Global Ischemia Research Articles

Cuban policosanol: a natural compound for ischemic stroke treatment

Stroke is among the leading causes of mortality and disability; therefore, it constitutes a relevant health problem. Cuban policosanol presents lipid-lowering, antiplatelet, antioxidant and vascular endothelium protective properties, all of which give it a comprehensive anti-atherosclerotic effect. This review is aimed to show, analyze and discuss the main preclinical and clinical evidence of the effects of Cuban policosanol on ischemic stroke. Preclinical studies evidenced the anti-ischemic effects of preventive and therapeutic oral treatment with Cuban policosanol in Mongolian gerbils with cerebral ischemia induced by unilateral and permanent ligation of a carotid artery, and in global cerebral ischemia induced by bilateral clamping and recirculation of both carotids; being similar or superior to other anti-ischemic agents. Also, combination therapy with aspirin produced greater anti-stroke efficacy compared with aspirin monotherapy, but being similar to policosanol plus atorvastatin combination. This anti-stroke effect was associated to a serum thromboxane A2 (TxA2) concentrations reduction and prostacyclin (PgI2) increase, leading to a favorable TxA2/PgI2 balance, and also to the malondialdehyde (MDA) and sulfhydryl groups (SHG, lipid peroxidation and protein oxidation markers, respectively) reduction. Cuban policosanol combined with aspirin (standard therapy) improved and benefited patients with prior ischemic stroke in terms of functional and neurological outcomes, in open-label studies and in randomized, double-blind, controlled studies. These beneficial effects on stroke patients were associated with antioxidant and antiplatelet effects of policosanol. Also, the combinations of Cuban policosanol plus aspirin and atorvastatin plus aspirin compared in a clinical study significantly and similarly improved the neurological recovery of patients with ischemic stroke. Cuban policosanol was safe and well tolerated, with no serious adverse events occurring during the trials. In conclusion, Cuban policosanol is a safe and effective natural drug for ischemic stroke treatment, which is supported by preclinical and clinical evidences.

Switching Off Vascular MAPK Signaling: A Novel Strategy to Prevent Delayed Cerebral Ischemia Following Subarachnoid Hemorrhage

AbstractPatients who initially survive the rupture and repair of a brain aneurysm often take a devastating turn for the worse some days later and die or suffer permanent neurologic deficits. This catastrophic sequela is attributed to a delayed phase of global cerebral ischemia (DCI) following aneurysmal subarachnoid hemorrhage (aSAH), but we lack effective treatment. Here we present our view, based on 20 years of research, that the initial drop in blood flow at the time of rupture triggers genomic responses throughout the brain vasculature that manifest days later as increased vasoconstriction and decreased cerebral blood flow. We propose a novel treatment strategy to prevent DCI by early inhibition of the vascular mitogen-activated protein kinase (MAPK) pathway that triggers expression of vasoconstrictor and inflammatory mediators. We summarize evidence from experimental SAH models showing early treatment with MAPK inhibitors “switches off” these detrimental responses, maintains flow, and improves neurological outcome. This promising therapy is currently being evaluated in clinical trials.

Hypothermia increases adenosine monophosphate and xanthosine monophosphate levels in the mouse hippocampus, preventing their reduction by global cerebral ischemia

Global cerebral ischemia (GCI) caused by clinical conditions such as cardiac arrest leads to delayed neuronal death in the hippocampus, resulting in physical and mental disability. However, the mechanism of delayed neuronal death following GCI remains unclear. To elucidate the mechanism, we performed a metabolome analysis using a mouse model in which hypothermia (HT) during GCI, which was induced by the transient occlusion of the bilateral common carotid arteries, markedly suppressed the development of delayed neuronal death in the hippocampus after reperfusion. Fifteen metabolites whose levels were significantly changed by GCI and 12 metabolites whose levels were significantly changed by HT were identified. Furthermore, the metabolites common for both changes were narrowed down to two, adenosine monophosphate (AMP) and xanthosine monophosphate (XMP). The levels of both AMP and XMP were found to be decreased by GCI, but increased by HT, thereby preventing their decrease. In contrast, the levels of adenosine, inosine, hypoxanthine, xanthine, and guanosine, the downstream metabolites of AMP and XMP, were increased by GCI, but were not affected by HT. Our results may provide a clue to understanding the mechanism by which HT during GCI suppresses the development of delayed neuronal death in the hippocampus.

