Inhibition of lymphocyte trafficking shields the brain against deleterious neuroinflammation after stroke

Distinct Cytokine Responses in Central and Systemic Compartments after Subarachnoid Haemorrhage

INTRODUCTION

Neuroinflammation may contribute to outcomes following subarachnoid haemorrhage (SAH). Human cerebrospinal fluid (CSF) cytokine data is limited and its relationship with systemic inflammation is unknown. This study compares the inflammatory responses in CSF and plasma compartments, and their associations with outcome.

METHODS

Ten cytokines were measured in CSF and plasma from 98 SAH patients and 18 control patients. Outcome was assessed with the modified Rankin scale (mRS) and Subarachnoid Haemorrhage Outcome Tool (SAHOT) at days 7, 28, 90 and 180. Regression analyses and principal component analysis (PCA) were performed.

RESULTS

Median levels of all CSF cytokines and plasma IL-6 were higher in SAH patients than controls (p < 0.001). Plasma IL-6 peaked earlier (3 days after SAH) than CSF cytokines (7-9 days after SAH). On day 7, CSF levels were greater than plasma levels for all cytokines (p < 0.001). There was no correlation between individual cytokines in the plasma and CSF. Only plasma IL-6 levels correlated with long-term outcome (mRS (p = 0.009) and SAHOT (p = 0.007) at day 180), accounting for WFNS and blood volume. Seven principal components of cytokines had an eigenvalue greater than 1. Only the first plasma principal component (dominated by IL-6, IL-8, IL-12, IL-13, and TNF-α) was associated with outcomes (p < 0.05). Mediation analysis suggested the effects of WFNS and blood volume on outcome were not mediated by IL-6 or this principal component.

CONCLUSION

SAH provokes an inflammatory response in CSF and plasma. The response pattern is different and distinct in each compartment. Each compartment's relationship with outcomes differ, suggesting separate roles in SAH pathophysiology. Plasma IL-6 is independently associated with outcomes.

Neural repair mechanisms after ischemic stroke

Ischemic stroke triggers inflammation that promotes neuronal injury, leading to disruption of neural circuits and exacerbated neurological deficits in patients. Immune cells contribute to not only the acute inflammatory responses but also the chronic neural repair. During the post-stroke recovery, reparative immune cells support the neural circuit reorganization that occurs around the infarct region to connect broad brain areas. This review highlights the time-dependent changes of neuro-immune interactions and reorganization of neural circuits after ischemic brain injury. Understanding the molecular mechanisms involving immune cells in acute inflammation, subsequent neural repair, and neuronal circuit reorganization that compensate for the lost brain function is indispensable to establish treatment strategies for stroke patients.

Extracellular vesicles lay the ground for neuronal plasticity by restoring mitochondrial function, cell metabolism and immune balance

Extracellular vesicles (EVs) convey complex signals between cells that can be used to promote neuronal plasticity and neurological recovery in brain disease models. These EV signals are multimodal and context-dependent, making them unique therapeutic principles. This review analyzes how EVs released from various cell sources control neuronal metabolic function, neuronal survival and plasticity. Preferential sites of EV communication in the brain are interfaces between pre- and postsynaptic neurons at synapses, between astrocytes and neurons at plasma membranes or tripartite synapses, between oligodendrocytes and neurons at axons, between microglial cells/macrophages and neurons, and between cerebral microvascular cells and neurons. At each of these interfaces, EVs support mitochondrial function and cell metabolism under physiological conditions and orchestrate neuronal survival and plasticity in response to brain injury. In the injured brain, the promotion of neuronal survival and plasticity by EVs is tightly linked with EV actions on mitochondrial function, cell metabolism, oxidative stress and immune responses. Via the stabilization of cell metabolism and immune balance, neuronal plasticity responses are activated and functional neurological recovery is induced. As such, EV lay the ground for neuronal plasticity.

The immunomodulatory effects of GLP-1 receptor agonists in neurogenerative diseases and ischemic stroke treatment

Glucagon-like peptide-1 (GLP-1) receptor is widely distributed in the digestive system, cardiovascular system, adipose tissue and central nervous system. Numerous GLP-1 receptor-targeting drugs have been investigated in clinical studies for various indications, including type 2 diabetes and obesity (accounts for 70% of the total studies), non-alcoholic steatohepatitis, Alzheimer's disease, and Parkinson's disease. This review presented fundamental information regarding two categories of GLP-1 receptor agonists (GLP-1RAs): peptide-based and small molecule compounds, and elaborated their potential neuroprotective effects by inhibiting neuroinflammation, reducing neuronal apoptosis, and ultimately improving cognitive function in various neurodegenerative diseases. As a new hypoglycemic drug, GLP-1RA has a unique role in reducing the concurrent risk of stroke in T2D patients. Given the infiltration of various peripheral immune cells into brain tissue, particularly in the areas surrounding the infarct lesion, we further investigated the potential immune regulatory mechanisms. GLP-1RA could not only facilitate the M2 polarization of microglia through both direct and indirect pathways, but also modulate the quantity and function of T cell subtypes, including CD4, CD8, and regulatory T cells, resulting into the inhibition of inflammatory responses and the promotion of neuronal regeneration through interleukin-10 secretion. Therefore, we believe that the "Tregs-microglia-neuron/neural precursor cells" axis is instrumental in mediating immune suppression and neuroprotection in the context of ischemic stroke. Given the benefits of rapid diffusion, favorable blood-brain barrier permeability and versatile administration routes, these small molecule compounds will be one of the important candidates of GLP-1RA. We look forward to the further clinical evidence of small molecule GLP-1RA intervention in ischemic stroke or T2D complicated by ischemic stroke.

The association between variation of neutrophil-to-lymphocyte ratio and post-thrombolysis early neurological outcomes in patients with stroke of different TOAST classification

Recent studies have shown that the neutrophil-to-lymphocyte ratio (NLR) can predict short-term and long-term outcomes in acute ischemic stroke (AIS) patients. However, the relationship of the variation of NLR (ΔNLR) with hemorrhage transformation (HT) and early neurological improvement (ENI) after intravenous thrombolysis (IVT) remains unclear. This study aimed to investigate the impact of ΔNLR on HT and ENI at 24 h post-IVT and its association with different TOAST classifications. AIS patients undergoing IVT between October 2021 and October 2023 were enrolled and classified by TOAST criteria. Patients were grouped based on the presence or absence of HT and ENI. Our study demonstrated that both HT and ENI were associated with ΔNLR, which was an independent influencing factor for HT and ENI following IVT. Specifically, the ΔNLR in the small artery occlusion (SAO) group was higher than that in the minor stroke of large artery atherosclerosis (LAA) subtype. Thus, ΔNLR may serve as a useful biomarker to assist in diagnosis and monitor the outcomes of thrombolytic therapy in AIS patients.

Bibliometric Analysis of Non-coding RNAs and Ischemic Stroke: Trends, Frontiers, and Challenges

More and more articles have shown that non-coding RNAs (ncRNAs) play a significant role in the pathogenesis and prognosis of ischemic stroke. However, the bibliometric analysis in ncRNAs and ischemic stroke is still lacking. This study retrieved the Web of Science Core Collection for relevant articles from January 1, 2010 to April 6, 2023. Bibliometrix R, VOSviewer, and CiteSpace were used to perform the bibliometric analysis. A total of 1058 articles were eligible for this review. The number of publications showed a fluctuating upward trend. The total citations were 28,698 times, and the average number of citations per article was 27.12 times. Our findings indicated ncRNAs has been increasingly investigated for its critical role in apoptosis, autophagy, angiogenesis, inflammation, oxidative stress, and blood-brain barrier after ischemic stroke by regulating target mRNAs, extracellular secretion, target proteins, and others. The microRNAs, circular RNAs, and long ncRNAs may be hotspots, and ferroptosis, METTL3, and exosome might be frontier in this field. Besides, ncRNAs have a promising future as diagnostic and prognostic biomarkers, molecular drug targets, and other targeted therapies for ischemic stroke. However, it still faces many challenges to be successfully applied in the clinical practice.

