Increased cathepsin B activity in multiple sclerosis brain.

Cathepsin B (CB) activity was measured in aqueous extracts of frozen autopsy specimens of centrum semiovale from three MS patients, five control patients with other neurological diseases, and five normal individuals. Mean activity was significantly increased in the MS tissue compared with controls. The mean activity in MS tissue containing demyelinating lesions was higher than that in normal appearing white matter which was higher than that in normal control specimens but the differences were not statistically significant. The mean CB activity in patients with other neurological diseases was higher than normal control activity and, although the difference was not statistically significant, this observation suggests that increases in CB may not be specific for MS. Immunohistochemical studies of the MS brain tissue analyzed biochemically suggested that monocytes, macrophages and reactive astrocytes are potential sources of increased CB in MS brain.