Polyhexamethylene Guanidine Phosphate Induces Apoptosis through Endoplasmic Reticulum Stress in Lung Epithelial Cells.

Mi Ho Jeong,Mi Seon Jeon,Ga Eun Kim,Ha Ryong Kim

doi:10.3390/ijms22031215

Abstract

Airway epithelial cell death contributes to the pathogenesis of lung fibrosis. Polyhexamethylene guanidine phosphate (PHMG-p), commonly used as a disinfectant, has been shown to be strongly associated with lung fibrosis in epidemiological and toxicological studies. However, the molecular mechanism underlying PHMG-p-induced epithelial cell death is currently unclear. We synthesized a PHMG-p–fluorescein isothiocyanate (FITC) conjugate and assessed its uptake into lung epithelial A549 cells. To examine intracellular localization, the cells were treated with PHMG-p–FITC; then, the cytoplasmic organelles were counterstained and observed with confocal microscopy. Additionally, the organelle-specific cell death pathway was investigated in cells treated with PHMG-p. PHMG-p–FITC co-localized with the endoplasmic reticulum (ER), and PHMG-p induced ER stress in A549 cells and mice. The ER stress inhibitor tauroursodeoxycholic acid (TUDCA) was used as a pre-treatment to verify the role of ER stress in PHMG-p-induced cytotoxicity. The cells treated with PHMG-p showed apoptosis, which was inhibited by TUDCA. Our results indicate that PHMG-p is rapidly located in the ER and causes ER-stress-mediated apoptosis, which is an initial step in PHMG-p-induced lung fibrosis.

Highlights

Was used as a pre-treatment to verify the role of endoplasmic reticulum (ER) stress in Polyhexamethylene guanidine phosphate (PHMG-p)-induced cytotoxicity
We identified the subcellular localization of PHMG-p in lung epithelial cells
A549 cells with stained ER, lysosomes, or mitochondria were incubated with 2 μg/mL PHMG-p–fluorescein isothiocyanate (FITC) for different periods of time

Summary

Introduction

Was used as a pre-treatment to verify the role of ER stress in PHMG-p-induced cytotoxicity. PHMG-p is rapidly located in the ER and causes ER-stress-mediated apoptosis, which is an initial step in PHMG-p-induced lung fibrosis. Lung fibrosis is considered to be the result of a dysregulated wound-repair response to lung injury. Repeated microscopic injuries cause the death of epithelial cells, which is followed by an inflammatory process, and the accumulation and persistence of activated reparative mesenchymal cells (myofibroblasts) that are responsible for the deposition of excessive extracellular matrix [1,2,3]. The importance of epithelial cells in the pathogenesis of lung fibrosis is implicated by the observation that inhibition of epithelial cell death attenuates the extent of lung fibrosis in animal models [6,7,8]. Prolonged or excessive ER stress is associated with the development and progression of lung fibrosis through induction of apoptosis in epithelial cells. Animal models have shown that ER stress contributes to fibrotic remodeling in the lungs [11,12,13]

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Conclusion