An update on reactive astrocytes in chronic pain

Crosstalk between bone metastatic cancer cells and sensory nerves in bone metastatic progression

Although the role of peripheral nerves in cancer progression has been appreciated, little is known regarding cancer/sensory nerve crosstalk and its contribution to bone metastasis and associated pain. In this study, we revealed that the cancer/sensory nerve crosstalk plays a crucial role in bone metastatic progression. We found that (i) periosteal sensory nerves expressing calcitonin gene-related peptide (CGRP) are enriched in mice with bone metastasis; (ii) cancer patients with bone metastasis have elevated CGRP serum levels; (iii) bone metastatic patient tumor samples express elevated calcitonin receptor-like receptor (CRLR, a CGRP receptor component); (iv) higher CRLR levels in cancer patients are negatively correlated with recurrence-free survival; (v) CGRP induces cancer cell proliferation through the CRLR/p38/HSP27 pathway; and (vi) blocking sensory neuron-derived CGRP reduces cancer cell proliferation in vitro and bone metastatic progression in vivo. This suggests that CGRP-expressing sensory nerves are involved in bone metastatic progression and that the CGRP/CRLR axis may serve as a potential therapeutic target for bone metastasis.

Deciphering pain: molecular mechanisms and neurochemical pathways-challenges and future opportunities

This review delves into the intricate biological underpinnings of pain perception. It encompasses nociceptive signaling pathways, the molecular mechanisms involved, and the subjective experience of discomfort in humans. The initial focus is on nociceptor transduction, where specialized neurons transform noxious stimuli into electrical impulses. Subsequently, the review explores the central nervous system, elucidating how these signals are processed and modulated by critical elements such as ion channels, receptors, and neurotransmitters (e.g., substance P, glutamate, GABA). Shifting gears toward chronic pain, the review examines the concept of neuroplasticity, highlighting its potential to induce maladaptive responses through alterations in neural networks. The burgeoning field of pain genomics, alongside established genetic research, offers valuable insights that could pave the way for a framework of personalized pain management strategies. Finally, the review emphasizes the significance of these molecular insights in facilitating accurate therapeutic interventions. The overarching objective is to establish an integrative framework for precision medicine in pain management by incorporating this information alongside biopsychosocial models. This framework serves to translate the heterogeneous landscape of pain mechanisms into a coherent roadmap for the development of effective therapies.

Hypoxic postconditioning modulates neuroprotective glial reactivity in a 3D cortical ischemic-hypoxic injury model

Stroke remains one of the major health challenges due to its high rates of mortality and long-term disability, necessitating the development of effective therapeutic treatment. This study aims to explore the neuroprotective effects of hypoxic postconditioning (HPC) using a cell-based 3D cortical ischemic-hypoxic injury model. Our model employs murine cells to investigate HPC-induced modulation of glial cell reactivity and intercommunication post-oxygen-glucose deprivation-reoxygenation (OGD-R) injury. We found that a single HPC session (1HPC) provided the most significant neuroprotection post-OGD-R compared to multiple intermittent hypoxic treatments, evidenced by improved spheroidal structure, enhanced cell survival and reduced apoptosis, optimal modulation of neuronal phenotypes, dampened ischemic responses, and augmented neurite outgrowth of spheroids. Furthermore, 1HPC suppressed both pro-inflammatory A1 and anti-inflammatory A2 astrocyte phenotypes despite the induction of astrocyte activation while reducing microglial activation with inhibited M1 and M2 reactive states. This was accompanied by a decrease in gene expression of the pro-inflammatory cytokines essential to microglia-astrocyte signaling, collectively suggesting a shift of glial cells away from their traditional reactive states for neuroprotection. This study highlights the potential of 1HPC as a novel therapeutic intervention for ischemic injury via the modulation of neuroprotective glial reactivity. Moreover, the 3D cortical ischemic-hypoxic injury model employed here holds enormous potential serving as a disease model to further elucidate the underlying mechanism of HPC, which can also extend to the applications in brain regeneration, drug development, and the modeling of neural diseases.

Role of astrocytes in Alzheimer's disease pathogenesis and the impact of exercise-induced remodeling

Alzheimer's disease (AD) is a prevalent and debilitating brain disorder that worsens progressively with age, characterized by cognitive decline and memory impairment. The accumulation of amyloid-beta (Aβ) leading to amyloid plaques and hyperphosphorylation of Tau, resulting in intracellular neurofibrillary tangles (NFTs), are primary pathological features of AD. Despite significant research investment and effort, therapies targeting Aβ and NFTs have proven limited in efficacy for treating or slowing AD progression. Consequently, there is a growing interest in non-invasive therapeutic strategies for AD prevention. Exercise, a low-cost and non-invasive intervention, has demonstrated promising neuroprotective potential in AD prevention. Astrocytes, among the most abundant glial cells in the brain, play essential roles in various physiological processes and are implicated in AD initiation and progression. Exercise delays pathological progression and mitigates cognitive dysfunction in AD by modulating astrocyte morphological and phenotypic changes and fostering crosstalk with other glial cells. This review aims to consolidate the current understanding of how exercise influences astrocyte dynamics in AD, with a focus on elucidating the molecular and cellular mechanisms underlying astrocyte remodeling. The review begins with an overview of the neuropathological changes observed in AD, followed by an examination of astrocyte dysfunction as a feature of the disease. Lastly, the review explores the potential therapeutic implications of exercise-induced astrocyte remodeling in the context of AD.

The Importance of Phosphoinositide 3-Kinase in Neuroinflammation

Neuroinflammation, characterised by the activation of immune cells in the central nervous system (CNS), plays a dual role in both protecting against and contributing to the progression of neurodegenerative diseases, such as Alzheimer's disease (AD) and multiple sclerosis (MS). This review explores the role of phosphoinositide 3-kinase (PI3K), a key enzyme involved in cellular survival, proliferation, and inflammatory responses, within the context of neuroinflammation. Two PI3K isoforms of interest, PI3Kγ and PI3Kδ, are specific to the regulation of CNS cells, such as microglia, astrocytes, neurons, and oligodendrocytes, influencing pathways, such as Akt, mTOR, and NF-κB, that control cytokine production, immune cell activation, and neuroprotection. The dysregulation of PI3K signalling is implicated in chronic neuroinflammation, contributing to the exacerbation of neurodegenerative diseases. Preclinical studies show promise in targeting neuronal disorders using PI3K inhibitors, such as AS605240 (PI3Kγ) and idelalisib (PI3Kδ), which have reduced inflammation, microglial activation, and neuronal death in in vivo models of AD. However, the clinical translation of these inhibitors faces challenges, including blood-brain barrier (BBB) permeability, isoform specificity, and long-term safety concerns. This review highlights the therapeutic potential of PI3K modulation in neuroinflammatory diseases, identifying key gaps in the current research, particularly in the need for brain-penetrating and isoform-specific inhibitors. These findings underscore the importance of future research to develop targeted therapies that can effectively modulate PI3K activity and provide neuroprotection in chronic neurodegenerative disorders.

Neuroinflammatory Pathways Associated with Chronic Post-Thoracotomy Pain: A Review of Current Literature

Chronic post-thoracotomy pain (CPTP) is a major clinical problem that affects up to 35-55% of patients undergoing thoracic incisions. Evidence suggests that multiple cellular signaling pathways and neuro-inflammatory mediators may play an essential role in the pathogenesis of CPTP. In this comprehensive review, we present the current evidence on the cellular signaling pathways and inflammatory changes associated with the initiation and maintenance of CPTP, focusing on the potential application of these findings in the clinical setting. An electronic search of Medline, EMBASE, Cochrane, Google Scholar, and ClinicalTrials.gov was performed, and 3652 abstracts were identified. After an initial abstract screening, 131 studies underwent a full-text review, and nine papers were eventually included in this review. Studies were included if they assessed the cellular signaling pathways or inflammatory processes associated with the induction and/or maintenance of CPTP. All the identified studies were pre-clinical studies conducted on animal models. Our search identified seven cellular pathways (NK-1 receptor (NK-1), Glutaminase 1, Toll-like receptor 4 (TLR4), Resolvins, Ror-2, Sonic hedgehog signaling (Shh), and Wnt5a/Wnts) and six cytokines (IL-1β, IL-6, IL-8, IL-10, IFN-γ, and TNF-α) that were investigated in the context of CPTP. Multiple cellular signaling pathways and inflammatory cytokines may play an important role in the neuroinflammatory changes associated with the induction and maintenance of chronic post-thoracotomy pain in animal models. However, the clinical impact and therapeutic utility of these neuroinflammatory changes in routine clinical practice have yet to be demonstrated.

Mechanisms and Therapeutic Prospects of Microglia-Astrocyte Interactions in Neuropathic Pain Following Spinal Cord Injury

Neuropathic pain is a prevalent and debilitating condition experienced by the majority of individuals with spinal cord injury (SCI). The complex pathophysiology of neuropathic pain, involving continuous activation of microglia and astrocytes, reactive gliosis, and altered neuronal plasticity, poses significant challenges for effective treatment. This review focuses on the pivotal roles of microglia and astrocytes, the two major glial cell types in the central nervous system, in the development and maintenance of neuropathic pain after SCI. We highlight the extensive bidirectional interactions between these cells, mediated by the release of inflammatory mediators, neurotransmitters, and neurotrophic factors, which contribute to the amplification of pain signaling. Understanding the microglia-astrocyte crosstalk and its impact on neuronal function is crucial for developing novel therapeutic strategies targeting neuropathic pain. In addition, this review discusses the fundamental biology, post-injury pain roles, and therapeutic prospects of microglia and astrocytes in neuropathic pain after SCI and elucidates the specific signaling pathways involved. We also speculated that the extracellular matrix (ECM) can affect the glial cells as well. Furthermore, we also mentioned potential targeted therapies, challenges, and progress in clinical trials, as well as new biomarkers and therapeutic targets. Finally, other relevant cell interactions in neuropathic pain and the role of glial cells in other neuropathic pain conditions have been discussed. This review serves as a comprehensive resource for further investigations into the microglia-astrocyte interaction and the detailed mechanisms of neuropathic pain after SCI, with the aim of improving therapeutic efficacy.

