IL-10 production by adult human derived microglial cells

Low-dose LPS alleviates early brain injury after SAH by modulating microglial M1/M2 polarization via USP19/FOXO1/IL-10/IL-10R1 signaling

BACKGROUND

Low-dose lipopolysaccharide (LPS) protects against early brain injury (EBI) after subarachnoid hemorrhage (SAH). However, the mechanism underlying the neuroprotective roles of low-dose LPS remain largely undefined.

METHODS

A SAH mice model was established and the pathological changes of brain were evaluated by wet-dry weight method, HE and Nissl staining, and blood-brain barrier (BBB) permeability assay. Cell apoptosis and inflammation were monitored by TUNEL, flow cytometry and ELISA assays. qRT-PCR, immunofluorescence and Western blot were used to detect the expression of microglial polarization-related or oxidative stress-associated markers. Bioinformatics analysis, luciferase and ChIP assays were employed to detect the direct association between FOXO1 and IL-10 promoter. The ubiquitination of FOXO1 in the in vitro SAH model was detected by co-IP.

RESULTS

Low-dose LPS alleviated SAH-induced neurological dysfunction, brain edema, BBB disruption, damage in the hippocampus, neuronal apoptosis and inflammation via modulating microglial M1/M2 polarization by IL-10/IL-10R1 signaling. Mechanistic studies showed that FOXO1 acted as a transcriptional activator of IL-10. USP19 mediated the deubiquitination of FOXO1 to activate IL-10/IL-10R1 signaling, thereby regulating microglial M1/M2 polarization. Functional experiments revealed that low-dose LPS upregulated USP19 to modulate microglial M1/M2 polarization via FOXO1/IL-10/IL-10R1 signaling in SAH mice.

CONCLUSION

Low-dose LPS protected against EBI after SAH by modulating microglial M1/M2 polarization via USP19/FOXO1/IL-10/IL-10R1 signaling.

Disease mechanisms as subtypes: Immune dysfunction in Parkinson's disease

In recent years, the contraposition between inflammatory and neurodegenerative processes has been increasingly challenged. Inflammation has been emphasized as a key player in the onset and progression of Parkinson disease (PD) and other neurodegenerative disorders. The strongest indicators of the involvement of the immune system derived from evidence of microglial activation, profound imbalance in phenotype and composition of peripheral immune cells, and impaired humoral immune responses. Moreover, peripheral inflammatory mechanisms (e.g., involving the gut-brain axis) and immunogenetic factors are likely to be implicated. Even though several lines of preclinical and clinical studies are supporting and defining the complex relationship between the immune system and PD, the exact mechanisms are currently unknown. Similarly, the temporal and causal connections between innate and adaptive immune responses and neurodegeneration are unsettled, challenging our ambition to define an integrated and holistic model of the disease. Despite these difficulties, current evidence is providing the unique opportunity to develop immune-targeted approaches for PD, thus enriching our therapeutic armamentarium. This chapter aims to provide an extensive overview of past and present studies that explored the implication of the immune system in neurodegeneration, thus paving the road for the concept of disease modification in PD.

Cellular Sources and Neuroprotective Roles of Interleukin-10 in the Facial Motor Nucleus after Axotomy

Facial motoneuron (FMN) survival is mediated by CD4+ T cells in an interleukin-10 (IL-10)-dependent manner after facial nerve axotomy (FNA), but CD4+ T cells themselves are not the source of this neuroprotective IL-10. The aims of this study were to (1) identify the temporal and cell-specific induction of IL-10 expression in the facial motor nucleus and (2) elucidate the neuroprotective capacity of this expression after axotomy. Immunohistochemistry revealed that FMN constitutively produced IL-10, whereas astrocytes were induced to make IL-10 after FNA. Il10 mRNA co-localized with microglia before and after axotomy, but microglial production of IL-10 protein was not detected. To determine whether any single source of IL-10 was critical for FMN survival, Cre/Lox mouse strains were utilized to selectively knock out IL-10 in neurons, astrocytes, and microglia. In agreement with the localization data reflecting concerted IL-10 production by multiple cell types, no single cellular source of IL-10 alone could provide neuroprotection after FNA. These findings suggest that coordinated neuronal and astrocytic IL-10 production is necessary for FMN survival and has roles in neuronal homeostasis, as well as neuroprotective trophism after axotomy.

Psychostimulant-induced aberrant DNA methylation in an in vitro model of human peripheral blood mononuclear cells

Background

Several reports have provided crucial evidence in animal models that epigenetic modifications, such as DNA methylation, may be involved in psychostimulant-induced stable changes at the cellular level in the brain. Epigenetic editors DNA methyltransferases (DNMTs) and ten-eleven translocation enzymes (TETs) coordinate expression of gene networks, which then manifest as long-term behavioural changes. However, the extent to which aberrant DNA methylation is involved in the mechanisms of substance use disorder in humans is unclear. We previously demonstrated that cocaine modifies gene transcription, via DNA methylation, throughout the brain and in peripheral blood cells in mice.

Results

We treated human peripheral blood mononuclear cells (PBMCs) from healthy male donors (n = 18) in vitro with psychostimulants (amphetamine, cocaine). After treatment, we assessed mRNA levels and enzymatic activities of TETs and DNMTs, conducted genome-wide DNA methylation assays and next-generation sequencing. We found that repeated exposure to psychostimulants decreased mRNA levels and enzymatic activity of TETs and 5-hydroxymethylation levels in PBMCs. These data were in line with observed hyper- and hypomethylation and mRNA expression of marker genes (IL-10, ATP2B4). Additionally, we evaluated whether the effects of cocaine on epigenetic editors (DNMTs and TETs) and cytokines interleukin-6 (IL-6) and IL-10 could be reversed by the DNMT inhibitor decitabine.

Indeed, decitabine eliminated cocaine’s effect on the activity of TETs and DNMTs and decreased cytokine levels, whereas cocaine increased IL-6 and decreased IL-10.

Conclusions

Our data suggest that repeated psychostimulant exposure decreases TETs’ enzymatic activity in PBMCs. Co-treatment with decitabine reversed TETs’ levels and modulated immune response after repeated cocaine exposure. Further investigation is needed to clarify if TET could represent a putative biomarker of psychostimulant use and if DNMT inhibition could have therapeutic potential.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-022-01303-w.

Routine culture and study of adult human brain cells from neurosurgical specimens

When modeling disease in the laboratory, it is important to use clinically relevant models. Patient-derived human brain cells grown in vitro to study and test potential treatments provide such a model. Here, we present simple, highly reproducible coordinated procedures that can be used to routinely culture most cell types found in the human brain from single neurosurgically excised brain specimens. The cell types that can be cultured include dissociated cultures of neurons, astrocytes, microglia, pericytes and brain endothelial and neural precursor cells, as well as explant cultures of the leptomeninges, cortical slice cultures and brain tumor cells. The initial setup of cultures takes ~2 h, and the cells are ready for further experiments within days to weeks. The resulting cells can be studied as purified or mixed population cultures, slice cultures and explant-derived cultures. This protocol therefore enables the investigation of human brain cells to facilitate translation of neuroscience research to the clinic.

Monitoring and Modulating Inflammation-Associated Alterations in Synaptic Plasticity: Role of Brain Stimulation and the Blood-Brain Interface

Inflammation of the central nervous system can be triggered by endogenous and exogenous stimuli such as local or systemic infection, trauma, and stroke. In addition to neurodegeneration and cell death, alterations in physiological brain functions are often associated with neuroinflammation. Robust experimental evidence has demonstrated that inflammatory cytokines affect the ability of neurons to express plasticity. It has been well-established that inflammation-associated alterations in synaptic plasticity contribute to the development of neuropsychiatric symptoms. Nevertheless, diagnostic approaches and interventional strategies to restore inflammatory deficits in synaptic plasticity are limited. Here, we review recent findings on inflammation-associated alterations in synaptic plasticity and the potential role of the blood–brain interface, i.e., the blood–brain barrier, in modulating synaptic plasticity. Based on recent findings indicating that brain stimulation promotes plasticity and modulates vascular function, we argue that clinically employed non-invasive brain stimulation techniques, such as transcranial magnetic stimulation, could be used for monitoring and modulating inflammation-induced alterations in synaptic plasticity.