Remote Ischemia Postconditioning Mitigates Hippocampal Neuron Impairment by Modulating Cav1.2-CaMKIIα-Aromatase Signaling After Global Cerebral Ischemia in Ovariectomized Rats

Brain-derived estrogen (BDE2) is gaining attention as an endogenous neurotransmitter. Recent research has revealed that selectively removing the aromatase gene, the pivotal enzyme responsible for BDE2 synthesis, in forebrain neurons or astrocytes can lead to synaptic loss and cognitive impairment. It is worth noting that remote ischemia post-conditioning (RIP), a non-invasive technique, has been shown to activate natural protective mechanisms against severe ischemic events. The aim of our study was to investigate whether RIP triggers aromatase-BDE2 signaling, shedding light on its neuroprotective mechanisms after global cerebral ischemia (GCI) in ovariectomized rats. Our findings are as follows: (1) RIP was effective in mitigating ischemic damage in hippocampal CA1 neurons and improved cognitive function after GCI. This was partially due to increased Aro-BDE2 signaling in CA1 neurons. (2) RIP intervention efficiently enhanced pro-survival kinase pathways, such as AKT, ERK1/2, CREB, and suppressed CaMKIIα signaling in CA1 astrocytes induced by GCI. Remarkably, inhibiting CaMKIIα activity led to elevated Aro-BDE2 levels and replicated the benefits of RIP. (3) We also identified the positive mediation of Cav1.2, an LVGCC calcium channel, on CaMKIIα-Aro/BDE2 pathway response to RIP intervention. (4) Significantly, either RIP or CaMKIIα inhibition was found to alleviate reactive astrogliosis, which was accompanied by increased pro-survival A2-astrocyte protein S100A10 and decreased pro-death A1-astrocyte marker C3 levels. In summary, our study provides compelling evidence that Aro-BDE2 signaling is a critical target for the reparative effects of RIP following ischemic insult. This effect may be mediated through the CaV1.2-CaMKIIα signaling pathway, in collaboration with astrocyte-neuron interactions, thereby maintaining calcium homeostasis in the neuronal microenvironment and reducing neuronal damage after ischemia.

Brain-Derived Neurotrophic Factor in Pediatric Acquired Brain Injury and Recovery.

We review emerging preclinical and clinical evidence regarding brain-derived neurotrophic factor (BDNF) protein, genotype, and DNA methylation (DNAm) as biomarkers of outcomes in three important etiologies of pediatric acquired brain injury (ABI), traumatic brain injury, global cerebral ischemia, and stroke. We also summarize evidence suggesting that BDNF is (1) involved in the biological embedding of the psychosocial environment, (2) responsive to rehabilitative therapies, and (3) potentially modifiable. BDNF's unique potential as a biomarker of neuroplasticity and neural repair that is reflective of and responsive to both pre- and post-injury environmental influences separates it from traditional protein biomarkers of structural brain injury with exciting potential to advance pediatric ABI management by increasing the accuracy of prognostic tools and informing clinical decision making through the monitoring of therapeutic effects.

Autophagy inhibitors 3-MA and BAF may attenuate hippocampal neuronal necroptosis after global cerebral ischemia-reperfusion injury in male rats by inhibiting the interaction of the RIP3/AIF/CypA complex.

Our previous study found that receptor interacting protein 3 (RIP3) and apoptosis-inducing factor (AIF) were involved in neuronal programmed necrosis during global cerebral ischemia-reperfusion (I/R) injury. Here, we further studied its downstream mechanisms and the role of the autophagy inhibitors 3-methyladenine (3-MA) and bafilomycin A1 (BAF). A 20-min global cerebral I/R injury model was constructed using the 4-vessel occlusion (4-VO) method in male rats. 3-MA and BAF were injected into the lateral ventricle 1 h before ischemia. Spatial and activation changes of proteins were detected by immunofluorescence (IF), and protein interaction was determined by immunoprecipitation (IP). The phosphorylation of H2AX (γ-H2AX) and activation of mixed lineage kinase domain-like protein (p-MLKL) occurred as early as 6 h after reperfusion. RIP3, AIF, and cyclophilin A (CypA) in the neurons after I/R injury were spatially overlapped around and within the nucleus and combined with each other after reperfusion. The survival rate of CA1 neurons in the 3-MA and BAF groups was significantly higher than that in the I/R group. Autophagy was activated significantly after I/R injury, which was partially inhibited by 3-MA and BAF. Pretreatment with both 3-MA and BAF almost completely inhibited nuclear translocation, spatial overlap, and combination of RIP3, AIF, and CypA proteins. These findings suggest that after global cerebral I/R injury, RIP3, AIF, and CypA translocated into the nuclei and formed the DNA degradation complex RIP3/AIF/CypA in hippocampal CA1 neurons. Pretreatment with autophagy inhibitors could reduce neuronal necroptosis by preventing the formation of the RIP3/AIF/CypA complex and its nuclear translocation.

