Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0030567 (Parkinson's disease)
 63,064 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Calpain is a ubiquitous calcium-sensitive protease that is essential for normal physiologic neuronal function. However, alterations in calcium homeostasis lead to persistent, pathologic activation of calpain in a number of neurodegenerative diseases. Pathologic activation of calpain results in the cleavage of a number of neuronal substrates that negatively affect neuronal structure and function, leading to inhibition of essential neuronal survival mechanisms. In this review, we examine the mechanistic underpinnings of calcium dysregulation resulting in calpain activation in the acute neurodegenerative diseases such as cerebral ischemia and in the chronic neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Huntington's disease, multiple sclerosis, prion-related encephalopathy, and amylotrophic lateral sclerosis. The premise of this paper is that analysis of the signaling and transcriptional consequences of calpain-mediated cleavage of its various substrates for any neurodegenerative disease can be extrapolated to all of the neurodegenerative diseases vulnerable to calcium dysregulation.
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PMID:Calpain-mediated signaling mechanisms in neuronal injury and neurodegeneration. 1868 46

Alpha-synuclein is likely to play a key role in the development of Parkinson's disease as well as other synucleinopathies. In animal models, overexpression of full-length or carboxy-terminally truncated alpha-synuclein has been shown to produce pathology. Although the proteosome and lysosome have been proposed to play a role in the degradation of alpha-synuclein, the enzyme(s) involved in alpha-synuclein clearance and generation of its carboxy-terminally truncated species have not been identified. In this study, the role of cathepsin D and calpain I in these processes was analyzed. In vitro experiments, using either recombinant or endogenous alpha-synuclein as substrates and purified cathepsin D or lysosomes, demonstrated that cathepsin D degraded alpha-synuclein very efficiently, and that limited proteolysis resulted in the generation of carboxy-terminally truncated species. Purified calpain I also cleaved alpha-synuclein, but carboxy-terminally truncated species were not the main cleavage products, and calpain I activity present in cellular lysates was not able to degrade the protein. Knockdown of cathepsin D in cells overexpressing wild-type alpha-synuclein increased total alpha-synuclein levels by 28% and lysosomal alpha-synuclein by 2-fold. In in vitro experiments, pepstatin A completely blocked the degradation of alpha-synuclein in purified lysosomes. Furthermore, lysosomes isolated from cathepsin D knockdown cells showed a marked reduction in alpha-synuclein degrading activity, indicating that cathepsin D is the main lysosomal enzyme involved in alpha-synuclein degradation. Our findings suggest that upregulation of cathepsin D could be an additional therapeutic strategy to lessen alpha-synuclein burden in synucleinopathies.
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PMID:Cathepsin D is the main lysosomal enzyme involved in the degradation of alpha-synuclein and generation of its carboxy-terminally truncated species. 1870 17

It is widely known that the pathophysiology of idiopathic Parkinson's disease (PD) is associated with neurodegeneration and inflammatory responses in the midbrain substantia nigra. However, the possibility of neurodegeneration and inflammatory responses in other areas of the central nervous system (CNS) in course of the pathogenesis of PD remains to be explored. In this investigation, we provide evidence in support of the hypothesis that spinal cord, the final coordinator of movement, is also involved during parkinsonian degeneration using two distinct experimental parkinsonism models induced by the neurotoxin 1-methyl-4-phenyl 1,2,3,6-tetrahydropyridine (MPTP) and the environmental toxin rotenone. A key focus of our study is the role that calpain, a Ca(2+)-activated neutral protease, plays in disrupting the structural-functional integrity of the spinal cord in the context of spinal cord degeneration in experimental parkinsonism. We examined the mechanisms of calpain-mediated neuronal death in differentiated spinal cord motoneuron cultures following exposure to the active parkinsonian toxins 1-methyl-4-phenyl-pyridinium ion (MPP(+)) and rotenone and also tested the neuroprotective efficacy of calpeptin, a calpain inhibitor, in these cell culture models of experimental parkinsonism. Our results implied that spinal cord motoneurons could be a potential extranigral target of neurodegeneration during pathogenesis of PD in the CNS and that calpain inhibition could provide neuroprotection.
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PMID:Extranigral neurodegeneration in Parkinson's disease. 1899 78

