Chronic Remote Ischemic Conditioning Is Cerebroprotective and Induces Vascular Remodeling in a VCID Model

Association of Carotid Artery Disease with Collateralization and Infarct Growth in Patients with Acute Middle Cerebral Artery Occlusion

BACKGROUND AND PURPOSE

Collaterals are important in large vessel occlusions (LVO), but the role of carotid artery disease (CAD) in this context remains unclear. This study aimed to investigate the impact of CAD on intracranial collateralization and infarct growth after thrombectomy in LVO.

MATERIALS AND METHODS

All patients who underwent thrombectomy due to M1 segment occlusion from 01/2015 to 12/2021 were retrospectively included. Internal carotid artery stenosis according to NASCET was assessed on the affected and nonaffected sides. Collaterals were assessed according to the Tan score. Infarct growth was quantified by comparing ASPECTS on follow-up imaging with baseline ASPECTS.

RESULTS

In total, 709 patients were included, 118 (16.6%) of whom presented with CAD (defined as severe stenosis ≥70% or occlusion ipsilaterally), with 42 cases (5.9%) being contralateral. Good collateralization (Tan 3) was present in 56.5% of the patients with ipsilateral CAD and 69.1% of the patients with contralateral CAD. The ipsilateral stenosis grade was an independent predictor of good collateral supply (adjusted OR: 1.01; NASCET point, 95% CI: 1.00-1.01; P = .009), whereas the contralateral stenosis grade was not (P = .34). Patients with ipsilateral stenosis of ≥70% showed less infarct growth (median ASPECTS decay: 1; IQR: 0-2) compared with patients with 0%-69% stenosis (median: 2; IQR: 1-3) (P = .005). However, baseline ASPECTS was significantly lower in patients with stenosis of 70%-100% (P < .001). The results of a multivariate analysis revealed that increasing ipsilateral stenosis grade (adjusted OR: 1.0; 95% CI: 0.99-1.00; P = .004) and good collateralization (adjusted OR: 0.5; 95% CI: 0.4-0.62; P < .001) were associated with less infarct growth.

CONCLUSIONS

CAD of the ipsilateral ICA is an independent predictor of good collateral supply. Patients with CAD tend to have larger baseline infarct size but less infarct growth.

Remote Ischemic Conditioning With Medical Management or Reperfusion Therapy for Acute Ischemic Stroke: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

Remote ischemic conditioning (RIC) is a low-cost, accessible, and noninvasive neuroprotective treatment strategy, but its efficacy and safety in acute ischemic stroke are controversial. With the publication of several randomized controlled trials (RCTs) and the recent results of the RESIST trial, it may be possible to identify the patient population that may (or may not) benefit from RIC. This systematic review and meta-analysis aims to evaluate the effectiveness and safety of RIC in patients with ischemic stroke receiving different treatments by pooling data of all randomized controlled studies to date.

METHODS

We searched the PubMed, Embase, Cochrane, Elsevier, and Web of Science databases to obtain articles in all languages from inception until May 25, 2023. The primary outcome was the modified Rankin Scale (mRS) score at the specified endpoint time in the trial. The secondary outcomes were change in NIH Stroke Scale (NIHSS) and recurrence of stroke events. The safety outcomes were cardiovascular events, cerebral hemorrhage, and mortality. The quality of articles was evaluated through the Cochrane risk assessment tool. This study was registered in PROSPERO (CRD42023430073).

RESULTS

There were 7,657 patients from 22 RCTs included. Compared with the control group, patients who received RIC did not have improved mRS functional outcomes, regardless of whether they received medical management, reperfusion therapy with intravenous thrombolysis (IVT), or mechanical thrombectomy (MT). In the medical management group, patients who received RIC had decreased incidence of stroke recurrence (risk ratio 0.63, 95% CI 0.43-0.92, p = 0.02) and lower follow-up NIHSS score by 1.72 points compared with the control group (p < 0.00001). There was no increased risk of adverse events including death or cerebral hemorrhage in the IVT or medical management group.

DISCUSSION

In patients with ischemic stroke who are not eligible for reperfusion therapy, RIC did not affect mRS functional outcomes but significantly improved the NIHSS score at the follow-up endpoint and reduced stroke recurrence, without increasing the risk of cerebral hemorrhage or death. In patients who received IVT or MT, the benefit of RIC was not observed.

Duration of Remote Ischemic Conditioning and Outcome in Acute Ischemic Stroke

BACKGROUND

Remote ischemic conditioning has been found to be effective in improving functional outcomes in acute ischemic stroke. We conducted a post hoc analysis of the RICAMIS (Remote Ischemic Conditioning for Acute Moderate Ischemic Stroke) trial to determine whether long-term remote ischemic conditioning duration after stroke onset is associated with better clinical outcomes in ischemic stroke.

METHODS AND RESULTS

Patients from the full analysis set were included in this secondary analysis. The primary outcome was the proportion of patients with an excellent functional outcome at 90 days, defined as a modified Rankin Scale score of 0 to 1. Among the 1776 patients, there were 55 patients in the 1 to 7 days remote ischemic conditioning group, 345 in the 8 to 10 days group, 412 in the 11 to 13 days group, 51 in the 14 to 16 days group, and 913 in the control group. Compared with the control group, a significantly higher proportion of excellent functional outcomes at 90 days was found in the 11 to 13 days remote ischemic conditioning group (adjusted absolute difference, 9.1% [95% CI, 3.7%-14.5%]; P =0.001), which was attenuated in the other groups (adjusted absolute difference in the 8-10 days group, 2.0% [95% CI, -4.0% to 8.0%]; P=0.51; adjusted absolute difference in the 14-16 days group, 7.4% [95% CI, -5.8% to 20.5%]; P=0.27), but compared to the control group, there was lower proportion of excellent functional outcomes in the 1 to 7 days group (adjusted absolute difference, -14.4% [95% CI, -27.8% to 0.0%]; P=0.05).

CONCLUSIONS

Among patients with acute moderate ischemic stroke, a higher likelihood of excellent clinical outcome was found in patients with longer duration of remote ischemic conditioning.

Exercise Improves Cerebral Blood Flow and Functional Outcomes in an Experimental Mouse Model of Vascular Cognitive Impairment and Dementia (VCID)

Vascular cognitive impairment and dementia (VCID) are a growing threat to public health without any known treatment. The bilateral common carotid artery stenosis (BCAS) mouse model is valid for VCID. Previously, we have reported that remote ischemic postconditioning (RIPostC) during chronic cerebral hypoperfusion (CCH) induced by BCAS increases cerebral blood flow (CBF), improves cognitive function, and reduces white matter damage. We hypothesized that physical exercise (EXR) would augment CBF during CCH and prevent cognitive impairment in the BCAS model. BCAS was performed in C57/B6 mice of both sexes to establish CCH. One week after the BCAS surgery, mice were randomized to treadmill exercise once daily or no EXR for four weeks. CBF was monitored with an LSCI pre-, post, and 4 weeks post-BCAS. Cognitive testing was performed for post-BCAS after exercise training, and brain tissue was harvested for histopathology and biochemical test. BCAS led to chronic hypoperfusion resulting in impaired cognitive function and other functional outcomes. Histological examination revealed that BCAS caused changes in neuronal morphology and cell death in the cortex and hippocampus. Immunoblotting showed that BCAS was associated with a significant downregulate of AMPK and pAMPK and NOS3 and pNOS3. BCAS also decreased red blood cell (RBC) deformability. EXR therapy increased and sustained improved CBF and cognitive function, muscular strength, reduced cell death, and loss of white matter. EXR is effective in the BCAS model, improving CBF and cognitive function, reducing white matter damage, improving RBC deformability, and increasing RBC NOS3 and AMPK. The mechanisms by which EXR improves CBF and attenuates tissue damage need further investigation.

