mTOR signaling inhibition modulates macrophage/microglia-mediated neuroinflammation and secondary injury via regulatory T cells after focal ischemia

Inflammatory aspects of epileptogenesis: contribution of molecular inflammatory mechanisms

OBJECTIVE

Epilepsy is a chronic neurological disease characterised with seizures. The aetiology of the most generalised epilepsies cannot be explicitly determined and the seizures are pronounced to be genetically determined by disturbances of receptors in central nervous system. Besides, neurotransmitter distributions or other metabolic problems are supposed to involve in epileptogenesis. Lack of adequate data about pharmacological agents that have antiepileptogenic effects point to need of research on this field. Thus, in this review, inflammatory aspects of epileptogenesis has been focussed via considering several concepts like role of immune system, blood-brain barrier and antibody involvement in epileptogenesis.

METHODS

We conducted an evidence-based review of the literatures in order to evaluate the possible participation of inflammatory processes to epileptogenesis and also, promising agents which are effective to these processes. We searched PubMed database up to November 2015 with no date restrictions.

RESULTS

In the present review, 163 appropriate articles were included. Obtained data suggests that inflammatory processes participate to epileptogenesis in several ways like affecting fibroblast growth factor-2 and tropomyosin receptor kinase B signalling pathways, detrimental proinflammatory pathways [such as the interleukin-1 beta (IL-1β)-interleukin-1 receptor type 1 (IL-1R1) system], mammalian target of rapamycin pathway, microglial activities, release of glial inflammatory proteins (such as macrophage inflammatory protein, interleukin 6, C-C motif ligand 2 and IL-1β), adhesion molecules that are suggested to function in signalling pathways between neurons and microglia and also linkage between these molecules and proinflammatory cytokines.

CONCLUSION

The literature research indicated that inflammation is a part of epileptogenesis. For this reason, further studies are necessary for assessing agents that will be effective in clinical use for therapeutic treatment of epileptogenesis.

Deleting IGF-1 receptor from forebrain neurons confers neuroprotection during stroke and upregulates endocrine somatotropin

Insulin-like growth factors control numerous processes, namely somatic growth, metabolism and stress resistance, connecting this pathway to aging and age-related diseases. Insulin-like growth factor signaling also impacts on neurogenesis, neuronal survival and structural plasticity. Recent reports demonstrated that diminished insulin-like growth factor signaling confers increased stress resistance in brain and other tissues. To better understand the role of neuronal insulin-like growth factor signaling in neuroprotection, we inactivated insulin-like growth factor type-1-receptor in forebrain neurons using conditional Cre-LoxP-mediated gene targeting. We found that brain structure and function, including memory performance, were preserved in insulin-like growth factor receptor mutants, and that certain characteristics improved, notably synaptic transmission in hippocampal neurons. To reveal stress-related roles of insulin-like growth factor signaling, we challenged the brain using a stroke-like insult. Importantly, when charged with hypoxia-ischemia, mutant brains were broadly protected from cell damage, neuroinflammation and cerebral edema. We also found that in mice with insulin-like growth factor receptor knockout specifically in forebrain neurons, a substantial systemic upregulation of growth hormone and insulin-like growth factor-I occurred, which was associated with significant somatic overgrowth. Collectively, we found strong evidence that blocking neuronal insulin-like growth factor signaling increases peripheral somatotropic tone and simultaneously protects the brain against hypoxic-ischemic injury, findings that may contribute to developing new therapeutic concepts preventing the disabling consequences of stroke.

Everolimus is better than rapamycin in attenuating neuroinflammation in kainic acid-induced seizures

Background

Microglia is responsible for neuroinflammation, which may aggravate brain injury in diseases like epilepsy. Mammalian target of rapamycin (mTOR) kinase is related to microglial activation with subsequent neuroinflammation. In the present study, rapamycin and everolimus, both as mTOR inhibitors, were investigated in models of kainic acid (KA)-induced seizure and lipopolysaccharide (LPS)-induced neuroinflammation.

Methods

In vitro, we treated BV2 cells with KA and LPS. In vivo, KA was used to induce seizures on postnatal day 25 in B6.129P-Cx3cr1^tm1Litt/J mice. Rapamycin and everolimus were evaluated in their modulation of neuroinflammation detected by real-time PCR, Western blotting, and immunostaining.

