Interleukin-1beta regulation of N-type Ca2+ channels in cortical neurons

Non-coding RNAs and Exosomal Non-coding RNAs in Traumatic Brain Injury: the Small Player with Big Actions

Nowadays, there is an increasing concern regarding traumatic brain injury (TBI) worldwide since substantial morbidity is observed after it, and the long-term consequences that are not yet fully recognized. A number of cellular pathways related to the secondary injury in brain have been identified, including free radical production (owing to mitochondrial dysfunction), excitotoxicity (regulated by excitatory neurotransmitters), apoptosis, and neuroinflammatory responses (as a result of activation of the immune system and central nervous system). In this context, non-coding RNAs (ncRNAs) maintain a fundamental contribution to post-transcriptional regulation. It has been shown that mammalian brains express high levels of ncRNAs that are involved in several brain physiological processes. Furthermore, altered levels of ncRNA expression have been found in those with traumatic as well non-traumatic brain injuries. The current review highlights the primary molecular mechanisms participated in TBI that describes the latest and novel results about changes and role of ncRNAs in TBI in both clinical and experimental research.

Enduring neuroimmunological consequences of developmental experiences: From vulnerability to resilience

The immune system is crucial for normal neuronal development and function (neuroimmune system). Both immune and neuronal systems undergo significant postnatal development and are sensitive to developmental programming by environmental experiences. Negative experiences from infection to psychological stress at a range of different time points (in utero to adolescence) can permanently alter the function of the neuroimmune system: given its prominent role in normal brain development and function this dysregulation may increase vulnerability to psychiatric illness. In contrast, positive experiences such as exercise and environmental enrichment are protective and can promote resilience, even restoring the detrimental effects of negative experiences on the neuroimmune system. This suggests the neuroimmune system is a viable therapeutic target for treatment and prevention of psychiatric illnesses, especially those related to stress. In this review we will summarise the main cells, molecules and functions of the immune system in general and with specific reference to central nervous system development and function. We will then discuss the effects of negative and positive environmental experiences, especially during development, in programming the long-term functioning of the neuroimmune system. Finally, we will review the sparse but growing literature on sex differences in neuroimmune development and response to environmental experiences.

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The immune system is essential for development and function of the central nervous system (neuroimmune system)

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Environmental experiences can permanently alter neuroimmune function and associated brain development

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Altered neuroimmune function following negative developmental experiences may play a role in psychiatric illnesses

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Positive experiences can promote resilience and rescue the effects of negative experiences on the neuroimmune system

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The neuroimmune system is therefore a viable therapeutic target for preventing and treating psychiatric illnesses

Increased levels of NLRP3 in children with febrile seizures

OBJECTIVE

Febrile seizures (FS) are the most common convulsions in childhood. Interleukin-1beta (IL-1β) is proposed to play an important role in the development of FS, from in vitro data and data from peripheral blood samples. IL-1β secretion is needed for activation of the NLR family, pyrin-domain containing 3(NLRP3) inflammasome. However, whether NLRP3 play a role in the development of FS remains unknown. This study aimed to investigate the role of NLRP3 in FS.

METHODS

Thirty-two FS cases and twenty-two matched controls were included in this study. Control samples were collected from children with febrile illness without seizures. We detected their levels of IL-1β and NLRP3 by Enzyme linked immunosorbent assay and Western blot, respectively.

RESULTS

Serum IL-1β levels weresignificantlyhigher in FS patients (Median = 301.64 pg/ml) than in fever only controls (Median = 159.48 pg/ml) (P < 0.05). Additionally, NLRP3 protein levels of peripheral blood mononuclear cells (PBMC) were significantly higher in typical FS than in fever only controls (P < 0.05). Moreover, serum levels of IL-1β were significantly correlated with levels of NLRP3 protein (r = 0.787, P < 0.001).

CONCLUSIONS

In this study, our results firstly indicated that NLRP3 protein was significantly up-regulated in the typical FS children compared in fever only controls. Increased NLRP3 can mediate IL-1β secretion that is responsible for the occurrence of FS.

Neuroimmunological effects of early life experiences

Exposure to adverse experiences during development increases the risk of psychiatric illness later in life. Growing evidence suggests a role for the neuroimmune system in this relationship. There is now substantial evidence that the immune system is critical for normal brain development and behaviour, and responds to environmental perturbations experienced early in life. Severe or chronic stress results in dysregulated neuroimmune function, concomitant with abnormal brain morphology and function. Positive experiences including environmental enrichment and exercise exert the opposite effect, promoting normal brain and immune function even in the face of early life stress. The neuroimmune system may therefore provide a viable target for prevention and treatment of psychiatric illness. This review will briefly summarise the neuroimmune system in brain development and function, and review the effects of stress and positive environmental experiences during development on neuroimmune function. There are also significant sex differences in how the neuroimmune system responds to environmental experiences early in life, which we will briefly review.

