Fas (CD95) induces alveolar epithelial cell apoptosis in vivo: implications for acute pulmonary inflammation

Activation of the Fas/FasL system induces apoptosis of susceptible cells, but may also lead to nuclear factor kappaB activation. Our goal was to determine whether local Fas activation produces acute lung injury by inducing alveolar epithelial cell apoptosis and by generating local inflammatory responses. Normal mice (C57BL/6) and mice deficient in Fas (lpr) were treated by intranasal instillation of the Fas-activating monoclonal antibody (mAb) Jo2 or an irrelevant control mAb, and studied 6 or 24 hours later using bronchoalveolar lavage (BAL), histopathology, DNA nick-end-labeling assays, and electron microscopy. Normal mice treated with mAb Jo2 had significant increases in BAL protein at 6 hours, and BAL neutrophils at 24 hours, as compared to lpr mice and to mice treated with the irrelevant mAb. Neutrophil recruitment was preceded by increased mRNA expression for tumor necrosis factor-alpha, macrophage inflammatory protein-1alpha, macrophage inflammatory protein-2, macrophage chemotactic protein-1, and interleukin-6, but not interferon-gamma, transforming growth factor-ss, RANTES, eotaxin, or IP-10. Lung sections from Jo2-treated normal mice showed neutrophilic infiltrates, alveolar septal thickening, hemorrhage, and terminal dUTP nick-end-labeling-positive cells in the alveolar septae and airspaces. Type II pneumocyte apoptosis was confirmed by electron microscopy. Fas activation in vivo results in acute alveolar epithelial injury and lung inflammation, and may be important in the pathogenesis of acute lung injury.     

Acute pulmonary toxicity of urban particulate matter and ozone.

We have investigated the acute lung toxicity of urban particulate matter in interaction with ozone. Rats were exposed for 4 hours to clean air, ozone (0.8 ppm), the urban dust EHC-93 (5 mg/m3 or 50 mg/m3), or ozone in combination with urban dust. The animals were returned to clean air for 32 hours and then injected (intraperitoneally) with [3H]thymidine to label proliferating cells and killed after 90 minutes. The lungs were fixed by inflation, embedded in glycol methacrylate, and processed for light microscopy autoradiography. Cell labeling was low in bronchioles (0.14 +/- 0.04%) and parenchyma (0.13 +/- 0.02%) of air control animals. Inhalation of EHC-93 alone did not induce cell labeling. Ozone alone increased (P < 0.05) cell labeling (bronchioles, 0.42 +/- 0.16%; parenchyma, 0.57 +/- 0.21%), in line with an acute reparative cell proliferation. The effects of ozone were clearly potentiated by co-exposure with either the low (3.31 +/- 0.31%; 0.99 +/- 0.18%) or the high (4.45 +/- 0.51%; 1.47 +/- 0.18%) concentrations of urban dust (ozone X EHC-93, P < 0.05). Cellular changes were most notable in the epithelia of terminal bronchioles and alveolar ducts and did not distribute to the distal parenchyma. Enhanced DNA synthesis indicates that particulate matter from ambient air can exacerbate epithelial lesions in the lungs. This may extend beyond air pollutant interactions, such as to effects of inhaled particles in the lungs of compromised individuals.     

Superoxide dismutase-overexpressing mice are resistant to ozone-induced tissue injury and increases in nitric oxide and tumor necrosis factor-alpha

Reactive oxygen intermediates have been implicated in lung injury induced by inhaled irritants. The present studies used mice overexpressing Cu/Zn-superoxide dismutase (SOD+/+) to analyze their role in ozone-induced lung inflammation and cytotoxicity. Treatment of wild-type mice with ozone (0.8 ppm, 3 h) resulted in increased bronchoalveolar lavage fluid protein, which was maximal after 24-48 h. Significant increases in lung macrophages and 4-hydroxyalkenals were also observed. In contrast, bronchoalveolar lavage fluid protein and macrophage content and 4-hydroxyalkenals were at control levels in ozone-treated SOD+/+ mice. There was also no evidence of peroxynitrite-mediated lung damage, demonstrating that SOD+/+ mice are resistant to ozone toxicity. Whereas alveolar macrophages from wild-type mice produced increased amounts of nitric oxide and expressed more inducible nitric oxide synthase, phospholipase A(2), and tumor necrosis factor-alpha after ozone inhalation, this was not evident in cells from SOD+/+ mice. Ozone-induced decreases in interleukin-10 were also not observed. In wild-type mice, ozone inhalation resulted in activation of nuclear factor-kappaB, which regulates proinflammatory gene activity. This response was significantly reduced in SOD+/+ mice. These data demonstrate that antioxidant enzymes play a critical role in ozone-induced tissue injury and in inflammatory mediator production.     

