The effect of interferon β-1b on lymphocyte-endothelial cell adhesion

Interferon β-1b (IFNβ-1b) (Betaseron®) has been recently approved forfor treatment of multiple sclerosis (MS), an inflammatory demyelinating disease of the central nervous system (CNS). The mechanism of action of IFNβ-1b is not understood, but its effect in reducing gadolinium enhanced MRI lesions suggest an effect at the blood brain barrier (BBB). Thus the objective of this study is to examine the effect of IFNβ-1b treatment of endothelial cells (EC) on lymphocyte-EC adhesion, and on the expression of the adhesion molecules (AM) ICAM-1, VCAM and E-selectin induced by IFN-γ, TNF-α, or IL-1β. Primary cultures of human umbilical vein EC (HUVEC) were used which under basal conditions expressed low levels of ICAM-1 but not VCAM or E-selectin. IFNβ-1b (1–1000 IU/ml) had minimal effect on basal expression of AM on HUVEC, but AM could be substantially upregulated by IFN-γ, IL-1β or TNF-α which was associated with a parallel increase in lymphocyte-EC adhesion. The effect of IFNβ-1b on AM expression induced by IFN-γ, IL-1β or TNF-α was slightly additive, and was associated with a modest increase in lymphocyte-EC adhesion. In contrast TGF-β, shown previously to downregulate lymphocyte-EC adhesion, inhibited this adhesion in our experiments. It is concluded that IFN-β does not downregulate the inducible expression of ICAM-1, VCAM or E-selectin on HUVEC and does not inhibit the adhesion of lymphocytes to HUVEC. These findings have implications on the mechanism of action of IFNβ-1b in MS.     

Interferon β-lb reduces Interferon γ-induced antigen-presenting capacity of human glial and B cells

Interferon (IFN) β-1b has been shown to alter the course of multiple sclerosis and to inhibit MHC class II expression, but its effect on antigen presentation has not been examined in a functional assay (Neurology 43 (1993) 655–661). The effect of IFNβ-1b on alloantigen presentation by human antigen-presenting cells (APC) including human fetal astrocytes (HFA) and microglia was examined. The effect of IFNβ-1b on the ability of B cells to present tetanus toxoid (TT) to TT-specific T cell lines was also examined. APC were pre-treated with IFNγ (100 units/ml), IFNβ-1b (10–2000 units/ml), or a combination of IFNγ and IFNβ-1b for 3 days and washed thoroughly prior to culture with allogeneic peripheral blood lymphocytes (PBL) for a period of 6 days. Lymphocyte proliferation was then measured by tritiated thymidine uptake. Treatment of the APC with IFNβ-1b resulted in a reduction in the IFNγ-enhanced alloantigen-induced T cell responses. This reduction ranged between 50 and 70%, was associated with a 30–50% reduction in HLA class II (DR) and 35–40% reduction in ICAM-1 expression on the HFA used as APC. IFNβ-1b pretreatment of B cells reduced their constitutive and IFNγ enhanced capacity to present TT to TT-specific T cell lines by 50–80%. This was associated with a 30 ± 11% mean reduction in class II (DR) expression and approximately 50 ± 1% reduction in ICAM-1 expression in IFNβ-1b + IFNγ-treated B cells compared to IFNγ-treated B cells (mean of three experiments). The reduction in antigen presentation and class II expression was not due to cellular toxicity as cell viability and tritiated thymidine uptake by APC were not altered significantly with treatment. The results suggest that IFNβ-1b can downregulate antigen presentation which could be related to altered expression of cell surface molecules on the APC and possibly also an effect on antigen processing.     

