kn-93 and Parkinson-Disease--Secondary

Levodopa (L-dopa) remains the best treatment for Parkinson's disease (PD). However, long-term L-dopa treatment induces dyskinesia. The mechanism of L-dopa-induced dyskinesia (LID) is not fully understood. Enhanced activity of protein kinase A (PKA) and pulsatile dopamine (DA) stimulation plays an important role in LID. Tyrosine hydroxylase (TH) is the rate-limiting enzyme for DA synthesis. Decreased TH activity causes reduced pulsatile DA stimulation, which in turn reduces LID. Moreover, TH is a substrate of CaMKII. However, it is unknown whether inhibition of CaMKII reduces LID by downregulating the activity of TH. In this study, we found that CaMKII antagonist KN-93 reduced DA released in PC12 cells; in the meantime, KN-93 reduced phosphorylated levels of CaMKIIα and TH at Ser 40. Intrastriatal administration of KN-93 reduced LID without affecting the antiparkinsonian effect of L-dopa in PD mice. Mechanistically, KN-93 treatmentreduced phosphorylated CaMKIIα levels and subsequently downregulated phosphorylated TH at Ser 40 expression. Consequently, extracellular DA efflux was reduced andthe activation threshold of the PKA pathway was lowered. Moreover, KN-93 treatment reduced the expression of Arc and Penk, two immediate early genes, induced by chronic L-dopa. These data indicate that inhibition of CaMKIIα decreases LID at least partially by suppressing TH activity and subsequently reducing extracellular DA efflux and the activity of the PKA pathway, suggesting that CaMKIIα may be an alternative target for the treatment of LID.

Topics: Animals; Antiparkinson Agents; Benzylamines; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Corpus Striatum; Disease Models, Animal; Dopamine; Dyskinesia, Drug-Induced; Levodopa; Male; Mice, Inbred C57BL; Oxidopamine; Parkinson Disease; Parkinson Disease, Secondary; PC12 Cells; Protein Kinase Inhibitors; Rats; Signal Transduction; Sulfonamides; Sympatholytics; Tyrosine 3-Monooxygenase

Recent evidence has linked striatal amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor function to the adverse effects of long-term dopaminergic treatment in Parkinson's disease. The phosphorylation of AMPA subunit, GluR1, reflects AMPA receptor activity. To determine whether serine phosphorylation of GluR1 subunit by activation of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) contributes to the process, we examined the effects of unilateral nigrostriatal depletion with 6-hydroxydopamine and subsequent L: -dopa treatment on motor responses and phosphorylation states. Three weeks of L: -dopa administration to rats shortened the duration of the rotational response. We found a significant reduction in the abundance of both phosphorylated GluR1 at serine-831 site (pGluR1S831) and GluR1 in the cell plasma membrane of lesioned striatum. Chronic treatment of lesioned rats with L: -dopa markedly upregulated the phosphorylation of GluR1 in lesioned striatum with a concomitant normalization of the plasma membrane GluR1 abundance, which lasted at least 1 day after withdrawal of chronic L: -dopa treatment. Our immunostaining data showed that these changes were confined to parvalbumin-positive neurons where GluR1 subunits are exclusively expressed. Both the altered motor response duration and the degree of pGluR1S831 were attenuated by the intrastriatal administration of CaMKII inhibitor KN-93. These findings suggest that activation of CaMKII contributes to both development and maintenance of motor response duration alterations, through a mechanism that involves an increase in pGluR1S831 within parvalbumin-positive neurons.

Topics: Animals; Antiparkinson Agents; Behavior, Animal; Benzylamines; Blotting, Western; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Calcium-Calmodulin-Dependent Protein Kinases; Enzyme Inhibitors; Female; Immunohistochemistry; Levodopa; Neostriatum; Nerve Tissue Proteins; Neurons; Oxidopamine; Parkinson Disease, Secondary; Phosphorylation; Rats; Rats, Sprague-Dawley; Receptors, AMPA; Stereotyped Behavior; Subcellular Fractions; Sulfonamides; Sympatholytics

Sensitization of striatal N-methyl-d-aspartate (NMDA) receptors has been implicated in the pathogenesis of the response alterations associated with dopaminomimetic treatment of parkinsonian animals and patients. To determine whether serine phosphorylation of NMDA receptor subunits by activation of Ca2+/calmodulin-dependent protein-kinase II (CaMKII) contributes to this process, we examined the effects of unilateral nigrostriatal ablation with 6-hydroxydopamine and subsequent treatment with levodopa, SKF 38393 (D1-preferring dopamine agonist), or quinpirole (D2-preferring agonist) on motor responses and phosphorylation states. Three weeks of twice-daily levodopa administration to rats shortened the duration of their rotational response to levodopa or SKF 38393 challenge, but prolonged the duration of quinpirole-induced rotation. At the same time, levodopa treatment elevated serine phosphorylation of striatal NR2A (p<0.02), but not that of NR2B subunits, without associated changes in subunit protein levels. Chronic treatment with SKF 38393 increased NR2A (p<0.0001) but decreased NR2B (p<0.004) serine phosphorylation. In contrast, chronic quinpirole treatment had no effect on NR2A but increased NR2B phosphorylation (p<0.0001). The acute intrastriatal injection of the CaMKII inhibitor KN93 (1.0 micrograms) not only normalized the levodopa-induced motor response alterations but also attenuated the D1 and D2 receptor-mediated serine phosphorylation of NR2A and NR2B subunits, respectively (p<0.02). These results suggest that a CaMKII-mediated rise in serine phosphorylation of NMDA receptor subunits induced by intermittent stimulation of D1 or D2 dopaminergic receptors contributes to the apparent enhancement in striatal NMDA receptor sensitivity and thus to the dopaminergic response plasticity in levodopa-treated parkinsonian rats.

Topics: 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; Animals; Antibodies; Antiparkinson Agents; Benzylamines; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Calcium-Calmodulin-Dependent Protein Kinases; Corpus Striatum; Dopamine; Dopamine Agonists; Enzyme Inhibitors; Levodopa; Male; Motor Neurons; Nerve Degeneration; Oxidopamine; Parkinson Disease, Secondary; Phosphorylation; Phosphoserine; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Serine; Sulfonamides; Sympatholytics