Effects of Ginkgo biloba extract on the proliferation of vascular smooth muscle cells in vitro and on intimal thickening and interleukin-1beta expression after balloon injury in cholesterol-fed rabbits in vivo

Potential dual inhibitors of PCSK-9 and HMG-R from natural sources in cardiovascular risk management

Atherosclerotic cardiovascular disease (ASCVD) stands amongst the leading causes of mortality worldwide and has attracted the attention of world's leading pharmaceutical companies in order to tackle such mortalities. The low-density lipoprotein-cholesterol (LDL-C) is considered the most prominent biomarker for the assessment of ASCVD risk. Distinct inhibitors of 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMG-R), the chief hepatic cholesterogenic enzyme, are being used since last seven decades to manage hypercholesterolemia. On the other hand, discovery and the association of proprotein convertase subtilisin/kexin type-9 (PCSK-9) with increased ASCVD risk have established PCSK-9 as a novel therapeutic target in cardiovascular medicine. PCSK-9 is well reckoned to facilitate the LDL-receptor (LDL-R) degradation and compromised LDL-C clearance leading to the arterial atherosclerotic plaque formation. The currently available HMG-R inhibitors (statins) and PCSK-9 inhibitors (siRNA, anti-sense oligonucleotides, and monoclonal antibodies) have shown great promises in achieving LDL-C lowering goals, however, their life long prescriptions have raised significant concerns. These deficits associated with the synthetic HMG-R and PCSK-9 inhibitors called for the discovery of alternative therapeutic candidates with potential dual HMG-R and PCSK-9 inhibitory activities from natural origins. Therefore, this report firstly describes the mechanistic insights into the cholesterol homeostasis through HMG-R, PCSK-9, and LDL-R functionality and then compiles the pharmacological effects of natural secondary metabolites with special emphasis on their dual HMG-R and PCSK-9 inhibitory action. In conclusion, various natural products exhibit atheroprotective effects via targeting HMG-R and PCSK-9 activities and lipoprotein metabolism, however, further clinical assessments are still warranted prior their approval for ASCVD risk management in hypercholesterolemic patients.

Role of Lipid Accumulation and Inflammation in Atherosclerosis: Focus on Molecular and Cellular Mechanisms

Atherosclerosis is a chronic lipid-driven and maladaptive inflammatory disease of arterial intima. It is characterized by the dysfunction of lipid homeostasis and signaling pathways that control the inflammation. This article reviews the role of inflammation and lipid accumulation, especially low-density lipoprotein (LDL), in the pathogenesis of atherosclerosis, with more emphasis on cellular mechanisms. Furthermore, this review will briefly highlight the role of medicinal plants, long non-coding RNA (lncRNA), and microRNAs in the pathophysiology, treatment, and prevention of atherosclerosis. Lipid homeostasis at various levels, including receptor-mediated uptake, synthesis, storage, metabolism, efflux, and its impairments are important for the development of atherosclerosis. The major source of cholesterol and lipid accumulation in the arterial wall is proatherogenic modified low-density lipoprotein (mLDL). Modified lipoproteins, such as oxidized low-density lipoprotein (ox-LDL) and LDL binding with proteoglycans of the extracellular matrix in the intima of blood vessels, cause aggregation of lipoprotein particles, endothelial damage, leukocyte recruitment, foam cell formation, and inflammation. Inflammation is the key contributor to atherosclerosis and participates in all phases of atherosclerosis. Also, several studies have shown that microRNAs and lncRNAs have appeared as key regulators of several physiological and pathophysiological processes in atherosclerosis, including regulation of HDL biogenesis, cholesterol efflux, lipid metabolism, regulating of smooth muscle proliferation, and controlling of inflammation. Thus, both lipid homeostasis and the inflammatory immune response are closely linked, and their cellular and molecular pathways interact with each other.

Targeting interleukin-β by plant-derived natural products: Implications for the treatment of atherosclerotic cardiovascular disease

Inflammation is the main contributing factor to atheroma formation in atherosclerosis. Interleukin-1 beta (IL-1β) is an inflammatory mediator found in endothelial cells and resident leukocytes. Canakinumab is a selective monoclonal antibody against IL-1β which attenuates inflammation and concurrently precipitates fatal infections and sepsis. Natural products derived from medicinal plants, herbal remedy and functional foods are widely used nowadays. Experimental and clinical trial evidence supports that some natural products such as curcumin, resveratrol, and quercetin have potential effects on IL-1β suppression. In this review, we tried to document findings that used medicinal plants and plant-based natural products for treating atherosclerosis and its related diseases through the suppression of IL-1β.

