Hypofunctional Dopamine Uptake and Antipsychotic Treatment-Resistant Schizophrenia

Transporters involved in adult rat cortical astrocyte dopamine uptake: Kinetics, expression and pharmacological modulation

Astrocytes, glial cells in the central nervous system, perform a multitude of homeostatic functions and are in constant bidirectional communication with neuronal cells, a concept named the tripartite synapse; however, their role in the dopamine homeostasis remains unexplored. The aim of this study was to clarify the pharmacological and molecular characteristics of dopamine transport in cultured cortical astrocytes of adult rats. In addition, we were interested in the expression of mRNA of dopamine transporters as well as dopamine receptors D1 and D2 and in the effect of dopaminergic drugs on the expression of these transporters and receptors. We have found that astrocytes possess both Na+-dependent and Na+-independent transporters. Uptake of radiolabelled dopamine was time-, temperature- and concentration-dependent and was inhibited by decynium-22, a plasma membrane monoamine transporter inhibitor, tricyclic antidepressants desipramine and nortriptyline, both inhibitors of the norepinephrine transporter. Results of transporter mRNA expression indicate that the main transporters involved in cortical astrocyte dopamine uptake are the norepinephrine transporter and plasma membrane monoamine transporter. Both dopamine receptor subtypes were identified in cortical astrocyte cultures. Twenty-four-hour treatment of astrocyte cultures with apomorphine, a D1/D2 agonist, induced upregulation of D1 receptor, norepinephrine transporter and plasma membrane monoamine transporter, whereas the latter was downregulated by haloperidol and L-DOPA. Astrocytes take up dopamine by multiple transporters and express dopamine receptors, which are sensitive to dopaminergic drugs. The findings of this study could open a promising area of research for the fine-tuning of existing therapeutic strategies.

Effects of chronic haloperidol treatment on the expression of fear memory and fear memory extinction in the cued fear-conditioned rats

AIM

Impairments in emotional memory are frequently observed in several mental disorders, highlighting their significance as potential therapeutic targets. Recent research on the cued fear conditioning model has elucidated the neural circuits involved in fear memory processing. However, contradictory findings have been reported concerning the role of dopamine and the impact of dopamine D2 receptor (D2R) antagonists. There is notably limited knowledge regarding the clinical utility of chronic D2R antagonist treatments. This study aimed to uncover how such treatments affect fear memory processing.

METHODS

We utilized a cued fear conditioning rat model and conducted chronic haloperidol treatment for 14 days. Subsequently, to investigate the effect of chronic haloperidol treatment on fear-conditioned memory expression and extinction, we observed freezing behavior under exposure to a conditioned stimulus for 14 days.

RESULTS

Chronic haloperidol treatment suppressed freezing time on the fear memory expression. In contrast, a single haloperidol administration enhanced the freezing time on fear memory expression and delayed extinction.

CONCLUSION

The results of this study suggest that chronic administration of antipsychotic drugs affects fear memory processing differently from single-dose administration. This indicates that the effects of chronic D2R antagonist treatment are distinct from the nonspecific effects of the drugs. This study provides fundamental insights that may contribute to our understanding of therapeutic mechanisms for fear memory disorders related to D2R in the future.

Schizophrenia Synaptic Pathology and Antipsychotic Treatment in the Framework of Oxidative and Mitochondrial Dysfunction: Translational Highlights for the Clinics and Treatment

Schizophrenia is a worldwide mental illness characterized by alterations at dopaminergic and glutamatergic synapses resulting in global dysconnectivity within and between brain networks. Impairments in inflammatory processes, mitochondrial functions, energy expenditure, and oxidative stress have been extensively associated with schizophrenia pathophysiology. Antipsychotics, the mainstay of schizophrenia pharmacological treatment and all sharing the common feature of dopamine D2 receptor occupancy, may affect antioxidant pathways as well as mitochondrial protein levels and gene expression. Here, we systematically reviewed the available evidence on antioxidants' mechanisms in antipsychotic action and the impact of first- and second-generation compounds on mitochondrial functions and oxidative stress. We further focused on clinical trials addressing the efficacy and tolerability of antioxidants as an augmentation strategy of antipsychotic treatment. EMBASE, Scopus, and Medline/PubMed databases were interrogated. The selection process was conducted in respect of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. Several mitochondrial proteins involved in cell viability, energy metabolism, and regulation of oxidative systems were reported to be significantly modified by antipsychotic treatment with differences between first- and second-generation drugs. Finally, antioxidants may affect cognitive and psychotic symptoms in patients with schizophrenia, and although the evidence is only preliminary, the results indicate that further studies are warranted.

