Crosstalk of Astrocytes and Other Cells during Ischemic Stroke

Systems-level computational modeling in ischemic stroke: from cells to patients

Ischemic stroke, a significant threat to human life and health, refers to a class of conditions where brain tissue damage is induced following decreased cerebral blood flow. The incidence of ischemic stroke has been steadily increasing globally, and its disease mechanisms are highly complex and involve a multitude of biological mechanisms at various scales from genes all the way to the human body system that can affect the stroke onset, progression, treatment, and prognosis. To complement conventional experimental research methods, computational systems biology modeling can integrate and describe the pathogenic mechanisms of ischemic stroke across multiple biological scales and help identify emergent modulatory principles that drive disease progression and recovery. In addition, by running virtual experiments and trials in computers, these models can efficiently predict and evaluate outcomes of different treatment methods and thereby assist clinical decision-making. In this review, we summarize the current research and application of systems-level computational modeling in the field of ischemic stroke from the multiscale mechanism-based, physics-based and omics-based perspectives and discuss how modeling-driven research frameworks can deliver insights for future stroke research and drug development.

The Janus face of HIF-1α in ischemic stroke and the possible associated pathways

Stroke is the most devastating disease, causing paralysis and eventually death. Many clinical and experimental trials have been done in search of a new safe and efficient medicine; nevertheless, scientists have yet to discover successful remedies that are also free of adverse effects. This is owing to the variability in intensity, localization, medication routes, and each patient's immune system reaction. HIF-1α represents the modern tool employed to treat stroke diseases due to its functions: downstream genes such as glucose metabolism, angiogenesis, erythropoiesis, and cell survival. Its role can be achieved via two downstream EPO and VEGF strongly related to apoptosis and antioxidant processes. Recently, scientists paid more attention to drugs dealing with the HIF-1 pathway. This review focuses on medicines used for ischemia treatment and their potential HIF-1α pathways. Furthermore, we discussed the interaction between HIF-1α and other biological pathways such as oxidative stress; however, a spotlight has been focused on certain potential signalling contributed to the HIF-1α pathway. HIF-1α is an essential regulator of oxygen balance within cells which affects and controls the expression of thousands of genes related to sustaining homeostasis as oxygen levels fluctuate. HIF-1α's role in ischemic stroke strongly depends on the duration and severity of brain damage after onset. HIF-1α remains difficult to investigate, particularly in ischemic stroke, due to alterations in the acute and chronic phases of the disease, as well as discrepancies between the penumbra and ischemic core. This review emphasizes these contrasts and analyzes the future of this intriguing and demanding field.

GFAP as Astrocyte-Derived Extracellular Vesicle Cargo in Acute Ischemic Stroke Patients-A Pilot Study

The utility of serum glial fibrillary acidic protein (GFAP) in acute ischemic stroke (AIS) has been extensively studied in recent years. Here, we aimed to assess its potential role as a cargo protein of extracellular vesicles (EVs) secreted by astrocytes (ADEVs) in response to brain ischemia. Plasma samples from eighteen AIS patients at 24 h (D1), 7 days (D7), and one month (M1) post-symptoms onset, and nine age, sex, and cardiovascular risk factor-matched healthy controls were obtained to isolate EVs using the Exoquick ULTRA EV kit. Subsets of presumed ADEVs were identified further by the expression of the glutamate aspartate transporter (GLAST) as a specific marker of astrocytes with the Basic Exo-Flow Capture kit. Western blotting has tested the presence of GFAP in ADEV cargo. Post-stroke ADEV GFAP levels were elevated at D1 and D7 but not M1 compared to controls (p = 0.007, p = 0.019, and p = 0.344, respectively). Significant differences were highlighted in ADEV GFAP content at the three time points studied (n = 12, p = 0.027) and between D1 and M1 (z = 2.65, p = 0.023). A positive correlation was observed between the modified Rankin Scale (mRS) at D7 and ADEV GFAP at D1 (r = 0.58, p = 0.010) and D7 (r = 0.57, p = 0.013), respectively. ADEV GFAP may dynamically reflect changes during the first month post-ischemia. Profiling ADEVs from peripheral blood could provide a new way to assess the central nervous system pathology.

