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1.
Cardiovasc Res ; 2024 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-38832935

RESUMO

AIMS: Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are increasingly used to treat type 2 diabetes and obesity. Albeit cardiovascular outcomes generally improve, treatment with GLP-1 RAs is associated with increased heart rate, the mechanism of which is unclear. METHODS AND RESULTS: We employed a large animal model, the female landrace pig, and used multiple in-vivo and ex-vivo approaches including pharmacological challenges, electrophysiology and high-resolution mass spectrometry to explore how GLP-1 elicits an increase in heart rate. In anaesthetized pigs, neither cervical vagotomy, adrenergic blockers (alpha, beta or combined alpha-beta blockade), ganglionic blockade (hexamethonium) nor inhibition of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels (ivabradine) abolished the marked chronotropic effect of GLP-1. GLP-1 administration to isolated perfused pig hearts also increased heart rate, which was abolished by GLP-1 receptor blockade. Electrophysiological characterization of GLP-1 effects in vivo and in isolated perfused hearts localized electrical modulation to the atria and conduction system. In isolated sinus nodes, GLP-1 administration shortened action potential cycle length of pacemaker cells and shifted the site of earliest activation. The effect was independent of HCN blockade. Collectively, these data support a direct effect of GLP-1 on GLP-1 receptors within the heart. Consistently, single nucleus RNA sequencing (snRNAseq) showed GLP-1 receptor expression in porcine pacemaker cells. Quantitative phosphoproteomics analyses of sinus node samples revealed that GLP-1 administration leads to phosphorylation changes of calcium cycling proteins of the sarcoplasmic reticulum, known to regulate heart rate. CONCLUSION: GLP-1 has direct chronotropic effects on the heart mediated by GLP-1 receptors in pacemaker cells of the sinus node, inducing changes in action potential morphology and the leading pacemaker site through a calcium signaling response characterized by PKA-dependent phosphorylation of Ca2+ cycling proteins involved in pace making. Targeting the pacemaker calcium clock may be a strategy to lower heart rate in GLP-1 RA recipients.

2.
Ann Surg ; 278(5): 676-682, 2023 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-37503631

RESUMO

OBJECTIVE: To provide mechanistic insight into key biological alterations in donation after circulatory death kidneys during continuous pefusion we performed mass spectrometry profiling of perfusate samples collected during a phase 3 randomized double-blind paired clinical trial of hypothermic machine perfusion with and without oxygen (COMPARE). BACKGROUND: Despite the clinical benefits of novel perfusion technologies aiming to better preserve donor organs, biological processes that may be altered during perfusion have remained largely unexplored. The collection of serial perfusate samples during the COMPARE clinical trial provided a unique resource to study perfusate proteomic profiles, with the hypothesis that in-depth profiling may reveal biologically meaningful information on how donor kidneys benefit from this intervention. METHODS: Multiplexed liquid chromatography-tandem mass spectrometry was used to obtain a proteome profile of 210 perfusate samples. Partial least squares discriminant analysis and multivariate analysis involving clinical and perfusion parameters were used to identify associations between profiles and clinical outcomes. RESULTS: Identification and quantitation of 1716 proteins indicated that proteins released during perfusion originate from the kidney tissue and blood, with blood-based proteins being the majority. Data show that the overall hypothermic machine perfusion duration is associated with increasing levels of a subgroup of proteins. Notably, high-density lipoprotein and complement cascade proteins are associated with 12-month outcomes, and blood-derived proteins are enriched in the perfusate of kidneys that developed acute rejection. CONCLUSIONS: Perfusate profiling by mass spectrometry was informative and revealed proteomic changes that are biologically meaningful and, in part, explain the clinical observations of the COMPARE trial.