Imaging of Angiogenesis in White Matter Hyperintensities

Background White matter hyperintensities (WMHs) are areas of increased signal intensity on T2-weighted magnetic resonance imaging (MRI). WMH penumbra may be a potential target for early intervention in WMHs. We explored the relationship between angiogenesis and WMH penumbra in patients with WMHs. Methods and Results Twenty-one patients with confluent WMHs of Fazekas grade ≥2 were included. All the participants underwent 68Ga-NOTA-PRGD2 positron emission tomography/magnetic resonance imaging. WMH penumbra was analyzed with masks created for the WMH and 7 normal-appearing white matter layers; each layer was dilated away from the WMH by 2 mm. Angiogenesis array and ELISA were used to detect the serum levels of angiogenic factors, inflammatory factors, HIF-1 alpha, and S100B. Fourteen patients with increased 68Ga-NOTA-PRGD2 maximum standardized uptake (>0.17) were classified into group 2. Seven patients with maximum standardized uptake ≤0.17 were classified as group 1. WMH volume and serum levels of integrin αvβ3, vascular endothelial growth factor receptor 22, and interleukin-1β tended to be higher in group 2 than in group 1. In group 2, 68Ga-NOTA-PRGD2 uptake was significantly increased at the border between the WMH and normal-appearing white matter than in WMHs (P=0.004). The structure penumbra, defined by fractional anisotropy, was wider in group 2 (8 mm) than in group 1 (2 mm). The cerebral blood flow penumbra was 12 mm in both groups. Angiogenesis showed a correlation with reduced cerebral blood flow and microstructure integrity. Conclusions Our study provides evidence that angiogenesis occurs in the WMH penumbra. Further studies are warranted to verify the effect of angiogenesis on WMH growth.

A brief overview of a mouse model of cerebral hypoperfusion by bilateral carotid artery stenosis

Vascular cognitive impairment (VCI) refers to all forms of cognitive disorder related to cerebrovascular diseases, including vascular mild cognitive impairment, post-stroke dementia, multi-infarct dementia, subcortical ischemic vascular dementia (SIVD), and mixed dementia. Among the causes of VCI, more attention has been paid to SIVD because the causative cerebral small vessel pathologies are frequently observed in elderly people and because the gradual progression of cognitive decline often mimics Alzheimer's disease. In most cases, small vessel diseases are accompanied by cerebral hypoperfusion. In mice, prolonged cerebral hypoperfusion is induced by bilateral carotid artery stenosis (BCAS) with surgically implanted metal micro-coils. This cerebral hypoperfusion BCAS model was proposed as a SIVD mouse model in 2004, and the spreading use of this mouse SIVD model has provided novel data regarding cognitive dysfunction and histological/genetic changes by cerebral hypoperfusion. Oxidative stress, microvascular injury, excitotoxicity, blood-brain barrier dysfunction, and secondary inflammation may be the main mechanisms of brain damage due to prolonged cerebral hypoperfusion, and some potential therapeutic targets for SIVD have been proposed by using transgenic mice or clinically used drugs in BCAS studies. This review article overviews findings from the studies that used this hypoperfused-SIVD mouse model, which were published between 2004 and 2021.

Compound from Magnolia officinalis Ameliorates White Matter Injury by Promoting Oligodendrocyte Maturation in Chronic Cerebral Ischemia Models

Chronic cerebral hypoperfusion leads to white matter injury (WMI), which subsequently causes neurodegeneration and even cognitive impairment. However, due to the lack of treatment specifically for WMI, novel recognized and effective therapeutic strategies are urgently needed. In this study, we found that honokiol and magnolol, two compounds derived from Magnolia officinalis, significantly facilitated the differentiation of primary oligodendrocyte precursor cells (OPCs) into mature oligodendrocytes, with a more prominent effect of the former compound. Moreover, our results demonstrated that honokiol treatment improved myelin injury, induced mature oligodendrocyte protein expression, attenuated cognitive decline, promoted oligodendrocyte regeneration, and inhibited astrocytic activation in the bilateral carotid artery stenosis model. Mechanistically, honokiol increased the phosphorylation of serine/threonine kinase (Akt) and mammalian target of rapamycin (mTOR) by activating cannabinoid receptor 1 during OPC differentiation. Collectively, our study indicates that honokiol might serve as a potential treatment for WMI in chronic cerebral ischemia.

Time from Onset to Remote Ischemic Conditioning and Clinical Outcome After Acute Moderate Ischemic Stroke

OBJECTIVE

We conducted a post hoc exploratory analysis of Remote Ischemic Conditioning for Acute Moderate Ischemic Stroke (RICAMIS) to determine whether early remote ischemic conditioning (RIC) initiation after stroke onset was associated with clinical outcome in patients with acute moderate ischemic stroke.

METHODS

In RICAMIS, patients receiving RIC treatment in the intention-to-treat analysis were divided into 2 groups based on onset-to-treatment time (OTT): early RIC group (OTT ≤ 24 hours) and late RIC group (OTT 24-48 hours). Patients receiving usual care without RIC treatment from intention-to-treat analysis were assigned as the control group. The primary outcome was excellent functional outcome at 90 days.

RESULTS

Among 1,776 patients from intention-to-treat analysis, 387 were in the early RIC group, 476 in the late RIC group, and 913 in the control group. In the post hoc exploratory analysis, a higher proportion of excellent functional outcome was found in the early RIC versus control group (adjusted absolute difference = 8.1%, 95% confidence interval [CI] = 2.5%-13.8%, p = 0.005), but no difference in outcomes was detected in the late RIC versus control group (adjusted absolute difference = 3.3%, 95% CI = -2.1% to 8.6%, p = 0.23), or in the early RIC versus late RIC group (adjusted absolute difference = 5.0%, 95% CI = -1.3% to 11.2%, p = 0.12). Similar results were found in the per-protocol analysis.

INTERPRETATION

Among patients with acute moderate ischemic stroke who are not candidates for intravenous thrombolysis or endovascular therapy, early RIC initiation within 24 hours of onset may be associated with higher likelihood of excellent clinical outcome. ANN NEUROL 2023;94:561-571.

Chronic remote ischemic conditioning treatment in patients with chronic stable angina (EARLY-MYO-CSA): a randomized, controlled proof-of-concept trial

BACKGROUND

Chronic remote ischemic conditioning (CRIC) has been shown to improve myocardial ischemia in experimental animal studies; however, its effectiveness in patients with chronic stable angina (CSA) has not been investigated. We conducted a proof-of-concept study to investigate the efficacy and safety of a six-month CRIC treatment in patients with CSA.

METHODS

The EARLY-MYO-CSA trial was a prospective, randomized, controlled trial evaluating the CRIC treatment in patients with CSA with persistent angina pectoris despite receiving ≥ 3-month guideline-recommended optimal medical therapy. The CRIC and control groups received CRIC (at 200 mmHg) or sham CRIC (at 60 mmHg) intervention for 6 months, respectively. The primary endpoint was the 6-month change of myocardial flow reserve (MFR) on single-photon emission computed tomography. The secondary endpoints were changes in rest and stress myocardial blood flow (MBF), angina severity according to the Canadian Cardiovascular Society (CCS) classification, the Seattle Angina Questionnaire (SAQ), and a 6-min walk test (6-MWT).

RESULTS

Among 220 randomized CSA patients, 208 (105 in the CRIC group, and 103 in the control group) completed the treatment and endpoint assessments. The mean change in MFR was significantly greater in the CRIC group than in the control group (0.27 ± 0.38 vs. - 0.04 ± 0.25; P < 0.001). MFR increased from 1.33 ± 0.48 at baseline to 1.61 ± 0.53 (P < 0.001) in the CRIC group; however, a similar increase was not seen in the control group (1.35 ± 0.45 at baseline and 1.31 ± 0.44 at follow-up, P = 0.757). CRIC treatment, when compared with controls, demonstrated improvements in angina symptoms assessed by CCS classification (60.0% vs. 14.6%, P < 0.001), all SAQ dimensions scores (P < 0.001), and 6-MWT distances (440 [400-523] vs. 420 [330-475] m, P = 0.016). The incidence of major adverse cardiovascular events was similar between the groups.

