Novel perspectives in the physio-pharmacological regulation of opioid receptors

The opioid peptide receptors encompass three major “classical” subclasses, namely, μ, δ and κ (MOP, DOP and KOP receptors respectively) and a more recently identified subclass, the NOP receptor. The endogenous opioid and dopaminergic systems are known to interact in the modulation of motor functions under physio-pathological conditions. In particular, degeneration of dopamine (DA) neurons and loss of DA innervation in Parkinson’s disease (PD) is known to trigger adaptive changes in opioid systems in the basal ganglia (BG), which may be viewed either as pathogenic or compensatory. In the present thesis we investigated the role of DA, and specifically the role of D2 receptor-mediated transmission, in the motor effects exerted by DOP and NOP receptors ligands. Nociceptin/orphanin FQ (N/OFQ), the endogenous ligand of the NOP receptor, exerts a dual control over motor function, low doses being facilitating and high ones being inhibitory. Since the same dual response has been observed after administration of NOP receptor antagonists, we hypothesized that the motor effects exerted by NOP receptors ligands might involve different DA receptor subtypes. To test our hypothesis we used both pharmacological (i.e. DA receptor selective ligands) and genetic (i.e. mice lacking the D2 receptor (D2R-/-) or its long isoform (D2L-/-)) tools. The D2/D3 antagonist raclopride prevented the motor facilitation induced by low doses of N/OFQ or the NOP antagonist J-113397, but was ineffective in preventing the motor impairment induced by high doses of J-113397. These effects suggest that motor facilitation and motor inhibition might rely on different D2 receptor subpopulations. Therefore to dissect out the contribution of pre- and post-synaptic D2 receptors, D2 knockout mice were used. We observed that the motor facilitation induced by low doses of N/OFQ or J-113397 was lost in D2R-/- and D2L-/- mice. The inhibitory effect of high doses of J-113397 was retained in D2L-/- mice, but disappeared in D2R-/- mice, whereas motor inhibition induced by high doses of N/OFQ occurs even in the absence of D2 receptors. Our results demonstrate that motor stimulation induced by low doses of N/OFQ or J-113397 is mediated by D2L receptors whereas motor inhibition induced by J-113397 involves D2S, possibly pre-synaptic, receptors. N/OFQ-induced hypolocomotion is independent from D2 receptors, and possibly due to direct inhibition of nigral DA cells. The same combined approach was followed to study the role of D2 transmission in DOP receptor-mediated motor effects. Evidence that DOP receptor is an attractive target for the treatment of neuropsychiatric disorders, among which PD, has been growing in recent years. The DOP receptor agonist SNC-80 did not increase motor activity in C57BL naïve mice. However, it restored motor activity in mice rendered hypokinetic with raclopride, or emiparkinsonian 6-OHDA lesioning. This finding corroborates the hypothesis that the DOP receptor system plays a compensatory role under conditions where DA transmission and, consequently, motor function is impaired. To further confirm the involvement of D2 receptors in the motor action exerted by DOP receptor agonist, SNC-80 was administered to D2R-/- and D2L-/- mice, and wild-type controls. SNC-80 was ineffective in D2R+/+ and D2L+/+ mice but improved motor function in D2R-/- and D2L-/- mice. These results show that the absence of post-synaptic D2 receptors discloses a motor promoting action of DOP receptor ligands, suggesting the existence of a D2/DOP receptor interaction both at the membrane and network level. Receptor signalling is typically accompanied by desensitization, a complex feedback regulatory process whereby receptor responsiveness decreases on continued agonist stimulation. Signaling of opioid receptors is regulated negatively by regulators of G protein signalling (RGS) proteins and in vitro studies provided evidence for a DOP receptor-specific effect of RGS4. Small molecule inhibitors of RGS-box-Gα interactions should serve to enhance G-protein signals and act as adjuvants or “potentiators” of GPCR agonists. Therefore, we tested the hypothesis that the coapplication of SNC-80 and CCG-203769, a small molecule inhibitor of RGS4, developed by R. Neubig at the University of Michigan, could potentiate the effects of SNC-80 on motor activity, both under physiological and parkinsonian conditions. We showed that the coapplication of sub-threshold doses of CCG-203769 disclosed a mild, but significant, effect of SNC-80 on motor activity in naïve mice. In addition, it synergized with SNC-80 in restoring motor activity in raclopride-treated, or 6-OHDA hemilesioned rats. These data show that RGS4 contribute to extinguish DOP-triggered motor responses, opening the way to the use of RGS4 inhibitors as adjuncts to DOP agonists in PD. Overall, the data provide evidence for an opposite role of DA transmission in the modulation of N/OFQergic and enkephalinergic opioid systems. Moreover, these results demonstrate that endogenous RGS4 exerts a regulatory role on DOP receptor signalling and that the inhibition of RGS4 might be beneficial in modulating DOP transmission in pathological conditions. Finally, this study proposes new possible targets to regulate motor activity, which may translate into new drugs useful in the treatment of PD and other brain disorders

