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Obesity is an important preventable risk factor for morbidity and mortality from cardiometabolic disease. Oxidative stress (including in visceral adipose tissue) and chronic low-grade inflammation are the major underlying pathomechanisms. Monoamine oxidase (MAO) has recently emerged as an important source of cardiovascular oxidative stress. The present study was conducted to evaluate the role of MAO as contributor to reactive oxygen species (ROS) production in white adipose tissue and vessels harvested from patients undergoing elective abdominal surgery. To this aim, visceral adipose tissue and mesenteric artery branches were isolated from obese patients with chronic inflammation and used for organ bath, ROS production, quantitative real-time PCR, and immunohistology studies. The human visceral adipose tissue and mesenteric artery branches contain mainly the MAO-A isoform, as shown by the quantitative real-time PCR and immunohistology experiments. A significant upregulation of MAO-A, the impairment in vascular reactivity, and increase in ROS production were found in obese vs. non-obese patients. Incubation of the adipose tissue samples and vascular rings with the MAO-A inhibitor (clorgyline, 30 min) improved vascular reactivity and decreased ROS generation. In conclusion, MAO-A is the predominant isoform in human abdominal adipose and vascular tissues, is overexpressed in the setting of inflammation, and contributes to the endothelial dysfunction. Key words: monoamine oxidases, obesity, inflammation, endothelial dysfunction. L'obesite est un important facteur de risque de morbidite et de mortalite liees a la maladie cardiometabolique qu'il est possible de prevenir. Le stress oxydatif (y compris dans le tissu adipeux visceral) et l'inflammation chronique de faible intensite en sont les principaux modes d'action sous-jacents. La monoamine-oxydase (MAO) est depuis peu reconnue comme etant une importante source de stress oxydatif cardiovasculaire. La presente etude a ete menee en vue d'evaluer la contribution de la MAO pour la production de derives reactifs de l'oxygene dans du tissu adipeux blanc et des vaisseaux sanguins preleves chez des patients subissant une intervention chirurgicale abdominale elective. A cette fin, nous avons isole du tissu adipeux visceral et des rameaux d'artere mesenterique chez des patients obeses presentant une inflammation chronique en vue de proceder a des etudes (i) en bain de tissu, (ii) sur la production de derives reactifs de l'oxygene, (iii) de PCR quantitatif en temps reel et (iv) d'immunohistologie. Comme l'ont montre ces deux dernieres techniques, chez l'homme, le tissu adipeux visceral et les rameaux d'artere mesenterique contiennent principalement l'isoforme MAO-A. Nous avons observe une regulation a la hausse de la MAO-A, une diminution de la reactivite vasculaire et une augmentation de la production de derives reactifs de l'oxygene plus marquer chez les patients obeses que chez les patients non obeses. L'incubation des echantillons de tissu adipeux et des anneaux vasculaires avec de la clorgyline (un inhibiteur de la MAO-A) pendant 30 minutes a permis d'ameliorer la reactivite vasculaire et de faire diminuer la production de derives reactifs de l'oxygene. En conclusion, la MAO-A est l'isoforme predominante dans les tissus adipeux et vasculaire abdominaux humains, est surexprimee en contexte d'inflammation et participe au dysfonctionnement endothelial. [Traduit par la Redaction] Mots-cles: monoamine-oxydases, obesite, inflammation, dysfonctionnement endothelial., Introduction Obesity is the most important modifiable risk factor for morbidity and mortality due to life-threatening cardiovascular diseases, type 2 diabetes, and certain cancers. With the increased adoption of the [...]

Endothelial dysfunction and the related increase in reactive oxygen species (ROS) production are important events in the pathophysiology of diabetes mellitus (DM). Methylene blue (MB) has been systematically investigated for its protective effects against refractory hypotension and mitochondrial dysfunction. We have previously demonstrated that MB improved mitochondrial respiration and partially decreased oxidative stress in diabetic rat hearts. The present study was aimed to investigate whether MB modulates vascular function and ROS production in thoracic aortic rings isolated from rats with streptozotocin-induced DM (after 4 weeks of hyperglycemia). The effects of MB (0.1 [micro]M, 30 min ex vivo incubation) on vascular reactivity in organ chamber (phenylephrine-induced contraction, acetylcholine-induced relaxation) and [H.sub.2][O.sub.2] production (assessed by ferrous iron xylenol orange oxidation assay) were investigated in vascular preparations with intact endothelium and after denudation. DM elicited a significant alteration of vascular function: increased contractility to phenylephrine, attenuation of acetylcholinedependent relaxation, and augmented [H.sub.2][O.sub.2] generation. Ex vivo incubation with MB partially reversed all these changes (by approximately 70%) in vascular segments with intact endothelial layer (but not in denuded vessels). In conclusion, MB might be useful in alleviating endothelial dysfunction and mitigating endothelial oxidative stress, observations that clearly require further investigation in the setting of cardiometabolic disease. Key words: methylene blue, endothelial dysfunction, oxidative stress, experimental diabetes. Le dysfonctionnement endothelial et l'augmentation de la production de derives reactifs de l'oxygene (ou ROS pour <>) qui y est liee constituent des evenements importants dans la physiopathologie du diabete sucre (DS). Le bleu de methylene (BM) a ete etudie systematiquement pour ses effets protecteurs contre l'hypotension refractaire et le dysfonctionnement mitochondrial. Nous avons montre precedemment que le BM permet d'ameliorer la respiration mitochondriale ainsi que de faire diminuer partiellement le stress oxydatif dans le creur du rat atteint de DS. Les presents travaux visaient a etudier si le BM permet de moduler la fonction vasculaire et la production de ROS dans des anneaux d'aortes thoraciques isolees de rats atteints de DS provoque par la streptozotocine (apres 4 semaines d'hyperglycemie). Nous avons etudie les effets du BM (a 0,1 [micro]M, incubation ex vivo de 30 minutes) sur la reactivite vasculaire en chambre d'organes (contraction provoquee par la phenylephrine, relaxation provoquee par l'acetylcholine) et la production de [H.sub.2][O.sub.2] (evaluee a l'aide du test d'oxydation de fer ferreux en presence de xylenol orange) dans des preparations vasculaires dont l'endothelium etait intact et apres denudation. Le DS a entraine une degradation notable de la fonction vasculaire : augmentation de la contractilite en reaction a la phenylephrine, attenuation de la relaxation dependante de l'acetylcholine et augmentation de la production d'[H.sub.2][O.sub.2]. L'incubation ex vivo avec du BM a permis d'inverser partiellement toutes ces variations (d'environ 70 %) dans les segments vasculaires dotes d'une couche endotheliale intacte (mais pas dans les vaisseaux denudes). En conclusion, le BM pourrait etre utile en vue d'attenuer le dysfonctionnement endothelial et le stress oxydatif endothelial. Ce sont des observations qui demanderaient clairement des recherches plus poussees dans un contexte de maladie cardiometabolique. [Traduit par la Redaction] Mots-cles: bleu de methylene, dysfonctionnement endothelial, stress oxydatif, diabete experimental., Introduction Diabetes mellitus (DM), a well-established independent risk factor for coronary heart disease, is currently the most serious threat to humanity health worldwide due to its alarming increase in prevalence [...]

