Chronic interleukin-6 alters NMDA receptor-mediated membrane responses and enhances neurotoxicity in developing CNS neurons

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.

Exposure to coal dust exacerbates cognitive impairment by activating the IL6/ERK1/2/SP1 signaling pathway

Coal dust (CD) is a common pollutant, and epidemiological surveys indicate that long-term exposure to coal dust not only leads to the occurrence of pulmonary diseases but also has certain impacts on cognitive abilities. However, there is little open-published literature on the effects and specific mechanisms of coal dust exposure on the cognition of patients with Mild Cognitive Impairment (MCI) and Alzheimer's Disease (AD). An animal model has been built in this study with clinical population samples to explore the changes in neuroinflammation and cognitive abilities with coal dust exposure. In the animal model, compared to C57BL/6 mice, APP/PS1 mice exposed to coal dust exhibited more severe cognitive impairment, accompanied by significantly elevated levels of neuroinflammatory factors Apolipoprotein E4 (AOPE4) and Interleukin-6 (IL6) in the hippocampus, and more severe neuronal damage. In clinical sample sequencing, it was found that there is significant upregulation of AOPE4, neutrophils, and IL6 expression in the peripheral blood of MCI patients compared to normal individuals. Mechanistically, cell experiments revealed that IL6 could promote the phosphorylation of ERK1/2 and enhance the expression of transcription factor SP1, thereby promoting AOPE4 expression. The results of this study suggest that coal dust can promote the upregulation of IL6 and AOPE4 in patients, exacerbating cognitive impairment.

Environmental Deprivation Effects on Myelin Ultrastructure in Huntington Disease and Wildtype Mice

Environmental deprivation can have deleterious effects on adaptive myelination and oligodendroglia function. Early stage Huntington disease (HD) is characterised by white-matter myelin abnormalities in both humans and animal models. However, whether deprived environments exacerbate myelin-related pathological features of HD is not clearly understood. Here, we investigated the impact of deprivation and social isolation on ultrastructural features of myelin in the corpus callosum of the YAC128 mouse model of HD and wildtype (WT) mice using transmission electron microscopy. HD pathology on its own leads to increased representation of altered myelin features, such as thinner sheaths and compromised morphology. Interestingly, deprivation mirrors these effects in WT mice but does not greatly exacerbate the already aberrant myelin in HD mice, indicating a disease-related floor effect in the latter animals. These novel findings indicate that environmental deprivation causes abnormalities in myelin ultrastructure in the otherwise healthy corpus callosum of wild-type mice but has distinct effects on HD mice, where compromised myelin integrity is manifest from early stages of the disease.

Mapping pathways to neuronal atrophy in healthy, mid-aged adults: From chronic stress to systemic inflammation to neurodegeneration?

Growing evidence implicates systemic inflammation in the loss of structural brain integrity in natural ageing and disorder development. Chronic stress and glucocorticoid exposure can potentiate inflammatory processes and may also be linked to neuronal atrophy, particularly in the hippocampus and the human neocortex. To improve understanding of emerging maladaptive interactions between stress and inflammation, this study examined evidence for glucocorticoid- and inflammation-mediated neurodegeneration in healthy mid-aged adults. N = 169 healthy adults (mean age = 39.4, 64.5% female) were sampled from the general population in the context of the ReSource Project. Stress, inflammation and neuronal atrophy were quantified using physiological indices of chronic stress (hair cortisol (HCC) and cortisone (HEC) concentration), systemic inflammation (interleukin-6 (IL-6), high-sensitive C-reactive protein (hs-CRP)), the systemic inflammation index (SII), hippocampal volume (HCV) and cortical thickness (CT) in regions of interest. Structural equation models were used to examine evidence for pathways from stress and inflammation to neuronal atrophy. Model fit indices indicated good representation of stress, inflammation, and neurological data through the constructed models (CT model: robust RMSEA = 0.041, robust χ2 = 910.90; HCV model: robust RMSEA <0.001, robust χ2 = 40.95). Among inflammatory indices, only the SII was positively associated with hair cortisol as one indicator of chronic stress (β = 0.18, p < 0.05). Direct and indirect pathways from chronic stress and systemic inflammation to cortical thickness or hippocampal volume were non-significant. In exploratory analysis, the SII was inversely related to mean cortical thickness. Our results emphasize the importance of considering the multidimensionality of systemic inflammation and chronic stress, with various indicators that may represent different aspects of the systemic reaction. We conclude that inflammation and glucocorticoid-mediated neurodegeneration indicated by IL-6 and hs-CRP and HCC and HEC may only emerge during advanced ageing and disorder processes, still the SII could be a promising candidate for detecting associations between inflammation and neurodegeneration in younger and healthy samples. Future work should examine these pathways in prospective longitudinal designs, for which the present investigation serves as a baseline.

Neurotoxic Microglial Activation via IFNγ-Induced Nrf2 Reduction Exacerbating Alzheimer's Disease

Microglial neuroinflammation appears to be neuroprotective in the early pathological stage, yet neurotoxic, which often precedes neurodegeneration in Alzheimer's disease (AD). However, it remains unclear how the microglial activities transit to the neurotoxic state during AD progression, due to complex neuron-glia interactions. Here, the mechanism of detrimental microgliosis in AD by employing 3D human AD mini-brains, brain tissues of AD patients, and 5XFAD mice is explored. In the human and animal AD models, amyloid-beta (Aβ)-overexpressing neurons and reactive astrocytes produce interferon-gamma (IFNγ) and excessive oxidative stress. IFNγ results in the downregulation of mitogen-activated protein kinase (MAPK) and the upregulation of Kelch-like ECH-associated Protein 1 (Keap1) in microglia, which inactivate nuclear factor erythroid-2-related factor 2 (Nrf2) and sensitize microglia to the oxidative stress and induces a proinflammatory microglia via nuclear factor kappa B (NFκB)-axis. The proinflammatory microglia in turn produce neurotoxic nitric oxide and proinflammatory mediators exacerbating synaptic impairment, phosphorylated-tau accumulation, and discernable neuronal loss. Interestingly, recovering Nrf2 in the microglia prevents the activation of proinflammatory microglia and significantly blocks the tauopathy in AD minibrains. Taken together, it is envisioned that IFNγ-driven Nrf2 downregulation in microglia as a key target to ameliorate AD pathology.

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.

