Proteins In Vascular Smooth Muscle Cells Research Articles

Nidogen-2 is a Novel Endogenous Ligand of LGR4 to Inhibit Vascular Calcification.

Vascular calcification is closely related to the all-cause mortality of cardiovascular events. Basement membrane protein nidogen-2 is a key component of the vascular extracellular matrix microenvironment and we recently found it is pivotal for the maintenance of contractile phenotype in vascular smooth muscle cells (VSMCs). However, whether nidogen-2 is involved in VSMCs osteochondrogenic transition and vascular calcification remains unclear. VSMCs was treated with high-phosphate to study VSMC calcification in vitro. Three different mice models (5/6 nephrectomy-induced chronic renal failure, cholecalciferol-overload, and periadventitially administered with CaCl2) were used to study vascular calcification in vivo. Membrane protein interactome, coimmunoprecipitation, flow cytometric binding assay, surface plasmon resonance, G protein signaling, VSMCs calcium assays were performed to clarify the phenotype and elucidate the molecular mechanisms. Nidogen-2 protein levels were significantly reduced in calcified VSMCs and aortas from mice in different vascular calcification model. Nidogen-2 deficiency exacerbated high-phosphate-induced VSMC calcification, whereas the addition of purified nidogen-2 protein markedly alleviated VSMC calcification in vitro. Nidogen-2-/- mice exhibited aggravated aorta calcification compared to wild-type (WT) mice in response to 5/6 nephrectomy, cholecalciferol-overload, and CaCl2 administration. Further unbiased coimmunoprecipitation and interactome analysis of purified nidogen-2 and membrane protein in VSMCs revealed that nidogen-2 directly binds to LGR4 (leucine-rich repeat G-protein-coupled receptor 4) with KD value 26.77 nM. LGR4 deficiency in VSMCs in vitro or in vivo abolished the protective effect of nidogen-2 on vascular calcification. Of interest, nidogen-2 biased activated LGR4-Gαq-PKCα (protein kinase Cα)-AMPKα1 (AMP-activated protein kinase α1) signaling to counteract VSMCs osteogenic transition and mineralization. Nidogen-2 is a novel endogenous ligand of LGR4 that biased activated Gαq- PKCα-AMPKα1 signaling and inhibited vascular calcification.

Parathyroid hormone-induced vascular smooth muscle cells calcification by endoplasmic reticulum stress.

Vascular smooth muscle cells (VSMCs) play a key role in vascular calcification, which is associated with enhanced mortality in chronic kidney disease. To ascertain the concentration of parathyroid hormone (PTH) that induces apoptosis of VSMCs and to explore whether the mechanism of endoplasmic reticulum (ER) stress is involved in PTH-induced calcification of VSMCs. The appropriate concentration and intervention time of PTH-inducing apoptosis of VSMCs were screened by flow cytometry. To investigate the effects of PTH on ER stress-related and apoptotic proteins in VSMCs, they were divided into four groups. These were the control group, the PTH group, the siC/EBP homologous protein (CHOP) + PTH group (in which siCHOP was used to knockdown the expression of CHOP at first), and the sp600125 + PTH group (in which the cells were pretreated with sp600125 at a concentration of 10 ng/ml for 24 h at first). Then, all groups except the control group were given 1x10-6 mol/L PTH to stimulate VSMCs. The changes in ER stress and apoptosis-related proteins in each group were detected, and the cell calcification was tested by Alizarin Red staining. Flow cytometry showed that the concentration of 1x10-6 mol/L PTH induced apoptosis most significantly. The apoptosis rate of the cells increased with the extension of stimulation time. The apoptosis of VSMCs pretreated with the Jun-N-terminal kinase (JNK) antagonist sp600125 was significantly reduced. The expression of cleaved caspase-3, PERK, IRE1, and CHOP was detected by Western blot analysis when cells were stimulated with 10-6 mol/L PTH for 14 days. After the knockdown of the CHOP expression by siCHOP, cleaved caspase-3 expression was significantly reduced. Alizarin Red staining showed siCHOP and sp600125 inhibits the VSMCs' calcification induced by PTH. In conclusion: the ER stress mechanism is involved in VSMCs' calcification induced by PTH.

442-P: Sorbs2 Deficiency–Mediated Vascular BK Channel Dysfunction in Type 2 Diabetes

