Dopamine D2 receptor-mediated modulation of adenosine A2A receptor agonist binding within the A2AR/D2R oligomer framework

The molecular interaction between adenosine A_2A and dopamine D₂ receptors (A_2ARs and D₂Rs, respectively) within an oligomeric complex has been postulated to play a pivotal role in the adenosine–dopamine interplay in the central nervous system, in both normal and pathological conditions (e.g. Parkinson’s disease). While the effects of A_2AR challenge on D₂R functioning have been largely studied, the reverse condition is still unexplored, a fact that might have impact in therapeutics. Here, we aimed to examine in a real-time mode the D₂R-mediated allosteric modulation of A_2AR binding when an A_2AR/D₂R oligomer is established. Thus, we synthesized fluorescent A_2AR agonists and evaluated, by means of a flow cytometry homogeneous no-wash assay and a real-time fluorescence resonance energy transfer (FRET)-based approach, the effects on A_2AR binding of distinct antiparkinsonian drugs in current clinical use (i.e. pramipexole, rotigotine and apomorphine). Our results provided evidence for the existence of a differential D₂R-mediated negative allosteric modulation on A_2AR agonist binding that was oligomer-formation dependent, and with apomorphine being the best antiparkinsonian drug attenuating A_2AR agonist binding. Overall, the here-developed methods were found valid to explore the ability of drugs acting on D₂Rs to modulate A_2AR binding, thus serving to facilitate the preliminary selection of D₂R-like candidate drugs in the management of Parkinson’s disease.     

Single-Molecule Imaging Reveals Aβ42:Aβ40 Ratio-Dependent Oligomer Growth on Neuronal Processes

Soluble oligomers of the amyloid-β peptide have been implicated as proximal neurotoxins in Alzheimer’s disease. However, the identity of the neurotoxic aggregate(s) and the mechanisms by which these species induce neuronal dysfunction remain uncertain. Physiologically relevant experimentation is hindered by the low endogenous concentrations of the peptide, the metastability of Aβ oligomers, and the wide range of observed interactions between Aβ and biological membranes. Single-molecule microscopy represents one avenue for overcoming these challenges. Using this technique, we find that Aβ binds to primary rat hippocampal neurons at physiological concentrations. Although amyloid-β(1–40) as well as amyloid-β(1–42) initially form larger oligomers on neurites than on glass slides, a 1:1 mix of the two peptides result in smaller neurite-bound oligomers than those detected on-slide or for either peptide alone. With 1 nM peptide in solution, Aβ40 oligomers do not grow over the course of 48 h, Aβ42 oligomers grow slightly, and oligomers of a 1:1 mix grow substantially. Evidently, small Aβ oligomers are capable of binding to neurons at physiological concentrations and grow at rates dependent on local Aβ42:Aβ40 ratios. These results are intriguing in light of the increased Aβ42:Aβ40 ratios shown to correlate with familial Alzheimer’s disease mutations.     

Adenosine A1 and A2A receptors are involved on guanosine protective effects against oxidative burst and mitochondrial dysfunction induced by 6-OHDA in striatal slices

6-Hydroxydopamine (6-OHDA) is the most used toxin in experimental Parkinson’s disease (PD) models. 6-OHDA shows high affinity for the dopamine transporter and once inside the neuron, it accumulates and undergoes non-enzymatic auto-oxidation, promoting reactive oxygen species (ROS) formation and selective damage of catecholaminergic neurons. In this way, our group has established a 6-OHDA in vitro protocol with rat striatal slices as a rapid and effective model for screening of new drugs with protective effects against PD. We have shown that co-incubation with guanosine (GUO, 100 μM) prevented the 6-OHDA-induced damage in striatal slices. As the exact GUO mechanism of action remains unknown, the aim of this study was to investigate if adenosine A₁ (A₁R) and/or A_2A receptors (A_2AR) are involved on GUO protective effects on striatal slices. Pre-incubation with DPCPX, an A₁R antagonist prevented guanosine effects on 6-OHDA-induced ROS formation and mitochondrial membrane potential depolarization, while CCPA, an A₁R agonist, did not alter GUO effects. Regarding A_2AR, the antagonist SCH58261 had similar protective effect as GUO in ROS formation and mitochondrial membrane potential. Additionally, SCH58261 did not affect GUO protective effects. The A_2AR agonist CGS21680, although, completely blocked GUO effects. Finally, the A₁R antagonist DPCPX, and the A_2AR agonist CGS21680 also abolished the preventive guanosine effect on 6-OHDA-induced ATP levels decrease. These results reinforce previous evidence for a putative interaction of GUO with A₁R-A_2AR heteromer as its molecular target and clearly indicate a dependence on adenosine receptors modulation to GUO protective effect.

