Inhibitory effect of pyridoxal 5'-phosphate on endothelial cell proliferation,replicative DNA polymerase and DNA topoisomerase

Recently, the anti-angiogenic effect of pyridoxal 5'-phosphate (PLP) and pyridoxal (PL) was demonstrated in an ex vivo serum-free matrix culture model using rat aortic ring. To clarify how vitamin B6 inhibits angiogenesis, this study was performed to examine the effect on human umbilical vein endothelial cell (HUVEC) proliferation and HUVEC tube formation. Consistent with the result on an ex vivo angiogenesis assay, PLP and PL at 250 microM markedly suppressed the proliferation of HUVEC, while pyridoxine (PN) and pyridoxamine (PM) were inactive at this concentration. Suppression in HUVEC proliferation by PLP and PL was evident in a dose-dependent manner within the range of 50-250 microM. However, the HUVEC tube formation was unaffected by PLP and PL. The activities of replicative DNA polymerase and DNA topoisomerases I and II were also inhibited by PLP. These results suggest that vitamin B6 suppresses endothelial cell proliferation and angiogenesis at least in part by inhibiting DNA polymerase and DNA topoisomerases.     

Preferential loss of DNA polymerase alpha following suppression of replicative DNA synthesis of guinea pig macrophages by the immunostimulants muramyl dipeptide or lipopolysaccharide

Oil-induced guinea pig peritoneal exudate macrophages were found to incorporate 3H-thymidine into trichloroacetic acid-insoluble fraction. In pulse-labeling experiments, the incorporated 3H-thymidine was detected in short fragments of DNA, which corresponded to the Okazaki fragments. These results indicate that the observed thymidine incorporation is due to nuclear DNA replication but not DNA repair. The observed DNA synthesis of the macrophages was remarkably suppressed when the cells were cultured in a presence of muramyl dipeptide (MDP) or bacterial lipopolysaccharide (LPS). The significant decrease of DNA polymerase alpha activity was found in the cells treated with MDP or LPS. In contrast, the activity of polymerase beta was not at all affected by the same treatment.     

Inhibitory effects of sulfobacin B on DNA polymerase and inflammation

The sulfonolipid, sulfobacin B, is isolated from Chryseobacterium sp. and functions both as a von Willebrand factor receptor antagonist and a DNA polymerase (pol) α inhibitor. Previously, we chemically synthesized sulfobacin B by starting from L-cysteine. In this study, we investigated the inhibitory effects of chemically synthesized sulfobacin B on the activity of pols and other DNA metabolic enzymes. Sulfobacin B selectively inhibited the activity of all animal pol species: Among the pols tested, the inhibitory effect of the compound on pol λ activity was the strongest with IC50 values of 1.6 μM. However, sulfobacin B did not influence the activity of plant or prokaryotic pols, or that of the other DNA metabolic enzymes such as primase of pol α, RNA polymerase, polynucleotide kinase or deoxyribonuclease I. As we previously found a positive relationship between pol λ inhibition and anti-inflammation, we examined whether sulfobacin B could inhibit inflammatory responses. The compound caused a marked reduction in 12-O-tetradecanoylphorbol-13-acetate-induced acute inflammation in the mouse ear. In a cell culture system using mouse macrophages, sulfobacin B strongly inhibited the production of tumor necrosis factor (TNF)-α and the action of nuclear factor-κB induced by lipopolysaccharide (LPS). In an in vivo mouse model of LPS-induced acute inflammation, the intraperitoneal injection of sulfobacin B to mice led to the suppression of serum TNF-α production. These results indicate that sulfobacin B is a potential chemotherapeutic agent for inflammation.     

