NEW INHIBITORS OF CALPAIN PREVENT DEGRADATION OF CYTOSKELETAL AND MYELIN PROTEINS IN SPINAL-CORD IN-VITRO

We have determined the effects of the calpain inhibitors AK275 and AK2 95 upon purified m-calpain and calcium-mediated degradation of neurofi lament protein (NFP) in rat spinal cord in vitro, After incubation the soluble radioactivity and/or extent of myelin basic protein (MBP) or NFP degradation was determined, Fifty percent of caseinolytic activity was inhibited by both inhibitors at 0.6 mu M concentration, while mor e than 90% inhibition was seen at 1.6 mu M. In contrast, 37% and 64% i nhibition of MBP degradation was seen with AK295 and AK275, respective ly, at 10 mu M concentration, The extent of NFP degradation in spinal cord was quantified from immunoblot enhanced chemiluminescence, The ca lcium-mediated breakdown of NFP was inhibited by both AK275 and AK295, and the inhibition was dose-dependent. A 50% inhibition of NFP degrad ation was seen with AK295 at 10 pill and was almost completely inhibit ed at 25-50 mu M. AK295 was slightly more potent than AK275, These stu dies suggest that these potent calpain inhibitors may be used therapeu tically to provide neuroprotection in vivo in experimental central ner vous system trauma and ischemia. (C) 1998 Wiley-Liss, Inc.