Ischemic conditioning-induced endogenous brain protection: Applications pre-, per- or post-stroke

Morphine Preconditioning Alleviates Ischemia/Reperfusion-induced Caspase-8-dependent Neuronal Apoptosis through cPKCγ-NF-κB-cFLIPL Pathway

BACKGROUND

Perioperative cerebral ischemia/reperfusion injury is a major contributor to postoperative death and cognitive dysfunction in patients. It was reported that morphine preconditioning (MP) can mimic ischemia/hypoxia preconditioning to protect against ischemia/reperfusion injury. However, the mechanism of MP on the ischemia/reperfusion-induced neuronal apoptosis has not been fully clarified.

METHODS

The middle cerebral artery occlusion/reperfusion (MCAO/R) model of mice and the oxygen-glucose deprivation/reoxygenation (OGD/R) model in primary cortical neurons were used to mimic ischemic stroke. In vivo, the infarct size was measured by using TTC staining; NDSS, Longa score system, and beam balance test were performed to evaluate the neurological deficits of mice; the expression of the protein was detected by using a western blot. In vitro, the viability of neurons was determined by using CCK-8 assay; the expression of protein and mRNA were assessed by using western blot, RT-qPCR, and immunofluorescent staining; the level of apoptosis was detected by using TUNEL staining.

RESULTS

MP can improve the neurological functions of mice following MCAO/R (P<0.001, n=10 per group). MP can decrease the infarct size (P<0.001, n=10 per group) and the level of cleaved-caspase-3 of mice following MCAO/R (P<0.01 or 0.001, n=6 per group). MP can increase the levels of cPKCγ membrane translocation, p-p65, and cFLIPL, and decrease the levels of cleaved-caspase-8, 3 in neurons after OGD/R or MCAO/R 1 d (P<0.05, 0.01 or 0.001, n=6 per group). In addition, MP could alleviate OGD/R-induced cell apoptosis (P<0.001, n=6 per group).

CONCLUSION

MP alleviates ischemia/reperfusion-induced Caspase 8-dependent neuronal apoptosis through the cPKCγ-NF-κB-cFLIPL pathway.

Photobiomodulation preconditioned diabetic adipose derived stem cells with additional photobiomodulation: an additive approach for enhanced wound healing in diabetic rats with a delayed healing wound

In this preclinical investigation, we examined the effects of combining preconditioned diabetic adipose-derived mesenchymal stem cells (AD-MSCs) and photobiomodulation (PBM) on a model of infected ischemic delayed healing wound (injury), (IIDHWM) in rats with type I diabetes (TIDM). During the stages of wound healing, we examined multiple elements such as stereology, macrophage polarization, and the mRNA expression levels of stromal cell-derived factor (SDF)-1α, vascular endothelial growth factor (VEGF), hypoxia-induced factor 1α (HIF-1α), and basic fibroblast growth factor (bFGF) to evaluate proliferation and inflammation. The rats were grouped into: (1) control group; (2) diabetic-stem cells were transversed into the injury site; (3) diabetic-stem cells were transversed into the injury site then the injury site exposed to PBM; (4) diabetic stem cells were preconditioned with PBM and implanted into the wound; (5) diabetic stem cells were preconditioned with PBM and transferred into the injury site, then the injury site exposed additional PBM. While on both days 4, and 8, there were advanced histological consequences in groups 2-5 than in group 1, we found better results in groups 3-5 than in group 2 (p < 0.05). M1 macrophages in groups 2-5 were lower than in group 1, while groups 3-5 were reduced than in group 2 (p < 0.01). M2 macrophages in groups 2-5 were greater than in group 1, and groups 3-5 were greater than in group 2. (p ≤ 0.001). Groups 2-5 revealed greater expression levels of bFGF, VEGF, SDF- 1α, and HIF- 1α genes than in group 1 (p < 0.001). Overall group 5 had the best results for histology (p < 0.05), and macrophage polarization (p < 0.001). AD-MSC, PBM, and AD-MSC + PBM treatments all enhanced the proliferative stage of injury repairing in the IIDHWM in TIDM rats. While AD-MSC + PBM was well than the single use of AD-MSC or PBM, the best results were achieved with PBM preconditioned AD-MSC, plus additional PBM of the injury.

Glymphatic and lymphatic communication with systemic responses during physiological and pathological conditions in the central nervous system

Crosstalk between central nervous system (CNS) and systemic responses is important in many pathological conditions, including stroke, neurodegeneration, schizophrenia, epilepsy, etc. Accumulating evidence suggest that signals for central-systemic crosstalk may utilize glymphatic and lymphatic pathways. The glymphatic system is functionally connected to the meningeal lymphatic system, and together these pathways may be involved in the distribution of soluble proteins and clearance of metabolites and waste products from the CNS. Lymphatic vessels in the dura and meninges transport cerebrospinal fluid, in part collected from the glymphatic system, to the cervical lymph nodes, where solutes coming from the brain (i.e., VEGFC, oligomeric α-syn, β-amyloid) might activate a systemic inflammatory response. There is also an element of time since the immune system is strongly regulated by circadian rhythms, and both glymphatic and lymphatic dynamics have been shown to change during the day and night. Understanding the mechanisms regulating the brain-cervical lymph node (CLN) signaling and how it might be affected by diurnal or circadian rhythms is fundamental to find specific targets and timing for therapeutic interventions.

Promising Cerebral Blood Flow Enhancers in Acute Ischemic Stroke

Ischemic stroke presents a major global economic and public health burden. Although recent advances in available endovascular therapies show improved functional outcome, a good number of stroke patients are either ineligible or do not have access to these treatments. Also, robust collateral flow during acute ischemic stroke independently predicts the success of endovascular therapies and the outcome of stroke. Hence, adjunctive therapies for cerebral blood flow (CBF) enhancement are urgently needed. A very clear overview of the pial collaterals and the role of genetics are presented in this review. We review available evidence and advancement for potential therapies aimed at improving CBF during acute ischemic stroke. We identified heme-free soluble guanylate cyclase activators; Sanguinate, remote ischemic perconditioning; Fasudil, S1P agonists; and stimulation of the sphenopalatine ganglion as promising potential CBF-enhancing therapeutics requiring further investigation. Additionally, we outline and discuss the critical steps required to advance research strategies for clinically translatable CBF-enhancing agents in the context of acute ischemic stroke models.

Remote Ischemic conditioning as an emerging tool to improve corticospinal transmission in individuals with chronic spinal cord injury

PURPOSE OF REVIEW

Remote ischemic conditioning (RIC) involves transient blood flow restriction to one limb leading to systemic tissue-protective effects. RIC shares some potential underlying mechanisms with intermittent hypoxia (IH), in which brief bouts of systemic hypoxia trigger increases in growth factor expression and neural plasticity. RIC has shown promise in acute myocardial infarction and stroke but may be applicable toward chronic neuropathology as well. Consequently, this review discusses similarities and differences between RIC and IH and presents preliminary and ongoing research findings regarding RIC.

RECENT FINDINGS

Several publications demonstrated that combining RIC with motor training may enhance motor learning in adults with intact nervous systems, though the precise mechanisms were unclear. Our own preliminary data has found that RIC, in conjunction with task specific exercise, can increase corticospinal excitability in a subset of people without neurological injury and in those with chronic cervical spinal cord injury or amyotrophic lateral sclerosis.

SUMMARY

RIC is a low-cost intervention easy to deliver in a clinical or home setting. Its potential application to facilitate neural plasticity and motor learning during rehabilitation training for individuals with chronic neurological disorders is a novel concept requiring further investigation to characterize mechanisms, safety, and efficacy.

Photobiomodulation, alone or combined with adipose-derived stem cells, reduces inflammation by modulation of microRNA-146a and interleukin-1ß in a delayed-healing infected wound in diabetic rats

Diabetic wounds are categorized by chronic inflammation, leading to the development of diabetic foot ulcers, which cause amputation and death. Herewith, we examined the effect of photobiomodulation (PBM) plus allogeneic diabetic adipose tissue-derived stem cells (ad-ADS) on stereological parameters and expression levels of interleukin (IL)-1ß and microRNA (miRNA)-146a in the inflammatory (day 4) and proliferation (day 8) stages of wound healing in an ischemic infected (with 2×107 colony-forming units of methicillin-resistant Staphylococcus aureus) delayed healing wound model (IIDHWM) in type I diabetic (TIDM) rats. There were five groups of rats: group 1 control (C); group 2 (CELL) in which rat wounds received 1×106 ad-ADS; group 3 (CL) in which rat wounds received the ad-ADS and were subsequently exposed to PBM(890 nm, 80 Hz, 3.5 J/cm2, in vivo); group 4 (CP) in which the ad-ADS preconditioned by the PBM(630 nm + 810 nm, 0.05 W, 1.2 J/cm2, 3 times) were implanted into rat wounds; group 5 (CLP) in which the PBM preconditioned ad-ADS were implanted into rat wounds, which were then exposed to PBM. On both days, significantly better histological results were seen in all experimental groups except control. Significantly better histological results were observed in the ad-ADS plus PBM treatment correlated to the ad-ADS alone group (p<0.05). Overall, PBM preconditioned ad-ADS followed by PBM of the wound showed the most significant improvement in histological measures correlated to the other experimental groups (p<0.05). On days 4 and 8, IL-1 β levels of all experimental groups were lower than the control group; however, on day 8, only the CLP group was different (p<0.01). On day 4, miR-146a expression levels were substantially greater in the CLP and CELL groups correlated to the other groups, on day 8 miR-146a in all treatment groups was upper than C (p<0.01). ad-ADS plus PBM, ad-ADS, and PBM all improved the inflammatory phase of wound healing in an IIDHWM in TIDM1 rats by reducing inflammatory cells (neutrophils, macrophages) and IL-1ß, and increasing miRNA-146a. The ad-ADS+PBM combination was better than either ad-ADS or PBM alone, because of the higher proliferative and anti-inflammatory effects of the PBM+ad-ADS regimen.

