Cerebral Tissue Oxidative Ischemia-Reperfusion Injury in Connection with Experimental Cardiac Arrest and Cardiopulmonary Resuscitation: Effect of Mild Hypothermia and Methylene Blue

The effects of methylene blue during and after cardiac arrest in a porcine model; a randomized, blinded, placebo-controlled study

PURPOSE

To evaluate the effect of methylene blue administered as a bolus on return of spontaneous circulation (ROSC), lactate levels, vasopressor requirements, and markers of neurological injury in a clinically relevant pig model of cardiac arrest.

MATERIALS AND METHODS

40 anesthetized pigs were subjected to acute myocardial infarction and 7 min of untreated cardiac arrest. Animals were randomized into three groups: one group received saline only (controls), one group received 2 mg/kg methylene blue and saline (MB + saline), and one group received two doses of 2 mg/kg methylene blue (MB + MB). The first intervention was given after the 3rd rhythm analysis, while the second dose was administered one hour after achieving ROSC. Animals underwent intensive care and observation for six hours, followed by cerebral magnetic resonance imaging (MRI). The primary outcome for this study was development in lactate levels after cardiac arrest. Categorical data were compared using Fisher's exact test and pointwise data were analyzed using one-way analysis of variance (ANOVA) or equivalent non-parametric test. Continuous data collected over time were analyzed using a linear mixed effects model. A value of p < .05 was considered statistically significant.

RESULTS

Lactate levels increased in all groups after cardiac arrest and resuscitation, however lactate levels in the MB + MB group decreased significantly faster compared with the control group (p = .007) and the MB + saline group (p = .02). The proportion of animals achieving initial ROSC was similar across groups: 11/13 (85%) in the control group, 10/13 (77%) in the MB + saline group, and 12/14 (86%) in the MB + MB group (p = .81). Time to ROSC did not differ between groups (p = .67). There was no significant difference in accumulated norepinephrine dose between groups (p = .15). Cerebral glycerol levels were significantly lower in the MB + MB group after resuscitation compared with control group (p = .03). However, MRI data revealed no difference in apparent diffusion coefficient, cerebral blood flow, or dynamic contrast enhanced MR perfusion between groups.

CONCLUSION

Treatment with a bolus of methylene blue during cardiac arrest and after resuscitation did not significantly improve hemodynamic function. A bolus of methylene blue did not yield the neuroprotective effects that have previously been described in animals receiving methylene blue as an infusion.

Early predictors of brain injury in patients with acute carbon monoxide poisoning and the neuroprotection of mild hypothermia

INTRODUCTION

Carbon monoxide (CO) poisoning can cause serious neurological sequelae. However, there is neither effective treatment strategy nor reliable indicators to determine the prognosis of patients with CO poisoning. The present study aimed to observe the changes of neurological function score, disease severity score, cerebral oxygen utilization (O₂UCc), bispectral (BIS) index and neuron-specific enolase (NSE) concentration, and to elucidate the clinical significance of these potential indicators and the neuroprotective effect of mild hypothermia on brain injury in patients with severe acute CO poisoning.

MATERIALS AND METHODS

A total of 277 patients with acute severe CO poisoning from 2013 to 2018 were enrolled in our hospital. Patients were divided into three groups according to their body temperature on the day of admission and their willingness to treat: a fever group (n = 78), a normal temperature group (NT group, n = 113), and a mild hypothermia group (MH group, n = 86). All patients were given hyperbaric oxygen therapy, while those in the MH group received additional mild hypothermia treatment. The severity of the disease, the neurobehavioral status, the incidence of delayed encephalopathy after acute carbon monoxide poisoning (DEACMP), and other indicators including BIS, O₂UCc, NSE were further evaluated in all patients at given time-points.

