Smooth Muscle Cell Phenotypic Switching Research Articles

Insulin Treatment Forces Arteriogenesis in Diabetes Mellitus by Upregulation of the Early Growth Response-1 (Egr-1) Pathway in Mice.

The process of arteriogenesis is severely compromised in patients with diabetes mellitus (DM). Earlier studies have reported the importance of Egr-1 in promoting collateral outward remodeling. However, the role of Egr-1 in the presence of DM in outward vessel remodeling was not studied. We hypothesized that Egr-1 expression may be compromised in DM which may lead to impaired collateral vessel growth. Here, we investigated the relevance of the transcription factor Egr-1 for the process of collateral artery growth in diabetic mice. Induction of arteriogenesis by femoral artery ligation resulted in an increased expression of Egr-1 on mRNA and protein level but was severely compromised in streptozotocin-induced diabetic mice. Diabetes mellitus mice showed a significantly reduced expression of Egr-1 endothelial downstream genes Intercellular Adhesion Molecule-1 (ICAM-1) and urokinase Plasminogen Activator (uPA), relevant for extravasation of leukocytes which promote arteriogenesis. Fluorescent-activated cell sorting analyses confirmed reduced leukocyte recruitment. Diabetes mellitus mice showed a reduced expression of the proliferation marker Ki-67 in growing collaterals whose luminal diameters were also reduced. The Splicing Factor-1 (SF-1), which is critical for smooth muscle cell proliferation and phenotype switch, was found to be elevated in collaterals of DM mice. Treatment of DM mice with insulin normalized the expression of Egr-1 and its downstream targets and restored leukocyte recruitment. SF-1 expression and the diameter of growing collaterals were normalized by insulin treatment as well. In summary, our results showed that Egr-1 signaling was impaired in DM mice; however, it can be rescued by insulin treatment.

Role of Vascular Smooth Muscle Cell Phenotypic Switching and Calcification in Aortic Aneurysm Formation

Aortic aneurysm is a vascular disease whereby the ECM (extracellular matrix) of a blood vessel degenerates, leading to dilation and eventually vessel wall rupture. Recently, it was shown that calcification of the vessel wall is involved in both the initiation and progression of aneurysms. Changes in aortic wall structure that lead to aneurysm formation and vascular calcification are actively mediated by vascular smooth muscle cells. Vascular smooth muscle cells in a healthy vessel wall are termed contractile as they maintain vascular tone and remain quiescent. However, in pathological conditions they can dedifferentiate into a synthetic phenotype, whereby they secrete extracellular vesicles, proliferate, and migrate to repair injury. This process is called phenotypic switching and is often the first step in vascular pathology. Additionally, healthy vascular smooth muscle cells synthesize VKDPs (vitamin K-dependent proteins), which are involved in inhibition of vascular calcification. The metabolism of these proteins is known to be disrupted in vascular pathologies. In this review, we summarize the current literature on vascular smooth muscle cell phenotypic switching and vascular calcification in relation to aneurysm. Moreover, we address the role of vitamin K and VKDPs that are involved in vascular calcification and aneurysm. Visual Overview- An online visual overview is available for this article.

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.

Advances in molecular mechanism of vascular remodeling in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a clinical hemodynamic syndrome characterized by elevated pulmonary arterial pressure and pulmonary vascular resistance leading to right heart failure and death. Vascular remodeling is the most prominent histopathological feature of PAH, which is regulated by many factors. Endoplasmic reticulum stress, calcium disorder and mitochondrial dysfunction are involved in the vascular cell proliferation and apoptosis by regulating intracellular calcium homeostasis and cellular metabolism. Epigenetic phenomenon such as DNA damage and abnormal expression of miRNA are also involved in the regulation of abnormal proliferation of vascular cells. Vascular cell phenotype switching including endothelial-mesenchymal transition and smooth muscle cell phenotype switching play an important role in abnormal proliferation of vascular cells. Vascular remodeling is produced by a variety of cells and molecular pathways, and aiming at multiple targets which is expected to find a new breakthrough in the treatment of PAH,and to improve abnormal vascular remodeling, delay or even reverse the progression of PAH.

