The Unfolded Protein Response Is an Important Regulator of Inflammatory Genes in Endothelial Cells

Gargalovic, Peter S.; Gharavi, Nima M.; Clark, Michael J.; Pagnon, Joanne; Yang, Wen-Pin; He, Aiqing; Truong, Amy; Baruch-Oren, Tamar; Berliner, Judith A.; Kirchgessner, Todd G.; Lusis, Aldons J.

doi:10.1161/01.atv.0000242903.41158.a1

Cited by 318 publications

(306 citation statements)

References 33 publications

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“…In the past decade, the ER has been identified as an important regulator of metabolic processes,35 and Gargalovic et al were among the first to directly link ER stress to endothelial disturbances 36. Experimental studies in cultured endothelial cells have demonstrated that chemically induced ER stress causes endothelial dysfunction and insulin resistance 37, 38.…”

Section: Discussionmentioning

confidence: 99%

Liraglutide Treatment Reduces Endothelial Endoplasmic Reticulum Stress and Insulin Resistance in Patients With Diabetes Mellitus

Bretón‐Romero

Weisbrod

Feng

et al. 2018

JAHA

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BackgroundPrior studies have shown that nutrient excess induces endoplasmic reticulum (ER) stress in nonvascular tissues from patients with diabetes mellitus (DM). ER stress and the subsequent unfolded protein response may be protective, but sustained activation may drive vascular injury. Whether ER stress contributes to endothelial dysfunction in patients with DM remains unknown.Methods and ResultsTo characterize vascular ER stress, we isolated endothelial cells from 42 patients with DM and 37 subjects without DM. Endothelial cells from patients with DM displayed higher levels of ER stress markers compared with controls without DM. Both the early adaptive response, evidenced by higher phosphorylated protein kinase–like ER eukaryotic initiation factor‐2a kinase and inositol‐requiring ER‐to‐nucleus signaling protein 1 (P=0.02, P=0.007, respectively), and the chronic ER stress response evidenced by higher C/EBPα‐homologous protein (P=0.02), were activated in patients with DM. Higher inositol‐requiring ER‐to‐nucleus signaling protein 1 activation was associated with lower flow–mediated dilation, consistent with endothelial dysfunction (r=0.53, P=0.02). Acute treatment with liraglutide, a glucagon‐like peptide 1 receptor agonist, reduced p‐inositol‐requiring ER‐to‐nucleus signaling protein 1 (P=0.01), and the activation of its downstream target c‐jun N‐terminal kinase (P=0.025) in endothelial cells from patients with DM. Furthermore, liraglutide restored insulin‐stimulated endothelial nitric oxide synthase activation in patients with DM (P=0.019).ConclusionsIn summary, our data suggest that ER stress contributes to vascular insulin resistance and endothelial dysfunction in patients with DM. Further, we have demonstrated that liraglutide ameliorates ER stress, decreases c‐jun N‐terminal kinase activation and restores insulin‐mediated endothelial nitric oxide synthase activation in endothelial cells from patients with DM.

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Section: Discussionmentioning

confidence: 99%

Liraglutide Treatment Reduces Endothelial Endoplasmic Reticulum Stress and Insulin Resistance in Patients With Diabetes Mellitus

Bretón‐Romero

Weisbrod

Feng

et al. 2018

JAHA

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“…First, a profound increase in IRE1 phosphorylation and XBP1s expression is observed in atherosclerotic plaques of mice and humans (8,10). Second, mechanical sheer stresses activate IRE1, whereas cardiovascular disease risk factors, such as oxidized phospholipids and homocysteine, induce both IRE1 and PERK (5,(25)(26)(27)(28)(29). Third, experimentally sustained Xbp1 mRNA splicing in the vessel wall promotes atherosclerosis, whereas its ablation ameliorates hypercholesterolemia in obese or apolipoprotein E-deficient (ApoE −/− ) mice (10,30).…”

