Carotid Artery Smooth Muscle Cells Research Articles

Multiomics of Tissue Extracellular Vesicles Identifies Unique Modulators of Atherosclerosis and Calcific Aortic Valve Stenosis.

Fewer than 50% of patients who develop aortic valve calcification have concomitant atherosclerosis, implying differential pathogenesis. Although circulating extracellular vesicles (EVs) act as biomarkers of cardiovascular diseases, tissue-entrapped EVs are associated with early mineralization, but their cargoes, functions, and contributions to disease remain unknown. Disease stage-specific proteomics was performed on human carotid endarterectomy specimens (n=16) and stenotic aortic valves (n=18). Tissue EVs were isolated from human carotid arteries (normal, n=6; diseased, n=4) and aortic valves (normal, n=6; diseased, n=4) by enzymatic digestion, (ultra)centrifugation, and a 15-fraction density gradient validated by proteomics, CD63-immunogold electron microscopy, and nanoparticle tracking analysis. Vesiculomics, comprising vesicular proteomics and small RNA-sequencing, was conducted on tissue EVs. TargetScan identified microRNA targets. Pathway network analyses prioritized genes for validation in primary human carotid artery smooth muscle cells and aortic valvular interstitial cells. Disease progression drove significant convergence (P<0.0001) of carotid artery plaque and calcified aortic valve proteomes (2318 proteins). Each tissue also retained a unique subset of differentially enriched proteins (381 in plaques; 226 in valves; q<0.05). Vesicular gene ontology terms increased 2.9-fold (P<0.0001) among proteins modulated by disease in both tissues. Proteomics identified 22 EV markers in tissue digest fractions. Networks of proteins and microRNA targets changed by disease progression in both artery and valve EVs revealed shared involvement in intracellular signaling and cell cycle regulation. Vesiculomics identified 773 proteins and 80 microRNAs differentially enriched by disease exclusively in artery or valve EVs (q<0.05); multiomics integration found tissue-specific EV cargoes associated with procalcific Notch and Wnt signaling in carotid arteries and aortic valves, respectively. Knockdown of tissue-specific EV-derived molecules FGFR2, PPP2CA, and ADAM17 in human carotid artery smooth muscle cells and WNT5A, APP, and APC in human aortic valvular interstitial cells significantly modulated calcification. The first comparative proteomics study of human carotid artery plaques and calcified aortic valves identifies unique drivers of atherosclerosis versus aortic valve stenosis and implicates EVs in advanced cardiovascular calcification. We delineate a vesiculomics strategy to isolate, purify, and study protein and RNA cargoes from EVs entrapped in fibrocalcific tissues. Integration of vesicular proteomics and transcriptomics by network approaches revealed novel roles for tissue EVs in modulating cardiovascular disease.

Long Noncoding RNA MIAT Controls Advanced Atherosclerotic Lesion Formation and Plaque Destabilization.

Long noncoding RNAs (lncRNAs) are important regulators of biological processes involved in vascular tissue homeostasis and disease development. The present study assessed the functional contribution of the lncRNA myocardial infarction-associated transcript (MIAT) to atherosclerosis and carotid artery disease. We profiled differences in RNA transcript expression in patients with advanced carotid artery atherosclerotic lesions from the Biobank of Karolinska Endarterectomies. The lncRNA MIAT was identified as the most upregulated noncoding RNA transcript in carotid plaques compared with nonatherosclerotic control arteries, which was confirmed by quantitative real-time polymerase chain reaction and in situ hybridization. Experimental knockdown of MIAT, using site-specific antisense oligonucleotides (LNA-GapmeRs) not only markedly decreased proliferation and migration rates of cultured human carotid artery smooth muscle cells (SMCs) but also increased their apoptosis. MIAT mechanistically regulated SMC proliferation through the EGR1 (Early Growth Response 1)-ELK1 (ETS Transcription Factor ELK1)-ERK (Extracellular Signal-Regulated Kinase) pathway. MIAT is further involved in SMC phenotypic transition to proinflammatory macrophage-like cells through binding to the promoter region of KLF4 and enhancing its transcription. Studies using Miat-/- and Miat-/-ApoE-/- mice, and Yucatan LDLR-/- mini-pigs, as well, confirmed the regulatory role of this lncRNA in SMC de- and transdifferentiation and advanced atherosclerotic lesion formation. The lncRNA MIAT is a novel regulator of cellular processes in advanced atherosclerosis that controls proliferation, apoptosis, and phenotypic transition of SMCs, and the proinflammatory properties of macrophages, as well.

Dysregulation of lncRNA SNHG1/miR-145 axis affects the biological function of human carotid artery smooth muscle cells as a mechanism of carotid artery restenosis.

