Balloon-injured Rat Carotid Arteries Research Articles

Ginsenoside Rg1 inhibits vascular intimal hyperplasia in balloon-injured rat carotid artery by down-regulation of extracellular signal-regulated kinase 2

Ethnopharmacological relevanceGinsenoside Rg1 (Rg1) is one of the main active components of Panax ginseng a well-known herbal medicine. It has been demonstrated to inhibit proliferation of vascular smooth muscle cells (VSMCs) induced by tumor necrosis factor-αin vitro. The present study is aimed to examine the possible effects of Rg1 on vascular neointimal hyperplasia in balloon-injured carotid artery of rats in vivo. Materials and methodsThe animal model was established by rubbing the endothelia with a balloon catheter in the common carotid artery (CCA) of male Sprague Dawley rats. Then the rats were intraperitoneally injected with distilled water in model group and sham operation control, or with Rg1 4, 8 and 16mg/kg/d in other balloon injured groups. After consecutive 14 days, the vascular intimal hyperplasia was evidenced by histopathological alterations of the CCA and by changes observed in the marker of the proliferation of VSMCs–the proliferating cell nuclear antigen (PCNA). The protein expressions of PCNA and the phosphorylated extracellular signal-regulated kinase2 (p-ERK2) as well as mitogen-ativated protein kinase phosphatase-1 (MKP-1) were examined by immunohistochemistry; while the expressions of proto-oncogene (c-fos), ERK2 and smooth muscle α-actin (SM α-actin) mRNA were analyzed by Real-Time RT-PCR. ResultsRg1 administration could significantly ameliorate the histopathology of CCA and decrease the protein expression of PCNA induced by endothelia rubbing; and Rg1 medication also significantly decreased the expressions of p-ERK2 protein, ERK2 and c-fos mRNA in vessel wall, but up-regulated the MKP-1 expression, which was reported to inactivate mitogen-ativated protein kinase pathway. Furthermore, Rg1 could elevate the decreased SM α-actin mRNA expression induced by balloon injury. ConclusionsRg1 can suppress the vascular neointimal hyperplasia induced by balloon injury, the mechanism may be involved in the inhibition on ERK2 signaling, and related, at least partly, to the increase in MKP-1 expression.

O-GlcNAc Modification of NFκB p65 Inhibits TNF-α-Induced Inflammatory Mediator Expression in Rat Aortic Smooth Muscle Cells

BackgroundWe have shown that glucosamine (GlcN) or O-(2-acetamido-2-deoxy-D-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAc) treatment augments O-linked-N-acetylglucosamine (O-GlcNAc) protein modification and attenuates inflammatory mediator expression, leukocyte infiltration and neointima formation in balloon injured rat carotid arteries and have identified the arterial smooth muscle cell (SMC) as the target cell in the injury response. NFκB signaling has been shown to mediate the expression of inflammatory genes and neointima formation in injured arteries. Phosphorylation of the p65 subunit of NFκB is required for the transcriptional activation of NFκB. This study tested the hypothesis that GlcN or PUGNAc treatment protects vascular SMCs against tumor necrosis factor (TNF)-α induced inflammatory stress by enhancing O-GlcNAcylation and inhibiting TNF-α induced phosphorylation of NFκB p65, thus inhibiting NFκB signaling.Methodology/Principal FindingsQuiescent rat aortic SMCs were pretreated with GlcN (5 mM), PUGNAc (10−4 M) or vehicle and then stimulated with TNF-α (10 ng/ml). Both treatments inhibited TNF-α-induced expression of chemokines [cytokine-induced neutrophil chemoattractant (CINC)-2β and monocyte chemotactic protein (MCP)-1] and adhesion molecules [vascular cell adhesion molecule (VCAM)-1 and P-Selectin]. Both treatments inhibited TNF-α induced NFκB p65 activation and promoter activity, increased NFκB p65 O-GlcNAcylation and inhibited NFκB p65 phosphorylation at Serine 536, thus promoting IκBα binding to NFκB p65.ConclusionsThere is a reciprocal relationship between O-GlcNAcylation and phosphorylation of NFκB p65, such that increased NFκB p65 O-GlcNAc modification inhibits TNF-α-Induced expression of inflammatory mediators through inhibition of NFκB p65 signaling. These findings provide a mechanistic basis for our previous observations that GlcN and PUGNAc treatments inhibit inflammation and remodeling induced by acute endoluminal arterial injury.

