Increased plasma agmatine levels in patients with schizophrenia

Pharmacological profile of agmatine: An in-depth overview

Agmatine, a naturally occurring polyamine derived from arginine via arginine decarboxylase, has been shown to play multifaceted roles in the mammalian body, impacting a wide range of physiological and pathological processes. This comprehensive review delineates the significant insights into agmatine's pharmacological profile, emphasizing its structure and metabolism, neurotransmission and regulation, and pharmacokinetics and function. Agmatine's biosynthesis is highly conserved across species, highlighting its fundamental role in cellular functions. In the brain, comparable to established neurotransmitters, agmatine acts as a neuromodulator, influencing the regulation, metabolism, and reabsorption of neurotransmitters that are key to mood disorders, learning, cognition, and the management of anxiety and depression. Beyond its neuromodulatory functions, agmatine exhibits protective effects across various cellular and systemic contexts, including neuroprotection, nephroprotection, cardioprotection, and cytoprotection, suggesting a broad therapeutic potential. The review explores agmatine's interaction with multiple receptor systems, including NMDA, α2-adrenoceptors, and imidazoline receptors, elucidating its role in enhancing cell viability, neuronal protection, and synaptic plasticity. Such interactions underpin agmatine's potential in treating neurological diseases and mood disorders, among other conditions. Furthermore, agmatine's pharmacokinetics, including its absorption, distribution, metabolism, and excretion, are discussed, underlining the complexity of its action and the potential for therapeutic application. The safety and efficacy of agmatine supplementation, demonstrated through various animal and human studies, affirm its potential as a beneficial therapeutic agent. Conclusively, the diverse physiological and therapeutic effects of agmatine, spanning neurotransmission, protection against cellular damage, and modulation of various receptor pathways, position it as a promising candidate for further research and clinical application. This review underscores the imperative for continued exploration into agmatine's mechanisms of action and its potential in pharmacology and medicine, promising advances in the treatment of numerous conditions.

Molecularly Imprinted Polymer Biosensor Based on Nitrogen-Doped Electrochemically Exfoliated Graphene/Ti3 CNTX MXene Nanocomposite for Metabolites Detection

Rapid and accurate quantification of metabolites in different bodily fluids is crucial for a precise health evaluation. However, conventional metabolite sensing methods, confined to centralized laboratory settings, suffer from time-consuming processes, complex procedures, and costly instrumentation. Introducing the MXene/nitrogen-doped electrochemically exfoliated graphene (MXene@N-EEG) nanocomposite as a novel biosensing platform in this work addresses the challenges associated with conventional methods, leveraging the concept of molecularly imprinted polymers (MIP) enables the highly sensitive, specific, and reliable detection of metabolites. To validate our biosensing technology, we utilize agmatine as a significant biologically active metabolite. The MIP biosensor incorporates electrodeposited Prussian blue nanoparticles as a redox probe, facilitating the direct electrical signaling of agmatine binding in the polymeric matrix. The MXene@N-EEG nanocomposite, with excellent metal conductivity and a large electroactive specific surface area, effectively stabilizes the electrodeposited Prussian blue nanoparticles. Furthermore, increasing the content of agmatine-imprinted cavities on the electrode enhances the sensitivity of the MIP biosensor. Evaluation of the designed MIP biosensor in buffer solution and plasma samples reveals a wide linear concentration range of 1.0 nM-100.0 μM (R2 = 0.9934) and a detection limit of 0.1 nM. Notably, the developed microfluidic biosensor offers low cost, rapid response time to the target molecule (10 min of sample incubation), good recovery results for detecting agmatine in plasma samples, and acceptable autonomous performance for on-chip detection. Moreover, its high reliability and sensitivity position this MIP-based biosensor as a promising candidate for miniaturized microfluidic devices with the potential for scalable production for point-of-care applications.

Advances in the Treatment of Autism Spectrum Disorder: Current and Promising Strategies

Autism spectrum disorder (ASD) is an umbrella term for developmental disorders characterized by social and communication impairments, language difficulties, restricted interests, and repetitive behaviors. Current management approaches for ASD aim to resolve its clinical manifestations based on the type and severity of the disability. Although some medications like risperidone show potential in regulating ASD-associated symptoms, a comprehensive treatment strategy for ASD is yet to be discovered. To date, identifying appropriate therapeutic targets and treatment strategies remains challenging due to the complex pathogenesis associated with ASD. Therefore, a comprehensive approach must be tailored to target the numerous pathogenetic pathways of ASD. From currently viable and basic treatment strategies, this review explores the entire field of advancements in ASD management up to cutting-edge modern scientific research. A novel systematic and personalized treatment approach is suggested, combining the available medications and targeting each symptom accordingly. Herein, summarize and categorize the most appropriate ways of modern ASD management into three distinct categories: current, promising, and prospective strategies.

Construction of an Exudative Age-Related Macular Degeneration Diagnostic and Therapeutic Molecular Network Using Multi-Layer Network Analysis, a Fuzzy Logic Model, and Deep Learning Techniques: Are Retinal and Brain Neurodegenerative Disorders Related?

Neovascular age-related macular degeneration (nAMD) is a leading cause of irreversible visual impairment in the elderly. The current management of nAMD is limited and involves regular intravitreal administration of anti-vascular endothelial growth factor (anti-VEGF). However, the effectiveness of these treatments is limited by overlapping and compensatory pathways leading to unresponsiveness to anti-VEGF treatments in a significant portion of nAMD patients. Therefore, a system view of pathways involved in pathophysiology of nAMD will have significant clinical value. The aim of this study was to identify proteins, miRNAs, long non-coding RNAs (lncRNAs), various metabolites, and single-nucleotide polymorphisms (SNPs) with a significant role in the pathogenesis of nAMD. To accomplish this goal, we conducted a multi-layer network analysis, which identified 30 key genes, six miRNAs, and four lncRNAs. We also found three key metabolites that are common with AMD, Alzheimer's disease (AD) and schizophrenia. Moreover, we identified nine key SNPs and their related genes that are common among AMD, AD, schizophrenia, multiple sclerosis (MS), and Parkinson's disease (PD). Thus, our findings suggest that there exists a connection between nAMD and the aforementioned neurodegenerative disorders. In addition, our study also demonstrates the effectiveness of using artificial intelligence, specifically the LSTM network, a fuzzy logic model, and genetic algorithms, to identify important metabolites in complex metabolic pathways to open new avenues for the design and/or repurposing of drugs for nAMD treatment.

