Determinants of Clara cell protein (CC16) concentration in serum: a reassessment with two different immunoassays

Effects of lifestyle and associated diseases on serum CC16 suggest complex interactions among metabolism, heart and lungs

INTRODUCTION

Clara cell 16-kDa protein (CC16) is an anti-inflammatory, immunomodulatory secreted pulmonary protein with reduced serum concentrations in obesity according to recent data.

OBJECTIVE

Studies focused solely on bodyweight, which does not properly reflect obesity-associated implications of the metabolic and reno-cardio-vascular system. The purpose of this study was therefore to examine CC16 in a broad physiological context considering cardio-metabolic comorbidities of primary pulmonary diseases.

METHODS

CC16 was quantified in serum samples in a subset of the FoCus (N = 497) and two weight loss intervention cohorts (N = 99) using ELISA. Correlation and general linear regression analyses were applied to assess CC16 effects of lifestyle, gut microbiota, disease occurrence and treatment strategies. Importance and intercorrelation of determinants were validated using random forest algorithms.

RESULTS

CC16 A38G gene mutation, smoking and low microbial diversity significantly decreased CC16. Pre-menopausal female displayed lower CC16 compared to post-menopausal female and male participants. Biological age and uricosuric medications increased CC16 (all p < 0.01). Adjusted linear regression revealed CC16 lowering effects of high waist-to-hip ratio (est. -11.19 [-19.4; -2.97], p = 7.99 × 10-3), severe obesity (est. -2.58 [-4.33; -0.82], p = 4.14 × 10-3) and hypertension (est. -4.31 [-7.5; -1.12], p = 8.48 × 10-3). ACEi/ARB medication (p = 2.5 × 10-2) and chronic heart failure (est. 4.69 [1.37; 8.02], p = 5.91 × 10-3) presented increasing effects on CC16. Mild associations of CC16 were observed with blood pressure, HOMA-IR and NT-proBNP, but not manifest hyperlipidemia, type 2 diabetes, diet quality and dietary weight loss intervention.

CONCLUSION

A role of metabolic and cardiovascular abnormalities in the regulation of CC16 and its modifiability by behavioral and pharmacological interventions is indicated. Alterations by ACEi/ARB and uricosurics could point towards regulatory axes comprising the renin-angiotensin-aldosterone system and purine metabolism. Findings altogether strengthen the importance of interactions among metabolism, heart and lungs.

Exploring the Role of Biomarkers Associated with Alveolar Damage and Dysfunction in Idiopathic Pulmonary Fibrosis-A Systematic Review

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is one of the most aggressive forms of interstitial lung diseases (ILDs), marked by an ongoing, chronic fibrotic process within the lung tissue. IPF leads to an irreversible deterioration of lung function, ultimately resulting in an increased mortality rate. Therefore, the focus has shifted towards the biomarkers that might contribute to the early diagnosis, risk assessment, prognosis, and tracking of the treatment progress, including those associated with epithelial injury.

METHODS

We conducted this review through a systematic search of the relevant literature using established databases such as PubMed, Scopus, and Web of Science. Selected articles were assessed, with data extracted and synthesized to provide an overview of the current understanding of the existing biomarkers for IPF.

RESULTS

Signs of epithelial cell damage hold promise as relevant biomarkers for IPF, consequently offering valuable support in its clinical care. Their global and standardized utilization remains limited due to a lack of comprehensive information of their implications in IPF.

CONCLUSIONS

Recognizing the aggressive nature of IPF among interstitial lung diseases and its profound impact on lung function and mortality, the exploration of biomarkers becomes pivotal for early diagnosis, risk assessment, prognostic evaluation, and therapy monitoring.

Is airway damage during physical exercise related to airway dehydration? Inputs from a computational model

In healthy subjects, at low minute ventilation (V̇e) during physical exercise, the water content and temperature of the airways are well regulated. However, with the increase in V̇e, the bronchial mucosa becomes dehydrated and epithelial damage occurs. Our goal was to demonstrate the correspondence between the ventilatory threshold inducing epithelial damage, measured experimentally, and the dehydration threshold, estimated numerically. In 16 healthy adults, we assessed epithelial damage before and following a 30-min continuous cycling exercise at 70% of maximal work rate, by measuring the variation pre- to postexercise of serum club cell protein (cc16/cr). Blood samples were collected at rest, just at the end of the standardized 10-min warm-up, and immediately, 30 min and 60 min postexercise. Mean V̇e during exercise was kept for analysis. Airway water and heat losses were estimated using a computational model adapted to the experimental conditions and were compared with a literature-based threshold of bronchial dehydration. Eleven participants exceeded the threshold for bronchial dehydration during exercise (group A) and five did not (group B). Compared with post warm-up, the increase in cc16/cr postexercise was significant (mean increase ± SE: 0.48 ± 0.08 ng·L-1 only in group A but not in group B (mean difference ± SE: 0.10 ± 0.04 ng·L-1). This corresponds to an increase of 101 ± 32% [range: 16%-367%] in group A (mean ± SE). Our findings suggest that the use of a computational model may be helpful to estimate an individual dehydration threshold of the airways that is associated with epithelial damage during physical exercise.NEW & NOTEWORTHY Using a computational model for heat and water transfers in the bronchi, we identified a threshold in ventilation during exercise above which airway dehydration is thought to occur. When this threshold was exceeded, epithelial damage was found. This threshold might therefore represent the ventilation upper limit during exercise in susceptible individuals. Our results might help to prevent maladaptation to chronic exercise such as exercise-induced bronchoconstriction or asthma.

Simulated biological fluids - a systematic review of their biological relevance and use in relation to inhalation toxicology of particles and fibres

The use of simulated biological fluids (SBFs) is a promising in vitro technique to better understand the release mechanisms and possible in vivo behaviour of materials, including fibres, metal-containing particles and nanomaterials. Applications of SBFs in dissolution tests allow a measure of material biopersistence or, conversely, bioaccessibility that in turn can provide a useful inference of a materials biodistribution, its acute and long-term toxicity, as well as its pathogenicity. Given the wide range of SBFs reported in the literature, a review was conducted, with a focus on fluids used to replicate environments that may be encountered upon material inhalation, including extracellular and intracellular compartments. The review aims to identify when a fluid design can replicate realistic biological conditions, demonstrate operation validation, and/or provide robustness and reproducibility. The studies examined highlight simulated lung fluids (SLFs) that have been shown to suitably replicate physiological conditions, and identify specific components that play a pivotal role in dissolution mechanisms and biological activity; including organic molecules, redox-active species and chelating agents. Material dissolution was not always driven by pH, and likewise not only driven by SLF composition; specific materials and formulations correspond to specific dissolution mechanisms. It is recommended that SLF developments focus on biological predictivity and if not practical, on better biological mimicry, as such an approach ensures results are more likely to reflect in vivo behaviour regardless of the material under investigation.

Continuous exercise induces airway epithelium damage while a matched-intensity and volume intermittent exercise does not

BACKGROUND

While continuous exercise (CE) induces greater ventilation ([Formula: see text]_E) when compared to intermittent exercise (IE), little is known of the consequences on airway damage. Our aim was to investigate markers of epithelial cell damage - i.e. serum levels of CC16 and of the CC16/SP-D ratio - during and following a bout of CE and IE of matched work.

METHODS

Sixteen healthy young adults performed a 30-min continuous (CE) and a 60-min intermittent exercise (IE; 1-min work: 1-min rest) on separate occasions in a random order. Intensity was set at 70% of their maximum work rate (WR_max). Heart rate (HR) and [Formula: see text]_E were measured throughout both tests. Blood samples were taken at rest, after the 10th min of the warm-up, at the end of both exercises, half way through IE (matched time but 50% work done for IE) as well as 30- and 60-min post-exercise. Lactate and CC16 and SP-D were determined.

RESULTS

Mean [Formula: see text]_E was higher for CE compared to IE (85 ± 17 l.min^- 1 vs 50 ± 8 l.min^- 1, respectively; P < 0.001). Serum-based markers of epithelial cell damage remained unchanged during IE. Interaction of test × time was observed for SP-D (P = 0.02), CC16 (μg.l^- 1) (P = 0.006) and CC16/SP-D ratio (P = 0.03). Maximum delta CC16/SP-D was significantly correlated with mean [Formula: see text]_E sustained (r = 0.83, P < 0.001) during CE but not during IE.

