in MVE-exposed mice.

Future Activities:

Aim 1: Compare potency of mixed emissions and photochemically transformed emissions in terms of serum inflammatory potential. This will be the focus of the remainder of the study, interacting closely with Dr. McDonald and Project 2. We will examine the relative systemic inflammatory potential following exposures to complex emissions.

References:

Aragon MJ, Chrobak I, Brower J, Roldan L, Fredenburgh LE, McDonald JD, Campen MJ. Inflammatory and vasoactive effects of serum following inhalation of varied complex mixtures. Cardiovascular Toxicology 2016;16(2):163-171.

Paffett ML, Zychowski KE, Sheppard L, Robertson S, Weaver JM, Lucas SN, Campen MJ. Ozone inhalation impairs coronary artery dilation via intracellular oxidative stress: evidence for serum-borne factors as drivers of systemic toxicity. Toxicological Sciences 2015;146(2):244-253.

Robertson S, Colombo ES, Lucas SN, Hall PR, Febbraio M, Paffett ML, Campen MJ. CD36 mediates endothelial dysfunction downstream of circulating factors induced by O3 exposure. Toxicological Sciences 2013;143(2):304-311.


Journal Articles on this Report : 1 Displayed | Download in RIS Format

Other subproject views: All 20 publications 13 publications in selected types All 13 journal articles
Other center views: All 172 publications 76 publications in selected types All 75 journal articles
Type Citation Sub Project Document Sources
Journal Article Aragon MJ, Chrobak I, Brower J, Roldan L, Fredenburgh LE, McDonald JD, Campen MJ. Inflammatory and vasoactive effects of serum following inhalation of varied complex mixtures. Cardiovascular Toxicology 2016;16(2):163-171. R834796 (2015)
R834796C003 (2015)
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  • Supplemental Keywords:

    atherosclerosis, carbon monoxide, coronary artery disease, oxidized phospholipids, ozone, particulate matter, volatile organic compounds, SVOCs;, Health, Scientific Discipline, Air, ENVIRONMENTAL MANAGEMENT, Air Quality, air toxics, Health Risk Assessment, Risk Assessments, mobile sources, Biochemistry, Environmental Monitoring, Risk Assessment, ambient air quality, atmospheric particulate matter, particulate matter, aerosol particles, air pollutants, motor vehicle emissions, vehicle emissions, air quality models, motor vehicle exhaust, airway disease, bioavailability, air pollution, particle exposure, atmospheric aerosols, ambient particle health effects, vascular dysfunction, cardiotoxicity, atmospheric chemistry, exposure assessment

    Relevant Websites:

    Center for Clean Air Research | Department of Environmental & Occupational Health Sciences | School of Public Health | University of Washington Exit

    Progress and Final Reports:

    Original Abstract
    2011 Progress Report
    2012 Progress Report
    2013 Progress Report
    2016 Progress Report


    Main Center Abstract and Reports:

    R834796    University of Washington Center for Clean Air Research

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R834796C001 Exposure Mapping – Characterization of Gases and Particles for ExposureAssessment in Health Effects and Laboratory Studies
    R834796C002 Simulated Roadway Exposure Atmospheres for Laboratory Animal and Human Studies
    R834796C003 Cardiovascular Consequences of Immune Modification by Traffic-Related Emissions
    R834796C004 Vascular Response to Traffic-Derived Inhalation in Humans
    R834796C005 Effects of Long-Term Exposure to Traffic-Derived Particles and Gases on Subclinical Measures of Cardiovascular Disease in a Multi-Ethnic Cohort