Serum and BAL Clara cell 10 kDa protein (CC10) levels and CC10-positive bronchiolar cells are decreased in smokers

Clara cell protein 16: A biomarker for detecting secondary respiratory complications in patients with multiple injuries

BACKGROUND

Clara cell protein 16 (CC16) has recently gained acceptance as a blood biomarker for detecting direct and indirect lung injury. Although the early elevation of CC16 serum levels has been shown to correlate with pulmonary damage in patients with multiple injuries, the subsequent time course of CC16 serum levels has not been investigated in these patients.

METHODS

Fifty-eight patients with multiple injuries, 32 with severe thoracic injury, and 12 healthy volunteers were enrolled in this study. CC16 serum levels were measured at the time they were admitted to the trauma ward "time 0" and subsequently until day 14 using the enzyme-linked immunosorbent assay technique. The correlation between CC16 serum levels and severe lung injury, onset of nosocomial pneumonia, acute respiratory distress syndrome or acute lung injury, and organ failure was measured. In addition, areas under the receiver operating characteristic curve were calculated (p < 0.05 = significant).

RESULTS

In patients with lung injury, initial "time 0" median CC16 values were significantly elevated (11.2 ng/mL) compared with patients without severe thoracic injury (6.9 ng/mL) and controls (6.3 ng/mL). The observed elevation in serum CC16 declined to control values within 12 to 24 hours after trauma unless patients secondarily developed pneumonia. In the latter patients, median CC16 serum levels were significantly elevated (14.5 ng/mL) at the onset of pneumonia compared with their levels (7.3 ng/mL) 1 day before. In contrast, no secondary elevation in CC16 serum levels was observed in patients without severe lung injury within the same 24-hour period. The area under the receiver operating characteristic curve for serum CC16 and pneumonia was 0.79 (0.62-0.97; p = 0.0011).

CONCLUSION

Our results confirm the previously described association between initial elevation in CC16 serum levels and severe thoracic injury in patients with multiple injuries. In addition, we found that the initial elevation in CC16 serum levels declines to control values within the first day after trauma and that a secondary elevation indicates respiratory complications.

LEVEL OF EVIDENCE

Diagnostic study, level II.

Reduced exposure evaluation of an Electrically Heated Cigarette Smoking System. Part 6: 6-Day randomized clinical trial of a menthol cigarette in Japan

A randomized, controlled, open-label, parallel-group, single-center study to determine biomarkers of exposure to 12 selected harmful and potentially harmful constituents (HPHC) in cigarette smoke, excretion of mutagenic material in urine, and serum Clara cell 16-kDa protein (CC16) in 102 male and female Japanese subjects who smoked Marlboro Ultra Lights Menthol cigarettes (M4J(M); 4 mg tar and 0.3mg nicotine) at baseline. Subjects were randomized to continue smoking M4J(M), or switch to smoking either the Electrically Heated Cigarette Smoking System menthol cigarette (EHCSS-K6(M); 5mg tar and 0.3mg nicotine) or the Lark One menthol cigarette (Lark1(M); 1mg tar and 0.1mg nicotine), or to no-smoking. The mean decreases from baseline to Day 5/6 were statistically significant (p ≤ 0.05) for exposure to 10 of 12 cigarette smoke HPHC including the primary endpoint (carbon monoxide) and urinary excretion of mutagenic material in the EHCSS-K6(M) group (-12.3% to -83.4%). Smaller, but statistically significant reductions (p ≤ 0.05) occurred in the Lark1(M) group (-3.3% to -35.2%), with the exception of urinary mutagens. The largest mean reductions (all p ≤ 0.05) in exposure to cigarette smoke HPHC and excretion of mutagenic material occurred in the no-smoking group (-1.4% to -93.6%). Serum CC16, an indicator of lung epithelial injury, was not significantly different between groups.

Unifying thoracic biomarkers: surfactant protein-D and beyond

Chronic obstructive pulmonary disease (COPD) is a progressive disorder that affects 300 million people worldwide and is responsible for 3 million deaths annually. Currently, there are no accepted biomarkers of COPD, which has impaired drug development and management of patients with COPD. Pneumoproteins, which are proteins synthesized predominantly in the lungs, are promising blood biomarkers because they have high specificity for lung disease. The most promising is surfactant protein-D, which is synthesized largely in Type 2 pneumocytes, and its blood concentrations have been associated with COPD and with certain clinical end points such as mortality. In this paper, we discuss surfactant protein-D and other pneumoproteins as promising biomarkers of COPD.

Systemic biomarkers of neutrophilic inflammation, tissue injury and repair in COPD patients with differing levels of disease severity

The identification and validation of biomarkers to support the assessment of novel therapeutics for COPD continues to be an important area of research. The aim of the current study was to identify systemic protein biomarkers correlated with measures of COPD severity, as well as specific protein signatures associated with comorbidities such as metabolic syndrome. 142 protein analytes were measured in serum of 140 patients with stable COPD, 15 smokers without COPD and 30 non-smoking controls. Seven analytes (sRAGE, EN-RAGE, NGAL, Fibrinogen, MPO, TGF-α and HB-EGF) showed significant differences between severe/very severe COPD, mild/moderate COPD, smoking and non-smoking control groups. Within the COPD subjects, univariate and multivariate analyses identified analytes significantly associated with FEV(1), FEV(1)/FVC and DLCO. Most notably, a set of 5 analytes (HB-EGF, Fibrinogen, MCP-4, sRAGE and Sortilin) predicted 21% of the variability in DLCO values. To determine common functions/pathways, analytes were clustered in a correlation network by similarity of expression profile. While analytes related to neutrophil function (EN-RAGE, NGAL, MPO) grouped together to form a cluster associated with FEV(1) related parameters, analytes related to the EGFR pathway (HB-EGF, TGF-α) formed another cluster associated with both DLCO and FEV(1) related parameters. Associations of Fibrinogen with DLCO and MPO with FEV(1)/FVC were stronger in patients without metabolic syndrome (r  =  -0.52, p  =  0.005 and r  =  -0.61, p =  0.023, respectively) compared to patients with coexisting metabolic syndrome (r  =  -0.25, p  =  0.47 and r  =  -0.15, p  =  0.96, respectively), and may be driving overall associations in the general cohort. In summary, our study has identified known and novel serum protein biomarkers and has demonstrated specific associations with COPD disease severity, FEV(1), FEV(1)/FVC and DLCO. These data highlight systemic inflammatory pathways, neutrophil activation and epithelial tissue injury/repair processes as key pathways associated with COPD.