Carotid angioplasty and stenting have developed into reliable options for patients with carotid stenosis. However, postoperative restenosis remains a serious and unresolved problem. Restenosis is partly caused by the proliferation of vascular smooth muscle cells. As certain long non-coding RNAs (lncRNAs) affect cell proliferation and migration, the present study aimed to investigate them as novel biomarkers for restenosis development and to further reveal the potential underlying mechanisms. The expression of lncRNA small nucleolar RNA host gene 1 (SNHG1) and microRNA145 (miR-145) in human carotid artery smooth muscle cells (hHCtASMCs) was analyzed using reverse transcription-quantitative PCR. In addition, a luciferase reporter assay was performed to investigate the interaction between SNHG1 and miR-145. The effects of the SNHG1/miR-145 axis on the proliferation and migration of hHCtASMCs were evaluated by Cell Counting Kit-8 and Transwell assays. Serum SNHG1 and miR-145 expression levels were increased and decreased, respectively, in patients with restenosis (all P<0.001). High SNHG1 and low miR-145 were identified as risk factors for restenosis onset (all P<0.01). Furthermore, decreasing SNHG1 expression levels in hHCtASMCs inhibited cell proliferation and migration. The luciferase reporter assay and expression results demonstrated that miR-145 may be a target of SNHG1 and mediated the effects of SNHG1 on hHCtASMC proliferation and migration. The results obtained suggested that abnormal expression of SNHG1 and miR-145 may be risk factors for restenosis. The present study revealed that the SNHG1/miR-145 axis regulates hHCtASMC proliferation and migration, indicating its potential for restenosis prevention and treatment.

Chitinase 3 like 1 is a regulator of smooth muscle cell physiology and atherosclerotic lesion stability.

Atherosclerotic cerebrovascular disease underlies the majority of ischaemic strokes and is a major cause of death and disability. While plaque burden is a predictor of adverse outcomes, plaque vulnerability is increasingly recognized as a driver of lesion rupture and risk for clinical events. Defining the molecular regulators of carotid instability could inform the development of new biomarkers and/or translational targets for at-risk individuals. Using two independent human endarterectomy biobanks, we found that the understudied glycoprotein, chitinase 3 like 1 (CHI3L1), is up-regulated in patients with carotid disease compared to healthy controls. Further, CHI3L1 levels were found to stratify individuals based on symptomatology and histopathological evidence of an unstable fibrous cap. Gain- and loss-of-function studies in cultured human carotid artery smooth muscle cells (SMCs) showed that CHI3L1 prevents a number of maladaptive changes in that cell type, including phenotype switching towards a synthetic and hyperproliferative state. Using two murine models of carotid remodelling and lesion vulnerability, we found that knockdown of Chil1 resulted in larger neointimal lesions comprised by de-differentiated SMCs that failed to invest within and stabilize the fibrous cap. Exploratory mechanistic studies identified alterations in potential downstream regulatory genes, including large tumour suppressor kinase 2 (LATS2), which mediates macrophage marker and inflammatory cytokine expression on SMCs, and may explain how CHI3L1 modulates cellular plasticity. CHI3L1 is up-regulated in humans with carotid artery disease and appears to be a strong mediator of plaque vulnerability. Mechanistic studies suggest this change may be a context-dependent adaptive response meant to maintain vascular SMCs in a differentiated state and to prevent rupture of the fibrous cap. Part of this effect may be mediated through downstream suppression of LATS2. Future studies should determine how these changes occur at the molecular level, and whether this gene can be targeted as a novel translational therapy for subjects at risk of stroke.

Long non-coding RNA cyclin-dependent kinase inhibitor 2B antisense ribonucleic acid 1 is associated with in-stent restenosis and promotes human carotid artery smooth muscle cell proliferation and migration by sponging miR-143-3p.

Carotid angioplasty and stenting (CAS) is an efficient therapeutic approach for carotid stenosis. However, in-stent restenosis (ISR) frequently occurs and seriously affects the therapeutic efficacy of CAS. Certain non-coding (nc)RNAs serve potential roles in ISR development and progression. Thus, the goals of the present study were to investigate novel biomarkers for ISR development and to further uncover the mechanisms underlying the progression of ISR. The expression of long ncRNA cyclin-dependent kinase inhibitor (CDKN)2B-antisense 1 (AS1) and microRNA (miR)-143-3p in patients with ISR and human carotid artery smooth muscle cells (hHCtASMCs) was analyzed using reverse transcription-quantitative PCR. A luciferase reporter assay was performed to examine the interaction between CDKN2B-AS1 and miR-143-3p. The effects of the CDKN2B/miR-143-3p axis on hHCtASMC proliferation and migration were assessed using Cell Counting Kit-8 and Transwell assays. The results indicated that serum CDKN2B-AS1 was increased and miR-143-3p was decreased in patients with ISR as compared with that in patients with no ISR (all P<0.001). CDKN2B-AS1 and miR-143-3p were identified as risk factors for ISR onset (all P<0.05) and knockdown of CDKN2B-AS1 in hHCtASMCs led to inhibited cell proliferation and migration. Furthermore, the luciferase reporter assay and expression analysis indicated that miR-143-3p is a target of CDKN2B-AS1 and may mediate the effects of CDKN2B-AS1 on hHCtASMC proliferation and migration. In conclusion, dysregulation of CDKN2B-AS1 and miR-143-3p may represent risk factors for the occurrence of ISR. The in vitro results suggested that the CDKN2B-AS1/miR-143-3p axis may regulate the proliferation and migration of hHCtASMCs, indicating its potential to be developed as a target for preventative measures and therapies for ISR.

