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Liu SH, Tzeng HP, Kuo ML, Lin-Shiau SY. Inhibition of inducible nitric oxide synthase by beta-lapachone in rat alveolar macrophages and aorta. Br J Pharmacol 1999; 126:746-50. [PMID: 10188987 PMCID: PMC1565848 DOI: 10.1038/sj.bjp.0702341] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Beta-lapachone, a plant product, has been shown to be a novel inhibitor of DNA topoisomerase. In this study, we performed experiments to examine the effects of beta-lapachone on lipopolysaccharide (LPS)-induced inducible nitric oxide (NO) synthase (iNOS) in rat alveolar macrophages and aortic rings. In alveolar macrophages, incubation with LPS (10 microg ml(-1)) for various time intervals resulted in a significant increase in nitrite production and iNOS protein synthesis, that was inhibited by coincubation with beta-lapachone (1-4.5 microM) without any cytotoxic effects. However, addition of beta-lapachone after induction of NO synthase by LPS failed to affect the nitrite production. Treatment with LPS (10 microg ml(-1)) for 6 h resulted in significant expression of mRNA for iNOS which was significantly inhibited in the presence of beta-lapachone (3 microM) in alveolar macrophages. In endothelium-intact rings of thoracic aorta, beta-lapachone (1 and 3 microM) markedly inhibited the hypocontractility to phenylephrine in aortic rings treated with LPS (10 microg ml(-1)) for 4 h. When beta-lapachone was added 3 h after LPS into the medium, the contractions evoked by phenylephrine were not significantly different in the presence or absence of beta-lapachone. Treatment with LPS (10 microg ml(-1)) for 4 h resulted in a significant increase in iNOS protein synthesis which was inhibited in the presence of beta-lapachone (3 microM), but did not affect the constitutive (endothelial and neuronal) NOS forms in aortic rings. These results indicate that beta-lapachone is capable of inhibiting expression and function of iNOS in rat alveolar macrophages and aortic rings. It is considered that beta-lapachone can be developed as a potential anti-inflammatory agent in the future.
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152
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Liu SH, Wang JH, Fang KT, Lin-Shiau SY. Involvement of protein kinase C in the nitric oxide-mediated peripheral nerve disturbance in endotoxemic rats. Neurosci Lett 1999; 259:99-102. [PMID: 10025567 DOI: 10.1016/s0304-3940(98)00910-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The role of protein kinase C (PKC) in nitric oxide (NO)-mediated peripheral nerve disturbance in lipopolysaccharide (endotoxin, LPS)-treated rat was studied. The impaired Na+,K+ -ATPase activities in sciatic nerves from LPS-treated rats were prevented by aminoguanidine (NO synthase inhibitor) and corrected by PKC agonist in vitro. Using Western blot to determine PKC isoforms alpha and beta polypeptide levels in LPS-treated rat sciatic nerves, we found that alpha isoform was markedly reduced in the particulate fraction, but the beta isoform was unaffected. The alpha and beta isoforms in the cytosolic fractions were not significantly different as compared with control. This diminished particulate PKC alpha isoform was prevented by the treatment of aminoguanidine. Moreover, the motor nerve conduction velocity was significantly reduced in endotoxemic rats and corrected by aminoguanidine. These results indicate that the alteration of PKC alpha isoform in Na+,K+ -ATPase-enriched fraction of sciatic nerve may be related to the NO-mediated peripheral nerve disturbance in endotoxemic rats.
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153
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Heimann PA, Lindle DW, Ferrett TA, Liu SH, Medhurst LJ, Piancastelli MN, Shirley DA, Becker U, Kerkhoff HG, Langer B, Szostak D, Wehlitz R. Shake-off on inner-shell resonances of Ar, Kr and Xe. ACTA ACUST UNITED AC 1999. [DOI: 10.1088/0022-3700/20/19/013] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Wong CM, McNeill JD, Gaffney KJ, Ge NH, Miller AD, Liu SH, Harris CB. Femtosecond Studies of Electron Dynamics at Dielectric-Metal Interfaces. J Phys Chem B 1998. [DOI: 10.1021/jp983913c] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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155
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Liu SH, Lin-Shiau SY. Involvement of nitric oxide in the potentiation of neurogenic contraction by manganese and nickel ions in mouse urinary bladder. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1998; 358:678-81. [PMID: 9879728 DOI: 10.1007/pl00005311] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Repetitive electrical field stimulation evoked muscle contractions of the isolated mouse detrusor strips, which could be abolished by tetrodotoxin (TTX). Both Mn2+ and Ni2+ (0.01-0.06 mM) enhanced neurogenic detrusor contractions in high Ca2+ (5 mM) medium. The non-cholinergic component of the evoked detrusor contractions (in the presence of atropine) was specifically sensitive to this enhancing effect by either Mn2+ or Ni2+. In contrast, the cholinergic component in alpha,beta-methylene ATP-treated detrusors remained unaffected. As compared with Mn2+ and Ni2+, other metal ions, Cu2+, Co2+, Cd2+ and UO2(2+), failed to enhancing the non-cholinergic component of neurogenic detrusor contractions. Nitric oxide synthase (NOS) inhibitors, NG-nitro-L-arginine methyl ester and 7-nitroindazole (a selective neuronal NOS inhibitor) markedly inhibited the enhancing effect by either Mn2+ or Ni2+ on the neurogenic detrusor contractions. Moreover, Mn2+ and Ni2+ did not affect the contractions induced by either carbachol or alpha,beta-methylene ATP. It is concluded from these findings that the neuronal NOS-NO generation pathway is apparently involved in the enhancing effect of Mn2+ and Ni2+ on the muscle contractions elicited by excitatory non-cholinergic neurotransmission in the mouse detrusor strips.
