Potentiation of the cytostatic effect of bleomycin on L5178y mouse lymphoma cells by pepleomycin

A new benzophenone glycoside from the leaves of Mitracarpus villosus

A new benzophenone glycoside, mitraphenone A (1), together with three known compounds (2-4) were isolated from the leaves of the traditionally used medicinal plant Mitracarpus villosus (Rubiaceae) collected in Nigeria. A combination of one- and two-dimensional NMR spectroscopic and mass spectrometric measurements were carried out to identify the structure of 1. All isolated compounds (1-4) were screened for their antibacterial activity against several Gram-positive and Gram-negative bacteria. Compound 1 exhibited moderate activity against Enterococcus faecium (strains ATCC 35667 and ATCC 700221) and Staphylococcus aureus ATCC 25923 with MIC values ranging from 25 to 50 μM.

Inhibition of Formation of Rev-RRE Complex by Pyronin Y

The interaction of pyronin Y, an RNA intercalating drug, with the binding of Rev protein from human immunodeficiency virus type 1 (HIV-1) to Rev-responsive element (RRE)-containing env RNA was studied. In gel retardation assays, recombinant Rev protein tightly bound to in vitro transcribed RRE RNA. Nitrocellulose-filter-binding studies revealed a dissociation constant of ≈(1–2) = 10−10M (Pfeifer et al., 1991). Pyronin Y efficiently suppressed formation of the Rev-RRE complex. At a concentration of 1 μg ml−1, complex formation was almost completely inhibited. Electron microscopy showed that Rev oligomerizes in the presence of RRE-containing RNA with the formation of short rod-like structures or long filaments, depending on the length of the transcript. Assembly of Rev protein along RRE-containing RNAs was abolished after addition of pyronin Y. Thus pyronin Y represents the first compound described to inhibit Rev-RRE complex formation.

Targeted solid phase fermentation of the soil dwelling fungus Gymnascella dankaliensis yields new brominated tyrosine-derived alkaloids

Seven new brominated alkaloids, gymnastatins T–Y (1–6) and dankastatin D (7), together with three known analogues were isolated from the soil fungus Gymnascella dankaliensis through fermentation on solid rice mediumcontaining NaBr.

Sorbicillactone A: a structurally unprecedented bioactive novel-type alkaloid from a sponge-derived fungus

This chapter deals with the discovery of sorbicillactone A, as an illustrative example of the fruitful cooperation within BIOTECmarin--its isolation and chemical characterization, and its biological activities. Sorbicillactone A was isolated from a strain of Penicillium chrysogenum cultured from a sample of the Mediterranean sponge Ircinia fasciculata; it possesses a unique bicyclic lactone structure, seemingly derived from sorbicillin. Among the numerous known sorbicillin-derived structures, it is the first found to contain nitrogen and thus the first representative of a novel type of 'sorbicillin alkaloids', apparently originating from a likewise remarkable biosynthesis. Furthermore, the compound exhibits promising activities in several mammalian and viral test systems, in particular a highly selective cytostatic activity against murine leukemic lymphoblasts (L5178y) and the ability to protect human T cells against the cytopathic effects of HIV-1. These properties qualify sorbicillactone A or one of its derivatives for animal and (hopefully) also future therapeutic human trials.

Modulation of intracellular calcium and proliferative activity of invertebrate and vertebrate cells by ethylene

BACKGROUND

Ethylene is a widely distributed alkene product which is formed enzymatically (e.g., in plants) or by photochemical reactions (e.g., in the upper oceanic layers from dissolved organic carbon). This gaseous compound was recently found to induce in cells from the marine sponge Suberites domuncula, an increase in intracellular Ca2+ level ([Ca2+]i) and an upregulation of the expression of two genes, the potential ethylene-responsive gene, SDERR, and a Ca2+/calmodulin-dependent protein kinase.

RESULTS

Here we describe for the first time, that besides sponge cells, mammalian cell lines (mouse NIH-3T3 and human HeLa and SaOS-2 cells) respond to ethylene, generated by ethephon, with an immediate and strong, transient increase in [Ca2+]i level, as demonstrated using Fura-2 imaging method. A rise of [Ca2+]i level was also found following exposure to ethylene gas of cells kept under pressure (SaOS-2 cells). The upregulation of [Ca2+]i was associated with an increase in the level of the cell cycle-associated Ki-67 antigen. In addition, we show that the effect of ethephon addition to S. domuncula cells depends on the presence of calcium in the extracellular milieu.

CONCLUSION

The results presented in this paper indicate that ethylene, previously known to act as a mediator (hormone) in plants only, deserves also attention as a potential signaling molecule in higher vertebrates. Further studies are necessary to clarify the specificity and physiological significance of the effects induced by ethylene in mammalian cells.

