MicroRNAs in Schizophrenia: Implications for Synaptic Plasticity and Dopamine-Glutamate Interaction at the Postsynaptic Density. New Avenues for Antipsychotic Treatment Under a Theranostic Perspective

Dopamine Dynamics and Neurobiology of Non-Response to Antipsychotics, Relevance for Treatment Resistant Schizophrenia: A Systematic Review and Critical Appraisal

Treatment resistant schizophrenia (TRS) is characterized by a lack of, or suboptimal response to, antipsychotic agents. The biological underpinnings of this clinical condition are still scarcely understood. Since all antipsychotics block dopamine D2 receptors (D2R), dopamine-related mechanisms should be considered the main candidates in the neurobiology of antipsychotic non-response, although other neurotransmitter systems play a role. The aims of this review are: (i) to recapitulate and critically appraise the relevant literature on dopamine-related mechanisms of TRS; (ii) to discuss the methodological limitations of the studies so far conducted and delineate a theoretical framework on dopamine mechanisms of TRS; and (iii) to highlight future perspectives of research and unmet needs. Dopamine-related neurobiological mechanisms of TRS may be multiple and putatively subdivided into three biological points: (1) D2R-related, including increased D2R levels; increased density of D2Rs in the high-affinity state; aberrant D2R dimer or heteromer formation; imbalance between D2R short and long variants; extrastriatal D2Rs; (2) presynaptic dopamine, including low or normal dopamine synthesis and/or release compared to responder patients; and (3) exaggerated postsynaptic D2R-mediated neurotransmission. Future points to be addressed are: (i) a more neurobiologically-oriented phenotypic categorization of TRS; (ii) implementation of neurobiological studies by directly comparing treatment resistant vs. treatment responder patients; (iii) development of a reliable animal model of non-response to antipsychotics.

Linking Inflammation, Aberrant Glutamate-Dopamine Interaction, and Post-synaptic Changes: Translational Relevance for Schizophrenia and Antipsychotic Treatment: a Systematic Review

Evidence from clinical, preclinical, and post-mortem studies supports the inflammatory/immune hypothesis of schizophrenia pathogenesis. Less evident is the link between the inflammatory background and two well-recognized functional and structural findings of schizophrenia pathophysiology: the dopamine-glutamate aberrant interaction and the alteration of dendritic spines architecture, both believed to be the “quantal” elements of cortical-subcortical dysfunctional network. In this systematic review, we tried to capture the major findings linking inflammation, aberrant glutamate-dopamine interaction, and post-synaptic changes under a direct and inverse translational perspective, a paramount picture that at present is lacking. The inflammatory effects on dopaminergic function appear to be bidirectional: the inflammation influences dopamine release, and dopamine acts as a regulator of discrete inflammatory processes involved in schizophrenia such as dysregulated interleukin and kynurenine pathways. Furthermore, the link between inflammation and glutamate is strongly supported by clinical studies aimed at exploring overactive microglia in schizophrenia patients and maternal immune activation models, indicating impaired glutamate regulation and reduced N-methyl-D-aspartate receptor (NMDAR) function. In addition, an inflammatory/immune-induced alteration of post-synaptic density scaffold proteins, crucial for downstream NMDAR signaling and synaptic efficacy, has been demonstrated. According to these findings, a significant increase in plasma inflammatory markers has been found in schizophrenia patients compared to healthy controls, associated with reduced cortical integrity and functional connectivity, relevant to the cognitive deficit of schizophrenia. Finally, the link between altered inflammatory/immune responses raises relevant questions regarding potential new therapeutic strategies specifically for those forms of schizophrenia that are resistant to canonical antipsychotics or unresponsive to clozapine.