Inhibitory effects of vitamin K3 on DNA polymerase and angiogenesis

Vitamins play essential roles in cellular reactions and maintain human health. Recent studies have revealed that some vitamins including D3, B6 and K2 and their derivatives have an anti-cancer effect. As a mechanism, their inhibitory effect on cancer-related angiogenesis has been demonstrated. Vitamin K2 (menaquinones) has an anti-cancer effect in particular for hepatic cancer and inhibits angiogenesis. In the current study, we demonstrated that sole vitamin K3 (menadione) selectively inhibits the in vitro activity of eukaryotic DNA polymerase gamma, which is a mitochondrial DNA polymerase, and suppresses angiogenesis in a rat aortic ring model. The anti-angiogenic effect of vitamin K3 has been shown in angiogenesis models using human umbilical vein endothelial cells (HUVECs) with regard to HUVEC growth, tube formation on reconstituted basement membrane and chemotaxis. These results suggest that vitamin K3 may be a potential anti-cancer agent like vitamin K2.     

Inhibitory effects of urine on the polymerase chain reaction for cytomegalovirus DNA.

The inhibitory effects of urine samples taken from neonates and older children, some of which were known to be infected with cytomegalovirus, on the polymerase chain reaction (PCR) were investigated. Urea was the major inhibitory component of urine and inhibited the PCR at a concentration of more than 50 mM. Urine samples from older children were more inhibitory than those from neonates. This correlated with the higher concentration of urea generally found in urine samples from older children compared with neonatal urines. Two of 13 neonatal urine samples, however, were inhibitory despite low urea concentrations--presumably due to metabolites derived from parenteral nutrition. The inhibitory effects of urine were effectively removed by simple dialysis or ultrafiltration. The sensitivity and specificity of PCR for detecting cytomegalovirus DNA in urine were further improved by using "nested" primers and a modified PCR protocol entailing the use of reduced reactants in the first 20 cycles of a two-stage 50 cycle PCR.     

SAMHD1 对HBV DNA 形成的抑制作用及其机制研究

目的:研究不同肝细胞SAMHD1 表达水平及其对HBV DNA 形成的抑制作用和相关机制。方法:通过实时荧光定量PCR 和Western blot 法检测Jurkat、THP-1、HepG2、HepG2.2.15 和Huh7 细胞等细胞SAMHD1 mRNA 和蛋白表达水平;通过对HepG2.2.15 细胞转染过表达质粒和shRNA,升高或者降低SAMHD1 的表达水平,观察不同SAMHD1 表达水平对HBV DNA 水平的影响;补充不同浓度的dNTP,比较不同dNTP 浓度对HBV DNA 水平的影响。结果:肝癌细胞系有较高的SAMHD1表达水平;降低SAMHD1 可以使HBV DNA 水平升高2.3 ~ 2.8 倍,升高SAMHD1 可以使HBV DNA 降低至33% 左右(P<0.01);升高dNTP 浓度可以促进HBV DNA 的合成水平,抵消SAMHD1 的抑制作用。结论:SAMHD1 可以抑制肝癌细胞内HBV DNA 的生成,可能是通过降低细胞内dNTP 浓度实现的。     

反义c-myc真核表达载体的构建及其对大鼠气道平滑肌细胞增殖的抑制作用

目的:观察反义c-myc真核表达载体对大鼠气道平滑肌细胞增殖的抑制作用。方法:构建反义和正义c-myc真核表达载体pcDNA3-myc-antisense和pcDNA3-myc-sense,利用lipofectin将正义及反义c-myc真核表达载体导入大鼠气道平滑肌细胞,MTT法观察正义和反义c-myc真核表达载体对大鼠气道平滑肌细胞增殖的作用,流式细胞技术检测细胞周期变化,免疫组织化学染色检测c-Myc蛋白的表达。结果:反义c-myc真核表达载体可抑制大鼠气道平滑肌细胞增殖,延长细胞S期,反义c-myc真核表达载体可降低气道平滑肌细胞c-Myc蛋白的表达。结论:反义c-myc真核表达载体可抑制大鼠气道平滑肌细胞增殖。     

Quantification of lymphocyte activation by measurement of DNA polymerase alpha activity

Measurement of the activity of the enzyme DNA polymerase alpha has been investigated with regard to its potential usefulness as a method for the detection and quantification of lymphocyte activation in vivo. A modified enzyme assay was developed in order to optimise measurement of activity in crude homogenates of cells or tissues, thus allowing the convenient handling of multiple samples. Specificity of the assay for polymerase alpha was ensured by the inclusion in the assay mixture of dideoxythymidine triphosphate, an inhibitor of the other eukaryotic DNA polymerases. The activity of DNA polymerase alpha was found to be closely correlated with [3H]thymidine incorporation in a mitogen-stimulated in vitro system. The usefulness of the polymerase alpha method for the quantification of lymphocyte activation was validated in 3 different in vivo systems of either immune-mediated or drug-induced lymphoid cell response.     

