Cardiac tyrosine hydroxylase activation and MB-COMT in dyskinetic monkeys.

The impact of age-associated disorders is increasing as the life expectancy of the population increments. Cardiovascular diseases and neurodegenerative disorders, such as Parkinson's disease, have the highest social and economic burden and increasing evidence show interrelations between them. Particularly, dysfunction of the cardiovascular nervous system is part of the dysautonomic symptoms of Parkinson's disease, although more studies are needed to elucidate the role of cardiac function on it. We analyzed the dopaminergic system in the nigrostriatal pathway of Parkinsonian and dyskinetic monkeys and the expression of some key proteins in the metabolism and synthesis of catecholamines in the heart: total and phosphorylated (phospho) tyrosine hydroxylase (TH), and membrane (MB) and soluble (S) isoforms of catechol-O-methyl transferase (COMT). The dopaminergic system was significantly depleted in all MPTP-intoxicated monkeys. MPTP- and MPTP + L-DOPA-treated animals also showed a decrease in total TH expression in both right (RV) and left ventricle (LV). We found a significant increase of phospho-TH in both groups (MPTP and MPTP + L-DOPA) in the LV, while this increase was only observed in MPTP-treated monkeys in the RV. MB-COMT analysis showed a very significant increase of this isoform in the LV of MPTP- and MPTP + L-DOPA-treated animals, with no significant differences in S-COMT levels. These data suggest that MB-COMT is the main isoform implicated in the cardiac noradrenergic changes observed after MPTP treatment, suggesting an increase in noradrenaline (NA) metabolism. Moreover, the increase of TH activity indicates that cardiac noradrenergic neurons still respond despite MPTP treatment.

Cardiac Noradrenaline Turnover and Heat Shock Protein 27 Phosphorylation in Dyskinetic Monkeys.

BACKGROUND: Autonomic dysfunction is a well-known dominant symptom in the advanced stages of Parkinson's disease. However, the role of cardiac sympathetic nerves still needs to be elucidated. OBJECTIVES: To evaluate cardiac sympathetic response in Parkinsonian and dyskinetic monkeys. METHODS: Adult male monkeys were divided into 1 of the following 3 groups: controls, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated monkeys, and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine+levodopa-treated animals. Noradrenaline, its metabolite normetanephrine, and phospho-Heat shock proten 27 (p-Hsp27) at serine 82 levels were analyzed in the left and right ventricles of the heart. Tyrosine hydroxylase immunohistochemistry was performed in the ventral mesencephalon. RESULTS: The results were the following: (1) 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine intoxication significantly increased normetanephrine levels and decreased noradrenaline turnover in the right ventricle without changes in the left ventricle; however, (2) levodopa treatment decreased noradrenaline levels and enhanced the normetanephrine/noradrenaline ratio in parallel with a very significant increase of Hsp27 activity in both ventricles. CONCLUSIONS: Levodopa treatment could induce protective cardiac effects through the increased Hsp27 activity. © 2019 International Parkinson and Movement Disorder Society.

Persistent phagocytic characteristics of microglia in the substantia nigra of long-term Parkinsonian macaques.

Patients with Parkinson's disease show persistent microglial activation in the areas of the brain where the degeneration of dopaminergic neurons takes place. The reason for maintaining this activated state is still unknown, but it is thought that this persistent microglial activation may contribute to the degeneration of dopaminergic neurons. In this study, we report the microanatomical details of microglia and the relationship between microglia and neurons in the substantia nigra pars compacta of Parkinsonian monkeys years after insult with MPTP. We observed that microglial cells appear polarized toward dopaminergic neurons in MPTP-treated macaques compared to untreated animals and present clear phagocytic characteristics, such as engulfing gliaptic contacts, an increase in Golgi apparatus protein machinery and ball-and-chain phagocytic buds. These results demonstrate that activated microglia maintain phagocytic characteristics years after neurotoxin insult, and phagocytosis may be a key contributor to the neurodegenerative process.

ROCK/Cdc42-mediated microglial motility and gliapse formation lead to phagocytosis of degenerating dopaminergic neurons in vivo.

