Antileishmanial Mechanism of Diamidines Involves Targeting Kinetoplasts

Abstract

bLeishmaniasis is a disease caused by pathogenic Leishmania parasites; current treatments are toxic and expensive, and drug resistance has emerged. While pentamidine, a diamidine-type compound, is one of the treatments, its antileishmanial mechanism of action has not been investigated in depth. Here we tested several diamidines, including pentamidine and its analog DB75, against Leishmania donovani and elucidated their antileishmanial mechanisms. We identified three promising new antileishmanial diamidine compounds with 50% effective concentrations (EC 50 s) of 3.2, 3.4, and 4.5 M, while pentamidine and DB75 exhibited EC 50 s of 1.46 and 20 M, respectively. The most potent antileishmanial inhibitor, compound 1, showed strong DNA binding properties, with a shift in the melting temperature (⌬T m ) of 24.2°C, whereas pentamidine had a ⌬T m value of 2.1°C, and DB75 had a ⌬T m value of 7.7°C. Additionally, DB75 localized in L. donovani kinetoplast DNA (kDNA) and mitochondria but not in nuclear DNA (nDNA). For 2 new diamidines, strong localization signals were observed in kDNA at 1 M, and at higher concentrations, the signals also appeared in nuclei. All tested diamidines showed selective and dose-dependent inhibition of kDNA, but not nDNA, replication, likely by inhibiting L. donovani topoisomerase IB. Overall, these results suggest that diamidine antileishmanial compounds exert activity by accumulating toward and blocking replication of parasite kDNA.

Twist and Turn—Topoisomerase Functions in Mitochondrial DNA Maintenance

“…The role of topoisomerases in organelle genome maintenance is perhaps best studied in trypanosomatid parasites such as Trypanosoma and Leishmania . In these organisms, the mitochondrial (kinetoplast) genome is organized in a complex network of interlocked circles, which requires both type I and II topoisomerase activity for maintenance [52,53]. The type I topoisomerase Top1A is required in the last phases of replication, while the type II Top2βmt re-attaches freshly replicated minicircles to the network and keeps the network intact [54].…”

Novel Catechol Derivatives of Arylimidamides as Antileishmanial Agents

“…290 -292°C, lit. [24] 2,5-Bis(4-aminophenyl)pyrrole (6). To a solution of 5 (0.93 g, 3 mmol) in absolute EtOH (4.5 mL), and AcOEt (22 mL) was added 10% Pd/C (0.13 g).…”

“…Since no effective vaccine has been approved yet, and the medications used for leishmaniasis have different limitations such as drug resistance and toxicity, there is an urgent need to develop new efficient drugs. [ ][ ] The diamidine pentamidine, as a first‐line drug for CL and as a second‐line agent for VL, [ ][ ] is one of the most widely used antiparasitic agents to treat antimony‐resistant leishmaniasis. [ ][ ] Aromatic diamidines have also exhibited promising antiprotozoal activity.…”

Therapeutic response and safety of the topical, sequential use of antiseptic, keratolytic, and pentamidine creams (3-PACK) on Leishmania (Viannia) braziliensis-infected mice

“…Salicylic acid (SA) is a lipid-soluble organic compound that can penetrate lipid membranes and decrease corneocyte cohesion 11 . Pentamidine (PMD) isethionate, the selected antileishmanial drug, is a synthetic diamidine derivative and cationic drug that is commercially available as diisethionate salt (Pentacarinat ® ) 12 . PMD’s main target is thought to be the parasites’ mitochondria.…”

“…PMD’s main target is thought to be the parasites’ mitochondria. Dramatic dilation, condensation, disruption of kinetoplast DNA, and collapse (decrease) of the parasites’ mitochondrial membrane potential have been demonstrated after treatment with PMD 12 . PMD isethionate is used as a second-line therapy for treating NW-CL [except for Leishmania (V.) guyanensis infections, for which it is a first-line treatment], 13 and is also recommended for the treatment of Pneumocystis jiroveci pneumonia and early stages of African trypanosomiasis 14 …”