Dwyer, A. T. | bioRxiv Science

bioRxiv2023

Aryl hydrocarbon receptor (AHR) and IL-13 signaling crosstalk in human keratinocytes and atopic dermatitis

Atopic dermatitis (AD) is an allergic skin disease mediated by skin barrier impairment and IL-13-driven immune response. Activation of the aryl hydrocarbon receptor (AHR) has shown promise in early clinical trials for AD, however, the mechanism by which AHR mediates this function is unknown. Herein, AHR signaling is shown to be dysregulated in AD patients using publicly available gene expression data from biopsies of patients with AD compared with controls. AHR target genes, CYP1A1, CYP1A2 and NFE2L2 were decreased in lesional skin compared with healthy control skin (p=0.001, p<1.0*10-10 and p=6.1*10-6 respectively). Single cell RNA sequencing studies demonstrated increased expression of AHR (p<1.0*10-4 and p=0.049) and decreased expression of CYP1A1 in lesional AD keratinocytes compared with healthy control keratinocytes (p=5.0*10-4 and p=0.21). AHR activation reversed IL-13-dependent gene expression of several key genes in AD pathogenesis, most notably the eosinophil chemoattractant, CCL26 (Eotaxin-3). There was substantial overlap between differentially expressed genes in keratinocytes of patients with atopic dermatitis and AHR-regulated genes. Mechanistically, there was evidence for direct transcriptional effects of AHR as its binding motifs were identified in the differentially expressed genes from lesional AD keratinocytes compared to control keratinocytes and AHR activation did not modify IL-13-dependent signal transducer and activator of transcription 6 (STAT6) translocation to the nucleus. Together these data imply that AHR modulates IL-13 downstream signaling in keratinocytes through genome-wide direct transcriptional regulatory effects.

immunology↗

bioRxiv2023

Aryl Hydrocarbon Receptor Suppresses Eosinophilic Esophagitis Responses through OVOL1 and SPINK7

Eosinophilic esophagitis (EoE) is a type 2 allergic disease characterized by esophageal inflammation and epithelial cell dysfunction. Acquired loss of the anti-serine protease of kazal type 7 (SPINK7) in the squamous epithelium of the esophagus has a causal role in EoE pathogenesis. Yet there is a limited understanding of the factors that regulate its expression and responsiveness to inflammatory stimuli. Herein, we identified the transcription factor, ovo like transcriptional repressor 1 (OVOL1) as an esophageal selective gene product that regulates SPINK7 promoter activity. Overexpression of OVOL1 increased SPINK7 expression, whereas, its depletion decreased SPINK7 expression, impaired epithelial barrier and increased production of the pro-atopy cytokine thymic stromal lymphopoietin (TSLP). Mechanistically, ligands of AHR induced nuclear translocation of OVOL1 which in turn promoted epithelial cell differentiation, barrier function and SPINK7 expression. Interleukin (IL)-4 and IL-13 abolished AHR ligand-induced OVOL1 nuclear translocation. Stimulation with IL-13 abrogated the nuclear translocation of OVOL1 and promoted enhanced degradation of OVOL1 protein. This effect of IL-13 was dependent on the esophageal specific cysteine protease calpain-14. Translational studies demonstrated loss of OVOL1 protein expression in patients with EoE. In summary, AHR mediates its action via OVOL1-induced SPINK7 transcription, and IL-4 and IL-13 repress this pathway in EoE. As such, activation of the AHR pathway is a potential intervention strategy for reversing EoE. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/541192v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@1e946a1org.highwire.dtl.DTLVardef@1c087forg.highwire.dtl.DTLVardef@71ecc8org.highwire.dtl.DTLVardef@17044da_HPS_FORMAT_FIGEXP M_FIG C_FIG The influence of the exposome on regulatory networks in EoE pathogenesis. AHR is activated and influenced by diet nutrients, environmental toxicants, microbiome composition, tryptophan metabolites, and drugs. When AHR is activated, it promotes translocation of OVOL1 to the nucleus, which in turn promotes expression of epithelial genes including SPINK7. SPINK7 expression promotes epithelial differentiation, barrier function, decreased proteolytic activity, and decreased TSLP production. IL-4 and IL-13 inhibit OVOL1 nuclear translocation and therefore, repress SPINK7 expression. IL-13-stimulated CAPN14 expression decreases OVOL1 protein expression and SPINK7 transcription.

immunology↗