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Background and Purpose Obstructive sleep apnea (OSA) frequently occurs in Parkinson Disease (PD), probably caused by upper airway dysfunctions or shared pathogenetic mechanisms. OSA may precede PD diagnosis or worsen throughout its course, but its relationship with clinical features and dopaminergic medication remains unclear. This meta‐analysis aimed to provide a reliable estimate of OSA prevalence in the PD population (PD‐OSA) and to clarify its clinical associated factors to help clinicians in understanding the underlying pathophysiological mechanisms. Methods A systematic literature search was performed up to April 2023 using the PubMed, Scopus, and PsycINFO databases. Articles were included if they provided data on PD patients with and without OSA. Pooled prevalence for PD‐OSA was calculated using the proportions of PD participants diagnosed with OSA. Demographic and clinical features associated with PD‐OSA were explored by comparing PD patients with and without OSA. Results Seventeen studies were included in the meta‐analysis. Pooled OSA prevalence was 45% of a total sample of 1448 PD patients and was associated with older age, male sex, higher body mass index (BMI), more severe motor disturbances and periodic limb movements, reduced risk of rapid eye movement sleep behavior disorder, intake of dopamine agonists, and worse excessive daytime sleepiness. No relationship emerged with cognitive functioning and neuropsychiatric manifestations. Conclusions OSA affects nearly half of PD patients as a secondary outcome of predisposing factors such as older age and higher BMI in addition to PD‐related motor impairment. Future studies should focus on determining the impact of both clinical features and dopaminergic medication on the development of PD‐OSA.

Treatment-resistant schizophrenia (TRS) affects up to one in three individuals with schizophrenia and is associated with a significant clinical, social, and economic burden. Different from treatment-responsive forms, TRS appears to involve other biological mechanisms extending beyond dopaminergic dysfunctions. This review outlines current knowledge on the molecular and cellular basis of TRS, focusing on alterations in glutamate signaling, imbalances between excitatory and inhibitory activity, disruptions in D-amino acid metabolism, and evidence of neuroinflammation, oxidative stress, and mitochondrial or endoplasmic reticulum dysfunction. Data from genomics, proteomics, metabolomics, preclinical models, and postmortem studies suggest that TRS may have a peculiar neurobiological substrate. Further, multimodal brain imaging studies reveal differences in brain structure, white matter integrity, and network connectivity when compared to treatment-responsive individuals. Altogether, these findings support a shift from the traditional dopamine hypothesis toward a more comprehensive model that includes multiple immune, metabolic, and synaptic factors. Understanding the possible interplay of these complex mechanisms may lead to the identification of potential biomarkers that may help to predict antipsychotic response, as well as the development of more targeted treatments. Early recognition and a deeper biological insight into TRS are essential for improving care and guiding personalized therapeutic strategies.

Glutamate metabotropic receptors (mGluRs) and their molecular partners at the postsynaptic density (PSD) represent a highly dynamic molecular hub that integrates multiple neurotransmitter signals and regulates synaptic plasticity and metaplasticity, which are putatively involved in the pathophysiology of psychiatric illnesses, including schizophrenia. Group I mGluRs (mGluR1 and mGluR5) interact with PSD adaptor and scaffolding proteins, such as Homer, Shank, Norbin, and PICK1, as well as intracellular downstream effectors, creating a molecular network that resembles a Lego-like structure, where modular protein interactions fine-tune glutamatergic transmission. Evidence from preclinical research indicates that dysregulation of mGluR expression and function, along with disrupted PSD protein expression, may contribute to the pathophysiology of schizophrenia by altering glutamatergic neurotransmission and synaptic stability. Antipsychotic mechanisms of action may involve, at least in part, the modulation of mGluR activity mediated through PSD proteins. Notably, novel agents that enhance spinogenesis by acting at the level of PSD proteins, such as SPG302, may open promising avenues for therapeutics aimed at restoring synaptic integrity. While Group I mGluRs dominate postsynaptic regulation, Group II (mGluR2/3) and III (mGluR4/6/7/8) receptors -primarily presynaptic- inhibit neurotransmitter release and plasticity, offering complementary therapeutic avenues. Emerging strategies, such as allosteric modulators of mGluRs, aim to rebalance synaptic signaling in treatment-resistant schizophrenia. This review synthesizes how PSD proteins and mGluRs interact in schizophrenia, exploring their potential as druggable targets for novel therapies.

