The role of TNF-alpha and its receptors in the production of NGF and GDNF by astrocytes

Methyl-CpG-Binding Protein 2 Emerges as a Central Player in Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorders

MECP2 and its product methyl-CpG binding protein 2 (MeCP2) are associated with multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD), which are inflammatory, autoimmune, and demyelinating disorders of the central nervous system (CNS). However, the mechanisms and pathways regulated by MeCP2 in immune activation in favor of MS and NMOSD are not fully understood. We summarize findings that use the binding properties of MeCP2 to identify its targets, particularly the genes recognized by MeCP2 and associated with several neurological disorders. MeCP2 regulates gene expression in neurons, immune cells and during development by modulating various mechanisms and pathways. Dysregulation of the MeCP2 signaling pathway has been associated with several disorders, including neurological and autoimmune diseases. A thorough understanding of the molecular mechanisms underlying MeCP2 function can provide new therapeutic strategies for these conditions. The nervous system is the primary system affected in MeCP2-associated disorders, and other systems may also contribute to MeCP2 action through its target genes. MeCP2 signaling pathways provide promise as potential therapeutic targets in progressive MS and NMOSD. MeCP2 not only increases susceptibility and induces anti-inflammatory responses in immune sites but also leads to a chronic increase in pro-inflammatory cytokines gene expression (IFN-γ, TNF-α, and IL-1β) and downregulates the genes involved in immune regulation (IL-10, FoxP3, and CX3CR1). MeCP2 may modulate similar mechanisms in different pathologies and suggest that treatments for MS and NMOSD disorders may be effective in treating related disorders. MeCP2 regulates gene expression in MS and NMOSD. However, dysregulation of the MeCP2 signaling pathway is implicated in these disorders. MeCP2 plays a role as a therapeutic target for MS and NMOSD and provides pathways and mechanisms that are modulated by MeCP2 in the regulation of gene expression.

Carnosine Counteracts the Molecular Alterations Aβ Oligomers-Induced in Human Retinal Pigment Epithelial Cells

Age-related macular degeneration (AMD) has been described as a progressive eye disease characterized by irreversible impairment of central vision, and unfortunately, an effective treatment is still not available. It is well-known that amyloid-beta (Aβ) peptide is one of the major culprits in causing neurodegeneration in Alzheimer's disease (AD). The extracellular accumulation of this peptide has also been found in drusen which lies under the retinal pigment epithelium (RPE) and represents one of the early signs of AMD pathology. Aβ aggregates, especially in the form of oligomers, are able to induce pro-oxidant (oxidative stress) and pro-inflammatory phenomena in RPE cells. ARPE-19 is a spontaneously arising human RPE cell line validated for drug discovery processes in AMD. In the present study, we employed ARPE-19 treated with Aβ oligomers, representing an in vitro model of AMD. We used a combination of methods, including ATPlite, quantitative real-time PCR, immunocytochemistry, as well as a fluorescent probe for reactive oxygen species to investigate the molecular alterations induced by Aβ oligomers. In particular, we found that Aβ exposure decreased the cell viability of ARPE-19 cells which was paralleled by increased inflammation (increased expression of pro-inflammatory mediators) and oxidative stress (increased expression of NADPH oxidase and ROS production) along with the destruction of ZO-1 tight junction protein. Once the damage was clarified, we investigated the therapeutic potential of carnosine, an endogenous dipeptide that is known to be reduced in AMD patients. Our findings demonstrate that carnosine was able to counteract most of the molecular alterations induced by the challenge of ARPE-19 with Aβ oligomers. These new findings obtained with ARPE-19 cells challenged with Aβ1-42 oligomers, along with the well-demonstrated multimodal mechanism of action of carnosine both in vitro and in vivo, able to prevent and/or counteract the dysfunctions elicited by Aβ oligomers, substantiate the neuroprotective potential of this dipeptide in the context of AMD pathology.

Astrocytes in Chronic Pain: Cellular and Molecular Mechanisms

Chronic pain is challenging to treat due to the limited therapeutic options and adverse side-effects of therapies. Astrocytes are the most abundant glial cells in the central nervous system and play important roles in different pathological conditions, including chronic pain. Astrocytes regulate nociceptive synaptic transmission and network function via neuron–glia and glia–glia interactions to exaggerate pain signals under chronic pain conditions. It is also becoming clear that astrocytes play active roles in brain regions important for the emotional and memory-related aspects of chronic pain. Therefore, this review presents our current understanding of the roles of astrocytes in chronic pain, how they regulate nociceptive responses, and their cellular and molecular mechanisms of action.

Association of the p75NTR Ser205Leu Polymorphism with Asymptomatic HTLV-1 Infection

Genetic variations in components of the immune response seem to be an important factor that contributes to the manifestation of symptoms of some diseases related to HTLV-1 infection. Nerve growth factor (NGF) and the p75 neurotrophin receptor (p75NTR) are related to the maintenance of neurons and the activation of the immune response. In this study, we evaluated the association of the NGF -198C/T, NGF Ala35Val, and p75NTR Ser205Leu polymorphisms with HTLV-1 infection and plasma cytokine levels in 166 samples from individuals infected with HTLV-1 (59 symptomatic and 107 asymptomatic). The genotyping and quantification of the proviral load were performed by real-time PCR, and cytokine levels were measured by ELISA. The NGF -198C/T and NGF Ala35Val polymorphisms were not associated with HTLV-1 infection. The frequency of the Ser/Leu genotype of p75NTR Ser205Leu was more frequent in the control group (p = 0.0385), and the Ser/Leu genotype and allele Leu were more frequent among the asymptomatic (p < 0.05), especially with respect to the HTLV-1-associated myelopathy (HAM) group (p < 0.05). The symptomatic showed a higher proviral load and higher TNF-α and IL-10 levels (p < 0.05). Asymptomatic carriers of the Ser/Leu genotype (p = 0.0797) had lower levels of proviral load and higher levels of TNF-α (p = 0.0507). Based on the results obtained, we conclude that the p75NTR Ser205Leu polymorphism may be associated with reduced susceptibility to HTLV-1 infection, a lower risk of developing symptoms, including HAM, and better infection control.

Role of Liver Growth Factor (LGF) in Parkinson's Disease: Molecular Insights and Therapeutic Opportunities

Parkinson's disease is the most common neurodegenerative movement disorder with unclear etiology and only symptomatic treatment to date. Toward the development of novel disease-modifying agents, neurotrophic factors represent a reasonable and promising therapeutic approach. However, despite the robust preclinical evidence, clinical trials using glial-derived neurotrophic factor (GDNF) and neurturin have been unsuccessful. In this direction, the therapeutic potential of other trophic factors in PD and the elucidation of the underlying molecular mechanisms are of paramount importance. The liver growth factor (LGF) is an albumin-bilirubin complex acting as a hepatic mitogen, which also exerts regenerative effects on several extrahepatic tissues including the brain. Accumulating evidence suggests that intracerebral and peripheral administration of LGF can enhance the outgrowth of nigrostriatal dopaminergic axonal terminals; promote the survival, migration, and differentiation of neuronal stem cells; and partially protect against dopaminergic neuronal loss in the substantia nigra of PD animal models. In most studies, these effects are accompanied by improved motor behavior of the animals. Potential underlying mechanisms involve transient microglial activation, TNF-α upregulation, and activation of the extracellular signal-regulated kinases 1/2 (ERK1/2) and of the transcription factor cyclic AMP response-element binding protein (CREB), along with anti-inflammatory and antioxidant pathways. Herein, we summarize recent preclinical evidence on the potential role of LGF in PD pathogenesis, aiming to shed more light on the underlying molecular mechanisms and reveal novel therapeutic opportunities for this debilitating disease.

Reactive Astrocytes: Critical Players in the Development of Chronic Pain

Chronic pain is associated with long term plasticity of nociceptive pathways in the central nervous system. Astrocytes can profoundly affect synaptic function and increasing evidence has highlighted how altered astrocyte activity may contribute to the pathogenesis of chronic pain. In response to injury, astrocytes undergo a shift in form and function known as reactive astrogliosis, which affects their release of cytokines and gliotransmitters. These neuromodulatory substances have been implicated in driving the persistent changes in central nociceptive activity. Astrocytes also release lactate which neurons can use to produce energy during synaptic plasticity. Furthermore, recent research has provided insight into lactate's emerging role as a signaling molecule in the central nervous system, which may be involved in directly modulating neuronal and astrocytic activity. In this review, we present evidence for the involvement of astrocyte-derived tumor necrosis factor alpha in pain-associated plasticity, in addition to research suggesting the potential involvement of gliotransmitters D-serine and adenosine-5'-triphosphate. We also discuss work implicating astrocyte-neuron metabolic coupling, and the possible role of lactate, which has been sparsely studied in the context of chronic pain, in supporting pathological changes in central nociceptive activity.