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Chen QM, Liu SH, Ji YG, Xue ZH, Fu P, Geng HR, Ma M, Sun Q, Liang D, Geng YQ. [Effect of changes of amino acids of N-terminal region of the mature protein on secretion of alpha-amylase in B. subtilis]. YI CHUAN XUE BAO = ACTA GENETICA SINICA 1998; 25:278-85. [PMID: 9800439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
The mutant plasmid pAmy413C, in which G takes the place of A at the 271 position of alpha-amylase gene on the pAmy413 from B. licheniformis, was constructed by site-direct mutagenesis. At the N-terminus of the mature alpha-amylase, amino acid +2Asn was substituted by +3Asp in the wild type protein. Then, the alpha-amylase output of the mutant plasmid pAmy413C in B. subtilis was 2.02-2.57 times higher than that of the wild type pAmy413C in the same strain. The amino acid sequencing at the N-terminus of the matural alpha-amylase revealsed that the recognition site of signal peptidase I moved one amino acid upstream, from Ala-(+2)Asn to AlaAla-(+3) Asp. That is, the +2Asn of the wild type was changed to the +3Asp of the mutant. The secondary structural analysis showed that a 14-cycle structure formed in the alpha-amylase mRNA when the free energy was -51.7 kcal. In this case, the mutant is identical with the wild type. The difference between them is that G at 271 position is no longer paired with U at 211 position, hence, a G-overhang is formed. The secondary structural analysis of protein showed that one amino acid diminished in the turn structure of amino acid at 33-37 position, and this very amino acid is involed in an alpha-helix structure. In short, all the changes mentioned above in conformation and charged amino acids contribute to the increase in the protein secretion in B. subtilis.
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Abstract
PURPOSE To determine whether defensin genes are expressed in human corneas and bovine corneal keratocytes. METHODS In situ hybridization and immunohistochemistry were used to localize defensin mRNA and protein in normal and diseased human corneas. Cultured bovine keratocytes were stimulated with IL-1alpha or TNFalpha to determine whether defensin mRNA production occurred. Reverse transcription polymerase chain reaction (RT-PCR) was performed to amplify defensin cDNA from cytokine-induced keratocytes, and Southern blots were used to verify the specificity of RT-PCR amplification products. RESULTS Defensin mRNA and protein were not detected in normal human corneal stroma, but were readily detectable in the corneal stroma in cases of rejected transplants and postinfectious keratitis. IL-1alpha was a potent inducer of defensin gene expression in keratocytes, which began 12 h after challenge and peaked at 18 to 24 h. TNFalpha weakly induced defensin mRNA in keratocytes at about 18 h. Southern blots of the RT-PCR products probed with an oligonucleotide complementary to internal sequences of defensin demonstrated the appropriately sized products (198 bp) specific for defensin. CONCLUSIONS This report demonstrates the presence of defensin in the human cornea and the capacity of corneal keratocytes to produce defensin mRNA in response to IL-1alpha and TNFalpha. Release of defensins by keratocytes in response to cytokines elaborated in corneal inflammation may contribute to the host defense response in microbial keratitis.
