Decrease in Oxidative Stress Parameters after Post-Ischaemic Recombinant Human Erythropoietin Administration in the Hippocampus of Rats Exposed to Focal Cerebral Ischaemia

Detection of lipid radicals generated via cerebral ischemia/reperfusion injury using a radiolabeled nitroxide probe

Reactive oxygen species generated via reperfusion cause lipid damage and induce lipid peroxidation, leading to cerebral ischemia/reperfusion injury and exacerbation of cerebral infarction. Lipid radicals are key molecules generated during lipid peroxidation. Therefore, understanding the spatiotemporal behavior of lipid radicals is important to improve the therapeutic outcomes of cerebral infarction. However, the behaviors of lipid radicals in the brain remain unclear. In this study, we aimed to evaluate the distribution of radioactivity in a transient middle cerebral artery occlusion (tMCAO) model using lipid radical detection probe [125I]1 to assess the behaviors of lipid radicals after cerebral ischemia/reperfusion. The tMCAO model administered [125I]1 exhibited significant differences in the timing and location of radioactivity accumulation between the ischemic and non-ischemic regions. Liquid chromatography/mass spectrometry analysis identified the lipid radical adducts formed by the reaction of 1 with the lipid radicals generated after reperfusion. More adducts were detected in the ischemic region samples than in the non-ischemic region samples. Therefore, 1 successfully detected the lipid radicals generated after cerebral ischemia/reperfusion. Overall, this study demonstrates the potential of nuclear medical imaging using radiolabeled 1 to detect the lipid radicals generated after cerebral ischemia/reperfusion. Our approach can aid in the development of new therapeutic agents scavenging lipid radicals after cerebral reperfusion by facilitating the determination of therapeutic efficacy and optimal administration period.

Modeling Central Nervous System Injury In Vitro: Current Status and Promising Future Strategies

The central nervous system (CNS) injury, which occurs because of mechanical trauma or ischemia/hypoxia, is one of the main causes of mortality and morbidity in the modern society. Until know, despite the fact that numerous preclinical and clinical studies have been undertaken, no significant neuroprotective strategies have been discovered that could be used in the brain trauma or ischemia treatment. Although there are many potential explanations for the failure of those studies, it is clear that there are questions regarding the use of experimental models, both in vivo and in vitro, when studying CNS injury and searching new therapeutics. Due to some ethical issues with the use of live animals in biomedical research, implementation of experimental strategies that prioritize the use of cells and tissues in the in vitro environment has been encouraged. In this review, we examined some of the most commonly used in vitro models and the most frequently utilized cellular platforms in the research of traumatic brain injury and cerebral ischemia. We also proposed some future strategies that could improve the usefulness of these studies for better bench-to-bedside translational outcomes.

The Nrf2 Pathway in Ischemic Stroke: A Review

Ischemic stroke, characterized by the sudden loss of blood flow in specific area(s) of the brain, is the leading cause of permanent disability and is among the leading causes of death worldwide. The only approved pharmacological treatment for acute ischemic stroke (intravenous thrombolysis with recombinant tissue plasminogen activator) has significant clinical limitations and does not consider the complex set of events taking place after the onset of ischemic stroke (ischemic cascade), which is characterized by significant pro-oxidative events. The transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2), which regulates the expression of a great number of antioxidant and/or defense proteins, has been pointed as a potential pharmacological target involved in the mitigation of deleterious oxidative events taking place at the ischemic cascade. This review summarizes studies concerning the protective role of Nrf2 in experimental models of ischemic stroke, emphasizing molecular events resulting from ischemic stroke that are, in parallel, modulated by Nrf2. Considering the acute nature of ischemic stroke, we discuss the challenges in using a putative pharmacological strategy (Nrf2 activator) that relies upon transcription, translation and metabolically active cells in treating ischemic stroke patients.

Changes in Gene Expression and Neuroinflammation in the Hippocampus after Focal Brain Ischemia: Involvement in the Long-Term Cognitive and Mental Disorders

Ischemic brain injuries are accompanied by the long-term changes in gene expression in the hippocampus, the limbic system structure, involved in the regulation of key aspects of the higher nervous activity, such as cognitive functions and emotions. The altered expression of genes and proteins encoded by them may be related to the development of post-ischemic psycho-emotional and cognitive disturbances. Activation of neuroinflammation following stroke in the hippocampus has been suggested to play an essential role in induction of long-lasting consequences. Identification of changes in the gene expression patterns after ischemia and investigation of the dynamics of these changes in the hippocampus are the necessary first steps toward understanding molecular pathways responsible for the development of post-stroke cognitive impairments and mental pathologies.

