The projection-specific signals that establish functionally segregated dopaminergic synapses

Ultrasensitive and Selective Detection of Dopamine Through Substituent-Regulated Evolution of Quantum Defects

Accurate detection and analysis of biomolecules like dopamine (DA) are vital for monitoring human health, particularly given DA's critical roles in a lot of medical disorders such as depression, Parkinson's and Alzheimer's diseases, and myopia. DA is often found at very low concentrations within certain body fluids, making it a challenging yet essential target for detection. This study presents an innovative and ultrasensitive detection methodology based on a quantum system, characterized by its exceptional sensitivity, selectivity, and linearity. By leveraging the unique quantum defect emission from semiconducting single-walled carbon nanotubes (SWCNTs) in the near-infrared II region, our approach effectively detects DA with high sensitivity, within the physiologically relevant range of nanomolar, and a detection limit as low as 1 nM. The sensing system maintains performance in phosphate-buffered saline and human urine environments. The interaction between aryldiazonium salts and DA that generates sp3 defects on the SWCNTs surface, regulated by specific substituents on the benzene ring, dictates the sensor's performance, ensuring superior selectivity against biologically relevant molecules. These advancements hold great potential for early disease detection, prevention, and treatment, marking an important advance in the field of biomedical diagnostics and nanosensor research.

Beyond the Brain: Exploring the multi-organ axes in Parkinson's disease pathogenesis

BACKGROUND

Parkinson's Disease (PD), a complex neurodegenerative disorder, is increasingly recognized as a systemic condition involving multi-organ interactions. Emerging evidence highlights roles of organ-brain axes (lung-, liver-, heart-, muscle-, bone-, and gut-brain) in PD pathogenesis. These axes communicate via neural, circulatory, endocrine, and inflammatory pathways, collectively driving neurodegeneration. For example, lung dysfunction in PD involves respiratory impairment and inflammatory signaling, while gut dysbiosis triggers α-synuclein aggregation via the vagus nerve. Such cross-organ interactions underscore PD's systemic nature, challenging traditional brain-centric models.

AIM OF REVIEW

1. Decipher mechanisms linking peripheral organs (e.g., lung, gut) to PD via shared pathways. 2. Explore bidirectional organ-brain interactions (e.g., liver metabolism affecting neurotoxin clearance). 3. Propose multi-organ therapeutic strategies targeting integrated signaling networks. Key Scientific Concepts of Review. 1. Lung-Brain Axis: Respiratory dysfunction (motor impairment, inflammation) exacerbates neurodegeneration. 2. Liver-Brain Axis: Metabolic dysregulation alters neurotoxin clearance; drugs (e.g., levodopa) impact liver function. 3. Heart-Brain Axis: Autonomic dysfunction reduces cerebral blood flow; neuroendocrine changes promote α-synuclein pathology. 4. Muscle-Brain Axis: Neuromuscular/metabolic disruptions worsen motor symptoms. 5. Bone-Brain Axis: Bone-derived hormones (osteocalcin, OCN) and inflammation influence cognition. 6. Gut-Brain Axis: Dysbiosis drives α-synuclein misfolding; gut metabolites modulate neuroinflammation. Integrated Mechanisms: Shared pathways (neuroinflammation, oxidative stress) create a regulatory network, suggesting therapies targeting multi-organ crosstalk (e.g., probiotics, anti-inflammatory agents).

The class-IIa HDAC inhibitor TMP269 promotes BMP-Smad signalling and is neuroprotective in in vitro and in vivo 6-hydroxydopamine models of Parkinson's disease

