Club Cell Secreted Protein CC16: Potential Applications in Prognosis and Therapy for Pulmonary Diseases

Updated epithelial barrier dysfunction in chronic rhinosinusitis: Targeting pathophysiology and treatment response of tight junctions

Tight junction (TJ) proteins establish a physical barrier between epithelial cells, playing a crucial role in maintaining tissue homeostasis by safeguarding host tissues against pathogens, allergens, antigens, irritants, etc. Recently, an increasing number of studies have demonstrated that abnormal expression of TJs plays an essential role in the development and progression of inflammatory airway diseases, including chronic obstructive pulmonary disease, asthma, allergic rhinitis, and chronic rhinosinusitis (CRS) with or without nasal polyps. Among them, CRS with nasal polyps is a prevalent chronic inflammatory disease that affects the nasal cavity and paranasal sinuses, leading to a poor prognosis and significantly impacting patients' quality of life. Its pathogenesis primarily involves dysfunction of the nasal epithelial barrier, impaired mucociliary clearance, disordered immune response, and excessive tissue remodeling. Numerous studies have elucidated the pivotal role of TJs in both the pathogenesis and response to traditional therapies in CRS. We therefore to review and discuss potential factors contributing to impair and repair of TJs in the nasal epithelium based on their structure, function, and formation process.

Chronic inhalation of H2S in low concentration induces immunotoxicity and inflammatory effects in lung tissue of rats

Hydrogen sulfide (H2S) is a typical odour compound mainly causing respiratory and central nervous system symptoms. However, the immunotoxicity of inhaled H2S and the underlying mechanisms remain largely unknown. In this study, a low-dose inhalation exposure to H2S was arranged to observe inflammatory response and immunotoxicity in lung tissue of rats. Low concentrations of H2S exposure affected the immune level of pulmonary tissue and peripheral blood. Significant pathological changes in lung tissue in the exposure group were observed. At low concentration, H2S not only induced the upregulation of AQP-4 and MMP-9 expression but also stimulated immune responses, initiating various anti-inflammatory and inflammatory factors, altering tissue homeostatic environments. The TNF and chemokine signaling pathway played an important role which can promote the deterioration of pulmonary inflammatory processes and lead to lung injury and fibrosis. Excessive immune response causes an inflammatory effect and blood-gas barrier damage. These data will be of value in evaluating future occupational health risks and providing technical support for the further development of reliable, sensitive, and easy-to-use screening indicators of exposure injury.

Dexmedetomidine improves lung injury after one-lung ventilation in esophageal cancer patients by inhibiting inflammatory response and oxidative stress

Aim

To explore the effect of Dexmedetomidine (DEX) on lung injury in patients undergoing One-lung ventilation (OLV).

Methods

Esophageal cancer patients undergoing general anesthesia with OLV were randomly divided into the DEX group and control group, with 30 cases in each group. Mean arterial pressure (MAP), heart rate (HR), arterial partial pressure of oxygen (PO2), and arterial partial pressure of nitrogen dioxide (PCO2) were recorded at the time points after anesthesia induction and before OLV (T1), OLV 30 min (T2), OLV 60 min (T3), OLV 120 min (T4), OLV end before (T5) and before leaving the room (T6) in both groups. Reverse Transcription-Polymerase Chain Reaction (RT-qPCR) was applied to detect the levels of CC16 mRNA. Enzyme-linked immunosorbent assay (ELISA) was used to detect serum CC16 protein levels. The content of malondialdehyde (MDA) in serum was determined by thio barbituric acid (TBA) method. ELISA was used to measure the concentrations of TNF-α (tumor necrosis factor-alpha)/and IL-6 (interleukin 6).

Results

DEX treatment slowed down HR at time points T1-T6 and increased PO2 and PCO2 at time points T2-T5 compared with the control group. Moreover, at time points T2-T6, DEX treatment reduced the levels of club cell secretory protein-16 (CC16) mRNA and serum CC16 protein levels. Furthermore, DEX treatment caused the reduction of MDA, TNF-α and IL-6 concentrations in serum of patients.

Conclusion

During the OLV process, DEX could reduce serum CC16 protein levels, inhibit inflammatory reactions and oxidative stress, and improve oxygenation index, indicating a protective effect on lung injury during OLV.

Potential mechanisms of lung injury and repair after hexavalent chromium [Cr(VI)] aerosol whole-body dynamic exposure

Hexavalent chromium [Cr(VI)], known as "Top Hazardous Substances", poses a significant threat to the respiratory system. Nevertheless, the potential mechanisms of toxicity and the lung's repair ability after injury remain incompletely understood. In this study, Cr(VI) aerosol whole-body dynamic exposure system simulating real exposure scenarios of chromate workers was constructed to evaluate the lung injury and repair effects. Subsequently, miRNA sequencing, mRNA sequencing and metabolomics analyses on lung tissue were performed to explore the underlying mechanisms. Our results revealed that Cr(VI) exposure led to an increase in lactic dehydrogenase activity and a time-dependent decline in lung function. Notably, after 13 w of Cr(VI) exposure, alveolar hemorrhage, thickening of alveolar walls, emphysema-like changes, mitochondrial damage of alveolar epithelial cells and macrophage polarization changes were observed. Remarkably, a two-week repair intervention effectively ameliorated lung function decline and pulmonary injury. Furthermore, significant disruptions in the expressions of miRNAs and mRNAs involved in oxidative phosphorylation, glycerophospholipid metabolism and inflammatory signaling pathways were found. The two-week repair period resulted in the reversal of expression of oxidative phosphorylation related genes, and inhibited the inflammatory signaling pathways. This study concluded that the inhibition of the mitochondrial oxidative phosphorylation pathway and the subsequent enhancement of inflammatory response might be key mechanisms underlying Cr(VI) pulmonary toxicity, and timely cessation of exposure could effectively alleviate the pulmonary injury. These findings shed light on the potential mechanisms of Cr(VI) toxicity and provide crucial insights into the health protection for occupational populations exposed to Cr(VI).

