CNS-peripheral immune interactions in hemorrhagic stroke

IL-33 exerts neuroprotective effects through activation of ST2/AKT signaling axis in microglia after subarachnoid hemorrhage in rats

BACKGROUND AND PURPOSE

ST2, a member of the interleukin-1 (IL-1) receptor family, along with its ligand IL-33, plays critical roles in immune regulation and inflammatory responses. This study investigates the roles of endogenous IL-33/ST2 signaling in subarachnoid hemorrhage (SAH) and elucidates the underlying mechanisms.

METHODS

Dynamic changes in endogenous IL-33 levels were examined following SAH induction in vivo. Rats underwent the endovascular perforation model of SAH and were randomly assigned to receive either recombinant IL-33 (rIL-33) or a vehicle, administered intranasally 1 h post-SAH. ST2 siRNA or an AKT selective inhibitor was administered intraperitoneally (i.p.) 48 h prior to SAH induction to explore the potential mechanisms of IL-33-mediated neuroprotection.

RESULTS

Endogenous IL-33 and ST2 levels were elevated in in vitro models of SAH. Exogenous IL-33 significantly alleviated neuronal apoptosis, reduced brain edema, and enhanced short-term neurofunction in a dose-dependent manner following SAH in rats.

CONCLUSION

Exogenous rIL-33 alleviates SAH-induced neurological deficits by promoting M2-like polarization of microglia post-SAH. These findings suggest a potential role of the microglial ST2/AKT axis in IL-33-related neuroprotection, which warrants further investigation.

Association of Chronic Periodontitis with Hemorrhagic Stroke: A Systematic Review and Meta-Analysis

Periodontitis is a chronic, multifactorial inflammatory condition linked to dysbiotic plaque biofilms and characterized by the gradual destruction of the structures supporting the teeth owing to compromised immune system function. Hemorrhagic stroke, which primarily occurs within the brain tissue or in the subarachnoid space as a blood leak of ruptured vessels, is a sudden neurological impairment caused by vascular damage in the central nervous system, resulting in focal neurological deficits. Chronic periodontitis (CP) and hemorrhagic stroke may share common pathogenic features involving inflammation and immune system activation, prompting researchers to investigate their potential connection. The aim of the study is to systematically review the literature on the epidemiological association between CP and hemorrhagic stroke in adults. The study protocol adhered to the PRISMA 2020 guidelines, and the design followed the Cochrane methodology. A thorough literature search encompassing PubMed, Scopus, and Web of Science databases and a manual search and evaluation of gray literature was conducted. Meta-analysis was performed using Review Manager (RevMan) 5.4, with the effect size represented by the odds ratio (OR) and a 95% confidence interval (CI). Heterogeneity was assessed using the chi-squared and I 2 statistics. The selected articles, written in English without time constraints, focused on observational studies involving patients and controls and included disease diagnostic criteria. Duplicate entries were eliminated. The reliability of each study's results was evaluated using the Newcastle-Ottawa Scale and GRADE tools. Two reviewers conducted the assessments, and a third reviewer resolved any disagreements. The meta-analysis comprised four observational studies involving 1,882 individuals. It revealed that individuals diagnosed with hemorrhagic stroke were notably more likely to have concurrent CP (OR: 6.32; 95% CI: 1.35-29.49; p = 0.02) or severe CP (OR: 3.08; 95% CI: 1.56-6.06; p = 0.001) compared with healthy controls. A notable occurrence of CP was detected in patients with hemorrhagic stroke compared with controls. Health care professionals need to acknowledge the connection between the two conditions, as it allows them to provide optimal holistic care through a thorough approach to diagnosis and treatment.

Single-cell sequencing reveals intracranial microvasculature-derived CXCL12 promotes CD8+ T-cell infiltration and blood-brain barrier dysfunction after subarachnoid hemorrhage in mice

BACKGROUND

Processes related to how the intracranial microvasculature initiates brain‒peripheral crosstalk for subsequent blood‒brain barrier (BBB) dysfunction at an early stage after subarachnoid hemorrhage (SAH) ictus are still unknown. This study elucidated the effect and potential mechanism of intracranial microvasculature-mediated T-cell infiltration on BBB function after SAH.

METHODS

Publicly available single-cell RNA sequencing data related to SAH ( https://ngdc.cncb.ac.cn/omix ; Accession No. OMIX006611) were retrieved and analyzed. The dataset was derived from the white matter region of adult male C57BL/6J mice at 1 and 7 days after experimental SAH. The SAH model was induced by endovascular perforation, and experiments were subsequently conducted at 1, 3, 7, and 14 days after SAH to evaluate T-cell infiltration, BBB integrity, neuronal injury, and neurological function.

