Club cell secretory protein and lung function in children with cystic fibrosis

Novel biomarkers in asthma

PURPOSE OF REVIEW

Asthma is a common global respiratory disease characterized by airway inflammation. It is a heterogenous group of disorders with overlapping biological mechanisms. This review will discuss the current state of the use of biomarkers in asthma with an eye to the future. The identification of biomarkers has advanced our understanding of inflammatory pathways in asthma and aided in development of targeted therapies. However, even with similar inflammatory biomarkers, not all patients respond uniformly. Thus, further research into novel biomarkers in asthma is needed.

RECENT FINDINGS

Recent literature highlights several key themes in biomarker research for asthma. Biomarkers can be derived from various sources, including sputum, blood, urine, and exhaled breath. Historically, studies have focused on eosinophilic inflammation, yet total blood eosinophil counts do not capture asthma pathology and treatment responses. Recent investigations explore eosinophil activity as well as eosinophil subpopulations based on surface protein expressions. Mast cell involvement, their mediators, and club cell secretory protein are further being examined across different asthma molecular phenotypes.

SUMMARY

The complexity of inflammatory pathways in asthma, influenced by various factors, underscores the inadequacy of relying on a single biomarker at one time point. Continued research is essential to identify appropriate biomarkers.

Circulating CC16, immune response to Mycoplasma pneumoniae and lung function: a population-based, multi-cohort study

BACKGROUND

Sufficient levels of club cell secretory protein (CC16) are essential to protect against lung function impairments. Experimental studies have demonstrated that CC16 modulates inflammatory responses and protects against airway hyperresponsiveness following Mycoplasma pneumoniae (Mp) infection. Individuals with asthma have low CC16 levels and increased susceptibility to Mp infection. Here we determine whether low CC16 and Mp seropositivity have combined effects on lung function deficits predisposing to airflow limitation, particularly in asthma.

METHODS

Serum levels of CC16 and IgG antibodies against Mp (MpIgG) were measured in adult participants from cohorts BAMSE, MAAS, LSC, and TESAOD. Participants were then stratified into four groups: normal CC16/MpIgG-, normal CC16/MpIgG+, low CC16/MpIgG-, low CC16/MpIgG+. Associations between these groups and lung function (FEV1 and FEV1/FVC) were assessed by linear regression, adjusting for covariates. Meta-analyzed estimates were calculated.

RESULTS

Low CC16 was associated with decreased lung function in the total population, but no combined effects of CC16 and MpIgG were observed. Among asthmatic participants, the low CC16/MpIgG + group had remarkably lower FEV1/FVC z-scores (-0.84, CI: 1.29, -0.38) compared to the reference group, and Mp seropositivity was associated with significant deficits in FEV1/FVC z-scores among those with low CC16 (-0.60, CI: 1.08, -0.12), but not among those with normal CC16 (-0.10, CI: 0.56, 0.36).

CONCLUSION

This suggests that individuals with asthma with low levels of CC16 combined with a history of Mp infection may be more susceptible to deficits in FEV1/FVC, the hallmark of airflow limitation, emphasizing the need for prospective studies designed to test this hypothesis.

A New Frontier in Cystic Fibrosis Pathophysiology: How and When Clock Genes Can Affect the Inflammatory/Immune Response in a Genetic Disease Model

Cystic fibrosis (CF) is a monogenic syndrome caused by variants in the CF Transmembrane Conductance Regulator (CFTR) gene, affecting various organ and systems, in particular the lung, pancreas, sweat glands, liver, gastrointestinal tract, vas deferens, and vascular system. While for some organs, e.g., the pancreas, a strict genotype-phenotype occurs, others, such as the lung, display a different pathophysiologic outcome in the presence of the same mutational asset, arguing for genetic and environmental modifiers influencing severity and clinical trajectory. CFTR variants trigger a pathophysiological cascade of events responsible for chronic inflammatory responses, many aspects of which, especially related to immunity, are not ascertained yet. Although clock genes expression and function are known modulators of the innate and adaptive immunity, their involvement in CF has been only observed in relation to sleep abnormalities. The aim of this review is to present current evidence on the clock genes role in immune-inflammatory responses at the lung level. While information on this topic is known in other chronic airway diseases (chronic obstructive pulmonary disease and asthma), CF lung disease (CFLD) is lacking in this knowledge. We will present the bidirectional effect between clock genes and inflammatory factors that could possibly be implicated in the CFLD. It must be stressed that besides sleep disturbance and its mechanisms, there are not studies directly addressing the exact nature of clock genes' involvement in inflammation and immunity in CF, pointing out the directions of new and deepened studies in this monogenic affection. Importantly, clock genes have been found to be druggable by means of genetic tools or pharmacological agents, and this could have therapeutic implications in CFLD.

