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C Paoletti

Publications and source records attributed to C Paoletti.

At least 73 records · Page 4Linked to original sources
PubMed1986

Peroxidase-catalyzed covalent binding of the antitumor drug N2-methyl-9-hydroxyellipticinium to DNA in vitro.

In the presence of DNA, the antitumor drug N2-methyl-9-hydroxyellipticinium (elliptinium; NMHE) [Le Pecq, J. B., Gosse, C., Dat-Xuong, N., & Paoletti, C. (1975) C. R. Seances Acad. Sci., Ser. D 281, 1365-1367] is oxidized by the horseradish peroxidase-hydrogen peroxide (HRP-H2O2) system to the quinone imine derivative N2-methyl-9-oxoellipticinium (NMOE) [Auclair, C., & Paoletti, C. (1981) J. Med. Chem. 24, 289-295], which interacts with DNA according to the intercalation mode. When excess H2O2 was used, the major part of the quinone imine was further oxidized to the o-quinone N2-methyl-9,10-dioxoellipticinium [Bernadou, J., Meunier, G., Paoletti, C., & Meunier, B. (1983) J. Med. Chem. 26, 574-579]. In the presence of stoichiometric amounts of H2O2 (H2O2/NMHE = 1), NMOE reacts with DNA, yielding a fluorescent compound irreversibly linked to the nucleic acid, which is related to the covalent binding of the ellipticinium chromophore. Under optimal reaction conditions, NMHE binding occurs according to a first-order process (k = 4.3 X 10(-3) min-1) with a linear increase with respect to drug to nucleotide ratio up to a maximum binding of 1 NMHE per 20 base pairs (r = 0.05). The fluorescence spectra (ex, 330 nm; em, 548 nm) of NMHE bound to DNA, the occurrence of energy transfer from the DNA to the drug, and the DNA length increase of the DNA-NMHE adduct suggest that the binding occurs at the intercalating site with limited denaturation of the DNA helix.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaloids↗
PubMed1986

Efficient breakage of DNA apurinic sites by the indoleamine related 9-amino-ellipticine.

The aromatic amine, 9-NH2-ellipticine, is a synthetic DNA intercalating derivative of the antitumor agent ellipticine, which breaks circular DNA containing apurinic sites. This breakage is inhibited when the apurinic (AP) sites are reduced. The concentration of 9-NH2-ellipticine required to get a significant effect (0.1 microM) is the lowest known among chemicals which induce the same breakage reaction. Comparison with the action of structurally related amines shows that the amino-indole structure is specific for AP sites. The ability of ellipticine derivatives to induce breakage in DNA containing apurinic sites is related to the nucleophile substituent in position 9. Two ellipticine derivatives with known antitumor activity, BD 40 and 9-OH-ellipticine, were able to break purified DNA at apurinic sites.

Alkaloids↗
PubMed1986

Uptake, cytofluorescence, and cytotoxicity of oxazolopyridocarbazoles (amino acid-ellipticine conjugates) in murine sarcoma cells.

The uptake, cytofluorescence, and cytotoxicity of elliptinium (NMHE) and a series of fluorescent oxazolopyridocarbazoles [amino acid-ellipticine conjugates (AA-NMHE)] were studied in murine sarcoma cells. For all these drugs, the uptake was rapid, directly proportional to the drug concentration, and unaffected by metabolic inhibitors which is consistent with a diffusion mechanism. By 4 h, the intracellular concentration of NMHE exceeded the external drug concentration by about 100 times; this suggests that the toxicity of NMHE is not, as previously assumed, limited by its transport across tumor cell membranes. Conjugation of NMHE with aliphatic amino acids increased the cellular uptake 5- to 7-fold. Cellular exposure to AA-NMHE conjugates resulted in the appearance of granular cytoplasmic fluorescence which was readily translocated to the nucleus upon continued exposure to fluorescent light. The cytotoxicity of the AA-NMHE conjugates (drug concentration required to reduce colony formation by 63% on the exponential part of the survival curve = 3-14 microM) was less than of NMHE (drug concentration required to reduce colony formation by 63% on the exponential part of the survival curve = 0.7 microM) as shown by colony formation following 4 h drug exposure. In contrast, the isoleucine-NMHE conjugate was the most cytotoxic compound (drug concentration required to reduce colony formation by 63% on the exponential part of the survival curve = 0.045 microM) when the drug exposure period was extended to 8 days. The general lower toxicity of the AA-NMHE conjugates is likely due to loss of the phenolic character of the NMHE moiety; therefore, attempts to link NMHE to amino acids remain attractive but will have to be done without affecting the 9-hydroxy group of NMHE.

Alkaloids↗
PubMed1985

A revised structure of the antitumor drug elliptinium--amino(acid) adducts.