Canonical and Non-Canonical Antipsychotics' Dopamine-Related Mechanisms of Present and Next Generation Molecules: A Systematic Review on Translational Highlights for Treatment Response and Treatment-Resistant Schizophrenia

Schizophrenia is a severe psychiatric illness affecting almost 25 million people worldwide and is conceptualized as a disorder of synaptic plasticity and brain connectivity. Antipsychotics are the primary pharmacological treatment after more than sixty years after their introduction in therapy. Two findings hold true for all presently available antipsychotics. First, all antipsychotics occupy the dopamine D2 receptor (D2R) as an antagonist or partial agonist, even if with different affinity; second, D2R occupancy is the necessary and probably the sufficient mechanism for antipsychotic effect despite the complexity of antipsychotics' receptor profile. D2R occupancy is followed by coincident or divergent intracellular mechanisms, implying the contribution of cAMP regulation, β-arrestin recruitment, and phospholipase A activation, to quote some of the mechanisms considered canonical. However, in recent years, novel mechanisms related to dopamine function beyond or together with D2R occupancy have emerged. Among these potentially non-canonical mechanisms, the role of Na²⁺ channels at the dopamine at the presynaptic site, dopamine transporter (DAT) involvement as the main regulator of dopamine concentration at synaptic clefts, and the putative role of antipsychotics as chaperones for intracellular D2R sequestration, should be included. These mechanisms expand the fundamental role of dopamine in schizophrenia therapy and may have relevance to considering putatively new strategies for treatment-resistant schizophrenia (TRS), an extremely severe condition epidemiologically relevant and affecting almost 30% of schizophrenia patients. Here, we performed a critical evaluation of the role of antipsychotics in synaptic plasticity, focusing on their canonical and non-canonical mechanisms of action relevant to the treatment of schizophrenia and their subsequent implication for the pathophysiology and potential therapy of TRS.

Altered nonlinear Granger causality interactions in the large-scale brain networks of patients with schizophrenia

Objective.It has been demonstrated that schizophrenia (SZ) is characterized by functional dysconnectivity involving extensive brain networks. However, the majority of previous studies utilizing resting-state functional magnetic resonance imaging (fMRI) to infer abnormal functional connectivity (FC) in patients with SZ have focused on the linear correlation that one brain region may influence another, ignoring the inherently nonlinear properties of fMRI signals.Approach. In this paper, we present a neural Granger causality (NGC) technique for examining the changes in SZ's nonlinear causal couplings. We develop static and dynamic NGC-based analyses of large-scale brain networks at several network levels, estimating complicated temporal and causal relationships in SZ patients.Main results. We find that the NGC-based FC matrices can detect large and significant differences between the SZ and healthy control groups at both the regional and subnetwork scales. These differences are persistent and significantly overlapped at various network sparsities regardless of whether the brain networks were built using static or dynamic techniques. In addition, compared to controls, patients with SZ exhibited extensive NGC confusion patterns throughout the entire brain.Significance. These findings imply that the NGC-based FCs may be a useful method for quantifying the abnormalities in the causal influences of patients with SZ, hence shedding fresh light on the pathophysiology of this disorder.

Sex Differences in Oxycodone/Naloxone vs. Tapentadol in Chronic Non-Cancer Pain: An Observational Real-World Study

Despite the large body of research on sex differences in pain, there is a lack of translation to real-world pain management. Our aim was to analyse the sex differences in the analgesic response to oxycodone/naloxone (OXN) and tapentadol (TAP), in comparison with other opioids (OPO) commonly prescribed for chronic non-cancer pain (CNCP). An observational and cross-sectional study was conducted on ambulatory CNCP patients (n = 571). Sociodemographic, clinical (pain intensity, relief, and quality of life), safety (adverse events (AEs), adverse drug reactions), hospital frequentations and pharmacological (morphine equivalent daily dose (MEDD)) variables were collected. Multiple linear regressions were carried out to assess the association between sex and outcomes. Sex differences were observed, with lower female tolerability and higher hospital frequentation, especially in the OXN group (OR AEs report = 2.8 [1.8−4.4], p < 0.001). Here, females showed higher hospital use (23% hospital admission, 30% prescription change, p < 0.05), requiring a higher MEDD (127 ± 103 mg/day, p < 0.05), compared to OXN men. Regardless of the opioid group, CNCP women were significantly older than men (three years), with significantly higher benzodiazepine use (OR = 1.6 [1.1−2.3]), more constipation (OR = 1.34 [0.93−1.90]) and headache (OR = 1.45 [0.99−2.13]) AEs, than men who were more likely to refer sexual dysfunction (OR = 2.77 [1.53−5.01]), and loss of libido (OR = 1.93 [1.22−3.04]). Sex-differences were found related to poorer female drug tolerability and higher hospital resources, even worst in OXN female users. Other differences related to older female ages and benzodiazepine prescription, need to be further analysed from a gender perspective.

Twenty-year effects of antipsychotics in schizophrenia and affective psychotic disorders

BACKGROUND

Studies that examine course and outcome in psychosis have reported considerable heterogeneity in terms of recovery, remission, employment, symptom presentation, social outcomes, and antipsychotic medication effects. Even with demonstrated heterogeneity in course and outcome, prophylactic antipsychotic maintenance therapy remains the prominent practice, particularly in participants with schizophrenia. Lack of efficacy in maintenance antipsychotic treatment and concerns over health detriments gives cause to re-examine guidelines.

METHODS

This study was conducted as part of the Chicago follow-up study designed as a naturalistic prospective longitudinal research study to investigate the course, outcome, symptomatology, and effects of antipsychotic medication on recovery and rehospitalization in participants with serious mental illness disorders. A total of 139 participants with 734 observations were included in the analysis. GEE logistic models were applied to adjust for confounding factors measured at index hospitalization and follow-ups.

