Physiology of microglia

Alterations of synaptic plasticity and brain oscillation are associated with autophagy induced synaptic pruning during adolescence

Adolescent brain development is characterized by significant anatomical and physiological alterations, but little is known whether and how these alterations impact the neural network. Here we investigated the development of functional networks by measuring synaptic plasticity and neural synchrony of local filed potentials (LFPs), and further explored the underlying mechanisms. LFPs in the hippocampus were recorded in young (21 ~ 25 days), adolescent (1.5 months) and adult (3 months) rats. Long term potentiation (LTP) and neural synchrony were analyzed. The results showed that the LTP was the lowest in adolescent rats. During development, the theta coupling strength was increased progressively but there was no significant change of gamma coupling between young rats and adolescent rats. The density of dendrite spines was decreased progressively during development. The lowest levels of NR2A, NR2B and PSD95 were detected in adolescent rats. Importantly, it was found that the expression levels of autophagy markers were the highest during adolescent compared to that in other developmental stages. Moreover, there were more co-localization of autophagosome and PSD95 in adolescent rats. It suggests that autophagy is possibly involved in synaptic elimination during adolescence, and further impacts synaptic plasticity and neural synchrony.

Potassium and calcium channels in different nerve cells act as therapeutic targets in neurological disorders

The central nervous system, information integration center of the body, is mainly composed of neurons and glial cells. The neuron is one of the most basic and important structural and functional units of the central nervous system, with sensory stimulation and excitation conduction functions. Astrocytes and microglia belong to the glial cell family, which is the main source of cytokines and represents the main defense system of the central nervous system. Nerve cells undergo neurotransmission or gliotransmission, which regulates neuronal activity via the ion channels, receptors, or transporters expressed on nerve cell membranes. Ion channels, composed of large transmembrane proteins, play crucial roles in maintaining nerve cell homeostasis. These channels are also important for control of the membrane potential and in the secretion of neurotransmitters. A variety of cellular functions and life activities, including functional regulation of the central nervous system, the generation and conduction of nerve excitation, the occurrence of receptor potential, heart pulsation, smooth muscle peristalsis, skeletal muscle contraction, and hormone secretion, are closely related to ion channels associated with passive transmembrane transport. Two types of ion channels in the central nervous system, potassium channels and calcium channels, are closely related to various neurological disorders, including Alzheimer's disease, Parkinson's disease, and epilepsy. Accordingly, various drugs that can affect these ion channels have been explored deeply to provide new directions for the treatment of these neurological disorders. In this review, we focus on the functions of potassium and calcium ion channels in different nerve cells and their involvement in neurological disorders such as Parkinson's disease, Alzheimer's disease, depression, epilepsy, autism, and rare disorders. We also describe several clinical drugs that target potassium or calcium channels in nerve cells and could be used to treat these disorders. We concluded that there are few clinical drugs that can improve the pathology these diseases by acting on potassium or calcium ions. Although a few novel ion-channel-specific modulators have been discovered, meaningful therapies have largely not yet been realized. The lack of target-specific drugs, their requirement to cross the blood-brain barrier, and their exact underlying mechanisms all need further attention. This review aims to explain the urgent problems that need research progress and provide comprehensive information aiming to arouse the research community's interest in the development of ion channel-targeting drugs and the identification of new therapeutic targets for that can increase the cure rate of nervous system diseases and reduce the occurrence of adverse reactions in other systems.

Effects of Argon in the Acute Phase of Subarachnoid Hemorrhage in an Endovascular Perforation Model in Rats

BACKGROUND

Subarachnoid hemorrhage (SAH) is a devastating disease with high morbidity and mortality. Neuroprotective effects of the noble gas argon have been shown in animal models of ischemia. The aim of this study was to investigate the effects of argon in the immediate early phase of SAH in a rat model.

METHODS

A total of 19 male Wistar rats were randomly assigned to three treatment groups. SAH was induced using a endovascular filament perforation model. Cerebral blood flow, mean arterial blood pressure (MAP), and body temperature were measured continuously. Group A received 2 h of ventilation by 50% argon/50% O2 (n = 7) immediately following SAH. Group B underwent a sham operation and was also ventilated by 50% argon/50% O2 (n = 6). Group C underwent SAH and 50% O2/50% N2 ventilation (n = 6). Preoperative and postoperative neurological and behavioral testing were performed. Histology and immunohistochemistry were used to evaluate the extent of brain injury and vasospasm.

RESULTS

The cerebral blood flow dropped in both treatment groups after SAH induction (SAH, 63.0 ± 11.6% of baseline; SAH + argon, 80.2 ± 8.2% of baseline). During SAH, MAP increased (135.2 ± 10.5%) compared with baseline values (85.8 ± 26.0 mm Hg) and normalized thereafter. MAP in both groups showed no significant differences (p = 0.3123). Immunohistochemical staining for neuronal nuclear antigen demonstrated a decrease of hippocampal immunoreactivity after SAH in the cornu ammonis region (CA) 1-3 compared with baseline hippocampal immunoreactivity (p = 0.0127). Animals in the argon-ventilated group showed less neuronal loss compared with untreated SAH animals (p < 0.0001). Ionized calcium-binding adaptor molecule 1 staining showed a decreased accumulation after SAH + argon (CA1, 2.57 ± 2.35%; CA2, 1.89 ± 1.89%; CA3, 2.19 ± 1.99%; DG, 2.6 ± 2.24%) compared with untreated SAH animals (CA1, 5.48 ± 2.39%; CA2, 4.85 ± 4.06%; CA3, 4.22 ± 3.01%; dentate gyrus (DG), 3.82 ± 3.23%; p = 0.0007). The neuroscore assessment revealed no treatment benefit after SAH compared with baseline (p = 0.385).

CONCLUSION

In the present study, neuroprotective effects of argon occurred early after SAH. Because neurological deterioration was similar in the preadministration and absence of argon, it remains uncertain if neuroprotective effects translate in improved outcome over time.

Modification of Neural Circuit Functions by Microglial P2Y6 Receptors in Health and Neurodegeneration

Neural circuits consisting of neurons and glial cells help to establish all functions of the CNS. Microglia, the resident immunocytes of the CNS, are endowed with UDP-sensitive P2Y6 receptors (P2Y6Rs) which regulate phagocytosis/pruning of excessive synapses during individual development and refine synapses in an activity-dependent manner during adulthood. In addition, this type of receptor plays a decisive role in primary (Alzheimer's disease, Parkinson's disease, neuropathic pain) and secondary (epilepsy, ischemic-, mechanical-, or irradiation-induced) neurodegeneration. A whole range of microglial cytokines controlled by P2Y6Rs, such as the interleukins IL-1β, IL-6, IL-8, and tumor necrosis factor-α (TNF-α), leads to neuroinflammation, resulting in neurodegeneration. Hence, small molecular antagonists of P2Y6Rs and genetic knockdown of this receptor provide feasible ways to alleviate inflammation-induced neurological disorders but might also interfere with the regulation of the synaptic circuitry. The present review aims at investigating this dual role of P2Y6Rs in microglia, both in shaping neural circuits by targeted phagocytosis and promoting neurodegenerative illnesses by fostering neuroinflammation through multiple transduction mechanisms.

Cognitive impairment following maternal separation in rats mediated by the NAD+/SIRT3 axis via modulation of hippocampal synaptic plasticity

Maternal separation (MS) during early life can induce behaviors in adult animals that resemble those seen in schizophrenia, manifesting cognitive deficits. These cognitive deficits may be indicative of oxidative stress linked to mitochondrial dysfunction. However, there is limited understanding of the molecular mechanisms regulating mitochondria in neural circuits that govern cognitive impairment relevant to schizophrenia, and their impact on neuronal structure and function. A 24-h MS rat model was utilized to simulate features associated with schizophrenia. Schizophrenia-associated behaviors and cognitive impairment were assessed using the open field test, pre-pulse inhibition, novel object recognition test, and Barnes maze test. The levels of mitochondrial proteins were measured using western blot analysis. Additionally, alterations in mitochondrial morphology, reduced hippocampal neuronal spine density, and impaired LTP in the hippocampus were observed. Nicotinamide (NAM) supplementation, administration of honokiol (HNK) (a SIRT3 activator), or overexpression of SIRT3 could inhibit cognitive deficits and cellular dysfunction. Conversely, administration of 3-TYP (a SIRT3 inhibitor) or knocking down SIRT3 expression in control rats led to deficits in behavioral and hippocampal neuronal phenotype. Our results suggest a causal role for the NAD+/SIRT3 axis in modulating cognitive behaviors via effects on hippocampal neuronal synaptic plasticity. The NAD+/SIRT3 axis could be a promising therapeutic target for addressing cognitive dysfunctions, such as those seen in schizophrenia.

