Solving a decades-long mystery in leishmaniasis drug development

Solving a decades-long mystery in leishmaniasis drug development

A breakthrough in understanding how a single-cell parasite ergosterol (its version of cholesterol) could lead to more effective drugs for human leishmaniasis, a parasitic disease that kills about 1 million people each year and kills about 30,000 people around the world.

The results, reported inNature communicationAlso solve a decades-long scientific puzzle that prevents drug makers from successfully using azole antifungals to treat visceral leishmaniasis, or VL.

About 30 years ago, scientists discovered the two types of single-cell parasites that cause VL, Leishmania Donovani and Leishmania Infantum, contain the same lipid sterol called ergosterol, as found in fungal azoles. These azole antifungals target a crucial enzyme for sterol biosynthesis, CYP51.

However, both Leishmania species share biochemical similarities with fungi in their plasma membrane, where ergosterol helps maintain cellular integrity and supports a variety of biological functions, as does cholesterol in humans.

People looked into the sterol profile of the parasites and found that they had mostly ergosterol. This sterol is the main component of their plasma membrane sterols. A similar case can be observed in mushrooms. Fungal organisms also have a high amount of ergosterol in their membranes. There was an initial instinct to use antifungal drugs -azoles to block this pathway. “

Michael Zhuo Wang,Study corresponding author,Professor of Pharmachemistry at the University of Kansas School of Pharmacy

However, scientists have not been able to effectively use antifungal drugs against VL.

"In the research lab and some of the clinical trials, some azoles worked a little, and some other azoles didn't work at all," Wang said. "I ended up focusing on this sterol pathway, a scientific question - if this parasite also uses ergosterol, you would think that all antifungals would work against this parasite."

With this in mind, Wang began his independent research career as part of a group at the University of North Carolina-Chapel Hill, the Parasitic Drug Development Consortium.

“We were interested in developing new drugs for neglected tropical diseases,” he said. "One of these diseases is leishmaniasis. The other is African sleeping sickness. Leishmaniasis, spread by a sand fly vector in warmer climates, can cause a truly devastating infection of internal organs such as the liver and spleen, as well as the bone marrow."

In his new scientific paper, Wang and his collaborators have largely resolved this long-standing scientific question. They show that the parasites that cause leishmaniasis are susceptible to the biosynthesis of their ergosterol, known as the CYP5122A1 enzyme, through a different pathway. Therefore, azole antifungals targeting the CYP5122A1 enzyme as well as the traditional CYP51 pathway should be much more effective in the treatment of leishmaniasis.

"So these azoles don't work very well against Leishmania unless you have an azole that also inhibits the new pathway, which is CYP5122A1," Wang said. "Then suddenly they're much more active against Leishmania. That's the main discovery in this study - we figured out the real drug target in Leishmania. They really need to hit this new enzyme, 22A1, to stop the parasites."

Wang's laboratory at KU showed that the CYP5122A1 gene encodes an essential sterol C4-methyloxidase in the Leishmania parasite through comprehensive biochemical characterization.

“This involved defining its biochemical function – what this enzyme does in terms of sterol biosynthesis,” he said. “We recorded its biochemical function and clarified its role in the ergosterol biosynthesis pathway.”

Already the researchers are publishing the follow-up scholarship and discovery based on their new breakthrough in understanding the sterol synthesis pathway in the parasites. They said drugmakers and researchers should develop therapies that target CYP5122A1. These should prove more effective in helping people survive leishmaniasis, Wang said.

“This shows us how we should retarget these existing antifungal azoles by screening against this new target,” said the KU researcher. “Those that actually inhibit this new target should have a better chance of working against Leishmania infections.”

Wang's co-authors at the KU School of Pharmacy were graduate students Yiru Jin and Mei Feng, who served as lead authors, and graduate student Lingli Qin as co-author from the Department of Pharmachemistry; Director Chamani Perera and PhD student of Indeewara Munasinghe from KU's Synthetic Chemical Biology Core Laboratory; Philip Gao, director of KU's protein production group; and Judy Qiju Wu, associate teaching professor of pharmacy practice.

The KU researchers were joined by Kai Zhang, Somrita Basu, Yu Ning, Robert Madden, Hannah Burks and Salma Waheed Sheikh from Texas Tech University; and Karl Werbevetz, Arline Joachim, Junan Li and April Joice from Ohio State University.

This study was supported in part by the U.S. National Institute of Allergy and Infectious Diseases, the U.S. Department of Defense, and the KU Centers for Biomedical Research (COBRE).

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