Interleukin-6 protects cultured cerebellar granule neurons against glutamate-induced neurotoxicity

The Neuroimmune System and the Cerebellum

The recognition that there is an innate immune system of the brain, referred to as the neuroimmune system, that preforms many functions comparable to that of the peripheral immune system is a relatively new concept and much is yet to be learned. The main cellular components of the neuroimmune system are the glial cells of the brain, primarily microglia and astrocytes. These cell types preform many functions through secretion of signaling factors initially known as immune factors but referred to as neuroimmune factors when produced by cells of the brain. The immune functions of glial cells play critical roles in the healthy brain to maintain homeostasis that is essential for normal brain function, to establish cytoarchitecture of the brain during development, and, in pathological conditions, to minimize the detrimental effects of disease and injury and promote repair of brain structure and function. However, dysregulation of this system can occur resulting in actions that exacerbate or perpetuate the detrimental effects of disease or injury. The neuroimmune system extends throughout all brain regions, but attention to the cerebellar system has lagged that of other brain regions and information is limited on this topic. This article is meant to provide a brief introduction to the cellular and molecular components of the brain immune system, its functions, and what is known about its role in the cerebellum. The majority of this information comes from studies of animal models and pathological conditions, where upregulation of the system facilitates investigation of its actions.

Interleukin-6 in Traumatic Brain Injury: A Janus-Faced Player in Damage and Repair

Traumatic brain injury (TBI) is a common and often devastating illness, with wide-ranging public health implications. In addition to the primary injury, victims of TBI are at risk for secondary neurological injury by numerous mechanisms. Current treatments are limited and do not target the profound immune response associated with injury. This immune response reflects a convergence of peripheral and central nervous system-resident immune cells whose interaction is mediated in part by a disruption in the blood-brain barrier (BBB). The diverse family of cytokines helps to govern this communication and among these, Interleukin (IL)-6 is a notable player in the immune response to acute neurological injury. It is also a well-established pharmacological target in a variety of other disease contexts. In TBI, elevated IL-6 levels are associated with worse outcomes, but the role of IL-6 in response to injury is double-edged. IL-6 promotes neurogenesis and wound healing in animal models of TBI, but it may also contribute to disruptions in the BBB and the progression of cerebral edema. Here, we review IL-6 biology in the context of TBI, with an eye to clarifying its controversial role and understanding its potential as a target for modulating the immune response in this disease.

Immune-Triggered Forms of Plasticity Across Brain Regions

Immune cells play numerous roles in the host defense against the invasion of microorganisms and pathogens, which induces the release of inflammatory mediators (e.g., cytokines and chemokines). In the CNS, microglia is the major resident immune cell. Recent efforts have revealed the diversity of the cell types and the heterogeneity of their functions. The refinement of the synapse structure was a hallmark feature of the microglia, while they are also involved in the myelination and capillary dynamics. Another promising feature is the modulation of the synaptic transmission as synaptic plasticity and the intrinsic excitability of neurons as non-synaptic plasticity. Those modulations of physiological properties of neurons are considered induced by both transient and chronic exposures to inflammatory mediators, which cause behavioral disorders seen in mental illness. It is plausible for astrocytes and pericytes other than microglia and macrophage to induce the immune-triggered plasticity of neurons. However, current understanding has yet achieved to unveil what inflammatory mediators from what immune cells or glia induce a form of plasticity modulating pre-, post-synaptic functions and intrinsic excitability of neurons. It is still unclear what ion channels and intracellular signaling of what types of neurons in which brain regions of the CNS are involved. In this review, we introduce the ubiquitous modulation of the synaptic efficacy and the intrinsic excitability across the brain by immune cells and related inflammatory cytokines with the mechanism for induction. Specifically, we compare neuro-modulation mechanisms by microglia of the intrinsic excitability of cerebellar Purkinje neurons with cerebral pyramidal neurons, stressing the inverted directionality of the plasticity. We also discuss the suppression and augmentation of the extent of plasticity by inflammatory mediators, as the meta-plasticity by immunity. Lastly, we sum up forms of immune-triggered plasticity in the different brain regions with disease relevance. Together, brain immunity influences our cognition, sense, memory, and behavior via immune-triggered plasticity.

Role of IL-6 in the regulation of neuronal development, survival and function

The pleiotropic cytokine interleukin-6 (IL-6) is emerging as a molecule with both beneficial and destructive potentials. It can exert opposing actions triggering either neuron survival after injury or causing neurodegeneration and cell death in neurodegenerative or neuropathic disorders. Importantly, neurons respond differently to IL-6 and this critically depends on their environment and whether they are located in the peripheral or the central nervous system. In addition to its hub regulator role in inflammation, IL-6 is recently emerging as an important regulator of neuron function in health and disease, offering exciting possibilities for more mechanistic insight into the pathogenesis of mental, neurodegenerative and pain disorders and for developing novel therapies for diseases with neuroimmune and neurogenic pathogenic components.

Alcohol and IL-6 Alter Expression of Synaptic Proteins in Cerebellum of Transgenic Mice with Increased Astrocyte Expression of IL-6

Recent studies indicate that neuroimmune factors, including the cytokine interleukin-6 (IL-6), play a role in the CNS actions of alcohol. The cerebellum is a sensitive target of alcohol, but few studies have examined a potential role for neuroimmune factors in the actions of alcohol on this brain region. A number of studies have shown that synaptic transmission, and in particular inhibitory synaptic transmission, is an important cerebellar target of alcohol. IL-6 also alters synaptic transmission, although it is unknown if IL-6 targets are also targets of alcohol. This is an important issue because alcohol induces glial production of IL-6, which could then covertly influence the actions of alcohol. The persistent cerebellar effects of both IL-6 and alcohol typically involve chronic exposure and, presumably, altered gene and protein expression. Thus, in the current studies we tested the possibility that proteins involved in inhibitory and excitatory synaptic transmission in the cerebellum are common targets of alcohol and IL-6. We used transgenic mice that express elevated levels of astrocyte produced IL-6 to model persistently elevated expression of IL-6, as would occur in alcohol use disorders, and a chronic intermittent alcohol exposure/withdrawal paradigm (CIE/withdrawal) that is known to produce alcohol dependence. Multiple cerebellar synaptic proteins were assessed by Western blot. Results show that IL-6 and CIE/withdrawal have both unique and common actions that affect synaptic protein expression. These common targets could provide sites for IL-6/alcohol exposure/withdrawal interactions and play an important role in cerebellar symptoms of alcohol use such as ataxia.

miR-140-5p regulates the odontoblastic differentiation of dental pulp stem cells via the Wnt1/β-catenin signaling pathway

BACKGROUND

MicroRNAs (miRNAs) play a key role in regulating cell differentiation. In the present study, we aimed to explore the role of miR-140-5p in odontoblastic differentiation of dental pulp stem cells (DPSCs).

METHODS

DPSCs from normal human impacted third molars were isolated and cultured. After overexpression or silencing of miR-140-5p in DPSCs, activity, proliferation, and odontoblastic differentiation of DPSCs were evaluated. The possible target gene of miR-140-5p was verified by luciferase reporter gene assay. Using gene transfection technology, RT-CPR, and Western blot to confirm miR-140-5p regulates the odontoblastic differentiation of DPSCs through Wnt1/β-catenin signaling.

RESULTS

We found the expression of miR-140-5p decreased in the differentiated DPSCs for odontoblastic cells, and at the same time, the expressions of Wnt1 and β-catenin increased. Wnt1 was the target gene of miR-140-5p which was confirmed by luciferase reporter gene system. miR-140-5p overexpression suppressed the expression of Wnt1. miR-140-5p inhibitor could promote the odontoblastic differentiation of DPSCs. miR-140-5p mimic could weaken the odontoblastic differentiation of DPSCs, which could be reversed by the overexpression of Wnt1.