Research progress of small-molecule natural medicines for the treatment of ischemic stroke

Stroke is the second leading cause of disability and mortality worldwide, imposing a substantial socioeconomic burden on individuals and healthcare systems. Annually, approximately 14 million people experience stroke, with ischemic stroke comprising nearly 85% of cases, of which 10% to 20% involve large vessel occlusions. Currently, recombinant tissue plasminogen activator (tPA) remains the only approved pharmacological intervention. However, its utility is limited due to a narrow therapeutic window and low recanalization rates, making it applicable to only a minority of patients. Therefore, there is an urgent need for novel therapeutic strategies, including pharmacological advancements and combinatory treatments. Small-molecule natural medicines, particularly those derived from traditional Chinese herbs, have demonstrated significant therapeutic potential in ischemic stroke management. These compounds exert multiple neuroprotective effects, such as antioxidation, anti-inflammatory action, and inhibition of apoptosis, all of which are critical in mitigating stroke-induced cerebral damage. This review comprehensively examines the pathophysiology of acute ischemic stroke (AIS) and highlights the recent progress in the development of small-molecule natural medicines as promising therapeutic agents for cerebral ischemic stroke.

Characteristics of peripheral immune response induced by large-vessel occlusion in patients with acute ischemic stroke

Introduction

Despite improvements in the treatment of acute ischemic stroke (AIS), some patients still suffer from functional impairments, indicating the poor understanding of pathophysiologic process of AIS. Inflammation plays an important role in the pathophysiology of AIS. The purpose of the study was to investigate the peripheral inflammation in different subtypes of AIS.

Methods

Here, retrospective data from AIS with large vessel occlusion (LVO) and small vessel occlusion (SVO), and healthy controls, were initially analyzed. Then, flow cytometry was performed to evaluate the levels of peripheral naïve and memory T-cells. Finally, we characterized the T cell receptors (TCR) repertoire using high-throughput sequencing.

Results

Elevated levels of leukocytes, neutrophils, and neutrophil-to-lymphocyte ratio (NLR), and decreased levels of lymphocytes were found in LVO group than that in SVO group, which were correlated with the severity of LVO. In addition, higher percentages of both effector memory (Tem) and central memory (Tcm) T cells, and lower percentage of naïve T cells in CD4+ and CD8+ T cells, were found in LVO group than that in SVO and healthy groups. Moreover, impaired TCR diversity, and different abundances of V-J gene combinations and amino acid sequences, were found in LVO as compared with healthy group, which would be potential biomarkers for LVO diagnosis.

Discussion

In conclusion, AIS with LVO can rapidly induce peripheral immune response, which provides new insight into the understanding of pathophysiology of AIS.

Short-chain fatty acids are a key mediator of gut microbial regulation of T cell trafficking and differentiation after traumatic brain injury

The gut microbiota has emerged as a pivotal regulator of host inflammatory processes after traumatic brain injury (TBI). However, the mechanisms by which the gut microbiota communicates to the brain in TBI are still under investigation. We previously reported that gut microbiota depletion (GMD) using antibiotics after TBI resulted in increased microglial activation, reduced neurogenesis, and reduced T cell infiltration. In the present study, we have demonstrated that intestinal T cells contribute to the pool of cells infiltrating the brain after TBI. Depletion or genetic deletion of T cells before injury reversed GMD induced reductions in post-TBI neurogenesis. Short-chain fatty acid supplementation increased T regulatory and T helper1 cell infiltration to the brain along with restoring neurogenesis and microglia activation after TBI with GMD. These data suggest that T cell subsets are essential cellular mediators by which the gut microbiota modulates TBI pathogenesis, a finding with important therapeutic implications.

Association of Serum Uric Acid to Lymphocyte Ratio with Clinical Outcomes in Cerebral Venous Sinus Thrombosis

Purpose

The serum uric acid to lymphocyte ratio (ULR) is a systemic marker of inflammation, and it has been studied as an indicator of prognosis in cardiovascular disease. This study investigates the relationship between ULR and clinical outcomes in patients with cerebral venous sinus thrombosis (CVST).

Patients and Methods

A total of 636 patients with CVST were included in the study and randomly divided into a training set (n = 445) and a testing set (n = 119) in a ratio of 7:3.Logistic regression analysis was employed to analyze the risk factors for poor outcomes. The nomogram was established using the training dataset, and its predictive performance was assessed with the testing dataset.

Results

ULR accurately predicted poor outcomes in CVST and was linked to a higher likelihood of poor outcomes (OR=1.015, 95% CI: 1.003-1.026, P = 0.013). Age, infection, intracranial hypertension, coma, and intracerebral hemorrhage were independent predictors of poor outcomes in CVST. Additionally, a new nomogram incorporating ULR was constructed to predict the risk of poor outcomes in CVST patients. The nomogram demonstrated good accuracy and reliability, as shown by the receiver operating characteristic curve, calibration curve, and decision curve analysis.

Conclusion

ULR independently forecasted poor outcomes in patients with CVST. The novel nomogram incorporating ULR could provide CVST patients with personalized risk assessment and treatment plans, leading to improved patient prognosis.

Unveiling the hidden culprit: How the brain-gut axis fuels neuroinflammation in ischemic stroke

Background

The brain-gut axis represents a bidirectional communication network between the gut microbiome and the central nervous system that plays an important role in homeostasis. Compelling evidence now confirms that ischemic stroke disrupts this delicate balance by inducing gut dysbiosis.

Methods

A comprehensive literature search was performed in PubMed, Web of Science, and Google Scholar for articles published between January 2000 and January 2023 using relevant keywords. Studies were limited to English and included original studies, literature, and systematic reviewers from peer-reviewed journals which discussed gut microbiota composition in models/subjects with ischemic stroke or assessed stroke impact on gut microbiota. Comments, meeting abstracts, and case reports were excluded. From the 80 relevant articles, we summarized key findings related to gut microbiota changes after stroke and their association with stroke outcomes.

Results

Emerging preclinical evidence underscores the pivotal role of the gut microbiome in glial cell development and function. Germ-free models exhibit compromised microglial activation and impaired cellular debris clearance, exacerbating tissue damage following ischemic stroke. Targeted interventions, including prebiotics, probiotics, and fecal microbiota transplantation, have demonstrated efficacy in rescuing glial phenotypes in preclinical stroke models. Beyond its local effects, the gut microbiome significantly influences systemic immunity. Ischemic stroke polarizes pro-inflammatory phenotypes of neutrophils and T cells, amplifying neurovascular inflammation. Microbiota manipulation modulates leukocyte trafficking and metabolic signaling, offering potential avenues to mitigate infarct pathology.

Conclusion

Our review demonstrates that in preclinical stroke models, modulating the lipopolysaccharide, short-chain fatty acid, and trimethylamine N-oxide pathways through the gut-brain axis reduces infarct sizes and edema and improves functional recovery after ischemic stroke. Further exploration of this important axis may unveil additional adjunctive stroke therapies by elucidating the complex interplay between the microbiome and the brain. Rigorously controlled clinical studies are now warranted to translate these promising preclinical findings and investigate whether manipulating the microbiome-brain relationship can help improve outcomes for stroke patients. Overall, continued research on the gut-brain axis holds exciting possibilities for developing novel treatment strategies that may enhance recovery after stroke.

Mechanism and application of immune interventions in intracerebral haemorrhage

Despite stroke being one of the major and increasing burdens to global health, therapeutic interventions in intracerebral haemorrhage (ICH) continue to be a challenge. Existing treatment methods, such as surgery and conservative treatment have shown limited efficacy in improving the prognosis of ICH. However, more and more studies show that exploring the specific process of immune response after ICH and taking corresponding immunotherapy may have a definite significance to improve the prognosis of cerebral haemorrhage. Therefore, immune interventions are currently under consideration as therapeutic interventions in the ICH. In this review, we aim to clarify unique immunological features of stroke, and consider the evidence for immune interventions. In acute ICH, activation of glial cells and cell death products trigger an inflammatory cascade that damages vessels and the parenchyma within minutes to hours of the haemorrhage. Immune interventions that ameliorate brain inflammation, vascular permeability and tissue oedema should be administered promptly to reduce acute immune destruction and avoid subsequent immunosuppression. A deeper understanding of the immune mechanisms involved in ICH is likely to lead to successful immune interventions.

The role of integrins in brain health and neurodegenerative diseases

Integrins are heterodimeric membrane proteins expressed on the surface of most cells. They mediate adhesion and signaling processes relevant for a wealth of physiological processes, including nervous system development and function. Interestingly, integrins are also recognized therapeutic targets for inflammatory diseases, such as multiple sclerosis. Here, we discuss the role of integrins in brain development and function, as well as in neurodegenerative diseases affecting the brain (Alzheimer's disease, multiple sclerosis, stroke). Furthermore, we discuss therapeutic targeting of these adhesion receptors in inflammatory diseases of the brain.

