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.

Comparative pathogenicity in Swiss mice of Trypanosoma cruzi IV from northern Brazil and Trypanosoma cruzi II from southern Brazil.

The geographical heterogeneity of Chagas disease (ChD) is mainly caused by genetic variability of the etiological agent Trypanosoma cruzi. Our hypothesis was that the pathogenicity for mice may vary with the genetic lineage (or Discrete Typing Unit - DTU) of the parasite. To test this hypothesis, parasitological and histopathological evaluations were performed in mice inoculated with strains belonging to the DTU T. cruzi IV (TcIV) from the State of Amazonas (northern Brazil), or the DTU T. cruzi II (TcII) from the State of Paraná (southern Brazil). Groups of 10 Swiss mice were inoculated with eight strains of TcIV obtained from acute cases (7) from two outbreaks of orally acquired ChD, and from the triatomine Rhodnius robustus (1) from Amazonas; and three strains of TcII obtained from chronic patients in Paraná. We evaluated the pre-patent period, patent period, maximum peak of parasitemia, day of maximum peak of parasitemia, area under the parasitemia curve, inflammatory process, and tissue parasitism in the acute phase. TcIV was less virulent than TcII, and showed significantly (p < 0.005) lower parasitemia levels. Although the levels of tissue parasitism did not differ statistically, mice infected with TcIV displayed significantly (p < 0.001) fewer inflammatory processes than mice infected with TcII. This supported the working hypothesis, since TcIV from Amazonas was less pathogenic than TcII from Paraná; and agreed with the lower severity of human cases of ChD in the Amazon region.

Ionized alkaline water reduces injury in BALB/c mice infected with Leishmania amazonensis.

Ionized water has been reported to contribute to the tissue repair process and wound healing. Water purifiers can generate ionized water by means of activated charcoal with silver and minerals, the main purpose of which are to reduce microbiological and physicochemical contaminants. Moreover, when water is subjected to a magnetic field an organization of water molecules occurs due to the presence of mineral salts. The resulting water is thus more alkaline, which has been shown to be non-toxic to mice and can actually prolong survival. Cutaneous leishmaniasis is a neglected tropical disease, caused by obligate uni- and intracellular protozoa belonging to the genus Leishmania, that can manifest in the form of skin lesions. Thus, the objective of this study was to compare the evolution of disease in L. amazonensis-infected BALB/c mice that received tap water (TW) or ionized alkaline water (IAW). As a control, additional groups of mice receiving TW or IAW were also treated with the antileishmanial miltefosine. All mouse groups received either TW or IAW as drinking water 30 days prior to infection and the groups continued to receive the respective drinking water for 4 weeks, after which the blood and plasma were collected. Biochemical assays of aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase, creatinine, urea, glucose, triglycerides, and cholesterol were performed, in addition to hematology tests. There was a significant decrease in the volume of the lesion for groups that received IAW, in which the ingestion of ionized alkaline water favored the non-evolution of the lesion in the footpads of the animals. The results of the blood count and leukogram tests were within the normal values for BALB/c mice demonstrating that ionized water has no toxic effects on blood factors.

Constitutive nitric oxide synthase activation is a significant route for nitroglycerin-mediated vasodilation.

The physiological effects of nitroglycerin as a potent vasodilator have long been documented. However, the molecular mechanisms by which nitroglycerin exerts its biological functions are still a matter of intense debate. Enzymatic pathways converting nitroglycerin to vasoactive compounds have been identified, but none of them seems to fully account for the reported clinical observations. Here, we demonstrate that nitroglycerin triggers constitutive nitric oxide synthase (NOS) activation, which is a major source of NO responsible for low-dose (1-10 nM) nitroglycerin-induced vasorelaxation. Our studies in cell cultures, isolated vessels, and whole animals identified endothelial NOS activation as a fundamental requirement for nitroglycerin action at pharmacologically relevant concentrations in WT animals.

The extended production of UV-induced reactive oxygen species in L929 fibroblasts is attenuated by posttreatment with Arrabidaea chica through scavenging mechanisms.

Ultraviolet radiation (UVR) exposure causes various injurious effects to human skin by generating reactive oxygen species (ROS). Excessive ROS production can lead to oxidative stress which may damage cellular components like lipids and proteins and causing photoaging. The use of natural photochemopreventive agents with antioxidant properties is an important alternative to improve the effectiveness of sunscreens and reduce skin photodamage. A crude extract (CE) from the leaves of Arrabidaea chica underwent partition by a liquid-liquid method. The hexane fraction (FH), chloroform fraction (FC), and ethyl acetate fraction (FEA) were obtained. The antioxidant capacity of the CE, FH, FC, and FEA was studied in a cell-free system using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method and the xanthine/luminol/xanthine oxidase system. The FC had the best antioxidant activity. We also evaluated the photochemoprotective effect of A. chica in protecting L929 fibroblasts against UV-A- and UV-B-induced cell damage. A. chica inhibited the extended production of ROS up to 3h. Posttreatment with the CE and FC attenuated UV-induced cell damage through scavenging mechanisms, including the quenching of intracellular ROS and mitochondrial O2- and preventing lipid peroxidation. These results suggest that A. chica may be a promising non-sunscreen photoprotector that can improve the effectiveness of commercial sunscreens.