Characterization of smooth muscle cells from human atherosclerotic lesions and their responses to Notch signaling

Atherosclerosis is the most common cause of heart disease and stroke. The use of animal models has advanced our understanding of the molecular signaling that contributes to atherosclerosis. Further understanding of this degenerative process in humans will require human tissue. Plaque removed during endarterectomy procedures to relieve arterial obstructions is usually discarded, but can be an important source of diseased cells. Resected tissue from carotid and femoral endarterectomy procedures were compared with carotid arteries from donors with no known cardiovascular disease. Vascular smooth muscle cells (SMC) contribute to plaque formation and may determine susceptibility to rupture. Notch signaling is implicated in the progression of atherosclerosis, and plays a receptor-specific regulatory role in SMC. We defined protein localization of Notch2 and Notch3 within medial and plaque SMC using immunostaining, and compared Notch2 and Notch3 levels in total plaques with whole normal arteries using immunoblot. We successfully derived SMC populations from multiple endarterectomy specimens for molecular analysis. To better define the protein signature of diseased SMC, we utilized sequential window acquisition of all theoretical spectra (SWATH) proteomic analysis to compare normal carotid artery SMC with endarterectomy-derived SMC. Similarities in protein profile and differentiation markers validated the SMC identity of our explants. We identified a subset of differentially expressed proteins that are candidates as functional markers of diseased SMC. To understand how Notch signaling may affect diseased SMC, we performed Jagged1 stimulation of primary cultures. In populations that displayed significant growth, Jagged1 signaling through Notch2 suppressed proliferation; cultures with low growth potential were non-responsive to Jagged1. In addition, Jagged1 did not promote contractile smooth muscle actin nor have a significant effect on the mature differentiated phenotype. Thus, SMC derived from atherosclerotic lesions show distinct proteomic profiles and have altered Notch signaling in response to Jagged1 as a differentiation stimulus, compared with normal SMC.

LncRNA CRNDE regulates the proliferation and migration of vascular smooth muscle cells.

Restenosis after angioplasty or stent is a major clinical problem. While long noncoding RNAs (lncRNAs) are implicated in a variety of diseases, their role in restenosis is not well understood. This study aims to investigate how dysregulated lncRNAs and messenger RNAs (mRNAs) contribute to restenosis. By microarray analysis, we identified 202 lncRNAs and 625 mRNAs (fold change > 2.0, p < 0.05) differentially expressed between the balloon-injured carotid artery and uninjured carotid artery in the rats. Among differentially expressed lncRNAs, LncRNA CRNDE had the highest fold change and the change was validated by reverse transcription polymerase chain reaction. We found that LncRNA CRNDE was significantly upregulated in injured rat carotid artery and vascular smooth muscle cells (VSMCs) stimulated by platelet-derived growth factor-BB (PDGF-BB). Knockdown of LncRNA CRNDE by small interference RNA significantly inhibited PDGF-BB stimulated proliferation and migration of VSMCs. Moreover, knockdown of LncRNA CRNDE attenuated PDGF-BB-induced phenotypic change of VSMCs. Taken together, our study reveals a novel mechanoresponsive LncRNA CRNDE which may be a therapeutic target for restenosis.

Inhibitory effects of growth differentiation factor 11 on autophagy deficiency-induced dedifferentiation of arterial smooth muscle cells.