Assuntos
Transplante de Rim , Humanos , Transplante de Rim/métodos , Proteoma/metabolismo , Proteômica , Preservação de Órgãos/métodos , Rim/metabolismo , Perfusão/métodos , Doadores de Tecidos
3.
PLoS One ; 18(6): e0287713, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37352336

RESUMO

Hypothermic machine perfusion (HMP) provides preservation superior to cold storage and may allow for organ assessment prior to transplantation. Since flavin mononucleotide (FMN) in perfusate has been proposed as a biomarker of organ quality during HMP of donor livers, the aim of this study was to validate FMN as a biomarker for organ quality in the context of HMP preserved kidneys. Perfusate samples (n = 422) from the paired randomised controlled COPE-COMPARE-trial, comparing HMP with oxygenation (HMPO2) versus standard HMP in kidneys, were used. Fluorescence intensity (FI) was assessed using fluorescence spectroscopy (excitation 450nm; emission 500-600nm) and validated by fluorospectrophotometer and targeted liquid chromatography mass spectrometry (LC-MS/MS). Fluorescence intensity (FI)(ex450;em500-600) increased over time during machine perfusion in both groups (p<0.0001). This increase was similar for both groups (p = 0.83). No correlation, however, was found between FI(ex450;em500-600) and post-transplant outcomes, including day 5 or 7 serum creatinine (p = 0.11; p = 0.16), immediate graft function (p = 0.91), creatinine clearance and biopsy-proven rejection at one year (p = 0.14; p = 0.59). LC-MS/MS validation experiments of samples detected FMN in only one perfusate sample, whilst the majority of samples with the highest fluorescence (n = 37/38, 97.4%) remained negative. In the context of clinical kidney HMP, fluorescence spectroscopy unfortunately appears to be not specific and probably unsuitable for FMN. This study shows that FMN does not classify as a clinically relevant predictive biomarker of kidney graft function after transplantation.


Assuntos
Mononucleotídeo de Flavina , Preservação de Órgãos , Cromatografia Líquida , Preservação de Órgãos/métodos , Espectrometria de Massas em Tandem , Diálise Renal , Rim , Perfusão/métodos , Biomarcadores
4.
Front Transplant ; 2: 1166661, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-39055309

RESUMO

Introduction: Currently there is an urgent need to translate interventions that may be beneficial to marginal donor kidneys prior to transplant, to improve their quality from bench to bedside. This project investigated the effects of CC-4066, a potent dual inhibitor of cyclophilin proteins A and D, treatment during static cold storage (SCS) in a porcine model of renal ischemia-reperfusion injury (IRI) using Normothermic Reperfusion (NR). Materials and methods: Porcine kidneys and autologous blood were retrieved in pairs from a local abattoir (n = 7). One kidney from each pair was randomly allocated to treatment and one allocated to control and flushed with preservation solution containing CC-4066 or vehicle. After 7 h of SCS kidneys underwent 3 h Normothermic Reperfusion (NR) with autologous whole blood while perfusion characteristics and samples were collected. Results: Perfusion and metabolic parameters showed similar trends and no statistical differences were observed between the groups. IL-6 showed a significant increase over time but no significant difference between groups (p-value 0.009 and 0.14 respectively, two-way ANOVA). Oxygen consumption and lactate levels were similar between groups but there was increased vacuolation on histology in the control group. Conclusions: The addition of CC-4066 during SCS of kidneys is safe and feasible and has no adverse or detrimental effects on perfusion during assessment on NR. There was no difference in cytokine levels although there was a trend towards less vacuolation on histology in the treatment group.

