[show abstract][hide abstract] ABSTRACT: Acrolein is a reactive unsaturated aldehyde that is produced during endogenous oxidative processes and is a major bioactive component of environmental pollutants such as cigarette smoke. Because in vitro studies demonstrate that acrolein can inhibit neutrophil apoptosis, we evaluated the effects of in vivo acrolein exposure on acute lung inflammation induced by LPS. Male C57BL/6J mice received 300 microg/kg intratracheal LPS and were exposed to acrolein (5 parts per million, 6 h/day), either before or after LPS challenge. Exposure to acrolein either before or after LPS challenge did not significantly affect the overall extent of LPS-induced lung inflammation, or the duration of the inflammatory response, as observed from recovered lung lavage leukocytes and histology. However, exposure to acrolein after LPS instillation markedly diminished the LPS-induced production of several inflammatory cytokines, specifically TNF-alpha, IL-12, and the Th1 cytokine IFN-gamma, which was associated with reduction in NF-kappaB activation. Our data demonstrate that acrolein exposure suppresses LPS-induced Th1 cytokine responses without affecting acute neutrophilia. Disruption of cytokine signaling by acrolein may represent a mechanism by which smoking contributes to chronic disease in chronic obstructive pulmonary disease and asthma.
The Journal of Immunology 08/2008; 181(1):736-45. · 5.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: The extracellular signal-regulated kinases 1 and 2 (ERK1/2) are phosphorylated after inhalation of asbestos. The effect of blocking this signaling pathway in lung epithelium is unclear. Asbestos-exposed transgenic mice expressing a dominant-negative mitogen-activated protein kinase kinase-1 (dnMEK1) (i.e., the upstream kinase necessary for phosphorylation of ERK1/2) targeted to lung epithelium exhibited morphologic and molecular changes in lung. Transgene-positive (Tg+) (i.e., dnMEK1) and transgene-negative (Tg-) littermates were exposed to crocidolite asbestos for 2, 4, 9, and 32 days or maintained in clean air (sham controls). Distal bronchiolar epithelium was isolated using laser capture microdissection and mRNA analyzed for molecular markers of proliferation and Clara cell secretory protein (CCSP). Lungs and bronchoalveolar lavage fluids were analyzed for inflammatory and proliferative changes and molecular markers of fibrogenesis. Distal bronchiolar epithelium of asbestos-exposed wild-type mice showed increased expression of c-fos at 2 days. Elevated mRNA levels of histone H3 and numbers of Ki-67-labeled proliferating bronchiolar epithelial cells were decreased at 4 days in asbestos-exposed Tg+ mice. At 32 days, distal bronchioles normally composed of Clara cells in asbestos-exposed Tg+ mouse lungs exhibited nonreplicating ciliated and mucin-secreting cells as well as decreased mRNA levels of CCSP. Gene expression (procollagen 3-a-1, procollagen 1-a-1, and IL-6) linked to fibrogenesis was also increased in lung homogenates of asbestos-exposed Tg- mice, but reduced in asbestos-exposed Tg+ mice. These results suggest a critical role of MEK1 signaling in epithelial cell proliferation and lung remodeling after toxic injury.
American Journal of Respiratory Cell and Molecular Biology 06/2008; 38(5):618-26. · 4.15 Impact Factor
[show abstract][hide abstract] ABSTRACT: Allergen sensitization and allergic airway disease are likely to come about through the inhalation of Ag with immunostimulatory molecules. However, environmental pollutants, including nitrogen dioxide (NO2), may promote adaptive immune responses to innocuous Ags that are not by themselves immunostimulatory. We tested in C57BL/6 mice whether exposure to NO2, followed by inhalation of the innocuous protein Ag, OVA, would result in allergen sensitization and the subsequent development of allergic airway disease. Following challenge with aerosolized OVA alone, mice previously exposed via inhalation to NO2 and OVA developed eosinophilic inflammation and mucus cell metaplasia in the lungs, as well as OVA-specific IgE and IgG1, and Th2-type cytokine responses. One hour of exposure to 10 parts per million NO2 increased bronchoalveolar lavage fluid levels of total protein, lactate dehydrogenase activity, and heat shock protein 70; promoted the activation of NF-kappaB by airway epithelial cells; and stimulated the subsequent allergic response to Ag challenge. Furthermore, features of allergic airway disease were not induced in allergen-challenged TLR2-/- and MyD88-/- mice exposed to NO2 and aerosolized OVA during sensitization. These findings offer a mechanism whereby allergen sensitization and asthma may result under conditions of high ambient or endogenous NO2 levels.
