Cytokine gene expression after inhalation of corn dust

Aminoguanidine affects systemic and lung inflammation induced by lipopolysaccharide in rats

Background

Nitric oxide is a mediator of potential importance in numerous physiological and inflammatory processes in the lung. Aminoguanidine (AG) has been shown to have anti-inflammation and radical scavenging properties. This study aimed to investigate the effects of AG, an iNOS inhibitor, on lipopolysaccharide (LPS)-induced systemic and lung inflammation in rats.

Methods

Male Wistar rats were divided into control, LPS (1 mg/kg/day i.p.), and LPS groups treated with AG 50, 100 or 150 mg/kg/day i.p. for five weeks. Total nitrite concentration, total and differential white blood cells (WBC) count, oxidative stress markers, and the levels of IL-4, IFN-γ, TGF-β1, and PGE2 were assessed in the serum or bronchoalveolar lavage fluid (BALF).

Results

Administration of LPS decreased IL-4 level (p < 0.01) in BALF, total thiol content, superoxide dismutase (SOD) and catalase (CAT) activities (p < 0.001) in BALF and serum, and increased total nitrite, malondialdehyde (MDA), IFN-γ, TGF-β1 and PGE2 (p < 0.001) concentrations in BALF. Pre-treatment with AG increased BALF level of IL-4 and total thiol as well as SOD and CAT activities (p < 0.05 to p < 0.001), but decreased BALF levels of total nitrite, MDA, IFN-γ, TGF-β1, and PGE2 (p < 0.01 to p < 0.001). AG treatment decreased total WBC count, lymphocytes and macrophages in BALF (p < 0.01 to p < 0.001) and improved lung pathological changes including interstitial inflammation and lymphoid infiltration (p < 0.05 to p < 0.001).

Conclusions

AG treatment reduced oxidant markers, inflammatory cytokines and lung pathological changes but increased antioxidants and anti-inflammatory cytokines. Therefore, AG may play a significant protective role against inflammation and oxidative stress that cause lung injury.

Innate immune activation by inhaled lipopolysaccharide, independent of oxidative stress, exacerbates silica-induced pulmonary fibrosis in mice

Acute exacerbations of pulmonary fibrosis are characterized by rapid decrements in lung function. Environmental factors that may contribute to acute exacerbations remain poorly understood. We have previously demonstrated that exposure to inhaled lipopolysaccharide (LPS) induces expression of genes associated with fibrosis. To address whether exposure to LPS could exacerbate fibrosis, we exposed male C57BL/6 mice to crystalline silica, or vehicle, followed 28 days later by LPS or saline inhalation. We observed that mice receiving both silica and LPS had significantly more total inflammatory cells, more whole lung lavage MCP-1, MIP-2, KC and IL-1β, more evidence of oxidative stress and more total lung hydroxyproline than mice receiving either LPS alone, or silica alone. Blocking oxidative stress with N-acetylcysteine attenuated whole lung inflammation but had no effect on total lung hydroxyproline. These observations suggest that exposure to innate immune stimuli, such as LPS in the environment, may exacerbate stable pulmonary fibrosis via mechanisms that are independent of inflammation and oxidative stress.

Bacterial lipopolysaccharide enhances PDGF signaling and pulmonary fibrosis in rats exposed to carbon nanotubes

