Episodes Of Ischemia-reperfusion Research Articles

Inhibition of NOX2 or NLRP3 inflammasome prevents cardiac remote ischemic preconditioning.

Introduction: Short episodes of ischemia-reperfusion (IR) in the heart (classical ischemic preconditioning, IPC) or in a limb (remote ischemic preconditioning, RIPC) before a prolonged ischemic episode, reduce the size of the infarct. It is unknown whether IPC and RIPC share common mechanisms of protection. Animals KO for NOX2, a superoxide-producing enzyme, or KO for NLRP3, a protein component of inflammasome, are not protected by IPC. The aim of this study was to investigate if NOX2 or NLRP3 inflammasome are involved in the protection induced by RIPC. Methods: We preconditioned rats using 4 × 5min periods of IR in the limb with or without a NOX2 inhibitor (apocynin) or an NLRP3 inhibitor (Bay117082). In isolated hearts, we measured the infarct size after 30min of ischemia and 60min of reperfusion. In hearts from preconditioned rats we measured the activity of NOX2; the mRNA of Nrf2, gamma-glutamylcysteine ligase, glutathione dehydrogenase, thioredoxin reductase and sulfiredoxin by RT-qPCR; the content of glutathione; the activation of the NLRP3 inflammasome and the content of IL-1β and IL-10 in cardiac tissue. In exosomes isolated from plasma, we quantified NOX2 activity. Results: The infarct size after IR decreased from 40% in controls to 9% of the heart volume after RIPC. This protective effect was lost in the presence of both inhibitors. RIPC increased NOX2 activity in the heart and exosomes, as indicated by the increased association of p47phox to the membrane and by the increased oxidation rate of NADPH. RIPC also increased the mRNA of Nrf2 and antioxidant enzymes. Also, RIPC increased the content of glutathione and the GSH/GSSG ratio. The inflammasome proteins NLRP3, procaspase-1, and caspase-1 were all increased in the hearts of RIPC rats. At the end of RIPC protocol, IL-1β increased in plasma but decreased in cardiac tissue. At the same time, IL-10 did not change in cardiac tissue but increased by 70% during the next 50min of perfusion. Conclusion: RIPC activates NOX2 which upregulates the heart's antioxidant defenses and activates the NLRP3 inflammasome which stimulates a cardiac anti-inflammatory response. These changes may underlie the decrease in the infarct size induced by RIPC.

Destabilization of the Organized Structure of Ventricular Fibrillation During Reperfusion

Aim: to study the effect of reperfusion on the organized frequency-amplitude structure of ventricular fibrillation (VF) in the dog heart.Materials and methods. We conducted 4 experiments on 8 dogs. In each experiment, the isolated heart of one dog was perfused with the blood of the second (supporting) dog. In 4 experiments on an isolated artificially perfused heart, 6 episodes of 3 min ischemia and 10 min reperfusion of the heart were performed in VF (1–2 episodes of ischemia-reperfusion in one experiment). Each episode of 3 min ischemia in VF was preceded by a 10 min perfusion of the heart in VF. Ventricular electrogram was recorded during VF episodes. A frequencyamplitude (spectral) analysis of 1 sec segments of the electrogram was performed, and the proportion (in %) of 0.5–15 Hz frequency oscillations in 10 sec segments of the electrogram was determined in 6 episodes of perfusion, ischemia and reperfusion in VF (M±m, N=60). The VF frequency-amplitude structures during ischemia and reperfusion were compared with the stable VF frequency-amplitude structure during perfusion taken as the control. The nonparametric Welch criterion in the «The R Project for Statistical Computing» software environment was used to compare the VF parameters during perfusion, ischemia and reperfusion. Results. 9–10 Hz frequency oscillations dominated in the VF frequency-amplitude structure during heart perfusion, taken as the control. In the first 30 sec of ischemia, the frequency and amplitude of the dominant oscillations did not significantly change vs VF control obtained during cardiac perfusion. A decrease of dominant oscillations frequency up to 6.5–7.5 Hz, and of the proportion of oscillations — up to 26% was documented at the 3rd min of ischemia. At the 1st min of reperfusion, the frequency of dominant oscillations increased to 13.5–14.5 Hz, but the proportion of oscillations remained reduced to 26%, as at the 3rd min of ischemia. At the 2nd min of reperfusion, the frequency of dominant oscillations decreased to 9.5–10.5 Hz, and the proportion of dominant oscillations increased to 33%. The frequency and amplitude of the dominant oscillations stabilized at 3–10 min of reperfusion: oscillations at 9–10 Hz frequency accounted for 32–33% of the spectral power.Conclusion. Reperfusion in VF is characterized by transient destabilization of VF organized structure at the 1st min of the procedure. VF organized structure regains stabilization within 2–10 min of reperfusion. Cardiac perfusion in intentionally induced VF can be used instead of cardioplegia during major cardiac surgery to boost cardiac resistance to ischemia and prevent or reduce reperfusion complications.

