Healthy subjects express differences in clinical responses to inhaled lipopolysaccharide that are related with inflammation and with atopy

Effects of Lipopolysaccharide-Binding Protein (LBP) Single Nucleotide Polymorphism (SNP) in Infections, Inflammatory Diseases, Metabolic Disorders and Cancers

Inflammation, which is induced by the immune response, is recognized as the driving factor in many diseases, including infections and inflammatory diseases, metabolic disorders and cancers. Genetic variations in pivotal genes associated with the immune response, particularly single nucleotide polymorphisms (SNPs), may account for predisposition and clinical outcome of diseases. Lipopolysaccharide (LPS)-binding protein (LBP) functions as an enhancer of the host response to LPS, the main component of the outer membrane of gram-native bacteria. Given the crucial role of LBP in inflammation, we will review the impact of SNPs in the LBP gene on infections and inflammatory diseases, metabolic disorders and cancers.

Unravelling the mechanisms driving multimorbidity in COPD to develop holistic approaches to patient-centred care

COPD is a major cause of morbidity and mortality worldwide. Multimorbidity is common in COPD patients and a key modifiable factor, which requires timely identification and targeted holistic management strategies to improve outcomes and reduce the burden of disease.We discuss the use of integrative approaches, such as cluster analysis and network-based theory, to understand the common and novel pathobiological mechanisms underlying COPD and comorbid disease, which are likely to be key to informing new management strategies.Furthermore, we discuss the current understanding of mechanistic drivers to multimorbidity in COPD, including hypotheses such as multimorbidity as a result of shared common exposure to noxious stimuli (e.g. tobacco smoke), or as a consequence of loss of function following the development of pulmonary disease. In addition, we explore the links to pulmonary disease processes such as systemic overspill of pulmonary inflammation, immune cell priming within the inflamed COPD lung and targeted messengers such as extracellular vesicles as a result of local damage as a cause for multimorbidity in COPD.Finally, we focus on current and new management strategies which may target these underlying mechanisms, with the aim of holistic, patient-centred treatment rather than single disease management.

Human lipopolysaccharide models provide mechanistic and therapeutic insights into systemic and pulmonary inflammation

Inflammation is a key feature in the pathogenesis of sepsis and acute respiratory distress syndrome (ARDS). Sepsis and ARDS continue to be associated with high mortality. A key contributory factor is the rudimentary understanding of the early events in pulmonary and systemic inflammation in humans, which are difficult to study in clinical practice, as they precede the patient's presentation to medical services. Lipopolysaccharide (LPS), a constituent of the outer membrane of Gram-negative bacteria, is a trigger of inflammation and the dysregulated host response in sepsis. Human LPS models deliver a small quantity of LPS to healthy volunteers, triggering an inflammatory response and providing a window to study early inflammation in humans. This allows biological/mechanistic insights to be made and new therapeutic strategies to be tested in a controlled, reproducible environment from a defined point in time. We review the use of human LPS models, focussing on the underlying mechanistic insights that have been gained by studying the response to intravenous and pulmonary LPS challenge. We discuss variables that may influence the response to LPS before considering factors that should be considered when designing future human LPS studies.

Endotoxin and particulate matter emitted by livestock farms and respiratory health effects in neighboring residents

BACKGROUND

Living in livestock-dense areas has been associated with health effects, suggesting airborne exposures to livestock farm emissions to be relevant for public health. Livestock farm emissions involve complex mixtures of various gases and particles. Endotoxin, a pro-inflammatory agent of microbial origin, is a constituent of livestock farm emitted particulate matter (PM) that is potentially related to the observed health effects. Quantification of livestock associated endotoxin exposure at residential addresses in relation to health outcomes has not been performed earlier.

OBJECTIVES

We aimed to assess exposure-response relations for a range of respiratory endpoints and atopic sensitization in relation to livestock farm associated PM₁₀ and endotoxin levels.

METHODS

Self-reported respiratory symptoms of 12,117 persons participating in a population-based cross-sectional study were analyzed. For 2494 persons, data on lung function (spirometry) and serologically assessed atopic sensitization was additionally available. Annual-average PM₁₀ and endotoxin concentrations at home addresses were predicted by dispersion modelling and land-use regression (LUR) modelling. Exposure-response relations were analyzed with generalized additive models.

RESULTS

Health outcomes were generally more strongly associated with exposure to livestock farm emitted endotoxin compared to PM₁₀. An inverse association was observed for dispersion modelled exposure with atopic sensitization (endotoxin: p = .004, PM₁₀: p = .07) and asthma (endotoxin: p = .029, PM₁₀: p = .022). Prevalence of respiratory symptoms decreased with increasing endotoxin concentration at the lower range, while at the higher range prevalence increased with increasing concentration (p < .05). Associations between lung function parameters with exposure to PM₁₀ and endotoxin were not statistically significant (p > .05).

CONCLUSIONS

Exposure to livestock farm emitted particulate matter is associated with respiratory health effects and atopic sensitization in non-farming residents. Results indicate endotoxin to be a potentially plausible etiologic agent, suggesting non-infectious aspects of microbial emissions from livestock farms to be important with respect to public health.

Association of Elevated Serum GM-CSF, IFN-γ, IL-4, and TNF-α Concentration with Tobacco Smoke Induced Chronic Obstructive Pulmonary Disease in a South Indian Population

Background

Chronic obstructive pulmonary disease (COPD) is a devastating condition with limited pharmacotherapeutic options and exceptionally high public-health burden globally as well as in India. Tobacco smoking is the primary cause for COPD among men in India. Systemic inflammation involving altered regulation of cytokines controlling the host defense mechanism is a hallmark of COPD pathogenesis. However, biomarker discovery studies are limited among Indian COPD patients.

Methods

We assessed the serum concentrations [median (25th-75th percentile) pg/ml] of interleukin (IL)-2,4,6,8,10, granulocyte macrophage colony stimulating factor (GM-CSF), interferon gamma (IFN-γ), and tumor necrosis factor alpha (TNF-α) using a multiplexed immunoassay. Our study cohort consisted of 30 tobacco smokers with COPD (TS COPD) and 20 tobacco smokers without COPD (TS CONTROL) from South India. The study population was matched for age, sex (male), and tobacco consumption (pack-years). COPD was diagnosed according to the global initiative for chronic obstructive lung disease (GOLD) criteria of persistent airflow obstruction determined by the ratio of postbronchodilator forced expiratory volume in 1 second/forced vital capacity (FEV₁/FVC) of <0.7. A validated structured questionnaire-based survey [Burden of Obstructive Lung Disease (BOLD) study] and spirometry were performed during house to house visit of the field study. Statistical analysis included nonparametric (two-tailed) Mann-Whitney U and Spearman rank test, as appropriate (significance: p<0.05).

Results

Serum GM-CSF [69.64 (46.67, 97.48); 36.78 (30.07, 53.88), p=0.014], IFN-γ [51.06 (17.00, 84.86); 11.70 (3.18, 32.81), p=0.017], IL-4 [9.09 (1.8, 19.9); 1.8 (1.8, 4.46); p=0.024], and TNF-α [20.68 (5.5, 29.26); 3.5 (3.5, 4.5); p<0.001] concentrations (pg/ml) were increased in TS COPD subjects compared to TS CONTROL. A weak correlation between lung function parameters and cytokine concentrations was detected.

Conclusion

Our pilot study reveals GM-CSF, IFN-γ, IL-4, and TNF-α as plausible COPD susceptibility biomarkers within the investigated South Indian population that needs to be validated in a larger cohort.

