Cell cycle-dependent regulation of smooth muscle cell activation

Schisandrin inhibits VSMCs proliferation and migration by arresting cell cycle and targeting JAK2 to regulating the JAK2/STAT3 pathway

Abnormal proliferation, migration, and foam cell formation of Vascular smooth muscle cells (VSMCs) each play a role in the development of atherosclerosis (AS). Schisandrin (Sch) is the active lignan ingredient with broad-spectrum pharmacological effects. However, the role of Sch in the AS process is not clear. Therefore, this study was proposed to explore the therapeutic effect and potential mechanism of Sch on VSMCs. Ox-LDL was selected to create an atherosclerosis injury environment for VSMCs and macrophages. The MTT assay, Oil red O staining, wound healing, transwell experiments and ELISA were used to investigate the phenotype effects of Sch. Network pharmacology, molecular docking, flow cytometry, and western blot were used to investigate the underlying mechanisms of Sch on AS progression. Our findings implied that Sch treatment inhibited the proliferation and migration of VSMCs, and suppressed the ROS production and inflammatory cytokines up-regulation of VSMCs and macrophages. Moreover, Sch reduced lipid uptake and foam cell formation through downregulating LOX-1. Mechanistically, we found that Sch can inhibit the activation of JAK2/STAT3 signaling by targeting JAK2, and arrest cell cycle in GO/G1 phase. In summary, Sch can inhibit VSMCs proliferation and migration by arresting cell cycle and targeting JAK2 to regulating the JAK2/STAT3 pathway. Sch may serve as a potential drug for patients with AS.

Drug-Eluting Stents

Endovascular revascularization strategies have advanced tremendously over the years and are now often considered first line for treatment of peripheral arterial disease. Drug-eluting stents (DESs) have been developed as one of the tools to overcome the limitations of elastic recoil and neointimal hyperplasia observed with balloon angioplasty and bare metal stents. While these stents have been extremely successful in coronary revascularization, they have not translated as effectively to the peripheral arteries which differ in their unique mechanical environments and differences in vessel and lesion composition. DESs, through their embedded pharmaceutical agent, seek to inhibit vascular smooth muscle cell (VSMC) proliferation and migration. Paclitaxel, sirolimus, and its derivatives (-limus family) achieve VSMC inhibition through unique mechanisms. Several clinical trials have been performed to evaluate the use of DES in the femoropopliteal and infrapopliteal territory and have demonstrated overall decrease in revascularization rates and improved clinical outcomes.

Carnosine Impedes PDGF-Stimulated Proliferation and Migration of Vascular Smooth Muscle Cells In Vitro and Sprout Outgrowth Ex Vivo

Carnosine, a naturally producing dipeptide, exhibits various beneficial effects. However, the possible role of carnosine in vascular disorders associated with pathological conditions, including proliferation and migration of vascular smooth muscle cells (VSMCs), largely remains unrevealed. Here, we investigated the regulatory role and mechanism of carnosine in platelet-derived growth factor (PDGF)-induced VSMCs. Carnosine inhibited the proliferation of PDGF-induced VSMCs without any cytotoxic effects. Carnosine treatment also induced G1-phase cell cycle arrest by causing a p21WAF1-mediated reduction in the expression of both cyclin-dependent kinases (CDKs) and cyclins in PDGF-treated VSMCs. Carnosine treatment suppressed c-Jun N-terminal kinase (JNK) phosphorylation in PDGF-stimulated signaling. Additionally, carnosine significantly prevented the migration of VSMCs exposed to PDGF. Carnosine abolished matrix metalloproteinase (MMP)-9 activity via reduced transcriptional binding activity of NF-κB, Sp-1, and AP-1 motifs in PDGF-treated VSMCs. Moreover, using aortic assay ex vivo, it was observed that carnosine addition attenuated PDGF-stimulated sprout outgrowth of VSMCs. Taken together, these results demonstrated that carnosine impeded the proliferation and migration of PDGF-stimulated VSMCs by regulating cell cycle machinery, JNK signaling, and transcription factor-mediated MMP-9 activity as well as prevented ex vivo sprout outgrowth of blood vessels. Thus, carnosine may be a potential candidate for preventing vascular proliferative disease.

Ruxolitinib attenuates intimal hyperplasia via inhibiting JAK2/STAT3 signaling pathway activation induced by PDGF-BB in vascular smooth muscle cells

BACKGROUND

Cardiovascular diseases are associated with proliferation and phenotypic switch. Platelet-derived growth factor-BB (PDGF-BB) is a major initiating factor for proliferative vascular diseases, such as neointimal lesion formation, restenosis after angioplasty, and atherosclerosis. Ruxolitinib, a potent Janus kinase (JAK) 1 and 2 inhibitor, has been reported to significantly block the proliferation-related signaling pathway of JAK2/signal transducers and activators of transcription 3 (STAT3) and harbor a broad spectrum of anti-cancer activities, including proliferation inhibition, apoptosis induction, and anti-inflammation. However, the role of ruxolitinib in regulating PDGF-BB-induced VSMC proliferation remains to be elucidated. Thus, this study investigates the role of ruxolitinib in regulating PDGF-BB-induced VSMC proliferation and its underlying mechanisms.

METHODS

In vivo, the medial thickness of the carotid artery was evaluated using a mouse carotid ligation model, ruxolitinib was administered orally to the mice every other day, and the mice were euthanized on day 28 to evaluate the therapeutic effects of ruxolitinib. Cell proliferation markers were measured using real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blotting. In vitro, VSMCs were treated with ruxolitinib with or without PDGF-BB at an indicated time and concentration. Cell proliferation and apoptosis were measured using Cell Counting Kit-8 assay, MTS assays and flow cytometry. The JAK2/STAT3 signaling pathway involved in the effects of ruxolitinib on VSMCs was detected by western blotting with the specific pathway inhibitor AG490.

RESULTS

In vivo, ruxolitinib significantly decreased the ratio-of-intima ratio (I/M ratio) by inhibiting the expression of PCNA and cyclinD1 (p <0.05). In vitro, ruxolitinib inhibited PDGF-BB-induced VSMC proliferation compared with the PDGF-BB treatment group (p <0.05). In addition, ruxolitinib inhibited the PDGF-BB-induced activation of the JAK2/STAT3 signaling pathway and decreased the expression of proliferation related-proteins cyclinD1 and PCNA in VSMCs (p <0.05).

CONCLUSION

Our findings suggest that ruxolitinib inhibits VSMC proliferation in vivo and in vitro by suppressing the activation of the JAK2/STAT3 signaling pathway. Therefore, ruxolitinib has a therapeutic potential for proliferative vascular diseases.

Surface Patterning and Innate Physicochemical Attributes of Silk Films Concomitantly Govern Vascular Cell Dynamics

Functional impairment of vascular cells is associated with cardiovascular pathologies. Recent literature clearly presents evidence relating cell microenvironment and their function. It is crucial to understand the cell-material interaction while designing a functional tissue engineered vascular graft. Natural silk biopolymer has shown potential for various tissue-engineering applications. In the present work, we aimed to explore the combinatorial effect of variable innate physicochemical properties and topographies of silk films on functional behavior of vascular cells. Silk proteins from different varieties (mulberry Bombyx mori, BM; and non-mulberry Antheraea assama, AA) possess unique inherent amino acid composition that leads to variable surface properties (roughness, wettability, chemistry, and mechanical stiffness). In addition, we engineered the silk film surfaces and printed a microgrooved pattern to induce unidirectional cell orientation mimicking their native form. Patterned silk films induced unidirectional alignment of porcine vascular cells. Regardless of alignment, endothelial cells (ECs) proliferated favorably on AA films; however, it suppressed production of nitric oxide (NO), an endogenous vasodilator. Unidirectional alignment of smooth muscle cells (SMCs) encouraged contractile phenotype as indicated by minimal cell proliferation, increment of quiescent (G0) phase cells, and upregulation of contractile genes. Moderately hydrophilic flat BM films induced cell aggregation and augmented the expression of contractile genes (for SMCs) and endothelial nitric oxide synthase, eNOS (for ECs). Functional studies further confirmed SMCs' alignment improving collagen production, remodeling ability (matrix metalloproteinase, MMP-2 and MMP-9 production) and physical contraction. Altogether, this study confirms vascular cells' functional behavior is crucially regulated by synergistic effect of their alignment and cell-substrate interfacial properties.