Schizophrenia (SCZ) is a complex mental disorder, whose pathogenesis involves both environmental and genetic factors. Genetic risk is conferred through a combination of common variants and rare mutations, with point mutations and copy number variants (CNVs). Many of the genetic variants associated with SCZ have pleiotropic effects, influencing brain development and being shared with other neurodevelopmental disorders (NDDs), such as intellectual disability (ID). This overlap supports the concept of a neurodevelopmental continuum, suggesting shared genetic risk, at least between SCZ and ID, and most presumably among SCZ and many other NDDs. Here, we describe the case of a male patient whose clinical features align with this hypothesis. He presented cognitive and behavioral impairments preceding psychotic symptoms, further reinforcing the genetic and clinical interaction between SCZ and other NDDs. The patient’s genetic profile was analyzed using array comparative genomic hybridization (a-CGH) and whole-exome sequencing (WES) to investigate the genetic determinants underlying his clinical condition. The genetic testing identified variants in loci associated with both SCZ and NDDs. Our findings highlight the need to integrate genetic assessments into psychiatrists’ clinical practice. Moreover, this report contributes to the current body of evidence supporting the thesis on the neurodevelopmental continuum of SCZ.

Introduction Impulse control disorders (ICDs) frequently occur in Parkinson’s disease (PD), and an early identification is essential to prevent severe psychosocial consequences. The Questionnaire for Impulsive-Compulsive Disorders in Parkinson’s Disease–Rating Scale (QUIP-RS) has been developed to evaluate the severity of ICDs along with a range of impulsive-compulsive behaviors (ICBs) in PD; however, its Italian version has not yet been validated. Methods One hundred consecutive outpatients with PD were administered an Italian version of the QUIP-RS and a brief neuropsychological assessment to evaluate global cognitive status and scales to measure depression, apathy and impulsive disorders. We evaluated the internal consistency, convergent and divergent validity, and factorial structure of QUIP-RS. We also explored the possible association between QUIP-RS scores and clinical factors and dopaminergic medication. Results Subsyndromal ICDs manifestations were observed in 54% of the patients, and one in four (22%) reported two or more ICDs or related behaviors. The QUIP-RS demonstrated good internal consistency (Cronbach’s alpha = 0.806) and construct validity, and its factorial structure reflected different ICDs and ICBs domains. No association emerged between QUIP-RS scores and the clinical aspects of PD and dopaminergic medication. Conclusion We provided, for the first time, an Italian translation of the QUIP-RS and demonstrated its feasibility in clinical and research settings. Severity of ICDs was independent of clinical factors and dopaminergic medication, underlining the need to adopt a broader perspective on their etiopathology in PD.

Neuropathic pain is a pathological condition induced by a lesion or disease affecting the somatosensory system, with symptoms like allodynia and hyperalgesia. It has a multifaceted pathogenesis as it implicates several molecular signaling pathways involving peripheral and central nervous systems. Affective and cognitive dysfunctions have been reported as comorbidities of neuropathic pain states, supporting the notion that pain and mood disorders share some common pathogenetic mechanisms. The understanding of these pathophysiological mechanisms requires the development of animal models mimicking, as far as possible, clinical neuropathic pain symptoms. Among them, the Spared Nerve Injury (SNI) model has been largely characterized in terms of behavioral and functional alterations. This model is associated with changes in neuronal firing activity at spinal and supraspinal levels, and induces late neuropsychiatric disorders (such as anxious-like and depressive-like behaviors, and cognitive impairments) comparable to an advanced phase of neuropathy. The goal of this review is to summarize current findings in preclinical research, employing the SNI model as a tool for identifying pathophysiological mechanisms of neuropathic pain and testing pharmacological agent.

