Aberrant activation of hippocampal astrocytes causes neuroinflammation and cognitive decline in mice

Neuroimmune signaling mediates astrocytic nucleocytoplasmic disruptions and stress granule formation associated with TDP-43 pathology

Alterations in transactivating response region DNA-binding protein 43 (TDP-43) are prevalent in amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and other neurological disorders. TDP-43 influences neuronal functions and might also affect glial cells. However, specific intracellular effects of TDP-43 alterations on glial cells and underlying mechanisms are not clear. We report that TDP-43 dysregulation in mouse and human cortical astrocytes causes nucleoporin mislocalization, nuclear envelope remodeling, and changes in nucleocytoplasmic protein transport. These effects are dependent on interleukin-1 (IL-1) receptor activity and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling and are associated with the formation of cytoplasmic stress granules. Stimulation of IL-1 receptors and NF-κB signaling are necessary and sufficient to induce astrocytic stress granules and rapid nucleocytoplasmic changes, which are broadly alleviated by inhibition of the integrated stress response. These findings establish that TDP-43 alterations and neuroimmune factors can induce nucleocytoplasmic changes through NF-κB signaling, revealing mechanistic convergence of proteinopathy and neuroimmune pathways onto glial nucleocytoplasmic disruptions that may occur in diverse neurological conditions.

Chronic Chemogenetic Activation of Astrocytes in the Murine Mesopontine Region Leads to Disturbances in Circadian Activity and Movement

We have previously shown that neuromodulatory actions on astrocytes can elicit metabotropic glutamate- and N-methyl-D-aspartate receptor-dependent tonic changes in excitability in the mesopontine region. Although in vitro experiments explored robust effects, the in vivo significance of our findings remained unknown. In this project, chronic chemogenetic activation of mesopontine astrocytes and its actions on movement, circadian activity, acoustic startle and spatial memory were tested. The control group of young adult male mice where mesopontine astrocytes expressed only the mCherry fluorescent tag was compared to the group expressing the hM3D(Gq) chemogenetic actuator. Chronic chemogenetic astrocyte activation reduced the amplitude of the acoustic startle reflex and increased the locomotion speed in the resting period. Gait alterations were also demonstrated but no change in the spatial memory was explored. As a potential background of these findings, chronic astrocytic activation decreased the cholinergic neuronal number to 54% and reduced the non-cholinergic neuronal number to 76% of the control. In conclusion, chronic astrocytic activation and the consequential decrease in the neuronal number led to disturbances in movement and circadian activity resembling brainstem-related symptoms of progressive supranuclear palsy, raising the possibility that astrocytic overactivation is involved in the pathogenesis of this disease.

Advancing Alzheimer's disease therapy through engineered exosomal Macromolecules

Exosomes are a subject of continuous investigation due to their function as extracellular vesicles (EVs) that significantly contribute to the pathophysiology of certain neurodegenerative disorders (NDD), including Alzheimer's disease (AD). Exosomes have shown the potential to carry both therapeutic and pathogenic materials; hence, researchers have used exosomes for medication delivery applications. Exosomes have reduced immunogenicity when used as natural drug delivery vehicles. This guarantees the efficient delivery of the medication without causing significant side reactions. Exosomes have lately enabled the potential for drug delivery in AD, along with promising future therapeutic uses for the detection of neurodegenerative disorders. Furthermore, exosomes have been examined for their prospective use in illness diagnosis and prediction before the manifestation of symptoms. This review will document prior studies and will concentrate on the rationale behind the substantial potential of exosomes in the treatment of AD and their prospective use as a diagnostic and predictive tool for this condition.

