Paula Aracena | Universidad San Sebastián (original) (raw)
Papers by Paula Aracena
Http Dx Doi Org 10 1089 Ars 2005 7 870, Jul 5, 2005
binding to triads and abolished apoCaM binding. As both FKBP12 and CaCaM inhibit RyR1, decreased ... more binding to triads and abolished apoCaM binding. As both FKBP12 and CaCaM inhibit RyR1, decreased FKBP12 binding to RyR1 and/or decreased CaCaM binding to either RyR1 or dihydropyridine receptor in triad preparations may cause the reported enhanced activation of Ca 2+ -induced Ca 2+ release kinetics mediated by S-glutathionylation/S-nitrosylation. We discuss possible consequences of these redox modifications on RyR1-mediated Ca 2+ release in physiological or pathological conditions.
![Research paper thumbnail of [Methodological flaws on abortion estimates for Latin America: authors' reply to Singh and Bankole]](https://attachments.academia-assets.com/45317730/thumbnails/1.jpg)
](Ginecologia Y Obstetricia De Mexico, Nov 1, 2012
Esta carta debe citarse como: Koch E, Aracena P, Bravo M, Gatica S, Stecher JF, Valenzuela S, Ahl... more Esta carta debe citarse como: Koch E, Aracena P, Bravo M, Gatica S, Stecher JF, Valenzuela S, Ahlers I. Deficiencias en la estimación de abortos para Latinoamérica: Respuesta de los autores a Singh y Bankole. Ginecol Obstet Mex 2012;80(11):740-747.
Buddleja globosa Hope (matico) is a Chilean plant used by native medicine mainly in the treatment... more Buddleja globosa Hope (matico) is a Chilean plant used by native medicine mainly in the treatment of wound healing and as an anti‐inflammatory agent. We have developed a standardized hydroalcoholic extract from matico leaves, in terms of total polyphenolic content. This extract may be useful in accelerating the wound healing process. To this end, we studied the in vivo effects of this extract in a rat model, in terms of general homeostasis. Data showed that oral treatment of adult male Sprague‐Dawley rats with this extract, for up to 12 days, did not alter their hemogram and clinical chemistry parameters. In addition, we showed that topical treatment with the same extract was able to accelerate wound healing in these animals, most likely through shortening the inflammatory stage of the healing process. Altogether, our data demonstrate that local effects of this particular standardized matico extract are likely to retain their wound healing properties while not altering the general h...
BMJ open, 2015
To test whether there is an association between abortion legislation and maternal mortality outco... more To test whether there is an association between abortion legislation and maternal mortality outcomes after controlling for other factors thought to influence maternal health. Population-based natural experiment. Official maternal mortality data from 32 federal states of Mexico between 2002 and 2011. Maternal mortality ratio (MMR), MMR with any abortive outcome (MMRAO) and induced abortion mortality ratio (iAMR). Abortion legislation grouped as less (n=18) or more permissive (n=14); constitutional amendment protecting the unborn (n=17); skilled attendance at birth; all-abortion hospitalisation ratio; low birth weight rate; contraceptive use; total fertility rates (TFR); clean water; sanitation; female literacy rate and intimate-partner violence. Over the 10-year period, states with less permissive abortion legislation exhibited lower MMR (38.3 vs 49.6; p<0.001), MMRAO (2.7 vs 3.7; p<0.001) and iAMR (0.9 vs 1.7; p<0.001) than more permissive states. Multivariate regression mo...
![Research paper thumbnail of [Overestimation of the ocurrence of induced abortions in Colombia and other Latinoamerican countries]](https://attachments.academia-assets.com/45317701/thumbnails/1.jpg)
](Ginecología y obstetricia de México, 2012
Recently, the Guttmacher Institute estimated a number of 400,400 clandestine abortions for Colomb... more Recently, the Guttmacher Institute estimated a number of 400,400 clandestine abortions for Colombia. Because of the strong implications that such brief could have in different areas of interest, a full revision of the methodology of estimation was performed. The methodology used by the Guttmacher Institute was as follows: first, the authors estimated the losses from spontaneous and induced abortions from the opinion of 289 subjects who work in an equal number of Colombian health institutions through the opinion survey entitled "Health Facilities Survey". Subsequently, an expansive multiplier (x3, x4, x5, etc.) was applied to the numbers obtained by this survey that also emerges from a subjective opinion of another 102 respondents of the "Health Professional Survey" selected by convenience. There is no objective data based on real vital events, the whole estimate is based on imagining/numbers underlying mere opinions. Even as public opinion survey, the sampling te...
![Research paper thumbnail of [Methodological flaws on abortion estimates for Latin America: authors' reply to Singh and Bankole]](https://attachments.academia-assets.com/45317702/thumbnails/1.jpg)
](Ginecología y obstetricia de México, 2012
Esta carta debe citarse como: Koch E, Aracena P, Bravo M, Gatica S, Stecher JF, Valenzuela S, Ahl... more Esta carta debe citarse como: Koch E, Aracena P, Bravo M, Gatica S, Stecher JF, Valenzuela S, Ahlers I. Deficiencias en la estimación de abortos para Latinoamérica: Respuesta de los autores a Singh y Bankole. Ginecol Obstet Mex 2012;80(11):740-747.