The association between endotoxin in house dust with atopy and exercise-induced bronchospasm in children with asthma

BACKGROUND

Studies have reported protective and adverse associations between microbial exposure and childhood asthma. However, among children with asthma the relationships between endotoxin and exercise-induced bronchospasm (EIB) is less clear.

OBJECTIVE

We investigated the association between exposure to endotoxin in house dust with atopy and EIB in children with asthma.

METHODS

A cross-sectional survey was conducted among schoolchildren (aged 7-17 years) in the province of Saskatchewan, Canada. A subpopulation with asthma (n = 116) were identified from 335 participants using a validated asthma algorithm. We determined atopy among the asthma subpopulation by skin prick testing (SPT) while EIB was evaluated using exercise challenge testing (ECT). Dust samples were collected from mattress and play area floors, and endotoxin was measured in dust extracts. Logistic regression analyses were used to explore associations between endotoxin with atopy and EIB.

RESULTS

Among the 116 children with asthma, 99 completed SPT and all had completed ECT. Of these, 71/99 (71.7%) were atopic and 26/116 (22.4%) had EIB. Exposure to high play area endotoxin concentration [adjusted odds ratio (aOR) = 0.15, 95% CI: 0.03-0.85] and load (aOR = 0.11, 95% CI: 0.02-0.73) were negatively associated with atopy. In contrast, EIB was positively associated with high mattress endotoxin concentration (aOR = 6.01, 95% CI: 1.20-30.13).

CONCLUSION

Indoor microbial endotoxin exposure has varied associations with atopy and exercise-induced bronchospasm among children with asthma.

Long-term alterations in monocyte function after elective cardiac surgery

Optimal immunological homoeostasis determines the long-term recovery of patients in the postoperative period. The functional adaptability of monocytes plays a pivotal role in adjusting the host's response to an insult, immunostasis and long-term health, and may help to determine successful recovery. We undertook a longitudinal analysis of the functional adaptability of monocytes in 20 patients undergoing heart surgery with cardiopulmonary bypass, as a model of severe stress. Using each patient's pre-cardiopulmonary bypass data as a baseline, we investigated the characteristics of peripheral blood monocytes' functional plasticity in-vitro before elective bypass, and three months afterwards. Approximately 30% of subjects showed diminished monocyte plasticity, as demonstrated by decreased monocyte differentiation into dendritic cells three months after bypass. Diminished monocyte functional plasticity was related to over-production of macrophage colony-stimulating factor. Adding a neutralising antibody to macrophage colony-stimulating factor corrected the monocytes' differentiation defect. Finally, patients with reduced monocyte plasticity had significantly elevated serum C-reactive protein, with a concomitant increase in cytomegalovirus IgG antibody titres, suggestive of the acquisition of immuno-suppressive traits. Our study shows that severe surgical stress resulted in a lasting immunological defect in individuals who had seemingly recovered.

Chronic exposure to indoxacarb and pulmonary expression of toll-like receptor-9 in mice

AIM

Chronic exposure to indoxacarb and pulmonary expression of toll-like receptor 9 (TLR-9) in mice.

MATERIALS AND METHODS

In this study, healthy male Swiss albino mice (n=30) aging 8-10 weeks were used to evaluate TLR-9 expression in lungs of mice following indoxacarb exposure with and without lipopolysaccharide (LPS). Indoxacarb was administered orally dissolved in groundnut oil at 4 and 2 mg/kg/day for 90 days. On day 91, five animals from each group were challenged with LPS/normal saline solution at 80 µg/animal. The lung tissues were processed for real time and immunohistochemical studies.

RESULTS

LPS resulted increase in fold change m-RNA expression level of TLR-9 as compare to control, while indoxacarb (4 mg/kg) alone and in combination with LPS resulted 16.21-fold change and 29.4-fold change increase in expression of TLR-9 m-RNA, respectively, as compared to control. Similarly, indoxacarb (2 mg/kg) alone or in combination with LPS also altered TLR-9 expression. Further at protein level control group showed minimal expression of TLR-9 in lungs as compare to other groups, however, LPS group showed intense positive staining in bronchial epithelium as well as in alveolar septal cells. Indoxacarb at both doses individually showed strong immuno-positive reaction as compare to control, however when combined with LPS resulted intense staining in airway epithelium as compare to control.

CONCLUSION

Chronic oral administration of indoxacarb for 90 days (4 and 2 mg/kg) alters expression of TLR-9 at m-RNA and protein level and co-exposure with LPS exhibited synergistic effect.

Role of lipopolysaccharide (LPS) in asthma and other pulmonary conditions

Endotoxin significantly contaminates house dust and is an enhancing factor for asthma severity. Natural exposure to endotoxin in early life could influence immune development and protect from the risk of developing atopy. This article will focus on published data showing that home environmental contamination by endotoxin can participate in chronic airways diseases, in particular asthma.

Review: Endotoxin in the environment — exposure and effects

This review deals with endotoxin in the environment and its relation to disease among exposed persons. Data are presented on levels of endotoxin in different environments with maximum values of several μg/m3. The cellular reactions of importance for inhalation exposure effects are attachment to lipopolysaccharide binding protein, CD14 cell surface protein and TLR-4 receptors. The internalisation of endotoxin in macrophages and endothelial cells results in local production of inflammatory cytokines with subsequent migration of inflammatory cells into the lung and the penetration of cytokines into the blood. These events orchestrate clinical effects in terms of toxic pneumonitis, airways' inflammation and systemic symptoms. Inhalation challenges with pure endotoxin and field studies confirm the relation between these effects and exposure to dusts containing endotoxin. It is possible that polymorphism in genes determining endotoxin reactivity, particularly TLR-4, influences the risk for disease after environmental exposures. Some data suggest that the inflammation caused by inhaled endotoxin may decrease the risk for atopic sensitisation among children and lung cancer among workers exposed to organic dust. Additional research is needed to clarify the role of other environmental agents that are present in connection with endotoxin, particularly (1→3)-β-D-glucan from mold cell walls.

Systemic and bronchial inflammation following LPS inhalation in asthmatic and healthy subjects

Background: Inhaled endotoxin is known to induce airway inflammation, causing bronchial hyper-reactivity.

Objective: We characterized the response to lipopolysaccharide-inhalation by measuring exhaled nitric oxide (eNO) and inflammatory mediators.

Patients and Methods : A total of 43 adult volunteers (13 asthmatics, 30 healthy controls) inhaled stepwise LPS every 30 min up to a cumulative dose of 100 µg (2.5, 10.5, 42, 45 µg). After each provocation and up to 24 h later, FEV1 was determined; the procedure was stopped when FEV1 declined more than 12.5%. We measured eNO, leucocytes, eosinophils, polymorphonuclear neutrophils (PMNs), C-reactive protein (CrP), lipopolysaccharide binding protein (LBP), eosinophilic cationic protein (ECP), leucotriene B4 (LTB4), thromboxane B2 (TXB2), and body temperature.

Results: Initial eNO values were higher in asthmatics ( P < 0.01), but only increased in an asthmatic subgroup. Marked differences were observed in the systemic response to LPS inhalation. Significant increases were found for CrP, LBP, and PMNs. There was no correlation between FEV1 decrease and basal eNO levels.

Conclusions: Inhalation of endotoxin was followed by clinical and laboratory signs of systemic inflammation, with asthmatics responding to the challenge similar as healthy subjects. Bronchial eNO increased only temporarily in asthmatics.

School Endotoxin Exposure and Asthma Morbidity in Inner-city Children

BACKGROUND

Endotoxin exposure is associated with airway inflammation. Children spend 6 to 8 h/d in school, yet the effect of school-specific endotoxin exposure on asthma morbidity is not well understood.

