H W Leung

Hong Kong Baptist University, Chiu-lung, Kowloon City, Hong Kong

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Publications (9)32.71 Total impact

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    ABSTRACT: The major active constituents of ginseng are ginsenosides, and Rg(1) is a predominant compound of the total extract. Recent studies have demonstrated that Rg(1) can promote angiogenesis in vivo and in vitro. In this study, we used a DNA microarray technology to elucidate the mechanisms of action of Rg(1). We report that Rg(1) induces the proliferation of HUVECs, monitored using [(3)H]-thymidine incorporation and Trypan blue exclusion assays. Furthermore, Rg(1) (150-600 nM) also showed an enhanced tube forming inducing effect on the HUVEC. Rg(1) was also demonstrated to promote angiogenesis in an in vivo Matrigel plug assay, and increase endothelial sprouting in the ex vivo rat aorta ring assay. Differential gene expression profile of HUVEC following treatment with Rg(1) revealed the expression of genes related to cell adhesion, migration and cytoskeleton, including RhoA, RhoB, IQGAP1, CALM2, Vav2 and LAMA4. Our results suggest that Rg(1) can promote angiogenesis in multiple models, and this effect is partly due to the modulation of genes that are involved in the cytoskeletal dynamics, cell-cell adhesion and migration.
    Angiogenesis 02/2005; 8(3):205-16. DOI:10.1007/s10456-005-9000-2 · 4.88 Impact Factor
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    ABSTRACT: Ginseng is a commonly used nutraceutical. Intriguingly, existing literature reports both wound-healing and antitumor effects of ginseng extract through opposing activities on the vascular system. To elucidate this perplexity, we merged a chemical fingerprinting approach with a deconstructional study of the effects of pure molecules from ginseng extract on angiogenesis. A mass spectrometric compositional analysis of American, Chinese and Korean, and Sanqi ginseng revealed distinct "sterol ginsenoside" fingerprints, especially in the ratio between a triol, Rg1, and a diol, Rb1, the 2 most prevalent constituents. Using a Matrigel implant model and reconstituting the extracts using distinct ratios of the 2 ginsenosides, we demonstrate that the dominance of Rg1 leads to angiogenesis, whereas Rb1 exerts an opposing effect. Rg1 also promoted functional neovascularization into a polymer scaffold in vivo and the proliferation of, chemoinvasion of, and tubulogenesis by endothelial cells in vitro, an effect mediated through the expression of nitric oxide synthase and the phosphatidylinositol-3 kinase-->Akt pathway. In contrast, Rb1 inhibited the earliest step in angiogenesis, the chemoinvasion of endothelial cells. The present study explains, for the first time, the ambiguity about the effects of ginseng in vascular pathophysiology based on the existence of opposing active principles in the extract. We also unraveled a speciogeographic variation impinging on the compositional fingerprint that may modulate the final phenotype. This emphasizes the need for regulations standardizing herbal therapy, currently under the Dietary Supplement and Health Education Act. Furthermore, we propose that Rg1 could be a prototype for a novel group of nonpeptide molecules that can induce therapeutic angiogenesis, such as in wound healing.
    Circulation 10/2004; 110(10):1219-25. DOI:10.1161/01.CIR.0000140676.88412.CF · 14.43 Impact Factor
  • S Q Sun · M Q Wang · H W Leung · H W Yeung ·
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    ABSTRACT: In this article, a method of using Fourier-transform infrared (FTIR) spectrometry to identify four Lyeium barbarum L. (Gouqizi) in turn of colour, shape, taste and water content. The four features (include color is red or black, shape is round or long, quality is dry or wet, taste is sweet or bitter) are related with the FTIR absorption peaks, this is based on the chemical components and their relative contents are different in various Gouqizi. These differences can be reflected in the FTIR spectra. So a new idea is brought up in the research area of identification of traditional Chinese medicine. Alao, FTIR is proved to be a rapid, simple, reliable and non-destructive qualification method.
    Guang pu xue yu guang pu fen xi = Guang pu 01/2002; 21(6):787-9. · 0.29 Impact Factor
  • N K Mak · H L Lung · R. N. S. Wong · H W Leung · HY Tsang · K N Leung ·
