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BACKGROUND-: Exposure to air pollution has been identified as a possible environmental contributor to Alzheimer’s Disease (AD) risk. As the number of people with AD worldwide continues to rise, it becomes vital to understand the nature of this potential gene-environment interaction. This study assessed the effects of short-term exposures to concentrated ambient ultrafine particulates (UFP

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Infants born prematurely often require supplemental oxygen, which contributes to aberrant lung development and increased pulmonary morbidity following a respiratory viral infection. We have been using a mouse model to understand how early-life hyperoxia affects the adult lung response to influenza A virus (IAV) infection. Prior studies showed how neonatal hyperoxia (100% oxygen) increased sensitivity of adult mice to infection with IAV [IAV (A/Hong Kong/X31) H3N2] as defined by persistent inflammation, pulmonary fibrosis, and mortality. Since neonatal hyperoxia alters lung structure, we used a novel fluorescence-expressing reporter strain of H1N1 IAV [A/Puerto Rico/8/34 mCherry (PR8-mCherry)] to evaluate whether it also altered early infection of the respiratory epithelium. Like Hong Kong/X31, neonatal hyperoxia increased morbidity and mortality of adult mice infected with PR8-mCherry. Whole lung imaging and histology suggested a modest increase in mCherry expression in adult mice exposed to neonatal hyperoxia compared with room air-exposed animals. However, this did not reflect an increase in airway or alveolar epithelial infection when mCherry-positive cells were identified and quantified by flow cytometry. Instead, a modest increase in the number of CD45-positive macrophages expressing mCherry was detected. While neonatal hyperoxia does not alter early epithelial infection with IAV, it may increase the activity of macrophages toward infected cells, thereby enhancing early epithelial injury.

Alveolar epithelial type II cells (AEC2) maintain pulmonary homeostasis by producing surfactant, expressing innate immune molecules, and functioning as adult progenitor cells for themselves and alveolar epithelial type I cells (AEC1). How the proper number of alveolar epithelial cells is determined in the adult lung is not well understood. Here, BrdU labeling, genetic lineage tracing, and targeted expression of the anti-oxidant extracellular superoxide dismutase in AEC2s are used to show how the oxygen environment at birth influences postnatal expansion of AEC2s and AEC1s in mice. Birth into low (12%) or high (≥60%) oxygen stimulated expansion of AEC2s through self-renewal and differentiation of the airway Scgb1a1 + lineage. This non-linear or hormesis response to oxygen was specific for the alveolar epithelium because low oxygen stimulated and high oxygen inhibited angiogenesis as defined by changes in V-cadherin and PECAM (CD31). Although genetic lineage tracing studies confirmed adult AEC2s are stem cells for AEC1s, we found no evidence that postnatal growth of AEC1s were derived from self-renewing Sftpc + or the Scbg1a1 + lineage of AEC2s. Taken together, our results show how a non-linear response to oxygen at birth promotes expansion of AEC2s through two distinct lineages. Since neither lineage contributes to the postnatal expansion of AEC1s, the ability of AEC2s to function as stem cells for AEC1s appears to be restricted to the adult lung.

Background Previous work has demonstrated size, surface charge and skin barrier dependent penetration of nanoparticles into the viable layers of mouse skin. The goal of this work was to characterize the tissue distribution and mechanism of transport of nanoparticles beyond skin, with and without Ultraviolet Radiation (UVR) induced skin barrier disruption. Atomic absorption spectroscopy (AAS), flow cytometry and confocal microscopy were used to examine the effect of UVR dose (180 and 360 mJ/cm2 UVB) on the skin penetration and systemic distribution of quantum dot (QD) nanoparticles topically applied at different time-points post UVR using a hairless C57BL/6 mouse model. Results Results indicate that QDs can penetrate mouse skin, regardless of UVR exposure, as evidenced by the increased cadmium in the local lymph nodes of all QD treated mice. The average % recovery for all treatment groups was 69.68% with ~66.84% of the applied dose recovered from the skin (both epicutaneous and intracutaneous). An average of 0.024% of the applied dose was recovered from the lymph nodes across various treatment groups. When QDs are applied 4 days post UV irradiation, at the peak of the skin barrier defect and LC migration to the local lymph node, there is an increased cellular presence of QD in the lymph node; however, AAS analysis of local lymph nodes display no difference in cadmium levels due to UVR treatment. Conclusions Our data suggests that Langerhans cells (LCs) can engulf QDs in skin, but transport to the lymph node may occur by both cellular (dendritic and macrophage) and non-cellular mechanisms. It is interesting that these specific nanoparticles were retained in skin similarly regardless of UVR barrier disruption, but the observed skin immune cell interaction with nanoparticles suggest a potential for immunomodulation, which we are currently examining in a murine model of skin allergy. Electronic supplementary material The online version of this article (doi:10.1186/s12989-017-0191-7) contains supplementary material, which is available to authorized users.

Whereas amyloid-β (Aβ) accumulates in the brain of normal animals dosed with low levels of copper (Cu), the mechanism is not completely known. Cu could contribute to Aβ accumulation by altering its clearance and/or its production. Because Cu homeostasis is altered in transgenic mice overexpressing Aβ precursor protein (APP), the objective of this study was to elucidate the mechanism of Cu-induced Aβ accumulation in brains of normal mice and then to explore Cu's effects in a mouse model of Alzheimer's disease. In aging mice, accumulation of Cu in brain capillaries was associated with its reduction in low-density lipoprotein receptor-related protein 1 (LRP1), an Aβ transporter, and higher brain Aβ levels. These effects were reproduced by chronic dosing with low levels of Cu via drinking water without changes in Aβ synthesis or degradation. In human brain endothelial cells, Cu, at its normal labile levels, caused LRP1-specific down-regulation by inducing its nitrotyrosination and subsequent proteosomal-dependent degradation due in part to Cu/cellular prion protein/LRP1 interaction. In APP(sw/0) mice, Cu not only down-regulated LRP1 in brain capillaries but also increased Aβ production and neuroinflammation because Cu accumulated in brain capillaries and, unlike in control mice, in the parenchyma. Thus, we have demonstrated that Cu's effect on brain Aβ homeostasis depends on whether it is accumulated in the capillaries or in the parenchyma. These findings should provide unique insights into preventative and/or therapeutic approaches to control neurotoxic Aβ levels in the aging brain.

