A morphological and ultrastructural investigation of normal mouse brain tissue after intracerebral injection of tumor necrosis factor

TNF-alpha microinjection upregulates chemokines and chemokine receptors in the central nervous system without inducing leukocyte infiltration

Chemokines (chemoattractant cytokines) are key players in the initiation of inflammatory cell accumulation in the central nervous system (CNS). Mechanisms leading to upregulation of chemokines in CNS pathologic conditions remain largely unknown. Numerous in vitro studies showed that inflammatory cytokines stimulate cultured CNS cells to produce chemokines. The main goal of this study was to analyze if an individual proinflammatory cytokine is sufficient to upregulate the chemokine system in the adult CNS in vivo. We analyzed CC chemokine ligand and receptor expression in brains from two different strains of mice (SJL and BALB) after stereotaxic, intracerebral injection of tumor necrosis factor-alpha (TNF-alpha). In both strains, we detected similarly increased expression of chemokines RANTES/CCL5, macrophage inflammatory protein-1alpha (MIP-1alpha)/CCL3, MIP-1beta/CCL4, and MIP-2, as well as chemokine receptors CCR1, CCR2, and CCR5. Interestingly, we did not observe parenchymal leukocyte infiltrates after local TNF-alpha delivery. This observation shows that upregulation of chemokines by TNF-alpha is not sufficient to cause accumulation of leukocytes in the CNS parenchyma in both strains of mice.

Interferon-beta prevents cytokine-induced neutrophil infiltration and attenuates blood-brain barrier disruption

Inflammation can contribute to brain injury, such as that resulting from ischemia or trauma. The authors have previously shown that the cytokine interferon-beta (IFN-beta) affords protection against ischemic brain injury, which was associated with a diminished infiltration of neutrophils and a reduction in blood-brain barrier (BBB) disruption. The goal of the current study was to directly assess the effects of IFN-beta on neutrophil infiltration, with the use of an in vivo assay of neutrophil infiltration with relevance to ischemic brain injury. Intrastriatal injection of recombinant rat cytokine-induced neutrophil chemoattractant-1, a member of the interleukin-8 family (1 microg in 1 microl), triggered massive infiltration of neutrophils and extensive BBB disruption 6 hours later, as measured using immunofluorescence microscopy and magnetic resonance imaging in the rat, respectively. Depleting the animals of neutrophils before interleukin-8 injection prevented BBB disruption. Treatment with IFN-beta (5 x 106 U/kg) almost completely prevented neutrophil infiltration and attenuated BBB damage. Gelatinase zymography showed matrix metalloproteinase-9 expression in the ipsilateral striatum after interleukin-8 injection. Both neutrophil depletion and IFN-beta treatment downregulated matrix metalloproteinase-9. IFN-beta has already been approved for human use as a treatment for the chronic inflammatory disorder multiple sclerosis. The potential value of IFN-beta as a treatment that can attenuate acute brain inflammation is considered.

Tumour necrosis factor-alpha has few morphological effects within the dorsal columns of the spinal cord, in contrast to its effects in the peripheral nervous system

There is circumstantial evidence implicating the pro-inflammatory cytokine tumour necrosis factor (TNF) in the pathogenesis of multiple sclerosis (MS), but there is no direct evidence that TNF can produce demyelination in the central nervous system (CNS). We demonstrate here that single injections of TNF into the dorsal columns of adult rats produced a mild inflammatory response indistinguishable from that seen in control cords, but did not induce demyelination. A similar response was seen when TNF-alpha was injected into dorsal columns where central axons had been remyelinated by Schwann cells. In marked contrast, single intraneural injections of TNF into sciatic nerves produced acute changes in the endoneurial microvascular bed that were followed by demyelination and degeneration.

Late-onset chronic inflammatory encephalopathy in immune-competent and severe combined immune-deficient (SCID) mice with astrocyte-targeted expression of tumor necrosis factor

To examine the role of tumor necrosis factor (TNF)-alpha in the pathogenesis of degenerative disorders of the central nervous system (CNS), transgenic mice were developed in which expression of murine TNF-alpha was targeted to astrocytes using a glial fibrillary acidic protein (GFAP)-TNF-alpha fusion gene. In two independent GFAP-TNFalpha transgenic lines (termed GT-8 or GT-2) adult (>4 months of age) animals developed a progressive ataxia (GT-8) or total paralysis affecting the lower body (GT-2). Symptomatic mice had prominent meningoencephalitis (GT-8) or encephalomyelitis (GT-2) in which large numbers of B cells and CD4+ and CD8+ T cells accumulated at predominantly perivascular sites. The majority of these lymphocytes displayed a memory cell phenotype (CD44high, CD62Llow, CD25-) and expressed an early activation marker (CD69). Parenchymal lesions contained mostly CD45+ high, MHC class II+, and Mac-1+ cells of the macrophage microglial lineage with lower numbers of neutrophils and few CD4+ and CD8+ T cells. Cerebral expression of the cellular adhesion molecules ICAM-1, VCAM-1, and MAdCAM as well as a number of alpha- and beta-chemokines was induced or upregulated and preceded the development of inflammation, suggesting an important signaling role for these molecules in the CNS leukocyte migration. Degenerative changes in the CNS of the GFAP-TNFalpha mice paralleled the development of the inflammatory lesions and included primary and secondary demyelination and neurodegeneration. Disease exacerbation with more extensive inflammatory lesions that contained activated cells of the macrophage/microglial lineage occurred in GFAP-TNFalpha mice with severe combined immune deficiency. Thus, persistent astrocyte expression of murine TNF-alpha in the CNS induces a late-onset chronic inflammatory encephalopathy in which macrophage/microglial cells but not lymphocytes play a central role in mediating injury.

