Allosteric modulators of G protein-coupled dopamine and serotonin receptors: a new class of atypical antipsychotics

Schizophrenia was first described by Emil Krapelin in the 19th century as one of the major mental illnesses causing disability worldwide. Since the introduction of chlorpromazine in 1952, strategies aimed at modifying the activity of dopamine receptors have played a major role for the treatment of schizophrenia. The introduction of atypical antipsychotics with clozapine broadened the range of potential targets for the treatment of this psychiatric disease, as they also modify the activity of the serotoninergic receptors. Interestingly, all marketed drugs for schizophrenia bind to the orthosteric binding pocket of the receptor as competitive antagonists or partial agonists. In recent years, a strong effort to develop allosteric modulators as potential therapeutic agents for schizophrenia was made, mainly for the several advantages in their use. In particular, the allosteric binding sites are topographically distinct from the orthosteric pockets, and thus drugs targeting these sites have a higher degree of receptor subunit specificity. Moreover, “pure” allosteric modulators maintain the temporal and spatial fidelity of native orthosteric ligand. Furthermore, allosteric modulators have a “ceiling effect”, and their modulatory effect is saturated above certain concentrations. In this review, we summarize the progresses made in the identification of allosteric drugs for dopamine and serotonin receptors, which could lead to a new generation of atypical antipsychotics with a better profile, especially in terms of reduced side effects

An Exploratory Study of Field Failures

Field failures, that is, failures caused by faults that escape the testing phase leading to failures in the field, are unavoidable. Improving verification and validation activities before deployment can identify and timely remove many but not all faults, and users may still experience a number of annoying problems while using their software systems. This paper investigates the nature of field failures, to understand to what extent further improving in-house verification and validation activities can reduce the number of failures in the field, and frames the need of new approaches that operate in the field. We report the results of the analysis of the bug reports of five applications belonging to three different ecosystems, propose a taxonomy of field failures, and discuss the reasons why failures belonging to the identified classes cannot be detected at design time but shall be addressed at runtime. We observe that many faults (70%) are intrinsically hard to detect at design-time

Bright light exposure reduces TH-positive dopamine neurons: implications of light pollution in Parkinson's disease epidemiology.

This study explores the effect of continuous exposure to bright light on neuromelanin formation and dopamine neuron survival in the substantia nigra. Twenty-one days after birth, Sprague-Dawley albino rats were divided into groups and raised under different conditions of light exposure. At the end of the irradiation period, rats were sacrificed and assayed for neuromelanin formation and number of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra. The rats exposed to bright light for 20 days or 90 days showed a relatively greater number of neuromelanin-positive neurons. Surprisingly, TH-positive neurons decreased progressively in the substantia nigra reaching a significant 29% reduction after 90 days of continuous bright light exposure. This decrease was paralleled by a diminution of dopamine and its metabolite in the striatum. Remarkably, in preliminary analysis that accounted for population density, the age and race adjusted Parkinson's disease prevalence significantly correlated with average satellite-observed sky light pollution

Eyes as Gateways for Environmental Light to the Substantia Nigra: Relevance in Parkinson’s Disease

Recent data indicates that prolonged bright light exposure of rats induces production of neuromelanin and reduction of tyrosine hydroxylase positive neurons in the substantia nigra. This effect was the result of direct light reaching the substantia nigra and not due to alteration of circadian rhythms. Here, we measured the spectrum of light reaching the substantia nigra in rats and analysed the pathway that light may take to reach this deep brain structure in humans. Wavelength range and light intensity, emitted from a fluorescent tube, were measured, using a stereotaxically implanted optical fibre in the rat mesencephalon. The hypothetical path of environmental light from the eye to the substantia nigra in humans was investigated by computed tomography and magnetic resonance imaging. Light with wavelengths greater than 600 nm reached the rat substantia nigra, with a peak at 709 nm. Eyes appear to be the gateway for light to the mesencephalon since covering the eyes with aluminum foil reduced light intensity by half. Using computed tomography and magnetic resonance imaging of a human head, we identified the eye and the superior orbital fissure as possible gateways for environmental light to reach the mesencephalon