Does Disruption of Optic Atrophy-1 (OPA1) Contribute to Cell Death in HL-1 Cardiomyocytes Subjected to Lethal Ischemia-Reperfusion Injury?

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.

DNA repair factor KAT5 prevents ischemic acute kidney injury through glomerular filtration regulation

SummaryThe “preconditioning effect” in AKI is a phenomenon in which an episode of ischemia-reperfusion results in tolerance to subsequent ischemia-reperfusion injury. However, its relationship between DNA damage repair has not been elucidated. Here, we show the role of KAT5 in the preconditioning effect. Preconditioning attenuated DNA damage in proximal tubular cells with elevated KAT5 expression. Ischemia-reperfusion (IR) injuries were exacerbated, and preconditioning effect vanished in proximal tubular-cell-specific KAT5 knockout mice. Investigation of tubuloglomerular feedback (TGF) by MALDI-IMS and urinary adenosine revealed that preconditioning caused attenuated TGF at least in part via KAT5. In addition, K-Cl cotransporter 3 (KCC3) expression decreased in damaged proximal tubular cells, which may be involved in accelerated TGF following IR. Furthermore, KAT5 induced KCC3 expression by maintaining chromatin accessibility and binding to the KCC3 promoter. These results suggest a novel mechanism of the preconditioning effect mediated by the promotion of DNA repair and attenuation of TGF through KAT5.

Determinants of reperfusion arrhythmias: action potential duration versus dispersion of repolarization.

The role of a border zone in arrhythmogenesis is not fully understood. In this study we evaluated independent contributions of action potential duration (APD) and dispersion of repolarization (DOR) across the normal/ischemic border to the development of ventricular tachycardia and/or fibrillation (VT/VF). Ischemia-reperfusion episodes were induced in anesthetized rats by transient coronary occlusion. Unipolar electrograms were recorded from ischemic and perfused areas using a 64-lead array to obtain activation times (ATs), repolarization times (RTs), activation-repolarization intervals (ARIs, a surrogate for APD) and dispersion of repolarization (DOR, as a difference between the earliest and latest RTs). Pinacidil (0.3 mg/kg) and glibenclamide (2 mg/kg) were applied to reduce DOR and to clamp APD at a lower and upper levels, respectively. In the control animals, APD shortened in the ischemic zone, DOR increased to 9 ± 3 ms, and VT/VF developed at reperfusion (6 out of 10). Pre-occlusion application of glibenclamide prolonged APD in the ischemic and perfused zones, decreased DOR to 5 ± 2 ms and did not affect VT/VF development (4 out of 11). Post-occlusion infusion of pinacidil shortened APD in the perfused zone, decreased DOR to 6 ± 3 ms and VT/VF incidence (2 out of 11). Extrasystolic burden at reperfusion was associated with VT/VF incidence in logistic regression analysis (β = 1.182, 95%CI 1.008 - 1.386, p = 0.04) and was lesser (p < 0.01) in the pinacidil group as compared to the control and glibenclamide groups. In conclusion, the results of this study suggest that the APDs in the perfused zone were a superior arrhythmogenic factor in respect to DOR in the present ischemia-reperfusion model.

