Brain Natriuretic Peptide as a Biomarker of Asymptomatic Clozapine-Related Heart Dysfunction: A Criterion for a More Cautious Administration.

Clozapine-related pericarditis is a rare side effect of the drug. We reported the clinical cases of two women, aged 22 and 28 years, affected by schizophrenia with pericarditis symptoms related to clozapine treatment of 200 mg/day. Clozapine was discontinued in both patients, resulting in normalization of the ECG changes, and echocardiography confirmed the progressive disappearance of the pericardial effusion. Interestingly, while inflammatory indices and pro-brain natriuretic peptide (pro-BNP) plasma levels were high in both patients, only one of them showed tachycardia, subjective chest pain, shortness of breath and dyspnea, with a clinical symptomatology suggesting a cardiac involvement. BNP is a vasoactive peptide synthetized by the ventricular myocardium which splits in two fragments: BNP and the N-terminal (pro-BNP). Both are considered valuable biomarkers in clinical practice for the prediction of disease state and prognosis in patients with suspected heart failure. Pro-BNP acts as a key regulator in the homeostasis of water and salt excretion and in the maintenance of blood pressure, mainly by inhibiting the renin-angiotensin-aldosterone axis and blocking the sympathetic nervous activity. In our cases, pro-BNP plasma levels proved to be a profitable way to identify subjects with asymptomatic cardiac impairment who could benefit from a therapy preventing progression to heart failure.

Pattern of acute induction of Homer1a gene is preserved after chronic treatment with first- and second-generation antipsychotics: effect of short-term drug discontinuation and comparison with Homer1a-interacting genes.

Homer1a is a glutamate-related gene whose expression is induced by antipsychotics acutely (i.e. 90 min after treatment). Acute Homer1a expression is preserved after prolonged antipsychotic treatments, while the effects of short-term discontinuation after chronic antipsychotic treatment have not yet been assessed. Here, we studied early and long-term effects on gene expression by antipsychotics for Homer1a and other components of glutamatergic synapses. In the first paradigm, we evaluated Homer1a acute expression by single administration of antipsychotics (haloperidol 0.8 mg/kg, ziprasidone 10 and 4 mg/kg, clozapine 15 mg/kg). Haloperidol and ziprasidone induced Homer1a in the striatum. Induction by ziprasidone was dose-dependent. These results suggest that acute Homer1a expression correlates with dopaminergic affinity and motor side effects of antipsychotics. In the second paradigm, we studied antipsychotic-mediated long-term changes in Homer1a and glutamate-related genes. Rats were treated (21 days) with haloperidol 0.8 mg/kg, ziprasidone 4 mg/kg, or vehicle, and then sacrificed at 90 min (early time-point) or 24 h (delayed time-point) after last injection. Gene expression at these two time-points was compared. Homer1a preserved its pattern of expression at the early but not at the delayed time-point. Significant changes were also observed for PSD-95. The results suggest that Homer1a preserves its expression profile after chronic antipsychotics.

Haloperidol induces higher Homer1a expression than risperidone, olanzapine and sulpiride in striatal sub-regions.

Homer1a and Yotiao are two post-synaptic density proteins at the crossroad of dopamine-glutamate neurotransmission. Homer1a has been implicated in the pathophysiology of schizophrenia and is differentially induced by typical and atypical antipsychotics, perhaps according to their dopaminergic profile. Yotiao has been involved in glutamate and dopamine post-synaptic signalling. Here, we seek to determine whether Homer1a and Yotiao might be implicated in post-synaptic response to antipsychotics with affinity to different dopamine D(2) receptors: haloperidol (0.8mg kg(-1)), risperidone (3mg kg(-1)), olanzapine (2.5mg kg(-1)) and (-)-sulpiride (50mg kg(-1)). Homer1a expression was significantly induced by haloperidol compared to vehicle and to atypical antipsychotics in almost all striatal sub-regions. Atypical antipsychotics induced the gene in the lateral putamen and in the core of the accumbens only. All antipsychotics, with the exclusion of sulpiride, elicited a dorsolateral-to-ventromedial distribution pattern of Homer1a expression. No significant induction was detected for Yotiao. These results suggest that the quantitative and topographical pattern of Homer1a expression may putatively be related to antipsychotics affinity and/or occupancy at dopamine D(2) receptors.

Postsynaptic density scaffolding proteins at excitatory synapse and disorders of synaptic plasticity: implications for human behavior pathologies.

Excitatory synapses are characterized by an electron-dense thickening at the cytoplasmic surface of the postsynaptic membrane, called the postsynaptic density (PSD). The PSD is a fibrous specialization of the submembrane cytoskeleton approximately 30-40 nm thick and about 100 nm wide. Hundreds of molecules have been identified in the PSD: ion-gated and G-protein-coupled receptors, association, adaptors, and scaffolding proteins, key enzymes involved in phosphorylation-dephosphorylation mechanisms, and cytoskeletal proteins. Each of these proteins may have a pivotal function in setting the molecular scenario for the development of synaptic plasticity. Scaffolding proteins are major players in the organization of the postsynaptic signal transduction machinery,they regulate receptor trafficking and clustering, modulate axon pathfinding,and drive the correct targeting of neuronal proteins to their appropriate cytoplasmic compartment. Emerging findings suggest a relevant involvement of PSD scaffolding/adaptor proteins in behavior modulation in animal models of synaptic plasticity disorders and pharmacological isomorphisms.