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Romero AH, Aguilera E, Gotopo L, Cabrera G, Dávila B, Cerecetto H. Optimization of the 2-arylquinazoline-4(3 H)one scaffold for a selective and potent antitrypanosomal agent: modulation of the mechanism of action through chemical functionalization. RSC Med Chem 2023; 14:1992-2006. [PMID: 37859724 PMCID: PMC10583831 DOI: 10.1039/d3md00243h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 07/07/2023] [Indexed: 10/21/2023] Open
Abstract
We sought to identify a potent and selective antitrypanosomal agent through modulation of the mechanism of action of a 2-arylquinazoline scaffold as an antitrypanosomal agent via chemical functionalization at the 4-position. We wished to use the: (i) susceptibility of trypanosomatids towards nitric oxide (NO) and reactive oxygen species (ROS); (ii) capacity of the 4-substituted quinazoline system to act as an antifolate agent. Three quinazolin-based moieties that differed from each other by having at the 4-position key pharmacophores targeting the induction of NO and ROS production were evaluated in vitro against Leishmania infantum and Trypanosoma cruzi parasites and their modes of action were explored. Replacement of an oxygen moiety at the 4-position of the antifolate 2-arylquinazolin-4(3H)one by hydrazinyl and 5-nitrofuryl-hydrazinyl pharmacophores enhanced antitrypanosomatid activity significantly due to promotion of an additional mechanism beyond the antifolate response such as NO or ROS production, respectively. Among the three types of chemical functionalization, the 5-nitrofuryl-hydrazinyl moiety generated the most potent compounds. Compound 3b was a potential candidate thanks to its sub-micromolar response against the promastigotes/amastigotes of L. infantum and epimastigote of T. cruzi, moderate toxicity on macrophages (J774.1), good selectivity index (∼15.1-17.6) and, importantly, non-mutagenic effects. 2-Arylquinazoline could be an attractive platform to design new anti-trypanosomatid agents with the use of key pharmacophores.
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Affiliation(s)
- Angel H Romero
- Grupo de Química Orgánica Medicinal, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la Republica Igual 4225 11400 Montevideo Uruguay
| | - Elena Aguilera
- Grupo de Química Orgánica Medicinal, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la Republica Igual 4225 11400 Montevideo Uruguay
| | - Lourdes Gotopo
- Laboratorio de Síntesis de Orgánica, Facultad de Ciencias, Universidad Central de Venezuela Los Chaguaramos Caracas 1041-A Venezuela
| | - Gustavo Cabrera
- Laboratorio de Síntesis de Orgánica, Facultad de Ciencias, Universidad Central de Venezuela Los Chaguaramos Caracas 1041-A Venezuela
| | - Belén Dávila
- Grupo de Química Orgánica Medicinal, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la Republica Igual 4225 11400 Montevideo Uruguay
| | - Hugo Cerecetto
- Grupo de Química Orgánica Medicinal, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la Republica Igual 4225 11400 Montevideo Uruguay
- Área de Radiofarmacia, Centro de Investigaciones Nucleares, Facultad de Ciencias, Universidad de la Republica Mataojo 42055 11400 Montevideo Uruguay
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2
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Romero AH, Aguilera E, Gotopo L, Charris J, Rodríguez N, Oviedo H, Dávila B, Cabrera G, Cerecetto H. Synthesis and Antitrypanosomal and Mechanistic Studies of a Series of 2-Arylquinazolin-4-hydrazines: A Hydrazine Moiety as a Selective, Safe, and Specific Pharmacophore to Design Antitrypanosomal Agents Targeting NO Release. ACS OMEGA 2022; 7:47225-47238. [PMID: 36570252 PMCID: PMC9773939 DOI: 10.1021/acsomega.2c06455] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 11/23/2022] [Indexed: 06/17/2023]
Abstract
Nitric oxide (NO) represents a valuable target to design antitrypanosomal agents by its high toxicity against trypanosomatids and minimal side effects on host macrophages. The progress of NO-donors as antitrypanosomal has been restricted by the high toxicity of their agents, which usually is based on NO-heterocycles and metallic NO-complexes. Herein, we carried out the design of a new class of NO-donors based on the susceptibility of the hydrazine moiety connected to an electron-deficient ring to be reduced to the amine moiety with release of NO. Then, a series of novel 2-arylquinazolin-4-hydrazine, with the potential ability to disrupt the parasite folate metabolism, were synthesized. Their in vitro evaluation against Leishmania and Trypanosoma cruzi parasites and mechanistic aspects were investigated. The compounds displayed significant leishmanicidal activity, identifying three potential candidates, that is, 3b, 3c, and 3f, for further assays by their good antiamastigote activities against Leishmania braziliensis, low toxicity, non-mutagenicity, and good ADME profile. Against T. cruzi parasites, derivatives 3b, 3c, and 3e displayed interesting levels of activities and selectivities. Mechanistic studies revealed that the 2-arylquinazolin-4-hydrazines act as either antifolate or NO-donor agents. NMR, fluorescence, and theoretical studies supported the fact that the quinazolin-hydrazine decomposed easily in an oxidative environment via cleavage of the N-N bond to release the corresponding heterocyclic-amine and NO. Generation of NO from axenic parasites was confirmed by the Griess test. All the evidence showed the potential of hydrazine connected to the electron-deficient ring to design effective and safe NO-donors against trypanosomatids.