The acute effects of endurance exercise on epithelial integrity of the airways in athletes and non-athletes: A systematic review and meta-analysis

INTRODUCTION

Acute endurance exercise may induce airway epithelium injury. However, the response of epithelial integrity markers of the airways including club cell secretory protein (CC16) and surfactant protein D (SP-D) to endurance exercise have not been systematically reviewed. Therefore, the aim of this systematic review and meta-analysis was to assess the acute effects of endurance exercise on markers of epithelial integrity of the airways (CC16, SP-D and the CC16/SP-D ratio) in athletes and non-athletes.

METHODS

A systematic search was performed utilizing PubMed/Medline, EMBASE, Web of Science, and hand searching bibliographies of retrieved articles through to September 2022. Based on the inclusion criteria, articles with available data about the acute effects of endurance exercise on serum or plasma concentrations of CC16, SP-D and CC16/SP-D ratio in athletes and non-athletes were included. Quality assessment of studies and statistical analysis were conducted via Review Manager 5.4 software.

RESULTS

The search resulted in 908 publications. Finally, thirteen articles were included in the review. Acute endurance exercise resulted in an increase in CC16 (P = 0.0006, n = 13) and CC16/SP-D ratio (P = 0.005, n = 2) whereas SP-D (P = 0.47, n = 3) did not change significantly. Subgroup analysis revealed that the type (P = 0.003), but not the duration of exercise (P = 0.77) or the environmental temperature (P = 0.06) affected the CC16 response to endurance exercise.

CONCLUSIONS

Acute endurance exercise increases CC16 and the CC16/SP-D ratio, as markers of epithelial integrity, but not SP-D in athletes and non-athletes.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Circulating CC16 and Asthma: A Population-based, Multicohort Study from Early Childhood through Adult Life

Rationale: Club cell secretory protein (CC16) is an antiinflammatory protein highly expressed in the airways. CC16 deficiency has been associated with lung function deficits, but its role in asthma has not been established conclusively. Objectives: To determine 1) the longitudinal association of circulating CC16 with the presence of active asthma from early childhood through adult life and 2) whether CC16 in early childhood predicts the clinical course of childhood asthma into adult life. Methods: We assessed the association of circulating CC16 and asthma in three population-based birth cohorts: the Tucson Children's Respiratory Study (years 6-36; total participants, 814; total observations, 3,042), the Swedish Barn/Children, Allergy, Milieu, Stockholm, Epidemiological survey (years 8-24; total participants, 2,547; total observations, 3,438), and the UK Manchester Asthma and Allergy Study (years 5-18; total participants, 745; total observations, 1,626). Among 233 children who had asthma at the first survey in any of the cohorts, baseline CC16 was also tested for association with persistence of symptoms. Measurements and Main Results: After adjusting for covariates, CC16 deficits were associated with increased risk for the presence of asthma in all cohorts (meta-analyzed adjusted odds ratio per 1-SD CC16 decrease, 1.20; 95% confidence interval [CI], 1.12-1.28; P < 0.0001). The association was particularly strong for asthma with frequent symptoms (meta-analyzed adjusted relative risk ratio, 1.40; 95% CI, 1.24-1.57; P < 0.0001), was confirmed for both atopic and nonatopic asthma, and was independent of lung function impairment. After adjustment for known predictors of persistent asthma, children with asthma in the lowest CC16 tertile had a nearly fourfold increased risk for having frequent symptoms persisting into adult life compared with children with asthma in the other two CC16 tertiles (meta-analyzed adjusted odds ratio, 3.72; 95% CI, 1.78-7.76; P < 0.0001). Conclusions: Circulating CC16 deficits are associated with the presence of asthma with frequent symptoms from childhood through midadult life and predict the persistence of asthma symptoms into adulthood. These findings support a possible protective role of CC16 in asthma and its potential use for risk stratification.

The Impact of CC16 on Pulmonary Epithelial-Driven Host Responses during Mycoplasma pneumoniae Infection in Mouse Tracheal Epithelial Cells

Club Cell Secretory Protein (CC16) plays many protective roles within the lung; however, the complete biological functions, especially regarding the pulmonary epithelium during infection, remain undefined. We have previously shown that CC16-deficient (CC16-/-) mouse tracheal epithelial cells (MTECs) have enhanced Mp burden compared to CC16-sufficient (WT) MTECs; therefore, in this study, we wanted to further define how the pulmonary epithelium responds to infection in the context of CC16 deficiency. Using mass spectrometry and quantitative proteomics to analyze proteins secreted apically from MTECs grown at an air-liquid interface, we investigated the protective effects that CC16 elicits within the pulmonary epithelium during Mycoplasma pneumoniae (Mp) infection. When challenged with Mp, WT MTECs have an overall reduction in apical protein secretion, whereas CC16-/- MTECs have increased apical protein secretion compared to their unchallenged controls. Following Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) assessment, many of the proteins upregulated from CC16-/- MTECS (unchallenged and during Mp infection) were related to airway remodeling, which were not observed by WT MTECs. These findings suggest that CC16 may be important in providing protection within the pulmonary epithelium during respiratory infection with Mp, which is the major causative agent of community-acquired pneumoniae.

Predicting Lung Function Using Biomarkers in Alpha-1 Antitrypsin Deficiency

Lung disease progression in alpha-1 antitrypsin deficiency (AATD) is heterogenous and manifests in different ways. Blood biomarkers are an attractive method of monitoring diseases as they are easy to obtain and repeatable. In non-AATD COPD, blood biomarker panels have predicted disease severity, progression, and mortality. We measured a panel of seven serum biomarkers in 200 AATD patients and compared levels between those with COPD and those without. We assessed whether biomarkers were associated with baseline lung function parameters (FEV1 and TLco) or absolute change in these parameters. In total, 111 patients with a severely deficient genotype of AATD (PiZZ) and COPD were included in the analyses. Pearson's correlation coefficient was measured for biomarker correlations and models were compared using ANOVA. CRP and CCL18 were significantly higher in the serum of AATD COPD versus AATD with no COPD. Biomarkers were not predictive of cross-sectional lung function measurements, however, CC16 was significantly associated with an absolute change in TLco (p = 0.018). An addition of biomarkers to the predictive model for TLco added significant value over covariates alone (R2 0.13 vs. 0.02, p = 0.028). Our findings suggest that CC16 is predictive of emphysema progression in AATD COPD. Proteomics data may reveal alternative candidate biomarkers and further work should include the use of longitudinal biomarker measurements.