IL-10 normalizes aberrant amygdala GABA transmission and reverses anxiety-like behavior and dependence-induced escalation of alcohol intake

Alcohol elicits a neuroimmune response in the brain contributing to the development and maintenance of alcohol use disorder (AUD). While pro-inflammatory mediators initiate and drive the neuroimmune response, anti-inflammatory mediators provide an important homeostatic mechanism to limit inflammation and prevent pathological damage. However, our understanding of the role of anti-inflammatory signaling on neuronal physiology in critical addiction-related brain regions and pathological alcohol-dependence induced behaviors is limited, precluding our ability to identify promising therapeutic targets. Here, we hypothesized that chronic alcohol exposure compromises anti-inflammatory signaling in the central amygdala, a brain region implicated in anxiety and addiction, consequently perpetuating a pro-inflammatory state driving aberrant neuronal activity underlying pathological behaviors. We found that alcohol dependence alters the global brain immune landscape increasing IL-10 producing microglia and T-regulatory cells but decreasing local amygdala IL-10 levels. Amygdala IL-10 overexpression decreases anxiety-like behaviors, suggesting its local role in regulating amygdala-mediated behaviors. Mechanistically, amygdala IL-10 signaling through PI3K and p38 MAPK modulates GABA transmission directly at presynaptic terminals and indirectly through alterations in spontaneous firing. Alcohol dependence-induces neuroadaptations in IL-10 signaling leading to an overall IL-10-induced decrease in GABA transmission, which normalizes dependence-induced elevated amygdala GABA transmission. Notably, amygdala IL-10 overexpression abolishes escalation of alcohol intake, a diagnostic criterion of AUD, in dependent mice. This highlights the importance of amygdala IL-10 signaling in modulating neuronal activity and underlying anxiety-like behavior and aberrant alcohol intake, providing a new framework for therapeutic intervention.

Classical and Alternative Activation of Rat Microglia Treated with Ultrapure Porphyromonas gingivalis Lipopolysaccharide In Vitro

The possible relationship between periodontal disease resulting from the infection of gingival tissue by the Gram-negative bacterium Porphyromonas gingivalis (P. gingivalis) and the development of neuroinflammation remains under investigation. Recently, P. gingivalis lipopolysaccharide (LPS) was reported in the human brain, thus suggesting it might activate brain microglia, a cell type participating in neuroinflammation. We tested the hypothesis of whether in vitro exposure to ultrapure P. gingivalis LPS may result in classical and alternative activation phenotypes of rat microglia, with the concomitant release of cytokines and chemokines, as well as superoxide anion (O₂^-), thromboxane B₂ (TXB₂), and matrix metalloprotease-9 (MMP-9). After an 18-h exposure of microglia to P. gingivalis LPS, the concentration-dependent responses were the following: 0.1-100 ng/mL P. gingivalis LPS increased O₂^- generation, with reduced inflammatory mediator generation; 1000-10,000 ng/mL P. gingivalis LPS generated MMP-9, macrophage inflammatory protein 1α (MIP-1α/CCL3), macrophage inflammatory protein-2 (MIP-2/CXCL2) release and significant O₂^- generation; 100,000 ng/mL P. gingivalis LPS sustained O₂^- production, maintained MMP-9, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) release, and triggered elevated levels of MIP-1α/CCL3, MIP-2/CXCL2, and cytokine-induced neutrophil chemoattractant 1 (CINC-1/CXCL-1), with a very low release of lactic dehydrogenase (LDH). Although P. gingivalis LPS was less potent than Escherichia coli (E. coli) LPS in stimulating TXB₂, MMP-9, IL-6 and interleukin 10 (IL-10) generation, we observed that it appeared more efficacious in enhancing the release of O₂^-, TNF-α, MIP-1α/CCL3, MIP-2/CXCL2 and CINC-1/CXCL-1. Our results provide support to our research hypothesis because an 18-h in vitro stimulation with ultrapure P. gingivalis LPS resulted in the classical and alternative activation of rat brain microglia and the concomitant release of cytokines and chemokines.

Loss of IL-10 Promotes Differentiation of Microglia to a M1 Phenotype

Microglia represent the primary resident immune cells of the central nervous system (CNS) and modulate local immune responses. Depending on their physiological functions, microglia can be classified into pro- (M1) and anti-inflammatory (M2) phenotype. Interleukin (IL)-10 is an important modulator of neuronal homeostasis, with anti-inflammatory and neuroprotective functions, and can be released by microglia. Here, we investigated how IL-10 deficiency affected the M1/2 polarization of primary microglia upon lipopolysaccharide (LPS) stimulation in vitro. Microglia phenotypes were analyzed via flow cytometry. Cytokine and chemokine secretion were examined by ELISA and bead-based multiplex LEGENDplex^TM. Our results showed that genetic depletion of IL-10 led to elevated M1 like phenotype (CD86+ CD206−) under pro-inflammatory conditions associated with increased frequency of IL-6+, TNF-α+ cells and enhanced release of several pro-inflammatory chemokines. Absence of IL-10 led to an attenuated M2 like phenotype (CD86− CD206+) and a reduced secretion of TGF-β1 upon LPS stimulation. In conclusion, IL-10 deficiency may promote the polarization of microglia into M1-prone phenotype under pro-inflammatory conditions.

When encephalitogenic T cells collaborate with microglia in multiple sclerosis

Immune cells mediate critical inflammatory and neurodegenerative processes in the CNS in individuals with multiple sclerosis (MS). In MS, activated microglia, border-associated macrophages and monocyte-derived macrophages in the CNS can encounter T cells that have infiltrated the brain parenchyma from the circulation. Although microglia and T cells both contribute to normal CNS development and homeostasis, evidence suggests that the meeting of activated microglia and macrophages with encephalitogenic T cells exacerbates their capacity to inflict injury. This crosstalk involves many cell-surface molecules, cytokines and neurotoxic factors. In this Review, we summarize the mechanisms and consequences of T cell-microglia interactions as identified with in vitro experiments and animal models, and discuss the challenges that arise when translating this preclinical knowledge to MS in humans. We also consider therapeutic approaches to MS of which the mechanisms involve prevention or modulation of T cell and microglia responses and their interactions.

Cyanobacteria Scytonema javanicum and Scytonema ocellatum Lipopolysaccharides Elicit Release of Superoxide Anion, Matrix-Metalloproteinase-9, Cytokines and Chemokines by Rat Microglia In Vitro

Cosmopolitan Gram-negative cyanobacteria may affect human and animal health by contaminating terrestrial, marine and freshwater environments with toxins, such as lipopolysaccharide (LPS). The cyanobacterial genus Scytonema (S) produces several toxins, but to our knowledge the bioactivity of genus Scytonema LPS has not been investigated. We recently reported that cyanobacterium Oscillatoria sp. LPS elicited classical and alternative activation of rat microglia in vitro. Thus, we hypothesized that treatment of brain microglia in vitro with either cyanobacteria S. javanicum or S. ocellatum LPS might stimulate classical and alternative activation with concomitant release of superoxide anion (O₂^-), matrix metalloproteinase-9 (MMP-9), cytokines and chemokines. Microglia were isolated from neonatal rats and treated in vitro with either S. javanicum LPS, S. ocellatum LPS, or E. coli LPS (positive control), in a concentration-dependent manner, for 18 h at 35.9 °C. We observed that treatment of microglia with either E. coli LPS, S. javanicum or S. ocellatum LPS generated statistically significant and concentration-dependent O₂^-, MMP-9 and pro-inflammatory cytokines IL-6 and TNF-α, pro-inflammatory chemokines MIP-2/CXCL-2, CINC-1/CXCL-1 and MIP-1α/CCL3, and the anti-inflammatory cytokine IL-10. Thus, our results provide experimental support for our working hypothesis because both S. javanicum and S. ocellatum LPS elicited classical and alternative activation of microglia and concomitant release of O₂^-, MMP-9, cytokines and chemokines in a concentration-dependent manner in vitro. To our knowledge this is the first report on the toxicity of cyanobacteria S. javanicum and S. ocellatum LPS to microglia, an immune cell type involved in neuroinflammation and neurotoxicity in the central nervous system.