Vascular BK channels, composed of the pore-forming α-subunits (BK-α) and the regulatory β1 subunits (BK-β1) , is a key determinant of vasoreactivity, and its function is impaired in diabetes. However, our understanding of the mechanisms causing BK channel dysfunction in diabetic vessels is incomplete. The Sorbin and SH3 domain-containing protein 2 (Sorbs2) is abundantly expressed in vascular smooth muscle cells (SMCs) . We hypothesize that Sorbs2 is critical for vascular BK channel physiology. In this study, we compared vascular BK channel function between Sorbs2 KO and WT mice at 4 months of age. There was no difference in body weight and blood glucose between WT and Sorbs2 KO mice (body weight: 25.9±1.3 g of WT vs. 23.3±1.5 g of KO, n=14, p=N.S.; blood glucose: 166.4±7.7 mg/dL of WT vs. 152.2±12.2 mg/dL of KO, n=14, p=N.S.) . However, Sorbs2 KO mice have markedly reduced cell surface and cytoplasmic expression of BK-α and BK-β1, as well as BK channel-mediated vasodilation in carotid arteries with a maximal dilatation of 64.70±1.92% for WT mice (n=4) and 20.74±4.66% for KO mice (n=5, p<0.05) . Patch clamp experiments revealed that BK channel sensitivity to Ca2+ activation was impaired in the coronary SMCs of Sorbs2 KO mice (EC50: 2.87±0.68 µM, n=13, p<0.05) with decreased Hill coefficient (nH: 1.26) , compared to those of WT mice (EC50: 0.48±0.µM, nH: 2.70, n=13) . In vivo studies showed that Sorbs2 interacted with BK-α and BK-β1 protein in vascular SMCs. Silencing of Sorbs2 by shRNA decreased BK-α and BK-β1 expression, while adenoviral expression of Sorbs2 increased BK-α and BK-β1 expression in vascular SMCs. Most importantly, Sorbs2 expression was significantly reduced in the arteries of db/db type 2 diabetic mice and high fat diet-induced diabetic mice. Our results indicate that Sorbs2 plays an important role in regulating BK channel function and expression in vascular SMCs. Sorbs2 deficiency is a risk factor of BK channelopathy and vasculopathy in diabetes, independent of obesity and glucotoxicity. Disclosure T.Lu: None.

A Transcriptional Regulation Bioinformatics Pipeline to Predict Co‐Regulated Genes in Vascular Smooth Muscle Cell Phenotypic Transitions During Atherosclerosis

The rupture of vulnerable or advanced atherosclerotic lesions contributes to myocardial infarctions and strokes, the leading causes of death globally. During all stages of atherosclerosis, vascular smooth muscle cells (VSMCs) are recruited as a major source of plaque cells within lesions, where they undergo phenotypic modulation and give rise to both plaque‐stabilizing and destabilizing phenotypes. Because most atherosclerosis studies test the functional role of single transcription factors, genes, and proteins in VSMCs, many aspects of how VSMC plasticity can be clinically exploited to prevent the rupture of vulnerable atherosclerotic lesions remain unclear. Systems biology approaches have emerged as a promising avenue for characterizing cellular dynamics at the organismal level, but they remain under‐utilized in the field of cardiovascular medicine. This study proposes a novel systems biology pipeline that integrates experimental and computational tools with large datasets measuring the transcriptomes and epigenomes of phenotypically transitioning VSMCs. Our pipeline allows users to identify candidate transcription factors that co‐regulate mouse or human gene sets controlling specific VSMC phenotypic transitions during atherosclerosis. The computational algorithms developed in this workflow integrate an array of publicly available databases, such as the Ensembl genome database and the JASPAR transcription factor database. To demonstrate the translational potential of our pipeline, we used it to test the hypothesis that the murine mesenchymal marker stem cell antigen‐1 Sca1(Ly6a) has a human ortholog, which has not been previously validated as a target in clinical therapies. To test the hypothesis that there are sets of genes co‐regulated with Ly6ain human VSMCs which, when expressed in concert, promote a distinct phenotypic state marked by Ly6ain mice, we integrated genomic and ATAC‐seq analyses of VSMCs to identify murine genes with human orthologs that bind Ly6a‐specific transcription factors. Specifically, we predict that the transcription factors ETS1, KLF5, GATA6, and SOX10 co‐regulate sets of human genes with Ly6a. While prior studies have associated these transcription factors with VSMC proliferation and phenotypic modulation, we specifically predict these Ly6a‐specific transcription factor co‐regulate the following human gene sets: PHACTR1, EFHC1, LAMC2(ETS1); TTC33, RUNX1, KIAA1217(KLF5); TMEM50A(GATA6); and ZBTB20, MYLK2(SOX10). To validate these predictions, we will determine if these transcription factors and their co‐regulated genes are expressed in single cell RNA‐sequencing analyses of human carotid arteries and can be detected with immunofluorescence staining of human coronary artery sections. We will also use siRNA to target these candidate transcription factors and genes in cultured VSMCs. The results of our pipeline will help identify novel transcriptional regulatory networks in VSMCs that can be therapeutically targeted for the treatment of advanced atherosclerosis.

