Mioara D. Manole

Lipidomics identifies cardiolipin oxidation as a mitochondrial target for redox therapy of brain injury

The brain contains a highly diversified complement of molecular species of a mitochondria-specific phospholipid, cardiolipin, which, because of its polyunsaturation, can readily undergo oxygenation. Using global lipidomics analysis in experimental traumatic brain injury (TBI), we found that TBI was accompanied by oxidative consumption of polyunsaturated cardiolipin and the accumulation of more than 150 new oxygenated molecular species of cardiolipin. RNAi-based manipulations of cardiolipin synthase and cardiolipin levels conferred resistance to mechanical stretch, an in vitro model of traumatic neuronal injury, in primary rat cortical neurons. By applying a brain-permeable mitochondria-targeted electron scavenger, we prevented cardiolipin oxidation in the brain, achieved a substantial reduction in neuronal death both in vitro and in vivo, and markedly reduced behavioral deficits and cortical lesion volume. We conclude that cardiolipin oxygenation generates neuronal death signals and that prevention of it by mitochondria-targeted small molecule inhibitors represents a new target for neuro-drug discovery.

Magnetic Resonance Imaging Assessment of Regional Cerebral Blood Flow after Asphyxial Cardiac Arrest in Immature Rats

Cerebral blood flow (CBF) alterations after asphyxial cardiac arrest (CA) are not defined in developmental animal models or humans. We characterized regional and temporal changes in CBF from 5 to 150 mins after asphyxial CA of increasing duration (8.5, 9, 12 min) in postnatal day (PND) 17 rats using the noninvasive method of arterial spin-labeled magnetic resonance imaging (ASL-MRI). We also assessed blood-brain barrier (BBB) permeability, and evaluated the relationship between CBF and mean arterial pressure after resuscitation. After all durations of asphyxia CBF alterations were region dependent. After 8.5- and 9-min asphyxia, intense subcortical hyperemia at 5 min was followed by return of CBF to baseline values by 10 mins. After 12-min asphyxia, hyperemia was absent and hypoperfusion reached a nadir of 38% to 65% of baselines with the lowest values in the cortex. BBB was impermeable to gadoteridol 150 mins after CA. CBF in the 12-min CA group was blood pressure passive at 60 min assessed via infusion of epinephrine. ASL-MRI assessment of CBF after asphyxial Ca in PND 17 rats reveals marked duration and region-specific reperfusion patterns and identifies possible new therapeutic targets.

Normoxic versus hyperoxic resuscitation in pediatric asphyxial cardiac arrest: Effects on oxidative stress

Objective:To determine the effects of normoxic vs. hyperoxic resuscitation on oxidative stress in a model of pediatric asphyxial cardiac arrest. Design:Prospective, interventional study. Setting:University research laboratory. Subjects:Postnatal day 16–18 rats (n = 5 per group). Interventions:Rats underwent asphyxial cardiac arrest for 9 min. Rats were randomized to receive 100% oxygen, room air, or 100% oxygen with polynitroxyl albumin (10 mL·kg−1 intravenously, 0 and 30 min after resuscitation) for 1 hr from the start of cardiopulmonary resuscitation. Shams recovered in 100% oxygen or room air after surgery. Measurements and Main Results:Physiological variables were recorded at baseline to 1 hr after resuscitation. At 6 hrs after asphyxial cardiac arrest, levels of reduced glutathione and protein-thiols (fluorescent assay), activities of total superoxide dismutase and mitochondrial manganese superoxide dismutase (cytochrome c reduction method), manganese superoxide dismutase expression (Western blot), and lipid peroxidation (4-hydroxynonenal Michael adducts) were evaluated in brain tissue homogenates. Hippocampal 3-nitrotyrosine levels were determined by immunohistochemistry 72 hrs after asphyxial cardiac arrest. Survival did not differ among groups. At 1 hr after resuscitation, Pao2, pH, and mean arterial pressure were decreased in room air vs. 100% oxygen rats (59 ± 3 vs. 465 ± 46 mm Hg, 7.36 ± 0.05 vs. 7.42 ± 0.03, 35 ± 4 vs. 45 ± 5 mm Hg; p < .05). Rats resuscitated with 100% oxygen had decreased hippocampal reduced glutathione levels vs. sham (15.3 ± 0.4 vs. 20.9 ± 4.1 nmol·mg protein−1; p < .01). Hippocampal manganese superoxide dismutase activity was significantly increased in 100% oxygen rats vs. sham (14 ± 2.4 vs. 9.5 ± 1.6 units·mg protein−1, p < .01), with no difference in protein expression of manganese superoxide dismutase. Room air and 100% oxygen plus polynitroxyl albumin groups had hippocampal reduced glutathione and manganese superoxide dismutase activity levels comparable with sham. Protein thiol levels were unchanged across groups. Compared with all other groups, rats receiving 100% oxygen had increased immunopositivity for 3-nitrotyrosine in the hippocampus and increased lipid peroxidation in the cortex. Conclusions:Resuscitation with 100% oxygen leads to increased oxidative stress in a model that mimics pediatric cardiac arrest. This may be prevented by using room air or giving an antioxidant with 100% oxygen resuscitation.