Sarcophytolide: a new neuroprotective compound from the soft coral Sarcophyton glaucum

Bioactivity-guided fractionation of an alcohol extract of the soft coral Sarcophyton glaucum collected from the intertidal areas and the fringing coral reefs near Hurghada, Red Sea, Egypt resulted in the isolation of a new lactone cembrane diterpene, sarcophytolide. The structure of this compound was deduced from its spectroscopic data and by comparison of the spectral data with those of known closely related cembrane-type compounds. In antimicrobial assays, the isolated compound exhibited a good activity towards Staphylococcus aureus, Pseudomonas aeruginosa, and Saccharomyces cerevisiae. Sarcophytolide was found to display a strong cytoprotective effect against glutamate-induced neurotoxicity in primary cortical cells from rat embryos. Preincubation of the neurons with 1 or 10 microg/ml of sarcophytolide resulted in a significant increase of the percentage of viable cells from 33 +/- 4% (treatment of the cells with glutamate only) to 44 +/- 4 and 92 +/- 6%, respectively. Administration of sarcophytolide during the post-incubation period following glutamate treatment did not prevent neuronal cell death. Pretreatment of the cells with sarcophytolide for 30 min significantly suppressed the glutamate-caused increase in the intracellular Ca2+ level ([Ca2+]i). Evidence is presented that the neuroprotective effect of sarcophytolide against glutamate may be partially due to an increased expression of the proto-oncogene bcl-2. The coral secondary metabolite, sarcophytolide, might be of interest as a potential drug for treatment of neurodegenerative disorders.

Anti-HIV-1 activity of inorganic polyphosphates

Human blood plasma, serum, peripheral blood mononuclear cells, and erythrocytes contain significant amounts of inorganic polyphosphates (ranging from 53 to 116 microM, in terms of phosphate residues). Here we demonstrate that at higher concentrations linear polyphosphates display cytoprotective and antiviral activity. Sodium tetrapolyphosphate and the longer polymers, with average chain lengths of 15, 34, and 91 phosphate residues, significantly inhibited human immunodeficiency virus type 1 (HIV-1) infection of cells in vitro at concentrations > or = 33.3 microg/ml (> or = 283-324 microM phosphate residues), whereas sodium tripolyphosphate was ineffective. In the tested concentration range, these compounds had no effect on cell growth. The longer-chain polyphosphates (polyphosphates with mean chain lengths of 15 and 34) but not sodium tripolyphosphate and sodium tetrapolyphosphate also inhibited HIV-1-induced syncytium formation at a concentration of 160 microg/ml (1.51-1.54 mM phosphate residues). The results obtained with the syncytium assay and by cell-virus binding experiments indicate that the anti-HIV effect of these nontoxic polyanions may be caused by binding of the compounds to both the host cell surface and the virus, thereby inhibiting adsorption of the virus. Competition experiments revealed that binding of [32P]polyphosphate to Molt-3 cells was only partially inhibited by the antibody OKT4A.

Pulmonary toxicity of the combination of bleomycin and peplomycin--an experimental study in rats

Combination of the two drugs bleomycin (BLM) and peplomycin (PEP) may enhance their antineoplastic effects; however, it is not known as to whether this enhancement is accompanied by a concomitant increase in toxicity, especially toxic lung damage. A histologic and stereologic investigation was carried out to compare the pulmonary toxicity of BLM, PEP, and a combination of the two drugs in animals. A total of 180 female Wistar rats were randomly assigned to 4 groups: 45 animals were treated with daily i.p. injections of 4 mg/kg BLM, 45 rats received 2.5 mg/kg i.p. PEP daily, 45 animals were given i.p. injections of a combination of 2.5 mg/kg BLM and 1 mg/kg PEP, and 45 rats received 1 ml 0.9% NaCl solution. Histological examination of the lungs demonstrated varying degrees of exudative and fibrosing alveolitis in animals treated with BLM, PEP, and BLM-PEP. Stereological analysis revealed a significant thickening of the alveolar wall after 20-60 days and a significant decrease in the surface density of alveolar walls after 40-60 days in all treated groups. Both histological examination and stereological parameters indicated more pronounced inflammatory changes in the alveolar walls and a prior loss of alveolar surface after 20 and 30 days in animals receiving PEP and PEP-BLM as compared with those undergoing BLM treatment. After 40-60 days, during which time irreversible fibrotic changes prevailed, significant stereological differences between the three treated groups could not be detected. Thus, our experimental observations did not show any potentiation of the toxic pulmonary effect of BLM and PEP following their combined administration.

