Klf4, Klf2, and Zfp148 activate autophagy-related genes in smooth muscle cells during aortic aneurysm formation

FAM3A reshapes VSMC fate specification in abdominal aortic aneurysm by regulating KLF4 ubiquitination

Reprogramming of vascular smooth muscle cell (VSMC) differentiation plays an essential role in abdominal aortic aneurysm (AAA). However, the underlying mechanisms are still unclear. We explore the expression of FAM3A, a newly identified metabolic cytokine, and whether and how FAM3A regulates VSMC differentiation in AAA. We discover that FAM3A is decreased in the aortas and plasma in AAA patients and murine models. Overexpression or supplementation of FAM3A significantly attenuate the AAA formation, manifested by maintenance of the well-differentiated VSMC status and inhibition of VSMC transformation toward macrophage-, chondrocyte-, osteogenic-, mesenchymal-, and fibroblast-like cell subpopulations. Importantly, FAM3A induces KLF4 ubiquitination and reduces its phosphorylation and nuclear localization. Here, we report FAM3A as a VSMC fate-shaping regulator in AAA and reveal the underlying mechanism associated with KLF4 ubiquitination and stability, which may lead to the development of strategies based on FAM3A to restore VSMC homeostasis in AAA.

Dexmedetomidine Alleviates Abdominal Aortic Aneurysm by Activating Autophagy Via AMPK/mTOR Pathway

BACKGROUND

Abdominal aortic aneurysms (AAA) are a critical global health issue with increasing prevalence. Dexmedetomidine (DEX) is a highly selective α2-adrenoceptor agonist that has previously been shown to play a protective role in AAA. Nevertheless, the mechanisms underlying its protection effect remain not fully understood.

METHODS

A rat AAA model was established via intra-aortic porcine pancreatic elastase perfusion with or without DEX administration. The abdominal aortic diameters of rats were measured. Hematoxylin-eosin and Elastica van Gieson staining were conducted for histopathological observation. TUNEL and immunofluorescence staining were utilized to detect cell apoptosis and α-SMA/LC3 expression in the abdominal aortas. Protein levels were determined using western blotting.

RESULTS

DEX administration repressed the dilation of aortas, alleviated pathological damage and cell apoptosis, and suppressed phenotype switching of vascular smooth muscle cells (VSMCs). Moreover, DEX activated autophagy and regulated the AMP-activated protein kinase/mammalian target of the rapamycin (AMPK/mTOR) signaling pathway in AAA rats. Administration of the AMPK inhibitor attenuated the DEX-mediated ameliorative effects on AAA in rats.

CONCLUSION

DEX ameliorates AAA in rat models by activating autophagy via the AMPK/mTOR pathway.

Transcriptional regulation of autophagy and its implications in human disease

Macroautophagy/autophagy is a conserved catabolic pathway that is vital for maintaining cell homeostasis and promoting cell survival under stressful conditions. Dysregulation of autophagy is associated with a variety of human diseases, such as cancer, neurodegenerative diseases, and metabolic disorders. Therefore, this pathway must be precisely regulated at multiple levels, involving epigenetic, transcriptional, post-transcriptional, translational, and post-translational mechanisms, to prevent inappropriate autophagy activity. In this review, we focus on autophagy regulation at the transcriptional level, summarizing the transcription factors that control autophagy gene expression in both yeast and mammalian cells. Because the expression and/or subcellular localization of some autophagy transcription factors are altered in certain diseases, we also discuss how changes in transcriptional regulation of autophagy are associated with human pathophysiologies.

