Search Results (156)

Parkinson’s disease (PD) is a neurodegenerative pathology defined by specific, distinctive signs, primarily the progressive loss of dopaminergic neurons (DAergic) in the substantia nigra pars compacta (SNpc), associated with gliosis phenomena. The mechanisms that trigger the degeneration of DAergic neurons are not yet fully elucidated, although it is recognized that the interaction between genetic and environmental factors acts as a critical modulator of neuronal vulnerability. Strong evidence points to glial reactivity as a central element in PD pathophysiology; however, it remains a controversial topic whether this activation has a protective effect or, on the contrary, whether it contributes to exacerbating DAergic neuronal loss. The use of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)—a neurotoxic substance—represented a turning point in Parkinson’s research, allowing the clarification of various molecular mechanisms of the disease. The primary aim of this review is to explore the current state of knowledge regarding the role of astrocytes in the processes of DAergic neurodegeneration, neuroprotection, and neurorepair. We focused on the relationship between astrocytic origin factors and neurogenic signals that mediate MPTP-induced plasticity in DAergic neurons of the nigrostriatal system. The contribution of reactive astrocytes in promoting DAergic neurogenesis starting from Neural Stem/Progenitor Cells (NPCs) present in the adult midbrain is also analyzed. Among the mediators released by astrocytes, we have previously identified the Wnt/β-catenin signaling pathway as a fundamental element capable of positively influencing neuroplasticity and dopaminergic neuronal repair induced by the toxic MPTP. In conclusion, deciphering the intrinsic plasticity of nigrostriatal DAergic neurons and signals that facilitate communication between astrocytes and NPCs is crucial for the identification of potential therapeutic targets aimed at stimulating neuronal repair. Full article

Per- and polyfluoroalkyl substances are persistent environmental contaminants increasingly implicated in neurotoxicity. Establishing causality and mechanisms relevant to Alzheimer’s disease, Parkinson’s disease, and multiple sclerosis requires human-relevant systems that capture exposure, barrier function, and brain circuitry. We review advanced cellular platforms—iPSC-derived neuronal and glial cultures, cerebral and midbrain organoids, and chip-based microphysiological systems—that model disease-relevant phenotypes (Aβ/tau pathology, dopaminergic vulnerability, myelination defects) under controlled PFAS exposures and defined genetic risk backgrounds. Modular, fluidically coupled BBB-on-chip → brain-organoid microphysiological systems have been reported, enabling chronic, low-dose PFAS perfusion under physiological shear, real-time barrier integrity readouts such as transepithelial/transendothelial electrical resistance (TEER), quantification of PFAS partitioning and translocation, and downstream neuronal–glial responses assessed by electrophysiology and multi-omics. Across platforms, convergent PFAS-responsive processes emerge—mitochondrial dysfunction and oxidative stress, lipid/ceramide dysregulation, neuroinflammatory signaling, and synaptic/network impairments—providing a mechanistic scaffold for biomarker discovery and gene–environment interrogation with isogenic lines. We outline principles for exposure design (environmentally relevant ranges, longitudinal paradigms), multimodal endpoints (omics, electrophysiology, imaging), and cross-lab standardization to improve comparability. Together, these models advance the quantitative evaluation of PFAS neurotoxicity and support translation into risk assessment and therapeutic strategies. Full article

Background: Alpha-synuclein is a key protein involved in the pathogenesis of Parkinson disease (PD). Its intermediate aggregated forms disturb the normal function of dopaminergic (DA) neurons. Furthermore, the loss of intraneuronal connections may precede nerve cell death in PD. Disturbance of presynaptic functions of alpha-synuclein and its family members, beta- and gamma-synuclein, can apparently be the first step in nigrostriatal system dysfunction. Based on their structure homology and subcellular localization, the three synuclein proteins could have overlapping functions. This also indicates necessitates to study each protein in isolation. Methods: We have established a unique mouse line with conditional knockout (KO) of alpha-synuclein inactivation on the background of gamma-synuclein KO. Results: During the early phase of alpha-synuclein loss of function, mice demonstrate reduced explorer activity, decreased gene expression of Mao-B in the midbrain, and transiently increased levels of beta-synuclein protein in the striatum after alpha-synuclein inactivation, as results, metabolism of dopamine stays unscathed. These changes can be caused by specific regulation of Mao-B by alpha-synuclein or can be a physiological reaction aimed at restoring alpha-synuclein levels. No significant changes in gene expression patterns of dopamine-related enzymes in the midbrain or protein levels in the striatum and midbrain were observed. Conclusions: Our data suggest that sudden alpha-synuclein depletion leads to an increase in beta-synuclein levels, likely as functional replacement. This result supports that beta-synuclein can compensate the loss of alpha-synuclein. In general, this process may characterize synapse reconstruction in early alpha-synuclein dysfunction with gamma-synuclein absence and form the basis for replacement therapeutic strategies in PD. Full article