中药露蜂房醇提取物对人红白血病K562细胞的生长抑制及凋亡诱导作用

目的：研究中药露蜂房(Nidus Vespae,NV)醇提取物对K562细胞的作用及其机制。方法：利用^3H-TdR掺入、透射电镜、原位末端标记(TUNEL)技术、免疫组织化学和图象分析等方法。结果：不同浓度NV醇提取物对。K562细胞生长具有明显抑制作用(27％～56％)。NV醇提取物组K562细胞呈典型的凋亡形态学改变,其Bcl-2蛋白表达显著减弱、Bax蛋白表达显著增强。结论：中药NV醇提取物可明显抑制K562细胞增殖,其作用机制可能是通过Bcl-2、Bax的表达,从而诱导白血病细胞凋亡。     

Transcription by T7 RNA polymerase of DNA containing abasic sites

The effects of abasic (AP) sites on RNA synthesis were studied in vitro, using T7 RNA polymerase and a plasmid template containing a T7 promoter. The presence of increasing numbers of AP sites caused a progressive decline in RNA synthesis. The average RNA chain length, calculated from the ratio of initiation to chain elongation, decreased with increasing numbers of AP sites, revealing that complete blocks must occur during synthesis. The probability that RNA polymerase would be blocked at an AP site in the DNA template strand was estimated to be 0.3 in our experimental conditions. These results demonstrate that RNA synthesis by T7 RNA polymerase is inhibited by AP sites and that readthrough of the lesion occurs more frequently than premature chain termination. Chemical reduction of AP sites in the template did not change the block/bypass pattern. © 1994 Wiley-Liss, Inc.     

Herpes simplex virus replication in the presence of DNA polymerase alpha inhibitors

2-(p-n-butylanilino)deoxyadenosine (BuAdA), and N-2-(p-n-butylphenyl)deoxyguanosine (BuPdG), selective inhibitors of mammalian DNA polymerase alpha, were added to BHK-21(C13) cell cultures infected with herpes simplex virus type 1 (HSV-1) strain 17 syn +. Infectious virus production decreased significantly in the presence of the inhibitor at concentrations varying from 1 nM to 100 microM. BuPdG was more effective than BuAdA at all concentrations tested, while it inhibited virus yield as much as BuAdA when CVG2, a thymidine kinase deficient (TK-) HSV-1, was employed. HSV DNA synthesis, determined by quantitation of CsCl separated DNA peaks, was inhibited by each compound. BuPdG inhibited viral DNA replication more than BuAdA, while the effect on cell DNA synthesis was the same as that of BuAdA. CVG2 DNA replication was inhibited to the same level by BuAdA as by BuPdG. These results indicate that HSV DNA replication is partially dependent on cell DNA polymerase alpha activity, and that the greater effect of BuPdG on viral replication may be ascribed to its action on HSV thymidine kinase.     

Inhibitory effect of midaglizole on alpha adrenoceptor agonist-induced contractions of canine tracheal smooth muscle

To determine why midaglizole is effective in some patients with severe asthma, we investigated the inhibitory effects of midaglizole, prazosin or yohimbine on the BHT 920-, phenylephrine-, or noradrenaline-induced contractions of canine tracheal smooth muscle. After pretreatment with atropine (10(-6) M) and propranolol (10(-6) M) and precontraction with serotonin (3 x 10(-7) M), the tracheal muscle showed contractile responses to the exogenous administration of both alpha 1 and alpha 2 adrenoceptor agonists. Every alpha antagonist inhibited these agonist-induced contractions. Inhibitory activity of midaglizole (10(-4) M) for the alpha agonists was BHT-920 greater than noradrenaline greater than or equal to phenylephrine, while that of prazosin (3 x 10(-6) M) was phenylephrine greater than noradrenaline greater than BHT-920. Moreover, yohimbine completely inhibited the contractions at the lower concentration of 3 x 10(-7) M than that of other two antagonists. Our findings demonstrate that midaglizole dose-dependently inhibits airway contractions induced by alpha adrenoceptor agonists.     

