scholarly journals Hypertrophic adipocyte-derived exosomal miR-802-5p contributes to insulin resistance in cardiac myocytes through targeting HSP60

2020 ◽  
Author(s):  
Zhongyuan Wen ◽  
Junfeng Li ◽  
Yalin Fu ◽  
Yuyang Zheng ◽  
Mingke Ma ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Insulin Resistance ◽  
Underlying Mechanism ◽  
Luciferase Reporter ◽  
Heat Shock Protein 60 ◽  
Protein Levels ◽  
Unfolded Protein ◽  
Reporter Assays ◽  
The Unfolded Protein Response ◽  
Protein Response

Abstract Epicardial adipose tissue (EAT) is implicated in insulin resistance, which has been recognized as a strongest predictor of the development of diabetic cardiomyopathy and subsequent heart failure. However, the underlying mechanism remains incompletely understood. Herein, we investigated the effect of hypertrophic adipocytes on cardiac insulin resistance. We found that hypertrophic adipocyte-derived exosomes (h-Exo) induced insulin resistance in NRVMs. Furthermore, h-Exo high-expressed miR-802-5p. Insulin sensitivity of NRVMs was impaired by miR-802-5p mimic but improved by its inhibitor. TargetScan and luciferase reporter assays revealed that heat shock protein 60 (HSP60) was a direct target of miR-802-5p. Both h-Exo and miR-802-5p mimic could downregulate HSP60 protein levels. In addition, HSP60 silencing induced insulin resistance and mitigated the insulin-sensitizing effects of adiponectin. HSP60 depletion also significantly increased the expression levels of CHOP, a marker of the unfolded protein response (UPR), and enhanced oxidative stress, accompanied by the increased phosphorylation of JNK and IRS-1 Ser307. Inhibition of both miR-802-5p and endocytosis abolished the impacts of HSP60 knockdown on the UPR and oxidative stress. In summary, hypertrophic adipocyte-derived exosomal miR-802-5p caused cardiac insulin resistance in NRVMs through downregulating HSP60. These findings provide a novel mechanism by which EAT impairs cardiac function.

scholarly journals Hypertrophic adipocyte-derived exosomal miR-802-5p contributes to insulin resistance in cardiac myocytes through targeting HSP60

2020 ◽  
Author(s):  
Zhongyuan Wen ◽  
Junfeng Li ◽  
Yalin Fu ◽  
Yuyang Zheng ◽  
Mingke Ma ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Insulin Resistance ◽  
Insulin Sensitivity ◽  
Ventricular Myocytes ◽  
Underlying Mechanism ◽  
Neonatal Rat ◽  
Luciferase Reporter ◽  
Heat Shock Protein 60 ◽  
Akt Phosphorylation ◽  
Protein Levels

Abstract Background : Epicardial adipose tissue (EAT) is implicated in insulin resistance, which has been recognized as a strongest predictor of the development of diabetic cardiomyopathy and subsequent heart failure. However, the underlying mechanism remains incompletely understood. Herein, we investigated the effect of hypertrophic adipocytes on cardiac insulin resistance. Methods : Palmitate was used to induce hypertrophic 3T3-L1 adipocytes. Exosomes were purified from normal control or hypertrophic 3T3-L1 adipocyte-associated conditioned medium. Exosome-exposed neonatal rat ventricular myocytes (NRVMs) were treated with insulin to investigate the effects of exosomes on insulin signaling. Insulin sensitivity was evaluated by measuring insulin-stimulated Akt phosphorylation and glucose uptake. SiRNA techniques were used to downregulate protein levels and its efficiency was evaluated by western blot.Results : Hypertrophic adipocyte-derived exosomes (h-Exo) induced insulin resistance in NRVMs. Furthermore, h-Exo high-expressed miR-802-5p. Insulin sensitivity of NRVMs was impaired by miR-802-5p mimic but improved by its inhibitor. TargetScan and luciferase reporter assays revealed that heat shock protein 60 (HSP60) was a direct target of miR-802-5p. Both h-Exo and miR-802-5p mimic could downregulate HSP60 protein levels. In addition, HSP60 silencing induced insulin resistance and mitigated the insulin-sensitizing effects of adiponectin. HSP60 depletion also significantly increased the expression levels of CHOP, a marker of the unfolded protein response (UPR), and enhanced oxidative stress, accompanied by the increased phosphorylation of JNK and IRS-1 Ser307. Inhibition of both miR-802-5p and endocytosis abolished the impacts of HSP60 knockdown on the UPR and oxidative stress. Conclusion : Hypertrophic adipocyte-derived exosomal miR-802-5p caused cardiac insulin resistance in NRVMs through downregulating HSP60. These findings provide a novel mechanism by which EAT impairs cardiac function.

