Comprehensive analysis of acidic pharyngeal reflux before and after proton pump inhibitor treatment in patients with suspected laryngopharyngeal reflux

Increased Sensitivity of Cough Reflex is Not the Mechanism of Cough Attributed to Laryngopharyngeal Reflux

OBJECTIVES

In laryngopharyngeal reflux (LPR) patients acid reaches laryngopharyngeal area and stimulates/sensitizes respiratory nerve terminals mediating cough. We addressed several hypothesis: if stimulation of respiratory nerves is responsible for coughing then acidic LPR should correlate with coughing and proton pump inhibitor (PPI) treatment should reduce both LPR and coughing. If sensitization of respiratory nerves is responsible for coughing then cough sensitivity should correlate with coughing and PPI should reduce both coughing and cough sensitivity.

STUDY DESIGN/METHODS

In this prospective single center study, patients with positive reflux symptom index (RSI > 13) and/or reflux finding score (RFS > 7) and ≥1 LPR episode/24 hours were enrolled. We evaluated LPR by dual channel 24-hour pH/impedance. We determined number of LPR events with pH drop at levels 6.0, 5.5, 5.0, 4.5, and 4.0. Cough reflex sensitivity was determined as lowest capsaicin concentration causing at least 2/5 coughs (C2/C5) by single breath capsaicin inhalation challenge. For statistical analysis C2/C5 values were -log transformed. Troublesome coughing was evaluated on the scale 0-5.

RESULTS

We enrolled 27 LPR patients. The number of LPR events with pH 6.0, 5.5, 5.0, 4.5, and 4.0 was 14[8-23],4[2-6],1[1-3],1[0-2] and 0[0-1], respectively. There was no correlation between number of LPR episodes at any pH level and coughing (Pearson range -0.34 to 0.21, P = NS). There was no correlation between cough reflex sensitivity C2/C5 and coughing (R = -0.29 to 0.34, P = NS). Of patients that completed PPI treatment, 11 had RSI normalized (18.36 ± 2.75 vs. 7 ± 1.35, P < 0.01). There was no change in cough reflex sensitivity in PPI-responders. C2 threshold was 1.41 ± 0.19 vs. 1.2 ± 0.19 (P = 0.11) before and after PPI.

CONCLUSIONS

No correlation between cough sensitivity and coughing and no change in cough sensitivity despite improvement of coughing by PPI argue that an increased cough reflex sensitivity is not mechanism of cough in LPR. We identified no simple relationship between LPR and coughing suggesting that this relationship is more complex.

H+/K+ATPase Expression in the Larynx of Laryngopharyngeal Reflux and Laryngeal Cancer Patients

OBJECTIVES

The gastric H+/K+ ATPase proton pump has previously been shown to be expressed in the human larynx, however its contribution to laryngopharyngeal reflux (LPR) signs, symptoms and associated diseases such as laryngeal cancer is unknown. Proton pump expression in the larynx of patients with LPR and laryngeal cancer was investigated herein. A human hypopharyngeal cell line expressing the proton pump was generated to investigate its effects.

STUDY DESIGN

In-vitro translational.

METHODS

Laryngeal biopsies were obtained from three LPR and eight LSCC patients. ATP4A, ATP4B and HRPT1 were assayed via qPCR. Human hypopharyngeal FaDu cell lines stably expressing proton pump were created using lentiviral transduction and examined via transmission electron microscopy and qPCR for genes associated with inflammation or laryngeal cancer.

RESULTS

Expression of ATP4A and ATP4B was detected in 3/3 LPR, 4/8 LSCC-tumor and 3/8 LSCC-adjacent specimens. Expression of ATP4A and ATP4B in FaDu elicited mitochondrial damage and expression of IL1B, PTGS2, and TNFA (P < .0001); expression of ATP4B alone did not.

CONCLUSIONS

Gastric proton pump subunits are expressed in the larynx of LPR and LSCC patients. Mitochondrial damage and changes in gene expression observed in cells expressing the full proton pump, absent in those expressing a single subunit, suggest that acid secretion by functional proton pumps expressed in upper airway mucosa may elicit local cell and molecular changes associated with inflammation and cancer.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:130-135, 2021.