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Abstract
PURPOSE A host-parasite interaction is thought to be involved in the pathogenesis of Mooren's ulcer. We have identified a cornea-associated antigen (CO-Ag), which may be a target for the autoimmune process resulting in Mooren's ulcer. This study presents the cloning, expression, and identification of a cDNA encoding human CO-Ag. METHODS Reverse transcription-polymerase chain reaction (RT-PCR) was performed to amplify a cDNA encoding CO-Ag in the human cornea. The cDNA fragment was cloned into a prokaryotic expression vector and the resulting plasmid was transformed into DH5 E. coli cells. Autoantibody reactivity to the CO-Ag fusion protein in patient sera was tested by Western blots. RESULTS A cDNA encoding human CO-Ag was amplified by RT-PCR. The entire mRNA coding region was 273 nucleotides in length, predicting a 91-amino acid protein with a molecular weight of 10,683 daltons. The cDNA sequence was identical to human neutrophil calgranulin C (CaGC). Human CO-Ag was expressed in E. coli carrying a plasmid in which the CO-Ag cDNA was under control of the E. coli trc promoter. The CO-Ag fusion protein, which comprised as much as 15% of the total bacterial protein, was purified to 90% homogeneity by affinity chromatography on an immobilized metal column. The recombinant CO-Ag protein produced was recognized by autoantibodies in the sera of 6 of 15 patients with Mooren's ulcer and none of 14 normal control sera by Western blots. CONCLUSION CO-Ag is identical to calgranulin C, a neutrophil protein found on the surface of filarial nematodes. A host-parasite interaction may cause autoimmunity to CO-Ag (CaGC) in the cornea resulting in a Mooren's ulcer.
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Liu TK, Liu SH, Chang CH, Yang RS. Concentration of metal elements in the blood and urine in the patients with cementless total knee arthroplasty. TOHOKU J EXP MED 1998; 185:253-62. [PMID: 9865472 DOI: 10.1620/tjem.185.253] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Titanium (Ti), cobalt (Co) and chromium (Cr) element concentrations in the whole blood and urine specimen in 40 patients with cementless total knee arthroplasty were determined by the electrothermal atomic absorption spectrophotometry. Their ages ranged from 55 to 78 years (mean, 65 years). Twenty of them had loosening of prosthesis and underwent revision surgery, including 4 subjects with Ti-6Al-4V alloy prosthesis and 16 subjects with Co-Cr-Mo alloy prosthesis. The other 20 patients had well-functioning stable prosthesis, including 5 subjects with Ti-6Al-4V alloy prosthesis and 15 subjects with Co-Cr-Mo alloy prosthesis. The mean duration of prostheses implantation in patients with loosened or well-functioning prostheses were 6.5 and 4.0 years, respectively. The control group consisted of 20 age-matched normal subjects who did not undergo any metal implant surgery. Analysis of variance showed that the metal element concentrations in the whole blood, either Co, Cr or Ti, was statistically higher in the patients with loosened prosthesis than the other two groups. However, the metal element concentrations in the urine did not show any difference. The linear regression analysis showed a moderate positive relationship between the metal element concentrations, either Co or Cr elements, in whole blood and urine only in the patients with loosened prostheses. In conclusion, elevated concentration of metal elements may indicate a loosening of prosthesis while the clinical significance of the metal element concentration in the urine needs further investigation.
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160
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Lee KH, Liu SH, Jiang SJ. Determination of cadmium and lead in urine by electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry. Analyst 1998; 123:1557-60. [PMID: 9830167 DOI: 10.1039/a800485d] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry (ETV-ID-ICP-MS) was applied to the determination of Cd and Pb in urine samples. The isotope ratios for each element in each analytical run were calculated from the peak areas of each isotope. A relatively low vaporization temperature was used, which separated the analyte from the major matrix components and improved the ion signals of Cd and Pb significantly. Various chemical modifiers were tested to obtain the best signal of Cd and Pb. After preliminary studies, 1% HNO3 was added to the samples as the chemical modifier. The ETV-ID-ICP-MS method was applied to the determination of Cd and Pb in freeze-dried urine reference material NIST SRM 2670 and several fresh urine samples. The results for NIST SRM 2670 agreed satisfactorily with the certified values. The results for other samples obtained by isotope dilution and the method of standard additions agreed satisfactorily. The detection limits were 0.02 and 0.005 ng ml-1 for Cd and Pb, respectively. The precision between sample replicates was better than 11% for all determinations.
