Multinucleated giant cell formation by microglia: induction by interleukin (IL)-4 and IL-13

To investigate the cellular origin and the mechanisms of multinucleated giant cell (MGC) formation in the CNS, various cytokines were applied to isolated murine microglia. All the single cytokines failed to induce MGC. However, interleukin (IL)-13 and IL-4 induced microglial MGC formation in the presence of colony stimulating factors, which was inhibited by either anti-IL-13 or anti-fms antibody. T helper 2 (Th2)-derived cytokines can induce MGC formation even in the absence of infectious agents.     

Inter-relation between Interleukin (IL)-1, IL-6 and Body Fat Regulating Circuits of the Hypothalamic Arcuate Nucleus

Interleukin (IL)-1 and IL-6 are immune modulating cytokines that also affect metabolic function because both IL-1 receptor I deficient (IL-1RI^−/−) and IL-6 deficient (IL-6^−/−) mice develop late-onset obesity and leptin resistance. Both IL-1 and IL-6 appear to target the central nervous system (CNS) to increase energy expenditure. The hypothalamic arcuate nucleus (ARC) is a major relay between the periphery and CNS in body fat regulation (e.g. by being a target of leptin). The present study aimed to investigate the possible mechanisms responsible for the effects exerted by endogenous IL-1 and IL-6 on body fat at the level of the ARC, as well as possible interactions between IL-1 and IL-6. Therefore, we measured the gene expression of neuropeptides of the ARC involved in energy balance in IL-1RI^−/− and IL-6^−/− mice. We also investigated the interactions between expression of IL-1 and IL-6 in these mice, and mapped IL-6 receptor α (IL-6Rα) in the ARC. The expression of the obesity promoting peptide neuropeptide Y (NPY), found in the ARC, was increased in IL-1RI^−/− mice. The expression of NPY and agouti-related peptide (AgRP), known to be co-expressed with NPY in ARC neurones, was increased in cold exposed IL-6^−/− mice. IL-6Rα immunoreactivity was densely localised in the ARC, especially in the medial part, and was partly found in NPY positive cell bodies and also α-melanocyte-stimulating hormone positive cell bodies. The expression of hypothalamic IL-6 was decreased in IL-1RI^−/− mice, whereas IL-1ß expression was increased in IL-6^−/− mice. The results of the present study indicate that depletion of the activity of the fat suppressing cytokines IL-1 and IL-6 in knockout mice can increase the expression of the obesity promoting neuropeptide NPY in the ARC. Depletion of IL-1 activity suppresses IL-6 expression, and IL-6Rα-like immunoreactivity is present in neurones in the medial ARC, including neurones containing NPY. Therefore, IL-6, IL-1 and NPY/AgRP could interact at the level of the hypothalamic ARC in the regulation of body fat.     

Interleukin (IL)-6 and IL-1 beta act synergistically within the brain to induce sickness behavior and fever in rats

Pro-inflammatory cytokines interleukin (IL)-6 and IL-1β can act in the brain (centrally) to cause fever. Sickness behaviors which accompany fever also appear to involve the central action of IL-1β. We injected species-homologous rat IL-6 and IL-1β directly into the brains of conscious rats to examine the effect of these cytokines on fever, and two behaviors affected by sickness, voluntary wheel-running and food intake. Male Sprague–Dawley rats selected for their predisposition to spontaneously run on running wheels were used in the experiment. Each rat was anaesthetized and had a temperature-sensitive radiotransmitter implanted intra-abdominally, and a 23-gauge stainless steel guide cannula inserted stereotaxically over the lateral cerebral ventricle. Rats were randomly assigned to receive intracerebroventricular injections of three doses of either IL-1β or IL-6 (100 ng, 1 ng or 0.1 ng IL-1β and 200 ng, 20 ng or 2 ng IL-6), or one of three different combinations of IL-1β and IL-6. Rats receiving either IL-1β or IL-6 showed a dose-dependent increase in body temperature and decrease in wheel-running (ANOVA, p < 0.0001). Only rats receiving the highest dose of IL-1β significantly decreased food intake and body mass compared to rats receiving vehicle (ANOVA, p < 0.001). Doses of IL-1β and IL-6 which, when injected on their own were non-pyrogenic and did not affect food intake and body mass, induced fever and anorexia when they were co-injected centrally. These results show that species-homologous rat IL-6 and IL-1β can act directly within the brain to decrease voluntary activity and suggest they also can act synergistically to induce anorexia and fever.     

