The expression of TNF-alpha receptors 1 and 2 on peripheral blood mononuclear cells in chronic inflammatory demyelinating polyneuropathy

The proportion of peripheral blood mononuclear cells (PBMCs) expressing TNF-alpha and its receptors (TNFR1, TNFR2) and the serum concentrations of its soluble forms were analyzed by FACS and ELISA in the patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and in controls. Elevated levels of TNFR2 were observed on blood T cells in CIDP and idiopathic polyneuropathy. Low levels of TNFR1 were detected on monocytes in the subgroup of patients with CIDP examined after treatment with intravenous immunoglobulin. However, the proliferative activity of PBMCs in CIDP was not influenced by soluble recombinant TNFR1. Our limited data suggested the exact role of TNF-alpha and its receptors need to study further in CIDP, as well as in idiopathic neuropathies.     

Microglial cell upregulation of HIV-1 expression in the chronically infected promonocytic cell line U1: the role of tumor necrosis factor-α

Culture supernatants from lipopolysaccharide (LPS)-treated murine microglial cells were found to markedly induce the expression of human immunodeficiency virus (HIV)-1 in the chronically infected human promonocytic cell line U1 as detected by measurements of HIV-1 p24 antigen release into U1 culture supernatants. Antibody to tumor necrosis factor (TNF)-α had an inhibitory effect on the induction of virus by microglial cell supernatants. Also, treatment of microglia with pentoxifylline, an inhibitor of TNF-α production, resulted in suppressed amounts of TNF in the supernatants of LPS-treated microglia and in a reduced stimulatory capacity of these supernatants on HIV-1 expression in U1 cells. These findings support the concept that TNF-α production by glial cells plays a pathogenetic role in HIV-1-associated brain disease by promoting the expression of the virus in infected cells.     

Brain interleukin-1β and tumor necrosis factor-α are involved in lipopolysaccharide-induced delayed rectal allodynia in awake rats

Recently, we have developped a model of delayed (12 h) increase in sensitivity (allodynia) to rectal distension (RD) induced by intraperitoneal lipopolysaccharide (LPS) in awake rats. Thus, we examined whether central interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) are involved in LPS response. Abdominal contractions (criterion of visceral pain) were recorded in rats equipped with intramuscular electrodes. RDs were performed at various times after pharmacological treatments. RD induced abdominal contractions from a threshold volume of distension of 0.8 ml. At lowest volume (0.4 ml), this number was significantly increased 12 h after LPS. Intracerebroventricular (i.c.v.) injection of IL-1 receptor antagonist, IL-1β converting enzyme inhibitor or recombinant human TNF-α soluble receptor reduced LPS-induced increase of abdominal contractions at 0.4 ml volume of distension. When injected i.c.v., recombinant human IL-1β and recombinant bovine TNF-α reproduced LPS response at 9 and 12 h and at 6 and 9 h, respectively. These data suggest that IL-1β and TNF-α act centrally to induce delayed rectal hypersensitivity and that central release of these cytokines is responsible of LPS-induced delayed (12 h) rectal allodynia.     

In vivo relationship of tumor necrosis factor-α to blood-brain barrier damage in patients with active multiple sclerosis

Tumor necrosis factor-alpha (TNF-alpha) has well recognized effects on cerebral endothelial cells and, therefore, may mediate disruption of blood-brain barrier in patients with multiple sclerosis (MS). To evaluate the in vivo relationship of TNF-alpha to blood-brain barrier impairment in MS, levels of this cytokine in cerebrospinal fluid (CSF) and serum samples from 38 patients with active MS and 48 controls were correlated with CSF to serum albumin ratios. TNF-alpha was detected in the serum of 74% and the CSF of 66% of patients with active MS. CSF levels of TNF-alpha were significantly higher in active MS compared to stable MS or other controls, and were significantly higher than corresponding serum levels. In patients with active MS, only those with detectable TNF-alpha showed signs of blood-brain barrier damage. Moreover, intrathecal levels of TNF-alpha in active MS correlated with albumin ratios and with the degree of barrier damage. Our findings are important in understanding some of the pathological changes in active multiple sclerosis.     