Urolithin-A Derivative UAS03 Improves Cognitive Deficits and Memory by Activating Nrf2 Pathways to Alleviate Oxidative Stress and Neuroinflammation

Neuroinflammation is a key factor in age-related cognitive decline and memory impairment. UAS03, a potent synthetic analogue of Urolithin-A, has demonstrated anti-inflammatory and antioxidant properties. This investigation examined the neuroprotective effect of UAS03 on lipopolysaccharide (LPS) induced neuroinflammation, and its associated cognitive impairments, memory deficits, and depression-like behaviors. Intracerebroventricular administration of LPS (12 μg/kg) was performed to induce neuroinflammation in mice, followed by a 7 day treatment with UAS03 at 10 and 30 mg/kg doses. Mice were evaluated for depressive and anxiety-like behavior, spatial memory, and learning functions using a series of neurobehavioral test paradigms. Histopathological and molecular analyses were conducted using hematoxylin-eosin and cresyl violet staining, immunohistochemistry, ELISA, and Western blotting techniques. We have found that, UAS03 significantly enhanced cognitive and memory functions impaired by LPS while concurrently reducing depressive symptoms. Furthermore, the compound attenuated neuronal damage and decreased the expression of IBA-1 and GFAP in hippocampal region. Through the activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway, UAS03 effectively mitigated markers of oxidative stress and reduced levels of pro-inflammatory factors, including IL-1β, TNF-α, and COX-2. Cumulatively, this study provides compelling evidence that UAS03 exerts neuroprotective effects by regulating essential pathways involved in anti-inflammatory and neuroprotective mechanisms, suggesting its potential as a preventative measure against age-related cognitive decline and memory impairments associated with neuroinflammation.

Astrocytes Mediate Psychostimulant-Induced Alterations of Spike-Timing Dependent Synaptic Plasticity

At cellular and circuit levels, drug addiction is considered a dysregulation of synaptic plasticity. In addition, dysfunction of the glutamate transporter 1 (GLT-1) in the nucleus accumbens (NAc) has also been proposed as a mechanism underlying drug addiction. However, the cellular and synaptic impact of GLT-1 alterations in the NAc remain unclear. Here we show in the NAc that 10 days withdraw after 5 days treatment with cocaine or amphetamine decreases GLT-1 expression in astrocytes, which results in the prolongation of the excitatory postsynaptic potential (EPSP) decay kinetics in D1 receptor-containing medium spiny neurons (D1R-MSNs). Using the spike timing dependent plasticity (STDP) paradigm, we found that enlargement of EPSP duration results in switching the LTP elicited in control animals to LTD in psychostimulant-treated mice. In contrast to D1-MSNs, D2-MSNs did not display changes in EPSP kinetics and synaptic plasticity. Notably, the psychostimulant-induced synaptic transmission and synaptic plasticity effects were absent in IP3R2-/- mice, which lack astrocyte calcium signal, but were mimicked by the selective astrocytes stimulation with DREADDs. Finally, ceftriaxone, which upregulates GLT-1, restored normal GLT-1 function, EPSP kinetics, and synaptic plasticity in psychostimulant-treated mice. Therefore, we propose that cocaine and amphetamine increase dopaminergic levels in the NAc, which stimulates astrocytes and downregulates the GLT-1. The decreased GLT-1 function prolonged the EPSP kinetics, leading to the modulation of the STDP, transforming the LTP observed in control animals into LTD in psychostimulant-treated mice. Present work reveals a novel mechanism underlying the synaptic plasticity changes induced by these drugs of abuse.

Decreased hippocampal neurite density in late middle-aged adults following prenatal exposure to higher levels of maternal inflammation

In animal models, exposure to heightened maternal inflammation in utero is associated with altered offspring hippocampal development, including reduced dendritic arborization and density. However, the effects of prenatal maternal inflammation (PNMI) on offspring hippocampal microstructure in humans remains unclear. Here, we examined the relationship between exposure to PNMI and neurite density in the hippocampus and its subfields among offspring during late middle age. Participants included 72 mother-offspring dyads from the Child Health and Development Studies (CHDS) cohort. Data for four inflammatory biomarkers (IL-6, IL-8, IL-1 receptor antagonist [IL-1RA], and soluble TNF receptor-II [sTNF-RII]) were available from first and second trimester maternal sera. Neurite density in the offspring hippocampus and its subfields was estimated using microstructural modeling of offsprings' diffusion-weighted Magnetic Resonance Imaging data (mean age of offspring at imaging = 59 years; 51% male). We estimated the relationship between each biomarker and region-of-interest's neurite density. Higher first trimester maternal IL-1RA and IL-6 levels were associated with lower offspring hippocampal neurite density. These relationships were specific to the CA3, CA4, dentate gyrus, and subiculum subfields. In addition, higher second trimester IL-6 was associated with lower subiculum neurite density. Our findings reveal that exposure to heightened prenatal levels of maternal inflammation is linked to altered offspring hippocampal microstructure in late middle age, which could have implications for memory decreases during this period and may be relevant for understanding risk of aging-related cognitive changes.