METHODS

In this longitudinal cohort study, 248 students with asthma, from 38 inner-city schools, underwent baseline phenotyping and follow-up. Clinical outcomes were evaluated throughout the academic school year and linked to classroom-specific dust and air endotoxin levels as well as home dust endotoxin levels. The primary outcome was maximum asthma symptom-days per 2-week period.

RESULTS

Classrooms had higher settled dust endotoxin levels compared with homes (14.3 endotoxin unit/mg vs 11.3 endotoxin unit/mg; P = .02). Airborne endotoxin levels exceeding recommended occupational exposure limits for adults were recorded in 22.0% of classrooms. Classroom air endotoxin levels were independently associated with increased maximum symptom-days in children with nonatopic asthma, but not in those with atopic asthma (interaction P = .03). Adjusting for home exposures, classroom endotoxin exposure was independently associated with a dose-dependent increase in asthma symptom-days for children with nonatopic asthma (adjusted incidence rate ratio, 1.16 [95% CI, 1.03-1.31]; P = .02). In these subjects, maximum symptom-days increased by 1.3 days for each 14-day period when comparing students in classrooms with the lowest endotoxin levels compared with average measured levels.

CONCLUSIONS

Inner-city children with asthma are exposed to high levels of airborne endotoxin at school, resulting in increased asthma symptoms in children with nonatopic asthma. Mitigation of school-related exposures may represent a strategy to decrease asthma morbidity in this population.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01756391; URL: www.clinicaltrials.gov.

[Bacterial endotoxin as a trigger for eosinophilic asthma]

INTRODUCTION

Lipopolysaccharide is a component of the outer membrane of gram-negative bacteria. It plays an important role in asthma as an adjuvant to allergens in activating the airway epithelium.

CASE REPORT

Following treatment of a cutaneous mycosis by injection of endotoxin from Salmonella (Pyrogenalum), a 49-year-old non-smoking man developed an acute bronchitis followed by persistent cough, sometimes productive of sputum. Clinical examination was unremarkable. Lung function tests showed airway obstruction, FEV1 54% predicted, partly reversible with salbutamol, and exhaled NO was increased to 73.5 ppb. There was a moderate blood eosinophilia ranging from 540 to 890 per mm(3) (7.4 to 9.6%). Lung CT scan showed no parenchymal or bronchial abnormalities, and ENT examination showed nasal polyposis.

CONCLUSION

Besides its critical adjuvant role in the development of asthma when inhaled, this case suggests that endotoxin can also provoke asthma when administered systemically.

Lipopolysaccharide amplifies eosinophilic inflammation after segmental challenge with house dust mite in asthmatics

BACKGROUND

House dust contains mite allergens as well as bacterial products such as lipopolysaccharide (LPS). Asthma exacerbations are associated with the level of exposure to allergens and LPS. LPS can potentiate allergen effects in steroid-naïve patients. Long-acting β2-agonists (LABA) were shown to inhibit LPS-induced bronchial inflammation in healthy volunteers. The aim of this study was to assess the effect of LPS on the allergen-induced eosinophilic inflammation [primary endpoints: eosinophil counts and eosinophil cationic protein (ECP)] induced by bronchial instillation of house dust mite (HDM) in patients with asthma on maintenance treatment with inhaled corticosteroids (ICS).

METHODS

Thirty-two nonsmoking asthmatics with HDM allergy were treated with run-in medication (fluticasone propionate 100 μg bid) during 2 weeks before the study day. All patients underwent bronchial challenge with HDM, and half of them were randomized to receive additional LPS. Both groups were randomized to receive pretreatment with a single inhalation of 100 μg salmeterol 30 min before bronchial segmental challenge. Six hours later, bronchoalveolar lavage (BAL) was collected for leukocyte cell count, differentials, and cellular activation markers.

RESULTS

Challenge with HDM/LPS induced a significant increase in eosinophil cationic protein (P = 0.036) and a trend toward an increase in BALF eosinophils as compared to HDM challenge.

CONCLUSION

Lipopolysaccharide promotes eosinophilic airway inflammation in patients with asthma despite being on maintenance treatment with ICS.

Expression of calgranulin A/B heterodimer after acute inhalation of endotoxin: proteomic approach and validation

Background

The acute inhalation of endotoxin mimicks several aspects of the inflammation related to chronic obstructive pulmonary disease (COPD). The aim of the current study was to identify and to validate biomarkers of endotoxin-induced airways’ inflammation.

Methods

The cellular count in the induced-sputum, was measured before and after an inhalation of 20 mcg endotoxin, in 8 healthy volunteers. A proteomic analysis was applied to identify the more relevant proteins expression, before measurement by ELISA. The amplitude and the repeatability of the markers were evaluated among another population of 12 healthy subjects.

Results

There was a significant rise of viable cells (p <0.01), macrophages (p <0.05), and neutrophils (p <0.02) 24 hours after endotoxin inhalation, and of neutrophils (p <0.02) and lymphocytes (p <0.05) at 6 hours. Among the highest amplitude responses, the two dimensional electrophoretic separation shown proteolytic activity and overexpression of protein spots. By MALDI-TOF mass spectrometry, the last were identified as calgranulin A and B. The expression of the bioactive A/B heterodimeric complex was confirmed by ELISA both in the sputum (p <0.01) and at the blood level (p <0.01). The intra-subject repeatability of the sputum calgranulin A/B was highly significant (p <0.0001).

Conclusion

In healthy subjects, the inhalation of endotoxin induced expression of sputum calgranulin A/B that could be a biomarker of the endotoxin response/exposure.

Lipopolysaccharide inhibits Th2 lung inflammation induced by house dust mite allergens in mice

The complex biology of asthma compels the use of more relevant human allergens, such as house dust mite (HDM), to improve the translation of animal models into human asthma. LPS exposure is associated with aggravations of asthma, but the mechanisms remain unclear. Here, we studied the effects of increasing LPS doses on HDM-evoked allergic lung inflammation. To this end, mice were intranasally sensitized and challenged with HDM with or without increasing doses of LPS (0.001-10 μg). LPS dose-dependently inhibited HDM-induced eosinophil recruitment into the lungs and mucus production in the airways. LPS attenuated the production of Th2 cytokines (IL-4, IL-5, IL-10, and IL-13) in HDM-challenged lungs, while enhancing the HDM-induced release of IL-17, IL-33, IFN-γ, and TNF-α. The shift toward a Th1 inflammatory response was further illustrated by predominant neutrophilic lung inflammation after LPS administration at higher doses. LPS did not influence HDM-induced plasma IgE concentrations. Although LPS did not significantly affect the activation of coagulation or complement in HDM-challenged lungs, it reduced HDM-initiated endothelial cell activation. This study is the first to provide insights into the effects of LPS in an allergic lung inflammation model making use of a clinically relevant allergen without a systemic adjuvant, revealing that LPS dose-dependently inhibits HDM-induced pulmonary Th2 responses.

Time course of endotoxin-induced airways' inflammation in healthy subjects

Few data are available on the kinetic of the airways' inflammation induced by inhaled endotoxin in a given subject. The purpose of this study was to evaluate in healthy subjects the time-related endotoxin-induced airways' inflammation. The cells counts from the induced-sputum were evaluated before, 6 and 24 h, and 7 days after an exposure to 20 mcg inhaled endotoxin, in eight pre-selected volunteers. To avoid interference of the induced-sputum procedure on the response to endotoxin, each time-point was evaluated in randomized order at 2-weeks interval after three separate inhalations of endotoxin. A significant rise of the relative number of lymphocytes (p<0.05) and polymorphonuclear neutrophils (PMN; p<0.02) and of the absolute number of PMN (p<0.05) occurring at 6 h, followed by an increase of the absolute number of the total viable cells (p<0.01), macrophages (p<0.001), neutrophils (p<0.01), and lymphocytes (p<0.05) at 24 h after endotoxin inhalation. The inflammatory response recovered totally after 7 days. In human beings, the inhalation of endotoxin induced a transient airway inflammation after 6 h, peaked at 24 h and recovered after 7 days. When repeated endotoxin inhalations are used as a model of inflammation, a wash-out period of at least 7 days should be applied between each exposure in each subject.

