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Benaim G, Paniz-Mondolfi A. Unmasking the Mechanism behind Miltefosine: Revealing the Disruption of Intracellular Ca 2+ Homeostasis as a Rational Therapeutic Target in Leishmaniasis and Chagas Disease. Biomolecules 2024; 14:406. [PMID: 38672424 PMCID: PMC11047903 DOI: 10.3390/biom14040406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 03/20/2024] [Accepted: 03/22/2024] [Indexed: 04/28/2024] Open
Abstract
Originally developed as a chemotherapeutic agent, miltefosine (hexadecylphosphocholine) is an inhibitor of phosphatidylcholine synthesis with proven antiparasitic effects. It is the only oral drug approved for the treatment of Leishmaniasis and American Trypanosomiasis (Chagas disease). Although its precise mechanisms are not yet fully understood, miltefosine exhibits broad-spectrum anti-parasitic effects primarily by disrupting the intracellular Ca2+ homeostasis of the parasites while sparing the human hosts. In addition to its inhibitory effects on phosphatidylcholine synthesis and cytochrome c oxidase, miltefosine has been found to affect the unique giant mitochondria and the acidocalcisomes of parasites. Both of these crucial organelles are involved in Ca2+ regulation. Furthermore, miltefosine has the ability to activate a specific parasite Ca2+ channel that responds to sphingosine, which is different to its L-type VGCC human ortholog. Here, we aimed to provide an overview of recent advancements of the anti-parasitic mechanisms of miltefosine. We also explored its multiple molecular targets and investigated how its pleiotropic effects translate into a rational therapeutic approach for patients afflicted by Leishmaniasis and American Trypanosomiasis. Notably, miltefosine's therapeutic effect extends beyond its impact on the parasite to also positively affect the host's immune system. These findings enhance our understanding on its multi-targeted mechanism of action. Overall, this review sheds light on the intricate molecular actions of miltefosine, highlighting its potential as a promising therapeutic option against these debilitating parasitic diseases.
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Affiliation(s)
- Gustavo Benaim
- Unidad de Señalización Celular y Bioquímica de Parásitos, Instituto de Estudios Avanzados (IDEA), Caracas 1080, Venezuela
- Laboratorio de Biofísica, Instituto de Biología Experimental, Facultad de Ciencias, Universidad Central de Venezuela, Caracas 1040, Venezuela
| | - Alberto Paniz-Mondolfi
- Department of Pathology, Molecular and Cell-Based Medicine, Icahn School of Medicine at Mount Sinai, Division of Microbiology, New York, NY 10029, USA;
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Conserva GA, Costa-Silva TA, Quirós-Guerrero LM, Marcourt L, Wolfender JL, Queiroz EF, Tempone AG, Lago JHG. Kaempferol-3-O-α-(3,4-di-E-p-coumaroyl)-rhamnopyranoside from Nectandra oppositifolia releases Ca 2+ from intracellular pools of Trypanosoma cruzi affecting the bioenergetics system. Chem Biol Interact 2021; 349:109661. [PMID: 34537181 DOI: 10.1016/j.cbi.2021.109661] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 08/12/2021] [Accepted: 09/15/2021] [Indexed: 12/22/2022]
Abstract
Phytochemical analysis of EtOH extract from leaves of Nectandra oppositifolia afforded three flavonoids: kaempferol (1), kaempferol-3-O-α-rhamnopyranoside (2) and kaempferol-3-O-α-(3,4-di-E-p-coumaroyl)-rhamnopyranoside (3), which were characterized by NMR and ESI-HRMS. When tested against the protozoan parasite Trypanosoma cruzi, the etiologic agent of Chagas disease, flavonoids 1 and 3 were effective to kill the trypomastigotes with IC50 values of 32.0 and 6.7 μM, respectively, while flavonoid 2 was inactive. Isolated flavonoids 1-3 were also tested in mammalian fibroblasts and showed CC50 values of 24.8, 48.7 and 153.1 μM, respectively. Chemically, these results suggested that the free aglycone plays an important role in the bioactivity while the presence of p-coumaroyl unities linked in the rhamnoside unity is important to enhance the antitrypanosomal activity and reduce the mammalian cytotoxicity. The mechanism of cellular death was investigated for the most potent flavonoid 3 in the trypomastigotes using fluorescent and luminescent-based assays. It indicated that this compound induced neither permeabilization of the plasma membrane nor depolarization of the membrane electric potential. However, early time incubation (20 min) with flavonoid 3 resulted in a constant elevation of the Ca2+ levels inside the parasite. This effect was followed by a mitochondrial imbalance, leading to a hyperpolarization and depolarization of the mitochondrial membrane potential, with reduction of the ATP levels. During this time, the levels of reactive oxygen species levels (ROS) were unaltered. The leakage of Ca2+ from the intracellular pools can affect the bioenergetics system of T. cruzi, leading to the parasite death. Therefore, flavonoid 3 can be a useful tool for future studies against T. cruzi parasites.
