Ginkgetin Promotes M2 Polarization of Microglia and Exert Neuroprotection in Ischemic Stroke via Modulation of PPARγ Pathway

Integrating Single-Cell Sequencing and Transcriptome Analysis to Investigate the Role of Ferroptosis in Ischemic Stroke and the Molecular Mechanisms of Immune Checkpoints

BACKGROUND

Early diagnosis of ischemic stroke (IS) remains challenging. Given the crucial role of ferroptosis in IS, this study aims to identify key genes associated with ferroptosis in IS, providing insights into its molecular mechanisms and potential biomarkers for early detection.

METHODS

The single-cell transcriptome dataset GSE247474 from the Gene Expression Omnibus. Ferroptosis scores in astrocytes were calculated using the WP_FERROPTOSIS gene set, and differential analysis was conducted to compare ferroptosis activity between the disease and control groups. Key ferroptosis-related genes were identified using Lasso regression and support vector machine algorithms, and their diagnostic potential was assessed through receiver operating characteristic curve analysis. Additionally, we performed immune infiltration analysis and transcription factor network prediction. Pseudotime analysis was used to explore the differentiation trajectories of astrocytes and T-cell subsets.

RESULTS

Astrocytes in the disease group showed significantly higher ferroptosis scores than those in the control group. Using machine learning algorithms, we identified 3 key ferroptosis-related genes-SLC3A2 (solute carrier family 3 member 2), FDFT1 (farnesyl-diphosphate farnesyltransferase 1), and BACH1 (BTB and CNC homology 1)-and validated their diagnostic value (area under the curve >0.9). Immune infiltration analysis revealed that SLC3A2 and BACH1 expression levels were positively correlated with CD4+ follicular T cells and negatively correlated with CD4+ memory T cells. FDFT1 showed positive correlations with both mast cells and CD4+ memory T cells. Pseudotime analysis demonstrated dynamic changes in key gene expression along the differentiation trajectories of astrocytes and T cells.

CONCLUSIONS

SLC3A2, FDFT1, and BACH1 are potential molecular markers for IS diagnosis.

Cell polarization in ischemic stroke: molecular mechanisms and advances

Ischemic stroke is a cerebrovascular disease associated with high mortality and disability rates. Since the inflammation and immune response play a central role in driving ischemic damage, it becomes essential to modulate excessive inflammatory reactions to promote cell survival and facilitate tissue repair around the injury site. Various cell types are involved in the inflammatory response, including microglia, astrocytes, and neutrophils, each exhibiting distinct phenotypic profiles upon stimulation. They display either proinflammatory or anti-inflammatory states, a phenomenon known as 'cell polarization.' There are two cell polarization therapy strategies. The first involves inducing cells into a neuroprotective phenotype in vitro, then reintroducing them autologously. The second approach utilizes small molecular substances to directly affect cells in vivo. In this review, we elucidate the polarization dynamics of the three reactive cell populations (microglia, astrocytes, and neutrophils) in the context of ischemic stroke, and provide a comprehensive summary of the molecular mechanisms involved in their phenotypic switching. By unraveling the complexity of cell polarization, we hope to offer insights for future research on neuroinflammation and novel therapeutic strategies for ischemic stroke.

Metabolic reprogramming and astrocytes polarization following ischemic stroke

Astrocytes are critical for maintaining neuronal activity. Activation of astrocytes, occurs within minutes from ischemic stroke onset due to ischemic causes and subsequent inflammatory damage. Activated astrocytes, also known as reactive astrocytes, are divided into two different phenotypes: A1 (pro-inflammatory) and A2 (anti-inflammatory) astrocytes. A2 astrocytes support neuronal survival and promote tissue healing, while A1 astrocytes have neurotoxic effects. Thus, polarization of reactive astrocyte into A1 or A2 genotype is closely correlated with the development of cerebral ischemia/reperfusion (I/R) injury. Metabolic reprogramming is a process that various metabolic pathways upregulate in cells to balance energy, alter their phenotype, and produce building-block requirements. A1 and A2 astrocytes display different metabolic reprogramming, such as glycolysis, glutamate uptake, and glycogenolysis. Accumulating evidence suggested that manipulation of energy metabolism homeostasis can induce astrocytes to switch from A1 to A2 phenotype. This review disucss the potential factors in affecting astrocytic polarization, emphasizes metabolic reprogramming in reactive astrocytes within the pathophysiological context of cerebral I/R, and explores the relationship between metabolic reprogramming and astrocytic polarization. Importantly, we reveal that regulating metabolic reprogramming in reactive astrocytes may be a potential therapeutic target for cerebral I/R injury.