Ablation of interleukin-19 improves motor function in a mouse model of amyotrophic lateral sclerosis

Neuroinflammation by activated microglia and astrocytes plays a critical role in progression of amyotrophic lateral sclerosis (ALS). Interleukin-19 (IL-19) is a negative-feedback regulator that limits pro-inflammatory responses of microglia in an autocrine and paracrine manner, but it remains unclear how IL-19 contributes to ALS pathogenesis. We investigated the role of IL-19 in ALS using transgenic mice carrying human superoxide dismutase 1 with the G93A mutation (SOD1G93A Tg mice). We generated IL-19-deficient SOD1G93A Tg (IL-19-/-/SOD1G93A Tg) mice by crossing SOD1G93A Tg mice with IL-19-/- mice, and then evaluated disease progression, motor function, survival rate, and pathological and biochemical alternations in the resultant mice. In addition, we assessed the effect of IL-19 on glial cells using primary microglia and astrocyte cultures from the embryonic brains of SOD1G93A Tg mice and IL-19-/-/SOD1G93A Tg mice. Expression of IL-19 in primary microglia and lumbar spinal cord was higher in SOD1G93A Tg mice than in wild-type mice. Unexpectedly, IL-19-/-/SOD1G93A Tg mice exhibited significant improvement of motor function. Ablation of IL-19 in SOD1G93A Tg mice increased expression of both neurotoxic and neuroprotective factors, including tumor necrosis factor-α (TNF-α), IL-1β, glial cell line-derived neurotrophic factor (GDNF), and transforming growth factor β1, in lumbar spinal cord. Primary microglia and astrocytes from IL-19-/-/SOD1G93A Tg mice expressed higher levels of TNF-α, resulting in release of GDNF from astrocytes. Inhibition of IL-19 signaling may alleviate ALS symptoms.

Therapeutic Effects of hiPSC-Derived Glial and Neuronal Progenitor Cells-Conditioned Medium in Experimental Ischemic Stroke in Rats

Transplantation of various types of stem cells as a possible therapy for stroke has been tested for years, and the results are promising. Recent investigations have shown that the administration of the conditioned media obtained after stem cell cultivation can also be effective in the therapy of the central nervous system pathology (hypothesis of their paracrine action). The aim of this study was to evaluate the therapeutic effects of the conditioned medium of hiPSC-derived glial and neuronal progenitor cells in the rat middle cerebral artery occlusion model of the ischemic stroke. Secretory activity of the cultured neuronal and glial progenitor cells was evaluated by proteomic and immunosorbent-based approaches. Therapeutic effects were assessed by overall survival, neurologic deficit and infarct volume dynamics, as well as by the end-point values of the apoptosis- and inflammation-related gene expression levels, the extent of microglia/macrophage infiltration and the numbers of formed blood vessels in the affected area of the brain. As a result, 31% of the protein species discovered in glial progenitor cells-conditioned medium and 45% in neuronal progenitor cells-conditioned medium were cell type specific. The glial progenitor cell-conditioned media showed a higher content of neurotrophins (BDNF, GDNF, CNTF and NGF). We showed that intra-arterial administration of glial progenitor cells-conditioned medium promoted a faster decrease in neurological deficit compared to the control group, reduced microglia/macrophage infiltration, reduced expression of pro-apoptotic gene Bax and pro-inflammatory cytokine gene Tnf, increased expression of anti-inflammatory cytokine genes (Il4, Il10, Il13) and promoted the formation of blood vessels within the damaged area. None of these effects were exerted by the neuronal progenitor cell-conditioned media. The results indicate pronounced cytoprotective, anti-inflammatory and angiogenic properties of soluble factors secreted by glial progenitor cells.

Glial Cell Line-Derived Neurotrophic Factor and Focal Ischemic Stroke

Focal ischemic stroke (FIS) is a leading cause of human debilitation and death. Following the onset of a FIS, the brain experiences a series of spatiotemporal changes which are exemplified in different pathological processes. One prominent feature of FIS is the development of reactive astrogliosis and glial scar formation in the peri-infarct region (PIR). During the subacute phase, astrocytes in PIR are activated, referred to as reactive astrocytes (RAs), exhibit changes in morphology (hypotrophy), show an increased proliferation capacity, and altered gene expression profile, a phenomenon known as reactive astrogliosis. Subsequently, the morphology of RAs remains stable, and proliferation starts to decline together with the formation of glial scars. Reactive astrogliosis and glial scar formation eventually cause substantial tissue remodeling and changes in permanent structure around the PIR. Glial cell line-derived neurotrophic factor (GDNF) was originally isolated from a rat glioma cell-line and regarded as a potent survival neurotrophic factor. Under normal conditions, GDNF is expressed in neurons but is upregulated in RAs after FIS. This review briefly describes properties of GDNF, its receptor-mediated signaling pathways, as well as recent studies regarding the role of RAs-derived GDNF in neuronal protection and brain recovery. These results provide evidence suggesting an important role of RA-derived GDNF in intrinsic brain repair and recovery after FIS, and thus targeting GDNF in RAs may be effective for stroke therapy.

TNF-α inhibits GDNF levels in Sertoli cells, through a NF-κB-dependent, HES1-dependent mechanism

BACKGROUND

Glial cell line-derived neurotrophic factor (GDNF) is a soluble molecule crucial for the regulation of the spermatogonial stem cells (SSC) of the testis. The effects of GDNF on target cells have been extensively described, but mechanisms underlying GDNF regulation are currently under investigation. In the nervous system, GDNF expression is regulated by pro-inflammatory cytokines including lipopolysaccharide (LPS), interleukin 1 beta (IL-1β), and tumor necrosis factor alpha (TNF-α) but the effect of these cytokines on GDNF expression in the testis is unclear.

OBJECTIVES

The aim of the present study was to investigate the impact of TNF-α on GDNF expression levels using primary murine Sertoli cells as experimental model.

MATERIAL AND METHODS

The expression of TNF-α-regulated genes including Gdnf in different culture conditions was determined by real-time PCR. GDNF protein levels were determined by ELISA. The activation of the NF-κb pathway and HES1 levels were assessed by Western Blot analysis and immunofluorescence. HES1 expression was downregulated by RNAi.

RESULTS

In primary Sertoli cells, TNF-α downregulates GDNF levels through a nuclear factor-κB (NF-κB)-dependent mechanism. Mechanistically, TNF-α induces the transcriptional repressor HES1 by a NF-Κb-dependent mechanism, which in turn downregulates GDNF.

DISCUSSION

Under physiological conditions, TNF-α is secreted by germ cells suggesting that this cytokine plays a role in the paracrine control of SSC niche by modulating GDNF levels. HES1, a well-known target of the Notch pathway, is implicated in the regulation of GDNF expression. In Sertoli cells, TNF-α and Notch signaling may converge at molecular level, to regulate the expression of HES1 and HES1- target genes, including GDNF.

CONCLUSIONS

Because of the importance of GDNF for spermatogonial stem cell self-renewal and proliferation, this data may give important insights on how cytokine signals in the testis modulate the expression of niche-derived factors.

