Microglial Inhibitor Research Articles

Microglia stimulation produces antidepressant-like effects in a mouse depression model induced by adolescent chronic unpredictable stress.

Depression triggered by harmful stress in adolescents is a common phenomenon that can lead to serious social problems. Its treatment is still frustrating in the clinic. We reported the phenomenon that a 12-day chronic unpredictable stress (CUS), starting on postnatal day 28, led to a significant decrease in the number of microglia in the dentate gyrus of the hippocampus in adult mice. Reversal of this decline by a single injection of low-dose lipopolysaccharide (LPS), a classical immunostimulant, could rapidly reverse the depression-like behaviors induced by 12 days of CUS stimulation during adolescence. In the dose-dependent experiment, a single injection of LPS at doses of 75 and 100 μg/kg, but not at doses of 25 and 50 μg/kg, produced an antidepressant effect in mice exposed to 12-day CUS during adolescence. The time-dependent experiment showed that the antidepressant effect of the single LPS injection (100 μg/kg) occurred at time points 5 and 8 hours, but not 3 hours after LPS injection. The antidepressant effect of the single LPS injection (100 μg/kg) lasted for at least 7 days, and 14 days after the single LPS injection, a repeated injection could still induce the depressed mice to develop an antidepressant phenotype. Furthermore, inhibition of microglia by minocycline or depletion of microglia by PLX3397 was found to prevent the antidepressant effect of the single LPS injection. These results suggest that reversing the decline of microglia in the dentate gyrus may be a potential strategy for the treatment of depression induced by harmful stress in adolescents.

A novel monomeric amyloid β-activated signaling pathway regulates brain development via inhibition of microglia.

Amyloid β (Aβ) forms aggregates in the Alzheimer's disease brain and is well known for its pathological roles. Recent studies show that it also regulates neuronal physiology in the healthy brain. Whether Aβ also regulates glial physiology in the normal brain, however, has remained unclear. In this article, we describe the discovery of a novel signaling pathway activated by the monomeric form of Aβ in vitro that plays essential roles in the regulation of microglial activity and the assembly of neocortex during mouse development in vivo. We find that activation of this pathway depends on the function of amyloid precursor and the heterotrimeric G protein regulator Ric8a in microglia and inhibits microglial immune activation at transcriptional and post-transcriptional levels. Genetic disruption of this pathway during neocortical development results in microglial dysregulation and excessive matrix proteinase activation, leading to basement membrane degradation, neuronal ectopia, and laminar disruption. These results uncover a previously unknown function of Aβ as a negative regulator of brain microglia and substantially elucidate the underlying molecular mechanisms. Considering the prominence of Aβ and neuroinflammation in the pathology of Alzheimer's disease, they also highlight a potentially overlooked role of Aβ monomer depletion in the development of the disease.

A novel monomeric amyloid β-activated signaling pathway regulates brain development via inhibition of microglia

A novel monomeric amyloid β-activated signaling pathway regulates brain development via inhibition of microglia

Efficacy and safety of minocycline in retinitis pigmentosa: a prospective, open-label, single-arm trial

Retinitis pigmentosa (RP) is characterized by progressive photoreceptor cells death accelerated by the proliferation and activation of microglia pathologically. No consensus exists on the treatment. Minocycline is recognized as a microglia inhibitor with great anti-inflammatory and neuro-protective functions. However, efficacy of minocycline in RP patients is lacking. We conducted a prospective, open-label, and single-arm trial, in which daily oral minocycline of 100 mg was administered for 12 months in RP patients with light-adapted 30 Hz flicker electroretinography (ERG) amplitude >0 µV in at least one eye (NCT04068207). The primary outcome was the proportion of participants with improvement in the ERG amplitude at month 12. The secondary outcomes included improvements of the following items: other ERGs amplitudes, visual field, best-corrected visual acuity, contrast sensitivity, color vision, and NEI-VFQ-25. 35 of 288 patients met inclusive criteria were enrolled (median [IQR] age, 36 [31–45] years; 17 female [48.6%]). 32 participants completed all examinations, while 3 participants completed the 12-month online visit via conducting NEI-VFQ-25. The primary outcome showed improvement was 34.3% (12 of 35 [95% CI 19.1–52.2]). Similarly, all secondary outcomes showed improvements. Adverse events were reported in 22 participants (62.9%) and were all resolved without extra medication during the study period. No severe adverse events were recorded. Our findings identified daily oral minocycline of 100 mg for 12 months was beneficial in improving the visual function of RP patients with good safety. This study indicates minocycline may be a promising therapy for RP, but a randomized controlled trial is still needed of further exploration.

