Experimental animal models and inflammatory cellular changes in cerebral ischemic and hemorrhagic stroke

Impact of Ambient Air Pollution with PM2.5 on Stroke Occurrence: Data from Kaunas (Lithuania) Stroke Register (2010–2022)

Background: Ambient particulate matter of ≤2.5 μm in diameter (PM2.5) is named as a risk factor for cerebrovascular diseases. This investigation aimed to evaluate the impact of ambient air pollution with PM2.5 on stroke occurrence. Methods: The study was performed in Kaunas, Lithuania, from 2010 to 2022. The daily numbers of ISs, subarachnoid hemorrhages (SAHs), and intracerebral hemorrhages (ICHs) were obtained from the Kaunas Stroke Register. The association between stroke occurrence and PM2.5 exposure was assessed by time- and seasonally stratified Poisson regression. Results: Among middle-aged persons, 3377 had a stroke, of which 2686 (79.5%) had an IS, 469 (13.9%) had an ICH, and 222 (6.6%) had SAH. The relative risk (RR) of SAH was increased by 1.7% with an increase in daily PM2.5 by 1 μg/m3 on the same day and at a lag of 1 day, and by 2.2% with an increase in mean PM2.5 concentration at a lag 0–1 days by 1 μg/m3. The RR of having a SAH was increased by 0.7% with an increase in daily PM2.5 by 1 μg/m3 on the same day. Conclusions: Significant associations between stroke occurrence and air pollution with PM2.5 were found in the SAH and HS patients, and only in middle-aged subjects.

The Promising Key Factors Mediating Secondary Neuronal Damage in the Perihematomal Region of Intracerebellar Hemorrhage of Mice

ABSTRACT

The underlying mechanisms of secondary neuronal damage following intracerebellar hemorrhage (ICbH) have not yet been clearly understood. Our previous study reported apoptotic neuronal damage in the perihematomal region (PH) in mice. However, the possible key factors causing secondary neuronal damage in ICbH are not yet known. Therefore, we aimed to study the vital factors in the mediation of secondary neuronal damage following ICbH induced by collagenase type VII (0.4 U/μL of saline) into the cerebellum of mice. The mice were grouped into four groups: (1) control group ( n = 12), (2) day-1 group ( n = 12), (3) day-3 group ( n = 12), and (4) day-7 group ( n = 12). All mice underwent behavior assessment following induction of ICbH and were subsequently sacrificed on days 1, 3, and 7. Perihaematoma samples were collected to study morphological changes, immunohistochemistry, nitric oxide (NO) estimation, and oxidative stress markers, respectively. Mouse behavior was disturbed following ICbH on days 3 and 7 compared to the control. In addition, neuronal damage was found in the PH region. Glial fibrillary acidic protein (GFAP) and excitatory amino acid transporter 1 (EAAT1) were highly expressed on day 7, while gamma-aminobutyric acid receptor subunit alpha-1 (GABA A α1)-containing receptor subunit was detected on days 1 and 3. NO increased on day 1 post-induction and decreased on days 3 and 7. The expressions of superoxide dismutase (SOD), catalase (CAT), neuronal nitric oxide synthases (nNOSs), glutathione peroxidase 1, and cyclooxygenase-2 (COX-2) were significantly increased on day 3. Morphological studies of the PH and tissue showed that neuronal damage occurred from day 1 onward and peaked on day 3, associated with alterations in NO, reactive astrocytes (GFAP), glutamate transport regulation (EAAT1), and GABA receptor. Briefly, significant changes in the key markers in the PH regions at different time points are possibly crucial factors facilitating secondary neuronal damage in the PH region. Identifying the time window of these vital changes could help prevent secondary damage and optimize the treatment to occur at proper time points.

Systemic immune inflammation index and risk of stroke: a cross-sectional study of the National Health and Nutrition Examination Survey 2005-2018

Background

The incidence of stroke has increased globally, resulting in medical expenditures and social burdens over the past few decades. We aimed to explore the relationship between systemic immune inflammatory index (SII) and stroke using the National Health and Nutrition Examination Survey (NHANES) from 2005 to 2018.

Methods

Based on NHANES data, 902 stroke patients and 27,364 non-stroke patients were included in this study. SII was the independent variable and stroke was the dependent variable. Univariate and multivariate logistic regression analyses were used to explore the association between SII and stroke. Restricted cubic spline (RCS) method was used to test the nonlinear association between SII and stroke.

Results

Weighted logistic regression analysis showed a significant association between SII and stroke (OR: 1.985, 95% CI: 1.245-3.166, p = 0.004). The interaction test showed that the association between SII and stroke was not significant between strata (p > 0.05). A significant positive association between SII and stroke risk (OR >1, p < 0.05) was observed in the crude model, model I and model II. RCS analysis showed no nonlinear positive association between SII and stroke risk after adjusting for all confounders.

Conclusion

Our study determined that SII is associated with stroke risk. Given the inherent limitations of cross-sectional studies, further research is necessary to validate the causality of this association and to demystify the underlying mechanisms between inflammation and stroke.

Nrdp1-mediated Macrophage Phenotypic Regulation Promotes Functional Recovery in Mice with Mild Neurological Impairment after Intracerebral Hemorrhage

Neuregulin receptor degradation protein 1 (Nrdp1) is a ring finger E3 ubiquitin ligase involved in some inflammation through ubiquitination, including macrophage polarization following cerebral hemorrhage. However, there is limited understanding regarding the mechanisms through which Nrdp1 modulates macrophage polarization and the potential impact of this modulation on neurological function. Using stereotactic injection and adenoviral transfection techniques, the corresponding animal models were constructed through injecting adenovirus, saline, or blood into the mouse striatum at different periods of time in this research. The alteration in the ratio of various M1/M2 phenotype-associated markers (e.g., CD86, CD206, IL-6, IL-10, etc.) was evaluated through immunohistochemistry, immunofluorescence, western blotting, and elisa assays. Additionally, neurological function scores and behavioral tests were utilized to evaluate changes in neurological function in mice after cerebral hemorrhage. Our results show that overexpression of Nrdp1 promotes the expression of a variety of M2 macrophage-associated markers and enhance transcriptional activity of arginase-1 (Arg1) protein through ubiquitination for early regulation M2 macrophage polarization. Additionally, Nrdp1 promotes hematoma absorption, increases IL-10 expression, inhibits inducible nitric oxide synthase (iNOS), IL-6, and TNF-α production, alleviates neurological impairment and brain edema, and accelerates functional recovery. These findings suggest that modulating macrophage polarization through Nrdp1 could be a therapeutic strategy for neurofunctional impairment in cerebral hemorrhage.

Microglia-neuron-vascular interactions in ischemia

Cerebral ischemia is a devastating condition that results in impaired blood flow in the brain leading to acute brain injury. As the most common form of stroke, occlusion of cerebral arteries leads to a characteristic sequence of pathophysiological changes in the brain tissue. The mechanisms involved, and comorbidities that determine outcome after an ischemic event appear to be highly heterogeneous. On their own, the processes leading to neuronal injury in the absence of sufficient blood supply to meet the metabolic demand of the cells are complex and manifest at different temporal and spatial scales. While the contribution of non-neuronal cells to stroke pathophysiology is increasingly recognized, recent data show that microglia, the main immune cells of the central nervous system parenchyma, play previously unrecognized roles in basic physiological processes beyond their inflammatory functions, which markedly change during ischemic conditions. In this review, we aim to discuss some of the known microglia-neuron-vascular interactions assumed to contribute to the acute and delayed pathologies after cerebral ischemia. Because the mechanisms of neuronal injury have been extensively discussed in several excellent previous reviews, here we focus on some recently explored pathways that may directly or indirectly shape neuronal injury through microglia-related actions. These discoveries suggest that modulating gliovascular processes in different forms of stroke and other neurological disorders might have presently unexplored therapeutic potential in combination with neuroprotective and flow restoration strategies.

Physiological and pathological functions of circular RNAs in the nervous system

Circular RNAs (circRNAs) are a class of covalently closed single-stranded RNAs that are expressed during the development of specific cells and tissues. CircRNAs play crucial roles in physiological and pathological processes by sponging microRNAs, modulating gene transcription, controlling the activity of certain RNA-binding proteins, and producing functional peptides. A key focus of research at present is the functionality of circRNAs in the nervous system and several advances have emerged over the last 2 years. However, the precise role of circRNAs in the nervous system has yet to be comprehensively reviewed. In this review, we first summarize the recently described roles of circRNAs in brain development, maturity, and aging. Then, we focus on the involvement of circRNAs in various diseases of the central nervous system, such as brain cancer, chronic neurodegenerative diseases, acute injuries of the nervous system, and neuropathic pain. A better understanding of the functionality of circRNAs will help us to develop potential diagnostic, prognostic, and therapeutic strategies to treat diseases of the nervous system.