The Effect of Endurance Training on Brain-Derived Neurotrophic Factor and Inflammatory Markers in Healthy People and Parkinson's Disease. A Narrative Review

Background: One purpose of the training conducted by people is to lose bodyweight and improve their physical condition. It is well-known that endurance training provides many positive changes in the body, not only those associated with current beauty standards. It also promotes biochemical changes such as a decreased inflammatory status, memory improvements through increased brain-derived neurotrophic factor levels, and reduced stress hormone levels. The positive effects of training may provide a novel solution for people with Parkinson's disease, as a way to reduce the inflammatory status and decrease neurodegeneration through stimulation of neuroplasticity and improved motor conditions. Aim: This narrative review aims to focus on the relationship between an acute bout of endurance exercise, endurance training (continuous and interval), brain-derived neurotrophic factor and inflammatory status in the three subject groups (young adults, older adult, and patients with Parkinson's disease), and to review the current state of knowledge about the possible causes of the differences in brain-derived neurotrophic factor and inflammatory status response to a bout of endurance exercise and endurance training. Furthermore, short practical recommendations for PD patients were formulated for improving the efficacy of the training process during rehabilitation. Methods: A narrative review was performed following an electronic search of the database PubMed/Medline and Web of Science for English-language articles between January 2010 and January 2020. Results: Analysis of the available publications with partial results revealed (1) a possible connection between the brain-derived neurotrophic factor level and inflammatory status, and (2) a more beneficial influence of endurance training compared with acute bouts of endurance exercise. Conclusion: Despite the lack of direct evidence, the results from studies show that endurance training may have a positive effect on inflammatory status and brain-derived neurotrophic factor levels. Introducing endurance training as part of the rehabilitation in Parkinson's disease might provide benefits for patients in addition to pharmacological therapy supplementation.

The delicate balance between neurotoxicity and neuroprotection in the context of HIV-1 infection

Human immunodeficiency virus type-1 (HIV-1) causes a spectrum of neurological impairments, termed HIV-associated neurocognitive disorder (HAND), following the infiltration of infected cells into the brain. Even though the implementation of antiretroviral therapy reduced the systemic viral load, the prevalence of HAND remains unchanged and infected patients develop persisting neurological disturbances affecting their quality of life. As a result, HAND have gained importance in basic and clinical researches, warranting the need of developing new adjunctive treatments. Nonetheless, a better understanding of the molecular and cellular mechanisms remains necessary. Several studies consolidated their efforts into elucidating the neurotoxic signaling leading to HAND including the deleterious actions of HIV-1 viral proteins and inflammatory mediators. However, the scope of these studies is not sufficient to address all the complexity related to HAND development. Fewer studies focused on an altered neuroprotective capacity of the brain to respond to HIV-1 infection. Neurotrophic factors are endogenous polyproteins involved in neuronal survival, synaptic plasticity, and neurogenesis. Any defects in the processing or production of these crucial factors might compose a risk factor rendering the brain more vulnerable to neuronal damages. Due to their essential roles, they have been investigated for their diverse interplays with HIV-1 infection. In this review, we present a complete description of the neurotrophic factors involved in HAND. We discuss emerging concepts for their therapeutic applications and summarize the complex mechanisms that down-regulate their production in favor of a neurotoxic environment. For certain factors, we finally address opposing roles that rather lead to increased inflammation.

Neurovascular Unit as a Source of Ischemic Stroke Biomarkers-Limitations of Experimental Studies and Perspectives for Clinical Application

Cerebral stroke, which is one of the most frequent causes of mortality and leading cause of disability in developed countries, often leads to devastating and irreversible brain damage. Neurological and neuroradiological diagnosis of stroke, especially in its acute phase, is frequently uncertain or inconclusive. This results in difficulties in identification of patients with poor prognosis or being at high risk for complications. It also makes difficult identification of these stroke patients who could benefit from more aggressive therapies. In contrary to the cardiovascular disease, no single biomarker is available for the ischemic stroke, addressing the abovementioned issues. This justifies the need for identifying of effective diagnostic measures characterized by high specificity and sensitivity. One of the promising avenues in this area is studies on the panels of biomarkers characteristic for processes which occur in different types and phases of ischemic stroke and represent all morphological constituents of the brains' neurovascular unit (NVU). In this review, we present the current state of knowledge concerning already-used or potentially applicable biomarkers of the ischemic stroke. We also discuss the perspectives for identification of biomarkers representative for different types and phases of the ischemic stroke, as well as for different constituents of NVU, which concentration levels correlate with extent of brain damage and patients' neurological status. Finally, a critical analysis of perspectives on further improvement of the ischemic stroke diagnosis is presented.

Neuroimmune System as a Driving Force for Plasticity Following CNS Injury

Following an injury to the central nervous system (CNS), spontaneous plasticity is observed throughout the neuraxis and affects multiple key circuits. Much of this spontaneous plasticity can elicit beneficial and deleterious functional outcomes, depending on the context of plasticity and circuit affected. Injury-induced activation of the neuroimmune system has been proposed to be a major factor in driving this plasticity, as neuroimmune and inflammatory factors have been shown to influence cellular, synaptic, structural, and anatomical plasticity. Here, we will review the mechanisms through which the neuroimmune system mediates plasticity after CNS injury. Understanding the role of specific neuroimmune factors in driving adaptive and maladaptive plasticity may offer valuable therapeutic insight into how to promote adaptive plasticity and/or diminish maladaptive plasticity, respectively.

Liver Growth Factor Induces Glia-Associated Neuroprotection in an In Vitro Model of Parkinson´s Disease

Parkinson's disease is a neurodegenerative disorder characterized by the progressive death of dopaminergic (DA) neurons in the substantia nigra (SN), which leads to a loss of the neurotransmitter dopamine in the basal ganglia. Current treatments relieve the symptoms of the disease, but none stop or delay neuronal degeneration. Liver growth factor (LGF) is an albumin-bilirubin complex that stimulates axonal growth in the striatum and protects DA neurons in the SN of 6-hydroxydopamine-lesioned rats. Our previous results suggested that these effects observed in vivo are mediated by microglia and/or astrocytes. To determine if these cells are LGF targets, E14 (embryos from Sprague Dawley rats of 14 days) rat mesencephalic glial cultures were used. Treatment with 100 pg/mL of LGF up-regulated the mitogen-activated protein kinases (MAPKs) extracellular signal-regulated kinases 1/2 (ERK1/2) and the cyclic AMP response element binding protein (CREB) phosphorylation in glial cultures, and it increased the microglia marker Iba1 and tumor necrosis factor alpha (TNF-alpha) protein levels. The treatment of E14 midbrain neurons with a glial-conditioned medium from LGF-treated glial cultures (GCM-LGF) prevented the loss of DA neurons caused by 6-hydroxy-dopamine. This neuroprotective effect was not observed when GCM-LGF was applied in the presence of a blocking antibody of TNF-alpha activity. Altogether, our findings strongly suggest the involvement of microglia and TNF-alpha in the neuroprotective action of LGF on DA neurons observed in vitro.

The role of prebiotics in cognition, anxiety, and depression

The disruption of the gut microbial composition, defined as dysbiosis, has been associated with many neurological disorders with inflammatory components. The alteration of the gut microbiota leads to an increase in pro-inflammatory cytokines that are associated with metabolic diseases (such as obesity and type 2 diabetes), autoimmune arthritis, and neuropsychiatric diseases. Prebiotics are defined as non-digestible carbohydrates and promote the growth of beneficial bacteria such as bifidobacteria and lactobacillus, exert beneficial effects on improving dysbiosis and its associated inflammatory state. Preclinical and clinical data indicated that some prebiotics also have positive impacts on the central nervous system (CNS) due to the modulation of neuroinflammation and thus may have a key role in the modulation of cognitive impairment, anxiety, and depression. The present manuscript reviews the state-of-art of the effects of prebiotics in cognitive impairment, anxiety, and depressive disorders. Data from clinical studies are still scarce, and further clinical trials are needed to corroborate the potential therapeutic cognitive, antidepressant, and anxiolytic of prebiotics. Prebiotics may provide patients suffering from cognitive deficits, depression, and anxiety with a new tool to minimize disease symptoms and increase the quality of life.

TNFR2 limits proinflammatory astrocyte functions during EAE induced by pathogenic DR2b-restricted T cells

Multiple sclerosis (MS) is an autoimmune neuroinflammatory disease where the underlying mechanisms driving disease progression have remained unresolved. HLA-DR2b (DRB1*15:01) is the most common genetic risk factor for MS. Additionally, TNF and its receptors TNFR1 and TNFR2 play key roles in MS and its preclinical animal model, experimental autoimmune encephalomyelitis (EAE). TNFR2 is believed to ameliorate CNS pathology by promoting remyelination and Treg function. Here, we show that transgenic mice expressing the human MHC class II (MHC-II) allele HLA-DR2b and lacking mouse MHC-II and TNFR2 molecules, herein called DR2bΔR2, developed progressive EAE, while disease was not progressive in DR2b littermates. Mechanistically, expression of the HLA-DR2b favored Th17 cell development, whereas T cell-independent TNFR2 expression was critical for restraining of an astrogliosis-induced proinflammatory milieu and Th17 cell responses, while promoting remyelination. Our data suggest the TNFR2 signaling pathway as a potentially novel mechanism for curtailing astrogliosis and promoting remyelination, thus providing new insights into mechanisms limiting progressive MS.