RESULTS

Our data show that the majority of participants with schizophrenia or affective psychosis experience future episodes of psychosis at some point during the 20-year follow-up. There was a significant diagnostic difference between groups showing an increase in the number of future episodes of psychosis in participants with schizophrenia. Participants with schizophrenia not on antipsychotics after the first 2 years have better outcomes than participants prescribed antipsychotics. The adjusted odds ratio of not on antipsychotic medication was 5.989 (95% CI 3.588-9.993) for recovery and 0.134 (95% CI 0.070-0.259) for rehospitalization. That is, regardless of diagnosis, after the second year, the absence of antipsychotics predicted a higher probability of recovery and lower probability of rehospitalization at subsequent follow-ups after adjusting for confounders.

CONCLUSION

This study reports multiple findings that bring into question the use of continuous antipsychotic medications, regardless of diagnosis. Even when the confound by indication for prescribing antipsychotic medication is controlled for, participants with schizophrenia and affective psychosis do better than their medicated cohorts, strongly confirming the importance of exposing the role of aiDSP and antipsychotic drug resistance.

Clozapine's multiple cellular mechanisms: What do we know after more than fifty years? A systematic review and critical assessment of translational mechanisms relevant for innovative strategies in treatment-resistant schizophrenia

Almost fifty years after its first introduction into clinical care, clozapine remains the only evidence-based pharmacological option for treatment-resistant schizophrenia (TRS), which affects approximately 30% of patients with schizophrenia. Despite the long-time experience with clozapine, the specific mechanism of action (MOA) responsible for its superior efficacy among antipsychotics is still elusive, both at the receptor and intracellular signaling level. This systematic review is aimed at critically assessing the role and specific relevance of clozapine's multimodal actions, dissecting those mechanisms that under a translational perspective could shed light on molecular targets worth to be considered for further innovative antipsychotic development. In vivo and in vitro preclinical findings, supported by innovative techniques and methods, together with pharmacogenomic and in vivo functional studies, point to multiple and possibly overlapping MOAs. To better explore this crucial issue, the specific affinity for 5-HT₂R, D1R, α_2c, and muscarinic receptors, the relatively low occupancy at dopamine D2R, the interaction with receptor dimers, as well as the potential confounder effects resulting in biased ligand action, and lastly, the role of the moiety responsible for lipophilic and alkaline features of clozapine are highlighted. Finally, the role of transcription and protein changes at the synaptic level, and the possibility that clozapine can directly impact synaptic architecture are addressed. Although clozapine's exact MOAs that contribute to its unique efficacy and some of its severe adverse effects have not been fully understood, relevant information can be gleaned from recent mechanistic understandings that may help design much needed additional therapeutic strategies for TRS.

Acid sphingomyelinase/ceramide system in schizophrenia: implications for therapeutic intervention as a potential novel target

Schizophrenia is a severe mental illness, as the efficacies of current antipsychotic medications are far from satisfactory. An improved understanding of the signaling molecules involved in schizophrenia may provide novel therapeutic targets. Acid sphingomyelinase (ASM) catalyzes cellular membrane sphingomyelin into ceramide, which is further metabolized into sphingosine-1-phophate (S1P). ASM, ceramide, and S1P at the cell surface exert critical roles in the regulation of biophysical processes that include proliferation, apoptosis, and inflammation, and are thereby considered important signaling molecules. Although research on the ASM/ceramide system is still in its infancy, structural and metabolic abnormalities have been demonstrated in schizophrenia. ASM/ceramide system dysfunction is linked to the two important models of schizophrenia, the dopamine (DA) hypothesis through affecting presynaptic DA signaling, and the vulnerability-stress-inflammation model that includes the contribution of stress on the basis of genetic predisposition. In this review, we highlight the current knowledge of ASM/ceramide system dysfunction in schizophrenia gained from human and animal studies, and formulate future directions from the biological landscape for the development of new treatments. Collectively, these discoveries suggest that aberrations in the ASM/ceramide system, especially in ASM activity and levels of ceramide and S1P, may alter cerebral microdomain structure and neuronal metabolism, leading to neurotransmitter (e.g., DA) dysfunction and neuroinflammation. As such, the ASM/ceramide system may offer therapeutic targets for novel medical interventions. Normalization of the aberrant ASM/ceramide system or ceramide reduction by using approved functional inhibitors of ASM, such as fluvoxamine and rosuvastatin, may improve clinical outcomes of patients with schizophrenia. These transformative findings of the ASM/ceramide system in schizophrenia, although intriguing and exciting, may pose scientific questions and challenges that will require further studies for their resolution.

Treatment-resistant schizophrenia: Addressing white matter integrity, intracortical glutamate levels, clinical and cognitive profiles between early- and adult-onset patients

BACKGROUND

Treatment-resistance in schizophrenia is 30-40%. Its neurobiology remains unclear; to explore it, we conducted a combined spectrometry/tractography/cognitive battery and psychopathological rating study on patients with treatment-resistant schizophrenia (TRS), dividing the sample into early-onset (N = 21) and adult-onset TRS (N = 20). Previous studies did not differentiate between early- (onset 13-18 years) and adult-onset (>18 years at formal diagnosis of schizophrenia) TRS.

