Tangeretin, a citrus flavonoid, inhibits PGDF-BB-induced proliferation and migration of aortic smooth muscle cells by blocking AKT activation

Natural Flavonoids Derived From Fruits Are Potential Agents Against Atherosclerosis

Atherosclerosis, as a chronic inflammatory response, is one of the main causes of cardiovascular diseases. Atherosclerosis is induced by endothelial cell dysfunction, migration and proliferation of smooth muscle cells, accumulation of foam cells and inflammatory response, resulting in plaque accumulation, narrowing and hardening of the artery wall, and ultimately leading to myocardial infarction or sudden death and other serious consequences. Flavonoid is a kind of natural polyphenol compound widely existing in fruits with various structures, mainly including flavonols, flavones, flavanones, flavanols, anthocyanins, isoflavones, and chalcone, etc. Because of its potential health benefits, it is now used in supplements, cosmetics and medicines, and researchers are increasingly paying attention to its role in atherosclerosis. In this paper, we will focus on several important nodes in the development of atherosclerotic disease, including endothelial cell dysfunction, smooth muscle cell migration and proliferation, foam cell accumulation and inflammatory response. At the same time, through the classification of flavonoids from fruits, the role and potential mechanism of flavonoids in atherosclerosis were reviewed, providing a certain direction for the development of fruit flavonoids in the treatment of atherosclerosis drugs.

Integrative Bioinformatics Study of Tangeretin Potential Targets for Preventing Metastatic Breast Cancer

Agents that target metastasis are important to improve treatment efficacy in patients with breast cancer. Tangeretin, a citrus flavonoid, exhibits antimetastatic effects on breast cancer cells, but its molecular mechanism remains unclear. Tangeretin targets were retrieved from PubChem, whereas metastatic breast cancer regulatory genes were downloaded from PubMed. In total, 58 genes were identified as potential therapeutic target genes of tangeretin (PTs). GO and KEGG pathway enrichment analyses of PTs were performed using WebGestalt (WEB-based Gene SeT AnaLysis Toolkit). The PPI network was analyzed using STRING-DB v11.0 and visualized by Cytoscape software. Hub genes were selected on the basis of the highest degree score as calculated by the CytoHubba plugin. Genetic alterations of the PTs were analyzed using cBioPortal. The prognostic values of the PTs were evaluated with the Kaplan-Meier plot. The expression of PTs across breast cancer samples was confirmed using GEPIA. The reliability of the PTs in metastatic breast cancer cells was validated using ONCOMINE. Molecular docking was performed to foresee the binding sites of tangeretin with PIK3Cα, MMP9, PTGS2, COX-2, and IKK. GO analysis showed that PTs participate in the biological process of stimulus response, are the cellular components of the nucleus and the membrane, and play molecular roles in enzyme regulation. KEGG pathway enrichment analysis revealed that PTs regulate the PI3K/Akt pathway. Genetic alterations for each target gene were MTOR (3%), NOTCH1 (4%), TP53 (42%), MMP9 (4%), NFKB1 (3%), PIK3CA (32%), PTGS2 (15%), and RELA (5%). The Kaplan-Meier plot showed that patients with low mRNA expression levels of MTOR, TP53, MMP9, NFKB1, PTGS2, and RELA and high expression of PIK3CA had a significantly better prognosis than their counterparts. Further validation of gene expression by using GEPIA revealed that the mRNA expression of MMP9 was significantly higher in breast cancer tissues than in normal tissues, whereas the mRNA expression of PTGS2 showed the opposite. Analysis with ONCOMINE demonstrated that the mRNA expression levels of MMP9 and NFKB1 were significantly higher in metastatic breast cancer cells than in normal tissues. The results of molecular docking analyses revealed the advantage of tangeretin as an inhibitor of PIK3CA, MMP9, PTGS2, and IKK. Tangeretin inhibits metastasis in breast cancer cells by targeting TP53, PTGS2, MMP9, and PIK3CA and regulating the PI3K/Akt signaling pathway. Further investigation is needed to validate the results of this study.

The Polymethoxy Flavonoid Sudachitin Inhibits Interleukin-1β-Induced Inflammatory Mediator Production in Human Periodontal Ligament Cells

Sudachitin, which is a polymethoxylated flavonoid found in the peel of Citrus sudachi, has some biological activities. However, the effect of sudachitin on periodontal resident cells is still uncertain. The aim of this study was to examine if sudachitin could decrease the expression of inflammatory mediators such as cytokines, chemokines, or matrix metalloproteinase (MMP) in interleukin- (IL-) 1β-stimulated human periodontal ligament cells (HPDLC). Sudachitin inhibited IL-1β-induced IL-6, IL-8, CXC chemokine ligand (CXCL)10, CC chemokine ligand (CCL)2, MMP-1, and MMP-3 production in HPDLC. On the other hand, tissue inhibitor of metalloproteinase- (TIMP-) 1 expression was increased by sudachitin treatment. Moreover, we found that the nuclear factor- (NF-) κB and protein kinase B (Akt) pathways in the IL-1β-stimulated HPDLC were inhibited by sudachitin treatment. These findings indicate that sudachitin is able to reduce inflammatory mediator production in IL-1β-stimulated HPDLC by inhibiting NF-κB and Akt pathways.