Advances in Optogenetics and Thermogenetics for Control of Non-Neuronal Cells and Tissues in Biomedical Research

Optogenetics and chemogenetics are relatively new biomedical technologies that emerged 20 years ago and have been evolving rapidly since then. This has been made possible by the combined use of genetic engineering, optics, and electrophysiology. With the development of optogenetics and thermogenetics, the molecular tools for cellular control are continuously being optimized, studied, and modified, expanding both their applications and their biomedical uses. The most notable changes have occurred in the basic life sciences, especially in neurobiology and the activation of neurons to control behavior. Currently, these methods of activation have gone far beyond neurobiology and are being used in cardiovascular research, for potential cancer therapy, to control metabolism, etc. In this review, we provide brief information on the types of molecular tools for optogenetic and thermogenetic methods─microbial rhodopsins and proteins of the TRP superfamily─and also consider their applications in the field of activation of non-neuronal tissues and mammalian cells. We also consider the potential of these technologies and the prospects for the use of optogenetics and thermogenetics in biomedical research.

Melanocortin 4 Receptor-Dependent Mechanism of ACTH in Preventing Anxiety-Like Behaviors and Normalizing Astrocyte Proteins after Early Life Seizures

Epilepsy, affecting millions globally, often leads to significant cognitive and psychiatric comorbidities, particularly in children. Anxiety and depression are particularly prevalent, with roughly a quarter of pediatric epilepsy patients having a comorbid diagnosis. Current treatments inadequately address these issues. Adrenocorticotropic hormone (ACTH), a melanocortin peptide, has shown promise in mitigating deficits after early-life seizures (ELS), potentially through mechanisms beyond its canonical action on the melanocortin 2 receptor. This study explores the hypothesis that recurrent ELS is associated with long-term anxiety and that treatment with ACTH can prevent this anxiety through a mechanism that involves the melanocortin 4 receptor (MC4R) in the brain. Our findings reveal that ACTH ameliorates anxiety-like behavior associated with ELS, without altering seizure parameters, in wild-type but not in male and female MC4R knock-out mice. Our findings also show that knocking-in MC4R in either neurons or astrocytes was able to rescue the anxiety-like behavior after ACTH treatment. Furthermore, our results show that ACTH normalizes important astrocytic proteins like glial fibrillary acidic protein and aquaporin-4 after ELS. This suggests that ACTH's beneficial effects on anxiety are mediated through MC4R activation in both neuronal and astrocytic populations. This study underscores the therapeutic potential of targeting MC4R as a treatment, highlighting its role in mitigating anxiety-like behaviors associated with ELS.

Regulation of Postoperative Cognitive Dysfunction by Glutathione Under Various Pathways: A Narrative Review

Postoperative cognitive dysfunction (POCD) is a common neurological complication after surgery and general anesthesia, and the incidence increases with age. Will have a negative impact on patients, family and society. At present, neuroinflammation and oxidative stress are the main recognized mechanisms. Glutathione (GSH) is a powerful reducing agent and may be related to POCD.

DATA COLLECTION

Using medical search engines such as PubMed, Web of Science, we analyzed articles on topics such as: POCD, GSH, microglia, astrocyte, oligodendrocyte, ferroptosis, BDNF, Neuroinflammation, oxidative stress. The above topics are searched in databases using Boolean operations. We included original articles, reviews and other article types such as medical books.

RESULTS

According to the reviewed literature, GSH may be a treatment for POCD.

CONCLUSIONS

Specific and targeted therapies for POCD still sparse, therefore, the implementation of preventive strategies appears to remain the optimal attitude. Further research is needed for a better understanding of GSH and POCD.

