[Histone deacetylase and histone acetyltransferase inhibitors as antischistosomal agents: a review].

Schistosomiasis is a neglected zoonotic parasitic disease. Currently, praziquantel is the drug of choice for the treatment of schistosomiasis, and is the only effective chemical for treatment of schistosomiasis japonica. Since its introduction in the 1970s, praziquantel has been used for large-scale chemotherapy of schistosomiasis for over 40 years. However, there have been reports pertaining to the resistance to praziquantel in schistosomes. Therefore, development of novel antischistosomal agents as alternatives of praziquantel, is of great need. Histone deacetylases and histone acetyltransferases have been recently reported to play critical roles in the growth, development and reproduction of schistosomes, and are considered as potential drug targets for the treatment of schistosomiasis. This review summarizes the latest advances of histone deacetylase and histone acetyltransferase inhibitors in the research on antischistosomal drugs, so as to provide insights into research and development of novelantischistosomal agents.

In vitro and in vivo efficacy of the amiodarone and praziquantel combination against the blood fluke Schistosoma mansoni.

Schistosomiasis, a widespread parasitic disease caused by the blood fluke of the genus Schistosoma, affects over 230 million people, primarily in developing countries. Praziquantel, the sole drug currently approved for schistosomiasis treatment, demonstrates effectiveness against patent infections. A recent study highlighted the antiparasitic properties of amiodarone, an anti-arrhythmic drug, exhibiting higher efficacy than praziquantel against prepatent infections. This study assessed the efficacy of amiodarone and praziquantel, both individually and in combination, against Schistosoma mansoni through comprehensive in vitro and in vivo experiments. In vitro experiments demonstrated synergistic activity (fractional inhibitory concentration index ≤0.5) for combinations of amiodarone with praziquantel. In a murine model of schistosomiasis featuring prepatent infections, treatments involving amiodarone (200 or 400 mg/kg) followed by praziquantel (200 or 400 mg/kg) yielded a substantial reduction in worm burden (60%-70%). Given the low efficacy of praziquantel in prepatent infections, combinations of amiodarone with praziquantel may offer clinical utility in the treatment of schistosomiasis.

In vitro effects of febrifugine on Schistosoma mansoni adult worms.

BACKGROUND: Reports on the antischistosomal effect of several antimalarial drugs such as artesunate, mefloquine, and amodiaquine suggest that febrifugine, which exerts an antimalarial effect, can also be expected to possess antischistosomal potential. The present study investigates the antischistosomal effects of febrifugine. METHODS: In experiment 1, Schistosoma mansoni adult worm pairs were incubated in a medium alone as a control or supplemented with febrifugine at 0.05, 0.1, 0.2, and 0.5 µg/ml for 14 days. The morphology of the worms and the egg production of the female worms were observed simultaneously. In experiment 2, the incubation was conducted as in experiment 1, except that the febrifugine concentrations were reduced to 0.005, 0.01, and 0.02 µg/ml. In addition, S. mansoni adult worms were incubated with either 0.5 µg/ml febrifugine or none as a control for 5 days and stained with neutral red dye. RESULTS: Febrifugine significantly reduced the survival of S. mansoni male and female worms at concentrations of 0.02-0.5 µg/ml following incubation for 14 days and remarkably inhibited the daily egg output of the female worms. The non-treated male and female worms remained morphologically normal within the period of 14 days, whereas male and female worms treated with febrifugine at different concentrations gradually twisted and subsequently died. In addition, S. mansoni adult worms were incubated with either 0.5 µg/ml febrifugine or none as a control for 5 days and stained with neutral red dye. Non-treated male worms were morphologically normal and stained dark red with neutral red, while febrifugine-treated male worms appeared similar to those in the control group and were stained at a slightly lower level of dark red than the non-treated male worms. Non-treated female worms were morphologically normal, and their intestinal tract and vitellaria were stained deep red and dark red, respectively. In contrast, febrifugine-treated female worms were morphologically damaged, and their intestinal tract and vitellaria remained mostly unstained and stained dark red, respectively. CONCLUSION: Febrifugine exerts potent antischistosomal effects and can be expected to contribute to the development of a novel antischistosomal drug.

Targeting thioredoxin glutathione reductase as a potential antischistosomal drug target.

Schistosomiasis represents a world health major problem affecting more than 206 million people worldwide. Up to date, praziquantel (PZQ) is the sole chemotherapeutic agent used in clinics for the treatment of schistosomiasis. The resistance to PZQ chemotherapy that has been emerged against some schistosome phenotypes represents the most serious PZQ-related problem so far. Therefore, it is clear that there is a substantial need to develop novel and effective antischistosomal agents in order to ensure the effective drug control of schistosomiasis in the future. It is well-documented that the thiol redox homeostasis of schistosomes is entirely based on a single enzyme named thioredoxin-glutathione reductase (TGR). Thus, TGR is an essential protein for the survival of schistosomes which means that TGR is a valid and promising target for the recent antischistosomal drug-discovery approaches. This review aimed to shed light on potential lead compounds that may inhibit TGR activity and consequently could be tested as a potential antischistsomal drugs. In the current review we discussed multiple drug discovery approaches for new compounds targeting TGR and its implementation.