Diesel exhaust particulates exacerbate asthma-like inflammation by increasing CXC chemokines

Particulate matter heavily pollutes the urban atmosphere, and several studies show a link between increased ambient particulate air pollution and exacerbation of pre-existing pulmonary diseases, including asthma. We investigated how diesel exhaust particulates (DEPs) aggravate asthma-like pulmonary inflammation in a mouse model of asthma induced by a house dust extract (HDE) containing cockroach allergens and endotoxin. BALB/c mice were exposed to three pulmonary challenges via hypopharyngeal administration of an HDE collected from the home of an asthmatic child. One hour before each pulmonary challenge, mice were exposed to DEP or PBS. Pulmonary inflammation was assessed by histological features, oxidative stress, respiratory physiological features, inflammatory cell recruitment, and local CXC chemokine production. To prove the role of CXC chemokines in the augmented inflammation, CXC chemokine-specific antibodies were delivered to the lungs before DEP exposure. DEP exacerbated HDE-induced airway inflammation, with increased airway mucus production, oxidative stress, inflammatory cell infiltration, bronchoalveolar lavage concentrations of CXC chemokines, and airway hyperreactivity. Neutralization of airway keratinocyte-derived chemokine and macrophage inflammatory protein-2 significantly improves the respiratory function in addition to decreasing the infiltration of neutrophils and eosinophils. Blocking the chemokines also decreased airway mucus production. These results demonstrate that DEP exacerbates airway inflammation induced by allergen through increased pulmonary expression of the CXC chemokines (keratinocyte-derived chemokine and macrophage inflammatory protein-2).     

Accumulation of iron in the rat lung after tracheal instillation of diesel particles

Oxidant generation catalyzed by metals has been postulated to account for a lung injury following exposure to air pollution particles. In particles that are predominantly carbonaceous, it is difficult to implicate such an oxidative stress as the responsible mechanism, since concentrations of metals can be extremely low. Comparable to these air pollution particles, mineral oxide particles can include only minute amounts of metal, but lung injury following their exposure can be associated with an accumulation of endogenous iron from the host and an oxidative stress. We tested the hypothesis that diesel exhaust particulate (DEP) effects an accumulation of biologically active iron in the rat lung, with both oxidative stress and a lung injury resulting. Characterization of the DEP confirmed a high concentration of carbon, whereas metals were low in quantity. The concentration of total lavage iron in animals instilled with saline was low, but this concentration increased with exposure to DEP. Non-heme iron in lung tissue was similarly elevated after instillation of the diesel product. Particle instillation was associated with a decrease in lavage ascorbate concentration supporting an oxidative stress. Relative to saline exposure, DEP resulted in elevated lavage concentrations of the inflammatory mediators macrophage inflammatory protein-2 and tumor necrosis factor. Finally, an injury after particle instillation was evident with increased neutrophils and an elevation of lavage protein and lactic dehydrogenase. We conclude that DEP exposure effected an accumulation of iron in the rat lung. This accrual of iron was associated with an oxidative stress, release of oxidant-sensitive mediators, and a neutrophilic lung injury.     

