Adaptive Immunity Regulation and Cerebral Ischemia

Identification of key genes and immune infiltration in peripheral blood biomarker analysis of delayed cerebral ischemia: Valproic acid as a potential therapeutic drug

BACKGROUND

Delayed cerebral ischemia (DCI) is a common and serious complication of subarachnoid hemorrhage (SAH). Its pathogenesis is not fully understood. Here, we developed a predictive model based on peripheral blood biomarkers and validated the model using several bioinformatic multi-analysis methods.

METHODS

Six datasets were obtained from the GEO database. Characteristic genes were screened using weighted correlation network analysis (WGCNA) and differentially expressed genes. Three machine learning algorithms, elastic networks-LASSO, support vector machines (SVM-RFE) and random forests (RF), were also used to construct diagnostic prediction models for key genes. To further evaluate the performance and predictive value of the diagnostic models, nomogram model were constructed, and the clinical value of the models was assessed using Decision Curve Analysis (DCA), Area Under the Check Curve (AUC), Clinical Impact Curve (CIC), and validated in the mouse single-cell RNA-seq dataset. Mendelian randomization(MR) analysis explored the causal relationship between SAH and stroke, and the intermediate influencing factors. We validated this by retrospectively analyzing the qPCR levels of the most relevant genes in SAH and SAH-DCI patients. This experiment demonstrated a statistically significant difference between SAH and SAH-DCI and normal group controls. Finally, potential small molecule compounds interacting with the selected features were screened from the Comparative Toxicogenomics Database (CTD).

RESULTS

The fGSEA results showed that activation of Toll-like receptor signaling and leukocyte transendothelial cell migration pathways were positively correlated with the DCI phenotype, whereas cytokine signaling pathways and natural killer cell-mediated cytotoxicity were negatively correlated. Consensus feature selection of DEG genes using WGCNA and three machine learning algorithms resulted in the identification of six genes (SPOCK2, TRRAP, CIB1, BCL11B, PDZD8 and LAT), which were used to predict DCI diagnosis with high accuracy. Three external datasets and the mouse single-cell dataset showed high accuracy of the diagnostic model, in addition to high performance and predictive value of the diagnostic model in DCA and CIC. MR analysis looked at stroke after SAH independent of SAH, but associated with multiple intermediate factors including Hypertensive diseases, Total triglycerides levels in medium HDL and Platelet count. qPCR confirmed that significant differences in DCI signature genes were observed between the SAH and SAH-DCI groups. Finally, valproic acid became a potential therapeutic agent for DCI based on the results of target prediction and molecular docking of the characterized genes.

CONCLUSION

This diagnostic model can identify SAH patients at high risk for DCI and may provide potential mechanisms and therapeutic targets for DCI. Valproic acid may be an important future drug for the treatment of DCI.

Research progress on immune-related therapeutic targets of brain injury caused by cerebral ischemia

Stroke is the second leading cause of death worldwide and a leading cause of disability. The innate immune response occurs immediately after cerebral ischemia, resulting in adaptive immunity. More and more experimental evidence has proved that the immune response caused by cerebral ischemia plays an important role in early brain injury and later the recovery of brain injury. Innate immune cells and adaptive cells promote the occurrence of cerebral ischemic injury but also protect brain cells. A large number of studies have shown that cytokines and immune-related substances also have dual functions of promoting injury, reducing injury, or promoting injury recovery in the later stage of cerebral ischemia. They can be an important target for treating cerebral ischemic recovery. Therefore, this study discussed the immune cells, cytokines, and immune-related substances with dual roles in cerebral ischemia and summarized the therapeutic targets of cerebral ischemia. To explore more effective methods to treat cerebral ischemia, promote the recovery of brain function, and improve the prognosis of patients.

