Protease inhibitors as a model for NCL disease, with special emphasis on the infantile and adult forms.

An animal model of NCL disease has been developed with the use of protease inhibitors. Young rats received a continuous infusion of various specific protease inhibitors or of physiological saline into the lateral ventricle of the brain using osmotic mini-pumps. Treatment lasted for 2 weeks, at which time animals were sacrificed and the brains were removed and processed for light or electron microscopic analysis. The thiol protease inhibitors leupeptin and E64C, but not saline or the serine protease inhibitor aprotinin, caused a massive accumulation of ceroid-lipofuscin (CL) in brain cells that bore a strong morphological resemblance to the CL in the infantile and adult forms of NCL disease, and bore similarity to the CL of the late infantile and juvenile forms. Leupeptin also caused the death of cerebellar Purkinje cells, as is seen in the infantile and adult forms of NCL. Further evidence is presented in support of the hypothesis (Ivy et al.: Science 226:985-987, 1984) that decreased or defective lysosomal thiol proteases or their substrates may underly the pathogenesis of at least the infantile and adult forms of NCL disease. Administration of protease inhibitors to the brains of young rats provides an important model for studying the cellular mechanisms of ceroid-lipofuscino-genesis.