Role Of Microglial Activation Research Articles

MicroRNA367 negatively regulates the inflammatory response of microglia by targeting IRAK4 in intracerebral hemorrhage.

BackgroundIntracerebral hemorrhage (ICH) induces microglial activation and the release of inflammatory cytokines, leading to inflammation in the brain. IRAK4, an essential component of the MyD88-dependent pathway, activates subsets of divergent signaling pathways in inflammation.MethodsIn the experiment, microglia were stimulated with erythrocyte lysates, and then miR-367, IRAK4, NF-ĸB activation and downstream proinflammatory mediator production were analyzed. In addition, inflammation, brain edema, and neurological functions in ICH mice were also assessed.ResultsHere, we report that ICH downregulated miR-367 expression but upregulated IRAK4 expression in primary microglia. We also demonstrate that miR-367 suppressed IRAK4 expression by directly binding its 3′-untranslated region. MiR-367 inhibited NF-ĸB activation and downstream proinflammatory mediator production. Knocking down IRAK4 in microglia significantly decreased the IRAK4 expression and inhibited the NF-ĸB activation and the downstream production of proinflammatory mediators. In addition, our results indicate that miR-367 could inhibit expression of proinflammatory cytokines, reduce brain edema, and improve neurological functions in ICH mice.ConclusionsIn conclusion, our study demonstrates that miR-367/IRAK4 pathway plays an important role in microglial activation and neuroinflammation in ICH. Our finding also suggests that miR-367 might represent a potential therapeutic target for ICH.

Widespread microglial activation in patients deceased from traumatic brain injury

Primary objective: The role of microglial activation in traumatic brain injury (TBI) has been extensively described in established animal models. In contrast, very few studies have analysed this process in human patients, the majority being focused on the local reaction in the contused parenchyma. In this work, the main objective was the analysis of microglial activation in brain regions distant from the primary lesion.Research design: Morphological changes of microglia were evaluated in the cerebral cortex of patients deceased from TBI in comparison with control subjects.Methods and procedures: Cortical samples from five cases with TBI and 10 controls were evaluated using Ricinus communis lectin histochemistry and conventional Hematoxylin-eosin staining.Main outcomes and results: It was observed that microglial cells from patients with TBI presented shorter and thicker cellular projections compared with controls. Moreover, the percentage of histological area reactive to lectin was statistically higher in samples from subjects with TBI. These signs of microglial activation were observed in all of the analysed cortical areas, thus indicating a generalized effect on the whole cerebral cortex. The results are consistent with previous imaging PET studies performed in living patients with the 11C-PK11195 radiotracer.Conclusions: The findings indicate that TBI induces a widespread activation of brain microglia which affects all cortical areas, including those distant from the contusion site.

In vivo dynamics of retinal microglial activation during neurodegeneration: confocal ophthalmoscopic imaging and cell morphometry in mouse glaucoma.

Microglia, which are CNS-resident neuroimmune cells, transform their morphology and size in response to CNS damage, switching to an activated state with distinct functions and gene expression profiles. The roles of microglial activation in health, injury and disease remain incompletely understood due to their dynamic and complex regulation in response to changes in their microenvironment. Thus, it is critical to non-invasively monitor and analyze changes in microglial activation over time in the intact organism. In vivo studies of microglial activation have been delayed by technical limitations to tracking microglial behavior without altering the CNS environment. This has been particularly challenging during chronic neurodegeneration, where long-term changes must be tracked. The retina, a CNS organ amenable to non-invasive live imaging, offers a powerful system to visualize and characterize the dynamics of microglia activation during chronic disorders. This protocol outlines methods for long-term, in vivo imaging of retinal microglia, using confocal ophthalmoscopy (cSLO) and CX3CR1(GFP/+) reporter mice, to visualize microglia with cellular resolution. Also, we describe methods to quantify monthly changes in cell activation and density in large cell subsets (200-300 cells per retina). We confirm the use of somal area as a useful metric for live tracking of microglial activation in the retina by applying automated threshold-based morphometric analysis of in vivo images. We use these live image acquisition and analyses strategies to monitor the dynamic changes in microglial activation and microgliosis during early stages of retinal neurodegeneration in a mouse model of chronic glaucoma. This approach should be useful to investigate the contributions of microglia to neuronal and axonal decline in chronic CNS disorders that affect the retina and optic nerve.