Results

Everolimus was significantly more effective than rapamycin in inhibiting iNOS and mTOR signaling pathways in both models of neuroinflammation (LPS) and seizure (KA). Everolimus significantly attenuated the mRNA expression of iNOS by LPS and nitrite production by KA and LPS than that by rapamycin. Only everolimus attenuated the mRNA expression of mTOR by LPS and KA treatment. In the present study, we also found that the modulation of mTOR under LPS and KA treatment was not mediated by Akt pathway but was primarily mediated by ERK phosphorylation, which was more significantly attenuated by everolimus. This inhibition of ERK phosphorylation and microglial activation in the hippocampus by everolimus was also confirmed in KA-treated mice.

Conclusions

Rapamycin and everolimus can block the activation of inflammation-related molecules and attenuated the microglial activation. Everolimus had better efficacy than rapamycin, possibly mediated by the inhibition of ERK phosphorylation. Taken together, mTOR inhibitor can be a potential pharmacological target of anti-inflammation and seizure treatment.

Positive effects of intermittent fasting in ischemic stroke

Intermittent fasting (IF) is a dietary protocol where energy restriction is induced by alternate periods of ad libitum feeding and fasting. Prophylactic intermittent fasting has been shown to extend lifespan and attenuate the progress and severity of age-related diseases such as cardiovascular (e.g. stroke and myocardial infarction), neurodegenerative (e.g. Alzheimer's disease and Parkinson's disease) and cancerous diseases in animal models. Stroke is the second leading cause of death, and lifestyle risk factors such as obesity and physical inactivity have been associated with elevated risks of stroke in humans. Recent studies have shown that prophylactic IF may mitigate tissue damage and neurological deficit following ischemic stroke by a mechanism(s) involving suppression of excitotoxicity, oxidative stress, inflammation and cell death pathways in animal stroke models. This review summarizes data supporting the potential hormesis mechanisms of prophylactic IF in animal models, and with a focus on findings from animal studies of prophylactic IF in stroke in our laboratory.

Essential Role of mTORC1 in Self-Renewal of Murine Alveolar Macrophages

Alveolar macrophages (AMϕ) have the capacity of local self-renewal through adult life; however, mechanisms that regulate AMϕ self-renewal remain poorly understood. We found that myeloid-specific deletion of Raptor, an essential component of the mammalian/mechanistic target of rapamycin complex (mTORC)1, resulted in a marked decrease of this population of cells accompanying altered phenotypic features and impaired phagocytosis activity. We demonstrated further that Raptor/mTORC1 deficiency did not affect AMϕ development, but compromised its proliferative activity at cell cycle entry in the steady-state as well as in the context of repopulation in irradiation chimeras. Mechanically, mTORC1 confers AMϕ optimal responsiveness to GM-CSF-induced proliferation. Thus, our results demonstrate an essential role of mTORC1 for AMϕ homeostasis by regulating proliferative renewal.

Differential Kv1.3, KCa3.1, and Kir2.1 expression in "classically" and "alternatively" activated microglia

Microglia are highly plastic cells that can assume different phenotypes in response to microenvironmental signals. Lipopolysaccharide (LPS) and interferon-γ (IFN-γ) promote differentiation into classically activated M1-like microglia, which produce high levels of pro-inflammatory cytokines and nitric oxide and are thought to contribute to neurological damage in ischemic stroke and Alzheimer's disease. IL-4 in contrast induces a phenotype associated with anti-inflammatory effects and tissue repair. We here investigated whether these microglia subsets vary in their K⁺ channel expression by differentiating neonatal mouse microglia into M(LPS) and M(IL-4) microglia and studying their K⁺ channel expression by whole-cell patch-clamp, quantitative PCR and immunohistochemistry. We identified three major types of K⁺ channels based on their biophysical and pharmacological fingerprints: a use-dependent, outwardly rectifying current sensitive to the K_V 1.3 blockers PAP-1 and ShK-186, an inwardly rectifying Ba²⁺ -sensitive K_ir 2.1 current, and a Ca²⁺ -activated, TRAM-34-sensitive K_Ca 3.1 current. Both K_V 1.3 and K_Ca 3.1 blockers inhibited pro-inflammatory cytokine production and iNOS and COX2 expression demonstrating that K_V 1.3 and K_Ca 3.1 play important roles in microglia activation. Following differentiation with LPS or a combination of LPS and IFN-γ microglia exhibited high K_V 1.3 current densities (∼50 pA/pF at 40 mV) and virtually no K_Ca 3.1 and K_ir currents, while microglia differentiated with IL-4 exhibited large K_ir 2.1 currents (∼ 10 pA/pF at -120 mV). K_Ca 3.1 currents were generally low but moderately increased following stimulation with IFN-γ or ATP (∼10 pS/pF). This differential K⁺ channel expression pattern suggests that K_V 1.3 and K_Ca 3.1 inhibitors could be used to inhibit detrimental neuroinflammatory microglia functions. GLIA 2016;65:106-121.