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Affiliation(s)
- Geanne A Conserva
- Center of Natural Sciences and Humanities, Federal University of ABC, Santo Andre, SP, 09210-180, Brazil.
| | - Thais A Costa-Silva
- Center of Natural Sciences and Humanities, Federal University of ABC, Santo Andre, SP, 09210-180, Brazil.
| | - Luis M Quirós-Guerrero
- School of Pharmaceutical Sciences, University of Geneva, Geneva, Switzerland; Institute of Pharmaceutical Sciences of Western Switzerland (ISPSW), University of Geneva, Geneva, Switzerland.
| | - Laurence Marcourt
- School of Pharmaceutical Sciences, University of Geneva, Geneva, Switzerland; Institute of Pharmaceutical Sciences of Western Switzerland (ISPSW), University of Geneva, Geneva, Switzerland.
| | - Jean-Luc Wolfender
- School of Pharmaceutical Sciences, University of Geneva, Geneva, Switzerland; Institute of Pharmaceutical Sciences of Western Switzerland (ISPSW), University of Geneva, Geneva, Switzerland.
| | - Emerson F Queiroz
- School of Pharmaceutical Sciences, University of Geneva, Geneva, Switzerland; Institute of Pharmaceutical Sciences of Western Switzerland (ISPSW), University of Geneva, Geneva, Switzerland.
| | - Andre G Tempone
- Centre for Parasitology and Mycology, Instituto Adolfo Lutz, São Paulo, SP, 01246-000, Brazil.
| | - João Henrique G Lago
- Center of Natural Sciences and Humanities, Federal University of ABC, Santo Andre, SP, 09210-180, Brazil.
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Benaim G, Paniz-Mondolfi AE, Sordillo EM, Martinez-Sotillo N. Disruption of Intracellular Calcium Homeostasis as a Therapeutic Target Against Trypanosoma cruzi. Front Cell Infect Microbiol 2020; 10:46. [PMID: 32133302 PMCID: PMC7040492 DOI: 10.3389/fcimb.2020.00046] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 01/24/2020] [Indexed: 12/15/2022] Open
Abstract
There is no effective cure for Chagas disease, which is caused by infection with the arthropod-borne parasite, Trypanosoma cruzi. In the search for new drugs to treat Chagas disease, potential therapeutic targets have been identified by exploiting the differences between the mechanisms involved in intracellular Ca2+ homeostasis, both in humans and in trypanosomatids. In the trypanosomatid, intracellular Ca2+ regulation requires the concerted action of three intracellular organelles, the endoplasmic reticulum, the single unique mitochondrion, and the acidocalcisomes. The single unique mitochondrion and the acidocalcisomes also play central roles in parasite bioenergetics. At the parasite plasma membrane, a Ca2+-−ATPase (PMCA) with significant differences from its human counterpart is responsible for Ca2+ extrusion; a distinctive sphingosine-activated Ca2+ channel controls Ca2+ entrance to the parasite interior. Several potential anti-trypansosomatid drugs have been demonstrated to modulate one or more of these mechanisms for Ca2+ regulation. The antiarrhythmic agent amiodarone and its derivatives have been shown to exert trypanocidal effects through the disruption of parasite Ca2+ homeostasis. Similarly, the amiodarone-derivative dronedarone disrupts Ca2+ homeostasis in T. cruzi epimastigotes, collapsing the mitochondrial membrane potential (ΔΨm), and inducing a large increase in the intracellular Ca2+ concentration ([Ca2+]i) from this organelle and from the acidocalcisomes in the parasite cytoplasm. The same general mechanism has been demonstrated for SQ109, a new anti-tuberculosis drug with potent trypanocidal effect. Miltefosine similarly induces a large increase in the [Ca2+]i acting on the sphingosine-activated Ca2+ channel, the mitochondrion and acidocalcisomes. These examples, in conjunction with other evidence we review herein, strongly support targeting Ca2+ homeostasis as a strategy against Chagas disease.