Evaluating ginkgetin from Ginkgo biloba as a novel agent for sleep promotion through molecular docking and in vivo studies

Objectives

Sleep impacts the well-being and quality of life of millions. Given conventional pharmacotherapy's limitations and side effects, the quest for adequate and proper sleep promotion is imperative. This study aims to identify a suitable and effective compound for sleep by examining qualified herbal compounds in the PubChem database using in silico methods. Ultimately, the extracted compound (ginkgetin, a bioactive flavonoid from Ginkgo biloba) through molecular docking by considering the GABAA receptors will be evaluated through the in vivo method in an animal model to serve as proof for the findings from the molecular docking process.

Materials and Methods

Utilizing a comprehensive approach, this research employed molecular docking to screen 2299 phytochemicals for their affinity towards the GABAA receptor, focusing on the GABA, benzodiazepine, and steroid-binding sites. Ginkgetin emerged as a top candidate due to its high binding affinity. Subsequent in vivo electrophysiological assessments in rats treated with G. biloba extract containing ginkgetin evaluated alterations in sleep architecture, REM, and NREM sleep phases.

Results

Molecular docking identified ginkgetin as possessing the highest binding affinity among the screened phytochemicals. In vivo studies corroborated these findings, demonstrating that rats treated with Ginkgo biloba extract significantly enhanced REM and NREM sleep compared to controls.

Conclusion

Ginkgetin, derived from G. biloba, shows promising potential as a novel therapeutic agent for sleep disorders, supported by its strong affinity to key receptor sites and its efficacy in modulating sleep architecture in vivo. These findings contribute to the expanding evidence base for the therapeutic use of G. biloba in sleep promotion and underscore the need for further research to elucidate the mechanisms and clinical applicability of ginkgetin in sleep disorder treatment.

In vitro modelling of the neurovascular unit for ischemic stroke research: Emphasis on human cell applications and 3D model design

Ischemic stroke has garnered global medical attention as one of the most serious cerebrovascular diseases. The mechanisms involved in both the development and recovery phases of ischemic stroke are complex, involving intricate interactions among different types of cells, each with its own unique functions. To better understand the possible pathogenesis, neurovascular unit (NVU), a concept comprising neurons, endothelial cells, mural cells, glial cells, and extracellular matrix components, has been used in analysing various brain diseases, particularly in ischemic stroke, aiming to depict the interactions between cerebral vasculature and neural cells. While in vivo models often face limitations in terms of reproducibility and the ability to precisely mimic human pathophysiology, it is now important to establish in vitro NVU models for ischemic stroke research. In order to accurately portray the pathological processes occurring within the brain, a diverse array of NVU 2D and 3D in vitro models, each possessing unique characteristics and advantages, have been meticulously developed. This review presents a comprehensive overview of recent advancements in in vitro models specifically tailored for investigating ischemic stroke. Through a systematic categorization of these developments, we elucidate the intricate links between NVU components and the pathogenesis of ischemic stroke. Furthermore, we explore the distinct advantages offered by innovative NVU models, notably 3D models, which closely emulate in vivo conditions. Additionally, an examination of current therapeutic modalities for ischemic stroke developed utilizing in vitro NVU models is provided. Serving as a valuable reference, this review aids in the design and implementation of effective in vitro models for ischemic stroke research.

