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BACKGROUND: Brain injury is a leading cause of morbidity and mortality in patients resuscitated from cardiac arrest. Mitochondrial dysfunction contributes to brain injury following cardiac arrest; therefore, therapies that limit mitochondrial dysfunction have the potential to improve neurological outcomes. Generation of reactive oxygen species (ROS) during ischemia-reperfusion injury in the brain is a critical component of mitochondrial injury and is dependent on hyperactivation of mitochondria following resuscitation. Our previous studies have provided evidence that modulating mitochondrial function with specific near-infrared light (NIR) wavelengths can reduce post-ischemic mitochondrial hyperactivity, thereby reducing brain injury during reperfusion in multiple small animal models. METHODS: Isolated porcine brain cytochrome c oxidase (COX) was used to investigate the mechanism of NIR-induced mitochondrial modulation. Cultured primary neurons from mice expressing mitoQC were utilized to explore the mitochondrial mechanisms related to protection with NIR following ischemia-reperfusion. Anesthetized pigs were used to optimize the delivery of NIR to the brain by measuring the penetration depth of NIR to deep brain structures and tissue heating. Finally, a model of out-of-hospital cardiac arrest with CPR in adult pigs was used to evaluate the translational potential of NIR as a noninvasive therapeutic approach to protect the brain after resuscitation. RESULTS: Molecular evaluation of enzyme activity during NIR irradiation demonstrated COX function was reduced in an intensity-dependent manner with a threshold of enzyme inhibition leading to a moderate reduction in activity without complete inhibition. Mechanistic interrogation in neurons demonstrated that mitochondrial swelling and upregulation of mitophagy were reduced with NIR treatment. NIR therapy in large animals is feasible, as NIR penetrates deep into the brain without substantial tissue heating. In a translational porcine model of CA/CPR, transcranial NIR treatment for two hours at the onset of return of spontaneous circulation (ROSC) demonstrated significantly improved neurological deficit scores and reduced histologic evidence of brain injury after resuscitation from cardiac arrest. CONCLUSIONS: NIR modulates mitochondrial function which improves mitochondrial dynamics and quality control following ischemia/reperfusion. Noninvasive modulation of mitochondria, achieved by transcranial treatment of the brain with NIR, mitigates post-cardiac arrest brain injury and improves neurologic functional outcomes.
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Lesiones Encefálicas , Reanimación Cardiopulmonar , Enfermedades Mitocondriales , Paro Cardíaco Extrahospitalario , Humanos , Ratones , Animales , Porcinos , Mitocondrias , Isquemia , Modelos Animales de EnfermedadRESUMEN
NEW FINDINGS: What is the topic of this review? Remote ischaemic preconditioning (RIPC) and hypoxic preconditioning as novel therapeutic approaches for cardiac and neuroprotection. What advances does it highlight? There is improved understanding of mechanisms and signalling pathways associated with ischaemic and hypoxic preconditioning, and potential pitfalls with application of these therapies to clinical trials have been identified. Novel adaptations of preconditioning paradigms have also been developed, including intermittent hypoxia training, RIPC training and RIPC-exercise, extending their utility to chronic settings. ABSTRACT: Myocardial infarction and stroke remain leading causes of death worldwide, despite extensive resources directed towards developing effective treatments. In this Symposium Report we highlight the potential applications of intermittent ischaemic and hypoxic conditioning protocols to combat the deleterious consequences of heart and brain ischaemia. Insights into mechanisms underlying the protective effects of intermittent hypoxia training are discussed, including the activation of hypoxia-inducible factor-1 and Nrf2 transcription factors, synthesis of antioxidant and ATP-generating enzymes, and a shift in microglia from pro- to anti-inflammatory phenotypes. Although there is little argument regarding the efficacy of remote ischaemic preconditioning (RIPC) in pre-clinical models, this strategy has not consistently translated into the clinical arena. This lack of translation may be related to the patient populations targeted thus far, and the anaesthetic regimen used in two of the major RIPC clinical trials. Additionally, we do not fully understand the mechanism through which RIPC protects the vital organs, and co-morbidities (e.g. hypercholesterolemia, diabetes) may interfere with its efficacy. Finally, novel adaptations have been made to extend RIPC to more chronic settings. One adaptation is RIPC-exercise (RIPC-X), an innovative paradigm that applies cyclical RIPC to blood flow restriction exercise (BFRE). Recent findings suggest that this novel exercise modality attenuates the exaggerated haemodynamic responses that may limit the use of conventional BFRE in some clinical settings. Collectively, intermittent ischaemic and hypoxic conditioning paradigms remain an exciting frontier for the protection against ischaemic injuries.