Quercetin Protects Against Global Cerebral ischemia‒reperfusion Injury by Inhibiting Microglial Activation and Polarization.

This study aims to investigate the protective effect of quercetin against global cerebral ischemia‒reperfusion (GCI/R) injury in rats and elucidate the underlying mechanism. A GCI/R injury rat model was established using a four-vessel occlusion (4-VO) method. An oxygen-glucose deprivation/reoxygenation (OGD/R) injury model was induced in BV2 cells. The extent of injury was assessed by evaluating neurological deficit scores (NDS) and brain water content and conducting behavioral tests. Pathomorphological changes in the prefrontal cortex were examined. Additionally, the study measured the levels of inflammatory cytokines, the degree of microglial activation and polarization, and the protein expression of Toll-like receptor 4 (TLR4) and TIR-domain-containing adaptor inducing interferon-β (TRIF). Quercetin pretreatment significantly ameliorated neurological impairment, improved learning and memory abilities, and reduced anxiety in rats subjected to GCI/R injury. Furthermore, quercetin administration effectively mitigated neuronal injury and brain edema. Notably, it suppressed microglial activation and hindered polarization toward the M1 phenotype. Simultaneously, quercetin downregulated the expression of TLR4 and TRIF proteins and attenuated the release of IL-1β and TNF-α. This study highlights the novel therapeutic potential of quercetin in alleviating GCI/R injury. Quercetin demonstrates its neuroprotective effects by inhibiting neuroinflammation and microglial activation while impeding their transformation into the M1 phenotype through modulation of the TLR4/TRIF pathway.

Rapamycin Alleviates Neuronal Injury and Modulates Microglial Activation After Cerebral Ischemia.

Neurons and microglia are sensitive to cerebral microcirculation and their responses play a crucial part in the pathological processes, while they are also the main target cells of many drugs used to treat brain diseases. Rapamycin exhibits beneficial effects in many diseases; however, whether it can affect neuronal injury or alter the microglial activation after global cerebral ischemia remains unclear. In this study, we performed global cerebral ischemia combined with rapamycin treatment in CX3CR1GFP/+ mice and explored the effects of rapamycin on neuronal deficit and microglial activation. Our results showed that rapamycin reduced neuronal loss, neurodegeneration, and ultrastructural damage after ischemia by histological staining and transmission electron microscopy (TEM). Interestingly, rapamycin suppressed de-ramification and proliferation of microglia and reduced the density of microglia. Immunofluorescence staining indicated that rapamycin skewed microglial polarization toward an anti-inflammatory state. Furthermore, rapamycin as well suppressed the activation of astrocytes. Meanwhile, quantitative real-time polymerase chain reaction (qRT-PCR) analyses revealed a significant reduction of pro-inflammatory factors as well as an elevation of anti-inflammatory factors upon rapamycin treatment. As a result of these effects, behavioral tests showed that rapamycin significantly alleviated the brain injury after stroke. Together, our study suggested that rapamycin attenuated neuronal injury, altered microglial activation state, and provided a more beneficial immune microenvironment for the brain, which could be used as a promising therapeutic approach to treat ischemic cerebrovascular diseases.