Class I PI3K inhibitor ZSTK474 mediates a shift in microglial/macrophage phenotype and inhibits inflammatory response in mice with cerebral ischemia/reperfusion injury

Background

Microglia/macrophages play a critical role in the inflammatory and immune processes of cerebral ischemia/reperfusion injury. Since microglia/macrophages can reversibly shift their phenotype toward either a “detrimental” or a “restorative” state in the injured central nervous system (CNS), compounds mediate that shift which could inhibit inflammation and restore the ability to alleviate cerebral ischemia/reperfusion injury would have therapeutic potential.

Methods

Transient middle cerebral artery occlusion was induced in male C57BL/6 mice. Mice were randomly separated into a sham-operated group, a control group, and a ZSTK474-treated group. We investigated the effect of ZSTK474 by assessing neurological deficits, infarct volume, and histopathological changes. We then determined the potential mechanism by immunofluorescent staining, quantitative real-time polymerase chain reaction (PCR), and Western blot analysis. The Tukey’s test or Mann–Whitney U test was used to compare differences among the groups.

Results

ZSTK474 alleviated neurological deficits and reduced infarct volume in the cerebral ischemia/reperfusion injury model. Presumably, ZSTK474 shifted the phenotype of microglia/macrophages to a restorative state, since this treatment decreased the secretion of pro-inflammatory factors and advanced the secretion of anti-inflammatory factors. These neuroprotective properties of ZSTK474 may be mediated by the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin complex 1 (mTORC1) pathway.

Conclusions

ZSTK474 can mediate a shift in microglia/macrophage phenotype and inhibit the inflammatory response in cerebral ischemia reperfusion injury of mice. These effects appeared to ensue via the PI3K/AKT/mTORC1 pathway. Therefore, ZSTK474 may represent a therapeutic intervention with potential for circumventing the catastrophic aftermath of ischemic stroke.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0660-1) contains supplementary material, which is available to authorized users.

Inhibition of mammalian target of rapamycin attenuates early brain injury through modulating microglial polarization after experimental subarachnoid hemorrhage in rats

Here, we aimed to study the role and underlying mechanism of mTOR in early brain injury (EBI) after subarachnoid hemorrhage (SAH). Experiment 1, the time course of mTOR activation in the cortex following SAH. Experiment 2, the role of mTOR in SAH-induced EBI. Adult SD rats were divided into four groups: sham group (n=18), SAH+vehicle group (n=18), SAH+rapamycin group (n=18), SAH+AZD8055 group (n=18). Experiment 3, we incubated enriched microglia with OxyHb. Rapamycin and AZD8055 were also used to demonstrate the mTOR's role on microglial polarization in vitro. The phosphorylation levels of mTOR and its substrates were significantly increased and peaked at 24h after SAH. Rapamycin or AZD8055 markedly decreased the phosphorylation levels of mTOR and its substrates and the activation of microglia in vivo, and promoted the microglial polarization from M1 phenotype to M2 phenotype. In addition, administration of rapamycin and AZD8055 following SAH significantly ameliorated EBI, including neuronal apoptosis, neuronal necrosis, brain edema and blood-brain barrier permeability. Our findings suggested that the rapamycin and AZD8055 could attenuate the development of EBI in this SAH model, possibly through inhibiting the activation of microglia by mTOR pathway.