Degeneration of midbrain nigrostriatal dopaminergic neurons is a pathological hallmark of Parkinson's disease (PD). Peripheral delivery of a compound(s) to arrest or slow this dopaminergic degeneration is a key therapeutic goal. Pan-inhibitors of histone deacetylase (HDAC) enzymes, key epigenetic regulators, have shown therapeutic promise in PD models. However as there are several classes of HDACs (ClassI-IV), class-specific inhibition will be important to ensure target specificity. Here we examine the neuroprotective potential of the Class-IIa HDAC inhibitor, TMP269. We show that TMP269 protected against 6-hydroxydopamine (6-OHDA)-induced neurite injury in SH-SY5Y cells and cultured rat ventral mesencephalic dopaminergic neurons. We find that TMP269 upregulated the neurotrophic factor BMP2 and BMP-Smad dependent transcription signalling in SH-SY5Y cells, which was necessary for its neuroprotective effect against 6-OHDA-induced injury. Furthermore, peripheral continuous infusion of 0.5 mg/kg of TMP269 for 7 days via a mini-osmotic pump, reduced forelimb impairments induced by striatal 6-OHDA administration. TMP269 also protected dopaminergic neurons in the substantia nigra and their striatal terminals from striatal 6-OHDA-induced neurodegeneration and prevented the 6-OHDA-induced increases in the numbers of IBA1-positive microglia in the striatum and substantia nigra in vivo. TMP269 also prevented 6-OHDA-induced decreases in BMP2, pSmad1/5 and acetylated histone 3 levels, and it reversed 6-OHDA-induced increase in nuclear HDAC5 in dopaminergic neurons in the substantia nigra. These data add to the growing body of evidence that Class-IIa specific HDAC inhibitors may be pharmacological agents of interest for peripheral delivery with the goal of neuroprotection in PD.

Large-scale proteomic analyses of incident Parkinson's disease reveal new pathophysiological insights and potential biomarkers

The early pathophysiology of Parkinson's disease (PD) is poorly understood. We analyzed 2,920 Olink-measured plasma proteins in 51,804 UK Biobank participants, identifying 859 incident PD cases after 14.45 years. We found 38 PD-related proteins, with six of the top ten validated in the Parkinson's Progression Markers Initiative (PPMI) cohort. ITGAV, HNMT and ITGAM showed consistent significant association (hazard ratio: 0.11-0.57, P = 6.90 × 10-24 to 2.10 × 10-11). Lipid metabolism dysfunction was evident 15 years before PD onset, and levels of BAG3, HPGDS, ITGAV and PEPD continuously decreased before diagnosis. These proteins were linked to prodromal symptoms and brain measures. Mendelian randomization suggested ITGAM and EGFR as potential causes of PD. A predictive model using machine learning combined the top 16 proteins and demographics, achieving high accuracy for 5-year (area under the curve (AUC) = 0.887) and over-5-year PD prediction (AUC = 0.816), outperforming demographic-only models. It was externally validated in PPMI (AUC = 0.802). Our findings reveal early peripheral pathophysiological changes in PD crucial for developing early biomarkers and precision therapies.

Multi-omics analysis reveals the potential mechanisms underlying long-term exercise-induced enhancement of learning and memory in male mice

Exercise is widely recognized for improving physical functions, learning, and memory. However, the mechanisms behind these effects are not fully understood. This study aims to investigate the potential mechanisms through which exercise enhances learning and memory in mice using multi-omics analysis. Twenty male C57BL/6J mice were divided into exercise and control groups. The exercise group underwent a 4-month treadmill training regimen (12 m/min). Learning and memory abilities were assessed using the Morris water maze test. Brain, serum, and fecal samples were collected for neurotransmitter analysis, serum metabolomics analysis, and gut microbiota analysis. Data from neurotransmitter and serum metabolomics analyses were integrated with gut microbiota analysis. For comparisons between the two groups, the independent sample t-test was employed. For comparisons involving multiple groups, a repeated measures one-way analysis of variance (ANOVA) with random unit group design was applied. Statistical significance was defined as P < 0.05. The Morris water maze test significantly improved learning and memory in the exercise group (P < 0.05). Neurotransmitter analysis revealed significant differences in cognitive function-related neurotransmitters and pathways between the exercise and control groups (P < 0.05). Serum metabolomics analysis identified differences in serum metabolites between the two groups, which were linked to key pathways involved in neural repair and cognitive function. Microbial sequencing showed greater gut microbiota diversity in the exercise group, with the most notable changes at the genus level, particularly in Allobaculum, A2, and Clostridium_sensu_stricto_1 (P < 0.05). Integrated analysis indicated correlations between changes in gut microbiota and serum metabolites associated with cognitive function. Long-term exercise enhances learning and memory in mice through multiple mechanisms, including neurotransmitter regulation, serum metabolite changes, and modulation of gut microbiota. These findings provide new insights into the neuroprotective effects of exercise.