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Encéfalo/fisiopatología , Corazón/fisiopatología , Hipoxia/fisiopatología , Infarto del Miocardio/fisiopatología , Accidente Cerebrovascular/fisiopatología , Animales , Ejercicio Físico/fisiología , Hemodinámica/fisiología , Humanos , Precondicionamiento Isquémico/métodosRESUMEN
Myocardial infarction is a prevalent major cardiovascular event that arises from myocardial ischemia with or without reperfusion, and basic and translational research is needed to better understand its underlying mechanisms and consequences for cardiac structure and function. Ischemia underlies a broad range of clinical scenarios ranging from angina to hibernation to permanent occlusion, and while reperfusion is mandatory for salvage from ischemic injury, reperfusion also inflicts injury on its own. In this consensus statement, we present recommendations for animal models of myocardial ischemia and infarction. With increasing awareness of the need for rigor and reproducibility in designing and performing scientific research to ensure validation of results, the goal of this review is to provide best practice information regarding myocardial ischemia-reperfusion and infarction models. Listen to this article's corresponding podcast at ajpheart.podbean.com/e/guidelines-for-experimental-models-of-myocardial-ischemia-and-infarction/.
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Investigación Biomédica/normas , Cardiología/normas , Infarto del Miocardio , Isquemia Miocárdica , Publicaciones Periódicas como Asunto/normas , Fisiología/normas , Animales , Células Cultivadas , Consenso , Exactitud de los Datos , Modelos Animales de Enfermedad , Preparación de Corazón Aislado/normas , Ratones , Infarto del Miocardio/metabolismo , Infarto del Miocardio/patología , Infarto del Miocardio/fisiopatología , Isquemia Miocárdica/metabolismo , Isquemia Miocárdica/patología , Isquemia Miocárdica/fisiopatología , Miocardio/metabolismo , Miocardio/patología , Control de CalidadRESUMEN
Remote ischemic preconditioning (RIPC), the phenomenon whereby brief ischemic episodes in distant tissues or organs render the heart resistant to infarction, has been exhaustively demonstrated in preclinical models. Moreover, emerging evidence suggests that exosomes play a requisite role in conveying the cardioprotective signal from remote tissue to the myocardium. However, in cohorts displaying clinically common comorbidities-in particular, type-2 diabetes-the infarct-sparing effect of RIPC may be confounded for as-yet unknown reasons. To investigate this issue, we used an integrated in vivo and in vitro approach to establish whether: (1) the efficacy of RIPC is maintained in the Zucker fatty rat model of type-2 diabetes, (2) the humoral transfer of cardioprotective triggers initiated by RIPC are transported via exosomes, and (3) diabetes is associated with alterations in exosome-mediated communication. We report that a standard RIPC stimulus (four 5-min episodes of hindlimb ischemia) reduced infarct size in normoglycemic Zucker lean rats, but failed to confer protection in diabetic Zucker fatty animals. Moreover, we provide novel evidence, via transfer of serum and serum fractions obtained following RIPC and applied to HL-1 cardiomyocytes subjected to hypoxia-reoxygenation, that diabetes was accompanied by impaired humoral communication of cardioprotective signals. Specifically, our data revealed that serum and exosome-rich serum fractions collected from normoglycemic rats attenuated hypoxia-reoxygenation-induced HL-1 cell death, while, in contrast, exosome-rich samples from Zucker fatty rats did not evoke protection in the HL-1 cell model. Finally, and unexpectedly, we found that exosome-depleted serum from Zucker fatty rats was cytotoxic and exacerbated hypoxia-reoxygenation-induced cardiomyocyte death.