Circular RNA circPTK2 regulates oxygen-glucose deprivation-activated microglia-induced hippocampal neuronal apoptosis via miR-29b-SOCS-1-JAK2/STAT3-IL-1β signaling

Oxygen-glucose deprivation (OGD)-activated microglia contribute to neuronal apoptosis via releasing pro-inflammatory cytokines, and some miRNAs have been reported to be involved in this process. Circular RNAs (circRNAs) have been reported to function as miRNA sponges, but it remains unknown whether and how circRNAs contribute to OGD-activated microglia-induced neuronal apoptosis. Here, we investigated the function and relationship of miR-29b and circPTK2 in OGD-activated microglia-induced neuronal apoptosis. We found upregulation of TNF-α and IL-1β, and downregulation of miR-29b in OGD-activated microglia. miR-29b inhibited OGD-activated microglia-induced neuronal apoptosis. Meanwhile, miR-29b promoted SOCS-1 expression, and suppressed JAK2/STAT3 signaling. In addition, inhibition of JAK2/STAT3 signaling downregulated IL-1β expression, while upregulation of miR-29b or SOCS-1 also inhibited IL-1β production. IL-1β was confirmed to be an apoptosis inducer of hippocampal neurons. Moreover, either SOCS-1 upregulation or blockade of JAK2/STAT3 signaling suppressed OGD-activated microglia-induced neuronal apoptosis. These data suggest that miR-29b inhibits OGD-activated microglia-induced neuronal apoptosis via inducing SOCS-1 expression, blocking JNK2/STAT3 signaling, and inhibiting IL-1β production. circPTK2 was confirmed to inhibit miR-29b expression in OGD model by directly binding to miR-29b. Function assay showed that circPTK2 regulated microglia-induced neuronal apoptosis via sponging miR-29b. Collectively, these findings suggest that circPTK2 regulates OGD-activated microglia-induced neuronal apoptosis via miR-29b-SOCS-1-JAK2/STAT3-IL-1β signaling.

Glial responses to implanted electrodes in the brain

The use of implants that can electrically stimulate or record electrophysiological or neurochemical activity in nervous tissue is rapidly expanding. Despite remarkable results in clinical studies and increasing market approvals, the mechanisms underlying the therapeutic effects of neuroprosthetic and neuromodulation devices, as well as their side effects and reasons for their failure, remain poorly understood. A major assumption has been that the signal-generating neurons are the only important target cells of neural-interface technologies. However, recent evidence indicates that the supporting glial cells remodel the structure and function of neuronal networks and are an effector of stimulation-based therapy. Here, we reframe the traditional view of glia as a passive barrier, and discuss their role as an active determinant of the outcomes of device implantation. We also discuss the implications that this has on the development of bioelectronic medical devices.

Modulating Effect of Cytokines on Mechanisms of Synaptic Plasticity in the Brain

After accumulation of data showing that resident brain cells (neurons, astrocytes, and microglia) produce mediators of the immune system, such as cytokines and their receptors under normal physiological conditions, a critical need emerged for investigating the role of these mediators in cognitive processes. The major problem for understanding the functional role of cytokines in the mechanisms of synaptic plasticity, de novo neurogenesis, and learning and memory is the small number of investigated cytokines. Existing concepts are based on data from just three proinflammatory cytokines: interleukin-1 beta, interleukin-6, and tumor necrosis factor-alpha. The amount of information in the literature on the functional role of antiinflammatory cytokines in the mechanisms of synaptic plasticity and cognitive functions of mature mammalian brain is dismally low. However, they are of principle importance for understanding the mechanisms of local information processing in the brain, since they modulate the activity of individual cells and local neural networks, being able to reconstruct the processes of synaptic plasticity and intercellular communication, in general, depending on the local ratio of the levels of different cytokines in certain areas of the brain. Understanding the functional role of cytokines in cellular mechanisms of information processing and storage in the brain would allow developing preventive and therapeutic means for the treatment of neuropathologies related to impairment of these mechanisms.