A2 reactive astrocyte-derived exosomes alleviate cerebral ischemia-reperfusion injury by delivering miR-628

Ischemia and hypoxia activate astrocytes into reactive types A1 and A2, which play roles in damage and protection, respectively. However, the function and mechanism of A1 and A2 astrocyte exosomes are unknown. After astrocyte exosomes were injected into the lateral ventricle, infarct volume, damage to the blood-brain barrier (BBB), apoptosis and the expression of microglia-related proteins were measured. The dual luciferase reporter assay was used to detect the target genes of miR-628, and overexpressing A2-Exos overexpressed and knocked down miR-628 were constructed. qRT-PCR, western blotting and immunofluorescence staining were subsequently performed. A2-Exos obviously reduced the infarct volume, damage to the BBB and apoptosis and promoted M2 microglial polarization. RT-PCR showed that miR-628 was highly expressed in A2-Exos. Dual luciferase reporter assays revealed that NLRP3, S1PR3 and IRF5 are target genes of miR-628. After miR-628 was overexpressed or knocked down, the protective effects of A2-Exos increased or decreased, respectively. A2-Exos reduced pyroptosis and BBB damage and promoted M2 microglial polarization through the inhibition of NLRP3, S1PR3 and IRF5 via the delivery of miR-628. This study explored the mechanism of action of A2-Exos and provided new therapeutic targets and concepts for treating cerebral ischemia.

Microglia in Ischemic Stroke: Pathogenesis Insights and Therapeutic Challenges

Ischemic stroke is the most common type of stroke, which is the main cause of death and disability on a global scale. As the primary immune cells in the brain that are crucial for preserving homeostasis of the central nervous system microenvironment, microglia have been found to exhibit dual or even multiple effects at different stages of ischemic stroke. The anti-inflammatory polarization of microglia and release of neurotrophic factors may provide benefits by promoting neurological recovery at the lesion in the early phase after ischemic stroke. However, the pro-inflammatory polarization of microglia and secretion of inflammatory factors in the later phase of injury may exacerbate the ischemic lesion, suggesting the therapeutic potential of modulating the balance of microglial polarization to predispose them to anti-inflammatory transformation in ischemic stroke. Microglia-mediated signaling crosstalk with other cells may also be key to improving functional outcomes following ischemic stroke. Thus, this review provides an overview of microglial functions and responses under physiological and ischemic stroke conditions, including microglial activation, polarization, and interactions with other cells. We focus on approaches that promote anti-inflammatory polarization of microglia, inhibit microglial activation, and enhance beneficial cell-to-cell interactions. These targets may hold promise for the creation of innovative therapeutic strategies.

Exploring Chinese herbal medicine for ischemic stroke: insights into microglia and signaling pathways

Ischemic stroke is a prevalent clinical condition affecting the central nervous system, characterized by a high mortality and disability rate. Its incidence is progressively rising, particularly among younger individuals, posing a significant threat to human well-being. The activation and polarization of microglia, leading to pro-inflammatory and anti-inflammatory responses, are widely recognized as pivotal factors in the pathogenesis of cerebral ischemia and reperfusion injury. Traditional Chinese herbal medicines (TCHMs) boasts a rich historical background, notable efficacy, and minimal adverse effects. It exerts its effects by modulating microglia activation and polarization, suppressing inflammatory responses, and ameliorating nerve injury through the mediation of microglia and various associated pathways (such as NF-κB signaling pathway, Toll-like signaling pathway, Notch signaling pathway, AMPK signaling pathway, MAPK signaling pathway, among others). Consequently, this article focuses on microglia as a therapeutic target, reviewing relevant pathway of literature on TCHMs to mitigate neuroinflammation and mediate IS injury, while also exploring research on drug delivery of TCHMs. The ultimate goal is to provide new insights that can contribute to the clinical management of IS using TCHMs.

Microglia dynamic response and phenotype heterogeneity in neural regeneration following hypoxic-ischemic brain injury

Hypoxic-ischemic brain injury poses a significant threat to the neural niche within the central nervous system. In response to this pathological process, microglia, as innate immune cells in the central nervous system, undergo rapid morphological, molecular and functional changes. Here, we comprehensively review these dynamic changes in microglial response to hypoxic-ischemic brain injury under pathological conditions, including stroke, chronic intermittent hypoxia and neonatal hypoxic-ischemic brain injury. We focus on the regulation of signaling pathways under hypoxic-ischemic brain injury and further describe the process of microenvironment remodeling and neural tissue regeneration mediated by microglia after hypoxic-ischemic injury.

Regulatory mechanisms of natural compounds from traditional Chinese herbal medicines on the microglial response in ischemic stroke

BACKGROUND

Development of clinically effective neuroprotective agents for stroke therapy is still a challenging task. Microglia play a critical role in brain injury and recovery after ischemic stroke. Traditional Chinese herbal medicines (TCHMs) are based on a unique therapeutic principle, have various formulas, and have long been widely used to treat stroke. Therefore, the active compounds in TCHMs and their underlying mechanisms of action are attracting increasing attention in the field of stroke drug development.

