XBP 1-Deficiency Abrogates Neointimal Lesion of Injured Vessels Via Cross Talk With the PDGF Signaling

Current state of epigenetics in giant cell arteritis: Focus on microRNA dysregulation

Giant cell arteritis (GCA) is a primary systemic vasculitis affecting the elderly, characterized by a granulomatous vessel wall inflammation of large- and medium-sized arteries. The immunopathology of GCA is complex, involving both the innate and adaptive arms of the immune system, where a maladaptive inflammatory-driven vascular repair process ultimately results in vessel wall thickening, intramural vascular smooth muscle cell proliferation, neovascularization and vessel lumen occlusion, which can lead to serious ischemic complications such as visual loss and ischemic stroke. Over the past decade, microRNA (miRNA) dysregulation has been highlighted as an important contributing factor underlying the pathogenesis of GCA. Since current understanding of miRNA involvement in GCA remains largely based on extrapolation of previously determined miRNA functions in vitro or in loss- or gain-of-function studies, an overall insight into the role of miRNA alteration in GCA pathophysiology remains limited. In this narrative review, we summarize the current knowledge on aberrantly expressed miRNAs in GCA and thoroughly discuss the impact of their altered regulatory role in the context of GCA setting. Furthermore, we address challenges and future perspectives in utilization of miRNA-based diagnostic and prognostic biomarkers of GCA in clinical settings.

Emerging role of IRE1α in vascular diseases

A mounting body of evidence suggests that the endoplasmic reticulum stress and the unfolded protein response are involved in the underlying mechanisms responsible for vascular diseases. Inositol-requiring protein 1α (IRE1α), the most ancient branch among the UPR-related signaling pathways, can possess both serine/threonine kinase and endoribonuclease (RNase) activity and can perform physiological and pathological functions. The IRE1α-signaling pathway plays a critical role in the pathology of various vascular diseases. In this review, we provide a general overview of the physiological function of IRE1α and its pathophysiological role in vascular diseases.

Targeting PDGF/PDGFR Signaling Pathway by microRNA, lncRNA, and circRNA for Therapy of Vascular Diseases: A Narrow Review

Despite the significant progress in diagnostic and therapeutic strategies, vascular diseases, such as cardiovascular diseases (CVDs) and respiratory diseases, still cannot be successfully eliminated. Vascular cells play a key role in maintaining vascular homeostasis. Notably, a variety of cells produce and secrete platelet-derived growth factors (PDGFs), which promote mitosis and induce the division, proliferation, and migration of vascular cells including vascular smooth muscle cells (SMCs), aortic SMCs, endothelial cells, and airway SMCs. Therefore, PDGF/PDGR receptor signaling pathways play vital roles in regulating the homeostasis of blood vessels and the onset and development of CVDs, such as atherosclerosis, and respiratory diseases including asthma and pulmonary arterial hypertension. Recently, accumulating evidence has demonstrated that microRNA, long-chain non-coding RNA, and circular RNA are involved in the regulation of PDGF/PDGFR signaling pathways through competitive interactions with target mRNAs, contributing to the occurrence and development of the above-mentioned diseases. These novel findings are useful for laboratory research and clinical studies. The aim of this article is to conclude the recent progresses in this field, particular the mechanisms of action of these non-coding RNAs in regulating vascular remodeling, providing potential strategies for the diagnosis, prevention, and treatment of vascular-dysfunction-related diseases, particularly CVDs and respiratory diseases.

Crosstalk between endoplasmic reticulum stress and non-coding RNAs in cardiovascular diseases

Cells are exposed to various pathological stimulus within the cardiovascular system that challenge cells to adapt and survive. Several of these pathological stimulus alter the normal function of the endoplasmic reticulum (ER), leading to the accumulation of unfolded and misfolded proteins, thus triggering the unfolded protein response (UPR) to cope with the stress or trigger apoptosis of damaged cells. Downstream components of the UPR regulate transcription and translation reprogramming to ensure selective gene expression in response to pathological stimulus, including the expression of non-coding RNAs (ncRNAs). The ncRNAs play crucial roles in regulating transcription and translation, and their aberrant expression is associated with the development of cardiovascular disease (CVD). Notably, ncRNAs and ER stress can modulate each other and synergistically affect the development of CVD. Therefore, studying the interaction between ER stress and ncRNAs is necessary for effective prevention and treatment of CVD. In this review, we discuss the UPR signaling pathway and ncRNAs followed by the interplay regulation of ER stress and ncRNAs in CVD, which provides further insights into the understanding of the pathogenesis of CVD and therapeutic strategies. This article is categorized under: RNA in Disease and Development > RNA in Disease.

The Role of TGF-β3 in Radiation Response

Transforming growth factor-beta 3 (TGF-β3) is a ubiquitously expressed multifunctional cytokine involved in a range of physiological and pathological conditions, including embryogenesis, cell cycle regulation, immunoregulation, and fibrogenesis. The cytotoxic effects of ionizing radiation are employed in cancer radiotherapy, but its actions also influence cellular signaling pathways, including that of TGF-β3. Furthermore, the cell cycle regulating and anti-fibrotic effects of TGF-β3 have identified it as a potential mitigator of radiation- and chemotherapy-induced toxicity in healthy tissue. This review discusses the radiobiology of TGF-β3, its induction in tissue by ionizing radiation, and its potential radioprotective and anti-fibrotic effects.

Molecular Mechanism Underlying Role of the XBP1s in Cardiovascular Diseases

Spliced X-box binding protein-1 (XBP1s) is a protein that belongs to the cAMP-response element-binding (CREB)/activating transcription factor (ATF) b-ZIP family with a basic-region leucine zipper (bZIP). There is mounting evidence to suggest that XBP1s performs a critical function in a range of different cardiovascular diseases (CVDs), indicating that it is necessary to gain a comprehensive knowledge of the processes involved in XBP1s in various disorders to make progress in research and clinical therapy. In this research, we provide a summary of the functions that XBP1s performs in the onset and advancement of CVDs such as atherosclerosis, hypertension, cardiac hypertrophy, and heart failure. Furthermore, we discuss XBP1s as a novel therapeutic target for CVDs.

Defective endoplasmic reticulum stress response via X box-binding protein 1 is a major cause of poor liver regeneration after partial hepatectomy in mice with non-alcoholic steatohepatitis

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease. Poor regeneration after hepatectomy in NAFLD is well recognized, but the mechanism is unclear. Endoplasmic reticulum (ER) stress plays an important role in the development of NAFLD. Here, we show that an impaired ER stress response contributes to poor liver regeneration in partially hepatectomized mice.