Diabetic cardiomyopathy has been systematically associated with compromised mitochondrial energetics and increased generation of reactive oxygen species (ROS) that underlie its progression to heart failure. Methylene blue is a redox drug with reported protective effects mainly on brain mitochondria. The purpose of the present study was to characterize the effects of acute administration of methylene blue on mitochondrial respiration, [H.sub.2][O.sub.2] production, and calcium sensitivity in rat heart mitochondria isolated from healthy and 2 months (streptozotocin-induced) diabetic rats. Mitochondrial respiratory function was assessed by high-resolution respirometry. [H.sub.2][O.sub.2] production and calcium retention capacity were measured spectrofluorimetrically. The addition of methylene blue (0.1 [micro]mol x [L.sup.-1]) elicited an increase in oxygen consumption of mitochondria energized with complex I and II substrates in both normal and diseased mitochondria. Interestingly, methylene blue elicited a significant increase in [H.sub.2][O.sub.2] release in the presence of complex I substrates (glutamate and malate), but had an opposite effect in mitochondria energized with complex II substrate (succinate). No changes in the calcium retention capacity of healthy or diabetic mitochondria were found in the presence of methylene blue. In conclusion, in cardiac mitochondria isolated from diabetic and nondiabetic rat hearts, methylene blue improved respiratory function and elicited a dichotomic, substrate-dependent effect on ROS production. Key words: rat heart mitochondria, diabetes mellitus, methylene blue, mitochondrial respiration, reactive oxygen species. On a systematiquement associe la cardiomyopathie diabetique a une atteinte de la fonction energetique des mitochondries et a une augmentation de la production de derives reactifs de l'oxygene (ROS), lesquels phenomenes sous-tendent son evolution vers l'insuffisance cardiaque. Le bleu de methylene est un medicament redox avec des effets protecteurs rapportes principalement dans les mitochondries cerebrales. La presente etude a ete realisee en vue de caracteriser les effets de l'administration aigue de bleu de methylene sur la respiration mitochondriale, la production de [H.sub.2][O.sub.2] et la sensibilite au calcium dans des mitochondries isolees de creurs de rats sains ou diabetiques de 2 mois (diabete provoque par la streptozotocine). Nous avons evalue la fonction respiratoire mitochondriale a l'aide de la respirometrie a haute resolution. Nous avons mesure la production de peroxyde d'hydrogene et la capacite de retention calcique a l'aide de la spectrofluorometrie. L'ajout de bleu de methylene (0,1 [micro]mol x [L.sup.-1]) a provoque une augmentation de la consommation d'oxygene par des mitochondries energisees par des substrats des complexes I et II, et ce, chez les mitochondries normales et lesees a la fois. Il est interessant de noter que le bleu de methylene a provoque une augmentation marquee de la liberation de [H.sub.2][O.sub.2] en presence de substrats du complexe I (glutamate et malate), mais qu'il avait un effet contraire dans les mitochondries energisees avec le substrat du complexe II (succinate). En presence de bleu de methylene, nous n'avons observe aucune variation de la capacite de retention du calcium dans les mitochondries saines ou diabetiques. En conclusion, dans les mitochondries isolees de creurs de rats sains ou diabetiques, le bleu de methylene permettait d'ameliorer la fonction respiratoire et provoquait un effet dichotomique et dependant du substrat sur la production de ROS. [Traduit par la Redaction] Mots-cles : mitochondrie de creur de rat, diabete sucre, bleu de methylene, respiration mitochondriale, derives reactifs de l'oxygene., Introduction Coronary heart disease is the leading cause of mortality due to myocardial infarction and of morbidity due to heart failure. In the past decades, mitochondrial dysfunction has emerged as [...]