     

Effects of Hydroxylated Carbon Nanotubes on the Aggregation of Aβ16–22 Peptides: A Combined Simulation and Experimental Study

The pathogenesis of Alzheimer’s disease (AD) is associated with the aggregation of amyloid-β (Aβ) peptides into toxic aggregates with β-sheet character. In a previous computational study, we showed that pristine single-walled carbon nanotubes (SWCNTs) can inhibit the formation of β-sheet-rich oligomers in the central hydrophobic core fragment of Aβ (Aβ_16–22). However, the poor solubility of SWCNTs in water hinders their use in biomedical applications and nanomedicine. Here, we investigate the influence of hydroxylated SWCNT, a water-soluble SWCNT derivative, on the aggregation of Aβ_16–22 peptides using all-atom explicit-water replica exchange molecular dynamics simulations. Our results show that hydroxylated SWCNTs can significantly inhibit β-sheet formation and shift the conformations of Aβ_16–22 oligomers from ordered β-sheet-rich structures toward disordered coil aggregates. Detailed analyses of the SWCNT-Aβ interaction reveal that the inhibition of β-sheet formation by hydroxylated SWCNTs mainly results from strong electrostatic interactions between the hydroxyl groups of SWCNTs and the positively charged residue K16 of Aβ_16–22 and hydrophobic and aromatic stacking interactions between SWCNTs and F19 and F20. In addition, our atomic force microscopy and thioflavin T fluorescence experiments confirm the inhibitory effect of both pristine and hydroxylated SWCNTs on Aβ_16–22 fibrillization, in support of our previous and present replica exchange molecular dynamics simulation results. These results demonstrate that hydroxylated SWCNTs efficiently inhibit the aggregation of Aβ_16–22; in addition, they offer molecular insight into the inhibition mechanism, thus providing new clues for the design of therapeutic drugs against amyloidosis.     

G-protein coupled receptor solubilization and purification for biophysical analysis and functional studies,in the total absence of detergent

G-protein coupled receptors (GPCRs) constitute the largest class of membrane proteins and are a major drug target. A serious obstacle to studying GPCR structure/function characteristics is the requirement to extract the receptors from their native environment in the plasma membrane, coupled with the inherent instability of GPCRs in the detergents required for their solubilization. In the present study, we report the first solubilization and purification of a functional GPCR [human adenosine A_2A receptor (A_2AR)], in the total absence of detergent at any stage, by exploiting spontaneous encapsulation by styrene maleic acid (SMA) co-polymer direct from the membrane into a nanoscale SMA lipid particle (SMALP). Furthermore, the A_2AR–SMALP, generated from yeast (Pichia pastoris) or mammalian cells, exhibited increased thermostability (∼5°C) compared with detergent [DDM (n-dodecyl-β-D-maltopyranoside)]-solubilized A_2AR controls. The A_2AR–SMALP was also stable when stored for prolonged periods at 4°C and was resistant to multiple freeze-thaw cycles, in marked contrast with the detergent-solubilized receptor. These properties establish the potential for using GPCR–SMALP in receptor-based drug discovery assays. Moreover, in contrast with nanodiscs stabilized by scaffold proteins, the non-proteinaceous nature of the SMA polymer allowed unobscured biophysical characterization of the embedded receptor. Consequently, CD spectroscopy was used to relate changes in secondary structure to loss of ligand binding ([³H]ZM241385) capability. SMALP-solubilization of GPCRs, retaining the annular lipid environment, will enable a wide range of therapeutic targets to be prepared in native-like state to aid drug discovery and understanding of GPCR molecular mechanisms.     

