Final Report: Animal models: Cardiovascular Disease, CNS Injury and Ultrafine Particle Biokinetics

EPA Grant Number: R832415C004
Subproject: this is subproject number 004 , established and managed by the Center Director under grant R832415
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Rochester PM Center
Center Director: Oberdörster, Günter
Title: Animal models: Cardiovascular Disease, CNS Injury and Ultrafine Particle Biokinetics
Investigators: Oberdörster, Günter , Elder, Alison C.P. , Oakes, David , Couderc, Jean-Philippe , Phipps, Richard , Gelein, Robert , Kreyling, Wolfgang
Institution: University of Rochester , GSF-National Research Center for Environment and Health
EPA Project Officer: Chung, Serena
Project Period: October 1, 2005 through September 30, 2010 (Extended to September 30, 2012)
RFA: Particulate Matter Research Centers (2004) RFA Text |  Recipients Lists
Research Category: Human Health , Air


The animal studies were designed to be complementary to the epidemiological and clinical studies and further test hypotheses derived from those studies, but also to explore novel areas of PM research such as effects on the brain, on the developing organism, or the impact of using cleaner fuel on diesel exhaust-induced health effects. Thus, response measurements took into account endpoints determined in the epidemiological (Core 2) and clinical (Core 3) studies. In addition, based on our earlier findings of translocation of inhaled UFP from nasal deposits to the brain, effects on the CNS were also assessed.

Summary/Accomplishments (Outputs/Outcomes):

Title: Pulmonary and cardiovascular effects of ambient ultrafine particle-containing aerosols in a rat model of cardiovascular disease
Several studies were done using JCR rats, a model of type II diabetes. Although these rats are not hyperglycemic, the JCR cp/cp rats are obese, hyperlipidemic, hyperinsulinemic, and have atherosclerotic and ischemic lesions that are hallmark features of human type II diabetes. We completed two studies with the JCR rats, one in which they were exposed to freshly-generated diesel exhaust emission aerosols (two fuel types with high and low sulfur content) in a mobile laboratory and another where the rats were exposed to concentrated ambient UFP-containing aerosols using the Harvard ultrafine particle concentrator (HUCAPS). Endpoints related to lung inflammation, inflammatory cell activation, acute phase responses, and platelet activation were measured after exposure. Groups of rats were also implanted with radiotransmitters to continuously monitor changes in heart rate, blood pressure, temperature, and activity associated with exposure to exhaust emissions or clean, filtered air.
Exposures of Rats to Freshly-Generated On-Road Aerosols Background: Humans with type II diabetes have been shown in recent epidemiological studies to be susceptible to the adverse health effects related to ambient particulate matter exposures. There are several animal models of diabetes, of which one is the JCR:LA-cp rat. Although these rats are not hyperglycemic (according to published literature and our results), the JCR cp/cp rats are obese, hyperlipidemic, hyperinsulinemic, and have atherosclerotic and ischemic lesions that are hallmark features of human type II diabetes. Heterozygotes or homozygous normals (designated by JCR +/?) are not obese or hyperinsulinemic and do not exhibit the arteriosclerotic lesions that the cp/cp rats do. Females of the same strain are similar to the +/? rats, which is why males are used exclusively in our studies.
Objective: One of the hypotheses being investigated in our studies in coordination with the Cores 2 and
3 projects is that some of the adverse health effects associated with exposure to ambient particulate pollution are causally related to inhaled ultrafine particles (UFP) and their gaseous co-pollutants, especially when aerosols are freshly-generated. Our previous studies using an on-road tractor-trailer exposure system have been conducted in old F-344 rats and spontaneously hypertensive (SH) rats. Since our first study showed that there was high variability in particle number and gas concentrations when “chasing” other vehicles, we made modifications to the system (i.e. use of telescoping exhausts inlets mounted on the rear of the trailer [Fig. 1]) to achieve more continuous exposures by taking in the exhaust produced by the mobile laboratory's engine (primary particle size, 13-19 nm; mass concentration, 9-27 µg/m3; number concentration, 1.6-4.3 x 106/cm3). This design allowed different fuels to be used to create specific exhausts under realistic environmental dilutions. In the most recent truck study, we exclusively used the JCR rats, focusing on our mechanistic hypothesis relating to the sensitivity imparted by vascular lesions.
