Luciana M. R. Antinarelli

7-Chloro-4-quinolinyl Hydrazones: A Promising and Potent Class of Antileishmanial Compounds

In this work, we report the antileishmanial evaluation of twenty 7‐chloro‐4‐quinolinyl hydrazone derivatives (1–20). Firstly, the compounds were tested against promastigotes of four different Leishmania species. After that, all derivatives were assayed against L. braziliensis amastigotes and murine macrophages. Furthermore, it was investigated whether the antiamastigote L. braziliensis effect of the compounds could be associated with nitric oxide production. Compounds 6 and 7 showed a strong leishmanicidal activity against intracellular parasite with IC50 in nanogram levels (30 and 20 ng/mL, respectively). Appreciable activity of three compounds tested can be considered an important finding for the rational design of new leads for antileishmanial compounds.

Increase of leishmanicidal and tubercular activities using steroids linked to aminoquinoline

Background Aminoquinoline/steroid conjugates were synthesized based on the fact that steroid transporters have been shown to accept and carry a variety of drugs. So, in continuing our research of antileishmanial and antitubercular drugs, aminoquinoline/steroid conjugates (12, 13, and 14) were regioselectively synthesized via 1, 3-dipolar cycloaddition of alkynes 3, 5, and 7 with azide 12. The aminoquinoline/steroids conjugates were evaluated in vitro against Leishmania major and Mycobacterium tuberculosis. Results Regioselective synthesis of the novel aminoquinoline/steroid conjugates was achieved in very high yield. All aminoquinoline/steroid conjugates (12, 13, and 14) exhibited best results against Leishmania and M. tuberculosis than the respective alkyne intermediate structures (3, 5, and 7, respectively). Among them, the compound 12 exhibited the best activity for M. tuberculosis (MIC = 8.8 μM). This result is comparable to drugs commonly used in tuberculosis treatment. Also, for antileishmanial assay, the aminoquinoline/steroid conjugates demonstrated a significant activity against promastigote and amastigote forms of L. major. Conclusions Addition of a steroid group to aminoquinoline molecules enhanced the leishmanicidal and antitubercular activities. These results highlight the importance of steroids as carrier.

4-Aminoquinoline Derivatives as Potential Antileishmanial Agents

The leishmanicidal activity of a series of 4‐aminoquinoline (AMQ) derivatives was assayed against Leishmania amazonensis. This activity against the intracellular parasite was found stronger than for L. amazonensis promastigotes. Neither compound was cytotoxic against macrophages. The compound AMQ‐j, which exhibited a strong activity against promastigotes and amastigotes of L. amazonensis (IC50 values of 5.9 and 2.4 μg/mL, respectively) and similar leishmanicidal activity to reference drugs, was chosen for studies regarding its possible mechanism of action toward parasite death. The results showed that the compound AMQ‐j induced depolarization of the mitochondrial membrane potential in promastigotes and in L. amazonensis‐infected macrophages, but not in uninfected macrophages. Furthermore, the depolarization of the mitochondrial membrane potential was dose dependent in infected macrophages. We have established that promastigotes and L. amazonensis‐infected macrophages treated with AMQ‐j were submitted to oxidative stress. This is in line with the increase in the level of reactive oxygen species (ROS). Leishmania amazonensis‐infected macrophages treated with AMQ‐j did not show a significant increase in the production of nitric oxide. Our results indicate the effective and selective action of AMQ‐j against L. amazonensis, and its mechanism of action appears to be mediated by mitochondrial dysfunction associated with ROS production.

Effect of 1,2,3-triazole salts, non-classical bioisosteres of miltefosine, on Leishmania amazonensis

Here, we report the effect of new non-classical bioisosteres of miltefosine on Leishmania amazonensis. Fifteen compounds were synthesized and the compound dhmtAc, containing an acetate anion, a side chain of 10 carbon atoms linked to N-1 and a methyl group linked to N-3, showed high and selective biological activity against L. amazonensis. On the intracellular amastigotes, stages of the parasite related to human disease, the IC50 values were near or similar to the 1.0μM (0.9, 0.8 and 1.0μM on L. amazonensis-WT, and two transgenic L. amazonensis expressing GFP and RFP, respectively), being more active than miltefosine. Furthermore, dhmtAc did not show toxic effects on human erythrocytes and macrophages (CC50=115.9μM) being more destructive to the intracellular parasites (selectivity index>115). Promastigotes and intramacrophage amastigotes treated with dhmtAc showed low capacity for reversion of the effect of the compound. A study of the mechanism of action of this compound showed some features of metazoan apoptosis, including cell volume decreases, loss of mitochondrial membrane potential, ROS production, an increase in the intracellular lipid bodies, in situ labeling of DNA fragments by TUNEL labeling and phosphatidylserine exposure to the outerleaflet of the plasma membrane. In addition, the plasma membrane disruption, revealed by PI labeling, suggests cell death by necrosis. No increase in autophagic vacuoles formation in treated promastigotes was observed. Taken together, the data indicate that the bioisostere of miltefosine, dhmtAc, has promising antileishmanial activity that is mediated via apoptosis and necrosis.

