Clara cell protein 16 release from the nasal mucosa in allergic rhinitis, chronic rhinosinusitis, and exposure to air pollutants

Different levels of mucus inflammatory mediators in nasal polyposis with and without aeroallergen sensitivity

Objectives

Biomarker levels in nasal secretions can reflect the inflammatory status of nasal mucosa and evolution of sinus disease. The aim of this study was to evaluate the relationship between local inflammatory mediator production and clinical characteristics of patients with nasal polyposis (NP).

Methods

Thirty‐one nonaeroallergen sensitized patients with NP (NANP), 29 aeroallergen sensitized patients with NP (ANP), and 30 subjects without inflammation of nasal mucosa as controls (C) entered this prospective, cross‐sectional study. Clinical parameters (symptoms, endoscopic, and radiological findings) were assessed. The concentrations of heat shock protein 70 (HSP70), eosinophil cationic protein (ECP), tryptase, substance P and Clara cell protein 16 (CC16) were measured in the nasal secretion samples of all participants by ELISA method.

Results

Our results showed higher concentrations of HSP70, ECP, and tryptase in ANP than in NANP and C (p < .001 for all markers). On the other hand, levels of CC16 were significantly higher in C than in NANP and ANP groups (p < .001; p < .001, respectively). We found positive correlations between HSP70, ECP, tryptase, and substance P levels and nasal symptom score in patients with NP. Also, HSP70, ECP, tryptase, and substance P showed different levels of positive correlation among themselves, with HSP70 showing highest positive correlation with ECP. Finally, relatively strong negative correlations were found between the levels of CC16 and nasal symptoms, as well as between the CC16 levels and levels of other four mediators in nasal fluid.

Conclusion

HSP70, ECP, tryptase, and substance P might play a role in the pathogenesis of NP. The results suggest that chronic inflammation in NP involves a self‐sustaining local release of HSP70, ECP, and tryptase, independent of aeroallergen stimulation of the mucosal layer, although the production of these mediators is higher in aeroallergen sensitized NP patients.

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.

The Similarity of Biomarkers Level between Direct Nasal Fluid and Nasal Lavage Fluid in Allergic Rhinitis Patients

Background and Objectives: Biomarkers of allergic rhinitis (AR) have been studied; however, little is known regarding their practical application in the diagnosis of AR. Previous studies collected samples using saline lavage, nasal brushing, or nasal biopsy. To utilize nasal fluid as a diagnostic tool, we need to standardize the method of sample collection. Therefore, this study aimed to evaluate the difference in concentration of biomarkers depending on the method of nasal fluid collection.Materials and Method: Forty-five AR patients who had greater than moderate AR symptoms and who had positive results on skin prick test and serum-specific IgE tests were enrolled in this study. Nasal fluid was collected using the direct method or saline lavage method. The concentration of each biomarker was analyzed using enzyme-linked immunosorbent assay and the values compared.Results: Nasal fluid samples were collected directly from 14 patients and were collected via saline lavage in 31 patients. No significant differences were found in the median value of each biomarker between the two methods of nasal sample collection.Conclusion: Nasal fluid collection method does not significantly affect biomarker concentration.

Clara cell 16 KDa protein mitigates house dust mite-induced airway inflammation and damage via regulating airway epithelial cell apoptosis in a manner dependent on HMGB1-mediated signaling inhibition

Background

House dust mite (HDM) inhalation can cause airway epithelial damage which is implicated in the process of airway inflammation in asthma. High mobility group box 1 (HMGB1) is critically required for cellular damage and apoptosis as an important endogenous danger signal. Recently, Clara cell 16KDa protein (CC16) has been identified to exert anti-inflammatory and immunomodulatory influence in various injury-related diseases model. However, little is known about its ability to protect against airway epithelial injury in allergic asthma. This study was aimed to clarify the protective roles of CC16 on airway epithelia in HDM-induced asthma and the regulation of HMGB1 by CC16.