The Journal of Immunology 10/2007; 179(6):3680-8. · 5.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: Silicosis features foci of inflammation where macrophages and lymphocytes precede and accompany fibroblast proliferation, alveolar epithelial hyperplasia, and increased deposition of connective tissue matrix material. In the mouse following silica inhalation there is recruitment of natural killer-, B-, and CD4+ and CD8+ lymphocytes to the alveolar spaces, enlargement of bronchial-associated lymphoid tissues (BALT), and aggregation of lymphocytes surrounding small airways and blood vessels. A substantial fraction of the recruited lung lymphocytes produce interferon-gamma (IFN-gamma), and IFN-gamma gene-deleted mice develop less silicosis than wild-type mice. Interleukin-12 (IL-12) is an important pathway for driving the adaptive immune response towards a TH1-like phenotype. We hypothesized that IL-12 might stimulate lymphocyte activation and the up-regulation of IFN-gamma, and consequently be an essential mediator for silicosis.
C57Bl/6 wild-type (WT) and IL-12 deficient (IL-12 KO) mice were exposed to sham-air or crystobalite silica (61 mg/m3) by inhalation for 5 hours/day for 12 days and then studied from 1 to 112 days after exposure. Mice exposed to sham-air had normal lung histology at all time points. WT mice exposed to titanium dioxide (72 mg/m3) showed pulmonary macrophage recruitment but no increase in lung collagen. Both WT and IL-12 KO mice exposed to silica showed similar progressive lung pathology, increased wet lung weight and increased total lung collagen (hydroxyproline). IL-12 p35 mRNA was not increased in either strain after silica exposure; IL-12 p40 mRNA was up-regulated after silica in WT mice and constitutively absent in the IL-12 KO mice. IL-18 mRNA was not increased after silica exposure. The expression of IL-15 (an important driver for innate immunity, Natural Killer cell activation, and IFN-gamma production) was abundant in air-exposed mice and was increased slightly in the lungs of mice with silicosis.
The axis of IL-12 driving IFN-gamma production is not essential for the full manifestations of silicosis in mice exposed to a crystobalite silica aerosol.
Particle and Fibre Toxicology 02/2006; 3:2. · 9.18 Impact Factor
[show abstract][hide abstract] ABSTRACT: In addition to being an air pollutant, NO2 is a potent inflammatory oxidant generated endogenously by myeloperoxidase and eosinophil peroxidase. In these studies, we sought to determine the effects of NO2 exposure on mice with ongoing allergic airway disease pathology. Mice were sensitized and challenged with the antigen ovalbumin (OVA) to generate airway inflammation and subsequently exposed to 5 or 25 ppm NO2 for 3 days or 5 days followed by a 20-day recovery period. Whereas 5 ppm NO2 elicited no pathological changes, inhalation of 25 ppm NO2 alone induced acute lung injury, which peaked after 3 days and was characterized by increases in protein, LDH, and neutrophils recovered by BAL, as well as lesions within terminal bronchioles. Importantly, 25 ppm NO2 was also sufficient to cause AHR in mice, a cardinal feature of asthma. The inflammatory changes were ameliorated after 5 days of inhalation and completely resolved after 20 days of recovery after the 5-day inhalation. In contrast, in mice immunized and challenged with OVA, inhalation of 25 ppm NO2 caused a marked augmentation of eosinophilic inflammation and terminal bronchiolar lesions, which extended significantly into the alveoli. Moreover, 20 days postcessation of the 5-day 25 ppm NO2 inhalation regimen, eosinophilic and neutrophilic inflammation, pulmonary lesions, and AHR were still present in mice immunized and challenged with OVA. Collectively, these observations suggest an important role for NO2 in airway pathologies associated with asthma, both in modulation of degree and duration of inflammatory response, as well as in induction of AHR.
