The Potential Role of Aspiration in the Asthmatic Airway

Unmet needs and future directions of treatment options for chronic cough

INTRODUCTION

Chronic cough is a persistent condition that significantly affects patients' quality of life and poses diagnostic and therapeutic challenges. Traditional anatomical diagnostic approaches often fail to address the underlying mechanisms, leading to suboptimal treatment outcomes.

AREA COVERED

This review aims to summarize the challenges of the management of chronic cough and highlights recent advances of several promising drug candidates in cough trials. PUBMED/CINAHL/Web of Science/Scopus were searched (February 2025).

EXPERT OPINION

Over the past 40 years, chronic cough has evolved from a mere symptom to a recognized disease. A key observation is that hypersensitivity of the afferent vagus and its central projections cause the state of cough hypersensitivity leading to the urge to cough being precipitated by otherwise innocuous stimuli. Clinical trial designs have also advanced, incorporating placebo run-in periods to reduce placebo effects and refining patient-reported outcomes to modern standards. Additionally, the realization that the variability in chronic cough, both diurnal and day-to-day, has highlighted the need for continuous cough monitoring, which has only recently been available consequence to the revolution in electronic applications. However, progress is hindered by a widespread lack of awareness among healthcare professionals and patients, underscoring the urgent need for education on this condition.

Chinese expert consensus on diagnosis and management of gastroesophageal reflux disease in the elderly (2023)

Gastroesophageal reflux disease (GERD) in the elderly is characterized by atypical symptoms, relatively severe esophageal injury, and more complications, and when GERD is treated, it is also necessary to fully consider the general health condition of the elderly patients. This consensus summarized the epidemiology, pathogenesis, clinical manifestations, and diagnosis and treatment characteristics of GERD in the elderly, and provided relevant recommendations, providing guidance for medical personnel to correctly understand and standardize the diagnosis and treatment of GERD in the elderly.

The Controversy of Pepsinogen A/Pepsin A in Detecting Extra-Gastroesophageal Reflux

BACKGROUND

Pepsinogen A (PGA)/pepsin A is often used as a diagnostic marker of extra-gastroesophageal reflux. We aimed to explore whether its positivity in upper aerodigestive tract (UADT) was specific enough to diagnose reflux.

METHODS

PGA/pepsin A protein levels were examined in 10 types of tissues and 10 types of body fluid by immunological staining, western blot or Elisa, using three different commercially available brands simultaneously. Liquid chromatography-tandem mass spectrometry parallel reaction monitoring (LC-MS/MS PRM) served as a gold reference for the detection of PGA/pepsin A proteins. PGA gene expression was analyzed by reverse transcriptase sequencing methods for tissue samples. Specifically, 24 hour pH monitoring technique was conducted for patients who donated saliva samples.

RESULTS

Eight out of ten types of human tissue samples (stomach, esophagus, lung, kidney, colon, parotid gland, nasal turbinate and nasal polyps) were confirmed positive for PGA/pepsin A gene and protein by genetic and PRM technique, respectively. Two out of ten types of body fluid samples (gastric fluid, urine) were confirmed positive for PGA/pepsin A protein by PRM technique. The consistence rates of PGA/pepsin A positivity among three commercial antibody brands and Elisa kit were poor, and Elisa results of salivary did not match with 24-hour pH monitoring.

CONCLUSIONS

Multiple tissues and body fluid could be detected baseline expression levels of PGA/pepsin A gene and protein. However, those commercially available PGA/pepsin A antibodies achieved poor sensitivity and specificity, therefore, relying on the detection of PGA/pepsin A in UADT by single antibodies to diagnose extra-gastroesophageal reflux without a specific positive cut-off value is unreliable.

Pepsin and the Lung—Exploring the Relationship between Micro-Aspiration and Respiratory Manifestations of Gastroesophageal Reflux Disease

Gastroesophageal reflux disease (GERD) is one of the most commonly encountered disorders in clinical practice nowadays, with an increasing burden on healthcare systems worldwide. GERD-related respiratory symptoms such as unexplained chronic cough, bronchial asthma or chronic obstructive pulmonary disease (COPD) with frequent exacerbations often pose diagnostic and therapeutic challenges and may require a multidisciplinary approach. Moreover, a potential role of GERD as a risk factor has been proposed for chronic rejection in patients who underwent lung transplantation. Pepsin has gained considerable attention from the scientific community in the last few years as a possible surrogate biomarker for GERD. The aim of this narrative review was to provide an overview of the potential utility of pepsin detection as a marker of micro-aspiration in various biological fluids retrieved from patients with suspected GERD-induced respiratory manifestations and in lung transplant patients with allograft dysfunction. Data on the subject remains highly contradictory, and while certain studies support its applicability in investigating atypical GERD manifestations, at the moment, it would be realistic to accept a modest utility at best. A major lack of consensus persists regarding topics such as the optimal timeframe for fluid collection and cut-off values. Further research is warranted in order to address these issues.