Predictive value of serum β2-microglobulin in cardiac valve calcification in maintenance hemodialysis patients

Background

Cardiac valve calcification (CVC) is associated with adverse cardiovascular events. We studied the risk factors of CVC in maintenance hemodialysis (MHD) patients and the value of serum β2-microglobulin (β2-MG) levels in predicting the incidence of CVC. β2-MG is a middle molecular weight toxin. In recent years, researchers found that elevated blood β2-MG was associated with coronary, thoracic, and abdominal aortic calcifications with significant correlations. β2-MG has been emerging as a strong biomarker for cardiovascular mortality in uremic patients but its role in CVC is not well studied. This study looked specifically at CVC occurrence in relation to β2-MG for MHD patients.

Methods

Patients who underwent MHD for more than 3 months in the First People's Hospital of Nantong City from November 2012 to November 2019 with complete available data were included in the study. The patients were divided into the CVC group and the non-CVC group. The general information and clinical laboratory indicators of the patients were collected in a retrospective manner. We analyzed the risk factors for developing CVC in MHD patients using binary logistic regression method. Receiver operating characteristic (ROC) curves were used to calculate the cut-off value of β2-MG for predicting CVC. The decision tree (DT) method was used to classify and explore the probability of CVC in patients with MHD.

Results

The β2-MG in the CVC group was significantly higher than that in the non-CVC group (t=6.750, P<0.001). Multivariate binary logistic regression analysis showed that gender, age, serum β2-MG, and hemodialysis (HD) adequacy (Kt/V urea) were independent risk factors for CVC in MHD patients. ROC analysis showed that a β2-MG value of 25 µg/L was the best cut-off point for predicting CVC in MHD patients. According to binary logistic regression analysis, the β2-MG ≥25 µg/L group was 3.39 times more likely to develop CVC than the β2-MG <25 µg/L group [odds ratio (OR), 3.39; 95% confidence interval (CI), 1.63-7.06; P=0.001]. The DT model determined that serum β2-MG ≥25 µg/L and age >69 years were important determinants for predicting CVC in MHD patients.

Conclusions

Serum β2-MG in MHD patients has a positive correlation with the severity and occurrence of CVC.

TREM2, microglial and ischemic stroke

Ischemic stroke (IS) is a leading cause of morbidity and mortality worldwide. Immunity and inflammation are key factors in the pathophysiology of IS. The inflammatory response is involved in all stages of stroke, and microglia are the predominant cells involved in the post-stroke inflammatory response. Resident microglia are the main immune cells of the brain and the first line of defense of the nervous system. After IS, activated microglia can be both advantageous and detrimental to surrounding tissue; they can be divided into the harmful M1 types or the neuro-protective M2 type. Currently, with the latest progress of transcriptomics analysis, different and more complex phenotypes of microglia activation have been described, such as disease-related microglia (DAM) associated with Alzheimer's disease (AD), white matter associated microglia (WAMs) in aging, and stroke-related microglia (SAM) etc. The triggering receptor expressed on myeloid cell 2 (TREM2) is an immune-related receptor on the surface of microglia. Its expression increases after IS, which is related to microglial inflammation and phagocytosis, however, its relationship with the microglia phenotype is not clear. This paper reviews the following: 1) the phenotypic changes of microglia in various pathological stages after IS and its relationship with inflammatory factors; 2) the relationship between the expression of the TREM2 receptor and inflammatory factors; 3) the relationship between phenotypic changes of microglia and its surface receptor TREM2; 4) the TREM2-related signalling pathway of microglia after IS and treatment for TREM2 receptor; and finally 5) To clarify the relationship among TREM2, inflammation, and microglia phenotype after IS, as well as the mechanism among them and the some possible treatment of IS targeting TREM2. Moreover, the relationship between the new phenotype of microglia such as SAM and TREM2 has also been systematically summarized, but there are no relevant research reports on the relationship between TREM2 and SAM after IS.

Serum β2-microglobulin is closely associated with 3-month outcome of acute intracerebral hemorrhage: a retrospective cohort study

BACKGROUND

Intracerebral hemorrhage (ICH) is a frequent type of hemorrhagic stroke. Numerous studies have suggested that inflammation plays an important role in the injury and recovery of ICH. β2-microglobulin (β2M) is an inflammatory indicator with an unclear association with ICH development. This study aimed to explore the role of β2M in the outcome of patients with ICH after 3 months of ICH onset.

METHODS

The β2M and other baseline information of 231 patients with ICH were assessed (83 females and 148 males). We followed up with all patients 3 months after ICH onset, and severe disability or a worse outcome was our main focus. We collected the serum β2M levels, National Institutes of Health Stroke Scale (NIHSS) and modified Rankin scale (mRS) scores, and other relevant baseline information of each patient. We used multiple regression analysis to explore the association between β2M levels and follow-up outcomes.

RESULTS

Our results indicated that the β2M level of the good outcome (2.35 ± 0.84 mg/l) group was significantly lower than that of the poor outcome group (3.06 ± 1.71 mg/l) (P < 0.001). Further multiple regression analysis showed that β2M was regarded as a risk factor that was closely associated with the poor outcome 3 months after ICH onset (odds ratio = 2.26, 95% confidence interval = 1.22-4.19, P = 0.009). Further correlation analysis revealed that β2M was significantly correlated with NIHSS scores (r = 0.187, P = 0.004) and follow-up mRS scores (r = 0.25, P < 0.001).

CONCLUSION

β2M was a risk factor for early outcome after ICH onset, and high β2M level was associated with short-time poor prognosis of ICH patients.

Mechanical digit sensory stimulation: a randomized control trial on neurological and motor recovery in acute stroke

Background

Mechanical digit sensory stimulation (MDSS) is a novel therapy designed to accelerate the recovery of upper limb (including hand) function in patients with hemiplegia following a stroke. The primary goal of this study was to investigate the effect of MDSS on patients with acute ischemic stroke (AIS).

Methods

Sixty-one inpatients with AIS were randomly divided into conventional rehabilitation group (RG) and stimulation group (SG), and the latter group received MDSS therapy. A healthy group consisting of 30 healthy adults was also included. The interleukin-17A (IL-17A), vascular endothelial growth factor A (VEGF-A), and tumor necrosis factor-alpha (TNF-α) plasma levels were measured in all subjects. The neurological and motor functions of patients were evaluated using the National Institutes of Health Stroke Scale (NIHSS), Mini-Mental State Examination (MMSE), Fugel-Meyer Assessment (FMA), and Modified Barthel Index (MBI).

Results

After 12 days of intervention, the IL-17A, TNF-α, and NIHSS levels were significantly decreased, while the VEGF-A, MMSE, FMA, and MBI levels were significantly increased in both disease groups. No significant difference was observed between both disease groups after intervention. The levels of IL-17A and TNF-α were positively correlated with NIHSS but negatively correlated with MMSE, FMA, and MBI. The VEGF-A levels were negatively correlated with NIHSS but positively correlated with MMSE, FMA, and MBI.

Conclusion

Both MDSS and conventional rehabilitation significantly reduce the production of IL-17A and TNF-α, increase the VEGF-A levels, and effectively improve cognition and motor function of hemiplegic patients with AIS, and the effects of MDSS and conventional rehabilitation are comparable.

The Implications of Microglial Regulation in Neuroplasticity-Dependent Stroke Recovery

Stroke causes varying degrees of neurological deficits, leading to corresponding dysfunctions. There are different therapeutic principles for each stage of pathological development. Neuroprotection is the main treatment in the acute phase, and functional recovery becomes primary in the subacute and chronic phases. Neuroplasticity is considered the basis of functional restoration and neurological rehabilitation after stroke, including the remodeling of dendrites and dendritic spines, axonal sprouting, myelin regeneration, synapse shaping, and neurogenesis. Spatiotemporal development affects the spontaneous rewiring of neural circuits and brain networks. Microglia are resident immune cells in the brain that contribute to homeostasis under physiological conditions. Microglia are activated immediately after stroke, and phenotypic polarization changes and phagocytic function are crucial for regulating focal and global brain inflammation and neurological recovery. We have previously shown that the development of neuroplasticity is spatiotemporally consistent with microglial activation, suggesting that microglia may have a profound impact on neuroplasticity after stroke and may be a key therapeutic target for post-stroke rehabilitation. In this review, we explore the impact of neuroplasticity on post-stroke restoration as well as the functions and mechanisms of microglial activation, polarization, and phagocytosis. This is followed by a summary of microglia-targeted rehabilitative interventions that influence neuroplasticity and promote stroke recovery.