Analysis of plasma multiplex cytokines and increased level of IL-10 and IL-1Ra cytokines in febrile seizures

Background

Febrile seizures are the most common form of childhood seizures. Fever generation involves many cytokines, including both pro- and anti-inflammatory cytokines. Some of these cytokines also induce febrile seizures. We compared cytokine production in children with a fever alone (healthy control group) and febrile seizure children group. Also, we evaluated the cytokine level of children with a fever alone and febrile seizure history.

Methods

Fifty febrile seizure patients and 39 normal control patients who visited the emergency department of Konkuk University Hospital from December 2015 to December 2016 were included in this study. Blood was taken from the peripheral vessels of children in all groups within 1 h of the seizure, and serum was obtained immediately. Serum samples from patients with only a fever and a febrile seizure history (N = 13) and afebrile seizure controls (N = 12) were also analyzed.

Results

The serum IL-10 and IL-1Ra levels were significantly higher in the febrile seizure patients than in the fever-only control, fever only with a febrile seizure history, and afebrile seizure groups (p < 0.05). The serum IFN-γ and IL-6 levels were significantly higher in the febrile seizure patients than in the afebrile seizure group (p < 0.05). The serum IL-8 levels were higher in the febrile seizure patients than in the fever only controls (p < 0.05).

Conclusions

The serum levels of the IFN-γ, IL-6, and IL-8 pro-inflammatory cytokines and the serum levels of the IL-10 and IL-1Ra anti-inflammatory cytokines were significantly higher in the febrile seizure children. Furthermore, the serum level of IL-1Ra was more increased in the febrile seizure group than in the same patients with only a fever. Our data suggest that increased serum IL-10 and IL-1Ra may play potential roles as anti-inflammatory cytokines in a compensation mechanism that shortens the seizure duration or prevents a febrile seizure attack. Therefore, anti-inflammatory cytokines, including IL-10 and IL-1Ra, have potential as therapeutic targets for the prevention of seizures and nervous system development of children.

Interleukin-10 release from astrocytes suppresses neuronal apoptosis via the TLR2/NFκB pathway in a neonatal rat model of hypoxic-ischemic brain damage

The biological function of interleukin-10 (IL-10) and the relationship between IL-10 secretion and the Toll-like receptor 2 (TLR2) expression levels in the central nervous system following hypoxic-ischemic brain damage (HIBD) are poorly understood. Here, we intend to elucidate the biological function and mechanism of IL-10 secretion following HIBD. In this study, we used a neonatal rat model of HIBD and found that rats injected with adeno-associated virus-IL-10-shRNA (short hairpin RNA) exhibited partially impaired learning and memory function compared to rats administered adeno-associated virus-control-shRNA. In vitro oxygen-glucose deprivation (OGD) induced IL-10 release from astrocytes but not from neurons. Pretreatment with exogenous recombinant IL-10 alleviated OGD-mediated apoptosis of neurons but not astrocytes. In addition, we also observed that hypoxic injury induced a marked increase in IL-10 expression in astrocytes as a result of activation of the TLR2/phosphorylated nuclear factor kappa B (p-NFκB) p65 signaling cascade; furthermore, this effect disappeared upon small interfering RNA targeting rat TLR2 gene (siTLR2) treatment. Pyrrolidinedithiocarbamate, an inhibitor of NFκB activation, reduced the IL-10 expression levels in both OGD-injured astrocytes in vitro and the hippocampi of HIBD rats in vivo but did not significantly affect TLR2 expression. Furthermore, a luciferase assay revealed that p-NFκB p65 could bind the -1700/-1000 bp proximal region of the IL-10 gene promoter to regulate IL-10 secretion from astrocytes and that this interaction could be controlled by OGD treatment. These data suggest that HIBD induces IL-10 secretion from astrocytes to exert a paracrine-induced anti-apoptotic effect on injured neurons via the TLR2/NFκB signaling pathway, which may improve learning and memory dysfunction after ischemic injury.

Association of TGFB, but not IL10, single nucleotide polymorphisms with febrile seizures

PURPOSE

Febrile seizures (FS) are the most common convulsive event in children. Inflammatory elements and genetics seem to have major roles in their pathogenesis.

METHODS

Seventy nine patients with FS were enrolled in this study and compared with 140 controls. Cytokine genotyping was performed, using polymerase chain reaction with sequence-specific primers. The allele and genotype frequency of three single nucleotide polymorphisms (SNPs) within the IL-10 gene at -1082, -819 and -592 positions (rs1800896, rs1800871, rs1800872), and two SNPs within the TGFB at codons 10 and 25 (rs1982037, rs1800471) were determined.

RESULTS

No significant difference was detected in allelic frequency of IL-10 at -1082, -819 and -592 positions (rs1800896, rs1800871, rs1800872) and TGFB at codon 25 (rs1800471), between patients and controls. A significant negative association was observed at the codon 10/CT (rs1982037) in the patient group (OR, 0.5; 95%CI, 0.27-0.93; p=0.026). Further, a negative association was detected in patients with simple FS at same position (OR, 0.41; 95%CI, 0.18-0.93; p=0.03), thus revealing a protective effects in FS patients. There was no significant difference in allelic and genotype frequency between simple and complex FS samples. Furthermore, haplotype analysis revealed significant difference in frequency of TGFB/TC haplotype in comparison between complex FS patients and controls (p=0.048).

CONCLUSION

Certain alleles, genotypes, and haplotypes in TGFB genes were over represented in patients with FS, which possibly could predispose individuals to this disease.

Cytokines in the cerebrospinal fluids of patients with chronic fatigue syndrome/myalgic encephalomyelitis

Objectives. Previous research has provided evidence for dysregulation in peripheral cytokines in patients with Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME). To date only one study has examined cytokines in cerebrospinal fluid (CSF) samples of CFS/ME patients. The purpose of this pilot study was to examine the role of cytokines in CSF of CFS/ME patients. Methods. CSF was collected from 18 CFS/ME patients and 5 healthy controls. The CSF samples were examined for the expression of 27 cytokines (interleukin- (IL-) 1β, IL-1ra, IL-2, IL-4, IL-6, IL-7, IL-8, IL-9, IL-10, IL-12p70, IL-13, IL-15, IL-17, basic FGF, eotaxin, G-CSF, GM-CSF, IFN-γ, IP-10, MCP-1 (MCAF), MIP-1α, MIP-1β, PDGF-BB, RANTES, TNF-α, and VEGF) using the Bio-Plex Human Cytokine 27-plex Assay. Results. Of the 27 cytokines examined, only IL-10 was significantly reduced in the CFS/ME patients in comparison to the controls. Conclusions. This preliminary investigation suggests that perturbations in inflammatory cytokines in the CSF of CFS/ME patients may contribute to the neurological discrepancies observed in CFS/ME.

Innate immunity and neuroinflammation

Inflammation of central nervous system (CNS) is usually associated with trauma and infection. Neuroinflammation occurs in close relation to trauma, infection, and neurodegenerative diseases. Low-level neuroinflammation is considered to have beneficial effects whereas chronic neuroinflammation can be harmful. Innate immune system consisting of pattern-recognition receptors, macrophages, and complement system plays a key role in CNS homeostasis following injury and infection. Here, we discuss how innate immune components can also contribute to neuroinflammation and neurodegeneration.

Interleukin-10 promoter polymorphisms in Chinese patients with Parkinson's disease

Interleukin-10 (IL-10), an important anti-inflammatory cytokine, may influence the risk for the development of onset of sparadic Parkinson's disease (PD) in the inflammatory process. In this study, two DNA polymorphisms at IL-10 gene promoter (-819 T/C and -592 A/C) were examined in 355 sporadic PD patients and 200 healthy controls in Han Chinese Population. For both polymorphisms, no significant difference in genotype or allele distribution was found between PD patients and the controls. For -819 T/C polymorphisms, there was significant difference in genotype distribution between EOPD (EOPD, <50 years of age) patients and each healthy-matched control subgroup (P=0.011), as well as between female PD patients and each healthy-matched control subgroup (P=0.024), For -592 A/C polymorphisms, there were no significant gender- and age-related differences in genotype distribution between PD patients and the controls subgroup. Results from our study revealed that the IL-10 promoter (-819 and -592) polymorphism is not a risk factor of sporadic Parkinson's disease, but the IL-10 promoter -819 polymorphism is a risk factor of EOPD and female PD patients in Han Chinese population.