Psychological treatments and psychotherapies in the neurorehabilitation of pain. Evidences and recommendations from the italian consensus conference on pain in neurorehabilitation

BACKGROUND: It is increasingly recognized that treating pain is crucial for effective care within neurological rehabilitation in the setting of the neurological rehabilitation. The Italian Consensus Conference on Pain in Neurorehabilitation was constituted with the purpose identifying best practices for us in this context. Along with drug therapies and physical interventions, psychological treatments have been proven to be some of the most valuable tools that can be used within a multidisciplinary approach for fostering a reduction in pain intensity. However, there is a need to elucidate what forms of psychotherapy could be effectively matched with the specific pathologies that are typically addressed by neurorehabilitation teams. OBJECTIVES: To extensively assess the available evidence which supports the use of psychological therapies for pain reduction in neurological diseases. METHODS: A systematic review of the studies evaluating the effect of psychotherapies on pain intensity in neurological disorders was performed through an electronic search using PUBMED, EMBASE, and the Cochrane Database of Systematic Reviews. Based on the level of evidence of the included studies, recommendations were outlined separately for the different conditions. RESULTS: The literature search yielded 2352 results and the final database included 400 articles. The overall strength of the recommendations was medium/low. The different forms of psychological interventions, including Cognitive-Behavioral Therapy, cognitive or behavioral techniques, Mindfulness, hypnosis, Acceptance and Commitment Therapy (ACT), Brief Interpersonal Therapy, virtual reality interventions, various forms of biofeedback and mirror therapy were found to be effective for pain reduction in pathologies such as musculoskeletal pain, fibromyalgia, Complex Regional Pain Syndrome, Central Post-Stroke pain, Phantom Limb Pain, pain secondary to Spinal Cord Injury, multiple sclerosis and other debilitating syndromes, diabetic neuropathy, Medically Unexplained Symptoms, migraine and headache. CONCLUSIONS: Psychological interventions and psychotherapies are safe and effective treatments that can be used within an integrated approach for patients undergoing neurological rehabilitation for pain. The different interventions can be specifically selected depending on the disease being treated. A table of evidence and recommendations from the Italian Consensus Conference on Pain in Neurorehabilitation is also provided in the final part of the pape

Long-Term Drug Survival and Effectiveness of Secukinumab in Patients with Moderate to Severe Chronic Plaque Psoriasis: 42-Month Results from the SUPREME 2.0 Study

Purpose: SUPREME, a phase IIIb study conducted in Italy, demonstrated safety and high efficacy of secukinumab for up to 72 weeks in patients with moderate-to-severe plaque-type psoriasis. SUPREME 2.0 study aimed to provide real-world data on the long-term drug survival and effectiveness of secukinumab beyond 72 weeks. Patients and Methods: SUPREME 2.0 is a retrospective observational chart review study conducted in patients previously enrolled in SUPREME study. After the end of the SUPREME study, eligible patients continued treatment as per clinical practice, and their effectiveness and drug survival data were retrieved from medical charts. Results: Of the 415 patients enrolled in the SUPREME study, 297 were included in SUPREME 2.0; of which, 210 (70.7%) continued secukinumab treatment throughout the 42-month observation period. Patients in the biologic-naïve cohort had higher drug survival than those in the biologic-experienced cohort (74.9% vs 61.7%), while HLA-Cw6–positive and HLA-Cw6–negative patients showed similar drug survival (69.3% and 71.9%). After 42 months, Psoriasis Area and Severity Index (PASI) 90 was achieved by 79.6% of patients overall; with a similar proportion of biologic-naïve and biologic-experienced patients achieving PASI90 (79.8% and 79.1%). The mean absolute PASI score reduced from 21.94 to 1.38 in the overall population, 21.90 to 1.24 in biologic-naïve and 22.03 to 1.77 in biologic-experienced patients after 42 months. The decrease in the absolute PASI score was comparable between HLACw6–positive and HLA–Cw6-negative patients. The baseline Dermatology Life Quality Index scores also decreased in the overall patients (10.5 to 2.32) and across all study sub-groups after 42 months. Safety was consistent with the known profile of secukinumab, with no new findings. Conclusion: In this real-world cohort study, secukinumab showed consistently high long-term drug survival and effectiveness with a favourable safety profile

