Interleukin-4, interleukin-10, and interleukin-1-receptor antagonist but not transforming growth factor-beta induce ramification and reduce adhesion molecule expression of rat microglial cells

The activity of microglial cells is strictly controlled in order to maintain central nervous system (CNS) immune privilege. We hypothesized that several immunomodulatory factors present in the CNS parenchyma, i.e., the Th2-derived cytokines interleukin (IL)-4 and IL-10, interleukin-1-receptor-antagonist (IL-1-ra), or transforming growth factor (TGF)-beta can modulate microglial morphology and functions. Microglial cells were incubated with IL-4, IL-10, IL-1-ra, TGF-beta, or with astrocyte conditioned media (ACM) and were analyzed for morphological changes, expression of intercellular adhesion molecule (ICAM)-1, and secretion of IL-1beta or tumor necrosis factor (TNF)-alpha. Whereas untreated controls showed an amoeboid morphology both Th2-derived cytokines, IL-1-ra, and ACM induced a morphological transformation to the ramified phenotype. In contrast, TGF-beta-treated microglial cells showed an amoeboid morphology. Even combined with the neutralizing antibodies against IL-4, IL-10, or TGF-beta ACM induced microglial ramification. Furthermore, ACM did not contain relevant amounts of IL-4 and IL-10, as measured by enzyme-linked immunosorbent assay (ELISA). Flow cytometry showed that lipopolysaccharide (LPS)-induced ICAM-1-expression on microglial cells was strongly suppressed by ACM, significantly modulated by IL-4, IL-10, or IL-1-ra, but not influenced by TGF-beta. The LPS-induced secretion of IL-1beta and TNF-alpha was only reduced after application of ACM, whereas IL-4 or IL-10 did not inhibit IL-1beta- or TNF-alpha secretion. TGF-beta enhanced IL-1beta- but not TNF-alpha secretion. In summary, we demonstrate that IL-4, IL-10, and IL-1-ra induce microglial ramification and reduce ICAM-1-expression, whereas the secretion of proinflammatory cytokines is not prevented. TGF-beta has no modulating effects. Importantly, unidentified astrocytic factors that are not identical with IL-4, IL-10, or TGF-beta possess strong immunomodulatory properties.     

Inhibition of endotoxin-induced nitric oxide synthase production in microglial cells by the presence of astroglial cells: A role for transforming growth factor β

In mixed glial cell cultures from cerebral cortices of newborn rats, endotoxin induces inducible nitric oxide (iNOS), nitric oxide (NO), and interleukin-1β (IL-1β) production in microglial cells. Earlier we demonstrated that endotoxin induced iNOS but not IL-1β expression in microglial cells is inhibited by the presence of astroglial cells. In the present paper we describe studies on the mechanism by which astroglial cells exert selective suppressive action on iNOS expression by microglial cells. Expression of iNOS and IL-1β was studied by single or double label immunocytochemical techniques and cell identification was performed with GSA-I-B₄-isolectin and an antibody against GFAP. Production of IL-1β and NO was determined by measurement of IL-1β and nitrite concentrations in cell lysates and the culture medium, respectively. TGFβ, a cytokine known to inhibit NO production by endotoxin challenged macrophages, was measured in culture medium of mixed glial cell cultures using a bioassay. Microglial, astroglial, and mixed glial cell cultures produced similar concentrations of TGFβ. The potential effect of TGFβ was studied by using immunoneutralizing antibodies against TGFβ1 and TGFβ2 on the induction of iNOS in microglial cells in the presence of astroglial cells. Incubation of the mixed glial cell culture with these TGFβ antibodies (3 μg/ml) markedly increased endotoxin-induced NO production and iNOS expression in microglial cells, whereas the production of IL-1β was not affected. The antibodies against TGFβ1 and TGFβ2 marginally increased NO production in pure microglial cell cultures, nonetheless in cultures of purified microglial cells recombinant TGFβ1 and TGFβ2 together with endotoxin inhibited NO production. We conclude that the presence of astroglial cells is essential for the inhibitory effect of TGFβ on NO production by microglial cells (possibly) by activation of TGFβ or by increasing the sensitivity of microglial cells for TGFβ. GLIA 19:190–198, 1997. © 1997 Wiley-Liss, Inc.     