Rhoa/ROCK, mTOR and Secretome-Based Treatments for Ischemic Stroke: New Perspectives

Ischemic stroke triggers a complex cascade of cellular and molecular events leading to neuronal damage and tissue injury. This review explores the potential therapeutic avenues targeting cellular signaling pathways implicated in stroke pathophysiology. Specifically, it focuses on the articles that highlight the roles of RhoA/ROCK and mTOR signaling pathways in ischemic brain injury and their therapeutic implications. The RhoA/ROCK pathway modulates various cellular processes, including cytoskeletal dynamics and inflammation, while mTOR signaling regulates cell growth, proliferation, and autophagy. Preclinical studies have demonstrated the neuroprotective effects of targeting these pathways in stroke models, offering insights into potential treatment strategies. However, challenges such as off-target effects and the need for tissue-specific targeting remain. Furthermore, emerging evidence suggests the therapeutic potential of MSC secretome in stroke treatment, highlighting the importance of exploring alternative approaches. Future research directions include elucidating the precise mechanisms of action, optimizing treatment protocols, and translating preclinical findings into clinical practice for improved stroke outcomes.

Exploring the in vitro anti-inflammatory activity of gross saponins of Tribulus terrestris L. fruit by using liquid chromatography-mass spectrometry-based cell metabolomics approach

Our previous studies confirmed the efficacy of gross saponins of Tribulus terrestris L. fruit in treating cerebral ischemia. This study aimed to investigate the related mechanisms in vitro. The lipopolysaccharide-induced BV2 cells model was constructed and treated with gross saponins at different concentrations to explore its anti-inflammatory activity. The cell metabolite changes were tracked by liquid chromatography-mass spectrometry (LC-MS)-based metabolomics, and the metabolic biomarkers and related metabolic pathways were analyzed. Molecular biochemistry analysis was further used to verify the relevant inflammatory pathways. The results showed that the saponins reduced nitric oxide release and the secretion of tumor necrosis factor-alpha, interleukin-1β, and interleukin-6 from lipopolysaccharide-induced BV2 cells. Metabolic perturbations occurred in lipopolysaccharide-treated BV2 cells, which could be reversed by drug treatment via mainly regulating glycerophospholipid metabolism, tryptophan metabolism, purine metabolism pathways, etc. The western blot analysis demonstrated that saponin could suppress the activation of the inflammatory-related signaling pathway. The present study explored the in vitro anti-inflammatory mechanism of gross saponins of Tribulus terrestris L. fruit using an LC-MS-based cell metabolomics approach, which confirms the great potential of LC-MS for drug efficacy evaluation and can be applied in other herbal medicine-related analyses.

Molecular chaperones in stroke-induced immunosuppression

Stroke-induced immunosuppression is a process that leads to peripheral suppression of the immune system after a stroke and belongs to the central nervous system injury-induced immunosuppressive syndrome. Stroke-induced immunosuppression leads to increased susceptibility to post-stroke infections, such as urinary tract infections and stroke-associated pneumonia, worsening prognosis. Molecular chaperones are a large class of proteins that are able to maintain proteostasis by directing the folding of nascent polypeptide chains, refolding misfolded proteins, and targeting misfolded proteins for degradation. Various molecular chaperones have been shown to play roles in stroke-induced immunosuppression by modulating the activity of other molecular chaperones, cochaperones, and their associated pathways. This review summarizes the role of molecular chaperones in stroke-induced immunosuppression and discusses new approaches to restore host immune defense after stroke.

Animal Models of Ischemic Stroke with Different Forms of Middle Cerebral Artery Occlusion

Ischemic stroke is a common type of stroke that significantly affects human well-being and quality of life. In order to further characterize the pathophysiology of ischemic stroke and develop new treatment strategies, ischemic stroke models with controllable and consistent response to potential clinical treatments are urgently needed. The middle cerebral artery occlusion (MCAO) model is currently the most widely used animal model of ischemic stroke. This review discusses various methods for constructing the MCAO model and compares their advantages and disadvantages in order to provide better approaches for studying ischemic stroke.

Hydrogen sulfide and its donors for the treatment of cerebral ischaemia-reperfusion injury: A comprehensive review