CCN2 deficiency in smooth muscle cells triggers cell reprogramming and aggravates aneurysm development

Vascular smooth muscle cell (SMC) phenotypic switching is widely recognized as a key mechanism responsible for the pathogenesis of several aortic diseases, such as aortic aneurysm. Cellular communication network factor 2 (CCN2), often upregulated in human pathologies and animal disease models, exerts myriad context-dependent biological functions. However, current understanding of the role of SMC-CCN2 in SMC phenotypic switching and its function in the pathology of abdominal aortic aneurysm (AAA) is lacking. Here, we show that SMC-restricted CCN2 deficiency causes AAA in the infrarenal aorta of angiotensin II-infused (Ang II-infused) hypercholesterolemic mice at a similar anatomic location to human AAA. Notably, the resistance of naive C57BL/6 WT mice to Ang II-induced AAA formation is lost upon silencing of CCN2 in SMC. Furthermore, the pro-AAA phenotype of SMC-CCN2-KO mice is recapitulated in a different model that involves the application of elastase-β-aminopropionitrile. Mechanistically, our findings reveal that CCN2 intersects with TGF-β signaling and regulates SMC marker expression. Deficiency of CCN2 triggers SMC reprograming associated with alterations in Krüppel-like factor 4 and contractile marker expression, and this reprograming likely contributes to the development of AAA in mice. These results identify SMC-CCN2 as potentially a novel regulator of SMC phenotypic switching and AA biology.

The participation of non-canonical autophagic proteins in the autophagy process and their potential as therapeutic targets

INTRODUCTION

Autophagy is a conserved catabolic process that helps recycle intracellular components to maintain homeostasis. The completion of autophagy requires the synergistic effect of multiple canonical autophagic proteins. Defects in autophagy machinery have been reported to promote diseases, rendering autophagy a bone fide health-modifying agent. However, the clinical implication of canonical pan-autophagic activators or inhibitors has often led to undesirable side effects, making it urgent to find a safer autophagy-related therapeutic target. The discovery of non-canonical autophagic proteins has been found to specifically affect the development of diseases without causing a universal impact on autophagy and has shed light on finding a safer way to utilize autophagy in the therapeutic context.

AREAS COVERED

This review summarizes recently discovered non-canonical autophagic proteins, how these proteins influence autophagy, and their potential therapeutic role in the disease due to their interaction with autophagy.

EXPERT OPINION

Several therapies have been studied thus far and continued research is needed to identify the potential that non-canonical autophagic proteins have for treating certain diseases. In the meantime, continue to uncover new non-canonical autophagic proteins and examine which are likely to have therapeutic implications.

Kruppel-like factor 2 contributes to blood-spinal cord barrier integrity and functional recovery from spinal cord injury by augmenting autophagic flux

Background: Increasing evidence suggests that acute traumatic spinal cord injury (SCI)-induced defects in autophagy and autophagy-lysosomal pathway (ALP) may contribute to endothelial barrier disruption following injury. Recently, Kruppel-like factor 2 (KLF2) was reported as a key molecular switch on regulating autophagy. Whether KLF2 coordinates endothelial endothelial ALP in SCI is not known. Methods: Genetic manipulations of KLF2 were performed in bEnd.3 cells and SCI model. Western blot, qRT-PCR, immunofluorescence staining and Lyso-Tracker Red staining, Evans blue dye extravasation, behavioral assessment via Basso mouse scale (BMS), electrophysiology and footprint analysis were performed. Results: In SCI, autophagy flux disruption in endothelial cells contributes to TJ proteins degradation, leading to blood-spinal cord barrier (BSCB) impairment. Furthermore, the KLF2 level was decreased in SCI, overexpression of which alleviated TJ proteins loss and BSCB damage, which improve motor function recovery in SCI mice, while knockdown of KLF2 displayed the opposite effects. At the molecular level, KLF2 overexpression alleviated the TJ proteins degradation and the endothelial permeability by tuning the ALP dysfunction caused by SCI and oxygen glucose deprivation (OGD). Conclusions: Endothelial KLF2 as one of the key contributors to SCI-mediated ALP dysfunction and BSCB disruption. KLF2 could be a promising pharmacological target for the management and treatment of SCI.

