Antipsychotics affect multiple calcium calmodulin dependent proteins

CaMKK2 as an emerging treatment target for bipolar disorder

Current pharmacological treatments for bipolar disorder are inadequate and based on serendipitously discovered drugs often with limited efficacy, burdensome side-effects, and unclear mechanisms of action. Advances in drug development for the treatment of bipolar disorder remain incremental and have come largely from repurposing drugs used for other psychiatric conditions, a strategy that has failed to find truly revolutionary therapies, as it does not target the mood instability that characterises the condition. The lack of therapeutic innovation in the bipolar disorder field is largely due to a poor understanding of the underlying disease mechanisms and the consequent absence of validated drug targets. A compelling new treatment target is the Ca2+-calmodulin dependent protein kinase kinase-2 (CaMKK2) enzyme. CaMKK2 is highly enriched in brain neurons and regulates energy metabolism and neuronal processes that underpin higher order functions such as long-term memory, mood, and other affective functions. Loss-of-function polymorphisms and a rare missense mutation in human CAMKK2 are associated with bipolar disorder, and genetic deletion of Camkk2 in mice causes bipolar-like behaviours similar to those in patients. Furthermore, these behaviours are ameliorated by lithium, which increases CaMKK2 activity. In this review, we discuss multiple convergent lines of evidence that support targeting of CaMKK2 as a new treatment strategy for bipolar disorder.

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.

Case Report: Developmental Delay and Acute Neuropsychiatric Episodes Associated With a de novo Mutation in the CAMK2B Gene (c.328G>A p.Glu110Lys)

Mutations in the genes encoding calcium/calmodulin dependent protein kinase II (CAMK2) isoforms cause a newly recognized neurodevelopmental disorder (ND), for which the full clinical spectrum has yet to be described. Here we report the detailed description of a child with a de novo gain of function (GoF) mutation in the gene Ca/Calmodulin dependent protein kinase 2 beta (CAMK2B c.328G > A p.Glu110Lys) who presents with developmental delay and periodic neuropsychiatric episodes. The episodes manifest as encephalopathy with behavioral changes, headache, loss of language and loss of complex motor coordination. Additionally, we provide an overview of the effect of different medications used to try to alleviate the symptoms. We show that medications effective for mitigating the child’s neuropsychiatric symptoms may have done so by decreasing CAMK2 activity and associated calcium signaling; whereas medications that appeared to worsen the symptoms may have done so by increasing CAMK2 activity and associated calcium signaling. We hypothesize that by classifying CAMK2 mutations as “gain of function” or “loss of function” based on CAMK2 catalytic activity, we may be able to guide personalized empiric treatment regimens tailored to specific CAMK2 mutations. In the absence of sufficient patients for traditional randomized controlled trials to establish therapeutic efficacy, this approach may provide a rational approach to empiric therapy for physicians treating patients with dysregulated CAMK2 and associated calcium signaling.

The Anti-social Brain in Schizophrenia: A Role of CaMKII?

Current pharmacological therapy has limited effects on the cognitive impairments and negative symptoms associated with schizophrenia. Therefore, understanding the molecular underpinnings of this disorder is essential for the development of effective treatments. It appears that a reduction in calcium/calmodulin-dependent protein kinase II (α-CaMKII) activity is a common mechanism underlying the abnormal social behavior and cognitive deficits associated with schizophrenia. In addition, in a previous study social interaction with a partner of the same sex and weight increased the activity of α-CaMKII in rats. Here, we propose that boosting of CaMKII signaling, in a manner that counteracts this neuropsychiatric disease without disrupting the normal brain function, might ameliorate the abnormalities in social cognition and the negative symptoms of schizophrenia.

When Paranoia Comes with the Treatment: Psychosis Associated with Tacrolimus Use

Tacrolimus is an immunosuppressive drug frequently used in solid organ transplant recipients. This drug has well-documented neuropsychiatric side effects in the literature, although emergence of psychotic symptoms is rare, being only described in a very few case reports. We present a case of a renal transplant recipient with no prior psychiatric history, who developed a severe psychosis secondary to supratherapeutic tacrolimus' blood concentrations. This case highlights the importance of clinical awareness to rare but severe neuropsychiatric effects due to tacrolimus use.

