AKT/GSK3β-dependent autophagy contributes to the neuroprotection of limb remote ischemic postconditioning in the transient cerebral ischemic rat model

Repurposing ezetimibe as a neuroprotective agent in a rotenone-induced Parkinson's disease model in rats: Role of AMPK/SIRT-1/PGC-1α signaling and autophagy

As a severe neurological disorder, Parkinson's disease (PD) is distinguished by dopaminergic neuronal degeneration in the substantia nigra (SN), culminating in motor impairments. Several studies have shown that activation of the AMPK/SIRT1/PGC1α pathway contributes to an increase in mitochondrial biogenesis and is a promising candidate for the management of PD. Furthermore, turning on the AMPK/SIRT1/PGC1α pathway causes autophagy activation, which is fundamental for maintaining neuronal homeostasis. Interestingly, ezetimibe is an antihyperlipidemic agent that was recently reported to possess pleiotropic properties in neurology by triggering the phosphorylation and activation of AMPK. Thus, our study aimed to investigate the neuroprotective potential of ezetimibe in rats with rotenone-induced PD by activating AMPK. Adult male Wistar rats received rotenone (1.5 mg/kg, s.c.) every other day for 21 days to induce experimental PD. Rats were treated with ezetimibe (5 mg/kg/day, i.p.) 1 h before rotenone. Ezetimibe ameliorated the motor impairments in open field, rotarod and grip strength tests, restored striatal dopamine and tyrosine hydroxylase in the SN, up-regulated p-AMPK, SIRT1, and PGC1α striatal expression, upsurged the expression of ULK1, beclin1, and LC3II/I, reduced Bax/Bcl2 ratio, and alleviated rotenone-induced histopathological changes in striatum and SN. Our findings also verified the contribution of AMPK activation to the neuroprotective effect of ezetimibe by using the AMPK inhibitor dorsomorphin. Together, this work revealed that ezetimibe exerts a neuroprotective impact in rotenone-induced PD by activating AMPK/SIRT-1/PGC-1α signaling, enhancing autophagy, and attenuating apoptosis. Thus, ezetimibe's activation of AMPK could hold significant therapeutic promise for PD management.

Ischemia-reperfusion injury: molecular mechanisms and therapeutic targets

Ischemia-reperfusion (I/R) injury paradoxically occurs during reperfusion following ischemia, exacerbating the initial tissue damage. The limited understanding of the intricate mechanisms underlying I/R injury hinders the development of effective therapeutic interventions. The Wnt signaling pathway exhibits extensive crosstalk with various other pathways, forming a network system of signaling pathways involved in I/R injury. This review article elucidates the underlying mechanisms involved in Wnt signaling, as well as the complex interplay between Wnt and other pathways, including Notch, phosphatidylinositol 3-kinase/protein kinase B, transforming growth factor-β, nuclear factor kappa, bone morphogenetic protein, N-methyl-D-aspartic acid receptor-Ca2+-Activin A, Hippo-Yes-associated protein, toll-like receptor 4/toll-interleukine-1 receptor domain-containing adapter-inducing interferon-β, and hepatocyte growth factor/mesenchymal-epithelial transition factor. In particular, we delve into their respective contributions to key pathological processes, including apoptosis, the inflammatory response, oxidative stress, extracellular matrix remodeling, angiogenesis, cell hypertrophy, fibrosis, ferroptosis, neurogenesis, and blood-brain barrier damage during I/R injury. Our comprehensive analysis of the mechanisms involved in Wnt signaling during I/R reveals that activation of the canonical Wnt pathway promotes organ recovery, while activation of the non-canonical Wnt pathways exacerbates injury. Moreover, we explore novel therapeutic approaches based on these mechanistic findings, incorporating evidence from animal experiments, current standards, and clinical trials. The objective of this review is to provide deeper insights into the roles of Wnt and its crosstalk signaling pathways in I/R-mediated processes and organ dysfunction, to facilitate the development of innovative therapeutic agents for I/R injury.

Neuronal Zinc Transporter ZnT3 Modulates Cerebral Ischemia-Induced Blood-Brain Barrier Disruption

Zinc plays important roles in both physiological and pathological processes in the brain. Accumulation of free zinc in ischemic tissue is recognized to contribute to blood-brain barrier (BBB) disruption following cerebral ischemia, but little is known either about the source of free zinc in microvessels or the mechanism by which free zinc mediates ischemia-induced BBB damage. We utilized cellular and animal models of ischemic stroke to determine the source of high levels of free zinc and the mechanism of free zinc-mediated BBB damage after ischemia. We report that cerebral ischemia elevated the level of extracellular fluid (ECF-Zn) of ischemic brain, leading to exacerbated BBB damage in a rat stroke model. Specifically suppressing zinc release from neurons, utilizing neuronal-specific zinc transporter 3 (ZnT3) knockout mice, markedly reduced ECF-Zn and BBB permeability after ischemia. Intriguingly, the activity of zinc-dependent metalloproteinase-2 (MMP-2) was modulated by ECF-Zn levels. Elevated ECF-Zn during ischemia directly bound to MMP-2 in extracellular fluid, increased its zinc content and augmented MMP-2 activity, leading to the degradation of tight junction protein in cerebral microvessels and BBB disruption. These findings suggest the role of neuronal ZnT3 in modulating ischemia-induced BBB disruption and reveal a novel mechanism of MMP-2 activation in BBB disruption after stroke, demonstrating ZnT3 as an effective target for stroke treatment.

The Notch pathway regulates autophagy after hypoxic-ischemic injury and affects synaptic plasticity

Following neonatal hypoxic-ischemia (HI) injury, it is crucial factor to reconstruct neural circuit and maintain neural network homeostasis for neurological recovery. A dynamic balance between the synthesis and degradation of synaptic protein is required for maintaining synaptic plasticity. Protein degradation is facilitated by autophagy. This study aimed to investigate the regulation of synaptic structural plasticity by the Notch pathway, by assessing changes in Notch pathway activation and their effects on synaptic proteins and autophagy after HI injury. The study involved 48 male newborn Yorkshire piglets, each weighing 1.0-1.5 kg and 3 days old. They were randomly assigned to two groups: the HI group and the Notch pathway inhibitor + HI group (n = 24 per group). Each group was further divided into six subgroups according to HI duration (n = 4 per group): a control subgroup, and 0-6, 6-12, 12-24, 24-48, and 48-72 h subgroups. The expression of Notch pathway-related proteins, including Notch1, Hes1, and Notch intracellular domains, increased following HI injury. The expression of autophagy proteins increased at 0-6 h and 6-12 h post-HI. The expression of synaptic proteins, such as postsynaptic density protein 95 (PSD95) and synaptophysin, increased 6-12 h and 12-24 h after HI, respectively. Notably, the increased expression of these proteins was reversed by a Notch pathway inhibitor. Transmission electron microscopy revealed the presence of autophagosome structures in synapses. These findings shed light on the underlying mechanisms of neurological recovery after HI injury and may provide insights into potential therapeutic targets for promoting neural circuit reconstruction and maintaining neural network homeostasis.

Wnt/β-catenin signaling pathway-a versatile player in apoptosis and autophagy

The Wnt/β-catenin signaling pathway is a highly conserved pathway that is involved in cell development, proliferation, differentiation, apoptosis and autophagy. Among these processes, apoptosis and autophagy occur physiologically during host defense and the maintenance of intracellular homeostasis. Mounting evidence suggests that the crosstalk between Wnt/β-catenin-regulated apoptosis and autophagy has broad functional significance in various diseases. Herein, we summarize the recent studies in understanding the role of the Wnt/β-catenin signaling pathway in apoptosis and autophagy, and draw the following conclusions: a) For apoptosis, the regulation of Wnt/β-catenin is generally positive. However, a small amount of evidence indicates the presence of a negatively regulated relationship between Wnt/β-catenin and apoptosis; b) Wnt/β-catenin influences the occurrence and development of autophagy by regulating autophagy-related factors, and these factors in turn affect Wnt/β-catenin pathway; c) Wnt/β-catenin always balances the molecular damage caused by the crosstalk between autophagy and apoptosis in a compensatory manner. Understanding the specific role of the Wnt/β-catenin signaling pathway during different stages of autophagy and apoptosis may provide new insights into the progression of related diseases regulated by the Wnt/β-catenin signaling pathway.