Proanthocyanidin Polymer-Rich Fraction of Stryphnodendron adstringens Promotes in Vitro and in Vivo Cancer Cell Death via Oxidative Stress.

Cervical cancer is the fourth most common cancer that affects women, mainly through human papilloma virus (HPV) infection with high-risk HPV16 and HPV18. The present study investigated the in vitro anticancer activity and mechanism of action of a proanthocyanidin polymer-rich fraction of Stryphnodendron adstringens (F2) in cervical cancer cell lines, including HeLa (HPV18-positive), SiHa (HPV16-positive), and C33A (HPV-negative) cells, and also evaluated in vivo anticancer activity. In vitro, cell viability was determined by the MTT assay. Cell migration was determined by the wound healing assay. The mechanism of action was investigated by performing ultrastructural analysis and evaluating reactive oxygen species (ROS) production, mitochondrial metabolism, lipoperoxidation, BCL-2 family expression, caspase expression, and DNA and cell membrane integrity. In vivo activity was evaluated using the murine Ehrlich solid tumor model. F2 time- and dose-dependently reduced cell viability and significantly inhibited the migration of cervical cancer cells. HeLa and SiHa cells treated with F2 (IC50) exhibited intense oxidative stress (i.e., increase in ROS and decrease in antioxidant species) and mitochondrial damage (i.e., mitochondrial membrane potential depolarization and a reduction of intracellular levels of adenosine triphosphate). Increases in the Bax/BCL-2 ratio and caspase 9 and caspase 3 expression, were observed, with DNA damage that was sufficient to trigger mitochondria-dependent apoptosis. Cell membrane disruption was observed in C33A cells (IC50 and IC90) and HeLa and SiHa cells (IC90), indicating progress to late apoptosis/necrosis. The inhibition of ROS production by N-acetylcysteine significantly suppressed oxidative stress in all three cell lines. In vivo, F2 significantly reduced tumor volume and weight of the Ehrlich solid tumor, and significantly increased lipoperoxidation, indicating that F2 also induces oxidative stress in the in vivo model. These findings indicate that the proanthocyanidin polymer-rich fraction of S. adstringens may be a potential chemotherapeutic candidate for cancer treatment.

The reactivity of ortho-methoxy-substituted catechol radicals with sulfhydryl groups: contribution for the comprehension of the mechanism of inhibition of NADPH oxidase by apocynin.

Redox processes are involved in the mechanism of action of NADPH oxidase inhibitors such as diphenyleneiodonium and apocynin. Here, we studied the structure-activity relationship for apocynin and analogous ortho-methoxy-substituted catechols as inhibitors of the NADPH oxidase in neutrophils and their reactivity with peroxidase. Aiming to alter the reduction potential, the ortho-methoxy-catechol moiety was kept constant and the substituents at para position related to the hydroxyl group were varied. Two series of compounds were employed: methoxy-catechols bearing electron-withdrawing groups (MC-W) such as apocynin, vanillin, 4-nitroguaiacol, 4-cyanoguaiacol, and methoxy-catechol bearing electron-donating groups (MC-D) such as 4-methylguaiacol and 4-ethylguaiacol. We found that MC-D were weaker inhibitors compared to MD-W. Furthermore, the radicals generated by oxidation of MC-W via MPO/H(2)O(2), but not for MC-D, were able to oxidize glutathione (GSH) as verified by the formation of thiyl radicals, depletion of GSH, and recycling of the ortho-methoxy-catechols during their oxidations. The capacity of oxidizing sulfhydryl (SH) groups was also verified when ovalbumin was incubated with MC-W, but not for MC-D. Since the effect of apocynin has been correlated with inactivation of the cytosolic fractions of the NADPH oxidase complex and its oxidation during the inhibitory process develops a special role in this process, we suggest that the close relationship between the reactivity of the radicals of MC-W compounds with thiol groups and their efficacy as NADPH oxidase inhibitor could be the chemical pathway behind the mechanism of action of apocynin and should be taken into account in the design of new and specific NADPH oxidase inhibitors.

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.

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.

Melatonin and its kynurenin-like oxidation products affect the microbicidal activity of neutrophils.

