Endoplasmic Reticulum Stress Is Involved in Glucocorticoid-Induced Apoptosis in PC12 Cells.

Shanyong Yi,Min Zuo,Songjun Wang,Weibo Shi,Bin Cong,Rufei Ma,Haitao Bi,Yingmin Li,Enayatollah Seydi

doi:10.1155/2021/5565671

Abstract

Objective The present study selected PC12 cells to construct a neuronal injury model induced by glucocorticoids (GC) in vitro, aiming to explore whether the endoplasmic reticulum stress (ERS) PKR-like endoplasmic reticulum kinase (PERK)-activating transcription factor 4 (ATF4)-C/EBP-homologous protein (CHOP) and inositol requirement 1 (IRE1)-apoptosis signal regulating kinase 1 (ASK1)-C-Jun amino-terminal kinase (JNK) signaling pathways are associated with the neuronal injury process induced by GC and provide morphological evidence. Methods Cell models with different doses and different durations of GC exposure were established. The viability of PC12 cells was detected by the CCK-8 assay, and the apoptosis rate of PC12 cells was detected by the flow cytometry assay. The expression of microtubule-associated protein 2 (Map2); glucocorticoids receptor (GR); cellular oncogene fos (C-fos); and ERS-related proteins, glucose-regulated protein 78 (GRP78), p-PERK, p-IRE1, ATF4, ASK1, JNK, and CHOP, was observed by immunofluorescence staining. Results The results of immunofluorescence staining showed that PC12 cells abundantly expressed Map2 and GR. The CCK-8 assay revealed that high-concentration GC exposure significantly inhibited the cell viability of PC12 cells. The flow cytometry assay indicated that high-concentration GC exposure significantly increased the apoptosis rate of PC12 cells. Immunofluorescence staining showed that GC exposure significantly increased the expression of C-fos, GRP78, p-PERK, p-IRE1, ATF4, ASK1, JNK, and CHOP. Treatment with ERS inhibitor 4-phenylbutyric acid (4-PBA) and GR inhibitor RU38486 attenuated related damage and downregulated the expression of the abovementioned proteins. Conclusion High-concentration GC exposure can significantly inhibit the viability of PC12 cells and induce apoptosis. PERK-ATF4-CHOP and IRE1-ASK1-JNK pathways are involved in the above damage process.

Highlights

When stimulated by various internal and external factors, the HPA axis will be activated to increase the synthesis and secretion of GC, and proper secretion of GC can maintain body homeostasis [1]
When endoplasmic reticulum stress (ERS) persists, PKR-like endoplasmic reticulum kinase (PERK) and inositol requirement 1 (IRE1) can dissociate from glucose-regulated protein 78 (GRP78) and undergo autophosphorylation; the downstream activating transcription factor 4 (ATF4)-C/EBP-homologous protein (CHOP) and apoptosis signal regulating kinase 1 (ASK1)-Jun amino-terminal kinase (JNK) signaling pathways are activated
Continuous high expression of CHOP and JNK can promote cell apoptosis [11,12,13]. It remains unclear whether the PERK-ATF4CHOP and IRE1-ASK1-JNK signaling pathways are associated with the neuronal injury process induced by GC

Summary

Introduction

When stimulated by various internal and external factors, the HPA axis will be activated to increase the synthesis and secretion of GC, and proper secretion of GC can maintain body homeostasis [1]. High levels of GC can downregulate the expression of GC receptors in tissue cells, which can inhibit the HPA axis, cause disorders of the hormone secretion system, inhibit the body’s immune system, and reduce the body’s resistance, eventually leading to metabolic disorders and severe damage [4]. Moderate ERS can be resolved by reducing protein translation and promoting the production of chaperone proteins; the ER can restore homeostasis [9, 10]. Continuous high expression of CHOP and JNK can promote cell apoptosis [11,12,13]

Methods

Results

Conclusion