Melatonin Treatment Does Not Modify Ectopic Activity During Ischemia and Reperfusion in Rats

Introduction Ventricular tachycardia and/or ventricular fibrillation (VT/VF), a life-threatening complication of acute myocardial ischemia are based on the interaction between a vulnerable arrhythmogenic substrate and an arrhythmic trigger. Melatonin was proposed as a potential antiarrhythmic medication and was shown to ameliorate the arrhythmogenic substrate. Also, melatonin provides a sympatholytic effect and thereby can attenuate ectopic activity, which provides the triggers for VT/VF. However, little is known about a melatonin effect on the arrhythmic triggering. In the present study, we aimed at evaluation of the melatonin effects on catecholamine synthesis in normal and ischemic myocardium and heart rhythm disturbances during an episode of ischemia and reperfusion. Methods Experiments were done in 30 control and 32 melatonin-treated (10 mg/kg, daily, for 7 days) male rats. The hearts from 10 control and 10 treated animals were taken for histochemical analysis of sympathetic fibers (glyoxylic acid-induced fluorescence). Continuous ECG recording was performed in 20 control and 22 treated anesthetized animals before and during an ischemia-reperfusion episode induced by reversible 5-min occlusion of the left anterior descending coronary artery. Tyrosine hydroxylase expression in normal and ischemic myocardial regions was assessed by Western blotting analysis in 12 control and 12 melatonin-treated animals. Results No differences in the state of sympathetic innervation (density and fluorescence intensity) were observed in histochemical analysis. However, Western blotting demonstrated that melatonin treatment suppressed tyrosine hydroxylase expression in normal (p<0.05 vs control) but not in ischemic regions of myocardium. Melatonin-treated animals had longer RR-intervals in the baseline state, but this difference progressively disappeared during the period of ischemia due to tachycardic response to ischemia in the treated group (Figure). No differences in the number of extrasystoles were found between the control and treated groups during ischemia and reperfusion periods (Figure). Conclusion Chronic melatonin treatment led to the peripheral sympatholytic effect in myocardium, which was associated with decreased heart rate in preischemic conditions. However, this effect attenuated during ischemia and no differences in heart rate or extrasystolic burden were found between the control and treated animals during ischemia and reperfusion.

Brain Ischemia as a Prelude to Alzheimer's Disease.

Transient ischemic brain injury causes massive neuronal death in the hippocampus of both humans and animals. This was accompanied by progressive atrophy of the hippocampus, brain cortex, and white matter lesions. Furthermore, it has been noted that neurodegenerative processes after an episode of ischemia-reperfusion in the brain can continue well-beyond the acute stage. Rarefaction of white matter was significantly increased in animals at 2 years following ischemia. Some rats that survived 2 years after ischemia developed severe brain atrophy with dementia. The profile of post-ischemic brain neurodegeneration shares a commonality with neurodegeneration in Alzheimer's disease. Furthermore, post-ischemic brain injury is associated with the deposition of folding proteins, such as amyloid and tau protein, in the intracellular and extracellular space. Recent studies on post-ischemic brain neurodegeneration have revealed the dysregulation of Alzheimer's disease-associated genes such as amyloid protein precursor, α-secretase, β-secretase, presenilin 1, presenilin 2, and tau protein. The latest data demonstrate that Alzheimer's disease-related proteins and their genes play a key role in the development of post-ischemic brain neurodegeneration with full-blown dementia in disease types such as Alzheimer's. Ongoing interest in the study of brain ischemia has provided evidence showing that ischemia may be involved in the development of the genotype and phenotype of Alzheimer's disease, suggesting that brain ischemia can be considered as a useful model for understanding the mechanisms responsible for the initiation of Alzheimer's disease.

Oxymatrine improves blood-brain barrier integrity after cerebral ischemia-reperfusion injury by downregulating CAV1 and MMP9 expression

BackgroundIschemic stroke (IS) is a major neurological condition associated with extremely high morbidity and mortality worldwide. Oxymatrine (OMT), a quinolizidine alkaloid extracted from the root of Sophora flavescens, has neuroprotective properties and protects against IS. However, whether its protective effect involves alterations in the integrity of the blood-brain barrier (BBB) is unknown. PurposeHere, we used in vivo and in vitro models of IS to evaluate the protective effects of OMT and to establish whether its effects are mediated via the modulation of the BBB function. MethodsWe assessed the effects of OMT by using neurological function scores, triphenyltetrazolium chloride staining, Nissl staining, and terminal deoxynucleotidyl transferase dUTP nick end labeling. ResultsOMT significantly prevented cellular damage, improved neurological function, and reduced BBB permeability in a mouse model of cerebral ischemia-reperfusion. Additionally, OMT protected the function of the tight junctions of bEend.3 cells against the consequences of oxygen-glucose deprivation. Furthermore, intracranial lentivirus injection of short hairpin RNA targeting Cav1 decreased caveolin-1 expression and inhibited the neuroprotective effects of OMT. ConclusionsOMT attenuated ischemia-reperfusion injury-induced damage to the BBB, and this neuroprotective action was at least partially dependent on the expression levels of CAV1 and MMP9 proteins. Therefore, OMT may offer effective protection against BBB injury induced by ischemia-reperfusion episodes.

