Dual microglia effects on blood brain barrier permeability induced by systemic inflammation

Review of the therapeutic effects of traditional Chinese medicine in sepsis-associated encephalopathy

ETHNOPHARMACOLOGICAL RELEVANCE

Sepsis-associated encephalopathy (SAE) is a common and serious complication during the acute phase of and after recovery from sepsis that seriously affects the quality of life of patients. Traditional Chinese medicine (TCM) has been widely used in modern medicine for neurological anomalies and has become a therapeutic tool for the treatment of SAE due to its multitargeting effects and low toxicity and side effects.

AIMS OF THE STUDY

This review provides insights into the pathogenesis and treatments of SAE, focusing on the clinical and experimental impacts of TCM formulations and their single components.

METHODS

Several known databases such as PubMed, Web of Science, Google Scholar, China National Knowledge Infrastructure (CNKI), and others were extensively explored with keywords and phrases such as "sepsis-associated encephalopathy", "traditional Chinese medicine", "herbs", "SAE", "sepsis", "cerebral" or other relevant terms to obtain literature between 2018 and 2024.

RESULTS

Extensive evidence indicated that TCM could decrease mortality and normalize neurological function in patients with sepsis; these effects might be associated with factors such as reduced oxidative stress and downregulated expression of inflammatory factors.

CONCLUSIONS

TCM shows notable efficacy in treating SAE, warranting deeper mechanistic studies to optimize its clinical application.

Associations of the immune system in aggression traits and the role of microglia as mediators

There is an important relationship between the immune system and aggressive behavior. Aggressive encounters acutely increase the levels of proinflammatory cytokines, and there are positive correlations between aggressive traits and peripheral proinflammatory cytokines. Endotoxin lipopolysaccharide (LPS) treatment, which results in peripheral immune activation, decreases aggressive behavior as one of the sickness behavioral symptoms. In contrast, certain brain infections and chronic interferon treatment are associated with increased aggression. Indeed, the effects of proinflammatory cytokines on the brain in aggressive behavior are bidirectional, depending on the type and dose of cytokine, target brain region, and type of aggression. Some studies have suggested that microglial activation and neuroinflammation influence intermale aggression in rodent models. In addition, pathological conditions as well as physiological levels of cytokines produced by microglia play an important role in social and aggressive behavior in adult animals. Furthermore, microglial function in early development is necessary for the establishment of the social brain and the expression of juvenile social behaviors, including play fighting. Overall, this review discusses the important link between the immune system and aggressive traits and the role of microglia as mediators of this link.

Sex-dependent effects of antimicrobials and lipopolysaccharide on blood-brain-barrier permeability in pubertal male and female CD1 mice

Exposure to stressors during puberty can disrupt normal development and possibly increase susceptibility to neurodegenerative disorders later in life. However, the mechanisms underlying the relationship between pubertal stress exposure and neurodegeneration remain unclear. As such, the current study was designed to examine the effects of pubertal antimicrobial (AMNS) and lipopolysaccharide (LPS) treatments on intestinal and blood-brain-barrier (BBB) permeability in male and female mice. Moreover, we also examined the sex-specific effects of pubertal AMNS and LPS treatments on gross motor activity, heart rate, and core body temperature. At four weeks of age, male and female CD1 mice were implanted with the G2 HR E-Mitter telemetry system. At five weeks of age, mice received 200 μL of broad-spectrum antimicrobial or water, through oral gavage, twice daily for seven days. Mice received an intraperitoneal injection of either saline or LPS at six weeks of age. BBB and intestinal permeability were examined 24 h, 72 h, and one week post-LPS/saline treatment. Telemetric data was collected for 48 h post-LPS/saline treatment. The results showed that pubertal AMNS and LPS treatments increased sickness behaviours and decreased body temperature and heart rate, in a sex-dependent manner. Furthermore, pubertal AMNS and LPS treatments resulted in sex-dependent regional increases in BBB permeability 24 h and 72 h post-LPS/saline treatment, while global increases in BBB permeability were only observed one week post-LPS/saline treatment. These results further our understanding of the combined effects of AMNS and LPS treatments on physiology and on the enduring negative changes observed following pubertal exposure to stressors.

The role of microglia in neuronal and cognitive function during high altitude acclimatization

Due to their interactions with the neurovasculature, microglia are implicated in maladaptive responses to hypobaric hypoxia at high altitude (HA). To explore these interactions at HA, pharmacological depletion of microglia with the colony-stimulating factor-1 receptor inhibitor, PLX5622, was employed in male C57BL/6J mice maintained at HA or sea level (SL) for 3-weeks, followed by assessment of ex-vivo hippocampal long-term potentiation (LTP), fear memory recall and microglial dynamics/physiology. Our findings revealed that microglia depletion decreased LTP and reduced glucose levels by 25% at SL but did not affect fear memory recall. At HA, the absence of microglia did not significantly alter HA associated deficits in fear memory or HA mediated decreases in peripheral glucose levels. In regard to microglial dynamics in the cortex, HA enhanced microglial surveillance activity, ablation of microglia resulted in increased chemotactic responses and decreased microglia tip proliferation during ball formation. In contrast, vessel ablation increased cortical microglia tip path tortuosity. In the hippocampus, changes in microglial dynamics were only observed in response to vessel ablation following HA. As the hippocampus is critical for learning and memory, poor hippocampal microglial context-dependent adaptation may be responsible for some of the enduring neurological deficits associated with HA.

Use of machine learning algorithms to determine the relationship between air pollution and cognitive impairment in Taiwan

Air pollution has become a major global threat to human health. Urbanization and industrialization over the past few decades have increased the air pollution. Plausible connections have been made between air pollutants and dementia. This study used machine learning algorithms (k-nearest neighbors, random forest, gradient-boosted decision trees, eXtreme gradient boosting, and CatBoost) to investigate the association between cognitive impairment and air pollution. Data from the Taiwan Biobank and 75 air-pollution-monitoring stations in Taiwan were analyzed to determine individual levels of exposure to air pollutants. The pollutants examined were particulate matter with a diameter of ≤ 2.5 μm (PM2.5), nitrogen dioxide, nitric oxide, carbon monoxide, and ozone. The results revealed that the most strongly correlated with cognitive impairment were ozone, PM2.5, and carbon monoxide levels with adjustment of educational level, age, and household income. The model based on these factors achieved accuracy as high as 0.97 for detecting cognitive impairment, indicating a positive association between air pollutions and cognitive impairment.

Loss of Cldn5 -and increase in Irf7-in the hippocampus and cerebral cortex of diabetic mice at the early symptomatic stage

Analyzing changes in gene expression within specific brain regions of individuals with Type 2 Diabetes (T2DM) who do not exhibit significant cognitive deficits can yield valuable insights into the mechanisms underlying the progression towards a more severe phenotype. In this study, transcriptomic analysis of the cortex and hippocampus of mice with long-term T2DM revealed alterations in the expression of 28 genes in the cerebral cortex and 15 genes in the hippocampus. Among these genes, six displayed consistent changes in both the cortex and hippocampus: Interferon regulatory factor 7 (Irf7), Hypoxia-inducible factor 3 alpha (Hif-3α), period circadian clock 2 (Per2), xanthine dehydrogenase (Xdh), and Transforming growth factor β-stimulated clone 22/TSC22 (Tsc22d3) were upregulated, while Claudin-5 (Cldn5) was downregulated. Confirmation of these changes was achieved through RT-qPCR. At the protein level, CLDN5 and IRF7 exhibited similar alterations, with CLDN5 being downregulated and IRF7 being upregulated. In addition, the hippocampus and cortex of the T2DM mice showed decreased levels of IκBα, implying the involvement of NF-κB pathways as well. Taken together, these results suggest that the weakening of the blood-brain barrier and an abnormal inflammatory response via the Interferon 1 and NF-κB pathways underlie cognitive impairment in individuals with long-standing T2DM.

Vagus nerve stimulation (VNS) preventing postoperative cognitive dysfunction (POCD): two potential mechanisms in cognitive function

Postoperative cognitive dysfunction (POCD) impacts a significant number of patients annually, frequently impairing their cognitive abilities and resulting in unfavorable clinical outcomes. Aimed at addressing cognitive impairment, vagus nerve stimulation (VNS) is a therapeutic approach, which was used in many mental disordered diseases, through the modulation of vagus nerve activity. In POCD model, the enhancement of cognition function provided by VNS was shown, demonstrating VNS effect on cognition in POCD. In the present study, we primarily concentrates on elucidating the role of the VNS improving the cognitive function in POCD, via two potential mechanisms: the inflammatory microenvironment and epigenetics. This study provided a theoretical support for the feasibility that VNS can be a potential method to enhance cognition function in POCD.