Neuroplasticity to autophagy cross-talk in a therapeutic effect of physical exercises and irisin in ADHD

Adaptive neuroplasticity is a pivotal mechanism for healthy brain development and maintenance, as well as its restoration in disease- and age-associated decline. Management of mental disorders such as attention deficit hyperactivity disorder (ADHD) needs interventions stimulating adaptive neuroplasticity, beyond conventional psychopharmacological treatments. Physical exercises are proposed for the management of ADHD, and also depression and aging because of evoked brain neuroplasticity. Recent progress in understanding the mechanisms of muscle-brain cross-talk pinpoints the role of the myokine irisin in the mediation of pro-cognitive and antidepressant activity of physical exercises. In this review, we discuss how irisin, which is released in the periphery as well as derived from brain cells, may interact with the mechanisms of cellular autophagy to provide protein recycling and regulation of brain-derived neurotrophic factor (BDNF) signaling via glia-mediated control of BDNF maturation, and, therefore, support neuroplasticity. We propose that the neuroplasticity associated with physical exercises is mediated in part by irisin-triggered autophagy. Since the recent findings give objectives to consider autophagy-stimulating intervention as a prerequisite for successful therapy of psychiatric disorders, irisin appears as a prototypic molecule that can activate autophagy with therapeutic goals.

Determination of significant parameters in remote ischemic postconditioning for ischemic stroke in experimental models: A systematic review and meta-analysis study

Objectives

To systematically review studies using remote ischemia postconditioning (RIPostC) for ischemic stroke in experimental models and obtain factors that significantly influence treatment outcomes.

Materials and Methods

Peer‐reviewed studies were identified and selected based on the eligibility criteria, followed by extraction of data on potentially influential factors related to model preparation, postconditioning, and measure time based on outcome measures including infarct size, neurological scales, and cell tests with autophagy, apoptosis, normal‐neuron, and damaged‐neuron counting. Then, all data were preprocessed, grouped, and meta‐analyzed with the indicator of the standardized mean difference.

Results

Fifty‐seven studies with 224 experiments (91 for infarct size, 92 for neurological scales, and 41 for cell‐level tests) were included. There was little statistical difference between different model preparations, treated body parts, number of treatments, and sides. And treatment effect was generally a positive correlation with the duration of conditioning time to stroke onset with exceptions at some time points. Based on infarct size, the number of cycles per treatment, duration of occlusion, and release per cycle showed significant differences. Combined with the effect sizes by other measures, the occlusion/release duration of 8–10 min per cycle is better than 5 min, and three cycles per treatment were most frequently used with good effects. Effect also varied when measuring at different times, showing statistical differences in infarct size and most neurological scales. RIPostC is confirmed as an effective therapeutic intervention for ischemic stroke, while the RIPostC‐mediated autophagy level being activated or inhibited remained conflicting.

Conclusions

Conditioning time, number of cycles per treatment, duration of occlusion, and release per cycle were found to influence the treatment effects of RIPostC significantly. More studies on the relevant influential factors and autophagy mechanisms are warranted.

Novel Therapeutic Strategies for Ischemic Stroke: Recent Insights into Autophagy

Stroke is one of the leading causes of death and disability worldwide. Autophagy is a conserved cellular catabolic pathway that maintains cellular homeostasis by removal of damaged proteins and organelles, which is critical for the maintenance of energy and function homeostasis of cells. Accumulating evidence demonstrates that autophagy plays important roles in pathophysiological mechanisms under ischemic stroke. Previous investigations show that autophagy serves as a “double-edged sword” in ischemic stroke as it can either promote the survival of neuronal cells or induce cell death in special conditions. Following ischemic stroke, autophagy is activated or inhibited in several cell types in brain, including neurons, astrocytes, and microglia, as well as microvascular endothelial cells, which involves in inflammatory activation, modulation of microglial phenotypes, and blood-brain barrier permeability. However, the exact mechanisms of underlying the role of autophagy in ischemic stroke are not fully understood. This review focuses on the recent advances regarding potential molecular mechanisms of autophagy in different cell types. The focus is also on discussing the “double-edged sword” effect of autophagy in ischemic stroke and its possible underlying mechanisms. In addition, potential therapeutic strategies for ischemic stroke targeting autophagy are also reviewed.

Normobaric hyperoxia plays a neuroprotective role after cerebral ischemia by maintaining the redox homeostasis and the level of connexin43 in astrocytes

Introduction

Acute cerebral ischemia is caused by an insufficient blood supply to brain tissue. Oxygen therapy, which is able to aid diffusion to reach the ischemic region, has been regarded as a possible treatment for cerebral ischemia. Recent animal and pilot clinical studies have reported that normobaric hyperoxia (NBO) showed neuroprotective effects if started soon after the onset of stroke. However, little is known about the role and mechanism of NBO treatment in astrocytes. Connexin43, one of the main gap junction proteins in astrocytes, is extremely sensitive to hypoxia and oxidative stress after cerebral ischemia.

Aims

In the present study, we used sutures to develop an ischemia/reperfusion model in rats to mimic clinical recanalization and investigated the role of connexin43 in NBO‐treated stroke rats, as well as the underlying mechanism of NBO therapy.

Results

Normobaric hyperoxia treatment maintained the homeostasis of oxidoreductases: glutathione peroxidase 4 (GPX4) and NADPH oxidase 4 (two important oxidoreductases) and rescued the ischemia/reperfusion‐induced downregulation of connexin43 protein in astrocytes. Furthermore, NBO treatment attenuated cerebral ischemia‐induced cytochrome c release from mitochondria and was involved in neuroprotective effects by regulating the GPX4 and connexin43 pathway, using Ferrostatin‐1 (an activator of GPX4) or Gap27 (an inhibitor of connexin43).

Conclusions

This study showed the neuroprotective effects of NBO treatment by reducing oxidative stress and maintaining the level of connexin43 in astrocytes, which could be used for the clinical treatment of ischemic stroke.

Effects of ischemic postconditioning and long non-coding RNAs in ischemic stroke

Stroke is a main cause of disability and death among adults in China, and acute ischemic stroke accounts for 80% of cases. The key to ischemic stroke treatment is to recanalize the blocked blood vessels. However, more than 90% of patients cannot receive effective treatment within an appropriate time, and delayed recanalization of blood vessels causes reperfusion injury. Recent research has revealed that ischemic postconditioning has a neuroprotective effect on the brain, but the mechanism has not been fully clarified. Long non-coding RNAs (lncRNAs) have previously been associated with ischemic reperfusion injury in ischemic stroke. LncRNAs regulate important cellular and molecular events through a variety of mechanisms, but a comprehensive analysis of potential lncRNAs involved in the brain protection produced by ischemic postconditioning has not been conducted. In this review, we summarize the common mechanisms of cerebral injury in ischemic stroke and the effect of ischemic postconditioning, and we describe the potential mechanisms of some lncRNAs associated with ischemic stroke.

Preclinical evidence of remote ischemic conditioning in ischemic stroke, a metanalysis update

Remote ischemic conditioning (RIC) is a promising therapeutic approach for ischemic stroke patients. It has been proven that RIC reduces infarct size and improves functional outcomes. RIC can be applied either before ischemia (pre-conditioning; RIPreC), during ischemia (per-conditioning; RIPerC) or after ischemia (post-conditioning; RIPostC). Our aim was to systematically determine the efficacy of RIC in reducing infarct volumes and define the cellular pathways involved in preclinical animal models of ischemic stroke. A systematic search in three databases yielded 50 peer-review articles. Data were analyzed using random effects models and results expressed as percentage of reduction in infarct size (95% CI). A meta-regression was also performed to evaluate the effects of covariates on the pooled effect-size. 95.3% of analyzed experiments were carried out in rodents. Thirty-nine out of the 64 experiments studied RIPostC (61%), sixteen examined RIPreC (25%) and nine tested RIPerC (14%). In all studies, RIC was shown to reduce infarct volume (- 38.36%; CI - 42.09 to - 34.62%) when compared to controls. There was a significant interaction caused by species. Short cycles in mice significantly reduces infarct volume while in rats the opposite occurs. RIPreC was shown to be the most effective strategy in mice. The present meta-analysis suggests that RIC is more efficient in transient ischemia, using a smaller number of RIC cycles, applying larger length of limb occlusion, and employing barbiturates anesthetics. There is a preclinical evidence for RIC, it is safe and effective. However, the exact cellular pathways and underlying mechanisms are still not fully determined, and its definition will be crucial for the understanding of RIC mechanism of action.