Focal Adhesion Kinase–Related Nonkinase Inhibits Vascular Smooth Muscle Cell Invasion by Focal Adhesion Targeting, Tyrosine 168 Phosphorylation, and Competition for p130 Cas Binding

Focal adhesion kinase-related nonkinase (FRNK), the C-terminal domain of focal adhesion kinase (FAK), is a tyrosine-phosphorylated, vascular smooth muscle cell (VSMC)-specific inhibitor of cell migration. FRNK inhibits both FAK and proline-rich tyrosine kinase 2 (PYK2) in cultured VSMCs, and both kinases may be involved in VSMC invasion during vascular remodeling. Adenovirally mediated gene transfer of green fluorescent protein-tagged, wild-type (wt) FRNK into balloon-injured rat carotid arteries confirmed that FRNK overexpression inhibited both FAK and PYK2 phosphorylation and downstream signaling in vivo. To identify which kinase was involved in regulating VSMC invasion, adenovirally mediated expression of specific short hairpin RNAs was used to knock down FAK versus PYK2 in cultured VSMCs, but only FAK short hairpin RNA was effective in reducing VSMC invasion. The role of FRNK tyrosine phosphorylation was then examined using adenoviruses expressing nonphosphorylatable (Tyr168Phe-, Tyr232Phe-, and Tyr168,232Phe-) green fluorescent protein-FRNK mutants. wtFRNK and all FRNK mutants localized to FAs, but only Tyr168 phosphorylation was required for FRNK to inhibit invasion. Preventing Tyr168 phosphorylation also increased FRNK-paxillin interaction, as determined by coimmunoprecipitation, total internal reflection fluorescence microscopy, and fluorescence recovery after photobleaching. Furthermore, wtFRNK competed with FAK for binding to p130(Cas) (a critically important regulator of cell migration) and prevented its phosphorylation. However, Tyr168Phe-FRNK was unable to bind p130(Cas). We propose a 3-stage mechanism for FRNK inhibition: focal adhesion targeting, Tyr168 phosphorylation, and competition with FAK for p130 binding and phosphorylation, which are all required for FRNK to inhibit VSMC invasion.

Use of remote film loading methodology to entrap sirolimus into liposomes: Preparation, characterization and in vivo efficacy for treatment of restenosis

The main objective of this study was to formulate an effective controlled-release liposomal drug delivery system for sirolimus (SIR), a potent antiproliferative and anti-inflammatory drug, to be used for the treatment of restenosis following local vascular delivery. Liposomes were prepared using remote film loading method and characterized with regard to entrapment efficiency (EE), size distribution and zeta potential. The effects of key formulation and proceeding variables on both EE and drug release were studied using a fractional factorial design. By means of this entrapment technique, 98% SIR incorporation was achieved. Nanoliposomes were found to have average size of 110 nm and zeta potential of −9 mV. Developed formulations were found to have prolonged drug release for up to 3 weeks in vitro; this was best fitted by the Higuchi model. Other scopes of this work were to determine the applicability of sirolimus-loaded nanoliposomes (SIR-L) as drug carriers for the treatment of restenosis and to evaluate the effect of the presence of rigid lipids on the in vivo efficacy of the liposomal carrier of SIR. In vivo studies in balloon injured rat carotid arteries revealed the potential of SIR-loaded liposomes as efficient local and controlled drug delivery systems to reduce restenosis.