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Diabetes Mellitus Tipo 2/terapia , Exosomas/metabolismo , Miembro Posterior/irrigación sanguínea , Precondicionamiento Isquémico/métodos , Infarto del Miocardio/prevención & control , Miocitos Cardíacos/metabolismo , Transducción de Señal , Animales , Muerte Celular , Línea Celular , Diabetes Mellitus Tipo 2/sangre , Diabetes Mellitus Tipo 2/patología , Diabetes Mellitus Tipo 2/fisiopatología , Modelos Animales de Enfermedad , Exosomas/patología , Masculino , Infarto del Miocardio/sangre , Infarto del Miocardio/patología , Infarto del Miocardio/fisiopatología , Miocitos Cardíacos/patología , Ratas Zucker , Flujo Sanguíneo RegionalRESUMEN
OBJECTIVE: Unlike currently approved adenosine diphosphate receptor antagonists, the new diadenosine tetraphosphate derivative GLS-409 targets not only P2Y12 but also the second human platelet adenosine diphosphate receptor P2Y1 and may, therefore, be a promising antiplatelet drug candidate. The current study is the first to investigate the in vivo antithrombotic effects of GLS-409. APPROACH AND RESULTS: We studied (1) the in vivo effects of GLS-409 on agonist-stimulated platelet aggregation in anesthetized rats, (2) the antithrombotic activity of GLS-409 and the associated effect on the bleeding time in a canine model of platelet-mediated coronary artery thrombosis, and (3) the inhibition of agonist-stimulated platelet aggregation by GLS-409 versus selective P2Y1 and P2Y12 inhibition in vitro in samples from healthy human subjects before and 2 hours after aspirin intake. In vivo treatment with GLS-409 significantly inhibited adenosine diphosphate- and collagen-stimulated platelet aggregation in rats. Further, GLS-409 attenuated cyclic flow variation, that is, platelet-mediated thrombosis, in vivo in our canine model of unstable angina. The improvement in coronary patency was accompanied by a nonsignificant 30% increase in bleeding time. Of note, GLS-409 exerted its effects without affecting rat and canine hemodynamics. Finally, in vitro treatment with GLS-409 showed effects similar to that of cangrelor and the combination of cangrelor with the selective P2Y1 inhibitor MRS 2179 on agonist-stimulated platelet aggregation in human platelet-rich plasma and whole blood before and 2 hours after aspirin intake. CONCLUSIONS: Synergistic inhibition of both P2Y1 and P2Y12 adenosine diphosphate receptors by GLS-409 immediately attenuates platelet-mediated thrombosis and effectively blocks agonist-stimulated platelet aggregation irrespective of concomitant aspirin therapy.
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Plaquetas/efectos de los fármacos , Trombosis Coronaria/tratamiento farmacológico , Fosfatos de Dinucleósidos/farmacología , Fibrinolíticos/farmacología , Inhibidores de Agregación Plaquetaria/farmacología , Agregación Plaquetaria/efectos de los fármacos , Antagonistas del Receptor Purinérgico P2Y/farmacología , Receptores Purinérgicos P2Y12/efectos de los fármacos , Receptores Purinérgicos P2Y1/efectos de los fármacos , Adenosina Difosfato/análogos & derivados , Adenosina Difosfato/farmacología , Adenosina Monofosfato/análogos & derivados , Adenosina Monofosfato/farmacología , Adulto , Animales , Aspirina/farmacología , Coagulación Sanguínea/efectos de los fármacos , Plaquetas/metabolismo , Trombosis Coronaria/sangre , Modelos Animales de Enfermedad , Perros , Relación Dosis-Respuesta a Droga , Femenino , Humanos , Masculino , Pruebas de Función Plaquetaria , Ratas Sprague-Dawley , Receptores Purinérgicos P2Y1/sangre , Receptores Purinérgicos P2Y12/sangre , Factores de Tiempo , Adulto JovenRESUMEN
BACKGROUND: Rapid and accurate diagnosis of patients presenting with symptoms of stroke is needed to facilitate the timely delivery of proven effective treatment for patients with acute ischemic stroke (AIS). The aim of this study was to determine whether early assessment of platelet reactivity in patients presenting with symptoms of AIS was associated with a diagnosis of AIS, transient ischemic attack (TIA), or stroke mimic. METHODS: This prospective study included patients with symptoms of AIS treated at an inner-city emergency department (ED). Blood samples were obtained and assayed for platelet reactivity (quantified by closure time). Patients were grouped by discharge diagnosis into: AIS, TIA, or stroke mimic. Binary logistic regression model was used to predict the association of closure time with the final diagnosis of 1) either AIS or TIA or, 2) stroke mimic. RESULTS: Of 114 patients enrolled, 32 were diagnosed with AIS, 33 TIA, and 49 were diagnosed as a stroke mimic. There was no significant difference in closure times among patients with a diagnosis of AIS or TIA versus stroke mimic. A history of migraines and history of seizures were independently associated with lower odds of an AIS or TIA diagnosis (OR 0.31, 95% CI 0.10 to 0.94 and OR 0.08, 95% CI 0.01 to 0.88, respectively). CONCLUSION: Closure time was not found to be a clinically reliable differentiator of patients with a diagnosis of AIS, TIA, or stroke mimic in the ED.