Microbiota-gut-brain axis impairment in the pathogenesis of stroke: implication as a potent therapeutic target

The human microbiota-gut-brain axis has an enormous role in the maintenance of homeostasis and health. Over the last two decades, it has received concerted research attention and focus due to a rapidly emerging volume of evidence that has established that impairment within the microbiota-gut-brain axis contributes to the development and progression of various diseases. Stroke is one of the entities identified to be associated with microbiota-gut-brain axis impairment. Currently, there are still limitations in the clinical treatment of stroke, and the presence of a non-nervous factor from gut microbiota that can alter the course of stroke presents a novel strategy towards the search for a therapeutic silver bullet against stroke. Hence, the aim herein, was to focus on the involvement of microbiota-gut-brain axis impairment in the pathogenesis stroke as well as elucidate its implications as a potent therapeutic target against stroke. The findings of studies to date have revealed and extended the role microbiota-gut-brain axis impairment in the pathogenesis of stroke, and studies have identified from both clinical and pre-clinical perspectives targets within the microbiota-gut-brain axis and successfully modulated the outcome of stroke. It was concluded that the microbiota-gut-brain axis stands as potent target to salvage the neurons in the ischemic penumbra for the treatment of stroke. Assessment of the microbiota profile and its metabolites status holds enormous clinical potentials as a non-invasive indicator for the early diagnosis and prognosis of stroke.

Effect of dynamic cerebral autoregulation on the association between deep medullary vein changes and cerebral small vessel disease

Changes in the deep medullary vein (DMV) are reported to be associated with cerebral small vessel disease (CSVD). While the mechanisms of this association are unclear, dynamic cerebral autoregulation (dCA) has been speculated to participate in this association. Thus, we aimed to verify the association between DMV changes and total CSVD burden and further investigate the effect of dCA function on this correlation. In this prospective study, 95 Asian patients aged ≥18 years were included in the final assessment. DMV scores and total CSVD burden were determined using magnetic resonance imaging sequences. Transfer function analysis was performed to analyze dCA function. Generalized linear regressions were used to assess the relationship between DMV changes and total CSVD burden as well as between DMV changes and dCA function. An interaction model was utilized to assess the effect of dCA function on the association between DMV changes and total CSVD burden. Generalized linear models showed a significant positive association between DMV changes and total CSVD burden (p = 0.039) and a significant negative association between DMV changes and dCA function (p = 0.018). The interaction model demonstrated a significant positive interaction of dCA impairment on the association between DMV changes and the total CSVD burden (p = 0.02). Thus, we came to the conclusion that changes in DMV were correlated independently with both CSVD and dCA impairment and furthermore, impaired dCA function play an interaction effect on the association between DMV changes and the total CSVD burden. Our results can help improve the understanding of the complex pathogenesis and progression of CSVD, thereby facilitating early intervention and treatment development.

The Role of LincRNA-EPS/Sirt1/Autophagy Pathway in the Neuroprotection Process by Hydrogen against OGD/R-Induced Hippocampal HT22 Cells Injury

Cerebral ischemia/reperfusion (CI/R) injury causes high disability and mortality. Hydrogen (H2) enhances tolerance to an announced ischemic event; however, the therapeutic targets for the effective treatment of CI/R injury remain uncertain. Long non-coding RNA lincRNA-erythroid prosurvival (EPS) (lincRNA-EPS) regulate various biological processes, but their involvement in the effects of H2 and their associated underlying mechanisms still needs clarification. Herein, we examine the function of the lincRNA-EPS/Sirt1/autophagy pathway in the neuroprotection of H2 against CI/R injury. HT22 cells and an oxygen-glucose deprivation/reoxygenation (OGD/R) model were used to mimic CI/R injury in vitro. H2, 3-MA (an autophagy inhibitor), and RAPA (an autophagy agonist) were then administered, respectively. Autophagy, neuro-proinflammation, and apoptosis were evaluated by Western blot, enzyme-linked immunosorbent assay, immunofluorescence staining, real-time PCR, and flow cytometry. The results demonstrated that H2 attenuated HT22 cell injury, which would be confirmed by the improved cell survival rate and decreased levels of lactate dehydrogenase. Furthermore, H2 remarkably improved cell injury after OGD/R insult via decreasing pro-inflammatory factors, as well as suppressing apoptosis. Intriguingly, the protection of H2 against neuronal OGD/R injury was abolished by rapamycin. Importantly, the ability of H2 to promote lincRNA-EPS and Sirt1 expression and inhibit autophagy were abrogated by the siRNA-lincRNA-EPS. Taken together, the findings proved that neuronal cell injury caused by OGD/R is efficiently prevented by H2 via modulating lincRNA-EPS/Sirt1/autophagy-dependent pathway. It was hinted that lincRNA-EPS might be a potential target for the H2 treatment of CI/R injury.

The effect of repeated remote ischemic postconditioning after an ischemic stroke (REPOST): A randomized controlled trial

BACKGROUND AND AIMS

A potential strategy to treat ischemic stroke may be the application of repeated remote ischemic postconditioning (rIPostC). This consists of several cycles of brief periods of limb ischemia followed by reperfusion, which can be applied by inflating a simple blood pressure cuff and subsequently could result in neuroprotection after stroke.

METHODS

Adult patients admitted with an ischemic stroke in the past 24 h were randomized 1:1 to repeated rIPostC or sham-conditioning. Repeated rIPostC was performed by inflating a blood pressure cuff around the upper arm (4 × 5 min at 200 mm Hg), which was repeated twice daily during hospitalization with a maximum of 4 days. Primary outcome was infarct size after 4 days or at discharge. Secondary outcomes included the modified Rankin Scale (mRS)-score after 12 weeks and the National Institutes of Health Stroke Scale (NIHSS) at discharge.

RESULTS

The trial was preliminarily stopped after we included 88 of the scheduled 180 patients (average age: 70 years, 68% male) into rIPostC (n = 40) and sham-conditioning (n = 48). Median infarct volume was 2.19 mL in rIPostC group and 5.90 mL in sham-conditioning, which was not significantly different between the two groups (median difference: 3.71; 95% CI: -0.56 to 6.09; p = 0.31). We found no significant shift in the mRS score distribution between groups. The adjusted common odds ratio was 2.09 (95% CI: 0.88-5.00). We found no significant difference in the NIHSS score between groups (median difference: 1.00; 95% CI: -0.99 to 1.40; p = 0.51).

CONCLUSION

This study found no significant improvement in infarct size or clinical outcome in patients with an acute ischemic stroke who were treated with repeated remote ischemic postconditioning. However, due to a lower-than-expected inclusion rate, no definitive conclusions about the effectiveness of rIPostC can be drawn.

Remote ischemic postconditioning ameliorates stroke injury via the SDF-1α/CXCR4 signaling axis in rats

Remote Ischemic Postconditioning (RIPostC) has become a research hotspot due to its protective effect on the brain in clinical studies related to ischemic stroke. The purpose of this study is to investigate the protective effect of RIPostC after ischemic stroke in rats. The middle cerebral artery occlusion/reperfusion (MCAO/R) model was established by the wire embolization method. RIPostC was obtained by inducing temporary ischemia in the hind limbs of rats. First, based on the results of short-term behavioral measures and long-term neurological function experiments, RIPostC was found to have a protective effect on the MCAO/R model and to improve neurological recovery in rats. Compared to the sham group, RIPostC upregulated the expression levels of C-X-C motif chemokine receptor 4(CXCR4) in the brain and stromal cell-derived factor-1(SDF-1α) in peripheral blood. In addition, RIPostC upregulated CXCR4 expression on CD34+ stem cells in peripheral blood in flow cytometric assays. Meanwhile, according to the results of EdU/DCX co-staining and CD31 staining, it was found that the effect of RIPostC on ameliorating brain injury via SDF-1α/CXCR4 signaling axis may be associated with vascular neogenesis. Finally, after inhibiting the SDF-1α/CXCR4 signaling axis using AMD3100(Plerixafor), we found that the neuroprotective effect of RIPostC was diminished. Taken together, RIPostC can improve neurobehavioral damage induced by MCAO/R in rats, and its mechanism may be related to SDF-1α/CXCR4 signaling axis. Therefore, RIPostC can be used as an intervention strategy for stroke. SDF-1α/CXCR4 signaling axis can also be a potential target for intervention.