Unlike our earlier studies, the rats did not receive any pre-treatments, e.g. inhaled endotoxin or instilled influenza virus. Due to the limitation on the total number of animals that could be exposed, we focused on
genetic background and exhaust atmosphere as being the response modifiers. Exposures (6 hr/day; 1 or 4 days in a row) to low- and ultralow-sulfur Diesel fuel exhaust emission aerosols were conducted in compartmentalized whole-body chambers while the truck was driven between Rochester and Utica (NY I-90). Endpoints related to lung inflammation, inflammatory cell activation, acute phase responses, platelet activation, and atherosclerotic lesion progression were measured after exposure. As in the past, groups of rats had also been implanted with radiotransmitters to continuously monitor changes in heart rate, blood pressure, temperature, and activity associated with exposure to exhaust emissions or clean, filtered air.
Results: There was an obvious effect of obesity and insulin resistance on baseline lavage inflammatory parameters, namely that the JCR cp/cp (obese) rats had higher total cell numbers, percentages of PMNs, and lavage fluid protein content and LDH andβ-glucuronidase activities than their lean litter mates. However, the emission aerosols did not have any consistent effects on these parameters. We also measured several parameters in serum and lavage fluid related to inflammation (PAI-1, IL-1β, IL-6, MCP-1, TNF-α) and metabolism (insulin, leptin) using bead array technology (rat adipokine panel, Luminex detector system). There was a lot of variability in the results, more so in the JCR cp/cp than in +/? rats, but the obese rats had higher levels for most of the parameters we measured. MCP-1 was not detectable in lavage fluid, whereas IL-6 was not detectable in serum. The only strikingly obvious effect of exposure was in serum leptin levels, which were increased in JCR cp/cp rats in low- and ultralow-sulfur fuel-exposed rats as compared to gas-phase only and filtered air-exposed rats. We also measured, through collaboration with Dr. Petia Simeonova (CDC/NIOSH), the levels of mitochondrial DNA (mtDNA) in aortae as a marker of oxidative injury. Although we have previously observed decreases in mtDNA amplification and there was slightly lower amplification in exhaust emission-exposed rats, there were no significant differences between exposure groups.
Based on our previous studies showing that solid UFP are translocated to the brain and, in one case, that glial fibrillary acidic protein (GFAP) was increased (a marker of astrocyte activation), we sampled tissues from several distinct brain regions for an analysis of GFAP protein content. While there was a trend that JCR cp/cp rats had lower levels of GFAP in the sampled brain regions (olfactory bulb, olfactory tract, cortex, striatum, cerebellum, hippocampus), there was no consistent pattern of response of this protein to the exhaust emission aerosols. CCl2 (MCP-1) and TNF-α mRNA levels were also quantitated via PCR in olfactory bulb tissue; the JCR cp/cp rats had higher transcript levels as compared to JCR +/?, but, again, there was no consistent effect of treatment on inflammatory mediator gene expression.
Exposure of JCR Rats to Concentrated Ambient Ultrafine Particles
We continued our studies in male JCR cp/cp (obese, insulin-resistant) and +/? (lean) rats that were exposed to concentrated ambient ultrafine particle-containing aerosols (count median diameter ~75 nm; number concentration ~0.05-1.3 x 106/cm3) using the Harvard system (HUCAPS). We completed a study in which rats were exposed for 6 hrs/day, 5 days/week for 4 weeks (total of 20 exposure days). We obtained bronchoalveolar lavage fluid, blood, and various tissues (lung, heart, aorta, brain regions, kidney, spleen, liver, pancreas) from aerosol- and clean, filtered air-exposed rats ~18 hrs after the end of the 4 week exposure.
