Inhibition of Calpains Prevents Neuronal and Behavioral Deficits in an MPTP Mouse Model of Parkinson's Disease

Abstract

The molecular mechanisms mediating degeneration of midbrain dopamine neurons in Parkinson's disease (PD) are poorly understood. Here, we provide evidence to support a role for the involvement of the calcium-dependent proteases, calpains, in the loss of dopamine neurons in a mouse model of PD. We show that administration of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) evokes an increase in calpain-mediated proteolysis in nigral dopamine neurons in vivo. Inhibition of calpain proteolysis using either a calpain inhibitor (MDL-28170) or adenovirus-mediated overexpression of the endogenous calpain inhibitor protein, calpastatin, significantly attenuated MPTP-induced loss of nigral dopamine neurons. Commensurate with this neuroprotection, MPTP-induced locomotor deficits were abolished, and markers of striatal postsynaptic activity were normalized in calpain inhibitor-treated mice. However, behavioral improvements in MPTP-treated, calpain inhibited mice did not correlate with restored levels of striatal dopamine. These results suggest that protection against nigral neuron degeneration in PD may be sufficient to facilitate normalized locomotor activity without necessitating striatal reinnervation. Immunohistochemical analyses of postmortem midbrain tissues from human PD cases also displayed evidence of increased calpain-related proteolytic activity that was not evident in age-matched control subjects. Taken together, our findings provide a potentially novel correlation between calpain proteolytic activity in an MPTP model of PD and the etiology of neuronal loss in PD in humans.

Hypersensitivity of DJ-1-deficient mice to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrindine (MPTP) and oxidative stress

“…At 14 days post-MPTP treatment, all mice were killed and their neurons analyzed. For mice pretreated with adenoviral vectors, viruses were injected unilaterally into the right striatum as described (30). The adenovirus was delivered into the striatum 7 days before the initiation of MPTP treatment.…”

“…Loss of TH ϩ or cresyl violet-stained cells in the nigral region was used as an index of dopaminergic cell loss after MPTP treatment. For adenoviral experiments, TH ϩ cell counts were performed as described (30) at the level of medial terminal nucleus, the region in which adenovirus-mediated gene expression is highest (30). For analyses of TH and dopamine transporter protein (DAT) intensity in the striatum, sections were analyzed by densitometry by using NORTHERN ECLIPSE IMAGE software, as described (30).…”

“…Novel environment. Walled 30 ϫ 30-inch square arenas were used for open field testing of mice by using a video camera and analysis software, as described (30). Motor impairments.…”

“…Animals were monitored for 24 h before MPTP treatment or starting on day 13 after the initiation of MPTP treatment. To assess ''dopaminerelated'' behavioral output, mice were monitored for 1 hr after amphetamine challenge (2 mg͞kg) (30).…”

Novel Mechanisms of Target Cell Death and Survival and of Therapeutic Action of IVIg in Pemphigus

“…calpain inhibitor Z-DCB-MK that had been successfully used in animal experiments 44,45 To better define the cell death pathways elicited by PV autoantibodies in vivo, we also tested anti-acantholytic activities of each inhibitor under consideration. Although the calpain inhibitor MDL-28170 significantly (P Ͻ 0.05) decreased acantholysis in the epidermis of pups injected with PVIgG-1b, the caspase inhibitor Z-DCB-MK significantly (P Ͻ 0.05) reduced extent of epidermal clefting induced by PVIgG-2b ( Figure 4B).…”