Neuroprotective Role of Acidosis in Ischemia: Review of the Preclinical Evidence

Efforts to develop effective neuroprotective therapies for ischemic stroke have had little success to date. One promising approach to neuroprotection is ischemic postconditioning, which utilizes brief bouts of ischemia after acute ischemic stroke to elicit neuroprotection, although the mechanism is largely unknown. As the primary components of transient ischemia are local hypoxia and acidosis, and hypoxic postconditioning has had little success, it is possible that the acidosis component may be the primary driver. To address the evidence behind this, we performed a systematic review of preclinical studies focused on the neuroprotective role of transient acidosis after ischemia. Animal studies demonstrated that mild-to-moderate acidosis after ischemic events led to better functional neurologic outcomes with reduced infarct volumes, while severe acidosis often led to cerebral edema and worse functional outcomes. In vitro studies demonstrated that mild-to-moderate acidosis improves neuronal survival largely through two means: (1) inhibition of harmful superoxide formation in the excitotoxic pathway and (2) remodeling neuronal mitochondria to allow for efficient ATP production (i.e., oxidative phosphorylation), even in the absence of oxygen. Similar to the animal studies, acidotic postconditioning in humans would entail short cycles of carbon dioxide inhalation, which has already been demonstrated to be safe as part of a hypercapnic challenge when measuring cerebrovascular reactivity. Due to the preclinical efficacy of acidotic postconditioning, its relatively straightforward translation into humans, and the growing need for neuroprotective therapies, future preclinical studies should focus on filling the current knowledge gaps that are currently restricting the development of phase I/II clinical trials.

Remote but not Distant: a Review on Experimental Models and Clinical Trials in Remote Ischemic Conditioning as Potential Therapy in Ischemic Stroke

Stroke is one of the main causes of neurological disability worldwide and the second cause of death in people over 65 years old, resulting in great economic and social burden. Ischemic stroke accounts for 85% of total cases, and the approved therapies are based on re-establishment of blood flow, and do not directly target brain parenchyma. Thus, novel therapies are urgently needed. In this review, limb remote ischemic conditioning (RIC) is revised and discussed as a potential therapy against ischemic stroke. The review targets both (i) fundamental research based on experimental models and (ii) clinical research based on clinical trials and human interventional studies with healthy volunteers. Moreover, it also presents two approaches concerning RIC mechanisms in stroke: (i) description of the underlying cerebral cellular and molecular mechanisms triggered by limb RIC that promote neuroprotection against stroke induced damage and (ii) the identification of signaling factors involved in inter-organ communication following RIC procedure. Limb to brain remote signaling can occur via circulating biochemical factors, immune cells, and/or stimulation of autonomic nervous system. In this review, these three hypotheses are explored in both humans and experimental models. Finally, the challenges involved in translating experimentally generated scientific knowledge to a clinical setting are also discussed.

Neuroprotective effects of methylcobalamin in cerebral ischemia/reperfusion injury through activation of the ERK1/2 signaling pathway

Despite advances in the understanding of the pathophysiology of ischemic stroke, therapeutic options remain limited. Methylcobalamin is an endogenous vitamin B12 that exhibits anti-inflammatory and antiapoptotic activities in a variety of diseases. In this study, we aimed to explore the neuroprotective effects and mechanism of action of methylcobalamin on cerebral ischemic injury in vitro and in vivo. The oxygen and glucose deprivation/reperfusion model and middle cerebral artery occlusion model were used to simulate cerebral ischemic injury in vitro and in vivo. Cell viability, inflammatory factors, cell apoptosis, and protein expression levels were determined. Further, autophagy flux and the cerebral infarction volume were measured. The modified neurological severity score, Longa score, Rotarod assay, and foot-fault test were used to evaluate behavioral changes and neurological deficits in rats. In vitro, methylcobalamin significantly increased cell viability, decreased lactate dehydrogenase release, attenuated inflammatory cytokine expression, reduced the apoptotic proportion, and enhanced autophagy flux after OGD treatment. In addition, Bcl-2 and Beclin1 expression levels and the LC3 II/I ratio were increased, whereas levels of Bax and cleaved caspase-3 were decreased. In vivo, methylcobalamin significantly reduced the cerebral infarction volume and neurological deficits in the rats. Furthermore, methylcobalamin activated the ERK1/2 pathway, whereas ERK1/2 inhibitors diminished its effects in the in vitro and in vivo models. In conclusion, methylcobalamin may exert a neuroprotective effect on cerebral ischemia and is a promising drug candidate for developing novel neuroprotective therapies.

The effects of metformin on autophagy

Metformin is the first-line option for treating newly diagnosed diabetic patients and also involved in other pharmacological actions, including antitumor effect, anti-aging effect, polycystic ovarian syndrome prevention, cardiovascular action, and neuroprotective effect, etc. However, the mechanisms of metformin actions were not fully illuminated. Recently, increasing researches showed that autophagy is a vital medium of metformin playing pharmacological actions. Nevertheless, results on the effects of metformin on autophagy were inconsistent. Apart from few clinical evidences, more data focused on kinds of no-clinical models. First, many studies showed that metformin could induce autophagy via a number of signaling pathways, including AMPK-related signaling pathways (e.g. AMPK/mTOR, AMPK/CEBPD, MiTF/TFE, AMPK/ULK1, and AMPK/miR-221), Redd1/mTOR, STAT, SIRT, Na⁺/H⁺ exchangers, MAPK/ERK, PK2/PKR/AKT/ GSK3β, and TRIB3. Secondly, some signaling pathways were involved in the process of metformin inhibiting autophagy, such as AMPK-related signaling pathways (AMPK/NF-κB and other undetermined AMPK-related signaling pathways), Hedgehog, miR-570-3p, miR-142-3p, and MiR-3127-5p. Thirdly, two types of signaling pathways including PI3K/AKT/mTOR and endoplasmic reticulum (ER) stress could bidirectionally impact the effectiveness of metformin on autophagy. Finally, multiple signal pathways were reviewed collectively in terms of affecting the effectiveness of metformin on autophagy. The pharmacological effects of metformin combining its actions on autophagy were also discussed. It would help better apply metformin to treat diseases in term of mediating autophagy.

Advances in intervention methods and brain protection mechanisms of in situ and remote ischemic postconditioning

Ischemic postconditioning (PostC) conventionally refers to a series of brief blood vessel occlusions and reperfusions, which can induce an endogenous neuroprotective effect and reduce cerebral ischemia/reperfusion (I/R) injury. Depending on the site of adaptive ischemic intervention, PostC can be classified as in situ ischemic postconditioning (ISPostC) and remote ischemic postconditioning (RIPostC). Many studies have shown that ISPostC and RIPostC can reduce cerebral IS injury through protective mechanisms that increase cerebral blood flow after reperfusion, decrease antioxidant stress and anti-neuronal apoptosis, reduce brain edema, and regulate autophagy as well as Akt, MAPK, PKC, and KATP channel cell signaling pathways. However, few studies have compared the intervention methods, protective mechanisms, and cell signaling pathways of ISPostC and RIPostC interventions. Thus, in this article, we compare the history, common intervention methods, neuroprotective mechanisms, and cell signaling pathways of ISPostC and RIPostC.

Remote ischemic conditioning: A potential therapeutic strategy of type 2 diabetes

Type 2 diabetes (T2D) is one of the major public diseases which is characterized by peripheral insulin resistance (IR) and progressive pancreatic β-cell failure. While in the past few years, some new factors, such as inflammation, oxidative stress, immune responses and other potential pathways, have been identified to play critical roles in T2D, and thereby provide novel promising targets for the treatment of T2D. Remote ischemic conditioning (RIC) is a non-invasive and convenient operation performed by transient, repeated ischemia in distant place. Nowadays, RIC has been established as a potentially powerful therapeutic tool for many diseases, especially in I/R injuries. Through activating a series of neural, humoral and immune pathways, it can release multiple protective signals, which then regulating inflammation, oxidative stress, immune response and so on. Interestingly, several recent studies have discovered that the beneficial effects of RIC on I/R injuries might be abolished by T2D, wherein the higher basal levels of inflammation and oxidative stress, dysregulation of immune system and some potential pathways secondary to hyperglycemia may play critical roles. In contrast, a higher intensity of conditioning could restore the protective effects. Based on the overlapped mechanisms RIC and T2D performs, we provide a hypothesis that RIC may also play a protective role in T2D via targeting these signaling pathways.

