Antiproliferative effects of isopentenylated coumarins isolated from Phellolophium madagascariense Baker

From the leaves of Phellolophium madagascariense Baker (Apiaceae), an endemic herb to Madagascar, three known coumarins (osthol, murraol and meranzin hydrate) have been isolated and identified. This is the first report of these compounds in this species. The structural elucidations were based on the analysis of physical and spectroscopic data. The anticancer activity of the three isolated compounds and of a synthetic sample of osthol was evaluated on L1210 mouse leukemia and on human prostatic cancer hormonosensitive LNCaP and hormonoindependent PC3 and DU145 cell lines.

Copper-dependent oxidative and topoisomerase II-mediated DNA cleavage by a netropsin/4'-(9-acridinylamino)methanesulfon-m-anisidide combilexin

A conjugate molecule was synthesized by linking the DNA-intercalative antitumor drug 4'-(9-acridinylamino)methanesulfon-manisidide (mAMSA) via a 4-carboxamide side chain to a dipyrrolecarboxamide moiety structurally related to the minor groove-binding antibiotic netropsin. The molecule (netropsin/ mAMSA) behaves as a threading intercalator. Its netropsin-like tail becomes located in the minor groove of the double helix and serves to drive the hybrid molecule preferentially to AT-rich sites on various DNA fragments as revealed by DNase I footprinting. The hybrid retains the susceptibility to copper-dependent oxidation characteristic of the parent mAMSA moiety as well as its ability to generate oxygen radicals, which can mediate DNA damage, mainly at cytidine and guanosine nucleotides. It also retains the property of stimulating the formation of cleavable complexes with DNA in the presence of topoisomerase II, but its netropsin-like moiety confers little or no influence on the reaction with topoisomerase I. Although netropsin/mAMSA is less potent than mAMSA at producing cleavable complexes with topoisomerase II, it promotes the appearance of cleavage sites at much the same nucleotide sequences as does the parent compound. The dipyrrolecarboxamide tail is not silent, however, since it modifies the concentration-dependence of cleavable complex formation.

[Conformational analysis of peptide antagonists in the design of pseudopeptide and non-peptide antagonists]

The comparative conformational analysis of four Substance P antagonists (NK1-) having different chemical structures allowed to formulate an hypothesis for a peptidic NK1 pharmacophore. The salient features of this pharmacophore (three aromatic groups and two carbonyl functions) belong to a beta-turn conformation. Thus, this kind of conformation might be the basis for the design of newer pseudo-peptidic and non-peptidic NK1 antagonists.

Pharmacological and functional characterisation of the wild-type and site-directed mutants of the human H1 histamine receptor stably expressed in CHO cells

A cDNA clone for the human histamine H1 receptor was isolated from a lung cDNA library and stably expressed in CHO cells. The recombinant receptor protein present in the cell membranes, displayed the functional and binding characteristics of histamine H1 receptors. Mutation of Ser155 to Ala in the fourth transmembrane domain did not significantly change the affinity of the receptor for histamine and H1 antagonists. However, mutation of the fifth transmembrane Asn198 to Ala resulted in a dramatic decrease of the affinity for histamine binding, and for the histamine-induced polyphosphoinositides breakdown, whereas the affinity towards antagonists was not significantly modified. In addition, mutation of another fifth transmembrane amino acid, Thr194 to Ala also diminished, but to a lesser extent, the affinity for histamine. These data led us to propose a molecular model for histamine interaction with the human H1 receptor. In this model, the amide moiety of Asn198 and the hydroxyl group of Thr194 are involved in hydrogen bonding with the nitrogen atoms of the imidazole ring of histamine. Moreover, mutation of Thr194 to Ala demonstrated that this residue is responsible for the discrimination between enantiomers of cetirizine.