RESULTS

Mild hypothermia therapy improved the prognosis of patients with CO poisoning, significantly decreased the value of O₂UCc and NSE, and up-regulated BIS. The incidence of DEACMP at 6 months was 27% in the fever group, 23% in the NT group, and 8% in the MH group. The values of Glasgow-Pittsburgh coma scale (G-P score), BIS index and NSE were closely related to the occurrence of DEACMP, the cutoff values were 12.41, 52.17 and 35.20 ng/mL, and the sensitivity and specificity were 79.3%, 77.6%, 79.3% and 67.6%, 89.5%, 88.6% in the receiver operating characteristic curve (ROC), respectively.

CONCLUSIONS

Early mild hypothermia treatment could significantly reduce the severity of brain injury after CO poisoning, and might be further popularized in clinic. G-P scores, NSE and BIS index can be regarded as the prediction indicators in the occurrence and development of DEACMP.

CLINICAL TRIAL REGISTRATION

The study protocol was granted from Qingdao University Research Ethics Committee (Clinical trial registry and ethical approval number: QD81571283).

High Oxygen Does Not Increase Reperfusion Injury Assessed with Lipid Peroxidation Biomarkers after Cardiac Arrest: A Post Hoc Analysis of the COMACARE Trial

The products of polyunsaturated fatty acid peroxidation are considered reliable biomarkers of oxidative injury in vivo. We investigated ischemia-reperfusion-related oxidative injury by determining the levels of lipid peroxidation biomarkers (isoprostane, isofuran, neuroprostane, and neurofuran) after cardiac arrest and tested the associations between the biomarkers and different arterial oxygen tensions (PaO₂). We utilized blood samples collected during the COMACARE trial (NCT02698917). In the trial, 123 patients resuscitated from out-of-hospital cardiac arrest were treated with a 10–15 kPa or 20–25 kPa PaO₂ target during the initial 36 h in the intensive care unit. We measured the biomarker levels at admission, and 24, 48, and 72 h thereafter. We compared biomarker levels in the intervention groups and in groups that differed in oxygen exposure prior to randomization. Blood samples for biomarker determination were available for 112 patients. All four biomarker levels peaked at 24 h; the increase appeared greater in younger patients and in patients without bystander-initiated life support. No association between the lipid peroxidation biomarkers and oxygen exposure either before or after randomization was found. Increases in the biomarker levels during the first 24 h in intensive care suggest continuing oxidative stress, but the clinical relevance of this remains unresolved.

Neuroprotective effects of insulin like growth factor-1 on engineered metal nanoparticles Ag, Cu and Al induced blood-brain barrier breakdown, edema formation, oxidative stress, upregulation of neuronal nitric oxide synthase and brain pathology

Military personnel are vulnerable to environmental or industrial exposure of engineered nanoparticles (NPs) from metals. Long-term exposure of NPs from various sources affect sensory-motor or cognitive brain functions. Thus, a possibility exists that chronic exposure of NPs affect blood-brain barrier (BBB) breakdown and brain pathology by inducing oxidative stress and/or nitric oxide production. This hypothesis was examined in the rat intoxicated with Ag, Cu or Al (50-60nm) nanoparticles (50mg/kg, i.p. once daily) for 7 days. In these NPs treated rats the BBB permeability, brain edema, neuronal nitric oxide synthase (nNOS) immunoreactivity and brain oxidants levels, e.g., myeloperoxidase (MP), malondialdehyde (MD) and glutathione (GT) was examined on the 8th day. Cu and Ag but not Al nanoparticles increased the MP and MD levels by twofold in the brain although, GT showed 50% decline. At this time increase in brain water content and BBB breakdown to protein tracers were seen in areas exhibiting nNOS positive neurons and cell injuries. Pretreatment with insulin like growth factor-1 (IGF-1) in high doses (1μg/kg, i.v. but not 0.5μg/kg daily for 7 days) together with NPs significantly reduced the oxidative stress, nNOS upregulation, BBB breakdown, edema formation and cell injuries. These novel observations demonstrate that (i) NPs depending on their metal constituent (Cu, Ag but not Al) induce oxidative stress and nNOS expression leading to BBB disruption, brain edema and cell damage, and (ii) IGF-1 depending on doses exerts powerful neuroprotection against nanoneurotoxicity, not reported earlier.