Biological Trace Element Research, 2009
Glutathione S-transferases (GSTs) are isoenzymes occurring in the cytoplasm and as integral membr... more Glutathione S-transferases (GSTs) are isoenzymes occurring in the cytoplasm and as integral membrane proteins. In addition to their role in drug metabolism by conjugating electrophilic and lipophilic compounds with glutathione (GSH), these enzymes display multiple functions in cells, including antioxidant action. It has been generalized that reactive oxygen species (ROS) inhibit cytosolic GSTs and activate microsomal GSTs; some evidence shows, however, that different ROS-generating systems can inhibit microsomal GST activity. We therefore tested the effect of Fe 3+ /ascorbate, another ROS-generating system, on cytosolic and microsomal GST activities from rat liver cytosol and microsomes, respectively, and compared it to that of hydrogen peroxide (H 2 O 2 ). We found that, while both agents displayed similar inhibitory effects on cytosolic GST activity, they promoted opposite effects on microsomal GST activity. Using specific antioxidant enzymes, we corroborated that the effect of Fe 3+ /ascorbate involves generation of O 2 À without dismutation into H 2 O 2 . Since these ROS have physicochemical properties and redox potentials that are very distinct, their reactivity is different, and their oxidative action is likely to have different targets. We discuss how these properties are related with the oxidative potency of ROS, especially those of O 2 À and H 2 O 2 .
Developments in Cardiovascular Medicine, 2005
Ginecol Obstet …, 2012
Hace poco, el Instituto Guttmacher estimó que en Colombia se realizan 400,400 abortos clandestino... more Hace poco, el Instituto Guttmacher estimó que en Colombia se realizan 400,400 abortos clandestinos. Por las implicaciones que este informe pudiera tener en distintas áreas de interés, se revisó en detalle el método de estimación. La metodología utilizada por el Instituto Guttmacher fue la siguiente: primero los autores estimaron las pérdidas espontáneas y los abortos a partir de la opinión de 289 sujetos en un número igual de instituciones de salud colombianas mediante la encuesta de opinión denominada "Encuestas IPS". Posteriormente, a los números obtenidos con la encuesta se les aplicó un factor multiplicador expansivo (x3, x4, x5, etc.) que también emergió de la opinión subjetiva de otros 102 entrevistados seleccionados por conveniencia. No hay datos objetivos basados en hechos vitales reales; toda la estimación se basa en números imaginarios subyacentes de opiniones. Aún como encuesta de opinión, la técnica de muestreo tuvo graves sesgos de selección en el levantamiento de la información. Con la utilización de métodos epidemiológicos de estimación válidos, objetivos y reproducibles, escogiendo los casos paradigmáticos de Chile y España como tasas estándar aplicadas a estadísticas vitales colombianas, se observó que la metodología del Instituto Guttmacher sobrestima en más de nueve veces las complicaciones hospitalarias por aborto inducido y en más de 18 veces el número total de abortos. En otros países de Latinoamérica, como Argentina, Brasil, Chile, México, Perú, Guatemala y República Dominicana, la metodología del Instituto Guttmacher también sobrestimó largamente la cifra de abortos. Estos resultados llaman a la cautela con este tipo de informes que alarman a la opinión pública.
Toxicology in Vitro, 2002
Metallothionein (MT) and reduced glutathione (GSH) play an important role in the intracellular ha... more Metallothionein (MT) and reduced glutathione (GSH) play an important role in the intracellular handling of copper by preventing the generation and favouring the removal of copper-derived free radicals. The present study addressed the changes in MT and GSH that follow chronic (2 or 5 weeks) exposure of human hepatoblastoma cells (HepG2) to excess copper. Copper treatment (100 μm, 2 weeks)
Toxicology in Vitro, 2011
Adverse reactions of acetaminophen have been associated to oxidative stress, which may be elicite... more Adverse reactions of acetaminophen have been associated to oxidative stress, which may be elicited by reactive oxygen species (ROS) and/or production of the metabolite NAPQI. Both phenomena would arise through the activity of liver cytochrome P450 (CYP450) system, but their contribution to this oxidative stress is yet to be clarified. A NADPH oxidase activity has been proposed in rat liver microsomes. This activity may be due to the presence of NAD(P)H oxidase (NOX) isoforms in liver endoplasmic reticulum. Both NOX and the CYP450 system activities can catalyze ROS generation using NADPH as a cofactor. Therefore, acetaminophen biotransformation, which requires NADPH, may promote ROS generation through either activity or both. To discriminate between these possibilities, rat liver microsomes were incubated with acetaminophen and NADPH in the presence or absence of specific inhibitors. Incubation with NADPH and acetaminophen elicited lipid peroxidation and decreased thiol content and glutathione-S-transferase (GST) activity. The NOX inhibitors apocynin and plumbagin prevented all these phenomena but the decrease in thiol content. In contrast, this decrease was completely prevented by the specific CYP450 system inhibitor SKF-525A. These data suggest that ROS generation following incubation of microsomes with acetaminophen and NADPH appears to be mainly caused by a NOX activity. In light of these data, toxicity of acetaminophen is discussed.