Melatonin pretreatment does not modify extrasystolic burden in the rat ischemia-reperfusion model.

The mechanism of reentrant ventricular tachyarrhythmias complicating acute myocardial ischemia is largely based on the interaction between an arrhythmogenic substrate and triggers. Melatonin was proposed as an antiarrhythmic medication and was shown to ameliorate the arrhythmogenic substrate. Also, melatonin provides a sympatholytic effect in different settings and might attenuate ectopic activity, which provides reentry triggers. In the present study, we aimed at evaluating the melatonin effects on cardiac sympathetic activity and the incidence of premature ventricular beats during the episode of ischemia-reperfusion. Experiments were done in a total of 26 control and 28 melatonin-treated (10 mg/kg, daily, for 7 days) male rats. Sympathetic fibers density was assessed by glyoxylic acid-induced fluorescence. Continuous electrocardiograms recording was performed during ischemia-reperfusion episodes (5 min/5 min, respectively) induced by reversible coronary occlusion. Myocardial expression of tyrosine hydroxylase, a rate-limiting enzyme of catecholamine biosynthesis was assessed by Western blotting. No differences in the state of sympathetic innervation were observed in histochemical analysis. However, Western blotting analysis demonstrated that melatonin treatment suppressed tyrosine hydroxylase expression in the non-ischemic (p < 0.05 versus control) but not ischemic regions of myocardium. The melatonin-treated animals had longer RR-intervals in the baseline state than the control animals (264 ± 48 ms versus 237 ± 33 ms, p = 0.044, respectively), but this difference decayed during the period of ischemia due to the increase of heart rate in the treated group. The number of premature ventricular beats did not differ between the control and treated groups during the ischemic and reperfusion periods. One-week melatonin pretreatment caused a slight peripheral sympatholytic effect that attenuated during ischemia and completely disappeared by the onset of reperfusion. The slight expression of sympathetic downregulation was associated with the lack of any effect of melatonin on extrasystolic burden. Collectively, the data suggest that melatonin cannot target the triggers of reentrant arrhythmias.

Remote ischemic conditioning enhances heart and brain antioxidant defense.

BackgroundIschemia-reperfusion injury contributes to morbidity after revascularization procedures. Along with early reperfusion, tissue conditioning by alternating intervals of brief ischemia-reperfusion episodes is considered the best approach to limit tissue damage. Remote ischemic conditioning is conducted remotely, in tissues other than those under ischemia. Despite this, remote ischemic conditioning protection mechanisms are poorly understood, which can lead to misapplication.ObjectivesTo assess whether remote ischemic conditioning works in the heart and brain through enhancement of cells’ antioxidant defenses and whether the response is sustained or temporary.MethodsTwenty-one male Wistar rats were assigned to three groups (n = 7): SHAM: same procedure as the other groups, but no remote ischemic conditioning was carried out. RIC 10: heart and brain were harvested 10 minutes after the remote ischemic conditioning protocol. RIC 60: heart and brain were harvested 60 minutes after the remote ischemic conditioning protocol. The remote ischemic conditioning protocol consisted of 3 cycles of 5 min left hindlimb ischemia followed by 5 min left hindlimb perfusion, lasting 30 min in total. Heart and brain samples were used to measure the tissue antioxidant capacity.ResultsRemote ischemic conditioning increased heart and brain antioxidant capacity after 10 minutes (0.746 ± 0.160/0.801 ± 0.227 mM/L) when compared to SHAM (0.523 ± 0.078/0.404 ± 0.124 mM/L). No enhancement of heart or brain antioxidant capacity was detected 60 minutes after remote ischemic conditioning (0.551 ± 0.073/0.455 ± 0.107 mM/L).ConclusionsRemote ischemic conditioning temporarily enhances heart and brain antioxidant defenses in male Wistar rats.

