AT1R autoantibody promotes phenotypic transition of smooth muscle cells by activating AT1R-OAS2

Phenotypic transition of vascular smooth muscle cells (VSMCs) is an early event in the onset and progression of several cardiovascular diseases. As an important mediator of the renin-angiotensin system (RAS), activation of the angiotensin II type 1 receptor (AT1R) induces phenotypic transition of VSMCs. AT1R autoantibodies (AT1-AAs), which are agonistic autoantibodies of AT1R, have been detected in the sera of patients with a variety of cardiovascular diseases associated with phenotypic transition. However, the effect of AT1-AA on phenotypic transition is currently unknown. In this study, AT1-AA-positive rat model was established by active immunization to detect markers of VSMCs phenotypic transition. The results showed that AT1-AA-positive rats showed phenotypic transition of VSMCs, which was evidenced by the decrease of contractile markers, while the increase of synthetic markers in the thoracic aorta. However, in AT1-AA-positive AT1R knockout rats, the phenotypic transition-related proteins were not altered. In vitro, after stimulating human aortic smooth muscle cells with AT1-AA for 48 h, 2'-5' oligoadenylate synthase 2 (OAS2) was identified as the key differentially expressed gene by RNA sequencing and bioinformatics analysis. Furthermore, high expression of OAS2 was found in aorta of AT1-AA-positive rats; knockdown of OAS2 by siRNA can reverse the phenotypic transition of VSMCs induced by AT1-AA. In summary, this study suggests that AT1-AA can promote phenotypic transition of VSMCs through AT1R-OAS2 pathway, and OAS2 might serve as a potential therapeutic target to prevent pathological phenotypic transition of smooth muscle cells.

H3.3B controls aortic dissection progression by regulating vascular smooth muscle cells phenotypic transition and vascular inflammation

Aortic dissection is a devastating cardiovascular disease with a high lethality. Histone variants maintain the genomic integrity and play important roles in development and diseases. However, the role of histone variants in aortic dissection has not been well identified. In the present study, H3f3b knockdown reduced the synthetic genes expression of VSMCs, while overexpressing H3f3b exacerbated the cellular immune response of VSMCs induced by inflammatory cytokines. Combined RNA-seq and ChIP-seq analyses revealed that histone variant H3.3B directly bound to the genes related to extracellular matrix, VSMC synthetic phenotype, cytokine responses and TGFβ signaling pathway, and regulated their expressions. In addition, VSMC-specific H3f3b knockin aggravated aortic dissection development in mice, while H3f3b knockout significantly reduced the incidence of aortic dissection. In term of mechanisms, H3.3B regulated Spp1 and Ccl2 genes, inducing the apoptosis of VSMCs and recruiting macrophages. This study demonstrated the vital roles of H3.3B in phenotypic transition of VSMCs, loss of media VSMCs, and vascular inflammation in aortic dissection.

miR-342-5p promotes vascular smooth muscle cell phenotypic transition through a negative-feedback regulation of Notch signaling via targeting FOXO3

AIM

Under various pathological conditions such as cancer, vascular smooth muscle cells (vSMCs) transit their contractile phenotype into phenotype(s) characterized by proliferation and secretion, a process called vSMC phenotypic transition (vSMC-PT). Notch signaling regulates vSMC development and vSMC-PT. This study aims to elucidate how the Notch signal is regulated.

MAIN METHODS

Gene-modified mice with a SM22α-CreER^T2 transgene were generated to activate/block Notch signaling in vSMCs. Primary vSMCs and MOVAS cells were cultured in vitro. RNA-seq, qRT-PCR and Western blotting were used to evaluated gene expression level. EdU incorporation, Transwell and collagen gel contraction assays were conducted to determine the proliferation, migration and contraction, respectively.