Neuroprotection by agmatine: Possible involvement of the gut microbiome?

Agmatine, an endogenous polyamine derived from L-arginine, elicits tremendous multimodal neuromodulant properties. Alterations in agmatinergic signalling are closely linked to the pathogeneses of several brain disorders. Importantly, exogenous agmatine has been shown to act as a potent neuroprotectant in varied pathologies, including brain ageing and associated comorbidities. The antioxidant, anxiolytic, analgesic, antidepressant and memory-enhancing activities of agmatine may derive from its ability to regulate several cellular pathways; including cell metabolism, survival and differentiation, nitric oxide signalling, protein translation, oxidative homeostasis and neurotransmitter signalling. This review briefly discusses mammalian metabolism of agmatine and then proceeds to summarize our current understanding of neuromodulation and neuroprotection mediated by agmatine. Further, the emerging exciting bidirectional links between agmatine and the resident gut microbiome and their implications for brain pathophysiology and ageing are also discussed.

Peripheral S100B Protein Levels in Five Major Psychiatric Disorders: A Systematic Review

Five major psychiatric disorders: schizophrenia, major depressive disorder, bipolar disorder, autistic spectrum disorder, and attention-deficit/hyperactivity disorder, show a shared genetic background and probably share common pathobiological mechanisms. S100B is a calcium-binding protein widely studied in psychiatric disorders as a potential biomarker. Our systematic review aimed to compare studies on peripheral S100B levels in five major psychiatric disorders with shared genetic backgrounds to reveal whether S100B alterations are disease-specific. EMBASE, Web of Science, and PubMed databases were searched for relevant studies published until the end of July 2023. This study was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis Protocols (PRISMA) guidelines. Overall, 1215 publications were identified, of which 111 full-text articles were included in the systematic review. Study designs are very heterogeneous, performed mostly on small groups of participants at different stages of the disease (first-episode or chronic, drug-free or medicated, in the exacerbation of symptoms or in remission), and various clinical variables are analyzed. Published results are inconsistent; most reported elevated S100B levels across disorders included in the review. Alterations in S100B peripheral levels do not seem to be disease-specific.

Vascular-related biomarkers in psychosis: a systematic review and meta-analysis

Background

While the molecular underpinnings of vascular dysfunction in psychosis are under active investigation, their implications remain unclear due to inconsistent and sometimes sparse observations. We conducted a comprehensive meta-analysis to critically assess the alterations of vascular-related molecules in the cerebrospinal fluid (CSF) and blood of patients with psychotic disorders compared with healthy individuals.

Methods

Databases were searched from inception to February 23, 2023. Meta-analyses were performed using a random-effects model. Meta-regression and subgroup analyses were conducted to assess the effects of clinical correlates.

Results

We identified 93 eligible studies with 30 biomarkers investigated in the CSF and/or blood. Among the biomarkers examined, psychotic disorders were associated with elevated CSF-to-serum albumin ratio (standardized mean difference [SMD], 0.69; 95% confidence interval [CI], 0.35-1.02); blood S100B (SMD, 0.88; 95% CI, 0.59-1.17), matrix metalloproteinase-9 (MMP-9; SMD, 0.66; 95% CI, 0.46-0.86), and zonulin (SMD, 1.17; 95% CI, 0.04-2.30). The blood levels of S100B, MMP-9, nerve growth factor (NGF), vascular endothelial growth factor (VEGF), intercellular adhesion molecule 1 (ICAM-1), and vascular adhesion molecule 1 (VCAM-1) were altered in patient subgroups differing in demographic and clinical characteristics. Blood S100B level was positively correlated with age and duration of illness. Substantial between-study heterogeneity was observed in most molecules.

Conclusion

The alterations in certain vascular-related fluid markers in psychotic disorders suggest disturbances in normal vascular structures and functions. However, not all molecules examined displayed clear evidence of changes. While potential impacts of clinical factors, including the administered treatment, were identified, the exploration remained limited. Further studies are needed to investigate the diverse patterns of expression, and understand how these abnormalities reflect the pathophysiology of psychosis and the impact of clinical factors.

Characterization of early psychosis patients carrying a genetic vulnerability to redox dysregulation: a computational analysis of mechanism-based gene expression profile in fibroblasts

In view of its heterogeneity, schizophrenia needs new diagnostic tools based on mechanistic biomarkers that would allow early detection. Complex interaction between genetic and environmental risk factors may lead to NMDAR hypofunction, inflammation and redox dysregulation, all converging on oxidative stress. Using computational analysis, the expression of 76 genes linked to these systems, known to be abnormally regulated in schizophrenia, was studied in skin-fibroblasts from early psychosis patients and age-matched controls (N = 30), under additional pro-oxidant challenge to mimic environmental stress. To evaluate the contribution of a genetic risk related to redox dysregulation, we investigated the GAG trinucleotide polymorphism in the key glutathione (GSH) synthesizing enzyme, glutamate-cysteine-ligase-catalytic-subunit (gclc) gene, known to be associated with the disease. Patients and controls showed different gene expression profiles that were modulated by GAG-gclc genotypes in combination with oxidative challenge. In GAG-gclc low-risk genotype patients, a global gene expression dysregulation was observed, especially in the antioxidant system, potentially induced by other risks. Both controls and patients with GAG-gclc high-risk genotype (gclcGAG-HR) showed similar gene expression profiles. However, under oxidative challenge, a boosting of other antioxidant defense, including the master regulator Nrf2 and TRX systems was observed only in gclcGAG-HR controls, suggesting a protective compensation against the genetic GSH dysregulation. Moreover, RAGE (redox/inflammation interaction) and AGMAT (arginine pathway) were increased in the gclcGAG-HR patients, suggesting some additional risk factors interacting with this genotype. Finally, the use of a machine-learning approach allowed discriminating patients and controls with an accuracy up to 100%, paving the way towards early detection of schizophrenia.