Rebuilding insight into the pathophysiology of Alzheimer's disease through new blood-brain barrier models

The blood-brain barrier is a unique function of the microvasculature in the brain parenchyma that maintains homeostasis in the central nervous system. Blood-brain barrier breakdown is a common pathology in various neurological diseases, such as Alzheimer's disease, stroke, multiple sclerosis, and Parkinson's disease. Traditionally, it has been considered a consequence of neuroinflammation or neurodegeneration, but recent advanced imaging techniques and detailed studies in animal models show that blood-brain barrier breakdown occurs early in the disease process and may precede neuronal loss. Thus, the blood-brain barrier is attractive as a potential therapeutic target for neurological diseases that lack effective therapeutics. To elucidate the molecular mechanism underlying blood-brain barrier breakdown and translate them into therapeutic strategies for neurological diseases, there is a growing demand for experimental models of human origin that allow for functional assessments. Recently, several human induced pluripotent stem cell-derived blood-brain barrier models have been established and various in vitro blood-brain barrier models using microdevices have been proposed. Especially in the Alzheimer's disease field, the human evidence for blood-brain barrier dysfunction has been demonstrated and human induced pluripotent stem cell-derived blood-brain barrier models have suggested the putative molecular mechanisms of pathological blood-brain barrier. In this review, we summarize recent evidence of blood-brain barrier dysfunction in Alzheimer's disease from pathological analyses, imaging studies, animal models, and stem cell sources. Additionally, we discuss the potential future directions for blood-brain barrier research.

A comprehensive review on the neuroprotective potential of resveratrol in ischemic stroke

Stroke is the second leading cause of death and the third leading cause of disability worldwide. Globally, 68 % of all strokes are ischemic, with 32 % being hemorrhagic. Ischemic stroke (IS) poses significant challenges globally, necessitating the development of effective therapeutic strategies. IS is among the deadliest illnesses. Major functions are played by neuroimmunity, inflammation, and oxidative stress in the multiple intricate pathways of IS. Secondary brain damage is specifically caused by the early pro-inflammatory activity that follows cerebral ischemia, which is brought on by excessive activation of local microglia and the infiltration of circulating monocytes and macrophages. Resveratrol, a natural polyphenol found in grapes and berries, has shown promise as a neuroprotective agent in IS. This review offers a comprehensive overview of resveratrol's neuroprotective role in IS, focusing on its mechanisms of action and therapeutic potential. Resveratrol exerts neuroprotective effects by activating nuclear factor erythroid 2-related factor 2 (NRF2) and sirtuin 1 (SIRT1) pathways. SIRT1 activation by resveratrol triggers the deacetylation and activation of downstream targets like peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α) and forkhead box protein O (FOXO), regulating mitochondrial biogenesis, antioxidant defense, and cellular stress response. Consequently, resveratrol promotes cellular survival and inhibits apoptosis in IS. Moreover, resveratrol activates the NRF2 pathway, a key mediator of the cellular antioxidant response. Activation of NRF2 through resveratrol enhances the expression of antioxidant enzymes, like heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase 1 (NQO1), which neutralize reactive oxygen species and mitigate oxidative stress in the ischemic brain. Combined, the activation of SIRT1 and NRF2 pathways contributes to resveratrol's neuroprotective effects by reducing oxidative stress, inflammation, and apoptosis in IS. Preclinical studies demonstrate that resveratrol improves functional outcomes, reduces infarct size, regulates cerebral blood flow and preserves neuronal integrity. Gaining a comprehensive understanding of these mechanisms holds promise for the development of targeted therapeutic interventions aimed at promoting neuronal survival and facilitating functional recovery in IS patients and to aid future studies in this matter.

Immuno-MRI for Stroke Diagnosis and Prognosis

Following a stroke, an inflammatory response occurs, characterized by an increased blood-brain barrier permeability, expression of endothelial trafficking molecules, and infiltration of immune cells. Adhesion molecules expressed on activated brain endothelial cells are potential biomarkers of intraparenchymal inflammation. However, in current clinical practice, it is not possible to measure endothelial activation using clinically available imaging. Using targeted micro-sized particles of iron oxide (MPIO), immuno-MRI enables the detection of endothelial adhesion molecules at high resolution and, consequently, facilitates the detection of stroke-induced brain inflammation. In this review, we highlight the most recent studies that used immuno-MRI in models of neurovascular disorders, including transient ischemic attack, ischemic stroke, intracranial hemorrhage, and subarachnoid hemorrhage. We also discuss the potential of immuno-MRI in clinical practice and the necessary next steps for its implementation in patients.

New Perspectives in Neuroprotection for Ischemic Stroke

The constant failure of new neuroprotective therapies for ischemic stroke has partially halted the search for new therapies in recent years, mainly because of the high investment risk required to develop a new treatment for a complex pathology, such as stroke, with a narrow intervention window and associated comorbidities. However, owing to recent progress in understanding the stroke pathophysiology, improvement in patient care in stroke units, development of new imaging techniques, search for new biomarkers for early diagnosis, and increasingly widespread use of mechanical recanalization therapies, new opportunities have opened for the study of neuroprotection. This review summarizes the main protective agents currently in use, some of which are already in the clinical evaluation phase. It also includes an analysis of how recanalization therapies, new imaging techniques, and biomarkers have improved their efficacy.

Spatiotemporal sphingosine-1-phosphate receptor 3 expression within the cerebral vasculature after ischemic stroke

Sphingosine-1-phosphate receptors (S1PRs) are promising therapeutic targets in cardiovascular disease, including ischemic stroke. However, important spatiotemporal information for alterations of S1PR expression is lacking. Here, we investigated the role of S1PR3 in ischemic stroke in rodent models and patient samples. We show that S1PR3 is acutely upregulated in perilesional reactive astrocytes after stroke, and that stroke volume and behavioral deficits are improved in mice lacking S1PR3. Further, we find that administration of an S1PR3 antagonist at 4-h post-stroke, but not at later timepoints, improves stroke outcome. Lastly, we observed higher plasma S1PR3 concentrations in experimental stroke and in patients with ischemic stroke. Together, our results establish S1PR3 as a potential drug target and biomarker in ischemic stroke.

Flow cytometry-based peripheral blood analysis as an easily friendly tool for prognostic monitoring of acute ischemic stroke: a multicenter study

Background and objective

Acute ischemic stroke (AIS) is a leading cause of mortality, severe neurological and long-term disability world-wide. Blood-based indicators may provide valuable information on identified prognostic factors. However, currently, there is still a lack of peripheral blood indicators for the prognosis of AIS. We aimed to identify the most promising prognostic indicators and establish prognostic models for AIS.

Methods

484 subjects enrolled from four centers were analyzed immunophenotypic indicators of peripheral blood by flow cytometry. Least absolute shrinkage and selection operator (LASSO) regression was applied to minimize the potential collinearity and over-fitting of variables measured from the same subject and over-fitting of variables. Univariate and multivariable Cox survival analysis of differences between and within cohorts was performed by log-rank test. The areas under the receiving operating characteristic (ROC) curves were used to evaluate the selection accuracy of immunophenotypic indicators in identifying AIS subjects with survival risk. The prognostic model was constructed using a multivariate Cox model, consisting of 402 subjects as a training cohort and 82 subjects as a testing cohort.

Results

In the prospective study, 7 immunophenotypic indicators of distinct significance were screened out of 72 peripheral blood immunophenotypic indicators by LASSO. In multivariate cox regression, CTL (%) [HR: 1.18, 95% CI: 1.03-1.33], monocytes/μl [HR: 1.13, 95% CI: 1.05-1.21], non-classical monocytes/μl [HR: 1.09, 95% CI: 1.02-1.16] and CD56high NK cells/μl [HR: 1.13, 95% CI: 1.05-1.21] were detected to decrease the survival probability of AIS, while Tregs/μl [HR:0.97, 95% CI: 0.95-0.99, p=0.004], BM/μl [HR:0.90, 95% CI: 0.85-0.95, p=0.023] and CD16+NK cells/μl [HR:0.93, 95% CI: 0.88-0.98, p=0.034] may have the protective effect. As for indicators' discriminative ability, the AUC for CD56highNK cells/μl attained the highest of 0.912. In stratification analysis, the survival probability for AIS subjects with a higher level of Tregs/μl, BM/μl, CD16+NK cells/μl, or lower levels of CD56highNK cells/μl, CTL (%), non-classical monocytes/μl, Monocytes/μl were more likely to survive after AIS. The multivariate Cox model showed an area under the curve (AUC) of 0.805, 0.781 and 0.819 and 0.961, 0.924 and 0.982 in the training and testing cohort, respectively.

