Strain specific variation in cytokine regulated ICAM-1 expression by rat brain-endothelial cells

Pharmacological Targeting of ICAM-1 Signaling in Brain Endothelial Cells: Potential for Treating Neuroinflammation

(1) The vasculature of the blood-brain barrier allows only comparatively few leukocytes to enter and survey the healthy central nervous system (CNS). However, during pathological CNS inflammation, the number of leukocytes adhering to and penetrating the CNS vasculature increases strongly. (2) Endothelial adhesion molecules do not only mediate firm adhesion of leukocyte to vascular beds but also trigger signaling cascades within the endothelial cell, which play a crucial role in modulating subsequent leukocyte diapedesis. (3) Signaling through endothelial intercellular adhesion molecule-1 (ICAM-1, CD54) has been shown to induce changes of the endothelial cytoskeleton, transcription, and interendothelial junctions, all of which may be important in modulating endothelial disposition to infiltrating leukocytes. Furthermore, a number of recent reports document that drugs interfering with endothelial ICAM-1 signaling, efficiently reduce leukocyte migration both in vitro and in animal models of CNS inflammation. (4) These approaches are novel in as much as they target vascular beds rather than the penetrating leukocytes. Since endothelial ICAM-1 signaling appears to differ between different vascular beds we propose that such compounds could potentially be used as exquisite drugs in the treatment of neuroinflammatory diseases.

Substance P antagonist blocks leakage and reduces activation of cytokine-stimulated rat brain endothelium

We recently demonstrated that substance P mediates increased permeability of brain endothelium exposed to HIV-1 gp120. To test whether substance P is involved in immune processes at the blood-brain barrier (BBB), we stimulated rat brain endothelial cultures prepared from cerebral microvessels with Interferon-gamma (IFN-gamma) and Tumor necrosis factor-alpha (TNF-alpha), two proinflammatory cytokines that alter the BBB and measured permeability to albumin and expression of adhesion molecule ICAM-1 and MHC class II antigen in the presence and absence of spantide, a powerful substance P antagonist. In a dose-dependent manner, spantide completely neutralized increased permeability induced by TNF-alpha and IFN-gamma and expression of MHC class II molecule induced by IFN-gamma and prevented associated cell morphological changes as revealed by scanning electron microscope. Spantide also reduced expression of ICAM-1 induced by TNF-alpha and IFN-gamma by 35% and 30%, respectively. Substance P mRNA was found in unstimulated brain endothelial cells and was upregulated after stimulation with TNF-alpha and IFN-gamma. These in vitro findings demonstrate that substance P plays a major pathogenetic role in damaging and activating the BBB vascular component in the presence of proinflammatory cytokines.

The adhesion molecule ICAM-1 and its regulation in relation with the blood-brain barrier

The blood-brain barrier (BBB) is formed by high resistance tight junctions within the capillary endothelium perfusing the vertebrate brain. Normal BBB maintains a unique microenvironment within the central nervous system (CNS). In neurodegenerative disorders (for example multiple sclerosis, MS), the BBB becomes impaired. Perivascular cells (astrocytes, macrophages and microglial cells) and brain microvascular endothelial cells (BMEC) produce various inflammatory factors that affect the BBB permeability and the expression of adhesion molecules. Indeed, cytokines can stimulate the expression of several adhesion molecules on brain microvascular endothelial cells. Among these adhesion molecules, the intercellular adhesion molecule-1 (ICAM-1) binds to its leukocyte ligands and allows activated leukocytes entry into the CNS. This review is dealing with the expression and regulation of ICAM-1 in relation with several properties of the BBB. Particularly, the role of ICAM-1 in the control of the leukocyte traffic into the CNS, as well as in cerebral malaria and in CNS infection by viruses, is discussed.