CONCLUSIONS

CSA patients benefit from 6-month CRIC treatment with improvements in MFR, angina symptoms, and exercise performance. This treatment is well-tolerated and can be recommended for symptom relief in this clinical population.

TRIAL REGISTRATION

[chictr.org.cn], identifier [ChiCTR2000038649].

Assessment of remote ischemic conditioning delivery with optical sensor in acute ischemic stroke: Randomised clinical trial protocol

BACKGROUND

Remote ischemic conditioning (RIC) is delivered by a blood pressure cuff over the limb, raising pressure 50 mmHg above the systolic blood pressure, to a maximum of 200 mmHg. The cuff is inflated for five minutes and then deflated for five minutes in a sequential ischemia-reperfusion cycle 4-5 times per session. Elevated pressure in the limb may be associated with discomfort and consequently reduced compliance. Continuous assessment of relative blood concentration and oxygenation with a tissue reflectance spectroscopy (a type of optical sensor device) placed over the forearm during the RIC sessions of the arm will allow us to observe the effect of inflation and deflation of the pressure cuff. We hypothesize, in patients with acute ischemic stroke (AIS) and small vessel disease, RIC delivered together with a tissue reflectance sensor will be feasible.

METHODS

The study is a prospective, single-center, randomized control trial testing the feasibility of the device. Patients with AIS within 7 days from symptoms onset; who also have small vessel disease will be randomized 2:1 to intervention or sham control arms. All patients randomized to the intervention arm will receive 5 cycles of ischemia/reperfusion in the non-paralyzed upper limb with a tissue reflectance sensor and patients in the sham control arm will receive pressure by keeping the cuff pressure at 30 mmHg for 5 minutes. A total of 51 patients will be randomized, 17 in the sham control arm and 34 in the intervention arm. The primary outcome measure will be the feasibility of RIC delivered for 7 days or at the time of discharge. The secondary device-related outcome measures are fidelity of RIC delivery and the completion rate of intervention. The secondary clinical outcome includes a modified Rankin scale, recurrent stroke and cognitive assessment at 90 days.

DISCUSSION

RIC delivery together with a tissue reflectance sensor will allow insight into the blood concentration and blood oxygenation changes in the skin. This will allow individualized delivery of the RIC and improve compliance.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05408130, June 7, 2022.

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.

Magnetic resonance imaging reveals microemboli-mediated pathological changes in brain microstructure in diabetic rats: relevance to vascular cognitive impairment/dementia

Diabetes doubles the risk of vascular cognitive impairment, but the underlying reasons remain unclear. In the present study, we determined the temporal and spatial changes in the brain structure after microemboli (ME) injection using diffusion MRI (dMRI). Control and diabetic rats received cholesterol crystal ME (40-70 µm) injections. Cognitive tests were followed up to 16 weeks, while dMRI scans were performed at baseline and 12 weeks post-ME. The novel object recognition test had a lower d2 recognition index along with a decrease in spontaneous alternations in the Y maze test in diabetic rats with ME. dMRI showed that ME injection caused infarction in two diabetic animals (n=5) but none in controls (n=6). In diabetes, radial diffusivity (DR) was increased while fractional anisotropy (FA) was decreased in the cortex, indicating loss of tissue integrity and edema. In the dorsal hippocampus, mean diffusivity (MD), axial diffusivity (DA), and DR were significantly increased, indicating loss of axons and myelin damage. Histological analyses confirmed more tissue damage and microglial activation in diabetic rats with ME. These results suggest that ME injury and associated cerebrovascular dysfunction are greater in diabetes, which may cause cognitive deficits. Strategies to improve vascular function can be a preventive and therapeutic approach for vascular cognitive impairment.

Vascular endothelium deploys caveolin-1 to regulate oligodendrogenesis after chronic cerebral ischemia in mice

Oligovascular coupling contributes to white matter vascular homeostasis. However, little is known about the effects of oligovascular interaction on oligodendrocyte precursor cell (OPC) changes in chronic cerebral ischemia. Here, using a mouse of bilateral carotid artery stenosis, we show a gradual accumulation of OPCs on vasculature with impaired oligodendrogenesis. Mechanistically, chronic ischemia induces a substantial loss of endothelial caveolin-1 (Cav-1), leading to vascular secretion of heat shock protein 90α (HSP90α). Endothelial-specific over-expression of Cav-1 or genetic knockdown of vascular HSP90α restores normal vascular-OPC interaction, promotes oligodendrogenesis and attenuates ischemic myelin damage. miR-3074(-1)-3p is identified as a direct inducer of Cav-1 reduction in mice and humans. Endothelial uptake of nanoparticle-antagomir improves myelin damage and cognitive deficits dependent on Cav-1. In summary, our findings demonstrate that vascular abnormality may compromise oligodendrogenesis and myelin regeneration through endothelial Cav-1, which may provide an intercellular mechanism in ischemic demyelination.

Pharmacological Inhibition of Class III Alcohol Dehydrogenase 5: Turning Remote Ischemic Conditioning Effective in a Diabetic Stroke Model

The restoration of cerebral blood flow (CBF) to achieve brain tissue oxygenation (PbtO₂) is the primary treatment for ischemic stroke, a significant cause of adult mortality and disability worldwide. Nitric oxide (NO) and its bioactive s-nitrosylated (SNO) reservoirs, such as s-nitrosoglutathione (GSNO), induce hypoxic vasodilation to enhance CBF during ischemia. The endogenous pool of SNOs/GSNO is enhanced via the activation of endothelial NO synthase (eNOS/NOS3) and by the suppression of class III alcohol dehydrogenase 5 (ADH5), also known as GSNO reductase (GSNOR). Remote ischemic conditioning (RIC), which augments NOS3 activity and SNO, is an emerging therapy in acute stroke. However, RIC has so far shown neutral effects in stroke clinical trials. As the majority of stroke patients are presented with endothelial dysfunctions and comorbidities, we tested the hypothesis that NOS3 dysfunction and diabetes will abolish the protective effects of RIC therapy in stroke, and the prior inhibition of GSNOR will turn RIC protective. Our data demonstrate that RIC during thrombotic stroke failed to enhance the CBF and the benefits of thrombolysis in NOS3 mutant (NOS3^+/−) mice, a genetic model of NOS3 dysfunction. Interestingly, thrombotic stroke in diabetic mice enhanced the activity of GSNOR as early as 3 h post-stroke without decreasing the plasma nitrite (NO₂⁻). In thrombotic stroke, neither a pharmacological inhibitor of GSNOR (GRI) nor RIC therapy alone was protective in diabetic mice. However, prior treatment with GRI followed by RIC enhanced the CBF and improved recovery. In a reperfused stroke model, the GRI–RIC combination therapy in diabetic mice augmented PbtO₂, a translatory signature of successful microvascular reflow. In addition, RIC therapy unexpectedly increased the inflammatory markers at 6 h post-stroke in diabetic stroke that were downregulated in combination with GRI while improving the outcomes. Thus, we conclude that preexisting NOS3 dysfunctions due to comorbidities may neutralize the benefits of RIC in stroke, which can be turned protective in combination with GRI. Our findings may support the future clinical trial of RIC in comorbid stroke. Further studies are warranted to test and develop SNO reservoirs as the blood-associated biomarker to monitor the response and efficacy of RIC therapy in stroke.