CONCLUSION

Our data demonstrated that miR-140-5p regulates the odontoblastic differentiation of DPSCs via targeting Wnt1/β-catenin signaling. Therefore, miR-140-5p might be a molecular target to regulate the odontoblastic differentiation for the therapeutic agents in dental medicine.

Is psychosis a multisystem disorder? A meta-review of central nervous system, immune, cardiometabolic, and endocrine alterations in first-episode psychosis and perspective on potential models

People with psychotic disorders show abnormalities in several organ systems in addition to the central nervous system (CNS); and this contributes to excess mortality. However, it is unclear how strong the evidence is for alterations in non-CNS systems at the onset of psychosis, how the alterations in non-CNS systems compare to those in the CNS, or how they relate to symptoms. Here, we consider these questions, and suggest potential models to account for findings. We conducted a systematic meta-review to summarize effect sizes for both CNS (focusing on brain structural, neurophysiological, and neurochemical parameters) and non-CNS dysfunction (focusing on immune, cardiometabolic, and hypothalamic-pituitary-adrenal (HPA) systems) in first-episode psychosis (FEP). Relevant meta-analyses were identified in a systematic search of Pubmed and the methodological quality of these was assessed using the AMSTAR checklist (A Measurement Tool to Assess Systematic Reviews). Case-control data were extracted from studies included in these meta-analyses. Random effects meta-analyses were re-run and effect size magnitudes for individual parameters were calculated, as were summary effect sizes for each CNS and non-CNS system. We also grouped studies to obtain overall effect sizes for non-CNS and CNS alterations. Robustness of data for non-CNS and CNS parameters was assessed using Rosenthal's fail-safe N. We next statistically compared summary effect size for overall CNSand overall non-CNS alterations, as well as for each organ system separately. We also examined how non-CNS alterations correlate CNS alterations, and with psychopathological symptoms. Case-control data were extracted for 165 studies comprising a total sample size of 13,440. For people with first episode psychosis compared with healthy controls, we observed alterations in immune parameters (summary effect size: g = 1.19), cardiometabolic parameters (g = 0.23); HPA parameters (g = 0.68); brain structure (g = 0.40); neurophysiology (g = 0.80); and neurochemistry (g = 0.43). Grouping non-CNS organ systems together provided an effect size for overall non-CNS alterations in patients compared with controls (g = 0.58), which was not significantly different from the overall CNS alterations effect size (g = 0.50). However, the summary effect size for immune alterations was significantly greater than that for brain structural (P < 0.001) and neurochemical alterations (P < 0.001), while the summary effect size for cardiometabolic alterations was significantly lower than neurochemical (P = 0.04), neurophysiological (P < 0.001), and brain structural alterations (P = 0.001). The summary effect size for HPA alterations was not significantly different from brain structural (P = 0.14), neurophysiological (P = 0.54), or neurochemical alterations (P = 0.22). These outcomes remained similar in antipsychotic naive sensitivity analyses. We found some, but limited and inconsistent, evidence that non-CNS alterations were associated with CNS changes and symptoms in first episode psychosis. Our findings indicate that there are robust alterations in non-CNS systems in psychosis, and that these are broadly similar in magnitude to a range of CNS alterations. We consider models that could account for these findings and discuss implications for future research and treatment.

Inflammatory Profiles of the Interleukin Family and Network in Cerebral Hemorrhage

Cerebral hemorrhage is a series of devastating cerebrovascular diseases with high mortality, morbidity and recurrence rate. Localized and systemic immuno-reactions are involved. Aggregation of immunocytes, which were both recruited from the peripheral circulation and resident in the central nervous system, is induced and activated by hematoma-related blood components. Subsequently, various cytokines, chemokines, free radicals and toxic chemicals are secreted to participant host defense responses. Among these, neuro-inflammation plays critical roles in both the pathologic processes of secondary injuries and recovery of neural damages. Numerous treatment strategies have been proposed, aiming at controlling the balance between anti- and proinflammation. Here, we summarized our current understanding and potential clinical applications for cytokines of the interleukin family in the pathogenesis of hemorrhagic stroke. In addition, we conducted protein-protein network, gene ontology and KEGG analysis on the interleukins using online bioinformatic tools to further elaborate the comprehensive mechanisms of interleukins in cerebral hemorrhage.

Adult Fmr1 knockout mice present with deficiencies in hippocampal interleukin-6 and tumor necrosis factor-α expression

Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by a single genetic mutation in the FMR1 gene. Mutations in the FMR1 gene are the largest monogenic cause of autism spectrum disorder (ASD), and thus both disorders share many of the same cognitive and behavioral impairments. There is increasing evidence suggesting that dysregulated immune responses play a role in the pathophysiology of ASD; however, the association between FXS and altered immunity requires further investigation. This study examined whether Fmr1 knockout (KO) and wild-type mice on a FVB/NJ background strain had altered cytokine expression at baseline levels in the hippocampus. Results showed Fmr1 KO mice to have decreased proinflammatory cytokine hippocampal mRNA expression, specifically interleukin (IL)-6 and tumor necrosis factor-α, compared with wild-type mice. However, no differences were detected in the expression levels of IL-1β, MCP-1, interferon-γ, or IL-10. Despite the high comorbidity between FXS and ASD, these results suggest that the Fmr1 KO mouse does not mimic the increased proinflammatory cytokine expression commonly found in ASD mouse models and patients. Further investigation of the immune profile of the Fmr1 KO mouse is critical to understand whether this deficiency of cytokines in the hippocampus is indicative of a broader immunologic deficit associated with FXS.

Assessment of systemic cellular inflammatory response after spontaneous intracerebral hemorrhage

OBJECTIVE

After spontaneous intracerebral hemorrhage (ICH) a local and systemic inflammatory response is activated. Interleukin-6 (IL) is one of most relevant orchestrators of inflammatory responses in the brain and is released from multiple immune cells, including neutrophils. Herby we assessed the relevance of systemic inflammation in patients suffering ICH.

METHODS

From October 2010 to October 2011 we included in our routine of laboratory investigations besides to C-reactive protein (CRP), the addition of IL-6 and an analysis of the subpopulation of circulating blood cells. Values at admission, at 3rd and 7th day after admission were evaluated. We analyzed 43 patients with non-traumatic ICH; stroke-related ICH or tumor associated hemorrhage were excluded. Outcome variables were 30 and 90-day mortality and NIHSS at discharge. A natural logarithmic transformation of IL-6, lymphocytes, and monocytes was used.

RESULTS

8.6% died within 30-days and mortality increased to 39.5% at 90th day. Total leukocytes and neutrophils as well as IL-6 at admission were statistically significant increased among patients who died within 30days after ICH onset (p=0.002). IL-6 and CRP in follow-up (3rd and 7th day) were higher among patients with poor outcome (NIHSS >15). The number of circulating lymphocytes and monocytes was not different in measurement. Leukocytes and neutrophils at 3rd day after admission were augmented in patients with respiratory infection and CRP in follow-up increased if some kind of infection was clinically or microbiologically detected. IL-6 at admission and in follow-up and monocytes at 7th day were related to ICH volume. CRP-values at 3rd or 7th day but not at admission were associated to bigger ICH-volume. The values of IL-6 were highly correlated to 30-day mortality and volume of ICH as CRP only with ICH volume.

