RLIPostC protects against cerebral ischemia through improved synaptogenesis in rats

The potential mechanism and clinical application value of remote ischemic conditioning in stroke

Some studies have confirmed the neuroprotective effect of remote ischemic conditioning against stroke. Although numerous animal researches have shown that the neuroprotective effect of remote ischemic conditioning may be related to neuroinflammation, cellular immunity, apoptosis, and autophagy, the exact underlying molecular mechanisms are unclear. This review summarizes the current status of different types of remote ischemic conditioning methods in animal and clinical studies and analyzes their commonalities and differences in neuroprotective mechanisms and signaling pathways. Remote ischemic conditioning has emerged as a potential therapeutic approach for improving stroke-induced brain injury owing to its simplicity, non-invasiveness, safety, and patient tolerability. Different forms of remote ischemic conditioning exhibit distinct intervention patterns, timing, and application range. Mechanistically, remote ischemic conditioning can exert neuroprotective effects by activating the Notch1/phosphatidylinositol 3-kinase/Akt signaling pathway, improving cerebral perfusion, suppressing neuroinflammation, inhibiting cell apoptosis, activating autophagy, and promoting neural regeneration. While remote ischemic conditioning has shown potential in improving stroke outcomes, its full clinical translation has not yet been achieved.

Effect of RICAS (Remote Ischemic Preconditioning on Collaterals of Atherosclerosis Stroke): Rationale and Design

BACKGROUND

As a noninvasive, low-cost, nonpharmacological procedure with excellent properties of safety, remote ischemic conditioning (RIC) has been demonstrated to prevent recurrence of stroke among patients with ischemic stroke of large artery atherosclerosis origin. We hypothesized that the benefit is attributed to the improvement of collaterals by chronic RIC in this population, and we aimed to explore the influence of chronic RIC on collateral status evaluated by digital subtraction angiography in this population.

METHODS

The RICAS (Remote Ischemic Preconditioning on Collaterals of Atherosclerosis Stroke) study is a prospective, randomized, blind end point, multicenter study. Eligible patients with ischemic stroke of anterior circulation caused by large artery atherosclerosis, poor collateral compensation, and more than 1 month of symptom onset, are randomly assigned into experimental and control groups with a ratio of 1:1. The patients in the experiment group will receive treatment with RIC (bilateral upper limbs, for a total procedure time of 50 minutes, twice daily) for 1 year as an adjunct to guideline-based treatment, while patients in the control group only receive guideline-based treatment. A maximum of 300 patients (150 participants per group) are required to test the superiority hypothesis with 80% power (using a 2-sided α=0.05) to detect a 15% difference. Subgroup analyses for the primary end point will be performed on 8 prespecified subgroups by age, sex, ischemic event (acute ischemic stroke ore transient ischemic stroke), tandem lesion, history of hypertension, hypercholesterolemia, diabetes, and myocardial infarction. The primary outcome is the proportion of collateral status improvement, which is defined as an increase of ≥1 point on the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology score, as assessed by digital subtraction angiography at 12 months after randomization. The safety outcomes include RIC-related adverse events.

CONCLUSIONS

This study may provide the direct evidence for the potential effect of chronic RIC treatment on the improvement of collateral status.

REGISTRATION

URL: https://clinicaltrials.gov. Unique identifier: NCT06170944.

Remote ischaemic conditioning for neurological disorders-a systematic review and narrative synthesis

INTRODUCTION

Remote ischaemic conditioning (RIC) refers to the use of controlled transient ischemic and reperfusion cycles, commonly of the upper or lower limb, to mitigate cellular damage from ischaemic injury. Preclinical studies demonstrate that RIC may have a neuroprotective effect and therefore could represent a novel therapeutic option in the management of neurological disorders. The aim of this review is to comprehensively describe the current clinical evidence of RIC in neurological disorders.

METHODS

A computerised search of EMBASE and OVID MEDLINE was conducted from 2002 to October 2023 for randomised controlled trials (RCTs) investigating RIC in neurological diseases.

RESULTS

A total of 46 different RCTs in 12 different neurological disorders (n = 7544) were included in the analysis. Conditions included acute ischaemic stroke, symptomatic intracranial stenosis and vascular cognitive impairment. The most commonly used RIC protocol parameters in the selected studies were as follows: cuff pressure at 200 mmHg (27 trials), 5-min cycle length (42 trials), 5 cycles of ischaemia and reperfusion (24 trials) and the application to the upper limb unilaterally (23 trials).