Morphological and functional differences between hippocampal and cortical microglia and its impact on neuronal over-excitation in a germline Pten mutant mouse model

High-throughput, transcriptomic analyses of the brain have revealed significant differences of microglia between the hippocampus and the cortex. However, it remains unclear whether these regional differences translate into different microglial behaviors and impact disease progression. Here, we show that microglia possess higher morphological complexity and phagocytic capacity in the hippocampus compared to the cortex of wild-type mice. These regional differences are preserved in mice harboring a germline Pten mutation, which have a general increase of microglial ramification and phagocytic capacity. Moreover, we find that Pten-mutant microglia protect neurons from over-excitation through pruning excessive excitatory synapses and forming more microglia-neuron junctions. However, Pten-mutation induced neuronal over-excitation is normalized in the hippocampus but not the cortex which we are attributing to regional differences of microglia in both function and morphology. These Pten-mutant microglia may protect Pten mutant mice from developing spontaneous seizures, but cannot eliminate their heightened risk of provoked seizure. Collectively, our findings have revealed a potential protective role of microglia in an over-excited brain, underscoring the impact of microglial regional heterogeneity in disease development and highlighting their prospect as a therapeutic target for epilepsy.

Procyanidin B2 attenuates microvascular dysfunction in diabetic retinopathy via inhibition of caspase-1/GSDMD mediated pyroptosis

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Chinese medicine (TCM), grape seeds (Vitis vinifera) are believed to nourish the liver and kidney and improve blood circulation, which aligns with the pathophysiological needs of conditions characterized by microvascular dysfunction. Procyanidin B2 (PB2), a major active compound in grape seeds, has shown potent anti-inflammatory and vascular-protective effects. However, the specific role of PB2 in diabetic retinal microvasculature and its underlying molecular mechanisms remain unexplored.

AIMS OF THE STUDY

This study aimed to evaluate the therapeutic potential of Procyanidin B2 (PB2) in alleviating microvascular damage in diabetic retinopathy and the possible mechanisms.

MATERIALS AND METHODS

Pyroptosis in endothelial cells was analyzed under high glucose conditions and in the retinas of diabetic mice. The effects of PB2 on pyroptosis and endothelial dysfunction were examined through in vitro assays evaluating cell proliferation, migration, and tube formation. In vivo experiments using diabetic mouse models were conducted to assess retinal vascular integrity, with a focus on PB2's impact on endothelial pyroptosis and its associated molecular mechanisms.

RESULTS

PB2 significantly suppressed pyroptosis in endothelial cells exposed to high glucose by inhibiting the caspase-1/GSDMD signaling pathway. This suppression enhanced endothelial cell proliferation, migration, and tube formation. In diabetic mice, PB2 treatment effectively alleviated retinal microvascular dysfunction by reducing pyroptosis and preserving retinal vascular integrity.

CONCLUSION

These findings provide a molecular basis for PB2's therapeutic potential in DR and support its further development as an intervention for diabetic vascular complications.

Radial glia integrin avb8 regulates cell autonomous microglial TGFβ1 signaling that is necessary for microglial identity

Microglial diversity arises from the interplay between inherent genetic programs and external environmental signals. However, the mechanisms by which these processes develop and interact within the growing brain are not yet fully understood. Here, we show that radial glia-expressed integrin beta 8 (ITGB8) activates microglia-expressed TGFβ1 to drive microglial development. Domain-restricted deletion of Itgb8 in these progenitors results in regionally restricted and developmentally arrested microglia that persist into adulthood. In the absence of autocrine TGFβ1 signaling, microglia adopt a similar phenotype, leading to neuromotor symptoms almost identical to Itgb8 mutant mice. In contrast, microglia lacking the canonical TGFβ signal transducers Smad2 and Smad3 have a less polarized dysmature phenotype and correspondingly less severe neuromotor dysfunction. Our study describes the spatio-temporal regulation of TGFβ activation and signaling in the brain necessary to promote microglial development, and provides evidence for the adoption of microglial developmental signaling pathways in brain injury or disease.

PI3K/AKT pathway: A potential therapeutic target in cerebral ischemia-reperfusion injury

Cerebral ischemia is a prevalent cerebrovascular disorder, with the restoration of blocked blood vessels serving as the current standard clinical treatment. However, reperfusion can exacerbate neuronal damage and neurological dysfunction, resulting in cerebral ischemia-reperfusion (I/R) injury. Presently, clinical treatment strategies for cerebral I/R injury are limited, creating an urgent need to identify new effective therapeutic targets. The PI3K/AKT signaling pathway, a pro-survival pathway associated with cerebral I/R injury, has garnered significant attention. We conducted a comprehensive review of the literature on the PI3K/AKT pathway in the context of cerebral I/R. Our findings indicate that activation of the PI3K/AKT signaling pathway following cerebral I/R can alleviate oxidative stress, reduce endoplasmic reticulum stress (ERS), inhibit inflammatory responses, decrease neuronal apoptosis, autophagy, and pyroptosis, mitigate blood-brain barrier (BBB) damage, and promote neurological function recovery. Consequently, this pathway ultimately reduces neuronal death, alleviates brain tissue damage, decreases the volume of cerebral infarction, and improves behavioral impairments. These results suggest that the PI3K/AKT signaling pathway is a promising therapeutic target for further research and drug development, holding significant potential for the treatment of cerebral I/R injury.

GDF11 Regulates M1 and M2 Polarization of BV2 Microglial Cells via p38 MAPK Signaling Pathway

Growth differentiation factor 11 (GDF11), a member of the transforming growth factor β (TGF-β) superfamily, exhibits great neurological and mental diseases modulating potential. However, its specific effects on microglia, which are the primary immune cells of the nervous system, remain unclear. To investigate the mechanism by which GDF11 affects BV2 microglial cells in vitro and to elucidate its regulatory mechanisms, we carried out a systematic examination of how GDF11 affects the various functions of lipopolysaccharide (LPS)-induced BV2 microglial cells and found that endogenous GDF11 could significantly inhibit cell proliferation, apoptosis, and migration. Specifically, GDF11 inhibited the polarization of BV2 cells to the proinflammatory M1 phenotype and promoted their polarization to the anti-inflammatory M2 phenotype, precipitating a reduction in the expression of CD86 and nitric oxide synthase 2 (NOS2), and an increase in the expression of CD206 and arginase-1. Additionally, RNA-seq and Western blotting experiments revealed that GDF11 activated the p38 MAPK (mitogen-activated protein kinase) pathway, mediating its effects on BV2 cells. Taken together, GDF11 could crucially regulate microglial responses and promote an anti-inflammatory microglial phenotype through the p38 MAPK signaling axis, which may have potential therapeutic implications in neuroinflammatory diseases.

Regulation of macrophage efferocytosis by the CLCF1/NF-κB pathway improves neurological and cognitive impairment following CO poisoning

Severe carbon monoxide (CO) poisoning can induce structural and functional damage to the nervous system, resulting in persistent cognitive impairments. Properly terminating inflammation caused by neuronal damage is essential for tissue repair. Macrophages clear cell corpses and fragments through efferocytosis and produce cytokines to coordinate the immune response, thus promoting neuronal repair and regeneration. However, within the microenvironment of the CO-affected nervous system, macrophage efferocytosis is disrupted. Our study found that macrophages regulate efferocytosis by releasing Cardiotrophin-like cytokine factor 1 (CLCF1), which modulates the NF-κB pathway in both macrophages and microglia, thereby controlling inflammation and promoting nervous system repair. Furthermore, efferocytosis regulates the secretion of cytokines such as TNF-α, IL-1β, and IL-10, promoting M2 polarization of macrophages, which aids in neuronal repair and regeneration. Regulating macrophage CLCF1 expression also leads to improvements in the memory, learning, and motor abilities of rats poisoned with CO.

