Pepsin in gastroesophageal and extraesophageal reflux: molecular pathophysiology and diagnostic utility

Pepsin Inhibitors Prevent Inflammation and Loss of Laryngeal Barrier Function in Mice with Gastroesophageal Reflux

OBJECTIVE

This study aimed to evaluate the role of pepsin inhibitors in the inflammatory response and their effects on laryngeal mucosal integrity during gastroesophageal reflux (GERD) under in vivo conditions.

METHODS

A surgical model of GERD was used, in which mice were treated with pepstatin (0.3 mg/kg) or darunavir (8.6 mg/kg) for 3 days. On the third day after the experimental protocol, the laryngeal samples were collected to assess the severity of inflammation (wet weight and myeloperoxidase activity) and mucosal integrity (transepithelial electrical resistance and paracellular epithelial permeability to fluorescein).

RESULTS

The surgical GERD model was reproduced. It showed features of inflammation and loss of barrier function in the laryngeal mucosa. Pepstatin and darunavir administration suppressed laryngeal inflammation and preserved laryngeal mucosal integrity.

CONCLUSION

Pepsin inhibition by the administration of pepstatin and darunavir improved inflammation and protected the laryngeal mucosa in a mouse experimental model of GERD.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:3080-3085, 2024.

Pepsin-mediated inflammation in laryngopharyngeal reflux via the ROS/NLRP3/IL-1β signaling pathway

BACKGROUND

Laryngopharyngeal reflux (LPR) is one of the most common disorders in otorhinolaryngology, affecting up to 10% of outpatients visiting otolaryngology departments. In addition, 50% of hoarseness cases are related to LPR. Pepsin reflux-induced aseptic inflammation is a major trigger of LPR; however, the underlying mechanisms are unclear. The nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3) inflammasome has become an important bridge between stimulation and sterile inflammation and is activated by intracellular reactive oxygen species (ROS) in response to danger signals, leading to an inflammatory cascade. In this study, we aimed to determine whether pepsin causes LPR-associated inflammatory injury via mediating inflammasome activation and explore the potential mechanism.

METHODS

We evaluated NLRP3 inflammasome expression and ROS in the laryngeal mucosa using immunofluorescence and immunohistochemistry. Laryngeal epithelial cells were exposed to pepsin and analyzed using flow cytometry, western blotting, and real-time quantitative PCR to determine ROS, NLRP3, and pro-inflammatorycytokine levels.

RESULTS

Pepsin expression was positively correlated with ROS as well as caspase-1 and IL-1β levels in laryngeal tissues. Intracellular ROS levels were elevated by increased pepsin concentrations, which were attenuated by apocynin (APO)-a ROS inhibitor-in vitro. Furthermore, pepsin significantly induced the mRNA and protein expression of thioredoxin-interacting protein, NLRP3, caspase-1, and IL-1β in a dose-dependent manner. APO and the NLRP3 inhibitor, MCC950, inhibited NLRP3 inflammasome formation and suppressed laryngeal epithelial cell damage.

CONCLUSION

Our findings verified that pepsin could regulate the NLRP3/IL-1β signaling pathway through ROS activation and further induce inflammatory injury in LPR. Targeting the ROS/NLRP3 inflammasome signaling pathway may help treat patients with LPR disease.

The Dubai Definition and Diagnostic Criteria of Laryngopharyngeal Reflux: The IFOS Consensus

OBJECTIVE

The objective of this work was to gather an international consensus group to propose a global definition and diagnostic approach of laryngopharyngeal reflux (LPR) to guide primary care and specialist physicians in the management of LPR.

METHODS

Forty-eight international experts (otolaryngologists, gastroenterologists, surgeons, and physiologists) were included in a modified Delphi process to revise 48 statements about definition, clinical presentation, and diagnostic approaches to LPR. Three voting rounds determined a consensus statement to be acceptable when 80% of experts agreed with a rating of at least 8/10. Votes were anonymous and the analyses of voting rounds were performed by an independent statistician.