Serum s100b protein levels as a neuroinflammatory biomarker of acutely relapsed paranoid schizophrenia patients

OBJECTIVE

The s100b inflammatory protein is involved in schizophrenia pathophysiology. We aim at studying the evolution of the s100b serum levels in acutely relapsed paranoid schizophrenia patients at three different time points (admission, discharge and 3 months after hospital discharge 3MAHD).

METHODS

Twenty-three paranoid schizophrenia inpatients meeting DSM-IV criteria participated in the research. Twenty-three healthy subjects matched by age, gender and season acted as the control group. Psychopathology was measured with the Positive and Negative Syndrome Scale (PANSS). Serum s100b levels were determined at 12:00 and 24:00 h with an enzyme-linked immunoassay kit.

RESULTS

Patients had significant higher serum s100b levels at admission and discharge (12:00 h) than the group of healthy subjects. At admission and discharge, s100b serum levels at 24 h had decreased compared to the 24:00 h s100b levels of the healthy subjects. At 3MAHD patients and healthy subjects had similar levels of serum s100b protein. Positive and negative PANSS scores decreased significantly between admission and discharge. Positive and negative PANSS scores decreased between discharge and 3MAHD, but these changes had no statistical significance.

CONCLUSIONS

Our study confirms that the acute inflammatory response produced in acutely relapsed patients is reversed after 3 month of hospital discharge. The variations of serum s100b concentrations when the patients suffer from an acute relapse may be a useful predictor of disease evolution.

Systematic Review and Meta-Analysis of Damage Associated Molecular Patterns HMGB1 and S100B in Schizophrenia

OBJECTIVE

Immune system dysregulation is hypothesised to be central to the aetiopathogenesis of schizophrenia; however, the role of sterile inflammation remains unclear. Damage associated molecular patterns are key initiators of sterile inflammation and are detectable in peripheral blood.

METHODS

A defined systematic search of the Web of Science, PubMed, and Scopus was performed to identify adult case-control studies published between January 1990 and June 2022. Three studies consisting of 242 cases and 83 controls met inclusion for the systematic review and meta-analysis of HMGB1 while twenty-eight studies consisting of 1,544 cases and 1,248 healthy controls were included for S100B.

RESULTS

A significant standardised mean difference in peripheral S100B and HMGB1 concentrations was detected between cases and controls. S100B subgroup analysis determined the largest significant effect size for unmedicated individuals diagnosed with schizophrenia.

CONCLUSION

This study provides evidence that peripheral S100B and HMGB1 concentrations are elevated in individuals diagnosed with schizophrenia when compared with healthy controls. These results should be interpreted with caution as significant heterogeneity was present during meta-analysis of S100B in the entire sample and in sub-group analysis. The persistence of significant heterogeneity throughout subgroup analysis indicates that the current diagnostic groupings may be a barrier to understanding human behaviours and emotions.

Polyamines and polyamine-metabolizing enzymes in schizophrenia: Current knowledge and concepts of therapy

Polyamines play preeminent roles in a variety of cellular functions in the central nervous system and other organs. A large body of evidence suggests that the polyamine pathway is prominently involved in the etiology and pathology of schizophrenia. Alterations in the expression and activity of polyamine metabolizing enzymes, as well as changes in the levels of the individual polyamines, their precursors and derivatives, have been measured in schizophrenia and animal models of the disease. Additionally, neuroleptic treatment has been shown to influence polyamine concentrations in brain and blood of individuals with schizophrenia. Thus, the polyamine system may appear to be a promising target for neuropharmacological treatment of schizophrenia. However, for a number of practical reasons there is currently only limited hope for a polyamine-based schizophrenia therapy.

Effects of agmatine, glutamate, arginine, and nitric oxide on executive functions in children with attention deficit hyperactivity disorder

In this study, we aimed to investigate the effects of agmatine, nitric oxide (NO), arginine, and glutamate, which are the metabolites in the polyamine pathway,  on the performance of executive functions (EF) in attention deficit hyperactivity disorder (ADHD). The ADHD group included 35 treatment-naive children (6-14 years old) who were ewly diagnosed with ADHD. The control group consisted of 35 healthy children with the same age and sex, having no previous psychiatric disorders. In the study groups, Stroop test (ST) and trail making test (TMT) were used to monitor EF, and blood samples were collected to measure agmatine with ultra-high-performance liquid chromatography and NO, glutamate, and arginine with enzyme-linked immunosorbent assay (ELISA). The EFs were significantly impaired in the ADHD group. The agmatine and arginine levels of the ADHD group were significantly higher than their peers. The NO and glutamate levels were also higher in the ADHD group compared to the control group, but these differences did not reach statistical significance. Children with ADHD had more difficulties during EF tasks compared to healthy children. The elevated NO and glutamate levels may be related with the impairment during EF tasks. Therefore, agmatine and arginine may increase to improve EF tasks through its inhibitory effect on the synthesis of NO and glutamate. Further studies are needed about polyamine pathway molecules to shed light on the pathophysiology of ADHD.

Clozapine-induced transcriptional changes in the zebrafish brain

Clozapine is an atypical antipsychotic medication that is used to treat schizophrenia patients who are resistant to other antipsychotic drugs. The molecular mechanisms mediating the effects of clozapine are not well understood and its use is often associated with severe side-effects. In this study, we exposed groups of wild-type zebrafish to two doses of clozapine (‘low’ (20 µg/L) and ‘high’ (70 µg/L)) over a 72-h period, observing dose-dependent effects on behaviour. Using RNA sequencing (RNA-seq) we identified multiple genes differentially expressed in the zebrafish brain following exposure to clozapine. Network analysis identified co-expression modules characterised by striking changes in module connectivity in response to clozapine, and these were enriched for regulatory pathways relevant to the etiology of schizophrenia. Our study highlights the utility of zebrafish as a model for assessing the molecular consequences of antipsychotic medications and identifies genomic networks potentially involved in schizophrenia.