TNF alpha induces IL-6 production by astrocytes but not by microglia.

Astrocytes and microglia, both produced interleukin-6 (IL-6) in culture by lipopolysaccharide (LPS) stimulation. IL-6 activity was detected 3-5 h after LPS stimulation and reached a maximum at 10 h. Microglia responded faster than astrocytes. Tumor necrosis factor alpha and interleukin 1 also induced IL-6 mRNA and biological activity in astrocytes, but not in microglia. Among these stimuli, LPS was the most potent inducer of IL-6 production by astrocytes. Our results suggest that different regulatory mechanisms for cytokine production exist in glial cells. The possible roles of astrocytes and microglia in CNS immune responses are also discussed.     

Interleukin (IL)-1beta-mediated apoptosis of human astrocytes.

Apoptosis of brain cells is observed in many inflammatory disorders of the central nervous system. Nitric oxide (NO) has been shown to induce apoptosis in several brain cell types, but not previously in astrocytes. In the present study, the hypothesis was examined that interleukin (IL)-1beta would induce production of NO by astrocytes which, in turn, would signal apoptotic death in these glial cells. TUNEL staining demonstrated apoptosis in astrocytes treated with IL-1beta. Using an ELISA method, IL-1 receptor antagonist protein completely abrogated this astrocyte apoptosis, while N(G)monomethyl-L-arginine partially prevented apoptosis but almost entirely blocked NO production. Thus, IL-1beta appears to signal apoptosis of astrocytes by a mechanism involving, in part, the induction of NO.     

Regulation of IL-10 expression by upstream stimulating factor (USF-1) in glioma-associated microglia

Understanding the local CNS immune response to neoplasms is essential in the development of immune-based treatments for malignant brain tumors. Using rodent glioma models, we have recently found tumor-associated microglia/macrophages (MG/MP) to be less responsive to known MG/MP activators such as CpG, LPS and IFN-gamma. To understand the mechanism of MG/MP suppression, nuclear extracts from rodent intracranial C6 gliomas, C6 glioma-associated MG/MP, normal brain, and normal MG/MP were obtained and studied using Electrophoretic Mobility Shift Assay (EMSA). Among the nuclear factors studied (AP-1, IRF, USF-1 and Stat-1) only USF-1, which is constitutively expressed in most cells, was down-regulated in tumor-associated MG/MP, but not normal MG/MP. Because tumor-associated MG/MP had higher expression of IL-10 (but not TNF-alpha or TGF-beta), we evaluated the role of USF-1 on IL-10 expression. siRNA mediated inhibition of USF-1 expression in primary MG/MP cultures resulted in up-regulation of IL-10 mRNA but not TNF-alpha or TGF-beta. These findings suggest that USF-1 may play a role in IL-10 regulation in MG/MP in brain tumors.     