Activated phagocytes oxidize the hormone melatonin to N1-acethyl-N2-formyl-5-methoxykynuramine (AFMK) in a superoxide anion- and myeloperoxidase-dependent reaction. We examined the effect of melatonin, AFMK and its deformylated-product N-acetyl-5-methoxykynuramine (AMK) on the phagocytosis, the microbicidal activity and the production of hypochlorous acid by neutrophils. Neither neutrophil and bacteria viability nor phagocytosis were affected by melatonin, AFMK or AMK. However these compounds affected the killing of Staphylococcus aureus. After 60 min of incubation, the percentage of viable bacteria inside the neutrophil increased to 76% in the presence of 1 mM of melatonin, 34% in the presence of AFMK and 73% in the presence of AMK. The sole inhibition of HOCl formation, expected in the presence of myeloperoxidase substrates, was not sufficient to explain the inhibition of the killing activity. Melatonin caused an almost complete inhibition of HOCl formation at concentrations of up to 0.05 mM. Although less effective, AMK also inhibited the formation of HOCl. However, AFMK had no effect on the production of HOCl. These findings corroborate the present view that the killing activity of neutrophils is a complex phenomenon, which involves more than just the production of reactive oxygen species. Furthermore, the action of melatonin and its oxidation products include additional activities beyond their antioxidant property. The impairment of the neutrophils' microbicidal activity caused by melatonin and its oxidation products may have important clinical implications, especially in those cases in which melatonin is pharmacologically administered in patients with infections.

C5 induces different cell death pathways in promastigotes of Leishmania amazonensis.

Leishmaniasis is a neglected infection that is caused by Leishmania protozoa, affecting millions of people worldwide, mainly in tropical and subtropical regions. This disease has different clinical forms: cutaneous, mucocutaneous, and visceral. The drugs that are currently available for the treatment of this infection have limitations, such as high toxicity, long-term treatment, and leads to drug-resistant strains. Numerous studies, in various experimental models, have sought to develop more effective and less toxic chemotherapeutic agents against leishmaniasis. In the present study, we evaluated the mechanism of cell death that is induced by n-benzyl 1-(4-methoxy)phenyl-9H-ß-carboline-3-carboxamide (C5) against Leishmania amazonensis. C5 increased reactive oxygen species production, depolarization of the mitochondrial membrane, DNA fragmentation, decrease of cell volume, lipoperoxidation, the accumulation of lipid bodies, and acidic vesicular organelles (AVOs) and caused the intense formation of autophagic compartments in L. amazonensis promastigotes. The results indicate that C5 causes L. amazonensis death through different pathways.

Mitochondrial Dysfunction Induced by N-Butyl-1-(4-Dimethylamino)Phenyl-1,2,3,4-Tetrahydro-ß-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-ß-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.

Eupomatenoid-5 Isolated from Leaves of Piper regnellii Induces Apoptosis in Leishmania amazonensis.

Leishmania spp. are protozoa responsible for leishmaniasis, a neglected disease that kills up to 50,000 people every year. Current therapies mainly rely on antimonial drugs that are inadequate because of their poor efficacy and safety and increased drug resistance. An urgent need exists to find new and more affordable drugs. Our previous study demonstrated the antileishmanial activity of eupomatenoid-5, a neolignan obtained from leaves of Piper regnellii var. pallescens. The aim of the present study was to clarify the mode of action of eupomatenoid-5 against L. amazonensis. We used biochemical and morphological techniques and demonstrated that eupomatenoid-5 induced cell death in L. amazonensis promastigotes, sharing some phenotypic features observed in metazoan apoptosis, including increased reactive oxygen species production, hypopolarization of mitochondrial potential, phosphatidylserine exposure, decreased cell volume, and G0/G1 phase cell cycle arrest.

The Effects of N-Butyl-1-(4-dimethylamino)phenyl-1,2,3,4-tetrahydro- ß -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-ß-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.

Antioxidant effects of quercetin and naringenin are associated with impaired neutrophil microbicidal activity.

Naringenin and quercetin are considered antioxidant compounds with promising activity against oxidative damage in human cells. However, no reports have described their effects on reactive oxygen species (ROS) production by phagocytes during microbicidal activity. Thus, the present study evaluated the effects of naringenin and quercetin on ROS production, specifically hypochlorous acid (HOCl), and their involvement in the microbicidal activity of neutrophils. Naringenin and quercetin inhibited HOCl production through different systems, but this inhibition was more pronounced for quercetin, even in the cell-free systems. With regard to the microbicidal activity of neutrophils, both naringenin and quercetin completely inhibited the killing of Staphylococcus aureus. Altogether, these data indicate that the decrease in the oxidant activity of neutrophils induced by these compounds directly impaired the microbicidal activity of neutrophils. Naringenin and quercetin exerted their effects by controlling the effector mechanisms of ROS production, with both positive and negative effects of these antioxidant agents in oxidative stress conditions and on ROS in the microbicidal activity of phagocytes. The present results challenge the traditional view of antioxidants as improvers of pathological conditions.