The hormetic and hermetic role of IL-6

Interleukin-6 is a pleiotropic cytokine regulating different tissues and organs in diverse and sometimes discrepant ways. The dual and sometime hermetic nature of IL-6 action has been highlighted in several contexts and can be explained by the concept of hormesis, in which beneficial or toxic effects can be induced by the same molecule depending on the intensity, persistence, and nature of the stimulation. According with hormesis, a low and/or controlled IL-6 release is associated with anti-inflammatory, antioxidant, and pro-myogenic actions, whereas increased systemic levels of IL-6 can induce pro-inflammatory, pro-oxidant and pro-fibrotic responses. However, many aspects regarding the multifaceted action of IL-6 and the complex nature of its signal transduction remains to be fully elucidated. In this review we collect mechanistic insight into the molecular networks contributing to normal or pathologic changes during advancing age and in chronic diseases. We point out the involvement of IL-6 deregulation in aging-related diseases, dissecting the hormetic action of this key mediator in different tissues, with a special focus on skeletal muscle. Since IL-6 can act as an enhancer of detrimental factor associated with both aging and pathologic conditions, such as chronic inflammation and oxidative stress, this cytokine could represent a "Gerokine", a determinant of the switch from physiologic aging to age-related diseases.

Echinacoside Protects Dopaminergic Neurons Through Regulating IL-6/JAK2/STAT3 Pathway in Parkinson’s Disease Model

Echinacoside (ECH), the major active constituent of Cistanche deserticola, was found to exert neuroprotection through neurotrophic and anti-inflammatory functions in Parkinson’s disease (PD) models. However, a clear intermediate molecule or pathway that unifies these two effects has to be found. In this study, our results demonstrate that ECH can protect DA neurons in PD mice with Western blot and immunohistochemistry staining. The quantitative real-time polymerase chain reaction was adapted to confirm its anti-inflammatory function with decreased cytokines (interleukin- (IL-) 6, IL-1β, and TNF-α) in PD mice and LPS-induced BV2 cells. Further studies found that ECH inhibited the IL-6/JAK2/STAT3 pathway and decreased phosphorylation of STAT3 on tyr705 by Western blot. It can also increase p-STAT3 (ser727) and brain-derived neurotrophic factor (BDNF) expression in PD mice and LPS-induced BV2 cells. This study revealed that ECH exerts neurotrophic and anti-inflammatory effects by regulating the IL-6/JAK2/STAT3 pathway and the phosphorylation of STAT3, promoting the mutually beneficial influence of the two effects to maximize its neuroprotective function.

Maternal Immune Activation Causes Social Behavior Deficits and Hypomyelination in Male Rat Offspring with an Autism-Like Microbiota Profile

Maternal immune activation (MIA) increases the risk of autism spectrum disorder (ASD) in offspring. Microbial dysbiosis is associated with ASD symptoms. However, the alterations in the brain-gut-microbiota axis in lipopolysaccharide (LPS)-induced MIA offspring remain unclear. Here, we examined the social behavior, anxiety-like and repetitive behavior, microbiota profile, and myelination levels in LPS-induced MIA rat offspring. Compared with control offspring, MIA male rat offspring spent less time in an active social interaction with stranger rats, displayed more anxiety-like and repetitive behavior, and had more hypomyelination in the prefrontal cortex and thalamic nucleus. A fecal microbiota analysis revealed that MIA offspring had a higher abundance of Alistipes, Fusobacterium, and Ruminococcus and a lower abundance of Coprococcus, Erysipelotrichaies, and Actinobacteria than control offspring, which is consistent with that of humans with ASD. The least absolute shrinkage and selection operator (LASSO) method was applied to determine the relative importance of the microbiota, which indicated that the abundance of Alistipes and Actinobacteria was the most relevant for the profile of defective social behavior, whereas Fusobacterium and Coprococcus was associated with anxiety-like and repetitive behavior. In summary, LPS-induced MIA offspring showed an abnormal brain-gut-microbiota axis with social behavior deficits, anxiety-like and repetitive behavior, hypomyelination, and an ASD-like microbiota profile.

Neural Mechanisms of Cancer Cachexia

Simple Summary

Cancer cachexia is a devastating wasting syndrome that occurs in many illnesses, with signs and symptoms including anorexia, weight loss, cognitive impairment and fatigue. The brain is capable of exerting overarching homeostatic control of whole-body metabolism and is increasingly being recognized as an important mediator of cancer cachexia. Given the increased recognition and discovery of neural mechanisms of cancer cachexia, we sought to provide an in-depth review and update of mechanisms by which the brain initiates and propagates cancer cachexia programs. Furthermore, recent work has identified new molecular mediators of cachexia that exert their effects through their direct interaction with the brain. Therefore, this review will summarize neural mechanisms of cachexia and discuss recently identified neural mediators of cancer cachexia.

Abstract

Nearly half of cancer patients suffer from cachexia, a metabolic syndrome characterized by progressive atrophy of fat and lean body mass. This state of excess catabolism decreases quality of life, ability to tolerate treatment and eventual survival, yet no effective therapies exist. Although the central nervous system (CNS) orchestrates several manifestations of cachexia, the precise mechanisms of neural dysfunction during cachexia are still being unveiled. Herein, we summarize the cellular and molecular mechanisms of CNS dysfunction during cancer cachexia with a focus on inflammatory, autonomic and neuroendocrine processes and end with a discussion of recently identified CNS mediators of cachexia, including GDF15, LCN2 and INSL3.

Prenatal Hyperhomocysteinemia Induces Glial Activation and Alters Neuroinflammatory Marker Expression in Infant Rat Hippocampus

Maternal hyperhomocysteinemia is one of the common complications of pregnancy that causes offspring cognitive deficits during postnatal development. In this study, we investigated the effect of prenatal hyperhomocysteinemia (PHHC) on inflammatory, glial activation, and neuronal cell death markers in the hippocampus of infant rats. Female Wistar rats received L-methionine (0.6 g/kg b.w.) by oral administration during pregnancy. On postnatal days 5 and 20, the offspring’s hippocampus was removed to perform histological and biochemical studies. After PHHC, the offspring exhibited increased brain interleukin-1β and interleukin-6 levels and glial activation, as well as reduced anti-inflammatory interleukin-10 level in the hippocampus. Additionally, the activity of acetylcholinesterase was increased in the hippocampus of the pups. Exposure to PHHC also resulted in the reduced number of neurons and disrupted neuronal ultrastructure. At the same time, no changes in the content and activity of caspase-3 were found in the hippocampus of the pups. In conclusion, our findings support the hypothesis that neuroinflammation and glial activation could be involved in altering the hippocampus cellular composition following PHHC, and these alterations could be associated with cognitive disorders later in life.

