A DNase from the trypanosomatid Crithidia fasciculata

We have purified to homogeneity a DNase from a Crithidia fasciculata crude mitochondrial lysate. The enzyme is present in two forms, either as a 32 kDa polypeptide or as a multimer containing the 32 kDa polypeptide in association with a 56 kDa polypeptide. Native molecular weight measurements indicate that these forms are a monomer and possibly an alpha 2 beta 2 tetramer, respectively. The monomeric and multimeric forms of the enzyme are similar in their catalytic activities. Both digest double-stranded DNA about twice as efficiently as single-stranded DNA. They introduce single-strand breaks into a supercoiled plasmid but do not efficiently make double-strand breaks. They degrade a linearized plasmid more efficiently than a nickel plasmid. Both enzymes degrade a 5'-32P-labeled double-stranded oligonucleotide to completion, with the 5'-terminal nucleotide ultimately being released as a 5'-mononucleotide. One difference between the monomeric and multimeric forms of the enzyme, demonstrated by a band shift assay, is that the multimeric form binds tightly to double-stranded DNA, possibly aggregating it.

Induction of apoptosis by beta-lapachone in human prostate cancer cells

beta-Lapachone, a plant product, has been shown to be a novel inhibitor of DNA topoisomerase I, with a mode of action different from camptothecin and a chemical structure distinct from those of current anti-cancer drugs. We observed that beta-lapachone, at concentrations of less than 8 microM, induces cell death with characteristics of apoptosis in human prostate cancer cell lines. This effect of beta-lapachone was also observed in a human promyelocytic leukemia cell line (HL-60). beta-Lapachone-induced apoptosis is independent of p53 expression, and ectopic overexpression of bcl-2 did not confer significant resistance to beta-lapachone. Among other human carcinoma and adenoma cell lines tested, human breast and ovary carcinoma showed sensitivity to the cytotoxic effect of beta-lapachone without manifesting signs of apoptosis. These results suggest that beta-lapachone is a potential compound to be added to cancer chemotherapy, particularly for prostate cancer.

Reciprocal modulations between p53 and Tat of human immunodeficiency virus type 1

Infection by human immunodeficiency virus type 1 (HIV-1) causes acquired immunodeficiency syndrome (AIDS) after a long clinical latency. This disease is associated with a spectrum of cancers. Here we report that wild-type p53 is a potent suppressor of Tat, a major transactivator of HIV-1. Reciprocally, Tat inhibits the transcription of p53. Downregulation of p53 by upregulated tat may be important for the establishment of productive viral infection in a cell and also may be involved in the development of AIDS-related malignancies.

[The study on the mechanism of EGF inducing the in vitro meiotic maturation resumption of mouse oocytes]

The effect and mechanism of EGF and progesterone on the meiotic maturation resumption were studied. The results showed that progesterone regulated the action of EGF. The inhibitor of 3 beta-HSD, the key enzyme of progesterone synthesis, Epostane could not only prevent the effect of EGF, but inhibit the progesterone production promoted by EGF in cultured ovary granulosa cells as well. On the other hand, heparin could lessen the function of EGF and progesterone, which implies that calcium participated the effect of EGF and progesterone. Fura-2 was used to indicate the changes of intracellular calcium level in single cumulus cell. It is found that a calcium wave appeared in cumulus cell when EGF or progesterone acted. But Ca2+ level returned to normal immediately after progesterone was added, and Ca2+ in the cumulus cell still remained higher level after EGF acted. This results indicated that calcium in cumulus cell adjusted the action of EGF and progesterone.

Induction of apoptosis in uninfected lymphocytes by HIV-1 Tat protein

Infection by human immunodeficiency virus-type 1 (HIV-1) is typified by the progressive depletion of CD4 T lymphocytes and deterioration of immune function in most patients. A central unresolved issue in acquired immunodeficiency syndrome (AIDS) pathogenesis is the mechanism underlying this T cell depletion. HIV-1 Tat protein was shown to induce cell death by apoptosis in a T cell line and in cultured peripheral blood mononuclear cells from uninfected donors. This Tat-induced apoptosis was inhibitable by growth factors and was associated with enhanced activation of cyclin-dependent kinases.