Vulnerability to acid reflux of the airway epithelium in severe asthma

BACKGROUND

Severe asthma is associated with multiple co-morbidities, including gastro-oesophageal reflux disease (GORD) which can contribute to exacerbation frequency and poor quality of life. Since epithelial dysfunction is an important feature in asthma, we hypothesised that in severe asthma the bronchial epithelium is more susceptible to the effects of acid reflux.

METHODS

We developed an in vitro model of GORD using differentiated bronchial epithelial cells (BECs) from normal or severe asthmatic donors exposed to a combination of pepsin, acid pH, and bile acids using a multiple challenge protocol (MCP-PAB). We also analysed bronchial biopsies and undertook RNA-sequencing of bronchial brushings from controls and severe asthmatics without or with GORD.

RESULTS

Exposure of BECs to the MCP-PAB caused structural disruption, increased permeability, IL-33 expression, inflammatory mediator release and changes in gene expression for multiple biological processes. Cultures from severe asthmatics were significantly more affected than those from healthy donors. Analysis of bronchial biopsies confirmed increased IL-33 expression in severe asthmatics with GORD. RNA-sequencing of bronchial brushings from this group identified 15 of the top 37 dysregulated genes found in MCP-PAB treated BECs, including genes involved in oxidative stress responses.

CONCLUSIONS

By affecting epithelial permeability, GORD may increase exposure of the airway submucosa to allergens and pathogens, resulting in increased risk of inflammation and exacerbations.

CLINICAL IMPLICATION

These results suggest the need for research into alternative therapeutic management of GORD in severe asthma.

Positive bronchoalveolar lavage pepsin assay associated with viral and fungal respiratory infections in children with chronic cough

OBJECTIVE

To assess the association between commonly obtained endoscopic and serologic data and bronchoalveolar lavage pepsin assay (BAL) results in children with chronic cough.

STUDY DESIGN

We performed a retrospective chart review of 72 children with a BAL pepsin obtained through our Aerodigestive Center over an 18-month period. BAL outcomes include evidence of viral, bacterial, or fungal infection, presence of lipid-laden macrophages, and cytology (eosinophils, neutrophils, and lymphocytes). Gastrointestinal outcomes include esophagogastroduodenoscopy (EGD) and pH impedance probe findings. Other characteristics include serum eosinophils, neutrophils, and lymphocytes; spirometry; FeNO; and IgE.

RESULTS

Seventy-two patients underwent BAL pepsin testing. Median age was 4.9 years, 30.6% had severe persistent asthma, and 59.2% were on reflux medication. There was an association between positive BAL pepsin assay and positive viral panel (p = .002) or fungal culture (p = .027). No significant association found between positive BAL bacterial culture; BAL cytology; the presence of BAL lipid-laden macrophages; IgE; spirometry; FeNO; CBC neutrophil, eosinophil, or lymphocytes; pH impedance testing parameters; or EGD pathology.

CONCLUSIONS

BAL pepsin is associated with a positive BAL viral PCR or fungal culture. Lack of correlation between pepsin-positivity and pH-impedance parameters or EGD pathology suggests microaspiration may be due to an acute event (such as a respiratory infection) rather than chronic gastroesophageal reflux disease. This may be especially true in the presence of a positive viral panel or fungal culture when a BAL pepsin is obtained.

[Treatment of GERD in asthma]

Gastro-oesophageal reflux disease (GORD) is one of the most frequent conditions associated with asthma. GORD has an impact on asthma control and quality of life of asthmatic patients. Its treatment relies on lifestyle modifications, anti-acidic treatment with proton pump inhibitors (PPI) and/or surgical management by fundoplication in some situations. The impact of lifestyle modifications has not been analysed on asthma outcomes alone. Several randomised controlled trials assessed the efficacy of PPI on asthma control, peak expiratory flow and/or quality of life. The impact of fundoplication in asthma has mainly been analysed in retrospective or prospective observational studies. This review highlights the limited impact of GORD treatment on asthma control. Current guidelines are to restrict GORD treatment in asthma to asthmatic patients with actual symptomatic GORD. Given the lack of controlled studies, the place of surgical management of GORD in asthma is currently not defined.

