Clara cell secretory protein. Levels in BAL fluid after smoking cessation

A genomic perspective of the aging human and mouse lung with a focus on immune response and cellular senescence

BACKGROUND

The aging lung is a complex process and influenced by various stressors, especially airborne pathogens and xenobiotics. Additionally, a lifetime exposure to antigens results in structural and functional changes of the lung; yet an understanding of the cell type specific responses remains elusive. To gain insight into age-related changes in lung function and inflammaging, we evaluated 89 mouse and 414 individual human lung genomic data sets with a focus on genes mechanistically linked to extracellular matrix (ECM), cellular senescence, immune response and pulmonary surfactant, and we interrogated single cell RNAseq data to fingerprint cell type specific changes.

RESULTS

We identified 117 and 68 mouse and human genes linked to ECM remodeling which accounted for 46% and 27%, respectively of all ECM coding genes. Furthermore, we identified 73 and 31 mouse and human genes linked to cellular senescence, and the majority code for the senescence associated secretory phenotype. These cytokines, chemokines and growth factors are primarily secreted by macrophages and fibroblasts. Single-cell RNAseq data confirmed age-related induced expression of marker genes of macrophages, neutrophil, eosinophil, dendritic, NK-, CD4+, CD8+-T and B cells in the lung of aged mice. This included the highly significant regulation of 20 genes coding for the CD3-T-cell receptor complex. Conversely, for the human lung we primarily observed macrophage and CD4+ and CD8+ marker genes as changed with age. Additionally, we noted an age-related induced expression of marker genes for mouse basal, ciliated, club and goblet cells, while for the human lung, fibroblasts and myofibroblasts marker genes increased with age. Therefore, we infer a change in cellular activity of these cell types with age. Furthermore, we identified predominantly repressed expression of surfactant coding genes, especially the surfactant transporter Abca3, thus highlighting remodeling of surfactant lipids with implications for the production of inflammatory lipids and immune response.

CONCLUSION

We report the genomic landscape of the aging lung and provide a rationale for its growing stiffness and age-related inflammation. By comparing the mouse and human pulmonary genome, we identified important differences between the two species and highlight the complex interplay of inflammaging, senescence and the link to ECM remodeling in healthy but aged individuals.

Rate of progression of CT-quantified emphysema in male current and ex-smokers: a follow-up study

BACKGROUND

Little is known about the factors associated with CT-quantified emphysema progression in heavy smokers. The objective of this study was to investigate the effect of length of smoking cessation and clinical / demographical factors on the rate of emphysema progression and FEV1-decline in male heavy smokers.

METHODS

3,670 male smokers with mean (SD) 40.8 (17.9) packyears underwent chest CT scans and pulmonary function tests at baseline and after 1 and 3 years follow-up. Smoking status (quitted ≥5, ≥1-<5, <1 years or current smoker) was noted. Rate of progression of emphysema and FEV1-decline after follow-up were assessed by analysis of variance adjusting for age, height, baseline pulmonary function and emphysema severity, packyears, years in study and respiratory symptoms. The quitted ≥5 group was used as reference.

RESULTS

Median (Q1-Q3) emphysema severity,<-950 HU, was 8.8 (5.1 - 14.1) and mean (SD) FEV1 was 3.4 (0.73) L or 98.5 (18.5) % of predicted. The group quitted '>5 years' showed significantly lower rates of progression of emphysema compared to current smokers, 1.07% and 1.12% per year, respectively (p<0.001). Current smokers had a yearly FEV1-decline of 69 ml, while subjects quit smoking >5 years had a yearly decline of 57.5 ml (p<0.001).

CONCLUSION

Quit smoking >5 years significantly slows the rate of emphysema progression and lung function decline.

TRIAL REGISTRATION

Registered at http://www.trialregister.nl with trial number ISRCTN63545820.

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.

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 Clara-Cell Protein and β2-Microglobulin as Early Markers of Occupational Exposure to Nitric Oxides

Biochemical effects of NOx on 60 workers (both genders) of nitric acid production were studied. The control group consisted of 61 nonexposed people employed elsewhere in the plant. Although the actual threshold limit valuetime weighted averages (TLV-TWA) were not exceeded in the specific conditions of our study, the subjects were exposed to NO2 and NO during several exposure episodes with peak maximal concentrations of 140 ppm and 515 ppm, respectively. Additional cross-week evaluation of several biochemical biomarkers in 15 NOx-exposed workers from one shift was performed. The objective of the study was to evaluate the value of serum Clara-cell protein (CC16) as a marker of bronchoalveolar epithelium activity. Antioxidant status was assessed by measuring activity of enzymes: glutathione peroxidase (GSH-Px), ceruloplasmin (Cp) in plasma, or superoxide dismutase (SOD), gluthatione S-transferase (GST), and nonenzymatic alpha-tocopherol in erythrocytes and thiobarbituric acid-reactive substances (TBARS) in plasma. Serum hyaluronic acid (HA) determining the connective tissue matrix status of airways, and beta2-microglobulin in serum (beta2M-S) and urine (beta2M-U) as a marker of renal function in occupational exposure to NOx were also employed. Exposure to NOx initiates peroxidative chain depleting of lipoprotein pool (alpha-tocopherol) in blood. Serum CC16 levels in NOx-exposed workers were found to be closely connected with alpha-tocopherol content. In NOx-exposed workers, the beta2M-S level was significantly higher than in the nonexposed ones, with the exception of smokers. Results of the cross-week study confirm cumulative systemic effects of NOx on several examined biomarkers. SOD and GST were found to be depleted. A transient higher level of HA after a 5-d shift significantly inversely correlated with CC16 level. The data imply that NOx-depleted levels of CC16 are detectable already after an 8-h shift. Our results demonstrate that even low NOx human exposure can cause characteristic changes in bronchiolar epithelium cells and renal effects. Serum CC16 level, although a nonspecific marker, was lowest in NOx-exposed subjects. The most sensitive parameters in exposed workers were beta2M-S and a-tocopherol. Spirometric assessment was not useful to describe low occupational exposure to NOx. In studying the effects of NOx on biomarkers, it is essential to carefully select suitable time of sampling. Screening of CC16, beta2M-S, and a-tocopherol can be successfully employed for biological monitoring of exposure to NOx.