Microglia regulate motor neuron plasticity via reciprocal fractalkine and adenosine signaling

We report an important role for microglia in regulating neuroplasticity within phrenic motor neurons. Brief episodes of low oxygen (acute intermittent hypoxia; AIH) elicit a form of respiratory motor plasticity known as phrenic long-term facilitation (pLTF) that is regulated by the balance of competing serotonin vs adenosine-initiated cellular mechanisms. Serotonin arises from brainstem raphe neurons, but the source of adenosine is unknown. We tested if hypoxic episodes initiate phrenic motor neuron to microglia fractalkine signaling that evokes extracellular adenosine formation using a well-defined neurophysiology preparation in male rats. With moderate AIH, phrenic motor neuron adenosine 2A receptor activation undermines serotonin-dominant pLTF whereas severe AIH induces pLTF by the adenosine-dependent mechanism. Consequently, phrenic motor neuron fractalkine knockdown, microglial fractalkine receptor inhibition, and microglial ablation enhance moderate AIH, but suppress severe AIH-induced pLTF. We conclude, microglia play important roles in healthy spinal cords, regulating plasticity in motor neurons responsible for breathing.

A bottom-up approach identifies the antipsychotic and antineoplastic trifluoperazine and the ribose derivative deoxytubercidin as novel microglial phagocytosis inhibitors.

Phagocytosis is an indispensable function of microglia, the brain professional phagocytes. Microglia is particularly efficient phagocytosing cells that undergo programmed cell death (apoptosis) in physiological conditions. However, mounting evidence suggests microglial phagocytosis dysfunction in multiple brain disorders. These observations prompted us to search for phagocytosis modulators (enhancers or inhibitors) with therapeutic potential. We used a bottom-up strategy that consisted on the identification of phagocytosis modulators using phenotypic high throughput screenings (HTSs) in cell culture and validation in organotypic cultures and in vivo. We performed two complementary HTS campagnes: at Achucarro, we used primary cultures of mouse microglia and compounds of the Prestwick Chemical Library; at Roche, we used human iPSC derived macrophage-like cells and a proprietary chemo-genomic library with 2200 compounds with known mechanism-of-action. Next, we validated the more robust compounds using hippocampal organotypic cultures and identified two phagocytosis inhibitors: trifluoperazine, a dopaminergic and adrenergic antagonist used as an antipsychotic and antineoplastic; and deoxytubercidin, a ribose derivative. Finally, we tested whether these compounds were able to modulate phagocytosis of apoptotic newborn cells in the adult hippocampal neurogenic niche in vivo by administering them into the mouse hippocampus using osmotic minipumps. We confirmed that both trifluoperazine and deoxytubercidin have anti-phagocytic activity in vivo, and validated our bottom-up strategy to identify novel phagocytosis modulators. These results show that chemical libraries with annotated mechanism of action are an starting point for the pharmacological modulation of microglia in drug discovery projects aiming at the therapeutic manipulation of phagocytosis in brain diseases.

Sinomenine Ameliorated Microglial Activation and Neuropathic Pain After Chronic Constriction Injury Via TGF-β1/ALK5/Smad3 Signalling Pathway.