Astrocyte-Secreted Lcn2 Modulates Dendritic Spine Morphology

Learning and memory formation rely on synaptic plasticity, the process that changes synaptic strength in response to neuronal activity. In the tripartite synapse concept, molecular signals that affect synapse strength and morphology originate not only from the pre- and post-synaptic neuronal terminals but also from astrocytic processes ensheathing many synapses. Despite significant progress made in understanding astrocytic contribution to synaptic plasticity, only a few astrocytic plasticity-related proteins have been identified so far. In this study, we present evidence indicating the role of astrocyte-secreted Lipocalin-2 (Lcn2) in neuronal plasticity. We show that Lcn2 expression is induced in hippocampal astrocytes in a kainate-evoked aberrant plasticity model. Next, we demonstrate that chemically induced long-term potentiation (cLTP) similarly increases Lcn2 expression in astrocytes of neuronal-glial co-cultures, and that glutamate causes the immediate release of Lcn2 from these cultures. Additionally, through experiments in primary astrocytic cultures, we reveal that Lcn2 release is triggered by calcium signaling, and we demonstrate that a brief treatment of neuronal-glial co-cultures with Lcn2 alters the morphology of dendritic spines. Based on these findings, we propose Lcn2 as an activity-dependent molecule released by astrocytes that influences dendritic spine morphology.

Astrocyte Reactivity Polygenic Risk Score May Predict Cognitive Decline in Alzheimer's Disease

Alzheimer's disease (AD) is a polygenic disorder with a prolonged prodromal phase, complicating early diagnosis. Recent research indicates that increased astrocyte reactivity is associated with a higher risk of pathogenic tau accumulation, particularly in amyloid-positive individuals. However, few clinical tools are available to predict which individuals are likely to exhibit elevated astrocyte activation and, consequently, be susceptible to hyperphosphorylated tau-induced neurodegeneration. Polygenic risk scores (PRS) aggregate the effects of multiple genetic loci to provide a single, continuous metric representing an individual's genetic risk for a specific phenotype. We hypothesized that an astrocyte activation PRS could aid in the early detection of faster clinical decline. Therefore, we constructed an astrocyte activation PRS and assessed its predictive value for cognitive decline and AD biomarkers (i.e., cerebrospinal fluid [CSF] levels of Aβ1-42, total tau, and p-tau181) in a cohort of 791 elderly individuals. The astrocyte activation PRS showed significant main effects on cross-sectional memory (β = -0.07, p = 0.03) and longitudinal executive function (β = -0.01, p = 0.03). Additionally, the PRS interacted with amyloid positivity (p.intx = 0.02), whereby indicating that amyloid burden modifies the association between the PRS and annual rate of language decline. Furthermore, the PRS was negatively associated with CSF Aβ1-42 levels (β = -3.4, p = 0.07) and interacted with amyloid status, such that amyloid burden modifies the association between the PRS and CSF phosphorylated tau levels (p.intx = 0.08). These findings suggest that an astrocyte activation PRS could be a valuable tool for early disease risk prediction, potentially enabling intervention during the interval between pathogenic amyloid and tau accumulation.

Lipocalin-2 as a therapeutic target for diabetes neurological complications

INTRODUCTION

Diabetes mellitus, a chronic disorder with persistent hyperglycemia, severely affects the quality of life through significant neurological impairments, including neuropathy and cognitive dysfunction. Inflammation and oxidative stress are key factors in these complications, and Lipocalin-2 (LCN2), which is involved in inflammation and iron homeostasis, is crucial in these processes.

AREA COVERED

This review explores the potential of LCN2 as a therapeutic target for mitigating diabetes neurological complications. By examining the mechanisms by which LCN2 contributes to neuroinflammation, we discuss the therapeutic strategies that target LCN2 to alleviate diabetic neuropathy and cognitive dysfunction.

EXPERT OPINION

To fully grasp the impact of LCN2 on neurological health, it is essential to understand its multifaceted role in metabolic regulation. Because effective LCN2-targeting drugs must penetrate the blood - brain barrier, various strategies are being developed to meet this requirement. Such therapeutics could treat various neurological complications, including diabetic encephalopathy, retinopathy, and peripheral neuropathy. While animal models offer insights into pathophysiology and potential treatments, their limitations must be acknowledged. Therefore, future research should bridge the gaps between animal findings, human studies, and clinical applications. Moreover, comprehensive personalized approaches, including LCN2-targeting drugs, lifestyle changes, and regularly monitoring individual patients, may be required to manage diabetic complications.

