Disruption of the Na+/K+-ATPase-purinergic P2X7 receptor complex in microglia promotes stress-induced anxiety.

Na+/K+-ATPase (NKA) plays an important role in the central nervous system. However, little is known about its function in the microglia. Here, we found that NKAα1 forms a complex with the purinergic P2X7 receptor (P2X7R), an adenosine 5'-triphosphate (ATP)-gated ion channel, under physiological conditions. Chronic stress or treatment with lipopolysaccharide plus ATP decreased the membrane expression of NKAα1 in microglia, facilitated P2X7R function, and promoted microglia inflammatory activation via activation of the NLRP3 inflammasome. Accordingly, global deletion or conditional deletion of NKAα1 in microglia under chronic stress-induced aggravated anxiety-like behavior and neuronal hyperexcitability. DR5-12D, a monoclonal antibody that stabilizes membrane NKAα1, improved stress-induced anxiety-like behavior and ameliorated neuronal hyperexcitability and neurogenesis deficits in the ventral hippocampus of mice. Our results reveal that NKAα1 limits microglia inflammation and may provide a target for the treatment of stress-related neuroinflammation and diseases.

Interleukin-10 Prevents Pathological Microglia Hyperactivation following Peripheral Endotoxin Challenge.

Microglia, the resident macrophages of the brain parenchyma, are key players in central nervous system (CNS) development, homeostasis, and disorders. Distinct brain pathologies seem associated with discrete microglia activation modules. How microglia regain quiescence following challenges remains less understood. Here, we explored the role of the interleukin-10 (IL-10) axis in restoring murine microglia homeostasis following a peripheral endotoxin challenge. Specifically, we show that lipopolysaccharide (LPS)-challenged mice harboring IL-10 receptor-deficient microglia displayed neuronal impairment and succumbed to fatal sickness. Addition of a microglial tumor necrosis factor (TNF) deficiency rescued these animals, suggesting a microglia-based circuit driving pathology. Single cell transcriptome analysis revealed various IL-10 producing immune cells in the CNS, including most prominently Ly49D+ NK cells and neutrophils, but not microglia. Collectively, we define kinetics of the microglia response to peripheral endotoxin challenge, including their activation and robust silencing, and highlight the critical role of non-microglial IL-10 in preventing deleterious microglia hyperactivation.

RND3 modulates microglial polarization and alleviates neuroinflammation in Parkinson's disease by suppressing NLRP3 inflammasome activation.

Neuroinflammation mediated by microglia plays an important role in the etiology of Parkinson's disease (PD). Rho family GTPase 3 (RND3) exerts anti-inflammatory effects and may act as a potential new inducer of neuroprotective phenotypes in microglia. However, whether RND3 can be used to regulate microglia activation or reduce neuroinflammation in PD remains elusive. The study investigated the microglia modulating effects and potential anti-inflammatory effects of RND3 in vivo and in vitro, using animal models of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD and cell models of BV-2 cells stimulated by LPS plus IFN-γ with or without RND3-overexpression. The results showed that RND3 was highly expressed in the MPTP-induced PD mouse model and BV-2 cells treated with LPS and IFN-γ. In vivo experiments confirmed that RND3 overexpression could modulate microglia phenotype and ameliorate MPTP-induced neuroinflammation through inhibiting activation of the NLRP3 inflammasome in substantia nigra pars compacta (SNpc). In vitro study showed that RND3 overexpression could attenuate the production of pro-inflammatory factors in BV2 cells stimulated by LPS and IFN-γ. Mechanistically, RND3 reduced the activation of the NLRP3 inflammasome upon LPS and IFN-γ stimulation. Taken together, these findings suggest that RND3 modulates microglial polarization and alleviates neuroinflammation in Parkinson's disease by suppressing NLRP3 inflammasome activation.

Interleukin-9 protects from microglia- and TNF-mediated synaptotoxicity in experimental multiple sclerosis.