As an endogenous gas signalling molecule, hydrogen sulfide (H₂S) is frequently present in a variety of mammals and plays a significant role in the cardiovascular and nervous systems. Reactive oxygen species (ROS) are produced in large quantities as a result of cerebral ischaemia-reperfusion, which is a very serious class of cerebrovascular diseases. ROS cause oxidative stress and induce specific gene expression that results in apoptosis. H₂S reduces cerebral ischaemia-reperfusion-induced secondary injury via anti-oxidative stress injury, suppression of the inflammatory response, inhibition of apoptosis, attenuation of cerebrovascular endothelial cell injury, modulation of autophagy, and antagonism of P2X7 receptors, and it plays an important biological role in other cerebral ischaemic injury events. Despite the many limitations of the hydrogen sulfide therapy delivery strategy and the difficulty in controlling the ideal concentration, relevant experimental evidence demonstrating that H₂S plays an excellent neuroprotective role in cerebral ischaemia-reperfusion injury (CIRI). This paper examines the synthesis and metabolism of the gas molecule H₂S in the brain as well as the molecular mechanisms of H₂S donors in cerebral ischaemia-reperfusion injury and possibly other unknown biological functions. With the active development in this field, it is expected that this review will assist researchers in their search for the potential value of hydrogen sulfide and provide new ideas for preclinical trials of exogenous H₂S.

Hyperacute immune responses associate with immediate neuropathology and motor dysfunction in large vessel occlusions

OBJECTIVE

Despite successful endovascular therapy, a proportion of stroke patients exhibit long-term functional decline, regardless of the cortical reperfusion. Our objective was to evaluate the early activation of the adaptive immune response and its impact on neurological recovery in patients with large vessel occlusion (LVO).

METHODS

Nineteen (13 females, 6 males) patients with acute LVO were enrolled in a single-arm prospective cohort study. During endovascular therapy (EVT), blood samples were collected from pre and post-occlusion, distal femoral artery, and median cubital vein (controls). Cytokines, chemokines, cellular and functional profiles were evaluated with immediate and follow-up clinical and radiographic parameters, including cognitive performance and functional recovery.

RESULTS

In the hyperacute phase (within hours), adaptive immune activation was observed in the post-occlusion intra-arterial environment (post). Ischemic vascular tissue had a significant increase in T-cell-related cytokines, including IFN-γ and MMP-9, while GM-CSF, IL-17, TNF-α, IL-6, MIP-1a, and MIP-1b were decreased. Cellularity analysis revealed an increase in inflammatory IL-17+ and GM-CSF+ helper T-cells, while natural killer (NK), monocytes and B-cells were decreased. A correlation was observed between hypoperfused tissue, infarct volume, inflammatory helper, and cytotoxic T-cells. Moreover, helper and cytotoxic T-cells were also significantly increased in patients with improved motor function at 3 months.

INTERPRETATION

We provide evidence of the activation of the inflammatory adaptive immune response during the hyperacute phase and the association of pro-inflammatory cytokines with greater ischemic tissue and worsening recovery after successful reperfusion. Further characterization of these immune pathways is warranted to test selective immunomodulators during the early stages of stroke rehabilitation.

Identification of immune characteristic landscapes related to autophagy in ischemic stroke

Ischemic stroke (IS) is a common and grievous nervous system disease. Both autophagy activation and immune response after cerebral ischemia play important roles in the development of IS. Many studies have revealed a close interplay between autophagy and immunity. However, little is known about how autophagy influences the immune characteristics of IS. Hence, the study aims to systematically explore the role of autophagy and its impact on immune characteristics in IS. We first compared the expression differences of autophagy genes in a training set and identified 20 dysregulated autophagy genes between healthy and IS samples. An autophagy-related classifier composed of seven genes was further established and could well distinguish healthy and IS samples. Then, the association between autophagy and immune characteristics, including infiltrating immunocytes, activity of immune reactions, and HLA gene expression, was investigated. The results showed that autophagy closely correlated with immune characteristics, such as NAMPT and ARNT significantly related to infiltrating immunocytes; PPP1R15A and CASP3 significantly related to activity of immune reactions; and NAMPT and ATG16L2 significantly related to HLA genes. Next, two distinct autophagy expression patterns were identified by unsupervised clustering analysis, and diverse immune characteristics were discovered between them. A total of 5481 autophagy phenotype-related genes were obtained between two expression patterns, and their biological functions revealed that these genes were involved in immune-related biological pathways. Finally, five dysregulated autophagy genes (FOS, MAP1LC3B, ERO1L, ARNT, and PPP1R15A) were proved between IS and healthy samples using another two validation sets. Our results illustrated that autophagy had a dramatic effect on the immunity of IS and provided a novel sight into understanding the pathogenesis of IS.