As was true from the on-road truck study with JCR rats, many baseline parameters were elevated in the obese, insulin-resistant rats (JCR cp/cp) as compared to the lean controls (JCR +/?). The parameters that were elevated in cp/cp as compared to +/? JCR rats included total lavage cell number; lavage fluid protein
concentration and LDH and β-glucuronidase activities; plasma fibrinogen; total white blood cell number; and the number of blood leukocyte aggregates.
After three days of exposure, we found statistically significant increases in lavage fluid protein concentration and LDH activity in the HUCAPS-exposed JCR cp/cp rats as compared to filtered air-exposed and +/? rats. These changes occurred in the absence of increases in the percentage of lavage fluid PMNs. These changes were not observed following 4 weeks of exposure. Platelet (hematology, flow cytometry measurements) and platelet microparticle (flow cytometry) numbers were slightly decreased by three days of exposure and could be due to the increased aggregations with leukocytes that we observed in HUCAPS-exposed rats. However, these platelet-leukocyte as well as leukocyte-leukocyte aggregates seemed to be blunted in the obese diabetic rats. We did not observe these changes after 4 weeks of exposure and, rather, found that the platelet number decreased following HUCAPS exposure in both the cp/cp and +/? rats. An intriguing piece of data from the 3-day exposure was that aortic mtDNA amplification was blunted in HUCAPS-exposed JCR cp/cp rats relative to air-exposed controls and +/? rats, suggesting that oxidative DNA damage had occurred. However, this finding could not be confirmed with samples from the 4-week study, as the long fragment from the extracted mtDNA was degraded due to technical issues.
We also examined the same brain tissues as listed above for GFAP protein content and inflammatory cytokine/chemokines message levels. As we also described above, the GFAP levels in all of the brain regions tended to be lower in the JCR cp/cp rats as compared to the +/? rats. However, there were no changes in the levels of GFAP protein or TNF- or MCP-1 mRNA levels that were related to exposure atmosphere.
The JCR cp/cp rats are the animal model of choice for the Core 4 studies of this PM Center due to their obesity and insulin resistance-related atherosclerotic lesions. Humans with Type 2 diabetes have been shown to be more susceptible to the effects of ambient air pollution and they also have such lesions. However, our data thus far does not indicate that the cp/cp rats are more sensitive than their non-obese litter mates and, in fact, are perhaps less sensitive than F-344 rats. These findings, then, require some pursuit. We collaborated with Dr. Andrew Ghio (US EPA), whose interests is iron homeostasis in humans and animal models used in air pollution research. Analysis of samples from the HUCAPS-exposed cp/cp and +/? rats showed that iron homeostasis is disrupted in the cp/cp rats such that they have higher loads of lavage fluid, liver and lung tissue Fe as well as higher levels of transferrin and ferritin in lavage fluid. These findings imply that the cp/cp rats may have higher baseline levels of oxidative stress and may, therefore, compensate by synthesizing higher levels of antioxidants. In addition, we found that leptin levels were high in cp/cp rats, both in the serum and lavage fluid. Recent in vitro studies have shown that leptin induces surfactant exocytosis from type II alveolar epithelial cells, which may impart greater resistance to the effects of freshly-generated exhaust emission and concentrated ambient ultrafine particle-containing aerosols.
Title: CNS effects of inhaled ultrafine particles
Exposures of R6/2 Mice to Concentrated Ambient Ultrafine Particles
Background: Based on previous studies from our group demonstrating that inhaled poorly-soluble laboratory-generated UFP travel to the brain (Oberdörster et al., 2002, 2004) and evidence that they cause oxidative stress and inflammation in those regions where particles accumulate (Elder et al., 2006), we hypothesized that ambient UFP can induce similar effects, particularly in an animal model that exhibits early-onset neurodegeneration (in this case Huntington's disease, HD; Mangiarini et al., 1996). Transgenic R6/2 mice express 105-150 polyglutamine (polyQ) repeats in the huntingtin protein (Htt) and are the best characterized and most widely used of the HD animal models. Nuclear inclusions of aggregated Htt are abundant throughout the whole brain in these mice and can be detected as early as three weeks of age (8). The mice exhibit subtle motor deficits as early as one month of age, which then lead to overt symptoms by two months; death occurs within three to four months (Carter et al., 1999; Lione et al., 1999; Murphy et al., 2000).
