Sp1-dependent activation of KLF4 is required for PDGF-BB-induced phenotypic modulation of smooth muscle

N6-methyladenosine-driven miR-143/145-KLF4 circuit orchestrates the phenotypic switch of pulmonary artery smooth muscle cells

Pulmonary hypertension (PH) is characterized by vascular remodeling predominantly driven by a phenotypic switching in pulmonary artery smooth muscle cells (PASMCs). However, the underlying mechanisms for this phenotypic alteration remain incompletely understood. Here, we identified that RNA methyltransferase METTL3 is significantly elevated in the lungs of hypoxic PH (HPH) mice and rats, as well as in the pulmonary arteries (PAs) of HPH rats. Targeted deletion of Mettl3 in smooth muscle cells exacerbated hemodynamic consequences of hypoxia-induced PH and accelerated pulmonary vascular remodeling in vivo. Additionally, the absence of METTL3 markedly induced phenotypic switching in PASMCs in vitro. Mechanistically, METTL3 depletion attenuated m6A modification and hindered the processing of pri-miR-143/145, leading to a downregulation of miR-143-3p and miR-145-5p. Inhibition of hnRNPA2B1, an m6A mediator involved in miRNA maturation, similarly resulted in a significant reduction of miR-143-3p and miR-145-5p. We demonstrated that miR-145-5p targets Krüppel-like factor 4 (KLF4) and miR-143-3p targets fascin actin-bundling protein 1 (FSCN1) in PASMCs. The decrease of miR-145-5p subsequently induced an upregulation of KLF4, which in turn suppressed miR-143/145 transcription, establishing a positive feedback circuit between KLF4 and miR-143/145. This regulatory circuit facilitates the persistent suppression of contractile marker genes, thereby sustaining PASMC phenotypic switch. Collectively, hypoxia-induced upregulation of METTL3, along with m6A mediated regulation of miR-143/145, might serve as a protective mechanism against phenotypic switch of PASMCs. Our results highlight a potential therapeutic strategy targeting m6A modified miR-143/145-KLF4 loop in the treatment of PH.

Basal ATP release signals through the P2Y2 receptor to maintain the differentiated phenotype of vascular smooth muscle cells

BACKGROUND AND AIMS

Vascular smooth muscle cell (VSMC) dedifferentiation contributes substantively to vascular disease. VSMCs spontaneously release low levels of ATP that modulate vessel contractility, but it is unclear if autocrine ATP signaling in VSMCs is critical to the maintenance of the VSMC contractile phenotype.

METHODS

We used pharmacological inhibitors to block ATP release in human aortic smooth muscle cells (HASMCs) for studying changes in VSMC differentiation marker gene expression. We employed RNA interference and generated mice with SMC-specific inducible deletion of the P2Y2 receptor (P2Y2R) gene to evaluate resulting phenotypic alterations.

RESULTS

HASMCs constitutively release low levels of ATP that when blocked results in a significant decrease in VSMC differentiation marker gene expression, including smooth muscle actin (SMA), smooth muscle myosin heavy chain (SMMHC), SM-22α and calponin. Basal release of ATP represses transcriptional activation of the Krüppel-Like Factor 4 (KFL4) thereby preventing platelet-derived growth factor-BB (PDGF-BB) from inhibiting expression of SMC contractile phenotype markers. SMC-restricted conditional deletion of P2Y2R evoked dedifferentiation characterized by decreases in aortic contractility and contractile phenotype markers expression. This loss was accompanied by a transition to the synthetic phenotype with the acquisition of extracellular matrix (ECM) proteins characteristic of dedifferentiation, such as osteopontin and vimentin.

CONCLUSIONS

Our data establish the first direct evidence that an autocrine ATP release mechanism maintains SMC cytoskeletal protein expression by inhibiting VSMCs from transitioning to a synthetic phenotype, and further demonstrate that activation of the P2Y2R by basally released ATP is required for maintenance of the differentiated VSMC phenotype.

4,4'-Methylene diphenyl diisocyanate exposure induces expression of alternatively activated macrophage-associated markers and chemokines partially through Krüppel-like factor 4 mediated signaling in macrophages

Occupational exposure to the most widely used monomeric diisocyanate (dNCO), 4,4'-methylene diphenyl diisocyanate (MDI), may lead to the development of occupational asthma (OA). Alveolar macrophages with alternatively activated (M2) phenotype have been implicated in allergic airway responses and the pathogenesis of asthma. Recent in vivo studies demonstrate that M2 macrophage-associated markers and chemokines are induced by MDI-exposure, however, the underlying molecular mechanism(s) by which this proceeds is unclear.Following MDI exposure (in vivo and in vitro) M2 macrophage-associated transcription factors (TFs), markers, and chemokines were determined by RT-qPCR, western blots, and ELISA.Expression of M2 macrophage-associated TFs and markers including Klf4/KLF4, Cd206/CD206, Tgm2/TGM2, Ccl17/CCL17, Ccl22/CCL22, and CCL24 were induced by MDI/MDI-GSH exposure in bronchoalveolar lavage cells (BALCs)/THP-1 macrophages. The expression of CD206, TGM2, CCL17, CCL22, and CCL24 are upregulated by 3.83-, 7.69-, 6.22-, 6.08-, and 1.90-fold in KLF4-overexpressed macrophages, respectively. Endogenous CD206 and TGM2 were downregulated by 1.65-5.17-fold, and 1.15-1.78-fold, whereas CCL17, CCL22, and CCL24 remain unchanged in KLF4-knockdown macrophages. Finally, MDI-glutathione (GSH) conjugate-treated macrophages show increased chemotactic ability to T-cells and eosinophils, which may be attenuated by KLF4 knockdown.Our data suggest that MDI exposure may induce M2 macrophage-associated markers partially through induction of KLF4.

Smooth muscle cells-specific loss of OCT4 accelerates neointima formation after acute vascular injury

Introduction

There is growing evidence that smooth muscle cell (SMC) phenotypic transitions play critical roles during normal developmental and tissue recovery processes and in pathological conditions such as atherosclerosis. However, the molecular mechanisms responsible for these transitions are not well understood. Recently, we found that the embryonic stem cell/induced pluripotent stem cell (iPSC) factor OCT4, which was believed to be silenced in somatic cells, plays an atheroprotective role in SMC, and regulates angiogenesis after corneal alkali burn and hindlimb ischemia by mediating microvascular SMC and pericyte migration. However, the kinetics of OCT4 activation in arterial SMC and its role in acute pathological conditions are still unknown.

Methods and Results

Here, using an Oct4-IRES-GFP reporter mouse model, we found that OCT4 is reactivated in the carotid artery 18 hours post-acute ligation-induced injury, a common in vivo model of the SMC phenotypic transitions. Next, using a tamoxifen-inducible Myh11-CreERT2 Oct4 knockout mouse model, we found that the loss of OCT4, specifically in SMC, led to accelerated neointima formation and increased tunica media following carotid artery ligation, at least in part by increasing SMC proliferation within the media. Bulk RNA sequencing analysis on the cultured SMC revealed significant down-regulation of the SMC contractile markers and dysregulation of the genes belonging to the regulation of cell proliferation and, positive and negative regulation for cell migration ontological groups following genetic inactivation of Oct4. We also found that loss of Oct4 resulted in suppression of contractile SMC markers after the injury and in cultured aortic SMC. Further mechanistic studies revealed that OCT4 regulates SMC contractile genes, ACTA2 and TAGLN, at least in part by direct binding to the promoters of these genes.

Conclusion

These results demonstrate that the pluripotency factor OCT4 is quickly activated in SMC after the acute vascular injury and inhibits SMC hyperproliferation, which may be protective in preventing excessive neointima 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.

Multi-omics in thoracic aortic aneurysm: the complex road to the simplification

BACKGROUND

Thoracic aortic aneurysm (TAA) is a serious condition that affects the aorta, characterized by the dilation of its first segment. The causes of TAA (e.g., age, hypertension, genetic syndromes) are heterogeneous and contribute to the weakening of the aortic wall. This complexity makes treating this life-threatening aortopathy challenging, as there are currently no etiological therapy available, and pharmacological strategies, aimed at avoiding surgical aortic replacement, are merely palliative. Recent studies on novel therapies for TAA have focused on identifying biological targets and etiological mechanisms of the disease by using advanced -omics techniques, including epigenomics, transcriptomics, proteomics, and metabolomics approaches.

METHODS

This review presents the latest findings from -omics approaches and underscores the importance of integrating multi-omics data to gain more comprehensive understanding of TAA.