Comparative psychopharmacology of autism and psychotic-affective disorders suggests new targets for treatment

The first treatments showing effectiveness for some psychiatric disorders, such as lithium for bipolar disorder and chlorpromazine for schizophrenia, were discovered by accident. Currently, psychiatric drug design is seen as a scientific enterprise, limited though it remains by the complexity of brain development and function. Relatively few novel and effective drugs have, however, been developed for many years. The purpose of this article is to demonstrate how evolutionary biology can provide a useful framework for psychiatric drug development. The framework is based on a diametrical nature of autism, compared with psychotic-affective disorders (mainly schizophrenia, bipolar disorder and depression). This paradigm follows from two inferences: (i) risks and phenotypes of human psychiatric disorders derive from phenotypes that have evolved along the human lineage and (ii) biological variation is bidirectional (e.g. higher vs lower, faster vs slower, etc.), such that dysregulation of psychological traits varies in two opposite ways. In this context, the author review the evidence salient to the hypothesis that autism and psychotic-affective disorders represent diametrical disorders in terms of current, proposed and potential psychopharmacological treatments. Studies of brain-derived neurotrophic factor, the PI3K pathway, the NMDA receptor, kynurenic acid metabolism, agmatine metabolism, levels of the endocannabinoid anandamide, antidepressants, anticonvulsants, antipsychotics, and other treatments, demonstrate evidence of diametric effects in autism spectrum disorders and phenotypes compared with psychotic-affective disorders and phenotypes. These findings yield insights into treatment mechanisms and the development of new pharmacological therapies, as well as providing an explanation for the longstanding puzzle of antagonism between epilepsy and psychosis. Lay Summary: Consideration of autism and schizophrenia as caused by opposite alterations to brain development and function leads to novel suggestions for pharmacological treatments.

α2-Adrenoceptor signaling in cardiomyocytes of spontaneously hypertensive rats starts to impair already at early age

α2-Adrenoceptors (α2-AR) found in the cardiomyocyte's sarcolemma represent a very important negative feedback for control of myocardial contractility by endogenous catecholamines. Earlier, we showed that the endogenous neurotransmitter agmatine in micromolar concentrations via α2-AR activates the nitric oxide (NO) synthesis, enhancing the Ca²⁺ pumping into sarcoplasmic reticulum (SR). In the millimolar doses it inhibits Ca²⁺ sequestration by SR Ca²⁺ ATPase (SERCA), acting through the first type of imidazoline receptors. Here, we study the functional activity of agmatine, as well as a specific α2-agonist, guanabenz, in respect to spontaneous Ca²⁺-transients in SHR cardiomyocytes of the early age (2-2.5 months), and adulthood animals (8-9 months). α2-mediated cardioprotective effect was almost twofold decreased in SHR cardiac cells compared to normotensive rats of the corresponding age, despite the fact that both α2A- and α2B-AR protein levels were significantly increased in SHR cardiomyocytes. NO-mediated facilitation of SERCA activity is substantially reduced in SHR cardiomyocytes vs. normotensive rats. These data suggest that the SHR phenotype starting from early age shows signs of the impaired sarcolemmal α2-AR signaling, which can aggravate the development of this cardiovascular pathology.

l-Arginine metabolism before and after 10 weeks of antipsychotic treatment in first-episode psychotic patients

Agmatine is an endogenous NMDA (N-methyl-d-aspartate) antagonist which is synthesized from l-Arginine and described as a novel neurotransmitter. Agmatine is considered to play an important role for the development of schizophrenia. The aim of the present study is to explore the role of agmatine and l-arginine metabolism in medication-naive first-episode psychosis (FEP). We conducted a case control study in medication-naive patients with FEP (n = 40). The healthy volunteers with no family history of schizophrenia (n = 35) matched for age, gender and education level were selected as a control group. The patients were recruited to the study and followed up for 10 weeks. The plasma l-arginine, l-citrulline, l-ornithine and agmatine levels were measured using modified liquid chromatography/mass spectrometry. The plasma levels of l-arginine, l-citrulline and agmatine (p < 0.0001), but not l-ornithine and agmatinase (p > 0.05), were significantly increased during baseline analysis. After 10 weeks of treatment, plasma l-arginine and l-citrulline levels were still significantly increased (p < 0.05) while l-ornithine and agmatinase levels remained unchanged (p > 0.05). Conversely, plasma agmatine levels were significantly decreased after the treatment (p < 0.0001). Positive and negative predictive values of agmatine used for evaluating the diagnostic accuracy were 95.1% and 97.1%, respectively (p < 000.1). This is the first study of arginine metabolism and agmatine in medication-naive first-episode patients and provides evidence of increased levels of an endogenous NMDA antagonist which decreases following antipsychotic treatment.

Therapeutic Effect of Agmatine on Neurological Disease: Focus on Ion Channels and Receptors

The central nervous system (CNS) is the most injury-prone part of the mammalian body. Any acute or chronic, central or peripheral neurological disorder is related to abnormal biochemical and electrical signals in the brain cells. As a result, ion channels and receptors that are abundant in the nervous system and control the electrical and biochemical environment of the CNS play a vital role in neurological disease. The N-methyl-D-aspartate receptor, 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl) propanoic acid receptor, kainate receptor, acetylcholine receptor, serotonin receptor, α2-adrenoreceptor, and acid-sensing ion channels are among the major channels and receptors known to be key components of pathophysiological events in the CNS. The primary amine agmatine, a neuromodulator synthesized in the brain by decarboxylation of L-arginine, can regulate ion channel cascades and receptors that are related to the major CNS disorders. In our previous studies, we established that agmatine was related to the regulation of cell differentiation, nitric oxide synthesis, and murine brain endothelial cell migration, relief of chronic pain, cerebral edema, and apoptotic cell death in experimental CNS disorders. In this review, we will focus on the pathophysiological aspects of the neurological disorders regulated by these ion channels and receptors, and their interaction with agmatine in CNS injury.

Cardiovascular Effects Mediated by Imidazoline Drugs: An Update

OBJECTIVE

Clonidine is a centrally acting antihypertensive drug. Hypotensive effect of clonidine is mediated mainly by central α2-adrenoceptors and/or imidazoline receptors located in a complex network of the brainstem. Unfortunately, clonidine produces side effects such as sedation, mouth dry, and depression. Moxonidine and rilmenidine, compounds of the second generation of imidazoline drugs, with fewer side effects, display a higher affinity for the imidazoline receptors compared with α2-adrenoceptors. The antihypertensive action of these drugs is due to inhibition of the sympathetic outflow primarily through central I1-imidazoline receptors in the RVLM, although others anatomical sites and mechanisms/receptors are involved. Agmatine is regarded as the endogenous ligand for imidazoline receptors. This amine modulates the cardiovascular function. Indeed, when administered in the RVLM mimics the hypotension of clonidine.