Astrocytic Ryk signaling coordinates scarring and wound healing after spinal cord injury

Wound healing after spinal cord injury involves highly coordinated interactions among multiple cell types, which is poorly understood. Astrocytes play a central role in creating a border against the non-neural lesion core. To do so, astrocytes undergo dramatic morphological changes by first thickening the processes and then elongating and overlap them. We show here show that the expression of a cell-surface receptor, Ryk, is induced in astrocytes after injury in both rodent and human spinal cord. Astrocyte-specific knockout of Ryk dramatically elongated the reactive astrocytes and accelerated the formation of the border and reduced the size of the scar. Astrocyte-specific knockout of Ryk also accelerated the injury responses of multiple cell types, including the resolution of neuroinflammation. Single cell transcriptomics analyses revealed a broad range of changes cell signaling among astrocytes, microglia, fibroblasts, endothelial cell, etc, after astrocyte-specific Ryk knockout, suggesting that Ryk not only regulates the injury response of astrocytes but may also regulate signals which coordinate the responses of multiple cell types. The elongation is mediated by NrCAM, a cell adhesion molecule induced by astrocyte-specific conditional knockout of Ryk after spinal cord injury. Our findings suggest a promising therapeutic target to accelerate wound healing and promote neuronal survival and enhance functional recovery.

Targeting astrocytes polarization after spinal cord injury: a promising direction

Spinal cord injury (SCI) is a serious neurological injury that causes severe trauma to motor and sensory functions. Although long considered incurable, recent research has brought new hope for functional recovery from SCI. After SCI, astrocytes are activated into many polarization states. Here we discuss the two most important classical phenotypes: the 'A1' neurotoxic phenotype and the 'A2' neuroprotective phenotype, with A1 astrocytes being neurotoxic and impeding neurorecovery, and A2 astrocytes being neuroprotective. This paper discusses the changes in astrocyte responsiveness after SCI and the pros and cons of their polarization in SCI. It also elucidates the feasibility of astrocyte polarization as a therapeutic target for neuroprotection. In the future, multiple intervention strategies targeting astrocyte polarization are expected to gain wider clinical application, ultimately improving motor-sensory function and quality of life in SCI patients.

Vitexin attenuates neuropathic pain by regulating astrocyte autophagy flux and polarization via the S1P/ S1PR1-PI3K/ Akt axis

Neuropathic pain (NP) is associated with astrocytes activation induced by nerve injury. Reactive astrocytes, strongly induced by central nervous system damage, can be classified into A1 and A2 types. Vitexin, a renowned flavonoid compound, is known for its anti-inflammatory and analgesic properties. However, its role in NP remains unexplored. This study aims to investigate the effects of vitexin on astrocyte polarization and its underlying mechanisms. A mouse model of NP was established, and primary astrocytes were stimulated with sphingosine-1-phosphate (S1P) to construct a cellular model. The results demonstrated significant activation of spinal astrocytes on days 14 and 21. Concurrently, reactive astrocytes predominantly differentiated into the A1 type. Western blot analysis revealed an increase in A1 astrocyte-associated protein (C3) and a decrease in A2 astrocyte-associated protein (S100A10). Serum S1P levels increased on days 14 and 21, alongside a significant upregulation of Sphingosine-1-phosphate receptor 1 (S1PR1) mRNA expression and elevated expression of chemokines. In vitro, stimulation with S1P inhibited the Phosphatidylinositol 3-kinase and protein kinase B (PI3K/Akt) signaling pathway and autophagy flux, promoting polarization of astrocytes towards the A1 phenotype while suppressing the polarization of A2 astrocytes. Our findings suggest that vitexin, acting on astrocytes but not microglia, attenuates S1P-induced downregulation of PI3K/Akt signaling, restores autophagy flux in astrocytes, regulates A1/A2 astrocyte ratio, and reduces chemokine and S1P secretion, thereby alleviating neuropathic pain caused by nerve injury.

Analgesic Effect of Exercise on Neuropathic Pain via Regulating the Complement Component 3 of Reactive Astrocytes

BACKGROUND

Exercise has been proven to be an efficient intervention in attenuating neuropathic pain. However, the underlying mechanisms that drive exercise analgesia remain unknown. In this study, we aimed to examine the role of complement component 3 (C3) in neuropathic pain and whether antinociceptive effects are produced by exercise via regulating C3 in mice.

METHODS

In this study, using a spared nerve injury (SNI)-induced neuropathic pain mice model, C57BL/6J mice were divided into 3 groups: Sham mice, SNI mice, and SNI + Exercise (Ex) mice with 30-minute low-intensity aerobic treadmill running (10 m/min, no inclination). Paw withdrawal threshold; thermal withdrawal latency; and glial fibrillary acidic protein, C3, tumor necrosis factor-α, and interlukin-1β expression in the spinal cord were monitored. C3 knockout (KO) mice were further used to verify the role of C3 in neuropathic pain.

RESULTS

von Frey test, acetone test, and CatWalk gait analysis revealed that treadmill exercise for 4 weeks reversed pain behaviors. In addition, exercise reduced astrocyte reactivity (SNI mean = 14.5, 95% confidence interval [CI], 12.7-16.3; SNI + Ex mean = 10.3, 95% CI, 8.77-11.9, P = .0003 SNI + Ex versus SNI) and inflammatory responses in the spinal cord after SNI. Moreover, it suppressed the SNI-induced upregulation of C3 expression in the spinal cord (SNI mean = 5.46, 95% CI, 3.39-7.53; SNI + Ex mean = 2.41, 95% CI, 1.42-3.41, P = .0054 SNI + Ex versus SNI in Western blot). C3 deficiency reduced SNI-induced pain and spinal astrocyte reactivity (wild type mean = 7.96, 95% CI, 6.80-9.13; C3 KO mean = 5.98, 95% CI, 5.14-6.82, P = .0052 C3 KO versus wild type). Intrathecal injection of recombinant C3 (rC3) was sufficient to produce mechanical (rC3-Ex mean = 0.77, 95% CI, 0.15-1.39; rC3 mean = 0.18, 95% CI, -0.04 to 0.41, P = .0168 rC3-Ex versus rC3) and cold (rC3-Ex mean = 1.08, 95% CI, 0.40-1.77; rC3 mean = 3.46, 95% CI, 1.45-5.47, P = .0025 rC3-Ex versus rC3) allodynia in mice. Importantly, exercise training relieved C3-induced mechanical and cold allodynia, and the analgesic effect of exercise was attenuated by a subeffective dose of intrathecal injection of C3.

CONCLUSIONS

Overall, these results suggest that exercise suppresses neuropathic pain by regulating astroglial C3 expression and function, thereby providing a rationale for the analgesic effect of exercise as an acceptable alternative approach for treating neuropathic pain.

Chronic Pain-Related Cognitive Deficits: Preclinical Insights into Molecular, Cellular, and Circuit Mechanisms

Cognitive impairment is a common comorbidity of chronic pain, significantly disrupting patients' quality of life. Despite this comorbidity being clinically recognized, the underlying neuropathological mechanisms remain unclear. Recent preclinical studies have focused on the fundamental mechanisms underlying the coexistence of chronic pain and cognitive decline. Pain chronification is accompanied by structural and functional changes in the neural substrate of cognition. Based on the developments in electrophysiology and optogenetics/chemogenetics, we summarized the relevant neural circuits involved in pain-induced cognitive impairment, as well as changes in connectivity and function in brain regions. We then present the cellular and molecular alternations related to pain-induced cognitive impairment in preclinical studies, mainly including modifications in neuronal excitability and structure, synaptic plasticity, glial cells and cytokines, neurotransmitters and other neurochemicals, and the gut-brain axis. Finally, we also discussed the potential treatment strategies and future research directions.