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Affiliation(s)
- Gustavo Benaim
- Instituto de Estudios Avanzados, Caracas, Venezuela.,Facultad de Ciencias, Instituto de Biología Experimental, Universidad Central de Venezuela, Caracas, Venezuela
| | - Alberto E Paniz-Mondolfi
- Instituto de Estudios Avanzados, Caracas, Venezuela.,Department of Pathology, Molecular, and Cell-Based Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Emilia Mia Sordillo
- Department of Pathology, Molecular, and Cell-Based Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States.,Institute for Health Sciences, Mount Sinai St. Luke's & Mount Sinai West, New York, NY, United States
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Menna-Barreto RF, de Castro SL. The double-edged sword in pathogenic trypanosomatids: the pivotal role of mitochondria in oxidative stress and bioenergetics. Biomed Res Int 2014; 2014:614014. [PMID: 24800243 DOI: 10.1155/2014/614014] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 02/17/2014] [Indexed: 11/17/2022]
Abstract
The pathogenic trypanosomatids Trypanosoma brucei, Trypanosoma cruzi, and Leishmania spp. are the causative agents of African trypanosomiasis, Chagas disease, and leishmaniasis, respectively. These diseases are considered to be neglected tropical illnesses that persist under conditions of poverty and are concentrated in impoverished populations in the developing world. Novel efficient and nontoxic drugs are urgently needed as substitutes for the currently limited chemotherapy. Trypanosomatids display a single mitochondrion with several peculiar features, such as the presence of different energetic and antioxidant enzymes and a specific arrangement of mitochondrial DNA (kinetoplast DNA). Due to mitochondrial differences between mammals and trypanosomatids, this organelle is an excellent candidate for drug intervention. Additionally, during trypanosomatids' life cycle, the shape and functional plasticity of their single mitochondrion undergo profound alterations, reflecting adaptation to different environments. In an uncoupling situation, the organelle produces high amounts of reactive oxygen species. However, these species role in parasite biology is still controversial, involving parasite death, cell signalling, or even proliferation. Novel perspectives on trypanosomatid-targeting chemotherapy could be developed based on better comprehension of mitochondrial oxidative regulation processes.
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Abstract
PURPOSE To evaluate whether the gentian violet staining of the anterior lens capsule during the cataract surgery is cytotoxic for the human lens epithelial cells, as an indirect indication of possible toxicity towards the corneal endothelium and the safety of gentian violet application. MATERIALS AND METHODS Two groups of anterior lens capsules obtained during the cataract surgery, gentian violet stained and non-stained, were incubated with fluorescent dye Fura-2. Their fluorescence, upon excitation at 360 and 380 nm, was imaged to monitor changes in free intracellular calcium concentration ([Ca(2+)]i) in response to pharmacological stimulation by acetylcholine. The [Ca(2+)]i homeostasis is the indicator of cellular function. The changes in [Ca(2+)]i were compared between the two groups. RESULTS Epithelial cells responded to acetylcholine in both groups of capsules - gentian violet stained (n = 17) and non-stained ones (n = 33). No significant differences of the elicited responses were found in rise time (p = 0.89), decay time (p = 0.61) or amplitude of [Ca(2+)]i (p = 0.96 for 63× and p = 0.26 for 40× objectives) between the two groups of capsules (Student t test). CONCLUSIONS The staining of the anterior lens capsule with gentian violet during phacoemulsification in concentration of 0.01%, does not have detectable cytotoxic effects, which would affect the [Ca(2+)]i homeostasis in lens epithelial cells. The data, if extrapolated to corneal endothelium, exposed to the same concentration, suggest that gentian violet in concentration of 0.01% is safe as an adjunct for capsule visualization in cataract surgery.
