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SCIENTIFIC LITERATURE · PPR

Cardiac Tyrosine Hydroxylase Activation and MB-COMT in Dyskinetic Monkeys 

· 2020-10-07

DOI: 10.21203/rs.3.rs-86161/v1

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Abstract Background: 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 . Methods: 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). Results: The number of dopaminergic neurons in the Substantia Nigra pars compacta and the optical density of TH+ fibers and dopamine transporter in the striatum were significantly decreased 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. However, we found 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 NA metabolism. Moreover, the increase of TH activity indicates that cardiac noradrenergic neurons still respond despite MPTP treatment. Conclusions: These results could help to elucidate the possible role of alterations in the catecholaminergic system that can contribute to noradrenergic deficiency in the hearts of PD patients. Therefore, this information might be relevant to clinical field, contributing to the therapeutic design of the disease.

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