Andrea de Bartolomeis

Association of the HTR2C gene and antipsychotic induced weight gain : a meta-analysis

The 5-HT2C receptor has been hypothesized to represent an important modulator in feeding behaviour. Evidence was based on the observation that knock-out mice for the 5-HT2C receptor gene (HTR2C) develop obesity and that many atypical antipsychotics with potent 5-HT2C antagonism may induce weight gain in susceptible individuals. Pharmacogenetic studies focusing mainly on the -759C/T promoter polymorphism (rs3813929) of the X-linked HTR2C gene revealed controversial results. We investigated the association of the HTR2C gene and weight gain using meta-analytical techniques, combining all published data while restricting our analysis to studies investigating the 759C/T. We also investigated whether ancestry (Caucasian vs. Asian) and clinical factors moderated any association. We found evidence for a slight association of -759C/T with weight gain and significance between studies for heterogeneity. Our meta-analysis provides support for the association of HTR2C in weight gain but indicates that firmly establishing the role of pharmacogenetics in clinical psychiatry requires much larger sample sizes that have been hitherto reported.

Treatment-Resistant Schizophrenia: Treatment Response and Resistance in Psychosis (TRRIP) Working Group Consensus Guidelines on Diagnosis and Terminology

OBJECTIVE Research and clinical translation in schizophrenia is limited by inconsistent definitions of treatment resistance and response. To address this issue, the authors evaluated current approaches and then developed consensus criteria and guidelines. METHOD A systematic review of randomized antipsychotic clinical trials in treatment-resistant schizophrenia was performed, and definitions of treatment resistance were extracted. Subsequently, consensus operationalized criteria were developed through 1) a multiphase, mixed methods approach, 2) identification of key criteria via an online survey, and 3) meetings to achieve consensus. RESULTS Of 2,808 studies identified, 42 met inclusion criteria. Of these, 21 studies (50%) did not provide operationalized criteria. In the remaining studies, criteria varied considerably, particularly regarding symptom severity, prior treatment duration, and antipsychotic dosage thresholds; only two studies (5%) utilized the same criteria. The consensus group identified minimum and optimal criteria, employing the following principles: 1) current symptoms of a minimum duration and severity determined by a standardized rating scale; 2) moderate or worse functional impairment; 3) prior treatment consisting of at least two different antipsychotic trials, each for a minimum duration and dosage; 4) systematic monitoring of adherence and meeting of minimum adherence criteria; 5) ideally at least one prospective treatment trial; and 6) criteria that clearly separate responsive from treatment-resistant patients. CONCLUSIONS There is considerable variation in current approaches to defining treatment resistance in schizophrenia. The authors present consensus guidelines that operationalize criteria for determining and reporting treatment resistance, adequate treatment, and treatment response, providing a benchmark for research and clinical translation.

Permanent Focal Brain Ischemia Induces Isoform-Dependent Changes in the Pattern of Na+/Ca2+ Exchanger Gene Expression in the Ischemic Core, Periinfarct Area, and Intact Brain Regions

Dysregulation of sodium [Na+]i and calcium [Ca2+]i homeostasis plays a pivotal role in the pathophysiology of cerebral ischemia. Three gene products of the sodium–calcium exchanger family NCX1, NCX2, and NCX3 couple, in a bidirectional way, the movement of these ions across the cell membrane during cerebral ischemia. Each isoform displays a selective distribution in the rat brain. To determine whether NCX gene expression can be regulated after cerebral ischemia, we used NCX isoform-specific antisense radiolabeled probes to analyze, by radioactive in situ hybridization histochemistry, the pattern of NCX1, NCX2, and NCX3 transcripts in the ischemic core, periinfarct area, as well as in nonischemic brain regions, after 6 and 24 h of permanent middle cerebral artery occlusion (pMCAO) in rats. We found that in the focal region, comprising divisions of the prefrontal, somatosensory, and insular cortices, all three NCX transcripts were downregulated. In the periinfarct area, comprising part of the motor cortex and the lateral compartments of the caudate-putamen, NCX2 messenger ribonucleic acid (mRNA) was downregulated, whereas NCX3 mRNA was significantly upregulated. In remote nonischemic brain regions such as the prelimbic and infralimbic cortices, and tenia tecta, both NCX1 and NCX3 transcripts were upregulated, whereas in the medial caudate-putamen only NCX3 transcripts increased. In all these intact regions, NCX2 signal strongly decreased. These results indicate that NCX gene expression is regulated after pMCAO in a differential manner, depending on the exchanger isoform and region involved in the insult. These data may provide a better understanding of each NCX subtypes pathophysiologic role and may allow researchers to design appropriate pharmacological strategies to treat brain ischemia.