COVID-19 Vaccination Is Associated with a Better Outcome in Acute Ischemic Stroke Patients: A Retrospective Observational Study

Background: It is unclear whether and how COVID-19 vaccination may affect the outcome of patients with acute ischemic stroke (AIS). We investigated this potential association in a retrospective study by comparing previously vaccinated (VAX) versus unvaccinated (NoVAX) stroke patients. Methods: We collected clinical reports for all consecutive AIS patients admitted to our hospital and evaluated the outcome predictors in VAX and NoVAX groups. Adjustments were made for possible confounders in multivariable logistic regression analysis, and adjusted hazard ratios were calculated. Results: A total of 466 AIS patients (287 VAX and 179 NoVAX) were included in this study. The NIHSS score at discharge and mRS score at a 3-month follow-up visit were significantly lower in VAX patients compared to NoVAX patients (p < 0.001). Good outcomes (mRS 0−2) were significantly associated with COVID-19 vaccination before AIS (adjusted hazard ratio, 0.400 [95% CI = 0.216−0.741]). Conclusions: The observation that COVID-19 vaccination can influence the outcome of AIS provides support for further studies investigating the role of immunity in ischemic brain damage.

Th1/Th2 polarization of peripheral immune response in atherothrombotic and cardioembolic stroke: a prospective study

Compelling evidence suggest a key role of immune system in the development and progression of ischemic stroke. Although the balance between proinflammatory CD4 + T helper (Th)-1 lymphocytes, expressing T-bet transcription factor, and anti-inflammatory Th2 cells expressing GATA3 seems to influence the outcome in experimental stroke, the role of peripheral immune response in acute stroke patients is poorly understood. We aimed to evaluate the peripheral Th1/Th2 balance in acute atherothrombotic (ATHS) and cardioembolic stroke (CES) patients and in age- and sex-matched healthy subjects. Using flow cytometry, we analyzed the percentage of CD4 + T-bet + T cells and CD4 + GATA3 + T cells from peripheral blood of ATHS and CES patients (2,4 and 7 days after stroke onset). Patients and controls were screened for infectious conditions, autoimmune, inflammatory, or cancerous diseases. On day 2 circulating CD4 + T-bet + T cells were significantly higher in stroke patients compared to controls, and in ATHS compared to CES and controls. On day 7, we observed a significant increase of CD4 + T-bet + T cells in both ATHS and CES patients compared to baseline. No difference was observed in circulating CD4 + GATA3 + T cells among ATHS, CES patients, and controls. These data suggest that circulating CD4 + T-bet + T cells could be useful marker indicating atherothrombotic genesis of stroke and provide new insight into the peripheral adaptive immune response in acute stroke.

Contribution of P2X purinergic receptor in cerebral ischemia injury

The development of cerebral ischemia involves brain damage and abnormal changes in brain function, which can cause neurosensory and motor dysfunction, and bring serious consequences to patients. P2X purinergic receptors are expressed in nerve cells and immune cells, and are mainly expressed in microglia. The P2X4 and P2X7 receptors in the P2X purinergic receptors play a significant role in regulating the activity of microglia. Moreover, ATP-P2X purine information transmission is involved in the progression of neurological diseases, including the release of pro-inflammatory factors, driving factors and cytokines after cerebral ischemia injury, inducing inflammation, and aggravating cerebral ischemia injury. P2X receptors activation can mediate the information exchange between microglia and neurons, induce neuronal apoptosis, and aggravate neurological dysfunction after cerebral ischemia. However, inhibiting the activation of P2X receptors, reducing their expression, inhibiting the activation of microglia, and has the effect of protecting nerve function. In this paper, we discussed the relationship between P2X receptors and nervous system function and the role of microglia activation inducing cerebral ischemia injury. Additionally, we explored the potential role of P2X receptors in the progression of cerebral ischemic injury and their potential pharmacological targets for the treatment of cerebral ischemic injury.

