Inhalation Of Endotoxin Research Articles

LIPOPOLYSACCHARIDE-ENHANCED, TOLL-LIKE RECEPTOR 4-DEPENDENT, T HELPER CELL TYPE 2 RESPONSES TO INHALED ANTIGEN

Eisenbarth SC, Piggott DA, Huleatt JW, et al. J Exp Med. 2002;196:1645–1651To evaluate the dose-dependent effects of lipopolysaccharide (LPS) (endotoxin) inhalation and LPS-induced activation of toll-like receptor 4 (TLR4) on the generation of T helper (Th) cell type 2-dependent allergic inflammatory responses to an inhaled antigen, ovalbumin (OVA).Wild-type or TLR4-deficient, 6- to 10-week-old, female mice were studied.Mice were sensitized with intranasal exposure to LPS-depleted OVA or OVA with either a low (0.1 μg) or high (100 μg) dose of LPS. After intranasal OVA challenge, pulmonary inflammatory responses were assessed through enumerating bronchoalveolar lavage cells, performing histopathologic analyses, measuring OVA-dependent cytokine production by lung-draining lymph node cells, and determining OVA-specific serum antibody levels. Dendritic cell responses to OVA with LPS were evaluated in cytokine production, activation marker expression, and cell migration studies.After antigen challenge, mice sensitized to OVA with low-dose LPS exhibited a Th2-associated response, with pulmonary eosinophilia, airway mucus secretion, Th2 cytokine (interleukin-5 and -13) production by lymph node cells, and production of high levels of OVA-specific immunoglobulin E and immunoglobulin G1. In contrast, mice sensitized to OVA with high-dose LPS developed a Th1-associated response, with a predominance of neutrophils, no airway mucus secretion, Th1 cytokine (interferon-γ) production by lymph node cells, and production of high levels of OVA-specific immunoglobulin G2a. No pulmonary inflammatory responses were observed with mice sensitized to LPS-depleted OVA. OVA sensitization of TLR4-deficient mice with either low- or high-dose LPS failed to generate inflammatory responses. However, treatment with tumor necrosis factor, which is secreted by LPS-stimulated dendritic cells, compensated for deficient dendritic cell activation, restoring the responses of TLR4-deficient mice to OVA with either low- or high-dose LPS.The authors concluded that inhalation of low doses of LPS with OVA antigen was necessary to induce allergic or Th2-dependent responses in the lung, whereas inhalation of high doses of LPS with antigen induced nonallergic or Th1-dependent responses. The LPS-mediated effects on allergic sensitization were dependent on signaling through TLR4 on dendritic cells.The effects of endotoxin exposure on the development of atopy and asthma are seemingly paradoxical. Although studies show that exposure to endotoxin early in life inhibits the development of asthma and atopic disease, other studies demonstrate adverse effects of endotoxin on airway function. Although endotoxin is ubiquitous in children’s environments, the exposure level can vary and may be the factor influencing the development of atopy. For example, this dosage effect may help explain the protection from atopy associated with growing up on a farm, where endotoxin exposure is excessive. The results of this study are an intriguing advance toward understanding the basis for these conflicting data, suggesting a mechanism through which the dose of endotoxin present during aeroallergen exposure could influence the incidence of allergic sensitization.

LIPOPOLYSACCHARIDE-ENHANCED, TOLL-LIKE RECEPTOR 4-DEPENDENT, T HELPER CELL TYPE 2 RESPONSES TO INHALED ANTIGEN

Eisenbarth SC, Piggott DA, Huleatt JW, et al. J Exp Med . 2002;196:1645–1651 To evaluate the dose-dependent effects of lipopolysaccharide (LPS) (endotoxin) inhalation and LPS-induced activation of toll-like receptor 4 (TLR4) on the generation of T helper (Th) cell type 2-dependent allergic inflammatory responses to an inhaled antigen, ovalbumin (OVA). Wild-type or TLR4-deficient, 6- to 10-week-old, female mice were studied. Mice were sensitized with intranasal exposure to LPS-depleted OVA or OVA with either a low (0.1 μg) or high (100 μg) dose of LPS. After intranasal OVA challenge, pulmonary inflammatory responses …