Engineered multi-walled carbon nanotubes (MWCNT) represent a possible health risk for pulmonary fibrosis due to their fiber-like shape and potential for persistence in the lung. We postulated that bacterial lipopolysaccharide (LPS), a ubiquitous agent in the environment that causes lung inflammation, would enhance fibrosis caused by MWCNT. Rats were exposed to LPS and then intratracheally instilled with MWCNT or carbon black (CB) nanoparticles 24 hours later. Pulmonary fibrosis was observed 21 days after MWCNT exposure, but not with CB. LPS alone caused no fibrosis but enhanced MWCNT-induced fibrosis. LPS plus CB did not significantly increase fibrosis. MWCNT increased platelet-derived growth factor-AA (PDGF-AA), a major mediator of fibrosis. PDGF-AA production in response to MWCNT, but not CB, was synergistically enhanced by LPS. Immunostaining showed PDGF-AA in bronchiolar epithelial cells and macrophages. Since macrophages engulfed MWCNT, were positive for PDGF-AA, and mediate fibroblast responses, experiments were performed with rat lung macrophages (NR8383 cells) and rat lung fibroblasts in vitro. LPS exposure increased PDGF-A mRNA levels in NR8383 cells and enhanced MWCNT-induced PDGF-A mRNA levels. Moreover, LPS increased MWCNT- or CB-induced PDGF receptor-alpha (PDGF-Ralpha) mRNA in fibroblasts. Our data suggest that LPS exacerbates MWCNT-induced lung fibrosis by amplifying production of PDGF-AA in macrophages and epithelial cells, and by increasing PDGF-Ralpha on pulmonary fibroblasts. Our findings also suggest that individuals with pre-existing pulmonary inflammation are at greater risk for the potential adverse effects of MWCNT.

Chronic LPS inhalation causes emphysema-like changes in mouse lung that are associated with apoptosis

Lipopolysaccharide (LPS) is ubiquitous in the environment. Recent epidemiologic data suggest that occupational exposure to inhaled LPS can contribute to the progression of chronic obstructive pulmonary disease. To address the hypothesis that inhaled LPS can cause emphysema-like changes in mouse pulmonary parenchyma, we exposed C57BL/6 mice to aerosolized LPS daily for 4 weeks. By 3 days after the end of the 4-week exposure, LPS-exposed mice developed enlarged airspaces that persisted in the 4-week recovered mice. These architectural alterations in the lung are associated with enhanced type I, III, and IV procollagen mRNA as well as elevated levels of matrix metalloproteinase (MMP)-9 mRNA, all of which have been previously associated with human emphysema. Interestingly, MMP-9-deficient mice were not protected from the development of LPS-induced emphysema. However, we demonstrate that LPS-induced airspace enlargement was associated with apoptosis within the lung parenchyma, as shown by prominent TUNEL staining and elevated cleaved caspase 3 immunoreactivity. Antineutrophil antiserum-treated mice were partially protected from the lung destruction caused by chronic inhalation of LPS. Taken together, these findings demonstrate that inhaled LPS can cause neutrophil-dependent emphysematous changes in lung architecture that are associated with apoptosis and that these changes may be occurring through mechanisms different than those induced by cigarette smoke.

The IL-1 type 1 receptor is required for the development of LPS-induced airways disease

BACKGROUND

The contribution of IL-1beta signaling through the IL-1 type 1 receptor (IL-1R1) to the development of persistent LPS-induced airway disease has not been investigated.

OBJECTIVE

To determine the importance of signaling through the IL-1 type 1 receptor in the development of LPS-induced airway disease.

METHODS

We exposed IL-1R1-deficient (C57BL/6(IL-1RI-/-)) mice to an aerosol of LPS or filtered air for 1 day, 1 week, or 4 weeks.

RESULTS

After 4 weeks of LPS inhalation, C57BL/6(IL-1RI-/-) mice failed to develop significant submucosal thickening, whereas C57BL/6 mice had significantly thickened submucosa in small, medium, and large airways compared with those of unexposed control mice. Cell proliferation in the airways of both the 1-week and 4-week LPS-exposed C57BL/6(IL-1RI-/-) mice was significantly reduced compared with LPS-exposed C57BL/6 mice. mRNA for type III alpha-3 procollagen was significantly elevated over baseline in C57BL/6 yet remained unchanged compared with baseline in C57BL/6(IL-1RI-/-) mice after 1 week or 4 weeks of LPS inhalation. mRNA for tissue inhibitor of metalloprotease 1 in C57BL/6 mice in the 1-week and 4-week groups was significantly elevated over both control mice and C57BL/6(IL-1RI-/-) mice.