CONCLUSION

The 30-min CE performed at 70% WR_max induced mild airway damage, while a time- or work-matched IE did not. The extent of the damage during CE was associated with the higher ventilation rate.

Biomarkers of respiratory allergy in laboratory animal care workers: an observational study

OBJECTIVES

Laboratory animal allergy is a highly prevalent occupational disease among exposed workers. The aim of the study was to validate the biomarkers of airway inflammation in laboratory animal (LA) care workers.

METHODS

All of the participants in this observational study (63 LA care workers and 64 controls) were administered a clinical questionnaire, underwent spirometry and a skin prick or radioallergosorbent test for common and occupational aeroallergens, and the fraction of exhaled nitric oxide (FeNO₅₀), exhaled breath condensate hydrogen peroxide (EBC H₂O₂) and serum pneumoprotein levels were measured. Multivariate analysis (ANCOVA) was used to assess the interactions of the variables.

RESULTS

FeNO₅₀ levels correlated with exposure (p = 0.002), sensitisation (p = 0.000) and age (p = 0.001), but there was no interaction between exposure and sensitisation when age was considered in the model (p = 0.146). EBC-H₂O₂ levels were higher in the sensitised workers than in the sensitised controls [0.14 (0.08-0.29) µM vs 0.07 (0.05-0.12) µM; p < 0.05]. Serum surfactant protein A (SP-A) levels were unaffected by exposure, sensitisation or age, although higher levels were observed in symptomatic workers; however, SP-D levels were influenced by exposure (p = 0.024) and age (p = 0.022), and club cell 16 levels were influenced by sensitisation (p = 0.027) and age (p = 0.019).

CONCLUSIONS

The presence of the clinical symptoms associated with LA exposure and high FeNO levels should prompt further medical assessments in LA workers. Although EBC-H₂O₂ levels do not seem to reflect eosinophilic inflammation, serum SP-A levels could be used to monitor progression from rhinitis to asthma.

Serum club cell protein 16 is associated with asymptomatic airway responsiveness in adults: Findings from the French epidemiological study on the genetics and environment of asthma

BACKGROUND AND OBJECTIVE

Club cell secretory protein (CC-16) is a sensitive biomarker of airways epithelium integrity. It has gained interest as a biological marker in chronic lung diseases because of its presumed relationship to inflammation. Little is known about the association between CC-16 serum level and asthma, lung function and airway responsiveness (AR).

METHODS

Serum CC-16 level was determined by latex immunoassay in 1298 participants from the French Epidemiological case-control and family-based study on Genetics and Environment of Asthma (EGEA) (mean age 43 years; 49% men, 38% with asthma). Pre-bronchodilator lung function (forced expiratory volume in 1 s (FEV1 ), forced vital capacity (FVC) and FEV1 /FVC) and degree of AR, expressed as a function of the dose-response slope to methacholine test were measured. Standardized residuals CC-16 z-scores were obtained by regressing CC-16 level on the glomerular filtration rate. CC-16 z-scores were correlated with asthma, lung function and AR in participants with and without asthma.

RESULTS

CC-16 geometric mean level was 12.4 μg/L (range: 2.2-70.6 μg/L). In participants without asthma, lower CC-16 z-scores was associated with impaired FEV1 /FVC% (β = 0.50 (95% CI: 0.06, 0.95) and with higher degree of AR (β = 0.24 (95% CI: 0.09, 0.39)). CC-16 was not associated with impaired lung function or AR in participants with asthma.

CONCLUSIONS

Lower CC-16 serum level was associated with impaired lung function and AR, suggesting that serum CC-16 level may reflect early damages to the lung epithelium in adults without asthma.

Chlorinated pool attendance, airway epithelium defects and the risks of allergic diseases in adolescents: Interrelationships revealed by circulating biomarkers

It has been suggested that allergic diseases might be epithelial disorders driven by various environmental stressors but the epidemiological evidence supporting this concept is limited. In a cross-sectional study of 835 school adolescents (365 boys; mean age, 15.5 yr), we measured the serum concentrations of Club cell protein (CC16), surfactant-associated protein D (SP-D) and of total and aeroallergen-specific IgE. We used the serum CC16/SP-D concentration ratio as an index integrating changes in the permeability (SP-D) and secretory function (CC16) of the airway epithelium. In both sexes, early swimming in chlorinated pools emerged as the most consistent and strongest predictor of low CC16 and CC16/SP-D ratio in serum. Among girls, a low CC16/SP-D ratio was associated with increased odds (lowest vs. highest tertile) for pet sensitization (OR 2.97, 95% CI 1.19-8.22) and for hay fever in subjects sensitized to pollen (OR 4.12, 95% CI 1.28-14.4). Among boys, a low CC16/SP-D ratio was associated with increased odds for house-dust mite (HDM) sensitization (OR 2.01, 95% CI 1.11-3.73), for allergic rhinitis in subjects sensitized to HDM (OR 3.52, 95% CI 1.22-11.1) and for asthma in subjects sensitized to any aeroallergen (OR 3.38, 95% CI 1.17-11.0), HDM (OR 5.20, 95% CI 1.40-24.2) or pollen (OR 5.82, 95% CI 1.51-27.4). Odds for allergic sensitization or rhinitis also increased with increasing SP-D or decreasing CC16 in serum. Our findings support the hypothesis linking the development of allergic diseases to epithelial barrier defects due to host factors or environmental stressors such as early swimming in chlorinated pools.

Serum levels of club cell secretory protein (Clara) and short- and long-term exposure to particulate air pollution in adolescents

BACKGROUND

Studies in populations have shown that particulate air pollution is associated with changes in lung function in adolescents.

OBJECTIVE

We investigated the effect of short- and long-term exposure to particulate matter (PM10) on the pulmonary health of adolescents, using serum lung club cell secretory protein (Clara) (CC16) as a biomarker for respiratory epithelium integrity.

METHODS

We measured serum CC16 in 825 adolescents (57% girls, mean age: 15 years). Short-term and long-term exposure to ambient PM10 was estimated for each participant's home address using a kriging interpolation method. To explore the association between PM10 and serum CC16 we applied restricted cubic splines with 5 knots located at the 5th, 25th, 50th, 75th and 95th percentiles of the PM10 distribution. The explorative analyses showed a change in the slope of this association, after which a change-point analysis was performed.

RESULTS

After adjustment for potential covariates, the analysis showed strong associations between PM10 concentrations, averaged over the week preceding the clinical examination, and serum CC16 levels. Each 5 μg/m(3) increase in mean PM10 concentration in the week before the clinical examination was associated with a substantial increase of 0.52 μg/l (95% confidence interval: 0.31 to 0.73; p<0.0001) in serum CC16 levels. The association appears nonlinear with a flattening out of the slope at mean week PM10 levels above 37 μg/m(3). There was no evidence of an association between long-term exposure to PM10 and serum CC16 concentrations.

CONCLUSIONS

Our findings suggest that short-term exposure to particulate air pollution may compromise the integrity of the lung epithelium and lead to increased epithelial barrier permeability in the lungs of adolescents, even at low concentrations.

Nasal epithelium biomarkers in young children: associations with allergic sensitization and environmental stressors

BACKGROUND

Recent studies suggest that allergic diseases might have their onset in early epithelial barrier defects. To test this hypothesis, we assessed associations between nasal epithelium biomarkers, environmental stressors, and the risks of allergic sensitization.

METHODS

In a cross-sectional study of 288 kindergarten children (mean age, 5.7 years), we measured aeroallergen-specific IgE in nasal mucosa and the concentrations of urea, albumin, and Clara cell protein (CC16) in nasal lavage fluid (NALF). Albumin and CC16 in NALF were expressed per liter or as a ratio to urea. We also calculated the NALF CC16/albumin ratio as an index integrating the permeability and the secretory function of the nasal epithelium.