5.
Circ Res ; 131(6): 528-541, 2022 09 02.
Artigo em Inglês | MEDLINE | ID: mdl-35959683

RESUMO

BACKGROUND: Inhibiting SDH (succinate dehydrogenase), with the competitive inhibitor malonate, has shown promise in ameliorating ischemia/reperfusion injury. However, key for translation to the clinic is understanding the mechanism of malonate entry into cells to enable inhibition of SDH, its mitochondrial target, as malonate itself poorly permeates cellular membranes. The possibility of malonate selectively entering the at-risk heart tissue on reperfusion, however, remains unexplored. METHODS: C57BL/6J mice, C2C12 and H9c2 myoblasts, and HeLa cells were used to elucidate the mechanism of selective malonate uptake into the ischemic heart upon reperfusion. Cells were treated with malonate while varying pH or together with transport inhibitors. Mouse hearts were either perfused ex vivo (Langendorff) or subjected to in vivo left anterior descending coronary artery ligation as models of ischemia/reperfusion injury. Succinate and malonate levels were assessed by liquid chromatography-tandem mass spectrometry LC-MS/MS, in vivo by mass spectrometry imaging, and infarct size by TTC (2,3,5-triphenyl-2H-tetrazolium chloride) staining. RESULTS: Malonate was robustly protective against cardiac ischemia/reperfusion injury, but only if administered at reperfusion and not when infused before ischemia. The extent of malonate uptake into the heart was proportional to the duration of ischemia. Malonate entry into cardiomyocytes in vivo and in vitro was dramatically increased at the low pH (≈6.5) associated with ischemia. This increased uptake of malonate was blocked by selective inhibition of MCT1 (monocarboxylate transporter 1). Reperfusion of the ischemic heart region with malonate led to selective SDH inhibition in the at-risk region. Acid-formulation greatly enhances the cardioprotective potency of malonate. CONCLUSIONS: Cardioprotection by malonate is dependent on its entry into cardiomyocytes. This is facilitated by the local decrease in pH that occurs during ischemia, leading to its selective uptake upon reperfusion into the at-risk tissue, via MCT1. Thus, malonate's preferential uptake in reperfused tissue means it is an at-risk tissue-selective drug that protects against cardiac ischemia/reperfusion injury.


Assuntos
Traumatismo por Reperfusão Miocárdica , Animais , Cromatografia Líquida , Células HeLa , Humanos , Isquemia , Malonatos/farmacologia , Malonatos/uso terapêutico , Camundongos , Camundongos Endogâmicos C57BL , Traumatismo por Reperfusão Miocárdica/tratamento farmacológico , Traumatismo por Reperfusão Miocárdica/prevenção & controle , Miócitos Cardíacos , Espectrometria de Massas em Tandem
6.
Redox Biol ; 55: 102429, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35961099

RESUMO

Mitochondria-targeted H2S donors are thought to protect against acute ischemia-reperfusion (IR) injury by releasing H2S that decreases oxidative damage. However, the rate of H2S release by current donors is too slow to be effective upon administration following reperfusion. To overcome this limitation here we develop a mitochondria-targeted agent, MitoPerSulf that very rapidly releases H2S within mitochondria. MitoPerSulf is quickly taken up by mitochondria, where it reacts with endogenous thiols to generate a persulfide intermediate that releases H2S. MitoPerSulf is acutely protective against cardiac IR injury in mice, due to the acute generation of H2S that inhibits respiration at cytochrome c oxidase thereby preventing mitochondrial superoxide production by lowering the membrane potential. Mitochondria-targeted agents that rapidly generate H2S are a new class of therapy for the acute treatment of IR injury.

7.
Transpl Int ; 35: 10420, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35711321

RESUMO

Donor kidney assessment may improve organ utilisation. Normothermic Machine Perfusion (NMP) has the potential to facilitate this advance. The mechanism of action is not yet determined and we aimed to assess mitochondrial function during NMP. Anaesthetised pigs (n = 6) had one kidney clamped for 60 min. The healthy contralateral kidney was removed and underwent NMP for 8 h (healthy control (HC), n = 6). Following 60 min warm ischaemia the injured kidney underwent HMP for 24 h, followed by NMP for 8 h (n = 6). Mitochondria were extracted from fresh tissue for analysis. Injured kidneys were analysed as two separate groups (IMa, n = 3 and IMb, n = 3). Renal resistance was higher (0.39ï, ± 0.29 vs. 1.65ï, ± 0.85; p = 0.01) and flow was lower (55ï, ± 28 vs. 7ï, ± 4; p = 0.03) during HMP in IMb than IMa. NMP blood flow was higher in IMa versus IMb (2-way ANOVA; p < 0.001) After 60 min NMP, O2 consumption was significantly lower in IMb versus IMa (p ≤ 0.002). State-3 respiration was significantly different between the groups (37ï, ± 19 vs. 24ï, ± 14 vs. 10ï, ± 8; nmolO2/min/mg; p = 0.049). Lactate levels were significantly lower in IMa versus IMb (p = 0.028). Mitochondrial respiration levels during NMP may be suggestive of kidney viability. Oxygen consumption, renal blood flow and lactate can differentiate severity of kidney injury during NMP.


