Introduction: Eosinophilic esophagitis (EoE) is a T-helper 2 (Th2), eosinophilic disease associated with pathologic tissue remodeling that leads to end-organ dysfunction. During early-stage disease, inflammation and subepithelial fibrosis are coupled and reversible, but in late-stage or therapy-resistant disease, there can be uncoupling of these features with progressive esophageal rigidity and strictures contributing to clinical dysphagia and food impactions. No current pharmacotherapeutic interventions directly target esophageal fibrosis. Based on the ability of the thiazolidinediones (TZD) to regulate intestinal and hepatic fibrosis, we tested the antifibrotic effects of the TZDs, rosiglitazone and pioglitazone, in preclinical studies using primary human esophageal fibroblasts.
Methods: Primary fibroblasts isolated from normal or EoE esophagi were treated with transforming growth factor (TGF)-β1 in the absence or presence of TZDs and, in some experiments, without or with budesonide and analyzed by quantitative real-time PCR and immunoblotting. Immunohistochemical analysis of human esophageal biopsies was performed.
Results: EoE esophageal biopsies and esophageal fibroblasts expressed higher levels of the TZD receptor, peroxisome proliferator-activated receptor-γ (PPAR-γ), than normal controls. PPAR-γ was inducible by the Th2 cytokine, interleukin 4 (IL-4). TZD significantly reduced TGF-β1-induced myofibroblast and fibrotic gene and protein expression preferentially in EoE, but not normal esophageal fibroblasts. In esophageal fibroblasts, TGF-β1 increased phosphorylated Smad2/3 and p38, but TZDs preferentially inhibited p38 phosphorylation, suggesting signaling pathway-specific effects. The TZDs were more potent than budesonide at decreasing collagen-1α1 expression.
Discussion: The TZDs preferentially exert antifibrotic effects in TGF-β1-activated EoE fibroblasts and provide a preclinical foundation for further investigation of the potential of the TZDs in EoE pathologic remodeling.