Final Report: Studies of Oxidant Mechanisms

EPA Grant Number: R827353C011
Subproject: this is subproject number 011 , established and managed by the Center Director under grant R827353
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: EPA Harvard Center for Ambient Particle Health Effects
Center Director: Koutrakis, Petros
Title: Studies of Oxidant Mechanisms
Investigators: Godleski, John J. , Gonzalez-Flecha, Beatriz
Institution: Harvard University
EPA Project Officer: Chung, Serena
Project Period: June 1, 1999 through May 31, 2005 (Extended to May 31, 2006)
RFA: Airborne Particulate Matter (PM) Centers (1999) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air

Objective:

Theme III focused upon mechanisms of cardiac vulnerability as a result of air pollution exposure. Many of our concentrated ambient particles (CAPs) animal toxicology and human panel studies have linked pulmonary and cardiovascular health outcomes to different particulate matter (PM) components such as trace metals, elemental carbon, sulfates and silicon (Batalha, et al., 2002; Clarke, et al., 2000; Saldiva, et al., 2002). Reanalysis of the Harvard Six Cities study provided strong evidence of increased toxicity associated with combustion-related PM from traffic and power plants compared to soil dust (Laden, et al., 2000).

The objectives of Theme III were to identify the particulate and gaseous air pollutants responsible for increased cardiac vulnerability as an adverse health effect and to define the biological mechanisms that lead to this outcome. As part of this theme, we specifically worked to: (1) identify the physical and chemical properties of particulate matter responsible for the observed adverse health effects; (2) determine whether gaseous co-pollutants exacerbate the effects of particles; (3) investigate the biological mechanisms by which particulate matter produces mortality and acute or chronic morbidity; and (4) examine particle deposition patterns and fate in the respiratory tract. These objectives were addressed in several areas of research that explored the components of air pollution that cause adverse health effects and the biological mechanisms that may lead to fatal outcomes. The projects under this theme built upon the findings from a number of our previous animal studies, which made it possible to explore and define both cardiac and pulmonary responses to inhaled fly ash and concentrated ambient particles (Killingsworth, et al., 1997).

A primary mechanistic hypothesis by which ambient air particles have a significant negative impact on human health is via the induction of pulmonary inflammatory responses mediated through the generation of reactive oxygen species (ROS). The objective of this study was to evaluate whether air particulates interact directly with protective enzymes involved in oxidative stress responses.

Our Environmental Protection Agency (EPA) PM Center has supported the innovative studies of Dr. Beatriz Gonzalez-Flecha and her colleagues on oxidant mechanisms of particles in the lung. Dr. Gonzalez-Flecha and her colleagues completed and published a study confirming the role of oxidants in the inflammatory response to CAPs in adult rats (Rhoden, et al., 2004).

Summary/Accomplishments (Outputs/Outcomes):

We performed enzyme activity assays on four enzymes involved in oxidative stress responses (Cu/Zn superoxide dismutase, Mn superoxide dismutase, glutathione peroxidase and glutathione reductase) in the presence of particles of varying toxicities and found distinctive inhibition patterns (Hatzis, et al., 2006). We demonstrated that particles interact directly and inhibit in vitro the specific activity of enzymes involved in oxidative stress response. Moreover, for the different particle types tested, the inhibitory capacity of the particulates on the selected enzymes correlates with the in vivo toxicity of the particles (Mount St. Helen’s volcanic ash [MSHA] < National Institute of Standards and Technology [NIST] < residual oil fly ash [ROFA]). Our findings suggest that the potential to generate oxidative stress of ambient particles may be determined, at least in principle, on the basis of the pattern of inhibition of the enzymatic activity of a carefully selected panel of enzymes. On the basis of these findings, we suggest a strategy for an enzyme bioassay that could be used to assess the potential of particles to generate ROS-induced responses.

