Myoloid-Related Protein 8, an Endogenous Ligand of Toll-Like Receptor 4, Is Involved in Epileptogenesis of Mesial Temporal Lobe Epilepsy Via Activation of the Nuclear Factor-κB Pathway in Astrocytes

Role of Innate Immune Receptor TLR4 and its endogenous ligands in epileptogenesis

Understanding the interplay between the innate immune system, neuroinflammation, and epilepsy might offer a novel perspective in the quest of exploring new treatment strategies. Due to the complex pathology underlying epileptogenesis, no disease-modifying treatment is currently available that might prevent epilepsy after a plausible epileptogenic insult despite the advances in pre-clinical and clinical research. Neuroinflammation underlies the etiopathogenesis of epilepsy and convulsive disorders with Toll-like receptor (TLR) signal transduction being highly involved. Among TLR family members, TLR4 is an innate immune system receptor and lipopolysaccharide (LPS) sensor that has been reported to contribute to epileptogenesis by regulating neuronal excitability. Herein, we discuss available evidence on the role of TLR4 and its endogenous ligands, the high mobility group box 1 (HMGB1) protein, the heat shock proteins (HSPs) and the myeloid related protein 8 (MRP8), in epileptogenesis and post-traumatic epilepsy (PTE). Moreover, we provide an account of the promising findings of TLR4 modulation/inhibition in experimental animal models with therapeutic impact on seizures.

The Study of Genetic Susceptibility and Mitochondrial Dysfunction in Mesial Temporal Lobe Epilepsy

The aim of this study is to investigate the mitochondrial dysfunction and pathogenic role of the mitochondrial genome in the progression of mesial temporal lobe epilepsy (MTLE) in vivo and in vitro. Mitochondrial DNA (mtDNA) and nuclear DNA were detected in the hippocampal samples and peripheral blood of patients with MTLE. Mitochondrial functions were detected in vivo and in vitro. In 20 patients with MTLE, mtDNA mutations involving single or multiple deletions in the hippocampus were found in 5 patients but were not detected in the peripheral blood. Two patients carried pathogenic mutations of RELN, both in the hippocampus and blood. A pathogenic mutation of DNA2 was found in the hippocampus of the 2 patients with multiple deletions but not in the blood samples. The mtDNA copy numbers showed dynamic changes in the MTLE models. In MTLE patients, low metabolism in mesial temporal lobe and hippocampus was observed by using PET-CT. Under electron microscope, the mitochondrial cristae were disordered, the density of mitochondrial matrix decreased and even vacuolated in the hippocampus neurons. In the MTLE rat models, there were dynamic changes in mitochondrial morphology; the ATP production rate decreased in the acute phase, the latent phase, and the chronic phase. Mitochondrial enzyme complex I activity decreased in both acute and chronic phases, and there was no significant difference in latent period. Decreased mitochondrial membrane potential and calcium homeostasis were detected in the epileptic cell models. We first identified somatic mutations in mtDNA in MTLE patients and comprehensively evaluated mitochondrial dysfunction in the pathogenesis of MTLE in vivo and in vitro. This evidence supports the environmental and modifying genetic interactions that contribute to the development of MTLE.

The treatment value of IL-1β monoclonal antibody under the targeting location of alpha-methyl-L-tryptophan and superparamagnetic iron oxide nanoparticles in an acute temporal lobe epilepsy model

BACKGROUND

Temporal lobe epilepsy (TLE) is a common and often refractory brain disease that is closely correlated with inflammation. Alpha-methyl-L-tryptophan (AMT) is recognized as a surrogate marker for epilepsy, characterized by high uptake in the epileptic focus. There are many advantages of using the magnetic targeting drug delivery system of superparamagnetic iron oxide nanoparticles (SPIONs) to treat many diseases, including epilepsy. We hypothesized that AMT and an IL-1β monoclonal antibody (anti-IL-1β mAb) chelated to SPIONs would utilize the unique advantages of SPIONs and AMT to deliver the anti-IL-1β mAb across the blood-brain barrier (BBB) as a targeted therapy.

METHODS

Acute TLE was induced in 30 rats via treatment with lithium-chloride pilocarpine. The effects of plain-SPIONs, anti-IL-1β-mAb-SPIONs, or AMT-anti-IL-1β-mAb-SPIONs on seizure onset were assessed 48 h later. Perl's iron staining, Nissl staining, immunofluorescence staining and western blotting were performed after magnetic resonance imaging examination.

