Role of tryptophan pyrrolase in endotoxin poisoning

Using substrate induction as a tool, we attempted to determine the role of tryptophan pyrrolase in the response to endotoxin in mice. Previous results have shown that the administration of the ld(50) of endotoxin lowers tryptophan pyrrolase activity. alpha-Methyltryptophan was found to maintain tryptophan pyrrolase activity above control levels in endotoxin-poisoned mice without increasing survival. 5-Hydroxytryptophan, by contrast, lowered tryptophan pyrrolase activity but did not sensitize mice to endotoxin. These results suggest that tryptophan pyrrolase per se does not play a unique role in survival of mice poisoned with endotoxin. This enzyme, however, may reflect the fate of other liver enzymes inducible by adrenocorticoids. In mice given concurrent injections of tryptophan and endotoxin, tryptophan pyrrolase activity was elevated to a level intermediate between that of normal mice and that of mice given tryptophan alone. The mice injected with tryptophan and endotoxin also had about the same mortality as mice given endotoxin alone. Mice treated with tryptophan 4 hr after endotoxin, at a time when the substrate did not fully elevate tryptophan pyrrolase activity, died convulsively and in larger numbers than those given endotoxin alone. This effect was reversed by prior treatment with cyproheptadine, an antiserotonin drug. These results indicate that the depression of tryptophan pyrrolase activity previously observed in vitro after injection of endotoxin reflects an actual decrease in the in vivo activity of the enzyme.     

Novel cyanoguanidines with potent oral antitumour activity

4-Pyridyl cyanoguanidines with hydrophobic aromatic side chains showed potent antiproliferative activity in the human breast and lung cancer cell lines MCF-7, NYH and H460. In vivo, treatment with N-(6-chlorophenoxyhexyl)-N′-cyano-N″-4-pyridylguanidine (18, 20 mg/kg/day po.), gave a complete remission of tumours in a model of NYH inoculated nude mice.     

人参皂甙的抗肿瘤研究进展

人参是我国传统的名贵中草药材,人参皂甙是人参抗肿瘤作用的主要有效成分。对人参皂甙,特别是人参皂甙-Rg3和人参皂甙-Rh2在抗肿瘤方面研究的进展给予了综述,深入讨论了人参皂甙的抗肿瘤活性构效关系。详细讨论从其它人参皂甙通过糖基改造制备具有高的抗肿瘤活性的人参皂甙-Rg3和人参皂甙-Rh2的方法,对人参皂甙研究状况做了展望。     

Synthesis and antitumour activity of glycyrrhetinic acid derivatives

Glycyrrhetinic acid (GA) is one of many interesting triterpenoic acids showing anticancerogenic potential. GA is known to trigger apoptosis in tumour cell lines, although GA has a low cytotoxicity. In our study we were able to prepare derivatives of GA that show lowered the IC(50) values as determined by a sulforhodamine B (SRB) assay using 15 different human tumour cell lines. Thus, combining an ester group combined with the presence of an amino acid moiety led to a ca. 60-fold improved antitumor activity. Experiments on mouse embryonic fibroblasts (NiH3T3) revealed that these compounds showed a better selectivity for tumour cells compared to the parent compound GA. An apoptotic effect of some of these compounds was determined using an acridine orange/ethidium bromide (AO/EB) test and DNA laddering experiments.     

Molecular mechanisms of endotoxin activity

Endotoxin (lipopolysaccharide, LPS), a constitutent of the outer membrane of the cell wall of gramnegative bacteria, exerts a wide variety of biological effects in humans. This review focuses on the molecular mechanisms underlying these activities and discusses structure-function relationships of the endotoxin molecule, its interaction with humoral and cellular receptors involved in cell activation, and transmembrane and intra-cellular signal transduction pathways.     

Molecular weight and antitumour activity of Zymomonas mobilis levans

Levans produced by several Zymomonas mobilis strains were classified by their viscosity average molecular weight and tested against sarcoma 180. Measurements of the samples' polydispersity were carried out to characterise the molecular weight distribution. The antitumour activities of levan samples were plotted against the viscosity average molecular weight and a maximum value of this activity was found at Mv = 210,000 (Mw = 456,900 and PD = 16.2). The results indicate that levan antitumour activities depend on the polysaccharide molecular weight and that a specific class of molecular weight may be responsible for this effect.     