Conclusion

Our study identified 7 immunophenotypic indicators in peripheral blood may have great clinical significance in monitoring the prognosis of AIS and provide a convenient and valuable predictive model for AIS.

Social isolation initiated post-weaning augments ischemic brain injury by promoting pro-inflammatory responses

Social isolation is associated with poor stroke outcome, but the underlying molecular mechanisms were largely unknown. In male Balb/C mice exposed to transient middle cerebral artery occlusion (MCAo), we examined the effects of social isolation initiated post-weaning on ischemic injury, cytokine/chemokine responses and cell signaling using a broad panel of techniques that involved immunocytochemistry, cytokine/chemokine array and Western blots. Social isolation initiated post-weaning elevated infarct size, brain edema and neuronal injury in the ischemic brain tissue 3 days after MCAo, and increased microglia/ macrophage and leukocyte accumulation. In line with the increased immune cell recruitment, levels of several proinflammatory cytokines (e.g., IL-1α, IL-1β, IL-13, IL-17, TNF-α, IFN-γ), chemokines (e.g., CCL3, CCL4, CCL12, CXCL2, CXCL9, CXCL12) and adhesion molecules (i.e., ICAM-1) were increased in the ischemic brain tissue of socially isolated compared with paired housing mice, whereas levels of selected cytokines (IL-5, IL-6, IL-16) and colony-stimulating factors (G-CSF, GM-CSF) were reduced. The activity of the transcription factor nuclear factor-ĸB (NF-ĸB), which promotes cell injury via pro-inflammatory responses, was increased by social isolation, whereas that of nuclear factor erythroid related factor-2 (Nrf-2), which mediates anti-oxidative responses under oxidative stress conditions, was reduced. Our study shows that social isolation profoundly alters post-ischemic cell signaling in a way promoting pro-inflammatory responses. Our results highlight the importance of social support in preventing deleterious health effects of social isolation.

Targeting brain-peripheral immune responses for secondary brain injury after ischemic and hemorrhagic stroke

The notion that the central nervous system is an immunologically immune-exempt organ has changed over the past two decades, with increasing evidence of strong links and interactions between the central nervous system and the peripheral immune system, both in the healthy state and after ischemic and hemorrhagic stroke. Although primary injury after stroke is certainly important, the limited therapeutic efficacy, poor neurological prognosis and high mortality have led researchers to realize that secondary injury and damage may also play important roles in influencing long-term neurological prognosis and mortality and that the neuroinflammatory process in secondary injury is one of the most important influences on disease progression. Here, we summarize the interactions of the central nervous system with the peripheral immune system after ischemic and hemorrhagic stroke, in particular, how the central nervous system activates and recruits peripheral immune components, and we review recent advances in corresponding therapeutic approaches and clinical studies, emphasizing the importance of the role of the peripheral immune system in ischemic and hemorrhagic stroke.

Brain-Heart Axis and the Inflammatory Response: Connecting Stroke and Cardiac Dysfunction

BACKGROUND

In recent years, the mechanistic interaction between the brain and heart has been explored in detail, which explains the effects of brain injuries on the heart and those of cardiac dysfunction on the brain. Brain injuries are the predominant cause of post-stroke deaths, and cardiac dysfunction is the second leading cause of mortality after stroke onset.

SUMMARY

Several studies have reported the association between brain injuries and cardiac dysfunction. Therefore, it is necessary to study the influence on the heart post-stroke to understand the underlying mechanisms of stroke and cardiac dysfunction. This review focuses on the mechanisms and the effects of cardiac dysfunction after the onset of stroke (ischemic or hemorrhagic stroke).

KEY MESSAGES

The role of the site of stroke and the underlying mechanisms of the brain-heart axis after stroke onset, including the hypothalamic-pituitary-adrenal axis, inflammatory and immune responses, brain-multi-organ axis, are discussed.

Succinylation modification: a potential therapeutic target in stroke

Stroke is a leading cause of mortality and disability worldwide. Ischemic cell death triggered by the compromised supply of blood oxygen and glucose is one of the major pathophysiology of stroke-induced brain injury. Impaired mitochondrial energy metabolism is observed minutes after stroke and is closely associated with the progression of neuropathology. Recently, a new type of post-translational modification, known as lysine succinylation, has been recognized to play a significant role in mitochondrial energy metabolism after ischemia. However, the role of succinylation modification in cell metabolism after stroke and its regulation are not well understood. We aimed to review the effects of succinylation on energy metabolism, reactive oxygen species generation, and neuroinflammation, as well as Sirtuin 5 mediated desuccinylation after stroke. We also highlight the potential of targeting succinylation/desuccinylation as a promising strategy for the treatment of stroke. The succinylation level is dynamically regulated by the nonenzymatic or enzymatic transfer of a succinyl group to a protein on lysine residues and the removal of succinyl catalyzed by desuccinylases. Mounting evidence has suggested that succinylation can regulate the metabolic pathway through modulating the activity or stability of metabolic enzymes. Sirtuins, especially Sirtuin 5, are characterized for their desuccinylation activity and have been recognized as a critical regulator of metabolism through desuccinylating numerous metabolic enzymes. Imbalance between succinylation and desuccinylation has been implicated in the pathophysiology of stroke. Pharmacological agents that enhance the activity of Sirtuin 5 have been employed to promote desuccinylation and improve mitochondrial metabolism, and neuroprotective effects of these agents have been observed in experimental stroke studies. However, their therapeutic efficacy in stroke patients should be validated.

Changes in Adhesion and the Expression of Adhesion Molecules in PBMCs after Aneurysmal Subarachnoid Hemorrhage: Relation to Cerebral Vasospasm

Aneurysmal subarachnoid hemorrhage (aSAH) is a neurovascular disease produced by extravasation of blood to the subarachnoid space after rupture of the cerebral vessels. After bleeding, the immune response is activated. The role of peripheral blood mononuclear cells (PBMCs) in this response is a current subject of research. We have analysed the changes in PBMCs of patients with aSAH and their interaction with the endothelium, focusing on their adhesion and the expression of adhesion molecules. Using an in vitro adhesion assay, we observed that the adhesion of PBMCs of patients with aSAH is increased. Flow cytometry analysis shows that monocytes increased significantly in patients, especially in those who developed vasospasm (VSP). In aSAH patients, the expression of CD162, CD49d, CD62L and CD11a in T lymphocytes and of CD62L in monocytes increased. However, the expression of CD162, CD43, and CD11a decreased in monocytes. Furthermore, monocytes from patients who developed arteriographic VSP had lower expression of CD62L. In conclusion, our results confirm that after aSAH, monocyte count and adhesion of PBMCs increase, especially in patients with VSP, and that the expression of several adhesion molecules is altered. These observations can help predict VSP and to improve the treatment of this pathology.

Immune cell expression patterns of CD39/CD73 ectonucleotidases in rodent models of cardiac arrest and resuscitation

Background

Cardiac arrest (CA) is a significant public health concern. There is the high imminent mortality and survival in those who are resuscitated is substantively compromised by the post-CA syndrome (PCAS), characterized by multiorgan ischemia-reperfusion injury (IRI). The inflammatory response in PCAS is complex and involves various immune cell types, including lymphocytes and myeloid cells that have been shown to exacerbate organ IRI, such as myocardial infarction. Purinergic signaling, as regulated by CD39 and CD73, has emerged as centrally important in the context of organ-specific IRI. Hence, comprehensive understanding of such purinergic responses may be likewise imperative for improving outcomes in PCAS.

Methods

We have investigated alterations of immune cell populations after CA by utilizing rodent models of PCAS. Blood and spleen were collected after CA and resuscitation and underwent flow cytometry analysis to evaluate shifts in CD3+CD4+ helper T cells, CD3+CD8a+ cytotoxic T cells, and CD4/CD8a ratios. We then examined the expression of CD39 and CD73 across diverse cell types, including myeloid cells, T lymphocytes, and B lymphocytes.