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.

Biomarkers of therapeutic response in patients with chronic obstructive pulmonary disease: a critical review of the literature

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality across the world. Unfortunately, none of the current therapies, except for smoking cessation and supplemental domiciliary oxygen for hypoxaemic patients, can modify its natural course or alter survival. The pipeline for new compounds is not very promising owing to repeated failures, and many large pharmaceutical companies have abandoned COPD drug discovery altogether. One major barrier to new drug discovery is the lack of modifiable biomarkers that can be used as surrogates of clinical outcomes such as exacerbation and mortality. The only accepted marker in COPD is forced expiratory volume in 1 second (FEV(1)). However, by definition, COPD is a non-reversible or poorly reversible condition with respect to FEV(1). Thus, very few drugs except for bronchodilators have been able to address this endpoint. Of many candidate molecules, sputum neutrophil counts, exhaled corrected alveolar nitric oxide and proline-glycine-proline (PGP) and N-α-PGP, which are breakdown products of collagen, are promising lung-based biomarkers. However, their clinical utility has not been validated in large clinical trials. Promising blood biomarkers include surfactant protein D, and pulmonary- and activation-regulated chemokine (PARC/CCL-18). However, the clinical data have been inconsistent. Non-specific inflammatory biomarkers such as C-reactive protein and interleukin-6 lack specificity for COPD and thus are of limited clinical usefulness.

Circulating levels of Clara cell protein 16 but not surfactant protein D identify and quantify lung damage in patients with multiple injuries

BACKGROUND

Almost 60% of all patients with severe multiple injuries sustain severe chest trauma with aggravating effect on morbidity and mortality. Diagnosis of lung contusion is performed by early posttraumatic multislice computed tomography. Because this diagnostic procedure requires time, resources, and exposure to radiation, a noninvasive approach with easy follow-up measurements is warranted.

METHODS

Serum levels of Clara cell protein 16 (CC16) and surfactant protein D as lung-specific biomarkers were obtained on admission from 104 patients with multiple injuries using enzyme-linked immunosorbent assay technique. Patients were divided into those with severe lung injury ([LI]; n = 68) and without LI (NLI; n = 36). Nonsmoking healthy volunteers served as controls. In addition, volume of lung contusions were calculated planimetrically on serial multislice computed tomography scans obtained after admission. Factors influencing CC16 serum levels were determined in uni- and multivariate analyses, and Spearman rank coefficients were calculated for correlations.

RESULTS

Patients with LI showed a significant (p < 0.05) elevation of median CC16 levels (10.2 ng/mL) compared with NLI patients (5.4 ng/mL) and controls (5.2 ng/mL). Serum CC16 levels correlated with the volume of lung contusions (r = 0.78, p < 0.0001) and were not influenced by overall injury severity, age, gender, or preclinical ventilation. In contrast, circulating surfactant protein D levels were not associated with the presence of LI or the extent of lung contusions.

CONCLUSIONS

Our results advocate CC16 as a potential biomarker for LI in severely injured patients because of its high correlation with the volume of contused lung parenchyma. Therefore, this parameter may allow a specified initial treatment of patients with multiple injuries.

Sputum and nasal lavage lung-specific biomarkers before and after smoking cessation

Background

Little is known about the effect of smoking cessation on airway inflammation. Secretory Leukocyte Protease Inhibitor (SLPI), Clara Cell protein 16 (CC16), elafin and human defensin beta-2 (HBD-2) protect human airways against inflammation and oxidative stress. In this longitudinal study we aimed to investigate changes in sputum and nasal lavage SLPI, CC16, elafin and HBD-2 levels in healthy smokers after 6 and 12 months of smoking cessation.

Methods

Induced sputum and nasal lavage was obtained from healthy current smokers (n = 76) before smoking cessation, after 6 months of smoking cessation (n = 29), after 1 year of smoking cessation (n = 22) and from 10 healthy never smokers. SLPI, CC16, elafin and HBD-2 levels were measured in sputum and nasal lavage supernatants by commercially available ELISA kits.

Results

Sputum SLPI and CC-16 levels were increased in healthy smokers before smoking cessation versus never-smokers (p = 0.005 and p = 0.08 respectively). SLPI and CC16 levels did not differ before and 6 months after smoking cessation (p = 0.118 and p = 0.543 respectively), neither before and 1 year after smoking cessation (p = 0.363 and p = 0.470 respectively). Nasal lavage SLPI was decreased 12 months after smoking cessation (p = 0.033). Nasal lavage elafin levels were increased in healthy smokers before smoking cessation versus never-smokers (p = 0.007), but there were no changes 6 months and 1 year after smoking cessation.

Conclusions

Only nasal lavage SLPI decrease after 1 year after smoking cessation. We may speculate that there is an ongoing inflammatory process stimulating the production of counter-regulating proteins in the airways of healthy ex-smokers.

Use of serum clara cell 16-kDa (CC16) levels as a potential indicator of active pulmonary fibrosis in systemic sclerosis

OBJECTIVE

To clarify the clinical significance of concentrations of serum Clara cell 16-kDa protein (CC16; previously denoted CC10) in the diagnosis and monitoring of pulmonary fibrosis (PF) in patients with systemic sclerosis (SSc); and to compare CC16 levels with levels of the current most reliable serum markers for PF, such as Krebs von den Lungen-6 (KL-6) antigen and surfactant protein-D (SP-D).

METHODS

Serum levels of CC16, KL-6, and SP-D were determined by ELISA in 92 patients with SSc, 20 patients with systemic lupus erythematosus (SLE), and 20 healthy controls. In a retrospective longitudinal study, correlation of serum CC16 levels with the activity of PF was assessed in 16 SSc patients with PF.

RESULTS

Although CC16 levels were higher in patients with SSc than in SLE patients or healthy controls, the difference was not significant. Increased serum CC16 levels were associated with involvement of PF, especially active PF, as well as KL-6 and SP-D. Receiver operating characteristic curve analysis revealed that the utility of CC16 is slightly inferior to KL-6, but was comparable with that of SP-D for detecting PF in patients with SSc. In the longitudinal study, serum levels of CC16, KL-6, and SP-D were significantly decreased in the inactive disease phase compared to the active disease phase.