METHODS

We evaluated cross-sectionally 41 TRS patients (26 male and 15 female) and 20 matched healthy controls (HCs) with psychopathological and cognitive testing prior to participating in brain imaging scanning using magnetic resonance spectroscopy and diffusion tensor imaging to determine the relationship between their symptoms and their glutamate levels and white matter integrity.

RESULTS

TRS patients scored lower than HCs on all cognitive domains; early-onset patients performed better than adult-onset patients only on the Symbol Coding domain. TRS correlated with symptom severity, especially negative symptoms. Glutamate levels and glutamate/creatine were increased in anterior cingulate cortex. Diffusion tensor imaging showed low fractional anisotropy in TRS patients in specific white matter tracts compared to HCs (bilateral anterior thalamic radiation, cortico-spinal tract, forceps minor, inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, superior longitudinal fasciculus, and right uncinate fasciculus).

CONCLUSIONS

We identified specific magnetic resonance spectroscopy and diffusion tensor imaging alterations in TRS patients. Adult-onset TRS differed little from early-onset TRS on most measures; this points to alterations being present since the outset of schizophrenia and may constitute a biological signature of treatment-resistance.

Reduced erythrocyte membrane polyunsaturated fatty acid levels indicate diminished treatment response in patients with multi- versus first-episode schizophrenia

Antipsychotic effects seem to decrease in relapsed schizophrenia patients and the underlying mechanisms remain to be elucidated. Based on the essential role of polyunsaturated fatty acids in brain function and the treatment of schizophrenia, we hypothesize that disordered fatty acid metabolism may contribute to treatment resistance in multi-episode patients. We analyzed the erythrocyte membrane fatty acids in 327 schizophrenia patients under various episodes (numbers of patients: first-episode drug naïve 89; 2–3 episodes 110; 4–6 episodes 80; over 6 episodes 48) and 159 age- and gender-matched healthy controls. Membrane fatty acid levels and PANSS scales were assessed at baseline of antipsychotic-free period and one-month of follow-up after treatment. Totally, both saturated and unsaturated fatty acids were reduced at baseline when compared to healthy controls. Subgroup analyses among different episodes indicated that in response to atypical antipsychotic treatment, the membrane fatty acids were only increased in patients within 3 episodes, and this therapeutic effects on omega-3 index were merely present in the first episode. Results of fatty acid ratios suggested that dysregulations of enzymes such as D6 desaturase, D5 desaturase, and elongases for polyunsaturated fatty acids in patients with multi-episode schizophrenia could account for the differences. Additionally, certain fatty acid level/ratio changes were positively correlated with symptom improvement. The alterations of C22:5n3 and omega-3 index, gender, and the number of episodes were significant risk factors correlated with treatment responsiveness. Using targeted metabolomic approach, we revealed the potential mechanisms underlying abnormal fatty acid metabolism responsible for reduced treatment response in patients with multi-episode schizophrenia.

Development of novel antipsychotic agents by inhibiting dopamine transporter – in silico approach

Various in silico methods were employed for the development of antipsychotic agents by dopamine transporter inhibition.

Potential Mechanisms for Why Not All Antipsychotics Are Able to Occupy Dopamine D3 Receptors in the Brain in vivo

Dysfunctions of the dopaminergic system are believed to play a major role in the core symptoms of schizophrenia such as positive, negative, and cognitive symptoms. The first line of treatment of schizophrenia are antipsychotics, a class of medications that targets several neurotransmitter receptors in the brain, including dopaminergic, serotonergic, adrenergic and/or muscarinic receptors, depending on the given agent. Although the currently used antipsychotics display in vitro activity at several receptors, majority of them share the common property of having high/moderate in vitro affinity for dopamine D₂ receptors (D₂Rs) and D₃ receptors (D₃Rs). In terms of mode of action, these antipsychotics are either antagonist or partial agonist at the above-mentioned receptors. Although D₂Rs and D₃Rs possess high degree of homology in their molecular structure, have common signaling pathways and similar in vitro pharmacology, they have different in vivo pharmacology and therefore behavioral roles. The aim of this review, with summarizing preclinical and clinical evidence is to demonstrate that while currently used antipsychotics display substantial in vitro affinity for both D₃Rs and D₂Rs, only very few can significantly occupy D₃Rs in vivo. The relative importance of the level of endogenous extracellular dopamine in the brain and the degree of in vitro D₃Rs receptor affinity and selectivity as determinant factors for in vivo D₃Rs occupancy by antipsychotics, are also discussed.

Accumbens D2-MSN hyperactivity drives antipsychotic-induced behavioral supersensitivity

Antipsychotic-induced dopamine supersensitivity, or behavioral supersensitivity, is a problematic consequence of long-term antipsychotic treatment characterized by the emergence of motor abnormalities, refractory symptoms, and rebound psychosis. The underlying mechanisms are unclear and no approaches exist to prevent or reverse these unwanted effects of antipsychotic treatment. Here we demonstrate that behavioral supersensitivity stems from long-lasting pre, post and perisynaptic plasticity, including insertion of Ca2+-permeable AMPA receptors and loss of D2 receptor-dependent inhibitory postsynaptic currents (IPSCs) in D2 receptor-expressing medium spiny neurons (D2-MSNs) in the nucleus accumbens core (NAcore). The resulting hyperexcitability, prominent in a subpopulation of D2-MSNs (21%), caused locomotor sensitization to cocaine and was associated with behavioral endophenotypes of antipsychotic treatment resistance and substance use disorder, including disrupted extinction learning and augmented cue-induced cocaine-seeking behavior. Chemogenetic restoration of IPSCs in D2-MSNs in the NAcore was sufficient to prevent antipsychotic-induced supersensitivity, pointing to an entirely novel therapeutic direction for overcoming this condition.

