Abstract
Ghrelin is a gastric endocrine peptide that has been found to be involved in the process of energy homeostasis and bone physiology in recent years. To explore the effects of ghrelin on endoplasmic reticulum stress (ERS) in MC3T3E1 cells and its possible mechanism, an ERS model was induced by tunicamycin (TM) in the osteoblast line MC3T3E1. TM at 1.5 μg/mL was selected as the experimental concentration found by CCK8 assay. Through the determination of apoptosis, reactive oxygen species production, and endoplasmic reticulum stress-related gene expression, we found that ERS induced by TM can be relieved by ghrelin in a concentration-dependent manner (P < 0.001). Compared with the TM group, ghrelin reduced the expression of ERS-related marker genes induced by TM. Compared with the GSK621 + TM group without ghrelin pretreatment, the mRNA expression of genes in the ghrelin pretreatment group decreased significantly (P < 0.001). The results of protein analysis showed that the levels of BIP, p-AMPK, and cleaved-caspase3 in the TM group increased significantly, while the levels decreased after ghrelin pretreatment. In group GSK621 + TM compared with group GSK621 + ghrelin+TM, ghrelin pretreatment significantly reduced the level of p-AMPK, which is consistent with the trend of the ERS-related proteins BIP and cleaved-caspase3. In conclusion, ghrelin alleviates the ERS induced by TM in a concentration-dependent manner and may or at least partly alleviate the apoptosis induced by ERS in MC3T3E1 cells by inhibiting the phosphorylation of AMPK.
Highlights
As a hidden and common disease, osteoporosis is characterized by a decrease in bone mass and a change in bone microstructure
It was found that the incidence of osteoporosis increased significantly after subtotal gastrectomy [9], and ghrelin polypeptide decreased significantly after surgery [10], which is closely related to the pathogenesis of osteoporosis, but the mechanism has not been elucidated
Endoplasmic Reticulum Stress in MC3T3E1 Cells Induced by Tunicamycin
Summary
As a hidden and common disease, osteoporosis is characterized by a decrease in bone mass and a change in bone microstructure. Previous studies have shown that apoptosis induced by endoplasmic reticulum stress (ERS) in osteoblasts plays an important role [1]. ERS is an “unfolded protein reaction (UPR)” [2] in the endoplasmic reticulum caused by endogenous and exogenous factors such as heat shock, ultraviolet radiation, oxidative damage, hypoxia, and hypoglycemia. The accumulation of unfolded or misfolded proteins triggers a stress response in the endoplasmic reticulum to remove these proteins, and excessive ERS can lead to apoptosis. Ghrelin has been found to play a role in various aspects, such as energy homeostasis [4], cell proliferation and autophagy [5], cardiovascular disease [6], respiratory disease [7], and the immune system [8]. It was found that the incidence of osteoporosis increased significantly after subtotal gastrectomy [9], and ghrelin polypeptide decreased significantly after surgery [10], which is closely related to the pathogenesis of osteoporosis, but the mechanism has not been elucidated
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