Sinomenine (SIN), a bioactive isoquinoline alkaloid extracted from the roots and stems of Sinomenium acutum, is efficacious against various chronic pain conditions. Inhibition of microglial activation at the spinal level contributes to the analgesic effects of SIN. Microglial activation in the spinal dorsal horn is key to sensitising neuropathic pain. Consequently, this study aimed to investigate whether the antinociceptive effects of SIN in neuropathic pain are induced through microglial inhibition and the underlying mechanisms. In this study, we observed that SIN alleviated chronic constriction injury (CCI)-induced pain hypersensitivity, spinal microglial activation and neuroinflammation. Consistently, SIN evoked the upregulation of transforming growth factor-beta1 (TGF-β1) and phosphorylated Smad3 in the L4-6 ipsilateral spinal dorsal horn of CCI mice. Intrathecal injection of TGF-β1 siRNA and an activin receptor-like receptor (ALK5) inhibitor reversed SIN's antinociceptive and antimicroglial effects on CCI mice. Moreover, targeting Smad3 invitro with siRNA dampened the inhibitory effect of TGF-β1 on lipopolysaccharide-induced microglial activation. Finally, targeting Smad3 abrogated SIN-induced pain relief and microglial inhibition in CCI mice. These findings indicate that the TGF-β1/ALK5/Smad3 axis plays a key role in the antinociceptive effects of SIN on neuropathic pain, indicating its suppressive ability on microglia.

Polymer nanotherapeutics: A promising approach toward microglial inhibition in neurodegenerative diseases.

Nanoparticles (NPs) that target multiple transport mechanisms facilitate targeted delivery of active therapeutic agents to the central nervous system (CNS) and improve therapeutic transport and efficacy across the blood-brain barrier (BBB). CNS nanotherapeutics mostly target neurons and endothelial cells, however, microglial immune cells are the first line of defense against neuronal damage and brain infections. Through triggering release of inflammatory cytokines, chemokines and proteases, microglia can however precipitate neurological damage-a significant factor in neurodegenerative diseases. Thus, microglial inhibitory agents are attracting much attention among those researching and developing novel treatments for neurodegenerative disorders. The most established inhibitors of microglia investigated to date are resveratrol, curcumin, quercetin, and minocycline. Thus, there is great interest in developing novel agents that can bypass or easily cross the BBB. One such approach is the use of modified-nanocarriers as, or for, delivery of, therapeutic agents to the brain and wider CNS. For microglial inhibition, polymeric NPs are the preferred vehicles for choice. Here, we summarize the immunologic and neuroinflammatory role of microglia, established microglia inhibitor agents, challenges of CNS drug delivery, and the nanotherapeutics explored for microglia inhibition to date. We also discuss applications of the currently considered "most useful" polymeric NPs for microglial-inhibitor drug delivery in CNS-related diseases.

The microglial innate immune receptor TREM2 participates in fear memory formation through excessive prelimbic cortical synaptic pruning.

Fear memory formation has been implicated in fear- and stress-related psychiatric disorders, including post-traumatic stress disorder (PTSD) and phobias. Synapse deficiency and microglial activation are common among patients with PTSD, and induced in animal models of fear conditioning. Increasing studies now focus on explaining the specific mechanisms between microglia and synapse deficiency. Though newly-identified microglia regulator triggering receptor expressed on myeloid cells 2 (TREM2) plays a role in microglial phagocytic activity, its role in fear-formation remains unknown. We successfully constructed a fear- formation model by foot-shock. Four days after foot-shock, microglial capacity of synaptic pruning was investigated via western blotting, immunofluorescence and Golgi-Cox staining. Prelimbic chemical deletion or microglia inhibition was performed to detect the role of microglia in synaptic loss and neuron activity. Finally, Trem2 knockout mice or wild-type mice with Trem2 siRNA injection were exposed to foot-shock to identify the involvement of TREM2 in fear memory formation. The results herein indicate that the foot-shock protocol in male mice resulted in a fear formation model. Mechanistically, fear conditioning enhanced the microglial capacity for engulfing synapse materials, and led to glutamatergic neuron activation in the prelimbic cortex. Prelimbic chemical deletion or microglia inhibition improved fear memory formation. Further investigation demonstrated that TREM2 regulates microglial phagocytosis, enhancing synaptic pruning. Trem2 knockout mice showed remarkable reductions in prelimbic synaptic pruning and reduced neuron activation, with decreased fear memory formation. Our cumulative results suggest that prelimbic TREM2-mediated excessive microglial synaptic pruning is involved in the fear memory formation process, leading to development of abnormal stress-related behavior.