Assessment of Cardiac Abnormalities in Sickle Cell Disease Patients Using Echocardiography

Background: Sickle Cell Disease (SCD) is characterized by chronic anemia and recurrent ischemia-reperfusion episodes that contribute to high output heart failure. The effects of SCD on the heart are significantly underrecognized. Methods: SCD patients who underwent echocardiography between March 2016 and March 2018 were retrospectively analyzed. Patients with reduced Left Ventricular Ejection Fraction (LVEF) and valvular heart disease were excluded. Cardiac chamber size, systolic and diastolic function parameters, and LV and RV strain were compared between hemoglobin SS (most severe form of SCD) and SC (less severe form) subtypes and against healthy controls. Wilcoxon signed rank test was used for statistical analysis. Results: SS patients (n = 48, mean age 31.9) had lower mean hemoglobin 8.9 g/dl vs 11.3 g/dl (p &lt; 0.001) and hematocrit 25.8% vs 31.4% (p = 0.008) and higher LDH 437 IU/L vs 258 IU/L (p &lt; 0.001) compared to SC patients (n = 11, mean age 34.4). Both SS and SC patients had worse diastolic function compared to healthy controls: higher E velocity 98.9 cm/s (SS), 86.4 cm/s (SC), 76.4 cm/s (control) (SS vs control, p &lt; 0.01; SC vs control, p &lt; 0.05) and higher E/A ratio 1.76 (SS), 1.59 (SC), 1.15 (control) (SS vs control, p &lt; 0.001; SC vs control, p &lt; 0.01). SS patients had larger indexed left atrial volume compared to SC patients (39.3 ml/m2 vs 28.4 ml/m2, p = 0.007). There was no significant difference in LVEF, left ventricular global longitudinal strain, or right ventricular strain between SS and SC subtypes compared to healthy controls. Furthermore, SS patients with a serum LDH &gt; 500 IU/L had higher E/e' ratio (11.3 vs 7.2, p=0.001) and larger indexed Left Ventricular End Diastolic Volume (LVEDVi) (80.8 ml/m2 vs 53.4 ml/m2, p=0.002) compared to SS patients with LDH &lt; 500 IU/L. Conclusion: SCD genotype adversely determines the degree of cardiac dysfunction in patients with SCD. LVEDVi, left atrial size, E velocity, E/A ratio, and E/e' ratio may serve as useful echocardiographic parameters to follow in this patient population. Serum LDH has been associated with poor clinical outcomes in patients with SCD, and as demonstrated by our study, it also portends worsening cardiac function in this population at high risk for heart failure. Figure Disclosures No relevant conflicts of interest to declare.

LPS protects macrophages from AIF-independent parthanatos by downregulation of PARP1 expression, induction of SOD2 expression, and a metabolic shift to aerobic glycolysis

In inflamed tissues or during ischemia-reperfusion episodes, activated macrophages produce large amounts of reactive species and are, thus, exposed to the damaging effects of reactive species. Here, our goal was to investigate the mechanism whereby activated macrophages protect themselves from oxidant stress-induced cell death. Hydrogen peroxide-treated mouse bone marrow-derived macrophages (BMDM) and THP-1 human monocyte-derived cells were chosen as models. We found a gradual development of resistance: first in monocyte-to-macrophage differentiation, and subsequently after lipopolysaccharide (LPS) exposure. Investigating the mechanism of the latter, we found that exposure to intense hydrogen peroxide stress causes poly(ADP-ribose) polymerase-1 (PARP-1) dependent programmed necrotic cell death, also known as parthanatos, as indicated by the protected status of PARP-1 knockout BMDMs and the protective effect of the PARP inhibitor PJ-34. In hydrogen peroxide-treated macrophages, however, apoptosis inducing factor (AIF) proved dispensable for parthanatos; nuclear translocation of AIF was not observed. A key event in LPS-mediated protection against the hydrogen peroxide-induced AIF independent parthanatos was downregulation of PARP1 mRNA and protein. The importance of this event was confirmed by overexpression of PARP1 in THP1 cells using a viral promoter, which lead to stable PARP1 levels even after LPS treatment and unresponsiveness to LPS-induced cytoprotection. In BMDMs, LPS-induced PARP1 suppression lead to prevention of NAD+ depletion. Moreover, LPS also induced expression of antioxidant proteins (superoxide dismutase-2, thioredoxin reductase 1 and peroxiredoxin) and triggered a metabolic shift to aerobic glycolysis, also known as the Warburg effect. In summary, we provide evidence that in macrophages intense hydrogen peroxide stress causes AIF-independent parthanatos from which LPS provides protection. The mechanism of LPS-mediated cytoprotection involves downregulation of PARP1, spared NAD+ and ATP pools, upregulation of antioxidant proteins, and a metabolic shift from mitochondrial respiration to aerobic glycolysis.