Increased levels of HMGB1 and pro-inflammatory cytokines in children with febrile seizures

OBJECTIVE

Febrile seizures are the most common form of childhood seizures. Fever is induced by pro-inflammatory cytokines during infection, and pro-inflammatory cytokines may trigger the development of febrile seizures. In order to determine whether active inflammation, including high mobility group box-1 (HMGB1) and pro-inflammatory cytokines, occurs in children with febrile seizures or epilepsy, we analyzed cytokine profiles of patients with febrile seizures or epilepsy.

METHODS

Forty-one febrile seizure patients who visited the emergency department of Seoul National University Boramae Hospital from June 2008 to May 2009 were included in this study. Blood was obtained from the febrile seizure child patients within 30 minutes of the time of the seizure; subsequently, serum cytokine assays were performed. Control samples were collected from children with febrile illness without convulsion (N = 41) and similarly analyzed. Serum samples from afebrile status epilepticus attacks in intractable epilepsy children (N = 12), afebrile seizure attacks in generalized epilepsy with febrile seizure plus (GEFSP) children (N = 6), and afebrile non-epileptic controls (N = 7) were also analyzed.

RESULTS

Serum HMGB1 and IL-1β levels were significantly higher in febrile seizure patients than in fever only controls (p < 0.05). Serum IL-6 levels were significantly higher in typical febrile seizures than in fever only controls (p < 0.05). Serum IL-1β levels were significantly higher in status epilepticus attacks in intractable epilepsy patients than in fever only controls (p < 0.05). Serum levels of IL-1β were significantly correlated with levels of HMGB1, IL-6, and TNF-α (p < 0.05).

CONCLUSIONS

HMGB1 and pro-inflammatory cytokines were significantly higher in febrile seizure children. Although it is not possible to infer causality from descriptive human studies, our data suggest that HMGB1 and the cytokine network may contribute to the generation of febrile seizures in children. There may be a potential role for anti-inflammatory therapy targeting cytokines and HMGB1 in preventing or limiting febrile seizures or subsequent epileptogenesis in the vulnerable, developing nervous system of children.

Regional difference in inflammatory response to LPS-injection in the brain: role of microglia cell density

To elucidate whether density of cells could contribute to the extent of microglial activation, we performed in vitro assays using three different densities of N13 microglia stimulated with LPS. Our results showed that induction of pro-inflammatory factors as TNF-α and iNOS was directly related to cell density, meanwhile the induction of the anti-inflammatory IL-10 was inversely related to cell density. Accordingly, in vivo assays showed that after LPS-injection, iNOS expression was more intense in substantia nigra, a brain area showing specific susceptibility to neurodegeneration after microglia activation, whereas IL-10 expression was more sustained in striatum, an area resistant to damage. These results support that microglia density is pivotal to control the balance between pro- and anti-inflammatory factors release.

Reduced lymphocyte infiltration during cytomegalovirus brain infection of interleukin-10-deficient mice

Interleukin (IL)-10 deficiency results in highly elevated levels of interferon (IFN)-gamma, as well as the IFN-gamma-inducible chemokines CXCL9 and CXCL10 within murine cytomegalovirus (MCMV)-infected brains. To test the hypothesis that these elevated chemokine levels would result in enhanced brain infiltration, we compared immune cell infiltration in response to MCMV brain infection between wild-type and IL-10 knockout (KO) mice. Longitudinal analysis following adoptive transfer of cells from beta-actin-luciferase transgenic wild-type mice showed maximal brain infiltration by peripheral immune cells occurred at 5 days post infection. Although the overall percentage of CD45(hi) cells infiltrating the brain was not altered by IL-10 deficiency, paradoxically, despite elevated chemokine levels, reduced T lymphocyte (CD8+) and natural killer (NK) (CD49b+) cell infiltration into the brain was observed in IL-10-deficient animals. This decreased lymphocyte infiltration was associated with elevated levels of the lymph node homing receptor L-selectin/CD62L on CD8+ T cells. Lymph node cells obtained from MCMV-infected mice deficient in IL-10 also displayed reduced migration towards CXCL10 when compared to wild-type animals. Taken together, these data show that despite elevated chemokine levels, absence of IL-10 results in reduced lymphocyte infiltration into MCMV-infected brains.

Role of cytokines as mediators and regulators of microglial activity in inflammatory demyelination of the CNS

As the resident innate immune cells of the central nervous system (CNS), microglia fulfil a critical role in maintaining tissue homeostasis and in directing and eliciting molecular responses to CNS damage. The human disease Multiple Sclerosis and animal models of inflammatory demyelination are characterized by a complex interplay between degenerative and regenerative processes, many of which are regulated and mediated by microglia. Cellular communication between microglia and other neural and immune cells is controlled to a large extent by the activity of cytokines. Here we review the role of cytokines as mediators and regulators of microglial activity in inflammatory demyelination, highlighting their importance in potentiating cell damage, promoting neuroprotection and enhancing cellular repair in a context-dependent manner.

Relation of anti- to pro-inflammatory cytokine ratios with acute myocardial infarction

BACKGROUND/AIMS

Acute myocardial infarction (AMI) is a leading cause of death. Inflammatory processes play an important role in atherosclerosis, which is intimately related to AMI. The aim of this study was to investigate the association between anti-inflammatory and pro-inflammatory cytokines ratios and AMI.

METHODS

A total of 90 AMI patients and 90 age-and sex-matched controls were recruited in this study. Plasma cytokines and conventional risk factors were determined by standard methods.

RESULTS

Patients with AMI showed increased interleukin (IL)-6 and tumor necrosis factor-alpha levels and lower anti- to pro-inflammatory cytokine ratios as compared with controls. A multivariate logistic regression analysis revealed that IL-10 to IL-6 ratio was independently associated with the occurrence of AMI (odds ratio [OR], 5.39; 95% confidence interval [CI], 2.39 to 12.17; p < 0.0001). In contrast, IL-6 levels were no longer significant in the multivariate model (OR, 1.02; 95% CI, 0.932 to 1.12; p = 0.603). A receiver operating characteristic (ROC) curve analysis indicated that IL-6 levels and IL-10 to IL-6 ratios were a significant predictor of AMI (area under ROC curve, 0.892 and 0.851, respectively).

CONCLUSIONS

Our results suggest that the ratio of IL-10 to IL-6 is independently associated with AMI, and reduced levels of this ratio may favor the development of AMI.

Control of neuroinflammation as a therapeutic strategy for amyotrophic lateral sclerosis and other neurodegenerative disorders

Neurodegenerative diseases, Alzheimer's and Parkinson's diseases, and amyotrophic lateral sclerosis (ALS) are progressive and devastating disorders of the nervous system without cure. Although a number of distinct, but not mutually exclusive, mechanisms can affect disease pathogenesis, neuroinflammation stands in common. Neuroinflammatory responses occur as a consequence of oxidative and excitotoxic neuronal damage, mitochondrial dysfunction, and protein aggregation. Thus, it is believed drugs that modulate inflammation may combat disease progression. Such strategies include those commented on in the report by Arie Neymotin et al. demonstrating lenalidomide's anti-inflammatory and neuroprotective responses in the G93A mutant superoxide dismutase-1 mouse model of ALS (Neymotin et al., 2009). While anti-inflammatory interventions may be required, they may not be sufficient to positively affect clinical outcomes. The targeting of combinations of pathogenic events including clearance of disaggregated proteins together with neuroprotective and immune modulatory strategies may all be required to facilitate positive therapeutic outcomes. This may include the targeting of both innate and adaptive neurotoxic immune responses. This commentary is designed to summarize the promises and perils in achieving immunoregulation for brain homeostatic responses and inevitable therapeutic gain. Promising new ways to optimize immunization schemes and measure their clinical efficacy are discussed with a particular focus on ALS.