Quercetin-Induced Enhancement of Nasal Epithelial Cells' Ability to Produce Clara Cell 10-kD Protein In Vitro and In Vivo

Background: Quercetin, a polyphenolic flavonoid found in various plants and foods, is known to have antioxidant, antiviral and anticancer effects. Although quercetin is well known to exert anti-inflammatory and anti-allergic effects, the precise mechanisms by which quercetin favorably modifies the clinical status of allergic diseases, such as allergic rhinitis (AR), remain unclear. The present study examined whether quercetin could modulate the production of the endogenous anti-inflammatory molecule, Clara cell 10-kD protein (CC10), in vitro and in vivo. Methods: Human nasal epithelial cells (1 × 10⁵ cells/mL) were stimulated with 20 ng/mL of tumor necrosis factor-alpha (TNF) in the presence of quercetin for 24 h. CC10 levels in culture supernatants were examined by ELISA. Sprague Dawley rats were sensitised with toluene 2,4-diisocyanate (TDI) by intranasal instillation of 10% TDI in ethyl acetate at a volume of 5.0 μL once daily for five days. This sensitisation procedure was repeated after an interval of two days. The rats were treated with different dosages of quercetin once daily for five days starting on the 5th day following the second sensitization. Nasal allergy-like symptoms induced by the bilateral application of 5.0 μL of 10% TDI were assessed by counting sneezing and nasal-rubbing behaviours for 10 min immediately after the TDI nasal challenge. The levels of CC10 in nasal lavage fluids obtained 6 h after TDI nasal challenge were examined using ELISA. Results: The treatment of cells with low doses of quercetin (<2.5 μM) scarcely affected TNF-induced CC10 production from nasal epithelial cells. However, the ability of nasal epithelial cells to produce CC10 after TNF stimulation significantly increased on treatment with quercetin doses (>5.0 μM). The oral administration of quercetin (>25 mg/kg) for five days significantly increased the CC10 content in nasal lavage fluids and attenuated the nasal symptoms induced by the TDI nasal challenge. Conclusions: Quercetin inhibits AR development by increasing the ability of nasal epithelial cells to produce CC10.

Core genes in lung adenocarcinoma identified by integrated bioinformatic analysis

This study aims to identify potential core genes of lung adenocarcinoma (LUAD). Three datasets (GSE32863, GSE43458, and GSE116959) were retrieved from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) between LUAD and normal tissues were filtrated by GEO2R tool. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed via Metascape database. The protein-protein interaction (PPI) network was constructed and core genes were identified using STRING and Cytoscape. Core genes expressions and their relevant clinical characteristics were performed via Oncomine and UALCAN databases respectively. The correlation between core genes and immune infiltrates was investigated by TIMER database. Kaplan-Meier plotter was performed for survival analysis. The signal pathway network of core genes was mapped by KEGG Mapper analysis tool. In this study, ten core genes were significantly related to overall survival (OS) of LUAD patients, which can provide clues for prognosis of LUAD.

Diagnosis of Fibrotic Hypersensitivity Pneumonitis: Is There a Role for Biomarkers?

Hypersensitivity pneumonitis is a complex interstitial lung syndrome and is associated with significant morbimortality, particularly for fibrotic disease. This condition is characterized by sensitization to a specific antigen, whose early identification is associated with improved outcomes. Biomarkers measure objectively biologic processes and may support clinical decisions. These tools evolved to play a crucial role in the diagnosis and management of a wide range of human diseases. This is not the case, however, with hypersensitivity pneumonitis, where there is still great room for research in the path to find consensual diagnostic biomarkers. Gaps in the current evidence include lack of validation, validation against healthy controls alone, small sampling and heterogeneity in diagnostic and classification criteria. Furthermore, discriminatory accuracy is currently limited by overlapping mechanisms of inflammation, damage and fibrogenesis between ILDs. Still, biomarkers such as BAL lymphocyte counts and specific serum IgGs made their way into clinical guidelines, while others including KL-6, SP-D, YKL-40 and apolipoproteins have shown promising results in leading centers and have potential to translate into daily practice. As research proceeds, it is expected that the emergence of novel categories of biomarkers will offer new and thriving tools that could complement those currently available.

Low CC16 mRNA Expression Levels in Bronchial Epithelial Cells Are Associated with Asthma Severity

Rationale: CC16 is a protein mainly produced by nonciliated bronchial epithelial cells (BECs) that participates in host defense. Reduced CC16 protein concentrations in BAL and serum are associated with asthma susceptibility. Objectives: Few studies have investigated the relationship between CC16 and asthma progression, and none has focused on BECs. In this study, we sought to determine if CC16 mRNA expression levels in BECs are associated with asthma severity. Methods: Association analyses between CC16 mRNA expression levels in BECs (242 asthmatics and 69 control subjects) and asthma-related phenotypes in Severe Asthma Research Program were performed using a generalized linear model. Measurements and Main Results: Low CC16 mRNA expression levels in BECs were significantly associated with asthma susceptibility and asthma severity, high systemic corticosteroids use, high retrospective and prospective asthma exacerbations, and low pulmonary function. Low CC16 mRNA expression levels were significantly associated with high T2 inflammation biomarkers (fractional exhaled nitric oxide and sputum eosinophils). CC16 mRNA expression levels were negatively correlated with expression levels of Th2 genes (IL1RL1, POSTN, SERPINB2, CLCA1, NOS2, and MUC5AC) and positively correlated with expression levels of Th1 and inflammation genes (IL12A and MUC5B). A combination of two nontraditional T2 biomarkers (CC16 and IL-6) revealed four asthma endotypes with different characteristics of T2 inflammation, obesity, and asthma severity. Conclusions: Our findings indicate that low CC16 mRNA expression levels in BECs are associated with asthma susceptibility, severity, and exacerbations, partially through immunomodulation of T2 inflammation. CC16 is a potential nontraditional T2 biomarker for asthma development and progression.

