Dauricine inhibits insulin-like growth factor-I-induced hypoxia inducible factor 1α protein accumulation and vascular endothelial growth factor expression in human breast cancer cells

Aim:

To investigate the effects of dauricine (Dau) on insulin-like growth factor-I (IGF-I)-induced hypoxia inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF) expression in human breast cancer cells (MCF-7).

Methods:

Serum-starved MCF-7 cells were pretreated for 1 h with different concentrations of Dau, followed by incubation with IGF-I for 6 h. HIF-1α and VEGF protein expression levels were analyzed by Western blotting and ELISA, respectively. HIF-1α and VEGF mRNA levels were determined by real-time PCR. In vitro angiogenesis was observed via the human umbilical vein endothelial cell (HUVEC) tube formation assay. An in vitro invasion assay on HUVECs was performed.

Results:

Dau significantly inhibited IGF-I-induced HIF-1α protein expression but had no effect on HIF-1α mRNA expression. However, Dau remarkably suppressed VEGF expression at both protein and mRNA levels in response to IGF-I. Mechanistically, Dau suppressed IGF-I-induced HIF-1α and VEGF protein expression mainly by blocking the activation of PI-3K/AKT/mTOR signaling pathway. In addition, Dau reduced IGF-I-induced HIF-1α protein accumulation by inhibiting its synthesis as well as by promoting its degradation. Functionally, Dau inhibited angiogenesis in vitro. Moreover, Dau had a direct effect on IGF-I-induced invasion of HUVECs.

Conclusion:

Dau inhibits human breast cancer angiogenesis by suppressing HIF-1α protein accumulation and VEGF expression, which may provide a novel potential mechanism for the anticancer activities of Dau in human breast cancer.     

A positive circuit of VEGF increases Glut-1 expression by increasing HIF-1α gene expression in human retinal endothelial cells

Treatment of human retinal microvascular endothelial cells (HRMECs) with vascular endothelial growth factor 165 (VEGF₁₆₅) increased hypoxia-inducible factor 1α (HIF-1α), VEGF, and glucose transporter 1 (Glut-1) mRNA expression and Glut-1 protein localization to the membrane. In contrast, treatment of human retinal pigment epithelium cells with VEGF₁₆₅ did not induce HIF-1α, VEGF, and Glut-1 gene expression. Microvascular endothelial cells are surrounded by astrocytic end feet in the retina. Astrocyte-derived A-kinase anchor protein 12 overexpression during hypoxia downregulated VEGF secretion, and this conditioned medium reduced VEGF and Glut-1 expression in HRMECs, suggesting that communications between astrocytes and endothelial cells may be the determinants of the blood vessel network. In HRMECs, HIF-1α small interfering RNA transfection blocked the VEGF₁₆₅-mediated increase in VEGF and Glut-1 gene expression. Inhibition of protein kinase C (PKC) with inhibitor GF109203X or with a small interfering RNA targeting PKCζ attenuated the VEGF₁₆₅-induced Glut-1 protein expression and VEGF and Glut-1 mRNA expression. In addition, results of an immunoprecipitation assay imply an interaction between VEGF receptor 2 (VEGFR2) and PKCζ in HRMECs. Therefore, VEGF secretion by hypoxic astrocytes may upregulate HIF-1α gene expression, inducing VEGF and Glut-1 expression via the VEGFR2–PKCζ axis in HRMECs.     

TNF-α induces CXCL1 chemokine expression and release in human vascular endothelial cells in vitro via two distinct signaling pathways

Aim： Chemokines usually direct the movement of circulating leukocytes to sites of inflammation or injury. CXCL1/GRO-a has been shown to be upregulated in atherosclerotic lesions and various cancers. The aim of this study was to investigate the mechanisms underlying the TNF-α-induced release of CXCL1 from human vascular endothelial cells in vitro. Methods： Human umbilical vein endothelial cells （HUVECs） were treated with different proinflam-matory mediators and growth factors. CXCL1 expression and secretion were determined using RT-PCR and ELISA, respectively. TNF-a-induced cell signaling was assayed with Western blotting. Cell viability/growth was determined using MTTassay. Monocyte migration was measured with transwell migration assay. Results： Among the 17 mediators and growth factors tested, TNF-α, LPS and thrombin induced marked increase in CXCL1 release from HUVEC cells. TNF-α （2, 5 ng/mL） induced CXCL1 release and mRNA expression in the cells in concentration- and time-dependent manners. TNF-α （5 ng/mL） caused activation of JNK, p38 MAPK, PI3K and Akt, whereas pretreatment with JNK inhibitor （SP600125）, p38 MAPK inhibitor （SB202190） or PI-3K inhibitor （LY294002） significantly suppressed TNF-a-induced CXCL1 release from the cells. But only SP600125 significantly reduced TNF-a-induced CXCL1 mRNA expression in the cells. Moreover, dexamethasone （up to 500 nmol/L） failed to affect TNF-a-induced CXCL1 release from the cells. In functional studies, recombinant CXCL1 enhanced HUVEC proliferation, and both recombinant CXCL1 and TNF-a-induced CXCL1 from HUVECs attracted human monocyte migration. Conclusion： TNF-a stimulates CXCL1 release from human ECs through JNK-mediated CXCL1 mRNA expression and p38 MAPK- and PI-3K-mediated CXCL1 secretory processes.     