Short-chain fatty acid on blood-brain barrier and glial function in ischemic stroke

Stroke is the second most common cause of death and one of the most common causes of disability worldwide. The intestine is home to several microorganisms that fulfill essential functions for the natural and physiological functioning of the human body. There is an interaction between the central nervous system (CNS) and the gastrointestinal system that enables bidirectional communication between them, the so-called gut-brain axis. Based on the gut-brain axis, there is evidence of a link between the gut microbiota and the regulation of microglial functions through glial activation. This interaction is partly due to the immunological properties of the microbiota and its connection with the CNS, such that metabolites produced by the microbiota can cross the gut barrier, enter the bloodstream and reach the CNS and significantly affect microglia, astrocytes and other cells of the immune system. Studies addressing the effects of short-chain fatty acids (SCFAs) on glial function and the BBB in ischemic stroke are still scarce. Therefore, this review aims to stimulate the investigation of these associations, as well as to generate new studies on this topic that can clarify the role of SCFAs after stroke in a more robust manner.

The dual role of microglia in intracerebral hemorrhage

Intracerebral hemorrhage has the characteristics of high morbidity, disability and mortality, which has caused a heavy burden to families and society. Microglia are resident immune cells in the central nervous system, and their activation plays a dual role in tissue damage after intracerebral hemorrhage. The damage in cerebral hemorrhage is embodied in the following aspects: releasing inflammatory factors and inflammatory mediators, triggering programmed cell death, producing glutamate induced excitotoxicity, and destroying blood-brain barrier; The protective effect is reflected in the phagocytosis and clearance of harmful substances by microglia, and the secretion of anti-inflammatory and neurotrophic factors. This article summarizes the function of microglia and its dual regulatory mechanism in intracerebral hemorrhage. In the future, drugs, acupuncture and other clinical treatments can be used to intervene in the activation state of microglia, so as to reduce the harm of microglia.

Microglia are not necessary for maintenance of blood-brain barrier properties in health, but PLX5622 alters brain endothelial cholesterol metabolism

Microglia, the resident immune cells of the central nervous system, are intimately involved in the brain's most basic processes, from pruning neural synapses during development to preventing excessive neuronal activity throughout life. Studies have reported both helpful and harmful roles for microglia at the blood-brain barrier (BBB) in the context of disease. However, less is known about microglia-endothelial cell interactions in the healthy brain. To investigate the role of microglia at a healthy BBB, we used the colony-stimulating factor 1 receptor (CSF1R) inhibitor PLX5622 to deplete microglia and analyzed the BBB ultrastructure, permeability, and transcriptome. Interestingly, we found that, despite their direct contact with endothelial cells, microglia are not necessary for the maintenance of BBB structure, function, or gene expression in the healthy brain. However, we found that PLX5622 treatment alters brain endothelial cholesterol metabolism. This effect was independent from microglial depletion, suggesting that PLX5622 has off-target effects on brain vasculature.

Hepcidin depending on astrocytic NEO1 ameliorates blood-brain barrier dysfunction after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) significantly compromises the blood-brain barrier (BBB) and impairs patient recovery. This study elucidates the critical role of astrocytic Neogenin-1 (NEO1) in BBB integrity post-SAH and examines the regulatory effects of hepcidin on endothelial cell (EC) function amid NEO1-mediated disruptions in iron homeostasis. Proteomic analyses of cerebrospinal fluid (CSF) from SAH patients revealed a substantial decrease in NEO1 expression, identifying it as a key factor in BBB integrity. 111 CSF proteins were significantly reduced in early SAH stages (days 1-3), with NEO1 among the most significantly altered. This dysregulation was linked to poorer patient outcomes, as indicated by a negative correlation between NEO1 levels and Modified Rankin Scale scores six months post-SAH (R = -0.4743, P < 0.0001). Experimental models further highlighted the importance of NEO1: SAH model and NEO1GFAP-Cre mice exhibited exacerbated EC dysfunction and increased BBB permeability, evidenced by significant Evans Blue retention and dextran leakage in the parietal cortex, effects that were mitigated by hepcidin administration. Our findings highlight the complex interplay between astrocytic signaling and endothelial function in SAH pathophysiology. The loss of astrocytic NEO1 led to increased EC proliferation and altered BBB structure, as confirmed by transmission electron microscopy and immunostaining for PECAM-1, indicating heightened blood vessel density in the affected cortex. Hepcidin treatment effectively reversed the EC dysfunction and BBB disruption in both NEO1-cKO mice and the SAH model, highlighting its potential as a therapeutic agent to enhance recovery and improve prognosis following SAH.

Blood-brain barrier disruption: a culprit of cognitive decline?

Cognitive decline covers a broad spectrum of disorders, not only resulting from brain diseases but also from systemic diseases, which seriously influence the quality of life and life expectancy of patients. As a highly selective anatomical and functional interface between the brain and systemic circulation, the blood-brain barrier (BBB) plays a pivotal role in maintaining brain homeostasis and normal function. The pathogenesis underlying cognitive decline may vary, nevertheless, accumulating evidences support the role of BBB disruption as the most prevalent contributing factor. This may mainly be attributed to inflammation, metabolic dysfunction, cell senescence, oxidative/nitrosative stress and excitotoxicity. However, direct evidence showing that BBB disruption causes cognitive decline is scarce, and interestingly, manipulation of the BBB opening alone may exert beneficial or detrimental neurological effects. A broad overview of the present literature shows a close relationship between BBB disruption and cognitive decline, the risk factors of BBB disruption, as well as the cellular and molecular mechanisms underlying BBB disruption. Additionally, we discussed the possible causes leading to cognitive decline by BBB disruption and potential therapeutic strategies to prevent BBB disruption or enhance BBB repair. This review aims to foster more investigations on early diagnosis, effective therapeutics, and rapid restoration against BBB disruption, which would yield better cognitive outcomes in patients with dysregulated BBB function, although their causative relationship has not yet been completely established.

Social deficits mirror delayed cerebrovascular dysfunction after traumatic brain injury

Traumatic brain injury (TBI) survivors face debilitating long-term psychosocial consequences, including social isolation and depression. TBI modifies neurovascular physiology and behavior but the chronic physiological implications of altered brain perfusion on social interactions are unknown. Adult C57/BL6 male mice received a moderate cortical TBI, and social behaviors were assessed at baseline, 3-, 7-, 14-, 30-, and 60-days post injury (dpi). Magnetic resonance imaging (MRI, 9.4T) using dynamic susceptibility contrast perfusion weighted MRI were acquired. At 60dpi mice underwent histological angioarchitectural mapping. Analysis utilized standardized protocols followed by cross-correlation metrics. Social behavior deficits at 60dpi emerged as reduced interactions with a familiar cage-mate (partner) that mirrored significant reductions in cerebral blood flow (CBF) at 60dpi. CBF perturbations were dynamic temporally and across brain regions including regions known to regulate social behavior such as hippocampus, hypothalamus, and rhinal cortex. Social isolation in TBI-mice emerged with a significant decline in preference to spend time with a cage mate. Cortical vascular density was also reduced corroborating the decline in brain perfusion and social interactions. Thus, the late emergence of social interaction deficits mirrored the reduced vascular density and CBF in regions known to be involved in social behaviors. Vascular morphology and function improved prior to the late decrements in social function and our correlations strongly implicate a linkage between vascular density, cerebral perfusion, and social interactions. Our study provides a clinically relevant timeline of alterations in social deficits alongside functional vascular recovery that can guide future therapeutics.

Super-enhancer-driven LIF promotes the mesenchymal transition in glioblastoma by activating ITGB2 signaling feedback in microglia

BACKGROUND

The mesenchymal (MES) subtype of glioblastoma (GBM) is believed to be influenced by both cancer cell-intrinsic alterations and extrinsic cellular interactions, yet the underlying mechanisms remain unexplored.

METHODS

Identification of microglial heterogeneity by bioinformatics analysis. Transwell migration, invasion assays, and tumor models were used to determine gene function and the role of small molecule inhibitors. RNA sequencing, chromatin immunoprecipitation, and dual-luciferase reporter assays were performed to explore the underlying regulatory mechanisms.