CONCLUSION

After ICH onset a systemic activation of immune system seems to be induced and may be influencing outcome. Peripheral recruitment of leukocytes, especially neutrophils could be a target for future therapeutic interventions. Because of the tighter correlation of IL-6 at admission, it might be more accurate for prognostic issues than CRP.

Transcriptional landscapes at the intersection of neuronal apoptosis and substance P-induced survival: exploring pathways and drug targets

A change in the delicate equilibrium between apoptosis and survival regulates the neurons fate during the development of nervous system and its homeostasis in adulthood. Signaling pathways promoting or protecting from apoptosis are activated by multiple signals, including those elicited by neurotrophic factors, and depend upon specific transcriptional programs. To decipher the rescue program induced by substance P (SP) in cerebellar granule neurons, we analyzed their whole-genome expression profiles after induction of apoptosis and treatment with SP. Transcriptional pathways associated with the survival effect of SP included genes encoding for proteins that may act as pharmacological targets. Inhibition of one of these, the Myc pro-oncogene by treatment with 10058-F4, reverted in a dose-dependent manner the rescue effect of SP. In addition to elucidate the transcriptional mechanisms at the intersection of neuronal apoptosis and survival, our systems biology-based perspective paves the way towards an innovative pharmacology based on targets downstream of neurotrophic factor receptors.

Regulation of TRPM7 Function by IL-6 through the JAK2-STAT3 Signaling Pathway

Aims

Previous studies have demonstrated that expression of the TRPM7 channel, which may induce delayed cell death by mediating calcium influx, is precisely regulated. However, functional regulation of TRPM7 channels by endogenous molecules has not been elucidated. The proinflammatory cytokine IL-6 contributes to regulation of Ca²⁺ influx in cerebral ischemia, but the role of IL-6 in regulating TRPM7 functioning is unknown. Thus, we here investigated the interaction between IL-6 and TRPM7 channels and the relevant mechanisms.

Materials and Methods

Using whole-cell patch-clamping, we first investigated the effect of IL-6 on TRPM7-like currents in primary cultured cortical neurons. Next, TRPM7-overexpressing HEK293 cells were used to confirm the effect of IL-6/sIL-6R on TRPM7. Finally, we used specific signaling pathway inhibitors to investigate the signaling pathways involved.

Results

IL-6 or IL-6/sIL-6R dose-dependently inhibited inward TRPM7 currents, in both primary cultured neurons and HEK293 cells overexpressing TRPM7. In intracellular Mg²⁺-free conditions, extracellular Ca²⁺ or the α-kinase domain of TRPM7 did not participate in this regulation. The inhibitory effect of IL-6 on TRPM7 could be blocked by specific inhibitors of the JAK2−STAT3 pathway, but not of the PI3K, ERK1/2, or PLC pathways.

Conclusions

IL-6 inhibits the inward TRPM7 current via the JAK2−STAT3 signaling pathway.

Cerebrospinal fluid levels of IL-6 are decreased and correlate with cognitive status in DLB patients

Introduction

Inflammatory processes have previously been shown to influence cognition and progression of dementia. An involvement of interleukin (IL)-6 has in particular been suggested as altered levels of IL-6 in cerebrospinal fluid (CSF) have been found in patients with Alzheimer’s disease (AD). Also, an association between cognitive decline and levels of IL-6 in CSF have been reported. The aim of the present study was to investigate whether patients clinically diagnosed with dementia with Lewy bodies (DLB) display altered CSF IL-6 levels in comparison with patients with AD and control subjects without dementia and whether the IL-6 levels are correlated with cognitive status and biomarkers for AD and synucleinopathy.

Methods

To analyse CSF of patients with AD (n = 45), patients with DLB (n = 29) and control subjects without dementia (n = 36), we used immunoassays to measure levels of IL-6 (multiplex electrochemiluminescence); AD markers phosphorylated tau, total tau and amyloid-β_1–42 (enzyme-linked immunosorbent assay [ELISA]); and α-synuclein (ELISA). Cognitive status was evaluated using the Mini Mental State Examination (MMSE).

Results

Our analysis showed significantly lower levels of IL-6 in CSF from patients with DLB than in CSF from patients with AD and control subjects without dementia. The IL-6 levels were also negatively correlated with MMSE and positively correlated with α-synuclein CSF levels.

Conclusions

Our findings support previous studies by demonstrating a link between inflammatory processes and dementia progression and further strengthen the hypothesis that IL-6 is involved in dementia pathology and cognitive decline.

Unraveling the Specific Ischemic Core and Penumbra Transcriptome in the Permanent Middle Cerebral Artery Occlusion Mouse Model Brain Treated with the Neuropeptide PACAP38

Our group has been systematically investigating the effects of the neuropeptide pituitary adenylate-cyclase activating polypeptide (PACAP) on the ischemic brain. To do so, we have established and utilized the permanent middle cerebral artery occlusion (PMCAO) mouse model, in which PACAP38 (1 pmol) injection is given intracerebroventrically and compared to a control saline (0.9% sodium chloride, NaCl) injection, to unravel genome‑wide gene expression changes using a high-throughput DNA microarray analysis approach. In our previous studies, we have accumulated a large volume of data (gene inventory) from the whole brain (ipsilateral and contralateral hemispheres) after both PMCAO and post-PACAP38 injection. In our latest research, we have targeted specifically infarct or ischemic core (hereafter abbreviated IC) and penumbra (hereafter abbreviated P) post-PACAP38 injections in order to re-examine the transcriptome at 6 and 24 h post injection. The current study aims to delineate the specificity of expression and localization of differentially expressed molecular factors influenced by PACAP38 in the IC and P regions. Utilizing the mouse 4 × 44 K whole genome DNA chip we show numerous changes (≧/≦ 1.5/0.75-fold) at both 6 h (654 and 456, and 522 and 449 up- and down-regulated genes for IC and P, respectively) and 24 h (2568 and 2684, and 1947 and 1592 up- and down-regulated genes for IC and P, respectively) after PACAP38 treatment. Among the gene inventories obtained here, two genes, brain-derived neurotrophic factor (Bdnf) and transthyretin (Ttr) were found to be induced by PACAP38 treatment, which we had not been able to identify previously using the whole hemisphere transcriptome analysis. Using bioinformatics analysis by pathway- or specific-disease-state focused gene classifications and Ingenuity Pathway Analysis (IPA) the differentially expressed genes are functionally classified and discussed. Among these, we specifically discuss some novel and previously identified genes, such as alpha hemoglobin stabilizing protein (Ahsp), cathelicidin antimicrobial peptide (Camp), chemokines, interferon beta 1 (Ifnb1), and interleukin 6 (Il6) in context of PACAP38-mediated neuroprotection in the ischemic brain. Taken together, the DNA microarray analysis provides not only a great resource for further study, but also reinforces the importance of region-specific analyses in genome-wide identification of target molecular factors that might play a role in the neuroprotective function of PACAP38.

Cytokine gene variations associated with subsyndromal depressive symptoms in patients with breast cancer

PURPOSE

This study explored the relationships between variations in cytokines genes and depressive symptoms in a sample of patients who were assessed prior to and for six months following breast cancer surgery. Phenotypic differences between Resilient (n = 155) and Subsyndromal (n = 180) depressive symptom classes, as well as variations in cytokine genes were evaluated.

METHOD

Patients were recruited prior to surgery and followed for six months. Growth mixture modeling was used to identify distinct latent classes based on Center for Epidemiological Studies Depression (CES-D) Scale scores. Eighty-two single nucleotide polymorphisms and 35 haplotypes among 15 candidate cytokine genes were evaluated.