RESULTS

Recent findings have shown that imidazoline drugs also exert biological response directly on the cardiovascular tissues, which can contribute to their antihypertensive response. Currently, new imidazoline receptors ligands are in development.

CONCLUSION

In the present review, we provide a brief update on the cardiovascular effects of clonidine, moxonidine, rilmenidine, and the novel imidazoline agents since representing an important therapeutic target for some cardiovascular diseases.

Variation within voltage-gated calcium channel genes and antipsychotic treatment response in a South African first episode schizophrenia cohort

Voltage-gated calcium channels have been implicated in schizophrenia aetiology; however, little is known about their involvement in antipsychotic treatment response. This study investigated variants within the calcium channel subunit genes for association with antipsychotic treatment response in a first episode schizophrenia cohort. Twelve regulatory variants within seven genes were shown to be significantly associated with treatment outcome. Most notably, the CACNA1B rs2229949 CC genotype was associated with improved negative symptomology, where the C allele was predicted to abolish a miRNA-binding site (has-mir-5002-3p), suggesting a possible mechanism of action through which this variant may have an effect. These results implicate the calcium channel subunits in antipsychotic treatment response and suggest that increased activation of these channels may be explored to enhance or predict antipsychotic treatment outcome.

Agmatine modulates calcium handling in cardiomyocytes of hibernating ground squirrels through calcium-sensing receptor signaling

True hibernators are remarkable group of mammals whose hearts are resistant to such stressors as deep hypothermia, ischemia, arrhythmia. Capability of cardiac cells from hibernating species to effectively rule Ca²⁺ homeostasis during torpor is poorly studied. Better understanding of these mechanisms could allow to introduce new strategies for improvement the cardiac performance and may be useful for cardiovascular medicine. Here for the first time we have shown that the regulation of Ca²⁺ handling and thereby cardiomyocyte contractility by endogenous neurotransmitter agmatine occurs through the modulation of calcium-sensing receptor (CaSR). In isolated cardiocytes of hibernating ground squirrels generating stationary Ca²⁺ transients in the absence of actual myocellular excitation, low doses of this polyamine (up to 500 μM) induce the G_βγ-dependent activation of PI₃-kinase with subsequent stimulation of Akt-kinase and nitric oxide (NO) production by endothelial NO-synthase (eNOS). NO production abolishes Ca²⁺ oscillations in virtue of the enhancement of Ca²⁺ reuptake by sarco(endo)plasmic Ca²⁺ ATPase (SERCA). Simultaneously, the activation of phospholipase A₂ (PLA₂) and arachidonic-acid dependent Ca²⁺ entry occur providing replenishment of Ca²⁺ store. High concentrations of agmatine (> 2 mM) induce other CaSR-mediated pathways involving phospholipase C (PLC) pathway, the formation of inositoltriphosphate (IP₃) and diacylglicerol (DAG) followed by induction of their targets: IP₃ receptors and protein kinase C isoforms (PKC), respectively. Furthermore, it is also responsible for the stimulation of PLA₂ and elevation of intracellular calcium caused by arachidonic acid-regulated Ca²⁺-permeable (ARC) channels. Additionally, there is a potent store-operated Ca²⁺ entry (SOC) in cardiomyocyte. Negative (NPS 2143) and positive (R 568) allosteric modulators of CaSR recapitulate effects of low and high agmatine doses on Ca²⁺ handling and NO synthesis. These facts and the alteration of agmatine influence in response to an increase of extracellular Ca²⁺, which is the direct agonist of CaSR, may confirm the participation of CaSR in regulation of Ca²⁺ handling and excitability of cardiomyocytes by agmatine.

Evidence of Reduced Agmatine Concentrations in the Cerebral Cortex of Suicides

BACKGROUND

The polyamines are a group of ubiquitous low-molecular-weight aliphatic molecules that play an essential role in various physiological functions of the mammalian CNS. Previous literature has indicated alterations in the expression of polyamine-related genes in the brains of individuals who died by suicide, including downregulation of spermidine/spermine N1-acetyltransferase, a key enzyme involved in polyamine catabolism. One such polyamine, agmatine, has been shown to act as an antidepressant in animal models of depressive-like behavior. However, agmatine concentrations have not been explored in postmortem human brain of individuals who died by suicide.

METHODS

To measure agmatine in postmortem human brain tissue, we employed our previously published high-resolution capillary gas chromatography in combination with mass spectrometry method. Using this method, we analyzed agmatine levels in a total of 120 tissue samples from Brodmann areas 4, 11, and 44 of 40 male subjects comprising controls (n=13), individuals who died by suicide and met criteria for major depressive disorder (n=14), and subjects who died by suicide and did not meet criteria for major depressive disorder (n=13).

RESULTS

Agmatine fell within the expected nanomolar range and was significantly reduced in the cortex of suicides, irrespective of meeting criteria for major depressive disorder compared with controls.

CONCLUSIONS

This is the first gas chromatography-mass spectrometry study to analyze agmatine concentrations in human postmortem brain of individuals who died by suicide. These results add to our mechanistic understanding of the role that the polyamine stress response pathway may play in the neurobiology of major depression and/or suicide.

Effects of maternal immune activation on brain arginine metabolism of postnatal day 2 rat offspring

l-Arginine is a versatile semi-essential amino acid with a number of bioactive metabolites, and altered arginine metabolism has been implicated in the pathogenesis of schizophrenia. Earlier research has demonstrated that maternal immune activation (MIA; a risk factor for schizophrenia) alters arginine metabolism in the prefrontal cortex and hippocampus of the adult offspring. The present study investigated how MIA affected the levels of l-arginine and its downstream metabolites in the whole forebrain, frontal cortex, hippocampus and cerebellum of male and female rat offspring at the age of postnatal day 2. While no effects were evident in the forebrain, MIA significantly increased l-arginine, glutamate, putrescine, spermidine and spermine levels and the glutamate/GABA ratio, but decreased the glutamine/glutamate ratio, in the frontal cortex, hippocampus and/or cerebellum with no marked sex differences. Cluster analyses revealed that l-arginine and its main metabolites formed distinct groups, which changed as a function of MIA or sex in all four brain regions examined. These results demonstrate, for the first time, that MIA alters brain arginine metabolism in the rat offspring during early neonatal development, and further support the involvement of arginine metabolism in the pathogenesis of schizophrenia.