Activation of heme oxygenase-1 by Ginkgo biloba extract differentially modulates endothelial and smooth muscle-like progenitor cells for vascular repair

Vascular progenitors such as endothelial progenitor cells (EPCs) and smooth muscle-like progenitor cells (SMPCs) may play different roles in vascular repair. Ginkgo biloba extract (GBE) is an exogenous activator of heme oxygenase (HO)-1, which has been suggested to improve vascular repair; however, the detailed mechanisms have yet to be elucidated. This study aimed to investigate whether GBE can modulate different vascular progenitor cells by activating HO-1 for vascular repair. A bone marrow transplantation mouse model was used to evaluate the in vivo effects of GBE treatment on wire-injury induced neointimal hyperplasia, which is representative of impaired vascular repair. On day 14 of GBE treatment, the mice were subjected to wire injury of the femoral artery to identify vascular reendothelialization. Compared to the mice without treatment, neointimal hyperplasia was reduced in the mice that received GBE treatment for 28 days in a dose-dependent manner. Furthermore, GBE treatment increased bone marrow-derived EPCs, accelerated endothelial recovery, and reduced the number of SMPCs attached to vascular injury sites. The effects of GBE treatment on neointimal hyperplasia could be abolished by co-treatment with zinc protoporphyrin IX, an HO-1 inhibitor, suggesting the in vivo role of HO-1. In this in vitro study, treatment with GBE activated human early and late EPCs and suppressed SMPC migration. These effects were abolished by HO-1 siRNA and an HO-1 inhibitor. Furthermore, GBE induced the expression of HO-1 by activating PI3K/Akt/eNOS signaling in human late EPCs and via p38 pathways in SMPCs, suggesting that GBE can induce HO-1 in vitro through different molecular mechanisms in different vascular progenitor cells. Accordingly, GBE could activate early and late EPCs, suppress the migration of SMPCs, and improve in vivo vascular repair after mechanical injury by activating HO-1, suggesting the potential role of pharmacological HO-1 activators, such as GBE, for vascular protection in atherosclerotic diseases.

Salvia miltiorrhiza Bunge (Danshen) for Treatment and Prevention of Urolithiasis: A Drosophila Animal Study

Traditional Chinese medicine (TCM) has been prescribed for the treatment of stone disease for thousands of years. Salvia miltiorrhiza (Danshen) was previously shown to have potential for treatment of stone disease in animal and clinical studies. In this study, we further studied the antiurolithiasis effect of Danshen in a fly model. Wild-type male Drosophila melanogaster CS flies were used in this study, with 0.25% ethylene glycol (EG) as a lithogenic agent. 2% potassium citrate (K-citrate) was the positive control agent for prevention (all agents added at the start of experiment) and treatment (drugs added after 2-week addition of lithogenic agent) studies compared with 15, 30, and 60 μg/ml of Danshen extract. In the prevention study, both 2% K-citrate and Danshen (30 and 60 μg/ml) significantly inhibited EG-induced calcium oxalate (CaOx) crystal formation. In the treatment study, only 2% K-citrate and high-dose of Danshen (60 μg/ml) significantly inhibited EG-induced CaOx crystal formation. Survival analysis for EG with Danshen was compared with that for EG with K-citrate. The mean lifespan was significantly reduced by administration of EG, and the results in the Danshen group were similar to those in the control group. In conclusion, Danshen revealed both preventive and treatment effects on CaOx crystal formation in a fly model.

Tocilizumab, a Humanized Monoclonal Antibody Against the Interleukin-6 Receptor, Inhibits High Glucose-Induced Vascular Smooth Muscle Cell Migration Through Mitogen-Activated Protein Kinase Signaling Pathways

Rheumatoid arthritis (RA) with diabetes increases the risk of cardiovascular diseases. Interleukin-6 (IL-6) promotes the disease activity of RA and insulin resistance. This study aimed to evaluate the potential effects and molecular mechanisms of IL-6 blocker, tocilizumab, in atherosclerosis with diabetes. Human aortic smooth muscle cells (HASMCs) cultured under hyperglycemic conditions were evaluated for migration, expression of adhesion molecules, and matrix metalloproteinases before and after treatment with tocilizumab. High glucose (HG) significantly increased expression of IL-6, intercellular adhesion molecule (ICAM-1), matrix metalloproteinase-2 & 9, and migration of vascular smooth muscle cells. Tocilizumab suppressed HG-induced expression of ICAM-1, MMP-2, and MMP-9. Pretreatment with tocilizumab also inhibited migration, MAPK signaling, and nuclear translocation of p65-NF-κB in HG-stimulated HASMCs. Our data suggested that tocilizumab may exert an antiatherosclerotic activity in diabetes.

Treatment of Urolithiasis with Medicinal Plant Salvia miltiorrhiza: A Nationwide Cohort Study

Salvia miltiorrhiza Bunge (Danshen), a common medicinal plant in traditional Chinese medicine, has been tested effectively to prevent urolithiasis in animals; nevertheless, the clinical application for urolithiasis remains unclear. We thus investigated the clinical effect of Danshen by analyzing the database from the Taiwan National Institute of Health. The cohort "Danshen-users" was prescribed Chinese herb medicine Danshen after the initial diagnosis of calculus. The control group (non-Danshen-users) was not given Danshen after the initial diagnosis of calculus. The date of first using Danshen after new diagnosis date of calculus was considered as index date. The outcome variables were categorized into two categories: the first category included calculus surgical treatment, including extracorporeal shock wave lithotripsy, ureteroscopy, percutaneous nephrostomy with fragmentation, and ureterolithotomy; the second category included any bleeding disorders, including gastrointestinal bleeding, intracranial hemorrhage, and blood transfusions. The incidence of calculus surgical treatment in the Danshen-users was less than that in the non-Danshen-users: 1.071% in 1,000 person-years (200 people followed up for 5 years) and 3.142% in 1,000 person-years, respectively. The adjusted hazard ratio for calculus surgical treatment in the Danshen-users was 0.34 (95% confidence intervals: 0.31-0.38) as compared to the non-Danshen-users. When stratified by sex, the incidence of calculus surgical treatment in Danshen-users was 0.685% in 1,000 person-years and 1.575% in 1,000 person-years for women and men, respectively, which was lower than that in non-Danshen-users. Danshen decreased the ratio of subsequent stone treatment after the first treatment in the study population; there was no increased bleeding risk due to long-term Danshen use.