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161
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Dutschman GE, Bridges EG, Liu SH, Gullen E, Guo X, Kukhanova M, Cheng YC. Metabolism of 2',3'-dideoxy-2',3'-didehydro-beta-L(-)-5-fluorocytidine and its activity in combination with clinically approved anti-human immunodeficiency virus beta-D(+) nucleoside analogs in vitro. Antimicrob Agents Chemother 1998; 42:1799-804. [PMID: 9661024 PMCID: PMC105686 DOI: 10.1128/aac.42.7.1799] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
2',3'-Dideoxy-2',3'-didehydro-beta-L(-)-5-fluorocytidine [L(-)Fd4C] has been reported to be a potent inhibitor of the human immunodeficiency virus (HIV) in cell culture. In the present study the antiviral activity of this compound in two-drug combinations and its intracellular metabolism are addressed. The two-drug combination of L(-)Fd4C plus 2',3'-didehydro-2'-3'-dideoxythymidine (D4T, or stavudine) or 3'-azido-3'-deoxythymidine (AZT, or zidovudine) synergistically inhibited replication of HIV in vitro. Additive antiviral activity was observed with L(-)Fd4C in combination with 2',3'-dideoxycytidine (ddC, or zalcitabine) or 2',3'-dideoxyinosine (ddI, or didanosine). This beta-L(-) nucleoside analog has no activity against mitochondrial DNA synthesis at concentrations up to 10 microM. As we previously reported for other beta-L(-) nucleoside analogs, L(-)Fd4C could protect against mitochondrial toxicity associated with D4T, ddC, and ddI. Metabolism studies showed that this drug is converted intracellularly to its mono-, di-, and triphosphate metabolites. The enzyme responsible for monophosphate formation was identified as cytoplasmic deoxycytidine kinase, and the K(m) is 100 microM. L(-)Fd4C was not recognized in vitro by human mitochondrial deoxypyrimidine nucleoside kinase. Also, L(-)Fd4C was not a substrate for deoxycytidine deaminase. L(-)Fd4C 5'-triphosphate served as an alternative substrate to dCTP for incorporation into DNA by HIV reverse transcriptase. The favorable anti-HIV activity and protection from mitochondrial toxicity by L(-)Fd4C in two-drug combinations favors the further development of L(-)Fd4C as an anti-HIV agent.
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Zhu YL, Dutschman DE, Liu SH, Bridges EG, Cheng YC. Anti-hepatitis B virus activity and metabolism of 2',3'-dideoxy-2',3'-didehydro-beta-L(-)-5-fluorocytidine. Antimicrob Agents Chemother 1998; 42:1805-10. [PMID: 9661025 PMCID: PMC105687 DOI: 10.1128/aac.42.7.1805] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
2',3'-Dideoxy-2',3'-didehydro-beta-L(-)-5-fluorocytidine [L(-)Fd4C] was found to be at least 10 times more potent than beta-L-2',3'-dideoxy-3'-thiacytidine [L(-)SddC; also called 3TC, or lamivudine]against hepatitis B virus (HBV) in culture. Its cytotoxicity against HepG2 growth in culture was also greater than that of L(-)SddC (3TC). There was no activity of this compound against mitochondrial DNA synthesis in cells at concentrations upto 10 microM. The dynamics of recovery of virus from the medium of cells pretreated with equal drug concentrations were slower with L(-)Fd4C than with L(-)SddC (3TC). L(-)Fd4C could be metabolized to mono-, di-, and triphosphate forms. The degree of L(-)Fd4C phosphorylation to the 5'-triphosphate metabolite was higher than the degree of L(-)SddC (3TC) phosphorylation when equal extracellular concentrations of the two drugs were used. The apparent K(m) of L(-)Fd4C phosphorylated metabolites formed intracellularly was higher than that for L(-)SddC (3TC). This may be due in part to a difference in the behavior of L(-)Fd4C and L(-)SddC (3TC) towards cytosolic deoxycytidine kinase. Furthermore, L(-)Fd4C 5'-triphosphate was retained longer within cells than L(-)SddC (3TC) 5-triphosphate. L(-)Fd4C 5'-triphosphate inhibited HBV DNA polymerase in competition with dCTP with a Ki of 0.069 +/- 0.015 microM. Given the antiviral potency and unique pharmacodynamic properties of L(-)Fd4C, this compound should be considered for development as an expanded-spectrum anti-HBV drug.
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Chen L, Xu XY, Liu SH, Zhu HQ, Huang PT, Huang CF. [The analysis of biological characteristics for the tissue-plasminogen activator (t-PA) mutant engineered cell line]. SHI YAN SHENG WU XUE BAO 1998; 31:111-6. [PMID: 12014139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
The morphology of t-PA mutant engineered cell line FSGGI48 is similar to that of CHO-dhfr- cell in polygon. When aminopterin (MTX) concentration is 5 x 10(-6) mol/L, a part of cells become slim, but they are still in polygon. Therefore, the morphology of FSGGI48 cell line is normal. The expression level is 4000 IU/10(6) cells/24 h in serum-free medium. The cell line is bequeathed for three months in vitro and revived after freezing three months, the greater part of cells are stable. The expression level is 3000-4000 IU/10(6) cells/24 h. The assay of tumorigenesis shows that the cells, cellular DNA and purified products don't form tumors in nude mice. The cell line hasn't been contaminated by mycoplasma. The results of chromosomal analysis show that the chromosomal number of CHO-dhfr- cell is 20 and the abnormal rate is 6%. FSGGI48 cell line is same as CHO-dhfr- cell in chromosomal number and the abnormal rate is 15%-18%, it is normal in scope. Therefore, the engineered cell line FSGGI48 is excellent.