Enhanced Pulmonary Inflammatory Response to Inhaled Endotoxin in Pregnant Rats

Evidence suggests that pregnant animals are more sensitive than nonpregnant animals to the systemic administration of endotoxin. Studies were undertaken to assess whether an enhanced sensitivity of the pulmonary system to aerosolized endotoxin might exist during pregnancy. Pregnant Sprague-Dawley female rats (17 d of gestation) or age-matched virgin female rats were exposed to air or endotoxin (lipopolysaccharide) by inhalation for 3 h. At 18 h following exposure to endotoxin, lactate dehydrogenase activity levels in bronchoalveolar lavage (BAL) fluid samples from pregnant rats were 1.5-fold greater than those from endotoxin-exposed virgin rats. BAL polymorphonuclear leukocyte (PMN) numbers were also approximately twofold greater in pregnant rats than in virgins following the inhalation of endotoxin. The increases in BAL PMNs in pregnant rats following endotoxin exposure were observed just following exposure to endotoxin as well as at 18 h following exposure. These results indicate that an increased pulmonary inflammatory response to inhaled endotoxin occurs during pregnancy in rats. Additional findings suggest that these pregnancy-linked pulmonary responses to endotoxin cannot be explained by the following potential mechanisms: changes in the inhaled dose of endotoxin, or alterations in the responsiveness of alveolar macrophages to endotoxin. To our knowledge this is the first study that has evaluated pulmonary responses to inhaled endotoxin during pregnancy. Our finding that pregnancy is associated with an increased lung inflammatory response to aerosolized endotoxin raises the possibility that there may be a generalized enhancement of pulmonary responses to inhaled toxic agents during pregnancy.

Cellulosic building insulation versus mineral wool, fiberglass or perlite: installer's exposure by inhalation of fibers, dust, endotoxin and fire-retardant additives.

A task-specific exposure matrix was designed for workers installing building insulation materials. A priori, a matrix element was defined by type of task (installer or helper), type of work area (attic spaces or wall cavities) and type of insulation material (slabs from mineral wool, fiberglass or flax; loose-fill cellulosic material or perlite). In the laboratory a mock-up (full scale) of a one-family house was used for simulated installation of insulation materials (four replicates per matrix element). Personal exposure to dust and fibers was measured. The dust was analyzed for content of endotoxin and some trace elements (boron and aluminum) from fire-retardant or mold-resistant additives. Fibers were characterized as WHO fibers or non-WHO fibers. In support of the exposure matrix, the dustiness of all the materials was measured in a rotating drum tester. For installers in attic spaces, risk of exposure was low for inhalation of dust and WHO fibers from slab materials of mineral wool or fiberglass. Slab materials from flax may cause high risk of exposure to endotoxin. The risk of exposure by inhalation of dust from loose-fill materials was high for installers in attic spaces and for some of the materials risk of exposure was high for boron and aluminum. Exposure by inhalation of cellulosic WHO fibers was high but little is known about the health effects and a risk assessment is not possible. For the insulation of walls, the risk of installers' exposure by inhalation of dust and fibers was low for the slab materials, while a high risk was observed for loose-fill materials. The exposure to WHO fibers was positively correlated to the dust exposure. A dust level of 6.1 mg/m3 was shown to be useful as a proxy for screening exposure to WHO fibers in excess of 10(6) fibers/m3. In the rotating drum, slabs of insulation material from mineral wool or fiberglass were tested as not dusty. Cellulosic loose-fill materials were tested as very dusty, and perlite proved to be extremely dusty.