Vasoactive intestinal peptide inhibits interleukin (IL)-2 and IL-4 production in murine thymocytes activated via the TCR/CD3 complex

During their development in the thymus, T cells acquire interleukin (IL)-2 and IL-4 inducibility in a developmentally controlled manner. Although the role of IL-2 and IL-4 in T cell development is still unclear, several reports indicated that IL-2/IL-2R and IL-4/IL-4R interactions in the thymus could play an important role in T cell development. The presence of vasoactive intestinal peptide (VIP)-immunoreactive cells and nerve fibers in the thymus suggests the possible local release of the neuropeptide in the thymic microenvironment. VIP has been previously reported to inhibit IL-2 and IL-4 production, as well as the proliferation of mitogen- or antigen-stimulated peripheral T cells. Here we report on the effect of VIP on IL-2 and IL-4 production by and proliferation of murine thymocytes stimulated through the TCR/CD3 receptor. VIP inhibited both IL-2 and IL-4 production, as well as the proliferation of murine thymocytes in a dose-dependent and specific manner. Structurally related peptides such as secretin or glucagon had little or no inhibitory activity. The intact VIP molecule was inquired for the inhibitory effect, since amino- or carboxy-terminal fragments did not inhibit IL-2 production. The inhibitory effect of VIP was observed for VIP additions up to 12 h after the initiation of the cultures, and incubations longer than 3 h were required for maximum inhibitory effects. Through its downregulatory effect on IL-2 and IL-4 production, locally released VIP could potentially effect T cell development within the thymus.     

精神分裂症脑脊液细胞产生IL—6的研究

本研究在精神分裂症脑脊液细胞微量培养技术的基础上，应用ＥＬＩＳＡ双抗体夹心法检测了患者脑脊液中及培养的脑脊液细胞细胞产生ＩＬ－６的情况，实验结果表明，精神分裂症患者脑脊液细胞在ＰＨＡ刺激下，产生ＩＬ－６的能力明显增强，且与脑脊液细胞产生ＩｇＧ的功能密切相关。提示增高的ＩＬ－６引起的免疫调节紊乱和促发免疫损伤可能是精神分裂症致病因素之一。     

Spinal interleukin-6 (IL-6) inhibits nociceptive transmission following neuropathy

Interleukin-6 (IL-6) is a neuropoietic cytokine which is dramatically upregulated following peripheral nerve injury at the site of injury, in the dorsal root ganglion (DRG) and in the spinal cord. The functional effects of IL-6 in nociception in normal conditions and following nerve injury are unclear. Thus the aim of this study was to assess the effect of spinal IL-6 administration on nociceptive transmission in naive, sham-operated and neuropathic (spinal nerve ligation, SNL) rats using in vivo electrophysiology to elucidate the possible role of IL-6 in neuropathic pain. In anaesthetised rats, extracellular recordings were made from individual convergent dorsal horn neurones following electrical and natural (mechanical and thermal) stimulation of peripheral receptive fields. Exogenous spinal IL-6 (100-500 ng) had no significant effect on electrically evoked neuronal responses in naive rats. In contrast, following neuropathy, spinal IL-6 produced a dose-related inhibition of the electrically evoked C-fibre, initial C-fibre and measures of neuronal hyperexcitability (post discharge and wind-up). In addition, spinal IL-6 markedly inhibited mechanical neuronal responses in neuropathic rats. Higher doses of spinal IL-6 also inhibited, to a lesser degree, the initial C-fibre, post discharge and wind-up responses in sham-operated rats. These studies show that following nerve injury the actions of the cytokine alter so that spinal administration of IL-6 elicits anti-nociceptive effects not observed under normal conditions. Moreover, the inhibitory effects of IL-6 on C-fibre activity and neuronal hyperexcitability, suggest IL-6 to be a potential modulator of neuropathic pain.     

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.     

Interleukin (IL)1beta, IL-1alpha, and IL-1 receptor antagonist gene polymorphisms in patients with temporal lobe epilepsy

