Trypanocidal action of eupomatenoid-5 is related to mitochondrion dysfunction and oxidative damage in Trypanosoma cruzi

Exploring Synthetic Dihydrobenzofuran and Benzofuran Neolignans as Antiprotozoal Agents against Trypanosoma cruzi

Chagas disease is a neglected tropical disease that affects more than 8 million people. Although there are therapies against this disease, the search for new drugs is important because the current treatments show limited effectiveness and high toxicity. In this work, eighteen dihydrobenzofuran-type neolignans (DBNs) and two benzofuran-type neolignans (BNs) were synthesized and evaluated against amastigote forms of two Trypanosoma cruzi strains. The in vitro cytotoxicity and hemolytic activity of the most active compounds were also evaluated and their relationships with T. cruzi tubulin DBNs were investigated by an in silico approach. Four DBNs demonstrated activity against the T. cruzi Tulahuen lac-Z strain (IC₅₀ from 7.96 to 21.12 µM), and DBN 1 exhibited the highest activity against the amastigote forms of the T. cruzi Y strain (IC₅₀ 3.26 μM). Compounds 1-4 showed CC₅₀ values higher than antitrypanosomal activities, except for DBN 3. All DBNs with antitrypanosomal activity demonstrated CH₅₀ higher than 100 µM. The in silico results indicated that DBNs 1, 2, and 4 are capable of destabilizing the dynamics of the tubulin-microtubule from the vinca site. These compounds displayed promising in vitro activity against T. cruzi, especially compound 1, and can be considered molecular prototypes for the development of new antiparasitic drugs.

Natural compounds based chemotherapeutic against Chagas disease and leishmaniasis: mitochondrion as a strategic target

Over the past years, natural products have been explored in order to find biological active substances to treat various diseases. Regarding their potential action against parasites such as trypanosomatids, specially Trypanosoma cruzi and Leishmania spp., much advance has been achieved. Extracts and purified molecules of several species from genera Piper, Tanacetum, Porophyllum, and Copaifera have been widely investigated by our research group and exhibited interesting antitrypanosomal and antileishmanial activities. These natural compounds affected different structures in parasites, and we believe that the mitochondrion is a strategic target to induce parasite death. Considering that these trypanosomatids have a unique mitochondrion, this cellular target has been extensively studied aiming to find more selective drugs, since the current treatment of these neglected tropical diseases has some challenges such as high toxicity and prolonged treatment time. Here, we summarise some results obtained with natural products from our research group and we further highlighted some strategies that must be considered to finally develop an effective chemotherapeutic agent against these parasites.

In Vitro Nematocidal Effect and Anthelmintic Activity of Artemisia cina Against Haemonchus contortus in Gerbils and Relative Expression of Hc29 Gene in Transitional Larvae (L3-L4)

PURPOSE

(1) To assess the in vitro activity of Artemisia cina against Haemonchus contortus L₃ (HcL₃) and in transitional (L₃-L₄) larvae (HcTrL₃-L₄); (2) to quantify the relative expression of the Hc29 gene in HcTrL₃-L₄ exposed to the A. cina n-hexane extract; and (3) to assess the anthelmintic activity (AA) of the A. cina organic extracts in gerbils artificially infected with H. contortus (HcArt/inf/gerbs).

METHODS

The in vitro assay was carried out in 96-well microtitration plates. The following A. cina extracts: ethyl acetate (Ac-EtOAcEx), n-hexane (Ac-n-HexEx), and methanol (Ac-MethEx) were assessed at 1 and 2 mg/mL against HcL₃ and HcTrL₃-L₄ at 24 h exposure. Relative expression of the Hc29 gene in HcTrL₃-L₄ was obtained by RT-PCR. For assessing the AA, six groups of five HcArt/inf/gerbs were used. Groups were treated orally with 4 mg/kg BW of A. cina extracts. Five days after treatment, the gerbils were necropsied and nematodes counted.

RESULTS

The highest in vitro activities (75 and 82.6%) were shown by Ac-n-HexEx at 1 and 2 mg/mL, respectively. For HcTrL₃-L₄ the highest in vitro activities (69 and 23%) were shown by Ac-n-HexEx and isoguaiacine at 0.625 mg/mL, respectively. Also, upregulation of H. contortus Hc29 gene by 13- and 80-fold (p < 0.01) was observed on the HcTrL₃-L₄ stage after exposure to Ac-n-HexEx extract and isoguaiacine at 0.078 mg/mL, respectively. Reduction percentage was 100% in HcArt/inf/gerbs treated with Ac-n-HexEx.