P22phox promotes Ang-II-induced vascular smooth muscle cell phenotypic switch by regulating KLF4 expression

NADPH oxidase (Nox) is the main source of reactive oxygen species in vascular diseases, which have been implicated in promoting VSMCs phenotypic switch. P22phox, the indispensable component of the complex Nox, is required for their activity and stability. Krüppel-like factor 4 (KLF4) is an important transcriptional regulator of VSMCs phenotypic switch. Both KLF4 and p22phox are involved in the proliferation, migration and differentiation of VSMC. This study aims to determine whether and how p22phox regulates KLF4 expression in phenotypic switching of VSMCs. In cultured primary rat VSMCs, we noticed that the expression of P22phox was significantly increased in combination with VSMCs phenotypic switch and up-regulated KLF4 expression in Ang-II-treated cells. Ang-II-induced VSMC dedifferentiation, proliferation, migration, KLF4 expression, H2O2 production and the phosphorylation of AKT, ERK1/2 were all inhibited by knockdown of P22phox. Furthermore, H2O2 treatment effectively enhanced the phosphorylation of AKT, ERK1/2 and the expression of KLF4, whereas LY294002 (a specific inhibitor of PI3K), U0126 (a specific inhibitor of ERK1/2) significantly attenuated the H2O2-induced up-regulation of KLF4. In conclusion, these results demonstrated that p22phox promotes Ang-II-induced VSMC phenotypic switch via the H2O2-ERK1/2/AKT-KLF4 signaling pathway.

LncRNA ENST00000602558.1 regulates ABCG1 expression and cholesterol efflux from vascular smooth muscle cells through a p65-dependent pathway

Background and aimsLong non-coding RNAs (lncRNAs) have proven to be involved in the progression of atherosclerosis and dyslipidemia. In addition, vascular smooth muscle cells (VSMCs) phenotype switching, including VSMCs-derived foam cells formation, plays a key role in the pathogenesis of atherosclerosis. LncRNA ENST00000602558.1, one of the differentially expressed lncRNAs between coronary artery disease (CAD) patients and healthy controls identified by our previous study, was located to TG and HDL susceptibility loci, but its role and underlying mechanism in the pathogenesis of atherosclerosis remain unclear. The present study aims to explore the role and underlying mechanism of ENST00000602558.1 in the regulation of cholesterol efflux from VSMCs. MethodsABCG1 mRNA and protein expression in VSMCs was detected using qRT-PCR and Western blot, respectively. ABCG1-mediated cholesterol efflux to HDL from VSMCs was measured by means of NBD-cholesterol fluorescence intensity. The binding of ENST00000602558.1 to p65 and p65 to ABCG1 promoter region was detected by RNA immunoprecipitation (RIP) assay and chromatin immunoprecipitation (ChIP) assay, respectively. ResultsOverexpression of ENST00000602558.1 downregulated ABCG1 mRNA and protein expression, while knockdown of ENST00000602558.1 upregulated ABCG1 mRNA and protein expression. Consistently, ENST00000602558.1 overexpression decreased ABCG1-mediated cholesterol efflux to HDL from VSMCs by 30.38% (p < 0.001), and knockdown of ENST00000602558.1 increased ABCG1-mediated cholesterol efflux to HDL from VSMCs by 30.41% (p = 0.001). In addition to cholesterol efflux, overexpression of ENST00000602558.1 increased lipid accumulation and TC/TG levels, while knockdown of ENST00000602558.1 decreased lipid accumulation and TC/TG levels in VSMCs. Furthermore, we confirmed that ENST00000602558.1 regulated ABCG1 expression and ABCG1-mediated cholesterol efflux from VSMCs through binding to p65. ConclusionsIn conclusion, ENST00000602558.1 played an important role in mediating cholesterol efflux to HDL from VSMCs by regulating ABCG1 expression through binding to p65.