RESULTS

Literature suggests that the alterations in TAA mediators frequently involve members of pro-fibrotic process (i.e., TGF-β signaling pathways) or proteins associated with cell/extracellular structures (e.g., aggrecans). Further analyses often reported the importance in TAA of processes as inflammation (PCR, CD3, leukotriene compounds), oxidative stress (chromatin OXPHOS, fatty acids), mitochondrial respiration and glycolysis/gluconeogenesis (e.g., PPARs and HIF1a). Of note, more recent metabolomics studies added novel molecular markers to the list of TAA-specific detrimental mediators (proteoglycans).

CONCLUSION

It is increasingly clear that integrating data from different -omics branches, along with clinical data, is essential as well as complicated both to reveal hidden relevant information and to address complex diseases such as TAA. Importantly, recent progresses in metabolomics highlighted novel potential and unprecedented marks in TAA diagnosis and therapy.

Roles of Vascular Smooth Muscle Cells in Atherosclerotic Calcification

The accumulation of calcium in atherosclerotic plaques is a prominent feature of advanced atherosclerosis, and it has a strong positive correlation with the total burden of atherosclerosis. Atherosclerotic calcification usually appears first at the necrotic core, indicating that cell death and inflammatory processes are involved in calcification. During atherosclerotic inflammation, various cell types, such as vascular smooth muscle cells, nascent resident pericytes, circulating stem cells, or adventitial cells, have been assumed to differentiate into osteoblastic cells, which lead to vascular calcification. Among these cell types, vascular smooth muscle cells are considered a major contributor to osteochondrogenic cells in the atherosclerotic milieu. In this review, we summarize the molecular mechanisms underlying the osteochondrogenic switch of vascular smooth muscle cells in atherosclerotic plaques.

Smooth Muscle Cell Phenotypic Switch Induced by Traditional Cigarette Smoke Condensate: A Holistic Overview

Cigarette smoke (CS) is a risk factor for inflammatory diseases, such as atherosclerosis. CS condensate (CSC) contains lipophilic components that may represent a systemic cardiac risk factor. To better understand CSC effects, we incubated mouse and human aortic smooth muscle cells (SMCs) with CSC. We evaluated specific markers for contractile [i.e., actin, aortic smooth muscle (ACTA2), calponin-1 (CNN1), the Kruppel-like factor 4 (KLF4), and myocardin (MYOCD) genes] and inflammatory [i.e., IL-1β, and IL-6, IL-8, and galectin-3 (LGALS-3) genes] phenotypes. CSC increased the expression of inflammatory markers and reduced the contractile ones in both cell types, with KLF4 modulating the SMC phenotypic switch. Next, we performed a mass spectrometry-based differential proteomic approach on human SMCs and could show 11 proteins were significantly affected by exposition to CSC (FC ≥ 2.7, p ≤ 0.05). These proteins are active in signaling pathways related to expression of pro-inflammatory cytokines and IFN, inflammasome assembly and activation, cytoskeleton regulation and SMC contraction, mitochondrial integrity and cellular response to oxidative stress, proteostasis control via ubiquitination, and cell proliferation and epithelial-to-mesenchymal transition. Through specific bioinformatics resources, we showed their tight functional correlation in a close interaction niche mainly orchestrated by the interferon-induced double-stranded RNA-activated protein kinase (alternative name: protein kinase RNA-activated; PKR) (EIF2AK2/PKR). Finally, by combining gene expression and protein abundance data we obtained a hybrid network showing reciprocal integration of the CSC-deregulated factors and indicating KLF4 and PKR as the most relevant factors.

Vascular smooth muscle cells in intimal hyperplasia, an update

Arterial occlusive disease is the leading cause of death in Western countries. Core contemporary therapies for this disease include angioplasties, stents, endarterectomies and bypass surgery. However, these treatments suffer from high failure rates due to re-occlusive vascular wall adaptations and restenosis. Restenosis following vascular surgery is largely due to intimal hyperplasia. Intimal hyperplasia develops in response to vessel injury, leading to inflammation, vascular smooth muscle cells dedifferentiation, migration, proliferation and secretion of extra-cellular matrix into the vessel's innermost layer or intima. In this review, we describe the current state of knowledge on the origin and mechanisms underlying the dysregulated proliferation of vascular smooth muscle cells in intimal hyperplasia, and we present the new avenues of research targeting VSMC phenotype and proliferation.

Somatic Variants in SVIL in Cerebral Aneurysms

Background and Objectives

While somatic mutations have been well-studied in cancer, their roles in other complex traits are much less understood. Our goal is to identify somatic variants that may contribute to the formation of saccular cerebral aneurysms.

Methods

We performed whole-exome sequencing on aneurysm tissues and paired peripheral blood. RNA sequencing and the CRISPR/Cas9 system were then used to perform functional validation of our results.

Results

Somatic variants involved in supervillin (SVIL) or its regulation were found in 17% of aneurysm tissues. In the presence of a mutation in theSVILgene, the expression level of SVIL was downregulated in the aneurysm tissue compared with normal control vessels. Downstream signaling pathways that were induced by knockdown ofSVILvia the CRISPR/Cas9 system in vascular smooth muscle cells (vSMCs) were determined by evaluating changes in gene expression and protein kinase phosphorylation. We found thatSVILregulated the phenotypic modulation of vSMCs to the synthetic phenotype via Krüppel-like factor 4 and platelet-derived growth factor and affected cell migration of vSMCs via the RhoA/ROCK pathway.

Discussion

We propose that somatic variants form a novel mechanism for the development of cerebral aneurysms. Specifically, somatic variants inSVILresult in the phenotypic modulation of vSMCs, which increases the susceptibility to aneurysm formation. This finding suggests a new avenue for the therapeutic intervention and prevention of cerebral aneurysms.

Phosphorylation of the smooth muscle master splicing regulator RBPMS regulates its splicing activity

We previously identified RBPMS as a master regulator of alternative splicing in differentiated smooth muscle cells (SMCs). RBPMS is transcriptionally downregulated during SMC dedifferentiation, but we hypothesized that RBPMS protein activity might be acutely downregulated by post-translational modifications. Publicly available phosphoproteomic datasets reveal that Thr113 and Thr118 immediately adjacent to the RRM domain are commonly both phosphorylated. An RBPMS T113/118 phosphomimetic T/E mutant showed decreased splicing regulatory activity both in transfected cells and in a cell-free in vitro assay, while a non-phosphorylatable T/A mutant retained full activity. Loss of splicing activity was associated with a modest reduction in RNA affinity but significantly reduced RNA binding in nuclear extract. A lower degree of oligomerization of the T/E mutant might cause lower avidity of multivalent RNA binding. However, NMR analysis also revealed that the T113/118E peptide acts as an RNA mimic which can loop back and antagonize RNA-binding by the RRM domain. Finally, we identified ERK2 as the most likely kinase responsible for phosphorylation at Thr113 and Thr118. Collectively, our data identify a potential mechanism for rapid modulation of the SMC splicing program in response to external signals during the vascular injury response and atherogenesis.

miR-335-5p regulates the proliferation, migration and phenotypic switching of vascular smooth muscle cells in aortic dissection by directly regulating SP1

Uncontrolled proliferation, migration and phenotypic switching of vascular smooth muscle cells (VSMCs) are important steps in the development and progression of aortic dissection (AD). The function and potential mechanism of miR-335-5p in the pathogenesis of AD are explored in this study. Specifically, the biological function of miR-335-5p is explored in vitro through CCK-8, Transwell, immunofluorescence, EdU, wound-healing, RT-qPCR and western blotting assays. In addition, an AD model induced by angiotensin II is used to investigate the function of miR-335-5p in vivo. A dual-luciferase assay is performed to verify the targeting relationship between miR-335-5p and specificity protein 1 (SP1). Experiments involving the loss of SP1 function are performed to demonstrate the function of SP1 in the miR-335-5p-mediated regulation of human aortic-VSMCs (HA-VSMCs). AD tissues and platelet-derived growth factor BB (PDGF-BB)-stimulated HA-VSMCs show significant downregulation of miR-335-5p expression and upregulated SP1 expression. Overexpression of miR-335-5p effectively suppresses cell proliferation, migration and synthetic phenotype markers and enhances contractile phenotype markers induced by PDGF-BB treatment. Additionally, SP1 is identified as a target gene downstream of miR-335-5p, and its expression is negatively correlated with miR-335-5p in AD. Upregulation of SP1 partially reverses the inhibitory effect of miR-335-5p on HA-VSMCs, whereas the downregulation of SP1 has the opposite effect. Furthermore, Ad-miR-335-5p clearly suppresses aorta dilatation and vascular media degeneration in the AD model. Our results suggest that miR-335-5p inhibits HA-VSMC proliferation, migration and phenotypic switching by negatively regulating SP1, and indicate that miR-335-5p may be a potential therapeutic target in AD.