Organoids allow to model healthy and diseased human tissues. and have applications in developmental biology, drug discovery, and cell therapy. Traditionally cultured in immersion/suspension, organoids face issues like lack of standardization, fusion, hypoxia-induced necrosis, continuous agitation, and high media volume requirements. To address these issues, we developed an air–liquid interface (ALi) technology for culturing organoids, termed AirLiwell. It uses non-adhesive microwells for generating and maintaining individualized organoids on an air–liquid interface. This method ensures high standardization, prevents organoid fusion, eliminates the need for agitation, simplifies media changes, reduces media volume, and is compatible with Good Manufacturing Practices. We compared the ALi method to standard immersion culture for midbrain organoids, detailing the process from human pluripotent stem cell (hPSC) culture to organoid maturation and analysis. Air–liquid interface organoids (3D-ALi) showed optimized size and shape standardization. RNA sequencing and immunostaining confirmed neural/dopaminergic specification. Single-cell RNA sequencing revealed that immersion organoids (3D-i) contained 16% fibroblast-like, 23% myeloid-like, and 61% neural cells (49% neurons), whereas 3D-ALi organoids comprised 99% neural cells (86% neurons). Functionally, 3D-ALi organoids showed a striking electrophysiological synchronization, unlike the heterogeneous activity of 3D-i organoids. This standardized organoid platform improves reproducibility and scalability, demonstrated here with midbrain organoids. The use of midbrain organoids is particularly relevant for neuroscience and neurodegenerative diseases, such as Parkinson’s disease, due to their high incidence, opening new perspectives in disease modeling and cell therapy. In addition to hPSC-derived organoids, the method’s versatility extends to cancer organoids and 3D cultures from primary human cells. Full article

Despite the abundant expression of the microRNA-degrading Translin (TN)/Trax (TX) complex in midbrain dopaminergic (DA) neurons and its implication in neuropsychiatric disorders, its cell-autonomous roles in metabolic and behavioral responses remain unclear. To address this, we generated DA neuron-specific conditional knockout (cKO) mice for Tsn (TN) or Tsnax (TX) using DAT-Cre. Immunostaining confirmed efficient TX loss in Tsnax cKO DA neurons without affecting TN, while Tsn deletion abolished TX expression, revealing asymmetric protein dependency. Body composition analysis showed no alterations in adiposity in either cKO model. Locomotor responses to acute or repeated administration of cocaine (20 mg/kg) or amphetamine (2.5 mg/kg) were unchanged in Tsn or Tsnax cKO mice. Furthermore, amphetamine-induced conditioned place preference (1 mg/kg) was unaffected. These results demonstrate that the TN/TX complex within DA neurons is dispensable for regulating adiposity, psychostimulant-induced locomotion (both acute and sensitized), or amphetamine reward-related behavior, suggesting its critical functions may lie outside these specific domains. Full article

The neurobiology of chronic pain is complex and multifaceted, intertwining with the mesocorticolimbic system to regulate the behavioral and perceptional response to adverse stimuli. Specifically, the ventral tegmental area (VTA), the dopaminergic hub of the reward pathways located deep within the midbrain, is crucial for regulating the release of dopamine (DA) throughout the central nervous system (CNS). To better understand the nuances among chronic pain, VTA response, and therapeutics, implementing progressive approaches for mapping and visualizing the deep brain in real time during nociceptive stimulation is crucial. In this study, we utilize a fluorescence imaging platform with a genetically encoded calcium indicator (GCaMP6s) to directly visualize activity in the VTA during acute nociceptive stimulation in both healthy adult mice and adult mice with partial nerve ligation (PNL)-induced neuropathic pain. We also investigate the visualization of the analgesic properties of morphine. Deep brain imaging using our self-fabricated µ-complementary metal–oxide–semiconductor (CMOS) imaging device allows the tracking of the VTA’s response to adverse stimuli. Our findings show that nociceptive stimulation is associated with a reduction in VTA fluorescence activity, supporting the potential of this platform for visualizing pain-related responses in the central nervous system. Additionally, treatment with morphine significantly reduces the neuronal response caused by mechanical stimuli and is observable using the CMOS imaging platform, demonstrating a novel way to potentially assess and treat neuropathic pain. Full article