CONCLUSION

CC16 levels can be used as a potential serum biomarker for PF in addition to KL-6 and SP-D in patients with SSc.

Clara cell protein in bronchoalveolar lavage fluid: a predictor of ventilator-associated pneumonia?

Introduction

Clara cell protein 10 (CC-10) has been associated with inflammatory and infectious pulmonary diseases. This study evaluates CC-10 concentrations in bronchoalveolar lavage (BAL) fluid as a potential marker of ventilator-associated pneumonia (VAP).

Methods

Between January 2003 and December 2007, BAL fluid samples obtained from critically ill patients at the intensive care unit of the Maastricht University Medical Centre clinically suspected of having VAP were included. Patients were divided into two groups: (1) microbiologically confirmed VAP (the VAP group) and (2) microbiologically unconfirmed VAP (the non-VAP group). The concentration of CC-10 was measured by means of a commercially available enzyme-linked immunosorbent assay kit, and retrospective analysis was performed. Areas under the curve of receiver operating characteristic curves were calculated for CC-10 concentrations.

Results

A total of 196 patients (122 men, 74 women) were included. A total of 79 (40%) of 196 cases of suspected VAP were microbiologically confirmed. The median CC-10 concentration in the VAP group was 3,019 ng/mL (range, 282 to 65,546 ng/mL) versus 2,504 ng/mL (range, 62 to 30,240 ng/mL) in the non-VAP group (P = 0.03). There was no significant difference in CC-10 concentrations between patients treated with or without corticosteroids (P = 0.26) or antibiotic therapy (P = 0.9). The CC-10 concentration did not differ significantly between patients with Gram-positive versus Gram-negative bacteria that caused the VAP (P = 0.06). However, CC-10 concentrations did differ significantly between the late-onset VAP group and the non-VAP group.

Conclusions

The CC-10 concentration in BAL fluid yielded low diagnostic accuracy in confirming the presence of VAP.

Site-specific differences in gene expression of secreted proteins in the mouse lung: comparison of methods to show differences by location

Studies on the effects of pulmonary toxicants on the lung often overlook the fact that site-specific changes are likely to occur in response to chemical exposure. These changes can be highly focal and may be undetected by methods that do not examine specific lung regions. This problem is especially acute for studies of the conducting airways. In this study, differential gene expression of secreted proteins in the lung by different methods of collection (whole lung, gross airway microdissection, and laser capture microdissection) and by airway levels (whole lobe, whole airway tree, proximal airways, airway bifurcations, and terminal bronchioles) was examined. Site-specific sampling approaches were combined with methods to detect both gene and corresponding protein expression in different lung regions. Differential expression of mRNA by both airway level and lung region was determined for Clara cell secretory protein, calcitonin gene-related peptide, uteroglobin-related protein 2, surfactant protein A, and surfactant protein C. Therefore, for maximal enrichment of mRNA and maximal ability to identify changes in mRNA levels in the diseased state or in response to chemical exposure, it is critical to choose the appropriate airway region and sample collection method to enrich detection of the transcript(s) of interest.

Exercise but not mannitol provocation increases urinary Clara cell protein (CC16) in elite swimmers

Elite swimmers have an increased risk of developing asthma, and exposure to chloramine is believed to be an important trigger factor. The aim of the present study was to explore pathophysiological mechanisms behind induced bronchoconstriction in swimmers exposed to chloramine, before and after swim exercise provocation as well as mannitol provocation. Urinary Clara cell protein (CC16) was used as a possible marker for epithelial stress. 101 elite aspiring swim athletes were investigated and urinary samples were collected before and 1 h after completed exercise and mannitol challenge. CC16, 11β-prostaglandin (PG)F(2α) and leukotriene E(4) (LTE(4)) were measured. Urinary levels of CC16 were clearly increased after exercise challenge, while no reaction was seen after mannitol challenge. Similar to CC16, the level of 11β-PGF(2α) was increased after exercise challenge, but not after mannitol challenge, while LTE(4) was reduced after exercise. There was no significant difference in urinary response between those with a negative compared to positive challenge, but a tendency of increased baseline levels of 11β-PGF(2α) and LTE(4) in individuals with a positive mannitol challenge. The uniform increase of CC16 after swim exercise indicates that CC16 is of importance in epithelial stress, and may as such be an important pathogenic factor behind asthma development in swimmers. The changes seen in urinary levels of 11β-PGF(2α) and LTE(4) indicate a pathophysiological role in both mannitol and exercise challenge.

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.

Association between occupational exposure to arsenic and neurological, respiratory and renal effects

Occupational exposure by inhalation in copper smelter is associated with several subclinical health phenomena. The respiratory tract is usually involved in the process of detoxication of inhaled noxious agents which, as arsenic, can act as inductors of oxidative stress (Lantz, R.C., Hays, A.M., 2006. Role of oxidative stress in arsenic-induced toxicity. Drug Metab. Rev. 38, 791-804). It is also known that irritating fumes affect distal bronchioles of non-ciliated, epithelial Clara cells, which secrete anti-inflammatory and immunosuppressive Clara cell protein (CC16) into the respiratory tract. The study group comprised 39 smelters employed at different workplaces in a copper foundry, matched for age and smoking habits with the control group (n=16). Subjective neurological symptoms (SNS), visual evoked potentials (VEP), electroneurographic (EneG) and electroencephalographic (EEG) results were examined in the workers and the relationships between As concentration in the air (As-Air) and urine (As-U) were assessed. Effects of exposure were expressed in terms of biomarkers: CC16 as early pulmonary biomarker and beta(2)-microglobulin (beta(2)M) in urine and serum and retinol binding protein (RBP) as renal markers, measured by sensitive latex immunoassay. The concentrations of arsenic exceeded about two times the Threshold Limit Values (TLV) (0.01 mg/m(3)). The contents of lead did not exceed the TLV (0.05 mg/m(3)). Low CC16 levels in serum (12.1 microg/l) of workers with SNS and VEP symptoms and highest level As-U (x(a) 39.0 microg/l) were noted earliest in relation to occupational time. Moreover, those effects were associated with increased levels of urinary and serum beta(2)M and urinary RBP. Results of our study suggested the initiative key role of oxidative stress in triggering the processes that eventually lead to the subclinical effects of arsenic on the nervous system.