Cross Dimerization of Amyloid-β and αSynuclein Proteins in Aqueous Environment: A Molecular Dynamics Simulations Study

Self-assembly of the intrinsically unstructured proteins, amyloid beta (Aβ) and alpha synclein (αSyn), are associated with Alzheimer’s Disease, and Parkinson’s and Lewy Body Diseases, respectively. Importantly, pathological overlaps between these neurodegenerative diseases, and the possibilities of interactions between Aβ and αSyn in biological milieu emerge from several recent clinical reports and in vitro studies. Nevertheless, there are very few molecular level studies that have probed the nature of spontaneous interactions between these two sequentially dissimilar proteins and key characteristics of the resulting cross complexes. In this study, we have used atomistic molecular dynamics simulations to probe the possibility of cross dimerization between αSyn_1–95 and Aβ _1–42, and thereby gain insights into their plausible early assembly pathways in aqueous environment. Our analyses indicate a strong probability of association between the two sequences, with inter-protein attractive electrostatic interactions playing dominant roles. Principal component analysis revealed significant heterogeneity in the strength and nature of the associations in the key interaction modes. In most, the interactions of repeating Lys residues, mainly in the imperfect repeats ‘KTKEGV’ present in αSyn_1–95 were found to be essential for cross interactions and formation of inter-protein salt bridges. Additionally, a hydrophobicity driven interaction mode devoid of salt bridges, where the non-amyloid component (NAC) region of αSyn_1–95 came in contact with the hydrophobic core of Aβ _1–42 was observed. The existence of such hetero complexes, and therefore hetero assembly pathways may lead to polymorphic aggregates with variations in pathological attributes. Our results provide a perspective on development of therapeutic strategies for preventing pathogenic interactions between these proteins.     

K(v) 7 (KCNQ) channel openers normalize central 2-deoxyglucose uptake in a mouse model of mania and increase prefrontal cortical and hippocampal serine-9 phosphorylation levels of GSK3β

In the CNS, an antagonistic interaction has been shown between adenosine A_2A and dopamine D₂ receptors (A_2ARs and D₂Rs) that may be relevant both in normal and pathological conditions (i.e., Parkinson's disease). Thus, the molecular determinants mediating this receptor–receptor interaction have recently been explored, as the fine tuning of this target (namely the A_2AR/D₂R oligomer) could possibly improve the treatment of certain CNS diseases. Here, we used a fluorescence resonance energy transfer‐based approach to examine the allosteric modulation of the D₂R within the A_2AR/D₂R oligomer and the dependence of this receptor–receptor interaction on two regions rich in positive charges on intracellular loop 3 of the D₂R. Interestingly, we observed a negative allosteric effect of the D₂R agonist quinpirole on A_2AR ligand binding and activation. However, these allosteric effects were abolished upon mutation of specific arginine residues (217–222 and 267–269) on intracellular loop 3 of the D₂R, thus demonstrating a major role of these positively charged residues in mediating the observed receptor–receptor interaction. Overall, these results provide structural insights to better understand the functioning of the A_2AR/D₂R oligomer in living cells.     

The E3 ligase TRIM1 ubiquitinates LRRK2 and controls its localization,degradation, and toxicity

Missense mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common cause of familial Parkinson’s disease (PD); however, pathways regulating LRRK2 subcellular localization, function, and turnover are not fully defined. We performed quantitative mass spectrometry–based interactome studies to identify 48 novel LRRK2 interactors, including the microtubule-associated E3 ubiquitin ligase TRIM1 (tripartite motif family 1). TRIM1 recruits LRRK2 to the microtubule cytoskeleton for ubiquitination and proteasomal degradation by binding LRRK2_911–919, a nine amino acid segment within a flexible interdomain region (LRRK2_853–981), which we designate the “regulatory loop” (RL). Phosphorylation of LRRK2 Ser910/Ser935 within LRRK2 RL influences LRRK2’s association with cytoplasmic 14-3-3 versus microtubule-bound TRIM1. Association with TRIM1 modulates LRRK2’s interaction with Rab29 and prevents upregulation of LRRK2 kinase activity by Rab29 in an E3-ligase–dependent manner. Finally, TRIM1 rescues neurite outgrowth deficits caused by PD-driving mutant LRRK2 G2019S. Our data suggest that TRIM1 is a critical regulator of LRRK2, controlling its degradation, localization, binding partners, kinase activity, and cytotoxicity.     