Adenovirus-mediated gene transfer of TIMP-4 reduces neointimal hyperplasia in balloon-injured rat carotid artery

Objective To determine the effects of a recombinant replication-deficient adenovirus encoding human tissue inhibitor of metalloproteinase-4 (Ad.TIMP-4) on vascular smooth muscle cell (VSMC) function in vitro and neointimal development in the injured rat carotid artery. Methods Western blotting, gelatin zymography and reverse zymography were used to characterize the expression and functional activity of the TIMP-4 secreted by Ad.TIMP-4-infected VSMCs. The migration and proliferation of VSMCs in vitro were separately detected by using Millicell-PCF invasion chambers and [ 3H]-thymidine incorporation assay. Immunohistochemistry and morphometric analysis were used to determine the local expression of TIMP-4 and its effect on neointima development in a rat carotid artery balloon injury model. Results VSMCs infected with Ad.TIMP-4 expressed functionally active human TIMP-4 which increased with the duration of infection. TIMP-4 expression inhibited VSMC migration, but not significantly affect VSMC proliferation. In a balloon-injured rat carotid artery model, a significant 62% reduction in neointimal area was found in Ad.TIMP-4–infected vessels at 14 days after injury. Ad.TIMP-4 infection had no effect on medial area. Conclusion Our results indicated TIMP-4 over expression can significantly inhibit the migration of cultured VSMCs and prevent neointimal formation after vascular injury. Our findings provide additional evidence that TIMP-4 could play an important role in vascular pathophysiology, and may be an important therapeutic target for future drug development.

Nitric Oxide Inhibits Vascular Smooth Muscle Cell Proliferation and Neointimal Hyperplasia by Increasing the Ubiquitination and Degradation of UbcH10

Nitric oxide (NO) limits formation of neointimal hyperplasia in animal models of arterial injury in large part by inhibiting vascular smooth muscle cell (VSMC) proliferation through cell cycle arrest. The ubiquitin-conjugating enzyme UbcH10 is responsible for ubiquitinating cell cycle proteins for proper exit from mitosis. We hypothesize that NO prevents VSMC proliferation, and hence neointimal hyperplasia, by decreasing levels of UbcH10. Western blotting and immunofluorescent staining showed that NO reduced UbcH10 levels in a concentration-dependent manner in VSMC harvested from the abdominal aortas of Sprague-Dawley rats. Treatment with NO or siRNA to UbcH10 decreased both UbcH10 levels and VSMC proliferation (P<0.001), while increasing UbcH10 levels by plasmid transfection or angiotensin II stimulation increased VSMC proliferation to 150% (P=0.008) and 212% (P=0.002) of control, respectively. Immunofluorescent staining of balloon-injured rat carotid arteries showed a ~4-fold increase in UbcH10 levels, which was profoundly decreased following treatment with NO. Western blotting of carotid artery lysates showed no UbcH10 in uninjured vessels, a substantial increase in the injury alone group, and a significant decrease in the injury+NO group (~3-fold reduction versus injury alone). Importantly, in vitro and in vivo, a marked increase in polyubiquitinated UbcH10 was observed in the NO-treated VSMC and carotid arteries, respectively, indicating that NO may be decreasing unmodified UbcH10 levels by increasing its ubiquitination. Central to our hypothesis, we report that NO decreases UbcH10 levels in VSMC in vitro and following arterial injury in vivo in association with increasing polyubiquitinated-UbcH10 levels. These changes in UbcH10 levels correlate with VSMC proliferation and neointimal hyperplasia, making UbcH10 a promising therapeutic target for inhibiting this proliferative disease.

Inhibitory Effect of n‐Butylidenephthalide on Neointimal Hyperplasia in Balloon Injured Rat Carotid Artery

This investigation was designed to determine the inhibitory effects and mechanisms of n-butylidenephthalide (BP) from Angelica sinensis on smooth muscle cell (SMC) proliferation in vitro and in balloon injured rat carotid artery. Treatment of cultured rat aorta SMC-derived A7r5 cells with 25-100 μg/mL BP significantly inhibited the proliferation and arrested the cell cycle in G(0)/G(1) phase. BP induced the expression and migration of Nur77 from the nucleus to the cytoplasm. Among signal pathways, JNK and p38 MAPK were phosphorylated after BP treatment. In vivo, the neointimal area of common carotid artery 2 weeks after balloon injury reduced significantly in Sprague-Dawley rats treated with 150-300 mg/kg BP compared with the control. The proliferative activity indicated by immunohistochemical detection of Ki-67 positive cells in the neointima was significantly decreased in the 60-300 mg/kg BP treatment groups. The apoptotic activity indicated by cleaved caspase-3 positive cells and Nur77 positive cells in the neointima was significantly increased in rats treated with 60-300 mg/kg BP. This study demonstrated BP inhibited neointimal hyperplasia in balloon injured rat carotid artery due to its dual effects of proliferative inhibition and apoptotic induction on SMCs. Up-regulation of Nur77 gene may partly explain the antihyperplasia activity of BP on the neointima.