Cellular targets of exogenous tumour necrosis factor-alpha (TNF alpha) in human gliomas

To identify the cellular targets of TNF alpha in human gliomas, a total of 30 surgical specimens (12 glioblastomas, 4 anaplastic astrocytomas, 3 astrocytomas, 7 brains adjacent to tumour (BAT), 4 histologically normal-appearing brains) were examined by in vitro binding technique using biotinylated TNF alpha. The TNF-binding sites (TNF-BS) were recognized in the tumour cells in 8 of the 12 glioblastomas, 3 of the 4 anaplastic astrocytomas and in all the 3 astrocytomas. The TNF-BS were also recognized in the vascular endothelial cells in all these cases. The presence of TNF-BS in blood vessels ranged from 7.7 to 74.4% of the background vessels. This wide range of variation in the presence of TNF-BS within the tumour cells and tumour blood vessels may be relevant to the variable response of individual tumours to TNF alpha therapy. Since the tissue of normal brain, which lacks TNF-BS, might hardly be affected by this cytokine, administration of TNF alpha may be considered as an adjuvant therapy in selected groups of patients.

Tumor necrosis factor expression during mouse hepatitis virus-induced demyelinating encephalomyelitis

Neutralizing anti-tumor necrosis factor alpha (TNF-alpha) antibody treatment of mice infected with the neurotropic JHMV strain of mouse hepatitis virus showed no reduction of either virus-induced encephalomyelitis or central nervous system demyelination. TNF-alpha-positive cells were present in the central nervous system during infection; however, TNF-alpha could not be colocalized with JHMV-infected cells. In vitro, TNF-alpha mRNA rapidly accumulated following JHMV infection; however, no TNF-alpha was secreted because of inhibition of translation. Both live and UV-inactivated virus inhibited TNF-alpha secretion induced by lipopolysaccharide. These data show that TNF-alpha is not secreted from infected cells and indicate that if contributes to either JHMV-induced acute encephalomyelitis nor primary demyelination.

Growth-inhibiting effect of intratumoral recombinant human tumor necrosis factor on an experimental model of primitive neuroectodermal tumor

The effect of intratumoral administration of recombinant human tumor necrosis factor on an experimental model of primitive neuroectodermal neoplasia was studied. A clear inhibition of tumor growth was achieved by immunotherapy that consisted in intralesion injections of 100 micrograms of tumor necrosis factor daily, the first three days of each week, for a period of four weeks. At this time, tumor size was 2.21 +/- 0.66 cm2 (mean +/- standard deviation) in the treated group, versus 7.62 +/- 0.43 cm2 in the control group. These data support previous studies on the influence of tumor necrosis factor on the development of ethyl-nitrosourea-induced tumors, and suggest the potential usefulness of this cytokine in human primitive neuroectodermal neoplasms.

Effect of recombinant tumor necrosis factor-alpha on three-dimensional growth, morphology, and invasiveness of human glioblastoma cells in vitro

In order to investigate the antiproliferative and anti-invasive effects of tumor necrosis factor (TNF)-alpha on human glioblastoma cells, an in vitro three-dimensional (anchorage-independent) assay was performed using Matrigel, a mixture of extracellular matrix proteins. Four glioblastoma-derived cell lines, including one cloned line, were cultured in Matrigel with or without TNF-alpha. In the Matrigel containing TNF-alpha, three of the four cell lines, including the cloned line, showed significant growth inhibition in a dose-dependent manner. Dramatic three-dimensional morphological differences were observed between TNF-treated and untreated glioblastoma cells cultured in Matrigel. Untreated cells formed large and highly branched colonies throughout the gel. In contrast, the majority of TNF-treated cells demonstrated truncated branching processes and, at a high TNF-alpha dose, an increasing number of cells remained in relatively small spherical aggregates, their cell processes being significantly reduced. Quantitative invasion assay using a micro-Boyden chamber system confirmed that TNF-treated cells lost invasiveness in a dose-dependent manner. These results suggest that TNF-alpha exerts not only antiproliferative but also anti-invasive effects on human glioblastoma cells in vitro. It is believed that this is the first report showing the anti-invasive effect of TNF-alpha on tumor cells.

The future of therapy for glioblastoma

Effective therapy for malignant gliomas has centered on traditional approaches such as surgery and radiation therapy. Over the past two decades, more innovative approaches involving the use of chemotherapy and immunotherapy have been developed. Although these techniques have improved the quality of survival for many patients, the median survival following diagnosis and adjuvant treatment still remains only about a year. Recently, genetically engineered viruses for gene transduction and targeted cell killing have been used successfully in the experimental treatment of glioblastoma multiforme. We provide a review of the current and possible future therapies for malignant glioma with the belief that molecular biologic and genetic techniques offer the greatest hope of significantly altering the course of disease.