Adolescent alcohol exposure disrupts episodic-like memory by impairing dopamine synapses in the mouse prelimbic cortex

Heavy alcohol use during adolescence has a significant impact on cognitive functions, such as episodic memory, even after detoxification. However, in animal models, defects in episodic memory by adolescent alcohol exposure have not been consistently replicated, and thus, the brain regions and systems that are involved remain to be elucidated. Here, we show that adolescent alcohol exposure impairs episodic memory through the impairment of the dopamine system in the prelimbic region (PrL) of the medial prefrontal cortex in both females and males. Using mice as a model, we first show that adolescent alcohol exposure disrupts episodic-like memory in female and male adult mice. We then show that adolescent alcohol exposure decreases dopaminergic presynaptic terminals in the PrL in female and male mice. This decrease persists into adulthood. Finally, we show that the adult application of a D1 dopamine receptor agonist into the PrL of adolescent alcohol-exposed mice rescues episodic-like memory in female and male mice. Together, our results identify that dopaminergic synapses in the PrL play critical roles in the effects of adolescent alcohol use on episodic memory and provide a potential strategy to reverse memory deficits caused by adolescent alcohol use in both sexes.

Human Midbrain Organoids Enriched With Dopaminergic Neurons for Long-Term Functional Evaluation

Human midbrain organoids with functional dopaminergic (DA) neurons are invaluable for the therapeutic development of Parkinson's disease (PD). However, current methods face significant limitations, including challenges in generating pint-sized organoids enriched with DA neurons and the lack of robust functional assays for efficiently evaluating neural networks over extended periods. Here we present an innovative approach that combines developmental patterning with mechanical cutting to produce small midbrain organoids, with diameters less than 300 μm, suitable for long-term evaluation, along with a comprehensive functional assay system consisting of calcium transient assay, neurite extension assay, and multielectrode array (MEA) assay. Radial cutting of organoids into four to eight portions according to their sizes at the appropriate developmental stage significantly increases the yield of viable organoids while reducing necrotic cell regions. Using the functional assay system, we demonstrate that DA neurons within the organoids extend long projections, respond to dopamine stimulation, and form neural networks characterised by giant depolarising potential-like events. Our approach supports the generation of midbrain organoids and PD models that can be used for long-term functional testing.

Nigrostriatal Degeneration Underpins Sensorimotor Dysfunction in an Inducible Mouse Model of Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS)

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder caused by moderately expanded CGG trinucleotide repeats in the 5' untranslated region (UTR) of the FMR1 gene. Characterized by motor deficits such as action tremor and cerebellar gait ataxia, FXTAS is further distinguished by ubiquitin-positive intranuclear inclusions in neurons and glia. However, its clinical spectrum often overlaps with other neurodegenerative conditions such as Parkinson's disease (PD). Sensorimotor gating deficits, commonly associated with disorders affecting the nigrostriatal pathway such as PD, have been reported in FXTAS, but the underlying connection between these two phenotypes remains undetermined. In this study, we used the P90CGG mouse model of FXTAS, which expresses 90 CGG repeats upon doxycycline induction, to investigate sensorimotor gating deficits and their relationship to nigrostriatal degeneration. After induction, the P90CGG model exhibited late-onset impairments in prepulse inhibition (PPI), a cross-species measure of sensorimotor gating. These deficits coincided with pronounced nigrostriatal degeneration but occurred without evidence of inclusion formation in the substantia nigra. Our findings highlight nigrostriatal degeneration, which has not previously been reported in animal models of FXTAS, and suggest a potential link to sensorimotor gating dysfunction within the context of the disorder.