METHODS

Non-alcoholic fatty liver (NAFL) or non-alcoholic steatohepatitis (NASH) was induced in mice using our patented feed and 70% partial hepatectomy (PH) was performed. Mice were sacrificed 0, 4, 8, 24, or 48 hours, or 7 days after PH, and liver regeneration and the mRNA expression of ER stress markers were assessed.

RESULTS

Non-alcoholic fatty liver disease activity score was calculated as 4-6 points for NAFL and 7 points for NASH. NASH was characterized by inflammation and high ER stress marker expression before PH. After PH, NASH mice showed poorer liver regeneration than controls. High expression of proinflammatory cytokine genes was present in NASH mice 4 hours after PH. Xbp1-s mRNA expression was high in control and NAFL mice after PH, but no higher in NASH mice.

CONCLUSIONS

Dysfunction of the ER stress response might be a cause of poor liver regeneration in NASH.

IRE1/XBP1 and endoplasmic reticulum signaling - from basic to translational research for cardiovascular disease

Most cellular protein synthesis, including synthesis of membrane-targeted and secreted proteins, which are critical for cellular and organ crosstalk, takes place at the endoplasmic reticulum (ER), placing the ER at the nexus of cellular signaling, growth, metabolism, and stress sensing. Ample evidence has established the dysregulation of protein homeostasis and the ER unfolded protein response (UPR) in cardiovascular disease. However, the mechanisms of stress sensing and signaling in the ER are incompletely defined. Recent studies have defined notable functions for the inositol-requiring kinase 1 (IRE1)/X-box- binding protein-1 (XBP1) branch of the UPR in regulation of cardiac function. This review highlights the mechanisms underlying IRE1 activation and the IRE1 interactome, which reveals unexpected functions for the UPR and summarizes our current understanding of the functions of IRE1 in cardiovascular disease.

The substitution of SERCA2 redox cysteine 674 promotes pulmonary vascular remodeling by activating IRE1α/XBP1s pathway

Pulmonary hypertension (PH) is a life-threatening disease characterized by pulmonary vascular remodeling, in which hyperproliferation of pulmonary artery smooth muscle cells (PASMCs) plays an important role. The cysteine 674 (C674) in the sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase 2 (SERCA2) is the critical redox regulatory cysteine to regulate SERCA2 activity. Heterozygous SERCA2 C674S knock-in mice (SKI), where one copy of C674 was substituted by serine to represent partial C674 oxidative inactivation, developed significant pulmonary vascular remodeling resembling human PH, and their right ventricular systolic pressure modestly increased with age. In PASMCs, substitution of C674 activated inositol requiring enzyme 1 alpha (IRE1α) and spliced X-box binding protein 1 (XBP1s) pathway, accelerated cell cycle and cell proliferation, which reversed by IRE1α/XBP1s pathway inhibitor 4μ8C. In addition, suppressing the IRE1α/XBP1s pathway prevented pulmonary vascular remodeling caused by substitution of C674. Similar to SERCA2a, SERCA2b is also important to restrict the proliferation of PASMCs. Our study articulates the causal effect of C674 oxidative inactivation on the development of pulmonary vascular remodeling and PH, emphasizing the importance of C674 in restricting PASMC proliferation to maintain pulmonary vascular homeostasis. Moreover, the IRE1α/XBP1s pathway and SERCA2 might be potential targets for PH therapy.

Effect Of XBP1 Deficiency In Cartilage On The Regulatory Network Of LncRNA/circRNA-miRNA-mRNA

X-box binding protein 1(XBP1) is a critical component for unfolded protein response (UPR) in ER stress. According to previous studies performed with different XBP1-deficient mice, the XBP1 gene affects mouse cartilage development and causes other related diseases. However, how the complete transcriptome, including mRNA and ncRNAs, affects the function of cartilage and other tissues when XBP1 is deficient in chondrocytes is unclear. In this study, we aimed to screen the differentially expressed (DE) mRNAs, circRNAs, lncRNAs and miRNAs in XBP1 cartilage-specific knockout (CKO) mice using high throughput sequencing and construct the circRNA-miRNA-mRNA and lncRNA-miRNA-mRNA regulatory networks. DE LncRNAs (DE-LncRNAs), circRNAs (DE-circRNAs), miRNAs (DE-miRNAs), and mRNAs [differentially expressed genes (DEGs)] between the cartilage tissue of XBP1 CKO mice and controls were identified, including 441 DE-LncRNAs, 15 DE-circRNAs, 6 DE-miRNAs, and 477 DEGs. Further, 253,235 lncRNA-miRNA-mRNA networks and 1,822 circRNA-miRNA-mRNA networks were constructed based on the correlation between lncRNAs/circRNAs, miRNAs, mRNAs. The whole transcriptome analysis revealed that XBP1 deficiency in cartilage affects the function of cartilage and other different tissues, as well as associated diseases. Overall, our findings may provide potential biomarkers and mechanisms for the diagnosis and treatment of cartilage and other related diseases.

Galangin inhibits neointima formation induced by vascular injury via regulating the PI3K/AKT/mTOR pathway

Galangin inhibits neointimal hyperplasia after vascular injury by inhibiting vascular smooth muscle cell proliferation, migration, phenotypic switching and promoting autophagy.

X-box Binding Protein 1: An Adaptor in the Pathogenesis of Atherosclerosis

Atherosclerosis (AS), the formation of fibrofatty lesions in the vessel wall, is the primary cause of heart disease and stroke and is closely associated with aging. Disrupted metabolic homeostasis is a primary feature of AS and leads to endoplasmic reticulum (ER) stress, which is an abnormal accumulation of unfolded proteins. By orchestrating signaling cascades of the unfolded protein response (UPR), ER stress functions as a double-edged sword in AS, where adaptive UPR triggers synthetic metabolic processes to restore homeostasis, whereas the maladaptive response programs the cell to the apoptotic pathway. However, little is known regarding their precise coordination. Herein, an advanced understanding of the role of UPR in the pathological process of AS is reviewed. In particular, we focused on a critical mediator of the UPR, X-box binding protein 1 (XBP1), and its important role in balancing adaptive and maladaptive responses. The XBP1 mRNA is processed from the unspliced isoform (XBP1u) to the spliced isoform of XBP1 (XBP1s). Compared with XBP1u, XBP1s predominantly functions downstream of inositol-requiring enzyme-1α (IRE1α) and transcript genes involved in protein quality control, inflammation, lipid metabolism, carbohydrate metabolism, and calcification, which are critical for the pathogenesis of AS. Thus, the IRE1α/XBP1 axis is a promising pharmaceutical candidate against AS.