Assuntos
Rim , Preservação de Órgãos , Animais , Humanos , Rim/metabolismo , Lactatos/metabolismo , Mitocôndrias , Consumo de Oxigênio , Perfusão , Suínos , Sobrevivência de Tecidos
8.
Cardiovasc Drugs Ther ; 36(1): 1-13, 2022 02.
Artigo em Inglês | MEDLINE | ID: mdl-32648168

RESUMO

PURPOSE: Mitochondrial reactive oxygen species (ROS) production upon reperfusion of ischemic tissue initiates the ischemia/reperfusion (I/R) injury associated with heart attack. During ischemia, succinate accumulates and its oxidation upon reperfusion by succinate dehydrogenase (SDH) drives ROS production. Inhibition of succinate accumulation and/or oxidation by dimethyl malonate (DMM), a cell permeable prodrug of the SDH inhibitor malonate, can decrease I/R injury. However, DMM is hydrolysed slowly, requiring administration to the heart prior to ischemia, precluding its administration to patients at the point of reperfusion, for example at the same time as unblocking a coronary artery following a heart attack. To accelerate malonate delivery, here we developed more rapidly hydrolysable malonate esters. METHODS: We synthesised a series of malonate esters and assessed their uptake and hydrolysis by isolated mitochondria, C2C12 cells and in mice in vivo. In addition, we assessed protection against cardiac I/R injury by the esters using an in vivo mouse model of acute myocardial infarction. RESULTS: We found that the diacetoxymethyl malonate diester (MAM) most rapidly delivered large amounts of malonate to cells in vivo. Furthermore, MAM could inhibit mitochondrial ROS production from succinate oxidation and was protective against I/R injury in vivo when added at reperfusion. CONCLUSIONS: The rapidly hydrolysed malonate prodrug MAM can protect against cardiac I/R injury in a clinically relevant mouse model.


Assuntos
Cardiotônicos/farmacologia , Malonatos/farmacologia , Infarto do Miocárdio/prevenção & controle , Traumatismo por Reperfusão Miocárdica/tratamento farmacológico , Animais , Cardiotônicos/síntese química , Cardiotônicos/química , Linhagem Celular , Modelos Animais de Doenças , Ésteres/química , Feminino , Humanos , Masculino , Malonatos/síntese química , Malonatos/química , Camundongos , Camundongos Endogâmicos C57BL , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Traumatismo por Reperfusão Miocárdica/fisiopatologia , Pró-Fármacos , Ratos , Ratos Wistar , Espécies Reativas de Oxigênio/metabolismo , Ácido Succínico/metabolismo
9.
Am J Transplant ; 22(2): 344-370, 2022 02.
Artigo em Inglês | MEDLINE | ID: mdl-34657378

RESUMO

Despite decennia of research and numerous successful interventions in the preclinical setting, renal ischemia reperfusion (IR) injury remains a major problem in clinical practice, pointing toward a translational gap. Recently, two clinical studies on renal IR injury (manifested either as acute kidney injury or as delayed graft function) identified metabolic derailment as a key driver of renal IR injury. It was reasoned that these unambiguous metabolic findings enable direct alignment of clinical with preclinical data, thereby providing the opportunity to elaborate potential translational hurdles between preclinical research and the clinical context. A systematic review of studies that reported metabolic data in the context of renal IR was performed according to the PRISMA guidelines. The search (December 2020) identified 35 heterogeneous preclinical studies. The applied methodologies were compared, and metabolic outcomes were semi-quantified and aligned with the clinical data. This review identifies profound methodological challenges, such as the definition of IR injury, the follow-up time, and sampling techniques, as well as shortcomings in the reported metabolic information. In light of these findings, recommendations are provided in order to improve the translatability of preclinical models of renal IR injury.


