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

Abstract

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.

Evaluation of the Anti-Schistosoma mansoni Activity of Thiosemicarbazones and Thiazoles

“…The thick tegument that covers the entire surface of schistosomes is an important target for drugs because the functioning of the surface membrane and the integrity of the tegument are critical for the survival and proliferation of the Schistosoma parasite (13). These structures play vital roles in the immune evasion, nutrient absorption, and cholesterol metabolism of the host (13,50).…”

“…Current schistosomiasis treatment is based on the use of praziquantel (PZQ), a pirazylisoquinoline, which is effective against all Schistosoma species infecting humans (11,12) and has been successfully used over the last 20 years as the drug of choice in most areas where the disease is endemic (3,13,14). Even though PZQ the antihelminthic drug of choice and despite its advantages, which include tolerability, safety, efficacy, and low cost, PZQ does not protect individuals from reinfection and is not active against the immature stages of the worm, such as the schistosomula and preadult and juvenile adult stages (13,15).…”

“…Even though PZQ the antihelminthic drug of choice and despite its advantages, which include tolerability, safety, efficacy, and low cost, PZQ does not protect individuals from reinfection and is not active against the immature stages of the worm, such as the schistosomula and preadult and juvenile adult stages (13,15).…”

“…Hence, the massive use of PZQ in zones of endemicity with the possibility of the emergence of drug-resistant Schistosoma, combined with the lack of any other effective antischistosomal drug, requires new effective schistosomicidal compounds to be developed and further studies to be carried out with a view to developing alternative therapies that could either replace or complement the use of PZQ for treatment of S. mansoni infection (4,13).…”

Ultrastructural study of morphological changes in Schistosoma mansoni after in vitro exposure to the monoterpene rotundifolone

“…Praziquantel is a pirazyl isoquinoline and is effective against all Schistosoma species infecting humans 8 ; it has been successfully used over the last 20 years as the drug of choice in most areas where the disease is endemic [9][10][11] . Although PZQ has several advantages, including tolerability, safety, efficacy, and low cost, it does not protect individuals from reinfection and is not active against the immature stages of the worm, such as the schistosomula, pre-adult and juvenile adult stages 12 .…”