Effects of calpain inhibition on dopaminergic markers and motor function following intrastriatal 6-hydroxydopamine administration in rats.
The neurotoxin 6-hydroxydopamine has been widely used to model aspects of Parkinson's disease in rodents, but the mechanisms underlying toxin-induced dopaminergic degeneration and functional impairment have not been fully elucidated. The main aim of the present study was to assess a possible role for calpains in neurochemical and behavioral deficits following unilateral infusion of intrastriatal 6-hydroxydopamine in adult rats. Toxin administration produced a profound dopaminergic denervation, as indicated by a 90-95% reduction in dopamine transporter radiolabeling measured in the caudate-putamen at 2 weeks post-lesion. Treatment with 6-hydroxydopamine also resulted in calpain activation in both caudate-putamen and substantia nigra, as measured by the appearance of calpain-specific spectrin breakdown products. Calpain activation peaked at 24 h after 6-hydroxydopamine infusion and remained elevated at later time points. In contrast, caspase-3-mediated spectrin cleavage subsided within 48 h in both brain areas. In a subsequent experiment, calpain inhibition was achieved by intrastriatal infusion of an adenovirus expressing the endogenous calpain inhibitor, calpastatin. Calpastatin delivery abolished the lesion-induced calpain-mediated spectrin cleavage and alleviated forelimb asymmetries resulting from unilateral intrastriatal 6-hydroxydopamine. Unexpectedly, dopamine transporter and tyrosine hydroxylase labeling revealed significant neuroprotection, not in the nigrostriatal pathway but rather in the ventral tegmental area. These findings support a role for calpain activation in 6-hydroxydopamine-induced degeneration of dopaminergic neurons. However, after near-total dopaminergic depletion, the primary benefit of calpain inhibition may not occur within the nigrostriatal dopaminergic pathway itself.
Grant
R J
RJ
Department of Pharmacology and Therapeutics, McGill University, 3655 Promenade Sir-William-Osler Room 1325, Montreal, Quebec, Canada H3G 1Y6.
Sellings
L H L
LH
Crocker
S J
SJ
Melloni
E
E
Park
D S
DS
Clarke
P B S
PB
D018663:Adrenergic Agents / Q000008:administration & dosage*; D000818:Animals; D001345:Autoradiography; D002135:Calcium-Binding Proteins / Q000494:pharmacology; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D003042:Cocaine / Q000031:analogs & derivatives / Q000378:metabolism; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism; D007839:Functional Laterality / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000235:genetics; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D016627:Oxidopamine / Q000008:administration & dosage*; D011597:Psychomotor Performance / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013049:Spectrin / Q000378:metabolism; D013997:Time Factors; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
D018663:Adrenergic Agents; D002135:Calcium-Binding Proteins; D050483:Dopamine Plasma Membrane Transport Proteins; D013049:Spectrin; D049452:Green Fluorescent Proteins; C069723:2beta-carbomethoxy-3beta-(4-iodophenyl)tropane; C033668:calpastatin; D016627:Oxidopamine; D014446:Tyrosine 3-Monooxygenase; D002154:Calpain; D053148:Caspase 3; D003042:Cocaine; D004298:Dopamine