RESULTS

Patients in the Subsyndromal class were significantly younger, more likely to be married or partnered, and reported a significantly lower functional status. Variation in three cytokine genes (i.e., interferon gamma receptor 1 (IFNGR1 rs9376268), interleukin 6 (IL6 rs2069840), tumor necrosis factor alpha (TNFA rs1799964)), as well as age and functional status predicted membership in the Subsyndromal versus the Resilient class.

CONCLUSIONS

A variation in TNFA that was associated with Subsyndromal depressive symptoms in a sample of patients and their family caregivers was confirmed in this sample. Variations in cytokine genes may place these patients at higher risk for the development of Subsyndromal levels of depressive symptoms.

Neuroprotection effect of interleukin (IL)-17 secreted by reactive astrocytes is emerged from a high-level IL-17-containing environment during acute neuroinflammation

An increase in interleukin (IL)-17A-producing cells, particularly at sites of tissue inflammation, is observed frequently, yet the mechanism is not fully understood. This study aims to dissect the role of IL-17 in autoimmunity-mediated neuroinflammation. The cytokine milieu containing elevated IL-17, which often appears in active states of autoimmunity, was mimicked in vitro by a supernatant obtained from rat peripheral blood monocytes stimulated with phorbol mystistate acetate (PMA)/ionomycin. The application of such inflammatory media on only primary cultured cerebellar granule neurones resulted in significant apoptosis, but the presence of astrocytes largely prevented the effect. The supernatants of the stimulated astrocytes, especially those that contained the highest level of IL-17, achieved the best protection, and this effect could be blocked by anti-IL-17 antibodies. Protein IL-17 inhibited intracellular calcium increase and protected the neurones under inflammatory attack from apoptosis. IL-17, but not interferon (IFN)-γ, in the inflammatory media contributed to astrocyte secretion of IL-17, which depended on the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway activation. The astrocytes that were treated with IL-17 alone or with prolonged treatment of the inflammatory media failed to produce sufficient levels of IL-17. Moreover, confirmatory data were obtained in vivo in a monophasic experimental autoimmune uveitis (EAU) in Lewis rats; in this preparation, the high-level IL-17-containing the cytokine milieu was demonstrated, along with IL-17 secretion by the resident neural cells. The antagonism of IL-17 at a late stage disturbed the disease resolution and resulted in significant neural apoptosis. Our data show a dynamic role of IL-17 in the maintenance of homeostasis and neuroprotection in active neuroinflammation.

Interleukin-6 inhibits voltage-gated sodium channel activity of cultured rat spinal cord neurons

OBJECTIVE

Interleukin-6 (IL-6) is a pleiotropic proinflammatory cytokine that plays a key role in the injuries and diseases of the central nervous system (CNS). A voltage-gated Na+ channel (VGSC) is essential for the excitability and electrical properties of the neurons. However, there is still limited information on the role of IL-6 in voltage-gated sodium channels. Our study aimed to investigate the effects of IL-6 on Na+ currents in cultured spinal-cord neurons.

METHODS

VGSC currents were activated and recorded using whole-cell patch-clamp technique in the cultured rat spinal cord neurons. The effects of IL-6 concentration and exposure duration were examined. To determine whether any change in the number of channels in the plasma membrane can inhibit IL-6 on VGSC currents, we examined the expression of α1A (SCN1α) subunit mRNA level and protein level in the neurons before and after IL-6 induction using real-time polymerase chain reaction.

RESULTS

We verified that IL-6, through a receptor-mediated mechanism, suppressed Na+ currents in a time- and dose-dependent manner, but did not alter the voltage-dependent activation and inactivation. Gp130 was involved in this inhibition. Furthermore, the spike amplitude was also inhibited by IL-6 in the doses that decreased the Na+ currents.

CONCLUSION

VGSC currents are significantly inhibited by IL-6. Our findings reveal that the potential neuroprotection of IL-6 may result from the inhibitory effects on VGSC currents.

Hippocampal dysfunctions in tumor-bearing mice

Individuals with cancer are particularly susceptible to depression and cognitive impairment. However, the precise mechanisms underlying cancer-induced hippocampal dysfunction are poorly understood. We investigated the effects of a peripheral tumor on emotional behavior, hippocampus-dependent memory and associated molecular and cellular features using an experimental animal model. Behavioral alterations were examined; stress-related parameters measured; hippocampal neurogenesis evaluated; and the levels of pro-inflammatory cytokines, brain-derived neurotrophic factor (BDNF) and cyclooxygenase-2 (COX-2) assayed, 2 weeks after inoculation of adult BALB/c mice with cells of a colon carcinoma cell line (CT26). As the tumors developed, CT26-inoculated mice showed significant increases in the depression-like behavior (measured using the tail suspension test) and memory impairment (in terms of object recognition) compared with vehicle-inoculated controls. The presence of a peripheral tumor significantly elevated the hippocampal levels of mRNAs encoding interleukin-6 (IL-6) and tumor necrosis factor-α, as well as plasma IL-6 and corticosterone levels. Additionally, the adrenal glands became enlarged, and the numbers of Ki-67-positive proliferating hippocampal cells and doublecortin-positive immature progenitor neurons, as well as the constitutive levels of mRNAs encoding BDNF and COX-2 were significantly reduced. Therefore, a peripheral tumor alone may be sufficient to induce hippocampal dysfunction, possibly by reducing the rate of neurogenesis and the levels of BDNF and COX-2 in that tissue and also by increasing stress-related parameters and the circulating levels of pro-inflammatory cytokines.

Brain IL-6 and autism

Autism is a severe neurodevelopmental disorder characterized by impairments in social interaction, deficits in verbal and non-verbal communication, and repetitive behavior and restricted interests. Emerging evidence suggests that aberrant neuroimmune responses may contribute to phenotypic deficits and could be appropriate targets for pharmacologic intervention. Interleukin (IL)-6, one of the most important neuroimmune factors, has been shown to be involved in physiological brain development and in several neurological disorders. For instance, findings from postmortem and animal studies suggest that brain IL-6 is an important mediator of autism-like behaviors. In this review, a possible pathological mechanism behind autism is proposed, which suggests that IL-6 elevation in the brain, caused by the activated glia and/or maternal immune activation, could be an important inflammatory cytokine response involved in the mediation of autism-like behaviors through impairments of neuroanatomical structures and neuronal plasticity. Further studies to investigate whether IL-6 could be used for therapeutic interventions in autism would be of great significance.

Research review: the role of cytokines in depression in adolescents: a systematic review

BACKGROUND

While cytokines have been implicated in the pathophysiology of depression in adults, the potential role in younger age groups such as adolescents is less clear. This article therefore reviews the literature (a) to explore the relationship between cytokines and depression in adolescents, and (b) to examine how cytokines may be related to adolescent depression in the context of other neurobiological theories of depression.

METHOD

A systematic review of the scientific literature on the subject was conducted in February 2013, searching the Web of Knowledge, PubMed (Medline), PsycInfo and Cochrane electronic databases.

RESULTS

Eighteen studies were identified measuring both depression or depressive symptoms and cytokines or immune markers in adolescents. Adolescents with depression show age-specific characteristics of the immune and inflammatory system, specifically in NK cell activity and in pro-inflammatory cytokines (such as IL-1β and TNF-α). In addition, the role of cytokines in adolescent depression is influenced by neurodevelopment, hormonal changes, stress and trauma.

CONCLUSIONS

There may be differences in the neurobiology of adolescent major depressive disorder (MDD) compared with adult MDD. Increased understanding of the role of cytokines in adolescent MDD may lead to improved outcomes in the treatment of adolescent depression.