Baicalin inhibits proliferation and promotes apoptosis of vascular smooth muscle cells by regulating the MEG3/p53 pathway following treatment with ox‑LDL

Atherosclerosis (AS) is a systemic disease associated with lipid metabolic disorders and abnormal proliferation of smooth muscle cells. Baicalin is a flavonoid compound isolated from the dry roots of Scutellaria baicalensis Georgi and exerts anti-proliferative effects in various types of cells. However, the effect of baicalin on AS remains unclear. In the present study, serum samples were collected from patients with AS and an in vitro model of AS was established using oxidized low-density lipoprotein (ox-LDL)-treated human aorta vascular smooth muscle cells (HA-VSMCs). The siRNA transfection and overexpression efficiency of endogenous maternally expressed gene 3 (MEG3) and the expression level of MEG3 were analyzed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The effects of alterations in expression levels of MEG3 were assessed by MTT assay, bromodeoxyuridine incorporation assay, 5-ethynyl-2′-deoxyuridine staining, wound healing assay, immunofluorescence and western blotting in HA-VSMCs. qPCR indicated that the expression of MEG3 was reduced in serum samples from patients with AS and ox-LDL-treated HA-VSMCs, compared with serum samples from healthy patients and untreated HA-VSMCs, respectively. Further experiments indicated that ox-LDL-induced decrease of MEG3 expression was reversed by treatment with baicalin in a concentration-dependent manner. Following treatment with ox-LDL, decreased expression of MEG3 promoted proliferation and migration, and suppressed apoptosis in HA-VSMCs. Furthermore, treatment with baicalin reversed these effects on proliferation and apoptosis in ox-LDL-treated HA-VSMCs. The current study indicated that downregulated expression of MEG3 increased cell cycle-associated protein expression. However, treatment with baicalin inhibited the expression of cell-cycle associated proteins in HA-VSMCs with MEG3 knockdown. In addition, baicalin activated the p53 signaling pathway and promoted the expression and transport of p53 from the cytoplasm to nucleus following MEG3 knockdown in ox-LDL-treated HA-VSMCs. Baicalin inhibited proliferation and promoted apoptosis by regulating the expression of MEG3/p53, indicating that baicalin may serve a role in AS by activating the MEG3/p53 signaling pathway. The present study suggested a potential mechanism underlying the protective role of baicalin in the in vitro model of AS, and these results may be used to develop novel therapeutic approaches for the affected patients.

Inhibitory effect of PDGF-BB and serum-stimulated responses in vascular smooth muscle cell proliferation by hinokitiol via up-regulation of p21 and p53

INTRODUCTION

Vascular smooth muscle cell (VSMC) proliferation plays a major role in the progression of vascular diseases. In the present study, we established the efficacy and the mechanisms of action of hinokitiol, a tropolone derivative found in Chamaecyparis taiwanensis, Cupressaceae, in relation to platelet-derived growth factor-BB (PDGF-BB) and serum-dependent VSMC proliferation.

MATERIAL AND METHODS

Primary cultured rat VSMCs were pre-treated with hinokitiol and then stimulated by PDGF-BB (10 ng/ml) or serum (10% fetal bovine serum). Cell proliferation and cytotoxicity were determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and lactose dehydrogenase assay, respectively. The degree of DNA synthesis was evaluated by BrdU-incorporation measurements and observed using confocal microscopy. Immunoblotting was utilized to determine the protein level of p-extracellular signal-regulated kinase (ERK) 1/2, p-Akt, p-phosphoinositide 3-kinase (PI3K), p-Janus kinase 2 (JAK2), p-p53, and p21^Cip1. The promoter activity of p21 and p53 activity were measured by dual luciferase reporter assay.

RESULTS

Treatment with hinokitiol (1-10 μM) inhibited PDGF-BB and serum-induced VSMC proliferation and DNA synthesis in a concentration-dependent manner. Cytotoxicity was not observed in hinokitiol-treated VSMCs at the studied concentrations. Pre-incubation of VSMCs with hinokitiol did not alter PDGF-BB-induced phosphorylation of ERK1/2, Akt, PI3K or JAK2. Interestingly, hinokitiol induced promoter activity of p21 and p21 protein expression in VSMCs. Furthermore, hinokitiol augmented p53 protein phosphorylation and subsequently led to enhanced p53 activity.

CONCLUSIONS

These data suggest that the anti-proliferative effects of hinokitiol in VSMCs may be mediated by activation of p21 and p53 signaling pathways, and it may contribute to the prevention of vascular diseases associated with VSMC proliferation.

Rubiarbonone C inhibits platelet-derived growth factor-induced proliferation and migration of vascular smooth muscle cells through the focal adhesion kinase, MAPK and STAT3 Tyr705 signalling pathways

BACKGROUND AND PURPOSE

The proliferation and migration of vascular smooth muscle cells (VSMCs) induced by platelet-derived growth factor (PDGF) are important steps in cardiovascular diseases, including neointimal lesion formation, myocardial infarction and atherosclerosis. Here, we evaluated the rubiarbonone C-mediated signalling pathways that regulate PDGF-induced VSMC proliferation and migration.

EXPERIMENTAL APPROACH

Cell proliferation and migration were measured in cells treated with rubiarbonone C followed by PDGF BB using the MTT assay, [³ H]-thymidine incorporation, flow cytometry and wound-healing migration assay, MMP gelatin zymography, a fluorescence assay for F-actin. Western blotting of molecules including MAPK, focal adhesion kinase (FAK) and STAT3 and an immunofluorescence assay using anti-PCNA and -STAT3 antibodies were performed to evaluate rubiarbonone C signalling pathway(s). The medial thickness of the carotid artery was evaluated using a mouse carotid ligation model.

KEY RESULTS

Rubiarbonone C inhibited PDGF-induced VSMC proliferation and migration and diminished the ligation-induced increase in medial thickness of the carotid artery. In PDGF-stimulated VSMCs rubiarbonone C decreased the following: (i) levels of cyclin-dependent kinases, cyclins, PCNA and hyperphosphorylated retinoblastoma protein; (ii) levels and activity of MMP2 and MMP9; (iii) activation of MAPK; (iv) F-actin reorganization, by reducing FAK activation; (v) activation of STAT3.

CONCLUSIONS AND IMPLICATIONS

These findings suggest that rubiarbonone C inhibits the proliferation and migration of VSMCs by inhibiting the FAK, MAPK and STAT3 signalling pathways. Therefore, rubiarbonone C could be a good candidate for the treatment of cardiovascular disease.

Towards the Identification of Hemodynamic Parameters Involved in Arteriovenous Fistula Maturation and Failure: A Review

Native arteriovenous fistulas have a high failure rate mainly due to the lack of maturation and uncontrolled neo-intimal hyperplasia development. Newly established hemodynamics is thought to be central in driving the fistula fate, after surgical creation. To investigate the effects of realistic wall shear stress stimuli on endothelial cells, an in vitro approach is necessary in order to reduce the complexity of the in vivo environment. After a systematic review, realistic WSS waveforms were selected and analysed in terms of magnitude, temporal gradient, presence of reversing phases (oscillatory shear index, OSI) and frequency content (hemodynamics index, HI). The effects induced by these waveforms in cellular cultures were also considered, together with the materials and methods used to cultivate and expose cells to WSS stimuli. The results show a wide heterogeneity of experimental approaches and WSS waveform features that prevent a complete understanding of the mechanisms that regulate mechanotransduction. Furthermore, the hemodynamics derived from the carotid bifurcation is the most investigated (in vitro), while the AVF scenario remains poorly addressed. In conclusion, standardisation of the materials and methods employed, as well as the decomposition of realistic WSS profiles, are required for a better understanding of the hemodynamic effects on AVF outcomes. This standardisation may also lead to a new classification of WSS features according to the risk associated with vascular dysfunction.