Nintedanib regulates intestinal smooth muscle hyperplasia and phenotype in vitro and in TNBS colitis in vivo

Chronic inflammation of the human intestine in Crohn’s disease (CD) causes bowel wall thickening, which typically progresses to stricturing and a recurrent need for surgery. Current therapies have limited success and CD remains idiopathic and incurable. Recent evidence shows a key role of intestinal smooth muscle cell (ISMC) hyperplasia in stricturing, which is not targeted by current anti-inflammatory therapeutics. However, progression of idiopathic pulmonary fibrosis, resembling CD in pathophysiology, is controlled by the tyrosine kinase inhibitors nintedanib (NIN) or pirfenidone, and we investigated these drugs for their effect on ISMC. In a culture model of rat ISMC, NIN inhibited serum- and PDGF-BB-stimulated growth and cell migration, and promoted the differentiated phenotype, while increasing secreted collagen. NIN did not affect signaling through PDGF-Rβ or NFκB but did inhibit cytokine-induced expression of the pro-inflammatory cytokines IL-1β and TNFα, supporting a transcriptional level of control. In TNBS-induced colitis in mice, which resembles CD, NIN decreased ISMC hyperplasia as well as expression of TNFα and IL-1β, without effect in control animals. NIN also inhibited growth of human ISMC in response to human serum or PDGF-BB, which further establishes a broad range of actions of NIN that support further trial in human IBD.

Fibrotic Signaling in Cardiac Fibroblasts and Vascular Smooth Muscle Cells: The Dual Roles of Fibrosis in HFpEF and CAD

Patients with heart failure with preserved ejection fraction (HFpEF) and atherosclerosis-driven coronary artery disease (CAD) will have ongoing fibrotic remodeling both in the myocardium and in atherosclerotic plaques. However, the functional consequences of fibrosis differ for each location. Thus, cardiac fibrosis leads to myocardial stiffening, thereby compromising cardiac function, while fibrotic remodeling stabilizes the atherosclerotic plaque, thereby reducing the risk of plaque rupture. Although there are currently no drugs targeting cardiac fibrosis, it is a field under intense investigation, and future drugs must take these considerations into account. To explore similarities and differences of fibrotic remodeling at these two locations of the heart, we review the signaling pathways that are activated in the main extracellular matrix (ECM)-producing cells, namely human cardiac fibroblasts (CFs) and vascular smooth muscle cells (VSMCs). Although these signaling pathways are highly overlapping and context-dependent, effects on ECM remodeling mainly act through two core signaling cascades: TGF-β and Angiotensin II. We complete this by summarizing the knowledge gained from clinical trials targeting these two central fibrotic pathways.

Anti-Allergic Effects of Myrciaria dubia (Camu-Camu) Fruit Extract by Inhibiting Histamine H1 and H4 Receptors and Histidine Decarboxylase in RBL-2H3 Cells

Although Myrciaria dubia (camu-camu) has been shown to exert anti-oxidant and anti-inflammatory effects in both in vitro and in vivo studies, its use in allergic responses has not been elucidated. In the present study, the anti-allergic effect of 70% ethanol camu-camu fruit extract was tested on calcium ionophore (A23187)-induced allergies in RBL-2H3 cells. The RBL-2H3 cells were induced with 100 nM A23187 for 6 h, followed by a 1 h camu-camu fruit extract treatment. A23187 sanitization exacerbated mast cell degranulation; however, camu-camu fruit extract decreased the release of histamine and β-hexosaminidase, which are considered as key biomarkers in cell degranulation. Camu-camu fruit extract inhibited cell exocytosis by regulating the calcium/nuclear factor of activated T cell (NFAT) signaling. By downregulating the activation of mitogen-activated protein kinase (MAPK) signaling, camu-camu fruit extract hindered the activation of both histamine H1 and H4 receptors and inhibited histidine decarboxylase (HDC) expression by mediating its transcription factors KLF4/SP1 and GATA2/MITF. In A23187-induced ROS overproduction, camu-camu fruit extract activated nuclear factor erythroid-2-related factor 2 (Nrf2) to protect mast cells against A23187-induced oxidative stress. These findings indicate that camu-camu fruit extract can be developed to act as a mast cell stabilizer and an anti-histamine. This work also “opens the door” to new investigations using natural products to achieve breakthroughs in allergic disorder treatment.

An update on the phenotypic switching of vascular smooth muscle cells in the pathogenesis of atherosclerosis

Vascular smooth muscle cells (VSMCs) are involved in phenotypic switching in atherosclerosis. This switching is characterized by VSMC dedifferentiation, migration, and transdifferentiation into other cell types. VSMC phenotypic transitions have historically been considered bidirectional processes. Cells can adopt a physiological contraction phenotype or an alternative "synthetic" phenotype in response to injury. However, recent studies, including lineage tracing and single-cell sequencing studies, have shown that VSMCs downregulate contraction markers during atherosclerosis while adopting other phenotypes, including macrophage-like, foam cell, mesenchymal stem-like, myofibroblast-like, and osteochondral-like phenotypes. However, the molecular mechanism and processes regulating the switching of VSMCs at the onset of atherosclerosis are still unclear. This systematic review aims to review the critical outstanding challenges and issues that need further investigation and summarize the current knowledge in this field.

Distinct roles of KLF4 in mesenchymal cell subtypes during lung fibrogenesis

During lung fibrosis, the epithelium induces signaling to underlying mesenchyme to generate excess myofibroblasts and extracellular matrix; herein, we focus on signaling in the mesenchyme. Our studies indicate that platelet-derived growth factor receptor (PDGFR)-β⁺ cells are the predominant source of myofibroblasts and Kruppel-like factor (KLF) 4 is upregulated in PDGFR-β⁺ cells, inducing TGFβ pathway signaling and fibrosis. In fibrotic lung patches, KLF4 is down-regulated, suggesting KLF4 levels decrease as PDGFR-β⁺ cells transition into myofibroblasts. In contrast to PDGFR-β⁺ cells, KLF4 reduction in α-smooth muscle actin (SMA)⁺ cells non-cell autonomously exacerbates lung fibrosis by inducing macrophage accumulation and pro-fibrotic effects of PDGFR-β⁺ cells via a Forkhead box M1 to C-C chemokine ligand 2-receptor 2 pathway. Taken together, in the context of lung fibrosis, our results indicate that KLF4 plays opposing roles in PDGFR-β⁺ cells and SMA⁺ cells and highlight the importance of further studies of interactions between distinct mesenchymal cell types.

Regulation of Macrophage Activation and Differentiation in Atherosclerosis

Chronic inflammation is a hallmark of atherosclerosis and macrophages play a central role in controlling inflammation at all stages of atherosclerosis. In atherosclerosis, macrophages and monocyte-derived macrophages are continuously exposed to cholesterol, oxidized lipids, cell debris, cytokines, and chemokines. Not only do these stimuli induce a specific macrophage phenotype, but they also interact extensively, leading to macrophage heterogeneity in atherosclerotic plaques. Herein, we review the diverse phenotypes of macrophages, the mechanisms underlying macrophage activation, and the contributions of macrophages to atherosclerosis in this context. We also summarize recent studies on foamy macrophages and monocyte-derived macrophages in plaque during disease progression. We provide a comprehensive overview of transcriptional, epigenetic, and metabolic reprogramming of macrophages and discuss the emerging concepts of targeting cytokines and macrophages to modulate atherosclerosis.

Therapeutic MK2 inhibition blocks pathological vascular smooth muscle cell phenotype switch

Vascular procedures, such as stenting, angioplasty, and bypass grafting, often fail due to intimal hyperplasia (IH), wherein contractile vascular smooth muscle cells (VSMCs) dedifferentiate to synthetic VSMCs, which are highly proliferative, migratory, and fibrotic. Previous studies suggest MAPK-activated protein kinase 2 (MK2) inhibition may limit VSMC proliferation and IH, although the molecular mechanism underlying the observation remains unclear. We demonstrated here that MK2 inhibition blocked the molecular program of contractile to synthetic dedifferentiation and mitigated IH development. Molecular markers of the VSMC contractile phenotype were sustained over time in culture in rat primary VSMCs treated with potent, long-lasting MK2 inhibitory peptide nanopolyplexes (MK2i-NPs), a result supported in human saphenous vein specimens cultured ex vivo. RNA-Seq of MK2i-NP-treated primary human VSMCs revealed programmatic switching toward a contractile VSMC gene expression profile, increasing expression of antiinflammatory and contractile-associated genes while lowering expression of proinflammatory, promigratory, and synthetic phenotype-associated genes. Finally, these results were confirmed using an in vivo rabbit vein graft model where brief, intraoperative treatment with MK2i-NPs decreased IH and synthetic phenotype markers while preserving contractile proteins. These results support further development of MK2i-NPs as a therapy for blocking VSMC phenotype switch and IH associated with cardiovascular procedures.