The major histocompatibility complex class II transactivator is differentially regulated by interferon-gamma and transforming growth factor-beta in microglial cells

We evaluated the regulation of the major histocompatibility complex class II (MHC II) transactivator (CIITA) gene expression in two microglial cell lines, EOC2 and EOC20. We demonstrate that interferon-gamma (IFN-gamma) activates type III- and IV-CIITA mRNA and high levels of MHC II in EOC20. However, in EOC2 cells only low levels of type IV-CIITA mRNA and MHC II are detectable following IFN-gamma treatment. Transforming growth factor-beta1 (TGF-beta1) inhibits both type III- and IV-CIITA expression in EOC20 cells while, in EOC2 cells TGF-beta1 enhances IFN-gamma induced pIV-CIITA expression. Trichostatin A (TSA), a histone deacetylase (HDAC) inhibitor, abrogates the TGF-beta1 mediated repression of the IFN-gamma induced CIITA in EOC20. Evidence is presented that the TG-interacting factor (TGIF), a co-repressor known to recruit HDACs, plays a role in determining the effects of TGF-beta1 on microglial cells.     

Regulation of FLRG expression in rat primary astroglial cells and injured brain tissue by transforming growth factor-beta 1 (TGF-beta 1)

Follistatin-related gene (FLRG) is a member of the follistatin family of proteins and interacts with transforming growth factor (TGF) superfamily proteins like follistatin. To understand the expression level of FLRG in brain tissue, we examined whether primary neurons and glial cells from rat embryos express FLRG mRNA and produce its protein product. FLRG and follistain mRNAs were mainly expressed in astroglial cells, while activin A mRNA was abundant in primary neurons. TGF-beta1 highly enhanced expression levels of FLRG mRNA in astroglial cells, compared with those of follistatin and activin A mRNAs. Particularly, TGF-beta1 facilitated the secretion of FLRG protein from primary astroglial cells in a dose-dependent manner. Moreover, changes in expression levels of FLRG mRNA and protein in brain tissue were also analyzed after a penetrating injury, using quantitative polymerase chain reactin (PCR) and immunohistochemical methods. Expression levels of FLRG mRNA were significantly increased in damaged regions after penetrating injury together with those of activin A and TGF-beta1 mRNAs. Immunohistochemical observations showed that positive signals of FLRG protein were colocalized in glial fibrillary acidic protein-positive reactive astroglial cells located in damaged regions after a penetrating injury. The expression of follistatin mRNA rather decreased in damage regions after the brain injury. These results suggest that FLRG is synthesized in and secreted from astroglial cells. In particular, FLRG, but not follistatin, may play a role in the regulation of activin A in brain wound healing in response to TGF-beta1.     

The production of nitric oxide in EL4 lymphoma cells overexpressing growth hormone

Growth hormone (GH) is produced by immunocompetent cells and has been implicated in the regulation of a multiplicity of functions in the immune system involved in growth and activation. However, the actions of endogenous or lymphocyte GH and its contribution to immune reactivity when compared with those of serum or exogenous GH are still unclear. In the present study, we overexpressed lymphocyte GH in EL4 lymphoma cells, which lack the GH receptor (GHR), to determine the role of endogenous GH in nitric oxide (NO) production and response to genotoxic stress. Western blot analysis demonstrated that the levels of GH increased approximately 40% in cells overexpressing GH (GHo) when compared with cells with vector alone. The results also show a substantial increase in NO production in cells overexpressing GH that could be blocked by N(G)-monomethyl-L-arginine (L-NMMA), an L-arginine analogue that competitively inhibits all three isoforms of nitric oxide synthase (NOS). No evidence was obtained to support an increase in peroxynitrite in cells overexpressing GH. Overexpression of GH increased NOS activity, inducible nitric oxide synthase (iNOS) promoter activity, and iNOS protein expression, whereas endothelial nitric oxide synthase and neuronal nitric oxide synthase protein levels were essentially unchanged. In addition, cells overexpressing GH showed increased arginine transport ability and intracellular arginase activity when compared with control cells. GH overexpression appeared to protect cells from the toxic effects of the DNA alkylating agent methyl methanesulfonate. This possibility was suggested by maintenance of the mitochondrial transmembrane potential in cells overexpressing GH when compared with control cells that could be blocked by L-NMMA. Taken together, the data support the notion that lymphocyte GH, independently of the GH receptor, may play a key role in the survival of lymphocytes exposed to stressful stimuli via the production of NO.     