Subcutaneous Toxicity of Agmatine in Rats

Objectives

The aim of this study was to investigate the effects of repetitive agmatine administration on sensorimotor gating in rats first but, as unexpected, ulcerative necrotic cutaneous lesions appeared, thus, the study was directed primarily to clarify these results.

Materials and Methods

In the first set of experiments, we administered agmatine (40, 80 and 160 mg/kg) and saline (control group) subcutaneously to male Wistar albino rats (n=8 for each group) for 14 consecutive days. Ulcerative necrotic cutaneous lesions appeared following the third day of agmatine administration. We decided to explore the potential toxic dermal effects of agmatine and conducted second set of experiments with two groups (n=8) to compare the effects of subcutaneous vs. intraperitoneal agmatine (80 mg/kg) injection to understand if the injection route determines the toxicity.

Results

Our results showed that prolonged subcutaneous but not intraperitoneal administration of agmatine leads to a delayed dermal reaction in rats. Histopathologic examination of skin samples revealed cutaneous aseptic necrosis at the injection site whereas blood tests were found to be normal.

Conclusion

This finding is important to point out the risks of prolonged subcutaneous administration of agmatine to rats within the concept of animal welfare. In addition, the results raise questions about the possible risks of over-the-counter use of agmatine among humans although the agent is taken via oral route.

Agmatine: multifunctional arginine metabolite and magic bullet in clinical neuroscience?

Agmatine, the decarboxylation product of arginine, was largely neglected as an important player in mammalian metabolism until the mid-1990s, when it was re-discovered as an endogenous ligand of imidazoline and α2-adrenergic receptors. Since then, a wide variety of agmatine-mediated effects have been observed, and consequently agmatine has moved from a wallflower existence into the limelight of clinical neuroscience research. Despite this quantum jump in scientific interest, the understanding of the anabolism and catabolism of this amine is still vague. The purification and biochemical characterization of natural mammalian arginine decarboxylase and agmatinase still are open issues. Nevertheless, the agmatinergic system is currently one of the most promising candidates in order to pharmacologically interfere with some major diseases of the central nervous system, which are summarized in the present review. Particularly with respect to major depression, agmatine, its derivatives, and metabolizing enzymes show great promise for the development of an improved treatment of this common disease.

Day/night changes in serum S100B protein concentrations in acute paranoid schizophrenia

There are day/night and seasonal changes in biological markers such as melatonin and cortisol. Controversial changes in serum S100B protein levels have been described in schizophrenia. We aim studying whether serum S100B levels present day/night variations in schizophrenia patients and whether S100B levels are related to psychopathology. Sixty-five paranoid schizophrenic inpatients participated in the study. Psychopathology was assessed with the Positive and Negative Syndrome Scale (PANSS) at admission and discharge. Blood was drawn at 12:00 (midday) and 00:00 (midnight) hours at admission and discharge. Sixty-five healthy subjects matched by age, gender and season acted as control group. At admission and discharge patients had significantly higher serum S100B concentrations at midday and midnight than healthy subjects. At admission, patients showed a day/night variation of S100B levels, with higher S100B levels at 12:00 than at 00:00h (143.7±26.3pg/ml vs. 96.9±16.6pg/ml). This day/night difference was not present in the control group. Midday and midnight S100B at admission decreased when compared to S100B at discharge (midday, 143.7±26.3 vs. 83.0±12, midnight 96.9±16.6 vs. 68.6±14.5). There was a positive correlation between the PANSS positive subscale and S100B concentrations at admission. This correlation was not present at discharge.

CONCLUSIONS

acute paranoid schizophrenia inpatients present a day/night change of S100B serum levels at admission that disappears at discharge. The correlation between serum S100B concentrations and the PANSS positive scores at admission as well as the decrease of S100B at discharge may be interpreted as an acute biological response to the clinical state of the patients.

Theranostic Biomarkers for Schizophrenia

Schizophrenia is a highly heritable, chronic, severe, disabling neurodevelopmental brain disorder with a heterogeneous genetic and neurobiological background, which is still poorly understood. To allow better diagnostic procedures and therapeutic strategies in schizophrenia patients, use of easy accessible biomarkers is suggested. The most frequently used biomarkers in schizophrenia are those associated with the neuroimmune and neuroendocrine system, metabolism, different neurotransmitter systems and neurotrophic factors. However, there are still no validated and reliable biomarkers in clinical use for schizophrenia. This review will address potential biomarkers in schizophrenia. It will discuss biomarkers in schizophrenia and propose the use of specific blood-based panels that will include a set of markers associated with immune processes, metabolic disorders, and neuroendocrine/neurotrophin/neurotransmitter alterations. The combination of different markers, or complex multi-marker panels, might help in the discrimination of patients with different underlying pathologies and in the better classification of the more homogenous groups. Therefore, the development of the diagnostic, prognostic and theranostic biomarkers is an urgent and an unmet need in psychiatry, with the aim of improving diagnosis, therapy monitoring, prediction of treatment outcome and focus on the personal medicine approach in order to improve the quality of life in patients with schizophrenia and decrease health costs worldwide.

Effects of withdrawal from repeated phencyclidine administration on behavioural function and brain arginine metabolism in rats

Phencyclidine (PCP) induces behavioural changes in humans and laboratory animals that resemble positive and negative symptoms, and cognitive impairments in schizophrenia. It has been shown repeated treatment of PCP leading to persistent symptoms even after the drug discontinuation, and there is a growing body of evidence implicating altered arginine metabolism in the pathogenesis of schizophrenia. The present study investigated the effects of withdrawal from repeated daily injection of PCP (2mg/kg) for 12 consecutive days on animals'behavioural performance and arginine metabolism in the hippocampus and prefrontal cortex in male young adult rats. Repeated PCP treatment reduced spontaneous alternations in the Y-maze and exploratory and locomotor activities in the open field under the condition of a washout period of 24h, but not 4days. Interestingly, the PCP treated rats also displayed spatial working memory deficits when tested 8-10days after withdrawal from PCP and showed altered levels of arginase activities and eight out of ten l-arginine metabolites in neurochemical- and region-specific manner. Cluster analyses showed altered relationships among l-arginine and its three main metabolites as a function of withdrawal from repeated PCP treatment in a duration-specific manner. Multiple regression analysis revealed significant neurochemical-behavioural correlations. Collectively, the results suggest both the residual and long-term effects of withdrawal from repeated PCP treatment on behavioural function and brain arginine metabolism. These findings demonstrate, for the first time, the influence of the withdrawal duration on animals' behaviour and brain arginine metabolism.