Upregulation of hemeoxygenase enzymes HO-1 and HO-2 following ischemia-reperfusion injury in connection with experimental cardiac arrest and cardiopulmonary resuscitation: Neuroprotective effects of methylene blue

Oxidative stress plays an important role in neuronal injuries after cardiac arrest. Increased production of carbon monoxide (CO) by the enzyme hemeoxygenase (HO) in the brain is induced by the oxidative stress. HO is present in the CNS in two isoforms, namely the inducible HO-1 and the constitutive HO-2. Elevated levels of serum HO-1 occurs in cardiac arrest patients and upregulation of HO-1 in cardiac arrest is seen in the neurons. However, the role of HO-2 in cardiac arrest is not well known. In this review involvement of HO-1 and HO-2 enzymes in the porcine brain following cardiac arrest and resuscitation is discussed based on our own observations. In addition, neuroprotective role of methylene blue- an antioxidant dye on alterations in HO under in cardiac arrest is also presented. The biochemical findings of HO-1 and HO-2 enzymes using ELISA were further confirmed by immunocytochemical approach to localize selective regional alterations in cardiac arrest. Our observations are the first to show that cardiac arrest followed by successful cardiopulmonary resuscitation results in significant alteration in cerebral concentrations of HO-1 and HO-2 levels indicating a prominent role of CO in brain pathology and methylene blue during CPR followed by induced hypothermia leading to superior neuroprotection after return of spontaneous circulation (ROSC), not reported earlier.

Translation from animal studies of novel pharmacological therapies to clinical trials in cardiac arrest: A systematic review

BACKGROUND

There is a lack of new promising therapies to improve the dismal outcomes from cardiac arrest. The objectives of this study were: (1) To identify novel pharmacological therapies investigated in experimental animal studies and (2) to identify pharmacological therapies translated from experimental animal studies to clinical trials.

METHODS

PubMed was searched to first identify relevant experimental cardiac arrest animal models published within the last 20 years. Based on this, a list of interventions was created and a second search was performed to identify clinical trials testing one of these interventions. Data extraction was performed using standardised data extraction forms.

RESULTS

We identified 415 animal studies testing 190 different pharmacological interventions. The most commonly tested interventions were classified as vasopressors, anaesthetics/gases, or interventions aimed at molecular targets. We found 43 clinical trials testing 26 different interventions identified in the animal studies. Of these, 13 trials reported positive findings and 30 trials reported neutral findings with regards to the primary endpoint. No study showed harm of the intervention. Some interventions tested in human clinical trials, had previously been tested in animal studies without a positive effect on outcomes. A large number of animal studies was performed after publication of a clinical trial.

CONCLUSION

Numerous different pharmacological interventions have been tested in experimental animal models. Despite this only a limited number of these interventions have advanced to clinical trials, however several of the clinical trials tested interventions that were first tested in experimental animal models.

MEF2D upregulation protects neurons from oxygen-glucose deprivation/re-oxygenation-induced injury by enhancing Nrf2 activation

Accumulating evidence suggests that myocyte enhancer factor 2D (MEF2D) is a pro-survival factor for neurons. However, whether MEF2D is involved in protecting neurons from cerebral ischemia/reperfusion injury remains unknown. The current study was designed to investigate the exact role and mechanism of MEF2D in regulating oxygen-glucose deprivation/re-oxygenation (OGD/R)-induced neuronal injury, an in vitro model used to study cerebral ischemia/reperfusion injury. MEF2D expression was significantly induced in neurons in response to OGD/R injury. Functional analysis demonstrated that MEF2D upregulation significantly rescued the decreased viability of OGD/R-injured neurons and suppressed OGD/R-induced apoptosis and reactive oxygen species (ROS) production. By contrast, MEF2D knockdown increased the sensitivity of neurons to OGD/R-induced injury. Moreover, MEF2D overexpression increased the expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and enhanced the activation of Nrf2 antioxidant signaling. However, Nrf2 knockdown partially blocked the MEF2D-mediated neuroprotective effect in OGD/R-exposed neurons. Overall, these results reveal that MEF2D overexpression attenuates OGD/R-induced injury by enhancing Nrf2-mediated antioxidant signaling. These findings suggest that MEF2D may serve as a neuroprotective target with a potential application for treatment of cerebral ischemia/reperfusion injury.

