Abnormal endothelial tight junctions in active lesions and normal-appearing white matter in multiple sclerosis

Blood-brain barrier (BBB) breakdown, demonstrable in vivo by enhanced MRI is characteristic of new and expanding inflammatory lesions in relapsing remitting and chronic progressive multiple sclerosis (MS). Subtle leakage may also occur in primary progressive MS. However, the anatomical route(s) of BBB leakage have not been demonstrated. We investigated the possible involvement of interendothelial tight junctions (TJ) by examining the expression of TJ proteins (occludin and ZO-1 ) in blood vessels in active MS lesions from 8 cases of MS and in normal-appearing white (NAWM) matter from 6 cases. Blood vessels (10-50 per frozen section) were scanned using confocal laser scanning microscopy to acquire datasets for analysis. TJ abnormalities manifested as beading, interruption, absence or diffuse cytoplasmic localization of fluorescence, or separation of junctions (putative opening) were frequent (affecting 40% of vessels) in oil red-O-positive active plaques but less frequent in NAWM (15%), and in normal (

Differences in expression of junctional adhesion molecule-A and beta catenin in multiple sclerosis brain tissue: increasing evidence for the role of tight junction pathology

Previously we have employed antibodies to the tight junction (TJ)-associated proteins ZO-1 and occludin to describe endothelial tight junction abnormalities, in lesional and normal appearing white matter, in primary and secondary progressive multiple sclerosis (MS). This work is extended here by use of antibodies to the independent TJ-specific proteins and junctional adhesion molecule A & B (JAM-A, JAM-B). We have also assessed the expression in MS of ß-catenin, a protein specific to the TJ-associated adherens junction. Immunocytochemistry and semiquantitative confocal microscopy for JAM-A and ß-catenin was performed on snap-frozen sections from MS cases (n = 11) and controls (n = 6). Data on 1,443 blood vessels was acquired from active lesions (n = 13), inactive lesions (n = 13), NAWM (n = 20) and control white matter (n = 13). In MS abnormal JAM-A expression was found in active (46%) and inactive lesions (21%), comparable to previous data using ZO-1. However, a lower level of TJ abnormality was found in MS NAWM using JAM-A (3%) compared to ZO-1 (13%). JAM-B was strongly expressed on a small number of large blood vessels in control and MS tissues but at too low a level for quantitative analysis. By comparison with the high levels of abnormality observed with the TJ proteins, the adherens junction protein ß-catenin was normally expressed in all MS and control tissue categories. These results confirm, by use of the independent marker JAM-A, that TJ abnormalities are most frequent in active white matter lesions. Altered expression of JAM-A, in addition to affecting junctional tightness may also both reflect and affect leukocyte trafficking, with implications for immune status within the diseased CNS. Conversely, the adherens junction component of the TJ, as indicated by ß-catenin expression is normally expressed in all MS and control tissue categories.

Upregulation of osteopontin and alpha B crystallin in the normal-appearing white matter of multiple sclerosis: an immunohistochemical study utilizing tissue microarrays

Tissue microarrays assembled from control and multiple sclerosis (MS) brain tissue have been used to assess the expression patterns and cellular distribution of two antigens, the proinflammatory cytokine osteopontin and the inducible heat shock protein alpha B -crystallin, which have previously been implicated in MS pathogenesis. Tissue cores were taken from paraffin-embedded donor blocks containing chronic active or chronic inactive plaques and normal-appearing white matter (NAWM) in seven MS cases, and white matter (WM) in five control cases. Expression patterns of both proteins were assessed against myelin density and microglial activation in the different tissue categories. Both proteins showed increased expression in all categories of MS tissue compared with control WM. The results indicate progressive up-regulation of expression of osteopontin with increased plaque activity, while elevation of alpha B-crystallin expression in MS tissue was independent of demyelination. In MS NAWM a significant correlation was observed between high levels of expression of osteopontin and alpha B -crystallin. Osteopontin expression was predominantly confined to astrocytes throughout MS tissues. alpha B -crystallin was expressed on astrocytes, oligodendrocytes and occasionally on demyelinated axons. Taken together, these data indicate a wider distribution of osteopontin and alpha B -crystallin in MS tissues than previously described and support their proposed role in MS pathogenesis.

Monocyte-derived dendritic cells: a potential target for therapy in multiple sclerosis (MS)

Monocytes can differentiate into dendritic cells (DC), cells with a pivotal role in both protective immunity and tolerance. Defects in the maturation or function of DC may be important in the development of autoimmune disease. We sought to establish if there were differences in the cytokine (granulocyte-macrophage colony-stimulating factor and IL-4)-driven maturation of monocytes to DC in patients with MS and whether drugs used to treat MS affected this process in vitro. We have demonstrated that there is no defect in the ability of magnetic activated cell sorting (MACS)-purified monocytes from patients with MS to differentiate to DC, but equally they show no tendency to acquire a DC phenotype without exogenous cytokines. Interferon-beta1a prevents the acquisition of a full DC phenotype as determined by light and electron microscopy and by flow cytometry. Methylprednisolone not only prevents the development of monocyte-derived DC but totally redirects monocyte differentiation towards a macrophage phenotype. Evidence is evolving for a role for DC in central nervous system immunity, either within the brain or in cervical lymph nodes. The demonstrated effect of both drugs on monocyte differentiation may represent an important site for immune therapy in MS.