Dietary supplementation with resveratrol and/or docosahexaenoic acid alters hippocampal gene expression in adult C57Bl/6 mice

The hippocampus is an important brain structure for multiple cognitive functions, including memory formation. It is particularly sensitive to insults, such as stress, ischemia, and aging; all of these can affect hippocampal and therefore cognitive function. To understand the potential of diet for the preservation of hippocampal function, we investigated the effects of dietary supplementation with resveratrol (RES) or docosahexaenoic acid (DHA), or their combination, on hippocampal gene expression in adult C57BL/6 mice. Animals in the supplemented group received either 50 mg/kg/day of RES or DHA, while the combination group received 50 mg/kg/day of each supplement. Dietary supplements were mixed with the AIN93G diet, and supplementation lasted 6 weeks. The control group received AIN93G diet alone for the same period. At the end of the experiment, the hippocampi were processed for genome-wide gene expression and pathway analyses. Most of the genes that were significantly altered were associated with inflammatory responses as determined by pathway analysis. RES-supplemented animals showed decreased expression of IL-6 (P=.001), MAPKapk2 (P=.015), and increased expression for PI3KR2 (P=.034) and Wnt7a (P=.004) expression. DHA-supplemented animals showed a decreased IL-6 (P=.003) and an increased Wnt7a (P=.003) expression. Animals on the combination diet showed a decreased IL-6 (P=.005) and Apolipoprotien E (ApoE) (P=.035) expression. Our findings demonstrate that hippocampal gene expression is significantly altered by all three dietary supplementation regimes. Moreover, our analysis indicates that RES and DHA likely exert their beneficial effects through antiinflammatory mechanisms.

Astrocytes protect neurons against methylmercury via ATP/P2Y(1) receptor-mediated pathways in astrocytes

Methylmercury (MeHg) is a well known environmental pollutant that induces serious neuronal damage. Although MeHg readily crosses the blood-brain barrier, and should affect both neurons and glial cells, how it affects glia or neuron-to-glia interactions has received only limited attention. Here, we report that MeHg triggers ATP/P2Y1 receptor signals in astrocytes, thereby protecting neurons against MeHg via interleukin-6 (IL-6)-mediated pathways. MeHg increased several mRNAs in astrocytes, among which IL-6 was the highest. For this, ATP/P2Y1 receptor-mediated mechanisms were required because the IL-6 production was (i) inhibited by a P2Y1 receptor antagonist, MRS2179, (ii) abolished in astrocytes obtained from P2Y1 receptor-knockout mice, and (iii) mimicked by exogenously applied ATP. In addition, (iv) MeHg released ATP by exocytosis from astrocytes. As for the intracellular mechanisms responsible for IL-6 production, p38 MAP kinase was involved. MeHg-treated astrocyte-conditioned medium (ACM) showed neuro-protective effects against MeHg, which was blocked by anti-IL-6 antibody and was mimicked by the application of recombinant IL-6. As for the mechanism of neuro-protection by IL-6, an adenosine A1 receptor-mediated pathway in neurons seems to be involved. Taken together, when astrocytes sense MeHg, they release ATP that autostimulates P2Y1 receptors to upregulate IL-6, thereby leading to A1 receptor-mediated neuro-protection against MeHg.

Interleukin-6 inhibits L-type calcium channel activity of cultured cerebellar granule neurons

Our previous work has shown that interleukin-6 (IL-6) implements its neuroprotective effect by inhibiting the intracellular Ca(2+) overload in neurons. Here, we examined whether regulation of L-type calcium channels (LCCs) activities is involved in the neuroprotective action of IL-6. In cultured cerebellar granule neurons (CGNs), patch-clamp recording showed that the whole-cell Ca(2+) current and LCC current were significantly reduced by IL-6 pretreatment (120 ng/ml, for 24 h). Calcium imaging data indicated that IL-6 significantly suppressed high K(+)-induced intracellular Ca(2+) overload and LCC Ca(2+) influx. Moreover, expression of the LCC subunit, Ca(v)1.2, was remarkably downregulated by IL-6 in cultured CGNs. These findings suggest that IL-6 exerts a neurotrophic effect by preventing Ca(2+) overload, at least partly through inhibition of LCC activity in cultured CGNs.

Interleukin-6 gene (IL-6): a possible role in brain morphology in the healthy adult brain

Background

Cytokines such as interleukin 6 (IL-6) have been implicated in dual functions in neuropsychiatric disorders. Little is known about the genetic predisposition to neurodegenerative and neuroproliferative properties of cytokine genes. In this study the potential dual role of several IL-6 polymorphisms in brain morphology is investigated.

Methodology

In a large sample of healthy individuals (N = 303), associations between genetic variants of IL-6 (rs1800795; rs1800796, rs2069833, rs2069840) and brain volume (gray matter volume) were analyzed using voxel-based morphometry (VBM). Selection of single nucleotide polymorphisms (SNPs) followed a tagging SNP approach (e.g., Stampa algorigthm), yielding a capture 97.08% of the variation in the IL-6 gene using four tagging SNPs.

Principal findings/results

In a whole-brain analysis, the polymorphism rs1800795 (−174 C/G) showed a strong main effect of genotype (43 CC vs. 150 CG vs. 100 GG; x = 24, y = −10, z = −15; F(2,286) = 8.54, p_uncorrected = 0.0002; p_{AlphaSim-corrected} = 0.002; cluster size k = 577) within the right hippocampus head. Homozygous carriers of the G-allele had significantly larger hippocampus gray matter volumes compared to heterozygous subjects. None of the other investigated SNPs showed a significant association with grey matter volume in whole-brain analyses.

Conclusions/significance

These findings suggest a possible neuroprotective role of the G-allele of the SNP rs1800795 on hippocampal volumes. Studies on the role of this SNP in psychiatric populations and especially in those with an affected hippocampus (e.g., by maltreatment, stress) are warranted.

Expression of pancreatitis-associated protein after traumatic brain injury: a mechanism potentially contributing to neuroprotection in human brain

Neuronal cell death after severe traumatic brain injury (TBI) is caused by a complex interplay of pathological mechanisms including excitotoxicity, oxidative stress, mitochondrial dysfunction, extensive neuroinflammation, and ischemia-reperfusion injury. Pancreatitis-associated protein I (PAP I/reg2) was reported to be a survival factor for peripheral neurons, particularly sensory and motor neurons. In rat brains, by experimental TBI as well as by kainic acid induced brain seizure, PAP I and PAP III were found to be up-regulated in central neurons. In this study, we performed immunohistochemical staining in postmortem human brain from patients who died after severe TBI to demonstrate PAP expression on protein level in cerebellar Purkinje cells, pyramidal and granular neurons in cerebral cortex, and cortical neurons in the fore- and mid-brain. In primary cultures of rat brain cortical, hippocampal, and cerebellar neurons, we found neuroprotective effects for PAP I on H(2)O(2)-induced oxidative stress. Moreover, serum K(+)-deprivation induces apoptotic cell death in 55% of cerebellar granule neurons (CGN), whereas upon treatment with PAP I only 32% of CGN are apoptotic. Using Western blot analyses, we compared protein phosphorylation in neuronal signaling pathways activated by PAP I versus Interleukin-6 (IL-6). We found a rapid activation of Akt-kinase phosphorylation by PAP I with a peak at 15 min, whereas IL-6 induces Akt-phosphorylation lasting longer than 30 min. Phosphorylation of MAP-42/44 kinases is stimulated in a comparable fashion. Both, IL-6 and PAP I increase phosphorylation of NFκB for activation of gene transcription, whereas only IL-6 recruits STAT3 phosphorylation, indicating that STAT3 is not a target of PAP I transcription activation in brain neurons. Application of the Akt-inhibitor Wortmanin reveals only a partial inhibition of PAP I-dependent protection of CGN from H(2)O(2)-induced oxidative stress. Based on our findings, we suggest that PAP I is a long lasting neurotrophic signal for central neurons. The neuroprotective effects parallel those that have been described for effects of PAP I in ciliary neurotrophic factor (CNTF)-mediated survival of sensory and motor neurons. PAP I may act in autocrine and/or paracrine fashion and thus may contribute to endogenous protective mechanisms relevant under harmful conditions like oxidative stress, brain injury, or neurodegeneration.

