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.