Effect of inhaled endotoxin on airway and circulating inflammatory cell phagocytosis and CD11b expression in atopic asthmatic subjects

Background: In a cohort of 8 normal and 10 allergic asthmatic volunteers, we previously reported that inhalation of 5 μg of endotoxin (LPS) induced airway inflammation that correlated with CD14 expression that was, in turn, correlated with eosinophil numbers in the airway. Macrophage and neutrophil functions have been reported to be modified by endotoxin in vitro and in vivo, and response to endotoxin is mediated largely by airway phagocytes and related to allergic inflammation. Objective: We sought to examine functional and cell-surface phenotype changes in phagocytes recovered from atopic asthmatic subjects after endotoxin challenge. Methods: Sputum and peripheral blood from 10 allergic asthmatic subjects was recovered after saline and LPS challenge. Assessment of phagocytosis and cell-surface phenotype (CD11b, CD14, and CD64) was performed on phagocytes obtained from sputum (n = 7) and blood samples (n = 10). Results: Phagocytosis of blood and sputum phagocytes was blunted after LPS challenge in a fashion that correlated with the increase in airway neutrophils after LPS challenge. Cell-surface expression of CD14 (membrane-bound CD14) was increased in sputum cells, whereas CD11b was decreased in sputum and circulating phagocytes. Baseline expression of CD11b in blood correlated with the magnitude of the neutrophil response after LPS inhalation, as well as (inversely) with baseline airway eosinophil levels. Conclusions: Inhalation of endotoxin at levels adequate to induce a neutrophil influx to the airways (but not systemic symptoms) results in decreased phagocytosis in both airway and circulating cells and modifies CD11b expression in a way that implicates its involvement in phagocyte responsiveness to inhaled LPS. (J Allergy Clin Immunol 2003;112:353-61.)

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.

Inhaled endotoxin and organic dust particulates have synergistic proinflammatory effects in equine heaves (organic dust-induced asthma).

Equine heaves is a naturally occurring organic dust-induced asthma characterized by airway neutrophilia, mucus hypersecretion and obstructive lung dysfunction. However, the relative role of different dust components in disease severity remains unclear. This study investigated the relative contribution of inhaled endotoxin and organic dust particulates (mainly mould spores) in inducing heaves in heaves-susceptible horses. Control and heaves-susceptible horses received inhalation challenges with hay dust suspension (HDS) before and after lipopolysaccharide (LPS) depletion. Heaves-susceptible horses also received inhalation challenge with HDS particulates with and without the addition of LPS and were housed in two separate dusty environments during which mould and endotoxin exposure was measured. The airway inflammatory and functional response to each challenge was measured. Depletion of endotoxin from HDS attenuated the airway neutrophilia and abrogated the airway dysfunction induced in heaves horses by inhaled HDS. The airway response was re-established by adding back LPS to the depleted HDS, confirming that the attenuation in airway response was due specifically to endotoxin depletion. Interestingly, the magnitude of alteration in airway response following endotoxin depletion and add-back was greater than that which could be attributed solely to endotoxin per se, indicating that the LPS activity was enhanced by the other dust components. Consistent with this possibility, washed particulates harvested from HDS enhanced the airway response to inhaled LPS in heaves horses. Heaves horses given two different hay/straw challenges had a significantly different severity of airway inflammation and dysfunction, despite airborne dust and endotoxin concentrations in the horses' breathing zones being similar. Although inhaled endotoxin appears not to be the only determinant of disease severity in heaves, it does contribute significantly to the induction of airway inflammation and dysfunction. This contribution is largely via the synergistic action of inhaled endotoxin and organic dust particulates, although other soluble dust components also contribute to a lesser degree.

Dust mite allergens: mitigation and control.