PDGFR-β signaling mediates HMGB1 release in mechanically stressed vascular smooth muscle cells

Mechanically stressed vascular smooth muscle cells (VSMCs) have potential roles in the development of vascular complications. However, the underlying mechanisms are unclear. Using VSMCs cultured from rat thoracic aorta explants, we investigated the effects of mechanical stretch (MS) on the cellular secretion of high mobility group box 1 (HMGB1), a major damage-associated molecular pattern that mediates vascular complications in stressed vasculature. Enzyme-linked immunosorbent assay (ELISA) demonstrated an increase in the secretion of HMGB1 in VSMCs stimulated with MS (0-3% strain, 60 cycles/min), and this secretion was markedly and time-dependently increased at 3% MS. The increased secretion of HMGB1 at 3% MS was accompanied by an increased cytosolic translocation of nuclear HMGB1; the acetylated and phosphorylated forms of this protein were significantly increased. Among various inhibitors of membrane receptors mediating mechanical signals, AG1295 (a platelet-derived growth factor receptor (PDGFR) inhibitor) attenuated MS-induced HMGB1 secretion. Inhibitors of other receptors, including epidermal growth factor, insulin-like growth factor, and fibroblast growth factor receptors, did not inhibit this secretion. Additionally, MS-induced HMGB1 secretion was markedly attenuated in PDGFR-β-deficient cells but not in cells transfected with PDGFR-α siRNA. Likewise, PDGF-DD, but not PDGF-AA, directly increased HMGB1 secretion in VSMCs, indicating a pivotal role of PDGFR-β signaling in the secretion of this protein in VSMCs. Thus, targeting PDGFR-β-mediated secretion of HMGB1 in VSMCs might be a promising therapeutic strategy for vascular complications associated with hypertension.

MiR-145 attenuatesphenotypic transformation of aortic vascular smooth muscle cells to prevent aortic dissection.

Background miR‐145 is closely related to vascular smooth muscle cells (VSMC) phenotype transformation; however, the regulatory mechanisms through which miR‐145 regulates the VSMC phenotype transformation under mechanical stretching are unclear. In this study, we evaluated the roles of miR‐145 in VSMCs subjected to mechanical stretching in aortic dissection (AD).MethodsThe expression of miR‐145 in the aortic vessel wall of model animals and patients with AD was analyzed by quantitative polymerase chain reaction. miR‐145‐related protein‐protein interaction networks and Wikipathways were used to analyze VSMC phenotypic transformation pathways regulated by miR‐145. We used gain‐ and loss‐of‐function studies to evaluate the effects of miR‐145 on VSMC differentiation under mechanical stretch induction and assessed whether Krüppel‐like factor 4 (KLF4) was regulated by miR‐145 in the aorta under mechanical stretch conditions.Results miR‐145 was abundantly expressed in the walls of the normal human aorta, but was significantly downregulated in animal models and the walls of patients with dissection. We found that contractile phenotype‐related proteins were downregulated in VSMCs subjected to mechanical stretching, whereas the expression of secreted phenotype‐related proteins increased. miR‐145 overexpression also downregulated contractile phenotype‐related proteins in VSMCs and suppressed upregulation of phenotype‐related proteins. Finally, under mechanical stretching, KLF4 expression was significantly increased in VSMCs, and overexpression of miR‐145 blocked this effect.ConclusionOur results confirmed that mechanical stretch‐induced phenotypic transformation of VSMCs to promote AD via upregulation of KLF4; this mechanism was regulated by miR‐145, which directly modulated KLF4 expression and VSMC differentiation.

Angiotensin II-Induced Long Non-Coding RNA Alivec Regulates Chondrogenesis in Vascular Smooth Muscle Cells.

Long non-coding RNAs (lncRNAs) play key roles in Angiotensin II (AngII) signaling but their role in chondrogenic transformation of vascular smooth muscle cells (VSMCs) is unknown. We describe a novel AngII-induced lncRNA Alivec (Angiotensin II-induced lncRNA in VSMCs eliciting chondrogenic phenotype) implicated in VSMC chondrogenesis. In rat VSMCs, Alivec and the nearby gene Acan, a chondrogenic marker, were induced by growth factors AngII and PDGF and the inflammatory cytokine TNF-α. AngII co-regulated Alivec and Acan through the activation of AngII type1 receptor signaling and Sox9, a master transcriptional regulator of chondrogenesis. Alivec knockdown with GapmeR antisense-oligonucleotides attenuated the expression of AngII-induced chondrogenic marker genes, including Acan, and inhibited the chondrogenic phenotype of VSMCs. Conversely, Alivec overexpression upregulated these genes and promoted chondrogenic transformation. RNA-pulldown coupled to mass-spectrometry identified Tropomyosin-3-alpha and hnRNPA2B1 proteins as Alivec-binding proteins in VSMCs. Furthermore, male rats with AngII-driven hypertension showed increased aortic expression of Alivec and Acan. A putative human ortholog ALIVEC, was induced by AngII in human VSMCs, and this locus was found to harbor the quantitative trait loci affecting blood pressure. Together, these findings suggest that AngII-regulated lncRNA Alivec functions, at least in part, to mediate the AngII-induced chondrogenic transformation of VSMCs implicated in vascular dysfunction and hypertension.

Effect of Activated Protein Kinase C Beta Type Mediated Phosphorylation of Signal Transducer and Activator of Transcription 4 on Proliferation and Phenotypic Transformation of Vascular Smooth Muscle Cells After Vascular Injury Induced by Nano-SiO₂.