Comparison of proteomic and transcriptomic profiles in the bronchial airway epithelium of current and never smokers

BACKGROUND

Although prior studies have demonstrated a smoking-induced field of molecular injury throughout the lung and airway, the impact of smoking on the airway epithelial proteome and its relationship to smoking-related changes in the airway transcriptome are unclear.

METHODOLOGY/PRINCIPAL FINDINGS

Airway epithelial cells were obtained from never (n = 5) and current (n = 5) smokers by brushing the mainstem bronchus. Proteins were separated by one dimensional polyacrylamide gel electrophoresis (1D-PAGE). After in-gel digestion, tryptic peptides were processed via liquid chromatography/ tandem mass spectrometry (LC-MS/MS) and proteins identified. RNA from the same samples was hybridized to HG-U133A microarrays. Protein detection was compared to RNA expression in the current study and a previously published airway dataset. The functional properties of many of the 197 proteins detected in a majority of never smokers were similar to those observed in the never smoker airway transcriptome. LC-MS/MS identified 23 proteins that differed between never and current smokers. Western blotting confirmed the smoking-related changes of PLUNC, P4HB1, and uteroglobin protein levels. Many of the proteins differentially detected between never and current smokers were also altered at the level of gene expression in this cohort and the prior airway transcriptome study. There was a strong association between protein detection and expression of its corresponding transcript within the same sample, with 86% of the proteins detected by LC-MS/MS having a detectable corresponding probeset by microarray in the same sample. Forty-one proteins identified by LC-MS/MS lacked detectable expression of a corresponding transcript and were detected in

CONCLUSIONS/SIGNIFICANCE

1D-PAGE coupled with LC-MS/MS effectively profiled the airway epithelium proteome and identified proteins expressed at different levels as a result of cigarette smoke exposure. While there was a strong correlation between protein and transcript detection within the same sample, we also identified proteins whose corresponding transcripts were not detected by microarray. This noninvasive approach to proteomic profiling of airway epithelium may provide additional insights into the field of injury induced by tobacco exposure.

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Key Words Collapse

MESH Headings

• Adult
• Blotting, Western
• Bronchi/cytology
• Bronchi/drug effects
• Bronchi/metabolism
• Chromatography, Liquid/methods
• Electrophoresis, Polyacrylamide Gel/methods
• Epithelial Cells/cytology
• Epithelial Cells/drug effects
• Epithelial Cells/physiology
• Female
• Gene Expression Profiling
• Glycoproteins/metabolism
• Humans
• Male
• Microarray Analysis
• Middle Aged
• Molecular Sequence Data
• Phosphoproteins/metabolism
• Procollagen-Proline Dioxygenase/metabolism
• Protein Disulfide-Isomerases/metabolism
• Proteome/analysis
• Respiratory Mucosa/cytology
• Respiratory Mucosa/drug effects
• Smoking/adverse effects
• Tandem Mass Spectrometry/methods
• Nicotiana
• Uteroglobin/metabolism
• Young Adult

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Grants

• R01 CA124640 NCI NIH HHS
• U01 ES016035 NIEHS NIH HHS
• R01CA124640 NCI NIH HHS
• U01ES016035 NIEHS NIH HHS

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Affiliation(s)

Katrina Steiling The Pulmonary Center, Boston University Medical Center, Boston, Massachusetts, United States of America.
Aran Y Kadar
Agnes Bergerat
James Flanigon
Sriram Sridhar
Vishal Shah
Q Rushdy Ahmad
Jerome S Brody
Marc E Lenburg
Martin Steffen
Avrum Spira

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Associations between environmental exposures and serum concentrations of Clara cell protein among elderly men in Oslo, Norway

Cardiopulmonary morbidity and mortality is associated with several environmental exposures. Mechanistically, pathophysiological changes in the cardiopulmonary system may lead to the induction of inflammatory responses. In the present study we explored associations between environmental exposures and serum concentrations of lung Clara cell protein 16kDa, a biomarker that has recently been used to assess the integrity of the lung epithelium. Serum Clara cell protein concentrations were associated with both number of cigarettes smoked per day and number of pack-years of smoking. There was no evidence of an association between long-term exposure to ambient air pollution, as assessed at each participant's home address, and serum concentrations of CC16. However, short-term variations in both ambient air pollution and temperature were associated with increases in serum Clara cell concentrations. All findings were robust when other factors were adjusted for. These findings suggest that acute environmental exposures may compromise the integrity of the lung epithelium and lead to increased epithelial barrier permeability in the lungs of elderly men.

Serum pneumoproteins and biomarkers of exposure to urban air pollution: a cross-sectional comparison of policemen and foresters

Very few biomarkers are available for the non-invasive detection of effects of urban air pollution on the respiratory tract. The objective was to evaluate whether Clara cell protein (CC16) and surfactant-associated protein-A (SP-A), two pulmonary secretory proteins, were useful in the detection of effects of urban air pollutants on the pulmonary epithelium. These proteins were determined in the serum of 53 policemen working in Brussels, Belgium, and a control group of 59 foresters working in the countryside. Except for ozone (O(3)), annual concentrations of the main air pollutants (PM(10), NO(2), CO, SO(2) and benzene) were significantly higher in Brussels than in the country. The proportion of smokers was lower in urban policemen compared with foresters, but they smoked on average a similar number of cigarettes per day as confirmed by their urinary excretion of cotinine. Muconic acid, a marker of benzene exposure, was significantly higher in urban policemen than in foresters, in both smokers and non-smokers. Multiple regression analysis showed that the type of work, smoking habits and time spent outdoors and in a car were significant determinants of benzene uptake. Tobacco smoking impaired lung function to a similar extent in urban policemen and foresters. The serum levels of SP-A were significantly increased in smokers but were not different between policemen and foresters. Serum CC16 was significantly reduced by tobacco smoking and slightly decreased in policemen compared with foresters. Interestingly, the reduction of serum CC16 was more pronounced in the subgroup of traffic compared with survey policemen, the latter being also less exposed to benzene. The results suggest that serum pneumoproteins and especially serum CC16 could be useful in the detection of chronic effects of urban air pollutants on the respiratory epithelium of populations particularly at risk.

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.