Proinflammatory cytokines, including interleukin (IL)-1beta, are known to modulate effects of neurotoxic neurotransmitters discharged during excitation or inflammation in the central nervous system (CNS). They also regulate development of glial scars at sites of CNS injury. To elucidate a genetic predisposition of temporal lobe epilepsy with hippocampal sclerosis (TLE-HS+), we studied polymorphisms in the IL-1beta, IL-1alpha, and IL-1 receptor antagonist (IL-1RA) genes in 50 patients with TLE-HS+ and in 112 controls. Fifty-three patients who had TLE without HS were also examined (TLE-HS-) as disease controls. The distribution of the biallelic polymorphism in the promoter region at position -511 of the IL-1beta gene (IL-1B-511) was significantly different both between TLE-HS+ patients and controls and between TLE-HS+ and TLE-HS- patients. The differences were due to overrepresentation of the homozygotes for IL-1B-511*2, which is suggested to be a high producer of IL-1beta, in TLE-HS+ patients compared with both controls and TLE-HS- patients. In contrast, there was no difference between TLE-HS- patients and controls. Our data suggest that, in the homozygotes for IL-IB-511*2, minor events in development such as febrile convulsions could set up a cascade leading to HS.     

Single-Nucleotide Polymorphisms in Interleukin 6 (IL-6) Gene Are Associated with Suicide Behavior in an Iranian Population

Previous association studies have demonstrated the association between immune regulatory genes and suicide behavior. Among these genes are those coding for cytokines. In the present study, we genotyped two interleukin 6 (IL-6) variants (rs2069845 and rs1800795) in 320 suicide attempters, 236 suicide completers, and 341 individuals without any history of psychiatric disorders or suicide ideation. The rs2069845 was not associated with suicide behavior. The rs1800795 C allele was significantly more common among suicide completers compared with suicide attempters (OR (95% CI)?=?1.33 (1.04–1.71)), adjusted P?=?0.04). Besides, the rs1800795 was associated with the lethality of suicide attempt in recessive model (adjusted P value?=?0.01). Consequently, the present study supports the role of IL-6 in suicide behavior and warrants further researches to confirm its effect and explain the underlying mechanism.     

Leptomeningeal cells activate microglia and astrocytes to induce IL-10 production by releasing pro-inflammatory cytokines during systemic inflammation

The leptomeninges covering the surface of the brain parenchyma play the physical role at the cerebrospinal fluid-blood barrier. We report here that leptomeningeal cells may transduce peripheral proinflammatory signals to the central anti-inflammatory response through the activation of glial cells in the brain parenchyma. After adjuvant injection, both microglia and astrocytes in the cerebral cortex localized in the proximity of the leptomeninges were activated. The protein levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10) in the cortical extracts were significantly increased at different time after adjuvant injection. The TNF-alpha immunoreactivity was most prominent in the leptomeninges covering astrocytes. On the other hand, the IL-10 immunoreactivity was observed in both activated microglia and astrocytes localized along the leptomeninges. Cultured leptomeningeal cells covering the cerebral cortex released TNF-alpha which was significantly increased by lipopolysaccharide (LPS). Upon stimulation with LPS, cultured leptomeningeal cells also secreted interleukin-1beta and interleukin-6 with differential time-courses. When primary cultured rat astrocytes and microglia were treated with the conditioned medium of LPS-activated cultured leptomeningeal cells, the immunoreactivity of IL-10 was markedly increased. These observations strongly suggest that leptomeningeal cells release pro-inflammatory cytokines to activate both microglia and astrocytes during systemic inflammation. The activated astrocytes and microglia may in turn regulate anti-inflammatory response in the brain by providing IL-10.     

IL-4, IL-10 and IL-13 modulate A beta(1--42)-induced cytokine and chemokine production in primary murine microglia and a human monocyte cell line