Glutamatergic Postsynaptic Density Protein Dysfunctions in Synaptic Plasticity and Dendritic Spines Morphology: Relevance to Schizophrenia and Other Behavioral Disorders Pathophysiology, and Implications for Novel Therapeutic Approaches

Emerging researches point to a relevant role of postsynaptic density (PSD) proteins, such as PSD-95, Homer, Shank, and DISC-1, in the pathophysiology of schizophrenia and autism spectrum disorders. The PSD is a thickness, detectable at electronic microscopy, localized at the postsynaptic membrane of glutamatergic synapses, and made by scaffolding proteins, receptors, and effector proteins; it is considered a structural and functional crossroad where multiple neurotransmitter systems converge, including the dopaminergic, serotonergic, and glutamatergic ones, which are all implicated in the pathophysiology of psychosis. Decreased PSD-95 protein levels have been reported in postmortem brains of schizophrenia patients. Variants of Homer1, a key PSD protein for glutamate signaling, have been associated with schizophrenia symptoms severity and therapeutic response. Mutations in Shank gene have been recognized in autism spectrum disorder patients, as well as reported to be associated to behaviors reminiscent of schizophrenia symptoms when expressed in genetically engineered mice. Here, we provide a critical appraisal of PSD proteins role in the pathophysiology of schizophrenia and autism spectrum disorders. Then, we discuss how antipsychotics may affect PSD proteins in brain regions relevant to psychosis pathophysiology, possibly by controlling synaptic plasticity and dendritic spine rearrangements through the modulation of glutamate-related targets. We finally provide a framework that may explain how PSD proteins might be useful candidates to develop new therapeutic approaches for schizophrenia and related disorders in which there is a need for new biological treatments, especially against some symptom domains, such as negative symptoms, that are poorly affected by current antipsychotics.

Homer 1a Gene Expression Modulation by Antipsychotic Drugs: Involvement of the Glutamate Metabotropic System and Effects of D-Cycloserine

N-methyl-D-aspartate receptor hypofunction has been suggested to play a role in the pathophysiology of schizophrenia. New glutamatergic mechanisms involving metabotropic receptors have been recently proposed to further expand this hypothesis. “Homer” is a family of postsynaptic density proteins functionally and physically attached to glutamate metabotropic receptors. We investigated the activation of the early gene form of Homer after acute treatment with typical or atypical antipsychotic drugs alone or with the adjunction of D-cycloserine. This activation was compared with that of c-fos, considered a putative molecular marker of brain regions activated by antipsychotics. Male Sprague-Dawley rats were treated intraperitoneally with haloperidol (0.8 mg/Kg) or clozapine (15 mg/Kg) alone or with the adjunction of D-cycloserine (20 mg/Kg). Rats were sacrificed ninety minutes after injection and the brains were processed for quantitative in situ hybridization histochemistry. Haloperidol induced a statistically significant increase of Homer both in caudate-putamen and nucleus accumbens compared with controls; clozapine induced Homer significantly only in the accumbens. The adjunction of D-cycloserine attenuated the haloperidol-induced increase of Homer expression in caudate-putamen and nucleus accumbens and attenuated the clozapine-induced increase in the accumbens. The c-fos gene expression was potently induced by haloperidol in caudate-putamen and nucleus accumbens, and by clozapine only in the accumbens. The adjunction of D-cycloserine enhanced c-fos expression only for clozapine in both regions of the forebrain. These results demonstrate a differential involvement of glutamatergic metabotropic system in gene expression modulation induced by typical or atypical antipsychotic drugs and may suggest new molecular basis for the augmentation strategy by a glycine site partial agonist.

Targeting glutamate system for novel antipsychotic approaches: Relevance for residual psychotic symptoms and treatment resistant schizophrenia

Antipsychotics are the mainstay of schizophrenia treatment. However, approximately one third of schizophrenic patients do not respond or respond poorly to antipsychotics. Therefore, there is a need for new approaches that can improve schizophrenia treatment significantly. Promising strategies arise from the modulation of glutamatergic system, according to its proposed involvement in schizophrenia pathogenesis. In this review, we critically updated preclinical and clinical data on the modulation of glutamate N-methyl-D-aspartate (NMDA) receptor activity by NMDA-Rs co-agonists, glycine transporters inhibitors, AMPAkines, mGluR5 agonists, NMDA-Rs partial agonists. We focused on: 1) preclinical results in animal models mimicking the pathophysiology of psychosis, mainly believed to be responsible of negative and cognitive symptoms, and predicting antipsychotic-like activity of these compounds; and 2) clinical efficacy in open-label and double-blind trials. Albeit promising preclinical findings for virtually all compounds, clinical efficacy has not been confirmed for D-cycloserine. Contrasting evidence has been reported for glycine and D-serine, that may however have a role as add-on agents. More promising results in humans have been found for glycine transporter inhibitors. AMPAkines appear to be beneficial as pro-cognitive agents, while positive allosteric modulators of mGluR5 have not been tested in humans. Memantine has been proposed in early stages of schizophrenia, as it may counteract the effects of glutamate excitotoxicity correlated to high glutamate levels, slowing the progression of negative symptoms associated to more advanced stages of the illness.