RESULTS

After the third round, 79.2% of statements (N = 38/48) were approved. LPR was defined as a disease of the upper aerodigestive tract resulting from the direct and/or indirect effects of gastroduodenal content reflux, inducing morphological and/or neurological changes in the upper aerodigestive tract. LPR is associated with recognized non-specific laryngeal and extra-laryngeal symptoms and signs that can be evaluated with validated patient-reported outcome questionnaires and clinical instruments. The hypopharyngeal-esophageal multichannel intraluminal impedance-pH testing can suggest the diagnosis of LPR when there is >1 acid, weakly acid or nonacid hypopharyngeal reflux event in 24 h.

CONCLUSION

A global consensus definition for LPR is presented to improve detection and diagnosis of the disease for otolaryngologists, pulmonologists, gastroenterologists, surgeons, and primary care practitioners. The approved statements are offered to improve collaborative research by adopting common and validated diagnostic approaches to LPR.

LEVEL OF EVIDENCE

5 Laryngoscope, 134:1614-1624, 2024.

Inhaled fosamprenavir for laryngopharyngeal reflux: Toxicology and fluid dynamics modeling

Objectives

Approximately 25% of Americans suffer from laryngopharyngeal reflux (LPR), a disease for which no effective medical therapy exists. Pepsin is a predominant source of damage during LPR and a key therapeutic target. Fosamprenavir (FOS) inhibits pepsin and prevents damage in an LPR mouse model. Inhaled FOS protects at a lower dose than oral; however, the safety of inhaled FOS is unknown and there are no inhalers for laryngopharyngeal delivery. A pre-Good Lab Practice (GLP) study of inhaled FOS was performed to assess safety and computational fluid dynamics (CFD) modeling used to predict the optimal particle size for a laryngopharyngeal dry powder inhaler (DPI).

Methods

Aerosolized FOS, amprenavir (APR), or air (control) were provided 5 days/week for 4 weeks (n = 6) in an LPR mouse model. Organs (nasal cavity, larynx, esophagus, trachea, lung, liver, heart, and kidney) were assessed by a pathologist and bronchoalveolar lavage cytokines and plasma cardiotoxicity markers were assessed by Luminex assay. CFD simulations were conducted in a model of a healthy 49-year-old female.

Results

No significant increase was observed in histologic lesions, cytokines, or cardiotoxicity markers in FOS or APR groups relative to the control. CFD predicted that laryngopharyngeal deposition was maximized with aerodynamic diameters of 8.1-11.5 μm for inhalation rates of 30-60 L/min.

Conclusions

A 4-week pre-GLP study supports the safety of inhaled FOS. A formal GLP assessment is underway to support a phase I clinical trial of an FOS DPI for LPR.

Level of Evidence

NA.

Personalized Treatments Based on Laryngopharyngeal Reflux Patient Profiles: A Narrative Review

OBJECTIVE

To review the current findings of the literature on the existence of several profiles of laryngopharyngeal reflux (LPR) patients and to propose personalized diagnostic and therapeutic approaches.

METHODS

A state-of-the art review of the literature was conducted using the PubMED, Scopus, and Cochrane Library databases. The information related to epidemiology, demographics, clinical presentations, diagnostic approaches, and therapeutic responses were extracted to identify outcomes that may influence the clinical and therapeutic courses of LPR.

RESULTS

The clinical presentation and therapeutic courses of LPR may be influenced by gender, age, weight, comorbidities, dietary habits and culture, anxiety, stress, and saliva enzyme profile. The clinical expression of reflux, including laryngopharyngeal, respiratory, nasal, and eye symptoms, and the hypopharyngeal-esophageal multichannel intraluminal impedance-pH monitoring profile of patients are important issues to improve in patient management. The use of more personalized therapeutic strategies appears to be associated with better symptom relief and cures over the long-term. The role of pepsin in LPR physiology is well-established but the lack of information about the role of other gastrointestinal enzymes in the development of LPR-related mucosa inflammation limits the development of future enzyme-based personalized diagnostic and therapeutic approaches.

CONCLUSION

Laryngopharyngeal reflux is a challenging ear, nose, and throat condition associated with poor therapeutic responses and a long-term burden in Western countries. Artificial intelligence should be used for developing personalized therapeutic strategies based on patient features.