Neuroprotective effects of pre-ischemic exercise are linked to expression of NT-3/NT-4 and TrkB/TrkC in rats

INTRODUCTION AND OBJECTIVE

Stroke causes irreversible damage, particularly to the hippocampus. Evidence suggests that exercise training may mitigate adverse structural and functional consequences of an ischemic lesion in the brain. The purpose of this study was to investigate the effects of preconditioning exercise on expression of neurotrophic factor genes and proteins in hippocampalCA1 region and their relationship with sensorimotor recovery following global ischemia/reperfusion (Is/Re) injury in a rat model of stroke.

METHODS

Male Wistar rats were randomly assigned to Exercise+Ischemia/Reperfusion (Ex+Is/Re),Control+Ischemia/Reperfusion (Co+Is/Re), and Sham treatments. Rats in the exercise groups ran on a treadmill for 45 min/d for five days/week for 8 consecutive weeks prior to Is/Re lesion.Ischemia was induced by common carotid artery occlusion (CCAO). The ladder rung walking task was used to assess functional impairments and recovery following ischemic lesion.Tissue from hippocampal area CA1 was inspected for ischemia-induced cell loss and gene and protein expression linked to neurotrophins NT-3, NT-4, and their receptorsTrkB and TrkC.

RESULTS

CCAO caused hippocampal cell death in CA1 and resulted in significant sensori motor impairments in the ladder rung walking task. In contrast, pre-ischemic exercise considerably reduced cell death and supported sensorimotor recovery following CCAO.In addition, NT-3, NT-4,TrkB and TrkC gene expression and their protein levels were significantly increased inthe Ex+Is/Re group compared to Co+Is/Re (p < 0.05).

CONCLUSION

The findings showed that pre-ischemic exercise can exert neuroprotective effects via NT-3 and NT-4 pathways against ischemia in hippocampal CA1 neurons and promote post-injury sensorimotor recovery.

Effects of different remote ischemia perconditioning methods on cerebral infarct volume and neurological impairment in rats

Remote ischemic perconditioning (RIPerC) is a novel neuroprotective method against cerebral infarction that has shown efficacy in animal studies but has not been consistently neuroprotective in clinical trials. We focused on the temporal regulation of ischemia-reperfusion by RIPerC to establish an optimal method for RIPerC. Rats were assigned to four groups: 10 min ischemia, 5 min reperfusion; 10 min ischemia, 10 min reperfusion; 5 min ischemia, 10 min reperfusion; and no RIPerC. RIPerC interventions were performed during ischemic stroke, which was induced by a 60-min left middle cerebral artery occlusion. Infarct volume, sensorimotor function, neurological deficits, and cellular expressions of brain-derived neurotrophic factor (BDNF), B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), and caspase 3 were evaluated 48 h after the induction of ischemia. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) was also performed. RIPerC of 10 min ischemia/10 min reperfusion, and 5 min ischemia/10 min reperfusion decreased infarct volume, improved sensorimotor function, decreased Bax, caspase 3, and TUNEL-positive cells, and increased BDNF and Bcl-2 expressions. Our findings suggest RIPerC with a reperfusion time of approximately 10 min exerts its neuroprotective effects via an anti-apoptotic mechanism. This study provides important preliminary data to establish more effective RIPerC interventions.

Prediction of stroke reconvalescence after coronary bypass surgery indicated by CT scan parameters

BACKGROUND

Stroke in the postoperative time course after heart surgery remains a serious risk. Cranial computer tomography (CCT) is the first line option to detect severe intracranial damage. However, only few data are available to predict neurological outcome. Using visual rating scales (VRSs), this study addresses reliability and effectivity to indicate neurological status and likelyhood of improvement.

METHODS

In a single-center retrospective evaluation, 3719 patients underwent coronary bypass surgery. Because of a delayed recovery phase and neurologic deficits after cardiac surgery 109 patients had a cranial CT scan in the early postoperative period. The incidence of clinically relevant findings within the imaging was rated by an experienced neuroradiologist using two VRS, that is, the age-related white matter changes (ARWMCs) and the Mendes-Ribeiro visual rating scale (MRVRS). Both are computer-assisted measurement schemes to detect stroke-related intracranial damage. Follow-up was investigated with regard to clinical outcome and patient-related risk profiles.

RESULTS

Of 109 patients with postoperative cranial CT scans due to prolonged recovery phases or proven neurological damage 44.5% had one cerebral defect in CCT imaging scans only. The others showed multiple defects. During hospital stay, 92.3% experienced neurological improvement exposing reduced ARWMC, while 7.1% had no improvement and correlating high scores. Of both scales, the ARWMC-VRS demonstrated superior accuracy and discrimination. The preoperative ejection fraction (EF), arteriosclerotic degeneration of carotid arteries, and reduced glomerular filtration rate were found to have a high correlation (r = 0.0005) with the latter group. In-hospital mortality of this cohort was 8.18%.

CONCLUSION

Both the ARWMC and MRVRS were found to be appropriate. They reliably discriminate the groups of stroke patients after coronary artery bypass grafting (CABG)  in the analysis of CCT images. When applied at the onset of neurological symptoms both scales are able to predict neurological reconvalescence upon hospital dismission. The ARWMC scale appeared superior as it demonstrated better accuracy and discrimination. The use of both VRS in patients with suspected stroke after CABG surgery can give insightful information toward a progression of neurological dysfunction or postoperative improvement.

Neuroprotection in Acute Ischemic Stroke: A Battle Against the Biology of Nature

Stroke is the second most common cause of global death following coronary artery disease. Time is crucial in managing stroke to reduce the rapidly progressing insult of the ischemic penumbra and the serious neurologic deficits that might follow it. Strokes are mainly either hemorrhagic or ischemic, with ischemic being the most common of all types of strokes. Thrombolytic therapy with recombinant tissue plasminogen activator and endovascular thrombectomy are the main types of management of acute ischemic stroke (AIS). In addition, there is a vital need for neuroprotection in the setting of AIS. Neuroprotective agents are important to investigate as they may reduce mortality, lessen disability, and improve quality of life after AIS. In our review, we will discuss the main types of management and the different modalities of neuroprotection, their mechanisms of action, and evidence of their effectiveness after ischemic stroke.

Safety and efficacy of remote ischemic preconditioning in patients with severe carotid artery stenosis before carotid artery stenting: A proof-of-concept, randomized controlled trial

Background: Remote ischemic preconditioning (RIPC) has been proposed as a possible potential treatment for ischemic stroke. This study aimed to investigate the frequency of micro-embolic brain infarcts after RIPC in patients with stroke who underwent elective carotid artery stenting (CAS) treatment. Methods: This study was managed at Shiraz University of Medical Sciences in southwest Iran. Patients undergoing CAS were randomly allocated into RIPC and control groups. Patients in the RIPC group received three intermittent cycles of 5-minute arm ischemia followed by reperfusion using manual blood cuff inflation/deflation less than 30 minutes before CAS treatment. Afterward, stenting surgery was conducted. Magnetic resonance imaging (MRI), including diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC), was acquired within the first 24 hours after CAS. Results: Seventy-four patients were recruited (79.7% men, age: 72.30 ± 8.57). Both groups of RIPC and control had no significant difference in baseline parameters (P > 0.05). Fifteen patients (40.5%) in the RIPC group and 19 (54.1%) patients in the control group developed restricted lesions in DWI MRI. In DWI+ patients, there were no significant differences according to the number of lesions, lesion surface area, largest lesion diameter, cortical infarcts percent, and ipsilateral and bilateral infarcts between the two groups. Conclusion: Although RIPC is a safe and non-invasive modality before CAS to decrease infarcts, this study did not show the advantage of RIPC in the prevention of infarcts following CAS. It may be because of the small sample size.

Neuroprotective Effect of Physical Activity in Ischemic Stroke: Focus on the Neurovascular Unit

Cerebral ischemia is one of the major diseases associated with death or disability among patients. To date, there is a lack of effective treatments, with the exception of thrombolytic therapy that can be administered during the acute phase of ischemic stroke. Cerebral ischemia can cause a variety of pathological changes, including microvascular basal membrane matrix, endothelial cell activation, and astrocyte adhesion, which may affect signal transduction between the microvessels and neurons. Therefore, researchers put forward the concept of neurovascular unit, including neurons, axons, astrocytes, microvasculature (including endothelial cells, basal membrane matrix, and pericyte), and oligodendrocytes. Numerous studies have demonstrated that exercise can produce protective effects in cerebral ischemia, and that exercise may protect the integrity of the blood-brain barrier, promote neovascularization, reduce neuronal apoptosis, and eventually lead to an improvement in neurological function after cerebral ischemia. In this review, we summarized the potential mechanisms on the effect of exercise on cerebral ischemia, by mainly focusing on the neurovascular unit, with the aim of providing a novel therapeutic strategy for future treatment of cerebral ischemia.