Role of Microglial Activation in the Pathophysiology of Bacterial Meningitis.

Bacterial meningitis is a life-threatening infection associated with cognitive impairment in many survivors. The pathogen invades the central nervous system (CNS) by penetrating through the luminal side of the cerebral endothelium, which is an integral part of the blood-brain barrier. The replication of bacteria within the subarachnoid space occurs concomitantly with the release of their compounds that are highly immunogenic. These compounds known as pathogen-associated molecular patterns (PAMPs) may lead to both an increase in the inflammatory response in the host and also microglial activation. Microglia are the resident macrophages of the CNS which, when activated, can trigger a host of immunological pathways. Classical activation increases the production of pro-inflammatory cytokines, chemokines, and reactive oxygen species, while alternative activation is implicated in the inhibition of inflammation and restoration of homeostasis. The inflammatory response from classical microglial activation can facilitate the elimination of invasive microorganisms; however, excessive or extended microglial activation can result in neuronal damage and eventually cell death. This review aims to discuss the role of microglia in the pathophysiology of bacterial meningitis as well as the process of microglial activation by PAMPs and by endogenous constituents that are normally released from damaged cells known as danger-associated molecular patterns (DAMPs).

SIRT2 is required for lipopolysaccharide-induced activation of BV2 microglia.

It has been reported that inhibition of sirtuin 2 (SIRT2), a sirtuin family protein, can decrease cellular and tissue injuries in models of Parkinson's disease (PD) and Huntington's disease (HD); however, the mechanisms underlying these observations have remained unclear. Because inflammation plays key pathological roles in multiple major neurological disorders including PD and HD, in our current study we tested our hypothesis that SIRT2 plays an important role in microglial activation. We found that treatment of BV2 microglia with lipopolysaccharides led to significant increases in NO and inducible nitric oxide synthase mRNA levels, as well as increases in the levels of tumor necrosis factor-α and interleukin 6 mRNA, which indicated microglial activation. These increases were significantly decreased in the cells with SIRT2 silencing-produced decreases in the SIRT2 level. These observations suggest that SIRT2 is required for lipopolysaccharide-induced microglial activation. The findings also suggest that SIRT2 may be a therapeutic target for inhibiting the inflammatory responses in neurological disorders such as PD and HD.

Effect of bilateral cervical vagotomy on microglial activation in spinal cord in a rat model of persistent postoperative pain

Objective To investigate the effect of bilateral cervical vagotomy on microglial activation in spinal cord in a rat model of persistent postoperative pain evoked by skin/muscle incision and retraction (SMIR). Methods Thirty six male Sprague-Dawley rats were randomly divided into three groups (n= 12 each group): group sham operation, group SMIR, and group SMIR+ bilateral cervical vagotomy (SV). The rat model of persistent postoperative pain evoked by SMIR was established according to the method described by Flatter. Pain behavior was assessed by paw mechanical withdrawal threshold (MWT) to von Frey filament stimulation at 1, 3, and 5 days after operation. Four animals were sacrificed at each time point in each group to detect the expression of Iba-1 (a specific marker of microglia) in the spinal dorsal horn with immunofluorescence and the microglia was counted. Results MWT was significantly decreased at T1-5 in SMIR and SV (10.3±0.6, 9.7±0.8, 9.6±0.5; 8.0±0.7, 7.7±0.4, 7.6±0.3), while the expression of Iba-1 and microglia counts in the spinal dorsal horn were significantly increased at T1-5 in SMIR and SV (1428±134, 1245±129, and 1001±117; 8.0±0.7, 7.7±0.4, and 7.6±0.3; 187±13, 164±11, and 142±14; and 241±21, 230±21, and 202±19). In group SV as compared to group SMIR, MWT was significantly decreased at T1-5, while the expression of Iba-1 and microglia counts in the spinal dorsal horn were significantly increased at T1-5. Conclusions Vagus nerve plays an important role in microglial activation in spinal cord in a rat model of persistent postoperative pain evoked by skin/muscle incision and retraction. Key words: Vagotomy; Pain, postoperative; Microglia; Rats, Sprague-Dawley

Inhibition of microglial activation and induction of neurotrophic factors by flavonoids: a potential therapeutic strategy against Parkinson's disease.