Effects of remote ischemic conditioning on cognitive performance: A systematic review

The aging process leads to subtle decline in cognitive function, and in some overt dementia. Like physical activity Remote Ischemic Conditioning (RIC) may ameliorate these changes on cognitive impairment in humans. The purpose of this study was to compared the effects of single, repeated short-term and long-term treatment RIC, and analyze its effect registered as immediate vs. long-term on cognitive performance in humans. This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and was registered with PROSPERO, number (CRD42021285668). A systematic review was conducted to identify relevant studies through six healthcare science databases (Cochrane, PubMed, EMBASE, EBSCO, Scopus, and Web of Science) up to December 2021. Eligibility criteria included (1) a study sample of participants aged ≥18 years, (2) post-intervention changes on cognitive performance in humans, and (3) this systematic review included only randomized controlled trials of RIC in humans. The quality of the included studies was assessed by GRADEpro tool. A total of 118 articles were initially identified, 35 of which met the inclusion criteria. Based on title/abstract, age and RIC protocol, 14 articles were included in this review: 5 studies investigated the immediate and long-term effect of a single RIC (n = 370 patients), 4 studies examined intermittent short-term RIC (n = 174 patients) and 5 studies evaluated repeated long-term RIC (n = 228 patients). A single pre-operative RIC treatment had an immediate effect that disappeared at one week. Short-term RIC showed either a positive or no effects on cognitive function. The majority of studies examining long-term RIC treatment showed improvements in cognitive performance, particularly in very old adults and older patients with cognitive impairments. Single RIC treatment did not show any persisting effect on cognition. However, repeated short term RIC showed some improvement and long-term RIC may improve cognitive performance after stroke or enhance neuropsychological tests in patients diagnosed with vascular dementia. The mixed results might be explained by different RIC treatment protocols and populations investigated.

Epigenetic conditioning induces intergenerational resilience to dementia in a mouse model of vascular cognitive impairment

INTRODUCTION

Epigenetic stimuli induce beneficial or detrimental changes in gene expression, and consequently, phenotype. Some of these phenotypes can manifest across the lifespan-and even in subsequent generations. Here, we used a mouse model of vascular cognitive impairment and dementia (VCID) to determine whether epigenetically induced resilience to specific dementia-related phenotypes is heritable by first-generation progeny.

METHODS

Our systemic epigenetic therapy consisted of 2 months of repetitive hypoxic "conditioning" (RHC) prior to chronic cerebral hypoperfusion in adult C57BL/6J mice. Resultant changes in object recognition memory and hippocampal long-term potentiation (LTP) were assessed 3 and 4 months later, respectively.

RESULTS

Hypoperfusion-induced memory/plasticity deficits were abrogated by RHC. Moreover, similarly robust dementia resilience was documented in untreated cerebral hypoperfused animals derived from RHC-treated parents.

CONCLUSIONS

Our results in experimental VCID underscore the efficacy of epigenetics-based treatments to prevent memory loss, and demonstrate for the first time the heritability of an induced resilience to dementia.

Complement C3a Receptor (C3aR) Mediates Vascular Dysfunction, Hippocampal Pathology, and Cognitive Impairment in a Mouse Model of VCID

Vascular contributions to cognitive impairment and dementia (VCID) secondary to chronic mild-moderate cerebral ischemia underlie a significant percentage of cases of dementia. We previously reported that either genetic deficiency of the complement C3a receptor (C3aR) or its pharmacological inhibition protects against cerebral ischemia in rodents, while others have implicated C3aR in the pathogenesis seen in rodent transgenic models of Alzheimer's disease. In the present study, we evaluated the role of complement C3a-C3aR signaling in the onset and progression of VCID. We utilized the bilateral common carotid artery stenosis (BCAS) model to induce VCID in male C57BL/6 wild-type and C3aR-knockout (C3aR-/-) mice. Cerebral blood flow (CBF) changes, hippocampal atrophy (HA), white matter degeneration (WMD), and ventricular size were assessed at 4 months post-BCAS using laser speckle contrast analysis (LSCI) and magnetic resonance imaging (MRI). Cognitive function was evaluated using the Morris water maze (MWM), and novel object recognition (NOR), immunostaining, and western blot were performed to assess the effect of genetic C3aR deletion on post-VCID outcomes. BCAS resulted in decreased CBF and increased HA, WMD, and neurovascular inflammation in WT (C57BL/6) compared to C3aR-/- (C3aR-KO) mice. Moreover, C3aR-/- mice exhibited improved cognitive function on NOR and MWM relative to WT controls. We conclude that over-activation of the C3a/C3aR axis exacerbates neurovascular inflammation leading to poor VCID outcomes which are mitigated by C3aR deletion. Future studies are warranted to dissect the role of cell-specific C3aR in VCID.

Effect of Remote Ischemic Conditioning vs Usual Care on Neurologic Function in Patients With Acute Moderate Ischemic Stroke: The RICAMIS Randomized Clinical Trial

IMPORTANCE

Preclinical and clinical studies have suggested a neuroprotective effect of remote ischemic conditioning (RIC), which involves repeated occlusion/release cycles on bilateral upper limb arteries; however, robust evidence in patients with ischemic stroke is lacking.

OBJECTIVE

To assess the efficacy of RIC for acute moderate ischemic stroke.

DESIGN, SETTING, AND PARTICIPANTS

This multicenter, open-label, blinded-end point, randomized clinical trial including 1893 patients with acute moderate ischemic stroke was conducted at 55 hospitals in China from December 26, 2018, through January 19, 2021, and the date of final follow-up was April 19, 2021.

INTERVENTIONS

Eligible patients were randomly assigned within 48 hours after symptom onset to receive treatment with RIC (using a pneumatic electronic device and consisting of 5 cycles of cuff inflation for 5 minutes and deflation for 5 minutes to the bilateral upper limbs to 200 mm Hg) for 10 to 14 days as an adjunct to guideline-based treatment (n = 922) or guideline-based treatment alone (n = 971).

MAIN OUTCOMES AND MEASURES

The primary end point was excellent functional outcome at 90 days, defined as a modified Rankin Scale score of 0 to 1. All end points had blinded assessment and were analyzed on a full analysis set.

RESULTS

Among 1893 eligible patients with acute moderate ischemic stroke who were randomized (mean [SD] age, 65 [10.3] years; 606 women [34.1%]), 1776 (93.8%) completed the trial. The number with excellent functional outcome at 90 days was 582 (67.4%) in the RIC group and 566 (62.0%) in the control group (risk difference, 5.4% [95% CI, 1.0%-9.9%]; odds ratio, 1.27 [95% CI, 1.05-1.54]; P = .02). The proportion of patients with any adverse events was 6.8% (59/863) in the RIC group and 5.6% (51/913) in the control group.

CONCLUSIONS AND RELEVANCE

Among adults with acute moderate ischemic stroke, treatment with remote ischemic conditioning compared with usual care significantly increased the likelihood of excellent neurologic function at 90 days. However, these findings require replication in another trial before concluding efficacy for this intervention.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03740971.

Quantitative Collateral Assessment on CTP in the Prediction of Stroke Etiology

BACKGROUND AND PURPOSE

Patients with stroke etiology of large-artery atherosclerosis were thought to have better collateral circulation compared with patients with other stroke etiologies. We aimed to investigate the association between stroke etiology and collateral circulation with a new quantitative collateral assessment method.

MATERIALS AND METHODS

This retrospective study reviewed data from consecutive patients with proximal anterior artery occlusion who underwent CTP before reperfusion therapy. CBF maps were derived from CTP. A new indicator, maximum CBF of collateral vessels within the Sylvian fissure (cCBF_max), was applied to quantitatively assess the collateral status. The relationship between collateral status and stroke etiology was investigated.

RESULTS

A total of 296 patients were finally analyzed. The median cCBF_max was significantly higher in patients with large-artery atherosclerosis than in those without it (92 [interquartile range, 65-123] mL/100 g/min versus 62 [interquartile range, 46-82] mL/100 g/min; P < .001). Multivariable analysis revealed that a higher cCBF_max score was independently associated with large-artery atherosclerosis etiology (OR, 1.010; 95% CI, 1.002-1.018; P = .017) after adjustment. The area under the curve, sensitivity, and specificity of the final model in predicting the etiology of large-artery atherosclerosis were 0.870, 89.7%, and 75.2%, respectively.

