Li-Kang Ho

National Yang Ming University, T’ai-pei, Taipei, Taiwan

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Publications (15)34.79 Total impact

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    ABSTRACT: Abstract Purpose: Retinal ischemia-associated ocular disorders are vision threatening. This study examined whether the flavonoid baicalein is able to protect against retinal ischemia/reperfusion. Methods: Using rats, the intraocular pressure was raised to 120 mmHg for 60 min to induce retinal ischemia. In vitro, an ischemic-like insult, namely oxidative stress, was established by incubating dissociated retinal cells with 100 μM ascorbate and 5 μM FeSO4 (iron) for 1 h. The rats or the dissociated cells had been pretreated with baicalein (in vivo: 0.05 or 0.5 nmol; in vitro: 100 μM), vehicle (1% ethanol), or trolox (in vivo: 5 nmol; in vitro: 100 μM or 1 mM). The effects of these treatments on the retina or the retinal cells were evaluated by electrophysiology, immunohistochemistry, terminal deoxynucleotidyl-transferase-mediated dUTP nick end-labeling (TUNEL) staining, Western blotting, or in vitro dichlorofluorescein assay. In addition, real-time-polymerase chain reaction was used to assess the retinal expression of hypoxia-inducible factor-1α (HIF-1α), matrix metalloproteinase-9 (MMP-9), vascular endothelium growth factor (VEGF), and heme oxygenase-1 (HO-1). Results: The retinal changes after ischemia included a decrease in the electroretinogram b-wave amplitude, a loss of choline acetyltransferase immunolabeling amacrine cell bodies/neuronal processes, an increase in vimentin immunoreactivity, which is a marker for Müller cells, an increase in apoptotic cells in the retinal ganglion cell layer linked to a decrease in the Bcl-2 protein, and changes in the mRNA levels of HIF-1α, VEGF, MMP-9, and HO-1. Of clinical importance, the ischemic detrimental effects were concentration dependently and/or significantly (0.05 nmol and/or 0.5 nmol) altered when baicalein was applied 15 min before retinal ischemia. Most of all, 0.5 nmol baicalein significantly reduced the upregulation of MMP-9; in contrast, 5 nmol trolox only had a weak attenuating effect. In dissociated retinal cells subjected to ascorbate/iron, there was an increase in the levels of reactive oxygen species, which had been significantly attenuated by 100 μM baicalein and trolox (100 μM or 1 mM; a stronger antioxidative effect at 1 mM). Conclusions: Baicalein would seem to protect against retinal ischemia via antioxidation, antiapoptosis, upregulation of HO-1, and downregulation of HIF-1α, VEGF, and MMP-9. The antioxidative effect of baicalein would appear to play a minor role in downregulation of MMP-9.
    No preview · Article · Mar 2013 · Journal of ocular pharmacology and therapeutics: the official journal of the Association for Ocular Pharmacology and Therapeutics
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    ABSTRACT: Age-related macular degeneration (AMD) is a leading cause of blindness in the elderly. At a later stage, neovascular or exudative AMD can lead to severe central vision loss that is related to aging-associated cumulative oxidative stress of the human retinal pigment epithelium (hRPE) and choroid capillary. Early prevention with antioxidants is mandatory. The aim of this study was to determine whether and how mannitol can act as an antioxidant. The methods used included measurements of cell viability, oxygen free radical (OFR) levels, lipid peroxide (LP) levels, and OFR-related enzyme protein levels. H(2)O(2) dose-dependently reduced the cell viability of hRPE cells. This negative effect was significantly counteracted by pretreatment with mannitol (1 mM). H(2)O(2) significantly stimulated the formation of OFR and LP. These increases were dose-dependently and significantly blunted by mannitol. Furthermore, treatment with H(2)O(2) was associated with a reduction in the level of catalase, but not of manganese superoxide dismutase (MnSOD). In contrast, it was shown that mannitol protected hRPE cells against the H(2)O(2)-induced oxidative stress by increasing the level of catalase, but not the level of MnSOD. This study supports an antioxidative role for mannitol that acts through up-regulating the level of catalase, which is decreased by H(2)O(2).