Astrocyte-Derived Extracellular Vesicles for Ischemic Stroke: Therapeutic Potential and Prospective

Stroke is a leading cause of death and disability in the world. Astrocytes are special glial cells within the central nervous system and play important roles in mediating neuroprotection and repair processes during stroke. Extracellular vesicles (EVs) are lipid bilayer particles released from cells that facilitate intercellular communication in stroke by delivering proteins, lipids, and RNA to target cells. Recently, accumulating evidence suggested that astrocyte-derived EVs (ADEVs) are actively involved in mediating numerous biological processes including neuroprotection and neurorepair in stroke and they are realized as an excellent therapeutic approach for treating stroke. In this review we systematically summarize the up-to-date research on ADEVs in stroke, and prospects for its potential as a novel therapeutic target for stroke. We also provide an overview of the effects and functions of ADEVs on stroke recovery, which may lead to developing clinically relevant therapies for stroke.

Neuroprotective effects of gemfibrozil in neurological disorders: Focus on inflammation and molecular mechanisms

BACKGROUND

Gemfibrozil (Gem) is a drug that has been shown to activate PPAR-α, a nuclear receptor that plays a key role in regulating lipid metabolism. Gem is used to lower the levels of triglycerides and reduce the risk of coronary heart disease in patients. Experimental studies in vitro and in vivo have shown that Gem can prevent or slow the progression of neurological disorders (NDs), including cerebral ischemia (CI), Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Neuroinflammation is known to play a significant role in these disorders.

METHOD

The literature review for this study was conducted by searching Scopus, Science Direct, PubMed, and Google Scholar databases.

RESULT

The results of this study show that Gem has neuroprotective effects through several cellular and molecular mechanisms such as: (1) Gem has the ability to upregulate pro-survival factors (PGC-1α and TFAM), promoting the survival and function of mitochondria in the brain, (2) Gem strongly inhibits the activation of NF-κB, AP-1, and C/EBPβ in cytokine-stimulated astroglial cells, which are known to increase the expression of iNOS and the production of NO in response to proinflammatory cytokines, (3) Gem protects dopamine neurons in the MPTP mouse model of PD by increasing the expression of PPARα, which in turn stimulates the production of GDNF in astrocytes, (4) Gem reduces amyloid plaque pathology, reduces the activity of glial cells, and improves memory, (5) Gem increases myelin genes expression (MBP and CNPase) via PPAR-β, and (6) Gem increases hippocampal BDNF to counteract depression.

CONCLUSION

According to the study, Gem was investigated for its potential therapeutic effect in NDs. Further research is needed to fully understand the therapeutic potential of Gem in NDs.

The Role of Circadian Rhythms in Stroke: A Narrative Review

Stroke, a debilitating condition often leading to long-term disability, poses a substantial global concern and formidable challenge. The increasing incidence of stroke has drawn the attention of medical researchers and neurologists worldwide. Circadian rhythms have emerged as pivotal factors influencing stroke's onset, pathogenesis, treatment, and outcomes. To gain deeper insights into stroke, it is imperative to explore the intricate connection between circadian rhythms and stroke, spanning from molecular mechanisms to pathophysiological processes. Despite existing studies linking circadian rhythm to stroke onset, there remains a paucity of comprehensive reviews exploring its role in pathogenesis, treatment, and prognosis. This review undertakes a narrative analysis of studies investigating the relationship between circadian variation and stroke onset. It delves into the roles of various physiological factors, including blood pressure, coagulation profiles, blood cells, catecholamines, cortisol, and the timing of antihypertensive medication, which contribute to variations in circadian-related stroke risk. At a molecular level, the review elucidates the involvement of melatonin, circadian genes, and glial cells in the pathophysiology. Furthermore, it provides insights into the diverse factors influencing stroke treatment and outcomes within the context of circadian variation. The review underscores the importance of considering circadian rhythms when determining the timing of stroke interventions, emphasizing the necessity for personalized stroke management strategies that incorporate circadian rhythms. It offers valuable insights into potential molecular targets and highlights areas that require further exploration to enhance our understanding of the underlying pathophysiology. In comparison to the published literature, this manuscript distinguishes itself through its coverage of circadian rhythms' impact on stroke across the entire clinical spectrum. It presents a unique synthesis of epidemiological, clinical, molecular, and cellular evidence, underscoring their collective significance.