RESULTS

We identified the inflammatory microglial subtype of tumor-associated microglia (TAM) and found that its specific gene integrin beta 2 (ITGB2) was highly expressed in TAM of MES GBM tissues. Mechanistically, the activation of ITGB2 in microglia promoted the interaction between the SH2 domain of STAT3 and the cytoplasmic domain of ITGB2, thereby stimulating the JAK1/STAT3/IL-6 signaling feedback to promote the MES transition of GBM cells. Additionally, microglia communicated with GBM cells through the interaction between the receptor ITGB2 on microglia and the ligand ICAM-1 on GBM cells, while an increased secretion of ICAM-1 was induced by the proinflammatory cytokine leukemia inhibitory factor (LIF). Further studies demonstrated that inhibition of cyclin-dependent kinase 7 substantially reduced the recruitment of SNW1 to the super-enhancer of LIF, resulting in transcriptional inhibition of LIF. We identified notoginsenoside R1 as a novel LIF inhibitor that exhibited synergistic effects in combination with temozolomide.

CONCLUSIONS

Our research reveals that the epigenetic-mediated interaction of GBM cells with TAM drives the MES transition of GBM and provides a novel therapeutic avenue for patients with MES GBM.

Red light-induced localized release of carbon monoxide for alleviating postoperative cognitive dysfunction

Inflammation within the central nervous system (CNS), which may be triggered by surgical trauma, has been implicated as a significant factor contributing to postoperative cognitive dysfunction (POCD). The relationship between mitigating inflammation at peripheral surgical sites and its potential to attenuate the CNS inflammatory response, thereby easing POCD symptoms, remains uncertain. Notably, carbon monoxide (CO), a gasotransmitter, exhibits pronounced anti-inflammatory effects. Herein, we have developed carbon monoxide-releasing micelles (CORMs), a nanoparticle that safely and locally liberates CO upon exposure to 650 nm light irradiation. In a POCD mouse model, treatment with CORMs activated by light (CORMs + hv) markedly reduced the concentrations of interleukin (IL)-6, IL-1β, and tumor necrosis factor-alpha (TNF-α) in both the peripheral blood and the hippocampus, alongside a decrease in ionized calcium-binding adapter molecule 1 in the hippocampal CA1 region. Furthermore, CORMs + hv treatment diminished Evans blue extravasation, augmented the expression of tight junction proteins zonula occludens-1 and occludin, enhanced neurocognitive functions, and fostered fracture healing. Bioinformatics analysis and experimental validation has identified Htr1b and Trhr as potential key regulators in the neuroactive ligand-receptor interaction signaling pathway implicated in POCD. This work offers new perspectives on the mechanisms driving POCD and avenues for therapeutic intervention.

Dynamics of Endothelial Cell Diversity and Plasticity in Health and Disease

Endothelial cells (ECs) are vital structural units of the cardiovascular system possessing two principal distinctive properties: heterogeneity and plasticity. Endothelial heterogeneity is defined by differences in tissue-specific endothelial phenotypes and their high predisposition to modification along the length of the vascular bed. This aspect of heterogeneity is closely associated with plasticity, the ability of ECs to adapt to environmental cues through the mobilization of genetic, molecular, and structural alterations. The specific endothelial cytoarchitectonics facilitate a quick structural cell reorganization and, furthermore, easy adaptation to the extrinsic and intrinsic environmental stimuli, known as the epigenetic landscape. ECs, as universally distributed and ubiquitous cells of the human body, play a role that extends far beyond their structural function in the cardiovascular system. They play a crucial role in terms of barrier function, cell-to-cell communication, and a myriad of physiological and pathologic processes. These include development, ontogenesis, disease initiation, and progression, as well as growth, regeneration, and repair. Despite substantial progress in the understanding of endothelial cell biology, the role of ECs in healthy conditions and pathologies remains a fascinating area of exploration. This review aims to summarize knowledge and concepts in endothelial biology. It focuses on the development and functional characteristics of endothelial cells in health and pathological conditions, with a particular emphasis on endothelial phenotypic and functional heterogeneity.

Blood-brain barrier alterations and their impact on Parkinson's disease pathogenesis and therapy

There is increasing evidence for blood-brain barrier (BBB) alterations in Parkinson's disease (PD), the second most common neurodegenerative disorder with rapidly rising prevalence. Altered tight junction and transporter protein levels, accumulation of α-synuclein and increase in inflammatory processes lead to extravasation of blood molecules and vessel degeneration. This could result in a self-perpetuating pathophysiology of inflammation and BBB alteration, which contribute to neurodegeneration. Toxin exposure or α-synuclein over-expression in animal models has been shown to initiate similar pathologies, providing a platform to study underlying mechanisms and therapeutic interventions. Here we provide a comprehensive review of the current knowledge on BBB alterations in PD patients and how rodent models that replicate some of these changes can be used to study disease mechanisms. Specific challenges in assessing the BBB in patients and in healthy controls are discussed. Finally, a potential role of BBB alterations in disease pathogenesis and possible implications for therapy are explored. The interference of BBB alterations with current and novel therapeutic strategies requires more attention. Brain region-specific BBB alterations could also open up novel opportunities to target specifically vulnerable neuronal subpopulations.

Adenosine triggers early astrocyte reactivity that provokes microglial responses and drives the pathogenesis of sepsis-associated encephalopathy in mice

Molecular pathways mediating systemic inflammation entering the brain parenchyma to induce sepsis-associated encephalopathy (SAE) remain elusive. Here, we report that in mice during the first 6 hours of peripheral lipopolysaccharide (LPS)-evoked systemic inflammation (6 hpi), the plasma level of adenosine quickly increased and enhanced the tone of central extracellular adenosine which then provoked neuroinflammation by triggering early astrocyte reactivity. Specific ablation of astrocytic Gi protein-coupled A1 adenosine receptors (A1ARs) prevented this early reactivity and reduced the levels of inflammatory factors (e.g., CCL2, CCL5, and CXCL1) in astrocytes, thereby alleviating microglial reaction, ameliorating blood-brain barrier disruption, peripheral immune cell infiltration, neuronal dysfunction, and depression-like behaviour in the mice. Chemogenetic stimulation of Gi signaling in A1AR-deficent astrocytes at 2 and 4 hpi of LPS injection could restore neuroinflammation and depression-like behaviour, highlighting astrocytes rather than microglia as early drivers of neuroinflammation. Our results identify early astrocyte reactivity towards peripheral and central levels of adenosine as an important pathway driving SAE and highlight the potential of targeting A1ARs for therapeutic intervention.

Cellular and molecular mechanisms of the blood-brain barrier dysfunction in neurodegenerative diseases

BACKGROUND

Maintaining the structural and functional integrity of the blood-brain barrier (BBB) is vital for neuronal equilibrium and optimal brain function. Disruptions to BBB performance are implicated in the pathology of neurodegenerative diseases.

MAIN BODY

Early indicators of multiple neurodegenerative disorders in humans and animal models include impaired BBB stability, regional cerebral blood flow shortfalls, and vascular inflammation associated with BBB dysfunction. Understanding the cellular and molecular mechanisms of BBB dysfunction in brain disorders is crucial for elucidating the sustenance of neural computations under pathological conditions and for developing treatments for these diseases. This paper initially explores the cellular and molecular definition of the BBB, along with the signaling pathways regulating BBB stability, cerebral blood flow, and vascular inflammation. Subsequently, we review current insights into BBB dynamics in Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis. The paper concludes by proposing a unified mechanism whereby BBB dysfunction contributes to neurodegenerative disorders, highlights potential BBB-focused therapeutic strategies and targets, and outlines lessons learned and future research directions.

CONCLUSIONS

BBB breakdown significantly impacts the development and progression of neurodegenerative diseases, and unraveling the cellular and molecular mechanisms underlying BBB dysfunction is vital to elucidate how neural computations are sustained under pathological conditions and to devise therapeutic approaches.

Stress and the gut-brain axis: an inflammatory perspective

The gut-brain axis (GBA) plays a dominant role in maintaining homeostasis as well as contributes to mental health maintenance. The pathways that underpin the axis expand from macroscopic interactions with the nervous system, to the molecular signals that include microbial metabolites, tight junction protein expression, or cytokines released during inflammation. The dysfunctional GBA has been repeatedly linked to the occurrence of anxiety- and depressive-like behaviors development. The importance of the inflammatory aspects of the altered GBA has recently been highlighted in the literature. Here we summarize current reports on GBA signaling which involves the immune response within the intestinal and blood-brain barrier (BBB). We also emphasize the effect of stress response on altering barriers' permeability, and the therapeutic potential of microbiota restoration by probiotic administration or microbiota transplantation, based on the latest animal studies. Most research performed on various stress models showed an association between anxiety- and depressive-like behaviors, dysbiosis of gut microbiota, and disruption of intestinal permeability with simultaneous changes in BBB integrity. It could be postulated that under stress conditions impaired communication across BBB may therefore represent a significant mechanism allowing the gut microbiota to affect brain functions.