mTORC1 pathway disruption ameliorates brain inflammation following stroke via a shift in microglia phenotype from M1 type to M2 type

Inflammatory factors secreted by microglia play an important role in focal ischemic stroke. The mammalian target of rapamycin (mTOR) pathway is a known regulator of immune responses, but the role that mTORC1 signaling plays in poststroke neuroinflammation is not clear. To explore the relationship between microglial action in the mTORC1 pathway and the impact on stroke, we administered the mTORC1 inhibitors sirolimus and everolimus to mice. Presumably, disrupting the mTORC1 pathway after focal ischemic stroke should clarify the subsequent activity of microglia. For that purpose, we generated mice deficient in the regulatory associated protein of mTOR (Raptor) in microglia, whose mTORC1 signaling was blocked, by crossing Raptor loxed (Raptor^flox/flox) mice with CX3CR1^CreER mice, which express Cre recombinase under the control of the CX3C chemokine receptor 1 promoter. mTORC1 blockade reduced lesion size, improved motor function, dramatically decreased production of proinflammatory cytokines and chemokines, and reduced the number of M1 type microglia. Thus, mTORC1 blockade apparently attenuated behavioral deficits and poststroke inflammation after middle cerebral artery occlusion by preventing microglia polarization toward the M1 type.-Li, D., Wang, C., Yao, Y., Chen, L., Liu, G., Zhang, R., Liu, Q., Shi, F.-D., Hao, J. mTORC1 pathway disruption ameliorates brain inflammation following stroke via a shift in microglia phenotype from M1 type to M2 type.

Host Resistance and Immune Aging

Human immune system aging results in impaired responses to pathogens or vaccines. In the innate immune system, which mediates the earliest pro-inflammatory responses to immunologic challenge, processes ranging from Toll-like Receptor function to Neutrophil Extracellular Trap formation are generally diminished in older adults. Dysregulated, enhanced basal inflammation with age reflecting activation by endogenous damage-associated ligands contributes to impaired innate immune responses. In the adaptive immune system, T and B cell subsets and function alter with age. The control of cytomegalovirus infection, particularly in the T lineage, plays a dominant role in the differentiation and diversity of the T cell compartment.

Resveratrol Pretreatment Protected against Cerebral Ischemia/Reperfusion Injury in Rats via Expansion of T Regulatory Cells

BACKGROUND

It is well accepted that repetitive resveratrol (RV) pretreatment (PRC) exerts neuroprotective effect on ischemic stroke. RV was shown to be able to enhance the production of T regulatory cells (Tregs) in autoimmune diseases whereas Tregs are considered to be the cerebroprotective immunomodulator in ischemic stroke. Thus, we hypothesized whether Tregs contributed to PRC-induced neuroprotection against cerebral ischemia/reperfusion (I/R) injury.

METHODS

Cerebral I/R injury was induced by middle cerebral artery occlusion for 90 minutes in rats. Adult male Sprague-Dawley rats were randomly assigned to 2 groups: I/R and RV I/R. RV (50 mg/kg) was administrated intraperitoneally once a day for 7 days prior to ischemia onset.

RESULTS

PRC significantly ameliorated neurological defects and reduced cerebral infarct volume, accompanied by the significantly increased frequencies of Tregs in the spleens and ischemic hemisphere, the significantly increased levels of interleukin-10 (IL-10) in the plasma and ischemic hemisphere, and the significantly decreased levels of tumor necrosis factor-α and IL-6 in the plasma and ischemic hemisphere at 24 hours after ischemia onset. In addition, we also found that PRC significantly improved the frequency and suppressive function of Tregs in the spleens prior to ischemia onset.

CONCLUSIONS

Thus, PRC-induced neuroprotection was in part mediated by more Treg accumulation and activation in vivo prior to ischemia onset except for less inflammation response at 24 hours after ischemia onset.