The experimental protocol included exposures to filtered air (sham) or CAPs aerosols (CAPs, 5 hours exposure, average mass concentration of 1100 ± 300 g/m3) in the presence or absence of 50 mg/Kg N-acetyl cysteine (NAC). Bronchoalveolar lavage (BAL), tissue and blood samples were collected 24 hours after exposure. The results of this study showed a dramatic increase of polymorphonuclear neutrophil (PMN) number in BAL as a result of CAPs exposures. This increase was mediated by oxidants, since pre-administration of NAC effectively prevented PMN influx into the lung (Rhoden, et al., 2004). Additional data support our hypotheses that CAPs promotes oxidant-mediated cardiac dysfunction and that autonomic activation after CAPs deposition in the lung is critical for CAPs cardiotoxicity. Adult Sprague-Dawley rats were treated with the 1-adrenoreceptor antagonist atenolol, the muscarinic receptor antagonist glycopyrrolate or saline prior to exposure to urban ambient particles (UAP) (United Agri Products, standard reference material (SRM) 1649, 750 g/Kg). Thirty minutes after UAP instillation the animals were anesthetized and assayed immediately for cardiac levels of oxidants (in situ chemiluminescence: CL). Tissue samples were collected and assayed for edema. Intratracheal instillation of UAP led to significant increases in heart oxidants and edema. β-blockage by atenolol and muscarinic blockade by glycopyrrolate effectively prevented cardiac oxidative stress and damage. These observations were confirmed in a model of inhalation exposure to CAPs.

To determine the role of oxidants in the development of cardiac malfunction rats were treated with NAC one hour prior to UAP instillation or CAPs inhalation. NAC prevented changes in heart rate and heart rate variability in UAP-exposed rats (Rhoden, et al., 2005). These data strongly suggest that PM exposure increases cardiac oxidants via autonomic signals and the resulting oxidative stress is associated with significant functional alterations in the heart.

Conclusions:

The research associated with this project found particle exposures inhibited the specific activity of enzymes involved in oxidative stress response, with the inhibitory capacity of the correlating with the in vivo toxicity of the particles. Additional work showed particulate exposures to be associated with increases in neutrophils, cardiac oxidants and edema. Resulting oxidative stress was associated with significant functional alterations in the heart.

References:

Batalha JRF, Saldiva PHN, Clarke RW, Coull BA, Stearns RC, Lawrence J, Krishna Murthy GG, Koutrakis P, Godleski JJ. Concentrated ambient air particles induce vasoconstriction of small pulmonary arteries in rats. Environmental Health Perspectives 2002;110(12):1191-1197.

Clarke RW, Coull BA, Reinisch U, Catalano P, Killingsworth CR, Koutrakis P, Kavouras I, Krishna Murthy GG, Lawrence J, Lovett EG, Wolfson JM, Verrier RL, Godleski JJ. Inhaled concentrated ambient particles are associated with hematologic and bronchoalveolar lavage changes in canines. Environmental Health Perspectives 2000;108(12):1179-1187.

Hatzis C, Godleski JJ, Gonzalez-Flecha B, Wolfson JM, Koutrakis P. Ambient particulate matter exhibits direct inhibitory effects on oxidative stress enzymes. Environmental Science & Technology 2006;40(8):2805-2811.

Killingsworth C, Alessandrini F, Murthy G, Catalano P, Paulauskis J, Godleski J. Inflammation, chemokine expression, and death in monocrotaline-treated rats following fuel oil fly ash inhalation. Inhalation Toxicology 1997;9:541-565.

Laden F, Neas L, Dockery D, Schwartz J. Association of fine particulate matter from different sources with daily mortality in six U.S. cities. Environmental Health Perspectives 2000;108(10):941-947.

Rhoden CR, Lawrence J, Godleski JJ, Gonzalez-Flecha B. N-Acetylcysteine prevents lung inflammation after short-term inhalation exposure to concentrated ambient particles. Toxicological Sciences 2004;79(2):296-303.

Rhoden CR, Wellenius GA, Ghelfi E, Lawrence J, Gonzalez-Flecha B. PM-induced cardiac oxidative stress and dysfunction are mediated by autonomic stimulation. Biochimica et Biophysica Acta (BBA)-General Subjects 2005;1725(3):305-313.

Saldiva PH., Clarke RW, Coull BA, Stearns RC, Lawrence J, Koutrakis P, Suh H, Tsuda A, Godleski JJ. Acute pulmonary inflammation induced by concentrated ambient air particles is related to particle composition. American Journal of Respiratory and Critical Care Medicine 2002;165(12):1610-1617.