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Affiliation(s)
- Sofija Andjelić
- Eye Hospital, University Medical Centre , Ljubljana , Slovenia and
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Urbina JA, Moreno B, Vierkotter S, Oldfield E, Payares G, Sanoja C, Bailey BN, Yan W, Scott DA, Moreno SN, Docampo R. Trypanosoma cruzi contains major pyrophosphate stores, and its growth in vitro and in vivo is blocked by pyrophosphate analogs. J Biol Chem 1999; 274:33609-15. [PMID: 10559249 DOI: 10.1074/jbc.274.47.33609] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
High field (31)P nuclear magnetic resonance spectroscopy showed that inorganic pyrophosphate (P(2)O(7)(4-)) is more abundant than ATP in Trypanosoma cruzi, the causative agents of Chagas' disease. These results were confirmed by specific analytical assays, which showed that in epimastigotes, the concentrations of inorganic pyrophosphate and ATP were 194.7 +/- 25.9 and 37.6 +/- 5.5 nmol/mg of protein, respectively, and for the amastigote form, the corresponding concentrations were 358.0 +/- 17.0 and 36.0 +/- 1.9 nmol/mg of protein. High performance liquid chromatographic analysis of perchloric acid extracts of epimastigotes labeled for 3 h with (32)P-orthophosphate showed a significant incorporation of the precursor into inorganic pyrophosphate. Inorganic pyrophosphate was not uniformly distributed in T. cruzi but was shown by (31)P-NMR and chemical analysis to be particularly associated with acidocalcisomes, organelles shown previously to contain large amounts of phosphorus and various elements. Electron microscopy analysis of pyrophosphatase-treated permeabilized epimastigotes showed disappearance of the electron density of the acidocalcisomes. Nonmetabolizable analogs of pyrophosphate, currently used for the treatment of bone resorption disorders, selectively inhibited the proliferation of intracellular T. cruzi amastigotes and produced a profound suppression in the number of circulating trypomastigotes in mice with an acute infection of T. cruzi, offering a potentially new route to chemotherapy.
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Affiliation(s)
- J A Urbina
- Department of Chemistry, Department of Pathobiology, University of Illinois, Urbana-Champaign, Illinois 61802, USA
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Zhang HS, McDonald TV, Tanowitz HB, Wittner M, Weiss LM, Bilezikian JP, Morris SA. Intracellular Ca2+ homeostasis in trypomastigotes of Trypanosoma cruzi. J Eukaryot Microbiol 1998; 45:80-6. [PMID: 9495036 DOI: 10.1111/j.1550-7408.1998.tb05073.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Trypomastigotes of Trypanosoma cruzi maintain an intracellular Ca2+ concentration ([Ca2+]i) of 64 +/- 30 nM. Equilibration of trypomastigotes in an extracellular buffer containing 0.5 mM [Ca2+]o (preloaded cells) increased [Ca2+]i < 20 nM whereas total cell Ca2+ increased by 1.5 to 2.0 pmole/cell. This amount of Ca2+ would be expected to increase [Ca2+]i to > 10 microM suggesting active sequestration of Ca2+. We tested the hypothesis that maintenance of [Ca2+]i involved both the sequestration into intracellular storage sites and extrusion into the extracellular space. Pharmacological probes known to influence [Ca2+]i through well characterized pathways in higher eukaryotic cells were employed. [Ca2+]i responses in the presence or absence of [Ca2+]o were measured to asses the relative contribution of sequestration or extrusion processes in [Ca2+]i homeostasis. In the presence of 0.5 mM [Ca2+]o, the ability of several agents to increase [Ca2+]i was magnified in the order ionomycin >>> nigericin > thapsigargin > monensin > valinomycin. In contrast, preloading markedly enhanced the increase in [Ca2+]i observed only in response to monensin. Manoalide, an inhibitor of phospholipase A2, enhanced the accumulation of [Ca2+]i due to all agents tested, particularly ionomycin and thapsigargin. Our results suggest that sequestration of [Ca2+]i involved storage sites sensitive to monensin and ionomycin whereas extrusion of Ca2+ may involve phospholipase A2 activity. A Na+/Ca2+ exchange mechanism did not appear to contribute to Ca2+ homeostasis.