Importance of Per2 in cardiac mitochondrial protection during stress

During myocardial injury, inflammatory mediators and oxidative stress significantly increase to impair cardiac mitochondria. Emerging evidence has highlighted interplays between circadian protein—period 2 (Per2) and mitochondrial metabolism. However, besides circadian rhythm regulation, the direct role of Per2 in mitochondrial performance particularly following acute stress, remains unknown. In this study, we aim to determine the importance of Per2 protein’s regulatory role in mitochondrial function following exposure to inflammatory cytokine TNFα and oxidative stressor H2O2 in human cardiomyocytes. Global warm ischemia (37 °C) significantly impaired complex I activity with concurrently reduced mitochondrial Per2 in adult mouse hearts. TNFα or H2O2 decreased Per2 protein levels and damaged mitochondrial respiratory function in adult mouse cardiomyocytes. Next, mitochondrial membrane potential (Δψ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta \\psi$$\\end{document}M) using JC-1 fluorescence probe and mitochondrial respiration capacity via Seahorse Cell Mito Stress Test were then detected in Per2 or control siRNA transfected AC16 Human Cardiomyocytes (HCM) that were subjected to 2 h-treatment of TNFα (100 ng/ml) or H2O2 (100 μM). After 4 h-treatment, cell death was also measured using Annexin V and propidium iodide apoptosis kit through flow cytometry. We found that knockdown of Per2 enhanced TNFα-induced cell death and TNFα- or H2O2-disrupted Δψ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta \\psi$$\\end{document}M, as well as TNFα- or H2O2-impaired mitochondrial respiration function. In conclusion, Per2 knockdown increases likelihood of cell death and mitochondrial dysfunction in human cardiomyocytes exposed to either TNFα or H2O2, supporting the protective role of Per2 in HCM during stress with a focus on mitochondrial function.

Electroacupuncture at the Dazhui and Baihui acupoints and different frequencies (10 and 50 Hz) protects against apoptosis by up-regulating ERK1/2-mediated signaling in rats after global cerebral ischemia.

This study assessed the effects of electroacupuncture (EA) stimulation at different frequencies at the Dazhui and Baihui acupoints in the subacute phase after transient global cerebral ischemia (GCI). Rats were subjected to GCI for 25 min, followed by reperfusion for 7 days. EA at acupoints was performed at 10, 30, or 50 Hz, 1 day after reperfusion and then once daily for 6 consecutive days. EA at acupoints at 10 and 50 Hz effectively down-regulated apoptosis in the hippocampal cornu ammonis 1(CA1) area and ameliorated memory deficits. Moreover, EA treatment at 10 and 50 Hz markedly increased phospho (p)-extracellular signal-regulated protein kinase 1/2 (ERK1/2), p-ERK1/2/neuronal nuclei (NeuN), p-cAMP response element-binding protein (CREB)/p-ERK1/2, B-cell lymphoma-2 (Bcl-2)/p-CREB, and X-linked inhibitor of apoptosis protein/NeuN expression levels and decreased Bcl-2 homologous antagonist/killer, second mitochondria-derived activator of caspase/direct inhibitor of apoptosis-binding protein with low pI, cytochrome c, cleaved caspase-3, and apoptosis-inducing factor expression levels. Furthermore, 10-Hz EA treatment effectively increased p-p38 mitogen-activated protein kinase (MAPK), p-p38 MAPK/NeuN, and p-CREB/p-p38 MAPK expression levels. Pretreatment with U0126 (ERK1/2 inhibitor) completely abrogated the effects of 10- and 50-Hz EA treatments on the aforementioned protein expression levels. Similarly, pretreatment with SB203580 (p38 MAPK inhibitor) completely abrogated the effects of 10-Hz treatment on the aforementioned protein expression levels. The effects of 10- and 50-Hz EA treatments on mitochondria-related apoptosis can be attributed to the activation of ERK1/2/p38 MAPK/CREB/Bcl-2- and ERK1/2/CREB/Bcl-2-mediated signaling, respectively, in the hippocampal CA1 area at 7 days after transient GCI.

Additive Effects of Esaxerenone, a Nonsteroidal Mineralocorticoid Receptor Blocker, on Cardioplegic Arrest in Rat Hearts.

Esaxerenone, a mineralocorticoid receptor blocker, attenuates global ischemia-induced myocardial damage and coronary endothelial dysfunction. This study aimed to determine whether esaxerenone exerted cardioprotective effects against cardioplegic arrest in Wistar rat hearts. Isolated male Wistar rat hearts aerobically perfused via the Langendorff method for 20 min were randomly allocated to the Control (n = 6; perfused for an additional 10 min and subjected to no treatment) or Esax (n = 6; perfused with 0.1 μmol/L esaxerenone in perfusate for 10 min before ischemia) groups. Hearts in both groups were perfused with St. Thomas' Hospital No. 2 solution (STH2) for 2 min and subjected to 28 min of global ischemia. The recovery of left ventricular developed pressure (LVDP) and total troponin T leakage were measured after reperfusion. The final recovery of LVDP (expressed as a percentage of pre-ischemic value) in the Control and Esax groups was 50.8 ± 3.5% and 62.1 ± 5.6%, respectively (p <0.05, Esax vs. Control). The total troponin T leakage in the Control and Esax groups was 138.8 ± 18.5 ng/g heart wt and 74.3 ± 18.6 ng/g heart wt, respectively (p <0.05, Esax vs. Control). The administration of esaxerenone before cardioplegic arrest enhanced the cardioprotective effect exerted by STH2.