CONCLUSIONS

We conclude that the Ac-n-HexEx and isoguaiacine compound had anthelmintic efficacy against H. contortus and L₃ and HcTrL₃-L₄.

Relationship between Environmental Covariates and Ceylon Tea Cultivation in Sri Lanka

How the current distribution of tea cultivation is influenced by specific environmental conditions in Sri Lanka is yet to be explored. Therefore, this study aims to assess the differences between tea and non-tea growing areas with respect to climatic and topographic covariates, and to determine the major covariates that control tea distributions. Climatic data of temperature and rainfall were extracted from WorldClim-Global Climate Data; the elevation, slopes, and aspects were obtained from Global Multi-resolution Terrain Elevation Data; and the solar radiation data was computed using a clear-sky solar radiation model. Random points were created on rasterised environmental layers for tea-growing and non-tea growing areas, stratified into low, mid, and high regions, using ArcGIS version 10.4.1 (Environmental Systems Research Institute: ESRI Redlands, CA, USA).Correlations were derived between covariates and tea and non-tea growing areas. According to the logistic regression analysis, there was no significant influence of the south-west, west, and north-west aspect compared to the north aspect when all other covariates were held constant. The odds ratio indicated that an area with a one-unit higher solar radiation was 1.453 times more likely to be a tea growing area. Similarly, a per unit increase in slope increases the likelihood of an area being suitable for tea cultivation by 1.039 times. When the annual mean temperature increased, the suitability of tea cultivation decreased, but an increased rainfall had increased the suitability of an area for tea cultivation. Areas with a north facing slope had the highest suitability for tea cultivation. This research demonstrated that tea growing could be expanded into a variety of locations as long as these variables are either found or managed in order to obtain the critical levels. In addition, it is proposed that the results of this study could be utilised in the assessment of the climate or/and land suitability for tea.

Anti-Trypanosoma cruzi action of a new benzofuran derivative based on amiodarone structure

Chagas disease is a neglected tropical affection caused by the protozoan parasite Trypanosoma cruzi. There is no current effective treatment since the only two available drugs have a limited efficacy and produce side effects. Thus, investigation efforts have been directed to the identification of new drug leads. In this context, Ca²⁺ regulating mechanisms have been postulated as targets for antiparasitic compounds, since they present paramount differences when compared to host cells. Amiodarone is an antiarrhythmic with demonstrated trypanocidal activity acting through the disruption of the parasite intracellular Ca²⁺ homeostasis. We now report the effect of a benzofuran derivative based on the structure of amiodarone on T. cruzi. This derivative was able to inhibit the growth of epimastigotes in culture and of amastigotes inside infected cells, the clinically relevant phase. We also show that this compound, similarly to amiodarone, disrupts Ca²⁺ homeostasis in T. cruzi epimastigotes, via two organelles involved in the intracellular Ca²⁺ regulation and the bioenergetics of the parasite. We demonstrate that the benzofuran derivative was able to totally collapse the membrane potential of the unique giant mitochondrion of the parasite and simultaneously produced the alkalinization of the acidocalcisomes. Both effects are evidenced by a large increase in the intracellular Ca²⁺ concentration of T. cruzi.

Neolignans from leaves of Nectandra leucantha (Lauraceae) display in vitro antitrypanosomal activity via plasma membrane and mitochondrial damages