Endothelial pannexin-1 channels modulate macrophage and smooth muscle cell activation in abdominal aortic aneurysm formation

Pannexin-1 (Panx1) channels have been shown to regulate leukocyte trafficking and tissue inflammation but the mechanism of Panx1 in chronic vascular diseases like abdominal aortic aneurysms (AAA) is unknown. Here we demonstrate that Panx1 on endothelial cells, but not smooth muscle cells, orchestrate a cascade of signaling events to mediate vascular inflammation and remodeling. Mechanistically, Panx1 on endothelial cells acts as a conduit for ATP release that stimulates macrophage activation via P2X7 receptors and mitochondrial DNA release to increase IL-1β and HMGB1 secretion. Secondly, Panx1 signaling regulates smooth muscle cell-dependent intracellular Ca²⁺ release and vascular remodeling via P2Y2 receptors. Panx1 blockade using probenecid markedly inhibits leukocyte transmigration, aortic inflammation and remodeling to mitigate AAA formation. Panx1 expression is upregulated in human AAAs and retrospective clinical data demonstrated reduced mortality in aortic aneurysm patients treated with Panx1 inhibitors. Collectively, these data identify Panx1 signaling as a contributory mechanism of AAA formation.

Pannexin-1 ion channels on endothelial cells regulate vascular inflammation and remodeling to mediate aortic aneurysm formation. Pharmacological blockade of Pannexin-1 channels may offer translational therapeutic mitigation of aneurysmal pathology.

The Role of KLF2 in the Regulation of Atherosclerosis Development and Potential Use of KLF2-Targeted Therapy

Kruppel like factor 2 (KLF2) is a mechanosensitive transcription factor participating in the regulation of vascular endothelial cells metabolism. Activating KLF2 in endothelial cells induces eNOS (endothelial nitric oxide synthase) expression, subsequent NO (nitric oxide) release, and vasodilatory effect. In addition, many KLF2-regulated genes participate in the anti-thrombotic, antioxidant, and anti-inflammatory activities, thereby preventing atherosclerosis development and progression. In this review, we summarise recent evidence suggesting that KLF2 plays a major role in regulating atheroprotective effects in endothelial cells. We also discuss several recently identified repurposed drugs and natural plant-based bioactive compounds with KLF2-mediated atheroprotective activities. Herein, we present a comprehensive overview of the role of KLF2 in atherosclerosis and as a pharmacological target for different drugs and natural compounds and highlight the potential application of these phytochemicals for the treatment of atherosclerosis.

Leveraging cell-type-specific regulatory networks to interpret genetic variants in abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a common and severe disease with major genetic risk factors. In this study we generated enhancer-promoter contact data to identify regulatory elements in AAA-relevant cell types and identified changes in their predicted chromatin accessibility between AAA patients and controls. We integrated this information with disease-associated variants in regulatory elements and gene bodies to further understand the etiology and pathogenetic mechanisms of AAA. Our study combined whole-genome sequencing data with gene regulatory relations in disease-relevant cell types to reveal the important roles of the interleukin 6 pathway and ERG and KLF regulation in AAA pathogenesis.

Abdominal aortic aneurysm (AAA) is a common degenerative cardiovascular disease whose pathobiology is not clearly understood. The cellular heterogeneity and cell-type-specific gene regulation of vascular cells in human AAA have not been well-characterized. Here, we performed analysis of whole-genome sequencing data in AAA patients versus controls with the aim of detecting disease-associated variants that may affect gene regulation in human aortic smooth muscle cells (AoSMC) and human aortic endothelial cells (HAEC), two cell types of high relevance to AAA disease. To support this analysis, we generated H3K27ac HiChIP data for these cell types and inferred cell-type-specific gene regulatory networks. We observed that AAA-associated variants were most enriched in regulatory regions in AoSMC, compared with HAEC and CD4⁺ cells. The cell-type-specific regulation defined by this HiChIP data supported the importance of ERG and the KLF family of transcription factors in AAA disease. The analysis of regulatory elements that contain noncoding variants and also are differentially open between AAA patients and controls revealed the significance of the interleukin-6-mediated signaling pathway. This finding was further validated by including information from the deleteriousness effect of nonsynonymous single-nucleotide variants in AAA patients and additional control data from the Medical Genome Reference Bank dataset. These results shed important insights into AAA pathogenesis and provide a model for cell-type-specific analysis of disease-associated variants.

