In vitro and in vivo trypanocidal synergistic activity of N-butyl-1-(4-dimethylamino)phenyl-1,2,3,4-tetrahydro-β-carboline-3-carboxamide associated with benznidazole

A Promising Amphotericin B Derivative Induces Morphological Alterations, Mitochondrial Damage, and Oxidative Stress In Vitro and Prevents Mice from Death Produced by a Virulent Strain of Trypanosoma cruzi

Chagas Disease is a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi, affecting 6-8 million people, mainly in Latin America. The medical treatment is based on two compounds, benznidazole and nifurtimox, with limited effectiveness and that produce severe side effects; consequently, there is an urgent need to develop new, safe, and effective drugs. Amphotericin B is the most potent antimycotic known to date. A21 is a derivative of this compound with the property of binding to ergosterol present in cell membranes of some organisms. In the search for a new therapeutic drug against T. cruzi, the objective of this work was to study the in vitro and in vivo effects of A21 derivative on T. cruzi. Our results show that the A21 increased the reactive oxygen species and reduced the mitochondrial membrane potential, affecting the morphology, metabolism, and cell membrane permeability of T. cruzi in vitro. Even more important was finding that in an in vivo murine model of infection, A21 in combination with benznidazole was able to reduce blood parasitemia, diminish the immune inflammatory infiltrate in skeletal muscle and rescue all the mice from death due to a virulent T. cruzi strain.

Influence of sexual hormones on Chagas disease

OBJECTIVE

Analyze sex hormone's influence during Chagas´ Disease.

METHODS

Male and female BALB/c mice were divided into six groups, four experimental (sham, orchiectomized, orchiectomized and supplemented with estradiol, orchiectomized supplemented with testosterone, oophorectomized, oophorectomized and supplemented with estradiol, and oophorectomized and supplemented with testosterone), and two control (healthy and intraperitoneally with T. cruzi strain NINOA infected). Clinical data were recorded daily, parasitemia was evaluated using a Neubauer chamber during the infection, and heart histopathological analysis was performed using the paraffin embedding technique. To analyze parasitemia curves and the area under the parametric curves, two-way ANOVA test was performed to correlate groups´ data. P-values <0.05 were considered statistically significant.

RESULTS

Higher mortality rates, cardiomegaly, hepatomegaly, ascites, edema, higher parasitemia levels, more amastigote nests, and more severe inflammatory infiltrate were found in higher testosterone concentration mice, whereas in higher estradiol concentration groups, paresia, prostration, edema, and necrosis were found.

CONCLUSIONS

Our results showed that testosterone increased infection severity, whereas estradiol had the opposite effect. This research improves the understanding of sex hormones´infuence upon this infection to contribute with the handling of Chagas´disease.

Mice Intragastric Infected with Insect and Blood Trypomastigotes of Trypanosoma cruzi IV: Differences and Similarities on the Evolution Profile and Response to Etiological Treatment

PURPOSE

Our goal was to analyze the outcome of infection and response to benznidazole (BZ) treatment in mice intragastrically inoculated with trypomastigotes forms of Trypanosoma cruzi from different origins.

METHODS

Twenty-four Swiss mice were divided in two groups and inoculated, by gavage, with 1 × 10⁴ blood trypomastigotes (BT) or insect-derived metacyclic trypomastigotes (IT) of AM14 strain (T. cruzi IV). Half of the animals of each group were treated with BZ (TBZ), from 10 to 30th days after the inoculation, and the other constituted the untreated control groups (NT). After the etiological treatment, all mice were immunosuppressed with cyclophosphamide for three weeks. Parasitological and molecular parameters, infectivity, cumulative mortality, and reactivation post-immunosuppression rates were obtained.

RESULTS

Animals inoculated with BT showed lower pre-patent period and early day of the maximum parasitemia, as well as a higher maximum peak of parasitemia than the IT animals. However, both, BT and IT animals, did not respond to BZ treatment (0.0% of cure).

CONCLUSION

We conclude that the infective form influences in the outcome of infection, but not the response to the etiological treatment in mice intragastrically infected with the T. cruzi IV strain studied.