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Affiliation(s)
- Angel H. Romero
- Grupo
de Química Orgánica Medicinal, Instituto de Química
Biológica, Facultad de Ciencias, Universidad de la Republica, Iguá 4225, Montevideo 11400, Uruguay
- Laboratorio
de Ingeniería Genética, Instituto de Biomedicina, Facultad
de Medicina, Universidad Central de Venezuela, San Luis, Caracas 1073, Venezuela
| | - Elena Aguilera
- Grupo
de Química Orgánica Medicinal, Instituto de Química
Biológica, Facultad de Ciencias, Universidad de la Republica, Iguá 4225, Montevideo 11400, Uruguay
| | - Lourdes Gotopo
- Laboratorio
de Síntesis de Orgánica, Facultad de Ciencias, Universidad Central de Venezuela, Los Chaguaramos, Caracas 1041-A, Venezuela
| | - Jaime Charris
- Laboratorio
de Síntesis de Medicamentos, Facultad de Farmacia, Universidad Central de Venezuela, Los Chaguaramos, Caracas 1041-A, Venezuela
| | - Noris Rodríguez
- Laboratorio
de Ingeniería Genética, Instituto de Biomedicina, Facultad
de Medicina, Universidad Central de Venezuela, San Luis, Caracas 1073, Venezuela
| | - Henry Oviedo
- Laboratorio
de Ingeniería Genética, Instituto de Biomedicina, Facultad
de Medicina, Universidad Central de Venezuela, San Luis, Caracas 1073, Venezuela
| | - Belén Dávila
- Grupo
de Química Orgánica Medicinal, Instituto de Química
Biológica, Facultad de Ciencias, Universidad de la Republica, Iguá 4225, Montevideo 11400, Uruguay
| | - Gustavo Cabrera
- Laboratorio
de Síntesis de Orgánica, Facultad de Ciencias, Universidad Central de Venezuela, Los Chaguaramos, Caracas 1041-A, Venezuela
| | - Hugo Cerecetto
- Grupo
de Química Orgánica Medicinal, Instituto de Química
Biológica, Facultad de Ciencias, Universidad de la Republica, Iguá 4225, Montevideo 11400, Uruguay
- Área
de Radiofarmacia, Centro de Investigaciones Nucleares, Facultad de
Ciencias, Universidad de la Republica, Mataojo 2055, Montevideo 11400, Uruguay
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3
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Ávila LR, Gomes CM, Oliveira PG, Gomes RS, Vinaud MC, Dorta ML, Uliana SRB, Ribeiro-Dias F, Oliveira MAP. Promastigote parasites cultured from the lesions of patients with mucosal leishmaniasis are more resistant to oxidative stress than promastigotes from a cutaneous lesion. Free Radic Biol Med 2018; 129:35-45. [PMID: 30196081 DOI: 10.1016/j.freeradbiomed.2018.09.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 09/03/2018] [Accepted: 09/05/2018] [Indexed: 01/03/2023]
Abstract
Human leishmaniasis caused by Leishmania (Viannia) braziliensis can be presented as localized cutaneous leishmaniasis (LCL) or mucosal leishmaniasis (ML). Macrophages kill parasites using nitric oxide (NO) and reactive oxygen species (ROS). The aim of this study was to evaluate the ability of parasites obtained from patients with LCL or ML to produce and resist NO or ROS. Promastigotes and amastigotes from LCL or ML isolates produced similar amounts of NO in culture. Promastigotes from ML isolates were more resistant to NO and H2O2 than LCL parasites in a stationary phase, whereas amastigotes from LCL isolates were more resistant to NO. In addition, in the stationary phase, promastigote isolates from patients with ML expressed more thiol-specific antioxidant protein (TSA) than LCL isolates. Therefore it is suggested that infective promastigotes from ML isolates are more resistant to microbicidal mechanisms in the initial phase of infection. Subsequently, amastigotes lose this resistance. This behavior of ML parasites can decrease the number of parasites capable of stimulating the host immune response shortly after the infection establishment.