Parkinson’s disease(PD)is characterized by the progressive degeneration of dopaminergic(DA)neurons and a decrease in striatal dopamine,which is associated with clinical movement disorders including a tremor at rest,rigidity of the limbs,bradykinesia(slowness and paucity of voluntary movement)and postural instability(a tendency to fall even in the absence of

The role of Galectin-3 in α-synuclein-induced microglial activation.

BackgroundParkinson’s disease (PD) is the most prevalent neurodegenerative motor disorder. The neuropathology is characterized by intraneuronal protein aggregates of α-synuclein and progressive degeneration of dopaminergic neurons within the substantia nigra. Previous studies have shown that extracellular α-synuclein aggregates can activate microglial cells, induce inflammation and contribute to the neurodegenerative process in PD. However, the signaling pathways involved in α-synuclein-mediated microglia activation are poorly understood. Galectin-3 is a member of a carbohydrate-binding protein family involved in cell activation and inflammation. Therefore, we investigated whether galectin-3 is involved in the microglia activation triggered by α-synuclein.ResultsWe cultured microglial (BV2) cells and induced cell activation by addition of exogenous α-synuclein monomers or aggregates to the cell culture medium. This treatment induced a significant increase in the levels of proinflammatory mediators including the inducible Nitric Oxide Synthase (iNOS), interleukin 1 Beta (IL-1β) and Interleukin-12 (IL-12). We then reduced the levels of galectin-3 expression using siRNA or pharmacologically targeting galectin-3 activity using bis-(3-deoxy-3-(3-fluorophenyl-1H-1,2,3-triazol-1-yl)-β-D-galactopyranosyl)-sulfane. Both approaches led to a significant reduction in the observed inflammatory response induced by α-synuclein. We confirmed these findings using primary microglial cells obtained from wild-type and galectin-3 null mutant mice. Finally, we performed injections of α-synuclein in the olfactory bulb of wild type mice and observed that some of the α-synuclein was taken up by activated microglia that were immunopositive for galectin-3.ConclusionsWe show that α-synuclein aggregates induce microglial activation and demonstrate for the first time that galectin-3 plays a significant role in microglia activation induced by α-synuclein. These results suggest that genetic down-regulation or pharmacological inhibition of galectin-3 might constitute a novel therapeutic target in PD and other synucleinopathies.Electronic supplementary materialThe online version of this article (doi:10.1186/s40478-014-0156-0) contains supplementary material, which is available to authorized users.

Lithium ameliorates lipopolysaccharide-induced microglial activation via inhibition of toll-like receptor 4 expression by activating the PI3K/Akt/FoxO1 pathway.

BackgroundLithium, an effective mood stabilizer for the treatment of bipolar disorders, has been recently suggested to have a role in neuroprotection during neurodegenerative diseases. The pathogenesis of neurological disorders often involves the activation of microglia and associated inflammatory processes. Thus, in this study, we aimed to understand the role of lithium in microglial activation and to elucidate the underlying mechanism(s).MethodsPrimary microglial cells were pretreated with lithium and stimulated with lipopolysaccharide (LPS). The cells were assessed regarding the responses of pro-inflammatory cytokines, and the associated signaling pathways were evaluated.ResultsLithium significantly inhibited LPS-induced microglial activation and pro-inflammatory cytokine production. Further analysis showed that lithium could activate PI3K/Akt signaling. Analyses of the associated signaling pathways demonstrated that the lithium pretreatment led to the suppression of LPS-induced toll-like receptor 4 (TLR4) expressions via the PI3K/Akt/FoxO1 pathway.ConclusionsThis study demonstrates that lithium can inhibit LPS-induced TLR4 expression and microglial activation through the PI3K/Akt/FoxO1 signaling pathway. These results suggest that lithium plays an important role in microglial activation and neuroinflammation-related diseases, which may lead to a new therapeutic strategy for the treatment of neuroinflammation-related disorders.