Science Signaling, 2005
This information is current as of 13 September 2011.
Journal of Biological Chemistry, 2003
We have analyzed the effects of the endogenous redoxactive agents S-nitrosoglutathione and glutat... more We have analyzed the effects of the endogenous redoxactive agents S-nitrosoglutathione and glutathione disulfide, and the NO donor NOR-3, on calcium release kinetics mediated by ryanodine receptor channels. Incubation of triad-enriched sarcoplasmic reticulum vesicles isolated from mammalian skeletal muscle with these three agents elicits different responses. Glutathione disulfide significantly reduces the inhibitory effect of Mg 2؉ without altering Ca 2؉ activation of release kinetics, whereas NOR-3 enhances Ca 2؉ activation of release kinetics without altering Mg 2؉ inhibition. Incubation with S-nitrosoglutathione produces both effects; it significantly enhances Ca 2؉ activation of release kinetics and diminishes the inhibitory effect of Mg 2؉ on this process. Triad incubation with [ 35 S]nitrosoglutathione at pCa 5 promoted 35 S incorporation into 2.5 cysteine residues per channel monomer; this incorporation decreased significantly at pCa 9. These findings indicate that S-nitrosoglutathione supports S-glutathionylation as well as the reported S-nitrosylation of ryanodine receptor channels (Sun, J., Xu, L., Eu, J. P., Stamler, J. S., and Meissner, G. . The combined results suggest that S-glutathionylation of specific cysteine residues can modulate channel inhibition by Mg 2؉ , whereas S-nitrosylation of different cysteines can modulate the activation of the channel by Ca 2؉ . Possible physiological and pathological implications of the activation of skeletal Ca 2؉ release channels by endogenous redox species are discussed.
Journal of Biological Chemistry, 2006
The skeletal muscle Ca 2؉ -release channel (ryanodine receptor type 1 (RyR1)) is a redox sensor, ... more The skeletal muscle Ca 2؉ -release channel (ryanodine receptor type 1 (RyR1)) is a redox sensor, susceptible to reversible S-nitrosylation, S-glutathionylation, and disulfide oxidation. So far, Cys-3635 remains the only cysteine residue identified as functionally relevant to the redox sensing properties of the channel. We demonstrate that expression of the C3635A-RyR1 mutant in RyR1-null myotubes alters the sensitivity of the ryanodine receptor to activation by voltage, indicating that Cys-3635 is involved in voltage-gated excitation-contraction coupling. However, H 2 O 2 treatment of C3635A-RyR1 channels or wildtype RyR1, following their expression in human embryonic kidney cells, enhances [ 3 H]ryanodine binding to the same extent, suggesting that cysteines other than Cys-3635 are responsible for the oxidative enhancement of channel activity. Using a combination of Western blotting and sulfhydryl-directed fluorescent labeling, we found that two large regions of RyR1 (amino acids 1-2401 and 3120 -4475), previously shown to be involved in disulfide bond formation, are also major sites of both S-nitrosylation and S-glutathionylation. Using selective isotopecoded affinity tag labeling of RyR1 and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy, we identified, out of the 100 cysteines in each RyR1 subunit, 9 that are endogenously modified (Cys-36, Cys-315, Cys-811, Cys-906, Cys-1591, Cys-2326, Cys-2363, Cys-3193, and Cys-3635) and another 3 residues that were only modified with exogenous redox agents (Cys-253, Cys-1040, and Cys-1303). We also identified the types of redox modification each of these cysteines can undergo. In summary, we have identified a discrete subset of cysteines that are likely to be involved in the functional response of RyR1 to different redox modifications (S-nitrosylation, S-glutathionylation, and oxidation to disulfides).
Journal of Applied Toxicology, 2009
Copper toxicity has been associated to the capacity of free copper ions to catalyze the productio... more Copper toxicity has been associated to the capacity of free copper ions to catalyze the production of superoxide anion and hydroxyl radical, reactive species that modify the structure and/or function of biomolecules. In addition, nonspecifi c Cu 2+ -binding to thiol enzymes, which modifi es their catalytic activities, has been reported. Cytochrome P450 (CYP450) monooxygenase is a thiol protein that binds substrates in the fi rst and limiting step of CYP450 system catalytic cycle, necessary for the metabolism of lipophilic xenobiotics. Therefore, copper ions have the potential to oxidize and bind to cysteinyl residues of this monooxygenase, altering the CYP450 system activity. To test this postulate, we studied the eff ect of Cu 2+ alone and Cu 2+ /ascorbate in rat liver microsomes, to independently evaluate its nonspecifi c binding and its pro-oxidant eff ects, respectively. We assessed these eff ects on the absorbance spectrum of the monooxygenase, as a measure of structural damage, and p-nitroanisole O-demethylating activity of CYP450 system, as a marker of functional impairment. Data obtained indicate that Cu 2+ could both oxidize and bind to some amino acid residues of the CYP450 monooxygenase but not to its heme group. The diff erences observed between the eff ects of Cu 2+ and Cu 2+ /ascorbate show that both mechanisms are involved in the catalytic activity inhibition of CYP450 system by copper ions. The signifi cance of these fi ndings on the pharmacokinetics and pharmacodynamics of drugs is discussed.