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    ABSTRACT: Euxanthone, a potent neuritogenic compound isolated from the roots of the medicinal herb Polygala caudata, has recently been shown to induce the differentiation of murine neuroblastoma Neuro 2A (BU-1) cells. In this study, the role of protein kinase C (PKC) and the expression of various PKC isoforms in euxanthone-treated BU-1 cells were examined. mRNA phenotyping using the reverse-transcription polymerase chain reaction (RT-PCR) showed that BU-1 cells express six different PKC isoforms, namely PKC-alpha, -beta, -delta, -epsilon, -lambda, and -zeta. Differential regulation and expression of PKC isoforms was observed in BU-1 cells treated with 100 microM euxanthone. PKC-apha, -beta, -delta, -lambda and -zeta were all up-regulated, with 1.7- to 9.5-fold increase, at around 30 to 60 minutes after euxanthone treatment. The expression level of PKC-epsilon remained relatively constant during the treatment. PKC-gamma, -eta, and -theta were not detected in both untreated and euxanthone-treated BU-1 cells. Staurosporine, a broad spectrum PKC inhibitor, was found to inhibit both spontaneous and euxanthone-induced neuritogenesis in BU-1 cells. A significant reduction of the euxanthone-induced neuritogenic effect was also observed when the PKC isoform-specific inhibitor Go6976 was included in the culture. These results suggest that the euxanthone-induced differentiation of the neuroblastoma BU-1 cells may be mediated through the differential expression of PKC-alpha, -beta, -delta, -lambda and -zeta isoforms.
    Planta Medica 08/2001; 67(5):400-5. DOI:10.1055/s-2001-15809 · 2.15 Impact Factor
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    ABSTRACT: The RAPD (random amplified polymorphic DNA) technique was applied for the first time to distinguish Lycium barbarum from other closely related species of the same genus. In this study, eight samples were collected, including five species, two varieties and one cultivated variety. A total of fifty arbitrary primers were used in the RAPD analysis. Distinctive DNA fingerprints corresponding to different Lycium species were successfully obtained from ten primers. Similarity index (S.I.) analysis revealed that the values are higher between intraspecies than interspecies. These results confirmed that the RAPD technique can be employed for distinguishing closely related species of Lycium.
    Planta Medica 07/2001; 67(4):379-81. DOI:10.1055/s-2001-14310 · 2.15 Impact Factor
  • S B Chen · GY Gao · H W Leung · H W Yeung · J S Yang · P G Xiao ·
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    ABSTRACT: Two new flavonoid alkaloids, aquiledine (1) and isoaquiledine (2), were isolated from the whole herb of Aquilegia ecalcarata, and their structures were determined by detailed spectral analysis. Three known flavonoids were also isolated from this extract-apigenin, apigenin-7,4'-dimethyl ether, and luteolin-and have not been reported previously from A. ecalcarata.
    Journal of Natural Products 02/2001; 64(1):85-7. DOI:10.1021/np000256i · 3.80 Impact Factor
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    ABSTRACT: The growth inhibitory and differentiation inducing effects of euxanthone (1,7-dihydroxyxanthone) from the medicinal plant Polygala caudata on the neuroblastoma (Neural 2A, subclone BU-1) were investigated. At the concentration range of 0-100 microM, euxanthone inhibits the growth of BU-1 cells in a dose dependent manner. The 50% growth inhibitory concentration (IC50) was 41 microM. Significant induction of morphological differentiation and neurite growth was observed at the concentration of 100 microM. Frequency of proliferative neuroblastoma cells was determined after induction of differentiation. The frequency of proliferating BU-1 cells was markedly reduced from 1/1.1 to <1/99. Confocal microscopy also confirmed that the morphological differentiation of BU-1 was associated with the expression of neurite specific marker MAP-2 protein in neurites. These data suggest that euxanthone may be one of the neuropharmacological active compounds in the medicinal plant Polygala caudata.
    Life Sciences 01/2000; 66(4):347-54. DOI:10.1016/S0024-3205(99)00596-2 · 2.70 Impact Factor
  • R S Chen · H W Leung · Y C Dong · R. N. S. Wong ·
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    ABSTRACT: A fundamental problem in biochemistry and molecular biology is understanding the spatial structure of macromolecules and then analyzing their functions. In this study, the three-dimensional structure of a ribosome-inactivating protein luffin-alpha was predicted using a neural network method and molecular dynamics simulation. A feedforward neural network with the backpropagation learning algorithm were trained on model class of homologous proteins including trichosanthin and alpha-momorcharin. The distance constraints for the C alpha atoms in the protein backbone were utilized to generate a folded crude conformation of luffin-alpha by model building and the steepest descent minimization approach. The crude conformation was refined by molecular dynamics techniques and a simulated annealing procedure. The interaction between luffin-alpha and its analogous substrate GAGA was also simulated to understand its action mechanism.
    Journal of Protein Chemistry 11/1996; 15(7):649-57. DOI:10.1007/BF01886747
  • Y.-C. Dong · R. N.-S. Wong · P.-C. Shaw · H.-W. Leung · H.-W. Yeung ·

    Acta Crystallographica Section A Foundations of Crystallography 08/1993; 49. DOI:10.1107/S0108767378095458 · 2.31 Impact Factor