Potent inhibition of hepatitis B virus production in vitro by modified pyrimidine nucleosides

2',3'-Dideoxy-3'-fluorothymidine (FddThd), 2',3'-didehydro-2',3'- dideoxythymidine (ddeThd), and 3'-fluoro-5-methyl-deoxycytidine (FddMeCyt) are, in their triphosphate forms, selective inhibitors of human immunodeficiency virus type 1 reverse transcriptase. We report that 0.3 microM FddThd, FddMeCyt, or ddeThd as well as 3'-chloro-5-methyl-deoxycytidine (ClddMeCyt) or 3'-amino-5-methyl-deoxycytidine (AddMeCyt) almost completely blocked production of hepatitis B virus (HBV) particles by HBV DNA-transfected cell line 2.2.15 in vitro. Only at an at least 10-fold-higher concentration was a cytotoxic effect observed. These results indicate that FddThd, FddMeCyt, ClddMeCyt, AddMeCyt, and ddeThd are potent anti-HBV agents in vitro.

Inhibition of intrinsic protein tyrosine kinase activity of EGF-receptor kinase complex from human breast cancer cells by the marine sponge metabolite (+)-aeroplysinin-1

1. (+)-Aeroplysinin-1, a naturally occurring tyrosine metabolite from the marine sponge Verongia aerophoba, was found to inhibit the phosphorylation of lipocortin-like proteins by a highly purified preparation of the epidermal growth factor (EGF) receptor-tyrosine protein kinase complex from MCF-7 breast carcinoma cells. 2. (+)-Aeroplysinin-1 blocked the EGF-dependent proliferation of both MCF-7 and ZR-75-1 human breast cancer cells and inhibited the ligand-induced endocytosis of the EGF receptor in vitro. 3. Treatment with aeroplysinin-1 in the concentration range at 0.25-0.5 microM resulted in a time- and dose-dependent total tumor cell death in vitro. 4. At a 10-fold higher concentration the compound did not reveal any cytostatic activity in normal human fibroblasts. 5. From these data we conclude that (+)-aeroplysinin-1 represents a compound which displays a strong anti-tumor effect on EGF-dependent tumor cell lines.

Treatment of human clonogenic tumor cells and bone marrow progenitor cells with bleomycin and peplomycin under 40.5 degrees C hyperthermia in vitro

Tumor cells derived from 13 different individual human tumors were plated in a colony forming monolayer assay. The effect of bleomycin and peplomycin on colony formation was assessed in normothermic conditions and after a hyperthermic treatment at 40.5 degrees C for 2 h at the beginning of the culture. In three out of the 13 tumor samples (two colon carcinomas, one malignant melanoma), hyperthermic incubation resulted in a thermal enhancement of the effects of bleomycin and peplomycin. In addition, human bone marrow progenitor cells (CFU-C) were subjected to the same procedure. Peplomycin proved to be less toxic to CFU-C than bleomycin. In samples from eight different donors, homogeneous dose-response curves were observed. There was no difference between normo- and hyperthermic incubation.

Differential modulation of host cell and HIV gene expression by combinations of avarol and AZT in vitro

Human immunodeficiency virus type 1 (HIV-1) gene expression is modulated by some virus-encoded proteins, possibly acting at multiple levels of control, which are also known to be involved in the regulation of gene expression in uninfected cells (transcriptional, post-transcriptional, nucleocytoplasmic transport, and translational control). Two anti-HIV-1 drugs, Avarol and 3'-azido-3'-deoxythymidine, which inhibit viral replication by differential mechanisms, were used to study the role of cytoplasmic factors in independent regulation of host cell and viral gene expression. Both drugs were found to inhibit viral replication and synthesis of virus-encoded protein in a synergistic manner, while at cytostatic concentrations, both compounds act antagonistically. ATP-induced transport of viral messengers from isolated nuclei is enhanced by total cytosolic protein from HIV-1-infected cells; a strong increase of the nucleocytoplasmic transport of pol mRNA was measured and, to a lesser extent the transport of certain cellular mRNA (e.g. interleukin-2) was augmented, while the transport of other cellular mRNA (actin) was not affected at all.

Comparison of bleomycin and peplomycin toxicity on clonogenic tumor cells from various human tumors

The cytotoxic effect of bleomycin and peplomycin was compared using a methylcellulose monolayer assay for the cultivation of human tumor cells. In 3 out of 4 samples from human malignant melanomas peplomycin proved to be more cytotoxic than bleomycin. Peplomycin was more cytotoxic than bleomycin in 1 of 5 myosarcoma samples, whereas 2 samples from squamous cell carcinomas of the lung showed identical dose response curves. In 1 carcinoma of the gall bladder peplomycin was more toxic than bleomycin.