Costimulatory Effects of Interferon-γ and Interleukin-1β or Tumor Necrosis Factor α on the Synthesis of Aβ1-40 and Aβ1-42 by Human Astrocytes

Chronic inflammation and astrocytosis are characteristic histopathological features of Alzheimer's Disease (AD). Astrocytes are one of the predominant cell types in the brain. In AD they are activated and produce inflammatory components such as complement components, acute phase proteins, and cytokines. In this study we analyzed the effect of cytokines on the production of amyloid β (Aβ) in the astrocytoma cell line U373 and in primary human astrocytes isolated postmortem from healthy aged persons as well as from patients with AD. Astrocytes did not produce Aβ in the absence of stimuli or following stimulation with IL-1β, TNFα, IL-6, and TGF-β1. Neither did combinations of TNFα and IL-1β, IL-6 or TGF-β1, or the coadministration of IFNγ and IL-6 or TGF-β1 induce Aβ production. In contrast, pronounced production of Aβ1-40 and Aβ1-42 was observed when primary astrocytes or astrocytoma cells were stimulated with combinations of IFNγ and TNFα or IFNγ and IL-1β. Induction of Aβ production was accompanied by decreased glycosylation of APP as well as by increased secretion of APPsβ. Our results suggest that astrocytes may be an important source of Aβ in the presence of certain combinations of inflammatory cytokines. IFNγ in combination with TNFα or IL-1β seems to trigger Aβ production by supporting β-secretase cleavage of the immature APP molecule.     

Tumor necrosis factor α and interleukin-6 mRNA expression in neonatal Lewis rat Schwann cells and a neonatal rat Schwann cell line following interferon γ stimulation

There is increasing evidence that Schwann cells play an important role in the pathogenesis of autoimmune inflammatory peripheral nerve disease. Schwann cells have been reported to express major histocompatibility complex class I and II (MHC I and II) and intercellular adhesion molecule-1 (ICAM-1), and to produce interleukin-1 (IL-1), prostaglandin E2 and thromboxane A2. In this study we investigated freshly dissociated neonatal Lewis rat Schwann cells and a SV40 transfected neonatal rat Schwann cell line (Schwann cell line) for production of mRNA for the immunomodulatory cytokines IL-2, IL-4, IL-6, IL-10, interferon-gamma (IFNγ), and tumor necrosis factor-alpha (TNFα) employing RT-PCR. Primary Schwann cells and Schwann cell line were examined following IFNγ stimulation and were found to express TNFα and IL-6 mRNA. These results further support a role for Schwann cell participation in inflammatory responses within the peripheral nervous system (PNS).     

The antihyperalgesic activity of a selective P2X7 receptor antagonist, A-839977, is lost in IL-1αβ knockout mice

The pro-inflammatory cytokine interleukin-1β (IL-1β) has been implicated in both inflammatory processes and nociceptive neurotransmission. Activation of P2X7 receptors is the mechanism by which ATP stimulates the rapid maturation and release of IL-1β from macrophages and microglial cells. Recently, selective P2X7 receptor antagonists have been shown to reduce inflammatory and neuropathic pain in animal models. However, the mechanisms underlying these analgesic effects are unknown. The present studies characterize the pharmacology and antinociceptive effects of a structurally novel P2X7 antagonist. A-839977 potently (IC₅₀ = 20–150 nM) blocked BzATP-evoked calcium influx at recombinant human, rat and mouse P2X7 receptors. A-839977 also potently blocked agonist-evoked YO-PRO uptake and IL-1β release from differentiated human THP-1 cells. Systemic administration of A-839977 dose-dependently reduced thermal hyperalgesia produced by intraplantar administration of complete Freund's adjuvant (CFA) (ED₅₀ = 100 μmol/kg, i.p.) in rats. A-839977 also produced robust antihyperalgesia in the CFA model of inflammatory pain in wild-type mice (ED₅₀ = 40 μmol/kg, i.p.), but the antihyperalgesic effects of A-839977 were completely absent in IL-1αβ knockout mice. These data demonstrate that selective blockade of P2X7 receptors in vivo produces significant antinociception in animal models of inflammatory pain and suggest that the antihyperalgesic effects of P2X7 receptor blockade in an inflammatory pain model in mice are mediated by blocking the release of IL-1β.     