Protective Effect of Tangeretin and 5-Hydroxy-6,7,8,3',4'-Pentamethoxyflavone on Collagen-Induced Arthritis by Inhibiting Autophagy via Activation of the ROS-AKT/mTOR Signaling Pathway

Rheumatoid arthritis (RA) is an autoimmune disease characterized by long duration and repeated relapse. This study explored the preventive effect of tangeretin (TAN) and 5-hydroxy-6,7,8,3',4'-pentamethoxyflavone (5-HPMF) on RA, and the underlying molecular mechanism based on a rat model stimulated by bovine type II collagen (BIIC). After the intervention of TAN or 5-HPMF (TAN/5-HPMF) for 5 weeks, the RA lesions and autophagy levels of the synovial tissue were significantly reduced, and the ROS content and HO-1 expression level were down-regulated simultaneously. The relative expression levels of p-AKT and p-mTOR were down-regulated after TAN/5-HPMF feeding. Meanwhile, the relative expression level of p62 increased by more than two-fold for TAN/5-HPMF treated rats at 200 mg/kg BW comparing with those in BIIC group. Results of immunofluorescence staining and Western blotting further confirmed that TAN/5-HPMF treatment reduced BIIC-induced conversion from LC3I to LC3II. Observations under transmission electron microscope also demonstrated that the autophagy level was reduced upon TAN/5-HPMF intervention. Collectively, these results revealed that TAN and 5-HPMF prevented the pathological process of BIIC-stimulated arthritis through inhibiting the autophagy of synovial cells, achieved via the ROS-AKT/mTOR signal axis. Thus, our findings confirmed the protective potential of TAN and 5-HPMF for RA disease.

Effects of Lipid-Based Encapsulation on the Bioaccessibility and Bioavailability of Phenolic Compounds

Phenolic compounds (quercetin, rutin, cyanidin, tangeretin, hesperetin, curcumin, resveratrol, etc.) are known to have health-promoting effects and they are accepted as one of the main proposed nutraceutical group. However, their application is limited owing to the problems related with their stability and water solubility as well as their low bioaccessibility and bioavailability. These limitations can be overcome by encapsulating phenolic compounds by physical, physicochemical and chemical encapsulation techniques. This review focuses on the effects of encapsulation, especially lipid-based techniques (emulsion/nanoemulsion, solid lipid nanoparticles, liposomes/nanoliposomes, etc.), on the digestibility characteristics of phenolic compounds in terms of bioaccessibility and bioavailability.

Pleotropic Effects of Polyphenols in Cardiovascular System

Numerous epidemiological and clinical studies demonstrate the beneficial effects of naturally occurring, polyphenol supplementations, on cardiovascular system. The present review emphasizes on the risk factors associated with cardiovascular disorders (involving heart and blood vessels), and overview of preclinical and clinical trials on polyphenols for the treatment of cardiovascular diseases. The review collaborates PUBMED, Google Scholar and Research gate databases, which were explored using keywords and their combinations such as polyphenols, cardiovascular disease, flavonoids, atherosclerosis, cardiovascular risk factors and several others, to create an eclectic manuscript. The potency and efficacy of these polyphenols are mainly depending upon the amount of consumption and bioavailability. Recent data showed that polyphenols also exert beneficial actions on vascular system by blocking platelet aggregation and oxidation of low-density lipoprotein (LDL), ameliorating endothelial dysfunction, reducing blood pressure, improving antioxidant defenses and alleviating inflammatory responses. Several studies evidently support the cardioprotective actions mediated by polyphenols, however, some studies or long-term follow-up of human studies, did not demonstrate decisive outcomes because of variations in dose regimen and lack of appropriate controls. Therefore, more data is required to explore the therapeutic benefits of bioactive compounds as a preventive therapy for CVDs.

Activation of Inward Rectifier K+ Channel 2.1 by PDGF-BB in Rat Vascular Smooth Muscle Cells through Protein Kinase A

Platelet-derived growth factor-BB (PDGF-BB) can induce the proliferation, migration, and phenotypic modulation of vascular smooth muscle cells (VSMCs). We used patch clamp methods to study the effects of PDGF-BB on inward rectifier K⁺ channel 2.1 (Kir2.1) channels in rat thoracic aorta VSMCs (RASMCs). PDGF-BB (25 ng/mL) increased Kir2.x currents (−11.81 ± 2.47 pA/pF, P < 0.05 vs. CON, n = 10). Ba²⁺(50 μM) decreased Kir2.x currents (−2.13 ± 0.23 pA/pF, P < 0.05 vs. CON, n = 10), which were promoted by PDGF-BB (−6.98 ± 1.03 pA/pF). PDGF-BB specifically activates Kir2.1 but not Kir2.2 and Kir2.3 channels in HEK-293 cells. The PDGF-BB-induced stimulation of Kir2.1 currents was blocked by the PDGF-BB receptor β (PDGF-BBRβ) inhibitor AG1295 and was not affected by the PDGF-BBRα inhibitor AG1296. The PDGF-BB-induced stimulation of Kir2.1 currents was blocked by the protein kinase A inhibitor Rp-8-CPT-cAMPs; however, the antagonist of protein kinase B (GSK690693) had marginal effects on current activity. The PDGF-BB-induced stimulation of Kir2.1 currents was enhanced by forskolin, an adenylyl cyclase (AC) activator, and was blocked by the AC inhibitor SQ22536. We conclude that PDGF-BB increases Kir2.1 currents via PDGF-BBRβ through activation of cAMP-PKA signaling in RASMCs.

Sudachitin Inhibits Matrix Metalloproteinase-1 and -3 Production in Tumor Necrosis Factor-α-Stimulated Human Periodontal Ligament Cells

Sudachitin, a polymethoxylated flavonoid found in the skin of Citrus sudachi, is a biologically active substance. The aim of this study was to examine whether sudachitin could be used to inhibit the expression of matrix metalloproteinase (MMP)-1 and MMP-3, which are involved in the destruction of periodontal tissues in periodontal lesions, in tumor necrosis factor (TNF)-α-stimulated human periodontal ligament cells (HPDLC). Sudachitin suppressed TNF-α-induced MMP-1 and MMP-3 production in HPDLC. On the other hand, it enhanced tissue inhibitor of metalloproteinase (TIMP)-1 expression. The level of Akt phosphorylation in the TNF-α-stimulated HPDLC was decreased by sudachitin treatment. Moreover, an Akt inhibitor reduced MMP-1 and MMP-3 production and increased TIMP-1 production. These findings indicate that sudachitin reduces MMP-1 and MMP-3 production in TNF-α-stimulated HPDLC by inhibiting the Akt pathway.

