ACS Chemical Neuroscience最新文献

Alzheimer's disease (AD) and Parkinson's disease (PD) are multifactorial, chronic diseases involving neurodegeneration. According to recent studies, it is hypothesized that the intraneuronal and postsynaptic accumulation of misfolded proteins such as α-synuclein (α-syn) and tau, responsible for Lewy bodies (LB) and tangles, respectively, disrupts neuron functions. Considering the co-occurrence of α-syn and tau inclusions in the brains of patients afflicted with subtypes of dementia and LB disorders, the discovery and development of small molecules for the inhibition of α-syn and tau aggregation can be a potentially effective strategy to delay neurodegeneration. Urea is a chaotropic agent that alters protein solubilization and hydrophobic interactions and inhibits protein aggregation and precipitation. The presence of three hetero atoms (O/S and N) in proximity can coordinate with neutral, mono, or dianionic groups to form stable complexes in the biological system. Therefore, in this study, we evaluated urea and thiourea linkers with various substitutions on either side of the carbamide or thiocarbamide functionality to compare the aggregation inhibition of α-syn and tau. A thioflavin-T (ThT) fluorescence assay was used to evaluate the level of fibril formation and monitor the anti-aggregation effect of the different compounds. We opted for transmission electron microscopy (TEM) as a direct means to confirm the anti-fibrillar effect. The oligomer formation was monitored via the photoinduced cross-linking of unmodified proteins (PICUP). The anti-inclusion and anti-seeding activities of the best compounds were evaluated using M17D intracellular inclusion and biosensor cell-based assays, respectively. Disaggregation experiments were performed with amyloid plaques extracted from AD brains. The analogues with indole, benzothiazole, or N,N-dimethylphenyl on one side with halo-substituted aromatic moieties had shown less than 15% cutoff fluorescence obtained with the ThT assay. Our lead molecules 6T and 14T reduced α-syn oligomerization dose-dependently based on the PICUP assays but failed at inhibiting tau oligomer formation. The anti-inclusion effect of our lead compounds was confirmed using the M17D neuroblastoma cell model. Compounds 6T and 14T exhibited an anti-seeding effect on tau using biosensor cells. In contrast to the control, disaggregation experiments showed fewer Aβ plaques with our lead molecules (compounds 6T and 14T). Pharmacokinetics (PK) mice studies demonstrated that these two thiourea-based small molecules have the potential to cross the blood-brain barrier in rodents. Urea and thiourea linkers could be further improved for their PK parameters and studied for the anti-inclusion, anti-seeding, and disaggregation effects using transgenic mice models of neurodegenerative diseases.

Serotonergic psychedelics, known for their hallucinogenic effects, have attracted interest due to their ability to enhance neuronal plasticity and potential therapeutic benefits. Although psychedelic-enhanced neuroplasticity is believed to require activation of 5-hydroxytryptamine (serotonin) 2A receptors (5-HT_2ARs), serotonin itself is less effective in promoting such plasticity. Also, the psychoplastogenic effects of these molecules correlate with their lipophilicity, leading to suggestions that they act by influencing the intracellular receptors. However, their lipophilicity also implies that a significant quantity of lipids is accumulated in the lipid bilayer, potentially altering the physical properties of the membrane. Here, we probe whether the serotonergic psychedelic 2,5-dimethoxy-4-iodoamphetamine (DOI) can affect the properties of artificial lipid bilayers and if that can potentially affect processes such as membrane fusion. Solid-state NMR spectroscopy shows that the DOI strongly induces disorder in the lipid acyl chains. Atomic force microscopy shows that it can shrink the ordered domains in a biphasic lipid bilayer and can reduce the force needed to form nanopores in the membrane. Fluorescence correlation spectroscopy shows that DOI can promote vesicle association, and total internal fluorescence microscopy shows that it enhances vesicle fusion to a supported lipid bilayer. While serotonin has also recently been shown to cause similar effects, DOI is more than two orders of magnitude more potent in evoking these. Our results suggest that the receptor-independent effects of serotonergic psychedelics on lipid membranes may contribute to their biological actions, especially those that require significant membrane remodeling, such as neuronal plasticity.