Assuntos
Injúria Renal Aguda , Transplante de Rim , Traumatismo por Reperfusão , Injúria Renal Aguda/etiologia , Humanos , Rim/metabolismo , Traumatismo por Reperfusão/metabolismo
10.
Cell Chem Biol ; 29(4): 636-649.e14, 2022 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-34739852

RESUMO

Mammalian complex I can adopt catalytically active (A-) or deactive (D-) states. A defining feature of the reversible transition between these two defined states is thought to be exposure of the ND3 subunit Cys39 residue in the D-state and its occlusion in the A-state. As the catalytic A/D transition is important in health and disease, we set out to quantify it by measuring Cys39 exposure using isotopic labeling and mass spectrometry, in parallel with complex I NADH/CoQ oxidoreductase activity. To our surprise, we found significant Cys39 exposure during NADH/CoQ oxidoreductase activity. Furthermore, this activity was unaffected if Cys39 alkylation occurred during complex I-linked respiration. In contrast, alkylation of catalytically inactive complex I irreversibly blocked the reactivation of NADH/CoQ oxidoreductase activity by NADH. Thus, Cys39 of ND3 is exposed in complex I during mitochondrial respiration, with significant implications for our understanding of the A/D transition and the mechanism of complex I.


Assuntos
Complexo I de Transporte de Elétrons , NAD , Animais , Catálise , Complexo I de Transporte de Elétrons/metabolismo , Mamíferos/metabolismo , Mitocôndrias/metabolismo , Respiração
11.
Transpl Int ; 34(9): 1630-1642, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34448276

RESUMO

Static cold storage (SCS) is the standard method for pancreas preservation prior to transplantation; however, it does not permit organ assessment. Normothermic reperfusion (NR) is utilized clinically for other organs to assess viability. Our aim was to develop NR using normothermic machine perfusion technique to simulate reperfusion at the time of transplantation, enabling evaluation of oxygenated hypothermic machine perfusion (HMPO2) as a newer strategy to optimize pancreas preservation. 13 porcine pancreases procured after circulatory death were divided into 3 groups: 4 pancreases preserved using SCS, and 2 groups preserved by HMPO2 (n = 4 and n = 5, differing by type of preservation solution). Duration of perfusion or cold storage was 6 hours before the 1-hour assessment using NR. Outcome measures were perfusion characteristics, biochemistry and change in tissue water mass as oedema assessment. During NR, the HMPO2 groups demonstrated better perfusion characteristics, normal macroscopic appearances, decreased water mass and one HMPO2 group demonstrated a response to glucose stimulation. Conversely, the SCS group showed an increased water mass and developed early macroscopic appearances of oedema, interstitial haemorrhage and minimal portal outflow. This study suggests that ex situ assessment of pancreases by NR is promising, and that HMPO2 may be better than SCS.


Assuntos
Preservação de Órgãos , Pancrelipase , Animais , Pâncreas/cirurgia , Perfusão , Reperfusão , Suínos
12.
Int J Mol Sci ; 22(10)2021 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-34068301

RESUMO

Maintaining organ viability between donation and transplantation is of critical importance for optimal graft function and survival. To date in pancreas transplantation, static cold storage (SCS) is the most widely practiced method of organ preservation. The first experiments in ex vivo perfusion of the pancreas were performed at the beginning of the 20th century. These perfusions led to organ oedema, hemorrhage, and venous congestion after revascularization. Despite these early hurdles, a number of factors now favor the use of perfusion during preservation: the encouraging results of HMP in kidney transplantation, the development of new perfusion solutions, and the development of organ perfusion machines for the lung, heart, kidneys and liver. This has led to a resurgence of research in machine perfusion for whole organ pancreas preservation. This review highlights the ischemia-reperfusion injuries assessment during ex vivo pancreas perfusion, both for assessment in pre-clinical experimental models as well for future use in the clinic. We evaluated perfusion dynamics, oedema assessment, especially by impedance analysis and MRI, whole organ oxygen consumption, tissue oxygen tension, metabolite concentrations in tissue and perfusate, mitochondrial respiration, cell death, especially by histology, total cell free DNA, caspase activation, and exocrine and endocrine assessment.