2D and 3D Mechanobiology in Human and Nonhuman Systems

Mechanobiology involves the investigation of mechanical forces and their effect on the development, physiology, and pathology of biological systems. The human body has garnered much attention from many groups in the field, as mechanical forces have been shown to influence almost all aspects of human life ranging from breathing to cancer metastasis. Beyond being influential in human systems, mechanical forces have also been shown to impact nonhuman systems such as algae and zebrafish. Studies of nonhuman and human systems at the cellular level have primarily been done in two-dimensional (2D) environments, but most of these systems reside in three-dimensional (3D) environments. Furthermore, outcomes obtained from 3D studies are often quite different than those from 2D studies. We present here an overview of a select group of human and nonhuman systems in 2D and 3D environments. We also highlight mechanobiological approaches and their respective implications for human and nonhuman physiology.

Herbal composition of Cinnamomum cassia, Pinus densiflora, Curcuma longa and Glycyrrhiza glabra prevents atherosclerosis by upregulating p27 (Kip1) expression

Background

Kiom-18 is a novel composition of Cinnamomum cassia, Pinus densiflora, Curcuma longa and Glycyrrhiza glabra. Curcuma longa and Glycyrrhiza glabra, which are traditional medicines in Asia, have been reported to demonstrate preventive effects against atherosclerosis; however, they have not yet been developed into functional atherosclerosis treatments. We therefore studied the anti-atherosclerotic effects and possible molecular mechanisms of Kiom-18 using vascular smooth muscle cells (VSMCs).

Methods

To assess the anti-proliferative effect of Kiom-18 in vitro, we performed thymidine incorporation, cell cycle progression, immunoblotting and immunofluorescence assays in VSMCs stimulated by platelet derived-growth factor (PDGF)-BB. In addition, we used LDLr knockout mice to identify the effects of Kiom-18 as a preliminary result in an atherosclerosis animal model.

Results

Kiom-18 inhibited platelet-derived growth factor (PDGF)-BB-stimulated-VSMC proliferation and DNA synthesis. Additionally, Kiom-18 arrested the cell cycle transition of G₀/G₁ stimulated by PDGF-BB and its cell cycle-related proteins. Correspondingly, the level of p27^kip1 expression was upregulated in the presence of the Kiom-18 extract. Moreover, in an atherosclerosis animal model of LDLr knockout mice, Kiom-18 extract showed a preventive effect for the formation of atherosclerotic plaque and suppressed body weight, fat weight, food treatment efficiency, neutrophil count, and triglyceride level.

Conclusions

These results indicate that Kiom-18 exerts anti-atherosclerotic effects by inhibiting VSMC proliferation via G₀/G₁ arrest, which upregulates p27^Kip1 expression.

High glucose concentration induces endothelial cell proliferation by regulating cyclin-D2-related miR-98

Cyclin D2 is involved in the pathology of vascular complications of type 2 diabetes mellitus (T2DM). This study investigated the role of cyclin‐D2‐regulated miRNAs in endothelial cell proliferation of T2DM. Results showed that higher glucose concentration (4.5 g/l) significantly promoted the proliferation of rat aortic endothelial cells (RAOECs), and significantly increased the expression of cyclin D2 and phosphorylation of retinoblastoma 1 (p‐RB1) in RAOECs compared with those under low glucose concentration. The cyclin D2‐3′ untranslated region is targeted by miR‐98, as demonstrated by miRNA analysis software. Western blot also confirmed that cyclin D2 and p‐RB1 expression was regulated by miR‐98. The results indicated that miR‐98 treatment can induce RAOEC apoptosis. The suppression of RAOEC growth by miR‐98 might be related to regulation of Bcl‐2, Bax and Caspase 9 expression. Furthermore, the expression levels of miR‐98 decreased in 4.5 g/l glucose‐treated cells compared with those treated by low glucose concentration. Similarly, the expression of miR‐98 significantly decreased in aortas of established streptozotocin (STZ)‐induced diabetic rat model compared with that in control rats; but cyclin D2 and p‐RB1 levels remarkably increased in aortas of STZ‐induced diabetic rats compared with those in healthy control rats. In conclusion, this study demonstrated that high glucose concentration induces cyclin D2 up‐regulation and miR‐98 down‐regulation in the RAOECs. By regulating cyclin D2, miR‐98 can inhibit human endothelial cell growth, thereby providing novel therapeutic targets for vascular complication of T2DM.

Murrayafoline A Induces a G0/G1-Phase Arrest in Platelet-Derived Growth Factor-Stimulated Vascular Smooth Muscle Cells

The increased potential for vascular smooth muscle cell (VSMC) growth is a key abnormality in the development of atherosclerosis and post-angioplasty restenosis. Abnormally high activity of platelet-derived growth factor (PDGF) is believed to play a central role in the etiology of these pathophysiological situations. Here, we investigated the anti-proliferative effects and possible mechanism(s) of murrayafoline A, a carbazole alkaloid isolated from Glycosmis stenocarpa Guillamin (Rutaceae), on PDGF-BB-stimulated VSMCs. Murrayafoline A inhibited the PDGF-BB-stimulated proliferation of VSMCs in a concentration-dependent manner, as measured using a non-radioactive colorimetric WST-1 assay and direct cell counting. Furthermore, murrayafoline A suppressed the PDGF-BB-stimulated progression through G₀/G₁ to S phase of the cell cycle, as measured by [³H]-thymidine incorporation assay and cell cycle progression analysis. This anti-proliferative action of murrayafoline A, arresting cell cycle progression at G₀/G₁ phase in PDGF-BB-stimulated VSMCs, was mediated via down-regulation of the expression of cyclin D1, cyclin E, cyclin-dependent kinase (CDK)2, CDK4, and proliferating cell nuclear antigen (PCNA), and the phosphorylation of retinoblastoma protein (pRb). These results indicate that murrayafoline A may be useful in preventing the progression of vascular complications such as restenosis after percutaneous transluminal coronary angioplasty and atherosclerosis.

Cinnamon and its Components Suppress Vascular Smooth Muscle Cell Proliferation by Up-Regulating Cyclin-Dependent Kinase Inhibitors

Cinnamomum cassia bark has been used in traditional herbal medicine to treat a variety of cardiovascular diseases. However, the antiproliferative effect of cinnamon extract on vascular smooth muscle cells (VSMCs) and the corresponding restenosis has not been explored. Hence, after examining the effect of cinnamon extract on VSMC proliferation, we investigated the possible involvement of signal transduction pathways associated with early signal and cell cycle analysis, including regulatory proteins. Besides, to identify the active components, we investigated the components of cinnamon extract on VSMC proliferation. Cinnamon extract inhibited platelet-derived growth factor (PDGF)-BB-induced VSMC proliferation and suppressed the PDGF-stimulated early signal transduction. In addition, cinnamon extract arrested the cell cycle and inhibited positive regulatory proteins. Correspondingly, the protein levels of p21 and p27 not only were increased in the presence of cinnamon extract, also the expression of proliferating cell nuclear antigen (PCNA) was inhibited by cinnamon extract. Besides, among the components of cinnamon extract, cinnamic acid (CA), eugenol (EG) and cinnamyl alcohol significantly inhibited the VSMC proliferation. Overall, the present study demonstrates that cinnamon extract inhibited the PDGF-BB-induced proliferation of VSMCs through a G0/G1 arrest, which down-regulated the expression of cell cycle positive regulatory proteins by up-regulating p21 and p27 expression.

