Role of glia and extracellular matrix in controlling neuroplasticity in the central nervous system

Reactive spinal glia convert 2-AG to prostaglandins to drive aberrant astroglial calcium signaling

The endogenous cannabinoid 2-arachidonoylglycerol (2-AG) influences neurotransmission in the central nervous system mainly by activating type 1 cannabinoid receptor (CB1). Following its release, 2-AG is broken down by hydrolases to yield arachidonic acid, which may subsequently be metabolized by cyclooxygenase-2 (COX-2). COX-2 converts arachidonic acid and also 2-AG into prostanoids, well-known inflammatory and pro-nociceptive mediators. Here, using immunohistochemical and biochemical methods and pharmacological manipulations, we found that reactive spinal astrocytes and microglia increase the expression of COX-2 and the production of prostaglandin E2 when exposed to 2-AG. Both 2-AG and PGE2 evoke calcium transients in spinal astrocytes, but PGE2 showed 30% more efficacy and 55 times more potency than 2-AG. Unstimulated spinal dorsal horn astrocytes responded to 2-AG with calcium transients mainly through the activation of CB1. 2-AG induced exaggerated calcium transients in reactive astrocytes, but this increase in the frequency and area under the curve of calcium signals was only partially dependent on CB1. Instead, aberrant calcium transients were almost completely abolished by COX-2 inhibition. Our results suggest that both reactive spinal astrocytes and microglia perform an endocannabinoid-prostanoid switch to produce PGE2 at the expense of 2-AG. PGE2 in turn is responsible for the induction of aberrant astroglial calcium signals which, together with PGE2 production may play role in the development and maintenance of spinal neuroinflammation-associated disturbances such as central sensitization.

Extracellular vesicles set the stage for brain plasticity and recovery by multimodal signalling

Extracellular vesicles (EVs) are extremely versatile naturally occurring membrane particles that convey complex signals between cells. EVs of different cellular sources are capable of inducing striking therapeutic responses in neurological disease models. Differently from pharmacological compounds that act by modulating defined signalling pathways, EV-based therapeutics possess multiple abilities via a variety of effectors, thus allowing the modulation of complex disease processes that may have very potent effects on brain tissue recovery. When applied in vivo in experimental models of neurological diseases, EV-based therapeutics have revealed remarkable effects on immune responses, cell metabolism and neuronal plasticity. This multimodal modulation of neuroimmune networks by EVs profoundly influences disease processes in a highly synergistic and context-dependent way. Ultimately, the EV-mediated restoration of cellular functions helps to set the stage for neurological recovery. With this review we first outline the current understanding of the mechanisms of action of EVs, describing how EVs released from various cellular sources identify their cellular targets and convey signals to recipient cells. Then, mechanisms of action applicable to key neurological conditions such as stroke, multiple sclerosis and neurodegenerative diseases are presented. Pathways that deserve attention in specific disease contexts are discussed. We subsequently showcase considerations about EV biodistribution and delineate genetic engineering strategies aiming at enhancing brain uptake and signalling. By sketching a broad view of EV-orchestrated brain plasticity and recovery, we finally define possible future clinical EV applications and propose necessary information to be provided ahead of clinical trials. Our goal is to provide a steppingstone that can be used to critically discuss EVs as next generation therapeutics for brain diseases.

[Validation of a C57/BL6J mouse model of focal cerebral ischemia established by electrocoagulation of the middle cerebral artery]

OBJECTIVE

To modify the method for establishing mouse models of middle cerebral artery occlusion (MCAO)-induced focal cerebral ischemia using electrocoagulation.

METHODS

Forty-six C57/BL6J male mice were divided into MCAO model group (n=34) and sham-operated group (n=12). In the model group, MCAO was induced by permanent coagulation of the right middle cerebral artery (MCA) using a coagulator, and cerebral blood flow perfusion was monitored before and at 20 min and 1 day after modeling. Neurological deficits of the mice at 1, 7, and 14 days after modeling were evaluated using Longa score, mNSS score, beam walking test, cylinder test and corner test. TTC staining was used to measure the cerebral infarct size, and Western blotting was performed to detect the expressions of BDNF, GFAP and DCX proteins in the ischemic cortex.

RESULTS

The mice in the model group showed significantly reduced cerebral blood flow in the MCA on the ischemic side and obvious neurological deficits with increased forelimb use asymmetry on days 1, 7 and 14 after modeling (P < 0.05). In the cerebral cortex on the ischemic side of the model mice, the expressions of GFAP and DCX increased significantly at 1, 7, and 14 days (P < 0.05) and the expression of BDNF increased at 1 day after modeling ischemia (P < 0.05).

CONCLUSION

We successfully prepared mouse models of MCAO using a modified method by changing the electrocoagulation location from the distal location of the junction between the MCA and the inferior cerebral vein to a 2 mm segment medial to the junction between the MCA and the olfactory bundle.

Interplay of G-proteins and Serotonin in the Neuroimmunoinflammatory Model of Chronic Stress and Depression: A Narrative Review

INTRODUCTION

This narrative review addresses the clinical challenges in stress-related disorders such as depression, focusing on the interplay between neuron-specific and pro-inflammatory mechanisms at the cellular, cerebral, and systemic levels.