Astrocyte Intracellular Ca2+and TrkB Signaling in the Hippocampus Could Be Involved in the Beneficial Behavioral Effects of Antidepressant Treatment

Although monoaminergic-based antidepressant drugs are largely used to treat major depressive disorder (MDD), their mechanisms are still incompletely understood. Intracellular Ca²⁺ (iCa²⁺) and Calmodulin 1(CaM-1) homeostasis have been proposed to participate in the therapeutic effects of these compounds. We investigated whether intra-hippocampal inhibition of CaM-1 would modulate the behavioral responses to chronic treatment with imipramine (IMI) or 7-nitroindazole (7-NI), a selective inhibitor of the neuronal nitric oxide synthase 1 (NOS1) enzyme that shows antidepressant-like effects. We also investigated the interactions of IMI and CaM-1 on transient astrocyte iCa²⁺ evoked by glutamate stimuli. Intra-hippocampal microinjection of the lentiviral delivered (LV) short hairpin iRNA-driven against the CaM-1 mRNA (LV-shRNA-CaM-1) or the CaM-1 inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalene sulphonamide (W-7) blocked the antidepressant-like effect of chronic treatment with IMI or 7-NI. The shRNA also inhibited the mRNA expression of the tropomyosin receptor kinase B (TrkB) in the microinjection region. The iCa²⁺ in ex vivo hippocampus slices stained with fluorescent Ca²⁺indicator Oregon Green 488 BAPTA-1 revealed that IMI increased the intensity and duration of iCa²⁺ oscillation and reduced the number of events evoked by glutamate stimuli, evaluated by using CCD imaging and the % ΔF/Fo parameters. The pre-treatment with W-7 fully antagonized this effect. The present results indicate that the behavioral benefits of chronic antidepressant treatment might be associated with astrocyte intracellular Ca²⁺dynamics and TrkB mRNA expression in the hippocampus.

Akkouh I, Hughes T, Frei E, A. Andreassen O, Djurovic S. Using iPSC Models to Understand the Role of Estrogen in Neuron-Glia Interactions in Schizophrenia and Bipolar Disorder

Schizophrenia (SCZ) and bipolar disorder (BIP) are severe mental disorders with a considerable disease burden worldwide due to early age of onset, chronicity, and lack of efficient treatments or prevention strategies. Whilst our current knowledge is that SCZ and BIP are highly heritable and share common pathophysiological mechanisms associated with cellular signaling, neurotransmission, energy metabolism, and neuroinflammation, the development of novel therapies has been hampered by the unavailability of appropriate models to identify novel targetable pathomechanisms. Recent data suggest that neuron-glia interactions are disturbed in SCZ and BIP, and are modulated by estrogen (E2). However, most of the knowledge we have so far on the neuromodulatory effects of E2 came from studies on animal models and human cell lines, and may not accurately reflect many processes occurring exclusively in the human brain. Thus, here we highlight the advantages of using induced pluripotent stem cell (iPSC) models to revisit studies of mechanisms underlying beneficial effects of E2 in human brain cells. A better understanding of these mechanisms opens the opportunity to identify putative targets of novel therapeutic agents for SCZ and BIP. In this review, we first summarize the literature on the molecular mechanisms involved in SCZ and BIP pathology and the beneficial effects of E2 on neuron-glia interactions. Then, we briefly present the most recent developments in the iPSC field, emphasizing the potential of using patient-derived iPSCs as more relevant models to study the effects of E2 on neuron-glia interactions.

Ca2+ signaling as a mechanism of haloperidol-induced cytotoxicity in human astrocytes and assessing the protective role of a Ca2+ chelator

