T202. THE EFFECT OF ANTIPSYCHOTIC DRUGS ON MEMBRANE FUSION: AN IN VITRO STUDY

• Published in: Schizophrenia bulletin 2020-05, Vol.46 (Supplement_1), p.S308-S309
• Main Authors: Adrien, Vladimir, Fumat, Hugo, Tessier, Cédric, Nuss, Philippe, Tareste, David
• Format: Article
• Language: English
• Subjects: Poster Session III
• ISSN: 0586-7614; 1745-1701
• DOI: 10.1093/schbul/sbaa029.762

Abstract Background Common clinical use of antipsychotics (AP) drugs shows that their therapeutic mode of action still needs further clarification although it is admitted that the Dopamine receptor D2 (D2R) antagonism plays a significant role. For instance, clozapine (CLOZ) - which is known to be the most effective AP in treating schizophrenic symptoms - has strikingly the lowest D2R antagonism. Non direct receptor-related effects might thus be involved in the activity of AP at the synapse level. AP, as well as neurotransmitters, are mostly lipophilic and insert within membranes. This characteristic is of interest as a significant proportion of schizophrenic patients has specific and abnormal membrane lipid composition. This possible proxy of the disease biotype can participate in the disease’s physiopathology but also be critical for the effect of AP drugs. We hypothesize that AP insertion into lipid membranes also contribute to their therapeutic effect. AP-induced modifications of synaptic membranes biophysics are likely to influence neurotransmission. In this study, we focus on the effect of AP on membrane fusion, a crucial step for the exocytosis of neurotransmitters. Methods Liposomes modelling synaptic vesicles were reconstituted in saline buffer. Two standard ternary and quaternary lipid mixtures have been studied: phosphatidylcholine:phosphatidylethanolamine:phosphatidylserine (PC:PE:PS) [65:25:10] and the synaptic-like PC:PE:PS:sphingomyelin:cholesterol (PC:PE:PS:SM:CHOL) [25:25:10:10:30]. Some liposomes were protein-free and others were functionalized with Soluble N-ethylmaleimide-sensitive-factor Attachment protein Receptor (SNARE) proteins, which trigger in vivo the fusion of synaptic vesicles with the pre-synaptic plasma membrane. The liposome size was checked by Dynamic Light Scattering. Insertion of AP within the membrane was checked by second derivative spectroscopy. Fusion was measured by Fluorescence Resonance Energy Transfer in the absence or presence of CLOZ or chlorpromazine (CPZ) at various lipid:AP ratios (10:1 to 100000:1). Protein-free liposomes were fused with Polyethylene glycol (PEG) and SNARE liposomes through the action of cognate SNARE proteins residing in their membrane. Results Liposomes of the same lipid composition were of the same size, with no effect of the addition of AP drugs at various concentrations. Molar partition coefficient of AP drugs within the membrane of protein-free liposomes was approximately 70–85%. CPZ o