Assuntos
Preservação de Órgãos/métodos , Transplante de Pâncreas , Pâncreas/fisiologia , Traumatismo por Reperfusão/prevenção & controle , Sobrevivência de Tecidos , Animais , Humanos
13.
Cardiovasc Res ; 117(4): 1188-1201, 2021 03 21.
Artigo em Inglês | MEDLINE | ID: mdl-32766828

RESUMO

AIMS: Succinate accumulates several-fold in the ischaemic heart and is then rapidly oxidized upon reperfusion, contributing to reactive oxygen species production by mitochondria. In addition, a significant amount of the accumulated succinate is released from the heart into the circulation at reperfusion, potentially activating the G-protein-coupled succinate receptor (SUCNR1). However, the factors that determine the proportion of succinate oxidation or release, and the mechanism of this release, are not known. METHODS AND RESULTS: To address these questions, we assessed the fate of accumulated succinate upon reperfusion of anoxic cardiomyocytes, and of the ischaemic heart both ex vivo and in vivo. The release of accumulated succinate was selective and was enhanced by acidification of the intracellular milieu. Furthermore, pharmacological inhibition, or haploinsufficiency of the monocarboxylate transporter 1 (MCT1) significantly decreased succinate efflux from the reperfused heart. CONCLUSION: Succinate release upon reperfusion of the ischaemic heart is mediated by MCT1 and is facilitated by the acidification of the myocardium during ischaemia. These findings will allow the signalling interaction between succinate released from reperfused ischaemic myocardium and SUCNR1 to be explored.


Assuntos
Mitocôndrias Cardíacas/metabolismo , Transportadores de Ácidos Monocarboxílicos/metabolismo , Infarto do Miocárdio/terapia , Traumatismo por Reperfusão Miocárdica/metabolismo , Reperfusão Miocárdica/efeitos adversos , Miócitos Cardíacos/metabolismo , Ácido Succínico/metabolismo , Simportadores/metabolismo , Animais , Células Cultivadas , Modelos Animais de Doenças , Feminino , Preparação de Coração Isolado , Masculino , Metaboloma , Camundongos Endogâmicos C57BL , Camundongos Knockout , Transportadores de Ácidos Monocarboxílicos/genética , Infarto do Miocárdio/genética , Infarto do Miocárdio/metabolismo , Traumatismo por Reperfusão Miocárdica/genética , Oxirredução , Ratos , Espécies Reativas de Oxigênio/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Sus scrofa , Simportadores/genética , Fatores de Tempo
14.
Free Radic Biol Med ; 134: 678-687, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30731114

RESUMO

Reactive oxygen species (ROS) have an equivocal role in myocardial ischaemia reperfusion injury. Within the cardiomyocyte, mitochondria are both a major source and target of ROS. We evaluate the effects of a selective, dose-dependent increase in mitochondrial ROS levels on cardiac physiology using the mitochondria-targeted redox cycler MitoParaquat (MitoPQ). Low levels of ROS decrease the susceptibility of neonatal rat ventricular myocytes (NRVMs) to anoxia/reoxygenation injury and also cause profound protection in an in vivo mouse model of ischaemia/reperfusion. However higher doses of MitoPQ resulted in a progressive alteration of intracellular [Ca2+] homeostasis and mitochondrial function in vitro, leading to dysfunction and death at high doses. Our data show that a primary increase in mitochondrial ROS can alter cellular function, and support a hormetic model in which low levels of ROS are cardioprotective while higher levels of ROS are cardiotoxic.