BACKGROUND: Multiple sclerosis (MS) is a progressive neurodegenerative disease of the central nervous system characterized by inflammation-driven synaptic abnormalities. Interleukin-9 (IL-9) is emerging as a pleiotropic cytokine involved in MS pathophysiology. METHODS: Through biochemical, immunohistochemical, and electrophysiological experiments, we investigated the effects of both peripheral and central administration of IL-9 on C57/BL6 female mice with experimental autoimmune encephalomyelitis (EAE), a model of MS. RESULTS: We demonstrated that both systemic and local administration of IL-9 significantly improved clinical disability, reduced neuroinflammation, and mitigated synaptic damage in EAE. The results unveil an unrecognized central effect of IL-9 against microglia- and TNF-mediated neuronal excitotoxicity. Two main mechanisms emerged: first, IL-9 modulated microglial inflammatory activity by enhancing the expression of the triggering receptor expressed on myeloid cells-2 (TREM2) and reducing TNF release. Second, IL-9 suppressed neuronal TNF signaling, thereby blocking its synaptotoxic effects. CONCLUSIONS: The data presented in this work highlight IL-9 as a critical neuroprotective molecule capable of interfering with inflammatory synaptopathy in EAE. These findings open new avenues for treatments targeting the neurodegenerative damage associated with MS, as well as other inflammatory and neurodegenerative disorders of the central nervous system.

The RNA m6A modification might participate in microglial activation during hypoxic-ischemic brain damage in neonatal mice.

BACKGROUND: The RNA m6A modification has been implicated in multiple neurological diseases as well as macrophage activation. However, whether it regulates microglial activation during hypoxic-ischemic brain damage (HIBD) in neonates remains unknown. Here, we aim to examine whether the m6A modification is involved in modulating microglial activation during HIBD. We employed an oxygen and glucose deprivation microglial model for in vitro studies and a neonatal mouse model of HIBD. The brain tissue was subjected to RNA-seq to screen for significant changes in the mRNA m6A regulator. Thereafter, we performed validation and bioinformatics analysis of the major m6A regulators. RESULTS: RNA-seq analysis revealed that, among 141 m6A regulators, 31 exhibited significant differential expression (FC (abs) ≥ 2) in HIBD mice. We then subjected the major m6A regulators Mettl3, Mettl14, Fto, Alkbh5, Ythdf1, and Ythdf2 to further validation, and the results showed that all were significantly downregulated in vitro and in vivo. GO analysis reveals that regulators are mainly involved in the regulation of cellular and metabolic processes. The KEGG results indicate the involvement of the signal transduction pathway. CONCLUSIONS: Our findings demonstrate that m6A modification of mRNA plays a crucial role in the regulation of microglial activation in HIBD, with m6A-associated regulators acting as key modulators of microglial activation.

Binge ethanol exposure in advanced age elevates neuroinflammation and early indicators of neurodegeneration and cognitive impairment in female mice.

Binge drinking is rising among aged adults (>65 years of age), however the contribution of alcohol misuse to neurodegenerative disease development is not well understood. Both advanced age and repeated binge ethanol exposure increase neuroinflammation, which is an important component of neurodegeneration and cognitive dysfunction. Surprisingly, the distinct effects of binge ethanol exposure on neuroinflammation and associated degeneration in the aged brain have not been well characterized. Here, we establish a model of intermittent binge ethanol exposure in young and aged female mice to investigate the effects of advanced age and binge ethanol on these outcomes. Following intermittent binge ethanol exposure, expression of pro-inflammatory mediators (tnf-α, il-1ß, ccl2) was distinctly increased in isolated hippocampal tissue by the combination of advanced age and ethanol. Binge ethanol exposure also increased measures of senescence, the nod like receptor pyrin domain containing 3 (NLRP3) inflammasome, and microglia reactivity in the brains of aged mice compared to young. Binge ethanol exposure also promoted neuropathology in the hippocampus of aged mice, including tau hyperphosphorylation and neuronal death. We further identified advanced age-related deficits in contextual memory that were further negatively impacted by ethanol exposure. These data suggest binge drinking superimposed with advanced age promotes early markers of neurodegenerative disease development and cognitive decline, which may be driven by heightened neuroinflammatory responses to ethanol. Taken together, we propose this novel exposure model of intermittent binge ethanol can be used to identify therapeutic targets to prevent advanced age- and ethanol-related neurodegeneration.

The role of the Toll like receptor 4 signaling in sex-specific persistency of depression-like behavior in response to chronic stress.