Mesenchymal Stem Cells Alter MicroRNA Expression and Attenuate Thoracic Aortic Aneurysm Formation

BACKGROUND

Thoracic aortic aneurysms (TAA) are a progressive disease characterized by inflammation, smooth muscle cell activation and matrix degradation. We hypothesized that mesenchymal stem cells (MSCs) can immunomodulate vascular inflammation and remodeling via altered microRNA (miRNAs) expression profile to attenuate TAA formation.

MATERIALS AND METHODS

C57BL/6 mice underwent topical elastase application to form descending TAAs. Mice were also treated with MSCs on days 1 and 5 and aortas were analyzed on day 14 for aortic diameter. Cytokine array was performed in aortic tissue and total RNA was tagged and hybridized for miRNAs microarray analysis. Immunohistochemistry was performed for elastin degradation and leukocyte infiltration.

RESULTS

Treatment with MSCs significantly attenuated aortic diameter and TAA formation compared to untreated mice. MSC administration also attenuated T-cell, neutrophil and macrophage infiltration and prevented elastic degradation to mitigate vascular remodeling. MSC treatment also attenuated aortic inflammation by decreasing proinflammatory cytokines (CXCL13, IL-27, CXCL12 and RANTES) and upregulating anti-inflammatory interleukin-10 expression in aortic tissue of elastase-treated mice. TAA formation demonstrated activation of specific miRNAs that are associated with aortic inflammation and vascular remodeling. Our results also demonstrated that MSCs modulate a different set of miRNAs that are associated with decrease leukocyte infiltration and vascular inflammation to attenuate the aortic diameter and TAA formation.

CONCLUSIONS

These results indicate that MSCs immunomodulate specific miRNAs that are associated with modulating hallmarks of aortic inflammation and vascular remodeling of aortic aneurysms. Targeted therapies designed using MSCs and miRNAs have the potential to regulate the growth and development of TAAs.

Telocytes in the human ascending aorta: Characterization and exosome-related KLF-4/VEGF-A expression

Telocytes (TCs), a novel interstitial cell entity promoting tissue regeneration, have been described in various tissues. Their role in inter‐cellular signalling and tissue remodelling has been reported in almost all human tissues. This study hypothesizes that TC also contributes to tissue remodelling and regeneration of the human thoracic aorta (HTA). The understanding of tissue homeostasis and regenerative potential of the HTA is of high clinical interest as it plays a crucial role in pathogenesis from aortic dilatation to lethal dissection. Therefore, we obtained twenty‐five aortic specimens of heart donors during transplantation. The presence of TCs was detected in different layers of aortic tissue and characterized by immunofluorescence and transmission electron microscopy. Further, we cultivated and isolated TCs in highly differentiated form identified by positive staining for CD34 and c‐kit. Aortic‐derived TC was characterized by the expression of PDGFR‐α, PDGFR‐β, CD29/integrin β‐1 and αSMA and the stem cell markers Nanog and KLF‐4. Moreover, TC exosomes were isolated and characterized for soluble angiogenic factors by Western blot. CD34⁺/c‐kit⁺ TCs shed exosomes containing the soluble factors VEGF‐A, KLF‐4 and PDGF‐A. In summary, TC occurs in the aortic wall. Correspondingly, exosomes, derived from aortic TCs, contain vasculogenesis‐relevant proteins. Understanding the regulation of TC‐mediated aortic remodelling may be a crucial step towards designing strategies to promote aortic repair and prevent adverse remodelling.