Validation of Prognostic Club Cell Secretory Protein (CC16) Cut-point in an Independent ALTA Cohort

Background

Club cell secretory protein (CC16) has demonstrated utility as a lung-specific biomarker in predicting mortality in acute respiratory distress syndrome (ARDS). These findings have been observed in pre-clinical trials and a re-analysis of a large, randomized controlled trial of ARDS (Fluid and Catheter Treatment Trial (FACTT)).

Objectives

The purpose of this study was to validate previous findings by evaluating CC16 level as a mortality predictor in patients from the albuterol to treat acute lung injury (ALTA) trial.

Design and Method

In this secondary biomarker analysis, plasma CC16 level was measured from 100 ALTA subjects using enzyme-linked immunosorbent assay (ELISA). The rate of mortality was assessed in patients with high (⩾45 ng/mL) versus low CC16 (<45 ng/mL) levels. This cut-off level was applied based on our previous analysis from FACTT trial. Significance was assessed using Kaplan-Meier curves and a log-rank test.

Results

Subjects were an average of 50 years old and 46% of them were females. Patients with high CC16 levels had higher 90-day mortality compared to those with low CC16 levels, (37.73% vs 8.95%, P < .001). Other clinical outcomes including ICU-free days, ventilator-free days, and organ failure free days were significantly different between the groups (All P < .05).

Conclusion

In this validation study, we demonstrated that ARDS patients with high plasma CC16 concentration had a higher mortality rate than those with low CC16 levels, confirming previous findings that CC16 levels are associated with ARDS mortality.

CC16 as an Inflammatory Biomarker in Induced Sputum Reflects Chronic Obstructive Pulmonary Disease (COPD) Severity

Purpose

The progression of an abnormal inflammatory response plays a crucial role in the lung function decline of chronic obstructive pulmonary disease (COPD) patients. Compared to serum biomarkers, inflammatory biomarkers in induced sputum would be a more reliable reflection of inflammatory processes in the airways.

Patients and Methods

A total of 102 COPD participants were divided into a mild-to-moderate group (FEV1%pred≥ 50%, n=57) and a severe-to-very-severe group (FEV1%pred<50%, n=45). We measured a series of inflammatory biomarkers in induced sputum and analyzed their association with lung function and SGRQ in COPD patients. To evaluate the relationship between inflammatory biomarkers and the inflammatory phenotype, we also analyzed the correlation between biomarkers and airway eosinophilic phenotype.

Results

We found increased mRNA levels of MMP9, LTB4R, and A1AR and decreased levels of CC16 mRNA in induced sputum in the severe-to-very-severe group. After adjustment for age, sex and other biomarkers, CC16 mRNA expression was positively associated with FEV1%pred (r=0.516, p=0.004) and negatively correlated with SGRQ scores (r=-0.3538, p=0.043). As previously known, decreased CC16 was related to the migration and aggregation of eosinophils in airway. It was also found that CC16 had a moderate negative correlation with the eosinophilic inflammation in airway (r=-0.363, p=0.045) in our COPD patients.

Conclusion

Low CC16 mRNA expression levels in induced sputum were associated with low FEV1%pred and a high SGRQ score in COPD patients. Sputum CC16 as a potential biomarker for predicting COPD severity in clinical practice might attribute to the involvement of CC16 in airway eosinophilic inflammation.

Brief Research Report: Serum clara cell 16 kDa protein levels are increased in patients hospitalized for severe SARS-CoV-2 or sepsis infection

Background

Clara cell 16 kDa protein (CC16) is a secretory protein primarily expressed in epithelial cells in the lungs. Previous studies show that CC16 exerts anti-inflammatory and immune-modulatory properties in both acute and chronic pulmonary diseases. However, despite the evidence of CC16’s high biomarker potential, evaluation of its role in infectious diseases is yet very limited.

Methods

Serum CC16 concentrations were measured by ELISA and assessed in two different types of severe infections. Using a case-control study design, patients treated for either severe SARS-CoV-2 or severe non-pulmonary sepsis infection were compared to age- and sex-matched healthy human subjects.

Results

Serum CC16 was significantly increased in both types of infection (SARS-CoV-2: 96.22 ± 129.01 ng/ml vs. healthy controls: 14.05 ± 7.48 ng/ml, p = 0.022; sepsis: 35.37 ± 28.10 ng/ml vs. healthy controls: 15.25 ± 7.51 ng/ml, p = 0.032) but there were no distinct differences between infections with and without pulmonary focus (p = 0.089). Furthermore, CC16 serum levels were positively correlated to disease duration and inversely to the platelet count in severe SARS-CoV-2 infection.

Conclusions

Increased CC16 serum levels in both SARS-CoV-2 and sepsis reinforce the high potential as a biomarker for epithelial cell damage and bronchoalveolar−blood barrier leakage in pulmonary as well as non-pulmonary infectious diseases.

CCAAT/Enhancer-Binding Proteins in Fibrosis: Complex Roles Beyond Conventional Understanding

CCAAT/enhancer-binding proteins (C/EBPs) are a family of at least six identified transcription factors that contain a highly conserved basic leucine zipper domain and interact selectively with duplex DNA to regulate target gene expression. C/EBPs play important roles in various physiological processes, and their abnormal function can lead to various diseases. Recently, accumulating evidence has demonstrated that aberrant C/EBP expression or activity is closely associated with the onset and progression of fibrosis in several organs and tissues. During fibrosis, various C/EBPs can exert distinct functions in the same organ, while the same C/EBP can exert distinct functions in different organs. Modulating C/EBP expression or activity could regulate various molecular processes to alleviate fibrosis in multiple organs; therefore, novel C/EBPs-based therapeutic methods for treating fibrosis have attracted considerable attention. In this review, we will explore the features of C/EBPs and their critical functions in fibrosis in order to highlight new avenues for the development of novel therapies targeting C/EBPs.