International Journal of Women's Health, 2012
In countries where induced abortion is legally restricted, as in most of Latin America, evaluatio... more In countries where induced abortion is legally restricted, as in most of Latin America, evaluation of statistics related to induced abortions and abortion-related mortality is challenging. The present article reexamines recent reports estimating the number of induced abortions and abortion-related mortality in Mexico, with special reference to the International Classification of Diseases (ICD). We found significant overestimations of abortion figures in the Federal District of Mexico (up to 10-fold), where elective abortion has been legal since 2007. Significant overestimation of maternal and abortion-related mortality during the last 20 years in the entire Mexican country (up to 35%) was also found. Such overestimations are most likely due to the use of incomplete in-hospital records as well as subjective opinion surveys regarding induced abortion figures, and due to the consideration of causes of death that are unrelated to induced abortion, including flawed denominators of live births. Contrary to previous publications, we found important progress in maternal health, reflected by the decrease in overall maternal mortality (30.6%) from 1990 to 2010. The use of specific ICD codes revealed that the mortality ratio associated with induced abortion decreased 22.9% between 2002 and 2008 (from 1.48 to 1.14 deaths per 100,000 live births). Currently, approximately 98% of maternal deaths in Mexico are related to causes other than induced abortion, such as hemorrhage, hypertension and eclampsia, indirect causes, and other pathological conditions. Therefore, only marginal or null effects would be expected from changes in the legal status of abortion on overall maternal mortality rates. Rather, maternal health in Mexico would greatly benefit from increasing access to emergency and specialized obstetric care. Finally, more reliable methodologies to assess abortion-related deaths are clearly required.
Chemico-Biological Interactions, 2010
Melatonin, an endogenous hormone, is used as an antioxidant drug in doses quite higher than the e... more Melatonin, an endogenous hormone, is used as an antioxidant drug in doses quite higher than the endogenous circulating levels of this hormone. Hepatic endoplasmic reticulum contains the cytochrome P450 (CYP450) system, which catalyzes one biotransformation pathway of melatonin; this organelle is also one of the main sources of reactive oxygen species in cells. Therefore, we proposed that the antioxidant activity of this hormone may have a biological relevance in the organelle where it is biotransformed. To evaluate this postulate, we used Fe 3+ /ascorbate, an oxygen free radical generating system that leads to lipid peroxidation, loss of protein-thiol content, and activation of UDP-glucuronyltransferase in rat liver microsomes. We found that mM concentrations of melatonin prevented all these oxidative phenomena. We also found that Fe 3+ /ascorbate leads to structural alterations in the CYP450 monooxygenase, the enzyme that binds the substrate in the CYP450 system catalytic cycle, probably through direct oxidation of the protein, and also inhibited p-nitroanisole O-demethylation, a reaction catalyzed by the CYP450 system. Notably, melatonin prevented both phenomena at M concentrations. We provide evidence suggesting that melatonin may be oxidized by oxygen free radicals. Thus, we postulate that melatonin may be acting as an oxygen free radical scavenger, and Fe 3+ /ascorbate-modified melatonin would be directly protecting the CYP450 system through an additional specific mechanism. Pharmacological relevance of this phenomenon is discussed.
Chemico-Biological Interactions, 2010
Iron and copper ions, in their unbound form, may lead to the generation of reactive oxygen specie... more Iron and copper ions, in their unbound form, may lead to the generation of reactive oxygen species via Haber-Weiss and/or Fenton reactions. In addition, it has been shown that copper ions can irreversibly and non-specifically bind to thiol groups in proteins. This non-specific binding property has not been fully addressed for iron ions. Thus, the present study compares both the pro-oxidant and the non-specific binding properties of Fe 3+ and Cu 2+ , using rat liver cytosol and microsomes as biological systems. Our data show that, in the absence of proteins, Cu 2+ /ascorbate elicited more oxygen consumption than Fe 3+ /ascorbate under identical conditions. Presence of cytosolic and microsomal protein, however, differentially altered oxygen consumption patterns. In addition, Cu 2+ /ascorbate increased microsomal lipid peroxidation and decreased cytosolic and microsomal content of thiol groups more efficiently than Fe 3+ /ascorbate. Finally, Fe 3+ /ascorbate and Cu 2+ /ascorbate inhibited in different ways cytosolic and microsomal glutathione S-transferase (GST) activities, which are differentially sensitive to oxidants. Moreover, in the absence of ascorbate, only Cu 2+ decreased the content of cytosolic and microsomal thiol groups and inhibited cytosolic and microsomal GST activities. Catechin partially prevented the damage to thiol groups elicited by Fe 3+ /ascorbate and Cu 2+ /ascorbate but not by Cu 2+ alone. N-Acetylcysteine completely prevented the damage elicited by Cu 2+ /ascorbate, Fe 3+ /ascorbate and Cu 2+ alone. N-Acetylcysteine also completely reversed the damage to thiol groups elicited by Fe 3+ /ascorbate, partially reversed that of Cu 2+ /ascorbate but failed to reverse the damage promoted by Cu 2+ alone. Our data are discussed in terms to the potential damage that the accumulation of iron and copper ions can promote in biological systems.