Interferon β-1a downregulates TNFα-induced intercellular adhesion molecule 1 expression on brain microvascular endothelial cells through a tyrosine kinase-dependent pathway

TNFα (100 U/ml, 24 h) upregulated intercellular adhesion molecule 1 (ICAM1) expression on brain microvascular endothelial cell (BMEC) culture. The tyrosine kinase (TK) inhibitor genestein (100 μg/ml), the protein kinase C (PKC) inhibitor staurosporin (1 nM), and interferon (IF) β-1a (1000 U/ml) antagonized TNFα effect. When an ineffective dose of IFβ-1a (100 U/ml) was challenged with ineffective doses of either genestein (10 μg/ml) or staurosporin (0.1 nM), the combination IFβ-1a–genestein significantly reduced TNFα-induced ICAM1 expression whereas IFβ-1a–staurosporin did not. These findings indicate that a TK- rather than a PKC-dependent mechanism is involved in the modulation of TNFα response by IFβ-1a on BMECs.     

α2, α2A, α2B/2C-Adrenoceptor subtype antagonists prevent lipopolysaccharide-induced fever response in rabbits

Exogenous pyrogens, e.g., bacterial lipopolysaccharides (LPS), are thought to stimulate macrophages to release endogenous pyrogens, e.g., TNFα, IL-1 β, and IL-6, which act in the hypothalamus to produce fever. We studied the effect of different α₁⁻ and α₂-adrenoceptor subtype antagonists, applied intraperitoneally, on the febrile response induced by LPS in rabbits. Evidence was obtained that prazosin, an α₁⁻ and α_2B/2C-adrenoceptor antagonist; WB-4101, an α₁⁻ and α_2A-adrenoceptor antagonist; CH-38083, a highly selective α₂-adrenoceptor antagonist (α₂: α₁ > 2000); BRL-44408, an α_2A-adrenoceptor antagonist; and ARC-239, an α_2B/2C⁻ and also α₁-adrenoceptor antagonist, blocked the increase of colonic temperature of the rabbit produced by 2 μg/kg LPS administered intravenously without being able in themselves to affect colonic temperature. In addition, prazosin, WB-4101 and CH-38083 antagonized the fall in skin temperature that occurred at the time when the colonic temperature was rising in control animals injected with LPS. All these results suggest that norepinephrine, through stimulation of both α₁⁻andα₂⁻ (α_2A⁻andα_2B/2C⁻) adrenoceptor subtypes, is involved in producing fever in response to bacterial LPS.     

Interferon gamma up-regulates α2 macroglobulin expression in human astrocytoma cells

An established human astrocytoma cell line (T67) was shown to constitutively produce the proteinase inhibitor α₂macroglobulin (α₂M). Interferon gamma (IFNγ), a potent immunoregulatory lymphokine, was able to increase the synthesis of α₂M by these cells, as measured by ELISA on cell supernatants. The α₂M induction was also observed in other human glioma cell lines (T70 and ADF) and in human fetal astrocyte cultures following IFNγ treatment. In T67 cells this effect was dose-dependent and the maximum (2.7-fold increase) was obtained with 2000 U/ml of IFNγ. A corresponding enhanced α₂M mRNA accumulation was demonstrated by PCR and Northern blot techniques. Our results suggest an important role of α₂M during inflammatory and immune processes in the CNS. An increased release of α₂M following IFNγ stimulation may allow the removal of the bulk of proteases released at the site of inflammation, strengthening at the same time the antigen presentation processes.     