Comparative Study Regarding the Properties of Methylene Blue and Proflavine and Their Optimal Concentrations for In Vitro and In Vivo Applications

Methylene blue and proflavine are fluorescent dyes used to stain nucleic acid from the molecular level to the tissue level. Already clinically used for sentinel node mapping, detection of neuroendocrine tumors, methemoglobinemia, septic shock, ifosfamide-induced encephalopathy, and photodynamic inactivation of RNA viruses, the antimicrobial, anti-inflammatory, and antioxidant effect of methylene blue has been demonstrated in different in vitro and in vivo studies. Proflavine was used as a disinfectant and bacteriostatic agent against many gram-positive bacteria, as well as a urinary antiseptic involved in highlighting cell nuclei. At the tissue level, the anti-inflammatory effects of methylene blue protect against pulmonary, renal, cardiac, pancreatic, ischemic-reperfusion lesions, and fevers. First used for their antiseptic and antiviral activity, respectively, methylene blue and proflavine turned out to be excellent dyes for diagnostic and treatment purposes. In vitro and in vivo studies demonstrated that both dyes are efficient as perfusion and tissue tracers and permitted to evaluate the minimal efficient concentration in different species, as well as their pharmacokinetics and toxicity. This review aims to identify the optimal concentrations of methylene blue and proflavine that can be used for in vivo experiments to highlight the vascularization of the skin in the case of a perforasome (both as a tissue tracer and in vascular mapping), as well as their effects on tissues. This review is intended to be a comparative and critical presentation of the possible applications of methylene blue (MB) and proflavine (PRO) in the surgical field, and the relevant biomedical findings from specialized literature to date are discussed as well.

SOD3 overexpression alleviates cerebral ischemia-reperfusion injury in rats

Background

Ischemic stroke is a deadly disease that poses a serious threat to human life. Superoxide dismutase 3 (SOD3, ECSOD) is the main antioxidant enzyme that removes superoxide anions from cells. This study aimed to investigate the effect of SOD3 overexpression on cerebral ischemia‐reperfusion injury in rats.

Methods

GV230‐EGFP‐ECSOD, the recombinant SOD3‐overexpressed vector, was constructed by genetic engineering technology, and mesenchymal stem cells (MSCs) were infected with lentiviral packaging. In animal experiment, cerebral ischemia‐reperfusion injury model rats were successfully established. ECSOD‐MSCs are the MSCs that successfully transfected with SOD3 overexpression vector. The animals were injected with ECSOD‐MSCs (ECSOD‐MSC group), normal MSCs (MSCs group), PBS (PBS group), and not do any processing (Model group) via the tail vein. Then MRI was used to detect the infarct volume of rats, modified Neurological Severity Scores (mNSS), and immunohistochemistry were used to evaluate the expression of neurological function and apoptosis‐related genes in rats.

Results

Western blot analysis revealed that the SOD3 was highly expressed in MSCs. Animal experiments showed that the transplantation of ECSOD‐MSCs significantly reduced the infarct volume of ischemic stroke rats (p < 0.05), significantly improved neurological function in rats (p < 0.05), and found proapoptotic gene, Bax, expression was significantly decreased (p < 0.05), the expression of anti‐apoptotic gene, Bcl‐2, was significantly increased (p < 0.05). The highly expressed SOD3 has no correction with brain infarct volume, and the highly expressed SOD3 has a positive correlation with cell apoptosis. It is speculated that overexpression of SOD3 affects the expression of Bax and Bcl‐2, and improves apoptosis to alleviate ischemic stroke.