GPCR Pharmacological Profiling of Aaptamine from the Philippine Sponge Stylissa sp. Extends Its Therapeutic Potential for Noncommunicable Diseases

We report the first isolation of the alkaloid aaptamine from the Philippine marine sponge Stylissa sp. Aaptamine possessed weak antiproliferative activity against HCT116 colon cancer cells and inhibited the proteasome in vitro at 50 µM. These activities may be functionally linked. Due to its known, more potent activity on certain G-protein coupled receptors (GPCRs), including α-adrenergic and δ-opioid receptors, the compound was profiled more broadly at sub-growth inhibitory concentrations against a panel of 168 GPCRs to potentially reveal additional targets and therapeutic opportunities. GPCRs represent the largest class of drug targets. The primary screen at 20 µM using the β-arrestin functional assay identified the antagonist, agonist, and potentiators of agonist activity of aaptamine. Dose-response analysis validated the α-adrenoreceptor antagonist activity of aaptamine (ADRA2C, IC₅₀ 11.9 µM) and revealed the even more potent antagonism of the β-adrenoreceptor (ADRB2, IC₅₀ 0.20 µM) and dopamine receptor D4 (DRD4, IC₅₀ 6.9 µM). Additionally, aaptamine showed agonist activity on selected chemokine receptors, by itself (CXCR7, EC₅₀ 6.2 µM; CCR1, EC₅₀ 11.8 µM) or as a potentiator of agonist activity (CXCR3, EC₅₀ 31.8 µM; CCR3, EC₅₀ 16.2 µM). These GPCRs play a critical role in the treatment of cardiovascular disease, diabetes, cancer, and neurological disorders. The results of this study may thus provide novel preventive and therapeutic strategies for noncommunicable diseases (NCDs).

Schizophrenia: Antipsychotics and drug development

The introduction of chlorpromazine and the work that ensued provided the foundation to reposition schizophrenia as a biological illness. The present paper follows the evolution of antipsychotics and their shift from 'typical' to 'atypical'. Atypicality is reviewed in reference to its original definition, clozapine's role, and developments that now leave the concept's utility in question. In a similar fashion, drug development is reviewed in the context of the illness' multiple symptom domains, as well as differences captured by clinical staging and phenotyping. Collectively, the evidence argues for a more nuanced approach to drug development that aligns with the illness' heterogeneity and complexity. Just as 'atypical' as a descriptor for antipsychotics may be outdated, it may be time to set aside the notion of developing drugs that treat 'schizophrenia'.

ErbB4 regulate extracellular dopamine through the p38 MAPK signaling pathway

ErbB4 loss-of-function in catecholaminergic neurons induces catecholamine dyshomeostasis. Despite ErbB4's significant role in neuropathology, the signaling pathways that regulate these changes are still widely unknown. In this study, we attempt to identify the downstream pathway of ErbB4 that regulates catecholamine homeostasis. The SH-SY5Y human neuroblastoma cell line was used as the in vitro model for catecholaminergic neurons. Western blotting, enzyme-linked immunosorbent assay, and pharmacological and genetic manipulations by agonist/antagonist or small interference RNA were used to investigate the relationship between ErbB4 and extracellular catecholamines. We confirmed that ErbB4 is abundantly expressed in undifferentiated and retinoic acid-differentiated catecholaminergic cells from the SH-SY5Y cell line. ErbB4 inhibition increase the ratio of phosphorylated p38 to total p38 in SH-SY5Y human neuroblastoma cells. Consistent with previous in vivo observations in mice, ErbB4 deficiency led to increases in extracellular dopamine and norepinephrine levels. However, the resulting increase in extracellular dopamine, but not norepinephrine, could be suppressed by p38 inhibitor SB202190. Our results suggest that both extracellular dopamine and norepinephrine homeostasis could be regulated by ErbB4 in human catecholaminergic cells, and ErbB4 may regulate extracellular dopamine, but not norepinephrine, through the p38 MAPK signaling pathway, thus indicating different regulatory pathways of dopamine and norepinephrine by ErbB4 in catecholaminergic neurons.

Glutathione Levels and Glutathione-Glutamate Correlation in Patients With Treatment-Resistant Schizophrenia

