2002 Progress Report: Immunomodulation by PM: Role of Metal Composition and Pulmonary Phagocyte Iron Status

EPA Grant Number: R827351C008
Subproject: this is subproject number 008 , 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: Immunomodulation by PM: Role of Metal Composition and Pulmonary Phagocyte Iron Status
Investigators: Cohen, Mitchell
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, 2001 through May 31, 2002
RFA: Airborne Particulate Matter (PM) Centers (1999) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air

Objective:

Particulate matter (PM) of less than 2.5 µm in diameter (PM2.5) has been shown in epidemiological analyses to induce/exacerbate infectious lung disease and, in toxicological studies, to alter the manner by which the lung responds to bacteria. This research has sought to validate the following hypotheses: (1) PM2.5 modulates lung phagocyte antibacterial function by altering cellular iron (Fe) status; (2) metals (as opposed to organics, biomatter, etc.) in PM2.5 underlie any change in lung leukocyte Fe status; and (3) relative Fe content in PM2.5 governs these effects. With respect to the latter, in PM2.5 with a high relative Fe content, uptake/slow dissolution of PM2.5-associated insoluble Fe and an increase in cellular deposition of soluble Fe (due to transferrin [Tf] activity) will lead to Fe overload and decreased antibacterial function. Conversely, with low relative Fe content-PM2.5, a presence of relatively greater levels (with respect to Fe) of competitors for Tf binding (e.g., aluminum [Al], manganese [Mn], and vanadium [V]) will cause an Fe deficit and reduced antibacterial function due to inhibited transport of endogenous Fe to the phagocytes.

To test these hypotheses, the objectives of this project are as follows: (1) in cooperation with the Los Angeles (LA) and Seattle PM Centers, to collect daily PM2.5 samples in the three metropolitan regions over a 3-month period to characterize any distinct patterns of proportionality of Fe to Al, Mn, and V; (2) to determine in vitro if a presence of Al, Mn, and V impacted on Fe homeostasis in a rat lung macrophage cell line (i.e., NR8383) when varying doses of each metal (reflective of their relative amounts within each city's PM2.5) were utilized; (3) to use NR8383 cells treated with intact PM2.5 to prove that the metals in PM alone were responsible for any effects on Fe homeostasis; and (4) to use the in vitro results to extrapolate a minimal effective PM2.5 dose, to instill rats with regional PM2.5 and examine effects from each city's PM2.5 on lung Tf status, Fe status, and antibacterial function of lung macrophages recovered from these rats.

Progress Summary:

Progress in Year 1 of the Project (Year 3 of NYU PM Center). Daily regional PM2.5 samples were collected and analyzed by x-ray fluorescent spectroscopy (XRF) to determine elemental compositions in general, and the relative and absolute Fe, Al, Mn, and V content in particular. Results indicated that the PM2.5 samples from NYC, LA, and Seattle reflected disparate metal compositions; factor analyses suggested that three factors could explain 73 percent and 82 percent of the variances in LA and NYC, respectively, whereas four factors (covering 85 percent of variance) were probable in Seattle. Due to the limited number of observations, however, chemical mass balance also will be explored as a model for source apportionment in each city. The XRF results also indicated that wide variations in absolute and relative Fe, Mn, Al, and V contents existed among the three metropolitan areas, and that there were significant differences in the relative ratios of each of the metal competitors to Fe.

Based on these differences in absolute content and relative Fe content versus Mn, V, and Al among the three cities, in vitro studies with NR8383 cells were sought to first determine whether each competitor (at levels encountered in a given day's PM2.5) did in fact alter cell Fe homeostasis, and which competitor was most important for inducing the effect. Using induction of iron response protein (IRP) immunofluorescent response element (IRE) sequence-binding activity as an indicator of intracellular shift in iron balance, cultures were treated with Fe (as Fe3+) alone or with V, Al, or Mn (individually or in combinations) at levels equivalent to those expected in 500 µg of a given PM2.5 sample. Individually, each competitor revealed Fe deficiency in the cells-whether this is due to an interruption Tf-mediated delivery of Fe alone, is under investigation. By employing increasing molar ratios of competitor:Fe, the determination was made that V had the greatest effect on Fe status and Mn the least, although each induced a significant effect even at a molar ratio of 0.01:1 compared with Fe (or approx 10 ng/µg Fe in intact PM2.5). Studies using combinations of two or all three competitors indicated a synergistic effect when V and Mn were both present; a co-presence of Al with Mn or V had little impact.