Clinicopathological studies and the effectiveness of dopaminergic replacement therapy establish that dopamine loss is the key pathology causing motor symptoms in Parkinson’s disease. The dopamine neurons that are impaired in Parkinson’s disease reside in the substantia nigra and ventral tegmental area in the midbrain. These neurons project into the striatum, where dopamine axons bifurcate repeatedly and form dense axon networks (the striatum is separated into the caudate nucleus and putamen by the internal capsule). Midbrain dopamine neurons also innervate many other areas of the brain, including the cerebral cortex. Therefore, there are preclinical and clinical studies investigating extrastriatal dopamine mechanisms in motor control and Parkinson’s disease pathophysiology and treatment. While extrastriatal dopamine can contribute, this contribution needs to be compared with the contribution of the striatal dopamine system. An isolated view of the extrastriatal dopamine system is like examining only the ear of an elephant and may lead to distorted assessments for preclinical and clinical research and diagnostic work. Thus, photographs of the whole brain dopamine system are important. For these reasons, we photographed the dopamine systems in whole mouse brain sagittal sections, showing clearly that, under identical imaging conditions, dopamine innervation is highly concentrated and intense in the striatum but sparse and weak in the cerebral cortex. Full article

Background/Objectives: Parkinson’s disease (PD) is a rapidly growing neurological disorder in the developed world, affecting millions over the age of 60. The decline in motor functions occurs due to a progressive loss of midbrain dopaminergic neurons, resulting in lowered dopamine levels and impaired muscle function. Studies show defective mitochondrial autophagy (or “mitophagy”) links to PD. Rho-associated coiled-coil containing protein kinases (ROCK) 1 and ROCK2 are serine/threonine kinases, and their inhibition can enhance neuroprotection in PD by promoting mitophagy. Methods: We examine the effects of ROCK inhibitor SR3677, delivered via macrophage-derived small extracellular vesicles (sEVs) to Parkin Q311X(A) PD mouse models. sEVs with SR3677, administered intranasally, increased mitophagy gene expression, reduced inflammatory factors, and elevated dopamine levels in brain tissues. Results: ROCK2 expression decreased, showing the drug’s inhibitory effect. sEV-SR3677 treatment was more effective than treatment with the drug alone, although sham EVs showed lower effects. This suggests that EV-SR3677 not only activates mitochondrial processes but also promotes the degradation of damaged mitochondria through autophagy. Mitochondrial functional assays and oxygen consumption in ex vivo glial cultures revealed that sEV-SR3677 significantly improved mitochondrial respiration compared to that in untreated or SR3677-only treated cells. Conclusion: We demonstrated the efficacy of ROCK2 inhibition on mitochondrial function via sEV-SR3677 in the PD mouse model, necessitating further studies to explore design challenges and mechanisms of sEV-SR3677 as mitochondria-targeted therapy for PD Full article

Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterized by the selective loss of dopaminergic (DA) neurons in the midbrain. While dopamine precursor levodopa and D2 receptor agonists are commonly used to alleviate PD symptoms, these treatments do not halt or reverse disease progression. Thus, developing effective neuroprotective strategies remains a critical goal. In this study, we explored neuroprotective mechanisms in a Drosophila primary neuronal culture model of PD, created by administering the environmental toxin rotenone. Using the chemogenetic DREADD (designer receptors exclusively activated by designer drugs) system, we selectively activated cAMP signaling in DA neurons within the rotenone-induced model. Our results demonstrate that increasing cAMP signaling via Gs-coupled DREADD (rM3Ds) is protective against DA neurodegeneration. Furthermore, overexpression of the catalytic PKA-C1 subunit fully rescued DA neurons from rotenone-induced degeneration, with this effect restricted to DA neurons where PKA-C1 was specifically overexpressed. These findings reveal that cAMP-PKA signaling activation is neuroprotective in DA neurons against rotenone-induced degeneration, offering promising insights for developing targeted therapeutic strategies to slow or prevent PD pathology progression. Full article