CONCLUSIONS

The comprehensive analysis of the included studies reveals promising results regarding the safety and therapeutic effect of RIC as an option for managing neurological diseases. Particularly, the strongest evidence supports its potential use in chronic stroke patients and vascular cognitive impairment. The neuroprotective effects of RIC, as demonstrated in preclinical studies, suggest that this therapeutic approach could extend its benefits to various other diseases affecting the nervous system. However, to establish the efficacy of RIC across different neurological disorders, further trials with larger sample sizes and more diverse patient populations are warranted. Upcoming trials are expected to provide valuable evidence that will not only confirm the efficacy of RIC in neurological disease management but also help identify the most optimal RIC regimen for specific conditions.

The Function of Spag6 to Repair Brain Edema Damage After Cerebral Ischemic Stroke-reperfusion

Sperm associated antigen 6 (Spag6) is the PF16 homolog of Chlamydomonas and participates in the regulation of cilia movement. Studies have shown that Spag6 is expressed in the brain, and its loss will lead to cerebral edema caused by a defect in motor cilium function in ependymal cells. However, it has not been reported whether the limited or extensive cerebral edema resulting from ischemic strokes is related to the expression regulation of Spag6. Therefore, this study aimed to investigate the effect and related mechanism of Spag6 in alleviating Cerebral Ischemic stroke-reperfusion (CIS/R) damage. Our experimental results showed that Spag6 overexpression alleviated CIS/R-mediated motor cilia structural disorder, improved cerebral edema, inhibited nerve injuries in rats with cerebral ischemia, and alleviated synaptic and dendritic spinal injuries by regulating the expressions of synaptic-related proteins such as CaMKII, PSD95, and CREB. Based on significant changes in PI3K/AKT-mTOR signaling pathway activity after CIS/R determination, we determined that Spag6 regulates the abnormal expression of CIS/R-induced inflammatory factors NF-κB, NLRP3, IL-10, and the autophagy-related proteins Beclin-1, LC3, and P62 by activating the PI3K/AKT-mTOR signaling pathway. This inhibits inflammation and autophagy in the brain tissue. In summary, this study revealed that Spag6 alleviates brain edema damage after CIS/R by maintaining the structural function of the motor cilium, regulating the PI3K/AKT-mTOR signaling pathway, and inhibiting inflammation and autophagy reaction.

Inhibition of A1 Astrocytes and Activation of A2 Astrocytes for the Treatment of Spinal Cord Injury

Spinal cord injury (SCI) is a serious injury to the central nervous system that causes significant physical and psychological trauma to the patient. SCI includes primary spinal cord injuries and secondary spinal cord injuries. The secondary injury refers to the pathological process or reaction after the primary injury. Although SCI has always been thought to be an incurable injury, the human nerve has the ability to repair itself after an injury. However, the reparability is limited because glial scar formation impedes functional recovery. There is a type of astrocyte that can differentiate into two forms of reactive astrocytes known as 'A1' and 'A2' astrocytes. A1 astrocytes release cytotoxic chemicals that cause neurons and oligodendrocytes to die and perform a harmful role. A2 astrocytes can produce neurotrophic factors and act as neuroprotectors. This article discusses ways to block A1 astrocytes while stimulating A2 astrocytes to formulate a new treatment for spinal cord injury.

A review of remote ischemic conditioning as a potential strategy for neural repair poststroke

Ischemic stroke is one of the major disabling health-care problem and multiple different approaches are needed to enhance rehabilitation, in which neural repair is the structural basement. Remote ischemic conditioning (RIC) is a strategy to trigger endogenous protect. RIC has been reported to play neuroprotective role in acute stage of stroke, but the effect of RIC on repair process remaining unclear. Several studies have discovered some overlapped mechanisms RIC and neural repair performs. This review provides a hypothesis that RIC is a potential therapeutic strategy on stroke rehabilitation by evaluating the existing evidence and puts forward some remaining questions to clarify and future researches to be performed in the field.

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.

Remote ischaemic conditioning for stroke: unanswered questions and future directions

Remote ischaemic conditioning (RIC) refers to a process whereby periods of intermittent ischaemia, typically via the cyclical application of a blood pressure cuff to a limb at above systolic pressure, confers systemic protection against ischaemia in spatially distinct vascular territories. The mechanisms underlying this have not been characterised fully but have been shown to involve neural, hormonal and systemic inflammatory signalling cascades. Preclinical and early clinical studies have been promising and suggest beneficial effects of RIC in acute ischaemic stroke, symptomatic intracranial stenosis and vascular cognitive impairment. Through systematic searches of several clinical trials databases we identified 48 active clinical trials of RIC in ischaemic stroke, intracerebral haemorrhage and subarachnoid haemorrhage. We summarise the different RIC protocols and outcome measures studied in ongoing clinical trials and highlight which studies are most likely to elucidate the underlying biological mechanisms of RIC and characterise its efficacy in the near future. We discuss the uncertainties of RIC including the optimal frequency and duration of therapy, target patient groups, cost-effectiveness, the confounding impact of medications and the absence of a clinically meaningful biomarker of the conditioning response. With several large clinical trials of RIC expected to report their outcomes within the next 2 years, this review aims to highlight the most important studies and unanswered questions that will need to be addressed before this potentially widely accessible and low-cost intervention can be used in clinical practice.