HD and other neurodegenerative diseases have in common abnormal protein folding and aggregation (e.g. Alzheimer's, Creutzfeldt-Jakob, Parkinson's). However, the significance of protein aggregation in these diseases is not entirely clear, as there is debate regarding whether the aggregated proteins are toxic or the misfolded monomers. Nonetheless, recent acellular assays have shown that particles of different sizes, shapes, and surface chemistries can induce the unfolding and subsequent fibrillation (aggregation) of proteins (Linse et al., 2007). We hypothesized that the UFP present in ambient aerosols could be translocated to the brain, potentiate the aggregation of Htt, and accelerate neurodegeneration in exposed R6/2 mice.
Methods: We exposed the R6/2 mice, starting at 1-2 weeks of age, to concentrated ambient UFP- containing (HUCAPS) aerosols for 4 hrs/day, 5 days/week, for a total of 6 weeks in whole-body exposure chambers. About 1 week after the mouse pups were weaned, they were trained on an apparatus that allows an evaluation of locomotor function (Rotarod) and then re-tested every week through the end of exposure (a total of 4 evaluation points).
Results: Statistical analyses revealed that, unlike non-transgenic mice, the Rotarod performance of the transgenic mice declined over time. For those mice exposed to HUCAPS aerosols, the performance was significantly lower by the third week of testing, whereas for filtered air-exposed mice, performance did not drop significantly until the fourth testing week (Fig. 2). The mice were euthanized 24-48 hrs after the last exposure, with one group being used for evaluations of lung inflammatory responses and one used to collect tissue samples for histopathological analyses. Serial coronal sections of brain tissue were evaluated for striatal atrophy and huntingtin protein (Htt) expression and aggregation. There were no significant differences between filered air and HUCAPs exposed mice.
Another cohort of pups was exposed to HUCAPS aerosols or filtered air for 6 weeks and then recovered for 4 weeks. As with the study described above, locomotor function testing using the Rotarod system was done. In addition, their performance during the recovery period in a beam-break apparatus was evaluated to assess additional aspects of locomotor function, such as travelled distance and jumping. The mice were euthanized at the end of the 4-week recovery period and the same endpoints evaluated in brain tissue, lavage fluid, and blood. While the transgenic mice showed significant decreases in locomotor performance, there were no significant differences between filtered air and HUCAPs exposed mice (Fig.3).
Studies of Nanoparticle Toxicity in a Mouse Model of Alzheimer’s Disease
Background: Exposure to pollutant mixtures can lead to CNS toxicity by both direct and indirect mechanisms. A direct mechanism is the translocation of particles to the brain and we have previously shown that very poorly-soluble ultrafine 13C and Mn oxide particles translocate to the olfactory bulb, with evidence for penetration to more distal brain regions (Oberdorster, Sharp et al. 2004; Elder, Gelein et al. 2006). Furthermore, increases in inflammatory mediators (TNFα, MIP2) and inflammatory cell activation (GFAP) were found in those regions where Mn accumulated (e.g. olfactory bulb, frontal cortex, striatum). In addition, peripheral or systemic inflammation can result in the diffusion of proinflammatory cytokines across the blood-brain barrier, where they can then interact with brain macrophages and microglial cells. Cytokines also activate the brain endothelium itself.