The excessive proliferation, endothelial migration, and phenotype transformation of vascular smooth muscle cells (VSMC) lead to increased extracellular matrix secretion, which induces vascular intimal hyperplasia, which is an important restenosis mechanism after vascular injury. In our study, we verified the cytotoxicity of SiO₂ nanoparticles to VSMC. To explore the role of endothelial repairs and molecular mechanisms after vascular injuries, we sequenced the transcriptome of injured vessels in the carotid artery of mice. The results showed the differentially expressed genes in normal vascular tissues, and that vascular tissues were mainly enriched with NF-κB signaling pathways, chemokine signaling pathways and other biological functions, by the leukocyte activation and adhesion of the KEGG pathway in the immune response, and by DNA binding, DNA transcription regulatory region binding, and other molecular functions. Core proteins included PRKCB, STAT4, CCL5, and BCL-2. To verify the roles of these core proteins, RT-qPCR andWestern blot techniques were used to detect their transcription and translation levels, and HE staining was used to detect morphological changes in blood vessels. To further clarify the role of core proteins in VSMC, PRKCB over expression plasmids were constructed, and the RT-qPCR and Western blot techniques were again used to detect the expression of core proteins. The results showed that the levels of transcription and translation, and of PRKCB and STAT4 phosphorylation, increased significantly after vascular injury, and then noticeably decreased three days later- and that CCL5 and Bcl-2 expression trends were consistent with this. HE staining showed that when the vascular endothelium was damaged, smooth muscle cells proliferated significantly, and that the intima thickened three days after vascular injury. After over expression of PRKCB, the expression and activation of STAT4, CCL5, and Bcl-2 significantly increased, α-SMA and Vimentin were down-regulated, OPN was up-regulated, and VSMC activity was enhanced. From these results, it could be concluded that PRKCB is activated by vascular injury, and that over-activation of PRKCB promotes activation of STAT4 and the expression of CCL5 and BCL-2-which in turn leads to enhanced VSMC activity and transformation of its contraction phenotype to the secretion phenotype. We were also able to establish that the cytotoxicity of SiO₂ nanoparticles to VSMC was positively correlated with dose and time.

Genetic Regulation of Atherosclerosis-Relevant Phenotypes in Human Vascular Smooth Muscle Cells.

Coronary artery disease (CAD) is a major cause of morbidity and mortality worldwide. Recent genome-wide association studies revealed 163 loci associated with CAD. However, the precise molecular mechanisms by which the majority of these loci increase CAD risk are not known. Vascular smooth muscle cells (VSMCs) are critical in the development of CAD. They can play either beneficial or detrimental roles in lesion pathogenesis, depending on the nature of their phenotypic changes. To identify genetic variants associated with atherosclerosis-relevant phenotypes in VSMCs. We quantified 12 atherosclerosis-relevant phenotypes related to calcification, proliferation, and migration in VSMCs isolated from 151 multiethnic heart transplant donors. After genotyping and imputation, we performed association mapping using 6.3 million genetic variants. We demonstrated significant variations in calcification, proliferation, and migration. These phenotypes were not correlated with each other. We performed genome-wide association studies for 12 atherosclerosis-relevant phenotypes and identified 4 genome-wide significant loci associated with at least one VSMC phenotype. We overlapped the previously identified CAD loci with our data set and found nominally significant associations at 79 loci. One of them was the chromosome 1q41 locus, which harbors MIA3. The G allele of the lead risk single nucleotide polymorphism (SNP) rs67180937 was associated with lower VSMC MIA3 expression and lower proliferation. Lentivirus-mediated silencing of MIA3 (melanoma inhibitory activity protein 3) in VSMCs resulted in lower proliferation, consistent with human genetics findings. Furthermore, we observed a significant reduction of MIA3 protein in VSMCs in thin fibrous caps of late-stage atherosclerotic plaques compared to early fibroatheroma with thick and protective fibrous caps in mice and humans. Our data demonstrate that genetic variants have significant influences on VSMC function relevant to the development of atherosclerosis. Furthermore, high MIA3 expression may promote atheroprotective VSMC phenotypic transitions, including increased proliferation, which is essential in the formation or maintenance of a protective fibrous cap.