Growth differentiation factor (GDF)11 has been reported to reverse age-related cardiac hypertrophy in mice and cause youthful regeneration of cardiomyocytes. The present study attempted to test a hypothesis that GDF11 counteracts the pathologic dedifferentiation of mouse carotid arterial smooth muscle cells (CASMCs) due to deficient autophagy. By real-time RT-PCR and Western blot analysis, exogenously administrated GDF11 was found to promote CASMC differentiation with increased expression of various differentiation markers (α-smooth muscle actin, myogenin, myogenic differentiation, and myosin heavy chain) as well as decreased expression of dedifferentiation markers (vimentin and proliferating cell nuclear antigen). Upregulation of the GDF11 gene by trichostatin A (TSA) or CRISPR-cas9 activating plasmids also stimulated the differentiation of CASMCs. Either GDF11 or TSA treatment blocked 7-ketocholesterol-induced CASMC dedifferentiation and autophagosome accumulation as well as lysosome inhibitor bafilomycin-induced dedifferentiation and autophagosome accumulation. Moreover, in CASMCs from mice lacking the CD38 gene, an autophagy deficiency model in CASMCs, GDF11 also inhibited its phenotypic transition to dedifferentiation status. Correspondingly, TSA treatment was shown to decrease GDF11 expression and reverse CASMC dedifferentiation in the partial ligated carotid artery of mice. The inhibitory effects of TSA on dedifferentiation of CASMCs were accompanied by reduced autophagosome accumulation in the arterial wall, which was accompanied by attenuated neointima formation in partial ligated carotid arteries. We concluded that GDF11 promotes CASMC differentiation and prevents the phenotypic transition of these cells induced by autophagosome accumulation during different pathological stimulations, such as Western diet, lysosome function deficiency, and inflammation. NEW & NOTEWORTHY The present study demonstrates that growth differentiation factor (GDF)11 promotes autophagy and subsequent differentiation in carotid arterial smooth muscle cells. Upregulation of GDF11 counteracts dedifferentiation under different pathological conditions. These findings provide novel insights into the regulatory role of GDF11 in the counteracting of sclerotic arterial diseases and also suggest that activation or induction of GDF11 may be a new therapeutic strategy for the treatment or prevention of these diseases.

Abstract TP404: A Novel Adipokine DPPIV Induces Inflammation and Apoptosis of Carotid Artery Smooth Muscle Cells: Implications for Atherosclerotic Plaque Instability

Background: Carotid Atherosclerotic (CA) plaque rupture is associated with ischemic stroke. Smooth muscle cells (SMC) play key role in plaque development. SMC also produce collagen fibers and maintain the fibrous cap thickness and strength, and SMC apoptosis and inflammation can lead to plaque rupture. Molecular mechanisms leading to plaque instability and stroke are not completely understood. Our study has shown that an adipokine dipeptidyl peptidase (DPPIV) is significantly upregulated in post-stroke rat brain, and in the plasma of over 75% of CA patients, suggesting a role for DPPIV in CA and stroke. In this study, we examined the effects of DPPIV on SMC viability, apoptosis, and identified responsible signaling pathways. Methods: Mouse carotid artery SMC were exposed to oxygen glucose deprivation (OGD). Cells were treated with either physiological (200-500 ng/ml) or high (1000-2000 ng/ml) dose of DPPIV. Using transcriptome array, we examined the expression profile of apoptotic and inflammatory pathway specific genes in these cells. DPPIV levels were examined by PCR and immunofluorescence staining. MTT assay was used to assess cell viability. Live/dead cell assay detected apoptosis. Mitochondrial membrane potential was detected using tetra-methyl-rhodamine ethyl ester (TMRE). Results: Ischemia/hypoxia upregulates DPPIV mRNA and protein levels in association with increased pro-apoptotic genes including caspase 7, Nod1, and Gadd45a. Transcriptome array data demonstrated that higher dose of exogenous DPPIV results in significant increase in same pro-apoptotic pathway genes including caspase 3,7, Nod1, Trp63, and Gadd45a. On the other hand, DPPIV decreased the expression of anti-apoptotic genes including Atf5 and Birc3. Levels of pro-inflammatory cytokines including IL1-beta and Ccl26/Eotaxin were increased in both DPPIV and ischemic SMCs. Higher dose of DPPIV increased apoptosis, decreased viability and mitochondrial membrane potential in SMCs. Conclusion: Higher levels of DPP4 activates the inflammatory and apoptotic signaling cascade resulting in the apoptosis of SMC. Further research in this area will enhance our understanding of the mechanism of CA progression and may provide clues to efficient therapeutic intervention for CA.

Abstract 13: Inhibition of Nudt6 Stabilizes Advanced Atherosclerotic Plaques

Natural antisense transcripts (NATs), a non-coding RNA subclass, being transcribed in antisense direction to protein coding genes, are an intriguing novel class of targetable modulators, exerting crucial effects on gene expression. Aim of the current study was to investigate the contribution of NATs to atherosclerotic plaque vulnerability. Using laser capture micro-dissection, we isolated fibrous caps tissue of carotid artery plaques from 20 symptomatic patients with ruptured lesions vs. 20 samples from asymptomatic patients with stable lesions. A human transcriptome array (HTA; GeneChip 2.0 ) was used to profile the expression of all currently annotated RNA transcripts. Nucleoside diphosphate-linked moiety X motif 6 (NUDT6) was identified as one of the most significantly up-regulated transcripts in fibrous caps of ruptured lesions. Interestingly, NUDT6 is an established antisense RNA targeting the fibroblast growth factor 2 (FGF2). Of importance, FGF2 was among the most significantly down-regulated transcripts in ruptured lesions, corresponding to elevated NUDT6 expression. In situ hybridization in both, human and mouse carotid atherosclerotic plaques, confirmed substantially higher expression levels of NUDT6 in ruptured lesions compared to stable. In addition, in situ hybridization revealed a distinct co-localization with smooth muscle cells (SMCs) in advanced plaques. Overexpression of NUDT6 in cultured human carotid artery SMCs effectively limited FGF2 on the mRNA as well as protein level. Furthermore, reduction of NUDT6 via siRNA stimulated proliferation and blocked apoptosis in SMCs. In an inducible atherosclerotic plaque rupture model using incomplete ligation and cuff placement on common carotid arteries of male apoE -/- mice, NUDT6 inhibition with gapmeRs was able to significantly improve SMC survival rates, leading to thicker fibrous caps, and to reduce the plaque rupture rate compared to scramble-gapmeR control-treated mice (22% vs . 63%, p = 0.03). The present study presents NUDT6 as a novel crucial antisense regulator of fibrous cap stability through steering SMC survival via targeting its sense RNA transcript FGF2.