Subcellular distribution of glycolyltransferases in rodent liver and their significance in special reference to the synthesis of N-glycolyneuraminic acid

The enzymic synthesis, transfer, and utilization of glycolyl-CoA (i.e. 2-hydroxyacetyl-CoA) have been studied in rat and mouse livers. On the one hand, these tissues contain the enzyme activities allowing the synthesis of glycolyl-CoA from fatty acids (palmitate omega-hydroxylase, omega-hydroxypalmitoyl-CoA synthetase, and mitochondrial beta-oxidation of omega-hydroxypalmitoyl-CoA) and 3-hydroxypyruvic acid (oxidation by intact mitochondria). On the other hand, three types of glycolyltransferase activities can be demonstrated in rodent livers, depending on either carnitine, glucosamine, or glucosamine-6-phosphate. The subcellular distributions of these glycolyltransferase activities are similar to those of the corresponding acetyltransferase counterparts. Concerning carnitine glycolytransferase, the activity is widely distributed in the subcellular fractions, pointing out its occurrence in most cell compartments. By contrast, the glucosamine and glucosamine-6-phosphate glycolytransferase activities were located preferentially in the microsomal fraction. The condensation between glycolyl-CoA and glucosamine (or glucosamine-6-phosphate) raises the interesting question of the nature and the role of the resulting glycolylglucosamine molecule, especially in an alternative N-glycolylneuraminic acid synthesis pathway.

DNA-binding properties of a distamycin-ellipticine hybrid molecule

We have synthesized a distamycin-ellipticine hybrid compound and investigated its interaction with DNA, using various optical and gel electrophoresis techniques. Binding of the hybrid to DNA is evidenced by spectral shifts, fluorescence quenching, and induced linear dichroism. Absorbance measurements have been used to generate Scatchard plots, which reveal that the interaction cannot be described adequately in terms of a single binding mode, probably because of simultaneous intercalation and minor groove binding of the ligand. Competition with added distamycin has been used to verify involvement of the N-methyl-pyrrole portion of the hybrid molecule in the binding reaction. From electric linear dichroism experiments, it is estimated that the orientation of the DNA-bound ellipticine chromophore in the hybrid differs by about 10 degrees from the orientation of the equivalent chromophore lacking a distamycin tail. Topoisomerase assays establish that binding of the hybrid unwinds the DNA helix by a minimum of 11 degrees, which is consistent with intercalation but notably smaller than the unwinding angle of ellipticine. In footprinting experiments, it is found that the AT- and GC-specificity of distamycin and ellipticine, respectively, appear to be merged in the binding of the hybrid, which produces a pattern of protection distinct from the characteristic patterns for either of the parent compounds. The hybrid is an extremely effective inhibitor of cutting by DNase I.

The coordination of copper(II) to 1-hydroxy-4-(glycyl-histidyl-lysine)-anthraquinone; a synthetic model of anthraquinone anti-cancer drugs

Results are reported of a pH-metric and spectroscopic (CD and ESR) study of the complexes formed between the pseudo-peptide 1-hydroxy-4-(Gly-His-Lys)-anthraquinone (Q-GHK) since, when complexed to copper ions, Q-GHK has been shown to be very effective in promoting the formation of free radicals and inducing DNA cleavage. Q-GHK forms very stable complexes with copper, the major species being bonded to three nitrogen donors in the coordination plane: an imidazole-N of the His residue and the peptide nitrogens of the Gly and His residues. This species is probably stabilized through bonding of the fourth planar coordination site of Cu(II) to the 9-anthraquinone oxygen. At high Q-GHK:copper ratios a second Q-GHK molecule is coordinated through its imidazole-N donor.

Comparison between synthetic nuclear localization signal peptides from the steroid/thyroid hormone receptors superfamily

The main objective of the study is to demonstrate that short basic peptides from the steroid/thyroid hormone receptors superfamily act as Nuclear Localization Signals out of receptors context. Such synthesized peptides, chemically coupled to Bovine Serum Albumin, were shown to enable the corresponding BSA-conjugate to be transported to the nucleus. A second objective is to demonstrate the utility of viral cointernalization as a good method for rapid quantitation, comparison and competition in nuclear entry.

Antagonistic effect of a vasoactive intestinal peptide fragment, vasoactive intestinal peptide(1-11), on guinea pig trachea smooth muscle relaxation

The conformation of various regions of vasoactive intestinal peptide (VIP) has been analyzed by semiempirical methods, CD, and NMR spectroscopy, indicating that residues 11-21 are most likely to be helical, whereas the amino-terminal portion VIP(1-11) could exhibit two beta-turn structures. VIP(1-11) inhibits 125I-VIP binding to intact guinea pig tracheal epithelial cells and the VIP-induced smooth muscle response. However, the endecapeptide exhibits no effect on the muscle tone. All these data suggest that VIP(1-11) may be a useful tool in studying VIP receptor recognition, its regulation, and cellular functions.

