The Experts below are selected from a list of 24 Experts worldwide ranked by ideXlab platform

A Scarpa - One of the best experts on this subject based on the ideXlab platform.

  • amine transport into chromaffin ghosts kinetic measurements of net uptake of biologically and pharmacologically relevant amines using an on line amperometric technique
    FEBS Journal, 2008
    Co-Authors: Sally E Carty, Robert G Johnson, Tom Vaughan, Adam Pallant, A Scarpa
    Abstract:

    The kinetic parameters for net transport of dopamine, epinephrine, norepinephrine, 5-hydroxytryptamine, S Alpha-Methyldopamine, R Alpha-Methyldopamine, and 1R,2S Alpha-methylnorepinephrine into highly purified bovine chromaffin ghosts were determined using an on-line amperometric technique. Chromaffin ghosts devoid of endogenous amines were formed from lysis of chromaffin granules under hypotonic conditions, extensive washing of the scattered membranes, followed by resuspension in iso-osmotic media and overnight dialysis. When chromaffin ghosts formed so as to generate and maintain a large delta pH were suspended in 185 mM KCl, 10 mM Hepes at pH 7.0, 37 degrees C, the addition of MgATP resulted in rapid acidification of the intravesicular space, which was maintained at pH 6.0 (+/- 0.1) for over 30 min. Kinetic net amine transport was subsequently measured with a glassy carbon electrode. The initial rates of uptake were found to follow Michaelis-Menten kinetics. Computer based statistical analysis of the data using distribution-free procedures yielded Km (and V) values as follows: in microM (nmol X mg protein-1 X min-1) dopamine, 16.2 (14.0); R-norepinephrine, 32.5 (12.9); R-epinephrine, 35.1 (15.2); 5-hydroxytryptamine, 4.7 (5.1); S Alpha-Methyldopamine, 17.7 (11.2); R Alpha-Methyldopamine, 44.2 (9.9); 1R,2S Alpha-methylnorepinephrine, 76.5 (12.5). The physiologic and pharmacologic implications of these kinetic parameters are discussed.

Sally E Carty - One of the best experts on this subject based on the ideXlab platform.

  • amine transport into chromaffin ghosts kinetic measurements of net uptake of biologically and pharmacologically relevant amines using an on line amperometric technique
    FEBS Journal, 2008
    Co-Authors: Sally E Carty, Robert G Johnson, Tom Vaughan, Adam Pallant, A Scarpa
    Abstract:

    The kinetic parameters for net transport of dopamine, epinephrine, norepinephrine, 5-hydroxytryptamine, S Alpha-Methyldopamine, R Alpha-Methyldopamine, and 1R,2S Alpha-methylnorepinephrine into highly purified bovine chromaffin ghosts were determined using an on-line amperometric technique. Chromaffin ghosts devoid of endogenous amines were formed from lysis of chromaffin granules under hypotonic conditions, extensive washing of the scattered membranes, followed by resuspension in iso-osmotic media and overnight dialysis. When chromaffin ghosts formed so as to generate and maintain a large delta pH were suspended in 185 mM KCl, 10 mM Hepes at pH 7.0, 37 degrees C, the addition of MgATP resulted in rapid acidification of the intravesicular space, which was maintained at pH 6.0 (+/- 0.1) for over 30 min. Kinetic net amine transport was subsequently measured with a glassy carbon electrode. The initial rates of uptake were found to follow Michaelis-Menten kinetics. Computer based statistical analysis of the data using distribution-free procedures yielded Km (and V) values as follows: in microM (nmol X mg protein-1 X min-1) dopamine, 16.2 (14.0); R-norepinephrine, 32.5 (12.9); R-epinephrine, 35.1 (15.2); 5-hydroxytryptamine, 4.7 (5.1); S Alpha-Methyldopamine, 17.7 (11.2); R Alpha-Methyldopamine, 44.2 (9.9); 1R,2S Alpha-methylnorepinephrine, 76.5 (12.5). The physiologic and pharmacologic implications of these kinetic parameters are discussed.

Carvalho Félix - One of the best experts on this subject based on the ideXlab platform.

  • Metabolism is required for the expression of ecstasy-induced cardiotoxicity in vitro
    'American Chemical Society (ACS)', 2004
    Co-Authors: Carvalho Márcia, Milhazes Nuno, Borges Fernanda, Remião Fernando, Fernandes Eduarda, Monteiro, Maria Do Céu, Gonçalves, Maria José, Seabra Vítor, Amado Francisco, Carvalho Félix
    Abstract:

    Cardiovascular complications associated with 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) abuse have increasingly been reported. The indirect effect of MDMA mediated by a sustained high level of circulating biogenic amines may contribute to the cardiotoxic effects, but other factors, like the direct toxic effects of MDMA and its metabolites in cardiac cells, remain to be investigated. Thus, the objective of the present in vitro study was to evaluate the potential cardiotoxic effects of MDMA and its major metabolites 3,4-methylenedioxyamphetamine (MDA), N-methyl-Alpha-Methyldopamine (N-Me-Alpha-MeDA), and Alpha-Methyldopamine (Alpha-MeDA) using freshly isolated adult rat cardiomyocytes. The cell suspensions were incubated with these compounds in the final concentrations of 0.1, 0.2, 0.4, 0.8, and 1.6 mM for 4 h. Alpha-MeDA, N-Me-Alpha-MeDA, and their respective aminochromes (oxidation products) were quantified in cell suspensions by HPLC-DAD. The toxic effects were evaluated at hourly intervals for 4 h by measuring the percentage of cells with normal morphology, glutathione (GSH), and glutathione disulfide (GSSG); intracellular Ca(2+), ATP, and ADP; and the cellular activities of glutathione peroxidase, glutathione reductase, and glutathione-S-transferase. No toxic effects were found after exposure of rat cardiomyocytes to MDMA or MDA at any of the tested concentrations for 4 h. In contrast, their catechol metabolites N-Me-Alpha-MeDA and Alpha-MeDA induced significant toxicity in rat cardiomyocytes. The toxic effects were characterized by a loss of normal cell morphology, which was preceded by a loss of GSH homeostasis due to conjugation of GSH with N-Me-Alpha-MeDA and Alpha-MeDA, sustained increase of intracellular Ca(2+) levels, ATP depletion, and decreases in the antioxidant enzyme activities. The oxidation of N-Me-Alpha-MeDA and Alpha-MeDA into the toxic compounds N-methyl-Alpha-methyldopaminochrome and Alpha-methyldopaminochrome, respectively, was also verified in cell suspensions incubated with these MDMA metabolites. The results obtained in this study provide evidence that the metabolism of MDMA into N-Me-Alpha-MeDA and Alpha-MeDA is required for the expression of MDMA-induced cardiotoxicity in vitro, being N-Me-Alpha-MeDA the most toxic of the studied metabolites.info:eu-repo/semantics/publishedVersio

  • Hepatotoxicity of 3,4-methylenedioxyamphetamine and α-Methyldopamine in isolated rat hepatocytes: formation of glutathione conjugates
    'Springer Science and Business Media LLC', 2004
    Co-Authors: Bastos, Maria De Lourdes, Milhazes Nuno, Borges Fernanda, Carvalho Márcia, Remião Fernando, Fernandes Eduarda, Amado Francisco, Monks, Terrence J., Carvalho Félix
    Abstract:

    The amphetamine designer drugs 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy") and its N-demethylated analogue 3,4-methylenedioxyamphetamine (MDA or "love") have been extensively used as recreational drugs of abuse. MDA itself is a main MDMA metabolite. MDMA abuse in humans has been associated with numerous reports of hepatocellular damage. Although MDMA undergoes extensive hepatic metabolism, the role of metabolites in MDMA-induced hepatotoxicity remains unclear. Thus, the aim of the present study was to evaluate the effects of MDA and Alpha-Methyldopamine (Alpha-MeDA), a major metabolite of MDA, in freshly isolated rat hepatocyte suspensions. The cells were incubated with MDA or Alpha-MeDA at final concentrations of 0.1, 0.2, 0.4, 0.8, or 1.6 mM for 3 h. The toxic effects induced following incubation of hepatocyte suspensions with these metabolites were evaluated by measuring cell viability, the extent of lipid peroxidation, levels of glutathione (GSH) and glutathione disulfide (GSSG), the formation of GSH conjugates, and the activities of GSSG reductase (GR), GSH peroxidase (GPX), and GSH S-transferase (GST). MDA induced a concentration- and time-dependent GSH depletion, but had a negligible effect on lipid peroxidation, cell viability, or on the activities of GR, GPX, and GST. In contrast, Alpha-MeDA (1.6 mM, 3 h) induced a marked depletion of GSH accompanied by a loss on cell viability, and decreases in GR, GPX and GST activities, although no significant effect on lipid peroxidation was found. For both metabolites, GSH depletion was not accompanied by increases in GSSG levels; rather, 2-(glutathion- S-yl)-Alpha-MeDA and 5-(glutathion- S-yl)-Alpha-MeDA were identified by HPLC-DAD/EC within cells incubated with MDA or Alpha-MeDA. The results provide evidence that one of the early consequences of MDMA metabolism is a disruption of thiol homeostasis, which may result in loss of protein function and the initiation of a cascade of events leading to cellular damage.info:eu-repo/semantics/publishedVersio

  • The toxicity of N-methyl-α-Methyldopamine to freshly isolated rat hepatocytes is prevented by ascorbic acid and N-acetylcysteine
    'Elsevier BV', 2004
    Co-Authors: Carvalho Márcia, Milhazes Nuno, Borges Fernanda, Remião Fernando, Fernandes Eduarda, Carvalho Félix, Bastos, Maria De Lourdes
    Abstract:

    In the past decade, clinical evidence has increasingly shown that the liver is a target organ for 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") toxicity. The aims of the present in vitro study were: (1) to evaluate and compare the hepatotoxic effects of MDMA and one of its main metabolites, N-methyl-Alpha-Methyldopamine (N-Me-Alpha-MeDA) and (2) to investigate the ability of antioxidants, namely ascorbic acid and N-acetyl-L-cysteine (NAC), to prevent N-Me-Alpha-MeDA-induced toxic injury, using freshly isolated rat hepatocytes. Cell suspensions were incubated with MDMA or N-Me-Alpha-MeDA in the final concentrations of 0.1, 0.2, 0.4, 0.8, and 1.6 mM for 3 h. To evaluate the potential protective effects of antioxidants, cells were preincubated with ascorbic acid in the final concentrations of 0.1 and 0.5 mM, or NAC in the final concentrations of 0.1 and 1 mM for 15 min before treatment with 1.6 mM N-Me-Alpha-MeDA for 3 h (throughout this incubation period the cells were exposed to both compounds). The toxic effects were evaluated by measuring the cell viability, glutathione (GSH) and glutathione disulfide (GSSG), ATP, and the cellular activities of GSH peroxidase (GPX), GSSG reductase (GR), and GSH S-transferase (GST). MDMA induced a concentration- and time-dependent GSH depletion, but had a negligible effect on cell viability, ATP levels, or on the activities of GR, GPX, and GST. In contrast, N-Me-Alpha-MeDA was shown to induce not only a concentration- and time-dependent depletion of GSH, but also a depletion of ATP levels accompanied by a loss in cell viability, and decreases in the antioxidant enzyme activities. For both compounds, GSH depletion was not accompanied by increases in GSSG levels, which seems to indicate GSH depletion by adduct formation. Importantly, the presence of ascorbic acid (0.5 mM) or NAC (1 mM) prevented cell death and GSH depletion induced by N-Me-Alpha-MeDA. The results provide evidence that MDMA and its metabolite N-Me-Alpha-MeDA induce toxicity to freshly isolated rat hepatocytes. Oxidative stress may play a major role in N-Me-Alpha-MeDA-induced hepatic toxicity since antioxidant defense systems are impaired and administration of antioxidants prevented N-Me-Alpha-MeDA toxicity.info:eu-repo/semantics/publishedVersio

  • Role of metabolites in MDMA (ecstasy)-induced nephrotoxicity: an in vitro study using rat and human renal proximal tubular cells
    'Springer Science and Business Media LLC', 2002
    Co-Authors: Carvalho Márcia, Milhazes Nuno, Borges Fernanda, Fernandes Eduarda, Carvalho Félix, Monks, Terrence J., Hawksworth Gabrielle, Bastos, Maria De Lourdes
    Abstract:

    The metabolism of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) has recently been implicated in the mechanisms underlying ecstasy-induced neurotoxicity and hepatotoxicity. However, its potential role in ecstasy-induced kidney toxicity has yet to be investigated. Thus, primary cultures of rat and human renal proximal tubular cells (PTCs) were used to investigate the cytotoxicity induced by MDMA and its metabolites methylenedioxyamphetamine (MDA), Alpha-Methyldopamine (Alpha-MeDA), and the glutathione (GSH) conjugates 5-(glutathion- S-yl)-Alpha-MeDA and 2,5- bis(glutathion- S-yl)-Alpha-MeDA. Cell viability was evaluated using the mitochondrial MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. MDMA and MDA were not found to be toxic to either rat or human PTCs at any concentration tested (100-800 micro M). In contrast, 800 micro M Alpha-MeDA caused 60% and 40% cell death in rat and human PTCs, respectively. Conjugation of Alpha-MeDA with GSH resulted in the formation of even more potent nephrotoxicants. Thus, exposure of rat and human PTC monolayers to 400 micro M 5-(glutathion- S-yl)-Alpha-MeDA caused approximately 80% and 70% cell death, respectively. 5-(Glutathion- S-yl)-Alpha-MeDA (400 micro M) was more toxic than 2,5- bis(glutathion- S-yl)-Alpha-MeDA to rat renal PTCs but equally potent in human renal PTCs. Pre-incubation of rat PTCs with either acivicin, an inhibitor of gamma-glutamyl transpeptidase (gamma-GT), or bestatin, an inhibitor of aminopeptidase M, resulted in increased toxicity of 5-(glutathion- S-yl)-Alpha-MeDA but had no effect on 2,5- bis(glutathion- S-yl)-Alpha-MeDA-mediated cytotoxicity. The present data provide evidence that metabolism is required for the expression of MDMA-induced renal toxicity in vitro. In addition, metabolism of 5-(glutathion- S-yl)-Alpha-MeDA by gamma-GT and aminopeptidase M to the corresponding cystein- S-yl-glycine and/or cystein- S-yl conjugates is likely to be associated with detoxication of this compound. Thus, it appears that toxicity induced by thioether metabolites of ecstasy at the apical membrane of renal proximal tubular cells is the result of extracellular events, presumably redox cycling.info:eu-repo/semantics/publishedVersio

Milhazes Nuno - One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of the lipophilic properties of opioids, amphetamine-like drugs, and metabolites through electrochemical studies at the interface between two immiscible solutions
    2007
    Co-Authors: Gulaboski Rubin, Cordeiro, Natalia M. D. S., Milhazes Nuno, Garrido Jorge, Borges Fernanda, Jorge Miguel, Pereira, Carlos M., Bogeski Ivan, Morales, Aluska Helguera, Naumoski Blaze
    Abstract:

    For the first time, the partition coefficients of the ionized forms of several opioids, amphetamine-like drugs, and their metabolites were determined by studying their ionic transfer process across the bare interface water/organic solvent. The ionic partition coefficients of the monocationic forms of 12 compounds heroin, 6-monoacetylmorphine (6-MAM), morphine, acetylcodeine, codeine, dihydrocodeine, methamphetamine, amphetamine, 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy"), 3,4-methylenedioxyamphetamine (MDA), 3-methoxy-Alpha-Methyldopamine (3-OMe-Alpha-MeDA), and Alpha-Methyldopamine (Alpha-MeDA)-were attained using electrochemical measurements, by cyclic voltammetry, at the interface between two immiscible electrolyte solutions (ITIES). Then the acquired lipophilicity values were correlated to the chemical structure of the compounds and with the metabolic pathways central to each class of drugs. Although the mechanisms of biotoxicity of this type of drugs are still unclear, the data obtained evidence that the lipophilicity of metabolites may be a contributing factor for the qualitative differences found in their activity. In addition, the partition coefficients of the ionic drugs were calculated using three available software packages: ModesLab, Dragon, and HyperChem. As shown by cross-comparison of the experimental and calculated values, HyperChem was the most reliable software for achieving the main goal. The data obtained so far seem to be correlated to the proposed metabolic pathways of the drugs and could be of great value in understanding their pharmacological and/or toxicological profiles at the molecular level. This study may also contribute to gaining an insight into the mechanisms of biotransportation of this type of compounds given that the ionic partition coefficients reflect their ability to cross the membrane barriers. (c) 2006 Elsevier Inc. All rights reserved

  • Metabolism is required for the expression of ecstasy-induced cardiotoxicity in vitro
    'American Chemical Society (ACS)', 2004
    Co-Authors: Carvalho Márcia, Milhazes Nuno, Borges Fernanda, Remião Fernando, Fernandes Eduarda, Monteiro, Maria Do Céu, Gonçalves, Maria José, Seabra Vítor, Amado Francisco, Carvalho Félix
    Abstract:

    Cardiovascular complications associated with 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) abuse have increasingly been reported. The indirect effect of MDMA mediated by a sustained high level of circulating biogenic amines may contribute to the cardiotoxic effects, but other factors, like the direct toxic effects of MDMA and its metabolites in cardiac cells, remain to be investigated. Thus, the objective of the present in vitro study was to evaluate the potential cardiotoxic effects of MDMA and its major metabolites 3,4-methylenedioxyamphetamine (MDA), N-methyl-Alpha-Methyldopamine (N-Me-Alpha-MeDA), and Alpha-Methyldopamine (Alpha-MeDA) using freshly isolated adult rat cardiomyocytes. The cell suspensions were incubated with these compounds in the final concentrations of 0.1, 0.2, 0.4, 0.8, and 1.6 mM for 4 h. Alpha-MeDA, N-Me-Alpha-MeDA, and their respective aminochromes (oxidation products) were quantified in cell suspensions by HPLC-DAD. The toxic effects were evaluated at hourly intervals for 4 h by measuring the percentage of cells with normal morphology, glutathione (GSH), and glutathione disulfide (GSSG); intracellular Ca(2+), ATP, and ADP; and the cellular activities of glutathione peroxidase, glutathione reductase, and glutathione-S-transferase. No toxic effects were found after exposure of rat cardiomyocytes to MDMA or MDA at any of the tested concentrations for 4 h. In contrast, their catechol metabolites N-Me-Alpha-MeDA and Alpha-MeDA induced significant toxicity in rat cardiomyocytes. The toxic effects were characterized by a loss of normal cell morphology, which was preceded by a loss of GSH homeostasis due to conjugation of GSH with N-Me-Alpha-MeDA and Alpha-MeDA, sustained increase of intracellular Ca(2+) levels, ATP depletion, and decreases in the antioxidant enzyme activities. The oxidation of N-Me-Alpha-MeDA and Alpha-MeDA into the toxic compounds N-methyl-Alpha-methyldopaminochrome and Alpha-methyldopaminochrome, respectively, was also verified in cell suspensions incubated with these MDMA metabolites. The results obtained in this study provide evidence that the metabolism of MDMA into N-Me-Alpha-MeDA and Alpha-MeDA is required for the expression of MDMA-induced cardiotoxicity in vitro, being N-Me-Alpha-MeDA the most toxic of the studied metabolites.info:eu-repo/semantics/publishedVersio

  • Hepatotoxicity of 3,4-methylenedioxyamphetamine and α-Methyldopamine in isolated rat hepatocytes: formation of glutathione conjugates
    'Springer Science and Business Media LLC', 2004
    Co-Authors: Bastos, Maria De Lourdes, Milhazes Nuno, Borges Fernanda, Carvalho Márcia, Remião Fernando, Fernandes Eduarda, Amado Francisco, Monks, Terrence J., Carvalho Félix
    Abstract:

    The amphetamine designer drugs 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy") and its N-demethylated analogue 3,4-methylenedioxyamphetamine (MDA or "love") have been extensively used as recreational drugs of abuse. MDA itself is a main MDMA metabolite. MDMA abuse in humans has been associated with numerous reports of hepatocellular damage. Although MDMA undergoes extensive hepatic metabolism, the role of metabolites in MDMA-induced hepatotoxicity remains unclear. Thus, the aim of the present study was to evaluate the effects of MDA and Alpha-Methyldopamine (Alpha-MeDA), a major metabolite of MDA, in freshly isolated rat hepatocyte suspensions. The cells were incubated with MDA or Alpha-MeDA at final concentrations of 0.1, 0.2, 0.4, 0.8, or 1.6 mM for 3 h. The toxic effects induced following incubation of hepatocyte suspensions with these metabolites were evaluated by measuring cell viability, the extent of lipid peroxidation, levels of glutathione (GSH) and glutathione disulfide (GSSG), the formation of GSH conjugates, and the activities of GSSG reductase (GR), GSH peroxidase (GPX), and GSH S-transferase (GST). MDA induced a concentration- and time-dependent GSH depletion, but had a negligible effect on lipid peroxidation, cell viability, or on the activities of GR, GPX, and GST. In contrast, Alpha-MeDA (1.6 mM, 3 h) induced a marked depletion of GSH accompanied by a loss on cell viability, and decreases in GR, GPX and GST activities, although no significant effect on lipid peroxidation was found. For both metabolites, GSH depletion was not accompanied by increases in GSSG levels; rather, 2-(glutathion- S-yl)-Alpha-MeDA and 5-(glutathion- S-yl)-Alpha-MeDA were identified by HPLC-DAD/EC within cells incubated with MDA or Alpha-MeDA. The results provide evidence that one of the early consequences of MDMA metabolism is a disruption of thiol homeostasis, which may result in loss of protein function and the initiation of a cascade of events leading to cellular damage.info:eu-repo/semantics/publishedVersio

  • The toxicity of N-methyl-α-Methyldopamine to freshly isolated rat hepatocytes is prevented by ascorbic acid and N-acetylcysteine
    'Elsevier BV', 2004
    Co-Authors: Carvalho Márcia, Milhazes Nuno, Borges Fernanda, Remião Fernando, Fernandes Eduarda, Carvalho Félix, Bastos, Maria De Lourdes
    Abstract:

    In the past decade, clinical evidence has increasingly shown that the liver is a target organ for 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") toxicity. The aims of the present in vitro study were: (1) to evaluate and compare the hepatotoxic effects of MDMA and one of its main metabolites, N-methyl-Alpha-Methyldopamine (N-Me-Alpha-MeDA) and (2) to investigate the ability of antioxidants, namely ascorbic acid and N-acetyl-L-cysteine (NAC), to prevent N-Me-Alpha-MeDA-induced toxic injury, using freshly isolated rat hepatocytes. Cell suspensions were incubated with MDMA or N-Me-Alpha-MeDA in the final concentrations of 0.1, 0.2, 0.4, 0.8, and 1.6 mM for 3 h. To evaluate the potential protective effects of antioxidants, cells were preincubated with ascorbic acid in the final concentrations of 0.1 and 0.5 mM, or NAC in the final concentrations of 0.1 and 1 mM for 15 min before treatment with 1.6 mM N-Me-Alpha-MeDA for 3 h (throughout this incubation period the cells were exposed to both compounds). The toxic effects were evaluated by measuring the cell viability, glutathione (GSH) and glutathione disulfide (GSSG), ATP, and the cellular activities of GSH peroxidase (GPX), GSSG reductase (GR), and GSH S-transferase (GST). MDMA induced a concentration- and time-dependent GSH depletion, but had a negligible effect on cell viability, ATP levels, or on the activities of GR, GPX, and GST. In contrast, N-Me-Alpha-MeDA was shown to induce not only a concentration- and time-dependent depletion of GSH, but also a depletion of ATP levels accompanied by a loss in cell viability, and decreases in the antioxidant enzyme activities. For both compounds, GSH depletion was not accompanied by increases in GSSG levels, which seems to indicate GSH depletion by adduct formation. Importantly, the presence of ascorbic acid (0.5 mM) or NAC (1 mM) prevented cell death and GSH depletion induced by N-Me-Alpha-MeDA. The results provide evidence that MDMA and its metabolite N-Me-Alpha-MeDA induce toxicity to freshly isolated rat hepatocytes. Oxidative stress may play a major role in N-Me-Alpha-MeDA-induced hepatic toxicity since antioxidant defense systems are impaired and administration of antioxidants prevented N-Me-Alpha-MeDA toxicity.info:eu-repo/semantics/publishedVersio

  • Role of metabolites in MDMA (ecstasy)-induced nephrotoxicity: an in vitro study using rat and human renal proximal tubular cells
    'Springer Science and Business Media LLC', 2002
    Co-Authors: Carvalho Márcia, Milhazes Nuno, Borges Fernanda, Fernandes Eduarda, Carvalho Félix, Monks, Terrence J., Hawksworth Gabrielle, Bastos, Maria De Lourdes
    Abstract:

    The metabolism of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) has recently been implicated in the mechanisms underlying ecstasy-induced neurotoxicity and hepatotoxicity. However, its potential role in ecstasy-induced kidney toxicity has yet to be investigated. Thus, primary cultures of rat and human renal proximal tubular cells (PTCs) were used to investigate the cytotoxicity induced by MDMA and its metabolites methylenedioxyamphetamine (MDA), Alpha-Methyldopamine (Alpha-MeDA), and the glutathione (GSH) conjugates 5-(glutathion- S-yl)-Alpha-MeDA and 2,5- bis(glutathion- S-yl)-Alpha-MeDA. Cell viability was evaluated using the mitochondrial MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. MDMA and MDA were not found to be toxic to either rat or human PTCs at any concentration tested (100-800 micro M). In contrast, 800 micro M Alpha-MeDA caused 60% and 40% cell death in rat and human PTCs, respectively. Conjugation of Alpha-MeDA with GSH resulted in the formation of even more potent nephrotoxicants. Thus, exposure of rat and human PTC monolayers to 400 micro M 5-(glutathion- S-yl)-Alpha-MeDA caused approximately 80% and 70% cell death, respectively. 5-(Glutathion- S-yl)-Alpha-MeDA (400 micro M) was more toxic than 2,5- bis(glutathion- S-yl)-Alpha-MeDA to rat renal PTCs but equally potent in human renal PTCs. Pre-incubation of rat PTCs with either acivicin, an inhibitor of gamma-glutamyl transpeptidase (gamma-GT), or bestatin, an inhibitor of aminopeptidase M, resulted in increased toxicity of 5-(glutathion- S-yl)-Alpha-MeDA but had no effect on 2,5- bis(glutathion- S-yl)-Alpha-MeDA-mediated cytotoxicity. The present data provide evidence that metabolism is required for the expression of MDMA-induced renal toxicity in vitro. In addition, metabolism of 5-(glutathion- S-yl)-Alpha-MeDA by gamma-GT and aminopeptidase M to the corresponding cystein- S-yl-glycine and/or cystein- S-yl conjugates is likely to be associated with detoxication of this compound. Thus, it appears that toxicity induced by thioether metabolites of ecstasy at the apical membrane of renal proximal tubular cells is the result of extracellular events, presumably redox cycling.info:eu-repo/semantics/publishedVersio

Borges Fernanda - One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of the lipophilic properties of opioids, amphetamine-like drugs, and metabolites through electrochemical studies at the interface between two immiscible solutions
    2007
    Co-Authors: Gulaboski Rubin, Cordeiro, Natalia M. D. S., Milhazes Nuno, Garrido Jorge, Borges Fernanda, Jorge Miguel, Pereira, Carlos M., Bogeski Ivan, Morales, Aluska Helguera, Naumoski Blaze
    Abstract:

    For the first time, the partition coefficients of the ionized forms of several opioids, amphetamine-like drugs, and their metabolites were determined by studying their ionic transfer process across the bare interface water/organic solvent. The ionic partition coefficients of the monocationic forms of 12 compounds heroin, 6-monoacetylmorphine (6-MAM), morphine, acetylcodeine, codeine, dihydrocodeine, methamphetamine, amphetamine, 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy"), 3,4-methylenedioxyamphetamine (MDA), 3-methoxy-Alpha-Methyldopamine (3-OMe-Alpha-MeDA), and Alpha-Methyldopamine (Alpha-MeDA)-were attained using electrochemical measurements, by cyclic voltammetry, at the interface between two immiscible electrolyte solutions (ITIES). Then the acquired lipophilicity values were correlated to the chemical structure of the compounds and with the metabolic pathways central to each class of drugs. Although the mechanisms of biotoxicity of this type of drugs are still unclear, the data obtained evidence that the lipophilicity of metabolites may be a contributing factor for the qualitative differences found in their activity. In addition, the partition coefficients of the ionic drugs were calculated using three available software packages: ModesLab, Dragon, and HyperChem. As shown by cross-comparison of the experimental and calculated values, HyperChem was the most reliable software for achieving the main goal. The data obtained so far seem to be correlated to the proposed metabolic pathways of the drugs and could be of great value in understanding their pharmacological and/or toxicological profiles at the molecular level. This study may also contribute to gaining an insight into the mechanisms of biotransportation of this type of compounds given that the ionic partition coefficients reflect their ability to cross the membrane barriers. (c) 2006 Elsevier Inc. All rights reserved

  • Metabolism is required for the expression of ecstasy-induced cardiotoxicity in vitro
    'American Chemical Society (ACS)', 2004
    Co-Authors: Carvalho Márcia, Milhazes Nuno, Borges Fernanda, Remião Fernando, Fernandes Eduarda, Monteiro, Maria Do Céu, Gonçalves, Maria José, Seabra Vítor, Amado Francisco, Carvalho Félix
    Abstract:

    Cardiovascular complications associated with 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) abuse have increasingly been reported. The indirect effect of MDMA mediated by a sustained high level of circulating biogenic amines may contribute to the cardiotoxic effects, but other factors, like the direct toxic effects of MDMA and its metabolites in cardiac cells, remain to be investigated. Thus, the objective of the present in vitro study was to evaluate the potential cardiotoxic effects of MDMA and its major metabolites 3,4-methylenedioxyamphetamine (MDA), N-methyl-Alpha-Methyldopamine (N-Me-Alpha-MeDA), and Alpha-Methyldopamine (Alpha-MeDA) using freshly isolated adult rat cardiomyocytes. The cell suspensions were incubated with these compounds in the final concentrations of 0.1, 0.2, 0.4, 0.8, and 1.6 mM for 4 h. Alpha-MeDA, N-Me-Alpha-MeDA, and their respective aminochromes (oxidation products) were quantified in cell suspensions by HPLC-DAD. The toxic effects were evaluated at hourly intervals for 4 h by measuring the percentage of cells with normal morphology, glutathione (GSH), and glutathione disulfide (GSSG); intracellular Ca(2+), ATP, and ADP; and the cellular activities of glutathione peroxidase, glutathione reductase, and glutathione-S-transferase. No toxic effects were found after exposure of rat cardiomyocytes to MDMA or MDA at any of the tested concentrations for 4 h. In contrast, their catechol metabolites N-Me-Alpha-MeDA and Alpha-MeDA induced significant toxicity in rat cardiomyocytes. The toxic effects were characterized by a loss of normal cell morphology, which was preceded by a loss of GSH homeostasis due to conjugation of GSH with N-Me-Alpha-MeDA and Alpha-MeDA, sustained increase of intracellular Ca(2+) levels, ATP depletion, and decreases in the antioxidant enzyme activities. The oxidation of N-Me-Alpha-MeDA and Alpha-MeDA into the toxic compounds N-methyl-Alpha-methyldopaminochrome and Alpha-methyldopaminochrome, respectively, was also verified in cell suspensions incubated with these MDMA metabolites. The results obtained in this study provide evidence that the metabolism of MDMA into N-Me-Alpha-MeDA and Alpha-MeDA is required for the expression of MDMA-induced cardiotoxicity in vitro, being N-Me-Alpha-MeDA the most toxic of the studied metabolites.info:eu-repo/semantics/publishedVersio

  • Hepatotoxicity of 3,4-methylenedioxyamphetamine and α-Methyldopamine in isolated rat hepatocytes: formation of glutathione conjugates
    'Springer Science and Business Media LLC', 2004
    Co-Authors: Bastos, Maria De Lourdes, Milhazes Nuno, Borges Fernanda, Carvalho Márcia, Remião Fernando, Fernandes Eduarda, Amado Francisco, Monks, Terrence J., Carvalho Félix
    Abstract:

    The amphetamine designer drugs 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy") and its N-demethylated analogue 3,4-methylenedioxyamphetamine (MDA or "love") have been extensively used as recreational drugs of abuse. MDA itself is a main MDMA metabolite. MDMA abuse in humans has been associated with numerous reports of hepatocellular damage. Although MDMA undergoes extensive hepatic metabolism, the role of metabolites in MDMA-induced hepatotoxicity remains unclear. Thus, the aim of the present study was to evaluate the effects of MDA and Alpha-Methyldopamine (Alpha-MeDA), a major metabolite of MDA, in freshly isolated rat hepatocyte suspensions. The cells were incubated with MDA or Alpha-MeDA at final concentrations of 0.1, 0.2, 0.4, 0.8, or 1.6 mM for 3 h. The toxic effects induced following incubation of hepatocyte suspensions with these metabolites were evaluated by measuring cell viability, the extent of lipid peroxidation, levels of glutathione (GSH) and glutathione disulfide (GSSG), the formation of GSH conjugates, and the activities of GSSG reductase (GR), GSH peroxidase (GPX), and GSH S-transferase (GST). MDA induced a concentration- and time-dependent GSH depletion, but had a negligible effect on lipid peroxidation, cell viability, or on the activities of GR, GPX, and GST. In contrast, Alpha-MeDA (1.6 mM, 3 h) induced a marked depletion of GSH accompanied by a loss on cell viability, and decreases in GR, GPX and GST activities, although no significant effect on lipid peroxidation was found. For both metabolites, GSH depletion was not accompanied by increases in GSSG levels; rather, 2-(glutathion- S-yl)-Alpha-MeDA and 5-(glutathion- S-yl)-Alpha-MeDA were identified by HPLC-DAD/EC within cells incubated with MDA or Alpha-MeDA. The results provide evidence that one of the early consequences of MDMA metabolism is a disruption of thiol homeostasis, which may result in loss of protein function and the initiation of a cascade of events leading to cellular damage.info:eu-repo/semantics/publishedVersio

  • The toxicity of N-methyl-α-Methyldopamine to freshly isolated rat hepatocytes is prevented by ascorbic acid and N-acetylcysteine
    'Elsevier BV', 2004
    Co-Authors: Carvalho Márcia, Milhazes Nuno, Borges Fernanda, Remião Fernando, Fernandes Eduarda, Carvalho Félix, Bastos, Maria De Lourdes
    Abstract:

    In the past decade, clinical evidence has increasingly shown that the liver is a target organ for 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") toxicity. The aims of the present in vitro study were: (1) to evaluate and compare the hepatotoxic effects of MDMA and one of its main metabolites, N-methyl-Alpha-Methyldopamine (N-Me-Alpha-MeDA) and (2) to investigate the ability of antioxidants, namely ascorbic acid and N-acetyl-L-cysteine (NAC), to prevent N-Me-Alpha-MeDA-induced toxic injury, using freshly isolated rat hepatocytes. Cell suspensions were incubated with MDMA or N-Me-Alpha-MeDA in the final concentrations of 0.1, 0.2, 0.4, 0.8, and 1.6 mM for 3 h. To evaluate the potential protective effects of antioxidants, cells were preincubated with ascorbic acid in the final concentrations of 0.1 and 0.5 mM, or NAC in the final concentrations of 0.1 and 1 mM for 15 min before treatment with 1.6 mM N-Me-Alpha-MeDA for 3 h (throughout this incubation period the cells were exposed to both compounds). The toxic effects were evaluated by measuring the cell viability, glutathione (GSH) and glutathione disulfide (GSSG), ATP, and the cellular activities of GSH peroxidase (GPX), GSSG reductase (GR), and GSH S-transferase (GST). MDMA induced a concentration- and time-dependent GSH depletion, but had a negligible effect on cell viability, ATP levels, or on the activities of GR, GPX, and GST. In contrast, N-Me-Alpha-MeDA was shown to induce not only a concentration- and time-dependent depletion of GSH, but also a depletion of ATP levels accompanied by a loss in cell viability, and decreases in the antioxidant enzyme activities. For both compounds, GSH depletion was not accompanied by increases in GSSG levels, which seems to indicate GSH depletion by adduct formation. Importantly, the presence of ascorbic acid (0.5 mM) or NAC (1 mM) prevented cell death and GSH depletion induced by N-Me-Alpha-MeDA. The results provide evidence that MDMA and its metabolite N-Me-Alpha-MeDA induce toxicity to freshly isolated rat hepatocytes. Oxidative stress may play a major role in N-Me-Alpha-MeDA-induced hepatic toxicity since antioxidant defense systems are impaired and administration of antioxidants prevented N-Me-Alpha-MeDA toxicity.info:eu-repo/semantics/publishedVersio

  • Role of metabolites in MDMA (ecstasy)-induced nephrotoxicity: an in vitro study using rat and human renal proximal tubular cells
    'Springer Science and Business Media LLC', 2002
    Co-Authors: Carvalho Márcia, Milhazes Nuno, Borges Fernanda, Fernandes Eduarda, Carvalho Félix, Monks, Terrence J., Hawksworth Gabrielle, Bastos, Maria De Lourdes
    Abstract:

    The metabolism of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) has recently been implicated in the mechanisms underlying ecstasy-induced neurotoxicity and hepatotoxicity. However, its potential role in ecstasy-induced kidney toxicity has yet to be investigated. Thus, primary cultures of rat and human renal proximal tubular cells (PTCs) were used to investigate the cytotoxicity induced by MDMA and its metabolites methylenedioxyamphetamine (MDA), Alpha-Methyldopamine (Alpha-MeDA), and the glutathione (GSH) conjugates 5-(glutathion- S-yl)-Alpha-MeDA and 2,5- bis(glutathion- S-yl)-Alpha-MeDA. Cell viability was evaluated using the mitochondrial MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. MDMA and MDA were not found to be toxic to either rat or human PTCs at any concentration tested (100-800 micro M). In contrast, 800 micro M Alpha-MeDA caused 60% and 40% cell death in rat and human PTCs, respectively. Conjugation of Alpha-MeDA with GSH resulted in the formation of even more potent nephrotoxicants. Thus, exposure of rat and human PTC monolayers to 400 micro M 5-(glutathion- S-yl)-Alpha-MeDA caused approximately 80% and 70% cell death, respectively. 5-(Glutathion- S-yl)-Alpha-MeDA (400 micro M) was more toxic than 2,5- bis(glutathion- S-yl)-Alpha-MeDA to rat renal PTCs but equally potent in human renal PTCs. Pre-incubation of rat PTCs with either acivicin, an inhibitor of gamma-glutamyl transpeptidase (gamma-GT), or bestatin, an inhibitor of aminopeptidase M, resulted in increased toxicity of 5-(glutathion- S-yl)-Alpha-MeDA but had no effect on 2,5- bis(glutathion- S-yl)-Alpha-MeDA-mediated cytotoxicity. The present data provide evidence that metabolism is required for the expression of MDMA-induced renal toxicity in vitro. In addition, metabolism of 5-(glutathion- S-yl)-Alpha-MeDA by gamma-GT and aminopeptidase M to the corresponding cystein- S-yl-glycine and/or cystein- S-yl conjugates is likely to be associated with detoxication of this compound. Thus, it appears that toxicity induced by thioether metabolites of ecstasy at the apical membrane of renal proximal tubular cells is the result of extracellular events, presumably redox cycling.info:eu-repo/semantics/publishedVersio