Changes in Clara cell 10 kDa protein (CC10)-positive cell distribution in acute lung injury following repeated lipopolysaccharide challenge in the rat

Clara cell 10 kDa protein (CC10) is the major secretory protein of Clara cells and is thought to play a protective role in the lung owing to its anti-inflammatory properties. There is little information on the anatomical distribution of CC10-positive cells in rat lung following lipopolysaccharide (LPS) challenge. We have determined the expression of CC10 along the tracheobronchial tree in saline-treated and LPS-treated rats. Saline-treated rats showed sporadic CC10 staining in central airways and abundant staining in bronchioles. In transitional airways, most cells were positive except for squamous cells. Following LPS challenge, there was a reduction in staining in the upper airways but little change within bronchioles. Squamous epithelia within the transitional airways now showed positive staining. These cells also co-stained for pancytokeratin and appeared to co-localize with surfactant D- and Ki67-positive cells, indicating the presence of a dedifferentiated cell type with both epithelial and pneumocyte phenotypes. These data show that diffuse inflammatory injury results in generalized loss of CC10 in central airways. Conversely, the transitional airways showed evidence of a dedifferentiated population of squamous cells that now stained for CC10. We hypothesize that this is an attempt by peripheral lung to maintain alveolar sac integrity during an inflammatory episode.

Uteroglobin: a steroid-inducible immunomodulatory protein that founded the Secretoglobin superfamily

Blastokinin or uteroglobin (UG) is a steroid-inducible, evolutionarily conserved, secreted protein that has been extensively studied from the standpoint of its structure and molecular biology. However, the physiological function(s) of UG still remains elusive. Isolated from the uterus of rabbits during early pregnancy, UG is the founding member of a growing superfamily of proteins called Secretoglobin (Scgb). Numerous studies demonstrated that UG is a multifunctional protein with antiinflammatory/ immunomodulatory properties. It inhibits soluble phospholipase A(2) activity and binds and perhaps sequesters hydrophobic ligands such as progesterone, retinols, polychlorinated biphenyls, phospholipids, and prostaglandins. In addition to its antiinflammatory activities, UG manifests antichemotactic, antiallergic, antitumorigenic, and embryonic growth-stimulatory activities. The tissue-specific expression of the UG gene is regulated by several steroid hormones, although a nonsteroid hormone, prolactin, further augments its expression in the uterus. The mucosal epithelia of virtually all organs that communicate with the external environment express UG, and it is present in the blood, urine, and other body fluids. Although the physiological functions of this protein are still under investigation, a single nucleotide polymorphism in the UG gene appears to be associated with several inflammatory/autoimmune diseases. Investigations with UG-knockout mice revealed that the absence of this protein leads to phenotypes that suggest its critical homeostatic role(s) against oxidative damage, inflammation, autoimmunity, and cancer. Recent studies on UG-binding proteins (receptors) provide further insight into the multifunctional nature of this protein. Based on its antiinflammatory and antiallergic properties, UG is a potential drug target.

Clara cell 16 protein in COPD sputum: A marker of small airways damage?

RATIONALE

The development of chronic obstructive pulmonary disease (COPD) in smokers and their susceptibility to infections is not fully understood. Recent evidences suggest that Clara cells play a part in host defense, immunomodulatory response and airways remodelling through the production of specific factors such as Clara cell 16 (CC-16). This protein has never been related to patients' lung function tests, blood gases parameters and diseases severity.

OBJECTIVES

To evaluate a possible correlation between CC-16 expression in sputum, measured by a new methodological approach, and the degree of severity in patients with moderate and severe COPD. We also analyzed possible correlations between CC-16 and cytological sputum population, arterial blood gases and lung function.

MAIN FINDINGS

We analyzed 20 patients, mean age 72.95, classified on the basis of the global initiative for chronic obstructive lung disease guidelines (GOLD 2006). The samples were processed for cytological analysis and CC-16 levels were assessed by Western blot. We found lower levels of CC-16 in severe COPD compared to moderate ones (p<0.027). No statistically significant differences were found between CC-16 expression and sputum cellularity (except for macrophages), arterial blood gases, and spirometric parameters. Multiple linear regression analysis of CC-16 versus functional and cytological parameters showed no significance.

CONCLUSIONS

We found a significantly different expression of CC-16 in COPD patients, according to their stage of severity, as defined by the GOLD 2006 guidelines. Considering CC-16 properties in innate immunity, a possible link between protein expression, innate immune system, and COPD infectious exacerbations may be hypothesized but further investigation are needed.

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.

Clara cell 16-kd protein downregulates T(H)2 differentiation of human naive neonatal T cells

BACKGROUND

Levels of the Clara cell 16-kd protein (CC16) are lower in plasma and bronchoalveolar lavage fluid from adults with asthma relative to those seen in healthy control subjects, and CC16 inhibits the T(H)2 cytokine production from murine T cells.

OBJECTIVE

We sought to determine the plasma levels of CC16 in infants and to investigate whether CC16 might inhibit the T(H)2 cytokine production from neonatal T cells.

METHODS

Cord blood and blood samples at 4, 18, and 36 months of age were taken from 64 children prospectively, and CC16 levels were analyzed in plasma. Cord monocyte-derived dendritic cells (DCs) were pulsed with birch allergen extract alone or together with CC16 or prostaglandin D(2) receptor inhibitors, after which autologous naive CD4(+) T cells were added to the DCs. The production of IL-5, IL-13, and IFN-gamma was measured by means of ELISA and flow cytometry.

RESULTS

The plasma levels of CC16 in children peaked at 4 months. CC16 did not directly affect the cytokine production from human T(H)2 cells. However, CC16 inhibited birch pollen extract-stimulated T(H)2 differentiation of naive T cells through the DC. Inhibition of the prostaglandin D(2) receptors did not consistently result in suppressed T(H)2 differentiation.

CONCLUSION

The production of CC16 seems to peak early in life, and CC16 has an inhibitory effect on T(H)2 cell differentiation from human infants by affecting DCs.

CLINICAL IMPLICATIONS

CC16 is an immunoregulatory protein, and its inhibitory effect on T(H)2 cell differentiation might be of importance in the pathogenesis of allergy in infants.

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.

