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Brain Sciences May 2024The utility of transcranial sonography (TCS) remains unclarified for the auxiliary diagnosis of Parkinson's disease (PD). We investigated iodine-123...
The utility of transcranial sonography (TCS) remains unclarified for the auxiliary diagnosis of Parkinson's disease (PD). We investigated iodine-123 metaiodobenzylguanidine (MIBG) and TCS during the examination and diagnosis of high-signal-intensity substantia nigra lesion (HSI-SNL) incidence in PD patients previously diagnosed with dopamine transporter scintigraphy (DAT). The subjects were 67 patients with definitively diagnosed PD after DAT evaluation. Patients with midbrain substantia nigra visible during TCS who previously underwent MIBG were analyzed. The SN+ group comprised patients with extensive pathological HSI-SNL of Okawa class III/IV observed during TCS. The MIBG+ group comprised patients with a heart-to-mediastinum ratio of ≤2.2 during MIBG. TCS was performed to divide patients into the SN+ and SN- groups, and patient characteristics and MIBG findings were compared between the groups. PD was definitively diagnosed in 67 patients, among whom midbrain was visualized during TCS in 43 (64.1%) patients and pathological HSI-SNL was observed in 24 (35.8%). The MIBG findings were normal in six patients (27.3%) with HSI-SNL, and abnormal in seven (63.6%) without HSI-SNL. No significant differences were noted by Okawa classification in clinical characteristics based on the presence or absence of HSI-SNL. Multiple patients with normal findings during MIBG may have HSI-SNL. Thus, confirmatory imaging of HSI-SNL with TCS may be useful for diagnosis.
PubMed: 38928525
DOI: 10.3390/brainsci14060524 -
Biomedicines Jun 2024Playing a key role in the organization of striatal motor output, the dopamine (DA)-ergic system regulates both innate and complex learned behaviors. Growing evidence...
Playing a key role in the organization of striatal motor output, the dopamine (DA)-ergic system regulates both innate and complex learned behaviors. Growing evidence clearly indicates the involvement of the DA-ergic system in different forms of repetitive (perseverative) behavior. Some of these behaviors accompany such disorders as obsessive-compulsive disorder (OCD), Tourette's syndrome, schizophrenia, and addiction. In this study, we have traced how the inflexibility of repetitive reactions in the recently developed animal model of hyper-DA-ergia, dopamine transporter knockout rats (DAT-KO rats), affects the realization of innate behavior (grooming) and the learning of spatial (learning and reversal learning in T-maze) and non-spatial (extinction of operant reaction) tasks. We found that the microstructure of grooming in DAT-KO rats significantly differed in comparison to control rats. DAT-KO rats more often demonstrated a fixed syntactic chain, making fewer errors and very rarely missing the chain steps in comparison to control rats. DAT-KO rats' behavior during inter-grooming intervals was completely different to the control animals. During learning and reversal learning in the T-maze, DAT-KO rats displayed pronounced patterns of hyperactivity and perseverative (stereotypical) activity, which led to worse learning and a worse performance of the task. Most of the DAT-KO rats could not properly learn the behavioral task in question. During re-learning, DAT-KO rats demonstrated rigid perseverative activity even in the absence of any reinforcement. In operant tasks, the mutant rats demonstrated poor extinction of operant lever pressing: they continued to perform lever presses despite no there being reinforcement. Our results suggest that abnormally elevated DA levels may be responsible for behavioral rigidity. It is conceivable that this phenomenon in DAT-KO rats reflects some of the behavioral traits observed in clinical conditions associated with endogenous or exogenous hyper-DA-ergia, such as schizophrenia, substance abuse, OCD, patients with Parkinson disease treated with DA mimetics, etc. Thus, DAT-KO rats may be a valuable behavioral model in the search for new pharmacological approaches to treat such illnesses.
PubMed: 38927477
DOI: 10.3390/biomedicines12061270 -
Biomolecules Jun 2024Modafinil analogs with either a sulfoxide or sulfide moiety have improved binding affinities at the human dopamine transporter (hDAT) compared to modafinil, with lead...