The link between CNS inflammation and neurodegenerative disease is well established in the case of Alzheimer's disease (AD). For example, systemic inflammation (elevated serum TNF-α) was recently reported to be associated with a 2-fold faster rate of cognitive decline in a human AD cohort (Holmes, Cunningham et al. 2009). In addition, several groups have found associations between "pro-inflammatory" single-nucleotide polymorphisms in toll-like receptor 4 (TLR4) and AD (Minoretti, Gazzaruso et al. 2006; Balistreri, Grimaldi et al. 2008; Balistreri, Colonna-Romano et al. 2009). Current thinking is that inflammation accelerates underlying neuropathology in AD, rather than having a causal role. The cells of the CNS responsible for producing pro- inflammatory mediators include astrocytes, microglia, and neurons (Strohmeyer and Rogers 2001). Acute and chronic models of brain inflammation have been developed to probe how this process affects AD pathology and synaptic integrity/neuronal activity. The 3xTg-AD mouse model of AD (presenilin knock-in mice, which also express mutant forms of human tau and amyloid beta proteins), which develops both amyloid plaques and tau pathology in a progressive and age-dependent pattern (Oddo et al., 2003; Mastrangelo and Bowers, 2008), exhibits a 15-fold up-regulation of TNF-α and 11-fold up-regulation of MCP-1 in the entorhinal cortex as compared to non-transgenic mice (Janelsins, Mastrangelo et al. 2005). Additionally, this increase correlates with a specific increase in F4/80-positive microglia and macrophages in the 3xTg-AD entorhinal cortex. The link between neuroinflammation and disease severity is well-established for AD, as demonstrated for example by the blockade of TNF signaling after systemic administration of endotoxin (McAlpine, Lee et al. 2009).
Methods: Our previous work showed that inhalation of poorly-soluble Mn oxide UFP led to accumulation of Mn in the brain following olfactory translocation and that markers of inflammation and oxidative stress were upregulated (Elder, Gelein et al. 2006). We, therefore, hypothesized that inhaled Mn oxide UFP would impact the progression of pathology in a mouse AD model. Using 4 month-old 3xTg-AD mice in pilot-type studies, we undertook a 12-day exposure (4 hrs/day) to poorly-soluble Mn oxide UFP alone or in combination with weekly inhalation exposures to aerosolized endotoxin (lipopolysaccharide, LPS). Groups of mice were left untreated (naïve) or received only the LPS aerosols. One day and two months following the final exposure, mice were sacrificed, perfused with 4% paraformaldehyde, and brains were progressively dehydrated in 30% sucrose and coronally sectioned at 30 µm. Free-floating sections were separately processed for microglia staining using the Iba1 antibody or astrocytes using a GFAP-specific antibody. Quantitative image analysis revealed heightened activation of Iba1-expressing microglia in the hippocampus and dentate gyrus one days following Mn oxide aerosol exposure alone or in combination with LPS (Figure 4). Quantitative image analysis of staining intensities for GFAP indicated that astrocyte activation was similarly enhanced. These results indicate enhanced activation of the innate immune system in brain regions that are relevant to the pathology of AD and raise the possibility that disease severity could be accelerated with inhaled pollutant exposures. Furthermore, these changes in inflammatory cell activation state persisted through two months post-exposure (Figures 5-7).
These findings using Mn oxide model UFP raise the intriguing possibility that more environmentally- relevant exposure mixtures could have similar effects in AD mice. Indeed, the findings presented elsewhere in this report by Drs. Johnston and Cory-Slechta showing persistent glial cell activation in adult mice that were exposed to HUCAPS aerosols in the neonatal period lend support to this notion. As we pursue these findings and attempt to explain them mechanistically, it will be critical to distinguish between direct (i.e. particle translocation) and indirect (inflammatory mediator production).
Title: Early life exposure and developmental effects of ultrafine particle-containing aerosols
Background: Children may be affected by environmental contaminants in ways that adults are not, both because their exposures may be higher and because they may be more vulnerable to the toxicological effects of the pollutants. Early life exposures may contribute to diseases, either during childhood or later in life. We hypothesized that early life exposure to ambient ultrafine particles alters lung response and structural development leading to increased sensitivity to low level environmental challenges as adults. We conducted five different exposure studies to begin to address this hypothesis and to determine effects of early life exposure to ambient ultrafine particles mixed with ozone on later-life environmental challenges.