Arteriovenous fistula (AVF) is the 'lifeline' for patients with end-stage renal disease (ESRD) undergoing hemodialysis. AVF maturation failure is a poorly understood process, one of the contributors being endothelial dysfunction due to oxidative stress. Monoamine oxidases (MAOs) A and B were recently identified as novel sources of vascular oxidative stress. The aim of the present study was to assess the contribution of MAOs to the endothelial dysfunction in patients with ESDR with indication of hemodialysis. Fragments of brachial artery collaterals were harvested from ESRD patients during the surgical procedure aimed at creating the vascular access in the cubital fossa. The effect of increasing concentrations (10, 30,100 [micro]mol/L) of the irreversible MAO-A inhibitor, clorgyline, and MAO-B inhibitor, selegiline, on endothelial-dependent relaxation (EDR) in response to cumulative doses of acetylcholine was studied in isolated phenylephrine-preconstricted vascular rings. Hydrogen peroxide ([H.sub.2][O.sub.2]) production was assessed using ferrous oxidation xylenol orange assay. We showed that incubation of brachial rings with MAO inhibitors significantly improved EDR and attenuated [H.sub.2][O.sub.2] generation in patients with ESRD. MAO-related oxidative stress might contribute to the primary dysfunction/non-maturation of the AVF and MAO inhibitors could improve maturation and long-term patency of the vascular access in dialysis patients. Key words: arteriovenous fistula, monoamine oxidases, oxidative stress, endothelial dysfunction. La fistule arterioveineuse (FAV) represente la ligne de vie des patients atteints d'insuffisance renale terminale (IRT) hemodialyses. L'echec de la maturation de la FAV est un processus que l'on comprend mal, l'un des facteurs contributeurs etant le dysfonctionnement endothelial cause par le stress oxydatif. On a recemment caracterise les monoamines-oxydases (MAO) A et B comme etant de nouvelles sources de stress oxydatif vasculaire. La presente etude avait comme objectif d'evaluer la contribution des MAO dans le dysfonction endothelial chez des patients atteints d'IRT avec indication d'hemodialyse. Nous avons preleve des fragments de collaterales d'arteres brachiales de patients atteints d'IRT pendant l'intervention chirurgicale visant a creer l'acces vasculaire dans le pli du coude. Nous avons etudie l'effet de concentrations croissantes (10, 30,100 [micro]mol/L) de clorgyline, un inhibiteur irreversible de la MAO-A, et de selegiline, un inhibiteur de la MAO-B, sur la relaxation dependante de l'endothelium (RDE) en reaction a des doses cumulatives d'acetylcholine dans des anneaux vasculaires isoles precontractes par la phenylephrine. Nous avons evalue la production de peroxyde d'hydrogene ([H.sub.2][O.sub.2]) a l'aide de l'epreuve d'oxydation ferreuse avec l'orange de xylenol. Nous avons montre que l'incubation d'anneaux brachiaux avec des inhibiteurs de la MAO permettait nettement d'ameliorer la RDE et d'attenuer la production d'[H.sub.2][O.sub.2] chez les patients atteints d'IRT. Le stress oxydatif lie aux MAO pourrait contribuer au dysfonctionnement ou a la non-maturation primaires de la FAV, et les inhibiteurs de la MAO pourraient permettre d'ameliorer la maturation et la permeabilite a long terme de l'acces vasculaire chez les patients dialyses. [Traduit par la Redaction] Mots-cles: fistule arterioveineuse, monoamines-oxydases, stress oxydatif, dysfonctionnement endothelial., Introduction Chronic kidney disease (CKD) is a characterized by an irreversible alteration of renal structure and function, lasting more than 3 months, and the association with a plethora of complications: [...]

Monoamine oxidases (MAOs) have recently emerged as important mitochondrial sources of oxidative stress in the cardiovascular system. Generation of reactive oxygen species during the brief episodes of ischemic preconditioning (IPC) is responsible for the cardioprotection at reperfusion. The aim of this study was to assess the effects of two MAO inhibitors (clorgyline and pargyline) on the IPC-related protection in isolated rat hearts. Animals subjected to 30 min global ischemia and 120 min reperfusion were assigned to the following groups: (i) Control, no additional intervention; (ii) IPC, 3 cycles of 5 min ischemia and 5 min reperfusion before the index ischemia; (iii) IPC-clorgyline, IPC protocol bracketed for 5 min with clorgyline (50 µmol/L); (iv) IPC-pargyline, IPC protocol bracketed for 5 min with pargyline (0.5 mmol/L). The postischemic functional recovery was assessed by the left ventricular developed pressure (LVDP) and the indices of contractility (+dLVP/dt max) and relaxation (-dLVP/dt max). Infarct size (IS) was quantified by TTC staining. In both genders, IPC significantly improved functional recovery that was further enhanced in the presence of either clorgyline or pargyline. IS reduction was comparable among all the preconditioned groups, regardless of the presence of MAO inhibitors. In isolated rat hearts, acute inhibition of MAOs potentiates the IPC-induced postischemic functional recovery without interfering with the anti-necrotic protection. Key words: monoamine oxidase, MAO inhibitors, ischemic preconditioning, isolated rat heart. Les monoamine oxydases (MAOs) se sont recemment revelees d'importantes sources de stress oxydatif mitochondrial dans le systeme cardiovasculaire. La generation de derives reactifs de l'oxygene au cours d'episodes brefs de preconditionnement ischemique (PCI) est responsable de la cardioprotection lors de la reperfusion. La presente etude visait a evaluer les effets de deux inhibiteurs de la MAO (la clorgyline et la pargyline) sur le PCI dans un modele de caeur isole de rat. Nous avons soumis les animaux a une ischemie globale de 30 min, puis a une reperfusion de 120 min et les avons repartis dans les groupes suivants: (i) temoin (aucune intervention supplementaire), (ii) PCI (3 cycles de 5 min d'ischemie suivis de 5 min de reperfusion avant l'ischemie de reference), (iii) PCI-clorgyline (protocole de PCI alternant avec l'administration de clorgyline a 50 µmol/L pendant 5 min) et (iv) PCI-pargyline (protocole de PCI alternant avec l'administration de pargyline a 0,5 mmol/L pendant 5 min). Nous avons ensuite evalue le retablissement fonctionnel post-ischemique en mesurant la pression ventriculaire gauche developpee (PVGD) ainsi que les indices de contractilite (+dP/dt max) et de relaxation (-dP/dt max). Enfin, nous avons quantifie la taille de l'infarctus par la technique de coloration au TTC. Chez les animaux des deux sexes, le PCI a permis d'ameliorer clairement le retablissement fonctionnel qui a ete accentue en presence de clorgyline ou de pargyline. Par ailleurs, la diminution de la taille de l'infarctus etait comparable dans tous les groupes soumis au preconditionnement, et ce, sans egard a la presence d'inhibiteurs de la MAO. En somme, dans les caeurs isoles de rat, l'administration a court terme d'inhibiteurs de la MAO potentialise la recuperation fonctionnelle post-ischemique induite par le PCI, sans nuire a la protection contre la necrose. [Traduit par la Redaction] Mots-cles: monoamine-oxydase, inhibiteurs de la MAO, preconditionnement ischemique, caeur isole de rat., Introduction Coronary heart disease remains the leading cause of mortality and morbidity due to heart failure worldwide (Go et al. 2014). In the past decades, mitochondria have emerged as key [...]

