RESUMO
INTRODUCTION: Malignant Infantile Osteopetrosis (MIOP) is a rare and severe genetic disorder due to abnormal osteoclast activity. OBJECTIVE: To report an infant who presented Malignant Infantile Osteopetrosis, reviewing the most relevant diagnostic and therapeutic aspects. CLINICAL CASE: A ten- month-old male infant with diagnosis of MIOP confirmed after presenting thrombocytopenia and visceromegaly. He was the first child of non-consanguineous parents, and among the findings, he presented severe hepatosplenomegaly, thrombocytopenia, and anemia; visual and hearing impair ment, and repeated infections. The diagnosis was confirmed by genetic study, which identified two heterozygous mutations in the TCIRG1 gene. Hematopoietic stem cells were transplanted without hematological recovery. The patient died due to occlusive venous disease. DISCUSSION: MIOP is a rare, severe, and early-onset disease, with a high rate of suspicion necessary in the presence of hepa- tosplenomegaly and bone marrow failure. Early diagnosis and hematopoietic stem cells transplanta tion are the only potentially therapeutic interventions of this lethal entity.
Assuntos
Transplante de Células-Tronco Hematopoéticas/métodos , Osteopetrose/diagnóstico , ATPases Vacuolares Próton-Translocadoras/genética , Evolução Fatal , Humanos , Lactente , Masculino , Mutação , Osteopetrose/genética , Osteopetrose/fisiopatologiaRESUMO
Increased production of reactive nitrogen (RNS) and oxygen (ROS) species and its detrimental effect to mitochondria are associated with endothelial dysfunction. This study was designed to determine the effect of a peroxynitrite flux, promoted by 1,3-morpholinosydnonimine (SIN-1), in mitochondrial function and some redox homeostasis parameters in bovine aortic endothelial cells (BAEC). Moreover, the effect of diphenyl diselenide (PhSe)2, a simple organic selenium compound, in preventing peroxynitrite-mediated cytotoxicity was also investigated. Our results showed that overnight exposure to SIN-1 (250 µM) caused a profound impairment of oxygen consumption, energy generation and reserve capacity in mitochondria of BAEC. Mitochondrial dysfunction resulted in an additional intracellular production of peroxynitrite, amplifying the phenomenon and leading to changes in redox homeostasis. Moreover, we observed an extensive decline in mitochondrial membrane potential (ΔΨm) induced by peroxynitrite and this event was associated with apoptotic-type cell death. Alternatively, the pretreatment of BAEC with (PhSe)2, hindered peroxynitrite-mediated cell damage by preserving mitochondrial and endothelial function and consequently preventing apoptosis. The protective effect of (PhSe)2 was related to its ability to improve the intracellular redox state by increasing the expression of different isoforms of peroxiredoxins (Prx-1-3), efficient enzymes in peroxynitrite detoxification.
Assuntos
Derivados de Benzeno/farmacologia , Células Endoteliais/efeitos dos fármacos , Metabolismo Energético/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Molsidomina/análogos & derivados , Compostos Organosselênicos/farmacologia , Peroxirredoxinas/metabolismo , Ácido Peroxinitroso/metabolismo , Animais , Aorta/citologia , Bovinos , Células Endoteliais/enzimologia , Homeostase/efeitos dos fármacos , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Mitocôndrias/enzimologia , Molsidomina/química , Oxirredução , Ácido Peroxinitroso/química , Ácido Peroxinitroso/toxicidadeRESUMO
Nitric oxide participates in a wide array of physiological processes, ranging from neurotransmission to precursor of cytotoxic effector molecules of the immune system. Although nitric oxide is a mildly reactive intermediary, it can act as a precursor of strong oxidants under pathological conditions associated with oxidative stress including cardiovascular, inflammatory and neurodegenerative disorders. Peroxynitrite, the reaction product of nitric oxide with superoxide radicals, emerges as one of the principal players of nitric oxidederived toxicity due to its facile formation and ability to react with several critical cellular targets including, thiols, proteins, lipids and DNA. The extent of "nitroxidative stress" is determined by several factors, including the concentration and exposure time to this reactive species or its derived radicals and by the ability of the cell to face the oxidative challenge by means of its antioxidant defenses. The inflicted biomolecular damage can result on minimal and reversible changes to cell and tissue physiology, to alteration in bioenergetics, disruption of DNA integrity, mitochondrial dysfunction and even cell death. Although dissecting the free radical chemistry pathways responsible of cell/tissue disturbance of oxidative signaling and promotion of oxidative damage arising from nitric oxide-derived oxidants in a biological context is a vast endeavor, is an ineludible task in order to generate a rational therapeutic approach to modulate nitroxidative stress. Several redox-based pharmacological strategies with a collection of compounds with varying mechanisms of action have been tested at the cellular, preclinical and even clinical levels, and some novel and promising developments are underway. This review deals with key kinetic and biochemical aspects of nitric oxide-derived oxidant formation and reactions in biological systems, emphasizing the current evidence at the biochemical, cell/tissue and animal/human levels that support a pathophysiological role for peroxynitrite and related species in human pathology. In addition, a selection of available pharmacological tools will be discussed as an effort to rationalize antioxidant and/or redox-based therapeutic interventions in disease models.