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Affiliation(s)
- H S Zhang
- Department of Pathology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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Núñez-Vergara LJ, Squella JA, Bollo-Dragnic S, Morello A, Repetto Y, Aldunate J, Letelier ME. Nitro aryl 1,4-dihydropyridine derivatives: effects on Trypanosoma cruzi. Comp Biochem Physiol C Pharmacol Toxicol Endocrinol 1997; 118:105-11. [PMID: 9366041 DOI: 10.1016/s0742-8413(97)00078-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A series of nitro aryl 1,4-dihydropyridine derivatives produced inhibition of both cell growth and oxygen consumption on Tulahuen and LQ strains, and clone Dm 28c of epimastigotes of Trypanosoma cruzi. Nicardipine was found to be the most potent derivative in both growth cell (I50 = 70 microM) and oxygen uptake (I50 = 26 microM in intact parasites, I50 = 325 microM in situ mitochondria). A correlation between the inhibitory effects on the growth cell and the apparent first order kinetic for the uptake of the 1,4-dihypyridine derivatives by T. cruzi epimastigotes was found. Thus, nicardipine, the most potent derivative, exhibited the highest apparent rate constant, ku, (0.043 min-1). On the other hand, no susceptibility differences by strains and clone Dm 28c to the action of these drugs were found.
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Affiliation(s)
- L J Núñez-Vergara
- Laboratory of Bioelectrochemistry, Faculty of Chemical and Pharmaceutical Sciences, University of Chile, Santiago, Chile
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Goulart MO, Zani CL, Tonholo J, Freitas LR, de Abreu FC, Oliveira AB, Raslan DS, Starling S, Chiari E. Trypanocidal activity and redox potential of heterocyclic- and 2-hydroxy-naphthoquinones. Bioorg Med Chem Lett 1997; 7:2043-8. [DOI: 10.1016/s0960-894x(97)00354-5] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Felibertt P, Bermúdez R, Cervino V, Dawidowicz K, Dagger F, Proverbio T, Marín R, Benaim G. Ouabain-sensitive Na+,K(+)-ATPase in the plasma membrane of Leishmania mexicana. Mol Biochem Parasitol 1995; 74:179-87. [PMID: 8719159 DOI: 10.1016/0166-6851(95)02497-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The mechanism responsible for the regulation of intracellular Na+ and K+ concentrations in trypanosomatids is unknown. In higher eukaryotes a ouabain-sensitive Na+,K(+)-ATPase located in the plasma membrane is the main mechanism for the regulation of the intracellular concentrations of Na+ and K+, while in trypanosomatids there are conflicting evidences about the existence of this type of ATPase. By the use of a highly enriched plasma membrane fraction, we showed that an ouabain-sensitive Na+,K(+)-ATPase is present in L. mexicana. The affinity of the enzyme for Na+ and K+ is similar to that reported for the mammalian Na+,K(+)-ATPase, showing also the same kinetic parameters regarding the relative concentration of those cations that give the optimal activity. Vanadate (10 microM) fully inhibits the ATPase activity, suggesting that the enzyme belongs to the P-type family of ionic pumps. The enzyme is sensitive to ouabain and other cardiac glycosides. These cardiac glycosides do not show any appreciable effect on the higher Mg(2+)-ATPase activity present in the same preparation. By the use of [3H]ouabain, we also show in this report that the binding of the inhibitor to the enzyme was specific. Taken together, these results demonstrate that an ouabain-sensitive Na+,K(+)-ATPase is present in the plasma membrane of Leishmania mexicana. Therefore, this Na+,K(+)-ATPase should participate in the intracellular regulation of these cations in Leishmania.