Methylprednisolone Does Not Enhance Paraoxonase 1 Activity During Cardiopulmonary Bypass Surgery—A Randomized, Controlled Clinical Trial

ObjectivesCardiopulmonary bypass (CPB) is linked to systemic inflammatory responses and oxidative stress. Paraoxonase 1 (PON1) is an antioxidant enzyme with a cardioprotective role, whose activity is decreased in systemic inflammation, and in patients with acute myocardial and global ischemia. Glucocorticoids counteract the effect of oxidative stress by up-regulating PON1 gene expression. We aimed to determine the effect of methylprednisolone on PON1 activity during cardiac surgery on CPB. DesignProspective, randomized, controlled clinical trial. SettingThe study was conducted at the University Medical Centre Ljubljana, Slovenia. Participants40 adult patients, who underwent complex cardiac surgery on CPB between February 2016 and December 2017, were randomized into methylprednisolone and control group (n=20 each). InterventionsPatients in the methylprednisolone group received 1g of methylprednisolone in the CPB priming solution, while patients in the control group were not given methylprednisolone during CPB. Measurements and Main ResultsWe compared the effect of methylprednisolone from CPB priming solution with standard care during CPB on PON1 activity until the 5. postoperative day. Correlations of PON1 activity with lipid status, mediators of inflammation, and hemodynamics were analyzed as well. No significant differences existed between study groups for PON1 activity, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) in any of the measurement intervals (p>0.016). Methylprednisolone group had significantly lower TNF-a (p<0.001), IL-6 (p<0.001), as well as CRP and procalcitonin (p<0.016) after surgery. No significant difference was found between groups for hemodynamic parameters. A positive correlation existed between PON1 and lipid status, whereas a negative correlation was found between PON1 activity and TNF-a, IL-6, as well as CPB duration. ConclusionsMethylprednisolone doesn't influence PON1 activity during cardiac surgery on CPB.

Metabolically Glycoengineered Neural Stem Cells Boost Neural Repair After Cardiac Arrest.

Cardiac arrest (CA)-induced cerebral ischemia remains challenging with high mortality and disability. Neural stem cell (NSC) engrafting is an emerging therapeutic strategy with considerable promise that, unfortunately, is severely compromised by limited cell functionality after in vivo transplantation. This groundbreaking report demonstrates that metabolic glycoengineering (MGE) using the "Ac5ManNTProp (TProp)" monosaccharide analog stimulates the Wnt/β-catenin pathway, improves cell adhesion, and enhances neuronal differentiation in human NSCs in vitro thereby substantially increasing the therapeutic potential of these cells. For the first time, MGE significantly enhances NSC efficacy for treating ischemic brain injury after asphyxia CA in rats. In particular, neurological deficit scores and neurobehavioral tests experience greater improvements when the therapeutic cells are pretreated with TProp than with "stand-alone" NSC therapy. Notably, the TProp-NSC group exhibits significantly stronger neuroprotective functions including enhanced differentiation, synaptic plasticity, and reduced microglia recruitment; furthermore, Wnt pathway agonists and inhibitors demonstrate a pivotal role for Wnt signaling in the process. These findings help establish MGE as a promising avenue for addressing current limitations associated with NSC transplantation via beneficially influencing neural regeneration and synaptic plasticity, thereby offering enhanced therapeutic options to boost brain recovery following global ischemia.

Specific and rapid guanidinium CEST imaging using double saturation power and QUASS analysis in a rodent model of global ischemia.