Zoledronate Inhibits Intimal Hyperplasia in Balloon-injured Rat Carotid Artery

Zoledronate Inhibits Intimal Hyperplasia in Balloon-injured Rat Carotid Artery

3‐Morpholinosydnonimine participates in the attenuation of neointima formation via inhibition of annexin A2‐mediated vascular smooth muscle cell migration

3-Morpholinosydnonimine (SIN-1) affects vascular smooth muscle cell migration and proliferation, processes essential for atherosclerosis. However, the mechanism by which SIN-1 exerts these effects has not been elucidated. We used 2-DE followed by MALDI-TOF/TOF MS to identify responses in protein expression to SIN-1 in rat aortic smooth muscle. Platelet-derived growth factor-BB increased cell migration and proliferation in rat aortic smooth muscle cells, and subsequent SIN-1 treatment inhibited it. Administration of SIN-1 in vivo attenuated neointima formation in balloon-injured rat carotid arteries. Proteomic analysis showed that glutathione peroxidase and 40S ribosomal protein S12 were differentially expressed in aortic strips exposed to SIN-1. Expression of annexin A2 was decreased by SIN-1. Platelet-derived growth factor-BB-induced cell migration was increased and inhibited in rat aortic smooth muscle cells with overexpression and knockdown of annexin A2 gene, respectively. The expression of annexin A2 was increased in vascular neointima compared with the intact control, which was inhibited by SIN-1 treatment. These results demonstrate that SIN-1 may attenuate vascular neointima formation by inhibiting annexin A2-mediated migration. Therefore, annexin A2 may be a potential target for therapeutic strategies for atherosclerosis.

Zoledronate Inhibits Intimal Hyperplasia in Balloon-injured Rat Carotid Artery

Background and objective Zoledronate has been reported to inhibit the proliferation, adhesion and migration of vascular smooth muscle cells. In the present study, we assessed whether systemic and local delivery of zoledronate would be sufficient to prevent intimal hyperplasia. Methods Twenty-four male Sprague-Dawley rats were assigned into four groups: non-treated group, systemic zoledronate-treated group, local collagen-treated group and local zoledronate-treated group. All four groups underwent balloon injury to the right common carotid artery. The left uninjured carotid arteries of the non-treated group were considered as normal artery samples. Twenty-one days after arterial injury and treatment, the right and left common carotid arteries were fixed, sectioned, stained and measured by computer-aided image analysis. Results At 3 weeks, there was a 59% reduction of the intima/media area ratio in the systemic zoledronate-treated group compared with the non-treated group ( P < 0.01). There was an 87% reduction of the intima/media area ratio in the local zoledronate-treated group compared with the local collagen-treated group ( P < 0.01). Conclusions Both systemic and local delivery of zoledronate correspond to a significant reduction in intimal hyperplasia seen at 3 weeks.

MiR‐146a and Krüppel‐like factor 4 form a feedback loop to participate in vascular smooth muscle cell proliferation

MicroRNAs are phenotypic regulators of vascular smooth muscle cells (VSMCs). In this paper, we demonstrate that miR-146a targets the Krüppel-like factor 4 (KLF4) 3'-untranslated region and has an important role in promoting VSMC proliferation in vitro and vascular neointimal hyperplasia in vivo. Silencing of miR-146a in VSMCs increases KLF4 expression, whereas overexpression of miR-146a decreases KLF4 levels. Furthermore, we demonstrate that KLF4 competes with Krüppel-like factor 5 (KLF5) to bind to and regulate the miR-146a promoter, and that KLF4 and KLF5 exert opposing effects on the miR-146a promoter. Overexpression of KLF4 in VSMCs decreases miR-146a transcription levels. By using both gain-of-function and loss-of-function approaches, we found that miR-146a promotes VSMC proliferation in vitro. Transfection of antisense miR-146a oligonucleotide into balloon-injured rat carotid arteries markedly decreased neointimal hyperplasia. These findings suggest that miR-146a and KLF4 form a feedback loop to regulate each other's expression and VSMC proliferation.