RESULTS

Median NALF concentrations of CC16 and albumin were 8.2 µg/L and 34.5 mg/L, respectively. While there were no significant gender differences when proteins were expressed per liter, the CC16 to albumin and CC16 to urea ratios in NALF were higher in girls than in boys (P = 0.02 and 0.055, respectively. The nasal epithelial barrier function, as reflected by these NALF biomarkers, was positively influenced by probiotics and age, and negatively by environmental stressors such as pool chlorine. The risk of house dust mite (HDM) sensitization increased with decreasing log NALF CC16 concentration, whether expressed per liter (2.59, 95% CI: 1.15-5.82, P = 0.02), as a ratio to urea (1.98, 95% CI: 0.96-4.06, P = 0.06), or as a ratio to albumin (OR, 2.03, 95% CI: 1.10-3.74, P = 0.02). Children in the highest and intermediate tertiles of the NALF albumin/urea ratio were three times more likely to be sensitized to HDM than those in the lowest tertile (both P = 0.04).

CONCLUSION

Defects in the nasal epithelium barrier function of young children, as reflected by the concentrations of CC16 and albumin in NALF, are associated with environmental factors, including pool chlorine, and with increased risks of HDM sensitization.

Effects on airways of short-term exposure to two kinds of wood smoke in a chamber study of healthy humans

INTRODUCTION

Air pollution causes respiratory symptoms and pulmonary disease. Airway inflammation may be involved in the mechanism also for cardiovascular disease. Wood smoke is a significant contributor to air pollution, with complex and varying composition. We examined airway effects of two kinds of wood smoke in a chamber study.

MATERIALS AND METHODS

Thirteen subjects were exposed to filtered air and to wood smoke from the start-up phase and the burn-out phase of the wood-burning cycle. Levels of PM(2.5) were 295 µg/m(3) and 146 µg/m(3), number concentrations 140 000/cm(3) and 100 000/cm(3). Biomarkers in blood, breath and urine were measured before and on several occasions after exposure. Effects of wood smoke exposure were assessed adjusting for results with filtered air.

RESULTS

After exposure to wood smoke from the start-up, but not the burn-out session, Clara cell protein 16 (CC16) increased in serum after 4 hours, and in urine the next morning. CC16 showed a clear diurnal variation. Fraction of exhaled nitric oxide (FENO) increased after wood smoke exposure from the burn-out phase, but partly due to a decrease after exposure to filtered air. No other airway markers increased.

CONCLUSIONS

The results indicate that relatively low levels of wood smoke exposure induce effects on airways. Effects on airway epithelial permeability was shown for the start-up phase of wood burning, while FENO increased after the burn-out session. CC16 seems to be a sensitive marker of effects of air pollution both in serum and urine, but its function and the significance need to be clarified.

Nasal epithelium integrity, environmental stressors, and allergic sensitization: a biomarker study in adolescents

Changes in the airways epithelium caused by environmental insults might play a role in the development of allergic rhinitis. We measured albumin and Clara cell protein (CC16) in the nasal lavage fluid (NALF) from 474 adolescents (263 girls and 211 boys). The NALF CC16/albumin ratio, integrating the permeability and cellular integrity of the nasal epithelium, decreased mostly with time spent in chlorinated pools. In boys, a lower CC16/albumin ratio in NALF was associated with an increased risk of house dust mite sensitization. The results suggest that the CC16/albumin ratio in NALF can be used to detect nasal epithelium alterations linked to allergic sensitization.

Lung function in volunteers before and after exposure to trichloramine in indoor pool environments and asthma in a cohort of pool workers

OBJECTIVES

Exposure to trichloramine (NCl(3)) in indoor swimming-pool environments is known to cause mucous membrane irritation, but if it gives rise to changes in lung function or asthma in adults is not known. (1) We determined lung function in volunteers before and after exposure to indoor pool environments. (2) We studied the occurrence of respiratory symptoms and asthma in a cohort of pool workers. DESIGN/METHODS/PARTICIPANTS: (1) We studied two groups of volunteers, 37 previously non-exposed healthy persons and 14 pool workers, who performed exercise for 2 h in an indoor pool environment. NCl(3) in air was measured during pool exposures and in 10 other pool environments. Filtered air exposures were used as controls. Lung function and biomarkers of pulmonary epithelial integrity were measured before and after exposure. (2) We mailed a questionnaire to 1741 persons who indicated in the Swedish census 1990 that they worked at indoor swimming-pools.

RESULTS

(1) In previously non-exposed volunteers, statistically significant decreases in FEV(1) (forced expiratory volume) and FEV(%) (p=0.01 and 0.05, respectively) were found after exposure to pool air (0.23 mg/m(3) of NCl(3)). In pool workers, a statistically significant decrease in FEV(%) (p=0.003) was seen (but no significant change of FEV(1))(.) In the 10 other pool environments the median NCl(3) concentration was 0.18 mg/m(3). (2) Our nested case/control study in pool workers found an OR for asthma of 2.31 (95% CI 0.79 to 6.74) among those with the highest exposure. Exposure-related acute mucous membrane and respiratory symptoms were also found.

CONCLUSIONS

This is the first study in adults showing statistically significant decreases in lung function after exposure to NCl(3). An increased OR for asthma among highly exposed pool workers did not reach statistical significance, but the combined evidence supports the notion that current workroom exposures may contribute to asthma development. Further research on sensitive groups is warranted.

Non-invasive assessment of small airway remodelling in smokers

Smoking associated COPD progression is likely to be directly linked to differential injury and repair dynamics in small airways (SA). Although IL8 is a well-accepted marker for injured airway epithelium, Clara cells [the predominant proliferating cells in SA] and SCGB1A1 protein [their major secretory product] have only recently emerged as potential SA repair markers. We therefore postulate that the SCGB1A1/IL8 ratio in the airways of smokers would be inversely associated with physiological, radiological and clinical measures of COPD. A cross-sectional cohort of 28 smokers undergoing surgery for peripheral nodule was recruited (24M/4F, age 61 +/- 11 y, FEV1s 76 +/- 20%, smoking 40 +/- 12 p.y). SCGB1A1 and IL8 were measured by ELISA in the induced sputum (IS) 3 to 5 days prior to surgery as well as by immunohistochemistry from lung tissue (also assessed morphometrically) obtained distant to the cancer surgery site. COPD was assessed using standard clinical, functional and radiological parameters. Log-transformed IS-SCGB1A1 was linearly correlated with SCGB1A1-positive epithelial cells detected via immunohistochemistry (r = .533, p = .001), while IS-IL8 was positively related to SA infiltrating neutrophils (Elastase-positive cells). There was a striking negative correlation between IS-SCGB1A1/IL8 levels and whole airway thickness [SA < 2 mm] at morphometry (r = -0.83, p < 0.0001). IS-SCGB1A1/IL8 levels were also inversely associated with nitrogen slope [r = -0.52, p < 0.001] and HRCT SA score [r = -0.51, p < 0.001]. In a multivariate analysis the IS-SCGB1A1/IL8 ratio was a stronger predictor than both the physiological and radiological measures of SA disease assessed. The SCGB1A1/IL8 ratio measured in sputum is a potentially valuable biomarker for non-invasive assessment of SA remodelling in smokers.

Higher levels of the anti-inflammatory protein CC10 are associated with improvement in bronchial dysplasia and sputum cytometric assessment in individuals at high risk for lung cancer

PURPOSE

CC10, a 10-kDa anti-inflammatory protein secreted by bronchiolar Clara cells, is infrequently expressed in non-small cell lung cancer and its overexpression in non-small cell lung cancer cell lines results in a less malignant phenotype. Several lines of evidence have shown that bronchial dysplasia and sputum atypia are predictors of lung cancer. We investigated whether changes in CC10 expression correlate with regression of bronchial dysplasia and/or improvement in sputum abnormalities as measured by image cytometry.

EXPERIMENTAL DESIGN

High-risk smokers enrolled in a chemoprevention trial underwent serial bronchoscopies with biopsies and bronchoalveolar lavage (BAL) collection, sputum assessment by image cytometry, and blood collection. CC10 was measured by competitive ELISA in BAL and plasma. Logistic regression analyses were done to determine the associations between CC10 levels and the improvement in bronchial dysplasia and sputum cytometric assessment.

RESULTS

The net change in the BAL CC10 levels in subjects with improved bronchial lesions or improved sputum cytometry assessment was significantly higher than in those without improvement (P < 0.05). The odds ratio (95% confidence interval) associated with 1-unit increase in CC10 was 2.72 (1.31-5.64) for regression of dysplastic lesions and 2.94 (1.22-7.05) for improvement in sputum cytometry assessment after multivariate adjustment. Plasma CC10 was not significantly associated with either outcome.