Increased Calcitonin Gene-Related Peptide and Macrophages Are Involved in Astragalus membranaceus-Mediated Peripheral Nerve Regeneration in Rats

Astragalus membranaceus (AM) is one of 50 fundamental herbs in traditional Chinese medicine. Previous studies have shown that AM extract can be a potential nerve growth-promoting factor, being beneficial for the growth of peripheral nerve axons. We further investigated the effects of AM extract on regeneration in a rat sciatic nerve transection model. Rats were divided into three groups ([Formula: see text]): normal saline (intraperitoneal) as the control, and 1.5[Formula: see text]g/kg or 3.0[Formula: see text]g/kg of AM extract (every other day for four weeks), respectively. We evaluated neuronal electrophysiology, neuronal connectivity, macrophage infiltration, expression levels and location of calcitonin gene-related peptide (CGRP), and expression levels of both nerve growth factors (NGFs) and immunoregulatory factors. In the high-dose AM group, neuronal electrophysiological function (measured by nerve conductive velocity and its latency) was significantly improved ([Formula: see text]). Expression levels of CGRP and macrophage density were also drastically enhanced ([Formula: see text]). Expression levels of fibroblast growth factor (FGF), NGF, platelet-derived growth factor (PDGF), transforming growth factor-[Formula: see text], interleukin-1 (IL-1), and interferon (IFN)-[Formula: see text] were reduced in the high-dose AM group ([Formula: see text]), while FGF, NGF, PDGF, IL-1, and IFN-[Formula: see text] were increased in the low-dose AM group ([Formula: see text]). These results suggest that AM can modulate local inflammatory conditions, enhance nerve regeneration, and potentially increase recovery of a severe peripheral nerve injury.

Transcriptome analysis of Ginkgo biloba kernels

Ginkgo biloba is a dioecious species native to China with medicinally and phylogenetically important characteristics; however, genomic resources for this species are limited. In this study, we performed the first transcriptome sequencing for Ginkgo kernels at five time points using Illumina paired-end sequencing. Approximately 25.08-Gb clean reads were obtained, and 68,547 unigenes with an average length of 870 bp were generated by de novo assembly. Of these unigenes, 29,987 (43.74%) were annotated in publicly available plant protein database. A total of 3,869 genes were identified as significantly differentially expressed, and enrichment analysis was conducted at different time points. Furthermore, metabolic pathway analysis revealed that 66 unigenes were responsible for terpenoid backbone biosynthesis, with up to 12 up-regulated unigenes involved in the biosynthesis of ginkgolide and bilobalide. Differential gene expression analysis together with real-time PCR experiments indicated that the synthesis of bilobalide may have interfered with the ginkgolide synthesis process in the kernel. These data can remarkably expand the existing transcriptome resources of Ginkgo, and provide a valuable platform to reveal more on developmental and metabolic mechanisms of this species.

Epigallocatechin gallate attenuates proliferation and oxidative stress in human vascular smooth muscle cells induced by interleukin-1β via heme oxygenase-1

Proliferation of vascular smooth muscle cells (VSMCs) triggered by inflammatory stimuli and oxidative stress contributes importantly to atherogenesis. The association of green tea consumption with cardiovascular protection has been well documented in epidemiological observations, however, the underlying mechanisms remain unclear. This study aimed to elucidate the effects of the most active green tea catechin derivative, (−)-epigallocatechin-3-gallate (EGCG), in human aortic smooth muscle cells (HASMCs), focusing particularly on the role of a potent anti-inflammatory and antioxidative enzyme heme oxygenase-1 (HO-1). We found that pretreatment of EGCG dose- and time-dependently induced HO-1 protein levels in HASMCs. EGCG inhibited interleukin- (IL-)1β-induced HASMC proliferation and oxidative stress in a dose-dependent manner. The HO-1 inducer CoPPIX decreased IL-1β-induced cell proliferation, whereas the HO-1 enzyme inhibitor ZnPPIX significantly reversed EGCG-caused growth inhibition in IL-1β-treated HASMCs. At the molecular level, EGCG treatment significantly activated nuclear factor erythroid-2-related factor (Nrf2) transcription activities. These results suggest that EGCG might serve as a complementary and alternative medicine in the treatment of these pathologies by inducing HO-1 expression and subsequently decreasing VSMC proliferation.