Heterogeneity of microglial activation in the innate immune response in the brain

The immune response in the brain has been widely investigated and while many studies have focused on the proinflammatory cytotoxic response, the brain’s innate immune system demonstrates significant heterogeneity. Microglia, like other tissue macrophages, participate in repair and resolution processes after infection or injury to restore normal tissue homeostasis. This review examines the mechanisms that lead to reduction of self-toxicity and to repair and restructuring of the damaged extracellular matrix in the brain. Part of the resolution process involves switching macrophage functional activation to include reduction of proinflammatory mediators, increased production and release of anti-inflammatory cytokines, and production of cytoactive factors involved in repair and reconstruction of the damaged brain. Two partially overlapping and complimentary functional macrophage states have been identified and are called alternative activation and acquired deactivation. The immunosuppressive and repair processes of each of these states and how alternative activation and acquired deactivation participate in chronic neuroinflammation in the brain are discussed.

Current status and challenges of cytokine pharmacology

The major concern of pharmacology about cytokines has originated from plentiful data showing association between gross changes in their production and pathophysiological processes. Despite the enigmatic role of cytokines in diseases, a number of them have become a subject of cytokine and anti-cytokine immunotherapies. Production of cytokines can be influenced by many endogenous and exogenous stimuli including drugs. Cells of the immune system, such as macrophages and lymphocytes, are richly endowed with receptors for the mediators of physiological functions, such as biogenic amines, adenosine, prostanoids, steroids, etc. Drugs, agonists or antagonists of these receptors can directly or indirectly up- and down-regulate secretion of cytokines and expression of cytokine receptors. Vice versa, cytokines interfere with drug pharmacokinetics and pharmacodynamics through the interactions with cytochrome P450 and multiple drug resistance proteins. The aim of the review is to encourage more intensive studies in these fields of cytokine pharmacology. It also outlines major areas of searching promising candidates for immunotherapeutic interventions.

Circulating interleukin-10 and interleukin-12 in Parkinson's disease

BACKGROUND

Interleukin (IL)-12 is a heterodimeric cytokine produced by activated blood monocytes, macrophages and glial cells. It enhances differentiation and proliferation of T cells and increases production of proinflammatory cytokines. IL-10 is a pleiotropic cytokine produced by both lymphocytes and mononuclear phagocytes including microglia. Recent studies demonstrated the neuroprotective effect of IL-10. There is little information about the involvement of IL-12 or IL-10 in the pathophysiology of Parkinson's disease (PD).

OBJECTIVES

The objective of our study was to assess the role of IL-12 as a potential marker of immune reactions in patients with PD and to investigate whether IL-10, an immunosuppressive cytokine, may have a neuroprotective effect in the pathogenesis of PD.

PATIENTS AND METHODS

We measured using immunoassay serum IL-12 and IL-10 levels in 41 patients with PD in comparison with serum levels in 19 healthy subjects (controls) age and sex matched. IL-12 and IL-10 levels were tested for correlation with sex, age, disease duration, Hoehn and Yahr stage and the UPDRS III score.

RESULTS

The PD group presented with significantly increased IL-10 levels when compared with the control group (P = 0.02). The increase observed was not affected by the treatment status. A strong and significant correlation between IL-10 and IL-12 levels was observed in patients with PD (R(S) = 0.7, P < 0.000001).

CONCLUSIONS

Our findings suggest that IL-10 may be involved in the pathogenetic mechanisms of PD. The elevation of IL-10 and the significant correlation between IL-10 and IL-12, a proinflammatory cytokine, may suggest that immunological disturbances and neuroprotective mechanisms are involved in patients with PD.

Interleukin-10 is associated with resistance to febrile seizures: genetic association and experimental animal studies

PURPOSE

Febrile seizures (FS) are the most common form of childhood convulsions. Many reports have shown that a proinflammatory cytokine, interleukin-1 (IL-1) beta, may have a facilitatory effect on the development of FS. We have previously shown that the IL1B -511C/T single nucleotide polymorphism (SNP) is associated with simple FS of sporadic occurrence. The balance between pro- and antiinflammatory cytokines influences the regulation of infections and could, therefore, play a role in the pathogenesis of FS. Here, to determine whether pro- and antiinflammatory cytokine genes are responsible for the susceptibility to FS, we have performed an association study on functional SNPs of cytokine genes in FS patients and controls.

METHODS

The promoter SNPs of four inflammatory cytokine genes (IL6 -572C/G, IL8 -251A/T, IL10 -592A/C and TNFA -1037C/T) were examined in 249 patients with FS (186 simple and 63 complex FS) and 225 controls. Because the IL10 -592 SNP showed a positive association with FS, two additional SNPs (IL10 -1082A/G and -819T/C) were subjected to haplotype analysis. Furthermore, we examined the in vivo role of IL-10 in hyperthermia-induced seizures using immature animal models.

RESULTS

The frequencies of the IL10 -592C allele and -1082A/-819C/-592C haplotype were significantly decreased in FS as compared with in controls (p = 0.014 and 0.013, respectively). The seizure threshold temperature in the IL-10-administered rats was significantly higher than that in the saline-treated control ones (p = 0.027).

CONCLUSIONS

The present study suggests that IL-10 is genetically associated with FS and, contrary to IL-1beta, confers resistance to FS.

Toll-like receptors in neurodegeneration

The key roles of toll-like receptors (TLRs) as mediators of the detection and responses of immune cells to invading pathogens are well known. There are at least 13 mammalian TLRs which are integral membrane proteins with a leucine-rich extracellular domain and a cytoplasmic domain similar to that of the interleukin-1 receptor which initiates downstream signaling through kinases to activate transcription factors such as AP-1 and NFkappaB. TLRs are activated in glial cells (microglia, astrocytes and oligodendrocytes) and lymphocytes that infiltrate the nervous system in response to inflammation caused by infectious agents, tissue injury or autoimmune conditions. By inducing the production of pro-inflammatory cytokines and cell adhesion molecules in immune cells, TLRs may indirectly damage neurons in conditions such as ischemic stroke and multiple sclerosis. Recent findings suggest that neurons also express a subset of TLRs and that their activation promotes neuronal degeneration in experimental models of stroke and Alzheimer's disease. TLRs may also play roles in regulating the processes of neurogenesis and neurite outgrowth, suggesting roles in neuronal plasticity. A better understanding of the molecular and cellular biology of TLRs in the normal and diseased nervous system, may lead to novel approaches for preventing neuronal degeneration and promoting recovery of function in an array of neurodegenerative conditions.

Effect of treatment with methylprednisolone on the serum levels of IL-12, IL-10 and CCL2 chemokine in patients with multiple sclerosis in relapse

OBJECTIVES

Interleukin-12 (IL-12), a proinflammatory cytokine produced by Th1 cells, and interleukin-10 (IL-10), a product of Th2 cells, are involved in the pathogenetic mechanisms of multiple sclerosis (MS). CCL2 chemokine expression is induced by Th2 cytokines and is decreased in MS relapse. The mechanisms responsible for the beneficial effects of IVmethylprednisolone in attacks are not clearly established and the duration of the effect of this treatment remains controversial.

PATIENTS AND METHODS

We measured by enzyme-like immunosorbent assay (ELISA) serum levels of IL-12, IL-10 and CCL2 before, 5 days and 1 month after the initiation of treatment with IVMP in 20 patients with MS in relapse.

RESULTS

A significant increase of IL-10 and decrease of CCL2 serum levels was observed (p=0.0028 and 0.045 respectively) five days after the onset of steroid treatment but not after one month. Steroid treatment had no influence in serum levels of IL-12.

CONCLUSIONS

The clinical improvement of our MS patients with relapse following the treatment with methylprednisolone may be associated with an immediate but not a long-term modification of serum levels of IL-10 and CCL2. IL-12 may not be influenced by steroid treatment.

Interleukin-10 gene polymorphism in Parkinson's disease patients

BACKGROUND

The etiology of sporadic Parkinson's disease (PD) is not well established. Recent studies revealed that inflammatory processes might also play an important role in the pathogenesis of PD. We hypothesized that genetically determined differences in the immune response, especially in anti-inflammatory cytokines production, might influence the risk of sporadic PD development and/or onset. To prove this hypothesis, two DNA polymorphisms at IL-10 promoter (-1082 and -519) were examined in sporadic PD patients.

