Bimodal modulation of store-operated Ca2+ channels by clozapine in astrocytes

Profiling of ERBB receptors and downstream pathways reveals selectivity and hidden properties of ERBB4 antagonists

ERBB receptor tyrosine kinases are involved in development and diseases like cancer, cardiovascular, neurodevelopmental, and mental disorders. Although existing drugs target ERBB receptors, the next generation of drugs requires enhanced selectivity and understanding of physiological pathway responses to improve efficiency and reduce side effects. To address this, we developed a multilevel barcoded reporter profiling assay, termed 'ERBBprofiler', in living cells to monitor the activity of all ERBB targets and key physiological pathways simultaneously. This assay helps differentiate on-target therapeutic effects from off-target and off-pathway side effects of ERBB antagonists. To challenge the assay, eight established ERBB antagonists were profiled. Known effects were confirmed, and previously uncharacterized properties were discovered, such as pyrotinib's preference for ERBB4 over EGFR. Additionally, two lead compounds selectively targeting ERBB4 were profiled, showing promise for clinical trials. Taken together, this multiparametric profiling approach can guide early-stage drug development and lead to improved future therapeutic interventions.

The role of hypothalamic endoplasmic reticulum stress in schizophrenia and antipsychotic-induced weight gain: A narrative review

Schizophrenia (SCZ) is a serious mental illness that affects 1% of people worldwide. SCZ is associated with a higher risk of developing metabolic disorders such as obesity. Antipsychotics are the main treatment for SCZ, but their side effects include significant weight gain/obesity. Despite extensive research, the underlying mechanisms by which SCZ and antipsychotic treatment induce weight gain/obesity remain unclear. Hypothalamic endoplasmic reticulum (ER) stress is one of the most important pathways that modulates inflammation, neuronal function, and energy balance. This review aimed to investigate the role of hypothalamic ER stress in SCZ and antipsychotic-induced weight gain/obesity. Preliminary evidence indicates that SCZ is associated with reduced dopamine D2 receptor (DRD2) signaling, which significantly regulates the ER stress pathway, suggesting the importance of ER stress in SCZ and its related metabolic disorders. Antipsychotics such as olanzapine activate ER stress in hypothalamic neurons. These effects may induce decreased proopiomelanocortin (POMC) processing, increased neuropeptide Y (NPY) and agouti-related protein (AgRP) expression, autophagy, and leptin and insulin resistance, resulting in hyperphagia, decreased energy expenditure, and central inflammation, thereby causing weight gain. By activating ER stress, antipsychotics such as olanzapine activate hypothalamic astrocytes and Toll-like receptor 4 signaling, thereby causing inflammation and weight gain/obesity. Moreover, evidence suggests that antipsychotic-induced ER stress may be related to their antagonistic effects on neurotransmitter receptors such as DRD2 and the histamine H1 receptor. Taken together, ER stress inhibitors could be a potential effective intervention against SCZ and antipsychotic-induced weight gain and inflammation.

The Impact of the Antipsychotic Medication Chlorpromazine on Cytotoxicity through Ca2+ Signaling Pathway in Glial Cell Models

Chlorpromazine, an antipsychotic medication, is conventionally applied to cope with the psychotic disorder such as schizophrenia. In cellular studies, chlorpromazine exerts many different actions through calcium ion (Ca²⁺) signaling, but the underlying pathways are elusive. This study explored the effect of chlorpromazine on viability, Ca²⁺ signaling pathway and their relationship in glial cell models (GBM 8401 human glioblastoma cell line and Gibco® Human Astrocyte (GHA)). First, chlorpromazine between 10 and 40 μM induced cytotoxicity in GBM 8401 cells but not in GHA cells. Second, in terms of Ca²⁺ homeostasis, chlorpromazine (10-30 μM) increased intracellular Ca²⁺ concentrations ([Ca²⁺]_i) rises in GBM 8401 cells but not in GHA cells. Ca²⁺ removal reduced the signal by approximately 55%. Furthermore, chelation of cytosolic Ca²⁺ with BAPTA-AM reduced chlorpromazine (10-40 μM)-induced cytotoxicity in GBM 8401 cells. Third, in Ca²⁺-containing medium of GBM 8401 cells, chlorpromazine-induced Ca²⁺ entry was inhibited by the modulators of store-operated Ca²⁺ channel (2-APB and SKF96365). Lastly, in Ca²⁺-free medium of GBM 8401 cells, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor thapsigargin completely inhibited chlorpromazine-increased [Ca²⁺]_i rises. Conversely, treatment with chlorpromazine abolished thapsigargin-increased [Ca²⁺]_i rises. Inhibition of phospholipase C (PLC) with U73122 abolished chlorpromazine-increased [Ca²⁺]_i rises. Together, in GBM 8401 cells but not in GHA cells, chlorpromazine increased [Ca²⁺]_i rises by Ca²⁺ influx via store-operated Ca²⁺ entry and PLC-dependent Ca²⁺ release from the endoplasmic reticulum. Moreover, the Ca²⁺ chelator BAPTA-AM inhibited cytotoxicity in chlorpromazine-treated GBM 8401 cells. Therefore, Ca²⁺ signaling was involved in chlorpromazine-induced cytotoxicity in GBM 8401 cells.

Pathogenesis and management of Brugada syndrome in schizophrenia: A scoping review

CONTEXT

Excess cardiovascular morbidity and an increased prevalence of sudden cardiac death (SCD) contributes to premature mortality in schizophrenia. Brugada syndrome (BrS) is an important but underrecognized cause of SCD. It is more commonly seen in schizophrenia than in general population controls.

METHODS

We conducted a scoping review to describe the pathogenesis of BrS in schizophrenia and to identify the psychotropic medications that increase the risk of unmasking BrS and associated ventricular arrhythmias resulting in SCD.

FINDINGS

Schizophrenia and BrS share similar calcium channel abnormalities, which may result in aberrant myocardial conductivity. It remains uncertain if there is a genetic pre-disposition for BrS in a subset of patients with schizophrenia. However, the unmasking of Brugada ECG patterns with the use of certain antipsychotics and antidepressants increases the risk of precipitating SCD, independent of QT prolongation.

CONCLUSIONS AND FUTURE DIRECTIONS

Specific cardiology assessment and interventions may be required for the congenital or unmasked Brugada ECG pattern in schizophrenia. The current long-term standard of care for BrS is an implantable cardioverter defibrillator (ICD), but post-implantation psychological effects must be considered. Careful use of antipsychotic and other psychotropic medications is necessary to minimize proarrhythmic effects due to impact on cardiac sodium and calcium ion channels. When prescribing such drugs to patients with schizophrenia, clinicians should be mindful of the potentially fatal unmasking of Brugada ECG patterns and how to manage it. We present recommendations for psychiatrists managing this patient population.