A hallmark of the immunopathology associated with Alzheimer's disease (AD) is the presence of activated microglia surrounding senile plaque deposits of beta-amyloid (A beta) peptides. A beta peptides have been shown to be potent activators of microglia and macrophages, but little is known about endogenous factors that may modulate their responses to amyloid. We investigated whether the 'anti-inflammatory' cytokines IL-4, IL-10 and IL-13 could regulate A beta-induced production of the inflammatory cytokines IL-1 alpha, IL-1 beta, TNF-alpha, IL-6 and the chemokine MCP-1. A beta(1-42) time- and dose-dependently induced the production and secretion of these inflammatory proteins in the human THP-1 monocyte cell line and in primary murine microglia, similar to what was observed for lipopolysaccharide (LPS) stimulated cells. IL-10 was found to suppress all A beta and LPS-induced inflammatory proteins measured (IL-1 alpha, IL-1 beta, IL-6, TNF-alpha and MCP-1) in both cell types with the exception of LPS-induced MCP-1 in THP-1 cells where no change was observed. In contrast to the inhibition observed for IL-10, both IL-4 and IL-13 enhanced MCP-1 secretion. IL-4 and IL-13 reduced IL-6 secretion, but effects on IL-1 alpha, IL-1 beta or TNF-alpha were dependent on cell type and stimulus conditions. Additional experiments using RT-PCR showed that IL-4, IL-10 and IL-13 mRNA is found to be present in human brain tissue. These results show that IL-4, IL-10, and IL-13 differentially regulate microglial responses to A beta and may play a role in the inflammation pathology observed surrounding senile plaques.     

Interleukin-10 attenuates production of HSV-induced inflammatory mediators by human microglia

Infection of the central nervous system (CNS) with herpes simplex virus (HSV)-1 initiates a rapidly progressive, necrotizing, and fatal encephalitis in humans. Even with the advent of antiviral therapy, effective treatments for HSV-1 brain infection are limited because the cause of the resulting neuropathogenesis is not completely understood. We previously reported that human microglial cells, while nonproductively infected, respond to HSV-1 by producing robust amounts of pro-inflammatory mediators, such as tumor necrosis factor(TNF), interleukin (IL)-1beta, CCL5 (RANTES), and CXCL10 (IP-10). Although initiation of immune responses by glial cells is an important protective mechanism in the CNS, unrestrained inflammatory responses may result in irreparable brain damage. To elucidate the potential immunomodulatory role of anti-inflammatory cytokines, we investigated the effects of IL-4, IL-10, and transforming growth factor (TGF)-beta on microglial cell cytokine and chemokine production in response to HSV-1. Results from these studies demonstrated a consistent IL-10-mediated suppression of TNF-alpha (60% +/- 2%), IL-1beta (68% +/- 3%), CCL5 (62 +/- 4%), but not CXCL10 production by HSV-1-infected microglial cells. This inhibition was associated with decreased HSV-1-induced activation of NF-kappaB. These results suggest that IL-10 has the ability to regulate microglial cell production of immune mediators and thereby, dampen the pro-inflammatory response to HSV-1.     

Serum levels of interleukin (IL)-18, IL-23 and IL-17 in Chinese patients with multiple sclerosis

It has been reported that cytokines play an important role in the pathogenesis of multiple sclerosis (MS). The aim of this study was to evaluate the serum levels of interleukin (IL)-18, IL-23 and IL-17 in Chinese patients with MS. We compared the serum concentrations of pro-inflammatory cytokines IL-18, IL-23 and IL-17 in 39 patients with MS and 39 healthy controls matched with sex and age. Serum cytokines were measured by FlowCytomix, a kind of cytometric bead-based assay. Correlations between the serum levels of the three cytokines and disability (expanded disability status scale, EDSS), disease duration, current age and age at onset were examined. Serum concentrations of all IL-18, IL-23 and IL-17 were significantly higher in MS patients than healthy controls. There were no significant differences of the three cytokines' levels between female and male healthy controls, while the serum IL-18 level was observed significantly higher (P=0.049) in male MS patients than female MS patients. No significant correlations were observed between any of the three cytokines' levels and EDSS, disease duration and current age. However, IL-23 was found negatively correlated with age at onset in male MS patients (r(s)=-0.775, P=0.041). Our data suggest that all IL-18, IL-23 and IL-17 may be involved in the pathogenesis of MS. However, the relationships of the three cytokines and clinical characteristics of MS need to be further investigated in the future.