Defining the role of GPX3 in Eosinophilic Esophagitis

Vanderbilt University Medical Center, Nashville TN

Investigators

Abstract

1 This research proposal investigates the role of Glutathione Peroxidase 3 (GPX3) in regulating 2 esophageal epithelial remodeling, subepithelial fibrosis, and eosinophil recruitment, all histologic 3 features characteristic of Eosinophilic Esophagitis (EoE). In order to maintain esophageal 4 epithelial homeostasis, reactive oxygen species (ROS) might be tightly regulated, and GPX3 is 5 crucial in this process as it catalyzes the reduction of ROS. We have demonstrated that in the 6 esophagus, GPX3 is expressed most highly in differentiated epithelial cells but is also expressed 7 by fibroblasts. In patients with EoE, GPX3 is reduced in these same cell types as compared with 8 non-EoE controls, and IL-13, which induces a large percentage of the epithelial transcriptional 9 changes in EoE, reduces GPX3 and glutathione peroxidase enzymatic activity in epithelial cells. 10 Consistent with these observations, the esophagus of Gpx3-/- mice exhibits histologic features of 11 EoE, including increased basal cell thickness, epithelial proliferation, expansion of transitioning 12 cells, and subepithelial fibrosis. Similarly, Gpx3-/- three-dimensional ex vivo esophageal organoids 13 phenocopy the same epithelial changes seen in mice. Additionally, we have shown that a 14 reduction in GPX3 results in increased susceptibility to activation of signaling pathways central to 15 EoE pathogenesis. Knocking down GPX3 in an esophageal epithelial cell line results in increased 16 activation of STAT6 after IL-13 treatment, suggesting that GPX3 dampens immunoactivation and 17 reduces eosinophil recruitment. Gpx3-/- esophageal organoids and fibroblasts both secrete 18 increased TGF-b1 as compared with wild-type (WT), and organoid culture media from Gpx3-/- 19 results in increased contraction of WT fibroblasts suspended in collagen. Collectively, these data 20 suggest that both epithelial and fibroblast GPX3 may contribute to subepithelial fibrosis through 21 activation of the TGF-b1 pathway. This is important not only because TGF-b1 is a significant driver 22 of fibrosis in EoE, but also because it suggests that the epithelium and subepithelium may be a 23 critical source of TGF-b1 in addition to immune cells. While it is clear that GPX3 is important in 24 regulating esophageal epithelial and subepithelial phenotypes, what is unclear is the mechanism 25 underlying how GPX3 alters these processes critical for EoE pathogenesis. Thus, the aims of this 26 proposal are 1) to determine the mechanism by which GPX3 regulates epithelial remodeling, 2) 27 to dissect how GPX3 regulates eosinophil recruitment and subepithelial fibrosis, and 3) to 28 leverage this information as a therapeutic for EoE. By uncovering a deeper understanding of the 29 molecular function of GPX3 and its regulatory networks, we will discover fundamental insights 30 into EoE pathogenesis, offering potential therapeutic strategies.