Mitochondrial repair as potential pharmacological target in cerebral ischemia

Cerebral ischemia and its consequences like transient ischemic attack, aneurysm and stroke are the common and devastating conditions which remain the leading cause of mortality after coronary heart disease in developed countries and are the greatest cause of disability, leaving 50% of survivors permanently disabled. Despite recognition of risk factors and mechanisms involved in the pathology of the disease, treatment of ischemic disorders is limited to thrombolytic drugs like recombinant tissue plasminogen activator (rt-PA) and clinical rendition of the neuroprotective agents have not been so successful. Recent studies evidenced the role of mitochondrial dysfunction in neuronal damage that occurred after cerebral ischemia. This review article will focus on the various fundamental mechanisms responsible for neuronal damage because of mitochondrial dysfunction including cell signaling pathways, autophagy, apoptosis/necrosis, generation of reactive oxygen species, calcium overload, the opening of membrane permeability transition pore (mPTP), mitochondrial dynamics and biogenesis. Recent studies have concerned the significant role of mitochondrial biogenesis in mitochondrial repair and transfer of healthy mitochondria from astrocytes to the damaged neurons, providing neuroprotection and neural recovery following ischemia. Novel and influential studies have evidenced the significant role of mitochondria transfer and mitochondrial transplantation in reviving cell energy and in replacement of impaired or dysfunctional mitochondria with healthy mitochondria after ischemic episode. This review article will focus on recent advances in mitochondrial interventions and exogenous therapeutic modalities like mitochondria transfer technique, employment of stem cells, mitochondrial transplantation, miRNA inhibition and mitochondrial-targeted Sirtuin1 activator for designing novel and promising treatment for cerebral ischemia induced pathological states.

Direct Ischemic Postconditioning After Carotid Endarterectomy in the Prevention of Postoperative Cerebral Ischemic Complications—Observational Case–Control Study

Introduction:

Ischemic postconditioning (IPCT) represents one of the several therapeutic strategies to attenuate ischemic reperfusion injury (IR) after carotid endarterectomy (CEA). We here present the first in-human study of IPCT in carotid surgery.

Methods:

The study represents an observational case-control study, with the data collected in our Institution carotid database. From December 2015 to December 2020, a total of 300 patients were included in our study; IPCT group consisted of 148 patients in whom ischemic postconditioning was performed while control group consisted of 152 patients in whom IPCT was not performed. Indications for IPCT technique were: severe unilateral internal carotid artery (ICA) stenosis (>90%), severe bilateral ICA stenosis (>80%), severe ICA stenosis (>80%) with contralateral ICA occlusion and ICA subocclusion. IPCT was performed by applying 6 cycles of 30 sec reperfusion (declamping of ICA)/30 sec ischemia (clamping of ICA) after finishing the procedure and initial declamping. Two groups of patients were compared in terms of occurrence of intrahospital and early postoperative stroke, TIA (transient ischemic attack) and neurologic morbidity.

Results:

Cumulative incidence of intrahospital postoperative stroke or TIA was significantly higher in the control group (5.3% vs 0.7%, P = .036). According to carotid plaque characteristics, patients in the IPCT group had significantly more frequent presence of heterogenous plaque, as well as ulcerated plaque, which was associated with the absence of postoperative stroke and significantly lower cumulative rate of TIA/stroke when compared to the control group (43.9% vs 8% and 47.3% vs 1.5%). During the follow-up period of 1 month after the surgery, there were no cases of stroke, TIA and deaths due to neurological causes in both groups of patients.

Conclusion:

Our results showed that IPCT significantly reduced the incidence of postoperative cerebral ischemic complications after CEA in high-risk patients for IR injury when compared to the control group.

The role of FUNDC1 in mitophagy, mitochondrial dynamics and human diseases

Mitochondria are the principal sites of energy metabolism and provide most of the energy needed for normal cellular function. They are dynamic organelles that constantly undergo fission, fusion and mitophagy to maintain their homeostasis and function. However, dysregulated mitochondrial dynamics and mitophagy leads to reduced ATP generation and mutation of their DNA, which ultimately leads to cell death. Increasing evidence has shown that the FUN14 domain-containing protein 1 (FUNDC1), a novel mitophagy receptor, participates in the process of mitochondrial dynamics and mitophagy and plays a critical role in various human diseases. Herein, we review the role of FUNDC1 in mitophagy and mitochondrial dynamics, thus providing a better understanding of the relationship between the two processes. Moreover, we summarize the treatments targeting FUNDC1, and suggest that FUNDC1 may represent a promising therapeutic target for the treatment of several human diseases such as cardiovascular diseases, metabolic syndrome, cancer and chronic obstructive pulmonary disease (COPD).

Neuroprotective effects of long noncoding RNAs involved in ischemic postconditioning after ischemic stroke

During acute reperfusion, the expression profiles of long noncoding RNAs in adult rats with focal cerebral ischemia undergo broad changes. However, whether long noncoding RNAs are involved in neuroprotective effects following focal ischemic stroke in rats remains unclear. In this study, RNA isolation and library preparation was performed for long noncoding RNA sequencing, followed by determining the coding potential of identified long noncoding RNAs and target gene prediction. Differential expression analysis, long noncoding RNA functional enrichment analysis, and co-expression network analysis were performed comparing ischemic rats with and without ischemic postconditioning rats. Rats were subjected to ischemic postconditioning via the brief and repeated occlusion of the middle cerebral artery or femoral artery. Quantitative real-time reverse transcription-polymerase chain reaction was used to detect the expression levels of differentially expressed long noncoding RNAs after ischemic postconditioning in a rat model of ischemic stroke. The results showed that ischemic postconditioning greatly affected the expression profile of long noncoding RNAs and mRNAs in the brains of rats that underwent ischemic stroke. The predicted target genes of some of the identified long noncoding RNAs (cis targets) were related to the cellular response to ischemia and stress, cytokine signal transduction, inflammation, and apoptosis signal transduction pathways. In addition, 15 significantly differentially expressed long noncoding RNAs were identified in the brains of rats subjected to ischemic postconditioning. Nine candidate long noncoding RNAs that may be related to ischemic postconditioning were identified by a long noncoding RNA expression profile and long noncoding RNA-mRNA co-expression network analysis. Expression levels were verified by quantitative real-time reverse transcription-polymerase chain reaction. These results suggested that the identified long noncoding RNAs may be involved in the neuroprotective effects associated with ischemic postconditioning following ischemic stroke. The experimental animal procedures were approved by the Animal Experiment Ethics Committee of Kunming Medical University (approval No. KMMU2018018) in January 2018.

Remote Ischemic Conditioning May Improve Disability and Cognition After Acute Ischemic Stroke: A Pilot Randomized Clinical Trial

Background and Aim: Remote ischemic conditioning is a procedure purported to reduce the ischemic injury of an organ. This study aimed to explore the efficiency and safety of remote ischemic conditioning in patients with acute ischemic stroke. We hypothesized that remote ischemic conditioning administered from the first day of hospital admission would improve the infarct volume and clinical outcome at 180 days. Material and Methods: We performed a unicentric double-blind randomized controlled trial. We included all patients consecutively admitted to an Emergency Neurology Department with acute ischemic stroke, ineligible for reperfusion treatment, up to 24 hours from onset. All subjects were assigned to receive secondary stroke prevention treatment along with remote ischemic conditioning on the non-paretic upper limb during the first 5 days of hospitalization, twice daily - a blood pressure cuff placed around the arm was inflated to 20 mmHg above the systolic blood pressure (up to 180 mmHg) in the experimental group and 30 mmHg in the sham group. The primary outcome was the difference in infarct volume (measured on brain CT scan) at 180 days compared to baseline, whereas the secondary outcomes included differences in clinical scores (NIHSS, mRS, IADL, ADL) and cognitive/mood changes (MoCA, PHQ-9) at 180 days compared to baseline. Results: We enrolled 40 patients; the mean age was 65 years and 60% were men. Subjects in the interventional group had slightly better recovery in terms of disability, as demonstrated by the differences in disability scores between admission and 6 months (e.g., the median difference score for Barthel was -10 in the sham group and -17.5 in the interventional group, for ADL -2 in the sham group and -2.5 in the interventional group), as well as cognitive performance (the median difference score for MoCA was -2 in the sham group and -3 in the interventional group), but none of these differences reached statistical significance. The severity of symptoms (median difference score for NIHSS = 5 for both groups) and depression rate (median difference score for PHQ-9 = 0 for both groups) were similar in the two groups. The median difference between baseline infarct volume and final infarct volume at 6 months was slightly larger in the sham group compared to the interventional group (p = 0.4), probably due to an initial larger infarct volume in the former. Conclusion: Our results suggest that remote ischemic conditioning might improve disability and cognition. The difference between baseline infarct volume and final infarct volume at 180 days was slightly larger in the sham group.