Apamin inhibits PDGF-BB-induced vascular smooth muscle cell proliferation and migration through suppressions of activated Akt and Erk signaling pathway

The increased proliferation and migration of vascular smooth muscle cells (VSMC) are key process in the development of atherosclerosis lesions. Platelet-derived growth factor (PDGF) initiates a multitude of biological effects that contribute to VSMC proliferation and migration. Apamin, a component of bee venom, has been known to block the Ca(2+)-activated K(+) channels. However, the effects of apamin in the regulation PDGF-BB-induced VSMC proliferation and migration has not been identified. In this study, we investigate the inhibitory effect of apamin on PDGF-BB-induced VSMC proliferation and migration. Apamin suppressed the PDGF-BB-induced VSMC proliferation and migration with no apparent cytotoxic effect. In accordance with these findings, apamin induced the arrest of cell cycle progression at G0/G1 phase. Apamin also decreased the expressions of G0/G1 specific regulatory proteins including proliferating cell nuclear antigen (PCNA), cyclin D1, cyclin-dependent kinases (CDK) 4, cyclin E and CDK2, as well as increased the expression of p21(Cip1) in PDGF-BB-induced VSMC. Moreover, apamin inhibited PDGF-BB-induced phosphorylation of Akt and Erk1/2. These results suggest that apamin plays an important role in prevention of vascular proliferation and migration through the G0/G1 cell cycle arrest by PDGF signaling pathway. Thus, apamin may be a promising candidate for the therapy of atherosclerosis.

Geminin interference facilitates vascular smooth muscle cell proliferation by upregulation of CDK-1

PURPOSE

Geminin has been correlated with vascular smooth muscle cell (VSMC) proliferation, but its mechanism is unclear. We selectively silenced the geminin gene of rat VSMCs by using RNAi technology and examined how geminin regulated VSMC proliferation.

METHODS

By using RNA interference in A10 cells and flow cytometry, (3)H-thymidine and 5-ethynyl-2'-deoxyuridine (EdU) measurements were used to detect VSMC proliferation. We performed a Western blot, polymerase chain reaction, and immunohistochemistry to detect the expression and location of geminin and cyclin-dependent kinase-1 (CDK1) in VSMCs.

RESULTS

Silencing geminin significantly increased (3)H-thymidine and EdU incorporation in VSMCs. We observed a significant increase in (3)H-thymidine incorporation 24 h after a serum challenge in the geminin-RNAi-lentiviral vector group (4401.38 ± 438.39 cpm/mg), versus the non-targeting geminin-lentiviral vector (2836.88 ± 476.18 cpm/mg) and control groups (3069.50 ± 508.18 cpm/mg; P < 0.05). In the geminin-RNAi-lentiviral vector group, the EdU-positive cell rate was significantly increased (0.75 ± 0.03; P < 0.05), versus the non-targeting geminin-lentiviral vector (0.41 ± 0.0) or control group (0.40 ± 0.03). Geminin promoted VSMC proliferation, accelerating G0/G1-S cell-cycle progression (G0/G1 cells, 10 % decrease; S-phase cells, approximate 6 % increase) 12 h after serum withdrawal. Both CDK1 protein and mRNA expression were significantly increased in the positive group versus the controls. The immunofluorescence and co-immunoprecipitation results revealed a close interaction existed between CDK1 and the geminin gene in VSMC proliferation.

CONCLUSIONS

Geminin gene inhibition could augment VSMC proliferation by increasing CDK1 expression; thus, geminin may be a potential target for treating vascular diseases, specifically VSMCs.

BubR1 Insufficiency Inhibits Neointimal Hyperplasia Through Impaired Vascular Smooth Muscle Cell Proliferation in Mice

Objective—

BubR1, a cell cycle–related protein, is an essential component of the spindle checkpoint that regulates cell division. Mice with BubR1 expression reduced to 10% of the normal level display a phenotype characterized by progeria; however, the involvement of BubR1 in vascular diseases is still unknown. We generated mice in which BubR1 expression was reduced to 20% ( BubR1 L/L mice) of that in wild-type mice ( BubR1 +/+ ) to investigate the effects of BubR1 on arterial intimal hyperplasia.

Approach and Results—

Ten-week-old male BubR1 L/L and age-matched wild-type littermates ( BubR1 +/+ ) were used in this study. The left common carotid artery was ligated, and histopathologic examinations were conducted 4 weeks later. Bone marrow transplantation was also performed. Vascular smooth muscle cells (VSMCs) were isolated from the thoracic aorta to examine cell proliferation, migration, and cell cycle progression. Severe neointimal hyperplasia was observed after artery ligation in BubR1 +/+ mice, whereas BubR1 L/L mice displayed nearly complete inhibition of neointimal hyperplasia. Bone marrow transplantation from all donors did not affect the reconstitution of 3 hematopoietic lineages, and neointimal hyperplasia was still suppressed after bone marrow transplantation from BubR1 +/+ mice to BubR1 L/L mice. VSMC proliferation was impaired in BubR1 L/L mice because of delayed entry into the S phase. VSMC migration was unaffected in these BubR1 L/L mice. p38 mitogen–activated protein kinase–inhibited VSMCs showed low expression of BubR1, and BubR1-inhibited VSMCs showed low expression of p38.

Conclusions—

BubR1 may represent a new target molecule for treating pathological states of vascular remodeling, such as restenosis after angioplasty.

Rice hull extracts inhibit proliferation of MCF-7 cells with G₁ cell cycle arrest in parallel with their antioxidant activity

Rice (Oryza sativa L.) has been a major dietary staple worldwide for centuries. Growing interest in the beneficial effects of antioxidants has inspired investigation of rice hulls as an attractive source of chemopreventive compounds for breast cancer intervention. We prepared methanol extracts from rice hulls of three Korean bred cultivars (japonica), Ilpum, Heugjinju, and Jeogjinju, and one japonica weedy rice, WD-3. We examined the antiproliferative potential of the hull extracts on MCF-7 human breast cancer cells and the related mechanisms thereof. Hull extracts inhibited proliferation of the cells and mediated G0/G1 phase arrest by suppressing cyclins and cyclin-dependent kinases, where WD-3 extract showed the most potent. Blockage of p21 expression by small interfering RNA transfection attenuated G1 phase arrest induced by WD-3 extract. The WD-3 extract exhibited greater antioxidant potential and total phenolic compounds, compared with other rice hulls. Gas chromatography-mass spectrometry analysis for the F4 fractioned from WD-3 extract revealed that cinnamic acid derivatives were the major active constituents. The F4 fraction most potently inhibited proliferation of MCF-7 cells than WD-3 extract through the suppression of cell cycle regulatory factors. Collectively, our results suggest that the pigmented rice hulls possess greater antioxidant and chemopreventive activity against breast cancer than the other rice cultivars tested, demonstrating that WD-3 rice hulls are an attractive source of chemopreventive bioactive compounds.

Fermented soshiho-tang with Lactobacillus plantarum enhances the antiproliferative activity in vascular smooth muscle cell

Background

Soshiho-tang (SST) is a traditional medicine widely used for the treatment of chronic hepatitis. SST has been shown to confer a variety of pharmacological activities, including prevention of hepatotoxicity, promotion of liver regeneration, and modulation of liver fibrosis. In this study, we investigated the antiproliferative activity of native and fermented (FSST) formulations of SST in vascular smooth muscle cells (VSMCs) and examined the potential underlying mechanisms driving these effects.

Methods

SST, along with preparations fermented with Lactobacillus plantarum KFRI-144 (S-A144), L. amylophilus KFRI-161 (S-A161) and L. bulgaricus KFRI-344 (S-A344), were investigated to determine their effects on the proliferation and viability of VSMCs, along with the signalling pathways underlying these effects.

Results

S-A144 exhibited a strong, dose-dependent inhibition of VSMC proliferation relative to untreated controls, but the others did not affect. In addition, S-A144 significantly decreased the phosphorylation of Akt and PLCγ1 in a dose-dependent manner and induced cell cycle arrest at the G₀/G₁ phase characterised by decreased expression of CDKs, cyclins and PCNA.