Pyk2 inhibition promotes contractile differentiation in arterial smooth muscle

Modulation from contractile to synthetic phenotype of vascular smooth muscle cells is a central process in disorders involving compromised integrity of the vascular wall. Phenotype modulation has been shown to include transition from voltage-dependent toward voltage-independent regulation of the intracellular calcium level, and inhibition of non-voltage dependent calcium influx contributes to maintenance of the contractile phenotype. One possible mediator of calcium-dependent signaling is the FAK-family non-receptor protein kinase Pyk2, which is activated by a number of stimuli in a calcium-dependent manner. We used the Pyk2 inhibitor PF-4594755 and Pyk2 siRNA to investigate the role of Pyk2 in phenotype modulation in rat carotid artery smooth muscle cells and in cultured intact arteries. Pyk2 inhibition promoted the expression of smooth muscle markers at the mRNA and protein levels under stimulation by FBS or PDGF-BB and counteracted phenotype shift in cultured intact carotid arteries and balloon injury ex vivo. During long-term (24-96 hr) treatment with PF-4594755, smooth muscle markers increased before cell proliferation was inhibited, correlating with decreased KLF4 expression and differing from effects of MEK inhibition. The Pyk2 inhibitor reduced Orai1 and preserved SERCA2a expression in carotid artery segments in organ culture, and eliminated the inhibitory effect of PDGF stimulation on L-type calcium channel and large-conductance calcium-activated potassium channel expression in carotid cells. Basal intracellular calcium level, calcium wave activity, and store-operated calcium influx were reduced after Pyk2 inhibition of growth-stimulated cells. Pyk2 inhibition may provide an interesting approach for preserving vascular smooth muscle differentiation under pathophysiological conditions.

Abstract 512: The Long Non-coding Rna MIAT Regulates Smooth Muscle Cell Proliferation and Macrophage Activity in Advanced Atherosclerotic Lesions

Background: Long noncoding RNAs (lncRNAs) have emerged as critical epigenetic regulators in various biological processes and diseases. Here we sought to identify and functionally characterize the lncRNA MIAT as a novel regulator in atherosclerotic plaque stability. Methods and results: We profiled RNA transcript expression in patients with advanced atherosclerotic lesions from the Biobank of Karolinska Endarterectomies (BiKE). By microarray analysis, lncRNA MIAT was identified as one of the most highly up-regulated non-coding RNAs in carotid plaques compared to iliac artery controls, which was confirmed by qRT-PCR and in situ hybridization. Additional in silico analysis indicated a substantial positive correlation of MIAT with markers of inflammation, apoptosis and matrix degradation in carotid plaques. Experimental knock-down of MIAT, utilizing site-specific antisense oligonucleotides (LNA-GapmeRs) not only markedly decreased proliferation and migration rates of cultured human carotid artery smooth muscle cells (hCASMCs), but also increased their levels of apoptosis. In addition, MIAT inhibition significantly impaired oxidized LDL (oxLDL) uptake of murine peritoneal as well as human monocyte-differentiated macrophages in vitro. In contrast, induction of MIAT expression by lipoprotein-a (LPa) treatment, displayed the opposite effect. Conditioned medium from macrophage cultures after MIAT knock-down substantially decreased hCASMC proliferation, indicating a potential involvement of MIAT in macrophage-SMC interactions during advanced stages of atherosclerosis. Conclusion: The lncRNA MIAT is a novel regulator of cellular processes in atherosclerosis and plaque stability, which influences SMC proliferation and apoptosis and interacts with disease-triggering macrophages.

Tongxinluo Induces nNOS Expression Through ERK Activation: Possible Contribution to the Effects of Tongxinluo to Attenuate Vasoconstriction.