Garcinielliptone FC: antiparasitic activity without cytotoxicity to mammalian cells.

Garcinielliptone FC (GFC) is a natural prenylated benzophenone found in the seeds of Platonia insignis Mart. (Clusiaceae), a native Brazilian plant. It has been chemically characterized and it is known that GFC has several biological activities such as antioxidant and vasorelaxant properties. In this study, we report the in vitro effect of GFC against the blood fluke Schistosoma mansoni, the parasite responsible for schistosomiasis mansoni. The anti-S. mansoni activity and cytotoxicity toward mammalian cells were determined for the compound. GFC⩾6.25 µM showed antischistosomal activity and confocal laser scanning microscopy analysis demonstrated several morphological alterations on the tegument of worms, and a correlation between viability and tegumental damage was observed. In addition, at sub-lethal concentrations of GFC (⩽3.125 µM), the number of S. mansoni eggs was reduced. More importantly, GFC exhibited no activity toward mammalian cells and, therefore, there is an appreciable selectivity of this compound against the helminths. In conclusion, these findings indicate the potential of GFC as an antiparasitic agent.

Comparison of the in vitro Effects of One-day Exposure to Amodiaquine and Praziquantel on Schistosoma mansoni Adult Worm Pairs.

It has been demonstrated that continuous exposure to amodiaquine (AQ) alone elicits in vitro antischistosomal activities at concentrations of 1-10 µg/ml. However, orally administered drugs reach a peak blood concentration within one or two hours and then gradually decrease. The blood concentration does not remain at a constant level over several days as in vitro concentration of continuous drug exposure. In vitro activities by one day exposure to AQ better reflect the actual antischistosomal activities after oral administration than those elicited by continuous exposure. The objective of the present study is to compare the antischistosomal potential of one-day exposure to AQ with that to praziquantel (PZQ), a current antischistosomal drug. Schistosoma mansoni adult worm pairs were incubated with 0 (control), 1, 2, 5 and 10 µg/ml AQ as well as 0.01, 0.02, 0.05 and 0.1 µg/ml PZQ for the first day, and were subsequently incubated in drug-free media for a period of 14 days. The one-day exposure to AQ significantly reduced the daily egg output of the worm pairs at 1-10 µg/ml. The inhibitory effect on egg production continued at 5 and 10 µg/ml but proved temporary at 1 and 2 µg/ml. Furthermore, AQ-induced specific morphological alterations (severe swelling and/or localization of hemozoin) were observed in the worms at 5 and 10 µg/ml. The AQ-specific appearance of the male worms gradually faded during subsequent incubation in drug-free media, although the female worms showed elongation. Meanwhile, PZQ inhibited the egg output of adult worm pairs at concentrations of 0.01-0.1 µg/ml during exposure. The inhibitory effect on egg production continued at 0.05 and 0.1 µg/ml but proved temporary at 0.01 and 0.02 µg/ml. Furthermore, PZQ induced a visible contraction and shortening of the male and female worms at 0.05 and 0.1 µg/ml during exposure, but the PZQ-specific alterations quickly disappeared during subsequent incubation in drug-free media. To our knowledge, this is the first report showing that one-day exposure to AQ inhibits the egg production of adult worm pairs at 1-10 µg/ml and induces specific morphological alterations in the worms at 5 and 10 µg/ml. The present findings have important implications for the evaluation of the therapeutic effects of both AQ monotherapy and combination therapy with artesunate on schistosomiasis in clinical field trials.

<i>Comparison of the in vitro</i> effects of one-day exposure to amodiaquine and praziquantel on <i>Schistosoma mansoni</i> adult worm pairs

