Vascular Smooth Muscle Cells Phenotypic Switching Research Articles

Targeting vascular smooth muscle cell dysfunction with xanthine derivative KMUP-3 inhibits abdominal aortic aneurysm in mice

Background and aimsInflammation, oxidative stress, matrix degradation, medial calcification and vascular smooth muscle cell (VSMC) loss are prominent features in abdominal aortic aneurysm (AAA). VSMC phenotypic switch to a proinflammatory state and VSMC apoptosis could be targetable mechanisms implicated in the pathogenesis of AAA formation. Herein, we investigated the hypothesis that a xanthine derivative (KMUP-3) might suppress AAA through inhibition of VSMC phenotypic switch and apoptosis. MethodsIn vitro, VSMC calcification was induced using β-glycerophosphate. In vivo, AAA was induced using angiotensin II (1000 ng/kg per minute) infusion for 4 weeks in apolipoprotein E-deficient mice. ResultsAs determined by alizarin red S staining and calcium content measurements, KMUP-3 suppressed VSMC calcification. During VSMC calcification, KMUP-3 inhibited mTOR and β-catenin upregulation, essential for VSMC phenotypic switch, while it enhanced AMP-activated protein kinase (AMPK) activation that protects against VSMC phenotypic switch. Moreover, KMUP-3 attenuated VSMC apoptosis with an increased Bcl-2/Bax ratio and reduced activated caspase-3 expression. During AAA formation, treatment with KMUP-3 inhibited phosphorylated mTOR expression and increased phosphorylated AMPK expression in the medial layer. In addition, KMUP-3 treatment suppressed aortic dilatation together with reduction in proinflammatory cytokines and infiltrating macrophages, attenuation of medial VSMC apoptosis and mitigation of reactive oxygen species generation, matrix-degrading proteinase activities, elastin breakdown and vascular calcification. ConclusionsTreatment with KMUP-3 inhibits aneurysm growth possibly through its interference with signaling pathways involved in VSMC phenotypic switch and apoptosis. These findings provide a proof-of-concept validation for VSMC dysfunction as a potential therapeutic target in AAA.

Abstract 137: Vascular Smooth Muscle Cell MYPT1 Deficiency Induces Phenotype Switching and Disrupts Blood-Brain Barrier After Stroke

Objectives: Cerebral autoregulation and blood brain barrier (BBB) are often impaired in hypertensive and aging individuals, contributing to the development of stroke. Vascular smooth muscle cells (VSMC) play a vital role in cerebral blood flow control and maintenance of BBB. Ischemic injury triggers VSMC to switch into a detrimental phenotype in peripheral blood vessels, however, the pathological phenotype switching in cerebral VSMC and the impact of VSMC on BBB are not elucidated thoroughly in stroke with hypertension. Methods: Hypertensive mice with smooth muscle–specific deletion of MYPT1 (MYPT1 SMKO mice) were generated. Middle cerebral artery occlusion (MCAO) was conducted in adult MYPT1 SMKO mice and their wild-type (WT) mice for 60 min. Ischemic infarct volumes and neurological function were evaluated. Evens blue, immunofluorescence (IF), western blot (WB) and so on were performed to evaluate the permeability of BBB after stroke. The phenotype switching of VSMC was measured by WB, IF and quantitative real-time polymerase chain reaction (q-PCR) in oxygen glucose deprivation (OGD) and co-cultured in vitro models. Proteomic analysis was performed in cerebral capillaries. The q-PCR and WB were used for further validation. Results: It was found that the infarct volumes and neurological deficits were aggravated in MYPT1 SMKO mice and the permeability of BBB was increased. The loss of pericyte cells and degradation of basement membrane of BBB were more severe in MYPT1 SMKO mice. Furthermore, the protein expression of α-SMA in MYPT1 SMKO mice after MCAO was reduced and the protein expression of Calponin and SM-22α was reduced. The ability of migration and proliferation in VSMC of MYPT1-knockout was altered after OGD. Proteomic analysis showed that the expression of protein associated with inflammation in VSMC of MYPT1 SMKO mice was increased than that of WT mice, but the specific protein underlying the mechanism needs further verification. Conclusions: The damage of BBB was increased in MYPT1 SMKO hypertensive mice. And there is a phenotype switching in cerebral VSMC after stroke in MYPT1 SMKO hypertensive mice. The potential mechanism may involve the increasing expression of protein associated with inflammation in VSMC that needs further verification.