The Drosophila Model: Exploring Novel Therapeutic Compounds against Neurodegenerative Diseases

Polyphenols are secondary metabolites of plants, fruits, and vegetables. They act as antioxidants against free radicals from UV light, pathogens, parasites, and oxidative stress. In Drosophila models, feeding with various polyphenols results in increased antioxidant capacity and prolonged lifespan. Therefore, dietary polyphenols have several health advantages for preventing many human diseases, including cardiovascular diseases, cancer, and neurodegenerative diseases. However, the exact role of polyphenols in neurodegenerative diseases is still yet to be completely defined. This review focuses on the most recent studies related to the therapeutic effect of polyphenols in neurodegenerative disease management and provides an overview of novel drug discovery from various polyphenols using the Drosophila model.

STRIP2 silencing inhibits vascular smooth muscle cell proliferation and migration via P38-AKT-MMP-2 signaling pathway

STRIP2 (FAM40B) was reported to regulate tumor cell migration. Our study aims to discuss the effect of STRIP2 in mouse aortic smooth muscle cell (MOVAS) proliferation and migration processes, which contributes greatly to atherosclerosis formation. In MOVAS cells, STRIP2 depletion suppressed cell proliferation and migration, which were related to a remarkable decrease in matrix metalloproteinases-2 (MMP-2)/MMP-9 expression. Additionally, P38 mitogen-activated protein kinases and Protein kinase B (AKT) are inactivated while extracellular signal-regulated kinase (ERK1/2) and jun N-terminal kinase (JNK) are activated upon STRIP2 silencing. SB203580 (P38 inhibitor) further reduced AKT phosphorylation (p-AKT) while dehydrocorydaline chloride (Dc; P38 activator) reversed this effect. Furthermore, Dc significantly recovered MMP-2 expression in STRIP2-knockdown cells. As expected, overexpressing STRIP2 exhibited a contrary effect. Dc and AKT activator SC79 reversed the inhibition of cell proliferation and migration induced by STRIP2 silencing. Interestingly, STRIP2 depletion increased vascular endothelial growth factor level significantly. Taken together, STRIP2 contributed to cell proliferation and migration through P38-AKT-MMP-2 signaling in MOVAS cells, indicating the importance of STRIP2 in atherosclerosis.

Downregulation of the transcriptional co-activator PCAF inhibits the proliferation and migration of vascular smooth muscle cells and attenuates NF-κB-mediated inflammatory responses

P300/CBP-associated factor (PCAF) regulates vascular inflammation. This study was to explore the effect of PCAF on the proliferation and migrationof vascular smooth muscle cells (VSMCs) and neointimal hyperplasia in balloon-injured rat carotid artery. Downregulation of PCAF remarkably suppressed VSMCs proliferation and migration induced by lipopolysaccharide, and also significantly inhibit the nuclear translocation of nuclear factor-kappaB p65. Meanwhile, downregulation of PCAF inhibited the mRNA expression of tumor necrosis factor-α and interleukin-6, and also the levels in culture supernatants. Moreover, downregulation of PCAF profoundly reduced the intima area and the ratio of intima area to media area in balloon-injured rat carotid artery. In addition, the expression of PCNA and NF-κB p65 in intima were decreased by downregulation of PCAF. These results highlight that PCAF may be a potential target for prevention and treatment of neointimal hyperplasia and restenosis after angioplasty.

Vascular smooth muscle cell proliferation as a therapeutic target. Part 2: Natural products inhibiting proliferation

Many natural products have been so far tested regarding their potency to inhibit vascular smooth muscle cell proliferation, a process involved in atherosclerosis, pulmonary hypertension and restenosis. Compounds studied in vitro and in vivo as VSMC proliferation inhibitors include, for example indirubin-3'-monoxime, resveratrol, hyperoside, plumericin, pelargonidin, zerumbone and apamin. Moreover, taxol and rapamycin, the most prominent compounds applied in drug-eluting stents to counteract restenosis, are natural products. Numerous studies show that natural products have proven to yield effective inhibitors of vascular smooth muscle cell proliferation and ongoing research effort might result in the discovery of further clinically relevant compounds.

Acarbose inhibits the proliferation and migration of vascular smooth muscle cells via targeting Ras signaling

Atherosclerosis involves the proliferation and migration of vascular smooth muscle cells (VSMCs). The migration of VSMCs from the media into the intima and their subsequent proliferation are important processes in neointima formation in atherosclerosis and restenosis after percutaneous coronary interventions. Acarbose, an alpha-glucosidase inhibitor, has been demonstrated to not affect serum levels of glucose and decrease the progression of intima-media thickening in rabbits fed with a high cholesterol diet (HCD). We previously showed that increased Ras protein levels enhanced the migration of TNF-α treated A7r5 cells. The aim of this study was to determine the inhibitory effects of acarbose on Ras expression in A7r5 cells. Acarbose also inhibited the phosphorylation of focal adhesion kinase (FAK) and Akt, activities of the matrix metalloproteinases (MMPs) MMP-2 and MMP-9, and protein expressions of small G proteins (Ras, Cdc42, RhoA, and Rac1) in a dose-dependent manner. We also found that acarbose could effectively inhibit the proliferation and migration of Ras^G12V A7r5 cells by blocking small G proteins and phosphoinositide-3-kinase (PI3K)/Akt signaling. These studies demonstrated that acarbose could theoretically decrease atherosclerosis by targeting Ras signaling.