Decreased levels of interleukin-10 and transforming growth factor-beta 2 in cerebrospinal fluid of patients with high grade astrocytoma

OBJECTIVE: Glioma cells can produce anti-inflammatory cytokines such as interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) which inhibit T cell and monocyte function. It is unknown if production of these cytokines is limited to the site of tumor or these molecules are also released to cerebrospinal fluid and blood. The goal of our study was to determine if patients with astrocytoma have increased levels of IL-10 and TGF-beta 2 in cerebrospinal fluid (CSF) and serum. METHODS: CSF and serum samples were taken from 16 patients with astrocytoma of grade III or grade IV according to the WHO classification and from 28 age- and gender-matched controls (patients with normal pressure hydrocephalus or with lumbar disk herniation). Cytokine concentrations were measured using ELISA methods. RESULTS AND DISCUSSION: There was no difference in serum levels of IL-10 and TGF-beta 2 between groups. Patients with astrocytoma had decreased levels of IL-10 (0.9 +/- 1.2 versus 3.5 +/- 9.2 pg/ml, p=0.01) and TGF-beta 2 (0.0 +/- 0.0 versus 5.4 +/- 9.4 pg/ml, p=0.05) in CSF compared to controls. Because serum IL-10 and TGF-beta 2 levels are similar in patients with astrocytoma and in controls, these cytokines are probably not directly involved in peripheral monocyte and T cell deactivation.     

Decreased levels of interleukin-10 and transforming growth factor-beta2 in cerebrospinal fluid of patients with high grade astrocytoma

Abstract

Objective: Glioma cells can produce anti-inflammatory cytokines such as interleukin-10 (IL-10) and transforming growth factor-beta (TGF-β) which inhibit T cell and monocyte function. It is unknown if production of these cytokines is limited to the site of tumor or these molecules are also released to cerebrospinal fluid and blood. The goal of our study was to determine if patients with astrocytoma have increased levels of IL-10 and TGF-β2 in cerebrospinal fluid (CSF) and serum.

Methods: CSF and serum samples were taken from 16 patients with astrocytoma of grade III or grade IV according to the WHO classification and from 28 age- and gender-matched controls (patients with normal pressure hydrocephalus or with lumbar disk herniation). Cytokine concentrations were measured using ELISA methods.

Results and discussion: There was no difference in serum levels of IL-10 and TGF-β2 between groups. Patients with astrocytoma had decreased levels of IL-10 (0.9 ± 1.2 versus 3.5 ± 9.2 pg/ml, p=0.01) and TGF-β2 (0.0 ± 0.0 versus 5.4 ± 9.4 pg/ml, p=0.05) in CSF compared to controls. Because serum IL-10 and TGF-β2 levels are similar in patients with astrocytoma and in controls, these cytokines are probably not directly involved in peripheral monocyte and T cell deactivation.     

