In vivo inhibition of reduced thiol compounds from Entamoeba histolytica HK9 by phenothiazines and related tricyclic drugs

In Vitro Antiproliferative Effects of Neuroleptics, Antimycotics and Antibiotics on the Human Pathogens Acanthamoeba polyphaga and Naegleria fowleri

BACKGROUND

Using reproducible conditions in vitro, the aim of this study was to obtain a comparative evaluation of the efficacies of several tricyclic neuroleptics, antimycotics and antibiotics with antiproliferative activities against Acanthamoeba polyphaga and Naegleria fowleri trophozoites.

METHODS

We used reproducible conditions in vitro to obtain results.

RESULTS

In the case of A.polyphaga, the tricyclic neuroleptics trifluoperazine and chlorpromazine had the best inhibitory (IC50) effects followed by mepacrine, ketoconazole, pentamidine, miconazole, amphotericin B, and metronidazole. Of all, rifampicin was the least effective. Mepacrine was the most effective compound with the minimum inhibitory concentration (MIC100) against A.polyphaga [corrected] The most effective drugs against N. fowleri expressed as (IC50) were as follows: the antimycotics ketoconazole and amphotericin B, followed by trifluoperazine, mepacrine, chlorpromazine, miconazole, and metronidazole. The least effectives were rifampicin and pentamidine. The most potent growth inhibitors (MIC100) against N. fowleri were the antimycotics amphotericin B and ketoconazole and the neuroleptic trifluoperazine. It was clear that there are major differences between the two amebas in their susceptibility to some of the drugs.

CONCLUSIONS

The drugs with the minimal inhibitory concentration (MIC) values could be considered alone or in combination as potential anti-amebic agents for the treatment of the diseases produced by these amebas.

The effects by neuroleptics, antimycotics and antibiotics on disulfide reducing enzymes from the human pathogens Acanthamoeba polyphaga and Naegleria fowleri

This paper discusses the effects of two neuroleptic agents, chlorpromazine and trifluoperazine; three antimycotics, amphotericin B, ketoconazole and miconazole and four antibiotics, pentamidine, rifampicin, mepacrine and metronidazole on the NADPH-dependent disulfide reducing enzymes cystine reductase (CysR), glutathione reductase (GR) trypanothione reductase (TR) and a putative disulfide reductase for compound X in Acanthamoeba polyphaga from the human pathogens A. polyphaga and Naegleria fowleri. Against A. polyphaga, all nine drugs studied had the capacity to inhibit the putative disulfide reductase from the trophozoites at a concentration of 32microg/ml during a 24h incubation and they were: the neuroleptics trifluoperazine (100%) and chlorpromazine (96%), the antimycotics miconazole (89%) ketoconazole (81%) and amphotericin B, (53%) and the antibiotics pentamidine (89%), rifampicin (64%), mepacrine (57%) and metronidazole (14%). Only six of the nine drugs simultaneously inhibited CysR, GR and the putative disulfide reductase. In N. fowleri, the most potent inhibitors of trypanothione reductase were amphotericin B and miconazole which inhibited 100% at a concentration of 32microg/ml during the 24h incubation followed by the neuroleptics trifluoperazine (92%) and chlorpromazine (80%) and the antibiotic mepacrine (70%). All these also inhibited CysR and GR from the trophozoites other than mepacrine which inhibited only CysR and TR. Ketoconazole, rifampicin (which did not affect CysR), pentamidine and metronidazole had opposite effects since they did not inhibit but increased the amount of the three thiols.