Mechanical acupuncture at HT7 attenuates alcohol self-administration in rats by modulating neuroinflammation and altering mPFC-habenula-VTA circuit activity.

Alcohol use disorder is a chronic disorder with significant limitations in pharmacological treatments, necessitating the exploration of non-pharmacological interventions. We used a model of alcohol self-administration (10% v/v) to analyze behavioral, neurochemical, and signaling mechanisms. Our findings demonstrate that stimulation of the HT7 acupuncture point significantly decreased the frequency of active lever presses in rats self-administering alcohol (p < 0.05). Alcohol self-administration increased microglial activity and sigma 1 receptor expression in the habenula (Hb), while HT7 stimulation mitigated these effects, decreasing microglial activity and sigma 1 receptor levels (p < 0.05). Additionally, alcohol self-administration reduced brain-derived neurotrophic factor (BDNF) expression in the medial prefrontal cortex (mPFC) and increased tyrosine hydroxylase (TH) levels in the ventral tegmental area (VTA) (p < 0.05). HT7 stimulation reversed these alterations by increasing BDNF expression in the mPFC and decreasing TH levels in the VTA (p < 0.05). Further investigation revealed that BDNF microinjection into the mPFC inhibited sigma 1 receptor activity in the Hb, while microglial inhibition in the Hb decreased TH expression in the VTA (p < 0.05). The administration of the microglial inhibitor MINO to the Hb also reduced alcohol self-administration (p < 0.05). These results suggest that HT7 stimulation regulates the mPFC-Hb-VTA circuit, leading to decreased alcohol-seeking behavior. Our study demonstrates that HT7 acupuncture can modulate the mPFC-Hb-VTA circuit, providing a potential non-pharmacological treatment for alcohol-seeking behavior by influencing microglial activity, sigma 1 receptor expression, and TH levels. These findings contribute to a deeper understanding of the neural mechanisms underlying acupuncture's therapeutic effects on alcohol use disorder.

Telencephalic stab wound injury induces regenerative angiogenesis and neurogenesis in zebrafish: unveiling the role of vascular endothelial growth factor signaling and microglia.

JOURNAL/nrgr/04.03/01300535-202510000-00025/figure1/v/2024-11-26T163120Z/r/image-tiff After brain damage, regenerative angiogenesis and neurogenesis have been shown to occur simultaneously in mammals, suggesting a close link between these processes. However, the mechanisms by which these processes interact are not well understood. In this work, we aimed to study the correlation between angiogenesis and neurogenesis after a telencephalic stab wound injury. To this end, we used zebrafish as a relevant model of neuroplasticity and brain repair mechanisms. First, using the Tg( fli1:EGFP × mpeg1.1:mCherry ) zebrafish line, which enables visualization of blood vessels and microglia respectively, we analyzed regenerative angiogenesis from 1 to 21 days post-lesion. In parallel, we monitored brain cell proliferation in neurogenic niches localized in the ventricular zone by using immunohistochemistry. We found that after brain damage, the blood vessel area and width as well as expression of the fli1 transgene and vascular endothelial growth factor ( vegfaa and vegfbb ) were increased. At the same time, neural stem cell proliferation was also increased, peaking between 3 and 5 days post-lesion in a manner similar to angiogenesis, along with the recruitment of microglia. Then, through pharmacological manipulation by injecting an anti-angiogenic drug (Tivozanib) or Vegf at the lesion site, we demonstrated that blocking or activating Vegf signaling modulated both angiogenic and neurogenic processes, as well as microglial recruitment. Finally, we showed that inhibition of microglia by clodronate-containing liposome injection or dexamethasone treatment impairs regenerative neurogenesis, as previously described, as well as injury-induced angiogenesis. In conclusion, we have described regenerative angiogenesis in zebrafish for the first time and have highlighted the role of inflammation in this process. In addition, we have shown that both angiogenesis and neurogenesis are involved in brain repair and that microglia and inflammation-dependent mechanisms activated by Vegf signaling are important contributors to these processes. This study paves the way for a better understanding of the effect of Vegf on microglia and for studies aimed at promoting angiogenesis to improve brain plasticity after brain injury.

