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PubMed2006

Mode of action of beta-cyclodextrin as an absorption enhancer of the water-soluble drug meglumine antimoniate.

It has been previously reported that beta-cyclodextrin (beta-CD) enhances the oral absorption of the pentavalent antimony (Sb) drug, meglumine antimoniate (MA). Contrary to the drugs commonly used in association with beta-CD, MA is highly soluble in water (solubility >300 mg/mL) and, therefore, the mode of action of beta-CD in this system requires clarification. ESI(-)-MS analysis of MA and of the MA/beta-CD composition indicated the formation of a 1:1 association compound between 1:1 Sb-meglumine complex and beta-CD. A stability constant on the order of 100 Lmol(-1) was determined for this association compound. When MA solution was heated for 48 h at 55 degrees C to mimic the conditions used to prepare MA/beta-CD, MA was found to suffer dissociation, from high molecular weight Sb complexes into species of lower molecular weight. Strikingly, heated MA was found to be more extensively absorbed in mice by the oral route than MA freshly prepared at room temperature. In vitro skin permeation experiments using MA and MA/beta-CD indicated a two-fold increase in the Sb flux for MA/beta-CD. These findings support the hypothesis that the improved oral absorption of Sb arises from the increased permeation of MA across lipid bilayers, as a result of the enhanced availability of 1:1 Sb-meglumine complex.

Administration, Oral↗
PubMed2005

Removal of p-aminophenol and p-nitrophenol from aqueous solution through adsorption on antimony, cadmium, and zirconium ferrocyanides.

Adsorptive interaction of p-aminophenol and p-nitrophenol in the concentration range 10(-4)-10(-5) M and at room temperature (30+/-1 degrees C) was studied with antimony, cadmium, and zirconium ferrocyanides. The interaction followed the Langmuir type of adsorption in general. The p-nitrophenol was found to have greater affinity for the antimony, cadmium, and zirconium ferrocyanides then the p-aminophenol.

Adsorption↗
PubMed2005

Development of a modified MTT assay for screening antimonial resistant field isolates of Indian visceral leishmaniasis.

The semi-automated MTT colorimetric assay has previously been applied on Leishmania promastigotes based on the ability of viable parasites to reduce the tetrazolium salt to an insoluble formazan product. As promastigotes are non-adherent, application of the MTT assay in its original form has a major drawback of a high and variable background absorbance due to incomplete removal of phenol red, a component of most media. We have accordingly optimised a modified MTT assay wherein the absorbance linearity was maintained for cells ranging from 1x10(4) to 1x10(7) being 0.04+/-0.003-2.38+/-0.04. In contrast, the original MTT assay had a narrower linearity range of 1x10(6)-1x10(7) cells, absorbances being 0.05+/-0.005-1.54+/-0.005. The modified MTT assay was effectively applied to study growth kinetics and identification of antimonial resistant field isolates. Considering the growing problem of antimonial unresponsiveness in the Indian subcontinent, this modified MTT assay is a useful tool for Leishmania research.

Amphotericin B↗
PubMed2006

Possibility of membrane modification as a mechanism of antimony resistance in Leishmania donovani.

Resistance to antimonials has become a clinical threat in the treatment of visceral leishmaniasis (VL). Unravelling the resistance mechanism needs attention to circumvent the problem of drug resistance. In one of the resistant isolates, we earlier identified a gene (PG1) implicated in antimony resistance whose localization in the present study was confirmed on the pellicular plasma membrane of the parasite thereby indicating towards membrane modification as a mechanism of resistance in this resistant isolate.

Animals↗
PubMed2006

Evaluation of renal and hepatic functions in dogs naturally infected by visceral leishmaniasis submitted to treatment with meglumine antimoniate.