Antileishmanial activity of some Brazilian plants, with particular reference to Casearia sylvestris

Leishmaniasis is a complex of diseases caused by Leishmania protozoa which treatment is restricted to a limited number of drugs that exhibit high toxicity, collateral effects and are often costly. There are a variety of tropical plants distributed in Brazil, and for many poor people the therapy for several diseases is based mainly on the use of traditional herbal remedies. In this work, the cytotoxic activity of 17 plant methanol extracts was evaluated on several Leishmania species and murine macrophages. Among them, the extract of Casearia sylvestris, Piptocarpha macropoda, Trembleya parviflora, Samanea tubulosa and Plectranthus neochilus showed a promissing leishmanicidal activity, exhibiting IC50 values below of 20 µg/mL against at least one species of Leishmania. Casearia sylvestris showed the most expressive activity against all promastigote forms of Leishmania species (IC50 values of 5.4 µg/mL, 5.0 µg/mL, 8.5 µg/mL and 7.7 µg/mL for L. amazonensis, L. braziliensis, L. chagasi and L. major, respectively), being more effective than the reference drug miltefosine. In spite of the cytotoxic effect on macrophages (CC50 value of 5.2 µg/mL), C. sylvestris exhibited a strong inhibition against intracellular amastigotes of L. braziliensis (IC50 value of 1.3 µg/mL). Further studies, including bio-guided fractionation will be conducted to identify the active compounds.

HPLC-DAD Analysis, Antileishmanial, Antiproliferative, and Antibacterial Activities of Lacistema pubescens: An Amazonian Medicinal Plant

Species of the genus Lacistema are traditionally used by Brazilian and Peruvian indigenous communities. The present study investigated the in vitro antileishmanial activity against several Leishmania species, cytotoxicity in murine peritoneal macrophages, antiproliferative activity against HL60 and Jurkat cells, and antibacterial activities against seven bacteria strains of the aerial parts of the methanolic crude extract and fractions of Lacistema pubescens. In addition, their chemical profile was also evaluated. Hexane fraction showed the most significant IC50 values against all promastigotes of Leishmania species tested, except for L. chagasi (IC50 = 4.2 µg/mL for L. major and IC50 = 3.5 µg/mL for L. amazonensis). This fraction also exhibited a strong activity against amastigotes of L. amazonensis (IC50 = 6.9 µg/mL). The antiproliferative activity was also observed for methanolic extract and hexane fraction with IC50 = 47.2 µg/mL and IC50 = 39.7 µg/mL for HL60, respectively. Regarding the antimicrobial activity, the overall antibacterial activity was not very significative. Phytol and sitosterol were identified in the methanolic extract. Additionally, previous studies also revealed the presence of those compounds in the hexane fraction. Among other compounds, phytol and sitosterol were probably involved in the antileishmanial and cytotoxicity activities observed in this study.

What do we know about the role of regulatory B cells (Breg) during the course of infection of two major parasitic diseases, malaria and leishmaniasis?

Abstract Parasitic diseases, such as malaria and leishmaniasis, are relevant public health problems worldwide. For both diseases, the alarming number of clinical cases and deaths reported annually has justified the incentives directed to better understanding of host’s factors associated with susceptibility to infection or protection. In this context, over recent years, some studies have given special attention to B lymphocytes with a regulator phenotype, known as Breg cells. Essentially important in the maintenance of immunological tolerance, especially in autoimmune disease models such as rheumatoid arthritis and experimentally induced autoimmune encephalomyelitis, the function of these lymphocytes has so far been poorly explored during the course of diseases caused by parasites. As the activation of Breg cells has been proposed as a possible therapeutic or vaccine strategy against several diseases, here we reviewed studies focused on understanding the relation of parasite and Breg cells in malaria and leishmaniasis, and the possible implications of these strategies in the course of both infections.