The Relationship between 10 Years Risk of Cardiovascular Disease and Schizophrenia Symptoms: Preliminary Results

OBJECTIVE

Previous research shows that patients with schizophrenia have increased cardiovascular disease risk than general population. Increased cardiovascular risk in schizophrenia patients have been associated with many reasons such as antipsychotic drugs, genetic predisposition, andlifestyle. In this study, we aimed to investigate the relationship between the risk of heart disease and schizophrenia symptomatology.

METHODS

The 10-year cardiovascular risk was assessed by the Framingham Risk Score (FRS) in 103 patients with schizophrenia and in 39 healthy controls. Sociodemographic characteristics, age at schizophrenia onset, duration of illness, number of hospitalizations, the course of the disease and antipsychotic medications were recorded. Patients' symptoms were evaluated via The Scale for the Assessment of Negative Symptoms (SANS), The Scale for the Assessment of Positive Symptoms (SAPS), and Calgary Depression Scale for Schizophrenia (CDSS).

RESULTS

Ten-year cardiovascular risk was 5.16% inpatients with schizophrenia, and 3.02% in control group (p=0.030). No significant correlation was found between FRS scores, SANS, SAPS, and CDSS scores. However, FRS scores were significantly correlated with age, number of hospitalizations and duration of disease (r=0.300, 0.261, 0.252, respectively). Moreover FRS scores were higher (p=0.008) and high-density lipoprotein (HDL) levels were lower (p=0.048) in patients using multiple antipsychotics.

CONCLUSION

Our findings suggest a relationship between the risk of cardiovascular disease and the duration and overall severity of schizophrenia and also highlights the role of antipsychotics in this relationship.

Modification of the association between antipsychotic treatment response and childhood adversity by MMP9 gene variants in a first-episode schizophrenia cohort

Antipsychotics remain the most effective, and wide used option for ameliorating the symptoms of schizophrenia. However, inter-individual differences in treatment outcome are vast and suggest a role for genetic and environmental factors in affording favourable outcomes. A notable epigenetic relationship which has gained considerable traction in recent literature is the way in which the severity of childhood trauma can modify associations seen between genetic variation and antipsychotic treatment response. A potential mechanism of action which may facilitate this relationship is synaptic plasticity. This study investigated the role of variants in matrix metallopeptidase 9 (MMP9), a gene involved in synaptic plasticity, with treatment outcome considering the severity of childhood trauma as an interacting variable. The cohort comprised South African first episode schizophrenia patients treated with a single injectable antipsychotic, flupenthixol decanoate, monitored over 12 months. Relationships between novel and previously described variants, and haplotypes, with antipsychotic treatment response were found to be modified when considering childhood trauma as an interacting variable. This study provides the first evidence for the involvement of polymorphisms within MMP9 and the severity of childhood trauma in antipsychotic treatment response, and warrants further investigation into the role gene-environment interactions may play in the betterment of antipsychotic treatment strategies.

Nicotine and caffeine modulate haloperidol-induced changes in postsynaptic density transcripts expression: Translational insights in psychosis therapy and treatment resistance

Caffeine and nicotine are widely used by schizophrenia patients and may worsen psychosis and affect antipsychotic therapies. However, they have also been accounted as augmentation strategies in treatment-resistant schizophrenia. Despite both substances are known to modulate dopamine and glutamate transmission, little is known about the molecular changes induced by these compounds in association to antipsychotics, mostly at the level of the postsynaptic density (PSD), a site of dopamine-glutamate interplay. Here we investigated whether caffeine and nicotine, alone or combined with haloperidol, elicited significant changes in the levels of both transcripts and proteins of the PSD members Homer1 and Arc, which have been implicated in synaptic plasticity, schizophrenia pathophysiology, and antipsychotics molecular action. Homer1a mRNA expression was significantly reduced by caffeine and nicotine, alone or combined with haloperidol, compared to haloperidol. Haloperidol induced significantly higher Arc mRNA levels than both caffeine and caffeine plus haloperidol in the striatum. Arc mRNA expression was significantly higher by nicotine plus haloperidol vs. haloperidol in the cortex, while in striatum gene expression by nicotine was significantly lower than that by both haloperidol and nicotine plus haloperidol. Both Homer1a and Arc protein levels were significantly increased by caffeine, nicotine, and nicotine plus haloperidol. Homer1b mRNA expression was significantly increased by nicotine and nicotine plus haloperidol, while protein levels were unaffected. Locomotor activity was not significantly affected by caffeine, while it was reduced by nicotine. These data indicate that both caffeine and nicotine trigger relevant molecular changes in PSD sites when given in association with haloperidol.