Photoreceptor cells constitutively express functional TLR4

Toll-like receptor 4 (TLR4) is expressed on a number of cells including neurons in the brain. However, it has yet to be determined if TLR4 is expressed on photoreceptor cells in the retina. In this report, we examined primary photoreceptor cells and an established photoreceptor cell line (661W). We found that functional TLR4 is constitutively expressed on photoreceptor cells, and can be activated by LPS. We conclude that TLR4 on photoreceptor cells could directly contribute to retinal inflammatory diseases and photoreceptor cell survival.

Interleukin-6, a mental cytokine

Almost a quarter of a century ago, interleukin-6 (IL-6) was discovered as an inflammatory cytokine involved in B cell differentiation. Today, IL-6 is recognized to be a highly versatile cytokine, with pleiotropic actions not only in immune cells, but also in other cell types, such as cells of the central nervous system (CNS). The first evidence implicating IL-6 in brain-related processes originated from its dysregulated expression in several neurological disorders such as multiple sclerosis, Alzheimer's disease and Parkinson's disease. In addition, IL-6 was shown to be involved in multiple physiological CNS processes such as neuron homeostasis, astrogliogenesis and neuronal differentiation. The molecular mechanisms underlying IL-6 functions in the brain have only recently started to emerge. In this review, an overview of the latest discoveries concerning the actions of IL-6 in the nervous system is provided. The central position of IL-6 in the neuroinflammatory reaction pattern, and more specifically, the role of IL-6 in specific neurodegenerative processes, which accompany Alzheimer's disease, multiple sclerosis and excitotoxicity, are discussed. It is evident that IL-6 has a dichotomic action in the CNS, displaying neurotrophic properties on the one hand, and detrimental actions on the other. This is in agreement with its central role in neuroinflammation, which evolved as a beneficial process, aimed at maintaining tissue homeostasis, but which can become malignant when exaggerated. In this perspective, it is not surprising that 'well-meant' actions of IL-6 are often causing harm instead of leading to recovery.

Neuroprotection of interleukin-6 against NMDA-induced apoptosis and its signal-transduction mechanisms

We have previously shown that interleukin-6 (IL-6)-protected neurons against the suppression of neuronal vitality and overload of intracellular Ca(2+) induced by glutamate or N-methyl-D: -aspartate (NMDA). Herein we provide further evidence for IL-6 neuroprotection against NMDA-induced apoptosis and explore the signal-transduction mechanisms underlying the anti-apoptotic action of IL-6. Cerebellar granule neurons (CGNs) from postnatal 8-day infant rats were chronically exposed to IL-6 (40 or 120 ng/ml) for 8 days, and stimulated with NMDA (100 μM) for 30 min. To observe the signaling pathways, we employed AG490 (5 or 10 μM), an inhibitor of Janus kinases (JAKs), or LY294002 (5 or 10 μM), an inhibitor of phosphatidylinositol 3-kinase (PI3K), to pretreat the CGNS together with IL-6. The levels of phosphorylation for the downstream effectors of JAKs and PI3K, i.e., phosphorylated STAT3 and Akt, were quantified by Western blot assay. In the cultured CGNs with various drug exposures, the expressions of Bcl-2, Bax, and caspase-3 were measured by real-time PCR and Western blot, and the percentage of apoptotic nuclei was tested by Hoechst 33342 staining. After the CGNs were chronically exposed to IL-6, NMDA stimulation led to an increase in the expression of Bcl-2 mRNA and a decrease in the expression of Bax and caspase-3 mRNAs and proteins when compared with those neurons lacking IL-6 exposure. IL-6 pretreatment of the neurons without NMDA stimulation concentration-dependently enhanced the expressions of Bcl-2 mRNA and protein while attenuating the expressions of Bax and caspase-3 mRNAs and proteins in comparison with control lacking any treatment. Furthermore, IL-6 prevented the increase in the percentage of apoptotic neurons induced by NMDA. The combined pretreatment of the CGNs with AG490 and IL-6 or with LY294002 and IL-6 reduced these anti-apoptotic effects of IL-6. Neither AG490 nor LY294002 exposure alone altered the expressions of Bcl-2, Bax, and cleaved caspase-3 proteins. IL-6 up-regulated the levels of phosphorylated STAT3 and Akt, and this was blocked by AG490 and LY294002, respectively. These results suggest that IL-6 protects neurons against NMDA-induced apoptosis, and that the IL-6 neuroprotection is jointly mediated by JAK-STAT3 and PI3K-Akt signaling pathways.

RANTES release contributes to the protective action of PACAP38 against sodium nitroprusside in cortical neurons

Pituitary adenylate cyclase activating polypeptide (PACAP), a promising neuroprotective peptide, plays an important role during development of the nervous system and in regeneration after injury. PACAP directly promotes survival via multiple signaling systems in neurons. This neuropeptide also has immuno-modulatory properties and can regulate the expression of various inflammatory mediators such as chemokines in nonneuronal cells. Chemokines and their G protein-coupled receptors are widely distributed in the brain, suggesting important functions for these inflammatory proteins in the CNS. The ability of brain endothelial cells and glia to release chemokines has been well documented, whether neurons are also a source for these mediators is unclear. The objective of this study is to determine whether PACAP38 affects expression of regulated on activation normal T expressed and secreted (RANTES) and macrophage inflammatory protein 1-alpha (MIP-1alpha) in cultured neurons and if these chemokines contribute to the neuroprotective effect of PACAP38. The data show that incubation of neuronal cultures with both PACAP38 and sodium nitroprusside (SNP) reduces the neuronal cell death evoked by SNP alone. PACAP38 dose-dependently increases immunodetectable levels of both RANTES and MIP-1alpha released in the media by cultured neurons. Co-treatment with a neutralizing antibody to RANTES decreases the PACAP38-mediated protection against SNP. Although RANTES treatment of neurons increased MIP-1alpha levels in the media and MIP-1alpha supports neuronal survival in unstressed cultures, MIP-1alpha does not protect neurons from SNP-induced toxicity. Furthermore, co-treatment with a MIP-1alpha neutralizing antibody did not affect PACAP38-induced protection against SNP. These results show that the protective effect of PACAP38 on cultured neurons is mediated, in part, by release of RANTES. The ability of PACAP to directly enhance neuronal survival through multiple intracellular signaling pathways as well as via the release of neuroprotective mediators such as RANTES highlights its utility as a potential therapeutic agent for the treatment of neurodegenerative diseases.