Unspliced XBP1 Counteracts β-catenin to Inhibit Vascular Calcification

Background: Vascular calcification is a prevalent complication in chronic kidney disease and contributes to increased cardiovascular morbidity and mortality. XBP1 (X-box binding protein 1), existing as the unspliced (XBP1u) and spliced (XBP1s) forms, is a key component of the endoplasmic reticulum stress involved in vascular diseases. However, whether XBP1u participates in the development of vascular calcification remains unclear. Methods: We aim to investigate the role of XBP1u in vascular calcification.XBP1u protein levels were reduced in high phosphate (Pi)-induced calcified vascular smooth muscle cells (VSMCs), calcified aortas from mice with adenine diet-induced chronic renal failure (CRF) and calcified radial arteries from CRF patients. Results: Inhibition of XBP1u rather than XBP1s upregulated in the expression of the osteogenic markers runt-related transcription factor 2 (Runx2) and msh homeobox2 (Msx2), and exacerbated high Pi-induced VSMC calcification, as verified by calcium deposition and Alizarin red S staining. In contrast, XBP1u overexpression in high Pi-induced VSMCs significantly inhibited osteogenic differentiation and calcification. Consistently, SMC-specific XBP1 deficiency in mice markedly aggravated the adenine diet- and 5/6 nephrectomy-induced vascular calcification compared with that in the control littermates. Further interactome analysis revealed that XBP1u bound directly to β-catenin, a key regulator of vascular calcification, via aa 205-230 in its C-terminal degradation domain. XBP1u interacted with β-catenin to promote its ubiquitin-proteasomal degradation and thus inhibited β-catenin/T-cell factor (TCF)-mediated Runx2 and Msx2 transcription. Knockdown of β-catenin abolished the effect of XBP1u deficiency on VSMC calcification, suggesting a β-catenin-mediated mechanism. Moreover, the degradation of β-catenin promoted by XBP1u was independent of glycogen synthase kinase 3β (GSK-3β)-involved destruction complex. Conclusions: Our study identified XBP1u as a novel endogenous inhibitor of vascular calcification by counteracting β-catenin and promoting its ubiquitin-proteasomal degradation, which represents a new regulatory pathway of β-catenin and a promising target for vascular calcification treatment.

Xbp1s-Ddit3 promotes MCT-induced pulmonary hypertension

Pulmonary hypertension (PH) is a life-threatening disease characterized by vascular remodeling. Exploring new therapy target is urgent. The purpose of the present study is to investigate whether and how spliced x-box binding protein 1 (xbp1s), a key component of endoplasmic reticulum stress (ERS), contributes to the pathogenesis of PH. Forty male SD rats were randomly assigned to four groups: Control, Monocrotaline (MCT), MCT+AAV-CTL (control), and MCT+AAV-xbp1s. The xbp1s protein levels were found to be elevated in lung tissues of the MCT group. Intratracheal injection of adeno-associated virus serotype 1 carrying xbp1s shRNA (AAV-xbp1s) to knock down the expression of xbp1s effectively ameliorated the MCT-induced elevation of right ventricular systolic pressure (RVSP), total pulmonary resistance (TPR), right ventricular hypertrophy and medial wall thickness of muscularized distal pulmonary arterioles. The abnormally increased positive staining rates of proliferating cell nuclear antigen (PCNA) and Ki67 and decreased positive staining rates of terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) in pulmonary arterioles were also reversed in the MCT+AAV-xbp1s group. For mechanistic exploration, bioinformatics prediction of the protein network was performed on the STRING database, and further verification was performed by qRT-PCR, Western blots and co-immunoprecipitation (Co-IP). DNA damage-inducible transcript 3 (Ddit3) was identified as a downstream protein that interacted with xbp1s. Overexpression of Ddit3 restored the decreased proliferation, migration and cell viability caused by silencing of xbp1s. The protein level of Ddit3 was also highly consistent with xbp1s in the animal model. Taken together, our study demonstrated that xbp1s-Ddit3 may be a potential target to interfere with vascular remodeling in PH.

Huotan Jiedu Tongluo Decoction Inhibits Balloon-Injury-Induced Carotid Artery Intimal Hyperplasia in the Rat through the PERK-eIF2α-ATF4 Pathway and Autophagy Mediation

In-stent restenosis (ISR) is the main factor affecting the outcome of percutaneous coronary intervention (PCI), and its main pathological feature is neointimal hyperplasia. Huotan Jiedu Tongluo decoction (HTJDTLD) is an effective traditional Chinese medicine (TCM) prescription for the treatment of vascular stenosis diseases. However, the precise anti-ISR mechanism of HTJDTLD remains unclear. Here, we investigated whether HTJDTLD can inhibit the excessive activation of endoplasmic reticulum stress (ERS) and reduce the level of autophagy factors through regulating the PERK-eIF2α-ATF4 pathway, thereby inhibiting the proliferation of the intima of blood vessels damaged by balloon injury (BI) and preventing the occurrence of ISR. In this study, a 2F Fogarty balloon was used to establish a common carotid artery (CCA) BI model in male Sprague-Dawley rats. Then, HTJDTLD (16.33 g/kg/d) or atorvastatin (1.19 mg/kg/d) was administered by gavage. Four weeks later, hematoxylin-eosin (HE) and Masson staining of the injured CCA were performed to observe the histological changes in the CCA. Immunohistochemistry (IHC) was used to assess the proliferation and dedifferentiation of vascular smooth muscle cells (VSMCs) in the CCA. Western blotting and RT-PCR were used to measure the expression of ERS- and autophagy-related proteins and mRNAs in the CCA. The results indicated that HTJDTLD significantly alleviated BI-induced carotid artery intimal hyperplasia and fibrosis and reduced the neointimal area (NIA) and NIA/medial area (MA) ratio. In addition, HTJDTLD inhibited the proliferation and dedifferentiation of VSMCs, reduced the expression of proliferating cell nuclear antigen (PCNA), and increased the smooth-muscle-α-actin- (SMα-actin-) positive area. HTJDTLD also significantly reduced the expression of the ERS-related factors: GRP78, p-PERK/PERK, p-eIF2α/eIF2α, ATF4, and CHOP. In addition, the expression of the autophagy-related factors, Beclin1, LC3B, and ATG12, was significantly decreased. In addition, in vitro experiments showed that HTJDTLD inhibited the above-mentioned ERS signal molecules in human umbilical vein endothelial cells (HUVEC) and rat aortic smooth muscle cells (A7R5) induced by tunicamycin (TM) and played a crucial role in protecting cells from damage. HTJDTLD may be a very promising drug for the treatment of ISR.