The role of microglia activation in the development of sepsis-induced long-term cognitive impairment.

Oxidative stress and inflammation is likely to be a major step in the development of sepsis-associated encephalopathy (SAE) and long-term cognitive impairment. To date, it is not known whether brain inflammation and oxidative damage are a direct consequence of systemic inflammation or whether these events are driven by brain resident cells, such as microglia. Therefore, the aim of this study is to evaluate the effect of minocycline on behavioral and neuroinflammatory parameters in rats submitted to sepsis. Male Wistar rats were subjected to sepsis by cecal ligation and puncture (CLP). The animals were divided into sham-operated (Sham+control), sham-operated plus minocycline (sham+MIN), CLP (CLP+control) and CLP plus minocycline (CLP+MIN) (100 μg/kg, administered as a single intracerebroventricular (ICV) injection). Some animals were killed 24h after surgery to assess the breakdown of the blood brain barrier, cytokine levels, oxidative damage to lipids (TBARS) and proteins in the hippocampus. Some animals were allowed to recover for 10 days when step-down inhibitory avoidance and open-field tasks were performed. Treatment with minocycline prevented an increase in markers of oxidative damage and inflammation in the hippocampus after sepsis. This was associated with an improvement in long-term cognitive performance. In conclusion, we demonstrated that the inhibition of the microglia by an ICV injection of minocycline was able to decrease acute brain oxidative damage and inflammation as well as long-term cognitive impairment in sepsis survivors.

Inflammation-related and Brain-enriched MicroRNAs Influence the Activation of Microglia Response to In vitro Oxygen-Glucose Deprivation

Microglia is one of the major resident immunecompetent cells in the central nervous system (CNS) and has become an important cellular component for understanding brain diseases. MicroRNAs (miRNAs) are small, noncoding RNAs that regulate the post-transcriptional expression of protein-coding mRNAs; miRNAs may play key roles in microglial activation in response to brain ischemia and other stressors. Through culturing primary rat microglial cells and establishing a microglial activation model by oxygen-glucose deprivation (OGD). We found that the viability of the microglia was time-dependent. Expressions of inflammation-related miRNAs (miR-146a, -21, -181a, -221, and -222), and brain-enriched miRNAs (miR-124, -134, -9, -132, and -138) in microglia were modulated in an OGD model of ischemic insult. This research highlight discusses the findings of the recent study and the investigators’ active research endeavors.

Effects of Brilliant Blue G on Serum Tumor Necrosis Factor-α Levels and Depression-like Behavior in Mice after Lipopolysaccharide Administration.

ObjectiveAccumulating evidence suggests that inflammation plays a role in the pathophysiology of major depression. The adenosine triphosphate (ATP)-sensitive P2X7 receptor (P2X7R) plays a crucial role in microglial activation caused by inflammation. The dye brilliant blue G (BBG) is a P2X7R antagonist. This study examined whether BBG shows antidepressant effects in an inflammation-induced model of depression.MethodsWe examined the effects of BBG (12.5, 25, or 50 mg/kg) on serum tumor necrosis factor-α (TNF-α) levels after administering the bacterial endotoxin lipopolysaccharide (LPS; 0.5 mg/kg) and the effects of BBG (50 mg/kg) on depression-like behavior in the tail-suspension test (TST) and forced swimming test (FST).ResultsPretreatment with BBG (12.5, 25, or 50 mg/kg) significantly blocked the increase in serum TNF-α levels after a single dose of LPS (0.5 mg/kg). Furthermore, BBG (50 mg/kg) significantly attenuated the increase in immobility time in the TST and FST after LPS (0.5 mg/kg) administration.ConclusionThe results suggest that BBG has anti-inflammatory and antidepressant effects in mice after LPS administration. Therefore, P2X7R antagonists are potential therapeutic drugs for inflammation-related major depression.