Haloperidol, a typical antipsychotic medication, has been shown to possess various biological effects in different brain models. However, the impact of haloperidol on Ca²⁺ signaling in astrocytes is elusive. This study explored the effect of haloperidol on cytosolic free Ca²⁺ levels ([Ca²⁺]_i) and viability, and established these two connections in Gibco® Human Astrocytes (GHAs) and DI TNC1 rat astrocytes. Haloperidol (5-20 μM) caused [Ca²⁺]_i rises in a concentration-dependent manner in GHAs but not in DI TNC1 cells. Furthermore, removal of extracellular Ca²⁺ reduced haloperidol's effect by approximately 30% in GHAs. Haloperidol (20-40 μM) evoked concentration-dependent cytotoxicity in GHAs and DI TNC1 cells. However, chelating cytosolic Ca²⁺ with the Ca²⁺ chelator BAPTA/AM significantly reversed haloperidol's cytotoxicity only in GHAs. In GHAs, haloperidol-induced Ca²⁺ entry was inhibited by store-operated Ca²⁺ modulators (2-APB and SKF96365) and the protein kinase C (PKC) inhibitor GF109203X. This Ca²⁺ entry induced by haloperidol was confirmed by Mn²⁺ entry-induced quench of fura-2 fluorescence. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) abolished haloperidol-induced [Ca²⁺]_i rises. Conversely, treatment with haloperidol inhibited 45% of BHQ-evoked [Ca²⁺]_i rises. Moreover, haloperidol-induced Ca²⁺ release from the endoplasmic reticulum was abolished by inhibition of phospholipase C (PLC) by U73122. Together, in GHAs but not in DI TNC1 cells, haloperidol caused Ca²⁺-associated cell death, induced Ca²⁺ entry via PKC-sensitive store-operated Ca²⁺ channels, and evoked PLC-dependent Ca²⁺ release from the endoplasmic reticulum. The protective effect of Ca²⁺ chelating on haloperidol-induced cytotoxicity in human astrocytes was also demonstrated.

Catatonia Due to Tacrolimus Toxicity 16 Years After Renal Transplantation: Case Report and Literature Review

Tacrolimus, a potent posttransplant immunosuppressant, has been associated with major neuropsychiatric complications, including catatonia and psychosis. We report a novel case of tacrolimus-induced encephalopathy that developed 16 years after renal transplantation while the drug was at a therapeutic level. Discontinuation of tacrolimus and switching to an alternative immunosuppressant resulted in significant clinical improvement over 1 week. Our experience illustrates the possibility of acute neurotoxicity from tacrolimus even when the patient has tolerated the drug for 16 years and drug levels are within the therapeutic range. This case also highlights the importance of collaboration between psychiatry and transplant clinicians.

Behavioral cross-sensitization between cocaine and ethanol is accompanied by parallel changes in the activity of AMPK system

Behavioral sensitization is thought to be relevant to the psychopathology of drug addiction. A previous study from our research group demonstrated cross-sensitization between cocaine and ethanol. Although these findings suggest a common mechanism of action between these two drugs, little is known about the molecular or cellular aspects of this commonality. The AMPK pathway functions as an intracellular energy sensor and plays a critical role in maintaining cellular energy homeostasis. Thus, the present study examined AMPK signaling following reciprocal cross-sensitization between cocaine and ethanol in the rat prefrontal cortex and dorsal striatum. Male Sprague-Dawley rats were repeatedly treated with either cocaine (15 mg/kg, 5 times) or ethanol (0.5 g/kg, 15 times) and then challenged reciprocally with the other drug. When sensitized to either cocaine or ethanol, the phosphorylation in response to additional challenges with the same drug was enhanced, indicating the development of sensitization. However, responses to the cocaine challenge were enhanced in the ethanol-sensitized state, whereas the responses to the ethanol challenge were not apparently enhanced in the cocaine-sensitized state. This was likely due to the ceiling effect of cocaine sensitization, which suggested that cocaine had more robust effects than ethanol. Although the same changes were found for two upstream kinases of AMPK (LKB1 and CaMK4), TAK1 responded differently and was not affected by acute challenges from either cocaine or ethanol. In the prefrontal cortex, there was an increase in activity, whereas there was a decrease in activity in the dorsal striatum. This difference might be due to dopamine D1 receptor dominance in the prefrontal cortex and D2 receptor dominance in the dorsal striatum. Taken together, these results suggest that both cocaine and ethanol may share overlapping molecular pathways in the process of behavioral sensitization. However, the action of cocaine was stronger than that of ethanol.