Neuroprotective effects of CysLT2R antagonist on Angiostrongylus cantonensis-induced edema and meningoencephalitis

Cysteinyl leukotrienes (CysLTs) can induce a disruption of the blood-brain barrier (BBB), and this reaction is mediated by cysteinyl-leukotriene receptors. In this study, we used A. cantonensis-induced eosinophilic meningoencephalitis as a model to investigate whether the CysLT2 receptor involved in the pathogenesis of angiostrongyliasis meningoencephalitis. The present study provides evidence that the CysLT2 receptor antagonist HAMI3379 reduced the number of infiltrated eosinophils and brain edema in eosinophilic meningoencephalitis. Additionally, we found that HAMI3379 significantly decreased the protein levels of M1 polarisation markers (CD80, iNOS, IL-5 and TNF-α), increased the expression of M2 polarisation markers (CD206, IL-10 and TGF-β) both in vivo and in vitro. Matrix metalloproteinase-9, S100B, GFAP, fibronectin, and claudin-5 were markedly lower after HAMI3379 treatment. Therefore, HAMI3379 reduced the BBB dysfunction in angiostrongyliasis meningoencephalitis. We have identified microRNA-155 as a BBB dysfunction marker in eosinophilic meningoencephalitis. The results showed that microRNA-155 was 15-fold upregulated in eosinophilic meningoencephalitis and 20-fold upregulated after HAMI3379 treatment. Our results suggest that CysLT2R may be involved in A. cantonensis-induced brain edema and eosinophilic meningoencephalitis and that down-regulation of CysLT2R could be a novel and potential therapeutic strategy for the treatment of angiostrongyliasis meningoencephalitis.

Microglial Inflammatory Mechanisms in Stroke: The Jury Is Still Out

Microglia represent the main immune cell population in the CNS with unique homeostatic roles and contribution to broad neurological conditions. Stroke is associated with marked changes in microglial phenotypes and induction of inflammatory responses, which emerge as key modulators of brain injury, neurological outcome and regeneration. However, due to the limited availability of functional studies with selective targeting of microglia and microglia-related inflammatory pathways in stroke, the vast majority of observations remain correlative and controversial. Because extensive review articles discussing the role of inflammatory mechanisms in different forms of acute brain injury are available, here we focus on some specific pathways that appear to be important for stroke pathophysiology with assumed contribution by microglia. While the growing toolkit for microglia manipulation increasingly allows targeting inflammatory pathways in a cell-specific manner, reconsideration of some effects devoted to microglia may also be required. This may particularly concern the interpretation of inflammatory mechanisms that emerge in response to stroke as a form of sterile injury and change markedly in chronic inflammation and common stroke comorbidities.

Microglia as a Game Changer in Epilepsy Comorbid Depression

As one of the most common neurological diseases, epilepsy is often accompanied by psychiatric disorders. Depression is the most universal comorbidity of epilepsy, especially in temporal lobe epilepsy (TLE). Therefore, it is urgently needed to figure out potential mechanisms and the optimization of therapeutic strategies. Microglia play a pivotal role in the coexistent relationship between epilepsy and depression. Activated microglia released cytokines like IL-6 and IL-1β, orchestrating neuroinflammation especially in the hippocampus, worsening both depression and epilepsy. The decrease of intracellular K+ is a common part in various molecular changes. The P2X7-NLRP3-IL-1β is a major inflammatory pathway that disrupts brain network. Extra ATP and CX3CL1 also lead to neuronal excitotoxicity and blood-brain barrier (BBB) disruption. Regulating neuroinflammation aiming at microglia-related molecules is capable of suspending the vicious mutual aggravating circle of epilepsy and depression. Other overlaps between epilepsy and depression lie in transcriptomic, neuroimaging, diagnosis and treatment. Hippocampal sclerosis (HS) and amygdala enlargement (AE) may be the underlying macroscopic pathological changes according to current studies. Extant evidence shows that cognitive behavioral therapy (CBT) and antidepressants like selective serotonin-reuptake inhibitors (SSRIs) are safe, but the effect is limited. Improvement in depression is likely to reduce the frequency of seizure. More comprehensive experiments are warranted to better understand the relationship between them.

Ldl-stimulated microglial activation exacerbates ischemic white matter damage

The role of microglia in triggering the blood-brain barrier (BBB) impairment and white matter damage after chronic cerebral hypoperfusion is unclear. Here we demonstrated that the vessel-adjacent microglia were specifically activated by the leakage of plasma low-density lipoprotein (LDL), which led to BBB breakdown and ischemic demyelination. Interestingly, we found that LDL stimulation enhanced microglial phagocytosis, causing excessive engulfment of myelin debris and resulting in an overwhelming lipid burden in microglia. Surprisingly, these lipid-laden microglia exhibited a suppressed profile of inflammatory response and compromised pro-regenerative properties. Microglia-specific knockdown of LDLR or systematic medication lowering circulating LDL-C showed protective effects against ischemic demyelination. Overall, our findings demonstrated that LDL-stimulated vessel-adjacent microglia possess a disease-specific molecular signature, characterized by suppressed regenerative properties, which is associated with the propagation of demyelination during ischemic white matter damage.

Imaging quantitative changes in blood-brain barrier permeability using [18F]2-fluoro-2-deoxy-sorbitol ([18F]FDS) PET in relation to glial cell recruitment in a mouse model of endotoxemia

The quantitative relationship between the disruption of the blood-brain barrier (BBB) and the recruitment of glial cells was explored in a mouse model of endotoxemia. [18F]2-Fluoro-2-deoxy-sorbitol ([18F]FDS) PET imaging was used as a paracellular marker for quantitative monitoring of BBB permeability after i.v injection of increasing doses of lipopolysaccharide (LPS) or vehicle (saline, n = 5). The brain distribution of [18F]FDS (VT, mL.cm-3) was estimated using kinetic modeling. LPS dose-dependently increased the brain VT of [18F]FDS after injection of LPS 4 mg/kg (5.2 ± 2.4-fold, n = 4, p < 0.01) or 5 mg/kg (9.0 ± 9.1-fold, n = 4, p < 0.01) but not 3 mg/kg (p > 0.05, n = 7). In 12 individuals belonging to the different groups, changes in BBB permeability were compared with expression of markers of astrocyte (GFAP) and microglial cell (CD11b) using ex vivo immunohistochemistry. Increased expression of CD11b and GFAP expression was observed in mice injected with 3 mg/kg of LPS, which did not increase with higher LPS doses. Quantitative [18F]FDS PET imaging can capture different levels of BBB permeability in vivo. A biphasic effect was observed with the lowest dose of LPS that triggered neuroinflammation without disruptive changes in BBB permeability, and higher LPS doses that increased BBB permeability without additional recruitment of glial cells.

LncRNA H19 knockdown promotes neuropathologic and functional recovery via the Nrf2/HO-1 axis after traumatic brain injury

AIMS

Traumatic brain injury (TBI) stands as a significant concern in public health, frequently leading to enduring neurological deficits. Long non-coding RNA H19 (lncRNA H19) exerts a potential regulator role in the pathology of brain injury. This study investigates the effects of lncRNA H19 knockdown (H19-KD) on the pathophysiology of TBI and its potential neuroprotective mechanisms.

METHODS

Controlled cortical impact was employed to establish a stable TBI mouse model. The expression levels of various genes in perilesional cortex and striatum tissue after TBI was detected by RT-qPCR. AAV9-shRNA-H19 was injected into the lateral ventricle of mice to knockdown the expression of lncRNA H19. Various behavioral tests were performed to evaluate sensorimotor and cognitive functions after TBI. Immunofluorescence and Nissl staining were performed to assess brain tissue damage and neuroinflammation. The Nrf2 and HO-1 expression was performed by Western blot.