It has been demonstrated that continuous exposure to amodiaquine (AQ) alone elicits <i>in vitro</i> antischistosomal activities at concentrations of 1 - 10 µg/ml. However, orally administered drugs reach a peak blood concentration within one or two hours and then gradually decrease. The blood concentration does not remain at a constant level over several days as <i>in vitro</i> concentration of continuous drug exposure. <i>In vitro</i> activities by one day exposure to AQ better reflect the actual antischistosomal activities after oral administration than those elicited by continuous exposure.The objective of the present study is to compare the antischistosomal potential of one-day exposure to AQ with that to praziquantel (PZQ), a current antischistosomal drug. <i>Schistosoma mansoni</i> adult worm pairs were incubated with 0 (control), 1, 2, 5 and 10 µg/ml AQ as well as 0.01, 0.02, 0.05 and 0.1 µg/ml PZQ for the first day, and were subsequently incubated in drug-free media for a period of 14 days. The one-day exposure to AQ significantly reduced the daily egg output of the worm pairs at 1 - 10 µg/ml. The inhibitory effect on egg production continued at 5 and 10 µg/ml but proved temporary at 1 and 2 µg/ml. Furthermore, AQ-induced specific morphological alterations (severe swelling and/or localization of hemozoin) were observed in the worms at 5 and 10 µg/ml. The AQ-specific appearance of the male worms gradually faded during subsequent incubation in drug-free media, although the female worms showed elongation. Meanwhile, PZQ inhibited the egg output of adult worm pairs at concentrations of 0.01 - 0.1 µg/ml during exposure. The inhibitory effect on egg production continued at 0.05 and 0.1 µg/ml but proved temporary at 0.01 and 0.02 µg/ml. Furthermore, PZQ induced a visible contraction and shortening of the male and female worms at 0.05 and 0.1 µg/ml during exposure, but the PZQ-specific alterations quickly disappeared during subsequent incubation in drug-free media. To our knowledge, this is the first report showing that one-day exposure to AQ inhibits the egg production of adult worm pairs at 1 - 10 µg/ml and induces specific morphological alterations in the worms at 5 and 10 µg/ml. The present findings have important implications for the evaluation of the therapeutic effects of both AQ monotherapy and combination therapy with artesunate on schistosomiasis in clinical field trials.

Comparison of the <i>in vitro</i> Effects of One-day Exposure to Amodiaquine and Praziquantel on <i>Schistosoma mansoni</i> Adult Worm Pairs

It has been demonstrated that continuous exposure to amodiaquine (AQ) alone elicits <i>in vitro</i> antischistosomal activities at concentrations of 1–10 μg/ml. However, orally administered drugs reach a peak blood concentration within one or two hours and then gradually decrease. The blood concentration does not remain at a constant level over several days as <i>in vitro</i> concentration of continuous drug exposure. <i>In vitro</i> activities by one day exposure to AQ better reflect the actual antischistosomal activities after oral administration than those elicited by continuous exposure.The objective of the present study is to compare the antischistosomal potential of one-day exposure to AQ with that to praziquantel (PZQ), a current antischistosomal drug. <i>Schistosoma mansoni</i> adult worm pairs were incubated with 0 (control), 1, 2, 5 and 10 μg/ml AQ as well as 0.01, 0.02, 0.05 and 0.1 μg/ml PZQ for the first day, and were subsequently incubated in drug-free media for a period of 14 days. The one-day exposure to AQ significantly reduced the daily egg output of the worm pairs at 1–10 μg/ml. The inhibitory effect on egg production continued at 5 and 10 μg/ml but proved temporary at 1 and 2 μg/ml. Furthermore, AQ-induced specific morphological alterations (severe swelling and/or localization of hemozoin) were observed in the worms at 5 and 10 μg/ml. The AQ-specific appearance of the male worms gradually faded during subsequent incubation in drug-free media, although the female worms showed elongation. Meanwhile, PZQ inhibited the egg output of adult worm pairs at concentrations of 0.01–0.1 μg/ml during exposure. The inhibitory effect on egg production continued at 0.05 and 0.1 μg/ml but proved temporary at 0.01 and 0.02 μg/ml. Furthermore, PZQ induced a visible contraction and shortening of the male and female worms at 0.05 and 0.1 μg/ml during exposure, but the PZQ-specific alterations quickly disappeared during subsequent incubation in drug-free media. To our knowledge, this is the first report showing that one-day exposure to AQ inhibits the egg production of adult worm pairs at 1–10 μg/ml and induces specific morphological alterations in the worms at 5 and 10 μg/ml. The present findings have important implications for the evaluation of the therapeutic effects of both AQ monotherapy and combination therapy with artesunate on schistosomiasis in clinical field trials.

In vitro effects of amodiaquine on paired Schistosoma mansoni adult worms at concentrations of less than 5 µg/mL

In this study, the in vitro effects of amodiaquine (AQ) monotherapy on the egg output of paired adult Schistosoma mansoni worms and their survival during in vitro culture were assessed. In addition, the gross morphological alterations of male and female worms caused by AQ were visually observed under a dissecting microscope. AQ significantly reduced the daily egg output of paired adult S. mansoni worms following incubation for 14 days at 1-5 µg/mL, but not at 0.5 µg/mL, compared with the control group. AQ also reduced the survival of male and female worms at concentrations of 2 and 5 µg/mL, respectively. Moreover, exposure to 5 µg/mL AQ caused severe swelling and/or localisation of black content in the body of all male and female worms within one or two days of incubation; subsequently, shrinkage in the male worms and elongation in the female worms were observed. The initial morphological alterations caused by AQ occurred along the intestinal tract of the male and female worms. To our knowledge, this is the first study to report not only the efficacy of AQ at concentrations lower than 5 µg/mL on paired adult S. mansoni worms, but also the effects of AQ on the intestinal tracts of worms in in vitro culture.