Autophagy-mitophagy induction attenuates cardiovascular inflammation in a murine model of Kawasaki disease vasculitis

Kawasaki disease (KD) is the leading cause of acquired heart disease among children. Murine and human data suggest that the NLRP3-IL-1β pathway is the main driver of KD pathophysiology. NLRP3 can be activated during defective autophagy/mitophagy. We used the Lactobacillus casei cell wall extract (LCWE) murine model of KD vasculitis, to examine the role of autophagy/mitophagy on cardiovascular lesion development. LCWE-injected mice had impaired autophagy/mitophagy and increased levels of ROS in cardiovascular lesions, together with increased systemic 8-OHdG release. Enhanced autophagic flux significantly reduced cardiovascular lesions in LCWE-injected mice, whereas autophagy blockade increased inflammation. Vascular smooth muscle cell specific deletion of Atg16l1 and global Parkin-/- significantly increased disease formation, supporting the importance of autophagy/mitophagy in this model. Ogg1-/- mice had significantly increased lesions with increased NLRP3 activity, whereas treatment with MitoQ, reduced vascular tissue inflammation, ROS production and systemic 8-OHdG release. Treatment with MN58b or Metformin (increasing AMPK and reducing ROS), resulted in decreased disease formation. Our results demonstrate that impaired autophagy/mitophagy and ROS-dependent damage exacerbate the development of murine KD vasculitis. This pathway can be efficiently targeted to reduce disease severity. These findings enhance our understanding of KD pathogenesis and identify novel therapeutic avenues for KD treatment.

SDF-1α/CXCR4 Pathway Mediates Hemodynamics-Induced Formation of Intracranial Aneurysm by Modulating the Phenotypic Transformation of Vascular Smooth Muscle Cells

The objective of this study is to explore the role of the SDF-1α/CXCR4 pathway in the development of intracranial aneurysm (IA) induced by hemodynamic forces. We collected 12 IA and six superficial temporal artery samples for high-throughput sequencing, hematoxylin and eosin staining, and immunohistochemistry to examine vascular remodeling and determine the expression of the components of the SDF-1α/CXCR4 pathway, structural proteins (α-SMA and calponin) of vascular smooth muscle cells (VSMCs), and inflammatory factors (MMP-2 and TNF-α). Computational fluid dynamics (CFD) was used for hemodynamic analysis. Mouse IA model and dynamic co-culture model were established to explore the mechanism through which the SDF-1α/CXCR4 pathway regulates the phenotypic transformation of VSMCs in vivo and in vitro. We detected a significant elevation of SDF-1α and CXCR4 in IA, which was accompanied by vascular remodeling in the aneurysm wall (i.e., the upregulation of inflammatory factors, MMP-2 and TNF-α, and the downregulation of contractile markers, α-SMA and calponin). In addition, hemodynamic analysis revealed that compared with unruptured aneurysms, ruptured aneurysms were associated with lower wall shear stress and higher MMP-2 expression. In vivo and in vitro experiments showed that abnormal hemodynamics could activate the SDF-1α/CXCR4, P38, and JNK signaling pathways to induce the phenotypic transformation of VSMCs, leading to IA formation. Hemodynamics can induce the phenotypic transformation of VSMCs and cause IA by activating the SDF-1α/CXCR4 signaling pathway.

Curcumin nicotinate suppresses abdominal aortic aneurysm pyroptosis via lncRNA PVT1/miR-26a/KLF4 axis through regulating the PI3K/AKT signaling pathway