The Impact of Endoplasmic Reticulum-Associated Protein Modifications, Folding and Degradation on Lung Structure and Function

The accumulation of unfolded/misfolded proteins in the endoplasmic reticulum (ER) causes ER stress and induces the unfolded protein response (UPR) and other mechanisms to restore ER homeostasis, including translational shutdown, increased targeting of mRNAs for degradation by the IRE1-dependent decay pathway, selective translation of proteins that contribute to the protein folding capacity of the ER, and activation of the ER-associated degradation machinery. When ER stress is excessive or prolonged and these mechanisms fail to restore proteostasis, the UPR triggers the cell to undergo apoptosis. This review also examines the overlooked role of post-translational modifications and their roles in protein processing and effects on ER stress and the UPR. Finally, these effects are examined in the context of lung structure, function, and disease.

Gastric cancer-secreted exosomal X26nt increases angiogenesis and vascular permeability by targeting VE-cadherin

Angiogenesis is closely associated with tumorigenesis, invasion, and metastasis by providing oxygen and nutrients. Recently, increasing evidence indicates that cancer-derived exosomes which contain proteins, coding, and noncoding RNAs (ncRNAs) were shown to have proangiogenic function in cancer. A 26-nt-long ncRNA (X26nt) is generated in the process of inositol-requiring enzyme 1 alpha (IRE1α)-induced unspliced XBP1 splicing. However, the role of X26nt in the angiogenesis of gastric cancer (GC) remains largely unknown. In the present study, we found that X26nt was significantly elevated in GC and GC exosomes. Then, we verified that X26nt could be delivered into human umbilical vein endothelial cells (HUVECs) via GC cell exosomes and promote the proliferation, migration, and tube formation of HUVECs. We revealed that exosomal X26nt decreased vascular endothelial cadherin (VE-cadherin) by directly combining the 3'UTR of VE-cadherin mRNA in HUVECs, thereby increasing vascular permeability. We further demonstrated that X26nt accelerates the tumor growth and angiogenesis in a mouse subcutaneous tumor model. Our findings investigate a unique intercellular communication mediated by cancer-derived exosomes and reveal a novel mechanism of exosomal X26nt in the regulation of tumor vasculature.

PERK Inhibition Promotes Post-angioplasty Re-endothelialization via Modulating SMC Phenotype Changes

BACKGROUND

Drug-eluting stents impair post-angioplasty re-endothelialization thus compromising restenosis prevention while heightening thrombotic risks. We recently found that inhibition of protein kinase RNA-like endoplasmic reticulum kinase (PERK) effectively mitigated both restenosis and thrombosis in rodent models. This motivated us to determine how PERK inhibition impacts re-endothelialization.

METHODS

Re-endothelialization was evaluated in endothelial-denuded rat carotid arteries after balloon angioplasty and periadventitial administration of PERK inhibitor in a hydrogel. To study whether PERK in smooth muscle cells (SMCs) regulates re-endothelialization by paracrinally influencing endothelial cells (ECs), denuded arteries exposing SMCs were lentiviral-infected to silence PERK; in vitro, the extracellular vesicles isolated from the medium of PDGF-activated, PERK-upregulating human primary SMCs were transferred to human primary ECs.

RESULTS

Treatment with PERK inhibitor versus vehicle control accelerated re-endothelialization in denuded arteries. PERK-specific silencing in the denuded arterial wall (mainly SMCs) also enhanced re-endothelialization compared to scrambled shRNA control. In vitro, while medium transfer from PDGF-activated SMCs impaired EC viability and increased the mRNA levels of dysfunctional EC markers, either PERK inhibition or silencing in donor SMCs mitigated these EC changes. Furthermore, CXCL10, a paracrine cytokine detrimental to ECs, was increased by PDGF activation and decreased after PERK inhibition or silencing in SMCs.

CONCLUSIONS

Attenuating PERK activity pharmacologically or genetically provides an approach to accelerating post-angioplasty re-endothelialization in rats. The mechanism may involve paracrine factors regulated by PERK in SMCs that impact neighboring ECs. This study rationalizes future development of PERK-targeted endothelium-friendly vascular interventions.

X-box binding protein 1-mediated COL4A1s secretion regulates communication between vascular smooth muscle and stem/progenitor cells

Vascular smooth muscle cells (VSMCs) contribute to the deposition of extracellular matrix proteins (ECMs), including Type IV collagen, in the vessel wall. ECMs coordinate communication among different cell types, but mechanisms underlying this communication remain unclear. Our previous studies have demonstrated that X-box binding protein 1 (XBP1) is activated and contributes to VSMC phenotypic transition in response to vascular injury. In this study, we investigated the participation of XBP1 in the communication between VSMCs and vascular progenitor cells (VPCs). Immunofluorescence and immunohistology staining revealed that Xbp1 gene was essential for type IV collagen alpha 1 (COL4A1) expression during mouse embryonic development and vessel wall ECM deposition and stem cell antigen 1-positive (Sca1+)-VPC recruitment in response to vascular injury. The Western blot analysis elucidated an Xbp1 gene dose-dependent effect on COL4A1 expression and that the spliced XBP1 protein (XBP1s) increased protease-mediated COL4A1 degradation as revealed by Zymography. RT-PCR analysis revealed that XBP1s in VSMCs not only upregulated COL4A1/2 transcription but also induced the occurrence of a novel transcript variant, soluble type IV collagen alpha 1 (COL4A1s), in which the front part of exon 4 is joined with the rear part of exon 42. Chromatin-immunoprecipitation, DNA/protein pulldown and in vitro transcription demonstrated that XBP1s binds to exon 4 and exon 42, directing the transcription from exon 4 to exon 42. This leads to transcription complex bypassing the internal sequences, producing a shortened COL4A1s protein that increased Sca1+-VPC migration. Taken together, these results suggest that activated VSMCs may recruit Sca1+-VPCs via XBP1s-mediated COL4A1s secretion, leading to vascular injury repair or neointima formation.

MicroRNA-674-5p induced by HIF-1α targets XBP-1 in intestinal epithelial cell injury during endotoxemia

Intestinal mucosal integrity dysfunction during endotoxemia can contribute to translocation of intestinal bacteria and a persistent systemic inflammatory response, which both fuel the pathophysiological development of sepsis or endotoxemia. The pathogenesis of intestinal damage induced by endotoxemia remains poorly understood. Here, we identified the microRNA (miR)-674-5p/X-box binding protein 1 (XBP-1) axis as a critical regulator and therapeutic target in preventing intestinal crypt cell proliferation during endotoxemia. MiR-674-5p was markedly increased in intestinal epithelial cells (IECs) during endotoxemia and its induction depended on hypoxia-inducible factor-1α (HIF-1α). Intriguingly, gene expression microanalysis revealed that expression of XBP-1 was down-regulated in IECs with over-expression of miR-674-5p. miR-674-5p was found to directly target XBP-1 protein expression. Upon in vitro, anti-miR-674-5p enhanced sXBP-1 expression and facilitated intestinal crypt cell proliferation. Blockade of miR-674-5p promoted XBP-1 activity, attenuated intestinal inflammation, and expedited intestinal regeneration, resulting in protection against endotoxemia-induced intestinal injury in mice. More importantly, the survival in endotoxemia mice was significantly improved by inhibiting intestinal miR-674-5p. Collectively, these data indicate that control of a novel miR-674-5p/XBP-1 signaling axis may mitigate endotoxemia -induced intestinal injury.

