Suppression of dendritic cell functions contributes to the anti-inflammatory action of granulocyte-colony stimulating factor in experimental stroke

Evaluation of the causal effects of immune cells on ischemic stroke: a Mendelian randomization study

Background

Ischemic stroke (IS) is a cerebrovascular disease caused by various factors, and its etiology remains inadequately understood. The role of immune system dysfunction in IS has been increasingly recognized. Our objective was to evaluate whether circulating immune cells causally impact IS risk.

Methods

We conducted two-sample Mendelian randomization analyses to evaluate the causal effects of 731 immune cell traits on IS, utilizing publicly available genome-wide association studies (GWAS) summary statistics for 731 immune cell traits as exposure data, and two GWAS statistics for IS as outcome data. A set of sensitivity analyses, including Cochran's Q test, I 2 statistics, MR-Egger intercept test, MR-PRESSO global test, and leave-one-out sensitivity analyses, were performed to assess the robustness of the results. Additionally, meta-analyses were conducted to combine the results from the two different IS datasets. Finally, we extracted instrumental variables of immune cell traits with causal effects on IS in both IS datasets for SNP annotation.

Results

A total of 41 and 35 immune cell traits were identified to have significant causal effects on IS based on two different IS datasets, respectively. Among them, the immune cell trait CD62L- plasmacytoid Dendritic Cell AC and CD4+ CD8dim T cell%leukocyte respectively served as risk factor and protective element in both IS datasets. The robustness of the causal effects was confirmed through the sensitivity analyses. The results of the meta-analyses further support the causal effects of CD62L- plasmacytoid Dendritic Cell AC (pooled OR=1.030, 95%CI: 1.011-1.049, P=0.002) and CD4+ CD8dim T cell%leukocyte (pooled OR=0.959, 95%CI: 0.935-0.984, P=0.001). Based on these two immune cell traits, 33 genes that may be related to the causal effects were mapped.

Conclusions

Our study demonstrated the potential causal effects of circulating immune cells on IS, providing valuable insights for future studies aimed at preventing IS.

Inhibiting leukocyte-endothelial cell interactions by Chinese medicine Tongxinluo capsule alleviates no-reflow after arterial recanalization in ischemic stroke

AIMS

Despite successful vascular recanalization in stroke, one-fourth of patients have an unfavorable outcome due to no-reflow. The pathogenesis of no-reflow is fully unclear, and therapeutic strategies are lacking. Upon traditional Chinese medicine, Tongxinluo capsule (TXL) is a potential therapeutic agent for no-reflow. Thus, this study is aimed to investigate the pathogenesis of no-reflow in stroke, and whether TXL could alleviate no-reflow as well as its potential mechanisms of action.

METHODS

Mice were orally administered with TXL (3.0 g/kg/d) after transient middle cerebral artery occlusion. We examined the following parameters: neurological function, no-reflow, leukocyte-endothelial cell interactions, HE staining, leukocyte subtypes, adhesion molecules, and chemokines.

RESULTS

Our results showed stroke caused neurological deficits, neuron death, and no-reflow. Adherent and aggregated leukocytes obstructed microvessels as well as leukocyte infiltration in ischemic brain. Leukocyte subtypes changed after stroke mainly including neutrophils, lymphocytes, regulatory T cells, suppressor T cells, helper T type 1 (Th1) cells, Th2 cells, B cells, macrophages, natural killer cells, and dendritic cells. Stroke resulted in upregulated expression of adhesion molecules (P-selectin, E-selectin, and ICAM-1) and chemokines (CC-chemokine ligand (CCL)-2, CCL-3, CCL-4, CCL-5, and chemokine C-X-C ligand 1 (CXCL-1)). Notably, TXL improved neurological deficits, protected neurons, alleviated no-reflow and leukocyte-endothelial cell interactions, regulated multiple leukocyte subtypes, and inhibited the expression of various inflammatory mediators.

CONCLUSION

Leukocyte-endothelial cell interactions mediated by multiple inflammatory factors are an important cause of no-reflow in stroke. Accordingly, TXL could alleviate no-reflow via suppressing the interactions through modulating various leukocyte subtypes and inhibiting the expression of multiple inflammatory mediators.