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164
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Lu X, Yu H, Liu SH, Brodsky FM, Peterlin BM. Interactions between HIV1 Nef and vacuolar ATPase facilitate the internalization of CD4. Immunity 1998; 8:647-56. [PMID: 9620685 DOI: 10.1016/s1074-7613(00)80569-5] [Citation(s) in RCA: 212] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
CD4 is the primary receptor for the human immunodeficiency virus (HIV). Nef is an accessory protein of HIV that decreases the expression of CD4 on the surface of infected cells. In this study, we identified the Nef binding protein 1 (NBP1), which interacts specifically with Nef in vitro and in vivo. Since it shares sequence similarity with the catalytic subunit of the vacuolar ATPase (V-ATPase) and complements the loss of this VMA13 gene in yeast, NBP1 is the human homolog of Vma13p. Direct interactions between Nef and NBP1 were correlated with the ability of Nef to internalize CD4. The expression of the antisense NBP1 abrogated these effects. We conclude that NBP1 helps to connect Nef with the endocytic pathway.
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Lin MJ, Liu SH, Lin-Shiau SY. Phorbol ester-induced contractions of mouse detrusor muscle are inhibited by nifedipine. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1998; 357:553-7. [PMID: 9650809 DOI: 10.1007/pl00005207] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The effects of phorbol esters on contractions of detrusor strips isolated from mouse urinary bladder were studied. Beta-phorbol-12,13-dibutyrate (beta-PDBu, 10 nM) significantly enhances both the neurogenic and myogenic detrusor contractions to a similar extent. By contrast, an inactive isoform of protein kinase C (PKC) stimulation, alpha-phorbol-12,13-dibutyrate (100 nM) has no such enhancing effect on the muscle contraction. The effect of beta-PDBu was dependent on the extracellular Ca2+ concentration. Nifedipine (0.3 microM, a L-type Ca2+ channel blocker), staurosporine (1 microM) and bisindolylmaleimide I (microM, a selective PKC inhibitor) but not omega-conotoxin GVIA (an N-type Ca2+ channel blocker) abolished the enhancing effect of beta-PDBu. In other words, beta-PDBu failed to augment the nifedipine-insensitive component of the muscle contraction. Moreover, beta-PDBu not only enhances the muscle response induced by exogenous agonists (acetylcholine or ATP) and KCl but also increases the resting tone of detrusor muscle, an effect which is also inhibited by nifedipine and bisindolylmaleimide I. From these findings, it is concluded that the enhancing effect of beta-PDBu is due to activation of the L-type Ca2+ channel through phosphorylation by protein kinase C. This allows more Ca2+ influx from the extracellular medium, leading to an increase in the contractions of the mouse detrusor muscle.
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Liu SH, Grove KL, Cheng YC. Unique metabolism of a novel antiviral L-nucleoside analog, 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil: a substrate for both thymidine kinase and deoxycytidine kinase. Antimicrob Agents Chemother 1998; 42:833-9. [PMID: 9559792 PMCID: PMC105551 DOI: 10.1128/aac.42.4.833] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
2'-Fluoro-5-methyl-beta-L-arabinofuranosyluracil (L-FMAU) is the first L-nucleoside analog with low cytotoxicity discovered to have potent antiviral activities against both hepatitis B virus and Epstein-Barr virus but not human immunodeficiency virus. This spectrum of activity is different from those of the other L-nucleoside analogs examined. L-FMAU enters cells through equilibrative-sensitive and -insensitive nucleoside transport as well as through nonfacilitated passive diffusion. L-FMAU is phosphorylated stepwise in cells to its mono-, di-, and triphosphate forms. In the present study the enzymes responsible for the first step of L-FMAU phosphorylation were identified. This is the first thymidine analog shown to be a substrate not only for cytosolic thymidine kinase and mitochondrial deoxypyrimidine kinase but also for deoxycytidine kinase. This finding suggests that the antiviral activity of L-FMAU will not be limited by the loss or alteration of any of these deoxynucleoside kinases.