Establishing functionally segregated dopaminergic circuits

Despite accounting for only ~0.001% of all neurons in the human brain, midbrain dopaminergic neurons control numerous behaviors and are associated with many neuropsychiatric disorders that affect our physical and mental health. Dopaminergic neurons form various anatomically and functionally segregated pathways. Having such defined dopaminergic pathways is key to controlling varied sets of brain functions; therefore, segregated dopaminergic pathways must be properly and uniquely formed during development. How are these segregated pathways established? The three key developmental stages that dopaminergic neurons go through are cell migration, axon guidance, and synapse formation. In each stage, dopaminergic neurons and their processes receive unique molecular cues to guide the formation of specific dopaminergic pathways. Here, we outline the molecular mechanisms underlying the establishment of segregated dopaminergic pathways during each developmental stage in the mouse brain, focusing on the formation of the three major dopaminergic pathways: the nigrostriatal, mesolimbic, and mesocortical pathways. We propose that multiple stage-specific molecular gradients cooperate to establish functionally segregated dopaminergic circuits.

Neurotrophic factors for Parkinson's disease: Current status, progress, and remaining questions. Conclusions from a 2023 workshop

In 2023, a workshop was organized by the UK charity Cure Parkinson's with The Michael J Fox Foundation for Parkinson's Research and Parkinson's UK to review the field of growth factors (GFs) for Parkinson's disease (PD). This was a follow up to a previous meeting held in 2019.1 This 2023 workshop reviewed new relevant data that has emerged in the intervening 4 years around the development of new GFs and better models for studying them including the merit of combining treatments as well as therapies that can be modulated. We also discussed new insights into GF delivery and trial design that have emerged from the analyses of completed GDNF trials, including the patient voice, as well as the recently completed CDNF trial.2 We then concluded with our recommendations on how GF studies in PD should develop going forward.

The nucleus accumbens in reward and aversion processing: insights and implications

The nucleus accumbens (NAc), a central component of the brain's reward circuitry, has been implicated in a wide range of behaviors and emotional states. Emerging evidence, primarily drawing from recent rodent studies, suggests that the function of the NAc in reward and aversion processing is multifaceted. Prolonged stress or drug use induces maladaptive neuronal function in the NAc circuitry, which results in pathological conditions. This review aims to provide comprehensive and up-to-date insights on the role of the NAc in motivated behavior regulation and highlights areas that demand further in-depth analysis. It synthesizes the latest findings on how distinct NAc neuronal populations and pathways contribute to the processing of opposite valences. The review examines how a range of neuromodulators, especially monoamines, influence the NAc's control over various motivational states. Furthermore, it delves into the complex underlying mechanisms of psychiatric disorders such as addiction and depression and evaluates prospective interventions to restore NAc functionality.

Control of neuronal excitation-inhibition balance by BMP-SMAD1 signalling

Throughout life, neuronal networks in the mammalian neocortex maintain a balance of excitation and inhibition, which is essential for neuronal computation1,2. Deviations from a balanced state have been linked to neurodevelopmental disorders, and severe disruptions result in epilepsy3-5. To maintain balance, neuronal microcircuits composed of excitatory and inhibitory neurons sense alterations in neural activity and adjust neuronal connectivity and function. Here we identify a signalling pathway in the adult mouse neocortex that is activated in response to increased neuronal network activity. Overactivation of excitatory neurons is signalled to the network through an increase in the levels of BMP2, a growth factor that is well known for its role as a morphogen in embryonic development. BMP2 acts on parvalbumin-expressing (PV) interneurons through the transcription factor SMAD1, which controls an array of glutamatergic synapse proteins and components of perineuronal nets. PV-interneuron-specific disruption of BMP2-SMAD1 signalling is accompanied by a loss of glutamatergic innervation in PV cells, underdeveloped perineuronal nets and decreased excitability. Ultimately, this impairment of the functional recruitment of PV interneurons disrupts the cortical excitation-inhibition balance, with mice exhibiting spontaneous epileptic seizures. Our findings suggest that developmental morphogen signalling is repurposed to stabilize cortical networks in the adult mammalian brain.