CONCLUSION

These data support the hypothesis that signaling through the IL-1 receptor modulates extracellular matrix homeostasis in response to inhaled LPS.

CLINICAL IMPLICATIONS

Attenuating IL-1R1-mediated signaling might be an effective therapy against the development of airway remodeling in chronic inflammatory diseases.

CD14 is an essential mediator of LPS-induced airway disease

Chronic lipopolysaccharide (LPS) inhalation in rodents recapitulates many classic features of chronic obstructive pulmonary disease seen in humans, including airways hyperresponsiveness, neutrophilic inflammation, cytokine production in the lung, and small airways remodeling. CD14-deficient mice (C57BL/6(CD14-/-)) have an altered response to systemic LPS, and yet the role of CD14 in the response to inhaled LPS has not been defined. We observed that C57BL/6(CD14-/-) mice demonstrate no discernable physiological or inflammatory response to a single LPS inhalation challenge. However, the physiological (airways hyperresponsiveness) and inflammatory (presence of neutrophils and TNF-alpha in whole lung lavage fluid) responsiveness to inhaled LPS in C57BL/6(CD14-/-) mice was restored by instilling soluble CD14 intratracheally. Intratracheal instillation of wild-type macrophages into C57BL/6(CD14-/-) mice restored neutrophilic inflammation only and failed to restore airways hyperresponsiveness or TNF-alpha protein in whole lung lavage. These findings demonstrate that CD14 is critical to LPS-induced airway disease and that macrophage CD14 is sufficient to initiate neutrophil recruitment into the airways but that CD14 may need to interact with other cell types as well for the development of airways hyperresponsiveness and for cytokine production.

Kinetics of pulmonary neutrophil recruitment and clearance in a natural and spontaneously resolving model of airway inflammation

BACKGROUND

Neutrophil apoptosis and phagocytic clearance have been proposed as key determinants affecting the resolution of airway inflammation. Objective To determine the kinetics of neutrophil priming, recruitment, activation and subsequent clearance in a naturally occurring equine disease model of neutrophilic pulmonary inflammation.

METHODS AND RESULTS

A 5 h mouldy hay/straw challenge in hypersensitive horses induced transient pulmonary dysfunction lasting 4 days. At 24 h circulating neutrophils were primed and displayed delayed rates of spontaneous apoptosis in vitro. Neutrophil numbers in the airspaces peaked at 5 h and then fell abruptly, returning to pre-challenge levels by 4 days. Airspace neutrophils demonstrated increased respiratory burst activity compared with circulating cells and equine neutrophil elastase 2A concentrations increased in parallel with neutrophil numbers indicating in vivo priming and degranulation. The number of apoptotic neutrophils and proportion of alveolar macrophages containing phagocytosed apoptotic neutrophils increased significantly at 24 h and 4 days post-challenge corresponding to the period of most rapid neutrophil clearance.

CONCLUSION

This is the first demonstration of spontaneous neutrophil apoptosis and phagocytic removal in a natural disease model of airway inflammation and provides critical kinetic data to support the hypothesis that this clearance pathway plays a central role in the resolution of neutrophilic inflammation.

The critical role of hematopoietic cells in lipopolysaccharide-induced airway inflammation