Nicotine addiction is a serious global public health problem, so there is an urgent necessity to develop novel effective smoking cessation treatments with fewer adverse effects. Spontaneous behavioral sensitization induced by repeated intermittent exposure to the addictive substance represents a classical animal model of addiction research. A significant contributor to nicotine addiction is its interaction with α6β2* nAChRs located on midbrain dopaminergic neurons, which leads to an increase in dopamine (DA) release. α-Conotoxin (α-CTx) TxIB is a novel potent antagonist of the α6/α3β2β3* nAChRs, with an IC50 value of 28.4 nM developed by our group. In this study, we aimed to investigate the effectiveness of α-CTx TxIB in countering nicotine-induced behavioral sensitization and moderating the impact of nicotine on dopamine accumulation in the midbrain. Our results demonstrated that repeated nicotine administration remarkably elevated the locomotor activity of mice, including the number of entries, average speed, and total distance traveled, which could be effectively attenuated by α-CTx TxIB intervention in a dose-dependent manner (1 nmol and 5 nmol TxIB per mouse). Furthermore, 5 nmol α-CTx TxIB significantly reduced the nicotine-elevated DA and norepinephrine (NE) levels in the ventral tegmental area (VTA) and nucleus accumbens (NAc) of mice. 5 nmol α-CTx TxIB also markedly decreased the expression of critical proteins such as the dopamine transporter (DAT), N-methyl-D-aspartic acid receptor (NMDAR), and c-Fos in the NAc and prefrontal cortex (PFC) of the nicotine-exposed mice. This research provided the first compelling evidence that α-CTx TxIB attenuated nicotine-induced locomotor sensitization and inhibited the nicotine-induced dopamine elevation in mice. These results open up new avenues for exploring the therapeutic potential of α-CTx TxIB in the treatment of nicotine addiction. Full article

Parkinson’s disease (PD) is a prevalent neurodegenerative disorder marked by the progressive degeneration of midbrain dopaminergic neurons and resultant locomotor dysfunction. Despite over two centuries of recognition as a chronic disease, the exact pathogenesis of PD remains elusive. The onset and progression of PD involve multiple complex pathological processes, with dysfunctional autophagy and elevated oxidative stress serving as critical contributors. Notably, emerging research has underscored the interplay between autophagy and oxidative stress in PD pathogenesis. Given the limited efficacy of therapies targeting either autophagy dysfunction or oxidative stress, it is crucial to elucidate the intricate mechanisms governing their interplay in PD to develop more effective therapeutics. This review overviews the role of autophagy and nuclear factor erythroid 2-related factor 2 (Nrf2), a pivotal transcriptional regulator orchestrating cellular defense mechanisms against oxidative stress, and the complex interplay between these processes. By elucidating the intricate interplay between these key pathological processes in PD, this review will deepen our comprehensive understanding of the multifaceted pathological processes underlying PD and may uncover potential strategies for its prevention and treatment. Full article

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder. However, the core biology of the disorder that leads to the hypofunctioning of the cerebral dopaminergic network requires further elucidation. We investigated midbrain synaptic changes in male rats exposed to repeated hypoxia during the equivalent of extreme prematurity, which is a new animal model of the hyperactive/impulsive presentation of ADHD. We used a novel combination of a lentiviral vector, peroxidase-immunonanogold double-labelling, three-dimensional serial section transmission electron microscopy and stereological techniques to investigate the synapses formed between GABAergic axons of the rostromedial tegmental nucleus (RMTg) and dopaminergic neurons of the posterior ventral tegmental area (pVTA). This is a key site that sends extensive dopaminergic projections to the forebrain. We also compared the results to our previous study on a schizophrenia risk factor that produces cerebral hyperdopaminergia. In total, 117 reconstructed synapses were compared. Repeated hypoxic rats had a significantly thicker (22%) and longer (18%) postsynaptic density at RMTg GABAergic-pVTA dopaminergic synapses compared to their controls. These results were opposite to those previously observed in rats exposed to a schizophrenia risk factor. These findings for repeated hypoxic rats suggest that the enhanced inhibition of pVTA dopaminergic neurons may contribute to hypodopaminergia in ADHD motor hyperactivity. Synaptic triads, a key component of pVTA circuitry, were not detected in repeated hypoxic rats, indicating a marked deficit. The current knowledge may guide development in males of novel, site-specific ADHD drugs, which is necessary due to the rising prevalence of ADHD, the chronic nature of ADHD symptoms and the limitations of the currently available medications. Full article