RESULTS

After SAH, CXCL12 expression was increased in endothelial cells and pericytes, promoting CD8+ T-cell infiltration via the CXCR4 pathway. This immune infiltration appeared to exacerbate BBB disruption and contribute to worsened neurological function. Blocking CXCL12-CXCR4 signaling with a CXCL12 neutralizing antibody or the CXCR4-specific inhibitor AMD3100 significantly reduced CD8+ T-cell infiltration, attenuated BBB damage and improved the neurobehavioral outcomes of SAH mice.

CONCLUSION

This study suggests that, following SAH, both pericytes and endothelial cells may contribute to immune regulation by producing CXCL12, which promotes CD8⁺ T-cell infiltration into the brain. This mechanism may play a role in BBB disruption and neurological dysfunction. Targeting the CXCL12-CXCR4 axis could offer a potential approach for mitigating immune-mediated injury after SAH.

The Impact of Folic Acid Deficiency on Ischemic Stroke: Role of Inflammation and Long Noncoding RNA H19

It has been validated that folic acid deficiency (FD) is associated with an increased risk of stroke and a worse prognosis. However, the specific mechanisms by which FD exerts its detrimental effects on ischemic stroke (IS) have not been fully understood. The results of this case-control study indicated that patients with IS had a decreased serum folate level, along with up-regulated long non-coding RNA H19 (lncRNA H19) and enhanced inflammatory responses. Meanwhile, it was corroborated that the serum folate level was negatively correlated with H19 expression and the systemic immune-inflammation index (SII). Similarly, FD was demonstrated to exacerbate neurological injury in the middle cerebral artery occlusion/reperfusion (MCAO/R) rats by up-regulating the expression of inflammatory cytokines and H19 in both peripheral blood and brain tissue. Notably, the alterations in the expression of these factors in peripheral blood were consistent with those observed in brain tissue. Additionally, in a co-culture of N2a neurons and BV2 microglia, FD promoted the transition of BV2 cells towards a pro-inflammatory state by up-regulating the expression of H19, which aggravated neuronal injury. Moreover, blocking H19 in BV2 cells mitigated inflammation and partially reversed the injury in N2a cells exacerbated by FD after the treatment with oxygen-glucose deprivation and reperfusion (OGD/R). These findings provide a more in-depth insight into the regulatory role of H19-mediated systemic inflammatory responses in the context of FD, suggesting the potential clinical utility of folic acid in managing ischemic brain injury.

Remote Organ Damage Induced by Stroke: Molecular Mechanisms and Comprehensive Interventions

Significance: Damage after stroke is not only limited to the brain but also often occurs in remote organs, including the heart, lung, liver, kidney, digestive tract, and spleen, which are frequently affected by complex pathophysiological changes. The organs in the human body are closely connected, and signals transmitted through various molecular substances could regulate the pathophysiological changes of remote organs. Recent Advances: The latest studies have shown that inflammatory response plays an important role in remote organ damage after stroke, and can aggravate remote organ damage by activating oxidative stress, sympathetic axis, and hypothalamic axis, and disturbing immunological homeostasis. Remote organ damage can also cause damage to the brain, aggravating inflammatory response and oxidative damage. Critical Issues: Therefore, an in-depth exploration of inflammatory and oxidative mechanisms and adopting corresponding comprehensive intervention strategies have become necessary to reduce damage to remote organs and promote brain protection. Future Directions: The comprehensive intervention strategy involves multifaceted treatment methods such as inflammation regulation, antioxidants, and neural stem cell differentiation. It provides a promising treatment alternative for the comprehensive recovery of stroke patients and an inspiration for future research and treatment. The various organs of the human body are interconnected at the molecular level. Only through comprehensive intervention at the molecular and organ levels can we save remote organ damage and protect the brain after stroke to the greatest extent. Antioxid. Redox Signal. 00, 000-000.