Granulocyte Colony-Stimulating Factor Improved Core Symptoms of Autism Spectrum Disorder via Modulating Glutamatergic Receptors in the Prefrontal Cortex and Hippocampus of Rat Brains

Chronic neuroinflammation-induced anomalous glutamate receptor activation has been identified as one of the important factors in the pathogenesis of autism spectrum disorder (ASD). Thus, the current study was designed to elucidate the neuroprotective effect of the granulocyte colony-stimulating factor (G-CSF), a haemopoietic growth factor, an anti-inflammatory, and a neuroprotectant to decipher the underlying mechanism(s) in the valproic acid (VPA)-induced experimental model of ASD. Experimentally, the ASD rat model was induced by a single dose of VPA (600 mg/kg; i.p.) on gestation day 12.5 to the pregnant female rats. After birth, pups were treated with vehicle, normal saline 0.9% i.p., risperidone (2.5 mg/kg; i.p.), and G-CSF (10, 35, and 70 μg/kg; i.p.) from postnatal day (PND) 23 to 43. All the groups were subjected to various developmental and behavior tests from birth. The rats were sacrificed on PND 55, and their brain was excised and processed for biochemical parameters (oxidative stress, inflammatory markers, BDNF), histological examination (H&E, Nissl staining), NMDA, and AMPA receptor expression by immunohistochemistry, western blot, and real-time polymerase chain reaction evaluation. Also, the possible interaction of the G-CSF with NMDA and AMPA receptors was evaluated using the in-silico method. The results of the study showed that in VPA-exposed rats, postnatal treatment of G-CSF rescued all the behavioral abnormalities, oxidative stress, and inflammatory parameters in a dose-dependent manner while risperidone did not show any significant results. The in-silico analysis showed the direct interaction of G-CSF with NMDA and AMPA receptors. The upregulated expression of NMDA and AMPA both in the prefrontal cortex as well as hippocampus was alleviated by G-CSF thereby validating its anti-inflammatory and excitoprotective properties. Thus, G-CSF demonstrated neuroprotection against the core symptoms of autism in the VPA-induced rodent model, making it a potential candidate for the treatment of ASD.

Interactions between the Autonomic Nervous System and the Immune System after Stroke

Acute stroke is one of the leading causes of morbidity and mortality worldwide. Stroke-induced immune-inflammatory response occurs in the perilesion areas and the periphery. Although stroke-induced immunosuppression may alleviate brain injury, it hinders brain repair as the immune-inflammatory response plays a bidirectional role after acute stroke. Furthermore, suppression of the systemic immune-inflammatory response increases the risk of life-threatening systemic bacterial infections after acute stroke. Therefore, it is essential to explore the mechanisms that underlie the stroke-induced immune-inflammatory response. Autonomic nervous system (ANS) activation is critical for regulating the local and systemic immune-inflammatory responses and may influence the prognosis of acute stroke. We review the changes in the sympathetic and parasympathetic nervous systems and their influence on the immune-inflammatory response after stroke. Importantly, this article summarizes the mechanisms on how ANS regulates the immune-inflammatory response through neurotransmitters and their receptors in immunocytes and immune organs after stroke. To facilitate translational research, we also discuss the promising therapeutic approaches modulating the activation of the ANS or the immune-inflammatory response to promote neurologic recovery after stroke. © 2022 American Physiological Society. Compr Physiol 12:3665-3704, 2022.

Colony-Stimulating Factors on Mobilizing CD34+ Cells and Improving Neurological Functions in Patients With Stroke: A Meta-Analysis and a Systematic Review

Background and Purpose: CSF therapy is considered a promising therapeutic approach for stroke. We performed a meta-analysis to explore the safety and efficacy of CSF in published clinical stroke studies. Methods: We searched articles online and manually. Two reviewers selected studies independently, selecting data based on study quality, characteristics of intervention (administration time, observation time, type, dose, and injection approach of CSF), and the baseline characteristics of patients (age, sex, hypertension, diabetes, smoker, and lipids) were extracted. Main prognosis outcomes were measured as all-cause death in severe adverse events (SAE) and recurrent stroke in SAE. Secondary outcomes were measured as CD34+ cell counts in periphery blood at day 5, National Institutes of Health Stroke Scale (NIHSS), and Barthel index (BI), Side effects of CSF were taken as the indicator of safety. STATA13 software was used to perform the meta-analysis.Keywords: Stroke, Colony-stimulating factor, Meta-analysis, therapy, Neurological Diseases Results: This meta-analysis involved 485 patients from eight studies. Among them, 475 patients from seven studies were gauged SAE (all-cause death), 393 patients from six studies were checked SAE (recurrent stroke); 137 patients from three studies underwent CD34⁺ measurement, 389 patients from six studies were tested NIHSS and 307 patients from five studies accessed BI. Compared with the control group, both all-causes death (RR= 1.73, 95%CI= (0.61, 4.92), P=0.735, I²=0.0%) and recurrent stroke (RR= 0.43, 95%CI= (0.14, 1.32), P=0.214, I²=33.1%) present no statistical differences, indicating that the application of CSF does not statistically alter the prognosis of patients with stroke. The application of CSF effectively enhanced CD34+ cell counts in periphery blood at day 5 (SMD= 1.23, 95%CI= (0.54, 1.92), P=0.04, I²=69.0%) but did not statistically impact NIHSS (SMD= -0.40, 95%CI= (-0.93, 0.13), P ≤ 0.001, I²=79.7%) or BI (SMD= 0.04, 95%CI= (-0.38, 0.46), P=0.068, I²=54.3%). Conclusion: Our study consolidates the security of CSF administration for its exerting no effect on detrimental outcomes. It has proven to be effective in elevating CD34+ cell counts in periphery blood at day 5, indicating CSF may participate in stroke recovery, but its efficacy in stroke recovery remains detected.