In recent years, greater attention has been given to the role of indoor allergens as a cause of sensitization and allergic respiratory diseases. Although indoor allergen control measures to reduce symptoms in individuals allergic to mites have produced controversial results, environmental allergen avoidance is today one of the four primary goals of asthma management recommended in several guidelines of asthma treatment. Exposure to high indoor aeroallergen levels, especially to house dust mite allergens, is an important environmental risk factor for allergic sensitization and the subsequent development and exacerbation of asthma. Therefore, effective aeroallergen avoidance is of use to prevent and treat allergic diseases. Although endotoxin exposure may be protective in early life, it has been demonstrated that the inhalation of endotoxin may exacerbate asthma in house dust mite sensitized patients. Mite-allergic asthmatic patients should be aware of the dangerous combination of mite allergen exposure associated with high endotoxin levels in house dust. These two immunologically active substances have been associated with severe asthma and seasonal exacerbation of symptoms. Effective house dust mite allergen avoidance will never be achieved using a single control measure; various methods are required to affect the multiple factors that facilitate high indoor allergen levels. Education of the patients and their families is also an important component of environmental control strategies.

ENDOTOXIN POTENTIATES OZONE-INDUCED PULMONARY CHEMOKINE AND INFLAMMATORY RESPONSES

Urban air consists of a combination of environmental pollutants. Recent studies have suggested that normally innocuous doses of a particular pollutant may be rendered more toxic to the lung if primed by earlier events. Pulmonary inflammation has been observed in humans and in many animal species after endotoxin and ozone exposures. The present study was designed to test the hypothesis that inhalation of low levels of endotoxin following ozone exposure will potentiate ozone-induced lung injury. We exposed 8-week-old C57BL/6J mice to 1 ppm ozone for 24 hours; inhalation of low-dose endotoxin (37.5 EU) for 10 minutes; or 1 ppm ozone immediately followed by endotoxin inhalation (37.5 EU). The mice were examined 4 or 24 hours post exposure. After 24 hours of recovery, significant increases were measured in bronchoalveolar lavage (BAL) fluid levels of protein and lavageable polymorphonuclear neutrophils (PMNs) after coexposure to ozone followed immediately by endotoxin inhalation as compared to exposures individually. Messages encoding macrophage inflammatory protein (MIP)-1 β, MIP-1 α, MIP-2, monocyte chemoattractant protein (MCP)-1, interleukin (IL)-1 α, IL-1 β, IL-1Ra, IL-6, and Macrophage Migration Inhibitory Factor (MIF) were significantly elevated 24 hours post ozone followed by endotoxin as compared to exposure to ozone or endotoxin individually. These results demonstrate that preexposure to ozone, which primarily attacks the epithelium, can cause sensitization to a secondary stimulus through a mechanism that culminates in a greater and prolonged onset of inflammatory cell recruitment, pulmonary edema, and increased expression of chemokine and cytokine messages.

MCP-1 synthesis by diisocyanate antigen stimulated PBMCs is a more sensitive in vitro assay for diisocyanate asthma than specific antibodies

MCP-1 synthesis by diisocyanate antigen stimulated PBMCs is a more sensitive in vitro assay for diisocyanate asthma than specific antibodies

Human models of innate immunity: local and systemic inflammatory responses

We review human studies where different body sites (e.g. systemic--intravenous and local--skin or lung) are exposed to small amounts of bacterial components as a means to study innate immunity in vivo. Intravenous endotoxin administration is widely used to assess systemic inflammatory responses, and these have many similarities to those seen in early sepsis. While blood levels of cytokines, activated inflammatory cells, and stress hormones rise acutely, the alveolar space remains relatively protected from these inflammatory responses. Skin blister windows provide a means to study local neutrophil exudation without systemic inflammatory responses, and has been used to characterize defects in neutrophil transmigration. Recently, skin blister windows have been adapted to study phagocytic cell function in response to bacterial antigens in patients with cirrhosis. Inhalation of endotoxin leads to pulmonary inflammation with increases in broncho-alveolar lavage neutrophils and cytokines and mild systemic responses. Whole lung exposure to endotoxin provides a means to study the pathogenesis of occupational lung disease. These three models are important methods to study innate immune responses and their regulatory mechanisms in normal and diseased states.

Severe asthma: definition and mechanisms.

Severe asthma: definition and mechanisms.