Central innate immunization induces tolerance against post-traumatic stress disorder-like behavior and neuroinflammatory responses in male mice

Post-traumatic stress disorder (PTSD) is a severe psychiatric disorder associated with abnormally elevated neuroinflammatory responses. Suppression of neuroinflammation is considered to be effective in ameliorating PTSD-like behaviors in rodents. Since pre-stimulation of microglia prior to stress exposure can prevent neuroinflammation, we hypothesized that pre-stimulation of microglia may prevent PTSD in animals. The results show that a single injection of a classical immune stimulant, lipopolysaccharide (LPS), at 50, 100 or 500, but not 10 μg/kg, one day before stress exposure, prevented the anxiety- and fear-like behaviors induced by modified single prolonged stress (mSPS). The time-dependent analysis shows that a single injection of LPS (100 μg/kg) either one or five, but not ten, days before stress prevented mSPS-induced anxiety- and fear-like behaviors. A second low-dose LPS injection 10 days after the first injection or a repeated LPS injection (4 × ) 10 days before stress induced tolerance to mSPS. Mechanistic studies show that a single injection of LPS one day before stress stimulation prevented mSPS-induced increases in levels of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and IL-6 mRNA in the hippocampus and medial prefrontal cortex. Inhibition of microglia by pretreatment with minocycline or depletion of microglia by PLX3397 abolished the preventive effect of low-dose LPS pre-injection on mSPS-induced anxiety- and fear-like behavior and neuroinflammatory responses. These results suggest that pre-stimulation of microglia may prevent the development of PTSD-like behaviors by attenuating the development of neuroinflammatory responses. This could help to develop new strategies to prevent the damaging effects of harmful stress on the brain.

Linarin inhibits microglia activation-mediated neuroinflammation and neuronal apoptosis in mouse spinal cord injury by inhibiting the TLR4/NF-κB pathway

To investigate the mechanism underlying the neuroprotective effect of linarin (LIN) against microglia activation-mediated inflammation and neuronal apoptosis following spinal cord injury (SCI). Fifty C57BL/6J mice (8- 10 weeks old) were randomized to receive sham operation, SCI and linarin treatment at 12.5, 25, and 50 mg/kg following SCI (n=10). Locomotor function recovery of the SCI mice was assessed using the Basso Mouse Scale, inclined plane test, and footprint analysis, and spinal cord tissue damage and myelination were evaluated using HE and LFB staining. Nissl staining, immunofluorescence assay and Western blotting were used to observe surviving anterior horn motor neurons in injured spinal cord tissue. In cultured BV2 cells, the effects of linarin against lipopolysaccharide (LPS)‑induced microglia activation, inflammatory factor release and signaling pathway changes were assessed with immunofluorescence staining, Western blotting, RT-qPCR, and ELISA. In a BV2 and HT22 cell co-culture system, Western blotting was performed to examine the effect of linarin against HT22 cell apoptosis mediated by LPS-induced microglia activation. Linarin treatment significantly improved locomotor function (P < 0.05), reduced spinal cord damage area, increased spinal cord myelination, and increased the number of motor neurons in the anterior horn of the SCI mice (P < 0.05). In both SCI mice and cultured BV2 cells, linarin effectively inhibited glial cell activation and suppressed the release of iNOS, COX-2, TNF-α, IL-6, and IL-1β, resulting also in reduced neuronal apoptosis in SCI mice (P < 0.05). Western blotting suggested that linarin-induced microglial activation inhibition was mediated by inhibition of the TLR4/NF- κB signaling pathway. In the cell co-culture experiments, linarin treatment significantly decreased inflammation-mediated apoptosis of HT22 cells (P < 0.05). The neuroprotective effect of linarin is medicated by inhibition of microglia activation via suppressing the TLR4/NF‑κB signaling pathway, which mitigates neural inflammation and reduce neuronal apoptosis to enhance motor function of the SCI mice.

