2005 Progress Report: Effect of Diesel Exhaust Particulate Exposures on Endothelial Function in Humans: The Role of Oxidative Stress

EPA Grant Number: R830954
Title: Effect of Diesel Exhaust Particulate Exposures on Endothelial Function in Humans: The Role of Oxidative Stress
Investigators: Kaufman, Joel D. , Chandler, Wayne , Gill, Edward , Larson, Timothy V. , Leotta, Daniel , Sheppard, Lianne (Elizabeth) A. , Sullivan, Jeff , Trenga, Carol
Current Investigators: Kaufman, Joel D. , Chandler, Wayne , Gill, Edward , Koenig, Jane Q. , Larson, Timothy V. , Leotta, Daniel , Sheppard, Lianne (Elizabeth) A. , Sullivan, Jeff , Trenga, Carol , Yost, Michael
Institution: University of Washington
EPA Project Officer: Chung, Serena
Project Period: August 15, 2003 through August 14, 2006 (Extended to August 14, 2008)
Project Period Covered by this Report: August 15, 2004 through August 14, 2005
Project Amount: $1,036,972
RFA: Airborne Particulate Matter Health Effects: Cardiovascular Mechanisms (2002) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air , Health Effects

Objective:

Diesel exhaust particles are a substantial and biologically active fraction of urban fine particulate air pollution, which is associated with increases in cardiovascular morbidity and mortality. This research project addresses the overall hypothesis that ambient fine particulate matter (PM2.5) exerts cardiovascular health effects via alteration of endothelial homeostasis through a mechanism mediated by oxidative stress. These studies use a controlled human inhalation exposure to diesel exhaust as a model to address the following specific objectives: (1) determine whether exposure to inhaled diesel exhaust (DE) particulate is associated with endothelial dysfunction in a concentration-related manner; (2) determine whether exposure to inhaled DE is associated with evidence of systemic oxidative stress; and (3) determine whether antioxidant supplementation blunts the DE effect on endothelial function.

Progress Summary:

Diesel Exhaust Exposures

The study protocol for Experiments 1 and 2 calls for random-order exposures at three different nominal concentrations: 0, 100, and 200 µg/m3 of PM2.5. The concentrations were measured by the tapered element oscillating microbalance (TEOM) and confirmed by integrated filter samples collected during the nominal 2-hour exposure periods. Consecutive 10-minute discrete (nonoverlapping) TEOM concentrations were combined to obtain an average for the exposure session interval. Results are summarized below for 37 separate exposure sessions conducted in December 2004 and August 2005.

Table 1. Summary of PM2.5 Mass Concentrations From TEOM (Discrete 10-Minute Averaging Intervals)

Nominal Concentration (µg/m3)

Clean Air

100

200

Number

12

13

12

Average (µg/m3)

4.4

101.6

205.3

Standard Deviation (µg/m3)

3.00

1.83

6.33

Coefficient of Variation

68.8%

1.8%

3.1%

Minimum (µg/m3)*

-2.8

98.2

194.2

Maximum (µg/m3)

9.0

104.0

212.2

*negative value is caused by instrument variability in measurement that occurs when TEOM filter has just been replaced and measurable mass has not yet accumulated on filter.

Health Effects Studies

Brachial Artery Studies. Interim analysis of brachial artery reactivity data for 10 healthy adults and 7 adults with metabolic syndrome indicates that exposure to DE at 200 µg/m3 PM2.5 was associated with a decrease in brachial artery diameter compared with filtered air (FA). As shown in Table 2 the vasoconstrictive reaction to DE was consistent in both study groups, with a bigger magnitude in healthy subjects. Brachial Tools image analysis software has been implemented for assessment of brachial artery sonographic images.

Table 2. Postexposure Brachial Artery Response

Mean Percent Change in Artery Diameter

FA

200 μg/m3

Healthy

-0.34 ± 1.27

-5.20 ± 5.95

Metabolic Syndrome

1.03 ± 2.19

-1.78 ± 2.26

Blood and Urinary Measures

Blood samples were collected to measure markers of endothelial homeostasis, thrombosis, inflammation and oxidative stress. Preliminary data have been evaluated for D-dimer, C-reactive protein (CRP), plasminogen activator inhibitor type 1 (PAI-1), von Willebrand’s Factor (VWF), endothelin-1, and multiple cytokines (e.g., IL-2, IL-6, TNF-alpha) as described in the grant proposal.