    Full-text · Article · Jun 2010 · Journal of ocular pharmacology and therapeutics: the official journal of the Association for Ocular Pharmacology and Therapeutics
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    Ya-Ting Lee · Li-Kang Ho · Chieh-Fu Chen · Ming-Jaw Don
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    ABSTRACT: A series of phenolic amides has been prepared. The inhibition of Cu2+/O2-induced low density lipoprotein (LDL) lipid peroxidation activity and direct scavenging effect on 1,1-diphenyl-2-picryl hydrazyl (DPPH) of these phenolic amides have also been evaluated. The results showed that compounds 9 and 15 were strong inhibitors of lipid peroxidation, and compound 1 was the most potent compound on DPPH radical scavenging assay.
    Preview · Article · Jan 2007
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    ABSTRACT: The potential for neuroprotection by baicalein (5,6,7-trihydroxyflavone), a major constituent from the root of a widely used Chinese medicinal herb Scutellaria baicalensis Georgi, against methamphetamine-induced neurotoxicity was studied. All ICR mice were treated by 4-times repeated intraperitoneal administration, at 2 hr intervals, of either methamphetamine (5 mg/kg), saline, baicalein (1 mg/kg) or baicalein pretreatment followed by methamphetamine. In the striatum of mouse, the tissue level of dopamine was monitored on day 3 and nitric oxide was assayed after 1 hr, 24 hrs and 3 days of the above treatments. The results showed that striatal dopamine was significantly depleted by methamphetamine and elevated by baicalein. Pretreatment with baicalein prevented the methamphetamine-induced dopamine depletion. Nitric oxide was depressed by methamphetamine, elevated by baicalein, but remained suppressed with baicalein plus methamphetamine after 1 hr post-treatment. At 24 hrs nitric oxide concentration was unaffected by methamphetamine but was significantly elevated by baicalein or baicalein plus methamphetamine administration. On 3 days post-treatment nitric oxide was elevated by methamphetamine, baicalein and further markedly elevated by the admin-istration of baicalein plus methamphetamine. These results suggest a potential neuroprotective role for baicalein with the possible involvement of nitric oxide.
    Preview · Article · Dec 2006 · Journal of Food and Drug Analysis
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    ABSTRACT: abstraCt The alkaloid rutaecarpine exhibits antithrombotic and vasorelaxant effects. To characterize mouse cytochrome P450 (P450, CYP)-catalyzed rutaecarpine hydroxylations, the induction, inhibition, and kinetic properties of rutaecarpine hydroxylations were determined using liver microsomes of C57BL/6J mice. In untreated mice, rutaecarpine 10-, 11-, 12-, and 3-hydroxylation had K m and V max values ranging, respectively, between 11.6~16.7 μM and 62~197 pmol/min/mg protein. The formation rates of the four hydroxylated metabolites were inhibited by α-naphthoflavone and orphenadrine, but not by either sulfaphenazole or ketoconazole. 3-Methylcholanthrene-treatment increased rutaecarpine 11-, 12-, and 3-hydroxylation activities. Phenobarbital-treatment increased rutaecarpine 10-, 11-, 12-, and 3-hydroxylation activities. Dexamethasone had no effect on these hydroxylation reactions in mice. These results indicated that CYP1A and CYP2B, but not CYP3A, play major roles in rutaecarpine hydroxylations in mice. Abbreviations: CYP, cytochrome P450; 3-MC, 3-methylcholanthrene; G6P, glucose-6-phosphate; α-NF, α-naphthoflavone; β-NADP ± , β-nicotinamide adenine dinucleotide phosphate.