Interleukin-4 Ameliorates the Functional Recovery of Intracerebral Hemorrhage Through the Alternative Activation of Microglia/Macrophage

Neuro-inflammation plays an important role in the recovery of brain injury after stroke. Microglia/macrophage is the major executor in the neuro-inflammation, which can be polarized into two distinct phenotypes: injurious/toxic classical activation (M1 phenotype) and protective alternative activation (M2 phenotype). Here, we investigated whether intracerebral administration of interleukin-4 (IL-4) at an early stage could affect the activation of microglia/macrophage and the corresponding outcome after intracerebral hemorrhage (ICH). The neuro-behavior was recorded between different groups in the rat ICH model. The M1 and M2 markers were then determined by qRT-PCR, western blotting, ELISA, and immunofluorescence, respectively. We observed aberrant activation of microglia/macrophage after ICH. After intracerebral injection of IL-4, M1 activation was greatly inhibited while M2 activation was enhanced, along with improving neurobehavioral recovery from deficits after ICH. Our study showed that early intracerebral injection of IL-4 potentially promotes neuro-functional recovery, probably through enhancing the alternative activation of microglia/macrophage.

Effects of rapamycin on cerebral oxygen supply and consumption during reperfusion after cerebral ischemia

Activation of the mammalian target of rapamycin (mTOR) leads to cell growth and survival. We tested the hypothesis that inhibition of mTOR would increase infarct size and decrease microregional O2 supply/consumption balance after cerebral ischemia-reperfusion. This was tested in isoflurane-anesthetized rats with middle cerebral artery blockade for 1h and reperfusion for 2h with and without rapamycin (20mg/kg once daily for two days prior to ischemia). Regional cerebral blood flow was determined using a C(14)-iodoantipyrine autoradiographic technique. Regional small-vessel arterial and venous oxygen saturations were determined microspectrophotometrically. The control ischemic-reperfused cortex had a similar blood flow and O2 consumption to the contralateral cortex. However, microregional O2 supply/consumption balance was significantly reduced in the ischemic-reperfused cortex. Rapamycin significantly increased cerebral O2 consumption and further reduced O2 supply/consumption balance in the reperfused area. This was associated with an increased cortical infarct size (13.5±0.8% control vs. 21.5±0.9% rapamycin). We also found that ischemia-reperfusion increased AKT and S6K1 phosphorylation, while rapamycin decreased this phosphorylation in both the control and ischemic-reperfused cortex. This suggests that mTOR is important for not only cell survival, but also for the control of oxygen balance after cerebral ischemia-reperfusion.

Dynamics of T cell responses after stroke

T cells are integral to the pathophysiology of stroke. The initial inflammatory cascade leads to T cell migration, which results in deleterious and protective effects mediated through CD4(+), CD(8)+, γδ T cells and regulatory T cells, respectively. Cytokines are central to the T cell responses, with key roles established for TNF-α, IFN-γ, IL-17, IL-21 and IL-10. Through communication with the systemic immune system via neural and hormonal pathways, there is also transient immunosuppression after severe strokes. With time, the inflammatory process eventually transforms to one more conducive of repair and recovery, though some evidence also suggests ongoing chronic inflammation. The role of antigen-specific T cell responses requires further investigation. As our understanding develops, there is increasing scope to modulate the T cell response after stroke.

Hepatic CD206-positive macrophages express amphiregulin to promote the immunosuppressive activity of regulatory T cells in HBV infection

Hepatitis B virus is a major cause of chronic liver inflammation worldwide. Innate and adaptive immune responses work together to restrain or eliminate hepatitis B virus in the liver. Compromised or failed adaptive immune response results in persistent virus replication and spread. How to promote antiviral immunity is a research focus for hepatitis B virus prevention and therapy. In this study, we investigated the role of macrophages in the regulation of antiviral immunity. We found that F4/80(+)CD206(+)CD80(lo/+) macrophages were a particular hepatic macrophage subset that expressed amphiregulin in our mouse hepatitis B virus infection model. CD206(+) macrophage-derived amphiregulin promoted the immunosuppressive activity of intrahepatic regulatory T cells, demonstrated by higher expression of CTLA-4, ICOS, and CD39, as well as stronger inhibition of antiviral function of CD8(+) T cells. Amphiregulin-neutralizing antibody diminished the effect of CD206(+) macrophages on regulatory T cells. In addition, we found that CD206(+) macrophage-derived amphiregulin activated mammalian target of rapamycin signaling in regulatory T cells, and this mammalian target of rapamycin activation was essential for promotion of regulatory T cell activity by CD206(+) macrophages. Adoptive transfer of CD206(+) macrophages into hepatitis B virus-infected mice increased cytoplasmic hepatitis B virus DNA in hepatocytes and also increased serum hepatitis B surface antigen. The antiviral activity of CD8(+) T cells was decreased after macrophage transfer. Therefore, our research indicated that amphiregulin produced by CD206(+) macrophages plays an important role in modulating regulatory T cell function and subsequently restrains the antiviral activity of CD8(+) T cells. Our study offers new insights into the immunomodulation in hepatitis B virus infection.