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Servicio de Urgencia en Hospital , Pruebas de Función Plaquetaria/instrumentación , Sistemas de Atención de Punto , Accidente Cerebrovascular/diagnóstico , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Plaquetas , Femenino , Humanos , Masculino , Persona de Mediana Edad , Activación Plaquetaria , Guías de Práctica Clínica como Asunto , Estudios Prospectivos , Reproducibilidad de los Resultados , Adulto JovenRESUMEN
Global brain ischemia/reperfusion induces neuronal damage in vulnerable brain regions, leading to mitochondrial dysfunction and subsequent neuronal death. Induction of neuronal death is mediated by release of cytochrome c (cyt c) from the mitochondria though a well-characterized increase in outer mitochondrial membrane permeability. However, for cyt c to be released it is first necessary for cyt c to be liberated from the cristae junctions which are gated by Opa1 oligomers. Opa1 has two known functions: maintenance of the cristae junction and mitochondrial fusion. These roles suggest that Opa1 could play a central role in both controlling cyt c release and mitochondrial fusion/fission processes during ischemia/reperfusion. To investigate this concept, we first utilized in vitro real-time imaging to visualize dynamic changes in mitochondria. Oxygen-glucose deprivation (OGD) of neurons grown in culture induced a dual-phase mitochondrial fragmentation profile: (i) fragmentation during OGD with no apoptosis activation, followed by fusion of mitochondrial networks after reoxygenation and a (ii) subsequent extensive fragmentation and apoptosis activation that preceded cell death. We next evaluated changes in mitochondrial dynamic state during reperfusion in a rat model of global brain ischemia. Evaluation of mitochondrial morphology with confocal and electron microscopy revealed a similar induction of fragmentation following global brain ischemia. Mitochondrial fragmentation aligned temporally with specific apoptotic events, including cyt c release, caspase 3/7 activation, and interestingly, release of the fusion protein Opa1. Moreover, we uncovered evidence of loss of Opa1 complexes during the progression of reperfusion, and electron microscopy micrographs revealed a loss of cristae architecture following global brain ischemia. These data provide novel evidence implicating a temporal connection between Opa1 alterations and dysfunctional mitochondrial dynamics following global brain ischemia.
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Isquemia Encefálica/metabolismo , Dinámicas Mitocondriales , Daño por Reperfusión/metabolismo , Animales , Apoptosis , Región CA1 Hipocampal/irrigación sanguínea , Región CA1 Hipocampal/metabolismo , Hipoxia de la Célula , Línea Celular , Células Cultivadas , GTP Fosfohidrolasas/metabolismo , Masculino , Ratones , Mitocondrias/metabolismo , Mitocondrias/ultraestructura , Ratas , Ratas Sprague-DawleyRESUMEN
Recent attention has focused on the concept that mitochondrial dynamics-that is, the balance between mitochondrial fusion and fission (fragmentation)-may play a pivotal role in determining cell fate in the setting of myocardial ischemia-reperfusion injury. In this regard, there is an emerging consensus that: (1) ischemia-reperfusion favors mitochondrial fragmentation and (2) strategies aimed at inhibiting the translocation of dynamin-related protein 1 (DRP1: the 'master regulator' of fission) from the cytosol to the mitochondria, when initiated as a pretreatment, are cardioprotective. However, direct molecular evidence of a cause-and-effect relationship between mitochondrial fission and cardiomyocyte death has not been established. To address this issue, we used a well-characterized in vitro, immortal cultured cardiomyocyte model to establish whether subcellular redistribution of DRP1 to mitochondria: (1) is triggered by hypoxia-reoxygenation; (2) plays a causal role in hypoxia-reoxygenation-induced cytochrome c release (harbinger of apoptosis) and cardiomyocyte death; and (3) represents a molecular mechanism that can be targeted in a clinically relevant time frame to render cells resistant to lethal hypoxia-reoxygenation injury. Our results provide direct evidence that the redistribution of DRP1 to mitochondria contributes to cardiomyocyte death, and corroborate the previous observations that the pre-ischemic inhibition of DRP1 translocation is cardioprotective. Moreover, we report the novel finding that-in marked contrast to the data obtained with pretreatment-inhibition of DRP1 translocation initiated at the time of reoxygenation had complex, unexpected and unfavorable consequences: i.e., attenuated cardiomyocyte apoptosis but exacerbated total cell death, possibly via concurrent upregulation of necroptosis.