KEY FINDINGS

Notch activation upregulated, while Notch blockade downregulated, miR-342-5p and its host gene Evl in vSMCs. However, miR-342-5p overexpression promoted vSMC-PT as shown by altered gene expression profile, increased migration and proliferation, and decreased contraction, while miR-342-5p blockade exhibited the opposite effects. Moreover, miR-342-5p overexpression significantly suppressed Notch signaling, and Notch activation partially abolished miR-342-5p-induced vSMC-PT. Mechanically, miR-342-5p directly targeted FOXO3, and FOXO3 overexpression rescued miR-342-5p-induced Notch repression and vSMC-PT. In a simulated tumor microenvironment, miR-342-5p was upregulated by tumor cell-derived conditional medium (TCM), and miR-342-5p blockade abrogated TCM-induced vSMC-PT. Meanwhile, conditional medium from miR-342-5p-overexpressing vSMCs significantly enhanced tumor cell proliferation, while miR-342-5p blockade had the opposite effects. Consistently, in a co-inoculation tumor model, miR-342-5p blockade in vSMCs significantly delayed tumor growth.

SIGNIFICANCE

miR-342-5p promotes vSMC-PT through a negative-feedback regulation of Notch signaling via downregulating FOXO3, which could be a potential target for cancer therapy.

Evolocumab loaded Bio-Liposomes for efficient atherosclerosis therapy

PCSK9, which is closely related to atherosclerosis, is significantly expressed in vascular smooth muscle cells (VSMCs). Moreover, Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) mediated phenotypic transformation, abnormal proliferation, and migration of VSMCs play key roles in accelerating atherosclerosis. In this study, by utilizing the significant advantages of nano-materials, a biomimetic nanoliposome loading with Evolocumab (Evol), a PCSK9 inhibitor, was designed to alleviate atherosclerosis. In vitro results showed that (Lipo + M)@E NPs up-regulated the levels of α-SMA and Vimentin, while inhibiting the expression of OPN, which finally result in the inhibition of the phenotypic transition, excessive proliferation, and migration of VSMCs. In addition, the long circulation, excellent targeting, and accumulation performance of (Lipo + M)@E NPs significantly decreased the expression of PCSK9 in serum and VSMCs within the plaque of ApoE^-/- mice.

PUM2 regulates the formation of thoracic aortic dissection through EFEMP1

Thoracic aortic dissection (TAD) is a severe cardiovascular disease attributed to the abnormal phenotypic switch of vascular smooth muscle cells (VSMCs). We found that the RNA-binding protein PUM2 and the fibulin protein EFEMP1 were significantly decreased at the TAD anatomical site. Therefore, we constructed expression and silencing vectors for PUM2 and EFEMP1 to analyze differential expression. Overexpression of PUM2 inhibited VSMC proliferation and migration. Western blot analysis indicated that PUM2 overexpression in VSMCs upregulated α-SMA and SM22α and downregulated OPN and MMP2. Immunofluorescence demonstrated that PUM2 and EFEMP1 were co-expressed in VSMCs. Immunoprecipitation confirmed that PUM2 bound to EFEMP1 mRNA to promote EFEMP1 expression. An Ang-II-induced aortic dissection mouse model showed that PUM2 impedes the development of aortic dissection in vivo. Our study demonstrates that PUM2 inhibits the VSMC phenotypic switch to prevent aortic dissection by targeting EFEMP1 mRNA. These findings could assist the development of targeted therapy for TAD.

Exosomes: mediators regulating the phenotypic transition of vascular smooth muscle cells in atherosclerosis

Cardiovascular disease is one of the leading causes of human mortality worldwide, mainly due to atherosclerosis (AS), and the phenotypic transition of vascular smooth muscle cells (VSMCs) is a key event in the development of AS. Exosomes contain a variety of specific nucleic acids and proteins that mediate intercellular communication. The role of exosomes in AS has attracted attention. This review uses the VSMC phenotypic transition in AS as the entry point, introduces the effect of exosomes on AS from different perspectives, and discusses the status quo, deficiencies, and potential future directions in this field to provide new ideas for clinical research and treatment of AS. Video Abstract.