Nimodipine attenuates neuroinflammation and delayed apoptotic neuronal death induced by trimethyltin in the dentate gyrus of mice

L-type voltage-gated calcium channels (L-VGCCs) are thought to be involved in epileptogenesis and acute excitotoxicity. However, little is known about the role of L-VGCCs in neuroinflammation or delayed neuronal death following excitotoxic insult. We examined the effects of repeated treatment with the L-VGCC blocker nimodipine on neuroinflammatory changes and delayed neuronal apoptosis in the dentate gyrus following trimethyltin (TMT)-induced convulsions. Male C57BL/6 N mice were administered TMT (2.6 mg/kg, i.p.), and the expression of the Cav1.2 and Cav1.3 subunits of L-VGCC were evaluated. The expression of both subunits was significantly decreased; however, the astroglial expression of Cav1.3 L-VGCC was significantly induced at 6 and 10 days after TMT treatment. Furthermore, astroglial Cav1.3 L-VGCCs colocalized with both the pro-inflammatory phenotype marker C3 and the anti-inflammatory phenotype marker S100A10 of astrocytes. Nimodipine (5 mg/kg, i.p. × 5 at 12-h intervals) did not significantly affect TMT-induced astroglial activation. However, nimodipine significantly attenuated the pro-inflammatory phenotype changes, while enhancing the anti-inflammatory phenotype changes in astrocytes after TMT treatment. Consistently, nimodipine reduced the levels of pro-inflammatory astrocytes-to-microglia mediators, while increasing the levels of anti-inflammatory astrocytes-to-microglia mediators. These effects were accompanied by an increase in the phosphorylation of extracellular signal-regulated kinase (ERK), supporting our previous finding that p-ERK is a signaling factor that regulates astroglial phenotype changes. In addition, nimodipine significantly attenuated TMT-induced microglial activation and delayed apoptosis of dentate granule neurons. Our results suggest that L-VGCC blockade attenuates neuroinflammation and delayed neurotoxicity following TMT-induced convulsions through the regulation of astroglial phenotypic changes by promoting ERK signaling.

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.

Astrocyte-Mediated Neuroinflammation in Neurological Conditions

Astrocytes are one of the key glial types of the central nervous system (CNS), accounting for over 20% of total glial cells in the brain. Extensive evidence has established their indispensable functions in the maintenance of CNS homeostasis, as well as their broad involvement in neurological conditions. In particular, astrocytes can participate in various neuroinflammatory processes, e.g., releasing a repertoire of cytokines and chemokines or specific neurotrophic factors, which result in both beneficial and detrimental effects. It has become increasingly clear that such astrocyte-mediated neuroinflammation, together with its complex crosstalk with other glial cells or immune cells, designates neuronal survival and the functional integrity of neurocircuits, thus critically contributing to disease onset and progression. In this review, we focus on the current knowledge of the neuroinflammatory responses of astrocytes, summarizing their common features in neurological conditions. Moreover, we highlight several vital questions for future research that promise novel insights into diagnostic or therapeutic strategies against those debilitating CNS diseases.

Evaluation of the beneficial effects of a GABA-based product containing Melissa officinalis on post-inflammatory irritable bowel syndrome: a preclinical study

Introduction

Visceral pain represents the most common digestive issue, frequently resulting from long-term inflammation, such as inflammatory bowel diseases. The lack of effective drugs prompted search of new therapeutic approaches. In this regard, gamma-aminobutyric acid (GABA) and Melissa officinalis (Mo) appear as excellent candidates as they were recognized to have several positive effects on the digestive system. The aim of this research was to evaluate the effects of a compound containing GABA and Mo (GABA-Mo 5:1) in inflammation-induced intestinal damage and visceral pain.

Methods

Colitis was induced in rats by intrarectal 2,4-dinitrobenzenesulfonic acid (DNBS) administration. DNBS-treated animals received GABA-Mo (80 mg/kg BID), starting 3 days before DNBS administration, until 14 days after colitis induction (preventive protocol), or starting 7 days after DNBS until day 21 (curative protocol). Visceral pain was assessed by measuring the viscero-motor response (VMR) and the abdominal withdrawal reflex (AWR) to colorectal distension on day 7, 14 (both protocols) and 21 (curative protocol) after DNBS administration.

Results

In the preventive protocol, GABA-Mo reduced AWR at day 14 but had no effect on VMR. In the spinal cord, treatment with GABA-Mo significantly prevented microglia reactivity (Iba-1 positive cells). In the colon, the supplement significantly decreased malondialdehyde (MDA, index of oxidative stress) and IL-1β levels and counteracted the decreased expression of claudin-1. Moreover, GABA-Mo normalized the increased levels of plasma lipopolysaccharide binding protein (LBP, index of altered intestinal permeability). In the curative protocol, GABA-Mo significantly counteracted visceral hypersensitivity persistence in DNBS-treated animals (day 14 and 21). In the spinal cord, GABA-Mo significantly reduced GFAP positive cell density (astrocytes). Histological evaluations highlighted a mild but significant effect of GABA-Mo in promoting healing from DNBS-induced colon damage. Colonic MDA and myeloperoxidase (index of leukocyte infiltration) levels were reduced, while the decreased colonic claudin-1 expression was normalized. In addition, the increased levels of plasma LBP were normalized by GABA-Mo administration.

Discussion

In conclusion GABA-Mo, particularly in the curative protocol, was able to reduce visceral pain and intestinal inflammation, likely through a reinforcement of intestinal barrier integrity, thus representing a suitable approach for the management of abdominal pain, especially in the remission stages of colitis.

Nociplastic pain in axial spondyloarthritis and psoriatic arthritis: role of JAK kinases in immunopathology and therapeutic impact of JAK inhibitors

INTRODUCTION

Pain in both peripheral and axial joints is a major symptom in patients with psoriatic arthritis (PsA) and axial spondyloarthritis (axSpA). Emerging evidence demonstrates pain mechanisms, beyond those related to inflammation or joint damage, based on aberrant processing of nociceptive stimuli peripherally as well as centrally. The Janus kinase/signal transducers and activators of transcription (JAK-STAT) signaling pathway has been implicated in the processing of pain beyond its role in mediating inflammation and inhibitors of this pathway approved for the treatment of axSpA and PsA have been shown to alleviate a broad array of pain outcomes in both axial and peripheral joints.

AREAS COVERED

We review recent definitions and standardization of the nomenclature for categorizing chronic pain according to causality, assessment tools to evaluate nociplastic pain, the pathophysiologic role of JAK-STAT signaling in nociplastic pain, evidence for the presence of nociplastic pain in axSpA and PsA, and the impact of JAK inhibitors (JAKi) on pain outcomes in clinical trials (PubMed: 01/01/2019-04/01-2024).

EXPERT OPINION

Nociplastic pain assessment has been confined almost entirely to the use of a limited number of questionnaires in cross-sectional studies of these diseases. Though effective for alleviating pain, it is unclear if JAKi specifically impact nociplastic pain.

Cannabidiol in the dorsal hippocampus attenuates emotional and cognitive impairments related to neuropathic pain: The role of prelimbic neocortex-hippocampal connections

BACKGROUND AND PURPOSE

Chronic neuropathic pain (NP) is commonly associated with cognitive and emotional impairments. Cannabidiol (CBD) presents a broad spectrum of action with a potential analgesic effect. This work investigates the CBD effect on comorbidity between chronic NP, depression, and memory impairment.

EXPERIMENTAL APPROACH

The connection between the neocortex and the hippocampus was investigated with biotinylated dextran amine (BDA) deposits in the prelimbic cortex (PrL). Wistar rats were submitted to chronic constriction injury (CCI) of the sciatic nerve and CA1 treatment with CBD (15, 30, 60 nmol).

KEY RESULTS

BDA-labeled perikarya and terminal buttons were found in CA1 and dentate gyrus. CCI-induced mechanical and cold allodynia increased c-Fos protein expression in the PrL and CA1. The number of astrocytes in PrL and CA1 increased, and the number of neuroblasts decreased in CA1. Animals submitted to CCI procedure showed increasing depressive-like behaviors, such as memory impairment. CBD (60 nmol) treatment decreased mechanical and cold allodynia, attenuated depressive-associated behaviors, and improved memory performance. Cobalt chloride (CoCl2: 1 nM), WAY-100635 (0.37 nmol), and AM251 (100 nmol) intra-PrL reversed the effect of CA1 treatment with CBD (60 nmol) on nociceptive, cognitive, and depressive behaviors.

CONCLUSION

CBD represents a promising therapeutic perspective in the pharmacological treatment of chronic NP and associated comorbidities such as depression and memory impairments. The CBD effects possibly recruit the CA1-PrL pathway, inducing neuroplasticity. CBD acute treatment into the CA1 produces functional and molecular morphological improvements.

Long COVID diagnostic with differentiation from chronic lyme disease using machine learning and cytokine hubs

The absence of a long COVID (LC) or post-acute sequelae of COVID-19 (PASC) diagnostic has profound implications for research and potential therapeutics given the lack of specificity with symptom-based identification of LC and the overlap of symptoms with other chronic inflammatory conditions. Here, we report a machine-learning approach to LC/PASC diagnosis on 347 individuals using cytokine hubs that are also capable of differentiating LC from chronic lyme disease (CLD). We derived decision tree, random forest, and gradient-boosting machine (GBM) classifiers and compared their diagnostic capabilities on a dataset partitioned into training (178 individuals) and evaluation (45 individuals) sets. The GBM model generated 89% sensitivity and 96% specificity for LC with no evidence of overfitting. We tested the GBM on an additional random dataset (106 LC/PASC and 18 Lyme), resulting in high sensitivity (97%) and specificity (90%) for LC. We constructed a Lyme Index confirmatory algorithm to discriminate LC and CLD.