    Preview · Article · Jun 2006 · Journal of Food and Drug Analysis
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    ABSTRACT: Rutaecarpine is the main active alkaloid of the herbal medicine, Evodia rutaecarpa. To identify the major human cytochrome P450 (P450) participating in rutaecarpine oxidative metabolism, human liver microsomes and bacteria-expressed recombinant human P450 were studied. In liver microsomes, rutaecarpine was oxidized to 10-, 11-, 12-, and 3-hydroxyrutaecarpine. Microsomal 10- and 3-hydroxylation activities were strongly inhibited by ketoconazole. The 11- and 12-hydroxylation activities were inhibited by alpha-naphthoflavone, quinidine, and ketoconazole. These results indicated that multiple hepatic P450s including CYP1A2, CYP2D6, and CYP3A4 participate in rutaecarpine hydroxylations. Among recombinant P450s, CYP1A1 had the highest rutaecarpine hydroxylation activity. Decreased metabolite formation at high substrate concentration indicated that there was substrate inhibition of CYP1A1- and CYP1A2-catalyzed hydroxylations. CYP1A1-catalyzed rutaecarpine hydroxylations had V(max) values of 1,388 to approximately 1,893 pmol/min/nmol P450, K(m) values of 4.1 to approximately 9.5 microM, and K(i) values of 45 to approximately 103 microM. These results indicated that more than one molecule of rutaecarpine is accessible to the CYP1A active site. The major metabolite 10-hydroxyrutaecarpine decreased CYP1A1, CYP1A2, and CYP1B1 activities with respective IC(50) values of 2.56 +/- 0.04, 2.57 +/- 0.11, and 0.09 +/- 0.01 microM, suggesting that product inhibition might occur during rutaecarpine hydroxylation. The metabolite profile and kinetic properties of rutaecarpine hydroxylation by human P450s provide important information relevant to the clinical application of rutaecarpine and E. rutaecarpa.
    Preview · Article · Jun 2006 · Drug Metabolism and Disposition
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    ABSTRACT: 10-Hydroxycamptothecin (10-HCPT), an indole alkaloid isolated from a Chinese tree, Camptotheca acuminate, inhibits the activity of topoisomerase I and has a broad spectrum of anticancer activity in vitro and in vivo. However, its use has been limited due to its water-insolubility and toxicity with i.v. administration. The purpose of this study was to investigate the efficacy, toxicity and proper dosage of 10-HCPT as a single agent by oral administration in the treatment of human colon cancer. 10-HCPT significantly repressed the proliferation of Colo 205 cells at a relatively low concentration (5-20 nM). Flow cytometry analysis and western blot and apoptosis assays demonstrated that low-dose 10-HCPT arrested Colo 205 cells in the G2 phase of the cell cycle and triggered apoptosis through a caspase-3-dependent pathway. Moreover, following oral administration at doses of 2.5-7.5 mg/kg/2 days, significant suppression of tumor growth by 10-HCPT was observed in mouse xenografts. No acute toxicity was observed after an oral challenge of 10-HCPT in BALB/c-nude mice every 2 days. The results of this study suggest that a relatively low dose of 10-HCPT (p.o.) is able to inhibit the growth of colon cancer, facilitating the development of a new protocol of human trials with this anticancer drug.
    No preview · Article · Jun 2006 · Oncology Reports
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    ABSTRACT: Many phenolic acid phenethyl esters possess diverse biological effects including anti-cancer activity. A series of 14 derivatives were synthesized for the evaluation of their cytotoxic effect on oral cancer cells. These derivatives were tested by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric and trypan blue dye exclusion assay on the growth of oral squamous cell carcinoma (SAS), oral epidermoid carcinoma-Meng 1 (OEC-M1), and normal human oral fibroblast (NHOF) cells, respectively. Caffeic acid phenethyl esters, 3a (CAPE), and 3b, 3c, and 3d showed cytotoxic effects on the SAS and OEC-M1 cell lines, but not the NHOF cell line at a 5-100 microM dose range. Flow cytometric analysis showed that 3c caused OEC-M1 cell arrest at G2/M phase. Such differential effects on representative cancer and normal cells suggested these compounds might be useful in oral cancer chemotherapy.
