The Trypanocidal Activity of Amidine Compounds Does Not Correlate with Their Binding Affinity to Trypanosoma cruzi Kinetoplast DNA

Abstract

Due to limited efficacy and considerable toxicity, the therapy for Chagas' disease is far from being ideal, and thus new compounds are desirable. Diamidines and related compounds such as arylimidamides have promising trypanocidal activity against Trypanosoma cruzi. To better understand the mechanism of action of these heterocyclic cations, we investigated the kinetoplast DNA (kDNA) binding properties and trypanocidal efficacy against T. cruzi of 13 compounds. Four diamidines (DB75, DB569, DB1345, and DB829), eight arylimidamides (DB766, DB749, DB889, DB709, DB613, DB1831, DB1852, and DB2002), and one guanylhydrazone (DB1080) were assayed in thermal denaturation (T m ) and circular dichroism (CD) studies using whole purified T. cruzi kDNA and a conserved synthetic parasite sequence. The overall CD spectra using the whole kDNA were similar to those found for the conserved sequence and were indicative of minor groove binding. Our findings showed that some of the compounds that exhibited the highest trypanocidal activities (e.g., DB766) caused low or no change in the T m measurements. However, while some active compounds, such as DB766, induced profound alterations of kDNA topology, others, like DB1831, although effective, did not result in altered T m and CD measurements. Our data suggest that the strong affinity of amidines with kDNA per se is not sufficient to generate and trigger their trypanocidal activity. Cell uptake differences and possibly distinct cellular targets need to be considered in the final evaluation of the mechanisms of action of these compounds.Protozoan parasites display a wide range of peculiarities, including polycistronic transcription, trans-splicing of precursor mRNAs, the anchoring of surface proteins by glycosylphosphatidylinositol (GPI), and the presence of glycosomes, and this is likely due to the early divergence of the eukaryotic lineage (15). Mitochondrial DNA organization and the RNAediting process are remarkable features of kinetoplastids, which harbor a single mitochondrion enclosing a unique type of DNA organization called kinetoplast DNA (kDNA),

Evaluation of Arylimidamides DB1955 and DB1960 as Candidates against Visceral Leishmaniasis and Chagas' Disease: In Vivo Efficacy, Acute Toxicity, Pharmacokinetics, and Toxicology Studies

“…As expected, the biological activity of the hydrochloride salts was nearly identical to the activity of the corresponding mesylate salts in the intracellular Leishmania assay and the peritoneal macrophage toxicity assay. DB1852 did not display DNA binding, as judged by its negligible ⌬T m value obtained using poly(dA·dT) 2 DNA, consistent with the ⌬T m data obtained for this compound using T. cruzi kinetoplast DNA (10). The mesylate salt of DB1852, DB1955, also gave no ⌬T m increase.…”

Studies on the Antileishmanial Mechanism of Action of the Arylimidamide DB766: Azole Interactions and Role of CYP5122A1

“…The activity of AIAs against T. cruzi does not correlate with the ability of these compounds to bind kDNA (24), and treatment of T. cruzi intracellular amastigotes with AIAs resulted in not only swelling of the mitochondrion and disorganization of kDNA but also vacuolization and the appearance of electron-dense bodies in the cytoplasm, the development of vesicles in the flagellar pocket, and disorganization of subpellicular microtubules (7). In terms of apicomplexan parasites, exposure to AIAs compromised the viability of intracellular forms of both Neospora caninum and Toxoplasma gondii specifically through the modulation of host cell processes (25).…”

Synthesis, DNA binding and antileishmanial activity of low molecular weight bis-arylimidamides

“…Little is known about the mode of action of AIAs, despite the fact that they were originally conceived as DNA minor groove binders [10]. Their DNA affinity has been found to be highly variable with structure, ranging from quite weak to moderately strong [10,14,17]. It has been shown that the T. cruzi activity of AIAs is not correlated with their binding to T. cruzi kinetoplast DNA [17].…”

“…Their DNA affinity has been found to be highly variable with structure, ranging from quite weak to moderately strong [10,14,17]. It has been shown that the T. cruzi activity of AIAs is not correlated with their binding to T. cruzi kinetoplast DNA [17]. Given the potent antiprotozoal activity and promising pharmacokinetic properties of AIAs, despite their relatively high molecular weights (e.g.…”