The present study aimed to evaluate the renal and hepatic responses in eight dogs with visceral leishmaniasis submitted to treatment with meglumine antimoniate and to verify the occurrence of possible side effects. Urinalysis, hepatic and renal function tests were carried out in all animals at up to seven moments. After the end of a six-month observation period, all dogs were euthanized. Before the beginning of the experiment urinary and biochemical alterations were observed in four dogs due to the changes caused by the parasite itself. These alterations included the presence of renal cells, cylindruria, proteinuria, azotemia, hyperproteinemia and hypoalbuminemia. One dog died on the third day after treatment because an aggravation of the clinical picture, probably due to the medication. During the course of the study, an increase in hepatic enzymes was verified in two animals. Sixty days after the beginning of the treatment four dogs showed remission of clinical signs. The other three were asymptomatic with persistent biochemical alterations. From these, two presented recurrence of clinical signs about 150 days after the beginning of the treatment while in the other, hyperproteinemia persisted. Meglumine antimoniate was not efficient to treat dogs with severe renal dysfunction and the side effects observed were pain at the site of injection and the probable transient hepatotoxicity, evidenced by biochemical examinations, but without the presence of clinical signs.

Animals↗
PubMed2005

Antimony trioxide-induced apoptosis is dependent on SEK1/JNK signaling.

Very little is known concerning the toxicity of antimony, despite its commercial use as a flame retardant and medical use as a treatment for parasitic infections. Our previous studies show that antimony trioxide (Sb(2)O(3)) induces growth inhibition in patient-derived acute promyelocytic leukemia (APL) cell lines, a disease in which a related metal, arsenic trioxide (As(2)O(3)), is used clinically. However, signaling pathways initiated by Sb(2)O(3) treatment remain undefined. Here, we show that Sb(2)O(3) treatment of APL cells is associated with increased apoptosis as well as differentiation markers. Sb(2)O(3)-induced reactive oxygen species (ROS) correlated with increased apoptosis. In addition, when we decreased the buffering capacity of the cell by depleting glutathione, ROS production and apoptosis was enhanced. Arsenic-resistant APL cells with increased glutathione levels exhibited increased cross-resistance to Sb(2)O(3). Based on studies implicating c-jun kinase (JNK) in the mediation of the response to As(2)O(3), we investigated the role for JNK in Sb(2)O(3)-induced apoptosis. Sb(2)O(3) activates JNK and its downstream target, AP-1. In fibroblasts with a genetic deletion in SEK1, an upstream regulator of JNK, Sb(2)O(3)-induced growth inhibition as well as JNK activation was decreased. These data suggest roles for ROS and the SEK1/JNK pathway in the cytotoxicity associated with Sb(2)O(3) exposure.

Antimony↗
PubMed2001

Experimental studies on the evolution of antimony-resistant phenotype during the in vitro life cycle of Leishmania infantum: implications for the spread of chemoresistance in endemic areas.

Pentavalent antimonial unresponsiveness is an emerging problem in endemic areas and information on factors which could modulate the transmission of drug-resistant phenotypes and parasites during life cycle are warranted. Using axenic amastigotes resistant to potassium antimonyl tartrate (Sb(III)) we investigated the modulation of antimonyl resistance during the in vitro life cycle. We assessed: (i) the stability of the drug-resistant phenotype during the in vitro life cycle; (ii) the transmission of drug-resistant clones when mixed with a wild-type clone at different susceptible/chemoresistant ratios (50/50,90/10,10/90) after one or two in vitro life cycles. We demonstrate that: (i) mutants which were 12,28,35 and 44 fold more resistant to Sb(III)-antimonial than their parental wild-type, were Glucantime Sb(V)-resistant when growing in THP-1 cells; (ii) the drug-resistant phenotype was partially retained during long-term in vitro culture (3 months) in drug free medium; (iii) the antimonyl-resistant phenotype was retained after one or more in vitro life cycles. However, when drug-resistant parasites were mixed with susceptible, mutants could not be detected in the resulting population, after one or two in vitro life cycles, whatever the initial wild-type/chemoresistant ratio. These results could be explained by the lower capacity of drug-resistant amastigotes to undergo the amastigote-promastigote differentiation process, leading probably to their sequential elimination during life cycle. Taken together, these observations demonstrate that different factors could modulate the transmission of Leishmania drug resistance during the parasite's life cycle.