Tuberculum sellae meningioma with possible tacrolimus neurotoxicity manifesting as manic-like psychosis after kidney transplantation

BACKGROUND

Although kidney transplantation is the best treatment option for chronic kidney disease, the accompanying immunosuppressive treatment can induce severe neurotoxicity presenting, on rare occasions, as psychosis. However, a brain tumor synchronous with immunosuppressant neurotoxicity has never been reported in a kidney transplant recipient. Herein, we report the first case of possible tacrolimus neurotoxicity with a meningioma manifesting as manic-like psychosis after kidney transplantation.

CASE PRESENTATION

A 63-year-old male presenting with acute psychotic mania was admitted to a psychiatric ward approximately 2 years after kidney transplantation. On brain magnetic resonance imaging, a tuberculum sellae meningioma was found, and hyperintense white matter lesions with possible tacrolimus-induced neurotoxicity were seen on fluid-attenuated inversion recovery images. Interestingly, the patient showed no visual field defects, and his blood tacrolimus concentration was within therapeutic ranges. After 3 weeks of adjunctive treatment with blonanserin, most of the symptoms had abated.

CONCLUSIONS

The present case highlights the fact that neuroimaging studies are necessary to investigate underlying causes, as well as immunosuppressant neurotoxicity, which should all be considered when atypical psychiatric symptoms develop after organ transplantation. Further, this case suggests that the additional use of atypical antipsychotics while maintaining immunosuppressants may be effective for manic-like psychotic symptoms secondary to possible immunosuppressant neurotoxicity synchronous with a meningioma.

Treatment-Refractory Mania with Psychosis in a Post-Transplant Patient on Tacrolimus: A Case Report

Bipolar affective disorder type I imparts significant morbidity and disease burden in the population. It is characterized by occurrence of one or more manic episodes which may be preceded or followed by a depressive or hypomanic phase. About half of these manic episodes are characterized by the presence of psychotic features. The condition is further complicated when the patient has multiple comorbid conditions. We report here the case of a Caucasian woman, aged 66 years, previously diagnosed with Bipolar disorder who developed treatment refractory mania with psychotic feature after being on the immunosuppressive agent, tacrolimus, after kidney transplantation.

Calcium as a Trojan horse in mental diseases-The role of PMCA and PMCA-interacting proteins in bipolar disorder and schizophrenia

Although first mentions about calcium disturbances in psychiatric diseases appeared more than 30 years ago, the most recent genomic and proteomic findings confirmed a significant role of Ca²⁺ and Ca²⁺-regulated pathways in development of neuropathological processes, including bipolar disorder and schizophrenia. Moreover, last decades have shown that due to multifactorial nature of both diseases, impairment in neuronal calcium homeostasis may depend not only on disturbed Ca²⁺ entry system, but also on altered extrusion system. A pivotal role in Ca²⁺ clearance mechanism is played by plasma membrane Ca²⁺-ATPase (PMCA), the enzyme responsible for returning the elevated levels of cytosolic Ca²⁺ back to the resting state. In this paper we summarize the current knowledge about the role of PMCA in bipolar disorder and schizophrenia pathologies, as well as the contribution of several proteins that by interaction with PMCA modify signal transduction mechanisms.

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

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

Proteome effects of antipsychotic drugs: Learning from preclinical models

Proteome-wide expression analyses are performed in the brain of schizophrenia patients to understand the biological basis of the disease and discover molecular paths for new clinical interventions. A major issue with postmortem analysis is the lack of tools to discern molecular modulation related to the disease from dysregulation due to medications. We review available proteome-wide analysis of antipsychotic treatment in rodents, highlighting shared dysregulated pathways that may contribute to an extended view of molecular processes underlying their pharmacological activity. Fourteen proteomic studies conducted with typical and atypical antipsychotic treatments were examined; hypothesis-based approaches are also briefly discussed. Treatment with antipsychotics mainly affects proteins belonging to metabolic pathways involved in energy generation, both in glycolytic and oxidative phosphorylation pathways, suggesting antipsychotics-induced impairments in metabolism. Nevertheless, schizophrenic patients show impaired glucose metabolism and mitochondrial dysfunctions independent of therapy. Other antipsychotics-induced changes shared by different studies implicate cytoskeletal and synaptic function proteins. The mechanism can be related to the reorganization of dendritic spines resulting from neural plasticity events induced by treatments affecting neurotransmitter circuitry. However, metabolic and plasticity pathways activated by antipsychotics can also play an authentic role in the etiopathological basis of schizophrenia.