Exosomes-based therapy of stroke, an emerging approach toward recovery

Based on clinical observations, stroke is touted as one of the specific pathological conditions, affecting an individual’s life worldwide. So far, no effective treatment has been introduced to deal with stroke post-complications. Production and release of several neurotrophic factors by different cells exert positive effects on ischemic areas following stroke. As a correlate, basic and clinical studies have focused on the development and discovery of de novo modalities to introduce these factors timely and in appropriate doses into the affected areas. Exosomes (Exo) are non-sized vesicles released from many cells during pathological and physiological conditions and participate in intercellular communication. These particles transfer several arrays of signaling molecules, like several neurotrophic factors into the acceptor cells and induce specific signaling cascades in the favor of cell bioactivity. This review aimed to highlight the emerging role of exosomes as a therapeutic approach in the regeneration of ischemic areas.

A Review on Preclinical Models of Ischemic Stroke: Insights Into the Pathomechanisms and New Treatment Strategies

BACKGROUND

Stroke is a serious neurovascular problem and the leading cause of disability and death worldwide. The disrupted demand to supply ratio of blood and glucose during cerebral ischemia develops hypoxic shock, and subsequently necrotic neuronal death in the affected regions. Multiple causal factors like age, sex, race, genetics, diet, and lifestyle play an important role in the occurrence as well as progression of post-stroke deleterious events. These biological and environmental factors may be contributed to vasculature variable architecture and abnormal neuronal activity. Since recombinant tissue plasminogen activator is the only clinically effective clot bursting drug, there is a huge unmet medical need for newer therapies for the treatment of stroke. Innumerous therapeutic interventions have shown promise in the experimental models of stroke but failed to translate it into clinical counterparts.

METHODS

Original publications regarding pathophysiology, preclinical experimental models, new targets and therapies targeting ischemic stroke have been reviewed since the 1970s.

RESULTS

We highlighted the critical underlying pathophysiological mechanisms of cerebral stroke and preclinical stroke models. We discuss the strengths and caveats of widely used ischemic stroke models, and commented on the potential translational problems. We also describe the new emerging treatment strategies, including stem cell therapy, neurotrophic factors and gut microbiome-based therapy for the management of post-stroke consequences.

CONCLUSION

There are still many inter-linked pathophysiological alterations with regards to stroke, animal models need not necessarily mimic the same conditions of stroke pathology and newer targets and therapies are the need of the hour in stroke research.

Changes and roles of IL-17A, VEGF-A and TNF-α in patients with cerebral infarction during the acute phase and early stage of recovery

BACKGROUND AND PURPOSE

Interleukin 17A (IL-17A), vascular endothelial growth factor A (VEGF-A) and tumour necrosis factor alpha (TNF-α) are important cytokines detected mostly within two weeks after stroke in previous clinical studies. Longer clinical studies investigating these cytokines are lacking. We aimed to explore the roles of these cytokines in patients within 35 days after cerebral infarction.

METHODS

Thirty patients with cerebral infarction and 30 healthy individuals were enrolled. Venous blood was collected from each patient at specific times and from each healthy individual only once. Coma and neurological functional deficits of the patients were evaluated by the Glasgow Coma Scale (GCS) and the National Institutes of Health Stroke Scale (NIHSS), respectively. Three cytokines were measured. The correlations among the three cytokines and between each cytokine and the GCS/NIHSS scores were analysed.

RESULTS

IL-17A and TNF-α began to increase on day 1 after cerebral infarction, peaked on day 4, then decreased, and increased again on day 18. IL-17A returned to normal on day 35, but TNF-α remained higher than normal on day 35. VEGF-A began to increase on day 1, peaked on day 7, and returned to normal on day 35. From days 18 to 35, IL-17A was positively correlated with the GCS scores, and both IL-17A and VEGF-A were negatively correlated with the NIHSS scores.

CONCLUSION

After cerebral infarction, VEGF-A from the acute phase and IL-17A from the early stage of recovery may be important for nerve protection and repair; TNF-α plays a complex role within 35 days.

Metabolic Changes Induced by Cerebral Ischemia, the Effect of Ischemic Preconditioning, and Hyperhomocysteinemia

1H Nuclear Magnetic Resonance (NMR) metabolomics is one of the fundamental tools in the fast-developing metabolomics field. It identifies and quantifies the most abundant metabolites, alterations of which can describe energy metabolism, activated immune response, protein synthesis and catabolism, neurotransmission, and many other factors. This paper summarizes our results of the 1H NMR metabolomics approach to characterize the distribution of relevant metabolites and their alterations induced by cerebral ischemic injury or its combination with hyperhomocysteinemia in the affected tissue and blood plasma in rodents. A decrease in the neurotransmitter pool in the brain tissue likely follows the disordered feasibility of post-ischemic neurotransmission. This decline is balanced by the increased tissue glutamine level with the detected impact on neuronal health. The ischemic injury was also manifested in the metabolomic alterations in blood plasma with the decreased levels of glycolytic intermediates, as well as a post-ischemically induced ketosis-like state with increased plasma ketone bodies. As the 3-hydroxybutyrate can act as a likely neuroprotectant, its post-ischemic increase can suggest its supporting role in balancing ischemic metabolic dysregulation. Furthermore, the 1H NMR approach revealed post-ischemically increased 3-hydroxybutyrate in the remote organs, such as the liver and heart, as well as decreased myocardial glutamate. Ischemic preconditioning, as a proposed protective strategy, was manifested in a lower extent of metabolomic changes and/or their faster recovery in a longitudinal study. The paper also summarizes the pre- and post-ischemic metabolomic changes in the rat hyperhomocysteinemic models. Animals are challenged with hyperglycemia and ketosis-like state. A decrease in several amino acids in plasma follows the onset and progression of hippocampal neuropathology when combined with ischemic injury. The 1H NMR metabolomics approach also offers a high potential for metabolites in discriminatory analysis in the search for potential biomarkers of ischemic injury. Based on our results and the literature data, this paper presents valuable findings applicable in clinical studies and suggests the precaution of a high protein diet, especially foods which are high in Met content and low in B vitamins, in the possible risk of human cerebrovascular neuropathology.

Dodging blood brain barrier with "nano" warriors: Novel strategy against ischemic stroke

Ischemic stroke (IS) is one of the leading causes of death and disability resulting in inevitable burden globally. Ischemic injury initiates cascade of pathological events comprising energy dwindling, failure of ionic gradients, failure of blood brain barrier (BBB), vasogenic edema, calcium over accumulation, excitotoxicity, increased oxidative stress, mitochondrial dysfunction, inflammation and eventually cell death. In spite of such complexity of the disease, the only treatment approved by US Food and Drug Administration (FDA) is tissue plasminogen activator (t-PA). This therapy overcome blood deficiency in the brain along with side effects of reperfusion which are responsible for considerable tissue injury. Therefore, there is urgent need of novel therapeutic perspectives that can protect the integrity of BBB and salvageable brain tissue. Advancement in nanomedicine is empowering new approaches that are potent to improve the understanding and treatment of the IS. Herein, we focus nanomaterial mediated drug delivery systems (DDSs) and their role to bypass and cross BBB especially via intranasal drug delivery. The various nanocarriers used in DDSs are also discussed. In a nut shell, the objective is to provide an overview of use of nanomedicine in the diagnosis and treatment of IS to facilitate the research from benchtop to bedside.