Avarol, a cytostatically active compound from the marine sponge Dysidea avara

A main metabolic product of the sponge Dysidea avara was isolated and purified and subsequently identified as avarol by applying a series of analytical techniques, e.g. [13C]NMR, [1H]NMR and i.r. spectroscopy. This sesquiterpenoid hydroquinone was found to possess strong cytostatic activity. Using the L5178y mouse lymphoma cell system in vitro (roller tube assays) avarol reduced cell growth to 50% at a concentration of 0.9 microM. Avarol treated cells did not show "unbalanced growth". Avarol interfered with mitotic processes, preventing telophase formation. Incorporation studies with precursors for DNA, RNA, protein and glycoprotein syntheses revealed increased incorporation rates in response to avarol treatment. From these results and further autoradiographical experiments it is suggested that inhibition of cell growth is due to changes of the intracellular pools and/or alterations of the permeability properties of the cell membrane for the precursors. Avarol diacetate caused the same cytostatic effect as avarol.

Differential stimulation of lymphocyte cell growth in vitro by cephalosporins

The in vitro effect of three cephalosporins (cefodizime, cefotaxime, and ceftizoxime) on the growth of the following lymphocytes or their derivatives was tested: L 5178y mouse lymphoma cells, Molt-4 cells, and murine splenic lymphocytes. Within the concentration range of 0.1 to 50 microM, the cephalosporins had no effect on L 5178y cell growth. However, Molt-4 cell growth was significantly stimulated by 0.3 to 20 microM cefotaxime and cefodizime but was not influenced by ceftizoxime. Binding studies with [14C]cefotaxime revealed that the Molt-4 cells responding to the drug bind this cephalosporin to their cell surface (1.9 X 10(5) molecules per cell); no significant binding was observed in the assays with L 5178y cells. Determinations of the extractable activities of DNA-synthesizing enzymes from cefodizime-treated Molt-4 cells showed a direct correlation between cell growth and DNA polymerase alpha as well as terminal deoxynucleotidyl transferase activity; the DNA polymerase beta activity remained unchanged. Cefodizime (0.15 to 50 microM) which was added to mouse spleen cell cultures significantly increased [3H]thymidine incorporation into lymphocytes. This stimulatory effect was less pronounced in concanavalin A-stimulated cultures. These findings suggest that some cephalosporins display a growth-stimulating influence on some lymphocyte populations.

Induction of DNA polymerase alpha and terminal deoxynucleotidyl transferase in the human lymphoblastoid cell line Molt-4 by the immunomodulator bestatin

The influence of the immunomodulator bestatin on the expression of terminal deoxynucleotidyl transferase and of DNA polymerase alpha and beta in Molt-4 cells has been studied. Bestatin was found to stimulate cell growth within the range of 0.3-33 microM, while concentrations higher than 300 microM were inhibitory during an incubation period of 48 h. The cell surface bound microsomal leucine aminopeptidase (bestatin receptor) activity decreased gradually during incubation at concentrations of bestatin above 3 microM. This effect was also observed after incubation with amastatin, but not with leupeptin or tunicamycin. Determinations of the activities of DNA synthesizing enzymes from bestatin-treated Molt-4 cells revealed a direct correlation between the decrease of the surface bound microsomal leucine aminopeptidase activity and the increase of the terminal deoxynucleotidyl transferase and DNA polymerase alpha activity; the DNA polymerase beta activity remained unchanged. From these experiments it is hypothesized that bestatin might cause a promoting effect on the differentiation processes of precursor T cells in vivo.

Clavines. New antibiotics with cytostatic activity

The cytostatic potentials of ten ergolines were determined in the L5178y mouse lymphoma cell system; six of them belong to the clavines (agroclavine, 1-propyl-agroclavine, 1-propyl-festuclavine, 1-allyl-festuclavine, 6-cyano-6-nor-festuclavine and 1-hydroxymethyl-festuclavine) and four to the lysergic acid derivatives (methylergometrine, lysergic acid amide, isolysergic acid amide and lysergic acid diethylamide). It is shown that agroclavine (ED50: 3.9 microM), 1-propyl-agroclavine (3.5 microM), 1-propylfestuclavine (4.3 microM) and 1-allyl-festuclavine (4.3 microM) are potent cytostatic agents. Up to 2 X ED50 concentration the inhibitory effect was completely reversible. Incorporation studies suggested that the compounds inhibit DNA synthesis; this assumption was also supported by the findings which revealed that after incubation with these clavines, the cells showed slight 'unbalanced growth'. 6-Cyano-6-nor-festuclavine was less inhibitory (ED50 11.8 microM). 1-Hydroxymethyl-festuclavine and all lysergic acid derivatives tested were without any detectable activity.