Http Dx Doi Org 10 1089 Ars 2005 7 870, Jul 5, 2005
binding to triads and abolished apoCaM binding. As both FKBP12 and CaCaM inhibit RyR1, decreased ... more binding to triads and abolished apoCaM binding. As both FKBP12 and CaCaM inhibit RyR1, decreased FKBP12 binding to RyR1 and/or decreased CaCaM binding to either RyR1 or dihydropyridine receptor in triad preparations may cause the reported enhanced activation of Ca 2+ -induced Ca 2+ release kinetics mediated by S-glutathionylation/S-nitrosylation. We discuss possible consequences of these redox modifications on RyR1-mediated Ca 2+ release in physiological or pathological conditions.
Ginecologia Y Obstetricia De Mexico, Nov 1, 2012
Esta carta debe citarse como: Koch E, Aracena P, Bravo M, Gatica S, Stecher JF, Valenzuela S, Ahl... more Esta carta debe citarse como: Koch E, Aracena P, Bravo M, Gatica S, Stecher JF, Valenzuela S, Ahlers I. Deficiencias en la estimación de abortos para Latinoamérica: Respuesta de los autores a Singh y Bankole. Ginecol Obstet Mex 2012;80(11):740-747.
Buddleja globosa Hope (matico) is a Chilean plant used by native medicine mainly in the treatment... more Buddleja globosa Hope (matico) is a Chilean plant used by native medicine mainly in the treatment of wound healing and as an anti‐inflammatory agent. We have developed a standardized hydroalcoholic extract from matico leaves, in terms of total polyphenolic content. This extract may be useful in accelerating the wound healing process. To this end, we studied the in vivo effects of this extract in a rat model, in terms of general homeostasis. Data showed that oral treatment of adult male Sprague‐Dawley rats with this extract, for up to 12 days, did not alter their hemogram and clinical chemistry parameters. In addition, we showed that topical treatment with the same extract was able to accelerate wound healing in these animals, most likely through shortening the inflammatory stage of the healing process. Altogether, our data demonstrate that local effects of this particular standardized matico extract are likely to retain their wound healing properties while not altering the general h...
BMJ open, 2015
To test whether there is an association between abortion legislation and maternal mortality outco... more To test whether there is an association between abortion legislation and maternal mortality outcomes after controlling for other factors thought to influence maternal health. Population-based natural experiment. Official maternal mortality data from 32 federal states of Mexico between 2002 and 2011. Maternal mortality ratio (MMR), MMR with any abortive outcome (MMRAO) and induced abortion mortality ratio (iAMR). Abortion legislation grouped as less (n=18) or more permissive (n=14); constitutional amendment protecting the unborn (n=17); skilled attendance at birth; all-abortion hospitalisation ratio; low birth weight rate; contraceptive use; total fertility rates (TFR); clean water; sanitation; female literacy rate and intimate-partner violence. Over the 10-year period, states with less permissive abortion legislation exhibited lower MMR (38.3 vs 49.6; p<0.001), MMRAO (2.7 vs 3.7; p<0.001) and iAMR (0.9 vs 1.7; p<0.001) than more permissive states. Multivariate regression mo...
Ginecología y obstetricia de México, 2012
Recently, the Guttmacher Institute estimated a number of 400,400 clandestine abortions for Colomb... more Recently, the Guttmacher Institute estimated a number of 400,400 clandestine abortions for Colombia. Because of the strong implications that such brief could have in different areas of interest, a full revision of the methodology of estimation was performed. The methodology used by the Guttmacher Institute was as follows: first, the authors estimated the losses from spontaneous and induced abortions from the opinion of 289 subjects who work in an equal number of Colombian health institutions through the opinion survey entitled "Health Facilities Survey". Subsequently, an expansive multiplier (x3, x4, x5, etc.) was applied to the numbers obtained by this survey that also emerges from a subjective opinion of another 102 respondents of the "Health Professional Survey" selected by convenience. There is no objective data based on real vital events, the whole estimate is based on imagining/numbers underlying mere opinions. Even as public opinion survey, the sampling te...
Ginecología y obstetricia de México, 2012
Esta carta debe citarse como: Koch E, Aracena P, Bravo M, Gatica S, Stecher JF, Valenzuela S, Ahl... more Esta carta debe citarse como: Koch E, Aracena P, Bravo M, Gatica S, Stecher JF, Valenzuela S, Ahlers I. Deficiencias en la estimación de abortos para Latinoamérica: Respuesta de los autores a Singh y Bankole. Ginecol Obstet Mex 2012;80(11):740-747.