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MESH Headings
- Animals
- Antioxidants/chemistry
- Antioxidants/metabolism
- Antiprotozoal Agents/pharmacology
- Culture Media/chemistry
- Female
- Host-Parasite Interactions
- Humans
- Hydrogen Peroxide/pharmacology
- Immunity, Innate
- Leishmania braziliensis/drug effects
- Leishmania braziliensis/growth & development
- Leishmania braziliensis/isolation & purification
- Leishmania braziliensis/metabolism
- Leishmaniasis, Diffuse Cutaneous/immunology
- Leishmaniasis, Diffuse Cutaneous/metabolism
- Leishmaniasis, Diffuse Cutaneous/parasitology
- Leishmaniasis, Mucocutaneous/immunology
- Leishmaniasis, Mucocutaneous/metabolism
- Leishmaniasis, Mucocutaneous/parasitology
- Life Cycle Stages/drug effects
- Life Cycle Stages/physiology
- Male
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Mice, Knockout
- Nitric Oxide/metabolism
- Nitric Oxide/pharmacology
- Nitric Oxide Donors/pharmacology
- Nitroprusside/pharmacology
- Protozoan Proteins/genetics
- Protozoan Proteins/metabolism
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Affiliation(s)
- Lucilla Ribeiro Ávila
- Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Rua 235 S/N, Goiânia, Goiás 74605-050, Brazil
| | - Clayson Moura Gomes
- Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Rua 235 S/N, Goiânia, Goiás 74605-050, Brazil; Pontifícia Universidade Católica de Goiás, Av, Universitária 1069, Setor Universitário, Goiânia, Goiás 74605-010, Brazil
| | - Pollyana Guimarães Oliveira
- Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Rua 235 S/N, Goiânia, Goiás 74605-050, Brazil
| | - Rodrigo Saar Gomes
- Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Rua 235 S/N, Goiânia, Goiás 74605-050, Brazil
| | - Marina Clare Vinaud
- Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Rua 235 S/N, Goiânia, Goiás 74605-050, Brazil
| | - Miriam Leandro Dorta
- Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Rua 235 S/N, Goiânia, Goiás 74605-050, Brazil
| | - Silvia Reni Bortolin Uliana
- Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, Av. Prof. Lineu Prestes 1374, São Paulo, SP 05508-000, Brazil
| | - Fátima Ribeiro-Dias
- Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Rua 235 S/N, Goiânia, Goiás 74605-050, Brazil
| | - Milton Adriano Pelli Oliveira
- Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Rua 235 S/N, Goiânia, Goiás 74605-050, Brazil.