RESULTS

After TBI, the expression of lncRNA H19 was elevated in perilesional tissue and gradually reverted to baseline. Behavioral tests demonstrated that H19-KD significantly promoted the recovery of sensorimotor and cognitive functions after TBI. Besides, H19-KD reduced brain tissue loss, preserved neuronal integrity, and ameliorated white matter damage at the histological level. In addition, H19-KD restrained the pro-inflammatory and facilitated anti-inflammatory phenotypes of microglia/macrophages, attenuating the neuroinflammatory response after TBI. Furthermore, H19-KD promoted activation of the Nrf2/HO-1 axis after TBI, while suppression of Nrf2 partially abolished the neuroprotective effect.

CONCLUSION

H19-KD exerts neuroprotective effects after TBI in mice, partially mediated by the activation of the Nrf2/HO-1 axis.

CNS-Active p38α MAPK Inhibitors for the Management of Neuroinflammatory Diseases: Medicinal Chemical Properties and Therapeutic Capabilities

During the last two decades, many p38α mitogen-activated protein kinase (p38α MAPK) inhibitors have been developed and tested in preclinical/clinical studies for the treatment of various disorders, especially problems with the origin of inflammation. Previous studies strongly suggest the involvement of the p38α MAPK pathway in the pathogenesis of neurodegenerative disorders. Despite the significant progress made in this field, so far no studies have focused on p38α MAPK inhibitors that have the capability to be used for the treatment of neurodegenerative disorders. In the present review, we evaluated a wide range of well-known p38α MAPK inhibitors (more than 140 small molecules) by measuring key physicochemical parameters to identify those capable of successfully crossing the blood-brain barrier (BBB). As a result, we identify about 50 naturally occurring and synthetic p38α MAPK inhibitors with high potential to cross the BBB, which can be further explored in the future for the treatment of neurodegenerative disorders. In addition, a detailed analysis of the previously released X-ray crystal structure of the inhibitors in the active site of the p38α MAPK enzyme revealed that some residues such as Met109 play a critical role in the occurrence of effective interactions by constructing strong H-bonds. This study can encourage scientists to focus more on the design, production, and biological evaluation of new central nervous system (CNS)-active p38α MAPK inhibitors in the future.

Low-intensity pulsed ultrasound stimulation (LIPUS) modulates microglial activation following intracortical microelectrode implantation

Microglia are important players in surveillance and repair of the brain. Implanting an electrode into the cortex activates microglia, produces an inflammatory cascade, triggers the foreign body response, and opens the blood-brain barrier. These changes can impede intracortical brain-computer interfaces performance. Using two-photon imaging of implanted microelectrodes, we test the hypothesis that low-intensity pulsed ultrasound stimulation can reduce microglia-mediated neuroinflammation following the implantation of microelectrodes. In the first week of treatment, we found that low-intensity pulsed ultrasound stimulation increased microglia migration speed by 128%, enhanced microglia expansion area by 109%, and a reduction in microglial activation by 17%, indicating improved tissue healing and surveillance. Microglial coverage of the microelectrode was reduced by 50% and astrocytic scarring by 36% resulting in an increase in recording performance at chronic time. The data indicate that low-intensity pulsed ultrasound stimulation helps reduce the foreign body response around chronic intracortical microelectrodes.

Associations of serum uric acid variability with neuroimaging metrics and cognitive decline: a population-based cohort study

BACKGROUND

The relationship between variation in serum uric acid (SUA) levels and brain health is largely unknown. This study aimed to examine the associations of long-term variability in SUA levels with neuroimaging metrics and cognitive function.

METHODS

This study recruited 1111 participants aged 25-83 years from a multicenter, community-based cohort study. The SUA concentrations were measured every two years from 2006 to 2018. We measured the intraindividual SUA variability, including the direction and magnitude of change by calculating the slope value. The associations of SUA variability with neuroimaging markers (brain macrostructural volume, microstructural integrity, white matter hyperintensity, and the presence of cerebral small vessel disease) and cognitive function were examined using generalized linear models. Mediation analyses were performed to assess whether neuroimaging markers mediate the relationship between SUA variation and cognitive function.

RESULTS

Compared with the stable group, subjects with increased or decreased SUA levels were all featured by smaller brain white matter volume (beta =  - 0.25, 95% confidence interval [CI] - 0.39 to - 0.11 and beta =  - 0.15, 95% CI - 0.29 to - 0.02). Participants with progressively increased SUA exhibited widespread disrupted microstructural integrity, featured by lower global fractional anisotropy (beta =  - 0.24, 95% CI - 0.38 to - 0.10), higher mean diffusivity (beta = 0.16, 95% CI 0.04 to 0.28) and radial diffusivity (beta = 0.19, 95% CI 0.06 to 0.31). Elevated SUA was also associated with cognitive decline (beta =  - 0.18, 95% CI - 0.32 to - 0.04). White matter atrophy and impaired brain microstructural integrity mediated the impact of SUA increase on cognitive decline.

CONCLUSIONS

It is the magnitude of SUA variation rather than the direction that plays a critical negative role in brain health, especially for participants with hyperuricemia. Smaller brain white matter volume and impaired microstructural integrity mediate the relationship between increased SUA level and cognitive function decline. Long-term stability of SUA level is recommended for maintaining brain health and preventing cognitive decline.

Estrogen-immuno-neuromodulation disorders in menopausal depression

A significant decrease in estrogen levels puts menopausal women at high risk for major depression, which remains difficult to cure despite its relatively clear etiology. With the discovery of abnormally elevated inflammation in menopausal depressed women, immune imbalance has become a novel focus in the study of menopausal depression. In this paper, we examined the characteristics and possible mechanisms of immune imbalance caused by decreased estrogen levels during menopause and found that estrogen deficiency disrupted immune homeostasis, especially the levels of inflammatory cytokines through the ERα/ERβ/GPER-associated NLRP3/NF-κB signaling pathways. We also analyzed the destruction of the blood-brain barrier, dysfunction of neurotransmitters, blockade of BDNF synthesis, and attenuation of neuroplasticity caused by inflammatory cytokine activity, and investigated estrogen-immuno-neuromodulation disorders in menopausal depression. Current research suggests that drugs targeting inflammatory cytokines and NLRP3/NF-κB signaling molecules are promising for restoring homeostasis of the estrogen-immuno-neuromodulation system and may play a positive role in the intervention and treatment of menopausal depression.

The influence of sleep disorders on perioperative neurocognitive disorders among the elderly: A narrative review

This review comprehensively assesses the epidemiology, interaction, and impact on patient outcomes of perioperative sleep disorders (SD) and perioperative neurocognitive disorders (PND) in the elderly. The incidence of SD and PND during the perioperative period in older adults is alarmingly high, with SD significantly contributing to the occurrence of postoperative delirium. However, the clinical evidence linking SD to PND remains insufficient, despite substantial preclinical data. Therefore, this study focuses on the underlying mechanisms between SD and PND, underscoring that potential mechanisms driving SD-induced PND include uncontrolled central nervous inflammation, blood-brain barrier disruption, circadian rhythm disturbances, glial cell dysfunction, neuronal and synaptic abnormalities, impaired central metabolic waste clearance, gut microbiome dysbiosis, hippocampal oxidative stress, and altered brain network connectivity. Additionally, the review also evaluates the effectiveness of various sleep interventions, both pharmacological and nonpharmacological, in mitigating PND. Strategies such as earplugs, eye masks, restoring circadian rhythms, physical exercise, noninvasive brain stimulation, dexmedetomidine, and melatonin receptor agonists have shown efficacy in reducing PND incidence. The impact of other sleep-improvement drugs (e.g., orexin receptor antagonists) and methods (e.g., cognitive-behavioral therapy for insomnia) on PND is still unclear. However, certain drugs used for treating SD (e.g., antidepressants and first-generation antihistamines) may potentially aggravate PND. By providing valuable insights and references, this review aimed to enhance the understanding and management of PND in older adults based on SD.