Multicentre prospective study to evaluate effectiveness and safety of gel-forming and hyaluronic-acid containing chewable tablets as add-on treatment in patients with gastroesophageal reflux disease (GERD) symptoms and unsatisfying proton pump inhibitor therapy

BACKGROUND

Gastroesophageal reflux disease (GERD) is a common disease which in the majority of patients is treated with proton pump inhibitors (PPI). However, up to 45% of the patients remain symptomatic on a standard dose of PPI. This study investigated the effectiveness and safety of an add-on therapy with the gel-forming chewable tablet Sobrade® in patients unsatisfied with PPI treatment. The bioadhesive gel covers the oesophagus and thereby protects the mucosa from reflux events.

METHODS

47 patients with symptomatic GERD despite PPI treatment participated in this study. The gel-forming tablets were taken up to four times daily after meals and prior to bedtime. Severity and frequency of GERD symptoms were evaluated during two onsite visits prior and following 14 days of treatment and used to calculate the GERD score of the Reflux Disease Questionnaire. Furthermore, patients recorded symptoms as well as onset and duration of symptoms relief daily in their electronic dairies. Effectiveness of treatment was analysed using non-parametric paired Wilcoxon test. In addition, anchor-based minimal important differences (MID) were assessed.

RESULTS

Treatment resulted in significant reduction of GERD symptoms. Severity and frequency of 8 of the 9 assessed symptoms improved significantly during the treatment phase whereby most pronounced improvement was observed for heartburn. In agreement, all three subscales of the GERD score improved significantly. MID results suggest that patients considered a mean improvement of symptoms > 30% of initial severity as beneficial. Self-assessments by patients revealed first significant improvements of symptoms like heartburn and regurgitation from day 5 of treatment onwards. 49% of patients reported relief of symptoms within 15 min which lasted on average for 3.5 h. During the study no treatment emergent adverse events were reported and in 98% of all cases tolerability of the product was rated as very good or good.

CONCLUSIONS

This study revealed a pronounced improvement of the symptoms after add-on treatment with the gel-forming medical device. The very good safety and tolerability profile indicate an advantageous risk-benefit ratio.

TRIAL REGISTRATION

This non-interventional study was prospectively positively evaluated by the responsible ethic-committees.

Amprenavir inhibits pepsin-mediated laryngeal epithelial disruption and E-cadherin cleavage in vitro

Background

Laryngopharyngeal reflux (LPR) causes chronic cough, throat clearing, hoarseness, and dysphagia and can promote laryngeal carcinogenesis. More than 20% of the US population suffers from LPR and there is no effective medical therapy. Pepsin is a predominant source of damage during LPR which disrupts laryngeal barrier function potentially via E-cadherin cleavage proteolysis and downstream matrix metalloproteinase (MMP) dysregulation. Fosamprenavir (FDA-approved HIV therapeutic and prodrug of amprenavir) is a pepsin-inhibiting LPR therapeutic candidate shown to rescue damage in an LPR mouse model. This study aimed to examine amprenavir protection against laryngeal monolayer disruption and related E-cadherin proteolysis and MMP dysregulation in vitro.

Methods

Laryngeal (TVC HPV) cells were exposed to buffered saline, pH 7.4 or pH 4 ± 1 mg/mL pepsin ± amprenavir (10-60 min). Analysis was performed by microscopy, Western blot, and real time polymerase chain reaction (qPCR).

Results

Amprenavir (1 μM) rescued pepsin acid-mediated cell dissociation (p < .05). Pepsin acid caused E-cadherin cleavage indicative of regulated intramembrane proteolysis (RIP) and increased MMP-1,3,7,9,14 24-h postexposure (p < .05). Acid alone did not cause cell dissociation or E-cadherin cleavage. Amprenavir (10 μM) protected against E-cadherin cleavage and MMP-1,9,14 induction (p < .05).

Conclusions

Amprenavir, at serum concentrations achievable provided the manufacturer's recommended dose of fosamprenavir for HIV, protects against pepsin-mediated cell dissociation, E-cadherin cleavage, and MMP dysregulation thought to contribute to barrier dysfunction and related symptoms during LPR. Fosamprenavir to amprenavir conversion by laryngeal epithelia, serum and saliva, and relative drug efficacies in an LPR mouse model are under investigation to inform development of inhaled formulations for LPR.