What is the role of the placebo effect for pain relief in neurorehabilitation? Clinical implications from the Italian consensus conference on pain in neurorehabilitation

Background: It is increasingly acknowledged that the outcomes of medical treatments are influenced by the context of the clinical encounter through the mechanisms of the placebo effect. The phenomenon of placebo analgesia might be exploited to maximize the efficacy of neurorehabilitation treatments. Since its intensity varies across neurological disorders, the Italian Consensus Conference on Pain in Neurorehabilitation (ICCP) summarized the studies on this field to provide guidance on its use. Methods: A review of the existing reviews and meta-analyses was performed to assess the magnitude of the placebo effect in disorders that may undergo neurorehabilitation treatment. The search was performed on Pubmed using placebo, pain, and the names of neurological disorders as keywords. Methodological quality was assessed using a pre-existing checklist. Data about the magnitude of the placebo effect were extracted from the included reviews and were commented in a narrative form. Results: 11 articles were included in this review. Placebo treatments showed weak effects in central neuropathic pain (pain reduction from 0.44 to 0.66 on a 0-10 scale) and moderate effects in postherpetic neuralgia (1.16), in diabetic peripheral neuropathy (1.45), and in pain associated to HIV (1.82). Moderate effects were also found on pain due to fibromyalgia and migraine; only weak short-term effects were found in complex regional pain syndrome. Confounding variables might have influenced these results. Clinical implications: These estimates should be interpreted with caution, but underscore that the placebo effect can be exploited in neurorehabilitation programs. It is not necessary to conceal its use from the patient. Knowledge of placebo mechanisms can be used to shape the doctor-patient relationship, to reduce the use of analgesic drugs and to train the patient to become an active agent of the therapy

Involvement of metabotropic glutamate receptor subtype mGlu5 in the pathophysiology of Fragile X Syndrome.