PURPOSE

To summarize the regulatory mechanisms of TCHM-derived natural compounds on the microglial response in animal models of ischemic stroke.

METHODS

We searched studies published until 10 April 2023 in the Web of Science, PubMed, and ScienceDirect using the following keywords: natural compounds, natural products or phytochemicals, traditional Chinese Medicine or Chinese herbal medicine, microglia, and ischemic stroke. This review was prepared according to PRISMA (Preferred Reporting Item for Systematic Reviews and Meta-Analysis) guidelines.

RESULTS

Natural compounds derived from TCHMs can attenuate the M1 phenotype of microglia, which is involved in the detrimental inflammatory response, via inhibition of NF-κB, MAPKs, JAK/STAT, Notch, TLR4, P2X7R, CX3CR1, IL-17RA, the NLRP3 inflammasome, and pro-oxidant enzymes. Additionally, the neuroprotective response of microglia with the M2 phenotype can be enhanced by activating Nrf2/HO-1, PI3K/AKT, AMPK, PPARγ, SIRT1, CB2R, TREM2, nAChR, and IL-33/ST2. Several clinical trials showed that TCHM-derived natural compounds that regulate microglial responses have significant and safe therapeutic effects, but further well-designed clinical studies are needed.

CONCLUSIONS

Further research regarding the direct targets and potential pleiotropic or synergistic effects of natural compounds would provide a more reasonable approach for regulation of the microglial response with the possibility of successful stroke drug development.

Protective effects and mechanisms of Yi Qi Huo Xue Fang in cerebral ischemic stroke based on network pharmacology and experimental verification

ETHNOPHARMACOLOGICAL RELEVANCE

Yi Qi Huo Xue Fang (YQHXF) is an effective formula for treating cerebral ischemic stroke (CIS). However, its active ingredients and mechanism of action remain unclear.

AIM OF THE STUDY

This study aimed to reveal the mechanism of action of YQHXF in the treatment of ischemic stroke based on network pharmacology and experimental validation.

MATERIALS AND METHODS

This study identified the chemical components in YQHXF and the components absorbed by rat serum based on UPLC-Q-TOF/MS technology and used network pharmacology to predict key candidate targets. A protein-protein-interaction (P-P-I) network was constructed using String 11.0 database and Cytoscape, and R software for gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis. Finally, molecular docking combined with animal experiments was used to verify network pharmacology results.

RESULTS

This study identified and confirmed 36 chemical components of YQHXF and five chemical ingredients that were absorbed into the blood of rats and screened 66 key candidate targets. All targets in the P-P-I network were mainly related to inflammation and vascular processes. KEGG enrichment results revealed that these 66 key candidate targets were primarily involved in the "AGE-RAGE signaling pathway," "TNF-α signaling pathway, and "T cell receptor signaling pathway." Molecular docking results revealed that Prostaglandin-endoperoxidase synthase 2(PTGS-2), Nitric oxide synthase, endothelial (NOS3), and peroxisome proliferator-activated receptor gamma (PPARG) were more stably bound to their active ingredients. Animal experiments demonstrated that YQHXF promoted M2 polarization, inhibited M1 polarization in microglia, and promoted angiogenesis, which may be related to the PPARG pathway.

CONCLUSION

This study revealed the key active components and effective targets of YQHXF, identified the mechanism of action of YQHXF, laid the foundation for further research on YQHXF, and provided ideas for developing new drugs for CIS.

Else_BRB_110660Docosahexaenoic acid promotes M2 microglia phenotype via activating PPARγ-mediated ERK/AKT pathway against cerebral ischemia-reperfusion injury