Ozone-induced lung injury and sterile inflammation. Role of toll-like receptor 4

Inhalation of toxic doses of ozone is associated with a sterile inflammatory response characterized by an accumulation of macrophages in the lower lung which are activated to release cytotoxic/proinflammatory mediators that contribute to tissue injury. Toll-like receptor 4 (TLR4) is a pattern recognition receptor present on macrophages that has been implicated in sterile inflammatory responses. In the present studies we used TLR4 mutant C3H/HeJ mice to analyze the role of TLR4 in ozone-induced lung injury, oxidative stress and inflammation. Acute exposure of control C3H/HeOuJ mice to ozone (0.8ppm for 3h) resulted in increases in bronchoalveolar lavage (BAL) lipocalin 24p3 and 4-hydroxynonenal modified protein, markers of oxidative stress and lipid peroxidation. This was correlated with increases in BAL protein, as well as numbers of alveolar macrophages. Levels of surfactant protein-D, a pulmonary collectin known to regulate macrophage inflammatory responses, also increased in BAL following ozone inhalation. Ozone inhalation was associated with classical macrophage activation, as measured by increased NF-κB binding activity and expression of TNFα mRNA. The observation that these responses to ozone were not evident in TLR4 mutant C3H/HeJ mice demonstrates that functional TLR4 contributes to ozone-induced sterile inflammation and macrophage activation.     

Aggravation of bleomycin-induced pulmonary inflammation and fibrosis in mice lacking peroxiredoxin I

Oxidative stress plays an important role in the pathogenesis of acute lung injury and pulmonary fibrosis. Peroxiredoxin (Prx) I is a cellular antioxidant enzyme induced under stress conditions. In the present study, the protective effects of Prx I on the development of bleomycin-induced acute pulmonary inflammation and pulmonary fibrosis were investigated using Prx I-deficient mice. Survival of Prx I-deficient mice after bleomycin administration was significantly lower than that of wild-type mice, corresponding with enhanced acute pulmonary inflammation and fibrosis. The level of inflammatory cytokines and chemokines, such as TNF-α, macrophage inflammatory protein-2, and monocyte chemotactic protein-1, was significantly elevated in the bronchoalveolar lavage fluid of Prx I-deficient mice after bleomycin administration. Furthermore, the level of 8-isoprostane, an oxidative stress marker, and the concentration and alveolar macrophage expression of macrophage migration inhibitory factor were elevated in the lungs of Prx I-deficient mice after bleomycin administration. The exacerbation of bleomycin-induced pulmonary inflammation and fibrosis in Prx I-deficient mice was inhibited by treatment with N-acetyl-L-cysteine, a radical scavenger, or with (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester, a tautomerase inhibitor of macrophage migration inhibitory factor. These findings suggest that mice lacking Prx I are highly susceptible to bleomycin-induced pulmonary inflammation and fibrosis because of increases in pulmonary oxidant levels and macrophage migration inhibitory factor activity in response to bleomycin.     

Alterations in bronchoalveolar lavage constituents, oxidant/antioxidant status, and lung histology following intratracheal instillation of respirable suspended particulate matter.

Urban suspended particulate pollutants differ with place of occurrence, meteorological conditions, physicochemical compositions, and the response of the bronchopulmonary apparatus. Lung injury following intratracheal instillation of respirable suspended particulate matter (RSPM) collected in an urban setting in India was investigated in rats. The animals were killed 15 days after exposure to 2.5, 5.0, and 10.0 mg of RSPM. We examined the changes in lung histology, enzymatic activity in the bronchoalveolar lavage (BAL), and the oxidant/ antioxidant status in lung homogenates.The alterations in these parameters were compared with those in rats instilled with quartz particulates, which were used as positive controls. Exposure to RSPM resulted in an increase in the relative weight of lungs and inflammatory changes evidenced by an increase in the total cellularity of the lungs, predominantly polymorphonuclear cells, demonstrable both in the lungs sections and in the bronchoalveolar lavage of the exposed animals. An increase in the protein content and in the lactate dehydrogenase activity in the BAL was found in the RSPM-exposed rats. A marked increase in the output of lipid peroxides and a dose-dependent increase in the formation of reactive nitrogen species (NO) in lung homogenates and BAL, respectively, was found in the RSPM-exposed rats. A significant decrease in the enzymatic lung antioxidants, superoxide dismutase, and catalase was observed. However, the alterations in the levels of glutathione in the lungs of the RSPM-exposed animals were not significant. The inflammatory reaction, oxidative changes, and enzyme release, were more marked in quartz-exposed animals in comparison to the RSPM-exposed rats.     