The role of Galectin-3 in ¿-synuclein-induced microglial activation

BackgroundParkinson's disease (PD) is the most prevalent neurodegenerative motor disorder. The neuropathology is characterized by intraneuronal protein aggregates of α-synuclein and progressive degeneration of dopaminergic neurons within the substantia nigra. Previous studies have shown that extracellular α-synuclein aggregates can activate microglial cells, induce inflammation and contribute to the neurodegenerative process in PD. However, the signaling pathways involved in α-synuclein-mediated microglia activation are poorly understood. Galectin-3 is a member of a carbohydrate-binding protein family involved in cell activation and inflammation. Therefore, we investigated whether galectin-3 is involved in the microglia activation triggered by α-synuclein.ResultsWe cultured microglial (BV2) cells and induced cell activation by addition of exogenous α-synuclein monomers or aggregates to the cell culture medium. This treatment induced a significant increase in the levels of proinflammatory mediators including the inducible Nitric Oxide Synthase (iNOS), interleukin 1 Beta (IL-1β) and Interleukin-12 (IL-12). We then reduced the levels of galectin-3 expression using siRNA or pharmacologically targeting galectin-3 activity using bis-(3-deoxy-3-(3-fluorophenyl-1H-1,2,3-triazol-1-yl)-β-D-galactopyranosyl)-sulfane. Both approaches led to a significant reduction in the observed inflammatory response induced by α-synuclein. We confirmed these findings using primary microglial cells obtained from wild-type and galectin-3 null mutant mice. Finally, we performed injections of α-synuclein in the olfactory bulb of wild type mice and observed that some of the α-synuclein was taken up by activated microglia that were immunopositive for galectin-3.ConclusionsWe show that α-synuclein aggregates induce microglial activation and demonstrate for the first time that galectin-3 plays a significant role in microglia activation induced by α-synuclein. These results suggest that genetic down-regulation or pharmacological inhibition of galectin-3 might constitute a novel therapeutic target in PD and other synucleinopathies.

Changes in Microglial Inflammation-Related and Brain-Enriched MicroRNAs Expressions in Response to In Vitro Oxygen–Glucose Deprivation

Microglia plays important role in central nervous system immune surveillance and has emerged as an essential cellular component for understanding brain diseases. MicroRNAs (miRs) are small, noncoding RNAs that regulate the post-transcriptional expression of protein-coding mRNAs, which may have key roles in microglial activation in response to brain ischemia and other stressors. Primary cultured rat microglial cells were prepared, and then microglial activation model was established by oxygen-glucose deprivation (OGD) method. Morphological observation, CD11b/c immunofluorence, MTT assay and Propidium iodide staining were done to test microglia viability at different OGD time points (0, 5, 10, 15, 30, 60min). qPCR were performed to detect the dynamic changes in expressions of inflammation-related miRs (146a, 21, 181a, 221, and 222) and brain-enriched miRs (124, 134, 9, 132, and 138) in resting microglia and after challenge with OGD for the same time points. The activation and viability of the microglia was time dependent. Similarly, expressions of different miRs in microglia were significantly upregulated and reached the peak at different time points before reaching the baseline level with extension of OGD. Our data demonstrates for the first time that OGD as a model of an ischemic insult modulates the expressions of some inflammation-related and brain-enriched miRs. These changes may help to explore the molecular basis of microglia activation on the post-transcriptional level in response to different time points of OGD.

Zinc is released by cultured astrocytes as a gliotransmitter under hypoosmotic stress-loaded conditions and regulates microglial activity