The role of microglial motility in the context of adult neurodegeneration is poorly understood. In the present work, we investigated the microanatomical details of microglia-neuron interactions in an experimental mouse model of Parkinson's disease following the intraperitoneal injection of MPTP. The specific intoxication of dopaminergic neurons induces the cellular polarization of microglia, leading to the formation of body-to-body neuron-glia contacts, called gliapses, which precede neuron elimination. Inhibiting ROCK/Cdc42-mediated microglial motility in vivo blocks the activating features of microglia, such as increased cell size and number of filopodia and diminishes their phagocyting/secreting domains, as the reduction of the Golgi apparatus and the number of microglia-neuron contacts has shown. High-resolution confocal images and three-dimensional rendering demonstrate that microglia engulf entire neurons at one-to-one ratio, and the microglial cell body participates in the formation of the phagocytic cup, engulfing and eliminating neurons in areas of dopaminergic degeneration in adult mammals.

Inflammatory response in Parkinsonism.

Inflammatory responses have been proposed as important factors in dopaminergic neuro-degeneration in Parkinsonism. Increasing evidence suggests that the alteration of the glial microenvironment induced by neuronal degeneration could be deleterious to the remaining neurons. The activation of microglia/macrophages and reactive astrocytes may have a negative effect on the surrounding parenchyma, perpetuating the neurodegenerative process. However, this alteration may also go beyond the brain parenchyma and stimulate other inflammatory changes in other systems, inducing the release of proinflammatory cytokines and probably Acute Phase Proteins (APP) and Glucocorticoids (GC). In this work we review the latest advances in the field to provide a picture of the state of the art of studies of inflammatory responses and Parkinsonism, hopefully opening up new therapeutic perspectives for patients with Parkinson's disease.

Increase of secondary processes of microglial and astroglial cells after MPTP-induced degeneration in substantia nigra pars compacta of non human primates.

Nigral dopaminergic areas from Parkinsonian patients show an increase of reactive astrocytes and active microglia. The reaction of these two cell types is a clear evidence of inflammatory response associated with dopaminergic cell loss. However, the function of this glial reaction remains unclear. This histological hallmark is also reproduced in induced Parkinsonian animals such as MPTP-treated monkeys. In this work, we analyze with confocal microscopy the number of processes of microglial cells and astrocytes in the SNpc of MPTP-treated monkeys and compare with control animals. We observe that secondary branches from microglia and astrocytes increase in MPTP-treated animals, while the scaffold of primary branches does not change. These results demonstrate that glial reaction in MPTP-treated monkeys is characterized by the emission of new filaments after the dopaminergic degeneration, suggesting that glial cells may increase their scanning progress and modify their microanatomy after dopaminergic injury.

CD20, CD3, and CD40 ligand microclusters segregate three-dimensionally in vivo at B-cell-T-cell immunological synapses after viral immunity in primate brain.

The clearance of virally infected cells from the brain is mediated by T cells that engage antigen-presenting cells to form supramolecular activation clusters at the immunological synapse. However, after clearance, the T cells persist at the infection site and remain activated locally. In the present work the long-term interactions of immune cells in brains of monkeys were imaged in situ 9 months after the viral inoculation. After viral immunity, the persistent infiltration of T cells and B cells was observed at the infection sites. T cells showed evidence of T-cell receptor signaling as a result of contacts with B cells. Three-dimensional analysis of B-cell-T-cell synapses showed clusters of CD3 in T cells and the segregation of CD20 in B cells, involving the recruitment of CD40 ligand at the interface. These results demonstrate that immunological synapses between B cells and T cells forming three-dimensional microclusters occur in vivo in the central nervous system and suggest that these interactions may be involved in the lymphocyte activation after viral immunity at the original infection site.

Increased plasma levels of TNF-alpha but not of IL1-beta in MPTP-treated monkeys one year after the MPTP administration.

The cause of Parkinson's disease remains unknown although some evidence suggests that an inflammatory reaction, mediated by cytokines such as TNF-alpha and IL-1beta, is related with dopaminergic degeneration in the brain. In the present work we measured the plasma levels of TNF-alpha and IL-1beta in parkinsonian monkeys one year after MPTP administration. TNF-alpha levels were seen to have increased in parkinsonian monkeys reflecting the clinical symptoms observed, while IL-1beta levels remained unchanged. These results suggest that TNF-alpha plays a role in sustaining of dopaminergic degeneration in chronic parkinsonism.