Long Noncoding RNA Hypoxia-Inducible Factor-1 Alpha-Antisense RNA 1 Regulates Vascular Smooth Muscle Cells to Promote the Development of Thoracic Aortic Aneurysm by Modulating Apoptotic Protease-Activating Factor 1 and Targeting let-7g

BackgroundThoracic aortic aneurysm (TAA) is a severe threat that is characterized by the increased aortic diameter. The dysfunction of vascular smooth muscle cells (VSMCs) contributes to the formation of TAA. Previous research indicated that long noncoding RNAs (lncRNAs) were involved in the development of TAA. This article aimed to explore the role of lncRNA hypoxia-inducible factor-1 alpha-antisense RNA 1 (HIF1A-AS1) and potential action mechanisms in VSMCs. MethodsThe expression of HIF1A-AS1, collagen I, collagen III, microRNA let-7g (let-7g) and apoptotic protease-activating factor 1 (APAF1) was detected by quantitative real-time polymerase chain reaction. Cell proliferation and cell apoptosis were assessed by Cell Counting Kit-8 and flow cytometry assays, respectively. The protein levels of proliferating cell nuclear antigen, Cleaved caspase-3 (Cleaved-cas3), B cell lymphoma/leukemia-2 (Bcl-2), Collagen I, Collagen III, and APAF1 were quantified by Western blot. The relationship between let-7g and HIF1A-AS1 or APAF1 was predicted by the online bioinformatics tool and verified by dual-luciferase reporter assay and RNA pull-down assay. ResultsHIF1A-AS1 was upregulated in TAA tissues and was a valuable diagnostic marker of TAA. HIF1A-AS1 overexpression suppressed proliferation, induced apoptosis, and reduced the expression of extracellular matrix proteins in VSMCs. let-7 g was a target of HIF1A-AS1, and its inhibition functioned the same role as HIF1A-AS1 overexpression. APAF1 was a target of let-7g, and its knockdown played the opposite role with HIF1A-AS1 overexpression. The reintroduction of let-7g or APAF1 knockdown reversed the effects of HIF1A-AS1 overexpression in VSMCs. ConclusionsHIF1A-AS1 regulated the proliferation, apoptosis ,and the activity of extracellular matrix proteins in VSMCs through modulating APAF1 by targeting let-7g, leading to the development of TAA.

Tripartite factors leading to molecular divergence between human and murine smooth muscle

A large number of pre-clinical and developmental investigations involve experimental vertebrate animals, of which mice have emerged as a favored organism. Recognition of the differences between humans and mice is essential for assessment of the relevance of animal studies to humans. The primary purpose of this study was to gauge the conservation between human and mouse vascular smooth muscle cell (VSMC) proteins mined from an analysis of the Human Protein Atlas. Two comparison were made: a) immunohistochemistry for 16 proteins in brain, heart, esophagus, bladder, stomach, lung, kidney, and aorta enabled comparison between human and mouse of protein localization in VSMC and non-vascular SMC; and b) multi-species primary protein sequence analysis of an expanded set vascular molecules enabled comparison between VSMC sequences among vertebrate species. In total, three dimensions of diversity were uncovered. First, a significant number of factors show human/mouse differences in cellular expression; these differences occurred in both VSMC and non-vascular SMC in an organ and cell-type dependent fashion. Many markers demonstrated notable cell-to-cell and regional heterogeneity in VSMC of the aorta and non-vascular SMC of the esophagus, bladder, and stomach. Second, species specificity can arise by genetic deletions as exemplified by the human protein adipogenesis regulatory factor (ADIRF), which is not present due to a large sequence gap in mice. Third, we describe significant cross-species protein sequence divergence in selected VSMC proteins which may result in altered orthologue function. In a sample of 346 vascular molecules, 15% demonstrate incomplete vertebrate species gene conservation. Divergence of predicted human/mouse VSMC protein sequences is higher than for endothelial proteins in all species examined. In the future, each of these three cross-species differences could be neutralized using gene manipulation, resulting in improved translational potential of murine experimental models.

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.

Impact of CD137-CD137L signaling on secretion of mouse vascular smooth muscle cells-derived exosomes: role of Rab7 pathway