Objective: Effects of early life exposure to ambient ultrafine particles and ozone mixtures on the early and late pulmonary responses of mice re-challenged with ovalbumin
Method: C57Bl6 mice were exposed to HUCAPS mixed with 0.3 ppm ozone, HUCAPS alone, 0.3 ppm ozone, or filtered air on postnatal days 4-7 and 10-13 for 4 hours/day. The median particle size was 78.5 nm and the mass concentration was 64.6 µg/m3. On day 13, three mice from each group were exposed to gold nanoparticles for 6 hours and examined 24 hours post-exposure in order to determine whether prior HUCAPS or mixture exposure altered translocation of nanoparticles to extrapulmonary tissues, including the CSN. Gold was measured in tissues by ICP-MS. Mice were allowed to recover for 24 hours before being analyzed.
Results: Examination of mRNA 24 hours post-exposure demonstrated no significant changes in message abundance for messages encoding inflammatory markers KC and IL-6, cell cycle marker P21, or the antioxidant, MnSOD. However, gold was detected in lung, liver, kidney, spleen and the brain. Our results demonstrated that nanoparticle translocation occurs during the postnatal lung growth period.
Method: A second group of mice was allowed to recover until they were 56 days old, creating 4 exposure groups as follows: postnatal air/6 weeks recovery, postnatal HUCAPS/6 weeks recovery, postnatal 0.3 ppm ozone /6 weeks recovery, postnatal HUCAPS + 0.3 ppm ozone/6 weeks recovery. Analysis of lung mRNA showed no significant changes from controls in any of the exposure groups. Brain sections were also stained at this time-point for markers of astrocyte and microglial activation.
Results: Mice that were exposed to HUCAPS and allowed to recover until 56 days of age demonstrated enhanced staining intensity of GFAP visualized throughout the ventral midbrain. The astrocytes were hypertrophied with thickened processes, indicative of glial activation. These observations demonstrate that astroglial activation is present in the adult ventral midbrain following HUCAPS exposure during the neonatal period. We also observed increased numbers of microglial cells and enhanced Iba-1 staining in all layers of the dentate gyrus. These cells also exhibited a more ameboid morphology and increased intensity of Iba-1 staining, which are features consistent with microglial activation (Fig. 8). A remarkable feature of this response is its persistence from early-life exposure to adulthood.
Method: A third group of mice was allowed to recover for 6 weeks, after which they were re-exposed starting at 56 days post birth for an additional 4 days, creating 4 exposure groups as follows: postnatal air/adult air, postnatal HUCAPS/adult HUCAPS, postnatal 0.3 ppm ozone /adult 0.3 ppm ozone, postnatal HUCAPS + 0.3 PPM ozone/adult HUCAPS + 0.3 ppm ozone. Mice were exposed at 56 days to concentrated UFP with a median particle size of 78.6 nm and mass concentration of 46.9 µg/m3.
Results: Message abundance of IL-6 and KC were reduced in the HUCAPS + ozone group only and were decreased by >50% as compared to sham-exposed mice.
Method: A fourth group of mice was allowed to recover for 24 weeks, after which they were re-exposed starting at 178 days post birth for an additional 4 days, creating 4 exposure groups as follows: postnatal air/adult air, postnatal HUCAPS/adult HUCAPS, postnatal 0.3 ppm ozone /adult 0.3 ppm ozone, postnatal HUCAPS + 0.3 ppm ozone/adult HUCAPS + 0.3 ppm ozone. Mice were exposed at 178 days to a median particle size of 78.6 nm and mass concentration was 34.3 µg/m3.
Results: Message abundance of KC, IL-6 and P21 were induced approximately 2-fold in the HUCAP +
ozone group as compared to sham-exposed mice.
Method: A fifth group of mice was intranasally infected with 120 hemagglutination units (HAU) of influenza virus A/HKx31 (H3N2) in order to study the impact of viral respiratory tract infection on ultrafine particle induced effects. Mice were exposed at the 178 day time point, creating 8 exposure groups as follows: postnatal HUCAPS + 0.3 ppm ozone / adult Influenza, postnatal HUCAPS / adult influenza, postnatal 0.3 ppm / adult influenza, postnatal air / adult Influenza, postnatal HUCAPS + 0.3 ppm ozone / adult Mock Influenza, postnatal HUCAPS / adult mock influenza, postnatal 0.3 ppm / adult mock influenza, postnatal air / adult mock Influenza. 14 days later, mice were sacrificed and tissues were collected for examination. Morbidity was monitored following changes in body weight and survival.