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.
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PMID:Effects of calpain inhibition on dopaminergic markers and motor function following intrastriatal 6-hydroxydopamine administration in rats. 1900 62

Development of neurodegenerative diseases such as Alzheimer's and Parkinson's disease is strongly age-associated. The impairment of calcium homeostasis is considered to be a key pathological event leading to neuronal dysfunction and cell death. However, the exact impact of aging on calcium homeostasis in neurons remains largely unknown. In the present work we have investigated intracellular calcium levels in cultured primary hippocampal neurons from young (2 months) and aged (24 months) rat brains. Upon stimulation with glutamate or hydrogen peroxide aged neurons in comparison to young neurons demonstrated an increased vulnerability to these disease-related toxins. Measurement of calpain activity using Western blot analysis showed a significant increase in basal activity of calpains in aged neurons. The observed increase of calpain activity was correlated with elevated protein levels of mu-calpain. Ca(2+)-imaging experiments performed on living individual neurons using the dye calcium green demonstrated a twofold increase in intracellular calcium concentration in aged neurons as compared to young neurons. The observed changes of intracellular calcium in aged neurons might play a role in their increased vulnerability to neurodegeneration.
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PMID:Impaired calcium homeostasis in aged hippocampal neurons. 1907 33

The major priming event in neurodegeneration is loss of neurons. Loss of neurons by apoptotic mechanisms is a theme for studies focused on determining therapeutic strategies. Neurons following an insult, activate a number of signal transduction pathways, of which, kinases are the leading members. Cyclin-dependent kinase 5 (Cdk5) is one of the kinases that have been linked to neurodegeneration. Cdk5 along with its principal activator p35 is involved in multiple cellular functions ranging from neuronal differentiation and migration to synaptic transmission. However, during neurotoxic stress, intracellular rise in Ca(2+) activates calpain, which cleaves p35 to generate p25. The long half-life of Cdk5/p25 results in a hyperactive, aberrant Cdk5 that hyperphosphorylates Tau, neurofilament and other cytoskeletal proteins. These hyperphosphorylated cytoskeletal proteins set the groundwork to forming neurofibrillary tangles and aggregates of phosphorylated proteins, hallmarks of neurodegenerative diseases like Alzheimer's disease, Parkinson's disease and Amyotropic Lateral Sclerosis. Attempts to selectively target Cdk5/p25 activity without affecting Cdk5/p35 have been largely unsuccessful. A polypeptide inhibitor, CIP (Cdk5 inhibitory peptide), developed in our laboratory, successfully inhibits Cdk5/p25 activity in vitro, in cultured primary neurons, and is currently undergoing validation tests in mouse models of neurodegeneration. Here, we discuss the therapeutic potential of CIP in regenerating neurons that are exposed to neurodegenerative stimuli.
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PMID:Targeting Cdk5 activity in neuronal degeneration and regeneration. 1945 15

Pesticides are the main environmental factor associated with the etiology of human neurodegenerative disorders such as Parkinson's disease. Our laboratory has previously demonstrated that the treatment of rats with low doses of dimethoate, zineb or glyphosate alone or in combination induces oxidative stress (OS) in liver and brain. The aim of the present work was to investigate if the pesticide-induced OS was able to affect brain and liver cell survival. The treatment of Wistar rats with the pesticides (i.p. 1/250 LD50, three times a week for 5 weeks) caused loss of mitochondrial transmembrane potential and cardiolipin content, especially in substantia nigra (SN), with a concomitant increase of fatty acid peroxidation. The activation of calpain apoptotic cascade (instead of the caspase-dependent pathway) would be responsible for the DNA fragmentation pattern observed. Thus, these results may contribute to understand the effect(s) of chronic and simultaneous exposure to pesticides on cell survival.
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PMID:Effect of pesticides on cell survival in liver and brain rat tissues. 1949 70