A genetic variant in CAMKK2 gene is possibly associated with increased risk of bipolar disorder

A recent large-scale study have reported that rs1063843, a single nucleotide polymorphism located in the CAMKK2 gene is highly associated with schizophrenia in European and Han Chinese populations. Increasing evidences show that schizophrenia and bipolar disorder have some common genetic variance. Here, we evaluated the association of this variant with schizophrenia and bipolar disorder in Iranian population. Genomic DNA was extracted from peripheral blood of 500 schizophrenic patients, 500 bipolar patients and 500 normal controls and all were genotyped for the rs1063843 using a PCR-RFLP method. The allele frequency of rs1063843 was significantly different in both schizophrenia and bipolar patients comparing to control group. For the first time, we showed that rs1063843 is highly associated with bipolar disorder, although more replication studies are needed to confirm our findings. Our results also support the findings of previous studies suggesting a significant association between rs1063843 and schizophrenia.

Review of lithium effects on immune cells

One of the remarkable discoveries in the field of psychopharmacology from late 1940s is Lithium (Li) that reminds of old but still gold. It continues to be a distinctive mood stabilizer that matches various standards recommended for mood stabilizers. Apart from this Li is also known to affect immune cell functions. Lithium response and regulations of different immune cells in bipolar patients, related immune disorders are not well defined. Here, we provide an overview of literature with regard to Li's effects on different immune cells. However, the use of Li is currently limited to bipolar disorders and there is no empirical evidence for immune cell disorders. The objective of this article is to provide the evaluations of Li responses towards the different immune cells based on the existing studies. Further, more studies are needed to understand the mechanistic basis and heterogeneous responses of Li's effect in bipolar, also unravel relative immune disorders.

CACNA1C genotype explains interindividual differences in amygdala volume among patients with schizophrenia

Affective deficits are one common denominator of schizophrenia (SZ), bipolar disorder (BD) and obsessive compulsive disorder (OCD) with the amygdala indicated as one of the major structures involved in emotion regulation. Previous findings of differences in amygdala volume between healthy controls and patients with SZ, BD or OCD diverge with respect to the affected hemisphere, size and direction of the effect. Variability in the CACNA1C gene has been linked to BD, SZ as well as structural and functional variation in the amygdala in healthy people and patients with BD. We were interested to investigate whether amygdala volumes differ between hemispheres, diagnostic or genotype groups, and whether any interactive effects exist. We combined genotyping of SNP rs1006737 in CACNA1C with structural MRI measurements of relative gray matter (GM) amygdala volume in patients with SZ, BD or OCD as well as healthy controls (N Total = 72). The CACNA1C genotype showed a significant effect on relative GM amygdala volume in patients with SZ. There was a significant left versus right relative GM amygdala volume decrease in patients with SZ or BD. The effects of hemisphere and diagnosis (controls vs. patients with SZ) on relative GM amygdala volume were genotype specific. Our data suggest that the CACNA1C genotype may account for some heterogeneity in the effects of hemisphere and diagnosis on amygdala volume when comparing patients with SZ and controls and point to disturbed Ca(2+)-signaling as a plausible mechanism contributing to the pathology in patients with SZ.

Regulator of calcineurin 1 modulates expression of innate anxiety and anxiogenic responses to selective serotonin reuptake inhibitor treatment