Neurodegenerative Disorders: The Role of Genetic Factors in Their Origin and the Efficiency of Treatment

The review considers the main molecular physiological causes of neurodegenerative disorders. The genetic factors involved in Parkinson’s and Alzheimer’s diseases are conventionally divided into pharmacodynamic and pharmacokinetic. The former are analyzed at the levels of dopamine (DA) neurons and polymorphism of the D₁, D₂, and D₃ DA receptors. The role of polymorphisms of some proteins such as parkin (PARK1-PARK10) and α-synuclein in generation of Lewy bodies is described. The pharmacokinetic factors play a role in Parkinson’s disease (PD) at the level of metabolism of DA, dioxyphenylalanine, and tyrosine and include polymorphisms of enzymes and proteins involved in the relevant metabolic reactions. The profile of DA metabolites may contribute to neurotoxicity and the development of PD. Prospects of drug therapy of PD and the risk of adverse drug effects such as mental disorders and dyskinesia are considered in terms of polymorphisms of enzymes and transport proteins.__________Translated from Fiziologiya Cheloveka, Vol. 31, No. 4, 2005, pp. 119–130.Original Russian Text Copyright © 2005 by Sukhanov, Ionov, Piruzyan.     

Memantine Attenuates Alzheimer’s Disease-Like Pathology and Cognitive Impairment

Deficiency of protein phosphatase-2A is a key event in Alzheimer’s disease. An endogenous inhibitor of protein phosphatase-2A, inhibitor-1, I₁ ^PP2A, which inhibits the phosphatase activity by interacting with its catalytic subunit protein phosphatase-2Ac, is known to be upregulated in Alzheimer’s disease brain. In the present study, we overexpressed I₁ ^PP2A by intracerebroventricular injection with adeno-associated virus vector-1-I₁ ^PP2A in Wistar rats. The I₁ ^PP2A rats showed a decrease in brain protein phosphatase-2A activity, abnormal hyperphosphorylation of tau, neurodegeneration, an increase in the level of activated glycogen synthase kinase-3beta, enhanced expression of intraneuronal amyloid-beta and spatial reference memory deficit; littermates treated identically but with vector only, i.e., adeno-associated virus vector-1-enhanced GFP, served as a control. Treatment with memantine, a noncompetitive NMDA receptor antagonist which is an approved drug for treatment of Alzheimer’s disease, rescued protein phosphatase-2A activity by decreasing its demethylation at Leu309 selectively and attenuated Alzheimer’s disease-like pathology and cognitive impairment in adeno-associated virus vector-1-I₁ ^PP2A rats. These findings provide new clues into the possible mechanism of the beneficial therapeutic effect of memantine in Alzheimer’s disease patients.     

Cocaine produces D2R-mediated conformational changes in the adenosine A2AR-dopamine D2R heteromer

Adenosine A_2A receptors (A_2ARs) and dopamine D₂ receptors (D₂Rs) form constitutive heteromers in living cells and exhibit a strong functional antagonistic interaction. Recent findings give neurochemical evidence that extended cocaine self-administration in the rat give rise to an up-regulation of functional A_2ARs in the nucleus accumbens that return to baseline expression levels during cocaine withdrawal. In the present work, the acute in vitro effects of a concentration of cocaine known to fully block the dopamine (DA) transporter without exerting any toxic actions were investigated on A_2AR and D_2LR formed heteromers in transiently co-transfected HEK-293T cells. In vitro treatment of cocaine was found to produce changes in D₂R homodimers and in A_2AR-D₂R heterodimers detected through bioluminescent energy transfer (BRET). Cocaine was found to produce a time- and concentration-dependent reduction in the BRET_max between A_2AR-D_2LR heterodimers and D_2LR homodimers, but not A_2AR homodimers, indicating its effect on D₂R. Cocaine was evaluated with regard to D₂R binding using a human D_2LR stable expressing CHO cell line and was found to produce an increase in the affinity of hD_2LR for DA. At the level of G protein-coupling, cocaine produced a small, but significant increase in DA-stimulated binding of GTPγS. However, cocaine failed to modulate D₂R agonist-induced inhibition of cAMP in stable hD_2LR CHO cells or the gating of GIRK channels in oocytes. Taken together, these results indicate a direct and specific effect of a moderate concentration of cocaine on the DA D_2LR, that results in enhanced agonist recognition, G protein-coupling and an altered conformational state of D₂R homodimers and A_2AR-D₂R heterodimers.     

Design, synthesis, and evaluation of fused heterocyclic analogs of SCH 58261 as adenosine A2A receptor antagonists

SCH 58261 is a reported adenosine A_2A receptor antagonist which is active in rat in vivo models of Parkinson’s Disease upon ip administration. However, it has poor selectivity versus the A₁ receptor and does not demonstrate oral activity. Quinoline analogs have improved upon the selectivity and pharmacokinetics of SCH 58261, but were difficult to handle due to poor aqueous solubility. We report the design and synthesis of fused heterocyclic analogs of SCH 58261 with aqueous solubility as well as improved A_2A receptor binding selectivity and pharmacokinetic properties. In particular, the tetrahydronaphthyridine 4s has excellent A_2A receptor in vitro binding affinity and selectivity, is active orally in a rat in vivo model of Parkinson’s Disease, and has aqueous solubility of 100 μM at physiological pH.     