The role of ACSL4 in stroke: mechanisms and potential therapeutic target

Stroke, as a neurological disorder with a poor overall prognosis, has long plagued the patients. Current stroke therapy lacks effective treatments. Ferroptosis has emerged as a prominent subject of discourse across various maladies in recent years. As an emerging therapeutic target, notwithstanding its initial identification in tumor cells associated with brain diseases, it has lately been recognized as a pivotal factor in the pathological progression of stroke. Acyl-CoA synthetase long-chain family member 4 (ACSL4) is a potential target and biomarker of catalytic unsaturated fatty acids mediating ferroptosis in stroke. Specifically, the upregulation of ACSL4 leads to heightened accumulation of lipid peroxidation products and reactive oxygen species (ROS), thereby exacerbating the progression of ferroptosis in neuronal cells. ACSL4 is present in various tissues and involved in multiple pathways of ferroptosis. At present, the pharmacological mechanisms of targeting ACSL4 to inhibit ferroptosis have been found in many drugs, but the molecular mechanisms of targeting ACSL4 are still in the exploratory stage. This paper introduces the physiopathological mechanism of ACSL4 and the current status of the research involved in ferroptosis crosstalk and epigenetics, and summarizes the application status of ACSL4 in modern pharmacology research, and discusses the potential application value of ACSL4 in the field of stroke.

Development of a Clinical and Laboratory-Based Predictive Nomogram Model for Unfavorable Functional Outcomes Among Patients Who Undergo Interventions for Aneurysmal Subarachnoid Hemorrhage

Objective: This study elucidates the prognostic significance of perioperative changes in laboratory indicators for aneurysmal SAH and develops a nomogram model for outcome prediction. Methods: Aneurysmal SAH patients who received clipping or coiling at our institution between January 2016 and December 2022 were included. All patients were randomly assigned to derivation and validation cohorts. Independent predictors of unfavorable outcomes were identified by multivariate analyses. Three models were conducted to evaluate whether perioperative laboratory changes improve prediction performance. A nomogram including all independent predictors was developed in the derivation cohort and verified in both cohorts. Results: Diabetes mellitus [OR (95% CI) = 2.84 (1.44-5.59)], WFNS grade 3-5 [OR: (95% CI), 9.17 (5.49-15.33)], clipping [OR (95% CI) = 1.71 (1.03-2.85)], perioperative changes in white blood cell count [OR (95% CI) = 2.15 (1.17-3.96)], and concentrations of ALT [OR (95% CI) = 1.41 (1.04-1.91)], sodium [OR (95% CI) = 5.40 (3.01-9.71)], and glucose [OR (95% CI) = 2.18 (1.05-4.53)] were independent predictors of an unfavorable outcome. The predictive nomogram incorporated the aforementioned predictors and performed well in the derivation cohort (AUC, 0.839; 95% CI: 0.810-0.866) and the validation cohort (AUC, 0.797; 95% CI: 0.734-0.850). Conclusions: Perioperative changes in laboratory indicators can be predictors of unfavorable outcomes in aneurysmal SAH patients. The nomogram based on clinical and laboratory risk factors can be used as a convenient tool to facilitate individualized decision making.

Causal relations between immune cells and cerebral hemorrhage: a bidirectional Mendelian randomization study

BACKGROUND

Previous studies have shown that an increased number of immune cells is closely associated with the onset and course changes of intracerebral hemorrhage, but the exact causal relationship has not been clarified. The aim of this study was to investigate the causal relationship between immune cells and intracerebral hemorrhage by a two-way Mendelian randomization method.

METHODS

Two sets of SNPs were used as instrumental variables and two-way Mendelian randomization analyses were performed and leave-one-out method were used to assess the validity and heterogeneity of the included genetic variation instruments. The level of multiplicity and heterogeneity of the included genetic variance instruments was assessed.

RESULTS

The results showed a clear causal relationship between three immune cells and intracerebral hemorrhage, and no heterogeneity between SNPs related to intracerebral hemorrhage, while scatterplot and funnel plot confirmed that the causality was less likely to be biased; MR-Egger results suggested that no genetic pleiotropy was found. Leave-one-out analysis was applied to suggest that the MR analysis results for a single SNP were robust; meanwhile, Meta-analysis was applied to combine the two intracerebral hemorrhage datasets, and the analysis results suggested that in the fixed-effects model and random-effects model, the immunocyte CD66b on Granulocytic Myeloid-Derived Suppressor Cells and other three immune cells were significantly causally associated with intracerebral hemorrhage, while the heterogeneity test suggested that there was no significant difference between the different datasets.

CONCLUSIONS

The present study found a significant causal relationship between specific immune cell phenotypes and intracerebral hemorrhage by Mendelian randomization analysis.

Interleukin-1 Receptor-Associated Kinase-3 Aggravates Neuroinflammatory Injury After Intracerebral Hemorrhage via Activation NF-κB/IL-17A Pathway in Mice

Background

Neuroinflammatory reactions are crucial factors in secondary brain damage following intracerebral hemorrhage (ICH). Although previous studies have shown that IRAK3 is involved in immune responses, the potential effects of IRAK3 on ICH remain unclear.