Distinctive effect of anesthetics on the effect of limb remote ischemic postconditioning following ischemic stroke

Limb remote ischemic postconditioning (LRIP) has been reported as an effective method to reduce the induced experimental stroke damage after ischemic reperfusion (IR) injury. Studies suggest that anesthetics used during induction of ischemic stroke can reduce IR injury, which could affect the actual mechanisms of neuroprotection by LRIP. This study focuses on the comparative effects of anesthetics such as isoflurane and ketamine-xylazine on ischemic injury when used during LRIP. Adult C57BL/6 mice were anesthetized by isoflurane or halothane, and transient middle cerebral artery occlusion (MCAO) was induced through insertion of the filament. Under isoflurane or ketamine-xylazine anesthesia, LRIP was performed after 90 min of reperfusion by carrying out three cycles of 5 min ischemia/5 min reperfusion of the bilateral hind limbs for one session per day for a total of 3 days. Results showed that the use of different anesthetics—isoflurane or ketamine-xylazine—during LRIP had no effects on body weight. However, LRIP was able to improve neurological function as observed by the neurological deficit score in ischemic mice. Interestingly, the neurological deficit in the group where ketamine-xylazine was used was better than the group where isoflurane was used during LRIP. Furthermore, the LRIP was able to prolong the period of the ischemic mice on the rotarod and this effect was more significant in the groups where ketamine-xylazine was used during LRIP. Moreover, LRIP significantly attenuated the infarction volume; however, this effect was independent of the anesthetic used during LRIP. From these results, we conclude that ischemic mice that were subjected to LRIP under ketamine-xylazine anesthesia had better neurological deficit outcomes after stroke.

Mode of action of granulocyte-colony stimulating factor (G-CSF) as a novel therapy for stroke in a mouse model

BACKGROUND

The FDA approved drug granulocyte-colony stimulating factor (G-CSF) displays anti-apoptotic and immunomodulatory properties with neurogenesis and angiogenic functions. It is known to demonstrate neuroprotective mechanisms against ischemic global stroke. Autophagy is a method for the degradation of intracellular components and in particular, unrestrained autophagy may lead to uncontrolled digestion of affected neurons as well as neuronal death in cerebral ischemia. Mitochondrial dynamics is vital for the regulation of cell survival and death after cerebral ischemia and an early upstream event in neuronal death is mitochondrial fission. We examined the pro-survival mechanisms of G-CSF against apoptosis resulting from autophagy, mitochondrial stress and endoplasmic reticulum (ER) stress.

METHODS

Male Swiss Webster mice (20 weeks of age) were subjected to bilateral common carotid artery occlusion (BCAO) for 30 min. After occlusion, mice were injected with G-CSF (50 μg/kg) subcutaneously for 4 days. Behavioral analysis was carried out using the corner test and locomotor activity test before animals were sacrificed on day 4 or day 7. Key proteins in ER stress, autophagy and mitochondrial stress induced apoptosis were analyzed by immunoblotting.

RESULTS

G-CSF improved neurological deficits and improved behavioral performance on corner and locomotor test. G-CSF binds to G-CSF receptors and its activation leads to upregulation of Akt phosphorylation (P-Akt) which in turn decreases levels of the ER stress sensor, GRP 78 and expression of proteins involved in ER stress apoptosis pathway; ATF6, ATF4, eIF2α, XBP1, Caspase 12 and CHOP. G-CSF treatment significantly decreased Beclin-1, an autophagy marker, and decreased mitochondrial stress biomarkers DRP1 and P53. G-CSF also up-regulated the mitochondrial fusion protein, OPA1 and anti-apoptotic protein Bcl-2 while down-regulating the pro-apoptotic proteins Bax, Bak and PUMA.

CONCLUSIONS

G-CSF is an endogenous ligand in the CNS that has a dual activity that is beneficial both in reducing acute neuronal degeneration and adding to long-term plasticity after cerebral ischemia. G-CSF treatment exerts neuroprotective effects on damaged neurons through the suppression of the ER stress and mitochondrial stress and maintains cellular homeostasis by decreasing pro-apoptotic proteins and increasing of anti-apoptotic proteins.

Effects of Remote Ischemic Conditioning on Cerebral Hemodynamics in Ischemic Stroke

Ischemic stroke is one of the most common cerebrovascular diseases and is the leading cause of disability all over the world. It is well known that cerebral blood flow (CBF) is disturbed or even disrupted when ischemic stroke happens. The imbalance between demand and shortage of blood supply makes ischemic stroke take place or worsen. The search for treatments that can preserve CBF, especially during the acute phase of ischemic stroke, has become a research hotspot. Animal and clinical experiments have proven that remote ischemic conditioning (RIC) is a beneficial therapeutic strategy for the treatment of ischemic stroke. However, the mechanism by which RIC affects CBF has not been fully understood. This review aims to discuss several possible mechanisms of RIC on the cerebral hemodynamics in ischemic stroke, such as the improvement of cardiac function and collateral circulation of cerebral vessels, the protection of neurovascular units, the formation of gas molecules, the effect on the function of vascular endothelial cells and the nervous system. RIC has the potential to become a therapeutic treatment to improve CBF in ischemic stroke. Future studies are needed to highlight our understanding of RIC as well as accelerate its clinical translation.

The Akt/glycogen synthase kinase-3β pathway participates in the neuroprotective effect of interleukin-4 against cerebral ischemia/reperfusion injury

Interleukin-4 (IL-4) has a protective effect against cerebral ischemia/reperfusion injury. Animal experiments have shown that IL-4 improves the short- and long-term prognosis of neurological function. The Akt (also called protein kinase B, PKB)/glycogen synthase kinase-3β (Akt/GSK-3β) signaling pathway is involved in oxidative stress, the inflammatory response, apoptosis, and autophagy. However, it is not yet clear whether the Akt/GSK-3β pathway participates in the neuroprotective effect of IL-4 against cerebral ischemia/reperfusion injury. In the present study, we established a cerebral ischemia/reperfusion mouse model by middle cerebral artery occlusion for 60 minutes followed by a 24-hour reperfusion. An IL-4/anti-IL-4 complex (10 μg) was intraperitoneally administered 30 minutes before surgery. We found that administration of IL-4 significantly alleviated the neurological deficits, oxidative stress, cell apoptosis, and autophagy and reduced infarct volume of the mice with cerebral ischemia/reperfusion injury 24 hours after reperfusion. Simultaneously, IL-4 activated Akt/GSK-3β signaling pathway. However, an Akt inhibitor LY294002, which was injected at 15 nmol/kg via the tail vein, attenuated the protective effects of IL-4. These findings indicate that IL-4 has a protective effect on cerebral ischemia/reperfusion injury by mitigating oxidative stress, reducing apoptosis, and inhibiting excessive autophagy, and that this mechanism may be related to activation of the Akt/GSK-3β pathway. This animal study was approved by the Animal Ethics Committee of Renmin Hospital of Wuhan University, China (approval No. WDRY2017-K037) on March 9, 2017.

Remote ischemic conditioning: a promising therapeutic intervention for multi-organ protection

Despite decades of formidable exploration, multi-organ ischemia-reperfusion injury (IRI) encountered, particularly amongst elderly patients with clinical scenarios, such as age-related arteriosclerotic vascular disease, heart surgery and organ transplantation, is still an unsettled conundrum that besets clinicians. Remote ischemic conditioning (RIC), delivered via transient, repetitive noninvasive IR interventions to distant organs or tissues, is regarded as an innovative approach against IRI. Based on the available evidence, RIC holds the potential of affording protection to multiple organs or tissues, which include not only the heart and brain, but also others that are likely susceptible to IRI, such as the kidney, lung, liver and skin. Neuronal and humoral signaling pathways appear to play requisite roles in the mechanisms of RIC-related beneficial effects, and these pathways also display inseparable interactions with each other. So far, several hurdles lying ahead of clinical translation that remain to be settled, such as establishment of biomarkers, modification of RIC regimen, and deep understanding of underlying minutiae through which RIC exerts its powerful function. As this approach has garnered an increasing interest, herein, we aim to encapsulate an overview of the basic concept and postulated protective mechanisms of RIC, highlight the main findings from proof-of-concept clinical studies in various clinical scenarios, and also to discuss potential obstacles that remain to be conquered. More well designed and comprehensive experimental work or clinical trials are warranted in future research to confirm whether RIC could be utilized as a non-invasive, inexpensive and efficient adjunct therapeutic intervention method for multi-organ protection.