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 alters IL-6 Signal Transduction in the CNS of Transgenic Mice with Increased Astrocyte Expression of IL-6

Neuroimmune factors, including the cytokine interleukin-6 (IL-6), are important chemical regulators of central nervous system (CNS) function under both physiological and pathological conditions. Elevated expression of IL-6 occurs in the CNS in a variety of disorders associated with altered CNS function, including excessive alcohol use. Alcohol-induced production of IL-6 has been reported for several CNS regions including the cerebellum. Cerebellar actions of alcohol occur through a variety of mechanisms, but alcohol-induced changes in signal transduction, transcription, and translation are known to play important roles. IL-6 is an activator of signal transduction that regulates gene expression. Thus, alcohol-induced IL-6 production could contribute to cerebellar effects of alcohol by altering gene expression, especially under conditions of chronic alcohol abuse, where IL-6 levels could be habitually elevated. To gain an understanding of the effects of alcohol on IL-6 signal transduction, we studied activation/expression of IL-6 signal transduction partners STAT3 (Signal Transducer and Activator of Transcription), CCAAT-enhancer binding protein (C/EBP) beta, and p42/p44 mitogen-activated protein kinase (MAPK) at the protein level. Cerebella of transgenic mice that express elevated levels of astrocyte produced IL-6 in the CNS were studied. Results show that the both IL-6 and chronic intermittent alcohol exposure/withdrawal affect IL-6 signal transduction partners and that the actions of IL-6 and alcohol interact to alter activation/expression of IL-6 signal transduction partners. The alcohol/IL-6 interactions may contribute to cerebellar actions of alcohol, whereas the effects of IL-6 alone may have relevance to cerebellar changes occurring in CNS disorders associated with elevated levels of IL-6.

Etoposide Induces Mitochondrial Dysfunction and Cellular Senescence in Primary Cultured Rat Astrocytes

Brain aging is an inevitable process characterized by structural and functional changes and is a major risk factor for neurodegenerative diseases. Most brain aging studies are focused on neurons and less on astrocytes which are the most abundant cells in the brain known to be in charge of various functions including the maintenance of brain physical formation, ion homeostasis, and secretion of various extracellular matrix proteins. Altered mitochondrial dynamics, defective mitophagy or mitochondrial damages are causative factors of mitochondrial dysfunction, which is linked to age-related disorders. Etoposide is an anti-cancer reagent which can induce DNA stress and cellular senescence of cancer cell lines. In this study, we investigated whether etoposide induces senescence and functional alterations in cultured rat astrocytes. Senescence-associated β-galactosidase (SA-β-gal) activity was used as a cellular senescence marker. The results indicated that etoposide-treated astrocytes showed cellular senescence phenotypes including increased SA-β-gal-positive cells number, increased nuclear size and increased senescence-associated secretory phenotypes (SASP) such as IL-6. We also observed a decreased expression of cell cycle markers, including Phospho- Histone H3/Histone H3 and CDK2, and dysregulation of cellular functions based on wound-healing, neuronal protection, and phagocytosis assays. Finally, mitochondrial dysfunction was noted through the determination of mitochondrial membrane potential using tetramethylrhodamine methyl ester (TMRM) and the measurement of mitochondrial oxygen consumption rate (OCR). These data suggest that etoposide can induce cellular senescence and mitochondrial dysfunction in astrocytes which may have implications in brain aging and neurodegenerative conditions.

Opioid receptor-mediated changes in the NMDA receptor in developing rat and chicken

The use of opioids during pregnancy has been associated with neurodevelopmental toxicity in exposed children, leading to cognitive and behavioural deficits later in life. The N-methyl-D-aspartate receptor (NMDAR) subunit GluN2B plays critical roles in cerebellar development, and methadone has been shown to possess NMDAR antagonist effect. Consequently, we wanted to explore if prenatal opioid exposure affected GluN2B subunit expression and NMDAR function in rat and chicken cerebellum. Pregnant rats were exposed to methadone (10 mg/kg/day) or buprenorphine (1 mg/kg/day) for the whole period of gestation, using an osmotic minipump. To further examine potential effects of prenatal opioid exposure in a limited time window, chicken embryos were exposed to a 20 mg/kg dose of methadone or morphine on embryonic days 13 and 14. Western blot analysis of cerebella isolated from 14 days old rat pups exposed to buprenorphine showed significantly lower level of the GluN2B subunit, while the opioid exposed chicken embryo cerebellar GluN2B expression remained unaffected at embryonic day 17. However, we observed increased NMDA/glycine-induced calcium influx in cerebellar granule neurone cultures from opioid exposed chicken embryos. We conclude that prenatal opioid exposure leads to opioid receptor-dependent reduction in the postnatal expression of GluN2B in rat cerebella, and increase in NMDA-induced calcium influx in chicken embryo cerebella.

Pretreatment Cancer-Related Cognitive Impairment-Mechanisms and Outlook

Cognitive changes are common in patients with active cancer and during its remission. This has largely been blamed on therapy-related toxicities and diagnosis-related stress, with little attention paid to the biological impact of cancer itself. A plethora of clinical studies demonstrates that cancer patients experience cognitive impairment during and after treatment. However, recent studies show that a significant portion of patients with non-central nervous system (CNS) tumors experience cognitive decline prior to treatment, suggesting a role for tumor-derived factors in modulating cognition and behavior. Cancer-related cognitive impairment (CRCI) negatively impacts a patient’s quality of life, reduces occupational and social functioning, and increases morbidity and mortality. Furthermore, patients with cancer cachexia frequently experience a stark neurocognitive decline, suggesting peripheral tumors exert an enduring toll on the brain during this chronic paraneoplastic syndrome. However, the scarcity of research on cognitive impairment in non-CNS cancers makes it difficult to isolate psychosocial, genetic, behavioral, and pathophysiological factors in CRCI. Furthermore, clinical models of CRCI are frequently confounded by complicated drug regimens that inherently affect neurocognitive processes. The severity of CRCI varies considerably amongst patients and highlights its multifactorial nature. Untangling the biological aspects of CRCI from genetic, psychosocial, and behavioral factors is non-trivial, yet vital in understanding the pathogenesis of CRCI and discovering means for therapeutic intervention. Recent evidence demonstrating the ability of peripheral tumors to alter CNS pathways in murine models is compelling, and it allows researchers to isolate the underlying biological mechanisms from the confounding psychosocial stressors found in the clinic. This review summarizes the state of the science of CRCI independent of treatment and focuses on biological mechanisms in which peripheral cancers modulate the CNS.