α-Hederin inhibits growth of lung cancer A549 cells in vitro and in vivo by decreasing c-Myc and HIF-1α dependent glycolysis

OBJECTIVE α-Hederin is an effective component of the traditional Chinese medicine Pulsatilla chinensis,which has been reported to exert many pharmacological activities. However, the effect of α-hederin on metabolism is still unclear. This study aimed to illuminate the role of α-hederin in glucose metabolism in lung cancer cells and investigate the molecular mechanism of α-hederin. METHODS CCK8 and colony formation assays were employed to assess the anti-proliferative effects induced by α-hederin. Glucose uptake, ATP generation, and reduced lactate production were measured using kits, and an A549 tumor xenograft mouse model of lung cancer was used to assess the in vivo antitumor effect of α-hederin(5, 10 mg·kg~(-1)). Glycolytic-related key enzymes were detected by Western blotting and immunohistochemical staining. RESULTS Cell proliferation was significantly inhibited by α-hederin in a dose-dependent manner and that α-hederin inhibited glucose uptake and ATP generation and reduced lactate production. Furthermore, α-hederin remarkably inhibited hexokinase 2(HK2), glucose transporters 1(GLUT1), pyruvate kinase M2(PKM2), lactate dehydrogenase A(LDHA), monocarboxylate transporter(MCT4), c-Myc, and hypoxia inducible factor-1α(HIF-1α) protein expression. Using inhibitors, we proved that α-hederin inhibits glycolysis by inhibiting glycolytic regulators. Moreover, a tumor xenograft mouse model of lung cancer further confirmed that α-hederin inhibits lung cancer growth via inhibiting glycolysisin vivo. CONCLUSION α-Hederin inhibits the growth of non-small cell lung cancer A549 cells by inhibiting glycolysis.The mechanism of glycolysis inhibition includes α-hederin inhibiting the expression of the glycolytic regulatory factors HIF-1α and c-Myc.     

Paeonol protects rat vascular endothelial cells from ox-LDL-induced injury in vitro via downregulating microRNA-21 expression and TNF-α release

Aim： Paeonol （2＇-hydroxy-4＇-methoxyacetophenone） from Cortex moutan root is a potential therapeutic agent for atherosclerosis. This study sought to investigate the mechanisms underlying anti-inflammatory effects of paeonol in rat vascular endothelial cells （VECs） in vitro.
Methods： VECs were isolated from rat thoracic aortas. The cells were pretreated with paeonol for 24 h, and then stimulated with ox-LDL for another 24 h. The expression of microRNA-21 （miR-21） and PTEN in VECs was analyzed using qRT-PCR. The expression of PTEN protein was detected by Western blotting. TNF-α release by VECs was measured by ELISA.

Results： Ox-LDL treatment inhibited VEC growth in dose- and time-dependent manners （the value of IC50 was about 20 mg/L at 24 h）. Furthermore, ox-LDL （20 mg/L） significantly increased miR-21 expression and inhibited the expression of PTEN, one of downstream target genes of miR-21 in VECs. In addition, ox-LDL （20 mg/L） significantly increased the release of TNF-α from VECs. Pretreatment with paeonol increased the survival rate of ox-LDL-treated VECs in dose- and time-dependent manners. Moreover, paeonol （120 μmol/L） prevented ox-LDL-induced increases in miR-21 expression and TNF-α release, and ox-LDL-induced inhibition in PTEN expression. A dual-luciferase reporter assay showed that miR-21 bound directly to PTEN＇s 3＇-UTR, thus inhibiting PTEN expression. In ox-LDL treated VECs, transfection with a miR-21 mimic significantly increased miR-21 expression and inhibited PTEN expression, and attenuated the protective effects of paeonol pretreatment, whereas transfection with an miR-21 inhibitor significantly decreased miR-21 expression and increased PTEN expression, thus enhanced the protective effects of paeonol pretreatment.