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Affiliation(s)
- P Felibertt
- Centro de Biología Celular, Facultad de Ciencias, Universidad Central de Venezuela, Caracas
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Abstract
[35S]methionine incorporation into proteins of either T. cruzi epimastigotes or trypomastigotes was drastically inhibited by low concentrations of crystal violet in a dose-dependent manner. This inhibition was not due to ATP depletion since cellular ATP levels did not change significantly after incubation of epimastigotes with 50 microM crystal violet for similar periods of time, and was unaffected by changes in the extracellular free calcium concentration. Although crystal violet was able to inhibit protein synthesis in a cell-free system from T. cruzi epimastigotes, half maximal inhibition was at 1 mM, a concentration three orders of magnitude higher than those that inhibited protein synthesis in intact cells. On the other hand, crystal violet was able to inhibit total [35S]methionine uptake at similar concentrations to those that inhibited protein synthesis while addition of increasing concentrations of cold methionine to the incubation medium protected the cells against crystal violet inhibition. Crystal violet also inhibited total [3H]proline uptake thus indicating that it has a general inhibitory effect upon the transport of amino acids, and not specifically upon methionine. These results indicate that inhibition of protein synthesis by crystal violet is probably due to inhibition of amino acid uptake.
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Affiliation(s)
- M E Hoffmann
- Department of Veterinary Pathobiology, University of Illinois at Urbana-Champaign 61801, USA
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Benaim G, Moreno SN, Hutchinson G, Cervino V, Hermoso T, Romero PJ, Ruiz F, de Souza W, Docampo R. Characterization of the plasma-membrane calcium pump from Trypanosoma cruzi. Biochem J 1995; 306 ( Pt 1):299-303. [PMID: 7532400 PMCID: PMC1136516 DOI: 10.1042/bj3060299] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Despite previous reports [McLaughlin (1985) Mol. Biochem. Parasitol. 15, 189-201; Ghosh, Ray, Sarkar and Bhaduri (1990) J. Biol. Chem. 265, 11345-11351; Mazumder, Mukherjee, Ghosh, Ray and Bhaduri (1992) J. Biol. Chem. 267, 18440-18446] suggesting that the plasma-membrane Ca(2+)-ATPases of different trypanosomatids differ from the Ca2+ pumps present in mammalian cells, Trypanosoma cruzi plasma-membrane Ca(2+)-ATPase shares several characteristics with the Ca2+ pumps present in other systems. This enzyme could be partially purified from epimastigote plasma-membrane vesicles using calmodulin-agarose affinity chromatography. The activity of the partially purified enzyme was stimulated by T. cruzi or bovine brain calmodulin. In addition, the enzyme cross-reacted with antiserum and monoclonal antibody 5F10 raised against human red-blood-cell Ca(2+)-ATPase, has a molecular mass of 140 kDa and forms Ca(2+)-dependent hydroxylamine-sensitive phosphorylated intermediates. These results, together with its high sensitivity to vanadate, indicate that this enzyme belongs to the P-type class of ionic pumps.
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Affiliation(s)
- G Benaim
- Department of Veterinary Pathobiology, University of Illinois at Urbana-Champaign 61801
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Abstract
A trypanothione reductase activity is present in all the main differentiation stages of Trypanosoma cruzi, amastigotes having the highest activity, and trypomastigotes the lowest. Trypanothione reductase could not be induced in epimastigotes exposed to H2O2. The trypanocidal drug crystal violet was a potent inhibitor of T. cruzi trypanothione reductase in vitro. The inhibition was competitive with respect to trypanothione with a Ki of 5.3 +/- 0.5 microM, uncompetitive with NADPH, and increased below pH 7.0 and above pH 8.0. Crystal violet, however, was not able to decrease the level of total reduced thiols in intact cells. Dihydrotrypanothione but not reduced glutathione, protected the enzyme from inhibition by crystal violet.