CONCLUSIONS

Patients with large-artery atherosclerosis had a more adequate collateral perfusion supply with the new quantitative collateral assessment. The new quantitative collateral measurement might contribute to the prediction of stroke etiology in the acute clinical scenario for patients with acute ischemic stroke.

Daily Remote Ischemic Conditioning Can Improve Cerebral Perfusion and Slow Arterial Progression of Adult Moyamoya Disease—A Randomized Controlled Study

Background and Purpose

Moyamoya disease (MMD) is a complicated cerebrovascular disease with recurrent ischemic or hemorrhagic events. This study aimed to prove the safety and efficacy of remote ischemic conditioning (RIC) on MMD.

Methods

In total, 34 patients with MMD participated in this pilot, prospective randomized controlled study for 1 year. 18 patients were allocated into the RIC group, and 16 patients accepted routine medical treatment only. RIC-related adverse events were recorded. The primary outcome was the improvement ratio of mean cerebral blood flow (mCBF) in middle cerebral artery territory measured by multidelay pseudocontinuous arterial spin labeling, and the secondary outcomes were the cumulative incidence of major adverse cerebrovascular events (MACEs), the prevalence of stenotic-occlusive progression, and periventricular anastomosis at 1-year follow-up.

Results

In total, 30 of the 34 patients with MMD completed the final follow-up (17 in the RIC group and 13 in the control group). No adverse events of RIC were observed. The mCBF improvement ratio of the RIC group was distinctively higher compared with the control group (mCBF−whole-brain: 0.16 ± 0.15 vs. −0.03 ± 0.13, p = 0.001). Stenotic-occlusive progression occurred in 11.8% hemispheres in the RIC group and 38.5% in the control group (p = 0.021). The incidence of MACE was 5.9% in the RIC group and 30.8% in the control group (hazard ratio with RIC, 0.174; 95% CI, 0.019–1.557; p = 0.118). No statistical difference was documented in the periventricular anastomosis between the two groups after treatment.

Conclusions

Remote ischemic conditioning has the potential to be a safe and effective adjunctive therapy for patients with MMD largely due to improving cerebral blood flow and slowing the arterial progression of the stenotic-occlusive lesions. These findings warrant future studies in larger trials.

Stimulation of angiotensin II receptor 2 preserves cognitive function and is associated with an enhanced cerebral vascular density after stroke

Angiotensin signaling is known to be sexually dimorphic. Although it is a well-studied target for intervention in stroke and cognitive impairment, female studies are rare. With females suffering a disproportionately greater negative impact of stroke and dementia vs. males, effective interventions are of utmost urgency. The aim of the current study was to determine the impact of activation of the angiotensin II type 2 receptor (AT2R) with the agonist compound 21 (C21) on the development of post-stroke cognitive impairment, after experimental ischemic stroke. Ovariectomized (OVX) spontaneously hypertensive rats (SHRs) were subjected to 1 h of middle cerebral artery occlusion (MCAO). At 24 h, rats with a significant neurologic deficit were randomized to receive either saline or C21 (0.03 mg/kg/day) intraperitoneally (IP) for 5 days, then orally (0.12 mg/kg/day) for a total of 6 weeks. Cognitive function, brain structure by MRI and vascular architecture by microCT angiography were measured. C21 preserved cognitive function, specifically spatial memory, and improved vascular density in the ischemic hemisphere at 6 weeks, reflecting both arteriogenesis and angiogenesis. In conclusion, C21 prevented cognitive impairment after stroke, likely through a mechanism involving vascular protection and restoration.

Nebulization of Low-Dose S-Nitrosoglutathione in Diabetic Stroke Enhances Benefits of Reperfusion and Prevents Post-Thrombolysis Hemorrhage

The COVID-19 pandemic has escalated the occurrence of hypoxia including thrombotic stroke worldwide, for which nitric oxide (NO) therapy seems very promising and translatable. Therefore, various modes/routes of NO-delivery are now being tested in different clinical trials for safer, faster, and more effective interventions against ischemic insults. Intravenous (IV) infusion of S-Nitrosoglutathione (GSNO), the major endogenous molecular pool of NO, has been reported to protect against mechanical cerebral ischemia-reperfusion (IR); however, it has been never tested in any kind of “clinically” relevant thromboembolic stroke models with or without comorbidities and in combination with the thrombolytic reperfusion therapy. Moreover, “IV-effects” of higher dose of GSNO following IR-injury have been contradicted to augment stroke injury. Herein, we tested the hypothesis that nebulization of low-dose GSNO will not alter blood pressure (BP) and will mitigate stroke injury in diabetic mice via enhanced cerebral blood flow (CBF) and brain tissue oxygenation (PbtO2). GSNO-nebulization (200 μg/kgbwt) did not alter BP, but augmented the restoration of CBF, improved behavioral outcomes and reduced stroke injury. Moreover, GSNO-nebulization increased early reoxygenation of brain tissue/PbtO2 as measured at 6.5 h post-stroke following thrombolytic reperfusion, and enervated unwanted effects of late thrombolysis in diabetic stroke. We conclude that the GSNO-nebulization is safe and effective for enhancing collateral microvascular perfusion in the early hours following stroke. Hence, nebulized-GSNO therapy has the potential to be developed and translated into an affordable field therapy against ischemic events including strokes, particularly in developing countries with limited healthcare infrastructure.

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.

Three-dimensional visualisation of the feto-placental vasculature in humans and rodents

Adequate development of the feto-placental circulation is critical for placental exchange function and healthy fetal growth. Understanding the structure of this circulation and how it informs fetal outcomes is important both in the human placenta, and the rodent, a purported comparative experimental model. Vascular casting and micro-CT imaging approaches enable detailed quantification of the complex vascular relationships in the feto-circulation, and provide detailed data to parameterise in silico models. Here, to assist researchers to apply these technically challenging methods we provide detailed approaches to cast and image; 1) human placentas at the cotyledon-level, and 2) whole rodent placentas.

Therapeutic Potential of Remote Ischemic Conditioning in Vascular Cognitive Impairment

Vascular cognitive impairment (VCI) is a heterogeneous disease caused by a variety of cerebrovascular diseases. Patients with VCI often present with slower cognitive processing speed and poor executive function, which affects their independence in daily life, thus increasing social burden. Remote ischemic conditioning (RIC) is a non-invasive and efficient intervention that triggers endogenous protective mechanisms to generate neuroprotection. Over the past decades, evidence from basic and clinical research has shown that RIC is promising for the treatment of VCI. To further our understanding of RIC and improve the management of VCI, we summarize the evidence on the therapeutic potential of RIC in relation to the risk factors and pathobiologies of VCI, including reducing the risk of recurrent stroke, decreasing high blood pressure, improving cerebral blood flow, restoring white matter integrity, protecting the neurovascular unit, attenuating oxidative stress, and inhibiting the inflammatory response.

Elevated cerebral perfusion and preserved cognition in elite Brazilian Jiu-Jitsu athletes: Evidence for neuroprotection

Brazilian Jiu-Jitsu (BJJ) is a popular martial art that exposes participants to recurrent intermittent asphyxiation due to controlled application of neck chokes. To what extent the sport impacts the regulation of cerebral blood flow (CBF) and cognition has not been examined. This study compared eleven elite Brazilian Jiu-Jitsu athletes (aged 30 ± 8 y) who trained 12 ± 6 hours/week for 8 ± 4 years against eleven cardiorespiratory fitness (CRF)- and age-matched controls. Internal carotid (ICA) and vertebral artery (VA) blood flow were measured via duplex ultrasound to determine global cerebral blood flow (gCBF). Mild cognitive impairment and sub-domains of memory, attention/concentration/visual motor coordination, and executive function were determined by psychometric testing. There was no evidence of mild cognitive impairment in the athletes, and cognitive function was comparable between groups (all p > 0.05). In contrast, resting gCBF was selectively elevated in the athletes (741 ± 186 mL∙min^-1 vs. 573 ± 166 mL∙min^-1 , p = 0.037) due to combined differences in ICA (+65 mL∙min^-1 , p = 0.079) and VA (+19 mL∙min^-1 , p = 0.277) flow. In conclusion, the sustained elevation in resting cerebral perfusion provides preliminary evidence for adaptive neuroprotection that is independent of CRF and likely mediated by choke-induced cerebral preconditioning and/or lifelong exposure to BJJ-specific high-intensity interval training.