The herbal extract HMC05 inhibits neointima formation in balloon-injured rat carotid arteries: Possible therapeutic implications of HMC05

In a previous study, HMC05, a water extract from eight medicinal herbs was demonstrated to possess anti-inflammatory effects in murine macrophages and anti-atherosclerotic effects in apoE(-/-) mice. HSP27 expression was shown to be decreased in advanced atherosclerotic plaques of human carotid arteries. In the present study, the role of HMC05 in the prevention of restenosis and the possible mechanisms involved in the decrease of neointima formation were investigated using in vivo balloon injury rat model and in vitro biochemical assays. A rat carotid artery balloon injury restenosis model was used. Different doses of HMC05 were administered to the rats by tube feeding, starting from four days before surgery and continuing twice per week for two weeks after carotid injury. Injured carotid arteries isolated from rats were embedded in paraffin block and tissue sections were stained with H&E to assess neointima formation. Mechanism by HMC05 that are involved in smooth muscle cell proliferation and migration was assessed by western blot assay, immunohistochemistry and confocal analysis. There was no significant difference in the medial area between the control and HMC05-treated groups. However, neointima formation was significantly inhibited in the HMC05-treated group, resulting in 47-fold lower intima to media ratios in rats treated with 25 mg/kg/day HMC05 as compared to the control. Surprisingly, monocytes infiltration in the neointima area was almost completely blocked by HMC05 administration. When rat vascular SMCs were treated with HMC05, the proliferation and migration of smooth muscle cells was dramatically inhibited in a dye uptake assay and in a scratch model in a culture dish, respectively. HMC05 dose-dependently inhibited PDGF-mediated MAPK and AKT activation. However, HMC05 did not affect PDGF-mediated HSP27 phosphorylation but it induced HSP27 overexpression and phosphorylation. In addition, medial SMCs in the arterial wall of rats treated with HMC05 showed a significant increase in HSP27 expression compared with that of the control rats. HMC05, a strong anti-inflammatory reagent, might use HSP27 as an effector molecule in SMCs to reduce neointimal hyperplasia by inhibiting PDGF-mediated MAPK and AKT activation. HMC05 could be a useful drug candidate for the prevention of restenosis after balloon injury of the arteries.

α-Lipoic Acid Prevents Neointimal Hyperplasia Via Induction of p38 Mitogen-Activated Protein Kinase/Nur77-Mediated Apoptosis of Vascular Smooth Muscle Cells and Accelerates Postinjury Reendothelialization

To explore whether α-lipoic acid (ALA), a naturally occurring antioxidant, inhibits neointimal hyperplasia by inducing apoptosis of vascular smooth muscle cells and to examine its potential effects on reendothelialization and platelet aggregation. Restenosis and late stent thrombosis, caused by neointimal hyperplasia and delayed reendothelialization, are significant clinical problems of balloon angioplasty and drug-eluting stents. ALA treatment strongly induced apoptosis of vascular smooth muscle cells and enhanced the expression and cytoplasmic localization of Nur77, which triggers intrinsic apoptotic events. Small interfering RNA-mediated downregulation of Nur77 diminished this proapoptotic effect of ALA. Moreover, ALA increased p38 mitogen-activated protein kinase phosphorylation, and inhibition of p38 mitogen-activated protein kinase completely blocked ALA-induced vascular smooth muscle cell apoptosis and Nur77 induction and cytoplasmic localization. In balloon-injured rat carotid arteries, ALA enhanced Nur77 expression and increased TUNEL-positive apoptotic cells in the neointima, leading to inhibition of neointimal hyperplasia. This preventive effect of ALA was significantly reduced by infection of an adenovirus encoding Nur77 small hairpin (sh)RNA. Furthermore, ALA reduced basal apoptosis of human aortic endothelial cells and accelerated reendothelialization after balloon injury. ALA also suppressed arachidonic acid-induced platelet aggregation. ALA could be a promising therapeutic agent to prevent restenosis and late stent thrombosis after angioplasty and drug-eluting stent implantation.