Maternal diesel inhalation increases airway hyperreactivity in ozone-exposed offspring

Air pollutant exposure is linked with childhood asthma incidence and exacerbations, and maternal exposure to airborne pollutants during pregnancy increases airway hyperreactivity (AHR) in offspring. To determine if exposure to diesel exhaust (DE) during pregnancy worsened postnatal ozone-induced AHR, timed pregnant C57BL/6 mice were exposed to DE (0.5 or 2.0 mg/m(3)) 4 hours daily from Gestation Day 9-17, or received twice-weekly oropharyngeal aspirations of the collected DE particles (DEPs). Placentas and fetal lungs were harvested on Gestation Day 18 for cytokine analysis. In other litters, pups born to dams exposed to air or DE, or to dams treated with aspirated diesel particles, were exposed to filtered air or 1 ppm ozone beginning the day after birth, for 3 hours per day, 3 days per week for 4 weeks. Additional pups were monitored after a 4-week recovery period. Diesel inhalation or aspiration during pregnancy increased levels of placental and fetal lung cytokines. There were no significant effects on airway leukocytes, but prenatal diesel augmented ozone-induced elevations of bronchoalveolar lavage cytokines at 4 weeks. Mice born to the high-concentration diesel-exposed dams had worse ozone-induced AHR, which persisted in the 4-week recovery animals. Prenatal diesel exposure combined with postnatal ozone exposure also worsened secondary alveolar crest development. We conclude that maternal inhalation of DE in pregnancy provokes a fetal inflammatory response that, combined with postnatal ozone exposure, impairs alveolar development, and causes a more severe and long-lasting AHR to ozone exposure.     

Characterization of urban atmospheres during inhalation exposure studies in Detroit and Grand Rapids, Michigan

An inhalation exposure study for particulate matter (PM) investigates links between exposure and observed changes in respiratory function by evaluating the interactions of chemical and physical properties of the PM with physiological mechanisms. Laboratory studies are useful in this regard, but provide limited information because of the difficulty in reproducing real atmospheric PM compositions and processes. To better understand the types of particles to which people are actually exposed in their daily lives, and the human health risks for source-specific PM, a real world assessment of the source-to-receptor pathways for ambient PM is vital. This was accomplished using a unique mobile air research laboratory (AirCARE1) which enables inhalation exposure studies in real-world settings. The overall goal of this study was to determine the effects of concentrated air particulates (CAPs) from 2 different urban atmospheres in Michigan on the lungs of ovalbumin-sensitized rats concurrently challenged with the allergen. Our work demonstrated that short-term (8 hours) exposure to ambient fine particulate matter (aerodynamic diameter 相似文献   

Ozone exposure of macrophages induces an alveolar epithelial chemokine response through IL-1alpha

Ozone is known to produce an acute influx of neutrophils, and alveolar epithelial cells can secrete chemokines and modulate inflammatory processes. However, direct exposure of alveolar epithelial cells and macrophages to ozone (O(3)) produces little chemokine response. To determine if cell-cell interactions might be responsible, we investigated the effect of alveolar macrophage-conditioned media after ozone exposure (MO(3)CM) on alveolar epithelial cell chemokine production. Serum-free media were conditioned by exposing a rat alveolar macrophage cell line NR8383 to ozone for 1 hour. Ozone stimulated secretion of IL-1alpha, IL-1beta, and IL-18 from NR8383 cells, but there was no secretion of chemokines or TNF-alpha. Freshly isolated type II cells were cultured, so as to express the biological markers of type I cells, and these cells are referred to as type I-like cells. Type I-like cells were exposed to diluted MO(3)CM for 24 hours, and this conditioned medium stimulated secretion of cytokine-induced neutrophil chemattractant-1 (CXCL1) and monocyte chemoattractant protein-1 (CCL2). Secretion of these chemokines was inhibited by the IL-1 receptor antagonist. Although both recombinant IL-1alpha and IL-1beta stimulated alveolar epithelial cells to secrete chemokines, recombinant IL-1alpha was 100-fold more potent than IL-1beta. Furthermore, neutralizing anti-rat IL-1alpha antibodies inhibited the secretion of chemokines by alveolar epithelial cells, whereas neutralizing anti-rat IL-1beta antibodies had no effect. These observations indicate that secretion of IL-1alpha from macrophages stimulates alveolar epithelial cells to secrete chemokines that can elicit an inflammatory response.     