The interplay of membrane cholesterol and substrate on vascular smooth muscle biomechanics.

Cardiovascular disease (CVD) remains the primary cause of death worldwide. Specifically, atherosclerosis is a CVD characterized as a slow progressing chronic inflammatory disease. During atherosclerosis, vascular walls accumulate cholesterol and cause fatty streak formation. The progressive changes in vascular wall stiffness exert alternating mechanical cues on vascular smooth muscle cells (VSMCs). The detachment of VSMCs in the media layer of the vessel and migration toward the intima is a critical step in atherosclerosis. VSMC phenotypic switching is a complicated process that modifies VSMC structure and biomechanical function. These changes affect the expression and function of cell adhesion molecules, thus impacting VSMC migration. Accumulating evidence has shown cholesterol is capable of regulating cellular migration, proliferation, and spreading. However, the interaction and coordinated effects of both cellular cholesterol and the extracellular matrix (ECM) stiffness/composition on VSMC biomechanics remains to be elucidated.

Canonical Transient Receptor Potential Channels and Vascular Smooth Muscle Cell Plasticity.

Vascular smooth muscle cells (VSMCs) play a pivotal role in the stability and tonic regulation of vascular homeostasis. VSMCs can switch back and forth between highly proliferative (synthetic) and fully differentiated (contractile) phenotypes in response to changes in the vessel environment. Abnormal phenotypic switching of VSMCs is a distinctive characteristic of vascular disorders, including atherosclerosis, pulmonary hypertension, stroke, and peripheral artery disease; however, how the control of VSMC phenotypic switching is dysregulated under pathological conditions remains obscure. Canonical transient receptor potential (TRPC) channels have attracted attention as a key regulator of pathological phenotype switching in VSMCs. Several TRPC subfamily member proteins—especially TRPC1 and TRPC6—are upregulated in pathological VSMCs, and pharmacological inhibition of TRPC channel activity has been reported to improve hypertensive vascular remodeling in rodents. This review summarizes the current understanding of the role of TRPC channels in cardiovascular plasticity, including our recent finding that TRPC6 participates in aberrant VSMC phenotype switching under ischemic conditions, and discusses the therapeutic potential of TRPC channels.

Biomarkers in VSMC phenotypic modulation and vascular remodeling.

Vascular smooth muscle cells (VSMCs) are not terminally differentiated and can change their phenotype in response to environmental cues. Phenotype switching of VSMCs to less differentiated forms has led to an underestimation of their role in the development of vascular remodeling and many vascular diseases in both humans and animal models of this disease. In recent studies, many factors, such as microRNAs, matrix metalloproteinases, integrins, oxidative stress, autophagy, have been shown to play important roles in the mechanisms of VSMC phenotypic switch and vascular remodeling. This review highlights the current knowledge regarding the molecular mechanisms of VSMC phenotypic modulation in vascular remodeling. In this review, we want to provide effective molecular targets and opportunities for the future development of new therapeutics to regulate vascular remodeling diseases.

The Role of Vascular Smooth Muscle Cells in Arterial Remodeling: Focus on Calcification-Related Processes.

Arterial remodeling refers to the structural and functional changes of the vessel wall that occur in response to disease, injury, or aging. Vascular smooth muscle cells (VSMC) play a pivotal role in regulating the remodeling processes of the vessel wall. Phenotypic switching of VSMC involves oxidative stress-induced extracellular vesicle release, driving calcification processes. The VSMC phenotype is relevant to plaque initiation, development and stability, whereas, in the media, the VSMC phenotype is important in maintaining tissue elasticity, wall stress homeostasis and vessel stiffness. Clinically, assessment of arterial remodeling is a challenge; particularly distinguishing intimal and medial involvement, and their contributions to vessel wall remodeling. The limitations pertain to imaging resolution and sensitivity, so methodological development is focused on improving those. Moreover, the integration of data across the microscopic (i.e., cell-tissue) and macroscopic (i.e., vessel-system) scale for correct interpretation is innately challenging, because of the multiple biophysical and biochemical factors involved. In the present review, we describe the arterial remodeling processes that govern arterial stiffening, atherosclerosis and calcification, with a particular focus on VSMC phenotypic switching. Additionally, we review clinically applicable methodologies to assess arterial remodeling and the latest developments in these, seeking to unravel the ubiquitous corroborator of vascular pathology that calcification appears to be.