Elevated levels of C-reactive protein and IL-6 among the antipsychotic medicating schizophrenia patients of Siliguri, West Bengal, India

PURPOSE

Chronic, low-grade inflammation is a proposed etiological factor associated with schizophrenia. Thus, various studies have been conducted to understand the role of inflammatory process in schizophrenia by using inflammatory maker C-reactive protein (CRP) with conflicting findings. Inadvertently, studies of CRP among the Indian schizophrenia patients are very few. Therefore, the present study was undertaken to investigate the role of inflammatory process among Indian Bengalee schizophrenia patients of Siliguri, using the marker CRP and its stimulating cytokine interleukin-6 (IL-6). In addition, the study also intended to investigate the immunomodulatory effect of antipsychotic medication on serum levels of CRP and IL-6.

MATERIALS AND METHODS

The serum levels of CRP and IL-6 were measured by Enzyme-Linked Immunosorbent Assay (ELISA) among 67 antipsychotic medicating, 28 psychotropic medication-free schizophrenia patients, and it was compared with 72 age, sex and ethnicity-matched controls.

RESULTS

A significantly higher level of CRP and IL-6 were recorded among the antipsychotic medicating patients. Although CRP was found to be higher among the psychotropic medication-free patients than the controls, it was not found to be significant. However, a significantly higher level of IL-6 was observed in this group.

CONCLUSIONS

The results provide the evidence for a possible immunomodulatory effect of antipsychotic drugs on CRP. Future investigations including the study of antipsychotics separately may help to understand the differential effects of individual antipsychotics on CRP level. Additional studies with a larger sample size of psychotropic medication-free patients may help to verify the role of inflammation in schizophrenia patients of this region.

Theiler's murine encephalomyelitis virus infection of SJL/J and C57BL/6J mice: Models for multiple sclerosis and epilepsy

Mouse models are great tools to study the mechanisms of disease development. Theiler's murine encephalomyelitis virus is used in two distinct viral infection mouse models to study the human diseases multiple sclerosis (MS) and epilepsy. Intracerebral (i.c.) infection of the SJL/J mouse strain results in persistent viral infection of the central nervous system and a MS-like disease, while i.c. infection of the C57BL/6J mouse strain results in acute seizures and epilepsy. Our understanding of how the immune system contributes to the development of two disparate diseases caused by the same virus is presented.

Aerobic Activity in the Healthy Elderly Is Associated with Larger Plasticity in Memory Related Brain Structures and Lower Systemic Inflammation

Cognitive abilities decline over the time course of our life, a process, which may be mediated by brain atrophy and enhanced inflammatory processes. Lifestyle factors, such as regular physical activities have been shown to counteract those noxious processes and are assumed to delay or possibly even prevent pathological states, such as dementing disorders. Whereas the impact of lifestyle and immunological factors and their interactions on cognitive aging have been frequently studied, their effects on neural parameters as brain activation and functional connectivity are less well studied. Therefore, we investigated 32 healthy elderly individuals (60.4 ± 5.0 SD; range 52–71 years) with low or high level of self-reported aerobic physical activity at the time of testing. A higher compared to a lower level in aerobic physical activity was associated with an increased encoding related functional connectivity in an episodic memory network comprising mPFC, thalamus, hippocampus precuneus, and insula. Moreover, encoding related functional connectivity of this network was associated with decreased systemic inflammation, as measured by systemic levels of interleukin 6.

Infections and Brain Development

Several different bodies of evidence support a link between infection and altered brain development. Maternal infections, such as influenza and human immunodeficiency virus, have been linked to the development of autism spectrum disorders, differences in cognitive test scores, and bipolar disorder; an association that has been shown in both epidemiologic and retrospective studies. Several viral, bacterial, and parasitic illnesses are associated with alterations in fetal brain structural anomalies including brain calcifications and hydrocephalus. The process of infection can activate inflammatory pathways causing the release of various proinflammatory biomarkers and histological changes consistent with an infectious intrauterine environment (chorioamnionitis) or umbilical cord (funisitis). Elevations in inflammatory cytokines are correlated with cerebral palsy, schizophrenias, and autism. Animal studies indicate that the balance of proinflammatory and anti-inflammatory cytokines is critical to the effect prenatal inflammation plays in neurodevelopment. Finally, chorioamnionitis is associated with cerebral palsy and other abnormal neurodevelopmental outcomes. In conclusion, a plethora of evidence supports, albeit with various degrees of certainty, the theory that maternal infection and inflammation that occur during critical periods of fetal development could theoretically alter brain structure and function in a time-sensitive manner.

Integrating neuroimmune systems in the neurobiology of depression

Data from clinical and preclinical studies indicate that immune dysregulation, specifically of inflammatory processes, is associated with symptoms of major depressive disorder (MDD). In particular, increased levels of circulating pro-inflammatory cytokines and concomitant activation of brain-resident microglia can lead to depressive behavioural symptoms. Repeated exposure to psychological stress has a profound impact on peripheral immune responses and perturbs the function of brain microglia, which may contribute to neurobiological changes underlying MDD. Here, we review these findings and discuss ongoing studies examining neuroimmune mechanisms that influence neuronal activity as well as synaptic plasticity. Interventions targeting immune-related cellular and molecular pathways may benefit subsets of MDD patients with immune dysregulation.

TLR2/NFκB signalling regulates endogenous IL-6 release from marrow-derived mesenchymal stromal cells to suppress the apoptosis of PC12 cells injured by oxygen and glucose deprivation

Two previous studies published by our group identified that mesenchymal stromal cells (MSCs) conferred neuroprotection in a rat model of hypoxic-ischaemic brain damage (HIBD), and that MSCs secreted abundant interleukin-6 (IL‑6) when co‑cultured with oxygen and glucose deprivation (OGD)‑injured PC12 cells. The present study has further investigated the role of IL‑6, and explored potential signalling pathways in vitro. In vitro models were established by co‑culturing OGD‑injured PC12 cells with MSCs. Subsequently, the expression levels of the signalling molecules, Toll‑like receptor 2 (TLR2)/nuclear factor κB (NFκB), and IL‑6 were altered separately in this in vitro model by treatment with an agonist, antagonist, siRNA or overexpression adenovirus. The expression levels of B cell lymphoma‑associated X (Bax), TLR2, NFκB and IL‑6 were detected by western blot analysis, real‑time polymerase chain reaction or ELISA. The resting membrane potential (RMP) of the PC12 cells was analysed by whole‑cell patch‑clamp recordings. Compared with controls or the PC12 co‑culture group, the MSC co‑cultured group induced less expression of Bax, but more IL‑6 secretion. Up- or down-regulation of the TLR2/NFκB signalling pathway resulted in a corresponding increase or decrease in the IL‑6 expression level in the MSCs. Co‑culture with siIL‑6‑MSCs increased the expression levels of Bax and increased the RMP in the OGD PC12 cells. In conclusion, the release of IL‑6 from MSCs was regulated via the TLR2/NFκB signalling pathway. Endogenous IL‑6 reduced apoptosis and protected OGD‑injured PC12 cells when they were co‑cultured with MSCs. The present study has reported a novel immunomodulatory effect of the microenvironment of neural damage during MSC cytotherapy.

