Ultrastructural analysis of ß-lapachone-induced surface membrane damage in male adult Schistosoma mansoni BH strain worms.

The present study provides, for the first time, conclusions on the in vitro schistosomicidal properties of ß-lap. Adult male Schistosoma mansoni worms of the BH strain were used for the study. Motility, mortality, cell viability and alterations in the tegument were employed as schistosomicidal parameters. Alterations in motility were observed 6h after incubation in concentrations of 50 and 100 µM. ß-lap decreased significantly the worm viability, reducing the formation of formazan in 17.7%, 27.4% and 54.8% at concentrations of 25, 50 and 100 µM, respectively. Mortality in concentrations of 50 and 100 µM was of 67% and 100%, respectively, after 24h. The death of the parasite was preceded by progressive surface membrane damage, characterized by tegument peeling, spine reduction and erosion, blister formation and rupture, and the emergence of holes. In addition to this, in the anterior portion, intense general edema, areas of cracking with a wrinkled surface, furrows and a fibrous appearance were also observed. The results of the present study thus provide a sound basis for further in-depth studies of the schistosomicidal properties of ß-lap, both in the laboratory and in the field.

Ultrastructural analysis of miltefosine-induced surface membrane damage in adult Schistosoma mansoni BH strain worms.

Schistosomiasis is an infectious parasitic disease caused by helminths from the genus Schistosoma; it affects over 200 million people globally and is endemic in 70 countries. In Brazil, 6 million individuals are infected with Schistosoma mansoni. Furthermore, as the prevalence of S. mansoni infections is increasing, approximately 26 million citizens in 19 Brazilian states are at risk for infection. Schistosomiasis disease control involves predominately the administration of a single drug, praziquantel. Although praziquantel exhibits chemotherapeutic efficacy and safety, its massive use in endemic zones, the possibility of the emergence of drug-resistant Schistosoma parasites, and the lack of another efficacious antischistosomal drug demand the discovery of new schistosomicidal compounds. First developed as anti-tumor drug, miltefosine is an alkylphospholipid derivative that exhibits bioactivity against Leishmania and Trypanosoma parasites, free-living protozoa, bacteria, and fungi. With its anti-parasite activity, miltefosine was the first orally administered drug against visceral and cutaneous leishmaniasis approved. Previously, by means of the MTT cytotoxic assay and a DNA fragmentation test, we verified that, at doses of 100 and 200 µM (40 and 80 µg/mL), miltefosine exhibited in vitro schistosomicidal activity against adult S. mansoni worms. Here, we present ultrastructural evidence of rapid, severe miltefosine-induced surface membrane damage in S. mansoni following drug treatment. The number of dead parasites was concentration- and time-dependent following miltefosine treatment. At a miltefosine concentration of 200 µM (∼80 µg/mL), in vitro parasite killing was initiated as early as 3 h post-incubation, and it was maximal after 24 h of treatment. The parasite death was preceded by progressive surface membrane damage, characterized by tegument peeling, spine reduction and erosion, blister formation and rupture, and the emergence of holes. According to our present results, miltefosine is very effective at inducing membrane destruction of S. mansoni with a short onset of pharmacological action.

Immunohistopathological changes in murine Schistosomiasis mansoni under the influence of N-acetyl-L-cysteine.

The main pathology associated with Schistosomiasis mansoni is granulomatous inflammation that may develop into hepatosplenic disease with fibrosis and hepatoesplenomegaly. It is known that N-acetyl-L-cysteine (NAC) reduces tissue damage in chronic liver diseases owing to its anti-inflammatory, antioxidant, and detoxifying properties. In this study, we investigated the imunohistopathological changes in murine schistosomiasis mansoni under the influence of NAC, in combination with Praziquantel (PZQ) or not. Three groups of mice were formed to evaluate the effects of NAC during infection in the acute, intermediate, and chronic phases. Each group was further subdivided into four subgroups: NAC, PZQ, NAC + PZQ and control (without treatment). Oral administration of NAC (200 mg/kg/day) was carried out on the first day after infection for the acute phase and on the 45th for the intermediate and chronic phases for 59 and 45, 75 days, respectively. PZQ (100 mg/kg/day), was given orally by gavage from the 45th to 49th day after infection. Histopathological analysis of liver tissue provided evidence that combined NAC + PZQ treatment reduced the development of granulomas observed in the chronic phase. Animals treated with NAC and/or PZQ showed a reduction in the size of granulomas and all those treated with NAC exhibited a lower degree of fibrosis. In all groups, NAC decreased the synthesis of interferon-γ and nitric oxide, while increasing the levels of interleukin-10, but it did not influence the production of interleukin-4. On the whole, NAC treatment induced an immunomodulatory effect and reduced liver damage during the granulomatous inflammation in S. mansoni-infected mice.