Methods

Collagenase IV-induced ICH mouse model. Western blotting was used to determine the expression of IRAK3 at different time points following ICH. Immunofluorescence was used to investigate the cellular localization of IRAK3. The ICH model was treated with recombinant human IRAK3 (rh-IRAK3) or IRAK3 siRNA via an intracerebroventricular injection. The effect of IRAK3 on ICH mice was assessed by Western blotting and short-term and long-term neurological function evaluation. RNA-seq was performed to explore the mechanism by which IRAK3 promotes inflammation after ICH. The mechanisms of IRAK3 and neuroinflammation will be further investigated by Western blotting, qRT-PCR and immunofluorescence. Recombinant IL-17A was used to investigate the connection between IRAK3 and the NF-κB/IL-17A signaling pathway in vivo and in vitro experiments.

Results

The expression of IRAK3 increased, peaking at 24 h, followed by a subsequent decrease after ICH. IRAK3 is mainly expressed in the microglia. RNA-seq analysis revealed 1,797 differentially expressed genes around the perihematomal brain tissue after IRAK3 siRNA treatment, with multiple inflammatory pathways being downregulated. Rh-IRAK3 treatment resulted in upregulation of the levels of inflammatory cytokines around the perihematomal tissue and exacerbated neurological function deficits. Furthermore, IRAK3 siRNA treatment markedly decreased the expression of inflammatory cytokines and microglial activation via the NF-κB/IL-17A signaling pathway. Recombinant IL-17A exacerbated the inflammatory response in vivo and in vitro; however, IRAK3 knockdown reversed this process.

Conclusion

IRAK3 aggravates neuroinflammation by activating the NF-κB/IL-17A signaling pathway, thereby exacerbating neurological deficits following ICH. Therefore, inhibition IRAK3 may be a promising approach for treating ICH.

Role of Regulatory T Cells in Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a common cerebrovascular disease that can lead to severe neurological dysfunction in surviving patients, resulting in a heavy burden on patients and their families. When ICH occurs, the blood‒brain barrier is disrupted, thereby promoting immune cell migration into damaged brain tissue. As important immunosuppressive T cells, regulatory T (Treg) cells are involved in the maintenance of immune homeostasis and the suppression of immune responses after ICH. Treg cells mitigate brain tissue damage after ICH in a variety of ways, such as inhibiting the neuroinflammatory response, protecting against blood‒brain barrier damage, reducing oxidative stress damage and promoting nerve repair. In this review, we discuss the changes in Treg cells in ICH clinical patients and experimental animals, the mechanisms by which Treg cells regulate ICH and treatments targeting Treg cells in ICH, aiming to support new therapeutic strategies for clinical treatment.

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.

Incorporating platelet-to-white blood cell ratio into survival prediction models for intracerebral hemorrhage: a nomogram approach

Background

Predicting long-term survival in intensive care unit patients with intracerebral hemorrhage (ICH) is crucial. This study aimed to develop a platelet-to-white blood cell ratio (PWR) incorporated nomogram for long-term survival prediction.

Methods

A retrospective analysis was conducted on 1,728 ICH patients in the MIMIC-IV 2.2 database. The independent prognostic value of PWR for 1-year mortality was assessed. A nomogram was developed using LASSO and Cox regression to predict 1-year survival, incorporating PWR and other factors. The performance of the nomogram was evaluated through calibration curves, area under the curve, Delong test, net reclassification index, integrated discrimination improvement, and decision curve analysis.

Results

The nomogram, which included age, weight, Glasgow Coma Scale (GCS) score, mechanical ventilation, glucose, red blood cell (RBC) count, blood urea nitrogen (BUN), and PWR, showed good predictive performance for 1-year survival. The C-index was 0.736 (95% CI = 0.716-0.756) for the training set and 0.766 (95% CI = 0.735-0.797) for the testing set. Higher age and ventilation increased mortality risk, while higher weight, GCS score, RBC count, and PWR decreased risk. The nomogram outperformed conventional scores.

Conclusions

A nomogram incorporating PWR as a prognostic factor accurately predicts long-term survival in ICH patients. However, validation in large-scale multicenter studies and further exploration of biomarkers are needed.

Prevalence and Risk Factors of Cognitive Frailty in Patients Undergoing Maintenance Hemodialysis: A Systematic Review and Meta-Analysis

BACKGROUND

The purpose of this study is to investigate the prevalence and risk factor of cognitive frailty in patients undergoing maintenance hemodialysis.