Guanidinium CEST is sensitive to metabolic changes and pH variation in ischemia, and it can offer advantages over conventional pH-sensitive amide proton transfer (APT) imaging by providing hyperintense contrast in stroke lesions. However, quantifying guanidinium CEST is challenging due to multiple overlapping components and a close frequency offset from water. This study aims to evaluate the applicability of a new rapid and model-free CEST quantification method using double saturation power, termed DSP-CEST, for isolating the guanidinium CEST effect from confounding factors in ischemia. To further reduce acquisition time, the DSP-CEST was combined with a quasi-steady state (QUASS) CEST technique to process non-steady-state CEST signals. The specificity and accuracy of the DSP-CEST method in quantifying the guanidinium CEST effect were assessed by comparing simulated CEST signals with/without the contribution from confounding factors. The feasibility of this method for quantifying guanidinium CEST was evaluated in a rat model of global ischemia induced by cardiac arrest and compared to a conventional multiple-pool Lorentzian fit method. The DSP-CEST method was successful in removing all confounding components and quantifying the guanidinium CEST signal increase in ischemia. This suggests that the DSP-CEST has the potential to provide hyperintense contrast in stroke lesions. Additionally, the DSP-CEST was shown to be a rapid method that does not require the acquisition of the entire or a portion of the CEST Z-spectrum that is required in conventional model-based fitting approaches. This study highlights the potential of DSP-CEST as a valuable tool for rapid and specific detection of viable tissues.

Tangeretin confers neuroprotection, cognitive and memory enhancement in global cerebral ischemia in rats.

Global cerebral ischemia is commonly associated with neurological deficits, including cognitive and memory impairments. The present study aims to investigate the neuroprotective, cognitive, and memory enhancement effects of Tangeretin, a flavonoid against global cerebral ischemia in rats. Bilateral common carotid artery occlusion (BCCAO) and reperfusion injury method was used to induce global cerebral ischemia in rats. Motor, cognitive, and memory functions were evaluated using rotarod, grip strength, Y-maze, and Morris water maze. Further, acetylcholine esterase (AchE) enzyme activity, acetylcholine (Ach), oxidative stress markers (ROS, SOD, MDA, and CAT), inflammation (IL-6 and TNF-α), and apoptotic markers (cytochrome C, caspase 9, and caspase 3) in BCCAO rats were measured following Tangeretin (5,10, and 20mg/kg, oral) treatment. Our findings show that Tangeretin treatment significantly improved cognition and memory by enhancing Ach levels through the amelioration of AchE enzyme activity in BCCAO rats. Moreover, Tangeretin exhibited neuroprotective effects through the mitigation of oxidative stress, inflammation, and apoptosis in the BCCAO rats. In summary, the current findings suggested that Tangeretin exhibited neuroprotection, cognitive and memory enhancement against global cerebral ischemia.

Global cerebral ischemia in adult female rats interrupts estrous cyclicity and induces lasting changes in hypothalamic-pituitary-gonadal axis signaling peptides

Persistent post-ischemic alterations to the hypothalamic–pituitary–adrenal (HPA) axis occur following global cerebral ischemia (GCI) in rodents. However, similar effects on hypothalamic-pituitary–gonadal (HPG) axis activation remain to be determined. Therefore, this study evaluated the effects of GCI in adult female rats (via four-vessel occlusion) on the regularity of the estrous cycle for 24-days post ischemia. A second objective aimed to assess persistent alterations of HPG axis activation through determination of the expression of estrogen receptor alpha (ERα), kisspeptin (Kiss1), and gonadotropin-inhibitory hormone (GnIH/RFamide-related peptide; RFRP3) in the medial preoptic area (POA), arcuate nucleus (ARC), dorsomedial nucleus (DMH) of the hypothalamus, and CA1 of the hippocampus 25 days post ischemia. Expression of glucocorticoid receptors (GR) in the paraventricular nucleus of the hypothalamus (PVN) and CA1 served as a proxy of altered HPA axis activation. Our findings demonstrated interruption of the estrous cycle in 87.5 % of ischemic rats, marked by persistent diestrus, lasting on average 11.86 days. Moreover, compared to sham-operated controls, ischemic female rats showed reduced Kiss1 expression in the hypothalamic ARC and POA, concomitant with elevated ERα in the ARC and increased GnIH in the DMH and CA1. Reduced GR expression in the CA1 was associated with increased GR-immunoreactivity in the PVN, indicative of lasting dysregulation of HPA axis activation. Together, these findings demonstrate GCI disruption of female rats’ estrous cycle over multiple days, with a lasting impact on HPG axis regulators within the reproductive axis.

Neuroprotective-Neurorestorative Effects Induced by Progesterone on Global Cerebral Ischemia: A Narrative Review.