Impaired metabolism of kynurenine and its metabolites in CSF of parkinson's disease

AIM

The kynurenine (KYN) pathway plays an important role in degrading molecules responsible for oxidative stress in the central nervous system (CNS), but can also have neurotoxic effects. Both 3-hydroxykynurenine (3-HK) and quinolinic acid are neurotoxic metabolites produced from this pathway. In Parkinson's disease (PD), oxidative stress is suspected to represent a key pathogenic mechanism. This study aimed to investigate the function of the KYN pathway and interactions between oxidative stress and neuroinflammation in PD.

METHODS

Participants comprised 20 patients with PD and 13 controls. Cerebrospinal fluid (CSF) levels of KYN and 3-HK were measured using high-performance liquid chromatography coupled with an electrochemical detector. CSF levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and interferon (IFN)-γ were measured with an enzyme-linked immunosorbent assay, and results were statistically compared between PD patients and controls.

RESULTS

Median CSF levels of KYN and 3-HK were 49.0 nM and 4.25 nM in PD and 30.5 nM and 1.55 nM in controls, respectively, showing significantly higher levels in PD (p < 0.05). CSF levels of measured cytokines showed that TNF-α and IL-1β were significantly higher in PD patients than in controls. No positive correlation between 3-HK and TNF-α was seen in PD.

CONCLUSION

Dysfunction of the KYN pathway may induce oxidative stress in the CNS in PD, and may also induce cytokine-mediated neuroinflammation. Functional amelioration of the KYN pathway may facilitate modification of neurodegenerative processes in PD.

Investigation of Neuregulin-1 and Glial Cell-Derived Neurotrophic Factor in Rodent Astrocytes and Microglia

Growth factors play a crucial role during de- and remyelination of the central nervous system (CNS) due to their neurotrophic functions. We have previously shown that the growth factors neuregulin-1 (Nrg-1) and glial cell-derived neurotrophic factor (Gdnf) are upregulated during the first 2 weeks after induction of toxic demyelination in the CNS. Nevertheless, the factors responsible for Nrg-1/Gdnf upregulation and their effects on glia cells are unknown. We investigated the effect on Nrg-1 and Gdnf expressions after stimulation of primary mouse microglia or astrocytes with various pro- and anti-inflammatory factors. Additionally, primary cells were incubated with NRG-1 and/or GDNF followed by determining the gene expression level of their receptors, chemokines, and other growth factors. We demonstrate that inflammatory stimuli have a distinct impact on the expression of Gdnf, Nrg-1, and their receptors in astrocytes and microglia. In microglia, LPS or simultaneous treatment with IFNγ plus TNFα led to downregulation of Nrg-1, whereas LPS treatment slightly increased Nrg-1 expression in astrocytes. Furthermore, Gdnf was slightly upregulated after TFG-β treatment in microglia, while Gdnf was significantly upregulated after LPS treatment in astrocytes. In contrast, treatment with GDNF or/and NRG-1 did not alter any measured gene expression in microglia or astrocytes. Taken together, our in vitro studies show that Nrg-1, Gdnf, and their receptors are differently regulated in astrocytes and microglia upon inflammatory stimuli. The lack of response of astrocytes and microglia to NRG-1 and GDNF suggests that both factors exert their effects directly on neurons.

The detrimental effects of lipopolysaccharide-induced neuroinflammation on adult hippocampal neurogenesis depend on the duration of the pro-inflammatory response

Adult hippocampal neurogenesis is a finely tuned process regulated by extrinsic factors. Neuroinflammation is a hallmark of several pathological conditions underlying dysregulation of neurogenesis. In animal models, lipopolysaccharide (LPS)-induced neuroinflammation leads to a neurogenic decrease mainly associated to the early inflammatory response. However, it is not well understood how the neuroinflammatory response progresses over time and if neurogenesis continues to be diminished during the late neuroinflammatory response. Moreover, it is unknown if repeated intermittent administration of LPS along time induces a greater reduction in neurogenesis. We administered one single intraperitoneal injection of LPS or saline or four repeated injections (one per week) of LPS or saline to young-adult mice. A cohort of new cells was labeled with three 5-bromo-2-deoxyuridine injections (one per day) 4 days after the last LPS injection. We evaluated systemic and neuroinflammation-associated parameters and compared the effects of the late neuroinflammatory response on neurogenesis induced by each protocol. Our results show that 1) a single LPS injection leads to a late pro-inflammatory response characterized by microglial activation, moderate astrocytic reaction and increased interleukin-6 levels. This response correlates in time with decreased neurogenesis and 2) a repeated intermittent injection of LPS does not elicit a late pro-inflammatory response although activated microglia persists. The latter profile is not accompanied by a continued long-term hippocampal neurogenic decrease. Hereby, we provide evidence that the neuroinflammatory response is a dynamic process that progresses in a milieu-dependent manner and does not necessarily lead to a neurogenic decrease, highlighting the complex interaction between the immune system and neurogenesis.

Soluble TNFα Signaling within the Spinal Cord Contributes to the Development of Autonomic Dysreflexia and Ensuing Vascular and Immune Dysfunction after Spinal Cord Injury

Cardiovascular disease and susceptibility to infection are leading causes of morbidity and mortality for individuals with spinal cord injury (SCI). A major contributor to these is autonomic dysreflexia (AD), an amplified reaction of the autonomic nervous system (hallmarked by severe hypertension) in response to sensory stimuli below the injury. Maladaptive plasticity of the spinal sympathetic reflex circuit below the SCI results in AD intensification over time. Mechanisms underlying this maladaptive plasticity are poorly understood, restricting the identification of treatments. Thus, no preventative treatments are currently available. Neuroinflammation has been implicated in other pathologies associated with hyperexcitable neural circuits. Specifically, the soluble form of TNFα (sTNFα) is known to play a role in neuroplasticity. We hypothesize that persistent expression of sTNFα in spinal cord underlies AD exacerbation. To test this, we intrathecally administered XPro1595, a biologic that renders sTNFα nonfunctional, after complete, high-level SCI in female rats. This dramatically attenuated the intensification of colorectal distension-induced and naturally occurring AD events. This improvement is mediated via decreased sprouting of nociceptive primary afferents and activation of the spinal sympathetic reflex circuit. We also examined peripheral vascular function using ex vivo pressurized arterial preparations and immune function via flow cytometric analysis of splenocytes. Diminishing AD via pharmacological inhibition of sTNFα mitigated ensuing vascular hypersensitivity and immune dysfunction. This is the first demonstration that neuroinflammation-induced sTNFα is critical for altering the spinal sympathetic reflex circuit, elucidating a novel mechanism for AD. Importantly, we identify the first potential pharmacological, prophylactic treatment for this life-threatening syndrome.SIGNIFICANCE STATEMENT Autonomic dysreflexia (AD), a disorder that develops after spinal cord injury (SCI) and is hallmarked by sudden, extreme hypertension, contributes to cardiovascular disease and susceptibility to infection, respectively, two leading causes of mortality and morbidity in SCI patients. We demonstrate that neuroinflammation-induced expression of soluble TNFα plays a critical role in AD, elucidating a novel underlying mechanism. We found that intrathecal administration after SCI of a biologic that inhibits soluble TNFα signaling dramatically attenuates AD and significantly reduces AD-associated peripheral vascular and immune dysfunction. We identified mechanisms behind diminished plasticity of neuronal populations within the spinal sympathetic reflex circuit. This study is the first to pinpoint a potential pharmacological, prophylactic strategy to attenuate AD and ensuing cardiovascular and immune dysfunction.