MicroRNAs Modulating Neuroinflammation in Parkinson's disease

Parkinson's disease (PD) is one of the most frequent age-associated neurodegenerative disorder. Presence of α-synuclein-containing aggregates in the substantia nigra pars compacta (SNpc) and loss of dopaminergic (DA) neurons are among the characteristic of PD. One of the hallmarks of PD pathophysiology is chronic neuroinflammation. Activation of glial cells and elevated levels of pro-inflammatory factors are confirmed as frequent features of the PD brain. Chronic secretion of pro-inflammatory cytokines by activated astrocytes and microglia exacerbates DA neuron degeneration in the SNpc. MicroRNAs (miRNAs) are among endogenous non-coding small RNA with the ability to perform post-transcriptional regulation in target genes. In that regard, the capability of miRNAs for modulating inflammatory signaling is the center of attention in many investigations. MiRNAs could enhance or limit inflammatory signaling, exacerbating or ameliorating the pathological consequences of extreme neuroinflammation. This review summarizes the importance of inflammation in the pathophysiology of PD. Besides, we discuss the role of miRNAs in promoting or protecting neural cell injury in the PD model by controlling the inflammatory pathway. Modifying the neuroinflammation by miRNAs could be considered a primary therapeutic strategy for PD.

Astroglial morphological changes in periaqueductal grey in different pain and itch mice models

BACKGROUND

The periaqueductal gray (PAG) plays a well-established pivotal role in the descending pain modulatory circuit. The objective of this study was to investigate morphological changes in the astroglia in models that are commonly used in pain and itch studies.

METHODS

Five different mouse models of pain, as well as two models of chronic itch, were established using complete Freund's adjuvant (CFA), spared nerve injury (SNI), bone cancer pain (BCP), cisplatin (CIS), and paclitaxel (PTX) for pain, and diphenylcyclopropenone (DCP) and acetone and diethyl ether followed by water (AEW) for chronic itch. von Frey tests and video recordings were employed to assess pain and itching behaviors. The immunofluorescence of S100β, pSTAT3, and glial fibrillary acidic protein (GFAP) was examined. Two- and three-dimensional studies were used to evaluate changes in astrocyte morphology.

RESULTS

Significant scratching was caused by DCP and AEW, whereas the administration of CFA, SNI, BCP, CIS, and PTX produced clear mechanical allodynia. The expression of GFAP in the lPAG/vlPAG was upregulated in CFA, SNI, BCP, CIS, PTX, and DCP mice but decreased in AEW mice. According to Sholl analysis, CFA, SNI, PTX, and BCP mice showed substantially higher astrocyte intersections in the vlPAG, whereas CFA, SNI, BCP, CIS, and DCP mice presented longer peak lengths. In three-dimensional analysis, CFA, SNI, PTX, and DCP mice showed increased astrocyte surface areas, while CIS and AEW mice showed both reduced surface areas and/or volumes of astrocytes.

CONCLUSION

The findings showed that different pain and itching conditions have different astrocyte morphologies, and these variations in morphological changes help to explain the pathophysiology of these conditions.

TRPM7 Mediates Neuropathic Pain by Activating mTOR Signaling in Astrocytes after Spinal Cord Injury in Rats

In this study, we investigated whether transient receptor melastatin 7 (TRPM7), known as a non-selective cation channel, inhibits neuropathic pain after spinal cord injury (SCI) and how TRPM7 regulates neuropathic pain. Neuropathic pain was developed 4 weeks after moderate contusive SCI and TRPM7 was markedly upregulated in astrocytes in the lamina I and II of L4-L5 dorsal horn. In addition, both mechanical allodynia and thermal hyperalgesia were significantly alleviated by a TRPM7 inhibitor, carvacrol. In particular, carvacrol treatment inhibited mechanistic target of rapamycin (mTOR) signaling, which was activated in astrocytes. When rats were treated with rapamycin, an inhibitor of mTOR signaling, neuropathic pain was significantly inhibited. Furthermore, blocking TRPM7 and mTOR signaling by carvacrol and rapamycin inhibited astrocyte activation in lamina I and II of dorsal spinal cord and reduced the level of p-JNK and p-c-Jun, which are known to be activated in astrocytes. Finally, inhibiting TRPM7/mTOR signaling also downregulated the production of pain-related factors such as tumor necrosis factor-α, interleukin-6, interleukin-1β, chemokine (C-C motif) ligand (CCL) 2, CCL-3, CCL-4, CCL-20, chemokine C-X-C motif ligand 1, and matrix metalloproteinase 9 which are known to be involved in the induction and/or maintenance of neuropathic pain after SCI. These results suggest an important role of TRPM7-mediated mTOR signaling in astrocyte activation and thereby induction and/or maintenance of neuropathic pain after SCI.

Effects of fasudil on glial cell activation induced by tooth movement

BACKGROUND

Orthodontic pain affects the physical and mental health of patients. The spinal trigeminal subnucleus caudalis (SPVC) contributes to the transmission of pain information and serves as a relay station for integrating orofacial damage information. Recently, glial cells have been found to be crucial for both acute and maintenance phases of pain. It has also been demonstrated that rho kinase (ROCK) inhibitors can manage different pain models by inhibiting glial cell activation. Here, we hypothesized that orthodontic pain is related to glial cells in the SPVC, and Fasudil, a representative rho/rock kinase inhibitor, can relieve orthodontic pain by regulating the function of glial cells and the related inflammatory factors. In this study, we constructed a rat model of tooth movement pain and used immunofluorescence staining to evaluate the activation of microglia and astrocytes. Quantitative real-time PCR was used to detect the release of related cytokines and the expression of pain-related genes in the SPVC. Simultaneously, we investigated the effect of Fasudil on the aforementioned indicators.

RESULTS

In the SPVC, the expression of c-Fos peaked on day 1 along with the expression of OX42 (related to microglial activation), CD16 (a pro-inflammatory factor), and CD206 (an anti-inflammatory factor) on day 3 after tooth movement, followed by a gradual decrease. GFAP-staining showed that the number of activated astrocytes was the highest on day 5 and that cell morphology became complex. After Fasudil treatment, the expression of these proteins showed a downward trend. The mRNA levels of pro-inflammatory factors (IL-1β and TNF-α) peaked on day 3, and the mRNA expression of the anti-inflammatory factor TGF-β was the lowest 3 days after tooth movement. Fasudil inhibited the mRNA expression of pain-related genes encoding CSF-1, t-PA, CTSS, and BDNF.

CONCLUSION

This study shows that tooth movement can cause the activation of glial cells in SPVC, and ROCK inhibitor Fasudil can inhibit the activation of glial cells and reduce the expression of the related inflammatory factors. This study presents for the first time the potential application of Fasudil in othodontic pain.

Neuroinflammation mechanism underlying neuropathic pain: the role of mesenchymal stem cell in neuroglia

Pain is an essential aspect of the body's physiological response to unpleasant noxious stimuli from either external sustained injuries or an internal disease condition that occurs within the body. Generally, pain is temporary. However, in patients with neuropathic pain, the experienced pain is persistent and uncontrollable, with an unsatisfactory treatment effectiveness. The activation of the immune system is a crucial factor in both central and peripheral neuropathic pain. The immune response plays an important role in the progression of the stages of neuropathic pain, and acts not only as pain mediators, but also produce analgesic molecules. Neuropathic pain has long been described as a result of dysfunctional nerve activities. However, there is substantial evidence indicating that the regulation of hyperalgesia is mediated by astrocytes and microglia activation. Mesenchymal stem cells currently hold an optimal potential in managing pain, as they can migrate to damaged tissues and have a robust immunosuppressive role for autologous or heterologous transplantation. Moreover, mesenchymal stem cells revealed their immunomodulatory capabilities by secreting growth factors and cytokines through direct cell interactions. The main idea underlying the use of mesenchymal stem cells in pain management is that these cells can replace damaged nerve cells by releasing neurotrophic factors. This property makes them the perfect option to modulate and treat neuropathic pain, which is notoriously difficult to treat.

The problem of residual pain in the assessment of rheumatoid arthritis activity

Residual pain is a major unmet medical need observed in patients suffering from rheumatoid arthritis (RA), which decreases their quality of life, even after achieving remission or low disease activity. The article has two aims: 1) to present mechanisms involved in the pathophysiology of residual pain, both inflammatory and non-inflammatory, i.e. neuropathic and nociplastic pain, as well as secondary pain syndromes, i.e. osteoarthritis and fibromyalgia, which can contribute to residual pain; 2) to show the limitations of current disease activity measures recommended by European Alliance of Associations for Rheumatology (EULAR) and American College of Rheumatology (ACR), which raise the need for a separate assessment of pain, and examples of methods that could be used by medical professionals to assess the pain and make a differential diagnosis. In conclusion, establishing a valid method to assess pain is essential to identify the pathomechanism of residual pain and to create treatments tailored specifically to individual RA patients.

Nobiletin regulates intracellular Ca2+ levels via IP3R and ameliorates neuroinflammation in Aβ42-induced astrocytes

Astrocytes are the major glial cells in the human brain and provide crucial metabolic and trophic support to neurons. The amyloid-β peptide (Aβ) alter the morphological and functional properties of astrocytes and induce inflammation and calcium dysregulation, contributing to Alzheimer's disease (AD) pathology. Recent studies highlight the role of Toll-like receptor (TLR) 4/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling in inflammation. Reactive oxygen species (ROS) generated due to Aβ, induce apoptosis in the brain cells worsening AD progression. Astrocytic cell surface receptors, such as purinergic receptors (P2Y1 and P2Y2), metabotropic glutamate receptor (mGLUR)5, α7 nicotinic acetylcholine receptor (α7nAChR), and N-methyl-d-aspartate receptors (NMDARs), have been suggested to interact with inositol trisphosphate receptor (IP3R) on the endoplasmic reticulum (ER) to induce Ca2+ movement from ER to cytoplasm, causing Ca2+ dysregulation. We found that the citrus flavonoid nobiletin (NOB) protected primary astrocytes from Aβ42-induced cytotoxicity and inhibited TLR4/NF-κB signaling in Aβ42-induced primary rat astrocytes. NOB was found to regulate Aβ42-induced ROS levels through Keap1-Nrf2 pathway. The receptors P2Y1, P2Y2, mGLUR5, α7nAChR, and NMDARs induced intracellular Ca2+ levels by activating IP3R and NOB regulated them, thereby regulating intracellular Ca2+ levels. Molecular docking analysis revealed a possible interaction between NOB and IP3R in IP3R regulation. Furthermore, RNA sequencing revealed various NOB-mediated biological signaling pathways, such as the AD-presenilin, AD-amyloid secretase, and Wnt signaling pathway, suggesting possible neuroprotective roles of NOB. To conclude, NOB is a promising therapeutic agent for AD and works by modulating AD pathology at various levels in Aβ42-induced primary rat astrocytes.