Interleukin-1β, but not IL-1α, mediates nerve growth factor secretion from rat astrocytes via type I IL-1 receptor

In astrocytes, nerve growth factor (NGF) synthesis and secretion is stimulated by the cytokine interleukin-1β (IL-1β). In the present study, the role of IL-1 receptor binding sites in the regulation of NGF release was evaluated by determining the pharmacological properties of astroglially localized IL-1 receptors, and, by comparing the effects of both the agonists (IL-1α and IL-1β) and the antagonist (IL-1ra)—members of the IL-1 family on NGF secretion from rat neonatal cortical astrocytes in primary culture. Using receptor-binding studies, binding of [¹²⁵I] IL-1β to cultured astrocytes was saturable and of high affinity. Mean values for the K_D and B_max were calculated to be 60.7±7.4 pM and 2.5±0.1 fmol mg^-1 protein, respectively. The binding was rapid and readily reversible. IL-1 receptor agonists IL-1α (K_i of 341.1 pM) and IL-1β (K_i 59.9 pM), as well as the antagonist IL-1ra (K_i 257.6 pM), displaced specific [¹²⁵I] IL-1β binding from cultured astrocytes in a monophasic manner. Anti-IL-1RI antibody completely blocked specific [¹²⁵I] IL-1β binding while anti-IL-1RII antibody had no inhibitory effect. Exposure of cultured astrocytes to IL-1α and IL-1β revealed the functional difference between the agonists in influencing NGF release. In contrast to IL-1β (10 U/ml), which caused a 3-fold increase in NGF secretion compared to control cells, IL-1α by itself had no stimulatory action on NGF release. The simultaneous application of IL-1α and IL-1β elicited no additive response. IL-1ra had no effect on basal NGF release but dose-dependently inhibited the stimulatory response induced by IL-1β. We concluded that IL-1β-induced NGF secretion from cultured rat cortical astrocytes is mediated by functional type I IL-1 receptors, whereas IL-1α and IL-1ra, in spite of their affinity for IL-1RI, have no effect on NGF secretion from these cells. Type II IL-1R is not present on rat neonatal cortical astrocytes.     

Alzheimer's β-amyloid peptides induce inflammatory cascade in human vascular cells: the roles of cytokines and CD40

Accumulating evidence suggests that β-amyloid (Aβ)-induced inflammatory reactions may partially drive the pathogenesis of Alzheimer's disease (AD). Recent data also implicate similar inflammatory processes in cerebral amyloid angiopathy (CAA). To evaluate the roles of Aβ in the inflammatory processes in vascular tissues, we have tested the ability of Aβ to trigger inflammatory responses in cultured human vascular cells. We found that stimulation with Aβ dose-dependently increased the expression of CD40, and secretion of interferon-γ (IFN-γ) and interleukin-1β (IL-1β) in endothelial cells. Aβ also induced expression of IFN-γ receptor (IFN-γR) both in endothelial and smooth muscle cells. Characterization of the Aβ-induced inflammatory responses in the vascular cells showed that the ligation of CD40 further increased cytokine production and/or the expression of IFN-γR. Moreover, IL-1β and IFN-γ synergistically increased the Aβ-induced expression of CD40 and IFN-γR. We have recently found that Aβ induces expression of adhesion molecules, and that cytokine production and interaction of CD40–CD40 ligand (CD40L) further increase the Aβ-induced expression of adhesion molecules in these same cells. These results suggest that Aβ can function as an inflammatory stimulator to activate vascular cells and induces an auto-amplified inflammatory molecular cascade, through interactions among adhesion molecules, CD40–CD40L and cytokines. Additionally, Aβ_1–42, the more pathologic form of Aβ, induces much stronger effects in endothelial cells than in smooth muscle cells, while the reverse is true for Aβ_1–40. Collectively, these findings support the hypothesis that the Aβ-induced inflammatory responses in vascular cells may play a significant role in the pathogenesis of CAA and AD.     