Inhaled endotoxin, a risk for airway disease in some people

Despite the tremendous inter-individual variability in the response to inhaled toxins, we simply do not understand why certain people develop disease when challenged with environmental agents and others remain healthy. To address this concern, we investigated whether the toll-4 (TLR4) gene, that has been shown to affect lipopolysaccharide (LPS) responsiveness in mice, underlies the variability in airway responsiveness to inhaled LPS in humans. Here we show that common, co-segregating missense mutations (Asp299Gly and Thr399Ile) in the extracellular domain of the TLR4 receptor are associated with a significantly blunted response to inhaled LPS in 83 humans. Transfection of THP-1 cells demonstrates that the Asp299Gly mutation (but not the Thr399Ile mutation) interrupts TLR4-mediated LPS signaling. Moreover, the wild type allele of TLR4 rescues the LPS hyporesponsive phenotype in either primary airway epithelial cells or alveolar macrophages obtained from individuals with the TLR4 mutations. Our findings provide the first genetic evidence that common mutations in TLR4 are associated with differences in LPS responsiveness in humans, and demonstrate that gene sequence changes can alter the ability of the host to respond to environmental stress.

The inflammatory response in humans after inhalation of bacterial endotoxin: a review.

There is increasing evidence that diseases caused by organic dusts are mainly of an inflammatory nature. Among the many agents present in organic dusts, bacterial endotoxin is a major candidate for the inflammatory reaction. The purpose of this paper was to review the inflammatory response in humans after inhalation of bacterial endotoxin (lipopolysaccharide, LPS) in order to improve the understanding of symptoms and reactions found among persons exposed to endotoxin-containing organic dusts. It has been reported that inhalation of LPS causes changes in forced expiratory volume in one second (FEV1), and forced vital capacity (FVC). At the alveolar level, inhalation of LPS can induce changes in the diffusion capacity. Activation and migration of neutrophils are major effects of acute LPS inhalation. Changes in mediators of inflammation, such as eosinophilic cationic protein (ECP), myeloperoxidase (MPO), interleukin-8 (IL-8), IL-1beta, tumor necrosis factor alpha (TNFalpha) and C-reactive protein (CRP) in the airways and/or blood, have also been found. Inhalation of 30-40 microg LPS seems to be a threshold level for inducing clinical symptoms and lung function changes in healthy subjects. The threshold dose for inducing changes in blood neutrophils may be less than 0.5 microg LPS. In conclusion, available data regarding the responses to LPS inhalation challenges demonstrate a local and a systemic inflammatory response at lower doses of LPS, while higher inhaled doses are required to elicit significant clinical and lung function responses. Future inhalation studies on LPS need to focus on relevant diagnostic tools for the inflammatory reaction among persons exposed to endotoxin-containing organic dusts and to evaluate whether the large variation between individuals in the response to organic dusts or endotoxin could be due to differences in the molecular mechanisms responsible for the toxicity of the agent.

CD14-dependent airway neutrophil response to inhaled LPS: Role of atopy

Background: Inhaled endotoxin (LPS) is associated with airway neutrophilic (PMN) inflammation in both asthmatic and control subjects, with asthmatic subjects demonstrating possibly higher sensitivity. CD14 is the principal receptor mediating LPS responses in vivo. It is unknown whether constitutive CD14 can predict the magnitude of the PMN response after LPS inhalation and whether atopy plays a role in this response. Objective: We sought to examine associations between constitutive airway CD14 expression and LPS-induced PMNs after 5 μg of LPS inhalation and to examine associations between markers of atopy (eosinophils and eosinophil cationic protein) and CD14 expression and LPS-induced PMNs. Methods: Ten atopic asthmatic subjects and 8 healthy control subjects inhaled 0.9% saline and LPS (Escherichia coli 026:B6, 5 μg) separated by 3 weeks. Induced sputum was collected at 24 hours before and 6 hours after inhalation. Induced sputum was analyzed for total and differential cell counts and soluble markers (soluble [s]CD14, eosinophil cationic protein, IL8, and total protein). Flow cytometry was used to analyze membrane-bound CD14 expression. Results: Significant associations were found between the LPS-induced PMN response (PMNs per milligram of sputum) and both constitutive sCD14 (R = 0.7, P = .005) and membrane-bound CD14 (R = 0.9, P = .01). Asthmatic subjects demonstrated significantly higher levels of constitutive sCD14 compared with control subjects, and baseline eosinophils were significantly associated with baseline sCD14 (R = 0.7, P = .01) and LPS-induced PMNs (R = 0.6, P = .03). Conclusion: Constitutive airway CD14 expression can predict the magnitude of the PMN response after inhaled LPS. Atopy appears to play a role in the level of CD14 expression and may contribute to LPS sensitivity in asthmatic subjects. (J Allergy Clin Immunol 2001;107:31-5.)