A substantial body of evidence indicates that pharmacological activation of mitochondrial ATP-sensitive potassium channels (m[K.sub.ATP]) in the heart is protective in conditions associated with ischemia/reperfusion injury. Several mechanisms have been postulated to be responsible for cardioprotection, including the modulation of mitochondrial respiratory function. The aim of the present study was to characterize the dose-dependent effects of novel synthetic benzopyran analogues, derived from a BMS-191095, a selective m[K.sub.ATP] opener, on mitochondrial respiration and reactive oxygen species (ROS) production in isolated rat heart mitochondria. Mitochondrial respiratory function was assessed by high-resolution respirometry, and [H.sub.2][O.sub.2] production was measured by the Amplex Red fluorescence assay. Four compounds, namely KL-1487, KL-1492, KL-1495, and KL-1507, applied in increasing concentrations (50, 75, 100, and 150 µmol/L, respectively) were investigated. When added in the last two concentrations, all compounds significantly increased State 2 and 4 respiratory rates, an effect that was not abolished by 5-hydroxydecanoate (5-HD, 100 µmol/L), the classic m[K.sub.ATP] inhibitor. The highest concentration also elicited an important decrease of the oxidative phosphorylation in a [K.sup.+] independent manner. Both concentrations of 100 and 150 µmol/L for KL-1487, KL-1492, and KL-1495, and the concentration of 150 µmol/L for KL-1507, respectively, mitigated the mitochondrial [H.sub.2][O.sub.2] release. In isolated rat heart mitochondria, the novel benzopyran analogues act as protonophoric uncouplers of oxidative phosphorylation and decrease the generation of reactive oxygen species in a dose-dependent manner. Key words: rat heart mitochondria, benzopyran analogues, protonophores, uncoupling, hydrogen peroxide. De plus en plus de donnees indiquent que l'activation pharmacologique des canaux potassiques sensibles a l'ATP de la mitochondrie (m[K.sub.ATP]) du coeur le protege lorsqu'il est expose a des conditions associees au dommage d'ischemie/reperfusion. Plusieurs mecanismes pourraient etre responsables de la cardioprotection incluant la modulation de la fonction respiratoire mitochondriale. Le but de l'etude presente etait de caracteriser les effets lies a la dose de nouveaux analogues synthetiques du benzopyrane, derives du BMS-191095, un compose qui ouvre selectivement les m[K.sub.ATP], sur la respiration mitochondriale et la production d'especes reactives d'oxygene (ERO) dans les mitochondries isolees du coeur de rat et ce. La fonction respiratoire mitochondriale a ete evaluee par respirometrie a haute resolution et la production de [H.sub.2][O.sub.2] a ete mesuree par un dosage en fluorescence a l'aide de la trousse Amplex Red. Quatre composes, a savoir KL-1487, KL-1492, KL-1495 et KL-1507, ajoutes en concentrations croissantes (50,75,100 et 150 µmol/L, respectivement), ont ete examines. Lorsqu'ajoutes aux deux concentrations les plus elevees, tous les composes accroissaient significativement les taux respiratoires aux etats 2 et 4, effet qui n'etait pas aboli par le 5-hydroxydecanoate (5-HD, 100 µmol/L), l'inhibiteur classique des m[K.sub.ATP]. La plus forte concentration induisait aussi une diminution importante de la phosphorylation oxydative de maniere independante du [K.sup.+]. Les deux concentrations de 100 µmol/L et 150 µmol/L de KL-1487, KL-1492 et KL-1495, et la concentration de 150 µmol/L de KL-1507 diminuaient respectivement la liberation de [H.sub.2][O.sub.2] de la mitochondrie. Les nouveaux analogues du benzopyrane agissent comme decouplants protonophores de la phosphorylation oxydative dans les mitochondries isolees du coeur de rat, et diminuent la generation d'especes reactives d'oxygene en fonction de leur concentration. [Traduit par la Redaction] Mots-cles : mitochondries du coeur de rat, analogues du benzopyrane, protonophores, effet decouplant, peroxyde d'hydrogene., Introduction In the past decades mitochondria have emerged as major contributors to the pathogenesis of myocardial ischemia/reperfusion (I/R) injury as well as important therapeutic targets in cardioprotection (Camara et al. [...]