AimAstrocytes contribute to the maintenance of brain homeostasis via the release of gliotransmitters such as ATP and glutamate. Here we examined whether zinc was released from astrocytes under stress-loaded conditions, and was involved in the regulation of microglial activity as a gliotransmitter. Main methodsHypoosmotic stress was loaded to astrocytes using balanced salt solution prepared to 214–314mOsmol/L, and then intra- and extra-cellular zinc levels were assessed using Newport Green DCF diacetate (NG) and ICP-MS, respectively. Microglial activation by the astrocytic supernatant was assessed by their morphological changes and poly(ADP-ribose) (PAR) polymer accumulation. Key findingsExposure of astrocytes to hypoosmotic buffer, increased the extracellular ATP level in osmolarity-dependent manners, indicating a load of hypoosmotic stress. In hypoosmotic stress-loaded astrocytes, there were apparent increases in the intra- and extra-cellular zinc levels. Incubation of microglia in the astrocytic conditioned medium transformed them into the activated “amoeboid” form and induced PAR formation. Administration of an extracellular zinc chelator, CaEDTA, to the astrocytic conditioned medium almost completely prevented the microglial activation. Treatment of astrocytes with an intracellular zinc chelator, TPEN, suppressed the hypoosmotic stress-increased intracellular, but not the extracellular, zinc level, and the increase in the intracellular zinc level was blocked partially by a nitric oxide synthase inhibitor, but not by CaEDTA, indicating that the mechanisms underlying the increases in the intra- and extra-cellular zinc levels might be different. SignificanceThese findings suggest that under hypoosmotic stress-loaded conditions, zinc is released from astrocytes and then plays a primary role in microglial activation as a gliotransmitter.

Mo1843 Parenteral Fish Oil Reverses Cholestasis in Parenteral Nutrition Associated Liver Disease

from liver failure. 2) Investigate the role of microglial activation and recruitment in the pathogenesis of HE. Methods: Male C57Bl/6 mice were injected with 100 mg/kg of the hepatotoxin azoxymethane (AOM) to induce HE. Mice were monitored for signs of cognitive impairment and brains were collected and dissected prior to neurological symptoms, at the onset of minor and major ataxia, and at coma. In parallel, mice were then injected with 100mg/kg/day of CCR2 antagonist or CCR4 antagonist for three days prior to the injection of AOM. Tissue was collected at the time that coma was reached. Immunofluorescence, immunoblotting, and real time PCR was performed for CCL2, CCR2, and CCR4. Microglia activation was assessed by immunofluorescence against the microglia marker Iba1. Results: CCL2 mRNA expression is greatly increased prior to the onset of neurological decline in the cortex and remains elevated when compared to vehicle-treated controls. CCL2 protein was significantly elevated in the cortex but not the cerebellum as determined by immunoblotting. Immunofluorescence validated this effect and found localized immunoreactivity of CCL2 with the neuron marker NeuN. Correlated with elevated CCL2 expression was increased microglia activation as demonstrated by Iba1 immunoreactivity. Treatment with CCR2 and CCR4 antagonists, which inhibit CCL2 activity, reducedmicroglia activation and neurological decline of AOM mice. Conclusions: The data demonstrates that CCL2 is upregulated during HE and inhibiting its activity via CCR2 or CCR4 antagonists slows HE progression. This supports that during HE neurons may release CCL2 to recruit and activate microglia leading to pathological inflammation.

Interaction of inflammatory and anti-inflammatory responses in microglia by Staphylococcus aureus-derived lipoteichoic acid

We investigated the interaction between proinflammatory and inflammatory responses caused by Staphylococcus aureus-derived lipoteichoic acid (LTA) in primary cultured microglial cells and BV-2 microglia. LTA induced inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein levels increase in a concentration- and time-dependent manner. Meanwhile, LTA also increased nitric oxide (NO) and PGE2 production in microglia. Administration of TLR2 antagonist effectively inhibited LTA-induced NO, iNOS, and COX-2 expression. Moreover, treatment of cells with LTA caused a time-dependent activation of ERK, p38, JNK, as well as AKT. We also found that LTA-induced iNOS and COX-2 up-regulation were attenuated by p38, JNK, and PI3-kinase inhibitors. On the other hand, LTA-enhanced HO-1 expression was attenuated by p38 and PI3-kinase inhibitors. Treatment of cells with NF-κB and AP-1 inhibitors antagonized LTA-induced iNOS and COX-2 expression. However, only NF-κB inhibitors reduced LTA-induced HO-1 expression in microglia. Furthermore, stimulation of cells with LTA also activated IκBα phosphorylation, p65 phosphorylation at Ser536, and c-Jun phosphorylation. Moreover, LTA-induced increases of κB-DNA and AP-1-DNA binding activity were inhibited by p38, JNK, and PI3-kinase inhibitors. HO-1 activator CoPP IX dramatically reversed LTA-induced iNOS expression. Our results provided mechanisms linking LTA and inflammation/anti-inflammation, and indicated that LTA plays a regulatory role in microglia activation.