CONCLUSIONS

Higher BAL CC10 levels are significantly correlated with regression of bronchial dysplasia and improvement in sputum cytometry assessment in smokers with high lung cancer risk. Whether CC10 levels can predict clinical outcomes among high-risk populations warrants further investigation.

Kinetics and determinants of the changes of CC16, a lung secretory protein in a rat model of toxic lung injury

PURPOSE

To investigate the kinetics and the determinants of the changes of the Clara cell 16 kDa protein (CC16) as a marker of lung injury following exposure to different toxicants.

METHODS

Rats were treated with 4-Ipomeanol (IPO), alpha-naphtylthiourea (ANTU), sodium chromate (Na(2)CrO(4)) or paraquat-(PQ). The changes of CC16, total protein, albumin, and cystatin-C were determined on BALF supernatan, and CC16, cystatin-C and creatinine levels were also determined in serum.

RESULTS

Bronchiolar insult due to IPO or ANTU resulted in an initial transient increase of serum CC16, parallel to that of albumin in BALF, and a subsequent reduction in both BALF and serum. A slight reduction of CC16 in BALF was already apparent one hour following treatment with PQ. In the serum, CC16 increased to 400% of basal value. With PQ and Na(2)CrO(4), the elevation of CC16 was mainly determined by the degree of renal impairment.

Lung epithelial injury markers are not influenced by use of lower tidal volumes during elective surgery in patients without preexisting lung injury

Clara cell protein levels are elevated in plasma of individuals with mild or subclinical lung injury. We studied the influence of two mechanical ventilation strategies on local and systemic levels of Clara cell protein (CC16) and compared them with levels of soluble receptor for advanced glycation end products (sRAGE) and surfactant proteins (SP)-A and -D in patients undergoing elective surgery. Saved samples from a previously reported investigation were used for the study. Forty patients planned for elective surgery were randomized to mechanical ventilation with either a conventional tidal volume (V(T)) of 12 ml/kg without positive end-expiratory pressure (PEEP) or low V(T) of 6 ml/kg and 10 cmH(2)O PEEP. Plasma and bronchoalveolar lavage fluid (BALF) was collected directly after intubation and after 5 h of mechanical ventilation. While systemic levels of SP-A and SP-D remained unchanged, systemic levels of CC16 and sRAGE increased significantly in both groups after 5 h (P < 0.001 for both). BALF levels of SP-A, SP-D, CC16, and sRAGE remained unaffected. No differences were found between the two mechanical ventilation strategies regarding any of the measured biological markers. In conclusion, systemic levels of CC16 and sRAGE rise after 5 h in patients receiving mechanical ventilation for elective surgery. Mechanical ventilation with lower tidal volumes and PEEP did not have a different effect on levels of biomarkers of lung epithelial injury compared with conventional mechanical ventilation.

A critical review of the use of Clara cell secretory protein (CC16) as a biomarker of acute or chronic pulmonary effects

Biomarkers associated with asthma aetiology and exacerbation have been sought to shed light on this multifactorial disease. One candidate is the serum concentration of the Clara cell secretory protein (CC16, sometimes referred to as CC10 or uteroglobin). In this review, we examine serum CC16's relation to asthma aetiology and exacerbation. There is evidence that acute exposures to certain pulmonary irritants can cause a transient increase in serum CC16 levels, and limited evidence also suggests that a transient increase in serum CC16 levels can be caused by a localized pulmonary inflammation. Research also indicates that a transient increase in serum CC16 is not associated with measurable pulmonary damage or impairment of pulmonary function. The biological interpretation of chronic changes in serum CC16 is less clear. Changes in serum CC16 concentrations (either transient or chronic) are not specific to any one agent, disease state, or aetiology. This lack of specificity limits the use of serum CC16 as a biomarker of specific exposures. To date, many of the critical issues that must be understood before serum CC16 levels can have an application as a biomarker of effect or exposure have not been adequately addressed.

Infant swimming practice, pulmonary epithelium integrity, and the risk of allergic and respiratory diseases later in childhood

OBJECTIVE

Irritant gases and aerosols contaminating the air of indoor swimming pools can affect the lung epithelium and increase asthma risk in children. We evaluated the impact of infant swimming practice on allergic status and respiratory health later in childhood.

METHODS

Clara cell protein, surfactant-associated protein D, and total and aeroallergen-specific immunoglobulin E were measured in the serum of 341 schoolchildren aged 10 to 13 years, among whom 43 had followed an infant swimming program. Asthma was defined as doctor-diagnosed asthma and/or positive exercise-induced bronchoconstriction (15% decrease in postexercise forced expiratory volume).

RESULTS

There were no significant differences between the infant swimming group and the other children regarding the levels of exhaled nitric oxide and total or aeroallergen-specific serum immunoglobulin E. Children who swam as infants showed, by contrast, a significant decrease of serum Clara cell protein and of the serum Clara cell protein/surfactant-associated protein D ratio integrating Clara cell damage and permeability changes of the lung epithelial barrier. These effects were associated with higher risks of asthma and of recurrent bronchitis. Passive exposure to tobacco alone had no effect on these outcomes but seemed to interact with infant swimming practice to increase the risk of asthma or of recurrent bronchitis.

CONCLUSIONS

Our data suggest that infant swimming practice in chlorinated indoor swimming pools is associated with airways changes that, along with other factors, seem to predispose children to the development of asthma and recurrent bronchitis.

The association between the anti-inflammatory protein CC10 and smoking status among participants in a chemoprevention trial

CC10, the secretory product of bronchiolar Clara cells, is infrequently expressed in non-small cell lung cancer (NSCLC), and its overexpression in NSCLC cell lines results in a less malignant phenotype. CC10 levels in bronchoalveolar lavage fluid (BAL) and serum are significantly lower in current smokers than healthy nonsmokers, but the effect of long-term smoking cessation on CC10 is unknown. We measured CC10 in baseline BAL and plasma collected from current (n = 81) and former (n = 23) smokers participating in a chemoprevention trial. Former smokers had significantly higher plasma CC10 levels compared with current smokers [mean, 62.1 ng/mL (95% CI, 43.0-81.2); range, 23.0-175.0 ng/mL for former smokers; and mean, 37.1 ng/mL (95% CI, 29.8-44.4); range, 5.0-171.0 ng/mL for current smokers; P < 0.001]. BAL CC10 levels also trended in the same direction. A significant positive correlation was found between CC10 plasma and BAL levels. After adjustment for age, sex, and pack-years of cigarette consumption, former smokers had 1.70 (95% CI, 1.23-2.36) times higher plasma CC10 levels than current smokers (P < 0.01), whereas former smokers also had nonsignificantly higher baseline BAL CC10 levels compared with current smokers [adjusted mean ratio (95% CI), 1.60 (0.92-2.80), P = 0.094 and 1.35 (0.86-2.10), P = 0.193 for the absolute and normalized BAL CC10, respectively]. These results show that sustained smoking cessation is associated with higher plasma CC10 levels, suggesting that at least some of the damage associated with tobacco smoke may be repaired by long-term smoking cessation.

House cleaning with chlorine bleach and the risks of allergic and respiratory diseases in children

Chlorine bleach or sodium hypochlorite can inactivate common indoor allergens. In this cross-sectional study we evaluated to what extent regular house cleaning with bleach can influence the risks of respiratory and allergic diseases in children. We studied a group of 234 schoolchildren aged 10-13 yr among whom 78 children were living in a house cleaned with bleach at least once per week. Children examination included a questionnaire, an exercise-induced bronchoconstriction test and the measurement of exhaled nitric oxide (NO) and of serum total and aeroallergen-specific immunoglobulin (Ig)E, Clara cell protein (CC16) and surfactant-associated protein D (SP-D). Children living in a house regularly cleaned with bleach were less likely to have asthma (OR, 0.10; CI, 0.02-0.51), eczema (OR, 0.22; CI, 0.06-0.79) and of being sensitized to indoor aeroallergens (OR, 0.53; CI, 0.27-1.02), especially house dust mite (OR, 0.43; CI, 0.19-0.99). These protective effects were independent of gender, ethnicity, previous respiratory infections, total serum IgE level and of family history of allergic diseases. They were however abolished by parental smoking, which also interacted with the use of bleach to increase the risk of recurrent bronchitis (OR, 2.03; CI, 1.12-3.66). House cleaning with bleach had effect neither on the sensitization to pollen allergens, nor on the levels of exhaled NO and of serum CC16 and SP-D. House cleaning with chlorine bleach appears to protect children from the risks of asthma and of sensitization to indoor allergens while increasing the risk of recurrent bronchitis through apparently an interaction with parental smoking. As chlorine bleach is one of the most effective cleaning agent to be found, these observations argue against the idea conveyed by the hygiene hypothesis that cleanliness per se increases the risk of asthma and allergy.