The role of BTG2/PI3K/AKT pathway-mediated microglial activation in T-2 toxin-induced neurotoxicity

T-2 toxin is one of the mycotoxins widely distributed in human food and animal feed. Our recent work has shown that microglial activation may contribute to T-2 toxin-induced neurotoxicity. However, the molecular mechanisms involved need to be further clarified. To address this, we employed high-throughput transcriptome sequencing and found altered B cell translocation gene 2 (BTG2) expression levels in microglia following T-2 toxin treatment. It has been shown that altered BTG2 expression is involved in a range of neurological pathologies, but whether it’s involved in the regulation of microglial activation is unclear. The aim of this study was to investigate the role of BTG2 in T-2 toxin-induced microglial activation. The results of animal experiments showed that T-2 toxin caused neurobehavioral disorders and promoted the expression of microglial BTG2 and pro-inflammatory activation of microglia in hippocampus and cortical, while microglial inhibitor minocycline inhibited these changes. The results of in vitro experiments showed that T-2 toxin enhanced BTG2 expression and pro-inflammatory microglial activation, and inhibited BTG2 expression weakened T-2 toxin-induced microglial activation. Moreover, T-2 toxin activated PI3K/AKT and its downstream NF-κB signaling pathway, which could be reversed after knock-down of BTG2 expression. Meanwhile, the PI3K inhibitor LY294002 also blocked this process. Therefore, BTG2 may be involved in T-2 toxin's ability to cause microglial activation through PI3K/AKT/NF-κB pathway.

ID2-ETS2 axis regulates the transcriptional acquisition of pro-tumoral microglia phenotype in glioma

Glioblastoma is a highly aggressive brain tumour that creates an immunosuppressive microenvironment. Microglia, the brain’s resident immune cells, play a crucial role in this environment. Glioblastoma cells can reprogramme microglia to create a supportive niche that promotes tumour growth. However, the mechanisms controlling the acquisition of a transcriptome associated with a tumour-supportive microglial reactive state are not fully understood. In this study, we investigated changes in the transcriptional profile of BV2 microglia exposed to C6 glioma cells. RNA-sequencing analysis revealed a significant upregulation of microglial inhibitor of DNA binding 1 (Id1) and Id2, helix-loop-helix negative transcription regulatory factors. The concomitant regulation of microglial ETS proto-oncogene 2, transcription factor (ETS2)-target genes, i.e., Dusp6, Fli1, Jun, Hmox1, and Stab1, led us to hypothesize that ETS2 could be regulated by ID proteins. In fact, ID2-ETS2 protein interactions increased in microglia exposed to glioma cells. In addition, perturbation of the ID2-ETS2 transcriptional axis influenced the acquisition of a microglial tumour-supportive phenotype. ID2 and ETS2 genes were found to be expressed by the tumour-associated microglia isolated from human glioblastoma tumour biopsies. Furthermore, ID2 and ETS2 gene expressions exhibited inverse prognostic values in patients with glioma in cohorts from The Cancer Genome Atlas. Collectively, our findings indicate that the regulation of ETS2 by ID2 plays a role in the transcriptional regulation of microglia in response to stimuli originating from glioblastoma cells, information that could lead to developing therapeutic strategies to manipulate microglial tumour-trophic functions.

