Toxicoproteomics reveals an effect of clozapine on autophagy in human liver spheroids.

Background: Clozapine is an atypical antipsychotic drug used to treat treatment-resistant schizophrenia. Its side effects, including liver enzyme abnormalities, experienced by many patients preclude its more common use as a first-line therapy for schizophrenia. Toxicoproteomic approaches have been demonstrated to effectively guide the identification of toxicological mechanisms.Methods: To further our understanding of the molecular effects of clozapine, we performed a data-independent acquisition (DIA)-based quantitative proteomics investigation of clozapine-treated human liver spheroid cultures.Results: In total, we quantified 4479 proteins across the five treatment groups (vehicle; 15 µM, 30 µM, and 60 µM clozapine; and 10 ng/mL TNFα + IL-1ß). Clozapine (60 µM) treatment yielded 36 differentially expressed proteins (FDR < 0.05). Gene-set enrichment analysis indicated perturbation of several gene sets, including interferon gamma signaling (e.g. interferon gamma receptor 1) and prominent autophagy-related processes (e.g. upregulation of sequestosome-1 (SQSTM1), MAP1LC3B/LC3B2, GABARAPL2, and nuclear receptor coactivator 4). The effects of clozapine on autophagy were confirmed by targeted mass spectrometry and western blotting using conventional SQSTM1 and LC3B markers.Conclusions: Combined with prior literature, our work suggests a broad contribution of autophagy to both the therapeutic and side effects of clozapine. Overall, this study demonstrates how proteomics can contribute to the elucidation of physiological and toxicological mechanisms of drugs.

Cystoid maculopathy is a frequent feature of Cohen syndrome-associated retinopathy.

Cohen syndrome (CS) is a rare syndromic form of rod-cone dystrophy. Recent case reports have suggested that cystoid maculopathy (CM) could affect CS patients with an early onset and high prevalence. Our study aims at improving our understanding and management of CM in CS patients through a retrospective case series of ten CS patients with identified pathogenic variants in VPS13B. Longitudinal optical coherence tomography (OCT) imaging was performed and treatment with carbonic anhydrase inhibitors (CAI) was provided to reduce the volume of cystoid spaces. CM affected eight out of ten patients in our cohort. The youngest patient showed a strong progression of macular cysts from the age of 4.5 to 5 years despite oral CAI medication. Other teenage and young adult patients showed stable macular cysts with and without treatment. One patient showed a moderate decrease of cystoid spaces in the absence of treatment at 22 years of age. Through a correlative analysis we found that the volume of cystoid spaces was positively correlated to the thickness of peripheral and macular photoreceptor-related layers. This study suggests that CAI treatments may not suffice to improve CM in CS patients, and that CM may resolve spontaneously during adulthood as photoreceptor dystrophy progresses.

Cohen Syndrome-Associated Cataract Is Explained by VPS13B Functions in Lens Homeostasis and Is Modified by Additional Genetic Factors.

Purpose: Cohen syndrome (CS) is a rare genetic disorder caused by variants of the VPS13B gene. CS patients are affected with a severe form of retinal dystrophy, and in several cases cataracts also develop. The purpose of this study was to investigate the mechanisms and risk factors for cataract in CS, as well as to report on cataract surgeries in CS patients. Methods: To understand how VPS13B is associated with visual impairments in CS, we generated the Vps13b∆Ex3/∆Ex3 mouse model. Mice from 1 to 3 months of age were followed by ophthalmoscopy and slit-lamp examinations. Phenotypes were investigated by histology, immunohistochemistry, and western blot. Literature analysis was performed to determine specific characteristic features of cataract in CS and to identify potential genotype-phenotype correlations. Results: Cataracts rapidly developed in 2-month-old knockout mice and were present in almost all lenses at 3 months. Eye fundi appeared normal until cataract development. Lens immunostaining revealed that cataract formation was associated with the appearance of large vacuoles in the cortical area, epithelial-mesenchymal transition, and fibrosis. In later stages, cataracts became hypermature, leading to profound retinal remodeling due to inflammatory events. Literature analysis showed that CS-related cataracts display specific features compared to other forms of retinitis pigmentosa-related cataracts, and their onset is modified by additional genetic factors. Corroboratively, we were able to isolate a subline of the Vps13b∆Ex3/∆Ex3 model with delayed cataract onset. Conclusions: VPS13B participates in lens homeostasis, and the CS-related cataract development dynamic is linked to additional genetic factors.