Conclusion： miR-21 is an important target of paeonol for its protective effects against ox-LDL-induced VEC injury, which may play critical roles in development of atherosclerosis.     

Nicotinic acetylcholine receptor α7 inhibits platelet-derived growth factor-induced migration of vascular smooth muscle cells by activating mitochondrial deacetylase SIRT3

OBJECTIVE Platelet-derived growth factorBB(PDGF-BB) is an angiogenic factor involved in cardiovascular diseases. Here, we investigated the possible effects of activation of nicotinic acetylcholine receptor α7 subtype(α7nAChR) on PDGF-BB-induced proliferation and migration in vascular smooth muscle cells(VSMCs).METHODS We were determined using transwell migra-tion assay and scratch-wound migration assay. To determine VSMCS migration. Cell viability was measured using CCK-8 assay. Cell proliferation was measured by Click-iTEdU Microplate Assay. Mitochondria were isolated using a commercial kit from Biovision. Intracellular reactive oxygen species(ROS) was determined by DCFH-DA probe. We used by SDS-PAGE to determined some proteins.NAD+levels were determined with acommercial NAD+quantification kit. Citrate synthase(CS) activity was measured by colorimetric assay kits. RESULTS PDGF-BB induced pronounced migration and proliferation in VSMCs. Activation ofα7nAChR by PNU-282987 blocked the PDGF-BBinduced VSMCs migration but not proliferation in WT VSMCs, whereas this effect was absent in α7nAChRknockout VSMCs. Accordingly, PNU-282987 attenuated PDGF-BB-induced phosphorylation of FAKTyr397 and Src Tyr416 in WT VSMCs. Mechanistically, PNU-282987 suppressed the PDGF-BB-induced oxidative stress,evidenced by the alterations in reactive oxygen species,H_2O_2 content, superoxide anion and total anti-oxidant activity. A SIRT3 inhibitor 3-(1 H-1, 2, 3-triazol-4-yl) pyridine or sh RNA-mediated SIRT3 knockdown abolished the inhibitory effect of PNU-282987. PNU-282987 treatment did not modulate SIRT3 protein expression, but enhanced mitochondrial SIRT3 deacetylase activity. In line with this action, PNU-282987 enhanced the deacetylation of mitochondrial FoxO3. At last, PNU-282987 treatment corrected PDGF-BB-induced mitochondrial dysfunction by increasing mitochondrial citrate synthase activity,ATP content and nicotinamide adenine dinucleotide pool.CONCLUSION Pharmacological y activation of α7nAChR inhibits PDGF-BB-induced VSMC migration via activating mitochondrial deacetylase SIRT3, implying an important role of α7nAChR in mitochondria biology and PDGF-related diseases.     

Glycyrrhetinic acid inhibits ICAM-1 expression via blocking JNK and NF-KB pathways in TNF-α-activated endothelial cells

Aim:

To investigate the effects of glycyrrhetinic acid (GA), an active component extracted from the root of Glycyrrhizae glabra, on the expression of intercellular adhesion molecule-1 (ICAM-1) in tumor necrosis factor-α (TNF-α)-activated human umbilical vein endothelial cells (HUVEC).

Methods:

ICAM-1 mRNA and protein levels were detected using RT-PCR and cell enzyme-linked immunosorbent assays. The adherence of human monocytic THP-1 cells labeled with [³H]thymidine to HUVEC was determined by counting radioactivity with a scintillation counter. The activation of mitogen-activated protein kinases as well as the degradation of IκB and nuclear factor-κB (NF-κB) or phospho-c-Jun in the nucleus were detected by western blots. NF-κB binding activity was detected using electrophoretic mobility shift assay.

Results:

GA (50 and 100 μmol/L) significantly inhibits TNF-α-induced ICAM-1 mRNA and protein expressions, as well as THP-1 cell adhesiveness in HUVEC. GA selectively inhibited TNF-α-activated signal pathway of c-Jun N-terminal kinase (JNK), without affecting extracellular signal-regulated kinase 1/2 and p38. Furthermore, GA apparently inhibited IκB/NF-κB signaling system by preventing IκB degradation, NF-κB translocation, and NF-κB/DNA binding activity. Finally, pretreatment with GA or the inhibitors of NF-κB, JNK, and p38 reduced the ICAM-1 protein expression induced by TNF-α.