Excessive manganese (Mn) uptake by brain cells, particularly in regions like the basal ganglia, can lead to toxicity. Mn(2+) is transported into cells via a number of mechanisms, while Mn(3+) is believed to be transported similarly to iron (Fe) via the transferrin (Tf) mechanism. Cellular Mn uptake is therefore determined by the activity of the mechanisms transporting Mn into each type of cell and by the amounts of Mn(2+), Mn(3+) and their complexes to which these cells are exposed; this complicates understanding the contributions of each transporter to Mn toxicity. While uptake of Fe(3+) via the Tf mechanism is well understood, uptake of Mn(3+) via this mechanism has not been systematically studied. The stability of the Mn(3+)Tf complex allowed us to form and purify this complex and label it with a fluorescent (Alexa green) tag. Using purified and labeled Mn(3+)Tf and biophysical tools, we have developed a novel approach to study Mn(3+)Tf transport independently of other Mn transport mechanisms. This approach was used to compare the uptake of Mn(3+)Tf into neuronal cell lines with published descriptions of Fe(3+) uptake via the Tf mechanism, and to obtain quantitative information on Mn uptake via the Tf mechanism. Results confirm that in these cell lines significant Mn(3+) is transported by the Tf mechanism similarly to Fe(3+)Tf transport; although Mn(3+)Tf transport is markedly slower than other Mn transport mechanisms. This novel approach may prove useful for studying Mn toxicity in other systems and cell types.

An aberrant oxygen environment at birth increases the severity of respiratory viral infections later in life through poorly understood mechanisms. Here, we show that alveolar epithelial cell (AEC) 2 cells (AEC2s), progenitors for AEC1 cells, are depleted in adult mice exposed to neonatal hypoxia or hyperoxia. Airway cells expressing surfactant protein (SP)-C and ATP binding cassette subfamily A member 3, alveolar pod cells expressing keratin (KRT) 5, and pulmonary fibrosis were observed when these mice were infected with a sublethal dose of HKx31, H3N2 influenza A virus. This was not seen in infected siblings birthed into room air. Genetic lineage tracing studies in mice exposed to neonatal hypoxia or hyperoxia revealed pre-existing secretoglobin 1a1+ cells produced airway cells expressing SP-C and ATP binding cassette subfamily A member 3. Pre-existing Kr5+ progenitor cells produced squamous alveolar cells expressing receptor for advanced glycation endproducts, aquaporin 5, and T1α in alveoli devoid of AEC2s. They were not the source of KRT5+ alveolar pod cells. These oxygen-dependent changes in epithelial cell regeneration and fibrosis could be recapitulated by conditionally depleting AEC2s in mice using diphtheria A toxin and then infecting with influenza A virus. Likewise, airway cells expressing SP-C and alveolar cells expressing KRT5 were observed in human idiopathic pulmonary fibrosis. These findings suggest that alternative progenitor lineages are mobilized to regenerate the alveolar epithelium when AEC2s are severely injured or depleted by previous insults, such as an adverse oxygen environment at birth. Because these lineages regenerate AECs in spatially distinct compartments of a lung undergoing fibrosis, they may not be sufficient to prevent disease.

Animal dung is a biomass fuel burned by vulnerable populations who cannot afford cleaner sources of energy, such as wood and gas, for cooking and heating their homes. Exposure to biomass smoke is the leading environmental risk for mortality, with over 4,000,000 deaths each year worldwide attributed to indoor air pollution from biomass smoke. Biomass smoke inhalation is epidemiologically associated with pulmonary diseases, including chronic obstructive pulmonary disease (COPD), lung cancer, and respiratory infections, especially in low and middle-income countries. Yet, few studies have examined the mechanisms of dung biomass smoke-induced inflammatory responses in human lung cells. Here, we tested the hypothesis that dung biomass smoke causes inflammatory responses in human lung cells through signaling pathways involved in acute and chronic lung inflammation. Primary human small airway epithelial cells (SAECs) were exposed to dung smoke at the air-liquid interface using a newly developed, automated, and reproducible dung biomass smoke generation system. The examination of inflammatory signaling showed that dung biomass smoke increased the production of several proinflammatory cytokines and enzymes in SAECs through activation of the activator protein (AP)-1 and arylhydrocarbon receptor (AhR) but not nuclear factor-κB (NF-κB) pathways. We propose that the inflammatory responses of lung cells exposed to dung biomass smoke contribute to the development of respiratory diseases.

There is an urgent need for in vitro screening assays to evaluate nanoparticle (NP) toxicity. However, the relevance of in vitro assays is still disputable. We administered doses of TiO(2) NPs of different sizes to alveolar epithelial cells in vitro and the same NPs by intratracheal instillation in rats in vivo to examine the correlation between in vitro and in vivo responses. The correlations were based on toxicity rankings of NPs after adopting NP surface area as dose metric, and response per unit surface area as response metric. Sizes of the anatase TiO(2) NPs ranged from 3 to 100 nm. A cell-free assay for measuring reactive oxygen species (ROS) was used, and lactate dehydrogenase (LDH) release, and protein oxidation induction were the in vitro cellular assays using a rat lung Type I epithelial cell line (R3/1) following 24 h incubation. The in vivo endpoint was number of PMNs in bronchoalveolar lavage fluid (BALF) after exposure of rats to the NPs via intratracheal instillation. Slope analyses of the dose response curves shows that the in vivo and in vitro responses were well correlated. We conclude that using the approach of steepest slope analysis offers a superior method to correlate in vitro with in vivo results of NP toxicity and for ranking their toxic potency.

Studies showed that certain cytotoxicity assays were not suitable for assessing nanoparticle (NP) toxicity. We evaluated a lactate dehydrogenase (LDH) assay for assessing copper (Cu-40, 40 nm), silver (Ag-35, 35 nm; Ag-40, 40 nm), and titanium dioxide (TiO2-25, 25 nm) NPs by examining their potential to inactivate LDH and interference with β-nicotinamide adenine dinucleotide (NADH), a substrate for the assay. We also performed a dissolution assay for some of the NPs. We found that the copper NPs, because of their high dissolution rate, could interfere with the LDH assay by inactivating LDH. Ag-35 could also inactivate LDH probably because of the carbon matrix used to cage the particles during synthesis. TiO2-25 NPs were found to adsorb LDH molecules. In conclusion, NP interference with the LDH assay depends on the type of NPs and the suitability of the assay for assessing NP toxicity should be examined case by case.

Engineered nanoparticles (NP) are being developed and incorporated in a number of commercial products, raising the potential of human exposure during manufacture, use, and disposal. Although data concerning the potential toxicity of some NP have been reported, validated simple assays are lacking for predicting their in vivo toxicity. The aim of this study was to evaluate new response metrics based on chemical and biological activity of NP for screening assays that can be used to predict NP toxicity in vivo. Two cell-free and two cell-based assays were evaluated for their power in predicting in vivo toxicity of eight distinct particle types with widely differing physicochemical characteristics. The cell-free systems comprised fluorescence- and electron spin resonance-based assays of oxidant activity. The cell-based systems also used electron spin resonance (ESR) as well as luciferase reporter activity to rank the different particle types in comparison to benchmark particles of low and high activity. In vivo experiments evaluated acute pulmonary inflammatory responses in rats. Endpoints in all assays were related to oxidative stress and responses were expressed per unit NP surface area to compare the results of different assays. Results indicated that NP are capable of producing reactive species, which in biological systems lead to oxidative stress. Copper NP had the greatest activity in all assays, while TiO(2) and gold NP generally were the least reactive. Differences in the ranking of NP activity among the assays were found when comparisons were based on measured responses. However, expressing the chemical (cell-free) and biological (cells; in vivo) activity per unit particle surface area showed that all in vitro assays correlated significantly with in vivo results, with the cellular assays correlating the best. Data from this study indicate that it is possible to predict acute in vivo inflammatory potential of NP with cell-free and cellular assays by using NP surface area-based dose and response metrics, but that a cellular component is required to achieve a higher degree of predictive power.

