Periodic Reporting for period 1 - D1-Glia (Astrocyte dopamine D1 receptor signaling in depression)
Periodo di rendicontazione: 2023-04-01 al 2025-03-31
The brain is energy-intensive, and our brain cells need a steady fuel supply to work properly. Astrocytes are homeostasis-providing cells and release L-lactate, a small molecule that neurons can use for energy. Dopamine, a chemical messenger, best known for its role in motivation and pleasure, may signal astrocytes when to boost this fuel production. To test this idea, we isolated astrocytes from rat brains and grew them in the lab, where we monitored changes in cytoplasmic L-lactate in real time using fluorescence imaging. We asked whether dopamine stimulates astrocytes to produce more L-lactate, and if so, through which molecular “switches”. Our experiments showed that dopamine increases L-lactate production in astrocytes, mainly through the activation of β1-adrenoreceptors rather than the dopaminergic D1 receptors. By identifying this specific signalling pathway, we built a step-by-step picture of how dopamine affects astrocyte metabolism. The knowledge gained may support future research exploring how astrocyte energy regulation contributes to overall brain function and emotional health.
This project investigated how dopamine affects the metabolic function of astrocytes, using primary astrocyte cultures derived from the rat brain. The work focused on three main areas: establishing the presence of dopamine receptors in astrocytes, measuring how dopamine regulates intracellular signalling and metabolism, and exploring how these responses are altered when key receptor-related genes are suppressed. First, we confirmed that astrocytes in our cultures expressed the dopamine D1 receptor, although another receptor type, the β-adrenoreceptor, was present at much higher levels. This suggested that dopamine might act through multiple pathways in these cells. Next, we used live-cell fluorescence imaging to track how astrocytes respond to dopamine. Dopamine increased levels of intracellular messengers such as cAMP and calcium, and also stimulated the production of L-lactate, a molecule that helps support neurons. Through pharmacological testing, we found that this lactate increase was mainly mediated by beta-adrenoreceptors, rather than D1 receptors. To better understand the role of these receptors, we reduced the expression of β1-adrenoreceptors using gene-silencing techniques. When these receptors were knocked down, dopamine-induced L-lactate production was significantly reduced. These results confirmed that β1-adrenoreceptors are involved in the metabolic response of astrocytes to dopamine. Together, these experiments provide new insight into how dopamine shapes astrocyte metabolism under laboratory conditions. The findings highlight receptor-specific pathways that may be important for future research on brain energy regulation and its potential relevance to mental health. The results were also presented at several scientific conferences and seminars, helping to communicate the results to the wider research community. Moreover, a manuscript is being prepared to be submitted to a peer-reviewed journal.
This project helped clarify how dopamine can influence energy metabolism in astrocytes, a type of support cell in the brain. While it was already known that noradrenaline can promote L-lactate production in astrocytes, our experiments showed that dopamine can also trigger this process. However, most likely through activating β-adrenoreceptors and not dopamine D1 receptors, as observed in cultured astrocytes. By combining live cell imaging with molecular tools to selectively block or reduce the amount of specific receptors, we were able to show that the β-adrenoreceptor pathway plays a central role in the dopamine-induced response in L-lactate production. These findings refine our understanding of how astrocytes regulate brain energy supply in response to neuromodulators.