Recent Update on the Anti-infective Potential of β-carboline Analogs

β-Carboline, a naturally occurring indole alkaloid, holds a momentous spot in the field of medicinal chemistry due to its myriad of pharmacological actions like anticancer, antiviral, antibacterial, antifungal, antileishmanial, antimalarial, neuropharmacological, anti-inflammatory and antithrombotic among others. β-Carbolines exhibit their pharmacological activity via diverse mechanisms. This review provides a recent update (2015-2020) on the anti-infective potential of natural and synthetic β-carboline analogs focusing on its antibacterial, antifungal, antiviral, antimalarial, antileishmanial and antitrypanosomal properties. In cases where enough details are available, a note on its mechanism of action is also added.

Essential oils from Syzygium aromaticum and Zingiber officinale, administered alone or in combination with benznidazole, reduce the parasite load in mice orally inoculated with Trypanosoma cruzi II

BACKGROUND

Trypanosoma cruzi is the etiological agent of Chagas disease (CD) or American trypanosomiasis, an important public health problem in Latin America. Benznidazole (BZ), a drug available for its treatment, has limited efficacy and significant side effects. Essential oils (EOs) have demonstrated trypanocidal activity and may constitute a therapeutic alternative. Our aim was to evaluate the efficacy of the EOs of clove (CEO - Syzygium aromaticum) and ginger (GEO - Zingiber officinale), administered alone and in combination with BZ, in Swiss mice infected with T. cruzi.

METHODS

The animals were inoculated with 10,000 blood trypomastigotes of the Y strain of T. cruzi II by gavage and divided into four groups (n = 12 to 15): 1) untreated control (NT); 2) treated with BZ; 3) treated with CEO or GEO; and 4) treated with BZ + CEO or GEO. The treatments consisted of oral administration of 100 mg/kg/day, from the 5th day after parasite inoculation, for 20 consecutive days. All groups were submitted to fresh blood examination (FBE), blood culture (BC), conventional PCR (cPCR) and real-time PCR (qPCR), before and after immunosuppression with cyclophosphamide.

RESULTS

Clove and ginger EOs, administered alone and in combination with BZ, promoted suppression of parasitemia (p < 0.0001), except for the animals treated with CEO alone, which presented a parasitemia curve similar to NT animals. However, there was a decrease in the BC positivity rate (p < 0.05) and parasite load (< 0.0001) in this group. Treatment with GEO alone, on the other hand, besides promoting a decrease in the BC positivity rate (p < 0.05) and parasite load (p < 0.01), this EO also resulted in a decrease in mortality rate (p < 0.05) of treated mice.

CONCLUSIONS

Decreased parasite load, as detected by qPCR, was observed in all treatment groups (BZ, CEO, GEO and BZ + EOs), demonstrating benefits even in the absence of parasitological cure, thus opening perspectives for further studies.

Antiproliferative activity of the dibenzylideneacetone derivate (E)-3-ethyl-4-(4-nitrophenyl)but‑3-en-2-one in Trypanosoma cruzi

Chagas disease is one of the most prevalent neglected diseases in the world. The illness is caused by Trypanosoma cruzi, a protozoan parasite with a complex life cycle and three morphologically distinct developmental stages. Nowadays, the only treatment is based on two nitro-derivative drugs, benznidazole and nifurtimox, which cause serious side effects. Since the treatment is limited, the search for new treatment options for patients with Chagas disease is highly necessary. In this study we analyzed the substance A11K3, a dibenzylideneacetone (DBA). DBAs have an acyclic dienone attached to aryl groups in both β-positions and studies have shown that they have biological activity against tumors cells, bacteria, and protozoa such as T. cruzi and Leishmania spp. Here we show that A11K3 is active against all three T. cruzi evolutionary forms: the epimastigote (IC₅₀ = 3.3 ± 0.8), the trypomastigote (EC₅₀ = 24 ± 4.3) and the intracellular amastigote (IC₅₀ = 9.3 ± 0.5 µM). A cytotoxicity assay in LLCMK₂ cells showed a CC₅₀ of 239.2 ± 15.7 µM giving a selectivity index (CC₅₀/IC₅₀) of 72.7 for epimastigotes, 9.9 for trypomastigotes and 25.9 for intracellular amastigotes. Morphological and ultrastructural analysis of the parasites treated with A11K3 by TEM and SEM revealed alterations in the Golgi complex, mitochondria, plasma membrane and cell body, with an increase of autophagic vacuoles and lipid bodies. Biochemical assays of A11K3-treated T. cruzi showed an increase of ROS, plasma membrane ruptures, lipid peroxidation, mitochondrial membrane depolarization with a decrease in ATP and accumulation of autophagic vacuoles. The results lead to the hypothesis that A11K3 causes death of the protozoan through events such as plasma membrane and mitochondrial alterations and autophagy, characteristic of cell collapse.