Threonine starvation of concanavalin A treated lymphocytes impairs DNA polymerase alpha activity

When cultured in a threonine-deficient medium, concanavalin A treated guinea-pig lymphocytes do not incorporate tritiated thymidine. DNA polymerase activity is strongly affected. The addition of the missing amino acid is followed by an early increase in protein and RNA synthesis and a delayed rise in DNA polymerase alpha activity associated with the onset of DNA synthesis.     

Inhibitory effect of buflomedil on prostate alpha1A adrenoceptor in the Wistar rat

The inhibitory effect of buflomedil on alpha1A-adrenoceptor (AR) in the prostate of Wistar rat was investigated in this study. Normotensive and spontaneous hypertensive rats were orally fed with buflomedil (150 mg/kg). The drug effects on blood pressure and heart rate were monitored by photoelectric volume oscillometric method. Prostate tissue strips from normotensive rats were contracted in vitro in organ bath by phenylephrine (10(-8) to 10(-2)M). The inhibitory effects of buflomedil (10(-9) to 10(-7)M) on the phenylephrine-induced contractions were measured. Radioligand binding displacement study by buflomedil was performed on rat prostate alpha1A-adrenoceptor (AR) and spleen alpha1B-AR. Furthermore the effects of buflomedil and WB-4101 on phenylephrine (10 microM) activated uptake of 2-[14C]-deoxy-d-glucose (2-DG) into C2C12 cells were evaluated. The results showed that buflomedil feeding did not alter the systolic blood pressure of either spontaneous hypertensive rats or normal rats. Dose-inhibition curves of phenylephrine-induced prostate contraction demonstrated a higher potency of buflomedil than tamsulosin. Buflomedil displaced [3H]prazosin binding in a concentration-dependent manner both in rat prostate alpha1A-AR and spleen alpha1B-AR. The ratio of affinity to alpha1A-AR and alpha1B-AR for buflomedil was 4.06/6.84, indicating selectivity on alpha1A-AR over alpha1B-AR. Activation of C2C12 cell alpha1A-AR by phenylephrine increased the glucose uptake to 116%. Both buflomedil and WB-4101 inhibited the uptake in a concentration-dependent manner. In conclusion, the findings showed that buflomedil has preferential alpha1A-AR antagonistic effect to inhibit prostate contraction without significantly affecting the blood pressure.     

Structural analysis of epolactaene derivatives as DNA polymerase inhibitors and anti-inflammatory compounds

Epolactaene (compound 1), a neuritogenic compound found in human neuroblastoma cells, was found to show anti-inflammatory activity in vivo in this study. DNA polymerases and DNA topoisomerase II (topo II) were some of the major molecular targets of compound 1. Since the agent seems to be a potential pharmaceutical medicine, we synthesized derivatives chemically and obtained seven compounds, 1 to 7 to screen clinically more efficient epolactaene derivatives. A comparison of its structural derivatives revealed that the long alkyl side chain seemed to have an important role in the inhibitory effect. Notably, C18-alkyl chain conjugated epolactaene (compound 5) was the strongest inhibitor of DNA polymerase alpha, beta, lambda (pol alpha, beta, lambda) and topo II, with IC50 values of 13, 135, 4.4 and 5 microM, respectively, and 500 microg of compound 5 caused a marked reduction in TPA (12-O-tetradecanoylphorbol-13-acetate)-induced inflammation (inhibitory effect, 65.0%). Compound 5 did not influence the activities of plant or prokaryotic DNA polymerases, or of other DNA metabolic enzymes such as telomerase, RNA polymerase and deoxyribonuclease I. Based on these results, the relationship among the three-dimensional structure of epolactaene derivatives and the inhibition of polymerases and topo II, and anti-inflammation is discussed.     