Diabetes mellitus (DM) is widely recognized as the most severe metabolic disease associated with increased cardiovascular morbidity and mortality. The generation of reactive oxygen species (ROS) is a major event causally linked to the development of cardiovascular complications throughout the evolution of DM. Recently, monoamine oxidases (MAOs) at the outer mitochondrial membrane, with 2 isoforms, MAO-A and MAO-B, have emerged as novel sources of constant hydrogen peroxide ([H.sub.2][O.sub.2]) production in the cardiovascular system via the oxidative deamination of biogenic amines and neurotransmitters. Whether MAOs are mediators of endothelial dysfunction in DM is unknown, and so we studied this in a streptozotocin-induced rat model of diabetes. MAO expression (mRNA and protein) was increased in both arterial samples and hearts isolated from the diabetic animals. Also, [H.sub.2][O.sub.2] production (ferrous oxidation--xylenol orange assay) in aortic samples was significantly increased, together with an impairment of endothelium-dependent relaxation (organ-bath studies). MAO inhibitors (clorgyline and selegiline) attenuated ROS production by 50% and partially normalized the endothelium-dependent relaxation in diseased vessels. In conclusion, MAOs, in particular the MAO-B isoform, are induced in aortas and hearts in the streptozotocin-induced diabetic rat model and contribute, via the generation of [H.sub.2][O.sub.2], to the endothelial dysfunction associated with experimental diabetes. Key words: monoamine oxidases, experimental diabetes mellitus, oxidative stress, endothelial dysfunction, clorgyline, selegiline. Il est largement accepte que le diabete sucre est la maladie metabolique la plus grave, associee a une morbidite et une mortalite cardiovasculares. La production de derives reactifs de l'oxygene (DRO) est une manifestation majeure entrainant des complications cardiovasculaires tout au long de la progression du diabete sucre. Recemment, les monoamine oxydases (MAO) de la membrane mitochondriale externe sous deux isoformes (MAO-A et MAO-B) se sont demarquees comme de nouvelles sources de production constante de peroxyde d'hydrogene ([H.sub.2][O.sub.2]) dans le systeme cardiovasculaire par l'intermediaire de la desamination oxydative des amines biogenes et des neurotransmetteurs. On ne sait pas si les MAO sont des mediateurs de la dysfonction endotheliale dans le diabete sucre, et c'est ce que nous avons etudie avec ce modele de diabete induit par la streptozotocine chez le rat. L'expression des MAO (ARNm et proteines) augmentait dans les echantillons arteriels comme dans les creurs isoles d'animaux diabetiques. De plus, la production de [H.sub.2][O.sub.2] (test de l'oxydation des ions ferreux revelee par le xylenol orange) dans des echantillons d'aorte etait nettement accrue et associee a un deficit de la relaxation dependante de l'endothelium (etudes en bain d'organe). L'administration des inhibiteurs des MAO (clorgyline et selegiline) a permis de diminuer la production de DRO de 50% et est parvenue en partie a retablir la relaxation dependante de l'endothelium a une valeur normale dans les vaisseaux atteints. En conclusion, dans le modele de diabete induit par la streptozotocine chez le rat, les MAO, en particulier l'isoforme MAO-B, sont induites dans les aortes et les creurs des animaux et contribuent par la production de [H.sub.2][O.sub.2] a la dysfonction endotheliale observee dans un modele experimental du diabete. [Traduit par la Redaction] Mots-cles: monoamine oxydases, diabete sucre experimental, stress oxydatif, dysfonction endotheliale, clorgyline, selegiline., Introduction Diabetes mellitus (DM), the most severe metabolic disease associated with increased cardiovascular morbidity and mortality, is widely recognized nowadays as a serious threat to global health, owing to its [...]

The past few decades have witnessed an enormous number of research strategies aimed at protecting the heart against myocardial ischemia-reperfusion injury. Several randomized clinical trials are nowadays in progress testing whether promising therapeutic strategies aimed at preventing lethal reperfusion injury can be translated from bench to bedside. Many of these interventions, either pharmacological or mechanical, are targeting mitochondria as the final effectors of cardioprotection. Despite encouraging pre-clinical studies and small proof of concept clinical trials, there are still several limitations that may jeopardize the efficacy of cardioprotective strategies. These limitations include clinical setting, patient profile, drug administration, and methods for evaluating treatment efficacy. Identifying potential mechanistic and methodological pitfalls in the field may improve future translational research. Key words: ischemia-reperfusion injury, cardioprotection, conditioning, translation, mitochondria. La derniere decennie a ete temoin du developpement d'un grand nombre de strategies de recherche visant a proteger le coeur du dommage d'ischemie-reperfusion myocardique. Plusieurs essais cliniques aleatoires sont actuellement en cours, afin de determiner si des strategies therapeutiques prometteuses visant a prevenir un dommage de reperfusion letal peuvent etre transferees de la paillasse au patient. Plusieurs de ces interventions, qu'elles soient pharmacologiques ou mecaniques, ciblent les mitochondries comme effecteurs finaux de la cardioprotection. Malgre les etudes precliniques et les petits essais cliniques de demonstration de faisabilite encourageants, il existe encore plusieurs limitations qui peuvent mettre en peril l'efficacite des strategies de cardioprotection. Ces limitations incluent le contexte clinique, le profil du patient, l'administration de medicaments et les methodes d'evaluation d'efficacite du traitement. L'identification des ecueils mecaniques et methodologiques potentiels dans ce domaine peut ameliorer la recherche translationnelle future. [Traduit par la Redaction] Mots-cles : dommage d'ischemie-reperfusion, cardioprotection, conditionnement, transfert, mitochondrie., Introduction Cardiovascular diseases, and in particular, coronary heart disease, remain the number one cause of death worldwide and have rapidly risen in prevalence in the past few years in the [...]