Non-Neuronal Cells Are Required to Mediate the Effects of Neuroinflammation: Results from a Neuron-Enriched Culture System

Chronic inflammation is associated with activated microglia and reactive astrocytes and plays an important role in the pathogenesis of neurodegenerative diseases such as Alzheimer’s. Both in vivo and in vitro studies have demonstrated that inflammatory cytokine responses to immune challenges contribute to neuronal death during neurodegeneration. In order to investigate the role of glial cells in this phenomenon, we developed a modified method to remove the non-neuronal cells in primary cultures of E16.5 mouse cortex. We modified previously reported methods as we found that a brief treatment with the thymidine analog, 5-fluorodeoxyuridine (FdU), is sufficient to substantially deplete dividing non-neuronal cells in primary cultures. Cell cycle and glial markers confirm the loss of ~99% of all microglia, astrocytes and oligodendrocyte precursor cells (OPCs). More importantly, under this milder treatment, the neurons suffered neither cell loss nor any morphological defects up to 2.5 weeks later; both pre- and post-synaptic markers were retained. Further, neurons in FdU-treated cultures remained responsive to excitotoxicity induced by glutamate application. The immunobiology of the FdU culture, however, was significantly changed. Compared with mixed culture, the protein levels of NFκB p65 and the gene expression of several cytokine receptors were altered. Individual cytokines or conditioned medium from β-amyloid-stimulated THP-1 cells that were, potent neurotoxins in normal, mixed cultures, were virtually inactive in the absence of glial cells. The results highlight the importance of our glial-depleted culture system and identifies and offer unexpected insights into the complexity of -brain neuroinflammation.

Transgenic mice with increased astrocyte expression of IL-6 show altered effects of acute ethanol on synaptic function

A growing body of evidence has revealed that resident cells of the central nervous system (CNS), and particularly the glial cells, comprise a neuroimmune system that serves a number of functions in the normal CNS and during adverse conditions. Cells of the neuroimmune system regulate CNS functions through the production of signaling factors, referred to as neuroimmune factors. Recent studies show that ethanol can activate cells of the neuroimmune system, resulting in the elevated production of neuroimmune factors, including the cytokine interleukin-6 (IL-6). Here we analyzed the consequences of this CNS action of ethanol using transgenic mice that express elevated levels of IL-6 through increased astrocyte expression (IL-6-tg) to model the increased IL-6 expression that occurs with ethanol use. Results show that increased IL-6 expression induces neuroadaptive changes that alter the effects of ethanol. In hippocampal slices from non-transgenic (non-tg) littermate control mice, synaptically evoked dendritic field excitatory postsynaptic potential (fEPSP) and somatic population spike (PS) at the Schaffer collateral to CA1 pyramidal neuron synapse were reduced by acute ethanol (20 or 60 mM). In contrast, acute ethanol enhanced the fEPSP and PS in hippocampal slices from IL-6 tg mice. Long-term synaptic plasticity of the fEPSP (i.e., LTP) showed the expected dose-dependent reduction by acute ethanol in non-tg hippocampal slices, whereas LTP in the IL-6 tg hippocampal slices was resistant to this depressive effect of acute ethanol. Consistent with altered effects of acute ethanol on synaptic function in the IL-6 tg mice, EEG recordings showed a higher level of CNS activity in the IL-6 tg mice than in the non-tg mice during the period of withdrawal from an acute high dose of ethanol. These results suggest a potential role for neuroadaptive effects of ethanol-induced astrocyte production of IL-6 as a mediator or modulator of the actions of ethanol on the CNS, including persistent changes in CNS function that contribute to cognitive dysfunction and the development of alcohol dependence.

Inflammation as a mediator of the relationship between cortical thickness and metabolic syndrome

Metabolic Syndrome (MetS), the clustering of obesity, high blood pressure, and disordered glucose and lipid/lipoprotein metabolism within a single individual, is associated with poorer cognitive function. It has been hypothesized that cognitive impairment in MetS occurs primarily within the context of inflammation. MetS risk factors are also associated with thinning of the cerebral cortex. However, the mechanisms by which MetS and inflammation affect the brain are poorly understood. The present study used statistical mediation to examine the relationship between MetS risk factors, cortical thickness in a priori regions of interest (ROIs) and inflammation. ROIs were chosen from the previous literature. Forty-three adults between the ages of 40 and 60 years underwent a health screen, neuropsychological testing and structural magnetic resonance imaging. Serum levels of pro-inflammatory markers (interleukin 1, interleukin 2, interleukin 6 and C-Reactive Protein) were measured using enzyme-linked immunosorbent assays. A higher number of MetS risk factors were associated with thinning in the inferior frontal ROI (β = -0.35, p = 0.019) as well as higher levels of serum interleukin 2 (β = 0.31, p = 0.04). A higher level of serum interleukin 2 was also associated with reduced thickness in the inferior frontal gyrus (β = -0.41, p = 0.013). After accounting for the effects of interleukin 2, the number of MetS risk factors was no longer associated with cortical thickness in the inferior frontal gyrus indicating successful statistical mediation. The results indicate a potentially important role for inflammation in linking MetS to cortical thinning and cognitive vulnerability.

α-Synuclein-induced internalization of NMDA receptors in hippocampal neurons is associated with reduced inward current and Ca(2+) influx upon NMDA stimulation

Abnormal α-synuclein (α-syn) expression and aggregation have been implicated in the pathogenesis of Parkinson's disease (PD), dementia with Lewy bodies (DLB), and Alzheimer's disease (AD). These neurodegenerative disorders, collectively known as synucleinopathies, are usually associated with cognitive impairment that could be caused by impaired hippocampal function. Although abnormal expressions of α-syn and N-methyl-d-aspartate (NMDA) receptor are frequently observed in the hippocampus of patients with synucleinopathies, how these proteins interact with each other in hippocampal neurons remains poorly understood. In the present study, primary cultures of hippocampal neurons and α-syn transgenic mice were used to investigate the effect of α-syn on NMDA receptors. Neurons were treated either by direct addition of recombinant human α-syn (hα-syn) to the medium, or by infection with the hα-syn gene, to increase intracellular levels of α-syn. In both cases, NMDA receptor NR1 subunits on the cell surface were reduced while the total amount of NR1 was unchanged, indicating an internalization of NR1 subunits. Neurons with elevated α-syn also showed a profound increase in Rab5B, an isoform of the small GTPases essential for NMDA receptor endocytosis. Knockdown of Rab5B expression by siRNA inhibited the α-syn-induced reduction in surface NR1. The in vitro findings were confirmed in α-syn transgenic mice, showing that increased α-syn expression was accompanied by reduced levels of surface NR1 and increased expression of Rab5B. Due to the essential role of NR1 subunits for assembling a complete NMDA receptor, its reduction on the cell surface indicated impaired receptor function. This was demonstrated by observations that neurons with elevated α-syn showed profound reductions in NMDA-elicited Ca(2+) influx and inward current, which were also inhibited by knockdown of Rab5B expression. Our data suggest that increased α-syn expression may impair NMDA receptor function in the hippocampus by reducing the density of NR1 subunits on the cell surface.

