scholarly journals Perfluorooctanoic Acid Promotes Pancreatic Β Cell Dysfunction and Apoptosis Through ER Stress and the ATF4/CHOP/TRIB3 Pathway

Author(s):  
Xiaowei He ◽  
Dan Wu ◽  
Yanan Xu ◽  
Yaqin Zhang ◽  
Yue Sun ◽  
...  

Abstract Perfluorooctanoic acid (PFOA), a widely used chemical substance, causes an increased risk of human type 2 diabetes (T2D) through a currently unknown mechanism. The aim of the present study was to investigate whether PFOA regulates the functions of pancreatic β cells, which are specialized for biosynthesis and secretion of insulin, and to reveal the underlying mechanism. Treatment of the MIN6 β-cell line with PFOA caused a time- and dose-dependent inhibition of cell viability in CCK-8 assays. Annexin V/PI and TUNEL staining results confirmed that exposure to a high PFOA dose (500 μM) promoted apoptosis of MIN6 cells, while a low dose (300 μM) had no effects on β-cell survival. PFOA treatment, even at a low dose, diminished glucose-stimulated insulin secretion (GSIS) in both primary islet perfusion and MIN6 cell experiments. Bulk RNA-sequencing data showed a significantly increased expression of endoplasmic reticulum (ER) stress-associated genes, with tribbles homolog 3 (Trib3) ranking first among the altered genes. Activation of ER stress pathways was verified by qRT-PCR assays, and the ATF4/CHOP/TRIB3 pathway contributed to PFOA-induced β-cell damage. Inhibition of TRIB3 expression significantly protected MIN6 cells from PFOA-induced GSIS defects and apoptosis by ameliorating ER stress. These findings reveal a link between ER stress and PFOA-induced β-cell defects, opening up an entirely new set of questions about the pathogenesis of T2D due to environmental chemicals.

2008 ◽  
Vol 294 (3) ◽  
pp. E540-E550 ◽  
Author(s):  
Elida Lai ◽  
George Bikopoulos ◽  
Michael B. Wheeler ◽  
Maria Rozakis-Adcock ◽  
Allen Volchuk

Chronic exposure to elevated saturated free fatty acid (FFA) levels has been shown to induce endoplasmic reticulum (ER) stress that may contribute to promoting pancreatic β-cell apoptosis. Here, we compared the effects of FFAs on apoptosis and ER stress in human islets and two pancreatic β-cell lines, rat INS-1 and mouse MIN6 cells. Isolated human islets cultured in vitro underwent apoptosis, and markers of ER stress pathways were elevated by chronic palmitate exposure. Palmitate also induced apoptosis in MIN6 and INS-1 cells, although the former were more resistant to both apoptosis and ER stress. MIN6 cells were found to express significantly higher levels of ER chaperone proteins than INS-1 cells, which likely accounts for the ER stress resistance. We attempted to determine the relative contribution that ER stress plays in palmitate-induced β-cell apoptosis. Although overexpressing GRP78 in INS-1 cells partially reduced susceptibility to thapsigargin, this failed to reduce palmitate-induced ER stress or apoptosis. In INS-1 cells, palmitate induced apoptosis at concentrations that did not result in significant ER stress. Finally, MIN6 cells depleted of GRP78 were more susceptible to tunicamycin-induced apoptosis but not to palmitate-induced apoptosis compared with control cells. These results suggest that ER stress is likely not the main mechanism involved in palmitate-induced apoptosis in β-cell lines. Human islets and MIN6 cells were found to express high levels of stearoyl-CoA desaturase-1 compared with INS-1 cells, which may account for the decreased susceptibility of these cells to the cytotoxic effects of palmitate.