Chronic stress is a major risk factor for Major Depressive Disorder (MDD), and it has been shown to impact the immune system and cause microglia activation in the medial prefrontal cortex (mPFC) involved in the pathogenesis of depression. The aim of this study is to further investigate cellular and molecular mechanisms underlying persistent depression behavior in sex specific manner, which is observed clinically. Here, we report that both male and female mice exhibited depression-like behavior following exposure to chronic stress. However, only female mice showed persistent depression-like behavior, which was associated with microglia activation in mPFC, characterized by distinctive alterations in the phenotype of microglia. Given these findings, to further investigate the underlying molecular mechanisms associated with persistent depression-like behavior and microglia activation in female mice, we used translating-ribosome affinity purification (TRAP). We find that Toll like receptor 4 (TLR4) signaling is casually related to persistent depression-like behavior in female mice. This is supported by the evidence that the fact that genetic ablation of TLR4 expression in microglia significantly reduced the persistent depression-like behavior to baseline levels in female mice. This study tentatively supports the hypothesis that the TLR4 signaling in microglia may be responsible for the sex differences in persistent depression-like behavior in female.

Free heme induces neuroinflammation and cognitive impairment by microglial activation via the TLR4/MyD88/NF-κB signaling pathway.

BACKGROUND: Red blood cells (RBCs) transfusion is related to perioperative neurocognitive disorders. The toxic effect of free heme has been identified in many pathologies. However, the underlying mechanisms of RBCs transfusion or free heme in cognitive impairment have not been clearly explored. Therefore, this research was conducted to determine the mechanism of free heme-induced neuroinflammation and cognitive impairment. METHODS: Rats were received intraperitoneal injection of hemin alone or combined with intracerebroventricular injection of Hemopexin (HPX), and MWM test was conducted to measure cognitive function. The amount of heme-HPX complexes was evaluated by flow cytometry for CD91 + cells. The microglial inflammatory response in rat brain was observed by immunofluorescence staining of Iba-1, and the inflammatory factors of TNF-α, IL-1ß and IL-6 in rat brain and BV2 cells were detected by ELISA analysis. Furthermore, neuronal apoptosis in HT22 cells alone and in HT22 + BV2 coculture system was detected by flow cytometry and immunofluorescence staining. Finally, western blot was conducted to detect TLR4/MyD88/NF-κB proteins in rat brain and BV2 cells treated with hemin or combined with pathway inhibitors. Additionally, the M1 surface marker CD86 was observed in BV2 cells to further confirm neuroinflammation. RESULTS: Intraperitoneal injection of hemin induced cognitive impairment, increase of CD91 + cells, up-regulation of TNF-α and IL-1ß, down-regulation of IL-6, activation of microglia, and activation of the TLR4/MyD88/NF-κB signaling pathway in rat brain. Significantly, intracerebroventricular injection of HPX reduced the above effects. Hemin induced boost of TNF-α, IL-1ß and IL-6 in BV2 cells, as well as apoptosis in HT22 cells. Notably, when HT22 cells were cocultured with BV2 cells, apoptosis was significantly increased. Hemin also induced activation of the TLR4/MyD88/NF-κB signaling pathway and increased the M1 surface marker CD86 in BV2 cells, and inhibiting this pathway reduced the inflammatory responses. CONCLUSIONS: Free heme induces cognitive impairment, and the underlying mechanism may involve neuronal apoptosis and microglial inflammation via the TLR4/MyD88/NF-κB signaling pathway. HPX may have potential therapeutic effects. Video Abstract.

Extracellular vesicles from hyperammonemic rats induce neuroinflammation in hippocampus and impair cognition in control rats.

Patients with liver cirrhosis show hyperammonemia and peripheral inflammation and may show hepatic encephalopathy with cognitive impairment, reproduced by rats with chronic hyperammonemia. Peripheral inflammation induces neuroinflammation in hippocampus of hyperammonemic rats, altering neurotransmission and leading to cognitive impairment. Extracellular vesicles (EVs) may transmit pathological effects from the periphery to the brain. We hypothesized that EVs from peripheral blood would contribute to cognitive alterations in hyperammonemic rats. The aims were to assess whether EVs from plasma of hyperammonemic rats (HA-EVs) induce cognitive impairment and to identify the underlying mechanisms. Injection of HA-EVs impaired learning and memory, induced microglia and astrocytes activation and increased TNFα and IL-1ß. Ex vivo incubation of hippocampal slices from control rats with HA-EVs reproduced these alterations. HA-EVs increased membrane expression of TNFR1, reduced membrane expression of TGFßR2 and Smad7 and IκBα levels and increased IκBα phosphorylation. This led to increased activation of NF-κB and IL-1ß production, altering membrane expression of NR2B, GluA1 and GluA2 subunits, which would be responsible for cognitive impairment. All these effects of HA-EVs were prevented by blocking TNFα, indicating that they were mediated by enhanced activation of TNFR1 by TNFα. We show that these mechanisms are very different from those leading to motor incoordination, which is due to altered GABAergic neurotransmission in cerebellum. This demonstrates that peripheral EVs play a key role in the transmission of peripheral alterations to the brain in hyperammonemia and hepatic encephalopathy, inducing neuroinflammation and altering neurotransmission in hippocampus, which in turn is responsible for the cognitive deficits.

