Gastroesophageal reflux disease (GERD) is one of the most prevalent gastrointestinal disorders worldwide and is one of the greatest risk factors in the pathogenesis of Barrett's esophagus and esophageal adenocarcinoma. GERD is characterized by a broad spectrum of typical symptoms, such as heartburn and acid regurgitation, and extra-esophageal manifestations, such as asthma, chronic cough and laryngitis. Although proton pump inhibitors (PPIs) are currently the most effective treatment for GERD and its complications, up to 45% of patients with GERD remain symptomatic on standard therapy. Long term use of PPIs can cause severe side effects including chronic kidney disease and myocardial infarction. Thus, there is an urgent need to develop new methods to treat PPI refractory GERD. Dilated intercellular space (DIS) in the esophageal squamous epithelium is one of the important early pathological features in GERD. In reflux disease, gastro-duodenal contents, the most important of which are stomach acid and bile acids, regurgitate into the distal esophagus and cause DIS formation and loss of barrier function through epithelial injury and disruption of tight and adherens junctions in the human esophagus as well as in animal models of the disease. Molecular analysis has shown in patients and animal models of GERD that levels of a number of tight junction and adherens junction proteins are reduced in this disease. Using a 3-D transwell culture of human EPC1 esophageal squamous cells as a GERD model, we have shown that bile acid at pH 5 damaged cell junctions and causes DIS. We have recently found that overexpression of the Na+,K+-ATPase ?1 subunit by electroporation of plasmids into healthy and injured lungs of mice and pigs protected them from subsequent lung injury and partially reversed existing lung injury through upregulation of tight junction proteins and barrier function. We have found similar upregulation of tight junction proteins in esophageal squamous epithelial cells following gene transfer of the Na+,K+-ATPase ?1 subunit. We hypothesize that by enhancing the levels of tight and adherens junction complexes in the esophageal squamous epithelium by gene transfer of the Na+,K+-ATPase ?1 subunit, we may be able to prevent or reverse the appearance and consequences of DIS during progression of GERD.
Aim 1 will test whether gene transfer of the Na+,K+-ATPase ?1 subunit increases, protects, and/or restores apical junctional complexes in an in vitro stratified 3-D model of human esophageal squamous cells and in murine esophageal organoids.
Aim 2 will determine whether electroporation-mediated gene delivery of the Na+,K+-ATPase ?1 subunit to the lower esophagus in living animals can increase apical junctional complexes.
Aim 3 will determine whether electroporation-mediated gene delivery of the Na+,K+- ATPase ?1 subunit to the lower esophagus can prevent and/or treat cell junction damage and DIS in a rabbit GERD model. These studies will provide proof of principle that this approach could be explored in future clinical trials to prevent and treat the local effects and symptoms of GERD in patients and its consequences.
GERD is a common disorder that damages the squamous mucosa of the lower esophagus, leading to a damaged epithelial barrier and Dilated Intercellular Space (DIS), Barrett's esophagus, and esophageal adenocarcinoma, which are not prevented by current GERD medication. Even with current therapy, up to 45% of patients continue to have pain that is refractory to treatment. This application proposes to determine if over- expression of the Na+,K+-ATPase in squamous esophageal cells in in vitro and in vivo models of GERD- induced DIS prevents the refractory GERD by upregulating cell junction complexes to repair and/or prevent barrier function. If successful, our studies could lead to new therapy to reduce GERD symptoms and consequences of this disease.