Investigating and re-evaluating the role of glycogen synthase kinase 3 beta kinase as a molecular target for cardioprotection by using novel pharmacological inhibitors

AIMS

Glycogen synthase kinase 3 beta (GSK3β) link with the mitochondrial Permeability Transition Pore (mPTP) in cardioprotection is debated. We investigated the role of GSK3β in ischaemia (I)/reperfusion (R) injury using pharmacological tools.

METHODS AND RESULTS

Infarct size using the GSK3β inhibitor BIO (6-bromoindirubin-3'-oxime) and several novel analogues (MLS2776-MLS2779) was determined in anaesthetized rabbits and mice. In myocardial tissue GSK3β inhibition and the specificity of the compounds was tested. The mechanism of protection focused on autophagy-related proteins. GSK3β localization was determined in subsarcolemmal (SSM) and interfibrillar mitochondria (IFM) isolated from Langendorff-perfused murine hearts (30'I/10'R or normoxic conditions). Calcium retention capacity (CRC) was determined in mitochondria after administration of the inhibitors in mice and in vitro. The effects of the inhibitors on mitochondrial respiration, reactive oxygen species (ROS) formation, ATP production, or hydrolysis were measured in SSM at baseline. Cyclosporine A (CsA) was co-administered with the inhibitors to address putative additive cardioprotective effects. Rabbits and mice treated with MLS compounds had smaller infarct size compared with control. In rabbits, MLS2776 and MLS2778 possessed greater infarct-sparing effects than BIO. GSK3β inhibition was confirmed at the 10th min and 2 h of reperfusion, while up-regulation of autophagy-related proteins was evident at late reperfusion. The mitochondrial amount of GSK3β was similar in normoxic SSM and IFM and was not altered by I/R. The inhibitors did not affect CRC or respiration, ROS and ATP production/hydrolysis at baseline. The co-administration of CsA ensured that cardioprotection was CypD-independent.

CONCLUSION

Pharmacological inhibition of GSK3β attenuates infarct size beyond mPTP inhibition.

Zinc accumulation in mitochondria promotes ischemia-induced BBB disruption through Drp1-dependent mitochondria fission

High concentration of zinc has been reported to act as a critical mediator of neuronal death in the ischemic brain. Our previous studies showed that labile zinc accumulates in cerebromicrovessels and contributes to blood-brain barrier (BBB) permeability increase after cerebral ischemia. However, the role of mitochondrial zinc in ischemia-induced BBB permeability alteration is still unclear. In this study, we showed that ischemia/reperfusion induced free zinc accumulation in endothelial cells (ECs), resulting in increased generation of reactive oxygen species (ROS) in both cultured ECs and in microvessels isolated from the brain of ischemic rats. Furthermore, we found that zinc was highly accumulated in mitochondria, leading to mitochondrial ROS generation under the ischemic condition. Moreover, zinc overload in mitochondria resulted in the collapse of the network of mitochondria, which was mediated through Dynamin-related protein-1 (Drp-1) dependent mitochondrial fission pathway. Finally, the zinc overload in mitochondria activated matrix metalloproteinase-2 and led to ischemia-induced BBB permeability increase. This study demonstrated that zinc-ROS pathway in mitochondria contributes to the ischemia-induced BBB disruption via Drp-1 dependent mitochondrial fission pathway.

Rapamycin in ischemic stroke: Old drug, new tricks?

The significant morbidity that accompanies stroke makes it one of the world's most devastating neurological disorders. Currently, proven effective therapies have been limited to thrombolysis and thrombectomy. The window for the administration of these therapies is narrow, hampered by the necessity of rapidly imaging patients. A therapy that could extend this window by protecting neurons may improve outcome. Endogenous neuroprotection has been shown to be, in part, due to changes in mTOR signalling pathways and the instigation of productive autophagy. Inducing this effect pharmacologically could improve clinical outcomes. One such therapy already in use in transplant medicine is the mTOR inhibitor rapamycin. Recent evidence suggests that rapamycin is neuroprotective, not only via neuronal autophagy but also through its broader effects on other cells of the neurovascular unit. This review highlights the potential use of rapamycin as a multimodal therapy, acting on the blood-brain barrier, cerebral blood flow and inflammation, as well as directly on neurons. There is significant potential in applying this old drug in new ways to improve functional outcomes for patients after stroke.

Immediate remote ischemic postconditioning reduces cerebral damage in ischemic stroke mice by enhancing leptomeningeal collateral circulation

Remote ischemic postconditioning (RIPC) is a promising neuroprotective strategy for ischemic stroke. Here, we employed a focal ischemic stroke mouse model to test the hypothesis that poststroke collateral circulation as a potent mechanism of action underlying the therapeutic effects of immediate RIPC. During reperfusion of cerebral ischemia, the mice were randomly assigned to receive RIPC, granulocyte colony‐stimulating factor (G‐CSF) as a positive control, or no treatment. At 24 hr, we found RIPC and G‐CSF increased monocytes/macrophages in the dorsal brain surface and in the spleen, coupled with enhanced leptomeningeal collateral flow compared with nontreatment group. Blood monocytes depletion by 5‐fluorouracil (5‐FU) significantly limited the neuroprotection of RIPC or G‐CSF treatment. The protein expression of proangiogenic factors such as Ang‐2 was increased by ischemia, but treatment with either RIPC or G‐CSF showed no further upregulation. Thus, immediate RIPC confers neuroprotection, in part, by enhancing leptomeningeal collateral circulation in a mouse model of ischemic stroke.

Ezetimibe, a NPC1L1 inhibitor, attenuates neuronal apoptosis through AMPK dependent autophagy activation after MCAO in rats

Autophagy activation exerts neuroprotective effects in the ischemic stroke model. Ezetimibe (Eze), a Niemann-Pick disease type C1-Like 1 (NPC1L1) pharmacological inhibitor, has been reported to protect hepatocytes from apoptosis via autophagy activation. In this study, we explored whether Eze could attenuate neuronal apoptosis in the rat model of middle cerebral artery occlusion (MCAO), specifically via activation of the AMPK/ULK1/autophagy pathway. Two hundred and one male Sprague-Dawley rats were subjected to transient MCAO followed by reperfusion. Eze was administered 1 h after MCAO. To elucidate the underlying molecular mechanism, Dorsomorphin, a selective AMPK inhibitor, and 3-methyladenine (3-MA), an autophagy inhibitor, were injected intracerebroventricularly before MCAO. Infarct volume, neurological score, brain cholesterol levels, immunofluorescence staining, Western blot, and Fluoro-Jade C (FJC) staining were used to evaluate the effects of Eze. The endogenous NPC1L1 expression increased and mainly expressed in neurons after MCAO. Intranasal administration of Eze reduced brain infarct volume at 24 and 72 h after MCAO, with improved short and long-term neurological functions after MCAO. Eze reduced brain cholesterol levels (total cholesterol, free cholesterol and cholesteryl esters) and the number of FJC-positive neurons. The expression of phosphorylated AMPK (p-AMPK) and downstream ULK1, Beclin1, LC3BII, Bcl-2, and Bcl-xl increased, while P62 and proapoptotic Bax decreased after treatment with Eze. Pretreatment with Dorsomorphin and 3-MA reversed the beneficial effects of Eze. These findings suggest that intranasal administration of Eze plays neuroprotective role through autophagy activation after MCAO in rats. Lowered cholesterol levels and AMPK activation may act in conjunction to induce autophagy after treatment with Eze. Eze merits further investigation as a potential therapeutic agent in ischemic stroke patients.

