Mechanism of inhibitory effect of glycyrrhizin on replication of human immunodeficiency virus (HIV)

Glycyrrhizin (GL) achieved a dose-dependent inhibition of the replication of human immunodeficiency virus type 1 (HIV-1) in MOLT-4 (clone No. 8) cells within the concentration range of 0.075 to 0.6 mM. Within this concentration range, GL also effected a dose-dependent reduction in the protein kinase C (PKC) activity of MOLT-4 (clone No. 8) cells. A well-known PKC inhibitor, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7), also proved inhibitory to HIV-1 replication in MOLT-4 (clone No. 8) cells. PKC inhibition may thus be considered as one of the mechanisms by which GL inhibits HIV-1 replication. In addition, GL may also owe its anti-HIV-1 activity, at least in part, to an interference with virus-cell binding, since the compound at 1.2 mM partially inhibited the adsorption of radiolabeled HIV-1 particles to MT-4 cells. At this concentration GL also suppressed giant cell formation induced by co-culturing MOLT-4 (clone No. 8) cells with MOLT-4/HTLV-III_B cells, whereas the PKC inhibitor H-7 failed to do so.     

The targeting effect of H7K(R2)2-modified pH-sensitive liposomes on U87-MG cells

The present study aimed to investigate the targeting effect of H₇K(R₂)₂-modified pH-sensitive liposomes on U87-MG cells. Using coumarin-6 as a fluorescence probe, we prepared H₇K(R₂)₂-modified pH-sensitive liposomes (designated as coumarin-6-PSL-H₇K(R₂)₂). The flow cytometry assay was used to evaluate the effect of H₇K(R₂)₂ proportions on the cellular uptake and endocytosis pathways of coumarin-6-PSL-H₇K(R₂)₂ on U87-MG cells_. The circular dichroism (CD) spectroscopy assay was used to investigate the secondary structures of H₇K(R₂)₂ peptide at pH 7.4 and pH 6.8, respectively. Our results indicated that the 2.5% proportion of H₇K(R₂)₂ in the coumarin-6-PSL-H₇K(R₂)₂ was superior to those of 1% and 3.5% of H₇K(R₂)₂. The uptake of coumarin-6-PSL-H₇K(R₂)₂ on U87-MG cells was not inhibited by filipin, M-β-CD or chlorpromazine. The secondary structure of H₇K(R₂)₂at pH 6.8 was mostly presented as β-turn. In conclusion, we suggested that the appropriate proportion of H₇K(R₂)₂ in the H₇K(R₂)₂-modified pH-sensitive liposomes could be set at 2.5%. The cellular uptake pathway for H₇K(R₂)₂-modified pH-sensitive liposomes was via the cell penetrating capacity of H₇K(R₂)₂ which responded to acidic condition. The secondary structure of H₇K(R₂)₂ at pH 6.8, which was presented as the shape of hairpin, might be mainly responsible for its targeting and cell penetrating effect.     

人参蛋白协同H2O2诱导SH-SY5Y细胞氧化损伤

目的:探讨人参蛋白(GP)协同H₂O₂诱导人神经母细胞瘤(SH-SY5Y)氧化应激损伤的作用,并筛选二者的最佳联合浓度。方法:首先采用不同浓度H₂O₂诱导SH-SY5Y细胞氧化损伤,然后采用不同浓度GP联合200 μmol·L^-1H₂O₂诱导SH-SY5Y细胞氧化损伤;采用倒置荧光显微镜观察细胞形态,MTT法检测细胞存活,Hoechst 33342染色法检测细胞凋亡。结果:SH-SY5Y细胞经GP-H₂O₂作用后,细胞数量减少,轴突缩短或消失,胞体变圆、缩小,大小不等;细胞存活率降低;Heochst 33342染色呈现高蓝光;GP 60 mg·L^-1+H₂O₂ 200 μmol·L^-1为联合诱导氧化应激损伤的最佳浓度。结论:GP有协同H₂O₂诱导SH-SY5Y细胞氧化损伤的作用,抑制细胞增殖、促进细胞凋亡是其可能的作用机制。     