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Dinaminas/metabolismo , Dinámicas Mitocondriales/fisiología , Daño por Reperfusión Miocárdica/metabolismo , Daño por Reperfusión Miocárdica/fisiopatología , Miocitos Cardíacos/patología , Animales , Muerte Celular , Técnicas de Silenciamiento del Gen , Ratones , Miocitos Cardíacos/metabolismo , Transporte de Proteínas/fisiologíaRESUMEN
To commemorate the auspicious occasion of the 30th anniversary of IPC, leading pioneers in the field of cardioprotection gathered in Barcelona in May 2016 to review and discuss the history of IPC, its evolution to IPost and RIC, myocardial reperfusion injury as a therapeutic target, and future targets and strategies for cardioprotection. This article provides an overview of the major topics discussed at this special meeting and underscores the huge importance and impact, the discovery of IPC has made in the field of cardiovascular research.
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Precondicionamiento Isquémico Miocárdico , Daño por Reperfusión Miocárdica , Animales , HumanosRESUMEN
Although there is a growing interest in the molecular cross-talk between the endocrine and cardiovascular systems, the cardiac effects of calcium-regulating hormones (i.e., parathyroid hormone-related peptide (PTHrP)) have not been explored. In this study, we examined the effect of PTHrP on the viability of isolated adult mouse cardiomyocytes subjected to oxidative stress. Myocytes from 19 to 22 week old male 129J/C57BL6 mice were exposed to oxidative insult in the form of H2O2 which led to more than 70% loss of cell viability. Herein we demonstrate, for the first time, that pretreatment with 100 nM PTHrP prior to 100 µM H2O2 incubation prevents H2O2 -induced cell death by more than 50%. Immunoblot analysis revealed H2O2 induction of MKP-1 protein expression while PTHrP decreased MKP-1 expression. Moreover, myocytes derived from MKP1 KO mice were resistant to oxidative injury. No added benefit of PTHrP treatment was noted in MKP-1 null cardiomyocytes. Using specific pharmacological inhibitors we demonstrated that P-p38, P-ERK and P-AKT mediated PTHrP's cardioprotective action. These data provide novel evidence that: i) down-regulation of MKP1 affords profound protection against oxidative stress; and ii) PTHrP is cardioprotective, possibly via down-regulation of MKP-1 and activation of MAPK and PI3K/AKT signaling.
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Miocitos Cardíacos/citología , Miocitos Cardíacos/metabolismo , Estrés Oxidativo , Proteína Relacionada con la Hormona Paratiroidea/metabolismo , Animales , Muerte Celular , Células Cultivadas , Fosfatasa 1 de Especificidad Dual/genética , Fosfatasa 1 de Especificidad Dual/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Fosfatidilinositol 3-Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Transducción de SeñalRESUMEN
Myocardial conditioning is an endogenous cardioprotective phenomenon that profoundly limits infarct size in experimental models. The current challenge is to translate this paradigm from the laboratory to the clinic. Accordingly, our goal in this review is to provide a critical summary of the progress toward, opportunities for, and caveats to, the successful clinical translation of postconditioning and remote conditioning, the 2 conditioning strategies considered to have the broadest applicability for real-world patient care. In the majority of phase II studies published to date, postconditioning evoked a ≈35% reduction of infarct size in ST-segment-elevation myocardial infarction patients. Essential criteria for the successful implementation of postconditioning include the appropriate choice of patients (ie, those with large risk regions and negligible collateral flow), timely application of the postconditioning stimulus (immediately on reperfusion), together with proper choice of end points (infarct size, with concomitant assessment of risk region). Remote conditioning has been applied in planned ischemic events (including cardiac surgery and elective percutaneous coronary intervention) and in ST-segment-elevation myocardial infarction patients during hospital transport. Controversies with regard to efficacy have emerged, particularly among surgical trials. These disparate outcomes in all likelihood reflect the remarkable heterogeneity within and among studies, together with a deficit in our understanding of the impact of these variations on the infarct-sparing effect of remote conditioning. Ongoing phase III trials will provide critical insight into the future role of postconditioning and remote conditioning as clinically relevant cardioprotective strategies.