Involvement of dopamine D2 receptor in the diurnal changes of tuberoinfundibular dopaminergic neuron activity and prolactin secretion in female rats

Background

An endogenous dopaminergic (DA) tone acting on D₃ receptors has been shown to inhibit tuberoinfundibular (TI) DA neuron activity and stimulate prolactin (PRL) surge in the afternoon of estrogen-primed ovariectomized (OVX+E₂) rats. Whether D₂ receptor (D₂R) is also involved in the regulation of TIDA and PRL rhythms was determined in this study.

Results

Intracerebroventricular (icv) injection of PHNO, a D₂R agonist, in the morning inhibited TIDA and midbrain DA neurons’ activities, and stimulated PRL secretion. The effects of PHNO were significantly reversed by co-administration of raclopride, a D₂R antagonist. A single injection of raclopride at 1200 h significantly reversed the lowered TIDA neuron activity and the increased serum PRL level at 1500 h. Dopamine D₂R mRNA expression in medial basal hypothalamus (MBH) exhibited a diurnal rhythm, i.e., low in the morning and high in the afternoon, which was opposite to that of TIDA neuron activity. The D₂R rhythm was abolished in OVX+E₂ rats kept under constant lighting but not in OVX rats with regular lighting exposures. Pretreatment with an antisense oligodeoxynucleotides (AODN, 10 μg/3 μl/day, icv) against D₂R mRNA for 2 days significantly reduced D₂R mRNAs in central DA neurons, and reversed both lowered TIDA neuron activity and increased serum PRL level in the afternoon on day 3. A diurnal rhythm of D₂R mRNA expression was also observed in midbrain DA neurons and the rhythm was significantly knocked down by the AODN pretreatment.

Conclusions

We conclude that a diurnal change of D₂R mRNA expression in MBH may underlie the diurnal rhythms of TIDA neuron activity and PRL secretion in OVX+E₂ rats.     

Progressive Indosinian N-S Deformation of the Jiaochang Structure in the Songpan-Ganzi Fold-Belt,Western China

Integrated field data, microstructural and three-dimensional strain analyses are used to document coaxial N-S shortening and southward increase in deformation intensity and metamorphism at the Jiaochang structure. Two episodes of deformation (D₁,D₂) with localized post-D₂ deformation have been identified in the area. The first deformation (D₁) episode is defined by a main axial-plane of parallel folds observable on a micro- to kilometer-scale, while the second episode of deformation (D₂) is defined by micro-scale metamorphic folds, associated with E–W oriented stretching lineation. These processes are the result of Indosinian tectonism (Late Triassic to Early Jurassic) characterized by nearly coaxial N-S compression and deformation. This is indicated by E–W trending, sub-parallel to parallel foliation (S₁, e.g. axial-plane of folds, and S₂, i.e. axial-plane of metamorphic folds, crenulation cleavage) and lineation (L₁, e.g. axis of folds, and L₂, i.e. stretching lineation, axis of metamorphic folds and B-axis of echelon lens). Most of the porphyroblasts and minerals (e.g. pyrite, biotite) show two growth phases with localized growth in the third phase (muscovite). The progressive D₁–D₂ structure is widespread in the south of the Jiaochang area, but only D₁ structure crops out at the north. The strain intensity (γ), compression ratios (c%) and octahedral strain intensity (ε_s) are similar across the Jiaochang structure (i.e., γ ≈ 1.8, c ≈ 27%, ε_s = 0.9), showing a broad range of Flinn values (K = 0.77 to 7.57). The long-axis orientations are roughly symmetric between two limbs of the structure. Therefore, we suggest that the architecture of the Jiaochang structure has been controlled by coaxial N-S shortening and deformation (D₁–D₂) during the Indosinian tectonic epoch, with insignificant post-D₂ deformation.     

Rotigotine Transdermal Patch in Parkinson’s Disease: A Systematic Review and Meta-Analysis

Background and Methods

The efficacy and safety of rotigotine transdermal patch in Parkinson’s disease (PD) were studied in some clinical trials. We performed a systematic review and meta-analysis of randomized controlled trials to evaluate the efficacy, tolerability, and safety of rotigotine transdermal patch versus placebo in PD.