RESULTS

The imaging and histopathology in combination with the molecular biology findings showed that AMT-anti-IL-1β-mAb-SPIONs were more likely to penetrate the BBB in the acute TLE model to reach the targeting location and deliver a therapeutic effect than plain-SPIONs and anti-IL-1β-mAb-SPIONs.

CONCLUSIONS

This study demonstrated the significance of anti-IL-1β-mAb treatment in acute TLE with respect to the unique advantages of SPIONs and the active location-targeting characteristic of AMT.

Hippocampal Mrp8/14 signaling plays a critical role in the manifestation of depressive-like behaviors in mice

Background

Depression is one of the most common mental disorders characterized mainly by low mood and loss of interest or pleasure. About a third of patients with depression do not respond to classic antidepressant treatments. Recent evidence suggests that Mrp8/14 (myeloid-related protein 8/14) plays a crucial role in cognitive dysfunction and neuroinflammatory diseases, yet its role in mood regulation remains largely uninvestigated. In the present work, we explored the potential role of Mrp8/14 in the progression of depression.

Methods

After 4 weeks of chronic unpredictable mild stress (CUMS), depressive-like symptoms and Mrp8/14 were determined. To verify the effects of Mrp8/14 on depressive-like behaviors, the inhibitor TAK-242 and recombinant Mrp8/14 were used. Furthermore, the molecular mechanisms in Mrp8/14-induced behavioral and biological changes were examined in vivo and ex vivo.

Results

Four-week CUMS contributed to the development of depressive symptoms. Mrp8 and Mrp14 were upregulated in the hippocampus and serum after exposure to CUMS. Pharmacological inhibition of Mrp14 attenuated CUMS-induced TLR4/NF-κB signaling activation and depressive-like behaviors. Furthermore, central administration of recombinant Mrp8, Mrp14, and Mrp8/14 resulted in neuroinflammation and depressive-like behaviors. Mrp8/14-provoked proinflammatory effects and depressive-like behaviors were improved by pretreatment with a TLR4 inhibitor. Moreover, pharmacological inhibition of TLR4 reduced the release of nitric oxide and reactive oxygen species in Mrp8/14-activated BV2 microglia.

Conclusions

These data suggest that the hippocampal Mrp8/14-TLR4-mediated neuroinflammation contributes to the development of depressive-like behaviors. Targeting the Mrp8/14 may be a novel promising antidepressant approach.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1296-0) contains supplementary material, which is available to authorized users.

Antiphospholipid antibodies in epilepsy: A systematic review and meta-analysis

BACKGROUND

Autoimmunity is believed to play an important causative role in the pathogenesis of epilepsy. There are evidences for the presence of autoantibodies in patients with epilepsy. To date, many studies have assessed the presence of antiphospholipid antibodies (aPLs) in epilepsy patients, though the relationship has been inconclusive.

AIMS

The aim of this systematic review and meta-analysis was to evaluate the presence of aPLs in epileptic patients as compared to healthy controls.

METHODS

Five electronic databases (PubMed, Web of Science, Embase, Scopus and Google Scholar) were searched systematically. Study-specific odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using random-effects model. Quality assessment was carried out by using the modified 9-star Newcastle-Ottawa Scale (NOS). L'Abbé plots were generated to visually inspect heterogeneity while publication bias was evaluated via visualization of contour- enhanced funnel plots, and Begg's and Egger's tests.