Differential inflammatory response to inhaled lipopolysaccharide targeted either to the airways or the alveoli in man

Endotoxin (Lipopolysaccharide, LPS) is a potent inducer of inflammation and there is various LPS contamination in the environment, being a trigger of lung diseases and exacerbation. The objective of this study was to assess the time course of inflammation and the sensitivities of the airways and alveoli to targeted LPS inhalation in order to understand the role of LPS challenge in airway disease.

In healthy volunteers without any bronchial hyperresponsiveness we targeted sequentially 1, 5 and 20 µg LPS to the airways and 5 µg LPS to the alveoli using controlled aerosol bolus inhalation. Inflammatory parameters were assessed during a 72 h time period. LPS deposited in the airways induced dose dependent systemic responses with increases of blood neutrophils (peaking at 6 h), Interleukin-6 (peaking at 6 h), body temperature (peaking at 12 h), and CRP (peaking at 24 h). 5 µg LPS targeted to the alveoli caused significantly stronger effects compared to 5 µg airway LPS deposition. Local responses were studied by measuring lung function (FEV₁) and reactive oxygen production, assessed by hydrogen peroxide (H₂O₂) in fractionated exhaled breath condensate (EBC). FEV₁ showed a dose dependent decline, with lowest values at 12 h post LPS challenge. There was a significant 2-fold H₂O₂ induction in airway-EBC at 2 h post LPS inhalation. Alveolar LPS targeting resulted in the induction of very low levels of EBC-H₂O₂.

Targeting LPS to the alveoli leads to stronger systemic responses compared to airway LPS targeting. Targeted LPS inhalation may provide a novel model of airway inflammation for studying the role of LPS contamination of air pollution in lung diseases, exacerbation and anti-inflammatory drugs.

Disturbed cytokine production at the systemic level in difficult-to-control atopic asthma: evidence for raised interleukin-4 and decreased interferon-γ release following lipopolysaccharide stimulation

BACKGROUND

Disturbed cytokine production is thought to govern inflammation in asthma, which, in its turn, may lead to uncontrolled disease. The aim of this study was to assess the relationship between cytokine production from blood leucocytes and the level of asthma control.

METHODS

We compared the production of interleukin (IL)-4, IL-6, IL-10, interferon (IFN)-γ and tumour necrosis factor-α from peripheral blood leucocytes in non-atopic healthy subjects (n = 22), atopic non-asthmatics (n = 10), well-controlled asthmatics [Juniper asthma control questionnaire (ACQ) score <1.5; n = 20] and patients with uncontrolled asthma despite inhaled or oral corticoids (ACQ score ≥1.5; n = 20). Fifty microlitres of peripheral blood was incubated for 24 h with RPMIc, lipopolysaccharide (LPS; 1 ng/ml) or phytohaemagglutinin (1 μg/ml), and cytokines were measured by immunotrapping (ELISA).

RESULTS

Both controlled and uncontrolled asthmatics as well as atopic non-asthmatics spontaneously produced more IL-4 than non-atopic healthy subjects (p < 0.001). IL-4 production induced by LPS was significantly greater (p < 0.05) in both asthma groups compared to atopic non-asthmatics and non-atopic healthy subjects. By contrast, IFN-γ release induced by LPS was lower in uncontrolled asthmatics than in non-atopic healthy subjects (p < 0.05) and controlled asthmatics (p < 0.05). IL-10 release after LPS was greater in uncontrolled asthmatics than in atopic non-asthmatics (p < 0.05). No difference was observed regarding other cytokines.

CONCLUSION

Blood cells from patients with difficult-to-control atopic asthma display highly skewed Th2 cytokine release following LPS stimulation.

Inhalation of LPS induces inflammatory airway responses mimicking characteristics of chronic obstructive pulmonary disease

AIM

Inhalation of lipopolysaccharide (LPS) produces both systemic and pulmonary inflammatory responses. The aim of this study was to further characterize the response to LPS in order to develop a human model suitable for early testing of drug candidates developed for the treatment for chronic obstructive pulmonary disease (COPD).

MATERIALS

Blood and induced sputum were obtained 4, 24 and 48 h following inhalation of saline and LPS (5 and 50 μg). Blood was analysed for C-reactive protein (CRP), α(1)-antitrypsin and neutrophils/leucocytes, and sputum was analysed for biomarkers of neutrophil inflammation and remodelling activities, i.e. neutrophil elastase (NE) protein/activity and α(1)-antitrypsin. Levels of tumour necrosis factor-α (TNFα) were measured in both blood and sputum. Urine was collected 0-24 and 24-48 h postchallenge, and desmosine, a biomarker of elastin degradation, was measured.

RESULTS

Lipopolysaccharide inhalation induced dose-dependent flu-like symptoms and increases in plasma CRP and α(1)-antitrypsin as well as increases in blood neutrophil/leucocyte numbers. Furthermore, LPS produced increases in sputum TNFα and sputum NE activity. Urine levels of desmosine were unaffected by the LPS challenge. All subjects recovered 48 h postchallenge, and indices of inflammatory activity were significantly lower at this observation point cf 24 h postchallenge.

CONCLUSION

Inhalation of LPS in healthy volunteers can be used as a safe and stable model of neutrophil inflammation. Blood/plasma and sputum indices can be employed to monitor the response to LPS. We suggest that this model may be used for initial human studies of novel COPD-active drugs.

The role of oxidative stress and innate immunity in O(3) and endotoxin-induced human allergic airway disease

Ozone (O(3)) and endotoxin are common environmental contaminants that cause asthma exacerbation. These pollutants have similar phenotype response characteristics, including induction of neutrophilic inflammation, changes in airway macrophage immunophenotypes, and ability to enhance response to inhaled allergen. Evoked phenotyping studies of volunteers exposed to O(3) and endotoxin were used to identify the response characteristics of volunteers to these pollutants. New studies support the hypotheses that similar innate immune and oxidant processes modulate response to these agents. These include TLR4 and inflammasome-mediated signaling and cytokine production. Innate immune responses are also impacted by oxidative stress. It is likely that continued discovery of common molecular processes which modulate response to these pollutants will occur. Understanding the pathways that modulate response to pollutants will also allow for discovery of genetic and epigenetic factors that regulate response to these pollutants and determine risk of disease exacerbation. Additionally, defining the mechanisms of response will allow rational selection of interventions to examine. Interventions focused on inhibition of Toll-like receptor 4 and inflammasome represent promising new approaches to preventing pollutant-induced asthma exacerbations. Such interventions include specific inhibitors of innate immunity and antioxidant therapies designed to counter the effects of pollutants on cell signaling.