Conclusion:

GA inhibits TNF-α-stimulated ICAM-1 expression, leading to a decrease in adherent monocytes to HUVEC. This inhibition is attributed to GA interruption of both JNK/c-Jun and IκB/NF-κB signaling pathways, which decrease activator protein-1 (AP-1) and NF-κB mediated ICAM-1 expressions. The results suggest that GA may provide a beneficial effect in treating vascular diseases associated with inflammation, such as atherosclerosis.     

Arsenic modulates heme oxygenase-1, interleukin-6, and vascular endothelial growth factor expression in endothelial cells: roles of ROS, NF-κB, and MAPK pathways

Chronic arsenic exposure has been linked to an increased risk of vascular diseases. To clarify the molecular mechanisms through which arsenic causes injuries to blood vessels, we analyzed the effects of arsenic trioxide on the cytotoxicity, intracellular reactive oxygen species (ROS), the expression of related genes, and signaling pathways involved in the SVEC4-10 mouse endothelial cells. Arsenic dose-dependently caused SVEC4-10 cell death, which is completely inhibited by α-lipoic acid (LA), a thioreductant, but partially ameliorated by Tiron, a potent superoxide scavenger. The mRNA levels of heme oxygenase-1 (HO-1), interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), and vascular endothelial growth factor (VEGF) were significantly increased by arsenic. The up-regulation of these can be blocked by LA instead of Tiron, suggesting ROS is not important in their increase. HO-1 competitive inhibitor zinc protoporphyrin improved the cytotoxicity of arsenic in an inverted-U dose-response curve, indicating the biphasic hormetic effect of HO-1. HO-1 siRNA decreased VEGF expression in response to arsenic. Arsenic exposure also enhanced NF-E2-related factor 2 (Nrf2) expression and increased activation of nuclear factor-κB (NF-κB). NF-κB inhibitor Bay 11-7082 reduced arsenic-mediated expression of HO-1 and IL-6. Selective blocking of the MAPK pathways with p38 inhibitor SB203580 significantly decreased arsenic-induced HO-1 and VEGF expression, while JNKs inhibitor SP600125 increased IL-6 expression. These results suggest that in arsenic-treated SVEC4-10 cells, HO-1 expression is mediated through Nrf2-, NF-κB-, and p38 MAPK-dependent signaling pathways and serves as an upstream regulator of VEGF. IL-6 expression is regulated by NF-κB and JNKs. In conclusion, oxidative stress may be associated with arsenic-induced cytotoxicity and endothelial gene up-regulation, but signaling transduction dominates the direct effects of ROS.     

Interaction of vascular endothelial cells with leukocytes, platelets and cancer cells in inflammation, thrombosis and cancer growth and metastasis

Adhesion and migration of mammalian cells are of crucial importance in a number of biological events, such as fertilization, embryogenesis, pattern, tissue and organ formation, and in a variety of physiological and pathological processes, including lymphocyte trafficking, leukocyte recruitment, hemostasis, wound healing, tumor angiogenesis and cancer metastasis. All these     

Cryptotanshinone and wogonin up-regulate eNOS in vascular endothelial cells via ERα and down-regulate iNOS in LPS stimulated vascular smooth muscle cells via ERβ

Phytoestrogens were widely used as natural alternatives to estrogen for treating cardiovascular diseases. They have been reported to have cardioprotective and anti-inflammatory response, but the mechanisms remain unclear. In this study, we found cryptotanshinone and wogonin exhibited phytoestrogenic property in an estrogen-responsive reporter assay. In EA.hy926 cells, treatment of cryptotanshinone and wogonin led to significant increase in NO production levels, which were inhibited by co-incubation of estrogen receptor (ER)α antagonist methyl-piperidino-pyrazole (MPP). The expression of endothelial NO synthase (eNOS) and ERα were up-regulated with the same treatment, indicating they stimulate NO and eNOS expression via ERα-dependent pathway in endothelial cells. While in lipopolysaccharide activated vascular smooth muscle cell line A7r5, cryptotanshinone and wogonin exerted anti-inflammatory effects by inhibiting NO and inducible NO synthase expression via ERβ-dependent pathway. The reduction of NO synthesis was not affected by MPP, and was abrogated by ERβ antagonist R,R-tetrahydrochrysene. Our findings provide the potential molecular mechanism of cryptotanshinone and wogonin as phytoestrogens for their cardioprotective effects, which exerted regulatory effects on NO synthesis through differential regulation of estrogen receptors. It can be employed as a basis for evaluating the beneficial effects of phytoestrogens in the treatment of patients at risk of cardiovascular disease.     