RESULTS

Based on the inclusion criteria, 14 studies were selected involving 1248 epilepsy patients and 800 healthy controls. The majority of epilepsy was categorised as generalised or partial and none had comorbidity with autoimmune diseases. Significant presence of both anticardiolipin (aCL) antibodies (OR: 5.16, 95% CI: 3.21-8.28, p < 0.00001) and anti-β2- glycoprotein I (anti-β2-GPI) antibodies (OR: 2.95, 95% CI: 1.07-8.11, p = 0.04) exhibited comorbid association with epilepsy patients as compared to healthy controls. Subgroup analyses revealed that presence of aCL antibodies was more specifically observed in paediatrics (OR: 4.57, 95% CI: 2.57-8.15, p < 0.00001) than adults (OR: 4.24, 95% CI: 1.80-10.01, p = 0.001). The odds of aCL antibody presence was higher in partial epilepsy patients (OR: 7.88, 95% CI: 3.23-19.24, p < 0.00001) than that of generalised (OR: 3.76, 95% CI: 2.15-6.59, p < 0.00001) and in Asian epileptic patients (OR: 9.56, 95% CI: 2.69-33.95, p = 0.0005) than Europeans (OR: 4.35, 95% CI: 2.74-6.92, p < 0.00001). The presence of anti-β2-GPI antibodies was significant in paediatric (OR: 6.44, 95% CI: 1.39-29.89, p = 0.02) and African population with epilepsies (OR: 10.59, 95% CI: 1.22-92.25, p = 0.03). NOS of the majority of the studies (11/14) indicated a high methodological quality. No substantial heterogeneity was observed either from the quantitative analysis or from the L'Abbé plots while no significant publication bias was detected from funnel plots; Begg's and Egger's tests.

CONCLUSION

Since none of the epilepsy subjects exhibited any comorbid autoimmune disorders, significant presence of aCL and anti-β2-GPI antibodies indicate towards their contribution in immune-mediated general pathogenesis of epilepsy.

MiR-181b inhibits P38/JNK signaling pathway to attenuate autophagy and apoptosis in juvenile rats with kainic acid-induced epilepsy via targeting TLR4

OBJECTIVE

To explore the role of miR-181b in alterations of apoptosis and autophagy in the kainic acid (KA)-induced epileptic juvenile rats via modulating TLR4 and P38/JNK signaling pathway.

METHODS

Dual-luciferase reporter assay was performed to testify the targeting relationship between miR-181b and TLR4. After intracerebroventricular injection (i.c.v.) of KA, rats were injected with miR-181b agomir and TLR4 inhibitor (TAK-242). The TLR-4 activator lipopolysaccharide (LPS) was also administered into rats immediately after injection with miR-181b agomir. Quantitative real-time-polymerase chain reaction (qRT-PCR) was used for detections of miR-181b and TLR4 expressions, hematoxylin-eosin (HE) and Nissl staining for observation of the hippocampus morphological changes, and TUNEL staining for apoptosis analysis. Moreover, western blot was determined to detect TLR4 and P38/JNK pathway proteins, as well as autophagy- and apoptosis-related proteins.

RESULTS

TLR4 was identified as a direct target of miR-181b using Dual-luciferase reporter assay. KA rats injected with miR-181b agomir or TAK-242 had improved learning and memory abilities, reduced seizure severity of Racine's scale, and lessened neuron injury. Additionally, miR-181b agomir or TAK-242 could significantly inhibit P38/JNK signaling, decrease LC3II/I, Beclin-1, ATG5, ATG7, ATG12, Bax, and cleaved caspases-3, but increase p62 and Bcl-2 expression. No significances were found between KA group and KA + miR-181b + LPS group.

CONCLUSION

MiR-181b could inhibit P38/JNK signaling pathway via targeting TLR4, thereby exerting protective roles in attenuating autophagy and apoptosis of KA-induced epileptic juvenile rats.

α-Asarone Attenuates Cognitive Deficit in a Pilocarpine-Induced Status Epilepticus Rat Model via a Decrease in the Nuclear Factor-κB Activation and Reduction in Microglia Neuroinflammation

Background

Temporal lobe epilepsy (TLE) is one of the most drug-resistant types of epilepsy with about 80% of TLE patients falling into this category. Increasing evidence suggests that neuroinflammation, which has a critical role in the epileptogenesis of TLE, is associated with microglial activation. Therefore, agents that act toward the alleviation in microglial activation and the attenuation of neuroinflammation are promising candidates to treat TLE. α-Asarone is a major active ingredient of the Acori Graminei Rhizoma used in Traditional Chinese Medicine, which has been used to improve various disease conditions including stroke and convulsions. In addition, an increasing number of studies suggested that α-asarone can attenuate microglia-mediated neuroinflammation. Thus, we hypothesized that α-asarone is a promising neuroprotective agent for the treatment of the TLE.