Chebulinic acid inhibits smooth muscle cell migration by suppressing PDGF-Rβ phosphorylation and inhibiting matrix metalloproteinase-2 expression

Excessive migration of vascular smooth muscle cells (VSMCs) after vascular injury contributes to the development of occlusive vascular disease. Inhibition of VSMC migration is a validated therapeutic modality for occlusive vascular diseases, such as atherosclerosis and restenosis. We investigated the inhibitory effect of chebulinic acid (CBA) on cell migration and matrix metalloproteinase (MMP)-2 activation in platelet-derived growth factor (PDGF)-BB-induced mouse and human VSMCs. CBA significantly inhibited PDGF-BB-induced migration in mouse and human VSMCs, without inducing cell death. Additionally, CBA significantly blocked PDGF-BB-induced phosphorylation of the PDGF receptor (PDGF-R), Akt, and extracellular signal-regulated kinase (ERK)1/2 by inhibiting the activation of the PDGF-BB signalling pathway. In both mouse and human VSMCs, CBA inhibited PDGF-induced MMP-2 mRNA and protein expression as well as the proteolytic activity of MMP-2. Moreover, CBA suppressed sprout outgrowth formation of VSMCs from endothelium-removed aortic rings as well as neointima formation following rat carotid balloon injury. Taken together, our findings indicated that CBA inhibits VSMC migration by decreasing MMP-2 expression through PDGF-R and the ERK1/2 and Akt pathways. Our data may improve the understanding of the antiatherogenic effects of CBA in VSMCs.

Tangeretin alters neuronal apoptosis and ameliorates the severity of seizures in experimental epilepsy-induced rats by modulating apoptotic protein expressions, regulating matrix metalloproteinases, and activating the PI3K/Akt cell survival pathway

PURPOSE

Epilepsy is complex neural disarray categorized by recurring seizures. Despite recent advances in pharmacotherapies for epilepsy, its treatment remains a challenge due to the contrary effects of the drugs. As a result, the identification of novel anti-epileptic drugs (AEDs) with neuroprotective properties and few side effects is of great value. Thus, the present study assessed the treatment effects of tangeretin using a rat model of pilocarpine-induced epilepsy.

MATERIALS AND METHODS

Separate groups of male Wistar rats received oral administrations of tangeretin at 50, 100, or 200mg/kg for 10 days and then, on the 10th day, they received an intraperitoneal injection of pilocarpine (30mg/kg). Subsequently, neuronal degeneration and apoptosis were assessed using Nissl staining and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay procedures. Additionally, the expressions of phosphatidylinositol-3-kinase (PI3K/Akt) pathway proteins, cleaved caspase-3, Bad, Bcl-2, Bcl-xL, and Bax were determined using Western blot analyses.

RESULTS

Tangeretin reduced the seizure scores and latency to first seizure of the rats and effectively activated the pilocarpine-induced suppression of PI3K/Akt signaling. Additionally, tangeretin effectively regulated the levels of apoptosis-inducing factor (AIF) in mitochondria as well as the expressions of apoptotic pathway proteins. Seizure-induced elevations in the activities and expressions of matrix metalloproteinases (MMPs)-2 and -9 were also modulated.

CONCLUSION

The present results indicate that tangeretin exerted potent neuroprotective effects against pilocarpine-induced seizures via the activation of PI3K/Akt signaling and the regulation of MMPs.

Multidrug-resistant cancer cells and cancer stem cells hijack cellular systems to circumvent systemic therapies, can natural products reverse this?

Chemotherapy is one of the most effective and broadly used approaches for cancer management and many modern regimes can eliminate the bulk of the cancer cells. However, recurrence and metastasis still remain a major obstacle leading to the failure of systemic cancer treatments. Therefore, to improve the long-term eradication of cancer, the cellular and molecular pathways that provide targets which play crucial roles in drug resistance should be identified and characterised. Multidrug resistance (MDR) and the existence of tumor-initiating cells, also referred to as cancer stem cells (CSCs), are two major contributors to the failure of chemotherapy. MDR describes cancer cells that become resistant to structurally and functionally unrelated anti-cancer agents. CSCs are a small population of cells within cancer cells with the capacity of self-renewal, tumor metastasis, and cell differentiation. CSCs are also believed to be associated with chemoresistance. Thus, MDR and CSCs are the greatest challenges for cancer chemotherapy. A significant effort has been made to identify agents that specifically target MDR cells and CSCs. Consequently, some agents derived from nature have been developed with a view that they may overcome MDR and/or target CSCs. In this review, natural products-targeting MDR cancer cells and CSCs are summarized and clustered by their targets in different signaling pathways.

Tangeretin induces cell cycle arrest and apoptosis through upregulation of PTEN expression in glioma cells

Tangeretin (TANG), present in peel of citrus fruits, has been shown to various medicinal properties such as chemopreventive and neuroprotective. However, the chemopreventive effect of TANG on glioblastoma cells has not been examined. The present study was designed to explore the anticancer potential of TANG in glioblastoma cells and to investigate the related mechanism. Human glioblastoma U-87MG and LN-18 cells were treated with 45μM concentration of TANG and cell growth was measured by MTT assay. The cell cycle distribution and cell death were measured by flow cytometry. The expression of cell cycle and apoptosis related genes were analyzed by quantitative RT-PCR and western blot. The cells treated with TANG were significantly increased cell growth suppression and cell death effects than vehicle treated cells. Further, TANG treatment increases G2/M arrest and apoptosis by modulating PTEN and cell-cycle regulated genes such as cyclin-D and cdc-2 mRNA and protein expressions. Moreover, the ability of TANG to decrease cell growth and to induce cell death was compromised when PTEN was knockdown by siRNA. Taken together, the chemopreventive effect of TANG is associated with regulation of cell-cycle and apoptosis in glioblastoma, thereby attenuating glioblastoma cell growth. Hence, the present findings suggest that TANG may be a therapeutic agent for glioblastoma treatment.