Mini Review (Part I): An Experimental Concept on Exercise and Ischemic Conditioning in Stroke Rehabilitation

Stroke remains a leading cause of adult death and disability. Poststroke rehabilitation is vital for reducing the long-term sequelae of brain ischemia. Recently, physical exercise training has been well established as an effective rehabilitation tool, but its efficacy depends on exercise parameters and the patient's capacities, which are often altered following a major cerebrovascular event. Thus, ischemic conditioning as a rehabilitation intervention was considered an “exercise equivalent,” but the investigation is still in its relative infancy. In this mini-review, we discuss the potential for physical exercise or ischemic conditioning and its relation to angiogenesis, neurogenesis, and plasticity in stroke rehabilitation. This allows the readers to understand the context of the research and the application of ischemic conditioning in poststroke rehabilitation.

Neuroprotection by Remote Ischemic Conditioning in Rodent Models of Focal Ischemia: a Systematic Review and Meta-Analysis

Remote ischemic conditioning (RIC) is a promising neuroprotective therapy for ischemic stroke. Preclinical studies investigating RIC have shown RIC reduced infarct volume, but clinical trials have been equivocal. Therefore, the efficacy of RIC in reducing infarct volume and quality of current literature needs to be evaluated to identify knowledge gaps to support future clinical trials. We performed a systematic review and meta-analysis of preclinical literature involving RIC in rodent models of focal ischemia. This review was registered with PROSPERO (CRD42019145441). Eligibility criteria included rat or mice models of focal ischemia that received RIC to a limb either before, during, or after stroke. MEDLINE and Embase databases were searched from 1946 to August 2019. Risk of bias was assessed using the SYRCLE risk of bias tool along with construct validity. Seventy-two studies were included in the systematic review. RIC was shown to reduce infarct volume (SMD - 2.19; CI - 2.48 to - 1.91) when compared to stroke-only controls and no adverse events were reported with regard to RIC. Remote ischemic conditioning was shown to be most efficacious in males (SMD - 2.26; CI - 2.58 to - 1.94) and when delivered poststroke (SMD - 1.34; CI - 1.95 to - 0.73). A high risk of bias was present; thus, measures of efficacy may be exaggerated. A limitation is the poor methodological reporting of many studies, resulting in unclear construct validity. We identified several important, but under investigated topics including the efficacy of RIC in different stroke models, varied infarct sizes and location, and potential sex differences.

Proteomics Analysis of Brain Tissue in a Rat Model of Ischemic Stroke in the Acute Phase

Background: Stroke is a leading health issue, with high morbidity and mortality rates worldwide. Of all strokes, approximately 80% of cases are ischemic stroke (IS). However, the underlying mechanisms of the occurrence of acute IS remain poorly understood because of heterogeneous and multiple factors. More potential biomarkers are urgently needed to reveal the deeper pathogenesis of IS.

Methods: We identified potential biomarkers in rat brain tissues of IS using an iTRAQ labeling approach coupled with LC-MS/MS. Furthermore, bioinformatrics analyses including GO, KEGG, DAVID, and Cytoscape were used to present proteomic profiles and to explore the disease mechanisms. Additionally, Western blotting for target proteins was conducted for further verification.

Results: We identified 4,578 proteins using the iTRAQ-based proteomics method. Of these proteins, 282 differentiated proteins, comprising 73 upregulated and 209 downregulated proteins, were observed. Further bioinformatics analysis suggested that the candidate proteins were mainly involved in energy liberation, intracellular protein transport, and synaptic plasticity regulation during the acute period. KEGG pathway enrichment analysis indicated a series of representative pathological pathways, including energy metabolite, long-term potentiation (LTP), and neurodegenerative disease-related pathways. Moreover, Western blotting confirmed the associated candidate proteins, which refer to oxidative responses and synaptic plasticity.

Conclusions: Our findings highlight the identification of candidate protein biomarkers and provide insight into the biological processes involved in acute IS.