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Liu SH, Marks MS, Brodsky FM. A dominant-negative clathrin mutant differentially affects trafficking of molecules with distinct sorting motifs in the class II major histocompatibility complex (MHC) pathway. J Cell Biol 1998; 140:1023-37. [PMID: 9490717 PMCID: PMC2132696 DOI: 10.1083/jcb.140.5.1023] [Citation(s) in RCA: 116] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/1997] [Revised: 01/06/1998] [Indexed: 02/06/2023] Open
Abstract
The role of clathrin in intracellular sorting was investigated by expression of a dominant-negative mutant form of clathrin, termed the hub fragment. Hub inhibition of clathrin-mediated membrane transport was established by demonstrating a block of transferrin internalization and an alteration in the intracellular distribution of the cation-independent mannose-6-phosphate receptor. Hubs had no effect on uptake of FITC-dextran, adaptor distribution, organelle integrity in the secretory pathway, or cell surface expression of constitutively secreted molecules. Hub expression blocked lysosomal delivery of chimeric molecules containing either the tyrosine-based sorting signal of H2M or the dileucine-based sorting signal of CD3gamma, confirming a role for clathrin-coated vesicles (CCVs) in recognizing these signals and sorting them to the endocytic pathway. Hub expression was then used to probe the role of CCVs in targeting native molecules bearing these sorting signals in the context of HLA-DM and the invariant chain (I chain) complexed to HLA-DR. The distribution of these molecules was differentially affected. Accumulation of hubs before expression of the DM dimer blocked DM export from the TGN, whereas hubs had no effect on direct targeting of the DR-I chain complex from the TGN to the endocytic pathway. However, concurrent expression of hubs, such that hubs were building to inhibitory concentrations during DM or DR-I chain expression, caused cell surface accumulation of both complexes. These observations suggest that both DM and DR-I chain are directly transported to the endocytic pathway from the TGN, DM in CCVs, and DR-I chain independent of CCVs. Subsequently, both complexes can appear at the cell surface from where they are both internalized by CCVs. Differential packaging in CCVs in the TGN, mediated by tyrosine- and dileucine-based sorting signals, could be a mechanism for functional segregation of DM from DR-I chain until their intended rendezvous in late endocytic compartments.
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Ybe JA, Greene B, Liu SH, Pley U, Parham P, Brodsky FM. Clathrin self-assembly is regulated by three light-chain residues controlling the formation of critical salt bridges. EMBO J 1998; 17:1297-303. [PMID: 9482727 PMCID: PMC1170478 DOI: 10.1093/emboj/17.5.1297] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Clathrin self-assembly into a polyhedral lattice mediates membrane protein sorting during endocytosis and organelle biogenesis. Lattice formation occurs spontaneously in vitro at low pH and, intracellularly, is triggered by adaptors at physiological pH. To begin to understand the cellular regulation of clathrin polymerization, we analyzed molecular interactions during the spontaneous assembly of recombinant hub fragments of the clathrin heavy chain, which bind clathrin light-chain subunits and mimic the self-assembly of intact clathrin. Reconstitution of hubs using deletion and substitution mutants of the light-chain subunits revealed that the pH dependence of clathrin self-assembly is controlled by only three acidic residues in the clathrin light-chain subunits. Salt inhibition of hub assembly identified two classes of salt bridges which are involved and deletion analysis mapped the clathrin heavy-chain regions participating in their formation. These combined observations indicated that the negatively charged regulatory residues, identified in the light-chain subunits, inhibit the formation of high-affinity salt bridges which would otherwise induce clathrin heavy chains to assemble at physiological pH. In the presence of light chains, clathrin self-assembly depends on salt bridges that form only at low pH, but is exquisitely sensitive to regulation. We propose that cellular clathrin assembly is controlled via the simple biochemical mechanism of reversing the inhibitory effect of the light-chain regulatory sequence, thereby promoting high-affinity salt bridge formation.
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169
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Aguesse-Germon S, Liu SH, Chevallier M, Pichoud C, Jamard C, Borel C, Chu CK, Trépo C, Cheng YC, Zoulim F. Inhibitory effect of 2'-fluoro-5-methyl-beta-L-arabinofuranosyl-uracil on duck hepatitis B virus replication. Antimicrob Agents Chemother 1998; 42:369-76. [PMID: 9527788 PMCID: PMC105416 DOI: 10.1128/aac.42.2.369] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The antiviral activity of 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil (L-FMAU), a novel L-nucleoside analog of thymidine known to be an inhibitor of hepatitis B virus (HBV) replication in hepatoma cells (2.2.1.5 cell line), was evaluated in the duck HBV (DHBV) model. Short-term oral administration (5 days) of L-FMAU (40 mg/kg of body weight/day) to experimentally infected ducklings induced a significant decrease in the level of viremia. This antiviral effect was sustained in animals when therapy was prolonged for 8 days. The histological study showed no evidence of liver toxicity in the L-FMAU-treated group. By contrast, microvesicular steatosis was found in the livers of dideoxycytidine-treated animals. L-FMAU administration in primary duck hepatocyte cultures infected with DHBV induced a dose-dependent inhibition of both virion release in culture supernatants and intracellular viral DNA synthesis, without clearance of viral covalently closed circular DNA. By using a cell-free system for the expression of an enzymatically active DHBV reverse transcriptase, it was shown that L-FMAU triphosphate exhibits an inhibitory effect on the incorporation of dAMP in the viral DNA primer. Thus, our data demonstrate that L-FMAU inhibits DHBV replication in vitro and in vivo. Long-term administration of L-FMAU for the eradication of viral infection in animal models of HBV infection should be evaluated.