Crosstalk Among Disrupted Glutamatergic and Cholinergic Homeostasis and Inflammatory Response in Mechanisms Elicited by Proline in Astrocytes

Hyperprolinemias are inherited disorder of proline (Pro) metabolism. Patients affected may present neurological manifestations, but the mechanisms of neural excitotoxicity elicited by hyperprolinemia are far from being understood. Considering that the astrocytes are important players in neurological disorders, the aim of the present work was to study the effects 1 mM Pro on glutamatergic and inflammatory parameters in cultured astrocytes from cerebral cortex of rats, exploring some molecular mechanisms underlying the disrupted homeostasis of astrocytes exposed to this toxic Pro concentration. We showed that cortical astrocytes of rats exposed to 1 mM Pro presented significantly elevated extracellular glutamate and glutamine levels, suggesting glutamate excitotoxicity. The excess of glutamate elicited by Pro together with increased glutamate uptake and upregulated glutamine synthetase (GS) activity supported misregulated glutamate homeostasis in astrocytic cells. High Pro levels also induced production/release of pro-inflammatory cytokines TNF-α, IL-1β, and IL-6. We also evidenced misregulation of cholinergic anti-inflammatory system with increased acetylcholinesterase (AChE) activity and decreased acetylcholine (ACh) levels, contributing to the inflammatory status in Pro-treated astrocytes. Our findings highlighted a crosstalk among disrupted glutamate homeostasis, cholinergic mechanisms, and inflammatory cytokines, since ionotropic (DL-AP5 and CNQX) and metabotropic (MCPG and MPEP) glutamate antagonists were able to restore the extracellular glutamate and glutamine levels; downregulate TNFα and IL6 production/release, modulate GS and AChE activities; and restore ACh levels. Otherwise, the non-steroidal anti-inflammatory drugs nimesulide, acetylsalicylic acid, ibuprofen, and diclofenac sodium decreased the extracellular glutamate and glutamine levels, downregulated GS and AChE activities, and restored ACh levels in Pro-treated astrocytes. Altogether, our results evidence that the vulnerability of metabolic homeostasis in cortical astrocytes might have important implications in the neurotoxicity of Pro.

Microglia in neuronal plasticity: Influence of stress

The central nervous system (CNS) has previously been regarded as an immune-privileged site with the absence of immune cell responses but this dogma was not entirely true. Microglia are the brain innate immune cells and recent findings indicate that they participate both in CNS disease and infection as well as facilitate normal CNS function. Microglia are highly plastic and play integral roles in sculpting the structure of the CNS, refining neuronal circuitry and connectivity, and contribute actively to neuronal plasticity in the healthy brain. Interestingly, psychological stress can perturb the function of microglia in association with an impaired neuronal plasticity and the development of emotional behavior alterations. As a result it seemed important to describe in this review some findings indicating that the stress-induced microglia dysfunction may underlie neuroplasticity deficits associated to many mood disorders. This article is part of a Special Issue entitled 'Neuroimmunology and Synaptic Function'.

IL-6 regulation of synaptic function in the CNS

A growing body of evidence supports a role for glial-produced neuroimmune factors, including the cytokine IL-6, in CNS physiology and pathology. CNS expression of IL-6 has been documented in the normal CNS at low levels and at elevated levels in several neurodegenerative or psychiatric disease states as well as in CNS infection and injury. The altered CNS function associated with these conditions raises the possibility that IL-6 has neuronal or synaptic actions. Studies in in vitro and in vivo models confirmed this possibility and showed that IL-6 can regulate a number of important neuronal and synaptic functions including synaptic transmission and synaptic plasticity, an important cellular mechanism of memory and learning. Behavioral studies in animal models provided further evidence of an important role for IL-6 as a regulator of CNS pathways that are critical to cognitive function. This review summarizes studies that have lead to our current state of knowledge. In spite of the progress that has been made, there is a need for a greater understanding of the physiological and pathophysiological actions of IL-6 in the CNS, the mechanisms underlying these actions, conditions that induce production of IL-6 in the CNS and therapeutic strategies that could ameliorate or promote IL-6 actions. This article is part of a Special Issue entitled 'Neuroimmunology and Synaptic Function'.

Interleukin 6 and cognitive dysfunction

The interleukin-6 (IL-6) is a pleiotropic cytokine that plays a key role in interaction between immune and nervous system. Although IL-6 has neurotrophic properties and beneficial effects in the CNS, its overexpression is generally detrimental, adding to the pathophysiology associated with CNS disorders. The source of the increase in peripheral IL-6 remains to be established and varies among different pathologies, but has been found to be associated with cognitive dysfunction in several pathologies. This comprehensive review provides an update summary of the studies performed in humans concerning the role of central and peripheral IL-6 in cognitive dysfunction in dementias and in other systemic diseases accompained by cognitive dysfuction such as cardiovascular, liver disease, Behçet's disease and systemic lupus erythematosus. Further research is needed to correlate specific deficits in IL-6 and its receptors in pathologies characterized by cognitive dysfunction and to understand how systemic IL-6 affects high cerebral function in order to open new directions in pharmacological treatments that modulate IL-6 signalling.