Combination Therapy Using Benznidazole and Aspirin during the Acute Phase of Experimental Chagas Disease Prevents Cardiovascular Dysfunction and Decreases Typical Cardiac Lesions in the Chronic Phase

Chagas disease, caused by the protozoan Trypanosoma cruzi, is one of the main causes of death due to cardiomyopathy and heart failure in Latin American countries. The treatment of Chagas disease is directed at eliminating the parasite, decreasing the probability of cardiomyopathy and disrupting the disease transmission cycle. Benznidazole (BZ) and nifurtimox (Nfx) are recognized as effective drugs for the treatment of Chagas disease by the World Health Organization, but both have high toxicity and limited efficacy, especially in the chronic disease phase. At low doses, aspirin (ASA) has been reported to protect against T. cruzi infection. We evaluated the effectiveness of BZ in combination with ASA at low doses during the acute disease phase and evaluated cardiovascular aspects and cardiac lesions in the chronic phase. ASA treatment prevented the cardiovascular dysfunction (hypertension and tachycardia) and typical cardiac lesions. Moreover, BZ+ASA-treated mice had a smaller cardiac fibrotic area than BZ-treated mice. These results were associated with an increase in numbers of eosinophils and reticulocytes and levels of nitric oxide in the plasma and cardiac tissue of ASA-treated mice relative to respective controls. These effects of ASA and BZ+ASA in chronically infected mice were inhibited by pretreatment with the lipoxin A₄ (LXA₄) receptor antagonist Boc-2, indicating that the protective effects of ASA are mediated by ASA-triggered lipoxin. These results emphasize the importance of exploring new drug combinations for treatments of the acute phase of Chagas disease that are beneficial for patients with chronic disease.

Looking for combination of benznidazole and Trypanosoma cruzi-triosephosphate isomerase inhibitors for Chagas disease treatment

BACKGROUND

The current chemotherapy for Chagas disease is based on monopharmacology with low efficacy and drug tolerance. Polypharmacology is one of the strategies to overcome these limitations.

OBJECTIVES

Study the anti-Trypanosoma cruzi activity of associations of benznidazole (Bnz) with three new synthetic T. cruzi-triosephosphate isomerase inhibitors, 2, 3, and 4, in order to potentiate their actions.

METHODS

The in vitro effect of the drug combinations were determined constructing the corresponding isobolograms. In vivo activities were assessed using an acute murine model of Chagas disease evaluating parasitaemias, mortalities and IgG anti-T. cruzi antibodies.

FINDINGS

The effect of Bnz combined with each of these compounds, on the growth of epimastigotes, indicated an additive action or a synergic action, when combining it with 2 or 3, respectively, and an antagonic action when combining it with 4. In vivo studies, for the two chosen combinations, 2 or 3 plus one fifth equivalent of Bnz, showed that Bnz can also potentiate the in vivo therapeutic effects. For both combinations a decrease in the number of trypomastigote and lower levels of anti-T. cruzi IgG-antibodies were detected, as well clear protection against death.

MAIN CONCLUSIONS

These results suggest the studied combinations could be used in the treatment of Chagas disease.

Efficacy of essential oil of Syzygium aromaticum alone and in combination with benznidazole on murine oral infection with Trypanosoma cruzi IV

Chagas disease (CD), caused by Trypanosoma cruzi, remains a serious public health problem. One of the causes of the high morbidity and mortality in patients is the lack of an effective drug therapy. Thus, the aim of this study was to evaluate the efficacy of the essential oil of Syzygium aromaticum alone and in combination with benznidazole (BZ) in mice orally inoculated with strain of T. cruzi IV obtained from oral CD outbreak occurred in Western Brazilian Amazonia. All the animals inoculated with metacyclic trypomastigote forms (AM14 strain, BZ resistant), derived from the insect Rhodnius robustus, became infected and there was no difference in the mortality rate between the experimental groups. When compared with untreated control animals (UTC), the treatment with essential oil of S. aromaticum (EOSA) alone promoted reduction in 1/5 parameters derived from the parasitemia curve, whereas the treatments with BZ alone or in combination (BZ + EOSA) promoted reduction in 4/5 of those parameters, presenting similar profiles of parasitemia curve. The animals treated with BZ and with the combination BZ + EOSA presented lower patency periods in comparison with the animals in EOSA group, and lower positivity of blood cultures when compared with the UTC group. The results of molecular analysis by qPCR in both blood and cardiac tissue did not show differences between the groups. The cure rates obtained with the different treatments presented the following ascending order: EOSA = 12.5% (1/8), BZ = 25.0% (2/8) and BZ + EOSA = 37.5% (3/8). Although there are no significant differences between them, these results claims that the use of this essential oil could be of interest for treatment of Chagas disease.