Indole-3-Propionic Acid Attenuates Neuroinflammation and Cognitive Deficits by Inhibiting the RAGE-JAK2-STAT3 Signaling Pathway

Cognitive disorders such as Alzheimer's disease (AD) are highly prevalent and place heavy burdens on society. Neuroinflammation is a driver of cognitive impairment, with no effective drugs. Indole 3-propionic acid (IPA) is a tryptophan metabolite mainly produced byClostridium sporogenes, which exhibits multiple functions, including antioxidant, anti-inflammatory, antiaging, and neuroprotective properties. However, the restorative effects and molecular mechanisms of IPA in cognitive impairment remain to be investigated. In this study, we found that IPA reduced LPS-induced apoptosis and oxidative damage in HT22 cells and decreased LPS-induced inflammation in BV2 cells. Besides, IPA promoted neurogenesis, inhibited glial cell activation, maintained the integrity of the BBB and intestinal barrier, and remodeled the gut microbiota, thereby alleviating memory impairment in LPS-induced cognitively impaired mice. At the mechanistic level, IPA inhibited the RAGE-JAK2-STAT3 signaling pathway and thus ameliorated neuroinflammation. Interestingly, Colivelin TFA, an activator of JAK2-STAT3 signaling, partially reversed the neurorestorative effects of IPA. In conclusion, IPA ameliorates neuroinflammation and cognitive deficits via the inhibition of the RAGE-JAK2-STAT3 signaling pathway. Thus, IPA may be a potential drug for the treatment of cognitive disorders.

Gut microbiota-related neuroinflammation at the crossroad of food reward alterations: implications for eating disorders

The link between gut microbiome and eating behaviours, especially palatable food intake, is a growing focus of scientific investigation. The complex ecosystem of microorganisms in the gut influences host metabolism, immune function and neurobehavioural signalling. This review explores the role of neuroinflammation in dysregulations of food-induced reward signalling and the potential causal role of the gut microbiota on these proinflammatory processes. Particular attention is given to eating disorders (ED, specifically anorexia nervosa, binge eating disorder and bulimia nervosa) and potential links with the gut microbiota, food reward alterations and neuroinflammation. Finally, we propose gut microbiota modulation as a promising therapeutic strategy in food reward alterations and ED.

Maternal immune activation followed by peripubertal stress combinedly produce reactive microglia and confine cerebellar cognition

The functional alteration of microglia arises in brains exposed to external stress during early development. Pathophysiological findings of neurodevelopmental disorders such as schizophrenia and autism spectrum disorder suggest cerebellar functional deficits. However, the link between stress-induced microglia reactivity and cerebellar dysfunction is missing. Here, we investigate the developmental immune environment in translational mouse models that combine two risk factors: maternal infection and repeated social defeat stress (2HIT). We find the synergy of inflammatory stress insults, leading to microglial increase specifically in the cerebellum of both sexes. Microglial turnover correlates with the Purkinje neuron loss in 2HIT mice. Highly multiplexed imaging-mass-cytometry identifies a cell transition to TREM2(+) stress-associated microglia in the cerebellum. Single-cell-proteomic clustering reveals IL-6- and TGFβ-signaling association with microglial cell transitions. Reduced excitability of remaining Purkinje cells, cerebellum-involved brain-wide functional dysconnectivity, and behavioral abnormalities indicate cerebellar cognitive dysfunctions in 2HIT animals, which are ameliorated by both systemic and cerebellum-specific microglia replacement.

Design, current states, and challenges of nanomaterials in anti-neuroinflammation: A perspective on Alzheimer's disease

Alzheimer's disease (AD), an age-related neurodegenerative disease, brings huge damage to the society, to the whole family and even to the patient himself. However, until now, the etiological factor of AD is still unknown and there is no effective treatment for it. Massive deposition of amyloid-beta peptide(Aβ) and hyperphosphorylation of Tau proteins are acknowledged pathological features of AD. Recent studies have revealed that neuroinflammation plays a pivotal role in the pathology of AD. With the rise of nanomaterials in the biomedical field, researchers are exploring how the unique properties of these materials can be leveraged to develop effective treatments for AD. This article has summarized the influence of neuroinflammation in AD, the design of nanoplatforms, and the current research status and inadequacy of nanomaterials in improving neuroinflammation in AD.

Electromagnetic pulse exposure induces neuroinflammation and blood-brain barrier disruption by activating the NLRP3 inflammasome/NF-κB signaling pathway in mice

The electromagnetic pulse (EMP) is a widespread electromagnetic disturbance that can disrupt electronic systems and pose health risks to personnel in operational areas. The biological effects of EMP radiation, especially on the central nervous system (CNS), are not yet fully understood but are gaining attention. This study examines the impact of EMP on the CNS using microglial cells as a model system. We found that mice exposed to a field strength of 600 kV/m with 1000 pulses per day for two weeks exhibited increased levels of oxidative stress. This exposure induced a microglia polarization to the M1 state, leading to neuroinflammation and disruption of the blood-brain barrier (BBB) by the pro-inflammatory response of microglia. Further analysis revealed that the NLRP3 inflammasome/NF-κB signaling pathway modulates the pro-inflammatory mechanisms of EMP irradiation. In conclusion, our findings show that EMP irradiation triggers neuroinflammation and BBB damage via NLRP3 inflammasome/NF-κB activation. This research highlights the effects of EMP radiation on the CNS and offers valuable insights into the potential targets for biomedical protection against it.

Therapeutic potential of pranlukast against cuprizone-induced inflammatory demyelination and sensory impairment in mice: Comparison with fingolimod

Inflammatory demyelination is present in debilitating diseases such as Multiple Sclerosis (MS). Several drugs are available for MS treatment, with fingolimod as a first-line oral option in the United States. However, a cure has yet to be established, and therapeutic failures are common, highlighting the need for continued research into new pharmacological targets. Pranlukast has shown positive effects on myelination in cell cultures and after LPC-induced demyelination in mice, but it is not yet part of the therapeutic arsenal for this disease. This study investigates pranlukast's effect on demyelination protection in an MS animal model, compared to fingolimod. For this purpose, young adult Swiss mice were treated for five weeks with a 0.2 % cuprizone diet and received daily intraperitoneal injections of pranlukast (0.1 mg/kg), fingolimod (1 mg/kg), or vehicle. Pranlukast treatment, like fingolimod, partially preserved sensory function in the tactile sensitivity test. Both treatments partially preserved myelin basic protein (MBP) levels, but only fingolimod preserved lipids and myelinated fibers in the corpus callosum (CC) at all g-ratio ranges. Cuprizone and Pranlukast groups presented more microglia/macrophages in the CC, but fewer presenting reactive microglia/macrophages and less NOS2 staining in pranlukast-treated when compared to the cuprizone group, while fingolimod treatment prevented the increase in Iba1 in the CC. In summary, this study demonstrated that pranlukast is a good candidate as a novel drug for use in conditions of inflammatory demyelination, such as MS, by restoring function through modulation of the inflammatory environment.

The Role of Complexity Theory in Understanding Brain's Neuron-Glia Interactions

Brain information processing complexity is conventionally recognized as derived from neuronal activity, with neurons and their dynamic signalling responsible for the transfer and processing of information. However, the brain also contains other non-neuronal cells, glial cells, which exceed the number of neurons and are involved in the processes related with information coding by neural networks and underlying brain functions. Decisive advances in the characterization of the molecular and physiological properties of glial cells shed light on their active roles in neurotransmission and neuronal physiopathology. This expanded relationship between neurons and glia challenges traditional neurobiology by highlighting their reciprocal influence, where it is difficult to determine whether neuronal or glial processes initiate and drive the interactions. This interplay creates a dilemma, where the causal hierarchy between these two cell types remains unresolved. A philosophical tool, the 'Theory of Complexity' of Edgard Morin can help to better explain and study the complexity of neuron-glia interactions. Morin's proposal on complexity is useful to transform brain knowledge, in order to review the brain molecular functions in antireductionist pattern. In this manuscript, we will discuss how to use the 'retroactive loop' principle from Morin's 'Theory of Complexity' at the brain molecular level, proposing a new philosophical-experimental grid that can help neuroscientists for a better understanding of the glia-neuron interactions in the brain.