[show abstract][hide abstract] ABSTRACT: Asbestos fibers are carcinogens causing oxidative stress and inflammation, but the sources and ramifications of oxidant production by asbestos are poorly understood. Here, we show that inhaled chrysotile asbestos fibers cause increased myeloperoxidase activity in bronchoalveolar lavage fluids (BALF) and myeloperoxidase immunoreactivity in epithelial cells lining distal bronchioles and alveolar ducts, sites of initial lung deposition of asbestos fibers. In comparison with sham mice, asbestos-exposed myeloperoxidase-null (MPO-/-) and normal (MPO+/+) mice exhibited comparable increases in polymorphonuclear leukocytes, predominately neutrophils, in BALF after 9 days of asbestos inhalation. Differential cell counts on BALF revealed decreased proportions of macrophages and increased lymphocytes in all mice exposed to asbestos, but numbers were decreased overall in asbestos-exposed myeloperoxidase-null versus normal mice. Asbestos-associated lung inflammation in myeloperoxidase-null mice was reduced (P < or = 0.05) in comparison with normal asbestos-exposed mice at 9 days. Decreased lung inflammation in asbestos-exposed myeloperoxidase-null mice at 9 days was accompanied by increases (P < or = 0.05) in Ki-67- and cyclin D1-positive immunoreactive cells, markers of cell cycle reentry, in the distal bronchiolar epithelium. Asbestos-induced epithelial cell proliferation in myeloperoxidase-null mice at 30 days was comparable to that found at 9 days. In contrast, inflammation and epithelial cell proliferation in asbestos-exposed normal mice increased over time. These results support the hypothesis that myeloperoxidase status modulates early asbestos-induced oxidative stress, epithelial cell proliferation, and inflammation.
Cancer Research 11/2005; 65(21):9670-7. · 8.65 Impact Factor
[show abstract][hide abstract] ABSTRACT: Asbestos is a ubiquitous naturally occurring fiber causing multiple cancers and fibroproliferativedisease. The mechanisms of epithelial cell hyperplasia, a hallmark of the initiation of lung cancers by asbestos, have been unclear. We demonstrate here that mice expressing a dominant-negative mutant epidermal growth factor receptor (EGFR) under the control of the human lung surfactant protein-C promoter exhibit decreased pulmonary epithelial cell proliferation without alterations in asbestos-induced inflammation. In contrast to transgene-negative littermates, inhalation of asbestos by mice expressing the mutant EGFR does not result in early and elevated expression of early response proto-oncogenes (fos/jun or activator protein 1 family members). Additionally, quantitative reverse transcriptase-PCR analysis for levels of c-jun and c-fos in bronchiolar epithelium isolated by laser capture microdissection demonstrates increases in expression of these genes in asbestos-exposed epithelial cells. Results show that the EGFR mediates both asbestos-induced proto-oncogene expression and epithelial cell proliferation, providing a rationale for modification of its phosphorylation in preventive and therapeutic approaches to lung cancers and mesothelioma.