Preterminal gasping and effects on the cardiac function.

Objective:Gasping, also known as agonal respirations, is the terminal pattern that occurs after anoxia or ischemia and is a universal phenomenon in mammals. In this article we review the physiology of gasping, the prevalence and significance of gasping in cardiac arrest, and the effects of gasping on cardiac function. Design:Review relevant human and animal literature on gasping and cardiac function during gasping. Results:Gasping originates in the medullary area of the central nervous system. Gasping is prevalent during cardiac arrest: it occurs in all animals during ventricular fibrillation, in a majority of infants (31 of 32) with sudden infant death syndrome, and in 30–40% of witnessed episodes of cardiac arrest in adults. Animal studies demonstrated that gasping is associated with a decrease in intrathoracic pressure during the inspiratory phase, which promotes venous return and an increase in intrathoracic pressure during the expiratory phase, which favors coronary perfusion. Gasping increases cardiac output and cardiac contractility in immature animals exposed to anoxia. Conclusions:Gasping is auto-resuscitative in immature mammals and improves the outcome of cardiopulmonary resuscitation in mature mammals. Gasping is associated with important cardiorespiratory changes: improved pulmonary gas exchange, increased venous return to the heart, increased cardiac output, cardiac contractility, aortic pressure, and coronary perfusion pressure.

Global and regional differences in cerebral blood flow after asphyxial versus ventricular fibrillation cardiac arrest in rats using ASL-MRI

Both ventricular fibrillation cardiac arrest (VFCA) and asphyxial cardiac arrest (ACA) are frequent causes of CA. However, only isolated reports compared cerebral blood flow (CBF) reperfusion patterns after different types of CA, and even fewer reports used methods that allow serial and regional assessment of CBF. We hypothesized that the reperfusion patterns of CBF will differ between individual types of experimental CA. In a prospective block-randomized study, fentanyl-anesthetized adult rats were subjected to 8min VFCA or ACA. Rats were then resuscitated with epinephrine, bicarbonate, manual chest compressions and mechanical ventilation. After the return of spontaneous circulation, CBF was then serially assessed via arterial spin-labeling magnetic resonance imaging (ASL-MRI) in cortex, thalamus, hippocampus and amygdala/piriform complex over 1h resuscitation time (RT). Both ACA and VFCA produced significant temporal and regional differences in CBF. All regions in both models showed significant changes over time (p<0.01), with early hyperperfusion and delayed hypoperfusion. ACA resulted in early hyperperfusion in cortex and thalamus (both p<0.05 vs. amygdala/piriform complex). In contrast, VFCA induced early hyperperfusion only in cortex (p<0.05 vs. other regions). Hyperperfusion was prolonged after ACA, peaking at 7min RT (RT7; 199% vs. BL, Baseline, in cortex and 201% in thalamus, p<0.05), then returning close to BL at ∼RT15. In contrast, VFCA model induced mild hyperemia, peaking at RT7 (141% vs. BL in cortex). Both ACA and VFCA showed delayed hypoperfusion (ACA, ∼30% below BL in hippocampus and amygdala/piriform complex, p<0.05; VFCA, 34-41% below BL in hippocampus and amygdala/piriform complex, p<0.05). In conclusion, both ACA and VFCA in adult rats produced significant regional and temporal differences in CBF. In ACA, hyperperfusion was most pronounced in cortex and thalamus. In VFCA, the changes were more modest, with hyperperfusion seen only in cortex. Both insults resulted in delayed hypoperfusion in all regions. Both early hyperperfusion and delayed hypoperfusion may be important therapeutic targets. This study was approved by the University of Pittsburgh IACUC 1008816-1.

Emergency department management of the pediatric patient with supraventricular tachycardia.

Supraventricular tachycardia (SVT) is the most common tachyarrhythmia that necessitates treatment in children. It is characterized by a rapid and regular heart rate, which generally exceeds 180 beats per minute in children and 220 beats per minute in adolescents. Supraventricular tachycardia results from conduction of electrical impulses along an accessory connection from the atrium to the ventricle (atrioventricular reentry tachycardias: orthodromic or antidromic) or conduction within the atrioventricular node (atrioventricular node reentry tachycardia). Emergency department management of SVT depends on the patients clinical status. Treatment of a stable patient with SVT includes vagal maneuvers and adenosine, whereas treatment of an unstable patient requires synchronized cardioversion. This article presents an overview of the etiology, pathophysiology, and clinical presentation of SVT and discusses the emergency department management of an infant or child with SVT.