Experimental verification and validation of immune biomarkers based on chromatin regulators in ischemic stroke

Ischemic stroke (IS) is a disease characterized by rapid progression and high mortality and disability rates. Its pathophysiological process is inseparable from immune dysfunction. Recently, chromatin regulators (CRs) have been described as a class of enzymes that can recognize, form, and maintain the epigenetic state of an organism, and are closely associated with immune regulation. Nevertheless, the role of CR-related genes in IS has not been fully elucidated. In this study, seven CR-related immune biomarkers in the GSE58294 and GSE22255 datasets were identified by combining differential gene expression analysis, weighted correlation network analysis, and single sample gene set enrichment analysis. After experimental validation using quantitative polymerase chain reaction, four genes (DPF2, LMNB1, MLLT3, and JAK2) were screened as candidate immune biomarkers. These four biomarkers demonstrated good predictive power in the clinical risk model (area under the curve, 0.775). Molecular docking simulations revealed that mevastatin, WP1066, cladribine, trichostatin A, mequitazine, and zuclomiphene may be potential immunomodulatory drugs for IS. Overall, the results of this study contribute to the identification of CR-related immune therapeutics target in IS and provide an important reference for further research.

Low-Molecular-Weight Heparin Versus Aspirin in Early Management of Acute Ischemic Stroke: A Systematic Review and Meta-Analysis

Objectives

To evaluate the difference between low-molecular-weight heparin (LMWH) and aspirin in preventing early neurological deterioration (END) and recurrent ischemic stroke (RIS), post-recovery independence, and safety outcomes in acute ischemic stroke.

Materials and Methods

We performed systematic searches of the PubMed, Embase, Web of Science, and Cochrane Library databases for full-text articles of randomized controlled trials (RCTs) of LMWH vs. aspirin in the early management of acute ischemic stroke. Information on study design, eligibility criteria, baseline information, and outcomes was extracted. Synthesized relative risks (RRs) with 95% confidence intervals (CIs) are used to present the differences between the two treatments based on fixed-effects models.

Results

Five RCTs were retrieved from the online databases. The results showed no significant difference in efficacy outcomes between the two groups among unselected patients. Subgroup analysis showed that LMWH was significantly related to a lower incidence of END events [relative risk (RR): 0.44, 95% confidence interval (CI): 0.35-0.56] and reduced occurrence of RIS during treatment (OR: 0.34, 95% CI: 0.16-0.75) in non-cardioembolic stroke. LMWH significantly increased the number of patients with a modified Rankin scale (mRS) score of 0-1 at 6 months in patients with large-artery occlusive disease (LAOD) (RR: 0.50, 95% CI: 0.27-0.91). LMWH had a similar effect on symptomatic intracranial hemorrhage (sICH) and major extracranial hemorrhage during treatment to that of aspirin, except that LMWH was related to an increased likelihood of extracranial hemorrhage.

Conclusions

In patients with acute non-cardioembolic ischemic stroke, especially that with large-artery stenosis, LMWH treatment significantly reduced the incidence of END and RIS, and improved the likelihood of independence (mRS 0-1) at 6 months compared with those with aspirin treatment. LMWH was related to an increased likelihood of extracranial hemorrhage among all patients; however, the difference in major extracranial hemorrhage and sICH was not significant. Choosing the appropriate patients and paying attention to the start time and duration of treatment are very important in the use of anticoagulation.

Systematic Review Registration

http://www.crd.york.ac.uk/PROSPERO, identifier CRD42020185446.

Sex-Specific Immune Responses in Stroke

In both acute and chronic diseases, functional differences in host immune responses arise from a multitude of intrinsic and extrinsic factors. Two of the most important factors affecting the immune response are biological sex and aging. Ischemic stroke is a debilitating disease that predominately affects older individuals. Epidemiological studies have shown that older women have poorer functional outcomes compared with men, in part due to the older age at which they experience their first stroke and the increased comorbidities seen with aging. The immune response also differs in men and women, which could lead to altered inflammatory events that contribute to sex differences in poststroke recovery. Intrinsic factors including host genetics and chromosomal sex play a crucial role both in shaping the host immune system and in the neuroimmune response to brain injury. Ischemic stroke leads to altered intracellular communication between astrocytes, neurons, and resident immune cells in the central nervous system. Increased production of cytokines and chemokines orchestrate the infiltration of peripheral immune cells and promote neuroinflammation. To maintain immunosurveillance, the host immune and central nervous system are highly regulated by a diverse population of immune cells which are strategically distributed within the neurovascular unit and become activated with injury. In this review, we provide a comprehensive overview of sex-specific host immune responses in ischemic stroke.