Lithium is a simple cation that has been used clinically since 1950 for the treatment of bipolar disorder. However in the last decade numerous studies either using animal models or human trials suggest that this cation may delay progression of neurodegenerative diseases. One of the main challenges facing researchers in the neurosciences is to identify key molecules in neuronal apoptosis. This would facilitate the identification of targets in order to design drugs for the treatment of Alzheimer's disease, Parkinson's disease and other neurological disorders. Although enormous effort has been made in the past few years and it has been demonstrated that the mitochondria comprise a key component of the neuronal apoptotic route, it seems that in addition to the mitochondria other intracellular components are implicated in this process. It has been proposed that DNA damage and re-entry into the cell cycle or the activation of different proteases, such as calpain, could constitute a common pathway in the apoptotic process and thus death processes in neurological diseases. The hypothesis about the implication of calpain in neuronal cell death is supported by existing data on neurodegenerative disorders in the brains of patients who show an increase in proteolytic activity of calpain compared with control brains. Indeed, studies performed in neuronal cell preparations suggest that activation of this protease is accompanied by other features such as structural modifications of the cytoskeleton, cleavage of several receptors, activation of kinases, such as cdk5 or GSK3ss, etc. Here, we summarize the potential routes involved in neurodegenerative disorders related to calpain activation, mainly those connected with changes in calcium homeostasis machinery, activation of kinase pathways, transcription factors, and the cell cycle.
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PMID:Calpains as a target for therapy of neurodegenerative diseases: putative role of lithium. 1968 41

Epidemiologic and laboratory studies suggest that paraquat can be an environmental etiologic factor in Parkinson's disease (PD). One mechanism by which paraquat may mediate cell death of dopaminergic neurons is by inducing endoplasmic reticulum (ER) stress, as suggested in a recent report. In this study, we further investigated this linkage by examining ER stress cascades. To this aim, human neuroblastoma cells (SH-SY5Y cells) were treated with paraquat and the signaling cascades through which ER stress results in apoptosis were examined. Then, it was examined whether ER stress is produced by paraquat. Paraquat increased ER stress biomarker proteins, glucose-regulated protein 78 (GRP78), ER degradation-enhancing alpha-mannosidae-like protein (EDEM), and C/EBP homologous protein (CHOP). Then, it was investigated which ER stress cascades are affected by paraquat. Paraquat activated inositol-requiring enzyme 1 (IRE1), apoptosis signal regulating kinase 1 (ASK1), and c-jun kinase (JNK). Also, paraquat activated calpain and caspase 3, but did not affect the levels of intracellular calcium and the activity of caspase 12. Finally, apoptotic DNA damage by paraquat was investigated and this damage was attenuated by salubrinal (ER stress inhibitor), thioredoxin (ASK1 inhibitor) and SP600125 (JNK inhibitor). Therefore, current data indicate that paraquat activates the IRE1/ASK1/JNK cascade associated with apoptosis in SY5Y cells.
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PMID:Paraquat activates the IRE1/ASK1/JNK cascade associated with apoptosis in human neuroblastoma SH-SY5Y cells. 1973 4

Calpain is a ubiquitous calcium-sensitive protease that is essential for normal physiologic neuronal function. However, mitochondrial-mediated-calcium homeostasis alterations may lead to its pathologic activation that jeopardizes neuronal structure and function. Here, we provide evidence to support a role for the involvement of calpain 1 in mitochondrial-induced neurodegeneration in a Parkinson's disease (PD) cellular model. We show that dysfunctional mitochondria increases cytosolic calcium, thereby, inducing calpain activation. Interestingly, its inhibition significantly attenuated the accumulation of alpha-synuclein oligomers and contributed to an increase of insoluble alpha-synuclein aggregates, known to be cytoprotective. Moreover, our data corroborate that calpain-1 overactivation in our mitochondrial-deficient cells promote caspase-3 activation. Overall, our findings further clarify the crucial role of dysfunctional mitochondria in the control of molecular mechanisms occurring in PD brain cells, providing a potentially novel correlation between the degradation of calpain substrates suggesting a putative role of calpain and calpain inhibition as a therapeutic tool in PD.
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PMID:Dysfunctional mitochondria uphold calpain activation: contribution to Parkinson's disease pathology. 2003 66


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