Costunolide normalizes neuroinflammation and improves neurogenesis deficits in a mouse model of depression through inhibiting microglial Akt/mTOR/NF-κB pathway

Neuroinflammation is crucial for the pathogenesis of major depression. Preclinical studies have shown the potential of anti-inflammatory agents, specifically costunolide (COS), correlate with antidepressant effects. In this study, we investigated the molecular mechanisms underlying the antidepressant actions of COS. Chronic restraint stress (CRS) was induced in male mice. The mice were treated with either intra-DG injection of COS (5 μM, 1 μL per side) or COS (20 mg/kg, i.p.) for 1 week. We showed that administration of COS through the both routes significantly ameliorated the depressive-like behavior in CRS-exposed mice. Furthermore, administration of COS significantly improved chronic stress-induced adult hippocampal neurogenesis deficits in the mice through attenuating microglia-derived neuroinflammation. We demonstrated that COS (5 μM) exerted anti-neuroinflammatory effects in LPS-treated BV2 cells via inhibiting microglial Akt/mTOR/NF-κB pathway; inactivation of mTOR/NF-κB/IL-1β pathway was required for the pro-neurogenic action of COS in CRS-exposed mice. Our results reveal the antidepressant mechanism of COS that is normalizing neuroinflammation to improve neurogenesis deficits, supporting anti-inflammatory agents as a potential therapeutic strategy for depression.

The Biflavonoid Agathisflavone Regulates Microglial and Astrocytic Inflammatory Profiles via Glucocorticoid Receptor

Nuclear receptors such as glucocorticoid receptors (GRs) are transcription factors with prominent regulatory effects on neuroinflammation. Agathisflavone is a biflavonoid that demonstrates neurogenic, neuroprotective, anti-inflammatory, antioxidant, and pro-myelinogenic effects in vitro. This study investigated whether the control of glial reactivity by agathisflavone is mediated by GRs. Primary cultures of astrocytes and microglia were induced to neuroinflammation by lipopolysaccharides (LPSs) and exposed to agathisflavone or not in the presence or absence of mifepristone, a GR antagonist. The microglia morphology and reactivity were evaluated by immunofluorescence against calcium-binding ionized adapter (Iba-1) and CD68. The astrocyte morphology and reactivity were evaluated by immunofluorescence against glial fibrillary acidic protein (GFAP). The inflammatory profile was evaluated by RT-qPCR. Molecular docking was performed to characterize agathisflavone and GR interactions. Microglial branching was increased in response to agathisflavone, an effect that was inhibited by mifepristone. CD68 and GFAP expression was decreased by agathisflavone but not in the presence of mifepristone. Agathisflavone decreased the expression of the pro-inflammatory cytokine IL-1β and increased the expression of the regulatory cytokine IL-10. The increase in IL-10 mRNA was inhibited by the GR antagonist. The in silico analysis showed that agathisflavone binds to a pocket at the glucocorticoid receptor. These interactions were stronger than mifepristone, dexamethasone, and the agathisflavone monomer apigenin. These results indicate that the GR is involved in the regulatory effects of agathisflavone on microglia and astrocyte inflammation, contributing to the elucidation of the molecular mechanisms of agathisflavone's effects in the nervous system.

Unveiling the Mechanisms of Pain in Endometriosis: Comprehensive Analysis of Inflammatory Sensitization and Therapeutic Potential

Endometriosis is a complicated, estrogen-dependent gynecological condition with a high morbidity rate. Pain, as the most common clinical symptom of endometriosis, severely affects women's physical and mental health and exacerbates socioeconomic burden. However, the specific mechanisms behind the occurrence of endometriosis-related pain remain unclear. It is currently believed that the occurrence of endometriosis pain is related to various factors, such as immune abnormalities, endocrine disorders, the brain-gut axis, angiogenesis, and mechanical stimulation. These factors induce systemic chronic inflammation, which stimulates the nerves and subsequently alters neural plasticity, leading to nociceptive sensitization and thereby causing chronic pain. In this paper, we compile and review the articles published on the study of nociceptive sensitization and endometriosis pain mechanisms. Starting from the factors influencing the chronic pain associated with endometriosis, we explain the relationship between these factors and chronic inflammation and further elaborate on the potential mechanisms by which chronic inflammation induces nociceptive sensitization. We aim to reveal the possible mechanisms of endometriosis pain, as well as nociceptive sensitization, and offer potential new targets for the treatment of endometriosis pain.

Unraveling microglial spatial organization in the developing human brain with DeepCellMap, a deep learning approach coupled with spatial statistics

Mapping cellular organization in the developing brain presents significant challenges due to the multidimensional nature of the data, characterized by complex spatial patterns that are difficult to interpret without high-throughput tools. Here, we present DeepCellMap, a deep-learning-assisted tool that integrates multi-scale image processing with advanced spatial and clustering statistics. This pipeline is designed to map microglial organization during normal and pathological brain development and has the potential to be adapted to any cell type. Using DeepCellMap, we capture the morphological diversity of microglia, identify strong coupling between proliferative and phagocytic phenotypes, and show that distinct spatial clusters rarely overlap as human brain development progresses. Additionally, we uncover an association between microglia and blood vessels in fetal brains exposed to maternal SARS-CoV-2. These findings offer insights into whether various microglial phenotypes form networks in the developing brain to occupy space, and in conditions involving haemorrhages, whether microglia respond to, or influence changes in blood vessel integrity. DeepCellMap is available as an open-source software and is a powerful tool for extracting spatial statistics and analyzing cellular organization in large tissue sections, accommodating various imaging modalities. This platform opens new avenues for studying brain development and related pathologies.

Transcriptomic Analysis Divulges Differential Expressions of Microglial Genes After Microglial Repopulation in Mice

Microglia are key immune cells in the central nervous system (CNS) and maintain hemostasis in physiological conditions. Microglial depletion leads to rapid repopulation, but the gene expression and signaling pathways related to repopulation remain unclear. Here, we used RNA sequencing (RNA-Seq) analysis to profile the transcriptome of microglia-depleted tissue by taking advantage of a conditional genetic microglial depletion model (CX3CR1CreER/+ system). Differential gene expression (DGE) sequencing analysis showed that 1226 genes were differentially up- and downregulated in both groups compared to control. Our data demonstrated that many microglial genes were highly regulated on day 3 after depletion but the numbers of differentially expressed genes were reduced by day 7. Gene ontology (GO) analysis categorized these differentially expressed genes on day 3 and day 7 to the specific biological processes, such as cell proliferation, cell activation, and cytokine and chemokine production. DGE analysis indicated that specific genes related to proliferation were regulated after depletion. Consistent with the changes in transcriptome, the histological analysis of transgenic mice revealed that the microglia after depletion undergo proliferation and activation from day 3 to day 7. Collectively, these results suggest that transcriptomic changes in microglial genes during depletion have a profound implication for the renewal and activation of microglia and may help to understand the regulatory mechanism of microglial activation in disease conditions.

Cell-type-specific expression of Nav1.6 in the developing brain of mice and its involvement in glial activation in Alzheimer's disease

Voltage-gated sodium channels (Nav's), particularly Nav1.6, are crucial for action potential generation in neurons and are linked to brain disorders. This study explores the cell-type-specific expression of Nav1.6 in C57BL/6 mice brains at various developmental stages. Coronal sections from embryonic day 14 to postnatal day 30 were examined. Nav1.6 expression increased at both protein and messenger RNA (mRNA) levels during this period. Immunofluorescence double staining revealed that Nav1.6 is primarily localized on neurons. Astrocytes show increasing expression from prenatal to postnatal stages, correlating with maturation. Microglia exhibit low-intensity expression throughout the development. Co-expression of Nav1.6 with oligodendrocyte precursor cell marker NG2 is observed from E14 through postnatal stages, with prominent co-expression on day 21 and day 30. Consistent co-expression with olig2 is observed from E16 to day 30. In primary cultures, astrocytes had higher Nav1.6 levels compared to microglia and oligodendrocyte precursor cells. Nav1.6 expression was upregulated in astrocytes and microglia in APP/amyloid beta precursor protein/presenilin 1 (PS1) transgenic mice. Down-regulating Nav1.6 in vitro reduced amyloid beta-induced microglial activation and cytokine levels (IL-1β, TNF-α). These findings highlight Nav1.6 as a potential target for therapeutic interventions against neurodegenerative diseases.