Role of the Balance of Akt and MAPK Pathways in the Exercise-Regulated Phenotype Switching in Spontaneously Hypertensive Rats.

The mechanisms regulating vascular smooth muscle cell (VSMC) phenotype switching and the critical signal modulation affecting the VSMCs remain controversial. Physical exercise acts as an effective drug in preventing elevated blood pressure and improving vascular function. This study was designed to explore the influence of aerobic exercise on the suppression of VSMC phenotype switching by balancing of the Akt, also known as PKB (protein kinase B) and mitogen-activated protein kinase (MAPK) signaling pathways. Spontaneously hypertensive rats (SHRs) and normotensive rats were subjected to exercise treatment before measuring the vascular morphological and structural performances. Exercise induced reverse expression of VSMC protein markers (α-SM-actin, calponin, and osteopontin (OPN)) in spontaneously hypertensive rats. It is noteworthy that the low expression of phosphorylated Akt significantly decreased the expression of VSMC contractile phenotype markers (α-SM-actin and calponin) and increased the expression of the VSMC synthetic phenotype marker (OPN). However, the MAPK signal pathway exerts an opposite effect. VSMCs and whole vessels were treated by inhibitors, namely the p-Akt inhibitor, p-ERK inhibitor, and p-p38 MAPK inhibitors. VSMC phenotype markers were reversed. It is important to note that a significant reverse regulatory relationship was observed between the expression levels of MAPK and the contractile markers in both normotensive and spontaneously hypertensive rats. We demonstrate that aerobic exercise regulates the VSMC phenotype switching by balancing the Akt and MAPK signaling pathways in SHRs.

Carbonic Anhydrase Inhibition Ameliorates Inflammation and Experimental Pulmonary Hypertension.

Inflammation and vascular smooth muscle cell (VSMC) phenotypic switching are causally linked to pulmonary arterial hypertension (PAH) pathogenesis. Carbonic anhydrase inhibition induces mild metabolic acidosis and exerts protective effects in hypoxic pulmonary hypertension. Carbonic anhydrases and metabolic acidosis are further known to modulate immune cell activation. To evaluate if carbonic anhydrase inhibition modulates macrophage activation, inflammation, and VSMC phenotypic switching in severe experimental pulmonary hypertension, pulmonary hypertension was assessed in Sugen 5416/hypoxia (SU/Hx) rats after treatment with acetazolamide or ammonium chloride (NH4Cl). We evaluated pulmonary and systemic inflammation and characterized the effect of carbonic anhydrase inhibition and metabolic acidosis in alveolar macrophages and bone marrow-derived macrophages (BMDMs). We further evaluated the treatment effects on VSMC phenotypic switching in pulmonary arteries and pulmonary artery smooth muscle cells (PASMCs) and corroborated some of our findings in lungs and pulmonary arteries of patients with PAH. Both patients with idiopathic PAH and SU/Hx rats had increased expression of lung inflammatory markers and signs of PASMC dedifferentiation in pulmonary arteries. Acetazolamide and NH4Cl ameliorated SU/Hx-induced pulmonary hypertension and blunted pulmonary and systemic inflammation. Expression of carbonic anhydrase isoform 2 was increased in alveolar macrophages from SU/Hx animals, classically (M1) and alternatively (M2) activated BMDMs, and lungs of patients with PAH. Carbonic anhydrase inhibition and acidosis had distinct effects on M1 and M2 markers in BMDMs. Inflammatory cytokines drove PASMC dedifferentiation, and this was inhibited by acetazolamide and acidosis. The protective antiinflammatory effect of acetazolamide in pulmonary hypertension is mediated by a dual mechanism of macrophage carbonic anhydrase inhibition and systemic metabolic acidosis.

Thymine DNA glycosylase is a key regulator of CaMKIIγ expression and vascular smooth muscle phenotype.