Results: Examination of body weight demonstrated no weight loss in any of the mock flu exposed groups; however, 7 days post infection sham mice lost approximately 15% body weight, ozone exposed mice lost approximately 15% body weight, HUCAPS + 0.3 ppm ozone mice lost approximately 20% body weight and HUCAPS only mice lost approximately 30% of body weight. All groups returned to near mock flu weight levels 14 days post infection. There was no lethality in any of the mock flu infected groups; however, there was approximately a 25% lethality in the sham, HUCAPS and HUCAPS + ozone groups with influenza infection. The ozone only group had approximately 50% lethality 14 days post infection. Animal lethality was first measured 6 days post infection. mRNA abundance was measured at 7 and 14 days post infection. Message abundance for KC was increased 2.5 and 3 fold in the HUCAPS and HUCAPS + ozone groups as compared to sham-exposed mice 7 days post infection (Figure 9). No significant changes were measured 14 days post infection. Message abundance for IL-6 was increased approximately 4 fold in the HUCAPS mice as compared to sham-exposed mice. No significant changes were measure 14 days post infection. Message abundance for P21 was increased 3 fold in the HUCAPS + ozone mice as compared to the sham exposed mice 14 days post infection. No other significant changes in mRNA abundance were measured.


Conclusions: Firstly, early neonatal life exposure to ultrafine particles show that they can translocate to several organs following postnatal lung exposure. Secondly, early life ultrafine particle and ozone inhalation induces inflammatory cell activation in the brain and this persists for several weeks post-exposure (into adulthood for this species). Third, early life ultrafine particle and ozone inhalation sensitizes the lung to later life environmental and viral challenges. An alternative interpretation is that aging enhances sensitivity to later life environmental challenges, something that we have reported before in PM Center-supported work.
Are ambient ultrafine particles a risk factor for Parkinson's Disease?
Background: Ultrafine particles can translocate from deposition sites on the nasal olfactory mucosa to the CNS. The hypothesis was tested that early life postnatal exposure to concentrated ambient ultrafine particles would sensitize the CNS to subsequent adult challenge with paraquat + maneb (PQ+MB), a well- established pesticide-based model of the Parkinson’s disease phenotype (PDP).
Results: Mice exposed postnatally to concentrated ambient ultrafine particles were significantly more sensitive to the locomotor-reducing effects of PQ+MB than sham controls, or those exposed to UFP alone or PQ+MB alone. UFP and PQ+MB significantly altered catecholamine levels in both the nigrostriatal and mesocortical dopamine pathways. UFP had a particular influence on striatum, increasing NE, DOPAC, and DA turnover (DOPAC/DA) levels, while PQ+MB generally impacted midbrain, decreasing 5HT, DOPAC and dopamine turnover. An interaction between UFP and PQ+MB on cortical 5-HT levels was evidenced as a significant 5-HT decrease in PQ+MB treated animals compared to both sham controls and UFP +PQ+MB treated mice. Cortical DA was also increased in PQ+MB treated animals.
Conclusions: This and additional findings of effects on dopamine pathways and 5-HT levels indicate that early life UFP enhances locomotor reduction in response to PQ+MB challenge and changes striatal catecholamines (DAergic cell terminals), a region critical to PD, while PQ+MB in the same animals produces catecholamine changes in the ventral midbrain (DAergic cell bodies). Conceivably, this concurrent damage to striatum and midbrain could increase nigral cell death and thereby contribute to a PDP.
Significance to the field:
The potential of inhaled ultrafine particles of ambient particulate air pollution for inducing effects on the CNS has been suggested based on several toxicological and some recent epidemiological studies. Knowledge of underlying direct and indirect mechanisms involving CNS translocation, role of adsorbed organic and inorganic chemicals and of systemically vs. locally-induced effects is necessary for assessing the contribution of ultrafine particles to the induction of adverse effects by particulate air pollution.