Results

In both rat and mouse models, there were significant increases in the frequency of CD3+CD4+ T lymphocytes in PCAS (rat, P < 0.01; mouse, P < 0.001), with consequently elevated CD4/CD8a ratios in whole blood (both, P < 0.001). Moreover, CD39 and CD73 expression on blood leukocytes were markedly increased (rat, P < 0.05; mouse, P < 0.01 at 24h). Further analysis in the experimental mouse model revealed that CD11b+ myeloid cells, with significant increase in their population (P < 0.01), had high level of CD39 (88.80 ± 2.05 %) and increased expression of CD73 (P < 0.05). CD19+ B lymphocytes showed slight increases of CD39 (P < 0.05 at 2h) and CD73 (P < 0.05 at 2h), while, CD3+ T lymphocytes had decreased levels of them. These findings suggested a distinct patterns of expression of CD39 and CD73 in these specific immune cell populations after CA.

Conclusions

These data have provided comprehensive insights into the immune response after CA, highlighting high-level expressions of CD39 and CD73 in myeloid cells.

Therapeutic potential of mitochondrial transplantation in modulating immune responses post-cardiac arrest: a narrative review

BACKGROUND

Mitochondrial transplantation (MTx) has emerged as a novel therapeutic strategy, particularly effective in diseases characterized by mitochondrial dysfunction. This review synthesizes current knowledge on MTx, focusing on its role in modulating immune responses and explores its potential in treating post-cardiac arrest syndrome (PCAS).

METHODS

We conducted a comprehensive narrative review of animal and human studies that have investigated the effects of MTx in the context of immunomodulation. This included a review of the immune responses following critical condition such as ischemia reperfusion injury, the impact of MTx on these responses, and the therapeutic potential of MTx in various conditions.

RESULTS

Recent studies indicate that MTx can modulate complex immune responses and reduce ischemia-reperfusion injury post-CA, suggesting MTx as a novel, potentially more effective approach. The review highlights the role of MTx in immune modulation, its potential synergistic effects with existing treatments such as therapeutic hypothermia, and the need for further research to optimize its application in PCAS. The safety and efficacy of autologous versus allogeneic MTx, particularly in the context of immune reactions, are critical areas for future investigation.

CONCLUSION

MTx represents a promising frontier in the treatment of PCAS, offering a novel approach to modulate immune responses and restore cellular energetics. Future research should focus on long-term effects, combination therapies, and personalized medicine approaches to fully harness the potential of MTx in improving patient outcomes in PCAS.

CCL5 mediated astrocyte-T cell interaction disrupts blood-brain barrier in mice after hemorrhagic stroke

The crosstalk between reactive astrocytes and infiltrated immune cells plays a critical role in maintaining blood-brain barrier (BBB) integrity. However, how astrocytes interact with immune cells and the effect of their interaction on BBB integrity after hemorrhagic stroke are still unclear. By performing RNA sequencing in astrocytes that were activated by interleukin-1α (IL-1α), tumor necrosis factor α (TNFα), and complement component 1q (C1q) treatment, we found CCL5 was among the top upregulated genes. Immunostaining and western blot results demonstrated that CCL5 was increased in mice brain after hemorrhagic stroke. Flow cytometry showed that knockout of astrocytic CCL5 reduced the infiltration of CD8+ but not CD4+ T and myeloid cells into the brain (p < 0.05). In addition, knockout CCL5 in astrocytes increased tight junction-related proteins ZO-1 and Occludin expression; reduced Evans blue leakage, perforin and granzyme B expression; improved neurobehavioral outcomes in hemorrhagic stroke mice (p < 0.05), while transplantation of CD8+ T cells reversed these protective effects. Moreover, co-culture of CD8+ T cells with bEnd.3 cells induced the apoptosis of bEnd.3 cells, which was rescued by inhibiting perforin. In conclusion, our study suggests that CCL5 mediated crosstalk between astrocytes and CD8+ T cells represents an important therapeutic target for protecting BBB in stroke.

Update on the role of T cells in cognitive impairment

The central nervous system (CNS) has long been considered an immune-privileged site, with minimal interaction between immune cells, particularly of the adaptive immune system. Previously, the presence of immune cells in this organ was primarily linked to events involving disruption of the blood-brain barrier (BBB) or inflammation. However, current research has shown that immune cells are found patrolling CNS under homeostatic conditions. Specifically, T cells of the adaptive immune system are able to cross the BBB and are associated with ageing and cognitive impairment. In addition, T-cell infiltration has been observed in pathological conditions, where inflammation correlates with poor prognosis. Despite ongoing research, the role of this population in the ageing brain under both physiological and pathological conditions is not yet fully understood. In this review, we provide an overview of the interactions between T cells and other immune and CNS parenchymal cells, and examine the molecular mechanisms by which these interactions may contribute to normal brain function and the scenarios in which disruption of these connections lead to cognitive impairment. A comprehensive understanding of the role of T cells in the ageing brain and the underlying molecular pathways under normal conditions could pave the way for new research to better understand brain disorders. LINKED ARTICLES: This article is part of a themed issue From Alzheimer's Disease to Vascular Dementia: Different Roads Leading to Cognitive Decline. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.6/issuetoc.

Inhibition of leukocyte migration after ischemic stroke by VE-cadherin mutation in a mouse model leads to reduced infarct volumes and improved motor skills

AIMS

To distinguish between the genuine cellular impact of the ischemic cascade by leukocytes and unspecific effects of edema and humoral components, two knock-in mouse lines were utilized. Mouse lines Y731F and Y685F possess point mutations in VE-cadherin, which lead to a selective inhibition of transendothelial leukocyte migration or impaired vascular permeability.

METHODS

Ischemic stroke was induced by a model of middle cerebral artery occlusion. Analysis contained structural outcomes (infarct volume and extent of brain edema), functional outcomes (survival analysis, rotarod test, and neuroscore), and the extent and spatial distribution of leukocyte migration (heatmaps and fluorescence-activated cell sorting (FACS) analysis).

RESULTS

Inhibition of transendothelial leukocyte migration as in Y731F mice leads to smaller infarct volumes (52.33 ± 4719 vs. 70.43 ± 6483 mm3 , p = .0252) and improved motor skills (rotarod test: 85.52 ± 13.24 s vs. 43.06 ± 15.32 s, p = .0285). An impaired vascular permeability as in Y685F mice showed no effect on structural or functional outcomes. Both VE-cadherin mutations did not influence the total immune cell count or spatial distribution in ischemic brain parenchyma.

CONCLUSION

Selective inhibition of transendothelial leukocyte migration by VE-cadherin mutation after ischemic stroke in a mouse model leads to smaller infarct volumes and improved motor skills.

Piezo1 as a potential player in intracranial hemorrhage: from perspectives on biomechanics and hematoma metabolism

Intracranial hemorrhage (ICH) causes numerous neurological deficits and deaths worldwide each year, leaving a significant health burden on the public. The pathophysiology of ICH is complicated, and involves both primary and secondary injury. Hematoma, as the prime pathology of ICH, undergoes metabolism and triggers biochemical and biomechanical alterations in the brain, leading to secondary injury. Past endeavors mainly aimed at biochemical-initiated mechanisms for causing secondary injury have made limited progress in recent years, although ICH itself is also highly biomechanics-related. The discovery of the mechanical-activated cation channel Piezo1 provides a new avenue to further explore underlying mechanisms of secondary injury. The current article reviews the structure and gating mechanisms of Piezo1, its roles in the physiology/pathophysiology of neurons, astrocytes, microglia, and bone-marrow-derived macrophages, and especially its roles in erythrocytic turnover and iron metabolism, revealing a potential interplay between the biomechanics and biochemistry of hematoma in ICH. Collectively, these advances provide deeper insights into the secondary injury of ICH and lay the foundations for future research.