Conclusions

The findings suggest that S-A144 exhibit enhanced inhibition of PDGF-BB-induced VSMC proliferation comparison to S-AOR through the suppression of cell cycle progression and expression of cell cycle-related proteins, along with the downregulation of Akt phosphorylation.

CDCA7L promotes hepatocellular carcinoma progression by regulating the cell cycle

The cell division cycle-associated 7-like protein (CDCA7L) is a recently-identified target gene of c-Myc which can also interact with c-Myc. It is known to be upregulated in many tumors, however, its role in tumor progression remains unclear. We investigated the role of CDCA7L expression in hepatocellular carcinoma (HCC). We confirmed that CDCA7L is strongly upregulated in human HCC, and demonstrated that ectopic overexpression of CDCA7L promotes HCC cell proliferation and colony formation. Conversely, knockdown of CDCA7L inhibits these malignant phenotypes. In an in vivo model, subcutaneous transplantation of the tumor in nude mice showed that overexpression of CDCA7L can accelerate the tumor growth rate. Mechanistic analyses indicated that CDCA7L was able to activate the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway and regulate the cell cycle, thus promoting HCC progression. Collectively, these findings show that CDCA7L plays a role in promoting the development of HCC and may constitute a potential therapeutic target in HCC.

Sulforaphane inhibits PDGF-induced proliferation of rat aortic vascular smooth muscle cell by up-regulation of p53 leading to G1/S cell cycle arrest

Vascular diseases such as atherosclerosis and restenosis artery angioplasty are associated with vascular smooth muscle cell (VSMC) proliferation and intimal thickening arterial walls. In the present study, we investigated the inhibitory effects of sulforaphane, an isothiocyanate produced in cruciferous vegetables, on VSMC proliferation and neointimal formation in a rat carotid artery injury model. Sulforaphane at the concentrations of 0.5, 1.0, and 2.0 μM significantly inhibited platelet-derived growth factor (PDGF)-BB-induced VSMC proliferation in a concentration-dependent manner, determined by cell count. The IC50 value of sulforaphane-inhibited VSMC proliferation was 0.8 μM. Sulforaphane increased the cyclin-dependent kinase inhibitor p21 and p53 levels, while it decreased CDK2 and cyclin E expression. The effects of sulforaphane on vascular thickening were determined 14 days after the injury to the rat carotid artery. The angiographic mean luminary diameters of the group treated with 2 and 4 μM sulforaphane were 0.25±0.1 and 0.09±0.1 mm², respectively, while the value of the control groups was 0.40±0.1 mm², indicating that sulforaphane may inhibit neointimal formation. The expression of PCNA, maker for cell cycle arrest, was decreased, while that of p53 and p21 was increased, which showed the same pattern as one in in-vitro study. These results suggest that sulforaphane-inhibited VSMC proliferation may occur through the G1/S cell cycle arrest by up-regulation of p53 signaling pathway, and then lead to the decreased neointimal hyperplasia thickening. Thus, sulforaphane may be a promising candidate for the therapy of atherosclerosis and post-angiography restenosis.

Camptothecin inhibits platelet-derived growth factor-BB-induced proliferation of rat aortic vascular smooth muscle cells through inhibition of PI3K/Akt signaling pathway

The abnormal proliferation of vascular smooth muscle cells (VSMCs) in arterial wall is a major cause of vascular disorders such as atherosclerosis and restenosis after angioplasty. In this study, we investigated not only the inhibitory effects of camptothecin (CPT) on PDGF-BB-induced VSMC proliferation, but also its molecular mechanism of this inhibition. CPT significantly inhibited proliferation with IC50 value of 0.58 μM and the DNA synthesis of PDGF-BB-stimulated VSMCs in a dose-dependent manner (0.5-2 μM ) without any cytotoxicity. CPT induced the cell cycle arrest at G0/G1 phase. Also, CPT decreased the expressions of G0/G1-specific regulatory proteins including cyclin-dependent kinase (CDK)2, cyclin D1 and PCNA in PDGF-BB-stimulated VSMCs. Pre-incubation of VSMCs with CPT significantly inhibited PDGF-BB-induced Akt activation, whereas CPT did not affect PDGF-receptor beta phosphorylation, extracellular signal-regulated kinase (ERK) 1/2 phosphorylation and phospholipase C (PLC)-γ1 phosphorylation in PDGF-BB signaling pathway. Our data showed that CPT pre-treatment inhibited VSMC proliferation, and that the inhibitory effect of CPT was enhanced by LY294002, a PI3K inhibitor, on PDGF-BB-induced VSMC proliferation. In addition, inhibiting the PI3K/Akt pathway by LY294002 significantly enhanced the suppression of PCNA expression and Akt activation by CPT. These results suggest that the anti-proliferative activity of CPT is mediated in part by downregulating the PI3K/Akt signaling pathway.

Dehydroglyasperin C, a component of liquorice, attenuates proliferation and migration induced by platelet-derived growth factor in human arterial smooth muscle cells

Liquorice is one of the botanicals used frequently as a traditional medicine in the West and in the East. Platelet-derived growth factor (PDGF)-BB is involved in the development of CVD by inducing abnormal proliferation and migration of vascular smooth muscle cells. In our preliminary study, dehydroglyasperin C (DGC), an active compound of liquorice, showed strong antioxidant activity. Since phytochemicals with antioxidant activities showed beneficial effects on chronic inflammatory diseases, the present study aimed to investigate the effects of DGC on PDGF-induced proliferation and migration of human aortic smooth muscle cells (HASMC). Treatment of HASMC with DGC for 24 h significantly decreased PDGF-induced cell number and DNA synthesis in a dose-dependent manner without any cytotoxicity, as demonstrated by the 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide test and thymidine incorporation. Upon cell cycle analysis, DGC blocked the PDGF-induced progression through the G0/G1 to S phase of the cell cycle, and down-regulated the expression of cyclin-dependent kinase (CDK); 2, cyclin E, CDK4 and cyclin D1. Furthermore, DGC significantly attenuated PDGF-stimulated phosphorylation of PDGF receptor-b, phospholipase C-g1, AKT and extracellular-regulated kinase 1/2, and DGC inhibited cell migration and the dissociation of actin filaments by PDGF. In a rat vascular balloon injury model, DGC suppressed an excessive reduction in luminal diameters and neointimal formation compared with the control group. These results demonstrate the mechanistic basis for the prevention of CVD and the potential therapeutic properties of DGC.

A microfluidic flow-stretch chip for investigating blood vessel biomechanics

This microfluidic flow-stretch chip integrates fluid shear stress (FSS) and cyclic stretch (CS), two major mechanical stimulations in cardiovascular systems, for cultured cells. The model chip can deliver FSS and CS simultaneously or independently to vascular cells to mimic the haemodynamic microenvironment of blood vessels in vivo. By imposing FSS-only, CS-only, and FSS+CS stimulation on rat mesenchymal stem cells and human umbilical vein endothelial cells, we found the alignment of the cellular stress fibers varied with cell type and the type of stimulation. The flow-stretch chip is a reliable tool for simulating the haemodynamic microenvironment.

