Chronic stress augments esophageal inflammation, and alters the expression of transient receptor potential vanilloid 1 and protease-activated receptor 2 in a murine model

Abstract

Stress is a pivotal factor for inflammation, reactive oxygen species (ROS) production and formation of visceral hypersensitivity (VH) in the process of gastroesophageal reflux disease (GERD). In the present study, the effects of stress on esophageal inflammation, oxidative stress and VH were investigated in a chronic restraint stress mouse model. C57BL/6J male mice were subjected to 2 weeks of intermittent restraint stress, and histopathological analysis revealed that stress induced esophageal inflammation and fibrosis, while no distinct changes were detected in non-stressed control mice. In addition, increased NADPH oxidase 4 expression was observed in the plasma and esophagus of stressed mice, indicating accumulation of ROS. The expression levels of antioxidants, including Mn-superoxide dismutase (MnSOD), Cu/Zn-SOD , catalase and glutathione peroxidase, were also analyzed using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). In addition, transient receptor potential vanilloid 1 (TRPV-1) and protease-activated receptor 2 (PAR- 2), which are crucial receptors for VH, were measured by immunohistochemistry and RT-qPCR. The results demonstrated that stress markedly reduced antioxidant expression, while it significantly upregulated TRPV-1 and PAR-2 expression levels in the mouse esophagus. Finally, 2 weeks of restraint stress significantly increased the esophageal and plasma levels of inflammatory cytokines, including interleukin (IL)-6, IL-8, interferon-γ and tumor necrosis factor-α. Taken together, the present study results indicated that stress-induced esophageal inflammation and ROS generation involves VH.