In Obesity, Esophagogastric Junction Fat Impairs Esophageal Barrier Function and Dilates Intercellular Spaces via HIF-2α

Abstract

BACKGROUND & AIMS

Dilated intercellular space (DIS) in esophageal epithelium, a sign of impaired barrier function, is a characteristic finding of GERD that also is found in obese patients without GERD. We have explored molecular mechanisms whereby adipose tissue products might impair esophageal barrier integrity.

METHODS

We established cultures of visceral fat obtained during foregut surgery from obese and non-obese patients. Monolayer and air-liquid interface (ALI) cultures of human esophageal cells were grown with conditioned medium (CM) from fat cultures. RNA sequencing, ELISA, western blot, immunostaining, histology, and analyses of barrier function were performed; inhibitors of HIF-2α (PT2385), caspase-1 (AC-YVAD-CHO), myosin light chain (MLC) kinase (PIK), and MLC phosphatase (PIP250) were applied; blebbistatin was used to disrupt actin-myosin interactions; NAC was used to scavenge reactive oxygen species (ROS).

RESULTS

CM from EGJ fat of obese patients (EGJ-CM-Obese) caused DIS with impaired barrier function in esophageal ALI cultures; these effects were blocked by PT2385. EGJ-CM-Obese induced ROS production that activated HIF-2α in esophageal cells. RNA sequencing analyses linked EGJ-CM-Obese-induced HIF-2α increases with innate immune response pathways. Cross-talk between HIF-2α and caspase-1 in esophageal cells led to IL-1β secretion, and IL-1β/IL-1R1 signaling caused DIS with impaired esophageal barrier function via actin-myosin interactions induced by MLC phosphorylation.

CONCLUSIONS

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