Pneumoproteins as markers of paraquat lung injury: a clinical case

OBJECTIVE

To describe the changes in lung-specific secretory proteins in biological fluids in a fatal case of paraquat ingestion and to present immunostaining data obtained on postmortem lung tissue specimens.

METHODS

A 20-year-old man committed suicide by ingesting 100ml of a 20% paraquat solution. Surfactant associated proteins A (SP-A), B (SP-B) and Clara cell 16kDa protein (CC16) were determined in the serum and on broncho-alveloar lavage performed 18h after admission. Renal failure progressed rapidly and the patient died from refractory hypoxia. Immunostaining studies using antibodies directed against CC16, SP-A and SP-B were performed on postmortem lung tissue specimens.

RESULTS

Serum CC16 seemed to increase gradually with the progression of renal impairment. Serum SP-A and SP-B levels increased before any significant changes in pulmonary gas exchanges. The immunostaining study showed that the labeling for SP-A and SP-B was reduced or absent following paraquat toxicity, while Clara cells were relatively preserved.

CONCLUSIONS

The elevation of serum CC16 with paraquat toxicity is probably mainly related to a reduced renal clearance. The increase of serum SP-A and SP-B could reflect an increased lung to blood leakage, independently of the alteration of the renal function.

Outcome value of Clara cell protein in serum of patients with acute respiratory distress syndrome

OBJECTIVE

Injury to the alveolocapillary barrier characterizes ALI/ARDS; therefore determining levels of lung epithelium-specific small proteins in serum may help predict clinical outcomes. We examined whether serum Clara cell protein (CC-16) concentration is correlated with the outcome, mechanical ventilation duration, and incidence of nonpulmonary organ failure.

DESIGN

Prospective multicenter observational study conducted by the Quebec Critical Care Network.

MEASUREMENTS

Seventy-eight adult ARDS patients requiring mechanical ventilation were enrolled and 28-day mortality was the primary outcome. Ventilatory parameters were computed and blood was sampled daily. Clinical information collected included cause of death, duration of mechanical ventilation, number of ventilator-free days, and organ failures.

RESULTS

Median serum levels of CC-16 were significantly higher in nonsurvivors than survivors on days 0-2 (19.93 microg/l, IQR 11.8-44.32, vs. 8.9, 5.66-26.38) and sustained up to day 14. CC-16 levels were correlated positively with the number of failing organs (rho 0.3623) and requirement for prolonged mechanical ventilation. Predictors of patient mortality included age, arterial carbon dioxide partial pressure, CC-16, and APACHE II score (odds ratios 1.35, 1.52, 1.37, 1.159, respectively).

CONCLUSIONS

Higher initial CC-16 serum level is associated with increased risk of death, fewer ventilator-free days, and increased frequency of nonpulmonary multiple organ failure. CC-16 is a valuable biomarker of ARDS that may help predict outcome among ARDS patients with high-risk mortality.

Exhaled metallic elements and serum pneumoproteins in asymptomatic smokers and patients with COPD or asthma

STUDY OBJECTIVES

The aim of this study was to characterize the elemental composition of exhaled breath condensate (EBC) in order to identify new biomarkers of exposure and susceptibility in COPD patients. Serum pneumoproteins were used as lung-specific biomarkers of effect.

DESIGN

EBC was obtained from 50 healthy subjects, 30 healthy smokers, 30 asthmatics, and 50 patients with stable COPD, and was collected by cooling exhaled air. Trace elements and toxic metals in the samples were measured by means of inductively coupled plasma-mass spectrometry and electrothermal atomic absorption spectroscopy. The serum pneumoproteins were immunoassayed.

RESULTS

The EBC of COPD subjects had higher levels of such toxic elements as lead, cadmium, and aluminum, and lower levels of iron and copper, than that of the nonsmoking control subjects. There were no between-group differences in surfactant protein (SP)-A and SP-B levels. Clara-cell protein and SP-D levels were negatively and positively influenced, respectively, by tobacco smoke.

CONCLUSIONS

Our results show that toxic metals and transition elements are detectable in the EBC of studied subjects. We propose new biomarkers of exposure as a means of assessing the target tissue dose of carcinogenic and pneumotoxic substances from tobacco smoke or polluted workplaces, and the use of the transition elements involved in redox systems of oxidative stress as disease biomarkers associated with effect or susceptibility. Together with biomarkers of effect, such as serum pneumoproteins, the elemental composition of EBC may be clinically useful in distinguishing similar diseases.

Biomonitoring of inhaled complex mixtures--ambient air, diesel exhaust and cigarette smoke

Human biomonitoring comprises the determination of biomarkers in body-fluids, cells and tissues. Biomarkers are generally assigned to one of three classes, namely, biomarkers of exposure, effect or susceptibility. Since biomarkers represent steps in an exposure-disease continuum, their application in epidemiological studies ('molecular epidemiology') shows promise. However, to be a predictor of disease, a biomarker has to be validated. Validation criteria for a biomarker include intrinsic qualities such as specificity, sensitivity, knowledge of background in the population, existence of dose-response relationships, degree of inter- and intra-individual variability, knowledge of the kinetics, confounding and modifying factors. In addition, properties of the sampling and analytical procedures are of relevance, including constraints and non-invasiveness of sampling, stability of sample as well as simplicity, high sensitivity, specificity and speed of the analytical method. It is of particular importance to prove by suitable studies that the biomarker of exposure indicates the actual exposure, the biomarker of effect strongly predicts the actual risk of disease and the biomarker of susceptibility actually modifies the risk. Biomonitoring of the exposure to complex mixtures such as polluted ambient air, diesel exhaust or tobacco smoke is a particular challenge since these exposures have many constituents in common and many people were exposed to more than one of these mixtures. Data on the exposure to polycyclic aromatic hydrocarbons (PAH) and benzene from ambient air, diesel exhaust and tobacco smoke will be presented. In addition, some source-specific biomarkers such as nitro-arenes and nicotine metabolites as well as their application in population groups will be discussed. The second part of the presentation addresses the application of biomarkers for assessing so called 'potentially reduced exposure products' (PREPs). According to a recent report of the Institute of Medicine (USA), "reducing risk of disease by reducing exposure to tobacco toxicants is feasible" and "surrogate biological markers that are associated with tobacco-related diseases could be used to offer guidance as to whether or not PREPs are likely to be risk-reducing." In general, the same validation criteria apply as discussed above. In addition, it is suggested that a panel of biomarkers should be used, representing both smoke phases (gas and particulate phase) and the various chemical classes of smoke constituents (e.g., carbonyls, benzene, PAH, tobacco-specific nitrosamines, aromatic amines). Also, a panel of biomarkers of effect should cover the major known adverse effects of smoking (e.g., oxidative stress, inflammatory processes, lipid peroxidation, lipometabolic disorders, mutagenic effects). Biomarkers of nicotine and carbon monoxide uptake are of interest for evaluating the smoking and inhalation behavior, respectively. Finally, suitable study designs for evaluating PREPs are discussed. It is concluded that suitable biomarkers for assessing the exposure to complex mixtures such as ambient air, diesel exhaust and tobacco smoke as well as for evaluating the exposure-reducing properties of PREPs are already available. Future efforts should focus on the development and validation of biomarkers of effect.