AIM2 inflammasome mediates hallmark neuropathological alterations and cognitive impairment in a mouse model of vascular dementia

Chronic cerebral hypoperfusion is associated with vascular dementia (VaD). Cerebral hypoperfusion may initiate complex molecular and cellular inflammatory pathways that contribute to long-term cognitive impairment and memory loss. Here we used a bilateral common carotid artery stenosis (BCAS) mouse model of VaD to investigate its effect on the innate immune response-particularly the inflammasome signaling pathway. Comprehensive analyses revealed that chronic cerebral hypoperfusion induces a complex temporal expression and activation of inflammasome components and their downstream products (IL-1β and IL-18) in different brain regions, and promotes activation of apoptotic and pyroptotic cell death pathways. Polarized glial-cell activation, white-matter lesion formation and hippocampal neuronal loss also occurred in a spatiotemporal manner. Moreover, in AIM2 knockout mice we observed attenuated inflammasome-mediated production of proinflammatory cytokines, apoptosis, and pyroptosis, as well as resistance to chronic microglial activation, myelin breakdown, hippocampal neuronal loss, and behavioral and cognitive deficits following BCAS. Hence, we have demonstrated that activation of the AIM2 inflammasome substantially contributes to the pathophysiology of chronic cerebral hypoperfusion-induced brain injury and may therefore represent a promising therapeutic target for attenuating cognitive impairment in VaD.

Limb Remote Ischemic Conditioning Ameliorates Cognitive Impairment in Rats with Chronic Cerebral Hypoperfusion by Regulating Glucose Transport

Cognitive impairment is closely associated with the slowing of glucose metabolism in the brain. Glucose transport, a rate-limiting step of glucose metabolism, plays a key role in this phenomenon. Previous studies have reported that limb remote ischemic conditioning (LRIC) improves cognitive performance in rats with chronic cerebral hypoperfusion (CCH). Here, we determined whether LRIC could ameliorate cognitive impairment in rats with CCH by regulating glucose transport. A total of 170 male Sprague-Dawley rats were used. Animals subjected to permanent double carotid artery occlusion (2VO) were assigned to the control or LRIC treatment group. LRIC was applied beginning 3 days after the 2VO surgery. We found that LRIC can improve learning and memory; decrease the ratio of ADP/ATP; increase glucose content; upregulate the expression of pAMPKα, GLUT1 and GLUT3; and increase the number of GLUT1 and GLUT3 transporters in cerebral cortical neurons. The expression of GLUT1 and GLUT3 in the cortex displayed a strong correlation with learning and memory. Pearson correlation analysis showed that the levels of GLUT1 and GLUT3 are correlated with neurological function scores. All of these beneficial effects of LRIC were ablated by application of the AMPK inhibitor, dorsomorphin. In summary, LRIC ameliorated cognitive impairment in rats with CCH by regulating glucose transport via the AMPK/GLUT signaling pathway. We conclude that AMPK-mediated glucose transport plays a key role in LRIC. These data also suggest that supplemental activation of glucose transport after CCH may provide a clinically applicable intervention for improving cognitive impairment.

Decreased parenchymal arteriolar tone uncouples vessel-to-neuronal communication in a mouse model of vascular cognitive impairment

Chronic hypoperfusion is a key contributor to cognitive decline and neurodegenerative conditions, but the cellular mechanisms remain ill-defined. Using a multidisciplinary approach, we sought to elucidate chronic hypoperfusion-evoked functional changes at the neurovascular unit. We used bilateral common carotid artery stenosis (BCAS), a well-established model of vascular cognitive impairment, combined with an ex vivo preparation that allows pressurization of parenchymal arterioles in a brain slice. Our results demonstrate that mild (~ 30%), chronic hypoperfusion significantly altered the functional integrity of the cortical neurovascular unit. Although pial cerebral perfusion recovered over time, parenchymal arterioles progressively lost tone, exhibiting significant reductions by day 28 post-surgery. We provide supportive evidence for reduced adenosine 1 receptor-mediated vasoconstriction as a potential mechanism in the adaptive response underlying the reduced baseline tone in parenchymal arterioles. In addition, we show that in response to the neuromodulator adenosine, the action potential frequency of cortical pyramidal neurons was significantly reduced in all groups. However, a significant decrease in adenosine-induced hyperpolarization was observed in BCAS 14 days. At the microvascular level, constriction-induced inhibition of pyramidal neurons was significantly compromised in BCAS mice. Collectively, these results suggest that BCAS uncouples vessel-to-neuron communication-vasculo-neuronal coupling-a potential early event in cognitive decline.

Deficiency of Endothelial Nitric Oxide Synthase (eNOS) Exacerbates Brain Damage and Cognitive Deficit in A Mouse Model of Vascular Dementia

Vascular Dementia (VaD) accounts for nearly 20% of all cases of dementia. eNOS plays an important role in neurovascular remodeling, anti-inflammation, and cognitive functional recovery after stroke. In this study, we investigated whether eNOS regulates brain damage, cognitive function in mouse model of bilateral common carotid artery stenosis (BCAS) induced VaD. Late-adult (6-8 months) C57BL/6J and eNOS knockout (eNOS-/-) mice were subjected to BCAS (n=12/group) or sham group (n=8/group). BCAS was performed by applying microcoils to both common carotid arteries. Cerebral blood flow (CBF) and blood pressure were measured. A battery of cognitive functional tests was performed, and mice were sacrificed 30 days after BCAS. Compared to corresponding sham mice, BCAS in wild-type (WT) and eNOS-/- mice significantly: 1) induces short term, long term memory loss, spatial learning and memory deficits; 2) decreases CBF, increases ischemic cell damage, including apoptosis, white matter (WM) and axonal damage; 3) increases blood brain barrier (BBB) leakage, decreases aquaporin-4 (AQP4) expression and vessel density; 4) increases microglial, astrocyte activation and oxidative stress in the brain; 5) increases inflammatory factor interleukin-1 receptor-associated kinase-1(IRAK-1) and amyloid beta (Aβ) expression in brain; 6) increases IL-6 and IRAK4 expression in brain. eNOS-/-sham mice exhibit increased blood pressure, decreased iNOS and nNOS in brain compared to WT-sham mice. Compared to WT-BCAS mice, eNOS-/-BCAS mice exhibit worse vascular and WM/axonal damage, increased BBB leakage and inflammatory response, increased cognitive deficit, decreased iNOS, nNOS in brain. eNOS deficit exacerbates BCAS induced brain damage and cognitive deficit.

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.

Pathological changes in neurovascular units: Lessons from cases of vascular dementia

Vascular dementia (VD) is the second leading cause of dementia after Alzheimer's disease (AD). The decrease of cerebral blood flow (CBF) to different degrees is one of the main causes of VD. Neurovascular unit (NVU) is a vessel‐centered concept, emphasizing all the cellular components play an integrated role in maintaining the normal physiological functions of the brain. More and more evidence shows that reduced CBF causes a series of changes in NVU, such as impaired neuronal function, abnormal activation of glial cells, and changes in vascular permeability, all of which collectively play a role in the pathogenesis of VD. In this paper, we review NVU changes as CBF decreases, focusing on each cellular component of NVU. We also highlight remote ischemic preconditioning as a promising approach for VD prevention and treatment from the NVU perspective of view.