Cancer Research 09/2002; 62(15):4169-75. · 8.65 Impact Factor
[show abstract][hide abstract] ABSTRACT: Nitrogen dioxide (*NO2) is commonly known as an indoor and outdoor air pollutant. Inhalation of *NO2 is associated with epithelial cell injury, inflammation, and the aggravation of asthma. *NO2 can also be formed during inflammation, by the metabolism of nitric oxide. We describe a gas-phase exposure system for in vitro exposure of lung epithelial cells to *NO2. Immunofluorescence revealed 3-nitrotyrosine immunoreactivity of rat alveolar type II epithelial cells exposed to 5 parts per million of *NO2 for 4 h. Comparative analysis of log-phase and confluent cultures demonstrated that cell death occurred extensively in log-phase cells, whereas minimal death was observed in confluent cultures. Peroxynitrite (ONOO-) or the ONOO- generator 3-morpholinosydnonimine (SIN-1) caused similar amounts of death. Further, exposure of wounded cell cultures to *NO(2) or SIN-1 revealed that death was restricted to cells repopulating a wounded area. Cycloheximide or actinomycin D, inhibitors or protein and messenger RNA synthesis, respectively, significantly reduced terminal transferase reactivity, suggesting that a new protein(s) may be required for cell death. These results suggest that during restitution after pulmonary injury, epithelium may be sensitive to cell death by reactive nitrogen species.
American Journal of Respiratory Cell and Molecular Biology 06/2001; 24(5):583-90. · 4.15 Impact Factor
[show abstract][hide abstract] ABSTRACT: Silicosis is characterized by mononuclear cell aggregation with mineral particles and fibrosis. Lymphocytes are abundant in these lesions. We exposed inbred strains of mice to a respirable aerosol of cristobalite silica (70 mg/m3, 5 h/d, 12 d) or shamair. Silicosis evolved over months after exposure. The silica-exposed mice showed the accumulation of lymphocytes in alveolar spaces (seen in bronchoalveolar lavage), in lung parenchymal lesions and nodules, and in enlarged bronchial-associated lymphoid tissues and thoracic lymph nodes. The lung lymphocytes were predominantly CD4+ T cells, but numerous CD8+ T cells, natural killer cells, and CD4- gammadelta-TCR+ T cells were present as well. Interferon-gamma (IFN-gamma) production was upregulated, suggesting a THelper-1-like response in silicosis. In silicotic lung tissue, mRNA transcripts for the macrophage-derived cytokines IL-12 and -18 were increased. IFN-gamma gene-deleted mice (C57Bl/6-Ifngtm1 Ts) exposed to silica developed less extensive silicosis and less lung collagen accumulation than wild-type mice. We hypothesize that there is a reiterative amplification cycle in which macrophages with silica may produce cytokines, such as IL-12 and -18, that attract and activate lymphocytes. These activated lymphocytes may then produce additional mediators that in turn attract and activate an expanded secondary population of macrophages. IFN-gamma would be a likely cause of macrophage activation in this cycle. More work is needed to understand the biological events that lead from the inhaled dust to the scarred lung, and to clarify the role of lymphocytes in this process.
Journal of Environmental Pathology Toxicology and Oncology 02/2001; 20 Suppl 1:53-65. · 0.92 Impact Factor
[show abstract][hide abstract] ABSTRACT: We recently described overproduction of interferon (IFN)-gamma by lung lymphocytes in mice with silicosis (11% of cells in air-control versus 19% of cells from silica-exposed mice; Davis and colleagues, Am. J. Respir. Cell Mol. Biol. 1999;20:813-824). We hypothesized that the increased IFN-gamma production might be due to selective enrichment of one lymphocyte phenotype. To test this hypothesis, small mononuclear cells from lung digest preparations of mice exposed 4 mo previously to cristobalite silica (70 mg/m(3), 12 d, 5 h/d) or to sham-air were stained for intracellular cytokines and surface antigen phenotypes, and examined by flow cytometry. Air-sham mouse lung digests included CD4(+) (16%) and CD8(+) (6%) T cells, gammadelta T-cell antigen receptor (TCR)(+) CD4(-)CD8(-) T cells (3%), natural killer (NK) cells (15%), B cells (6%), and macrophages (12%). The total number of lung lymphocytes was increased 1.7-fold in silicosis, but the phenotype frequencies did not change significantly. In the control lungs IFN-gamma was produced by three major phenotypes of lymphocytes: 5% of CD4(+) T cells, 5% of gammadelta-TCR(+) CD4(-)CD8(-) T cells, and 2% of NK cells. The percentage of each type producing IFN-gamma was increased 2- to 3-fold in silicosis. When multiplied by cell number, the increased percentages yielded a 3- to 5-fold increase in the total number of each IFN- gamma-producing phenotype in the lung. Our results demonstrate no selective phenotype enrichment but upregulated IFN-gamma production by at least three lymphocyte phenotypes. IFN-gamma may be an important signal driving lymphocyte differentiation and macrophage activation in silicosis.