Increased Na+/Ca2+ exchanger activity promotes resistance to excitotoxicity in cortical neurons of the ground squirrel (a Hibernator)

Ground squirrel, a hibernating mammalian species, is more resistant to ischemic brain stress than rat. Gaining insight into the adaptive mechanisms of ground squirrels may help us design treatment strategies to reduce brain damage in patients suffering ischemic stroke. To understand the anti-stress mechanisms in ground squirrel neurons, we studied glutamate toxicity in primary cultured neurons of the Daurian ground squirrel (Spermophilus dauricus). At the neuronal level, for the first time, we found that ground squirrel was more resistant to glutamate excitotoxicity than rat. Mechanistically, ground squirrel neurons displayed a similar calcium influx to the rat neurons in response to glutamate or N-methyl-D-aspartate (NMDA) perfusion. However, the rate of calcium removal in ground squirrel neurons was markedly faster than in rat neurons. This allows ground squirrel neurons to maintain lower level of intracellular calcium concentration ([Ca²⁺]_i) upon glutamate insult. Moreover, we found that Na⁺/Ca²⁺ exchanger (NCX) activity was higher in ground squirrel neurons than in rat neurons. We also proved that overexpression of ground squirrel NCX2, rather than NCX1 or NCX3, in rat neurons promoted neuron survival against glutamate toxicity. Taken together, our results indicate that ground squirrel neurons are better at maintaining calcium homeostasis than rat neurons and this is likely achieved through the activity of ground squirrel NCX2. Our findings not only reveal an adaptive mechanism of mammalian hibernators at the cellular level, but also suggest that NCX2 of ground squirrel may have therapeutic value for suppressing brain ischemic damage.

Neuromodulatory properties of inflammatory cytokines and their impact on neuronal excitability

Increasing evidence underlines that prototypical inflammatory cytokines (IL-1β, TNF-α and IL-6) either synthesized in the central (CNS) or peripheral nervous system (PNS) by resident cells, or imported by immune blood cells, are involved in several pathophysiological functions, including an unexpected impact on synaptic transmission and neuronal excitability. This review describes these unconventional neuromodulatory properties of cytokines, that are distinct from their classical action as effector molecules of the immune system. In addition to the role of cytokines in brain physiology, we report evidence that dysregulation of their biosynthesis and cellular release, or alterations in receptor-mediated intracellular pathways in target cells, leads to neuronal cell dysfunction and modifications in neuronal network excitability. As a consequence, targeting of these cytokines, and related signalling molecules, is considered a novel option for the development of therapies in various CNS or PNS disorders associated with an inflammatory component. This article is part of a Special Issue entitled 'Neuroimmunology and Synaptic Function'.

IL-1β: an important cytokine associated with febrile seizures?

Febrile seizures (FSs) are the most common convulsions in childhood. Studies have demonstrated a significant relationship between a history of prolonged FSs during early childhood and temporal sclerosis, which is responsible for intractable mesial temporal lobe epilepsy. It has been shown that interleukin-1β (IL-1β) is intrinsically involved in the febrile response in children and in the generation of FSs. We summarize the gene polymorphisms, changes of IL-1β levels and the putative role of IL-1β in the generation of FSs. IL-1β could play a role either in enhancing or in reducing neural excitability. If the enhancing and reducing effects are balanced, an FS does not occur. When the enhancing effect plays the leading role, an FS is generated. A mild imbalance can cause simple FSs while a severe imbalance can cause complex FSs and febrile status epilepticus. Therefore, anti-IL-1β therapy may help to treat FSs.

Does brain inflammation mediate pathological outcomes in epilepsy?

Inflammation in the central nervous system (CNS) is associated with epilepsy and is characterized by the increased levels of a complex set of soluble molecules and their receptors in epileptogenic foci with profound neuromodulatory effects. These molecules activate receptor-mediated pathways in glia and neurons that contribute to hyperexcitability in neural networks that underlie seizure generation. As a consequence, exciting new opportunities now exist for novel therapies targeting the various components of the immune system and the associated inflammatory mediators, especially the IL-1β system. This review summarizes recent findings that increased our understanding of the role of inflammation in reducing seizure threshold, contributing to seizure generation, and participating in epileptogenesis. We will discuss preclinical studies supporting the hypothesis that pharmacological inhibition of specific proinflammatory signalings may be useful to treat drug-resistant seizures in human epilepsy, and possibly delay or arrest epileptogenesis.