The angiotensin II receptors type 1 and 2 modulate astrocytes and their crosstalk with microglia and neurons in an in vitro model of ischemic stroke

BACKGROUND

Astrocytes are the most abundant cell type of the central nervous system and are fundamentally involved in homeostasis, neuroprotection, and synaptic plasticity. This regulatory function of astrocytes on their neighboring cells in the healthy brain is subject of current research. In the ischemic brain we assume disease specific differences in astrocytic acting. The renin-angiotensin-aldosterone system regulates arterial blood pressure through endothelial cells and perivascular musculature. Moreover, astrocytes express angiotensin II type 1 and 2 receptors. However, their role in astrocytic function has not yet been fully elucidated. We hypothesized that the angiotensin II receptors impact astrocyte function as revealed in an in vitro system mimicking cerebral ischemia. Astrocytes derived from neonatal wistar rats were exposed to telmisartan (angiotensin II type 1 receptor-blocker) or PD123319 (angiotensin II type 2 receptor-blocker) under normal conditions (control) or deprivation from oxygen and glucose. Conditioned medium (CM) of astrocytes was harvested to elucidate astrocyte-mediated indirect effects on microglia and cortical neurons.

RESULT

The blockade of angiotensin II type 1 receptor by telmisartan increased the survival of astrocytes during ischemic conditions in vitro without affecting their proliferation rate or disturbing their expression of S100A10, a marker of activation. The inhibition of the angiotensin II type 2 receptor pathway by PD123319 resulted in both increased expression of S100A10 and proliferation rate. The CM of telmisartan-treated astrocytes reduced the expression of pro-inflammatory mediators with simultaneous increase of anti-inflammatory markers in microglia. Increased neuronal activity was observed after treatment of neurons with CM of telmisartan- as well as PD123319-stimulated astrocytes.

CONCLUSION

Data show that angiotensin II receptors have functional relevance for astrocytes that differs in healthy and ischemic conditions and effects surrounding microglia and neuronal activity via secretory signals. Above that, this work emphasizes the strong interference of the different cells in the CNS and that targeting astrocytes might serve as a therapeutic strategy to influence the acting of glia-neuronal network in de- and regenerative context.

Interactions and Trends of Interleukins, PAI-1, CRP, and TNF-α in Inflammatory Responses during the Perioperative Period of Joint Arthroplasty: Implications for Pain Management-A Narrative Review

Inflammation during the perioperative period of joint arthroplasty is a critical aspect of patient outcomes, influencing both the pathophysiology of pain and the healing process. This narrative review comprehensively evaluates the roles of specific cytokines and inflammatory biomarkers in this context and their implications for pain management. Inflammatory responses are initiated and propagated by cytokines, which are pivotal in the development of both acute and chronic postoperative pain. Pro-inflammatory cytokines play essential roles in up-regulating the inflammatory response, which, if not adequately controlled, leads to sustained pain and impaired tissue healing. Anti-inflammatory cytokines work to dampen inflammatory responses and promote resolution. Our discussion extends to the genetic and molecular influences on cytokine production, which influence pain perception and recovery rates post-surgery. Furthermore, the role of PAI-1 in modulating inflammation through its impact on the fibrinolytic system highlights its potential as a therapeutic target. The perioperative modulation of these cytokines through various analgesic and anesthetic techniques, including the fascia iliac compartment block, demonstrates a significant reduction in pain and inflammatory markers, thus underscoring the importance of targeted therapeutic strategies. Our analysis suggests that a nuanced understanding of the interplay between pro-inflammatory and anti-inflammatory cytokines is required. Future research should focus on individualized pain management strategies.

Curcumin analogue NL04 inhibits spinal cord central sensitization in rats with bone cancer pain by inhibiting NLRP3 inflammasome activation and reducing IL-1β production

The management and therapy of bone cancer pain (BCP) remain formidable clinical challenges. Curcumin and its analogues have been shown to have anti-inflammatory and analgesic properties. In the present study, we investigated the efficacy of curcumin analogue NL04 (NL04) in modulating inflammation in spinal dorsal horn (SDH), thereby exploring its potential to reduce central sensitization of BCP in a rat model. Differing doses of NL04 and curcumin were administered intrathecally either once (on day 12 of BCP) or over seven consecutive days (from day 6-12 of BCP). Results indicated that the ED50 for NL04 and curcumin ameliorating BCP-induced mechanical hyperalgesia is 49.08 μg/kg and 489.6 μg/kg, respectively. The analgesic effects at various doses of NL04 lasted between 4 and 8 h, with sustained administration over a week maintaining pain relief for 1-4 days, while also ameliorating locomotor gait via gait analysis and reducing depressive and anxiety-like behaviors via open-field and light-dark transition tests. The analgesic effects at various doses of curcumin lasted 4 h, with sustained administration over a week maintaining pain relief for 0-2 days. ELISA, Western blotting, qPCR, and immunofluorescence assays substantiated that intrathecal administration of NL04 on days 6-12 of BCP dose-dependently lowered spinal IL-1β and IL-18 levels and significantly reduced the expression of IKKβ genes and proteins, as well as the downstream cleavage of the trans-Golgi network (TGN). Whole-cell patch-clamp results demonstrated that NL04 inhibits potassium ion efflux in rat primary spinal neurons. Thus, NL04 exhibits significant analgesic effects in a BCP rat model by downregulating IKKβ expression and inhibiting neuronal potassium ion efflux, which, in turn, suppresses the activation of NLRP3 inflammasomes and reduces IL-1β production, potentially ameliorating pain management in BCP.

Shenyu ningshen tablet reduced neuronal damage in the hippocampus of chronic restraint stress model rat by inhibiting A1-reactive astrocytes

Context

Shenyu Ningshen (SYNS) tablet is the first pure Chinese medicinal small compound preparation approved for clinical trials for the treatment of depression in China. Clinical experiments confirmed that the formulation had a significant Improvement effect against depression due to the deficiency of both qi and yin. It has been shown to exhibit noticeable anti-inflammatory effect in an animal model of depression. Our previous study showed that SYNS could effectively inhibit the inflammatory response in a depression model.

Aim of the study

The purpose of this study was to investigate the protective effects of SYNS on neurons and explore whether the underlying mechanism was associated with A1s.

Materials and methods

The depression model of solitary raising-chronic restraint stress (CRS) rats was established; body weight examination, sugar water preference test, open field test, and histological analysis were performed to preliminarily verify the efficacy of the formulation. Subsequently, neuronal nucleus (NeuN) and synaptic-associated proteins (MAP2 and PSD95) were labeled, and the protective effect of SYNS on hippocampal neurons was observed based on the fluorescence intensity of the above indicators. Western blotting, histological examination, and immunofluorescence were used to evaluate the inhibitory effects of SYNS on neuroinflammation and activation of A1s in CRS depression model.

Results

SYNS improved behavioral indicators such as weight loss, pleasure loss, and reduced exercise volume in CRS rat model. SYNS restored the CRS-induced histopathological changes in the hippocampus. SYNS showed a certain degree of protective effect on synapses. Further, SYNS inhibited the activation of A1s by inhibiting neuroinflammatory factors in the hippocampus.

Conclusion

Our results showed that SYNS had a certain degree of neuroprotective effect, which might be related to its inhibition of the inflammatory response and A1s.

Predictive value of S100B and brain derived neurotrophic factor for radiofrequency treatment of lumbar disc prolapse

BACKGROUND

This work aimed to analyze serum S100B levels and brain-derived neurotrophic factor (BDNF) in patients with lumbar disc prolapse to test their predictive values concerning the therapeutic efficacy of pulsed radiofrequency.

METHODS

This prospective interventional study was carried out on 50 patients candidates for radiofrequency for treating symptomatic lumbar disc prolapse. Pain severity and functional disability were assessed using the Numeric Rating Scale (NRS) and Functional rating index (FRI) before as well as two weeks, 1, 3, and 6 months after the radiofrequency. Quantitative assessment of serum S100B level and BDNF was done for all the included patients one day before radiofrequency.

RESULTS

The scores of NRS and FRI were significantly improved at two weeks, 1, 3, and 6 months following radiofrequency (P-value < 0.001 in all comparisons). Statistically significant positive correlations were found between duration of pain, NRS, and S100B serum level before radiofrequency, and both NRS (P-value = 0.001, 0.035, < 0.001 respectively) and FRI (P-value = < 0.001, 0.009, 0.001 respectively) 6 months following radiofrequency. Whereas there were statistically significant negative correlations between BDNF serum level before radiofrequency and both NRS and FRI 6 months following radiofrequency (P-value = 0.022, 0.041 respectively). NRS and S100B serum levels before radiofrequency were found to be independent predictors of NRS 6 months following radiofrequency (P-value = 0.040. <0.001, respectively).