[Metabolic treatment of cancer]

The aim of the metabolic therapy of cancer is to cure the disease by interfering with metabolism, and not with, as is the case in classical chemotherapy, the genotype of the cancer cell. Current advance and perspective in this novel topic are here presented.

Design, synthesis, DNA binding, and biological activity of a series of DNA minor-groove-binding intercalating drugs

A group of pseudopeptides, molecular combination of the natural antitumor agents distamycin or netropsin and the anilinoacridine chromophore (which is related to the synthetic antileukemic drug amsacrine) has been synthesized. Their DNA binding properties were determined and discussed in terms of their structural differences and in relation to their observed base-dependent binding. Binding data are consistent with a model in which the acridine nucleus occupies an intercalation site and the netropsin or distamycin residue resides in the DNA minor groove. Cytostatic and cytotoxic activities against a murine cell line are reported, as well as significant differences in the inhibition of DNA synthesis.

2,3-bis(2-pyridyl)-5,8-quinoxalinediones with metal chelating properties: synthesis and biological evaluation

The synthesis of 2,3-bis(2-pyridyl)-5,8-quinoxalinediones has been carried out in order to provide new antitumor drugs related to streptonigrin. Some derivatives have been found to possess significant cytotoxic properties and their mechanism of action has been studied. They were found to induce single-strand cleavage of covalently closed circular DNA (ccc-DNA). This biological activity requires an apparent in situ reduction (NADH activation) of the quinone to a hydroquinone or semiquinone radical, is facilitated by the presence of Cu(II), and involves activation of molecular oxygen to highly reactive radical species. Thus, although less active than the parent drugs, these molecules provide an attractive rationale for the observed cytotoxic and antitumor potency, as well as the cell-free single strand DNA cleavage efficacy of that family of drugs.

DNA-synthesis and tumor growth inhibitions by AGGA, a bleomycin-amsacrine hybrid derivative

AGGA, [[(amino-2-ethyl)-2-aminomethyl]-2-pyridine-6-carboxylhistidyl-ami no-4- butyrylglycylamino]-4-phenyl-1-amino-9-acridine is a synthetic model gathering the simplified metal-chelating part of bleomycin and the intercalating moiety of amsacrine. This molecule was found to possess the metal-complexing and intercalative properties of both antitumor parent drugs. On the basis of results obtained on L1210 and HeLa S3 cells growth inhibition studies and labeled thymidine assay, AGGA clearly indicates a cytostatic activity. On the other hand, the oxygenated free radicals produced in the presence of iron and oxygen do not seem to be able to cleave DNA as BLM does. This lack of cytotoxicity is analyzed in terms of fundamental differences between BLM and AGGA-DNA complexes.

Bistramide A, a new toxin from the urochordata Lissoclinum bistratum Sluiter: isolation and preliminary characterization

Two cases of human intoxication caused by the lyophilized powder of Lissoclinum bistratum Sluiter, a New Caledonian ascidian, are reported. The symptoms observed were caused by a substance designated bistramide A (C40H68N2O8) of hitherto unknown chemical structure. Preliminary toxicological investigations indicate that bistramide A may effect the central nervous system, leading to paresthesia and loss of muscle tone. A progressive decrease in cardiac rhythm was also observed in animals. Bistramide A (1.4 x 10(-6) M) did not alter the resting potential of frog heart and skeletal muscle but reduced the amplitude and duration of cardiac action potential and prolonged the interval between action potentials. Bistramide A also has a marked cytotoxic effect on cancer cells KB (IC50 = 4.5 x 10(-8) M) and P 388 (IC50 = 2.0 x 10(-8) M) and on normal endothelial cells (IC50 = 2.2 x 10(-8) M). However, it has not been possible to relate the cytotoxic property to the symptoms of intoxication. Bistramide A may originate from the urochordate itself or from symbiotic algae.