Cardiac arrest in children.

Major advances in the field of pediatric cardiac arrest (CA) were made during the last decade, starting with the publication of pediatric Utstein guidelines, the 2005 recommendations by the International Liaison Committee on Resuscitation, and culminating in multicenter collaborations. The epidemiology and pathophysiology of in-hospital and out-of-hospital CA are now well described. Four phases of CA are described and the term “post-cardiac arrest syndrome” has been proposed, along with treatment goals for each of its four phases: immediate post-arrest, early post-arrest, intermediate and recovery phase. Hypothermia is recommended to be considered as a therapy for post-CA syndrome in comatose patients after CA, and large multicenter prospective studies are underway. We reviewed landmark articles related to pediatric CA published during the last decade. We present the current knowledge of epidemiology, pathophysiology and treatment of CA relevant to pre-hospital and acute care health practitioners.

Preterminal Gasping During Hypoxic Cardiac Arrest Increases Cardiac Function in Immature Rats

Newborn animals are more resistant to anoxia than older animals, partly due to an increased tolerance of the immature heart to anoxia. Newborn animals also have a more robust preterminal gasp. We investigated the relationship between gasping and cardiac function in immature and maturing rats exposed to anoxia. Immature postnatal day 7 (PND7) rats (n = 13) and maturing PND17 rats (n = 13) were exposed to 100% nitrogen (anoxia) for 10 min. Echocardiography was used to calculate cardiac contractility (CC) by left ventricular shortening fraction and cardiac output (CO) from Doppler velocity recordings of pulmonary artery blood flow. In a separate group of PND7 rats, CC and CO were recorded after the paralytic agent pancuronium was used to prevent gasping. Anoxia decreased CC and CO in PND7 and PND17 rats, followed by a partial and transient recovery. Gasping preceded recovery of CO and was required to sustain CO. Gasping in PND7 rats lasted longer (541 s versus 351 s, p < 0.01) and resulted in a greater recovery of CC and CO. Anoxia-induced gasping and the associated recovery of cardiac function were abolished by paralysis. Thus, anoxia-induced gasping transiently improves cardiac function, and more robust gasping in immature rats is associated with increased cardiac anoxic tolerance.

Brain tissue oxygen monitoring identifies cortical hypoxia and thalamic hyperoxia after experimental cardiac arrest in rats

Background:Optimization of cerebral oxygenation after pediatric cardiac arrest (CA) may reduce neurological damage associated with the post-CA syndrome. We hypothesized that important alterations in regional partial pressure of brain tissue oxygen (PbO2) occur after resuscitation from CA and that clinically relevant interventions such as hyperoxia and blood pressure augmentation would influence PbO2.Methods:Cortical and thalamic PbO2 were monitored in immature rats subjected to asphyxial CA (9 or 12 min asphyxia) and sham-operated rats using oxygen sensors.Results:Thalamus and cortex showed similar baseline PbO2. Postresuscitation, there was early and sustained cortical hypoxia in an insult-duration dependent fashion. In contrast, thalamic PbO2 initially increased fourfold and afterwards returned to baseline values. PbO2 level was dependent on the fraction of inspired O2, and the response to oxygen was more pronounced after a 9 vs. 12 min CA. After a 12 min CA, PbO2 was modestly affected by blood pressure augmentation using epinephrine in the thalamus but not in the cortex.Conclusion:After asphyxial pediatric CA, there is marked regional variability of cerebral oxygenation. Cortical hypoxia is pronounced and appears early, whereas thalamic hyperoxia is followed by normoxia. Compromised PbO2 in the cortex may represent a relevant and clinically measurable therapeutic target aimed at improving neurological outcome after pediatric CA.

Cold stress protein RBM3 responds to temperature change in an ultra-sensitive manner in young neurons

Extremely mild hypothermia to 36.0 °C is not thought to appreciably differ clinically from 37.0 °C. However, it is possible that 36.0 °C stimulates highly sensitive hypothermic signaling mechanism(s) and alters biochemistry. To the best of our knowledge, no such ultra-sensitive pathway/mechanisms have been described. Here we show that cold stress protein RNA binding motif 3 (RBM3) increases in neuron and astrocyte cultures maintained at 33 °C or 36 °C for 24 or 48 h, compared to 37 °C controls. Neurons cultured at 36 °C also had increased global protein synthesis (GPS). Finally, we found that melatonin or fibroblast growth factor 21 (FGF21) augmented RBM3 upregulation in young neurons cooled to 36 °C. Our results show that a 1 °C reduction in temperature can induce pleiotropic biochemical changes by upregulating GPS in neurons which may be mediated by RBM3 and that this process can be pharmacologically mimicked and enhanced with melatonin or FGF21.