It is widely recognized that mitochondrial dysfunction is a key component of the multifactorial process of ageing. The effects of age on individual components of mitochondrial function vary across species and strains. In this study we investigated the oxygen consumption, the mitochondrial membrane potential (Δψ), the sensitivity of mitochondrial permeability transition pore (mPTP) to calcium overload, and the production of reactive oxygen species (ROS) in heart mitochondria isolated from old compared with adult healthy Sprague-Dawley rats. Respirometry studies and Δψ measurements were performed with an Oxygraph-2k equipped with a tetraphenylphosphonium electrode. ROS production and calcium retention capacity were measured spectrofluorimetrically. Our results show an important decline for all bioenergetic parameters for both complex I and complex II supported-respiration, a decreased Δψ in mitochondria energized with complex I substrates, and an increased mitochondrial ROS production in the old compared with the adult group. Mitochondrial sensitivity to [Ca.sup.2+]-induced mPTP opening was also increased in the old compared with the adult animals. Moreover, the protective effect of cyclosporine A on mPTP opening was significantly reduced in the old group. We conclude that healthy ageing is associated with a decrease in heart mitochondria function in Sprague-Dawley rats. Key words: ageing, oxidative phosphorylation, reactive oxygen species, calcium retention capacity. Il est generalement reconnu que la dysfonction mitochondriale est une composante cle du processus multifactoriel qu'est le vieillissement. Les effets de l'age sur les composantes individuelles de la fonction mitochondriale varient en fonction des especes et des souches. Dans cette etude, nous avons examine et compare la consommation d'oxygene, le potentiel membranaire (Δψ), la sensibilite du pore de transition de permeabilite mitochondriale (PTPM) a une surcharge en calcium et la production d'especes reactives d'oxygene (ERO) des mitochondries du coeur isolees de rats en sante Sprague-Dawley (SD) adultes vs ages. Les etudes en respirometrie et les mesures du Δψ ont ete realisees avec un Oxygraph-2k equipe d'une electrode au tetraphenylphosphonium. La production d'ERO et la capacite de retention du calcium (CRC) ont ete mesurees par spectrofluorometrie. Nos resultats ont montre un declin important de tous les parametres bioenergetiques de la respiration au niveau des complexes I et II, une diminution du Δψ dans les mitochondries tirant leur energie des substrats du complexe I et un accroissement de la production d'ERO mitochondriales chez le groupe age comparativement au groupe adulte. La sensibilite du PTPM a l'ouverture induite par le calcium etait aussi accrue chez les animaux ages comparativement aux adultes. De plus, l'effet protecteur de la cyclosporine A sur l'ouverture du PTPM etait significativement reduite chez le groupe age. En conclusion, le vieillissement normal est associe a la reduction de la fonction des mitochondries du coeur chez les rats Sprague-Dawley. [Traduit par la Redaction] Mots-cles: vieillissement, phosphorylation oxydative, especes reactives d'oxygene, capacite de retention du calcium., Introduction Ageing is the inexorable process of gradual decrease in body functional capacity, for which the underlying molecular basis remains largely elusive. It has been widely accepted that the functional [...]

Orotic acid and its salts chronically administered have been shown to significantly improve cardiac function in pathological settings associated with ischemia-reperfusion (I/R) injury. The aim of our study was to investigate the effect of magnesium orotate (Mg-Or) administration at the onset of post-ischemic reperfusion on myocardial function and infarct size (IS). Ex-vivo experiments performed on isolated perfused rat hearts were used to compare Mg-Or administration with a control group (buffer treated), ischemic post-conditioning, orotic acid treatment, and Mg[Cl.sub.2] treatment. Mg-Or administration was also investigated in an in-vivo model of regional I/R performed in rats undergoing reversible coronary ligation. The effect of Mg-Or on mitochondrial permeability transition pore (mPTP) opening after I/R was investigated in vitro to gain mechanistic insights. Both ex-vivo and in-vivo experiments showed a beneficial effect from Mg-Or administration at the onset of reperfusion on myocardial function and IS. In-vitro assays showed that Mg-Or significantly delayed mPTP opening after I/R. Our data suggest that Mg-Or administered at the very onset of reperfusion may preserve myocardial function and reduce IS. This beneficial effect may be related to a significant reduction of mPTP opening, a usual trigger of cardiac cell death following I/R. Key words: magnesium orotate, cardioprotection, ischemia-reperfusion, ischemic post-conditioning, in vivo. L'administration au long cours d'acide orotique ou de ses sels a montre un effet benefique sur la fonction cardiaque dans plusieurs situations pathologiques associees aux lesions d'ischemie-reperfusion (I/R). L'objectif de notre etude etait d'evaluer l'effet de l'orotate de magnesium (Mg-Or) administre en tout debut de reperfusion myocardique post ischemique sur la taille d'infarctus (TI) et la fonction cardiaque. Un modele ex vivo d'I/R sur cceur isole perfuse de rats a compare l'administration de Mg-Or avec les groupes experimentaux control (tampon), post conditionnement ischemique, acide orotique, et Mg[Cl.sub.2]. L'effet de Mg-Or a egalement ete evalue sur un modele in vivo d'I/R myocardique regional par ligature coronaire chez le rat. Une etude mecanistique a evalue l'effet de Mg-Or sur l'ouverture du port de permeabilite de transition mitochondriale (mPTP). L'administration de Mg-Or en debut de reperfusion sur les modeles ex vivo et in vivo entrame une diminution de la TI et une preservation de la fonction cardiaque. L'etude mecanistique montre que Mg-Or retarde l'ouverture du mPTP apres I/R myocardique. Nos resultats suggerent que Mg-Or administre en debut de reperfusion est susceptible de diminuer la TI et de preserver la fonction cardiaque. Cet effet est vraisemblablement lie a son action inhibitrice sur l'ouverture du mPTP, phenomene implique dans les processus de mort cellulaire post I/R myocardique. Mots-cles: orotate de magnesium, cardioprotection, ischemie-reperfusion, post conditionnement ischemique, in vivo., Introduction Myocardial infarction represents a major cause of morbidity and mortality worldwide. The cornerstone of treatment is represented by timely restoration of coronary reperfusion achieved either pharmacologically by thrombolysis and [...]