METHODS

Systematically searched PubMed, EmBase, Web of Science, Cochrane Library, SinoMed, China Knowledge Resource Integrated Database, Wanfang Database, and Weipu Database from inception until January 1, 2024. Two researchers were independently screened and cross-checked. Stata 15.1 software was used to perform the meta-analysis.

RESULTS

A total of 15 articles were included, including 5398 patients. The results showed that the prevalence of cognitive frailty in patients undergoing maintenance hemodialysis was 24%. Among them, age (odds ratio [OR] = 1.33, 95% CI [1.16, 1.53]), waist circumference (OR = 1.05, 95% CI [1.03, 1.08]), malnutrition (OR = 2.91, 95% CI [1.94, 4.35]), comorbidities (OR = 1.93, 95% CI [1.47, 2.54]), stroke history (OR = 2.94, 95% CI [1.72, 5.03]), and depression (OR = 3.26, 95% CI [1.91, 5.57]) were the main risk factors for cognitive frailty in patients undergoing maintenance hemodialysis. Education level (OR = 0.48, 95% CI [0.31, 0.73]) was protective factors for cognitive frailty in patients undergoing maintenance hemodialysis.

CONCLUSIONS

Current evidence showed that the prevalence of cognitive frailty in patients undergoing maintenance hemodialysis was high, and there were many risk factors. Therefore, early identification and intervention of cognitive frailty in maintenance hemodialysis patients should be carried out, which may be helpful to reduce the prevalence rate and occurrence of adverse events and improve the prognosis of patients.

The Role of Systemic Inflammation in the Pathogenesis of Spontaneous Intracranial Hemorrhage in the Presence or Absence of Effective Cerebral Blood Flow

Background: Spontaneous intracerebral hemorrhage (ICH) is one of the leading causes of mortality in intensive care units. The role of systemic hyperintense inflammation (SHI) in the pathogenesis of critical complications of ICH remains a poorly understood problem. There is a specific variant of severe ICH associated with increased intracranial pressure and occlusion of intracranial vessels, defined as ineffective cerebral blood flow (IECBF). Methods: To evaluate the role of SHI in the pathogenesis of severe (comatose) ICH in a dynamic comparison of patients with IECBF (n-26) and without IECBF (n-52). The SHI integral score criterion (SI scale) was used, including certain values of plasma concentrations of IL-6, IL-8, IL-10; TNF-α, PCT, cortisol, myoglobin, troponin I, D-dimer, and, additionally, SOFA scale values. Blood levels of ACTH and neuron-specific enolase (NSE) were also assessed. Results: Twenty-eight-day mortality in severe ICH reached 84.6% (without IECBF) and 96.2% (with IECBF). Clear signs of SHI were detected in 61.5%/87.8% (without IECBF) and 0.0%/8.7% (with IECBF) within 1-3/5-8 days from the onset of ICH manifestation. The lower probability of developing SHI in the IECBF group was associated with low blood NSE concentrations. Conclusions: The development of SHI in ICH is pathogenetically related to the permeability of the blood-brain barrier for tissue breakdown products and other neuroinflammatory factors.

Systematic Insights into the Relationship between the Microbiota-Gut-Brain Axis and Stroke with the Focus on Tryptophan Metabolism

Stroke, as a serious cerebral vascular disease with high incidence and high rates of disability and mortality, has limited therapeutic options due to the narrow time window. Compelling evidence has highlighted the significance of the gut microbiota and gut-brain axis as critical regulatory factors affecting stroke. Along the microbiota-gut-brain axis, tryptophan metabolism further acquires increasing attention for its intimate association with central nervous system diseases. For the purpose of exploring the potential role of tryptophan metabolism in stroke and providing systematic insights into the intricate connection of the microbiota-gut-brain axis with the pathological procedure of stroke, this review first summarized the practical relationship between microbiota and stroke by compiling the latest case-control research. Then, the microbiota-gut-brain axis, as well as its interaction with stroke, were comprehensively elucidated on the basis of the basic anatomical structure and physiological function. Based on the crosstalk of microbiota-gut-brain, we further focused on the tryptophan metabolism from the three major metabolic pathways, namely, the kynurenine pathway, serotonin pathway, and microbial pathway, within the axis. Moreover, the effects of tryptophan metabolism on stroke were appreciated and elaborated here, which is scarcely found in other reviews. Hopefully, the systematic illustration of the mechanisms and pathways along the microbiota-gut-brain axis will inspire more translational research from metabolic perspectives, along with more attention paid to tryptophan metabolism as a promising pharmaceutical target in order to reduce the risk of stroke, mitigate the stroke progression, and ameliorate the stroke prognosis.