Increased Hypothalamic Levels of Endozepines, Endogenous Ligands of Benzodiazepine Receptors, in a Rat Model of Sepsis

BACKGROUND

The mechanisms involved in septic anorexia are mainly related to the secretion of inflammatory cytokines. The term endozepines designates a family of neuropeptides, including the octadecaneuropeptide (ODN), originally isolated as endogenous ligands of benzodiazepine receptors. Previous data showed that ODN, produced and released by astrocytes, is a potent anorexigenic peptide. We have studied the effect of sepsis by means of a model of cecal ligation and puncture (CLP) on the hypothalamic expression of endozepines (DBI mRNA and protein levels), as well as on the level of neuropeptides controlling energy homeostasis mRNAs: pro-opiomelanocortin, neuropeptide Y, and corticotropin-releasing hormone. In addition, we have investigated the effects of two inflammatory cytokines, TNF-α and IL-1β, on DBI mRNA levels in cultured rat astrocytes.

METHODS

Studies were performed on Sprague-Dawley male rats and on cultures of rat cortical astrocytes. Sepsis was induced using the CLP method. Sham-operated control animals underwent the same procedure, but the cecum was neither ligated nor incised.

RESULTS

Sepsis caused by CLP evoked an increase of DBI mRNA levels in ependymal cells bordering the third ventricle and in tanycytes of the median eminence. CLP-induced sepsis was also associated with stimulated ODN-like immunoreactivity (ODN-LI) in the hypothalamus. In addition, TNF-α, but not IL-1β, induced a dose-dependent increase in DBI mRNA in cultured rat astrocytes. An increase in the mRNA encoding the precursor of the anorexigenic peptide α-melanocyte stimulating hormone, the pro-opiomelanocortin, and the corticotropin-releasing hormone was observed in the hypothalamus.

CONCLUSION

These results suggest that during sepsis, hypothalamic mRNA encoding endozepines, anorexigenic peptide as well as stress hormone could play a role in the anorexia/cachexia associated with inflammation due to sepsis and we suggest that this hypothalamic mRNA expression could involve TNF-α.

Neuroimmune and Inflammatory Signals in Complex Disorders of the Central Nervous System

An extensive microglial-astrocyte-monocyte-neuronal cross talk seems to be crucial for normal brain function, development, and recovery. However, under certain conditions neuroinflammatory interactions between brain cells and neuroimmune cells influence disease outcome and brain pathology. Microglial cells express a range of functional states with dynamically pleomorphic profiles from a surveilling status of synaptic transmission to an active player in major events of development such as synaptic elimination, regeneration, and repair. Also, inflammation mediates a series of neurotoxic roles in neuropsychiatric conditions and neurodegenerative diseases. The present review discusses data on the involvement of neuroinflammatory conditions that alter neuroimmune interactions in four different pathologies. In the first section of this review, we discuss the ability of the early developing brain to respond to a focal lesion with a rapid compensatory plasticity of intact axons and the role of microglial activation and proinflammatory cytokines in brain repair. In the second section, we present data of neuroinflammation and neurodegenerative disorders and discuss the role of reactive astrocytes in motor neuron toxicity and the progression of amyotrophic lateral sclerosis. In the third section, we discuss major depressive disorders as the consequence of dysfunctional interactions between neural and immune signals that result in increased peripheral immune responses and increase proinflammatory cytokines. In the last section, we discuss autism spectrum disorders and altered brain circuitries that emerge from abnormal long-term responses of innate inflammatory cytokines and microglial phenotypic dysfunctions.

Inflammatory Activation of Microglia and Astrocytes in Manganese Neurotoxicity

Neurotoxicity due to excessive exposure to manganese (Mn) has been described as early as 1837 (Couper, Br Ann Med Pharm Vital Stat Gen Sci 1:41-42, 1837). Extensive research over the past two decades has revealed that Mn-induced neurological injury involves complex pathophysiological signaling mechanisms between neurons and glial cells. Glial cells are an important target of Mn in the brain, both for sequestration of the metal, as well as for activating inflammatory signaling pathways that damage neurons through overproduction of numerous reactive oxygen and nitrogen species and inflammatory cytokines. Understanding how these pathways are regulated in glial cells during Mn exposure is critical to determining the mechanisms underlying permanent neurological dysfunction stemming from excess exposure. The subject of this review will be to delineate mechanisms by which Mn interacts with glial cells to perturb neuronal function, with a particular emphasis on neuroinflammation and neuroinflammatory signaling between distinct populations of glial cells.

A Neuroprotective Effect of the Glutamate Receptor Antagonist MK801 on Long-Term Cognitive and Behavioral Outcomes Secondary to Experimental Cerebral Malaria

Cerebral malaria (CM) is a life-threatening complication of Plasmodium falciparum infection, which can result in long-term cognitive and behavioral deficits despite successful anti-malarial therapy. Due to the substantial social and economic burden of CM, the development of adjuvant therapies is a scientific goal of highest priority. Apart from vascular and immune responses, changes in glutamate system have been reported in CM pathogenesis suggesting a potential therapeutic target. Based on that, we hypothesized that interventions in the glutamatergic system induced by blockage of N-methyl-D-aspartate (NMDA) receptors could attenuate experimental CM long-term cognitive and behavioral outcomes. Before the development of evident CM signs, susceptible mice infected with Plasmodium berghei ANKA (PbA) strain were initiated on treatment with dizocilpine maleate (MK801, 0.5 mg/kg), a noncompetitive NMDA receptor antagonist. On day 5 post-infection, mice were treated orally with a 10-day course chloroquine (CQ, 30 mg/kg). Control mice also received saline, CQ or MK801 + CQ therapy. After 10 days of cessation of CQ treatment, magnetic resonance images (MRI), behavioral and immunological assays were performed. Indeed, MK801 combined with CQ prevented long-term memory impairment and depressive-like behavior following successful PbA infection resolution. In addition, MK801 also modulated the immune system by promoting a balance of TH1/TH2 response and upregulating neurotrophic factors levels in the frontal cortex and hippocampus. Moreover, hippocampus abnormalities observed by MRI were partially prevented by MK801 treatment. Our results indicate that NMDA receptor antagonists can be neuroprotective in CM and could be a valuable adjuvant strategy for the management of the long-term impairment observed in CM.

Pharmacologic antagonism of dopamine receptor D3 attenuates neurodegeneration and motor impairment in a mouse model of Parkinson's disease

Neuroinflammation involves the activation of glial cells, which is associated to the progression of neurodegeneration in Parkinson's disease. Recently, we and other researchers demonstrated that dopamine receptor D3 (D3R)-deficient mice are completely refractory to neuroinflammation and consequent neurodegeneration associated to the acute intoxication with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In this study we examined the therapeutic potential and underlying mechanism of a D3R-selective antagonist, PG01037, in mice intoxicated with a chronic regime of administration of MPTP and probenecid (MPTPp). Biodistribution analysis indicated that intraperitoneally administered PG01037 crosses the blood-brain barrier and reaches the highest concentration in the brain 40 min after the injection. Furthermore, the drug was preferentially distributed to the brain in comparison to the plasma. Treatment of MPTPp-intoxicated mice with PG01037 (30 mg/kg, administrated twice a week for five weeks) attenuated the loss of dopaminergic neurons in the substantia nigra pars compacta, as evaluated by stereological analysis, and the loss of striatal dopaminergic terminals, as determined by densitometric analyses of tyrosine hydroxylase and dopamine transporter immunoreactivities. Accordingly, the treatment resulted in significant improvement of motor performance of injured animals. Interestingly, the therapeutic dose of PG01037 exacerbated astrogliosis and resulted in increased ramification density of microglial cells in the striatum of MPTPp-intoxicated mice. Further analyses suggested that D3R expressed in astrocytes favours a beneficial astrogliosis with anti-inflammatory consequences on microglia. Our findings indicate that D3R-antagonism exerts a therapeutic effect in parkinsonian animals by reducing the loss of dopaminergic neurons in the nigrostriatal pathway, alleviating motor impairments and modifying the pro-inflammatory phenotype of glial cells.