The traditional Chinese patented medicine Qingke Pingchuan granules alleviates acute lung injury by regenerating club cells

Qingke Pingchuan granules (QKPCG), a patented traditional Chinese medicine, clinically, are recommended for acute tracheobronchitis, cough, community‐acquired pneumonia, and other respiratory diseases. However, its potential protective effect and mechanism of action in acute lung injury (ALI) have not been explored. We aimed to explore the mechanisms underlying the protective role of QKPCG in ALI. The therapeutic efficacy of QKPCG was investigated in a lipopolysaccharide (LPS)‐induced ALI mouse model. Mice were divided into three groups, namely, the Control, LPS, and LPS + QKPCG groups. Mice in the LPS + QKPCG group were administered QKPCG intragastrically as a treatment once a day for a total of three days. QKPCG effectively increased survival and reduced lung injury in treated mice. It significantly reduced the LPS‐induced expression of interleukin (IL)‐6, tumor necrosis factor‐α (TNF‐α), IL‐1α, and IL‐1β. RNA‐sequencing followed by real‐time quantitative polymerase chain reaction validation suggested a critical role of the secretoglobin family 1A member 1 (Scgb1a1) gene in mediating the protective effect of QKPCG. Further, QKPCG reversed the LPS‐induced downregulation of the Clara cell 10 kDa protein (CC10), a pulmonary surfactant protein encoded by Scgb1a1, which is mainly secreted by club cells in the lungs. Exogenous supplementation of CC10 alleviated LPS‐induced ALI. Hematoxylin and eosin staining and enzyme‐linked immunosorbent assay results further confirmed the anti‐inflammatory properties of CC10, which were suggested as mediated via the inhibition of NFκB phosphorylation. In summary, our study provides evidence of the beneficial role of QKPCG in alleviating lung injury, mediated via the decreased disruption of club cells and higher expression of CC10, which leads to NFκB pathway inhibition.

Urinary CC16, a potential indicator of lung integrity and inflammation, increases in children after short-term exposure to PM2.5/PM10 and is driven by the CC16 38GG genotype

Particular matter (PM) exposure is a big hazard for public health, especially for children. Serum CC16 is a well-known biomarker of respiratory health. Urinary CC16 (U-CC16) can be a noninvasive alternative, albeit requiring adequate adjustment for renal handling. Moreover, the SNP CC16 G38A influences CC16 levels. This study aimed to monitor the effect of short-term PM exposure on CC16 levels, measured noninvasively in schoolchildren, using an integrative approach. We used a selection of urine and buccal DNA samples from 86 children stored in an existing biobank. Using a multiple reaction monitoring method, we measured U-CC16, as well as RBP4 (retinol binding protein 4) and β2M (beta-2-microglobulin), required for adjustment. Buccal DNA samples were used for CC16 G38A genotyping. Linear mixed-effects models were used to find relevant associations between U-CC16 and previously obtained data from recent daily PM ≤ 2.5 or 10 μm exposure (PM_2.5, PM₁₀) modeled at the child's residence. Our study showed that exposure to low PM at the child's residence (median levels 18.9 μg/m³ (PM_2.5) and 23.6 μg/m³ (PM₁₀)) one day before sampling had an effect on the covariates-adjusted U-CC16 levels. This effect was dependent on the CC16 G38A genotype, due to its strong interaction with the association between PM levels and covariates-adjusted U-CC16 (P = 0.024 (PM_2.5); P = 0.061 (PM₁₀)). Only children carrying the 38GG genotype showed an increase of covariates-adjusted U-CC16, measured 24h after exposure, with increasing PM_2.5 and PM₁₀ (β = 0.332; 95% CI: 0.110 to 0.554 and β = 0.372; 95% CI: 0.101 to 0.643, respectively). To the best of our knowledge, this is the first study using an integrative approach to investigate short-term PM exposure of children, using urine to detect early signs of pulmonary damage, and taking into account important determinants such as the genetic background and adequate adjustment of the measured biomarker in urine.

Emerging role of an immunomodulatory protein secretoglobin 3A2 in human diseases

Secretoglobin (SCGB) 3A2 was first identified in 2001 as a protein exhibiting similarities in amino acid sequence and gene structure to SCGB1A1, a multi-functional cytokine-like molecule highly expressed in airway epithelial Club cells that was the first identified and extensively studied member of the SCGB gene superfamily. SCGB3A2 is a small secretory protein of ~10 kDa that forms a dimer and a tetramer. SCGB3A2 is predominantly expressed in airway epithelial Club cells, and has anti-inflammatory, growth factor, anti-fibrotic, and anti-cancer activities that influence various lung diseases. This review summarizes the current understanding of SCGB3A2 biological functions and its role in human diseases with emphasis on its mechanisms of actions and signaling pathway.

Assessment of the Feasibility of a Future Integrated Larger-Scale Epidemiological Study to Evaluate Health Risks of Air Pollution Episodes in Children

Air pollution exposure can lead to exacerbation of respiratory disorders in children. Using sensitive biomarkers helps to assess the impact of air pollution on children’s respiratory health and combining protein, genetic and epigenetic biomarkers gives insights on their interrelatedness. Most studies do not contain such an integrated approach and investigate these biomarkers individually in blood, although its collection in children is challenging. Our study aimed at assessing the feasibility of conducting future integrated larger-scale studies evaluating respiratory health risks of air pollution episodes in children, based on a qualitative analysis of the technical and logistic aspects of a small-scale field study involving 42 children. This included the preparation, collection and storage of non-invasive samples (urine, saliva), the measurement of general and respiratory health parameters and the measurement of specific biomarkers (genetic, protein, epigenetic) of respiratory health and air pollution exposure. Bottlenecks were identified and modifications were proposed to expand this integrated study to a higher number of children, time points and locations. This would allow for non-invasive assessment of the impact of air pollution exposure on the respiratory health of children in future larger-scale studies, which is critical for the development of policies or measures at the population level.

