Biomedical subjects

Sheng-Chu Kuo

Publications and source records attributed to Sheng-Chu Kuo.

15 recordsLinked to original sources

PubMed2003

High-performance liquid chromatography determination of methionine adenosyltransferase activity using catechol-O-methyltransferase-coupled fluorometric detection.

A nonradioactive, sensitive, rapid, and specific method for the determination of methionine adenosyltransferase activity has been established. In this method, the methyl group of S-adenosyl-L-methionine was enzymatically transferred to esculetin with the aid of catechol-O-methyltransferase and then the resulting scopoletin was extracted with n-hexane:ethyl acetate (7:3, v/v) and measured by high-performance liquid chromatography with Si 60 column and fluorometric detection with excitation and emission wavelengths at 347 and 415 nm, respectively. The detection limit for scopoletin was about 100 fmol. Using this method to determine MAT activity in HL-60 cells required only about 2.5 microg of protein and the incubation time needed for enzymatic reaction is less than 30 min. The HPLC analysis procedure took only 5 min per sample. The kinetic study showed that MAT in HL-60 cells exhibited negative cooperativity with a Hill coefficient of 0.5. The values of K(m) and V(max) were 6.1+/-0.3 microM and 135.4+/-1.5 nmol AdoMet formed/mg protein/h, respectively.

Calibration↗

PubMed2003

A phenylacetate derivative, SCK6, inhibits cell proliferation via G1 cell cycle arrest and apoptosis.

Phenylacetate is a differentiation agent and has anticancer activity with relatively low toxicity. In the present study, we examined the anticancer effect of six synthetic phenylacetate derivatives in human lung cancer cells in our search for more effective phenylacetate analogous. Results showed that the antiproliferative effects of these synthetic compounds were stronger than those of phenylacetate, and that N-butyl-2-(2-fluorolphenyl)acetamide (SCK6) is the most potent compound. To address the mechanism of the antiproliferative effect of SCK6, cell cycle analysis was performed. Result showed that SCK6 (1 mM) induced G(1) arrest in CH27 cells. Western blot analysis of G(1) phase regulatory proteins demonstrated that the protein levels of cyclin-dependent kinase 2 (Cdk2), Cdk4, Cyclin E and Cyclin D3 were decreased after treatment with SCK6 but not those of Cdk6, Cyclin D1 and D2. In contrast, SCK6 increased the protein levels of p53 and p21(CIP1/WAF1). Data from in situ terminal transferase-mediated dUTP-fluorescensin nick end-labeling (TUNEL) assay and DNA fragmentation analysis demonstrated that SCK6 induced apoptotic cell death in CH27 cells. This SCK6-induced apoptosis was accompanied by a downregulation of Bcl-2 protein and activation of the caspase-9 cascade. Overexpression of Bcl-2 by adeno-Bcl-2 vector infection significantly inhibited SCK6-induced apoptosis. Moreover, treatment with caspase inhibitors also markedly reduced cell death induced by SCK6. Taken together, these results suggest that downregulation of G(1)-associated Cdks and cyclins and upregulation of p53 and p21(CIP1/WAF1) may contribute to SCK6-mediated G(1)-phase arrest. Furthermore, the decrease in Bcl-2 and the activation of caspase-9/caspase-3 may be the effector mechanism through which SCK6 induces apoptosis.

Acetamides↗

PubMed2003

Investigation of the cellular mechanism of inhibition of formyl-methionyl-leucyl-phenylalanine-induced superoxide anion generation in rat neutrophils by 2-benzyloxybenzaldehyde.