scholarly journals ATF6 is required for efficient rhodopsin clearance and retinal homeostasis in the P23H rho retinitis pigmentosa mouse model

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Eun-Jin Lee ◽  
Priscilla Chan ◽  
Leon Chea ◽  
Kyle Kim ◽  
Randal J. Kaufman ◽  
...  
Keyword(s):  
Retinitis Pigmentosa ◽  
Retinal Degeneration ◽  
Mrna Levels ◽  
Photoreceptor Layer ◽  
Protein Levels ◽  
Unfolded Protein ◽  
Activating Transcription Factor ◽  
The Unfolded Protein Response ◽  
Protein Response

AbstractRetinitis Pigmentosa (RP) is a blinding disease that arises from loss of rods and subsequently cones. The P23H rhodopsin knock-in (P23H-KI) mouse develops retinal degeneration that mirrors RP phenotype in patients carrying the orthologous variant. Previously, we found that the P23H rhodopsin protein was degraded in P23H-KI retinas, and the Unfolded Protein Response (UPR) promoted P23H rhodopsin degradation in heterologous cells in vitro. Here, we investigated the role of a UPR regulator gene, activating transcription factor 6 (Atf6), in rhodopsin protein homeostasis in heterozygous P23H rhodopsin (Rho+/P23H) mice. Significantly increased rhodopsin protein levels were found in Atf6−/−Rho+/P23H retinas compared to Atf6+/−Rho+/P23H retinas at early ages (~ P12), while rhodopsin mRNA levels were not different. The IRE1 pathway of the UPR was hyper-activated in young Atf6−/−Rho+/P23H retinas, and photoreceptor layer thickness was unchanged at this early age in Rho+/P23H mice lacking Atf6. By contrast, older Atf6−/−Rho+/P23H mice developed significantly increased retinal degeneration in comparison to Atf6+/−Rho+/P23H mice in all retinal layers, accompanied by reduced rhodopsin protein levels. Our findings demonstrate that Atf6 is required for efficient clearance of rhodopsin protein in rod photoreceptors expressing P23H rhodopsin, and that loss of Atf6 ultimately accelerates retinal degeneration in P23H-KI mice.

scholarly journals Reduced Paneth cell antimicrobial protein levels correlate with activation of the unfolded protein response in the gut of obese individuals

2011 ◽  
Vol 225 (2) ◽  
pp. 276-284 ◽  
Author(s):  
Caroline M Hodin ◽  
Froukje J Verdam ◽  
Joep Grootjans ◽  
Sander S Rensen ◽  
Fons K Verheyen ◽  
...  
Keyword(s):  
Unfolded Protein Response ◽  
Paneth Cell ◽  
Antimicrobial Protein ◽  
Protein Levels ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response

scholarly journals Exogenous Therapeutics of Microrna-29a Attenuates Development of Hepatic Fibrosis in Cholestatic Animal Model through Regulation of Phosphoinositide 3-Kinase p85 Alpha

2020 ◽  
Vol 21 (10) ◽  
pp. 3636 ◽  
Author(s):  
Ya-Ling Yang ◽  
Feng-Sheng Wang ◽  
Hung-Yu Lin ◽  
Ying-Hsien Huang
Keyword(s):  
Liver Fibrosis ◽  
Unfolded Protein Response ◽  
Luciferase Reporter ◽  
Heat Shock Protein 60 ◽  
Unfolded Protein ◽  
Duct Ligation ◽  
Phosphoinositide 3 Kinase ◽  
Human Liver Cirrhosis ◽  
Protein Response

Recent studies have found that microRNA-29a (miR-29a) levels are significantly lower in fibrotic livers, as shown with human liver cirrhosis. Such downregulation influences the activation of hepatic stellate cells (HSC). Phosphoinositide 3-kinase p85 alpha (PI3KP85α) is implicated in the regulation of proteostasis mitochondrial integrity and unfolded protein response (UPR) and apoptosis in hepatocytes. This study aimed to investigate the potential therapeutic role of miR-29a in a murine bile duct ligation (BDL)-cholestatic injury and liver fibrosis model. Mice were assigned to four groups: sham, BDL, BDL + scramble miRs, and BDL + miR-29a-mimic. Liver fibrosis and inflammation were assessed by histological staining and mRNA/protein expression of representative markers. Exogenous therapeutics of miR-29a in BDL-stressed mice significantly attenuated glutamic oxaloacetic transaminase (GOT)/glutamic-pyruvic transaminase (GPT) and liver fibrosis, and caused a significant downregulation in markers related to inflammation (IL-1β), fibrogenesis (TGF-β1, α-SMA, and COL1α1), autophagy (p62 and LC3B II), mitochondrial unfolded protein response (UPRmt; C/EBP homologous protein (CHOP), heat shock protein 60 (HSP60), and Lon protease-1 (LONP1, a mitochondrial protease), and PI3KP85α within the liver tissue. An in vitro luciferase reporter assay further confirmed that miR-29a mimic directly targets mRNA 3′ untranslated region (UTR) of PI3KP85α to suppress its expression in HepG2 cell line. Our data provide new insights that therapeutic miR-29a improves cholestasis-induced hepatic inflammation and fibrosis and proteotstasis via blocking PI3KP85α, highlighting the potential of miR-29a targeted therapy for liver injury.