Non-invasive biomarkers of pulmonary damage and inflammation: Application to children exposed to ozone and trichloramine

To date, airways injury or inflammation caused by air pollutants has been evaluated mainly by analysis of bronchoalveolar lavage, an invasive technique totally unsuitable to children. The assessment of respiratory risks in this particularly vulnerable population has thus for a long time relied on spirometric tests and self-reported symptoms which are relatively late and inaccurate indicators of lung damage. Research in the field of biomarkers is now opening new perspectives with the development of non-invasive tests allowing to monitor inflammation and damage in the deep lung. Blood tests measuring lung-specific proteins (pneumoproteins) such as Clara cell protein (CC16) and surfactant-associated proteins (A, B or D) are now available to evaluate the permeability and/or the cellular integrity of the pulmonary epithelium. The application of these tests to children has recently led to the discovery of a lung epithelium hyperpermeability caused by trichloramine (nitrogen trichloride), an irritant gas contaminating the air of indoor-chlorinated pools. Serum CC16 can also serve to detect increases of airway permeability during short-term exposures to ambient ozone. Indicators measurable in exhaled air such as nitric oxide (NO) appear more useful to detect airway inflammation. By applying the exhaled NO test to children attending summer camps, we recently found that ambient ozone produces an acute inflammatory response in children from levels slightly lower than current air quality guidelines. In a study exploring the links between atopy, asthma, and exposure to chlorination products in indoor pools, we also found that the exhaled NO test can serve to detect the chronic airway inflammation associated with excessive exposure to trichloramine. Lung-specific proteins measurable in serum and markers in exhaled air represent sensitive tools that can be used to assess non-invasively the effects of air pollutants on the respiratory tract of children.

Clara cell protein and surfactant protein�B in garbage collectors and in wastewater workers exposed to bioaerosols

OBJECTIVES

Inhalation of bioaerosols has been hypothesised to cause "toxic pneumonitis" that should increase lung epithelial permeability at the bronchioloalveolar level. Serum Clara cell protein (CC16) and serum surfactant protein B (SPB) have been proposed as sensitive markers of lung epithelial injury. This study was aimed at looking for increased lung epithelial permeability by determining CC16 and SPB in workers exposed to bioaerosols from wastewater or garbage.

METHODS

Subjects (778 wastewater, garbage and control workers; participation 61%) underwent a medical examination, lung function tests [American Thoracic Society (ATS) criteria], and determination of CC16 and SPB. Symptoms of endotoxin exposure and several potential confounders (age, gender, smoking, kidney function, obesity) were looked for. Results were examined with multiple linear or logistic regression.

RESULTS

Exposure to bioaerosols increased CC16 concentration in the wastewater workers. No effect of exposure on SPB was found. No clue to work-related respiratory diseases was found.

CONCLUSIONS

The increase in CC16 in serum supports the hypothesis that bioaerosols cause subclinical "toxic pneumonitis", even at low exposure.

Clara cell secretory protein: determination of serum levels by an enzyme immunoassay and its importance as an indicator of bronchial asthma in children

Clara cell secretory protein (CC16) is a 16kDa protein secreted by Clara cells in the lining fluid of bronchiolar and bronchial epithelium. CC16 presents several biologic properties, and has been shown to have immunomodulatory and anti-inflammatory activity. It may play a role in controlling inflammation in the airway. There is some evidence that the CC16 level is primarily lower in adult individuals with bronchial asthma, thus contributing to its pathophysiology. This study was designed to examine CC16 serum levels of children, healthy and with asthma. An enzyme solid phase immunoassay utilizing monoclonal antibody to CC16 was the analytical method to determine the protein concentration in blood sera. The method showed excellent linearity, high sensitivity (detection limit: <50 ng/l) and precision. It was found that asthmatic children appear significantly lower levels (P < 0.001) of CC16 in serum as compared to healthy ones. It is, therefore, concluded that CC16 may be a useful diagnostic index of bronchial asthma in the early child-age.

Pulmonary epithelial integrity in children: relationship to ambient ozone exposure and swimming pool attendance

Airway irritants such as ozone are known to impair lung function and induce airway inflammation. Clara cell protein (CC16) is a small anti-inflammatory protein secreted by the nonciliated bronchiolar Clara cells. CC16 in serum has been proposed as a noninvasive and sensitive marker of lung epithelial injury. In this study, we used lung function and serum CC16 concentration to examine the pulmonary responses to ambient O3 exposure and swimming pool attendance. The measurements were made on 57 children 10-11 years of age before and after outdoor exercise for 2 hr. Individual O3 exposure was estimated as the total exposure dose between 0700 hr until the second blood sample was obtained (mean O3 concentration/m3 times symbol hours). The maximal 1-hr value was 118 microg/m3 (59 ppb), and the individual exposure dose ranged between 352 and 914 microg/m3hr. These O3 levels did not cause any significant changes in mean serum CC16 concentrations before or after outdoor exercise, nor was any decrease in lung function detected. However, children who regularly visited chlorinated indoor swimming pools had significantly lower CC16 levels in serum than did nonswimming children both before and after exercise (respectively, 57 +/- 2.4 and 53 +/- 1.7 microg/L vs. 8.2 +/- 2.8 and 8.0 +/- 2.6 microg/L; p < 0.002). These results indicate that repeated exposure to chlorination by-products in the air of indoor swimming pools has adverse effects on the Clara cell function in children. A possible relation between such damage to Clara cells and pulmonary morbidity (e.g., asthma) should be further investigated.

Time and pressure dependence of transvascular Clara cell protein, albumin, and IgG transport during ventilator-induced lung injury in mice

We compared the transport of three proteins with different hydrodynamic radii with ultrastructural changes in lungs of intact mice ventilated at peak inflation pressures (PIP) of 15, 35, 45, and 55 cmH2O for 2 h and PIP of 55 cmH2O for 0.5 and 1 h. After 2 h of ventilation, significant increases were observed in plasma Clara cell secretory protein (1.9 nm radius) at 35 cmH2O PIP and in bronchoalveolar lavage fluid albumin (3.6 nm radius) at 45 cmH2O PIP and IgG (5.6 nm radius) at 55 cmH2O PIP. Increased concentrations of all three proteins and lung wet-to-dry weight ratios were significantly correlated with PIP and ventilation time. Clara cell secretory protein and albumin increased significantly after 0.5 h of 55 cmH2O PIP, but IgG increased only after 2 h. Separation of endothelium or epithelium to form blebs was apparent only in small vessels (15-30 μm diameter) at 45 cmH2O PIP and after 0.5 h at 55 cmH2O PIP but became extensive after 2 h of ventilation at 55 cmH2O PIP. Junctional gaps between cells were rarely observed. Ultrastructural lung injury and protein clearances across the air-blood barrier were related to ventilation time and PIP levels. Protein clearances increased in relation to molecular size, consistent with increasing dimensions and frequency of transmembrane aqueous pathways.

Serum pneumoproteins: a cross-sectional comparison of firefighters and police

BACKGROUND

Serum pneumoproteins provide a measure of the permeability of the lower respiratory tract, and have shown promise as a biomarker of acute and chronic exposure to respiratory toxicants.

METHODS

To evaluate the effects of chronic occupational smoke exposure, 105 firefighters were compared with 44 police controls in a cross-sectional study using spirometry, diffusing capacity of the lung, serum Clara cell protein (CC16), and serum surfactant-associated protein A (SP-A) measurements.

RESULTS

There were no significant differences in age, gender, height, spirometry (FVC and FEV(1)), and diffusing capacity between the two groups. Serum SP-A was lower in firefighters (260.1 +/- 121.2 microg/L) than police (316.0 +/- 151.4 microg/L, P = 0.019). Serum CC16 was also lower in firefighters (8.39 +/- 3.11 microg/L) than police (10.56 +/- 4.20 microg/L, P < 0.001), although this difference lost statistical significance when adjusted for confounders.

CONCLUSIONS

Firefighters have lower serum concentrations of SP-A than do police. Although the clinical significance of this finding is presently unknown, SP-A deserves further study as a biomarker of toxic exposure to the lower respiratory tract.

Lung hyperpermeability and asthma prevalence in schoolchildren: unexpected associations with the attendance at indoor chlorinated swimming pools

AIMS

To study whether exposure to nitrogen trichloride in indoor chlorinated pools may affect the respiratory epithelium of children and increase the risk of some lung diseases such as asthma.