Oxygen Sensing and Signaling in Alzheimer's Disease: A Breathtaking Story!

Oxygen sensing and homeostasis is indispensable for the maintenance of brain structural and functional integrity. Under low-oxygen tension, the non-diseased brain has the ability to cope with hypoxia by triggering a homeostatic response governed by the highly conserved hypoxia-inducible family (HIF) of transcription factors. With the advent of advanced neuroimaging tools, it is now recognized that cerebral hypoperfusion, and consequently hypoxia, is a consistent feature along the Alzheimer's disease (AD) continuum. Of note, the reduction in cerebral blood flow and tissue oxygenation detected during the prodromal phases of AD, drastically aggravates as disease progresses. Within this scenario a fundamental question arises: How HIF-driven homeostatic brain response to hypoxia "behaves" during the AD continuum? In this sense, the present review is aimed to critically discuss and summarize the current knowledge regarding the involvement of hypoxia and HIF signaling in the onset and progression of AD pathology. Importantly, the promises and challenges of non-pharmacological and pharmacological strategies aimed to target hypoxia will be discussed as a new "hope" to prevent and/or postpone the neurodegenerative events that occur in the AD brain.

Emerging role of PARP-1 and PARthanatos in ischemic stroke

Cell death is a key feature of neurological diseases, including stroke and neurodegenerative disorders. Studies in a variety of ischemic/hypoxic mouse models demonstrate that poly(ADP-ribose) polymerase 1 (PARP-1)-dependent cell death, also named PARthanatos, plays a pivotal role in ischemic neuronal cell death and disease progress. PARthanatos has its unique triggers, processors, and executors that convey a highly orchestrated and programmed signaling cascade. In addition to its role in gene transcription, DNA damage repair, and energy homeostasis through PARylation of its various targets, PARP-1 activation in neuron and glia attributes to brain damage following ischemia/reperfusion. Pharmacological inhibition or genetic deletion of PARP-1 reduces infarct volume, eliminates inflammation, and improves recovery of neurological functions in stroke. Here, we reviewed the role of PARP-1 and PARthanatos in stroke and their therapeutic potential.

Remote ischemic conditioning enhances oxygen supply to ischemic brain tissue in a mouse model of stroke: Role of elevated 2,3-biphosphoglycerate in erythrocytes

Oxygen supply for ischemic brain tissue during stroke is critical to neuroprotection. Remote ischemic conditioning (RIC) treatment is effective for stroke. However, it is not known whether RIC can improve brain tissue oxygen supply. In current study, we employed a mouse model of stroke created by middle cerebral artery occlusion (MCAO) to investigate the effect of RIC on oxygen supply to the ischemic brain tissue using a hypoxyprobe system. Erythrocyte oxygen-carrying capacity and tissue oxygen exchange were assessed by measuring oxygenated hemoglobin and oxygen dissociation curve. We found that RIC significantly mitigated hypoxic signals and decreased neural cell death, thereby preserving neurological functions. The tissue oxygen exchange was markedly enhanced, along with the elevated hemoglobin P50 and right-shifted oxygen dissociation curve. Intriguingly, RIC markedly elevated 2,3-biphosphoglycerate (2,3-BPG) levels in erythrocyte, and the erythrocyte 2,3-BPG levels were highly negatively correlated with the hypoxia in the ischemic brain tissue. Further, adoptive transfusion of 2,3-BPG-rich erythrocytes prepared from RIC-treated mice significantly enhanced the oxygen supply to the ischemic tissue in MCAO mouse model. Collectively, RIC protects against ischemic stroke through improving oxygen supply to the ischemic brain tissue where the enhanced tissue oxygen delivery and exchange by RIC-induced 2,3-BPG-rich erythrocytes may play a role.

Natural Compounds as Medical Strategies in the Prevention and Treatment of Psychiatric Disorders Seen in Neurological Diseases

Psychiatric disorders are frequently encountered in many neurological disorders, such as Alzheimer’s and Parkinson diseases along with epilepsy, migraine, essential tremors, and stroke. The most common comorbid diagnoses in neurological diseases are depression and anxiety disorders along with cognitive impairment. Whether the underlying reason is due to common neurochemical mechanisms or loss of previous functioning level, comorbidities are often overlooked. Various treatment options are available, such as pharmacological treatments, cognitive-behavioral therapy, somatic interventions, or electroconvulsive therapy. However oral antidepressant therapy may have some disadvantages, such as interaction with other medications, low tolerability due to side effects, and low efficiency. Natural compounds of plant origin are extensively researched to find a better and safer alternative treatment. Experimental studies have shown that phytochemicals such as alkaloids, terpenes, flavonoids, phenolic acids as well as lipids have significant potential in in vitro and in vivo models of psychiatric disorders. In this review, various efficacy of natural products in in vitro and in vivo studies on neuroprotective and their roles in psychiatric disorders are examined and their neuro-therapeutic potentials are shed light.

Endogenous neuroprotective mechanism of ATP2B1 in transcriptional regulation of ischemic preconditioning

Ischemic stroke is the main cause of disability and mortality in the world. Clinical studies have shown that patients who undergo mild transient ischemic attack (TIA) before more severe ischemic stroke have lower clinical severity of stroke and better functional prognosis. This phenomenon is called ischemic preconditioning (IPC). IPC is a powerful intrinsic protection of the brain against ischemic injury, but the underlying mechanism of IPC-mediated endogenous protection of the brain is not clear.

METHODS

Using transcriptome method, we sequenced the serum of 3 stroke patients with progenitor TIA and 3 stroke patients without prodromal TIA. We explored the expression profiles of miRNAs and mRNAs in response to IPC, and predicted the regulatory pathway of IPC related genes and their expression in cerebral neurons. The methylation consistent expression of IPC-related gene ATP2B1 in blood and brain and alternative polyadenylate (APA) analysis were used to identify the pathway and molecular mechanism of endogenous neuroprotection of IPC.

RESULTS

We found that the brain protective effect of IPC was related to platelet homeostasis and Ca²⁺ concentration. IPC-related gene ATP2B1 was highly expressed in γ-aminobutyric acid (GABA)-containing neurons in the brain. From the mechanism, we speculated that ATP2B1 was representative of the same methylation in blood and brain and was affected by alternative polyadenylation.

CONCLUSION

We speculate that IPC can induce alternative polyadenylation of ATP2B1 and trigger the mechanism of brain endogenous neuroprotection by regulating the decrease of Ca²⁺ concentration in platelet homeostasis pathway and the activation of GABAB receptor.

Molecular Aspects of Volatile Anesthetic-Induced Organ Protection and Its Potential in Kidney Transplantation

Ischemia reperfusion injury (IRI) is inevitable in kidney transplantation and negatively impacts graft and patient outcome. Reperfusion takes place in the recipient and most of the injury following ischemia and reperfusion occurs during this reperfusion phase; therefore, the intra-operative period seems an attractive window of opportunity to modulate IRI and improve short- and potentially long-term graft outcome. Commonly used volatile anesthetics such as sevoflurane and isoflurane have been shown to interfere with many of the pathophysiological processes involved in the injurious cascade of IRI. Therefore, volatile anesthetic (VA) agents might be the preferred anesthetics used during the transplantation procedure. This review highlights the molecular and cellular protective points of engagement of VA shown in in vitro studies and in vivo animal experiments, and the potential translation of these results to the clinical setting of kidney transplantation.

Effect of In-Hospital Remote Ischemic Perconditioning on Brain Infarction Growth and Clinical Outcomes in Patients With Acute Ischemic Stroke: The RESCUE BRAIN Randomized Clinical Trial

Importance

Treatment with remote ischemic perconditioning has been reported to reduce brain infarction volume in animal models of stroke. Whether this neuroprotective effect was observed in patients with acute ischemic stroke remains unknown.

Objective

To determine whether treatment with remote ischemic perconditioning administered to the leg of patients with acute ischemic stroke can reduce brain infarction volume growth.

Design, Setting, and Participants

This proof-of-concept multicenter prospective randomized open-label with blinded end point clinical trial was performed from January 12, 2015, to May 2, 2018. Patients were recruited from 11 stroke centers in France. Of the 188 patients who received magnetic resonance imaging within 6 hours of symptom onset and were confirmed to have carotid ischemic stroke, 93 were randomized to receive treatment with lower-limb remote ischemic perconditioning in addition to standard care (the intervention group), and 95 were randomized to receive standard care alone (the control group).

Interventions

Randomization on a 1:1 ratio to receive treatment with remote ischemic perconditioning (4 cycles of 5-minute inflations and 5-minute deflations to the thigh to 110 mm Hg above systolic blood pressure) in addition to standard care or standard care alone.