scholarly journals Suppression of Mouse AApoAII Amyloidosis Progression by Daily Supplementation with Oxidative Stress Inhibitors

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Jian Dai ◽  
Xin Ding ◽  
Hiroki Miyahara ◽  
Zhe Xu ◽  
Xiaoran Cui ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Protein Misfolding ◽  
Amyloid Fibrils ◽  
Treatment Strategies ◽  
Amyloid Deposition ◽  
Unfolded Protein ◽  
Antioxidative Effects ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Protein Misfolding And Aggregation

Amyloidosis is a group of diseases characterized by protein misfolding and aggregation to form amyloid fibrils and subsequent deposition within various tissues. Previous studies have indicated that amyloidosis is often associated with oxidative stress. However, it is not clear whether oxidative stress is involved in the progression of amyloidosis. We administered the oxidative stress inhibitors tempol and apocynin via drinking water to the R1.P1-Apoa2c mouse strain induced to develop mouse apolipoprotein A-II (AApoAII) amyloidosis and found that treatment with oxidative stress inhibitors led to reduction in AApoAII amyloidosis progression compared to an untreated group after 12 weeks, especially in the skin, stomach, and liver. There was no effect on ApoA-II plasma levels or expression of Apoa2 mRNA. Detection of the lipid peroxidation markers 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA) revealed that the antioxidative effects of the treatments were most obvious in the skin, stomach, and liver, which contained higher levels of basal oxidative stress. Moreover, the unfolded protein response was reduced in the liver and was associated with a decrease in oxidative stress and amyloid deposition. These results suggest that antioxidants can suppress the progression of AApoAII amyloid deposition in the improved microenvironment of tissues and that the effect may be related to the levels of oxidative stress in local tissues. This finding provides insights for antioxidative stress treatment strategies for amyloidosis.

scholarly journals The unfolded protein response in relation to mitochondrial biogenesis in skeletal muscle cells

2017 ◽  
Vol 312 (5) ◽  
pp. C583-C594 ◽  
Author(s):  
Zahra S. Mesbah Moosavi ◽  
David A. Hood
Keyword(s):  
Er Stress ◽  
Mitochondrial Biogenesis ◽  
Contractile Activity ◽  
Muscle Cells ◽  
Unfolded Proteins ◽  
Protein Levels ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Mitochondrial Adaptations

Mitochondria comprise both nuclear and mitochondrially encoded proteins requiring precise stoichiometry for their integration into functional complexes. The augmented protein synthesis associated with mitochondrial biogenesis results in the accumulation of unfolded proteins, thus triggering cellular stress. As such, the unfolded protein responses emanating from the endoplasmic reticulum (UPRER) or the mitochondrion (UPRMT) are triggered to ensure correct protein handling. Whether this response is necessary for mitochondrial adaptations is unknown. Two models of mitochondrial biogenesis were used: muscle differentiation and chronic contractile activity (CCA) in murine muscle cells. After 4 days of differentiation, our findings depict selective activation of the UPRMTin which chaperones decreased; however, Sirt3 and UPRERmarkers were elevated. To delineate the role of ER stress in mitochondrial adaptations, the ER stress inhibitor TUDCA was administered. Surprisingly, mitochondrial markers COX-I, COX-IV, and PGC-1α protein levels were augmented up to 1.5-fold above that of vehicle-treated cells. Similar results were obtained in myotubes undergoing CCA, in which biogenesis was enhanced by ~2–3-fold, along with elevated UPRMTmarkers Sirt3 and CPN10. To verify whether the findings were attributable to the terminal UPRERbranch directed by the transcription factor CHOP, cells were transfected with CHOP siRNA. Basally, COX-I levels increased (~20%) and COX-IV decreased (~30%), suggesting that CHOP influences mitochondrial composition. This effect was fully restored by CCA. Therefore, our results suggest that mitochondrial biogenesis is independent of the terminal UPRER. Under basal conditions, CHOP is required for the maintenance of mitochondrial composition, but not for differentiation- or CCA-induced mitochondrial biogenesis.