Short and long-term pulmonary response to inhaled nickel hydroxide nanoparticles (nano-Ni(OH)(2), CMD = 40 nm) in C57BL/6 mice was assessed using a whole body exposure system. For short-term studies mice were exposed for 4 h to nominal concentrations of 100, 500, and 1000 mg/m(3). For long-term studies mice were exposed for 5 h/d, 5 d/w, for up to 5 months (m) to a nominal concentration of 100 mg/m(3). Particle morphology, size distribution, chemical composition, solubility, and intrinsic oxidative capacity were determined. Markers of lung injury and inflammation in bronchoalveolar lavage fluid (BALF); histopathology; and lung tissue elemental nickel content and mRNA changes in macrophage inflammatory protein-2 (Mip-2), chemokine ligand 2 (Ccl2), interleukin 1-alpha (Il-1α), and tumor necrosis factor-alpha (Tnf-α) were assessed. Dose-related changes in BALF analyses were observed 24 h after short-term studies while significant changes were noted after 3 m and/or 5 m of exposure (24 h). Nickel content was detected in lung tissue, Ccl2 was most pronouncedly expressed, and histological changes were noted after 5 m of exposure. Collectively, data illustrates nano-Ni(OH)(2) can induce inflammatory responses in C57BL/6 mice.

Ultrafine particles (UFP) may contribute to the morbidity and mortality associated with exposure to ambient particles, but few data are available on ultrafine particle numbers in indoor air, where susceptible subjects spend most of their time. We measured particle number, UFP size distribution, and total suspended particulate (JSP) mass in three locations: (I) a medical floor in a large tertiary care hospital, (2) outdoor air above a construction site outside the hospital, and (3) an environmental exposure chamber with purification of intake air. Mass and number concentrations were recorded continuously in each location over 70-110 h. Mean ± SD particle (p) numbers were 3.63 ± 1.l5 } 10(3) p/cm(3) in the hospital, 3.05 ± 6.65 } 10(4) p/cm(3) outside, and 5.86 ± 2.11 } 10(2) p/cm(3) in the environmental chamber. In the hospital, particle number and mass declined during the evening hours when the unit was less active, with the particle number as low as 1.15 } 10(3) p/cm(3). Particle numbers peaked (2.78 } 10(4) p/cm(3)) in the morning hours when activity on the unit was the most intense. "Spikes" in fine particle number were often not accompanied by increases in TSP mass. In the hospital, a distinct population of ultrafine particles (median diameter approximately 23 nm) was observed during the lunch hour, suggesting a change in particle source during this time. Outdoor fine particle numbers above the construction site were highly variable, reaching peaks of greater than 1.7 } 10(6) p/cm(3). These data suggest that, in the indoor environment, particle numbers and size distribution vary with intensity and type of local activity, and significant peaks in particle number are not detected with daily averages. Monitoring of particle mass may be an inaccurate measure of exposure to ultrafine particles indoors.

An important step in assessing the toxicology of particles is to determine their fate after inhalation. Of particular interest to us are airborne ultrafine particles (UFPs; < 100 nm), which are abundant in ambient urban air and are of the same size as engineered nanoparticles. Translocation to extrapulmonary sites after respiratory tract deposition represents an important mechanism for these particles to cause direct effects in secondary target organs (Oberdorster et al. 2005). The extent to which this process occurs depends on several factors including particle solubility, particle or aggregate size, the site of deposition, and the integrity of the epithelial lining. UFPs deposit efficiently in all regions of the respiratory tract, depending on their size; specifically, as particle size decreases toward the smallest UFPs, nasopharyngeal deposition increases (International Committee on Radiological Protection 1994). Studies in rats have shown translocation of soluble manganese compounds from the nose along olfactory neuronal pathways to the olfactory bulb (Dorman et al. 2004; Henriksson and Tjalve 2000; Tjalve et al. 1996; Tjalve and Henriksson 1999) after inhalation or intranasal instillation exposures. Likewise, the few studies that have examined the fate of UFPs deposited on the nasal mucosa identified translocation along the neuronal olfactory route as a pathway to the olfactory bulb of the central nervous system (CNS). These include early studies in non-human primates, which demonstrated the translocation of solid nanosized particles (30 nm poliovirus; 50 nm silver-coated gold colloids) along the axons of olfactory nerves into the olfactory bulb (Bodian and Howe 1941a, 1941b; DeLorenzo 1970). We have also shown that inhaled elemental carbon particles (13C; 35 nm, count median diameter) accumulate in rat olfactory bulb after whole-body inhalation (Oberdorster et al. 2004). Regarding penetration into deeper brain regions, Tjalve et al. (1995) demonstrated that soluble ionic Mn instilled into the olfactory chamber of pike has the ability to pass synaptic junctions and migrate from the olfactory tract to more distal regions, including the hypothalamus. Dorman et al. (2004) found Mn in the striatum and cerebellum of rats after subchronic inhalation exposure to a soluble Mn salt (sulfate); however, this was attributed to uptake from the blood. Thus, contributions to brain Mn levels from the blood need to be considered and may also be an issue for inhaled solid UFPs. The effects of translocated particles in the brain are also important to determine. For example, preliminary information has emerged from populations of welders that some of them may develop parkinsonism 17 years earlier than the general population (Racette et al. 2001). Welding produces high amounts of fumes containing Mn UFPs (Zimmer et al. 2002). Several recent epidemiologic studies describe occupational exposure ranges of approximately 0.01–5 mg/m3 Mn in fumes from various welding processes and materials (Korczynski 2000; Li et al. 2004; Sinczuk-Walczak et al. 2001). Conflicting data emerge from animal studies, however, regarding effects of inhaled Mn compounds in the brain. Henriksson and Tjalve (2000) reported changes in glial fibrillary acidic protein (GFAP) and S-100b, markers of astrocyte activation, in several brain regions from rats exposed intranasally to Mn chloride. However, Dorman et al. (2004) did not find any evidence of changes in GFAP levels in the brain after exposure to Mn sulfate or phosphate. Potential contributing factors to the lack of concurrence in results include differences in the solubilities of the Mn salts used, the doses, and the contribution of olfactory epithelial damage. In the present study, we sought to address the hypothesis that a major translocation route for inhaled poorly soluble Mn oxide UFPs from deposits in the nose is to the olfactory bulb in the CNS. We characterized the size, oxidation state, and in vitro solubility of gas-phase–generated Mn oxide particles and also compared the translocation kinetics to the olfactory bulb of Mn oxide and MnCl2 that were applied to the nasal epithelium of rats via instillation. We then measured the accumulation of Mn in lung, liver, and olfactory bulb after repeated inhalation exposures with both nares patent or with one naris occluded. We show that Mn oxide UFPs are translocated to and retained in the olfactory bulb (ipsilateral to the patent naris only) and present evidence of exposure-induced effects in that region of the brain. These studies demonstrate the importance of UFPs size and of solubility in olfactory translocation processes.