Results

Six randomized controlled trials (1789 patients) were included in this meta-analysis. As compared with placebo, the use of rotigotine resulted in greater improvements in Unified Parkinson’s Disease Rating Scale activities of daily living score (weighted mean difference [WMD] –1.69, 95% confidence interval [CI] –2.18 to –1.19), motor score (WMD –3.86, 95% CI –4.86 to –2.86), and the activities of daily living and motor subtotal score (WMD –4.52, 95% CI –5.86 to –3.17). Rotigotine was associated with a significantly higher rate of withdrawals due to adverse events (relative risk [RR] 1.82, 95% CI 1.29–2.59), and higher rates of application site reactions (RR 2.92, 95% CI 2.29–3.72), vomiting (RR 5.18, 95% CI 2.25–11.93), and dyskinesia (RR 2.52, 95% CI 1.47–4.32) compared with placebo. No differences were found in the relative risks of headache, constipation, back pain, diarrhea, or serious adverse events.

Conclusions

Our meta-analysis showed that the use of rotigotine can reduce the symptoms of PD. However, rotigotine was also associated with a higher incidence of adverse events, especially application site reactions, compared with placebo.     

Genetic Variants of LRRK2 in Taiwanese Parkinson’s Disease

Genetic variants of leucine-rich repeat kinase 2 (LRRK2) were reported to alter the risk for Parkinson’s disease (PD). However, the genetic spectrum of LRRK2 variants has not been clearly disclosed yet in Taiwanese population. Herein, we sequenced LRRK2 coding region in 70 Taiwanese early onset PD patients (age at onset ≤ 50), and found six amino acid-changing single nucleotide polymorphisms (SNPs, N551K, R1398H, R1628P, S1647T, G2385R and M2397T), one reported (R1441H) and 2 novel missense (R767H and S885N) mutations. We examined the frequency of identified LRRK2 variants by genotyping 573 Taiwanese patients with PD and 503 age-matched control subjects. The results showed that PD patients demonstrated a higher frequency of G2385R A allele (4.6%) than control subjects (2.1%; odds ratio = 2.27, 95% confidence interval: 1.38–3.88, P = 0.0017). Fewer PD patients (27.7%) carried the 1647T-2397T haplotype as compared with the control subjects (33.0%; odds ratio = 0.80, 95% confidence interval: 0.65–0.97, P = 0.0215). However, the frequency of 1647T-2385R-2397T haplotype (4.3%) in PD patients was still higher than in control subjects (1.9%, odds ratio: 2.15, 95% confidence interval: 1.27–3.78, P = 0.0058). While no additional subject was found to carry R767H and R1441H, one more patient was observed to carry the S885N variant. Our results indicate a robust risk association regarding G2385R and a new possible protective haplotype (1647T-2397T). Gene-environmental interaction and a larger cohort study are warranted to validate our findings. Additionally, two new missense mutations (R767H and S885N) regarding LRRK2 in PD patients were identified. Functional studies are needed to elucidate the effects of these LRRK2 variants on protein function.     

High spatio-temporal resolution measurement of A1R and A2AR interactions combined with Iem-spFRET and E-FRET methods

A₁R-A_2AR heterodimers regulate striatal glutamatergic neurotransmission. However, few researches about kinetics have been reported. Here, we combined Iem-spFRET and E-FRET to investigate the kinetics of A₁R and A_2AR interaction. Iem-spFRET obtains the energy transfer efficiency of the whole cell. E-FRET gets energy transfer efficiency with high spatial resolution, whereas, it was prone to biases because background was easily selected due to manual operation. To study the interaction with high spatio-temporal resolution, Iem-spFRET was used to correct the deviation of E-FRET. In this paper, A₁R and A_2AR interaction was monitored, and the changes of FRET efficiency of the whole or/and partial cell membrane were described. The results showed that activation of A₁R or A_2AR leads to rapid aggregation, inhibition of A₁R or A_2AR leads to slow segregation, and the interaction is reversible. These results demonstrated that combination of Iem-spFRET and E-FRET could measure A₁R and A_2AR interaction with high spatio-temporal resolution.     