Berberine inhibits growth and induces G1 arrest and apoptosis in human cholangiocarcinoma QBC939 cells

The chemotherapeutic approach using non-toxic natural products may be one of the strategies for the management of the cholangiocarcinoma. Here we report that in vitro treatment of human cholangiocarcinoma QBC939 cells with berberine, a naturally occurring isoquinoline alkaloid, decreased cell viability and induced cell death in a dose-dependent manner, which was associated with an increase in G1 arrest. Our western blot analysis showed that berberine-induced G1 cell cycle arrest was mediated through the increased expression of cyclin-dependent kinase inhibitors (Cdki) proteins (Cip1/p21 and Kip1/p27); a simultaneous decrease in Cdk2 and Cdk4 and cyclins D1, and reduced activity of the Cyclins-Cdk complex. In additional studies, treatment of QBC939 cells with different concentrations (10, 40, 80 μM) of berberine for 48 h resulted in a significant dose-dependent increase in apoptosis compared to the non-berberine-treated control, which was associated with an increased expression of pro-apoptotic protein Bax and decreased expression of anti-apoptotic proteins Bcl-2 and Bcl-xL. Together, this study for the first time identified berberine as a chemotherapeutic agent against human cholangiocarcinoma cells QBC939 cells in vitro. Further in vivo studies are required to determine whether berberine could be an effective chemotherapeutic agent for the management of cholangiocarcinoma.

Clitocybin A, a novel isoindolinone, from the mushroom Clitocybe aurantiaca, inhibits cell proliferation through G1 phase arrest by regulating the PI3K/Akt cascade in vascular smooth muscle cells

Abnormal proliferation of vascular smooth muscle cells (VSMCs) plays an essential role in the pathogenesis of vascular diseases, such as atherosclerosis, hypertension, and restenosis. Clitocybin A, a novel isoindolinone, isolated from the culture broth of mushroom Clitocybe aurantiaca has been reported to possess free radical scavenging activity. However, the antiproliferative effects of clitocybin A on VSMCs are unknown. In the present study, we investigated the effect of clitocybin A on platelet-derived growth factor (PDGF)-BB-induced proliferation of VSMCs and examined the molecular basis of the underlying mechanism. Clitocybin A inhibited DNA synthesis and cell proliferation. In accordance with these findings, clitocybin A blocked the PDGF-BB-inducible progression through G0/G1 to S phase of the cell cycle in synchronized cells and decreased the expression of cyclin-dependent kinase (CDK) 2, CDK4, cyclin D1, cyclin E, and proliferative cell nuclear antigen. In addition, clitocybin A inhibited the PDGF-BB-induced phosphorylation of phosphatidylinositol 3 kinase (PI3K) / Akt kinase. However, clitocybin A did not change the expression levels of extracellular signal-related kinase (ERK) 1/2, phospholipase C-γ1, and PDGF-Rβ phosphorylation. These results indicate that clitocybin A may inhibit VSMCs proliferation through G1 phase arrest by regulating the PI3K/Akt pathway.

(2S)-naringenin from Typha angustata inhibits vascular smooth muscle cell proliferation via a G0/G1 arrest

ETHNOPHARMACOLOGICAL RELEVANCE

Typha angustata is used in traditional Chinese medicine for a variety of clinical disorders. Its pharmacological actions include beneficial effects on hyperlipidemia and myocardial infarction, as well as labor-inducing and antibacterial effects.

AIM OF THE STUDY

We investigated the mechanism underlying the ability of (2S)-naringenin, an active compound from Typha angustata, to inhibit the proliferation of vascular smooth muscle cells (VSMCs).

MATERIALS AND METHODS

After measuring the antiproliferative effect of (2S)-naringenin on VSMC proliferation using cell proliferation and viability assays, the possible involvement of a signaling pathway associated with platelet-derived growth factor receptor β (PDGF-Rβ), extracellular signal regulated kinase 1/2 (ERK1/2), phosphatidylinositol 3-kinase (PI3K)-linked protein kinase B (Akt/PKB), or phospholipase C-γ1 (PLCγ1) was investigated by immunoblotting. Moreover, the effect of (2S)-naringenin on DNA synthesis and the cell cycle was examined using a [(3)H]-thymidine incorporation assay and flow cytometry.

RESULTS

(2S)-Naringenin significantly inhibited PDGF-BB-induced VSMC proliferation in a concentration-dependent manner, but did not affect signaling pathways associated with PDGF-Rβ, Akt/PKB, ERK1/2, or PLCγ1. However, (2S)-naringenin suppressed DNA synthesis via a G(0)/G(1) cell cycle arrest. Accordingly, the expression of cyclins D1 and E and cyclin-dependent kinases 2 and 4 was inhibited in a concentration-dependent manner; moreover, the phosphorylation of retinoblastoma protein was suppressed.

CONCLUSIONS

Our results show that (2S)-naringenin inhibited the PDGF-BB-induced proliferation of VSMCs via a G(0)/G(1) arrest; thus, (2S)-naringenin may be valuable as a therapeutic agent for managing atherosclerosis and/or vascular restenosis.

Bufalin inhibits platelet-derived growth factor-BB-induced mesangial cell proliferation through mediating cell cycle progression

Bufalin, a traditional Chinese medicine, has been reported as a protective factor in many tumors. We therefore investigated the effect of bufalin on platelet-derived growth factor (PDGF)-BB-induced proliferation of cultured rat mesangial cells. The effect of bufalin on cell proliferation and its underlying mechanisms were investigated in cultured rat mesangial cells (MCs) by the methylthiazoletetrazolium (MTT) assay, flow cytometry, reverse transcription-polymerase chain reaction (RT-PCR), Western blotting, and cyclin-dependent kinases (CDK)2 and CDK4 kinase assays. Bufalin inhibited 20 ng/ml PDGF-BB-induced MC proliferation in a dose-dependent manner. Similar results were observed in different concentrations of bufalin, which blocked PDGF-BB-induced progression through G0/G1 to S phase of the cell cycle. Furthermore, bufalin not only inhibited upregulation of cyclin D1 and CDK4, but also downregulation of p21 in both mRNA and protein levels. Although bufalin did not affect p27 and CDK2 mRNA expression, it reversed downregulation of p27 and upregulation of CDK2 in protein level. Activity of CDK2 and CDK4 was also inhibited by bufalin. However, both bufalin and PDGF-BB did not affect cyclin E mRNA or protein expression. These results suggest that bufalin could inhibit MC proliferation by modulating cell cycle progress, indicating that bufalin could be a potential therapeutic agent for the prevention of mesangial proliferative glomerulonephritis.

Diethylstilbestrol induces arrest of rat vascular smooth muscle cell cycle progression through downregulation of cyclin D1 and cyclin E

Cardiovascular disease is associated with a multitude of pathophysiologic conditions, including vascular smooth muscle cell (VSMC) proliferation in response to vessel injury. Diethylstilbestrol (DES) was previously prescribed for at-risk pregnancies to prevent abortion, miscarriage, and premature labor. Our aim in this study was to elucidate the effects and molecular mechanism of DES on proliferation and cell cycle progression of platelet-derived growth factor (PDGF)-BB-stimulated rat aortic VSMCs. Treating the cells with DES (1-7 μM) dramatically inhibited cell proliferation in a dose-dependent manner without any cytotoxic effects. In addition, DES blocked cell cycle progression from PDGF-BB-stimulated cells, which we found was related to down-regulation of the cell cycle regulatory factors, cyclin D1, and cyclin E. Our data demonstrate that DES inhibits rat aortic VSMC proliferation and cell cycle progression through regulation of cell cycle-related proteins. Therefore, our observations may explain, in part, the mechanistic basis underlying the therapeutic effects of DES in cardiovascular disease.

Glyceollins inhibit platelet-derived growth factor-mediated human arterial smooth muscle cell proliferation and migration

Platelet-derived growth factor (PDGF)-BB can induce abnormal proliferation and migration of vascular smooth muscle cells (VSMC) that are involved in the development of CVD. In our preliminary study, phytoalexin glyceollins (glyceollins I, II and III) isolated from soyabean seeds cultured withAspergillus sojaeshowed strong antioxidant and anti-inflammatory activity. Since antioxidants showed beneficial effects on chronic inflammatory diseases, the purpose of the present study was to examine the effects of glyceollins on PDGF-induced proliferation and migration in human aortic smooth muscle cells (HASMC). Incubation of resting HASMC with glyceollins for 24 h significantly diminished PDGF-increased cell number and DNA synthesis in a dose-dependent manner without any cytotoxicity. In addition to blocking of the PDGF-inducible progression through the G0/G1to the S phase of the cell cycle, glyceollins down-regulated the expression of cyclin-dependent kinase (CDK)2 and cyclin D1, and up-regulated the expression of CDK inhibitors such as p27kip1and p53.Glyceollins also effectively inhibited reactive oxygen species generation and phosphorylation of PDGF receptor-β, phospholipase Cγ1, Akt and extracellular signal-regulated kinase 1/2 by PDGF stimulation. Furthermore, glyceollins were found to inhibit PDGF-induced dissociation of actin filaments and cell migration. Thus, the results suggest that glyceollins could become a potent therapeutic agent for regulating VSMC-associated vascular disease such as atherosclerosis and restenosis after angioplasty.