Immune-mediated disruption of the blood-brain barrier after intracerebral hemorrhage: Insights and potential therapeutic targets

AIMS

Intracerebral hemorrhage (ICH) is a condition that arises due to the rupture of cerebral blood vessels, leading to the flow of blood into the brain tissue. One of the pathological alterations that occurs during an acute ICH is an impairment of the blood-brain barrier (BBB), which leads to severe perihematomal edema and an immune response.

DISCUSSION

A complex interplay between the cells of the BBB, for example, pericytes, astrocytes, and brain endothelial cells, with resident and infiltrating immune cells, such as microglia, monocytes, neutrophils, T lymphocytes, and others accounts for both damaging and protective mechanisms at the BBB following ICH. However, the precise immunological influence of BBB disruption has yet to be richly ascertained, especially at various stages of ICH.

CONCLUSION

This review summarizes the changes in different cell types and molecular components of the BBB associated with immune-inflammatory responses during ICH. Furthermore, it highlights promising immunoregulatory therapies to protect the integrity of the BBB after ICH. By offering a comprehensive understanding of the mechanisms behind BBB damage linked to cellular and molecular immunoinflammatory responses after ICH, this article aimed to accelerate the identification of potential therapeutic targets and expedite further translational research.

Single-cell RNA sequencing reveals the evolution of the immune landscape during perihematomal edema progression after intracerebral hemorrhage

BACKGROUND

Perihematomal edema (PHE) after post-intracerebral hemorrhage (ICH) has complex pathophysiological mechanisms that are poorly understood. The complicated immune response in the post-ICH brain constitutes a crucial component of PHE pathophysiology. In this study, we aimed to characterize the transcriptional profiles of immune cell populations in human PHE tissue and explore the microscopic differences between different types of immune cells.

METHODS

9 patients with basal ganglia intracerebral hemorrhage (hematoma volume 50-100 ml) were enrolled in this study. A multi-stage profile was developed, comprising Group1 (n = 3, 0-6 h post-ICH, G1), Group2 (n = 3, 6-24 h post-ICH, G2), and Group3 (n = 3, 24-48 h post-ICH, G3). A minimal quantity of edematous tissue surrounding the hematoma was preserved during hematoma evacuation. Single cell RNA sequencing (scRNA-seq) was used to map immune cell populations within comprehensively resected PHE samples collected from patients at different stages after ICH.

RESULTS

We established, for the first time, a comprehensive landscape of diverse immune cell populations in human PHE tissue at a single-cell level. Our study identified 12 microglia subsets and 5 neutrophil subsets in human PHE tissue. What's more, we discovered that the secreted phosphoprotein-1 (SPP1) pathway served as the basis for self-communication between microglia subclusters during the progression of PHE. Additionally, we traced the trajectory branches of different neutrophil subtypes. Finally, we also demonstrated that microglia-produced osteopontin (OPN) could regulate the immune environment in PHE tissue by interacting with CD44-positive cells.

CONCLUSIONS

As a result of our research, we have gained valuable insight into the immune-microenvironment within PHE tissue, which could potentially be used to develop novel treatment modalities for ICH.

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.

Association Between Neutrophil-Lymphocyte Ratio and 30-Day Infection and Thrombotic Outcomes After Intraventricular Hemorrhage: A CLEAR III Analysis

BACKGROUND

Serum neutrophil-lymphocyte ratio (NLR) is a surrogate marker for the inflammatory response after intracerebral hemorrhage (ICH) and is associated with perihematomal edema and long-term functional outcomes. Whether NLR is associated with short-term ICH complications is poorly understood. We hypothesized that NLR is associated with 30-day infection and thrombotic events after ICH.

METHODS

We performed a post hoc exploratory analysis of the Clot Lysis: Evaluating Accelerated Resolution of Intraventricular Hemorrhage III trial. The study exposure was the serum NLR obtained at baseline and on days 3 and 5. The coprimary outcomes, ascertained at 30 days, were any infection and a thrombotic event, defined as composite of cerebral infarction, myocardial infarction, or venous thromboembolism; both infection and thrombotic event were determined through adjudicated adverse event reporting. Binary logistic regression was used to study the relationship between NLR and outcomes, after adjustment for demographics, ICH severity and location, and treatment randomization.