Rapid and selective recruitment of neutrophils into the airspace in response to LPS facilitates the clearance of bacterial pathogens. However, neutrophil infiltration can also participate in the development and progression of environmental airway disease. Previous data have revealed that Toll-like receptor 4 (tlr4) is required for neutrophil recruitment to the lung after either inhaled or systemically administrated LPS from Escherichia coli. Although many cell types express tlr4, endothelial cell expression of tlr4 is specifically required to sequester neutrophils in the lung in response to systemic endotoxin. To identify the cell types requiring trl4 expression for neutrophil recruitment after inhaled LPS, we generated chimeric mice separately expressing tlr4 on either hematopoietic cells or on structural lung cells. Neutrophil recruitment into the airspace was completely restored in tlr4-deficient mice receiving wild-type bone marrow. By contrast, wild-type animals receiving tlr4-deficient marrow had dramatically reduced neutrophil recruitment. Moreover, adoptive transfer of wild-type alveolar macrophages also restored the ability of tlr4-deficient recipient mice to recruit neutrophils to the lung. These data demonstrate the critical role of hematopoietic cells and alveolar macrophages in initiating LPS-induced neutrophil recruitment from the vascular space to the airspace.

Altered surfactant protein A gene expression and protein metabolism associated with repeat exposure to inhaled endotoxin

Chronically inhaled endotoxin, which is ubiquitous in many occupational and domestic environments, can adversely affect the respiratory system resulting in an inflammatory response and decreased lung function. Surfactant-associated protein A (SP-A) is part of the lung innate immune system and may attenuate the inflammatory response in various types of lung injury. Using a murine model to mimic occupational exposures to endotoxin, we hypothesized that SP-A gene expression and protein would be elevated in response to repeat exposure to inhaled grain dust and to purified lipopolysaccharide (LPS). Our results demonstrate that repeat exposure to inhaled endotoxin, either in the form of grain dust or purified LPS, results in increased whole lung SP-A gene expression and type II alveolar epithelial cell hyperplasia, whereas SP-A protein levels in lung lavage fluid are decreased. Furthermore, these alterations in SP-A gene activity and protein metabolism are dependent on an intact endotoxin signaling system.

Subchronic endotoxin inhalation causes persistent airway disease

The endotoxin component of organic dusts causes acute reversible airflow obstruction and airway inflammation. To test the hypothesis that endotoxin alone causes airway remodeling, we have compared the response of two inbred mouse strains to subchronic endotoxin exposure. Physiological and biological parameters were evaluated after 1 day, 5 days, or 8 wk of exposure to endotoxin [lipopolysaccharide (LPS)] in endotoxin-sensitive (C3HeB/FeJ) and endotoxin-resistant (C3H/HeJ) mice. After 5 days or 8 wk of LPS exposure, only C3HeB/FeJ had elevated airway hyperreactivity to inhaled methacholine. Only the C3HeB/FeJ mice had significant inflammation of the lower respiratory tract after 1 day, 5 days, or 8 wk of LPS exposure. Stereological measurements of small, medium, and large airways indicated that an 8-wk exposure to LPS resulted in expansion of the submucosal area only in the C3HeB/FeJ mice. Cell proliferation as measured by bromodeoxyuridine incorporation contributed to the expansion of the submucosa and was only significantly elevated in C3HeB/FeJ mice actively exposed to LPS. C3HeB/FeJ mice had significantly elevated levels of interleukin-1beta protein in whole lung lavage after 1 day and 5 days of LPS exposure and significantly elevated protein levels of total and active transforming growth factor-beta1 in whole lung lavage fluid after 5 days of LPS exposure. Our findings demonstrate that subchronic inhalation of LPS results in the development of persistent airway disease in endotoxin-responsive mice.

The role of the microtubules in tumor necrosis factor-alpha-induced endothelial cell permeability