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A substantial body of evidence indicates that pharmacological activation of mitochondrial ATP-sensitive potassium channels (mKATP) in the heart is protective in conditions associated with ischemia/reperfusion injury. Several mechanisms have been postulated to be responsible for cardioprotection, including the modulation of mitochondrial respiratory function. The aim of the present study was to characterize the dose-dependent effects of novel synthetic benzopyran analogues, derived from a BMS-191095, a selective mKATP opener, on mitochondrial respiration and reactive oxygen species (ROS) production in isolated rat heart mitochondria. Mitochondrial respiratory function was assessed by high-resolution respirometry, and H2O2 production was measured by the Amplex Red fluorescence assay. Four compounds, namely KL-1487, KL-1492, KL-1495, and KL-1507, applied in increasing concentrations (50, 75, 100, and 150 μmol/L, respectively) were investigated. When added in the last two concentrations, all compounds significantly increased State 2 and 4 respiratory rates, an effect that was not abolished by 5-hydroxydecanoate (5-HD, 100 μmol/L), the classic mKATP inhibitor. The highest concentration also elicited an important decrease of the oxidative phosphorylation in a K+ independent manner. Both concentrations of 100 and 150 μmol/L for KL-1487, KL-1492, and KL-1495, and the concentration of 150 μmol/L for KL-1507, respectively, mitigated the mitochondrial H2O2 release. In isolated rat heart mitochondria, the novel benzopyran analogues act as protonophoric uncouplers of oxidative phosphorylation and decrease the generation of reactive oxygen species in a dose-dependent manner. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Physiology & Pharmacology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Physiology & Pharmacology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mitochondrial dysfunction and reactive oxygen species (ROS) generation are critical events in the pathophysiology of ageing and chronic disorders, in the past years modulation of mitochondrial function becoming thus an important therapeutic target. Pharmacological agents able to improve mitochondrial function and/or to decrease ROS production are nowadays highly investigated. Among them an emerging compound is methylene blue (MB), a tricyclic phenothiazine, used for more than a century to treat a variety of disorders. Due to its redox activity, MB has a high affinity for numerous tissue oxidases, including those within mitochondria. Here we briefly review the use of MB in medicine and biology and discuss its beneficial effects as a mild-redox agent able to prevent mitochondria-driven disorders. Methylene blue has a significant potential to improve mitochondrial metabolism and represents a promising therapeutic approach in several conditions associated with mitochondrial dysfunction. [ABSTRACT FROM AUTHOR]

Orotic acid and its salts has been previously shown to improve the energy status of cardiomyocytes and to protect myocardium following transplantation and cardioplegic arrest. The present study carried out in Langendorff perfused rat hearts was purported to compare cardioprotection elicited by CsA with the one afforded by magnesium orotate (Mg-O) when administrated at reperfusion. To this aim isolated rat hearts (n 6-8/group) subjected to 30 mm of global ischemia and 30 mm of reperfusion were randomized to receive: (1) no intervention (Controls), (2) Mg-O (1 mM) and (3) CsA (0.2 μM) in the perfusion buffer throughout the reperfusion period. Recovery of post-is chemic ventricular function was assessed by the left ventricular developed pressure (LVDP), rate pressure product (RPP), and maximal and minimal first derivatives of left ventricular pressure (dLVP/dtmax and dLVP/dtmin) as indices of contractility and relaxation, respectively. All contractile parameters were expressed as percentage of their pre-ischemic values. At the end of the reperfusion period, both Mg-O and CsA induced a substantial recovery of contractile function parameters. Accordingly, LVDP was 59.4 ± 2.24% and 65.8 ± 1.56% in Mg-O and CsA groups, respectively vs. 36 ± 3.68% in Controls (p < 0.001). Similarly, both Mg-O and CsA administration improved contractility (59,4 ± 2.24% and 65.97 ± 1,6%, pNS) and relaxation indices (67,6 ± 0,8% and 65,8 ± 1,5%, pNS) when compared to Controls (p < 0.001). In isolated rat hearts, acute administration of Mg-O and CsA at reperfusion was associated with significant improvement of the postischemic contractile function. [ABSTRACT FROM AUTHOR]