Mitochondrial BKCa Mediates the Protective Effect of Low-Dose Ethanol Preconditioning on Oxygen-Glucose Deprivation and Reperfusion-Induced Neuronal Apoptosis

Ischemia-reperfusion (I/R) injury contributes to the morbidity and mortality of ischemic strokes. As an in vitro model, oxygen-glucose deprivation and reperfusion (OGD/R) exposure induces neuronal injury. Low-dose ethanol preconditioning (EtOH-PC) was reported to alleviate neuronal apoptosis during OGD/R. However, whether the mitochondrial BK_Ca (mitoBK_Ca) channel is involved in the neuroprotective effect of EtOH-PC during OGD/R is not clearly defined. This study attempts to explore the mediation of the mitoBK_Ca channel in the neuroprotective effect of EtOH-PC on OGD/R-induced neuronal apoptosis and the underlying mechanisms. OGD/R model was established using primary cortical neurons that were preincubated with ethanol. Subsequently, the cell viability was measured by CCK-8 assay, and the apoptotic cells were determined by TUNEL assay. Annexin V/7-AAD staining and mitochondrial membrane potential using JC-10 were detected by flow cytometry. Western blot analysis was performed to check the apoptosis-related proteins. In the mixed primary culture, 95% neurofilament-positive cells were cortical neurons. Low-dose EtOH-PC (10 mmol/L) for 24 h significantly attenuated the OGD2h/R24h-induced neuronal apoptosis through activating the BK_Ca channel. Further investigations suggested that ethanol pretreatment increased the mitochondrial membrane potential (MMP) and downregulated the production of cleaved caspase 3 in OGD/R-injured neurons by activating the mitoBK_Ca channel. Low-dose ethanol pretreatment significantly attenuated the OGD/R-induced neuronal apoptosis mediated by the mitoBK_Ca channel which modulated the mitochondrial function by impeding the uncontrolled opening of mitochondrial permeability transition pore (MPTP).

Nanomedicines, an emerging therapeutic regimen for treatment of ischemic cerebral stroke: A review

Owing to its intricate pathophysiology, cerebral stroke is a serious medical condition caused by interruption or obstruction of blood supply (blockage of vasculature) to the brain tissues which results in diminished supply of essential nutrients and oxygen (hypoxia) and ultimate necrosis of neuronal tissues. A prompt risks assessment and immediate rational therapeutic plan with proficient neuroprotection play critically important role in the effective management of this neuronal emergency. Various conventional medications are being used for treatment of acute ischemic cerebral stroke but fibrinolytic agents, alone or in combination with other agents are considered the mainstay. These clot-busting agents effectively restore blood supply (reperfusion) to ischemic regions of the brain; however, their clinical significance is hampered due to various factors such as short plasma half-life, limited distribution to brain tissues due to the presence of highly efficient physiological barrier, blood brain barrier (BBB), and lacking of target-specific delivery to the ischemic brain regions. To alleviate these issues, various types of nanomedicines such as polymeric nanoparticles (NPs), liposomes, nanoemulsion, micelles and dendrimers have been designed and evaluated. The implication of these newer therapies (nanomedicines) have revolutionized the therapeutic outcomes by improving the plasma half-life, permeation across BBB, efficient distribution to ischemic cerebral tissues and neuroprotection. Furthermore, the adaptation of some diverse techniques including PEGylation, tethering of targeting ligands on the surfaces of nanomedicines, and pH responsive features have also been pondered. The implication of these emerging adaptations have shown remarkable potential in maximizing the targeting efficiency of drugs to ischemic brain tissues, simultaneous delivery of drugs and imaging agents (for early prognosis as well as monitoring of therapy), and therapeutic outcomes such as long-term neuroprotection.

Inhibition of Perforin-Mediated Neurotoxicity Attenuates Neurological Deficits After Ischemic Stroke

Perforin-mediated cytotoxicity plays a crucial role in microbial defense, tumor surveillance, and primary autoimmune disorders. However, the contribution of the cytolytic protein perforin to ischemia-induced secondary tissue damage in the brain has not been fully investigated. Here, we examined the kinetics and subpopulations of perforin-positive cells and then evaluated the direct effects of perforin-mediated cytotoxicity on outcomes after ischemic stroke. Using flow cytometry, we showed that perforin⁺CD45⁺ immune cells could be detected at 12 h and that the percentage of these cells increased largely until on day 3 and then significantly declined on day 7. Surprisingly, the percentage of Perforin⁺CD45⁺ cells also unexpectedly increased from day 7 to day 14 after ischemic stroke in Perforin1-EGFP transgenic mice. Our results suggested that Perforin⁺CD45⁺ cells play vital roles in the ischemic brain at early and late stages and further suggested that Perforin⁺CD45⁺ cells are a heterogeneous population. Surprisingly, in addition to CD8⁺ T cells, NK cells, and NKT cells, central nervous system (CNS)-resident immune microglia, which are first triggered and activated within minutes after ischemic stroke in mice, also secreted perforin during ischemic brain injury. In our study, the percentage of perforin⁺ microglia increased from 12 h after ischemic stroke, increased largely until on day 3 after ischemic stroke, and then moderately declined from days 3 to 7. Intriguingly, the percentage of perforin⁺ microglia also dramatically increased from days 7 to 14 after ischemic stroke. Furthermore, compared with wild-type littermates, Perforin 1^-/- mice exhibited significant increases in the cerebral infarct volume, neurological deficits, and neurogenesis and inhibition of neurotoxic astrogliosis. Interestingly, the number of CD45⁺CD3⁺ T cells was significantly decreased in Perforin 1^-/- mice compared with their wild-type littermates, especially the number of γδ T cells. In addition, Perforin 1^-/- mice had lower levels of IL-17 than their wild-type littermates. Our results identified a critical function of perforin-mediated neurotoxicity in the ischemic brain, suggesting that targeting perforin-mediated neurotoxicity in brain-resident microglia and invading perforin⁺CD45⁺ immune cells may be a potential strategy for the treatment of ischemic stroke.

Integrated 16S rRNA Gene Sequencing and LC-MS Analysis Revealed the Interplay Between Gut Microbiota and Plasma Metabolites in Rats With Ischemic Stroke

Gut microbiome and plasma metabolome serve a role in the pathogenesis of ischemic stroke (IS). However, the relationship between the microbiota and metabolites remains unclear. This study aimed to reveal the specific asso-ciation between the microbiota and the metabolites in IS using integrated 16S rRNA gene sequencing and liquid chromatography-mass spectrometry (LC-MS) analysis. Male Sprague Dawley (SD) rats were divided into three groups: normal group (n = 8, Normal), model group (n = 9, IS), and sham-operated group (n = 8, Sham). Rats in the IS group were induced by middle cerebral artery occlusion (MCAO), and rats in the Sham group received an initial anesthesia and neck incision only. A neurological function test and 2,3,5-triphenyltetrazolium chloride (TTC) staining were used to assess the IS rat model. Then, the plasma samples were analyzed using untargeted LC-MS. The cecum samples were collected and analyzed using 16S rRNA sequencing. Pearson correlation analysis was performed to explore the association between the gut microbiota and the plasma metabolites. The 16S rRNA sequencing showed that the composition and diversity of the microbiota in the IS and control rats were significantly different. Compared with the Sham group, the abundance of the Firmicutes phylum was decreased, whereas Proteobacteria and Deferribacteres were increased in the IS group. Ruminococcus_sp_15975 and Lachnospiraceae_UCG_001 might be considered as biomarkers for the IS and Sham groups, respectively. LC-MS analysis revealed that many metabolites, such as L-leucine, L-valine, and L-phenylalanine, displayed different patterns between the IS and Sham groups. Pathway analysis indicated that these metabolites were mainly involved in mineral absorption and cholinergic synapse. Furthermore, integrated analysis correlated IS-related microbes with metabolites. For example, Proteobacteria were positively correlated with L-phenylalanine, while they were negatively correlated with eicosapentaenoic acid (EPA). Our results provided evidence of the relationship between the gut microbiome and plasma metabolome in IS, suggesting that these microflora-related metabolites might serve as potential diagnostic and therapeutic markers.

HTRA1 Variants and the Interaction with Smoking Confer the Genetic Susceptibility to Ischemic Stroke

High temperature requirement protein A1 (HtrA1) was identified as the causative gene of autosomal recessive arteriopathy and associated with lacunar ischemic stroke (IS) in European. This study aimed at evaluating the association of HTRA1 with IS and four tagging single-nucleotide polymorphisms (SNPs) were genotyped in a cohort of 4,098 Chinese. The mRNA level of HTRA1 in 72 IS cases and 72 hypertension controls were measured and compared. In whole population, SNP rs2268350 (C>T) was significantly associated with IS incidence (P=0.034). Stratification analysis observed significant association of rs2268350 in male, smoking and drinking populations, rs2672587 (C>G) in smoking and nonsmoking populations and rs3793917 (C>G) in smoking, nonsmoking and nondrinking populations with stroke respectively (P<0.05). The additive interaction and multiplicative interaction between rs2268350 and smoking were both of significant (P<0.05) after adjustment for the covariates. There was a cumulated risk of IS among genotypes of rs3793917 (P=0.009) and rs2672587 (P=0.047) in smoking population. The mRNA level of HTRA1 in non-smokers with rs2268350 CC was significantly higher than smokers with rs2268350 CT/TT (P=0.046) in IS cases. Our findings support that HTRA1 confers the genetic susceptibility to IS and smoking might modify the genetic effect of HTRA1 on IS by suppressing HTRA1 mRNA expression.