RESULTS

Among the 500 patients enrolled in the Clot Lysis: Evaluating Accelerated Resolution of Intraventricular Hemorrhage III trial, we included 303 (60.6%) without missing data on differential white blood cell counts at baseline. There were no differences in demographics, comorbidities, or ICH severity between patients with and without data on NLR. In adjusted logistic regression models, NLR ascertained at baseline (odds ratio [OR] 1.03; 95% confidence interval [CI] 1.01-1.07, p = 0.03) and NLR ascertained at day 3 were associated with infection (OR 1.15; 95% CI 1.05-1.20, p = 0.001) but not with thrombotic events. Conversely, NLR at day 5 was associated with thrombotic events (OR 1.07, 95% CI 1.01-1.13, p = 0.03) but not with infection (OR 1.13; 95% CI 0.76-1.70, p = 0.56). NLR at baseline was not associated with either outcome.

CONCLUSIONS

Serum NLR ascertained at baseline and on day 3 after randomization was associated with 30-day infection, whereas NLR obtained on day 5 was associated with thrombotic events after ICH, suggesting that NLR could be a potential early biomarker for ICH-related complications.

Identification of mitophagy and ferroptosis-related hub genes associated with intracerebral haemorrhage through bioinformatics analysis

BACKGROUND

Mitophagy and ferroptosis occur in intracerebral haemorrhage (ICH) but our understanding of mitophagy and ferroptosis-related genes remains incomplete.

AIM

This study aims to identify shared ICH genes for both processes.

METHODS

ICH differentially expressed mitophagy and ferroptosis-related genes (DEMFRGs) were sourced from the GEO database and literature. Enrichment analysis elucidated functions. Hub genes were selected via STRING, MCODE, and MCC algorithms in Cytoscape. miRNAs targeting hubs were predicted using miRWalk 3.0, forming a miRNA-hub gene network. Immune microenvironment variances were assessed with MCP and TIMER. Potential small molecules for ICH were forecasted via CMap database.

RESULTS

64 DEMFRGs and ten hub genes potentially involved in various processes like ferroptosis, TNF signalling pathway, MAPK signalling pathway, and NF-kappa B signalling pathway were discovered. Several miRNAs were identified as shared targets of hub genes. The ICH group showed increased infiltration of monocytic lineage and myeloid dendritic cells compared to the Healthy group. Ten potential small molecule drugs (e.g. Zebularine, TWS-119, CG-930) were predicted via CMap.

CONCLUSION

Several shared genes between mitophagy and ferroptosis potentially drive ICH progression via TNF, MAPK, and NF-kappa B pathways. These results offer valuable insights for further exploring the connection between mitophagy, ferroptosis, and ICH.

Autonomic dysfunction and treatment strategies in intracerebral hemorrhage

AIMS

Autonomic dysfunction with central autonomic network (CAN) damage occurs frequently after intracerebral hemorrhage (ICH) and contributes to a series of adverse outcomes. This review aims to provide insight and convenience for future clinical practice and research on autonomic dysfunction in ICH patients.

DISCUSSION

We summarize the autonomic dysfunction in ICH from the aspects of potential mechanisms, clinical significance, assessment, and treatment strategies. The CAN structures mainly include insular cortex, anterior cingulate cortex, amygdala, hypothalamus, nucleus of the solitary tract, ventrolateral medulla, dorsal motor nucleus of the vagus, nucleus ambiguus, parabrachial nucleus, and periaqueductal gray. Autonomic dysfunction after ICH is closely associated with neurological functional outcomes, cardiac complications, blood pressure fluctuation, immunosuppression and infection, thermoregulatory dysfunction, hyperglycemia, digestive dysfunction, and urogenital disturbances. Heart rate variability, baroreflex sensitivity, skin sympathetic nerve activity, sympathetic skin response, and plasma catecholamine concentration can be used to assess the autonomic functional activities after ICH. Risk stratification of patients according to autonomic functional activities, and development of intervention approaches based on the restoration of sympathetic-parasympathetic balance, would potentially improve clinical outcomes in ICH patients.

CONCLUSION

The review systematically summarizes the evidence of autonomic dysfunction and its association with clinical outcomes in ICH patients, proposing that targeting autonomic dysfunction could be potentially investigated to improve the clinical outcomes.

CD8+ T cells in brain injury and neurodegeneration

The interaction between the peripheral immune system and the brain is increasingly being recognized as an important layer of neuroimmune regulation and plays vital roles in brain homeostasis as well as neurological disorders. As an important population of T-cell lymphocytes, the roles of CD8+ T cells in infectious diseases and tumor immunity have been well established. Recently, increasing number of complex functions of CD8+ T cells in brain disorders have been revealed. However, an advanced summary and discussion of the functions and mechanisms of CD8+ T cells in brain injury and neurodegeneration are still lacking. Here, we described the differentiation and function of CD8+ T cells, reviewed the involvement of CD8+ T cells in the regulation of brain injury including stroke and traumatic brain injury and neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD), and discussed therapeutic prospects and future study goals. Understanding these processes will promote the investigation of T-cell immunity in brain disorders and provide new intervention strategies for the treatment of brain injury and neurodegeneration.

