IL-32 induces epithelial-mesenchymal transition by triggering endoplasmic reticulum stress in A549 cells

Ling Gong,Gang Liu,Daishun Liu,Hongbo Tang,Changlu Liu,Xiaoping Tang,Pengmei Li,Caihong Li,Kaifeng Wu,Jie Wu,Honglan Zhu

doi:10.1186/s12890-020-01319-z

Abstract

BackgroundEpithelial-mesenchymal transition (EMT) is a key process in the onset and development of idiopathic pulmonary fibrosis (IPF) with unclear mechanisms. Our previous studies found that bleomycin and tunicamycin could induce ER stress and consequently trigger EMT accompanying with IL-32 overexpression. This study was aimed to investigate the effects of IL-32 on EMT and ER stress to elucidate the pathogenesis of IPF.MethodsHuman lung adenocarcinoma A549 cells were treated with recombinant human (rh)IL-32, IL-32 siRNA and EMT inducer tunicamycin, or 4-phenylbutyric acid (4-PBA), respectively. Then the cell morphology was observed and the expression of ER-related markers and EMT-related markers were detected by RT-qPCR or western blotting.ResultsStimulation of A549 cells with rhIL-32 led to a morphological change from a pebble-like shape to an elongated shape in a portion of the cells, accompanied by down regulated expression of the epithelial cell marker E-cadherin and up regulated expression of the mesenchymal cell markers N-cadherin, Vimentin, and Zeb-1. However, these rhIL-32 induced changes were inhibited by the ER stress inhibitor 4-PBA. Suppression of IL-32 expression with siRNA inhibited TM-induced EMT. Further stimulation of the A549 cells with rhIL-32 demonstrated an increase in the expression of GRP78, although this increase was also inhibited by 4-PBA.ConclusionsThese results suggest that IL-32 induces EMT in A549 cells by triggering ER stress, and IL-32 may be a novel marker for IPF.

Highlights

Epithelial-mesenchymal transition (EMT) is a key process in the onset and development of idiopathic pulmonary fibrosis (IPF) with unclear mechanisms
These results suggest that IL-32 induces EMT in A549 cells by triggering endoplasmic reticulum (ER) stress, and IL-32 may be a novel marker for IPF
Tunicamycin treatment enhanced the expression of IL-32 in A549 cells Our previous study showing that TM can induce EMT in A549 cells, the cells were treated with 0.5 μg/ml TM for 24 h [11]

Summary

Introduction

Epithelial-mesenchymal transition (EMT) is a key process in the onset and development of idiopathic pulmonary fibrosis (IPF) with unclear mechanisms. This study was aimed to investigate the effects of IL-32 on EMT and ER stress to elucidate the pathogenesis of IPF. Idiopathic pulmonary fibrosis (IPF), a chronic progressive lung disease characterized by continuous scarring of the lungs, can lead to a progressive decline of lung function and respiratory failure, with high mortality rates [1]. Indepth investigations of the molecular mechanisms of IPF are of great significance for guiding the development of novel strategies for the prevention and treatment of the disease. Detailed studies have demonstrated that epithelial cells that have undergone EMT possess a contractile function and the ability to synthesize collagen [4], which are the key conditions for the onset and development of fibrosis. EMT appears to play an important role in IPF pathogenesis

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