Alginates for Protection Against Pepsin‐Acid Induced Aerodigestive Epithelial Barrier Disruption

Abstract

Objective Gastroesophageal reflux disease (GERD) and laryngopharyngeal reflux (LPR) are chronic conditions caused by backflow of gastric and duodenal contents into the esophagus and proximal aerodigestive tract, respectively. Mucosal barrier dysfunction resultant from the synergistic actions of chemical injury and the mucosal inflammatory response during reflux contributes to symptom perception. Alginates effectively treat symptoms of mild to moderate GERD and have recently shown benefit for LPR. In addition to forming a “raft” over gastric contents to reduce acidic reflux episodes, alginates have been found to bind the esophageal mucosa thereby preserving functional barrier integrity measured by transepithelial electrical resistance. The aim of this study was to further examine the topical protective capacity of alginate‐based Gaviscon Advance (GA) and Double Action (GDA) against pepsin‐acid mediated aerodigestive epithelial barrier dysfunction in vitro. Study Design Translational. Methods Immortalized human esophageal and vocal cord epithelial cells cultured in transwells were pretreated with liquid formula GA, GDA, matched viscous placebo solution, or saline (control), then treated for 1 h with saline, acid (pH 3–6) or pepsin (0.1–1 mg/ml) at pH 3–6. Endpoint measure was taken of horseradish peroxidase (HRP) allowed to diffuse across monolayers for 2 h. Results Pepsin (0.1‐1 mg/ml) at pH 3‐6 increased HRP flux through cultures pretreated with saline or placebo (p < 0.05); acid alone did not. GA and GDA prevented barrier dysfunction. Conclusions GA and GDA preserved epithelial barrier function during pepsin‐acid insult better than placebo suggesting that protection was due to alginate. These data support topical protection as a therapeutic approach to GERD and LPR. Laryngoscope, 132:2327–2334, 2022

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

“…Importantly, the pepsin inhibitor, amprenavir, attenuated or rescued these effects and provided concentrations found in the serum of patients taking the manufacturer-recommended dose of fosamprenavir for HIV [ 90 ]. These data are in alignment with prior work demonstrating that the pepsin inhibitor, pepstatin, prevents esophageal lesions in a surgical rat model of GERD [ 77 ] and that the pepsin inhibitor, sodium alginate, prevents esophageal and laryngeal epithelial barrier disruption by pepsin pH4 [ 39 ]. Pepsin-acid-induced E-cadherin RIP and protection by amprenavir appear to be conserved across cell types.…”

“…Jovov et al demonstrated that the deletion of E-cadherin in the adult mouse esophagus was sufficient to cause barrier dysfunction, as indicated by macromolecular flux [ 45 ]. In agreement with these findings, we recently demonstrated that E-cadherin was cleaved by weakly acidic pepsin (though not acid pH4 alone) in human esophageal and laryngeal cells in vitro and that E-cadherin cleavage was rescued by pepsin inhibitors (sodium alginate in esophageal cells and amprenavir in laryngeal cells) [ 38 , 81 ]. The E-cadherin cleavage fragments produced by human esophageal and laryngeal epithelial cells in response to pepsin were consistent with those observed in GERD and LPR biopsies and indicative of RIP.…”

“…Pepsin-acid-induced E-cadherin RIP and protection by amprenavir appear to be conserved across cell types. In a recently submitted work, we found that amprenavir abrogates epithelial cell disruption, E-cadherin cleavage, and MMP dysregulation by pepsin pH4 in laryngeal cells, supporting the potential utility of amprenavir for both GERD and LPR [ 38 ]. Given that amprenavir protects epithelial barrier integrity, which is, in turn, a facet of GERD symptom origination, the data herein suggest that amprenavir may provide relief for the 20–40% of GERD patients with symptoms recalcitrant to PPI therapy [ 91 , 92 , 93 ].…”

“…Goldberg et al demonstrated that acid pH > 1.3 alone caused minimal esophagitis in an in vivo cat model and that pepsin dramatically exacerbated esophagitis and histological epithelial damage at pH 1.6–2.0 in a dose-dependent manner [ 50 ]. Similarly, we recently demonstrated that weakly acidified pepsin, though not acid (pH4) alone, caused barrier dysfunction and cell detachment in a human esophageal cell culture model and that a pepsin inhibitor, sodium alginate, could prevent such damage [ 39 ].…”

“…Amprenavir inhibited pepsin at low micromolar concentrations and its prodrug fosamprenavir prevented histologic changes in an LPR mouse model [ 37 ]. In parallel work, we found that pepsin was required for esophageal and laryngeal epithelial barrier disruption at pH4 and that amprenavir preserved laryngeal epithelial integrity and prevented damage to a critical cell adhesion molecule elicited by pepsin at pH4 [ 38 , 39 ]. Barrier disruption is a key mechanism of GERD pathogenesis, contributing to symptom origination, sensitivity to reflux insult, immune cell infiltration, and prolonged recovery [ 40 , 41 , 42 , 43 , 44 ].…”