RESUMO
Eosinophilic Esophagitis (EoE) is a chronic allergic disorder, whose pathobiology is incompletely understood. Histamine-producing cells including mast cells and basophils have been implicated in EoE. However, very little is currently known about the role of histamine and histamine receptor (HR) expression and signaling in the esophageal epithelium. Herein, we characterized HR (H1R, H2R, H3R, and H4R) expression in human esophageal biopsies and investigate the role of histamine signaling in inducible cytokine expression in human esophageal epithelial cells in vitro. HR expression was quantified in esophageal biopsies from non-EoE control (N = 23), inactive EoE (<15 eos/hpf, N = 26) and active EoE (>15 eos/hpf, N = 22) subjects using qRT-PCR and immunofluorescent localization. HR expression and histamine-mediated cytokine secretion were evaluated in human primary and telomerase-immortalized esophageal epithelial cells. H1R, H2R, and H4R expression were increased in active EoE biopsies compared to inactive EoE and controls. H2R was the most abundantly expressed receptor, and H3R expression was negligible in all 3 cohorts. Infiltrating eosinophils expressed H1R, H2R, and H4R, which contributed to the observed increase in HR in active subjects. H1R and H2R, but not H3R or H4R, were constitutively expressed by primary and immortalized cells, and epithelial histamine stimulation induced GM-CSF, TNFα, and IL-8, but not TSLP or eotaxin-3 secretion. Epithelial priming with the TLR3 ligand poly (I:C) induced H1R and H2R expression, and enhanced histamine-induced GM-CSF, TNFα, and IL-8 secretion. These effects were primarily suppressed by H1R antagonists, but unaffected by H2R antagonism. Histamine directly activates esophageal epithelial cytokine secretion in vitro in an H1R dependent fashion. However, H1R, H2R and H4R are induced in active inflammation in EoE in vivo. While systemic antihistamine (anti-H1R) therapy may not induce clinical remission in EoE, our study suggests that further study of histamine receptor signaling in EoE is warranted and that targeting of additional histamine receptors may lead to novel treatment strategies for this important disease.
Assuntos
Esofagite Eosinofílica/genética , Expressão Gênica , Receptores Histamínicos/genética , Adolescente , Biópsia , Contagem de Células , Linhagem Celular , Criança , Pré-Escolar , Esofagite Eosinofílica/etiologia , Esofagite Eosinofílica/metabolismo , Esofagite Eosinofílica/patologia , Eosinófilos/patologia , Células Epiteliais/metabolismo , Feminino , Estudos de Associação Genética , Fator Estimulador de Colônias de Granulócitos e Macrófagos/metabolismo , Histamina/metabolismo , Humanos , Lactente , Interleucina-8/metabolismo , Masculino , Mucosa/metabolismo , Mucosa/patologia , Receptores Histamínicos/metabolismo , Receptores Histamínicos H1/genética , Receptores Histamínicos H1/metabolismo , Receptores Histamínicos H2/genética , Receptores Histamínicos H2/metabolismo , Receptores Histamínicos H3/genética , Receptores Histamínicos H3/metabolismo , Receptor 3 Toll-Like/agonistas , Receptor 3 Toll-Like/metabolismo , Fator de Necrose Tumoral alfa/metabolismoRESUMO
BACKGROUND AND AIMS: Eosinophilic esophagitis (EoE) is an allergic inflammatory disease that leads to esophageal fibrosis and stricture. We have recently shown that in EoE, esophageal epithelial cells undergo an epithelial to mesenchymal transition (EMT), characterized by gain of mesenchymal markers and loss of epithelial gene expression. Whether epithelial cells exposed to profibrotic cytokines can also acquire the functional characteristics of activated myofibroblasts, including migration, contraction, and extracellular matrix deposition, is relevant to our understanding and treatment of EoE-associated fibrogenesis. In the current study, we characterize cell migration, contraction, and collagen production by esophageal epithelial cells that have undergone cytokine-induced EMT in vitro. METHODS AND RESULTS: Stimulation of human non-transformed immortalized esophageal epithelial cells (EPC2-hTERT) with profibrotic cytokines TNFα, TGFß, and IL1ß for three weeks led to acquisition of mesenchymal αSMA and vimentin, and loss of epithelial E-cadherin expression. Upon removal of the profibrotic stimulus, epithelial characteristics were partially rescued. TGFß stimulation had a robust effect upon epithelial collagen production. Surprisingly, TNFα stimulation had the most potent effect upon cell migration and contraction, exceeding the effects of the prototypical profibrotic cytokine TGFß. IL1ß stimulation alone had minimal effect upon esophageal epithelial migration, contraction, and collagen production. CONCLUSIONS: Esophageal epithelial cells that have undergone EMT acquire functional characteristics of activated myofibroblasts in vitro. Profibrotic cytokines exert differential effects upon esophageal epithelial cells, underscoring complexities of fibrogenesis in EoE, and implicating esophageal epithelial cells as effector cells in EoE-associated fibrogenesis.