In ischemia-reperfusion stroke, microglia play a dual role in brain injury as well as brain repair, and promoting their switch from a pro-inflammatory M1 phenotype to an anti-inflammatory M2 phenotype is considered to be a potential therapeutic strategy. Docosahexaenoic acid (DHA) is an essential long-chain omega-3 polyunsaturated fatty acid that exhibits potent anti-inflammatory properties in the acute phase of ischemic stroke, but its effect on microglia polarization is unknown. Thus, the objective of this study was to investigate the neuroprotective effects of DHA on rat brain following ischemia-reperfusion injury, and to investigate the mechanism by which DHA regulates microglia polarization. We administered DHA 5mg/kg intraperitoneally daily for 3 d following a transient middle cerebral artery occlusion reperfusion model in rats. The protective effects of DHA on cerebral ischemia-reperfusion injury were detected by TTC staining, HE staining, Nissler staining, and TUNEL staining. Quantitative real-time PCR, immunofluorescence, western blot, and enzyme-linked immunosorbent assay were used to detect the expression of M1 and M2 microglia-associated markers and PPARγ-mediated ERK/AKT signaling pathway proteins. We found that DHA significantly improved brain injury by decreasing the expression of the M1 phenotypic marker (iNOS, CD16) and increasing the expression of the M2 phenotypic marker (Arg-1, CD206). DHA also increased the expression of peroxisome proliferator-activated receptor gamma (PPARγ) mRNA and protein, increased the expression of the pathway protein AKT, and decreased the expression of ERK1/2. In addition, DHA promoted the expression of anti-inflammatory factor IL-10 and decreased the expression of pro-inflammatory factors TNF-α and IL-1β. However, the PPARγ antagonist GW9662 greatly blocked these beneficial effects. These results suggest that DHA may activate PPARγ to inhibit ERK and activate AKT signaling pathways to regulate microglia polarization, thereby reducing neuroinflammation and promoting neurological recovery to alleviate cerebral ischemia-reperfusion injury.

Effects of Marginal Zn Excess and Thiamine Deficiency on Microglial N9 Cell Metabolism and Their Interactions with Septal SN56 Cholinergic Cells

Mild thiamine deficiency aggravates Zn accumulation in cholinergic neurons. It leads to the augmentation of Zn toxicity by its interaction with the enzymes of energy metabolism. Within this study, we tested the effect of Zn on microglial cells cultivated in a thiamine-deficient medium, containing 0.003 mmol/L of thiamine vs. 0.009 mmol/L in a control medium. In such conditions, a subtoxic 0.10 mmol/L Zn concentration caused non-significant alterations in the survival and energy metabolism of N9 microglial cells. Both activities of the tricarboxylic acid cycle and the acetyl-CoA level were not decreased in these culture conditions. Amprolium augmented thiamine pyrophosphate deficits in N9 cells. This led to an increase in the intracellular accumulation of free Zn and partially aggravated its toxicity. There was differential sensitivity of neuronal and glial cells to thiamine-deficiency-Zn-evoked toxicity. The co-culture of neuronal SN56 with microglial N9 cells reduced the thiamine-deficiency-Zn-evoked inhibition of acetyl-CoA metabolism and restored the viability of the former. The differential sensitivity of SN56 and N9 cells to borderline thiamine deficiency combined with marginal Zn excess may result from the strong inhibition of pyruvate dehydrogenase in neuronal cells and no inhibition of this enzyme in the glial ones. Therefore, ThDP supplementation can make any brain cell more resistant to Zn excess.

Neuroprotective Potential of Biflavone Ginkgetin: A Review

Neurological disorders are becoming more common, and there is an intense search for molecules that can help treat them. Several natural components, especially those from the flavonoid group, have shown promising results. Ginkgetin is the first known biflavonoid, a flavonoid dimer isolated from ginkgo (Ginkgo biloba L.). Later, its occurrence was discovered in more than 20 different plant species, most of which are known for their use in traditional medicine. Herein we have summarized the data on the neuroprotective potential of ginkgetin. There is evidence of protection against neuronal damage caused by ischemic strokes, neurotumors, Alzheimer's disease (AD), and Parkinson's disease (PD). Beneficial effects in ischemic strokes have been demonstrated in animal studies in which injection of ginkgetin before or after onset of the stoke showed protection from neuronal damage. AD protection has been the most studied to date. Possible mechanisms include inhibition of reactive oxygen species, inhibition of β-secretase, inhibition of Aβ fibril formation, amelioration of inflammation, and antimicrobial activity. Ginkgetin has also shown positive effects on the relief of PD symptoms in animal studies. Most of the available data are from in vitro or in vivo animal studies, where ginkgetin showed promising results, and further clinical studies should be conducted.