[Treatment of immunological infertility with Chinese medicinal herbs of ziyin jianghuo]

According to the microcosmic Syndrome Differentiation, immunological infertility is recognised as Kidney Yin Deficiency-Hyperactivity of Fire Syndrome. Zhibai Dihuang Pills, a recipe of Chinese medicinal herbs, was used to treat the infertile couples with antisperm and/or antizona pellucida antibodies in their blood serum. It was found that after the treatment, the antibodies were converted to negativeness in 81.3% of immunological infertile couples. All 8 cases of successful pregnancy occurred in 1-9 months after antibodies negative conversion and the negative status was maintained throughout the course of pregnancy.

[The meiosis arrest of mouse oocytes induced by adenine]

The effect of purine on the meiosis of mouse oocytes was studied. When adenine and benzyladenine, a similar substance of adenine, was microinjected into the germinal vesicle of oocytes, the meiotic maturation of oocytes could be obviously arrested depending on the dosage of injection. The stimulator of adenylate cyclase, NaF, could enhance the arrest effect of adenine. It indicated that cAMP played a important role in mouse oocytes meiotic resumption. Hypoxanthine and adenine had different effects in different medium. Hypoxanthine could obviously arrest the maturation of mouse cumulus oocyte complex (COC) and cumulus denuded oocytes (DO) in DMEM or EMEM. But only in DMEM adenine could obviously arrest the maturation of COC, and had co-effect with hypoxanthine in DMEM. They could almost arrest the maturation of COC and DO. Adenine in EMEM had little arrest effect on maturation of COC and DO. The different effects may result from the different adenine absorption by oocyte in DMEM and EMEM. Adding glutamine into EMEM could enhance the arrest effect of adenine to COC and DO.

Inhibitors of HIV-1 transcription

No curative drug against HIV has yet been found, despite enormous efforts aimed at reverse transcriptase and a variety of other targets. The long terminal repeat (LTR) of HIV-1 has recently become a promising site for antiviral action. This article briefly summarizes information on the nature of this target and potential anti-LTR expression drugs.

Camptothecin inhibits Tat-mediated transactivation of type 1 human immunodeficiency virus

Transcription of type 1 human immunodeficiency virus (HIV-1) is governed by the viral long terminal repeat (LTR). By using HIV-1 LTR-directed reporter gene systems, we found that the DNA topoisomerase I inhibitor camptothecin inhibits Tat-mediated transactivation of HIV-1 LTR. The 293.27.2 cells that carry a stably transfected HIV-1 LTR-directed lacZ gene expression vector (pNAZ) were used. Inhibitions of LTR were observed at camptothecin concentrations (IC50 about 0.03 microM, which was an order of magnitude lower than for Ro 24-7429), which had minor effects on cell survival, expression of the cellular gene gro, or Rous sarcoma virus-directed chloramphenicol acetyltransferase (CAT) gene expression. Inhibition was also seen with RPMI 8402, which is a human CD4-positive lymphocyte line transiently transfected with a HIV-1 LTR-directed (CAT) gene. Experiments with HIV-1 LTR mutants suggest that transactivation response sequence but not NF-kappa B is responsible for the inhibition by camptothecin. The target for camptothecin may be a cellular factor that is important for the activation of HIV-1 LTR by Tat and thus may offer a potential target for therapy of HIV-1 infection.