The CRP genotype, serum levels and lung function in men: the Caerphilly Prospective Study

Systemic CRP (C-reactive protein) has been associated with impaired lung function. A causal relationship would increase the value of CRP as both a diagnostic and therapeutic tool. We assessed the association between lung function parameters, circulating CRP and CRP polymorphisms using Mendelian randomization in efforts to attribute causality to known associations. Spirometric parameters of FEV1 (forced expiratory volume in 1 s) and FVC (forced vital capacity) were determined in 2173 men participating in the Caerphilly Prospective Study. Lung function measures on 1021 participants were available at follow-up (mean, 16.8 years later). Serum CRP levels were measured at baseline, and three CRP polymorphisms were analysed. Haplotype analysis was performed. Serum CRP levels at baseline were inversely associated with contemporaneous FEV1 and FVC as well as at follow-up (P<0.001) even after adjustment for conventional confounders. Serum CRP was associated with FEV1 decline (P=0.04). All three CRP polymorphisms (rs1800947, rs1130864 and rs1205) predicted serum CRP; however, there were no clear associations of the polymorphisms or haplotypes with lung function or with lung function decline. In conclusion, serum CRP was associated with lung function cross-sectionally; however, CRP polymorphisms were not associated with lung function or decline, suggesting that the CRP-lung function relationship is due to reverse causality, an unmeasured confounding factor or only has a modest causal effect.

Evaluation of inhaled carbon monoxide as an anti-inflammatory therapy in a nonhuman primate model of lung inflammation

Carbon monoxide (CO) confers anti-inflammatory protection in rodent models of lung injury when applied at low concentration. Translation of these findings to clinical therapies for pulmonary inflammation requires validation in higher mammals. We have evaluated the efficacy of inhaled CO in reducing LPS-induced lung inflammation in cynomolgus macaques. LPS inhalation resulted in profound neutrophil influx and moderate increases in airway lymphocytes, which returned to baseline levels within 2 wk following exposure. CO exposure (500 ppm, 6 h) following LPS inhalation decreased TNF-α release in bronchoalveolar lavage fluid but did not affect IL-6 or IL-8 release. Lower concentrations of CO (250 ppm, 6 h) did not reduce pulmonary neutrophilia. Pretreatment with budesonide, a currently used inhaled corticosteroid, decreased LPS-induced expression of TNF-α, IL-6, and IL-8, and reduced LPS-induced neutrophilia by ∼84%. In comparison, CO inhalation (500 ppm, for 6 h after LPS exposure) reduced neutrophilia by ∼67%. Thus, inhaled CO was nearly as efficacious as pretreatment with an inhaled corticosteroid at reducing airway neutrophil influx in cynomolgus macaques. However, the therapeutic efficacy of CO required relatively high doses (500 ppm) that resulted in high carboxyhemoglobin (COHb) levels (>30%). Lower CO concentrations (250 ppm), associated with anti-inflammatory protection in rodents, were ineffective in cynomolgus macaques and also yielded relatively high COHb levels. These studies highlight the complexity of interspecies variation of dose-response relationships of CO to COHb levels and to the anti-inflammatory functions of CO. The findings of this study warrant further investigations for assessing the therapeutic application of CO in nonhuman primate models of tissue injury and in human diseases. The study also suggests that akin to many new therapies in human diseases, the translation of CO therapy to human disease will require additional extensive and rigorous proof-of-concept studies in humans in the future.

Risk factors associated with allergic and non-allergic asthma in adolescents

INTRODUCTION

Risk factors for asthma have been investigated in a large number of studies in adults and children, with little progress in the primary and secondary prevention of asthma. The aim of this investigation was to investigate risk factors associated with allergic and non-allergic asthma in adolescents.

METHODS

In this study, 959 schoolchildren (13-14 years old) answered a questionnaire and performed exhaled nitric oxide (NO) measurements. All children (n = 238) with reported asthma, asthma-related symptoms and/or increased NO levels were invited to a clinical follow-up which included a physician evaluation and skin-prick testing.

RESULTS

Asthma was diagnosed in 96 adolescents, whereof half had allergic and half non-allergic asthma. Children with both allergic and non-allergic asthma had a significantly higher body mass index (BMI) (20.8 and 20.7 vs. 19.8 kg/m(2)) (p < 0.05) and a higher prevalence of parental asthma (30% and 32% vs. 16%) (p < 0.05). Early-life infection (otitis and croup) [adjusted odds ratio (OR) (95% confidence interval (CI)): 1.99 (1.02-3.88) and 2.80 (1.44-5.42), respectively], pets during the first year of life [2.17 (1.16-4.04)], window pane condensation [2.45 (1.11-5.40)] and unsatisfactory school cleaning [(2.50 (1.28-4.89)] was associated with non-allergic but not with allergic asthma.

CONCLUSION

This study indicates the importance of distinguishing between subtypes of asthma when assessing the effect of different risk factors. While the risk of both allergic and non-allergic asthma increased with increasing BMI, associations between early-life and current environmental exposure were primarily found in relation to non-allergic asthma.

Modeling human health risks of airborne endotoxin in homes during the winter and summer seasons

Endotoxin, a component of gram-negative bacterial cell walls, is a pro-inflammatory agent that induces local and systemic inflammatory responses in normal subjects which can contribute to the risk of developing asthma and chronic obstructive lung diseases. A probabilistic approach linking models of exposure, internal dosimetry, and health effects was carried out to quantitatively assess the potential inhalation risk of airborne endotoxin in homes during the winter and summer seasons. Combining empirical data and modeling results, we show that the half-maximum effect of the endotoxin dose (ED50) was estimated to be 707.9 (95% confidence interval (CI): 308.8-1287.0) endotoxin units (EU) for body temperature change, 481.8 (95% CI: 333.2-630.3) EU for elevation of neutrophils, and 1174.5 (95% CI: 816.0-1532.9) EU for elevation of the cytokine, interleukin-6. Our study also suggests that airborne endotoxin in homes may pose potential risks, and a higher risk for elevation of neutrophils and cytokine interleukin-6 appeared in winter season than in summer. Our study offers a risk-management framework for discussion of future studies of human respiratory exposure to airborne endotoxin.

[Role of indoor endotoxins in asthma symptoms]

INTRODUCTION

Endotoxin is a collective term designating a characteristic group of chemical constituents of the outer membrane of Gram negative bacteria, the lipopolysaccharides (LPS).

BACKGROUND

LPS provocation tests in healthy subjects (50 microg) induce asthma-like airflow obstruction with a neutrophilic inflammatory influx, similar to reactions observed in non-atopic asthma. Asthmatic subjects show the same reaction with smaller doses of LPS (20 microg), revealing higher sensitivity to LPS than normal subjects. Low levels (2 microg) of LPS do not induce either airflow obstruction or bronchial hyperreactivity. Among exposed workers, particularly in agriculture, endotoxin is the most significant component of the bioaerosol that is associated with airway disease. In clinical studies, exposure to LPS is associated with severe asthma. Conversely, epidemiological studies, in both urban and rural areas, assessing the relationship between exposure to LPS and asthma and asthma- related symptoms are inconsistent.

PERSPECTIVES

Longitudinal epidemiological studies, especially in farm children, may confirm the putative protective effects of LPS with respect to atopic asthma.

CONCLUSION

Exposure to indoor LPS is frequently associated with asthma and asthma-like symptoms in current studies. Their definitive role needs to be confirmed by birth cohort studies currently under way that should define the controversial protective effect of LPS with respect to atopic asthma in farming populations.

RAPID PULMONARY EXPRESSION OF ACUTE-PHASE REACTANTS AFTER LOCAL LIPOPOLYSACCHARIDE EXPOSURE IN MICE IS FOLLOWED BY AN INTERLEUKIN-6 MEDIATED SYSTEMIC ACUTE-PHASE RESPONSE

This study investigated local and systemic innate immune responses in lipopolysaccharide (LPS)-induced lung inflammation in mice. Intratracheal LPS exposure resulted in increased pulmonary mRNA expression for acute-phase reactants (APRs) alpha(1)-antitrypsin (alpha(1)-AT), alpha(1)-acid glycoprotein (AGP), and LPS-binding protein (LBP) from 4 hours post exposure. Although pulmonary serum amyloid P component (SAP) mRNA was not increased, systemic levels of SAP, AGP, and LBP were elevated from 24 hours post exposure. Systemic APRs increase was associated with hepatic mRNA expression. As in vivo neutralization of interleukin (IL)-6, but not tumor necrosis factor (TNF)-alpha, fully ablated hepatic APR mRNA expression, IL-6 may act as signaling molecule between lung and liver. In conclusion, pulmonary LPS exposure induced rapid APR expression in lung, which precedes IL-6-mediated systemic elevation of APRs associated with hepatic APRs expression.