Enhancing peptide and PMO delivery to mouse airway epithelia by chemical conjugation with the amphiphilic peptide S10

Delivery of antisense oligonucleotides (ASOs) to airway epithelial cells is arduous due to the physiological barriers that protect the lungs and the endosomal entrapment phenomenon, which prevents ASOs from reaching their intracellular targets. Various delivery strategies involving peptide-, lipid-, and polymer-based carriers are being investigated, yet the challenge remains. S10 is a peptide-based delivery agent that enables the intracellular delivery of biomolecules such as GFP, CRISPR-associated nuclease ribonucleoprotein (RNP), base editor RNP, and a fluorescent peptide into lung cells after intranasal or intratracheal administrations to mice, ferrets, and rhesus monkeys. Herein, we demonstrate that covalently attaching S10 to a fluorescently labeled peptide or a functional splice-switching phosphorodiamidate morpholino oligomer improves their intracellular delivery to airway epithelia in mice after a single intranasal instillation. Data reveal a homogeneous delivery from the trachea to the distal region of the lungs, specifically into the cells lining the airway. Quantitative measurements further highlight that conjugation via a disulfide bond through a pegylated (PEG) linker was the most beneficial strategy compared with direct conjugation (without the PEG linker) or conjugation via a permanent thiol-maleimide bond. We believe that S10-based conjugation provides a great strategy to achieve intracellular delivery of peptides and ASOs with therapeutic properties in lungs.

The multiple facets of the club cell in the pulmonary epithelium

The non-ciliated bronchiolar cell, also referred to as "club cell", serves as a significant multifunctional component of the airway epithelium. While the club cell is a prominent epithelial type found in rodents, it is restricted to the bronchioles in humans. Despite these differences, the club cell's importance remains undisputed in both species due to its multifunctionality as a regulatory cell in lung inflammation and a stem cell in lung epithelial regeneration. The objective of this review is to examine different aspects of club cell morphology and physiology in the lung epithelium, under both normal and pathological conditions, to provide a comprehensive understanding of its importance in the respiratory system.

Botanical formulation HX110B ameliorates PPE-induced emphysema in mice via regulation of PPAR/RXR signaling pathway

Chronic obstructive pulmonary disease (COPD), an inflammatory lung disease, causes approximately 3 million deaths each year; however, its pathological mechanisms are not fully understood. In this study, we examined whether HX110B, a mixture of Taraxacum officinale, Dioscorea batatas, and Schizonepeta tenuifolia extracts, could suppress porcine pancreatic elastase (PPE)-induced emphysema in mice and its mechanism of action. The therapeutic efficacy of HX110B was tested using a PPE-induced emphysema mouse model and human bronchial epithelial cell line BEAS-2B. In vivo data showed that the alveolar wall and air space expansion damaged by PPE were improved by HX110B administration. HX110B also effectively suppresses the expression levels of pro-inflammatory mediators including IL-6, IL-1β, MIP-2, and iNOS, while stimulating the expression of lung protective factors such as IL-10, CC16, SP-D, and sRAGE. Moreover, HX110B improved the impaired OXPHOS subunit gene expression. In vitro analysis revealed that HX110B exerted its effects by activating the PPAR-RXR signaling pathways. Overall, our data demonstrated that HX110B could be a promising therapeutic option for COPD treatment.

Circulating biomarkers of airflow limitation across the life span

BACKGROUND

Airflow limitation is a hallmark of chronic obstructive pulmonary disease, which can develop through different lung function trajectories across the life span. There is a need for longitudinal studies aimed at identifying circulating biomarkers of airflow limitation across different stages of life.

OBJECTIVES

This study sought to identify a signature of serum proteins associated with airflow limitation and evaluate their relation to lung function longitudinally in adults and children.