METHODS

In 226 healthy children, serum surfactant associated proteins A and B (SP-A and SP-B), 16 kDa Clara cell protein (CC16), and IgE were measured. Lung specific proteins were measured in the serum of 16 children and 13 adults before and after exposure to NCl(3) in an indoor chlorinated pool. Relations between pool attendance and asthma prevalence were studied in 1881 children. Asthma was screened with the exercise induced bronchoconstriction test (EIB).

RESULTS

Pool attendance was the most consistent predictor of lung epithelium permeability. A positive dose-effect relation was found with cumulated pool attendance and serum SP-A and SP-B. Serum IgE was unrelated to pool attendance, but correlated positively with lung hyperpermeability as assessed by serum SP-B. Changes in serum levels of lung proteins were reproduced in children and adults attending an indoor pool. Serum SP-A and SP-B were already significantly increased after one hour on the pool side without swimming. Positive EIB and total asthma prevalence were significantly correlated with cumulated pool attendance indices.

CONCLUSIONS

Regular attendance at chlorinated pools by young children is associated with an exposure dependent increase in lung epithelium permeability and increase in the risk of developing asthma, especially in association with other risk factors. We therefore postulate that the increasing exposure of children to chlorination products in indoor pools might be an important cause of the rising incidence of childhood asthma and allergic diseases in industrialised countries. Further epidemiological studies should be undertaken to test this hypothesis.

Inflammation markers in relation to cognition in a healthy aging population

The relation between serum inflammatory protein levels and cognitive performance was investigated in a healthy population. Individuals were tested during 6 years of follow-up. Serum concentrations of 10 inflammatory proteins were correlated to cognitive speed (Letter-Digit Coding Test, LDCT), attention and information processing (Stroop) and memory (Word Learning). Haptoglobin levels at baseline correlated negatively with cognitive performance on the Stroop and Word Learning Recall test over the 6 years follow-up period. C-reactive protein (CRP) levels at baseline correlated negatively with performance on the Word Learning tests over the 6 years follow-up period. Thus, relatively high concentrations of haptoglobin and C-reactive protein may be indicative for impaired cognitive performance.

Changes in serum pneumoproteins caused by short-term exposures to nitrogen trichloride in indoor chlorinated swimming pools

Nitrogen trichloride (NCl(3)) is an irritant gas released in the air of indoor pools sanitized with chlorine-based disinfectants. In the present study we investigated the effects of NCl(3) on the pulmonary epithelium of pool attendees by measuring the leakage into serum of three lung-specific proteins (pneumoproteins): the alveolar surfactant-associated proteins A and B (SP-A and SP-B) and the bronchiolar 16 kDa Clara cell protein (CC16). These pneumoproteins were measured in the serum of 29 recreational swimmers (16 children and 13 adults) before and after attending a chlorinated pool with a mean NCl(3) concentration of 490 microg m(-3). Pneumoprotein changes in serum were also studied in 14 trained swimmers performing an intensive 45 min standardized swimming session in a chlorinated pool (mean NCl(3) concentration of 355 microg m(-3)) and for the purposes of comparison in a non-chlorinated pool sanitized by the copper/silver method. Serum CC16 was not increased in recreational swimmers, but in trained swimmers serum levels of this protein peaked immediately after strenuous exercise, both in the copper/silver pool and in the chlorinated pool. This acute increase in airway permeability is probably the consequence of the mechanical stress on the epithelial barrier caused by overinflation and/or hyperventilation during intense exercise. Serum levels of SP-A and SP-B were unaffected by strenuous exercise in the copper/silver pool. The two proteins were, however, significantly increased in a time-dependent manner in recreational and trained swimmers attending the chlorinated pool. The intravascular leakage of SP-A and SP-B was already statistically significant after only 1 h of exposure to pool air without exercising and remained elevated for 12 h after. These changes were not associated with decrements in lung function. The ability of NCl(3) to acutely disrupt the lung epithelium barrier was confirmed in mice using serum CC16 and plasma proteins in bronchoalveolar lavage fluid as permeability markers. The significance of these permeability changes induced by NCl(3) in the deep lung is presently unknown. In view of the increasing and widespread human exposure to this gas not only in indoor pools but also in a variety of other situations, these findings warrant further study.

Decreased serum and bronchoalveolar lavage levels of Clara cell secretory protein (CC16) is associated with bronchiolitis obliterans syndrome and airway neutrophilia in lung transplant recipients

BACKGROUND

The major hinderance for long-term survival after lung transplantation is chronic rejection in the form of bronchiolitis obliterans syndrome (BOS). BOS is a fibrosing process in the small airways causing irreversible airway obstruction. BOS is associated with increased oxidative burden and activation of inflammatory and growth-stimulating mediators. The Clara cell secretory protein (CCSP or CC16) is a secreted differentiation marker for the bronchiolar epithelium with both antioxidative and antiinflammatory/immmunomodulatory properties. We asked whether this molecule could have a role in the development of BOS.

METHODS

Serum and bronchoalveolar lavage (BAL) fluid samples were collected from 22 consecutive lung transplant recipients, the majority (19) was followed for 2 years. Six patients developed BOS. CCSP in serum was measured in 162 samples from 19 patients with an ELISA method, and CCSP in 191 BAL samples from 22 patients with quantitative Western blot.

RESULTS

CCSP in both serum and BAL was significantly lower in BOS compared with acute rejection or no rejection. After the first postoperative month, serum and BAL CCSP levels were consistently lower in the patients who developed BOS than in those who did not. The percentage of neutrophils in BAL correlated negatively with CCSP in BAL.

CONCLUSIONS

Levels of CCSP in serum and BAL is lowered in BOS. Serum CCSP could have a potential as an early marker for BOS. The correlation between decreased CCSP and increased neutrophils in BAL suggests a loss of local airway defense capacity in BOS.

Clara cell protein (CC16) in serum and bronchoalveolar lavage fluid of subjects exposed to asbestos

The Clara cell protein (CC16) is a small and readily diffusible protein of 16 kDa secreted by bronchiolar Clara cells in the distal airspaces. These epithelial cells are altered in several pulmonary pathological processes induced by various lung toxicants. In the search for a new biomarker of asbestos-induced lung impairment, we used a sensitive immunoassay to determine the levels of CC16 in bronchoalveolar fluid (BALF) and serum of subjects exposed to asbestos compared with a group of healthy controls. In the BALF of asbestos-exposed subjects there was an insignificant trend towards CC16 elevation compared with controls, with a (mean +/- SD of 0.81 +/- 0.65 mg l-1 for asbestos-exposed subjects (n = 23) versus 0.39 +/- 0.19 mg l-1 for controls (n = 11) (p = 0.09). In serum, CC16 concentration was significantly increased among asbestos-exposed subjects, with values of 27.2 +/- 24.0 micrograms l-1 for asbestos-exposed subjects (n = 34) versus 16.1 +/- 7.6 micrograms l-1 for controls (n = 34) (p = 0.01). Regarding the effects of smoking, there were significant differences between generally lower CC16 levels in serum and BALF (p = 0.05 and 0.001, respectively) of smokers compared with the higher levels in non-smokers. Serum CC16 levels positively correlated with those in BALF, which is consistent with a diffusional transfer of CC16 from the bronchoalveolar space into the serum. No association, however, emerged between the levels of CC16 in serum or BALF and either the duration of asbestos exposure or the severity of the lung impairment as assessed by chest X-ray. These findings suggest that exposure to asbestos elicits early changes in the local and, importantly, also the systemic levels of CC16. This pneumoprotein therefore appears as a promising non-invasive biomarker of asbestos-induced lung injury and occupational disease in both smoking and non-smoking exposed subjects.

Analysis of native proteins from biological fluids by biomolecular interaction analysis mass spectrometry (BIA/MS): exploring the limit of detection, identification of non-specific binding and detection of multi-protein complexes

Biomolecular interaction analysis mass spectrometry (BIA/MS) is a two-dimensional analytical technique that quantitatively and qualitatively detects analytes of interests. In the first dimension, surface plasmon resonance (SPR) is utilized for detection of biomolecules in their native environment. Because SPR detection is non-destructive, analyte(s) retained on the SPR-active sensor surface can be analyzed in a second dimension using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. The qualitative nature of the MALDI-TOF MS analysis complements the quantitative character of SPR sensing and overcomes the shortcomings of the SPR detection stemming from the inability to differentiate and characterize multi-protein complexes and non-specific binding. In this work, the benefit of performing MS analysis following SPR sensing is established. Retrieval and detection of four markers present in biological fluids (cystatin C, beta-2-microglobulin, urinary protein 1 and retinol binding protein) was explored to demonstrate the effectiveness of BIA/MS in simultaneous detection of clinically related biomarkers and delineation of non-specific binding. Furthermore, the BIA/MS limit of detection at very low SPR responses was investigated. Finally, detection of in-vivo assembled protein complexes was achieved for the first time using BIA/MS.