GDNF From Human Periodontal Ligament Cells Treated With Pro-Inflammatory Cytokines Promotes Neurocytic Differentiation of PC12 Cells

Glial cell line-derived neurotrophic factor (GDNF) is known to mediate multiple biological activities such as promotion of cell motility and proliferation, and morphogenesis. However, little is known about its effects on periodontal ligament (PDL) cells. Recently, we reported that GDNF expression is increased in wounded rat PDL tissue and human PDL cells (HPDLCs) treated with pro-inflammatory cytokines. Here, we investigated the associated expression of GDNF and the pro-inflammatory cytokine interleukin-1 beta (IL-1β) in wounded PDL tissue, and whether HPDLCs secrete GDNF which affects neurocytic differentiation. Rat PDL cells near the wounded area showed intense immunoreactions against an anti-GDNF antibody, where immunoreactivity was also increased against an anti-IL-1β antibody. Compared with untreated cells, HPDLCs treated with IL-1β or tumor necrosis factor-alpha showed an increase in the secretion of GDNF protein. Conditioned medium of IL-1β-treated HPDLCs (IL-1β-CM) increased neurite outgrowth of PC12 rat adrenal pheochromocytoma cells. The expression levels of two neural regeneration-associated genes, growth-associated protein-43 (Gap-43), and small proline-rich repeat protein 1A (Sprr1A), were also upregulated in IL-1β-CM-treated PC12 cells. These stimulatory effects of IL-1β-CM were significantly inhibited by a neutralizing antibody against GDNF. In addition, U0126, a MEK inhibitor, inhibited GDNF-induced neurite outgrowth of PC12 cells. These findings suggest that an increase of GDNF in wounded PDL tissue might play an important role in neural regeneration probably via the MEK/ERK signaling pathway. J. Cell. Biochem. 118: 699-708, 2017. © 2016 Wiley Periodicals, Inc.

Disruption of the astrocytic TNFR1-GDNF axis accelerates motor neuron degeneration and disease progression in amyotrophic lateral sclerosis

Considerable evidence indicates that neurodegeneration in amyotrophic lateral sclerosis (ALS) can be conditioned by a deleterious interplay between motor neurons and astrocytes. Astrocytes are the major glial component in the central nervous system (CNS) and fulfill several activities that are essential to preserve CNS homeostasis. In physiological and pathological conditions, astrocytes secrete a wide range of factors by which they exert multimodal influences on their cellular neighbours. Among others, astrocytes can secrete glial cell line-derived neurotrophic factor (GDNF), one of the most potent protective agents for motor neurons. This suggests that the modulation of the endogenous mechanisms that control the production of astrocytic GDNF may have therapeutic implications in motor neuron diseases, particularly ALS. In this study, we identified TNF receptor 1 (TNFR1) signalling as a major promoter of GDNF synthesis/release from human and mouse spinal cord astrocytes in vitro and in vivo To determine whether endogenously produced TNFα can also trigger the synthesis of GDNF in the nervous system, we then focused on SOD1^G93A ALS transgenic mice, whose affected tissues spontaneously exhibit high levels of TNFα and its receptor 1 at the onset and symptomatic stage of the disease. In SOD1^G93A spinal cords, we verified a strict correlation in the expression of the TNFα, TNFR1 and GDNF triad at different stages of disease progression. Yet, ablation of TNFR1 completely abolished GDNF rises in both SOD1^G93A astrocytes and spinal cords, a condition that accelerated motor neuron degeneration and disease progression. Our data suggest that the astrocytic TNFR1-GDNF axis represents a novel target for therapeutic intervention in ALS.

Retinal Macroglial Responses in Health and Disease

Due to their permanent and close proximity to neurons, glial cells perform essential tasks for the normal physiology of the retina. Astrocytes and Müller cells (retinal macroglia) provide physical support to neurons and supplement them with several metabolites and growth factors. Macroglia are involved in maintaining the homeostasis of extracellular ions and neurotransmitters, are essential for information processing in neural circuits, participate in retinal glucose metabolism and in removing metabolic waste products, regulate local blood flow, induce the blood-retinal barrier (BRB), play fundamental roles in local immune response, and protect neurons from oxidative damage. In response to polyetiological insults, glia cells react with a process called reactive gliosis, seeking to maintain retinal homeostasis. When malfunctioning, macroglial cells can become primary pathogenic elements. A reactive gliosis has been described in different retinal pathologies, including age-related macular degeneration (AMD), diabetes, glaucoma, retinal detachment, or retinitis pigmentosa. A better understanding of the dual, neuroprotective, or cytotoxic effect of macroglial involvement in retinal pathologies would help in treating the physiopathology of these diseases. The extensive participation of the macroglia in retinal diseases points to these cells as innovative targets for new drug therapies.

Help-me signaling: Non-cell autonomous mechanisms of neuroprotection and neurorecovery

Self-preservation is required for life. At the cellular level, this fundamental principle is expressed in the form of molecular mechanisms for preconditioning and tolerance. When the cell is threatened, internal cascades of survival signaling become triggered to protect against cell death and defend against future insults. Recently, however, emerging findings suggest that this principle of self-preservation may involve not only intracellular signals; the release of extracellular signals may provide a way to recruit adjacent cells into an amplified protective program. In the central nervous system where multiple cell types co-exist, this mechanism would allow threatened neurons to "ask for help" from glial and vascular compartments. In this review, we describe this new concept of help-me signaling, wherein damaged or diseased neurons release signals that may shift glial and vascular cells into potentially beneficial phenotypes, and help remodel the neurovascular unit. Understanding and dissecting these non-cell autonomous mechanisms of self-preservation in the CNS may lead to novel opportunities for neuroprotection and neurorecovery.

A longitudinal genome-wide association study of anti-tumor necrosis factor response among Japanese patients with rheumatoid arthritis

Background

Studies of Caucasian patients with rheumatoid arthritis (RA) to identify genetic biomarkers of anti-tumor necrosis factor (TNF) response have used response at a single time point as the phenotype with which single nucleotide polymorphism (SNP) associations have been tested. The findings have been inconsistent across studies. Among Japanese patients, only a few SNPs have been investigated. We report here the first genome-wide association study (GWAS) to identify genetic biomarkers of anti-TNF response among Japanese RA patients, using response at 2 time-points for a more reliable clinical phenotype over time.

Methods

Disease Activity Scores based on 28 joint counts (DAS28) were assessed at baseline (before initial therapy), and after 3 and 6 months in 487 Japanese RA patients starting anti-TNF therapy for the first time or switching to a new anti-TNF agent. A genome-wide panel of SNPs was genotyped and additional SNPs were imputed. Using change in DAS28 scores from baseline at both 3 (ΔDAS-3) and 6 months (ΔDAS-6) as the response phenotype, a longitudinal genome-wide association analysis was conducted using generalized estimating equations (GEE) models, adjusting for baseline DAS28, treatment duration, type of anti-TNF agent and concomitant methotrexate. Cross-sectional analyses were performed using multivariate linear regression models, with response from a single time point (ΔDAS-3 or ΔDAS-6) as phenotype; all other variables were the same as in the GEE models.

Results

In the GEE models, borderline significant association was observed at 3 chromosomal regions (6q15: rs284515, p = 6.6x10⁻⁷; 6q27: rs75908454, p = 6.3x10⁻⁷ and 10q25.3: rs1679568, p = 8.1x10⁻⁷), extending to numerous SNPs in linkage disequilibrium (LD) across each region. Potential candidate genes in these regions include MAP3K7, BACH2 (6q15), GFRA1 (10q25.3), and WDR27 (6q27). The association at GFRA1 replicates a previous finding from a Caucasian dataset. In the cross-sectional analyses, ΔDAS-6 was significantly associated with the 6q15 locus (rs284511, p = 2.5x10⁻⁸). No other significant or borderline significant associations were identified.

Conclusion

Three genomic regions demonstrated significant or borderline significant associations with anti-TNF response in our dataset of Japanese RA patients, including a locus previously associated among Caucasians. Using repeated measures of response as phenotype enhanced the power to detect these associations.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-0920-6) contains supplementary material, which is available to authorized users.

Increased levels of tumour necrosis factor alpha (TNFα) but not transforming growth factor-beta 1 (TGFβ1) are associated with the severity of congenital hydrocephalus in the hyh mouse

AIMS

Here, we tested the hypothesis that glial responses via the production of cytokines such as transforming growth factor-beta 1 (TGFβ1) and tumour necrosis factor alpha (TNFα), which play important roles in neurodegenerative diseases, are correlated with the severity of congenital hydrocephalus in the hyh mouse model. We also searched for evidence of this association in human cases of primary hydrocephalus.