The inhibition of formyl-methionyl-leucyl-phenylalanine (fMLP)-induced superoxide anion (O2(.-)) generation by 2-benzyloxybenzaldehyde (CCY1a) was investigated in rat neutrophils, and the underlying mechanism of this inhibition was assessed. CCY1a concentration-dependently inhibited O2(.-) generation (IC(50)=18.5+/-4.3 microM). In cell-free systems, CCY1a failed to alter O2(.-) generation during dihydroxyfumaric acid autoxidation, in phorbol 12-myristate 13-acetate (PMA)-activated neutrophil particulate NADPH oxidase preparations, or during arachidonic acid-induced NADPH oxidase activation. CCY1a increased cellular cyclic AMP (cAMP) levels in a time- and concentration-dependent manner, and this cAMP-elevating effect was inhibited by the adenylyl cyclase inhibitor 9-(tetrahydro-2'-furyl)adenine (SQ22536), adenosine deaminase (ADA), and the adenosine receptor antagonist 8-(p-sulfophenyl)theophylline. In neutrophils, inhibition of O2(.-) generation by CCY1a was partially reversed by the protein kinase A inhibitor (9R,10S,12S)-2,3,9,10,11,12-hexahydro-10-hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-l][1,6]benzodiazocine-10-carboxylic acid, hexyl ester (KT5720). CCY1a did not affect fMLP-induced p38 mitogen-activated protein kinase phosphorylation, but concentration-dependently attenuated the phosphorylation of extracellular signal-regulated kinase (ERK) and Akt (IC(50) about 31.3 and 19.4 microM, respectively). The plateau phase, but not the initial spike, of fMLP-induced [Ca2+](i) changes was inhibited by CCY1a in a concentration-dependent manner. CCY1a inhibition of Ca2+ entry, ERK, and Akt phosphorylation was not prevented by SQ22536 or ADA. fMLP-induced phospholipase D (PLD) activation was inhibited by CCY1a (IC(50)=13.9+/-2.0 microM). ADA and KT5720 did not prevent the inhibition of PLD activation by CCY1a. Collectively, these results indicate that the inhibition by CCY1a of fMLP-induced O2(.-) generation in rat neutrophils can probably be attributed to the increase in cAMP levels, and to the blockade of Ca2+ entry, suppression of Akt, and PLD activation via cAMP-independent mechanisms.

Animals↗

PubMed2003

Enhancement of long-term potentiation by a potent nitric oxide-guanylyl cyclase activator, 3-(5-hydroxymethyl-2-furyl)-1-benzyl-indazole.

Nitric oxide (NO) is known to affect synaptic plasticity in various regions of the brain via the cGMP-cGMP-dependent protein kinase (PKG) pathway. We found that a novel compound 3-(5-hydroxymethyl-2-furyl)-1-benzyl-indazole (YC-1), a drug known to modulate the response of soluble guanylyl cyclase to NO, greatly potentiates long-term potentiation (LTP). This compound markedly enhanced the induction of LTP in rat hippocampal and amygdala slices by weak tetanic stimulation. The potentiation of LTP by YC-1 was greatly reduced by NO synthase inhibitor Ng-nitro-l-arginine-methylester, guanylyl cyclase inhibitor 1 H-[1,2,4]-oxadiazolo(4,3-a)-quinoxalin-1-one, and PKG inhibitor (9S,10R,12R)-2,3,9,10,11,12, hexahydro-10-methoxy-2,9-dimethyl-1-ox0-9.12-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-I][1,6]benzodiazocine-10-carboxylic acid methyl ester (KT5823). In addition, mitogen-activated protein kinase kinase inhibitor 2'-amino-3'-methoxyflavone (PD98059) also markedly inhibited LTP potentiating action of YC-1. Intracellular increase of Ca2+ concentration derived from N-methyl-d-aspartate and glutamate metabotropic receptors contributes to the potentiating action of YC-1. Concurrent perfusion of YC-1 and NO donor sodium nitroprusside for a short time period resulted in the induction of LTP by stimuli at a frequency as low as 0.02 Hz. Incubation of unstimulated hippocampal slices with YC-1 plus nitroprusside increased the immunofluorescence of phospho-extracellular signal-regulated kinase (ERK) and phospho-cAMP response element binding protein (CREB). Furthermore, the Western blot shows that the phosphorylation of ERKs 1 and 2 and CREB of unstimulated hippocampal slices was increased by YC-1 plus nitroprusside, which was inhibited by KT5823. The NO-cGMP-PKG-ERK signaling pathway thus plays important role in the potentiation of LTP by YC-1.