Vascular smooth muscle cells in atherosclerosis: time for a re-assessment

Vascular smooth muscle cells (VSMCs) are key participants in both early and late-stage atherosclerosis. VSMCs invade the early atherosclerotic lesion from the media, expanding lesions, but also forming a protective fibrous cap rich in extracellular matrix to cover the 'necrotic' core. Hence, VSMCs have been viewed as plaque-stabilizing, and decreased VSMC plaque content-often measured by expression of contractile markers-associated with increased plaque vulnerability. However, the emergence of lineage-tracing and transcriptomic studies has demonstrated that VSMCs comprise a much larger proportion of atherosclerotic plaques than originally thought, demonstrate multiple different phenotypes in vivo, and have roles that might be detrimental. VSMCs down-regulate contractile markers during atherosclerosis whilst adopting alternative phenotypes, including macrophage-like, foam cell-like, osteochondrogenic-like, myofibroblast-like, and mesenchymal stem cell-like. VSMC phenotypic switching can be studied in tissue culture, but also now in the media, fibrous cap and deep-core region, and markedly affects plaque formation and markers of stability. In this review, we describe the different VSMC plaque phenotypes and their presumed cellular and paracrine functions, the regulatory mechanisms that control VSMC plasticity, and their impact on atherogenesis and plaque stability.

Six Shades of Vascular Smooth Muscle Cells Illuminated by KLF4 (Krüppel-Like Factor 4)

Multiple layers of vascular smooth muscle cells (vSMCs) are present in blood vessels forming the media of the vessel wall. vSMCs provide a vessel wall structure, enabling it to contract and relax, thus modulating blood flow. They also play a crucial role in the development of vascular diseases, such as atherosclerosis and aortic aneurysm formation. vSMCs display a remarkable high degree of plasticity. At present, the number of different vSMC phenotypes has only partially been characterized. By mapping vSMC phenotypes in detail and identifying triggers for phenotype switching, the relevance of the different phenotypes in vascular disease may be identified. Up until recently, vSMCs were classified as either contractile or dedifferentiated (ie, synthetic). However, single-cell RNA sequencing studies revealed such dedifferentiated arterial vSMCs to be highly diverse. Currently, no consensus exist about the number of vSMC phenotypes. Therefore, we reviewed the data from relevant single-cell RNA sequencing studies, and classified a total of 6 vSMC phenotypes. The central dedifferentiated vSMC type that we classified is the mesenchymal-like phenotype. Mesenchymal-like vSMCs subsequently seem to differentiate into fibroblast-like, macrophage-like, osteogenic-like, and adipocyte-like vSMCs, which contribute differentially to vascular disease. This phenotype switching between vSMCs requires the transcription factor KLF4 (Kruppel-like factor 4). Here, we performed an integrated analysis of the data about the recently identified vSMC phenotypes, their associated gene expression profiles, and previous vSMC knowledge to better understand the role of vSMC phenotype transitions in vascular pathology.

A model of atherosclerosis using nicotine with balloon overdilation in a porcine

Pigs are important experimental animals for cardiovascular research. Few porcine coronary atherosclerosis models have been developed; however, their induction requires more than six months. We developed a porcine coronary artery atherosclerosis model using nicotine injection with a balloon overdilation. A coronary balloon was placed in the porcine coronary artery and overdilated to induce a mechanical injury. Nicotine was administrated via intramuscular injection every day, and changes in the coronary artery were observed after four weeks. Coronary angiography revealed nicotine injection with a balloon overdilation group showed narrowing of the coronary artery at the injury site. The combination of balloon and nicotine significantly increased the intimal hyperplasia in optical coherence tomography analysis. Proliferated tunica media were noted in the nicotine injection with balloon overdilation groups and lack of collagen was observed in the tunica media at eight weeks. Quantitative analysis showed increased smooth muscle actin alpha (SMA), cluster of differentiation 68 (CD68), and Krüppel-like factor 4 (KLF4) in the nicotine injection with balloon overdilation groups. Immunohistochemistry results showed CD68-positive cells displayed SMA- and KLF4-positive reactivity in the border zone of the intimal hyperplasia. Our results show that nicotine injection with balloon overdilation can induce atherosclerotic lesions within one month, which can serve as an alternative pig animal model for the development of coronary stents.

Molecular mechanisms underlying curcumin-mediated microRNA regulation in carcinogenesis; Focused on gastrointestinal cancers

Curcumin is a bioactive ingredient found in the Rhizomes of Curcuma longa. Curcumin is well known for its chemopreventive and anti-cancer properties. Recent findings have demonstrated several pharmacological and biological impacts of curcumin, related to the control and the management of gastrointestinal cancers. Mechanistically, curcumin exerts its biological impacts via antioxidant and anti-inflammatory effects through the interaction with various transcription factors and signaling molecules. Moreover, epigenetic modulators such as microRNAs (miRNAs) have been revealed as novel targets of curcumin. Curcumin was discovered to regulate the expression of numerous pathogenic miRNAs in gastric, colorectal, esophageal and liver cancers. The present systematic review was performed to identify miRNAs that are modulated by curcumin in gastrointestinal cancers.

ORAI1 Ca2+ Channel as a Therapeutic Target in Pathological Vascular Remodelling

In the adult, vascular smooth muscle cells (VSMC) are normally physiologically quiescent, arranged circumferentially in one or more layers within blood vessel walls. Remodelling of native VSMC to a proliferative state for vascular development, adaptation or repair is driven by platelet-derived growth factor (PDGF). A key effector downstream of PDGF receptors is store-operated calcium entry (SOCE) mediated through the plasma membrane calcium ion channel, ORAI1, which is activated by the endoplasmic reticulum (ER) calcium store sensor, stromal interaction molecule-1 (STIM1). This SOCE was shown to play fundamental roles in the pathological remodelling of VSMC. Exciting transgenic lineage-tracing studies have revealed that the contribution of the phenotypically-modulated VSMC in atherosclerotic plaque formation is more significant than previously appreciated, and growing evidence supports the relevance of ORAI1 signalling in this pathologic remodelling. ORAI1 has also emerged as an attractive potential therapeutic target as it is accessible to extracellular compound inhibition. This is further supported by the progression of several ORAI1 inhibitors into clinical trials. Here we discuss the current knowledge of ORAI1-mediated signalling in pathologic vascular remodelling, particularly in the settings of atherosclerotic cardiovascular diseases (CVDs) and neointimal hyperplasia, and the recent developments in our understanding of the mechanisms by which ORAI1 coordinates VSMC phenotypic remodelling, through the activation of key transcription factor, nuclear factor of activated T-cell (NFAT). In addition, we discuss advances in therapeutic strategies aimed at the ORAI1 target.

Phenotypic Modulation of Macrophages and Vascular Smooth Muscle Cells in Atherosclerosis-Nitro-Redox Interconnections

Monocytes/macrophages and vascular smooth muscle cells (vSMCs) are the main cell types implicated in atherosclerosis development, and unlike other mature cell types, both retain a remarkable plasticity. In mature vessels, differentiated vSMCs control the vascular tone and the blood pressure. In response to vascular injury and modifications of the local environment (inflammation, oxidative stress), vSMCs switch from a contractile to a secretory phenotype and also display macrophagic markers expression and a macrophagic behaviour. Endothelial dysfunction promotes adhesion to the endothelium of monocytes, which infiltrate the sub-endothelium and differentiate into macrophages. The latter become polarised into M1 (pro-inflammatory), M2 (anti-inflammatory) or Mox macrophages (oxidative stress phenotype). Both monocyte-derived macrophages and macrophage-like vSMCs are able to internalise and accumulate oxLDL, leading to formation of “foam cells” within atherosclerotic plaques. Variations in the levels of nitric oxide (NO) can affect several of the molecular pathways implicated in the described phenomena. Elucidation of the underlying mechanisms could help to identify novel specific therapeutic targets, but to date much remains to be explored. The present article is an overview of the different factors and signalling pathways implicated in plaque formation and of the effects of NO on the molecular steps of the phenotypic switch of macrophages and vSMCs.