Using simple organic reactions and spectrometric techniques (nuclear magnetic resonance and mass spectrometry), we propose a revised structure of the adducts obtained through the H2O2-peroxidase oxidation of the antitumor drug ellipticinium and aliphatic amino(acid) compounds. These derivatives display an oxazole ring structure between the O(9)- and N(10)- atoms.

Alkaloids↗
PubMed1985

Selective binding of elliptinium acetate onto the 3'-terminal ribose of diribonucleosides monophosphates.

We report the full structure of two elliptinium diribonucleosides monophosphate adducts: the oxidized form of this antitumor agent alkylates very selectively the pX ribose of ApX (X = G or U) leading to a spiro derivative, where the C10 atom of ellipticine skeleton is linked to both sugar oxygen atoms 2' and 3'. No other adducts could be detected, specially the expected ones corresponding to the usual alkylation sites of bases.

Alkaloids↗
PubMed1985

Evidence for electrophilic properties of N2-methyl-9-hydroxy ellipticinium acetate (Celiptium) from human biliary metabolites.

The human biliary metabolism of the antitumor agent N2-methyl-9-hydroxyellipticinium acetate is described. Three major compounds have been identified by high-performance liquid chromatography and comparison with synthetic reference derivatives: the unchanged drug, the O-glucuronide conjugate and the cysteinyl-ellipticinium adduct. The latter one is the expected detoxification compound of an intermediate electrophilic quinone-imine derivative generated in vivo. This result provides a further evidence that hydroxylated forms of ellipticine derivatives might be activated by a biooxidation route.

Adult↗
PubMed1985

Synthesis and cytotoxic activity of hydroxylated derivatives of olivacine in relation with their biotransformation.

The chemical synthesis of 9-hydroxyolivacine and 7-hydroxyolivacine based on a biomimetic approach is described. These two hydroxylated derivatives have been found as main in vitro metabolites of olivacine after incubation with rat hepatic microsomes. The pretreatment of animals with benzo[a]pyrene caused a large increase in both microsomal hydroxylations, whereas the pretreatment with phenobarbital caused a weak increase, with a preservation of 9-hydroxylation/7-hydroxylation ratio greater than 1 in both cases. The two hydroxyolivacines have been also found as principal in vivo metabolites of olivacine in rat bile as glucuronide and sulfate conjugates. The pretreatment of animals with benzo[a]pyrene reverses the 9-hydroxyolivacine/7-hydroxyolivacine ratio excretion in bile to a value that is less than 1. In both in vitro and in vivo experiments, the free metabolites were identified by HPLC and UV-visible, MS, and 1H NMR spectra. Hydroxylation at position 9 increases the in vitro cytotoxicity against leukemia L1210 cells (ID50 = 0.06 microM compared to 2.03 microM for olivacine) and an opposite effect is observed for hydroxylation at position 7 (ID50 = 12.8 microM). On the other hand, hydroxylation at position 9 has no effect on the in vivo antitumor activity against L1210. This might be related to the oxidative and conjugative metabolic pathways that play an important role in antitumor activity and deactivation of olivacine and its hydroxy metabolites.

Animals↗
PubMed1984

Covalent binding of the antitumor agent N2-methyl-9-hydroxy-ellipticinium acetate (NSC 264137) on RNA and poly A in vitro.

The antineoplastic compound N2-methyl-9-hydroxyellipticinium (9-OH-NME) is able to bind to different biological molecules after an oxidative activation by horseradish peroxidase and hydrogen peroxide. In this study, the efficient covalent binding in vitro of 9-OH-NME onto RNA and poly A is described. The phenomenon is analyzed by different HPLC methods and the yield of binding is determined using [3H]9-OH-NME. For an initial ratio drug per nucleotide of 0.07, the rb obtained (ratio of drug bound per nucleotide) of 0.026 for RNA and 0.044 for poly A, which represent respectively a yield of 40% and 60% for the drug fixation onto these macromolecules. These facts demonstrate the high electrophilicity of para-quinone-imine derivatives in ellipticinium series.

Alkaloids↗
PubMed1984

Potential antitumor agents: synthesis and biological properties of aliphatic amino acid 9-hydroxyellipticinium derivatives.

