2002 Progress Report: Role of PM-Associated Transition Metals in Exacerbating Infectious Pneumoniae in Exposed RatsEPA 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, 2002 through May 31, 2003
RFA: Airborne Particulate Matter (PM) Centers (1999) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air
The objectives of this research project are to: (1) determine whether particle size influences PM-induced alterations in the handling (i.e., uptake and/or killing) of an ongoing pulmonary infection with Streptococcus pneumoniae; (2) identify whether the soluble or insoluble portion of a given size fraction of ambient air PM is responsible for exacerbation of an ongoing pneumococcal-associated pneumonia; and (3) ascertain which transition metals (either individually or in combination), found most active in the previously identified portion of ambient PM, play significant roles in exacerbating ongoing pneumococcal-induced pneumonia in PM-exposed hosts.
Previous studies performed in this laboratory have demonstrated that ambient particulate matter (PM) exposure worsens the outcome of S. pneumoniae-associated pneumonia in rats. Although the aforementioned findings are compelling and provide a strong basis for the current studies, the question remains as to which factors and/or individual PM constituents are responsible for producing the observed effects upon pulmonary host resistance against infectious bacteria. Thus, these studies correlate the physical-chemical attributes of ambient PM with its in vivo immunotoxicity, so as to identify and characterize the role of particle form (i.e., soluble versus insoluble), size (i.e., coarse, fine, ultrafine), and constitutive transition metals on the ability of the particle to exacerbate an ongoing S. pneumoniae infection. This and related questions must be answered to better understand the mechanism(s) by which PM may act to increase morbidity and/or mortality in exposed individuals.
The central hypothesis of this study was that particle size and solubility play a critical role in mediating PM-associated pneumonia-related morbidity/mortality in exposed individuals. Moreover, any PM-induced changes in the ability of the host to "handle" infectious pneumonia-producing agents are likely due to, at least in part, the transition metals (either individually or in combination) associated with inhaled particulates. By exposing rats previously infected with S. pneumoniae (i.e., 48 hours prior to PM exposure) to ambient particles of varying size ranges and solubilities, or to chemically characterized constituents of ambient PM, individual physical-chemical attributes that influence the ability of PM to alter host resistance against infectious agents can be defined.
Progress in Years 1-3 of the Project. The first 3 years of the project focused on Objective 3. Studies employing uninfected 8-month-old Fisher 344 rats examined the immunological, histological, and biochemical changes associated with a single 5-hours inhalation exposure to FeCl2 at a concentration of approximately 100 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 LDH/protein levels, animals examined 1 hour post-exposure demonstrated altered blood cell profiles. Percentages of lymphocytes (L) and monocytes (M) in Fe-exposed animals were two- and three-fold lower, respectively, while neutrophils (N) were three-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 concentrated ambient PM studies, and may indicate a particle-induced stress response. At the same 18 hours post-exposure timepoint, proliferation of splenic T-lymphocytes was 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 control cells. Effects upon hydrogen peroxide (H2O2) production by Mø were dependent on time post-exposure. In another series of studies, rats were infected with S. pneumoniae 48 hours prior to exposure to either air or Fe. Rats were sacrificed either just before initiation of exposure or 18 hours later, and effects upon circulating blood cell profile and pulmonary bacterial burdens determined. Eighteen hours following exposure, percentages of blood N were similar in uninfected animals and in infected, 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 N and a 33 percent drop in L (compared to air controls). Moreover, although 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). The fact that S. pneumoniae are iron-sequestering organisms makes it difficult to determine whether Fe-induced changes in burdens were due to: (1) effects upon the bacteria; (2) alterations in immune mechanisms responsible for the clearance of the pathogen; or (3) combination of both factors. In another experiment in which already infected rats were examined 3 and 18 hours following Fe exposure, percentages of blood N were significantly reduced (compared to control) 3 hours following exposure, but returned to control values by 18 hours. In this same study, although 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 L and N than control animals by 18 hours.
Uninfected or S. pneumoniae-infected rats also 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 12-myristate 13-acetate stimulated superoxide anion production both were modestly elevated at this single timepoint. Moreover, as observed following Fe exposure, the percentages of circulating N and monocytes increased, while L 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 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. Additional studies to address this question are being carried out. In other studies, S. pneumoniae-infected or naive rats were exposed for 5 hours to either 100 µg/m3 of soluble nickel (Ni), zinc (Zn), or copper (Cu). Although inhalation of Cu had no effect on pulmonary antimicrobial immune defense mechanisms or bacterial clearance, Ni inhibited pulmonary bacterial clearance and altered circulating blood cell profiles, pulmonary histology, and lymphoproliferation in response to mitogen stimulation. Even more dramatic were the effects observed 18 hours following inhalation of 100 µg Zn/m3. In addition to suppressed bacterial clearance, a single exposure to Zn increased the severity/incidence of pneumoniae-associated lung lesions, depressed Mø-mediated production of free radicals, and altered lavageable cell numbers and profile.
Progress in Year 4 of the Project. During Year 4, the effects of Fe and Ni at a 10-fold lower inhaled concentration on naive and S. pneumoniae-infected rats were examined. In addition, studies were initiated to examine the effects of metal mixtures on pulmonary antimicrobial host defense and pulmonary bacterial clearance. At a 10-fold lower concentration (i.e., 10 µg/m3), inhalation of Fe alone consistently increased bacterial lung burdens in exposed hosts; alternatively, exposure to an equimolar concentration of Ni failed to affect bacterial clearance (compared to air-exposed controls). Inhalation exposure of 8-month-old rats to Zn in combination with Cu (each metal at 50 µg/m3) had no effect on pulmonary histology, cytokine production, Mø function, or bacterial clearance, but did alter the proliferative responses of splenic T-lymphocytes. However, in combination with Ni, inhalation of Zn reduced bacterial clearance, and altered lavageable cell numbers/viability and differential cell counts. Interestingly, although Fe alone (at both 100 and 10 µg/m3) produced the greatest effects on pulmonary immune cell function and bacterial clearance, effects were mostly ameliorated when inhaled in combination with Mn.
In the next year, we will continue to determine, identify, and ascertain the role of PM in worsening the outcome of S. pneumoniae-associated pneumonia. Given that equimolar doses of each metal (Fe, Ni, and Zn) were used for the Year 4 studies, future investigations will employ metals at the same concentration and ratios found to exist on ambient PM.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
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||Zelikoff JT, Schermerhorn KR, Fang K, Cohen MD, Schlesinger RB. A role for associated transition metals in the immunotoxicity of inhaled ambient particulate matter. Environmental Health Perspectives 2002;110(Suppl 5):871-875.||
Supplemental Keywords:air pollution, air pollutants, particulate matter, PM, fine particles, PM2.5, particulates, PM-associated transition metals, metals, iron, Fe, manganese, Mn, nickel, Ni, zinc, Zn, copper, Cu, infectious pneumonia, respiratory disease, pulmonary disease, health effects, respiratory effects, susceptible populations, health outcomes, ambient PM exposure, ambient PM, immunological changes, histological changes, biochemical changes, Streptococcus pneumoniae, immune mechanisms, pulmonary antimicrobial immune defense mechanisms, pulmonary bacterial clearance, lymphoproliferation., 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
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