Prospects on Repurposing a Live Attenuated Vaccine for the Control of Unrelated Infections

Live vaccines use attenuated microbes to acquire immunity against pathogens in a safe way. As live attenuated vaccines (LAVs) still maintain infectivity, the vaccination stimulates diverse immune responses by mimicking natural infection. Induction of pathogen-specific antibodies or cell-mediated cytotoxicity provides means of specific protection, but LAV can also elicit unintended off-target effects, termed non-specific effects. Such mechanisms as short-lived genetic interference and non-specific innate immune response or long-lasting trained immunity and heterologous immunity allow LAVs to develop resistance to subsequent microbial infections. Based on their safety and potential for interference, LAVs may be considered as an alternative for immediate mitigation and control of unexpected pandemic outbreaks before pathogen-specific therapeutic and prophylactic measures are deployed.

Club Cell Secretory Protein-Derived Acute Respiratory Distress Syndrome Phenotypes Predict 90-Day Mortality: A Reanalysis of the Fluids and Catheter Treatment Trial

Club cell secretory protein (CC16) is a protein with potential utility as a lung-specific biomarker for acute respiratory distress syndrome. The purpose of this study was to characterize CC16 in plasma from patients enrolled in the Fluid and Catheter Treatment Trial (FACTT) to determine the prognostic value for patient outcomes in our subgroup of FACTT patients.

Vitamin D3 alleviates cigarette smoke extract‑mediated epithelial‑mesenchymal transition and fibrogenesis by upregulating CC16 expression in bronchial epithelial cells

Vitamin D3 supplementation has been previously reported to inhibit the occurrence and development of chronic obstructive pulmonary disease (COPD). However, the underlying mechanism remains unclear. Epithelial-mesenchymal transition (EMT) and fibrogenesis have been associated with the development of COPD. The aim of the present study was to investigate the potential effects and mechanism of vitamin D3 in an in vitro model of cigarette smoke (CS)-induced EMT and fibrosis, with specific focus on the role of club cell protein 16 (CC16). CS extract (CSE) at different concentrations (5, 10 and 20%) was used to treat 16-HBE cells to induce EMT and fibrogenesis following which they were treated with vitamin D3. Subsequently, the 20% CSE group was selected for further experiments, where 16-HBE cells were divided into the following five groups: The control group; the CSE group; the low-dose vitamin D3 group (250 nM); the medium-dose vitamin D3 group (500 nM); and the high-dose vitamin D3 group (1,000 nM). Western blot analysis was used to detect the protein expression levels of the EMT-related proteins E-cadherin, N-cadherin, Slug and α-SMA, fibrogenesis-related proteins collagen Ⅳ and fibronectin 1, proteins involved in the TGF-β1/SMAD3 signaling pathway and CC16. Immunofluorescence was used to measure the protein expression levels of E-cadherin, N-cadherin and collagen Ⅳ. Specific CC16 knockdown was performed using short hairpin RNA transfection to investigate the role of CC16. The results of the present study found that vitamin D3 could increase the protein expression level of CC16 to inhibit the activation of the TGF-β1/SMAD3 signaling pathway; thereby reducing the 20% increase in CSE-induced EMT- and fibrogenesis-related protein expression levels. Following CC16 knockdown, the inhibitory effects of vitamin D3 on EMT- and fibrogenesis-related protein expression were partially reversed. To conclude, these results suggest that vitamin D3 can inhibit the protein expression levels of EMT- and fibrogenesis-related proteins induced by CSE, at least partially through the function of CC16. These findings are expected to provide novel theoretical foundations and ideas for the pathogenesis and treatment of COPD.

Elevated plasma levels of epithelial and endothelial cell markers in COVID-19 survivors with reduced lung diffusing capacity six months after hospital discharge

Background

Some COVID-19 survivors present lung function abnormalities during follow-up, particularly reduced carbon monoxide lung diffusing capacity (DLCO). To investigate risk factors and underlying pathophysiology, we compared the clinical characteristics and levels of circulating pulmonary epithelial and endothelial markers in COVID-19 survivors with normal or reduced DLCO 6 months after discharge.

Methods

Prospective, observational study. Clinical characteristics during hospitalization, and spirometry, DLCO and plasma levels of epithelial (surfactant protein (SP) A (SP-A), SP-D, Club cell secretory protein-16 (CC16) and secretory leukocyte protease inhibitor (SLPI)), and endothelial (soluble intercellular adhesion molecule 1 (sICAM-1), soluble E-selectin and Angiopoietin-2) 6 months after hospital discharge were determined in 215 COVID-19 survivors.

Results

DLCO was < 80% ref. in 125 (58%) of patients, who were older, more frequently smokers, had hypertension, suffered more severe COVID-19 during hospitalization and refer persistent dyspnoea 6 months after discharge. Multivariate regression analysis showed that age ≥ 60 years and severity score of the acute episode ≥ 6 were independent risk factors of reduced DLCO 6 months after discharge. Levels of epithelial (SP-A, SP-D and SLPI) and endothelial (sICAM-1 and angiopoietin-2) markers were higher in patients with reduced DLCO, particularly in those with DLCO ≤ 50% ref. Circulating SP-A levels were associated with the occurrence of acute respiratory distress syndrome (ARDS), organizing pneumonia and pulmonary embolisms during hospitalization.

Conclusions

Reduced DLCO is common in COVID-19 survivors 6 months after hospital discharge, especially in those older than 60 years with very severe acute disease. In these individuals, elevated levels of epithelial and endothelial markers suggest persistent lung damage.

Non-Invasive Systemic Biomarker of E-cigarette or Vaping use-Associated Lung Injury (EVALI): A pilot study

Background

Electronic cigarette (e-cigarette) vaping, containing nicotine and/or Δ⁸, Δ⁹ or Δ¹⁰ or Δ^o tetrahydrocannabinol (Δⁿ-THC), is associated with an outbreak of e-cigarette, or vaping, product use-associated lung injury (EVALI). Despite thousands being hospitalised with EVALI, much remains unknown about diagnosis, treatment and disease pathogenesis. Biomarkers of inflammation, oxidative stress and lipid mediators may help identify e-cigarette users with EVALI.

Methods

We collected plasma and urine along with demographic and vaping-related data of EVALI subjects (age 18–35 years) and non-users matched for sex and age in a pilot study. Biomarkers were assessed by ELISA/EIA and Luminex-based assays.