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170
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Kang JJ, Liu SH, Chen IL, Cheng YW, Lin-Shiau SY. Comparative studies on the induction of muscle contracture in mouse diaphragm and Ca2+ release from sarcoplasmic reticulum vesicles by organotin compounds. PHARMACOLOGY & TOXICOLOGY 1998; 82:23-7. [PMID: 9527642 DOI: 10.1111/j.1600-0773.1998.tb01393.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Effects of organotins, including triethyltin and tributyltin, on skeletal muscle were studied with diaphragm and isolated sarcoplasmic reticulum membrane vesicles. Triethyltin induced muscle contracture in mouse diaphragm while tributyltin had comparatively less potency and efficacy in inducing the muscle contracture. The contracture induced by tributyltin was inhibited when the diaphragm was pretreated with low Ca2+ medium or caffeine while the contracture induced by triethyltin persisted in the Ca2+-free medium but was inhibited by pretreatment of caffeine. Pretreatment of dithiothreitol blocked the contracture induced by tributyltin but not that by triethyltin. Triethyltin dose-dependently induced Ca2+ release from sarcoplasmic reticulum vesicles and inhibited the Ca2+-ATPase activity. These results suggested that triethyltin induced contracture in mouse diaphragm was mainly by induction of Ca2+ release and inhibition of Ca2+ uptake of the internal Ca2+ storage site the sarcoplasmic reticulum, while the tributyltin induced contracture might be due to enhancement of extracellular Ca2+ influx which further induce the release of internal Ca2+ through the Ca2+-induced Ca2+ release mechanism.
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171
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Lee CH, Lin RH, Liu SH, Lin-Shiau SY. Effects of germanium oxide and other chemical compounds on phenylmercury acetate-induced genotoxicity in cultured human lymphocytes. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 1998; 31:157-162. [PMID: 9544193 DOI: 10.1002/(sici)1098-2280(1998)31:2<157::aid-em7>3.0.co;2-j] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Phenylmercury acetate (PMA), which not only causes an elevation of sister chromatid exchanges (SCEs) but also induces high frequency of endoreduplication in human lymphocytes, may be genotoxic to humans. The major aim of our study was to investigate the effects of germanium oxide (GeO2), D-penicillamine (D-PA), dimercaprol (BAL), and diltiazem (DTM) on PMA-induced genotoxicity as quantified by SCEs. All concentrations of the four chemical compounds tested alone did not induce genotoxicity in cultured human lymphocytes. However, GeO2 significantly inhibited PMA-induced genotoxicity in a concentration-dependent manner. Similarly, D-PA at concentrations of 3 microM and 10 microM, and BAL at a concentration of 30 microM produced the antigenotoxic effects. In addition, GeO2 (1.5 microM) significantly reversed an increase of endoreduplication frequency caused by PMA. In a cell cycle kinetic study, GeO2 (0.5-5.0 microM) reversed the inhibition of PMA on the proliferating rate index (PRI) of lymphocytes. On the contrary, both D-PA and DTM at concentrations of 30-300 microM markedly potentiated PMA-induced inhibition of PRI. These findings show that GeO2, D-PA and BAL could antagonize PMA-induced genotoxicity, and GeO2 appears to be the most effective.
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172
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Liu SH, Lin-Shiau SY. Enhancement by nitric oxide of neurogenic contraction in the mouse urinary bladder. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1997; 356:850-2. [PMID: 9453473 DOI: 10.1007/pl00005127] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In isolated detrusor strips from the mouse urinary bladder, contractile responses to electrical field stimulation were mostly mediated by neurally released acetylcholine and ATP. The aim of this study is to investigate the possible role of nitric oxide (NO) involved in the neurogenic detrusor contraction. Repetitive electrical field stimulation evoked muscle contractions of the isolated mouse detrusor strips, which could be abolished by tetrodotoxin (TTX). NO donors including sodium nitroprusside (SNP) and S-nitroso-N-acetyl-penicillamine (SNAP) as well as exogenous NO increased, while hemoglobin and NO synthase inhibitor N(G)-nitro-L-arginine decreased the neurogenic detrusor contractions. The addition of L-arginine reversed the inhibitory effect of N(G)-nitro-L-arginine. SNP failed to affect the contractions induced by carbachol and alpha,beta-methylene ATP. These findings suggest that NO potentiated the excitatory neuromuscular transmission in electrically stimulated detrusor strips from the mouse.