Multifunctional Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a multigene family with isoform-specific regulation of vascular smooth muscle (VSM) functions. In previous studies, we found that vascular injury resulted in VSM dedifferentiation and reduced expression of the CaMKIIγ isoform in medial wall VSM. Smooth muscle knockout of CaMKIIγ enhanced injury-induced VSM neointimal hyperplasia, whereas CaMKIIγ overexpression inhibited VSM proliferation and neointimal formation. In this study, we evaluated DNA cytosine methylation/demethylation as a mechanism for regulating CaMKII isoform expression in VSM. Inhibition of cytosine methylation with 5-Aza-2'-deoxycytidine significantly upregulated CaMKIIγ expression in cultured VSM cells and inhibited CaMKIIγ downregulation in organ-cultured aorta ex vivo. With the use of methylated cytosine immunoprecipitation, the rat Camk2g promoter was found hypomethylated in differentiated VSM, whereas injury- or cell culture-induced VSM dedifferentiation coincided with Camk2g promoter methylation and decreased expression. We report for the first time that VSM cell phenotype switching is accompanied by marked induction of thymine DNA glycosylase (TDG) protein and mRNA expression in injured arteries in vivo and in cultured VSM synthetic phenotype cells. Silencing Tdg in VSM promoted expression of CaMKIIγ and differentiation markers, including myocardin, and inhibited VSM cell proliferation and injury-induced neointima formation. This study indicates that CaMKIIγ expression in VSM is regulated by cytosine methylation/demethylation and that TDG is an important determinant of this process and, more broadly, VSM phenotype switching and function.NEW & NOTEWORTHY Expression of the calcium calmodulin-dependent protein kinase II-γ isoform (CaMKIIγ) is associated with differentiated vascular smooth muscle (VSM) and negatively regulates proliferation in VSM synthetic phenotype (VSMSyn) cells. This study demonstrates that thymine DNA glycosylase (TDG) plays a key role in regulating CaMKIIγ expression in VSM through promoter cytosine methylation/demethylation. TDG expression is strongly induced in VSMSyn cells and plays key roles in negatively regulating CaMKIIγ expression and more broadly VSM phenotype switching.

Abstract 348: Homeobox A4 Suppresses Vascular Smooth Muscle Cell Phenotypic Switching as a Novel Regulator of YAP/TEAD Transcriptional Activity

The Hippo signaling pathway is involved in the pathophysiology of various cardiovascular diseases. Yes-associated protein (YAP) and transcriptional enhancer activator domain (TEAD) transcriptional factors, the main transcriptional complex of the Hippo pathway, were recently identified as modulators of phenotypic switching of vascular smooth muscle cells (VSMCs). However, the intrinsic regulator of YAP/TEAD-mediated gene expressions in VSMCs remains to be elucidated, then we sought to investigate a novel regulator of YAP/TEAD transactivation involved in vascular diseases. We first investigated novel YAP/TEAD regulators using lentiviral shRNA library in HEK 293T-based TEAD-responsive reporter cell line and detected Homeobox A4 (HOXA4) as a potent repressor of YAP/TEAD transcriptional activity. HOXA4 attenuated YAP/TEAD-mediated gene expression independently of YAP phosphorylation, and co-immunoprecipitation assays revealed that HOXA4 interacts with TEADs but not YAP. Mechanistically, HOXA4 attenuated YAP/TEAD-mediated transcription by competing with YAP for TEAD binding. We also clarified that the expression of HOXA4 is relatively abundant in the vasculature, especially in VSMCs. In vitro experiments in human VSMCs showed HOXA4 maintains the differentiation state of VSMCs via inhibition of YAP/TEAD-induced phenotypic switching characterized by cell morphology, cell proliferation, and gene expression patterns. We generated Hoxa4-decifient mice and confirmed the downregulation of smooth muscle-specific contractile genes and the exacerbation of vascular remodeling after carotid artery ligation in vivo. Our results demonstrate HOXA4 is a novel repressor of VSMC phenotypic switching by inhibiting YAP/TEAD-mediated transcription. These findings give us a better understanding of the vascular pathophysiology and a novel therapeutic approach for vascular remodeling.

