Ultrastructural alterations induced by ICI 195,739, a bis-triazole derivative with strong antiproliferative action against Trypanosoma (Schizotrypanum) cruzi

Albaconazole is an experimental triazole derivative with potent and broad-spectrum antifungal activity and a remarkably long half-life in dogs, monkeys, and humans. In the present work, we investigated the in vivo activity of this compound against two strains of the protozoan parasite Trypanosoma (Schizotrypanum) cruzi, the causative agent of Chagas' disease, using dogs as hosts. The T. cruzi strains used in the study were previously characterized (murine model) as susceptible (strain Berenice-78) and partially resistant (strain Y) to the drugs currently in clinical use, nifurtimox and benznidazole. Our results demonstrated that albaconazole is very effective in suppressing the proliferation of the parasite and preventing the death of infected animals. Furthermore, the parasitological, PCR, serological, and proliferative assay results indicated parasitological cure indices of 25 and 100% among animals inoculated with T. cruzi strain Y when they were treated with albaconazole at 1.5 mg/kg of body weight/day for 60 and 90 days, respectively. On the other hand, although albaconazole given at 1.5 mg/kg/day was very effective in suppressing the proliferation of the parasite in animals infected with the Berenice-78 T. cruzi strain, no parasitological cure was observed among them, even when a longer treatment period (150 doses) was used. In conclusion, our results demonstrate that albaconazole has trypanocidal activity in vivo and is capable of inducing radical parasitological cure, although natural resistance to this compound was also indicated. Furthermore, the compound can be used in long-term treatment schemes (60 to 150 days) with minimal toxicity and thus represents a potentially useful candidate for the treatment of human Chagas' disease.

Section: Discussionmentioning

confidence: 75%

Activity of the New Triazole Derivative Albaconazole against Trypanosoma ( Schizotrypanum ) cruzi in Dog Hosts

Guedes¹,

Urbina

Lana³

et al. 2004

“…14). In a previous study we observed the same type of mitochondrial alterations in T. cruzi epimastigotes and amastigotes treated with 22,26-azasterol (63), as well as in T. cruzi and L. amazonensis incubated in the presence of other EBIs such as ICI 195,739 (22), ketoconazole, and terbinafine (21,61). Taken together, these observations suggest that the presence of ergosterol and analogs is essential for the maintenance of a normal structural organization of the mitochondrial membrane in trypanosomatids, especially the inner one.…”

Section: Resultsmentioning

confidence: 82%

Ultrastructural and Biochemical Alterations Induced by 22,26-Azasterol, a Δ ²⁴⁽²⁵⁾ -Sterol Methyltransferase Inhibitor, on Promastigote and Amastigote Forms of Leishmania amazonensis

Rodrigues

Attias

Rodríguez

et al. 2002

117

110

We report on the antiproliferative effects and the ultrastructural and biochemical alterations induced in vitro by 22,26-azasterol, a sterol ⌬ 24(25) -methyltransferase (24-SMT) inhibitor, on Leishmania amazonensis. When promastigotes and amastigotes were exposed to 100 nM 22,26-azasterol, complete growth arrest and cell lysis ensued after 72 (promastigotes) or 120 (amastigotes) h. Exposure of parasites to this azasterol led to the complete depletion of parasite endogenous sterols (episterol and 5-dehydroepisterol) and their replacement by 24-desalkyl sterols (zymosterol, cholesta-5,7,24-trien-3␤-ol, and cholesta-7,24-dien-3␤-ol), while 14-methylzymosterol and 4,14-dimethyl-zymosterol accumulated as a result of simultaneous incubation of the parasites with 22,26-azasterol and ketoconazole, a known inhibitor of the parasite's sterol C14-demethylase. These results confirmed that 24-SMT is the primary site of action of the azasterol. Profound changes were also observed in the phospholipid compositions of treated cells, in which a twofold reduction in the content of phosphatidylserine was observed; this was accompanied by a concomitant increase in the content of phosphatidylinositol. Transmission electron microscopy showed that 22,26-azasterol induced marked morphological changes, including mitochondrial swelling, invaginations of the inner mitochondrial membrane, and the appearance of large bodies containing concentric membranes. Other modifications included increases in the numbers of acidocalcisomes, megasomes, and lipid inclusions and the appearance of typical autophagic structures and cell body protrusions toward the flagellar pocket. We conclude that the dramatic alteration of the lipid composition of the parasite's membranes induced by the drug underlies the ultrastructural alterations that lead to the loss of cell viability and that 24-SMT inhibitors could be useful as selective antileishmanial agents.

“…The main alteration was observed in the mitochondrion-kinetoplast complex, which showed intense mitochondrial swelling and some alterations in the mitochondrial membrane, such as its rupture at some sites, and an increase in the number of cristae. These alterations in the mitochondrion were observed in a previous study when L. amazonensis (35) and T. cruzi (10,11) were incubated with other ergosterol biosynthesis inhibitors, such as terbinafine, ketoconazole, and 22,26-azasterol. The presence of these changes in the mitochondrion of trypanosomatids treated with different ergosterol biosynthesis inhibitors suggests that the presence of ergosterol or 5-dehydroepisterol is essential for the preservation of a normal structural organization of the mitochondrial membrane in these parasites.…”

Section: Vol 48 2004 Azasterols As Antiparasitics 2943mentioning

confidence: 93%

Novel Azasterols as Potential Agents for Treatment of Leishmaniasis and Trypanosomiasis

Lorente

Rodrigues

Jimenez

et al. 2004

This paper describes the design and evaluation of novel azasterols as potential compounds for the treatment of leishmaniasis and other diseases caused by trypanosomatid parasites. Azasterols are a known class of (S)-adenosyl-L-methionine: ⌬ 24 -sterol methyltransferase(24-SMT) inhibitors in fungi, plants, and some parasitic protozoa. The compounds prepared showed activity at micromolar and nanomolar concentrations when tested against Leishmania spp. and Trypanosoma spp. The enzymatic and sterol composition studies indicated that the most active compounds acted by inhibiting 24-SMT. The role of the free hydroxyl group at position 3 of the sterol nucleus was also probed. When an acetate was attached to the 3␤-OH, the compounds did not inhibit the enzyme but had an effect on parasite growth and the levels of sterols in the parasite, suggesting that the acetate group was removed in the organism. Thus, an acetate group on the 3␤-OH may have application as a prodrug. However, there may be an additional mode(s) of action for these acetate derivatives. These compounds were shown to have ultrastructural effects on Leishmania amazonensis promastigote membranes, including the plasma membrane, the mitochondrial membrane, and the endoplasmic reticulum. The compounds were also found to be active against the bloodstream form (trypomastigotes) of Trypanosoma brucei rhodesiense, a causative agent of African trypanosomiasis.