2000 Progress Report: Role of PM-Associated Transition Metals in Exacerbating Infectious Pneumoniae in Exposed Rats

EPA Grant Number: R827351C007
Subproject: this is subproject number 007 , established and managed by the Center Director under grant R827351
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: EPA NYU PM Center: Health Risks of PM Components
Center Director: N/A
Title: Role of PM-Associated Transition Metals in Exacerbating Infectious Pneumoniae in Exposed Rats
Investigators: Zelikoff, Judith T.
Institution: New York University School of Medicine
EPA Project Officer: Chung, Serena
Project Period: June 1, 1999 through May 31, 2005 (Extended to May 31, 2006)
Project Period Covered by this Report: June 1, 2000 through May 31, 2001
RFA: Airborne Particulate Matter (PM) Centers (1999) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air

Objective:

The objective of this research project is to determine the role that particulate matter (PM)-associated transition metal solubility and concentration might play in bringing about previously observed changes in host immunocompetence. To this end, Streptococcus pneumoniae-infected rats are exposed to artificially generated atmospheres containing soluble/insoluble forms of individual metals found at the highest concentrations in immunoreactive New York City (NYC) PM samples. Similar studies will then employ mixtures of the soluble/insoluble forms of the metals so as to ascertain whether the immunosuppression in PM-exposed hosts is dependent, at least in part, upon any interactions between the metals present. Immunotoxic effects of metal exposure on non-infected animals are also examined in these studies so as to determine the extent to which the PM-associated metals are capable of producing immunodysfunction in and of themselves.

Progress Summary:

So as to determine relevant metal concentrations to use in these studies, NYC air particulates collected upon filters were extracted and the concentration (in parts per billion (ppb)) of five metals that have been shown in previous air pollution studies to be associated with PM were determined using graphite furnace atomic absorption spectroscopy. Zinc (Zn), manganese (Mn), copper (Cu), iron (Fe), and nickel (Ni) were present in the following order of concentration (total nanograms (ng)/sample weight): Cu > Zn > Fe > Ni > Mn.

Studies employing uninfected 8-month-old F-344 rats examined the immunological, histological, and biochemical changes associated with a single 5 hour inhalation exposure to FeCl2 at a concentration of approximately 100 micrograms (µg)/m3. Effects were examined 1, 18, and 48 hours post-metal exposure. In the absence of effects upon lavaged cell profile, viability, cell number, or lavageable lactate dehydrogenase (LDH)/protein levels, animals examined 1 hour post-exposure demonstrated altered blood cell profiles. Percentages of lymphocytes and monocytes in Fe-exposed animals were 2- and 3-fold lower, respectively, while neutrophils were 3-fold higher as compared to controls; by 18 hours post-exposure, differential blood counts returned to control levels. This time-related response is identical to that seen in our earlier NYC PM studies and may indicate a particle-induced stress response. At the same 18-hour post-exposure timepoint, proliferation of splenic T-lymphocytes decreased in Fe-exposed animals (compared to control), revealing effects upon the systemic immune response. At all post-exposure timepoints, superoxide anion production by macrophages (Mø) recovered from Fe-exposed rats was enhanced compared to production from control cells. Effects upon hydrogen peroxide (H2O2) production by Mø were dependent upon time post-exposure.

In another series of studies, rats were infected with S. pneumoniae 48 hours prior to either air or Fe exposure. Rats were sacrificed either just before initiation of exposure or 18 hours after exposure, and effects upon circulating blood cell profile and pulmonary bacterial burdens were determined. Eighteen hours following exposure, percentages of blood neutrophils were similar in infected and uninfected air-exposed control rats. However, infected animals exposed for 5 hours to Fe and examined 18 hours later had a 37 percent increase in blood neutrophils and a 33 percent drop in lymphocytes (compared to air controls). Moreover, while virtually all bacteria were cleared from the lungs of infected air-exposed rats by 48 hours post-infection, bacterial burdens in Fe-exposed animals were increased 10,000-fold (compared to those rats scarified immediately prior to exposure). Since S. pneumoniae are Fe-sequestering organisms, it is difficult to determine whether Fe-induced changes in burdens were due to effects upon the bacteria itself, to alterations in immune mechanisms responsible for the clearance of the pathogen, or a combination of both factors. In another experiment in which already-infected rats were examined 3 and 18 hours post Fe exposure, percentages of blood neutrophils were significantly reduced (compared to the control) 3 hours following exposure, but returned to control values by 18 hours post-exposure. In this same study, while no difference in lavaged cell profile was observed 3 hours post-exposure, rats exposed to Fe had significantly greater numbers of lavaged Mø, and fewer lymphocytes and neutrophils than control animals by 18 hours post-exposure.