Regulator of calcineurin 1 (RCAN1) controls the activity of calcium/calmodulin-dependent phosphatase calcineurin (CaN), which has been implicated in human anxiety disorders. Previously, we reported that RCAN1 functioned as an inhibitor of CaN activity in the brain. However, we now find enhanced phosphorylation of a CaN substrate, cAMP response element-binding protein (CREB), in the brains of Rcan1 knock-out (KO) mice. Consistent with enhanced CREB activation, we also observe enhanced expression of a CREB transcriptional target, brain-derived neurotrophic factor (BDNF) in Rcan1 KO mice. We also discovered that RCAN1 deletion or blockade of RCAN1-CaN interaction reduced CaN and protein phosphatase-1 localization to nuclear-enriched protein fractions and promoted CREB activation. Because of the potential links between CREB, BDNF, and anxiety, we examined the role of RCAN1 in the expression of innate anxiety. Rcan1 KO mice displayed reduced anxiety in several tests of unconditioned anxiety. Acute pharmacological inhibition of CaN rescued these deficits while transgenic overexpression of human RCAN1 increased anxiety. Finally, we found that Rcan1 KO mice lacked the early anxiogenic response to the selective serotonin reuptake inhibitor (SSRI) fluoxetine and had improved latency for its therapeutic anxiolytic effects. Together, our study suggests that RCAN1 plays an important role in the expression of anxiety-related and SSRI-related behaviors through CaN-dependent signaling pathways. These results identify RCAN1 as a mediator of innate emotional states and possible therapeutic target for anxiety.

Mechanistic analysis for time-dependent effects of cinacalcet on serum calcium, phosphorus, and parathyroid hormone levels in 5/6 nephrectomized rats

This study investigates the time-dependent effects of cinacalcet on serum calcium, phosphorus, and parathyroid hormone (PTH) levels in 5/6 nephrectomized (NX) rats with experimental chronic renal insufficiency. In this study, 5/6 NX male, Sprague-Dawley rats were treated with vehicle or cinacalcet (10 mg/kg, oral, 1× daily). On Day 0 (before treatment), Day 12 and 13 after treatment (to approximate the clinical practice), and also at 0, 1, 4, 8, 16, and 24 hours after the last dosing, blood was collected for analysis. After 12 or 13 days of cinacalcet treatment, modest changes were observed in serum Ca and phosphorus (Pi), while PTH decreased by >45% to Sham levels (152 ± 15 pg/mL). Detailed mapping found that cinacalcet caused a significant time-dependent decrease in serum Ca following dosing, reaching a lowest point at 8 hours (decrease by 20% to 8.43 ± 0.37 mg/dL), and then returning to normal at 24 hours. Cinacalcet also caused a significant increase in serum Pi levels (by 18%). To investigate the potential mechanism of action, a broad approach was taken by testing cinacalcet in a panel of 77 protein-binding assays. Cinacalcet interacted with several channels, transporters, and neurotransmitter receptors, some of which are involved in brain and heart, and may impact Ca homeostasis. Cinacalcet dose-dependently increased brain natriuretic peptide (BNP) mRNA expression by 48% in cardiomyocytes, but had no significant effects on left ventricular hypertrophy and cardiac function. The results suggest that cinacalcet's hypocalcemic effect may be due to its nonspecific interaction with other receptors in brain and heart.

Tacrolimus-induced paranoid delusions and fugue-like state

We report the case of a 43 year old male with no prior psychiatric history with apparent tacrolimus-induced psychosis. Previous reports have identified other neurotoxic adverse effects due to tacrolimus, however, to our knowledge, there are few reports that describe psychosis induced by the immunosuppressant drug. Although psychosis may be a rare adverse effect, it can have significant impact on the long-term prognosis and treatment in transplant recipients. It is imperative to quickly identify patients who develop a mental status change while on tacrolimus and to work with the appropriate transplant team in managing these patients. Treatment usually calls for prompt discontinuation of tacrolimus, substituting with another immunosuppressant, and possible use of antipsychotics.

The effect of clozapine on the AMPK-ACC-CPT1 pathway in the rat frontal cortex

Clozapine is an antipsychotic drug that has a greater efficacy than other medications in some contexts, especially for the treatment of treatment-resistant schizophrenia. However, clozapine induces more metabolic side-effects involving abnormality in lipid metabolism compared to other antipsychotics. AMP-activated protein kinase (AMPK) plays a central role in controlling lipid metabolism through modulating the downstream acetyl CoA carboxylase (ACC) and carnitine palmitoyl transferase 1 (CPT1) pathway. In this study, we investigated the effect of a single intraperitoneal injection of clozapine on the AMPK-ACC-CPT1 pathway in the rat frontal cortex, which has been implicated as a target site for this antipsychotic drug. At 2 h after injection, the clinically relevant dose of clozapine had activated AMPK, with increased phosphorylation of AMPKα at Thr(172), and had inactivated ACC, with increased phosphorylation of ACC at Ser(79). In addition, clozapine activated the brain-specific isoform of CPT1, CPT1c, whose activity is inhibited by unphosphorylated ACC, in the rat frontal cortex. Immunohistochemistry and immunofluorescence analysis showed that clozapine induced an increase in number of p-AMPKα (Thr(172))- and p-ACC (Ser(79))-positive cells among the neurons of the rat frontal cortex. Taken together, these results show that clozapine activated the AMPK-ACC-CPT1 pathway in the neurons of the rat frontal cortex. These findings indicate that the antipsychotic agent clozapine affects the lipid regulatory system of neurons in the brain.