Engineered Extracellular Vesicles Modified by Angiopep-2 Peptide Promote Targeted Repair of Spinal Cord Injury and Brain Inflammation

Engineered extracellular vesicles play an increasingly important role in the treatment of spinal cord injury. In order to prepare more effective engineered extracellular vesicles, we biologically modified M2 microglia. Angiopep-2 (Ang2) is an oligopeptide that can target the blood-brain barrier. Through single-cell sequencing and immunofluorescence experiments, we confirmed that the expression of LRP-1, the targeted receptor of Ang2, was elevated after spinal cord injury. Subsequently, we integrated the Ang2 peptide segment into M2 microglia to obtain Ang2-EVs, which could successfully target the site of spinal cord injury. However, in order to improve the function of Ang2-EVs, we pretreated M2 microglia with melatonin, which has anti-inflammatory effects, to obtain M-Ang2-EVs. The results of single-nucleus sequencing of the mouse spinal cord verified that neurons and OPCs gradually transformed into subtypes related to nerve repair functions after treatment with M-Ang2-EVs. This is consistent with the sequencing and enrichment analysis of miRNAs contained in M-Ang2-EVs. We further verified through experiments that M-Ang2-EVs can promote microglia/macrophages to phagocytose sphingomyelin, promote axon remyelination and axon elongation, and maintain the integrity of the blood-spinal barrier. Since Ang2 can also target the blood-brain barrier, we found that M-Ang2-EVs can also reduce brain inflammation that results from spinal cord injury. Our study applied the Angiopep-2 peptide to spinal cord injury to enhance the targeting of injured cells, and successfully construct engineered extracellular vesicles that can target the spinal cord injury site and the brain.

DOCK2 deficiency alleviates neuroinflammation and affords neuroprotection after spinal cord injury

Neuroinflammation-caused secondary injury is a key event after spinal cord injury (SCI). Dedicator of cytokinesis 2 (DOCK2) belonging to DOCK-A subfamily has a vital role in microglia polarization and neuroinflammation via mediating Rac activation. However, the role of DOCK2 in SCI is unclear. In the present study, SCI model in mice was established by an impactor at thoracic T10 level. DOCK2 expression was significantly increased in the spinal cord after SCI. After knocking down DOCK2 using a lentivirus-mediated method, SCI mice exhibited improved motor function recovery, as revealed by increased Basso Mouse Scale (BMS) score, angle of incline, and relatively coordinated footprint, and decreased damaged area in the spinal cord. DOCK2 deficiency reduced neuronal apoptosis in the spinal cord after injury. Besides, deficiency of DOCK2 suppressed neuroinflammation after SCI, demonstrated by the reduction in pro-inflammatory mediators including IFN-γ, IL-1β and IL-6 and the increase in IL-4, IL-10 and IL-13, anti-inflammatory factors. The CD86, iNOS and COX-2 were down-regulated in the spinal cord, whereas CD206, Arg-1 and TGF-β were up-regulated by DOCK2 deficiency. Rac activation was prevented by DOCK2 deficiency following SCI. In vitro experiments were conducted for further verification. Treatment of BV-2 microglia with lentivirus-mediated DOCK2 inhibited IFN-γ/LPS-induced pro-inflammatory microglia polarization but increased IL-4-induced anti-inflammatory microglia, through inhibiting Rac activation. In brief, our data reveal that DOCK2 deficiency improves functional recovery in mice after SCI, which is related to Rac activation.

All Three Supersystems-Nervous, Vascular, and Immune-Contribute to the Cortical Infarcts After Subarachnoid Hemorrhage

The recently published DISCHARGE-1 trial supports the observations of earlier autopsy and neuroimaging studies that almost 70% of all focal brain damage after aneurysmal subarachnoid hemorrhage are anemic infarcts of the cortex, often also affecting the white matter immediately below. The infarcts are not limited by the usual vascular territories. About two-fifths of the ischemic damage occurs within ~ 48 h; the remaining three-fifths are delayed (within ~ 3 weeks). Using neuromonitoring technology in combination with longitudinal neuroimaging, the entire sequence of both early and delayed cortical infarct development after subarachnoid hemorrhage has recently been recorded in patients. Characteristically, cortical infarcts are caused by acute severe vasospastic events, so-called spreading ischemia, triggered by spontaneously occurring spreading depolarization. In locations where a spreading depolarization passes through, cerebral blood flow can drastically drop within a few seconds and remain suppressed for minutes or even hours, often followed by high-amplitude, sustained hyperemia. In spreading depolarization, neurons lead the event, and the other cells of the neurovascular unit (endothelium, vascular smooth muscle, pericytes, astrocytes, microglia, oligodendrocytes) follow. However, dysregulation in cells of all three supersystems-nervous, vascular, and immune-is very likely involved in the dysfunction of the neurovascular unit underlying spreading ischemia. It is assumed that subarachnoid blood, which lies directly on the cortex and enters the parenchyma via glymphatic channels, triggers these dysregulations. This review discusses the neuroglial, neurovascular, and neuroimmunological dysregulations in the context of spreading depolarization and spreading ischemia as critical elements in the pathogenesis of cortical infarcts after subarachnoid hemorrhage.

Hippocampal neuroinflammation induced by lipopolysaccharide causes sex-specific disruptions in action selection, food approach memories, and neuronal activation

Hippocampal neuroinflammation is present in multiple diseases and disorders that impact motivated behaviour in a sex-specific manner, but whether neuroinflammation alone is sufficient to disrupt this behaviour is unknown. We investigated this question here using mice. First, the application of an endotoxin to primary cultures containing only hippocampal neurons did not affect their activation. However, when the same endotoxin was applied to mixed neuronal/glial cultures it did increase neuronal activation, providing initial indications of how it might be able to effect behavioural change. We next showed neuroinflammatory effects on behaviour directly, demonstrating that intra-hippocampal administration of the same endotoxin increased locomotor activity and accelerated goal-directed learning in both male and female mice. In contrast, lipopolysaccharide-induced hippocampal neuroinflammation caused sex-specific disruptions to the acquisition of instrumental actions and to Pavlovian food-approach memories. Finally, we showed that LPS-induced hippocampal neuroinflammation had a sexually dimorphic effect on neuronal activation: increasing it in females and decreasing it in males.

Neuronal cathepsin S increases neuroinflammation and causes cognitive decline via CX3CL1-CX3CR1 axis and JAK2-STAT3 pathway in aging and Alzheimer's disease

Aging is an intricate process involving interactions among multiple factors, which is one of the main risks for chronic diseases, including Alzheimer's disease (AD). As a member of cysteine protease, cathepsin S (CTSS) has been implicated in inflammation across various diseases. Here, we investigated the role of neuronal CTSS in aging and AD started by examining CTSS expression in hippocampus neurons of aging mice and identified a significant increase, which was negatively correlated with recognition abilities. Concurrently, we observed an elevation of CTSS concentration in the serum of elderly people. Transcriptome and fluorescence-activated cell sorting (FACS) results revealed that CTSS overexpression in neurons aggravated brain inflammatory milieu with microglia activation to M1 pro-inflammatory phenotype, activation of chemokine C-X3-C-motif ligand 1 (CX3CL1)-chemokine C-X3-C-motif receptor 1 (CX3CR1) axis and janus kinase 2 (JAK2)-signal transducer and activator of transcription 3 (STAT3) pathway. As CX3CL1 is secreted by neurons and acts on the CX3CR1 in microglia, our results revealed for the first time the role of neuron CTSS in neuron-microglia "crosstalk." Besides, we observed elevated CTSS expression in multiple brain regions of AD patients, including the hippocampus. Utilizing CTSS selective inhibitor, LY3000328, rescued AD-related pathological features in APP/PS1 mice. We further noticed that neuronal CTSS overexpression increased cathepsin B (CTSB) activity, but decreased cathepsin L (CTSL) activity in microglia. Overall, we provide evidence that CTSS can be used as an aging biomarker and plays regulatory roles through modulating neuroinflammation and recognition in aging and AD process.