Pepsin exposure in a non-acidic environment upregulates mucin 5AC (MUC5AC) expression via matrix metalloproteinase 9 (MMP9)/nuclear factor κB (NF-κB) in human airway epithelial cells

BACKGROUND

Gastric reflux (GR) is a backflow of gastric content to the aerodigestive tract. GR was previously found to be associated with inflammatory airway diseases and a potential cause of airway remodeling. Chronic exposure to gastric content may induce damage from nose to lung, because digestive enzymes and acidity are toxic to airway epithelial cells. Recently, the toxicity of pepsin in a non-acidic environment was found to increase proinflammatory cytokines and receptors in the epithelium of the aerodigestive tract. However, the effect of pepsin in non-acidic conditions on mucin expression has not been investigated in human airway epithelial cells. The purpose of this study was to evaluate the effect of pepsin on mucin 5AC (MUC5AC) expression in upper and lower airway epithelial cells as an important potential factor of non-acidic GR-related airway inflammation.

METHODS

In NCI-H292 cells and human nasal epithelial cells (HNEpCs), the effects and signaling pathways of pepsin on MUC5AC expression were examined using reverse-transcription polymerase chain reaction (RT-PCR), real-time PCR, enzyme immunoassay, zymography, Western blot, and immunofluorescence staining.

RESULTS

Pepsin increased MUC5AC expression in non-acidic condition of NCI-H292 cells and HNEpCs. Further, pepsin activated matrix metalloproteinase 9 (MMP9) and phosphorylated nuclear factor κB (NF-κB). Moreover, inhibitors of MMP9 and NF-κB significantly attenuated pepsin-induced MUC5AC expression, and the knockdown of NF-κB by small interfering RNA (siRNA) significantly blocked pepsin-induced MUC5AC expression in human airway epithelial cells.

CONCLUSION

These findings suggest that pepsin increased MUC5AC expression in non-acidic conditions via the activation of MMP9 and NF-κB in human airway epithelial cells.

Reflux-Aspiration in Chronic Lung Disease

Microaspiration, or silent aspiration, is commonly suspected in patients with refractory respiratory symptoms, including unexplained chronic cough, asthma, chronic obstructive pulmonary disease, bronchiolitis, bronchiectasis, and idiopathic pulmonary fibrosis. This suspicion is driven by the high prevalence of gastroesophageal reflux in these otherwise disparate disorders. Frequently, patients receive aggressive treatment for gastroesophageal reflux disease as a means of treating their underlying respiratory conditions, even in the absence of overt symptoms of reflux. However, clinical trials have not demonstrated a clear impact on outcomes with this strategy, and in some instances there may be potential for harm. Mechanistic studies have increasingly used gastric biomarkers obtained directly from the airways to confirm the association between reflux and respiratory disease, but results are limited by methodologic flaws and correlation. The best evidence of aspiration directly causing respiratory disorders is the histopathologic detection of foreign bodies. For most of the other chronic respiratory disorders, microaspiration may be uncommon or a secondary aggravating factor, as in patients with acute exacerbations of chronic obstructive pulmonary disease or idiopathic pulmonary fibrosis. In some cases, microaspiration is probably not a significant factor at all, such as in unexplained chronic cough. It is important to distinguish between conditions in which aspiration is primarily or directly causal and conditions in which aspiration may be indirectly aggravating, to help identify whether interventions targeting reflux and aspiration precautions should be recommended to patients. Our clinical review examines some of the evidence supporting reflux-aspiration as a mechanism for several chronic respiratory disorders and offers some management considerations when reflux-aspiration is suspected.

Current therapies for gastro-oesophageal reflux in the setting of chronic lung disease: state of the art review

The inter-relationship between chronic respiratory disease and reflux disease in the airway reflux paradigm is extremely complex and remains poorly characterised. Reflux disease is reported to cause or contribute to the severity of a number of respiratory tract diseases including laryngeal disorders, sinusitis, chronic cough, asthma, COPD, idiopathic pulmonary fibrosis, cystic fibrosis, bronchiectasis and bronchiolitis obliterans post lung transplant. It is now appreciated that reflux disease is not simply caused by liquid acid reflux but rather by a variety of chemical refluxates originating from the stomach and duodenum due to a number of different mechanisms. Reflux disease can be challenging to diagnose, particularly proving its role in the causation of direct respiratory epithelial damage. Significant advances in oesophageal assessment and gastric biomarkers have emerged in recent years as our understanding increases. There are a number of treatments available for reflux disease, both medical and surgical, but there is a paucity of large randomised trials to evaluate their efficacy in the setting of chronic respiratory disease. Everyday clinical practice, however, informs us that treatment failure in reflux disease is common. This clinical review summarises associations between reflux disease in the setting of chronic respiratory diseases and examines available evidence regarding potential therapeutic strategies.

