Serine proteases profiles of Leishmania (Viannia) braziliensis clinical isolates with distinct susceptibilities to antimony

Glucantime (SbV) is the first-line treatment against American Tegumentary Leishmaniasis. Resistance cases to this drug have been reported and related to host characteristics and parasite phenotypes. In this study, 12 Leishmania (Viannia) braziliensis isolates from patients that presented clinical cure (Responders—R) and relapse or therapeutic failure (Non-responders—NR) after treatment with antimony, were analyzed. These parasites were assessed by in vitro susceptibility to SbIII and SbV, serine proteases activity measured with substrate (z-FR-AMC) and specific inhibitors (TLCK, AEBSF and PMSF). In vitro susceptibility of axenic amastigotes to SbIII showed a significant difference between R and NR groups. The protease assays showed that TLCK inhibited almost 100% of activity in both axenic amastigotes and promastigotes while AEBSF inhibited around 70%, and PMSF showed lower inhibition of some isolates. Principal component and clustering analysis performed with these data yielded one homogeneous cluster with only NR isolates and three heterogeneous clusters with R and NR isolates. Additionally, differential expression of subtilisins (LbrM.13.0860 and LbrM.28.2570) and TXNPx (LbrM.15.1080) was evaluated in promastigotes and axenic amastigotes from both groups. The results showed a higher expression of LbrM.13.0860 and LbrM.15.1080 genes in axenic amastigotes, while LbrM.28.2570 gene had the lowest expression in all isolates, regardless of the parasite form. The data presented here show a phenotypic heterogeneity among the parasites, suggesting that exploration of in vitro phenotypes based on SbIII and serine proteases profiles can aid in the characterization of L. (V.) braziliensis clinical isolates.

Boswellic Acids Show In Vitro Activity against Leishmania donovani

In continuation of our search for leads from medicinal plants against protozoal pathogens, we detected antileishmanial activity in polar fractions of a dichloromethane extract from Boswellia serrata resin. 11-keto-β-boswellic acid (KBA) could be isolated from these fractions and was tested in vitro against Leishmania donovani axenic amastigotes along with five further boswellic acid derivatives. 3-O-acetyl-11-keto-β-boswellic acid (AKBA) showed the strongest activity with an IC50 value of 0.88 µM against axenic amastigotes but was inactive against intracellular amastigotes in murine macrophages

Quinolin-(1H)-imines as a new chemotype against leishmaniasis: biological evaluation and mechanistic studies

Leishmaniasis is one of the most challenging neglected tropical diseases and remains a global threat to public health. Currently available therapies for leishmaniases present significant drawbacks and are rendered increasingly inefficient due to parasite resistance, urging the need for more effective, safer, and cheaper drugs. In our efforts to identify novel chemical scaffolds for the development of antileishmanial agents, we have screened in house antiplasmodial libraries against axenic and intracellular forms of Leishmania infantum, L. amazonensis and L. major. Several of the screened compounds showed IC50 values against intracellular L. infantum parasites in the submicromolar range (1h: IC50 0.9 μM and 1n: IC50 0.7 μM) and selectivity indexes of 11 and 9.7, respectively. Compounds also displayed activity against L. amazonensis and L. major, albeit in the low micromolar range. Mechanistic studies revealed that 1n efficiently inhibits oxygen consumption and significantly decreases the mitochondrial membrane potential in L. infantum axenic amastigotes, suggesting that this chemotype acts, at least in part, by interfering with mitochondrial function. Structure-activity analysis suggests that 1n is a promising antileishmanial lead and emphasize the potential of the quinoline-(1H)-imine chemotype for the future development of new antileishmanial agents.

Serine Proteases Profiles of Leishmania (Viannia) Braziliensis Clinical Isolates With Distinct Susceptibilities to Antimony

Glucantime® (SbV) is the first-line treatment against leishmaniasis in South America. Its effectiveness has been associated with modulation of the parasite detoxification system that, in turn, is related to serine proteases such as subtilisins. In this study, 12 Leishmania (Viannia) braziliensis isolates from patients that presented clinical cure (Responders - R) and relapse or therapeutic failure (Non-responders - NR) were used. The parasites were assessed by in vitro susceptibility to SbIII and SbV, serine proteases activity – measured with z-FR-AMC as substrate and specific inhibitors – and expression of subtilisins and tryparedoxin-peroxidase (TXNPx). In vitro susceptibility of axenic amastigotes to SbIII showed a significant difference between R and NR groups. TLCK inhibited almost 100 % of activity in both axenic amastigotes and promastigotes while AEBSF inhibited around 70 %, and PMSF showed lower inhibition of specific isolates. Principal component and clustering analysis yielded one homogeneous cluster with only NR isolates and three heterogeneous clusters with R and NR isolates. Additionally, transcripts of subtilisins (LbrM.13.0860 and LbrM.28.2570) and TXNPx (LbrM.15.1080) were detected in promastigotes and axenic amastigotes from both groups. The data presented here show a phenotypic heterogeneity among the parasites, suggesting that exploration of in vitro phenotypes based on SbIII and serine proteases profiles can aid in the characterization of L. (V.) braziliensis clinical isolates.