Inhibitory effect of DNA topoisomerase inhibitor isoliquiritigenin on the growth of glioma cells

Objective: To investigate the effect of isoliquiritigenin on the activity of DNA topoisomerase (TOP I) and its inhibitory effect on the growth of U87 glioma cells. Methods: This study investigated the inhibitory effect of isoliquiritigenin on the growth of U87 glioma cells and its cytotoxicity by MTT method and determined the effect of isoliquiritigenin on TOP I activity by agarose gel electrophoresis. On this basis, we studied the interaction between isoliquiritigenin and TOP I and DNA. Finally, we further discussed the effect of isoliquiritigenin on the activity of Caspase 3, the apoptosis protein of U87 glioma cells. Results: Isoliquiritigenin could inhibit the growth of U87 glioma cells (half inhibitory concentration IC50: 0.221 mM) and is of low cytotoxicity to normal cells. Agarose gel electrophoresis showed that isoliquiritigenin had significant inhibitory effect on TOP I activity. Molecular simulation results indicated that isoliquiritigenin took priority of binding to the active center of TOP I, and formed hydrogen bonds with the catalytic site Try723. Finally, Caspase 3 activity detection results suggested that isoliquiritigenin could significantly increase the activity of Caspase 3 (P < 0.05). Conclusion: Isoliquiritigenin had a reversible inhibitory effect on TOP I activity, reduced the rate of single strand DNA unwinding in tumor cells, and thus played an important role in inducing the apoptosis of U87 glioma cells.     

Effect of new muramyl dipeptide derivatives on the major components of immunity

Immunomodulatory activity of five new synthetic muramyl dipeptide (MDP) derivatives (β-heptylglycoside-MDP, β-hexadecylglycoside-MDP, polyacrylamide-MDP, polyacrylamide-MDP-phosphatidylethanolamine, and dexal-MDP) is studiedin vitro in different test systems. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 117, N ^o 5, pp. 510–513, May, 1994 Presented by N. K. Permyakov, Member of the Russian Academy of Medical Sciences     

Follow-up of a group of workers exposed to dusts containing derivatives of Bacillus subtilis

Six rounds of investigations at 6-monthly intervals of ventilatory capacity, skin sensitivity and respiratory symptoms were carried out together with serological studies on a group of workers intermittently exposed to Bacillus subtilis derivatives containing proteolytic enzyme while compounding washing powder. 369 sets of readings of ventilatory capacity were made on seventy-seven males and 180 sets of readings on forty-one females. Overall, with change of employment and improvement in industrial hygiene, ventilatory capacity measurements improved. Subjects who became prick test positive, as a group showed a decrease in the ratio of observed to expected FEV₁ significantly greater than for the prick test negative group. There was no significant excess of symptoms developing in the prick test positive group during the course of the survey though smokers and those with previous dust exposure had a higher number of symptoms than non-smokers and those not exposed to other dusts respectively. A serological study of nine subjects initially prick test positive to B. subtilis who subsequently varied their skin reactions, showed them to have low levels of IgE and predominantly normal ventilatory capacities.     

Inhibitory effect of suramin on receptor binding and cytotoxic activity of tumor necrosis factor alpha.

The effect of suramin on the binding of human Tumor Necrosis Factor alpha (huTNF alpha) to specific cell-surface receptors as well as on its cytotoxic activity in vitro was investigated. Suramin inhibited both activities in a dose-dependent manner. Experiments designed to discriminate if suramin exerted its inhibitory activity on the ligand or on the receptor showed that the ligand (huTNF alpha) was the most likely target for suramin in this system. These results may explain, in part, the immunosuppressive activities of suramin that have been observed in vivo and suggest that suramin could be useful in those disease states in which hyperproduction of huTNF alpha has been shown to play a pathogenic role.