IFP35 family proteins promote neuroinflammation and multiple sclerosis.

Excessive activation of T cells and microglia represents a hallmark of the pathogenesis of human multiple sclerosis (MS). However, the regulatory molecules overactivating these immune cells remain to be identified. Previously, we reported that extracellular IFP35 family proteins, including IFP35 and NMI, activated macrophages as proinflammatory molecules in the periphery. Here, we investigated their functions in the process of neuroinflammation both in the central nervous system (CNS) and the periphery. Our analysis of clinical transcriptomic data showed that expression of IFP35 family proteins was up-regulated in patients with MS. Additional in vitro studies demonstrated that IFP35 and NMI were released by multiple cells. IFP35 and NMI subsequently triggered nuclear factor kappa B-dependent activation of microglia via the TLR4 pathway. Importantly, we showed that both IFP35 and NMI activated dendritic cells and promoted naïve T cell differentiation into Th1 and Th17 cells. Nmi-/- , Ifp35-/- , or administration of neutralizing antibodies against IFP35 alleviated the immune cells' infiltration and demyelination in the CNS, thus reducing the severity of experimental autoimmune encephalomyelitis. Together, our findings reveal a hitherto unknown mechanism by which IFP35 family proteins facilitate overactivation of both T cells and microglia and propose avenues to study the pathogenesis of MS.

Apigenin and inflammation in the brain: can apigenin inhibit neuroinflammation in preclinical models?

Apigenin is a flavone-kind of flavonoid present in fruits and vegetables. Apigenin exhibits biological activities including neuropharmacological effects against different neurological disorders. In this study, we summarize and discuss the molecular mechanisms of the anti-neuroinflammatory effects of apigenin in neurological disorders. A systematic review was conducted by searching Google Scholar, Web of Science, Scopus and PubMed. A total of 461 records were retrieved from the search. After screening of the records based on the inclusion criteria, 16 articles were selected and discussed in this study. The results from the selected studies showed that apigenin exhibited anti-neuroinflammatory effect in preclinical studies. The anti-neuroinflammatory mechanisms exhibited by apigenin include inhibition of overproduction of pro-inflammatory cytokines, attenuation of microglia activation via reduction of CD-11b-positive cells, inhibition of ROCK-1 expression and upregulation of miR-15a, p-ERK1/2, p-CREB, and BDNF, downregulation of NLRP3 inflammasome, iNOS and COX-2 expression, reduction of Toll-like receptor-4 expression and inhibition of nuclear factor-kappa B (NF-kB) activation. Overall, apigenin inhibited neuroinflammation which suggests it confers neuroprotective effect against neuronal degeneration in some neurodegenerative conditions. This review provides important neuropharmacological information on the neuroprotective mechanisms of apigenin against neuroinflammation which may be useful for future preclinical and clinical studies.

The effect of Banxia-houpo decoction on CUMS-induced depression by promoting M2 microglia polarization via TrkA/Akt signalling.