Bioactive Isocedrenes from Perezia multiflora

Four isocedrenes (1 – 4), including one new compound (2), were isolated from an ethanolic extract of the aerial parts of Perezia multiflora by bioactivity-guided fractionation. For compounds 1 and 3, a revised stereochemical assignment is proposed based on molecular modeling studies using DFT-NMR calculations. Antiparasitic activity of the four compounds was evaluated using an in vitro culture of Plasmodium falciparum and axenic amastigotes of Leishmania infantum. IC50 values ranged from 0.81 to 16.1 µM (P. falciparum) and 0.16 to 2.03 µM (L. infantum). Toxicity was evaluated against J774A.1 mouse macrophages or human macrophages generated from THP-1 monocytic cells (IC50 values ranging from 0.16 to 2.64 µM). Compound 4 exhibited weak selectivity against P. falciparum with a selectivity index (SI = CC50/IC50) of 3. No selectivity was observed for compounds 1 – 3 against both parasites.

New Amides Containing Selenium as Potent Leishmanicidal Agents Targeting Trypanothione Reductase

ABSTRACTTwo new series of 28 selenocyanate and diselenide derivatives containing amide moieties were designed, synthesized, and evaluated for their leishmanicidal activity against Leishmania infantum axenic amastigotes, and selectivity was assessed in human THP-1 cells. Eleven compounds exhibited excellent leishmanicidal activity with EC50 values lower than the reference drug miltefosine (EC50 = 2.84 μM). In addition, for six of them the selectivity index ranged from 9 to >1,442, greater than both references used. The most potent and selective compounds were compounds 2h, 2k, and 2m that displayed EC50 values of 0.52, 1.19, and 0.50 μM, respectively, and a high selectivity index (SI) when tested against THP-1 monocytic cells (SI = >1,442, >672, and >1,100, respectively). These derivatives showed an efficacy similar to that of the reference drugs but much better SI values. They also showed interesting activity values against infected macrophages. Trypanothione reductase (TryR) activity and intracellular thiol level measurement assays were performed for the three best compounds in an attempt to elucidate their mechanism of action. Despite that the new analogs exhibited comparable or better inhibitory activities than the reference TryR inhibitors, more studies are necessary to confirm this result. In summary, our findings suggest that the three compounds described here could constitute leading leishmanicidal drug candidates.

Serine Proteases Profiles of Leishmania (Viannia) Braziliensis Clinical Isolates With Distinct Susceptibilities to Antimony

Background: Glucantime® (SbV) is considered the first-line treatment against American Tegumentary Leishmaniasis in South America, though increased parasite resistance towards it have been reported and hampered its effectiveness. In this context, subtilisins serine proteases have been related to parasites’ susceptibility to drugs such as SbV and derivatives, through modulation of the parasite detoxification system. However, little is known about parasites causing ATL and their distinct responses towards this treatment.Methods: The study was conducted using Leishmania (Viannia) braziliensis clinical isolates from patients that presented clinical cure or Responders (R) and relapse/therapeutic failure or Non-responders (NR). Twelve clinical isolates were used to assess their in vitro susceptibility to SbIII and SbV, serine proteases activity, and expression of subtilisins-like and tryparedoxin-peroxidase (TXNPx) transcripts. Results: SbIII was able to better distinguish axenic amastigotes from each clinical group. These isolates were also assessed for serine protease activity, using z-FR-AMC as substrate and detecting distinct enzyme profiles with specific inhibitors. TLCK inhibited almost 100% of activity in both promastigotes and axenic amastigotes while AEBSF inhibited around 70%. PMSF showed low inhibition of specific isolates (35%). Gathering all the quantitative data, we performed principal component analysis and then used the K-means algorithm to cluster the isolates. This analysis yielded one cluster with only one isolate (R isolate), one homogeneous cluster (NR isolates), and three heterogeneous clusters (R and NR isolates). Additionally, gene transcripts of subtilisins and TXNPx were detected in promastigotes and axenic amastigotes from both groups. Conclusions: Cluster analysis showed that there is a phenotypic heterogeneity among the isolates, however, exploration of in vitro phenotypes based on SbIII and serine proteases profiles can aid in the characterization and better understanding of L. (V.) braziliensis clinical isolates.