Animals↗
PubMed1999

Antimony speciation in environmental samples by interfacing capillary electrophoresis on-line to an inductively coupled plasma mass spectrometer.

Antimony is a widely distributed trace element of ecotoxicological interest. A pathway via bioalkylation of inorganic Sb species is discussed in the literature, resulting in organically bound Sb species. Therefore, Sb speciation becomes increasingly a matter of interest for risk assessment in the environment. This contribution investigates the possibilities of CE on-line hyphenated to ICP-MS for Sb speciation. Two methods are employed, both highly resolving the species but only one preserving the species stability. The latter used Na2HPO4/NaH2PO4, 20 mM, pH 5.6 as the background electrolyte and NaOH or acetic acid as stacking electrolyte 1 or stacking electrolyte 2, respectively. Detection limits of 0.1 microgram/1-0.7 microgram/1, depending on species, were achieved. When analysing liquid phases from fouling and sewage sludge up to eight antimony species were detected. Sb (V) as well as methylated Sb species were found.

Antimony↗
PubMed1997

Can microorganisms convert antimony trioxide or potassium antimonyl tartrate to methylated stibines?

No evidence could be found for the production, in culture, of methylated antimony compounds from water-insoluble or soluble antimony derivatives by the aerobes, Scopulariopsis brevicaulis or Bacillus sp. or by anaerobes associated with cot mattress materials. The study does not support the hypothesis that volatile organoantimony compounds are a cause of cot deaths. Anaerobic cultures from a polluted pond generated trimethylstibine from potassium antimonyl tartrate.

Antimony↗
PubMed1994

Assessment of allopurinol plus meglumine antimoniate in the treatment of visceral leishmaniasis in patients infected with HIV.

We report on 11 patients with HIV infection and visceral leishmaniasis and who were treated with meglumine antimoniate plus allopurinol for 3 weeks (six patients) or 4 weeks (five patients). Clinical and parasitological cures were achieved in four of the five patients treated for 4 weeks and in one of the six patients treated for 3 weeks. Only one patient developed a severe maculopapular rash. Allopurinol plus meglumine antimoniate was found to be a safe combination of drugs for the treatment of visceral leishmaniasis in patients infected with HIV. The optimal length of this treatment is unknown but a course of at least 4 weeks' duration would appear to be necessary for obtaining parasitological cure in most cases.

AIDS-Related Opportunistic Infections↗
PubMed1998

Antimony trichloride induces DNA damage and apoptosis in mammalian cells.

Antimony compounds are widely used in various manufacturing and semiconducting industries. Previously, it has been shown that antimony trichloride (SbCl3) elevates sister chromatid exchange (SCE) rates in V79 cells after a 28-h incubation. However, only limited data on its genotoxic effects are available so far. The present results demonstrate that a 4-h exposure to > 50 microM SbCl3 could induce micronuclei (MN) formation in cultured Chinese hamster ovary (CHO-K1) cells, human bronchial epithelial (BES-6) cells and human fibroblasts (HF). The order of sensitivity to SbCl3 determined by Sulforhodamine B (SRB)-staining survival assay is HF > BES-6 cells > CHO-K1 cells, with LD50 values in these cells being approximately 40, 80 and 180 microM, respectively. Apoptosis and DNA fragmentation was not found in cells immediately following 4-h SbCl3 treatment. However, DNA fragmentation was detected in CHO-K1 cells after 4-h SbCl3 treatment and a 16 h or more post incubation in fresh medium by 1.5% agarose gel electrophoresis. The delayed apoptosis was also observed under microscopic examination in HF, BES-6 and CHO-K1 cells after similar treatment protocol. In addition, an increase in calcium accumulation appeared in CHO-K1 cells and HF immediately after a 4-h SbCl3 treatment, or after a 24-h post incubation in fresh medium. The present results provide important genotoxic and cytotoxic information characterizing the cellular changes induced by short-term SbCl3 exposure in rodent and human cells.

Animals↗
PubMed1999

Meglumine antimoniate, amiodarone and torsades de pointes: a case report.