Modafinil analogs with either a sulfoxide or sulfide moiety have improved binding affinities at the human dopamine transporter (hDAT) compared to modafinil, with lead sulfoxide-substituted analogs showing characteristics of atypical inhibition (e.g., JJC8-091). Interestingly, the only distinction between sulfoxide and sulfide substitution is the presence of one additional oxygen atom. To elucidate why such a subtle difference in ligand structure can result in different typical or atypical profiles, we investigated two pairs of analogs. Our quantum mechanical calculations revealed a more negatively charged distribution of the electrostatic potential surface of the sulfoxide substitution. Using molecular dynamics simulations, we demonstrated that sulfoxide-substituted modafinil analogs have a propensity to attract more water into the binding pocket. They also exhibited a tendency to dissociate from Asp79 and form a new interaction with Asp421, consequently promoting an inward-facing conformation of hDAT. In contrast, sulfide-substituted analogs did not display these effects. These findings elucidate the structural basis of the activity cliff observed with modafinil analogs and also enhance our understanding of the functionally relevant conformational spectrum of hDAT.
Topics: Modafinil; Dopamine Plasma Membrane Transport Proteins; Humans; Molecular Dynamics Simulation; Binding Sites; Dopamine Uptake Inhibitors; Structure-Activity Relationship; Protein Binding
PubMed: 38927116
DOI: 10.3390/biom14060713 -
Biomolecules Jun 2024One of the biggest problems in the treatment of idiopathic Parkinson's disease is the lack of new drugs that slow its progression. L-Dopa remains the star drug in the... (Review)
Review
One of the biggest problems in the treatment of idiopathic Parkinson's disease is the lack of new drugs that slow its progression. L-Dopa remains the star drug in the treatment of this disease, although it induces severe side effects. The failure of clinical studies with new drugs depends on the use of preclinical models based on neurotoxins that do not represent what happens in the disease since they induce rapid and expansive neurodegeneration. We have recently proposed a single-neuron degeneration model for idiopathic Parkinson's disease that requires years to accumulate enough lost neurons for the onset of motor symptoms. This single-neuron degeneration model is based on the excessive formation of aminochrome during neuromelanin synthesis that surpass the neuroprotective action of the enzymes DT-diaphorase and glutathione transferase M2-2, which prevent the neurotoxic effects of aminochrome. Although the neurotoxic effects of aminochrome do not have an expansive effect, a stereotaxic injection of this endogenous neurotoxin cannot be used to generate a preclinical model in an animal. Therefore, the aim of this review is to evaluate the strategies for pharmacologically increasing the expression of DT diaphorase and GSTM2-2 and molecules that induce the expression of vesicular monoamine transporter 2, such as pramipexole.
Topics: Humans; Parkinson Disease; Animals; Neurons; Nerve Degeneration; Glutathione Transferase; Neuroprotective Agents; Disease Models, Animal; Antiparkinson Agents
PubMed: 38927076
DOI: 10.3390/biom14060673 -
Addiction Biology Jun 2024Alcohol consumption occurring in a social or solitary setting often yields different behavioural responses in human subjects. For example, social drinking is associated...
Alcohol consumption occurring in a social or solitary setting often yields different behavioural responses in human subjects. For example, social drinking is associated with positive effects while solitary drinking is linked to negative effects. However, the neurobiological mechanism by which the social environment during alcohol intake impacts on behavioural responses remains poorly understood. We investigated whether distinct social environments affect behavioural responses to ethanol and the role of the dopamine system in this phenomenon in the fruit fly Drosophila melanogaster. The wild-type Canton-S (CS) flies showed higher locomotor response when exposed to ethanol in a group setting than a solitary setting, and there was no difference in females and males. Dopamine signalling is crucial for the locomotor stimulating effect of ethanol. When subjected to ethanol exposure alone, the dopamine transport mutant flies fumin (fmn) with hyper dopamine displayed the locomotor response similar to CS. When subjected to ethanol in a group setting, however, the fmn's response to the locomotor stimulating effect was substantially augmented compared with CS, indicating synergistic interaction of dopamine signalling and social setting. To identify the dopamine signalling pathway important for the social effect, we examined the flies defective in individual dopamine receptors and found that the D1 receptor dDA1/Dop1R1 is the major receptor mediating the social effect. Taken together, this study underscores the influence of social context on the neural and behavioural responses to ethanol.