Tumor necrosis factor (TNF)-alpha, a major proinflammatory cytokine, triggers endothelial cell activation and barrier dysfunction which are implicated in the pathogenesis of pulmonary edema associated with acute lung injury syndromes. The mechanisms of TNF-alpha-induced vascular permeability are not completely understood. Our initial experiments demonstrated that TNF-alpha-induced decreases in transendothelial electrical resistance across human pulmonary artery endothelial cells are independent of myosin light chain phosphorylation catalyzed by either myosin light chain kinase or Rho kinase. We next assessed the involvement of another cytoskeletal component, the tubulin-based microtubule network, and found TNF-alpha to induce a decrease in stable tubulin content and partial dissolution of peripheral microtubule network as evidenced by anti-acetylated tubulin and anti-beta-tubulin immunofluorescent staining, respectively. Microtubule-stabilizing agents, paclitaxel and epothilone B, significantly attenuated TNF-alpha-induced decreases in transendothelial electrical resistance, inhibited the cytokine-induced increases in actin stress fibers, formation of intercellular gap, and restored the TNF-alpha-compromised vascular endothelial (VE)-cadherin-based cell-cell junctions. Importantly, neither TNF-alpha nor paclitaxel treatment was associated with endothelial cell apoptosis. Inhibition of p38 mitogen-activated protein kinase by SB203580 significantly attenuated TNF-alpha-induced microtubule destabilization, actin rearrangement, and endothelial barrier dysfunction. These results strongly suggest the involvement of microtubule rearrangement in TNF-alpha-induced endothelial cell permeability via p38 mitogen-activated protein kinase activation.

Neutrophils play a critical role in development of LPS-induced airway disease

We investigated the role of neutrophils in the development of endotoxin-induced airway disease via systemic neutrophil depletion of C3H/HeBFeJ mice and coincident inhalation challenge with lipopolysaccharide (LPS) over a 4-wk period. Mice were made neutropenic with intraperitoneal injections of neutrophil antiserum before and throughout the exposure period. Experimental conditions included LPS-exposed, antiserum-treated; LPS-exposed, control serum-treated; air-exposed, antiserum-treated; and air-exposed, control serum-treated groups. Physiological, biological, and morphological assessments were performed after a 4-wk exposure and again after a 4-wk recovery period. After the 4-wk exposure, LPS-induced inflammation of the lower airways was significantly attenuated in the neutropenic mice, although airway responsiveness (AR) to methacholine (MCh) remained unchanged. After the recovery period, LPS-exposed neutrophil-replete mice had increased AR to MCh when compared with the LPS-exposed neutropenic animals. Morphometric data indicate that the 4-wk exposure to LPS leads to a substantial expansion of the subepithelial area of the medium-sized airways (90-129 microm diameter) in nonneutropenic mice but not neutropenic mice, and this difference persisted even after the recovery period. Expression of bronchial epithelial and subepithelial transforming growth factor-beta1 (TGF-beta1) was diminished in the challenged neutropenic mice compared with the neutrophil-sufficient mice. These studies demonstrate that neutrophils play a critical role in the development of chronic LPS-induced airway disease.

Airway inflammation and responsiveness in prostaglandin H synthase-deficient mice exposed to bacterial lipopolysaccharide

Bacterial lipopolysaccharide (LPS) is a risk factor for exacerbation of asthma and causes airway inflammation. The aim of this study was to examine the effects of disruption of prostaglandin (PG) H synthase (PGHS)-1 and PGHS-2 genes on pulmonary responses to inhaled LPS. PGHS-1(-/-), PGHS-2(-/-), and wild-type (WT) mice were exposed to 4 to 6 microg/m(3) LPS via aerosol. Enhanced pause (PenH), a measure of bronchoconstriction, was assessed using a whole-body plethysmograph before and immediately after a 4-h LPS exposure. Bronchoalveolar lavage (BAL) was performed after LPS exposure to assess inflammatory cells, cytokines/chemokines (tumor necrosis factor-alpha, interleukin-6, and macrophage inflammatory protein-2), and PGE(2). The degree of lung inflammation was scored on hematoxylin-and-eosin-stained sections. PGHS-1 and PGHS-2 protein levels were determined by immunoblotting. All mice exhibited increased PenH and methacholine responsiveness after LPS exposure; however, these changes were much more pronounced in PGHS-1(-/-) and PGHS-2(-/-) mice relative to WT mice (P < 0.05). There were no significant differences in inflammation as assessed by BAL fluid (BALF) cells or lung histology between the genotypes despite reduced BALF cytokines/chemokines and PGE(2) in PGHS-1(-/-) and PGHS-2(-/-) mice relative to WT mice (P < 0.05). PGHS-2 was upregulated more in PGHS-1(-/-) mice compared with WT mice after LPS exposure. We conclude that: (1) airway inflammation and hyperresponsiveness are dissociated in PGHS-1(-/-) and PGHS-2(-/-) mice exposed to LPS; (2) the balance of PGHS-1 and PGHS-2 is important in regulating the functional respiratory responses to inhaled LPS; and (3) neither PGHS-1 nor PGHS-2 is important in regulating basal lung function or the inflammatory responses of the lung to inhaled LPS.