Maternal tobacco smoking and lung epithelium-specific proteins in amniotic fluid

The bronchiolar 16 kD Clara cell secretory protein (CC16) and the alveolar surfactant-associated protein A (SP-A) are secreted in the amniotic fluid (AF), where they reflect the growth and the maturity of the fetal lung. To evaluate the possible effects of in utero tobacco smoke exposure upon infant bronchoalveolar epithelium function and maturity, CC16 and SP-A levels were determined in AF obtained at term (36-41 wk) from 28 nonsmoking, 18 smoke-exposed, and 28 smoking mothers with uncomplicated pregnancies. Tobacco smoke exposure was assessed by questionnaire and the assay in AF and maternal urine of cotinine, a stable nicotine metabolite. The specificity of the changes of CC16 and SP-A concentrations in AF was assessed by comparison with nonpulmonary proteins of high- (albumin and transferrin) or low-molecular weight (beta2-microglobulin, retinol binding protein, cystatin-C). Pulmonary and nonpulmonary AF proteins were also compared by two-dimensional gel electrophoresis between smoking and nonsmoking mothers. The levels of CC16 and SP-A as well as low- and high-molecular-weight proteins were not significantly different between the three smoking categories. The protein pattern of AF, established by two-dimensional gel electrophoresis, did not reveal any quantitative or qualitative difference between nonsmoking (n = 10), smoke-exposed (n = 5), and smoking mothers (n = 5). By multiple regression analysis of possible determinants, tobacco smoke did not emerge as a significant predictor of CC16 and SP-A concentrations in AF. SP-A level was dependent only on gestational age at birth (r2 = 0.1, p = 0.001), whereas CC16 correlated only with the levels of low-molecular weight proteins (r2 = 0.2, p = 0.0001). The latter correlation suggests that CC16 enters AF not only as a result of its secretion at the surface of the respiratory tract but also partly following its elimination by the fetal kidney. This study suggests that maternal smoking during pregnancy is not associated with alterations of the secretory functions of the epithelium of the distal airways and the alveoli at term.

Serum Clara cell protein (CC16), a marker of the integrity of the air-blood barrier in sarcoidosis

To test the hypothesis that sarcoidosis is associated with an intravascular leakage of lung epithelium secretory proteins, the occurrence and determinants in serum of sarcoid patients of CC16, a small size and readily diffusible lung-specific protein of 16 kDa secreted by bronchiolar Clara cells, was investigated. CC16 was measured by a sensitive latex immunoassay in the serum of 117 patients with established sarcoidosis and of 117 healthy subjects matched for age, sex and smoking status. Stepwise regression analysis was used to identify extrapulmonary variables of CC16 changes in serum. These changes were then compared with biochemical and cellular parameters in bronchoalveolar lavage fluid (BALF) as well as with the number of CC16 immunostaining cells on bronchial or pulmonary biopsy samples. CC16 concentration in serum of sarcoid patients was significantly increased, compared to their matched controls (25.9 +/- 16.2 versus 13.9 +/- 5.2 microg x L(-1)). In nonsmoking patients without significant renal impairment, CC16 in serum increased with the severity of the chest radiograph and computed tomography changes, and was on average 50-100% higher when parenchymal involvement was present. Sarcoid patients had, however, normal levels of CC16 in BALF and an unchanged number of CC16-immunopositive cells in lung biopsy samples, suggesting that an increased secretion of CC16 in the sarcoid lung is very unlikely, and that the elevation of CC16 in sarcoidosis results from an increased intravascular leakage of the protein across the air-blood barrier. The present study suggests that CC16 in serum might provide a useful tool to noninvasively evaluate the damage and increased permeability to proteins of the air-blood barrier associated with sarcoidosis.

Polymorphism of Quinone-metabolizing Enzymes and Susceptibility to Ozone-induced Acute Effects

The role of the genetic polymorphism of NAD(P)H:quinone oxidoreductase (NQO1) and glutathione-S-transferase micro-1 (GSTM1) in the responsiveness to O(3)-induced acute effects was investigated in 24 healthy nonsmokers performing 2-h bike rides at ambient O(3) varying from 32 to 103 ppb. Before and after rides, each subject performed spirometric tests and provided a blood sample for the measurement of the Clara cell protein CC16. NQO1 and GSTM1 polymorphisms were characterized by polymerase chain reaction- based methods. The 8-hydroxy-2'-deoxyguanosine (8-OHdG) adduct was also measured in DNA of peripheral leukocytes. Rides at O(3) > 80 ppb resulted in significant decrements of pulmonary function tests and increased levels of serum CC16, consistent with mild impairment in respiratory function and increased lung epithelial permeability, respectively. Whereas NQO1wt and GSTM1null subjects showed both functional changes and increased serum CC16 after acute O(3) exposure, people with other haplotypes showed a rise in serum CC16 but no changes in lung function tests. In NQO1wt and GSTM1null subjects, partial correlation analysis showed that functional decrements and increased serum CC16 are closely associated with each other and with O(3) levels, whereas no such relationships were found among subjects bearing other haplotypes. An increased reaction rate between O(3) and hydroquinones would be consistent with the greater increase in 8-OHdG after O(3) exposure in this "susceptible" group.

Adverse respiratory effects following overhaul in firefighters

Overhaul is the stage in which firefighters search for and extinguish possible sources of reignition. It is common practice not to wear respiratory protection during overhaul. Fifty-one firefighters in two groups, 25 without respiratory protection and 26 wearing cartridge respirators, were monitored for exposure to products of combustion and changes in spirometric measurements and lung permeability following overhaul of a structural fire. Testing at baseline and 1 hour after overhaul included forced vital capacity (FVC), forced expiratory volume in one second (FEV1), serum Clara cell protein (CC16), and serum surfactant-associated protein A (SP-A). Overhaul increased CC16 in both groups, indicating increased alveolarcapillary membrane permeability. Contrary to expectations, SP-A increased and FVC and FEV1 decreased in the firefighters wearing cartridge respirators. Changes in FEV1, CC16, and SP-A were associated with concentrations of specific products of combustion or carboxyhemoglobin levels. Firefighter exposures during overhaul have the potential to cause changes in spirometric measurements and lung permeability, and self-contained breathing apparatus should be worn during overhaul to prevent lung injury.

Association between plasma CC16 levels, the A38G polymorphism, and asthma

The effect of the A38G polymorphism on Clara cell secretory protein (CC16) gene expression and asthma was investigated by measuring plasma CC16 levels in 100 asthmatic and nonasthmatic children. Restriction digestion determined the A38G genotype and plasma CC16 levels were analyzed using a sensitive latex immunoassay. Asthmatics had lower mean plasma CC16 levels adjusted for age and gender (7.96 microg/L; 95% confidence interval [CI] = 6.79 to 9.31) than nonasthmatic subjects (9.98 microg/L; 95% CI = 8.83 to 11.26) (p = 0. 006). Similarly adjusted, mean plasma CC16 levels were also lower in 38A/38A (6.79 microg/L; 95% CI = 4.56 to 9.02) than 38G/38G subjects (10.01 microg/L; 95% CI = 7.90 to 12.12; p = 0.003). The odds ratio for asthma diagnosis of 38A/38A subjects was 4.78 (95% CI = 1.08 to 21.18; p = 0.04) compared with 38G/38G subjects. However, this was reduced when corrected from plasma CC16 level, suggesting that the odds of asthma was largely mediated through altered plasma CC16 levels. The 38A sequence was associated with reduced plasma CC16 levels and individuals with lower plasma CC16 levels were more likely to have asthma. This provides further evidence for a significant role of the CC16 gene, 38A allele in the development of asthma.