A novel PDGF receptor inhibitor-eluting stent attenuates in-stent neointima formation in a rabbit carotid model

A novel drug-eluting stent (DES) is required to target vascular smooth muscle cells (SMCs) without harming endothelial cells (ECs). Platelet-derived growth factor (PDGF) is critical for the proliferation and migration of SMCs. Sunitinib [a PDGF receptor (PDGFR) tyrosine kinase inhibitor]‑eluting stents may therefore inhibit neointimal formation. The aim of the present study was to examine the stent‑based delivery of sunitinib in a rabbit carotid model; in addition, the effects of sunitinib were evaluated in vitro. Local administration of sunitinib markedly reduced neointimal formation without delaying re-endothelialization in the carotid artery model. In vitro, sunitinib inhibited SMC proliferation; however, no effects were observed on ECs. Sunitinib caused necrosis of SMCs. In addition, sunitinib attenuated PDGF-stimulated SMC migration in a scratch wound assay and inhibited α‑SMA cytoskeleton polymerization. Furthermore, sunitinib inhibited PDGF-induced phosphorylation of extracellular signal-regulated kinase in vitro and in vivo. Therefore, this novel DES may be a potential strategy for the treatment of vascular disorders.

Anti-atherosclerotic plants which modulate the phenotype of vascular smooth muscle cells

BACKGROUND

Cardiovascular disease (CVD) remains the leading cause of global death, with atherosclerosis being a major contributor to this mortality. Several mechanisms are implicated in the pathogenesis of this disease. A key element in the development and progression of atherosclerotic lesions is the phenotype of vascular smooth muscle cells. Under pathophysiologic conditions such as injury, these cells switch from a contractile to a synthetic phenotype that often possesses high proliferative and migratory capacities.

PURPOSE

Despite major advances made in the management and treatment of atherosclerosis, mortality associated with this disease remains high. This mandates that other approaches be sought. Herbal medicine, especially for the treatment of CVD, has been gaining more attention in recent years. This is in no small part due to the evidence-based values associated with the consumption of many plants as well as the relatively cheaper prices, easier access and conventional folk medicine "inherited" over generations. Sections: In this review, we provide a brief introduction about the pathogenesis of atherosclerosis then we highlight the role of vascular smooth muscle cells in this disease, especially when a phenotypic switch of these cells arises. We then thoroughly discuss the various plants that show potentially beneficial effects as anti-atherosclerotic, with prime attention given to herbs and plants that inhibit the phenotypic switch of vascular smooth muscle cells.

CONCLUSION

Accumulating evidence provides the justification for the use of botanicals in the treatment or prevention of atherosclerosis. However, further studies, especially clinical ones, are warranted to better define several pharmacological parameters of these herbs, such as toxicity, tolerability, and efficacy.

Citrus Flavonoids as Regulators of Lipoprotein Metabolism and Atherosclerosis

Citrus flavonoids are polyphenolic compounds with significant biological properties. This review summarizes recent advances in understanding the ability of citrus flavonoids to modulate lipid metabolism, other metabolic parameters related to the metabolic syndrome, and atherosclerosis. Citrus flavonoids, including naringenin, hesperitin, nobiletin, and tangeretin, have emerged as potential therapeutics for the treatment of metabolic dysregulation. Epidemiological studies reveal an association between the intake of citrus flavonoid-containing foods and a decreased incidence of cardiovascular disease. Studies in cell culture and animal models, as well as a limited number of clinical studies, reveal the lipid-lowering, insulin-sensitizing, antihypertensive, and anti-inflammatory properties of citrus flavonoids. In animal models, supplementation of rodent diets with citrus flavonoids prevents hepatic steatosis, dyslipidemia, and insulin resistance primarily through inhibition of hepatic fatty acid synthesis and increased fatty acid oxidation. Citrus flavonoids blunt the inflammatory response in metabolically important tissues including liver, adipose, kidney, and the aorta. The mechanisms underlying flavonoid-induced metabolic regulation have not been completely established, although several potential targets have been identified. In mouse models, citrus flavonoids show marked suppression of atherogenesis through improved metabolic parameters as well as through direct impact on the vessel wall. Recent studies support a role for citrus flavonoids in the treatment of dyslipidemia, insulin resistance, hepatic steatosis, obesity, and atherosclerosis. Larger human studies examining dose, bioavailability, efficacy, and safety are required to promote the development of these promising therapeutic agents.

Magnobovatol inhibits smooth muscle cell migration by suppressing PDGF-Rβ phosphorylation and inhibiting matrix metalloproteinase-2 expression

The migration of vascular smooth muscle cells (VSMCs) may play a crucial role in the pathogenesis of vascular diseases, such as atherosclerosis and post-angioplasty restenosis. Platelet-derived growth factor (PDGF)-BB is a potent mitogen for VSMCs and plays an important role in the intimal accumulation of VSMCs. Magnobovatol, a new neolignan from the fruits of Magnolia obovata, has been shown to have anticancer properties. However, the effects of magnobovatol on VSMCs are unknown. In the present study, we examined the effects of magnobovatol on the PDGF-BB-induced migration of mouse and human VSMCs, as well as the underlying mechanisms. Magnobovatol significantly inhibited the PDGF-BB-induced migration of mouse and human VSMCs without inducing cell death (as shown by MTT assay and wound healing assay). Additionally, we demonstrated that magnobovatol significantly blocked the PDGF-BB-induced phosphorylation of the PDGF receptor (PDGF-R), Akt and extracellular signal-regulated kinase (ERK)1/2 by inhibiting the activation of the PDGF-BB signaling pathway. Moreover, in both mouse and human VSMCs, magnobovatol inhibited PDGF-induced matrix metalloproteinase (MMP)-2 expression at the mRNA and protein level, as well as the proteolytic activity of MMP-2 (as shown by western blot analysis, RT-PCR, gelatin zymography and ELISA). In addition, the sprout outgrowth formation of aortic rings induced by PDGF-BB was inhibited by magnobovatol (as shown by aortic ring assay). Taken together, our findings indicate that magnobovatol inhibits VSMC migration by decreasing MMP-2 expression through PDGF-R and the ERK1/2 and Akt pathways. Our data may improve the understanding of the anti-atherogenic effects of magnobovatol in VSMCs.