P2Y1 receptor signaling enhances neuroprotection by astrocytes against oxidative stress via IL-6 release in hippocampal cultures

Cell survival is a critical issue in the onset and progression of neurodegenerative diseases and following pathological events including ischemia and traumatic brain injury. Oxidative stress is the main cause of cell damage in such pathological conditions. Here, we report that adenosine 5'-triphosphate (ATP) protects hippocampal astrocytes from hydrogen peroxide (H(2)O(2))-evoked oxidative injury in astrocyte monocultures. The effect of ATP was prevented by a selective antagonist of or siRNAs against P2Y(1)R. Interestingly, in astrocyte-neuron cocultures, ATP also produced neuroprotective effects against H(2)O(2)-evoked neuronal cell death, whereas ATP did not produce any neuroprotective effects in monocultures. The ATP-induced neuroprotection in cocultures was completely inhibited by silencing of astrocytic P2Y(1)R expression, indicating that ATP acts on astrocytes and enhances their neuroprotective functions by activating P2Y(1)R. Furthermore, this neuroprotective effect was mimicked by applying conditioned medium from astrocytes that had been stimulated by ATP, implying an involvement of diffusible factors from astrocytes. We found that, in both purified astrocyte cultures and astrocyte-neuronal cocultures, ATP and the P2Y(1)R agonist 2-methylthioadenosine 5' diphosphate (2MeSADP) induced the release of interleukin-6 (IL-6), but this did not occur in neuron monocultures. Moreover, exogenous IL-6 produced a neuroprotective effect, and the neuroprotection induced by P2Y(1)R-stimulated astrocytes was prevented in the presence of an anti-IL-6 antibody. Taken together, these results suggest that P2Y(1)R-stimulated astrocytes protect against neuronal damage induced by oxidative stress, and that IL-6 is a crucial signaling molecule released from astrocytes. Thus, activation of P2Y(1)R in astrocytes may rescue neurons from secondary cell death under pathological conditions.

Achyranthes bidentata Blume extract protects cultured hippocampal neurons against glutamate-induced neurotoxicity

We have prepared an aqueous extract of Achyranthes bidentata Blume, a Chinese medicinal herb commonly prescribed for arthritis treatment or immnopotentiation, and have found that Achyranthes bidentata extract promotes nerve growth and prevents neuronal apoptosis.

AIM OF THE STUDY

To investigate the protective effect of Achyranthes bidentata extract against glutamate-induced neurotoxicity in primary culture of rat hippocampal neurons.

MATERIALS AND METHODS

We accomplished MTT assay for cell viability, Hoechst 33342 staining, and flow cytometry for cell apoptosis analysis to examine the effects of Achyranthes bidentata extract on glutamate-induced neurotoxicity, and also used Fluo 4-AM measurement, RT-PCR and Western blot analysis to determine the changes in intracellular calcium concentration [Ca(2+)](I), and mRNA and protein levels of Bcl-2, respectively, concurrently accompanied with the influences of Achyranthes bidentata extract.

RESULTS

Achyranthes bidentata extract was found to inhibit glutamate-induced neuronal damage in a dose- and time-dependent manner. On the other hand, Achyranthes bidentata extract depressed glutamate-induced elevation of intracellular calcium concentration [Ca(2+)](i), and also antagonized glutamate-evoked decreases in Bcl-2 expression at mRNA and protein levels.

CONCLUSION

The results suggest that Achyranthes bidentata extract prevents glutamate-induced cell damage in primarily cultured hippocampal neurons by inhibiting an increase in [Ca(2+)](i), and reversing the down-regulation of Bcl-2.

Neuroprotection of interleukin-6 against NMDA attack and its signal transduction by JAK and MAPK

Cytokine interleukin-6 (IL-6) has been well shown to be elevated in brain injury and diseases. However, the significance of IL-6 production in such neuropathologic states remains controversial, and the intracellular signal-transduction pathways involved in the brain IL-6 action are primarily unclear. We previously indicated that exogenous IL-6 protected neurons against glutamate and N-methyl-d-aspartate (NMDA) attacks and the effects of IL-6 was blocked by anti-gp130 antibody. Here, we provide further evidence for the IL-6 neuroprotection and show signal molecules transducing the IL-6 message. The cerebellar granule neurons from postnatal 8-day infant rats were exposed to IL-6 for 8 days, and also pretreated chronically with Janus kinase (JAK) inhibitor AG490 and mitogen-activated protein kinase (MAPK) inhibitor PD98059. NMDA stimulated the cultured neurons for 30 min to induce neuronal injury and death. Cell counting kit-8 assay and Western blot were employed to measure neuronal vitality and cleaved caspase-3 expression, respectively. The chronic IL-6 exposure prevented the suppression of the neuronal vitality and the enhancement of the cleaved caspase-3 level induced by NMDA. The neuroprotective effect of IL-6 depended on IL-6 concentration and neuronal damaged degree. IL-6-induced STAT3 phosphorylation was inhibited by AG490 but not by PD98059; and IL-6-induced ERK1/2 activation was blocked by PD98059 but not by AG490. Either AG490 or PD98059 blocked the IL-6 protection against the NMDA-elicited neuronal vitality decrease and caspase-3 activation increase. These findings suggest that IL-6 protects neurons from NMDA-induced excitoxicity and the IL-6 neuroprotection may be transduced by both JAK/STAT3 and RAS/MAPK pathways.

Chitooligosaccharides protect cultured hippocampal neurons against glutamate-induced neurotoxicity

Chitooligosaccharides (COSs), the biodegradation product of chitosan, have demonstrated a diverse array of biological activities. Here we report the protective effect of COSs (M.W. 800) against glutamate-induced neurotoxicity in cultured hippocampal neurons. The cell viability assessments, together with Hoechst 33342 staining and flow cytometry for cell apoptosis analysis, indicated that glutamate (125 microM)-induced cell apoptosis in cultured hippocampal neurons was attenuated in a concentration-dependent manner by COSs pretreatment. After measurement with Fluo 4-AM, COSs were found to depress glutamate-induced elevation in intracellular calcium concentration ([Ca(2+)](c)). The enzymatic assay indicated that COSs antagonized glutamate-evoked activation of caspase-3. These results collectively suggest that COSs prevent cultured hippocampal neurons from glutamate-induced cell damage by interfering with an increase in [Ca(2+)](c) and inhibiting caspase-3 activity.

Role of IFN-gamma in an experimental murine model of West Nile virus-induced seizures

Seizures are a major complication of viral encephalitis. However, the mechanisms of seizure-associated neuronal dysfunction remain poorly understood. We report that intranasal inoculation with West Nile virus (WNV) (Sarafend) causes limbic seizures in C57BL/6 mice, but not in interferon (IFN)-gamma-deficient (IFN-gamma-/-) mice. Both strains showed similar levels of virus in the brain, as well as similar concentrations of the cytokines, tumor necrosis factor and interleukin-6, both of which can alter neuronal excitability. Experiments in chimeric IFN-gamma-/- mice reconstituted with IFN-gamma-producing leukocytes showed that IFN-gamma is not required during central nervous system infection for limbic seizure development, suggesting a role for IFN-gamma in the developing brain. This was supported responses to pentylenetetrazole, kainic acid (KA), and N-methyl-d-aspartate (NMDA). Both strains of mice exhibited similar behavior after pentylenetetrazole challenge. However, while NMDA and KA treatment resulted in characteristic seizures in C57BL/6 mice, these responses were diminished (NMDA treatment) or absent (KA treatment) in IFN-gamma-/- mice. Furthermore, NMDA-receptor blockade with MK-801 in WNV-infected C57BL/6 mice abrogated seizures and prolonged survival. Our data show that IFN-gamma plays an important role in the development of the excitatory seizure pathways in the brain and that these cascades become pathogenic in encephalitic WNV infection.