Objective: To investigate whether CD137-CD137L signaling could affect the secretion of mouse vascular smooth muscle cells (VSMCs) -derived exosomes through autophagy mediated Rab7 pathway. Methods: Primary thoracic aorta VSMCs from C57BL/6J mouse were obtained by tissue block adherence method. VSMCs between the third to fifth passages were used and VSMCs were divided into 4 groups: control group, CD137 agonist group, lentivirus control group, Rab7 lentiviral interference group. VSMCs in CD137 agonist group were treated with recombinant protein of CD137L (10 μg/ml), VSMCs in lentivirus control group were treated with lentiviral followed by recombinant protein of CD137L (10 μg/ml), VSMCs in Rab7 lentiviral interference group were treated with Rab7 lentiviral intervention followed by recombinant protein of CD137L (10 μg/ml). Western blot was used to detect the protein expression of LC3Ⅱ, p62, Rab7, CD9, CD81 and Hsc70. Fluorescence microscopy was used to track the changes of autophagy in cells infected with mRFP-GFP-LC3. Transmission electron microscope was used to observe the morphology and size of VSMCs-derived exosomes. The nanoparticle tracking analysis(NTA) was used to detect the concentration and size of exosomes in each group. Results: (1) The expressions of Rab7, LC3Ⅱ and p62 protein in VSMCs of CD137 activation group were significantly higher than those in control group (all P<0.05). The expressions of Rab7, LC3Ⅱ and p62 protein in Rab7 lentivirus interference group was lower than in CD137 activation group (all P<0.05), while the expressions were similar between the lentivirus control group and the CD137 activation group (all P>0.05). (2) The total number of fluorescent spots and yellow fluorescent spots in the VSMCs of the CD137 activation group were higher than those in the control group (all P<0.05), and the number of yellow fluorescent spots was higher than that of the red fluorescent spots in the VSMCs of the CD137 activation group ((50.3±0.9) vs. (10.3±1.5)/cell). The total numbers of fluorescent spots and yellow fluorescent spots in VSMCs of Rab7 lentivirus interference group were lower than those of CD137 activation group (both P<0.05), and the number of red fluorescent spots in VSMCs was higher than that of yellow fluorescent spots ((40.7±4.0) and (10.7±1.2)/cell) in the Rab7 lentiviral interference group. The total numbers of fluorescent spots and yellow fluorescent spots in the VSMCs were similar between the lentivirus control group and the CD137 activation group (all P>0.05). (3) Under transmission electron microscopy, the size of the VSMCs-derived exosomes was about 30-150 nm. The exosome markers (CD9, CD81) could be detected in vesicles by Western blot. NTA results showed that the concentration of VSMCs-derived exosomes was significantly higher in the CD137-activated group than in the control group (P<0.05), which was significantly lower in the Rab7 lentiviral interference group than in the CD137-activation group (P<0.05) and was similar between the lentivirus control group and the CD137 activation group (P>0.05). The expression of Hsc70 protein in exosomes secreted by CD137 activation group was higher than that in the control group (P<0.05). The expression of Hsc70 protein in exosomes was lower in Rab7 lentivirus interference group than in the CD137 activation group (P<0.05), which was similar between the lentivirus control group and the CD137 activation group (P>0.05). The expression of LC3Ⅱ protein in exosome was higher in CD137 activation group than in control group (P<0.05), which was lower in Rab7 lentivirus interference group than in CD137 activation group (P<0.05), which was similar between the lentivirus control group and the CD137 activation group (P>0.05). Conclusion: The CD137-CD137L signaling may affect the secretion of mouse VSMCs-derived exosomes through modulating the Rab7 pathway mediated autophagy.

Overexpression of Egr‐1 contributes to the enhanced expression of Giα proteins and hyperproliferation of vascular smooth muscle cells from spontaneously hypertensive rats

Early growth response, Egr‐1, is known to activate the expression of several genes implicated in the development of vascular dysfunction. Earlier studies have shown that angiotensin II (Ang II) enhances the expression of Egr‐1 and Giα proteins in vascular smooth muscle cells (VSMC). In addition, the role of enhanced levels of endogenous Ang II has been shown to contribute to the enhanced expression of Giα proteins in spontaneously hypertensive rats (SHR). The present study was therefore undertaken to examine if VSMC from SHR also exhibit enhanced expression of Egr‐1 proteins and explore its role and underlying mechanisms in the hyperproliferation of VSMC in SHR. The levels of Egr‐1 proteins in VSMC from SHR started increasing at 2 weeks as compared to their normotensive control, WKY (Wistar‐Kyoto rats) and at 12 weeks, the levels of Egr‐1 proteins were increased significantly by 80%. The enhanced levels of Egr‐1 proteins were restored to control levels by losartan (an AT1 receptor antagonist), BQ123 (an ETA receptor antagonist), BQ788 (an ETB receptor antagonist), as well as by antioxidants, such as N‐acetyl‐L‐cysteine (NAC) and diphenyleneiodonium (DPI) but not by PD123319 (an AT2 receptor antagonist). In addition, pharmacological inhibitors of platelet‐derived growth factor (PDGF), insulin‐like growth factor (IGF) and epidermal growth factor (EGF) receptors also inhibited the overexpression of Egr‐1 proteins in VSMC from SHR. Furthermore, the enhanced expression of Egr‐1 proteins was attenuated by PD098059, an inhibitor of mitogen‐activated protein kinase (MAPK), but not by wortmannin, an inhibitor of phosphatidylinositol‐3‐kinase (PI‐3‐K). VSMC from SHR exhibit hyperproliferation which was attenuated by knocking down Egr‐1 by siRNA. In addition, siRNA of Egr‐1 also inhibited the overexpression of Giα‐2 and Giα‐3 proteins, as well as cell cycle proteins, including cyclin D1, cyclin E, cyclin dependent kinase 4 (Cdk4), Cdk2 and phosphorylated retinoblastoma protein (pRb). These results suggest that VSMC from SHR exhibit an overexpression of Egr‐1 proteins, which is attributed to the enhanced levels of endogenous Ang II and ET‐1, oxidative stress, growth factor receptors and MAPK and that the overexpression of Egr‐1, through the enhanced expression of Giα and cell cycle proteins, contributes to the hyperproliferation of VSMC from SHR.Support or Funding InformationGrant from CIHRThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Polymerase-δ-interacting protein 2 activates the RhoGEF epithelial cell transforming sequence 2 in vascular smooth muscle cells