In vitro findings of alterations in intracellular calcium homeostasis in schizophrenia

The pathogenesis of schizophrenia involves several complex cellular mechanisms and is not well understood. Recent research has demonstrated an association between primary disturbances characteristic of the disease, including altered dopaminergic and glutamatergic neurotransmission, and impairments in neuronal calcium (Ca(2+)) homeostasis and signaling. Emerging Ca(2+) hypothesis links and unifies various cellular processes involved in the pathogenesis of schizophrenia and suggests a central role of dysregulation of Ca(2+) homeostasis in the etiology of the disease. This review explores the in vitro data on Ca(2+) homeostasis and signaling in schizophrenia. Major limitation in this research is the lack of schizophrenia markers and validated disease models. As indicated in this review, one way to overcome these limitations may be analyses of Ca(2+) signalosomes in peripheral cells from schizophrenia patients. Validation of animal models of schizophrenia may permit the application of advanced Ca(2+) imaging techniques in living animals.

Systems biology of cell behavior

Systems Biology approaches to drug discovery largely focus on the increasing understanding of intracellular and cellular circuits, by computational representation of a molecular system followed by parameter validation against experimental data. This chapter outlines a universal approach to systems biology that allows the linking of intracellular molecular machinery and cellular activity. This procedure is achieved by applying mathematical modeling to molecular modules of a cell in the light of systems biology techniques.

Heteromerization of dopamine D2 receptors with dopamine D1 or D5 receptors generates intracellular calcium signaling by different mechanisms

The repertoire of signal transduction pathways activated by dopamine in brain includes the increase of intracellular calcium. However the mechanism(s) by which dopamine activated this important second messenger system was/were unknown. Although we showed that activation of the D5 dopamine receptor increased calcium concentrations, the restricted anatomic distribution of this receptor made this unlikely to be the major mechanism in brain. We have identified novel heteromeric dopamine receptor complexes that are linked to calcium signaling. The calcium pathway activated through the D1-D2 receptor heteromer involved coupling to Gq, through phospholipase C and IP(3) receptors to result in a rise in intracellular calcium. The calcium rise activated through the D2-D5 receptor heteromer involved a small rise in intracellular calcium through the Gq pathway that triggered a store-operated channel mediated influx of extracellular calcium. These novel receptor heteromeric complexes, for the first time, establish the link between dopamine action and rapid calcium signaling.

Monitoring of drug-associated electrolyte disturbances in a hospital

PURPOSE

The aim of our study was to find drug-associated changes in serum levels of major electrolytes using clinical-event monitoring method.

METHODS

During 1-year period, electrolyte disturbances in serum samples from patients of Clinical Center Kragujevac, Serbia, were monitored in central biochemical facility. A sample of 982 patients was randomly selected from total population of 43,120 patients whose electrolyte serum levels were measured in the facility during the study period.

RESULTS

Clinically important drug-associated electrolyte disturbances were detected in 181 patient. There were 25 significant associations between the drugs and electrolyte values outside the reference range. However, only four causal connections were established: use of normal saline infusion with hypernatremia (OR 6.97, 95%CI 2.24-21.67), theophylline with acid-base disturbances (7.75, 1.46-41.02), polygeline infusion with decrease in bicarbonate levels (4.08, 1.42-11.73), and association of risperidone and hypocalcemia (4.10, 1.42-11.81).

CONCLUSION

Although clinical-event monitoring method is far from optimal, it could quantify the known risks and provide evidence for credible hypothesis of drug adverse reactions, based on both relevant biological pathways and reasonable clinical thinking, as it was the case in our study.