Abnormal Salivary Total and Oligomeric Alpha-Synuclein in Parkinson’s Disease

In Parkinson’s disease (PD), alpha-synuclein (a-syn) can be detected in biological fluids including saliva. Although previous studies found reduced a-syn total (a-syn_total) concentration in saliva of PD patients, no studies have previously examined salivary a-syn oligomers (a-syn_olig) concentrations or assessed the correlation between salivary a-syn_total, a-syn_olig and clinical features in a large cohort of PD patients. Is well known that a-syn_olig exerts a crucial neurotoxic effect in PD. We collected salivary samples from 60 PD patients and 40 age- and sex-comparable healthy subjects. PD was diagnosed according to the United Kingdom Brain Bank Criteria. Samples of saliva were analyzed by specific anti-a-syn and anti-oligomeric a-syn ELISA kits. A complete clinical evaluation of each patient was performed using MDS-Unified Parkinson''s Disease Rating Scale, Beck Depression Inventory, Montreal Cognitive Assessment and Frontal Assessment Battery. Salivary a-syn_total was lower, whereas a-syn_olig was higher in PD patients than healthy subjects. The a-syn_olig/a-syn_total ratio was also higher in patients than in healthy subjects. Salivary a-syn_total concentration negatively correlated with that of a-syn_olig and correlated with several patients’ clinical features. In PD, decreased salivary concentration of a-syn_total may reflect the reduction of a-syn monomers (a-syn_mon), as well as the formation of insoluble intracellular inclusions and soluble oligomers. The combined detection of a-syn_total and a-syn_olig in the saliva might help the early diagnosis of PD.     

Adenosine receptor signalling in Alzheimer’s disease

Alzheimer’s disease (AD) is the most common dementia in the elderly and its increasing prevalence presents treatment challenges. Despite a better understanding of the disease, the current mainstay of treatment cannot modify pathogenesis or effectively address the associated cognitive and memory deficits. Emerging evidence suggests adenosine G protein-coupled receptors (GPCRs) are promising therapeutic targets for Alzheimer’s disease. The adenosine A₁ and A_2A receptors are expressed in the human brain and have a proposed involvement in the pathogenesis of dementia. Targeting these receptors preclinically can mitigate pathogenic β-amyloid and tau neurotoxicity whilst improving cognition and memory. In this review, we provide an accessible summary of the literature on Alzheimer’s disease and the therapeutic potential of A₁ and A_2A receptors. Although there are no available medicines targeting these receptors approved for treating dementia, we provide insights into some novel strategies, including allosterism and the targeting of oligomers, which may increase drug discovery success and enhance the therapeutic response.     

Clinical Characteristics with an Impact on ADL Functions of PD Patients with Cognitive Impairment Indicative of Dementia

Background

Dementia in Parkinson’s disease (PD) is defined as cognitive decline severe enough to affect activities of daily living function (ADL). The aim of our exploratory study was to compare two groups of PD patients. Both groups had cognitive deficits severe enough to justify diagnosis of dementia, but they differed according to caregivers’ rating on ADL dysfunction. Parameters which differed between the two groups were interpreted to affect the caregivers’ perception of ADL dysfunction in PD patients with cognitive impairment indicative of Parkinson’s disease dementia.

Methodology/Principal Findings

Thirty of 131 Parkinson’s disease patients fulfilled the Movement Disorders Society Task Force – recommended, cognitive Level-I-criteria for dementia. According to standardized caregiver ratings, volunteers were grouped into 18 patients with (ADL-) and 12 without instrumental activities of daily living dysfunction (ADL+). Caregiver activities of daily living function ratings closely correlated with self-estimates of patients and those of physician (p<0.001). ADL- patients performed worse on tests assessing visual-construction (p<0.05) and attention (p=0.03) than ADL+ patients. Moreover, the postural instability and gait disorder subtype was more frequent in ADL- patients (p=0.009). ADL- patients tended to have more communication problems (p=0.05), more anxiety (p=0.05) and showed a tendency to be treated more often with neuroleptics (p=0.049) than ADL+.

Conclusions/Significance

Results indicate that worse attention, visual-construction abilities, the postural instability and gait disorder subtype, communication problems, medication and presence of anxiety are related to activities of daily living dysfunctions in Parkinson’s disease patients with cognitive decline indicative of dementia. Our data suggests that not only cognitive factors but also non-cognitive factors seem to be linked to the diagnosis of Parkinson’s disease dementia associated with significant impact on instrumental activities of daily living function. Further studies with larger sample sizes are needed to verify our results.