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Precondicionamiento Isquémico Miocárdico/tendencias , Infarto del Miocardio/prevención & control , Investigación Biomédica Traslacional/tendencias , Animales , Ensayos Clínicos Fase II como Asunto , Ensayos Clínicos Fase III como Asunto , Modelos Animales de Enfermedad , Humanos , Factores de TiempoRESUMEN
A wealth of evidence has revealed that the heart can be "conditioned" and rendered less vulnerable to ischemia-reperfusion injury via the upregulation of endogenous protective signaling pathways. Three distinct conditioning strategies have been identified: (1) preconditioning, the phenomenon where brief episodes of myocardial ischemia (too brief to cause cardiomyocyte death) limit necrosis caused by a subsequent sustained ischemic insult; (2) postconditioning, the concept that relief of myocardial ischemia in a staged or stuttered manner attenuates lethal ischemia-reperfusion injury; and (3) remote conditioning, or upregulation of a cardioprotective phenotype initiated by ischemia in a remote organ or tissue and "transported" to the heart. Progress has been made in defining the technical requirements and limitations of each of the 3 ischemic conditioning models (including the timing and severity of the protective stimulus), as well as elucidating the molecular mechanisms (in particular, the receptor-mediated signaling pathways) responsible for conditioning-induced myocardial protection. Moreover, phase III clinical trials are in progress, seeking to capitalize on the protection that can be achieved by postconditioning and remote conditioning, and applying these strategies in patients undergoing cardiac surgery or angioplasty for the treatment of acute myocardial infarction. There is, however, a potentially important caveat to the clinical translation of myocardial conditioning: emerging data suggest that the efficacy of ischemic conditioning is compromised in aging, diabetic, and hypertensive cohorts, the specific populations in which myocardial protection is most relevant. Successful clinical application of myocardial conditioning will therefore require an understanding of the potential confounding consequences of these comorbidities on the "conditioned" phenotype.
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Precondicionamiento Isquémico Miocárdico/métodos , Infarto del Miocardio/patología , Infarto del Miocardio/prevención & control , Miocardio/patología , Animales , Humanos , Infarto del Miocardio/fisiopatología , Isquemia Miocárdica/patología , Isquemia Miocárdica/fisiopatología , Isquemia Miocárdica/prevención & controlRESUMEN
BACKGROUND: A relative shortage of pediatric neurologists in proportion to estimated neurological disorders often results in general pediatricians evaluating and treating children with complex neurological conditions. Dedicated rotations in pediatric neurology are not mandated during medical school or pediatric residency. We evaluated the perceptions of a large cohort of pediatric residents and program directors (PDs) regarding child neurology training. METHODS: Using an online tool, surveys were sent to pediatric residents and pediatric and pediatric neurology PDs. RESULTS: Response rates were 41% from pediatric residency programs, yielding 538 resident responses; 31% from pediatric PDs; and 62% from pediatric neurology PDs. Only 27% of the surveyed residents reported completing a neurology rotation during residency, 89% of whom expressed a subjective improvement in confidence with neurological assessments. Factors affecting comfort with eliciting a neurological history included exposure to a neurology rotation during residency, year of training, duration of neurology rotation in medical school, and inpatient exposure to neurological patients, whereas those associated with examination additionally included program size and postresidency plans. Overall, 80% of surveyed residents, 78% of pediatric PDs, and 96% of pediatric neurology PDs acknowledged the potential value of a mandatory pediatric neurology rotation during residency. CONCLUSION: We suggest that a mandatory pediatric neurology rotation will boost the confidence of current and future pediatric trainees in assessing common neurological conditions of childhood.
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Internado y Residencia , Neurología , Humanos , Niño , Estados Unidos , Educación de Postgrado en Medicina , Neurología/educación , Neurólogos , Curriculum , Encuestas y CuestionariosRESUMEN
Parathyroid hormone-related peptide (PTHrP) is well-known to play a role in bone formation, and abaloparatide, an analog of PTHrP(1-34), is approved for the treatment of osteoporosis in post-menopausal women. PTHrP has also been reported to have cardiovascular effects, with recent data demonstrating that exogenously administered PTHrP can limit the death of isolated cardiomyocytes subjected to oxidative stress via upregulation of classic 'survival kinase' signaling. Our aim in the current study was to extend this concept and, employing both in vitro and in vivo models, establish whether PTHrP(1-36) and abaloparatide are cardioprotective in the setting of lethal myocardial ischemia-reperfusion injury. We report that preischemic administration of PTHrP(1-36) and abaloparatide attenuated cell death in HL-1 cardiomyocytes subjected to simulated ischemia-reperfusion, an effect that was accompanied by the augmented expression of phospho-ERK and improved preservation of phospho-Akt, and blocked by co-administration of the MEK-ERK inhibitor PD98059. Moreover, using the translationally relevant swine model of acute coronary artery occlusion-reperfusion, we make the novel observation that myocardial infarct size was significantly reduced in pigs pretreated with PTHrP(1-36) when compared with placebo-controls (13.1 ± 3.3% versus 42.0 ± 6.6% of the area of at-risk myocardium, respectively; p < 0.01). Taken together, these data provide the first evidence in support of the concept that pretreatment with PTHrP(1-36) and abaloparatide renders cardiomyocytes resistant to lethal myocardial ischemia-reperfusion injury.