Terbinafine inhibits oral squamous cell carcinoma growth through anti-cancer cell proliferation and anti-angiogenesis

Terbinafine (TB), an oral antifungal agent used in the treatment of superficial mycosis, has been reported to exert an anti-tumor effect in various cancer cells. However, the effect of TB on oral cancer has not been evaluated. Herein we demonstrate that TB (0-60 µM) concentration-dependently decreased cell number in cultured human oral squamous cell carcinoma (OSCC), KB cells. The anti-proliferation effect of TB was also observed in two other OSCC cell lines, SAS and SCC 15. TB (60 µM) was not cytotoxic and its inhibition on KB cell growth was reversible. [(3) H]thymidine incorporation and flow cytometric analyses revealed that TB-inhibited DNA synthesis and induced the G0/G1 cell-cycle arrest. The TB-induced cell-cycle arrest occurred when the cyclin-dependent kinase 2 activity was inhibited just as the protein levels of p21(cip1) and p27(kip1) were increased. The TB-induced G0/G1 cell-cycle arrest was completely blocked when the expressions of p21(cip1) and p27(kip1) were knocked-down together. Taken together, these results suggest that the p21(cip1) - and p27(kip1) -associated signaling pathways might be involved in the TB-induced anti-proliferation in KB cells. In vivo, TB (50 mg/kg, i.p.) significantly inhibited the KB tumor size. In these TB-treated tumors, increases in the levels of p21(cip1) and p27(kip1) protein and decreases in the number of proliferating cell nuclear antigen-positive cells and the microvessel density were observed. These findings demonstrate for the first time that TB might have potential to serve as a therapeutic tool in the treatment of oral cancer.

Beta-estradiol attenuates hypoxic pulmonary hypertension by stabilizing the expression of p27kip1 in rats

BACKGROUND

Pulmonary vascular structure remodeling (PVSR) is a hallmark of pulmonary hypertension. P27(kip1), one of critical cyclin-dependent kinase inhibitors, has been shown to mediate anti-proliferation effects on various vascular cells. Beta-estradiol (β-E2) has numerous biological protective effects including attenuation of hypoxic pulmonary hypertension (HPH). In the present study, we employed β-E2 to investigate the roles of p27(kip1) and its closely-related kinase (Skp-2) in the progression of PVSR and HPH.

METHODS

Sprague-Dawley rats treated with or without β-E2 were challenged by intermittent chronic hypoxia exposure for 4 weeks to establish hypoxic pulmonary hypertension models, which resemble moderate severity of hypoxia-induced PH in humans. Subsequently, hemodynamic and pulmonary pathomorphology data were gathered. Additionally, pulmonary artery smooth muscle cells (PASMCs) were cultured to determine the anti-proliferation effect of β-E2 under hypoxia exposure. Western blotting or reverse transcriptional polymerase chain reaction (RT-PCR) were adopted to test p27(kip1), Skp-2 and Akt-P changes in rat lung tissue and cultured PASMCs.

RESULTS

Chronic hypoxia significantly increased right ventricular systolic pressures (RVSP), weight of right ventricle/left ventricle plus septum (RV/LV+S) ratio, medial width of pulmonary arterioles, accompanied with decreased expression of p27(kip1) in rats. Whereas, β-E2 treatment repressed the elevation of RVSP, RV/LV+S, attenuated the PVSR of pulmonary arterioles induced by chronic hypoxia, and stabilized the expression of p27(kip1). Study also showed that β-E2 application suppressed the proliferation of PASMCs and elevated the expression of p27(kip1) under hypoxia exposure. In addition, experiments both in vivo and in vitro consistently indicated an escalation of Skp-2 and phosphorylated Akt under hypoxia condition. Besides, all these changes were alleviated in the presence of β-E2.

CONCLUSIONS

Our results suggest that β-E2 can effectively attenuate PVSR and HPH. The underlying mechanism may partially be through the increased p27(kip1) by inhibiting Skp-2 through Akt signal pathway. Therefore, targeting up-regulation of p27(kip1) or down-regulation of Skp-2 might provide new strategies for treatment of HPH.

(E)-1-(3,4-dihydroxyphenethyl)-3-styrylurea inhibits proliferation of MCF-7 cells through G1 cell cycle arrest and mitochondria-mediated apoptosis

Growing interest in the beneficial effects of antioxidants has inspired the synthesis of new phenolic acid phenethyl ureas (PAPUs) with enhanced antioxidant potential. We have previously shown the capacity of one PAPU compound, (E)-1-(3,4-dihydroxyphenethyl)-3-styrylurea (PAPU1), to induce caspase-dependent apoptosis in melanoma cells. In the present study, we examined the anti-proliferative effects of PAPU compounds on MCF-7 human breast cancer cells and determined the molecular mechanisms involved. Treatment with PAPU compounds inhibited predominantly proliferation in these cells, where the PAPU1 was the most efficient form. Flow cytometric analysis showed that PAPU1 blocked cell cycle progression in the G(0)/G(1) phase, and reduced the proportion of cells in G(2)/M phase. This was related to the inhibition of cell cycle regulatory factors, including cyclin D/E and cyclin-dependent kinase (CDK) 2/4, through induction of p21(Cip1). PAPU1 also induced the mitochondrial-mediated and caspase-dependent apoptosis in MCF-7 cells. This was evidenced by cellular changes in the levels of Bcl-2 and Bax, loss of the mitochondrial membrane potential, release of cytochrome c into the cytosol, and caspase-9 activation. Collectively, our results suggest that G(1) cell cycle regulatory proteins and mitochondrial pathways are the crucial targets of PAPU1 in the chemoprevention of breast cancer cells.

β-Sitosterol inhibits cell cycle progression of rat aortic smooth muscle cells through increases of p21cip1 protein

Abnormal proliferation of vascular smooth muscle cells (VSMCs) plays a central role in the pathogenesis of atherosclerosis. β-Sitosterol, an important phytosterol found in plant food, is known to exert antiatherosclerosis activity. However, the molecular mechanisms underlying β-sitosterol-induced antiproliferation of VSMCs were still not clear. This study demonstrated that β-sitosterol (1-20 μM) concentration-dependently inhibited proliferation of rat aortic smooth muscle cells (RASMCs) without cytotoxic effect. Flow cytometric analysis revealed that β-sitosterol arrested cell cycle progression through down-regulation of cyclin E and cyclin-dependent kinase (CDK)2 and up-regulation of p21cip1. In the β-sitosterol-treated RASMCs, the formation of the CDK2-p21cip1 complex was increased and the assayable CDK2 activity was decreased. Knockdown of the expression of p21cip1 gene prevented β-sitosterol-induced cell cycle arrest in RASMCs. In conclusion, β-sitosterol inhibited VSMC proliferation by increasing the levels of p21cip1 protein, which in turn inhibited the CDK2 activity, and finally interrupted the progress of the cell cycle.