It has been reported that Banxia-houpo decoction (BXHPD) serves as the anti-depressant treatment for a mild and severe depressive disease with limited side effects. The present study was performed to evaluate the protective effect of BXHPD on chronic unpredicted mild stress (CUMS)-induced depression and explore its effect on TrkA/Akt-mediated microglia polarization. The CUMS procedure was carried out, and the mice were intragastrically treated with BXHPD once daily. The selective TrkA inhibitor GW441756 was applied to further investigate the role of TrkA in BXHPD-mediated microglia polarization. The behaviour test including open field test (OFT), sucrose preference test (SPT), novelty-suppressed feeding test (NSFT), tail suspension test (TST) and forced swim test (FST) was performed. The concentrations of pro-inflammatory cytokines IL-6, TNF-α, IL-1ß, IL-12 and anti-inflammatory cytokines IL-4, IL-10 were determined using Enzyme-linked immunosorbent assay. The population of Iba1+ cells and the length of microglia processes were observed under the fluorescence microscope. The mRNA expressions of Arg1, Ym1 and Fizzl1 were measured by PCR. The protein expressions of TrkA, p-Tyr490-TrkA, p-Ser473-Akt, p-Ser473-Akt1, p-Ser474-Akt2, p-CREB and Jmjd3 were detected by western blot. Our results showed that BXHPD attenuated CUMS-induced depressive-like behaviour, promoted anti-inflammatory cytokines, inhibited pro-inflammatory cytokines, suppressed microglia activation, promoted M2 phenotype-specific indices and upregulated the expressions of TrkA, p-Tyr490-TrkA, p-Ser473-Akt, p-Ser473-Akt1, p-Ser474-Akt2, p-CREB and Jmjd3. The above beneficial effect of BXHPD can be blocked by TrkA inhibitor GW441756. This work demonstrated that BXHPD exerted an anti-depressant effect by promoting M2 phenotype microglia polarization via TrkA/Akt pathway.

Pretreatment of the ROS Inhibitor Phenyl-N-tert-butylnitrone Alleviates Sleep Deprivation-Induced Hyperalgesia by Suppressing Microglia Activation and NLRP3 Inflammasome Activity in the Spinal Dorsal Cord.

Sleep deprivation, a common perioperative period health problem, causes ocular discomfort and affects postsurgical pain. However, the mechanism of sleep deprivation-induced increased pain sensitivity is elusive. This study aims to explore the role of ROS in sleep deprivation (SD)-induced hyperalgesia and the underlying mechanism. A 48-h continuous SD was performed prior to the hind paw incision pain modeling in mice. We measured ROS levels, microglial activation, DNA damage and protein levels of iNOS, NLRP3, p-P65 and P65 in mouse spinal dorsal cord. The involvement of ROS in SD-induced prolongation of postsurgical pain was further confirmed by intrathecal injection of ROS inhibitor, phenyl-N-tert-butylnitrone (PBN). Pretreatment of 48-h SD in mice significantly prolonged postsurgical pain recovery, manifesting as lowered paw withdrawal mechanical threshold and paw withdrawal thermal latency. It caused ROS increase and upregulation of iNOS on both Day 1 and 7 in mouse spinal dorsal cord. In addition, upregulation of NLRP3 and p-P65, microglial activation and DNA damage were observed in mice pretreated with 48-h SD prior to the incision. Notably, intrathecal injection of PBN significantly reversed the harmful effects of SD on postsurgical pain recovery, hyperalgesia, microglial activation and DNA damage via the NF-κB signaling pathway. Collectively, ROS increase is responsible for SD-induced hyperalgesia through activating microglial, triggering DNA damage and enhancing NLRP3 inflammasome activity in the spinal dorsal cord.

Taurine inhibits KDM3a production and microglia activation in lipopolysaccharide-treated mice and BV-2 cells.

Microglia activation has been suggested as the key factor in neuro-inflammation and thus participates in neurological diseases. Although taurine exhibits anti-inflammatory and neuro-protective effects, its underlying epigenetic mechanism is unknown. In this study, taurine was administered to lipopolysaccharide (LPS)-treated mice and BV-2 cells. Behavioral test, morphological analyze, detection of microglia activation, and lysine demethylase 3a (KDM3a) measurements were performed to investigate the mechanism by which taurine regulates KDM3a and subsequently antagonizes microglia activation. Taurine improved the sociability of LPS-treated mice, inhibited microglia activation in the hippocampus, and reduced generation of brain inflammatory factors, such as interleukin-6, tumor necrosis factor-α, inducible nitric oxide synthase, and cyclooxygenase-2. Meanwhile, taurine suppressed the LPS-induced increase in microglial KDM3a, and increased the level of mono-, di- or tri-methylation of lysine 9 on histone H3 (H3K9me1/2/3). Furthermore, taurine inhibited the LPS-induced increase in KDM3a, elevated the H3K9me1/2/3 level, and reduced inflammatory factors and reactive oxygen species in a concentration-dependent manner in LPS-stimulated BV-2 cells. In conclusion, taurine inhibited KDM3a and microglia activation, thereby playing an anti-inflammatory role in LPS-treated mice and BV-2 cells.

Dexmedetomidine postconditioning alleviates spinal cord ischemia-reperfusion injury in rats via inhibiting neutrophil infiltration, microglia activation, reactive gliosis and CXCL13/CXCR5 axis activation.

