Aberrant IL-20 Subfamily Signaling Disrupts Epithelial Barrier Function in Eosinophilic Esophagitis

The esophageal epithelium is the first line of defense against harmful environmental antigens. Impairment of the epithelial barrier function is associated with esophageal disorders, including eosinophilic esophagitis (EoE). Members of the interleukin (IL)-20 subfamily are essential mediators between the immune system and epithelial cells. Nonetheless, the function of the IL-20 subfamily in the esophagus is unexplored. In this Ph.D. thesis, we aim to describe the role of the IL-20 subfamily in regulating the esophageal epithelial barrier function during EoE. Analysis of esophageal biopsies and serum samples revealed elevated IL-19, IL-20, and IL-24 levels in active EoE. Combined transcriptome and proteome analysis of patient-derived esophageal organoids indicated that IL-20 subfamily cytokines downregulate the expression of filaggrins (FLG, FLG2) and other epithelial components resulting in a disturbed barrier function. Additionally, we observed that the genetic deletion of the IL-20 receptor subunit beta (IL-20RB/IL-20R2) attenuated experimental EoE and preserved esophageal FLG2 expression in an ovalbumin (OVA)-induced EoE mouse model. Furthermore, inhibition of the mitogen-activated protein kinase (MAPK) or signal transducer and activator of transcription 3 (STAT3) pathway revealed that IL-20 subfamily-mediated epithelial barrier dysfunction depends on the MAPK rather than the STAT3 pathway. Finally, MAPK inhibitor treatment reduces eosinophil and CD45+ immune cell infiltration in the EoE mouse model. Altogether, we have identified an IL-20 subfamily-mediated mechanism of esophageal barrier impairment in the pathophysiology of EoE

IL-20 subfamily cytokines impair the oesophageal epithelial barrier by diminishing filaggrin in eosinophilic oesophagitis.

OBJECTIVE Disruption of the epithelial barrier plays an essential role in developing eosinophilic oesophagitis (EoE), a disease defined by type 2 helper T cell (Th2)-mediated food-associated and aeroallergen-associated chronic inflammation. Although an increased expression of interleukin (IL)-20 subfamily members, IL-19, IL-20 and IL-24, in Th2-mediated diseases has been reported, their function in EoE remains unknown. DESIGN Combining transcriptomic, proteomic and functional analyses, we studied the importance of the IL-20 subfamily for EoE using patient-derived oesophageal three-dimensional models and an EoE mouse model. RESULTS Patients with active EoE have increased expression of IL-20 subfamily cytokines in the oesophagus and serum. In patient-derived oesophageal organoids stimulated with IL-20 cytokines, RNA sequencing and mass spectrometry revealed a downregulation of genes and proteins forming the cornified envelope, including filaggrins. On the contrary, abrogation of IL-20 subfamily signalling in Il20R2 -/- animals resulted in attenuated experimental EoE reflected by reduced eosinophil infiltration, lower Th2 cytokine expression and preserved expression of filaggrins in the oesophagus. Mechanistically, these observations were mediated by the mitogen-activated protein kinase (MAPK); extracellular-signal regulated kinases (ERK)1/2) pathway. Its blockade prevented epithelial barrier impairment in patient-derived air-liquid interface cultures stimulated with IL-20 cytokines and attenuated experimental EoE in mice. CONCLUSION Our findings reveal a previously unknown regulatory role of the IL-20 subfamily for oesophageal barrier function in the context of EoE. We propose that aberrant IL-20 subfamily signalling disturbs the oesophageal epithelial barrier integrity and promotes EoE development. Our study suggests that specific targeting of the IL-20 subfamily signalling pathway may present a novel strategy for the treatment of EoE

Epithelial GPR35 protects from Citrobacter rodentium infection by preserving goblet cells and mucosal barrier integrity.

Goblet cells secrete mucin to create a protective mucus layer against invasive bacterial infection and are therefore essential for maintaining intestinal health. However, the molecular pathways that regulate goblet cell function remain largely unknown. Although GPR35 is highly expressed in colonic epithelial cells, its importance in promoting the epithelial barrier is unclear. In this study, we show that epithelial Gpr35 plays a critical role in goblet cell function. In mice, cell-type-specific deletion of Gpr35 in epithelial cells but not in macrophages results in goblet cell depletion and dysbiosis, rendering these animals more susceptible to Citrobacter rodentium infection. Mechanistically, scRNA-seq analysis indicates that signaling of epithelial Gpr35 is essential to maintain normal pyroptosis levels in goblet cells. Our work shows that the epithelial presence of Gpr35 is a critical element for the function of goblet cell-mediated symbiosis between host and microbiota

Epithelial GPR35 protects from Citrobacter rodentium infection by preserving goblet cells and mucosal barrier integrity

Goblet cells secrete mucin to create a protective mucus layer against invasive bacterial infection and are therefore essential for maintaining intestinal health. However, the molecular pathways that regulate goblet cell function remain largely unknown. Although GPR35 is highly expressed in colonic epithelial cells, its importance in promoting the epithelial barrier is unclear. In this study, we show that epithelial Gpr35 plays a critical role in goblet cell function. In mice, cell-type-specific deletion of Gpr35 in epithelial cells but not in macrophages results in goblet cell depletion and dysbiosis, rendering these animals more susceptible to Citrobacter rodentium infection. Mechanistically, scRNA-seq analysis indicates that signaling of epithelial Gpr35 is essential to maintain normal pyroptosis levels in goblet cells. Our work shows that the epithelial presence of Gpr35 is a critical element for the function of goblet cell-mediated symbiosis between host and microbiota