No-reflow after recanalization in ischemic stroke: From pathomechanisms to therapeutic strategies

Endovascular reperfusion therapy is the primary strategy for acute ischemic stroke. No-reflow is a common phenomenon, which is defined as the failure of microcirculatory reperfusion despite clot removal by thrombolysis or mechanical embolization. It has been reported that up to 25% of ischemic strokes suffer from no-reflow, which strongly contributes to an increased risk of poor clinical outcomes. No-reflow is associated with functional and structural alterations of cerebrovascular microcirculation, and the injury to the microcirculation seriously hinders the neural functional recovery following macrovascular reperfusion. Accumulated evidence indicates that pathology of no-reflow is linked to adhesion, aggregation, and rolling of blood components along the endothelium, capillary stagnation with neutrophils, astrocytes end-feet, and endothelial cell edema, pericyte contraction, and vasoconstriction. Prevention or treatment strategies aim to alleviate or reverse these pathological changes, including targeted therapies such as cilostazol, adhesion molecule blocking antibodies, peroxisome proliferator-activated receptors (PPARs) activator, adenosine, pericyte regulators, as well as adjunctive therapies, such as extracorporeal counterpulsation, ischemic preconditioning, and alternative or complementary therapies. Herein, we provide an overview of pathomechanisms, predictive factors, diagnosis, and intervention strategies for no-reflow, and attempt to convey a new perspective on the clinical management of no-reflow post-ischemic stroke.

Role of microglia in stroke

Microglia play key roles in the post-ischemic inflammatory response and damaged tissue removal reacting rapidly to the disturbances caused by ischemia and working to restore the lost homeostasis. However, the modified environment, encompassing ionic imbalances, disruption of crucial neuron-microglia interactions, spreading depolarization, and generation of danger signals from necrotic neurons, induce morphological and phenotypic shifts in microglia. This leads them to adopt a proinflammatory profile and heighten their phagocytic activity. From day three post-ischemia, macrophages infiltrate the necrotic core while microglia amass at the periphery. Further, inflammation prompts a metabolic shift favoring glycolysis, the pentose-phosphate shunt, and lipid synthesis. These shifts, combined with phagocytic lipid intake, drive lipid droplet biogenesis, fuel anabolism, and enable microglia proliferation. Proliferating microglia release trophic factors contributing to protection and repair. However, some microglia accumulate lipids persistently and transform into dysfunctional and potentially harmful foam cells. Studies also showed microglia that either display impaired apoptotic cell clearance, or eliminate synapses, viable neurons, or endothelial cells. Yet, it will be essential to elucidate the viability of engulfed cells, the features of the local environment, the extent of tissue damage, and the temporal sequence. Ischemia provides a rich variety of region- and injury-dependent stimuli for microglia, evolving with time and generating distinct microglia phenotypes including those exhibiting proinflammatory or dysfunctional traits and others showing pro-repair features. Accurate profiling of microglia phenotypes, alongside with a more precise understanding of the associated post-ischemic tissue conditions, is a necessary step to serve as the potential foundation for focused interventions in human stroke.

Investigation of microglial diversity in a LRRK2 G2019S mouse model of Parkinson's disease

Microglia contribute to the outcomes of various pathological conditions including Parkinson's disease (PD). Microglia are heterogenous, with a variety of states recently identified in aging and neurodegenerative disease models. Here, we delved into the diversity of microglia in a preclinical PD model featuring the G2019S mutation in LRRK2, a known pathological mutation associated with PD. Specifically, we investigated the 'dark microglia' (DM) and the 'disease-associated microglia' (DAM) which present a selective enrichment of CLEC7A expression. In the dorsal striatum - a region affected by PD pathology - extensive ultrastructural features of cellular stress as well as reduced direct cellular contacts, were observed for microglia from old LRRK2 G2019S mice versus controls. In addition, DM were more prevalent while CLEC7A-positive microglia had extensive phagocytic ultrastructural characteristics in the LRRK2 G2019S mice. Furthermore, our findings revealed a higher proportion of DM in LRRK2 G2019S mice, and an increased number of CLEC7A-positive cells with age, exacerbated by the pathological mutation. These CLEC7A-positive cells exhibited a selective enrichment of ameboid morphology and tended to cluster in the affected animals. In summary, we provide novel insights into the occurrence and features of recently defined microglial states, CLEC7A-positive cells and DM, in the context of LRRK2 G2019S PD pathology.

CNS resident macrophages enhance dysfunctional angiogenesis and circulating monocytes infiltration in brain arteriovenous malformation

Myeloid immune cells are abundant in both ruptured and unruptured brain arteriovenous malformations (bAVMs). The role of central nervous system (CNS) resident and circulating monocyte-derived macrophages in bAVM pathogenesis has not been fully understood. We hypothesize that CNS resident macrophages enhance bAVM development and hemorrhage. RNA sequencing using cultured endothelial cells (ECs) and mouse bAVM samples revealed that downregulation of two bAVM causative genes, activin-like kinase 1 (ALK1) or endoglin, increased inflammation and innate immune signaling. To understand the role of CNS resident macrophages in bAVM development and hemorrhage, we administrated a colony-stimulating factor 1 receptor inhibitor to bAVM mice with brain focal Alk1 deletion. Transient depletion of CNS resident macrophages at an early stage of bAVM development mitigated the phenotype severity of bAVM, including a prolonged inhibition of angiogenesis, dysplastic vasculature formation, and infiltration of CNS resident and circulating monocyte-derived macrophages during bAVM development. Transient depletion of CNS resident macrophages increased EC tight junction protein expression, reduced the number of dysplasia vessels and severe hemorrhage in established bAVMs. Thus, EC AVM causative gene mutation can activate CNS resident macrophages promoting bAVM progression. CNS resident macrophage could be a therapeutic target to mitigate the development and severity of bAVMs.

Gut-brain axis in the pathogenesis of sepsis-associated encephalopathy

The gut-brain axis is a bidirectional communication network linking the gut and the brain, overseeing digestive functions, emotional responses, body immunity, brain development, and overall health. Substantial research highlights a connection between disruptions of the gut-brain axis and various psychiatric and neurological conditions, including depression and Alzheimer's disease. Given the impact of the gut-brain axis on behavior, cognition, and brain diseases, some studies have started to pay attention to the role of the axis in sepsis-associated encephalopathy (SAE), where cognitive impairment is the primary manifestation. SAE emerges as the primary and earliest form of organ dysfunction following sepsis, potentially leading to acute cognitive impairment and long-term cognitive decline in patients. Notably, the neuronal damage in SAE does not stem directly from the central nervous system (CNS) infection but rather from an infection occurring outside the brain. The gut-brain axis is posited as a pivotal factor in this process. This review will delve into the gut-brain axis, exploring four crucial pathways through which inflammatory signals are transmitted and elevate the incidence of SAE. These pathways encompass the vagus nerve pathway, the neuroendocrine pathway involving the hypothalamic-pituitary-adrenal (HPA) axis and serotonin (5-HT) regulation, the neuroimmune pathway, and the microbial regulation. These pathways can operate independently or collaboratively on the CNS to modulate brain activity. Understanding how the gut affects and regulates the CNS could offer the potential to identify novel targets for preventing and treating this condition, ultimately enhancing the prognosis for individuals with SAE.

Alleviating depressive-like behavior in DSS-induced colitis mice: Exploring naringin and poncirin from Poncirus trifoliata extracts

Patients with inflammatory bowel diseases (IBDs), including ulcerative colitis (UC) and Crohn's disease (CD), often have concomitant mental disorders such as depression and anxiety. Therefore, a bidirectional approach involving the gut and brain axes is necessary for the prevention and treatment thereof. In this study, we explored the potential of Poncirus trifoliata extract (PT), traditionally known for its neuroprotective effects against gastrointestinal diseases, as a natural treatment agent for IBD in a dextran sulfate sodium (DSS)-induced colitis model. Oral administration of PT ameliorated weight loss and inflammatory responses in mice with DSS-induced colitis. Furthermore, PT treatment effectively restored the colon length and ameliorated enterocyte death by inhibiting DSS-induced reactive oxygen species (ROS)-mediated necroptosis. The main bioactive components of PT, poncirin and naringin, confirmed using ultra-performance liquid chromatography-quadrupole time-of-flight (UPLC-qTOF), can be utilized to regulate necroptosis. The antidepressant-like effects of PT were confirmed using open field test (OFT) and tail suspension test (TST). PT treatment also restored vascular endothelial cell integrity in the hippocampus. In the Cornu Ammonis 1 (CA1) and dentate gyrus (DG) regions of the hippocampus, PT controlled the neuroinflammatory responses of proliferated microglia. In conclusion, PT, which contains high levels of poncirin and naringin, has potential as a bidirectional therapeutic agent that can simultaneously improve IBD-associated intestinal and mental disorders.