Astroglial Cells: Emerging Therapeutic Targets in the Management of Traumatic Brain Injury

Traumatic Brain Injury (TBI) represents a significant health concern, necessitating advanced therapeutic interventions. This detailed review explores the critical roles of astrocytes, key cellular constituents of the central nervous system (CNS), in both the pathophysiology and possible rehabilitation of TBI. Following injury, astrocytes exhibit reactive transformations, differentiating into pro-inflammatory (A1) and neuroprotective (A2) phenotypes. This paper elucidates the interactions of astrocytes with neurons, their role in neuroinflammation, and the potential for their therapeutic exploitation. Emphasized strategies encompass the utilization of endocannabinoid and calcium signaling pathways, hormone-based treatments like 17β-estradiol, biological therapies employing anti-HBGB1 monoclonal antibodies, gene therapy targeting Connexin 43, and the innovative technique of astrocyte transplantation as a means to repair damaged neural tissues.

The Role of Stem Cells as Therapeutics for Ischaemic Stroke

Stroke remains one of the leading causes of death and disability worldwide. Current reperfusion treatments for ischaemic stroke are limited due to their narrow therapeutic window in rescuing ischaemic penumbra. Stem cell therapy offers a promising alternative. As a regenerative medicine, stem cells offer a wider range of treatment strategies, including long-term intervention for chronic patients, through the reparation and replacement of injured cells via mechanisms of differentiation and proliferation. The purpose of this review is to evaluate the therapeutic role of stem cells for ischaemic stroke. This paper discusses the pathology during acute, subacute, and chronic phases of cerebral ischaemic injury, highlights the mechanisms involved in mesenchymal, endothelial, haematopoietic, and neural stem cell-mediated cerebrovascular regeneration, and evaluates the pre-clinical and clinical data concerning the safety and efficacy of stem cell-based treatments. The treatment of stroke patients with different types of stem cells appears to be safe and efficacious even at relatively higher concentrations irrespective of the route and timing of administration. The priming or pre-conditioning of cells prior to administration appears to help augment their therapeutic impact. However, larger patient cohorts and later-phase trials are required to consolidate these findings.

A bibliometric analysis of studies of exosomes in ischemic stroke published from 2002 to 2021

Recently, research on exosomes in ischemic stroke has become an attractive field worldwide, and therefore the number of relevant publications has increased. The objective of the present study is to visualize the current research status and hotspots in this area by performing bibliometric analysis and helping researchers predict future research trends. Studies regarding exosomes in ischemic stroke were retrieved from the Science Citation Index-Expanded and Social Sciences Citation Index databases of the Web of Science. Knowledge maps were constructed and visualization analysis was performed using VOSviewer and CiteSpace software. In total, 504 publications (336 articles and 168 reviews) published from 2002 to 2021 were identified in this bibliometric analysis. The leading publishing countries were China and the USA, and the top collaborating institutions were Henry Ford Hospital and Oakland University. Analyses of keywords and co-cited references revealed that microRNA, biomarkers, stem cells, therapeutic effects, neurogenesis, and neurovascular plasticity were significant hotspots and emerging trends. According to the bibliometric analysis results, our study identified the research hotspots and emerging trends relevant to exosome involvement in ischemic stroke.

A2A adenosine receptor-driven cAMP signaling in olfactory bulb astrocytes is unaffected in experimental autoimmune encephalomyelitis

Introduction

The cyclic nucleotide cyclic adenosine monophosphate (cAMP) is a ubiquitous second messenger, which is known to play an important anti-inflammatory role. Astrocytes in the central nervous system (CNS) can modulate inflammation but little is known about the significance of cAMP in their function.

Methods

We investigated cAMP dynamics in mouse olfactory bulb astrocytes in brain slices prepared from healthy and experimental autoimmune encephalomyelitis (EAE) mice.

Results

The purinergic receptor ligands adenosine and adenosine triphosphate (ATP) both induced transient increases in cAMP in astrocytes expressing the genetically encoded cAMP sensor Flamindo2. The A2A receptor antagonist ZM241385 inhibited the responses. Similar transient increases in astrocytic cAMP occurred when olfactory receptor neurons were stimulated electrically, resulting in ATP release from the stimulated axons that increased cAMP, again via A2A receptors. Notably, A2A-mediated responses to ATP and adenosine were not different in EAE mice as compared to healthy mice.

Discussion

Our results indicate that ATP, synaptically released by afferent axons in the olfactory bulb, is degraded to adenosine that acts on A2A receptors in astrocytes, thereby increasing the cytosolic cAMP concentration. However, this pathway is not altered in the olfactory bulb of EAE mice.