GPR55 Inactivation Diminishes Splenic Responses and Improves Neurological Outcomes in the Mouse Ischemia/Reperfusion Stroke Model

Although strokes are frequent and severe, treatment options are scarce. Plasminogen activators, the only FDA-approved agents for clot treatment (tissue plasminogen activators (tPAs)), are used in a limited patient group. Moreover, there are few approaches for handling the brain's inflammatory reactions to a stroke. The orphan G protein-coupled receptor 55 (GPR55)'s connection to inflammatory processes has been recently reported; however, its role in stroke remains to be discovered. Post-stroke neuroinflammation involves the central nervous system (CNS)'s resident microglia activation and the infiltration of leukocytes from circulation into the brain. Additionally, splenic responses have been shown to be detrimental to stroke recovery. While lymphocytes enter the brain in small numbers, they regularly emerge as a very influential leukocyte subset that causes secondary inflammatory cerebral damage. However, an understanding of how this limited lymphocyte presence profoundly impacts stroke outcomes remains largely unclear. In this study, a mouse model for transient middle cerebral artery occlusion (tMCAO) was used to mimic ischemia followed by a reperfusion (IS/R) stroke. GPR55 inactivation, with a potent GPR55-specific antagonist, ML-193, starting 6 h after tMCAO or the absence of the GPR55 in mice (GPR55 knock out (GPR55ko)) resulted in a reduced infarction volume, improved neurological outcomes, and decreased splenic responses. The inhibition of GPR55 with ML-193 diminished CD4+T-cell spleen egress and attenuated CD4+T-cell brain infiltration. Additionally, ML-193 treatment resulted in an augmented number of regulatory T cells (Tregs) in the brain post-tMCAO. Our report offers documentation and the functional evaluation of GPR55 in the brain-spleen axis and lays the foundation for refining therapeutics for patients after ischemic attacks.

Stroke and Neurogenesis: Bridging Clinical Observations to New Mechanistic Insights from Animal Models

Stroke was the 2nd leading cause of death and a major cause of morbidity. Unfortunately, there are limited means to promote neurological recovery post-stroke, but research has unearthed potential targets for therapies to encourage post-stroke neurogenesis and neuroplasticity. The occurrence of neurogenesis in adult mammalian brains, including humans, was not widely accepted until the 1990s. Now, adult neurogenesis has been extensively studied in human and mouse neurogenic brain niches, of which the subventricular zone of the lateral ventricles and subgranular zone of the dentate gyrus are best studied. Numerous other niches are under investigation for neurogenic potential. This review offers a basic overview to stroke in the clinical setting, a focused summary of recent and foundational research literature on cortical neurogenesis and post-stroke brain plasticity, and insights regarding how the meninges and choroid plexus have emerged as key players in neurogenesis and neuroplasticity in the context of focal cerebral ischemia disrupting the anterior circulation. The choroid plexus and meninges are vital as they are integral sites for neuroimmune interactions, glymphatic perfusion, and niche signaling pertinent to neural stem cells and neurogenesis. Modulating neuroimmune interactions with a focus on astrocyte activity, potentially through manipulation of the choroid plexus and meningeal niches, may reduce the exacerbation of stroke by inflammatory mediators and create an environment conducive to neurorecovery. Furthermore, addressing impaired glymphatic perfusion after ischemic stroke likely supports a neurogenic environment by clearing out inflammatory mediators, neurotoxic metabolites, and other accumulated waste. The meninges and choroid plexus also contribute more directly to promoting neurogenesis: the meninges are thought to harbor neural stem cells and are a niche amenable to neural stem/progenitor cell migration. Additionally, the choroid plexus has secretory functions that directly influences stem cells through signaling mechanisms and growth factor actions. More research to better understand the functions of the meninges and choroid plexus may lead to novel approaches for stimulating neuronal recovery after ischemic stroke.

A20 regulates lymphocyte adhesion in murine neuroinflammation by restricting endothelial ICOSL expression in the CNS

A20 is a ubiquitin-modifying protein that negatively regulates NF-κB signaling. Mutations in A20/TNFAIP3 are associated with a variety of autoimmune diseases, including multiple sclerosis (MS). We found that deletion of A20 in central nervous system (CNS) endothelial cells (ECs) enhances experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. A20ΔCNS-EC mice showed increased numbers of CNS-infiltrating immune cells during neuroinflammation and in the steady state. While the integrity of the blood-brain barrier (BBB) was not impaired, we observed a strong activation of CNS-ECs in these mice, with dramatically increased levels of the adhesion molecules ICAM-1 and VCAM-1. We discovered ICOSL to be expressed by A20-deficient CNS-ECs, which we found to function as adhesion molecules. Silencing of ICOSL in CNS microvascular ECs partly reversed the phenotype of A20ΔCNS-EC mice without reaching statistical significance and delayed the onset of EAE symptoms in WT mice. In addition, blocking of ICOSL on primary mouse brain microvascular ECs impaired the adhesion of T cells in vitro. Taken together, we propose that CNS EC-ICOSL contributes to the firm adhesion of T cells to the BBB, promoting their entry into the CNS and eventually driving neuroinflammation.

Elucidating the neuroimmunology of traumatic brain injury: methodological approaches to unravel intercellular communication and function

The neuroimmunology of traumatic brain injury (TBI) has recently gained recognition as a crucial element in the secondary pathophysiological consequences that occur following neurotrauma. Both immune cells residing within the central nervous system (CNS) and those migrating from the periphery play significant roles in the development of secondary brain injury. However, the precise mechanisms governing communication between innate and adaptive immune cells remain incompletely understood, partly due to a limited utilization of relevant experimental models and techniques. Therefore, in this discussion, we outline current methodologies that can aid in the exploration of TBI neuroimmunology, with a particular emphasis on the interactions between resident neuroglial cells and recruited lymphocytes. These techniques encompass adoptive cell transfer, intra-CNS injection(s), selective cellular depletion, genetic manipulation, molecular neuroimaging, as well as in vitro co-culture systems and the utilization of organoid models. By incorporating key elements of both innate and adaptive immunity, these methods facilitate the examination of clinically relevant interactions. In addition to these preclinical approaches, we also detail an emerging avenue of research that seeks to leverage human biofluids. This approach enables the investigation of how resident and infiltrating immune cells modulate neuroglial responses after TBI. Considering the growing significance of neuroinflammation in TBI, the introduction and application of advanced methodologies will be pivotal in advancing translational research in this field.

Learning CNS immunopathology from therapeutic interventions

Modulation of immune cell trafficking across the blood-brain barrier has not only introduced a therapeutic avenue for multiple sclerosis (MS) but also represents an example of reverse translational medicine. Data from clinical trials of drugs such as natalizumab and fingolimod have revealed the involvement of different compartments in relapsing versus non-relapsing MS immune biology, contributed to our understanding of central nervous system (CNS) immune surveillance, and stimulated new fields of research. Here, we discuss the results of these trials, as well as patient biomaterial-based scientific projects, and how both have informed our understanding of CNS immunopathology.

Evolving Clinical-Translational Investigations of Cerebroprotection in Ischemic Stroke

Ischemic stroke is a highly morbid disease, with over 50% of large vessel stroke (middle cerebral artery or internal carotid artery terminus occlusion) patients suffering disability despite maximal acute reperfusion therapy with thrombolysis and thrombectomy. The discovery of the ischemic penumbra in the 1980s laid the foundation for a salvageable territory in ischemic stroke. Since then, the concept of neuroprotection has been a focus of post-stroke care to (1) minimize the conversion from penumbra to core irreversible infarct, (2) limit secondary damage from ischemia-reperfusion injury, inflammation, and excitotoxicity and (3) to encourage tissue repair. However, despite multiple studies, the preclinical-clinical research enterprise has not yet created an agent that mitigates post-stroke outcomes beyond thrombolysis and mechanical clot retrieval. These translational gaps have not deterred the scientific community as agents are under continuous investigation. The NIH has recently promoted the concept of cerebroprotection to consider the whole brain post-stroke rather than just the neurons. This review will briefly outline the translational science of past, current, and emerging breakthroughs in cerebroprotection and use of these foundational ideas to develop a novel paradigm for optimizing stroke outcomes.

Neurovascular Inflammation and Complications of Thrombolysis Therapy in Stroke

Intravenous thrombolysis via tPA (tissue-type plasminogen activator) is the only approved pharmacological treatment for acute ischemic stroke, but its benefits are limited by hemorrhagic transformation. Emerging evidence reveals that tPA swiftly mobilizes immune cells which extravasate into the brain parenchyma via the cerebral vasculature, augmenting neurovascular inflammation, and tissue injury. In this review, we summarize the pronounced alterations of immune cells induced by tPA in patients with stroke and experimental stroke models. We argue that neuroinflammation, triggered by ischemia-induced cell death and exacerbated by tPA, compromises neurovascular integrity and the microcirculation, leading to hemorrhagic transformation. Finally, we discuss current and future approaches to attenuate thrombolysis-associated hemorrhagic transformation via uncoupling immune cells from the neurovascular unit.