The immune response of T cells and therapeutic targets related to regulating the levels of T helper cells after ischaemic stroke

Through considerable effort in research and clinical studies, the immune system has been identified as a participant in the onset and progression of brain injury after ischaemic stroke. Due to the involvement of all types of immune cells, the roles of the immune system in stroke pathology and associated effects are complicated. Past research concentrated on the functions of monocytes and neutrophils in the pathogenesis of ischaemic stroke and tried to demonstrate the mechanisms of tissue injury and protection involving these immune cells. Within the past several years, an increasing number of studies have elucidated the vital functions of T cells in the innate and adaptive immune responses in both the acute and chronic phases of ischaemic stroke. Recently, the phenotypes of T cells with proinflammatory or anti-inflammatory function have been demonstrated in detail. T cells with distinctive phenotypes can also influence cerebral inflammation through various pathways, such as regulating the immune response, interacting with brain-resident immune cells and modulating neurogenesis and angiogenesis during different phases following stroke. In view of the limited treatment options available following stroke other than tissue plasminogen activator therapy, understanding the function of immune responses, especially T cell responses, in the post-stroke recovery period can provide a new therapeutic direction. Here, we discuss the different functions and temporal evolution of T cells with different phenotypes during the acute and chronic phases of ischaemic stroke. We suggest that modulating the balance between the proinflammatory and anti-inflammatory functions of T cells with distinct phenotypes may become a potential therapeutic approach that reduces the mortality and improves the functional outcomes and prognosis of patients suffering from ischaemic stroke.

Different changes in granulocyte-colony stimulating factor and its correlation with inflammatory biomarkers in patients after traumatic brain injury

OBJECTIVE

This study analyzed changes in granulocyte-colony stimulating factor (G-CSF) and its correlation with leukocyte and neutrophil counts in patients after traumatic brain injury (TBI).

METHODS

Sixty TBI patients were included retrospectively. The serum levels of G-CSF, tumor necrosis factor-α (TNF-α), and peripheral leukocyte and neutrophil counts at different time points were measured and analyzed, and the 6-month functional outcomes were monitored.

RESULTS

The levels of G-CSF in mild and moderate TBI groups were higher than the control at the first three time points. G-CSF in the severe TBI group increased slowly and peaked at day 7, and was only significantly different from the control at day 7 and 14. The leukocyte and neutrophil counts of the mild group gradually decreased, but a second increase after day 4 was observed in the severe group. The cell counts were higher in the severe group compared to other groups. A positive correlation between G-CSF and leukocyte and neutrophil counts was observed in the severe group at day 1. G-CSF positively correlated with TNF-α in the severe group at day 4 and 7. In severe patients with a good outcome, G-CSF level at day 7 was significantly higher than those with a poor outcome.

CONCLUSION

The G-CSF levels in the severe TBI group exhibited a different pattern from those in the mild and moderate TBI groups, and these levels positively correlated with inflammatory biomarkers. Higher G-CSF levels in severe TBI at day 7 indicated a good outcome at 6 months.

Roles of Specialized Pro-Resolving Lipid Mediators in Cerebral Ischemia Reperfusion Injury

Ischemic stroke contributes to ~80% of all stroke cases. Recanalization with thrombolysis or endovascular thrombectomy are currently critical therapeutic strategies for rebuilding the blood supply following ischemic stroke. However, recanalization is often accompanied by cerebral ischemia reperfusion injury that is mediated by oxidative stress and inflammation. Resolution of inflammation belongs to the end stage of inflammation where inflammation is terminated and the repair of damaged tissue is started. Resolution of inflammation is mediated by a group of newly discovered lipid mediators called specialized pro-resolving lipid mediators (SPMs). Accumulating evidence suggests that SPMs decrease leukocyte infiltration, enhance efferocytosis, reduce local neuronal injury, and decrease both oxidative stress and the production of inflammatory cytokines in various in vitro and in vivo models of ischemic stroke. In this review, we summarize the mechanisms of reperfusion injury and the various roles of SPMs in stroke therapy.