American Journal of Respiratory Cell and Molecular Biology 05/2000; 22(4):491-501. · 4.15 Impact Factor
[show abstract][hide abstract] ABSTRACT: Pulmonary fibrosis is a disabling consequence of many lung diseases but is difficult to quantify. Lucifer yellow CH fluorescent dye (LY) appears to stain connective tissue matrix macromolecules selectively. Laser scanning confocal microscopy can quantify the intensity of fluorescence and determine the area of fluorescent material. We hypothesized that the abundance of lucifer yellow-stained matrix macromolecules in lung tissue sections could be measured by laser scanning confocal microscopy, would reflect differences between varying degrees of pulmonary fibrosis, and could be compared directly to biochemical measurements of lung collagen. We exposed C57B1/6 and 129 strains of mice by aerosol to cristobalite silica (70 mg/m3, 12 days, 5 hours/day) or sham-air and examined them 2 and 16 weeks after exposure. The area of LY-stained matrix in tissue sections was quantitated by laser scanning confocal microscopy, and total lung collagen was measured biochemically as hydroxyproline (OH-proline). The LY-stained connective tissue matrix appeared as bright linear bands in the alveolar septae, and was increased significantly by image analysis in C57B1/6 and 129 mice with silicosis 16 weeks after exposure. Total lung OH-proline was significantly increased in silica-exposed mice from both stains at both time points. Comparing all 8 groups, there was a significant linear correlation between the average area of connective tissue measured by LY stain and the total OH-proline per lung measured by chemical analysis (r = .72, P = .042). LY staining and confocal microscopy with image analysis offers a rapid technique for quantitative measurements of the extent of pulmonary fibrosis.
Experimental Lung Research 04/2000; 26(2):71-88. · 1.47 Impact Factor
[show abstract][hide abstract] ABSTRACT: Acid sulfate-coated solid particles are a significant environmental hazard produced primarily by the combustion of fossil fuels. We have previously described a system for the nascent generation of carbonaceous particles surface coated with approximately 140 microg/m(3) acid sulfate [cpSO(4)(2-); 10 mg/m(3) carbon black (CB) and 10 ppm sulfur dioxide (SO(2)) at 85% relative humidity (RH)]. The effects of inhaled cpSO(4)(2-) on pulmonary host defenses are assessed in the present work. Mice were acutely exposed (4 h) to either 10 mg/m(3) CB, 10 ppm SO(2), or their combination at 10% or 85% RH in a nose-only inhalation chamber. No evidence of an inflammatory response was found following any of the exposures as assessed by total cell counts and differential cell counts from bronchoalveolar lavage fluid. However, alveolar macrophage Fc receptor-mediated phagocytosis decreased only following exposure to 140 microg cpSO(4)(2-), significant suppression occurred after 24 h, maximal suppression occurred at 3 days postexposure, and recovery to preexposure levels required 7-14 days. Intrapulmonary bactericidal activity (IBA) was also suppressed only after exposure to 140 microg cpSO(4)(2-); suppression was maximal at 1 day postexposure and recovered by day 7. To assess the effects of lower cpSO(4)(2-) concentrations, mice were repeatedly exposed to 1 mg/m(3) CB and 1 ppm SO(2) at 85% RH ( approximately 20 microg/m(3) cpSO(4)(2-) for 4 h/day) for up to 6 days. A significant decrement in IBA was observed following 5 and 6 days of exposure. These studies indicated that acute or repeated exposure to cpSO(4)(2-) could alter pulmonary host defense mechanisms.
