In vivo reduction of age-dependent neuromelanin accumulation mitigates features of Parkinson's disease.

Humans accumulate with age the dark-brown pigment neuromelanin inside specific neuronal groups. Neurons with the highest neuromelanin levels are particularly susceptible to degeneration in Parkinson's disease, especially dopaminergic neurons of the substantia nigra, the loss of which leads to characteristic motor Parkinson's disease symptoms. In contrast to humans, neuromelanin does not appear spontaneously in most animals, including rodents, and Parkinson's disease is an exclusively human condition. Using humanized neuromelanin-producing rodents, we recently found that neuromelanin can trigger Parkinson's disease pathology when accumulated above a specific pathogenic threshold. Here, by taking advantage of this newly developed animal model, we assessed whether the intracellular build-up of neuromelanin that occurs with age can be slowed down in vivo to prevent or attenuate Parkinson's disease. Because neuromelanin derives from the oxidation of free cytosolic dopamine, we enhanced dopamine vesicular encapsulation in the substantia nigra of neuromelanin-producing rats by viral vector-mediated overexpression of vesicular monoamine transporter 2 (VMAT2). This strategy reduced the formation of potentially toxic oxidized dopamine species that can convert into neuromelanin and maintained intracellular neuromelanin levels below their pathogenic threshold. Decreased neuromelanin production was associated with an attenuation of Lewy body-like inclusion formation and a long-term preservation of dopamine homeostasis, nigrostriatal neuronal integrity and motor function in these animals. Our results demonstrate the feasibility and therapeutic potential of modulating age-dependent intracellular neuromelanin production in vivo, thereby opening an unexplored path for the treatment of Parkinson's disease and, in a broader sense, brain ageing.

Validation of a Reversed Phase UPLC-MS/MS Method to Determine Dopamine Metabolites and Oxidation Intermediates in Neuronal Differentiated SH-SY5Y Cells and Brain Tissue.

Dopamine is a key neurotransmitter in the pathophysiology of various neurological disorders such as addiction or Parkinson's disease. Disturbances in its metabolism could lead to dopamine accumulation in the cytoplasm and an increased production of o-quinones and their derivatives, which have neurotoxic potential and act as precursors in neuromelanin synthesis. Thus, quantification of the dopaminergic metabolism is essential for monitoring changes that may contribute to disease development. Here, we developed and validated an UPLC-MS/MS method to detect and quantify a panel of eight dopaminergic metabolites, including the oxidation product aminochrome. Our method was validated in differentiated SH-SY5Y cells and mouse brain tissue and was then employed in brain samples from humans and rats to ensure method reliability in different matrices. Finally, to prove the biological relevance of our method, we determined metabolic changes in an in vitro cellular model of dopamine oxidation/neuromelanin production and in human postmortem samples from Parkinson's disease patients. The current study provides a validated method to simultaneously monitor possible alterations in dopamine degradation and o-quinone production pathways that can be applied to in vitro and in vivo experimental models of neurological disorders and human brain samples.

Metabolic adaptation in the human gut microbiota during pregnancy and the first year of life.

BACKGROUND: The relationship between the gut microbiome and the human host is dynamic and we may expect adjustments in microbiome function if host physiology changes. Metatranscriptomic approaches should be key in unraveling how such adjustments occur. METHODS: We employ metatranscriptomic sequencing analyses to study gene expression in the gut microbiota of infants through their first year of life, and of their mothers days before delivery and one year afterwards. FINDINGS: In infants, hallmarks of aerobic metabolism disappear from the microbial metatranscriptome as development proceeds, while the expression of functions related to carbohydrate transport and metabolism increases and diversifies, approaching that observed in non-pregnant women. Butyrate synthesis enzymes are overexpressed at three months of age, even though most butyrate-producing organisms are still rare. In late pregnancy, the microbiota readjusts the expression of carbohydrate-related functions in a manner consistent with a high availability of glucose. INTERPRETATION: Our findings suggest that butyrate production may be ensured in the gut of young infants before the typical butyrate synthesizers of the adult gut become abundant. The late pregnancy gut microbiota may be able to access the high levels of blood glucose characteristic of this period. Moreover, late pregnancy gut bacteria may reach stationary phase, which may affect their likelihood of translocating across the intestinal epithelium. FUNDS: This work was supported by grants CSD2009-00006 (CONSOLIDER Program) and SAF2009-13032-C02-02 from MICINN (Ministry of Science and Innovation, Spain), and by grant SAF2012-31187 from MINECO (Ministry of Economics and Competitiveness, Spain).