Methods

The present study evaluated the therapeutic effects of α-asarone on microglia-mediated neuroinflammation and neuroprotection in vitro and in vivo, using an untreated control group, a status epilepticus (SE)-induced group, and an SE-induced α-asarone pretreated group. A pilocarpine-induced rat model of TLE was established to investigate the neuroprotective effects of α-asarone in vivo. For the in vitro study, lipopolysaccharide (LPS)-stimulated primary cultured microglial cells were used.

Results

The results indicated that the brain microglial activation in the rats of the SE rat model led to important learning and memory deficit. Preventive treatment with α-asarone restrained microglial activation and reduced learning and memory deficit. In the in vitro studies, α-asarone significantly suppressed proinflammatory cytokine production in primary cultured microglial cells and attenuated the LPS-stimulated neuroinflammatory responses. Our mechanistic study revealed that α-asarone inhibited inflammatory processes by regulation the transcription levels of kappa-B, by blocking the degradation pathway of kappa B-alpha [inhibitor kappa B-alpha (IκB-α)] and kappa B-beta (IκB-β) kinase in both the SE rats and in primary cultured microglial cells.

Conclusion

Taken together, these data demonstrate that α-asarone is a promising neuroprotective agent for the prevention and treatment of microglia-mediated neuroinflammatory conditions including TLE, for which further assessment studies are pertinent.

Anterior thalamic nuclei deep brain stimulation reduces disruption of the blood-brain barrier, albumin extravasation, inflammation and apoptosis in kainic acid-induced epileptic rats

Objective The therapeutic efficacy of anterior thalamic nuclei deep brain stimulation (ATN-DBS) against seizures has been largely accepted; however, the effects of ATN-DBS on disruption of the blood-brain barrier (BBB), albumin extravasation, inflammation and apoptosis still remain unclear. Methods Rats were distributed into four treatment groups: physiological saline (PS, N = 12), kainic acid (KA, N = 12), KA-sham-DBS (N = 12) and KA-DBS (N = 12). Seizures were monitored using video-electroencephalogram (EEG). One day after surgery, all rats were sacrificed. Then, samples were prepared for quantitative real-time PCR (qPCR), western blot, immunofluorescence (IF) staining, and transmission electron microscopy to evaluate the disruption of the BBB, albumin extravasation, inflammation, and apoptosis. Result Because of the KA injection, the disruption of the BBB, albumin extravasation, inflammation and apoptosis were more severe in the KA and the KA-sham-DBS groups compared to the PS group (all Ps < 0.05 or < 0.01). The ideal outcomes were observed in the KA-DBS group. ATN-DBS produced a 46.3% reduction in seizure frequency and alleviated the disruption of the BBB, albumin extravasation, inflammatory reaction and apoptosis in comparison to the KA-sham-DBS group (all Ps < 0.05 or < 0.01). Conclusion (1) Seizures can be reduced using ATN-DBS in the epileptogenic stage. (2) ATN-DBS can reduce the disruption of the BBB and albumin extravasation. (3) ATN-DBS has an anti-inflammatory effect in epileptic models.

Development and Characterisation of a Novel NF-κB Reporter Cell Line for Investigation of Neuroinflammation

Aberrant activation of the transcription factor NF-κB, as well as uncontrolled inflammation, has been linked to autoimmune diseases, development and progression of cancer, and neurological disorders like Alzheimer's disease. Reporter cell lines are a valuable state-of-the art tool for comparative analysis of in vitro drug screening. However, a reporter cell line for the investigation of NF-κB-driven neuroinflammation has not been available. Thus, we developed a stable neural NF-κB-reporter cell line to assess the potency of proinflammatory molecules and peptides, as well as anti-inflammatory pharmaceuticals. We used lentivirus to transduce the glioma cell line U251-MG with a tandem NF-κB reporter construct containing GFP and firefly luciferase allowing an assessment of NF-κB activity via fluorescence microscopy, flow cytometry, and luminometry. We observed a robust activation of NF-κB after exposure of the reporter cell line to tumour necrosis factor alpha (TNFα) and amyloid-β peptide [1-42] as well as to LPS derived from Salmonella minnesota and Escherichia coli. Finally, we demonstrate that the U251-NF-κB-GFP-Luc reporter cells can be used for assessing the anti-inflammatory potential of pharmaceutical compounds using Bay11-7082 and IMD0354. In summary, our newly generated cell line is a robust and cost-efficient tool to study pro- and anti-inflammatory potential of drugs and biologics in neural cells.