Secretory cells of the airway express molecules of the chemoreceptive cascade

Airway secretion is maintained by specialized non-ciliated epithelial cells whose phenotype varies with their topographical location. In addition, specialized epithelial cells located in the airway contain the molecular machinery of chemoreceptive elements. Our aim has been to evaluate whether the secretory cells themselves possess a chemoreceptive capability, which requires the simultaneous presence of chemosensory and secretory mechanisms. We performed immunohistochemical analysis with antibodies against the Clara-cell-specific secretory proteins, CC10 and CC26, as secretory markers. As chemoreceptive markers, we employed antibodies against alpha-gustducin and phospholipase C beta 2 (PLCbeta2), two components of the taste transduction pathway. We also attempted to characterize further the secretory cell type by using a marker of chloride secretion, cystic fibrosis transmembrane regulator (CFTR). We found alpha-gustducin localized in non-ciliated cells of the epithelium lining the trachea and bronchioles of adult rats, where it was also co-expressed with CC10 and CC26. Ultrastructural immunohistochemistry revealed alpha-gustducin in the apical cytoplasm of secretory cells, concentrated around and inside the granules. CFTR was also observed in a subpopulation of non-ciliated epithelial cells, co-localized with some alpha-gustducin- and PLCbeta2-immunoreactive cells, at all levels of the airway epithelium. We conclude that non-ciliated epithelial cells of the rat airway express components of distinct signaling mechanisms and suggest that secretory events are driven by a molecular mechanism activated by the binding of luminal substances to G-protein-coupled receptors.

Mechanistically identified suitable biomarkers of exposure, effect, and susceptibility for silicosis and coal-worker's pneumoconiosis: a comprehensive review

Clinical detection of silicosis is currently dependent on radiological and lung function abnormalities, both late manifestations of disease. Markers of prediction and early detection of pneumoconiosis are imperative for the implementation of timely intervention strategies. Understanding the underlying mechanisms of the etiology of coal workers pneumoconiosis (CWP) and silicosis was essential in proposing numerous biomarkers that have been evaluated to assess effects following exposure to crystalline silica and/or coal mine dust. Human validation studies have substantiated some of these proposed biomarkers and argued in favor of their use as biomarkers for crystalline silica- and CWP-induced pneumoconiosis. A number of "ideal" biological markers of effect were identified, namely, Clara cell protein-16 (CC16) (serum), tumor necrosis factor-alpha (TNF-alpha) (monocyte release), interleukin-8 (IL-8) (monocyte release), reactive oxygen species (ROS) measurement by chemiluminescence (neutrophil release), 8-isoprostanes (serum), total antioxidant levels measured by total equivalent antioxidant capacity (TEAC), glutathione, glutathione peroxidase activity, glutathione S-transferase activity, and platelet-derived growth factor (PDGF) (serum). TNF-alpha polymorphism (blood cellular DNA) was identified as a biomarker of susceptibility. Further studies are planned to test the validity and feasibility of these biomarkers to detect either high exposure to crystalline silica and early silicosis or susceptibility to silicosis in gold miners in South Africa.

Serum surfactant protein D is increased in acute and chronic inflammation in mice

Surfactant protein A (SP-A) and surfactant protein D (SP-D) are important components of innate immunity that can modify the inflammatory response. However, alterations and regulation of SP-A and SP-D in acute and chronic inflammation are not well defined. In addition, serum SP-D may serve as a biomarker of lung inflammation. We determined the expression of SP-A and SP-D in murine models. To study acute inflammation, we instilled bleomycin intrabronchially. To study chronic lung inflammation, we used a transgenic mouse that overexpresses tumor necrosis factor (TNF)-alpha under the control of the SP-C promoter. These mice have a chronic mononuclear cell infiltration, airspace enlargement, pulmonary hypertension, and focal pulmonary fibrosis. In acute inflammation model, levels of mRNA for all surfactant proteins were reduced after bleomycin administration. However, serum SP-D was increased from days 7 to 28 after instillation. In chronic inflammation model, SP-D mRNA expression was increased, whereas the expression of SP-A, SP-B and SP-C was reduced. Both serum and lung SP-D concentrations were increased in chronic lung inflammation. These data clarified profile of SP-A and SP-D in acute and chronic inflammation and indicated that serum SP-D can serve as a biomarker of lung inflammation in both acute and chronic lung injury in mice.

Construction of eukaryotic expression vector of human CC10 gene and expression of CC10 protein in lung adenocarcinoma A549 cell line

A mammalian expression plasmid pcDNA3. 1-hCC10 was constructed and identified, then CC10 protein expression in A549 lung cancer cell line was detected. A 273 bp cDNA fragment was amplified from the total RNA of normal lung tissue by using RT-PCR and cloned into expression plasmid cDNA3. 1, and the recombinant plasmid was identified by employing double digestion restriction enzymes Hind III and BamH I and the cDNA sequence was assayed by the Sanger dideoxy-mediated chain termination method. The segment was then transfected into the A549 lung cancer cell line. The protein expression of CC10 was detected by immunofluorescence and Western blot. Our results showed that the cDNA fragment included the entire coding region (273 bp). The recombinant eukaryotic cell expression vector of pcDNA3. 1-hCC10 was successfully constructed, and the sequence of the insert was identical to the published sequence. A549 cells line transfected with the pcDNA3. 1-hCC10 expressed high level of CC10 protein. The recombinant plasmid cDNA3. 1-hCC10 may serve as an effective tool for the study of tumorogenesis and tumor treatment.

Serum Clara Cell Protein as an Indicator of Pulmonary Impairment in Occupational Exposure at Aluminum Foundry

OBJECTIVES

Although some of the exposures in aluminum (Al) smelting have been well characterized, and respiratory disorders in aluminum production workers are well known, the relationship between internal aluminum loads and appropriate lung biomarkers have not been elucidated. The aim of our work was to carry out a comprehensive investigation in workers employed in the Aluminum Foundry Casting Department with special reference to currently existing hygiene standards, known as threshold limit values (TLV) based on aluminum effects on the respiratory system. The measurement of serum anti-inflammatory Clara cell protein (CC16) was employed as a peripheral marker of the lung epithelium function.

MATERIALS AND METHODS

A group of 50 casting smelters, 5 locksmiths, 11 sawyers and auxiliary workers exposed to dust containing 14% of aluminum, and a group of 42 controls were examined. Respiratory function tests were performed and forced volume capacity (FVC), forced expiratory volume in 1 s (FEV1), forced expiratory volume in the first percent (FEV1%), forced expiratory flows in 50% VC (FEV50), and markers of foundry workers' exposure and body burden, Al concentration in the breathing zone, blood and urine, biomarkers of the effects of exposure, concentration of CC16 and hyaluronic acid (HA) in serum were determined in all examined workers. Additional measurements comprised determinations of serum iron (Fe) levels, myeloperoxidase (MPO), eosinophil cationic protein (ECP), immunoglobulin E (IgE), glutathione S-transferase (GST), and superoxide dismutase (SOD) activity in erythrocytes.

