The antiprotease SPINK7 serves as an inhibitory checkpoint for esophageal epithelial inflammatory responses

Abstract

Loss of barrier integrity has an important role in eliciting type 2 immune responses, yet the molecular events that initiate and connect this with allergic inflammation remain unclear. We reveal an endogenous, homeostatic mechanism that controls barrier function and inflammatory responses in esophageal allergic inflammation. We show that a serine protease inhibitor, SPINK7 (serine peptidase inhibitor, kazal type 7), is part of the differentiation program of human esophageal epithelium and that SPINK7 depletion occurs in a human allergic, esophageal condition termed eosinophilic esophagitis. Experimental manipulation strategies reducing SPINK7 in an esophageal epithelial progenitor cell line and primary esophageal epithelial cells were sufficient to induce barrier dysfunction and transcriptional changes characterized by loss of cellular differentiation and altered gene expression known to stimulate allergic responses (for example, FLG and SPINK5). Epithelial silencing of SPINK7 promoted production of proinflammatory cytokines including thymic stromal lymphopoietin (TSLP). Loss of SPINK7 increased the activity of urokinase plasminogen-type activator (uPA), which in turn had the capacity to promote uPA receptor-dependent eosinophil activation. Treatment of epithelial cells with the broad-spectrum antiserine protease, α1 antitrypsin, reversed the pathologic features associated with SPINK7 silencing. The relevance of this pathway in vivo was supported by finding genetic epistasis between variants in TSLP and the uPA-encoding gene, PLAU. We propose that the endogenous balance between SPINK7 and its target proteases is a key checkpoint in regulating mucosal differentiation, barrier function, and inflammatory responses and that protein replacement with antiproteases may be therapeutic for select allergic diseases.

Toll‐like receptor 2 stimulation augments esophageal barrier integrity

“…42,53 A number of epithelial proteins including desmosomes, serine peptidase inhibitors, filaggrin, and calpains are involved in maintenance of esophageal epithelial barrier integrity. 13,25,54,55 We did not see alterations in the expression of desmoglein 1; however, further work will be required to determine the full scope of epithelial change in response to TLR2 stimulation. We hypothesize that TLR2 stimulation induces additional alterations in esophageal F I G U R E 4 Zymosan treatment of EPC2-hTERT cells upregulates expression of cell adhesion molecules.…”

Mechanisms of gastrointestinal allergic disorders

“…Interestingly, the chronic allergic disease eosinophilic esophagitis (EoE) is characterized by increased TGF-β. TGF-β is produced by many cell types in the esophagus, including eosinophils and mast cells, and promotes tissue fibrosis, epithelial-mesenchymal transition, and smooth muscle contraction; therefore, TGF-β likely has a dual pathogenic and immune-regulatory role in EoE rather than a sim-ment, including increased proteolytic activity with inflammatory consequences (29). Additional examples of dysregulated barrier genes are found among the epidermal differentiation complex (EDC) genes clustered on chromosome 1q21, including the genes FLG and IVL, which are markedly decreased in EoE (30).…”

Advances in eosinophilic diseases in 2018

“…These data elucidate the fine tuning that the esophagus undergoes to deal with acid exposure and present a mechanism that accounts for the barrier loss in patients with EoE, at least in part, as recently reviewed. 12 The interplay of acid and SLC9A3 with the anti-protease/protease imbalance that underscores EoE 13,14 will likely be an active area of research inquiry.…”