Irestatin, a potent inhibitor of IRE1α and the unfolded protein response, is a hypoxia-selective cytotoxin and impairs tumor growth

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 3514-3514 ◽  
Author(s):  
D. Feldman ◽  
A. C. Koong
Keyword(s):  
Tumor Growth ◽  
Er Stress ◽  
Unfolded Protein Response ◽  
Luciferase Activity ◽  
Single Agent ◽  
Luciferase Reporter ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Cells Cultured

3514 Background: The unfolded protein response (UPR) is an adaptive response to the toxic accumulation of misfolded proteins in the endoplasmic reticulum (ER), and is activated in solid tumors. IRE1a is a core component of the UPR and responds to ER stress through activation of its dual kinase and endonuclease domains. The IRE1a endonuclease splices the mRNA for XBP-1, generateing a potent transcription factor that is required for tumor growth. Methods: We developed a fibrosarcoma cell line expressing a fusion of unprocessed XBP-1 inserted upstream of firefly luciferase. Under ER stress, IRE1a catalyzes the removal of a 26-nt intronic sequence from the XBP-1 mRNA, introducing a shift in reading frame that permits translation of luciferase. We screened a chemical library of 66,000 small molecules for inhibitors of XBP-luciferase activity and identified 12 molecules, termed irestatins, which consistently inhibited the IRE1a signaling module without affecting the activity of a control CMV-luciferase reporter. We pursued several of the most potent irestatins, including irestatin 9389, which inhibited XBP-luciferase activity with an IC50 of ∼25 nM. Results: Irestatin-mediated inhibition of the IRE1a endonuclease impairs the growth of malignant myeloma cells and inhibits the survival of oxygen-starved tumor cells in vitro. Exposure to irestatin 9389 (2.5 μM) had a negligible effect on the survival of HT1080 cells cultured under normal oxygen conditions. However, in cells cultured under hypoxia for 48 hours, irestatin 9389 inhibited colony formation by nearly 80-fold (48% vs. 0.62%). A two-week course of treatment with single-agent irestatin 9389 (50 mg/kg) administered every other day by i.p. bolus injection was well tolerated and strongly inhibited the growth of subcutaneous HT1080 tumor xenografts (1790 ± 380 mm3 vs. 480 ± 210 mm3; P<0.01). Conclusion: Irestatins define a novel class of hypoxia- and ER stress-selective agents targeted to the underlying physiological response to the tumor microenvironment. Intratumoral inhibition of the UPR can potentiate cell death and impair tumor growth. Molecular intervention against central components of the UPR may represent an effective therapeutic strategy in cancer treatment. No significant financial relationships to disclose.

scholarly journals Transcription factor ATF4 directs basal and stress-induced gene expression in the unfolded protein response and cholesterol metabolism in the liver

2016 ◽  
Vol 27 (9) ◽  
pp. 1536-1551 ◽  
Author(s):  
Michael E. Fusakio ◽  
Jeffrey A. Willy ◽  
Yongping Wang ◽  
Emily T. Mirek ◽  
Rana J. T. Al Baghdadi ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Gene Expression ◽  
Transcription Factor ◽  
Er Stress ◽  
Unfolded Protein Response ◽  
Cholesterol Metabolism ◽  
Unfolded Protein ◽  
Expression Of Genes ◽  
The Unfolded Protein Response ◽  
Protein Response

Disturbances in protein folding and membrane compositions in the endoplasmic reticulum (ER) elicit the unfolded protein response (UPR). Each of three UPR sensory proteins—PERK (PEK/EIF2AK3), IRE1, and ATF6—is activated by ER stress. PERK phosphorylation of eIF2 represses global protein synthesis, lowering influx of nascent polypeptides into the stressed ER, coincident with preferential translation of ATF4 (CREB2). In cultured cells, ATF4 induces transcriptional expression of genes directed by the PERK arm of the UPR, including genes involved in amino acid metabolism, resistance to oxidative stress, and the proapoptotic transcription factor CHOP (GADD153/DDIT3). In this study, we characterize whole-body and tissue-specific ATF4-knockout mice and show in liver exposed to ER stress that ATF4 is not required for CHOP expression, but instead ATF6 is a primary inducer. RNA-Seq analysis indicates that ATF4 is responsible for a small portion of the PERK-dependent UPR genes and reveals a requirement for expression of ATF4 for expression of genes involved in oxidative stress response basally and cholesterol metabolism both basally and under stress. Consistent with this pattern of gene expression, loss of ATF4 resulted in enhanced oxidative damage, and increased free cholesterol in liver under stress accompanied by lowered cholesterol in sera.

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