Main Outcomes and Measures

The change in brain infarction volume growth between baseline and 24 hours, measured by a diffusion-weighted sequence of magnetic resonance imaging scans of the brain.

Results

A total of 188 patients (mean [SD] age, 67.2 [15.7] years; 98 men [52.1%]) were included in this intention-to-treat analysis. At hospital admission, the median National Institutes of Health Stroke Scale score was 10 (interquartile range [IQR], 6-16) and the median brain infarction volume was 11.4 cm3 (IQR, 3.6-35.8 cm3); 164 patients (87.2%) received intravenous thrombolysis, and 64 patients (34.0%) underwent mechanical thrombectomy. The median increase in brain infarction growth was 0.30 cm3 (IQR, 0.11-0.48 cm3) in the intervention group and 0.37 cm3 (IQR, 0.19-0.55 cm3) in the control group (mean between-group difference on loge-transformed change, -0.07; 95% CI, -0.33 to 0.18; P = .57). An excellent outcome (defined as a score of 0-1 on the 90-day modified Rankin Scale or a score equal to the prestroke modified Rankin Scale score) was observed in 46 of 90 patients (51.1%) in the intervention group and 37 of 91 patients (40.7%) in the control group (P = .12). No significant differences in 90-day mortality were observed between the intervention and control groups (14 of 90 patients; Kaplan-Meier estimate, 15.8% vs 10 of 91 patients; Kaplan-Meier estimate, 10.4%, respectively; P = .45) or with symptomatic intracerebral hemorrhage (4 of 88 patients [4.5%] in both groups; P = .97).

Conclusions and Relevance

In this study, treatment with remote ischemic perconditioning, during or after reperfusion therapies, had no significant effect on brain infarction volume growth at 24 hours after symptom onset.

Trial Registration

ClinicalTrials.gov Identifier: NCT02189928.

New Mechanistic Insights, Novel Treatment Paradigms, and Clinical Progress in Cerebrovascular Diseases

The past decade has brought tremendous progress in diagnostic and therapeutic options for cerebrovascular diseases as exemplified by the advent of thrombectomy in ischemic stroke, benefitting a steeply increasing number of stroke patients and potentially paving the way for a renaissance of neuroprotectants. Progress in basic science has been equally impressive. Based on a deeper understanding of pathomechanisms underlying cerebrovascular diseases, new therapeutic targets have been identified and novel treatment strategies such as pre- and post-conditioning methods were developed. Moreover, translationally relevant aspects are increasingly recognized in basic science studies, which is believed to increase their predictive value and the relevance of obtained findings for clinical application.This review reports key results from some of the most remarkable and encouraging achievements in neurovascular research that have been reported at the 10th International Symposium on Neuroprotection and Neurorepair. Basic science topics discussed herein focus on aspects such as neuroinflammation, extracellular vesicles, and the role of sex and age on stroke recovery. Translational reports highlighted endovascular techniques and targeted delivery methods, neurorehabilitation, advanced functional testing approaches for experimental studies, pre-and post-conditioning approaches as well as novel imaging and treatment strategies. Beyond ischemic stroke, particular emphasis was given on activities in the fields of traumatic brain injury and cerebral hemorrhage in which promising preclinical and clinical results have been reported. Although the number of neutral outcomes in clinical trials is still remarkably high when targeting cerebrovascular diseases, we begin to evidence stepwise but continuous progress towards novel treatment options. Advances in preclinical and translational research as reported herein are believed to have formed a solid foundation for this progress.

Differentially Expressed Genes and Their Clinical Significance in Ischaemic Stroke: An In-Silico Study

Background

Ischaemic stroke (IS), a multifactorial neurological disorder, is mediated by interplay between genes and the environment and, thus, blood-based IS biomarkers are of significant clinical value. Therefore, this study aimed to find global differentially expressed genes (DEGs) in-silico, to identify key enriched genes via gene set enrichment analysis (GSEA) and to determine the clinical significance of these genes in IS.

Methods

Microarray expression dataset GSE22255 was retrieved from the Gene Expression Omnibus (GEO) database. It includes messenger ribonucleic acid (mRNA) expression data for the peripheral blood mononuclear cells of 20 controls and 20 IS patients. The bioconductor-package ‘affy’ was used to calculate expression and a pairwise t-test was applied to screen DEGs (P < 0.01). Further, GSEA was used to determine the enrichment of DEGs specific to gene ontology (GO) annotations.

Results

GSEA analysis revealed 21 genes to be significantly plausible gene markers, enriched in multiple pathways among all the DEGs (n = 881). Ten gene sets were found to be core enriched in specific GO annotations. JunD, NCX3 and fibroblast growth factor receptor 4 (FGFR4) were under-represented and glycoprotein M6-B (GPM6B) was persistently over-represented.

Conclusion

The identified genes are either associated with the pathophysiology of IS or they affect post-IS neuronal regeneration, thereby influencing clinical outcome. These genes should, therefore, be evaluated for their utility as suitable markers for predicting IS in clinical scenarios.

Intermittent Hypoxic Conditioning Rescues Cognition and Mitochondrial Bioenergetic Profile in the Triple Transgenic Mouse Model of Alzheimer's Disease

The lack of effective disease-modifying therapeutics to tackle Alzheimer’s disease (AD) is unsettling considering the actual prevalence of this devastating neurodegenerative disorder worldwide. Intermittent hypoxic conditioning (IHC) is a powerful non-pharmacological procedure known to enhance brain resilience. In this context, the aim of the present study was to investigate the potential long-term protective impact of IHC against AD-related phenotype, putting a special focus on cognition and mitochondrial bioenergetics and dynamics. For this purpose, six-month-old male triple transgenic AD mice (3×Tg-AD) were submitted to an IHC protocol for two weeks and the behavioral assessment was performed at 8.5 months of age, while the sacrifice of mice occurred at nine months of age and their brains were removed for the remaining analyses. Interestingly, IHC was able to prevent anxiety-like behavior and memory and learning deficits and significantly reduced brain cortical levels of amyloid-β (Aβ) in 3×Tg-AD mice. Concerning brain energy metabolism, IHC caused a significant increase in brain cortical levels of glucose and a robust improvement of the mitochondrial bioenergetic profile in 3×Tg-AD mice, as mirrored by the significant increase in mitochondrial membrane potential (ΔΨm) and respiratory control ratio (RCR). Notably, the improvement of mitochondrial bioenergetics seems to result from an adaptative coordination of the distinct but intertwined aspects of the mitochondrial quality control axis. Particularly, our results indicate that IHC favors mitochondrial fusion and promotes mitochondrial biogenesis and transport and mitophagy in the brain cortex of 3×Tg-AD mice. Lastly, IHC also induced a marked reduction in synaptosomal-associated protein 25 kDa (SNAP-25) levels and a significant increase in both glutamate and GABA levels in the brain cortex of 3×Tg-AD mice, suggesting a remodeling of the synaptic microenvironment. Overall, these results demonstrate the effectiveness of the IHC paradigm in forestalling the AD-related phenotype in the 3×Tg-AD mouse model, offering new insights to AD therapy and forcing a rethink concerning the potential value of non-pharmacological interventions in clinical practice.

Characterizing Ischaemic Tolerance in Rat Pheochromocytoma (PC12) Cells and Primary Rat Neurons

Preconditioning tissue with sublethal ischaemia or hypoxia can confer tolerance (protection) against subsequent ischaemic challenge. In vitro ischaemic preconditioning (IPC) is typically achieved through oxygen glucose deprivation (OGD), whereas hypoxic preconditioning (HPC) involves oxygen deprivation (OD) alone. Here, we report the effects of preconditioning of OGD, OD or glucose deprivation (GD) in ischaemic tolerance models with PC12 cells and primary rat neurons. PC12 cells preconditioned (4 h) with GD or OGD, but not OD, prior to reperfusion (24 h) then ischaemic challenge (OGD 6 h), showed greater mitochondrial activity, reduced cytotoxicity and decreased apoptosis, compared to sham preconditioned PC12 cells. Furthermore, 4 h preconditioning with reduced glucose (0.565 g/L, reduced from 4.5 g/L) conferred protective effects, but not for higher concentrations (1.125 or 2.25 g/L). Preconditioning (4 h) with OGD, but not OD or GD, induced stabilization of hypoxia inducible factor 1α (HIF1α) and upregulation of HIF1 downstream genes (Vegf, Glut1, Pfkfb3 and Ldha). In primary rat neurons, only OGD preconditioning (4 h) conferred neuroprotection. OGD preconditioning (4 h) induced stabilization of HIF1α and upregulation of HIF1 downstream genes (Vegf, Phd2 and Bnip3). In conclusion, OGD preconditioning (4 h) followed by 24 h reperfusion induced ischaemic tolerance (against OGD, 6 h) in both PC12 cells and primary rat neurons. The OGD preconditioning protection is associated with HIF1α stabilization and upregulation of HIF1 downstream gene expression. GD preconditioning (4 h) leads to protection in PC12 cells, but not in neurons. This GD preconditioning-induced protection was not associated with HIF1α stabilization.