Agmatine, a potential novel therapeutic strategy for depression

Major depressive disorder is the most common psychiatric disorder with lifetime prevalence of up to 20% worldwide. It is responsible for more years lost to disability than any other disorder. Despite the fact that current available antidepressant drugs are safe and effective, they are far from ideal. In addition to the need to administer the drugs for weeks or months to obtain clinical benefit, side effects are still a serious problem. Agmatine is an endogenous polyamine synthesized by the enzyme arginine decarboxylase. It modulates several receptors and is considered as a neuromodulator in the brain. In this review, studies demonstrating the antidepressant effects of agmatine are presented and discussed, as well as, the mechanisms of action related to these effects. Also, the potential beneficial effects of agmatine for the treatment of other neurological disorders are presented. In particular, we provide evidence to encourage future clinical studies investigating agmatine as a novel antidepressant drug.

Behavioral sequelae of astrocyte dysfunction: focus on animal models of schizophrenia

Astrocytes regulate multiple processes in the brain ranging from trophic support of developing neurons to modulation of synaptic neurotransmission and neuroinflammation in adulthood. It is, therefore, understandable that pathogenesis and pathophysiology of major psychiatric disorders involve astrocyte dysfunctions. Until recently, there has been the paucity of experimental approaches to studying the roles of astrocytes in behavioral disease. A new generation of in vivo models allows us to advance our understanding of the roles of astrocytes in psychiatric disorders. This review will evaluate the recent studies that focus on the contribution of astrocyte dysfunction to behavioral alterations pertinent to schizophrenia and will propose the possible solutions of the limitations of the existing approaches.

Arginine decarboxylase: A novel biological target of mercury compounds identified in PC12 cells

Mercury compounds are well-known toxic environmental pollutants and potently induce severe neurotoxicological effects in human and experimental animals. Previous studies showed that one of the mechanisms of mercury compounds neurotoxicity arose from the over-activation of the N-methyl d-aspartate (NMDA)-type glutamate receptor induced by increased glutamate release. In this work, we aimed to investigate the molecular mechanisms of Hg compounds neurotoxicities by identifying their biological targets in cells. Firstly, the inhibitory effects of four Hg compounds, including three organic (methyl-, ethyl- and phenyl-mercury) and one inorganic (Hg²⁺) Hg compounds, on the activity of arginine decarboxylase (ADC), a key enzyme in the central agmatinergic system, were evaluated. They were found to inhibit the ADC activity significantly with methylmercury (MeHg) being the strongest (IC₅₀=7.96nM). Furthermore, they showed remarkable inhibitory effects on ADC activity in PC12 cells (MeHg>EtHg>PhHg>HgCl₂), and led to a marked loss in the level of agmatine, an endogenous neuromodulatory and neuroprotective agent that selectively blocks the activation of NMDA receptors. MeHg was detected in the immunoprecipitated ADC from the cells, providing unequivocal evidence for the direct binding of MeHg with ADC in the cell. Molecular dynamics simulation revealed that Hg compounds could form the coordination bond not only with cofactor PLP of ADC, but also with substrate arginine. Our finding indicated that MeHg could attenuate the neuroprotective effects of agmatine by the inhibition of ADC, a new cellular target of MeHg, which might be implicated in molecular mechanism of MeHg neurotoxicity.

Effects of agmatine on chlorpromazine toxicity in the liver of Wistar rats: the possible role of oxidant/antioxidant imbalance

Chlorpromazine (CPZ) is a member of a widely used class of antipsychotic agents. The metabolic pathways of CPZ toxicity were examined by monitoring oxidative/nitrosative stress markers. The aim of the study was to investigate the hypothesis that agmatine (AGM) prevents oxidative stress in the liver of Wistar rats 48 h after administration of CPZ. All tested compounds were administered intraperitoneally (i.p.) in one single dose. The animals were divided into control (C, 0.9% saline solution), CPZ (CPZ, 38.7 mg/kg b.w.), CPZ+AGM (AGM, 75 mg/kg b.w. immediately after CPZ, 38.7 mg/kg b.w. i.p.), and AGM (AGM, 75 mg/kg b.w.) groups. Rats were sacrificed by decapitation 48 h after treatment. The CPZ and CPZ+AGM treatments significantly increased thiobarbituric acid reactive substances (TBARS), the nitrite and nitrate (NO₂+NO₃) concentration, and superoxide anion (O₂^•-) production in rat liver homogenates compared with C values. CPZ injection decreased the capacity of the antioxidant defense system: superoxide dismutase (SOD) activity, catalase (CAT) activity, total glutathione (GSH) content, glutathione peroxidase (GPx) activity, and glutathione reductase (GR) activity compared with the values of the C group. However, treatment with AGM increased antioxidant capacity in the rat liver; it increased the CAT activity, GSH concentration, GPx activity, and GR activity compared with the values of the CPZ rats. Immunohistochemical staining of ED1 in rats showed an increase in the number of positive cells 48 h after acute CPZ administration compared with the C group. Our results showed that AGM has no protective effects on parameters of oxidative and/or nitrosative stress in the liver but that it absolutely protective effects on the antioxidant defense system and restores the antioxidant capacity in liver tissue after administration of CPZ.