    No preview · Article · Jul 2005 · Cancer Letters
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    ABSTRACT: Rutaecarpine is a quinazolinocarboline alkaloid of the medicinal herb Evodia rutaecarpa and shows a variety of pharmacological effects. Four oxidation metabolites of rutaecarpine were prepared from 3-methylcholanthrene-treated rat liver microsomes. These metabolites had an [M + H]+ ion at m/z 304. The structures of metabolites were identified by comparison of their liquid chromatograms and mass, absorbance, and 1H NMR spectra with those of synthetic standards. Rutaecarpine was metabolized by microsomal enzymes to form 3-, 10-, 11-, and 12-hydroxyrutaecarpine. The formation of 10-hydroxyrutaecarpine was highly induced by a cytochrome P450 1A inducer, 3-methylcholanthrene.
    No preview · Article · Jun 2005 · Journal of Chromatography A
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    ABSTRACT: Phenolic acids and their derivatives are widely distributed in plants. A series of phenolic acid esters and amides have been synthesized. We determined the effects of phenolic acid derivatives on antiinflammatory activity against phorbol 12-myristate 13-acetate (PMA) and N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced production of superoxide anion, an inflammatory mediator produced by neutrophils. When the cells were preincubated with phenolic acids and their derivatives, the superoxide generation induced by fMLP (1.0 micromol/l) and PMA (0.16 micromol/l) was inhibited to various degrees with compounds 1, 2 and 4 significantly suppressing such generation in a concentration-dependent manner. Phenolic acid derivatives may exert their antiinflammatory action through inhibiting superoxide generation.
    No preview · Article · Mar 2005 · Clinica Chimica Acta
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    ABSTRACT: Safrole is a natural plant constituent, found in sassafras oil and certain other essential oils. The carcinogenicity of safrole is mediated through 1'-hydroxysafrole formation, followed by sulfonation to an unstable sulfate that reacts to form DNA adducts. To identify the main cytochrome P450 (P450) involved in human hepatic safrole 1'-hydroxylation (SOH), we determined the SOH activities of human liver microsomes and Escherichia coli membranes expressing bicistronic human P450s. Human liver (n = 18) microsomal SOH activities were in the range of 3.5-16.9 nmol/min/mg protein with a mean value of 8.7 +/- 0.7 nmol/min/mg protein. In human liver (n = 3) microsomes, the mean K(m) and V(max) values of SOH were 5.7 +/- 1.2 mM and 0.14 +/- 0.03 micromol/min/nmol P450, respectively. The mean intrinsic clearance (V(max)/K(m)) was 25.3 +/- 2.3 microL/min/nmol P450. SOH was sensitive to the inhibition by a CYP2C9 inhibitor, sulfaphenazole, and CYP2E1 inhibitors, 4-methylpyrazole and diethyldithiocarbamate. The liver microsomal SOH activity showed significant correlations with tolbutamide hydroxylation (r = 0.569) and chlorzoxazone hydroxylation (r = 0.770) activities, which were the model reactions catalyzed by CYP2C9 and CYP2E1, respectively. Human CYP2C9 and CYP2E1 showed SOH activities at least 2-fold higher than the other P450s. CYP2E1 showed an intrinsic clearance 3-fold greater than CYP2C9. These results demonstrated that CYP2C9 and CYP2E1 were the main P450s involved in human hepatic SOH.
    No preview · Article · Sep 2004 · Chemical Research in Toxicology
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    ABSTRACT: A variety of anthracene- and anthraquinone-related derivatives, modified from three types of lead structures, including 9-acyloxy 1,5-dichloroanthracene (type I), 1,5-bisacyloxy-anthraquinones with O-linked substituents (type II) and 1,5-bisacyloxy-anthraquinones with S-linked substituents (type III), were synthesized and evaluated by an in-vitro bioassay for their anti-inflammatory and cytotoxic effects in human leucocytes. Among these derivatives, type I compounds displayed potent anti-inflammatory activity against phorbol-12-myristate-13-acetate (PMA)-induced superoxide anion production, a bio-marker of inflammatory mediator production by neutrophils, with 50% inhibition (IC50) concentrations (microM) for compounds 1f, 1g, 1h and 1m being 13.8 +/- 3.0, 6.3 +/- 4.1, 33.2 +/- 1.3 and 33.9 +/- 5.7, respectively. Type II and type III derivatives (i. e., 1,5-bisacyloxy anthraquinone-related compounds) and the reference compound, emodin, exhibited relatively minor (20-40%) inhibitory effect against superoxide production by neutrophils. Furthermore, none of these compounds showed a significant cytotoxic effect in human neutrophils. In conclusion, these results suggest that compounds modified from 9-acyloxy 1,5-dichloroanthracence (type I) are more powerful than the other two types as anti-inflammatory drugs. This is the first demonstration that derivatives modified from anthracenes or anthraquinones possess anti-inflammatory activity with no significant cytotoxicity in human neutrophils.