PERK Inhibition Mitigates Restenosis and Thrombosis: A Potential Low-Thrombogenic Antirestenotic Paradigm

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Drug-eluting stents impede neointimal smooth muscle cell hyperplasia but exacerbate endothelial cell dysfunction and thrombogenicity. It has been a challenge to identify a common target to inhibit both. Findings in this study suggest PERK as such a target.

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A PERK inhibitor administered either via an endovascular (in biomimetic nanocarriers) or perivascular (in hydrogel) route effectively mitigated neointimal hyperplasia in rats.

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Oral gavage of the PERK inhibitor partially preserved the normal blood flow in a mouse model of induced thrombosis.

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Dampening PERK activity inhibited STAT3 while activating SRF in smooth muscle cells, and also reduced prothrombogenic tissue factor and growth impairment of endothelial cells.

Developing endothelial-protective, nonthrombogenic antirestenotic treatments has been a challenge. A major hurdle to this has been the identification of a common molecular target in both smooth muscle cells and endothelial cells, inhibition of which blocks dysfunction of both cell types. The authors’ findings suggest that the PERK kinase could be such a target. Importantly, PERK inhibition mitigated both restenosis and thrombosis in preclinical models, implicating a low-thrombogenic antirestenotic paradigm.

Antagonistic relationship between the unfolded protein response and myocardin-driven transcription in smooth muscle

Smooth muscle cells (SMCs) are characterized by a high degree of phenotypic plasticity. Contractile differentiation is governed by myocardin-related transcription factors (MRTFs), in particular myocardin (MYOCD), and when their drive is lost, the cells become proliferative and synthetic with an expanded endoplasmic reticulum (ER). ER is responsible for assembly and folding of secreted proteins. When the load on the ER surpasses its capacity, three stress sensors (activating transcription factor 6 [ATF6], inositol-requiring enzyme 1α [IRE1α]/X-box binding protein 1 [XBP1], and PERK/ATF4) are activated to expand the ER and increase its folding capacity. This is referred to as the unfolded protein response (UPR). Here, we hypothesized that there is a reciprocal relationship between SMC differentiation and the UPR. Tight negative correlations between SMC markers (MYH11, MYOCD, KCNMB1, SYNPO2) and UPR markers (SDF2L1, CALR, MANF, PDIA4) were seen in microarray data sets from carotid arterial injury, partial bladder outlet obstruction, and bladder denervation, respectively. The UPR activators dithiothreitol (DTT) and tunicamycin (TN) activated the UPR and reduced MYOCD along with SMC markers in vitro. The IRE1α inhibitor 4μ8C counteracted the effect of DTT and TN on SMC markers and MYOCD expression. Transfection of active XBP1s was sufficient to reduce both MYOCD and the SMC markers. MRTFs also antagonized the UPR as indicated by reduced TN and DTT-mediated induction of CRELD2, MANF, PDIA4, and SDF2L1 following overexpression of MRTFs. The latter effect did not involve the newly identified MYOCD/SRF target MSRB3, or reduced production of either XBP1s or cleaved ATF6. The UPR thus counteracts SMC differentiation via the IRE1α/XBP1 arm of the UPR and MYOCD repression.

A histone deacetylase 7-derived peptide promotes vascular regeneration via facilitating 14-3-3γ phosphorylation

Histone deacetylase 7 (HDAC7) plays a pivotal role in the maintenance of the endothelium integrity. In this study, we demonstrated that the intron-containing Hdac7 mRNA existed in the cytosol and that ribosomes bound to a short open reading frame (sORF) within the 5'-terminal noncoding area of this Hdac7 mRNA in response to vascular endothelial growth factor (VEGF) stimulation in the isolated stem cell antigen-1 positive (Sca1⁺ ) vascular progenitor cells (VPCs). A 7-amino acid (7A) peptide has been demonstrated to be translated from the sORF in Sca1⁺ -VPCs in vitro and in vivo. The 7A peptide was shown to receive phosphate group from the activated mitogen-activated protein kinase MEKK1 and transfer it to 14-3-3 gamma protein, forming an MEKK1-7A-14-3-3γ signal pathway downstream VEGF. The exogenous synthetic 7A peptide could increase Sca1⁺ -VPCs cell migration, re-endothelialization in the femoral artery injury, and angiogenesis in hind limb ischemia. A Hd7-7sFLAG transgenic mice line was generated as the loss-of-function model, in which the 7A peptide was replaced by a FLAG-tagged scrabbled peptide. Loss of the endogenous 7A impaired Sca1⁺ -VPCs cell migration, re-endothelialization of the injured femoral artery, and angiogenesis in ischemic tissues, which could be partially rescued by the addition of the exogenous 7A/7Ap peptide. This study provides evidence that sORFs can be alternatively translated and the derived peptides may play an important role in physiological processes including vascular remodeling.

Calorie Restriction Curbs Proinflammation That Accompanies Arterial Aging, Preserving a Youthful Phenotype

Background

Aging exponentially increases the incidence of morbidity and mortality of quintessential cardiovascular disease mainly due to arterial proinflammatory shifts at the molecular, cellular, and tissue levels within the arterial wall. Calorie restriction (CR) in rats improves arterial function and extends both health span and life span. How CR affects the proinflammatory landscape of molecular, cellular, and tissue phenotypic shifts within the arterial wall in rats, however, remains to be elucidated.

Methods and Results

Aortae were harvested from young (6‐month‐old) and old (24‐month‐old) Fischer 344 rats, fed ad libitum and a second group maintained on a 40% CR beginning at 1 month of age. Histopathologic and morphometric analysis of the arterial wall demonstrated that CR markedly reduced age‐associated intimal medial thickening, collagen deposition, and elastin fractionation/degradation within the arterial walls. Immunostaining/blotting showed that CR effectively prevented an age‐associated increase in the density of platelet‐derived growth factor, matrix metalloproteinase type II activity, and transforming growth factor beta 1 and its downstream signaling molecules, phospho‐mothers against decapentaplegic homolog‐2/3 (p‐SMAD‐2/3) in the arterial wall. In early passage cultured vascular smooth muscle cells isolated from AL and CR rat aortae, CR alleviated the age‐associated vascular smooth muscle cell phenotypic shifts, profibrogenic signaling, and migration/proliferation in response to platelet‐derived growth factor.

