TGF-β1-induced phospholamban expression alters esophageal smooth muscle cell contraction in patients with eosinophilic esophagitis

Background: Eosinophilic esophagitis (EoE) is a chronic antigen-mediated disease characterized by esophageal eosinophilia, remodeling, and fibrosis. TGF-beta 1 is a central regulator of EoE remodeling and increases esophageal smooth muscle (ESM) cell contraction. Objective: In this study we aimed to understand the molecular mechanisms by which TGF-beta 1 could induce ESM cell contraction. Methods: We used primary human ESM cells and esophageal myofibroblasts (EMFs) to assess the mechanisms of TGF-beta 1-induced contraction. We analyzed the expression, phosphorylation, and function of phospholamban (PLN), a sarcoendoplasmic reticulum regulatory protein induced by TGF-beta 1. Expression of PLN, phospho-PLN, and its regulatory pathway was analyzed in the ESM of biopsy specimens from patients with EoE and control subjects. Gene silencing in EMFs from patients with EoE was used to understand the role of PLN in contraction. Results: TGF-beta 1 induced and phosphorylated PLN in primary human ESM cells and EMFs from patients with EoE. PLN and phospho-PLN levels were increased in smooth muscle from patients with EoE compared with that seen in smooth muscle from control subjects in vivo. PLN inhibition significantly diminished TGF-beta 1-induced EMF contraction in patients with EoE. PLN expression and ESM/EMF contraction depended on TGF-beta receptor I signals. Conclusion: We describe a previously unrecognized mechanism for ESM cell contraction that depends on TGF-beta 1, its receptors, and PLN. Because PLN levels are increased in smooth muscle from patients with EoE and PLN silencing diminishes contraction, we provide a novel potential mechanistic framework and therapeutic target for ESM dysfunction in patients with EoE.