The Relationship between Age-Related Macular Degeneration and Cardiovascular Disease: A Meta-Analysis

Background:

Age-related macular degeneration (AMD) and cardiovascular disease (CVD) share pathogenic mechanisms, and their lead-lag relationship remains unclear. We performed a meta-analysis of data from longitudinal studies to evaluate the interactive association between age-related macular degeneration (AMD) and cardiovascular disease (CVD).

Methods:

A literature search was performed in PubMed, Embase, and Cochrane Library up to Feb 2019. Estimates were pooled by study quality and type of AMD and CVD. Publication bias was assessed by Begg’s test.

Results:

We identified nine studies for the risk of AMD in CVD and ten studies for the risk of CVD in AMD. Overall, evidence for the risk of CVD in AMD patients was most robust. Both early and late AMD preceded CVD, but more solid significance existed in late AMD. Among the types of CVD, stroke was more tightly associated with AMD than coronary heart disease. Publication bias was not significant in either direction.

Conclusion:

AMD is a risk factor for CVD, which is primarily driven by the increased risk of stroke in patients with late AMD. Moreover, these results suggested that AMD treatment and screening for CVD in AMD patients may have unexplored clinical benefits.

Filling the gaps on stroke research: Focus on inflammation and immunity

For the last two decades, researchers have placed hopes in a new era in which a combination of reperfusion and neuroprotection would revolutionize the treatment of stroke. Nevertheless, despite the thousands of papers available in the literature showing positive results in preclinical stroke models, randomized clinical trials have failed to show efficacy. It seems clear now that the existing data obtained in preclinical research have depicted an incomplete picture of stroke pathophysiology. In order to ameliorate bench-to-bed translation, in this review we first describe the main actors on stroke inflammatory and immune responses based on the available preclinical data, highlighting the fact that the link between leukocyte infiltration, lesion volume and neurological outcome remains unclear. We then describe what is known on neuroinflammation and immune responses in stroke patients, and summarize the results of the clinical trials on immunomodulatory drugs. In order to understand the gap between clinical trials and preclinical results on stroke, we discuss in detail the experimental results that served as the basis for the summarized clinical trials on immunomodulatory drugs, focusing on (i) experimental stroke models, (ii) the timing and selection of outcome measuring, (iii) alternative entry routes for leukocytes into the ischemic region, and (iv) factors affecting stroke outcome such as gender differences, ageing, comorbidities like hypertension and diabetes, obesity, tobacco, alcohol consumption and previous infections like Covid-19. We can do better for stroke treatment, especially when targeting inflammation following stroke. We need to re-think the design of stroke experimental setups, notably by (i) using clinically relevant models of stroke, (ii) including both radiological and neurological outcomes, (iii) performing long-term follow-up studies, (iv) conducting large-scale preclinical stroke trials, and (v) including stroke comorbidities in preclinical research.

Inflammatory Response of Ischemic Tolerance in Circulating Plasma: Preconditioning-Induced by Transient Ischemic Attack (TIA) Phenomena in Acute Ischemia Patients (AIS)

Introduction: Ischemic tolerance (IT) refers to a state where cells are resistant to the damaging effects caused by periods of ischemia. In a clinical scenario, the IT phenomenon would be activated by a recent transient ischemic attack (TIA) before an ischemic stroke (IS). The characterization of inflammatory protein expression patterns will contribute to improved understanding of IT.

Methods: A total of 477 IS patients from nine hospitals, recruited between January 2011 and January 2016, were included in the current study and divided in three groups: 438 (91.9%) patients without previous TIA (group 1), 22 (4.6%) patients who suffered TIA 24 h before IS (group 2), and 17 (3.5%) patients who suffered TIA between 24 h and 7 days prior to IS (group 3). An inflammatory biomarker panel (IL-6, NT-proBNP, hsCRP, hs-Troponin, NSE, and S-100b) on plasma and a cytokine antibody array was performed to achieve the preconditioning signature potentially induced by TIA phenomena. Primary outcome was modified rankin scale (mRs) score at 90 days.

Results: Recent previous TIA was associated with better clinical outcome at 90 days (median mRS of group 1: 2.0 [1.0–4.0]; group 2: 2.0 [0.0–3.0]; group 3: 1.0 [0–2.5]; p = 0.086) and smaller brain lesion (group 1: 3.7 [0.7–18.3]; group 2: 0.8 [0.3–8.9]; group 3: 0.6 [0.1–5.5] mL; p = 0.006). All inflammation biomarkers were down regulated in the groups of recent TIA prior to IS compared to those who did not suffer a TIA events. Moreover, a cytokine antibody array revealed 30 differentially expressed proteins between the three groups. Among them, HRG1-alpha (Fold change 74.4 between group 1 and 2; 74.2 between group 1 and 3) and MAC-1 (Fold change 0.05 between group 1 and 2; 0.06 between group 1 and 3) expression levels would better stratify patients with TIA 7 days before IS. These two proteins showed an earlier inflammation profile that was not detectable by the biomarker panel.

Conclusion: Inflammatory pathways were activated by transient ischemic attack, however the period of time between this event and a further ischemic stroke could be determined by a protein signature that would contribute to define the role of ischemic tolerance induced by TIA.

Protective effects of natural compounds against oxidative stress in ischemic diseases and cancers via activating the Nrf2 signaling pathway: A mini review

Oxidative stress, an imbalance between reactive oxygen species and antioxidants, has been seen in the pathological states of many disorders such as ischemic diseases and cancers. Many natural compounds (NCs) have long been recognized to ameliorate oxidative stress due to their inherent antioxidant activities. The modulation of oxidative stress by NCs via activating the Nrf2 signaling pathway is summarized in the review. Three NCs, ursolic acid, betulinic acid, and curcumin, and the mechanisms of their cytoprotective effects are investigated in myocardial ischemia, cerebral ischemia, skin cancer, and prostate cancer. To promote the therapeutic performance of NCs with poor water solubility, the formulation approach, such as the nano drug delivery system, is elaborated as well in this review.

Enhancing the Therapeutic Potential of Mesenchymal Stem Cells with the CRISPR-Cas System

Mesenchymal stem cells (MSCs), also known as multipotent mesenchymal stromal stem cells, are found in the perivascular space of several tissues. These cells have been subject of intense research in the last decade due to their low teratogenicity, as well as their ability to differentiate into mature cells and to secrete immunomodulatory and trophic factors. However, they usually promote only a modest benefit when transplanted in experimental disease models, one of the limitations for their clinical application. The CRISPR-Cas system, in turn, is highlighted as a simple and effective tool for genetic engineering. This system was tested in clinical trials over a relatively short period of time after establishing its applicability to the edition of the mammalian cell genome. Similar to the research evolution in MSCs, the CRISPR-Cas system demonstrated inconsistencies that limited its clinical application. In this review, we outline the evolution of MSC research and its applicability, and the progress of the CRISPR-Cas system from its discovery to the most recent clinical trials. We also propose perspectives on how the CRISPR-Cas system may improve the therapeutic potential of MSCs, making it more beneficial and long lasting.

The role of exosomes in stroke

Stroke is induced by a partial disruption of cerebral blood flow to the brain and is related to high morbidity and mortality. In the central nervous system, exosomes have been proven to exert neuroprotective effects, reducing brain damage following a stroke. This review was performed by searching the relevant articles in the SCIENCEDIRECT, PUBMED, and Web of Science databases from respective inception to November 2018. We review the relationship between exosomes and angiogenesis, neurogenesis, antiapoptosis, autophagy, and the blood-brain barrier in stroke. Moreover, exosomes are found to be a promising tool for the diagnosis and treatment of stroke. In summary, exosomes provide a novel way to alleviate brain damage following a stroke.