Alzheimer's Disease, Obesity, and Type 2 Diabetes: Focus on Common Neuroglial Dysfunctions (Critical Review and New Data on Human Brain and Models)

BACKGROUND/OBJECTIVES

Obesity, type 2 diabetes (T2D), and Alzheimer's disease (AD) are pathologies that affect millions of people worldwide. They have no effective therapy and are difficult to prevent and control when they develop. It has been known for many years that these diseases have many pathogenic aspects in common. We highlight in this review that neuroglial cells (astroglia, oligodendroglia, and microglia) play a vital role in the origin, clinical-pathological development, and course of brain neurodegeneration. Moreover, we include the new results of a T2D-AD mouse model (APP+PS1 mice on a high-calorie diet) that we are investigating.

METHODS

Critical bibliographic revision and biochemical neuropathological study of neuroglia in a T2D-AD model.

RESULTS

T2D and AD are not only "connected" by producing complex pathologies in the same individual (obesity, T2D, and AD), but they also have many common pathogenic mechanisms. These include insulin resistance, hyperinsulinemia, hyperglycemia, oxidative stress, mitochondrial dysfunction, and inflammation (both peripheral and central-or neuroinflammation). Cognitive impairment and AD are the maximum exponents of brain neurodegeneration in these pathological processes. both due to the dysfunctions induced by metabolic changes in peripheral tissues and inadequate neurotoxic responses to changes in the brain. In this review, we first analyze the common pathogenic mechanisms of obesity, T2D, and AD (and/or cerebral vascular dementia) that induce transcendental changes and responses in neuroglia. The relationships between T2D and AD discussed mainly focus on neuroglial responses. Next, we present neuroglial changes within their neuropathological context in diverse scenarios: (a) aging involution and neurodegenerative disorders, (b) human obesity and diabetes and obesity/diabetes models, (c) human AD and in AD models, and (d) human AD-T2D and AD-T2D models. An important part of the data presented comes from our own studies on humans and experimental models over the past few years. In the T2D-AD section, we included the results of a T2D-AD mouse model (APP+PS1 mice on a high-calorie diet) that we investigated, which showed that neuroglial dysfunctions (astrocytosis and microgliosis) manifest before the appearance of amyloid neuropathology, and that the amyloid pathology is greater than that presented by mice fed a normal, non-high-caloric diet A broad review is finally included on pharmacological, cellular, genic, and non-pharmacological (especially diet and lifestyle) neuroglial-related treatments, as well as clinical trials in a comparative way between T2D and AD. These neuroglial treatments need to be included in the multimodal/integral treatments of T2D and AD to achieve greater therapeutic efficacy in many millions of patients.

CONCLUSIONS

Neuroglial alterations (especially in astroglia and microglia, cornerstones of neuroinflammation) are markedly defining brain neurodegeneration in T2D and A, although there are some not significant differences between each of the studied pathologies. Neuroglial therapies are a very important and p. promising tool that are being developed to prevent and/or treat brain dysfunction in T2D-AD. The need for further research in two very different directions is evident: (a) characterization of the phenotypic changes of astrocytes and microglial cells in each region of the brain and in each phase of development of each isolated and associated pathology (single-cell studies are mandatory) to better understand the pathologies and define new therapeutic targets; (b) studying new therapeutic avenues to normalize the function of neuroglial cells (preventing neurotoxic responses and/or reversing them) in these pathologies, as well as the phenotypic characteristics in each moment of the course and place of the neurodegenerative process.

Activity-induced reactivity of astrocytes impairs cognition

Glial cells such as astrocytes can modulate neuronal signaling. Astrocytes can also acquire a reactive phenotype that correlates with cognitive impairments in brain diseases. A study in PLOS Biology shows that prolonged activation of astrocytes can trigger both cognitive impairments and a reactive astrocyte phenotype.