PURPOSE: Spinal cord ischemia-reperfusion (I/R) injury is an unresolved complication and its mechanisms are still not completely understood. Here, we studied the neuroprotective effects of dexmedetomidine (DEX) postconditioning against spinal cord I/R injury in rats and explored the possible mechanisms. MATERIALS AND METHODS: In the study, rats were randomly divided into five groups: sham group, I/R group, DEX0.5 group, DEX2.5 group, and DEX5 group. I/R injury was induced in experimental rats; 0.5 µg/kg, 2.5 µg/kg, 5 µg/kg DEX were intravenously injected upon reperfusion respectively. Neurological function, histological assessment, and the disruption of blood-spinal cord barrier (BSCB) were evaluated via the BBB scoring, hematoxylin and eosin staining, Evans Blue (EB) extravasation and spinal cord edema, respectively. Neutrophil infiltration was evaluated via Myeloperoxidase (MPO) activity. Microglia activation and reactive gliosis was evaluated via ionized calcium-binding adapter molecule-1(IBA-1) and glial fibrillary acidic protein (GFAP) immunofluorescence, respectively. The expression of C-X-C motif ligand 13 (CXCL13), C-X-C chemokine receptor type 5(CXCR5), caspase-3 was determined by western blotting. The expression levels of interleukin 6(IL-6), tumor necrosis factor-α(TNF-α), IL-1ß were determined by ELISA assay. RESULTS: DEX postconditioning preserved neurological assessment scores, improved histological assessment scores, attenuated BSCB leakage after spinal cord I/R injury. Neutrophil infiltration, microglia activation and reactive gliosis were also inhibited by DEX postconditioning. The expression of CXCL13, CXCR5, caspase-3, IL-6, TNF-α, IL-1ß were reduced by DEX postconditioning. CONCLUSIONS: DEX postconditioning alleviated spinal cord I/R injury, which might be mediated via inhibition of neutrophil infiltration, microglia activation, reactive gliosis and CXCL13/CXCR5 axis activation.

Microglia polarization in nociplastic pain: mechanisms and perspectives.

Nociplastic pain is the third classification of pain as described by the International Association for the Study of Pain (IASP), in addition to the neuropathic and nociceptive pain classes. The main pathophysiological mechanism for developing nociplastic pain is central sensitization (CS) in which pain amplification and hypersensitivity occur. Fibromyalgia is the prototypical nociplastic pain disorder, characterized by allodynia and hyperalgesia. Much scientific data suggest that classical activation of microglia in the spinal cord mediates neuroinflammation which plays an essential role in developing CS. In this review article, we discuss the impact of microglia activation and M1/M2 polarization on developing neuroinflammation and nociplastic pain, besides the molecular mechanisms engaged in this process. In addition, we mention the impact of microglial modulators on M1/M2 microglial polarization that offers a novel therapeutic alternative for the management of nociplastic pain disorders. Illustrating the mechanisms underlying microglia activation in central sensitization and nociplastic pain. LPS lipopolysaccharide, TNF-α tumor necrosis factor-α, INF-γ Interferon gamma, ATP adenosine triphosphate, 49 P2Y12/13R purinergic P2Y 12/13 receptor, P2X4/7R purinergic P2X 4/7 receptor, SP Substance P, NK-1R Neurokinin 1 receptor, CCL2 CC motif ligand 2, CCR2 CC motif ligand 2 receptor, CSF-1 colony-stimulating factor 1, CSF-1R colony-stimulating factor 1 receptor, CX3CL1 CX3C motif ligand 1, CX3XR1 CX3C motif ligand 1 receptor, TLR toll-like receptor, MAPK mitogen-activated protein kinases, JNK jun N-terminal kinase, ERK extracellular signal-regulated kinase, iNOS Inducible nitric oxide synthase, IL-1ß interleukin-1ß, IL-6 interleukin-6, BDNF brain-derived neurotrophic factor, GABA γ-Aminobutyric acid, GABAR γ-Aminobutyric acid receptor, NMDAR N-methyl-D-aspartate receptor, AMPAR α-amino-3-hydroxy-5-methyl-4-isoxazolepropi-onic acid receptor, IL-4 interleukin-4, IL-13 interleukin-13, IL-10 interleukin-10, Arg-1 Arginase 1, FGF fibroblast growth factor, GDNF glial cell-derived neurotrophic factor, IGF-1 insulin-like growth factor-1, NGF nerve growth factor, CD Cluster of differentiation.