2015 ◽  
Vol 466 (3) ◽  
pp. 300-305 ◽  
Author(s):  
Jie Wang ◽  
Mi-Young Song ◽  
Joo Young Lee ◽  
Keun Sang Kwon ◽  
Byung-Hyun Park

2015 ◽  
Vol 290 (34) ◽  
pp. 20687-20699 ◽  
Author(s):  
Cong Yu ◽  
Shang Cui ◽  
Chen Zong ◽  
Weina Gao ◽  
Tongfu Xu ◽  
...  

The role of NR4A1 in apoptosis is controversial. Pancreatic β-cells often face endoplasmic reticulum (ER) stress under adverse conditions such as high free fatty acid (FFA) concentrations and sustained hyperglycemia. Severe ER stress results in β-cell apoptosis. The aim of this study was to analyze the role of NR4A1 in ER stress-mediated β-cell apoptosis and to characterize the related mechanisms. We confirmed that upon treatment with the ER stress inducers thapsigargin (TG) or palmitic acid (PA), the mRNA and protein levels of NR4A1 rapidly increased in both MIN6 cells and mouse islets. NR4A1 overexpression in MIN6 cells conferred resistance to cell loss induced by TG or PA, as assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and TUNEL assays indicated that NR4A1 overexpression also protected against ER stress-induced apoptosis. This conclusion was further confirmed by experiments exploiting siRNA to knockdown NR4A1 expression in MIN6 cells or exploiting NR4A1 knock-out mice. NR4A1 overexpression in MIN6 cells reduced C/EBP homologous protein (CHOP) expression and Caspase3 activation induced by TG or PA. NR4A1 overexpression in MIN6 cells or mouse islets resulted in Survivin up-regulation. A critical regulatory element was identified in Survivin promoter (−1872 bp to −1866 bp) with a putative NR4A1 binding site; ChIP assays demonstrated that NR4A1 physically associates with the Survivin promoter. In conclusion, NR4A1 protects pancreatic β-cells against ER stress-mediated apoptosis by up-regulating Survivin expression and down-regulating CHOP expression, which we termed as “positive and negative regulation.”


2021 ◽  
Vol 12 ◽  
Author(s):  
Jarin T. Snyder ◽  
Christine Darko ◽  
Rohit B. Sharma ◽  
Laura C. Alonso

Aging is associated with loss of proliferation of the insulin-secreting β-cell, a possible contributing factor to the increased prevalence of type 2 diabetes in the elderly. Our group previously discovered that moderate endoplasmic reticulum (ER) stress occurring during glucose exposure increases the adaptive β-cell proliferation response. Specifically, the ATF6α arm of the tripartite Unfolded Protein Response (UPR) promotes β-cell replication in glucose excess conditions. We hypothesized that β-cells from older mice have reduced proliferation due to aberrant UPR signaling or an impaired proliferative response to ER stress or ATF6α activation. To investigate, young and old mouse islet cells were exposed to high glucose with low-dose thapsigargin or activation of overexpressed ATF6α, and β-cell proliferation was quantified by BrdU incorporation. UPR pathway activation was compared by qPCR of target genes and semi-quantitative Xbp1 splicing assay. Intriguingly, although old β-cells had reduced proliferation in high glucose compared to young β-cells, UPR activation and induction of proliferation in response to low-dose thapsigargin or ATF6α activation in high glucose were largely similar between young and old. These results suggest that loss of UPR-led adaptive proliferation does not explain the reduced cell cycle entry in old β-cells, and raise the exciting possibility that future therapies that engage adaptive UPR could increase β-cell number through proliferation even in older individuals.


Author(s):  
Li Wu ◽  
Yuncheng Lv ◽  
Ying Lv ◽  
Sunmin Xiang ◽  
Zhibo Zhao ◽  
...  