Saikosaponins-b suppresses tumor growth and angiogenesis of hepatocellular carcinoma by regulating VEGF/ERK/HIF-1α signal pathway

OBJECTIVE Angiogenesis therapy has attracted interest as a potential treatment for hepatocellular carcinoma(HCC).In this study,we investigated the anti-proliferative activities and antiangiogenesis effects of saikosaponins(SS)-b on hepatocellular carcinoma(HCC)and its regulation on VEGF/ERK/HIF-1 αsignal pathway.METHODS H22 hepatoma-bearing mice model and HepG-2 cells were used to study the anti-tumor and anti-angiogenesis effects of SS-b in vivo and in vitro.Pathological change of tumor tissue was observed by HE staining,the microvascular changes were detected by immunohistochemical method.The effects of SS-b on angiogenesis were examined by using the chick embryo chorioallantoic membrane(CAM)model.The effects of SS-b on proliferation,migration and invasion were investigated by MTT assay,scratch wound healing assay and transwell assay inhuman umbilical vein endothelial cell(HUVEC)and HepG2 cells in vitro.Vascular endothelial growth factor(VEGF),matrix metalloproteinase-2/9(MMP-2/9),hypoxia-inducible factor-1α(HIF-1α)expression and the phosphorylation of extracellular regulated kinase(ERK)were analyzed using RT-PCR and Westernblot.RESULTS SS-b effectively inhibited the tumor growth of H22 mice in vivo.The inhibitory rate of tumor was 49.1%,50.7%,66.1%in SS-b 5,10 and 20 mg·kg-1group respectively.HE staining results showed that SS-b induced tumor necrosis and nuclear dissolution in H22 mice.Moreover,SS-b also reduced the number of microvessels of tumor tissue in H22 mice significantly and suppressed the angiogenesis of CAM induced by b-FGF.SS-b had an obvious inhibitory effect on cell proliferation,migration and invasion of HUVEC cells and HepG-2 cells.These effects were associated with downregulation of the expression of MMP2/9 and suppression of VEGF/ERK/HIF-1αsignaling in H22 mice and Hep-G2 cells.CONCLUSION Our findings showed that SS-b exerts anti-tumor effects by inhibiting tumor angiogenesis via regulating VEGF/ERK/HIF-1α signal pathway in vivo and in vitro.     

Deguelin inhibits expression of IκBα protein in Raji and U937 cells

AIM: To determine whether deguelin can regulate the expression of nuclear factor kappa B (NF-kappaB) binding protein (IkappaBalpha) in U937 human leukemia cells and Raji human B lymphoma cells. METHODS: The localization of IkappaBalpha protein was investigated by using an immunofluorescence method. The expression of IkappaBalpha and NF-kappaB /p65 proteins in Raji and U937 cells were investigated by using Western blotting. Apoptosis was detected through annexin V/PI double-labeled cytometry. RESULTS: IkappaBalpha localized in the cytoplasm in untreated and deguelin-treated cells. After treatment with tumor necrosis factor alpha (TNF-alpha) or deguelin plus TNF-alpha for 15 min, there was a substantial reduction in the amount of IkappaBalpha protein. The expression of IkappaBalpha was downregulated by deguelin in Raji and U937 cells. Deguelin induced apoptosis in U937 cells. CONCLUSION: Deguelin inhibited the expression of IkappaBalpha protein in U937 and Raji cells. The anti-proliferative activity of deguelin is related to the signal pathway of NF-kappaB.     

Immunosuppressor FK506 increases endoglin and activin receptor-like kinase 1 expression and modulates transforming growth factor-β1 signaling in endothelial cells