Treatment-resistant schizophrenia (TRS) has been suggested to involve glutamatergic dysfunction. Glutathione (GSH), a dominant antioxidant, is known to be involved in glutamatergic neurotransmission. To date, no study has examined GSH levels in patients with TRS. The aim of this study was to examine GSH levels in the dorsal anterior cingulate cortex (dACC) of patients with TRS. Patients with schizophrenia were categorized into 3 groups with respect to their antipsychotic response: (1) clozapine (CLZ) nonresponders, (2) CLZ responders, and (3) first-line responders (FLR). GSH and glutamine + glutamate (Glx) levels were measured using 3T proton magnetic resonance spectroscopy. Firstly, dACC GSH levels were compared among the patient groups and healthy controls (HCs). Further, relationships between GSH and Glx levels were compared between the groups and GSH levels were explored stratifying the patient groups based on the glutamate-cysteine ligase catalytic (GCLC) subunit polymorphism. There was no difference in GSH levels between the groups. FLR showed a more negative relationship between GSH and Glx levels in the dACC compared to HCs. There were no effects of GCLC genotype on the GSH levels. However, CLZ responders had a higher ratio of high-risk GCLC genotype compared to CLZ nonresponders. This study demonstrated different relationships between GSH and Glx in the dACC between groups. In addition, the results suggest a potential link between CLZ response and GCLC genotype. However, it still remains unclear how these differences are related to the underlying pathophysiology of schizophrenia subtypes or the mechanisms of action of CLZ.

Modulation of glutamatergic functional connectivity by a prototypical antipsychotic: Translational inference from a postsynaptic density immediate-early gene-based network analysis

BACKGROUND

Although extensively studied, the effect of antipsychotics is not completely understood at a network level. We tested the hypothesis that acute administration of haloperidol would modulate functional connectivity of brain regions relevant to schizophrenia pathophysiology. To assess putative changes in brain network properties and regional interactivity, we studied the expression of Homer1a, an Immediate Early Gene (IEG) demonstrated to be induced by antipsychotic administration and coding for a protein involved in glutamatergic synapses remodeling.

METHODS

Sprague-Dawley rats (n = 26) assigned to vehicle (VEH; NaCl 0.9%) or haloperidol (HAL; 0.8 mg/kg) were included in the network analysis. Homer1a mRNA induction was evaluated by in situ hybridization. Signal intensity analysis was performed in 33 Regions of Interest (ROIs) in the cortex, the caudate putamen, and the nucleus accumbens. A signal correlation analysis was performed, computing all possible pairwise Pearson correlations among ROIs in the two groups. Two networks were generated for HAL and VEH groups, and their properties and topography were explored.

RESULTS

VEH and HAL networks showed qualitative differences in global efficiency and clustering coefficient. The HAL network showed enhanced interactivity between cortical and striatal regions, and within caudate putamen subdivisions. On the other hand, it exhibited reduced inter-correlations between cingulate cortex and anterior insula and caudate putamen and nucleus accumbens. Moreover, haloperidol was able to modulate centrality of crucial functional hubs. These preclinical results corroborate and expand the clinical evidence that antipsychotics may modulate specific brain network properties and disease-related circuits' interactivity.

Crosstalk between the transcriptional regulation of dopamine D2 and cannabinoid CB1 receptors in schizophrenia: Analyses in patients and in perinatal Δ9-tetrahydrocannabinol-exposed rats

Perinatal exposure to Δ9-tetrahydrocannabinol (THC) affects brain development and might increase the incidence of psychopathology later in life, which seems to be related to a dysregulation of endocannabinoid and/or dopaminergic systems. We here evaluated the transcriptional regulation of the genes encoding for the cannabinoid CB1 receptor (Cnr1) and the dopamine D2 receptor (Drd2) in perinatal THC-(pTHC) exposed male rats, focusing on the role of DNA methylation analyzed by pyrosequencing. Simultaneously, the molecular and behavioral abnormalities at two different time points (i.e., neonatal age and adulthood) and the potential preventive effect of peripubertal treatment with cannabidiol, a non-euphoric component of Cannabis, were assessed. The DRD2 methylation was also evaluated in a cohort of subjects with schizophrenia. We observed an increase in both Cnr1 and Drd2 mRNA levels selectively in the prefrontal cortex of adult pTHC-exposed rats with a consistent reduction in DNA methylation at the Drd2 regulatory region, paralleled by social withdrawal and cognitive impairment which were reversed by cannabidiol treatment. These adult abnormalities were preceded at neonatal age by delayed appearance of neonatal reflexes, higher Drd2 mRNA and lower 2-arachidonoylglycerol (2-AG) brain levels, which persisted till adulthood. Alterations of the epigenetic mark for DRD2 were also found in subjects with schizophrenia. Overall, reported data add further evidence to the dopamine-cannabinoid interaction in terms of DRD2 and CNR1 dysregulation which could be implicated in the pathogenesis of schizophrenia spectrum disorders, suggesting that cannabidiol treatment may normalize pTHC-induced psychopathology by modulating the altered dopaminergic activity.

Pharmacotherapy of schizophrenia: Mechanisms of antipsychotic accumulation, therapeutic action and failure