Detection of spreading depolarizations in a middle cerebral artery occlusion model in swine

BACKGROUND

The main objective of this study was to generate a hemodynamically stable swine model to detect spreading depolarizations (SDs) using electrocorticography (ECoG) and intrinsic optical signal (IOS) imaging and laser speckle flowmetry (LSF) after a 30-h middle cerebral artery (MCA) occlusion (MCAo) in German Landrace Swine.

METHODS

A total of 21 swine were used. The study comprised a training group (group 1, n = 7), a group that underwent bilateral craniectomy and MCAo (group 2, n = 10) and a group used for 2,3,5-triphenyltetrazolium (TTC) staining (group 3, n = 5).

RESULTS

In group 2, nine animals that underwent MCAo survived for 30 h, and one animal survived for 12 h. We detected MCA variants with 2 to 4 vessels. In all cases, all of the MCAs were occluded. The intensity changes exhibited by IOS and LSF after clipping were closely correlated and indicated a lower blood volume and reduced blood flow in the middle cerebral artery territory. Using IOS, we detected a mean of 2.37 ± (STD) 2.35 SDs/h. Using ECoG, we detected a mean of 0.29 ± (STD) 0.53 SDs/h. Infarctions were diagnosed using histological analysis. TTC staining in group 3 confirmed that the MCA territory was compromised and that the anterior and posterior cerebral arteries were preserved.

CONCLUSIONS

We confirm the reliability of performing live monitoring of cerebral infarctions using our MCAo protocol to detect SDs.

Serum β2-Microglobulin Is Closely Associated With the Recurrence Risk and 3-Month Outcome of Acute Ischemic Stroke

Background and Purpose: Inflammation plays a significant role in the pathogenesis of acute ischemic stroke (AIS). The role of β2-microglobulin (β2M) as a potential initiator of the inflammatory response in AIS is unclear. The purpose of this study was to analyze the relationship of serum β2M with the recurrence risk and 3-month outcome of AIS.

Methods: A total of 205 patients with AIS were recruited, and their clinical and biochemical characteristics were collected. All patients were followed up for 3 months after stroke onset, and the occurrence of death or major disability at 3 months after onset was the outcome of interest in this study. We evaluated the association of serum β2M levels with the National Institute of Health Stroke Scale (NIHSS) scores, modified Rankin Scale (mRS) scores, and Essen Stroke Risk Score (ESRS) values in patients with AIS. Then, we used receiver operating curve analysis to calculate the optimal cutoff value for discriminating outcomes in patients with AIS and a binary logistic regression model to evaluate the risk factors for a poor outcome after AIS.

Results: Our results showed that serum β2M levels were significantly and positively correlated with ESRS values (r = 0.176, P < 0.001) and mRS scores (r = 0.402, P < 0.001), but the levels of β2M were not correlated with NIHSS scores (r = 0.080, P = 0.255) or with infarct volume (r = 0.013, P = 0.859). In a further study, we found that 121 patients (59.02%) had poor outcomes. The optimal β2M cutoff to predict the 3-month outcome of AIS in this study was 1.865 mg/l, and β2M was independently associated with a poor outcome at 3 months (OR = 3.325, 95% confidence interval: 1.089~10.148).

Conclusions: In conclusion, we inferred that serum β2M was positively associated with the recurrence risk and 3-month outcome of AIS, but it did not appear to be directly related to the severity of AIS or the size of the infarct at admission.

Neuroinflammation as a target for treatment of stroke using mesenchymal stem cells and extracellular vesicles

Ischemic stroke is the third cause of death in the developed countries and the main reason of severe disability. Brain ischemia leads to the production of damage-associated molecular patterns (DAMPs) by neurons and glial cells which results in astrocyte and microglia activation, pro-inflammatory cytokines and chemokines production, blood-brain barrier (BBB) disruption, infiltration of leukocytes from the peripheral blood into the infarcted area, and further exacerbation of tissue damage. However, some immune cells such as microglia or monocytes are capable to change their phenotype to anti-inflammatory, produce anti-inflammatory cytokines, and protect injured nervous tissue. In this situation, therapies, which will modulate the immune response after brain ischemia, such as transplantation of mesenchymal stem cells (MSCs) are catching interest. Many experimental studies of ischemic stroke revealed that MSCs are able to modulate immune response and act neuroprotective, through stimulation of neurogenesis, oligodendrogenesis, astrogenesis, and angiogenesis. MSCs may also have an ability to replace injured cells, but the release of paracrine factors directly into the environment or via extracellular vesicles (EVs) seems to play the most pronounced role. EVs are membrane structures containing proteins, lipids, and nucleic acids, and they express similar properties as the cells from which they are derived. However, EVs have lower immunogenicity, do not express the risk of vessel blockage, and have the capacity to cross the blood-brain barrier. Experimental studies of ischemic stroke showed that EVs have immunomodulatory and neuroprotective properties; therefore, they can stimulate neurogenesis and angiogenesis. Up to now, 20 clinical trials with MSC transplantation into patients after stroke were performed, from which two concerned on only hemorrhagic stroke and 13 studied only on ischemic stroke. There is no clinical trial with EV injection into patients after brain ischemia so far, but the case with miR-124-enriched EVs administration is planned and probably there will be more clinical studies with EV transplantation in the near future.

Dual Functions of Microglia in Ischemic Stroke

Ischemic stroke is a leading cause of morbidity and mortality worldwide. Resident microglia are the principal immune cells of the brain, and the first to respond to the pathophysiological changes induced by ischemic stroke. Traditionally, it has been thought that microglial activation is deleterious in ischemic stroke, and therapies to suppress it have been intensively explored. However, increasing evidence suggests that microglial activation is also critical for neurogenesis, angiogenesis, and synaptic remodeling, thereby promoting functional recovery after cerebral ischemia. Here, we comprehensively review the dual role of microglia during the different phases of ischemic stroke, and the possible mechanisms controlling the post-ischemic activity of microglia. In addition, we discuss the dynamic interactions between microglia and other cells, such as neurons, astrocytes, oligodendrocytes, and endothelial cells within the brain parenchyma and the neurovascular unit.

Role of CSE-Produced H2S on Cerebrovascular Relaxation via RhoA-ROCK Inhibition and Cerebral Ischemia-Reperfusion Injury in Mice

The role of CSE-produced H₂S on cerebrovascular relaxation and cerebral ischemia-reperfusion (I/R) injury was investigated using CSE knockout (CSE^-/-) and wild-type (CSE^+/+) mice. The relaxation of the cerebral basilar artery (BA) to CSE-produced H₂S and its mechanism were detected. The results revealed that both NaHS, a donor of exogenous H₂S, and ROCK inhibitor Y27632 could induce significant relaxation of the BA, but the relaxation of the BA to NaHS was significantly attenuated by Y27632. In addition, removal of endothelium could reduce the relaxation of the BA to Y27632; CSE knockout also significantly attenuated Y27632-induced BA relaxation with endothelium rather than without endothelium. By contrast, the contraction of the BA from CSE^-/- mice to RhoA agonist LPA or U₄₆₆₁₉ was stronger than that from CSE^+/+ mice. Furthermore, RhoA activity and ROCK protein expression remarkably increased in the BA vascular smooth muscle cells (VSMCs) from CSE^-/- mouse, which were inhibited by NaHS pretreatment. These findings revealed that the CSE-produced H₂S induced cerebrovascular relaxation is generated from endothelial cells and the mechanism of vascular relaxation may relate to inhibition of RhoA-ROCK pathway. We next sought to confirm the protective effect of CSE-produced H₂S on cerebral I/R injury produced by middle cerebral artery occlusion and bilateral common carotid artery occlusion in mice. We investigated the changes of neurological deficit, cerebral infarct, brain water content, LDH decrease, MDA increase as well as impairment of learning and memory function. The results showed that the cerebral injury became more grievous in CSE^-/-mice than that in CSE^+/+mice, which could be remarkably alleviated by NaHS pretreatment.

Impact of C57BL/6 substrain on sex-dependent differences in mouse stroke models

We have recently found significant variation in stroke vulnerability among substrains of C57BL/6 mice, observing that commonly used N-lineage substrains exhibit larger infarcts than C57BL/6J and related substrains. Parallel variation was also seen with respect to sex differences in stroke vulnerability, in that C57BL/6 mice of the N-lineage exhibited comparable infarct sizes in males and females, whereas infarcts tended to be smaller in females than in males of J-lineage substrains. This adds to the growing list of recognized phenotypic and genetic differences among C57BL/6 substrains. Although no previous studies have explicitly compared substrains with respect to sex differences in stroke vulnerability, unrecognized background mismatch has occurred in some studies involving control and genetically modified mice. The aims of this review are to: present the evidence for associated substrain- and sex-dependent differences in a mouse permanent occlusion stroke model; examine the extent to which the published literature in other models compares with these recent results; and consider the potential impact of unrecognized heterogeneity in substrain background on the interpretation of studies investigating the impact of genetic modifications on sex differences in stroke outcome. Substrain emerges as a critical variable to be documented in any experimental stroke study in mice.