Unconventional T cells in brain homeostasis, injury and neurodegeneration

The interaction between peripheral immune cells and the brain is an important component of the neuroimmune axis. Unconventional T cells, which include natural killer T (NKT) cells, mucosal-associated invariant T (MAIT) cells, γδ T cells, and other poorly defined subsets, are a special group of T lymphocytes that recognize a wide range of nonpolymorphic ligands and are the connection between adaptive and innate immunity. Recently, an increasing number of complex functions of these unconventional T cells in brain homeostasis and various brain disorders have been revealed. In this review, we describe the classification and effector function of unconventional T cells, review the evidence for the involvement of unconventional T cells in the regulation of brain homeostasis, summarize the roles and mechanisms of unconventional T cells in the regulation of brain injury and neurodegeneration, and discuss immunotherapeutic potential as well as future research goals. Insight of these processes can shed light on the regulation of T cell immunity on brain homeostasis and diseases and provide new clues for therapeutic approaches targeting brain injury and neurodegeneration.

Macrophage and monocyte subsets in response to ischemic stroke

Ischemic stroke is a leading cause of disability and mortality. Despite extensive efforts in stroke research, the only pharmacological treatment currently available is arterial recanalization, which has limited efficacy only in the acute phase of stroke. The neuroinflammatory response to stroke is believed to provide a wider time window than recanalization and has therefore been proposed as an attractive therapeutic target. In this review, we provide an overview of recent advances in the understanding of cellular and molecular responses of distinct macrophage populations following stroke, which may offer potential targets for therapeutic interventions. Specifically, we discuss the role of local responders in neuroinflammation, including the well-studied microglia as well as the emerging players, border-associated macrophages, and macrophages originating from the skull bone marrow. Additionally, we focus on the behavior of monocytes stemming from distant tissues such as the bone marrow and spleen. Finally, we highlight aging as a crucial factor modulating the immune response, which is often neglected in animal studies.

The glymphatic system: a new perspective on brain diseases

The glymphatic system is a brain-wide perivascular pathway driven by aquaporin-4 on the endfeet of astrocytes, which can deliver nutrients and active substances to the brain parenchyma through periarterial cerebrospinal fluid (CSF) influx pathway and remove metabolic wastes through perivenous clearance routes. This paper summarizes the composition, overall fluid flow, solute transport, related diseases, affecting factors, and preclinical research methods of the glymphatic system. In doing so, we aim to provide direction and reference for more relevant researchers in the future.

Neutrophil percentage to albumin ratio is associated with stroke-associated pneumonia and poor outcome in patients with spontaneous intracerebral hemorrhage

Background

The purpose of this study was to investigate the diagnostic performance of the neutrophil percentage-to-albumin ratio (NPAR) for predicting stroke-associated pneumonia (SAP) and functional outcome in patients with intracerebral hemorrhage (ICH).

Methods

We analyzed our prospective database of consecutive ICH patients who were admitted to the First Affiliated Hospital of Chongqing Medical University from January 2016 to September 2021. We included subjects with a baseline computed tomography available and a complete NPAR count performed within 6h of onset. The patients' demographic and radiological characteristics were analyzed. Good outcome was defined as a modifed Rankin Scale score of 0-3 at 90 days. Poor outcome was defined as a modifed Rankin Scale score of 4-6 at 90 days. Multivariable logistic regression models were used to investigate the association between NPAR, SAP, and functional outcome. Receiver operating characteristic (ROC) curve analysis was conducted to identify the optimal cutoff of NPAR to discriminate between good and poor outcomes in ICH patients.

Results

A total of 918 patients with ICH confirmed by non-contrast computed tomography were included. Of those, 316 (34.4%) had SAP, and 258 (28.1%) had poor outcomes. Multivariate regression analysis showed that higher NPAR on admission was an independent predictor of SAP (adjusted odds ratio: 2.45; 95% confidence interval, 1.56-3.84; P<0.001) and was associated with increased risk of poor outcome (adjusted odd ratio:1.72; 95% confidence interval, 1.03-2.90; P=0.040) in patients with ICH. In ROC analysis, an NPAR of 2 was identified as the optimal cutoff value to discriminate between good and poor functional outcomes.

Conclusion

Higher NPAR is independently associated with SAP and poor functional outcome in patients with ICH. Our findings suggest that early prediction of SAP is feasible by using a simple biomarker NPAR.