Gradual inhibition of inducible nitric oxide synthase but not of interleukin-1β production in rat microglial cells of endotoxin-treated mixed glial cell cultures

In cultures of purified microglial cells and astrocytes from newborn rats, the immunocytochemical localization of interleukin-1β (IL-1β) and inducible nitric oxide synthase (iNOS) using recently developed antibodies, as well as the release of IL-1β and nitric oxide (NO), was studied following exposure of the cells to endotoxin [lipopolysaccharide (LPS)]. In the absence of LPS, IL-1β- and iNOS-immunoreactive microglial cells and IL-1β or NO release were not observed, whereas in the presence of the endotoxin, the production of NO and IL-1β by microglial cells dramatically exceeded their synthesis and release by astrocytes. Interestingly, microglial cells cultured for 4–8 days in the presence of astrocytes appeared to lose their ability to produce iNOS, whereas the release of IL-1β remained unaltered. Moreover, endotoxin-stimulated microglial cells appeared to regain their ability to synthesize iNOS following their separation from astrocytes. These data show that microglia are primarily responsible for NO and IL-1β production in mixed glial cell cultures upon endotoxin stimulation. Moreover, in the presence of astrocytes the induction of iNOS, but not that of IL-1β in microglial cells is gradually inhibited. © 1996 Wiley-Liss, Inc.     

CD81 and microglial activation in vitro: proliferation, phagocytosis and nitric oxide production

CD81 (TAPA), a member of the tetraspanin family of proteins, is upregulated by astrocytes and microglia after traumatic injury to the rat central nervous system (CNS). To further understand the role of CD81 in the microglial response to injury, we analysed the functional effects of a CD81 antibody, AMP1, on cultured rat microglia. We found that AMP1 suppressed microglial proliferation in a dose-dependent manner. Furthermore, AMP1 stimulated myelin phagocytosis, probably by opsonizing the myelin. The phagocytosis of latex beads, as well as the production of nitric oxide, were not significantly influenced by AMP1. These data indicate that CD81 is involved in an important subset of microglial effector functions after CNS injury.     

Role of astrocyte-derived tissue-type plasminogen activator in the regulation of endotoxin-stimulated nitric oxide production by microglial cells

In mixed glial cell cultures from cerebral cortices of newborn rats, endotoxin induces nitric oxide (NO) production in microglial cells. Earlier we demonstrated that endotoxin induced NO production by microglial cells is inhibited in the presence of astroglial cells by transforming growth factor β (TGFβ). Both microglial and astroglial cells produce TGFβ in a biologically inactive form, which can be activated by plasmin generated by plasminogen activators (PA). In the present paper we describe studies on the mechanism by which glial cells may activate inactive TGFβ and its potential inhibitory effect on NO production by microglial cells. Inhibition of plasmin increased NO production in endotoxin-treated mixed glial cell cultures. Subsequently, antibodies against tissue-type plasminogen activator (tPA) increased NO production in endotoxin-treated mixed glial cell cultures while amiloride, an inhibitor for urokinase (uPA), had no effect. We hereby concluded that tPA is the crucial PA involved in plasmin production resulting in inhibition of NO production in mixed glial cell cultures. Zymography and Northern blot analysis of purified astroglial, microglial, and mixed glial cell cultures demonstrated that astroglial cells produce tPA and a plasminogen activator inhibitor (PAI-1) and are thereby responsible for the production of plasmin which may activate the inactive TGFβ in these cultures. In conclusion, astroglial-derived tPA plays a major role in the inhibition of NO production by endotoxin-treated microglial cells through enhanced plasmin production and possible subsequent TGFβ activation. GLIA 22:130–137, 1998. © 1998 Wiley-Liss, Inc.     

Life imaging of peroxynitrite in rat microglial and astroglial cells: Role of superoxide and antioxidants

Free radicals, such as superoxide and nitric oxide, are known to play a role in a number of inflammatory and degenerative brain diseases, in which resident microglia upregulate the inducible nitric oxide synthase (iNOS) and thus produce large amounts of nitric oxide. Simultaneously, microglia generate superoxide mainly via NADPH-oxidase, which reacts at a diffusion-limited rate with nitric oxide to form the powerful oxidant peroxynitrite. We used mixed astroglial/microglial cultures to study the effects of iNOS induction by lipopolysaccharide and interferon-gamma on free radical formation. Using the fluorogenic compound 2,7-dihydrodichlorofluorescein diacetate, we monitored cellular peroxynitrite formation by confocal laser microscopy. Peroxynitrite formation in continuously nitric oxide-producing microglial cells was rather limited. However, activation of the superoxide-generating enzyme NADPH-oxidase dramatically increased DCF fluorescence within a few minutes. We conclude that superoxide is the limiting factor for peroxynitrite formation. Since the formation and oxidant activity of peroxynitrite depends strongly on the availability of cellular antioxidants, we investigated the capacity of several compounds to influence peroxynitrite formation. Among the substances under investigation in this study, glutathione and the synthetic compound ebselen had a major effect on preventing peroxynitrite formation, whereas ascorbate failed to decrease peroxynitrite levels.     