Fragile X Syndrome (FXS) is the most common inherited form of intellectual disability and autism. FXS is caused by a mutation in the fragile X mental retardation 1 (Fmr1) gene which leads to the lack of the encoded FMRP protein. FMRP is an RNA binding protein involved in protein synthesis regulation at synapses. Many evidences suggest a central role of the Group-I metabotropic glutamate receptor subtype 5 (mGluR5) in the FXS pathophysiology. In particular, an exaggerated signaling response following mGluR5 activation may underlie synaptic dysfunction in this disorder. Although much work has focused on the dysregulation of synaptic protein synthesis as a consequence of this enhanced mGluR5 signaling, it becomes clear that in FXS there is also an altered balance of mGluR5 association with Homer scaffolding proteins, which are postsynaptic density (PSD) partners of mGluR5. Although an extensive literature describes the mGluR5/Homer association, very little is known about the consequences of the disruption of this interaction in the FXS context. Therefore, the goal of my thesis was to study the consequences of mGluR5/Homer crosstalk disruption in the Fmr1 knockout (KO) mouse model of FXS in term of properties and functions of mGluR5, such as expression during development, surface expression and axonal/dendritic targeting, agonist-induced internalization, surface dynamics and mGluR5-mediated modulation of NMDA receptor (NMDAR) currents. In a first set of experiments we investigated the mGluR5 surface expression in cultured hippocampal neurons from WT and Fmr1 KO mice by using immunofluorescence techniques and biotinylation assay. We found that mGluR5 was more expressed on the neuronal surface and was differently distributed in dendrites and axons of Fmr1 KO cultured neurons. We then hypothesized that these alterations were a direct consequence of the mGluR5/Homer crosstalk disruption. We demonstrated that these altered expression and targeting of mGluR5 were critically dependent on mGluR5/Homer crosstalk disruption. We also observed that mGluR5 did not undergo internalization upon sustained mGluR5 activation with DHPG in Fmr1 KO neurons. This latter phenotype, however, was not dependent on the disruption of the mGluR5/Homer crosstalk. Altogether, these results demonstrate that mGluR5/Homer crosstalk disruption contributes to the pathophysiology of FXS altering expression and targeting of mGluR5 on the surface of Fmr1 KO neurons. In the second part of my study we investigated the consequences of the disrupted mGluR5/Homer crosstalk for the mGluR5 surface dynamics, and consequently for NMDAR function in Fmr1 KO neurons. Using a combination of live-cell imaging and single-molecule tracking, we found that mGluR5/Homer crosstalk disruption specifically increased the mGluR5 lateral diffusion at the synapse of cultured Fmr1 KO hippocampal neurons. The higher mGluR5 mobility resulted in an increased probability of transient physical interaction with NMDAR in the PSD of Fmr1 KO. This interaction altered the mGluR5-mediated modulation of NMDAR currents as evidenced by the two following changes. First, using patch-clamp recordings from CA1 pyramidal neurons, we found that NMDAR-mediated excitatory postsynaptic currents (NMDAR-EPSCs) evoked by Schaffer collateral stimulation showed lower amplitudes in Fmr1 KO neurons. Second, the postsynaptic expression of mGluR5 mediated long term depression (LTD) of NMDAR-EPSCs was reduced in Fmr1 KO neurons. Finally, we demonstrated that these defects in NMDA currents were strongly dependent on the mGluR5/Homer crosstalk disruption and altered mGluR5 dynamics. Our results show that mGluR5/Homer disruption contributes to the mGluR5 dysregulation in Fmr1 KO neurons. This study might have implication for the treatment of mGluR5 synaptic dysfunctions in FXS by targeting mGluR5/Homer interaction and provide new suggestions to correct the defective signaling underlying cognitive impairment and autism

Distinctive binding properties of the negative allosteric modulator, [3H]SB269,652, at recombinant dopamine D3 receptors

Recently, employing radioligand displacement and functional coupling studies, we demonstrated that SB269,652 (N-[(1r,4r)-4-[2-(7-cyano-1,2,3,4-tetrahydroisoquinolin-2-yl)ethyl]cyclohexyl]-1H-indole-2-carboxamide) interacts in an atypical manner with dopamine D3 receptor displaying a unique profile reminiscent of a negative allosteric ligand. Here, we characterized the binding of radiolabelled [3H]SB269,652 to human dopamine D3 receptor stably expressed in Chinese Hamster Ovary cells. Under saturating conditions, SB269,652 showed a KD value of ≈ 1nM. Consistent with high selectivity for human dopamine D3 receptor, [3H]SB269,652 binding was undetectable in cells expressing human dopamine D1, D2L or D4 receptors and absent in synaptosomes from dopamine D3 receptor knockout vs. wild-type mice. In contrast to saturation binding experiments, the dissociation kinetics of [3H]SB269,652 from human dopamine D3 receptors initiated with an excess of unlabelled ligand were best fitted by a bi-exponential binding model. Supporting the kinetic data, competition experiments with haloperidol, S33084 (a dopamine D3 receptor antagonist) or dopamine, were best described by a two-site model. In co-transfection experiments binding of SB269,652 to dopamine D3 receptor was able to influence the functional coupling of dopamine D2 receptor, supporting the notion that SB269,652 is a negative allosteric modulator across receptor dimers. Hovever, because SB269,652 decreases the rate of [3H]nemonapride dissociation, the present data suggest that SB269,652 behaves as a bitopic antagonist at unoccupied dopamine D3 receptor, binding simultaneously to both orthosteric and allosteric sites, and as a pure negative allosteric modulator when receptors are occupied and it can solely bind to the allosteric site