Executive (dys)function after stroke: special considerations for behavioral pharmacology

Stroke is a worldwide leading cause of death and long-term disability with concurrent secondary consequences that are largely comprised of mood dysfunction, as well as sensory, motor, and cognitive deficits. This review focuses on the cognitive deficits associated with stroke specific to executive dysfunction (including decision making, working memory, and cognitive flexibility) in humans, nonhuman primates, and additional animal models. Further, we review some of the cellular and molecular underpinnings of the individual components of executive dysfunction and their neuroanatomical substrates after stroke, with an emphasis on the changes that occur during biogenic monoamine neurotransmission. We concentrate primarily on changes in the catecholaminergic (dopaminergic and noradrenergic) and serotonergic systems at the levels of neurotransmitter synthesis, distribution, reuptake, and degradation. We also discuss potential secondary stroke-related behavioral deficits (specifically, poststroke depression as well as drug-abuse potential and addiction) and their relationship with stroke-induced deficits in executive function, an especially important consideration given that the average age of the human stroke population is decreasing. In the final sections, we address pharmacological considerations for the treatment of ischemia and the subsequent functional impairment, as well as current limitations in the field of stroke and executive function research.

Large animal models of stroke and traumatic brain injury as translational tools

Acute central nervous system injury, encompassing traumatic brain injury (TBI) and stroke, accounts for a significant burden of morbidity and mortality worldwide. Studies in animal models have greatly enhanced our understanding of the complex pathophysiology that underlies TBI and stroke and enabled the preclinical screening of over 1,000 novel therapeutic agents. Despite this, the translation of novel therapeutics from experimental models to clinical therapies has been extremely poor. One potential explanation for this poor clinical translation is the choice of experimental model, given that the majority of preclinical TBI and ischemic stroke studies have been conducted in small animals, such as rodents, which have small lissencephalic brains. However, the use of large animal species such as nonhuman primates, sheep, and pigs, which have large gyrencephalic human-like brains, may provide an avenue to improve clinical translation due to similarities in neuroanatomical structure when compared with widely adopted rodent models. This purpose of this review is to provide an overview of large animal models of TBI and ischemic stroke, including the surgical considerations, key benefits, and limitations of each approach.

The Role of Inflammatory Response in Stroke Associated Programmed Cell Death

Stroke represents devastating pathology which is associated with a high morbidity and mortality. Initial damage caused directly by the onset of stroke, primary injury, may be eclipsed by secondary injury which may have a much more devastating effect on the brain. Primary injury is predominantly associated with necrotic cell death due to fatal insufficiency of oxygen and glucose. Secondary injury may on the contrary, lead apoptotic cell death due to structural damage which is not compatible with cellular functions or which may even represent the danger of malign transformation. The immune system is responsible for surveillance, defense and healing processes and the immune system plays a major role in triggering programmed cell death. Severe pathologies, such as stroke, are often associated with deregulation of the immune system, resulting in aggravation of secondary brain injury. The goal of this article is to overview the current knowledge about the role of immune system in the pathophysiology of stroke with respect to programmed neuronal cell death as well as to discuss current therapeutic strategies targeting inflammation after stroke.

Infiltration and persistence of lymphocytes during late-stage cerebral ischemia in middle cerebral artery occlusion and photothrombotic stroke models

Background

Evidence suggests that brain infiltration of lymphocytes contributes to acute neural injury after cerebral ischemia. However, the spatio-temporal dynamics of brain-infiltrating lymphocytes during the late stage after cerebral ischemia remains unclear.

Methods

C57BL/6 (B6) mice were subjected to sham, photothrombosis, or 60-min transient middle cerebral artery occlusion (MCAO) procedures. Infarct volume, neurodeficits, production of reactive oxygen species (ROS) and inflammatory factors, brain-infiltrating lymphocytes, and their activation as well as pro-inflammatory cytokine IFN-γ production were assessed. Brain-infiltrating lymphocytes were also measured in tissue sections from post-mortem patients after ischemic stroke by immunostaining.

Results

In mice subjected to transient MCAO or photothrombotic stroke, we found that lymphocyte infiltration persists in the ischemic brain until at least day 14 after surgery, during which brain infarct volume significantly diminished. These brain-infiltrating lymphocytes express activation marker CD69 and produce proinflammatory cytokines such as IFN-γ, accompanied with a sustained increase of reactive oxygen species (ROS) and inflammatory cytokines release in the brain. In addition, brain-infiltrating lymphocytes were observed in post-mortem brain sections from patients during the late stage of ischemic stroke.

Conclusion

Our results demonstrate that brain-infiltration of lymphocytes persists after the acute stage of cerebral ischemia, facilitating future advanced studies to reveal the precise role of lymphocytes during late stage of stroke.

Electronic supplementary material

The online version of this article (10.1186/s12974-017-1017-0) contains supplementary material, which is available to authorized users.

The cystathionine β-synthase/hydrogen sulfide pathway contributes to microglia-mediated neuroinflammation following cerebral ischemia

The mechanisms underlying neuroinflammation following cerebral ischemia remain unclear. Hydrogen sulfide (H₂S), a newly identified gasotransmitter, has been reported to regulate inflammation. In the current study, we investigated whether the endogenous H₂S production pathway contributed to microglia-mediated neuroinflammation following stroke. We used a mouse middle cerebral artery occlusion (MCAO) model and an in vitro cellular model to mimic ischemia-induced microglial neuroinflammation. Expression of the H₂S synthase cystathionine β-synthase (CBS) and H₂S synthetic activity were rapidly decreased in the ischemic brain tissue following MCAO. Consistently, when cultured microglia were polarized toward a pro-inflammatory phenotype with conditioned medium collected from neurons that had been subjected to oxygen-glucose deprivation (OGD neuron CM), they displayed reduced CBS expression and H₂S production. Enhancing H₂S bioavailability either by overexpressing CBS or by supplementing with exogenous H₂S donors promoted a shift in microglial polarization from ischemia-induced pro-inflammatory phenotypes toward anti-inflammatory phenotypes. Mechanistically, microglia that were exposed to OGD neuron CM displayed reduced activation of AMP-activated protein kinase (AMPK), which was rescued by overexpressing CBS or by supplementing with H₂S donors. Moreover, the promoting effects of H₂S donors on microglial anti-inflammatory polarization were abolished by an AMPK inhibitor or CaMKKβ inhibitor. Our results suggested that reduced CBS-H₂S-AMPK cascade activity contributed to microglia-mediated neuroinflammation following stroke. Targeting the CBS-H₂S pathway is a promising therapeutic approach for ischemic stroke.

Photobiomodulation therapy promotes neurogenesis by improving post-stroke local microenvironment and stimulating neuroprogenitor cells

Recent work has indicated that photobiomodulation (PBM) may beneficially alter the pathological status of several neurological disorders, although the mechanism currently remains unclear. The current study was designed to investigate the beneficial effect of PBM on behavioral deficits and neurogenesis in a photothrombotic (PT) model of ischemic stroke in rats. From day 1 to day 7 after the establishment of PT model, 2-minute daily PBM (CW, 808nm, 350mW/cm², total 294J at scalp level) was applied on the infarct injury area (1.8mm anterior to the bregma and 2.5mm lateral from the midline). Rats received intraperitoneal injections of 5-bromodeoxyuridine (BrdU) twice daily (50mg/kg) from day 2 to 8 post-stoke, and samples were collected at day 14. We demonstrated that PBM significantly attenuated behavioral deficits and infarct volume induced by PT stroke. Further investigation displayed that PBM remarkably enhanced neurogenesis and synaptogenesis, as evidenced by immunostaining of BrdU, Ki67, DCX, MAP2, spinophilin, and synaptophysin. Mechanistic studies suggested beneficial effects of PBM were accompanied by robust suppression of reactive gliosis and the production of pro-inflammatory cytokines. On the contrary, the release of anti-inflammatory cytokines, cytochrome c oxidase activity and ATP production in peri-infarct regions were elevated following PBM treatment. Intriguingly, PBM could effectively switch an M1 microglial phenotype to an anti-inflammatory M2 phenotype. Our novel findings indicated that PBM is capable of promoting neurogenesis after ischemic stroke. The underlying mechanisms may rely on: 1) promotion of proliferation and differentiation of internal neuroprogenitor cells in the peri-infarct zone; 2) improvement of the neuronal microenvironment by altering inflammatory status and promoting mitochondrial function. These findings provide strong support for the promising therapeutic effect of PBM on neuronal repair following ischemic stroke.