Interferon γ- and interleukin-4-secreting cells in multiple sclerosis

Interleukin 4 (IL-4)- and interferon γ (IFNγ)-secreting peripheral blood cells were enumerated by immunospot assay in 13 multiple sclerosis (MS) patients during exacerbations, in 24 patients with progressive multiple sclerosis (CPMS), and in 20 controls. Cells that spontaneously secreted IFNγ were significantly higher in MS patients experiencing an attack (P<0.001) than in controls or in CPMS (P<0.04). IL-4-secreting cell numbers were elevated significantly and to a comparable extent in both MS groups compared to controls. Our finding of increased numbers of IFNγ-secreting cells is in keeping with prior work showing increased IFNγ levels in the circulation prior to and durinng MS attacks and increased release of IFNγ to the supernatant in bulk cultured blood cells from MS patients. What role an increase in IL-4-secreting cells might play in MS is unclear, but it could relate to immune system regulation. Following in vitro exposure to MBP, IFNγ-secreting cell number rose above levels observed in the absence of stimulation in controls and in both MS groups with the rise in acutely exacerbating MS patients being significantly greater than in controls. Our results provide further evidence for reactivity to MBP in MS, the significance of which in terms of pathogenesis remains clouded.     

Inhibition of interleukin-1β and prostaglandin E2 thermogenesis by glycyl-glutamine, a pro-opiomelanocortin-derived peptide

Interleukin-1β (IL-1β) and other cytokines produce fever by stimulating prostaglandin E₂ (PGE₂) synthesis in thermoregulatory regions of the preoptic area and anterior hypothalamus (POA/AH). Prostaglandin E₂ is thought to raise body temperature, at least in part, by stimulating β-endorphin release from pro-opiomelanocortin neurons that innervate the POA/AH. In this study, we investigated whether glycyl-glutamine (β-endorphin_30–31), an inhibitory dipeptide synthesized from β-endorphin post-translationally, inhibits IL-1β and PGE₂-induced hyperthermia. Hyperthermic sites were identified by microinjecting PGE₂ (3 fmol/1 μl) into the medial preoptic area (mPOA) of conscious, unrestrained rats. Interleukin-1β (1 U) injection into the same PGE₂ responsive thermogenic sites in the mPOA elicited a prolonged rise in colonic temperature (T_c) (+1.02±0.06°C) that persisted for at least 2 h. Glycyl-glutamine (3 nmol) co-injection into the mPOA inhibited IL-1β thermogenesis completely (T_c=−0.18±0.22°C). Glycyl-glutamine had no effect on body temperature when given alone to normothermic rats. Co-injection of individual amino acids, glycine and glutamine (3 nmol each amino acid), failed to influence IL-1β-induced thermogenesis, which indicates that Gly-Gln hydrolysis does not explain its inhibitory activity. Glycyl-glutamine (3 nmol) also prevented the rise in body temperature produced by PGE₂ (PGE₂=0.89±0.05°C; PGE₂ plus Gly-Gln=−0.16±0.14°C), consistent with evidence that PGE₂ mediates IL-1β-induced fever. These findings demonstrate that Gly-Gln inhibits the thermogenic response to endogenous pyrogens.     

TNFα reduces glutamate induced intracellular Ca increase in cultured cortical astrocytes

The proinflammatory cytokine TNFα is locally released during various inflammatory CNS diseases and high cerebrospinal fluid (CSF) titers of TNFα were found in meningitis patients. We know from previous studies that TNFα also depolarizes astrocytes by reducing their inwardly rectifying K⁺ currents. We have now investigated the effect of TNFα on the glutamate induced intracellular Ca²⁺ increase in astrocytes, a process which seems to be involved in glial mediated modulation of neuronal synaptic transmisssion. Incubation with TNFα (50–1000 U/ml for 60 min) reduces the glutamate induced intracellular Ca²⁺ increase in astrocytes but not in neurons and this seems to be a phenomenon secondary to the TNFα induced depolarization. While other proinflammatory cytokines (interleukin 1β, IL-2, IL-6) did not interfere with the astrocytic glutamate response, incubation in CSF from septic meningitis patients (CSF–SM) also reduced the glutamate induced intracellular Ca²⁺ increase. The application of a neutralizing anti-TNFα antibody to the CSF–SM prior to cell incubation partially restored the glutamate response. Our data suggest that inflammatory molecules such as TNFα impair astrocytes’ response to glutamate and this may indirectly affect neuronal synaptic transmission.     