Assessment of Intra-Aortic Counterpulsation in an Animal Model of Heart Failure and Myocardial Ischemia.

The effectiveness of intra-aortic balloon pumping (IABP) is currently evaluated using indirect indexes. The diastolic pressure augmentation is quantified using the subendocardial viability ratio (SEVR) and the DABAC/SABAC index (areas beneath the aortic pressure-time signals during the diastolic and systolic periods, respectively). The SEVR requires invasive recordings of left ventricular pressure; the DABAC/SABAC index may represent an alternative, since it only requires an aortic pressure signal. Nonetheless, it has never been used in an animal model of counterpulsated heart failure and ischemia-reperfusion episode. The aims of this work were: (i) to develop an animal model of heart failure, with a myocardial ischemia-reperfusion episode, treated with IABP during the reperfusion period; (ii) to evaluate the effects of the IABP using the SEVR and DABAC/SABAC indices; and (iii) to assess the relationship between both ratios. Cardiovascular parameters were obtained in anesthetized sheep, in which induced heart failure and ischemia-reperfusion episodes were monitored with and without IABP 1:2. Systolic and diastolic blood pressure signals were assessed in the aorta and in the left ventricle. Values of cardiac output and left ventricular wall thickness signals were obtained. Induction of ischemia and heart failure determined decreases in SEVR and DABAC/SABAC indices with respect to their basal stage (0.807±0.118 vs. 0.601±0.107, P<0.05 and 1.062±0.136 vs. 0.902±0.161, P<0.05, respectively). Counterpulsated animals whose myocardial reperfusion was accompanied by heart failure showed a significant improvement of wall thickening fraction along time (R2 =0.7627, P<0.001). During counterpulsated heart failure accompanied by myocardial reperfusion, the SEVR was positively correlated with DABAC/SABAC index.

Tau Protein Dysfunction after Brain Ischemia.

Brain ischemia comprises blood-brain barrier, glial, and neuronal cells. The blood–brain barrier controls permeability of different substances and the composition of the neuronal cells ‘milieu’, which is required for their physiological functioning. Recent evidence indicates that brain ischemia itself and ischemic blood-brain barrier dysfunction is associated with the accumulation of neurotoxic molecules within brain tissue, e.g., different parts of amyloid-β protein precursor and changed pathologically tau protein. All these changes due to ischemia can initiate and progress neurodegeneration of the Alzheimer’s disease-type. This review presents brain ischemia and ischemic blood-brain barrier as a trigger for tau protein alterations. Thus, we hypothesize that the changes in pattern of phosphorylation of tau protein are critical to microtubule function especially in neurons, and contribute to the neurodegeneration following brain ischemia-reperfusion episodes with Alzheimer’s disease phenotype.

Possible role of ATP-sensitive potassium and MPTP channels in pharmacological postconditioning in mouse brain

Background: Brief episodes of ischemia reperfusion in form of post conditioning when given after prolong ischemia found to be beneficial in various models of I/R injury. Opening of KATP & closing of MPTP has been reported provide cardioprotection against I/R injury.

Cerebral Autoregulation, Brain Injury, and the Transitioning Premature Infant.