RESULTS

The group of casting smelters was characterized by the highest levels of aluminum in urine (Al-U) (43.7 microg L(-1)), high levels of MPO, ECP and IgE, high SOD activity, low CC16 levels, and low activity of GST. Lower Al-U excretion was observed in locksmiths (35.2 microg L(-1)) and sawyers (21.7 microg L(-1)). Serum CC16 proved to be the most sensitive biomarker, showing high inverse relationship with serum Al (Al-S) concentrations in casting smelters (p = 0.006).

CONCLUSIONS

The study showed that in conditions of occupational exposure, dusts containing Al2O3 < 1 mg m(-3) cause changes in the respiratory system and biomarkers in serum, especially in CC16, connected with altered functioning of this system. Changes in concentrations of the examined biomarkers and also in respiratory parameters of the study subjects were observed when Al-U concentration was > 40 microg L (-1).

Proteomic study of human bronchoalveolar lavage fluids from smokers with chronic obstructive pulmonary disease by combining surface-enhanced laser desorption/ionization-mass spectrometry profiling with mass spectrometric protein identification

Bronchoalveolar lavage fluid (BALF) is an important diagnostic source to investigate cellular and molecular changes in the course of lung disorders. The pattern of soluble proteins in BALF obtained from patients at different stages of respiratory disorders may provide deeper insights in the molecular mechanisms of the disease. We used surface-enhanced laser desorption/ionization mass spectrometry (MS) for differential protein display combined with reversed-phase chromatography and subsequent matrix-assisted laser desorption/ionization-MS or nanoliquid chromatography MS/MS analysis for protein identification to compare the protein pattern of BALF samples obtained from ten smokers suffering from chronic obstructive pulmonary disease (COPD), eight clinically asymptomatic smokers, and eight nonsmokers without pulmonary disease. In this context, we were able to identify small proteins and peptides, either differentially expressed or secreted in the course of COPD or in a direct response to cigarette smoke. The concentrations of neutrophil defensins 1 and 2, S100A8 (calgranulin A), and S100A9 (calgranulin B) were elevated in BALFs of smokers with COPD when compared to asymptomatic smokers. Increased concentrations in S100A8 (Calgranulin A), salivary proline-rich peptide P-C, and lysozyme C were detected in BALFs of asymptomatic smokers when compared to nonsmokers, whereas salivary proline-rich peptide P-D and Clara cell phospholipid-binding protein (CC10) were reduced in their concentration. The identified proteins and peptides might be useful in the future as diagnostic markers for smoke-induced lung irritations and COPD.

Preferential induction of CYP1A1 and CYP1B1 in CCSP-positive cells

Both benzo[a]pyrene (BaP) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) are potent ligands of aryl hydrocarbon receptors (AhR). Although animal studies indicate that both compounds induce pathological changes in the peripheral lung, the specific cell type involved remains unclear. Clara cells, expressing Clara cell specific protein (CCSP) and abundant in cytochrome P450, are nonciliated bronchiolar epithelial cells in the peripheral lung. Here we explore the hypothesis that CCSP-positive Clara cells are highly responsive to AhR ligands and are the primary cell type involved in BaP- and TCDD-induced toxicities. The responsiveness to AhR ligands was evaluated by measuring the respective mRNA and protein levels of cytochrome P450 1A1 (CYP1A1) and 1B1 (CYP1B1) using real-time RT-PCR and immunocytochemistry assays. Two in vitro models were used: primary cultures of human small airway epithelial (SAE) cells and rat lung slice cultures. In the presence of calcium, human SAE cells differentiated into CCSP-positive cells. BaP- and TCDD-induced mRNA and protein levels of CYP1A1 and CYP1B1 levels were significantly elevated in CCSP-positive cell cultures. Similarly, AhR mRNA and protein levels were increased in CCSP-positive cell cultures, as determined by real-time RT-PCR and Western blot analysis. When rat lung slice cultures were treated with BaP or TCDD for 24 h, CYP1A1 and CYP1B1 proteins were strongly induced in Clara cells. These results indicate that, in the peripheral lung of both rats and humans, CCSP-positive cells (Clara cells) may be more sensitive to AhR ligands than other cell types.

Prognostic significance of low serum levels of Clara cell phospholipid-binding protein in occupational aluminium neurotoxicity

The relationship between respiratory and neurological effects of exposure to aluminium (Al) was investigated in a group of foundry workers exposed to Al at concentrations below the threshold limit value (TLV) binding in Poland (2.0 mg Al2O3 m(-3)). Neurological and neurophysiological parameters indicated subclinical effects of Al exposure on the nervous system. The measurement of serum anti-inflammatory Clara cell protein (CC16) was employed as a peripheral marker of the lung epithelium function. There was a strong inverse relationship between serum Al (Al-S) and CC16 concentrations (p = 0.006). The lowest CC16 concentrations were found in serum of workers characterised by subjective symptoms of the central nervous system (CNS) and abnormal results of neurophysiological examinations (EEG and VEP). Low serum CC16 concentrations and enhanced Al and iron (Fe) levels were also observed in the younger age group of workers with the subjective CNS symptoms and abnormal VEP results, which suggests that Fe is implicated in strengthening of the neurotoxic Al potential. The results of our study support the hypothesis that subclinical neurological symptoms (especially abnormal VEP) are most likely associated with internalisation of Al ions with lipid fractions of the lung epithelium, which in turn may help Al ions overcome the blood-brain barrier. Low serum CC16 concentrations (<10 microg L(-1)) were noted in workers with the abnormal results of neurological (CNS) and neurophysiological (EEG and VEP) examinations as well as with Al body burden manifested by urinary excretion (Al-U) below 60 microg L(-1) and Al-S concentration of 2 microg L(-1). This concentration may be considered as a threshold allowable biological concentration of aluminium.