Microglial activation in the medial prefrontal cortex after remote fear recall participates in the regulation of auditory fear extinction

Excessive or inappropriate fear responses can lead to anxiety-related disorders, such as post-traumatic stress disorder (PTSD). Studies have shown that microglial activation occurs after fear conditioning and that microglial inhibition impacts fear memory. However, the role of microglia in fear memory recall remains unclear. In this study, we investigated the activated profiles of microglia after the recall of remote-cued fear memory and the role of activated microglia in the extinction of remote-cued fear in adult male C57BL/6 mice. The results revealed that the expression of the microglia marker Iba1 increased in the medial prefrontal cortex (mPFC) at 10 min and 1 h following remote-cued fear recall, which was accompanied by amoeboid morphology. Inhibiting microglial activation through PLX3397 treatment before remote fear recall did not affect recall, reconsolidation, or regular extinction but facilitated recall-extinction and mitigated spontaneous recovery. Moreover, our results demonstrated reduced co-expression of Iba1 and postsynaptic density protein 95 (PSD95) in the mPFC, along with decreases in the p-PI3K/PI3K ratio, p-Akt/Akt ratio, and KLF4 expression after PLX3397 treatment. Our results suggest that microglial activation after remote fear recall impedes fear extinction through the pruning of synapses in the mPFC, accompanied by alterations in the expression of the PI3K/AKT/KLF4 pathway. This finding can help elucidate the mechanism involved in remote fear extinction, contributing to the theoretical foundation for the intervention and treatment of PTSD.

GluR2 can Drive Neuroinflammation and Cognitive Impairments Following Peripherally Repeated Lipopolysaccharide Exposures.

Neuroinflammation is being increasingly recognized as a vital factor in the development of various neurological and neuropsychiatric diseases. Lipopolysaccharides (LPS), an outer membrane component of gram-negative bacteria, can trigger innate immune responses, resulting in neuroinflammation and subsequent cognitive deficits. The expression of glutamate receptors (GluRs) on glial cells can induce glial activation. Therefore, we hypothesized that repeated LPS exposure can increase GluR levels, promoting microglial activation and ultimately affecting synaptic plasticity and cognitive function. In this study, C57/BL6 mice were repeatedly exposed to LPS to construct a neuroinflammation animal model. The levels of GluRs, inflammatory cytokines, ionized calcium-binding adaptor molecule 1, postsynaptic density protein 95, synaptophysin 38, NMDA receptor 2A, and NMDA receptor 2B (GluN2B) were measured in the hippocampi. Furthermore, dendritic spine density in the CA1 hippocampal region was determined. Repeated LPS exposure induced cognitive impairments and microglial activation and increased GluR1 and GluR2 levels. This was accompanied by a significant decrease in GluN2B expression and dendritic spine density in the hippocampi. However, CFM-2, an α-amino-3- hydroxy-5-methyl-4-isoxazolepropionate receptor antagonist, reversed these anomalies. Furthermore, minocycline, a microglial inhibitor, reversed these anomalies and downregulated GluR2 but not GluR1 expression. In summary, we demonstrated that GluR2 plays an essential role in microglia-induced neuroinflammation, resulting in synaptic plasticity and cognitive impairment induced by repeated exposure to LPS.

Differential response of injured and healthy retinas to syngeneic and allogeneic transplantation of a clonal cell line of immortalized olfactory ensheathing glia: a double-edged sword.

JOURNAL/nrgr/04.03/01300535-202508000-00029/figure1/v/2024-09-30T120553Z/r/image-tiff Olfactory ensheathing glia promote axonal regeneration in the mammalian central nervous system, including retinal ganglion cell axonal growth through the injured optic nerve. Still, it is unknown whether olfactory ensheathing glia also have neuroprotective properties. Olfactory ensheathing glia express brain-derived neurotrophic factor, one of the best neuroprotectants for axotomized retinal ganglion cells. Therefore, we aimed to investigate the neuroprotective capacity of olfactory ensheating glia after optic nerve crush. Olfactory ensheathing glia cells from an established rat immortalized clonal cell line, TEG3, were intravitreally injected in intact and axotomized retinas in syngeneic and allogeneic mode with or without microglial inhibition or immunosuppressive treatments. Anatomical and gene expression analyses were performed. Olfactory bulb-derived primary olfactory ensheathing glia and TEG3 express major histocompatibility complex class II molecules. Allogeneically and syngenically transplanted TEG3 cells survived in the vitreous for up to 21 days, forming an epimembrane. In axotomized retinas, only the allogeneic TEG3 transplant rescued retinal ganglion cells at 7 days but not at 21 days. In these retinas, microglial anatomical activation was higher than after optic nerve crush alone. In intact retinas, both transplants activated microglial cells and caused retinal ganglion cell death at 21 days, a loss that was higher after allotransplantation, triggered by pyroptosis and partially rescued by microglial inhibition or immunosuppression. However, neuroprotection of axotomized retinal ganglion cells did not improve with these treatments. The different neuroprotective properties, different toxic effects, and different responses to microglial inhibitory treatments of olfactory ensheathing glia in the retina depending on the type of transplant highlight the importance of thorough preclinical studies to explore these variables.