Biological Trace Element Research, 2009
Glutathione S-transferases (GSTs) are isoenzymes occurring in the cytoplasm and as integral membr... more Glutathione S-transferases (GSTs) are isoenzymes occurring in the cytoplasm and as integral membrane proteins. In addition to their role in drug metabolism by conjugating electrophilic and lipophilic compounds with glutathione (GSH), these enzymes display multiple functions in cells, including antioxidant action. It has been generalized that reactive oxygen species (ROS) inhibit cytosolic GSTs and activate microsomal GSTs; some evidence shows, however, that different ROS-generating systems can inhibit microsomal GST activity. We therefore tested the effect of Fe 3+ /ascorbate, another ROS-generating system, on cytosolic and microsomal GST activities from rat liver cytosol and microsomes, respectively, and compared it to that of hydrogen peroxide (H 2 O 2 ). We found that, while both agents displayed similar inhibitory effects on cytosolic GST activity, they promoted opposite effects on microsomal GST activity. Using specific antioxidant enzymes, we corroborated that the effect of Fe 3+ /ascorbate involves generation of O 2 À without dismutation into H 2 O 2 . Since these ROS have physicochemical properties and redox potentials that are very distinct, their reactivity is different, and their oxidative action is likely to have different targets. We discuss how these properties are related with the oxidative potency of ROS, especially those of O 2 À and H 2 O 2 .
Developments in Cardiovascular Medicine, 2005
Ginecol Obstet …, 2012
Hace poco, el Instituto Guttmacher estimó que en Colombia se realizan 400,400 abortos clandestino... more Hace poco, el Instituto Guttmacher estimó que en Colombia se realizan 400,400 abortos clandestinos. Por las implicaciones que este informe pudiera tener en distintas áreas de interés, se revisó en detalle el método de estimación. La metodología utilizada por el Instituto Guttmacher fue la siguiente: primero los autores estimaron las pérdidas espontáneas y los abortos a partir de la opinión de 289 sujetos en un número igual de instituciones de salud colombianas mediante la encuesta de opinión denominada "Encuestas IPS". Posteriormente, a los números obtenidos con la encuesta se les aplicó un factor multiplicador expansivo (x3, x4, x5, etc.) que también emergió de la opinión subjetiva de otros 102 entrevistados seleccionados por conveniencia. No hay datos objetivos basados en hechos vitales reales; toda la estimación se basa en números imaginarios subyacentes de opiniones. Aún como encuesta de opinión, la técnica de muestreo tuvo graves sesgos de selección en el levantamiento de la información. Con la utilización de métodos epidemiológicos de estimación válidos, objetivos y reproducibles, escogiendo los casos paradigmáticos de Chile y España como tasas estándar aplicadas a estadísticas vitales colombianas, se observó que la metodología del Instituto Guttmacher sobrestima en más de nueve veces las complicaciones hospitalarias por aborto inducido y en más de 18 veces el número total de abortos. En otros países de Latinoamérica, como Argentina, Brasil, Chile, México, Perú, Guatemala y República Dominicana, la metodología del Instituto Guttmacher también sobrestimó largamente la cifra de abortos. Estos resultados llaman a la cautela con este tipo de informes que alarman a la opinión pública.
Toxicology in Vitro, 2002
Metallothionein (MT) and reduced glutathione (GSH) play an important role in the intracellular ha... more Metallothionein (MT) and reduced glutathione (GSH) play an important role in the intracellular handling of copper by preventing the generation and favouring the removal of copper-derived free radicals. The present study addressed the changes in MT and GSH that follow chronic (2 or 5 weeks) exposure of human hepatoblastoma cells (HepG2) to excess copper. Copper treatment (100 μm, 2 weeks)
Toxicology in Vitro, 2011
Adverse reactions of acetaminophen have been associated to oxidative stress, which may be elicite... more Adverse reactions of acetaminophen have been associated to oxidative stress, which may be elicited by reactive oxygen species (ROS) and/or production of the metabolite NAPQI. Both phenomena would arise through the activity of liver cytochrome P450 (CYP450) system, but their contribution to this oxidative stress is yet to be clarified. A NADPH oxidase activity has been proposed in rat liver microsomes. This activity may be due to the presence of NAD(P)H oxidase (NOX) isoforms in liver endoplasmic reticulum. Both NOX and the CYP450 system activities can catalyze ROS generation using NADPH as a cofactor. Therefore, acetaminophen biotransformation, which requires NADPH, may promote ROS generation through either activity or both. To discriminate between these possibilities, rat liver microsomes were incubated with acetaminophen and NADPH in the presence or absence of specific inhibitors. Incubation with NADPH and acetaminophen elicited lipid peroxidation and decreased thiol content and glutathione-S-transferase (GST) activity. The NOX inhibitors apocynin and plumbagin prevented all these phenomena but the decrease in thiol content. In contrast, this decrease was completely prevented by the specific CYP450 system inhibitor SKF-525A. These data suggest that ROS generation following incubation of microsomes with acetaminophen and NADPH appears to be mainly caused by a NOX activity. In light of these data, toxicity of acetaminophen is discussed.
Science Signaling, 2005
This information is current as of 13 September 2011.