Trypanocidal activity of 1,3,7-trihydroxy-2-(3-methylbut-2-enyl)-xanthone isolated from Kielmeyera coriacea.

This work evaluated the activity and ultrastructural and morphological alterations induced by the xanthone 1,3,7-trihydroxy-2-(3-methylbut-2-enyl)-xanthone (C23) isolated from Kielmeyera coriacea against Trypanosoma cruzi. This xanthone had inhibitory activity against the three forms of this protozoan and did not induce toxicity in mammalian cells. The best activity of this xanthone was against the intracellular amastigote form. Additionally, the mitochondrion was the main target of this compound, reflected by electronic microscopy and rhodamine 123 assays. Our MitoSOX assay results also indicated that C23 increased O2(-) production in mitochondrion. C23 might be a promising chemotherapeutic agent against T. cruzi because its trypanocidal action involves the disruption of mitochondrion, a specific target of Trypanosomatides.

Trypanocidal activity of organic extracts from the Brazilian and Spanish marine sponges

Abstract Chagas' disease is a parasitic infection caused by protozoan Trypanosoma cruzi that affect millions of people worldwide. The available drugs for treatment of this infection cause serious side effects and have variable efficacy, especially in the chronic phase of the disease. In this context, natural compounds have shown great potential for the discovery of new chemotherapies for the treatment of this infection and various other diseases. In present study, we evaluated the in vitro antiprotozoal activity of five species of Brazilian and Spanish marine sponges (Condrosia reniformes, Tethya rubra, Tethya ignis, Mycale angulosa and Dysidea avara) against T. cruzi. By GC–MS data, we observed that in these extracts were present the major classes of the following compounds: hydrocarbons, terpenes, steroids and alcohols. The extracts showed activity against the three forms of this parasite and did not induce toxicity in mammalian cells. Better activities were observed with the extracts of marine sponges, C. reniformes (EC50 = 0.6 μg/ml), D. avara (EC50 = 1.1 μg/ml) and M. angulosa (EC50 = 3.8 μg/ml), against trypomastigote forms. In intracellular amastigote forms, the extract of T. ignis showed IC50 of 7.2 μg/ml and SI of 24.65. On this basis, our results indicate that these extracts can be promising chemotherapeutic agents against T. cruzi.

High concentrations of the melatonin metabolite, N1-acetyl-N2-formyl-5-methoxykynuramine, in cerebrospinal fluid of patients with meningitis: a possible immunomodulatory mechanism.

We evaluated the presence of the melatonin metabolite N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK), in cerebrospinal fluid (CSF) of patients with viral meningitis (n = 20) and control samples (n = 8) and correlate AFMK levels with inflammatory markers such as cellularity, protein, tumor necrosis factor (TNF)-alpha, interleukin (IL)-8 and IL-1beta levels. A portion of the CSF was extracted with dichloromethane (1:5) and analyzed by high-performance liquid chromatography (HPLC) under standardized conditions for AFMK. AFMK was detected in 16 of 20 CSF samples of patients with viral meningitis; the concentration of AFMK was found to be above the quantification limit (50 nmol/L) in six of these samples. AFMK was not detected in any of the eight control samples. The samples were classified into groups according to AFMK levels: undetectable (<10 nmol/L, group I), detectable but below the quantification limit (< 50 nmol/L, group II), and quantified (>50 nmol/L, group III). Group II presented the highest levels of proteins and IL-8, whereas group III showed the lowest levels of the inflammatory parameters. This study supports our hypothesis that inflammation favors the formation of AFMK and that this compound has immunomodulatory activity in vivo.

Oxidação de melatonina e formação de N¹-acetil-N²-formil-5-metoxiquinuramina: possíveis efeitos biológicos / Melatonin oxidation and formation of N¹-acetyl-N²-formyl-5-methoxykynuramine: possible biological effects

Em trabalho anterior verificamos que neutrófilos oxidam o hormônio melatonina a N¹-acetil-N²-formil-5-metoxiquinuramina (AFMK), numa reação catalisada por mieloperoxidase e dependente de ânion superóxido. Neste trabalho acompanhamos a cinética de formação de AFMK e de seu produto de deformilação N¹-acetil-5-metoxiquinuramina (AMK) quando neutrófilos foram ativados por diferentes estímulos. No sentido de obtermos informações sobre a relevância biológica destas reações, avaliamos o efeito de melatonina, AFMK e AMK sobre a formação de HOCl, sobre a liberação de citocinas pró-inflamatórias (TNF-`alfa´ e IL-8) e sobre a apoptose de neutrófilos. Uma forte inibição da liberação de HOCl foi observada em concentrações de melatonina igual ou superior a 0,05 mM...