NLRC5 modulates phenotypic transition and inflammation of human venous smooth muscle cells by activating Wnt/β-catenin pathway via TLR4 in varicose veins

In varicose veins, abnormal phenotypic transition and inflammatory response is commonly found in venous smooth muscle cells (VSMCs). We aimed to explore the potential role and mechanism of NLRC5 exerted on VSMCs phenotypic transition and inflammation. NLRC5 expression was detected in varicose veins and platelet-derived growth factor (PDGF)-induced VSMCs by RT-qPCR and Western bolt assays. A loss-of-function assay was performed to evaluate the effects of NLRC5 knockdown on VSMC proliferation, migration, and phenotypic transition. ELISA was used to detect the contents of pro-inflammatory cytokines in the supernatant. The modulation of NLRC5 on TLR4 expression and Wnt/β-catenin signaling was also evaluated. We found that the expressions of NLRC5 in varicose veins and PDGF-induced VSMCs were upregulated. NLRC5 knockdown inhibited VSMC proliferation and migration. Extracellular matrix transformation was blocked by downregulating NLRC5 with increasing SM-22α expression and MMP-1/TIMP-1 ratio, as well as decreasing OPN and collagen I expressions. Besides, NLRC5 silencing reduced the contents of inflammatory cytokines. Furthermore, we found that NLRC5 regulated TLR4 expression, as well as subsequently activation of Wnt/β-catenin pathway and nuclear translocation of β-catenin, which was involved in NLRC5-mediated phenotypic transition and inflammatory in VSMCs. In conclusion, silencing NLRC5 depressed VSMCs' phenotypic transition and inflammation by modulating Wnt/β-catenin pathway via TLR4. This may provide a theoretical basis for treatment of varicose veins.

Farrerol maintains the contractile phenotype of VSMCs via inactivating the extracellular signal-regulated protein kinase 1/2 and p38 mitogen-activated protein kinase signaling

Farrerol, a dihydroflavone isolated from Rhododendron dauricum L., can inhibit vascular smooth muscle cell (VSMC) proliferation and exert a protective effect on H₂O₂-induced vascular endothelial cells injury. In this study, we investigated the effects of farrerol on VSMC phenotypic modulation and balloon injury-induced vascular neointimal formation and explored the underlying mechanisms. Serum-starved rat thoracic aorta SMCs (RASMCs) were first pretreated with farrerol (3, 10, and 30 μM, respectively), U0126 (a MEK kinase inhibitor), and SB203580 (a p38 kinase inhibitor), and followed by treatment with serum (10% FBS). The expression of several VSMC-specific markers, including α-SMA, SM22α, and OPN, were analyzed by western blot. Phosphorylation of extracellular signal-regulated protein kinase 1/2 (ERK 1/2) and p38 mitogen-activated protein kinase (MAPK) was also investigated. Farrerol inhibited the serum-induced transition of RASMCs from the contractile to the synthetic phenotype, and this was associated with a decrease in α-SMA and SM22α expression, and an increase in OPN expression. Farrerol also inhibited serum-induced phosphorylation of ERK1/2 and p38MAPK in RASMCs. Moreover, U0126 and SB203580 both inhibited the serum-induced phenotypic transition of RASMCs. These findings indicate that farrerol can maintain the contractile phenotype of VSMCs partly via inactivating the ERK1/2 and p38 MAPK signaling pathways. Using a rat model of carotid artery balloon injury, inhibition of VSMC phenotypic transition and suppression of neointimal formation were confirmed in vivo following the perivascular application of farrerol. Our results suggested that farrerol could be a promising lead compound for the treatment of vascular proliferative diseases.