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Disruption of mitochondrial structure/function is well-recognized to be a determinant of cell death in cardiomyocytes subjected to lethal episodes of ischemia-reperfusion (IR). However, the precise mitochondrial event(s) that precipitate lethal IR injury remain incompletely resolved. Using the in vitro HL-1 cardiomyocyte model, our aims were to establish whether: (1) proteolytic processing of optic atrophy protein-1 (OPA1), the inner mitochondrial membrane protein responsible for maintaining cristae junction integrity, plays a causal, mechanistic role in determining cardiomyocyte fate in cells subjected to lethal IR injury; and (2) preservation of OPA1 may contribute to the well-documented cardioprotection achieved with ischemic preconditioning (IPC) and remote ischemic conditioning. We report that HL-1 cells subjected to 2.5 h of simulated ischemia displayed increased activity of OMA1 (the metalloprotease responsible for proteolytic processing of OPA1) during the initial 45 min following reoxygenation. This was accompanied by processing of mitochondrial OPA1 (i.e., cleavage to yield short-OPA1 peptides) and release of short-OPA1 into the cytosol. However, siRNA-mediated knockdown of OPA1 content did not exacerbate lethal IR injury, and did not attenuate the cardioprotection seen with IPC and a remote preconditioning stimulus, achieved by transfer of 'reperfusate' medium (TRM-IPC) in this cell culture model. Taken together, our results do not support the concept that maintenance of OPA1 integrity plays a mechanistic role in determining cell fate in the HL-1 cardiomyocyte model of lethal IR injury, or that preservation of OPA1 underlies the cardioprotection seen with ischemic conditioning.
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Atrofia Óptica , Daño por Reperfusión , Muerte Celular , GTP Fosfohidrolasas/metabolismo , Humanos , Isquemia/metabolismo , Metaloproteasas/metabolismo , Miocitos Cardíacos/metabolismo , Atrofia Óptica/metabolismo , ARN Interferente Pequeño/metabolismo , Daño por Reperfusión/metabolismoRESUMEN
BACKGROUND: Emerging evidence suggests that "adaptive" induction of autophagy (the cellular process responsible for the degradation and recycling of proteins and organelles) may confer a cardioprotective phenotype and represent a novel strategy to limit ischemia-reperfusion injury. Our aim was to test this paradigm in a clinically relevant, large animal model of acute myocardial infarction. METHODS AND RESULTS: Anesthetized pigs underwent 45 minutes of coronary artery occlusion and 3 hours of reperfusion. In the first component of the study, pigs received chloramphenicol succinate (CAPS) (an agent that purportedly upregulates autophagy; 20 mg/kg) or saline at 10 minutes before ischemia. Infarct size was delineated by tetrazolium staining and expressed as a % of the at-risk myocardium. In separate animals, myocardial samples were harvested at baseline and 10 minutes following CAPS treatment and assayed (by immunoblotting) for 2 proteins involved in autophagosome formation: Beclin-1 and microtubule-associated protein light chain 3-II. To investigate whether the efficacy of CAPS was maintained with "delayed" treatment, additional pigs received CAPS (20 mg/kg) at 30 minutes after occlusion. Expression of Beclin-1 and microtubule-associated protein light chain 3-II, as well as infarct size, were assessed at end-reperfusion. CAPS was cardioprotective: infarct size was 25±5 and 41±4%, respectively, in the CAPS-pretreated and CAPS-delayed treatment groups versus 56±5% in saline controls (P<0.01 and P<0.05 versus control). Moreover, administration of CAPS was associated with increased expression of both proteins. CONCLUSIONS: Our results demonstrate attenuation of ischemia-reperfusion injury with CAPS and are consistent with the concept that induction of autophagy may provide a novel strategy to confer cardioprotection.