Foxp3 exhibits antiepileptic effects in ictogenesis involved in TLR4 signaling

Inflammatory processes play critical roles in epileptogenesis, but the exact mechanisms that underlie these processes are still not completely understood. In this study, we investigated the role of forkhead transcription factor 3 (Foxp3), a transcription factor that is involved in T-cell differentiation, in epileptogenesis. In both human epileptic tissues and experimental seizure models, we found significant up-regulation of Foxp3 in neurons and glial cells. Of importance, Foxp3^-/- mice were susceptible to kainic acid-induced seizures, whereas overexpression of Foxp3 reduced acute seizure occurrence and decreased chronic seizure recurrence. In addition, in vitro experiments revealed that Foxp3 inhibited neuronal excitability via glial cells and not neurons. The protective effects of Foxp3 were manifested as a reduction in glial cell activation and proinflammatory cytokine production and increased neuronal survival. Moreover, we showed that beneficial effects of Foxp3 involved the attenuation of TLR4 signaling and inflammation, which led to the inactivation of NR2B-containing NMDA receptors. These results suggest that Foxp3 in glial cells may play an antiepileptic role in epileptogenesis and may act as a modulator of TLR4. Taken together, our results indicate that Foxp3 may represent a novel therapeutic target for achieving anticonvulsant effects in patients with epilepsy that is currently resistant to drugs.-Wang, F.-X., Xiong, X.-Y., Zhong, Q., Meng, Z.-Y., Yang, H., Yang, Q.-W. Foxp3 exhibits antiepileptic effects in ictogenesis involved in TLR4 signaling.

[Effect of a microRNA-132 antagonist on pilocarpine-induced status epilepticus in young rats]

OBJECTIVE

To study the effect of a microRNA-132 antagonist on lithium-pilocarpine-induced status epilepticus (SE) in young Sprague-Dawley (SD) rats.

METHODS

Forty-five 3-week-old SD rats were randomly and equally divided into epilepticus model group, microRNA-132 antagonist group, and microRNA-132 antagonist negative control group. The young SD rat model of SE was established using lithium-pilocarpine. For the microRNA-132 antagonist group and the negative control group, pretreatment was performed 24 hours before the model establishment. Behavioral observation was performed to assess the latency of SE and success rate of induction of SE. The scale of Lado was used to evaluate the seizure severity. Electroencephalography (EEG) was used to assess the frequency and amplitude of epileptiform discharges. The mortality rate was calculated in each group.

RESULTS

There was no significant difference in the success rate of induction of SE between the three groups (P>0.05). Compared with the microRNA-132 negative control group and the epilepticus model group, the microRNA-132 antagonist group had significantly prolonged SE latency after model establishment (P<0.05), a significantly lower Lado score of seizure (P<0.05), significantly lower frequency and amplitude of epileptiform discharges on EEG (P<0.05), and a slightly reduced mortality rate.

CONCLUSIONS

The treatment with the microRNA-132 antagonist shows an inhibitory effect on the development and progression of lithium-pilocarpine-induced SE in young SD rats. The inhibition of microRNA-132 is likely to be a potential target or direction for drug treatment of SE.

Identification of an S100A8 Receptor Neuroplastin-β and its Heterodimer Formation with EMMPRIN

We previously reported a positive feedback loop between S100A8/A9 and proinflammatory cytokines mediated by extracellular matrix metalloproteinase inducer, an S100A9 receptor. Here, we identify neuroplastin-β as an unreported S100A8 receptor. Neuroplastin-β and extracellular matrix metalloproteinase inducer form homodimers and a heterodimer, and they are co-localized on the surface of cultured normal human keratinocytes. Knockdown of both receptors suppressed cell proliferation and proinflammatory cytokine induction. Upon stimulation with S100A8, neuroplastin-β recruited GRB2 and activated extracellular signal-regulated kinase, resulting in keratinocyte proliferation. Keratinocyte proliferation in response to inflammatory stimuli was accelerated in involucrin promoter-driven S100A8 transgenic mice. Further, S100A8 and S100A9 were strongly up-regulated and co-localized in lesional skin of atopic dermatitis patients. Our results indicate that neuroplastin-β and extracellular matrix metalloproteinase inducer form a functional heterodimeric receptor for S100A8/A9 heterodimer, followed by recruitment of specific adaptor molecules GRB2 and TRAF2, and this signaling pathway is involved in activation of both keratinocyte proliferation and skin inflammation in atopic skin. Suppression of this pathway might have potential for treatment of skin diseases associated with chronic inflammation such as atopic dermatitis.