Animals↗

PubMed2003

The role of PAR4 in thrombin-induced thromboxane production in human platelets.

There are two protease-activated receptors (PARs), PAR1 and PAR4, in human platelets. It has been suggested that PAR1 mediates platelet responses to low concentrations of thrombin, whereas PAR4 mediates signaling only at high concentrations. In the present study, we used a selective PAR4 blocker, YD-3, to investigate the role of PAR4 in thrombin-induced thromboxane formation in human platelets. YD-3 completely prevented thromboxane production by either a low concentration of thrombin (0.1 U/ml) or the PAR4 agonist peptide GYPGKF. In contrast, YD-3 did not affect thromboxane production caused by the PAR1 agonist peptide SFLLRN, collagen or arachidonic acid. YD-3 also decreased [(3) H]arachidonic acid release from thrombin-stimulated platelets. Moreover, desensitization of platelets with GYPGKF prevented low thrombin-induced thromboxane formation. The decreased thromboxane production by YD-3 is linked to inhibition of calcium influx in thrombin-stimulated platelets. These results suggest that PAR4 plays an important role in the regulation of thromboxane formation in platelets responding to thrombin through prolonged elevation of [Ca(2+)](i) and activation of phospholipase A(2). These data also indicate that PAR4 can be activated by relatively low concentrations of thrombin in human platelets. The selective inhibition of thrombin-induced thromboxane production by YD-3 may be of therapeutic benefit for thrombotic diseases.

Arachidonic Acid↗

PubMed2002

4-Fluoro-N-butylphenylacetamide: a synthetic phenylacetate derivative that upregulates Bcl-X(S), activates caspase cascade and induces apoptosis in human squamous lung cancer CH27 cells.

Phenylacetate (PA) and related aromatic fatty acids induce antiproliferation and differentiation of cancer cell; they have potent anti-tumor properties with relatively low toxicity. To search for more potent analogues of PA, PA derivatives have been synthesized. In this study, we investigated the effects of six synthetic PA derivatives on the growth of human lung cancer cells. Results showed that the anti-proliferative effects of these synthetic compounds were strong than those of PA, 4-fluoro-N-butylphenylacetamide (H6) is the most potent compound. 4,6-Diamidino-2-phenylindole (DAPI) staining, in situ TUNEL assay and DNA gel electrophoresis analysis indicated that a marked reduction in the number of CH27 cells with H6 was related to the induction of apoptosis. The apoptosis triggered by H6 was accompanied by up-regulation of Bcl-X(S), accumulation of cytosolic cytochrome c and activation of caspase cascade (caspase-9 and -3). Furthermore, H6 induces proteolytic cleavage of poly (ADP-ribose) polymerase, which followed the appearance of caspase activity and preceded DNA fragmentation. Pretreatment with caspase inhibitors markedly inhibited H6-induced caspase activity and apoptosis. These results suggest that H6 may induce apoptosis through a Bcl-X(S) and caspase-dependent mechanism.

Acetamides↗

PubMed2002

1-Benzyl-3-(5'-hydroxymethyl-2'-furyl)indazole (YC-1) derivatives as novel inhibitors against sodium nitroprusside-induced apoptosis.

Antiapoptotic agents based on 1-benzyl-3-(5'-hydroxymethyl-2'-furyl)indazole (22, YC-1) derivatives were explored for effective treatment of sepsis and septic shock. We found that compound 22, 1-benzyl-3-(5'-methoxymethyl-2'-furyl)indazole (27), and 1-phenyl-3-(5'-hydroxymethyl-2'-furyl)indazole (23) were the most effective inhibitors of sodium nitroprusside-induced vascular smooth muscle cell apoptosis. These three compounds are proposed as potential therapeutic agents for the treatment of sepsis.