Dysregulation of miRNA and its potential therapeutic application in schizophrenia

Although it is generally believed that genetic and developmental factors play critical roles in pathogenesis of schizophrenia, however, the precise etiological mechanism of schizophrenia remains largely unknown. Over past decades, miRNAs have emerged as an essential post-transcriptional regulator in gene expression regulation. The importance of miRNA in brain development and neuroplasticity has been well-established. Abnormal expression and dysfunction of miRNAs are known to involve in the pathophysiology of many neuropsychiatric diseases including schizophrenia. In this review, we summarized the recent findings in the schizophrenia-associated dysregulation of miRNA and functional roles in the development and pathogenesis of schizophrenia. We also discussed the potential therapeutic implications of miRNA regulation in the illness.

Common developmental genome deprogramming in schizophrenia - Role of Integrative Nuclear FGFR1 Signaling (INFS)

The watershed-hypothesis of schizophrenia asserts that over 200 different mutations dysregulate distinct pathways that converge on an unspecified common mechanism(s) that controls disease ontogeny. Consistent with this hypothesis, our RNA-sequencing of neuron committed cells (NCCs) differentiated from established iPSCs of 4 schizophrenia patients and 4 control subjects uncovered a dysregulated transcriptome of 1349 mRNAs common to all patients. Data reveals a global dysregulation of developmental genome, deconstruction of coordinated mRNA networks, and the formation of aberrant, new coordinated mRNA networks indicating a concerted action of the responsible factor(s). Sequencing of miRNA transcriptomes demonstrated an overexpression of 16 miRNAs and deconstruction of interactive miRNA-mRNA networks in schizophrenia NCCs. ChiPseq revealed that the nuclear (n) form of FGFR1, a pan-ontogenic regulator, is overexpressed in schizophrenia NCCs and overtargets dysregulated mRNA and miRNA genes. The nFGFR1 targeted 54% of all human gene promoters and 84.4% of schizophrenia dysregulated genes. The upregulated genes reside within major developmental pathways that control neurogenesis and neuron formation, whereas downregulated genes are involved in oligodendrogenesis. Our results indicate (i) an early (preneuronal) genomic etiology of schizophrenia, (ii) dysregulated genes and new coordinated gene networks are common to unrelated cases of schizophrenia, (iii) gene dysregulations are accompanied by increased nFGFR1-genome interactions, and (iv) modeling of increased nFGFR1 by an overexpression of a nFGFR1 lead to up or downregulation of selected genes as observed in schizophrenia NCCs. Together our results designate nFGFR1 signaling as a potential common dysregulated mechanism in investigated patients and potential therapeutic target in schizophrenia.

Treating the Synapse in Major Psychiatric Disorders: The Role of Postsynaptic Density Network in Dopamine-Glutamate Interplay and Psychopharmacologic Drugs Molecular Actions

