Leishmania donovani (visceral leishmaniasis) and the trypanosomatid parasites T. cruzi (American Chagas disease) and T. brucei (African sleeping sickness) are significant causes of morbidity and mortality in tropical and subtropical areas worldwide. Current drug treatments for these pathogens have toxic side effects and are only partially effective due to increasing parasite drug resistance and poor patient compliance and tolerance. There is an urgent need for improved chemoprophylactic regimens for these human pathogens. Artemisinin and its derivatives are a safe and highly effective class of drugs whose introduction has had a major impact on the treatment of malaria. New artemisinin derivatives, such as artemisone, are even more effective and less toxic than the original artemisinins. Recently the intracellular target of artemisinin was identified as the Plasmodium endoplasmic reticulum calcium pump (SERCA). SERCA pumps are essential proteins that regulate internal calcium homeostasis, controlling an impressive and varied array of cellular functions. Evidence from our lab and others indicates that artemisinin and its derivatives, including artemisone, also inhibit Leishmania and the trypanosomatid parasites. These observations offer a unique opportunity to exploit a novel class of drugs with an excellent safety profile for Leishmania and trypanosomatid therapy. We have recently cloned the SERCA pump from L. donovani and propose to study the effects of artemisinin on LDSERCA and establish a basis for future studies on the T. brucei and T. cruzi SERCA pumps. The hypothesis to be tested is that artemisinin and artemisinin derivatives exhibit anti-leishmanial activity by targeting the Leishmania LDSERCA pump.
Three specific aims are proposed.
Specific aim 1. Determine the effects of artemisinins on Leishmania donovani promastigotes (insect and culture form) and amastigotes (host macrophage intracellular form) and human cell lines.
Specific aim 2. Verify that the anti-leishmanial activity of artemisinins results from interaction with the L. donovani SERCA pump (LDSERCA).
Specific aim 3. Determine the in vivo efficacy of artemisinins on Leishmania donovani infected Syrian Golden hamsters (Mesocricetus auratus).
Specific aim 1 will establish that artemisinins have sufficient anti-leishmanial activity to merit consideration as a therapeutic option.
Specific aim 2 will validate LDSERCA as the cellular target of artemisinin in L. donovani.
Specific aim 3 will prove the efficacy of artemisinins in treating visceral leishmaniasis in an animal model. This will permit focused development of artemisinins as chemotherapeutic agents for visceral leishmaniasis and facilitate characterization of the effects of artemisinins on T. cruzi and T. brucei SERCAs. ? ? ?