Assuntos
Antioxidantes/uso terapêutico , Terapia de Alvo Molecular , Óxido Nítrico/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Ácido Peroxinitroso/metabolismo , Animais , Antioxidantes/farmacologia , Apoptose/efeitos dos fármacos , Humanos , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Necrose/tratamento farmacológico , Necrose/metabolismo , Óxido Nítrico/antagonistas & inibidores , Oxidantes/antagonistas & inibidores , Oxidantes/metabolismo , Ácido Peroxinitroso/antagonistas & inibidoresRESUMO
Virulence of Trypanosoma cruzi depends on a variety of genetic and biochemical factors. It has been proposed that components of the parasites' antioxidant system may play a key part in this process by pre-adapting the pathogen to the oxidative environment encountered during host cell invasion. Using several isolates (10 strains) belonging to the two major phylogenetic lineages (T. cruzi-I and T. cruzi-II), we investigated whether there was an association between virulence (ranging from highly aggressive to attenuated isolates at the parasitemia and histopathological level) and the antioxidant enzyme content. Antibodies raised against trypanothione synthetase (TcTS), ascorbate peroxidase (TcAPX), mitochondrial and cytosolic tryparedoxin peroxidases (TcMPX and TcCPX) and trypanothione reductase (TcTR) were used to evaluate the antioxidant enzyme levels in epimastigote and metacyclic trypomastigote forms in the T. cruzi strains. Levels of TcCPX, TcMPX and TcTS were shown to increase during differentiation from the non-infective epimastigote to the infective metacyclic trypomastigote stage in all parasite strains examined. Peroxiredoxins were found to be present at higher levels in the metacyclic infective forms of the virulent isolates compared with the attenuated strains. Additionally, an increased resistance of epimastigotes from virulent T. cruzi populations to hydrogen peroxide and peroxynitrite challenge was observed. In mouse infection models, a direct correlation was found between protein levels of TcCPX, TcMPX and TcTS, and the parasitemia elicited by the different isolates studied (Pearson's coefficient: 0.617, 0.771, 0.499; respectively, P<0.01). No correlation with parasitemia was found for TcAPX and TcTR proteins in any of the strains analyzed. Our data support that enzymes of the parasite antioxidant armamentarium at the onset of infection represent new virulence factors involved in the establishment of disease.
Assuntos
Antioxidantes/metabolismo , Doença de Chagas/enzimologia , Trypanosoma cruzi/enzimologia , Trypanosoma cruzi/patogenicidade , Fatores de Virulência/metabolismo , Virulência , Animais , Modelos Animais de Doenças , Masculino , CamundongosRESUMO
In this review we address current concepts on the biological occurrence, levels and consequences of protein tyrosine nitration in biological systems. We focused on mechanistic aspects, emphasizing on the free radical mechanisms of protein 3-nitrotyrosine formation and critically analyzed the restrictions for obtaining large tyrosine nitration yields in vivo, mainly due to the presence of strong reducing systems (e.g. glutathione) that can potently inhibit at different levels the nitration process. Evidence is provided to show that the existence of metal-catalyzed processes, the assistance of nitric oxide-dependent nitration steps and the facilitation by hydrophobic environments, provide individually and/or in combination, feasible scenarios for nitration in complex biological milieux. Recent studies using hydrophobic tyrosine analogs and tyrosine-containing peptides have revealed that factors controlling nitration in hydrophobic environments such as biomembranes and lipoproteins can differ to those in aqueous compartments. In particular, exclusion of key soluble reductants from the lipid phase will more easily allow nitration and lipid-derived radicals are suggested as important mediators of the one-electron oxidation of tyrosine to tyrosyl radical in proteins associated to hydrophobic environments. Development and testing of hydrophilic and hydrophobic probes that can compete with endogenous constituents for the nitrating intermediates provide tools to unravel nitration mechanisms in vitro and in vivo; additionally, they could also serve to play cellular and tissue protective functions against the toxic effects of protein tyrosine nitration.