Whether erythropoietin can be a neuroprotective agent against premature brain injury: cellular mechanisms and clinical efficacy

Preterm infants are at high risk of brain injury. With more understanding of the preterm brain injury's pathogenesis, neuroscientists are looking for more effective methods to prevent and treat it, among which erythropoietin (Epo) is considered as a prime candidate. This review tries to clarify the possible mechanisms of Epo in preterm neuroprotection and summarize updated evidence considering Epo as a pharmacological neuroprotective strategy in animal models and clinical trials. To date, various animal models have validated that Epo is an anti-apoptotic, anti-inflammatory, anti-oxidant, anti-excitotoxic, neurogenetic, erythropoietic, angiogenetic, and neurotrophic agent, thus preventing preterm brain injury. However, although the scientific rationale and preclinical data for Epo's neuroprotective effect are promising, when translated to bedside, the results vary in different studies, especially in its long-term efficacy. Based on existing evidence, it is still too early to recommend Epo as the standard treatment for preterm brain injury.

EPO and EPO-Receptor System as Potential Actionable Mechanism for the Protection of Brain and Heart in Refractory Epilepsy and SUDEP

The most important activity of erythropoietin (EPO) is the regulation of erythrocyte production by activation of the erythropoietin receptor (EPO-R), which triggers the activation of anti-apoptotic and proliferative responses of erythroid progenitor cells. Additionally, to erythropoietic EPO activity, an antiapoptotic effect has been described in a wide spectrum of tissues. EPO low levels are found in the central nervous system (CNS), while EPO-R is expressed in most CNS cell types. In spite of EPO-R high levels expressed during the hypoxicischemic brain, insufficient production of endogenous cerebral EPO could be the cause of determined circuit alterations that lead to the loss of specific neuronal populations. In the heart, high EPO-R expression in cardiac progenitor cells appears to contribute to myocardial regeneration under EPO stimulation. Several lines of evidence have linked EPO to an antiapoptotic role in CNS and in heart tissue. In this review, an antiapoptotic role of EPO/EPO-R system in both brain and heart under hypoxic conditions, such as epilepsy and sudden death (SUDEP) has been resumed. Additionally, their protective effects could be a new field of research and a novel therapeutic strategy for the early treatment of these conditions and avoid SUDEP.

PEGylated Erythropoietin Protects against Brain Injury in the MCAO-Induced Stroke Model by Blocking NF-κB Activation

Cerebral ischemia exhibits a multiplicity of pathophysiological mechanisms. During ischemic stroke, the reactive oxygen species (ROS) concentration rises to a peak during reperfusion, possibly underlying neuronal death. Recombinant human erythropoietin (EPO) supplementation is one method of treating neurodegenerative disease by reducing the generation of ROS. We investigated the therapeutic effect of PEGylated EPO (P-EPO) on ischemic stroke. Mice were administered P-EPO (5,000 U/kg) via intravenous injection, and middle cerebral artery occlusion (MCAO) followed by reperfusion was performed to induce in vivo ischemic stroke. P-EPO ameliorated MCAO-induced neurological deficit and reduced behavioral disorder and the infarct area. Moreover, lipid peroxidation, expression of inflammatory proteins (cyclooxygenase-2 and inducible nitric oxide synthase), and cytokine levels in blood were reduced by the P-EPO treatment. In addition, higher activation of nuclear factor kappa B (NF-κB) was found in the brain after MCAO, but NF-κB activation was reduced in the P-EPO-injected group. Treatment with the NF-κB inhibitor PS-1145 (5 mg/kg) abolished the P-EPO-induced reduction of infarct volume, neuronal death, neuroinflammation, and oxidative stress. Moreover, P-EPO was more effective than EPO (5,000 U/kg) and similar to a tissue plasminogen activator (10 mg/kg). An in vitro study revealed that P-EPO (25, 50, and 100 U/mL) treatment protected against rotenone (100 nM)-induced neuronal loss, neuroinflammation, oxidative stress, and NF-κB activity. These results indicate that the administration of P-EPO exerted neuroprotective effects on cerebral ischemia damage through anti-oxidant and anti-inflammatory properties by inhibiting NF-κB activation.