Topics: Animals; Ethanol; Dopamine; Drosophila melanogaster; Male; Female; Drosophila Proteins; Receptors, Dopamine D1; Social Environment; Signal Transduction; Locomotion; Receptors, Dopamine; Behavior, Animal; Central Nervous System Depressants; Social Behavior; Dopamine Plasma Membrane Transport Proteins; Motor Activity
PubMed: 38898729
DOI: 10.1111/adb.13420 -
BMC Medical Genomics Jun 2024Chronic kidney disease (CKD) and hypertension are chronic diseases affecting a large portion of the population frequently coexistent and interdependent. The inability to...
BACKGROUND
Chronic kidney disease (CKD) and hypertension are chronic diseases affecting a large portion of the population frequently coexistent and interdependent. The inability to produce/use adequate renal dopamine may contribute to the development of hypertension and renal dysfunction. The heterodimeric amino acid transporter LAT2/4F2hc (SLC7A8/SLC3A2 genes) promotes the uptake of L-DOPA, the natural precursor of dopamine. We examined the plausibility that SLC7A8/SLC3A2 gene polymorphisms may contribute to hypertensive CKD by affecting the L-DOPA uptake.
METHODS
421 subjects (203 men and 218 women, mean age of 78.9 ± 9.6 years) were recruited and divided in four groups according to presence/absence of CKD, defined as reduced estimated glomerular filtration rate (eGFR < 60 ml/min/m) calculated using the creatinine-based Berlin Initiative Study-1 (BIS1) equation, and to presence/absence of hypertension (systolic blood pressure ≥ 140 and/or diastolic blood pressure ≥ 90 mmHg). Subjects were analysed for selected SNPs spanning the SLC7A8 and SLC3A2 loci by Sequenom MassARRAY iPLEX platform.
RESULTS
The most significant SNP at the SLC3A2 (4F2hc) locus was rs2282477-T/C, with carriers of the C-allele having a lower chance to develop hypertension among CKD affected individuals [OR = 0.33 (CI 0.14-0.82); p = 0.016]. A similar association with hypertensive CKD was found for the SLC7A8 (LAT2) rs3783436-T/C, whose C-allele resulted associated with decreased risk of hypertension among subjects affected by CKD [OR = 0.56 (95% CI 0.35-0.90; p = 0.017]. The two variants were predicted to be potentially functional.
CONCLUSIONS
The association between SLC3A2 and SLC7A8 variants to hypertension development in patients with renal failure could be linked to changes in L-DOPA uptake and consequently dopamine synthesis. Although the associations do not survive correction for Bonferroni multiple testing, and additional research is needed, our study opens new avenues for future basic and translational research in the field of hypertensive CKD.
Topics: Aged; Aged, 80 and over; Female; Humans; Male; Fusion Regulatory Protein 1, Heavy Chain; Genetic Predisposition to Disease; Hypertension; Levodopa; Polymorphism, Single Nucleotide; Renal Insufficiency, Chronic; Risk Factors; Adaptor Proteins, Signal Transducing
PubMed: 38890684
DOI: 10.1186/s12920-024-01935-2 -
Neurobiology of Disease Jun 2024Substantial work has been devoted to better understand the contribution of the myriad of genes that may underly the development of Parkinson's disease (PD) and their...
Substantial work has been devoted to better understand the contribution of the myriad of genes that may underly the development of Parkinson's disease (PD) and their role in disease etiology. The small GTPase Ras-like without CAAX2 (RIT2) is one such genetic risk factor, with one single nucleotide polymorphism in the RIT2 locus, rs12456492, having been associated with PD risk in multiple populations. While RIT2 has previously been shown to influence signaling pathways, dopamine transporter trafficking, and LRRK2 activity, its cellular function remains unclear. In the current study, we have situated RIT2 to be upstream of various diverse processes associated with PD. In cellular models, we have shown that RIT2 is necessary for activity-dependent changes in the expression of genes related to the autophagy-lysosomal pathway (ALP) by regulating the nuclear translocation of MiT/TFE3-family transcription factors. RIT2 is also associated with lysosomes and can regulate autophagic flux and clearance by regulating lysosomal hydrolase expression and activity. Interestingly, upregulation of RIT2 can augment ALP flux and protect against α-synuclein aggregation in cortical neurons. Taken together, the present study suggests that RIT2 can regulates gene expression upstream of ALP function and that enhancing RIT2 activity may provide therapeutic benefit in PD.