Molecular Aspects Involved in the Mechanisms of Bothrops jararaca Venom-Induced Hyperalgesia: Participation of NK1 Receptor and Glial Cells.

Accidents caused by Bothrops jararaca (Bj) snakes result in several local and systemic manifestations, with pain being a fundamental characteristic. The inflammatory process responsible for hyperalgesia induced by Bj venom (Bjv) has been studied; however, the specific roles played by the peripheral and central nervous systems in this phenomenon remain unclear. To clarify this, we induced hyperalgesia in rats using Bjv and collected tissues from dorsal root ganglia (DRGs) and spinal cord (SC) at 2 and 4 h post-induction. Samples were labeled for Iba-1 (macrophage and microglia), GFAP (satellite cells and astrocytes), EGR1 (neurons), and NK1 receptors. Additionally, we investigated the impact of minocycline, an inhibitor of microglia, and GR82334 antagonist on Bjv-induced hyperalgesia. Our findings reveal an increase in Iba1 in DRG at 2 h and EGR1 at 4 h. In the SC, markers for microglia, astrocytes, neurons, and NK1 receptors exhibited increased expression after 2 h, with EGR1 continuing to rise at 4 h. Minocycline and GR82334 inhibited venom-induced hyperalgesia, highlighting the crucial roles of microglia and NK1 receptors in this phenomenon. Our results suggest that the hyperalgesic effects of Bjv involve the participation of microglial and astrocytic cells, in addition to the activation of NK1 receptors.

Dexamethasone attenuates neuropathic pain through spinal microglial expression of dynorphin A via the cAMP/PKA/p38 MAPK/CREB signaling pathway

This study aimed to elucidate the opioid mechanisms underlying dexamethasone-induced pain antihypersensitive effects in neuropathic rats. Dexamethasone (subcutaneous and intrathecal) and membrane-impermeable Dex-BSA (intrathecal) administration dose-dependently inhibited mechanical allodynia and thermal hyperalgesia in neuropathic rats. Dexamethasone and Dex-BSA treatments increased expression of dynorphin A in the spinal cords and primary cultured microglia. Dexamethasone specifically enhanced dynorphin A expression in microglia but not astrocytes or neurons. Intrathecal injection of the microglial metabolic inhibitor minocycline blocked dexamethasone-stimulated spinal dynorphin A expression; intrathecal minocycline, the glucocorticoid receptor antagonist Dex-21-mesylate, dynorphin A antiserum, and κ-opioid receptor antagonist GNTI completely blocked dexamethasone-induced mechanical antiallodynia and thermal antihyperalgesia. Additionally, dexamethasone elevated spinal intracellular cAMP levels, leading to enhanced phosphorylation of PKA, p38 MAPK and CREB. The specific adenylate cyclase inhibitor DDA, PKA inhibitor H89, p38 MAPK inhibitor SB203580 and CREB inhibitor KG-501 completely blocked dexamethasone-induced anti-neuropathic pain and increased microglial dynorphin A exprression. In conclusion, this study reveal that dexamethasone mitigateds neuropathic pain through upregulation of dynorphin A in spinal microglia, likely involving the membrane glucocorticoid receptor/cAMP/PKA/p38 MAPK/CREB signaling pathway.