Systemic and local airways inflammatory response to endotoxin

Endotoxin can be detected in house dust. Numerous studies have revealed that endotoxin exposure is a risk factor in increasing airway obstructive manifestations, both in occupational and domestic environments. In humans, inhalation of pure endotoxin induces systemic symptoms and a change in bronchial non-specific responsiveness, related with changes in blood and sputum inflammatory markers. However, some recent work suggests that, prior to airway disease development, endotoxin may have an atopy-protective effect. In particular, indoor endotoxin exposure in early life may protect against allergen sensitisation by enhancing type-1 immunity. Finally, since large variations between human immune responses to endotoxin have been reported, genetic mutations could alter the mechanisms of endotoxin recognition and contribute to the risk of atopy.

Toxicology of ultrafine particles:in vivostudies

Ultrafine particles (less than 100 nm in diameter) are encountered in ambient air and at the workplace. Normal background levels in the urban atmosphere for ultrafine particles are in the range 1–4 × 10 4 cm −3 ; however, their mass concentration is normally not greater than 2 μg m −3 . At the workplace, ultrafine particles occur regularly in metal fumes and polymer fumes, both of which can induce acute inflammatory responses in the lung upon inhalation. Although ultrafine particles occurring at the workplace are not representative, and, therefore, are not relevant for urban atmospheric particles, their use in toxicological studies can give valuable information on principles of the toxicity of ultrafine particles. Studies in rats using ultrafine polymer fumes of polytetrafluoroethylene (PTFE) (count median diameter ca . 18 nm) showed that (i) they induced very high pulmonary toxicity and lethality in rats after 15 min of inhalation at 50 μg m −3 ; (ii) ageing of PTFE fumes resulted in agglomeration to larger particles and loss of toxicity; (iii) repeated pre–exposure for very short periods protected against the toxic and lethal effects of a subsequent 15 min exposure; (iv) rapid translocation of PTFE particles occurred to epithelial, interstitial and endothelial sites. Since one characteristic of urban ultrafine particles is their carbonaceous nature, exposure of rats to laboratory–generated ultrafine carbonaceous (elemental, and organic, carbon) particles was carried out at a concentration of ca . 100 μg m −3 for 6 h. Modulating factors of responses were prior low–dose inhalation of endotoxin in order to mimic early respiratory tract infections, old age (22–month old rats versus 10–week old rats) and ozone co–exposure. Analysis of results showed that (i) ultrafine carbon particles can induce slight inflammatory responses; (ii) LPS priming and ozone co–exposure increase the responses to ultrafine carbon; (iii) the aged lung is at increased risk for ultrafine particle–induced oxidative stress. Other studies with ultrafine and fine TiO 2 showed that the same mass dose of ultrafine particles has a significantly greater inflammatory potential than fine particles. The increased surface area of ultrafine particles is apparently a most important determinant for their greater biological activity. In addition, the propensity of ultrafine particles to translocate may result in systemic distribution to extrapulmonary tissues.