[show abstract][hide abstract] ABSTRACT: Silicosis is characterized by mononuclear cell inflammation with macrophage activation, accumulation of lymphocytes, and fibrosis. Interferon-gamma (IFN-gamma) is a lymphocyte cytokine with broad effects, particularly macrophage activation. Mice exposed to an aerosol of cristobalite silica (70 mg/m3, 12 d, 5 h/d) developed diffuse pulmonary pathologic changes with macrophage, lymphocyte, and neutrophil recruitment, and increased lung collagen. IFN-gamma messenger RNA (mRNA) was more abundant by semiquantitative reverse transcription-polymerase chain reaction in the lungs of silica-exposed mice than in control animals. IFN-gamma mRNA transcripts were detected by in situ hybridization with digoxigenin-labeled complementary DNA probes in normal mouse lung tissue within bronchial-associated lymphoid tissues (BALT). In silica- exposed mice, mononuclear cells with IFN-gamma mRNA were more numerous in the silicotic lesions and enlarged BALT structures. Lung-cell suspensions were prepared by enzyme digestion, stained with fluorescent-labeled antibodies against intracellular cytokines, and enumerated by flow cytometry. The percentage of cells producing IFN-gamma was increased in silicotic mice (19% versus 11%). Interleukin (IL)-4 mRNA transcripts were less abundant in the lung tissue from silica-exposed mice than in control mice. Cells staining for IL-4 mRNA were found rarely in either the air-sham or the silica-exposed mouse lungs, and almost all appeared to be within BALT structures. Approximately 3% of cells stained for IL-4 in the digested lungs from both groups. Similar cytokine patterns were observed in mediastinal lymph node/thymus and spleen tissues. The augmented IFN-gamma response, with IL-4 unchanged or decreased, in the lung lesions and lymphoid tissue of mice with silicosis suggests a Th-1-like lymphocyte-mediated immune-inflammatory response.
American Journal of Respiratory Cell and Molecular Biology 05/1999; 20(4):813-24. · 4.15 Impact Factor
[show abstract][hide abstract] ABSTRACT: Numerous epidemiological studies have demonstrated a positive association between ambient air pollution and adverse health effects including respiratory morbidity, asthma, and lung cancer. It has been suggested in some experimental studies that airborne particulate matter (PM) can produce inflammatory effects, but nothing is known about the possible proliferative and carcinogenic effects of these particles on cells of the lung. We show here that exposure of pulmonary epithelial cells, a cell type affected in acute lung injury, asthma, and lung carcinomas, to nontoxic concentrations of PM in vitro results in increases in c-jun kinase activity, levels of phosphorylated cJun immunoreactive protein, and transcriptional activation of activator protein-1-dependent gene expression. These changes are accompanied by elevations in numbers of cells incorporating 5'-bromodeoxyuridine, a marker of unscheduled DNA synthesis and/or cell proliferation. Data here are the first to demonstrate that interaction of ambient PM with target cells of the lung initiates a cell signaling cascade related causally to aberrant cell proliferation and carcinogenesis.
Cancer Research 11/1998; 58(20):4543-7. · 8.65 Impact Factor
[show abstract][hide abstract] ABSTRACT: To evaluate the contribution of reactive nitrogen species to inflammation by asbestos, Fischer 344 rats were exposed to crocidolite or chrysotile asbestos by inhalation to determine whether increases occurred in nitric oxide (NO.) metabolites from alveolar macrophages (AMs). AMs from animals inhaling asbestos showed significant elevations (p < .05) in nitrite/nitrate levels which were ameliorated by NG-monomethyl-L-arginine (NMMA), an inhibitor of inducible nitric oxide synthase (iNOS) activity. Temporal patterns of NO. generation from AMs correlated with neutrophil influx in bronchoalveolar lavage samples after asbestos inhalation or bleomycin instillation, another model of pulmonary fibrosis. To determine the molecular mechanisms and specificity of iNOS promoter activation by asbestos, RAW 264.7 cells, a murine macrophage-like line, and AMs isolated from control rats were exposed to crocidolite asbestos in vitro. These cells showed increases in steady-state levels of iNOS mRNA in response to asbestos and more dramatic increases in both iNOS mRNA and immunoreactive protein after addition of lipopolysaccharide (LPS). After transfection of an iNOS promoter/luciferase reporter construct, RAW 264.7 cells exposed to LPS, crocidolite asbestos and its nonfibrous analog, riebeckite, revealed increases in luciferase activity whereas cristobalite silica had no effects. Studies suggest that NO. generation may be important in cell injury and inflammation by asbestos.