Abstract Excessive accumulation of cholesterol in β cells initiates endoplasmic reticulum (ER) stress and associated apoptosis. We have reported that excessive uptake of cholesterol by MIN6 cells decreases the expression of secretagogin (SCGN) and then attenuates insulin secretion. Here, we aimed to determine whether cholesterol-induced SCGN decrease is involved in the modulation of ER stress and apoptosis in pancreatic β cells. In this study, MIN6 cells were treated with oxidized low-density lipoprotein (ox-LDL) for 24 h, and then intracellular lipid droplets and cell apoptosis were quantified, and SCGN and ER stress markers were identified by western blot analysis. Furthermore, small interfer RNA (siRNA)-mediated SCGN knockdown and recombinant plasmid-mediated SCGN restoration experiments were performed to confirm the role of SCGN in ER stress and associated cell apoptosis. Finally, the interaction of SCGN with ATF4 was computationally predicted and then validated by a co-immunoprecipitation assay. We found that ox-LDL treatment increased the levels of ER stress markers, such as phosphorylated protein kinase-like endoplasmic reticulum kinase, phosphorylated eukaryotic initiation factor 2 alpha, activating transcription factor 4 (ATF4), and transcription factor CCAAT-enhancer-binding protein homologous protein, and promoted MIN6 cell apoptosis; in addition, the expression of SCGN was downregulated. siRNA-mediated SCGN knockdown exacerbated β-cell ER stress by increasing ATF4 expression. Pretreatment of MIN6 cells with the recombinant SCGN partly antagonized ox-LDL-induced ER stress and apoptosis. Furthermore, a co-immunoprecipitation assay revealed an interaction between SCGN and ATF4 in MIN6 cells. Taken together, these results demonstrated that pancreatic β-cell apoptosis induced by ox-LDL treatment can be attributed, in part, to an SCGN/ATF4-dependent ER stress response.


2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Yanmei Lou ◽  
Muyan Kong ◽  
Leyan Li ◽  
Yu Hu ◽  
Wenjun Zhai ◽  
...  

Type 1 diabetes mellitus (T1DM) is an autoimmune disease characterized by insulin deficiency due to pancreatic β-cell damage and leads to hyperglycemia. The precise molecular mechanisms of the etiology of T1DM are not completely understood. Oxidative stress and the antioxidant status of pancreatic β-cells play a vital role in the pathogenesis and progression of T1DM. The Keap1/Nrf2 signaling pathway plays a critical role in cellular resistance to oxidative stress. This study is aimed at investigating the role of the Keap1/Nrf2 signaling pathway in the progression of T1DM. An alloxan- (ALX-) stimulated T1DM animal model in wild-type (WT) and Nrf2 knockout (Nrf2-/-) C57BL/6J mice and a mouse pancreatic β-cell line (MIN6) were established. Compared with the tolerant (ALX exposure, nondiabetic) WT mice, the sensitive (ALX exposure, diabetic) WT mice exhibited higher blood glucose levels and lower plasma insulin levels. The Keap1/Nrf2 signaling pathway was significantly inhibited in the sensitive WT mice, which was reflected by overexpression of Keap1 and low expression of Nrf2, accompanied by a marked decrease in the expression of the antioxidative enzymes. Compared with WT mice, the Nrf2-/- mice had an increased incidence of T1DM and exhibited more severe pancreatic β-cell damage. The results of in vitro experiments showed that ALX significantly inhibited the viability and proliferation and promoted the apoptosis of MIN6 cells. ALX also markedly increased intracellular ROS production and caused DNA damage in MIN6 cells. In addition, the Keap1/Nrf2 signaling pathway was significantly inhibited in the damaged MIN6 cells. Moreover, Nrf2 silencing by transfection with Nrf2 siRNA markedly exacerbated ALX-induced MIN6 cell injury. Conclusively, this study demonstrates that inhibition of the Keap1/Nrf2 signaling pathway could significantly promote the incidence of T1DM. This study indicates that activation of Keap1/Nrf2 signaling in pancreatic β-cells may be a useful pharmacological strategy for the clinical prevention and treatment of T1DM.


2015 ◽  
Vol 59 (9) ◽  
pp. 1791-1802 ◽  
Author(s):  
Jie Wang ◽  
Mi-Young Song ◽  
Ui-Jin Bae ◽  
Jung Min Lim ◽  
Keun Sang Kwon ◽  
...  