Pharmacological mTOR inhibitors in ameliorating Alzheimer's disease: current review and perspectives

Traditionally, pharmacological mammalian/mechanistic targets of rapamycin (mTOR) kinase inhibitors have been used during transplantation and tumor treatment. Emerging pre-clinical evidence from the last decade displayed the surprising effectiveness of mTOR inhibitors in ameliorating Alzheimer's Disease (AD), a common neurodegenerative disorder characterized by progressive cognitive function decline and memory loss. Research shows mTOR activation as an early event in AD development, and inhibiting mTOR may promote the resolution of many hallmarks of Alzheimer's. Aberrant protein aggregation, including amyloid-beta (Aβ) deposition and tau filaments, and cognitive defects, are reversed upon mTOR inhibition. A closer inspection of the evidence highlighted a temporal dependence and a hallmark-specific nature of such beneficial effects. Time of administration relative to disease progression, and a maintenance of a functional lysosomal system, could modulate its effectiveness. Moreover, mTOR inhibition also exerts distinct effects between neurons, glial cells, and endothelial cells. Different pharmacological properties of the inhibitors also produce different effects based on different blood-brain barrier (BBB) entry capacities and mTOR inhibition sites. This questions the effectiveness of mTOR inhibition as a viable AD intervention strategy. In this review, we first summarize the different mTOR inhibitors available and their characteristics. We then comprehensively update and discuss the pre-clinical results of mTOR inhibition to resolve many of the hallmarks of AD. Key pathologies discussed include Aβ deposition, tauopathies, aberrant neuroinflammation, and neurovascular system breakdowns.

Glial Markers of Suicidal Behavior in the Human Brain-A Systematic Review of Postmortem Studies

Suicide is a major public health priority, and its molecular mechanisms appear to be related to glial abnormalities and specific transcriptional changes. This study aimed to identify and synthesize evidence of the relationship between glial dysfunction and suicidal behavior to understand the neurobiology of suicide. As of 26 January 2024, 46 articles that met the inclusion criteria were identified by searching PubMed and ISI Web of Science. Most postmortem studies, including 30 brain regions, have determined no density or number of total Nissl-glial cell changes in suicidal patients with major psychiatric disorders. There were 17 astrocytic, 14 microglial, and 9 oligodendroglial studies using specific markers of each glial cell and further on their specific gene expression. Those studies suggest that astrocytic and oligodendroglial cells lost but activated microglia in suicides with affective disorder, bipolar disorders, major depression disorders, or schizophrenia in comparison with non-suicided patients and non-psychiatric controls. Although the data from previous studies remain complex and cannot fully explain the effects of glial cell dysfunction related to suicidal behaviors, they provide risk directions potentially leading to suicide prevention.

Swimming short fibrous nasal drops achieving intraventricular administration

Adequate drug delivery across the blood-brain barrier (BBB) is a critical factor in treating central nervous system (CNS) disorders. Inspired by swimming fish and the microstructure of the nasal cavity, this study is the first to develop swimming short fibrous nasal drops that can directly target the nasal mucosa and swim in the nasal cavity, which can effectively deliver drugs to the brain. Briefly, swimming short fibrous nasal drops with charged controlled drug release were fabricated by electrospinning, homogenization, the π-π conjugation between indole group of fibers, the benzene ring of leucine-rich repeat kinase 2 (LRRK2) inhibitor along with charge-dipole interaction between positively charged poly-lysine (PLL) and negatively charged surface of fibers; this enabled these fibers to stick to nasal mucosa, prolonged the residence time on mucosa, and prevented rapid mucociliary clearance. In vitro, swimming short fibrous nasal drops were biocompatible and inhibited microglial activation by releasing an LRRK2 inhibitor. In vivo, luciferase-labelled swimming short fibrous nasal drops delivered an LRRK2 inhibitor to the brain through the nasal mucosa, alleviating cognitive dysfunction caused by sepsis-associated encephalopathy by inhibiting microglial inflammation and improving synaptic plasticity. Thus, swimming short fibrous nasal drops is a promising strategy for the treatment of CNS diseases.

BDNF Signaling in Vascular Dementia and Its Effects on Cerebrovascular Dysfunction, Synaptic Plasticity, and Cholinergic System Abnormality

Vascular dementia (VaD) is the second most common type of dementia and is characterized by memory impairment, blood-brain barrier disruption, neuronal cell loss, glia activation, impaired synaptic plasticity, and cholinergic system abnormalities. To effectively prevent and treat VaD a good understanding of the mechanisms underlying its neuropathology is needed. Brain-derived neurotrophic factor (BDNF) is an important neurotrophic factor with multiple functions in the systemic circulation and the central nervous system and is known to regulate neuronal cell survival, synaptic formation, glia activation, and cognitive decline. Recent studies indicate that when compared with normal subjects, patients with VaD have low serum BDNF levels and that BDNF deficiency in the serum and cerebrospinal fluid is an important indicator of VaD. Here, we review current knowledge on the role of BDNF signaling in the pathology of VaD, such as cerebrovascular dysfunction, synaptic dysfunction, and cholinergic system impairment.

SOCS3 regulates pathological retinal angiogenesis through modulating SPP1 expression in microglia and macrophages

Pathological ocular angiogenesis has long been associated with myeloid cell activation. However, the precise cellular and molecular mechanisms governing the intricate crosstalk between the immune system and vascular changes during ocular neovascularization formation remain elusive. In this study, we demonstrated that the absence of the suppressor of cytokine signaling 3 (SOCS3) in myeloid cells led to a substantial accumulation of microglia and macrophage subsets during the neovascularization process. Our single-cell RNA sequencing data analysis revealed a remarkable increase in the expression of the secreted phosphoprotein 1 (Spp1) gene within these microglia and macrophages, identifying subsets of Spp1-expressing microglia and macrophages during neovascularization formation in angiogenesis mouse models. Notably, the number of Spp1-expressing microglia and macrophages exhibited further elevation during neovascularization in mice lacking myeloid SOCS3. Moreover, our investigation unveiled the Spp1 gene as a direct transcriptional target gene of signal transducer and activator of transcription 3. Importantly, pharmaceutical activation of SOCS3 or blocking of SPP1 resulted in a significant reduction in pathological neovascularization. In conclusion, our study highlights the pivotal role of the SOCS3/STAT3/SPP1 axis in the regulation of pathological retinal angiogenesis.

Ectopic CD4+ T cells in choroid plexus mediate neuropsychiatric lupus symptoms in mice via interferon-γ induced microglia activation

Neuropsychiatric systemic lupus erythematosus (NPSLE) is a disabling and potentially life-threatening complication of SLE. This study aims to investigate whether ectopic CD4+ T cells in the choroid plexus mediate NPSLE in mice. Intracerebroventricular (ICV) injection of anti-CD4 antibody effectively depleted CP-resident CD4+ T cells and alleviated NPSLE-like symptoms in MRL/lpr mice. Following ICV injection, the majority of isolated lupus CD4+ T cells from donor MRL/lpr mice predominantly stayed in the CP for at least 28 days in recipient C57BL/6 mice, while nearly all isolated CD4+ T cells from MRL/MpJ mice disappeared within 7 days. ICV injection of lupus CD4+ T cells resulted in NPSLE-like symptoms, including impaired behavioral performances, increased microglial activation, and abnormal microstructure changes. Flow cytometry analysis revealed that the majority of isolated lupus CD4+ T cells were positive for IFN-γ. Neutralizing intracerebral IFN-γ alleviated NPSLE-like symptoms in MRL/lpr mice. Moreover, ICV injection of anti-IFN-γ antibody or microglial depletion by PLX3397 benefited most NPSLE-like symptoms in lupus CD4+ T-treated mice, while ICV injection of IFN-γ mimicked most NPSLE-like symptoms. In conclusion, CP-resident lupus CD4+ T cells contribute to NPSLE-like symptoms in mice via Interferon-γ induced microglia activation. Depleting CP-resident lupus CD4+ T cells, interferon-γ, or activated microglia may be potential therapeutic targets for NPSLE.