Cellular metabolic energy modulation by tangeretin in 7,12-dimethylbenz(a) anthracene-induced breast cancer

Breast cancer is the leading cause of death among women worldwide. Chemoprevention and chemotherapy play beneficial roles in reducing the incidence and mortality of cancer. Epidemiological and experimental studies showed that naturally-occurring antioxidants present in the diet may act as anticancer agents. Identifying the abnormalities of cellular energy metabolism facilitates early detection and management of breast cancer. The present study evaluated the effect of tangeretin on cellular metabolic energy fluxes in 7,12-dimethylbenz(a) anthracene (DMBA)-induced proliferative breast cancer. The results showed that the activities of glycolytic enzymes significantly increased in mammary tissues of DMBA-induced breast cancer bearing rats. The gluconeogenic tricarboxylic acid (TCA) cycle and respiratory chain enzyme activities significantly decreased in breast cancer-bearing rats. In addition, proliferating cell nuclear antigen (PCNA) was highly expressed in breast cancer tissues. However, the activities of glycolytic enzymes were significantly normalized in the tangeretin pre- and post-treated rats and the TCA cycle and respiratory chain enzyme activities were significantly increased in tangeretin treated rats. Furthermore, tangeretin down-regulated PCNA expression on breast cancer-bearing rats. Our study demonstrates that tangeretin specifically regulates cellular metabolic energy fluxes in DMBA-induced breast cancer-bearing rats.

Tangeretin enhances radiosensitivity and inhibits the radiation-induced epithelial-mesenchymal transition of gastric cancer cells

Irradiation has been reported to increase radioresistance and epithelial-mesenchymal transition (EMT) in gastric cancer (GC) cells. The Notch pathway is critically implicated in cancer EMT and radioresistance. In the present study, we investigated the use of a Notch-1 inhibiting compound as a novel therapeutic candidate to regulate radiation-induced EMT in GC cells. According to previous screening, tangeretin, a polymethoxylated flavonoid from citrus fruits was selected as a Notch-1 inhibitor. Tangeretin enhanced the radiosensitivity of GC cells as demonstrated by MTT and colony formation assays. Tangeretin also attenuated radiation-induced EMT, invasion and migration in GC cells, accompanied by a decrease in Notch-1, Jagged1/2, Hey-1 and Hes-1 expressions. Tangeretin triggered the upregulation of miR-410, a tumor-suppressive microRNA. Furthermore, re-expression of miR-410 prevented radiation-induced EMT and cell invasion. An in vivo tumor xenograft model confirmed the antimetastasis effect of tangeretin as we observed in vitro. In nude mice, tumor size was considerably diminished by radiation plus tangeretin co-treatment. Tangeretin almost completely inhibited lung metastasis induced by irradiation. Tangeretin may be a novel antimetastatic agent for radiotherapy.

Anticancer activities of citrus peel polymethoxyflavones related to angiogenesis and others

Citrus is a kind of common fruit and contains multiple beneficial nutrients for human beings. Flavonoids, as a class of plant secondary metabolites, exist in citrus fruits abundantly. Due to their broad range of pharmacological properties, citrus flavonoids have gained increased attention. Accumulative in vitro and in vivo studies indicate protective effects of polymethoxyflavones (PMFs) against the occurrence of cancer. PMFs inhibit carcinogenesis by mechanisms like blocking the metastasis cascade, inhibition of cancer cell mobility in circulatory systems, proapoptosis, and antiangiogenesis. This review systematically summarized anticarcinogenic effect of citrus flavonoids in cancer therapy, together with the underlying important molecular mechanisms, in purpose of further exploring more effective use of citrus peel flavonoids.

Tangeretin, a citrus pentamethoxyflavone, exerts cytostatic effect via p53/p21 up-regulation and suppresses metastasis in 7,12-dimethylbenz(α)anthracene-induced rat mammary carcinoma

Breast cancer is the most commonly diagnosed cancer among women worldwide, which is characterized by unregulated cell growth and metastasis. Many bioactive compounds of plant origin such as tangeretin have been shown to possess potent antioxidant and anticancerous properties. In the present study we have investigated the chemotherapeutic effect of tangeretin against 7,12-dimethylbenz(α)anthracene (DMBA)-induced rat mammary carcinogenesis and studied its underlying mechanism of action. Breast cancer was induced by "air pouch technique" with a single dose of 25mg/kg of DMBA. Tangeretin (50 mg/kg) was administered orally for four weeks. Remarkably, tangeretin treatment controlled the growth of cancer cells which was clearly evidenced by morphological and histological analysis. Also, serum levels of estradiol, progesterone and prolactin; lipid bound sialic acid and total sialic acid and the tissue levels of nitric oxide and protein carbonyls of cancer induced animals were decreased upon tangeretin treatment. Staining of breast tissues for nucleolar organizer regions, mast cells, glycoproteins, lipids and collagen showed that tangeretin treatment to breast cancer induced rats significantly reduced tumorigenesis. Oral tangeretin treatment also effectively reduced the tumor cell proliferation markers such as PCNA, COX-2 and Ki-67. Further, tangeretin treatment arrested the cancer cell division at the G1/S phase via p53/p21 up-regulation and inhibited metastasis by suppressing matrix metalloproteinase (MMP)-2, MMP-9 and vascular endothelial growth factor. Taken together, the data provides new evidence on the mechanism of action of tangeretin in breast cancer and hence extends the hypothesis supporting its potential use in chemotherapy.