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173
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Abstract
PURPOSE A cornea-associated antigen (CO-Ag) has been found to be the target for autoantibodies in patients with Mooren's ulcer. The study goals were to isolate a full-length clone encoding CO-Ag from a bovine corneal cDNA library and to express this clone in Escherichia coli (E. coli). METHODS A DNA fragment of CO-Ag was generated, using unique oligonucleotide primers and reverse transcription polymerase chain reaction. This fragment was used as a probe to obtain cDNA clones from a bovine corneal cDNA library. The clone with the longest cDNA insert was selected for sequence analysis. Expression of the CO-Ag protein in E. coli was induced by isopropyl beta-D-thiogalactopyranoside (IPTG). The bacterially-produced CO-Ag was partially purified by calcium (Ca2+)-dependent hydrophobic interaction chromatography. RESULTS The cDNA insert sequence was 273 nucleotides in length for the entire mRNA coding region, 212 nucleotides in the 5' untranslated region, 83 nucleotides in the 3' untranslated region and a poly(A) tail. The DNA base sequence of this clone also contained a standard initiation codon, termination codon, and the polyadenylation signal. This cDNA predicts a protein which contains 91 amino acids with a molecular weight of 10,584 daltons. The cDNA and deduced amino acid sequence of CO-Ag are completely identical to a S-100 protein, bovine calgranulin C. The cDNA was expressed in E. coli as a fusion protein consisting of 583 N-terminal amino acids of beta-galactosidase (beta-gal), 91 amino acids of CO-Ag, and possibly a number of additional N-terminal and C-terminal residues. The bacterially produced CO-Ag was fully functional with respect to hydrophobic interaction with phenyl-Sepharose matrix for its isolation. The fusion protein was recognized by antiserum raised against bovine CO-Ag protein on Western blots. CONCLUSIONS The isolation and analysis of a cDNA clone containing the complete coding sequence of the CO-Ag protein and the expression of the CO-Ag protein in E. coli is reported. The availability of a CO-Ag cDNA probe and larger quantities of the CO-Ag protein should aid in elucidating the possible pathogenic role of CO-Ag in Mooren's ulcer.
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Liu SH, Sheu TJ. The in vivo effect of lipopolysaccharide on Na+,K(+)-ATPase catalytic (alpha) subunit isoforms in rat sciatic nerve. Neurosci Lett 1997; 234:166-8. [PMID: 9364523 DOI: 10.1016/s0304-3940(97)00686-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The Na+,K(+)-ATPase catalytic (alpha) subunit in sciatic nerve of lipopolysaccharide (endotoxin, LPS)-treated rat was investigated. Using Western blot to determine subunit isoform polypeptide levels in rat sciatic nerve, we found a substantial reduction in alpha 1 polypeptide, but not that of alpha 2 and alpha 3 polypeptides, after the administration of LPS. Moreover, when rats were treated with polymyxin B (a LPS neutralizer) and NG-nitro-L-arginine (an inhibitor of nitric oxide (NO) synthase), the effects of LPS were reversed. These results implicate a specific marked deficit in alpha 1 subunit isoform of Na+,K(+)-ATPase in the pathogenesis of neuropathy during endotoxemia, through, at least in part, the L-arginine/NO pathway.
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Liu SH, Lai JL, Lin RH, Lin MJ, Lin-Shiau SY. Involvement of nitric oxide in the in vivo effects of lipopolysaccharide on the contractile and electrical properties of mouse diaphragm. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1997; 356:500-4. [PMID: 9349638 DOI: 10.1007/pl00005083] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The contractile and electrical properties of the mouse diaphragm during endotoxemia were studied, and the possible role of nitric oxide (NO) on these changes was investigated. The mice were injected intraperitoneally with E. coli. lipopolysaccharide (endotoxin, LPS) at various times before isolation of the diaphragm to induce endotoxemia. It was observed that direct twitch tension was slightly increased, and that there was a significant increase in tetanic tension when compared with controls. The potentiation of direct twitch tension induced by a Cl--channel blocker (9-anthracene carboxylic acid), but not the potentiation by a Na+-channel activator (veratridine) or by K+-channel blockers (uranyl ion, 4-aminopyridine and tetraethylammonium ion), was attenuated in the diaphragm of LPS-treated mice. Moreover, the resting membrane potential was significantly reduced and the membrane input resistance was significantly increased, largely due to a decrease in Cl--conductance. However, the membrane K+-conductance remained unaltered. These results imply that the sarcolemmal Cl--channel is markedly affected in the mouse diaphragm during endotoxemia. These changes of contractile and electrical characteristics of the mouse diaphragm during endotoxemia could be reversed by treatment with dexamethasone and N(G)-nitro-L-arginine (NO synthase inhibitors). On the other hand, in in vitro studies, LPS (20 microg/ml), by itself, applied directly to the diaphragm, did not alter the muscle contractions or the membrane potentials. A NO donor, added to the diaphragm bath, increased the tetanus/twitch ratio and induced a transient depolarization. All of these findings suggest that LPS may, at least in part, affect the sarcolemmal electrical properties and muscle contractions during endotoxemia through the L-arginine:NO pathway.
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