The Neurovascular Unit: Focus on the Regulation of Arterial Smooth Muscle Cells

The neurovascular unit is a physiological unit present in the brain, which is constituted by elements of the nervous system (neurons and astrocytes) and the vascular system (endothelial and mural cells). This unit is responsible for the homeostasis and regulation of cerebral blood flow. There are two major types of mural cells in the brain, pericytes and smooth muscle cells. At the arterial level, smooth muscle cells are the main components that wrap around the outside of cerebral blood vessels and the major contributors to basal tone maintenance, blood pressure and blood flow distribution. They present several mechanisms by which they regulate both vasodilation and vasoconstriction of cerebral blood vessels and their regulation becomes even more important in situations of injury or pathology. In this review, we discuss the main regulatory mechanisms of brain smooth muscle cells and their contributions to the correct brain homeostasis.

Differential mechanisms of tolerance induced by NMDA and 3,5-dihydroxyphenylglycine (DHPG) preconditioning

We investigated the molecular events triggered by NMDA and 3,5-dihydroxyphenylglycine (DHPG) preconditioning, that lead to neuroprotection against excitotoxic insults (AMPA or oxygen and glucose deprivation) in rat organotypic hippocampal slices, with particular attention on glutamate receptors and on cannabinoid system. We firstly evaluated the protein expression of NMDA and AMPA receptor subunits after preconditioning using western blot analysis performed in post-synaptic densities. We observed that following NMDA, but not DHPG preconditioning, the expression of GluA1 was significantly reduced and this reduction appeared to be associated with the internalization of AMPA receptors. Whole-cell voltage clamp recordings on CA1 pyramidal neurons of organotypic slices show that 24 hr after exposure to NMDA and DHPG preconditioning, AMPA-induced currents were significantly reduced. To clarify the mechanisms induced by DHPG preconditioning, we then investigated the involvement of the endocannabinoid system. Exposure of slices to the CB1 antagonist AM251 prevented the development of tolerance to AMPA toxicity induced by DHPG but not NMDA. Accordingly, the MAG-lipase inhibitor URB602, that increases arachidonoylglycerol (2-AG) content, but not the FAAH inhibitor URB597, that limits the degradation of anandamide, was also able to induce tolerance versus AMPA and OGD toxicity, suggesting that 2-AG is responsible for the DHPG-induced tolerance. In conclusion, preconditioning with NMDA or DHPG promotes differential neuroprotective mechanisms: NMDA by internalization of GluA1-AMPA receptors, DHPG by producing the endocannabinoid 2-AG.

Effects of Hypoxic and Ischemic Clinical Conditions on the Outcomes of Acute Ischemic Stroke Patients

Background

Several studies have shown the neuroprotective role afforded by hypoxic and ischemic preconditioning in cerebrovascular disorders. There are several clinical conditions which simulate the hypoxic and ischemic conditioning in humans. The aim of this retrospective study is to identify whether the presence of any clinical scenarios mimicking the hypoxic and ischemic conditions prior to the current acute ischemic stroke (AIS) has a neuroprotective role in these patients.

Materials and methods

Data were collected for patients >18 years of age who underwent endovascular treatment for AIS from January 2009 to June 2015. A good outcome was defined as modified Rankin score (mRS) of 0 to 3 at discharge and a poor outcome as mRS of 4-6. A logistic regression analysis was performed to identify independent predictors of outcomes at discharge in both groups. A p value of <0.05 was considered statistically significant for all analyses.

Results

A total of 102 patients, aged 67 ± 16 years with median preprocedural National Institute of Health Stroke Scale (NIHSS) score 17.5 (1-36), were included. Twenty-one (21%) patients had a good outcome (mRS: 0-3) and 81 (79%) had a poor outcome (mRS: 4-6). A logistic regression analysis identified higher NIHSS score [odds ratio (OR): 1.251, confidence interval (CI): 1.11-1.40, p = 0.0002] and history of transient ischemic attack (TIA; OR: 7.881, CI: 1.05-21.01, p < 0.04) as predictors of a poor outcome at discharge.

Conclusion

Our data suggest that the occurrence of TIA preceding an AIS may be associated with the poor outcomes in patients with AIS, although this finding needs confirmation in larger studies.

How to cite this article

Athiraman U, Tempelhoff R, Karanikolas M. Effects of Hypoxic and Ischemic Clinical Conditions on the Outcomes of Acute Ischemic Stroke Patients. Indian J Crit Care Med 2020;24(2):104-108.

Potential Neuroprotective Treatment of Stroke: Targeting Excitotoxicity, Oxidative Stress, and Inflammation

Stroke is a major cause of death and adult disability. However, therapeutic options remain limited. Numerous pathways underlie acute responses of brain tissue to stroke. Early events following ischemic damage include reactive oxygen species (ROS)-mediated oxidative stress and glutamate-induced excitotoxicity, both of which contribute to rapid cell death within the infarct core. A subsequent cascade of inflammatory events escalates damage progression. This review explores potential neuroprotective strategies for targeting key steps in the cascade of ischemia–reperfusion (I/R) injury. NADPH oxidase (NOX) inhibitors and several drugs currently approved by the U.S. Food and Drug Administration including glucose-lowering agents, antibiotics, and immunomodulators, have shown promise in the treatment of stroke in both animal experiments and clinical trials. Ischemic conditioning, a phenomenon by which one or more cycles of a short period of sublethal ischemia to an organ or tissue protects against subsequent ischemic events in another organ, may be another potential neuroprotective strategy for the treatment of stroke by targeting key steps in the I/R injury cascade.

The AAA + ATPase Thorase is neuroprotective against ischemic injury

Neuronal preconditioning in vitro or in vivo with a stressful but non-lethal stimulus leads to new protein expression that mediates a profound neuroprotection against glutamate excitotoxicity and experimental stroke. The proteins that mediate neuroprotection are relatively unknown and under discovery. Here we find that the expression of the AAA + ATPase Thorase is induced by preconditioning stimulation both in vitro and in vivo. Thorase provides neuroprotection in an ATP-dependent manner against oxygen-glucose deprivation (OGD) neurotoxicity or glutamate N-Methyl-D-aspartate (NMDA) receptor-mediated excitotoxicity in vitro. Knock-down of Thorase prevents the establishment of preconditioning induced neuroprotection against OGD or NMDA neurotoxicity. Transgenic overexpression of Thorase provides neuroprotection in vivo against middle cerebral artery occlusion (MCAO)-induced stroke in mice, while genetic deletion of Thorase results in increased injury in vivo following stroke. These results define Thorase as a neuroprotective protein and understanding Thorase signaling could offer a new therapeutic strategy for the treatment of neurologic disorders.

The effect of repeated remote ischemic postconditioning on infarct size in patients with an ischemic stroke (REPOST): study protocol for a randomized clinical trial

Background

Remote ischemic postconditioning (rIPostC) refers to the observation that repeated, short periods of ischemia protect remote areas against tissue damage during and after prolonged ischemia. Based on previous observations of a potential neuroprotective effect of rIPostC, the aim of this study is to evaluate whether repeated rIPostC after an ischemic stroke can reduce infarct size, which could be translated to an improvement in clinical outcomes.

Methods/design

We will enroll 200 ischemic stroke patients to daily rIPostC or sham conditioning during hospitalization into a randomized single-blind placebo-controlled trial. The intervention consists of twice daily exposure to four cycles of 5-min cuff inflation around the upper arm to > 20 mmHg above systolic blood pressure (i.e., rIPostC) or 50 mmHg (i.e., control), followed by 5 minutes of deflation. The primary outcome is infarct size, measured using an MRI diffusion-weighted image at the end of hospitalization. Secondary outcomes include the Modified Rankin Scale, National Institutes of Health Stroke Scale, quality of life, and cardiovascular and cerebrovascular morbidity and mortality. To explore possible underlying mechanisms of rIPostC, venous blood will be sampled to assess biomarkers of inflammation and vascular health.

Discussion

Previous studies in animals and humans, using a single bout of remote ischemic conditioning, report a potential effect of rIPostC in attenuating neural damage. Although repeated rIPostC has been investigated for cardiovascular disease patients and preclinical stroke models, no previous study has explored the potential physiological and clinical effects of repeatedly applying rIPostC during the hospitalization phase after a stroke.

Trial registration

Netherlands Trial Register, NTR6880. Registered on 8 December 2017.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3264-0) contains supplementary material, which is available to authorized users.