Particle concentrators are commonly used for controlling exposure levels to ambient ultrafine, fine, and coarse aerosols over a broad range of concentrations. For ultrafine aerosols, these concentrators require water condensation technology to grow and enrich these smaller sized particles (D a < 100 nm). Because the chemistry of the particles is directly related to their toxicity, any changes induced by ultrafine concentrators on ambient particles need to be better characterized in order to fully understand the results obtained in health exposure studies. Using aerosol time-of-flight mass spectrometry (ATOFMS), the size-resolved chemistry was measured of concentrated ultrafine and accumulation mode (50–300 nm) particles from several particle concentrators with different designs. This is the first report detailing the size-resolved distributions of elemental carbon (EC) and organic carbon (OC) particles sampled from concentrators. Experimental measurements of the single particle mixing state of particles i...

Dopaminergic (DAergic) systems have been identified as putative targets for polycholorinated biphenyl (PCB) actions. However, the precise mechanisms leading to neurotoxicity are unresolved. Reactive oxygen species (ROS) were recently shown to mediate injury in DAergic MN9D cells following exposure to Aroclor 1254 (A1254), a commercial PCB mixture. The oxidative stress response in DAergic cells included a persistent expression of heme oxygenase-1 (HO-1). This study tested the hypothesis that a sustained PCB-induced HO-1 response leads to abnormally high Fe levels, which generates ROS production and mediates death in the MN9D DAergic cell model. Accordingly, results indicated that A1254 augmented intracellular Fe levels in MN9D cells after 24 h. Fe chelation by desferoxamine or pharmacologic inhibition of HO activity with tin-protoporphyrin reduced Fe accumulation, ROS production, and cytotoxicity following A1254 exposure. HO-1 over-expression predisposed MN9D DAergic cells to enhanced ROS production and cell death in response to PCBs. Conversely, antisense inhibition of HO-1 expression prevented PCB-induced ROS production and cell death. These observations suggest that enhanced HO-1 catalytic activity and subsequent liberation of Fe participate in neurotoxic DAergic cell injury caused by A1254 exposure in vitro.

Given growing concerns over the observed relationship between ultrafine particles and adverse human health effects, there is a major need in the community performing human/animal exposure studies for methods that can be used for the generation of high concentrations of ultrafine particles (

Lead exposure continues to be a significant public health problem. In addition to acute toxicity, Pb has an extremely long half-life in bone. Individuals with past exposure develop increased blood Pb levels during periods of high bone turnover or resorption. Pb is known to affect osteoblasts, osteoclasts, and chondrocytes and has been associated with osteoporosis. However, its effects on skeletal repair have not been studied. We exposed C57/B6 mice to various concentrations of Pb acetate in their drinking water to achieve environmentally relevant blood Pb levels, measured by atomic absorption. After exposure for 6 weeks, each mouse underwent closed tibia fracture. Radiographs were followed and histologic analysis was performed at 7, 14, and 21 days. In mice exposed to low Pb concentrations, fracture healing was characterized by a delay in bridging cartilage formation, decreased collagen type II and type X expression at 7 days, a 5-fold increase in cartilage formation at day 14 associated with delayed maturation and calcification, and a persistence of cartilage at day 21. Fibrous nonunions at 21 days were prevalent in mice receiving very high Pb exposures. Pb significantly inhibited ex vivo bone nodule formation but had no effect on osteoclasts isolated from Pb-exposed animals. No significant effects on osteoclast number or activity were observed. We conclude that Pb delays fracture healing at environmentally relevant doses and induces fibrous nonunions at higher doses by inhibiting the progression of endochondral ossification.

Clodronate liposomes were given to rats via intratracheal inhalation to investigate the importance of alveolar macrophages (AMs) in inhaled endotoxin-induced lung injury. When AM depletion was maximal (87% to 90%), rats were exposed to lipopolysaccharide (LPS) or saline. Neither clodronate nor saline liposomes induced an influx of neutrophils (PMNs) into the lungs. However, depleted LPS-exposed rats had 5- to 8-fold higher numbers of lavage PMNs and greater lavage cell reactive oxygen species release compared to undepleted rats. Although AM depletion by itself did not significantly increase inflammatory cytokine expression in lung tissue, LPS-induced message levels for interleukin (IL)-1alpha, IL-1beta, IL-6, and tumor necrosis factor (TNF)-alpha were approximately 2-fold higher in AM-depleted rats compared to undepleted rats. These results indicate that cells other than AMs can recruit inflammatory cells into the lungs during acute LPS-induced injury and that AMs play an important suppressive role in the innate pulmonary inflammatory response.

Ultrafine particles (UFP, particles100 nm) are ubiquitous in ambient urban and indoor air from multiple sources and may contribute to adverse respiratory and cardiovascular effects of particulate matter (PM). Depending on their particle size, inhaled UFP are efficiently deposited in nasal, tracheobronchial, and alveolar regions due to diffusion. Our previous rat studies have shown that UFP can translocate to interstitial sites in the respiratory tract as well as to extrapulmonary organs such as liver within 4 to 24 h postexposure. There were also indications that the olfactory bulb of the brain was targeted. Our objective in this follow-up study, therefore, was to determine whether translocation of inhaled ultrafine solid particles to regions of the brain takes place, hypothesizing that UFP depositing on the olfactory mucosa of the nasal region will translocate along the olfactory nerve into the olfactory bulb. This should result in significant increases in that region on the days following the exposure as opposed to other areas of the central nervous system (CNS). We generated ultrafine elemental (13)C particles (CMD = 36 nm; GSD = 1.66) from [(13)C] graphite rods by electric spark discharge in an argon atmosphere at a concentration of 160 microg/m(3). Rats were exposed for 6 h, and lungs, cerebrum, cerebellum and olfactory bulbs were removed 1, 3, 5, and 7 days after exposure. (13)C concentrations were determined by isotope ratio mass spectroscopy and compared to background (13)C levels of sham-exposed controls (day 0). The background corrected pulmonary (13)C added as ultrafine (13)C particles on day 1 postexposure was 1.34 microg/lung. Lung (13)C concentration decreased from 1.39 microg/g (day 1) to 0.59 microg/g by 7 days postexposure. There was a significant and persistent increase in added (13)C in the olfactory bulb of 0.35 microg/g on day 1, which increased to 0.43 microg/g by day 7. Day 1 (13)C concentrations of cerebrum and cerebellum were also significantly increased but the increase was inconsistent, significant only on one additional day of the postexposure period, possibly reflecting translocation across the blood-brain barrier in certain brain regions. The increases in olfactory bulbs are consistent with earlier studies in nonhuman primates and rodents that demonstrated that intranasally instilled solid UFP translocate along axons of the olfactory nerve into the CNS. We conclude from our study that the CNS can be targeted by airborne solid ultrafine particles and that the most likely mechanism is from deposits on the olfactory mucosa of the nasopharyngeal region of the respiratory tract and subsequent translocation via the olfactory nerve. Depending on particle size,50% of inhaled UFP can be depositing in the nasopharyngeal region during nasal breathing. Preliminary estimates from the present results show that approximately 20% of the UFP deposited on the olfactory mucosa of the rat can be translocated to the olfactory bulb. Such neuronal translocation constitutes an additional not generally recognized clearance pathway for inhaled solid UFP, whose significance for humans, however, still needs to be established. It could provide a portal of entry into the CNS for solid UFP, circumventing the tight blood-brain barrier. Whether this translocation of inhaled UFP can cause CNS effects needs to be determined in future studies.