Journal of Biological Chemistry, 2003
We have analyzed the effects of the endogenous redoxactive agents S-nitrosoglutathione and glutat... more We have analyzed the effects of the endogenous redoxactive agents S-nitrosoglutathione and glutathione disulfide, and the NO donor NOR-3, on calcium release kinetics mediated by ryanodine receptor channels. Incubation of triad-enriched sarcoplasmic reticulum vesicles isolated from mammalian skeletal muscle with these three agents elicits different responses. Glutathione disulfide significantly reduces the inhibitory effect of Mg 2؉ without altering Ca 2؉ activation of release kinetics, whereas NOR-3 enhances Ca 2؉ activation of release kinetics without altering Mg 2؉ inhibition. Incubation with S-nitrosoglutathione produces both effects; it significantly enhances Ca 2؉ activation of release kinetics and diminishes the inhibitory effect of Mg 2؉ on this process. Triad incubation with [ 35 S]nitrosoglutathione at pCa 5 promoted 35 S incorporation into 2.5 cysteine residues per channel monomer; this incorporation decreased significantly at pCa 9. These findings indicate that S-nitrosoglutathione supports S-glutathionylation as well as the reported S-nitrosylation of ryanodine receptor channels (Sun, J., Xu, L., Eu, J. P., Stamler, J. S., and Meissner, G. . The combined results suggest that S-glutathionylation of specific cysteine residues can modulate channel inhibition by Mg 2؉ , whereas S-nitrosylation of different cysteines can modulate the activation of the channel by Ca 2؉ . Possible physiological and pathological implications of the activation of skeletal Ca 2؉ release channels by endogenous redox species are discussed.
Journal of Biological Chemistry, 2006
The skeletal muscle Ca 2؉ -release channel (ryanodine receptor type 1 (RyR1)) is a redox sensor, ... more The skeletal muscle Ca 2؉ -release channel (ryanodine receptor type 1 (RyR1)) is a redox sensor, susceptible to reversible S-nitrosylation, S-glutathionylation, and disulfide oxidation. So far, Cys-3635 remains the only cysteine residue identified as functionally relevant to the redox sensing properties of the channel. We demonstrate that expression of the C3635A-RyR1 mutant in RyR1-null myotubes alters the sensitivity of the ryanodine receptor to activation by voltage, indicating that Cys-3635 is involved in voltage-gated excitation-contraction coupling. However, H 2 O 2 treatment of C3635A-RyR1 channels or wildtype RyR1, following their expression in human embryonic kidney cells, enhances [ 3 H]ryanodine binding to the same extent, suggesting that cysteines other than Cys-3635 are responsible for the oxidative enhancement of channel activity. Using a combination of Western blotting and sulfhydryl-directed fluorescent labeling, we found that two large regions of RyR1 (amino acids 1-2401 and 3120 -4475), previously shown to be involved in disulfide bond formation, are also major sites of both S-nitrosylation and S-glutathionylation. Using selective isotopecoded affinity tag labeling of RyR1 and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy, we identified, out of the 100 cysteines in each RyR1 subunit, 9 that are endogenously modified (Cys-36, Cys-315, Cys-811, Cys-906, Cys-1591, Cys-2326, Cys-2363, Cys-3193, and Cys-3635) and another 3 residues that were only modified with exogenous redox agents (Cys-253, Cys-1040, and Cys-1303). We also identified the types of redox modification each of these cysteines can undergo. In summary, we have identified a discrete subset of cysteines that are likely to be involved in the functional response of RyR1 to different redox modifications (S-nitrosylation, S-glutathionylation, and oxidation to disulfides).
Journal of Applied Toxicology, 2009
Copper toxicity has been associated to the capacity of free copper ions to catalyze the productio... more Copper toxicity has been associated to the capacity of free copper ions to catalyze the production of superoxide anion and hydroxyl radical, reactive species that modify the structure and/or function of biomolecules. In addition, nonspecifi c Cu 2+ -binding to thiol enzymes, which modifi es their catalytic activities, has been reported. Cytochrome P450 (CYP450) monooxygenase is a thiol protein that binds substrates in the fi rst and limiting step of CYP450 system catalytic cycle, necessary for the metabolism of lipophilic xenobiotics. Therefore, copper ions have the potential to oxidize and bind to cysteinyl residues of this monooxygenase, altering the CYP450 system activity. To test this postulate, we studied the eff ect of Cu 2+ alone and Cu 2+ /ascorbate in rat liver microsomes, to independently evaluate its nonspecifi c binding and its pro-oxidant eff ects, respectively. We assessed these eff ects on the absorbance spectrum of the monooxygenase, as a measure of structural damage, and p-nitroanisole O-demethylating activity of CYP450 system, as a marker of functional impairment. Data obtained indicate that Cu 2+ could both oxidize and bind to some amino acid residues of the CYP450 monooxygenase but not to its heme group. The diff erences observed between the eff ects of Cu 2+ and Cu 2+ /ascorbate show that both mechanisms are involved in the catalytic activity inhibition of CYP450 system by copper ions. The signifi cance of these fi ndings on the pharmacokinetics and pharmacodynamics of drugs is discussed.
