Antimalarial Activity of Potential Inhibitors of Plasmodium falciparum Lactate Dehydrogenase Enzyme Selected by Docking Studies

Julia Penna-Coutinho,Tanos Celmar Costa França,Antoniana Ursine Krettli,Aline Alves Oliveira,Wilian Augusto Cortopassi,Mauricio Martins Rodrigues

doi:10.1371/journal.pone.0021237

Julia Penna-Coutinho, Tanos Celmar Costa França + Show 4 more

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https://doi.org/10.1371/journal.pone.0021237

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Abstract

The Plasmodium falciparum lactate dehydrogenase enzyme (PfLDH) has been considered as a potential molecular target for antimalarials due to this parasite's dependence on glycolysis for energy production. Because the LDH enzymes found in P. vivax, P. malariae and P. ovale (pLDH) all exhibit ∼90% identity to PfLDH, it would be desirable to have new anti-pLDH drugs, particularly ones that are effective against P. falciparum, the most virulent species of human malaria. Our present work used docking studies to select potential inhibitors of pLDH, which were then tested for antimalarial activity against P. falciparum in vitro and P. berghei malaria in mice. A virtual screening in DrugBank for analogs of NADH (an essential cofactor to pLDH) and computational studies were undertaken, and the potential binding of the selected compounds to the PfLDH active site was analyzed using Molegro Virtual Docker software. Fifty compounds were selected based on their similarity to NADH. The compounds with the best binding energies (itraconazole, atorvastatin and posaconazole) were tested against P. falciparum chloroquine-resistant blood parasites. All three compounds proved to be active in two immunoenzymatic assays performed in parallel using monoclonals specific to PfLDH or a histidine rich protein (HRP2). The IC50 values for each drug in both tests were similar, were lowest for posaconazole (<5 µM) and were 40- and 100-fold less active than chloroquine. The compounds reduced P. berghei parasitemia in treated mice, in comparison to untreated controls; itraconazole was the least active compound. The results of these activity trials confirmed that molecular docking studies are an important strategy for discovering new antimalarial drugs. This approach is more practical and less expensive than discovering novel compounds that require studies on human toxicology, since these compounds are already commercially available and thus approved for human use.

Highlights

Malaria is the most lethal parasitic disease in the world, annually affecting approximately 500 million people and resulting in 800,000 deaths, mostly in African sub-Saharan countries [1]
This result suggests that the software reproduced the appropriate conformation of NADH inside its binding pocket in the Plasmodium falciparum lactate dehydrogenase enzyme (PfLDH) active site
The active site residues that interact with NADH, itraconazole, atorvastatin and posaconazole inside PfLDH are shown in Table 2, and the H-bonds between each compound and the PfLDH active site are shown in Figures 2 and 3

Summary

Introduction

Malaria is the most lethal parasitic disease in the world, annually affecting approximately 500 million people and resulting in 800,000 deaths, mostly in African sub-Saharan countries [1]. Transmission occurs through the bite of Anopheles mosquitoes infected with the parasite and five different species may affect humans. The antimalarial treatment recommended for P. falciparum consists of drug combinations containing artemisinin derivatives (ACT) with other antimalarials, including quinoline compounds, such as amodiaquine and mefloquine. Despite the arsenal of drugs available for malaria treatment, the disease remains a worldwide public health problem. P. falciparum quickly develops resistance under selective drug pressure [5]. P. vivax, the most prevalent human parasite worldwide, has been shown to be resistant to chloroquine, including in Brazil [3]. Continuous efforts on the development of new antimalarials are required, and our primary method has been to use different approaches, such as testing natural products and synthetic molecules, as reviewed [6], [7]

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