G6PD activity contributes to the regulation of histone acetylation and gene expression in smooth muscle cells and to the pathogenesis of vascular diseases

We aimed to determine 1) the mechanism(s) that enables glucose-6-phosphate dehydrogenase (G6PD) to regulate serum response factor (SRF)- and myocardin (MYOCD)-driven smooth muscle cell (SMC)-restricted gene expression, a process that aids in the differentiation of SMCs, and 2) whether G6PD-mediated metabolic reprogramming contributes to the pathogenesis of vascular diseases in metabolic syndrome (MetS). Inhibition of G6PD activity increased (>30%) expression of SMC-restricted genes and concurrently decreased (40%) the growth of human and rat SMCs ex vivo. Expression of SMC-restricted genes decreased (>100-fold) across successive passages in primary cultures of SMCs isolated from mouse aorta. G6PD inhibition increased Myh11 (47%) while decreasing (>50%) Sca-1, a stem cell marker, in cells passaged seven times. Similarly, CRISPR-Cas9-mediated expression of the loss-of-function Mediterranean variant of G6PD (S188F; G6PDS188F) in rats promoted transcription of SMC-restricted genes. G6PD knockdown or inhibition decreased (48.5%) histone deacetylase (HDAC) activity, enriched (by 3-fold) H3K27ac on the Myocd promoter, and increased Myocd and Myh11 expression. Interestingly, G6PD activity was significantly higher in aortas from JCR rats with MetS than control Sprague-Dawley (SD) rats. Treating JCR rats with epiandrosterone (30 mg/kg/day), a G6PD inhibitor, increased expression of SMC-restricted genes, suppressed Serpine1 and Epha4, and reduced blood pressure. Moreover, feeding SD control (littermates) and G6PDS188F rats a high-fat diet for 4 mo increased Serpine1 and Epha4 expression and mean arterial pressure in SD but not G6PDS188F rats. Our findings demonstrate that G6PD downregulates transcription of SMC-restricted genes through HDAC-dependent deacetylation and potentially augments the severity of vascular diseases associated with MetS.NEW & NOTEWORTHY This study gives detailed mechanistic insight about the regulation of smooth muscle cell (SMC) phenotype by metabolic reprogramming and glucose-6-phosphate dehydrogenase (G6PD) in diabetes and metabolic syndrome. We demonstrate that G6PD controls the chromatin modifications by regulating histone deacetylase (HDAC) activity, which deacetylates histone 3-lysine 9 and 27. Notably, inhibition of G6PD decreases HDAC activity and enriches H3K27ac on myocardin gene promoter to enhance the expression of SMC-restricted genes. Also, we demonstrate for the first time that G6PD inhibitor treatment accentuates metabolic and transcriptomic reprogramming to reduce neointimal formation in coronary artery and large artery elastance in metabolic syndrome rats.

CARMN Loss Regulates Smooth Muscle Cells and Accelerates Atherosclerosis in Mice

[Figure: see text].

KLF4 inhibition by Kenpaullone induces cytotoxicity and chemo sensitization in B-NHL cell lines via YY1 independent

Krüppel-like factor 4 (KLF4) is a member of the KLF transcription factor family containing zinc-fingers, and is involved in the regulation of apoptosis, proliferation and differentiation of B cells and B-cell malignancies. KLF4 can act like an oncogene, we shown that KLF4 overexpression correlated with poor prognostic and chemoresistance in B-NHL. In addition, we shown that KLF4 is regulated by YY1. In this study, we demonstrate that chemical inhibition of KLF4 by Kenpaullone, results in suppression of proliferation, cell survival, downregulation of Bcl-2 and increases apoptosis in B-NHL cell lines through YY1 independent pathway. Combination of Kenpaullone and Doxorubicin, increased apoptosis. The co-expressions of KLF4/YY1 or KLF4/Bcl-2 in NHL was analyzed using Oncomine Database, exhibiting a positive correlation of expression. The present findings suggest that the chemical inhibition of KLF4 by Kenpaullone treatment could be a potential therapeutic alternatively in KLF4⁺ lymphomas.

Sympathetic and Sensory-Motor Nerves in Peripheral Small Arteries

Small arteries, which play important roles in controlling blood flow, blood pressure, and capillary pressure, are under nervous influence. Their innervation is predominantly sympathetic and sensory motor in nature, and while some arteries are densely innervated, others are only sparsely so. Innervation of small arteries is a key mechanism in regulating vascular resistance. In the second half of the previous century, the physiology and pharmacology of this innervation were very actively investigated. In the past 10-20 yr, the activity in this field was more limited. With this review we highlight what has been learned during recent years with respect to development of small arteries and their innervation, some aspects of excitation-release coupling, interaction between sympathetic and sensory-motor nerves, cross talk between endothelium and vascular nerves, and some aspects of their role in vascular inflammation and hypertension. We also highlight what remains to be investigated to further increase our understanding of this fundamental aspect of vascular physiology.

Curcumin inhibits proliferation, migration and neointimal formation of vascular smooth muscle via activating miR-22

Context: Curcumin has antitumor, antioxidative, anti-inflammatory, and anti-proliferative properties.Objective: To investigate the role of miR-22 during curcumin-induced changes in vascular smooth muscle cells (VSMC) and neointima formation in balloon-injured rat abdominal aorta.Materials and methods: Sprague-Dawley rats were randomised to the sham-operated (n = 10), operated control (injured, n = 10), and curcumin treatment (n = 10) groups. miR-22 expression was determined by real-time PCR. SP1 was assessed by western blot and real-time PCR. Rat aortic smooth muscle A7r5 cells were used to determine VSMC proliferation and migration, which were measured by the MTS, EdU staining, Transwell, and wound healing assays.Results: miR-22 levels declined following arterial balloon injury in vivo (48% at 3d, p < 0.05) and serum stimulation in vitro (45% at 24 h, p < 0.01). Functional studies revealed that miR-22 negatively regulated the proliferation and migration of VSMCs by directly targeting the SP1 transcription factor in VSMCs. Curcumin increased the expression of miR-22 (81%, p < 0.05) and decreased the protein expression of SP1 in VSMCs (25%, p < 0.05). miR-22 inhibition was found to attenuate the effects of curcumin on VSMC functions. Curcumin increased miR-22 (46%, p < 0.01), decreased the SP1 protein (19%, p < 0.05), and inhibited vascular neointimal area (48%, p < 0.01) in vivo.Discussion: The miR-22/SP1 pathway is involved in the protective role of curcumin during arterial balloon injury, but the mechanisms remain unclear.Conclusion: miR-22 is involved in the inhibitory effects of curcumin on VSMCs' proliferation, migration and neointima hyperplasia after arterial balloon injury in rats. Curcumin could be used to prevent neointimal hyperplasia after angioplasty.

RUES2 hESCs exhibit MGE-biased neuronal differentiation and muHTT-dependent defective specification hinting at SP1

RUES2 cell lines represent the first collection of isogenic human embryonic stem cells (hESCs) carrying different pathological CAG lengths in the HTT gene. However, their neuronal differentiation potential has yet to be thoroughly evaluated. Here, we report that RUES2 during ventral telencephalic differentiation is biased towards medial ganglionic eminence (MGE). We also show that HD-RUES2 cells exhibit an altered MGE transcriptional signature in addition to recapitulating known HD phenotypes, with reduced expression of the neurodevelopmental regulators NEUROD1 and BDNF and increased cleavage of synaptically enriched N-cadherin. Finally, we identified the transcription factor SP1 as a common potential detrimental co-partner of muHTT by de novo motif discovery analysis on the LGE, MGE, and cortical genes differentially expressed in HD human pluripotent stem cells in our and additional datasets. Taken together, these observations suggest a broad deleterious effect of muHTT in the early phases of neuronal development that may unfold through its altered interaction with SP1.

Pioglitazone protects blood vessels through inhibition of the apelin signaling pathway by promoting KLF4 expression in rat models of T2DM

Apelin, identified as the endogenous ligand of APJ, exerts various cardiovascular effects. However, the molecular mechanism underlying the regulation of apelin expression in vascular cells is poorly described. Pioglitazone (PIO) and Krüppel-like factor 4 (KLF4) exhibit specific biological functions on vascular physiology and pathophysiology by regulating differentiation- and proliferation-related genes. The present study aimed to investigate the roles of PIO and KLF4 in the transcriptional regulation of apelin in a high-fat diet/streptozotocin rat model of diabetes and in PIO-stimulated vascular smooth muscle cells (VSMCs). Immunohistochemistry, qRT-PCR, and Western blotting assays revealed that the aorta of the Type 2 diabetes mellitus (T2DM) rat models had a high expression of apelin, PIO could decrease the expression of apelin in the PIO-treated rats. In vitro, Western blotting assays and immunofluorescent staining results showed that the basal expression of apelin was decreased but that of KLF4 was increased when VSMCs were stimulated by PIO treatment. Luciferase and chromatin immunoprecipitation assay results suggested that KLF4 bound to the GKLF-binding site of the apelin promoter and negatively regulated the transcription activity of apelin in VSMCs under PIO stimulation. Furthermore, qRT-PCR and Western blotting assay results showed that the overexpression of KLF4 markedly decreased the basal expression of apelin, but the knockdown of KLF4 restored the PIO-induced expression of apelin. In conclusion, PIO inhibited the expression of apelin in T2DM rat models to prevent diabetic macroangiopathy, and negatively regulated the gene transcription of apelin by promoting transcription of KLF4 in the apelin promoter.