Tangeretin ameliorates oxidative stress in the renal tissues of rats with experimental breast cancer induced by 7,12-dimethylbenz[a]anthracene

Tangeretin, a citrus polymethoxyflavone, is an antioxidant modulator which has been shown to exhibit a surfeit of pharmacological properties. The present study was hypothesized to explore the therapeutic activity of tangeretin against 7,12-dimethylbenz[a]anthracene (DMBA) induced kidney injury in mammary tumor bearing rats. Recently, we have reported the chemotherapeutic effect of tangeretin in the breast tissue of DMBA induced rats. Breast cancer was induced by "air pouch technique" with a single dose of 25mg/kg of DMBA. Tangeretin (50mg/kg/day) was administered orally for four weeks. The renoprotective nature of tangeretin was assessed by analyzing the markers of oxidative stress, proinflammatory cytokines and antioxidant competence in DMBA induced rats. Tangeretin treatment revealed a significant decline in the levels of lipid peroxides, inflammatory cytokines and markers of DNA damage, and a significant improvement in the levels of enzymatic and non-enzymatic antioxidants in the kidney tissue. Similarly, mRNA, protein and immunohistochemical analysis substantiated that tangeretin treatment notably normalizes the renal expression of Nrf2/Keap1, its downstream regulatory proteins and the inflammatory cytokines in the DMBA induced rats. Histological and ultrastructural observations also evidenced that the treatment with tangeretin effectively protects the kidney from DMBA-mediated oxidative damage, hence, proving its nephroprotective nature.

Platelet-derived growth factor-BB restores HIV Tat -mediated impairment of neurogenesis: role of GSK-3β/β-catenin

Our previous study demonstrated that platelet-derived growth factor-BB (PDGF-BB) increased the cell proliferation of primary rat neuronal progenitor cells (NPCs). However, whether PDGF-BB regulates neurogenesis in HIV-associated neurological disorder (HAND) remains largely unknown. In this study we demonstrated that pre-treatment of NPCs with PDGF-BB restored Tat-mediated impairment of cell proliferation via activation of p38 and JNK MAPK pathways. Moreover, treatment with PDGF-BB induced inactivation of glycogen synthase kinase-3β (GSK-3β), evidenced by its phosphorylation at Ser9, this effect was significantly inhibited by the p38 and JNK inhibitors. Level of nuclear β-catenin, the primary substrate of GSK-3β, was also concomitantly increased following PDGF-BB treatment, suggesting that PDGF-BB stimulates NPC proliferation via acting on GSK-3β to promote nuclear accumulation of β-catenin. This was further validated by gain and loss of function studies using cells transfected with either the wild type or mutant GSK-3β constructs. Together these data underpin the role of GSK-3β/β-catenin as a novel target that regulates NPC proliferation mediated by PDGF-BB with implications for therapeutic intervention for reversal of impaired neurogenesis inflicted by Tat.

Tangeretin regulates platelet function through inhibition of phosphoinositide 3-kinase and cyclic nucleotide signaling

OBJECTIVE

Dietary flavonoids have long been appreciated in reducing cardiovascular disease risk factors, but their mechanisms of action are complex in nature. In this study, the effects of tangeretin, a dietary flavonoid, were explored on platelet function, signaling, and hemostasis.

APPROACH AND RESULTS

Tangeretin inhibited agonist-induced human platelet activation in a concentration-dependent manner. It inhibited agonist-induced integrin αIIbβ3 inside-out and outside-in signaling, intracellular calcium mobilization, and granule secretion. Tangeretin also inhibited human platelet adhesion and subsequent thrombus formation on collagen-coated surfaces under arterial flow conditions in vitro and reduced hemostasis in mice. Further characterization to explore the mechanism by which tangeretin inhibits platelet function revealed distinctive effects of platelet signaling. Tangeretin was found to inhibit phosphoinositide 3-kinase-mediated signaling and increase cGMP levels in platelets, although phosphodiesterase activity was unaffected. Consistent with increased cGMP levels, tangeretin increased the phosphorylation of vasodilator-stimulated phosphoprotein at S239.

CONCLUSIONS

This study provides support for the ability and mechanisms of action of dietary flavonoids to modulate platelet signaling and function, which may affect the risk of thrombotic disease.

Platelet-derived growth factor BB mediates the glioma-induced migration of bone marrow-derived mesenchymal stem cells by promoting the expression of vascular cell adhesion molecule-1 through the PI3K, P38 MAPK and NF-κB pathways

Platelet-derived growth factor BB (PDGFBB) has been shown to activate the migration of bone marrow-derived mesenchymal stem cells (BM-MSCs), and to contribute to mediating the tropism of BM-MSCs towards gliomas. However, the exact mechanism of this migratory behavior remains to be elucidated. The present study investigated the role of vascular cell adhesion molecule-1 (VCAM-1) in the PDGFBB-induced migration of BM-MSCs, the effect of PDGFBB on VCAM-1 expression of BM-MSCs and related signaling pathways involved in this process. Rat BM-MSCs were isolated and cultured by their characteristics of adherence to plastics. The concentrations of PDGFBB in the conditioned medium of C6 and U87 cells were measured using the ELISA method. In vitro migration assays using a VCAM-1 blocking antibody were performed to evaluate the role of VCAM-1 in PDGFBB-induced migration of BM-MSCs. The effect of rat recombinant PDGFBB on VCAM-1 expression of BM-MSCs was studied by RT-PCR and western blotting. LY294002, SB203580, PD98059, SP600125 and BAY11-7082 were used to explore the role of PI3K, p38 MAPK, MEK, JNK and NF-κB in the related intracellular signal transduction of PDGFBB stimulation on VCAM-1 expression of BM-MSCs. The data demonstrated that the neutralization of VCAM-1 inhibited the migration of BM-MSCs induced by PDGFBB. Additionally, PDGFBB stimulation increased VCAM-1 expression of BM-MSCs, which could be inhibited by LY294002, SB203580 and BAY11-7082. It is reasonable to conclude that PDGFBB significantly enhanced the expression of VCAM-1 in BM-MSCs, which facilitated the migration of BM-MSCs towards PDGFBB. PI3K, p38 MAPK and NF-κB were involved in the signal transduction of this process.