Effects of (1E,4E)-2-Methyl-1,5-bis(4-nitrophenyl)penta-1,4-dien-3-one on Trypanosoma cruzi and Its Combinational Effect with Benznidazole, Ketoconazole, or Fluconazole

This study reports the activity induced by (1E,4E)-2-methyl-1,5-bis(4-nitrophenyl)penta-1,4-dien-3-one (A3K2A3) against Trypanosoma cruzi. This compound showed trypanocidal activity against the multiplicative epimastigote and amastigote forms of this protozoan, with IC₅₀ values of 1.99 ± 0.17 and 1.20 ± 0.16 μM, respectively, and EC₅₀ value of 15.57 ± 0.34 μM against trypomastigotes. The combination of A3K2A3 with benznidazole or ketoconazole demonstrated strong synergism, increasing effectiveness against trypomastigotes or epimastigotes of T. cruzi. In addition, the drug combination of A3K2A3 with benznidazole or ketoconazole on LLCMK₂ cells demonstrated an antagonist effect, which resulted in greater protection of the cells from drug damage. The combination of the compound with fluconazole was not effective. Transmission and scanning electron micrographs showed changes on parasites, mainly in the cytoplasmatic membrane, nucleus, mitochondrion, and Golgi complex, and a large increase in the number of autophagosome-like structures and lipid-storage bodies, accompanied by volume reduction and rounding of the parasite. A3K2A3 might be a promising compound against T. cruzi.

Quantitative Laser Biospeckle Method for the Evaluation of the Activity of Trypanosoma cruzi Using VDRL Plates and Digital Analysis

In this paper we report a quantitative laser Biospeckle method using VDRL plates to monitor the activity of Trypanosoma cruzi and the calibration conditions including three image processing algorithms and three programs (ImageJ and two programs designed in this work). Benznidazole was used as a test drug. Variable volume (constant density) and variable density (constant volume) were used for the quantitative evaluation of parasite activity in calibrated wells of the VDRL plate. The desiccation process within the well was monitored as a function of volume and of the activity of the Biospeckle pattern of the parasites as well as the quantitative effect of the surface parasite quantity (proportion of the object's plane). A statistical analysis was performed with ANOVA, Tukey post hoc and Descriptive Statistics using R and R Commander. Conditions of volume (100μl) and parasite density (2-4x104 parasites/well, in exponential growth phase), assay time (up to 204min), frame number (11 frames), algorithm and program (RCommander/SAGA) for image processing were selected to test the effect of variable concentrations of benznidazole (0.0195 to 20μg/mL / 0.075 to 76.8μM) at various times (1, 61, 128 and 204min) on the activity of the Biospeckle pattern. The flat wells of the VDRL plate were found to be suitable for the quantitative calibration of the activity of Trypanosoma cruzi using the appropriate algorithm and program. Under these conditions, benznidazole produces at 1min an instantaneous effect on the activity of the Biospeckle pattern of T. cruzi, which remains with a similar profile up to 1 hour. A second effect which is dependent on concentrations above 1.25μg/mL and is statistically different from the effect at lower concentrations causes a decrease in the activity of the Biospeckle pattern. This effect is better detected after 1 hour of drug action. This behavior may be explained by an instantaneous effect on a membrane protein of Trypanosoma cruzi that could mediate the translocation of benznidazole. At longer times the effect may possibly be explained by the required transformation of the pro-drug into the active drug.