Administration, Oral↗

PubMed2002

2-Benzyloxybenzaldehyde inhibits formyl-methionyl-leucyl-phenylalanine stimulation of phospholipase D activation in rat neutrophils.

2-Benzyloxybenzaldehyde (CCY1a) inhibited the formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated phospholipase D (PLD)-mediated products, phosphatidic acid (PA) and phosphatidylethanol (PEt) formation in rat neutrophils in a concentration-dependent manner with IC(50) values of 15.8+/-2.5 and 13.9+/-2.0 microM, respectively. The underlying cellular signaling mechanism of CCY1a inhibition was investigated. CCY1a inhibited the plateau phase but not the initial Ca(2+) spike of fMLP-stimulated Ca(2+) signal. CCY1a did not inhibit the [Ca(2+)](i) change in Ca(2+)-free medium in response to fMLP, but inhibited the [Ca(2+)](i) change by the subsequent addition of Ca(2+). In addition, CCY1a treatment attenuated the fMLP-induced protein tyrosine phosphorylation. The membrane translocation of ADP-ribosylation factor (ARF) and Rho A proteins in neutrophils stimulated with fMLP was attenuated by CCY1a in a concentration-dependent manner. In a cell-free system, neither the membrane association of ARF and Rho A caused by GTPgammaS nor the phorbol myristate acetate-stimulated membrane translocation of Rho A was suppressed significantly by CCY1a. These results indicate that the attenuation of protein tyrosine phosphorylation, blockade of Ca(2+) entry, and the suppression of ARF and Rho A membrane translocation are probably obligatory for the CCY1a inhibition of PLD activity in rat neutrophils in response to fMLP.

ADP-Ribosylation Factors↗

PubMed2002

Inhibition of formyl-methionyl-leucyl-phenylalanine-stimulated respiratory burst by cirsimaritin involves inhibition of phospholipase D signaling in rat neutrophils.

In this study, the cellular localization of the inhibitory effect of a natural flavonoid cirsimaritin against formyl-methionyl-leucyl-phenylalanine (fMLP)-induced respiratory burst in rat neutrophils was investigated. Cirsimaritin concentration-dependently inhibited the superoxide anion (O(*-)(2))generation and O(2) consumption (IC(50) 11.5+/-2.2 micro M and 17.0+/-3.9 micro M, respectively) of neutrophils. Cirsimaritin did not reduce, but slightly enhanced the O(*-)(2) generation in phorbol 12-myristate 13-acetate (PMA)-activated or arachidonic acid-stimulated NADPH oxidase preparation as well as during the autoxidation of dihydroxyfumaric acid. Cirsimaritin did not elevate cellular cAMP levels, and only partially inhibited the fMLP-induced [Ca(2+)](i) changes in the presence or absence of extracellular Ca(2+). The phosphorylation of protein tyrosine, extracellular signal-regulated protein kinase and Akt caused by fMLP were attenuated by cirsimaritin in a concentration-dependent manner. In contrast, cirsimaritin had no effect on the phosphorylation of p38 mitogen-activated protein kinase. Cirsimaritin produced a concentration-dependent reduction in the formation of phosphatidic acid and phosphatidylethanol, in the presence of ethanol, from fMLP-stimulated neutrophils (IC(50) 15.1+/-6.5 micro M and 15.6+/-3.4 micro M, respectively), but did not affect the phosphatidylethanol formation in response to PMA. Under the similar concentration range, cirsimaritin attenuated the membrane translocation of ARF and Rho A. However, the GTPgammaS-stimulated membrane-associated ARF and Rho in cell lysate were unaffected by cirsimaritin. Collectively, these results indicate that the inhibition of fMLP-induced respiratory burst by cirsimaritin in rat neutrophils is likely mainly through the blockade of phospholipase D signaling pathway.