METHODS

The study enrolled 341 patients with diagnosed idiopathic PD. All cases of secondary parkinsonism were excluded from the study. For the purpose of this study the patients were also divided into two subgroups: group 1: patients with onset of Parkinson's disease, i.e., <50 years of age (early onset) included 60 patients, as well as group 2: patients with onset of Parkinson's disease >50 years of age (late onset) comprising 281 subjects. Control samples were from 315 randomly selected healthy individuals from the same geographical region who were free from signs of parkinsonism as evaluated by consultant neurologists. PCR-RFLP methods were used for genotyping.

RESULTS

No statistically significant differences between PD patients and controls were found in the frequency of a single locus (-1082, -519) of IL-10 promoter. Likewise, haplotype analysis did not demonstrate any significant differences between evaluated groups. The frequency of the evaluated IL-10 genotypes was also similar in EOPD and LOPD patients.

CONCLUSIONS

Results from our study revealed that the IL-10 (-1082G>A, -592C>A) polymorphism is not a risk factor of sporadic Parkinson's disease in a Polish population.

Dysregulated interferon-gamma responses during lethal cytomegalovirus brain infection of IL-10-deficient mice

Murine cytomegalovirus (MCMV) brain infection induces a transient increase in chemokine production, which precedes the infiltration of CD3(+) lymphocytes. In this study, we hypothesized that an absence of anti-inflammatory cytokines would result in sustained proinflammatory neuroimmune responses. Direct intracerebroventricular injection of MCMV into IL-10 knockout (KO) mice produced an unexpected result: while wild-type animals controlled MCMV, the infection was lethal in IL-10 KO animals. Identical infection of IL-4 KO animals did not produce lethal disease. To further characterize the role of IL-10, infected brain tissue from both wild-type and IL-10 KO animals was assessed for cytokine and chemokine levels, as well as viral gene expression. These data show vastly elevated levels of interferon (IFN)-gamma, and the IFN-gamma-inducible chemokines CXCL9 and CXCL10, as well as IL-6 in brain homogenates obtained from IL-10 KO animals. However, MCMV viral load, glycoprotein B mRNA levels, and titers of infectious virus were similar in both IL-10 KO and wild-type animals. Separation of cells isolated from murine brain tissue into distinct populations using FACS, along with subsequent quantitative RT real-time PCR, showed that brain-infiltrating CD45(hi)/CD11b(-) and CD45(hi)/CD11b(int) were the cellular source of IL-10 in the brain. Taken together, these data demonstrate that MCMV brain infection of IL-10-deficient mice causes lethal disease, which occurs in the presence of a dysregulated IFN-gamma-mediated neuroimmune response.

Rasmussen's encephalitis: interleukin-10-dependent Tc2 cell polarization may explain its pathophysiology and clinical course

Little is known about the cellular immune dynamics and pathophysiology of Rasmussen's encephalitis (RE). We investigated transcriptional expression of pro- and anti-inflammatory cytokines and characterized the T-cell subset types present in temporal and frontal lobe specimens obtained from a child with RE. Interleukin (IL)-10 and macrophage scavenger receptor type I mRNA assessed by semiquantitative reverse transcription polymerase chain reaction was found in temporal but not in affected frontal lobe tissue. Messenger RNA specific to tumor necrosis factor alpha, IL-l, IL-4, IL-6, IL-12, IL-15, IL-18, transforming growth factor beta, CD-14, and inducible nitric oxide synthase was not detected in either temporal or frontal tissue with histopathologically manifest evidence of disease. Virtually all lymphocytic infiltrate consisted of CD3+ CD8+ T cells. We speculate that RE is a disease mediated by Tc2 polarization of the immune response and that its immunohistopathology, natural history, and clinical evolution (chronic, staircase progression) reflect the dual/pleiotropic actions of IL-10, which, depending on the state of activation of the immune system, may be either cytolytic or immunosuppressant.

Calprotectin in microglia from frontal cortex is up-regulated in schizophrenia: evidence for an inflammatory process?

Schizophrenia is associated with a number of pathological changes, including alterations in levels of specific proteins. Calprotectin is a novel 36 kDa calcium-binding protein of the S100 family and appears to be a nonspecific marker of inflammation. Calprotectin has not previously been investigated in brain tissue. Samples of post-mortem brain tissue from Brodmann area 9 were obtained from prefrontal cortex from subjects with schizophrenia, bipolar affective disorder, major depression, and from controls. Calprotectin levels were determined by ELISA. To determine cellular localization, immunocytochemical and fluorescent double-labelling analyses were performed. Exogenous calprotectin was added to retinoic acid-differentiated human SH-SY5Y neuroblastoma cell cultures in order to investigate mechanisms of action of calprotectin. Calprotectin was detectable in all samples, and mean levels were noted to be highest in schizophrenic brains (P < 0.05) and lowest in controls. Levels were intermediate in bipolar affective disorder and major depression. Exogenous calprotectin appeared to induce dendritic extension in SH-SY5Y cell culture in a dose-dependent manner. Calprotectin was found to be localized to microglia. These findings suggest that increased levels of calprotecitn in the brain may reflect inflammatory processes, which play a role in the pathogenesis of major psychiatric disorders. Furthermore, calprotectin may influence dendritic plasticity.

Murine glia express the immunosuppressive cytokine, interleukin-10, following exposure toBorrelia burgdorferi orNeisseria meningitidis

There is growing appreciation that resident glial cells can initiate and/or regulate inflammation following trauma or infection in the central nervous system (CNS). We have previously demonstrated the ability of microglia and astrocytes, resident glial cells of the CNS, to respond to bacterial pathogens by rapid production of inflammatory mediators. However, inflammation within the brain parenchyma is notably absent during some chronic bacterial infections in humans and nonhuman primates. In the present study, we demonstrate the ability of the immunosuppressive cytokine, interleukin-10 (IL-10), to inhibit inflammatory immune responses of primary microglia and astrocytes to B. burgdorferi and N. meningitidis, two disparate gram negative bacterial species that can cross the blood-brain barrier in humans. Importantly, we demonstrate that these organisms induce the delayed production of significant quantities of IL-10 by both microglia and astrocytes. Furthermore, we demonstrate that such production occurs independent of the actions of bacterial lipopolysaccharide and is secondary to the autocrine or paracrine actions of other glia-derived soluble mediators. The late onset of IL-10 production by resident glia following activation, the previously documented expression of specific receptors for this cytokine on microglia and astrocytes, and the ability of IL-10 to inhibit bacterially induced immune responses by these cells, suggest a mechanism by which resident glial cells can limit potentially damaging inflammation within the CNS in response to invading pathogens, and could explain the suppression of inflammation seen within the brain parenchyma during chronic bacterial infections.

A pro- and an anti-inflammatory cytokine are synthesised in distinct brain macrophage cells during innate activation

Brain macrophages are known to exert dual and opposing functions on neuronal survival, which can be either beneficial or detrimental. The rationale of our study is that this duality could arise from an exclusive secretion of either pro- or anti-inflammatory cytokine by distinct cell subsets, cytokines that could respectively mediate neurotoxic or neurotrophic effects. Innate immune response was induced in macrophage cultures prepared from embryonic-day-16 to postnatal-day-8 mouse brains. By immunofluorescent detection of intracellular cytokines, we have assessed the occurrence of TNFalpha or IL10 synthesis at single cell level and observed distinct secretory patterns that include cells producing exclusively TNFalpha or IL10, cells producing both cytokines and non-producer cells. These secretory patterns are differentially regulated by MAP-kinase inhibitors. Altogether, these results demonstrate that synthesis of either a pro- or an anti-inflammatory cytokine can segregate distinct brain macrophages and suggests a functional cell-subset-specialisation.