[Mechanism of Mongolian drug Naru-3 in initiation of neuroinflammation of neuropathic pain from MMP9/IL-1ß signaling pathway].

Neuropathic pain(NP) has similar phenotypes but different sequential neuroinflammatory mechanisms in the pathological process. It is of great significance to inhibit the initiation of neuroinflammation, which has become a new direction of NP treatment and drug development in recent years. Mongolian drug Naru-3 is clinically effective in the treatment of trigeminal neuralgia, sciatica, and other NPs in a short time, but its pharmacodynamic characteristics and mechanism of analgesia are still unclear. In this study, a spinal nerve ligation(SNL) model simulating clinical peripheral nerve injury was established and the efficacy and mechanism of Naru-3 in the treatment of NPs was discussed by means of behavioral detection, side effect evaluation, network analysis, and experimental verification. Pharmacodynamic results showed that Naru-3 increased the basic pain sensitivity threshold(mechanical hyperalgesia and thermal radiation hyperalgesia) in the initiation of SNL in animals and relieved spontaneous pain, however, there was no significant effect on the basic pain sensitivity threshold and motor coordination function of normal animals under physiological and pathological conditions. Meanwhile, the results of primary screening of target tissues showed that Naru-3 inhibited the second phase of injury-induced nociceptive response of formalin test in mice and reduced the expression of inflammatory factors in the spinal cord. Network analysis discovered that Naru-3 had synergy in the treatment of NP, and its mechanism was associated with core targets such as matrix metalloproteinase-9(MMP9) and interleukin-1ß(IL-1ß). The experiment further took the dorsal root ganglion(DRG) and the stage of patho-logical spinal cord as the research objects, focusing on the core targets of inducing microglial neuroinflammation. By means of Western blot, immunofluorescence, agonists, antagonists, behavior, etc., the mechanism of Naru-3 in exerting NP analgesia may be related to the negative regulation of the MMP9/IL-1ß signaling pathway-mediated microglia p38/IL-1ß inflammatory loop in the activation phase. The relevant research enriches the biological connotation of Naru-3 in the treatment of NP and provides references for clinical rational drug use.

A novel aquaporin-4-associated optic neuritis rat model with severe pathological and functional manifestations.

BACKGROUND: Optic neuritis (ON) is a common manifestation of aquaporin-4 (AQP4) antibody seropositive neuromyelitis optica (NMO). The extent of tissue damage is frequently severe, often leading to loss of visual function, and there is no curative treatment for this condition. To develop a novel therapeutic strategy, elucidating the underlying pathological mechanism using a clinically relevant experimental ON model is necessary. However, previous ON animal models have only resulted in mild lesions with limited functional impairment. In the present study, we attempted to establish a feasible ON model with severe pathological and functional manifestations using a high-affinity anti-AQP4 antibody. Subsequently, we aimed to address whether our model is suitable for potential drug evaluation by testing the effect of minocycline, a well-known microglia/macrophage inhibitor. METHODS: AQP4-immunoglobulin G (IgG)-related ON in rats was induced by direct injection of a high-affinity anti-AQP4 monoclonal antibody, E5415A. Thereafter, the pathological and functional characterizations were performed, and the therapeutic potential of minocycline was investigated. RESULTS: We established an experimental ON model that reproduces the histological characteristics of ON in seropositive NMO, such as loss of AQP4/glial fibrillary acidic protein immunoreactivity, immune cell infiltration, and extensive axonal damage. We also observed that our rat model exhibited severe visual dysfunction. The histological analysis showed prominent accumulation of macrophages/activated microglia in the lesion site in the acute phase. Thus, we investigated the possible effect of the pharmacological inhibition of macrophages/microglia activation by minocycline and revealed that it effectively ameliorated axonal damage and functional outcome. CONCLUSIONS: We established an AQP4-IgG-induced ON rat model with severe functional impairments that reproduce the histological characteristics of patients with NMO. Using this model, we revealed that minocycline treatment ameliorates functional and pathological outcomes, highlighting the usefulness of our model for evaluating potential therapeutic drugs for ON in NMO.

Pregabalin mitigates microglial activation and neuronal injury by inhibiting HMGB1 signaling pathway in radiation-induced brain injury.