Assuntos
Modelos Animais de Doenças , Hormese , Mitocôndrias Cardíacas/metabolismo , Traumatismo por Reperfusão Miocárdica/prevenção & controle , Miócitos Cardíacos/citologia , Paraquat/farmacologia , Superóxidos/metabolismo , Animais , Animais Recém-Nascidos , Apoptose , Herbicidas/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Mitocôndrias Cardíacas/efeitos dos fármacos , Mitocôndrias Cardíacas/patologia , Traumatismo por Reperfusão Miocárdica/metabolismo , Traumatismo por Reperfusão Miocárdica/patologia , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Ratos , Ratos Wistar
15.
Cell Chem Biol ; 26(3): 449-461.e8, 2019 03 21.
Artigo em Inglês | MEDLINE | ID: mdl-30713096

RESUMO

Mitochondrial glutathione (GSH) and thioredoxin (Trx) systems function independently of the rest of the cell. While maintenance of mitochondrial thiol redox state is thought vital for cell survival, this was not testable due to the difficulty of manipulating the organelle's thiol systems independently of those in other cell compartments. To overcome this constraint we modified the glutathione S-transferase substrate and Trx reductase (TrxR) inhibitor, 1-chloro-2,4-dinitrobenzene (CDNB) by conjugation to the mitochondria-targeting triphenylphosphonium cation. The result, MitoCDNB, is taken up by mitochondria where it selectively depletes the mitochondrial GSH pool, catalyzed by glutathione S-transferases, and directly inhibits mitochondrial TrxR2 and peroxiredoxin 3, a peroxidase. Importantly, MitoCDNB inactivates mitochondrial thiol redox homeostasis in isolated cells and in vivo, without affecting that of the cytosol. Consequently, MitoCDNB enables assessment of the biomedical importance of mitochondrial thiol homeostasis in reactive oxygen species production, organelle dynamics, redox signaling, and cell death in cells and in vivo.


Assuntos
Mitocôndrias/metabolismo , Compostos de Sulfidrila/química , Animais , Cromatografia Líquida de Alta Pressão , Dinitroclorobenzeno/análise , Dinitroclorobenzeno/química , Dinitroclorobenzeno/metabolismo , Dinitroclorobenzeno/farmacologia , Glutationa/química , Glutationa/metabolismo , Glutationa Transferase/metabolismo , Células Hep G2 , Humanos , Fígado/química , Fígado/metabolismo , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Camundongos , Oxirredução , Espécies Reativas de Oxigênio/química , Espécies Reativas de Oxigênio/metabolismo , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/isolamento & purificação , Espectrometria de Massas em Tandem , Tiorredoxinas/antagonistas & inibidores , Tiorredoxinas/genética , Tiorredoxinas/metabolismo
16.
Aerosp Med Hum Perform ; 89(11): 1002-1004, 2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-30352653

RESUMO

BACKGROUND: In September 2004 a new pilot certificate, sport pilot, was established, which enabled pilots to fly with a valid driver's license in lieu of a valid third-class medical certificate. In 2016 Mills and DeJohn published a paper in which they demonstrated that sport pilots had a higher accident rate than private pilots with Class 3 medical certificates. They concluded that this privilege should not be extended to a broader range of pilots due to the higher accident rate. They failed to investigate why these pilots crashed. This short communication aims to fill that gap.METHODS: The NTSB database was reviewed for the entire period that sport pilot has been available, and reasons for the accidents were determined, both for sport pilots and private pilots with Class 3 medicals.RESULTS: Sport pilot accidents were caused by medical incapacitation 3.7% of the time. Private pilots with Class 3 medicals had accidents that cited medical incapacitation 2.5% of the time.DISCUSSION: Medical incapacitation represents either a probable cause or contributing factor in aviation accidents less than 5% of the time. There is a slightly higher rate of this incapacitation among pilots not receiving regular aeromedical evaluations, but the difference was not statistically significant.Mulvey JR. Aviation accident causes among sport pilots as compared to Class 3 private pilots from 2004-2017. Aerosp Med Hum Perform. 2018; 89(11):1002-1004.