In measures of blood coagulation markers from 10 healthy study subjects, D-dimer and PAI-1 both decreased following FA exposure (1.13-fold [95% CI 1.05, 1.22] and 3.74-fold [95% CI 1.82, 7.64], respectively), and PAI-1 also decreased over 4 hours of DE exposure (4.06-fold [95% CI 1.76, 9.39]). All other baseline analyses showed nonsignificant decreases in markers. Regarding the primary endpoints, there were no significant differences in changes in marker levels between the FA and DE exposures. However, the trend for D-dimer, VWF, and CRP was towards a DE-associated attenuation of decreases in levels. Significant decreases in D-dimer and PAI-1 with FA may reflect diurnal variation in these markers. Our inability to detect an effect of DE may be caused by small sample size, as suggested by the trends in D-dimer, VWF, and CRP, or may reflect an absence of effect in healthy individuals at this level of exposure.

Microarray studies of peripheral blood mononuclear cells were conducted in samples from five study subjects whose samples met quality control criteria. We observed a greater than 1.5-fold change in expression of genes involved in inflammatory response (e.g., TLR4, CLC6, CCR5), oxidative stress (e.g., CYP2A6, ALOX5), and vascular function (e.g., PDGF, VEGFR) when subjects were exposed to DE (200 mcg/m3 PM2.5) as compared to filtered air. These data suggest that DE exerts time-dependent changes in gene expression in humans via the above-proposed mechanisms.

In cooperation with a study by Dr. Chris Simpson, plasma for measurement of 3-nitrotyrosine and 3-nitro-4-hydroxyphenylacetic, has been archived from study samples. Urine samples have been collected from pilot study subjects for measurement of F2-alpha-isoprostane.

Four abstracts have been submitted to the American Thoracic Society for presentation at the May 2006 International Conference in San Diego, California.

Future Activities:

Experiments to evaluate concentration-related effects of DE on endothelial function and oxidative stress will be completed in Year 3. The goal is to have 24 subjects complete the Experiment 1 protocol, with a subset of 10 subjects also completing the more extensive protocol that comprises Experiment 2. We anticipate completion of data analysis and reporting from Experiments 1 and 2 during this period. During Year 3, an intervention protocol evaluating whether antioxidant supplementation can alter the effect of DE on endothelial function and oxidative stress will be implemented.

Journal Articles:

No journal articles submitted with this report: View all 33 publications for this project

Supplemental Keywords:

ambient air, human health, dose-response, mobile sources,, RFA, Health, Scientific Discipline, Air, HUMAN HEALTH, particulate matter, air toxics, Environmental Chemistry, Health Risk Assessment, Exposure, Risk Assessments, Susceptibility/Sensitive Population/Genetic Susceptibility, mobile sources, genetic susceptability, Biology, copollutant exposures, sensitive populations, engine exhaust, atmospheric particulate matter, cardiopulmonary responses, fine particles, morbidity, PM 2.5, airway epithelial cells, diesel engines, inhaled pollutants, acute lung injury, air pollution, automotive exhaust, diesel exhaust, susceptible subpopulations, endothelial function, cardiopulmonary response, chronic health effects, lung inflammation, oxidant gas, particulate exposure, heart rate, ambient particle pollution, Acute health effects, highrisk groups, inhaled, chronic obstructive pulmonary disease, human susceptibility, diesel exhaust particles, cardiopulmonary, cardiotoxicity, mortality, diesel exhaust particulate, acute exposure, air quality, cardiovascular disease, biomarker, toxics, concentrated particulate matter, environmental hazard exposures, air contaminant exposure, co-pollutants, airborne urban contaminants

Relevant Websites:

http://depts.washington.edu/envhlth/nlakeexplab/ Exit

Progress and Final Reports:

Original Abstract
  • 2004 Progress Report
  • 2006 Progress Report
  • 2007 Progress Report
  • Final Report