Chlamydia pneumoniae infection promotes vascular smooth muscle cell migration through a Toll-like receptor 2-related signaling pathway

The migration of vascular smooth muscle cells (VSMCs) from the media to the intima is proposed to be a key event in the development of atherosclerosis. Recently, we reported that Chlamydia pneumoniae infection is involved in VSMC migration. However, the exact mechanisms for C. pneumoniae infection-induced VSMC migration are not yet well elucidated. In this study, we examined the role of the Toll-like receptor 2 (TLR2) activation-related signaling pathway in VSMC migration induced by C. pneumoniae infection. An Affymetrix-based gene expression array was conducted to identify the changes of gene expression in rat primary VSMCs (rVSMCs) infected with C. pneumoniae. Both the microarray analysis and quantitative real-time reverse transcription (RT)-PCR revealed that TLR2 mRNA expression was strongly upregulated 12 h after C. pneumoniae infection. RT-PCR and Western blot analysis further showed that the expression levels of TLR2 mRNA and protein significantly increased at the different time points after infection. Immunocytochemical analysis suggested a TLR2 recruitment to the vicinity of C. pneumoniae inclusions. Cell migration assays showed that the TLR2-neutralizing antibody could significantly inhibit C. pneumoniae infection-induced rVSMC migration. In addition, C. pneumoniae infection stimulated Akt phosphorylation at Ser 473, which was obviously suppressed by the PI3K inhibitor LY294002, thereby inhibiting rVSMC migration caused by C. pneumoniae infection. Furthermore, both the infection-induced Akt phosphorylation and rVSMC migration were suppressed by the TLR2-neutralizing antibody. Taken together, these data suggest that C. pneumoniae infection can promote VSMC migration possibly through the TLR2-related signaling pathway.

Differential roles of CXCL2 and CXCL3 and their receptors in regulating normal and asthmatic airway smooth muscle cell migration

Structural cell migration plays a central role in the pathophysiology of several diseases, including asthma. Previously, we established that IL-17-induced (CXCL1, CXCL2, and CXCL3) production promoted airway smooth muscle cell (ASMC) migration, and consequently we sought to investigate the molecular mechanism of CXC-induced ASMC migration. Recombinant human CXCL1, CXCL2, and CXCL3 were used to assess migration of human primary ASMCs from normal and asthmatic subjects using a modified Boyden chamber. Neutralizing Abs or small interfering RNA (siRNA) knockdown and pharmacological inhibitors of PI3K, ERK1/2, and p38 MAPK pathways were used to investigate the receptors and the signaling pathways involved in CXC-induced ASMC migration, respectively. We established the ability of CXCL2 and CXCL3, but not CXCL1, to induce ASMC migration at the tested concentrations using normal ASMCs. We found CXCL2-induced ASMC migration to be dependent on p38 MAPK and CXCR2, whereas CXCL3-induced migration was dependent on p38 and ERK1/2 MAPK pathways via CXCR1 and CXCR2. While investigating the effect of CXCL2 and CXCL3 on asthmatic ASMC migration, we found that they induced greater migration of asthmatic ASMCs compared with normal ones. Interestingly, unlike normal ASMCs, CXCL2- and CXCL3-induced asthmatic ASMC migration was mainly mediated by the PI3K pathway through CXCR1. In conclusion, our results establish a new role of CXCR1 in ASMC migration and demonstrate the diverse mechanisms by which CXCL2 and CXCL3 mediate normal and asthmatic ASMC migration, suggesting that they may play a role in the pathogenesis of airway remodeling in asthma.

Vinpocetine suppresses pathological vascular remodeling by inhibiting vascular smooth muscle cell proliferation and migration

Abnormal vascular smooth muscle cell (SMC) activation is associated with various vascular disorders such as atherosclerosis, in-stent restenosis, vein graft disease, and transplantation-associated vasculopathy. Vinpocetine, a derivative of the alkaloid vincamine, has long been used as a cerebral blood flow enhancer for treating cognitive impairment. However, its role in pathological vascular remodeling remains unexplored. Herein, we show that systemic administration of vinpocetine significantly reduced neointimal formation in carotid arteries after ligation injury. Vinpocetine also markedly decreased spontaneous remodeling of human saphenous vein explants in ex vivo culture. In cultured SMCs, vinpocetine dose-dependently suppressed cell proliferation and caused G1-phase cell cycle arrest, which is associated with a decrease in cyclin D1 and an increase in p27Kip1 levels. In addition, vinpocetine dose-dependently inhibited platelet-derived growth factor (PDGF)-stimulated SMC migration as determined by the two-dimensional migration assays and three-dimensional aortic medial explant invasive assay. Moreover, vinpocetine significantly reduced PDGF-induced type I collagen and fibronectin expression. It is noteworthy that PDGF-stimulated phosphorylation of extracellular signal-regulated kinases 1/2 (ERK1/2), but not protein kinase B, was specifically inhibited by vinpocetine. Vinpocetine powerfully attenuated intracellular reactive oxidative species (ROS) production, which largely mediates the inhibitory effects of vinpocetine on ERK1/2 activation and SMC growth. Taken together, our results reveal a novel function of vinpocetine in attenuating neointimal hyperplasia and pathological vascular remodeling, at least partially through suppressing ROS production and ERK1/2 activation in SMCs. Given the safety profile of vinpocetine, this study provides insight into the therapeutic potential of vinpocetine in proliferative vascular disorders.