Role of microglial activation in dorsal root ganglia in a rat model of persistent postoperative pain evoked by skin/muscle incision and retraction

Objective To evaluate the role of microglial activation in dorsal root ganglia in a rat model of persistent postoperative pain evoked by skin/muscle incision and retraction (SMIR).Methods Seventy male Sprague-Dawley rats,weighing 200-250 g,were randomly divided into 2 groups (n =35 each):group sham operation (group S) and group SMIR.The rat model of persistent postoperative pain evoked by SMIR was established according to the method described by Flatters.Pain behavior was assessed by mechanical paw withdrawal threshold to yon Frey filament stimulation at 1 day before and 1,3,7,12,22 and 32 days after operation.Five animals were sacrificed at each time point in each group for microglia count in dorsal root ganglia.Results Compared with group S,mechanical paw withdrawal threshold was significantly decreased at 3-22 days after operation,and microglia count was significantly increased at 3-12 days after operation in group SMIR (P ＜ 0.05).Conclusion Microglial activation in dorsal root ganglia may be involved in the development of SMIR-evoked persistent postoperative pain in rats. Key words: Microglia; Pain, postoperative; Ganglia, spinal

Essential roles of mitochondrial depolarization in neuron loss through microglial activation and attraction toward neurons

As life spans increased, neurodegenerative disorders that affect aging populations have also increased. Progressive neuronal loss in specific brain regions is the most common cause of neurodegenerative disease; however, key determinants mediating neuron loss are not fully understood. Using a model of mitochondrial membrane potential (ΔΨm) loss, we found only 25% cell loss in SH-SY5Y (SH) neuronal mono-cultures, but interestingly, 85% neuronal loss occurred when neurons were co-cultured with BV2 microglia. SH neurons overexpressing uncoupling protein 2 exhibited an increase in neuron–microglia interactions, which represent an early step in microglial phagocytosis of neurons. This result indicates that ΔΨm loss in SH neurons is an important contributor to recruitment of BV2 microglia. Notably, we show that ΔΨm loss in BV2 microglia plays a crucial role in microglial activation and phagocytosis of damaged SH neurons. Thus, our study demonstrates that ΔΨm loss in both neurons and microglia is a critical determinant of neuron loss. These findings also offer new insights into neuroimmunological and bioenergetical aspects of neurodegenerative disease.

Prevention of inflammation‐mediated neurotoxicity by butylidenephthalide and its role in microglial activation

Microglial cells are the prime effectors in immune and inflammatory responses of the central nervous system (CNS). During pathological conditions, the activation of these cells helps restore CNS homeostasis. However, chronic microglial activation endangers neuronal survival through the release of various proinflammatory molecules and neurotoxins. Thus, negative regulators of microglial activation have been considered as potential therapeutic candidates to target neurodegeneration, such as that in Alzheimer's and Parkinson's diseases. The rhizome of Ligusticum chuanxiong Hort. (Ligusticum wallichii Franch) has been widely used for the treatment of vascular diseases in traditional oriental medicine. Butylidenephthalide (BP), a major bioactive component from L. chuanxiong, has been reported to have a variety of pharmacological activities, including vasorelaxant, anti-anginal, anti-platelet and anti-cancer effects. The aim of this study was to examine whether BP represses microglial activation. In rat brain microglia, BP significantly inhibited the lipopolysaccharide (LPS)-induced production of nitric oxide (NO), tumour necrosis factor-α and interleukin-1β. In organotypic hippocampal slice cultures, BP clearly blocked the effect of LPS on hippocampal cell death and inhibited LPS-induced NO production in culture medium. These results newly suggest that BP provide neuroprotection by reducing the release of various proinflammatory molecules from activated microglia.