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.

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.

Changes in markers of epithelial permeability and inflammation in chronic smokers switching to a nonburning tobacco device (Eclipse)

Eclipse, produced by R. J. Reynolds Tobacco Company, is a potential reduced exposure product (PREP) that heats rather than burns tobacco. We hypothesized that switching to Eclipse would result in relative normalization of pulmonary epithelial permeability, airway inflammation, and blood leukocyte activation in current smokers. We assessed 10 healthy smokers (aged 21-50 years, 19+/-8 pack-years) at baseline and after 2 and 4 weeks of switching to Eclipse, for symptoms, pulmonary function, airway inflammation, lung clearance of (99m)technicium-diethylenetriaminepentaacetic acid, and blood leukocyte activation and production of reactive oxygen species. Values were compared before and after Eclipse use and with those of healthy, lifetime nonsmokers (aged 18-53 years). Compared with baseline values before switching to Eclipse, lung permeability half-time increased from 33+/-3 to 43+/-6 min (p = .017) after 2 weeks and to 44+/-7 min (p = .10) after 4 weeks of Eclipse use. Carboxyhemoglobin levels increased from 5%+/-2% to 7%+/-2% (p<.01) at 4 weeks. Compared with smoking the usual brand of cigarettes, after smoking Eclipse the percentage of natural killer cells, the expression of intercellular adhesion molecule-1 on monocytes, and the expression of CD45RO on T cells showed significant improvement. However, expression of other surface markers, notably CD23 on monocytes, became more abnormal. Production of reactive oxygen species by smokers' neutrophils and monocytes increased further with Eclipse use. We found no significant effects on pulmonary function, cells in induced sputum, or exhaled nitric oxide. Switching to Eclipse reduces alveolar epithelial injury in some smokers but may increase carboxyhemoglobin levels and oxidative stress.

Glutaraldehyde-induced occupational asthma: BALF components and BALF and serum Clara cell protein (CC16) changes due to specific inhalatory provocation test

OBJECTIVES

The purpose of this study was to evaluate bronchoalveolar lavage fluid (BALF) components and Clara cell protein (CC16) concentration in serum and BALF in patients with glutaraldehyde (GA)-induced asthma, before and after a specific inhalatory provocation test (SIPT) with GA, in comparison to atopic asthmatics and healthy individuals.

METHODS

Spirometry and bronchoalveolar lavage were performed before and after SIPT. The serum and BALF concentrations of CC16 and cytogram content in BALF were evaluated.

RESULTS

In GA-sensitized asthmatics, the level of CC16 in BALF and serum was significantly lower at 24 h after SIPT in comparison with the values recorded prior to the experiment. There was a significant increase in the proportion of eosinophils, basophils and lymphocytes in BALF of GA-sensitized asthmatics obtained after SIPT.

CONCLUSIONS

The determination of CC16 either in serum or in BALF is a non-invasive test to detect Clara cell damage.

Pulmonary biomarkers in chronic obstructive pulmonary disease

There has been increasing interest in using pulmonary biomarkers to understand and monitor the inflammation in the respiratory tract of patients with chronic obstructive pulmonary disease (COPD). In this Pulmonary Perspective we discuss the merits of the various approaches by reviewing the current literature on pulmonary biomarkers in COPD and underscore the need for more systematic studies in the future. Bronchial biopsies and bronchoalveolar lavage provide valuable information about inflammatory cells and mediators, but are invasive, so that repeated measurements have to be very limited in assessing any interventions. Induced sputum has provided considerable information about the inflammatory process, including mediators and proteinases in COPD, but selectively samples proximal airways and may not closely reflect distal inflammatory processes. Exhaled gases and breath condensate are noninvasive procedures, so repeated measurements are possible, but for some assays the variability is relatively high. There is relatively little information about how any of these biomarkers relate to other clinical outcomes, such as progression of the disease, severity of disease, clinical subtypes, or response to therapy. More information is also needed about the variability in these measurements. In the future, pulmonary biomarkers may be useful in predicting disease progression, indicating disease instability, and in predicting response to current therapies and novel therapies, many of which are now in development.