Effect of anti-asthmatic drugs on the response to inhaled endotoxin

Endotoxin is a pro-inflammatory agent contaminating the dust that has been associated with the risk to develop pulmonary diseases. There is no data on the protective efficacy of anti-asthmatic drugs on the response induced by inhaled endotoxin in human. Twelve mildly asthmatic subjects were submitted weekly to bronchial challenge tests with 20 microg endotoxin. The response was evaluated by the changes in FEV1, blood cells count, neutrophils activation (measured with the luminol-enhanced chemiluminescence) and blood concentration in the acute phase proteins, C-reactive protein (CRP) and haptoglobin. In a double-blind randomized cross-over placebo-controlled design, a single dose each of 500 microg beclomethasone dipropionate, 200 microg salbutamol, and 50 microg salmeterol were administered 30 minutes before the endotoxin challenge test. The 20-microg endotoxin challenge test induced a significant decrease in FEV1 and luminol-enhanced chemiluminescence (P < .001 and <.05, respectively). There was an increase in the blood neutrophils count (P < .05), in CRP (P < .02) and in haptoglobin (P < .03) concentrations. Pretreatment with beclomethasone dipropionate did not have any significant effect on the response to inhaled endotoxin. Salbutamol and salmeterol completely prevent the FEV1 decline due to their potent bronchodilatation activity. Salmeterol and salbutamol did not have any significant effect on the blood inflammation induced by endotoxin inhalation. The bronchodilating properties of beta2-agonists prevent the lung function response to inhaled endotoxin. When given in a single dose, an inhaled corticosteroid does not have protective activity on the endotoxin-induced blood inflammation.

Delayed neutrophil elastase inhibition prevents subsequent progression of acute lung injury induced by endotoxin inhalation in hamsters.

To define the role of neutrophil elastase (NE) in the progression of acute lung injury (ALI), we examined the effects of post-treatment with a specific NE inhibitor, sivelestat sodium hydrate (sivelestat), on ALI induced by endotoxin (ET) inhalation in hamsters. Inhalation of ET (300 microg/ml, 30 min) in conscious hamsters increased inflammatory cell count, protein concentration, and hemorrhage in bronchoalveolar lavage fluid (BALF) that peaked 24 h after ET inhalation. These changes were significant 2 h after ET inhalation and paralleled the increase in NE activity in BALF. When intravenously infused from 2 to 24 h post-ET inhalation, sivelestat (0.03 to 3 mg/kg/h) dose-dependently attenuated changes in these BALF parameters at 24 h post-ET inhalation in a manner dependent on the inhibition of NE activity in BALF. Histopathological analysis also indicated that sivelestat prevented the progression of lung inflammation such as alveolar neutrophil infiltration and hemorrhage. In contrast, dexamethasone (3 mg/kg, intravenously) was not effective in this model when administered 2 h after ET inhalation, although it was highly effective when applied before ET. We conclude that delayed inhibition of NE activity with sivelestat prevents subsequent progression of ALI in hamsters after ET inhalation. Thus NE may play an important role in the progression of ALI.

Airborne endotoxin exposure and the development of airway antigen-specific allergic responses.

Repeated exposure of aerosolized antigen via respiratory tract can induce immunoglobulin (Ig) E isotype-specific tolerance to this antigen. However, the atopic individuals often produce a higher titre of IgE in response to airborne environmental allergens. The mechanisms of this differential regulation of airway allergen-specific immune responses are not fully understood. This study investigated the role of airborne endotoxin on the initiation of antigen-specific airway allergic responses. ELISA methods for detection of isotypes of antigen-specific antibodies and competitive reverse transcription polymerase chain reaction for detection mRNA of cytokines were used. In addition, Liu stain method was used to analyse the amounts of eosinophils in bronchoalveolar lavage fluid. Mice pre-exposed with airborne endotoxin mounted significantly higher amounts of OVA-specific IgE antibody responses to inhaled OVA than those OVA-only sensitized mice. Inhaled endotoxin could downregulate repeated airway antigen exposure-induced IgE isotype-specific tolerance and increase antigen-induced lung eosinophils infiltration. These data show that airborne endotoxin exposure could potentiate allergen-specific airway inflammation. The results should have potential implications for understanding the development of allergen-induced airway allergic responses.