Remote Preconditioning: Evaluating The Efficacy Of Cardioprotection In Type-2 Diabetes And Exploring The Mechanistic Role Of Exosomes

Remote preconditioning is a promising and robust treatment for myocardial ischemia/reperfusion injury that evokes cardioprotection through endogenous neural and/or humoral signaling. A recent study has reported that protective signaling is mediated by exosomes through the circulation; however this concept is supported by limited and inconsistent evidence. Despite overwhelming success in preclinical studies, the efficacy of remote preconditioning in human studies is inconclusive. Importantly, the majority of remote preconditioning studies use healthy animal models despite growing evidence that comorbidities, such as type-2 diabetes, may negatively influence outcomes. Nonetheless, the efficacy of remote preconditioning in the setting of type-2 diabetes has not been investigated. Using an established model of myocardial ischemia/reperfusion in the Zucker model of type-2 diabetes and a model of hypoxia/reoxygenation in cultured HL-1 cardiomyocytes we tested four hypotheses: i. remote preconditioning is ineffective in early-stage type-2 diabetes in vivo; ii. the traditional ultracentrifugation technique for exosomes isolating is inadequate to isolate protective factor(s) from remote preconditioning; iii. enhanced ultracentrifugation technique for exosome isolation sequesters a protective fraction of serum; iv. the humoral component of remote preconditioning is defective in type-2 diabetes. In support of Hypothesis I, we demonstrate that remote preconditioning failed to reduce infarct size caused by ischemia/reperfusion in the Zucker model of early-stage type-2 diabetes. Our results illustrate that the loss in efficacy is not the result of hyperglycemia per se nor sensitization of the myocardium to ischemia/reperfusion. Subsequently, we sought to isolate a subfraction of serum from remote preconditioned rats which contained exosomes that could communicate protection and render HL-1 cardiomyocytes resistant to hypoxia/reoxygenation-induced cell death. In agreement with Hypothesis II, we report that the traditional ultracentrifugation isolation technique (100,000 xg for 2 hr) did not isolate the protective component with the exosome-rich pellet from serum, suggesting that the protective component remained in the supernatant. In accordance with these observations, we enhanced the ultracentrifugation technique to improve exosome sedimentation and obtain a protective sub-fraction of serum. In agreement with Hypothesis III, the enhanced ultracentrifugation technique (300,000 xg for 12 hr) isolated a protective exosome-rich supernatant fraction from remote preconditioned serum. However, our enhanced ultracentrifugation technique also yielded an additional, exosome-rich pellet and an exosome-depleted fraction, neither of which evoked protection. Lastly, in support of Hypothesis IV, we demonstrate that unfractionated serum and the exosome-rich supernatant fraction obtained from remote preconditioned diabetic Zucker Fatty rats did not protect HL-1 cardiomyocytes from hypoxia/reoxygenation. In conclusion, our results illustrate for the first time that the infarct-sparing efficacy of remote preconditioning is abolished in the setting of early-stage type-2 diabetes. We demonstrate that exosomes, although not sufficient for protection, may be requisite in the humoral component of remote preconditioning. Finally, we report that the humoral component of remote preconditioning is defective in the setting of type-2 diabetes – a defect that may contribute to the failure of remote conditioning to limit infarct size in this comorbid model

Administration of Intranasal Insulin During Cardiopulmonary Resuscitation Improves Neurological Outcomes After Cardiac Arrest

INTRODUCTION: Over 325,000 people die from cardiac arrest each year. Prognosis is poor and survivors typically experience persistent neurologic deficits. Currently, neuroprotective treatments to reduce brain injury in cardiac arrest survivors are limited and ineffective. This study evaluates the potential neuroprotection induced by high dose intranasal insulin (HD-IN-I) in a rodent model of asphyxial cardiac arrest. METHODS: Male Long Evans rats were block randomized to sham-operated controls or 8-minute asphyxial cardiac arrest treated with placebo or HD-IN-I at the onset of CPR. To investigate mechanism of action, hippocampi were collected 30 minutes post-ROSC and analyzed by Western blot for phosphorylation of Akt. To assess long-term functional outcomes, neurobehavioral evaluation was conducted using neurologic function scores daily and Barnes maze, Rotarod, and passive avoidance on days 7-10 post-ROSC. Histologic quantification of surviving hippocampal CA1 pyramidal neurons was also conducted. RESULTS: Hippocampal phospho-Akt/total Akt ratio increased 2-fold in the placebo group and 5.7-fold in HD-IN-I group relative to shams (p \u3c 0.05). Rats treated with HD-IN-I had significantly improved performance on Rotarod, Barnes maze, and passive avoidance (p \u3c 0.05). HD-IN-I had no significant effect on ROSC rate, 10-day survival, systemic glycemic response, or on the number of surviving CA1 pyramidal neurons compared to placebo treatment. DISCUSSION: This study is the first to demonstrate that HD-IN-I administered at the onset of CPR, causes phosphorylation of brain Akt and results in significant neuroprotection. This primary work strongly suggests that intranasal insulin could be the first highly effective neuroprotective treatment for cardiac arrest patients

Mitochondrial Quality Control: Role in Cardiac Models of Lethal Ischemia-Reperfusion Injury