Transforming growth factor-β1 suppresses autoantigen-induced expression of pro-inflammatory cytokines but not of interleukin-10 in multiple sclerosis and myasthenia gravis

Multiple sclerosis (MS) is associated with high levels of circulating T lymphocytes that respond to the myelin antigens myelin basic protein (MBP) and proteolipid protein (PLP) by producing various cytokines including interferon-γ (IFN-γ) that makes MS worse and transforming growth factor-β (TGF-β), an endogenously produced immunosuppressant that might act beneficially. To further define the role of TGF-β in MS, we examined the effects of recombinant TGF-β1 (rTGF-β1) on autoantigen-mediated regulation of cytokines in MS and myasthenia gravis (MG). Blood mononuclear cells (MNC) were cultivated with or without rTGF-β1, and with or without autoantigen or the recall antigen PPD. MNC expressing cytokine mRNA were detected after in situ hybridization with radiolabeled cDNA oligonucleotide probes. Femtogram concentrations of rTGF-β1 suppressed MBP-, PLP- and PPD-induced upregulation of IFN-γ, IL-4, IL-6, tumor necrosis factor-α (TNF-α), TNF-α and perforin in MS, and acetylcholine receptor (AChR)-induced augmentation of these pro-inflammatory cytokines in MG, but had no effects on autoantigen- or PPD-induced expression of IL-10 or TGF-β itself. rTGF-β1 also suppressed numbers of myelin antigen-reactive IFN-γ- and IL-4-secreting cells in MS and AChR-reactive IFN-γ and IL-4 secreting cells in MG. The selective suppressive effects of TGF-β1 on autoantigen-induced upregulation of pro-inflammatory cytokines makes TGF-β1 attractive as a treatment alternative in MS and MG.     

转化生长因子β1对大鼠肾小管上皮细胞中基质细胞衍生因子1表达的影响★

目的：已知转化生长因子β1与肾脏组织纤维化形成有密切关系。拟进一步探讨转化生长因子β1对大鼠近端肾小管上皮细胞（NRK52E）中基质细胞衍生因子1表达的影响。 方法：实验于2006-03/2007-05在四川大学生物治疗国家重点实验室神经分子生物实验室完成。①实验材料：大鼠近端肾小管上皮细胞株NRK52E，由澳大利亚Monash医学中心肾内科实验室提供；转化生长因子β1由cytolab公司提供。②实验分组：将大鼠近端肾小管上皮细胞分为正常对照组：无转化生长因子β1 干预；实验组：又分为在同一转化生长因子β1浓度(2 μg/L)下，培养6，12，24 h；在不同的转化生长因子β1浓度(2，5，10 μg/L)下，培养24 h。③利用免疫细胞化学技术对同一转化生长因子β1浓度(2 μg/L)干预不同时间后的大鼠近端肾小管上皮细胞中基质细胞衍生因子１的蛋白表达进行半定量分析，选择出最佳的作用时间点；通过反转录-聚合酶链反应、Western-Blotting以检测大鼠近端肾小管上皮细胞中基质细胞衍生因子1在不同转化生长因子β1浓度干预下培养24 h后的mRNA、蛋白表达变化情况。 结果：①培养12，24 h时,大鼠近端肾小管上皮细胞中基质细胞衍生因子1的蛋白表达比0 h增高(P < 0.05)；24 h时表达略高于12 h (P > 0.05)。提示，基质细胞衍生因子1的表达到达一平台期，24 h为最佳的作用时间点。②从mRNA水平和蛋白水平均证实，2 μg/L转化生长因子β1干预24 h后的大鼠近端肾小管上皮细胞中基质细胞衍生因子1的表达高于正常对照组 (P < 0.05)；随着转化生长因子β1的浓度增大，表达呈下降趋势，10 μg/L时表达低于2 μg/L时的表达(P < 0.05)。 结论：基质细胞衍生因子1在正常的大鼠近端肾小管上皮细胞中呈低表达状态，对转化生长因子β1的干预表现出一定的时间、剂量依赖性，基质细胞衍生因子1可能参与了肾间质纤维化的发生、发展。     