Pterostilbene, a natural dimethylated analog of resveratrol, inhibits rat aortic vascular smooth muscle cell proliferation by blocking Akt-dependent pathway

Vascular smooth muscle cells (VSMCs) are the main cellular component in the arterial wall, and abnormal proliferation of VSMCs plays a central role in the pathogenesis of atherosclerosis and restenosis after angioplasty, and possibly in the development of hypertension. Pterostilbene, a natural dimethylated analog of resveratrol, is known to have diverse pharmacological activities including anti-cancer, anti-inflammation and anti-oxidant activities. The present study was designed to investigate the effects of pterostilbene on platelet-derived growth factor (PDGF)-BB-induced VSMCs proliferation as well as the molecular mechanisms of the antiproliferative effects. The cell growth of VSMCs was determined by cell counting and [(3)H]thymidine incorporation assays. Pterostilbene significantly inhibited the DNA synthesis and proliferation of PDGF-BB-stimulated VSMCs in a concentration-dependent manner. The inhibition percentages of pterostilbene at 1, 3 and 5microM to VSMCs proliferation were 68.5, 80.7 and 94.6%, respectively. The DNA synthesis of pterostilbene at 1, 3 and 5microM in VSMCs was inhibited by 47.4, 76.7 and 100%, respectively. Pterostilbene inhibited the PDGF-BB-stimulated phosphorylation of Akt kinase. However, pterostilbene did not change the expression of extracellular signal-related kinase (ERK) 1/2, PLCgamma1, phosphatidylinositol (PI)3 kinase and PDGF-Rbeta phosphorylation. In addition, pterostilbene down-regulated the cell cycle-related proteins including the expression of cyclin-dependent kinase (CDK) 2, cyclin E, CDK4, cyclin D1, retinoblastoma (Rb) proteins and proliferative cell nuclear antigen (PCNA). These findings suggest that the inhibition of pterostilbene to the cell proliferation and DNA synthesis of PDGF-BB-stimulated VSMCs may be mediated by the suppression of Akt kinase. Furthermore, pterostilbene may be a potential anti-proliferative agent for the treatment of atherosclerosis and angioplasty restenosis.

EGR-1 decoy ODNs inhibit vascular smooth muscle cell proliferation and neointimal hyperplasia of balloon-injured arteries in rat

AIMS

Early growth response factor-1 (EGR-1) plays a master regulatory role in multiple cardiovascular pathological processes, such as atherosclerosis and restenosis. For investigating the possibility of using "decoy" strategy to prevent and cure vascular hyperplasia disease, we synthesized the double-stranded, cis-element, decoy oligodeoxynucleotides (ODNs) targeting EGR-1.

MAIN METHODS

EGR-1 decoy ODNs were transfected into the balloon-injured arteria carotis of rat as well as primary cultures of vascular smooth muscle cells (VSMC). Changes in the thickness of the arterial intima were evaluated by hematoxylin-eosin (HE) staining. VSMC proliferation, DNA synthesis, cell cycle and apoptosis were observed via MTT assay, bromodeoxyuridine (BrdU) incorporation and flow cytometry (FCM). Changes in the expression of EGR-1, and cell cycle related genes, were detected by reverse transcriptase polymerase chain reaction (PT-PCR) and western blot.

KEY FINDINGS

As a result of specific binding to EGR-1 protein, transfected EGR-1 decoy ODNs can reduce EGR-1 promoter affinity, hamper the transcriptional activation of EGR-1-dependent genes, block cell cycle progression of VSMCs, and inhibit neointimal hyperplasia.

SIGNIFICANCE

Through regulating the cell cycle progression and transcription of target gene, this new "decoy" strategy targeting EGR-1 provides further experimental evidence demonstrating the effectiveness of gene therapy in the treatment of restenosis following percutaneous coronary interventions.

Protective role of clusterin/apolipoprotein J against neointimal hyperplasia via antiproliferative effect on vascular smooth muscle cells and cytoprotective effect on endothelial cells

OBJECTIVE

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.

METHODS AND RESULTS

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.

CONCLUSIONS

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.

Human IL-8 regulates smooth muscle cell VCAM-1 expression in response to endothelial cells exposed to atheroprone flow

OBJECTIVE

Interleukin-8 (IL-8) is a soluble human-specific chemokine implicated in the development of the chronic inflammatory disease atherosclerosis. Recently, we showed that atheroprone hemodynamics induced IL-8 secretion from endothelial cells (ECs) concurrent with increased EC/smooth muscle cell (SMC) VCAM-1 expression in a human hemodynamic coculture model. Despite an IL-8 association with inflammation, we show here that blocking IL-8 activity during atheroprone flow resulted in increased levels of EC/SMC VCAM-1 expression. We tested the hypothesis that IL-8 limits SMC VCAM-1 expression in response to inflammatory stimuli, either atheroprone flow or cytokine interleukin-1beta (IL-1beta) addition.

METHODS AND RESULTS

Atheroprone flow increased monocyte adhesion in both EC/SMCs, concurrent with the induction of VCAM-1 protein. VCAM-1 antisera attenuated this response. IL-1beta upregulated VCAM-1 in SMCs by 3-fold, a response inhibited by the addition of IL-8 at 24 hours. Neither IL-1beta nor IL-8 induced proliferation or migration. Neutralization of the IL-8 receptor, CXCR2, further induced VCAM-1 in the presence of IL-1beta, and phospho-p38 was required for NF-kappaB activation and VCAM-1 expression. Additionally, IL-8 reduced p38 activation and NF-kappaB activity induced by IL-1beta alone.

CONCLUSIONS

Together, these findings provide evidence for a novel role whereby IL-8 limits the inflammatory response in ECs/SMCs via VCAM-1 modulation.

RNA interference targeting ORC1 gene suppresses the proliferation of vascular smooth muscle cells in rats

BACKGROUND

The proliferation of vascular smooth muscle cells (VSMCs) plays an important role in the pathogenesis of vascular diseases such as atherosclerosis and postangioplasty restenosis. The largest subunit of the origin recognition complex (ORC), ORC1, plays a critical role during the initiation of DNA replication in eukaryotes. However, the involvement of ORC1 in the initiation of DNA replication in VSMCs has not been studied yet.

OBJECTIVE

The aim of this study was to silence ORC1 gene selectively by using RNA interference and analyze the effects of ORC1 gene on the proliferation and apoptosis of rat VSMCs.

METHODS

Freshly isolated rat VSMCs were transfected with siRNA targeting ORC1 gene capsulated in liposome. ORC1 protein expression was determined by Western blotting and ORC1 mRNA level by RT-PCR. DNA synthesis was analyzed by (3)H thymidine ((3)H-TdR) incorporation and cell proliferative activity and cell cycle distribution by flow cytometry. Two apoptosis-related proteins, Bax and Bcl-2, were examined immunohistochemically.

RESULTS

Down-regulation of ORC1 mRNA and protein expression was observed in rat VSMCs at 24 h after transfection with the three pairs of siRNA targeting ORC1 gene and this reduction persisted at least 7 days post-transfection. Down-regulation of ORC1 mRNA (60%) and protein (80%) expression was observed at 72 h post-transfection in the cells transfected with B-ORC1 siRNA. A significant decrease in (3)H thymidine incorporation was observed in rat VSMCs with ORC1 gene silencing after serum challenge, but not in the non-silenced control. A significant increase in the proliferation index and a significant decrease in the percentage of cells at G(0)/G(1) phase after serum challenge were observed in the non-silenced control, but not in ORC1 gene silenced cells. A significant increase in the ratio of Bcl-2/Bax was observed after serum challenge in the non-silenced control, but only a slight increase was found in the ORC1 gene silenced cells. ORC1 gene silencing disappeared 7 days after transfection. Continuous serum challenge stimulated VSMCs to synchronously reenter the cell cycle as evidenced by increases in [(3)H] thymidine incorporation, the proliferation index, and the ratio of Bcl-2/Bax, as non-silenced cells were induced to resume cell cycle progression by the addition of 15% fetal bovine serum to the culture medium.

CONCLUSION

ORC1 gene silencing causes rat VSMCs to enter a reversible G(0) quiescent, growth arrested state; thus, ORC1 gene may be an important new target for suppressing VSMCs proliferation.