Conclusion

Our results indicated that MSCs transfected with SOD3 can effectively alleviate cerebral ischemia‐reperfusion injury in rats.

A New Vision for Therapeutic Hypothermia in the Era of Targeted Temperature Management: A Speculative Synthesis

Three decades of animal studies have reproducibly shown that hypothermia is profoundly cerebroprotective during or after a central nervous system (CNS) insult. The success of hypothermia in preclinical acute brain injury has not only fostered continued interest in research on the classic secondary injury mechanisms that are prevented or blunted by hypothermia but has also sparked a surge of new interest in elucidating beneficial signaling molecules that are increased by cooling. Ironically, while research into cold-induced neuroprotection is enjoying newfound interest in chronic neurodegenerative disease, conversely, the scope of the utility of therapeutic hypothermia (TH) across the field of acute brain injury is somewhat controversial and remains to be fully defined. This has led to the era of Targeted Temperature Management, which emphasizes a wider range of temperatures (33–36°C) showing benefit in acute brain injury. In this comprehensive review, we focus on our current understandings of the novel neuroprotective mechanisms activated by TH, and discuss the critical importance of developmental age germane to its clinical efficacy. We review emerging data on four cold stress hormones and three cold shock proteins that have generated new interest in hypothermia in the field of CNS injury, to create a framework for new frontiers in TH research. We make the case that further elucidation of novel cold responsive pathways might lead to major breakthroughs in the treatment of acute brain injury, chronic neurological diseases, and have broad potential implications for medicines of the distant future, including scenarios such as the prevention of adverse effects of long-duration spaceflight, among others. Finally, we introduce several new phrases that readily summarize the essence of the major concepts outlined by this review—namely, Ultramild Hypothermia, the “Responsivity of Cold Stress Pathways,” and “Hypothermia in a Syringe.”

Neuroprotection of hydroxysafflor yellow A in experimental cerebral ischemia/reperfusion injury via metabolic inhibition of phenylalanine and mitochondrial biogenesis

Stroke is the second most frequent cause of mortality, resulting in a huge societal burden worldwide. Timely reperfusion is the most effective therapy; however, it is difficult to prevent ischemia/reperfusion (I/R) injury. In traditional Chinese medicine, hydroxysafflor yellow A (HSYA) has been widely used for the treatment of cerebrovascular disease and as a protective therapy against I/R injury. Evidence has demonstrated that HSYA could reduce the levels of reactive oxygen species and suppress cellular apoptosis; however, whether HSYA alters the metabolic profile as its underlying mechanism for neuroprotection remains unknown. In the present study, using a metabolomic screening, phenylalanine was identified to significantly increase in an experimental model of mouse cerebral I/R injury. Notably, western blotting and qPCR analysis were conducted to test the expression level of apoptosis-associated factors, and HSYA was identified to be able to protect neuronal cells by reducing phenylalanine level associated with I/R injury. Additionally, these findings were confirmed in primary mouse neurons and PC12 cells exposed to oxygen and glucose deprivation/reoxygenation (OGD/R) stress. Of note, HSYA was observed to regulate the mRNA expression of key metabolic enzymes, phenylalanine hydroxylase, tyrosine aminotransferase and aspartate aminotransferase, which are responsible for phenylalanine metabolism. Furthermore, by performing mitochondrial labeling and JC-1 fluorescence assay, HSYA was identified to promote mitochondrial function and biogenesis suppressed by OGD/R. The findings of the present study demonstrated that I/R injury could increase the levels of phenylalanine, and HSYA may inhibit phenylalanine synthesis to enhance mitochondrial function and biogenesis for neuroprotection. The present study proposed a novel metabolite biomarker for cerebral I/R injury and the evaluated the efficacy of HSYA as a potential therapeutic treatment I/R injury.