Results

Elevated levels of THC metabolite (11-nor-9-carboxy-Δ⁹-THC) were found in plasma from EVALI subjects compared to non-users. Levels of 8-hydroxy-2′-deoxyguanosine (8-OHdG), an oxidative DNA damage biomarker, and 8-isoprostane, an oxidative stress marker, were slightly increased in urine samples from EVALI subjects compared to non-users. Conversely, plasma levels of lipid mediators, including resolvin D₁ (RvD₁) and prostaglandin E₂ (PGE₂), were significantly lower in EVALI subjects compared to non-users. Both pro-inflammatory biomarkers, such as tumour necrosis factor-α, macrophage inflammatory protein-1β, RANTES (regulated on activation, normal T-cell expressed and secreted) and granulocyte–macrophage colony-stimulating factor, as well as anti-inflammatory biomarkers, such as interleukin-9 and CC10/16, were decreased in plasma from EVALI subjects compared to non-users, supportive of a possible dysregulated inflammatory response in EVALI subjects.

Conclusions

Significant elevations in urine and plasma biomarkers of oxidative stress, as well as reductions in lipid mediators, were shown in EVALI subjects. These noninvasive biomarkers (8-OHdG, 8-isoprostane, RvD₁ and CC10/16), either individually or collectively, may serve as tools in diagnosing future EVALI subjects.

Biomarkers 8-OHdG, 8-isoprostane, RvD₁ and CC10/16 are associated with electronic cigarettes and vapinghttps://bit.ly/3tJJV71

Relationships of serum CC16 levels with smoking status and lung function in COPD

BACKGROUND

The club cell secretory protein (CC16) has anti-inflammatory and antioxidant effects, and low CC16 serum levels have been associated with both risk and progression of COPD, yet the interaction between smoking and CC16 on lung function outcomes remains unknown.

METHODS

Utilizing cross-sectional data on United States veterans, CC16 serum concentrations were measured by ELISA and log transformed for analyses. Spirometry was conducted and COPD status was defined by post-bronchodilator FEV₁/FVC ratio < 0.7. Smoking measures were self-reported on questionnaire. Multivariable logistic and linear regression were employed to examine associations between CC16 levels and COPD, and lung function with adjustment for covariates. Unadjusted Pearson correlations described relationships between CC16 level and lung function measures, pack-years smoked, and years since smoking cessation.

RESULTS

The study population (N = 351) was mostly male, white, with an average age over 60 years. An interaction between CC16 and smoking status on FEV₁/FVC ratio was demonstrated among subjects with COPD (N = 245, p = 0.01). There was a positive correlation among former smokers and negative correlation among current or never smokers with COPD. Among former smokers with COPD, CC16 levels were also positively correlated with years since smoking cessation, and inversely related with pack-years smoked. Increasing CC16 levels were associated with lower odds of COPD (OR_adj = 0.36, 95% CI 0.22-0.57, P_adj < 0.0001).

CONCLUSIONS

Smoking status is an important effect modifier of CC16 relationships with lung function. Increasing serum CC16 corresponded to increases in FEV₁/FVC ratio in former smokers with COPD versus opposite relationships in current or never smokers. Additional longitudinal studies may be warranted to assess relationship of CC16 with smoking cessation on lung function among subjects with COPD.

CC16 Regulates Inflammation, ROS Generation and Apoptosis in Bronchial Epithelial Cells during Klebsiella pneumoniae Infection

Gram-negative (G-) bacteria are the leading cause of hospital-acquired pneumonia in the United States. The devastating damage caused by G- bacteria results from the imbalance of bactericidal effects and overwhelming inflammation. Despite decades of research, the underlying mechanisms by which runaway inflammation is developed remain incompletely understood. Clara Cell Protein 16 (CC16), also known as uteroglobin, is the major protein secreted by Clara cells and the most abundant protein in bronchoalveolar lavage fluid (BALF). However, the regulation and functions of CC16 during G- bacterial infection are unknown. In this study, we aimed to assess the regulation of CC16 in response to Klebsiella pneumoniae (K. pneu) and to investigate the role of CC16 in bronchial epithelial cells. After K. pneu infection, we found that CC16 mRNA expression was significantly decreased in bronchial epithelial cells. Our data also showed that K. pneu infection upregulated cytokine and chemokine genes, including IL-1β, IL-6, and IL-8 in BEAS-2B cells. Endogenously overexpressed CC16 in BEAS-2B cells provided an anti-inflammatory effect by reducing these markers. We also observed that endogenous CC16 can repress NF-κB reporter activity. In contrast, the recombinant CC16 (rCC16) did not show an anti-inflammatory effect in K. pneu-infected cells or suppression of NF-κB promoter activity. Moreover, the overexpression of CC16 reduced reactive oxygen species (ROS) levels and protected BEAS-2B cells from K. pneu-induced apoptosis.

Androgen-Binding Protein (Abp) Evolutionary History: Has Positive Selection Caused Fixation of Different Paralogs in Different Taxa of the Genus Mus?

Comparison of the androgen-binding protein (Abp) gene regions of six Mus genomes provides insights into the evolutionary history of this large murid rodent gene family. We identified 206 unique Abp sequences and mapped their physical relationships. At least 48 are duplicated and thus present in more than two identical copies. All six taxa have substantially elevated LINE1 densities in Abp regions compared with flanking regions, similar to levels in mouse and rat genomes, although nonallelic homologous recombination seems to have only occurred in Mus musculus domesticus. Phylogenetic and structural relationships support the hypothesis that the extensive Abp expansion began in an ancestor of the genus Mus. We also found duplicated Abpa27's in two taxa, suggesting that previously reported selection on a27 alleles may have actually detected selection on haplotypes wherein different paralogs were lost in each. Other studies reported that a27 gene and species trees were incongruent, likely because of homoplasy. However, L1MC3 phylogenies, supposed to be homoplasy-free compared with coding regions, support our paralog hypothesis because the L1MC3 phylogeny was congruent with the a27 topology. This paralog hypothesis provides an alternative explanation for the origin of the a27 gene that is suggested to be fixed in the three different subspecies of Mus musculus and to mediate sexual selection and incipient reinforcement between at least two of them. Finally, we ask why there are so many Abp genes, especially given the high frequency of pseudogenes and suggest that relaxed selection operates over a large part of the gene clusters.