O‐GlcNAc Transferase Plays a Direct Role in Vascular Smooth Muscle Cell Phenotypic Switching

Atherosclerotic complications account for increased morbidity and mortality in diabetic patients. Vascular smooth muscle cell (VSMC) transformation from quiescent contractile to synthetic proliferative phenotype is central to the evolution of atherosclerosis. Diabetic patients show increased propensity for VSMC migration and proliferation, a hallmark of SMC phenotypic de‐differentiation. Using specific pharmacological activators and inhibitors, we previously reported that augmented signaling via O‐linked N‐acetylglucosamine (O‐GlcNAc) transferase (OGT), the key enzyme catalyzing addition of O‐GlcNAc moieties to proteins, controls glucose‐induced VSMC proliferation. However, the mechanistic link between OGT and VSMC activation remains unknown. The goal of the current study was to investigate whether OGT plays a direct role in VSMC phenotypic transition. Using siRNA gene silencing in primary human aortic SMC (HASMC) cultures, we demonstrated that OGT deletion increased SM‐MHC and α‐SMA (SM contractile markers) expression concomitant to attenuated PCNA (proliferation marker) expression in response to high glucose in vitro, shown via immunoblotting and immunocytochemistry. Moreover, under glucose‐stimulated conditions, OGT knockdown decreased the expression of Cyclin E (cell cycle regulator) in OGT siRNA‐transfected HASMC vs. cells transfected with control siRNA. To interrogate the role of OGT in VSMC activation in vivo, we next developed the tamoxifen‐inducible VSMC‐specific OGT knockout mice by crossing OGTfl/fl female mice with tamoxifen‐inducible Myh11‐CreERT2 male mice; the resulting Cretg/OGTfl/Y male mice (produced in F1 generation) were used for Cre recombinase activation. Specifically, 6 wks old male mice were treated with tamoxifen (40 mg/Kg) or vehicle (peanut oil) i.p. once daily for 5 consecutive days. Aorta and heart were harvested from the mice 21 days after the last tamoxifen injection. Immunoblotting experiments confirmed loss of OGT expression in aortic vessels of tamoxifen‐treated Cretg/OGTfl/Y mice (smOGT−/Y) compared to vehicle‐treated Cretg/OGTfl/Y littermates and tamoxifen‐treated OGTfl/Y mice (smOGT+/Y, with intact OGT). In contrast, OGT expression remained unaffected in left ventricular tissue lysates derived from smOGT−/Y vs. smOGT+/Y mice, validating our SMC‐specific OGT knockout mouse model. Importantly, immunoblotting revealed increased SM‐MHC and α‐SMA expression in aortic vessels of smOGT−/Y mice compared to smOGT+/Y, with intact OGT; this increase in SM contractile marker expression was further accompanied with attenuated PCNA and IL1β (pro‐inflammatory marker) expression in smOGT−/Y mice. Together, these data demonstrate a direct role of OGT in VSMC phenotypic de‐differentiation. Our findings suggest a putative fundamental role of OGT in the etiology of diabetic vascular disease.Support or Funding InformationAHA‐Grant‐in‐Aid 16GRNT31200034; NIH‐NHLBI 1R56HL141409‐01This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

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.

Long non-coding RNA CASC2 suppresses pulmonary artery smooth muscle cell proliferation and phenotypic switch in hypoxia-induced pulmonary hypertension