麝香及其代用品人工麝香对H2O2诱导人脐静脉内皮细胞损伤保护作用比较研究

目的：研究麝香（TR）及其代用品人工麝香（RG）对H₂O₂诱导人脐静脉内皮细胞（HUVECs）损伤保护作用及机制。方法：将对数期生长的HUVECs细胞随机分为5组：空白对照、H₂O₂、H₂O₂+NAC、H₂O₂+TR和H₂O₂+RG。HUVECs细胞在H₂O₂作用2 h后,采用MTS法检测细胞增殖光密度值并计算存活率,利用试剂盒测定细胞外液LDH漏出量、细胞内MDA含量、SOD和GSH-Px活力。对HUVECs细胞进行伊红染色,然后用光学显微镜观察细胞形态变化。结果：与H₂O₂组相比较,麝香（50 μg·mL^-1）增加了细胞存活率（P<0.05）;使LDH漏出量和MDA含量显著降低（P<0.05,P<0.001）;使SOD和GSH-Px活力显著提高（P<0.01,P<0.05）;抑制了H₂O₂对HUVECs细胞形态的改变,减少了细胞内ROS水平。人工麝香（50 μg·mL^-1）对HUVECs细胞也有保护作用,但不具有统计学意义。结论：麝香对H₂O₂诱导的人脐静脉内皮细胞损伤具有保护作用,作用机制可能与有效改善细胞内抗氧化酶的活性,减轻氧化应激损伤有关。此外,麝香对人脐静脉内皮细胞的保护作用略强于人工麝香。     

Inhibition of proliferation of human immunodeficiency virus type 1 by novel heteropolyoxotungstates in vitro

Fifteen heteropolyoxotungstates were tested for their effects on the proliferation of human immunodeficiency virus type 1 (HIV-1) using an in vitro system consisting of MT-4 cells and HTLV-IIIb. Eight heteropolyoxotungstates (HPOTs) with the Keggin structure or dimerized deficient Keggin structure proved to be potent inhibitors of HIV-1. In contrast, seven non-Keggin HPOTs including HPA 23 did not have significant effects on HIV-1 proliferation at non-toxic doses. [PTi2W10O40]7- (PM-19) was the most potent inhibitor of HIV-1 among the 15 HPOTs tested. The inhibition of HIV-1 replication by PM-19 presumably results from impaired virus adsorption and/or penetration into target cells. Viral spread of HIV-1 and HIV-2 on cell-to-cell basis was also susceptible to PM-19. In combination, PM-19 and 3'-azido-3'-deoxythymidine were synergistic in inhibiting HIV-1 proliferation.     

曲美他嗪对内皮祖细胞氧化应激损伤的保护作用研究

目的: 研究曲美他嗪(TMZ)对过氧化氢(H₂O₂)诱导的内皮祖细胞(EPCs)氧化应激损伤的保护作用。方法: 采用密度梯度离心法分离人脐带血单个核细胞,使用EBM-2完全培养基诱导单个核细胞向内皮祖细胞分化,经细胞形态学变化及流式细胞术测定内皮祖细胞特异性标记物CD133、CD34和VEGFR抗原来鉴定内皮祖细胞。体外建立内皮祖细胞过氧化氢(100 μmol·L^-1)损伤模型,加入不同浓度曲美他嗪(0.1,0.5,1,5 μmol·L^-1),观察曲美他嗪作用不同时间后(0.5,1,6,12 h)内皮祖细胞增殖、黏附、迁移、一氧化氮(NO)分泌能力的变化。结果: 曲美他嗪呈剂量及时间依赖性降低过氧化氢对内皮祖细胞的氧化应激损伤,保护内皮祖细胞增殖、黏附、迁移、分泌的生物学功能。结论: 曲美他嗪在氧化应激条件下对内皮祖细胞生物学功能的保护可能是其心血管保护作用的机制之一。     

Bradykinin-induced release of thromboxane B2 into bronchoalveolar lavage fluid of guinea pigs: relationship to airflow obstruction