The Protease Inhibitor Amprenavir Protects against Pepsin-Induced Esophageal Epithelial Barrier Disruption and Cancer-Associated Changes

Gastroesophageal reflux disease (GERD) significantly impacts patient quality of life and is a major risk factor for the development of Barrett’s esophagus (BE) and esophageal adenocarcinoma (EAC). Proton pump inhibitors (PPIs) are the standard-of-care for GERD and are among the most prescribed drugs in the world, but do not protect against nonacid components of reflux such as pepsin, or prevent reflux-associated carcinogenesis. We recently identified an HIV protease inhibitor amprenavir that inhibits pepsin and demonstrated the antireflux therapeutic potential of its prodrug fosamprenavir in a mouse model of laryngopharyngeal reflux. In this study, we assessed the capacity of amprenavir to protect against esophageal epithelial barrier disruption in vitro and related molecular events, E-cadherin cleavage, and matrix metalloproteinase induction, which are associated with GERD severity and esophageal cancer. Herein, weakly acidified pepsin (though not acid alone) caused cell dissociation accompanied by regulated intramembrane proteolysis of E-cadherin. Soluble E-cadherin responsive matrix metalloproteinases (MMPs) were transcriptionally upregulated 24 h post-treatment. Amprenavir, at serum concentrations achievable given the manufacturer-recommended dose of fosamprenavir, protected against pepsin-induced cell dissociation, E-cadherin cleavage, and MMP induction. These results support a potential therapeutic role for amprenavir in GERD recalcitrant to PPI therapy and for preventing GERD-associated neoplastic changes.

Oral and Inhaled Fosamprenavir Reverses Pepsin-Induced Damage in a Laryngopharyngeal Reflux Mouse Model

OBJECTIVE

More than 20% of the US population suffers from laryngopharyngeal reflux. Although dietary/lifestyle modifications and alginates provide benefit to some, there is no gold standard medical therapy. Increasing evidence suggests that pepsin is partly, if not wholly, responsible for damage and inflammation caused by laryngopharyngeal reflux. A treatment specifically targeting pepsin would be amenable to local, inhaled delivery, and could prove effective for endoscopic signs and symptoms associated with nonacid reflux. The aim herein was to identify small molecule inhibitors of pepsin and test their efficacy to prevent pepsin-mediated laryngeal damage in vivo.

METHODS

Drug and pepsin binding and inhibition were screened by high-throughput assays and crystallography. A mouse model of laryngopharyngeal reflux (mechanical laryngeal injury once weekly for 2 weeks and pH 7 solvent/pepsin instillation 3 days/week for 4 weeks) was provided inhibitor by gavage or aerosol (fosamprenavir or darunavir; 5 days/week for 4 weeks; n = 3). Larynges were collected for histopathologic analysis.

RESULTS

HIV protease inhibitors amprenavir, ritonavir, saquinavir, and darunavir bound and inhibited pepsin with IC50 in the low micromolar range. Gavage and aerosol fosamprenavir prevented pepsin-mediated laryngeal damage (i.e., reactive epithelia, increased intraepithelial inflammatory cells, and cell apoptosis). Darunavir gavage elicited mild reactivity and no discernable protection; aerosol protected against apoptosis.

CONCLUSIONS

Fosamprenavir and darunavir, FDA-approved therapies for HIV/AIDS, bind and inhibit pepsin, abrogating pepsin-mediated laryngeal damage in a laryngopharyngeal reflux mouse model. These drugs target a foreign virus, making them ideal to repurpose. Reformulation for local inhaled delivery could further improve outcomes and limit side effects.

LEVEL OF EVIDENCE

NA. Laryngoscope, 133:S1-S11, 2023.

Changes of Pepsin Concentration in Saliva Sample According to Storage Period

OBJECTIVES

To determine whether the concentration of pepsin in the saliva sample changes according to the storage period of the sample.