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4
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Antileishmanial Activity and Inducible Nitric Oxide Synthase Activation by RuNO Complex. Mediators Inflamm 2016; 2016:2631625. [PMID: 27795620 PMCID: PMC5067336 DOI: 10.1155/2016/2631625] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 07/04/2016] [Accepted: 07/17/2016] [Indexed: 02/04/2023] Open
Abstract
Parasites of the genus Leishmania are capable of inhibiting effector functions of macrophages. These parasites have developed the adaptive ability to escape host defenses; for example, they inactivate the NF-κB complex and suppress iNOS expression in infected macrophages, which are responsible for the production of the major antileishmanial substance nitric oxide (NO), favoring then its replication and successful infection. Metal complexes with NO have been studied as potential compounds for the treatment of certain tropical diseases, such as ruthenium compounds, known to be exogenous NO donors. In the present work, the compound cis-[Ru(bpy)2SO3(NO)]PF6, or RuNO, showed leishmanicidal activity directly and indirectly on promastigote forms of Leishmania (Leishmania) amazonensis. In addition, treatment with RuNO increased NO production by reversing the depletion of NO caused by Leishmania. We also found increased expression of Akt, iNOS, and NF-κB in infected and treated macrophages. These results demonstrated that RuNO was able to kill the parasite by NO release and modulate the transcriptional capacity of the cell.
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5
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Kawakami NY, Tomiotto-Pellissier F, Cataneo AHD, Orsini TM, Thomazelli APFDS, Panis C, Conchon-Costa I, Pavanelli WR. Sodium nitroprusside has leishmanicidal activity independent of iNOS. Rev Soc Bras Med Trop 2016; 49:68-73. [DOI: 10.1590/0037-8682-0266-2015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 12/04/2015] [Indexed: 12/27/2022] Open
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Nitric oxide and Brazilian propolis combined accelerates tissue repair by modulating cell migration, cytokine production and collagen deposition in experimental leishmaniasis. PLoS One 2015; 10:e0125101. [PMID: 25973801 PMCID: PMC4431861 DOI: 10.1371/journal.pone.0125101] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 03/20/2015] [Indexed: 11/19/2022] Open
Abstract
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.
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7
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Synthesis, antileishmanial activity and structure–activity relationship of 1-N-X-phenyl-3-N′-Y-phenyl-benzamidines. Eur J Med Chem 2013; 67:166-74. [DOI: 10.1016/j.ejmech.2013.06.040] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Revised: 05/21/2013] [Accepted: 06/18/2013] [Indexed: 11/23/2022]
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8
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Costa ISF, de Souza GFP, de Oliveira MG, Abrahamsohn IDA. S-nitrosoglutathione (GSNO) is cytotoxic to intracellular amastigotes and promotes healing of topically treated Leishmania major or Leishmania braziliensis skin lesions. J Antimicrob Chemother 2013; 68:2561-8. [DOI: 10.1093/jac/dkt210] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
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9
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Verma RK, Singh AK, Mohan M, Agrawal AK, Verma PRP, Gupta A, Misra A. Inhalable microparticles containing nitric oxide donors: saying NO to intracellular Mycobacterium tuberculosis. Mol Pharm 2012; 9:3183-9. [PMID: 22978290 DOI: 10.1021/mp300269g] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Although nitric oxide (NO) is a bactericidal component of the macrophage's innate response to intracellular infections such as tuberculosis (TB), prolonged inhalation of NO gas has little benefit in chemotherapy of TB. The impact of controlled release of NO through intracellular delivery of NO donors to macrophages infected in vitro with Mycobacterium tuberculosis (Mtb) was investigated. Inhalable microparticles (MP) were prepared by spray-drying. Isosorbide mononitrate (ISMN), sodium nitroprusside (SNP), and diethylenetriamine nitric oxide adduct (DETA/NO) were incorporated in poly(lactic-co-glycolic acid) (PLGA) with encapsulation efficiencies of >90% to obtain MP yields of ∼70%. The mass median aerodynamic diameter (MMAD) of the MP was 2.2-2.4 μm within geometric standard deviations (GSD) of ≤0.1 μm. MP were phagocytosed by THP-1 derived macrophages in culture and significantly (P < 0.05) sustained NO secretion into culture supernatant from 6 to 72 h in comparison to equivalent amounts of drugs in solution. Significantly (P < 0.05) higher dose-dependent killing of intracellular Mtb by MP compared to equivalent amounts of drugs in solution was observed on estimation of colony forming units (CFU) surviving 24 h after exposure to drugs or MP. The cytotoxicity of MP toward macrophages was lower than that of dissolved drugs. It was concluded that inhalable MP can target NO donors to the macrophage, control NO release in the macrophage cytosol, and reduce Mtb CFU by up to 3-log in 24 h, at doses that are much lower than those required for cardiovascular effects.