BackgroundIn this study, we aimed to investigate whether and how lncRNA CASC2 was involved in hypoxia-induced pulmonary hypertension (PH)-related vascular remodeling.MethodsThe expression of lncRNAs or mRNAs was detected by qRT-PCR, and western blot analysis or immunochemistry was employed for detecting the protein expression. Cell number assay and EdU (5-ethynyl-2′-deoxyuridine) staining were performed to assess cell proliferation. Besides, flow cytometry and wound healing assay were employed for assessments of cell apoptosis and cell migration, respectively. Rat model of hypoxic PH was established and the hemodynamic measurements were performed. Hematoxylin and eosin (HE) and Masson′s trichrome staining were carried out for pulmonary artery morphometric analysis.ResultsThe expression of lncRNA CASC2 was decreased in hypoxia-induced rat pulmonary arterial tissues and pulmonary artery smooth muscle cells (PASMCs). Up-regulation of lncRNA CASC2 inhibited cell proliferation, migration yet enhanced apoptosis in vitro and in vivo in hypoxia-induced PH. Western blot analysis and immunochemistry showed that up-regulation of lncRNA CASC2 greatly decreased the expression of phenotype switch-related marker α-SMA in hypoxia-induced PH. Furthermore, it was indicated by the pulmonary artery morphometric analysis that lncRNA CASC2 suppressed vascular remodeling of hypoxia-induced rat pulmonary arterial tissues.ConclusionLncRNA CASC2 inhibited cell proliferation, migration and phenotypic switch of PASMCs to inhibit the vascular remodeling in hypoxia-induced PH.

Platelet microRNAs and vascular injury.

Vascular smooth muscle cell (VSMC) phenotype switching from a contractile state to a synthetic phenotype has been implicated in intimal remodeling during vascular injury. While multiple studies have focused on dedifferentiation of VSMCs, prevention of VSMC-mediated excessive repair remains poorly understood. In this issue of the JCI, Zeng et al. identified a mechanism by which platelet-derived microRNA-223 (miRNA-223) reverses VSMC dedifferentiation. The authors show that suppression of proliferation occurs after platelet internalization by VSMCs. Moreover, they demonstrate that miRNA-223 inhibits dedifferentiation and intimal hyperplasia in diabetic mice by decreasing PDGFRβ expression in VSMCs. Together, these results identify platelet-derived miRNA-223 as a potential therapeutic target in vascular injury.

SM22α (Smooth Muscle 22α) Prevents Aortic Aneurysm Formation by Inhibiting Smooth Muscle Cell Phenotypic Switching Through Suppressing Reactive Oxygen Species/NF-κB (Nuclear Factor-κB).

Objective- Vascular smooth muscle cell phenotypic transition plays a critical role in the formation of abdominal aortic aneurysms (AAAs). SM22α (smooth muscle 22α) has a vital role in maintaining the smooth muscle cell phenotype and is downregulated in AAA. However, whether manipulation of the SM22α gene influences the pathogenesis of AAA is unclear. Here, we investigated whether SM22α prevents AAA formation and explored the underlying mechanisms. Approach and Results- In both human and animal AAA tissues, a smooth muscle cell phenotypic switch was confirmed, as manifested by the downregulation of SM22α and α-SMA (α-smooth muscle actin) proteins. The methylation level of the SM22α gene promoter was dramatically higher in mouse AAA tissues than in control tissues. SM22α knockdown in ApoE-/- (apolipoprotein E-deficient) mice treated with Ang II (angiotensin II) accelerated the formation of AAAs, as evidenced by a larger maximal aortic diameter and more medial elastin degradation than those found in control mice, whereas SM22α overexpression exerted opposite effects. Similar results were obtained in a calcium chloride-induced mouse AAA model. Mechanistically, SM22α deficiency significantly increased reactive oxygen species production and NF-κB (nuclear factor-κB) activation in AAA tissues, whereas SM22α overexpression produced opposite effects. NF-κB antagonist SN50 or antioxidant N-acetyl-L-cysteine partially abrogated the exacerbating effects of SM22α silencing on AAA formation. Conclusions- SM22α reduction in AAAs because of the SM22α promoter hypermethylation accelerates AAA formation through the reactive oxygen species/NF-κB pathway, and therapeutic approaches to increase SM22α expression are potentially beneficial for preventing AAA formation.

The G-protein coupled receptor ChemR23 determines smooth muscle cell phenotypic switching to enhance high phosphate-induced vascular calcification.