Embryonic Stem Cells Generate Airway Epithelial Tissue

Embryonic stem (ES) cells are self-renewable and pluripotent cells derived from the inner cell mass of a blastocyst-stage embryo. ES cell pluripotency is being investigated increasingly to obtain specific cell lineages for therapeutic treatments and tissue engineering. Type II alveolar epithelial cells have been derived from murine ES cells, but the capacity of the latter to generate differentiated airway epithelial tissue has never been reported. Herein, we show by RT-PCR and immunocytochemistry that murine ES cells are able to differentiate into nonciliated secretory Clara cells, and that type I collagen induces this commitment. Moreover, when cultured at the air-liquid interface, ES cells give rise to a fully differentiated airway epithelium. By quantitative histologic examination, immunohistochemistry, and scanning electron microscopy, we show that the bioengineered epithelium is composed of basal, ciliated, intermediate, and Clara cells, similar to those of native tracheobronchial airway epithelium. Transmission electron microscopy and Western blotting reveal that the generated epithelium also exhibits the ultrastructural features and secretory functions characteristic of airway epithelial tissue. These results open new perspectives for cell therapy of injured epithelium in airway diseases, such as bronchopulmonary dysplasia, cystic fibrosis, or bronchiolitis obliterans.

Serum CC-10 in inflammatory lung diseases

BACKGROUND

Although Clara cell secretory protein (CC-10) has been ascribed an anti-inflammatory role in lung diseases, its precise role remains unclear.

OBJECTIVE

To further our understanding of the role of CC-10 in inflammatory lung diseases, CC-10 protein levels were measured.

METHODS

Sera or bronchoalveolar lavage (BAL) fluids were collected from patients with different inflammatory lung diseases including bronchial asthma, chronic obstructive lung disease (COPD), sarcoidosis, idiopathic interstitial pneumonia (IIP), chronic eosinophilic pneumonia (CEP), pneumonia and lung cancer. Serum CC-10 concentrations were measured by enzyme-linked immunosorbent assay using urinary protein-1 antibody. Then, the relationships between CC-10 concentrations and lung diseases were investigated. Immunohistochemistry was performed using lung biopsy samples.

RESULTS

Increased serum CC-10 levels were recognized in IIP patients, while CC-10 levels were decreased in bronchial asthma patients and CEP patients. Immunohistochemistry revealed an aberrant expression in areas of fibrosis in IIP patients. Serum CC-10 concentrations were not associated with severity among IIP, COPD, and sarcoidosis. In contrast, serum CC-10 concentrations were correlated with FEV(1)/FVC in bronchial asthma patients.

CONCLUSIONS

Although the number of patients was quite limited, these data provide new insights into the role of CC-10 in lung diseases, and the possibility that the CC-10 concentration in serum could be a new marker indicating the severity of bronchial asthma.

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.

Increased Susceptibility of Mice Lacking Clara Cell 10-kDa Protein to Lung Tumorigenesis by 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone, a Potent Carcinogen in Cigarette Smoke

Ninety percent of all human lung cancers are related to cigarette smoking. Both tobacco smoke and lung tumorigenesis are associated with drastically reduced levels of Clara cell 10-kDa protein (CC10), a multifunctional secreted protein, naturally produced by the airway epithelia of virtually all mammals. We previously reported that the expression of CC10 is markedly reduced in animals exposed to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, NNK, a potent carcinogen in tobacco smoke. Furthermore, it has been reported that CC10 expression, induced in certain tumor cells, reverses the transformed phenotype. We demonstrate here that NNK exposure of CC10-knock-out (CC10-KO) mice causes a significantly higher incidence of airway epithelial hyperplasia and lung adenomas compared with wild type (WT) littermates (30% CC10-KO versus 5% WT, p = 0.041). We also found that compared with NNK-treated WT mice, CC10-KO mice manifest increased frequency of K-ras mutation, elevated level of Fas ligand (FasL) expression, and increased MAPK/Erk phosphorylation, all of which are considered predisposing events in NNK-induced lung tumorigenesis. We propose that CC10 has a protective role against NNK-induced lung tumorigenesis mediated via down-regulation of the above-mentioned predisposing events.

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.

Comparative urine protein phenotyping using mass spectrometric immunoassay

Reported here, human urine samples were analyzed for beta-2-microglobulin (beta2m), transthyretin (TTR), cystatin C, urine protein 1 (UP1), retinol binding protein (RBP), albumin, transferrin, and human neutrophil defensin peptides (HNP) using mass spectrometric immunoassay (MSIA). MSIA is a unique analytical technique, which allows for the generation of distinct protein profiles of specific target proteins from each subject, which may be subsequently used in comparative protein expression profiling between all subjects. Comparative profiling allows for the rapid identification of variations within individual protein expression profiles. Although the majority of analyses performed in this study revealed homology between study participants, roughly one-quarter showed variation in the protein profiles. Some of these observed variants included a point mutation in TTR, absence of wild-type RBP, monomeric forms UP1, a novel beta2m glycated end product and altered HNP ratios. MSIA has been previously used in the analysis of blood proteins, but this study shows how MSIA easily transitions to the analysis, of urine samples. This study displays how qualitative urine protein differentiation is readily achievable with MSIA and is useful in identifying proteomic differences between subjects that might be otherwise overlooked with other analytical techniques due to complexity of the resulting data or insufficient sensitivity.

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.

Expression and regulation of xenobiotic-metabolizing cytochrome P450 (CYP) enzymes in human lung

Pathogenesis of lung diseases, such as lung cancer and chronic obstructive pulmonary disease, is tightly linked to exposure to environmental chemicals, most notably tobacco smoke. Many of the compounds associated with these diseases require an enzymatic activation to exert their deleterious effects on pulmonary cells. These activation reactions are mostly catalyzed by cytochrome P450 (CYP) enzymes. Interindividual differences in the in situ activation and inactivation of chemical toxicants may contribute to the risk of developing lung diseases associated with these compounds. This review summarizes in detail the expression of individual CYP forms in human pulmonary tissue and gives a view on the significance of the pulmonary expression of CYP enzymes. The localization of individual CYP enzymes in various cell types of human lung and the emerging field of regulation of human pulmonary CYP enzymes are discussed. At least CYP1A1 (in smokers), CYP1B1, CYP2B6, CYP2E1, CYP2J2, and CYP3A5 proteins are expressed in human lung, and also other CYP forms are likely to be expressed. Xenobiotic-metabolizing CYP enzymes are mostly expressed in bronchial and bronchiolar epithelium, Clara cells, type II pneumocytes, and alveolar macrophages in human lung, although individual CYP forms have different patterns of localization in pulmonary tissues. Problems in animal to human lung toxicity extrapolation and several specific aspects requiring more detailed assessment are identified.

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.