Role of histamine and cyclic nucleotides in implantation in the rabbit

Summary The effect of histamine on cAMP and cGMP levels in day 6 (144 h post coitum) rabbit blastocysts was determined. Histamine at 200 M and 1000 M concentrations stimulated the increased formation of cAMP in vitro, whereas stimulation of cGMP occurred only in the presence of 1000 M histamine. Furthermore, intrauterine injection of RMI-12330A (50 g or 500 g/uterine horn), an inhibitor of adenylyl cyclase, on day 5 of pregnancy interrupted embryro development and implantation of the embryo. The drug was also effective in reducing the cAMP level in the endometrial cells in vitro. A relationship between histamine and cyclic nucleotide changes in embryo development and implantation is suggested.     

In vitro and in vivo investigations on the antitumour activity of Chelidonium majus

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Biological activity of phthalated endotoxin.

Glycolipid (GL) was extracted from a heptoseless mutant of Salmonella minnesota by a mixture of phenol, chloroform, and petroleum ether. The GL was subjected to treatment with either acetic anhydride or phthalic anhydride; a portion of the GL was untreated. Both of the chemically treated preparations as well as the parent GL were examined for biological activity in the following systems: mouse lethality assays, rabbit pyrogenicity assays, and rabbit skin assays. The results of these studies indicated that both treated preparations were less toxic in mice than the parent GL. Compared with saline-treated controls, rabbits pretreated with either of the modified preparations exhibited a reduced pyrogenic response to a subsequent challenge dose of the homologous material but no reduction when challenged with the parent GL. Pretreatment with the unaltered GL rendered rabbits tolerant to the homologous material and to some degree to the modified preparations. Rabbits immunized witn any of the three Gl preparations exhibited dermal toxicity responses comparable with those in untreated animals. Based on these findings, it was concluded that treating GL with either phthalic anhydride or acetic anhydride results in a product which is less toxic in mice and less pyrogenic in rabbits than the parent GL, but which also exhibits a loss of ability to render rabbits tolerant to challenge with untreated GL.     

Role of Apolipoprotein A-Ⅰ in Protecting against Endotoxin Toxicity

High density lipoprotein (HDL) binds lipopolysaccharide (LPS or endotoxin) and neutralizes its toxicity. We investigated the function of Apolipoprotein A-I (ApoA-I), a major apolipoprotein in HDL, in this process. Mouse macrophages were incubated with LPS, LPS+ApoA-I, LPS+ApoA-I+LFF (lipoprotein-free plasma fraction d>1.210 g/ml), LPS+HDL, LPS+HDL+LFF, respectively. MTT method was used to detect the mortality of L-929 cells which were attacked by the release-out cytokines in LPS-activated macrophages. It was found that ApoA-I significantly decreased L-929 cells mortality caused by LPS treatment (LPS vs. LPS+ApoA-I, P<0.05) and this effect became even more significant when LFF was utilized (LPS vs. LPS+ApoA-I+LFF, P<0.01; LPS vs. LPS+HDL+LFF, P<0.01). There was no significant difference between LPS+ApoA-I+LFF and LPS+HDL+LFF treatment, indicating that ApoA-I was the main factor. We also investigated in vivo effects of ApoA-I on mouse mortality rate and survival time after LPS administration. We found that the mortality in LPS+ApoA-I group (20%) and in LPS+ApoA-I+LFF group (10%) was significantly lower than that in LPS group (80%) (P<0.05, P<0.01, respectively); the survival time was (43.20 +/- 10.13) h in LPS+ApoA-I group and (46.80 +/- 3.79) h in LPS+ApoA-I+LFF group, which were significantly longer than that in LPS group (16.25 +/- 17.28) h (P<0.01). We also carried out in vitro binding study to investigate the binding capacity of ApoA-I and ApoA-I+LFF to fluorescence labeled LPS (FITC-LPS). It was shown that both ApoA-I and ApoA-I+LFF could bind with FITC-LPS, however, the binding capacity of ApoA-I+LFF to FITC-LPS (64.47 +/- 8.06) was significantly higher than that of ApoA-I alone (24.35 +/- 3.70) (P<0.01). The results suggest that: (1) ApoA-I has the ability to bind with and protect against LPS; (2) LFF enhances the effect of ApoA-I; (3) ApoA-I is the major contributor for HDL anti-endotoxin function.     

Interactions between rnacrophage cytokines and eicosanoids in expression of antitumour activity

Cytokines and eicosanoid products of macrophages play an essential role in expression of antitumour activity of macrophages either in a cell-to-cell contact system between the effector and the target cell or as cell-free soluble products. In this review the relationship between three main monokines, namely TNF-alpha, IL-1 and IL-6 and the interrelationship between these monokines and eicosanoids (PGE(2), PGI(2), LTB(4), LTC(4)) in their production and in expression of antitumour activity is discussed. Emphasis is given to the effect of tumour burden on production of the monokines and of the eicosanoids and on the production of these compounds by the tumour cells. Finally, the therapeutic implications drawn from animal studies and clinical trials is discussed.