Post-traumatic stress disorder (PTSD) is a chronic psychiatric condition characterized by persistent cognitive and affective disturbances following exposure to severe trauma. In rodents, prolonged post-weaning social isolation is a well-established model of PTSD-like symptomatology. In this study, we investigated the behavioral effects of chronic cannabidiol (CBD) administration-either alone or in combination with two natural antioxidants, resveratrol (RES) and alpha-lipoic acid (ALA)in socially isolated mice. Male CD1 mice (n = 8) were isolated in individual cages from postnatal day 21 (PN21) and maintained in isolation for 30 days. They were then treated with CBD (2.5, 5, and 10 mg/kg), resveratrol (RES, 20 mg/kg), or alpha-lipoic acid (ALA, 10 mg/kg) for 15 days following social isolation. While low-dose CBD (2.5 mg/kg) alone was ineffective, its combination with either RES or ALA restored the latency to the first attack and significantly reduced aggressive behavior, comparable to high-dose CBD (10 mg/kg). Similarly, combined treatments with RES or ALA markedly reduced immobility time in the tail suspension test, indicating antidepressant-like effects. In contrast, no significant anxiolytic effect was observed with the combinations in the hole-board test, suggesting a limited action on anxiety-like behavior. These findings suggest that co-administration of CBD with RES or ALA exerts synergistic antidepressants and anti-aggressive effects in a PTSD-like model, potentially allowing for dose reduction of CBD. Further studies are warranted to explore the underlying molecular mechanisms.

d -Aspartate ( d -Asp) is a free d -amino acid detected in multiple brain regions and putative precursor of endogenous N -methyl- d -aspartate (NMDA) acting as agonist at NMDA receptors. In this study, we investigated whether d -Asp (20 mM) in drinking solution for 1 month affects pain responses and pain-related emotional, and cognitive behaviour in a model of neuropathic pain induced by the spared nerve injury (SNI) of the sciatic nerve in mice. SNI mice developed mechanical allodynia and motor coordination impairment 30 days after SNI surgery. SNI mice showed cognitive impairment, anxiety and depression-like behaviour, reduced sociability in the three chamber sociability paradigm, increased expression of NR2B subunit of NMDA receptor and Homer 1a in the medial prefrontal cortex (mPFC). The expression of (post synaptic density) PSD-95 and Shank 1was instead unaffected in the mPFC of the SNI mice. Treatment with d -Asp drinking solution, started right after the SNI (day 0), alleviated mechanical allodynia, improved cognition and motor coordination and increased social interaction. d -Asp also restored the levels of extracellular d -Asp, Homer 1a and NR2B subunit of the NMDA receptor to physiological levels and reduced Shank1 and PSD-95 protein levels in the mPFC. Amitriptyline, a tricyclic antidepressant used also to alleviate neuropathic pain in humans, reverted mechanical allodynia and cognitive impairment, and unlike d -Asp, was effective in reducing depression and anxiety-like behaviour in the SNI mice and increased PSD protein level. Altogether these findings demonstrate that d -Asp improves sensorial, motor and cognitive-like symptoms related to chronic pain possibly through glutamate neurotransmission normalization in neuropathic mice.

Autophagy is a highly conserved homeostatic process essential for the bulk degradation of cytoplasmic components and aggregated proteins. Multiple evidence indicates that impairment of (macro)autophagy leads to neurodegeneration, such as Parkinson disease (PD). Our previous work showed that p21 activated kinase 6 (PAK6) interacts with the PD-associated leucine-rich repeat kinase (LRRK2) to promote neurite outgrowth in the mouse striatum; still the function of PAK6 in the brain is largely unknown. Here, we found that downregulation of neuronal but not glial mbt, the D. melanogaster homolog of PAK6, impairs autophagy-lysosomal function. PAK6 overexpression in cells and in C. elegans increases transcription factor EB (TFEB) nuclear translocation in a kinase activity-dependent manner. Mechanistically, PAK6 forms a complex with TFEB to regulate its nuclear localization in a manner dependent on phosphorylation of and binding to 14-3-3 proteins and phosphorylation of TFEB at S467. In line with its ability to promote neuronal autophagy, mbt downregulation exacerbates alpha-synuclein toxicity in Drosophila dopaminergic neurons. Moreover, PAK6 overexpression in the substantia nigra of mutant LRRK2 mice reduces the burden of phosphorylated alpha-synuclein in dopaminergic neurons. Altogether, our study uncovers a novel role of PAK6 as a positive regulator of autophagy via TFEB and suggests that modulating its activity may represent a way to selectively turn on autophagy in neurons, with implications for the treatment of neurodegenerative disorders.