Assuntos
Acidentes Aeronáuticos/estatística & dados numéricos , Medicina Aeroespacial , Certificação , Pilotos/estatística & dados numéricos , Bases de Dados Factuais , Humanos , Pilotos/normas , Estados Unidos
17.
J Mol Cell Cardiol ; 123: 88-91, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30118790

RESUMO

Ischemia-reperfusion (IR) injury occurs when blood supply to an organ is disrupted and then restored, and underlies many disorders, notably myocardial infarction and stroke. While reperfusion of ischemic tissue is essential for survival, it also initiates cell death through generation of mitochondrial reactive oxygen species (ROS). Recent work has revealed a novel pathway underlying ROS production at reperfusion in vivo in which the accumulation of succinate during ischemia and its subsequent rapid oxidation at reperfusion drives ROS production at complex I by reverse electron transport (RET). Pharmacologically inhibiting ischemic succinate accumulation, or slowing succinate metabolism at reperfusion, have been shown to be cardioprotective against IR injury. Here, we determined whether ischemic preconditioning (IPC) contributes to cardioprotection by altering kinetics of succinate accumulation and oxidation during IR. Mice were subjected to a 30-minute occlusion of the left anterior descending coronary artery followed by reperfusion, with or without a protective IPC protocol prior to sustained ischemia. We found that IPC had no effect on ischemic succinate accumulation with both control and IPC mice having profound increases in succinate compared to normoxia. Furthermore, after only 1-minute reperfusion succinate was rapidly metabolised returning to near pre-ischemic levels in both groups. We conclude that IPC does not affect ischemic succinate accumulation, or its oxidation at reperfusion.


Assuntos
Precondicionamento Isquêmico Miocárdico , Traumatismo por Reperfusão Miocárdica/metabolismo , Oxirredução , Ácido Succínico/metabolismo , Análise de Variância , Animais , Modelos Animais de Doenças , Metabolismo Energético , Masculino , Metaboloma , Metabolômica/métodos , Camundongos , Mitocôndrias/metabolismo , Traumatismo por Reperfusão Miocárdica/etiologia , Traumatismo por Reperfusão Miocárdica/patologia , Traumatismo por Reperfusão Miocárdica/prevenção & controle , Miocárdio/metabolismo , Miocárdio/patologia , Espécies Reativas de Oxigênio/metabolismo
18.
Cell Chem Biol ; 24(10): 1285-1298.e12, 2017 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-28890317

RESUMO

Mitochondrial superoxide (O2⋅-) underlies much oxidative damage and redox signaling. Fluorescent probes can detect O2⋅-, but are of limited applicability in vivo, while in cells their usefulness is constrained by side reactions and DNA intercalation. To overcome these limitations, we developed a dual-purpose mitochondrial O2⋅- probe, MitoNeoD, which can assess O2⋅- changes in vivo by mass spectrometry and in vitro by fluorescence. MitoNeoD comprises a O2⋅--sensitive reduced phenanthridinium moiety modified to prevent DNA intercalation, as well as a carbon-deuterium bond to enhance its selectivity for O2⋅- over non-specific oxidation, and a triphenylphosphonium lipophilic cation moiety leading to the rapid accumulation within mitochondria. We demonstrated that MitoNeoD was a versatile and robust probe to assess changes in mitochondrial O2⋅- from isolated mitochondria to animal models, thus offering a way to examine the many roles of mitochondrial O2⋅- production in health and disease.


Assuntos
Mitocôndrias/metabolismo , Sondas Moleculares/metabolismo , Superóxidos/metabolismo , Animais , Transporte Biológico , Linhagem Celular , DNA/química , DNA/metabolismo , Masculino , Espectrometria de Massas , Camundongos , Modelos Moleculares , Sondas Moleculares/química , Conformação de Ácido Nucleico , Oxirredução
19.
Quant Finance ; 16(7): 1053-1067, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-28316507

RESUMO

We propose a new stock selection strategy that exploits rebalancing returns and improves portfolio performance. To effectively harvest rebalancing gains, we apply ideas from elliptical-copula graphical modelling and stability inference to select stocks that are as independent as possible. The proposed elliptical-copula graphical model has a latent Gaussian representation; its structure can be effectively inferred using the regularized rank-based estimators. The resulting algorithm is computationally efficient and scales to large data-sets. To show the efficacy of the proposed method, we apply it to conduct equity selection based on a 16-year health care stock data-set and a large 34-year stock data-set. Empirical tests show that the proposed method is superior to alternative strategies including a principal component analysis-based approach and the classical Markowitz strategy based on the traditional buy-and-hold assumption.

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