Vasoconstriction and hypersensitivity to the vasoconstrictive action of serotonin occurs in the early stage of atherosclerosis. Vascular neural nitric oxide synthase (nNOS) plays an important role in the regulation of vascular tone and is vasoprotective against atherosclerosis. In this study, we intended to investigate the possible role of nNOS in mediating the effect of Chinese medicine Tongxinluo (TXL) to attenuate vasoconstriction induced by the chronic injury in the collared carotid artery. Twenty-four male Wistar Kyoto rats were assigned to 2 treatments (n = 12): vehicle and TXL (400 mg·kg·d). After 2 weeks of treatment, adventitia injury was induced by placing a silicone collar around the left carotid artery for 2 weeks. Blood flow and vascular reactivity to serotonin were determined, and carotid arteries were harvested for morphometry, RT-PCR, and Western blotting analysis. Expression of nNOS and phosphorylated ERK1/2 was also analyzed in primary cultured vascular smooth muscle cells after TXL and/or ERK kinase inhibitor treatment. Adventitia injury induced by the placement of a silicone collar around the carotid artery for 2 weeks led to chronic vasoconstriction and vascular hypersensitivity to serotonin, which was attenuated by TXL treatment. TXL improved the carotid blood flow and normalized the vascular hypersensitivity to serotonin in collared carotid arteries. The expression of nNOS and phosphorylated ERK1/2 was increased by TXL treatment in both collared carotid artery and vascular smooth muscle cells indicating a possible contribution of ERK1/2 and nNOS signaling to the beneficial effects of TXL. Moreover, we showed that the effect of TXL to increase nNOS expression was mediated by the phosphorylated ERK1/2 since the effect could be abolished by the ERK kinase inhibitor PD98059. TXL increases nNOS expression in the collared carotid artery through activation of ERK1/2 signaling, which may have contributed to the attenuation of vasoconstriction induced by the collar-induced adventitia injury.

Abstract 500: Vitamin D Supplementation Attenuates ADAM-12-mediated Proliferation of Carotid Artery Smooth Muscle Cells of Hypercholesterolemic Swine

Introduction: Risk of hypertension, peripheral artery disease, myocardial infarction and development of human atherosclerosis has been linked to vitamin D deficiency. Atheromatous cytokines, including IL-6, TNF-α and epidermal growth factor receptor (EGFR) family growth factors are released at the site of atherosclerosis and boost the activity of proteolytic enzymes such as ADAMs (a disintegrin and metalloproteinases). ADAM-12 cleaves proHB-EGF (Heparin-binding EGF-like growth factor) activating EGFR, resulting in increased proliferation of smooth muscle cells (SMCs). The aim of this study was to examine the effect of vitamin D on IL-6 and TNF-α-induced ADAM-12, pEGFR expression, HB-EGF release and SMC proliferation. Methods: Micro-swine were fed with vitamin D-deficient high cholesterol diet, high cholesterol diet containing 900 IU of vitamin D, and high cholesterol diet containing 3000 IU of vitamin D for total of 12 months. After six months, serum cholesterol levels of 500-600 mg/dL were achieved in all the three groups. The protein expression of ADAM-12 &amp; pEGFR, and HB-EGF release, in presence or absence of IL-6, TNF-α and Calcitriol, in SMCs was quantified by western Blot. HB-EGF release was measured by ELISA. The proliferation was assayed by [3H]-Thymidine incorporation and cell counting method. Results: The protein expression of ADAM-12 &amp; pEGFR, HB-EGF release were significantly reduced in carotid artery SMCs isolated from Vitamin D-supplemented swine. IL-6 and TNF-α treatment increased the protein expression of ADAM-12 &amp; pEGFR and HB-EGF release in carotid artery SMCs. Proliferation capacity was higher in SMCs isolated from Vitamin D-deficient swine carotid artery, potentiated by IL-6 and TNF-α. Calcitriol inhibited the ADAM-12, pEGFR expression and HB-EGF released in SMCs of hypercholesterolemic swine. Calcitriol also inhibited the proliferation of carotid artery SMCs isolated from Vit D-deficient, D-sufficient and D-supplemented swine. Conclusion: Together, these results suggest that vitamin D deficiency enhances proliferation of SMCs, which is potentiated by atheromatous cytokines. Whereas, vitamin D supplementation regulates ADAM-12-mediated cleavage of proHB-EGF and activation of EGFR inhibiting SMC proliferation.