A Pluronic® F127-based polymeric micelle system containing an antileishmanial molecule is immunotherapeutic and effective in the treatment against Leishmania amazonensis infection

Clioquinol (5-chloro-7-iodoquinolin-8-ol or ICHQ) was recently showed to presents an in vitro effective antileishmanial action, causing changes in membrane permeability, mitochondrial functionality, and parasite morphology. In the present study, ICHQ was incorporated into a Poloxamer 407-based polymeric micelles system (ICHQ/M), and its antileishmanial activity was in vivo evaluated in L. amazonensis-infected BALB/c mice. Amphotericin B (AmpB) and its liposomal formulation (Ambisome®) were used as controls. Parasitological and immunological evaluations were performed 30 days after the treatment. Results indicated more significant reductions in the average lesion diameter and parasite burden in ICHQ or ICHQ/M-treated mice, which were associated with the development of a polarized Th1 immune response, based on production of high levels of IFN-γ, IL-12, TNF-α, GM-CSF, and antileishmanial IgG2a antibody. Control groups´ mice produced high levels of IL-4, IL-10, and IgG1 isotype antibody. No organic toxicity was found by using ICHQ or ICHQ/M to treat the animals, although those receiving AmpB and Ambisome® have presented higher levels of renal and hepatic damage markers. In conclusion, results suggested that the ICHQ/M composition can be considered as an antileishmanial candidate to be tested against human leishmaniasis.

Synthesis, characterization, and NMR studies of 1,2,3-triazolium ionic liquids: a good perspective regarding cytotoxicity

AbstractIonic liquids (ILs) have been extensively studied and are considered green solvents capable of replacing traditional organic solvents. In this study, seven 1,2,3-triazolium derivative ILs have been synthesized. In order to study the effect of the cation nature on the ILs cytotoxicity, their structures were first identified by 1H, 13C NMR 1D, and 2D spectroscopy. DFT calculations have also been performed in a way to help to provide an insightful structural analysis from 13C NMR spectroscopy. The comparison made with the NMR experimental shifts was quite important to show that the 1,2,3-triazolium derivatives have the expected structure shown here. The in vitro cytotoxicity of ILs toward macrophages showed that among the compounds tested, five did not exhibit expressive cytotoxicity on mammalian cells. Besides the well-established relationship between the carbonic chain size of the cation and the cytotoxicity, the log P of the compounds predicts that the toxicity increases with the size of the carbon chain, demonstrating that the most cytotoxic compound is also the most lipophilic one. The low cytotoxicity effect of ILs on mammalian cells points to their potential application in large-scale by industry. Graphical abstractSeven triazolium ILs were synthesized and their in vitro cytotoxicity on murine macrophages showed a relationship with the carbonic chain size.

Synthesis, Biological Activity, and Mechanism of Action of 2-Pyrazyl and Pyridylhydrazone Derivatives, New Classes of Antileishmanial Agents

In this work, we report the antileishmanial activity of 23 compounds based on 2‐pyrazyl and 2‐pyridylhydrazone derivatives. The compounds were tested against the promastigotes of Leishmania amazonensis and L. braziliensis, murine macrophages, and intracellular L. amazonensis amastigotes. The most potent antileishmanial compound was selected for investigation into its mechanism of action. Among the evaluated compounds, five derivatives [(E)‐3‐((2‐(pyridin‐2‐yl)hydrazono)methyl)benzene‐1,2‐diol (2 b), (E)‐4‐((2‐(pyridin‐2‐yl)hydrazono)methyl)benzene‐1,3‐diol (2 c), (E)‐4‐nitro‐2‐((2‐(pyrazin‐2‐yl)hydrazono)methyl)phenol (2 s), (E)‐2‐(2‐(pyridin‐2‐ylmethylene)hydrazinyl)pyrazine (2 u), and (E)‐2‐(2‐((5‐nitrofuran‐2‐yl)methylene)hydrazinyl)pyrazine (2 v)] exhibited significant activity against L. amazonensis amastigote forms, with IC50 values below 20 μm. The majority of the compounds did not show any toxic effect on murine macrophages. Preliminary studies on the mode of action of members of this hydrazine‐derived series indicate that the accumulation of reactive oxygen species (ROS) and disruption of parasite mitochondrial function are important for the pharmacological effect on L. amazonensis promastigotes.