Ginkgo biloba extract reduces high-glucose-induced endothelial adhesion by inhibiting the redox-dependent interleukin-6 pathways

BACKGROUND

Chronic elevation of glucose level activates vascular inflammation and increases endothelial adhesiveness to monocytes, an early sign of atherogenesis. This study aimed to elucidate the detailed mechanisms of high-glucose-induced endothelial inflammation, and to investigate the potential effects of Ginkgo biloba extract (GBE), an antioxidant herbal medicine, on such inflammation.

MATERIALS AND METHODS

Human aortic endothelial cells were cultured in high glucose or mannitol as osmotic control for 4 days. The expression of cytokines and adhesion molecules and the adhesiveness of endothelial cells to monocytes were examined. The effects of pretreatment of GBE or N-acetylcysteine, an antioxidant, were also investigated.

RESULTS

Either high glucose or mannitol significantly increased reactive oxygen species (ROS) production, interleukin-6 secretion, intercellular adhesion molecule-1 (ICAM-1) expression, as well as endothelial adhesiveness to monocytes. The high-glucose-induced endothelial adhesiveness was significantly reduced either by an anti-ICAM-1 antibody or by an interleukin-6 neutralizing antibody. Interleukin-6 (5 ng/ml) significantly increased endothelial ICAM-1 expression. Piceatannol, a signal transducer and activator of transcription (STAT) 1/3 inhibitor, but not fludarabine, a STAT1 inhibitor, suppressed high-glucose-induced ICAM-1 expression. Pretreatment with GBE or N-acetylcysteine inhibited high-glucose-induced ROS, interleukin-6 production, STAT1/3 activation, ICAM-1 expression, and endothelial adhesiveness to monocytes.

CONCLUSIONS

Long-term presence of high glucose induced STAT3 mediated ICAM-1 dependent endothelial adhesiveness to monocytes via the osmotic-related redox-dependent interleukin-6 pathways. GBE reduced high-glucose-induced endothelial inflammation mainly by inhibiting interleukin-6 activation. Future study is indicated to validate the antioxidant/anti-inflammatory strategy targeting on interleukin-6 for endothelial protection in in vivo and clinical hyperglycemia.

Central and local administration of Gingko biloba extract EGb 761® inhibits thermal hyperalgesia and inflammation in the rat carrageenan model

BACKGROUND

Oral administration of the standardized Ginkgo biloba extract EGb 761® has been shown to inhibit thermal hyperalgesia in rodent models of inflammatory and postsurgical pain, but the mechanism underlying these effects is not known. We sought to determine the site of action of EGb 761 by investigating the antihyperalgesic and antiinflammatory properties of EGb 761 after local and central drug administration in the rat carrageenan model of inflammation.

METHODS

Adult male Wistar rats received an intraplantar injection of carrageenan (3%) or saline into the left hindpaw followed 3 hours later by an intraplantar injection of EGb 761 (30, 100, or 300 μg) or vehicle into the left paw; or intrathecal injection of EGb 761 (0.5, 1, 3, 10, or 100 μg) or vehicle into the lumbar spinal cord region. Diclofenac (100 μg) was administered as a positive control. Hindpaw withdrawal latency (in seconds) to thermal stimulation, response threshold (in grams) to mechanical stimulation, and paw volume were measured at 0, 2, 4, 6, and 24 hours after carrageenan injection.

RESULTS

Both intraplantar (30, 100, and 300 μg) and intrathecal (0.5 and 1 μg) EGb 761 significantly inhibited carrageenan-induced thermal hyperalgesia and were equally as effective as diclofenac, but had no effect on mechanical hypersenitivity. Application ≥3 μg EGb 761 to the spinal cord induced adverse behavioral effects, which precluded further nociceptive testing. Intraplantar (300 μg) and intrathecal (1 μg) EGb 761 also significantly reduced paw edema.

CONCLUSION

These studies show that EGb 761 acts both at the site of inflammation and centrally at the spinal cord level to inhibit inflammation and thermal hyperalgesia, and may be useful in the treatment of inflammatory pain.

Salvianolic acid B inhibits low-density lipoprotein oxidation and neointimal hyperplasia in endothelium-denuded hypercholesterolaemic rabbits

BACKGROUND

Atherosclerosis and restenosis are inflammatory responses involving free radicals and lipid peroxidation and may be prevented/cured by antioxidant-mediated lipid peroxidation inhibition. Salvianolic acid (Sal B), a water-soluble antioxidant obtained from a Chinese medicinal herb, is believed to have multiple preventive and therapeutic effects against human vascular diseases. In this study the in vitro and in vivo inhibitory effects of Sal B on oxidative stress were determined.

RESULTS

In human aortic endothelial cells (HAECs), Sal B reduced oxidative stress, inhibited low-density lipoprotein (LDL) oxidation and reduced oxidised LDL-induced cytotoxicity. Sal B inhibited Cu(2+) -induced LDL oxidation in vitro (with a potency 16.3 times that of probucol) and attenuated HAEC-mediated LDL oxidation as well as reactive oxygen species (ROS) production. In cholesterol-fed New Zealand White rabbits (with probucol as positive control), Sal B intake reduced Cu(2+) -induced LDL oxidation, lipid deposition in the thoracic aorta, intimal thickness of the aortic arch and thoracic aorta and neointimal formation in the abdominal aorta.