Journal Articles on this Report : 3 Displayed | Download in RIS Format

Other subproject views: All 3 publications 3 publications in selected types All 3 journal articles
Other center views: All 200 publications 198 publications in selected types All 197 journal articles
Type Citation Sub Project Document Sources
Journal Article Hatzis C, Godleski JJ, Gonzalez-Flecha B, Wolfson JM, Koutrakis P. Ambient particulate matter exhibits direct inhibitory effects on oxidative stress enzymes. Environmental Science & Technology 2006;40(8):2805-2811. R827353 (Final)
R827353C011 (2004)
R827353C011 (Final)
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  • Journal Article Rhoden CR, Lawrence J, Godleski JJ, Gonzalez-Flecha B. N-Acetylcysteine prevents lung inflammation after short-term inhalation exposure to concentrated ambient particles. Toxicological Sciences 2004;79(2):296-303. R827353 (Final)
    R827353C011 (2003)
    R827353C011 (Final)
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  • Journal Article Rhoden CR, Wellenius GA, Ghelfi E, Lawrence J, Gonzalez-Flecha B. PM-induced cardiac oxidative stress and dysfunction are mediated by autonomic stimulation. Biochimica et Biophysica Acta (BBA)-General Subjects 2005;1725(3):305-313. R827353 (Final)
    R827353C011 (2004)
    R827353C011 (Final)
    R832416 (2008)
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  • Supplemental Keywords:

    RFA, Health, Scientific Discipline, Air, particulate matter, Toxicology, Environmental Chemistry, Epidemiology, Risk Assessments, Environmental Microbiology, Environmental Monitoring, tropospheric ozone, Molecular Biology/Genetics, Biology, Environmental Engineering, ambient air quality, particulates, chemical exposure, human health effects, ambient air monitoring, concentrated ambient particulates (CAPs), ambient air, ambient measurement methods, pulmonary disease, developmental effects, epidemelogy, respiratory disease, air pollution, particle exposure, biological mechanism , human exposure, inhalation, pulmonary, particulate exposure, ambient particle health effects, inhalation toxicology, oxidant mechanisms, measurement methods , cardiovascular disease, human health risk, respiratory, genetic susceptibility

    Relevant Websites:

    http://www.hsph.harvard.edu/epacenter/epa_center_99-05/index.html Exit

    Progress and Final Reports:

    Original Abstract
  • 1999
  • 2000
  • 2001
  • 2002
  • 2003 Progress Report
  • 2004 Progress Report

  • Main Center Abstract and Reports:

    R827353    EPA Harvard Center for Ambient Particle Health Effects

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R827353C001 Assessing Human Exposures to Particulate and Gaseous Air Pollutants
    R827353C002 Quantifying Exposure Error and its Effect on Epidemiological Studies
    R827353C003 St. Louis Bus, Steubenville and Atlanta Studies
    R827353C004 Examining Conditions That Predispose Towards Acute Adverse Effects of Particulate Exposures
    R827353C005 Assessing Life-Shortening Associated with Exposure to Particulate Matter
    R827353C006 Investigating Chronic Effects of Exposure to Particulate Matter
    R827353C007 Determining the Effects of Particle Characteristics on Respiratory Health of Children
    R827353C008 Differentiating the Roles of Particle Size, Particle Composition, and Gaseous Co-Pollutants on Cardiac Ischemia
    R827353C009 Assessing Deposition of Ambient Particles in the Lung
    R827353C010 Relating Changes in Blood Viscosity, Other Clotting Parameters, Heart Rate, and Heart Rate Variability to Particulate and Criteria Gas Exposures
    R827353C011 Studies of Oxidant Mechanisms
    R827353C012 Modeling Relationships Between Mobile Source Particle Emissions and Population Exposures
    R827353C013 Toxicological Evaluation of Realistic Emissions of Source Aerosols (TERESA) Study
    R827353C014 Identifying the Physical and Chemical Properties of Particulate Matter Responsible for the Observed Adverse Health Effects
    R827353C015 Research Coordination Core
    R827353C016 Analytical and Facilities Core
    R827353C017 Technology Development and Transfer Core