Proteome profiling of hippocampus reveals the neuroprotective effect of mild hypothermia on global cerebral ischemia-reperfusion injury in rats

Cerebral ischemia is one of the leading causes of disability and mortality worldwide. Blood reperfusion of ischemic cerebral tissue may cause cerebral ischemia-reperfusion (IR) injury. In this study, a rat model of global cerebral I/R injury was established via Pulsinelli's four-vessel occlusion (4-VO) method. The liquid chromatography-tandem mass spectrometry (LC-MS/MS) and bioinformatics analysis were employed to examine the ipsilateral hippocampus proteome profiles of rats with/without MH (32 °C) treatment after IR injury. Totally 2 122 proteins were identified, among which 153 proteins were significantly changed associated with MH (n = 7 per group, fold change-1.5, p < 0.05). GO annotation of the differentially expressed proteins (DEPs) revealed that cellular oxidant detoxification, response to zinc ions, aging, oxygen transport, negative regulation of catalytic activity, response to hypoxia, regulation of protein phosphorylation, and cellular response to vascular endothelial growth factor stimulus were significantly enriched with MH treatment. The KEGG analysis indicated that metabolic pathways, thermogenesis, pathways of neurodegeneration, chemical carcinogenesis-reactive oxygen species, fluid shear stress and atherosclerosis, and protein processing in endoplasmic reticulum were significantly enriched with MH treatment. Importantly, changes in 16 DEPs were reversed by MH treatment. Among them, VCAM-1, S100A8, CaMKK2 and MKK7 were verified as potential markers associated with MH neuroprotection by Western blot analysis. This study is one of the first to investigate the neuroprotective effects of MH on the hippocampal proteome of experimental models of cerebral IR injury. These DEPs may be involved in the most fundamental molecular mechanisms of MH neuroprotection, and provide a scientific foundation for further promotion of reparative strategies in cerebral IR injury.

Importance of microRNAs by mRNA-microRNA integration analysis in acute ischemic stroke patients

OBJECTS

The roles of mRNA and microRNA (miRNA) are well known in many diseases, including ischemic stroke; thus, integration analysis using mRNA and miRNA is important to elucidate pathogenesis. However, their contribution, especially that of miRNA-targeted mRNA, to the severity of acute ischemic stroke remains unclear. Therefore, we examined mRNA and miRNA integration analysis targeted for acute ischemic stroke to clarify the pathway related to acute stroke severity.

MATERIAL AND METHODS

We performed Ingenuity Pathway Analysis (IPA) using RNA extracted from the whole blood of four healthy controls, six minor acute ischemic stroke patients (MS; National Institutes of Health Stroke Scale [NIHSS] < 8), and six severe acute ischemic stroke patients (SS; NIHSS ≥ 8) on admission. mRNA and miRNA were measured using RNA sequencing and RNA expression variation; canonical pathway analysis (CPA) and upstream regulator analyses were performed.

RESULTS

Acute ischemic stroke patients demonstrated different RNA expressions to healthy controls. Compared to MS patients, in the SS patients, 1222 mRNA, 96 miRNA, and 935 miRNA-targeted mRNA expressions were identified among differentially expressed RNA expressions (p<0.05, |log2 fold change| >1.1). CPA by IPA using mRNAs or miRNA-targeted mRNAs showed that macrophage-stimulating protein (MSP)-recepteur d'origine nantais (RON) signaling was mostly activated in SS patients compared to in MS patients. In addition, upstream regulator analysis in IPA showed that most mRNAs located upstream are miRNAs.

CONCLUSIONS

In severe acute stroke, integration of mRNA and microRNA analysis showed activated MSP-RON signaling in macrophages, and multiple miRNAs comprehensively controlled the overall pathophysiology of stroke.

Stroke-heart syndrome: A case report and mini literature review

Despite the fact that cardiac troponin (cTn) elevation is commonly seen in the acute phase of ischemic stroke, investigating its etiology represents a challenge for healthcare practitioners. Therefore, we describe the case of an 86-year-old woman with dyspnea and cTn-elevation within the first days following acute ischemic stroke and discuss potential differential diagnoses and diagnostic dilemmas.

Impact of NKG2D Signaling on Natural Killer and T-Cell Function in Cerebral Ischemia

Background Typically defined as a thromboinflammatory disease, ischemic stroke features early and delayed inflammatory responses, which determine the extent of ischemia-related brain damage. T and natural killer cells have been implicated in neuronal cytotoxicity and inflammation, but the precise mechanisms of immune cell-mediated stroke progression remain poorly understood. The activating immunoreceptor NKG2D is expressed on both natural killer and T cells and may be critically involved. Methods and Results An anti-NKG2D blocking antibody alleviated stroke outcome in terms of infarct volume and functional deficits, coinciding with reduced immune cell infiltration into the brain and improved survival in the animal model of cerebral ischemia. Using transgenic knockout models devoid of certain immune cell types and immunodeficient mice supplemented with different immune cell subsets, we dissected the functional contribution of NKG2D signaling by different NKG2D-expressing cells in stroke pathophysiology. The observed effect of NKG2D signaling in stroke progression was shown to be predominantly mediated by natural killer and CD8⁺ T cells. Transfer of T cells with monovariant T-cell receptors into immunodeficient mice with and without pharmacological blockade of NKG2D revealed activation of CD8⁺ T cells irrespective of antigen specificity. Detection of the NKG2D receptor and its ligands in brain samples of patients with stroke strengthens the relevance of preclinical observations in human disease. Conclusions Our findings provide a mechanistic insight into NKG2D-dependent natural killer- and T-cell-mediated effects in stroke pathophysiology.

Brain Infection by Group B Streptococcus Induces Inflammation and Affects Neurogenesis in the Adult Mouse Hippocampus

Central nervous system infections caused by pathogens crossing the blood-brain barrier are extremely damaging and trigger cellular alterations and neuroinflammation. Bacterial brain infection, in particular, is a major cause of hippocampal neuronal degeneration. Hippocampal neurogenesis, a continuous multistep process occurring throughout life in the adult brain, could compensate for such neuronal loss. However, the high rates of cognitive and other sequelae from bacterial meningitis/encephalitis suggest that endogenous repair mechanisms might be severely affected. In the current study, we used Group B Streptococcus (GBS) strain NEM316, to establish an adult mouse model of brain infection and determine its impact on adult neurogenesis. Experimental encephalitis elicited neurological deficits and death, induced inflammation, and affected neurogenesis in the dentate gyrus of the adult hippocampus by suppressing the proliferation of progenitor cells and the generation of newborn neurons. These effects were specifically associated with hippocampal neurogenesis while subventricular zone neurogenesis was not affected. Overall, our data provide new insights regarding the effect of GBS infection on adult brain neurogenesis.

Thromboinflammatory challenges in stroke pathophysiology

Despite years of encouraging translational research, ischemic stroke still remains as one of the highest unmet medical needs nowadays, causing a tremendous burden to health care systems worldwide. Following an ischemic insult, a complex signaling pathway emerges leading to highly interconnected thrombotic as well as neuroinflammatory signatures, the so-called thromboinflammatory cascade. Here, we thoroughly review the cell-specific and time-dependent role of different immune cell types, i.e., neutrophils, macrophages, T and B cells, as key thromboinflammatory mediators modulating the neuroinflammatory response upon stroke. Similarly, the relevance of platelets and their tight crosstalk with a variety of immune cells highlights the relevance of this cell-cell interaction during microvascular dysfunction, neovascularization, and cellular adhesion. Ultimately, we provide an up-to-date overview of therapeutic approaches mechanistically targeting thromboinflammation currently under clinical translation, especially focusing on phase I to III clinical trials.

T-cell receptor signaling modulated by the co-receptors: Potential targets for stroke treatment

Stroke is a severe and life-threatening disease, necessitating more research on new treatment strategies. Infiltrated T lymphocytes, an essential adaptive immune cell with extensive effector function, are crucially involved in post-stroke inflammation. Immediately after the initiation of the innate immune response triggered by microglia/macrophages, the adaptive immune response associated with T lymphocytes also participates in the complex pathophysiology of stroke and partially informs the outcome of stroke. Preclinical and clinical studies have revealed the conflicting roles of T cells in post-stroke inflammation and as potential therapeutic targets. Therefore, exploring the mechanisms that underlie the adaptive immune response associated with T lymphocytes in stroke is essential. The T-cell receptor (TCR) and its downstream signaling regulate T lymphocyte differentiation and activation. This review comprehensively summarizes the various molecules that regulate TCR signaling and the T-cell response. It covers both the co-stimulatory and co-inhibitory molecules and their roles in stroke. Because immunoregulatory therapies targeting TCR and its mediators have achieved great success in some proliferative diseases, this article also summarizes the advances in therapeutic strategies related to TCR signaling in lymphocytes after stroke, which can facilitate translation. DATA AVAILABILITY: No data was used for the research described in the article.