beta-Lapachone, a novel DNA topoisomerase I inhibitor with a mode of action different from camptothecin

beta-Lapachone is a plant product that has been found to have many pharmacological effects. To date, very little is known about its biochemical target. In this study, we found that beta-lapachone inhibits the catalytic activity of topoisomerase I from calf thymus and human cells. But, unlike camptothecin, beta-lapachone does not stabilize the cleavable complex, indicating a different mechanism of action. beta-Lapachone inhibits topoisomerase I-mediated DNA cleavage induced by camptothecin. Incubation of topoisomerase I with beta-lapachone before adding DNA substrate dramatically increases this inhibition. Incubation of topoisomerase I with DNA prior to beta-lapachone makes the enzyme refractory, and treatment of DNA with beta-lapachone before topoisomerase has no effect. These results suggest a direct interaction of beta-lapachone with topoisomerase I rather than DNA substrate. beta-Lapachone does not inhibit binding of enzyme to DNA substrate. In cells, beta-lapachone itself does not induce a SDS-K(+)-precipitable complex, but it inhibits complex formation with camptothecin. We propose that the direct interaction of beta-lapachone with topoisomerase I does not affect the assembly of the enzyme-DNA complex but does inhibit the formation of cleavable complex.

Synthesis and cytotoxicity studies of novel cyclic peptide-2,6-dimethoxyhydroquinone-3-mercaptoacetic acid conjugates

In an effort to investigate the use of small-ring-size cyclic peptides as carriers of new antitumor agents, we synthesized three cyclic tripeptide-cytotoxic agent conjugates. The cytotoxic agent conjugated to the epsilon-amino group of the lysyl residue of the cyclic peptides is 2,6-dimethoxyhydroquinone-3-mercaptoacetic acid (DMQ-MA), (Sheh et al., 1992). The cyclic peptides were synthesized by coupling protected amino acid residues in solution and the subsequent cyclization performed by the pentafluorophenyl ester method as described previously (Sheh et al., 1985, 1987, 1990). After deblocking the lysyl-Z group of the peptides, the conjugation was achieved by reaction with the pentafluorophenyl ester of DMQ-MA. The three cyclic peptides exhibited potent cytotoxicity against two solid tumor cell lines (KB and PC-9) under the synergistic activation of L-ascorbic acid. Electron spin resonance (ESR) studies of DMQ-MA and two conjugates showed that massive hydroxyl radicals were generated as a non-linear function of L-ascorbic acid concentration. These studies indicate that the hydroxyl radical is a possible mediator of cytotoxicity for these conjugates and that small-ring-size cyclic peptides are potentially useful carriers of cytotoxic agents.

Augmentation of tumour delivery of macromolecular drugs with reduced bone marrow delivery by elevating blood pressure

Effects of angiotensin II (AT-II)-induced hypertension on the distribution of macromolecules to Walker carcinoma and to bone marrow of SMANCS [poly(styrene-co-maleic-acid)-neocarzinostatin conjugate] were investigated in rats. AT-II-induced hypertension from about 100 to 150 mmHg significantly increased the accumulation of the macromolecular drug SMANCS and 51Cr-labelled bovine serum albumin ([51Cr]BSA), representatives of macromolecular drugs, in tumour tissue. At 1 h after i.v. administration, intratumour concentrations of [51Cr]BSA and SMANCS were elevated by 1.2-1.8-fold. The higher drug accumulation in the tumour that was produced by the artificial hypertension was retained even 6 h after administration. This observation indicates an additive effect to that under normotensive conditions where intratumour macromolecular drug concentrations increase steadily during this period. Furthermore, distributions of these drugs in the bone marrow and the small intestine decreased during artificial hypertension to 60-80% of those in the normotensive state. Therefore, the drug concentration ratios of tumour/bone marrow and tumour/small intestine were increased by 1.8-2.4-fold. A decreased distribution of SMANCS to normal tissues under hypertensive conditions was also confirmed by the significant reduction of its toxicity e.g. leukopenia, diarrhoea, and body weight loss, even at a lethal dose. On the contrary, [3H]methylglucose showed no remarkable difference in tumour or bone marrow accumulation under this hypertensive condition. These results show the advantages of macromolecules over small molecules for AT-II-induced hypertension chemotherapy.

