Region-specific attenuation of a trypsin-like protease in substantia nigrafollowing dopaminergic neurotoxicity by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

We analysed apoptosis, caspase-1 and -3, and trypsin-like protease activity in the nigrostriatal pathway during 1-methyl-4-phenyl-1,2,3,6-tetrahydropy ridine (MPTP)-induced neurotoxicity. MPTP injected (30 mg/kg, i.p., twice, 16 h apart) mice were sacrificed on i, 2 and 7 days. DNA extracted from nuc leus caudatus putamen (NCP) and substantia nigra (SN) was subjected to agar ose gel electrophoresis. Typical apoptotic-like DNA cleavage was absent in SN or NCP after this dose of MPTP. A trypsin-like protease activity was sig nificantly decreased in SN and not in NCP. While caspase-3 activity in the whole brain was increased significantly, caspase-1 activity was unaffected. Striatal dopamine content was decreased to 75% by 7 days. The absence of t ypical DNA 'ladder' when there was severe striatal dopamine depletion sugge sts that in vivo MPTP-mediated dopaminergic neurotoxicity may not involve a poptotic cell death, and explains why in mice MPTP-induced dopamine depleti on is transient. The region-specific decrease in trypsin-like protease acti vity and absence of caspase-3 activation in SN signify the importance of tr ypsin-like protease in the regulation of apoptosis in MPTP-neurotoxicity in mice. (C) 2000 Elsevier Science B.V. All rights reserved.