Acute administration of antipsychotics modulates Homer striatal gene expression differentially

Typical and atypical antipsychotics, the mainstay of schizophrenia pharmacotherapy, have been demonstrated to affect differently neuronal gene expression in several preclinical paradigms. Here we report the differential gene expression of the glutamatergic post-synaptic density proteins Homer and PSD-95 in rat forebrain following acute haloperidol or olanzapine treatment. Moreover, considering the extensive interactions between dopaminergic and opioidergic systems we also measured striatal preproenkephalin mRNA. Male Sprague-Dawley rats were treated with haloperidol 1 mg/kg or olanzapine 0.5 mg/kg or vehicle, i.p. and sacrificed 3 h after the injection. Homer gene expression was significantly increased in caudate putamen and nucleus accumbens of rats treated with haloperidol and in the core of accumbens of rats treated with olanzapine. No changes were detected for Homer in prefrontal and parietal cortex in any of the experimental groups. PSD-95 gene expression was not modulated in our paradigm by administration of either typical or atypical antipsychotics. These results (1) suggest a differential modulation of Homer by typical and atypical antipsychotics; (2) confirm that Homer can be induced as an early gene with putative direct effect on neuronal plasticity and (3) demonstrate different response to antipsychotics by different classes of postsynaptic density proteins at glutamatergic synapses.

Decreased levels of d-aspartate and NMDA in the prefrontal cortex and striatum of patients with schizophrenia

The potential implication of a decrease in the function of N-methyl-d-aspartate receptors (NMDARs) in the pathophysiology of schizophrenia has long been hypothesised. Accordingly, compounds that inhibit the glycine-1 transporter or target the glycine-binding site of NMDARs, including the co-agonists D-serine and glycine, have shown promise in treating the symptoms of schizophrenia. Clinical interest for d-serine has also been supported by evidence for its abnormal metabolism in schizophrenic patients. Together with D-serine, another D-form amino acid, D-aspartate, exists in the brain of mammals. Synthesised by the enzyme aspartate racemase, D-aspartate is highly concentrated in the prenatal brain; after birth, its levels sharply decrease due to the catabolising activity of the enzyme D-aspartate oxidase. D-aspartate is able to stimulate NMDAR-dependent neurotransmission through direct action at the glutamate-binding site of NMDARs, thus functioning as an endogenous agonist for this subclass of glutamate receptors. In this study, we evaluated for the first time the content of D-aspartate and of its derivative, NMDA, in the post-mortem prefrontal cortex and striatum of schizophrenic patients. Moreover, in the same brain samples, we analysed the expression levels of the subunits that form NMDARs, which are the in vivo targets of D-aspartate and NMDA. Interestingly, we found that D-aspartate and NMDA are consistently decreased in schizophrenia brains compared to control brains. In the prefrontal cortex, this decrease is correlated with a marked downregulation of NMDAR subunits. Overall, these results agree with the innovative therapeutic research in schizophrenia that is aimed at targeting glutamatergic transmission via D-amino acids.

Scaffolding Proteins of the Post-synaptic Density Contribute to Synaptic Plasticity by Regulating Receptor Localization and Distribution: Relevance for Neuropsychiatric Diseases

Synaptic plasticity represents the long lasting activity-related strengthening or weakening of synaptic transmission, whose well-characterized types are the long term potentiation and depression. Despite this classical definition, however, the molecular mechanisms by which synaptic plasticity may occur appear to be extremely complex and various. The post-synaptic density (PSD) of glutamatergic synapses is a major site for synaptic plasticity processes and alterations of PSD members have been recently implicated in neuropsychiatric diseases where an impairment of synaptic plasticity has also been reported. Among PSD members, scaffolding proteins have been demonstrated to bridge surface receptors with their intracellular effectors and to regulate receptors distribution and localization both at surface membranes and within the PSD. This review will focus on the molecular physiology and pathophysiology of synaptic plasticity processes, which are tuned by scaffolding PSD proteins and their close related partners, through the modulation of receptor localization and distribution at post-synaptic sites. We suggest that, by regulating both the compartmentalization of receptors along surface membrane and their degradation as well as by modulating receptor trafficking into the PSD, postsynaptic scaffolding proteins may contribute to form distinct signaling micro-domains, whose efficacy in transmitting synaptic signals depends on the dynamic stability of the scaffold, which in turn is provided by relative amounts and post-translational modifications of scaffolding members. The putative relevance for neuropsychiatric diseases and possible pathophysiological mechanisms are discussed in the last part of this work.

Association study between the novel functional polymorphism of the serotonin transporter gene and suicidal behaviour in schizophrenia

A serotonin transporter gene linked polymorphic region (5-HTTLPR) has been investigated in several genetic association studies, including studies of schizophrenia and suicidality. The current study was designed to examine whether the new long (A/G) variant polymorphism of the 5-HTT gene may be associated with suicide attempts of 290 Caucasian schizophrenic patients. Among these patients, 92 had a history of suicide attempt. No association with history of suicide attempt was found in the multiallelic 5-HTTLPR (p = 0.305), however we found significant association with the intron 2 VNTR polymorphism (p = 0.018). When we performed a haplotype analysis, we found association between suicide attempt and haplotype distribution (p = 0.031). These findings suggest that the intron 2 VNTR polymorphism in serotonin transporter gene may influence suicidal behaviour in schizophrenia.