The Schistosoma mansoni Cytochrome P450 (CYP3050A1) Is Essential for Worm Survival and Egg Development.

Schistosomiasis affects millions of people in developing countries and is responsible for more than 200,000 deaths annually. Because of toxicity and limited spectrum of activity of alternatives, there is effectively only one drug, praziquantel, available for its treatment. Recent data suggest that drug resistance could soon be a problem. There is therefore the need to identify new drug targets and develop drugs for the treatment of schistosomiasis. Analysis of the Schistosoma mansoni genome sequence for proteins involved in detoxification processes found that it encodes a single cytochrome P450 (CYP450) gene. Here we report that the 1452 bp open reading frame has a characteristic heme-binding region in its catalytic domain with a conserved heme ligating cysteine, a hydrophobic leader sequence present as the membrane interacting region, and overall structural conservation. The highest sequence identity to human CYP450s is 22%. Double stranded RNA (dsRNA) silencing of S. mansoni (Sm)CYP450 in schistosomula results in worm death. Treating larval or adult worms with antifungal azole CYP450 inhibitors results in worm death at low micromolar concentrations. In addition, combinations of SmCYP450-specific dsRNA and miconazole show additive schistosomicidal effects supporting the hypothesis that SmCYP450 is the target of miconazole. Treatment of developing S. mansoni eggs with miconazole results in a dose dependent arrest in embryonic development. Our results indicate that SmCYP450 is essential for worm survival and egg development and validates it as a novel drug target. Preliminary structure-activity relationship suggests that the 1-(2,4-dichlorophenyl)-2-(1H-imidazol-1-yl)ethan-1-ol moiety of miconazole is necessary for activity and that miconazole activity and selectivity could be improved by rational drug design

The Schistosoma mansoni Cytochrome P450 (CYP3050A1) Is Essential for Worm Survival and Egg Development.

Schistosomiasis affects millions of people in developing countries and is responsible for more than 200,000 deaths annually. Because of toxicity and limited spectrum of activity of alternatives, there is effectively only one drug, praziquantel, available for its treatment. Recent data suggest that drug resistance could soon be a problem. There is therefore the need to identify new drug targets and develop drugs for the treatment of schistosomiasis. Analysis of the Schistosoma mansoni genome sequence for proteins involved in detoxification processes found that it encodes a single cytochrome P450 (CYP450) gene. Here we report that the 1452 bp open reading frame has a characteristic heme-binding region in its catalytic domain with a conserved heme ligating cysteine, a hydrophobic leader sequence present as the membrane interacting region, and overall structural conservation. The highest sequence identity to human CYP450s is 22%. Double stranded RNA (dsRNA) silencing of S. mansoni (Sm)CYP450 in schistosomula results in worm death. Treating larval or adult worms with antifungal azole CYP450 inhibitors results in worm death at low micromolar concentrations. In addition, combinations of SmCYP450-specific dsRNA and miconazole show additive schistosomicidal effects supporting the hypothesis that SmCYP450 is the target of miconazole. Treatment of developing S. mansoni eggs with miconazole results in a dose dependent arrest in embryonic development. Our results indicate that SmCYP450 is essential for worm survival and egg development and validates it as a novel drug target. Preliminary structure-activity relationship suggests that the 1-(2,4-dichlorophenyl)-2-(1H-imidazol-1-yl)ethan-1-ol moiety of miconazole is necessary for activity and that miconazole activity and selectivity could be improved by rational drug design

The Schistosoma mansoni Cytochrome P450 (CYP3050A1) Is Essential for Worm Survival and Egg Development.

Schistosomiasis affects millions of people in developing countries and is responsible for more than 200,000 deaths annually. Because of toxicity and limited spectrum of activity of alternatives, there is effectively only one drug, praziquantel, available for its treatment. Recent data suggest that drug resistance could soon be a problem. There is therefore the need to identify new drug targets and develop drugs for the treatment of schistosomiasis. Analysis of the Schistosoma mansoni genome sequence for proteins involved in detoxification processes found that it encodes a single cytochrome P450 (CYP450) gene. Here we report that the 1452 bp open reading frame has a characteristic heme-binding region in its catalytic domain with a conserved heme ligating cysteine, a hydrophobic leader sequence present as the membrane interacting region, and overall structural conservation. The highest sequence identity to human CYP450s is 22%. Double stranded RNA (dsRNA) silencing of S. mansoni (Sm)CYP450 in schistosomula results in worm death. Treating larval or adult worms with antifungal azole CYP450 inhibitors results in worm death at low micromolar concentrations. In addition, combinations of SmCYP450-specific dsRNA and miconazole show additive schistosomicidal effects supporting the hypothesis that SmCYP450 is the target of miconazole. Treatment of developing S. mansoni eggs with miconazole results in a dose dependent arrest in embryonic development. Our results indicate that SmCYP450 is essential for worm survival and egg development and validates it as a novel drug target. Preliminary structure-activity relationship suggests that the 1-(2,4-dichlorophenyl)-2-(1H-imidazol-1-yl)ethan-1-ol moiety of miconazole is necessary for activity and that miconazole activity and selectivity could be improved by rational drug design