Anti-high mobility group box-1 antibody attenuated vascular smooth muscle cell phenotypic switching and vascular remodelling after subarachnoid haemorrhage in rats

Although cerebral vascular smooth muscle cell (VSMC) phenotypic switching is involved in the vascular dysfunction after subarachnoid haemorrhage (SAH), the precise mechanisms are still unclear. High mobility group box-1 (HMGB1) has been identified as a modulator in VSMC proliferation. The purpose of this study was to investigate the potential role of HMGB1 in the VSMC phenotypic switching following SAH. An endovascular perforation SAH model was used in our experiments. The expression levels of HMGB1, α­smooth muscle actin (α-SMA), osteopontin (OPN), smooth muscle myosin heavy chain (SM-MHC), embryonic smooth muscle myosin heavy chain (Smemb), TXA2, PAR-1 and AT1 receptor were evaluated by Western blot analyses. Iba1-positive cells and apoptotic cells were determined by immunofluorescence staining and TUNEL staining, respectively. Vasoconstriction of the isolated basilar artery was stimulated by thrombin and KCl. We found that HMGB1 expression was markedly increased following SAH, and anti-HMGB1 mAb significantly reversed VSMC phenotypic switching and vascular remodelling in rats. However, the effects of HMGB1 on VSMC phenotypic switching were partly blocked in the presence of SC79, a potent activator of phosphatidylinositol-3-kinase-AKT (PI3K/AKT). Furthermore, the enhanced vasoconstriction and decreased cerebral cortical blood flow induced by SAH were reversed by anti-HMGB1 mAb. Finally, we found that anti-HMGB1 mAb attenuated microglial activation and brain oedema, ameliorating neurological dysfunction. These results indicated that HMGB1 is a useful regulator of VSMC phenotypic switching and vascular remodelling following SAH and might be exploited as a novel therapeutic target for delayed cerebral ischaemia.

Impaired autophagy mediates hyperhomocysteinemia-induced HA-VSMC phenotypic switching.

Hyperhomocysteinemia (HHcy) is a highly-related risk factor in vascular smooth muscle cell (VSMC) phenotypic modulation and atherosclerosis. Growing evidence indicated that autophagy is involved in pathological arterial changes. However, the risk mechanisms by which homocysteine and VSMC autophagy interact with cardiovascular disease are poorly understood. This study verified the homocysteine-responsive endoplasmic reticulum protein promotion of VSMC phenotypic switching, and the formation of atherosclerotic plaque in vitro. We found that impaired autophagy, as evidenced by decreased levels of MAP1LC3B II/MAP1LC3B I, has a vital role in HHcy-induced human aortic (HA)-VSMC phenotypic switching, with a decrease in contractile proteins (SM α-actin and calponin) and an increase in osteopontin. Knockdown of the essential autophagy gene Atg7 by small interfering RNA promoted HA-VSMC phenotypic switching, indicating that impaired autophagy induces phenotypic switching in these cells. HHcy co-treatment with rapamycin triggered autophagy, which alleviated HA-VSMC phenotypic switching. Finally, we found that Krüppel-like factor 4 (KLF4), a zinc-finger transcription factor for maintaining genomic stability by resisting oxidative stress and restoring autophagy, is closely involved in this process. HHcy clearly decreased KLF4 expression. KLF4-specific siRNA aggravated defective autophagy and phenotypic switching. Mechanistically, KLF4 regulated the HHcy-induced decrease in HA-VSMC autophagy via the m-TOR signaling pathway. In conclusion, these results demonstrated that the KLF4-dependent rapamycin signaling pathway is a novel mechanism underlying HA-VSMC phenotypic switching and is crucial for HHcy-induced HA-VSMCs with defective autophagy to accelerate early atherosclerosis.

LncRNA MRAK048635_P1 is critical for vascular smooth muscle cell function and phenotypic switching in essential hypertension.

Vascular remodeling caused by essential hypertension is a leading cause of death in patients, and vascular smooth muscle cell (VSMC) dysfunction and phenotypic switching result in vascular remodeling. Therefore, inhibiting cell dysfunction and phenotypic switching in VSMCs may be a new treatment strategy for essential hypertension. The aim of the current study is to explore the roles of long non-coding RNA (lncRNA) MRAK048635_P1 in VSMC function and phenotypic switching. The MRAK048635_P1 level was determined in spontaneously hypertensive rats (SHRs) and VSMCs isolated from SHRs. MRAK048635_P1 was knocked down using a specific siRNA in VSMCs isolated from the thoracic aorta of SHRs and Wistar–Kyoto rats. Then, the proliferation and migration of VSMCs were determined using a cell counting kit-8 (CCK-8), a 3H labeling method, a transwell assay, and a wound healing assay. Flow cytometry was used to test the effect of MRAK048635_P1 on VSMC apoptosis. The protein and mRNA levels of associated genes were measured through Western blotting, immunofluorescence, and Quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR). MRAK048635_P1 showed low expression during hypertension in vivo and in vitro. Down-regulation of lncRNA MRAK048635_P1 promoted proliferation and migration and inhibited apoptosis in VSMCs isolated from healthy rat vascular tissue and SHR-derived VSMCs. Importantly, we also found that down-regulation of MRAK048635_P1 could induce VSMC phenotypic switching from a contractile to a secretory phenotype. In conclusion, our findings reveal that decreased MRAK048635_P1 is probably an important factor for vascular remodeling by affecting VSMC cell function and phenotypic switching in essential hypertension.