BoNT/Action beyond neurons

Botulinum neurotoxin type A (BoNT/A) has expanded its therapeutic uses beyond neuromuscular disorders to include treatments for various pain syndromes and neurological conditions. Originally recognized for blocking acetylcholine release at neuromuscular junctions, BoNT/A's effects extend to both peripheral and central nervous systems. Its ability to undergo retrograde transport allows BoNT/A to modulate synaptic transmission and reduce pain centrally, influencing neurotransmitter systems beyond muscle control. BoNT/A also interacts with glial cells, such as Schwann cells, satellite glial cells, astrocytes, microglia, and oligodendrocytes. Schwann cells, key to peripheral nerve regeneration, are directly influenced by BoNT/A, which promotes their proliferation and enhances remyelination. Satellite glial cells, involved in sensory neuron regulation, show reduced glutamate release in response to BoNT/A, aiding in pain relief. In the CNS, BoNT/A modulates astrocyte activity, reducing excitotoxicity and inflammation, which is relevant in conditions like epilepsy. Microglia, the CNS's immune cells, shift from a pro-inflammatory to a neuroprotective state when treated with BoNT/A, enhancing tissue repair. Additionally, BoNT/A promotes oligodendrocyte survival and remyelination, especially after spinal cord injury. Overall, BoNT/A's ability to target both neurons and glial cells presents a multifaceted therapeutic strategy for neurological disorders, pain management, and CNS repair. Further research is necessary to fully elucidate its mechanisms and optimize its clinical application.

The microbiota-gut-brain axis: a potential target in the small-molecule compounds and gene therapeutic strategies for Parkinson's disease

BACKGROUNDS

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by motor symptoms and non-motor symptoms. It has been found that intestinal issues usually precede motor symptoms. Microorganisms in the gastrointestinal tract can affect central nervous system through the microbiota-gut-brain axis. Accumulating evidence has shown that disturbances in the microbiota-gut-brain axis are linked with PD. Thus, this pathway appears to be a promising therapeutic target for treatment of PD.

OBJECTIVES

In this review, we mainly described gut dysbiosis in PD and their underlying mechanisms for mediating neuroinflammation and peripheral immune response in PD pathology and futher discussed the potential small-molecule compounds and genic therapeutic strategies targeting the microbiota-gut-brain axis and their applications in PD.

CONCLUSIONS

Studies have found that some small molecule compounds and alterations of inflammation-related genes can improve the motor and non-motor symptoms of PD by improving the microbiota-gut-brain axis, which may provide potentially beneficial drugs and molecular targets for the therapies of PD.

Microglial modulation of neuronal network function and plasticity

Microglia are the resident immune cells of the central nervous system (CNS), which have been classically viewed as involved in CNS responses to damage and tissue repair. However, microglia are constantly sensing neuronal network activity and changes in the CNS milieu, establishing complex state-dependent microglia-neuron interactions that impact their functions. By doing so, microglia perform a wide range of physiological roles, including brain homeostasis maintenance, control of neural connectivity, network function modulation, as well as functional and morphological plasticity regulation in health and disease. Here, the author reviews recent evidence of the modulations induced by microglia, a highly heterogeneous cell type, on synaptic and intrinsic neuronal properties, and on neuronal network patterns during perinatal development and adulthood. The reviewed evidence clearly indicates that microglia are important, if not essential, for brain function and plasticity in both health and disease.

Gene expression of psychiatric disorder-related kinesin superfamily proteins (Kifs) is potentiated in alternatively activated primary cultured microglia

OBJECTIVE

Reactivity of microglia, the resident cells of the brain, underlies innate immune mechanisms (e.g., injury repair), and disruption of microglial reactivity has been shown to facilitate psychiatric disorder dysfunctions. Although cellular analyses based on cultured microglia have been conducted, the molecular mechanism regulating microglial polarization remains elusive. We established a primary microglia culture that enabled manipulation of the substate of cells. This allowed us to investigate the expression levels of psychiatric disorder-related Kifs messenger RNA (mRNA) in each condition. Kifs encode molecular motor proteins that transport cargo along microtubules, which are thought to dynamically reorganize during a substate change.

RESULTS

As a candidate for a crucial Kifs gene that is associated with microglia polarization, we selected psychiatric disorder-related Kifs including Kif17. We found that the relative amounts of Kif3a, Kif17, and Kif13a mRNA were potentiated in alternatively activated microglia, whereas there were no significant changes in activated microglia. Furthermore, the microglia derived from a mouse line which possesses a mutation inducing truncated KIF17 indicated disrupted morphological phenotype of alternatively activated microglia. These results suggest that the potentiation of specific molecular motor expression is required to maintain the function of alternatively activated microglia.

Development and characterization of in vitro inducible immortalization of a murine microglia cell line for high throughput studies

There are few in vitro models available to study microglial physiology in a homeostatic context. Recent approaches include the human induced pluripotent stem cell model, but these can be challenging for large-scale assays and may lead to batch variability. To advance our understanding of microglial biology while enabling scalability for high-throughput assays, we developed an inducible immortalized murine microglial cell line using a tetracycline expression system. The addition of doxycycline facilitates rapid cell proliferation, allowing for population expansion. Upon withdrawal of doxycycline, this monoclonal microglial cell line differentiates, resembling in vivo microglial physiology as demonstrated by the expression of microglial genes, innate immune responses, chemotaxis, and phagocytic abilities. We utilized live imaging and various molecular techniques to functionally characterize the clonal 2E11murine microglial cell line. Transcriptomic analysis showed that the 2E11 line exhibited characteristics of immature, proliferative microglia during doxycycline induction, and further differentiation led to a more homeostatic phenotype. Treatment with transforming growth factor-β modified the transcriptome of the 2E11 cell line, affecting cellular immune pathways. Our findings indicate that the 2E11 inducible immortalized cell line is a practical and convenient tool for studying microglial biology in vitro.

Mechanisms and environmental factors shaping the ecosystem of brain macrophages

Brain macrophages encompass two major populations: microglia in the parenchyma and border-associated macrophages (BAMs) in the extra-parenchymal compartments. These cells play crucial roles in maintaining brain homeostasis and immune surveillance. Microglia and BAMs are phenotypically and epigenetically distinct and exhibit highly specialized functions tailored to their environmental niches. Intriguingly, recent studies have shown that both microglia and BAMs originate from the same myeloid progenitor during yolk sac hematopoiesis, but their developmental fates diverge within the brain. Several works have partially unveiled the mechanisms orchestrating the development of microglia and BAMs in both mice and humans; however, many questions remain unanswered. Defining the molecular underpinnings controlling the transcriptional and epigenetic programs of microglia and BAMs is one of the upcoming challenges for the field. In this review, we outline current knowledge on ontogeny, phenotypic diversity, and the factors shaping the ecosystem of brain macrophages. We discuss insights garnered from human studies, highlighting similarities and differences compared to mice. Lastly, we address current research gaps and potential future directions in the field. Understanding how brain macrophages communicate with their local environment and how the tissue instructs their developmental trajectories and functional features is essential to fully comprehend brain physiology in homeostasis and disease.

Lipid droplets in central nervous system and functional profiles of brain cells containing lipid droplets in various diseases

Lipid droplets (LDs), serving as the convergence point of energy metabolism and multiple signaling pathways, have garnered increasing attention in recent years. Different cell types within the central nervous system (CNS) can regulate energy metabolism to generate or degrade LDs in response to diverse pathological stimuli. This article provides a comprehensive review on the composition of LDs in CNS, their generation and degradation processes, their interaction mechanisms with mitochondria, the distribution among different cell types, and the roles played by these cells-particularly microglia and astrocytes-in various prevalent neurological disorders. Additionally, we also emphasize the paradoxical role of LDs in post-cerebral ischemia inflammation and explore potential underlying mechanisms, aiming to identify novel therapeutic targets for this disease.