Three inhibitors of type 1 human immunodeficiency virus long terminal repeat-directed gene expression and virus replication

Transcription of type 1 human immunodeficiency virus (HIV-1) provirus is governed by the viral long terminal repeat (LTR). Drugs can block HIV-1 replication by inhibiting activity of its LTR. We report that topotecan, beta-lapachone, and curcumin are potent and selective inhibitors of HIV-1 LTR-directed gene expression, at concentrations that have minor effects on cells. At these concentrations, each drug inhibited p24 antigen production in cells either acutely or chronically infected with HIV-1. Their target is transcriptional function of the LTR.

[Mechanism of shen qian gujing granule in the treatment of menorrhagia]

Shen Qian Gujing Granule, a Chinese herbal preparation has shown its efficacy of 87.7% in treating menorrhagia. PGE2, PGE2 alpha, TXB2 and 6-Keto-PGF1 alpha levels were measured in the endometrium and menstrual blood of both normal menstrual women and patient with menorrhagia before and after the treatment. Local TXB2 values of endometrial and menstrual blood were significantly higher in menorrhagia patients than that in normal subjects (P < 0.05). And the local PGE2 values were higher in patients accompanied with Qi Deficiency (P < 0.05) and lower in patients without Qi Deficiency (P < 0.05). After the treatment, the local TXB2, PGE2 levels normalized. It suggests that Shen Qian Gujing Granule had a biphasic regulation on local PG values which yields good results for menorrhagia. Some mechanism were discussed.

Cytotoxicity studies on some novel 2,6-dimethoxyhydroquinone derivatives

Six synthetic 2,6-dimethoxyhydroquinone derivatives were shown to have different degrees of cytotoxicity to two human tumor cell lines (KB and PC-9) under the synergistic activation of L-ascorbic acid. Two representative compounds displayed very low time-schedule-independent index, showing that the cytotoxic action is independent of time of drug treatment. The addition of catalase produced a significant inhibitory effect on the cytotoxicity of two representative compounds, indicating that the cytotoxic action is mediated by the generation of H2O2, which may yield hydroxyl radicals via various mechanisms. ESR studies employing the spin-trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) showed that massive hydroxyl radicals were generated from four of these drugs as a non-linear function of L-ascorbic acid concentration. The results indicate the possible involvement of hydroxyl radicals in the cytotoxic action of these novel drugs.

The effects of perfusion of lateral ventricle with CaCl2 on the febrile response and cAMP content in plasma and cerebrospinal fluid during LP-induced fever

Artificial cerebrospinal fluid (c.s.f.) containing 40 mmol/L excess calcium was perfused through the lateral ventricles of New Zealand white rabbits in order to reduce the Na+/Ca++ ratio in the brain and the effects on both the febrile response and adenosine cyclic monophosphate (cAMP) concentration in plasma and c.s.f. during leucocytic pyrogen (LP)-induced fever were observed. The results showed that cAMP concentration in c.s.f. increased significantly during LP-induced fever while the cAMP level in Plasma remained unchanged, and the perfusion of artificial c.s.f. containing 40 mmol/L excess calcium can significantly inhibit not only the febrile response but also the increase in c.s.f. cAMP level, while there appears no effect on plasma cAMP concentration, thus demonstrating that the increase of Na+/Ca++ ratio causing the increase of cAMP content in the brain may be an essential link in the pathogenesis of LP-induced fever.

[On the standardization of new chemical risk evaluation with eye irritation test]

Three new chemicals, N-acyl glutamic acid as a stroma of cosmetics, an eye drops for myopia and 2, 4-dichloro-6-nitrophenylaminate (DCNP) as a new herbicide were evaluated with the eye irritation test. Japanese young rabbits were used, the right eye for test, the left as control. Before and after the test, the eye were stained with 2% sodium fluorescein and examined under slit-lamp microscope to observe the damage degree of cornea, and to record the reaction degree of conjunctiva and iris at the same time. Using the draize method to compare with three kinds of granding (method of bayard and hehir, of EPA and of NRC), the results were essentially the same. The severity of reaction to the eye irritation test is closely related to the kind of testing material and the concentration used and the length of time exposed. The standardization of eye irritation test is also discussed.

