Functional role of kallikrein 5 and proteinase-activated receptor 2 in eosinophilic esophagitis

Abstract

Eosinophilic esophagitis (EoE) is a chronic, food antigen–driven, inflammatory disease of the esophagus and is associated with impaired barrier function. Evidence is emerging that loss of esophageal expression of the serine peptidase inhibitor, kazal type 7 (SPINK7), is an upstream event in EoE pathogenesis. Here, we provide evidence that loss of SPINK7 mediates its pro-EoE effects via kallikrein 5 (KLK5) and its substrate, protease-activated receptor 2 (PAR2). Overexpression of KLK5 in differentiated esophageal epithelial cells recapitulated the effect of SPINK7 gene silencing, including barrier impairment and loss of desmoglein-1 expression. Conversely, KLK5 deficiency attenuated allergen-induced esophageal protease activity, modified commensal microbiome composition, and attenuated eosinophilia in a murine model of EoE. Inhibition of PAR2 blunted the cytokine production associated with loss of SPINK7 in epithelial cells and attenuated the allergen-induced esophageal eosinophilia in vivo. Clinical samples substantiated dysregulated PAR2 expression in the esophagus of patients with EoE, and delivery of the clinically approved drug α1 antitrypsin (A1AT, a protease inhibitor) inhibited experimental EoE. These findings demonstrate a role for the balance between KLK5 and protease inhibitors in the esophagus and highlight EoE as a protease-mediated disease. We suggest that antagonizing KLK5 and/or PAR2 has potential to be therapeutic for EoE.

Type 2 Inflammation in Eosinophilic Esophagitis: From Pathophysiology to Therapeutic Targets

“…Proteases also seem to play a role in EoE. Serine protease inhibitors (SERPINs), serine protease inhibitors, Kazal type (SPINKs) and Kallikrein serine peptidases (LRRC31) have been shown to be dysregulated in EoE ( D’Mello et al, 2016 ; Rochman et al, 2017 ; Azouz et al, 2018 , 2020 ), potentially contributing to epithelial damage.…”

Achieving Precision Medicine in Allergic Disease: Progress and Challenges

“…Wen et al have described two distinct T cell subsets in active EoE, one which constitutes an active Th2like (GATA3 + HPGDS + CRTH2 + IL-17RB + FFAR3 + CD4 + ) cell with high levels of IL-5 and IL-13 production, and a Treglike (FOXP3 + CD4 + MAF + CTLA4 + IL-10 + ) cell (56). Another scRNA-seq experiment in human esophageal tissue revealed 14 epithelial populations with distinct expression of kallikrein 5 and the proteinase-activated receptor (PAR)2 in EoE patients compared to control patients (57). Bulk RNA sequencing of esophageal biopsies in EoE has been performed more than single cell RNA sequencing, and has revealed important information about the molecular signatures of EoE (58).…”

Replication and meta-analyses nominate numerous eosinophilic esophagitis risk genes

“…Single-cell suspensions were prepared from esophageal biopsies as previously described. 45 Bulk population cells were directly subjected to the 103 mass genomics chip (10x genomics, Inc) targeting 10,000 simultaneously captured live events for next-generation sequencing. Each cell was uniquely barcoded and sequenced by the CCHMC Genetic Variation and Gene Discovery Core Facility at CCHMC on the Illumina HiSeq 2500, with total reads of approximately 320 M (2 lanes/flow cell).…”

“…The tag variant is located in an intron of ITIH5, a gene that affects epidermal morphology in mice 59 and encodes for a serine protease inhibitor, a class of proteins that have been implicated in EoE. 45,60 Because of the involvement of the esophageal epithelial barrier, the role of EoE risk variants in affecting ITIH5 expression and subsequent epithelial morphology and barrier function is likely important. Interestingly, the 10p14 locus has been genetically associated with another eosinophilic disease, eosinophilic granulomatosis with polyangiitis, and suggested to be mediated by GATA3 through long-range chromatin interaction.…”