The pediatric psychopharmacology of autism spectrum disorder: A systematic review - Part II: The future

Part I of this systematic review summarized the state-of-the-art of pediatric psychopharmacology for Autism Spectrum Disorder (ASD), a severe and lifelong neurodevelopmental disorder. The purpose of this Part II follow-up article is to provide a systematic overview of the experimental psychopharmacology of ASD. To this aim, we have first identified in the Clinicaltrials.gov website all the 157 pharmacological and nutraceutical compounds which have been experimentally tested in children and adolescents with ASD using the randomized placebo-controlled trial (RCT) design. After excluding 24 drugs already presented in Part I, a systematic review spanning each of the remaining 133 compounds was registered on Prospero (ID: CRD42023476555), performed on PubMed (August 8, 2024), and completed with EBSCO, PsycINFO (psychology and psychiatry literature) and the Cochrane Database of Systematic reviews, yielding a total of 115 published RCTs, including 57 trials for 23 pharmacological compounds and 48 trials for 17 nutraceuticals/supplements. Melatonin and oxytocin were not included, because recent systematic reviews have been already published for both these compounds. RCTs of drugs with the strongest foundation in preclinical research, namely arbaclofen, balovaptan and bumetanide have all failed to reach their primary end-points, although efforts to target specific patient subgroups do warrant further investigation. For the vast majority of compounds, including cannabidiol, vasopressin, and probiotics, insufficient evidence of efficacy and safety is available. However, a small subset of compounds, including N-acetylcysteine, folinic acid, l-carnitine, coenzyme Q10, sulforaphane, and metformin may already be considered, with due caution, for clinical use, because there is promising evidence of efficacy and a high safety profile. For several other compounds, such as secretin, efficacy can be confidently excluded, and/or the data discourage undertaking new RCTs. Part I and Part II summarize "drug-based" information, which will be ultimately merged to provide clinicians with a "symptom-based" consensus statement in a conclusive Part III, with the overarching aim to foster evidence-based clinical practices and to organize new strategies for future clinical trials.

New approach to control ischemic severity ex vivo

BACKGROUND

It is advantageous to be able to both control and define a metric for ischemia severity in ex vivo models to enable more precise comparisons to in vivo models and to facilitate more sophisticated mechanistic studies. Currently, the primary method to induce and study ischemia ex vivo is to completely deplete oxygen and glucose in the culture media; however, in vivo ischemia often involves varying degrees of severities.

NEW METHOD

In this work, we have successfully developed an approach to both control and characterize three different ischemic severities ex vivo and we define these standard condition metrics via an oxygen sensor: normoxia (control), mild ischemia (partial oxygen-glucose deprivation), and severe ischemia (complete oxygen-glucose deprivation).

RESULTS

To validate the extent to which controlling oxygen and glucose concentration ex vivo impacts cell expression, recruitment, and cell damage, we demonstrate changes in cytokine and HIF-1ɑ, an increase in glucose transporter expression level, changes in caspase-3, and rapid microglia recruitment to neurons within only 30 minutes.

COMPARISON TO EXISTING METHODS

To the best of our knowledge, this is the first time ischemic severity was controlled and shown to have a measurable effect on protein expression and cell movement within only 30 minutes ex vivo. Our new approach matches with existing literature for controlling ischemic severity in vivo.

CONCLUSIONS

Overall, this new approach will significantly impact our ability to expand ex vivo platforms for assessing ischemic damage and will provide a new experimental approach for investigating the molecular mechanisms involved in ischemia.

Physiology and pathophysiology of the retinal neuroglia

Neuroglia of the retina are represented by Müller glia, parenchymal astrocytes, microglia and oligodendrocytes mainly associated with the optic nerve. Müller glia are the most numerous glia, endowed with multiple homeostatic functions and indispensable for the retinal morphofunctional organization. Müller cells integrate retinal neurons into individual functional units (known as retinal columns) and act as a living light guide, transmitting photons to photoreceptors. In pathology, retinal neuroglia undergo complex changes, which include upregulation of neuroprotection, reactive gliosis, and functional asthenia. The balance between all these changes defines the progression and outcome of retinal disorders.

Neuroglia in neurodegeneration: Amyotrophic lateral sclerosis and frontotemporal dementia

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are devastating neurodegenerative diseases sharing significant pathologic and genetic overlap, leading to consider these diseases as a continuum in the spectrum of their pathologic features. Although FTD compromises only specific brain districts, while ALS involves both the nervous system and the skeletal muscles, several neurocentric mechanisms are in common between ALS and FTD. Also, recent research has revealed the significant involvement of nonneuronal cells, particularly glial cells such as astrocytes, oligodendrocytes, microglia, and peripheral immune cells, in disease pathology. This chapter aims to provide an extensive overview of the current understanding of the role of glia in the onset and advancement of ALS and FTD, highlighting the recent implications in terms of prognosis and future treatment options.

Neuroglia in epilepsy

Epilepsy is a group of neurologic diseases characterized by spontaneous, repetitive disruption to neuronal activity. Neurons have been at the core of epilepsy research efforts, and pharmacotherapies historically have been generated by targeting neuronal mechanisms. As a result, most currently available antiseizure drugs (ASDs) work to either decrease excitatory glutamatergic neurotransmission or to increase inhibitory GABAergic neurotransmission. However, ASDs may have undesirable side effects on cognition and also fail to control seizures in approximately 30% of epilepsy patients. In recent years, glia have surfaced as essential modulators of neuronal function in health and disease. The redirection of focus onto neuroglia provides new perspectives and opportunities to generate novel therapeutic targets that may treat refractory epilepsy and diminish the unwanted side effect profile of current treatments. In this chapter, we discuss the contribution of astroglia, oligodendroglia, and microglia to the genesis, development, and progression of epilepsy, and we highlight key enzymes, receptors, transporters, and channels that may be pursued as nonneuronal targets for novel ASDs.

The antipsychotic chlorpromazine reduces neuroinflammation by inhibiting microglial voltage-gated potassium channels

Neuroinflammation, the result of microglial activation, is associated with the pathogenesis of a wide range of psychiatric and neurological disorders. Recently, chlorpromazine (CPZ), a dopaminergic D2 receptor antagonist and schizophrenia therapy, was proposed to exert antiinflammatory effects in the central nervous system. Here, we report that the expression of Kv1.3 channel, which is abundant in T cells, is upregulated in microglia upon infection, and that CPZ specifically inhibits these channels to reduce neuroinflammation. In the mouse medial prefrontal cortex, we show that CPZ lessens Kv1.3 channel activity and reduces proinflammatory cytokine production. In mice treated with LPS, we found that CPZ was capable of alleviating both neuroinflammation and depression-like behavior. Our findings suggest that CPZ acts as a microglial Kv1.3 channel inhibitor and neuroinflammation modulator, thereby exerting therapeutic effects in neuroinflammatory psychiatric/neurological disorders.

Astrocytes and microglia in multiple sclerosis and neuromyelitis optica

Multiple sclerosis and neuromyelitis optica are autoimmune neurodegenerative diseases primarily targeting myelin sheath and neuroglia. In multiple sclerosis, autoantibodies destroy oligodendrocytes and myelin, which underlies primary neurologic symptoms. Focal damage to myelin triggers reactive astrogliosis and microgliosis, which contribute to and to a large extent define the disease progression. In neuromyelitis optica, autoantibodies against water channel aquaporin 4 (AQP4), which are localized at astrocytic endfeet mediate damage of the glia limitans thus facilitating infiltration of blood-borne molecules and cells that propagate the damage to nerves and neurons. This primary astrocytopathy recruits microglia, which contribute to the neuroinflammatory response. Neuroglial cells therefore are potential targets for cell-specific therapies.

Neuroglia in autoimmune encephalitis

Neuroglial cells play a crucial role in central nervous system (CNS) health and disease. Antibody-associated autoimmune encephalitis (AE) represents a group of inflammatory brain diseases with antibodies (Abs) against neuronal cell surface (e.g., anti-N-methyl-d-aspartate receptor (NMDAR), anti-leucine-rich glioma-inactivated 1 (LGI1), γ-aminobutyric acid (GABA) type A or B receptor (GABAA/BR)) or intracellular neuronal proteins. AE with Abs against glial antigens, e.g., myelin oligodendrocyte glycoprotein (MOG), glial fibrillary acidic protein (GFAP) are also described. Besides the known pathomechanisms with direct pathogenic effects of primary neuronal Abs and activation of innate (dendritic cells) and adaptive (B and T cells) immune systems, research findings suggest the involvement of glial cells including astrocytes, microglia, oligodendrocytes in the pathogenesis of Ab-associated AE, but only a limited number of studies is available. Neuropathologic findings showed reactive astrogliosis and microgliosis with microglial activation/proliferation, e.g., in anti-NMDAR and anti-LGI1 encephalitis. Direct effects of the GABAAR and NMDAR Abs on astrocytic receptors are discussed. Because of the primary involvement of B and T cells in the pathogenesis of Ab-associated AE it can be assumed that astrocytic and microglial activation is largely a response to the primary changes, but additional direct effects of Abs on astrocytic receptors are possible. Further research in this field is required to explore the exact role of glial cells in Ab-associated AE.