Time course of neuroinflammation after human stroke - a pilot study using co-registered PET and MRI

BACKGROUND

Microglial activation contributes to both inflammatory damage and repair in experimental ischemic stroke. However, because of the logistical challenges, there have been few clinical imaging studies directly describing inflammatory activation and its resolution after stroke. The purpose of our pilot study was to describe the spatio-temporal profile of brain inflammation after stroke using 18kD translocator protein (TSPO) positron emission tomography (PET) with magnetic resonance (MR) co-registration in the subacute and chronic stage after stroke.

METHODS

Three patients underwent magnetic resonance imaging (MRI) and PET scans with TSPO ligand [¹¹C]PBR28 15 ± 3 and 90 ± 7 days after an ischaemic stroke. Regions of interest (ROI) were defined on MRI images and applied to the dynamic PET data to derive regional time-activity curves. Regional uptake was quantified as standardised uptake values (SUV) over 60 to 90 min post-injection. ROI analysis was applied to identify binding in the infarct, and in frontal, temporal, parietal, and occipital lobes and cerebellum excluding the infarcted area.

RESULTS

The mean age of participants was 56 ± 20.4 years and mean infarct volume was 17.9 ± 18.1 ml. [¹¹C]PBR28 showed increased tracer signal in the infarcted area compared to non-infarcted areas of the brain in the subacute phase of stroke (Patient 1 SUV 1.81; Patient 2 SUV 1.15; Patient 3 SUV 1.64). [¹¹C]PBR28 uptake returned to the level of non-infarcted areas at 90 days Patient 1 SUV 0.99; Patient 3 SUV 0.80). No additional upregulation was detected elsewhere at either time point.

CONCLUSIONS

The neuroinflammatory reaction after ischaemic stroke is limited in time and circumscribed in space suggesting that post-ischaemic inflammation is tightly controlled but regulatory mechanisms.

Mechanism of action and therapeutic potential of dimethyl fumarate in ischemic stroke

Dimethyl fumarate (DMF) is an immunomodulatory drug currently approved for the treatment of multiple sclerosis and psoriasis. Its benefits on ischemic stroke outcomes have recently come to attention. To date, only tissue plasminogen activators (tPAs) and clot retrieval methods have been approved by the FDA for the treatment of ischemic stroke. Ischemic conditions lead to inflammation through diverse mechanisms, and recanalization can worsen the state. DMF and the nuclear factor erythroid-derived 2-related factor 2 (Nrf2) pathway it regulates seem to be important in postischemic inflammation, and animal studies have demonstrated that the drug improves overall stroke outcomes. Although the exact mechanism is still unknown, studies indicate that these beneficial impacts are due to the modulation of immune responses, blood-brain barrier permeability, and hemodynamic adjustments. One major component evaluated before, during, and after tPA therapy in stroke patients is blood pressure (BP). Recent studies have found that DMF may impact BP. Both hypotension and hypertension need correction before treatment, which may delay the appropriate intervention. Since BP management is crucial in managing stroke patients, it is important to consider DMF's role in this matter. That being said, it seems further investigations on DMF may lead to an alternative approach for stroke patients. In this article, we discuss the mechanistic roles of DMF and its potential role in stroke based on previously published literature and laboratory findings.

Targeting p53 for neuroinflammation: New therapeutic strategies in ischemic stroke

Ischemic stroke (IS) is characterized by high incidence, high recurrence, and high mortality and places a heavy burden on society and families. The pathological mechanisms of IS are complex, among which secondary neurological impairment mediated by neuroinflammation is considered to be the main factor in cerebral ischemic injury. At present, there is still a lack of specific therapies to treat neuroinflammation. The tumor suppressor protein p53 has long been regarded as a key substance in the regulation of the cell cycle and apoptosis in the past. Recently, studies have found that p53 also plays an important role in neuroinflammatory diseases, such as IS. Therefore, p53 may be a crucial target for the regulation of the neuroinflammatory response. Here, we provide a comprehensive review of the potential of targeting p53 in the treatment of neuroinflammation after IS. We describe the function of p53, the major immune cells involved in neuroinflammation, and the role of p53 in inflammatory responses mediated by these cells. Finally, we summarize the therapeutic strategies of targeting p53 in regulating the neuroinflammatory response after IS to provide new directions and ideas for the treatment of ischemic brain injury.

Electro-acupuncture treatment inhibits the inflammatory response by regulating γδ T and Treg cells in ischemic stroke

BACKGROUND

Electro-acupuncture (EA) is an effective and safe treatment for ischemic stroke. It is not only capable of reducing cerebral damage but also alleviating intestinal inflammation. However, its mechanism has not been fully elucidated.

METHODS

All rats were randomly divided into three experimental groups: the SHAM group, the MCAO group, and the MEA (MCAO+EA) group. Ischemic-reperfusion (I/R) injury was induced by MCAO surgery. Rats in the MEA group were treated with EA stimulation in the "Baihui" acupoint (1 mA, 2/15 Hz, 20 min for each time). The Real-time (RT)-qPCR was used to evaluate the mRNA expression of inflammation factors in the ischemic brain and the small intestine after I/R injury. In addition, our research evaluated the effects of EA on regulatory T cells (Tregs) and γδ T cells in the small intestine and brain via Flow cytometry analysis. Finally, we applied CM-Dil and CFSE injection and explored the potential connections of T cells between the ischemic hemisphere and the small intestine.

RESULTS

Our results suggested that EA treatment could significantly reduce the inflammation response in the ischemic brain and small intestine 3 days after I/R injury in rats. To be specific, EA increased the percentage of Tregs in the brain and the small intestine and decreased intestinal and cerebral γδ T cells. Concomitantly, after EA treatment, the percentage of cerebral CD3⁺TCRγδ⁺CFSE⁺ cells dropped from 12.06% to 6.52% compared with the MCAO group.

CONCLUSIONS

These findings revealed that EA could regulate the Tregs and γδ T cells in the ischemic brain and the small intestine, which indicated its effect on inhibiting inflammation. And, EA could inhibit the mobilization of intestinal T cells, which may contribute to the protection of EA after ischemic stroke.

Neuroimmune mechanisms and therapies mediating post-ischaemic brain injury and repair

The nervous and immune systems control whole-body homeostasis and respond to various types of tissue injury, including stroke, in a coordinated manner. Cerebral ischaemia and subsequent neuronal cell death activate resident or infiltrating immune cells, which trigger neuroinflammation that affects functional prognosis after stroke. Inflammatory immune cells exacerbate ischaemic neuronal injury after the onset of brain ischaemia; however, some of the immune cells thereafter change their function to neural repair. The recovery processes after ischaemic brain injury require additional and close interactions between the nervous and immune systems through various mechanisms. Thus, the brain controls its own inflammation and repair processes after injury via the immune system, which provides a promising therapeutic opportunity for stroke recovery.

Microglia/macrophages require vitamin D signaling to restrain neuroinflammation and brain injury in a murine ischemic stroke model

Vitamin D deficiency is associated with worse clinical outcomes after ischemic stroke; nevertheless, the pathophysiological mechanisms remain largely unexplored. In this study, we characterized the molecular mechanisms of how vitamin D signaling modulated stroke progression in male mouse ischemia-reperfusion stroke models. We found that vitamin D receptor (VDR) exhibited a predominant upregulation in peri-infarct microglia/macrophages following cerebral ischemia. Conditional Vdr inactivation in microglia/macrophages markedly augmented infarct volumes and neurological deficits. VDR-deficient microglia/macrophages exhibited a more primed proinflammatory phenotype with substantial secretion of TNF-α and IFN-γ. These inflammatory cytokines further enhanced CXCL10 release from endothelial cells and blood-brain barrier disruption, and ultimately infiltration of peripheral T lymphocytes. Notably, blocking TNF-α and IFN-γ significantly ameliorated stroke phenotypes in Vdr conditional knockout mice. Collectively, VDR signaling in microglia/macrophages plays a crucial role in restraining ischemia-elicited neuroinflammation and stroke progression. Our findings delineate a novel mechanism underlying the association between vitamin D deficiency and poor stroke outcomes, and underline the significance of maintaining a functional vitamin D signaling in the management of acute ischemic stroke.