Modulation of rat brain α- and β-adrenergic receptor populations by lesions of the dorsal noradrenergic bundle

Bilateral lesion of the ascending noradrenergic fibers in the dorsal bundle of adult Wistar rats with 4 μg 6-hydroxydopamine caused extensive depletion of norepinephrine in all forebrain areas, but led to a 54% increase in norepinephrine levels in the cerebellum. β-Adrenergic receptor binding of [³Hdihydroalprenolol was significantly increased in all forebrain areas depleted of norepinephrine except hypothalamus. The increase in [³Hdihydroalprenolol binding was due to 62% and 34% increases in the number of β-receptor sites in the frontal cerebral cortex and hippocampus respectively. Binding of [³HWB-4101 toα₁-adrenergic receptors after dorsal bundle lesion was augmented generally to a lesser extent than β-receptor binding, with significantly increased numbers of sites only in the frontal cortex (74%), thalamus (20%) and septum. Bothα₁-andβ-receptor binding sites were reduced in number by 25–28% in the cerebellum of dorsal bundle-lesioned rats, whereas intraventricular administration of 6-hydroxydopamine to adult rats, which depletes norepinephrine in the cerebellum by 96%, increased cerebellarα₁-andβ-receptor binding by 33–40%. Binding of [³Hclonidine to forebrainα₂-adrenergic receptors was significantly elevated in the frontal cortex, but reduced in the amygdala and septum, after dorsal bundle lesion.     

Activation of lateral geniculate neurons by norepinephrine: Mediation by an α-adrenergic receptor

Adrenergic receptors in the vicinity of neurons in the lateral geniculate nucleus (LGN) of the rat were pharmacologically characterized using extracellular single-cell recording and microiontophoretic techniques. Application of norepinephrine (NE) at low iontophoretic currents (1–15 nA) produced a delayed activation of most LGN neurons. This activation was mimicked by various sympathomimetic amines. The relative potency series of agonists was typical of postsynaptic α-adrenergic receptors:epinephrine>NE>phenylephrine α-methylnorepinephrine>dopamine>isoproterenol. The α-antagonists phentolamine, piperoxane and WB-4101, when applied at low iontophoretic currents (<10nA), produced a selective, dose-dependent and reversible blockade of the response to NE. The β-antagonist sotalol had weak and variable effects at these currents. At low currents, the presynaptic α-agonist clonidine was also able to block the response to NE but, at higher currents, produced a partial activation of some units, suggesting that it is a weak agonist. The ability of sympathomimetic amines to activate LGN neurons correlates well with their reported affinities for brainα₁-adrenoceptors labeled with [³H]WB-4101. It is concluded that NE activates neurons in the LGN via a postsynaptic orα₁-adrenergic receptor.     

Dual effects of interleukin-1β on N-methyl- -aspartate-induced retinal neuronal death in rat eyes

In this study we determine if interleukin-1β (IL-1β) modulates N-methyl- -aspartate (NMDA)-induced retinal damage. Sprague–Dawley rats were anesthetized with inhalation of halothane, after which a single injection of 5 μl of IL-1β (0.1 to 10 ng/eye) (and/or IL-1 receptor antagonist (IL-1ra)) for experimental eyes was administered. Two days later (or simultaneously), NMDA (20 nmol) was injected into the vitreous space. One week later, each eye was enucleated and transverse sections were subjected to morphometric analysis. Enzyme-linked immunosorbent assay (ELISA) was conducted for the determination of IL-1β levels in retina. Immunohistochemical and immunoblot studies were also performed. In eyes that received an intravitreal injection of IL-1β (0.1 to 10 ng/eye), significant thinning of the inner plexiform layer (IPL) was observed (P<0.05). Immunohistochemical and ELISA studies demonstrated upregulated expression of IL-1β in retinas that had undergone NMDA injection. Treatment with 10 ng of IL-1ra induced a protective effect against NMDA-induced retinal damage. Pretreatment with IL-1β induced a significant protective effect on NMDA-induced retinal damage. Our studies suggest that IL-1β induces neuronal cell death directly, as shown by the protective effects of IL-1ra, but has a protective effect on NMDA-induced retinal damage indirectly after an incubation time of at least 2 days.     