PubMed: 38885848
DOI: 10.1016/j.nbd.2024.106568 -
PCN Reports : Psychiatry and Clinical... Mar 2024This study aimed to clarify the abnormalities in dopamine transporter (DAT) availability in drug-naive adult patients with attention-deficit/hyperactivity disorder...
AIM
This study aimed to clarify the abnormalities in dopamine transporter (DAT) availability in drug-naive adult patients with attention-deficit/hyperactivity disorder (ADHD) and the relationship between ADHD symptoms and abnormalities in DAT availability.
METHODS
Single-photon emission tomography (SPECT) was performed using iodine-123-β-carbomethoxy-3β-(4-iodophenyltropane) (I-123 β CIT) as a tracer to measure in vivo DAT availability in 20 drug-naive patients with ADHD [mean age ± standard deviation (SD)]: 25 ± 3.44 years; male:female = 11:9] and 20 age- and sex-matched healthy controls (HCs) (mean age ± SD: 23.9 ± 2.27 years). Comparisons of DAT availability between HCs and adult patients with ADHD and the association between symptom severity and DAT availability within the ADHD group were analyzed using Statistical Parametric Mapping 12.
RESULTS
Drug-naive adults with ADHD showed significantly reduced DAT availability in the bilateral nucleus accumbens compared with HCs. Correlation analyses revealed a negative correlation between the severity of inattentive symptoms in adult patients with ADHD and DAT availability in the bilateral heads of the caudate nucleus, indicating the association between severe inattentive symptoms and lower DAT availability in the caudate nucleus.
CONCLUSION
In drug-naive adult patients with ADHD, DAT availability was reduced in the nucleus accumbens, an important part of the reward system. This finding indicates the importance of the DAT in the reward system in the pathogenesis of ADHD. Inattentiveness was associated with DAT availability in the caudate nucleus, suggesting involvement of the cortico-striato-thalamo-cortical circuit.
PubMed: 38868484
DOI: 10.1002/pcn5.177 -
PCN Reports : Psychiatry and Clinical... Sep 2023
PubMed: 38867818
DOI: 10.1002/pcn5.119 -
BioRxiv : the Preprint Server For... Jun 2024Age-related dopamine (DA) neuron loss is a primary feature of Parkinson's disease. However, it remains unclear whether similar biological processes occur during healthy...
Age-related dopamine (DA) neuron loss is a primary feature of Parkinson's disease. However, it remains unclear whether similar biological processes occur during healthy aging, albeit to a lesser degree. We therefore determined whether midbrain DA neurons degenerate during aging in mice and humans. In mice, we identified no changes in midbrain neuron numbers throughout aging. Despite this, we found age-related decreases in midbrain mRNA expression of tyrosine hydroxylase (), the rate limiting enzyme of DA synthesis. Among midbrain glutamatergic cells, we similarly identified age-related declines in vesicular glutamate transporter 2 () mRNA expression. In co-transmitting / neurons, and transcripts decreased with aging. Importantly, striatal Th and Vglut2 protein expression remained unchanged. In translating our findings to humans, we found no midbrain neurodegeneration during aging and identified age-related decreases in and mRNA expression similar to mouse. Unlike mice, we discovered diminished density of striatal TH dopaminergic terminals in aged human subjects. However, TH and VGLUT2 protein expression were unchanged in the remaining striatal boutons. Finally, in contrast to and mRNA, expression of most ribosomal genes in neurons was either maintained or even upregulated during aging. This suggests a homeostatic mechanism where age-related declines in transcriptional efficiency are overcome by ongoing ribosomal translation. Overall, we demonstrate species-conserved transcriptional effects of aging in midbrain dopaminergic and glutamatergic neurons that are not accompanied by marked cell death or lower striatal protein expression. This opens the door to novel therapeutic approaches to maintain neurotransmission and bolster neuronal resilience.
PubMed: 38854057
DOI: 10.1101/2024.06.01.596950