Inflammatory Disequilibrium in Stroke

Over the past several decades, there have been substantial advances in our knowledge of the pathophysiology of stroke. Understanding the benefits of timely reperfusion has led to the development of thrombolytic therapy as the cornerstone of current management of ischemic stroke, but there remains much to be learned about mechanisms of neuronal ischemic and reperfusion injury and associated inflammation. For ischemic stroke, novel therapeutic targets have continued to remain elusive. When considering modern molecular biological techniques, advanced translational stroke models, and clinical studies, a consistent pattern emerges, implicating perturbation of the immune equilibrium by stroke in both central nervous system injury and repair responses. Stroke triggers activation of the neuroimmune axis, comprised of multiple cellular constituents of the immune system resident within the parenchyma of the brain, leptomeninges, and vascular beds, as well as through secretion of biological response modifiers and recruitment of immune effector cells. This neuroimmune activation can directly impact the initiation, propagation, and resolution phases of ischemic brain injury. To leverage a potential opportunity to modulate local and systemic immune responses to favorably affect the stroke disease curve, it is necessary to expand our mechanistic understanding of the neuroimmune axis in ischemic stroke. This review explores the frontiers of current knowledge of innate and adaptive immune responses in the brain and how these responses together shape the course of ischemic stroke.

Decrease in circulating plasmacytoid dendritic cells during short-term systemic normobaric hypoxia

BACKGROUND

During exposure to high altitude, the immune system is altered. During hypoxia, an increase in interleukin (IL)-6 and high sensitivity C-reactive protein (hs-CRP), and an increase in natural killer cells and decrease in T cells in blood was shown. However, the impact of hypoxia on dendritic cells has not been investigated yet.

MATERIAL AND METHODS

Twelve healthy volunteers were subjected to a transient normobaric hypoxia for 6·5 h simulating an oxygen concentration at 5500 m. During exposure to hypoxia, blood samples were collected and analysed by flow cytometrical cell sorting (FACS) for circulating myeloid (mDCs) and plasmacytoid (pDCs) DCs. Serum levels of IL-6 and tumour necrosis factor (TNF)-α were analysed. In a cell culture hypoxia chamber, blood samples were subjected to the same hypoxia and analysed regarding DCs.

RESULTS

Exposure to normobaric hypoxia induced a significant decrease in circulating pDCs about 45% (P = 0·001) but not of mDC compared to baseline normoxia. Furthermore, we observed a significant increase of TNF-α about 340% (P = 0·03) and of IL-6 about 286% (P = 0·002). In cell culture experiments exposure of blood to hypoxia led to no significant changes in DCs, so that a direct cytotoxic effect was excluded. During hypoxia, we observed a transient increase in stromal-derived factor 1 (SDF-1) which is important for pDC tissue recruitment.

CONCLUSIONS

We show a significant decrease in circulating pDCs during hypoxia in parallel to a pro-inflammatory response. Further studies are necessary to evaluate whether the decrease in circulating pDCs might be the result of an enhanced tissue recruitment.

Granulocyte colony-stimulating factor (G-CSF) treatment in combination with transplantation of bone marrow cells is not superior to G-CSF treatment alone after cortical stroke in spontaneously hypertensive rats

Granulocyte-colony stimulating factor (G-CSF) and bone marrow derived mononuclear cells (BM-MNCs) have both been shown to improve functional outcome following experimental stroke. These effects are associated with increased angiogenesis and neurogenesis. In the present study, we aimed to determine synergistic effects of G-CSF and BM-NMC treatment on long-term structural and functional recovery after photothrombotic stroke. To model the etiology of stroke more closely, we used spontaneously hypertensive (SH) rats in our experiment. Bone marrow derived mononuclear cells transplantation was initiated 1 h after the onset of photothrombotic stroke. Repeated G-CSF treatment commenced immediately after BM-MNC treatment followed by daily injections for five consecutive days. The primary endpoint was functional outcome after ischemia. Secondary endpoints included analysis of neurogenesis and angiogenesis as well as determination of infarct size. Granulocyte-colony stimulating factor treated rats, either in combination with BM-MNC or alone showed improved somatosensory but not gross motor function following ischemia. No beneficial effect of BM-MNC monotherapy was found. Infarct volumes were comparable in all groups. In contrast to previous studies, which used healthy animals, post-stroke neurogenesis and angiogenesis were not enhanced by G-CSF. In conclusion, the combination of G-CSF and BM-MNC was not more effective than G-CSF alone. The reduced efficacy of G-CSF treatment and the absence of any beneficial effect of BM-MNC transplantation might be attributed to hypertension-related morbidity.