Chagas disease is a neglected tropical disease, caused by the protozoan parasite Trypanosoma cruzi, which affects more than eight million people in Tropical and Subtropical countries especially in Latin America. Current treatment is limited to nifurtimox and benznidazole, both with reduced effectiveness and high toxicity. In this work, the n-hexane extract from leaves of Nectandra leucantha (Lauraceae) displayed in vitro antitrypanosomal activity against T. cruzi. Using several chromatographic steps, four related neolignans were isolated and chemically characterized as dehydrodieugenol B (1), 1-(8-propenyl)-3-[3'-methoxy-1'-(8-propenyl)-phenoxy]-4,5-dimethoxybenzene (2), 1-[(7S)-hydroxy-8-propenyl]-3-[3'-methoxy-1'-(8'-propenyl)-phenoxy]-4-hydroxy-5-methoxybenzene (3), and 1-[(7S)-hydroxy-8-propenyl]-3-[3'-methoxy-1'-(8'-propenyl)-phenoxy]-4,5-dimethoxybenzene (4). These compounds were tested against intracellular amastigotes and extracellular trypomastigotes of T. cruzi and for mammalian cytotoxicity. Neolignan 4 showed the higher selectivity index (SI) against trypomastigotes (>5) and amastigotes (>13) of T. cruzi. The investigation of the mechanism of action demonstrated that neolignan 4 caused substantial alteration of the plasma membrane permeability, together with mitochondrial dysfunctions in trypomastigote forms. In silico studies of pharmacokinetics and toxicity (ADMET) properties predicted that all compounds were non-mutagenic, non-carcinogenic, non-genotoxic, weak hERG blockers, with acceptable volume of distribution (1.66-3.32 L/kg), and low rodent oral toxicity (LD₅₀ 810-2200 mg/kg). Considering some clinical events of cerebral Chagas disease, the compounds also demonstrated favorable properties, such as blood-brain barrier penetration. Unfavorable properties were also predicted as high promiscuity for P450 isoforms, high plasma protein binding affinity (>91%), and moderate-to-low oral bioavailability. Finally, none of the isolated neolignans was predicted as interference compounds (PAINS). Considering the promising chemical and biological properties of the isolated neolignans, these compounds could be used as starting points to develop new lead compounds for Chagas disease.

Proteomic profile of Mycobacterium tuberculosis after eupomatenoid-5 induction reveals potential drug targets

Aim: We investigated a proteome profile, protein–protein interaction and morphological changes of Mycobacterium tuberculosis after different times of eupomatenoid-5 (EUP-5) induction to evaluate the cellular response to the drug-induced damages. Methods: The bacillus was induced to sub-minimal inhibitory concentration of EUP-5 at 12 h, 24 h and 48 h. The proteins were separated by 2D gel electrophoresis, identified by LC/MS-MS. Scanning electron microscopy and Search Tool for the Retrieval of Interacting Genes/Proteins analyses were performed. Results: EUP-5 impacts mainly in M. tuberculosis proteins of intermediary metabolism and interactome suggests a multisite disturbance that contributes to bacilli death. Scanning electron microscopy revealed the loss of bacillary form. Conclusion: Some of the differentially expressed proteins have the potential to be drug targets such as citrate synthase (Rv0896), phosphoglycerate kinase (Rv1437), ketol-acid reductoisomerase (Rv3001c) and ATP synthase alpha chain (Rv1308).

Evaluation of Chemical Composition and Antileishmanial and Antituberculosis Activities of Essential Oils of Piper Species

Essential oils from fresh Piperaceae leaves were obtained by hydrodistillation and analyzed by gas chromatography mass spectrometry (GC-MS), and a total of 68 components were identified. Principal components analysis results showed a chemical variability between species, with sesquiterpene compounds predominating in the majority of species analyzed. The composition of the essential oil of Piper mosenii was described for the first time. The cytotoxicity of the essential oils was evaluated in peritoneal macrophages and the oils of P. rivinoides, P. arboretum, and P. aduncum exhibited the highest values, with cytotoxic concentration at 50% (CC50) > 200 µg/mL. Both P. diospyrifolium and P. aduncum displayed activity against Leishmania amazonensis, and were more selective for the parasite than for the macrophages, with a selectivity index (SI) of 2.35 and >5.52, respectively. These SI values were greater than the 1 for the standard drug pentamidine. The antileishmanial activity of the essential oils of P. diospyrifolium and P. aduncum was described for the first time. P. rivinoides, P. cernuum, and P. diospyrifolium displayed moderate activity against the Mycobacterium tuberculosis H37Rv bacillus, with a minimum inhibitory concentration (MIC) of 125 µg/mL. These results are relevant and suggests their potential for therapeutic purposes. Nevertheless, further studies are required to explain the exact mechanism of action of these essential oils.

