Spontaneous changes in brain striatal dopamine synthesis and storage dynamics ex vivo reveal end-product feedback-inhibition of tyrosine hydroxylase. (1st July 2022)

• Record Type: Journal Article
• Authors: González-Sepúlveda, Marta; Omar, Muhammad Yusof; Hamdon, Sally; Ma, Guofen; Rosell-Vilar, Santi; Raivio, Noora; Abass, Doaa; Martínez-Rivas, Anna; Vila, Miquel; Giraldo, Jesús; Carrascal, Montserrat; Abián, Joaquín; Gil, Carles; Sabriá, Josefa; Ortiz, Jordi; Moreno-Delgado, David
• Is Part Of: Neuropharmacology. Volume 212(2022)
• Publication Date: 2022-07-01
• Subjects: Striatum -- HPLC -- VMAT2 -- Tetrabenazine -- Quinpirole; DA dopamine -- l-DOPA levodopa -- Okadaic acid Ok -- TH tyrosine hydroxylase -- VMAT2 vesicular monoamine transporter 2 -- 5-HT serotonin; Neuropsychopharmacology -- Periodicals; Autonomic Agents -- Periodicals; Neuropsychopharmacologie -- Périodiques; Neuropsychopharmacology; Periodicals; Electronic journals; 615.78
• DOI: 10.1016/j.neuropharm.2022.109058
• Languages: English
• ISSNs: 0028-3908

Abstract

Abstract: Synaptic events are important to define treatment strategies for brain disorders. In the present paper, freshly obtained rat brain striatal minces were incubated under different times and conditions to determine dopamine biosynthesis, storage, and tyrosine hydroxylase phosphorylation. Remarkably, we found that endogenous dopamine spontaneously accumulated during tissue incubation at 37 °C ex vivo while dopamine synthesis simultaneously decreased. We analyzed whether these changes in brain dopamine biosynthesis and storage were linked to dopamine feedback inhibition of its synthesis-limiting enzyme tyrosine hydroxylase. The aromatic-l -amino-acid decarboxylase inhibitor NSD-1015 prevented both effects. As expected, dopamine accumulation was increased with l -DOPA addition or VMAT2-overexpression, and dopamine synthesis decreased further with added dopamine, the VMAT2 inhibitor tetrabenazine or D2 auto-receptor activation with quinpirole, accordingly to the known synaptic effects of these treatments. Phosphorylation activation and inhibition of tyrosine hydroxylase on Ser31 and Ser40 with okadaic acid, Sp-cAMP and PD98059 also exerted the expected effects. However, no clear-cut association was found between dopamine feedback inhibition of its own biosynthesis and changes of tyrosine hydroxylase phosphorylation, assessed by Western blot and mass spectrometry. The later technique also revealed a new Thr30 phosphorylation in rat tyrosine hydroxylase. Our methodological assessment of brain dopamine synthesis and storage dynamics ex vivo could be applied to predict the in vivo effects of pharmacological interventions in animal models of dopamine-related disorders. Graphical abstract: Chemical neurotransmitters -such as dopamine-are synthesized and stored by neurons in preparation to release. We describe here for the first-time endogenous dopamine accumulation ex vivo using a simple experimental method. This method allows to model brain dopamine dynamics in brain tissue under the influence of treatments used in Parkinson's disease, Huntington's disease, and schizophrenia. Neurotransmitter storage before release is relevant for the pharmacological treatments of these disorders as it can tonically modulate chemical communications between neurons. We show that neuronal dopamine synthesis and storage are intimately linked processes through a negative feedback mechanism. Image 1 Highlights: Dopamine synthesis becomes transiently hyperactive in brain incubated ex vivo. Dopamine storage dynamics determine feedback inhibition of tyrosine hydroxylase. Dopamine transport by VMAT2 into vesicles regulates tyrosine hydroxylase activity.