Changes in alveolar macrophage, monocyte, and neutrophil cell profiles after smoke inhalation injury.

Thirty two fire victims with smoke inhalation, with or without burns, and 26 control subjects had bronchoalveolar lavage performed. Cell yields and differential cell counts were assessed. All patients and controls were cigarette smokers. Patients with smoke inhalation (SI) injury generally showed higher total bronchoalveolar lavage (BAL) cell yields, and this was significant on repeat lavage from 12 patients. The increase was almost entirely due to an increase in the proportion of neutrophils in patients with smoke inhalation alone (S) and those with cutaneous burns as well as smoke inhalation (S + B). On sequential lavage of 12 patients with smoke inhalation (SI) the proportion of neutrophils had increased; this was significantly higher than on initial lavage. Using various macrophage markers, the proportions of macrophage subgroups were determined. There was an increase in UCHM1 and RFD9 positive cells in each subgroup: the increase in UCHM1 positive cells was significant in patients with burns as well as smoke inhalation, and the increase in RFD9 positive cells was significant in patients with smoke inhalation alone. Assessment of the role of such cells in the development of acute lung injury (such as adult respiratory distress syndrome) may be important in our understanding of the mechanisms entailed.     

Changes in collagen metabolism and proteinolysis after repeated inhalation exposure to ozone

To study the changes in collagen metabolism that occur in the pathogenesis of pulmonary fibrosis, female rats were exposed to 0, 0.57, and 1.1 ppm ozone for 19 hr/day for 11 days and sacrificed 12 or 60 days after initiation of exposure. The lungs of rats sacrificed at 12 days after initiation of exposure to 1.1 ppm had interstitial pneumonia characterized by a mixed inflammatory cell infiltrate, type II cell hyperplasia, and fibroplasia, a proliferation of the collagen-producing cells; increased cathepsin D and macrophage elastase activity, indicating macrophage-induced proteinolysis; a reduced percentage of the increased collagen production that was ultrafilterable, indicating a decreased rate of intracellular degradation of newly produced collagen prior to its secretion; and increased lavage fluid hydroxyproline, indicating turnover of extracellular collagenous matrix. Reduced intracellular collagen degradation correlated directly with both increased net collagen production and fibroplasia in rats exposed to 1.1 ppm ozone for 11 days. These changes preceded an increased total lung collagen and the development of modest fibroplasia and fibrosis in the alveolar duct regions by 60 days after the 1.1 ppm ozone exposure was initiated.     

Role of macrophage chemoattractant protein-1 in acute inflammation after lung contusion

Lung contusion (LC), commonly observed in patients with thoracic trauma is a leading risk factor for development of acute lung injury/acute respiratory distress syndrome. Previously, we have shown that CC chemokine ligand (CCL)-2, a monotactic chemokine abundant in the lungs, is significantly elevated in LC. This study investigated the nature of protection afforded by CCL-2 in acute lung injury/acute respiratory distress syndrome during LC, using rats and CC chemokine receptor (CCR) 2 knockout (CCR2(-/-)) mice. Rats injected with a polyclonal antibody to CCL-2 showed higher levels of albumin and IL-6 in the bronchoalveolar lavage and myeloperoxidase in the lung tissue after LC. Closed-chest bilateral LC demonstrated CCL-2 localization in alveolar macrophages (AMs) and epithelial cells. Subsequent experiments performed using a murine model of LC showed that the extent of injury, assessed by pulmonary compliance and albumin levels in the bronchoalveolar lavage, was higher in the CCR2(-/-) mice when compared with the wild-type (WT) mice. We also found increased release of IL-1β, IL-6, macrophage inflammatory protein-1, and keratinocyte chemoattractant, lower recruitment of AMs, and higher neutrophil infiltration and phagocytic activity in CCR2(-/-) mice at 24 hours. However, impaired phagocytic activity was observed at 48 hours compared with the WT. Production of CCL-2 and macrophage chemoattractant protein-5 was increased in the absence of CCR2, thus suggesting a negative feedback mechanism of regulation. Isolated AMs in the CCR2(-/-) mice showed a predominant M1 phenotype compared with the predominant M2 phenotype in WT mice. Taken together, the above results show that CCL-2 is functionally important in the down-modulation of injury and inflammation in LC.     