Selectivity and anti-Parkinson's potential of thiadiazolidinone RGS4 inhibitors

Many current therapies target G protein coupled receptors (GPCR), transporters, or ion channels. In addition to directly targeting these proteins, disrupting the protein−protein interactions that localize or regulate their function could enhance selectivity and provide unique pharmacologic actions. Regulators of G protein signaling (RGS) proteins, especially RGS4, play significant roles in epilepsy and Parkinson’s disease. Thiadiazolidinone (TDZD) inhibitors of RGS4 are nanomolar potency blockers of the biochemical actions of RGS4 in vitro. Here, we demonstrate the substantial selectivity (8- to >5000-fold) of CCG-203769 for RGS4 over other RGS proteins. It is also 300-fold selective for RGS4 over GSK-3β, another target of this class of chemical scaffolds. It does not inhibit the cysteine protease papain at 100 μM. CCG-203769 enhances Gαq-dependent cellular Ca2+ signaling in an RGS4-dependent manner. TDZD inhibitors also enhance Gαi-dependent δ-OR inhibition of cAMP production in SH-SY-5Y cells, which express endogenous receptors and RGS4. Importantly, CCG-203769 potentiates the known RGS4 mechanism of Gαi-dependent muscarinic bradycardia in vivo. Furthermore, it reverses raclopride-induced akinesia and bradykinesia in mice, a model of some aspects of the movement disorder in Parkinson’s disease. A broad assessment of compound effects revealed minimal off-target effects at concentrations necessary for cellular RGS4 inhibition. These results expand our understanding of the mechanism and specificity of TDZD RGS inhibitors and support the potential for therapeutic targeting of RGS proteins in Parkinson’s disease and other neural disorders

Social cognition in people with schizophrenia: A cluster-analytic approach

Background The study aimed to subtype patients with schizophrenia on the basis of social cognition (SC), and to identify cut-offs that best discriminate among subtypes in 809 out-patients recruited in the context of the Italian Network for Research on Psychoses. Method A two-step cluster analysis of The Awareness of Social Inference Test (TASIT), the Facial Emotion Identification Test and Mayer-Salovey-Caruso Emotional Intelligence Test scores was performed. Classification and regression tree analysis was used to identify the cut-offs of variables that best discriminated among clusters. Results We identified three clusters, characterized by unimpaired (42%), impaired (50.4%) and very impaired (7.5%) SC. Three theory-of-mind domains were more important for the cluster definition as compared with emotion perception and emotional intelligence. Patients more able to understand simple sarcasm (14 for TASIT-SS) were very likely to belong to the unimpaired SC cluster. Compared with patients in the impaired SC cluster, those in the very impaired SC cluster performed significantly worse in lie scenes (TASIT-LI <10), but not in simple sarcasm. Moreover, functioning, neurocognition, disorganization and SC had a linear relationship across the three clusters, while positive symptoms were significantly lower in patients with unimpaired SC as compared with patients with impaired and very impaired SC. On the other hand, negative symptoms were highest in patients with impaired levels of SC. Conclusions If replicated, the identification of such subtypes in clinical practice may help in tailoring rehabilitation efforts to the person's strengths to gain more benefit to the person

The interplay among psychopathology, personal resources, context-related factors and real-life functioning in schizophrenia: stability in relationships after 4 years and differences in network structure between recovered and non-recovered patients

Improving real-life functioning is the main goal of the most advanced integrated treatment programs in people with schizophrenia. The Italian Network for Research on Psychoses previously explored, by using network analysis, the interplay among illness-related variables, personal resources, context-related factors and real-life functioning in a large sample of patients with schizophrenia. The same research network has now completed a 4-year follow-up of the original sample. In the present study, we used network analysis to test whether the pattern of relationships among all variables investigated at baseline was similar at follow-up. In addition, we compared the network structure of patients who were classified as recovered at follow-up versus those who did not recover. Six hundred eighteen subjects recruited at baseline could be assessed in the follow-up study. The network structure did not change significantly from baseline to follow-up, and the overall strength of the connections among variables increased slightly, but not significantly. Functional capacity and everyday life skills had a high betweenness and closeness in the network at follow-up, as they had at baseline, while psychopathological variables remained more peripheral. The network structure and connectivity of non-recovered patients were similar to those observed in the whole sample, but very different from those in recovered subjects, in which we found few connections only. These data strongly suggest that tightly coupled symptoms/dysfunctions tend to maintain each other's activation, contributing to poor outcome in schizophrenia. Early and integrated treatment plans, targeting variables with high centrality, might prevent the emergence of self-reinforcing networks of symptoms and dysfunctions in people with schizophrenia