An essential role of PDCD4 in vascular smooth muscle cell apoptosis and proliferation: implications for vascular disease

It is well established that vascular smooth muscle cell (VSMC) apoptosis and proliferation are critical cellular events in a variety of human vascular diseases. However, the molecular mechanisms involved in controlling VSMC apoptosis and proliferation are still unclear. In the current study, we have found that programmed cell death 4 (PDCD4) is significantly downregulated in balloon-injured rat carotid arteries in vivo and in platelet-derived growth factor-stimulated VSMCs in vitro. Overexpression of PDCD4 via adenovirus (Ad-PDCD4) increases VSMC apoptosis in an apoptotic model induced by serum deprivation. In contrast, VSMC apoptosis is significantly decreased by knockdown of PDCD4 via its small interfering RNA. In the rat carotid arteries in vivo, VSMC apoptosis is increased by Ad-PDCD4. We have further identified that activator protein 1 is a downstream signaling molecule of PDCD4 that is associated with PDCD4-mediated effects on VSMC apoptosis. In addition, VSMC proliferation was inhibited by overexpression of PDCD4. The current study has identified, for the first time, that PDCD4 is an essential regulator of VSMC apoptosis and proliferation. The downregulation of PDCD4 expression in diseased vascular walls may be responsible for the imbalance of VSMC proliferation and apoptosis. The results indicate that PDCD4 may be a new therapeutic target in proliferative vascular diseases.

Receptor Interacting Protein 3 Suppresses Vascular Smooth Muscle Cell Growth by Inhibition of the Phosphoinositide 3-Kinase-Akt Axis

Proliferation of vascular smooth muscle cells (VSMCs) is a primary mechanism underlying cardiovascular proliferative disorders. Phosphoinositide 3-kinase (PI3K)-Akt (or protein kinase B) axis has been assigned at the center of pathways that regulate cell proliferation. Here we demonstrate that enhanced PI3K-Akt signaling by mitogenic stimulation or arterial injury profoundly elevates expression of receptor interacting protein 3 (RIP3) in primary cultured rat VSMCs and in vivo and that the up-regulation of RIP3 leads to VSMC growth arrest and apoptosis via inhibiting the PI3K-Akt signaling pathway, thereby alleviating balloon injury-induced neointimal formation. Specifically, mitogenic stimulation with platelet-derived growth factor-BB or angiotensin II leads to a profound increase in RIP3 expression, which is abolished by inhibition of PI3K or Akt, and increased PI3K-Akt signaling by expression of a constitutively active PI3K mutant also elevates RIP3 expression. Importantly, adenoviral overexpression of RIP3 not only triggers apoptosis but also causes cell cycle arrest at G(1)/G(0) phases that is associated with suppressed Akt activation. In sharp contrast, RIP3 gene silencing enhances serum- and platelet-derived growth factor-induced cell proliferation and Akt activation. In vivo adenoviral gene delivery of rat RIP3 (rRIP3) increased apoptosis and reduced VSMC proliferation, thus, effectively alleviating balloon injury-induced neointimal formation. The growth-suppressive and pro-apoptotic effects are independent of rRIP3 Ser/Thr kinase activity, because overexpression of a kinase-inactive mutant of rRIP3, similar to its wild type, is sufficient to induce growth arrest and apoptosis. These findings reveal a novel growth-suppressive action of RIP3, marking RIP3 as an important factor to prevent excessive mitogenic stimulation- or injury-induced vascular smooth muscle cells hyperplasia.

Essential role for STIM1/Orai1-mediated calcium influx in PDGF-induced smooth muscle migration