On-road experiments were conducted to determine the sensitivities of rats to real-world aerosol. This article summarizes the on-road aerosol and gas measurements and provides background information for the companion paper on the rat exposures. Measurements were carried out over 10 days, 6 h/day, driving a route from Rochester to Buffalo. Aerosol instrumentation used in this study included two scanning mobility particle sizers (SMPS) to determine the aerosol size distribution from 10 to 300 nm, 2 stand-alone condensation particle counters to determine the total aerosol number concentration, and an electrical aerosol detector to determine the aerosol length concentration. A thermal denuder (TD) was used with one of the SMPS instruments to determine the size distribution of the non-volatile fraction. Filter samples were collected and analyzed for elemental carbon, and gas analyzers measured ambient levels of CO, CO(2), and NO. Average daily total aerosol number concentration ranged from 200,000 to 560,000 particles/cm(3). Past studies on urban highways have measured total number concentrations ranging between 10(4) and 10(6) particles/cm(3). The average daily NO concentration ranged from 0.10 to 0.24 ppm and the corresponding CO(2) concentration ranged from 400 to 420 ppm. The average daily geometric number mean particle size determined by the SMPS ranged from 15 to 20 nm. The TD reduced the average SMPS number concentration between 87 and 95% and the SMPS volume between 54 and 83%, suggesting that most of the particles consisted of volatile material. The TD also increased the geometric number mean diameter from 15 to 20 nm to 30 to 40 nm.

Rat alveolar macrophages (AMs) were depleted via intratracheal inhalation (ITIH) of clodronate-containing liposomes. AM depletion following ITIH delivery of clodronate liposomes was 33.2 +/- 14.2 on day 1, 88.1 +/- 6.2 on day 3, and 91.4 +/- 1.8 on day 4 relative to control rats given saline-containing liposomes. Almost all (approximately 99%) of the AMs remaining at the 3-day time point were peroxidase negative, suggesting that immature macrophages were not recruited from the circulation to replace those undergoing cell death on that day. Only 0.5% +/- 0.5% of bronchoalveolar lavage (BAL) cells were neutrophils at this time (normalized to controls). Whole-body inhalation did not induce as much AM depletion at 3 days (37.6% +/- 10.1%) and required larger amounts of liposome-encapsulated clodronate compared to ITIH. Intratracheal instillation (as opposed to inhalation) of clodronate liposomes produced a significant inflammatory response characterized by the influx of both polymorphonuclear neutrophils (PMNs) and macrophages. In subsequent pilot studies, the response to intratracheally instilled crystalline silica (75 microg) was found to be markedly reduced in rats depleted of AMs by the ITIH method. We conclude that ITIH of clodronate liposomes in rats is both efficient and useful for examining the role of AMs in pulmonary toxicology.

Ambient particulate pollution is associated with adverse health effects in epidemiological studies of the elderly with cardiopulmonary diseases. We hypothesize that ultrafine particles (UFP) contribute to these effects, especially when they are freshly generated and occur at high number concentrations. Studies to determine adverse effects have been performed using laboratory-generated surrogates, diluted exhaust from stationary engines, or concentrated ambient UFPs. Methodological difficulties exist with such experiments, and questions remain about how well these particles model those found in ambient air. Freshly generated UFPs are present at high concentrations on highways and vehicle passengers are directly exposed to them. We wished to expose rats to these UFPs to test their potential to cause effects. Since such exposures have not been done before, one objective of our study was to demonstrate the feasibility of an on-road exposure study. Secondly, we wished to determine if there are significant exposure-related effects in aged, compromised rats. Old rats (21-mo F-344) were exposed directly on highways to either the aerosol (1 microm)/gas phase, gas phase only, or filtered air using an on-road exposure system. Some rats were pretreated with a low dose of inhaled endotoxin or with instilled influenza virus to induce lung inflammation. The exposures in compartmentalized whole-body chambers consisted of 6-h driving periods on I-90 between Rochester and Buffalo once or 3 days in a row. Endpoints related to lung inflammation, inflammatory cell activation, and acute-phase responses were measured after exposure. The on-road exposure system did not affect measured endpoints in filtered air-exposed rats, indicating that it was well tolerated by them. We observed the expected increases in response (inflammation, inflammatory cell activation) to the priming agents. We also found a significant particle-associated increase in plasma endothelin-2, suggesting alterations in vascular endothelial cell activation. In addition, we observed main effects of particles related to the acute-phase response and inflammatory-cell activation. Interactions between on-road particles and the priming agents were also found. These results suggest that exposures to on-road particle mixtures have effects on the pulmonary and cardiovascular system in compromised, old rats. Furthermore, they demonstrate that on-road exposures are feasible and could be performed in future studies with more continuous particle exposures.

An evaporation/condensation particle generator produced 30-50 nm count median diameter particles from both pure hydrocarbons and from a complex mixture--used motor oil--at a concentration above 1 2 10 6 /cm 3 . The objective was to generate ultrafine aerosols for inhalation toxicology studies using specified organic components as surrogates for the particulate emissions generated by diesel internal combustion engines. This nanoparticle generation system, assembled from commercially available components, produced smaller particle size and higher particle number concentration than has been previously documented using Sinclair-La Mer condensation generator technology. The paper describes both the experiments used to design and characterize the particle generator and the operating conditions used for a specific inhalation experiment as an example of the system capability.