Abdominal aortic aneurysm (AAA) is a chronic dilated disease of the aorta that is characterized by chronic inflammation. Curcumin (Cur) is previously showed to attenuate AAA by inhibiting inflammatory response in ApoE -/- mice. Since Cur has the limitations of aqueous solubility and instability. Here, we focus on the role of curcumin nicotinate (CurTn), a Cur derivative is derived from Cur and nicotinate. An in vitro model of AAA was established by treating vascular smooth muscle cells (VSMCs) with II (Ang-II). Gene and protein expressions were examined by quantitative real-time PCR (qPCR) or western blotting. Cell migration and pyroptosis were determined by transwell assay and flow cytometry. The interaction between plasmacytoma variant translocation 1 (PVT1), miR-26a and krüppel-like factor 4 (KLF4) was predicted by online prediction tool and confirmed by luciferase reporter assay. CurTn reduced Ang-II-induced AAA-associated proteins, inflammatory cytokine expressions, and attenuated pyroptosis in VSMCs. PVT1 overexpression suppressed the inhibitory effect of CurTn on AngII-induced pyroptosis and inflammatory in VSMCs by sponging miR-26a. miR-26a directly targeted KLF4 and suppressed its expression, which eventually led to the deactivation of the PI3K/AKT signaling pathway. Besides, the regulatory effect of CurTn on pyroptosis of VSMCs induced by Ang-II was reversed through the PVT1/miR-26a/KLF4 pathway. In short, CurTn suppressed VSMCs pyroptosis and inflammation though mediation PVT1/miR-26a/KLF4 axis by regulating the PI3K/AKT signaling pathway, CurTn might consider as a potential therapeutic target in the treatment of AAA.

Different types of cell death in vascular diseases

In a mature organism, tissue homeostasis is regulated by cell division and cell demise as the two major physiological procedures. There is increasing evidence that deregulation of these processes is important in the pathogenicity of main diseases, including myocardial infarction, stroke, atherosclerosis, and inflammatory diseases. Therefore, there are ongoing efforts to discover modulating factors of the cell cycle and cell demise planners aiming at shaping innovative therapeutically modalities to the therapy of such diseases. Although the life of a cell is terminated by several modes of action, a few cell deaths exist-some of which resemble apoptosis and/or necrosis, and most of them are different from one another-that contribute to a wide range of functions to either support or disrupt the homoeostasis. Even in normal physiological conditions, cell life is severe within the cardiovascular system. Cells are persistently undergoing stretch, contraction, injurious metabolic byproducts, and hemodynamic forces, and a few of cells sustain decade-long lifetimes. The duration of vascular disease causes further exposure of vascular cells to a novel range of offences, most of which induce cell death. There is growing evidence on consequences of direct damage to a cell, as well as on responses of adjacent and infiltrating cells, which also have an effect on the pathology. In this study, by focusing on different pathways of cell death in different vascular diseases, an attempt is made to open a new perspective on the therapeutic goals associated with cell death in these diseases.

Single-cell RNA sequencing reveals the cellular heterogeneity of aneurysmal infrarenal abdominal aorta

AIMS

The artery contains numerous cell types which contribute to multiple vascular diseases. However, the heterogeneity and cellular responses of these vascular cells during abdominal aortic aneurysm (AAA) progression have not been well characterized.

METHODS AND RESULTS

Single-cell RNA sequencing was performed on the infrarenal abdominal aortas (IAAs) from C57BL/6J mice at Days 7 and 14 post-sham or peri-adventitial elastase-induced AAA. Unbiased clustering analysis of the transcriptional profiles from >4500 aortic cells identified 17 clusters representing nine-cell lineages, encompassing vascular smooth muscle cells (VSMCs), fibroblasts, endothelial cells, immune cells (macrophages, T cells, B cells, and dendritic cells), and two types of rare cells, including neural cells and erythrocyte cells. Seurat clustering analysis identified four smooth muscle cell (SMC) subpopulations and five monocyte/macrophage subpopulations, with distinct transcriptional profiles. During AAA progression, three major SMC subpopulations were proportionally decreased, whereas the small subpopulation was increased, accompanied with down-regulation of SMC contractile markers and up-regulation of pro-inflammatory genes. Another AAA-associated cellular response is immune cell expansion, particularly monocytes/macrophages. Elastase exposure induced significant expansion and activation of aortic resident macrophages, blood-derived monocytes and inflammatory macrophages. We also identified increased blood-derived reparative macrophages expressing anti-inflammatory cytokines suggesting that resolution of inflammation and vascular repair also persist during AAA progression.

CONCLUSION

Our data identify AAA disease-relevant transcriptional signatures of vascular cells in the IAA. Furthermore, we characterize the heterogeneity and cellular responses of VSMCs and monocytes/macrophages during AAA progression, which provide insights into their function and the regulation of AAA onset and progression.