The Potential of Lung Epithelium Specific Proteins as Biomarkers for COVID-19-Associated Lung Injury

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection was first reported in Wuhan, China, and was declared a pandemic by the World Health Organization (WHO) on 20 March 2020. The respiratory system is the major organ system affected by COVID-19. Numerous studies have found lung abnormalities in patients with COVID-19, including shortness of breath, respiratory failure, and acute respiratory distress syndrome. The identification of lung-specific biomarkers that are easily measurable in serum would be valuable for both clinicians and patients with such conditions. This review is focused on the pneumoproteins and their potential to serve as biomarkers for COVID-19-associated lung injury, including Krebs von den Lungen-6 (KL-6), surfactant proteins (SP-A, SP-B, SP-C, SP-D), and Clara cell secretory protein (CC16). The current findings indicate the aforementioned pneumoproteins may reflect the severity of pulmonary manifestations and could serve as potential biomarkers in COVID-19-related lung injury.

CC16-TNF-α negative feedback loop formed between Clara cells and normal airway epithelial cells protects against diesel exhaust particles exposure-induced inflammation

CC16 is almost exclusively expressed in non-ciliated epithelial Clara cells, and widely used as a Clara cell marker. Diesel exhaust particles (DEPs), the fine particulate matters produced by diesel engines, cause or exacerbate airway-related diseases. Our previous study documented that DEP inhibits the CC16 expression in the immortalized mouse Clara cell line through methylation of C/EBPα promoter. However, the molecular mechanism by which DEP regulates CC16 secretion is unclear. Here, we isolated CC16 containing Clara cells (CC16⁺) from human distal lung, and found that DEP inhibited CC16 secretion from CC16⁺ cells via methylation of C/EBPα and inhibition of Munc18b transcription. CC16⁺ cell conditioned media containing different concentrations of CC16 was prepared and used for culture of airway epithelial cells BEAS-2B with no expression of CC16. A positive correlation was observed between CC16 level and DEP-induced autophagy activity, and a negative correlation between CC16 level and DEP-induced pro-inflammatory cytokine TNF-α, IL-6, and IL-8 level, suggesting that CC16 might mitigate DEP-induced inflammation via promoting autophagy in BEAS-2B cells. This result was further confirmed by adding recombinant CC16 to BEAS-2B cells exposed to DEP. Moreover, CC16 level was significantly increased when CC16⁺ cells were cultured in BEAS-2B cell conditioned medium containing TNF-α or the normal medium supplemented with recombinant TNF-α, suggesting that TNF-α induced CC16 production and secretion from CC16⁺ cells. Collectively, these data point that CC16 and TNF-α form a negative feedback loop, and this negative feedback loop between Clara cells and normal airway epithelial cells protects against DEP exposure-induced inflammation.

Inflammatory and coagulatory markers and exposure to different size fractions of particle mass, number and surface area air concentrations in the Swedish hard metal industry, in particular to cobalt

PURPOSE

To study the relationship between inhalation of airborne particles and cobalt in the Swedish hard metal industry and markers of inflammation and coagulation in blood.

METHODS

Personal sampling of inhalable cobalt and dust were performed for subjects in two Swedish hard metal plants. Stationary measurements were used to study concentrations of inhalable, respirable, and total dust and cobalt, PM₁₀ and PM_2.5, the particle surface area and the particle number concentrations. The inflammatory markers CC16, TNF, IL-6, IL-8, IL-10, SAA and CRP, and the coagulatory markers FVIII, vWF, fibrinogen, PAI-1 and D-dimer were measured. A complete sampling was performed on the second or third day of a working week following a work-free weekend, and additional sampling was taken on the fourth or fifth day. The mixed model analysis was used, including covariates.

RESULTS

The average air concentrations of inhalable dust and cobalt were 0.11 mg/m³ and 0.003 mg/m³, respectively. For some mass-based exposure measures of cobalt and total dust, statistically significant increased levels of FVIII, vWF and CC16 were found.

CONCLUSIONS

The observed relationships between particle exposure and coagulatory biomarkers may indicate an increased risk of cardiovascular disease.

Immune-Associated Proteins Are Enriched in Lung Tissue-Derived Extracellular Vesicles during Allergen-Induced Eosinophilic Airway Inflammation

Studying the proteomes of tissue-derived extracellular vesicles (EVs) can lead to the identification of biomarkers of disease and can provide a better understanding of cell-to-cell communication in both healthy and diseased tissue. The aim of this study was to apply our previously established tissue-derived EV isolation protocol to mouse lungs in order to determine the changes in the proteomes of lung tissue-derived EVs during allergen-induced eosinophilic airway inflammation. A mouse model for allergic airway inflammation was used by sensitizing the mice intraperitoneal with ovalbumin (OVA), and one week after the final sensitization, the mice were challenged intranasal with OVA or PBS. The animals were sacrificed 24 h after the final challenge, and their lungs were removed and sliced into smaller pieces that were incubated in culture media with DNase I and Collagenase D for 30 min at 37 °C. Vesicles were isolated from the medium by ultracentrifugation and bottom-loaded iodixanol density cushions, and the proteomes were determined using quantitative mass spectrometry. More EVs were present in the lungs of the OVA-challenged mice compared to the PBS-challenged control mice. In total, 4510 proteins were quantified in all samples. Among them, over 1000 proteins were significantly altered (fold change >2), with 614 proteins being increased and 425 proteins being decreased in the EVs from OVA-challenged mice compared to EVs from PBS-challenged animals. The associated cellular components and biological processes were analyzed for the altered EV proteins, and the proteins enriched during allergen-induced airway inflammation were mainly associated with gene ontology (GO) terms related to immune responses. In conclusion, EVs can be isolated from mouse lung tissue, and the EVs’ proteomes undergo changes in response to allergen-induced airway inflammation. This suggests that the composition of lung-derived EVs is altered in diseases associated with inflammation of the lung, which may have implications in type-2 driven eosinophilic asthma pathogenesis.