Morphine amplifies HIV-1 expression in chronically infected promonocytes cocultured with human brain cells

Previous studies have shown that morphine promotes the replication of human immunodeficiency virus (HIV)-1 in peripheral blood mononuclear cell cocultures. In the present study, we tested the hypothesis that morphine would amplify HIV-1 expression in the chronically infected promonocytic clone U1 when cocultured with lipopolysaccharide-stimulated human fetal brain cells. Marked upregulation of HIV-1 expression was observed in these cocultures (quantified by measurement of HIV-1 p24 antigen levels in supernatants), and treatment of brain cells with morphine resulted in a bell-shaped dose-dependent enhancement of viral expression. The mechanism of morphine's amplifying effect appears to be opioid receptor-mediated and to involve enhanced production of tumor necrosis factor-α by microglial cells.     

Changes in expressions of proinflammatory cytokines IL-1β, TNF-α and IL-6 in the brain of senescence accelerated mouse (SAM) P8

The senescence-accelerated mouse (SAM) is known to be a murine model for accelerated aging. The SAMP8 strain shows age-related deterioration of learning and memory at an earlier age than control mice (SAMR1). In the present study, we investigated the changes in expressions of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the brain of SAMP8. In the hippocampus of 10 months old SAMP8, the expression of IL-1 mRNA was significantly elevated in comparison with that of SAMR1. In both strains of SAMs, increases in IL-1β protein in the brain were observed at 10 months of age compared with 2 and 5 months. The only differences found between the strain in protein levels were at 10 months and were elevations in IL-1β in the hippocampus and hypothalamus, and in TNF-α and IL-6 in the cerebral cortex and the hippocampus in SAMP8 as compared with SAMR1. However, lipopolysaccharide-induced increases in the expression of these cytokines in brain did not differ between SAMP8 and SAMR1. Increases in expression of proinflammatory cytokines in the brain may be involved in the age-related neural dysfunction and/or learning deficiency in SAMP8.     

Exposure of tumor necrosis factor-α to luminal membrane of bovine brain capillary endothelial cells cocultured with astrocytes induces a delayed increase of permeability and cytoplasmic stress fiber formation of actin

Tumor necrosis factor-α (TNF-α), a proinflammatory cytokine, has long been known to be involved in the pathogenesis of central nervous system infections and of certain neurodegenerative diseases. However, the possible role of the blood-brain barrier (BBB), the active interface between the blood circulation and brain tissue, remained unknown during these pathological conditions. In our in vitro reconstructed BBB model, 1-hr exposure of recombinant human TNF-α (in concentrations of 50, 250, and 500 U/ml, respectively) to the luminal membrane of bovine brain capillary endothelial cells (BBCEC) did not change significantly the transendothelia: flux of either sucrose (m.w. 342 Da), or inulin (m.w. 5 kDa) up to 4 hr (early phase), except for a slight decrease (P< 0.05) in sucrose permeation at 2–4 hr with the highest dose of TNF-α On the other hand, at 16 hr after the 1-hr challenge with TNF-α (delayed phase) at all 3 concentrations, significant increase was induced in the permeability of BBCEC monolayers for both markers. These changes of permeability were accompanied by a selective reorganization of F-actin filaments into stress fibers, while the intracellular distribution of vimentin remained similar to the control. These results suggest that BBCEC can respond directly to TNF-α by a delayed increase of permeability and reorganization of actin filaments. ©1995 Wiley-Liss, Inc.     

Upregulation and interaction of TNFα and gelatinases A and B in painful peripheral nerve injury

Chronic constriction injury (CCI) to peripheral nerve causes a painful neuropathy in association with a process of axonal degeneration and endoneural remodeling that involves macrophage recruitment and local increase in extracellular proteases and tumor necrosis factor alpha (TNF-α). Cell surface activation of TNF-α from its transmembrane precursor, as well as sequestration of TNF-α receptors II and I, is performed by the zinc-dependent endopeptidase family of matrix metalloproteinases (MMPs). Among TNF-α-converting MMPs, basal lamina degrading gelatinases are thought to play a role in sciatic nerve injury. In the present study, we determined the forms of TNF-α involved in the development of CCI neuropathy in rats, using Western blot analysis, and the temporal correlation of TNF-α and TNFRI protein profiles with gelatinases activity at the site of peripheral nerve injury. We observed two peaks in TNF-α protein during the first week of CCI that correspond to previously reported peaks in painful behavior. We propose that the first peak at 6 h post-CCI is due to the local expression of the cytotoxic transmembrane 26 kDa TNF-α protein released by resident Schwann cells, mast cells and macrophages. This peak in TNF-α protein expression corresponds to an increase in gelatinase B (MMP-9) activity, which is greatly upregulated as early as 3 h following CCI to rat sciatic nerve. The second peak occurs at 5 days post-CCI, and may represent TNF-α protein released by hematogenously recruited macrophages. This peak is marked by the increase in active soluble 17 kDa TNF-α and by gelatinase A (MMP-2) upregulation. These observations suggest that there is a pathogenic role for the TNF-α-converting function of MMP-2 in painful CCI neuropathy. We conclude that severe nerve injury induces MMPs, TNF-α and TNFRI, which interactively control the privileged endoneurial environment and the pathogenesis of the painful neuropathies associated with the macrophage-dependent processes of Wallerian degeneration.     

