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

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.

Biological characterization of the Amazon coral Micrurus spixii snake venom: Isolation of a new neurotoxic phospholipase A2

“…Serial twofold dilutions (seven concentrations and one drug-free control) of the sample (20 mL/well) were dispensed into standard 96-well microculture plates and 180 mL of infected erythrocytes culture were added. The assay was done in triplicate, negative control cultures received only RPMI and control positive cultures received chloroquine (CQ), an antimalarial drug according to Penna-Coutinho et al (2011). The plates were incubated for 72 h in a gas mixture (5% CO 2 , 5% O 2 , 90% N 2 ) at 37 C. They were subsequently frozen-thawed twice to obtain complete hemolysis.…”

New approaches in antimalarial drug discovery and development: a review

“…Agents such as posaconazole (an inhibitor of ergosterol biosynthesis), itraconazole (an antifungal agent) and atorvastatin (widely used to reduce cholesterol levels) have proven to be active against P. falciparum blood stage parasites in vitro and against P. berghei-infected mice (Penna-Coutinho et al 2011). These compounds are candidates for clinical trials in combination with other antimalarials.…”

“…One of the promising approaches currently being used in the discovery of new antimalarials aimed at drug-resistant parasites and the interruption of the transmission of malaria is the testing of commercially available drugs that are currently prescribed for other indications; if successful, this approach will rapidly accelerate the production of new antimalarials at a lower cost. High-throughput screening (HTS) and molecular modelling (MM) have been successfully used in collaborative projects to select three potential antimalarial candidates (Penna-Coutinho et al 2011), as discussed below.…”

A Quest for New Antimalarial Agents with Improved Specificity Guided by Molecular Docking, 3D QSAR and Molecular Dynamics Simulation Studies

“…The simulation interaction analysis of designed molecule N1 showed similar interaction with active site residues, direct hydrogen bond interaction was retained with Glu 122 for maximum duration of the simulation time and retained all other hydrophobic interaction as chloroquine. This suggests that the designed molecule N1 has ability to specifically bind to the conserved Glu 122 residue of pfLDH were as in all mammalian and other forms of LDH there is phenylalanine residue at this position that is not capable of forming hydrogen bonding [22].…”