CONCLUSION

Serum level of S100B is a promising biomarker that can predict functional outcomes after pulsed radiofrequency in patients with lumbar disc prolapse.

Ion transporter cascade, reactive astrogliosis and cerebrovascular diseases

Cerebrovascular diseases and their sequalae, such as ischemic stroke, chronic cerebral hypoperfusion, and vascular dementia are significant contributors to adult disability and cognitive impairment in the modern world. Astrocytes are an integral part of the neurovascular unit in the CNS and play a pivotal role in CNS homeostasis, including ionic and pH balance, neurotransmission, cerebral blood flow, and metabolism. Astrocytes respond to cerebral insults, inflammation, and diseases through unique molecular, morphological, and functional changes, collectively known as reactive astrogliosis. The function of reactive astrocytes has been a subject of debate. Initially, astrocytes were thought to primarily play a supportive role in maintaining the structure and function of the nervous system. However, recent studies suggest that reactive astrocytes may have both beneficial and detrimental effects. For example, in chronic cerebral hypoperfusion, reactive astrocytes can cause oligodendrocyte death and demyelination. In this review, we will summarize the (1) roles of ion transporter cascade in reactive astrogliosis, (2) role of reactive astrocytes in vascular dementia and related dementias, and (3) potential therapeutic approaches for dementing disorders targeting reactive astrocytes. Understanding the relationship between ion transporter cascade, reactive astrogliosis, and cerebrovascular diseases may reveal mechanisms and targets for the development of therapies for brain diseases associated with reactive astrogliosis.

Astrocyte activation in hindlimb somatosensory cortex contributes to electroacupuncture analgesia in acid-induced pain

Background

Several studies have confirmed the direct relationship between extracellular acidification and the occurrence of pain. As an effective pain management approach, the mechanism of electroacupuncture (EA) treatment of acidification-induced pain is not fully understood. The purpose of this study was to assess the analgesic effect of EA in this type of pain and to explore the underlying mechanism(s).

Methods

We used plantar injection of the acidified phosphate-buffered saline (PBS; pH 6.0) to trigger thermal hyperalgesia in male Sprague-Dawley (SD) rats aged 6-8 weeks. The value of thermal withdrawal latency (TWL) was quantified after applying EA stimulation to the ST36 acupoint and/or chemogenetic control of astrocytes in the hindlimb somatosensory cortex.

Results

Both EA and chemogenetic astrocyte activation suppressed the acid-induced thermal hyperalgesia in the rat paw, whereas inhibition of astrocyte activation did not influence the hyperalgesia. At the same time, EA-induced analgesia was blocked by chemogenetic inhibition of astrocytes.

Conclusion

The present results suggest that EA-activated astrocytes in the hindlimb somatosensory cortex exert an analgesic effect on acid-induced pain, although these astrocytes might only moderately regulate acid-induced pain in the absence of EA. Our results imply a novel mode of action of astrocytes involved in EA analgesia.

White and Gray Matter Abnormality in Burning Mouth Syndrome Evaluated with Diffusion Tensor Imaging and Neurite Orientation Dispersion and Density Imaging

PURPOSE

Burning mouth syndrome (BMS) is defined by a burning sensation or pain in the tongue or other oral sites despite the presence of normal mucosa on inspection. Both psychiatric and neuroimaging investigations have examined BMS; however, there have been no analyses using the neurite orientation dispersion and density imaging (NODDI) model, which provides detailed information of intra- and extracellular microstructures. Therefore, we performed voxel-wise analyses using both NODDI and diffusion tensor imaging (DTI) models and compared the results to better comprehend the pathology of BMS.

METHODS

Fourteen patients with BMS and 11 age- and sex-matched healthy control subjects were prospectively scanned using a 3T-MRI machine using 2-shell diffusion imaging. Diffusion tensor metrics (fractional anisotropy [FA], mean diffusivity [MD], axial diffusivity [AD], and radial diffusivity [RD]) and neurite orientation and dispersion index metrics (intracellular volume fraction [ICVF], isotropic volume fraction [ISO], and orientation dispersion index [ODI]) were retrieved from diffusion MRI data. These data were analyzed using tract-based spatial statistics (TBSS) and gray matter-based spatial statistics (GBSS).

RESULTS

TBSS analysis showed that patients with BMS had significantly higher FA and ICVF and lower MD and RD than the healthy control subjects (family-wise error [FWE] corrected P < 0.05). Changes in ICVF, MD, and RD were observed in widespread white matter areas. Fairly small areas with different FA were included. GBSS analysis showed that patients with BMS had significantly higher ISO and lower MD and RD than the healthy control subjects (FWE-corrected P < 0.05), mainly limited to the amygdala.

CONCLUSION

The increased ICVF in the BMS group may represent myelination and/or astrocytic hypertrophy, and microstructural changes in the amygdala in GBSS analysis indicate the emotional-affective profile of BMS.

Impaired amygdala astrocytic signaling worsens neuropathic pain-associated neuronal functions and behaviors

Introduction: Pain is a clinically relevant health care issue with limited therapeutic options, creating the need for new and improved analgesic strategies. The amygdala is a limbic brain region critically involved in the regulation of emotional-affective components of pain and in pain modulation. The central nucleus of amygdala (CeA) serves major output functions and receives nociceptive information via the external lateral parabrachial nucleus (PB). While amygdala neuroplasticity has been linked causally to pain behaviors, non-neuronal pain mechanisms in this region remain to be explored. As an essential part of the neuroimmune system, astrocytes that represent about 40-50% of glia cells within the central nervous system, are required for physiological neuronal functions, but their role in the amygdala remains to be determined for pain conditions. In this study, we measured time-specific astrocyte activation in the CeA in a neuropathic pain model (spinal nerve ligation, SNL) and assessed the effects of astrocyte inhibition on amygdala neuroplasticity and pain-like behaviors in the pain condition. Methods and Results: Glial fibrillary acidic protein (GFAP, astrocytic marker) immunoreactivity and mRNA expression were increased at the chronic (4 weeks post-SNL), but not acute (1 week post-SNL), stage of neuropathic pain. In order to determine the contribution of astrocytes to amygdala pain-mechanisms, we used fluorocitric acid (FCA), a selective inhibitor of astrocyte metabolism. Whole-cell patch-clamp recordings were performed from neurons in the laterocapsular division of the CeA (CeLC) obtained from chronic neuropathic rats. Pre-incubation of brain slices with FCA (100 µM, 1 h), increased excitability through altered hyperpolarization-activated current (Ih) functions, without significantly affecting synaptic responses at the PB-CeLC synapse. Intra-CeA injection of FCA (100 µM) had facilitatory effects on mechanical withdrawal thresholds (von Frey and paw pressure tests) and emotional-affective behaviors (evoked vocalizations), but not on facial grimace score and anxiety-like behaviors (open field test), in chronic neuropathic rats. Selective inhibition of astrocytes by FCA was confirmed with immunohistochemical analyses showing decreased astrocytic GFAP, but not NeuN, signal in the CeA. Discussion: Overall, these results suggest a complex modulation of amygdala pain functions by astrocytes and provide evidence for beneficial functions of astrocytes in CeA in chronic neuropathic pain.

BM-MSC-Loaded Graphene-Collagen Cryogels Ameliorate Neuroinflammation in a Rat Spinal Cord Injury Model

A major obstacle to axonal regeneration following spinal cord injury (SCI) is neuroinflammation mediated by astrocytes and microglial cells. We previously demonstrated that graphene-based collagen hydrogels alone can decrease neuroinflammation in SCI. Their regenerative potential, however, is poorly understood and incomplete. Furthermore, stem cells have demonstrated both neuroprotective and regenerative properties in spinal cord regeneration, although there are constraints connected with the application of stem cell-based therapy. In this study, we have analyzed the regeneration capability of human bone marrow mesenchymal stem cell (BM-MSC)-loaded graphene-cross-linked collagen cryogels (Gr-Col) in a thoracic (T10-T11) hemisection model of SCI. Our study found that BM-MSC-loaded Gr-Col improves axonal regeneration, reduces neuroinflammation by decreasing astrocyte reactivity, and promotes M2 macrophage polarization. BM-MSC-loaded-Gr-Col demonstrated enhanced regenerative potential compared to Gr-Col and the injury group control. Next-generation sequencing (NGS) analysis revealed that BM-MSC-loaded-Gr-Col modulates the JAK2-STAT3 pathway, thus decreasing the reactive and scar-forming astrocyte phenotype. The decrease in neuroinflammation in the BM-MSC-loaded-Gr-Col group is attributed to the modulation of Notch/Rock and STAT5a/b and STAT6 signaling. Overall, Gene Set Enrichment Analysis suggests the promising role of BM-MSC-loaded-Gr-Col in promoting axonal regeneration after SCI by modulating molecular pathways such as the PI3/Akt pathway, focal adhesion kinase, and various inflammatory pathways.