Delta like 4 regulates cerebrovascular development and endothelial integrity via DLL4-NOTCH-CLDN5 pathway and is vulnerable to neonatal hyperoxia

The mechanisms governing brain vascularization during development remain poorly understood. A key regulator of developmental vascularization is delta like 4 (DLL4), a Notch ligand prominently expressed in endothelial cells (EC). Exposure to hyperoxia in premature infants can disrupt the development and functions of cerebral blood vessels and lead to long-term cognitive impairment. However, its role in cerebral vascular development and the impact of postnatal hyperoxia on DLL4 expression in mouse brain EC have not been explored. We determined the DLL4 expression pattern and its downstream signalling gene expression in brain EC using Dll4+/+ and Dll4+/LacZ mice. We also performed in vitro studies using human brain microvascular endothelial cells. Finally, we determined Dll4 and Cldn5 expression in mouse brain EC exposed to postnatal hyperoxia. DLL4 is expressed in various cell types, with EC being the predominant one in immature brains. Moreover, DLL4 deficiency leads to persistent abnormalities in brain microvasculature and increased vascular permeability both in vivo and in vitro. We have identified that DLL4 insufficiency compromises endothelial integrity through the NOTCH-NICD-RBPJ-CLDN5 pathway, resulting in the downregulation of the tight junction protein claudin 5 (CLDN5). Finally, exposure to neonatal hyperoxia reduces DLL4 and CLDN5 expression in developing mouse brain EC. We reveal that DLL4 is indispensable for brain vascular development and maintaining the blood-brain barrier's function and is repressed by neonatal hyperoxia. We speculate that reduced DLL4 signalling in brain EC may contribute to the impaired brain development observed in neonates exposed to hyperoxia. KEY POINTS: The role of delta like 4 (DLL4), a Notch ligand in vascular endothelial cells, in brain vascular development and functions remains unknown. We demonstrate that DLL4 is expressed at a high level during postnatal brain development in immature brains and DLL4 insufficiency leads to abnormal cerebral vasculature and increases vascular permeability both in vivo and in vitro. We identify that DLL4  regulates endothelial integrity through NOTCH-NICD-RBPJ-CLDN5 signalling. Dll4 and Cldn5 expression are decreased in mouse brain endothelial cells exposed to postnatal hyperoxia.

From the gut to the brain: the long journey of phenolic compounds with neurocognitive effects

The human gut microbiota is a complex community of micro-organisms that play a crucial role in maintaining overall health. Recent research has shown that gut microbes also have a profound impact on brain function and cognition, leading to the concept of the gut-brain axis. One way in which the gut microbiota can influence the brain is through the bioconversion of polyphenols to other bioactive molecules. Phenolic compounds are a group of natural plant metabolites widely available in the human diet, which have anti-inflammatory and other positive effects on health. Recent studies have also suggested that some gut microbiota-derived phenolic metabolites may have neurocognitive effects, such as improving memory and cognitive function. The specific mechanisms involved are still being studied, but it is believed that phenolic metabolites may modulate neurotransmitter signaling, reduce inflammation, and enhance neural plasticity. Therefore, to exert a protective effect on neurocognition, dietary polyphenols or their metabolites must reach the brain, or act indirectly by producing an increase in bioactive molecules such as neurotransmitters. Once ingested, phenolic compounds are subjected to various processes (eg, metabolization by gut microbiota, absorption, distribution) before they cross the blood-brain barrier, perhaps the most challenging stage of their trajectory. Understanding the role of phenolic compounds in the gut-brain axis has important implications for the development of new therapeutic strategies for neurological and psychiatric disorders. By targeting the gut microbiota and its production of phenolic metabolites, it may be possible to improve brain function and prevent cognitive decline. In this article, the current state of knowledge on the endogenous generation of phenolic metabolites by the gut microbiota and how these compounds can reach the brain and exert neurocognitive effects was reviewed.

Krüppel-like factors: potential roles in blood-brain barrier dysfunction and epileptogenesis

Epilepsy is a chronic and debilitating neurological disorder, known for the occurrence of spontaneous and recurrent seizures. Despite the availability of antiseizure drugs, 30% of people with epilepsy experience uncontrolled seizures and drug resistance, evidencing that new therapeutic options are required. The process of epileptogenesis involves the development and expansion of tissue capable of generating spontaneous recurrent seizures, during which numerous events take place, namely blood-brain barrier (BBB) dysfunction, and neuroinflammation. The consequent cerebrovascular dysfunction results in a lower seizure threshold, seizure recurrence, and chronic epilepsy. This suggests that improving cerebrovascular health may interrupt the pathological cycle responsible for disease development and progression. Krüppel-like factors (KLFs) are a family of zinc-finger transcription factors, encountered in brain endothelial cells, glial cells, and neurons. KLFs are known to regulate vascular function and changes in their expression are associated with neuroinflammation and human diseases, including epilepsy. Hence, KLFs have demonstrated various roles in cerebrovascular dysfunction and epileptogenesis. This review critically discusses the purpose of KLFs in epileptogenic mechanisms and BBB dysfunction, as well as the potential of their pharmacological modulation as therapeutic approach for epilepsy treatment.

Targeting brain tumors with innovative nanocarriers: bridging the gap through the blood-brain barrier

Background

Glioblastoma multiforme (GBM) is recognized as the most lethal and most highly invasive tumor. The high likelihood of treatment failure arises from the presence of the blood-brain barrier (BBB) and stem cells around GBM, which avert the entry of chemotherapeutic drugs into the tumor mass.

Objective

Recently, several researchers have designed novel nanocarrier systems like liposomes, dendrimers, metallic nanoparticles, nanodiamonds, and nanorobot approaches, allowing drugs to infiltrate the BBB more efficiently, opening up innovative avenues to prevail over therapy problems and radiation therapy.

Methods

Relevant literature for this manuscript has been collected from a comprehensive and systematic search of databases, for example, PubMed, Science Direct, Google Scholar, and others, using specific keyword combinations, including "glioblastoma," "brain tumor," "nanocarriers," and several others.

Conclusion

This review also provides deep insights into recent advancements in nanocarrier-based formulations and technologies for GBM management. Elucidation of various scientific advances in conjunction with encouraging findings concerning the future perspectives and challenges of nanocarriers for effective brain tumor management has also been discussed.

Molecular Basis of Neuronal and Microglial States in the Aging Brain and Impact on Cerebral Blood Vessels

Brain aging causes a wide variety of changes at the molecular and cellular levels, leading to the decline of cognitive functions and increased vulnerability to neurodegenerative disorders. The research aimed at understanding the aging of the brain has made much progress in recent decades. Technological innovations such as single-cell RNA-sequencing (scRNA-seq), proteomic analyses, and spatial transcriptomic analyses have facilitated the research on the dynamic changes occurring within neurons, glia, and other cells along with their impacts on intercellular communication during aging. In this review, we introduce recent trends of how neurons and glia change during aging and discuss the impact on the brain microenvironment such as the blood-brain barrier (BBB).

Microglia and macrophage metabolism: a regulator of cerebral gliomas

Reciprocal interactions between the tumor microenvironment (TME) and cancer cells play important roles in tumorigenesis and progression of glioma. Glioma-associated macrophages (GAMs), either of peripheral origin or representing brain-intrinsic microglia, are the majority population of infiltrating immune cells in glioma. GAMs, usually classified into M1 and M2 phenotypes, have remarkable plasticity and regulate tumor progression through different metabolic pathways. Recently, research efforts have increasingly focused on GAMs metabolism as potential targets for glioma therapy. This review aims to delineate the metabolic characteristics of GAMs within the TME and provide a summary of current therapeutic strategies targeting GAMs metabolism in glioma. The goal is to provide novel insights and therapeutic pathways for glioma by highlighting the significance of GAMs metabolism.

The Temporal Relationship between Blood-Brain Barrier Integrity and Microglial Response following Neonatal Hypoxia Ischemia

Blood-brain barrier (BBB) dysfunction and neuroinflammation are key mechanisms of brain injury. We performed a time-course study following neonatal hypoxia-ischemia (HI) to characterize these events. HI brain injury was induced in postnatal day 10 rats by single carotid artery ligation followed by hypoxia (8% oxygen, 90 min). At 6, 12, 24, and 72 h (h) post-HI, brains were collected to assess neuropathology and BBB dysfunction. A significant breakdown of the BBB was observed in the HI injury group compared to the sham group from 6 h in the cortex and hippocampus (p < 0.001), including a significant increase in albumin extravasation (p < 0.0033) and decrease in basal lamina integrity and tight-junction proteins. There was a decrease in resting microglia (p < 0.0001) transitioning to an intermediate state from as early as 6 h post-HI, with the intermediate microglia peaking at 12 h (p < 0.0001), which significantly correlated to the peak of microbleeds. Neonatal HI insult leads to significant brain injury over the first 72 h that is mediated by BBB disruption within 6 h and a transitioning state of the resident microglia. Key BBB events coincide with the appearance of the intermediate microglial state and this relationship warrants further research and may be a key target for therapeutic intervention.