MicroRNA-134-5p Regulates Media Degeneration through Inhibiting VSMC Phenotypic Switch and Migration in Thoracic Aortic Dissection

Abnormal phenotypic switch, migration, and proliferation of vascular smooth muscle cells (VSMCs) are hallmarks for pathogenesis of thoracic aortic dissection (TAD). In the current study, we identified miR-134-5p as a critical regulator controlling human VSMC phenotypic switch and migration to investigate whether miR-134-5p affects human VSMC functions and development of TAD. Using miRNA microarray of aorta specimens from 12 TAD and 12 controls, we identified miR-134-5p, which was significantly downregulated in TAD tissues. With qPCR detection, we found that miR-134-5p was also evidently decreased in human AoSMCs. Ectopic expression of miR-134-5p obviously promoted VSMC differentiation and expression of contractile markers, such as α-SMA, SM22α, and MYH11. miR-134-5p potently inhibited PDGF-BB-induced VSMC phenotypic switch and migration. We further identified STAT5B and ITGB1 as downstream targets of miR-134-5p in human VSMCs and proved them to be mediators in VSMC phenotypic switch and progression of TAD. Finally, Ad-miR-134-5p obviously suppressed the aorta dilatation and vascular media degeneration by 39% in TAD mice after vascular injury induced by Ang II. Our findings revealed that miR-134-5p was a novel regulator in vascular remodeling and pathological progress of TAD via targeting STAT5B/ITGB1 expression. Targeting miR-134-5p or its downstream molecules in VSMCs might develop new avenues in clinical treatment of TAD.

Nicotine-mediated autophagy of vascular smooth muscle cell accelerates atherosclerosis via nAChRs/ROS/NF-κB signaling pathway

Background and aimsCigarette smoking is an established risk factor for atherosclerosis. Nicotine, the major constituent of cigarettes, mediates the phenotype switching of vascular smooth muscle cells (VSMCs) and contributes to atherogenesis. Recent studies show that autophagy regulates atherogenesis via several pathways. The aim of this study is to determine whether nicotine regulates autophagy and subsequently mediates the phenotypic transition of VSMCs. Methods and resultsOil Red O and HE staining of aortic sections of ApoE−/− mice showed that nicotine promoted atherosclerosis, and in situ expression of α-SMA indicated the involvement of VSMCs. Western blotting documented that nicotine induced the aorta autophagy. Cultured VSMCs treated with nicotine resulted in the increase of LC3 II-to-LC3 I ratio and the decrease of P62, along with GFP-LC3 puncta assay and transmission electron microscopy, further reflecting nicotine-induced autophagy. In addition, Western blotting and quantitative real-time PCR showed that VSMCs exposed to nicotine underwent changes in the expression of differentiation markers (α-SMA, SM22α and osteopontin), confirming the role of nicotine in VSMC differentiation. Transwell migration and scratch assays demonstrated that nicotine increased the migratory capacity of VSMCs. Finally, nicotine also increased the levels of reactive oxygen species (ROS), as measured by DCFH-DA staining. After respectively inhibiting autophagy (3-MA), oxidative stress (NAC), NF-κB activity (BAY 11–7082, si-p65) and nicotinic acetylcholine receptors (nAChRs, hexamethonium), nicotine-induced autophagy and VSMC phenotype switching were reversed. ConclusionsNicotine-induced autophagy promotes the phenotype switching of VSMCs and accelerates atherosclerosis, which is partly mediated by the nAChRs/ROS/NF-κB signaling pathway.