Effect of angiotensin II receptor blocker therapy on markers of fibrosis and immune inflammation in hypertensive patients with chronic kidney disease after ischemic stroke

Aim. To compare the effect of angiotensin II receptor blocker therapy (azilsartan, telmisartan) on fibrosis and immune inflammation markers in hypertensive patients with chronic kidney disease (CKD) after ischemic stroke (IS).

Material and methods. The study included 76 hypertensive patients aged 60-74 years (mean age, 66±5 years) with CKD after IS. Patients were randomly divided into following pharmacotherapy groups: 38 patients — telmisartan group; 36 patients — azilsartan group. The control group consisted of 20 hypertensive people (mean age, 63±2 years) without a history of CKD and IS. The levels of matrix metalloproteinase 9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) were determined by enzyme-linked immunosorbent assay (ELISA Kit, USA). The levels of interleukin-1β (IL-1β), tumor necrosis factor α (TNF-α), interferon γ (INF-γ), monocytic chemoattractant protein 1 (MCP-1) were assessed using Vector-Best kit (Russia).

Results. Six-month azilsartan therapy led to a decrease in the levels of MMP-9 by 19,9% (p<0,01), TIMP-1 by 7,5% (p<0,05), IL-1β by 7,8%, TNF-α by 13,5%, INF-γ by 7,1%, MCP-1 by 13% (p<0,05). Telmisartan therapy was associated with a decrease in the levels of MMP-9 by 39,1% (p<0,01), TIMP-1 by 16,4%, IL-1β by 10,1% (p<0,05), TNF-α by 20,8% (p<0,01), INF-γ by 14,6% (p<0,05), MCP-1 by 21,3% (p<0,01). Intergroup comparison revealed more pronounced changes in the levels of MMP-9 by 19,2% (p<0,01), TIMP-1 by 7,2% (p<0,05), TNF-α by 7,3% (p<0,05), INF-γ by 7,5% (p<0,05), and MCP-1 by 8,3% (p<0,05) when using telmisartan compared to azilsartan. When using telmisartan, the increase in glomerular filtration rate (GFR) was 14,2% (p<0,05) higher compared to azilsartan.

Conclusion. Six-month telmisartan therapy in hypertensive patients with CKD after stroke was accompanied by a more pronounced decrease in markers of myocardial fibrosis (MMP-9, TIMP-1) and immune inflammation (TNF-α, INF-γ, MCP-1) compared with azilsartan, as well as with more pronounced improvement in renal function.

Androgen receptor contributes to microglial/macrophage activation in rats with intracranial hemorrhage by mediating the JMJD3/Botch/Notch1 axis

Intracerebral hemorrhage (ICH) is a leading medical problem and has no effective treatment approach up until now. The transcription factor androgen receptor (AR) has been indicated in the cerebrovascular function recently. However, its participation in ICH remains unclear. The present study aims to expound the regulation of AR in microglia/macrophage phenotypes and the secondary brain injury in a rat model with ICH, and to discuss the involved pathway. Following the induction of ICH in rats, we found that ICH led to increased mNSS score, enhanced microglial activity, and promoted levels of inflammatory factors and apoptosis of brain cells. Using microarray analysis, AR was found to be significantly overexpressed in ICH rat brain tissues. AR repressed the transcription of Jumonji d3 (JMJD3, histone 3 demethylase). JMJD3 inhibited the methylation of Botch and promoted the activity of Notch1. JMJD3 hampered microglial activity and ameliorated secondary brain injury in rats, whereas upregulation of AR or downregulation of Botch reversed the protective effects of JMJD3. In conclusion, we found that AR promoted microglial activation and secondary brain injury via transcriptionally repressing JMJD3 and mediating the subsequent Botch/Notch1 pathway, which may provide novel insights into therapeutic options for the treatment of ICH.