Ligand engagement of Toll-like receptors regulates their expression in cortical microglia and astrocytes

Background

Toll-like receptor (TLR) activation on microglia and astrocytes are key elements in neuroinflammation which accompanies a number of neurological disorders. While TLR activation on glia is well-established to up-regulate pro-inflammatory mediator expression, much less is known about how ligand engagement of one TLR may affect expression of other TLRs on microglia and astrocytes.

Methods

In the present study, we evaluated the effects of agonists for TLR2 (zymosan), TLR3 (polyinosinic-polycytidylic acid (poly(I:C)), a synthetic analogue of double-stranded RNA) and TLR4 (lipopolysaccaride (LPS)) in influencing expression of their cognate receptor as well as that of the other TLRs in cultures of rat cortical purified microglia (>99.5 %) and nominally microglia-free astrocytes. Elimination of residual microglia (a common contaminant of astrocyte cultures) was achieved by incubation with the lysosomotropic agent l-leucyl-l-leucine methyl ester (L-LME).

Results

Flow cytometric analysis confirmed the purity (essentially 100 %) of the obtained microglia, and up to 5 % microglia contamination of astrocytes. L-LME treatment effectively removed microglia from the latter (real-time polymerase chain reaction). The three TLR ligands robustly up-regulated gene expression for pro-inflammatory markers (interleukin-1 and interleukin-6, tumor necrosis factor) in microglia and enriched, but not purified, astrocytes, confirming cellular functionality. LPS, zymosan and poly(I:C) all down-regulated TLR4 messenger RNA (mRNA) and up-regulated TLR2 mRNA at 6 and 24 h. In spite of their inability to elaborate pro-inflammatory mediator output, the nominally microglia-free astrocytes (>99 % purity) also showed similar behaviours to those of microglia, as well as changes in TLR3 gene expression. LPS interaction with TLR4 activates downstream mitogen-activated protein kinase and nuclear factor-κB signalling pathways and subsequently causes inflammatory mediator production. The effects of LPS on TLR2 mRNA in both cell populations were antagonized by a nuclear factor-κB inhibitor.

Conclusions

TLR2 and TLR4 activation in particular, in concert with microglia and astrocytes, comprise key elements in the initiation and maintenance of neuropathic pain. The finding that both homologous (zymosan) and heterologous (LPS, poly(I:C)) TLR ligands are capable of regulating TLR2 gene expression, in particular, may have important implications in understanding the relative contributions of different TLRs in neurological disorders associated with neuroinflammation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-015-0458-6) contains supplementary material, which is available to authorized users.

The Effect of miR-132, miR-146a, and miR-155 on MRP8/TLR4-Induced Astrocyte-Related Inflammation

Astrocyte activation, associated with the release of pro-inflammatory cytokines interleukin 1-β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α), is a hallmark of multiple brain diseases, including mesial temporal lobe epilepsy. In recent years, several microRNAs have emerged as important controllers of Toll-like receptor (TLR) signaling. In this study, we investigated the effect of miR-132, miR-146a, and miR-155 on myeloid-related protein-8 (MRP8) induced astrocyte-related inflammation. Using quantitative polymerase chain reaction (qPCR) and western blot, we found clear upregulation of TLR4 and downstream inflammatory cytokines, along with dysregulation of miR-132, miR-146a, and miR-155 in in vitro astrocytes after exposing them to different concentrations of MRP8. In addition, we focused on the effect of miR-132 on astrocyte-related inflammation induced by MRP8 via lentiviral infection then evaluated the expression of its possible target genes: acetylcholinesterase (AChE) and interleukin-1 receptor-associated kinase (IRAK4). Our results show that miR-132 is a negative feedback regulator of IL-1β and IL-6, but not TNF-α, by targeting IRAK4. Together, our findings demonstrate the novel role of TLR4-related microRNAs, especially miR-132, in the regulation of MRP8-induced astrocyte activation and highlight the importance of miR-132 in the modulation of innate immune response induced by endogenous ligands in neurological diseases.