Gastro-oesophageal reflux disease is prevalent among patients with chronic respiratory disease. A number of medical and surgical treatment options are available for GORD. This review examines available evidence in the setting of chronic lung disease.https://bit.ly/34TcMJS

Care recommendations for the respiratory complications of esophageal atresia-tracheoesophageal fistula

Tracheoesophageal fistula (TEF) with esophageal atresia (EA) is a common congenital anomaly that is associated with significant respiratory morbidity throughout life. The objective of this document is to provide a framework for the diagnosis and management of the respiratory complications that are associated with the condition. As there are no randomized controlled studies on the subject, a group of experts used a modification of the Rand Appropriateness Method to describe the various aspects of the condition in terms of their relative importance, and to rate the available diagnostic methods and therapeutic interventions on the basis of their appropriateness and necessity. Specific recommendations were formulated and reported as Level A, B, and C based on whether they were based on "strong", "moderate" or "weak" agreement. The tracheomalacia that exists in the site of the fistula was considered the main abnormality that predisposes to all other respiratory complications due to airway collapse and impaired clearance of secretions. Aspiration due to impaired airway protection reflexes is the main underlying contributing mechanism. Flexible bronchoscopy is the main diagnostic modality, aided by imaging modalities, especially CT scans of the chest. Noninvasive positive airway pressure support, surgical techniques such as tracheopexy and rarely tracheostomy are required for the management of severe tracheomalacia. Regular long-term follow-up by a multidisciplinary team was considered imperative. Specific templates outlining the elements of the clinical respiratory evaluation according to the patients' age were also developed.

The presence of Aspergillus fumigatus in asthmatic airways is not clearly related to clinical disease severity

BACKGROUND

It is suggested that airway fungi, in particular Aspergillus may impinge on clinical phenotype in asthma. Indeed, the term severe asthma with fungal sensitization (SAFS) has been coined. We aimed to ascertain whether the presence of fungi, in particular Aspergillus fumigatus, in the airway correlated with asthma severity and control. Furthermore, we aimed to determine whether traditional markers of Aspergillus sensitization related to the presence of Aspergillus within the airway.

METHODS

Sixty-nine patients characterized by asthma severity (GINA) and level of control (ACQ-7) underwent bronchoscopy and bronchoalveolar lavage (BAL). Serum was assessed for A fumigatus-specific IgE and total IgE. Galactomannan and relevant cytokine levels were assessed in serum, plasma and BAL. BAL was analyzed for the presence of A fumigatus.

RESULTS

In BAL, fungi were visible by microscopy in 70% and present by qPCR in 86% of patients, while A fumigatus was detectable by qPCR in 46%. Plasma and BAL IL-4, IL-6, IL-10, IL-13 and TNF-α correlated with BAL fungal presence, while plasma IL-17 correlated with BAL fungal presence. Aspergillus positive BAL correlated with increased plasma and BAL IL-6 and BAL IL-13. There was no relationship between fungal airway presence and steroid dose, asthma severity or control. The presence of Aspergillus within the airway did not relate to serum IgE positivity for Aspergillus.

CONCLUSIONS

Fungi were present in a large proportion of our asthmatic patients' airways, but their presence was not predicted by traditional markers of sensitization, nor did it appear to be related to measures of disease severity or control.

Baicalein attenuates OVA-induced allergic airway inflammation through the inhibition of the NF-κB signaling pathway

Asthma is a type of chronic lung inflammation with restrictions in effective therapy. NF-κB pathway activation has been suggested to play an important role in the pathogenesis of asthma. Baicalein, one of the major active flavonoids found in Scutellaria baicalensis, exhibits potent anti-inflammatory properties by inhibiting NF-κB activity. Herein, we report that Baicalein significantly reduces OVA-induced airway hyperresponsiveness (AHR), airway inflammation, serum IgE levels, mucus production, and collagen deposition around the airway. Additionally, western blot analysis and immunofluorescence assay showed that Baicalein attenuates the activation of NF-κB, which was mainly reflected by IκBα phosphorylation and degradation, p65 nuclear translocation and downstream iNOS expression. Furthermore, in human epithelial cells, Baicalein blocked TNF-α-induced NF-κB activation. Our study provides evidence that Baicalein administration alleviates the pathological changes in asthma through inactivating the NF-κB/iNOS pathway. Baicalein might be a promising potential therapy agent for patients with allergic asthma in the future.