Hypoxic preconditioning induces neuroprotective stanniocalcin-1 in brain via IL-6 signaling

BACKGROUND AND PURPOSE

Exposure of animals for a few hours to moderate hypoxia confers relative protection against subsequent ischemic brain damage. This phenomenon, known as hypoxic preconditioning, depends on new RNA and protein synthesis, but its molecular mechanisms are poorly understood. Increased expression of IL-6 is evident, particularly in the lungs of animals subjected to hypoxic preconditioning. Stanniocalcin-1 (STC-1) is a 56-kDa homodimeric glycoprotein originally discovered in bony fish, where it regulates calcium/phosphate homeostasis and protects against toxic hypercalcemia. We originally reported expression of mammalian STC-1 in brain neurons and showed that STC-1 guards neurons against hypercalcemic and hypoxic damage.

METHODS

We treated neural Paju cells with IL-6 and measured the induction of STC-1 mRNA. In addition, we quantified the effect of hypoxic preconditioning on Stc-1 mRNA levels in brains of wild-type and IL-6 deficient mice. Furthermore, we monitored the Stc-1 response in brains of wild-type and transgenic mice, overexpressing IL-6 in the astroglia, before and after induced brain injury.

RESULTS

Hypoxic preconditioning induced an upregulated expression of Stc-1 in brains of wild-type but not of IL-6-deficient mice. Induced brain injury elicited a stronger STC-1 response in brains of transgenic mice, with targeted astroglial IL-6 expression, than in brains of wild-type mice. Moreover, IL-6 induced STC-1 expression via MAPK signaling in neural Paju cells.

CONCLUSIONS

These findings indicate that IL-6-mediated expression of STC-1 is one molecular mechanism of hypoxic preconditioning-induced tolerance to brain ischemia.

Peripheral inflammation and neuroprotection: systemic pretreatment with complete Freund's adjuvant reduces 6-hydroxydopamine toxicity in a rodent model of Parkinson's disease

Complete Freund's adjuvant (CFA), a pro-inflammatory agent, was inoculated, subcutaneously, to Sprague-Dawley rats prior to the intrastriatal injection of 6-hydroxydopamine (6-OHDA). Animals were sacrificed 7 and 28 days following 6-OHDA injection; neuronal damage, glial activation and cytokine levels, within the nigrostriatal system, were then investigated. Nigrostriatal degeneration induced by 6-OHDA was accompanied by early microglial and astroglial activation, which preceded the onset of dopaminergic cell loss, in the SNc, without significant changes in cytokine levels. CFA pretreatment markedly reduced the SNc neuronal loss and associated microglial activation, as well as the rotational response to apomorphine. These changes were associated with moderate, transient increases in the nigrostriatal levels of glial-cell-derived neurotrophic factor (GDNF) and pro-inflammatory cytokines, including interleukin (IL)-1alpha, IL-1beta and IL-6. Our results show that prior delivery of a peripheral, pro-inflammatory stimulus induces neuroprotection, in a rodent model of Parkinson's disease, possibly through the modulation of cytokine production at the nigrostriatal level.

Interleukin-1-induced neurotoxicity is mediated by glia and requires caspase activation and free radical release

Interleukin (IL)-1 expression is induced rapidly in response to diverse CNS insults and is a key mediator of experimentally induced neuronal injury. However, the mechanisms of IL-1-induced neurotoxicity are unknown. The aim of the present study was to examine the toxic effects of IL-1 on rat cortical cell cultures. Treatment with IL-1beta did not affect the viability of pure cortical neurones. However, IL-1 treatment of cocultures of neurones with glia or purified astrocytes induced caspase activation resulting in neuronal death. Neuronal cell death induced by IL-1 was prevented by pre-treatment with the IL-1 receptor antagonist, the broad spectrum caspase inhibitor Boc-Asp-(OMe)-CH(2)F or the antioxidant alpha-tocopherol. The NMDA receptor antagonist dizolcipine (MK-801) attenuated cell death induced by low doses of IL-1beta but the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX) had no effect. Inhibition of inducible nitric oxide synthase with N(omega)-nitro-l-arginine methyl ester had no effect on neuronal cell death induced by IL-1beta. Thus, IL-1 activates the IL-1 type 1 receptor in astrocytes to induce caspase-dependent neuronal death, which is dependent on the release of free radicals and may contribute to neuronal cell death in CNS diseases.

Nuclear factor-κB p65 and upregulation of interleukin-6 in retinal ischemia/reperfusion injury in rats

We previously demonstrated that endogenous interleukin-6 (IL-6) is upregulated and may be neuroprotective after retinal ischemia. The purpose of this study is to investigate the role of nuclear factor kappa-B (NF-kappaB) in regulating IL-6 expression after ischemia. NF-kappaB p65 mRNA levels were significantly elevated between 2 and 12 h after the insult. A high number of NF-kappaB p65 positive cells were detected in the inner retina at 12 h after ischemia. Activated nuclear NF-kappaB p65 and IL-6 were colocalized in cells, which were also marked by a microglial/phagocytic cell marker (ED1) in the inner retina. Carbobenzoxy-L-leucyl-L-leucyl-L-leucinal (MG-132, a proteasome inhibitor, which inhibits IkappaB degradation and hence prevents the activation and translocation of NF-kappaB into the nucleus) abolished the increase in NF-kappaB p65 mRNA levels after the insult, while there was no effect by helenalin (an inhibitor which inhibits NF-kappaB activity by alkylation of the p65 subunit, thereby blocking its binding to the target DNA). However, MG-132 and/or helenalin significantly diminished the increase in IL-6 mRNA levels after the insult. Small interfering RNAs (siRNAs, inhibit target gene expression through the sequence-specific destruction of the target messenger RNA) against NF-kappaB p65 significantly reduced the increase in NF-kappaB p65 mRNA levels as well as IL-6 mRNA levels after ischemia. The number of retinal ganglion cells (RGCs) was also significantly decreased using the inhibitors of NF-kappaB compared with those of the controls after ischemia. These findings support the hypothesis that upregulation of endogenous retinal IL-6 in retinal I/R injury in microglial/phagocytic cells is controlled predominantly by NF-kappaB p65.

Comparative study of microglia activation induced by amyloid-beta and prion peptides: Role in neurodegeneration

The inflammatory responses in Alzheimer's disease (AD) and prion-related encephalopathies (PRE) are dominated by microglia activation. Several studies have reported that the amyloid-beta (Abeta) peptides, which are associated with AD, and the pathogenic isoform of prion protein (PrPSc) have a crucial role in neuronal death and gliosis that occur in both of these disorders. In this study, we investigate whether Abeta and PrPSc cause microglia activation per se and whether these amyloidogenic peptides differentially affect these immunoeffector cells. In addition, we also determined whether substances released by Abeta- and PrP-activated microglia induce neuronal death. Cultures of rat brain microglia cells were treated with the synthetic peptides Abeta1-40, Abeta1-42 and PrP106-126 for different time periods. The lipopolysaccharide was used as a positive control of microglia activation. Our results show that Abeta1-40 and PrP106-126 caused similar morphological changes in microglia and increased the production of nitric oxide and hydroperoxides. An increase on inducible nitric oxide synthase expression was also observed in microglia treated with Abeta1-40 or PrP106. However, these peptides affected in a different manner the secretion of interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) secretion. In cocultures of microglia-neurons, it was observed that microglia treated with Abeta1-40 or PrP106-126 induced a comparable extent of neuronal death. The neutralizing antibody for IL-6 significantly reduced the neuronal death induced by Abeta- or PrP-activated microglia. Taken together, the data indicate that Abeta and PrP peptides caused microglia activation and differentially affected cytokine secretion. The IL-6 released by reactive microglia caused neuronal injury.