CONCLUSION

The data obtained in this study suggest that Sal B protects HAECs from oxidative injury-mediated cell death via inhibition of ROS production. The antioxidant activity of Sal B may help explain its efficacy in the treatment of vascular diseases.

Nrf-2 mediated heme oxygenase-1 expression, an antioxidant-independent mechanism, contributes to anti-atherogenesis and vascular protective effects of Ginkgo biloba extract

AIMS

Vascular protective effects of Ginkgo biloba extract (GBE) may involve both antioxidant-related and anti-inflammatory mechanisms. GBE was recently suggested as a heme oxygenase (HO)-1 inducer. The role of HO-1 in anti-atherogenesis and related vascular protective effects of GBE awaited further clarification.

METHODS AND RESULTS

Tumor necrosis factor (TNF)-α was used to stimulate adhesiveness of human aortic endothelial cells (HAECs) to monocytes, an in vitro sign simulating atherogenesis. Pretreatment with GBE reduced TNF-α-stimulated endothelial adhesiveness, which could be attenuated by HO-1 inhibitors ZnPP IX or SnPP IX. GBE increased HO-1 expression and enzyme activity in HAECs. Pretreatment with MAP kinase inhibitor SB203580 significantly reduced GBE-induced HO-1 expression. Furthermore, GBE activated the translocation of the transcription factor nuclear factor-erythroid 2-related factor 2 (Nrf2), and increased its binding to the antioxidant response element (ARE) of the HO-1 gene. Pretreatment with PEG-SOD or other antioxidant reagents did not alter GBE-induced endothelial HO-1 expression. In vivo study also showed that GBE treatment could reduce leukocyte adherence to injury arteries, and enhance HO-1 expression in circulating monocytes and in arteries after wire injury, suggesting the in vivo induction of HO-1 by GBE.

CONCLUSION

GBE could inhibit cytokine-induced endothelial adhesiveness by inducing HO-1 expression via the activation of p38 and Nrf-2 pathways, a mechanism in which oxidative stress is not directly involved. GBE might exert its anti-atherogenesis and vascular protective effects by inducing vascular HO-1 expression.

EGb761 ameliorates the formation of foam cells by regulating the expression of SR-A and ABCA1: role of haem oxygenase-1

AIMS

Accumulation of foam cells in the intima is a hallmark of early-stage atherosclerotic lesions. Ginkgo biloba extract (EGb761) has been reported to exert anti-oxidative and anti-inflammatory properties in atherosclerosis, yet the significance and the molecular mechanisms of action of EGb761 in the formation of macrophage foam cells are not fully understood.

METHODS AND RESULTS

Treatment with EGb761 resulted in a dose-dependent decrease in oxidized low-density lipoprotein (oxLDL)-mediated cholesterol accumulation in macrophages, a consequence that was due to a decrease in cholesterol uptake and an increase in cholesterol efflux. Additionally, EGb761 significantly down-regulated the mRNA and protein expression of class A scavenger receptor (SR-A) by decreasing expression of activator protein 1 (AP-1); however, EGb761 increased the protein stability of ATP-binding cassette transporter A1 (ABCA1) by reducing calpain activity without affecting ABCA1 mRNA expression. Small interfering RNA (siRNA) targeting haem oxygenase-1 (HO-1) abolished the EGb761-induced protective effects on the expression of AP-1, SR-A, ABCA1, and calpain activity. Accordingly, EGb761-mediated suppression of lipid accumulation in foam cells was also abrogated by HO-1 siRNA. Moreover, the lesion size of atherosclerosis was smaller in EGb761-treated, apolipoprotein E-deficient mice compared with the vehicle-treated mice, and the expression of HO-1, SR-A, and ABCA1 in aortas was modulated similar to that observed in macrophages.

CONCLUSION

These findings suggest that EGb761 confers a protection from the formation of foam cells by a novel HO-1-dependent regulation of cholesterol homeostasis in macrophages.

DNA damage and repair in a model of rat vascular injury

Restenosis rate following vascular interventions still limits their long-term success. Oxidative stress plays a relevant role in this pathophysiological phenomenon, but less attention has been devoted to its effects on DNA damage and to the subsequent mechanisms of repair. We analysed in a model of arteriotomy-induced stenosis in rat carotids the time-dependent expression of DNA damage markers and of DNA repair genes, together with the assessment of proliferation and apoptosis indexes. The expression of the oxidative DNA damage marker 7,8-dihydro-8-oxo-2'-deoxyguanosine was increased at 3 and 7 days after arteriotomy, with immunostaining distributed in the injured vascular wall and in perivascular tissue. The expression of the DNA damage marker phospho-H2A.X was less relevant but increasing from 4 hrs to 7 days after arteriotomy, with immunostaining prevalently present in the adventitia and, to a lesser extent, in medial smooth muscle cells at the injury site. RT-PCR indicated a decrease of 8 out of 12 genes of the DNA repair machinery we selected from 4 hrs to 7 days after arteriotomy with the exception of increased Muyth and Slk genes (p<0.05). Western Blot revealed a decrease of p53 and catalase at 3 days after arteriotomy (p<0.05). A maximal 7% of BrdU-positive cells in endothelium and media occurred at 7 days after arteriotomy, while the apoptotic index peaked at 3 days after injury (p<0.05). Our results highlight a persistent DNA damage presumably related to a temporary decreased expression of the DNA repair machinery and of the antioxidant enzyme catalase, playing a role in stenosis progression.