Inhibition of LPS-induced airway hyperresponsiveness and airway inflammation by LPS antagonists

To determine whether the inflammatory effects of inhaled endotoxin could be prevented, we pretreated mice with synthetic competitive antagonists (975, 1044, and 1287) for lipopolysaccharide (LPS) before a LPS inhalation challenge. In preliminary studies, we found that these LPS antagonists did not act as agonists in vitro (THP-1 cells) or in vivo (after intratracheal instillation of 10 microg) and that these compounds (at least 1 microg/ml) effectively antagonized the release of tumor necrosis factor-alpha by LPS-stimulated THP-1 cells. Pretreatment of mice with 10 microg of either 1044 or 1287 resulted in a decrease in the LPS-induced airway hyperreactivity. Moreover, pretreatment of mice with 10 microg of 975, 1044, or 1287 resulted in significant reductions in LPS-induced lung lavage fluid concentrations of total cells, neutrophils, and specific proinflammatory cytokines compared with mice pretreated with sterile saline. Using residual oil fly ash to induce airway inflammation, we found that the action of the LPS antagonists was specific to LPS-induced airway disease. These results suggest that LPS antagonists may be an effective and potentially safe treatment for endotoxin-induced airway disease.

Role of p38 MAP kinase in LPS-induced airway inflammation in the rat

We investigated the effect of the p38 kinase inhibitor SB 203580 on airway inflammation induced by aerosolized lipopolysaccharide (LPS) in male Wistar rats. SB 203580 significantly inhibited (ED(50)=15.8 mg kg(-1)) plasma levels of TNF-alpha in rats challenged with LPS (1.5 mg kg(-1), i.p.). Aerosolized LPS induced a peak in TNF-alpha levels and the initiation of a neutrophilic response in bronchoalveolar lavage (BAL) fluid at the 2 h time point. Furthermore, the 4 h time point was associated with the peak in IL-1beta levels and the initial plateau of neutrophilia observed in the BAL fluid. SB 203580 (100 mg kg(-1)), had no effect on peak TNF-alpha levels or the associated neutrophilia in the BAL. Interestingly, the PDE 4 inhibitor RP 73401 (100 mg kg(-1)) significantly reduced both TNF-alpha levels and neutrophilic inflammation. However, the BAL fluid from rats pre-treated with either compound significantly inhibited TNF-alpha release from cultured human monocytes 18 h after LPS treatment (83.6 and 44.5% inhibition, respectively). Alternatively, SB 203580 (100 mg kg(-1)) produced dose-related inhibition of BAL IL-1beta levels (67.5% inhibition, P<0.01) and BAL neutrophilia (45.9% inhibition, P<0.01) 4 h after LPS challenge. P38 protein was present in lung tissue and the level of expression was not affected by LPS treatment. P38 kinase appears to be involved in the release of IL-1beta and the sustained neutrophilic response in the BAL fluid. This data may suggest a role for p38 inhibitors in the treatment of airway inflammatory diseases in which neutrophilia is a feature of the lung pathology.