Molecular Mechanisms of Neuroimmune Crosstalk in the Pathogenesis of Stroke

Stroke disrupts the homeostatic balance within the brain and is associated with a significant accumulation of necrotic cellular debris, fluid, and peripheral immune cells in the central nervous system (CNS). Additionally, cells, antigens, and other factors exit the brain into the periphery via damaged blood–brain barrier cells, glymphatic transport mechanisms, and lymphatic vessels, which dramatically influence the systemic immune response and lead to complex neuroimmune communication. As a result, the immunological response after stroke is a highly dynamic event that involves communication between multiple organ systems and cell types, with significant consequences on not only the initial stroke tissue injury but long-term recovery in the CNS. In this review, we discuss the complex immunological and physiological interactions that occur after stroke with a focus on how the peripheral immune system and CNS communicate to regulate post-stroke brain homeostasis. First, we discuss the post-stroke immune cascade across different contexts as well as homeostatic regulation within the brain. Then, we focus on the lymphatic vessels surrounding the brain and their ability to coordinate both immune response and fluid homeostasis within the brain after stroke. Finally, we discuss how therapeutic manipulation of peripheral systems may provide new mechanisms to treat stroke injury.

SARS-CoV-2: Unique Challenges of the Virus and Vaccines

In November 2019, the highly infectious coronavirus SARS-CoV-2 emerged in Wuhan, China, and has since spread to almost all countries worldwide. Since its emergence, the COVID-19 infection has led to significant public health, economic and social problems. The current pandemic has inspired researchers to make every effort to design and develop an effective COVID-19 vaccine to provide sufficient protection against the virus and control the infection. In December 2020, the Pfizer vaccine was the first COVID-19 vaccine given Emergency Use Authorization (EUA), and the second FDA so-approved vaccine was the Moderna mRNA-1273 vaccine, which was introduced a week later. Both Pfizer and Moderna vaccines are mRNA-based vaccines, and are estimated to have an efficacy rate of more than 94%. The aim of this article is to provide a review of the attempts made to develop safe SARS-CoV-2 vaccines, highlighting potential challenges and concerns, such as disease enhancement, virus mutations, and public acceptance of the vaccine.

The lymphatic drainage system of the CNS plays a role in lymphatic drainage, immunity, and neuroinflammation in stroke

The lymphatic drainage system of the central nervous system (CNS) plays an important role in maintaining interstitial fluid balance and regulating immune responses and immune surveillance. The impaired lymphatic drainage system of the CNS might be involved in the onset and progression of various neurodegenerative diseases, neuroinflammation, and cerebrovascular diseases. A significant immune response and brain edema are observed after stroke, resulting from disrupted homeostasis in the brain. Thus, understanding the lymphatic drainage system of the CNS in stroke may lead to the development of new approaches for therapeutic interventions in the future. Here, we review recent evidence implicating the lymphatic drainage system of the CNS in stroke.

Temperature Plays an Essential Regulatory Role in the Tumor Immune Microenvironment

In recent years, emerging immunotherapy has been included in various malignant tumor treatment standards. Temperature has been considered to affect different pathophysiological reactions such as inflammation and cancer for a long time. However, in tumor immunology research, temperature is still rarely considered a significant variable. In this review, we discuss the effects of room temperature, body temperature, and the local tumor temperature on the tumor immune microenvironment from multiple levels and perspectives, and we discuss changes in the body's local and whole-body temperature under tumor conditions. We analyze the current use of ablation treatment-the reason for the opposite immune effect. We should pay more attention to the therapeutic potential of temperature and create a better antitumor microenvironment that can be combined with immunotherapy.

The Changes of Leukocytes in Brain and Blood After Intracerebral Hemorrhage

Preclinical and clinical research has demonstrated that inflammation is a critical factor regulating intracerebral hemorrhage (ICH)-induced brain injury. Growing evidence suggests that myeloid cells and lymphocytes have an effect on the pathophysiological processes associated with ICH, such as inflammation, immune responses, perihematomal edema formation, blood-brain barrier (BBB) integrity, and cell death. However, the underlying mechanisms remain largely unknown. We aimed to explore the role immune cells played at different stages of the ICH. To achieve this, novel bioinformatics algorithms were employed to analyze the gene expression profiles and three different analytical tools were utilized to predict the abundances of cell types. In this study, we found that natural killer (NK) cells infiltrated into the brain parenchyma after ICH. Infiltrating NK cells may mediate brain injury through degranulation and recruitment of other cells. Besides, in the acute phase of ICH, monocytes in peripheral blood carried out phagocytosis and secretion of cytokines. On the other hand, in the subacute stage, non-classical monocytes were activated and showed a stronger ability to carry out heme metabolism, wound healing, and antigen processing and presentation. In conclusion, our findings emphasize the significance of intracerebral infiltrating immunocytes in ICH and demonstrate that ICH is a systemic disease affected by peripheral blood. The hub genes identified might be promising therapeutic targets. We also provide a reference on how to use bioinformatics approaches to explore non-neoplastic immune-related diseases.