Polymerase-δ-interacting protein 2 (Poldip2) controls a wide variety of cellular functions and vascular pathologies. To mediate these effects, Poldip2 interacts with numerous proteins and generates reactive oxygen species via the enzyme NADPH oxidase 4 (Nox4). We have previously shown that Poldip2 can activate the Rho family GTPase RhoA, another signaling node within the cell. In this study, we aimed to better understand how Poldip2 activates Rho family GTPases and the functions of the involved proteins in vascular smooth muscle cells (VSMCs). RhoA is activated by guanine nucleotide exchange factors. Using nucleotide-free RhoA (isolated from bacteria) to pulldown active RhoGEFs, we found that the RhoGEF epithelial cell transforming sequence 2 (Ect2) is activated by Poldip2. Ect2 is a critical RhoGEF for Poldip2-mediated RhoA activation, because siRNA against Ect2 prevented Poldip2-mediated RhoA activity (measured by rhotekin pulldowns). Surprisingly, we were unable to detect a direct interaction between Poldip2 and Ect2, as they did not coimmunoprecipitate. Nox4 is not required for Poldip2-driven Ect2 activation, as Poldip2 overexpression induced Ect2 activation in Nox4 knockout VSMCs similar to wild-type cells. However, antioxidant treatment blocked Poldip2-induced Ect2 activation. This indicates a novel reactive oxygen species-driven mechanism by which Poldip2 regulates Rho family GTPases. Finally, we examined the function of these proteins in VSMCs, using siRNA against Poldip2 or Ect2 and determined that Poldip2 and Ect2 are both essential for vascular smooth muscle cell cytokinesis and proliferation.

Enhanced expression of Egr‐1 in vascular smooth muscle cells from spontaneously hypertensive rats: role of Giα proteins

Early growth response, Egr‐1, is known to activate the expression of several genes implicated in the development of vascular dysfunction. Earlier studies have shown that angiotensin II (AngII) enhances the expression of Egr‐1 and Giα proteins in vascular smooth muscle cells (VSMC). In addition, the role of enhanced levels of endogenous Ang II in enhanced expression of Giα proteins in spontaneously hypertensive rats (SHR) has also been shown. The present study was therefore undertaken to examine if VSMC from SHR also exhibit enhanced expression of Egr‐1 proteins and explore the underlying molecular mechanisms mediating this effect. The levels of Egr‐1 protein in VSMC from SHR were not different in 2 weeks old SHR as compared to WKY (Wistar‐Kyoto rats), however, it started increasing at 4 weeks and at 12 weeks, it was significantly increased by 80%. Knockdown of Giα‐2 proteins, using antisense and siRNA treatment, attenuated the enhanced expression of Egr‐1 proteins to control levels. In addition, the knockdown of Egr‐1 by siRNA also attenuated the expression of Giα‐2 and Giα‐3 proteins in VSMC from 12 week old SHR. The enhanced levels of Egr‐1 protein were attenuated by losartan (an AT1 receptor antagonist), BQ123 (an ETA receptor antagonist), BQ788 (an ETB receptor antagonist) but not by PD123319 (an AT2 receptor antagonist) in VSMC from 12 week SHR. These results suggest that VSMC from SHR exhibit an overexpression of Egr‐1 which is due to the enhanced levels of endogenous Ang II, ET‐1 and Giα proteins. In addition, Egr‐1 also regulates the expression of Giα proteins in VSMC from SHR and suggests a cross‐talk between Giα and Egr‐1.Support or Funding InformationSupported by CIHRThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Inhibition of overexpression of Giα proteins and nitroxidative stress contribute to sodium nitroprusside-induced attenuation of high blood pressure in SHR.

We earlier showed that vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) exhibit enhanced expression of Giα proteins which was attributed to the decreased levels of nitric oxide (NO), because elevation of the intracellular levels of NO by NO donors; sodium nitroprusside (SNP) and S‐Nitroso‐N‐acetyl‐DL‐penicillamine (SNAP), attenuated the enhanced expression of Giα proteins. Since the enhanced expression of Giα proteins is implicated in the pathogenesis of hypertension, the present study was undertaken to investigate if treatment of SHR with SNP could also attenuate the development of high blood pressure (BP) and explore the underlying molecular mechanisms. Intraperitoneal injection of SNP at a concentration of 0.5 mg/kg body weight twice a week for 2 weeks into SHR attenuated the high blood pressure by about 80 mmHg without affecting the BP in WKY rats. SNP treatment also attenuated the enhanced levels of superoxide anion (O2 −), hydrogen peroxide (H2O2), peroxynitrite (ONOO −), and NADPH oxidase activity in VSMC from SHR to control levels. In addition, the overexpression of different subunits of NADPH oxidase; Nox‐1, Nox‐2, Nox‐4, P22phox, and P47phox, and Giα proteins in VSMC from SHR were also attenuated by SNP treatment. On the other hand, SNP treatment augmented the decreased levels of intracellular NO, eNOS, and cGMP in VSMC from SHR. These results suggest that SNP treatment attenuates the development of high BP in SHR through the elevation of intracellular levels of cGMP and inhibition of the enhanced levels of Giα proteins and nitroxidative stress.