Conclusions

CR reduces matrix and cellular proinflammation associated with aging that occurs within the aortic wall and that are attributable to platelet‐derived growth factor signaling. Thus, CR reduces the platelet‐derived growth factor–associated signaling cascade, contributing to the postponement of biological aging and preservation of a more youthful aortic wall phenotype.

Endogenous intermedin protects against intimal hyperplasia by inhibiting endoplasmic reticulum stress

Extensive proliferation of vascular smooth muscle cell (VSMC) contributes to intimal hyperplasia following vascular injury, in which endoplasmic reticulum stress (ERS) plays a critical role. Intermedin (IMD) is a vascular paracrine/autocrine peptide exerting numerous beneficial effects in cardiovascular diseases. IMD overexpression could alleviate intimal hyperplasia. Here, we investigated whether endogenous IMD protects against intimal hyperplasia by inhibiting endoplasmic reticulum stress. The mouse left common carotid-artery ligation-injury model was established to induce intimal hyperplasia using IMD^-/-mice and C57BL/6 J wild-type (WT) mice. Platelet-derived growth factor-BB (PDGF-BB) was used to stimulate the proliferation of VSMC. IMD^-/- mice displayed exacerbated intimal hyperplasia induced by complete ligation of the left carotid artery at 14 d and 28 d compared to WT mice. However, IMD-deficiency had no effect on blood pressure, plasma triglyceride, and fasting blood glucose levels in mice. Furthermore, VSMCs derived from IMD^-/- mice showed increased cell proliferation and dramatically elevated levels of glucose regulated protein 78 (GRP78), activating transcription factor 4 (ATF4), ATF6 mRNA under PDGF-BB treatment compared to WT mice-derived VSMCs. In addition, exogenous administration of IMD significantly attenuated PDGF-BB-induced cell proliferation and GRP78, phosphorylase-inositol requiring enzyme 1α, ATF4, and ATF6 protein levels. Thus, endogenous IMD may counteract ERS to exert protective role in response to vascular injury and IMD is expected to be a therapeutic target for the prevention and treatment of restenosis.

MALAT1 rs619586 polymorphism functions as a prognostic biomarker in the management of differentiated thyroid carcinoma

This study aimed to explore the roles of miR-214 and MALAT1 rs619586 polymorphism in the control and survival of differentiated thyroid carcinoma (DTC) via Cox regression analyses. The levels of MALAT1, miR-214, and CTNNB1 in different experimental groups were compared to study the interaction among MALAT1, miR-214, and CTNNB1. MTT and colony assays were used to investigate the role of rs619586 polymorphism in cell growth. The G allele of rs619586 polymorphism obviously decreased the 5-year survival of patients with DTC. Additionally, compared with AA-genotyped patients, patients carrying the AG/GG genotypes of MALAT1 rs619586 polymorphism showed much higher levels of DTC grade and CTNNB1 expression, along with lower levels of MALAT1 and miR-214 expression. Furthermore, the transcription activity of MALAT1 was significantly lowered by the rs619586G allele or miR-214 mimic, while the miR-214 inhibitor upregulated the luciferase activity of MALAT1. Additionally, miR-214 inhibited CTNNB1 expression by targeting CTNNB1 3'-untranslated region. Finally, the G allele of MALAT1 rs619586 polymorphism apparently promoted cell proliferation. Our study indicated that miR-214 inhibited MALAT1 expression by directly binding to the G allele of MALAT1 rs619586 polymorphism, thus inhibiting CTNNB1 expression and promoting cell proliferation in the pathogenesis of DTC. Therefore, MALAT1 rs619586 polymorphism could be used to predict the prognosis of DTC.

A vascular smooth muscle cell X-box binding protein 1 and transglutaminase 2 regulatory circuit limits neointimal hyperplasia

Neointimal hyperplasia, stimulated by injury and certain vascular diseases, promotes artery obstruction and tissue ischemia. In vascular smooth muscle cell (VSMCs), multiple modulators of protein handling machinery regulate intimal hyperplasia. These include elements of the VSMC unfolded protein response to endoplasmic reticulum stress (UPRER), and transglutaminase 2 (TG2), which catalyzes post-translational protein modification. Previous results for deficiency of UPRER-specific mediator XBP1, and of TG2, have been significant, but in multiple instances contradictory, for effects on cultured VSMC function, and, using multiple models, for neointimal hyperplasia in vivo. Here, we engineered VSMC-specific deficiency of XBP1, and studied cultured VSMCs, and neointimal hyperplasia in response to carotid artery ligation in vivo. Intimal area almost doubled in Xbp1fl/fl SM22α-CRE+ mice 21 days post-ligation. Cultured murine Xbp1 deficient VSMCs migrated more in response to platelet derived growth factor (PDGF) than control VSMCs, and had an increased level of inositol-requiring enzyme 1α (Ire1α), a PDGF receptor-binding UPRER transmembrane endonuclease whose substrates include XBP1. Cultured XBP1-deficient VSMCs demonstrated decreased levels of TG2 protein, in association with increased TG2 polyubiquitination, but with increased TG transamidation catalytic activity. Moreover, IRE1α, and TG2-specific transamidation cross-links were increased in carotid artery neointima in Xbp1fl/fl SM22α-CRE+ mice. Cultured TG2-deficient VSMCs had decreased XBP1 associated with increased IRE1α, and increased migration in response to PDGF. Neointimal hyperplasia also was significantly increased in Tgm2fl/fl SM22α-CRE+ mice at 21 days after carotid ligation. In conclusion, a VSMC regulatory circuit between XBP1 and TG2 limits neointimal hyperplasia in response to carotid ligation.

Formononetin protects against balloon injury‑induced neointima formation in rats by regulating proliferation and migration of vascular smooth muscle cells via the TGF‑β1/Smad3 signaling pathway

The present study investigated the effects of formononetin (FMN) against balloon injury‑induced neointima formation in vivo and platelet‑derived growth factor (PDGF)‑BB‑induced proliferation and migration of vascular smooth muscle cells (VSMCs) in vitro, and explored the underlying mechanisms. A rat model of carotid artery injury was established, in order to examine the effects of FMN on balloon injury‑induced neointima formation. Histological observation of the carotid artery tissues was conducted by hematoxylin and eosin staining. VSMC proliferation during neointima formation was observed by proliferating cell nuclear antigen staining. Subsequently, rat aortic VSMCs were isolated, and the effects of FMN on PDGF‑BB‑induced VSMC proliferation and migration were determined using Cell Counting Kit‑8 and Transwell/wound healing assays, respectively. Immunohistochemical and immunocytochemical staining was applied to measure the expression of transforming growth factor (TGF)‑β in carotid artery tissues and VSMCs, respectively. SMAD family member 3 (Smad3)/phosphorylated (p)‑Smad3 expression was examined by western blotting. FMN treatment significantly inhibited the abnormal proliferation of smooth muscle cells in neointima, and alterations to the vascular structure were attenuated. In addition, pretreatment with FMN effectively inhibited the proliferation of PDGF‑BB‑stimulated VSMCs (P<0.05). FMN also reduced the number of cells that migrated to the lower surface of the Transwell chamber and decreased wound‑healing percentage (P<0.05). The expression levels of TGF‑β were decreased by FMN treatment in vivo and in vitro, and Smad3/p‑Smad3 expression was also markedly inhibited. In conclusion, FMN significantly protected against balloon injury‑induced neointima formation in the carotid artery of a rat model; this effect may be associated with the regulation of VSMC proliferation and migration through altered TGF‑β1/Smad3 signaling.