Endocrinology ◽  
2012 ◽  
Vol 153 (7) ◽  
pp. 3017-3028 ◽  
Author(s):  
Michela Miani ◽  
Maikel L. Colli ◽  
Laurence Ladrière ◽  
Miriam Cnop ◽  
Decio L. Eizirik

The prevalence of obesity and type 1 diabetes in children is increasing worldwide. Insulin resistance and augmented circulating free fatty acids associated with obesity may cause pancreatic β-cell endoplasmic reticulum (ER) stress. We tested the hypothesis that mild ER stress predisposes β-cells to an exacerbated inflammatory response when exposed to IL-1β or TNF-α, cytokines that contribute to the pathogenesis of type 1 diabetes. INS-1E cells or primary rat β-cells were exposed to a low dose of the ER stressor cyclopiazonic acid (CPA) or free fatty acids, followed by low-dose IL-1β or TNF-α. ER stress signaling was inhibited by small interfering RNA. Cells were evaluated for proinflammatory gene expression by RT-PCR and ELISA, gene reporter activity, p65 activation by immunofluorescence, and apoptosis. CPA pretreatment enhanced IL-1β- induced, but not TNF-α-induced, expression of chemokine (C-C motif) ligand 2, chemokine (C-X-C motif) ligand 1, inducible nitric oxide synthase, and Fas via augmented nuclear factor κB (NF-κB) activation. X-box binding protein 1 (XBP1) and inositol-requiring enzyme 1, but not CCAAT/enhancer binding protein homologous protein, knockdown prevented the CPA-induced exacerbation of NF-κB-dependent genes and decreased IL-1β-induced NF-κB promoter activity. XBP1 modulated NF-κB activity via forkhead box O1 inhibition. In conclusion, rat β-cells facing mild ER stress are sensitized to IL-1β, generating a more intense and protracted inflammatory response through inositol-requiring enzyme 1/XBP1 activation. These observations link β-cell ER stress to the triggering of exacerbated local inflammation.


2006 ◽  
Vol 291 (2) ◽  
pp. G238-G245 ◽  
Author(s):  
Constanze H. Kubisch ◽  
Maria Dolors Sans ◽  
Thiruvengadam Arumugam ◽  
Stephen A. Ernst ◽  
John A. Williams ◽  
...  

Endoplasmic reticulum (ER) stress mechanisms have been found to play critical roles in a number of diseases states, such as diabetes mellitus and Alzheimer disease, but whether they are involved in acute pancreatitis is unknown. Here we show for the first time that all major ER stress sensing and signaling mechanisms are present in exocrine acini and are activated early in the arginine model of experimental acute pancreatitis. Pancreatitis was induced in rats by intraperitoneal injection of 4.0 g/kg body wt arginine. Pancreatitis severity was assessed by analysis of serum amylase, pancreatic trypsin activity, water content, and histology. ER stress-related molecules PERK, eIF2α, ATF6, XBP-1, BiP, CHOP, and caspase-12 were analyzed. Arginine treatment induced rapid and severe pancreatitis, as indicated by increased serum amylase, pancreatic tissue edema, and acinar cell damage within 4 h. Arginine treatment also caused an early activation of ER stress, as indicated by phosphorylation of PERK and its downstream target eIF2α, ATF6 translocation into the nucleus (within 1 h), and upregulation of BiP (within 4 h). XBP-1 splicing and CHOP expression were observed within 8 h. After 24 h, increased activation of the ER stress-related proapoptotic molecule caspase-12 was observed along with an increase in caspase-3 activity and TdT (terminal deoxynucleotidyl transferase)-mediated dUDP nick-end labeling (TUNEL) staining in exocrine acini. These results indicate that ER stress is an important early acinar cell event that likely contributes to the development of acute pancreatitis in the arginine model.


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