Assuntos
Membrana Celular/metabolismo , Radicais Livres/metabolismo , Peptídeos/metabolismo , Proteínas/metabolismo , Tirosina/análogos & derivados , Tirosina/metabolismo , Dimerização , Interações Hidrofóbicas e Hidrofílicas , Tirosina/químicaRESUMO
Until recently, a capacity for apoptosis and synthesis of nitric oxide *NO) were viewed as exclusive to multicellular organisms. The existence of these processes in unicellular parasites was recently described, with their biological significance remaining to be elucidated. We have evaluated L-arginine metabolism in Trypanosoma cruzi in the context of human serum-induced apoptotic death. Apoptosis was evidenced by the induction of DNA fragmentation and the inhibition of [3H]thymidine incorporation, which were inhibited by the caspase inhibitor Ac-Asp-Glu-Val-aspartic acid aldehyde (DEVD-CHO). In T. cruzi exposed to death stimuli, supplementation with L-arginine inhibited DNA fragmentation, restored [3H]thymidine incorporation, and augmented parasite *NO production. These effects were inhibited by the *NO synthase inhibitor N(omega)-nitroarginine methyl ester (L-NAME). Exogenous *NO limited DNA fragmentation but did not restore proliferation rates. Because L-arginine is also a substrate for arginine decarboxylase (ADC), and its product agmatine is a precursor for polyamine synthesis, we evaluated the contribution of polyamines to limiting apoptosis. Addition of agmatine, putrescine, and the polyamines spermine and spermidine to T. cruzi sustained parasite proliferation and inhibited DNA fragmentation. Also, the ADC inhibitor difluoromethylarginine inhibited L-arginine-dependent restoration of parasite replication rates, while the protection from DNA fragmentation persisted. In aggregate, these results indicate that T. cruzi epimastigotes can undergo programmed cell death that can be inhibited by L-arginine by means of (i) a *NO synthase-dependent *NO production that suppresses apoptosis and (ii) an ADC-dependent production of polyamines that support parasite proliferation.
Assuntos
Apoptose/fisiologia , Arginina/metabolismo , Óxido Nítrico/metabolismo , Poliaminas/metabolismo , Poliaminas/farmacologia , Trypanosoma cruzi/fisiologia , Agmatina/farmacologia , Animais , Apoptose/efeitos dos fármacos , Arginina/farmacologia , Divisão Celular/efeitos dos fármacos , Inibidores de Cisteína Proteinase/farmacologia , Fragmentação do DNA , DNA de Protozoário/biossíntese , Humanos , NG-Nitroarginina Metil Éster/farmacologia , Oligopeptídeos/farmacologia , Putrescina/farmacologia , Espermidina/farmacologia , Espermina/farmacologia , Timidina/metabolismo , Trypanosoma cruzi/citologia , Trypanosoma cruzi/efeitos dos fármacosRESUMO
Peroxynitrite promotes oxidative damage and is implicated in the pathophysiology of various diseases that involve accelerated rates of nitric oxide and superoxide formation. The unambiguous detection of peroxynitrite in biological systems is, however, difficult due to the combination of a short biological half-life, limited diffusion, multiple target molecule reactions, and participation of alternative oxidation/nitration pathways. In this review, we provide the conceptual framework and a comprehensive analysis of the current experimental strategies that can serve to unequivocally define the existence and quantitation of peroxynitrite in biological systems of different levels of organization and complexity.
Assuntos
Nitratos/metabolismo , Tirosina/análogos & derivados , Animais , Dióxido de Carbono/metabolismo , Grupo dos Citocromos c/química , Grupo dos Citocromos c/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Corantes Fluorescentes , Radicais Livres/metabolismo , Humanos , Hidroxilação , Imuno-Histoquímica , Indicadores e Reagentes , Medições Luminescentes , Nitratos/química , Oxidantes/química , Oxidantes/metabolismo , Estresse Oxidativo , Fenóis/química , Fenóis/metabolismo , Tirosina/análise , Tirosina/metabolismoRESUMO
Several novel semicarbazone derivatives were prepared from 5-nitro-2-furaldehyde or 5-nitrothiophene-2-carboxaldehyde and semicarbazides bearing a spermidine-mimetic moiety. All derivatives presented the E-configuration, as determined by NMR-NOE experiments. These compounds were tested in vitro as potential antitrypanosomal agents, and some of them, together with the parent compounds, 5-nitro-2-furaldehyde and 5-nitrothiophene-2-carboxaldehyde semicarbazone derivatives, were also evaluated in vivo using infected mice. Structure-activity relationship studies were carried out using voltammetric response and lipophilic-hydrophilic balance as parameters. Two of the compounds (1 and 3) displayed the highest in vivo activity. A correlation was found between lipophilic-hydrophilic properties and trypanocidal activity, high R(M) values being associated with low in vivo effects.