The interplay among psychopathology, personal resources, context-related factors and real-life functioning in schizophrenia: stability in relationships after 4 years and differences in network structure between recovered and non-recovered patients

Improving real-life functioning is the main goal of the most advanced integrated treatment programs in people with schizophrenia. The Italian Network for Research on Psychoses previously explored, by using network analysis, the interplay among illness-related variables, personal resources, context-related factors and real-life functioning in a large sample of patients with schizophrenia. The same research network has now completed a 4-year follow-up of the original sample. In the present study, we used network analysis to test whether the pattern of relationships among all variables investigated at baseline was similar at follow-up. In addition, we compared the network structure of patients who were classified as recovered at follow-up versus those who did not recover. Six hundred eighteen subjects recruited at baseline could be assessed in the follow-up study. The network structure did not change significantly from baseline to follow-up, and the overall strength of the connections among variables increased slightly, but not significantly. Functional capacity and everyday life skills had a high betweenness and closeness in the network at follow-up, as they had at baseline, while psychopathological variables remained more peripheral. The network structure and connectivity of non-recovered patients were similar to those observed in the whole sample, but very different from those in recovered subjects, in which we found few connections only. These data strongly suggest that tightly coupled symptoms/dysfunctions tend to maintain each other's activation, contributing to poor outcome in schizophrenia. Early and integrated treatment plans, targeting variables with high centrality, might prevent the emergence of self-reinforcing networks of symptoms and dysfunctions in people with schizophrenia

Social cognition in people with schizophrenia: A cluster-analytic approach

Background The study aimed to subtype patients with schizophrenia on the basis of social cognition (SC), and to identify cut-offs that best discriminate among subtypes in 809 out-patients recruited in the context of the Italian Network for Research on Psychoses. Method A two-step cluster analysis of The Awareness of Social Inference Test (TASIT), the Facial Emotion Identification Test and Mayer-Salovey-Caruso Emotional Intelligence Test scores was performed. Classification and regression tree analysis was used to identify the cut-offs of variables that best discriminated among clusters. Results We identified three clusters, characterized by unimpaired (42%), impaired (50.4%) and very impaired (7.5%) SC. Three theory-of-mind domains were more important for the cluster definition as compared with emotion perception and emotional intelligence. Patients more able to understand simple sarcasm (14 for TASIT-SS) were very likely to belong to the unimpaired SC cluster. Compared with patients in the impaired SC cluster, those in the very impaired SC cluster performed significantly worse in lie scenes (TASIT-LI <10), but not in simple sarcasm. Moreover, functioning, neurocognition, disorganization and SC had a linear relationship across the three clusters, while positive symptoms were significantly lower in patients with unimpaired SC as compared with patients with impaired and very impaired SC. On the other hand, negative symptoms were highest in patients with impaired levels of SC. Conclusions If replicated, the identification of such subtypes in clinical practice may help in tailoring rehabilitation efforts to the person's strengths to gain more benefit to the person

ST-elevation myocardial infarction in the COVID-19 era

The worldwide pandemic caused by the novel acute respiratory syndrome coronavirus 2 (SARS-CoV2) has resulted in a new and lethal disease termed coronavirus disease 2019 (COVID-19). The risk of adverse outcomes in patients with COVID-19 is strongly associated with advanced age, comorbidities, and pre-existing cardiovascular risk factors. Moreover, the patient experienced a delay in clinical presentation reducing numbers of daily calls for primary PCI. We aimed at formally appraise the daily incidence and corresponding symptom-to-reperfusion time in patients with AMI at our institution between March 1 and March 19, 2020, comparing the findings with the same period in 2019. Our data showed that the COVID-19 scare is associated with fewer STEMIs and NSTEMIs, as well as calls to the STEMI networks and increase in symptom-to-balloon times

Genetic and pharmacological evidence that endogenous nociceptin/orphanin FQ contributes to dopamine cell loss in Parkinson's disease