Improving Collateral Circulation: A Potential Adjunctive Strategy to Prevent or Slow the Progression of Vascular Dementia

Vascular dementia (VaD), a cognitive disorder caused by cerebrovascular pathologies, is the most common cause of dementia in the elderly, being second only to Alzheimer's disease. Researches have shown that adequate cerebral blood flow (CBF) is the first condition for maintaining the structural integrity and normal function of the brain, and VaD is generally considered to be resulted from neuronal loss due to reduced CBF. Collateral circulation, a compensation mechanism for CBF, provides an alternative vascular pathway for blood to reach ischemic tissues, which has been confirmed to be associated with better clinical outcomes of ischemic diseases. At present, considerable effort has been devoted to enhancing the functional prognosis of acute ischemic stroke by improving collateral circulation. Since ischemic stroke is the primary contributor to VaD, it is necessary to explore whether improving collateral circulation is beneficial to prevent or slow the progression of VaD. This article reviews the compensatory characteristics of different levels of cerebral collateral circulation, addresses the relationship between collateral circulation and VaD, and highlights that improving collateral circulation may be a potential adjunctive strategy in preventing and slowing the progression of VaD.

Remote Ischemic Post-Conditioning Therapy is Protective in Mouse Model of Traumatic Optic Neuropathy

Traumatic optic neuropathy (TON) is characterized by visual dysfunction after indirect or direct injury to the optic nerve following blunt head trauma. TON is associated with increased oxidative stress and inflammation resulting in retinal ganglion cell (RGC) death. Remote ischemic post-conditioning (RIC) has been shown to enhance endogenous protective mechanisms in diverse disease models including stroke, vascular cognitive impairment (VCI), retinal injury and optic nerve injury. However, the protective mechanisms underlying the improvement of retinal function and RGC survival after RIC treatment remain unclear. Here, we hypothesized that RIC therapy may be protective following TON by preventing RGC death, oxidative insult and inflammation in the mouse retina. To carry out the study, mice were divided in three different groups (Control, TON and TON + RIC). We harvested retinal tissue 5 days after TON induction for western blotting and histochemical analysis. We observed increased TON-induced retinal cell death compared with controls by cleaved caspase-3 immunohistochemistry. Furthermore, the TON cohort demonstrated increased TUNEL positive cells which were significantly attenuated by RIC. Immunofluorescence data showed that oxidative stress markers dihydroethidium (DHE), NOX-2 and nitrotyrosine expression were elevated in the TON group relative to controls and RIC therapy significantly reduced the expression level of these markers. Next, we found that the proinflammatory cytokine TNF-α was increased and anti-inflammatory IL-10 was decreased in plasma of TON animals, and RIC therapy reversed this expression level. Interestingly, western blotting of retinal tissue showed that RGC marker Brn3a and tight junction proteins (ZO-1 and Occludin), and AMPKα1 expression were downregulated in the TON group compared to controls. However, RIC significantly increased the expression levels of these proteins. Together these data suggest that RIC therapy activates endogenous protective mechanisms which may attenuate TON-induced oxidative stress and inflammation, and improves BRB integrity.

Trial of remote ischaemic preconditioning in vascular cognitive impairment (TRIC-VCI): protocol

INTRODUCTION

Cerebral small vessel disease (cSVD) accounts for 20%-25% of strokes and is the most common cause of vascular cognitive impairment (VCI). In an animal VCI model, inducing brief periods of limb ischaemia-reperfusion reduces subsequent ischaemic brain injury with remote and local protective effects, with hindlimb remote ischaemic conditioning (RIC) improving cerebral blood flow, decreasing white-matter injury and improving cognition. Small human trials suggest RIC is safe and may prevent recurrent strokes. It remains unclear what doses of chronic daily RIC are tolerable and safe, whether effects persist after treatment cessation, and what parameters are optimal for treatment response.

METHODS AND ANALYSIS

This prospective, open-label, randomised controlled trial (RCT) with blinded end point assessment and run-in period, will recruit 24 participants, randomised to one of two RIC intensity groups: one arm treated once daily or one arm twice daily for 30 consecutive days. RIC will consistent of 4 cycles of blood pressure cuff inflation to 200 mm Hg for 5 min followed by 5 min deflation (total 35 min). Selection criteria include: age 60-85 years, evidence of cSVD on brain CT/MRI, Montreal Cognitive Assessment (MoCA) score 13-24 and preserved basic activities of living. Outcomes will be assessed at 30 days and 90 days (60 days after ceasing treatment). The primary outcome is adherence (completing ≥80% of sessions). Secondary safety/tolerability outcomes include the per cent of sessions completed and pain/discomfort scores from patient diaries. Efficacy outcomes include changes in cerebral blood flow (per arterial spin-label MRI), white-matter hyperintensity volume, diffusion tensor imaging, MoCA and Trail-Making tests.

ETHICS AND DISSEMINATION

Research Ethics Board approval has been obtained. The results will provide information on feasibility, dose, adherence, tolerability and outcome measures that will help design a phase IIb RCT of RIC, with the potential to prevent VCI. Results will be disseminated through peer-reviewed publications, organisations and meetings.

TRIAL REGISTRATION NUMBER

NCT04109963.

Diabetic rats are more susceptible to cognitive decline in a model of microemboli-mediated vascular contributions to cognitive impairment and dementia

Vascular disease plays an important role in all kinds of cognitive impairment and dementia. Diabetes increases the risk of vascular disease and dementia. However, it is not clear how existing vascular disease in the brain accelerates the development of small vessel disease and promotes cognitive dysfunction in diabetes. We used microemboli (ME) injection model in the current study to test the hypothesis that cerebrovascular dysfunction in diabetes facilitates entrapment of ME leading to inflammation and cognitive decline. We investigated cognitive function, axonal/white matter (WM) changes, neurovascular coupling, and microglial activation in control and diabetic male and female Wistar rats subjected to sham or low/high dose ME injection. Diabetic male animals had cognitive deficits, WM demyelination and greater microglial activation than the control animals even at baseline. Functional hyperemia gradually declined in diabetic male animals after ME injection. Both low and high ME injection worsened WM damage and increased microglial activation in diabetic male and female animals. Low ME did not cause cognitive decline in controls, while promoting learning/memory deficits in diabetic female rats and no further decline in diabetic male animals. High ME led to cognitive decline in control male rats and exacerbated the deficits in diabetic cohort. These results suggest that the existing cerebrovascular dysfunction in diabetes may facilitate ME-mediated demyelination leading to cognitive decline. It is important to integrate comorbidities/sex as a biological variable into experimental models for the development of preventive or therapeutic targets.

Hormesis: A potential strategic approach to the treatment of neurodegenerative disease

This review describes neuroprotective effects mediated by pre- and post-conditioning-induced processes that act via the quantitative features of the hormetic dose response. These lead to the development of acquired resilience that can protect neuronal systems from endogenous and exogenous stresses and insult. Particular attention is directed to issues of dose optimization, inter-individual variation, and potential ways to further study and employ hormetic-based preconditioning approaches in medical and public health efforts to treat and prevent neurodegenerative disease.

Relationship between stroke etiology and collateral status in anterior circulation large vessel occlusion

Background and purpose

Clinical outcome after mechanical thrombectomy (MT) for large vessel occlusion (LVO) stroke is influenced by the intracerebral collateral status. We tested the hypothesis that patients with preexisting ipsilateral extracranial carotid artery stenosis (CAS) would have a better collateral status compared to non-CAS patients. Additionally, we evaluated MT-related adverse events and outcome for both groups.

Methods

Over a 7-year period, we identified all consecutive anterior circulation MT patients (excluding extracranial carotid artery occlusion and dissection). Patients were grouped into those with CAS ≥ 50% according to the NASCET criteria and those without significant carotid stenosis (non-CAS). Collateral status was rated on pre-treatment CT- or MR-angiography according to the Tan Score. Furthermore, we assessed postinterventional infarct size, adverse events and functional outcome at 90 days.