The current standard of care for acute myocardial infarction or ‘heart attack’ is timely restoration of blood flow to the ischemic region of the heart. While reperfusion is essential for the salvage of ischemic myocardium, re-introduction of blood flow paradoxically kills (rather than rescues) a population of previously ischemic cardiomyocytes—a phenomenon referred to as ‘lethal myocardial ischemia-reperfusion (IR) injury’. There is long-standing and exhaustive evidence that mitochondria are at the nexus of lethal IR injury. However, during the past decade, the paradigm of mitochondria as mediators of IR-induced cardiomyocyte death has been expanded to include the highly orchestrated process of mitochondrial quality control. Our aims in this review are to: (1) briefly summarize the current understanding of the pathogenesis of IR injury, and (2) incorporating landmark data from a broad spectrum of models (including immortalized cells, primary cardiomyocytes and intact hearts), provide a critical discussion of the emerging concept that mitochondrial dynamics and mitophagy (the components of mitochondrial quality control) may contribute to the pathogenesis of cardiomyocyte death in the setting of ischemia-reperfusion

Comparison of SFRs and LFRs as Waste Burners

In this paper, two 600 MWe reactors are compared regarding safety relevant reactivity coefficients, waste-burning capabilities and reactivity swings during burn-up. Furthermore, comparisons of unprotected Loss-of-Flow and Loss-of-Heat Sink calculations are presented. In the first part of this paper, oxide fuels with an inert 92Mo matrix (occupying a 50% volume fraction) are investigated. This CERMET fuel is considered to be significantly more stable than an MgO matrix-based CERCER fuel and the isotopic tailoring of molybdenum appears affordable. Manufacturing and reprocessing aspects of these new fuels are discussed in some detail. The LFR core under consideration is considerably larger than the SFR core and has a slightly higher average TRU enrichment (50.0 to 43.0%). The LFR core is larger due to the larger pitch-to-diameter of 1.5 compared to 1.2 for SFR. By introducing additional pins with BeO moderator both cores show a negative Doppler that is larger than the positive coolant reactivity coefficient (LFR: Doppler –50 pcm and 38 pcm coolant reactivity increase, SFR: –54 and 36 pcm); reactivity coefficients refer to a 100 K heat-up. The burn-up swings for the BeO moderated core were –12.8$per year for the LFR and –23.8$ for the SFR. The LFR burner can annually transmute over 300 kg of plutonium and MAs corresponding roughly to the annual production of the transuranics of a 1.1 GWe LWR. Annual TRU consumption in the SFR burner is slightly less and equal to 263 kg. However, due to lower actinide inventory in the SFR, the actinide burn-up rate is larger than in the LFR. Another significant difference is in the safety behavior. The relatively large LFR overcomes the unprotected Loss-of-Flow due to its superior natural circulation whereas the SFR gets into sodium boiling. The latter may be avoided if fast negative structural feebacks could be proven to be large enough. In the unprotected Loss-of-Heat Sink accident the grace time of the LFR is considerably larger but for these longer times the lower grid expansion, which was not considered, would terminate the accidents. The use of thorium instead of the inert matrix appears to be quite attractive since 233U is generated without producing new minor actinides. Thus, potentially, a good new LWR fuel would become available. The reactivity coefficients of such a core look also quite good: for the LFR core and ThZrH1.6 the Doppler is -113 pcm and the coolant reactivity is 45 pcm. The burn-up swing is only about 0.4$ per year. The problem is the remote handling of the 233U that is due to the presence of a hard gamma emitter from a descendent of 232Th and also the 232U alpha emission. However, since remote handling is also used for MOX fuel, there should be no principal problem for reprocessing and fabricating a 233U / Th fuel. More studies are needed for the homogeneous burning of minor actinides in self-breeders, which in any case looks very promising. Finally, more detailed studies are required to further optimize core designs with respect to their fuel cycle performance, particularly for the SFR.JRC.F.4-Nuclear design safet

Relationships between Coping Styles, Emotional Distress, and Fear of COVID-19 among Workers in the Oil and Gas Industry in Malaysia during the COVID-19 Pandemic

The COVID-19 pandemic has had serious impacts on psychological health globally. However, very little is currently known regarding the link between fear of COVID-19 with psychological health and various coping styles, especially among oil and gas workers. This study aims to assess the prevalence of depression and anxiety among oil and gas workers, and subsequently examine the role of sociodemographic and occupational variables, various coping styles, and emotional distress in contributing to fear of COVID-19. A total of 299 oil and gas workers participated in this study. The DASS-21, Brief COPE, and Fear of COVID-19 (FCV-19) were used to assess the research variables. The descriptive analyses of DASS-21 indicated a prevalence of 26.8%, 33.5%, and 17.1% for depression, anxiety, and stress, respectively, among oil and gas workers. The results also indicated that all types of coping styles (problem-oriented, emotion-oriented, and dysfunctional-oriented) were significant predictors of fear of COVID-19. Sociodemographic and occupational variables and emotional distress variables were not significant predictors of fear of COVID-19. The study suggests how crucial it is for occupational mental health surveillance and prompt intervention for oil and gas workers

Parathyroid Hormone-Related Peptide and Its Analog, Abaloparatide, Attenuate Lethal Myocardial Ischemia-Reperfusion Injury

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

Profound cardioprotection with chloramphenicol succinate in the swine model of myocardial ischemia-reperfusion injury

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\u3c0.01 and P\u3c0.05 versus control). Moreover, administration of CAPS was associated with increased expression of both proteins. Conclusion-: 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. © 2010 American Heart Association, Inc