METHODS

Forty eight patients with suspected laryngopharyngeal reflux were included in this study. Saliva samples were collected from each patient and each sample divided into six and stored for different period of time. Pepsin concentration was measured using enzyme-linked immunosorbent assay. A comparison was made between the pepsin concentration measured immediately and the concentration measured after storage for 1 week, 2 weeks, 1 month, 3 months, and 6 months.

RESULTS

No significant difference in pepsin concentrations were detected between the sample analyzed immediately and those analyzed at 1 week, 2 weeks, 1 month, and 3 months after saliva collection. A significant difference in pepsin concentration was observed in the sample analyzed immediately and the sample analyzed 6 months after saliva collection.

CONCLUSIONS

Pepsin concentration in saliva samples did not demonstrate a significant difference between the concentration measured immediately and the concentration measured 3 months after saliva collection, although a significant difference was observed in the concentration measured 6 months after collection.

Correlation of Esophageal Mean Nocturnal Baseline Impedance With Markers of Laryngopharyngeal Reflux

OBJECTIVES

Mean nocturnal baseline impedance (MNBI) is a measure of the esophageal epithelial barrier function calculated via high-resolution impedance manometry and can be used as a diagnostic tool and treatment response predictor for gastroesophageal reflux disease (GERD). However, its utility for laryngopharyngeal reflux (LPR) has been minimally studied. We aimed to investigate the relationship of MNBI between patients with suspected LPR, healthy controls, and their 24-h multichannel intraluminal impedance-pH (MII-pH) study results.

METHODS

Retrospective patient series analysis was performed of patients with suspected LPR and healthy controls who underwent 24-h MII-pH monitoring. MNBI values were calculated from impedance channels at the level of the hypopharynx, proximal esophagus, and distal esophagus. We compared these MNBI values between the subject groups with secondary analysis on MII-pH results, reflux symptom index, reflux findings score, DeMeester score, and salivary pepsin levels.

RESULTS

Twenty-three patients with suspected LPR and 14 healthy controls were enrolled. Decreased distal esophageal MNBI was found to be significantly decreased in patients with suspected LPR compared with healthy controls (p < 0.01) and in subjects with positive MII-pH studies compared to negative MII-pH studies (p < 0.01). There were no significant correlations of MNBI at the hypopharynx or proximal esophagus.

CONCLUSION

Distal esophageal MNBI has significant correlations with many phenotypic and biological markers of LPR. These findings indicate that MNBI has the potential to be applied to LPR, similar to its emerging use as a diagnostic tool and treatment response predictor for GERD.

LEVEL OF EVIDENCE

3 Laryngoscope, 2022.

Association of Pepsin With Inflammatory Signaling and Effusion Viscosity in Pediatric Otitis Media

OBJECTIVE

Otitis media (OM) is a common inflammatory disease spectrum. Cytokine signaling, neutrophil activity, and mucin hypersecretion during recurrent and chronic OM contribute to persistent, viscous middle ear (ME) effusions, hearing loss, and potential for developmental delay. Extraesophageal reflux (EER), specifically pepsin, triggers inflammatory signaling in respiratory mucosa and is associated with OM. The objective of this study was to investigate the association of pepsin with ME inflammatory signaling and the outcomes and examine causality in vitro.

STUDY DESIGN

Cross-sectional study.

METHODS

ME fluid (MEF) and preoperative audiometric data were collected from 30 pediatric subjects undergoing tympanostomy tube placement for recurrent OM or OM with effusion. MEF viscosity was characterized by the surgeon. Pepsin, inflammatory molecules, and mucin were assayed by enzyme-linked immunosorbent assay (ELISA). ME epithelial primary culture was exposed to 0.1 to 1 mg/ml pepsin at pH 5, 6, and 7 for 30 minutes, and cytokine expression was assayed via qPCR.

RESULTS

Pepsin was observed in the MEF of 77% of patients (range 71-2,734 ng/ml). Pepsin correlated with effusion viscosity, interleukins -6 and -8, neutrophil elastase, and mucin 5B (P < .05). Pepsin-negative MEF was more frequently absent of interleukin 8 or mucin 5B (P < .05). Weak acid was generally insufficient to elicit cytokine expression in ME cells in vitro, however, pepsin induced IL6, IL8, and TNF at pH 7 (P < .05) and weak acid (pH 6) facilitated a response at lower pepsin concentration.