Results

We studied 281 LVO stroke patients, comprising 46 (16.4%) with underlying CAS ≥ 50%. Compared to non-CAS stroke patients (n = 235), patients with CAS-related stroke more often had favorable collaterals (76.1% vs. 46.0%). Recanalization rates were comparable between both groups. LVO stroke patients with underlying CAS more frequently had adverse events after MT (19.6% vs. 6.4%). Preexisting CAS was an independent predictor for favorable collateral status in multivariable models (Odds ratio: 3.3, p = 0.002), but post-interventional infarct size and functional 90-day outcome were not different between CAS and non-CAS patients.

Conclusions

Preexisting CAS ≥ 50% was associated with better collateral status in LVO stroke patients. However, functional 90-day outcome was independent from CAS, which could be related to a higher rate of adverse events.

C3a receptor antagonist therapy is protective with or without thrombolysis in murine thromboembolic stroke

BACKGROUND AND PURPOSE

Intravenous thrombolysis (IVT) after stroke enhances C3a generation, which may abrogate the benefits of reperfusion. The C3aR antagonist SB290157 is neuroprotective following transient but not permanent middle cerebral artery occlusion (MCAo). SB290157 remains untested in thromboembolic (TE) models, which better approximate human stroke and also facilitate testing in combination with IVT. We hypothesized SB290157 would confer neuroprotection in TE stroke with and without "late" IVT.

EXPERIMENTAL APPROACH

We used two different models of TE stroke to examine the efficacy of SB290157 alone and in combination with late IVT. We evaluated the benefit of SB290157 in attenuating post-ischaemic behavioural deficits, infarction, brain oedema and haemorrhage.

KEY RESULTS

Plasma C3a was elevated 6 hr after TE stroke alongside increased cerebrovascular C3aR expression, which was sustained to 4 weeks. Increased C3aR expression also was visualized in human ischaemic brain. In a photothrombotic (PT) stroke model, which exhibits rapid spontaneous reperfusion, SB290157 given at 1 hr post-PT significantly improved neurofunction and reduced infarction at 48 hr. In an embolic (eMCAo) model, SB290157 administered at 2 hr improved histological and functional outcomes. Conversely, late IVT administered 4.5 hr post-eMCAo was ineffective likely due to increased haemorrhage and brain oedema. However, SB290157 administered prior to late IVT ameliorated haemorrhage and oedema and improved outcomes.

CONCLUSIONS AND IMPLICATIONS

We conclude that SB290157 is safe and effective with and without late IVT following TE stroke. Therefore, C3a receptor antagonist therapy represents a promising candidate for clinical translation in stroke, particularly as an adjuvant to IVT.

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.

Obesity-related cognitive impairment: The role of endothelial dysfunction

Obesity is a global pandemic associated with macro- and microvascular endothelial dysfunction. Microvascular endothelial dysfunction has recently emerged as a significant risk factor for the development of cognitive impairment. In this review, we present evidence from clinical and preclinical studies supporting a role for obesity in cognitive impairment. Next, we discuss how obesity-related hyperinsulinemia/insulin resistance, systemic inflammation, and gut dysbiosis lead to cognitive impairment through induction of endothelial dysfunction and disruption of the blood brain barrier. Finally, we outline the potential clinical utility of dietary interventions, exercise, and bariatric surgery in circumventing the impacts of obesity on cognitive function.

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.

Chronic remote ischemic conditioning for cardiovascular protection

New treatments are needed to prevent adverse left ventricular remodelling following acute myocardial infarction (AMI), in order to prevent heart failure and improve clinical outcomes following AMI. Remote ischemic conditioning (RIC) using transient limb ischemia and reperfusion has been reported to reduce myocardial infarct (MI) size in AMI patients treated by primary percutaneous coronary intervention, and whether it can improve clinical outcomes is currently being investigated. Interestingly, repeated daily episode of limb RIC (termed 'chronic remote ischemic conditioning', or CRIC) has been shown in experimental and clinical studies to confer beneficial effects on post-AMI cardiac remodelling and chronic heart failure. In addition, the beneficial effects of CRIC extend to vascular function, peripheral arterial disease and stroke. In this review article, we focus on the therapeutic potential of CRIC as a strategy for cardiovascular protection and for improving clinical outcomes in patients with cardiovascular disease.

Potential Applications of Remote Limb Ischemic Conditioning for Chronic Cerebral Circulation Insufficiency

Chronic cerebral circulation insufficiency (CCCI) refers to a chronic decrease in cerebral blood perfusion, which may lead to cognitive impairment, psychiatric disorders such as depression, and acute ischemic stroke. Remote limb ischemic conditioning (RLIC), in which the limbs are subjected to a series of transient ischemic attacks, can activate multiple endogenous protective mechanisms to attenuate fatal ischemic injury to distant organs due to acute ischemia, such as ischemic stroke. Recent studies have also reported that RLIC can alleviate dysfunction in distant organs caused by chronic, non-fatal reductions in blood supply (e.g., CCCI). Indeed, research has indicated that RLIC may exert neuroprotective effects against CCCI through a variety of potential mechanisms, including attenuated glutamate excitotoxicity, improved endothelial function, increased cerebral blood flow, regulation of autophagy and immune responses, suppression of apoptosis, the production of protective humoral factors, and attenuated accumulation of amyloid-β. Verification of these findings is necessary to improve prognosis and reduce the incidence of acute ischemic stroke/cognitive impairment in patients with CCCI.

Peripheral Mechanisms of Remote Ischemic Conditioning

Ischemic conditioning induces an endogenous protective mechanism that allows organisms to develop resistance to subsequent insults. The conditioning effect occurs across organs and species. Recently, much attention has been given to remote ischemic limb conditioning due to its non-invasive nature and potential therapeutic applications. While tolerance is induced at the primary injury site (e.g. the heart in cardiac ischemia and the brain in stroke), the site of conditioning application is away from the target organ, suggesting the protective factors are extrinsic in nature rather than intrinsic. This review will focus on the peripheral factors that account for the induction of tolerance. Topics of particular interest are blood flow changes, peripheral neural pathways, humoral factors in circulation, and the peripheral immune system. This review will also discuss how conditioning may negatively affect metabolically compromised conditions, its optimal dose, and window for therapy development.

Efficacy of remote ischemic conditioning on improving WMHs and cognition in very elderly patients with intracranial atherosclerotic stenosis

Our previous study revealed that remote ischemic conditioning (RIC) reduced the incidence of stroke or TIA in octo- and nonagenarians with intracranial atherosclerotic stenosis (ICAS). Herein, we aimed to investigate whether RIC would influence the progression of white matter hyperintensities (WMHs) and cognitive impairment in the same group of patients. Fifty-eight patients with ICAS were randomly assigned in a 1:1 ratio to receive standard medical treatment with RIC (n=30) versus sham-RIC (n=28). The RIC protocol consisted of 5 cycles of alternating 5-min ischemia and 5-min reperfusion applied in the bilateral upper arms twice daily for 300 days. The efficacy outcomes included WMHs change on T2 FLAIR sequences, estimated by the Fazekas scale and Scheltens scale, cognitive change as assessed by the MMSE and MoCA, and some clinical symptoms within 300-day follow-up. Compared with the baseline, RIC treatment significantly reduced Fazekas and Scheltens scores at both 180-day (both p<0.05) and 300-day (both p<0.01) follow-ups, whereas no such reduction was observed in the control group. In the RIC group, Fazekas scores were significantly lower at 300-day follow-up (p<0.001) while Scheltens scores were significantly lower at both 180-day and 300-day follow-ups (both p<0.001), as compared with the control group. There were statistically significant between-group differences in the overall MMSE or MoCA scores, favoring RIC at 180-day and 300-day follow-ups (all p<0.05). RIC may serve as a promising adjunctive to standard medical therapy for preventing the progression of WMHs and ameliorating cognitive impairment in very elderly patients with ICAS.