The aim of this study was to evaluate the role of thromboxane A₂ in bradykinin-induced airflow obstruction in guinea pig in vivo. Airway insufflation pressure (P_i) was measured to assess airflow obstruction and the thromboxane B₂ (a stable metabolite of thromboxane A₂) concentration in bronchoalvelolar lavage fluid was determined by radioimmunoassay. The animals were pretreated with propranolol (1 mg/kg i.v.) and suxamethonium (5 mg i.v.) prior to bradykinin administration. Bradykinin instillation into the trachea (300 nmol) induced a P_i increase (47.5 ± 8.3 cm H₂O versus 23.8 ± 1.5 in sham) and significant thromboxane B₂ release into bronchoalveolar lavage fluid (79 ± 19 pg/ml versus 19 ± 6 in sham). A thromboxane synthase inhibitor (OKY-046, 30 mg/kg i.v.; ((E-E)-3-[p(1H-imidazole-1-yl-methyl) phenyl]-2-propenoic acid hydrochloride mono-hydrate)) or a thromboxane A₂ receptor antagonist (ICI192,605, 0.5 mg/kg i.v.; (4-(Z)-6-(2-o-chloro-phenyl-4-o-hydroxyphenyl-1,3-dioxan-cis-5-yl)hexenoic acid)) reduced the P_i increase evoked by bradykinin (38.7 ± 3.8 and 40.6 ± 3.8 cm H₂O, respectively). OKY-046 abolished the thromboxane B₂ release. A platelet-activating factor receptor antagonist, WEB2086 (1 mg/kg i.v.; (3-[4-(chlorophenyl)-9-methyl-6H-thienol [3,2-f][1,2,4]trizolo-[4,3-a][1,4] diazepin-2-yl]1-4-(4-morpholinyl)-1-propanon) did not significantly affect any measured parameter. We conclude that, in guinea pigs, bradykinin-induced airway effects are associated with a local thromboxane A₂ release.     

Pharmacological characterization of cardiac histamine receptors: Sensitivity to H1- and H2-receptor agonists and antagonists

In the isolated guinea pig heart, histamine H₁-receptor antagonists inhibit the histamine-induced negative dromotropic effect, but not the positive inotropic and chronotropic effects (Levi and Kuye, 1974, European J. Pharmacol. 27, 330). Burimamide, the H₂-receptor antagonist, inhibits the positive chronotropic effect of histamine (Black et al., 1972, Nature 236, 385). In this study, the hypothesis that H₁- and H₂-receptors selectively mediate the various cardiac effects of histamine was tested: (a) by investigating the inhibition of cardiac histamine effects by burimamide; (b) by studying the cardiac effects of 2-methylhistamine (an H₁-agonist) and 4-methylhistamine (an H₂-agonist). Burimamide, as a function of concentration, inhibited the positive inotropic and chronotropic effects of histamine, whereas it attenuated the negative dromotropic effect of histamine at the higher concentration only. 4-Methylhistamine caused dose-dependent positive inotropic and chronotropic but not negative dromotropic effects; conversely, with 2-methylhistamine the negative dromotropic effect prevailed. Sinus tachycardia and slowing of atrioventricular conduction were also obtained in the guinea pig in vivo by the i.v. administration of histamine. Burimamide selectively antagonized the positive chronotropic effect, whereas promethazine (an H₁-antagonist) selectively inhibited the negative dromotropic effect. These results substantiate the hypothesis that H₂-receptors mediate the histamine-induced increase in rate and contractility, whereas H₁-receptors mediate the slowing of atrioventricular conduction.     

Mechanism of the protective effect of heteropolyoxotungstate against herpes simplex virus type 2

The effects of heteropolyoxotungstate (K(7)[PTi(2)W(10)O(40)]. 6H(2)O; PM-19) on the replication of herpes simplex virus type 2 (HSV-2) were examined using a semiquantitative polymerase chain reaction of intracellular viral DNA established by us and also other methods. Vero cells were infected with HSV-2 strains: either the standard strain 169, or the acyclovir-resistant strain YS-4C-1. PM-19 was added at various stages during the replication of HSV-2. PM-19 strongly inhibited the synthesis of viral genomic DNA when it was added at the time of infection. The addition of PM-19 60-90 min after viral inoculation time-dependently decreased the antiviral activity and increased the relative yield of viral DNA, and the addition of PM-19 was completely ineffective at times later than 90 min. These results suggested that PM-19 inhibited viral penetration but did not affect the synthesis of viral DNA. Furthermore, PM-19 strongly inhibited a second round of infection.     

Effects of herbal products and their constituents on human cytochrome P4502E1 activity

Ethanolic extracts from fresh Echinacea purpurea and Spilanthes acmella and dried Hydrastis canadensis were examined with regard to their ability to inhibit cytochrome P450_2E1 mediated oxidation of p-nitrophenol in vitro. In addition, individual constituents of these extracts, including alkylamides from E. purpurea and S. acmella, caffeic acid derivatives from E. purpurea, and several of the major alkaloids from H. canadensis, were tested for inhibition using the same assay. H. canadensis (goldenseal) was a strong inhibitor of the P450_2E1, and the inhibition appeared to be related to the presence of the alkaloids berberine, hydrastine and canadine in the extract. These compounds inhibited 2E1 with K_I values ranging from 2.8 μM for hydrastine to 18 μM for berberine. The alkylamides present in E. purpurea and S. acmella also showed significant inhibition at concentrations as low as 25 μM, whereas the caffeic acid derivatives had no effect. Commercial green tea preparations, along with four of the individual tea catechins, were also examined and were found to have no effect on the activity of P450_2E1.     