Polymeric Nanoparticles of Brazilian Red Propolis Extract: Preparation, Characterization, Antioxidant and Leishmanicidal Activity

The ever-increasing demand for natural products and biotechnology derived from bees and ultra-modernization of various analytical devices has facilitated the rational and planned development of biotechnology products with a focus on human health to treat chronic and neglected diseases. The aim of the present study was to prepare and characterize polymeric nanoparticles loaded with Brazilian red propolis extract and evaluate the cytotoxic activity of "multiple-constituent extract in co-delivery system" for antileishmanial therapies. The polymeric nanoparticles loaded with red propolis extract were prepared with a combination of poly-ε-caprolactone and pluronic using nanoprecipitation method and characterized by different analytical techniques, antioxidant and leishmanicidal assay. The red propolis nanoparticles in aqueous medium presented particle size (200-280 nm) in nanometric scale and zeta analysis (-20 to -26 mV) revealed stability of the nanoparticles without aggregation phenomenon during 1 month. After freeze-drying method using cryoprotectant (sodium starch glycolate), it was possible to observe particles with smooth and spherical shape and apparent size of 200 to 400 nm. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and thermal analysis revealed the encapsulation of the flavonoids from the red propolis extract into the polymeric matrix. Ultra performance liquid chromatography coupled with diode array detector (UPLC-DAD) identified the flavonoids liquiritigenin, pinobanksin, isoliquiritigenin, formononetin and biochanin A in ethanolic extract of propolis (EEP) and nanoparticles of red propolis extract (NRPE). The efficiency of encapsulation was determinate, and median values (75.0 %) were calculated using UPLC-DAD. 2,2-Diphenyl-1-picryhydrazyl method showed antioxidant activity to EEP and red propolis nanoparticles. Compared to negative control, EEP and NRPE exhibited leishmanicidal activity with an IC50 value of ≅38.0 μg/mL and 31.3 μg/mL, 47.2 μg/mL, 154.2μg/mL and 193.2 μg/mL for NRPE A1, NRPE A2, NRPE A3 and NRPE A4, respectively. Nanoparticles loaded with red propolis extract in co-delivery system and EEP presented cytotoxic activity on Leishmania (V.) braziliensis. Red propolis extract loaded in nanoparticles has shown to be potential candidates as intermediate products for preparation of various pharmaceutical dosage forms containing red propolis extract in the therapy against negligible diseases such as leishmaniasis. Graphical Abstract Some biochemical mechanisms of cellular debridement of Leishmania (V.) braziliensis species by the flavonoids of red propolis extract (EEP) or NRPE loaded with red propolis extract.

Synthesis and evaluation of novel hybrids β-carboline-4-thiazolidinones as potential antitumor and antiviral agents

A series of novel hybrids β-carboline-4-thiazolidinones were synthesized and evaluated for their in vitro antitumor activity against human cancer cell lines and for antiviral activity towards Herpes simplex virus type-1 (HSV-1). From the N'-(2-ylidene-4-thiazolidinone)-β-carboline-3-carbohydrazide series (9-11), compounds 9c and 11d were the most active, showing growth inhibition 50% (GI₅₀) values less than 5 μM for all cell lines tested. Compound 9c, bearing the 4-dimethylaminophenyl group at C-1 of β-carboline was selected for further investigation concerning cell death and cell cycle profile, focusing on the human renal adenocarcinoma cell line 786-0. Treatments with 25 μM of compound 9c induced cell death after 15 h of treatment, characterized by phosphatidylserine exposure and loss of membrane integrity. Moreover, treatment with 12.5 μM promoted a sub-G1 arrest, which indicates cell death. Derivatives of the N-(2-substituted-aryl-4-thiazolidinone)-β-carboline-3-carboxamide series (18-23) showed a potent activity and high selectivity for glioma (U251) and ovarian (OVCAR-3) cancer cell lines. Also, some β-carboline-4-thiazolidinone hybrids showed potent antiviral activity against Herpes simplex virus type-1. The N-(2-substituted-aryl-4-thiazolidinone)-carboxamide moiety in 18, 19 and 22 confer a potent anti-HSV-1 activity for these derivatives, which presented EC₅₀ values of 0.80, 2.15 and 2.02 μM, respectively. The assay results showed that the nature of 4-thiazolidinone moiety and of the substituent attached at the 3- and 1- position of β-carboline nucleus influenced the antitumor and antiviral activities.