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.     

Epigallocatechin gallate ameliorates chronic fatigue syndrome in mice: Behavioral and biochemical evidence

Three decades after the coining of the term chronic fatigue syndrome, the diagnosis of this illness is still symptom based and the aetiology remains elusive. Chronic fatigue syndrome pathogenesis seems to be multifactorial and the possible involvement of immune system is supported. The present study was designed to evaluate the effects of the epigallocatechin gallate in a mouse model of immunologically induced chronic fatigue. On 19th day, after lipopolysaccharide/Brucella abortus administration, the mice showed significant increase in immobility period, post swim fatigue and thermal hyperalgesia. Behavioral deficits were coupled with enhanced oxidative–nitrosative stress as evident by increased lipid peroxidation, nitrite levels and decreased endogenous antioxidant enzymes (superoxide dismutase, reduced glutathione and catalase) and inflammation (increased levels of tumor necrosis factor-α and tissue growth factor-β). Chronic treatment with epigallocatechin gallate restored these behavioral and biochemical alterations in mice. The present study points out towards the beneficial effect of epigallocatechin gallate in the amelioration of chronic fatigue syndrome and thus may provide a new, effective and powerful strategy to treat chronic fatigue syndrome.     

Production and neuroprotective functions of fractalkine in the central nervous system

The CX3C-chemokine, fractalkine is reportedly to be expressed in the central nervous system, and up-regulated in certain pathological conditions, such as HIV encephalopathy and multiple sclerosis. In the present study, we examined the production of fractalkine and the expression of its receptor, CX3CR1 in murine glial and neuronal cell in vitro, and investigated its neuroprotective functions. Both fractalkine and CX3CR1 were expressed constitutively in neurons, microglia, and astrocytes. Neither the production of fractalkine nor its receptor expression was up-regulated by lipopolysaccharide (LPS), as measured by mRNA expression and protein synthesis. Fractalkine dose-dependently suppressed the production of nitric oxide (NO), interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha with activated microglia. It also significantly suppressed neuronal cell death induced by microglia activated with LPS and interferon-gamma, in a dose-dependent manner. These results suggest the possible functions of fractalkine as an intrinsic inhibitor against neurotoxicity by activated microglia.     

Differential effects of oligomeric and fibrillar amyloid-beta 1-42 on astrocyte-mediated inflammation

Activated glia, as a result of chronic inflammation, are associated with amyloid-beta peptide (Abeta) deposits in the brain of Alzheimer's disease (AD) patients. In vitro, glia are activated by Abeta inducing secretion of pro-inflammatory molecules. Recent studies have focused on soluble oligomers (or protofibrils) of Abeta as the toxic species in AD. In the present study, using rat astrocyte cultures, oligomeric Abeta induced initial high levels of IL-1beta decreasing over time and, in contrast, fibrillar Abeta increased IL-1beta levels over time. In addition, oligomeric Abeta, but not fibrillar Abeta, induced high levels of iNOS, NO, and TNF-alpha. Our results suggest that oligomers induced a profound, early inflammatory response, whereas fibrillar Abeta showed less increase of pro-inflammatory molecules, consistent with a more chronic form of inflammation.     

