Interferon-β counteracts inflammatory mediator-induced effects on brain endothelial cell tight junction molecules -: Implications for multiple sclerosis

To elucidate mechanisms of endothelial cell (EC) dysfunction in CNS inflammatory responses and beneficial effects of interferon-beta (IFN-beta) in multiple sclerosis (MS), we analyzed effects of individual and combinations of soluble inflammatory mediators on the intracellular localization of the EC tight junction-associated molecules zonula occludens-1 and -2 (ZO-1 and ZO-2) in human brain ECs. The cytoplasm in the majority of cells in control EC cultures was clear; ZO-1 and ZO-2 were localized peripherally near sites of cell contact and associated with submembranous cytoplasmic filaments. H2O2 induced reversible time- and concentration-dependent translocation of ZO-1 and ZO-2 to a random distribution within EC cytoplasm and retraction of EC borders. For low concentrations, these effects were accompanied by less prominent submembranous filaments but not by evidence of cytotoxicity, increased cell death or altered amounts of ZO-1. Tumor necrosis factor-alpha induced similar alterations but interferon-gamma did not. Co-treatment with either cytokine increased H2O2 effects whereas IFN-beta reversed H2O2-induced effects. In control white matter samples, EC cytoplasm was clear and ZO-1 was located on cell borders. In inflammatory/demyelinating lesions, EC ZO-1 was diffuse, indicating that the alterations induced in vitro mimic those in active MS lesions. These findings suggest that in MS patients, IFN-beta treatment may counteract inflammatory mediator effects on CNS EC tight junction molecules, thereby preserving EC barrier function.