Detection of pepsin and IL-8 in saliva of adult asthmatic patients

Objective: Asthma and gastric reflux disease are widespread and often coexisting diseases with complex interactions, leading some to suspect that asthma symptoms of patients with reflux may improve with anti-reflux therapy. The objective of this study was to determine whether pepsin in saliva, indicative of airway reflux, could be detected in patients with asthma of varying severity and test the requirement of citric acid as a pepsin preservative. Methods: Saliva samples were collected in the clinic (with/without citric acid) and upon waking the following morning from 25 asthmatic patients. Enzyme-linked immunosorbent assay was performed for pepsin and interleukin-8 (IL-8), an inflammatory cytokine induced by pepsin in other airway epithelia. Pepsin induction of IL-8 was tested in a lung epithelial cell culture model. Results: Pepsin was detected in saliva from 14/25 patients (56%; mean concentration of pepsin in specimens where observed ±SD =80.3±87.5 ng/mL); significant agreement was found between samples collected in the presence/absence of citric acid. No significant associations were found with pepsin and clinical measures of asthma severity. IL-8 was detected in saliva from 22/25 patients (88%; mean IL-8 in all specimens where observed =3.27±3.91 ng/mL). IL-8 was significantly upregulated in human lung epithelial cells exposed to pepsin at pH7 in vitro (P=0.041). Conclusion: In summary, more than half of the asthma patients in this study were found to have pepsin in their saliva, indicative of airway reflux. These data support the use of salivary pepsin as a noninvasive tool for future investigation of airway reflux in a larger cohort. The data further suggest that collection in citric acid as a sample preservative is not warranted and that pooling of multiple saliva samples collected at various timepoints may improve sensitivity of pepsin detection and reduce costs incurred by multiple sample analysis in future studies.

Reflux aspiration in lungs of dogs with respiratory disease and in healthy West Highland White Terriers

BACKGROUND

Gastroesophageal reflux and microaspiration (MA) of gastric juice are associated with various human respiratory diseases but not in dogs.

OBJECTIVE

To detect the presence of bile acids in bronchoalveolar lavage fluid (BALF) of dogs with various respiratory diseases.

ANIMALS

Twenty-seven West Highland White Terriers (WHWTs) with canine idiopathic pulmonary fibrosis (CIPF), 11 dogs with bacterial pneumonia (BP), 13 with chronic bronchitis (CB), 9 with eosinophilic bronchopneumopathy (EBP), 19 with laryngeal dysfunction (LD), 8 Irish Wolfhounds (IWHs) with previous BPs, 13 healthy WHWTs, all privately owned dogs, and 6 healthy research colony Beagles METHODS: Prospective cross-sectional observational study with convenience sampling of dogs. Bile acids were measured by mass spectrometry in BALF samples. Total bile acid (TBA) concentration was calculated as a sum of 17 different bile acids.

RESULTS

Concentrations of TBA were above the limit of quantification in 78% of CIPF, 45% of BP, 62% of CB, 44% of EBP, 68% of LD, and 13% of IWH dogs. In healthy dogs, bile acids were detected less commonly in Beagles (0/6) than in healthy WHWTs (10/13). Concentrations of TBA were significantly higher in CIPF (median 0.013 μM, range not quantifiable [n.q.]-0.14 μM, P < .001), healthy WHWTs (0.0052 μM, n.q.-1.2 μM, P = .003), LD (0.010 μM, n.q.-2.3 μM, P = .015), and CB (0.0078 μM, n.q.-0.073 μM, P = .018) groups compared to Beagles (0 μM, n.q.).

CONCLUSION AND CLINICAL IMPORTANCE

These results suggest that MA occurs in various respiratory diseases of dogs and also in healthy WHWTs.

Barium upper GI series in adults: a surgeon's perspective

Barium upper GI series performed by an interested and competent radiologist is still a very useful study to evaluate a variety of esophagogastric disorders. It usually provides information complementary to upper endoscopy and other foregut studies. Barium upper GI series is an important part of the diagnostic workup for gastroesophageal reflux disease, hiatal hernia, and esophageal motility disorders including achalasia. It is also an important part of the follow-up after operation for these common problems and after other operations such as resection or bariatric surgery. The GI radiologist should be an important member of the foregut surgery team.