Direct and astrocyte-mediated effects of ethanol on brain-derived endothelial cells

The effects of ethanol have been studied in the central nervous system, however there exists only scarce information about the effects of ethanol on endothelial cells forming the blood-brain barrier. As some properties of brain endothelial cells are modulated by underlying astrocytes, the effect of ethanol on cerebral microvasculature might be indirect and mediated by astrocytes. To analyse this question, we added to rat brain-derived endothelial cells (rbEC) in culture either only ethanol (0, 15 and 150 mM) or ethanol conjointly with soluble factors secreted by astrocytes. Alternatively, astrocytes were exposed to ethanol and the medium was added to rbEC. The effects of treatments were evaluated on cell growth and expression of specific proteolytic markers of rbEC. The experiments showed that while the addition of ethanol alone to rbEC increased the expression of gamma-glutamyltranspeptidase and cell growth following an initial toxic effect, the most significant effects were seen when ethanol was added to rbEC together with astrocytic factors or when medium conditioned by astrocytes exposed to ethanol was added to rbEC. In particular, the expression of angiotensin converting enzyme in endothelial cells was dose-dependently increased. These results indicate that the hypertensive and toxic effects of ethanol are mediated by ethanol and soluble factor(s) secreted by astrocytes and dependent on the expression of angiotensin converting enzyme in the brain endothelium. Thus, when evaluating in vitro the effects of toxic substances such as ethanol on the cerebral endothelium, the modulating effect of cells surrounding cerebral vessels must be accounted fo

Microglial cells induce cytotoxic effects toward colon carcinoma cells: measurement of tumor cytotoxicity with a gamma-glutamyl transpeptidase assay

Activated macrophages have been shown to exert cytostatic and cytotoxic effects toward tumor cells via nitric oxide (NO) release. In the CNS, microglial cells are considered to be the main resident population of immune effector cells. In this study, cytotoxic activity of N11, an immortalized murine microglial cell line, toward rat progressive DHD/PROb and regressive DHD/REGb colon carcinoma cells was examined in parallel with NO production. Cytotoxicity was evaluated using a novel method, the gamma-glutamyl transpeptidase (gamma-GTP) assay, based on the fact that DHD tumor cells expressed high levels of gamma-GTP activity, while no gamma-GTP activity was found in cells of the monocyte/macrophage lineage. Results showed that activation of N11 cells by interferon-gamma plus either lipopolysaccharide or tumor necrosis factor-alpha induced high amounts of NO release and cytotoxic effects toward DHD/PROb as well as DHD/REGb cells. NO release by activated N11 cells was augmented by addition of tumor cell-conditioned medium. Both NO release by N11 cells and cytotoxicity were blocked by addition of N(G)-monomethyl-L-arginine (L-NMA), an inhibitor of NO synthase, suggesting that cytotoxicity was mediated by N11-derived NO. However, in the presence of L-NMA an increased production of interleukin-6 was also observed. In conclusion, in opposition to information obtained with brain-derived endothelial cells, brain-derived microglial cells did not differentiate between progressive and regressive clones of colon carcinoma cells. Our results point to a specific role for both endothelial and microglial cell types in the context of brain metastasis. Microglial cells can be cytotoxic for tumor cells, and this cytotoxicity is mediated by N