PubMed Health⌕ Search

Biomedical subjects

D Cioli

Publications and source records attributed to D Cioli.

At least 19 recordsLinked to original sources
PubMed1992

Schistosoma mansoni: hycanthone/oxamniquine resistance is controlled by a single autosomal recessive gene.

Individual schistosomes of an hycanthone/oxamniquine-sensitive strain were crossed with individual schistosomes of the opposite sex and belonging either to the same sensitive population or to a different strain which exhibited high resistance to the two drugs. Schistosome crosses were performed by transfer of single worm pairs into the mesenteric veins of mice and the drug sensitivity/resistance of individual progeny worms was assessed using an in vitro test. Drug resistance behaved as an autosomal recessive trait, as shown by the results of the F1 and F2 generation and of the backcrosses. Drug-resistant worms appeared to be slightly less viable than their sensitive counterpart at all stages of the life cycle. The results are relevant for an interpretation of drug resistance and drug mechanisms and the approach used in this study may be applicable to different genetic markers in schistosomes.

Animals↗
PubMed1992

Hycanthone resistance in schistosomes correlates with the lack of an enzymatic activity which produces the covalent binding of hycanthone to parasite macromolecules.

Crude extracts of hycanthone sensitive Schistosoma mansoni incubated at 37 degrees C in the presence of ATP and Mg2+ induced the covalent binding of tritiated hycanthone (HC) to macromolecules. The same behavior was shown by the HC sensitive species, Schistosoma rodhaini, whereas two independently isolated HC resistant S. mansoni strains had no detectable activity. Sensitive male schistosomes had more activity than females or immature worms. Virtually no activity was present in mouse liver, in human liver, in HeLa cells or in the naturally resistant species Schistosoma japonicum. The activity was destroyed by boiling or by Proteinase K treatment. Covalent binding of tritiated HC to macromolecules could be inhibited by cold HC, oxamniquine or IA-4, while none of the in vitro ineffective analogs, like lucanthone, UK-3883 or 4-desmethyl lucanthone, were inhibitory. These results strongly support the previously advanced suggestion that HC is activated by enzymatic mechanisms which are present only in drug sensitive schistosomes.

Adenosine Triphosphate↗
PubMed1992

Genetic complementation analysis of two independently isolated hycanthone-resistant strains of Schistosoma mansoni.

The objective of this study is to determine whether various hycanthone resistant strains of schistosomes which have been independently isolated are all affected in the same gene. A strain obtained from a Brazilian patient was compared with a strain of Puerto Rican origin selected in the laboratory. If the mutation conferring resistance involved two different genes, one would expect that progeny of a cross between the two strains would show complementation, i.e. it would be sensitive to the drug. We have performed such a cross and obtained F1 hybrid worms which were essentially all resistant, thus suggesting that the mutation conferring resistance in the two strains involves the same gene.

Animals↗
PubMed1990

Mode of action of the schistosomicide hycanthone: site of DNA alkylation.

Condensation of hycanthone N-methylcarbamate (HNMC) with deoxyguanosine (dG) furnished a mixture of the N-1 and N2 adducts which were purified and characterized as their acetates. Condensation of HNMC with thymidine (T) gave the N-3 adduct in poor yield. Adenosine (A) and cytidine (C) did not react with HNMC. Incubation of schistosomes with either [3H]hycanthone (HC) or [3H]HNMC furnished DNA to which [3H]HC was covalently bound. The alkylated DNA was degraded enzymically and the radiolabeled nucleosides were separated using HPLC. Two major peaks were observed which coincided in retention time with the synthetic N-1 and N2 alkylated dG. Alkylated T was absent. Thus, the site of alkylation of DNA by either HC or HNMC is dG.

Alkylation↗
PubMed1989

Resistance of schistosomes to hycanthone and oxamniquine.

Genetic crosses between phenotypically resistant and sensitive schistosomes demonstrated that resistance to hycanthone and oxamniquine behaves like a recessive trait, thus suggesting that resistance is due to the lack of some factor. We hypothesized that, in order to kill schistosomes, hycanthone and oxamniquine need to be converted into an active metabolite by some parasite enzyme which, if inactive, results in drug resistance. Esterification of the drugs seemed to be the most likely event as it would lead to the production of an alkylating agent upon dissociation of the ester. An artificial ester of hycanthone was indeed active even in resistant worms, thus indirectly supporting our hypothesis. In addition, several lines of evidence demonstrated that exposure to hycanthone and oxamniquine results in alkylation of worm macromolecules. Thus, radioactive drugs formed covalent bonds with the DNA of sensitive (but not of resistant) schistosomes; an antiserum raised against hycanthone detected the presence of the drug in the purified DNA fraction of sensitive (but not of resistant) schistosomes; a drug-DNA adduct was isolated from hycanthone-treated worms and fully characterized as hycanthone-deoxyguanosine.