(+)-Borneol is neuroprotective against permanent cerebral ischemia in rats by suppressing production of proinflammatory cytokines

Stroke is one of the leading causes of disability and death globally. It occurs when a major artery is occluded in the brain and leads to death of cells within the injured tissue. (+)-Borneol, a simple bicyclic monoterpene extracted from traditional Chinese medicine, is widely used in various types of diseases. However, no study has proved the effects of (+)-borneol on functional recovery from permanent ischemic stroke and the mechanism is still unknown. Here, we report that in the rat model of permanent cerebral ischemia, we found that (+)-borneol (1.0 mg/kg) significantly ameliorated infarct size and neurological scoresvia reducing the expression of inducible nitric oxide synthase (iNOS) and tumor necrosis factor-alpha (TNF-α) in a dose dependent manner. Notably, (+)-borneol showed long-term effects on the improvement of sensorimotor functions in the photothrombotic model of stroke, which decreased the number of foot faults in the grid-walking task and forelimb asymmetry scores in the cylinder task, at least in part through reducing loss of dendritic spines in the length, brunch number and density. These findings suggest that (+)-borneol could serve as a therapeutic target for ischemic stroke.

(-)-Phenserine inhibits neuronal apoptosis following ischemia/reperfusion injury

Stroke commonly leads to adult disability and death worldwide. Its major symptoms are spastic hemiplegia and discordant motion, consequent to neuronal cell death induced by brain vessel occlusion. Acetylcholinesterase (AChE) is upregulated and allied with inflammation and apoptosis after stroke. Recent studies suggest that AChE inhibition ameliorates ischemia-reperfusion injury and has neuroprotective properties. (-)-Phenserine, a reversible AChE inhibitor, has a broad range of actions independent of its AChE properties, including neuroprotective ones. However, its protective effects and detailed mechanism of action in the rat middle cerebral artery occlusion model (MCAO) remain to be elucidated. This study investigated the therapeutic effects of (-)-phenserine for stroke in the rat focal cerebral ischemia model and oxygen-glucose deprivation/reperfusion (OGD/RP) damage model in SH-SY5Y neuronal cultures. (-)-Phenserine mitigated OGD/PR-induced SH-SY5Y cell death, providing an inverted U-shaped dose-response relationship between concentration and survival. In MCAO challenged rats, (-)-phenserine reduced infarction volume, cell death and improved body asymmetry, a behavioral measure of stoke impact. In both cellular and animal studies, (-)-phenserine elevated brain-derived neurotrophic factor (BDNF) and B-cell lymphoma 2 (Bcl-2) levels, and decreased activated-caspase 3, amyloid precursor protein (APP) and glial fibrillary acidic protein (GFAP) expression, potentially mediated through the ERK-1/2 signaling pathway. These actions mitigated neuronal apoptosis in the stroke penumbra, and decreased matrix metallopeptidase-9 (MMP-9) expression. In synopsis, (-)-phenserine significantly reduced neuronal damage induced by ischemia/reperfusion injury in a rat model of MCAO and cellular model of OGD/RP, demonstrating that its anti-apoptotic/neuroprotective/neurotrophic cholinergic and non-cholinergic properties warrant further evaluation in conditions of brain injury.

Risks of newly onset hemorrhagic stroke in patients with neovascular age-related macular degeneration

PURPOSE

Age-related macular degeneration (AMD) is an eye disease causing blindness in the elderly. It shares many common possible pathogenic mechanisms with cardiovascular diseases. Many studies have discussed the association between AMD and stroke, but the results were inconsistent. Our aim was to determine the associations between neovascular AMD and the risk of stroke in the Taiwanese population.

METHODS

This is a retrospective cohort study. We used claims data from National Health Insurance Research Database. Patients aged more than 45 years without stroke, myocardial infarction, or any AMD were selected from 2001 to 2008 and followed until 2010. The index date was defined as the date of nAMD diagnosis (ICD-9 code, 362.52). The comparison group was patients without an nAMD diagnosis with age- and sex-matched to nAMD subjects at a ratio of up to 10 to 1. Kaplan-Meier survival analysis and Cox regression analysis were used. The incidence of stroke events (ICD-9 codes, 430-434) and their subtypes (hemorrhagic and ischemic) were primary outcomes. Secondary outcomes included acute myocardial infarction (AMI), composite AMI/stroke, and all-cause mortality.

RESULTS

Patients with nAMD had a higher risk of developing stroke, with an adjusted HR of 1.30 (95% CI, 1.01-1.68). A higher risk for hemorrhagic stroke (HR, 1.70, 95% CI, 1.03-2.83) was also found. No significant differences were observed in ischemic stroke, the composite of AMI/stroke, and all-cause mortality.

CONCLUSIONS

Patients with nAMD had a significantly higher risk of developing stroke, which was driven mainly by the increased risk of developing the hemorrhagic subtype.

PD-L1 (Programmed Death Ligand 1) Protects Against Experimental Intracerebral Hemorrhage-Induced Brain Injury

BACKGROUND AND PURPOSE

Intracerebral hemorrhage (ICH) is a neurologically destructive stroke, for which no valid treatment is available. This preclinical study examined the therapeutic effect of PD-L1 (programmed death ligand 1), a B7 family member and a ligand for both PD-1 (programmed death 1) and B7-1 (CD80), in a murine ICH model.

METHODS

ICH was induced by injecting autologous blood into 252 male C57BL/6 and Rag1^-/- mice. One hour later, ICH mice were randomly assigned to receive an intraperitoneal injection of vehicle, PD-L1, or anti-PD-L1 antibody. Neurological function was assessed along with brain edema, brain infiltration of immune cells, blood-brain barrier integrity, neuron death, and mTOR (mammalian target of rapamycin) pathway products.

RESULTS

PD-L1 significantly attenuated neurological deficits, reduced brain edema, and decreased hemorrhage volume in ICH mice. PD-L1 specifically downsized the number of brain-infiltrating CD4⁺ T cells and the percentages of Th1 and Th17 cells but increased the percentages of Th2 and regulatory T cells. In the PD-L1-treated group, we observed an amelioration of the inflammatory milieu, decreased cell death, and enhanced blood-brain barrier integrity. PD-L1 also inhibited the mTOR pathway. The administration of anti-PD-L1 antibody produced the opposite effects to those of PD-L1 in ICH mice.

CONCLUSIONS

PD-L1 provided protection from the damaging consequences of ICH.

Low-Dose Ethanol Preconditioning Protects Against Oxygen-Glucose Deprivation/Reoxygenation-Induced Neuronal Injury By Activating Large Conductance, Ca2+-Activated K+ Channels In Vitro

Increasing evidence suggests that low to moderate ethanol ingestion protects against the deleterious effects of subsequent ischemia/reperfusion; however, the underlying mechanism has not been elucidated. In the present study, we showed that expression of the neuronal large-conductance, Ca²⁺-activated K⁺ channel (BK_Ca) α-subunit was upregulated in cultured neurons exposed to oxygen-glucose deprivation/reoxygenation (OGD/R) compared with controls. Preconditioning with low-dose ethanol (10 mmol/L) increased cell survival rate in neurons subjected to OGD/R, attenuated the OGD/R-induced elevation of cytosolic Ca²⁺ levels, and reduced the number of apoptotic neurons. Western blots revealed that ethanol preconditioning upregulated expression of the anti-apoptotic protein Bcl-2 and downregulated the pro-apoptotic protein Bax. The protective effect of ethanol preconditioning was antagonized by a BK_Ca channel inhibitor, paxilline. Inside-out patches in primary neurons also demonstrated the direct activation of the BK_Ca channel by 10 mmol/L ethanol. The above results indicated that low-dose ethanol preconditioning exerts its neuroprotective effects by attenuating the elevation of cytosolic Ca²⁺ and preventing neuronal apoptosis, and this is mediated by BK_Ca channel activation.