Animals↗

PubMed2002

Inhibition of lipopolysaccharide-stimulated nitric oxide production in RAW 264.7 macrophages by a synthetic carbazole, LCY-2-CHO.

In activated macrophages, large amounts of nitric oxide (NO) are generated by inducible nitric oxide synthase (iNOS). This is an important mechanism in macrophage-induced cytotoxicity and inflammation. In the present study, a synthetic carbazole compound, 9-(2-chlorobenzyl)-9H-carbazole-3-carbaldehyde (LCY-2-CHO), was found to have an inhibitory effect on lipopolysaccharide (LPS)-stimulated NO generation in RAW 264.7 macrophages (IC50 value of 1.3+/-0.4 microM). LCY-2-CHO did not induce cytotoxicity and had a negligible effect on iNOS activity. To explore the mechanism of inhibition of NO generation by LCY-2-CHO, the expression of the iNOS gene was examined. LCY-2-CHO abolished the LPS-induced expression of both iNOS protein and mRNA in a parallel concentration-dependent manner with IC50 values similar to those required for inhibition of NO generation. LCY-2-CHO did not enhance the degradation of iNOS mRNA. In cells transiently transfected with an iNOS promoter-chloramphenicol acetyltransferase (CAT) reporter construct, LCY-2-CHO attenuated the LPS-induced iNOS promoter activity. However, LCY-2-CHO had no effect on the degradation of IkappaB-alpha or IkappaB-beta, DNA binding activity, or transcriptional activity of nuclear factor-kappaB (NF-kappaB). These results indicate that LCY-2-CHO inhibits NO generation via a decrease in the transcription of iNOS mRNA through a signaling pathway that does not involve NF-kappaB activation.

Animals↗

PubMed2002

Marked decrease of cyclosporin absorption caused by phellamurin in rats.

Phellamurin is a flavonoid glycoside that is abundant in the leaves of Phellodendron wilsonii Hayata et Kanehira (Rutaceae). In vitro everted rat intestine study indicated that phellamurin inhibited intestinal P-glycoprotein in a dose-dependent manner. In order to investigate the effect of phellamurin on cyclosporin absorption and disposition, rats were given cyclosporin (5 mg/kg) with or without phellamurin in a parallel design. Fluorescence polarization immunoassay was used to determine the blood concentration of cyclosporin. Unanticipatedly, our results indicated that the coadministration of phellamurin significantly decreased the Cmax of cyclosporin by 77 % and reduced the AUC(0-infinity) of cyclosporin by 56 %. This indicated that a serious interaction occurred between phellamurin with cyclosporin. To ensure the efficacy of cyclosporin, we suggest that the coadministration of phellamurin or Phellodendron wilsonii with cyclosporin should be avoided.

Animals↗

PubMed2002

Synthesis of 2-alkoxy 1,4-naphthoquinone derivatives as antiplatelet, antiinflammatory, and antiallergic agents.

In our continuing search for novel antiplatelet, antiallergic, and antiinflammatory agents, 2-alkoxy derivatives of 1,4-naphthoquinone were prepared. Some of these compounds showed significant antiplatelet, antiallergic, and antiinflammatory activities. Among them, 2-propoxy-1,4-naphthoquinone and 2-butoxy-1,4-naphthoquinone exhibited potent inhibitory effect on neutrophil superoxide anion formation. These two compounds are worthy of further exploration.

Anti-Allergic Agents↗

PubMed2002

Selective inhibition of protease-activated receptor 4-dependent platelet activation by YD-3.