LH-induced Transcriptional Regulation of Klf4 Expression in Granulosa Cells Occurs via the cAMP/PKA Pathway and Requires a Putative Sp1 Binding Site

Krüppel-like factor 4 (Klf4) plays an important role in the transition from proliferation to differentiation in a wide variety of cells. Previous studies demonstrated its critical role in the luteal transition of preovulatory granulosa cells (GCs). This study used cultured rat preovulatory GCs to investigate the mechanism by which luteinizing hormone (LH) regulates Klf4 gene expression. Klf4 mRNA and protein were rapidly and transiently induced by LH treatment, reaching peak levels after 45 min and declining to basal levels by 3 h. Pretreatment with the protein synthesis inhibitor cycloheximide had no effect on LH-stimulated Klf4 expression, indicating that Klf4 is an immediate early gene in response to LH. To investigate the signaling pathway involved in LH-induced Klf4 regulation, the protein kinase A (PKA) and protein kinase C (PKC) pathways were evaluated. A-kinase agonists, but not a C-kinase agonist, mimicked LH in inducing Klf4 transcription. In addition, specific inhibitors of A-kinase abolished the stimulatory effect of LH on Klf4 expression. Truncation of a Klf4 expression construct to −715 bp (pKlf4-715/luc) had no effect on transcriptional activity, whereas deletion to −402 bp (pKlf4-402/luc) dramatically reduced it. ChIP analysis revealed in vivo binding of endogenous Sp1 to the −715/−500 bp region and maximal transcriptional responsiveness to LH required the Sp1 binding element at −698/−688 bp, which is highly conserved in mice, rats, and humans. These findings demonstrate that Klf4 is activated by LH via the cAMP/PKA pathway and a putative Sp1 binding element at −698/−688 bp is indispensable for activation and suggest that Klf4 could be a target for strategies for treating luteal phase insufficiency induced by an aberrant response to the LH surge.

Metabolic adaptations of cells at the vascular-immune interface during atherosclerosis

Metabolic reprogramming is a physiological cellular adaptation to intracellular and extracellular stimuli that couples to cell polarization and function in multiple cellular subsets. Pathological conditions associated to nutrients overload, such as dyslipidaemia, may disturb cellular metabolic homeostasis and, in turn, affect cellular response and activation, thus contributing to disease progression. At the vascular/immune interface, the site of atherosclerotic plaque development, many of these changes occur. Here, an intimate interaction between endothelial cells (ECs), vascular smooth muscle cells (VSMCs) and immune cells, mainly monocytes/macrophages and lymphocytes, dictates physiological versus pathological response. Furthermore, atherogenic stimuli trigger metabolic adaptations both at systemic and cellular level that affect the EC layer barrier integrity, VSMC proliferation and migration, monocyte infiltration, macrophage polarization, lymphocyte T and B activation. Rewiring cellular metabolism by repurposing “metabolic drugs” might represent a pharmacological approach to modulate cell activation at the vascular immune interface thus contributing to control the immunometabolic response in the context of cardiovascular diseases.

Single-Cell Transcriptomic Profiling of Vascular Smooth Muscle Cell Phenotype Modulation in Marfan Syndrome Aortic Aneurysm

OBJECTIVE

To delineate temporal and spatial dynamics of vascular smooth muscle cell (SMC) transcriptomic changes during aortic aneurysm development in Marfan syndrome (MFS). Approach and Results: We performed single-cell RNA sequencing to study aortic root/ascending aneurysm tissue from Fbn1C1041G/+ (MFS) mice and healthy controls, identifying all aortic cell types. A distinct cluster of transcriptomically modulated SMCs (modSMCs) was identified in adult Fbn1C1041G/+ mouse aortic aneurysm tissue only. Comparison with atherosclerotic aortic data (ApoE-/- mice) revealed similar patterns of SMC modulation but identified an MFS-specific gene signature, including plasminogen activator inhibitor-1 (Serpine1) and Kruppel-like factor 4 (Klf4). We identified 481 differentially expressed genes between modSMC and SMC subsets; functional annotation highlighted extracellular matrix modulation, collagen synthesis, adhesion, and proliferation. Pseudotime trajectory analysis of Fbn1C1041G/+ SMC/modSMC transcriptomes identified genes activated differentially throughout the course of phenotype modulation. While modSMCs were not present in young Fbn1C1041G/+ mouse aortas despite small aortic aneurysm, multiple early modSMCs marker genes were enriched, suggesting activation of phenotype modulation. modSMCs were not found in nondilated adult Fbn1C1041G/+ descending thoracic aortas. Single-cell RNA sequencing from human MFS aortic root aneurysm tissue confirmed analogous SMC modulation in clinical disease. Enhanced expression of TGF-β (transforming growth factor beta)-responsive genes correlated with SMC modulation in mouse and human data sets.

CONCLUSIONS

Dynamic SMC phenotype modulation promotes extracellular matrix substrate modulation and aortic aneurysm progression in MFS. We characterize the disease-specific signature of modSMCs and provide temporal, transcriptomic context to the current understanding of the role TGF-β plays in MFS aortopathy. Collectively, single-cell RNA sequencing implicates TGF-β signaling and Klf4 overexpression as potential upstream drivers of SMC modulation.

Nicotine in Senescence and Atherosclerosis

Cigarette smoke is a known exacerbator of age-related pathologies, such as cardiovascular disease (CVD), atherosclerosis, and cellular aging (senescence). However, the role of nicotine and its major metabolite cotinine is yet to be elucidated. Considering the growing amount of nicotine-containing aerosol use in recent years, the role of nicotine is a relevant public health concern. A number of recent studies and health education sites have focused on nicotine aerosol-induced adverse lung function, and neglected cardiovascular (CV) impairments and diseases. A critical review of the present scientific literature leads to the hypothesis that nicotine mediates the effects of cigarette smoke in the CV system by increasing MAPK signaling, inflammation, and oxidative stress through NADPH oxidase 1 (Nox1), to induce vascular smooth muscle cell (VSMC) senescence. The accumulation of senescent VSMCs in the lesion cap is detrimental as it increases the pathogenesis of atherosclerosis by promoting an unstable plaque phenotype. Therefore, nicotine, and most likely its metabolite cotinine, adversely influence atherosclerosis.

Transcriptional and epigenetic regulation of macrophages in atherosclerosis

Monocytes and macrophages provide defence against pathogens and danger signals. These cells respond to stimulation in a fast and stimulus-specific manner by utilizing complex cascaded activation by lineage-determining and signal-dependent transcription factors. The complexity of the functional response is determined by interactions between triggered transcription factors and depends on the microenvironment and interdependent signalling cascades. Dysregulation of macrophage phenotypes is a major driver of various diseases such as atherosclerosis, rheumatoid arthritis and type 2 diabetes mellitus. Furthermore, exposure of monocytes, which are macrophage precursor cells, to certain stimuli can lead to a hypo-inflammatory tolerized phenotype or a hyper-inflammatory trained phenotype in a macrophage. In atherosclerosis, macrophages and monocytes are exposed to inflammatory cytokines, oxidized lipids, cholesterol crystals and other factors. All these stimuli induce not only a specific transcriptional response but also interact extensively, leading to transcriptional and epigenetic heterogeneity of macrophages in atherosclerotic plaques. Targeting the epigenetic landscape of plaque macrophages can be a powerful therapeutic tool to modulate pro-atherogenic phenotypes and reduce the rate of plaque formation. In this Review, we discuss the emerging role of transcription factors and epigenetic remodelling in macrophages in the context of atherosclerosis and inflammation, and provide a comprehensive overview of epigenetic enzymes and transcription factors that are involved in macrophage activation.