Peripheral inflammation and blood-brain barrier disruption: effects and mechanisms

The blood–brain barrier (BBB) is an important physiological barrier that separates the central nervous system (CNS) from the peripheral circulation, which contains inflammatory mediators and immune cells. The BBB regulates cellular and molecular exchange between the blood vessels and brain parenchyma. Normal functioning of the BBB is crucial for the homeostasis and proper function of the brain. It has been demonstrated that peripheral inflammation can disrupt the BBB by various pathways, resulting in different CNS diseases. Recently, clinical research also showed CNS complications following SARS‐CoV‐2 infection and chimeric antigen receptor (CAR)‐T cell therapy, which both lead to a cytokine storm in the circulation. Therefore, elucidation of the mechanisms underlying the BBB disruption induced by peripheral inflammation will provide an important basis for protecting the CNS in the context of exacerbated peripheral inflammatory diseases. In the present review, we first summarize the physiological properties of the BBB that makes the CNS an immune‐privileged organ. We then discuss the relevance of peripheral inflammation‐induced BBB disruption to various CNS diseases. Finally, we elaborate various factors and mechanisms of peripheral inflammation that disrupt the BBB.

Platelet-Reactive Antibodies in Patients after Ischaemic Stroke-An Epiphenomenon or a Natural Protective Mechanism

Ischaemic brain damage induces autoimmune responses, including the production of autoantibodies with potential neuroprotective effects. Platelets share unexplained similarities with neurons, and the formation of anti-platelet antibodies has been documented in neurological disorders. The aim of this study was to investigate the presence of anti-platelet antibodies in the peripheral blood of patients after ischaemic stroke and determine any clinical correlations. Using a flow cytometry-based platelet immunofluorescence method, we detected platelet-reactive antibodies in 15 of 48 (31%) stroke patients and two of 50 (4%) controls (p < 0.001). Western blotting revealed heterogeneous reactivities with platelet proteins, some of which overlapped with brain proteins. Stroke patients who carried anti-platelet antibodies presented with larger infarcts and more severe neurological dysfunction, which manifested as higher scores on the National Institutes of Health Stroke Scale (NIHSS; p = 0.009), but they had a greater recovery in the NIHSS by the time of hospital discharge (day 7 ± 2) compared with antibody-negative patients (p = 0.043). Antibodies from stroke sera reacted more strongly with activated platelets (p = 0.031) and inhibited platelet aggregation by up to 30.1 ± 2.8% (p < 0.001), suggesting the potential to interfere with thrombus formation. In conclusion, platelet-reactive antibodies can be found in patients soon after ischaemic stroke and correlate with better short-term outcomes, suggesting a potential novel mechanism limiting thrombosis.

Genetic Aspects of Inflammation and Immune Response in Stroke

Genetic determinants play important role in the complex processes of inflammation and immune response in stroke and could be studied in different ways. Inflammation and immunomodulation are associated with repair processes in ischemic stroke, and together with the concept of preconditioning are promising modes of stroke treatment. One of the important aspects to be considered in the recovery of patients after the stroke is a genetic predisposition, which has been studied extensively. Polymorphisms in a number of candidate genes, such as IL-6, BDNF, COX2, CYPC19, and GPIIIa could be associated with stroke outcome and recovery. Recent GWAS studies pointed to the variant in genesPATJ and LOC as new genetic markers of long term outcome. Epigenetic regulation of immune response in stroke is also important, with mechanisms of histone modifications, DNA methylation, and activity of non-coding RNAs. These complex processes are changing from acute phase over the repair to establishing homeostasis or to provoke exaggerated reaction and death. Pharmacogenetics and pharmacogenomics of stroke cures might also be evaluated in the context of immuno-inflammation and brain plasticity. Potential novel genetic treatment modalities are challenged but still in the early phase of the investigation.