CONCLUSIONS

Pepsin may contribute to inflammatory signaling, persistent viscous effusion, and poorer OM outcomes.

LEVEL OF EVIDENCE

4 Laryngoscope, 2021.

Atypical Clinical Presentation of Laryngopharyngeal Reflux: A 5-Year Case Series

Background: Laryngopharyngeal reflux (LPR) is a common disease in otolaryngology characterized by an inflammatory reaction of the mucosa of the upper aerodigestive tract caused by digestive refluxate enzymes. LPR has been identified as the etiological or favoring factor of laryngeal, oral, sinonasal, or otological diseases. In this case series, we reported the atypical clinical presentation of LPR in patients presenting in our clinic with reflux. Methods: A retrospective medical chart review of 351 patients with LPR treated in the European Reflux Clinic in Brussels, Poitiers and Paris was performed. In order to be included, patients had to report an atypical clinical presentation of LPR, consisting of symptoms or findings that are not described in the reflux symptom score and reflux sign assessment. The LPR diagnosis was confirmed with a 24 h hypopharyngeal-esophageal impedance pH study, and patients were treated with a combination of diet, proton pump inhibitors, and alginates. The atypical symptoms or findings had to be resolved from pre- to posttreatment. Results: From 2017 to 2021, 21 patients with atypical LPR were treated in our center. The clinical presentation consisted of recurrent aphthosis or burning mouth (N = 9), recurrent burps and abdominal disorders (N = 2), posterior nasal obstruction (N = 2), recurrent acute suppurative otitis media (N = 2), severe vocal fold dysplasia (N = 2), and recurrent acute rhinopharyngitis (N = 1), tearing (N = 1), aspirations (N = 1), or tracheobronchitis (N = 1). Abnormal upper aerodigestive tract reflux events were identified in all of these patients. Atypical clinical findings resolved and did not recur after an adequate antireflux treatment. Conclusion: LPR may present with various clinical presentations, including mouth, eye, tracheobronchial, nasal, or laryngeal findings, which may all regress with adequate treatment. Future studies are needed to better specify the relationship between LPR and these atypical findings through analyses identifying gastroduodenal enzymes in the inflamed tissue.

Prevalence and Features of Laryngopharyngeal Reflux in Patients with Primary Burning Mouth Syndrome

OBJECTIVES/HYPOTHESIS

To investigate the prevalence and features of laryngopharyngeal reflux (LPR) in patients with primary burning mouth syndrome (BMS).

STUDY DESIGN

Prospective uncontrolled study.

METHODS

Patients who visited our Departments of Otolaryngology-Head and Neck and Maxillofacial surgery with BMS were prospectively recruited from September 2018 to September 2020. Patients benefited from dental, maxillofacial, otolaryngological examinations, and hypopharyngeal-esophageal impedance pH-monitoring (HEMII-pH). Oral, pharyngeal, and laryngeal findings and symptoms were rated with Reflux Sign Assessment (RSA) and Reflux Symptom Score-12 (RSS-12). Patients were treated with a combination of diet, pantoprazole, and alginate.

RESULTS

From the 81 included patients, 76 reported >1 pharyngeal reflux events (93.8%), accounting for 35 (46.1%), 24 (31.6%), and 17 (22.3%) acid, mixed, and nonacid LPR, respectively. Thirty-two patients had both LPR and gastroesophageal reflux disease (GERD). Thirty-eight patients benefited from pepsin saliva measurement, which was positive in 86.8% of cases. The mean scores of mouth/tongue burning, RSS-12, and RSA significantly improved from pre- to post-treatment (P < .004). At 3-month post-treatment, 62.5% of patients reported an improvement of mouth/tongue burning score. Patients with both GERD and LPR reported higher baseline RSS-12 and RSA scores.

CONCLUSION

Acid, weakly acid, and nonacid LPR may be involved in the development of BMS. The use of an appropriate treatment considering the reflux features is associated with an improvement of symptoms and findings.

LEVEL OF EVIDENCE

4 Laryngoscope, 2021.