mentioning

confidence: 99%

Targeting IRE1 with small molecules counteracts progression of atherosclerosis

Tufanlı

Telkoparan-Akillilar

Acosta‐Alvear

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

167

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Metaflammation, an atypical, metabolically induced, chronic lowgrade inflammation, plays an important role in the development of obesity, diabetes, and atherosclerosis. An important primer for metaflammation is the persistent metabolic overloading of the endoplasmic reticulum (ER), leading to its functional impairment. Activation of the unfolded protein response (UPR), a homeostatic regulatory network that responds to ER stress, is a hallmark of all stages of atherosclerotic plaque formation. The most conserved ERresident UPR regulator, the kinase/endoribonuclease inositol-requiring enzyme 1 (IRE1), is activated in lipid-laden macrophages that infiltrate the atherosclerotic lesions. Using RNA sequencing in macrophages, we discovered that IRE1 regulates the expression of many proatherogenic genes, including several important cytokines and chemokines. We show that IRE1 inhibitors uncouple lipid-induced ER stress from inflammasome activation in both mouse and human macrophages. In vivo, these IRE1 inhibitors led to a significant decrease in hyperlipidemia-induced IL-1β and IL-18 production, lowered T-helper type-1 immune responses, and reduced atherosclerotic plaque size without altering the plasma lipid profiles in apolipoprotein E-deficient mice. These results show that pharmacologic modulation of IRE1 counteracts metaflammation and alleviates atherosclerosis.endoplasmic reticulum stress | unfolded protein response | metaflammation | lipotoxicity | atherosclerosis C omplex molecular interactions between environment, diet, and genetics that take place at the metabolic and immune interface provoke a low-grade, chronic inflammatory responsemetaflammation-that engages cells of the immune system (macrophages, neutrophils, and lymphocytes) and metabolic tissues (adipocytes, hepatocytes, and pancreatic cells) (1). An important primer for metaflammation is chronic metabolic overloading of organelles, such as the endoplasmic reticulum (ER) and mitochondria, which results in impairment of their functions (2).The ER serves essential cellular functions that include the synthesis and folding of secreted and transmembrane proteins, calcium storage, and lipid synthesis for membrane biogenesis or energy storage. Disruption of any of these functions leads to ER stress and the subsequent activation of an elaborate network of adaptive responses, collectively known as the unfolded protein response (UPR) (3). The UPR reestablishes homeostasis through both transcriptional and translational layers of control. The UPR signals through three mechanistically distinct branches that are initiated by the ER-resident protein folding sensors inositolrequiring enzyme 1 (IRE1), protein kinase RNA-like endoplasmic reticulum kinase (PERK), and activating transcription factor 6 (ATF6) (3).IRE1 controls the phylogenetically most conserved branch of the UPR found from fungi to metazoans. It has an ER-lumenal sensor domain that recognizes unfolded peptides and cytosolic kinase and endoribonuclease (RNase) domains that relay the information to downstrea...

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“…It has also been reported that there is a link between XBP1 and human disease (16,17). Although ER stress is reported to be involved in atherosclerosis (18)(19)(20)(21)(22), the role of XBP1 in vascular disease has not been examined in detail. In the present study, we demonstrated that disturbed flow induces XBP1 splicing and sustained activation that led to EC apoptosis and the formation of atherosclerotic lesion in ApoE Ϫ/Ϫ mice.…”

mentioning

confidence: 99%

Sustained activation of XBP1 splicing leads to endothelial apoptosis and atherosclerosis development in response to disturbed flow

Zeng

Zampetaki

Margariti

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

195

183

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X-box binding protein 1 (XBP1) is a key signal transducer in endoplasmic reticulum stress response, and its potential role in the atherosclerosis development is unknown. This study aims to explore the impact of XBP1 on maintaining endothelial integrity related to atherosclerosis and to delineate the underlying mechanism. We found that XBP1 was highly expressed at branch points and areas of atherosclerotic lesions in the arteries of ApoE ؊/؊ mice, which was related to the severity of lesion development. In vitro study using human umbilical vein endothelial cells (HUVECs) indicated that disturbed flow increased the activation of XBP1 expression and splicing. Overexpression of spliced XBP1 induced apoptosis of HUVECs and endothelial loss from blood vessels during ex vivo cultures because of caspase activation and down-regulation of VE-cadherin resulting from transcriptional suppression and matrix metalloproteinase-mediated degradation. Reconstitution of VEcadherin by Ad-VEcad significantly increased Ad-XBP1s-infected HUVEC survival. Importantly, Ad-XBP1s gene transfer to the vessel wall of ApoE ؊/؊ mice resulted in development of atherosclerotic lesions after aorta isografting. These results indicate that XBP1 plays an important role in maintaining endothelial integrity and atherosclerosis development, which provides a potential therapeutic target to intervene in atherosclerosis.caspase ͉ endothelial integrity ͉ Ve-cadherin ͉ vessel graft ͉ mouse model A therosclerosis is a leading cause of death worldwide (1, 2).Accumulating evidence suggests that atherosclerosis is a multifactorial disease that can be initiated by risk factors (3-6). An important feature of atherosclerosis is its geographic distribution along the artery wall, i.e., occurring more frequently at curved or branching points in the vasculature, indicating that the flow pattern exerts an important role in the development of atherosclerotic lesions (7,8).Endothelial cells (ECs) are key cellular components of blood vessels, functioning as selectively permeable barriers between blood and tissues. It is believed that risk factors induce EC apoptosis, leading to the denudation or dysfunction of the intact endothelial monolayer, which causes lipid accumulation, monocyte adhesion, and inflammatory reactions that initiate atherosclerotic lesion (5, 9-12). Although information on risk factorinduced atherosclerosis has been accumulating, the underlying mechanism remains unclear.The X-box binding protein 1 (XBP1) was originally identified as a bZIP protein capable of binding to the cis-acting X box present in the promoter regions of human major histocompatibility complex class II genes (13) and is known to be essential for liver growth and B lymphocyte differentiation (14,15). In mammalian cells, XBP1 is a key signal transducer in the endoplasmic reticulum (ER) stress response. It has also been reported that there is a link between XBP1 and human disease (16,17). Although ER stress is reported to be involved in atherosclerosis (18)(19)(20)(21)(22), the role of XB...

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The Unfolded Protein Response Is an Important Regulator of Inflammatory Genes in Endothelial Cells

Cited by 318 publications

References 33 publications

Liraglutide Treatment Reduces Endothelial Endoplasmic Reticulum Stress and Insulin Resistance in Patients With Diabetes Mellitus

Liraglutide Treatment Reduces Endothelial Endoplasmic Reticulum Stress and Insulin Resistance in Patients With Diabetes Mellitus

Targeting IRE1 with small molecules counteracts progression of atherosclerosis

Sustained activation of XBP1 splicing leads to endothelial apoptosis and atherosclerosis development in response to disturbed flow

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