High densities of tumor necrosis factor-α in the cerebral cortex and basal ganglia in human immunodeficiency virus-1-associated cognitive/motor complex: A quantitative regional analysis study

This study determined the regional distribution of tumor necrosis factor-alpha (TNF-α)-positive cells in HIV-1-infected brains and controls, and evaluated its correlation to cognitive impairment in HIV-1-associated cognitive/motor complex (HCMC) using TNF-α and glial fibrillary acidic protein (GFAP) double immunohistochemistry. The TNF-α-positive cell density in the cerebral cortex and basal ganglia was significantly increased in patients with HCMC compared with that in HIV-1-seropositive nondemented patients (non-HCMC), and the basal ganglia TNF-α-positive cell density was significantly correlated with Mini-Mental Status Examination (MMSE) score. Glial fibrillary acidic protein-positive astrocytes were significantly increased in density compared with normal controls, but no significant difference between HCMC and non-HCMC patients was obtained. The density of GFAP-positive astrocytes and TNF-α-positive cells was well correlated other than in the basal ganglia. The basal ganglia TNF-α-positive cell densities showed a significant correlation with MMSE scores. The result suggests that the significantly high content of TNF-α-positive cells in the cortex and basal ganglia is a neurochemical feature characteristic of HCMC. The significant correlation of the basal ganglia TNF-α-positive cell density with degree of cognitive impairment might be associated with subcortical dementia during HIV-1 infection.     

A genome‐wide association study‐derived polygenic score for interleukin‐1β is associated with hippocampal volume in two samples

Accumulating research suggests that the pro‐inflammatory cytokine interleukin‐1β (IL‐1β) has a modulatory effect on the hippocampus, a brain structure important for learning and memory as well as linked with both psychiatric and neurodegenerative disorders. Here, we used an imaging genetics strategy to test an association between an IL‐1β polygenic score and hippocampal volume in two independent samples. Our polygenic score was derived using summary statistics from a recent genome‐wide association study of circulating cytokines that included IL‐1β (N = 3,309). In the first sample of 512 non‐Hispanic Caucasian university students (274 women, mean age 19.78 ± 1.24 years) from the Duke Neurogenetics Study, we identified a significant positive correlation between IL‐1β polygenic scores and hippocampal volume. This positive association was successfully replicated in a second sample of 7,960 white British volunteers (4,158 women, mean age 62.63 ± 7.45 years) from the UK Biobank. Our results lend further support in humans, to the link between IL‐1β and the structure of the hippocampus.     

Tumor necrosis factor and interleukin-1β: suppression of food intake by direct action in the central nervous system

Intracerebroventricular microinfusion of recombinant human tumor necrosis factor (rhTNF) and recombinant human interleukin-1β (rhIL-1β) suppressed food intake in rats. Central infusion of heat-inactivated rhTNF and rhIL-1β, bovine serum albumin, heparin or transforming growth factor-β had no such effect. Central infusion of rhIL-1β did not affect the dipsogenic response to central administration of angiotensin II. Peripheral administration of rhTNF and rhIL-1β in doses equivalent to or higher than those administered centrally had no effect. Electrophoretically applied rhTNF and rhIL-1β specifically suppressed the activity of glucose-sensitive neurons in the lateral hypothalamic area. Glucose-insensitive neurons were little affected. The results suggest that TNF and IL-1β act directly in the central nervous system to suppress feeding, and this effect may be operative during acute and chronic disease.     

Caspase activities and tumor necrosis factor receptor R1 (p55) level are elevated in the substantia nigra from Parkinsonian brain

Summary. The activities of caspase-1 and caspase-3 were measured by use of fluoropeptides as substrates for the first time in the brain (substantia nigra, caudate nucleus, putamen, cerebellum, and frontal cortex) from control and parkinsonian patients. The activities of caspases in the brain were significantly higher in the substantia nigra from parkinsonian patients than those in the brain from control patients (p < 0.01). However, the activities of caspases in the caudate nucleus, putamen, cerebellum, and frontal cortex showed no significant difference between parkinsonian and control patients. The tumor necrosis factor (TNF) receptor R1 (TNF-R1, p55) level was also elevated in the substantia nigra of the parkinsonian brain in comparison with that of controls (p < 0.05). Since both caspases and TNF-R1 may play important roles in apoptotic cell death through TNF-α-induced signaling pathway, our present data suggest the presence of a proapoptotic environment in the substantia nigra of parkinsonian brain, probably inducing vulnerability of neurons and glias towards a variety of noxious factors. Received May 17, 1999; accepted November 15, 1999