Molecular mechanisms underlying the cholesterol-lowering effect of Ginkgo biloba extract in hepatocytes: a comparative study with lovastatin

AIM

To explore the molecular mechanisms underlying the cholesterol-lowering effect of a Ginkgo biloba extract (GBE).

METHODS

Enzyme activity, cholesterol flux and changes in gene expression levels were assessed in cultured hepatocytes treated with GBE or lovastatin.

RESULTS

GBE decreased the total cholesterol content in cultured hepatocytes and inhibited the activity of HMG-CoA reductase, as determined by an in vitro enzyme activity assay. In addition, GBE decreased cholesterol influx, whereas lovastatin increased cholesterol influx. GBE treatment induced significant increases in the expression of cholesterogenic genes and genes involved in cholesterol metabolism, such as SREBF2, as determined by cDNA microarray and real-time RT-PCR. Furthermore, INSIG2, LDLR, LRP1, and LRP10 were differentially regulated by GBE and lovastatin. The data imply that the two compounds modulate cholesterol metabolism through distinct mechanisms.

CONCLUSION

By using a gene expression profiling approach, we were able to broaden the understanding of the molecular mechanisms by which GBE lowers cellular cholesterol levels. Specifically, we demonstrated that GBE exhibited dual effects on the cellular cholesterol pool by modulating both HMG-CoA reductase activity and inhibiting cholesterol influx.

Transcriptome profiling analysis reveals multiple modulatory effects of Ginkgo biloba extract in the liver of rats on a high-fat diet

Leaf extract of Ginkgo biloba (GBE) is increasingly used as a herbal medicine for the treatment of neurodegenerative, cardiovascular and cerebrovascular diseases. Several studies have demonstrated many protective effects of GBE in neurons, the endothelium and liver. In this study, we investigated the molecular mechanisms underlying the effects of GBE in disorders induced by long-term exposure to a high-fat diet (HFD). Rats were fed an HFD with or without the GBE product GBE50 for 19 weeks. We found that GBE50 reduced the development of fatty liver induced by an HFD and inhibited the commonly observed elevation of serum cholesterol and lactate dehydrogenase levels. Transcriptome profiling analysis showed that several genes were modulated by GBE50 in liver, including those involved in lipid metabolism, carbohydrate metabolism, vascular constriction, ion transportation, neuronal systems and drug metabolism. Notably, a number of genes coding for proteins involved in cholesterol metabolism were repressed, and some were upregulated. Fatty acid biosynthesis appeared to be repressed, whereas fatty acid metabolism appeared to be enhanced. In conclusion, using transcriptome profiling analysis, we demonstrated the molecular basis for the pleiotropic effects of GBE50, particularly those involved in lipid metabolism. This study provided new clues for further pharmacological study of GBEs.

Inhibitory effect of Ginkgo biloba extract on hyperhomocysteinemia-induced intimal thickening in rabbit abdominal aorta after balloon injury

Ginkgo biloba extract (GBE) has been widely used to treat cardiovascular and cerebrovascular disorders. Hyperhomocysteinemia (Hhcy) is associated with the risk of atherosclerosis and restenosis after angioplasty. The objective of this study was to investigate whether GBE could attenuate the Hhcy-induced intimal thickening after balloon injury in rabbit abdominal aorta. It was observed in this study that GBE could decrease the neointima area (NA) and the ratio of the neointima area to the media area (NA/MA), down-regulate the mRNA expression of matrix metalloproteinase-9 (MMP-9) and up-regulate the protein expression of p21 (WAF1/CIP1) (p21). It suggests that GBE can reverse the Hhcy-induced neointima formation in rabbits following balloon injury, and the suppressive effect of GBE on the migration and proliferation of vascular smooth muscle cells (VSMCs) may contribute to its actions.

Suppression of tissue necrosis factor-alpha or hydrogen peroxide-activated primary human T lymphocytes by Ginkgo biloba extract through down-regulation of activator protein-1 signal transduction

PURPOSE

It was unknown whether Ginkgo biloba extract has regulatory effects on human T lymphocytes activated by tissue necrosis factor-alpha (TNF-alpha), which has an important role on the progression of inflammatory atherosclerotic plaques. We evaluated the effects of G. biloba extract on activated human peripheral T lymphocytes, which were isolated from human whole blood.

METHODS

The human T lymphocytes were treated with 25-100 microg G. biloba extract for 2h first. Then they were activated by TNF-alpha and H(2)O(2) to investigate the modulatory effects of G. biloba extract on human T lymphocytes. Electrophoretic mobility shift assay, Western blot (Immunoblot) analysis and immunoprecipitation kinase assays were used.

RESULTS

The inhibition of activated human T lymphocyte specifically correlated with the down-regulation of AP-1 DNA-binding activities. G. biloba extract was unique in its ability to inhibit the activation of c-Jun NH2-terminal protein kinase.