METHODS

This study used data from 3 adult cohorts (TESAOD [Tucson Epidemiological Study of Airway Obstructive Disease], SAPALDIA [Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults], LSC [Lovelace Smoker Cohort]) and 1 birth cohort (TCRS [Tucson Children's Respiratory Study]) (N = 1940). In TESAOD, among 46 circulating proteins, we identified those associated with FEV1/forced vital capacity (FVC) percent (%) predicted levels and generated a score based on the sum of their z-scores. Cross-sectional analyses were used to test the score for association with concomitant lung function. Longitudinal analyses were used to test the score for association with subsequent lung function growth in childhood and decline in adult life.

RESULTS

After false discovery rate adjustment, serum levels of 5 proteins (HP, carcinoembryonic antigen, ICAM1, CRP, TIMP1) were associated with percent predicted levels of FEV1/FVC and FEV1 in TESAOD. In cross-sectional multivariate analyses the 5-biomarker score was associated with FEV1 % predicted in all adult cohorts (meta-analyzed FEV1 decrease for 1-SD score increase: -2.9%; 95% CI: -3.9%, -1.9%; P = 2.4 × 10-16). In multivariate longitudinal analyses, the biomarker score at 6 years of age was inversely associated with FEV1 and FEV1/FVC levels attained by young adult life (P = .02 and .005, respectively). In adults, persistently high levels of the biomarker score were associated with subsequent accelerated decline of FEV1 and FEV1/FVC (P = .01 and .001).

CONCLUSIONS

A signature of 5 circulating biomarkers of airflow limitation was associated with both impaired lung function growth in childhood and accelerated lung function decline in adult life, indicating that these proteins may be involved in multiple lung function trajectories leading to chronic obstructive pulmonary disease.

CC16 drives VLA-2-dependent SPLUNC1 expression

Rationale

CC16 (Club Cell Secretory Protein) is a protein produced by club cells and other non-ciliated epithelial cells within the lungs. CC16 has been shown to protect against the development of obstructive lung diseases and attenuate pulmonary pathogen burden. Despite recent advances in understanding CC16 effects in circulation, the biological mechanisms of CC16 in pulmonary epithelial responses have not been elucidated.

Objectives

We sought to determine if CC16 deficiency impairs epithelial-driven host responses and identify novel receptors expressed within the pulmonary epithelium through which CC16 imparts activity.

Methods

We utilized mass spectrometry and quantitative proteomics to investigate how CC16 deficiency impacts apically secreted pulmonary epithelial proteins. Mouse tracheal epithelial cells (MTECS), human nasal epithelial cells (HNECs) and mice were studied in naïve conditions and after Mp challenge.

Measurements and main results

We identified 8 antimicrobial proteins significantly decreased by CC16-/- MTECS, 6 of which were validated by mRNA expression in Severe Asthma Research Program (SARP) cohorts. Short Palate Lung and Nasal Epithelial Clone 1 (SPLUNC1) was the most differentially expressed protein (66-fold) and was the focus of this study. Using a combination of MTECs and HNECs, we found that CC16 enhances pulmonary epithelial-driven SPLUNC1 expression via signaling through the receptor complex Very Late Antigen-2 (VLA-2) and that rCC16 given to mice enhances pulmonary SPLUNC1 production and decreases Mycoplasma pneumoniae (Mp) burden. Likewise, rSPLUNC1 results in decreased Mp burden in mice lacking CC16 mice. The VLA-2 integrin binding site within rCC16 is necessary for induction of SPLUNC1 and the reduction in Mp burden.

Conclusion

Our findings demonstrate a novel role for CC16 in epithelial-driven host defense by up-regulating antimicrobials and define a novel epithelial receptor for CC16, VLA-2, through which signaling is necessary for enhanced SPLUNC1 production.

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.

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.

Club Cell Secretory Protein in Lung Disease: Emerging Concepts and Potential Therapeutics

Club cell secretory protein (CCSP), also known as secretoglobin 1A1 (gene name SCGB1A1), is one of the most abundant proteins in the lung, primarily produced by club cells of the distal airway epithelium. At baseline, CCSP is found in large concentrations in lung fluid specimens and can also be detected in the blood and urine. Obstructive lung diseases are generally associated with reduced CCSP levels, thought to be due to decreased CCSP production or club cell depletion. Conversely, several restrictive lung diseases have been found to have increased CCSP levels both in the lung and in the circulation, likely related to club cell dysregulation as well as increasedlung permeability. Recent studies demonstrate multiple mechanisms by which CCSP dampens acute and chronic lung inflammation. Given these anti-inflammatory effects, CCSP represents a novel potential therapeutic modality in lung disease.