Improvements in clinical management of the preterm infant have reduced the rates of the two most common forms of brain injury, such as severe intraventricular hemorrhage and white matter injury, both of which are contributory factors in the development of cerebral palsy. Nonetheless, they remain a persistent challenge and are associated with a significant increase in the risk of adverse neurodevelopment outcomes. Repeated episodes of ischemia–reperfusion represent a common pathway for both forms of injury, arising from discordance between systemic blood flow and the innate regulation of cerebral blood flow in the germinal matrix and periventricular white matter. Nevertheless, establishing firm hemodynamic boundaries, as a part of neuroprotective strategy, has challenged researchers. Existing measures either demonstrate inconsistent relationships with injury, as in the case of mean arterial blood pressure, or are not feasible for long-term monitoring, such as cardiac output estimated by echocardiography. These challenges have led some researchers to focus on the mechanisms that control blood flow to the brain, known as cerebrovascular autoregulation. Historically, the function of the cerebrovascular autoregulatory system has been difficult to quantify; however, the evolution of bedside monitoring devices, particularly near-infrared spectroscopy, has enabled new insights into these mechanisms and how impairment of blood flow regulation may contribute to catastrophic injury. In this review, we first seek to examine how technological advancement has changed the assessment of cerebrovascular autoregulation in premature infants. Next, we explore how clinical factors, including hypotension, vasoactive medications, acute and chronic hypoxia, and ventilation, alter the hemodynamic state of the preterm infant. Additionally, we examine how developmentally linked or acquired dysfunction in cerebral autoregulation contributes to preterm brain injury. In conclusion, we address exciting new approaches to the measurement of autoregulation and discuss the feasibility of translation to the bedside.

Neuronal Damage Induced by Perinatal Asphyxia Is Attenuated by Postinjury Glutaredoxin-2 Administration.

The general disruption of redox signaling following an ischemia-reperfusion episode has been proposed as a crucial component in neuronal death and consequently brain damage. Thioredoxin (Trx) family proteins control redox reactions and ensure protein regulation via specific, oxidative posttranslational modifications as part of cellular signaling processes. Trx proteins function in the manifestation, progression, and recovery following hypoxic/ischemic damage. Here, we analyzed the neuroprotective effects of postinjury, exogenous administration of Grx2 and Trx1 in a neonatal hypoxia/ischemia model. P7 Sprague-Dawley rats were subjected to right common carotid ligation or sham surgery, followed by an exposure to nitrogen. 1 h later, animals were injected i.p. with saline solution, 10 mg/kg recombinant Grx2 or Trx1, and euthanized 72 h postinjury. Results showed that Grx2 administration, and to some extent Trx1, attenuated part of the neuronal damage associated with a perinatal hypoxic/ischemic damage, such as glutamate excitotoxicity, axonal integrity, and astrogliosis. Moreover, these treatments also prevented some of the consequences of the induced neural injury, such as the delay of neurobehavioral development. To our knowledge, this is the first study demonstrating neuroprotective effects of recombinant Trx proteins on the outcome of neonatal hypoxia/ischemia, implying clinical potential as neuroprotective agents that might counteract neonatal hypoxia/ischemia injury.

Higher Myocardial and Skeletal Muscle Microvascular Flow in Sickle Cell Disease Patients on Hydroxyurea

Individuals with SCD have recurrent episodes of ischemia-reperfusion in vital organs, and abnormal microcirculation is considered a major determinant of end organ damage. Hydroxyurea (HU) treatment has been shown to produce ATP- and nitric oxide-mediated vasodilation, and to improve red cells deformability Few tools are available to quantitatively measure microvascular blood flow in vivo. The purpose of this study was to assess the ability of a novel ECHO based imaging modality to assess the effect of hydroxyurea on cardiac and skeletal muscle perfusion in patients with sickle cell anemia.Methods and Results: Twenty-one HBSS/B0 patients, of whom 15 were treated with HU(average daily dose of 18 ± 8 mg/kg/day), underwent brachial artery ultrasound, echocardiography and contrast enhanced ultrasound (CEU) perfusion imaging of deep flexor muscles of the forearm as well as the myocardium at rest and during vasodilator stress with regadenoson ( ClinicalTrials.gov NCT016028090). Quantitative image analysis was performed to obtain microvascular blood volume and flow velocity measurements. Patients on HU had a lower white blood cell count (6.7±2.1 K/uL vs 10.0±2.1 K/uL, p<0.05), higher mean corpuscular volume (103.6±11.5 fL vs 82.5±8.6 fL, p<0.05) , and lower reticulocyte count (9.3±3.4% vs 15.7±5.6%, p<0.05) as well as a trend towards higher hemoglobin (9.4±1.4g/dL vs 7.9±1.1g/dL , p=NS). Table 1. Cardiac output and total myocardial work was not affected by HU treatment and macrovascular flow in the brachial artery was not affected (Figure 1A). In contrast, both skeletal muscle microvascular flow and myocardial microvascular flow was significantly higher in the SCD patients on HU therapy (Figure 1B, 1C).Conclusions: The beneficial effects of HU therapy in SCD are varied, and clinical effects are often seen prior to a rise in fetal hemoglobin. Other effects, such as lower hemolysis, improved red cell deformability, and inhibition of adhesive properties in the microvasculature have been reported. Some of the beneficial effects of HU may be due to stimulation of nitric oxide synthase, induction of cyclic GMP dependent signaling and improved NO bioavailability. Our study indicates that SCD patients on chronic HU therapy have higher levels of myocardial and skeletal muscle microvascular blood flow. Long term studies are necessary to evaluate whether HU reduces end organ damage in SCA.Skeletal muscle and myocardial microvascular blood flow.Each panel shows blood flow in all SCD patients (red filled diamonds), SCD patients not on HU (red open triangles) and SCD patients on HU (red open inverted triangles).Panel A. Skeletal muscle perfusion normalized to hemoglobin (A x β x hemoglobin)Panel B. Myocardial perfusion normalized to hemoglobin level and total myocardial work. [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Targeting Mitochondrial Dysfunction with L-Alpha Glycerylphosphorylcholine.