Pentavalent antimonial drugs used for the treatment of leishmaniasis have been associated with sudden deaths, probably due to the development of ventricular tachyarrhythmias. Prolongation of the QT interval and ventricular tachyarrhymias have been described in patients on amiodarone therapy. We report a case of recurrent torsades de pointes following treatment with pentavalent antimonial drugs and amiodarone.

Aged↗
PubMed2002

Antimony(V) complex formation with adenine nucleosides in aqueous solution.

Despite the clinical use of pentavalent antimonial drugs for over half a century, their mode of action against leishmaniasis remains poorly understood. In this paper, we investigated the ability of Sb(V) to form in aqueous solution complexes with adenine nucleosides and deoxynucleosides, using circular dichroism (CD) and (1)H and (13)C NMR spectroscopies. We report that the ribonucleosides, adenosine (A) and adenosine monophosphate (AMP), form in water complexes with Sb(V), as evidenced by the changes induced in their CD spectra. On the other hand, 2'-deoxyadenosine (dA) did not show such a change. CD titration of the ribonucleosides with Sb(V) suggests the formation of 1:2 Sb(V)-nucleoside complexes. NMR analysis indicates that Sb(V) binds to the sugar moiety at the 2' position. Furthermore, the incubation of the antimonial drug, meglumine antimonate, with adenosine at 37 degrees C led to the transfer of Sb(V) from its original ligand to the nucleoside molecule, at acidic pH (pH 5), but not at neutral pH (7.2). Our data therefore suggests that the formation of such complexes may take place in vivo within the acidic cell compartments, including the phagolysosome of macrophage in which Leishmania resides.

Adenosine↗
PubMedDate not supplied

Embryotoxicity of meglumine antimoniate in the rat.

Meglumine antimoniate (MA) is a pentavalent antimonial (Sb(V)) drug used to treat leishmaniasis. Despite the fact that Sb(V) organic compounds have been used in clinical practice for more than 50 years, information on their safety during pregnancy is still scanty. This study was undertaken to evaluate the embryo/fetotoxicity of MA in the rat. Wistar rats were treated subcutaneously (s.c.) with MA (300 mg Sb(V)/kg body wt/day) on days 6 through 15 of pregnancy or with a higher dose (3 x 300 mg Sb(V)/kg body wt) on day 11 only. A control group treated with saline on days 6 through 15 and an untreated control group were evaluated as well. Cesarean sections were performed on day 21. No maternal toxicity and no reduction of fetal weight were noted in the groups treated with MA. The repeated administration of MA (days 6 through 15), but not the acute treatment (day 11), enhanced embryolethality. Treatment with MA on days 6 through 15 also caused a higher incidence of an atlas bone anomaly that occurs spontaneously at very low frequencies in our rat strain. These findings indicated that repeated administration of MA was embryolethal and teratogenic in rats.

Abnormalities, Drug-Induced↗
PubMed2002

Biomonitoring of a worker population exposed to low antimony trioxide levels.

Antimony trioxide (Sb2O3) is used as a flame retardant in the textile industry. We carried out a study in a factory for the evaluation of antimony (Sb) occupational exposure and urinary levels in workers exposed to Sb2O3. Urinary levels and airborne Sb2O3 personal exposure values were very low when compared to international occupational standards (500 microg/m3, as Sb). The range of forty-two personal exposures was 0.01-0.55 microg Sb/m3, while twenty-four area samplings ranged from < 0.01 microg Sb/m3 to 1.45 microg Sb/m3. The mean urinary Sb levels at the beginning (n = 39) and end of the shift (n = 39) were 0.31 +/- 0.25 microg/L and 0.35 +/- 0.29 microg/L respectively, without any significant statistical difference. When the workers were divided into two subgroups according to "higher" and 'lower" exposure levels, a statistical difference (P < 0.001) was observed between the mean Sb urinary levels of the two subgroups during the workweek, both at the beginning and end of the shift. A statistical difference was also observed between the above mentioned subgroups and the controls (n = 15). No correlation was found between personal Sb2O3 exposure and the difference in urinary Sb levels at the beginning and end of the workshift on the day the flame retardant was utilized. This lack of correlation could be due to low airborne Sb2O3 levels and Sb dietary intake, estimated as 3 microg/day in UK, but not yet fully investigated in Italy. Any accidental occupational Sb per os exposure however low, could further enhance the lack of correlation.