Tollip Negatively Regulates Vascular Smooth Muscle Cell-Mediated Neointima Formation by Suppressing Akt-Dependent Signaling

BACKGROUND

Tollip, a well-established endogenous modulator of Toll-like receptor signaling, is involved in cardiovascular diseases. The aim of this study was to investigate the role of Tollip in neointima formation and its associated mechanisms.

METHODS AND RESULTS

In this study, transient increases in Tollip expression were observed in platelet-derived growth factor-BB-treated vascular smooth muscle cells and following vascular injury in mice. We then applied loss-of-function and gain-of-function approaches to elucidate the effects of Tollip on neointima formation. While exaggerated neointima formation was observed in Tollip-deficient murine neointima formation models, Tollip overexpression alleviated vascular injury-induced neointima formation by preventing vascular smooth muscle cell proliferation, dedifferentiation, and migration. Mechanistically, we demonstrated that Tollip overexpression may exert a protective role in the vasculature by suppressing Akt-dependent signaling, which was further confirmed in rescue experiments using the Akt-specific inhibitor (AKTI).

CONCLUSIONS

Our findings indicate that Tollip protects against neointima formation by negatively regulating vascular smooth muscle cell proliferation, dedifferentiation, and migration in an Akt-dependent manner. Upregulation of Tollip may be a promising strategy for treating vascular remodeling-related diseases.

Unspliced XBP1 Confers VSMC Homeostasis and Prevents Aortic Aneurysm Formation via FoxO4 Interaction

RATIONALE

Although not fully understood, the phenotypic transition of vascular smooth muscle cells exhibits at the early onset of the pathology of aortic aneurysms. Exploring the key regulators that are responsible for maintaining the contractile phenotype of vascular smooth muscle cells (VSMCs) may confer vascular homeostasis and prevent aneurysmal disease. XBP1 (X-box binding protein 1), which exists in a transcriptionally inactive unspliced form (XBP1u) and a spliced active form (XBP1s), is a key component in response to endoplasmic reticular stress. Compared with XBP1s, little is known about the role of XBP1u in vascular homeostasis and disease.

OBJECTIVE

We aim to investigate the role of XBP1u in VSMC phenotypic switching and the pathogenesis of aortic aneurysms.

METHODS AND RESULTS

XBP1u, but not XBP1s, was markedly repressed in the aorta during the early onset of aortic aneurysm in both angiotensin II-infused apolipoprotein E knockout (ApoE-/-) and CaPO4 (calcium phosphate)-induced C57BL/6J murine models, in parallel with a decrease in smooth muscle cell contractile apparatus proteins. In vivo studies revealed that XBP1 deficiency in smooth muscle cells caused VSMC dedifferentiation, enhanced vascular inflammation and proteolytic activity, and significantly aggravated both thoracic and abdominal aortic aneurysms in mice. XBP1 deficiency, but not an inhibition of XBP1 splicing, induced VSMC switching from the contractile phenotype to a proinflammatory and proteolytic phenotype. Mechanically, in the cytoplasm, XBP1u directly associated with the N terminus of FoxO4 (Forkhead box protein O 4), a recognized repressor of VSMC differentiation via the interaction and inhibition of myocardin. Blocking the XBP1u-FoxO4 interaction facilitated nuclear translocation of FoxO4, repressed smooth muscle cell marker genes expression, promoted proinflammatory and proteolytic phenotypic transitioning in vitro, and stimulated aortic aneurysm formation in vivo.

CONCLUSIONS

Our study revealed the pivotal role of the XBP1u-FoxO4-myocardin axis in maintaining the VSMC contractile phenotype and providing protection from aortic aneurysm formation.

Regulation of the unfolded protein response by noncoding RNA

Cells are exposed to various intrinsic and extrinsic stresses in both physiological and pathological conditions. To adapt to those conditions, cells have evolved various mechanisms to cope with the disturbances in protein demand, largely through the unfolded protein response (UPR) in the endoplasmic reticulum (ER), but also through the integrated stress response (ISR). Both responses initiate downstream signaling to transcription factors that, in turn, trigger adaptive programs and/or in the case of prolonged stress, cell death mechanisms. Recently, noncoding RNAs, including microRNA and long noncoding RNA, have emerged as key players in the stress responses. These noncoding RNAs act as both regulators and effectors of the UPR and fine-tune the output of the stress signaling pathways. Although much is known about the UPR and the cross talk that exists between pathways, the contribution of small noncoding RNA has not been fully assessed. Herein we bring together and review the current known functions of noncoding RNA in regulating adaptive pathways in both physiological and pathophysiological conditions, illustrating how they operate within the known UPR functions and contribute to diverse cellular outcomes.

Inositol-Requiring Enzyme 1 Facilitates Diabetic Wound Healing Through Modulating MicroRNAs

Diabetic skin ulcers represent a challenging clinical problem with mechanisms not fully understood. In this study, we investigated the role and mechanism for the primary unfolded protein response (UPR) transducer inositol-requiring enzyme 1 (IRE1α) in diabetic wound healing. Bone marrow-derived progenitor cells (BMPCs) were isolated from adult male type 2 diabetic and their littermate control mice. In diabetic BMPCs, IRE1α protein expression and phosphorylation were repressed. The impaired diabetic BMPC angiogenic function was rescued by adenovirus-mediated expression of IRE1α but not by the RNase-inactive IRE1α or the activated X-box binding protein 1 (XBP1), the canonical IRE1α target. In fact, IRE1α RNase processes a subset of microRNAs (miRs), including miR-466 and miR-200 families, through which IRE1α plays an important role in maintaining BMPC function under the diabetic condition. IRE1α attenuated maturation of miR-466 and miR-200 family members at precursor miR levels through the regulated IRE1α-dependent decay (RIDD) independent of XBP1. IRE1α deficiency in diabetes resulted in a burst of functional miRs from miR-466 and miR-200 families, which directly target and repress the mRNA encoding the angiogenic factor angiopoietin 1 (ANGPT1), leading to decreased ANGPT1 expression and disrupted angiogenesis. Importantly, cell therapies using IRE1α-expressing BMPCs or direct IRE1α gene transfer significantly accelerated cutaneous wound healing in diabetic mice through facilitating angiogenesis. In conclusion, our studies revealed a novel mechanistic basis for rescuing angiogenesis and tissue repair in diabetic wound treatments.