转化生长因子β和脑源性神经营养因子联合诱导成年大鼠骨髓基质细胞向神经元样细胞的分化

BACKGROUND： It has been demonstrated that transforming growth factor-β （TGF-β） and brain- derived neurotrophic factor （BDNF） can induce stem cell differentiation into neuron-like cells. OBJECTIVE： To investigate the efficacy of TGF-β and BDNF at inducing the differentiation of adult rat bone marrow stromal cells （BMSCs） into neuron-like cells, both in combination or alone. DESIGN, TIME AND SETTING： A comparative observation experiment was performed at the Department of Orthopedics, First Affiliated Hospital of Liaoning Medical University between October 2007 and January 2008. MATERIALS： TGF-~ and BDNF were purchased from Sigma, USA; mouse anti-rat neuron specific enolase, neurofilament and glial fibrillary acidic protein were purchased from Beijing HMHL Biochem Ltd., China. METHODS： BMSCs were isolated from rats aged 4 weeks and incubated with TGF-β（1μ g/L） and/or BDNF （50 μ g/mL）. MAIN OUTCOME MEASURES： Expression of neuron-specific enolase, neurofilament and glial fibrillary acidic protein were determined by immunocytochemistry. RESULTS： BMSCs differentiated into neuron-like cells following induction of TGF-β and BDNF, and expressed both neuron-specific enolase and neurofilament. The percent of positive cells was significantly greater in the combination group than those induced with TGF-β or BDNF alone （P 〈 0.01）. CONCLUSION： Treatment of BMSCs with a combination of TGF-β and BDNF induced differentiation into neuron-like cells, with the induction being significantly greater than with TGF-β or BDNF alone.     

Neuron-like differentiation of adult rat bone marrow stromal cells induced by transforming growth factor-beta and brain-derived neurotrophic factor

BACKGROUND: It has been demonstrated that transforming growth factor-β (TGF-β) and brain-derived neurotrophic factor (BDNF) can induce stem cell differentiation into neuron-like cells.OBJECTIVE: To investigate the efficacy of TGF-β and BDNF at inducing the differentiation of adult rat bone marrow stromal cells (BMSCs) into neuron-like cells, both in combination or alone.DESIGN, TIME AND SETTING: A comparative observation experiment was performed at the Department of Orthopedics, First Affiliated Hospital of Liaoning Medical University between October 2007 and January 2008.MATERIALS: TGF-βand BDNF were purchased from Sigma, USA; mouse anti-rat neuron specific enolase, neurofilament and glial fibrillary acidic protein were purchased from Beijing HMHL Biochem Ltd., China.METHODS: BMSCs were isolated from rats aged 4 weeks and incubated with TGF-β(1μg/L) and/or BDNF (50μg/mL).MAIN OUTCOME MEASURES: Expression of neuron-specific enolase, neurofilament and glial fibrillary acidic protein were determined by immunocytochemistry.RESULTS: BMSCs differentiated into neuron-like cells following induction of TGF-β and BDNF, and expressed both neuron-specific enolase and neurofilament. The percent of positive cells was significantly greater in the combination group than those induced with TGF-β or BDNF alone (P<0.01).CONCLUSION: Treatment of BMSCs with a combination of TGF-β and BDNF induced differentiation into neuron-like cells, with the induction being significantly greater than with TGF-β or BDNF alone.