Notch signaling in bone marrow–derived FSP-1 cells initiates neointima formation in arteriovenous fistulas

Neointima formation is a major contributor to arteriovenous fistula (AVF) failure. We have previously shown that activation of the Notch signaling pathway contributes to neointima formation by promoting the migration of vascular smooth muscle cells (VSMCs) into the venous anastomosis. In the current study we investigated the mechanisms underlying the dedifferentiation and migration of VSMCs, and in particular the role of bone marrow-derived fibroblast specific protein 1 (FSP-1)+ cells, another cell type found in models of vascular injury. Using VSMC-specific reporter mice, we found that most of the VSMCs participating in AVF neointima formation originated from dedifferentiated VSMCs. We also observed infiltration of bone marrow-derived FSP-1+ cells into the arterial anastomosis where they could interact with VSMCs. Invitro, conditioned media from FSP-1+ cells stimulated VSMC proliferation and phenotype switching. Activated Notch signaling transformed FSP-1+ cells into type I macrophages and stimulated secretion of cytokines and growth factors. Pretreatment with a Notch inhibitor or knockout of the canonical downstream factor RBP-Jκ in bone marrow-derived FSP1+ cells decreased FSP1+ cell infiltration into murine AVFs, attenuating VSMC dedifferentiation and neointima formation. Our results suggest that targeting Notch signaling could provide a new therapeutic strategy to improve AVF patency.

A disintegrin and metalloprotease 22 accelerates neointima formation by activating ERK signaling

Background and aimsDespite the advantage of arterial expansion for life-threatening vascular pathologies, the occurrence of neointima formation remains a prominent complication, with the underlying mechanisms largely unknown. A disintegrin and metalloprotease 22 (ADAM22) belongs to the family of ADAMs that possesses various biological capacities regulating vascular physiopathology. However, little is known about ADAM22 in vascular smooth muscle cell (VSMC)-mediated neointima formation. Here, we aimed to evaluate the potential functional regulation of ADAM22 in neointima formation and to further explore the underlying mechanisms. MethodsIn our study, platelet-derived growth factor-BB (PDGF-BB)-induced VSMC proliferation was examined using a 5-bromo-2′-deoxyuridine (BrdU) incorporation assay and a cell counting kit-8 (CCK8) assay, while VSMC migration was detected using a modified Boyden chamber method and a scratch-wound assay. The functional role of ADAM22 in neointima formation was evaluated based on a left carotid artery wire injury model in mice at 14 and 28 days. ResultsADAM22 was significantly up-regulated in both PDGF-BB-challenged VSMCs and restenotic arteries of mice. When ADAM22 was overexpressed in VSMCs, cell proliferation, migration and phenotypic switching were simultaneously aggravated, whereas the opposite was observed when ADAM22 was knocked down in vitro. In ADAM22 heterozygote mice, wire-injury induced neointima formation was significantly ameliorated compared to wild-type control mice. Mechanistically, significantly up-regulated ERK phosphorylation is closely involved in the regulatory effects of ADAM22 in neointima formation. Interestingly, an ERK inhibitor largely reversed the aggravated VSMCs migration, proliferation and phenotypic switching induced by ADAM22 overexpression. ConclusionsOur results indicate that ADAM22 accelerates neointima formation by enhancing VSMC migration, proliferation and phenotypic switching via promoting ERK phosphorylation. Suppressing ADAM22 expression may be an effective strategy for ameliorating neointima formation.

NF-\u03baB-responsive miR-155 induces functional impairment of vascular smooth muscle cells by downregulating soluble guanylyl cyclase

Vascular smooth muscle cells (VSMCs) play an important role in maintaining vascular function. Inflammation-mediated VSMC dysfunction leads to atherosclerotic intimal hyperplasia and preeclamptic hypertension; however, the underlying mechanisms are not clearly understood. We analyzed the expression levels of microRNA-155 (miR-155) in cultured VSMCs, mouse vessels, and clinical specimens and then assessed its role in VSMC function. Treatment with tumor necrosis factor-α (TNF-α) elevated miR-155 biogenesis in cultured VSMCs and vessel segments, which was prevented by NF-κB inhibition. MiR-155 expression was also increased in high-fat diet-fed ApoE−/− mice and in patients with atherosclerosis and preeclampsia. The miR-155 levels were inversely correlated with soluble guanylyl cyclase β1 (sGCβ1) expression and nitric oxide (NO)-dependent cGMP production through targeting the sGCβ1 transcript. TNF-α-induced miR-155 caused VSMC phenotypic switching, which was confirmed by the downregulation of VSMC-specific marker genes, suppression of cell proliferation and migration, alterations in cell morphology, and NO-induced vasorelaxation. These events were mitigated by miR-155 inhibition. Moreover, TNF-α did not cause VSMC phenotypic modulation and limit NO-induced vasodilation in aortic vessels of miR-155−/− mice. These findings suggest that NF-κB-induced miR-155 impairs the VSMC contractile phenotype and NO-mediated vasorelaxation by downregulating sGCβ1 expression. These data suggest that NF-κB-responsive miR-155 is a novel negative regulator of VSMC functions by impairing the sGC/cGMP pathway, which is essential for maintaining the VSMC contractile phenotype and vasorelaxation, offering a new therapeutic target for the treatment of atherosclerosis and preeclampsia.