KLF4 Regulates Metabolic Homeostasis in Response to Stress

Cancerous cells are detrimental to the human body and can be incredibly resilient against treatments because of the complexities of molecular carcinogenic pathways. In particular, cancer cells are able to sustain increased growth under metabolic stress due to phenomena like the Warburg effect. Krüppel-like factor 4 (KLF4), a context-dependent transcription factor that can act as both a tumor suppressor and an oncogene, is involved in many molecular pathways that respond to low glucose and increased reactive oxygen species (ROS), raising the question of its role in metabolic stress as a result of increased proliferation of tumor cells. In this study, metabolic assays were performed, showing enhanced efficiency of energy production in cells expressing KLF4. Western blotting showed that KLF4 increases the expression of essential glycolytic proteins. Furthermore, we used immunostaining to show that KLF4 increases the localization of glucose transporter 1 (GLUT1) to the cellular membrane. 2',7'-Dichlorodihydrofluorescein diacetate (H2DCF-DA) was used to analyze the production of ROS, and we found that KLF4 reduces stress-induced ROS within cells. Finally, we demonstrated increased autophagic death in KLF4-expressing cells in response to glucose starvation. Collectively, these results relate KLF4 to non-Warburg metabolic behaviors that support its role as a tumor suppressor and could make KLF4 a target for new cancer treatments.

Role of autophagy in aneurysm and dissection of the ascending aorta

Maintenance of physiologically balanced levels of autophagy is crucial for cellular homeostasis and in the normal vessel wall, balanced autophagy can be considered a cytoprotective mechanism that preserves endothelial function and prevents cardiovascular disease. Recent studies pointed out the importance of the modulation of the autophagic flux in the pathogenesis of aortic dissection and aneurysms of the ascending aorta. Notably, shear stress (and its receptor p62), IL-6, Rab7 and Atg5/IRE1α pathways of autophagy may be considered the novel super-selective therapeutic target for the preventive and postoperative treatment of aortic aneurysm and aortic dissection. This review intends to summarize current evidences in this field trying to enlighten new avenues for future researches.

Endoplasmic reticulum stress and mitochondrial biogenesis are potential therapeutic targets for abdominal aortic aneurysm

Endoplasmic reticulum (ER) and mitochondria are crucial organelles for cell homeostasis and alterations of these organelles have been implicated in cardiovascular disease. However, their roles in abdominal aortic aneurysm (AAA) pathogenesis remain largely unknown. In a recent issue of Clinical Science, Navas-Madronal et al. ((2019), 133(13), 1421-1438) reported that enhanced ER stress and dysregulation of mitochondrial biogenesis are associated with AAA pathogenesis in humans. The authors also proposed that disruption in oxysterols network such as an elevated concentration of 7-ketocholestyerol in plasma is a causative factor for AAA progression. Their findings highlight new insights into the underlying mechanism of AAA progression through ER stress and dysregulation of mitochondrial biogenesis. Here, we will discuss the background, significance of the study, and future directions.

Spermidine Suppresses Development of Experimental Abdominal Aortic Aneurysms

Background

The protective effects of polyamines on cardiovascular disease have been demonstrated in many studies. However, the roles of spermidine, a natural polyamine, in abdominal aortic aneurysm (AAA) disease have not been studied. In this study, we investigated the influence and potential mechanisms of spermidine treatment on experimental AAA disease.