International Journal of Women's Health, 2012
In countries where induced abortion is legally restricted, as in most of Latin America, evaluatio... more In countries where induced abortion is legally restricted, as in most of Latin America, evaluation of statistics related to induced abortions and abortion-related mortality is challenging. The present article reexamines recent reports estimating the number of induced abortions and abortion-related mortality in Mexico, with special reference to the International Classification of Diseases (ICD). We found significant overestimations of abortion figures in the Federal District of Mexico (up to 10-fold), where elective abortion has been legal since 2007. Significant overestimation of maternal and abortion-related mortality during the last 20 years in the entire Mexican country (up to 35%) was also found. Such overestimations are most likely due to the use of incomplete in-hospital records as well as subjective opinion surveys regarding induced abortion figures, and due to the consideration of causes of death that are unrelated to induced abortion, including flawed denominators of live births. Contrary to previous publications, we found important progress in maternal health, reflected by the decrease in overall maternal mortality (30.6%) from 1990 to 2010. The use of specific ICD codes revealed that the mortality ratio associated with induced abortion decreased 22.9% between 2002 and 2008 (from 1.48 to 1.14 deaths per 100,000 live births). Currently, approximately 98% of maternal deaths in Mexico are related to causes other than induced abortion, such as hemorrhage, hypertension and eclampsia, indirect causes, and other pathological conditions. Therefore, only marginal or null effects would be expected from changes in the legal status of abortion on overall maternal mortality rates. Rather, maternal health in Mexico would greatly benefit from increasing access to emergency and specialized obstetric care. Finally, more reliable methodologies to assess abortion-related deaths are clearly required.
Chemico-Biological Interactions, 2010
Melatonin, an endogenous hormone, is used as an antioxidant drug in doses quite higher than the e... more Melatonin, an endogenous hormone, is used as an antioxidant drug in doses quite higher than the endogenous circulating levels of this hormone. Hepatic endoplasmic reticulum contains the cytochrome P450 (CYP450) system, which catalyzes one biotransformation pathway of melatonin; this organelle is also one of the main sources of reactive oxygen species in cells. Therefore, we proposed that the antioxidant activity of this hormone may have a biological relevance in the organelle where it is biotransformed. To evaluate this postulate, we used Fe 3+ /ascorbate, an oxygen free radical generating system that leads to lipid peroxidation, loss of protein-thiol content, and activation of UDP-glucuronyltransferase in rat liver microsomes. We found that mM concentrations of melatonin prevented all these oxidative phenomena. We also found that Fe 3+ /ascorbate leads to structural alterations in the CYP450 monooxygenase, the enzyme that binds the substrate in the CYP450 system catalytic cycle, probably through direct oxidation of the protein, and also inhibited p-nitroanisole O-demethylation, a reaction catalyzed by the CYP450 system. Notably, melatonin prevented both phenomena at M concentrations. We provide evidence suggesting that melatonin may be oxidized by oxygen free radicals. Thus, we postulate that melatonin may be acting as an oxygen free radical scavenger, and Fe 3+ /ascorbate-modified melatonin would be directly protecting the CYP450 system through an additional specific mechanism. Pharmacological relevance of this phenomenon is discussed.
Chemico-Biological Interactions, 2010
Iron and copper ions, in their unbound form, may lead to the generation of reactive oxygen specie... more Iron and copper ions, in their unbound form, may lead to the generation of reactive oxygen species via Haber-Weiss and/or Fenton reactions. In addition, it has been shown that copper ions can irreversibly and non-specifically bind to thiol groups in proteins. This non-specific binding property has not been fully addressed for iron ions. Thus, the present study compares both the pro-oxidant and the non-specific binding properties of Fe 3+ and Cu 2+ , using rat liver cytosol and microsomes as biological systems. Our data show that, in the absence of proteins, Cu 2+ /ascorbate elicited more oxygen consumption than Fe 3+ /ascorbate under identical conditions. Presence of cytosolic and microsomal protein, however, differentially altered oxygen consumption patterns. In addition, Cu 2+ /ascorbate increased microsomal lipid peroxidation and decreased cytosolic and microsomal content of thiol groups more efficiently than Fe 3+ /ascorbate. Finally, Fe 3+ /ascorbate and Cu 2+ /ascorbate inhibited in different ways cytosolic and microsomal glutathione S-transferase (GST) activities, which are differentially sensitive to oxidants. Moreover, in the absence of ascorbate, only Cu 2+ decreased the content of cytosolic and microsomal thiol groups and inhibited cytosolic and microsomal GST activities. Catechin partially prevented the damage to thiol groups elicited by Fe 3+ /ascorbate and Cu 2+ /ascorbate but not by Cu 2+ alone. N-Acetylcysteine completely prevented the damage elicited by Cu 2+ /ascorbate, Fe 3+ /ascorbate and Cu 2+ alone. N-Acetylcysteine also completely reversed the damage to thiol groups elicited by Fe 3+ /ascorbate, partially reversed that of Cu 2+ /ascorbate but failed to reverse the damage promoted by Cu 2+ alone. Our data are discussed in terms to the potential damage that the accumulation of iron and copper ions can promote in biological systems.