Octamethylcyclotetrasiloxane (D4) has been used for more than 40 years in industrial applications and consumer products, including the personal care industry. D4 possesses many properties suitable for personal care products, such as low surface tension, water repellency, and thermal and chemical stability. The skin is a major route of exposure to D4 for humans. The main objective of this study was to evaluate the percutaneous absorption of neat D4 in human skin using the human skin/nude mouse model. This information is needed to aid in assessing potential risks associated with the intended use of D4. To determine whether D4 accumulates in adipose tissue of the skin, the distribution of D4 in human skin layers following application of neat D4 was also evaluated. In this study, a mean of 1.09 ± 0.46% of the applied dose was absorbed by the animal under semioccluded conditions. Only about 0.02% of the applied dose remained in the skin after 24 h of exposure (or 72 h after application). The majority (94.59 ± 12.28%) of the dose evaporated from the site. Excretion in the volatile trap (or expired volatiles) accounted for 42% of the radioactivity that was absorbed, while 49% were excreted in the urine and feces. Despite the lipophilic properties of D4, a significant accumulation of D4 in adipose tissue of the skin was not observed 24 h following application to the surface of the skin. The small amount of D4 detected in the skin was distributed mainly in the epidermis (61%), with lower amounts in the dermis (29%) and subcutaneous adipose tissue (10%). Dermal absorption studies using human skin transplanted onto nude mice showed that this model could be successfully applied for in vivo percutaneous absorption studies of D4, and presumably of other cyclic siloxanes. The fraction of the percutaneous dose of D4 absorbed in this model was found to be consistent with results reported by others using different experimental approaches.

Chronic inhalation of crystalline silica can produce lung tumors in rats whereas this has not been shown for amorphous silica. At present the mechanisms underlying this rat lung tumor response are unknown, although a significant role for chronic inflammation and cell proliferation has been postulated. To examine the processes that may contribute to the development of rat lung tumors after silica exposure, we characterized the effects of subchronic inhalation of amorphous and crystalline silica in rats. Rats were exposed for 6 h/day, on 5 days/week, for up to 13 weeks to 3 mg/m(3) crystalline or 50 mg/m(3) amorphous silica. The effects on the lung were characterized after 6.5 and 13 weeks of exposure as well as after 3 and 8 months of recovery. Exposure concentrations were selected to induce high pulmonary inflammatory-cell responses by both compounds. Endpoints characterized after silica exposure included mutation in the HPRT gene of isolated alveolar cells in an ex vivo assay, changes in bronchoalveolar lavage fluid markers of cellular and biochemical lung injury and inflammation, expression of mRNA for the chemokine MIP-2, and detection of oxidative DNA damage. Lung burdens of silica were also determined. After 13 weeks of exposure, lavage neutrophils were increased from 0.26% (controls) to 47 and 55% of total lavaged cells for crystalline and amorphous silica, with significantly greater lavage neutrophil numbers after amorphous silica (9.3 x 10(7) PMNs) compared to crystalline silica (6.5 x 10(7) PMNs). Lung burdens were 819 and 882 microg for crystalline and amorphous silica, respectively. BAL fluid levels of LDH as an indicator of cytotoxicity were twice as high for amorphous silica compared to those of crystalline silica, at the end of exposure. All parameters remained increased for crystalline silica and decreased rapidly for amorphous silica in the 8-month recovery period. Increased MIP-2 expression was observed at the end of the exposure period for both amorphous and crystalline silica. After 8 months of recovery, those markers remained elevated in crystalline silica-exposed rats, whereas amorphous silica-exposed rats were not significantly different from controls. A significant increase in HPRT mutation frequency in alveolar epithelial cells was detected immediately after 13 weeks of exposure to crystalline, but not to amorphous silica. A significant increase in TUNEL staining was detected in macrophages and terminal bronchiolar epithelial cells of amorphous silica-exposed rats at the end of the exposure period; however, crystalline silica produced far less staining. The observation that genotoxic effects in alveolar epithelial cells occurred only after crystalline but not amorphous silica exposure, despite a high degree of inflammatory-cell response after subchronic exposure to both types of silica, suggests that in addition to an inflammatory response, particle biopersistence, solubility, and direct or indirect epithelial cell cytotoxicity may be key factors for the induction of either mutagenic events or target cell death.

Epidemiological studies have demonstrated a correlation between low levels of ambient particles and morbidity, particularly in the elderly with existing cardiopulmonary disease. Such correlations have been challenged due to doubts as to whether particles act alone to cause these detrimental effects. We hypothesized that ambient carbonaceous ultrafine particles (part of the urban fine particle mode) and ozone (O3) together would induce greater oxidative stress in the lung than when administered alone and that their effects would be amplified in the compromised, aging lung. We therefore exposed male F344 rats (10 wk, 20 mo) to ultrafine carbon particles (count median diameter 25 nm, 100 mug/m3, equivalent to 50 mug/m3 inhaled by humans) and to O3 (1 ppm) alone and in combination for 6 h. Low-dose endotoxin (lipopolysaccharide, LPS) priming by inhalation (70 endotoxin units estimated alveolar deposited dose) was used as a model of respiratory tract infection. Inflammatory parameters in bronchoalveolar lavage...

Lipopolysaccharide (LPS) is a component of the gram-negative bacterial cell wall that is known to activate inflammatory cells and enhance the production of inflammatory mediators in the lung. As it is a ubiquitous compound, inhalation exposure is highly likely in the human environment. Adaptation is a phenomenon by which a previous exposure results in improved survival or reduced injury as compared to a single exposure alone. We hypothesized that the basic proinflammatory effects of LPS in the lung could result in the development of adaptation in animals. Based on evidence of age- and species-related differences in lung injury, we used an acute lung injury model with inhaled LPS to compare the development of adaptation in young and old Fisher 344 rats and C57Bl/6J mice. Animals were exposed to low-dose (predicted lung deposition 20 ng in rats and 5 ng in mice) LPS aerosols for 10 min on 3 consecutive days; on day 4, a high dose (rats 200 ng; mice 25 ng) was delivered. Another group of animals received onl...

Clara cell secretory protein (CCSP), also known as uteroglobin (Ug), is a 16-kDa homodimeric protein of unknown function. Within rodent species, CCSP is expressed predominantly by nonciliated Clara cells that line conducting airways of the lung. To investigate in vivo functions for CCSP, we established mice homozygous for a null allele of the CCSP gene (CCSP-/-). We previously showed no overt phenotypic consequences associated with CCSP deficiency when CCSP-/- mice are maintained in the absence of environmental stress. However, CCSP-/- mice show an oxidant-sensitive phenotype that cannot be attributed to alterations in the inflammatory response when challenged by inhaled oxidant gases. The current study was undertaken to determine whether CCSP deficiency results in pathological changes to the kidney. This study was prompted by the recent description of severe systemic disease and kidney fibrosis/dysfunction in an independent line of CCSP-deficient mice, termed Ug-/- (Zhang et al, Science 276:1408-1412, 1997). CCSP-/- mice show normal growth and reproductive performance when maintained in two independent genetic backgrounds, inbred 129 and congenic C57BL/6. Strain 129 CCSP-/- mice have normal kidney function, as assessed by urinary glucose, lactate dehydrogenase, and glomerular filtration rate; they show no kidney fibrosis or abnormalities in fibronectin accumulation and no histological abnormalities in proximal convoluted tubules or glomeruli at either light or electron microscopic levels. CCSP deficiency is associated with mild proteinurea involving a modest increase in mouse major urinary protein-1. We conclude that CCSP (Ug) deficiency, per se, is not the cause of severe renal pathology and systemic disease reported for Ug-/- mice.