Lymphocyte-derived and lipoprotein-derived inflammatory ratios as biomarkers in bipolar disorder type I: Characteristics, predictive values, and influence of current psychopharmacological treatments

PURPOSE OF THIS RESEARCH

The purpose of this research was to investigate peripheral inflammation by analyzing lymphocyte and lipoprotein-derived inflammatory ratios in patients with bipolar disorder type I (BD-I) and healthy controls (HCs), considering mood stabilizer drug treatments, sex and clinical trajectories.

METHODS

This was a cross-sectional case-control study of BD-I patients (n=252) and healthy controls (n=62). We investigated peripheral inflammation biomarkers through blood count values (CBCs), lipoproteins and a complex panel of inflammatory ratios, including the neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), systemic inflammation response index (SIRI), neutrophil-to-HDL ratio (NHR), monocyte-to-HDL ratio (MHR), platelet-to-HDL ratio (PHR) and lymphocyte-to-HDL ratio (LHR). Furthermore, we examined the effects of sex, drug treatment and clinical outcome on the inflammatory profile.

RESULTS

We found that the monocyte-to-lymphocyte ratio (MLR) and lipoprotein-derived inflammatory ratio (NHR, MHR, PHR, and LHR) were significantly greater in BD-I patients than in control individuals. The monocyte-to-HDL ratio (MHR) showed acceptable accuracy as a disease predictor. Logistic regression analysis adjusted for sex, age and BMI indicated that the risk of having a BD-I diagnosis was greater for participants with MHR levels in quartiles 3 (OR= 5.2, p=0.001) and 4 (OR=13, p<0.001). There was a strong association between lithium treatment and increased inflammation represented by elevated lymphocyte-derived inflammatory ratios (NLR, MLR, PLR, SII, and SIRI) in lithium-treated BD-I patients compared to those in lithium-free or lithium treatment-naïve BD-I patients. The main limitations are the cross-sectional nature of the study and limited sample size of HCs.

MAJOR CONCLUSIONS

Several CBCs, lipoproteins, and a complex panel of inflammatory ratios, including lymphocyte-derived inflammatory ratios (NLR, MLR, PLR, SII, and SIRI) and lipoprotein-derived inflammatory ratios (NHR, MHR, PHR, and LHR), are altered in individuals diagnosed with BD-I. The monocyte-to-HDL ratio (MHR) emerged as a disease predictor in our BD-I sample. A remarkable finding is the association of lithium and valproate treatment with the inflammatory state. Considering the study limitations, our results underscore the importance of pharmacological treatments when researching inflammation markers in mood disorders. Lymphocyte-derived and lipoprotein-derived inflammatory ratios are easy-to-implement and relevant biomarkers in BD-I patients.

Fish microglia: Beyond the resident macrophages of the central nervous system - A review of their morphofunctional characteristics

From classical to modern literature on microglia, the importance of the potential and variability of these immune cells in vertebrates has been pointed out. Recent aspects such as relationships and interactions between microglia and neurons in both normal and injured neural tissues, as well as their nexus with other organs and with the microbiota, or how these cells are modulated during development and adulthood are current topics of major interest. State-of-the-art research methodologies, including microscopy and potent in vivo imaging techniques, genomic and proteomic methods, current culture conditions together with the easy maintenance and manipulation of some fish embryos and adult specimens such as zebrafish (Danio rerio), have emerged and adapted to the phylogenetic position of some fish species. Furthermore, these advancements have facilitated the development of successful protocols aimed at addressing significant hypotheses and unresolved questions regarding vertebrate glia. The present review aims to analyse the available information on fish microglia, mainly the most recent one concerning teleosts, to establish an overview of their structural and immune functional features as a basis for their potentialities, heterogeneity, diversification, involvement, and relationships with neurons under normal and pathological conditions.

A microglia-containing cerebral organoid model to study early life immune challenges

Prenatal infections and activation of the maternal immune system have been proposed to contribute to causing neurodevelopmental disorders (NDDs), chronic conditions often linked to brain abnormalities. Microglia are the resident immune cells of the brain and play a key role in neurodevelopment. Disruption of microglial functions can lead to brain abnormalities and increase the risk of developing NDDs. How the maternal as well as the fetal immune system affect human neurodevelopment and contribute to NDDs remains unclear. An important reason for this knowledge gap is the fact that the impact of exposure to prenatal risk factors has been challenging to study in the human context. Here, we characterized a model of cerebral organoids (CO) with integrated microglia (COiMg). These organoids express typical microglial markers and respond to inflammatory stimuli. The presence of microglia influences cerebral organoid development, including cell density and neural differentiation, and regulates the expression of several ciliated and mesenchymal cell markers. Moreover, COiMg and organoids without microglia show similar but also distinct responses to inflammatory stimuli. Additionally, IFN-γ induced significant transcriptional and structural changes in the cerebral organoids, that appear to be regulated by the presence of microglia. Specifically, interferon-gamma (IFN-γ) was found to alter the expression of genes linked to autism. This model provides a valuable tool to study how inflammatory perturbations and microglial presence affect neurodevelopmental processes.

Physiology of neuroglia of the central nervous system

Neuroglia of the central nervous system (CNS) are a diverse and highly heterogeneous population of cells of ectodermal, neuroepithelial origin (macroglia, that includes astroglia and oligodendroglia) and mesodermal, myeloid origin (microglia). Neuroglia are primary homeostatic cells of the CNS, responsible for the support, defense, and protection of the nervous tissue. The extended class of astroglia (which includes numerous parenchymal astrocytes, such as protoplasmic, fibrous, velate, marginal, etc., radial astrocytes such as Bergmann glia, Muller glia, etc., and ependymoglia lining the walls of brain ventricles and central canal of the spinal cord) is primarily responsible for overall homeostasis of the nervous tissue. Astroglial cells control homeostasis of ions, neurotransmitters, hormones, metabolites, and are responsible for neuroprotection and defense of the CNS. Oligodendroglia provide for myelination of axons, hence supporting and sustaining CNS connectome. Microglia are tissue macrophages adapted to the CNS environment which contribute to the host of physiologic functions including regulation of synaptic connectivity through synaptic pruning, regulation of neurogenesis, and even modifying neuronal excitability. Neuroglial cells express numerous receptors, transporters, and channels that allow neuroglia to perceive and follow neuronal activity. Activation of these receptors triggers intracellular ionic signals that govern various homeostatic cascades underlying glial supportive and defensive capabilities. Ionic signaling therefore represents the substrate of glial excitability.

Evolution of neuroglia: From worm to man

Neuroglia are a highly diversified class of neural cells of ectodermal (astroglia; oligodendroglia, glia of the peripheral nervous system) and mesodermal (microglia) origin. Glial cells emerged at the earliest stages of the evolution of the nervous system, seemingly evolving several times in phylogeny. Initially, glial cells were associated with sensory organs, an arrangement conserved throughout the species from worms to humans. Enhanced complexity of the nervous system increased the need for homeostatic support, which, in turn, led to an increase in complexity, functional heterogeneity, and versatility of neuroglia. In the brain of primates, and especially in the brain of humans, astrocytes become exceedingly complex. Likewise, new types of astroglial cells involved in interlayer communication/integration have evolved in the primates evolutionary closer to humans. Increases in animal size and the density of interneuronal connections stimulated the development of the myelin sheath, which was critical for the evolution of the highly complex brains of humans. The innate brain tissue macrophages, the microglia, emerged in invertebrates such as leeches. Microglia conserved their transcriptomic, morphologic, and functional signatures throughout the animal kingdom.