Different cell death responses induced by eupomatenoid-5 in MCF-7 and 786-0 tumor cell lines

Natural products remain an important source of new drugs, including anticancer drugs. Recently, our group reported the anticancer activity of eupomatenoid-5 (eup-5), a neolignan isolated from Piper regnellii (Miq.) C. DC. var. regnellii leaves. In vitro studies demonstrated that MCF-7 (breast) and 786-0 (kidney) were among the cancer cell lines most sensitive to eup-5 treatment. The current results demonstrate that mitochondrial membrane depolarization and generation of reactive oxygen species are implicated in eup-5-mediated cytotoxic effects on these cancer cells lines. In MCF-7 cells, eup-5 led to phosphatidylserine externalization and caspase activation, whereas the same did not occur in 786-0 cells. Scanning electron microscopy revealed a reduction of microvilli density, as well as cell morphology alterations. Moreover, treated MCF-7 cells exhibited well-characterized apoptosis alterations, while treated 786-0 cells exhibited characteristics of programmed necroptosis process. These findings support the possibility that different mechanisms may be targeted by eup-5 in cell death response.

Further evidence of the trypanocidal action of eupomatenoid-5: confirmation of involvement of reactive oxygen species and mitochondria owing to a reduction in trypanothione reductase activity

Our group assays natural products that are less toxic and more effective than available nitroheterocycles as promising therapeutic options for patients with Chagas disease. Our previous study reported the trypanocidal activity of eupomatenoid-5, a neolignan isolated from the leaves of Piper regnellii var. pallescens, against the three main parasitic forms of Trypanosoma cruzi. The present study further characterizes the biochemical and morphological alterations induced by this compound to elucidate the mechanisms of action involved in the cell death of T. cruzi. We show that eupomatenoid-5 induced oxidative imbalance in the three parasitic forms, especially trypomastigotes, reflected by a decrease in the activity of trypanothione reductase and increase in the formation of reactive oxygen species (ROS). A reduction of mitochondrial membrane potential was then triggered, further impairing the cell redox system through the production of more ROS and reactive nitrogen species. Altogether, these effects led to oxidative stress, reflected by lipid peroxidation and DNA fragmentation. These alterations are key events in the induction of parasite death through various pathways, including apoptosis, necrosis, and autophagy.

The Effects of N-Butyl-1-(4-dimethylamino)phenyl-1,2,3,4-tetrahydro- β -carboline-3-carboxamide against Leishmania amazonensis Are Mediated by Mitochondrial Dysfunction

Leishmaniasis is a disease that affects millions of people worldwide. The drugs that are available for the treatment of this infection exhibit high toxicity and various side effects. Several studies have focused on the development of new chemotherapeutic agents that are less toxic and more effective against trypanosomatids. We investigated the effects of N-butyl-1-(4-dimethylamino)phenyl-1,2,3,4-tetrahydro-β-carboline-3-carboxamide (C4) and its possible targets against L. amazonensis. The results showed morphological and ultrastructural alterations, depolarization of the mitochondrial membrane, the loss of cell membrane integrity, and an increase in the formation of mitochondrial superoxide anions in L. amazonensis treated with C4. Our results indicate that C4 is a selective antileishmanial agent, and its effects appear to be mediated by mitochondrial dysfunction.

The natural compounds piperovatine and piperlonguminine induce autophagic cell death on Trypanosoma cruzi

The currently available treatments for Chagas disease show limited therapeutic potential and are associated with serious side effects. Our group has been attempting to find alternative drugs isolated from natural products as a potential source of pharmacological agents against Trypanosoma cruzi. Here, we demonstrate the antitrypanosomal activity of the amides piperovatine and piperlonguminine isolated from Piper ovatum against epimastigotes and intracellular amastigotes. We also investigated the mechanisms of action of these compounds on extracellular amastigote and epimastigote forms of T. cruzi. These amides showed low toxicity to LLCMK(2) mammalian cells. By using transmission and scanning electron microscopy, we observed that the compounds caused severe alterations in T. cruzi. These alterations were mainly located in plasma membrane and mitochondria. Furthermore, the study of treated parasites labeled with Rh123, PI and MDC corroborate with our TEM data. These mitochondrial dysfunctions induced by the amides might trigger biochemical alterations that lead to cell death. Altogether, our data evidence a possible autophagic process.

Mitochondria Superoxide Anion Production Contributes to Geranylgeraniol-Induced Death in Leishmania amazonensis

Here we demonstrate the activity of geranylgeraniol, the major bioactive constituent from seeds of Bixa orellana, against Leishmania amazonensis. Geranylgeraniol was identified through (1)H and (13)C nuclear magnetic resonance imaging and DEPT. The compound inhibited the promastigote and intracellular amastigote forms, with IC(50) of 11 ± 1.0 and 17.5 ± 0.7 μg/mL, respectively. This compound was also more toxic to parasites than to macrophages and did not cause lysis in human blood cells. Morphological and ultrastructural changes induced by geranylgeraniol were observed in the protozoan by electronic microscopy and included mainly mitochondria alterations and an abnormal chromatin condensation in the nucleus. These alterations were confirmed by Rh 123 and TUNEL assays. Additionally, geranylgeraniol induces an increase in superoxide anion production. Collectively, our in vitro studies indicate geranylgeraniol as a selective antileishmanial that appears to be mediated by apoptosis-like cell death.