IL-1β increases intracellular calcium through an IL-1 type 1 receptor mediated mechanism in C6 astrocytic cells

Interleukin-1β (IL-1β) is a cytokine that regulates a variety of biological processes. In addition to its traditional role in the immune system, IL-1β plays an integral role in neural-immune and developmental processes in the nervous system. The pleiotropic ability of IL-1β may be due to the activation of different signal transduction mechanisms in specific cell types or under certain cellular conditions. We have previously demonstrated that IL-1β regulates healing and repair in the developing, mammalian nervous system. In the damaged perinatal mouse brain, IL-1β is expressed in astrocytes that change from a stellate to a spindle-shaped morphology. The spindle-shaped astrocytes enclose the wound, separating the healthy from damaged neural tissue. The shape change and subsequent repair processes are IL-1β activity-dependent, acting through the IL-1 type 1 receptor (IL-1R1), as co-application of the IL-1type 1 receptor antagonist protein (IL-1ra) blocks IL-1β induced effects. In the C6 astrocytic cell line, IL-1β induced similar shape changes and upregulated expression of the cytoskeletal protein, glial fibrillary acidic protein (GFAP). Since cytoskeletal changes, as well as specific signal transduction mechanisms, are associated with increases in intracellular calcium ([Ca²⁺]_i), studies were carried out to determine if increases in [Ca²⁺]_i induced by IL-1β occurred through activation of the IL-1R1 in C6 cells. Cells were treated with IL-1β and/or IL-1ra, followed by measurement of relative changes in [Ca²⁺]_i using fura-2 fluorescence imaging methods. IL-1β increased [Ca²⁺]_i levels in a dose and time dependent manner. Treatment with IL-1ra blocked IL-1β induced increases in [Ca²⁺]_i, indicating that IL-1β acts through the IL-1R1. Immunocytochemistry experiments showed that untreated C6 cells normally express IL-1β, IL-1ra, and IL-1R1. Thus, IL-1 system molecules may play a role in normal C6 astrocyte physiology.     

Tumor necrosis factor-α in immune-mediated demyelination and Wallerian degeneration of the rat peripheral nervous system

This study reports on the immunocytochemical localization of tumor necrosis factor-alpha (TNFα) in immune-mediated demyelination and Wallerian degeneration of the rat peripheral nervous system (PNS) using teased nerve fiber preparations. In experimental autoimmune neuritis induced by active immunization (EAN) or by adoptive transfer of autoreactive T cells (AT-EAN), macrophages passing blood vessels as well as macrophages adherent to nerve fibers were TNFα-positive. Large post-phagocytic macrophages at later stages of demyelination were TNFα-negative. Intraperitoneal application of an anti-TNFα antibody to EAN rats significantly reduced the degree of inflammatory demyelination, suggesting a pathogenic role for TNFα. After nerve transection only macrophages located within degenerating nerve fibers were TNFα-positive, while those entering and leaving nerves were negative. TNFα produced by macrophages seems to bevolved in immune-mediated demyelination and non-immune myelin degradation after axotomy. While interferon-gamma (IFNγ) is present in EAN nerves and may act as a local stimulus for TNF expression, the nature of this signal in Wallerian degeneration in the absence of IFNγ is unknown.