(Z)- and (E)-[2-Fluoro-2-(hydroxymethyl)cyclopropylidene]methylpurines and -pyrimidines, a new class of methylenecyclopropane analogues of nucleosides: synthesis and antiviral activity

The Z- and E-isomers of fluoromethylenecyclopropane analogues 11a-d and 12a-d were synthesized, and their antiviral activities were evaluated. The purine (Z,E)-methylenecyclopropane carboxylates 13 and 24 were selectively fluorinated using lithium diisopropylamide, LiCl, and N-fluorobenzenesulfonimide to give (Z,E)-fluoroesters 22 and 25. Reduction with LiBH(4) or diisobutylaluminum hydride gave after chromatographic separation Z-isomers 11a and 11e and E-isomers 12a and 12e. The O-demethylation of 11e and 12e afforded guanine analogues 11b and 12b. Fluorination of (Z,E)-cytosine and thymine esters 15 and 16 afforded (Z,E)-fluoroesters 26 and 27, which were resolved before the reduction to analogues 11c and 11d and 12c and 12d. Adenine Z-isomer 11a was the most effective against Towne and AD169 strains of human cytomegalovirus (HCMV, EC(50) 3.6 and 6.0 microM, respectively), but it was less effective against murine virus (MCMV, EC(50) 69 microM). Thymine Z-isomer 11d was effective against HSV-1 in BSC-1 cells (ELISA, EC(50) 2.5 microM) but inactive against HSV-1 or HSV-2 in Vero or HFF cells. All of the analogues with the exception of 12d were effective at least in one of the assays against Epstein-Barr virus (EBV) in Daudi or H-1 cells in a micromolar or submicromolar range. Cytosine and thymine Z-isomers 11c and 11d were active against varicella zoster virus (VZV) with EC(50) 0.62 microM. Adenine Z- and E-isomers 11a and 12a were effective against HIV-1 in MT-2 or MT-4 cells with EC(50) 12-22 and 2.3-7.6 microM, respectively, whereas only 12a was effective against hepatitis B virus (HBV) with EC(50) 15 microM. Analogues 11a and 12a were weak substrates for adenosine deaminase.     

Intercalation compounds of hydrotalcite-like anionic clays with antiinflammatory agents--I. Intercalation and in vitro release of ibuprofen

Hydrotalcite-like compounds are layered solids having positively charged layers and interlayer charge-compensating anions. The synthetic Mg_0.67Al_0.33(OH)₂ Cl_0.33·0.6H₂O, which is biocompatible, has been used to intercalate a model drug, ibuprofen, in order to prepare a modified release formulation. The intercalation compound was prepared via ion-exchange starting from the chloride form of hydrotalcite and its composition, determined both by elemental microanalysis and thermogravimetric analysis, was Mg_0.67Al_0.33(OH)₂IBU_0.33·0.47H₂O, drug content 50% (w/w). As a consequence of the intercalation, the interlayer distance of the host increased from 0.78 nm (interlayer distance of chloride form) to 2.17 nm. The result of dissolution tests at pH 7.5 showed that the in vitro drug release was modified if compared with that obtained with comparative formulations. The mechanism of modified drug release has been interpreted on the basis of the ion exchange process of the ibuprofen anion intercalated in the lamellar host and phosphates contained in the intestinal fluid buffer.     

Antiviral action of 5-amino-2-(2-dimethyl-aminoethyl)benzo-[de]-isoquinolin-1,3-dion e

A newly synthesized imide derivative of 3-nitro-1,8-naphthalic acid, 5-amino-2-(2-dimethylaminoethyl)benzo-[de]-isoquinolin-1,3-dione (designated M-FA-142), was tested on chick embryo cells against herpes simplex virus type 1 (HSV-1) and vaccinia virus (VV), and on Vero cells against African swine fever virus (ASFV). At a concentration of 4 micrograms/ml the drug inhibited VV replication by about one order of magnitude, and that of HSV-1 by about three orders of magnitude. A minor effect was shown against ASFV. Virus inhibition was found to depend on the amount of drug and multiplicity of infection. No virucidal effect was observed on the viruses tested, except for a slight effect on HSV-1. Inhibition of virus growth could be reversed when the drug was removed from the cell culture medium. Serial passages of HSV-1 and VV in the presence of the drug caused the appearance of drug-resistant viruses.     