The systemic and pulmonary LPS binding protein response to intratracheal lipopolysaccharide

LPS binding protein (LBP) is an acute-phase glycoprotein that facilitates LPS activation of immune cells through interactions with CD14 and Toll-like receptor 4. Initially, LBP production was thought to occur exclusively in the liver in response to stimulation with TNF-alpha, IL-1, and IL-6. More recently, it has been shown that type II pneumocytes are also capable of LBP production. Little is known, however, regarding the regulation and or distribution of this protein in response to localized intrapulmonary infection. We performed time-course experiments challenging C3H mice intratracheally with LPS (10 mug). In separate experiments, mice deficient in IL-6 were given the same dose of intratracheal LPS and euthanized 8 h later. Despite the intratracheal route of LPS administration, an increase in plasma LBP concentrations occurred earlier and was of greater magnitude than the increase observed in bronchoalveolar lavage fluid. Liver LBP mRNA increased to a greater extent than did lung LBP mRNA. Whereas the TNF-alpha response remained localized within the alveolar space, IL-6 was increased both locally and in plasma. Of several tissues analyzed, the lung was the greatest producer of IL-6 mRNA. Plasma LBP was significantly decreased in the IL-6-deficient mice compared with wild-type controls challenged with intratracheal LPS. We conclude that lung-derived IL-6 is an important mediator of hepatic LBP up-regulation. We speculate that the disruption of these lung-liver signaling pathways may be important to host response efforts to confine infection to the lung. If impaired, this may be one mechanism underlying the increased mortality observed in patients with liver disease who develop pneumonia.

Moldy environments and toxic pneumonitis

Exposure to organic dusts might cause an acute reaction with influenza like symptoms (toxic pneumonitis). Although it is well known that endotoxin, which is often present in organic dusts, may cause this reaction, there is no information about fungal cell wall agents as causative agents. The capacity of different fungal cell wall agents to induce an acute inflammation was evaluated in animal inhalation experiments. Guinea pigs were exposed to an aerosol of endotoxin, molds, and different fungal cell wall agents (FCWA) in a continuous flow exposure chamber, and the number of free lung cells was determined 24 h thereafter. Endotoxin caused a dose-dependent increase in the number of neutrophils and macrophages. None of the other agents tested caused a neutrophil response. The results suggest that toxic pneumonitis in environments with organic dusts is caused by the presence of inhaled endotoxin. Although no effect from FCWA was found, it is well known that this inhalation under chronic conditions will cause lung disease, particularly granulomatous pneumonitis.

Evaluation of oral corticosteroids and phosphodiesterase-4 inhibitor on the acute inflammation induced by inhaled lipopolysaccharide in human

BACKGROUND

Endotoxins are pro-inflammatory substances present in the environment. In man, inhalation of its purified derivative lipopolysaccharide (LPS) induces inflammation related to macrophages and neutrophils. Corticosteroids and phosphodiesterase (PDE)-4 inhibitors have inhibiting effects on macrophages and neutrophils, respectively. This study investigated the effect of prednisolone and of the PDE-4 inhibitor cilomilast on the LPS-induced acute inflammation.

METHODS

The study was a placebo-controlled, double-blind crossover design. On three occasions, at 2 weeks interval, 16 healthy subjects inhaled 50 microg LPS after a 6-day treatment with cilomilast (15 mg bd), prednisolone (10 mg bd) or placebo. For the assessment of the inflammatory response, induced sputum was obtained before inclusion and 6h post-LPS while blood samples were collected before, 6 and 24 h post-LPS.

RESULTS

Inhaled LPS induced an increase in sputum neutrophils (p<0.0001), logMMP-9 (p<0.05), logMMP-9/TIMP-1 (p<0.01) and logTNF-alpha (p<0.02). At the blood level there were significant rise in neutrophilia (p<0.001), E-selectin (p<0.02), C-reactive protein (CRP) (p<0.001) and LPS-binding protein (p<0.001). There was both a slight, but not significant, increase in body temperature and decrease in forced expiratory volume in 1 s (FEV(1)). Neither prednisolone nor cilomilast had protective effect on the LPS-induced airways' inflammation. The LPS-induced CRP acute-phase protein of inflammation (0.58+/-0.13 and 3.52+/-0.41 mg/dL, before and after LPS, respectively) was significantly inhibited by a pre-treatment with prednisolone (1.39+/-0.32 mg/dL, p<0.01) and attenuated (2.65+/-0.30 mg/dL, p=0.09) with cilomilast.

CONCLUSION

In healthy subjects, while the LPS-induced airways' inflammation was not modified either by oral prednisolone or by PDE-4 inhibitor cilomilast (at actual dosage), the LPS-induced acute phase of blood inflammation was reduced by prednisolone.

Occurrence of antibiotic-resistant bacteria and endotoxin associated with the land application of biosolids

The purpose of this study was to determine the prevalence of antibiotic-resistant bacteria and endotoxin in soil after land application of biosolids. Soil was collected over a 15 month period following land application of biosolids, and antibiotic resistance was ascertained using clinically relevant antibiotic concentrations. Ampicillin, cephalothin, ciprofloxacin, and tetracycline resistance were all monitored separately for any changes throughout the 15 month period. Endotoxin soil concentrations were monitored using commercially available endotoxin analysis reagents. Overall, land application of biosolids did not increase the percentage of antibiotic-resistant culturable bacteria above background soil levels. Likewise, land application of biosolids did not significantly increase the concentration of endotoxin in soil. This study determined and established a baseline understanding of the overall effect that land application of biosolids had on the land-applied field with respect to antibiotic-resistant bacterial and endotoxin soil densities.

Association between CD14 polymorphisms and serum soluble CD14 levels: effect of atopy and endotoxin inhalation

BACKGROUND

A prerequisite for activation of the innate immune response by endotoxin is its binding to CD14.

OBJECTIVE

The aim of this study was to evaluate the role of CD14 polymorphisms, atopy, and inhaled endotoxin in modulating serum CD14 levels.

METHODS

Healthy volunteers (n = 88) were genotyped for CD14 polymorphisms at the -1619, -1359, and -159 loci, relative to the transcription start site. Subjects inhaled 20 mug of endotoxin, and white blood cell, C-reactive protein, LPS-binding protein, and soluble CD14 (sCD14) levels were measured before and after exposure.

RESULTS

Homozygotes for the -1619G, -1359G, and -159T alleles had higher baseline levels of sCD14 than carriers of the CD14/-1619AA (P = .015), -1359GT/TT (P = .015), or -159CC (P = 0.017) genotypes. sCD14 levels increased within 24 hours of endotoxin inhalation (P < .0001 for all biomarkers); however, the association between CD14 polymorphisms and sCD14 levels was no longer present after exposure. The atopic status of an individual did not alter these associations. CD14 polymorphisms were not associated with levels of white blood cells, C-reactive protein, and LPS-binding protein before or after endotoxin challenge.

CONCLUSION

These data suggest that CD14 promoter polymorphisms and inhaled endotoxin modulate sCD14 levels.

