Neuroprotective Effect of Protein Kinase Cδ Inhibitor Rottlerin in Cell Culture and Animal Models of Parkinson's Disease

Abstract

Recent studies from our laboratory demonstrated that the protein kinase C (PKC) ␦ isoform is an oxidative stress-sensitive kinase and a key mediator of apoptotic cell death in Parkinson's Disease (PD) models (Eur J Neurosci 18:1387-1401, 2003; Mol Cell Neurosci 25: 406 -421, 2004). We showed that native PKC␦ is proteolytically activated by caspase-3 and that suppression of PKC␦ by dominant-negative mutant or small interfering RNA against the kinase can effectively block apoptotic cell death in cellular models of PD. In an attempt to translate the mechanistic studies to a neuroprotective strategy targeting PKC␦, we systematically characterized the neuroprotective effect of a PKC␦ inhibitor, rottlerin, in 1-methyl-4-phenylpyridinium (MPP ϩ )-treated primary mesencephalic neuronal cultures as well as in an 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) animal model of PD. Rottlerin treatment in primary mesencephalic cultures significantly attenuated MPP ϩ -induced tyrosine hydroxylase (TH)-positive neuronal cell and neurite loss. Administration of rottlerin, either intraperitoneally or orally, to C57 black mice showed significant protection against MPTP-induced locomotor deficits and striatal depletion of dopamine and its metabolite 3,4-dihydroxyphenylacetic acid. Notably, rottlerin post-treatment was effective even when MPTP-induced depletion of dopamine and its metabolites was greater than 60%, demonstrating its neurorescue potential. Furthermore, the dose of rottlerin used in neuroprotective studies effectively attenuated the MPTP-induced PKC␦ kinase activity. Importantly, stereological analysis of nigral neurons revealed rottlerin treatment significantly protected against MPTPinduced TH-positive neuronal loss in the substantia nigra compacta. Collectively, our findings demonstrate the neuroprotective effect of rottlerin in both cell culture and preclinical animal models of PD, and they suggest that pharmacological modulation of PKC␦ may offer a novel therapeutic strategy for treatment of PD.Parkinson's disease (PD) is a major neurodegenerative disorder characterized by progressive and substantial loss of dopaminergic neurons in the substantia nigra compacta (SNc), resulting in debilitating motor signs including tremors, bradykinesia, and rigidity. PD affects more than 1% of the population over the age of 60 in the United States (West et al., 2005), ranking it as the second most common neurodegenerative disorder. Although the existing approaches to PD treatment alleviate the signs, they fail to prevent the progression of the neurodegenerative process. Currently, no available drugs prevent the progressive loss of nigral dopaminergic neurons. The mechanisms underlying the dopaminergic degenerative process observed in PD are not well understood, which has hampered development of successful neuroprotective drugs. Several clinical studies in post-mortem PD human brain tissues and experimental studies in animal PD models indicate that oxidative stress, mitochondrial and ubiquitin proteasomal dysfunction, ...

Transcriptional Regulation of Pro-apoptotic Protein Kinase Cδ

“…Recently, we have provided evidence that PKC␦ serves as a key modulator of stress-induced dopaminergic neurodegeneration (5-7, 10, 36, 76). Intraperitoneal injection or oral administration of the PKC␦ inhibitor significantly protected nigral dopaminergic neurons in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced animal model of Parkinson disease (11). In this study, we found that the expression of PKC␦ is closely linked to the oxidative stressinduced neurodegeneration (Fig.…”

“…12). Taken together with our previous observation that PKC␦ plays a critical role in the oxidative stress-induced dopaminergic degeneration in PD (7,10) and that PKC␦ inhibition has been explored in preclinical models of PD (11,12), these findings have important implications for the utility of PKC␦ as a target in developing novel drug therapies against oxidative damage in PD.…”

Dopamine D3 Receptors Are Down-regulated following Heterologous Endocytosis by a Specific Interaction with G Protein-coupled Receptor-associated Sorting Protein-1

“…For example, a reduction in D 3 receptor-binding sites has been reported in the striatum and the substantia nigra of monkeys following 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine treatment (29), a model of Parkinson disease. Also, positron emission tomography studies in Parkinson disease patients have revealed a The loss of dopaminergic neurons in the substantia nigra, which contributes to the onset of Parkinson disease, is mediated by the persistent activation of PKC␦ (31). Administration of the PKC␦ inhibitor, rottlerin, prevents neuronal cell loss in primary cultures of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated mice and provides neuroprotection from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced locomotion (31).…”

“…Also, positron emission tomography studies in Parkinson disease patients have revealed a The loss of dopaminergic neurons in the substantia nigra, which contributes to the onset of Parkinson disease, is mediated by the persistent activation of PKC␦ (31). Administration of the PKC␦ inhibitor, rottlerin, prevents neuronal cell loss in primary cultures of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated mice and provides neuroprotection from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced locomotion (31). Intriguingly, PKC␦ is the isoform of PKC reported to be responsible for heterologous D 3 receptor endocytosis following PMA treatment (16).…”

Role of proteolytic activation of protein kinase Cδ in the pathogenesis of prion disease

“…To further validate the role of PKCδ signaling in TSE, we utilized PKCδ knockout PKCδ (−/−) C57 black mice, as described in our previous publication. 41 Specifically, we evaluated the motor function in PKCδ (−/−) C57 black mice following inoculation with murine-adapted RML scrapie and compared with that of wild-type C57 black mice. After inoculation with either NBH or RML, mice were subjected to weekly behavioral analysis using the horizontal bar test and grip strength meter to assess grip strength, stamina, and coordination.…”