Role of EPAC1 in chronic pain

Chronic pain usually lasts over three months and commonly occurs in chronic diseases (cancer, arthritis, and diabetes), injuries (herniated discs, torn ligaments), and many major pain disorders (neuropathic pain, fibromyalgia, chronic headaches). Unfortunately, there is currently a lack of effective treatments to help people with chronic pain to achieve complete relief. Therefore,it is particularly important to understand the mechanism of chronic pain and find new therapeutic targets. The exchange protein directly activated by cyclic adenosine monophosphate(cAMP) (EPAC) has been recognized for its functions in nerve regeneration, stimulating insulin release, controlling vascular pressure, and controlling other metabolic activities. In recent years, many studies have found that the subtype of EPAC, EPAC1 is involved in the regulation of neuroinflammation and plays a crucial role in the regulation of pain, which is expected to become a new therapeutic target for chronic pain. This article reviews the major contributions of EPAC1 in chronic pain.

Inhibition of NFAT5-Dependent Astrocyte Swelling Alleviates Neuropathic Pain

Astrocyte swelling is implicated in various neurological disorders. However, whether astrocyte swelling contributes to neuropathic pain remains elusive. This study elucidates the pivotal role of the nuclear factor of activated T-cells 5 (NFAT5) emerges as a master regulator of astrocyte swelling in the spinal dorsal horn (SDH) during neuropathic pain. Despite the ubiquitous expression of NFAT5 protein in SDH cell types, it selectively induces swelling specifically in astrocytes, not in microglia. Mechanistically, NFAT5 directly controls the expression of the water channel aquaporin-4 (AQP4), a key regulator exclusive to astrocytes. Additionally, aurora kinase B (AURKB) orchestrates NFAT5 phosphorylation, enhancing its protein stability and nuclear translocation, thereby regulating AQP4 expression. The findings establish NFAT5 as a crucial regulator for neuropathic pain through the modulation of astrocyte swelling. The AURKB-NFAT5-AQP4 pathway in astrocytes emerges as a potential therapeutic target to combat neuropathic pain.

CDDO regulates central and peripheral sensitization to attenuate post-herpetic neuralgia by targeting TRPV1/PKC-δ/p-Akt signals

Postherpetic neuralgia (PHN) is a notorious neuropathic pain featuring persistent profound mechanical hyperalgesia with significant negative impact on patients' life quality. CDDO can regulate inflammatory response and programmed cell death. Its derivative also protects neurons from damages by modulating microglia activities. As a consequence of central and peripheral sensitization, applying neural blocks may benefit to minimize the risk of PHN. This study aimed to explore whether CDDO could generate analgesic action in a PHN-rats' model. The behavioural test was determined by calibrated forceps testing. The number of apoptotic neurons and degree of glial cell reaction were assessed by immunofluorescence assay. Activation of PKC-δ and the phosphorylation of Akt were measured by western blots. CDDO improved PHN by decreasing TRPV1-positive nociceptive neurons, the apoptotic neurons, and reversed glial cell reaction in adult rats. It also suppressed the enhanced PKC-δ and p-Akt signalling in the sciatic nerve, dorsal root ganglia (DRG) and spinal dorsal horn. Our research is the promising report demonstrating the analgesic and neuroprotective action of CDDO in a PHN-rat's model by regulating central and peripheral sensitization targeting TRPV1, PKC-δ and p-Akt. It also is the first study to elucidate the role of oligodendrocyte in PHN.

IL-6 from cerebrospinal fluid causes widespread pain via STAT3-mediated astrocytosis in chronic constriction injury of the infraorbital nerve

BACKGROUND

The spinal inflammatory signal often spreads to distant segments, accompanied by widespread pain symptom under neuropathological conditions. Multiple cytokines are released into the cerebrospinal fluid (CSF), potentially inducing the activation of an inflammatory cascade at remote segments through CSF flow. However, the detailed alteration of CSF in neuropathic pain and its specific role in widespread pain remain obscure.

METHODS

A chronic constriction injury of the infraorbital nerve (CCI-ION) model was constructed, and pain-related behavior was observed on the 7th, 14th, 21st, and 28th days post surgery, in both vibrissa pads and hind paws. CSF from CCI-ION rats was transplanted to naïve rats through intracisternal injection, and thermal and mechanical allodynia were measured in hind paws. The alteration of inflammatory cytokines in CCI-ION's CSF was detected using an antibody array and bioinformatic analysis. Pharmacological intervention targeting the changed cytokine in the CSF and downstream signaling was performed to evaluate its role in widespread pain.

RESULTS

CCI-ION induced local pain in vibrissa pads together with widespread pain in hind paws. CCI-ION's CSF transplantation, compared with sham CSF, contributed to vibrissa pad pain and hind paw pain in recipient rats. Among the measured cytokines, interleukin-6 (IL-6) and leptin were increased in CCI-ION's CSF, while interleukin-13 (IL-13) was significantly reduced. Furthermore, the concentration of CSF IL-6 was correlated with nerve injury extent, which gated the occurrence of widespread pain. Both astrocytes and microglia were increased in remote segments of the CCI-ION model, while the inhibition of astrocytes in remote segments, but not microglia, significantly alleviated widespread pain. Mechanically, astroglial signal transducer and activator of transcription 3 (STAT3) in remote segments were activated by CSF IL-6, the inhibition of which significantly mitigated widespread pain in CCI-ION.

CONCLUSION

IL-6 was induced in the CSF of the CCI-ION model, triggering widespread pain via activating astrocyte STAT3 signal in remote segments. Therapies targeting IL-6/STAT3 signaling might serve as a promising strategy for the widespread pain symptom under neuropathological conditions.

Epigenetic regulation of autophagy in neuroinflammation and synaptic plasticity

Autophagy is a conserved cellular mechanism that enables the degradation and recycling of cellular organelles and proteins via the lysosomal pathway. In neurodevelopment and maintenance of neuronal homeostasis, autophagy is required to regulate presynaptic functions, synapse remodeling, and synaptic plasticity. Deficiency of autophagy has been shown to underlie the synaptic and behavioral deficits of many neurological diseases such as autism, psychiatric diseases, and neurodegenerative disorders. Recent evidence reveals that dysregulated autophagy plays an important role in the initiation and progression of neuroinflammation, a common pathological feature in many neurological disorders leading to defective synaptic morphology and plasticity. In this review, we will discuss the regulation of autophagy and its effects on synapses and neuroinflammation, with emphasis on how autophagy is regulated by epigenetic mechanisms under healthy and diseased conditions.

Multi-cohort cerebrospinal fluid proteomics identifies robust molecular signatures for asymptomatic and symptomatic Alzheimer's disease

Changes in Amyloid-β (A), hyperphosphorylated Tau (T) in brain and cerebrospinal fluid (CSF) precedes AD symptoms, making CSF proteome a potential avenue to understand the pathophysiology and facilitate reliable diagnostics and therapies. Using the AT framework and a three-stage study design (discovery, replication, and meta-analysis), we identified 2,173 proteins dysregulated in AD, that were further validated in a third totally independent cohort. Machine learning was implemented to create and validate highly accurate and replicable (AUC>0.90) models that predict AD biomarker positivity and clinical status. These models can also identify people that will convert to AD and those AD cases with faster progression. The associated proteins cluster in four different protein pseudo-trajectories groups spanning the AD continuum and were enrichment in specific pathways including neuronal death, apoptosis and tau phosphorylation (early stages), microglia dysregulation and endolysosomal dysfuncton(mid-stages), brain plasticity and longevity (mid-stages) and late microglia-neuron crosstalk (late stages).

Targeting the JAK2/STAT3 signaling pathway for chronic pain

Chronic pain is a notable health concern because of its prevalence, persistence, and associated mental stress. Drugs targeting chronic pain with potent abirritation, and minimal side effects remain unidentified. Substantial evidence indicates that the Janus Kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway plays a distinct and critical role in different stages of chronic pain. Aberrant activation of the JAK2/STAT3 signaling pathway is evident in multiple chronic pain models. Moreover, an increasing number of studies have demonstrated that the downregulation of JAK2/STAT3 can attenuate chronic pain in different animal models. In this review, we investigated the mechanism and role of the JAK2/STAT3 signaling pathway in modulating chronic pain. The aberrant activation of JAK2/STAT3 can trigger chronic pain by interacting with microglia and astrocytes, releasing proinflammatory cytokines, inhibiting anti-inflammatory cytokines, and regulating synaptic plasticity. We also retrospectively reviewed current reports on JAK2/STAT3 pharmacological inhibitors that demonstrated their significant therapeutic potential in different types of chronic pain. In summary, our results provide strong evidence that the JAK2/STAT3 signaling pathway is a promising therapeutic target for chronic pain.

Inhibition of spinal Rac1 attenuates chronic inflammatory pain by regulating the activation of astrocytes

BACKGROUND

Spinal astrocyte-mediated neuroinflammation is an important mechanism for the maintenance of chronic inflammatory pain. Previous studies have investigated that Ras-related C3 botulinum toxin substrate 1 (Rac1) is closely related to astrocyte activation after central nervous system injury. However, the role of Rac1 in astrocyte activation in chronic inflammatory pain has not been reported.

METHODS

Complete Freund's adjuvant (CFA)-induced chronic inflammatory pain model and LPS-stimulated astrocytes were used to investigate the role of Rac1 in astrocyte activation and the underlying mechanism. Rac1-interfering adeno-associated virus (AAV) targeting astrocytes was delivered to spinal astrocytes by intrathecal administration and a Rac1 specific inhibitor, NSC23766, was used to block cultured astrocytes. The glial fibrillary acidic protein (GFAP), proinflammatory cytokines, p-NF-κB, and nod-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome were detected by RT-qPCR, Western blotting, and immunofluorescence to investigate the activation of astrocytes.