Lipopolysaccharide administration to the allergic nose contributes to lower airway inflammation

BACKGROUND

Allergic rhinitis (AR) is an inflammatory reaction not confined to a single local compartment, but rather involving the whole airway system. Allergens known to induce AR are not always the sole trigger of the inflammatory reaction as infections and organic dust might also cause exacerbations of rhinitis and associated conditions.

OBJECTIVE

To examine the effects of intranasal lipopolysaccharide (LPS) exposure, as a surrogate for upper airway bacterial infections, in patients with symptomatic AR.

METHODS

Fourteen patients with a history of moderate to severe pollen-induced AR were challenged intranasally with LPS. After 3-6 weeks, the same patients were challenged again, first with allergen and 24 h later with LPS. Nasal symptom scores, nasal lavage leucocyte counts and nasal airway resistance were assessed at 6-24 h after each provocation along with measurements of nitric oxide (NO) levels in the nose and lung.

RESULTS

Six hours after the LPS challenge, an increased level of leucocytes could be obtained in the lavage fluid, but no symptoms were experienced and no increase in nasal resistance could be recorded. The NO production in the upper and lower airways was similar before and 6 h after the provocation. In contrast, in patients exposed to pollen before the LPS challenge, both the nasal and the pulmonary NO levels were enhanced. This was accompanied by an increase in leucocytes.

CONCLUSION

The present study demonstrates a priming effect of allergen on the nasal response to LPS as well as the presence of a systemic link between airway mucosal sites in the upper and lower airways. This suggests that exogenously derived signals, like upper airway infections, can interfere with the initiation, maintenance and progression of asthma.

LPS inhalation challenge: a new tool to characterize the inflammatory response in humans

Inhaling bacterial endotoxin and its derivative LPS can induce a distinct inflammatory response, varying among hosts. Experimental LPS-inhalation is an established procedure in inflammation research. We evaluated experimental LPS-inhalation in 20 young healthy volunteers to determine the safety and the reproducibility of markers of inflammation and clinical findings (symptoms, lung function, exhalative NO, and body temperature). LPS was increased every 30 min up to cumulative 100 microg, the protocol was repeated after 2, 4, and 6 weeks. During 71 provocations, 13 episodes of clinical complaints were observed in 10 subjects. Those were a total of 11 local reactions (15.5%, e.g., cough), and six systemic reactions (8.5%, e.g., fatigue). All adverse events resolved spontaneously within 10 h. Changes of FEV(1) and eNO showed no significant differences between the four visits. In the majority of our subjects (88.2% on visit 1-3, 76.5% on visit 4), a rise in body temperature (>0.5 degrees C) was recorded and normalised latest after 24 h. On the first and the last visit, serum concentrations of CrP and LBP increased significantly and correlated well with each other (r=0.71; P<0.001). LPS-challenge is a safe and tolerable tool to investigate inflammatory response in humans and could lead to better characterization of patients with chronic inflammatory disease.

Lipopolysaccharide-induced down-regulation of uteroglobin in the human nose

CONCLUSION

Lipopolysaccharide (LPS) challenge of the human nose has the capacity to reduce the amount of natural anti-inflammatory proteins, such as uteroglobin.

OBJECTIVES

Nasal challenge with LPS, an activator of innate immunity, has been shown to increase the amount of pro-inflammatory mediators in nasal lavage fluid. Uteroglobin is a newly described anti-inflammatory mediator that is secreted in the nose. This study examined the effect of nasal LPS application on the level of uteroglobin in nasal lavage fluid as well as on the expression of uteroglobin in nasal mucosa.

MATERIALS AND METHODS

Thirty-eight volunteers were challenged nasally with either 50 microg LPS or vehicle; 6 h later, nasal lavage fluid was collected and a nasal biopsy was obtained. Levels of uteroglobin, albumin and the pro-inflammatory mediators interleukin (IL)-6 and IL-8 were analysed in the lavage fluids using enzyme-linked immunosorbent assays (ELISAs). Biopsies were used for either quantification of uteroglobin mRNA by real-time PCR or for localization of the corresponding protein with immunohistochemistry.

RESULTS

The uteroglobin level decreased in nasal lavage fluid following LPS challenge, whereas the levels of IL-6 and albumin increased. Uteroglobin was mainly seen in the respiratory epithelium and its mRNA expression decreased as a consequence of the LPS challenge.

Gender differences in murine airway responsiveness and lipopolysaccharide-induced inflammation

The roles of gender and sex hormones in lung function and disease are complex and not completely understood. The present study examined the influence of gender on lung function and respiratory mechanics in naive mice and on acute airway inflammation and hyperresponsiveness induced by intratracheal LPS administration. Basal lung function characteristics did not differ between naive males and females, but males demonstrated significantly greater airway responsiveness than females following aerosolized methacholine challenge as evidenced by increased respiratory system resistance and elastance (p < 0.05). Following LPS administration, males developed more severe hypothermia and greater airway hyperresponsiveness than females (p < 0.05). Inflammatory indices including bronchoalveolar lavage fluid total cells, neutrophils, and TNF-alpha content were greater in males than in females 6 h following LPS administration (p < 0.05), whereas whole-lung TLR-4 protein levels did not differ among treatment groups, suggesting that differential expression of TLR-4 before or after LPS exposure did not underlie the observed inflammatory outcomes. Gonadectomy decreased airway inflammation in males but did not alter inflammation in females, whereas administration of exogenous testosterone to intact females increased their inflammatory responses to levels observed in intact males. LPS-induced airway hyperresponsiveness was also decreased in castrated males and was increased in females administered exogenous testosterone. Collectively, these data indicate that airway responsiveness in naive mice is influenced by gender, and that male mice have exaggerated airway inflammatory and functional responses to LPS compared with females. These gender differences are mediated, at least in part, by effects of androgens.

Endotoxin and occupational airway disease

PURPOSE OF REVIEW

This review provides an update on the role of bacterial endotoxin in occupational airway disease, a problem of importance from diagnostic and preventive points of view.

RECENT FINDINGS

Data from human inhalation studies have increased our understanding of the cell mechanisms underlying diseases related to endotoxin exposure. In addition, knowledge from molecular genetics may help us to identify individuals at risk. Several investigations have demonstrated that, apart from endotoxin, other microbial cell wall agents are also related to the risk for symptoms of occupational lung diseases, with pathogenic mechanisms different to those caused by endotoxin. Diagnostic methods have progressed from traditional lung function measurements to sampling of indicators of inflammation in the blood, nasal lavage and induced sputum. Investigations of a longitudinal design have provided important findings on the relationship between acute and chronic effects as well as exposures of risk and risk factors among individuals.

SUMMARY

Endotoxin, as well as other agents derived from microbes, are important causative agents for occupational respiratory and other diseases, and exposure may occur in a large variety of occupational environments. Recent data from longitudinal studies provide important information on diagnostic and preventive measures.

Safety of incremental inhaled lipopolysaccharide challenge in humans

BACKGROUND

Inhalation of environmental endotoxin is important in the pathogenesis of asthma and other environmental airway diseases. Inhaled airway challenge using lipopolysaccharide in humans has been performed for over 20 years to assess the airway response to endotoxin. However, there are no published data on the short-term safety of endotoxin inhalation protocols.

OBJECTIVE

To characterize the safety and tolerability of incremental inhaled lipopolysaccharide challenge in humans.

PATIENTS AND METHODS

We performed a retrospective analysis of data obtained from 119 subjects who underwent inhaled challenge with up to 41.5 mug of lipopolysaccharide. We measured pulmonary function, temperature, mean arterial pressure, heart rate, and systemic symptoms for 3 h after challenge.