CONCLUSIONS

G. biloba extract might have its novel therapeutic effects on inflammation-based atherosclerotic diseases.

Cilostazol attenuates MCP-1 and MMP-9 expression in vivo in LPS-administrated balloon-injured rabbit aorta and in vitro in LPS-treated monocytic THP-1 cells

Monocyte chemoattractant protein-1 (MCP-1) and matrix metalloproteinase-9 (MMP-9) are involved in vascular inflammation. We tested the hypothesis, and explored the underlining mechanisms that cilostazol, a phosphodiesterase 3 inhibitor with antiplatelet and antithrombotic properties, inhibits lipopolysaccharide (LPS)-induced MCP-1 and MMP-9 expression. In a rabbit aorta balloon-injury model, administration of LPS increased macrophage infiltration and MCP-1 and MMP-9 expression; cilostazol supplementation prevented this phenomenon and reduced intimal hyperplasia. In contrast, the reverse zymography showed that cilostazol did not affect TIMP-1 expression in serum. In monocytic THP-1 cells, cilostazol and N6,O2'-dibutyryl-cAMP (dioctanoyl-cAMP, a cAMP analog) dose-dependently inhibited LPS-induced MCP-1 protein expression and MMP-9 activation, but did not affect the tissue inhibitor of metalloproteinase-1. Quantitative real-time polymerase chain reaction (PCR) showed that cilostazol inhibited MCP-1 and MMP-9 mRNA expression. Cilostazol significantly inhibited LPS-induced activation of p38, JNK, and nuclear factor-kappaB, and the respective inhibitors of p38 and JNK greatly reduced the level of LPS-induced MCP-1 and MMP-9, suggesting the involvement of the p38 and JNK pathways. In conclusion, cilostazol administered with LPS in vivo reduced neointimal hyperplasia and macrophage infiltration in the balloon-injured rabbit aorta; in vitro, cilostazol inhibits LPS-induced MCP-1 and MMP-9 expression. These data suggest that cilostazol may play an important role in preventing endotoxin- and injured-mediated vascular inflammation.

Inhibitory effects of Ginkgo biloba leaf flavonoids on proliferation of human gastric cancer cell line BGC823 in vitro

AIM: To extract the flavonoids from Ginkgo biloba leaf, and to investigate its inhibitroy effects on the proliferation of human gastric cancer cell line BGC823 cultured in vitro.

METHODS: Ethanol (700 mL/L) was used to extract the flavonoids from the leaf of Ginkgo biloba. Three wavelength spectrophotometry was used to determine the content of flavonoids in the extracts. Human gastric cancer cells BGC823 cultured in vitro were treated with different concentrations of the flavonoids, and then the proliferation of the cells was detected by MTT assay and flow cytometry.

RESULTS: The content of flavonoids in the extracts was 140 mg/g. The flavonoids from Ginkgo biloba leaf inhibited the proliferation of BGC823 cells in a dose-dependent manner. The rate of cells in S phase was notably increased as compared with that in the controls (42.17±0.50% vs 32.13±0.45%, P = 0.001), and the apoptotic rate of the cells was also increased (4.10±0.03% vs 2.21±0.01%, P = 0.002).

CONCLUSION: Ginkgo biloba leaf flavonoids can inhibit the proliferation of human gastric cancer cell line BGC823 by affecting the cycle the cells.

Effect of Antioxidants on Atherosclerotic Plaque Formation in Balloon-Denuded and Irradiated Hypercholesterolemic Rabbits

The oxidative modification of low-density lipoprotein (LDL) hypothesis implies that antioxidants should be effective in suppressing atherosclerosis. This study is designed to test the potential of antioxidants to inhibit atherosclerotic plaque progression in balloon-denuded and irradiated hypercholesterolemic rabbits. Rabbits were fed with a 1% cholesterol diet supplemented with or without a mixture of antioxidants (vitamin E, vitamin C, selenium, zinc, copper, manganese, N-acetylcysteine, glutamine). At 7 days both iliac arteries were balloon denuded, and 4 weeks later, 1 iliac artery underwent endovascular irradiation (n=12), while the contralateral was sham treated (n=12). Four weeks after irradiation, animals were euthanized, and arteries were fixed and processed for histo- or immunohistochemistry for determining the plaque area, macrophage count, and oxidized LDL-positive areas. Plasma antioxidant levels were significantly higher in the animals fed with antioxidant diet. Plasma (thiobarbituric acid-reactive substances) and arterial tissue oxidized LDL (immunoreactive to specific oxidized LDL antibody) levels were significantly higher in the irradiated as compared with nonirradiated animals (0.69+/-0.09 and 31.05+/-4.21 versus 0.24+/-0.04 and 18.42+/-4.62, P<0.001 and 0.05), and antioxidants partially lowered the oxidized LDL levels (0.35+/-0.14 and 25.41+/-4.82, P<0.001 and 0.01). Plaque area in the irradiated animals was 175% greater than in nonirradiated animals (P<0.05). Antioxidant supplementation resulted in a 50% decrease in plaque area of both control and irradiated animals. Antioxidants reduced both the cholesterol-induced and radiation-enhanced circulating and tissue oxidized LDL levels, resulting in reduced plaque.