    No preview · Article · Aug 2004 · Journal of Pharmacy and Pharmacology
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    ABSTRACT: A series of anthracene derivatives have been synthesized, and their potential individual cytotoxicity was evaluated using Jurkat T cells and peripheral blood mononuclear cells (PBMCs) in vitro. These compounds, except for 2l, showed less cytotoxicity in PBMCs than mitoxantrone. We also analyzed the antiproliferative activity of these derivatives using the annexin V/propidium iodide assay. These synthetic compounds induced apoptosis, thus leading to antitumor effects. Compounds 2b, 2e, 2f, 2g, 2h, 2i, 2j, and mitoxantrone produced dose-dependent cytotoxicity, while the antiproliferative activity of the anthracene pharmacophore was retained in Jurkat T cells base on the detection of DNA degradation and membrane unpacking. These clearly indicate a correlation between cytotoxicity and antitumor activity. Unlike mitoxantrone, cytotoxic properties were observed, as documented by the reactivity of these novel compounds against Jurkat T cells and PBMCs as normal cells, respectively. Various concentrations of 2b, 2e, 2f, 2g, 2h, 2i, and 2j preparations also inhibited Jurkat T cell proliferation and induced apoptosis of Jurkat T cells, potentially confirmed through the detection of DNA degradation and membrane unpacking. In the present report we also investigated the antiinflammatory activity against phorbol-12-myristate-13-acetate induced superoxide anion production, a marker for an inflammatory mediator produced by neutrophils, with IC(50) (microM) values of 2b, 2h, 2l, and 2o of 4.28+/-0.89, 3.31+/-0.88, 4.38+/-0.25, and 5.45+/-1.78, respectively. These results suggest that, in addition to the specific chromosomal aberrations and cell death, elevated apoptosis could also be a marker for exposure to anthracene derivatives.
    No preview · Article · Jul 2004 · Biological & Pharmaceutical Bulletin
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    ABSTRACT: An in vivo microdialysis sampling method coupled to high-performance liquid chromatography has been applied for continuous monitoring of unbound ampicillin in rat blood. A microdialysis probe was inserted into the jugular vein/right atrium of Sprague-Dawley rats, and doses of 100 and 200 mg/kg ampicillin were then administered via the femoral vein. Dialysates were collected and directly injected into a liquid chromatographic system. Isocratic elution of ampicillin was achieved within 10 min using the liquid chromatographic system. The chromatographic mobile phase consisted of methanol-100 mM monosodium phosphoric acid (25:75, v/v, pH 5.5). The wavelength of the UV detector was set at 230 nm. The calibration curves from 0.25 to 50 μg/ml were linear with correlation coefficients of 0.995. The method provides a simple technique for rapid analysis of unbound ampicillin in rat blood for used in pharmacokinetic study.
    No preview · Article · Jan 2000 · Analytical Letters
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    Li-Li Yu · Li-Kang Ho · Jyh-Fei Liao · Chieh-Fu Chen
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    ABSTRACT: 5-Methoxy-N,N-dimethyltryptamine (1) and N,N-dimethyltryptamine (2) isolated from the dried, unripe fruit of Evodia rutaecarpa interacted with 5-HT1A receptors with Ki values of 28 nM and 0.41 μM, respectively. Compound 2 was found in the E. rutaecarpa fruit and the genus Evodia for the first time.
    Preview · Article · Nov 1997 · Journal of Natural Products