Paradoxical changes in innate immunity in aging: recent progress and new directions

Immunosenescence, describing alterations, including decline of immune responses with age, is comprised of inappropriate elevations, decreases, and dysregulated immune responses, leading to more severe consequences of bacterial and viral infections and reduced responses to vaccination. In adaptive immunity, these changes include increased proportions of antigen-experienced B and T cells at the cost of naïve cell populations. Innate immune changes in aging are complex in spanning multiple cell types, activation states, and tissue context. Innate immune responses are dampened in aging, yet there is also a paradoxical increase in certain signaling pathways and cytokine levels. Here, we review recent progress and highlight novel directions for expected advances that can lead the aging field to a new era of discovery that will embrace the complexity of aging in human populations.

Immunohistochemical Assessment of Phosphorylated mTORC1-Pathway Proteins in Human Brain Tumors

Background

Current pathological diagnostics include the analysis of (epi-)genetic alterations as well as oncogenic pathways. Deregulated mammalian target of rapamycin complex 1 (mTORC1) signaling has been implicated in a variety of cancers including malignant gliomas and is considered a promising target in cancer treatment. Monitoring of mTORC1 activity before and during inhibitor therapy is essential. The aim of our study is to provide a recommendation and report on pitfalls in the use of phospho-specific antibodies against mTORC1-targets phospho-RPS6 (Ser235/236; Ser240/244) and phospho-4EBP1 (Thr37/46) in formalin fixed, paraffin embedded material.

Methods and Findings

Primary, established cell lines and brain tumor tissue from routine diagnostics were assessed by immunocyto-, immunohistochemistry, immunofluorescent stainings and immunoblotting. For validation of results, immunoblotting experiments were performed. mTORC-pathway activation was pharmacologically inhibited by torin2 and rapamycin. Torin2 treatment led to a strong reduction of signal intensity and frequency of all tested antibodies. In contrast phospho-4EBP1 did not show considerable reduction in staining intensity after rapamycin treatment, while immunocytochemistry with both phospho-RPS6-specific antibodies showed a reduced signal compared to controls. Staining intensity of both phospho-RPS6-specific antibodies did not show considerable decrease in stability in a timeline from 0–230 minutes without tissue fixation, however we observed a strong decrease of staining intensity in phospho-4EBP1 after 30 minutes. Detection of phospho-signals was strongly dependent on tissue size and fixation gradient. mTORC1-signaling was significantly induced in glioblastomas although not restricted to cancer cells but also detectable in non-neoplastic cells.

Conclusion

Here we provide a recommendation for phospho-specific immunohistochemistry for patient-orientated therapy decisions and monitoring treatment response.

Rapamycin increases neuronal survival, reduces inflammation and astrocyte proliferation after spinal cord injury