Clomipramine and Benznidazole Act Synergistically and Ameliorate the Outcome of Experimental Chagas Disease

Chagas disease is an important public health problem in Latin America, and its treatment by chemotherapy with benznidazole (BZ) or nifurtimox remains unsatisfactory. In order to design new alternative strategies to improve the current etiological treatments, in the present work, we comprehensively evaluated the in vitro and in vivo anti-Trypanosoma cruzi effects of clomipramine (CMP) (a parasite-trypanothione reductase-specific inhibitor) combined with BZ. In vitro studies, carried out using a checkerboard technique on trypomastigotes (T. cruzi strain Tulahuen), revealed a combination index (CI) of 0.375, indicative of a synergistic effect of the drug combination. This result was correlated with the data obtained in infected BALB/c mice. We observed that during the acute phase (15 days postinfection [dpi]), BZ at 25 mg/kg of body weight/day alone decreased the levels of parasitemia compared with those of the control group, but when BZ was administered with CMP, the drug combination completely suppressed the parasitemia due to the observed synergistic effect. Furthermore, in the chronic phase (90 dpi), mice treated with both drugs showed less heart damage as assessed by the histopathological analysis, index of myocardial inflammation, and levels of heart injury biochemical markers than mice treated with BZ alone at the reference dose (100 mg/kg/day). Collectively, these data support the notion that CMP combined with low doses of BZ diminishes cardiac damage and inflammation during the chronic phase of cardiomyopathy. The synergistic activity of BZ-CMP clearly suggests a potential drug combination for Chagas disease treatment, which would allow a reduction of the effective dose of BZ and an increase in therapeutic safety.

Mitochondrial Dysfunction Induced by N-Butyl-1-(4-Dimethylamino)Phenyl-1,2,3,4-Tetrahydro-β-Carboline-3-Carboxamide Is Required for Cell Death of Trypanosoma cruzi

BACKGROUND

Chagas' disease is caused by the protozoan Trypanosoma cruzi and affects thousands of people worldwide. The available treatments are unsatisfactory, and new drugs must be developed. Our group recently reported the trypanocidal activity of the synthetic compound N-butyl-1-(4-dimethylamino)phenyl-1,2,3,4-tetrahydro-β-carboline-3-carboxamide (C4), but the mechanism of action of this compound was unclear.

METHODOLOGY/PRINCIPAL FINDINGS

We investigated the mechanism of action of C4 against epimastigote and trypomastigote forms of T. cruzi. The results showed alterations in mitochondrial membrane potential, alterations in cell membrane integrity, an increase in the formation of reactive oxygen species, phosphatidylserine exposure, a reduction of cell volume, DNA fragmentation, and the formation of lipid inclusions.

CONCLUSION/SIGNIFICANCE

These finding suggest that mitochondria are a target of C4, the dysfunction of which can lead to different pathways of cell death.

Nitric oxide and Brazilian propolis combined accelerates tissue repair by modulating cell migration, cytokine production and collagen deposition in experimental leishmaniasis

The fact that drugs currently used in the treatment of Leishmania are highly toxic and associated with acquired resistance has promoted the search for new therapies for treating American tegumentary leishmaniasis (ATL). In this study, BALB/c mice were injected in the hind paw with Leishmania (Leishmania) amazonensis and subsequently treated with a combination of nitric oxide (NO) donor (cis-[Ru(bpy) 2imN(NO)](PF6)3) (Ru-NO), given by intraperitoneal injection, and oral Brazilian propolis for 30 days. Ru-NO reached the center of the lesion and increased the NO level in the injured hind paw without lesion exacerbation. Histological and immunological parameters of chronic inflammation showed that this combined treatment increased the efficacy of macrophages, determined by the decrease in the number of parasitized cells, leading to reduced expression of proinflammatory and tissue damage markers. In addition, these drugs in combination fostered wound healing, enhanced the number of fibroblasts, pro-healing cytokines and induced collagen synthesis at the lesion site. Overall, our findings suggest that the combination of the NO donor Ru-NO and Brazilian propolis alleviates experimental ATL lesions, highlighting a new therapeutic option that can be considered for further in vivo investigations as a candidate for the treatment of cutaneous leishmaniasis.

