Endoplasmic reticulum stress-induced apoptosis and auto-immunity in diabetes.
ABSTRACT Increasing evidence suggests that stress signaling pathways emanating from the endoplasmic reticulum (ER) are important to the pathogenesis of both type 1 and type 2 diabetes. Recent observations indicate that ER stress signaling participates in maintaining the ER homeostasis of pancreatic beta-cells. Either a high level of ER stress or defective ER stress signaling in beta-cells may cause an imbalance in ER homeostasis and lead to beta-cell apoptosis and autoimmune response. In addition, it has been suggested that ER stress attributes to insulin resistance in patients with type 2 diabetes. It is necessary to study the relationship between ER stress and diabetes in order to develop new therapeutic approaches to diabetes based on drugs that block the ER stress-mediated cell-death pathway and insulin resistance.
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ABSTRACT: The endoplasmic reticulum (ER) is an organelle in which newly synthesized secretory and transmembrane proteins are assembled and folded into their correct tertiary structures. However, many of these ER proteins are misfolded as a result of various stimuli and gene mutations. The accumulation of misfolded proteins disrupts the function of the ER and induces ER stress. Eukaryotic cells possess a highly conserved signaling pathway, termed the unfolded protein response (UPR), to adapt and respond to ER stress conditions, thereby promoting cell survival. However, in the case of prolonged ER stress or UPR malfunction, apoptosis signaling is activated. Dysfunction of the UPR causes numerous conformational diseases, including neurodegenerative disease, metabolic disease, inflammatory disease, diabetes mellitus, cancer, and cardiovascular disease. Thus, ER stress-induced signaling pathways may serve as potent therapeutic targets of ER stress-related diseases. In this review, we will discuss the molecular mechanisms of the UPR and ER stress-induced apoptosis, as well as the possible roles of ER stress in several diseases.Genes. 01/2013; 4(3):306-33.
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ABSTRACT: Endoplasmic reticulum stress (ERS) plays an important role in diabetes mellitus (DM), but the association between DM and ERS is unknown. We have previously shown that streptozotocin (STZ)-induced diabetes in rats is characterized by increased levels of ERS markers. Here, we tested whether the chemical chaperone 4-phenylbutyric acid (4-PBA) ameliorated ERS-associated apoptosis in pancreatic β-cells in rats with STZ-induced diabetes. Male Sprague-Dawley rats were divided into 3 groups: control group, DM group, and DM model plus 4-PBA treatment group (4-PBA group). DM model rats were induced by injection of STZ (60 mg/kg) intraperitoneally, and 4-PBA was administered daily by gavage at a dose of 500 mg/kg body weight for 20 days. β-cell apoptosis was higher in the DM group than in the control group. Moreover, the expression of caspase-3, Bax, and the ERS indicators Bip and CHOP was markedly elevated in the pancreas of rats in the DM group, whereas the expression of Bcl-2 was lower in these rats (P < 0.05). Blood glucose concentration in diabetic rats gradually decreased with 4-PBA treatment but remained higher at the end of the experiment compared to the concentration in control rats. Consistent with this, 4-PBA raised the fasting insulin level in diabetic rats; it also suppressed the expression of caspase-3, Bax, and ERS indicators but enhanced the expression of Bcl-2. In conclusion, 4-PBA protects pancreatic β-cells from apoptosis in STZ-induced diabetes by attenuating the severity of ERS.Endocrine 12/2013; · 3.53 Impact Factor
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ABSTRACT: Inositol requiring enzyme-1 (IRE1) is highly conserved from yeasts to humans. Upon endoplasmic reticulum (ER) stress, IRE1 activates X-box-binding protein 1 (XBP1) by unconventional splicing of XBP1 mRNA, which activates unfolded protein response (UPR) to restore ER homeostasis. In mice, IRE1α plays an essential role in extraembryonic tissues. However, its precise action during the early stage of development is unknown. In this study, the gain and loss-of-function analyses were used to investigate the function of Xenopus IRE1α (xIRE1α). The effects of xIRE1α during embryo development were detected with RT-PCR and whole mount in situ hybridization. ER stress was induced by tunicamycin. The apoptotic cells were measured by TUNNEL assays. Although both gain and loss of xIRE1α function had no significant effect on Xenopus embryogenesis, knockdown of xIRE1α could rescue tunicamycin-induced developmental defects and apoptosis. The finding indicates that xIRE1α is not required for embryogenesis but is required for tunicamycin-induced developmental defects and apoptosis in Xenopus laevis.Journal of biomedical research. 07/2014; 28(4):275-81.