Dopamine-glutamate interplay dysfunctions have been suggested as pathophysiological key determinants of major psychotic disorders, above all schizophrenia and mood disorders. For the most part, synaptic interactions between dopamine and glutamate signaling pathways take part in the postsynaptic density, a specialized ultrastructure localized under the membrane of glutamatergic excitatory synapses. Multiple proteins, with the role of adaptors, regulators, effectors, and scaffolds compose the postsynaptic density network. They form structural and functional crossroads where multiple signals, starting at membrane receptors, are received, elaborated, integrated, and routed to appropriate nuclear targets. Moreover, transductional pathways belonging to different receptors may be functionally interconnected through postsynaptic density molecules. Several studies have demonstrated that psychopharmacologic drugs may differentially affect the expression and function of postsynaptic genes and proteins, depending upon the peculiar receptor profile of each compound. Thus, through postsynaptic network modulation, these drugs may induce dopamine-glutamate synaptic remodeling, which is at the basis of their long-term physiologic effects. In this review, we will discuss the role of postsynaptic proteins in dopamine-glutamate signals integration, as well as the peculiar impact of different psychotropic drugs used in clinical practice on postsynaptic remodeling, thereby trying to point out the possible future molecular targets of "synapse-based" psychiatric therapeutic strategies.

A preliminary analysis of microRNA-21 expression alteration after antipsychotic treatment in patients with schizophrenia

Schizophrenia is a severe and debilitating psychiatric disorder of unknown etiology, and its diagnosis is essentially based on clinical symptoms. Despite growing evidence on the relation of altered expression of miRNAs and schizophrenia, most patients with schizophrenia usually had an extensive antipsychotic treatment history before miRNA expression profile analysis, and the pharmacological effects on miRNA expression are largely unknown. To overcome these impediments, miRNA microarray analysis was performed in peripheral blood mononuclear cells (PBMCs) obtained from patients with schizophrenia who were not on antipsychotic medication and healthy controls. Then, using quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR), we verified the top 10 miRNAs with the highest fold-change values from microarray analysis in 82 patients with schizophrenia and 43 healthy controls, and nine miRNAs demonstrated significant differences in expression levels. Finally, we compared these nine miRNA profiles before and after antipsychotic treatment. Our results revealed that serum miR-21 expression decreased strikingly in patients after antipsychotic treatment. The change of miR-21 expression was negatively correlated with improvement of positive, general psychopathology, and aggressiveness symptoms. This study preliminarily analyzed the possible changes in circulating miRNAs expression in response to antipsychotic medication for schizophrenia, and the molecular mechanisms of this needs to be further explored.

Disruptions of sensorimotor gating, cytokines, glycemia, monoamines, and genes in both sexes of rats reared in social isolation can be ameliorated by oral chronic quetiapine administration

The pathogenesis of schizophrenia in patients with metabolic abnormalities remains unclear. Our previous study demonstrated that isolation rearing (IR) induced longitudinal concomitant changes of pro-inflammatory cytokine (pro-CK) levels and metabolic abnormalities with a developmental origin. However, the general consensus, believes that these abnormalities are caused by antipsychotic treatment in schizophrenic patients. The IR paradigm presents with face, construct, and predictive validity for schizophrenia. Therefore, we employed IR rats of both sexes to examine whether chronic quetiapine (QTP, a second-generation antipsychotic medication) treatment induces disruptions of metabolism (body weight, blood pressure, and the glycemic and lipid profiles) or cytokines [interleukin (IL)-1 beta, IL-6, IL-10, interferon-gamma, and tumor necrosis factor (TNF)-alpha], and further, whether it reverses deficits of behaviors [locomotor activity and prepulse inhibition (PPI)] and the expression of monoamines (dopamine and serotonin) and related genes (Htr1a, Htr2a, Htr3a, Drd1a, and Gabbr2). IR induced higher levels of pro-CK, dysglycemia, blood pressure, locomotor activity, and impaired PPI, simultaneously destabilizing cortico-striatal monoamines and relevant genes in both sexes, while QTP demonstrated dose-dependent reversal of these changes, suggesting that QTP might reduce the pro-CKs to regulate these abnormalities. Our data implied that antipsychotics may not be the solitary factor causing metabolic problems in schizophrenia and suggested that inflammatory changes may play a vital role in the developmental pathophysiology of schizophrenia and related metabolic abnormalities.