N-butyl-[1-(4-methoxy)phenyl-9H-β-carboline]-3-carboxamide prevents cytokinesis in Leishmania amazonensis

Leishmaniasis, a complex of diseases caused by protozoa of the genus Leishmania, is endemic in 98 countries, affecting approximately 12 million people worldwide. Current treatments for leishmaniasis have many disadvantages, such as toxicity, high costs, and prolonged treatment, making the development of new treatment alternatives highly relevant. Several studies have verified the antileishmanial activity of β-carboline compounds. In the present study, we investigated the in vitro antileishmanial activity of N-butyl-[1-(4-methoxy)phenyl-9H-β-carboline]-3-carboxamide (β-CB) against Leishmania amazonensis. The compound was active against promastigote, axenic amastigote, and intracellular amastigote forms of L. amazonensis, exhibiting high selectivity for the parasite. Moreover, β-CB did not exhibit hemolytic or mutagenic potential. Promastigotes treated with the alkaloid presented rounding of the body cell, cell membrane projections, an increase in the number of promastigotes presenting two flagella, and parasites of abnormal phenotype, with three or more flagella and/or nuclei. Furthermore, we observed an increase in the subpopulation of cells in the G2/M stage of the cell cycle. Altogether, these results suggest that β-CB likely prevents cytokinesis, although it does not interfere with the duplication of cell structures. We also verified an increase in O2(·-) production and the accumulation of lipid storage bodies. Cell membrane integrity was maintained, in addition to the absence of phosphatidylserine externalization, DNA fragmentation, and autophagosomes. Although the possibility of an apoptotic process cannot be discarded, β-CB likely exerts its antileishmanial activity through a cytostatic effect, thus preventing cellular proliferation.

The use of a heterogeneously controlled mouse population reveals a significant correlation of acute phase parasitemia with mortality in Chagas disease

Chagas disease develops upon infection with the protozoan parasite Trypanosoma cruzi and undergoes an acute phase characterized by massive parasite replication and the presence of parasites in the blood. This condition is known as acute phase parasitemia. This initial stage may result in a cure, in the development of the chronic stages of the disease or in the death of the infected host. Despite intensive investigation related to the characterization of the acute and chronic phases of the disease, the cause-effect relationship of acute phase parasitemia to the outcome of the disease is still poorly understood. In this study, we artificially generated a heterogeneously controlled mouse population by intercrossing F1 mice obtained from a parental breeding of highly susceptible A/J with highly resistant C57BL/6 mouse strains. This F2 population was infected and used to assess the correlation of acute phase parasitemia with the longevity of the animals. We used nonparametric statistical analyses and found a significant association between parasitemia and mortality. If males and females were evaluated separately, we found that the former were more susceptible to death, although parasitemia was similar in males and females. In females, we found a strong negative correlation between parasitemia and longevity. In males, however, additional factors independent of parasitemia may favor mouse mortality during the development of the disease. The correlations of acute phase parasitemia with mortality reported in this study may facilitate an appropriate prognostic approach to the disease in humans. Moreover, these results illustrate the complexity of the mammalian genetic traits that regulate host resistance during Chagas disease.

Trypanosoma cruzi infection results in an increase in intracellular cholesterol

Chagasic cardiomyopathy caused by Trypanosoma cruzi is a major health concern in Latin America and among immigrant populations in non-endemic areas. T. cruzi has a high affinity for host lipoproteins and uses the low density lipoprotein receptor (LDLr) for invasion. Herein, we report that T. cruzi infection is associated with an accumulation of LDL and cholesterol in tissues in both acute and chronic murine Chagas disease. Similar findings were observed in tissue samples from a human case of Chagasic cardiomyopathy. T. cruzi infection of cultured cells displayed increased invasion with increasing cholesterol levels in the medium. Studies of infected host cells demonstrated alterations in their cholesterol regulation. T. cruzi invasion/infection via LDLr appears to be involved in changes in intracellular cholesterol homeostasis. The observed changes in intracellular lipids and associated oxidative stress due to these elevated lipids may contribute to the development of Chagasic cardiomyopathy.

Pharmacological importance of optically active tetrahydro-β-carbolines and synthetic approaches to create the C1 stereocenter

1,2,3,4-Tetrahydro-β-carbolines (THβCs) are a pharmacologically important group of compounds belonging to the indole alkaloids. C1-Substituted optically active THβCs have been the target of extensive synthetic efforts due to the presence of the scaffold in numerous natural products and synthetic targets. This review briefly summarizes the methods to obtain the C1 stereocenter and concentrates on evaluating the pharmacological importance of optically active C1-substituted THβCs, including their PDE5-inhibitory, antimalarial, antiviral and antitumor activities.