Schizophrenia is a multi-dimensional disorder with a complex and mostly unknown etiology, leading to a severe decline in life quality. Antipsychotic drugs (APDs) remain beneficial interventions in the treatment of the disorder, but vary significantly in binding profile, clinical effects and adverse reactions. The present review summarizes the main principles of APD mechanisms of action with a particular focus on recent findings in APD accumulation and its role in the therapeutic efficacy and treatment failure. High and low doses of APDs were shown to be effective in different dimensions of antipsychotic-like behaviour in rodent models. Efficacy of the APDs correlates with high dopamine D2 receptor occupancy, which occurs quickly after drug administration. However, onset and peak of action are delayed up to several days or weeks. APD accumulation via acidic trapping in synaptic vesicles is considered to underlie the time course of APD action. Use-dependent exocytosis, co-release with dopamine and serotonin and inhibition of ion channels impact on the neuronal transmission and determine effects of APDs. Disruption in accumulating properties leads to diminished APD effects. In addition, long-term APD administration at therapeutic doses leads to treatment failure both in animal models and in humans. APD failure was associated with treatment induced neuroadaptations, including a decline in extracellular dopamine levels, dopamine transporter upregulation, and altered neuronal firing. However, enhanced synaptic vesicle release has also been reported. APD loss of efficacy may be reversed through inhibition of the dopamine transporter or switching the administration regimen from continuous to intermittent. Thus, manipulating the accumulation properties of APDs, changes in the administration regimen and doses, or co-administration with dopamine transporter inhibitors may be considered to yield benefits in the development of new effective strategies in the treatment of schizophrenia.

Reduction of dopamine and glycogen synthase kinase-3 signaling in rat striatum after continuous administration of haloperidol

BACKGROUND

Some individuals with schizophrenia present with a dopamine supersensitivity state (DSS) induced by a long-term administration of excessive antipsychotics; this is recognized as dopamine supersensitivity psychosis (DSP). The mechanisms underlying DSP are not established. Here, we investigated dopamine signaling in DSS rats.

METHODS

Haloperidol (HAL; 0.75 mg/kg/day for 14 days) or vehicle was administered to rats via an osmotic mini-pump. We then screened DSS rats from HAL-treated rats by a voluntary locomotion test. The striatal levels of dopamine (DA) and its metabolites 3,4-hydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were determined, as were the levels of protein kinase v-akt murine thymoma viral oncogene homolog (AKT), glycogen synthase kinase-3 (GSK-3), and phosphorylated GSK-3 in the striatal regions.

RESULTS

In the DSS rats, the DA, DOPAC, and HVA levels were significantly decreased. In a western blot analysis, the DSS rats exhibited a significant decrease in GSK-3α/β and an increase in the pGSK-3β/GSK-3β ratio, whereas AKT was not changed.

CONCLUSIONS

Our results indicated that the DSS rats had hypofunction of the basal dopamine release and AKT/GSK-3 signaling even at 7 days after the antipsychotic was discontinued. Protracted reductions in pre- and post-dopamine D2 receptor signaling might cause prolonged DSS.

Molecular imaging of schizophrenia: Neurochemical findings in a heterogeneous and evolving disorder

The past four decades have seen enormous efforts placed on a search for molecular markers of schizophrenia using positron emission tomography (PET) and single photon emission computed tomography (SPECT). In this narrative review, we cast a broad net to define and summarize what researchers have learned about schizophrenia from molecular imaging studies. Some PET studies of brain energy metabolism with the glucose analogue FDGhave have shown a hypofrontality defect in patients with schizophrenia, but more generally indicate a loss of metabolic coherence between different brain regions. An early finding of significantly increased striatal trapping of the dopamine synthesis tracer FDOPA has survived a meta-analysis of many replications, but the increase is not pathognomonic of the disorder, since one half of patients have entirely normal dopamine synthesis capacity. Similarly, competition SPECT studies show greater basal and amphetamine-evoked dopamine occupancy at post-synaptic dopamine D_2/3 receptors in patients with schizophrenia, but the difference is likewise not pathognomonic. We thus propose that molecular imaging studies of brain dopamine indicate neurochemical heterogeneity within the diagnostic entity of schizophrenia. Occupancy studies have established the relevant target engagement by antipsychotic medications at dopamine D_2/3 receptors in living brain. There is evidence for elevated frontal cortical dopamine D₁ receptors, especially in relation to cognitive deficits in schizophrenia. There is a general lack of consistent findings of abnormalities in serotonin markers, but some evidence for decreased levels of nicotinic receptors in patients. There are sparse and somewhat inconsistent findings of reduced binding of muscarinic, glutamate, and opioid receptors ligands, inconsistent findings of microglial activation, and very recently, evidence of globally reduced levels of synaptic proteins in brain of patients. One study reports a decline in histone acetylase binding that is confined to the dorsolateral prefrontal cortex. In most contexts, the phase of the disease and effects of past or present medication can obscure or confound PET and SPECT findings in schizophrenia.

Chemoinformatic studies on some inhibitors of dopamine transporter and the receptor targeting schizophrenia for developing novel antipsychotic agents