Differential metabolic alterations in IDH1 mutant vs. wildtype glioma cells promote epileptogenesis through distinctive mechanisms

Glioma-related epilepsy (GRE) is a hallmark clinical presentation of gliomas with significant impacts on patient quality of life. The current standard of care for seizure management is comprised of anti-seizure medications (ASMs) and surgical resection. Seizures in glioma patients are often drug-resistant and can often recur after surgery despite total tumor resection. Therefore, current research is focused on the pro-epileptic pathological changes occurring in tumor cells and the peritumoral environment. One important contribution to seizures in GRE patients is metabolic reprogramming in tumor and surrounding cells. This is most evident by the significantly heightened seizure rate in patients with isocitrate dehydrogenase mutated (IDHmut) tumors compared to patients with IDH wildtype (IDHwt) gliomas. To gain further insight into glioma metabolism in epileptogenesis, this review compares the metabolic changes inherent to IDHmut vs. IDHwt tumors and describes the pro-epileptic effects these changes have on both the tumor cells and the peritumoral environment. Understanding alterations in glioma metabolism can help to uncover novel therapeutic interventions for seizure management in GRE patients.

Research progress on the roles of neurovascular unit in stroke-induced immunosuppression

A complex pathophysiological mechanism is involved in brain injury following cerebral infarction. The neurovascular unit (NVU) is a complex multi-cellular structure consisting of neurons, endothelial cells, pericyte, astrocyte, microglia and extracellular matrix, etc. The dyshomeostasis of NVU directly participates in the regulation of inflammatory immune process. The components of NVU promote inflammatory overreaction and synergize with the overactivation of autonomic nervous system to initiate stroke-induced immunodepression (SIID). SIID can alleviate the damage caused by inflammation, however, it also makes stroke patients more susceptible to infection, leading to systemic damage. This article reviews the mechanism of SIID and the roles of NVU in SIID, to provide a perspective for reperfusion, prognosis and immunomodulatory therapy of cerebral infarction.

Glial Populations in the Human Brain Following Ischemic Injury

There is a growing interest in glial cells in the central nervous system due to their important role in maintaining brain homeostasis under physiological conditions and after injury. A significant amount of evidence has been accumulated regarding their capacity to exert either pro-inflammatory or anti-inflammatory effects under different pathological conditions. In combination with their proliferative potential, they contribute not only to the limitation of brain damage and tissue remodeling but also to neuronal repair and synaptic recovery. Moreover, reactive glial cells can modulate the processes of neurogenesis, neuronal differentiation, and migration of neurons in the existing neural circuits in the adult brain. By discovering precise signals within specific niches, the regulation of sequential processes in adult neurogenesis holds the potential to unlock strategies that can stimulate the generation of functional neurons, whether in response to injury or as a means of addressing degenerative neurological conditions. Cerebral ischemic stroke, a condition falling within the realm of acute vascular disorders affecting the circulation in the brain, stands as a prominent global cause of disability and mortality. Extensive investigations into glial plasticity and their intricate interactions with other cells in the central nervous system have predominantly relied on studies conducted on experimental animals, including rodents and primates. However, valuable insights have also been gleaned from in vivo studies involving poststroke patients, utilizing highly specialized imaging techniques. Following the attempts to map brain cells, the role of various transcription factors in modulating gene expression in response to cerebral ischemia is gaining increasing popularity. Although the results obtained thus far remain incomplete and occasionally ambiguous, they serve as a solid foundation for the development of strategies aimed at influencing the recovery process after ischemic brain injury.

Elastin-like polypeptide delivery of anti-inflammatory peptides to the brain following ischemic stroke

Inflammatory processes are activated following ischemic stroke that lead to increased tissue damage for weeks following the ischemic insult, but there are no approved therapies that target this inflammation-induced secondary injury. Here, we report that SynB1-ELP-p50i, a novel protein inhibitor of the nuclear factor kappa B (NF-κB) inflammatory cascade bound to the drug carrier elastin-like polypeptide (ELP), decreases NF-κB induced inflammatory cytokine production in cultured macrophages, crosses the plasma membrane and accumulates in the cytoplasm of both neurons and microglia in vitro, and accumulates at the infarct site where the blood-brain barrier (BBB) is compromised following middle cerebral artery occlusion (MCAO) in rats. Additionally, SynB1-ELP-p50i treatment reduces infarct volume by 11.86% compared to saline-treated controls 24 h following MCAO. Longitudinally, SynB1-ELP-p50i treatment improves survival for 14 days following stroke with no effects of toxicity or peripheral organ dysfunction. These results show high potential for ELP-delivered biologics for therapy of ischemic stroke and other central nervous system disorders and further support targeting inflammation in ischemic stroke.

Migratory Response of Cells in Neurogenic Niches to Neuronal Death: The Onset of Harmonic Repair?