Association of innate immune single-nucleotide polymorphisms with the electroencephalogram during desflurane general anaesthesia

The electroencephalogram (EEG) records the electrical activity of the brain and enables effects of anaesthetic drugs on brain functioning to be monitored. Identification of genes contributing to EEG variability during anaesthesia is important to the clinical application of anaesthesia monitoring and may provide an avenue to identify molecular mechanisms underlying the generation and regulation of brain oscillations. Central immune signalling can impact neuronal activity in the brain and accumulating evidence suggests an important role for cytokines as neuronal modulators. We tested 21 single-nucleotide polymorphisms (SNPs) in immune-related genes for associations with three anaesthesia-induced EEG patterns; spindle amplitude, delta power and alpha power, during general anaesthesia with desflurane in 111 patients undergoing general, gynaecological or orthopaedic surgery. Wide inter-patient variability was observed for all EEG variables. MYD88 rs6853 (p = 6.7 × 10(-4)) and IL-1β rs1143627 in conjunction with rs6853 (p = 1.5 × 10(-3)) were associated with spindle amplitude, and IL-10 rs1800896 was associated with delta power (p = 1.3 × 10(-2)) suggesting involvement of cytokine signalling in modulation of EEG patterns during desflurane anaesthesia. BDNF rs6265 was associated with alpha power (p = 3.9 × 10(-3)), suggesting differences in neuronal plasticity might also influence EEG patterns during desflurane anaesthesia. This is the first study we are aware of that has investigated genetic polymorphisms that may influence the EEG during general anaesthesia.

Calcium dysregulation and neuroinflammation: discrete and integrated mechanisms for age-related synaptic dysfunction

Some of the best biomarkers of age-related cognitive decline are closely linked to synaptic function and plasticity. This review highlights several age-related synaptic alterations as they relate to Ca(2+) dyshomeostasis, through elevation of intracellular Ca(2+), and neuroinflammation, through production of pro-inflammatory cytokines including interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α). Though distinct in many ways, Ca(2+) and neuroinflammatory signaling mechanisms exhibit extensive cross-talk and bidirectional interactions. For instance, cytokine production in glial cells is strongly dependent on the Ca(2+) dependent protein phosphatase calcineurin, which shows elevated activity in animal models of aging and disease. In turn, pro-inflammatory cytokines, such as TNF, can augment the expression/activity of L-type voltage sensitive Ca(2+) channels in neurons, leading to Ca(2+) dysregulation, hyperactive calcineurin activity, and synaptic depression. Thus, in addition to discussing unique contributions of Ca(2+) dyshomeostasis and neuroinflammation, this review emphasizes how these processes interact to hasten age-related synaptic changes.

Role of pro-inflammatory cytokines released from microglia in neurodegenerative diseases

Microglia are activated in response to a number of different pathological states within the CNS including injury, ischemia, and infection. Microglial activation results in their production of pro-inflammatory cytokines such as IL-1, IL-6, and TNF-α. While release of these factors is typically intended to prevent further damage to CNS tissue, they may also be toxic to neurons and other glial cells. Mounting evidence indicates that chronic microglial activation may also contribute to the development and progression of neurodegenerative disorders. Unfortunately, determining the role of pro-inflammatory cytokines in these disorders has been complicated by their dual roles in neuroprotection and neurodegeneration. The purpose of this review is to summarize current understanding of the involvement of cytokines in neurodegenerative disorders and their potential signaling mechanisms in this context. Taken together, recent findings suggest that microglial activation and pro-inflammatory cytokines merit interest as targets in the treatment of neurodegenerative disorders.

Ca(2+) channel currents of cortical neurons from pure and mixed cultures

Voltage-gated Ca(2+) channels (VGCCs) are key regulators of many neuronal functions, and involved in multiple central nervous system diseases. In the last 30 years, a large number of injury and disease models have been established based on cultured neurons. Culture with serum develops a mixture of neurons and glial cells, while culture without serum develops pure neurons. Both of these neuronal-culture methods are widely used. However, the properties of Ca(2+) currents in neurons from these two cultures have not been compared. In this study, we cultured rat cortical neurons in serum-containing or -free medium and then recorded the Ca(2+) channel currents using patch-clamp technique. Our results showed that there were significant differences in the amplitude and activation properties of whole-cell Ca(2+) channel currents, and of non-L-type Ca(2+) channel currents between the neurons from these two culture systems. Our data suggested that the difference of whole-cell Ca(2+) currents may result from the differences in non-L-type currents. Understanding of these properties will considerably advance studies of VGCCs in neurons from pure or mixed culture.

Regulation of immune-modulatory genes in left superior temporal cortex of schizophrenia patients: a genome-wide microarray study

OBJECTIVES

The role of neuroinflammation in schizophrenia has been an issue for long time. There are reports supporting the hypothesis of ongoing inflammation and others denying it. This may be partly ascribed to the origin of the materials (CSF, blood, brain tissue) or to the genes selected for the respective studies. Moreover, in some locations, inflammatory genes may be up-regulated, others may be down-regulated.

