In Obesity, Esophagogastric Junction Fat Impairs Esophageal Barrier Function and Dilates Intercellular Spaces via Hypoxia-Inducible Factor 2α.

BACKGROUND & AIMS: Dilated intercellular space in esophageal epithelium, a sign of impaired barrier function, is a characteristic finding of gastroesophageal reflux disease that is also found in obese patients without gastroesophageal reflux disease. We explored molecular mechanisms whereby adipose tissue products might impair esophageal barrier integrity.

METHODS

Cultures of visceral fat obtained during foregut surgery from obese and nonobese patients were established. Monolayer and air-liquid interface cultures of human esophageal cells were grown with conditioned medium (CM) from fat cultures. RNA sequencing, enzyme-linked immunosorbent assay, western blot, immunostaining, histology, and analyses of barrier function were performed; inhibitors of hypoxia-inducible factor 2α (HIF-2α [PT2385]), caspase-1 (AC-YVAD-CHO), myosin light chain kinase (Dreverse PIK), and myosin light chain phosphatase (permeant inhibitor of phosphatase 250) were applied; blebbistatin was used to disrupt actin-myosin interactions; N-acetylcysteine was used to scavenge reactive oxygen species.

RESULTS

CM from esophagogastric junction fat of obese patients caused dilated intercellular space with impaired barrier function in esophageal air-liquid interface cultures; these effects were blocked by PT2385. CM from esophagogastric junction fat of obese patients induced reactive oxygen species production that activated HIF-2α in esophageal cells. RNA-sequencing analyses linked CM from esophagogastric junction fat of obese patient-induced HIF-2α increases with innate immune response pathways. Cross-talk between HIF-2α and caspase-1 in esophageal cells led to interleukin 1β secretion, and interleukin 1β/interleukin 1 receptor 1 signaling caused dilated intercellular space with impaired esophageal barrier function via actin-myosin interactions induced by myosin light chain phosphorylation.

CONCLUSIONS

We have elucidated molecular mechanisms whereby visceral fat of obese patients can impair esophageal barrier integrity by secreting substances that generate reactive oxygen species, which activate HIF-2α in esophageal epithelial cells. These mechanisms could render the esophagus of obese individuals vulnerable to damage from acid and other noxious agents.