The Yin and Yang of innate immunity in stroke

Immune system plays an elementary role in the pathophysiological progress of ischemic stroke. It consists of innate and adaptive immune system. Activated within minutes after ischemic onset, innate immunity is responsible for the elimination of necrotic cells and tissue repair, while it is critically involved in the initiation and amplification of poststroke inflammation that amplifies ischemic damage to the brain tissue. Innate immune response requires days to be fully developed, providing a considerable time window for therapeutic intervention, suggesting prospect of novel immunomodulatory therapies against poststroke inflammation-induced brain injury. However, obstacles still exist and a comprehensive understanding of ischemic stroke and innate immune reaction is essential. In this review, we highlighted the current experimental and clinical data depicting the innate immune response following ischemic stroke, mainly focusing on the recognition of damage-associated molecular patterns, activation and recruitment of innate immune cells, and involvement of various cytokines. In addition, clinical trials targeting innate immunity were also documented regardless of the outcome, stressing the requirements for further investigation.

Different treatment settings of Granulocyte-Colony Stimulating Factor and their impact on T cell-specific immune response in experimental stroke

BACKGROUND

Cerebral ischemia is associated with infectious complications due to immunosuppression and decreased T lymphocyte activity. G-CSF, which has neuroprotective properties, is known to modulate inflammatory processes after induced stroke. The aim of our study was to investigate the impact of G-CSF in experimental stroke and to compare two different modes of treatment, focusing on circulating T lymphocytes.

METHODS

Cerebral ischemia was induced in Wistar rats by occlusion of the middle cerebral artery, followed by reperfusion after 1h. G-CSF was applied either as a single dose 30 min after occlusion, or daily for seven days. Silver staining was used to determine infarct size. T lymphocytes in the peripheral blood were measured before and 7 days after induced cerebral ischemia by flow cytometry. In addition, migration of CD3-expressing T lymphocytes into the brain was investigated by immunohistochemistry.

RESULTS

Both single dose and daily treatment with G-CSF significantly reduced infarct size. A significant improvement of neurological outcome was only observed after single application of G-CSF. While a decrease in peripheral T lymphocytes was detected seven days after induced stroke, no reduction was observed in the G-CSF-treated groups. Apart from that, G-CSF significantly reduced the number of brain migrated T lymphocytes in both treatment settings as compared to vehicle.

CONCLUSION

A single dose of G-CSF exerted neuroprotective effects in ischemic stroke, which were less pronounced after daily G-CSF application. Both treatment strategies inhibited stroke-induced reduction of T lymphocytes in peripheral blood, which may have contributed to the reduction of infarct size.

Modulation of neural stem/progenitor cell proliferation during experimental Herpes Simplex encephalitis is mediated by differential FGF-2 expression in the adult brain

Neural stem cells (NSCs) respond to inflammatory cues induced during brain injury and are thought to be involved in recovery from brain damage. Little is known about NSC response during brain infections. The present study evaluated NSC proliferation during Herpes Simplex Virus-1 brain infection. Total numbers of nestin(+) NSCs increased significantly in infected brains at 6 days post infection (p.i.). However, by 15 days p.i. the nestin(+) population decreased significantly below levels observed in uninfected brains and remained depressed through 30 days p.i. This initial increase in NSC population occurred concurrently with increased brain cell proliferation, which peaked at 3 days p.i. On closer examination, we found that while actively proliferating Sox2(+) NSCs increased in number at 6 days p.i., proliferating DCX(+) neuroblasts contributed to the increased response at 3 days p.i. However, overall proliferation decreased steadily from 15 days p.i. to below control levels. To determine the mechanisms involved in altering NSC proliferation, neurotrophin and growth factor expression profiles were assessed. FGF-2 gene expression increased at 5 days p.i. and was robustly down-regulated at 15 days p.i. (>1000-fold), which was further confirmed by increased FGF-2 immunostaining around the lateral ventricles. Furthermore, supplementing infected animals with recombinant FGF-2, at 15 days p.i., significantly increased the number of proliferating brain cells. These findings demonstrate that the temporal changes in NSC proliferation are mediated through the regulation of FGF-2 and that the NSC niche may benefit from supplementation with FGF-2 during HSV-1 brain infection.