Spinal cord injury (SCI) frequently leads to a permanent functional impairment as a result of the initial injury followed by secondary injury mechanism, which is characterised by increased inflammation, glial scarring and neuronal cell death. Finding drugs that may reduce inflammatory cell invasion and activation to reduce glial scarring and increase neuronal survival is of major importance for improving the outcome after SCI. In the present study, we examined the effect of rapamycin, an mTORC1 inhibitor and an inducer of autophagy, on recovery from spinal cord injury. Autophagy, a process that facilitates the degradation of cytoplasmic proteins, is also important for maintenance of neuronal homeostasis and plays a major role in neurodegeneration after neurotrauma. We examined rapamycin effects on the inflammatory response, glial scar formation, neuronal survival and regeneration in vivo using spinal cord hemisection model in mice, and in vitro using primary cortical neurons and human astrocytes. We show that a single injection of rapamycin, inhibited p62/SQSTM1, a marker of autophagy, inhibited mTORC1 downstream effector p70S6K, reduced macrophage/neutrophil infiltration into the lesion site, microglia activation and secretion of TNFα. Rapamycin inhibited astrocyte proliferation and reduced the number of GFAP expressing cells at the lesion site. Finally, it increased neuronal survival and axonogenesis towards the lesion site. Our study shows that rapamycin treatment increased significantly p-Akt levels at the lesion site following SCI. Similarly, rapamycin treatment of neurons and astrocytes induced p-Akt elevation under stress conditions. Together, these findings indicate that rapamycin is a promising candidate for treatment of acute SCI condition and may be a useful therapeutic agent.

Microglia in Glia-Neuron Co-cultures Exhibit Robust Phagocytic Activity Without Concomitant Inflammation or Cytotoxicity

A simple method to co-culture granule neurons and glia from a single brain region is described, and microglia activation profiles are assessed in response to naturally occurring neuronal apoptosis, excitotoxin-induced neuronal death, and lipopolysaccharide (LPS) addition. Using neonatal rat cerebellar cortex as a tissue source, glial proliferation is regulated by omission or addition of the mitotic inhibitor cytosine arabinoside (AraC). After 7-8 days in vitro, microglia in AraC(-) cultures are abundant and activated based on their amoeboid morphology, expressions of ED1 and Iba1, and ability to phagocytose polystyrene beads and the majority of neurons undergoing spontaneous apoptosis. Microglia and phagocytic activities are sparse in AraC(+) cultures. Following exposure to excitotoxic kainate concentrations, microglia in AraC(-) cultures phagocytose most dead neurons within 24 h without exacerbating neuronal loss or mounting a strong or sustained inflammatory response. LPS addition induces a robust inflammatory response, based on microglial expressions of TNF-α, COX-2 and iNOS proteins, and mRNAs, whereas these markers are essentially undetectable in control cultures. Thus, the functional effector state of microglia is primed for phagocytosis but not inflammation or cytotoxicity even after kainate exposure that triggers death in the majority of neurons. This model should prove useful in studying the progressive activation states of microglia and factors that promote their conversion to inflammatory and cytotoxic phenotypes.

Anti-inflammatory effects of Gualou Guizhi decoction in transient focal cerebral ischemic brains. [Corrected]

The aim of the present study was to explore the neuroprotective effects of Gualou Guizhi decoction (GLGZD) in a rat model of middle cerebral artery occlusion (MCAO). Sprague-Dawley rats were divided into three groups: Sham (no MCAO), MCAO (MCAO with no GLGZD treatment) and GLGZD (MCAO with GLGZD treatment). Rats in the MCAO and GLGZD groups were subjected to permanent occlusion of the left middle cerebral artery. Neurological function and infarct volume were measured. Microglial activation and inflammatory cell accumulation were measured using immunohistochemistry. mRNA and protein expression of inflammatory mediators were examined using reverse transcription-quantitative polymerase chain reaction and an enzyme-linked immunosorbent assay. The expression of proteins associated with the nuclear factor κ-B (NF-κB) inflammation signaling pathway was analyzed using western blotting. The results of the present study suggested that infarct size was significantly reduced and neurological behavior function was improved in rats with MCAO treated with GLGZD compared with rats in the MCAO group. Amoeboid microglial expansion and inflammatory cell migration were observed in the infarcted areas of rats in the GLGZD group and were not identified in those of the MCAO group. Target mRNA and protein levels, and inflammatory cell infiltration were significantly reduced in the GLGZD group compared with the MCAO model group. Notably, GLGZD treatment induced neuroprotective effects, reducing inflammation and inhibiting NF-κB signaling compared with the MCAO group. Therefore, GLGZD may exhibit anti-inflammatory effects against ischemia-reperfusion brain injury and may be a therapeutic target for ischemic stroke.

p53 inhibition provides a pivotal protective effect against ischemia-reperfusion injury in vitro via mTOR signaling