Alkylation↗
PubMed1988

Binding of tritiated hycanthone and hycanthone N-methylcarbamate to macromolecules of drug-sensitive and drug-resistant schistosomes.

Adult Schistosoma mansoni of the hycanthone-sensitive and of the hycanthone-resistant strain were exposed in vitro to tritium-labeled hycanthone. The drug was taken up in similar amounts by the two strains, a result which is not compatible with hypothetical mechanisms of resistance based on reduced drug entry into the schistosomes. Labeled hycanthone was found to bind irreversibly to macromolecules of sensitive schistosomes, whereas the binding was minimal in resistant worms. In particular, the DNA of sensitive schistosomes showed high levels of tightly bound hycanthone, while the corresponding fraction of resistant schistosomes failed to do so. Female schistosomes and immature worms, which are less sensitive to hycanthone, showed a diminished drug-DNA binding with respect to adult males. Tritiated hycanthone N-methylcarbamate, which is effective against sensitive and resistant schistosomes, bound in similar amounts to the DNA of both strains. These results strongly support a previously proposed mechanism of action of hycanthone, which is based essentially on the alkylation of worm macromolecules by a drug derivative produced in sensitive schistosomes.

Animals↗
PubMed1988

Preparation and antischistosomal and antitumor activity of hycanthone and some of its congeners. Evidence for the mode of action of hycanthone.

The synthesis of a series of esters of hycanthone (HC) and 7-hydroxyhycanthone, their antitumor activity, and their antischistosomal effects on HC-sensitive and HC-resistant schistosomes are reported. Binding studies using tritium-labeled HC and hycanthone N-methylcarbamate (HNMC) with calf thymus DNA provided evidence that HNMC but not HC alkylated the DNA. Tritiated HNMC also bound to the DNA of intact HeLa cells exposed to the drug while very little tritiated HC bound to DNA under the same conditions. The mechanism proposed previously to account for the antischistosomal action of HC, namely, drug esterification followed by alkylation of DNA, applies also to the antitumor action of the drug as shown in Scheme I.

Animals↗
PubMed1988

Studies on some derivatives of oxamniquine.

On the basis of the remarkable biological similarities between hycanthone and oxamniquine and as a sequel to our finding that some esters of hycanthone are active against hycanthone-resistant schistosomes, we prepared oxamniquine acetate, oxamniquine N-methylcarbamate, and four substituted phenylsulfonohydrazones of oxamniquine aldehyde. These compounds were tested for their effect on survival of and on [3H]uridine incorporation into hycanthone-sensitive and -resistant Schistosoma mansoni. All of these derivatives were effective to a greater or lesser degree in killing worms and in inhibiting [3H]uridine incorporation in the sensitive strain, but none was effective in the resistant strain.

Animals↗
PubMed1987

Synthesis and biological properties of some 6H-pyrido[4,3-b]carbazoles.

The effect of methyl substitution on the biological properties of the ellipticines was reexamined. 9-Hydroxy-6H-pyrido[4,3-b]carbazole was synthesized and shown to be devoid of antitumor activity in murine P388 lymphocytic leukemia in mice. 5-(Hydroxymethyl)-11-methyl-6H-pyrido[4,3-b]carbazole (46) and its N-methylcarbamate (48) were synthesized and their effect on macromolecular synthesis in HeLa cells and their antitumor properties were compared with those of ellipticine. In contrast to the alkaloid 1 and the hydroxymethyl derivative 46, which produced partially reversible inhibition of [3H]thymidine incorporation, the carbamate ester irreversibly blocked incorporation of the tritiated pyrimidine. The ester was also a more potent antitumor agent in P388 lymphocytic leukemia than 1 or 46.

Alkaloids↗
PubMed1986

A surface-labeled 18 kilodalton antigen in Schistosoma mansoni.

A mild surface-labeling procedure was applied to various developmental stages of Schistosoma mansoni. An 18 kDa protein was preferentially labeled in freshly transformed schistosomula. The labeled protein was equally present on skin-penetrated and mechanically prepared schistosomula and it disappeared upon digestion of intact parasites with proteolytic enzymes. The 18 kDa protein could be specifically precipitated with an antiserum raised against 3-h schistosomula. Six-day lung forms also presented a single major labeled protein component, but the apparent molecular weight of this protein in acrylamide gels was higher than 18 000. Fourteen-day-old and adult schistosomes showed only weak labeling distributed in several bands. The radioactivity pattern of adult worms (but not of schistosomula) could also be obtained by incubating fresh parasites in a medium which had previously been used to label schistosomes and to which a 100 000-fold excess of 127I over 125I had been added. Post-labeling incubation of parasites was found to be essential for the detection of stable surface proteins.

Animals↗
PubMed1986

Migration of Schistosoma mansoni in normal and passively immunized laboratory rats.