BACKGROUND: Radiation-induced brain injury (RIBI) is the most serious complication of radiotherapy in patients with head and neck tumors, which seriously affects the quality of life. Currently, there is no effective treatment for patients with RIBI, and identifying new treatment that targets the pathological mechanisms of RIBI is urgently needed. METHODS: Immunofluorescence staining, western blotting, quantitative real-time polymerase chain reaction (Q-PCR), co-culture of primary neurons and microglia, terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay, enzyme-linked immunosorbent assay (ELISA), and CRISPR-Cas9-mediated gene editing techniques were employed to investigate the protective effects and underlying mechanisms of pregabalin that ameliorate microglial activation and neuronal injury in the RIBI mouse model. RESULTS: Our findings showed that pregabalin effectively repressed microglial activation, thereby reducing neuronal damage in the RIBI mouse model. Pregabalin mitigated inflammatory responses by directly inhibiting cytoplasmic translocation of high-mobility group box 1 (HMGB1), a pivotal protein released by irradiated neurons which induced subsequent activation of microglia and inflammatory cytokine expression. Knocking out neuronal HMGB1 or microglial TLR2/TLR4/RAGE by CRISPR/Cas9 technique significantly inhibited radiation-induced NF-κB activation and pro-inflammatory transition of microglia. CONCLUSIONS: Our findings indicate the protective mechanism of pregabalin in mitigating microglial activation and neuronal injury in RIBI. It also provides a therapeutic strategy by targeting HMGB1-TLR2/TLR4/RAGE signaling pathway in the microglia for the treatment of RIBI.

Investigation and modulation of interleukin-6 following subarachnoid hemorrhage: targeting inflammatory activation for cerebral vasospasm.

BACKGROUND: Cerebral vasospasm (CV) can contribute to significant morbidity in subarachnoid hemorrhage (SAH) patients. A key unknown is how CV induction is triggered following SAH. METHODS: Human aneurysmal blood and cerebral spinal fluid were collected for evaluation. To confirm mechanism, c57/bl6 wild type and c57/bl6 IL-6 female knockout (KO) mice were utilized with groups: saline injected, SAH, SAH + IL-6 blockade, SAH IL-6 KO, SAH IL-6 KO + IL-6 administration, SAH + p-STAT3 inhibition. Dual-labeled microglia/myeloid mice were used to show myeloid diapedesis. For SAH, 50 µm blood was collected from tail puncture and administered into basal cisterns. IL-6 blockade was given at various time points. Various markers of neuroinflammation were measured with western blot and immunohistochemistry. Cerebral blood flow was also measured. Vasospasm was measured via cardiac injection of India ink/gelatin. Turning test and Garcia's modified SAH score were utilized. P < 0.05 was considered significant. RESULTS: IL-6 expression peaked 3 days following SAH (p < 0.05). Human IL-6 was increased in aneurysmal blood (p < 0.05) and in cerebral spinal fluid (p < 0.01). Receptor upregulation was periventricular and perivascular. Microglia activation following SAH resulted in increased caveolin 3 and myeloid diapedesis. A significant increase in BBB markers endothelin 1 and occludin was noted following SAH, but reduced with IL-6 blockade (p < 0.01). CV occurred 5 days post-SAH, but was absent in IL-6 KO mice and mitigated with IL-6 blockade (p < 0.05). IL-6 blockade, and IL-6 KO mitigated effects of SAH on cerebral blood flow (p < 0.05). SAH mice had impaired performance on turn test and poor modified Garcia scores compared to saline and IL-6 blockade. A distinct microglia phenotype was noted day 5 in the SAH group (overlap coefficients r = 0.96 and r = 0.94) for Arg1 and iNOS, which was altered by IL-6 blockade. Day 7, a significant increase in toll-like receptor 4 and Stat3 was noted. This was mitigated by IL-6 blockade and IL-6 KO, which also reduced Caspase 3 (p < 0.05). To confirm the mechanism, we developed a p-STAT3 inhibitor that targets the IL-6 pathway and this reduced NFΚB, TLR4, and nitrotyrosine (p < 0.001). Ventricular dilation and increased Tunel positivity was noted day 9, but resolved by IL-6 blockade (p < 0.05). CONCLUSION: Correlation between IL-6 and CV has been well documented. We show that a mechanistic connection exists via the p-STAT3 pathway, and IL-6 blockade provides benefit in reducing CV and its consequences mediated by myeloid cell origin diapedesis.