Two weeks of ischemic conditioning improves walking speed and reduces neuromuscular fatigability in chronic stroke survivors

This pilot study examined whether ischemic conditioning (IC), a noninvasive, cost-effective, and easy-to-administer intervention, could improve gait speed and paretic leg muscle function in stroke survivors. We hypothesized that 2 wk of IC training would increase self-selected walking speed, increase paretic muscle strength, and reduce neuromuscular fatigability in chronic stroke survivors. Twenty-two chronic stroke survivors received either IC or IC Sham on their paretic leg every other day for 2 wk (7 total sessions). IC involved 5-min bouts of ischemia, repeated five times, using a cuff inflated to 225 mmHg on the paretic thigh. For IC Sham, the cuff inflation pressure was 10 mmHg. Self-selected walking speed was assessed using the 10-m walk test, and paretic leg knee extensor strength and fatigability were assessed using a Biodex dynamometer. Self-selected walking speed increased in the IC group (0.86 ± 0.21 m/s pretest vs. 1.04 ± 0.22 m/s posttest, means ± SD; P < 0.001) but not in the IC Sham group (0.92 ± 0.47 m/s pretest vs. 0.96 ± 0.46 m/s posttest; P = 0.25). Paretic leg maximum voluntary contractions were unchanged in both groups (103 ± 57 N·m pre-IC vs. 109 ± 65 N·m post-IC; 103 ± 59 N·m pre-IC Sham vs. 108 ± 67 N·m post-IC Sham; P = 0.81); however, participants in the IC group maintained a submaximal isometric contraction longer than participants in the IC Sham group (278 ± 163 s pre-IC vs. 496 ± 313 s post-IC, P = 0.004; 397 ± 203 s pre-IC Sham vs. 355 ± 195 s post-IC Sham; P = 0.46). The results from this pilot study thus indicate that IC training has the potential to improve walking speed and paretic muscle fatigue resistance poststroke. NEW & NOTEWORTHY This pilot study is the first to demonstrate that ischemic conditioning can improve self-selected walking speed and reduce paretic muscle fatigue in stroke survivors. Ischemic conditioning has been shown to be safe in numerous patient populations, can be accomplished at home or at the bedside in only 45 min, and requires no specialized training. Future larger studies are warranted to determine the efficacy of ischemic conditioning as a neurorehabilitation therapy poststroke.

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

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

Intracranial atherosclerotic disease

Intracranial atherosclerosis (ICAS) is a progressive pathological process that causes progressive stenosis and cerebral hypoperfusion and is a major cause of stroke occurrence and recurrence around the world. Multiple factors contribute to the development of ICAS. Angiography imaging techniques can improve the diagnosis of and the selection of appropriate treatment regimens for ICAS. Neither aggressive medication nor endovascular interventions can eradicate stroke recurrence in patients with ICAS. Non-pharmacological therapies such as remote ischemic conditioning and hypothermia are emerging. Comprehensive therapy with medication in combination with endovascular intervention and/or non-pharmacological treatment may be a potential strategy for ICAS treatment in the future. We summarized the epidemiology, pathophysiological mechanisms, risk factors, biomarkers, imaging and management of ICAS.

Metabolomic Profiling Reveals That Reprogramming of Cerebral Glucose Metabolism Is Involved in Ischemic Preconditioning-Induced Neuroprotection in a Rodent Model of Ischemic Stroke

Ischemic tolerance renders the brain resistant to ischemia-reperfusion (I/R) injury as a result of the activation of endogenous adaptive responses triggered by various types of preconditioning. The complex underlying metabolic mechanisms responsible for the neuroprotection of cerebral ischemic preconditioning (IPC) remain elusive. Herein, gas chromatography-mass spectrometry (GC-MS) technique was applied to delineate the dynamic changes of brain metabolome in a rodent model of ischemic stroke (transient occlusion of the middle cerebral artery, tMCAO), alone or after pretreatment with nonlethal ischemic tolerance induction (transient occlusion of the bilateral common carotid arteries, tBCCAO). Metabolomic analysis showed that accumulation of glucose (concentration increased more than 4 fold) and glycolytic intermediates is the prominent feature of brain I/R-induced metabolic disturbance. IPC attenuated brain I/R damage by subduing postischemic hyperglycolysis, increasing the pentose phosphate pathway (PPP) flux and promoting the utilization of β-hydroxybutyrate. The expression analysis of pivotal genes and proteins involved in relevant metabolic pathways revealed that the downregulation of AMP-activated protein kinase (AMPK)-mediated glucose transporter-1 (GLUT-1) and 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 (PFKFB3) and reduced mRNA levels of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) subunits were associated with IPC-induced metabolic flexibility, which allows the brain to be more capable of withstanding severe I/R insults. The present study provided mechanistic insights into the metabolic signature of IPC and indicated that adaptively modulating brain glucose metabolism could be an effective approach for the therapeutic intervention of ischemic stroke.

A high risk of sleep apnea is associated with less postoperative cognitive dysfunction after intravenous anesthesia: results of an observational pilot study

Background

The obstructive sleep apnea syndrome (OSAS) is characterized by temporary cerebral hypoxia which can cause cognitive dysfunction. On the other hand, hypoxia induced neurocognitive deficits are detectable after general anesthesia.

The objective of this study was to evaluate the impact of a high risk of OSAS on the postoperative cognitive dysfunction after intravenous anesthesia.

Methods

In this single center trial between June 2012 and June 2013 43 patients aged 55 to 80 years with an estimated hospital stay of at least 3 days undergoing surgery were enrolled. Patients were screened for a high risk of OSAS using the STOP-BANG test. The cognitive function was assessed using a neuropsychological test battery, including the DemTect test for cognitive impairment and the RMBT test for memory, the day before surgery and within 36 h after extubation.

Results

Twenty-two of the 43 analyzed patients were identified as patients with a high risk of OSAS. Preoperatively, OSAS patients showed a significant worse performance only for the DemTect (p = 0.0043). However, when comparing pre- and postoperative test results, the OSAS patients did not show a significant loss in any test but significantly improved in RMBT test, whereas the control group showed a significant worse performance in three of eight tests. In five tests, we found a significant difference between the two groups with respect to the change from pre- to postoperative cognitive function.

Conclusion

Patients with a high risk of OSAS showed a less impairment of memory function and work memory performance after intravenous anesthesia. This might be explained by a beneficial effect of intrinsic hypoxic preconditioning in these patients.

Remote Limb Ischemic Conditioning and Motor Learning: Evaluation of Factors Influencing Response in Older Adults

Remote limb ischemic conditioning (RLIC) is a clinically feasible method of promoting tissue protection against subsequent ischemic insult. Recent findings from our lab demonstrated that RLIC robustly enhances motor learning in young, healthy humans. The next step is to determine which individuals would receive maximum benefit from RLIC before applying these findings to clinical rehabilitation populations such as stroke. Numerous factors, such as age, sex, body mass index (BMI), and cardiovascular comorbidities may influence the response. Sixty-nine participants aged 40-80 were randomized to receive either RLIC (n = 33) or sham (n = 36) conditioning. Participants underwent seven consecutive sessions consisting of RLIC or sham conditioning with a blood pressure cuff on the upper extremity and motor training on a stability platform balance task, with two follow-up sessions. Balance change (post-test-pre-test) was compared across participants, groups, and the factors of age, sex, BMI, and comorbidities. Participants in both groups improved their performance on the balance task from pre- to post-test. Overall balance change was independently associated with age and BMI. There was no difference in balance change between RLIC and Sham groups. However, RLIC significantly enhanced balance performance in participants with no comorbidities. Compared with our previous study in young adults, middle-aged and older adults demonstrated smaller improvements on the balance task. RLIC enhanced learning in middle-aged and older adults only in the absence of pre-defined comorbidities. RLIC may be a promising tool for enhancing motor recovery, but the accumulation of comorbidity with age may decrease its effectiveness.

RLIPostC protects against cerebral ischemia through improved synaptogenesis in rats

OBJECTIVE

Remote limb ischemic post-conditioning (RLIPostC) has been shown to be neuroprotective in cerebral ischemia, whereas the effect of RLIPostC on synaptogenesis remains elusive. In the present study, we investigated the effects of RLIPostC on synaptogenesis in an experimental stroke rat model.

METHODS

Sprague-Dawley rats were subjected to left middle cerebral artery occlusion (MCAO) and were randomly divided into a control group, an RLIPostC group and a sham group. The RLIPostC group received three cycles of RLIPostC treatment immediately after reperfusion (ten minutes ischemia and ten minutes reperfusion in bilateral femoral artery). The neurological function was assessed by neurological deficit scores and the foot fault test at days 7 and 14 after MCAO. At day 14 after MCAO, the infarct volume and oedema were determined by cresyl violet (CV) staining and by measuring brain water content, respectively. Synaptogenesis was evaluated by western blotting and immunofluorescence staining.

RESULTS

Our results showed that RLIPostC treatment significantly promoted the recovery of behavioural function, reduced infarct volume and brain oedema, and increased the expressions of SYN1, PSD95 and GAP43.

CONCLUSIONS

These results confirmed that RLIPostC treatment for cerebral ischemia was safe and effective. A possible molecular mechanism of the beneficial effects of RLIPostC treatment may be the promotion of synaptogenesis.