The Effect of 3'-Hydroxy-3,4,5,4'-Tetramethoxy -stilbene, the Metabolite of the Resveratrol Analogue DMU-212, on the Motility and Proliferation of Ovarian Cancer Cells

Targeting tumor cell motility and proliferation is an extremely important challenge in the prevention of metastasis and improving the effectiveness of cancer treatment. We recently published data revealing that DMU-214, the metabolite of firmly cytotoxic resveratrol analogue DMU-212, exerted significantly higher biological activity than the parent compound in ovarian cancer cells. The aim of the present study was to assess the molecular mechanism of the potential anti-migration and anti-proliferative effect of DMU-214 in ovarian cancer cell line SKOV-3. We showed that DMU-214 reduced the migratory capacity of SKOV-3 cells. The microarray analysis indicated ontology groups of genes involved in processes of negative regulation of cell motility and proliferation. Furthermore, we found DMU-214 triggered changes in expression of several migration- and proliferation-related genes (SMAD7, THBS1, IGFBP3, KLF4, Il6, ILA, SOX4, IL15, SRF, RGCC, GPR56) and proteins (GPR56, RGCC, SRF, SMAD7, THBS1), which have been shown to interact to each other to reduce cell proliferation and motility. Our study showed for the first time that DMU-214 displayed anti-migratory and anti-proliferative activity in SKOV-3 ovarian cancer cells. On the basis of whole transcriptome analysis of these cells, we provide new insight into the role of DMU-214 in inhibition of processes related to metastasis.

Transcriptomic profiling of experimental arterial injury reveals new mechanisms and temporal dynamics in vascular healing response

Objective

Endovascular interventions cause arterial injury and induce a healing response to restore vessel wall homeostasis. Complications of defective or excessive healing are common and result in increased morbidity and repeated interventions. Experimental models of intimal hyperplasia are vital for understanding the vascular healing mechanisms and resolving the clinical problems of restenosis, vein graft stenosis, and dialysis access failure. Our aim was to systematically investigate the transcriptional, histologic, and systemic reaction to vascular injury during a prolonged time.

Methods

Balloon injury of the left common carotid artery was performed in male rats. Animals (n = 69) were euthanized before or after injury, either directly or after 2 hours, 20 hours, 2 days, 5 days, 2 weeks, 6 weeks, and 12 weeks. Both injured and contralateral arteries were subjected to microarray profiling, followed by bioinformatic exploration, histologic characterization of the biopsy specimens, and plasma lipid analyses.

Results

Immune activation and coagulation were key mechanisms in the early response, followed by cytokine release, tissue remodeling, and smooth muscle cell modulation several days after injury, with reacquisition of contractile features in later phases. Novel pathways related to clonal expansion, inflammatory transformation, and chondro-osteogenic differentiation were identified and immunolocalized to neointimal smooth muscle cells. Analysis of uninjured arteries revealed a systemic component of the reaction after local injury, underlined by altered endothelial signaling, changes in overall tissue bioenergy metabolism, and plasma high-density lipoprotein levels.

Conclusions

We demonstrate that vascular injury induces dynamic transcriptional landscape and metabolic changes identifiable as early, intermediate, and late response phases, reaching homeostasis after several weeks. This study provides a temporal “roadmap” of vascular healing as a publicly available resource for the research community.

Endovascular intervention causes an injury to the arterial wall that subsequently induces a healing response to restore the vessel wall homeostasis. Complications after vascular interventions related to defective or excessive healing response, such as thrombosis or restenosis, are common and result in increased morbidity, suffering of the patient, need for repeated interventions, and possibly death. Thus, there is a need for better understanding of the underlying molecular mechanisms during vascular injury and healing response to identify and to assess the risk of complications in patients. Using an experimental model of vascular injury, this study demonstrates the full landscape of dynamic transcriptional changes in the resolution of vascular injury, accompanied also by systemic variations in plasma lipid levels and reaching homeostasis several weeks after injury. These results can guide the development of new strategies and molecular targets for modulation of the intimal response on endovascular interventions.

Upregulation of mitotic bookmarking factors during enhanced proliferation of human stromal cells in human platelet lysate

BACKGROUND

Innovative human stromal cell therapeutics require xeno-free culture conditions. Various formulations of human platelet lysate (HPL) are efficient alternatives for fetal bovine serum (FBS). However, a consistent lack of standardized manufacturing protocols and quality criteria hampers comparability of HPL-products. Aim of this study was to compare the biochemical composition of three differential HPL-preparations with FBS and to investigate their impact on stromal cell biology.

METHODS

Stromal cells were isolated from bone marrow (BM), white adipose tissue (WAT) and umbilical cord (UC) and cultured in medium supplemented with pooled HPL (pHPL), fibrinogen-depleted serum-converted pHPL (pHPLS), mechanically fibrinogen-depleted pHPL (mcpHPL) and FBS. Biochemical parameters were analyzed in comparison to standard values in whole blood. Distinct growth factors and cytokines were measured by bead-based multiplex technology. Flow cytometry of stromal cell immunophenotype, in vitro differentiation, and mRNA expression analysis of transcription factors SOX2, KLF4, cMYC, OCT4 and NANOG were performed.

RESULTS

Biochemical parameters were comparable in all pHPL preparations, but to some extent different to FBS. Total protein, glucose, cholesterol and Na⁺ were elevated in pHPL preparations, K⁺ and Fe³⁺ levels were higher in FBS. Compared to FBS, pHPL-based media significantly enhanced stromal cell propagation. Characteristic immunophenotype and in vitro differentiation potential were maintained in all four culture conditions. The analysis of growth factors and cytokines revealed distinct levels depending on the pre-existence in pHPL, consumption or secretion by the stromal cells. Interestingly, mRNA expression of the transcription and mitotic bookmarking factors cMYC and KLF4 was significantly enhanced in a source dependent manner in stromal cells cultured in pHPL- compared to FBS-supplemented media. SOX2 mRNA expression of all stromal cell types was increased in all pHPL culture conditions.

CONCLUSION

All pHPL-supplemented media equally supported proliferation of WAT- and UC-derived stromal cells significantly better than FBS. Mitotic bookmarking factors, known to enable a quick re-entry to the cell cycle, were significantly enhanced in pHPL-expanded cells. Our results support a better characterization and standardization of humanized culture media for stromal cell-based medicinal products.

Drug-Eluting Stent Targeting Sp-1-Attenuated Restenosis by Engaging YAP-Mediated Vascular Smooth Muscle Cell Phenotypic Modulation

Background

Activation of the YAP (Yes‐associated protein) pathway has been demonstrated to be related to smooth muscle cells (SMCs) phenotypic modulation and vessel restenosis. The aim of this study was to illustrate the molecular mechanisms that regulate the expression of YAP during the process of SMCs phenotypic switch. Whether the molecular basis identified in the study could be a potential therapeutic target for drug‐eluting stents is further tested.

Methods and Results

In cell culture and in rat carotid arterial injury models, Sp‐1 (specificity protein 1) expression was significantly induced, and correlated with SMCs proliferative phenotype. Overexpression of Sp‐1 promoted SMCs proliferation and migration. Conversely, siSp‐1 transfection or Sp‐1 inhibitor Mithramycin A treatment attenuates SMC proliferation and migration. Through gain‐ and loss‐function assays, we demonstrated that YAP was involved in Sp‐1‐mediated SMC phenotypic switch. Mechanistically, activated Sp‐1 regulated YAP transcriptional expression through binding to its promoter. Moreover, we fabricated a Sp‐1 inhibitor Mithramycin A‐eluting stent and further tested it. In the rabbit carotid model, Mithramycin A‐eluting stent inhibited YAP transcription and attenuated in‐stent restenosis through regulating YAP‐mediated SMC phenotypic switch.

Conclusions

Sp‐1 controls phenotypic modulation of SMC by regulating transcription factor YAP. Drug‐eluting stent targeting Sp‐1 might represent a novel therapeutic strategy to prevent in‐stent restenosis.

Vascular Diseases and Gangliosides

Vascular diseases, such as myocardial infarction and cerebral infarction, are most commonly caused by atherosclerosis, one of the leading causes of death worldwide. Risk factors for atherosclerosis include lifestyle and aging. It has been reported that lifespan could be extended in mice by targeting senescent cells, which led to the suppression of aging-related diseases, such as vascular diseases. However, the molecular mechanisms underlying the contribution of aging to vascular diseases are still not well understood. Several types of cells, such as vascular (endothelial cell), vascular-associated (smooth muscle cell and fibroblast) and inflammatory cells, are involved in plaque formation, plaque rupture and thrombus formation, which result in atherosclerosis. Gangliosides, a group of glycosphingolipids, are expressed on the surface of vascular, vascular-associated and inflammatory cells, where they play functional roles. Clarifying the role of gangliosides in atherosclerosis and their relationship with aging is fundamental to develop novel prevention and treatment methods for vascular diseases based on targeting gangliosides. In this review, we highlight the involvement and possible contribution of gangliosides to vascular diseases and further discuss their relationship with aging.