Adult↗
PubMed2003

Distribution and early diagenesis of antimony species in sediments and porewaters of freshwater lakes.

The study identifies the role played by different components of natural aquatic systems on the poorly known geochemistry of antimony. Different chemical forms of antimony were measured in porewaters and sediments of two Sudbury lakes characterized by contrasting redox conditions at the sediment-water interface. In porewaters, Sb(III) was present under reducing conditions where it could exist as SbS2- according to thermodynamic calculations. Sb(V) was detected mainly under oxic and mildly reducing environments where its presence was attributed to the oxidizing effect of iron and manganese oxyhydroxides or to the slow kinetics of reduction by dissolved sulfide or possible complexation by it. A third form of Sb identified as refractory was obtained after UV irradiation of the water samples, suggesting an association of Sb to low molecular weight natural organic matter. The distribution of Sb in sediments of the two lakes revealed (through the comparison of profiles and statistical correlations) the importance of iron and manganese oxyhydroxides in controlling the behavior of Sb, particularly in the lake where the interface was clearly oxic. Porewater profiles indicate that the dissolution of manganese and iron oxyhydroxides under anoxic conditions leads to the simultaneous release of dissolved Sb previously sorbed onto those compounds. In reducing sediments, the control of the solubility of Sb by iron sulfides is suggested.

Antimony↗
PubMed2006

Iron-mediated oxidation of antimony(III) by oxygen and hydrogen peroxide compared to arsenic(III) oxidation.

Antimony is used in large quantities in a variety of products, though it has been declared as a pollutant of priority interest by the Environmental Protection Agency of the United States (USEPA). Oxidation processes critically affect the mobility of antimony in the environment since Sb(V) has a greater solubility than Sb(lll). In this study, the cooxidation reactions of Sb(lIl) with Fe(ll) and both O2 and H2O2 were investigated and compared to those of As(III). With increasing pH, the oxidation rate coefficients of Sb(lll) in the presence of Fe(ll) and O2 increased and followed a similar pH trend as the Fe(ll) oxidation by O2. Half-lives of Sb(lll) were 35 and 1.4 h at pH 5.0 and pH 6.2, respectively. The co-oxidation with Fe(ll) and H2O2 is about 7000 and 20 times faster than with Fe(ll) and O2 at pH 3 and pH 7, respectively. For both systems, *OH radicals appear to be the predominant oxidant below approximately pH 4, while at more neutral pH values, other unknown intermediates become important. The oxidation of As(lll) follows a similar pH trend as the Sb(lll) oxidation; however, As(lll) oxidation was roughly 10 times slower and only partly oxidized in most of the experiments. This study shows that the Fe(ll)-mediated oxidation of Sb(Ill) can be an important oxidation pathway at neutral pH values.

Antimony↗
PubMed2000

Sensitive spectrophotometric assay for 3-hydroxy-substituted flavonoids, based on their binding with molybdenum, antimony, or bismuth.

A sensitive spectrophotometric assay has been developed for flavonoids based on their binding with molybdenum, antimony, or bismuth. Acetylation of the hydroxyl group of flavonoids abolished metal binding, thus suggesting a direct role of the hydroxyl groups. From a comparison of several related flavonoids differing in the position of hydroxyl substitutions, the hydroxyl group at position 3 was found to be an important requirement for the formation of a yellow complex. This flavonoid metal complex showed that a specific and significant bathochromic shift in the visible spectrum of the native flavonoid and the corresponding lambda(max) value was used for the colorimetric assays with different metal salts. The molybdenum complex was found to yield higher absorbance compared to antimony and bismuth complexes of various flavonoids. The present method offers a sensitive assay in the 5-25 nM range for these flavonoids and gave comparable results with HPLC quantitative determination.

Antimony↗