Genetic and morphological features of human iPSC-derived neurons with chromosome 15q11.2 (BP1-BP2) deletions

BACKGROUND

Copy number variation on chromosome 15q11.2 (BP1-BP2) causes deletion of CYFIP1, NIPA1, NIPA2 and TUBGCP5; it also affects brain structure and elevates risk for several neurodevelopmental disorders that are associated with dendritic spine abnormalities. In rodents, altered cyfip1 expression changes dendritic spine morphology, motivating analyses of human neuronal cells derived from iPSCs (iPSC-neurons).

METHODS

iPSCs were generated from a mother and her offspring, both carrying the 15q11.2 (BP1-BP2) deletion, and a non-deletion control. Gene expression in the deletion region was estimated using quantitative real-time PCR assays. Neural progenitor cells (NPCs) and iPSC-neurons were characterized using immunocytochemistry.

RESULTS

CYFIP1, NIPA1, NIPA2 and TUBGCP5 gene expression was lower in iPSCs, NPCs and iPSC-neurons from the mother and her offspring in relation to control cells. CYFIP1 and PSD95 protein levels were lower in iPSC-neurons derived from the CNV bearing individuals using Western blot analysis. At 10 weeks post-differentiation, iPSC-neurons appeared to show dendritic spines and qualitative analysis suggested that dendritic morphology was altered in 15q11.2 deletion subjects compared with control cells.

CONCLUSIONS

The 15q11.2 (BP1-BP2) deletion is associated with reduced expression of four genes in iPSC-derived neuronal cells; it may also be associated altered iPSC-neuron dendritic morphology.

Etiology of cardiovascular disease in patients with schizophrenia: current perspectives

Cardiovascular morbidity and mortality are important problems among patients with schizophrenia. A wide spectrum of reasons, ranging from genes to the environment, are held responsible for causing the cardiovascular risk factors that may lead to shortening the life expectancy of patients with schizophrenia. Here, we have summarized the etiologic issues related with the cardiovascular risk factors in schizophrenia. First, we focused on heritable factors associated with cardiovascular disease and schizophrenia by mentioning studies about genetics-epigenetics, in the first-episode or drug-naïve patients. In this context, the association and candidate gene studies about metabolic disturbances in schizophrenia are reviewed, and the lack of the effects of epigenetic/posttranscriptional factors such as microRNAs is mentioned. Increased rates of type 2 diabetes mellitus and disrupted metabolic parameters in schizophrenia are forcing clinicians to struggle with metabolic syndrome parameters and related issues, which are also the underlying causes for the risk of having cardiometabolic and cardiovascular etiology. Second, we summarized the findings of metabolic syndrome-related entities and discussed the influence of the illness itself, antipsychotic drug treatment, and the possible disadvantageous lifestyle on the occurrence of metabolic syndrome (MetS) or diabetes mellitus. Third, we emphasized on the risk factors of sudden cardiac death in patients with schizophrenia. We reviewed the findings on the arrhythmias such as QT prolongation, which is a risk factor for Torsade de Pointes and sudden cardiac death or P-wave prolongation that is a risk factor for atrial fibrillation. For example, the use of antipsychotics is an important reason for the prolongation of QT and some other cardiac autonomic dysfunctions. Additionally, we discussed relatively rare issues such as myocarditis and cardiomyopathy, which are important for prognosis in schizophrenia that may have originated from the use of antipsychotic medication. In conclusion, we considered that the studies and awareness about physical needs of patients with schizophrenia are increasing. It seems logical to increase cooperation and shared care between the different health care professionals to screen and treat cardiovascular disease (CVD)-risk factors, MetS, and diabetes in patients with psychiatric disorders, because some risk factors of MetS or CVD are avoidable or at least modifiable to decrease high mortality in schizophrenia. We suggested that future research should focus on conducting an integrated system of studies based on a holistic biopsychosocial evaluation.