Transcription Factors Targeted by miRNAs Regulating Smooth Muscle Cell Growth and Intimal Thickening after Vascular Injury

Neointima formation after percutaneous coronary intervention (PCI) is a manifestation of “phenotype switching” by vascular smooth muscle cells (SMC), a process that involves de-differentiation from a contractile quiescent phenotype to one that is richly synthetic. In response to injury, SMCs migrate, proliferate, down-regulate SMC-specific differentiation genes, and later, can revert to the contractile phenotype. The vascular response to injury is regulated by microRNAs (or miRNAs), small non-coding RNAs that control gene expression. Interactions between miRNAs and transcription factors impact gene regulatory networks. This article briefly reviews the roles of a range of miRNAs in molecular and cellular processes that control intimal thickening, focusing mainly on transcription factors, some of which are encoded by immediate-early genes. Examples include Egr-1, junB, KLF4, KLF5, Elk-1, Ets-1, HMGB1, Smad1, Smad3, FoxO4, SRF, Rb, Sp1 and c-Myb. Such mechanistic information could inform the development of strategies that block SMC growth, neointima formation, and potentially overcome limitations of lasting efficacy following PCI.

Tissue-Specific miRNAs Regulate the Development of Thoracic Aortic Aneurysm: The Emerging Role of KLF4 Network

MicroRNAs (miRNAs) are critical regulators of the functional pathways involved in the pathogenesis of cardiovascular diseases. Understanding of the disease-associated alterations in tissue and plasma will elucidate the roles of miRNA in modulation of gene expression throughout development of sporadic non-syndromic ascending thoracic aortic aneurysm (TAA). This will allow one to propose relevant biomarkers for diagnosis or new therapeutic targets for the treatment. The high-throughput sequencing revealed 20 and 17 TAA-specific miRNAs in tissue and plasma samples, respectively. qRT-PCR analysis in extended cohort revealed sex-related differences in miR-10a-5p, miR-126-3p, miR-155-5p and miR-148a-3p expression, which were the most significantly dysregulated in TAA tissues of male patients. Unexpectedly, the set of aneurysm-related miRNAs in TAA plasma did not resemble the tissue signature suggesting more complex organism response to the disease. Three of TAA-specific plasma miRNAs were found to be restored to normal level after aortic surgery, further signifying their relationship to the pathology. The panel of two plasma miRNAs, miR-122-3p, and miR-483-3p, could serve as a potential biomarker set (AUC = 0.84) for the ascending TAA. The miRNA-target enrichment analysis exposed TGF-β signaling pathway as sturdily affected by abnormally expressed miRNAs in the TAA tissue. Nearly half of TAA-specific miRNAs potentially regulate a key component in TGF-β signaling: TGF-β receptors, SMADs and KLF4. Indeed, using immunohistochemistry analysis we detected increased KLF4 expression in 27% of TAA cells compared to 10% of non-TAA cells. In addition, qRT-PCR demonstrated a significant upregulation of ALK1 mRNA expression in TAA tissues. Overall, these observations indicate that the alterations in miRNA expression are sex-dependent and play an essential role in TAA via TGF-β signaling.

Non-coding RNAs: key regulators of smooth muscle cell fate in vascular disease

The vascular smooth muscle cell (SMC) is one of the most plastic cells in the body. Understanding how non-coding RNAs (ncRNAs) regulate SMC cell-fate decision making in the vasculature has significantly enhanced our understanding of disease development, and opened up exciting new avenues for potential therapeutic applications. Recent studies on SMC physiology have in addition challenged our traditional view on their role and contribution to vascular disease, mainly in the setting of atherosclerosis as well as aneurysm disease, and restenosis after angioplasties. The impact of SMC behaviour on vascular disease is now recognized to be context dependent; SMC proliferation and migration can be harmful or beneficial, whereas their apoptosis, senescence, and switching into a more macrophage-like phenotype can promote inflammation and disease progression. This is in particular true for atherosclerosis-related diseases, where proliferation of SMCs was believed to promote lesion formation, but may also prevent plaque rupture by stabilizing the fibrous cap. Based on newer findings of genetic lineage tracing studies, it was revealed that SMC phenotypic switching can result in less-differentiated forms that lack classical SMC markers while exhibiting functions more related to macrophage-like cells. This switching can directly promote atherogenesis. The aim of this current review is to summarize and discuss how ncRNAs (mainly microRNAs and long ncRNAs) are involved in SMC plasticity, and how they directly affect vascular disease development and progression. Finally, we want to critically assess where potential future therapies could be useful to influence the burden of vascular diseases.

Smooth muscle cell fate and plasticity in atherosclerosis

Current knowledge suggests that intimal smooth muscle cells (SMCs) in native atherosclerotic plaque derive mainly from the medial arterial layer. During this process, SMCs undergo complex structural and functional changes giving rise to a broad spectrum of phenotypes. Classically, intimal SMCs are described as dedifferentiated/synthetic SMCs, a phenotype characterized by reduced expression of contractile proteins. Intimal SMCs are considered to have a beneficial role by contributing to the fibrous cap and thereby stabilizing atherosclerotic plaque. However, intimal SMCs can lose their properties to such an extent that they become hard to identify, contribute significantly to the foam cell population, and acquire inflammatory-like cell features. This review highlights mechanisms of SMC plasticity in different stages of native atherosclerotic plaque formation, their potential for monoclonal or oligoclonal expansion, as well as recent findings demonstrating the underestimated deleterious role of SMCs in this disease.

Krüppel-like factor 4 plays a role in the luteal transition in steroidogenesis by downregulating Cyp19A1 expression

The transition from granulosa cell (GC) to luteal cell involves a change from estrogen production to predominantly progesterone production. We analyzed the role of Krüppel-like factor 4 (Klf4), a transcriptional repressor used to generate pluripotent cells, in that transition. After luteinizing hormone (LH)/human chorionic gonadotropin treatment of preovulatory follicles, a major but transient increase in Klf4 transcript levels was detected. Therefore, we enquired whether Klf4 is involved in the rapid decline of aromatase, the key estrogen-producing enzyme, using preovulatory GCs obtained from pregnant mare serum gonadotropin-primed immature rat ovaries. Cyp19A1 expression in GCs transfected with FLAG-Klf4 or Klf4-specific siRNA was analyzed by real-time PCR and immunofluorescence staining. Cyp19A1 decreased when Klf4 was overexpressed, and Cyp19A1 and estradiol biosynthesis increased when Klf4 was knocked down. The mechanism by which Klf4 regulates Cyp19A1 expression was investigated using Cyp19A1 promoter-luciferase reporter assays and chromatin immunoprecipitation assays. The results revealed that the steroidogenic factor-1 (SF1)-binding motif, but not the specificity protein 1 (Sp1) binding element or the CACCC motif, was required for Klf4-mediated repression of Cyp19A1 promoter activity. Here we showed that Klf4 suppressed endogenous Cyp19A1 transcript and protein production, and this resulted from direct binding of Klf4 to the SF1 recognition motif in the Cyp19A1 promoter. These findings suggest that Klf4 is a physiologic regulator of Cyp19A1 expression in response to the LH surge in preovulatory GCs and that it has an essential role in the luteal transition in steroidogenesis.

Smooth muscle-specific Gsα deletion exaggerates angiotensin II-induced abdominal aortic aneurysm formation in mice in vivo

Objective:

Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease without an effective pharmaceutical treatment. Genetic studies have proved the involvement of smooth muscle phenotype switch in the development of AAA. The alpha subunit of the heterotrimeric G stimulatory protein (Gsα) mediates receptor-stimulated production of cyclic adenosine monophosphate (cAMP). However, the role of smooth muscle Gsα in AAA formation remains unknown.

Approach and results:

In this study, mice with knockout of smooth muscle-specific Gsα (Gsα^SMKO) were generated by cross-breeding Gsα^flox/flox mice with SM22-CreER^T2 transgenic mice, induced in adult mice by tamoxifen treatment. Gsα deficiency induced a smooth muscle phenotype switch from a contractile to a synthetic state. Mechanically, Gsα deletion reduced cAMP level and increased the level of human antigen R (HuR), which binds with the adenylate uridylate–rich elements of the 3′ untranslated region of Krüppel-like factor 4 (KLF4) mRNA, thereby increasing the stability of KLF4. Moreover, genetic knockdown of HuR or KLF4 rescued the phenotype switch in Gsα-deficient smooth muscle cells. Furthermore, with acute infusion of angiotensin II, the incidence of AAA was markedly higher in ApoE^−/−/Gsα^SMKO than ApoE^−/−/Gsα^flox/flox mice and induced increased elastic lamina degradation and aortic expansion. Finally, the levels of Gsα and SM α-actin were significantly lower while those of HuR and KLF4 were higher in human AAA samples than adjacent nonaneurysmal aortic sections.

Conclusions:

Gsα may play a protective role in AAA formation by regulating the smooth muscle phenotype switch and could be a potential therapeutic target for AAA disease.