In vitro investigation of potential pepsin inhibitors: new perspectives for the treatment of gastroesophageal reflux

Background: In patients with Gastroesophageal Reflux Desease (GERD), the digestive enzyme pepsin can reach the esophagus and extraesophageal sites and cause damage with inflammation and other tedious symptoms. Methods: In this work, a number of biocompatible, non-toxic, and hypoallergenic compounds were tested in vitro as pepsin inhibitors. The residual enzyme activity in the presence of the investigated compounds was measured through a convenient and reliable UV-vis method based on the cleavage of hemoglobin. This method is applicable even if the investigated additives are scarcely soluble in water and the test mixtures are dispersions rather than solutions. Results: A few negatively charged saccharides showed the highest effect among the investigated compounds. The inhibitory activity of pepstatin and lovastatin was also tested with the same method in a wide range of concentrations. These compounds turned out to be effective even if present in extremely low amounts. A docking/molecular dynamic investigation providesuseful insights into the binding site and the mechanism of action of pepstatin as an inactivating agent toward pepsin. Conclusion: In particular, the computational study indicates that the binding with this compound significantly increases the mobility of the active site residues and prevents them from cooperating in the reactive event.