Serotonin 5-HT₇ receptor (5-HT₇R), one of the most recently discovered members of the serotonergic system, has become a promising target in the search for central nervous system disorders. Despite the number of preclinical results, none of the selective 5-HT₇R agents has been approved; therefore, the clinical significance of this protein has not been confirmed yet. Recently, we described very promising, selective, and highly potent hydantoin-derived 5-HT₇R antagonists with confirmed antidepressant activity in vivo and a very good ADMET profile; however, they have been tested in behavioral studies as racemates. In this work, the synthesis of optically pure hydantoin-derived 5-HT₇R agents using cost-effective, classical methods has been presented for the first time. X-ray crystallographic analysis confirmed the absolute configuration on both stereogenic centers and allowed for the elucidation of the mechanism of introduction of epichlorohydrin into the hydantoin N3-position. The radioligand binding results showed a clear configuration preference for 5-HT₇R affinity. The molecular modeling results further indicated the key interaction responsible for lower affinity (with amino acid I3 × 29). Finally, the comparison of the antidepressant and anxiolytic effects of racemates versus stereoisomers suggests an influence of additional, apart from the action on 5HT₇R, factors responsible for the activity in vivo, which is worthy of deeper insight within further studies.

Inhibitory neurotransmission mediated by γ-aminobutyric acid (GABA) plays an important role in maintaining body homeostasis. Disturbances in GABA signaling are implicated in a multitude of neurologic and psychiatric conditions, including epilepsy, ischemia, anxiety, depression, insomnia, and mood disorders. Clinically relevant increases in GABA neurotransmitter level can be achieved by inhibition of its uptake into presynaptic neurons and surrounding glial cells, driven by GABA transporters (GAT1, BGT1, GAT2, and GAT3). Herein, we focused on the search for inhibitors of the BGT1 transporter which is understudied and for which the therapeutic potential of its inhibition is partly unknown. We applied multilevel virtual screening to identify compounds with inhibitory properties. Among selected hits, compound 9 was shown to be a preferential inhibitor of BGT1 (IC₅₀ 13.9 μM). The compound also revealed some inhibitory activity against GAT3 (4x lower) while showing no or low activity (IC₅₀ > 100 μM) toward GAT1 and GAT2, respectively. The predicted binding mode of compound 9 was confirmed by mutagenesis studies on E52A, E52Y, Q299L, and E52A+Q299L human BGT1 mutants. Subsequent evaluation showed that the selected hit displayed no affinity toward major GABA_A receptor subtypes. Moreover, it was nontoxic when tested on normal human astrocytes and even showed some neuroprotective activity in SH-SY5Y cells. Compound 9 is considered a promising candidate for further evaluation of the therapeutic potential of BGT1 transporter inhibition and the development of novel inhibitors.

Neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease, are associated with the formation of amyloid fibrils. In familial cases, the mutant causative genes accentuate disease progression through overexpression or misfolding of amyloidogenic proteins. Besides, considerable amyloidosis cases arise from external factors, but their origin and mechanisms are not yet fully understood. Herein, we found that amyloid fibrils generated from egg and milk proteins, in addition to their nutritional effects to intestinal cells, can selectively reduce the viability of nervous cells as well as pancreatic islet cells. In contrast, soy protein amyloid fibrils lacked cytotoxicity to the aforementioned cells. This protein source and cell type-dependent cytotoxicity are demonstrated to be associated with the significant upregulation of amyloidogenic proteins. The finding was also confirmed by the vein injection of beta-lactoglobulin fibrils to mice, exhibiting the pronounced upregulations of amyloid beta_1-42 (Aβ_1-42) and islet amyloid polypeptide in vivo. The study therefore provides insight into the health implications of exogenous amyloid fibrils.

Huntington's disease (HD) is a neurodegenerative disease that causes cognitive, movement, behavioral, and sleep disturbances, which over time result in progressive disability and eventually death. Clinical translation of novel therapeutics and imaging probes could be accelerated by additional testing in well-characterized large animal models of HD. The major goal of our preliminary cross-sectional study is to demonstrate the feasibility and utility of the unique transgenic sheep model of HD (OVT73) in positron emission tomography (PET) imaging. PET imaging studies were performed in healthy merino sheep (6 year old, n = 3) and OVT73 HD sheep (5.5 year old, n = 3, and 11 year old, n = 3). Region-of-interest and brain atlas labels were defined for regional analyses by using a sheep brain template. [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) was employed to compare the regional brain glucose metabolism and variations in FDG uptake between control and HD sheep. We also used [¹⁸F]fluoro-3,4-dihydroxyphenylalanine ([¹⁸F]FDOPA) to compare the extent of striatal dysfunction and evaluated the binding potential (BP_ND) in key brain regions between the groups. Compared with healthy controls and 11 year old HD sheep, the 5.5 year old HD sheep exhibited significantly increased [¹⁸F]FDG uptake in several cortical and subcortical brain regions (P < 0.05-0.01). No difference in [¹⁸F]FDG uptake was observed between healthy controls and 11 year old HD sheep. Analysis of the [¹⁸F]FDOPA BP_ND parametric maps revealed clusters of reduced binding potential in the 5.5 year old and 11 year old HD sheep compared to the 6 year old control sheep. In this first-of-its-kind study, we showed the usefulness and validity of HD sheep model in imaging cerebral glucose metabolism and dopamine uptake using PET imaging. The identification of discrete patterns of metabolic abnormality using [¹⁸F]FDG and decline of [¹⁸F]FDOPA uptake may provide a useful means of quantifying early HD-related changes in these models, particularly in the transition from presymptomatic to early symptomatic phases of HD.