Vascular calcification, a marker of increased cardiovascular risk, is an active process orchestrated by smooth muscle cells. Observational studies indicate that omega-3 fatty acids protect against vascular calcification, but the mechanisms are unknown. The G-protein coupled receptor ChemR23 transduces the resolution of inflammation induced by the omega-3-derived lipid mediator resolvin E1. ChemR23 also contributes to osteoblastic differentiation of stem cells and bone formation, but its role in vascular calcification is unknown. The aim of this study was to establish the role of ChemR23 in smooth muscle cell fate and calcification. Gene expression analysis in epigastric arteries derived from patients with chronic kidney disease and vascular calcification revealed that ChemR23 mRNA levels predicted a synthetic smooth muscle cell phenotype. Genetic deletion of ChemR23 in mice prevented smooth muscle cell de-differentiation. ChemR23-deficient smooth muscle cells maintained a non-synthetic phenotype and exhibited resistance to phosphate-induced calcification. Moreover, ChemR23-deficient mice were protected against vitamin D3-induced vascular calcification. Resolvin E1 inhibited smooth muscle cell calcification through ChemR23. Introduction of the Caenorhabditis elegans Fat1 transgene, leading to an endogenous omega-3 fatty acid synthesis and hence increased substrate for resolvin E1 formation, significantly diminished the differences in phosphate-induced calcification between ChemR23+/+ and ChemR23-/- mice. This study identifies ChemR23 as a previously unrecognized determinant of synthetic and osteoblastic smooth muscle cell phenotype, favouring phosphate-induced vascular calcification. This effect may be of particular importance in the absence of ChemR23 ligands, such as resolvin E1, which acts as a calcification inhibitor under hyperphosphatic conditions.

Targeting epigenetics and non-coding RNAs in atherosclerosis: from mechanisms to therapeutics.

Atherosclerosis, the principal cause of cardiovascular death worldwide, is a pathological disease characterized by fibro-proliferation, chronic inflammation, lipid accumulation, and immune disorder in the vessel wall. As the atheromatous plaques develop into advanced stage, the vulnerable plaques are prone to rupture, which causes acute cardiovascular events, including ischemic stroke and myocardial infarction. Emerging evidence has suggested that atherosclerosis is also an epigenetic disease with the interplay of multiple epigenetic mechanisms. The epigenetic basis of atherosclerosis has transformed our knowledge of epigenetics from an important biological phenomenon to a burgeoning field in cardiovascular research. Here, we provide a systematic and up-to-date overview of the current knowledge of three distinct but interrelated epigenetic processes (including DNA methylation, histone methylation/acetylation, and non-coding RNAs), in atherosclerotic plaque development and instability. Mechanistic and conceptual advances in understanding the biological roles of various epigenetic modifiers in regulating gene expression and functions of endothelial cells (vascular homeostasis, leukocyte adhesion, endothelial-mesenchymal transition, angiogenesis, and mechanotransduction), smooth muscle cells (proliferation, migration, inflammation, hypertrophy, and phenotypic switch), and macrophages (differentiation, inflammation, foam cell formation, and polarization) are discussed. The inherently dynamic nature and reversibility of epigenetic regulation, enables the possibility of epigenetic therapy by targeting epigenetic "writers", "readers", and "erasers". Several Food Drug Administration-approved small-molecule epigenetic drugs show promise in pre-clinical studies for the treatment of atherosclerosis. Finally, we discuss potential therapeutic implications and challenges for future research involving cardiovascular epigenetics, with an aim to provide a translational perspective for identifying novel biomarkers of atherosclerosis, and transforming precision cardiovascular research and disease therapy in modern era of epigenetics.

Teniposide regulates the phenotype switching of vascular smooth muscle cells in a miR-21-dependent manner