Increased astrocyte expression of IL-6 or CCL2 in transgenic mice alters levels of hippocampal and cerebellar proteins

Emerging research has identified that neuroimmune factors are produced by cells of the central nervous system (CNS) and play critical roles as regulators of CNS function, directors of neurodevelopment and responders to pathological processes. A wide range of neuroimmune factors are produced by CNS cells, primarily the glial cells, but the role of specific neuroimmune factors and their glial cell sources in CNS biology and pathology have yet to be fully elucidated. We have used transgenic mice that express elevated levels of a specific neuroimmune factor, the cytokine IL-6 or the chemokine CCL2, through genetic modification of astrocyte expression to identify targets of astrocyte produced IL-6 or CCL2 at the protein level. We found that in non-transgenic mice constitutive expression of IL-6 and CCL2 occurs in the two CNS regions studied, the hippocampus and cerebellum, as measured by ELISA. In the CCL2 transgenic mice elevated levels of CCL2 were evident in the hippocampus and cerebellum, whereas in the IL-6 transgenic mice, elevated levels of IL-6 were only evident in the cerebellum. Western blot analysis of the cellular and synaptic proteins in the hippocampus and cerebellum of the transgenic mice showed that the elevated levels of CCL2 or IL-6 resulted in alterations in the levels of specific proteins and that these actions differed for the two neuroimmune factors and for the two brain regions. These results are consistent with cell specific profiles of action for IL-6 and CCL2, actions that may be an important aspect of their respective roles in CNS physiology and pathophysiology.

Transcription factor C/EBP-β mediates downregulation of dipeptidyl-peptidase III expression by interleukin-6 in human glioblastoma cells

Dipeptidyl-peptidase III (DPP III) is a cytosolic metallo-aminopeptidase implicated in various physiological and pathological processes. A previous study from our laboratory indicated an elevated expression of DPP III in glioblastoma (U87MG) cells. In the present study we investigated the role of interleukin-6 (IL-6), a pleiotropic cytokine produced by glial tumors, in the regulation of DPP III expression. Immunohistochemistry, western blotting and quantitative RT-PCR were used for quantitation of DPP III and IL-6 in human glioblastoma cells and tumors. Cell transfections and DPP III promoter reporter assays were performed to study the transcriptional regulation of DPP III by IL-6. Promoter deletion analysis, site directed mutagenesis, chromatin immunoprecipitation assays and small interfering RNA (siRNA) technology was employed to elucidate the molecular mechanism of IL-6 mediated regulation of DPP III expression in glioblastoma cells. Our results for the first time demonstrate a negative correlation (r = 0.632, P = 0.01) between DPP III and IL-6 in both human tumors and cultured glioblastoma cells. Treatment of U87MG cells with IL-6 significantly decreased DPP III expression with a concomitant increase in the levels of transcription factor CCAAT/enhancer binding protein beta (C/EBP-β). Deletion/mutagenesis of C/EBP-β binding motif of DPP III promoter significantly increased its activity and abolished its responsiveness to IL-6. This effect could also be mimicked by C/EBP-β siRNA. In conclusion our study for the first time demonstrates C/EBP-β mediated transcriptional downregulation of DPP III by IL-6. Our results demonstrating a negative correlation between IL-6 and DPP III taken together with the previously reported prognostic significance of this cytokine in glioblastoma suggests that DPP III may prove useful as a prognostic marker.

Phytoestrogens mediated anti-inflammatory effect through suppression of IRF-1 and pSTAT1 expressions in lipopolysaccharide-activated microglia

Microglial activation has been implicated in various neurological disorders, including Alzheimer's disease, Parkinson's disease, multiple sclerosis, and HIV encephalopathy. Phytoestrogens have been shown to be neuroprotective in neurotoxicity models; however, their effect on microglia has not been well established. In the current study, we report that the soy phytoestrogens, genistein, daidzein, and coumestrol, decreased nitric oxide (NO) production induced by lipopolysaccharide (LPS) in the rat microglial cell line (HAPI). The levels of inducible NO synthase (iNOS) mRNA and protein expression were also reduced. Transcription factors known to govern iNOS expression including interferon regulatory factor-1 (IRF-1) and phosphorylated STAT1 were down regulated. These observations explain, at least in part, the inhibitory effect of phytoestrogens on NO production. The levels of monocyte chemoattractant protein-1 and interleukin-6 mRNA, proinflammatory chemokine and cytokine associated with various neurological disorders, were also reduced following LPS stimulation when HAPI cells were pretreated with phytoestrogens. Hence, genistein, daidzein, and coumestrol could serve as anti-inflammatory agents and may have beneficial effects in the treatment of neurodegenerative diseases.

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.

A human pluripotent carcinoma stem cell-based model for in vitro developmental neurotoxicity testing: effects of methylmercury, lead and aluminum evaluated by gene expression studies

The major advantage of the neuronal cell culture models derived from human stem cells is their ability to replicate the crucial stages of neurodevelopment such as the commitment of human stem cells to the neuronal lineage and their subsequent stages of differentiation into neuronal and glial-like cell. In these studies we used mixed neuronal/glial culture derived from the NTERA-2 (NT-2) cell line, which has been established from human pluripotent testicular embryonal carcinoma cells. After characterization of the different stages of cell differentiation into neuronal- and glial-like phenotype toxicity studies were performed to evaluate whether this model would be suitable for developmental neurotoxicity studies. The cells were exposed during the differentiation process to non-cytotoxic concentrations of methylmercury chloride, lead chloride and aluminum nitrate for two weeks. The toxicity was then evaluated by measuring the mRNA levels of cell specific markers (neuronal and glial). The results obtained suggest that lead chloride and aluminum nitrate at low concentrations were toxic primarily to astrocytes and at the higher concentrations it also induced neurotoxicity. In contrast, MetHgCl was toxic for both cell types, neuronal and glial, as mRNA specific for astrocytes and neuronal markers were affected. The results obtained suggest that a neuronal mixed culture derived from human NT2 precursor cells is a suitable model for developmental neurotoxicity studies and gene expression could be used as a sensitive endpoint for initial screening of potential neurotoxic compounds.

Role of the microenvironment in mantle cell lymphoma: IL-6 is an important survival factor for the tumor cells

Mantle cell lymphoma (MCL) is an aggressive B-cell non-Hodgkin lymphoma frequently involved in the lymph nodes, bone marrow, spleen, and gastrointestinal tract. We examined the role of IL-6 in MCL. Human MCL cells expressed the membrane gp130 and soluble gp80, and some of them also secreted IL-6. Neutralizing autocrine IL-6 and/or blocking IL-6 receptors in IL-6(+)/gp80(+) MCL cells inhibited cell growth, enhanced the rate of spontaneous apoptosis, and increased sensitivity to chemotherapy drugs. For IL-6(-) or gp80(low) MCL cells, paracrine or exogenous IL-6 or gp80 protected the cells from stress-induced death. Knockdown of gp80 in gp80(high) MCL cells rendered the cells more sensitive to chemotherapy drugs, even in the presence of exogenous IL-6. In contrast, overexpression of gp80 in gp80(low)/IL-6(+) MCL cells protected the cells from chemotherapy drug-induced apoptosis in vitro and compromised the therapeutic effect of chemotherapy in vivo. IL-6 activated the Jak2/STAT3 and PI3K/Akt pathways in MCL, and the inhibition of these pathways completely or partially abrogated IL-6-mediated protection of MCL cells. Hence, our study identifies IL-6 as a key cytokine for MCL growth and survival and suggests that targeting the IL-6 pathway may be a novel way to improve the efficacy of chemotherapy in MCL patients.