Normal and passively immunized Fischer rats were infected with 75Se-selenomethionine-labeled cercariae of Schistosoma mansoni. Migration of the parasites from skin to lungs to liver was monitored by autoradiographic analyses of these sites. Labeled parasites migrated from skin to lungs with high efficiency in normal and immune rats; disappearance of labeled parasites from the lungs was slower in immune rats. Labeled parasites accumulated in the liver, reaching maximal values by 11 days post-infection in both groups and remaining constant through day 21. Half the number of labeled parasites were detected in the liver of immune rats. The total number of labeled parasites detected in the skin, lungs, and liver was constant through day 5, then declined to about 60% of this value by day 11 in both groups. Over the next 10 days, the rate of decline decreased significantly in normal rats but did not change in immune rats. By day 21 post-infection, nearly 50% fewer labeled parasites were detectable in immune rats. We conclude that a subpopulation of parasites in the lungs is the target of protective antibody in the serum used for passive immunization. Target parasites, retained longer in the lungs, were probably prevented from migrating successfully to the liver. Another parasite subpopulation migrated to the liver with normal kinetics. Lung schistosomula isolated from normal and passively immunized rats were transferred by intravenous injection into recipient rats and their continued migration from lungs to liver compared. No differences in portal perfusion worm yields were detected in normal recipients; equally reduced yields were detected in passively immunized recipients. We conclude that the effects of antibodies during week 1 post-infection were insignificant or reversible.

Autoradiography↗
PubMed1986

Lack of correlation between schistosomicidal and anticholinergic properties of hycanthone and related drugs.

Visual observation of the motor activity of Schistosoma mansoni kept in vitro showed an increase of activity in the presence of hycanthone (HC). In addition, HC caused a delay in the paralytic effects of carbachol. Similar results were observed in the presence of oxamniquine (OXA). The same pattern of motor activity, however, was shown by HC-resistant worms, by Schistosoma japonicum, and by worms exposed to drug precursors (lucanthone and UK-3883), which are not schistosomicidal in vitro. Other analogs with in vitro killing activity (IA-4 and IA-4 N-oxide) showed minimal anticholinergic effects. The anticholinergic effects of HC and OXA were quickly reversible in vitro and in vivo, whereas their antischistosomal effects are irreversible and delayed. Incubation of schistosomes with high concentrations of carbachol or with anticholinergic drugs failed to compete with the schistosomicidal effects of HC. These results are viewed as contradictory to the hypothesis that HC kills schistosomes by blocking their acetylcholine receptors.

Animals↗
PubMed1985

Evidence for the mode of antischistosomal action of hycanthone.

Evidence is presented which supports the hypothesis that the mode of action, or a slight variant thereof, suggested by Hartman and Hulbert (11) to account for the mutagenic effects of hycanthone (HC) is the mechanism whereby HC exerts its antischistosomal activity. HC is metabolically activated to a reactive ester which, upon dissociation, alkylates DNA. If resistant schistosomes are unaffected because they cannot convert HC to a reactive ester they should be killed upon direct exposure to an appropriately esterified drug. Hycanthone N-methylcarbamate (HNMC) was synthesized and shown to bind to DNA and also alkylate 4-(p-nitrobenzyl)-pyridine. When tested with schistosomes kept in vitro, HNMC caused an irreversible inhibition of 3H-uridine incorporation not only in sensitive S. mansoni (as HC does) but also in HC-resistant and immature S. mansoni worms and S. japonicum worms which are only transiently inhibited by HC. After in vitro contact with HNMC for 1 h both sensitive and resistant schistosomes died in three weeks if either kept in culture or re-transplanted into the host animal. Mice infected with HC-resistant schistosomes showed a drastic worm reduction after in vivo HNMC administration.

Alkylating Agents↗
PubMed1985

Studies on the mode of action of oxamniquine and related schistosomicidal drugs.

Adult Schistosoma mansoni were incubated for 1 hour in vitro with various drugs and then returned into the mesenteric veins of permissive animal hosts. Survival of schistosomes was assessed 3-4 weeks later by portal perfusion. Under these conditions, oxamniquine and hycanthone proved effective in killing S. mansoni, whereas UK-3883, lucanthone and lucanthone-4-desmethyl had no lethal activity. The same drugs which were schistosomicidal in vitro also persistently inhibited DNA, RNA, and protein synthesis in S. mansoni, whereas they were only transiently inhibitory against Schistosoma japonicum, against hycanthone-resistant S. mansoni and against immature worms. When drugs were administered in vivo to infected mice and the synthesis of macromolecules was assayed in vitro on worms obtained 1 or 3 days after treatment, not only oxamniquine and hycanthone, but also UK-3883 and lucanthone, proved effective in inhibiting the synthesis of macromolecules in sensitive--but not in resistant--S. mansoni. It is suggested that oxamniquine, like hycanthone, may exert its schistosomicidal activity by inhibiting nucleic acid synthesis in the parasite.

Animals↗