International audienceTo investigate whether the endogenous neuropeptide nociceptin/orphanin FQ (N/OFQ) contributes to the death of dopamine neurons in Parkinson's disease, we undertook a genetic and a pharmacological approach using NOP receptor knockout (NOP(-/-)) mice, and the selective and potent small molecule NOP receptor antagonist (-)-cis-1-methyl-7-[[4-(2,6-dichlorophenyl)piperidin-1-yl]methyl]-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol (SB-612111). Stereological unbiased methods were used to estimate the total number of dopamine neurons in the substantia nigra of i) NOP(-/-) mice acutely treated with the parkinsonian neurotoxin 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP), ii) naïve mice subacutely treated with MPTP, alone or in combination with SB-612111, iii) rats injected with a recombinant adeno-associated viral (AAV) vector overexpressing human mutant p.A53T α-synuclein, treated with vehicle or SB-612111. NOP(-/-) mice showed a 50% greater amount of nigral dopamine neurons spared in response to acute MPTP compared to controls, which was associated with a milder motor impairment. SB-612111, given 4days after MPTP treatment to mimic the clinical condition, prevented the loss of nigral dopamine neurons and striatal dopaminergic terminals caused by subacute MPTP. SB-612111, administered a week after the AAV injections in a clinically-driven protocol, also increased by 50% both the number of spared nigral dopamine neurons and striatal dopamine terminals, and prevented accompanying motor deficits induced by α-synuclein. We conclude that endogenous N/OFQ contributes to dopamine neuron loss in pathogenic and etiologic models of Parkinson's disease through NOP receptor-mediated mechanisms. NOP receptor antagonists might prove effective as disease-modifying agents in Parkinson's disease, through the rescue of degenerating nigral dopamine neurons and/or the protection of the healthy ones

Lipid nanocarriers containing a Levodopa prodrug with potential antiparkinsonian activity

This paper describes the production, characterization and in vivo activity of lipid nanocarriers (LN) containing a levodopa prodrug (LD-PD) with therapeutic potential in Parkinson’s disease. LD is the mainstay of the pharmacotherapy of Parkinson’s disease. However, after a good initial response, motor fluctuations, dyskinesia and loss of efficacy, develop over time, partly due to oscillations in plasma and brain levels of the drug. LD-PD was produced with the aim of prolonging the pharmacological activity of LD. To improve solubility, and simultaneously provide a long lasting release and therapeutic efficacy, the prodrug was formulated in tristearin/lecithin LN. The obtained formulation was homogeneous in particle size and remained stable for up to two months from preparation. For the three different tested LD concentrations, namely 1.25, 2.5 and 5.0 mg/ml, the morphological characterization revealed no substantial differences between unloaded and LD-PD loaded LN. The calorimetric test showed an interaction between the lipid phase and the loaded prodrug. In vitro studies using the dialysis method and enzymatic degradation procedure showed that the LD-PD loaded LN provided a controlled prodrug release. Finally, two behavioural tests specific to akinesia (bar test) or akinesia/bradykinesia (drag test) performed in 6-hydroxydopamine hemilesioned mice (a model of Parkinson’s disease) demonstrated that the LD-PD loaded LN attenuated parkinsonian disabilities, showing a slightly reduced maximal efficacy but a longer lasting action (up to 24 hours) than an equal dose of LD. We conclude that LD-PD loaded LN may represent a future LD formulation useful in Parkinson’s disease therapy

GluD1 is a common altered player in neuronal differentiation from both MECP2-mutated and CDKL5-mutated iPS cells.

Rett syndrome is a monogenic disease due to de novo mutations in either MECP2 or CDKL5 genes. In spite of their involvement in the same disease, a functional interaction between the two genes has not been proven. MeCP2 is a transcriptional regulator; CDKL5 encodes for a kinase protein that might be involved in the regulation of gene expression. Therefore, we hypothesized that mutations affecting the two genes may lead to similar phenotypes by dysregulating the expression of common genes. To test this hypothesis we used induced pluripotent stem (iPS) cells derived from fibroblasts of one Rett patient with a MECP2 mutation (p.Arg306Cys) and two patients with mutations in CDKL5 (p.Gln347Ter and p.Thr288Ile). Expression profiling was performed in CDKL5-mutated cells and genes of interest were confirmed by real-time RT-PCR in both CDKL5- and MECP2-mutated cells. The only major change in gene expression common to MECP2- and CDKL5-mutated cells was for GRID1, encoding for glutamate D1 receptor (GluD1), a member of the δ-family of ionotropic glutamate receptors. GluD1 does not form AMPA or NMDA glutamate receptors. It acts like an adhesion molecule by linking the postsynaptic and presynaptic compartments, preferentially inducing the inhibitory presynaptic differentiation of cortical neurons. Our results demonstrate that GRID1 expression is downregulated in both MECP2- and CDKL5-mutated iPS cells and upregulated in neuronal precursors and mature neurons. These data provide novel insights into disease pathophysiology and identify possible new targets for therapeutic treatment of Rett syndrome