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Affiliation(s)
- Rahul K Verma
- Pharmaceutics Division, CSIR-Central Drug Research Institute, Lucknow, 226001, India
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10
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Role of trypanosomatid's arginase in polyamine biosynthesis and pathogenesis. Mol Biochem Parasitol 2012; 181:85-93. [DOI: 10.1016/j.molbiopara.2011.10.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 10/12/2011] [Accepted: 10/12/2011] [Indexed: 01/08/2023]
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11
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Increasing the activity of copper(II) complexes against Leishmania through lipophilicity and pro-oxidant ability. J Biol Inorg Chem 2011; 17:107-12. [DOI: 10.1007/s00775-011-0834-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Accepted: 08/08/2011] [Indexed: 02/06/2023]
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12
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Van Assche T, Deschacht M, da Luz RAI, Maes L, Cos P. Leishmania-macrophage interactions: insights into the redox biology. Free Radic Biol Med 2011; 51:337-51. [PMID: 21620959 DOI: 10.1016/j.freeradbiomed.2011.05.011] [Citation(s) in RCA: 158] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Revised: 04/24/2011] [Accepted: 05/07/2011] [Indexed: 11/19/2022]
Abstract
Leishmaniasis is a neglected tropical disease that affects about 350 million individuals worldwide. The protozoan parasite has a relatively simple life cycle with two principal stages: the flagellated mobile promastigote living in the gut of the sandfly vector and the intracellular amastigote within phagolysosomal vesicles of the vertebrate host macrophage. This review presents a state-of-the-art overview of the redox biology at the parasite-macrophage interface. Although Leishmania species are susceptible in vitro to exogenous superoxide radical, hydrogen peroxide, nitric oxide, and peroxynitrite, they manage to survive the endogenous oxidative burst during phagocytosis and the subsequent elevated nitric oxide production in the macrophage. The parasite adopts various defense mechanisms to cope with oxidative stress: the lipophosphoglycan membrane decreases superoxide radical production by inhibiting NADPH oxidase assembly and the parasite also protects itself by expressing antioxidant enzymes and proteins. Some of these enzymes could be considered potential drug targets because they are not expressed in mammals. In respect to antileishmanial therapy, the effects of current drugs on parasite-macrophage redox biology and its involvement in the development of drug resistance and treatment failure are presented.
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Affiliation(s)
- Tim Van Assche
- Laboratory of Microbiology Parasitology, and Hygiene, University of Antwerp, B-2020 Antwerp, Belgium
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Fabrino DL, Bleck CKE, Anes E, Hasilik A, Melo RCN, Niederweis M, Griffiths G, Gutierrez MG. Porins facilitate nitric oxide-mediated killing of mycobacteria. Microbes Infect 2009; 11:868-75. [PMID: 19460455 DOI: 10.1016/j.micinf.2009.05.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Revised: 05/03/2009] [Accepted: 05/08/2009] [Indexed: 11/26/2022]
Abstract
Non-pathogenic mycobacteria such us Mycobacterium smegmatis reside in macrophages within phagosomes that fuse with late endocytic/lysosomal compartments. This sequential fusion process is required for the killing of non-pathogenic mycobacteria by macrophages. Porins are proteins that allow the influx of hydrophilic molecules across the mycobacterial outer membrane. Deletion of the porins MspA, MspC and MspD significantly increased survival of M. smegmatis in J774 macrophages. However, the mechanism underlying this observation is unknown. Internalization of wild-type M. smegmatis (SMR5) and the porin triple mutant (ML16) by macrophages was identical indicating that the viability of the porin mutant in vivo was enhanced. This was not due to effects on phagosome trafficking since fusion of phagosomes containing the mutant with late endocytic compartments was unaffected. Moreover, in ML16-infected macrophages, the generation of nitric oxide (NO) was similar to the wild type-infected cells. However, ML16 was significantly more resistant to the effects of NO in vitro compared to SMR5. Our data provide evidence that porins render mycobacteria vulnerable to killing by reactive nitrogen intermediates within phagosomes probably by facilitating uptake of NO across the mycobacterial outer membrane.
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