Methods

Mice were sensitized and challenged by HDM extract and administrated intranasally with CC16 (5 μg/g or 10 μg/g) or saline in the challenged period. The BEAS-2B human airway epithelial cell line were cultured with CC16 or the control vehicle and then exposed to HDM. Knockdown or overexpression of HMGB1 was induced by cell transfection or intratracheal injection of recombinant adenovirus.

Results

CC16 treatment decreased airway inflammation and histological damage of airway epithelium dose-dependently in HDM-induced asthma model. Airway epithelia apoptosis upon HDM stimulation was noticeably abrogated by CC16 in vivo and in vitro. In addition, upregulation of HMGB1 expression and its related signaling were also detected under HDM conditions, while silencing HMGB1 significantly inhibited the apoptosis of BEAS-2B cells. Furthermore, the activity of HMGB1-mediated signaling was restrained after CC16 treatment whereas HMGB1 overexpression abolished the protective effect of CC16 on HDM-induced airway epithelia apoptosis.

Conclusions

Our data confirm that CC16 attenuates HDM-mediated airway inflammation and damage via suppressing airway epithelial cell apoptosis in a HMGB1-dependent manner, suggesting the role of CC16 as a potential protective option for HDM-induced asthma.

Airway Epithelial Dynamics in Allergy and Related Chronic Inflammatory Airway Diseases

Allergic rhinitis, chronic rhinosinusitis, and asthma are highly prevalent, multifactorial chronic airway diseases. Several environmental and genetic factors affect airway epithelial dynamics leading to activation of inflammatory mechanisms in the airways. This review links environmental factors to host epithelial immunity in airway diseases. Understanding altered homeostasis of the airway epithelium might provide important targets for diagnostics and therapy of chronic airway diseases.

Correlation of Nasal Fluid Biomarkers and Symptoms in Patients with Persistent Allergic Rhinitis

OBJECTIVES

This study investigated whether the biomarkers present in nasal fluid reflect the severity of symptoms in patients with persistent allergic rhinitis (PAR).

METHODS

We enrolled 29 PAR patients complaining of nasal symptoms and testing positive to skin prick test. Patients' total nasal symptom score (TNSS) was measured and their nasal lavage fluid (NALF) was collected. The levels of biomarkers including Clara cell protein 16 (CC16), tryptase, and interleukin 5 (IL-5) in NALF were determined via enzyme-linked immunosorbent assay (ELISA).

RESULTS

PAR patients were classified into persistent mild and persistent moderate-to-severe groups according to the Allergic Rhinitis and its Impact on Asthma (ARIA) guidelines. The CC16 alone was significantly negatively correlated with TNSS (P < .05). Further, the CC16 level was significantly lower in persistent moderate-to-severe group than persistent mild group of patients (P < .05).

CONCLUSIONS

The levels of CC16 alone among several NALF biomarkers showed an inverse correlation with symptoms of PAR patients.

Gene Expression Analysis to Investigate Biological Networks Underlying Nasal Inflammatory Dysfunctions Induced by Diesel Exhaust Particles Using an In Vivo System

OBJECTIVES

Diesel exhaust particles (DEP)s are notorious ambient pollutants composed of a complex mixture of a carbon core and diverse chemical irritants. Several studies have demonstrated significant relationships between DEP exposure and serious nasal inflammatory response in vitro, but available information regarding underlying networks in terms of gene expression changes has not sufficiently explained potential mechanisms of DEP-induced nasal damage, especially in vivo.

METHODS

In the present study, we identified DEP-induced gene expression profiles under short-term and long-term exposure, and identified signaling pathways based on microarray data for understanding effects of DEP exposure in the mouse nasal cavity.

RESULTS

Alteration in gene expression due to DEP exposure provokes an imbalance of the immune system via dysregulated inflammatory markers, predicted to disrupt protective responses against harmful exogenous substances in the body. Several candidate markers were identified after validation using qRT-PCR, including S100A9, CAMP, IL20, and S100A8.

CONCLUSIONS

Although further mechanistic studies are required for verifying the utility of the potential biomarkers suggested by the present study, our in vivo results may provide meaningful suggestions for understanding the complex cellular signaling pathways involved in DEP-induced nasal damages.