We recently demonstrated that thapsigargin-induced passive store depletion activates Ca(2+) entry in vascular smooth muscle cells (VSMC) through stromal interaction molecule 1 (STIM1)/Orai1, independently of transient receptor potential canonical (TRPC) channels. However, under physiological stimulations, despite the ubiquitous depletion of inositol 1,4,5-trisphosphate-sensitive stores, many VSMC PLC-coupled agonists (e.g., vasopressin and endothelin) activate various store-independent Ca(2+) entry channels. Platelet-derived growth factor (PDGF) is an important VSMC promigratory agonist with an established role in vascular disease. Nevertheless, the molecular identity of the Ca(2+) channels activated by PDGF in VSMC remains unknown. Here we show that inhibitors of store-operated Ca(2+) entry (Gd(3+) and 2-aminoethoxydiphenyl borate at concentrations as low as 5 microM) prevent PDGF-mediated Ca(2+) entry in cultured rat aortic VSMC. Protein knockdown of STIM1, Orai1, and PDGF receptor-beta (PDGFRbeta) impaired PDGF-mediated Ca(2+) influx, whereas Orai2, Orai3, TRPC1, TRPC4, and TRPC6 knockdown had no effect. Scratch wound assay showed that knockdown of STIM1, Orai1, or PDGFRbeta inhibited PDGF-mediated VSMC migration, but knockdown of STIM2, Orai2, and Orai3 was without effect. STIM1, Orai1, and PDGFRbeta mRNA levels were upregulated in vivo in VSMC from balloon-injured rat carotid arteries compared with noninjured control vessels. Protein levels of STIM1 and Orai1 were also upregulated in medial and neointimal VSMC from injured carotid arteries compared with noninjured vessels, as assessed by immunofluorescence microscopy. These results establish that STIM1 and Orai1 are important components for PDGF-mediated Ca(2+) entry and migration in VSMC and are upregulated in vivo during vascular injury and provide insights linking PDGF to STIM1/Orai1 during neointima formation.

Lentivirus-mediated RNAi Targeting CREB Binding Protein Attenuates Neointimal Formation and Promotes Re-endothelialization in Balloon Injured Rat Carotid Artery

Background/Aims: Lentiviral vectors provide a promising strategy for the treatment of cardiovascular diseases, owing to their ability to govern efficient and durable gene transfer. However, relatively few studies have been addressed on restenosis after balloon or stent associated arterial injury. We previously found that CREB binding protein (CBP), a powerful transcriptional coactivator, regulated cell proliferation and apoptosis in vascular endothelial and smooth muscle cells. Therefore, we investigated whether inhibition of CBP by lentivirus-mediated small interfering RNA can reduce neointimal formation after arterial injury. Methods: The carotid arteries from Sprague-Dawley rats were injured by balloon catheter, followed by incubating with 100 µl lentivirus expressing CBP or negative control (NC)-specific short hairpin RNAs (shRNAs) or PBS solution for 30 minutes. The rats were euthanized for real-time PCR, Western blot, immunohistochemical staining, and morphometric analysis at 4 weeks after balloon injury and in vivo gene transfer. Results: Lentiviral shRNA targeting CBP markedly reduced CBP expression. Moreover, CBP siRNA showed potent inhibition on balloon injury-induced Nuclear factor kappaB (NF-ĸB) acetylation. Compared with controls, the significant decrease of neointimal formation by CBP siRNA was accompanied by reduced cell proliferation in the neointima of injured arteries. However, no changes in medial area were observed among these different groups. Interestingly, endothelial cell marker CD31 immunostaining and morphometric analysis both showed that CBP knockdown significantly accelerated re-endothelialization. Conclusions: These findings suggest that CBP is involved in the control of neointimal formation and re-endothelialization via regulating NF-ĸB acetylation. Lentivirus-mediated CBP silencing may represent a novel therapeutic approach for the prevention of restenosis after vascular interventions.

S-phase kinase-associated protein-2 (Skp2) promotes vascular smooth muscle cell proliferation and neointima formation in vivo