Heterogeneity in the Proliferative Capacity of Smooth Muscle Cells (SMCs)

In cardiovascular disease, artery walls remodel through an increase in SMC numbers. The predominant hypothesis for this is that SMCs in the tunica media undergo phenotypic modulation into a proliferative cell type. However, direct evidence for SMC phenotypic modulation is scant. We therefore exploited time‐lapse microscopy methods to track the fate of freshly isolated, contractile SMCs. As SMCs isolated from different smooth muscle (SM) tissues are heterogeneous in nature, we have used time lapse microscopy in combination with immunocytochemistry to investigate the proliferative capacity of SMCs from portal vein (PV), carotid artery (CA) and distal colon.The adventia/endothelium and mucosa/serosa were mechanically removed before isolating cells by enzymatic digestion and trituration. Highly elongated, contractile SMCs that stained for both SM α‐actin (SMA) and SM myosin heavy chain (SM‐MHC) were obtained from all tissues. Significantly, both colon and PV tissues also contained large numbers of spherical cells that did not stain for SMA or SM‐MHC (nonSMCs). In standard culture conditions, the SMCs showed limited proliferative capacity: with the exception of one SMC that divided once (out of 15 tracked cells), colon SMCs did not proliferate. Of 11 PV SMCs tracked, 7 SMCs did divide, though none progressed beyond the 3rd generation (daughter of daughter) by confluency. Conversely, the nonSMCs proliferated rapidly (reaching the 5th generation in 5 days) and dominated the resulting cultures. In contrast, all CA cells stained for both SMA and SM‐MHC i.e. no nonSMCs were present. Whilst most CA SMCs underwent apoptosis early in culture (27 of 31 cells), those that survived went on to proliferate at varying rates (up to the 6th generation in 5 days). These results illustrate the complexities involved in creating models of SMC proliferation.

Angiotensin II enhances AT1-Nox1 binding and stimulates arterial smooth muscle cell migration and proliferation through AT1, Nox1, and interleukin-18

The redox-sensitive transcription factors NF-κB and activator protein-1 (AP-1) are critical mediators of ANG II signaling. The promitogenic and promigratory factor interleukin (IL)-18 is an NF-κB- and AP-1-responsive gene. Therefore, we investigated whether ANG II-mediated smooth muscle cell (SMC) migration and proliferation involve IL-18. ANG II induced rat carotid artery SMC migration and proliferation and IL-18 and metalloproteinase (MMP)-9 expression via ANG II type 1 (AT(1)) receptor. ANG II-induced superoxide generation, NF-κB and AP-1 activation, and IL-18 and MMP-9 induction were all markedly attenuated by losartan, diphenyleneiodonium chloride (DPI), and Nox1 knockdown. Similar to ANG II, addition of IL-18 also induced superoxide generation, activated NF-κB and AP-1, and stimulated SMC migration and proliferation, in part via Nox1, and both ANG II and IL-18 induced NOX1 transcription in an AP-1-dependent manner. AT(1) physically associates with Nox1 in SMC, and ANG II enhanced this binding. Interestingly, exogenous IL-18 neither induced AT(1) binding to Nox1 nor enhanced the ANG II-induced increase in AT(1)/Nox1 binding. Importantly, IL-18 knockdown, or pretreatment with IL-18 neutralizing antibodies, or IL-18 binding protein, all attenuated the migratory and mitogenic effects of ANG II. Continuous infusion of ANG II for 7 days induced carotid artery hyperplasia in rats via AT(1) and was associated with increased AT(1)/Nox1 binding (despite lower AT(1) levels); increased DPI-inhibitable superoxide production; increased phospho-IKKβ, JNK, p65, and c-Jun; and induction of IL-18 and MMP-9 in endothelium-denuded carotid arteries. These results indicate that IL-18 amplifies the ANG II-induced, redox-dependent inflammatory cascades by activating similar promitogenic and promigratory signal transduction pathways. The ANG II/Nox1/IL-18 pathway may be critical in hyperplastic vascular diseases, including atherosclerosis and restenosis.

Abstract 279: Vitamin D3 Attenuates ADAM-12--Mediated Shedding of EGFR in Carotid Artery Smooth Muscle Cells of Hypercholesterolemic Swine

Deficiency of Vitamin D is linked to an increased risk of hypertension, peripheral artery disease, and myocardial infarction and is a major risk factor for the development of human atherosclerosis. Atheromatous cytokines, including TNF-α, IL-6 and IFN-γ, and EGF receptor family growth factors are released at the site of atherosclerosis and act on proteolytic enzymes, MMPs (matrix metalloproteinases), ADAMs (a disintegrin and metalloproteinases), and ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs). ADAM-12 activates EGFR resulting in increased migration and proliferation of smooth muscle cells (SMCs). The aim of this study was to examine the effect of vitamin D on IL-6-induced ADAM-12 expression and SMC migration and proliferation. Micro-swine were fed with either vitamin D-deficient high cholesterol diet or high cholesterol diet containing 900 IU of vitamin D for 6 months. After six months when serum cholesterol levels ranged from 500-600 mg/dL, vitamin D-deficient group continued on the same deficient diet, whereas the other group received supplementation of vitamin D (1,000 IU/d) for 6 months. The mRNA expression of ADAM-12 and EGFR in whole carotid artery and in IL-6-treated SMCs was quantified by qPCR. The proliferation was assayed by CyQuant NF cell proliferation assay. The mRNA transcripts of ADAM-12 and EGFR were significantly increased in carotid arteries from Vitamin D-deficient than in vitamin D- supplemented swine. Treatment of SMCs with IL-6 also increased the mRNA transcripts of ADAM-12 and EGFR in vitamin D-deficient swine SMCs compared to vitamin D-supplemented swine SMCs. The cell proliferation was higher in SMCs isolated from Vitamin D-deficient swine carotid artery compared to vitamin D- supplemented swine carotid artery. Together, these results suggest that Vitamin D regulates ADAM-12-mediated activation of EGFR and vitamin D deficiency further enhances proliferation of SMCs, which is potentiated by atheromatous cytokines.