The switch of vascular smooth muscle cells (SMCs) from the contractile phenotype to proliferative one can make contributions to atherosclerosis and neointima formation. MiR-21 can prevent the rupture of advanced lesion plaques. We previously reported the protection of DNA topoisomerase II (Topo II) inhibitors against atherosclerosis and vascular calcification. However, it remains unknown if Topo II inhibitors can change SMC phenotypes. Herein, we show that teniposide protected SMC phenotype switching during atherosclerosis by enhancing expression of smooth muscle α-actin (SMA) while reducing osteopontin (OPN) expression in aortic lesion plaques. In vitro, teniposide induced expression of smooth muscle protein 22-α and calponin 1, but inhibited expression of OPN and epiregulin in human aortic SMCs (HASMCs). Moreover, teniposide attenuated platelet derived growth factor-BB-induced HASMC proliferation and migration. Mechanistically, the effect of teniposide on SMC phenotypes was completed, at least in part, by activating miR-21 expression. In addition, teniposide ameliorated ligation-induced carotid artery remodeling in C57BL/6J mice by regulating SMA and OPN expression. Taken together, our study demonstrates that teniposide regulates SMC phenotype switching by upregulating expression of contractile genes in a miR-21-dependent manner, and this function is an important anti-atherogenic mechanism of teniposide.

GW29-e0327 VPO1 Modulates Vascular Smooth Muscle Cell Phenotypic Switch in Abdominal Aortic Aneurysms

GW29-e0327 VPO1 Modulates Vascular Smooth Muscle Cell Phenotypic Switch in Abdominal Aortic Aneurysms

MiRNA Regulation of the Hyperproliferative Phenotype of Vascular Smooth Muscle Cells in Diabetes.

Harnessing the mechanisms underlying the exacerbated vascular remodeling in diabetes mellitus (DM) is pivotal to prevent the high toll of vascular diseases in patients with DM. miRNA regulates vascular smooth muscle cell (VSMC) phenotypic switch. However, miRNA modulation of the detrimental diabetic VSMC phenotype is underexplored. Streptozotocin-induced type 1 DM (T1DM) Wistar rats and type 2 DM (T2DM) Zucker rats underwent right carotid artery experimental angioplasty, and global miRNA/mRNA expression profiling was obtained by RNA sequencing (RNA-Seq). Two days after injury, a set of six miRNAs were found to be uniquely downregulated or upregulated in VSMCs both in T1DM and T2DM. Among these miRNAs, miR-29c and miR-204 were the most significantly misregulated in atherosclerotic plaques from patients with DM. miR-29c overexpression and miR-204 inhibition per se attenuated VSMC phenotypic switch in DM. Concomitant miR-29c overexpression and miR-204 inhibition fostered an additive reduction in VSMC proliferation. Epithelial membrane protein 2 (Emp2) and Caveolin-1 (Cav1) mRNAs were identified as direct targets of miR-29c and miR-204, respectively. Importantly, contemporary miR-29c overexpression and miR-204 inhibition in the injured artery robustly reduced arterial stenosis in DM rats. Thus, contemporaneous miR-29c activation and miR-204 inhibition in DM arterial tissues is necessary and sufficient to prevent the exaggerated VSMC growth upon injury.

The roles of mechanotransduction, vascular wall cells, and blood cells in atheroma induction.

This paper describes and analyzes the cellular and molecular mechanisms underlying atherosclerosis development. In particular, the roles of monocytes/macrophages, smooth muscle cells, and vascular endothelium in the formation of stable/unstable atheromatous plaques, and the contributions of some processes to atheroma formation. In this study we analyzed endothelium: function, dysfunction, and involvement into atherogenesis; cell proteins mediating mechanotransduction; proatherogenic role of monocytes; the role of macrophages in the development of unstable atheromatous plaques and smooth muscle cell origin in atherosclerosis. Smooth muscle cell phenotypic switching; their functioning; the ability to retain cholesterol and lipoproteins as well as secretion of pro- and anti-inflammatory molecules and extracellular matrix proteins, their response to extracellular stimuli secreted by other cells, and the effect of smooth muscle cells on the cells surrounding atheromatous plaques are fundamentally important for the insight into atherosclerosis molecular basis. Atheromatous plaque transcriptome studies will be helpful in the identification of the key genes involved in atheroma transformation and development as well as discovery of the new targets for diagnosis and therapy.

VPO1 Modulates Vascular Smooth Muscle Cell Phenotypic Switch by Activating Extracellular Signal-regulated Kinase 1/2 (ERK 1/2) in Abdominal Aortic Aneurysms.