Relationship to overall Center goals:
These studies are an obvious extension of our Center research focusing on ultrafine particles and their role in causing extrapulmonary effects, specifically with the CNS as a sensitive target organ.
Relevance to the Agency’s mission:
The ubiquitous ultrafine particle mode of ambient air pollution is not directly regulated with a specific NAAQS. Given the diversity of ultrafine particle sources involving both anthropogenic and natural sources a generic standard based on mass or number concentration would not be appropriate. Rather, specific sources may be targeted in terms of reducing emissions, based on the identification of hazard of ultrafine particles emitted into the atmosphere.
Conclusions from the animal studies are:
  • Six-hour exposure of obese diabetic and lean control rats to diesel exhaust (low and ultralow sulfur fuel) in a mobile lab on highway induced significant decreases in serum leptin; non-significant trend of higher levels in serum and lung lavage, of inflammatory cytokines; trend of lower GFAP level in brain regions and higher levels of inflammatory cytokines in olfactory bulb (non-significant).
  • Four-week exposure of obese diabetic and lean rats to concentrated ambient UFP showed increased lung lavage protein and LDH levels at 3 days of exposure but not at the end of 4-week exposure, indicating potential adaptive mechanisms. Platelet number decreased in both rat types at the end of 4-week exposure. The obese diabetic rats are not more sensitive than their lean litter mates.
  • Four-week exposure to concentrated ambient UFP resulted in a disruption of iron homeostasis in obese diabetic rats indicting higher baseline levels of oxidative stress.
  • Obese diabetic rats have higher leptin levels in serum and lavage fluid.
  • Concentrated UF particle exposure in an early onset neurodegeneration mouse model may accelerate decline in locomotor function.
  • Twelve-day ultrafine Mn-oxide exposure in a mouse model of Alzheimer's Disease induced enhanced activation of the innate immune system in hippocampus and dentate gyrus which persisted through two months post-exposure.
  • Neonatal mice inhalation exposure to gold nanoparticles confirmed their translocation to extrapulmonary tissues, including the olfactory bulb of the CNS.
  • Eight days of neonatal mouse inhalation exposure to concentrated ambient UF particles induced microglial activation in the dentate gyrus of the hippocampus, which was still present in adulthood.
  • Neonatal mouse inhalation exposure to concentrated ambient UF particles in combination with ozone sensitizes the lung to later life viral challenges.
  • Early life exposure of mice with a pesticide-based Parkinson's disease phenotype to concentrated UFP enhances locomotor reduction with concurrent damage to striatum and midbrain.


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Journal Articles:

No journal articles submitted with this report: View all 62 publications for this subproject

Supplemental Keywords:

RFA, Health, PHYSICAL ASPECTS, Scientific Discipline, Air, particulate matter, Toxicology, Health Risk Assessment, Risk Assessments, Physical Processes, atmospheric particulate matter, atmospheric particles, acute cardiovascular effects, airway disease, exposure, animal model, ambient particle health effects, atmospheric aerosol particles, ultrafine particulate matter, PM, inhalation toxicology, cardiovascular disease

Progress and Final Reports:

Original Abstract
  • 2006 Progress Report
  • 2007 Progress Report
  • 2008 Progress Report
  • 2009 Progress Report
  • 2010 Progress Report
  • 2011 Progress Report

  • Main Center Abstract and Reports:

    R832415    Rochester PM Center

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R832415C001 Characterization and Source Apportionment
    R832415C002 Epidemiological Studies on Extra Pulmonary Effects of Fresh and Aged Urban Aerosols from Different Sources
    R832415C003 Human Clinical Studies of Concentrated Ambient Ultrafine and Fine Particles
    R832415C004 Animal models: Cardiovascular Disease, CNS Injury and Ultrafine Particle Biokinetics
    R832415C005 Ultrafine Particle Cell Interactions In Vitro: Molecular Mechanisms Leading To Altered Gene Expression in Relation to Particle Composition