Side-chain derivatives of biologically active nucleosides. 1. Side-chain analogs of 3'-azido-3'-deoxythymidine (AZT).

Starting from 3-O-mesyl-1,2-O-isopropylidene-alpha-D-allofuranose (9) the anomeric mixtures of the requisite carbohydrates 1,2-di-O-acetyl-6-O-benzoyl-5-deoxy-3-O-mesyl-D-allofuranoses++ + 17A alpha/beta, 1,2-di-O-acetyl-5,6-di-O-benzoyl-3-O-mesyl-D-allofuranoses 17B alpha/beta, and 1,2-di-O-acetyl-5,6-di-O-benzoyl-3-O-mesyl-L-talofuranoses 17C alpha/beta were synthesized. 1,2-Di-O-acetyl-5-O-benzoyl-6-deoxy-3-O-mesyl-D-allofuranoses++ + 17D alpha/beta and the corresponding L-talofuranoses 17E alpha/beta were obtained from 6-deoxy-3,5-di-O-benzoyl-1,2-O-isopropylidene-alpha-D- allofuranose (12) and the corresponding beta-L-talofuranose 13. Coupling of these sugar derivatives with thymine gave the beta-nucleoside derivatives 18A-E. Treatment of compounds 18A-E with DBU produced the corresponding 2,3'-anhydro nucleosides 19A-E with a free 2'-OH group. After deoxygenation of 2'-O-[[(4-methylphenyl)oxy]thiocarbonyl] compounds 20A-E with tributyltin hydride the 2,3'-anhydro bridge of the 2'-deoxynucleosides 21A-E was opened with LiN3 to produce the protected 3'-azido-2,3'-dideoxynucleoside derivatives 22A-G. Saponification with NaOCH3 gave 1-(3'-azido-2',3',5'-trideoxy-beta-D-allofuranosyl)thymine (2; homo-AZT), the 5'-C-(hydroxymethyl) derivatives of AZT 1-(3'-azido-2',3'- dideoxy-beta-D-allofuranosyl)thymine (3) and 1-(3'-azido-2',3'-dideoxy-alpha-L-talofuranosyl)thymine (4), and the 5'-C-methyl derivatives of AZT 1-(3'-azido-2',3',6'-trideoxy-beta-D-allofuranosyl)thymine (5) and 1-(3'-azido-2',3',6'-trideoxy-alpha-L-talofuranosyl)thymine (6). Compounds 2-6 were evaluated for their inhibitory effect on human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) replication in MT-4 cells and found inactive at subtoxic concentrations. Compounds 2-4 and 6 are not effective against herpes simplex virus type 1 (HSV-1) and type 2 (HIV-2), vaccinia virus (VV), and vesicular stomatitis virus (VSV) at 400 micrograms/mL. 5 is slightly active against HSV-1, HSV-2 and VV at 150, 300, and 300 micrograms/mL, respectively.     

Difference in the inhibition of nitric oxide synthase and cytochrome P-450 by some H2-antagonists

The enzyme nitric oxide synthase (NOS) is reported to have some similarities to the family of cytochrome P-450 enzymes. In this study the histamine H₂-antagonists 2-methyl-4(4-isopropylaminomethyleneiminophenyl) imidazole (DA 5047), 2-guanidino-4(3-methylaminomethyleneiminophenyl)thiazole (DA 4643), tiotidine and cimetidine, which all display cytochrome P-450 inhibition were tested in a rat brain constitutive NOS (cNOS) assay. It was found that all four compounds inhibit rat brain cNOS in a competitive way. This was compared with the inhibition of cytochrome P-450 by these compounds reported previously by Rekka et al. (Rekka et al., 1989). The pIC₅₀ for cNOS inhibition correlated negatively with the pIC₅₀ found for P-450 inhibition. Apparently, the H₂-antagonists interact differently to NOS compared with cytochrome P-450, indicating that there is a functional difference in the molecular mechanism of both enzymes in contrast to what has been suggested.