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Cardiotónicos/farmacología , Cloranfenicol/análogos & derivados , Infarto del Miocardio/prevención & control , Daño por Reperfusión Miocárdica/prevención & control , Miocardio/metabolismo , Animales , Antibacterianos/farmacología , Proteínas Reguladoras de la Apoptosis/metabolismo , Autofagia/efectos de los fármacos , Cloranfenicol/farmacología , Manejo de la Enfermedad , Femenino , Regulación de la Expresión Génica/efectos de los fármacos , Humanos , Masculino , Proteínas Asociadas a Microtúbulos/biosíntesis , Infarto del Miocardio/metabolismo , Infarto del Miocardio/patología , Daño por Reperfusión Miocárdica/metabolismo , Daño por Reperfusión Miocárdica/patología , Miocardio/patología , PorcinosRESUMEN
Contrast medium administration during imaging and therapeutic procedures can cause renal injury, partly due to ischemia. Therefore, we hypothesized that brief ischemia and reperfusion episodes applied at a distant site - multiple balloon inflations and deflations during angioplasty - may serve as a remote-conditioning (RC) stimulus and thereby protect against contrast-induced kidney injury. To test this hypothesis, we (1) utilized cases from a prior study in which patients undergoing emergent angioplasty for ST segment elevation myocardial infarction received either 1-3 balloon inflations (controls) or were 'conditioned' with multiple (≥4) inflations, and (2) assessed renal function for 3 days in patients with an estimated glomerular filtration rate (eGFR) of <90 ml/min/1.73 m(2) prior to revascularization (mild kidney disease). Both groups displayed increased eGFR at day 1 after angioplasty versus baseline; attributed to in-hospital hydration (control: 77 ± 14 vs. 68 ± 12 ml/min/1.73 m(2); p < 0.01; RC: 81 ± 21 vs. 69 ± 12 ml/min/1.73 m(2); p < 0.01). In controls, this improvement was transient: eGFR subsequently decreased to 70 ± 14 ml/min/1.73 m(2) at day 3 (p < 0.05). In contrast, the RC group (despite receiving 25% more contrast volume) showed no functional decline at day 3 (80 ± 14 ml/min/1.73 m(2)). These results are consistent with remote ischemic conditioning providing a novel potential approach to attenuate contrast-associated renal injury.
Asunto(s)
Lesión Renal Aguda/prevención & control , Angioplastia Coronaria con Balón/efectos adversos , Medios de Contraste/efectos adversos , Precondicionamiento Isquémico Miocárdico/métodos , Infarto del Miocardio/diagnóstico por imagen , Infarto del Miocardio/terapia , Lesión Renal Aguda/inducido químicamente , Anciano , Análisis de Varianza , Angioplastia Coronaria con Balón/métodos , Nitrógeno de la Urea Sanguínea , Cateterismo Cardíaco/métodos , Estudios de Cohortes , Creatinina/sangre , Electrocardiografía/métodos , Urgencias Médicas , Femenino , Tasa de Filtración Glomerular , Humanos , Pruebas de Función Renal , Masculino , Persona de Mediana Edad , Pronóstico , Radiografía , Valores de Referencia , Estudios Retrospectivos , Medición de Riesgo , Tasa de Supervivencia , Resultado del TratamientoRESUMEN
Mitochondrial dynamics and mitophagy are constitutive and complex systems that ensure a healthy mitochondrial network through the segregation and subsequent degradation of damaged mitochondria. Disruption of these systems can lead to mitochondrial dysfunction and has been established as a central mechanism of ischemia/reperfusion (I/R) injury. Emerging evidence suggests that mitochondrial dynamics and mitophagy are integrated systems; however, the role of this relationship in the context of I/R injury remains unclear. To investigate this concept, we utilized primary cortical neurons isolated from the novel dual-reporter mitochondrial quality control knockin mice (C57BL/6-Gt(ROSA)26Sortm1(CAG-mCherry/GFP)Ganl/J) with conditional knockout (KO) of Drp1 to investigate changes in mitochondrial dynamics and mitophagic flux during in vitro I/R injury. Mitochondrial dynamics was quantitatively measured in an unbiased manner using a machine learning mitochondrial morphology classification system, which consisted of four different classifications: network, unbranched, swollen, and punctate. Evaluation of mitochondrial morphology and mitophagic flux in primary neurons exposed to oxygen-glucose deprivation (OGD) and reoxygenation (OGD/R) revealed extensive mitochondrial fragmentation and swelling, together with a significant upregulation in mitophagic flux. Furthermore, the primary morphology of mitochondria undergoing mitophagy was classified as punctate. Colocalization using immunofluorescence as well as western blot analysis revealed that the PINK1/Parkin pathway of mitophagy was activated following OGD/R. Conditional KO of Drp1 prevented mitochondrial fragmentation and swelling following OGD/R but did not alter mitophagic flux. These data provide novel evidence that Drp1 plays a causal role in the progression of I/R injury, but mitophagy does not require Drp1-mediated mitochondrial fission.