Ischemic Postconditioning Alleviates Cerebral Ischemia-Reperfusion Injury Through Activating Autophagy During Early Reperfusion in Rats

This study aimed to investigate whether ischemic postconditioning (IpostC) alleviates cerebral ischemia/reperfusion (I/R) injury involved in autophagy. Adult Sprague–Dawley rats were divided into five groups: sham (sham surgery), I/R (middle cerebral artery occlusion [MCAO] for 100 min, then reperfusion), IpostC (MCAO for 100 min, reperfusion for 10 min, MCAO for 10 min, then reperfusion), IpostC+3MA (3-methyladenine, an autophagy inhibitor, administered 30 min before first reperfusion), and IpostC+Veh (vehicle control for IpostC+3MA group). Infarct volume was measured using cresyl violet staining. Autophagy-related proteins were detected by western blot and immunohistochemistry. Autophagosomes, autophagolysosomes, and mitochondrial damage were identified by transmission electron microscopy. Cortical cell apoptosis was detected by the TUNEL assay. Neurologic function was assessed using the modified Neurologic Severity Score. IpostC improved neurological function and reduced infarct volume after I/R (P < 0.05). These effects of IpostC were inhibited by 3MA (P < 0.05). Autophagosome formation was increased in the I/R and IpostC+Veh groups (P < 0.05), but not in the IpostC+3MA group. The I/R group showed enhanced LC3-II/LC3-I ratio, p62, and Cathepsin B levels and decreased LAMP-2 level (all P < 0.05 vs. sham), indicating dysfunction of autophagic clearance. IpostC reduced p62 and Cathepsin B levels and increased the LC3-II/LC3-I ratio, and nuclear translocation of transcription factor EB (all P < 0.05); these effects of IpostC were reversed by 3MA, suggesting IpostC enhanced autophagic flux. Furthermore, IpostC attenuated I/R-induced mitochondrial translocation of Bax and mitochondrial cytochrome-c release (all P < 0.05); 3MA inhibited these effects of IpostC (P < 0.05). In conclusion, IpostC may alleviate cerebral I/R injury by activating autophagy during early reperfusion.

Ataxia telangiectasia mutated kinase deficiency impairs the autophagic response early during myocardial infarction

Ataxia telangiectasia mutated kinase (ATM) is activated in response to DNA damage. We have previously shown that ATM plays a critical role in myocyte apoptosis and cardiac remodeling after myocardial infarction (MI). Here, we tested the hypothesis that ATM deficiency results in autophagic impairment in the heart early during MI. MI was induced in wild-type (WT) and ATM heterozygous knockout (hKO) mice by ligation of the left anterior descending artery. Structural and biochemical parameters of the heart were measured 4 h after left anterior descending artery ligation. M-mode echocardiography revealed that MI worsens heart function, as evidenced by reduced percent ejection fraction and fractional shortening in both groups. However, MI-induced increase in left ventricular end-diastolic and end-systolic diameters and volumes were significantly lower in hKO hearts. ATM deficiency resulted in autophagic impairment during MI, as evidenced by decreased microtubule-associated protein light chain 3-II increased p62, decreased cathepsin D protein levels, and increased aggresome accumulation. ERK1/2 activation was only observed in WT-MI hearts. Activation of Akt and AMP-activated protein kinase (AMPK) was lower, whereas activation of glycogen synthase kinase (GSK)-3β and mammalian target of rapamycin (mTOR) was higher in hKO-MI hearts. Inhibition of ATM using KU-55933 resulted in autophagic impairment in cardiac fibroblasts, as evidenced by decreased light chain 3-II protein levels and formation of acidic vesicular organelles. This impairment was associated with decreased activation of Akt and AMPK but enhanced activation of GSK-3β and mTOR in KU-55933-treated fibroblasts. Thus, ATM deficiency results in autophagic impairment in the heart during MI and cardiac fibroblasts. This autophagic impairment may occur via the activation of GSK-3β and mTOR and inactivation of Akt and AMPK. NEW & NOTEWORTHY Ataxia telangiectasia mutated kinase (ATM) plays a critical role in myocyte apoptosis and cardiac remodeling after myocardial infarction (MI). Here, we provide evidence that ATM deficiency results in autophagic impairment during MI. Further investigation of the role of ATM in autophagy post-MI may provide novel therapeutic targets for patients with ataxia telangiectasia suffering from heart disease.

Hypoxia Inducible Factor 1α Plays a Key Role in Remote Ischemic Preconditioning Against Stroke by Modulating Inflammatory Responses in Rats

Background

Limb remote ischemic preconditioning (RIPC) protects against brain injury induced by stroke, but the underlying protective mechanisms remain unknown. As hypoxia inducible factor 1α (HIF‐1α) is neuroprotective in stroke and mediates neuroinflammation, we tested the hypothesis that HIF‐1α is a key factor of RIPC against stroke by mediating inflammation.

Methods and Results

Stroke was induced by transient middle cerebral artery occlusion in rats, and RIPC was conducted in both hind limbs. The HIF‐1α mRNA was examined by quantitative reverse transcription polymerase chain reaction after RIPC. In addition, inflammatory cytokines in the peripheral blood and brain were measured using the AimPlex multiplex immunoassays. Data showed that RIPC reduced the infarct size, improved neurological functions, and increased HIF‐1α mRNA levels, interleukin (IL)‐4, and IL‐10 protein levels in the peripheral blood. Intraperitoneal injection of the HIF activator, dimethyloxaloylglycine, reduced the infarct size and inhibited interferon‐γ protein levels, while promoting IL‐4 and IL‐10 protein levels, while decreasing interferon‐γ protein levels in both the peripheral blood and ischemic brain. In addition, injection of dimethyloxaloylglycine had a synergistic effect with RIPC on reducing infarction and improving neurological functions, as well as decreasing interferon‐γ in the peripheral blood and ischemic brain. In contrast, injection of the HIF inhibitor, acriflavine hydrochloride, abolished the protective effects of RIPC on infarction, and reduced IL‐4 and IL‐10 protein levels in both the peripheral blood and ischemic brain.

Conclusions

We conclude that HIF‐1α plays a key role in RIPC, likely mediated by a systemic modulation of the inflammatory response.

Remote limb ischemic postconditioning protects against cerebral ischemia-reperfusion injury by activating AMPK-dependent autophagy

Remote limb ischemic postconditioning (RIPoC) is a promising adjunct treatment for cerebral ischemia-reperfusion (IR) injury. However, the underlying mechanisms have not been fully elucidated yet. The present study aims to investigate potential involvement and regulatory mechanisms of autophagy in RIPoC treatment against cerebral IR injury in mice. Mice were subjected to 2 h middle cerebral artery occlusion (MCAO) then treated with vehicle, 3-methyladenine (3-MA, an autophagy inhibitor), or compound C (an AMPK inhibitor) at the onset of reperfusion. RIPoC was carried out by 3 cycles of 10-min occlusion-reperfusion of bilateral femoral artery at the beginning of the reperfusion. Infarct volume, neurological score, and brain water content of the mice were assessed after 12 h reperfusion. Autophagy markers, cell apoptosis markers, and AMPK pathway activity were also evaluated. Our results indicated that RIPoC treatment reduced neurological deficits, brain water content, and infarct volume after IR. Meanwhile, RIPoC was proved to induce autophagy and activate AMPK pathway. Furthermore, the RIPoC-induced autophagy and neuroprotection were abolished by 3-MA and partially blocked by compound C. In conclusion, the present study suggests that RIPoC attenuates cerebral IR injury by activating AMPK-dependent autophagy.

Limb Remote Ischemic Conditioning: Mechanisms, Anesthetics, and the Potential for Expanding Therapeutic Options

Novel and innovative approaches are essential in developing new treatments and improving clinical outcomes in patients with ischemic stroke. Remote ischemic conditioning (RIC) is a series of mechanical interruptions in blood flow of a distal organ, following end organ reperfusion, shown to significantly reduce infarct size through inhibition of oxidation and inflammation. Ischemia/reperfusion (I/R) is what ultimately leads to the irreversible brain damage and clinical picture seen in stroke patients. There have been several reports and reviews about the potential of RIC in acute ischemic stroke; however, the focus here is a comprehensive look at the differences in the three types of RIC (remote pre-, per-, and postconditioning). There are some limited uses of preconditioning in acute ischemic stroke due to the unpredictability of the ischemic event; however, it does provide the identification of biomarkers for clinical studies. Remote limb per- and postconditioning offer a more promising treatment during patient care as they can be harnessed during or after the initial ischemic insult. Though further research is needed, it is imperative to discuss the importance of preclinical data in understanding the methods and mechanisms involved in RIC. This understanding will facilitate translation to a clinically feasible paradigm for use in the hospital setting.