Exposure of humans to ambient levels of ozone for 6.6 hours causes cellular and biochemical changes in the lung.

An acute (2 h) exposure of humans to 0.4 ppm ozone initiates biochemical changes in the lung that result in the production of components mediating inflammation and acute lung damage as well as components having the potential to lead to long-term effects such as fibrosis. However, many people are exposed to lower levels of ozone than this, but for periods of several hours. Therefore, it is important to determine if a prolonged exposure to low levels of ozone is also capable of causing cellular and biochemical changes in the lung. Nonsmoking males were randomly exposed to filtered air and either 0.10 ppm ozone or 0.08 ppm ozone for 6.6 h with moderate exercise (40 liters/min). Bronchoalveolar lavage (BAL) was performed 18 h after each exposure, and cells and fluid were analyzed. The BAL fluid of volunteers exposed to 0.10 ppm ozone had significant increases in neutrophils (PMNs), protein, prostaglandin E2 (PGE2), fibronectin, interleukin-6 (IL-6), and lactate dehydrogenase (LDH) compared with BAL fluid from the same volunteers exposed to filtered air. In addition, there was a decrease in the ability of alveolar macrophages to phagocytize yeast via the complement receptor. Exposure to 0.08 ppm ozone resulted in significant increases in PMNs, PGE2, LDH, IL-6, alpha 1-antitrypsin, and decreased phagocytosis via the complement receptor. However, BAL fluid protein and fibronectin were no longer significantly elevated. We conclude that exposure of humans to as low a level as 0.08 ppm for 6.6 h is sufficient to initiate an inflammatory reaction in the lung.     

Deficiency in inducible nitric oxide synthase protects mice from ozone-induced lung inflammation and tissue injury

Inhalation of ozone causes Type I epithelial cell necrosis and Type II cell hyperplasia and proliferation. This is associated with an accumulation of activated macrophages in the lower lung, which we have demonstrated contribute to tissue injury. Nitric oxide (NO) is a highly reactive cytotoxic macrophage-derived mediator that has been implicated in lung damage. In the present studies we used knockout mice with a targeted disruption of the gene for inducible nitric oxide synthase (NOSII) to analyze the role of NO in ozone-induced lung inflammation and tissue injury. Treatment of wild-type control mice with ozone (0.8 ppm) for 3 h resulted in a time-dependent increase in protein and cells in bronchoalveolar lavage fluid, which reached a maximum 24-48 h after exposure. Alveolar macrophages isolated from animals treated with ozone were found to produce increased amounts of NO, as well as peroxynitrite. This was correlated with induction of NOSII protein and nitrotyrosine staining of lung macrophages in tissue sections and in culture. Production of superoxide anion and prostaglandin (PG)E2 by alveolar macrophages was also increased after ozone inhalation. In contrast, alveolar macrophages from NOSII knockout mice did not produce reactive nitrogen intermediates even after ozone inhalation. Moreover, production of PGE2 was at control levels. NOSII knockout mice were also protected from ozone-induced inflammation and tissue injury, as measured by bronchoalveolar lavage protein and cell number. There was also no evidence of peroxynitrite-mediated lung damage in these animals. Taken together, these data demonstrate that NO, produced via NOSII, and potentially, its reactive oxidative product peroxynitrite, play a critical role in ozone-induced release of inflammatory mediators and in tissue injury.     