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Affiliation(s)
- S N Moreno
- Department of Veterinary Pathobiology, University of Illinois at Urbana-Champaign 61801
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Abstract
An electrochemical proton gradient exists across the plasma membrane and the mitochondrial membrane of the bloodstream form of Trypanosoma brucei. The membrane potential across the plasma membrane and the regulation of the internal pH depend on the temperature. Leishmania donovani regulates its internal pH and maintains a constant electrochemical proton gradient across its plasma membrane under all conditions examined. The mitochondrion of the T. brucei bloodstream form is energized, even though the reactions taking place in it do not result in net ATP synthesis and the Kreb's cycle and the respiratory chain are absent. Glucose is transported across the plasma membrane of T. brucei by a facilitated diffusion carrier, that can transport a wider range of substrates than its mammalian counterparts. Pyruvate exits the cell via a facilitated diffusion transporter as well. Conflicting evidence exists for the mechanism of glucose transport in L. donovani; biochemical evidence suggests proton/glucose symport, while facilitated diffusion is indicated by physiological data.
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Benaim G, Lopez-Estraño C, Docampo R, Moreno SN. A calmodulin-stimulated Ca2+ pump in plasma-membrane vesicles from Trypanosoma brucei; selective inhibition by pentamidine. Biochem J 1993; 296 ( Pt 3):759-63. [PMID: 8280074 PMCID: PMC1137760 DOI: 10.1042/bj2960759] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Despite previous reports [McLaughlin (1985) Mol. Biochem. Parasitol. 15, 189-201; Ghosh, Ray, Sarkar and Bhaduri (1990) J. Biol. Chem. 265, 11345-11351; Mazumder, Mukherjee, Ghosh, Ray and Bhaduri (1992) J. Biol. Chem. 267, 18440-18446] that the plasma membrane of different trypanosomatids only contains Ca(2+)-ATPase that does not show any demonstrable dependence on Mg2+, a high-affinity (Ca(2+)-Mg2+)-ATPase was demonstrated in the plasma membrane of Trypanosoma brucei. The enzyme became saturated with micromolar amounts of Ca2+, reaching a Vmax. of 3.45 +/- 0.66 nmol of ATP/min per mg of protein. The Km,app. for Ca2+ was 0.52 +/- 0.03 microM. This was decreased to 0.23 +/- 0.05 microM, and the Vmax. was increased to 6.36 +/- 0.22 nmol of ATP/min per mg of protein (about 85%), when calmodulin was present. T. brucei plasma-membrane vesicles accumulated Ca2+ on addition of ATP only when Mg2+ was present, and released it to addition of the Ca2+ ionophore A23187. In addition, this Ca2+ transport was stimulated by calmodulin. Addition of NaCl to Ca(2+)-loaded T. brucei plasma-membrane vesicles did not result in Ca2+ release, thus suggesting the absence of a Na+/Ca2+ exchanger in these parasites. Therefore the (Ca(2+)-Mg2+)-ATPase would be the only mechanism so far described that is responsible for the long-term fine tuning of the intracellular Ca2+ concentration of these parasites. The trypanocidal drug pentamidine inhibited the T. brucei plasma-membrane (Ca(2+)-Mg2+)-ATPase and Ca2+ transport at concentrations that had no effect on the Ca(2+)-ATPase activity of human or pig erythrocytes. In this latter case, pentamidine behaved as a weak calmodulin antagonist, since it inhibited the stimulation of the erythrocyte Ca(2+)-ATPase by calmodulin.
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Affiliation(s)
- G Benaim
- Department of Veterinary Pathobiology, University of Illinois, Urbana 61801
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