Microglia and multiple sclerosis

Microglia participate in all phases of the multiple sclerosis (MS) disease process. As members of the innate immune system, these cells have evolved to respond to stranger/danger signals; such a response within the central nervous system (CNS) environment has the potential to induce an acute inflammatory response. Engagement of Toll-like receptors (TLRs), a major family of pattern-recognition receptors (PRRs), provides an important mechanism whereby microglia can interact with both exogenous and endogenous ligands within the CNS. Such interactions modulate the capacity of microglia to present antigens to cells of the adaptive immune system and thus contribute to the initiation and propagation of the more sophisticated antigen-directed responses. This inflammatory response introduces the potential for bidirectional feedback between CNS resident and infiltrating systemic cells. Such interactions acquire particular relevance in the era of therapeutics for MS because the infiltrating cells can be subjected to systemic immunomodulatory therapies known to change their functional properties. Phagocytosis by microglia/macrophages is a hallmark of the MS lesion; however, the extent of tissue damage and the type of cell death will dictate subsequent innate responses. Microglia/macrophages are armed with a battery of effector molecules, such as reactive nitrogen species, that may contribute to CNS tissue injury, specifically to the injury of oligodendrocytes that is associated with MS. A therapeutic challenge is to modulate the dynamic properties of microglia/macrophages so as to limit potentially damaging innate responses, to protect the CNS from injury, and to promote local recovery.

Investigations with cultured human microglia on pathogenic mechanisms of Alzheimer's disease and other neurodegenerative diseases

Inflammation-mediated mechanisms for human neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD) have evolved from being on the fringe of medical hypotheses to mainstream thinking. Pioneering immunopathology studies with human brain tissues identified microglia associated with neuropathologic hallmarks of these diseases. As activated macrophages were known to produce many potential toxic products, this gave rise to the hypothesis that activated microglia (brain resident macrophages) could be contributing to the degeneration of key target neurons in these diseases, as well as potential vascular dysfunction. Studies with microglia derived from different sources, including human brains, have confirmed that activated microglia can mediate neuronal cell death. Based on these theories, a number of human clinical trials with antiinflammatory agents have been carried out on AD patients. Results to date have indicated a lack of effectiveness at slowing disease progression and have begun to cast doubt on the significance of inflammation in AD. It has been shown recently that activating microglia through immunization of amyloid plaque-developing mice with amyloid beta peptide (Abeta) has promise as a therapeutic strategy and despite some setbacks, has potential as a treatment for AD patients. This article will consider experimental data with microglia to determine whether the additional targets need to be investigated. The use of human microglia cultures, in particular those derived from elderly diseased human brains, offers an experimental system that can closely model the cell type activated in human neurodegenerative diseases. Experimental data produced by our laboratory and others is reviewed to determine the contribution of this unique experimental model to understanding disease mechanisms and possibly discovering new therapeutic targets.

Immunosenescence and macrophage functional plasticity: dysregulation of macrophage function by age-associated microenvironmental changes

The macrophage lineage displays extreme functional and phenotypic heterogeneity, which appears to be because, in large part, of the ability of macrophages to functionally adapt to changes in their tissue microenvironment. This functional plasticity of macrophages plays a critical role in their ability to respond to tissue damage and/or infection and to contribute to clearance of damaged tissue and invading microorganisms, to recruitment of the adaptive immune system, and to resolution of the wound and of the immune response. Evidence has accumulated that environmental influences, such as stromal function and imbalances in hormones and cytokines, contribute significantly to the dysfunction of the adaptive immune system. The innate immune system also appears to be dysfunctional in aged animals and humans. In this review, the hypothesis is presented and discussed that the observed age-associated 'dysfunction' of macrophages is the result of their functional adaptation to the age-associated changes in tissue environments. The resultant loss of orchestration of the manifold functional capabilities of macrophages would undermine the efficacy of both the innate and adaptive immune systems. The macrophages appear to maintain functional plasticity during this dysregulation, making them a prime target of cytokine therapy that could enhance both innate and adaptive immune systems.

Role of microglia in central nervous system infections

The nature of microglia fascinated many prominent researchers in the 19th and early 20th centuries, and in a classic treatise in 1932, Pio del Rio-Hortega formulated a number of concepts regarding the function of these resident macrophages of the brain parenchyma that remain relevant to this day. However, a renaissance of interest in microglia occurred toward the end of the 20th century, fueled by the recognition of their role in neuropathogenesis of infectious agents, such as human immunodeficiency virus type 1, and by what appears to be their participation in other neurodegenerative and neuroinflammatory disorders. During the same period, insights into the physiological and pathological properties of microglia were gained from in vivo and in vitro studies of neurotropic viruses, bacteria, fungi, parasites, and prions, which are reviewed in this article. New concepts that have emerged from these studies include the importance of cytokines and chemokines produced by activated microglia in neurodegenerative and neuroprotective processes and the elegant but astonishingly complex interactions between microglia, astrocytes, lymphocytes, and neurons that underlie these processes. It is proposed that an enhanced understanding of microglia will yield improved therapies of central nervous system infections, since such therapies are, by and large, sorely needed.

Lipopolysaccharide/interferon-gamma and not transforming growth factor beta inhibits retinal microglial migration from retinal explant

BACKGROUND

/aims: The retina possesses a rich network of CD45(+) positive myeloid derived cells that both surround inner retinal vessels and lie within the retina (microglia). Microglia migrate and accumulate in response to neurodegeneration and inflammation. Although microglia express MHC class II, their role remains undefined. The aims of this study are to investigate changes in human microglia phenotype, migration, and activation status in response to pro-inflammatory and anti-inflammatory stimulation.

METHODS

Donor eyes were obtained from the Bristol Eye Bank with consent and whole retina was removed. 5 mm retinal trephines were cultured in glucose enhanced RPMI on cell culture insert membranes for up to 72 hours. The effects of lipopolysaccharide/interferon-gamma (LPS/IFNgamma) and transforming growth factor beta inhibits (TGFbeta) stimulation, alone or in combination, on migration, phenotype, and activation status (iNOS expression) of microglia were studied using immunofluorescence and cytokine analysis by ELISA.

RESULTS

CD45(+) MHC class II(+) retinal microglia were observed within retinal explants, and in culture microglia readily migrated, adhered to culture membrane, downregulated MHC class II expression, and produced interleukin 12 (IL-12) and tumour necrosis factor alpha (TNFalpha). Following LPS/IFNgamma stimulation microglia remained MHC class II(-) iNOS(-), and secreted IL-10. Migration was suppressed and this could be reversed by neutralising IL-10 activity. TGFbeta did not affect ability of microglia to migrate and was unable to reverse LPS/IFNgamma induced suppression.

CONCLUSIONS

Microglia readily migrate from retinal explants and are subsequently MHC class II(-), iNOS(-), and generate IL-12. In response to LPS/IFNgamma microglia produce IL-10, which inhibits both their migration and activation. TGFbeta was unable to counter LPS/IFNgamma effects. The data infer that microglia respond coordinately, dependent upon initial cytokine stimulation, but paradoxically respond to classic myeloid activation signals.

Differential effects of Th1 and Th2 lymphocyte supernatants on human microglia

We assessed the effects of soluble molecules (supernatants) produced by pro- (Th1) and anti- (Th2) inflammatory T-cell lines on the capacity of adult human CNS-derived microglia to express or produce selected cell surface and soluble molecules that regulate immune reactivity or impact on tissue protection/repair within the CNS. Treatment of microglia with supernatants from allo-antigen and myelin basic protein-specific Th1 cell lines augmented expression of cell surface molecules MHC class II, CD80, CD86, CD40, and CD54, enhanced the functional antigen-presenting cell capacity of microglia in a mixed lymphocyte reaction, and increased cytokine/chemokine secretion (TNFalpha, IL-6, and CXCL10/IP-10). These Th1-induced effects were not reproduced by interferon-gamma (IFNgamma) alone and were only incompletely blocked by anti-IFNgamma antibody. Th2 cell supernatant treatments did not alter costimulatory/adhesion molecule expression or induce cytokine/chemokine production by microglia. Th2 treatment, furthermore, failed to reduce the induction observed in response to Th1 supernatants. Neither Th1 nor Th2 supernatants induced production of the neurotrophin molecules, nerve growth factor, or brain-derived neurotrophic factor. Our results suggest that soluble molecules released by Th1 and not Th2 cells that infiltrate the CNS can stimulate resident microglia to acquire enhanced effector and accessory cell functions; the Th1-induced effects were not downregulated by Th2 supernatant-mediated bystander suppression.