Tumor suppressor p53 has recently been reported to have numerous functions independent of tumorigenesis, including neuronal survival during ischemia. The mammalian target of rapamycin (mTOR) signaling pathway plays a central role in the regulation of metabolism, cell growth, development, and cell survival. Our recent work has demonstrated the neuroprotective effects of the mTOR pathway. Considering that p53 is also an important regulator of mTOR, to further clarify the role of p53 and the mTOR signaling pathway in neuronal ischemic-reperfusion injury, we used mouse primary mixed cultured neurons with an oxygen glucose deprivation (OGD) model to mimic an ischemic-reperfusion injury in vitro. A lentiviral system was also used to inhibit or overexpress p53 to determine whether p53 alteration affects OGD and reperfusion injury. Our results show that activated p53 was induced and it suppressed mTOR expression in primary mixed cultured neurons after OGD and reperfusion. Inhibiting p53, using either a chemical inhibitor or lentiviral-mediated shRNA, exhibited neuroprotective effects in primary cultured neurons against OGD and reperfusion injury through the upregulation of mTOR activity. Such protective effects could be reversed by rapamycin, an mTOR inhibitor. Conversely, p53 overexpression tended to exacerbate the detrimental effects of OGD injury by downregulating mTOR activity. These results suggest that p53 inhibition has a pivotal protective effect against an in vitro ischemia-reperfusion injury via mTOR signaling and provides a potential and promising therapeutic target for stroke treatment.

Amplification of Regulatory T Cells Using a CD28 Superagonist Reduces Brain Damage After Ischemic Stroke in Mice

Background and Purpose—

Neuroinflammation plays an important role in ischemic brain injury. Regulatory T cells (Treg) are important endogenous immune modulators. We tested the hypothesis that Treg amplification with a CD28 superagonistic monoclonal antibody (CD28SA) reduces brain damage in murine cerebral ischemia.

Methods—

Cerebral ischemia was induced by coagulation of the distal middle cerebral artery or by 60 minutes filament occlusion of the proximal middle cerebral artery in C57BL6 mice. 150 μg CD28SA was injected intraperitoneally 3 or 6 hours after ischemia onset. Outcome was determined by infarct volumetry and behavioral testing. Brain-infiltrating leukocyte subpopulations were analyzed by flow cytometry and immunohistochemistry 3 and 7 days after middle cerebral artery occlusion.

Results—

CD28SA reduced infarct size in both models and attenuated functional deficit 7 days after stroke induction. Mice treated with CD28SA increased numbers of Treg in spleen and brain. Tregs were functionally active and migrated into the brain where they accumulated and proliferated in the peri-infarct area. More than 60% of brain infiltrating Treg produced interleukin-10 in CD28SA compared with 30% in control.

Conclusions—

In vivo expansion and amplification of Treg by CD28SA attenuates the inflammatory response and improves outcome after experimental stroke.

A new model of cuprizone-mediated demyelination/remyelination

In the central nervous system, demyelinating diseases, such as multiple sclerosis, result in devastating long-term neurologic damage, in part because of the lack of effective remyelination in the adult human brain. One model used to understand the mechanisms regulating remyelination is cuprizone-induced demyelination, which allows investigation of remyelination mechanisms in adult animals following toxin-induced demyelination. Unfortunately, the degree of demyelination in the cuprizone model can vary, which complicates understanding the process of remyelination. Previous work in our laboratory demonstrated that the Akt/mTOR pathway regulates active myelination. When given to young postnatal mice, the mTOR inhibitor, rapamycin, inhibits active myelination. In the current study, the cuprizone model was modified by the addition of rapamycin during cuprizone exposure. When administered together, cuprizone and rapamycin produced more complete demyelination and provided a longer time frame over which to investigate remyelination than treatment with cuprizone alone. The consistency in demyelination will allow a better understanding of the mechanisms initiating remyelination. Furthermore, the slower rate of remyelination provides a longer window of time in which to investigate the diverse contributing factors that regulate remyelination. This new model of cuprizone-induced demyelination could potentially aid in identification of new therapeutic targets to enhance remyelination in demyelinating diseases.