METHODS

Hyh mice, which exhibit either severe or compensated long-lasting forms of hydrocephalus, were examined and compared with wild-type mice. TGFβ1, TNFα and TNFαR1 mRNA levels were quantified using real-time PCR. TNFα and TNFαR1 were immunolocalized in the brain tissues of hyh mice and four hydrocephalic human foetuses relative to astroglial and microglial reactions.

RESULTS

The TGFβ1 mRNA levels were not significantly different between hyh mice exhibiting severe or compensated hydrocephalus and normal mice. In contrast, severely hydrocephalic mice exhibited four- and two-fold increases in the mean levels of TNFα and TNFαR1, respectively, compared with normal mice. In the hyh mouse, TNFα and TNFαR1 immunoreactivity was preferentially detected in astrocytes that form a particular periventricular reaction characteristic of hydrocephalus. However, these proteins were rarely detected in microglia, which did not appear to be activated. TNFα immunoreactivity was also detected in the glial reaction in the small group of human foetuses exhibiting hydrocephalus that were examined.

CONCLUSIONS

In the hyh mouse model of congenital hydrocephalus, TNFα and TNFαR1 appear to be associated with the severity of the disease, probably mediating the astrocyte reaction, neurodegenerative processes and ischaemia.

Neurotrophic Activity of Cultured Cell Line U87 is Up-Regulated by Proline-Rich Polypeptide Complex and Its Constituent Nonapeptide

Neurotrophins such as nerve growth factor (NGF) and brain-derived neurotrophic factor, as well as cytokines, for example, interleukin-6 (IL-6) play an important role in neuroprotection and in the control of the central nervous system (CNS) function. Reduced expression of neurotrophic factors can lead to dysregulation of neuron function and neuronal death. There is also evidence for mutual interactions between neurotrophins and IL-6. Therefore, the up-regulating the level of neuroprotective substances is one of the key manners to control the nervous system development and function. It can be a promising aim in the therapy of neurodegenerative disease in which the decreased level of neurotrophins is observed. In our recent studies, the role of proline-rich polypeptide complex (PRP) and its nonapeptide fragment (NP) in the regulation of neurotrophic activity in cultured astrocytes was shown. PRP and NP stimulate human astrocytoma cell line U87 to release the significant amounts of NGF to the extracellular space both in its precursor and mature form. We also provide the evidence that in NP-treated cells, the level of βNGF mRNA was increased. NP-treated cells used in this study produced also increasing amounts of IL-6. This finding indicates that PRP and its nonapeptide fragment NP up-regulate neurotrophic activity of U87 cell line by increase of NGF synthesis and its release into the extracellular space. It was also shown that NP-dependent increased production of IL-6 can enhance the NGF activity.

Transcriptional Regulation of Brain-Derived Neurotrophic Factor (BDNF) by Methyl CpG Binding Protein 2 (MeCP2): a Novel Mechanism for Re-Myelination and/or Myelin Repair Involved in the Treatment of Multiple Sclerosis (MS)

Multiple sclerosis (MS) is a chronic progressive, neurological disease characterized by the targeted immune system-mediated destruction of central nervous system (CNS) myelin. Autoreactive CD4+ T helper cells have a key role in orchestrating MS-induced myelin damage. Once activated, circulating Th1-cells secrete a variety of inflammatory cytokines that foster the breakdown of blood-brain barrier (BBB) eventually infiltrating into the CNS. Inside the CNS, they become reactivated upon exposure to the myelin structural proteins and continue to produce inflammatory cytokines such as tumor necrosis factor α (TNFα) that leads to direct activation of antibodies and macrophages that are involved in the phagocytosis of myelin. Proliferating oligodendrocyte precursors (OPs) migrating to the lesion sites are capable of acute remyelination but unable to completely repair or restore the immune system-mediated myelin damage. This results in various permanent clinical neurological disabilities such as cognitive dysfunction, fatigue, bowel/bladder abnormalities, and neuropathic pain. At present, there is no cure for MS. Recent remyelination and/or myelin repair strategies have focused on the role of the neurotrophin brain-derived neurotrophic factor (BDNF) and its upstream transcriptional repressor methyl CpG binding protein (MeCP2). Research in the field of epigenetic therapeutics involving histone deacetylase (HDAC) inhibitors and lysine acetyl transferase (KAT) inhibitors is being explored to repress the detrimental effects of MeCP2. This review will address the role of MeCP2 and BDNF in remyelination and/or myelin repair and the potential of HDAC and KAT inhibitors as novel therapeutic interventions for MS.

Human Adenomyosis Endometrium Stromal Cells Secreting More Nerve Growth Factor: Impact and Effect

Abnormal expression of nerve growth factor (NGF) was found in adenomyosis (AM). We collected AM foci from patients and eutopic endometrium from non-AM controls. Endometrium stromal cells (ESCs) were cultured. Different levels of 17β-estradiol, tumor necrosis factor (TNF), CoCl2, and H2O2 were added to the culture system separately, then the expression level of NGF in ESCs was detected. After adding different levels of NGF, the proliferation and apoptosis of ESCs and aromatase expression were detected. We found that 17β-estradiol promoted NGF production in AM ESCs but not in control ESCs; TNF promoted NGF production in both AM and control ESCs; and CoCl2 inhibited NGF production in control ESCs, but had no effect in AM ESCs. Nerve growth factor promoted the proliferation and synthesis of aromatase in AM ESCs. In conclusion, locally increased estrogen levels and inflammation may cause increased NGF production in the uterus of patients with AM. Nerve growth factor stimulated the proliferation and increased aromatase expression of ESCs from AM foci, suggesting NGF might contribute to the pathology and etiology of AM.

Transient transfection of human CDNF gene reduces the 6-hydroxydopamine-induced neuroinflammation in the rat substantia nigra

BACKGROUND

The anti-inflammatory effect of the cerebral dopamine neurotrophic factor (CDNF) was shown recently in primary glial cell cultures, yet such effect remains unknown both in vivo and in 6-hydroxydopamine (6-OHDA) models of Parkinson's disease (PD). We addressed this issue by performing an intranigral transfection of the human CDNF (hCDNF) gene in the critical period of inflammation after a single intrastriatal 6-OHDA injection in the rat.

METHODS

At day 15 after lesion, the plasmids p3xNBRE-hCDNF or p3xNBRE-EGFP, coding for enhanced green florescent protein (EGFP), were transfected into the rat substantia nigra (SN) using neurotensin (NTS)-polyplex. At day 15 post-transfection, we measured nitrite and lipoperoxide levels in the SN. We used ELISA to quantify the levels of TNF-α, IL-1β, IL-6, endogenous rat CDNF (rCDNF) and hCDNF. We also used qRT-PCR to measure rCDNF and hCDNF transcripts, and immunofluorescence assays to evaluate iNOS, CDNF and glial cells (microglia, astrocytes and Neuron/Glial type 2 (NG2) cells). Intact SNs were additional controls.

RESULTS

In the SN, 6-OHDA triggered nitrosative stress, increased inflammatory cytokines levels, and activated the multipotent progenitor NG2 cells, which convert into astrocytes to produce rCDNF. In comparison with the hemiparkinsonian rats that were transfected with the EGFP gene or without transfection, 6-OHDA treatment and p3xNBRE-hCDNF transfection increased the conversion of NG2 cells into astrocytes resulting in 4-fold increase in the rCDNF protein levels. The overexpressed CDNF reduced nitrosative stress, glial markers and IL-6 levels in the SN, but not TNF-α and IL-1β levels.

CONCLUSION

Our results show the anti-inflammatory effect of CDNF in a 6-OHDA rat of Parkinson's disease. Our results also suggest the possible participation of TNF-α, IL-1β and IL-6 in rCDNF production by astrocytes, supporting their anti-inflammatory role.