A quinoxaline derivative as a potent chemotherapeutic agent, alone or in combination with benznidazole, against Trypanosoma cruzi

Background

Chagas’ disease is a condition caused by the protozoan Trypanosoma cruzi that affects millions of people, mainly in Latin America where it is considered endemic. The chemotherapy for Chagas disease remains a problem; the standard treatment currently relies on a single drug, benznidazole, which unfortunately induces several side effects and it is not successful in the cure of most of the chronic patients. In order to improve the drug armamentarium against Chagas’ disease, in the present study we describe the synthesis of the compound 3-chloro-7-methoxy-2-(methylsulfonyl) quinoxaline (quinoxaline 4) and its activity, alone or in combination with benznidazole, against Trypanosoma cruzi in vitro.

Methodology/Principal Findings

Quinoxaline 4 was found to be strongly active against Trypanosoma cruzi Y strain and more effective against the proliferative forms. The cytotoxicity against LLCMK₂ cells provided selective indices above one for all of the parasite forms. The drug induced very low hemolysis, but its anti-protozoan activity was partially inhibited when mouse blood was added in the experiment against trypomastigotes, an effect that was specifically related to blood cells. A synergistic effect between quinoxaline 4 and benznidazole was observed against epimastigotes and trypomastigotes, accompanied by an antagonistic interaction against LLCMK₂ cells. Quinoxaline 4 induced several ultrastructural alterations, including formations of vesicular bodies, profiles of reticulum endoplasmic surrounding organelles and disorganization of Golgi complex. These alterations were also companied by cell volume reduction and maintenance of cell membrane integrity of treated-parasites.

Conclusion/Significance

Our results demonstrated that quinoxaline 4, alone or in combination with benznidazole, has promising effects against all the main forms of T. cruzi. The compound at low concentrations induced several ultrastructural alterations and led the parasite to an autophagic-like cell death. Taken together these results may support the further development of a combination therapy as an alternative more effective in Chagas’ disease treatment.

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.

Evaluation of benznidazole treatment combined with nifurtimox, posaconazole or AmBisome® in mice infected with Trypanosoma cruzi strains

The present work aimed to investigate the curative effect of benznidazole (BZL) in combination with other patented drugs [nifurtimox (NFX), posaconazole (POS) or AmBisome(®) (AMB)] in mice acutely or chronically infected with either a BZL-susceptible (Tulahuen) or a BZL-partially-resistant (Y) strain of Trypanosoma cruzi. To appreciate the eventual advantage of such combinations, infected mice were treated for short durations (non-curative) of each individual treatment. Cure rates were determined by investigating blood parasites (microscopic examination) and parasite DNA (quantitative PCR) after submitting treated mice to immune suppression with cyclophosphamide. The results mainly suggest that shorter durations of treatment combining BZL and POS or NFX might cure mice acutely or chronically infected with the Tulahuen strain, whereas the combination of BZL with AMB does not have such an effect. Moreover, the association BZL+POS does not improve the curative effect of POS (all used for shorter durations) in infection with the Y strain. Shortening the duration of treatment whilst keeping a complete curative effect deserves interest in limiting adverse reactions due to dose-cumulative toxic effects of long treatment. Genotyping of the T. cruzi strain(s) infecting patients might also allow a better adaptation of individual therapeutic schedules, improving both the efficiency and safety of trypanocidal treatment. This preliminary experimental study should encourage further investigations to find the best combination of adequate drug concentrations and timing of treatment.

Synthesis and evaluation of new β-carboline-3-(4-benzylidene)-4H-oxazol-5-one derivatives as antitumor agents

In the present work, we report the synthesis and in vitro anticancer and antimicrobial activity evaluation of a new series of 1-substituted-β-carboline derivatives bearing a 4-benzylidene-4H-oxazol-5-one unity at C-3. The compound 2-[1-(4-methoxyphenyl)-9H-β-carbolin-3-yl]-4-(benzylidene)-4H-oxazol-5-one (11) was the most active derivative, exhibiting a potent cytotoxic activity against glioma (U251), prostate (PC-3) and ovarian (OVCAR-03) cancer cell lines with IC₅₀ values of 0.48, 1.50 and 1.07 µM, respectively. An in silico study of the ADME properties of the novel synthesized β-carboline derivatives was also performed.