Free Radical Biology and Medicine 03/1998; 24(5):778-88. · 5.27 Impact Factor
[show abstract][hide abstract] ABSTRACT: To evaluate the contribution of reactive nitrogen species to inflammation by asbestos, Fischer 344 rats were exposed to crocidolite or chrysotile asbestos by inhalation to determine whether increases occurred in nitric oxide (NO·) metabolites from alveolar macrophages (AMs). AMs from animals inhaling asbestos showed significant elevations ( p < .05) in nitrite/nitrate levels which were ameliorated by NG-monomethyl-l-arginine (NMMA), an inhibitor of inducible nitric oxide synthase (iNOS) activity. Temporal patterns of NO· generation from AMs correlated with neutrophil influx in bronchoalveolar lavage samples after asbestos inhalation or bleomycin instillation, another model of pulmonary fibrosis. To determine the molecular mechanisms and specificity of iNOS promoter activation by asbestos, RAW 264.7 cells, a murine macrophage-like line, and AMs isolated from control rats were exposed to crocidolite asbestos in vitro. These cells showed increases in steady-state levels of iNOS mRNA in response to asbestos and more dramatic increases in both iNOS mRNA and immunoreactive protein after addition of lipopolysaccharide (LPS). After transfection of an iNOS promoter/luciferase reporter construct, RAW 264.7 cells exposed to LPS, crocidolite asbestos and its nonfibrous analog, riebeckite, revealed increases in luciferase activity whereas cristobalite silica had no effects. Studies suggest that NO· generation may be important in cell injury and inflammation by asbestos.
Free Radical Biology and Medicine - FREE RADICAL BIOL MED. 01/1998; 24(5):778-788.
[show abstract][hide abstract] ABSTRACT: Experimental silicosis allows study of the mechanisms of lung injury, inflammation, and fibrosis. Inbred mice are an attractive species in which to study these mechanisms because of recent progress in murine immunology, molecular biology, and genetics. We exposed mice to an aerosol of silica and examined the effects of exposure dose, the evolution of disease features over time, and the variation in responses among four inbred strains. In C3H/HeN mice incremental cumulative exposure doses of cristobalite silica caused increased initial lung dust burden 12 to 16 weeks post-exposure, progressively intense pathological responses, and increased total lung collagen (hydroxyproline). The histopathological changes and total lung collagen increased progressively over time after exposure. We compared the features of silicosis in four strains of inbred mice selected for common use or immunologic reactivity 16 weeks after aerosol inhalation exposure to crystalline cristobalite silica (70 mg/m3, 5 hours/day, 12 days). C3H/HeN mice demonstrated histopathological silicotic lesions and enlarged intrapulmonary lymphoid tissue, and increased lung wet weight, bronchoalveolar lavage (BAL) recovery of macrophages, lymphocytes, and neutrophils, and total lung collagen (hydroxyproline). BALB/c mice developed slight pulmonary lesions; MRL/MpJ mice demonstrated prominent pulmonary infiltrates with lymphocytes; New Zealand Black mice developed extensive alveolar proteinaceous deposits, inflammation, and fibrosis. Our findings demonstrate orderly dose-time-response relationships, and a substantial variation of responses among inbred strains of mice. This model should prove valuable for future experimental interventions into the mechanisms of silicosis.