METHODS

Genome-wide microarrays have been used for expression profiling in post-mortem brains of schizophrenia patients. Array data have been analyzed by gene set enrichment analysis (GSEA) and further confirmed with selected genes by real-time PCR.

RESULTS

In Brodman Area 22 of left superior temporal cortex, at least 70 genes (19%) out of 369 down-regulated genes (P < 0.05) belonged to the immune system. 23 from those 70 genes were randomly selected for real-time PCR. Six reached significance level at P < 0.05.

CONCLUSIONS

The present data support a brain-specific view of the role immune-modulatory genes may play in the left superior temporal cortex in schizophrenia, because immune functions in the patients are not disturbed. In keeping with comparable, previous studies supporting the notion that schizophrenia is a disease of the synapse, we hypothesize that dysregulation of immune-related genes modifies synaptic functions and stability in this region.

Ion channels in inflammation

Most physical illness in vertebrates involves inflammation. Inflammation causes disease by fluid shifts across cell membranes and cell layers, changes in muscle function and generation of pain. These disease processes can be explained by changes in numbers or function of ion channels. Changes in ion channels have been detected in diarrhoeal illnesses, pyelonephritis, allergy, acute lung injury and systemic inflammatory response syndromes involving septic shock. The key role played by changes in ion transport is directly evident in inflammation-induced pain. Expression or function of all major categories of ion channels like sodium, chloride, calcium, potassium, transient receptor potential, purinergic receptor and acid-sensing ion channels can be influenced by cyto- and chemokines, prostaglandins, leukotrienes, histamine, ATP, reactive oxygen species and protons released in inflammation. Key pathways in this interaction are cyclic nucleotide, phosphoinositide and mitogen-activated protein kinase-mediated signalling, direct modification by reactive oxygen species like nitric oxide, ATP or protons and disruption of the cytoskeleton. Therapeutic interventions to modulate the adverse and overlapping effects of the numerous different inflammatory mediators on each ion transport system need to target adversely affected ion transport systems directly and locally.

Mode of action of cytokines on nociceptive neurons

Cytokines are pluripotent soluble proteins secreted by immune and glial cells and are key elements in the induction and maintenance of pain. They are categorized as pro-inflammatory cytokines, which are mostly algesic, and anti-inflammatory cytokines, which have analgesic properties. Progress has been made in understanding the mechanisms underlying the action of cytokines in pain. To date, several direct and indirect pathways are known that link cytokines with nociception or hyperalgesia. Cytokines may act via specific cytokine receptors inducing downstream signal transduction cascades, which then modulate the function of other receptors like the ionotropic glutamate receptor, the transient vanilloid receptors, or sodium channels. This receptor activation, either through amplification of the inflammatory reaction, or through direct modulation of ion channel currents, then results in pain sensation. Following up on results from animal experiments, cytokine profiles have recently been investigated in human pain states. An imbalance of pro- and anti-inflammatory cytokine expression may be of importance for individual pain susceptibility. Individual cytokine profiles may be of diagnostic importance in chronic pain states, and, in the future, might guide the choice of treatment.

Cell-specific and concentration-dependent actions of interleukin-1 in acute brain inflammation

Interleukin (IL)-1 is a pivotal pro-inflammatory cytokine and an important mediator of both acute and chronic central nervous system (CNS) injuries. Despite intense research in CNS IL-1 biology over the past two decades, its precise mechanism of action in inflammatory responses to acute brain disorders remains largely unknown. In particular, much effort has been focussed on using in vitro approaches to better understand the cellular and signalling mechanisms of actions of IL-1, yet some discrepancies in the literature regarding the effects produced by IL-1beta in in vitro paradigms of injury still exist, particularly as to whether IL-1 exerts neurotoxic or neuroprotective effects. Here we aim to review the cell-specific and concentration-dependent actions of IL-1 in brain cells, to depict the mechanism by which this cytokine induces neurotoxicity or neuroprotection in acute brain injury.

Effect of cytokines on neuronal excitability

Numerous studies have shown that proinflammatory cytokines induce or facilitate pain and hyperalgesia in the presence of inflammation, injury to the nervous system or cancer. Besides acting as inflammatory mediators, increasing evidence indicates that cytokines may also specifically interact with receptor and ion channels regulating neuronal excitability, synaptic plasticity and injury under both physiological and pathological conditions. Here we summarize findings on two prototypical proinflammatory cytokines, tumor-necrosis factor-alpha and interleukin-1 beta, and their effects on neuronal excitability and ion channels with special regards to pain and hyperalgesia.