Cytotoxic action and cell cycle effects of ALGA, a peptidic derivative of the antileukemic drug amsacrine

4'-(9-acridinylamino) methanesulfon-m-anisidide (amsacrine or AMSA), an antitumor drug which has been tested in clinical trials, is known to bind to DNA by the intercalation of its 9-amino acridine moiety between DNA base pairs. Like AMSA, a peptidic derivative of 4-(9-acridinylamino) aniline, 4-(9-acridinylamino)-N-(lysylglycyl) aniline (ALGA) binds to DNA by intercalation and its affinity for the target was found to be higher than the parent drug. The antitumor effect of AMSA and ALGA has been monitored by drug exposure assays on EMT 6 cells. AMSA showed a slightly higher cytotoxic activity. The cell cycle effects of both drugs were studied using flow cytofluorimetry; an accumulation of cells in the S phase followed by a cycle arrest in the G2 phase, characteristic of intercalating drugs, was observed.

Grossularine-1 and grossularine-2, alpha carbolines from Dendrodoa grossularia, as possible intercalative agents

Dendrodoine A, grossularines-1 and -2, metabolites isolated from the tunicate Dendrodoa grossularia, have exhibited a cytotoxic activity on L1210 leukemia cells in culture. The inhibition of DNA synthesis induced by grossularines and the plane structure of the alpha-carboline common moiety were in favor of an intercalative process for their mechanism of action. In fact, the results of viscometry, fluorescence quenching and DNA melting experiments clearly indicated the intercalative properties of grossularine-2 explained by its quasi-planar structure and the non-intercalative DNA binding of grossularine-1 explained by the presence of a bulky indole chain at the 2-position of the alpha-carboline ring.

A new bithiazole derivative with intercalative properties

In the course of studies related to new molecules with intercalative properties, we have been led to design and synthesize a bithiazole derivative, namely the 2-phenyl-6-[2'-(4'-(ethoxy-carbonyl)thiazolyl)]thiazolo[3,2- b][1,2,4]triazole (PETT). Its interaction with calf thymus DNA was studied using thermal denaturation and viscometry. Our results set in evidence that PETT acts as an intercalator, giving delta Tm, elongation and unwinding of DNA comparable to the values obtained for daunorubicin. The discrepancy between the data presented herein and those precedently obtained for bleomycin and bleomycin models provide evidence that these bithiazole derivatives interact differently with DNA.

Opiate receptor interaction of a new analgesic drug 2-piperidinoethyl dibenzylglycolate

The pharmacological properties of a new analgesic drug, 2-piperidinoethyl dibenzylglycolate (PDG), have been demonstrated by classical tests. The technique of iontophoresis was used in order to compare the effects of PDG with those of Tyr-D-Ser-Gly-Phe-Leu-Thr (DSTLE), syndyphalin, morphine and naloxone (NAL) on hypothalamic neurones. PDG as other four substances evoked only inhibitory responses. Some neurones, on which were tested three substances, were sensitive to one, two or three of these substances. The differential responses so obtained suggested that PDG does not act on mu- and delta-receptors but on an unidentified receptor for which morphine and NAL have a high affinity as agonist. Structural requirements for activity on different receptors were also proposed on the basis of crystallographic data and the above results.

Subcellular distribution of spin-labeled bithiazoles and bleomycin in living KB cells: an ESR study

Spin-labeled derivatives of bithiazole and bleomycin were studied with respect to their uptake and localization in KB cells in vivo. It was found that the amidification of the C-terminal carboxylic group of bleomycinic acid was essential for the penetration of the probes in the cells and that the subcellular localization depended on the number and spacing of positively charged groups.

Design, synthesis and DNA-binding capacity of a new peptidic bifunctional intercalating agent

A lysyl-lysine bifunctional derivative of 9-aminoacridine has been synthesized and its DNA-binding capacity established by electron-paramagnetic-resonance study. For this purpose the binding parameters of a spin-labelled aminoacridine probe were estimated and the affinities of the lysylacridinyl-lysyldiamino-octane dimer and of 9-amino-acridine could be evaluated by competitive assays. The competition study provided quantitative results concerning the dissociation constant (KD) of the dimer. The obtained value was closely similar to the KD of 9-aminoacridine determined by the same method and to the KD previously reported for the anti-tumour and antibiotic bifunctional intercalator quinomycins.

Synthesis and structure--activity relationship of a pyrimido[4,5-d]pyrimidine derivative with antidepressant activity

The synthesis and antidepressant properties of a new pyrimido[4,5-d]pyrimidine are described. Spectral data determined in solution and in the solid state allowed establishment of the relationship between the activity and the conformation of the molecule. The spatial structure seems to be in accordance with a possible binding at the presynaptic alpha-receptor sites.