The role of macrophages in the clearance of inhaled ultrafine titanium dioxide particles

The role of macrophages in the clearance of particles with diameters less than 100 nm (ultrafine or nanoparticles) is not well established, although these particles deposit highly efficiently in peripheral lungs, where particle phagocytosis by macrophages is the primary clearance mechanism. To investigate the uptake of nanoparticles by lung phagocytes, we analyzed the distribution of titanium dioxide particles of 20 nm count median diameter in macrophages obtained by bronchoalveolar lavage at 1 hour and 24 hours after a 1-hour aerosol inhalation. Differential cell counts revealing greater than 96% macrophages and less than 1% neutrophils and lymphocytes excluded inflammatory cell responses. Employing energy-filtering transmission electron microscopy (EFTEM) for elemental microanalysis, we examined 1,594 macrophage profiles in the 1-hour group (n = 6) and 1,609 in the 24-hour group (n = 6). We found 4 particles in 3 macrophage profiles at 1 hour and 47 particles in 27 macrophage profiles at 24 hours. Model-based data analysis revealed an uptake of 0.06 to 0.12% ultrafine titanium-dioxide particles by lung-surface macrophages within 24 hours. Mean (SD) particle diameters were 31 (8) nm at 1 hour and 34 (10) nm at 24 hours. Particles were localized adjacent (within 13-83 nm) to the membrane in vesicles with mean (SD) diameters of 592 (375) nm at 1 hour and 414 (309) nm at 24 hours, containing other material like surfactant. Additional screening of macrophage profiles by conventional TEM revealed no evidence for agglomerated nanoparticles. These results give evidence for a sporadic and rather unspecific uptake of TiO(2)-nanoparticles by lung-surface macrophages within 24 hours after their deposition, and hence for an insufficient role of the key clearance mechanism in peripheral lungs.     

Cell injury and interstitial inflammation in rat lung after inhalation of ozone and urban particulates

Coexposure of the lung to urban dust along with ozone appears to potentiate ozone-induced injury. This conclusion was derived from whole-lung studies involving tissue and lavaged cells, but we now speculate that the injury and inflammatory response at the main site of reactivity, the bronchoalveolar duct region, is underestimated by such whole-lung studies. We exposed rats to ozone at 0.8 ppm and urban particulates (EHC93) at 50 mg/m3 for 4 h. Animals were killed 33 h later with tritiated thymidine (3HT) injected 1.5 h before death. Lungs were fixed by vascular perfusion to avoid disturbing any epithelial cell changes or local inflammation and edema in the air spaces. Tissue was embedded from central and peripheral areas of the lung, then counts of labeled cells, polymorphonuclear leukocytes (PMN), and macrophages (MAC) were made separately on methacrylate sections. The results showed that epithelial cell injury and regeneration (% of 3HT-labeled cells) was greatest in the ozone plus dust group, and was three times higher in periductal areas than in whole-lung counts. Although some increase in inflammatory cells in the air spaces was found in the coexposure group, much higher numbers of PMN and MAC were counted in the lung tissue compartment, and counts were significantly higher than those found after ozone or dust alone. Values from the latter groups were also higher than those from air controls or samples of distal lung taken from any inhalation group. The results demonstrate that inhalation of an urban dust at a level that causes few lung effects when inhaled alone can potentiate ozone toxicity, particularly in the vicinity of the alveolar duct, where the accumulation of interstitial inflammatory cells may be an important factor in the development of any subsequent pathologic changes.     

Regulatory effects of interleukin-11 during acute lung inflammatory injury.

The role of interleukin-11 (IL-11) was evaluated in the IgG immune complex model of acute lung injury in rats. IL-11 mRNA and protein were both up-regulated during the course of this inflammatory response. Exogenously administered IL-11 substantially reduced, in a dose-dependent manner, the intrapulmonary accumulation of neutrophils and the lung vascular leak of albumin. These in vivo anti-inflammatory effects of IL-11 were associated with reduced NF-kappaB activation in lung, reduced levels of tumor necrosis factor alpha (TNF-alpha) in bronchoalveolar lavage (BAL) fluids, and diminished up-regulation of lung vascular ICAM-1. It is interesting that IL-11 did not affect BAL fluid content of the CXC chemokines, macrophage inflammatory protein-2 (MIP-2) and cytokine-inducible neutrophil chemoattractant (CINC); the presence of IL-11 did not affect these chemokines. However, BAL content of C5a was reduced by IL-11. These data indicate that IL-11 is a regulatory cytokine in the lung and that, like other members of this family, its anti-inflammatory properties appear to be linked to its suppression of NF-kappaB activation, diminished production of TNF-alpha, and reduced up-regulation of lung vascular ICAM-1.