Hereditary hemorrhagic telangiectasia (HHT), or Rendu-Osler-Weber syndrome, is an autosomal-dominant vascular disease. The clinical manifestations are epistaxis, mucocutaneous and gastrointestinal telangiectases, and arteriovenous malformations in internal organs. Patients show severe epistaxis, and/or gastrointestinal bleeding, both of which notably interfere with their quality of life. There are two predominant types of HHT caused by mutations in endoglin (ENG) and ACVRL1/activin receptor-like kinase 1 (ALK1) genes, named HHT1 and HHT2, respectively. ENG and ALK1 code for proteins involved in the transforming growth factor (TGF)-β1 signaling pathway, and it is widely accepted that HHT pathogenicity results from haploinsufficiency. No cure for HHT has been found, so identification of drugs able to increase the expression of these genes is essential when proposing new therapies. We report the efficacy of tacrolimus (FK506) in increasing ENG and ALK1 expression. The rationale comes from a case report of a patient with HHT who received a liver transplantation after hepatic failure due to a liver arteriovenous malformation. The liver was transplanted, and the immunosuppressor FK506 was used to prevent the rejection. After the first month of FK506 treatment, the internal and external telangiectases, epistaxes, and anemia disappeared. Here, we find that the immunosuppressor FK506 increases the protein and mRNA expression of ENG and ALK1 in cultured endothelial cells and enhances the TGF-β1/ALK1 signaling pathway and endothelial cell functions like tubulogenesis and migration. These results suggest that the mechanism of action of FK506 involves a partial correction of endoglin and ALK1 haploinsufficiency and may therefore be an interesting drug for use in patients with HHT who undergo transplantation.     

Protective effects of paeoniflorin against cobalt chloride-induced apoptosis of endothelial cells via HIF-1α pathway

Accumulating evidence has suggested the importance of hypoxia in the initiation and development of atherosclerotic lesion, and hypoxia has a profound impact on endothelial cell properties during cardiovascular disease processes. Paeoniflorin, isolated from the root of Paeonia lactiflora pall, can protect endothelial cells from hypoxic damage in a variety of ways, such as by enhancing the production of nitric oxide (NO) and decreasing the expressions of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). This study evaluated the protective effects of paeoniflorin against cobalt chloride (CoCl₂, a hypoxia-mimicking agent)-induced apoptosis of endothelial cells (CRL-1730) and the underlying mechanisms in vitro. Endothelial cells were exposed to CoCl₂ with or without pre-treatment with different concentrations of paeoniflorin. After treated with 0.6 mM CoCl₂ for 24 h, endothelial cells showed significant decrease in cell viability and increased apoptosis rate, which could be reversed by pre-treatment with paeoniflorin. Similarly, pre-treatment with paeoniflorin could prevent CoCl₂-induced hypoxia-induced factor-1α (HIF-1α) accumulation and down-regulate the expressions of p53 and Bcl-2/adenovirus E1B 19 kDa interacting protein 3 (BNIP3). These findings indicate that paeoniflorin had effective protection against hypoxia-induced apoptosis of endothelial cells and that HIF-1α, p53 and BNIP3 might be involved in this process.     

2,3,4',5-Tetrahydroxystilbene-2-O-β-d-glucoside inhibits platelet-derived growth factor-induced proliferation of vascular smooth muscle cells by regulating the cell cycle

1. 2,3,4',5-Tetrahydroxystilbene-2-O-β-d-glucoside (TSG) has been shown to have an anti-atherosclerotic effect. Vascular smooth muscle cell (VSMC) proliferation contributes to the pathobiology of atherosclerosis. The aim of the present study was to investigate the effects of TSG on platelet-derived growth factor (PDGF)-BB-induced VSMC proliferation and to explore the molecular mechanisms underlying the effects. 2. Cultured rat VSMC were pretreated with TSG (l-50 μmol/L) for 1 h, followed by exposure to PDGF-BB (10 ng/mL) for 24 h, after which cell proliferation and cell cycle stages were examined. The expression of protein cell cycle regulators, including retinoblastoma (Rb), cyclin D1/E, cyclin-dependent kinase (CDK) 2/4, CDK inhibitors p21 and p27 and proliferative cell nuclear antigen (PCNA), was examined. Activation of extracellular signal-regulated kinase (ERK) 1/2 was evaluated to elucidate the possible upstream mechanism by which TSG affects cell cycle regulators. 3. The results showed that TSG dose-dependently inhibited PDGF-BB-induced VSMC proliferation, possibly by blocking the progression of the cell cycle from the G(1) to S phase. In addition, TSG significantly inhibited PDGF-BB-induced phosphorylation of Rb and the expression of cyclin D1, CDK4, cyclin E, CDK2 and PCNA. In addition, TSG suppressed PDGF-BB-induced downregulation of p27 and upregulation of p21, as well as PDGF-BB-induced activation of ERK1/2. 4. Together, the findings of the present study provide the first evidence that TSG can inhibit PDGF-BB-stimulated VSMC proliferation via cell cycle arrest in association with modulation of the expression of cell cycle regulators, which may be mediated, at least in part, by suppression of ERK1/2 activation.