Chemoinformatic studies were carried on some inhibitors of dopamine transporter to develop a predictive and robust QSAR model and also to elucidate binding mode and molecular interactions between the ligands (inhibitors) and the receptor targeting schizophrenia as novel Antipsychotic agents. Density Functional Theory (DFT) approach was utilized to optimize the ligands at B3LYP/6-31G∗ at the ground state and Multi-linear regression of the genetic function approximation (MLR-GFA) method was employed in building Penta-parametric linear equation models. The best model with statistically significant parameters has squared correlation coefficient R²= 0.802, adjusted squared correlation coefficient R²_adj = 0.767, Leave one out (LOO) cross-validation coefficient (Q²) = 0.693, lack of fit score (LOF) = 0.406, R²_Test = 0.77, Y-randomization test (cR²p) = 0.714, Chi-squared (χ²) =0.026, bootstrapping (Systematic errors = 0.272) and Variance Inflation Factor (VIF) <2 . The obtained results were compared with standard validation parameters to ascertain the predictivity, reliability, and robustness of the model. Also, the mechanistic interpretation of the descriptors found in the model revealed that two out of five descriptors; MATS7s (32.3%) and RDF95m (30.4%) having pronounced influence on the observed antipsychotic property of the compounds evidenced by their highest percentage contributions. More so, the molecular docking investigation showed that the binding affinity of the selected ligands ranges from -10.05 to -9.0 kcal/mol and with ligand 21 possessed the highest binding affinity (-10.05 kcal/mol). Furthermore, all the selected ligands displayed hydrogen bonds and hydrophobic interactions with the amino acid residues of the target (4M48) which could account for their higher binding energy. Our findings revealed that the developed model passed the general requirements for an acceptable QSAR model and also satisfied the OECD principles for model development. Hence, the developed model would be practically useful as a blueprint in developing novel antipsychotic agents with improved activity for the treatment of schizophrenia mental disorder.

Dopamine Receptor Subtypes, Physiology and Pharmacology: New Ligands and Concepts in Schizophrenia

Dopamine receptors are widely distributed within the brain where they play critical modulator roles on motor functions, motivation and drive, as well as cognition. The identification of five genes coding for different dopamine receptor subtypes, pharmacologically grouped as D1- (D1 and D5) or D2-like (D2S, D2L, D3, and D4) has allowed the demonstration of differential receptor function in specific neurocircuits. Recent observation on dopamine receptor signaling point at dopamine-glutamate-NMDA neurobiology as the most relevant in schizophrenia and for the development of new therapies. Progress in the chemistry of D1- and D2-like receptor ligands (agonists, antagonists, and partial agonists) has provided more selective compounds possibly able to target the dopamine receptors homo and heterodimers and address different schizophrenia symptoms. Moreover, an extensive evaluation of the functional effect of these agents on dopamine receptor coupling and intracellular signaling highlights important differences that could also result in highly differentiated clinical pharmacology. The review summarizes the recent advances in the field, addressing the relevance of emerging new targets in schizophrenia in particular in relation to the dopamine - glutamate NMDA systems interactions.

Serum galectin-3 levels are decreased in schizophrenia

Objective:

To determine whether changes in serum galectin-3 (gal-3) concentrations in schizophrenia patients have etiopathogenetic importance. Since very little research has assessed the connection between galectins and schizophrenia, we wanted to examine alterations in the inflammatory marker gal-3 in schizophrenia and investigate possible correlations between clinical symptomatology and serum concentrations.

Methods:

Forty-eight schizophrenia patients and 44 healthy controls were included in this study. The Scale for the Assessment of Positive Symptoms (SAPS) and the Scale for the Assessment of Negative Symptoms (SANS) were administered to determine symptom severity. Venous blood samples were collected, and serum gal-3 levels were measured.

Results:

Mean serum gal-3 levels were significantly lower in schizophrenia patients, and there were no significant differences in age or sex with the control group. There was also a significant positive correlation between serum gal-3 concentrations and negative schizophrenia symptoms according to the SANS.

Conclusion:

The results indicate that gal-3 is decreased in schizophrenia patients, which could contribute to inflammation in the pathogenesis of schizophrenia.

Kynurenines and the Endocannabinoid System in Schizophrenia: Common Points and Potential Interactions

Schizophrenia, which affects around 1% of the world’s population, has been described as a complex set of symptoms triggered by multiple factors. However, the exact background mechanisms remain to be explored, whereas therapeutic agents with excellent effectivity and safety profiles have yet to be developed. Kynurenines and the endocannabinoid system (ECS) play significant roles in both the development and manifestation of schizophrenia, which have been extensively studied and reviewed previously. Accordingly, kynurenines and the ECS share multiple features and mechanisms in schizophrenia, which have yet to be reviewed. Thus, the present study focuses on the main common points and potential interactions between kynurenines and the ECS in schizophrenia, which include (i) the regulation of glutamatergic/dopaminergic/γ-aminobutyric acidergic neurotransmission, (ii) their presence in astrocytes, and (iii) their role in inflammatory mechanisms. Additionally, promising pharmaceutical approaches involving the kynurenine pathway and the ECS will be reviewed herein.

Delusional parasitosis in dementia with Lewy bodies: a case report

BACKGROUND

Dementia with Lewy bodies (DLB) is characterized by fluctuating cognitive impairments, recurrent visual hallucinations, the motor symptoms of parkinsonism and REM sleep behavior disorder. Various neuropsychiatric symptoms including hallucination and delusions occur frequently; however, delusional parasitosis is rare in DLB. Here, we report a case of DLB patient with delusional parasitosis.

CASE PRESENTATION

The patient was an 89-year-old woman. At the age of 88, she began to complain her oral cenesthopathy, and developed cognitive decline, delusional parasitosis and parkinsonism. As a result of examination, she was diagnosed as DLB and treated with combination of donepezil 5 mg/day and aripiprazole 1.5 mg/day, and her complaint was disappeared.

CONCLUSIONS

Further studies are needed to investigate the association between delusional parasitosis and underlying pathophysiology of DLB, and the utility of antipsychotics for delusional parasitosis in DLB has to be examined through more cases.