Effect of dexamethasone on glial fibrillary acidic protein in peritumorous edema of cats: a morphometric study

Tumour necrosis factor receptor superfamily member 9 (TNFRSF9) is up-regulated in reactive astrocytes in human gliomas

AIMS

The prognosis of patients with malignant gliomas is still dismal despite maximum treatment. Novel therapeutic alternatives targeting tumorigenic pathways are, therefore, demanded. In murine glioma models, targeting of tumour necrosis factor receptor superfamily (TNFRSF) 9 led to complete tumour eradication. Thus, TNFRSF9 might also constitute a promising target in human diffuse gliomas. As there is a lack of data, we aimed to define the expression pattern and cellular source of TNFRSF9 in human gliomas.

METHODS

We investigated TNFRSF9 expression in normal human central nervous system (CNS) tissue and glioma specimens using immunohistochemistry, immunofluorescence and Western blotting techniques.

RESULTS

Our results show that TNFRSF9 is considerably up-regulated in human gliomas when compared with normal brain tissue. In addition, our data provides evidence for an immune cell-independent de novo expression pattern of TNFRSF9 in mainly non-neoplastic reactive astrocytes and excludes classic immunological cell types, namely lymphocytes and microglia as the source of TNFRSF9. Moreover, TNFRSF9 is predominantly expressed in a perivascular and peritumoural distribution with significantly higher expression in IDH-1 mutant gliomas.

CONCLUSIONS

Our findings provide a novel, TNFRSF9-positive, reactive astrocytic phenotype and challenge the therapeutic suitability of TNFRSF9 as a promising target for human gliomas.

Determination of endogenous serum proteins in normal and oedematous brain tissue of cat by rocket and crossed immunoelectrophoresis

A quantitative method for determination of endogenous serum proteins has been established and tested in an experimental model of peritumoural brain oedema in cats. Rocket and crossed immunoelectrophoresis were applied for determination of total serum proteins, albumin, IgG and haemoglobin in blood and brain homogenates. Modifications such as the use of non-ionic detergents and of antisera with different specificity were established for each antigen under investigation. The content of total serum proteins, albumin and IgG was substantially higher in tumour and peritumoural brain tissue than in the non-oedematous brain. The measurement of haemoglobin allowed the calculation of blood volume and, in consequence, the differentiation between intra- and extravascular serum proteins. The results are in line with earlier measurements obtained by different analytical methods and demonstrate that the present technique provides a reliable approach for the quantitative assessment of serum protein extravasation.

Immunohistochemical study of glial reaction and serum-protein extravasation in relation to neuronal damage in rat hippocampus after ischemia

Transient forebrain ischemia of 30 min duration was produced in anaesthetized rats by four-vessel occlusion. After survival periods of 3 h to three days brains were perfusion-fixed and sections through the mid-dorsal hippocampus were processed for conventional staining and immunohistochemical analysis. Neuronal damage in the hilus was manifested 3-8 h after ischemia; neurons in the CA1 and CA2 sector suffered delayed neuronal death after 48-72 h whereas the dentate gyrus and the CA3 sector were normal. Vasogenic edema formation was visualized using antibodies against rat serum-proteins, serum albumin and immunoglobulins. By 3 h after ischemia, only faint and diffuse serum-staining was detected. At 8 h survival, weak astrocytic-staining was present. After 24-72 h CA1-CA2 exhibited massive serum extravasation. The molecular layer of the dentate gyrus showed edema formation in the absence of granule cell damage. The glial reaction was studied using antibodies against glial fibrillary acidic protein, vimentin and S-100 protein. Glial fibrillary acidic protein and S-100 protein-staining increased in areas with either edema or neuronal damage. In contrast, changes in vimentin were only detected in areas with neuronal necrosis. The observations demonstrate that following 30 min of ischemia neuronal damage is accompanied by changes in blood-brain barrier function and reactive glial alterations. The dissociation between neuronal necrosis and astroglial hypertrophy and hyperplasia reflects differences in cellular responsiveness which constitute inherent features of postischemic hippocampal injury.

Experimental transplantation gliomas in the adult cat brain. 1. Experimental model and neuropathology

Tumours were produced in the adult cat brain by injection of the rapidly growing anaplastic rat glioma clone F98 in order to study their neuropathology, pathophysiology, regional biochemistry and magnetic reasonance imaging. We report here the neuropathological behaviour of cell suspensions in the basal ganglia and the left cerebral hemisphere one, two, three, four and six weeks after stereotactic implantation with respect to tumour growth, immunological tumour regression and alterations of the blood-brain barrier with associated vasogenic brain oedema. Injected cell suspensions produce consistently growing tumours during the first, second and third weeks. Tumour sizes varied according to the survival time and were only slightly dependent on the inoculated cell number, i.e., 3 and 6 x 10(6) tumour cells, respectively. Immunohistochemistry with respect to proteins of the cytoskeleton and other cell markers showed positive tumour cell immunoreactions for vimentin and S 100, but not for GFAP, Leu-7, Leu-M1 and MBP. While leucocyte infiltration is apparent after only one week, major tumour regression phenomena develop after three weeks in conjunction with severe lymphocytic reactions of the host, resulting in complete tumour rejection with scar gliosis after four and six weeks, respectively. This transplantation glioma model is accompanied by vasogenic brain oedema both within the tumour area and in the homolateral hemisphere. Immunohistochemistry of serum proteins, i.e. total serum protein, albumin and IgG reveals impairment of the blood-brain barrier after one week, reaching its maximum after two and three weeks. The oedematous changes decrease dramatically after four and six weeks, when most of the serum proteins are reabsorbed by cellular activities in the tumour scar. The vasogenic brain oedema in this xenogeneic glioma transplantation model may be enhanced by the immunological reactions in the brain.

Effect of dexamethasone on blood-brain barrier in the normal mouse

Dexamethasone ameliorates cerebral edema, but its effect on normal blood-brain barrier is unknown, as is the site of action. Sixteen normal mice were given dexamethasone, 3 mg/kg intramuscularly or 2 mg/kg intravenously. One to two hours later 10 mg of horseradish peroxidase (HRP) in 0.1 ml of saline was administered intravenously and allowed to circulate for 15 minutes. Brain slices were examined by light and electron microscopy. The number of HRP-permeable arteriolar segments per brain was less in dexamethasone-treated than in control mice (p less than 0.001). In addition, the number of small HRP-filled endothelial vesicles of capillaries and of HRP-permeable and -impermeable arterial segments was less in dexamethasone-treated mice than that for similar vessels in control mice (p less than 0.005, p less than 0.05, and p less than 0.01, respectively). The total number of small vesicles and the number of larger HRP-filled vesicles in arterioles was the same in treated and control mice. Dexamethasone therefore decreased the normal permeability of cerebral blood vessels to HRP. This decrease was accompanied by a decrease in the number of HRP-containing small endothelial vesicles. These data suggest that dexamethasone influences cerebral edema by decreasing the permeability of the cerebral vasculature for macromolecules.