Methods and Results

Experimental AAAs were induced in 8‐ to 10‐week‐old male C57BL/6J mice by transient intra‐aortic infusion of porcine pancreatic elastase. Spermidine was administered via drinking water at a concentration of 3 mmol/L. Spermidine treatment prevented experimental AAA formation with preservation of medial elastin and smooth muscle cells. In immunostaining, macrophages, T cells, neutrophils, and neovessels were significantly reduced in aorta of spermidine‐treated, as compared with vehicle‐treated elastase‐infused mice. Additionally, flow cytometric analysis showed that spermidine treatment reduced aortic leukocyte infiltration and circulating inflammatory cells. Furthermore, we demonstrated that spermidine treatment promoted autophagy‐related proteins in experimental AAAs using Western blot analysis, immunostaining, and transmission electron microscopic examination. Autophagic function was evaluated for human abdominal aneurysmal and nonaneurysmal adjacent aortae from AAA patients using Western blot analysis and immunohistochemistry. Dysregulated autophagic function, as evidenced by increased SQSTM1/p62 protein and phosphorylated mTOR, was found in aneurysmal, as compared with nonaneurysmal, aortic segments.

Conclusions

Our results suggest that spermidine supplementation limits experimental AAA formation associated with preserved aortic structural integrity, attenuated aortic inflammatory infiltration, reduced circulating inflammatory monocytes, and increased autophagy‐related proteins. These findings suggest that spermidine may be a promising treatment for AAA disease.

A novel STAT3 inhibitor attenuates angiotensin II-induced abdominal aortic aneurysm progression in mice through modulating vascular inflammation and autophagy

Abdominal Aortic aneurysm (AAA) is associated with chronic inflammation, cells apoptosis, and impairment of autophagy. BP-1-102, a novel potent STAT3 inhibitor, has been recently reported to significantly block inflammation-related signaling pathways of JAK2/STAT3 and NF-κB, as well as regulate autophagy. However, its role in vascular inflammation and AAA progression remains to be elucidated. In the present study, the effect and potential mechanisms of BP-1-102 on angiotensin II (AngII) induced AAA in ApoE^−/− mice were investigated. AAA was induced in ApoE^−/− mice with infusion of AngII for 28 days. BP-1-102 was administrated orally to mice every other day. Mice were sacrificed on day 7, day 14, and day 28 to evaluate the treatment effects. BP-1-102 markedly decreased AAA incidence and aortic diameter, maintained elastin structure and volume, reduced the expression of pro-inflammatory cytokines and MMPs, and inhibited inflammatory cells infiltration. Moreover, BP-1-102 dramatically reduced the expression of JAK2, p-STAT3, p-NF-κB, and Bcl-xL but maintained the expression of LC3B and Beclin in AAA tissues. In vitro, vascular smooth muscle cells (VSMCs) were treated with AngII and/or BP-1-102 at indicated time and concentration. BP-1-102 inhibited AngII-induced JAK2/STAT3 and NF-κB signaling activation and maintained autophagy-related proteins expression in VSMCs. Taken together, our findings suggest that BP-1-102 inhibits vascular inflammation and AAA progression through decreasing JAK2/STAT3 and NF-κB activation and maintaining autophagy.

Acidic pH derived from cancer cells as a double-edged knife modulates wound healing through DNA repair genes and autophagy

Wound healing is a sequester program that involves diverse cell signalling cascades. Notwithstanding, complete signal transduction pathways underpinning acidic milieu derived from cancer cells is not clear, yet. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, fluorescein diacetate/propidium iodide staining, and cell cycle flow cytometry revealed that acidic media decreased cell viability and cell number along with enhanced dead cells and S-phase arrest in normal fibroblasts. Notably, the trends of intracellular reactive oxygen species production and lactate dehydrogenase release significantly increased with time. It seems the downregulation of Klf4 is in part due to acidosis-induced DNA damage. It promoted cells towards S-phase arrest and diminished cell proliferation. Klf4 downregulation had a direct correlation with the P53 level while acidic microenvironment promotes cells towards cell death mechanisms including apoptosis and autophagy. Noteworthily, the unchanged levels of Rb and Mlh1 indicated in those genes had no dominant role in the repairing of DNA damage in fibroblasts treated with the acidic microenvironment. Therefore, cells owing to not entering to mitosis and accumulation of DNA damage were undergone cell death to preserve cell homeostasis. Since acidic media decreased the level of tumour suppressor and DNA repair genes and altered the normal survival pathways in fibroblasts, caution should be exercised to not lead to cancer rather than wound healing.