Limb remote ischemic post‑conditioning reduces injury and improves long‑term behavioral recovery in rats following subarachnoid hemorrhage: Possible involvement of the autophagic process

Hemorrhage‑related neurologic injury is a primary cause of disability and mortality following subarachnoid hemorrhage (SAH). The aim of the present study was to investigate the potential neuroprotective effect and the possible role of autophagy in limb remote ischemic post‑conditioning (RIPostC) using an endovascular puncture rat model of SAH. RIPostC was induced by three cycles of occlusion (10 min) and release (10 min) in the bilateral femoral artery using an aneurysm clip. Early RIPostC began immediately following SAH, delayed RIPostC began following a 30 min delay and the repeated RIPostC group underwent the protocol every day for 3 days. Brain water content, SAH grading, terminal deoxynucleotidyl transferase dUTP nick end labeling‑DAPI staining, transmission electron microscopy, and neurological and behavioral tests were conducted three days following surgery. Long term outcomes of behavior and memory were assessed using a rotarod test and Morris water maze test 1 month subsequently. Biomarkers of autophagy, including Beclin‑1 and light chain 3 (LC3), were assessed using western blotting. The results of the present study demonstrated that, compared with other groups, repeated RIPostC was able to alleviate brain edema, prevent neuronal apoptosis, and improve short term and long term neurological function and memory. Beclin‑1 and LC3 in the cortex were upregulated following treatment with repeated RIPostC. Autolysosomes increased 3 days following SAH and were maintained for 1 month in the repeated RIPostC group. Therefore, the present study indicated that the optimized repeated RIPostC may provide a noninvasive strategy to induce neuroprotection, and improve the short and long term outcomes of SAH‑related cerebral injury, possibly involving the autophagy pathway.

Treatment Effects of Ischemic Stroke by Berberine, Baicalin, and Jasminoidin from Huang-Lian-Jie-Du-Decoction (HLJDD) Explored by an Integrated Metabolomics Approach

Berberine, baicalin, and jasminoidin were major active ingredients of Huang-Lian-Jie-Du-Decoction (HLJDD), a famous prescription of traditional Chinese medicine (TCM), which has been used for the treatment of ischemic stroke. The aim of the present study was to classify their roles in the treatment effects of ischemic stroke. A rat model of middle cerebral artery occlusion (MCAO) was constructed to mimic ischemic stroke and treatment effects of berberine, baicalin, and jasminoidin, and HLJDD was assessed by neurologic deficit scoring, infarct volume, histopathology, immunohistochemistry, biochemistry, quantitative real-time polymerase chain reaction (qRT-PCR), and Western blotting. In addition, the ¹H NMR metabolomics approach was used to assess the metabolic profiles, which combined with correlation network analysis successfully revealed metabolic disorders in ischemic stroke concerning the treatment of the three principal compounds from HLJDD for the first time. The combined results suggested that berberine, baicalin, and jasminoidin are responsible for the effectiveness of HLJDD on the treatment of ischemic stroke by amelioration of abnormal metabolism and regulation of oxidative stress, neuron autophagy, and inflammatory response. This integrated metabolomics approach showed its potential in understanding the function of complex formulae and clarifying the role of its components in the overall treatment effects.

Neuroprotective effects respond to cerebral ischemia without susceptibility to HB-tumorigenesis in VHL heterozygous knockout mice

The von Hippel-Lindau (VHL) tumor suppressor gene plays a prominent role in the development of hemangioblastomas (HBs) within specific regions of the human' central nervous system (CNS). Alterations in VHL gene are rarely observed in the more common features of human VHL-related tumors in animal models, and VHL heterozygous knockout (VHL+/-) mice do not develop HBs. We tested whether VHL heterozygous knockout mice exhibited genetic predisposition to the development of HBs and conferred a selective advantage involving growth of blood vessels to its carrier. No differences were observed between wild-type and VHL+/- mice in development ad reproduction. The heterozygous VHL+/- mice did not develop higher genetic susceptibility to CNS-HBs over their lifetime. Furthermore, this recessive VHL gene heterozygosity is relatively stable. Interestingly, we found these heterozygous VHL+/- mice gained an advantage conferring to angiogenic ability in a particular environment, compared with wild-type mice. The heterozygous VHL+/- mice obviously enhanced hypoxia inducible factor-1 (HIF)-dependent and Twist1 angiogenic mechanism in response to acute cerebral ischemia, resulting in decreased cerebral tissue damage and neuroprotective response through neovascularization. Our findings provide evidence of partial loss function of VHL as a novel precise therapeutic target in acute cerebral ischemia.

TLR4 signal ablation attenuated neurological deficits by regulating microglial M1/M2 phenotype after traumatic brain injury in mice

Traumatic brain injury (TBI) initiates inflammatory responses that result in an enduring cascade of secondary neuronal loss and behavioural impairment. Toll-like receptor 4 (TLR4), predominantly expressed by microglia, recognizes damage-associated molecular patterns (DAMPs) and regulates inflammatory processes. Interestingly, the switch of microglial M1/M2 phenotypes after TBI is highly important regarding damage and restoration of neurological function. Therefore, we investigated the role and mechanisms of the TLR4 signalling pathway in regulating microglial M1/M2 phenotypes. Using a controlled cortical impact (CCI) model, we found that TLR4 knockout (KO) mice exhibited decreased infarct volumes and improved outcomes in behavioural tests. In addition, mice lacking TLR4 had higher expression of M2 phenotype biomarkers but lower expression of M1 phenotype biomarkers. Compared with microglia derived from wild-type (WT) mice, increased expression of M2 phenotype biomarkers and decreased expression of M1 phenotype biomarkers were also noted in primary cultures of microglia from TLR4 KO mice. In TLR4 KO mice, the expression levels of downstream signalling molecules of TLR4, such as active Rac-1 and phospho-AKT, were higher, while MyD88 and phospho-NF-κB p65 expression levels were lower than in WT mice. Our results demonstrate that the absence of TLR4 induces microglial polarization toward the M2 phenotype and promotes microglial migration and, in turn, alleviates the development of neuroinflammation, which indicates potential neuroprotective effects in the TBI mouse model. Furthermore, up-regulation of IL-4 expression in TLR4 KO mice could contribute to anti-inflammatory functions and promote microglial polarization toward the M2 phenotype, which might be mediated by active Rac-1 expression. Taken together, TLR4 deficiency contributes to regulating microglia to switch to the M2 phenotype, which ameliorates neurological impairment after TBI.

PARK2-dependent mitophagy induced by acidic postconditioning protects against focal cerebral ischemia and extends the reperfusion window

Prompt reperfusion after cerebral ischemia is critical for neuronal survival. Any strategies that extend the limited reperfusion window will be of great importance. Acidic postconditioning (APC) is a mild acidosis treatment that involves inhaling CO₂ during reperfusion following ischemia. APC attenuates ischemic brain injury although the underlying mechanisms have not been elucidated. Here we report that APC reinforces ischemia-reperfusion-induced mitophagy in middle cortical artery occlusion (MCAO)-treated mice, and in oxygen-glucose deprivation (OGD)-treated brain slices and neurons. Inhibition of mitophagy compromises neuroprotection conferred by APC. Furthermore, mitophagy and neuroprotection are abolished in Park2 knockout mice, indicating that APC-induced mitophagy is facilitated by the recruitment of PARK2 to mitochondria. Importantly, in MCAO mice, APC treatment extended the effective reperfusion window from 2 to 4 h, and this window was further extended to 6 h by exogenously expressing PARK2. Taken together, we found that PARK2-dependent APC-induced mitophagy renders the brain resistant to ischemic injury. APC treatment could be a favorable strategy to extend the thrombolytic time window for stroke therapy.