Vascular smooth muscle cell phenotypic transition regulates gap junctions of cardiomyocyte

Atrial fibrillation (AF) is one of the most prevalent arrhythmias. Myocardial sleeves of the pulmonary vein are critical in the occurrence of AF. Our study aims to investigate the effect of synthetic vascular smooth muscle cells (SMCs) on gap junction proteins in cardiomyocytes. (1) Extraction of vascular SMCs from the pulmonary veins of Norway rats. TGF-β1 was used to induce the vascular SMCs switching to the synthetic phenotype and 18-α-GA was used to inhibit gap junctions of SMCs. The contractile and synthetic phenotype vascular SMCs were cocultured with HL-1 cells; (2) Western blotting was used to detect the expression of Cx43, Cx40 and Cx45 in HL-1 cells, and RT-PCR to test microRNA 27b in vascular SMCs or in HL-1 cells; (3) Lucifer yellow dye transfer experiment was used to detect the function of gap junctions. (1) TGF- β1 induced the vascular SMCs switching to synthetic phenotype; (2) Cx43 was significantly increased, and Cx40 and Cx45 were decreased in HL-1 cocultured with synthetic SMCs; (3) The fluorescence intensity of Lucifer yellow was higher in HL-1 cocultured with synthetic SMCs than that in the cells cocultured with contractile SMCs, which was inhibited by18-α-GA; (4) the expression of microRNA 27b was increased in HL-1 cocultured with synthetic SMCs, which was attenuated markedly by 18-α-GA. (5) the expression of ZFHX3 was decreased in HL-1 cocultured with synthetic SMCs, which was reversed by 18-α-GA. The gap junction proteins of HL-1 were regulated by pulmonary venous SMCs undergoing phenotypic transition in this study, accompanied with the up-regulation of microRNA 27b and the down-regulation of ZFHX3 in HL-1 cells, which was associated with heterocellular gap junctions between HL-1 and pulmonary venous SMCs.

The miR-29b/Matrix Metalloproteinase 2 Axis Regulates Transdifferentiation and Calcification of Vascular Smooth Muscle Cells in a Calcified Environment

BACKGROUND

Vascular calcification (VC) is a common pathological lesion that promotes progress and mortality in cardiovascular disease. Vascular smooth muscle cells (VSMCs) acquiring an osteogenic phenotype facilitate VC occurrence and development. We recently reported that miR-29b-3p directly regulates the expression of matrix metalloproteinase 2 (MMP2). Herein, we test whether miR-29b-3p functions in the phenotypic transition and calcification in a calcified environment.

METHODS AND RESULTS

VSMC calcification in vitro was induced with calcification medium containing β-glycerophosphoric acid or high calcium. MiR-29b-3p expression in VSMCs tended to decrease during culturing in calcification medium. MiR-29b-3p overexpression ameliorated VSMC calcification, whereas miR-29b-3p knockdown exacerbated VSMC calcification. Furthermore, ectopic expression of miR-29b-3p inhibited the expression of osteogenic markers and MMP2 (a known target gene of miR-29b-3p). By contrast, miR-29b-3p deficiency facilitated VSMC osteogenesis differentiation and upregulated MMP2 expression.

CONCLUSION

Our research suggests that miR-29b-3p regulates VSMC calcification and osteogenesis differentiation, at least in part, by targeting MMP2. Regulation of miR-29b-3p expression is therefore a potential therapeutic target for VSMC calcification.

Role of integrin-linked kinase in the hypoxia-induced phenotypic transition of pulmonary artery smooth muscle cells: Implications for hypoxic pulmonary hypertension