In the present study, the antiplatelet effect and its mechanism of a new synthetic compound YD-3 [1-benzyl-3-(ethoxycarbonylphenyl)-indazole] were examined. YD-3 inhibited the aggregation of washed human platelets caused by protease-activated receptor (PAR) 4 agonist peptide GYPGKF (IC50 = 0.13 +/- 0.02 microM), but had no or little effect on that by thrombin, PAR1 agonist peptide SFLLRN, collagen or U46619. YD-3 produced a parallel, rightward shift of the concentration-response curve for GYPGKF without decreasing of the maximum platelet aggregation, indicating a competitive antagonism. In contrast to human platelets, both thrombin- and GYPGKF-induced mouse platelet shape change and aggregation were completely inhibited by YD-3. YD-3 also selectively prevented GYPGKF-induced intracellular Ca2+ mobilization in human platelets. Furthermore, in the PAR1-desensitized human platelets, thrombin induced a relatively slow rise and decay of calcium mobilization that was significantly inhibited by YD-3. In addition, the synergistic effect of SFLLRN and GYPGKF on platelet activation was prevented by YD-3. YD-3 also inhibits both fMLP-stimulated neutrophil- and purified cathepsin G-induced platelet aggregation, which has been demonstrated to be PAR4-dependent. Taken together, our results suggest that YD-3 selectively inhibits PAR4-dependent platelet activation through blockade of PAR4. To the best of our knowledge, it is the first non-peptide PAR4 antagonist.

Animals↗

PubMedDate not supplied

Inhibition of Ras-mediated cell proliferation by benzyloxybenzaldehyde.

Excessive proliferation of vascular smooth muscle cells (VSMC) in the intima is an important etiologic factor in vascular proliferative disorders such as atherosclerosis and restenosis after balloon angioplasty. Therefore, control of VSMC growth may be a suitable therapeutic intervention in vascular proliferative disorders. In the present work, we have studied the 2-benzyloxybenzaldehyde (CCY1a)-mediated antiproliferative effect and its mechanisms of action. CCY1a inhibited serum-induced VSMC proliferation in a concentration-dependent manner, as demonstrated using [(3)H]thymidine incorporation and MTT assays; the IC(50) values were calculated to be 7.0 x 10(-6) and 1.2 x 10(-5) M, respectively. Furthermore, it also significantly suppressed serum-induced progression of the cell cycle, as shown by flow cytometric analysis. CCY1a as well as PD98059 almost completely abolished serum-induced activation of p42/44 mitogen-activated protein kinase (MAPK), the downstream effectors of c-fos and c-jun mRNA expression and activator protein-1 (AP-1) DNA binding activity, suggesting the central roles of these signaling cascades. Interestingly, CCY1a also effectively blocked serum-induced Ikappa B-alpha phosphorylation, Ikappa B-alpha degradation and nuclear factor-kappa B (NF-kappa B) binding activity. Based on these observations, we examined the effect of CCY1a on serum-mediated Ras activity, an upstream regulator of the above signaling events. The data demonstrated a marked inhibition of Ras activation by CCY1a. We conclude that CCY1a blocks cell proliferation via inhibition of the upstream effector of Ras and downstream events, including p42/44 MAPK activation and c-fos and c-jun mRNA expression, as well as NF-kappa B and AP-1 DNA binding activities.

Animals↗

PubMedDate not supplied

Determination of nalidixic acid by fluorometry with sodium borohydride and hydrogen peroxide.

A simple and sensitive fluorometric method for the determination of nalidixic acid was established by using 0.75M sodium borohydride and 7.5% hydrogen peroxide solution as fluorogenic reagents. Analyte concentrations of 0.0232-11.6 pg/mL could be determined with high precision and accuracy by the method. A relative standard deviation of 1.75% was obtained for a nalidixic acid concentration of 0.232 pg/mL. The method was satisfactorily applied to the determination of nalidixic acid in human serum, fish muscle, and chicken muscle, and the calibration curves were linear from 0.23 to 58.00 pg/mL, from 9.28 to 32.48 mg/kg, and from 4.64 to 23.20 mg/kg, respectively. The specificity of the reaction is also discussed.

Animals↗