Progesterone (P4) is a neuroactive hormone having pleiotropic effects, supporting its pharmacological potential to treat global (cardiac-arrest-related) cerebral ischemia, a condition associated with an elevated risk of dementia. This review examines the current biochemical, morphological, and functional evidence showing the neuroprotective/neurorestorative effects of P4 against global cerebral ischemia (GCI). Experimental findings show that P4 may counteract pathophysiological mechanisms and/or regulate endogenous mechanisms of plasticity induced by GCI. According to this, P4 treatment consistently improves the performance of cognitive functions, such as learning and memory, impaired by GCI. This functional recovery is related to the significant morphological preservation of brain structures vulnerable to ischemia when the hormone is administered before and/or after a moderate ischemic episode; and with long-term adaptive plastic restoration processes of altered brain morphology when treatment is given after an episode of severe ischemia. The insights presented here may be a guide for future basic research, including the study of P4 administration schemes that focus on promoting its post-ischemia neurorestorative effect. Furthermore, considering that functional recovery is a desired endpoint of pharmacological strategies in the clinic, they could support the study of P4 treatment for decreasing dementia in patients who have suffered an episode of GCI.

Regulation of ABCB1 Protein Function in the Cerebral Cortex with the Underlying Global Cerebral Ischemia

INTRODUCTION: ABCB1 is a membrane transporter protein responsible for efflux of a wide range of drugs from cells. The study of the mechanisms of regulation of the functioning of ABCB1 protein in the brain in its ischemia will permit to propose new approaches to pharmacotherapy of cerebral ischemic pathology.&#x0D; AIM: To study the regulation of ABCB1 protein function in the cerebral cortex of rats with global cerebral ischemia.&#x0D; MATERIALS AND METHODS: The experiment was performed on 30 male rats with global cerebral ischemia modeled by bilateral occlusion of the common carotid arteries. The amount of ABCB1 protein and Nrf2 and HIF-1α transcription factors in the cerebral cortex was determined by enzyme immunoassay. The free radical status of the cerebral cortex was assessed by the concentration of malondialdehyde, SH groups, and by glutathione peroxidase (G-per) activity.&#x0D; RESULTS: Bilateral occlusion of the common carotid arteries caused an increase in the level of ABCB1 protein in the cerebral cortex of rats by the 4th hour of ischemia; in 24 hours it remained elevated, and in 72 hours decreased to values that did not differ from those of falsely operated rats. The content of malondialdehyde in the cerebral cortex increased in 2 and 4 hours after occlusion and then gradually decreased to the initial values. In 30 minutes and 4 hours after ischemia modeling, G-per activity decreased compared to the control values. The content of Nrf2 in the cerebral cortex increased in 2 and 4 hours after occlusion, then slightly decreased on the next day, and reached the initial values on the 3rd day of the experiment. The amount of HIF-1α increased only in 24 and 72 hours after the surgery.&#x0D; CONCLUSION: The amount of ABCB1 protein in the cerebral cortex of rats with global cerebral ischemia depends on the severity of oxidative stress, with Nrf2 and HIF-1α transcription factors playing a role in its regulation. Reduction of the amount of the transporter in the blood-brain barrier through the influence on the lipid peroxidation processes or synthesis of the studied transcription factors expands the possibilities of using ABCB1 protein substrates for improving the effectiveness of pharmacotherapy of diseases of the central nervous system.

Electrical auricular tragus stimulation induces release of circulating cardioprotective factors in healthy human volunteers