The phenotypic transition of pulmonary artery smooth muscle cells (PASMCs) from a contractile/differentiated to synthetic/de-differentiated phenotype is an important mechanism for the occurrence and development of hypoxic pulmonary hypertension (HPH). Integrin-linked kinase (ILK) is an early hypoxic response factor whose kinase activity is significantly affected during early hypoxia. Myocardin and ETS-like protein 1 (Elk-1) are co-activators of serum response factor (SRF) and can bind to SRF to mediate the phenotypic transition of PASMCs. However, little is known about the role of ILK on the phenotypic transition of these PASMCs. Thus, in our study, we explored the role of ILK in this process. We found that the expression of ILK and myocardin decreased gradually with the increase in hypoxia exposure time in the pulmonary arteries of rats. We observed that hypoxia exposure for 1 h caused an increase in the phosphorylation of Elk-1 but did not affect the expression of ILK, myocardin, or SRF. Exposure to hypoxic treatment for 1 h decreased ILK kinase activity and caused Elk-1 to suppress myocardin binding to SRF and the smooth muscle (SM) α-actin gene promoters. In addition, hypoxia exposure for 24 h decreased the expression of ILK, myocardin, SM α-actin, and calponin but increased the expression of osteopontin. Silencing of the myocardin gene significantly decreased the expression of SM α-actin and calponin but increased the expression of osteopontin. Silencing of the ILK gene significantly decreased the expression of myocardin, SM α-actin, and calponin but increased the expression of osteopontin. ILK overexpression reversed the effects of 24 h of hypoxia on the expression of myocardin, SM α-actin, calponin, and osteopontin and reversed the decrease in binding of myocardin to the SM α-actin promoter caused by 24 h of hypoxia exposure. Thus, our results suggest that ILK initiates the phenotypic transition of PASMCs. The underlying mechanism may involve hypoxia downregulating ILK kinase activity and protein expression, causing Elk-1 to compete with myocardin for binding to the SM α-actin promoter, which downregulates the expression of the downstream target myocardin and results in the phenotypic transition of PASMCs from a contractile to a synthetic phenotype. This may be an important mechanism in the development of HPH.

IL-33 promotes the progression of nonrheumatic aortic valve stenosis via inducing differential phenotypic transition in valvular interstitial cells

OBJECTIVE

Interleukin (IL)-33 is a mediator in the pathogenesis of several inflammatory diseases. Its receptor, ST2, is overexpressed in nonrheumatic aortic valve stenosis (NR-AS). This study compared smooth muscle α-actin (α-SMA), osteopontin (OPN), and suppression of tumorigenicity 2 (ST2) expression between specimens from fibrotic and calcific stages of NR-AS and observed the effects and mechanisms of phenotypic transition of porcine valvular interstitial cells (VICs) in the presence of IL-33.

METHODS

Peripheral blood IL-1 family mRNA and protein levels in NR-AS patients and healthy adults were quantified by real-time quantitative polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay. Immunohistochemistry and immunofluorescence were used to detect the expression and coexpression of α-SMA, OPN, and ST2 in NR-AS specimens. Porcine VICs were stimulated with IL-33, IL-33+SB203580, or IL-33+SC75741. mRNA and protein expression levels of porcine VICs were detected by RT-qPCR and western blot.

RESULTS

The mRNA and protein levels of IL-33 and sST2 in peripheral blood of NR-AS patients were higher than those in healthy adults. Immunohistochemistry and immunofluorescence showed higher expression of α-SMA, OPN, and ST2 in the calcific stage of NR-AS than in the fibrotic stage. Coexpression of ST2/α-SMA or ST2/OPN was found only in the calcific stage. Nuclear factor (NF)-κB and p38 mitogen-activated protein kinase (MAPK) phosphorylation levels were associated with IL-33-induced porcine VIC differentiation into myofibroblasts and osteoblasts, respectively. IL-33 stimulation also promoted the coexpression of ST2/OPN or α-SMA/OPN/ST2.

CONCLUSION

IL-33 might be a potential biomarker for NR-AS. IL-33-induced porcine VIC differential phenotypic transition and differentiation into myofibroblasts and osteoblasts were dependent on the NF-κB and p38 MAPK signaling pathways, respectively.

rBMSCs/ITGA5B1 Promotes Human Vascular Smooth Muscle Cell Differentiation via Enhancing Nitric Oxide Production

Background and Objectives

Previous studies have shown that integrins alpha5beta1 (ITGA5B1) gene-modified rat bone marrow mesenchymal stem cells (rBMSCs) could prevent cell anoikis and increase the nitric oxide (NO) production. Here we examined the capability of rBMSCs/ITGA5B1 on the phenotype modulation of Human Pulmonary Artery Smooth Muscle Cell (HPASMC) in vitro.