RESULTS

Fever occurred in 30% of subjects and was associated with a higher cumulative dose of lipopolysaccharide. Reduced mean arterial pressure occurred in 21% of subjects and was dose-related. There was no association between fever or decreased mean arterial pressure and airway responsiveness to inhaled lipopolysaccharide. Common symptoms reported by subjects included: chills (64%), malaise (56%), cough (56%), chest tightness (49%), headache (43%), and myalgias (27%). None of the subjects experienced delayed discharge or a serious adverse event.

CONCLUSIONS

Inhaled lipopolysaccharide causes dose-related systemic responses that include fever, reduced blood pressure, and constitutional symptoms that are not associated with the airway response to inhaled lipopolysaccharide. Systemic responses to inhaled lipopolysaccharide should be expected and subjects undergoing inhaled lipopolysaccharide challenge in the research setting should be carefully monitored for non-pulmonary adverse events for several hours after challenge.

Importance of the personal endotoxin cloud in school-age children with asthma

BACKGROUND

A number of studies have observed associations between the amount of endotoxin in urban dust and chronic asthma severity, but a direct relationship between personal exposure to household endotoxin and acute asthma worsening has not yet been defined.

OBJECTIVE

We sought to investigate the relationship between day-to-day changes in personal endotoxin exposure and asthma severity.

METHODS

In the winter and spring of 1999 through 2000, endotoxin exposures were monitored in asthmatic schoolchildren by using portable, as opposed to stationary, monitors designed to measure inhalable and respirable particulate matter less than or equal to 2.5 and 10 microm in diameter. Children were followed with daily measurements of FEV(1) and asthma symptoms.

RESULTS

Over a 24-hour period, median daily personal endotoxin exposures ranged from 0.08 EU/m(3) (measured at a particulate matter size range </=2.5 microm in diameter) to 0.37 EU/m(3) (measured at a particulate matter size range </=10 microm in diameter). Personal exposures were significantly (P < .001) higher than endotoxin measurements from either indoor or outdoor stationary monitors. Moreover, individual exposures did not correlate with stationary measurements, suggesting that exposures derived from sources in close proximity to the children's personal activities might be better correlated with disease severity. Increases in personal endotoxin exposures were associated with decreased FEV(1) values and increased symptoms.

CONCLUSIONS

These findings demonstrate the importance of using personal monitoring to both measure and correlate endotoxin exposure with asthma severity.

Organic dust induced inflammation--role of atopy and TLR-4 and CD14 gene polymorphisms

BACKGROUND

Polymorphisms in the genes controlling for CD14 and TLR-4 may influence the outcome of endotoxin-induced effects.

MATERIALS AND METHODS

A study was performed on 146 workers in industries with exposure to organic dust containing endotoxin and 53 controls. Endotoxin exposure was measured at representative work sites. Inflammagenic markers, cytokines, and CD14 and TLR-4 polymorphisms were determined in blood.

RESULTS

Among workers, serum levels of esinophilic cationic protein (ECP) were lower compared to controls and the proportion of atopics was lower. Atopic persons had lower levels of IL-6 and IL-8, both among controls and exposed. IL-6 and ECP values were lower among those with TLR-4 /+896 AG and GG polymorphisms as compared to AA. Among atopic workers with CD-14(-550) polymorphism CC, IL-8 was lower.

COMMENTS

The results suggest that CD14 and TLR-4 polymorphisms influence regulators of the inflammation induced by endotoxin in organic dusts. Atopic persons have a lower secretion of certain inflammatory cytokines.

A single exposure to organic dust of non-naïve non-exposed volunteers induces long-lasting symptoms of endotoxin tolerance

BACKGROUND

Work with occupational levels of organic dust is associated with a chronic inflammatory response that must somehow be controlled. Endotoxin tolerance has previously been described in vitro and animal studies as a mechanism that modifies the threshold at which response occurs.

OBJECTIVE

We investigated the response of non-naïve, currently non-exposed persons to a single exposure of organic dust in a swine confinement building.

METHODS

We exposed 16 non-naïve persons in a swine confinement building with low-to-moderate representative levels of organic dust and characterized their acute immune response.

RESULTS

Under work-like 3-hour exposure conditions, non-naïve volunteers developed an inflammatory response documented by an increase in interleukin-6 (IL-6) in bronchoalveolar lavage (BAL) from 3.1 to 6.1 pg/ml and visual indices of bronchial inflammation. Similarly, serum IL-6 increased with a peak 3 h after exposure. Tumor necrosis factor (TNF)-alpha was not detected in BAL, and serum TNF-alpha was reduced from 3.7 pg/ml at baseline to less than 2 pg/ml within 3 h after exposure, and remained decreased until 2 weeks after exposure. This is a cardinal marker for immune suppression which was confirmed by other markers: reduction in HLA-DR expression on alveolar macrophages and CD14 expression on blood monocytes.

CONCLUSION

We report findings that suggest that long-lasting endotoxin tolerance and immune suppression may be induced by a brief exposure to organic dust concentrations in the medium-low range of occupational levels.

Antiinflammatory effects of salmeterol after inhalation of lipopolysaccharide by healthy volunteers

RATIONALE

Salmeterol is a beta2-adrenoreceptor agonist used in the treatment of obstructive pulmonary disease. Salmeterol inhibits inflammatory responses by neutrophils and mononuclear cells in vitro and in mouse models of lung inflammation in vivo.

OBJECTIVE

To determine the effect of salmeterol on LPS-induced lung inflammation in humans.

METHODS

Thirty-two healthy subjects were enrolled in a single-blinded, placebo-controlled study. Subjects inhaled 100 microg salmeterol or placebo (t=-0.5 h) followed by 100 microg LPS or normal saline (t=0 h; n=8/group). Measurements were performed in bronchoalveolar lavage fluid and purified alveolar macrophages obtained 6 h post-challenge.

MEASUREMENTS AND MAIN RESULTS

Inhalation of LPS was associated with neutrophil influx, neutrophil degranulation (myeloperoxidase, bactericidal/permeability-increasing protein and elastase), release of cytokines (tumor necrosis factor alpha and interleukin 6) and chemokines (interleukin 8, epithelial cell-derived neutrophil attractant 78, macrophage inflammatory proteins 1alpha and 1beta), activation of alveolar macrophages (upregulation of HLA-DR and CD71; enhanced expression of mRNAs for 13 different mediators of inflammation), and protein leakage (all p<0.05 vs. placebo/saline). Pretreatment with salmeterol inhibited LPS-induced neutrophil influx, neutrophil degranulation (myeloperoxidase), tumor necrosis factor alpha release, and HLA-DR expression (all p<0.05 vs. placebo/LPS), while not significantly influencing other responses.

CONCLUSION

Salmeterol exerts antiinflammatory effects in the pulmonary compartment of humans exposed to LPS.

Another explanation for the low allergy rate in the rural Alpine foothills

A low allergy rate in coal and wood heated homes has been described in the small villages in the Alpine foothills and subsequently found to be associated with the farming environment. This was interpreted within the framework of the hygiene hypothesis but there are also alternative explanations. Lower air pollution could be one reason, which is, however, unlikely since the differences between the Bavarian countryside and the Munich municipal area were only weak. There could be genetic differences between the urban and rural population by previous isolation or by self-selection. The potential drop-out of allergy genes, however, will also not explain the absent increase of allergies in two generations. More likely, other lifestyle factors are important. Dietary habits are different in farmers and a less frequent vitamin D supplementation of newborns (otherwise expected to be allergy promoting) has been shown recently. The underlying cause for the "non-allergic farm child" remains speculative until the transfer of any farm-associated factor is leading to a similar risk reduction in the general population.