Endotoxin responsiveness and subchronic grain dust-induced airway disease

Endotoxin is one of the principal components of grain dust that causes acute reversible airflow obstruction and airway inflammation. To determine whether endotoxin responsiveness influences the development of chronic grain dust-induced airway disease, physiological and airway inflammation remodeling parameters were evaluated after an 8-wk exposure to corn dust extract (CDE) and again after a 4-wk recovery period in a strain of mice sensitive to (C3H/HeBFeJ) and one resistant to (C3H/HeJ) endotoxin. After the CDE exposure, both strains of mice had equal airway hyperreactivity to a methacholine challenge; however, airway hyperreactivity persisted only in the C3H/HeBFeJ mice after the recovery period. Only the C3H/HeBFeJ mice showed significant inflammation of the lower airway after the 8-wk exposure to CDE. After the recovery period, this inflammatory response completely resolved. Lung stereological measurements indicate that an 8-wk exposure to CDE resulted in persistent expansion of the airway submucosal cross-sectional area only in the C3H/HeBFeJ mice. Collagen type III and an influx of cells into the subepithelial area participated in the expansion of the submucosa. Our findings demonstrate that subchronic inhalation of grain dust extract results in the development of chronic airway disease only in mice sensitive to endotoxin but not in mice that are genetically hyporesponsive to endotoxin, suggesting that endotoxin is important in the development of chronic airway disease.

TNF-alpha and IL-1 beta are not essential to the inflammatory response in LPS-induced airway disease

To determine the role of tumor necrosis factor (TNF)-alpha and interleukin (IL)-1 beta in the lower respiratory tract inflammatory response after inhalation of lipopolysaccharide (LPS), we conducted inhalation exposure studies in mice lacking expression of TNF-alpha and/or IL-1 receptor type 1 and in mice with functional blockade of these cytokines using adenoviral vector delivery of soluble receptors to one or both cytokines. Alterations in airway physiology were assessed by pulmonary function testing before and immediately after 4 h of LPS exposure, and the cellular inflammatory response was measured by whole lung lavage and assessment of inflammatory cytokine protein and mRNA expression. Airway resistance after LPS exposure was similarly increased in all groups of mice without evidence that blockade of either or both cytokines was protective from this response. Additionally, all groups of mice demonstrated significant increases in lung lavage fluid cellularity with a complete shift in the population of cells to a predominantly neutrophilic infiltrate as well as elevation in inflammatory cytokine protein and mRNA levels. There were no significant differences between the groups in measures of lung inflammation. These results indicate that TNF-alpha and IL-1 beta do not appear to have an essential role in mediating the physiological or inflammatory response to inhaled LPS.

Bronchial hyperreactivity is associated with enhanced grain dust-induced airflow obstruction

Bronchial hyperreactivity (BHR) is associated with the presence of airway inflammation in asthma and is seen in individuals occupationally exposed to grain dust. To better understand the relationship between BHR and pulmonary inflammation after grain dust exposure, we carried out an inhalation challenge to corn dust extract (CDE) on seven subjects with BHR [a 20% or greater decrease in forced expiratory volume in 1 s (FEV(1)) compared with diluent FEV(1) with a cumulative dose of histamine </=47.3 breath units] and compared their physiological and inflammatory responses with those of seven matched control subjects. BHR subjects were exposed to nebulized CDE (target dose of 0.16 microg/kg endotoxin) as tolerated; matched controls received equal amounts of CDE. Subjects with BHR complained of chest tightness and dyspnea within the 2 h after inhalation of CDE significantly more frequently than controls. Similarly, subjects with BHR developed significantly greater percent declines in FEV(1) at time points up to 4 h after exposure to CDE. Significant increases in total cells, neutrophils, tumor necrosis factor-alpha, interleukin-6, and interleukin-8 were detected in bronchoalveolar lavage fluid 4 h after inhalation of CDE in all subjects, but no differences were detected between the control and BHR groups. These results suggest that, although subjects with BHR develop a more precipitous decline in FEV(1) after exposure to CDE, the inflammatory response to CDE is similar in subjects with and without BHR.