Parkinson’s disease (PD) is the second most prevalent neurodegenerative disorder. It is characterized by the progressive loss of dopaminergic (DAnergic) neurons in the substantia nigra and decreased dopamine (DA) levels, which lead to both motor and non-motor symptoms. Conventional PD treatments aim to alleviate symptoms, but do not delay disease progression. PD gene therapy offers a promising approach to improving current treatments, with the potential to alleviate significant PD symptoms and cause fewer adverse effects than conventional therapies. DA replacement approaches and DA enzyme expression do not slow disease progression. However, DA replacement gene therapies, such as adeno-associated virus (AAV)–glutamic acid decarboxylase (GAD) and L-amino acid decarboxylase (AADC) gene therapies, which increase DA transmitter levels, have been demonstrated to be safe and efficient in early-phase clinical trials. Disease-modifying strategies, which aim to slow disease progression, appear to be potent. These include therapies targeting downstream pathways, neurotrophic factors, and midbrain DAnergic neuronal factors, all of which have shown potential in preclinical and clinical trials. These approaches focus on maintaining the integrity of DAnergic neurons, not just targeting the DA transmitter level itself. In particular, critical midbrain developmental and maintenance factors, such as Nurr1 and Foxa2, can interact synergistically with neighboring glia, in a paracrine mode of action, to protect DAnergic neurons against various toxic factors. Similar outcomes could be achieved by targeting both DAnergic neurons and glial cells with other candidate gene therapies, but in-depth research is needed. Neurotrophic factors, such as neurturin, the glial-cell-line-derived neurotrophic factor (GDNF), the brain-derived neurotrophic factor (BDNF), and the vascular endothelial growth factor (VEGF), are also being investigated for their potential to support DAnergic neuron survival. Additionally, gene therapies targeting key downstream pathways, such as the autophagy–lysosome pathway, mitochondrial function, and endoplasmic reticulum (ER) stress, offer promising avenues. Gene editing and delivery techniques continue to evolve, presenting new opportunities to develop effective gene therapies for PD. Full article

The present investigation aims to examine the role of α-synuclein seed amplification assays for screening Parkinson’s disease. Parkinson’s disease (PD) is a debilitating neurodegenerative disorder caused by the loss of dopaminergic neurons in the midbrain, leading to symptoms such as tremors, bradykinesia, postural instability, dementia, and depression. It is classified as an α-synucleinopathy related to the role of α-synuclein aggregates in neuron degeneration. Diagnosis relies on clinical assessment without premortem diagnostic tests or imaging, often resulting in delayed detection and impaired symptom management. In this regard, our study explores a screening technique using an amplification assay to measure α-synuclein levels in cerebrospinal fluid, which could potentially identify early pathological changes and improve diagnostic accuracy and patient outcomes. While preliminary results are promising, further studies are needed to evaluate this approach’s accuracy and clinical feasibility. A review of numerous trials demonstrates that α-synuclein seeding amplification assays (SAA) are a highly reliable, sensitive, and specific diagnostic tool for PD. This assay offers a promising opportunity to improve early diagnosis and quantify severity, especially for asymptomatic individuals or those with a family history of PD, allowing for earlier intervention and more effective disease management. In summary, the emerging body of evidence supporting α-synuclein as a biomarker should allow patients with PD to be detected and treated sooner, enhancing patients’ quality of life and potentially changing the disease trajectory. Full article

Background/Objectives: Parkinson’s disease (PD) is a debilitating neurodegenerative disease that targets the nigrostriatal dopaminergic (DAnergic) system residing in the human midbrain and is currently incurable. The aim of this study is to investigate the neuroprotective effects of ascorbic acid, vanillic acid, and ferulic acid in a zebrafish model of PD induced by MPTP by assessing the impact of these compounds on DAnergic neurons, focusing on gene expression, mitochondrial dynamics, and cellular stress responses. Methods/Results: Following exposure and qPCR and immunohistochemical analyses, ascorbic acid enhanced DAnergic function, indicated by an upregulation of the dopamine transporter (dat) gene and increased eGFP+ DAnergic cells, suggesting improved dopamine reuptake and neuroprotection. Ascorbic acid also positively affected mitochondrial dynamics and stress response pathways, countering MPTP-induced dysregulation. Vanillic acid only had modest, if any, neuroprotective effects on DAnergic neurons following MPTP administration. Ferulic acid exhibited the largest neuroprotective effects through the modulation of gene expression related to DAnergic neurons and mitochondrial dynamics. Conclusions: These findings suggest that ascorbic acid and ferulic acid can act as potential protective interventions for DAnergic neuron health, demonstrating various beneficial effects at the molecular and cellular levels. However, further investigation is needed to translate these results into clinical applications. This study enhances the understanding of neuroprotective strategies in neurodegenerative diseases, emphasizing the importance of considering interactions between physiological systems. Full article