The transversal deformation response force is an useful parameter for in vivo evaluation of skeletal muscle contractile response in basal conditions, electrical stimulation (induced tetany) or after myorelaxing drugs administration. The present device allows the recording of the transversal deformation response force which represents the parameter for the evaluation of skeletal muscle tone. The purpose of this study was to evaluate the in vivo relaxing effects of a new purified Helleborus Purpurascens root extract (ACSw05) on skeletal muscle tone, using an experimental device. In this study we used Sprague Dawley rats (200-250g), that were immobilized on the contention table, after they have been anesthetized with Nembutal 20 mg/kg i.p. The evaluation of ACSw05 extract effects on skeletal muscle tone was performed by analyzing the plotted length-force curves; the follow-up period was 90 minutes. First we performed a control recording curve and afterwards we injected intramuscular 200 μl ACSw05 extract. We noticed a decrease of length-force curve slope and a 40% decrease of the contractile muscle response compared with the control recording curve. The relaxation curve slope hasn't shown significant changes compared to the control recording curve. The device and method for skeletal muscle tone evaluation by measuring the transversal deformation response force can be used to compare the effects of different physical, chemical factors and drugs on skeletal muscle. [ABSTRACT FROM AUTHOR]

Monoamine oxidases (MAOs) are mitochondrial enzymes with 2 isoforms that have emerged as important contributors to cardiovascular oxidative stress via the constant generation of hydrogen peroxide. The present study was purported to assess whether MAO-derived H2O2 contributes to the endothelial dysfunction in mammary arteries harvested from coronary heart disease patients with and without diabetes mellitus subjected to coronary artery bypass grafting. To this aim, the effects of MAO inhibition on vascular contractility to phenylephrine and endothelial-dependent relaxation (EDR) in response to acetylcholine were studied in vascular segments. Clorgyline (irreversible MAO-A inhibitor), selegiline (irreversible MAO-B inhibitor), and moclobemide (reversible MAO-A inhibitor) were applied in the organ bath (10 μmol/L). MAO expression was assessed by immunohistochemistry. We found a constant impairment of EDR that has been significantly attenuated in the presence of the MAO-A and MAO-B inhibitors in both groups of coronary heart disease patients. MAO-B was the dominant isoform in all human diseased vessels. In conclusion, in vitro inhibition of MAO significantly improved EDR in human mammary arteries, regardless of the presence of diabetes. These data suggest that MAO inhibitors might be useful in restoring endothelial response in clinical conditions associated with increased oxidative stress, such as coronary artery disease and diabetes. [ABSTRACT FROM AUTHOR]

Pravastatin (PR), a HMG-CoA reductase inhibitor, and nicotinic acid (NA), a water-soluble vitamin B, are widely prescribed lipid-modifying drugs. Controversy exists about the effects of these agents on mitochondrial function. The present study was purported to characterize the acute effects of PR and NA (10 μM) on mitochondrial respiration in H9c2 cardiomyoblasts. Mitochondrial respiration of permeabilized cells was assessed by high-resolution respirometry using the Oxygraph-2k in the presence of complex I and complex II substrates (glutamate/malate and succinate) and, of the successive addition of the electron transport chain inhibitors: rotenone, oligomycin, FCCP, and antimycin A, respectively. Our preliminary data show an inhibitory effect on mitochondrial respiration in the presence of pravastatin, whereas nicotinic acid stimulated respiration in H9c2 cardiomyoblasts. [ABSTRACT FROM AUTHOR]

Monoamine oxidases (MAOs) have recently emerged as important mitochondrial sources of oxidative stress in the cardiovascular system. Generation of reactive oxygen species during the brief episodes of ischemic preconditioning (IPC) is responsible for the cardioprotection at reperfusion. The aim of this study was to assess the effects of two MAO inhibitors (clorgyline and pargyline) on the IPC-related protection in isolated rat hearts. Animals subjected to 30 min global ischemia and 120 min reperfusion were assigned to the following groups: ( i) Control, no additional intervention; ( ii) IPC, 3 cycles of 5 min ischemia and 5 min reperfusion before the index ischemia; ( iii) IPC-clorgyline, IPC protocol bracketed for 5 min with clorgyline (50 μmol/L); ( iv) IPC-pargyline, IPC protocol bracketed for 5 min with pargyline (0.5 mmol/L). The postischemic functional recovery was assessed by the left ventricular developed pressure (LVDP) and the indices of contractility (+dLVP/dt max) and relaxation (-dLVP/dt max). Infarct size (IS) was quantified by TTC staining. In both genders, IPC significantly improved functional recovery that was further enhanced in the presence of either clorgyline or pargyline. IS reduction was comparable among all the preconditioned groups, regardless of the presence of MAO inhibitors. In isolated rat hearts, acute inhibition of MAOs potentiates the IPC-induced postischemic functional recovery without interfering with the anti-necrotic protection. [ABSTRACT FROM AUTHOR]

Endothelial vasodilator dysfunction assessed by brachial artery flow - mediated dilatation (FMD) is an indicator of subclinical atherosclerotic disease. The aim of the study was to observe if there is a relationship between FMD and classical cardiovascular risk factors in a group of hypertensive patients. We measured FMD by ultrasound in 75 subjects aged between 42 and 62 years. We examined its correlation and interaction with traditionally cardiovascular risk factors. Endothelial function was assessed by means of flow mediated dilation (FMD) on brachial artery, using B - mode ultrasonography. The values of FMD were 8, 00 ± 2, 02%. We found a weak but significant correlation between FMD and systolic arterial hypertension (r = - 0,125, p < 0, 05), between FMD and diastolic arterial hypertension (r = -0,237, p < 0, 05), between FMD and HDL cholesterol (r = 0,368, p < 0, 05), between FMD and LDL cholesterol (r = - 0,403, p < 0, 05) and between FMD and triglycerides (r = - 0,325, p < 0, 01). We observed a moderate but significant correlation between FMD and total cholesterol (r = - 0,511, p < 0, 01). In conclusion, in hypertensive patients, FMD measurement is an important tool for evaluation of arterial wall remodeling and can be used as valid marker of atherosclerosis in cardiovascular risk prediction. [ABSTRACT FROM AUTHOR]