Methods and Results

The synthetic (dedifferentiated) phenotype of HPASMC was induced by monocrotaline (MCT, 1μM) for 24 h and then co-cultured with rBMSCs/ITGA5B1 in a transwell culture system. The activation of NO/cGMP (nitric oxide/Guanosine-3', 5'-cyclic monophosphate) signaling was investigated in HPASMC. The changes of pro-inflammatory factors, oxidative stress, vasodilator, vasoconstrictor, contractile and synthetic genes, and the morphological changes of HPASMC were investigated. The results of this study showed that the NO/cGMP signal, endothelial nitric oxide synthase (eNOS) expression, the expression of the vasoprotective genes heme oxygenase-1 (HMOX1) and prostaglandin-endoperoxide synthase 2 (PTGS2) were increased, but the expression of transforming growth factor-β1 (TGF-β1), CCAAT/enhancer-binding proteins delta (Cebpd), Krüppel-like factor 4 (KLF4), and activating transcription factor 4 (ATF4) were reduced in MCT treated HPASMC co-cultured with rBMSCs/ITGA5B1. The synthetic smooth muscle cells (SMCs) phenotype markers thrombospondin-1, epiregulin and the vasoconstrictor endothelin (ET)-1, thromboxane A2 receptor (TbxA2R) were down-regulated, whereas the contractile SMCs phenotype marker transgelin expression was up-regulated by rBMSCs/ITGA5B1. Furthermore, rBMSCs/ITGA5B1 promoted the morphological restoration from synthetic (dedifferentiation) to contractile (differentiation) phenotype in MCT treated HPASMC.

Conclusions

rBMSCs/ITGA5B1 could inhibit inflammation and oxidative stress related genes to promote the HPASMC cell differentiation by activation NO/cGMP signal.

Transcriptional program for nitrogen starvation-induced lipid accumulation in Chlamydomonas reinhardtii

BACKGROUND

Algae accumulate lipids to endure different kinds of environmental stresses including macronutrient starvation. Although this response has been extensively studied, an in depth understanding of the transcriptional regulatory network (TRN) that controls the transition into lipid accumulation remains elusive. In this study, we used a systems biology approach to elucidate the transcriptional program that coordinates the nitrogen starvation-induced metabolic readjustments that drive lipid accumulation in Chlamydomonas reinhardtii.

RESULTS

We demonstrate that nitrogen starvation triggered differential regulation of 2147 transcripts, which were co-regulated in 215 distinct modules and temporally ordered as 31 transcriptional waves. An early-stage response was triggered within 12 min that initiated growth arrest through activation of key signaling pathways, while simultaneously preparing the intracellular environment for later stages by modulating transport processes and ubiquitin-mediated protein degradation. Subsequently, central metabolism and carbon fixation were remodeled to trigger the accumulation of triacylglycerols. Further analysis revealed that these waves of genome-wide transcriptional events were coordinated by a regulatory program orchestrated by at least 17 transcriptional regulators, many of which had not been previously implicated in this process. We demonstrate that the TRN coordinates transcriptional downregulation of 57 metabolic enzymes across a period of nearly 4 h to drive an increase in lipid content per unit biomass. Notably, this TRN appears to also drive lipid accumulation during sulfur starvation, while phosphorus starvation induces a different regulatory program. The TRN model described here is available as a community-wide web-resource at http://networks.systemsbiology.net/chlamy-portal.

CONCLUSIONS

In this work, we have uncovered a comprehensive mechanistic model of the TRN controlling the transition from N starvation to lipid accumulation. The program coordinates sequentially ordered transcriptional waves that simultaneously arrest growth and lead to lipid accumulation. This study has generated predictive tools that will aid in devising strategies for the rational manipulation of regulatory and metabolic networks for better biofuel and biomass production.