SUMOylation of Vps34 by SUMO1 promotes phenotypic switching of vascular smooth muscle cells by activating autophagy in pulmonary arterial hypertension

IntroductionPulmonary arterial hypertension (PAH) is a life-threatening disease without effective therapies. PAH is associated with a progressive increase in pulmonary vascular resistance and irreversible pulmonary vascular remodeling. SUMO1 (small ubiquitin-related modifier 1) can bind to target proteins and lead to protein SUMOylation, an important post-translational modification with a key role in many diseases. However, the contribution of SUMO1 to PAH remains to be fully characterized. MethodsIn this study, we explored the role of SUMO1 in the dedifferentiation of vascular smooth muscle cells (VSMCs) involved in hypoxia-induced pulmonary vascular remodeling and PAH in vivo and in vitro. ResultsIn a mouse model of hypoxic PAH, SUMO1 expression was significantly increased, which was associated with activation of autophagy (increased LC3b and decreased p62), dedifferentiation of pulmonary arterial VSMCs (reduced α-SMA, SM22 and SM-MHC), and pulmonary vascular remodeling. Similar results were obtained in a MCT-induced PAH model. Overexpression of SUMO1 significantly increased VSMCs proliferation, migration, hypoxia-induced VSMCs dedifferentiation, and autophagy, but these effects were abolished by inhibition of autophagy by 3-MA in aortic VSMCs. Furthermore, SUMO1 knockdown reversed hypoxia-induced proliferation and migration of PASMCs. Mechanistically, SUMO1 promotes Vps34 SUMOylation and the assembly of the Beclin-1-Vps34-Atg14 complex, thereby inducing autophagy, whereas Vps34 mutation K840R reduces Vps34 SUMOylation and inhibits VSMCs dedifferentiation. DiscussionOur data uncovers an important role of SUMO1 in VSMCs proliferation, migration, autophagy, and phenotypic switching (dedifferentiation) involved in pulmonary vascular remodeling and PAH. Targeting of the SUMO1-Vps34-autophagy signaling axis may be exploited to develop therapeutic strategies to treat PAH.

MiR-9 promotes the phenotypic switch of vascular smooth muscle cells by targeting KLF5

Background/aimDiabetic vascular smooth muscle cells (VSMCs) are characterized by increased proliferation and migration. Small noncoding microRNAs (miRNAs) have been considered critical modulators of the VSMC phenotypic switch after an environmental stimulus. However, microRNA in high glucose-induced proinflammation and its atherogenic effect is still ambiguous. Materials and methods The technique of qRT-PCR was used to examine the expression of miR-9 in VSMCs. The downstream signaling protein relative to miR-9 regulation, Krüppel-like factor 5, and some marker genes of contractile VSMCs were analyzed by western blotting and qRT-PCR. Luciferase reporter assay was used to detect the expression of KLF5, which is regulated by miR-9. To examine the function of a miR-9 inhibitor in VSMC proliferation and migration, VSMC proliferation and migration assays were performed. Results Reduced transcriptional levels of miR-9 and expression of specific genes of contractile VSMCs were observed in the SMC cell line C-12511 treated with high glucose and SMCs, which were isolated from db/db mice. Moreover, the activity of KLF5 3′-UTR was dramatically reduced by a miR-9 mimic and increased by a miR-9 inhibitor. The proliferation and migration of SMCs were reduced by the miR-9 mimic. Conclusion miR-9 inhibits the proliferation and migration of SMC by targeting KLF5 in db/db mice.