Medetomidine is an FDA-approved α₂-adrenoreceptor (α₂-AR) agonist used as a veterinary sedative due to its analgesic, sedative, and anxiolytic properties. While it is marketed for veterinary use as a racemic mixture under the brand name Domitor, the pharmacologically active enantiomer, dexmedetomidine, is approved for sedation and analgesia in the hospital setting. Medetomidine has recently been detected in the illicit drug supply alongside fentanyl, xylazine, cocaine, and heroin, producing pronounced sedative effects that are not reversed by naloxone. The pharmacological effects along with the low cost of supply and lack of regulation for medetomidine has made it a target for misuse. Since 2022, medetomidine has been found as an adulterant in samples of seized drugs, as well as in toxicological analyses of patients admitted to the emergency department after suspected overdoses across several U.S. states and Canada. This Review will discuss the history, chemistry, structure-activity relationships, drug metabolism and pharmacokinetics (DMPK), pharmacology, and emergence of medetomidine as an adulterant in drug mixtures in the context of the current opioid drug crisis.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the aggregation of α-synuclein into toxic amyloid fibrils. Recent research suggests that bile acids altered in PD may influence their aggregation. This study investigates the effects of lithocholic acid (LCA) and deoxycholic acid (DCA) on α-synuclein aggregation and toxicity. LCA significantly accelerates aggregation, reducing the lag phase by 75%, while DCA has a milder impact, decreasing the lag phase by 30%. Binding studies show that LCA interacts with the NAC region and DCA with the N-terminal region of α-synuclein. Aggregation assays and electrophoresis reveal that LCA promotes the formation of toxic, SDS-resistant oligomers more effectively than DCA. Cytotoxicity assays confirm a lower cell viability in LCA-treated samples. Additionally, combined LCA and DCA treatment results in enhanced aggregation and toxicity, indicating a synergistic effect. These findings highlight the role of bile acids in α-synuclein aggregation and PD pathogenesis, suggesting that targeting bile acid metabolism could be a therapeutic strategy for PD.

The formation of neurofibrillary tangles (NFTs), composed of tau protein aggregates, is a hallmark of neurodegenerative diseases known as tauopathies, including Alzheimer's disease (AD). NFTs consist of paired helical filaments (PHFs) of tau protein with a dominant β-sheet secondary structure. Within these PHFs, the PHF6 hexapeptide (Val₃₀₆-Gln-Ile-Val-Tyr-Lys₃₁₁) has been commonly highlighted as a key site for tau protein nucleation. Palmatine chloride (PC) has been identified as an inhibitor of PHF6 aggregation, capable of reducing aggregation propensity at submicromolar concentrations. In pursuit of novel anti-AD drugs targeting early tau aggregation stages, we conducted an in silico study to elucidate PC's mechanism of action during PHF6 aggregation. Our observations suggest that while PHF6 can still initiate self-aggregation in the presence of PC, PC molecules subtly influence PHF6 aggregation dynamics, favoring smaller aggregates over larger complexes. The study underlined the key roles of aromatic rings in PC binding to different PHF6 aggregates by interacting through π-π stacking with the PHF6 Tyr310 side chain. The presence of aromatic rings in compounds to be able to inhibit the earlier complexation phase seems to be essential. These in silico findings lay a foundation for the design of compounds that could intervene in resolving the neurotoxicity of protein aggregates in AD.

Antihistaminic drugs are widely used clinically and have long been primarily known for their use to treat severe allergic conditions caused by histamine release. Antihistaminic drugs also exert central nervous system (CNS) effects, acting as anxiolytics, hypnotics, and neuroleptics. However, these drugs also have multiple serious neuropharmacological side-effects, inducing delirium, hyperarousal, disorganized behavior, and hallucinations. Due to their robust CNS effects, antihistamines are also increasingly abused, with occasional overdoses and life-threatening toxicity. Here, we discuss chemical and neuropharmacological aspects of antihistaminic drugs in both human and animal (experimental) models and outline their current societal and mental health importance as neuroactive substances.