Uninfected or S. pneumoniae-infected rats were exposed for 5 hours to MnCl2 at a concentration of approximately 100 µg/m3. In all cases, any observed effects from Mn upon lymphoproliferation, blood/lavage cell profiles, and oxyradical production were only seen 1 hour post-exposure. For example, splenic T-cell proliferation and phorbol myristate acetate (PMA)-stimulated superoxide anion production were both modestly elevated at this single timepoint. Moreover, as observed following Fe exposure, the percentages of circulating neutrophils and monocytes increased, while lymphocyte levels dropped compared to control.

S. pneumoniae-infected rats exposed to MnCl2 for 5 hours and sacrificed 18 hours post-exposure had a greater increase in bacterial killing/clearance (as compared to the control). Because of the antibacterial properties of some forms of Mn, it is unknown whether changes in bacterial burdens were due to direct effects upon the pathogen, Mn-induced alterations in antimicrobial immune defense mechanisms, or a combination of both factors.

Future Activities:

Studies examining the effects of metal combinations on host antimicrobial defense mechanisms will be performed. Studies are currently underway to determine the effects of Fe and Mn mixtures on the same immunological endpoints examined for each metal alone. In addition, studies will assess the effects of insoluble salts of these same five metals (i.e., Fe, Mn, Ni, Zn, and Cu), alone and in combination, so as to determine whether it is the soluble or insoluble metal forms that play the most important role in particle-induced effects upon antimicrobial lung defenses.

Journal Articles:

No journal articles submitted with this report: View all 3 publications for this subproject

Supplemental Keywords:

particulate matter, PM, exposure, animal, rat, toxicology, metal, pneumonia, Streptococcus pheumoniae, immunotoxic., RFA, Health, PHYSICAL ASPECTS, Scientific Discipline, Air, ENVIRONMENTAL MANAGEMENT, particulate matter, Toxicology, Environmental Chemistry, Health Risk Assessment, Risk Assessments, Analytical Chemistry, Physical Processes, Environmental Monitoring, Atmospheric Sciences, Risk Assessment, ambient air quality, atmospheric particulate matter, particulates, metal absorption, air toxics, atmospheric particles, chemical characteristics, ambient air monitoring, acute cardiovascular effects, acute lung injury, airborne particulate matter, environmental risks, exposure, epidemelogy, Sulfur dioxide, air pollution, pneumonia, aerosol composition, atmospheric aerosol particles, human exposure, PM, exposure assessment

Progress and Final Reports:

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

  • Main Center Abstract and Reports:

    R827351    EPA NYU PM Center: Health Risks of PM Components

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R827351C001 Exposure Characterization Error
    R827351C002 X-ray CT-based Assessment of Variations in Human Airway Geometry: Implications for Evaluation of Particle Deposition and Dose to Different Populations
    R827351C003 Asthma Susceptibility to PM2.5
    R827351C004 Health Effects of Ambient Air PM in Controlled Human Exposures
    R827351C005 Physicochemical Parameters of Combustion Generated Atmospheres as Determinants of PM Toxicity
    R827351C006 Effects of Particle-Associated Irritants on the Cardiovascular System
    R827351C007 Role of PM-Associated Transition Metals in Exacerbating Infectious Pneumoniae in Exposed Rats
    R827351C008 Immunomodulation by PM: Role of Metal Composition and Pulmonary Phagocyte Iron Status
    R827351C009 Health Risks of Particulate Matter Components: Center Service Core
    R827351C010 Lung Hypoxia as Potential Mechanisms for PM-Induced Health Effects
    R827351C011 Urban PM2.5 Surface Chemistry and Interactions with Bronchoalveolar Lavage Fluid (BALF)
    R827351C012 Subchronic PM2.5 Exposure Study at the NYU PM Center
    R827351C013 Long Term Health Effects of Concentrated Ambient PM2.5
    R827351C014 PM Components and NYC Respiratory and Cardiovascular Morbidity
    R827351C015 Development of a Real-Time Monitoring System for Acidity and Soluble Components in Airborne Particulate Matter
    R827351C016 Automated Real-Time Ambient Fine PM Monitoring System