ObjectiveVascular smooth muscle cell (VSMC) proliferation plays an important role in the development of postangioplasty or in-stent restenosis, venous graft failure, and atherosclerosis. Our previous work has demonstrated S-phase kinase-associated protein-2 (Skp2), an F-box subunit of SCFSkp2 ubiquitin ligase, as an important mediator and common final pathway for growth factors, extracellular matrices, and cyclic-nucleotides to regulate VSMC proliferation in vitro. However, whether alteration of Skp2 function also regulates VSMC proliferation in vivo and neointimal thickening postvascular injury remains unclear. We investigated the effect of Skp2 on VSMC proliferation and neointimal formation in vivo.Methods and ResultsFirstly, we demonstrated that Skp2-null mice developed significantly smaller neointimal areas than wild-type mice after carotid ligation. Secondly, to further identify a local rather than a systemic effect of Skp2 alteration, we demonstrated that adenovirus-mediated expression of dominant-negative Skp2 in the balloon-injured rat carotid artery significantly increased medial p27Kip1 levels, inhibited VSMC proliferation, and the subsequent neointimal thickening. Lastly, to determine if Skp2 alone is sufficient to drive VSMC proliferation and lesion development in vivo, we demonstrated that adenovirus-delivery of wild-type Skp2 to the minimally-injured rat carotids is sufficient to downregulate p27Kip1 protein levels, enhanced medial VSMC proliferation, and the neointimal thickening.ConclusionThis data provides, we believe for the first time, a more comprehensive understanding of Skp2 in the regulation of VSMC proliferation and neointimal formation and suggests that Skp2 is a promising target in the treatment of vasculoproliferative diseases.

Protective Role of Clusterin/Apolipoprotein J Against Neointimal Hyperplasia via Antiproliferative Effect on Vascular Smooth Muscle Cells and Cytoprotective Effect on Endothelial Cells

Clusterin is induced in vascular smooth muscle cells (VSMCs) during atherosclerosis and injury-induced neointimal hyperplasia. However, its functional roles in VSMCs and endothelial cells remain controversial and elusive. This study was undertaken to clarify the role of clusterin in neointimal hyperplasia and elucidate its mechanism of action. Adenovirus-mediated overexpression of clusterin (Ad-Clu) repressed TNF-alpha-stimulated expression of MCP-1, fractalkine, ICAM-1, VCAM-1, and MMP-9, leading to inhibition of VSMC migration. Both Ad-Clu and secreted clusterin suppressed VSMC proliferation by inhibiting DNA synthesis, but not by inducing apoptosis. Ad-Clu upregulated p53 and p21(cip1/waf1) but downregulated cyclins D and E, leading to suppression of pRb phosphorylation and subsequent induction of G1 arrest in VSMCs. Clusterin deficiency augmented VSMC proliferation in vitro and accelerated neointimal hyperplasia in vivo, but concomitantly impaired reendothelialization in wire-injured murine femoral arteries. Moreover, Ad-Clu significantly reduced neointimal thickening in balloon-injured rat carotid arteries. Clusterin also diminished TNF-alpha-induced apoptosis of human umbilical vein endothelial cells and restored endothelial nitric oxide synthase expression suppressed by TNF-alpha. These results suggest that upregulation of clusterin during vascular injury may be a protective response against, rather than a causative response to, the development of neointimal hyperplasia.

Propylthiouracil, independent of its antithyroid effect, promotes vascular smooth muscle cells differentiation via PTEN induction

Propylthiouracil (PTU), independent of its antithyroid effect, is recently found to have an antiatherosclerotic effect. The aim of this study is to determine the impact of PTU on phenotypic modulation of vascular smooth muscle cells (VSMCs), as phenotypic modulation may contribute to the growth of atherosclerotic lesions and neointimal formation after arterial injury. Propylthiouracil reduced neointimal formation in balloon-injured rat carotid arteries. In vitro, PTU may convert VSMCs from a serum-induced dedifferentiation state to a differentiated state, as indicated by a spindle-shaped morphology and an increase in the expression of SMC differentiation marker contractile proteins, including calponin and smooth muscle (SM)-myosin heavy chain (SM-MHC). Transient transfection studies in VSMCs demonstrated that PTU induced the activity of SMC marker genes (calponin and SM-MHC) promoters, indicating that PTU up-regulates these genes expression predominantly at the transcriptional level. Furthermore, PTU enhanced the expression of PTEN and inhibition of PTEN by siRNA knockdown blocked PTU-induced activation of contractile proteins expression and promoter activity. In the rat carotid injury model, PTU reversed the down-regulation of contractile proteins and up-regulated PTEN in the neointima induced by balloon injury. Propylthiouracil promotes VSMC differentiation, at lest in part, via induction of the PTEN-mediated pathway. These findings suggest a possible mechanism by which PTU may contribute to its beneficial effects on atherogenesis and neointimal formation after arterial injury.