Protease-Activated Receptor-2 Modulates Protease-Activated Receptor-1–Driven Neointimal Hyperplasia

Emerging evidence suggests that protease-activated receptors-1 and -2 (PAR1 and PAR2) can signal together in response to proteases found in the rapidly changing microenvironment of damaged blood vessels. However, it is unknown whether PAR1 and PAR2 promote or mitigate the hyperplastic response to arterial injury. Using cell-penetrating PAR1 pepducins and mice deficient in PAR1 or PAR2, we set out to determine the respective contributions of the receptors to hyperplasia and phenotypic modulation of smooth muscle cells (SMCs) in response to arterial injury. SMCs were strongly activated by PAR1 stimulation, as evidenced by increased mitogenesis, mitochondrial activity, and calcium mobilization. The effects of chronic PAR1 stimulation following vascular injury were studied by performing carotid artery ligations in mice treated with the PAR1 agonist pepducin, P1pal-13. Histological analysis revealed that PAR1 stimulation caused striking hyperplasia, which was ablated in PAR1(-/-) and, surprisingly, PAR2(-/-) mice. P1pal-13 treatment yielded an expression pattern consistent with a dedifferentiated phenotype in carotid artery SMCs. Detection of PAR1-PAR2 complexes provided an explanation for the hyperplastic effects of the PAR1 agonist requiring the presence of both receptors. We conclude that PAR2 regulates the PAR1 hyperplastic response to arterial injury leading to stenosis.

The role of redox changes in oxygen sensing

The specialized oxygen-sensing tissues include the carotid body and arterial smooth muscle cells in the pulmonary artery (PA) and ductus arteriosus (DA). We discuss the evidence that changes in oxygen tension are sensed through changes in redox status. "Redox" changes imply the giving or accepting of electrons. This might occur through the direct tunneling of electrons from mitochondria or redox couples to an effector protein (e.g. ion channel). Alternatively, the electron might be transferred through reactive oxygen species from mitochondria or an NADPH oxidase isoform. The PA's response to hypoxia and DA's response to normoxia result from reduction or oxidation, respectively. These opposing redox stimuli lead to K+ channel inhibition, membrane depolarization and an increase in cytosolic calcium and/or calcium sensitization that causes contraction. In the neuroendocrine cells (the type 1 cell of the carotid body, neuroepithelial body and adrenomedullary cells), the response is secretion. We examine the roles played by superoxide anion, hydrogen peroxide and the anti-oxidant enzymes in the signaling of oxygen tensions.

Tumor necrosis factor inhibitors as novel therapeutic tools for vascular remodeling diseases

Vascular remodeling diseases (VRDs) are characterized by enhanced inflammation and proliferative and apoptosis-resistant vascular smooth muscle cells (VSMCs). The sustainability of this phenotype has been attributed in part to the activation of the transcription factor hypoxia-inducible factor-1 (HIF-1). There is evidence that circulating cytokines can act as HIF-1 activators in a variety of tissues, including VSMCs. Increased circulating tumor necrosis factor (TNF) levels have been associated with vascular diseases, but the mechanisms involved remain unknown. We hypothesized that increased circulating levels of TNF promotes VRDs by the activation of HIF-1, resulting in VSMC proliferation and resistance to apoptosis. Circulating TNF levels were significantly increased in patients with vascular diseases (n = 19) compared with healthy donors (n = 15). Using human carotid artery smooth muscle cells (CASMCs), we demonstrated that TNF (100 ng/ml) activates HIF-1 (HIF-1α expression), leading to increased CASMC proliferation (Ki-67 and PCNA staining) and resistance to mitochondrial-dependent apoptosis [tetramethylrhodamine methyl ester perchlorate (TMRM), terminal deoxynucleotide transferase-mediated dUTP nick end labeling (TUNEL), annexin-V staining]. In vivo, TNF inhibition using polyethylene glycol coupled with TNF membrane receptor 1 (PEGsTNFR1), a soluble TNF receptor inhibiting circulating TNF, prevented carotid artery postinjury media remodeling and neointima development in rats. This effect was associated with lowered HIF-1 activation and decreased CASMC proliferation. In conclusion, we demonstrate for the first time that the inhibition of the TNF/Akt/HIF-1 axis prevents vascular remodeling. TNF inhibitors may therefore represent new and interesting therapeutic tools against VRDs.