Cytokines, neurophysiology, neuropsychology, and psychiatric symptoms

Recent research has overcome the old paradigms of the brain as an immunologically privileged organ, and of the exclusive role of neurotransmitters and neuropeptides as signal transducers in the central nervous system. Growing evidence suggests that the signal proteins of the immune system - the cytokines - are also involved in modulation of behavior and induction of psychiatric symptoms. This article gives an overview on the nature of cytokines and the proposed mechanisms of immune-to-brain interaction. The role of cytokines in psychiatric symptoms, syndromes, and disorders like sickness behavior, major depression, and schizophrenia are discussed together with recent immunogenetic findings.

Maternal immune activation by LPS selectively alters specific gene expression profiles of interneuron migration and oxidative stress in the fetus without triggering a fetal immune response

Maternal immune activation (MIA) is a risk factor for the development of schizophrenia and autism. Infections during pregnancy activate the mother's immune system and alter the fetal environment, with consequential effects on CNS function and behavior in the offspring, but the cellular and molecular links between infection-induced altered fetal development and risk for neuropsychiatric disorders are unknown. We investigated the immunological, molecular, and behavioral effects of MIA in the offspring of pregnant Sprague-Dawley rats given an intraperitoneal (0.25 mg/kg) injection of lipopolysaccharide (LPS) on gestational day 15. LPS significantly elevated pro-inflammatory cytokine levels in maternal serum, amniotic fluid, and fetal brain at 4 h, and levels decreased but remained elevated at 24 h. Offspring born to LPS-treated dams exhibited reduced social preference and exploration behaviors as juveniles and young adults. Whole genome microarray analysis of the fetal brain at 4 h post maternal LPS was performed to elucidate the possible molecular mechanisms by which MIA affects the fetal brain. We observed dysregulation of 3285 genes in restricted functional categories, with increased mRNA expression of cellular stress and cell death genes and reduced expression of developmentally-regulated and brain-specific genes, specifically those that regulate neuronal migration of GABAergic interneurons, including the Distal-less (Dlx) family of transcription factors required for tangential migration from progenitor pools within the ganglionic eminences into the cerebral cortex. Our results provide a novel mechanism by which MIA induces the widespread down-regulation of critical neurodevelopmental genes, including those previously associated with autism.

Immunomodulation in schizophrenia: A study among the Indian schizophrenia patients of Siliguri, West Bengal

Authors investigated the circumstantial evidence for autoimmunity in schizophrenia patients of Siliguri by considering the immune parameters like HLA Class I genes, IL-2 and IL6 and T cell subsets. Low resolution PCR-SSP method was applied for typing the HLA genes. Serum levels of IL-2 and IL-6 were measured by ELISA method. The CD4+ and CD8+ subset count were done using flow cytometry. A significant increase in HLA A*03 gene was observed in patients along with the significant decrease of HLA-A*31 and HLA-B*51. Both IL-2 and IL-6 were found to have decreased levels in the patients. Although the mean percentage of CD4+ and CD8+ cells was higher in patients but not significantly higher than controls. These cumulative preliminary findings are suggestive of alterations in the immune system of schizophrenia patients of this region.

Neuroadaptive changes in cerebellar neurons induced by chronic exposure to IL-6

IL-6 is an important signaling molecule in the CNS. CNS neurons express IL-6 receptors and their signal transduction molecules, consistent with a role for IL-6 in neuronal physiology. Research indicates that IL-6 levels are low in the normal brain but can be significantly elevated in CNS injury and disease. Relatively little is known about how the elevated levels of IL-6 affect neurons. In the current study we show that under conditions of chronic exposure, IL-6 induces alterations in the level of protein expression in developing CNS cells. Such changes may play a role in the altered CNS function observed in CNS conditions associated with elevated levels of IL-6 in the CNS.

Heteroarylketones inhibit astroglial interleukin-6 expression via a STAT3/NF-κB signaling pathway

Background

Elevated brain levels of the pleiotropic cytokine interleukin-6, which is mainly secreted from activated local astrocytes, contribute to pathological events including neuroinflammation and neurodegeneration. Thus, inhibition of pathological IL-6 expression provides a rationale strategy for targeting the onset or further progression of neurological disorders including Alzheimer's disease, multiple sclerosis, Parkinson's disease and traumatic brain injury. The purpose of this study was to identify and to characterize new potent inhibitors of astrocytic IL-6 expression for further therapeutic development of novel anti-inflammatory and neuroprotective drugs.

Methods

Oncostatin M (OSM)-treated human glioma U343 cells were used as model for induction of astrocytic IL-6 expression. This model was characterized by immunoblotting, siRNA technique, ELISA and qRT-PCR and used to screen low molecular weight compound libraries for IL-6-lowering effects. To validate bioactive compounds identified from library screens, bacterial lipopolysaccharide was used to induce IL-6 expression in cultivated primary astrocytes and in mice in vivo. To dissect underlying molecular mechanisms, protein extracts from OSM-treated U343 cells were analyzed by phospho-specific immunoblotting and immunocytochemistry as well as by co-immunoprecipitation.

Results

OSM-treatment (100 ng/ml; 24 h) led to 30-fold increase of IL-6 secretion from U343 cells. The temporal profile of IL-6 mRNA induction displayed a biphasic induction pattern with peak synthesis at 1 h (6.5-fold) and 16 h (5.5-fold) post stimulation. IL-6 protein release did not show that biphasic pattern and was detected as early as 3 h post stimulation reaching a maximum at 24 h. The screen of compound libraries identified a set of heteroarylketones (HAKs) as potent inhibitors of IL-6 secretion. HAK compounds affected the second peak in IL-6 mRNA synthesis, whereas the first peak was insensitive to HAK treatment. HAK compounds also suppressed lipopolysaccharide-induced IL-6 expression in primary murine astrocytes as well as in brain and plasma samples from lipopolysaccharide-treated mice. Finally, HAK compounds were demonstrated to specifically suppress the OSM-induced phosphorylation of STAT3 at serine 727 and the physical interaction of pSTAT3^S727 with p65.

Conclusion

Heteroarylketone compounds are potent inhibitors of IL-6 expression in vitro and in vivo and may represent a new class of potent anti-inflammatory and neuroprotective drugs.