Journal of Environmental Pathology Toxicology and Oncology 01/1998; 17(2):81-97. · 0.92 Impact Factor
[show abstract][hide abstract] ABSTRACT: The cytokines interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNFalpha), derived from macrophages and other cells, may promote mononuclear cell inflammation and fibrosis in pulmonary silicosis. C3H/HeN mice were exposed to control air or to an aerosol of 70 mg/m3 cristobalite silica for 5 h/d for 12 days and examined at 2 and 16 weeks after exposure. This exposure resulted in murine silicosis, as manifested by focal mononuclear cell accumulations, diffuse interstitial fibrosis, lymphoid tissue enlargement, recruitment of inflammatory cells into BAL fluid, and increased total lung collagen. Semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) with designed primers and membrane hybridization with biotinylated cDNA probes were used to assess the abundance of IL-1beta and TNFalpha mRNA. In situ hybridization with digoxigenin-labeled cDNA probes was used to localize gene expression. Persistent overexpression of both IL-1beta and TNFalpha were found at 2 and 16 weeks in the lungs of silica-exposed mice compared with air-sham control mice. IL-1beta and TNFalpha expression localized to individual mononuclear cells in the alveolar spaces, groups of cells within the aggregate lesions, and scattered mononuclear cells in BALT and lymphoid nodules. Thus, cells producing IL-1beta and TNFalpha appear to be intimately associated with the evolving lesions of silicosis, and the lymphoid tissue of the lung may be important in driving the pathogenesis of this disease.
Journal of Environmental Pathology Toxicology and Oncology 01/1998; 17(2):99-114. · 0.92 Impact Factor
[show abstract][hide abstract] ABSTRACT: Silicosis is primarily a mononuclear cell inflammatory and fibrotic disease of the pulmonary parenchyma. It is known that lung-associated lymph nodes are also affected. To study the involvement of lymphocytes in silicosis, we examined lymph nodes of rats 12 months after an 8-day silica aerosol exposure. We found that 2 thoracic lymph nodes close to the thymus were enormously enlarged in silicotic rats and contained a 49-fold higher cell number than control lymph nodes. The higher cell number was caused by parallel increases in T- and B-lymphocytes, natural killer (NK) cells, and macrophages without change in the relative proportions when compared with control thoracic lymph nodes. By examining interleukin-2 (IL-2) receptor and intercellular adhesion molecule-1 expression, we detected a significantly higher percentage of activated CD8+ T cells and, to a lower degree, of CD4+ T cells in thoracic lymph nodes of silicotic animals. In contrast, no differences in the activation state were found in T cells obtained from cervical or mesenteric lymph nodes of silicotic and control rats. The occurrence of activated T cells in thoracic lymph nodes of silicotic rats was documented further by selectively enhanced interferon-gamma (IFN-gamma) mRNA expression in the absence of IL-2 and IL-4 mRNA changes. These data show that T-lymphocytes of thoracic lymph nodes have become activated with an enhanced IFN-gamma gene transcription which may be an important cause of macrophage activation during silicosis.
American Journal of Respiratory Cell and Molecular Biology 04/1997; 16(3):309-16. · 4.15 Impact Factor
[show abstract][hide abstract] ABSTRACT: A flow-past nose-only inhalation system was used for the co-exposure of mice to carbon black aerosols (CBA) and sulfur dioxide (SO2) at varying relative humidities (RH). The conversion of SO2 to sulfate (SO4(-2)) on the CBA, at a fixed aerosol concentration, was dependent on RH and SO2 concentration. The effect of the aerosol-gas mixture on alveolar macrophage (AM) phagocytosis was assessed three days following exposure for 4 h. Exposure to 10 mg/m3 CBA alone at low RH (10%) and high RH (85%), to 10 ppm SO2 alone at both RH, and to the mixture at low RH had no effect on AM phagocytosis. In contrast, AM phagocytosis was significantly suppressed following co-exposure at 85% RH, the only circumstance in which significant chemisorption of the gas by the aerosol and oxidation to SO4(-2) occurred. The results suggest that fine carbon particles can be an effective vector for the delivery of toxic amounts of SO4(-2) to the periphery of the lung.