Effects of Ginkgo biloba extract (EGb 761) on hydroxyl radical-induced thymocyte apoptosis and on age-related thymic atrophy and peripheral immune dysfunctions in mice

In this study, the effect of EGb 761, a standard extract of Ginkgo biloba leaf, on thymocyte apoptosis and age-related thymic atrophy and on peripheral immune dysfunctions was investigated in mice. When primary culture of thymocytes was preincubated with 100 microg/ml EGb 761 before their exposure to hydroxyl radicals (*OH) generated by Fe(2+)-mediated Fenton reaction, apoptotic cell death induced by *OH was distinctly prevented as determined by DNA laddering, the TUNEL assay and flow cytometric analysis. Furthermore, oral EGb 761 administration (about 1.5 mg/day/mouse) for 60 consecutive days led to a significant thymic regrowth in 22-month-old mice as revealed by the increment of thymus weight and total numbers of thymocytes. Partial recovery of peripheral immune capacities such as mitogen responsiveness and NK cell activity were also found in the old mice after 60 days of EGb 761 supplementation. Taken together, our study indicates that in addition to its protective and rescuing abilities on neurodegenerative disorders and cardiovascular diseases, EGb 761 was also found active in the rejuvenation of degenerated thymus and accordingly the strengthening of the immune system. These beneficial effects of EGb 761 on immune system are based on its antioxidant properties as well as the cell proliferation-stimulating effect.

Effects of Ginkgo biloba extract on cell proliferation and cytotoxicity in human hepatocellular carcinoma cells

AIM: To study the effect of Ginkgo biloba extract (EGb 761) containing 22%-27% flavonoids (ginkgo-flavone glycosides) and 5%-7% terpenoids (ginkgolides and bilobalides) on cell proliferation and cytotoxicity in human hepatocellular carcinoma (HCC) cells.

METHODS: Human HCC cell lines (HepG2 and Hep3B) were incubated with various concentrations (0-1000 mg/L) of EGb 761 solution. After 24 h incubation, cell proliferation and cytotoxicity were determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay and lactate dehydrogenase (LDH) release, respectively. After 48 h incubation, the expression of proliferating cell nuclear antigen (PCNA) and p53 protein was measured by Western blotting.

RESULTS: The results showed that EGb 761 (50-1000 mg/L) significantly suppressed cell proliferation and increased LDH release (P < 0.05) in HepG2 and Hep3B cells compared with the control group. The cell proliferation of HepG2 and Hep3B cells treated with EGb 761 (1000 mg/L) was 45% and 39% of the control group (P < 0.05), respectively. LDH release of HepG2 cells without and with EGb 761 (1000 mg/L) treatment was 6.7% and 37.7%, respectively, and that of Hep3B cells without and with EGb 761 (1000 mg/L) treatment was 7.2% and 40.3%, respectively. The expression of PCNA and p53 protein in HepG2 cells treated with EGb 761 (1000 mg/L) was 85% and 174% of the control group, respectively.

CONCLUSION: Ginkgo biloba extract significantly can suppress proliferation and increase cytotoxicity in HepG2 and Hep3B cells. Additionally, Ginkgo biloba extract can decrease PCNA and increase p53 expression in HepG2 cells.

Ginkgo biloba extract inhibits tumor necrosis factor-alpha-induced reactive oxygen species generation, transcription factor activation, and cell adhesion molecule expression in human aortic endothelial cells

OBJECTIVE

This study was conducted to examination whether Ginkgo biloba extract (GBE), a Chinese herb with antioxidant activity, could reduce cytokine-induced monocyte/human aortic endothelial cell (HAEC) interaction, a pivotal early event in atherogenesis.

METHODS AND RESULTS

Pretreatment of HAECs with GBE (50 and 100 microg/mL for 18 hours) significantly suppressed cellular binding between the human monocytic cell line U937 and tumor necrosis factor-alpha (TNF-alpha)-stimulated HAECs by using in vitro binding assay (68.7% and 60.1% inhibitions, respectively). Cell enzyme-linked immunosorbent assay and immunoblot analysis showed that GBE (50 microg/mL for 18 hours) significantly attenuated TNF-alpha-induced cell surface and total protein expression of vascular cellular adhesion molecule-1 and intracellular adhesion molecule-1 (63.5% and 69.2%, respectively; P<0.05). However, pretreatment with probucol (5 micromol/L for 18 hours) reduced the expression of vascular cellular adhesion molecule-1 but not intracellular adhesion molecule-1. Preincubation of HAECs with GBE or probucol significantly reduced intracellular reactive oxygen species formation induced by TNF-alpha (76.8% and 68.2% inhibitions, respectively; P<0.05). Electrophoretic mobility shift assay demonstrated that both GBE and probucol inhibited transcription factor nuclear factor-kappaB activation in TNF-alpha-stimulated HAECs (55.2% and 65.6% inhibitions, respectively) but only GBE could inhibit the TNF-alpha-stimulated activator protein 1 activation (45.1% inhibition, P<0.05).

CONCLUSIONS

GBE could reduce cytokine-stimulated endothelial adhesiveness by downregulating intracellular reactive oxygen species formation, nuclear factor-kappaB and activator protein 1 activation, and adhesion molecule expression in HAECs, supporting the notion that the natural compound Ginkgo biloba may have potential implications in clinical atherosclerosis disease.