Abstract Background Vagal activation during remote ischemic conditioning (RIC) with subsequent release of cardioprotective factors from the spleen into the circulation reduces infarct size. These humoral cardioprotective factors can be transferred with plasma-dialysate from human donors undergoing RIC to isolated recipient hearts where they reduce infarct size. Electrical auricular tragus stimulation (ATS) has been demonstrated to reduce the release of cardiac injury biomarkers and ventricular arrhythmias and to improve contractile function in patients with acute myocardial infarction. Purpose To determine whether ATS, as RIC, induces release of cardioprotective factors into the circulation. Methods Healthy volunteers (3 females, 7 males, 26±5 years) were randomized to receive ATS or RIC, respectively, with an interval of at least two weeks between protocols. ATS was induced by bipolar electrical rectangular pulses of 200 µs width and a frequency of 30 Hz. The amplitude (5.5 ± 0.81 mA) was set for each volunteer to not be perceived as uncomfortable. A microprocessor-controlled circuit periodically interrupted the stimulation signal after 5 s of stimulation for 5 s. ATS was continued over 30 min. RIC served as a reference to induce the release of cardioprotective factors by 3 x 5 min blood pressure cuff inflation at 200 mmHg on the left upper arm/ 5 min deflation. Venous blood samples were taken before and 60 min after ATS or RIC, respectively, and used to prepare plasma-dialysates (1:10 dialysis against buffer for 24 h, cut-off 12-14 kDa). Male Lewis rats were sacrificed and their hearts isolated and perfused at constant pressure with buffer. Plasma-dialysates from samples taken before and 60 min after ATS or RIC, respectively, were infused for 8 min into rat hearts followed by 2 min washout before global 30 min ischemia/ 120 min reperfusion. Infarct size was demarcated by triphenyl tetrazolium chloride staining and calculated as percent of ventricular mass. Results With infusion of plasma-dialysate before ATS, infarct size was 30.9 ± 4.5% of ventricular mass and not different from that with infusion of plasma-dialysate before RIC (35.8 ± 5.8 %). Infusion of plasma-dialysate after ATS reduced infarct size to 18.3 ± 3.9 %. This cardioprotective effect was similar to that seen with infusion of plasma-dialysate after RIC (20.1 ± 3.5 %). Conclusion ATS induces the release of cardioprotective factors into the circulation of healthy volunteers. Plasma-dialysates after ATS or RIC, respectively, reduce myocardial infarct size by the same magnitude in ex vivo isolated perfused rat hearts with global ischemia/ reperfusion.

Nicotinamide riboside cardioprotection is mediated through glycolysis activation

Abstract Purpose Low NAD+ levels are observed in pathologies such as ageing, diabetes, heart failure and ischemia-reperfusion (IR) injury. Nicotinamide riboside (NR) has emerged as promising therapeutic NAD+ precursor [1,2]. NR was recently reported to protect against in vivo cardiac IR injury [3], but underlying mechanisms of protection were unexplored. Here we used the isolated mouse heart allowing metabolic control to examine NR’s metabolic mechanisms of cardiac protection. Methods Isolated C57BL/6N hearts were Langendorff-perfused with 5.5 mM glucose and 0.2 mM fatty acids (FA), and subjected to 35 min global ischemia and 90 min reperfusion. NR (50 mg/L) or vehicle were administered for 25 min before ischemia, and during the first 25 min of reperfusion. Cardiac functional recovery and cell death parameters (lactate dehydrogenase (LDH) release, % infarct size) were determined. To examine NR’s effects on cardiac metabolism, hearts were perfused with 5.5 mM 13C-glucose and 0.2 mM FA and analyzed by metabolomics and fluxomics using LC-MS techniques before ischemia. The dependency of NR’s protection on glycolysis was tested in hearts perfused with glucose replaced by pyruvate and lactate ("no glycolysis" hearts). Finally, NR’s protection and effects on cardiac metabolism were also examined in "high glycolysis" hearts, by adding insulin to the perfusate. Results NR reduced infarct size, LDH release and improved cardiac functional recovery for glucose/FA perfused hearts, demonstrating NR’s cardioprotection. In these glucose/FA hearts, metabolomics analysis showed NR increased NAD+, glycolytic intermediate phosphoenolpyruvate (PEP), Krebs cycle intermediate succinate and pentose phosphate pathway (PPP) intermediates ribose-5P (R5P) and sedoheptulose-7P (S7P) (Fig. 1). Fluxomics analysis demonstrated that NR’s protection was associated with activated glycolysis, without changes in tricarboxylic acid (TCA) cycle or PPP activities. No 13C-labeling of S7P was observed (Fig. 1). NR protection was lost in the "no glycolysis" hearts. In the "high glycolysis" hearts, NR was unable to protect the heart and increase glycolysis and reduced anaerobic glycolysis and ATP with increases in AMP, indicative of NR-induced energetic stress (Fig. 2). Remarkably, in these insulin perfused hearts, NR still increased PPP intermediates, with high 13C-labeling of S7P (Fig. 2). Conclusions NR’s protection against IR injury is only present in hearts with low glycolysis, associated with activation of pre-ischemic glycolysis. When activation of glycolysis was prevented, through either examining "no glycolysis" hearts or "high glycolysis" hearts, NR protection was abolished. NR treatment increased pre-ischemic PPP intermediates in either low or high glycolysis hearts, whereby insulin was necessary to incorporate 13C-glucose into S7P. The data suggest that NR’s acute cardioprotective effects are mediated through the activation of glycolysis.NR effects in low-glycolysis heartsNR effects in high-glycolysis hearts