OBJECTIVE

We aim to elucidate the molecular mechanisms linking chronic psychological stress with low-grade neuroinflammation in key brain regions, particularly focusing on the roles of G proteins and serotonin (5-HT) receptors.

METHODS

This comprehensive review of the literature employs systematic, narrative, and scoping review methodologies, combined with systemic approaches to general pathology. It synthesizes current research on shared signaling pathways involved in stress responses and neuroinflammation, including calcium-dependent mechanisms, mitogen-activated protein kinases, and key transcription factors like NF-κB and p53. The review also focuses on the role of G protein-coupled neurotransmitter receptors (GPCRs) in immune and pro-inflammatory responses, with a detailed analysis of how 13 of 14 types of human 5-HT receptors contribute to depression and neuroinflammation.

RESULTS

The review reveals a complex interaction between neurotransmitter signals and immunoinflammatory responses in stress-related pathologies. It highlights the role of GPCRs and canonical inflammatory mediators in influencing both pathological and physiological processes in nervous tissue.

CONCLUSION

The proposed Neuroimmunoinflammatory Stress Model (NIIS Model) suggests that proinflammatory signaling pathways, mediated by metabotropic and ionotropic neurotransmitter receptors, are crucial for maintaining neuronal homeostasis. Chronic mental stress can disrupt this balance, leading to increased pro-inflammatory states in the brain and contributing to neuropsychiatric and psychosomatic disorders, including depression. This model integrates traditional theories on depression pathogenesis, offering a comprehensive understanding of the multifaceted nature of the condition.

Asteroid impact: the potential of astrocytes to modulate human neural networks within organoids

Astrocytes are a vital cellular component of the central nervous system that impact neuronal function in both healthy and pathological states. This includes intercellular signals to neurons and non-neuronal cells during development, maturation, and aging that can modulate neural network formation, plasticity, and maintenance. Recently, human pluripotent stem cell-derived neural aggregate cultures, known as neurospheres or organoids, have emerged as improved experimental platforms for basic and pre-clinical neuroscience compared to traditional approaches. Here, we summarize the potential capability of using organoids to further understand the mechanistic role of astrocytes upon neural networks, including the production of extracellular matrix components and reactive signaling cues. Additionally, we discuss the application of organoid models to investigate the astrocyte-dependent aspects of neuropathological diseases and to test astrocyte-inspired technologies. We examine the shortcomings of organoid-based experimental platforms and plausible improvements made possible by cutting-edge neuroengineering technologies. These advancements are expected to enable the development of improved diagnostic strategies and high-throughput translational applications regarding neuroregeneration.

Novel treatments for anorexia nervosa: Insights from neuroplasticity research

OBJECTIVE

Treatment for anorexia nervosa (AN) remains challenging; there are no approved psychopharmacological interventions and psychotherapeutic strategies have variable efficacy. The investigation of evidence-based treatments has so far been compounded by an underdeveloped understanding into the neurobiological changes associated with the acute stages of AN. There is converging evidence of deficiencies in neuroplasticity in AN.

METHOD

This paper provides an overview of neuroimaging, neuropsychological, molecular and qualitative findings relating to neuroplasticity in AN, translating these findings to the identification of novel biological and psychotherapeutic strategies.

RESULTS

Novel psychopharmacological approaches that may ameliorate deficiencies in neuroplasticity include medications such as ketamine, psilocybin and human recombinant leptin. Anti-inflammatory medications and brain-derived neurotrophic factor mimetics may emerge as potential treatments following further research. Psychotherapeutic strategies that may target neuroplastic deficiencies, as well as having wider effects on identity, include imagery rescripting, memory specificity training, cognitive remediation therapy, exposure therapies, narrative therapies, cultural interventions (e.g. music and arts therapies) and yoga/mindfulness-based interventions.

CONCLUSIONS

Treatments specifically targeted towards mitigating the neurobiological sequalae of AN are warranted, and emerging neurobiological and neuropsychological research utilising longitudinal designs and large sample sizes, as well as initial feasibility studies, are necessitated to bolster translational efforts.

Astrocyte metabolism and signaling pathways in the CNS

Astrocytes comprise half of the cells in the central nervous system and play a critical role in maintaining metabolic homeostasis. Metabolic dysfunction in astrocytes has been indicated as the primary cause of neurological diseases, such as depression, Alzheimer's disease, and epilepsy. Although the metabolic functionalities of astrocytes are well known, their relationship to neurological disorders is poorly understood. The ways in which astrocytes regulate the metabolism of glucose, amino acids, and lipids have all been implicated in neurological diseases. Metabolism in astrocytes has also exhibited a significant influence on neuron functionality and the brain's neuro-network. In this review, we focused on metabolic processes present in astrocytes, most notably the glucose metabolic pathway, the fatty acid metabolic pathway, and the amino-acid metabolic pathway. For glucose metabolism, we focused on the glycolysis pathway, pentose-phosphate pathway, and oxidative phosphorylation pathway. In fatty acid metabolism, we followed fatty acid oxidation, ketone body metabolism, and sphingolipid metabolism. For amino acid metabolism, we summarized neurotransmitter metabolism and the serine and kynurenine metabolic pathways. This review will provide an overview of functional changes in astrocyte metabolism and provide an overall perspective of current treatment and therapy for neurological disorders.