Functional polymorphism of lncRNA MALAT1 contributes to pulmonary arterial hypertension susceptibility in Chinese people

Background:

The long noncoding RNAs (lncRNAs) have gradually been reported to be an important class of RNAs with pivotal roles in regulation of gene expression, and thus are involved in multitudinous human complex diseases. However, the biological functions and precise mechanisms of the majority of lncRNAs are still poorly understood.

Methods:

In the study, we tested genomic variations in lncRNA-metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) loci, and their potentially functional correlationship with pulmonary arterial hypertension (PAH) susceptibility based on a case-control study with a total of 587 PAH patients and 736 healthy controls in southern Chinese.

Results:

We found that the rs619586A>G single nucleotide polymorphism (SNP) was significantly associated with PAH risk. The carriers with G variant genotypes had a decreased risk of PAH (odds ratio [OR]=0.69, 95% confidence interval [CI]=0.53–0.90, p=0.007) compared to the rs619586AA genotype. Further functional experiments indicated that the alteration from rs619586A to G in MALAT1 could directly upregulate X box-binding protein 1 (XBP1) expression via functioning as the competing endogenous RNA (ceRNA) for miR-214, and consequentially inhibiting the vascular endothelial cells proliferation and migration in vitro by shortening S-M phase transition.

Conclusions:

Taken together, our findings propose that functional polymorphism rs619586A>G in MALAT1 gene plays an important role in PAH pathogenesis and may serve as a potential indicator for PAH susceptibility.

Imatinib attenuates cerebrovascular injury and phenotypic transformation after intracerebral hemorrhage in rats

This study explored the hypothesis that intracerebral hemorrhage (ICH) promotes release of diffusible factors that can significantly influence the structure and function of cerebral arteries remote from the site of injury, through action on platelet-derived growth factor (PDGF) receptors. Four groups of adult male Sprague-Dawley rats were studied (n = 8 each): 1) sham; 2) sham + 60 mg/kg ip imatinib; 3) ICH (collagenase method); and 4) ICH + 60 mg/kg ip imatinib given 60 min after injury. At 24 h after injury, sham artery passive diameters (+3 mM EGTA) averaged 244 ± 7 µm (at 60 mmHg). ICH significantly increased passive diameters up to 6.4% and decreased compliance up to 42.5%. For both pressure- and potassium-induced contractions, ICH decreased calcium mobilization up to 26.2% and increased myofilament calcium sensitivity up to 48.4%. ICH reduced confocal colocalization of smooth muscle α-actin (αActin) with nonmuscle myosin heavy chain (MHC) and increased its colocalization with smooth muscle MHC, suggesting that ICH promoted contractile differentiation. ICH also enhanced colocalization of myosin light chain kinase (MLCK) with both αActin and regulatory 20-kDa myosin light chain. All effects of ICH on passive diameter, compliance, contractility, and contractile protein colocalization were significantly reduced or absent in arteries from animals treated with imatinib. These findings support the hypothesis that ICH promotes release into the cerebrospinal fluid of vasoactive factors that can diffuse to and promote activation of cerebrovascular PDGF receptors, thereby altering the structure, contractile protein organization, contractility, and smooth muscle phenotype of cerebral arteries remote from the site of hemorrhage.

FGF21 represses cerebrovascular aging via improving mitochondrial biogenesis and inhibiting p53 signaling pathway in an AMPK-dependent manner

Cerebrovascular aging has a high relationship with stroke and neurodegenerative disease. In the present study, we evaluated the influence of fibroblast growth factor 21 (FGF21) on angiotensin (Ang II)-mediated cerebrovascular aging in human brain vascular smooth muscle cells (hBVSMCs). Ang II induced remarkable aging-phenotypes in hBVSMCs, including enhanced SA-β-gal staining and NBS1 protein expression. First, we used immunoblotting assay to confirm protein expression of FGF21 receptor (FGFR1) and the co-receptor β-Klotho in cultured hBVSMCs. Second, we found that FGF21 treatment partly prevented the aging-related changes induced by Ang II. FGF21 inhibited Ang II-enhanced ROS production/superoxide anion levels, rescued the Ang II-reduced Complex IV and citrate synthase activities, and suppressed the Ang II-induced meprin protein expression. Third, we showed that FGF21 not only inhibited the Ang II-induced p53 activation, but also blocked the action of Ang II on Siah-1-TRF signaling pathway which is upstream factors for p53 activation. At last, either chemical inhibition of AMPK signaling pathway by a specific antagonist Compound C or knockdown of AMPKα1/2 isoform using siRNA, successfully abolished the anti-aging action of FGF21 in hBVSMCs. These results indicate that FGF21 protects against Ang II-induced cerebrovascular aging via improving mitochondrial biogenesis and inhibiting p53 activation in an AMPK-dependent manner, and highlight the therapeutic value of FGF21 in cerebrovascular aging-related diseases such as stroke and neurodegenerative disease.

XBP1 splicing triggers miR-150 transfer from smooth muscle cells to endothelial cells via extracellular vesicles

The interaction between endothelial cells (ECs) and smooth muscle cells (SMCs) plays a critical role in the maintenance of vessel wall homeostasis. The X-box binding protein 1 (XBP1) plays an important role in EC and SMC cellular functions. However, whether XBP1 is involved in EC-SMC interaction remains unclear. In this study, In vivo experiments with hindlimb ischemia models revealed that XBP1 deficiency in SMCs significantly attenuated angiogenesis in ischemic tissues, therefore retarded the foot blood perfusion recovery. In vitro studies indicated that either overexpression of the spliced XBP1 or treatment with platelet derived growth factor-BB up-regulated miR-150 expression and secretion via extracellular vesicles (EVs). The XBP1 splicing-mediated up-regulation of miR-150 might be due to increased stability. The SMC-derived EVs could trigger EC migration, which was abolished by miR-150 knockdown in SMCs, suggesting miR-150 is responsible for SMC-stimulated EC migration. The SMC-derived miR-150-containing EVs or premiR-150 transfection increased vascular endothelial growth factor (VEGF)-A mRNA and secretion in ECs. Both inhibitors SU5416 and LY294002 attenuated EVs-induced EC migration. This study demonstrates that XBP1 splicing in SMCs can control EC migration via SMC derived EVs-mediated miR-150 transfer and miR-150-driven VEGF-A/VEGFR/PI3K/Akt pathway activation, thereby modulating the maintenance of vessel wall homeostasis.