Altered brain arginine metabolism in schizophrenia

Previous research implicates altered metabolism of l-arginine, a versatile amino acid with a number of bioactive metabolites, in the pathogenesis of schizophrenia. The present study, for we believe the first time, systematically compared the metabolic profile of l-arginine in the frontal cortex (Brodmann's area 8) obtained post-mortem from schizophrenic individuals and age- and gender-matched non-psychiatric controls (n=20 per group). The enzyme assays revealed no change in total nitric oxide synthase (NOS) activity, but significantly increased arginase activity in the schizophrenia group. Western blot showed reduced endothelial NOS protein expression and increased arginase II protein level in the disease group. High-performance liquid chromatography and liquid chromatography/mass spectrometric assays confirmed significantly reduced levels of γ-aminobutyric acid (GABA), but increased agmatine concentration and glutamate/GABA ratio in the schizophrenia cases. Regression analysis indicated positive correlations between arginase activity and the age of disease onset and between l-ornithine level and the duration of illness. Moreover, cluster analyses revealed that l-arginine and its main metabolites l-citrulline, l-ornithine and agmatine formed distinct groups, which were altered in the schizophrenia group. The present study provides further evidence of altered brain arginine metabolism in schizophrenia, which enhances our understanding of the pathogenesis of schizophrenia and may lead to the future development of novel preventions and/or therapeutics for the disease.

Biomarkers in schizophrenia: A focus on blood based diagnostics and theranostics

Identifying biomarkers that can be used as diagnostics or predictors of treatment response (theranostics) in people with schizophrenia (Sz) will be an important step towards being able to provide personalized treatment. Findings from the studies in brain tissue have not yet been translated into biomarkers that are practical in clinical use because brain biopsies are not acceptable and neuroimaging techniques are expensive and the results are inconclusive. Thus, in recent years, there has been search for blood-based biomarkers for Sz as a valid alternative. Although there are some encouraging preliminary data to support the notion of peripheral biomarkers for Sz, it must be acknowledged that Sz is a complex and heterogeneous disorder which needs to be further dissected into subtype using biological based and clinical markers. The scope of this review is to critically examine published blood-based biomarker of Sz, focusing on possible uses for diagnosis, treatment response, or their relationship with schizophrenia-associated phenotype. We sorted the studies into six categories which include: (1) brain-derived neurotrophic factor; (2) inflammation and immune function; (3) neurochemistry; (4) oxidative stress response and metabolism; (5) epigenetics and microRNA; and (6) transcriptome and proteome studies. This review also summarized the molecules which have been conclusively reported as potential blood-based biomarkers for Sz in different blood cell types. Finally, we further discusses the pitfall of current blood-based studies and suggest that a prediction model-based, Sz specific, blood oriented study design as well as standardize blood collection conditions would be useful for Sz biomarker development.

Serum S100B Is Related to Illness Duration and Clinical Symptoms in Schizophrenia-A Meta-Regression Analysis

S100B has been linked to glial pathology in several psychiatric disorders. Previous studies found higher S100B serum levels in patients with schizophrenia compared to healthy controls, and a number of covariates influencing the size of this effect have been proposed in the literature. Here, we conducted a meta-analysis and meta-regression analysis on alterations of serum S100B in schizophrenia in comparison with healthy control subjects. The meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement to guarantee a high quality and reproducibility. With strict inclusion criteria 19 original studies could be included in the quantitative meta-analysis, comprising a total of 766 patients and 607 healthy control subjects. The meta-analysis confirmed higher values of the glial serum marker S100B in schizophrenia if compared with control subjects. Meta-regression analyses revealed significant effects of illness duration and clinical symptomatology, in particular the total score of the Positive and Negative Syndrome Scale (PANSS), on serum S100B levels in schizophrenia. In sum, results confirm glial pathology in schizophrenia that is modulated by illness duration and related to clinical symptomatology. Further studies are needed to investigate mechanisms and mediating factors related to these findings.

Glial cells as key players in schizophrenia pathology: recent insights and concepts of therapy

The past decade has witnessed an explosion of knowledge on the impact of glia for the neurobiological foundation of schizophrenia. A plethora of studies have shown structural and functional abnormalities in all three types of glial cells. There is convincing evidence of reduced numbers of oligodendrocytes, impaired cell maturation and altered gene expression of myelin/oligodendrocyte-related genes that may in part explain white matter abnormalities and disturbed inter- and intra-hemispheric connectivity, which are characteristic signs of schizophrenia. Earlier reports of astrogliosis could not be confirmed by later studies, although the expression of a variety of astrocyte-related genes is abnormal in psychosis. Since astrocytes play a key role in the synaptic metabolism of glutamate, GABA, monoamines and purines, astrocyte dysfunction may contribute to certain aspects of disturbed neurotransmission in schizophrenia. Finally, increased densities of microglial cells and aberrant expression of microglia-related surface markers in schizophrenia suggest that immunological/inflammatory factors are of considerable relevance for the pathophysiology of psychosis. This review describes current evidence for the multifaceted role of glial cells in schizophrenia and discusses efforts to develop glia-directed therapies for the treatment of the disease.

Systematic review and meta-analysis of circulating S100B blood levels in schizophrenia

S100B is a calcium-binding protein secreted in central nervous system from astrocytes and other glia cells. High blood S100B levels have been linked to brain damage and psychiatric disorders. S100B levels have been reported to be higher in schizophrenics than healthy controls. To quantify the relationship between S100B blood levels and schizophrenia a systematic literature review of case-control studies published on this topic within July 3rd 2014 was carried out using three bibliographic databases: Medline, Scopus and Web of Science. Studies reporting mean and standard deviation of S100B blood levels both in cases and controls were included in the meta-analysis. The meta-Mean Ratio (mMR) of S100B blood levels in cases compared to controls was used as a measure of effect along with its 95% Confidence Intervals (CI). 20 studies were included totaling for 994 cases and 785 controls. Schizophrenia patients showed 76% higher S100B blood levels than controls with mMR = 1.76 95% CI: 1.44-2.15. No difference could be found between drug-free patients with mMR = 1.84 95%CI: 1.24-2.74 and patients on antipsychotic medication with mMR = 1.75 95% CI: 1.41-2.16). Similarly, ethnicity and stage of disease didn't affect results. Although S100B could be regarded as a possible biomarker of schizophrenia, limitations should be accounted when interpreting results, especially because of the high heterogeneity that remained >70%, even after carrying out subgroups analyses. These results point out that approaches based on traditional categorical diagnoses may be too restrictive and new approaches based on the characterization of new complex phenotypes should be considered.