Hypothermia suppresses inducible nitric oxide synthase and stimulates cyclooxygenase-2 in lipopolysaccharide stimulated BV-2 cells

Hypothermia is neuroprotective, possibly through suppression of microglial activation. We investigated the effects of hypothermia on lipopolysaccharide (LPS) stimulated BV-2 cells. At 37 degrees C, LPS elicited strong increases in inducible nitric oxide synthase (iNOS), nitric oxide (NO), cyclooxygenase-2 (COX-2), tumour necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6), accompanied by translocation of nuclear factor-kappaB (NF-kappaB) to the nucleus. Hypothermia (33 degrees C) caused complete suppression of iNOS and NO, a partial reduction of IL-6 but did not prevent TNF-alpha production or NF-kappaB translocation. In contrast, LPS induced cyclooxygenase-2 (COX-2) to higher levels under hypothermic conditions. These results show that hypothermia selectively suppresses iNOS in microglia.

Expression and regulation of interleukin-10 and interleukin-10 receptor in rat astroglial and microglial cells

Activated glial cells crucially contribute to brain inflammatory responses. Interleukin-10 (IL-10) is an important modulator of glial cell responses in the brain. In the present study we describe the expression of IL-10 and the IL-10 receptor (IL-10R1) in primary cocultures of rat microglial and astroglial cells. Using quantitative RT-PCR and ELISA, we show that IL-10 mRNA expression and subsequent IL-10 secretion is time-dependently induced by lipopolysaccharide (LPS). IL-10R1, however, is constitutively expressed in glial cell cocultures, as shown by RT-PCR and immunocytochemistry. Radioligand binding studies using 125I-IL-10 reveal that rat glial cells express a single binding site with an apparent affinity of approximately 600 pm for human IL-10. Observations in enriched cultures of either microglial or astroglial cells indicate that both cell types express IL-10 mRNA and are capable of secreting IL-10. Both cell types also express IL-10R1 mRNA and protein. However, in glial cell cocultures immunoreactive IL-10R1 protein is predominantly observed in astrocytes, suggesting that microglial expression of IL-10R1 in cocultures is suppressed by astrocytes. In addition, exogenous IL-10 is highly potent in down-regulating LPS-induced IL-1beta and IL-10 mRNA, and, at a higher dose, IL-10R1 mRNA in untreated and LPS-treated cultures, suggesting that IL-10 autoregulates its expression and inhibits that of IL-1beta at the transcriptional level. Together the findings support the concept that IL-10, produced by activated microglial and astroglial cells, modulates glia-mediated inflammatory responses through high-affinity IL-10 receptors via paracrine and autocrine interactions.

Cytokines, chemokines, and cytokine receptors in human microglia

Enriched populations of human microglial cells were isolated from mixed cell cultures prepared from embryonic human telencephalon tissues. Human microglial cells exhibited cell type-specific antigens for macrophage-microglia lineage cells including CD11b (Mac-1), CD68, B7-2 (CD86), HLA-ABC, HLA-DR and ricinus communis aggulutinin lectin-1 (RCA-1), and actively phagocytosed latex beads. Gene expression and protein production of cytokines, chemokines and cytokine/chemokine receptors were investigated in the purified populations of human microglia. Normal unstimulated human microglia expressed constitutively mRNA transcripts for interleukin- 1beta (IL-1beta) -6, -8, -10, -12, -15, tumor necrosis factor-alpha (TNF-alpha), macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-1beta, and monocyte chemoattractant protein-1 (MCP-1), while treatment with lipopolysaccharide (LPS) or amyloid beta peptides (Abeta) led to increased expression of mRNA levels of IL-8, IL-10, IL-12, TNF-alpha, MIP-1alpha, MIP-1beta, and MCP-1. Human microglia, in addition, expressed mRNA transcripts for IL-1RI, IL-1RII, IL-5R, IL-6R, IL-8R, IL-9R, IL-10R, IL-12R, IL-13R, and IL-15R. Enzyme-linked immunosorbent assays (ELISA) showed increased protein levels in culture media of IL-1beta, IL-8, TNF-alpha, and MIP-1alpha in human microglia following treatment with LPS or Abeta. Increased TNF-alpha release from human microglia following LPS treatment was completely inhibited with IL-10 pretreatment, but not with IL-6, IL-9, IL-12, IL-13, or transforming growth factor-beta (TGF-beta). Present results should help in understanding the basic microglial biology, but also the pathophysiology of activated microglia in neurological diseases such as Alzheimer disease, Parkinson disease, Huntington disease, amyotrophic lateral sclerosis, stroke, and neurotrauma.

Thrombin induces IL-10 production in microglia as a negative feedback regulator of TNF-alpha release

Interleukin-10 (IL-10), an immunosuppressive cytokine, is produced by monocyte/macrophage lineage cells, T cells, and B cells in the immune system. Here, we show that thrombin induces IL-10 expression in cultured rat microglia. Thrombin treatment increases IL-10 mRNA expression after 3 h and IL-10 release into the culture medium 12 h after thrombin treatment. Neutralizing antibodies against IL-10 significantly enhanced TNF-alpha release from thrombin-treated microglia. IL-10 release was suppressed by an inhibitor of p38 MAPK, SB203580 but not by an inhibitor of ERK pathway, PD98059, whereas both SB203580 and PD98059 inhibited TNF-alpha release. These results suggest that thrombin induces IL-10 and TNF-alpha expression through different signaling mechanisms, and that IL-10 inhibits TNF-alpha release as a negative feedback regulation.

Inflammation and stroke: the Leiden 85-Plus Study

BACKGROUND

Experimental evidence indicates that interleukin-10 (IL-10) deficiency is associated with the development of cardiovascular and cerebrovascular disease. We analyzed the relation between low IL-10 production levels, history of stroke, and incident fatal stroke.

SUMMARY OF REPORT

All 85-year-old inhabitants of Leiden, Netherlands (n=599) were visited at their place of residence (response rate, 87%). Production levels of the anti-inflammatory cytokine IL-10 were assessed in a whole blood assay whereby lipopolysaccharide was used as a stimulus. Plasma concentrations of C-reactive protein (CRP) were also used as a marker of inflammation. A history of stroke was obtained at baseline (prevalence, 10%). The number of fatal strokes was prospectively obtained for a median follow-up of 2.6 years (incidence, 1.82 per 100 person-years at risk). Subjects with a history of stroke had significantly lower median IL-10 production levels at baseline than subjects without stroke (558 versus 764 pg/mL; P<0.05). They also had significantly higher median CRP concentrations (6 versus 3 mg/L; P<0.05). The odds ratio for a history of stroke increased to 2.30 (95% CI, 1.12 to 4.72) over strata representing decreasing production levels of IL-10. The relative risk for incident fatal stroke was 2.94 (95% CI, 1.01 to 8.53) when we compared subjects with low or intermediate baseline IL-10 production levels to those with high production levels of IL-10.

CONCLUSIONS

Our data support the hypothesis that subjects with low IL-10 production levels have an increased risk of stroke.

Association between promoter polymorphic haplotypes of interleukin-10 gene and schizophrenia

BACKGROUND

Schizophrenia is one of the most severe psychiatric disorders, with a worldwide incidence of 1%. Several reports show abnormal cytokine levels in psychotic patients and indicate a possible role of the immune response system in the pathogenesis of schizophrenia. Increased concentrations of interleukin 10 (IL-10) have been found in plasma of schizophrenic patients, suggesting its potential role as a candidate gene for susceptibility to schizophrenia. IL-10 gene maps on chromosome 1 (q31-q32), a locus associated with genetic susceptibility to schizophrenia. Three functional haplotypes of the gene (GCC, ACC, ATA) have been described, derived from different combinations of three "single nucleotide polymorphisms" and directly related to the expression levels of the protein.

METHODS

We analyzed allele, genotype, and haplotype distributions in an association case-control study involving 106 schizophrenic patients and 143 unrelated healthy volunteers using polymerase chain reaction (PCR)-Single Strand Conformation Polymorphism and PCR Restriction Fragment Length Polymorphism methods.

RESULTS

Our results show a significant increase of GCC homozygotes (the high IL-10-producing haplotype) in schizophrenic patients compared to control subjects (chi(2) = 13, p =.023; odds ratio = 3.03; 95% confidence interval, 1.274-7.355).

CONCLUSIONS

These data could partly explain the abnormal secretion of IL-10 occurring in schizophrenic patients in response to infections or different stressors and suggest a potential role of IL-10 as a candidate gene for susceptibility to schizophrenia.