BackgroundWe hypothesized that L-alpha-glycerylphosphorylcholine (GPC), a deacylatedphosphatidylcholine derivative, can influence the mitochondrial respiratory activity and in this way, may exert tissue protective effects.MethodsRat liver mitochondria were examined with high-resolution respirometry to analyze the effects of GPC on the electron transport chain in normoxic and anoxic conditions. Besides, Sprague-Dawley rats were subjected to sham operation or standardized liver ischemia-reperfusion (IR), with or without GPC administration. The reduced glutathione (GSH) and oxidized glutathione disulfide (GSSG), the tissue myeloperoxidase, xanthine oxidoreductase and NADPH oxidases activities were measured. Tissue malondialdehyde and nitrite/nitrate formation, together with blood superoxide and hydrogen-peroxide production were assessed.ResultsGPC increased the efficacy of complex I-linked mitochondrial oxygen consumption, with significantly lower in vitro leak respiration. Mechanistically, liver IR injury was accompanied by deteriorated mitochondrial respiration and enhanced ROS production and, as a consequence, by significantly increased inflammatory enzyme activities. GPC administration decreased the inflammatory activation in line with the reduced oxidative and nitrosative stress markers.ConclusionGPC, by preserving the mitochondrial complex I function respiration, reduced the biochemical signs of oxidative stress after an IR episode. This suggests that GPC is a mitochondria-targeted compound that indirectly suppresses the activity of major intracellular superoxide-generating enzymes.

Nanocapsulated Ascorbic Acid in Combating Cerebral Ischemia Reperfusion- Induced Oxidative Injury in Rat Brain.

Recent evidences suggest that cerebral ischemia-reperfusion insult plays significant role in pathogenic diseases like Alzheimer's disease (AD) and other neurodegenerative diseases. Toxic reactive oxygen species (ROS) generated by induced oxidative stress in the episodes of cerebral ischemia-reperfusion (CIR) plays major role in neurodegeneration. As the prime source of ROS generation, neuronal mitochondria, the cellular energy metabolic centre experience severe damage because of CIR-induced oxidative stress. The process of mitochondrial dysfunction is accelerated by CIR that may pave the pathway for neurodegeneration in AD among aged individuals. Prevention of CIR injury may be a shunt in order to minimize the risk of dementia of Alzheimer's type in aged individuals. The use of chemical antioxidants in CIR is not suitable as the blood- brain barrier (BBB) doesn't allow the entry of molecules from blood circulation into the brain. Thus L-ascorbic acid loaded polylactide nanocapsules were prepared and fed orally to assess the role of nanocapsulated ascorbic acid (NAA) against CIR induced oxidative injury in mitochondrial region of rat brains. Mitochondrial injury was assessed by the extent of lipid peroxidation and in situ antioxidant enzyme status. The levels of cytochrome c (cyt c), cyclooxygenase- 2 (COX-2) and iNOS were determined. Results showed that in comparison to free ascorbic acid (AA), NAA exerted better protection to the brain mitochondria by preventing oxidative damage in ROS mediated CIR injury.