Homer binds to Orai1 and TRPC channels in the neointima and regulates vascular smooth muscle cell migration and proliferation

The molecular components of store-operated Ca2+ influx channels (SOCs) in proliferative and migratory vascular smooth muscle cells (VSMCs) are quite intricate with many channels contributing to SOCs. They include the Ca2+-selective Orai1 and members of the transient receptor potential canonical (TRPC) channels, which are activated by the endoplasmic reticulum Ca2+ sensor STIM1. The scaffolding protein Homer assembles SOC complexes, but its role in VSMCs is not well understood. Here, we asked whether these SOC components and Homer1 are present in the same complex in VSMCs and how Homer1 contributes to VSMC SOCs, proliferation, and migration leading to neointima formation. Homer1 expression levels are upregulated in balloon-injured vs. uninjured VSMCs. Coimmunoprecipitation assays revealed the presence and interaction of all SOC components in the injured VSMCs, where Homer1 interacts with Orai1 and various TRPC channels. Accordingly, knockdown of Homer1 in cultured VSMCs partially inhibited SOCs, VSMC migration, and VSMC proliferation. Neointimal area was reduced after treatment with an adeno-associated viral vector expressing a short hairpin RNA against Homer1 mRNA (AAV-shHomer1). These findings stress the role of multiple Ca2+ influx channels in VSMCs and are the first to show the role of Homer proteins in VSMCs and its importance in neointima formation.

Nitric oxide attenuates overexpression of Giα proteins in vascular smooth muscle cells from SHR: Role of ROS and ROS-mediated signaling.

Vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) exhibit decreased levels of nitric oxide (NO) that may be responsible for the overexpression of Giα proteins that has been shown as a contributing factor for the pathogenesis of hypertension in SHR. The present study was undertaken to investigate if increasing the intracellular levels of NO by NO donor S-Nitroso-N-acetyl-DL-penicillamine (SNAP) could attenuate the enhanced expression of Giα proteins in VSMC from SHR and explore the underlying mechanisms responsible for this response. The expression of Giα proteins and phosphorylation of ERK1/2, growth factor receptors and c-Src was determined by Western blotting using specific antibodies. Treatment of VSMC from SHR with SNAP for 24 hrs decreased the enhanced expression of Giα-2 and Giα-3 proteins and hyperproliferation that was not reversed by 1H (1, 2, 4) oxadiazole (4, 3-a) quinoxalin-1-one (ODQ), an inhibitor of soluble guanylyl cyclase, however, PD98059, a MEK inhibitor restored the SNAP-induced decreased expression of Giα proteins towards control levels. In addition, the increased production of superoxide anion, NAD(P)H oxidase activity, overexpression of AT1 receptor, Nox4, p22phox and p47phox proteins, enhanced levels of TBARS and protein carbonyl, increased phosphorylation of PDGF-R, EGF-R, c-Src and ERK1/2 in VSMC from SHR were all decreased to control levels by SNAP treatment. These results suggest that NO decreased the enhanced expression of Giα-2/3 proteins and hyperproliferation of VSMC from SHR by cGMP-independent mechanism and involves ROS and ROS-mediated transactivation of EGF-R/PDGF-R and MAP kinase signaling pathways.

Nicotine facilitates VSMC dysfunction through a miR-200b/RhoGDIA/cytoskeleton module

Nicotine can induce the abnormal migration and proliferation of vascular smooth muscle cells (VSMCs). We have previously shown that cytoskeletal proteins and RhoGDIA, a negative regulator of the Rho GTPase pathway, are involved in the nicotine-induced dysfunction of VSMCs. Here, we found that nicotine can activate the Rho GTPase pathway and induce the synthesis of the cytoskeletal proteins in VSMCs through the activation of intracellular downstream signaling pathways, including targets such as MYPT1, PAK1 and PI3K/AKT. Upon nicotine treatment, the mRNA level of RhoGDIA is increased but protein level is decreased both in vitro and in vivo, which suggested a mechanism of post-translational regulation. By the dual luciferase reporter assay, we identified the microRNA-200b (miR-200b) as a modulator of the behavioural changes of VSMCs in response to nicotine through targeting RhoGDIA directly. Introducing miR-200b inhibitors into cultured VSMCs significantly attenuated cell proliferation and migration. Additionally, we found that hypomethylation in the CpG island shore region of miR-200b was responsible for the nicotine-induced miR-200b up-regulation in VSMCs. The study demonstrates that nicotine facilitates VSMC dysfunction through a miR-200b/RhoGDIA/cytoskeleton module through the hypomethylation of miR-200b promoter and suggests that epigenetic modifications may play an important role in the pathological progression.