RESULTS

CFA induced spinal astrocyte activation and increased the expression of active Rac1 in spinal astrocytes. Knockdown of astrocyte Rac1 alleviated chronic inflammatory pain and inhibited astrocyte activation. Inhibition of Rac1 activation in cultured astrocytes decreased the expression of GFAP and proinflammatory cytokines. Knockdown of Rac1 inhibited the increase of expression of NLRP3 inflammasome and phosphorylation of NF-κB in the spinal lumbar enlargement after CFA injection. Similarly, the inhibition of Rac1 suppressed the increase of NLRP3 inflammasome and p-NF-κB protein level after LPS stimulation.

CONCLUSION

Knockdown of astrocyte Rac1 attenuated CFA-induced hyperalgesia and astrocyte activation possibly by blocking the expression of NLRP3 inflammasome and phosphorylation of NF-κB.

Dietary Supplementation with 23-Hydroxy Ursolic Acid Reduces the Severity and Incidence of Acute Experimental Autoimmune Encephalomyelitis (EAE) in a Murine Model of Multiple Sclerosis

23-Hydroxy ursolic acid (23-OH UA) is a potent atheroprotective and anti-obesogenic phytochemical, with anti-inflammatory and inflammation-resolving properties. In this study, we examined whether dietary 23-OH UA protects mice against the acute onset and progression of experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis (MS). Female C57BL/6 mice were fed either a defined low-calorie maintenance diet (MD) or an MD supplemented with 0.2% wgt/wgt 23-OH UA for 5 weeks prior to actively inducing EAE and during the 30 days post-immunization. We observed no difference in the onset of EAE between the groups of mice, but ataxia and EAE disease severity were suppressed by 52% and 48%, respectively, and disease incidence was reduced by over 49% in mice that received 23-OH UA in their diet. Furthermore, disease-associated weight loss was strikingly ameliorated in 23-OH UA-fed mice. ELISPOT analysis showed no significant differences in frequencies of T cells producing IL-17 or IFN-γ between 23-OH UA-fed mice and control mice, suggesting that 23-OH UA does not appear to regulate peripheral T cell responses. In summary, our findings in EAE mice strongly suggest that dietary 23-OH UA may represent an effective oral adjunct therapy for the prevention and treatment of relapsing-remitting MS.

Shinbaro2 enhances axonal extension beyond the glial scar for functional recovery in rats with contusive spinal cord injury

Spinal cord injury (SCI) is a devastating event that often results in the inflammatory condition of glial scar tissue formation, impeding neural regeneration and recovery. Reducing the inflammatory response and inhibiting glial formation are promising strategies for improving SCI outcomes. Here, we introduce a new role for Shinbaro2 (Sh2), known for its anti-inflammatory and pain-reducing effects, in ameliorating glial scars formed in the damaged spinal cord and promoting axon growth after SCI. Sh2 was applied at various concentrations to cultivate primary spinal cord neurons. Concentrations of 1 and 2 mg/mL effectively enhanced cell viability and axonal outgrowth in spinal cord neurons subjected to hydrogen peroxide or laceration injury. Sh2 helped reduce neuroinflammation by increasing anti-inflammatory M2 macrophages (arginase 1) and decreasing inflammatory cells, ultimately reducing lesion size. In scar formation, Sh2 inhibited the expression of β-catenin and nestin in reactive astrocytes in the injured spinal cord. Moreover, Sh2 suppressed the expression of chondroitin sulfate proteoglycans and SOX9, which are involved in scar formation. Furthermore, Sh2 promoted the sprouting of serotonergic axons and the growth of neurofibrillary tangles, enhancing motor function recovery in SCI. These findings highlight the potential of Sh2 as an SCI therapeutic intervention, offering hope for neural and functional restoration in individuals with this debilitating condition.

Combination Gene Delivery Reduces Spinal Cord Pathology in Rats With Peripheral Neuropathic Pain

Although peripheral neuropathic pain is caused by peripheral nerve injury, it is not simply a peripheral nervous system disease. It causes abnormalities in both the central and peripheral nervous systems. Pathological phenomena, such as hyperactivation of sensory neurons and inflammation, are observed in both the dorsal root ganglion and spinal cord. Pain signals originating from the periphery are transmitted to the brain via the SC, and the signals are modulated by pathologically changing SC conditions. Therefore, the modulation of SC pathology is important for peripheral NP treatment. We investigated the effects of KLS-2031 (recombinant adeno-associated viruses expressing glutamate decarboxylase 65, glial cell-derived neurotrophic factor, and interleukin-10) delivered to the dorsal root ganglion on aberrant neuronal excitability and neuroinflammation in the SC of rats with peripheral NP. Results showed that KLS-2031 administration restored excessive excitatory transmission and inhibitory signals in substantia gelatinosa neurons. Moreover, KLS-2031 restored the in vivo hypersensitivity of wide dynamic range neurons and mitigated neuroinflammation in the SC by regulating microglia and astrocytes. Collectively, these findings demonstrated that KLS-2031 efficiently suppressed pathological pain signals and inflammation in the SC of peripheral NP model, and is a potential novel therapeutic approach for NP in clinical settings. PERSPECTIVE: Our study demonstrated that KLS-2031, a combination gene therapy delivered by transforaminal epidural injection, not only mitigates neuroinflammation but also improves SC neurophysiological function, including excitatory-inhibitory balance. These findings support the potential of KLS-2031 as a novel modality that targets multiple aspects of the complex pathophysiology of neuropathic pain.

A solid lipid particle formulation of long pepper extract reduces pain and astrocyte activation in a rat model of neuropathic pain

OBJECTIVES

To investigate the effects of solid lipid microparticle (SLM) creams containing a long pepper extract (LPE) or piperine on neuropathy-related pain and the expression of glial fibrillary acidic protein (GFAP) as a measure of astrogliosis.

METHODS

Neuropathic pain in male Spraque Dawley rats was induced by sciatic nerve ligation (SNL) and followed by treatment with LPE-SLM, piperine-SLM, capsaicin or vehicle creams. The pain score was assessed by thermal hyperalgesia test. The GFAP expression in the spinal cord was determined by immunohistochemistry.

RESULTS

Pain scores were significantly increased after SNL and decreased when treated by LPE-SLM. The number of GFAP immunopositive cells was significantly increased in the SNL rats. Treated by LPE-SLM and capsaicin creams resulted in a significant reduction of the number of GFAP immunopositive cells. The LPE-SLM treated rats showed greater effects than the piperine and capsaicin preparations.

CONCLUSIONS

The LPE-SLM cream has a potential effect on pain attenuation via a decrease of spinal astrocyte activation-related mechanism. The LPE in SLM preparation could provide an alternative therapeutic strategy for treating neuropathic pain.

PEG hydrogel containing dexamethasone-conjugated hyaluronic acid reduces secondary injury and improves motor function in a rat moderate TBI model

Traumatic brain injury (TBI) leads to long-term impairments in motor and cognitive function. TBI initiates a secondary injury cascade including a neuro-inflammatory response that is detrimental to tissue repair and limits recovery. Anti-inflammatory corticosteroids such as dexamethasone can reduce the deleterious effects of secondary injury; but challenges associated with dosing, administration route, and side effects have hindered their clinical application. Previously, we developed a hydrolytically degradable hydrogel (PEG-bis-AA/HA-DXM) composed of poly (ethylene) glycol-bis-(acryloyloxy acetate) (PEG-bis-AA) and dexamethasone-conjugated hyaluronic acid (HA-DXM) for local and sustained dexamethasone delivery. In this study, we evaluated the effect of locally applied PEG-bis-AA/HA-DXM hydrogel on secondary injury and motor function recovery after moderate controlled cortical impact (CCI) TBI. Hydrogel treatment significantly improved motor function evaluated by beam walk and rotarod tests compared to untreated rats over 7 days post-injury (DPI). We also observed that the hydrogel treatment reduced lesion volume, inflammatory response, astrogliosis, apoptosis, and increased neuronal survival compared to untreated rats at 7 DPI. These results suggest that PEG-bis-AA/HA-DXM hydrogels can mitigate secondary injury and promote motor functional recovery following moderate TBI.

Levodopa-induced dyskinesia: interplay between the N-methyl-D-aspartic acid receptor and neuroinflammation

Parkinson's disease (PD) is a common neurodegenerative disorder of middle-aged and elderly people, clinically characterized by resting tremor, myotonia, reduced movement, and impaired postural balance. Clinically, patients with PD are often administered levodopa (L-DOPA) to improve their symptoms. However, after years of L-DOPA treatment, most patients experience complications of varying severity, including the "on-off phenomenon", decreased efficacy, and levodopa-induced dyskinesia (LID). The development of LID can seriously affect the quality of life of patients, but its pathogenesis is unclear and effective treatments are lacking. Glutamic acid (Glu)-mediated changes in synaptic plasticity play a major role in LID. The N-methyl-D-aspartic acid receptor (NMDAR), an ionotropic glutamate receptor, is closely associated with synaptic plasticity, and neuroinflammation can modulate NMDAR activation or expression; in addition, neuroinflammation may be involved in the development of LID. However, it is not clear whether NMDA receptors are co-regulated with neuroinflammation during LID formation. Here we review how neuroinflammation mediates the development of LID through the regulation of NMDA receptors, and assess whether common anti-inflammatory drugs and NMDA receptor antagonists may be able to mitigate the development of LID through the regulation of central neuroinflammation, thereby providing a new theoretical basis for finding new therapeutic targets for LID.