Harmonic mechanisms orchestrate neurogenesis in the healthy brain within specific neurogenic niches, which generate neurons from neural stem cells as a homeostatic mechanism. These newly generated neurons integrate into existing neuronal circuits to participate in different brain tasks. Despite the mechanisms that protect the mammalian brain, this organ is susceptible to many different types of damage that result in the loss of neuronal tissue and therefore in alterations in the functionality of the affected regions. Nevertheless, the mammalian brain has developed mechanisms to respond to these injuries, potentiating its capacity to generate new neurons from neural stem cells and altering the homeostatic processes that occur in neurogenic niches. These alterations may lead to the generation of new neurons within the damaged brain regions. Notwithstanding, the activation of these repair mechanisms, regeneration of neuronal tissue within brain injuries does not naturally occur. In this review, we discuss how the different neurogenic niches respond to different types of brain injuries, focusing on the capacity of the progenitors generated in these niches to migrate to the injured regions and activate repair mechanisms. We conclude that the search for pharmacological drugs that stimulate the migration of newly generated neurons to brain injuries may result in the development of therapies to repair the damaged brain tissue.

Role of P2Y receptors in astrocyte physiology and pathophysiology

Astrocytes are active constituents of the brain that manage ion homeostasis and metabolic support of neurons and directly tune synaptic transmission and plasticity. Astrocytes express all known P2Y receptors. These regulate a multitude of physiological functions such as cell proliferation, Ca²⁺ signalling, gliotransmitter release and neurovascular coupling. In addition, P2Y receptors are fundamental in the transition of astrocytes into reactive astrocytes, as occurring in many brain disorders such as neurodegenerative diseases, neuroinflammation and epilepsy. This review summarizes the current literature addressing the function of P2Y receptors in astrocytes in the healthy brain as well as in brain diseases.

Applications of Induced Pluripotent Stem Cell-Derived Glia in Brain Disease Research and Treatment

Glia are integral components of neural networks and are crucial in both physiological functions and pathological processes of the brain. Many brain diseases involve glial abnormalities, including inflammatory changes, mitochondrial damage, calcium signaling disturbance, hemichannel opening, and loss of glutamate transporters. Induced pluripotent stem cell (iPSC)-derived glia provide opportunities to study the contributions of glia in human brain diseases. These cells have been used for human disease modeling as well as generating new therapies. This chapter introduces glial involvement in brain diseases, then summarizes different methods of generating iPSC-derived glia disease models of these cells. Finally, strategies for treating disease using iPSC-derived glia are discussed. The goal of this chapter is to provide an overview and shed light on the applications of iPSC-derived glia in brain disease research and treatment.

The Effect of a New N-hetero Cycle Derivative on Behavior and Inflammation against the Background of Ischemic Stroke

Ischemic stroke triggers a whole cascade of pathological changes in the brain, one of which is postischemic inflammation. Since in such cases thrombolytic therapy is often not possible, methods that modulate inflammation and affect microglia become particularly interesting. We synthesized 3-(2-oxo-4-phenylpyrrolidin-1-yl)propane-1-sulfonate calcium(II) (Compound 4) and studied its anti-inflammatory activity in in vitro and in vivo models of inflammation and ischemia. Macrophage cell line RAW 264.7 was treated with lipopolysaccharides (LPS) and Compound 4 at various dosages to study the cytokine profile using real-time PCR and cytometric bead array (CBA). Stroke in rats was simulated by the middle cerebral artery occlusion method (MCAO). Several tests were performed to characterize the neurological deficit and locomotor activity of the rats, and afterwards, postmortem, the number of astrocytes was counted using immunohistochemistry. Compound 4 in in vitro tests dose-dependently reduced the expression of interleukin-1β (IL1β), and inducible nitric oxide synthase (iNOS) genes in cell culture and increased the concentration of cytokines: interleukin-2, 4, 6 (IL-2, IL-4, and IL-6). In vivo Compound 4 increased the orienting-exploratory behavior, and reduced neurological and motor deficit. The number of astrocytes that promote and support inflammation was lower in the group treated with Compound 4. The stroke volume measured by magnetic resonance imaging (MRI) showed no difference. We have shown that Compound 4 demonstrates anti-inflammatory activity by increasing the synthesis of anti-inflammatory and reducing pro-inflammatory cytokines, and positively affects the neurological deficit in rats. Thus, Compound 4 has a high therapeutic potential in the management of patients after a stroke and requires further study of its neuroprotective properties.