Microglial regulation of immunological and neuroprotective functions of astroglia

Microglia and astroglia play critical roles in the development, function, and survival of neurons in the CNS. However, under inflammatory conditions the role of astrogliosis in the inflammatory process and its effects on neurons remains unclear. Here, we used several types of cell cultures treated with the bacterial inflammogen LPS to address these questions. We found that the presence of astroglia reduced inflammation-driven neurotoxicity, suggesting that astrogliosis is principally neuroprotective. Neutralization of supernatant glial cell line-derived neurotrophic factor (GDNF) released from astroglia significantly reduced this neuroprotective effect during inflammation. To determine the immunological role of astroglia, we optimized a highly-enriched astroglial culture protocol and demonstrated that LPS failed to induce the synthesis and release of TNF-α and iNOS/NO. Instead we found significant enhancement of TNF-α and iNOS expression in highly-enriched astroglial cultures required the presence of 0.5-1% microglia, respectively. Thus suggesting that microglial-astroglial interactions are required for LPS to induce the expression of pro-inflammatory factors and GDNF from astroglia. Specifically, we found that microglia-derived TNF-α plays a pivotal role as a paracrine signal to regulate the neuroprotective functions of astrogliosis. Taken together, these findings suggest that astroglia may not possess the ability to directly recognize the innate immune stimuli LPS, but rather depend on crosstalk with microglia to elicit release of neurotrophic factors as a counterbalance to support neuronal survival from the collateral damage generated by activated microglia during neuroinflammation.

Neuroimmune regulation of microglial activity involved in neuroinflammation and neurodegenerative diseases

Neuroinflammation constitutes a fundamental process involved in the progression of several neurodegenerative disorders, such as Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis and multiple sclerosis. Microglial cells play a central role in neuroinflammation, promoting neuroprotective or neurotoxic microenvironments, thus controlling neuronal fate. Acquisition of different microglial functions is regulated by intercellular interactions with neurons, astrocytes, the blood-brain barrier, and T-cells infiltrating the central nervous system. In this study, an overview of the regulation of microglial function mediated by different intercellular communications is summarised and discussed. Afterward, we focus in T-cell-mediated regulation of neuroinflammation involved in neurodegenerative disorders.

Early responses to deep brain stimulation in depression are modulated by anti-inflammatory drugs

Deep brain stimulation (DBS) in the subgenual cingulated gyrus (SCG) is a promising new technique that may provide sustained remission in resistant major depressive disorder (MDD). Initial studies reported a significant early improvement in patients, followed by a decline within the first month of treatment, an unexpected phenomenon attributed to potential placebo effects or a physiological response to probe insertion that remains poorly understood. Here we characterized the behavioural antidepressant-like effect of DBS in the rat medial prefrontal cortex, focusing on modifications to rodent SCG correlate (prelimbic and infralimbic (IL) cortex). In addition, we evaluated the early outcome of DBS in the SCG of eight patients with resistant MDD involved in a clinical trial. We found similar antidepressant-like effects in rats implanted with electrodes, irrespective of whether they received electrical brain stimulation or not. This effect was due to regional inflammation, as it was temporally correlated with an increase of glial-fibrillary-acidic-protein immunoreactivity, and it was blocked by anti-inflammatory drugs. Indeed, inflammatory mediators and neuronal p11 expression also changed. Furthermore, a retrospective study indicated that the early response of MDD patients subjected to DBS was poorer when they received anti-inflammatory drugs. Our study demonstrates that electrode implantation up to the IL cortex is sufficient to produce an antidepressant-like effect of a similar magnitude to that observed in rats receiving brain stimulation. Moreover, both preclinical and clinical findings suggest that the use of anti-inflammatory drugs after electrode implantation may attenuate the early anti-depressive response in patients who are subjected to DBS.

The role of nerve growth factor in neuropathic pain inhibition produced by resiniferatoxin treatment in the dorsal root ganglia

BACKGROUND

Resiniferatoxin (RTX), an excitotoxic agonist for vanilloid receptor 1, is a promising candidate for intractable pain treatment.

OBJECTIVE

We evaluated the effects of RTX, applied to dorsal root ganglia (DRG) at high doses (1200 ng), in sensory-motor function and nerve growth factor (NGF) alterations in a photochemical sciatic nerve injury rat model.

METHODS

Following RTX injection into the L3-6 DRG at high doses and behavioral evaluation, the rats were sacrificed and the DRG were tested by immunohistochemistry and mRNA analysis for NGF and its' receptors, tyrosine kinase A (TrkA) and p75. The correlation between neuropathic pain and NGF, TrkA, and p75 expression was analyzed.

RESULTS

The treated rats had preserved touch, cold, pain, and high-heat sensations, and exhibited hypoalgesia to low-heat stimulation. After RTX treatment, TrkA and p75 altered their expressions from one neuronal type to another in the DRG. NGF and p75 expression changed from the small-size neurons in neuropathic rat DRG to the large- and medium-size neurons in non-neuropathic and RTX-treated animals, concomitantly with neuropathic pain suppression. TrkA was expressed in the small-size neurons in neuropathic rat DRG, and was drastically reduced in all size neurons after RTX treatment. NGF, TrkA, and p75 mRNA expression supported these phenotypic changes in the DRG.

CONCLUSION

The pathway of NGF-TrkA expressed in the small-size neurons, associated with neuropathic pain, was shifted to the NGF-p75 pathway expressed in the large-size neurons after RTX treatment, in association with neuropathic pain inhibition. These findings may play an important role in clinical trial designs.

TNF-α/NF-κB signaling in the CNS: possible connection to EPHB2

Tumor necrosis factor-alpha, TNF-α, is a cytokine that is a well-known factor in multiple disease conditions and is recognized for its major role in central nervous system signaling. TNF-α signaling is most commonly associated with neurotoxicity, but in some conditions it has been found to be neuroprotective. TNF-α has long been known to induce nuclear factor-kappa B, NF-κB, signaling by, in most cases, translocating the p65 (RelA) DNA binding factor to the nucleus. p65 is a key member of NF-κB, which is well established as a family of transcription factors that regulates many signaling events, including growth and process development, in neuronal cell populations. NF-κB has been shown to affect both the receiving aspect of neuronal signaling events in dendritic development as well as the sending of neuronal signals in axonal development. In both cases, NK-κB functions as a promoter and/or inhibitor of growth, depending on the environmental conditions and signaling cascade. In addition, NF-κB is involved in memory formation or neurogenesis, depending on the region of the brain in which the signaling occurs. The ephrin (Eph) receptor family represents a subfamily of receptor tyrosine kinases, RTKs, which received much attention due to its potential involvement in neuronal cell health and function. There are two subsets of ephrin receptors, Eph A and Eph B, each with distinct functions in cardiovascular and skeletal development and axon guidance and synaptic plasticity. The presence of multiple binding sites for NF-κB within the regulatory region of EphB2 gene and its potential regulation by NF-κB pathway suggests that TNF-α may modulate EphB2 via NF-κB and that this may contribute to the neuroprotective activity of TNF-α.

Various roles of astrocytes during recovery from repeated exposure to different doses of lipopolysaccharide

Previous studies have demonstrated that the outcomes associated with neuroinflammation induced by intraperitoneal injection of lipopolysaccharide (LPS) at different dosages vary and either resolve or result in sepsis. The mechanisms underlying differential recoveries from varying doses of LPS are unclear. Additionally, changes in recovery involving chronic or continuous systemic inflammatory responses remain unclear. The present experiments were designed to evaluate the effects of systemic inflammation induced by repeated intraperitoneal injection of LPS at different doses on cognitive impairment. These experiments were also designed to investigate the roles of microglia and astrocytes in systemic inflammation and confirm the mechanisms that influence these processes. Kunming mice were given intraperitoneal injections of LPS at either 5mg/kg or 10mg/kg or saline for 7 consecutive days. Following the 7-day course of injections, a number of mice were kept undisturbed in their home cage for 30 days (30-day recovery), and other mice were similarly kept for 90 days (90-day recovery). The results revealed that the cognitive and physiological changes induced by 5mg/kg LPS included weight loss, impairments in spatial learning and memory, phenotypic changes in glia cells, and altered levels of pro-inflammatory cytokines; all of which were reversible. A potential recovery mechanism involves a neuroprotective function of activated astrocytes that secreted glial-derived neurotrophic factor (GDNF) following 30-day recovery. The changes induced by 10mg/kg LPS included weight loss, phenotypic changes in glia cells, and altered levels of pro-inflammatory cytokines were also reversible; however, a longer recovery was required (90 days). Although 10mg/kg LPS-induced neuroinflammation was reversible, the associated impairments in spatial learning and memory were permanent. A potential mechanism underlying permanent damage associated with 10mg/kg LPS involves the role of the activated astrocytes changing from neuroprotection to destruction, which is mediated by increased pro-inflammatory cytokines in more serious neuroinflammation.