Clinical studies on bladder tumor-associated antigen in serum of patients with bladder cancer by using monoclonal antibody and sandwich ELISA

Investigations on tumor-associated antigen in the serum of patients with bladder cancer by using monoclonal antibody Hb 7A and sandwich ELISA were carried out on 36 patients with bladder cancer (BCa group), 18 patients with other tissue tumor (OTT group) and 22 normal subjects (control group). The average OD value of Hb 7A antigen of BCa group, OTT group and control group was 0.315 +/- 0.033, 0.124 +/- 0.026 and 0.12 +/- 0.021 respectively. The OD value of Hb 7A antigen in BCa group was significantly higher than that of control group and of OTT group (P less than 0.01), but there was no obvious difference between the control group and OTT group (P greater than 0.05). The positive detection rate in BCa group was 86% (31/36), while detection in all 22 normal subjects and the 18 patients of OTT group yielded negative results. The results indicated that the method of using McAb Hb 7A and sandwich ELISA, characterized by high specificity and sensitivity, is of value for clinical diagnosis and follow-up of patients with bladder cancer and general survey of persons at high risk of bladder cancer.

[Citation analysis of Acta Pharmacologica Sinica 1984-1989]

Citation analysis was made bibliometrically on the collection and dispersion of the references in Acta Pharmacologica Sinica 1984-1989. Core periodicals were sorted out: 31 in foreign languages and 6 in Chinese. Suggestions are proposed to the information services.

Effects of sodium salicylate on the febrile response and increased levels of cyclic AMP in cerebrospinal fluid during endogenous pyrogen-induced fever in rabbits

To further evaluate the causality between endogenous pyrogen (EP)-induced fever and cyclic adenosine-3',5'-monophosphate (cyclic AMP) level, the effects of sodium salicylate (SS) on the febrile response and increased levels of cyclic AMP in both cerebrospinal fluid (c.s.f.) and plasma during EP-induced fever in rabbits were observed. The results suggest that cyclic AMP is probably involved in the central mediation of EP-induced fever and that increased concentration of cyclic AMP in c.s.f. associated with EP-induced fever is not the result of temperature elevation but appears to be caused by the increased synthesis in the central nervous system. In addition it is confirmed that blood is impossibly a contributory source of increased cyclic AMP in c.s.f. during EP fever, and that SS may act subsequent to the increase in cyclic AMP.

[Hypothermic effect of intracerebroventricular injections of taurine on endotoxin-induced fever in rabbits]

Taurine (Tau) was infused by intracerebroventricular (icv) injection 20 min after iv endotoxin (ET). Cerebrospinal fluid was taken from the posterior cisterns at 0, 60, 210 and 390 min after Tau infusion. The concentrations of cAMP and PGE2 in the samples were determined by radioimmunoassay. In the control groups, an equivalent isotonic saline (NS) (non-pyrogenic) instead of Tau or ET was used respectively. The rectal and ear skin temperatures of the rabbits in a non-fasting state were recorded automatically. Tau icv 1.0 mg/50 microliters, followed by the slow infusion of Tau 0.06-0.22 mg/(kg.min) for about 20 min into rabbits, caused sedation and peripheral vasodilation (rise in ear skin temperature), and initially blocked the rise in rectal temperature induced by ET (iv, 1 micrograms/kg). The results for the control groups were significantly different from those of the ET + Tau group. In the ET + NS group, the fluctuations in concentrations of PGE2 and cAMP paralleled the change in rectal temperature, but in the ET + Tau group, the changes in PGE2 and cAMP concentrations were similar to those of the ET + NS group, even though the fever was initially inhibited. There were no changes in the concentrations of these mediators in the NS + Tau group.