Activity of anti-fungal imidazole CYP450 inhibitors on larval and adult <i>Schistosoma mansoni</i> worms.

<p>Survival of schistosomula (A) after 2 d culture and adult worms (B) after 5 d culture for miconazole (black diamond), clotrimazole (black square), and ketoconazole (black triangle). (C) In house SAR on known miconazole analogs against adult worms. Numbers in the parenthesis are survival (%) of adult worms on day 7 in 10 μM of respective compound.</p

Comparison of <i>Schistosoma mansoni</i> CYP450 protein (Sman) with CYP450 proteins from other species.

<p>Multiple alignment of CYP450 proteins from <i>S</i>. <i>mansoni</i> (csm305A); rabbit CYP450 2C5 (1nr6_a); human CYP450 2C9 (1r9o_a); human CYP450 2C19 (4gqs_a); human CYP450 1A1 (4i8v_a); and human CYP450 2b6 (4rrt_a). The residues are shown in one letter code and colored by type: red- negatively charged, blue—positively charged, yellow—Cys, green—hydrophobic, cyan—Gly, ochre—Pro, purple—aromatic. The residues are shown in brighter colors for conserved positions. The ‘P450-signature’ sequence, which forms a channel for electron transfer, and the CYP450 consensus motif responsible for heme-binding and interaction with molecular oxygen and the relevant substrates are boxed. Predicted helices in the secondary structure based on homology modelling of SmCYP450 are indicated by the bold letters A-L based on rabbit CYP450 2C5 [<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0004279#pntd.0004279.ref038" target="_blank">38</a>].</p

CYP450 messenger RNA abundance during the lifecycle of <i>Schistosoma mansoni</i>.

<p>Whole RNA was extracted from different stages of <i>S</i>. <i>mansoni</i> (cercariae, 1-day old schistosomula; juvenile liver worms (23 days post infection), adult males (49 days post infection), adult females (49 days post infection) and eggs) using TRIzol reagent and chloroform/ethanol extraction protocol. cDNA was synthesized from whole RNA and used for qRT-PCR, with reactions done in triplicate. Adult males (= 1) were used as calibrator stage and mRNA abundance was normalized to α-tubulin. Error bars indicate standard error of the mean with n ≥ 3 biological replicates. Numbers indicate fold change relative to adult males and all values are significantly different from adult males; p < 0.05; student t-test. The results indicate that <i>S</i>. <i>mansoni</i> CYP450 is expressed in all stages investigated and that its expression is developmentally regulated.</p

Effect of miconazole on egg development.

<p>(A) Example of egg development scoring scheme. Upper panel shows fluorescent images of eggs representative of each developmental stage scored; the bottom panel shows brightfield images of the same eggs. (B) Scoring of egg development in cultured eggs treated with 0, 5, or 10 μM miconazole. The percentage of eggs scored at developmental stages I-III (black bars) and eggs scored at developmental stages IV-V (gray bars) are indicated. For 0 μM miconazole, n = 55 eggs scored; for 5 μM miconazole, n = 56 eggs scored; for 10 μM miconazole, n = 62 eggs scored.</p

Chemical structures of CYP450 inhibitors used in this study.

<p>Chemical structures of CYP450 inhibitors used in this study.</p

Structural modeling of <i>S</i>. <i>mansoni</i> CYP450 (CYP3050A1) and comparison to the structure determined for rabbit CYP450 2C5 (1nr6_a) [38].

<p>The heme is shown is each model as a space-filling projection. The J and J’ helices in rabbit CYP450 2C5, which are absent in <i>S</i>. <i>mansoni</i> CYP450, are highlighted in yellow.</p