Our past studies in rats have confirmed the high pulmonary toxicity of inhaled Teflon fumes containing ultrafine particles. These previous studies had been performed in young adult animals. We hypothesized that older animals would be more susceptible to induction of an inflammatory response. The purpose of our study was to characterize the acute pulmonary inflammatory response in the lungs of healthy C57BL/6 adult mice of 8wk and 18 mo of age after short-term (30 min) exposure to low concentrations (

Inhaled endotoxin (lipopolysaccharide, LPS) can induce acute lung injury and at high doses may lead to respiratory distress syndrome. Using a mouse model of acute lung inflammation induced by inhalation of low doses of LPS we examined the kinetics of chemokine, proinflammatory cytokine, and metallothionein. Eight-week-old C57BL/6 mice were dosed for 10 min with LPS, resulting in an estimated alveolar dose of

In the midst of research focusing on the neurodevelopmental effects of mercury vapor in rats, we detected significant levels of mercury (30-60 ng/g) in the blood of nonexposed control subjects. We determined that the dominant form of the mercury was organic and that the standard laboratory chow we used in our vivarium was the source of the contamination. The dietary levels were deemed of potential biologic significance, even though they might have fallen below the limits of measurement specified by the supplier. All investigators employing animals in research must assess such potential contamination because dietary agents may alter a) conclusions based on intentionally administered doses, b) outcomes by interacting with other agents that are the primary focus of the research, and c) outcomes of research unrelated to the toxic effects of experimentally administered agents.

Heating of polytetrafluoroethylene (PTFE) has been described to release fumes containing ultrafine particles (approximately 18 nm diam). These fumes can be highly toxic in the respiratory tract inducing extensive pulmonary edema with hemorrhagic inflammation. Fischer-344 rats were exposed to PTFE fumes generated by temperatures ranging from 450 to 460 degrees C for 15 min at an exposure concentration of 5 x 10(5) particles/cm3, equivalent to approximately 50 micrograms/m3. Responses were examined 4 hr post-treatment when these rats demonstrated 60-85% neutrophils (PMNs) in their lung lavage. Increases in abundance for messages encoding the antioxidants manganese superoxide dismutase and metallothionein (MT) increased 15- and 40-fold, respectively. For messages encoding the pro- and anti-inflammatory cytokines: inducible nitric oxide synthase, interleukin 1 alpha, 1 beta, and 6 (IL-1 alpha, IL-1 beta, and IL-6), macrophage inflammatory protein-2, and tumor necrosis factor-alpha (TNF alpha) increases of 5-, 5-, 10-, 40-, 40-, and 15-fold were present. Vascular endothelial growth factor, which may play a role in the integrity of the endothelial barrier, was decreased to 20% of controls. In situ sections were hybridized with 33P cRNA probes encoding IL-6, MT, surfactant protein C, and TNF alpha. Increased mRNA abundance for MT and IL-6 was expressed around all airways and interstitial regions with MT and IL-6 demonstrating similar spatial distribution. Large numbers of activated PMNs expressed IL-6, MT, and TNF alpha. Additionally, pulmonary macrophages and epithelial cells were actively involved. These observations support the notion that PTFE fumes containing ultrafine particles initiate a severe inflammatory response at low inhaled particle mass concentrations, which is suggestive of an oxidative injury. Furthermore, PMNs may actively regulate the inflammatory process through cytokine and antioxidant expression.

Ultraviolet radiation (UVR) skin exposure is a common exogenous insult that can alter skin barrier and immune functions. With the growing presence of nanoparticles (NPs) in consumer goods and technological applications the potential for NPs to contact UVR-exposed skin is increasing. Therefore it is important to understand the effect of UVR on NP skin penetration and the potential for systemic translocation. Previous studies qualitatively showed that UVR skin exposure can increase the penetration of NPs below the stratum corneum. In this work, an in vivo mouse model was used to quantitatively examine the skin penetration of carboxylated (CdSe/ZnS, core/shell) quantum dots (QDs) through intact and UVR barrier-disrupted murine skin by organ Cd mass analysis. Transepidermal water loss was used to measure the magnitude of the skin barrier defect as a function of UVR dose and time post-UVR exposure. QDs were applied to mice 3-4 days post-UVR exposure at the peak of the skin barrier disruption. Our results reveal unexpected trends that suggest these negative-charged QDs can penetrate barrier intact skin and that penetration and systemic transport depends on the QD application time post-UVR exposure. The effect of UVR on skin-resident dendritic cells and their role in the systemic translocation of these QDs are described. Our results suggest that NP skin penetration and translocation may depend on the specific barrier insult and the inflammatory status of the skin.

Iron is critical in multiple aspects of CNS development, but its role in neurodevelopment—the ability of iron deficiency to alter normal development—is difficult to dissociate from the effects of anemia. We developed a novel dietary restriction model in the rat that allows us to study the effects of iron deficiency in the absence of severe anemia. Using a combination of auditory brainstem response analyses (ABR) and electron microscopy, we identified an unexpected impact of nonanemic iron deficiency on axonal diameter and neurofilament regulation in the auditory nerve. These changes are associated with altered ABR latency during development. In contrast to models of severe iron deficiency with anemia, we did not find consistent or prolonged defects in myelination. Our data demonstrate that iron deficiency in the absence of anemia disrupts normal development of the auditory nerve and results in altered conduction velocity.

It is well acknowledged from observations in humans that iron deficiency during pregnancy can be associated with a number of developmental problems in the newborn and developing child. Due to the obvious limitations of human studies, the stage during gestation at which maternal iron deficiency causes an apparent impairment in the offspring remains elusive. In order to begin to understand the time window(s) during pregnancy that is/are especially susceptible to suboptimal iron levels, which may result in negative effects on the development of the fetus, we developed a rat model in which we were able to manipulate and monitor the dietary iron intake during specific stages of pregnancy and analyzed the developing fetuses. We established four different dietary-feeding protocols that were designed to render the fetuses iron deficient at different gestational stages. Based on a functional analysis that employed Auditory Brainstem Response measurements, we found that maternal iron restriction initiated prior to conception and during the first trimester were associated with profound changes in the developing fetus compared to iron restriction initiated later in pregnancy. We also showed that the presence of iron deficiency anemia, low body weight, and changes in core body temperature were not defining factors in the establishment of neural impairment in the rodent offspring. Our data may have significant relevance for understanding the impact of suboptimal iron levels during pregnancy not only on the mother but also on the developing fetus and hence might lead to a more informed timing of iron supplementation during pregnancy.

