The Role of a Novel Calpain Inhibitor for the Treatment of Experimental Autoimmune Encephalomyelitis (EAE).

Abstract

Aberrant activation of calpain plays a key role in the pathophysiology of neurodegenerative disorders including multiple sclerosis (MS). Calpain is increasingly expressed in inflammatory cells in experimental autoimmune encephalomyelitis (EAE) and is significantly elevated in the white matter of patients with multiple sclerosis, thus calpain inhibition could be a target for therapeutic intervention. A novel drug cysteic-leucyl-argininal (CYLA) was designed by attaching a cysteic acid to the protease inhibiting part of leupeptin. Cysteic acid has similar functional group as in taurine, an amino acid that is being transported across the blood-brain barrier (BBB) using two taurine transporters. The experiments of this thesis addressed the effect of CYLA, targeted to the central nervous system (CNS), in a myelin oligodendrocyte glycoprotein (MOG)-induced EAE in C57Bl/6 mice. Daily intraperitoneal application of 0.5 to 2mg of this novel calpain inhibitor or oral administration of 2mg of the prodrug was found to significantly reduce the clinical signs, demyelination, and inflammatory infiltration in a dose-and time-dependant manner. Measurement of calpain content by a fluorogenic method and calpain activity by Western blot analysis of substrate degradation (alpha-fodrin) revealed that this inhibitor could cross the blood-brain barrier and inhibit calpain. In addition, the effect of CYLA in suppressing axonal injury was examined in chronic EAE. Markers for axonal injury were barely detectable in the CYLA treated mice groups. Both the free aldehyde form of CYLA, which was administered by injection, and the diacetal prodrug which was given orally, were able to ameliorate the disease course and its progression. We concluded that CYLA has a potential for the treatment of MS and other neurodegenerative disease in which elevated calpain activity is suspected.