Calpain Upregulation and Neuron Death in Spinal Cord of MPTP‐Induced Parkinsonism in Mice

Abstract

Parkinson's disease (PD) is a neurodegenerative disorder resulting in slowness, tremors, and imbalance. Treatment of mice with 1‐methyl‐4‐phenyl‐1,2,3,6 tetrahydropyridine (MPTP) is one of several models used to mimic PD in humans. Administration of MPTP leads to the production of 1‐methyl‐4‐phenyl‐2,3 dihydropyridinium (MPP+). MPP+ is taken up by dopaminergic neurons, causing mitochondrial dysfunction and cell death. Because calpain is involved in neuronal cell death and mitochondrial dysfunction, we examined the level of calpain in neurons in the substantia nigra (SN) and hippocampus of MPTP‐treated C57BL/6 mice. Because of the interconnections between spinal cord and upper central nervous system neurons, we examined morphology, calpain activity, and calpain expression in neurons by double immunofluorescence using calpain and neuron marker (NeuN) antibodies. In controls, calpain expression was low in SN, hippocampus, and spinal cord NeuN+ cells, and the NeuN stain was concentrated around the nucleus. In mice sacrificed 24 h after administration of three 20 mg/kg doses of MPTP, calpain expression was slightly increased in SN and hippocampal neurons and moderately increased in spinal cord neurons. In these animals, the NeuN stain was less concentrated around the nuclear membrane. One week after MPTP treatment, calpain content in NeuN+ cells was greatly increased in SN, hippocampus, and spinal cord. Morphologically, SN and spinal cord neurons, treated for one week, were necrotic with a granular cytoplasmic NeuN content. Also, MPTP treatment upregulated calpain activity and mRNA level in spinal cord. These data suggest that following MPTP treatment, calpain causes neuronal death in SN as well as in spinal cord.

Loss of spinal motor neurons and alteration of alpha-synuclein immunostaining in MPTP induced Parkinsonism in mice

“…Additionally, based on the dosing issue, reported above, some studies, looking at MPTP neurotoxicity on spinal cord were carried out using MPTP at dose/dosing less effective compared with those used here. This is the case of the following papers: Chera et al (2002): 10 mg/kg  1; Chera et al (2004); Samantaray et al (2008a,b): 50 mg/kg  1. Finally, this is the first study which was designed to quantify directly a potential motor neuron loss induced by MPTP.…”

“…Finally, this is the first study which was designed to quantify directly a potential motor neuron loss induced by MPTP. In fact, the few previous studies were based on indirect parameters, such as cleaved caspase-3 (Samantaray et al, 2008b) or 76 kDa calpain activation (Chera et al, 2002). This indicates that, just like DA neurons, MPTP neurotoxicity on spinal motor neurons depends on dose and dosing.…”

Calpain inhibition protected spinal cord motoneurons against 1-methyl-4-phenylpyridinium ion and rotenone

“…Focus of the present study was to determine whether intrinsic mitochondrial pathway of apoptosis coupled to aberrant intracellular Ca 2+ -homeostatsis and activation of proteolytic enzymes calpain and caspase-3 was involved in the process of motoneuron damage and death, as previously found in brain and spinal cord of animals with experimental parkinsonism (Ray et al, 2000; Chera et al, 2002, 2004; Crocker et al, 2003; Samantaray et al, 2006, 2007, 2008c). Calpeptin, a cell-permeable peptide aldehyde inhibitor of calpain, was examined for its efficacy to render cytoprotection.…”

Spinal cord and parkinsonism: Neuromorphological evidences in humans and experimental studies

“…The same authors showed TUNEL positive neurons (Samantaray et al, 2008b) and increased levels of active 76 kDa calpain (Chera et al, 2004;Samantaray et al, 2008a) throughout dorsal and ventral horn of lumbar spinal cord, from mice treated with MPTP, a neurotoxin which induces parkinsonism and neurodegeneration when it is oxidized in its drawn neurotoxin 1-methyl-4-phenylpyridinium ion (MPP + ) (Chiba et al, 1984;Markey et al, 1984). Calpain mediated neuronal death had been shown also in cultured spinal motoneurons exposed to MPP + or rotenone (Samantaray et al, 2008a), highlighting the role of calpain in mediating MPTP or rotenone induced neuronal death in the mice spinal cord (Ray et al, 2000;Chera et al, 2002Chera et al, , 2004.…”