The infiltration of leukocytes into the central nervous system is associated with many pathologic conditions of the brain. The mechanisms by which these immune cells can penetrate the blood-brain barrier and remain within the brain are not understood. However, elevated brain levels of the pro-inflammatory cytokine IL-1 appear to accompany pathogenesis. The present study provides the first evidence that IL-1 can induce the expression of adhesion molecules for leukocytes on glial cells and suggests a role for the transcription factor NF-kappa B in the induction process. Human rIL-1 alpha was found to induce the expression of the cell adhesion molecules, vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) but not E-selectin in human 1321N1 astrocytoma. Both VCAM-1 and ICAM-1 were detectable from 3 h and remained sustained for up to 72 h. Induction was inhibited by the IL-1 receptor antagonist. IL-1 alpha was also shown to induce the expression of VCAM-1 and ICAM-1 in a receptor-dependent fashion in human A172 glioblastoma. Activation of the transcription factor NF-kappa B was also observed in 1321N1 astrocytoma in response to IL-1 alpha treatment and was similarly abolished by pretreatment of cells with antagonist. Activated NF-kappa B was apparent from 20 min and remained for up to 24 h. N-acetylcysteine (NAC) and pyrollidinedithiocarbamate (PDTC), which were shown to inhibit activation of NF-kappa B in Jurkat E6.1 lymphoblasts and EL4.NOB-1 thymoma, failed to block IL-1 activation of NF-kappa B in 1321N1 astrocytoma. However, both of these antioxidants demonstrated complex modulatory effects on the induction of cell adhesion molecule expression by IL-1. The induction of VCAM-1 but not of ICAM-1 proved susceptible to inhibition by both PDTC and NAC. The expression of adhesion molecules for leukocytes on glial cells in response to IL-1 may represent an important mechanism for retention of immune cells in the central nervous system that may be a prologue to inflammatory conditions in the brain.

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