Conventional therapy and promising plant-derived compounds against trypanosomatid parasites

Leishmaniasis and trypanosomiasis are two neglected and potentially lethal diseases that affect mostly the poor and marginal populations of developing countries around the world and consequently have an important impact on public health. Clinical manifestations such as cutaneous, mucocutaneous, and visceral disorders are the most frequent forms of leishmaniasis, a group of diseases caused by several Leishmania spp. American trypanosomiasis, or Chagas disease, is caused by Trypanosoma cruzi, a parasite that causes progressive damage to different organs, particularly the heart, esophagus, and lower intestine. African trypanosomiasis, or sleeping sickness, is caused by Trypanosoma brucei and is characterized by first presenting as an acute form that affects blood clotting and then becoming a chronic meningoencephalitis. The limited number, low efficacy, and side effects of conventional anti-leishmania and anti-trypanosomal drugs and the resistance developed by parasites are the major factors responsible for the growth in mortality rates. Recent research focused on plants has shown an ingenious way to obtain a solid and potentially rich source of drug candidates against various infectious diseases. Bioactive phytocompounds present in the crude extracts and essential oils of medicinal plants are components of an important strategy linked to the discovery of new medicines. These compounds have proven to be a good source of therapeutic agents for the treatment of leishmaniasis and trypanosomiasis. This work highlights some chemotherapeutic agents while emphasizing the importance of plants as a source of new and powerful drugs against these widespread diseases.

Benzaldehyde thiosemicarbazone derived from limonene complexed with copper induced mitochondrial dysfunction in Leishmania amazonensis

Background

Leishmaniasis is a major health problem that affects more than 12 million people. Treatment presents several problems, including high toxicity and many adverse effects, leading to the discontinuation of treatment and emergence of resistant strains.

Methodology/Principal Findings

We evaluated the in vitro antileishmanial activity of benzaldehyde thiosemicarbazone derived from limonene complexed with copper, termed BenzCo, against Leishmania amazonensis. BenzCo inhibited the growth of the promastigote and axenic amastigote forms, with IC₅₀ concentrations of 3.8 and 9.5 µM, respectively, with 72 h of incubation. Intracellular amastigotes were inhibited by the compound, with an IC₅₀ of 10.7 µM. BenzCo altered the shape, size, and ultrastructure of the parasites. Mitochondrial membrane depolarization was observed in protozoa treated with BenzCo but caused no alterations in the plasma membrane. Additionally, BenzCo induced lipoperoxidation and the production of mitochondrial superoxide anion radicals in promastigotes and axenic amastigotes of Leishmania amazonensis.

Conclusion/Significance

Our studies indicated that the antileishmania activity of BenzCo might be associated with mitochondrial dysfunction and oxidative damage, leading to parasite death.

Trypanocidal action of (-)-elatol involves an oxidative stress triggered by mitochondria dysfunction

Natural compounds have shown good potential for the discovery of new chemotherapeutics for the treatment of Chagas' disease. Recently, our group reported the effective trypanocidal activity of (-)-elatol, extracted from the red macroalgae Laurencia dendroidea present in the Brazilian coast against Trypanosoma cruzi. However, the mechanism of action of this compound has remained unclear. There are only hypotheses concerning its action on mitochondrial function. Here, we further investigated the mechanisms of action of (-)-elatol on trypomastigotes of T. cruzi. For this, we evaluated some biochemical alterations in trypomastigotes treated with (-)-elatol. Our results show that (-)-elatol induced depolarization of the mitochondrial membrane, an increase in the formation of mitochondrial superoxide anion and loss of cell membrane and DNA integrity. Additionally, (-)-elatol induced formation of autophagic vacuoles and a decrease in cell volume. All together, these results suggest that the trypanocidal action of (-)-elatol involves multiple events and mitochondria might be the initial target organelle. Our hypothesis is that the mitochondrial dysfunction leads to an increase of ROS production through the electron transport chain, which affects cell membrane and DNA integrity leading to different types of parasite death.