Because wide variations in Fe levels (i.e., 1-13 µg Fe/500 µg PM2.5 in NYC) were noted in the XRF analyses, ongoing studies are being conducted to clarify if the effects of the competitors are only relevant to PM2.5 samples that contain low-to-moderate Fe levels. Resolving whether the Al-, Mn-, and/or V-mediated competition still occurs in the presence of high levels of Fe is important; disturbing the clearance/uptake of these increased amounts of Fe would not only impact on lung phagocyte functionality, but would greatly accommodate growth potentials of siderophore-utilizing microbes that may be present or subsequently enter the lungs. Finally, studies to downsize (from 100 mm dish to 6-well plate) the assay also are in progress to reduce the amounts of archived intact PM2.5 samples required to prove that metals in PM2.5 alone were responsible for the effects on Fe homeostasis (and, consequently, more of the PM2.5 will be available for the proposed in vivo studies).

In preparation for in vivo studies with regional PM2.5 samples, examinations of the effects from Fe and Mn on rat lung Tf were initiated. Lung Tf levels were quantified in the lavages of rats sacrificed 1 and 18 hours after deposition of approximately 1 µg Mn2+ or Fe3+. The results indicated that in rats that received Fe3+, Tf levels were initially decreased and then increased by 18 hours compared to Tf levels in control rats. This pattern reflects the fact that Tf levels will decrease as the protein first sequesters and transports the Fe to lung cells. In contrast, Mn2+ exposure resulted in no significant change in amounts of Tf (relative to controls) at 1 or 18 hours. This suggests that binding of Mn to Tf not only blocked normal transport of Fe into cells (as demonstrated in the NR8383 IRP studies), but that it also may affect the ability of Tf to bind with or enter cells during the normal transport process used to acquire Fe from the cell’s external milieu. Similar studies with V and Al are underway to ascertain if these other competitors also might disrupt normal Tf processing as part of their mechanisms to alter Fe homeostasis in lung phagocytes.

Future Activities:

We will continue ongoing studies to clarify if the effects of the competitors are only relevant to PM2.5 samples that contain low-to-moderate Fe levels. Studies to downsize (from 100 mm dish to 6-well plate) the assay to reduce the amounts of archived intact PM2.5 samples required to prove that metals in PM2.5 alone were responsible for the effects on Fe homeostasis will continue. The proposed in vivo studies will be initiated. In addition, we will continue studies with V and Al that are underway to ascertain if these other competitors might disrupt normal Tf processing as part of their mechanisms to alter Fe homeostasis in lung phagocytes.

Journal Articles:

No journal articles submitted with this report: View all 5 publications for this subproject

Supplemental Keywords:

immunomodulation, particulate matter, PM, fine particles, fine particulates, PM2.5, ultrafine particles, health effects, lung disease, infectious lung disease, respiratory disease, pulmonary disease, lung phagocyte, lung phagocyte antibacterial function, iron, Fe, aluminum, Al, manganese, Mn, vanadium, V, cellular iron status, lung leukocyte iron status, Los Angeles PM Center, Seattle PM Center, New York City, New York, NY, Los Angeles, California, CA, Seattle, Washington, WA, transferrin levels, PM components., RFA, Health, Scientific Discipline, PHYSICAL ASPECTS, Air, ENVIRONMENTAL MANAGEMENT, particulate matter, Environmental Chemistry, Health Risk Assessment, Risk Assessments, Analytical Chemistry, Environmental Monitoring, Physical Processes, Atmospheric Sciences, Risk Assessment, ambient air quality, atmospheric particulate matter, particulates, lung injury, metal absorption, air toxics, atmospheric particles, chemical characteristics, toxicology, ambient air monitoring, acute lung injury, airborne particulate matter, environmental risks, exposure, epidemelogy, Sulfur dioxide, air pollution, pneumonia, leukocyte function, aerosol composition, atmospheric aerosol particles, human exposure, PM, exposure assessment, human health risk, metals

Relevant Websites:

http://charlotte.med.nyu.edu/epa-pm-center/ Exit

Progress and Final Reports:

Original Abstract
  • 1999
  • 2000 Progress Report
  • 2001 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