Limb Remote Ischemic Postconditioning Reduces Ischemia-Reperfusion Injury by Inhibiting NADPH Oxidase Activation and MyD88-TRAF6-P38MAP-Kinase Pathway of Neutrophils

Limb remote ischemic postconditioning (LRIP) has been confirmed to reduce the ischemia-reperfusion injury but its mechanisms are still not clear. This study clarified the mechanism of LRIP based on the nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase and Myeloid differentiation factor 88 (MyD88)-Tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6)-P38 pathway of neutrophils. Rat middle cerebral artery occlusion (MCAO) model was used in this study. Ischemia-reperfusion injury was carried out by MCAO 1.5 h followed by 24 h reperfusion. LRIP operation was performed to the left femoral artery at 0, 1 or 3 h after reperfusion. Behavioral testing, including postural reflex test, vibrissae-elicited forelimb placing test and tail hang test, showed that LRIP operated at 0 h of reperfusion could significantly ameliorate these behavioral scores. Pathological examinations, infarct size, Myeloperoxidase (MPO) activity showed that LRIP operated at 0 h of reperfusion could significantly ameliorate the pathological scores, reduce the infarct size and MPO activity in the brain and increase the MPO activity in the left leg. By using Neutrophil counting, immunofluorescence and real-time PCR techniques, we found that LRIP operated at 0 h of reperfusion could reduce neutrophil counts in the peripheral blood and downregulate the activation of neutrophil in the peripheral blood and rat brain. Western blots revealed that MyD88, TRAF6, p38 mitogen-activated protein kinase (p38-MAPK) in neutrophils and the phosphorylation of p47phox (Ser 304 and Ser 345) in neutrophil could be downregulated by LRIP. Our study suggests that LRIP inhibits the number and activation of neutrophils in the rat brain and peripheral blood linked to down-regulating the activation of NADPH oxidase in neutrophils by MyD88/TRAF6/p38-MAPK pathway.

Zinc contributes to acute cerebral ischemia-induced blood-brain barrier disruption

Zinc ions are stored in synaptic vesicles and cerebral ischemia triggers their release from the terminals of neurons. Zinc accumulation in neurons has been shown to play an important role in neuronal death following ischemia. However, almost nothing is known about whether zinc is involved in ischemia-induced blood-brain barrier (BBB) disruption. Herein, we investigated the contribution of zinc to ischemia-induced acute BBB disruption and the possible molecular mechanisms using both cellular and animal models of cerebral ischemia. Zinc greatly increased BBB permeability and exacerbated the loss of tight junction proteins (Occludin and Claudin-5) in the endothelial monolayer under oxygen glucose deprivation conditions. In cerebral ischemic rats, a dramatically elevated level of zinc accumulation in microvessels themselves was observed in isolated microvessels and in situ, showing the direct interaction of zinc on ischemic microvessels. Treatment with a specific zinc chelator N,N,N',N'-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN), even at 60-min post-ischemia onset, could greatly attenuate BBB permeability in the ischemic rats as measured by Evan's Blue extravasation, edema volume and magnetic resonance imaging. Furthermore, zinc accumulation in microvessels activated the superoxide/matrix metalloproteinase-9/-2 pathway, which leads to the loss of tight junction proteins (Occludin and Claudin-5) and death of endothelial cells in microvessels themselves. Our findings reveal a novel mechanism of cerebral ischemia-induced BBB damage, and implicate zinc as an effective and viable new target for reducing acute BBB damage following ischemic stroke.

Tideglusib, a chemical inhibitor of GSK3β, attenuates hypoxic-ischemic brain injury in neonatal mice

BACKGROUND

Hypoxia-ischemia is an important cause of brain injury and neurological morbidity in the newborn infants. The activity of glycogen synthase kinase-3β (GSK-3β) is up-regulated following neonatal stroke. Tideglusib is a GSK-3β inhibitor which has neuroprotective effects against neurodegenerative diseases in clinical trials. However, the effect of tideglusib on hypoxic-ischemic (HI) brain injury in neonates is still unknown.

METHODS

Postnatal day 7 (P7) mouse pups subjected to unilateral common carotid artery ligation followed by 1h of hypoxia or sham surgery was performed. HI animals were administered tideglusib (5mg/kg) or vehicle intraperitoneally 20min prior to the onset of ischemia. The brain infarct volume and whole brain images, were used in conjunction with Nissl staining to evaluate the protective effects of tideglusib. Protein levels of glial fibrillary acidic protein (GFAP), Notch1, cleaved caspase-3/9, phosphorylated signal transducer and activator of transcription 3 (STAT3), GSK-3β and protein kinase B (Akt) were detected to identify potentially involved molecules.

RESULTS

Tideglusib significantly reduced cerebral infarct volume at both 24h and 7days after HI injury. Tideglusib also increased phosphorylated GSK-3β(Ser9) and Akt(Ser473), and reduced the expression of GFAP and p-STAT3(Tyr705). In addition, pretreatment with tideglusib also enhanced the protein level of Notch1. Moreover, tideglusib reduced the cleavage of pro-apoptotic signal caspase proteins, including caspase 3 and caspase 9 following HI.

CONCLUSION

These results indicate that tideglusib shows neuroprotection against hypoxic-ischemic brain injury in neonatal mice.

GENERAL SIGNIFICANCE

Tideglusib is a potential compound for the prevention or treatment of hypoxic-ischemic brain injury in neonates.

Systems Biology of Immunomodulation for Post-Stroke Neuroplasticity: Multimodal Implications of Pharmacotherapy and Neurorehabilitation

AIMS

Recent studies indicate that anti-inflammatory drugs, act as a double-edged sword, not only exacerbating secondary brain injury but also contributing to neurological recovery after stroke. Our aim is to explore whether there is a beneficial role for neuroprotection and functional recovery using anti-inflammatory drug along with neurorehabilitation therapy using transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS), so as to improve functional recovery after ischemic stroke.

METHODS

We develop a computational systems biology approach from preclinical data, using ordinary differential equations, to study the behavior of both phenotypes of microglia, such as M1 type (pro-inflammatory) vis-à-vis M2 type (anti-inflammatory) under anti-inflammatory drug action (minocycline). We explore whether pharmacological treatment along with cerebral stimulation using tDCS and rTMS is beneficial or not. We utilize the systems pathway analysis of minocycline in nuclear factor kappa beta (NF-κB) signaling and neurorehabilitation therapy using tDCS and rTMS that act through brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB) signaling pathways.

RESULTS

We demarcate the role of neuroinflammation and immunomodulation in post-stroke recovery, under minocycline activated-microglia and neuroprotection together with improved neurogenesis, synaptogenesis, and functional recovery under the action of rTMS or tDCS. We elucidate the feasibility of utilizing rTMS/tDCS to increase neuroprotection across the reperfusion stage during minocycline administration. We delineate that the signaling pathways of minocycline by modulation of inflammatory genes in NF-κB and proteins activated by tDCS and rTMS through BDNF, TrkB, and calmodulin kinase (CaMK) signaling. Utilizing systems biology approach, we show that the activation pathways for pharmacotherapy (minocycline) and neurorehabilitation (rTMS applied to ipsilesional cortex and tDCS) results into increased neuronal and synaptic activity that commonly occur through activation of N-methyl-d-aspartate receptors. We construe that considerable additive neuroprotection effect would be obtained and delayed reperfusion injury can be remedied, if one uses multimodal intervention of minocycline together with tDCS and rTMS.

CONCLUSION

Additive beneficial effect is, thus, noticed for pharmacotherapy along with neurorehabilitation therapy, by maneuvering the dynamics of immunomodulation using anti-inflammatory drug and cerebral stimulation for augmenting the functional recovery after stroke, which may engender clinical applicability for enhancing plasticity, rehabilitation, and neurorestoration.

Remote limb ischemic conditioning treatment for intracranial atherosclerotic stenosis patients

OBJECTIVE

The recurrence rate of ischemic stroke remains high among symptomatic intracranial atherosclerotic stenosis patients with either ischemic stroke or transient ischemic attack. The aim of our study is to evaluate whether remote limb ischemic conditioning (RLIC) prevents cerebral ischemic events in symptomatic intracranial atherosclerotic stenosis patients.

METHODS

Symptomatic intracranial atherosclerotic stenosis patients with either ischemic stroke or transient ischemic attack will be recruited from more than 60 hospitals in China to participate in a randomized, double-blind, parallel-controlled clinical trial that will compare the efficacy and safety of RLIC for the prevention of recurrent stroke. Following randomization, patients allocated to the RLIC group (n = 1500) will receive RLIC once daily for 12 months, with treatment consisting of five cycles of 5 min of pressure treatment at 200 mm Hg, followed by 5 min of reperfusion. The sham group (n = 1500) will be treated identically, with the exception of pressure treatment at 60 mm Hg.

RESULTS

The primary endpoint will be an ischemic stroke event during the study period. Secondary endpoints will include composite fatal and nonfatal stroke, fatal and nonfatal myocardial infarction, and transient ischemic attack. Patients will be assessed periodically over a approximate 3-year study period using the modified Rankin Scale, National Institutes of Health Stroke Scale, and Barthel Activities of Daily Living Index.

CONCLUSION

We predict that RLIC treatment for 12 months will safely reduce the ischemic stroke recurrence rate.