Aliphatic amino acids glycine, alanine, valine, and leucine were conjugated to the antitumor drug N2-methyl-9-hydroxyellipticinium (NMHE) through a peroxidase-catalyzed oxidation reaction. NMR studies of the adducts so obtained have indicated (i) that the amino acids were linked to NMHE between the nitrogen of their primary amine and the C-10 position of the ellipticine ring and (ii) that a double bond was present between the nitrogen and the alpha-carbon of the amino acid moiety. All amino acid-NMHE adducts exhibit a higher lipophilic property than the parent compound (NMHE) directly correlated with the length of the aliphatic chain of the amino acids. The adducts interact with DNA through an intercalating process with apparent binding constant ranging from 2 X 10(5) to 5 X 10(5) M-1 at pH 7.40. The presence of the amino acid moiety linked to NMHE results (i) in a slight decrease of the cytotoxicity on L1210 cells in vitro (ID50 ranged from 0.20 to 0.50 microM) as compared to NMHE (ID50 = 0.05 microM), (ii) in a decrease of the antitumor efficiency in vivo against L1210 leukemia for leucine-NMHE and valine-NMHE (ILS at LD0/2 = 35% and 31%, respectively), (iii) in a suppression of the antitumor activity for alanine-NMHE and glycine-NMHE (ILS less than 25%), (iv) in a strong increase in the bacteriostatic activity on the quaternary ammonium sensitive Escherichia coli BL101 strain and on Salmonella typhimurium TA98 strain. The bacteriostatic effect is directly correlated with the lipophilic property of the drugs. These findings are discussed in terms of a structure-activity relationship.

Alkaloids↗
PubMed1984

Regioselective arylation of ribose in adenosine and guanosine with the antitumor drug N2-methyl-9-hydroxyellipticinium acetate.

The transformation of the antitumor drug N2-methyl-9-hydroxy-ellipticinium by a peroxidase-hydrogen peroxide system, which has been shown to occur in vivo, leads to an electrophilic quinone-imine derivative. This unstable molecule arylates in vitro purine nucleosides and nucleotides, leading to regioselective adducts substituted only at the 2'-O position of the ribose, as shown by mass spectrometry and NMR. It is likely that an important preliminary step in this reaction is a stacking process between the ellipticinium ion and the purine rings, which might explain this regioselectivity.

Adenosine↗
PubMed1983

Different levels of induction of RecA protein in E. coli (PQ 10) after treatment with two related carcinogens.

By means of an immunoradiometric assay the induction of protein RecA in E. coli PQ 10 was measured after treatment by two related carcinogens. On an adduct basis N-Acetoxy-N-2-acetylaminofluorene was shown to induce the protein RecA at a similar level as U.V. On the other hand, N-hydroxy-N-2-aminofluorene shows only a poor induction capacity of the RecA protein. The difference in the SOS inducing potential of the aminofluorene and acetylaminofluorene adducts is discussed in relation to the major difference in the local conformational change the two adducts induce in DNA.

2-Acetylaminofluorene↗
PubMed1983

Purification and characterization of recA protein from salmonella typhimurium.

recA protein was purified to homogeneity from Salmonella typhimurium TA98 strain after induction of the cells by nalidixic acid. The purification was monitored with a radioimmune assay and involved a specific elution of the protein by ATP from a single-stranded DNA-cellulose column. From 240 liters of cell culture we obtained 40 mg of recA protein which was more than 98% pure. This protein exhibited the same molecular weight as measured on sodium dodecyl sulfate-polyacrylamide gel and the same isoelectric point as the Escherichia coli recA protein purified by a similar procedure. In addition, the S. typhimurium recA protein is endowed with a single-stranded DNA-dependent ATPase activity and cleaves the phage lambda repressor in vitro at the same rate as E. coli recA protein and with the same qualitative requirements. However, peptide mapping with the Staphylococcus aureus V8 protease and cross-reaction with heterologous antibodies show that these two proteins are slightly different.

Adenosine Triphosphatases↗
PubMed1983

Lack of single-strand DNA-binding protein amplification under conditions of SOS induction in E. coli.

A two site immunoradiometric assay (IRMA) for quantification of the recA protein has been recently described (Paoletti et al. 1982). We have used a similar technique to monitor the possible amplification of the ssb protein in E. coli after induction of the SOS repair process by various DNA damaging agents. Under these conditions, while we have been able to detect a full amplification of recA protein, we failed to observed any amplification of the ssb protein.

Bacterial Proteins↗
PubMed1983

omicron-Quinone formation in the biochemical oxidation of the antitumor drug N2-methyl-9-hydroxyellipticinium acetate.

The activation of N2-methyl-9-hydroxyellipticinium acetate (4) by a peroxidase--H2O2 system leads to the formation of an omicron-quinone (7a). This omicron-quinone is not directly generated from the starting material but through a quinone imine intermediate (6) which is subsequently oxidized. This reaction is highly dependent on pH values. The omicron-quinone 7a is easily protonated (7b), gives an addition product with methanol (9), and is reduced by cysteine. The omicron-quinone 7b has a rather low inhibitory effect against L1210 leukemia cell multiplication but acts as an electron carrier and dramatically augments the oxygen consumption in xanthine oxidase-NADH and rat liver microsomes-NADPH systems.

Alkaloids↗