Neuroprotective Effects of Gabapentin Against Cerebral Ischemia Reperfusion-Induced Neuronal Autophagic Injury via Regulation of the PI3K/Akt/mTOR Signaling Pathways

Gabapentin (GBP), an analgesic, adjunct antiepileptic, and migraine prophylactic drug, reduces neuronal injury induced by cerebral ischemia reperfusion (IR). However, the underlying biological molecular mechanism of GBP neuroprotection is not clear. In this study, we confirmed that dose-dependent (75 and 150 mg/kg) GBP treatment could significantly reduce IR-induced neuronal death. IR-induced neuronal death was inhibited by pretreatment with 150 mg/kg GBP in a middle cerebral artery occlusion rat model. In addition, 150 mg/kg GBP treatment remarkably promoted the levels of antioxidants and reduced the autophagy of neurons in the infarct penumbra. Moreover, the phosphoinositide-3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway was activated by pretreatment with 150 mg/kg GBP, as detected by Western blot analyses. In vitro, pretreatment of PC12 cells with 450 µM GBP significantly reduced cell death induced by oxygen-glucose deprivation, increased antioxidant function, and reduced the levels of autophagy and reactive oxygen species via activation of the PI3K/Akt/mTOR pathway. This neuroprotection by GBP was inhibited significantly by 10 µM LY294002. In summary, dose-dependent pretreatment with GBP protected against cerebral IR injury via activation of the PI3K/Akt/mTOR pathway, which provided a neuroprotective function to inhibit oxidative stress-related neuronal autophagy.

Early-life N-arachidonoyl-dopamine exposure increases antioxidant capacity of the brain tissues and reduces functional deficits after neonatal hypoxia in rats

Perinatal hypoxia-ischemia is one of the most common causes of perinatal brain injury and subsequent neurological disorders in children. The aim of this work was to evaluate the potential antioxidant and neuroprotective effects of N-arachidonoyl-dopamine (NADA) in the model of acute neonatal hypoxia (ANH) in rat pups. Male and female Wistar rats were exposed to a hypoxic condition (8% oxygen for 120 min) at postnatal day 2 (P2). Transcription factor HIF1-α and glutathione peroxidases GPx2 and GPx4 gene expression was increased in rat brains in the hypoxic group compared to control 1.5 h but not 4 days after ANH. There were no post-hypoxic changes in reduced (GSH) and oxidised (GSSG) glutathione levels in the brain of rat pups 1.5 h and 4 d after hypoxia. Hypoxic rats displayed retarded performance in the righting reflex and the negative geotaxis tests. ANH resulted in increased ambulation in Open field test and impaired retention in the Barnes maze task under stressful conditions as compared with the control group. Treatment with NADA significantly attenuated the delayed development of sensorimotor reflexes and stress-evoked disruption of memory retention in hypoxic rats but had no effect on the hypoxia-induced hyperactivity. In rats exposed to hypoxia, treatment with NADA decreased GPx2 gene expression and increased GSH/GSSG ratio in whole brains 1.5 h after ANH. These results suggest that the long-lasting beneficial effects of NADA on hypoxia-induced neurobehavioural deficits are mediated, at least in part, by its antioxidant properties.

Critical Role of Nrf2 in Experimental Ischemic Stroke

Ischemic stroke is one of the leading causes of death and long-term disability worldwide; however, effective clinical approaches are still limited. The transcriptional factor Nrf2 is a master regulator in cellular and organismal defense against endogenous and exogenous stressors by coordinating basal and stress-inducible activation of multiple cytoprotective genes. The Nrf2 network not only tightly controls redox homeostasis but also regulates multiple intermediary metabolic processes. Therefore, targeting Nrf2 has emerged as an attractive therapeutic strategy for the prevention and treatment of CNS diseases including stroke. Here, the current understanding of the Nrf2 regulatory network is critically examined to present evidence for the contribution of Nrf2 pathway in rodent ischemic stroke models. This review outlines the literature for Nrf2 studies in preclinical stroke and focuses on the in vivo evidence for the role of Nrf2 in primary and secondary brain injuries. The dynamic change and functional importance of Nrf2 signaling, as well as Nrf2 targeted intervention, are revealed in permanent, transient, and global cerebral ischemia models. In addition, key considerations, pitfalls, and future potentials for Nrf2 studies in preclinical stroke investigation are discussed.