BackgroundHydrogen peroxide (H2O2) is a critical molecular signal in the development of abdominal aortic aneurysm (AAA) formation. Vascular peroxidase 1 (VPO1) catalyzes the production of hypochlorous acid (HOCl) from H2O2 and significantly enhances oxidative stress. The switch from a contractile phenotype to a synthetic one in vascular smooth muscle cells (VSMCs) is driven by reactive oxygen species and is recognized as an early and important event in AAA formation. This study aims to determine if VPO1 plays a critical role in the development of AAA by regulating VSMC phenotypic switch.Methods and Results VPO1 is upregulated in human and elastase‐induced mouse aneurysmal tissues compared with healthy control tissues. Additionally, KLF4, a nuclear transcriptional factor, is upregulated in aneurysmatic tissues along with a concomitant downregulation of differentiated smooth muscle cell markers and an increase of synthetic phenotypic markers, indicating VSMC phenotypic switch in these diseased tissues. In cultured VSMCs from rat abdominal aorta, H2O2 treatment significantly increases VPO1 expression and HOCl levels as well as VSMC phenotypic switch. In support of these findings, depletion of VPO1 significantly attenuates the effects of H2O2 and HOCl treatment. Furthermore, HOCl treatment promotes VSMC phenotypic switch and ERK1/2 phosphorylation. Pretreatment with U0126 (a specific inhibitor of ERK1/2) significantly attenuates HOCl‐induced VSMC phenotypic switch.ConclusionsOur results demonstrate that VPO1 modulates VSMC phenotypic switch through the H2O2/VPO1/HOCl/ERK1/2 signaling pathway and plays a key role in the development of AAA. Our findings also implicate VPO1 as a novel signaling node that mediates VSMC phenotypic switch and plays a key role in the development of AAA.Clinical Trial Registration URL: http://www.chictr.org.cn. Unique identifier: ChiCTR1800016922.

ABCA1 and HDL3 are required to modulate smooth muscle cells phenotypic switch induced by cigarette smoke

ABCA1 and HDL3 are required to modulate smooth muscle cells phenotypic switch induced by cigarette smoke

Knockdown of Herp alleviates hyperhomocysteinemia mediated atherosclerosis through the inhibition of vascular smooth muscle cell phenotype switching

BackgroundPhenotypic switching of vascular smooth muscle cells (VSMCs) plays a key role in atherosclerosis. We aimed to investigate whether Homocysteine-responsive endoplasmic reticulum protein (Herp) was involved in VSMC phenotypic switching and affected atheroprogression. MethodsTo assess the role of Herp in homocysteine (Hcy)-associated atherosclerosis, Herp−/− and LDLR−/− double knockout mice were generated and fed with a high methionine diet (HMD) to induce Hyperhomocysteinemia (HHcy). Atherosclerotic lesions, cholesterol homeostasis, endoplasmic reticulum (ER) stress activation, and the phenotype of VSMCs were assessed in vivo. We used siRNAs to knockdown Herp in cultured VSMCs to further validate our findings in vitro. ResultsHMD significantly activated the activating transcription factor 6 (ATF6)/Herp arm of ER stress in LDLR−/− mice, and induced the phenotypic switch of VSMCs, with the loss of contractile proteins (SMA and calponin) and an increase of OPN protein. Herp−/−/LDLR−/− mice developed reduced atherosclerotic lesions in the aortic sinus and the whole aorta when compared with LDLR−/− mice. However, Herp deficiency had no effect on diet-induced HHcy and hyperlipidemia. Inhibition of VSMC phenotypic switching, decreased proliferation and collagen accumulation were observed in Herp−/−/LDLR−/− mice when compared with LDLR−/− mice. In vitro experiments demonstrated that Hcy caused VSMC phenotypic switching, promoted cell proliferation and migration; this was reversed by Herp depletion. We achieved similar results via inhibition of ER stress using 4-phenylbutyric-acid (4-PBA) in Hcy-treated VSMCs. ConclusionHerp deficiency inhibits the phenotypic switch of VSMCs and the development of atherosclerosis, thus providing novel insights into the role of Herp in atherogenesis.