A method to investigate the dependence of the physicochemical properties of nanoparticles (e.g. size, surface area and crystal phase) on their oxidant generating capacity is proposed and demonstrated for TiO(2) nanoparticles. Gas phase synthesis methods that allow for strict control of size and crystal phase were used to prepare TiO(2) nanoparticles. The reactive oxygen species (ROS) generating capacity of these particles was then measured. The size dependent ROS activity was established using TiO(2) nanoparticles of 9 different sizes (4 - 195 nm) but the same crystal phase. For a fixed total surface area, an S-shaped curve for ROS generation per unit surface area was observed as a function of particle size. The highest ROS activity per unit area was observed for 30 nm particles, and observed to be constant above 30 nm. There was a decrease in activity per unit area as size decreased from 30 nm to 10 nm; and again constant for particles smaller than 10 nm. The correlation between crystal phase and oxidant capacity was established using TiO(2) nanoparticles of 11 different crystal phase combinations but similar size. The ability of different crystal phases of TiO(2) nanoparticles to generate ROS was highest for amorphous, followed by anatase, and then anatase/rutile mixtures, and lowest for rutile samples. Based on evaluation of the entire dataset, important dose metrics for ROS generation are established. Their implications of these ROS studies on biological and toxicological studies using nanomaterials are discussed.

The dispersion in air of nanoparticles of different sizes, materials and morphologies with controlled agglomeration involving aerosol delivery for in vivo and in vitro studies is one of the most difficult challenges in the field of nanoparticle toxicology. We describe here a nanoparticle dispersion system using an electrospray method to deliver airborne nanoparticles (approximately 10-100 nm) with spatial uniformity and controllable particle concentration for in vitro and in vivo studies. With the dispersion method, single nanoparticles (polystyrene latex particles, TiO(2), Au, Mn, quantum dots, and carbon nanotubes) can be delivered to cells and animals via the air. The degree of agglomeration can be controlled by changing the suspension feeding rate to simulate realistic conditions for exposure studies.

Despite its potentially adverse effects on lung development and function, supplemental oxygen is often used to treat premature infants in respiratory distress. To understand how neonatal hyperoxia can permanently disrupt lung development, we previously reported increased lung compliance, greater alveolar simplification, and disrupted epithelial development in adult mice exposed to 100% inspired oxygen fraction between postnatal days 1 and 4. Here, we investigate whether oxygen-induced changes in lung function are attributable to defects in surfactant composition and activity, structural changes in alveolar development, or both. Newborn mice were exposed to room air or 40%, 60%, 80%, or 100% oxygen between postnatal days 1 and 4 and allowed to recover in room air until 8 wk of age. Lung compliance and alveolar size increased, and airway resistance, airway elastance, tissue elastance, and tissue damping decreased, in mice exposed to 60–80% oxygen; changes were even greater in mice exposed to 100% oxygen. These alterations in lung function were not associated with changes in total protein content or surfactant phospholipid composition in bronchoalveolar lavage. Moreover, surface activity and total and hydrophobic protein content were unchanged in large surfactant aggregates centrifuged from bronchoalveolar lavage compared with control. Instead, the number of type II cells progressively declined in 60–100% oxygen, whereas levels of T1α, a protein expressed by type I cells, were comparably increased in mice exposed to 40–100% oxygen. Thickened bundles of elastin fibers were also detected in alveolar walls of mice exposed to ≥60% oxygen. These findings support the hypothesis that changes in lung development, rather than surfactant activity, are the primary causes of oxygen-altered lung function in children who were exposed to oxygen as neonates. Furthermore, the disruptive effects of oxygen on epithelial development and lung mechanics are not equivalently dose dependent.

Background Many populations are exposed to multiple species of mercury (Hg), predominantly organic Hg as methylmercury (MeHg) from fish, and inorganic Hg as Hg vapor from dental amalgams. Most of our knowledge of the neurotoxicity of Hg is based on research devoted to studying only one form at a time, mostly MeHg. Objectives In this study we investigated the effects of prenatal exposure to MeHg and Hg vapor on Hg concentrations in the brain of neonatal rats. Methods Female Long-Evans hooded rats were exposed to MeHg (0, 3, 6, or 9 ppm as drinking solution), Hg vapor (0, 300, or 1,000 μg/m3 for 2 hr/day), or the combination of both, from 30 days before breeding through gestational day 18. On postnatal day 4, whole brains were taken from one male and one female from each of four litters in each treatment group to assess organic and inorganic Hg in the brain by cold vapor atomic absorption spectrometry. Results Statistical analysis using linear mixed effects models showed that MeHg dose was the primary determinant of both organic and inorganic brain Hg levels. For both outcomes, we also found significant interactions between MeHg and Hg vapor exposure. These interactions were driven by the fact that among animals not exposed to MeHg, animals exposed to Hg vapor had significantly greater organic and inorganic brain Hg levels than did unexposed animals. Conclusion This interaction, heretofore not reported, suggests that coexposure to MeHg and Hg vapor at levels relevant to human exposure might elevate neurotoxic risks.

Rats were exposed to different sizes of Ti02 or AI2O3 particles by intratracheal instillation or by aerosol inhalation. The lungs were analyzed at days 1, 29 and 59 or 60 after exposure for TiO2 and Al2O3 content and for the lung's free cell responses. An extensive lung lavage was used in an attempt to distinguish between the particles retained in the alveoli and airways and particles translocated into the pulmonary tissue itself. After intratracheal instillation of 500 μg, particles of TiO2 and A12O3 with a primary particle diameter of ∼20 nm were translocated into the pulmonary tissue from the alveoli to a greater extent than particles with 250-500 nm diameter. The enhanced translocation resulted in an increase of particle content in the hilar lymph nodes. This was accompanied by an acute inflammatory response as indexed by the abnormal abundance of polymorphonuclear leukocytes. After 10 similar inhalation exposures, no difference in translocation of ultrafine (∼20 nm) and larger (∼250 nm) TiO2...

The purpose of our studies is to elucidate the basic mechanism of lung tissue injury which may be common for particles of high or low toxicity. In experiments on rats we compared particle translocation of two types of TiO 2 and of two types of Al 2 O 3 . The types of TiO 2 or Al 2 O 3 differ in origin, manufacturing technology and most importantly in the size of the primary particles, but not in chemical or crystallographic characteristics

The objective of this study was to investigate mechanisms underlying species specificity in particle-induced lung inflammation.Rats, mice, and hamsters exposed to air, 1, 7, or 50 mg/m3 of carbon black for 13 weeks were killed at 1 day, 3 months, and 11 months after exposure. Bronchoalveolar lavage was performed and characterized for cell number, cell type, reactive oxygen and nitrogen species, and cytokine levels. Ex vivo mutational analysis of inflammatory cells was evaluated by coincubating with lung epithelial cells. Lung tissue was evaluated for gene expression of various antiinflammatory mediators.There was a dose- and time-related effect with all the parameters. Rats demonstrated greater propensity for generating a proinflammatory response, whereas mice and hamsters demonstrated an increased antiinflammatory response.These differences in pro- and antiinflammatory responses may contribute to the apparent species differences in inflammation and tumorigenesis.