Recent data described that patients with lysosomal storage disorders (LSDs) may have clinical schizophrenia (SCZ) features. Disruption of lipid metabolism in SCZ pathogenesis was found. Clinical features of schizophrenia (SCZ) have been demonstrated in patients with several lysosomal storage disorders (LSDs). Taking into account the critical role of lysosomal function for neuronal cells’ lysosomal dysfunction could be proposed in SCZ pathogenesis. The current study analyzed lysosomal enzyme activities and the alpha-synuclein level in the blood of patients with late-onset SCZ. In total, 52 SCZ patients with late-onset SCZ, 180 sporadic Parkinson’s disease (sPD) patients, and 176 controls were recruited. The enzymatic activity of enzymes associated with mucopolysaccharidosis (alpha-L-Iduronidase (IDUA)), glycogenosis (acid alpha-glucosidase (GAA)) and sphingolipidosis (galactosylceramidase (GALC), glucocerebrosidase (GCase), alpha-galactosidase (GLA), acid sphingomyelinase (ASMase)) and concentration of lysosphingolipids (hexosylsphingosine (HexSph), globotriaosylsphingosine (LysoGb3), and lysosphingomyelin (LysoSM)) were measured using LC-MS/MS. The alpha-synuclein level was estimated in magnetically separated CD45+ blood cells using the enzyme-linked immunosorbent assay (ELISA). Additionally, NGS analysis of 11 LSDs genes was conducted in 21 early-onset SCZ patients and 23 controls using the gene panel PGRNseq-NDD. Decreased ASMase, increased GLA activities, and increased HexSpn, LysoGb3, and LysoSM concentrations along with an accumulation of the alpha-synuclein level were observed in late-onset SCZ patients in comparison to the controls (p < 0.05). Four rare deleterious variants among LSDs genes causing mucopolysaccharidosis type I (IDUA (rs532731688, rs74385837) and type III (HGSNAT (rs766835582)) and sphingolipidosis (metachromatic leukodystrophy (ARSA (rs201251634)) were identified in five patients from the group of early-onset SCZ patients but not in the controls. Our findings supported the role of sphingolipid metabolism in SCZ pathogenesis. Aberrant enzyme activities and compounds of sphingolipids associated with ceramide metabolism may lead to accumulation of alpha-synuclein and may be critical in SCZ pathogenesis.

Introduction. Mutations in a GBA1 gene, which encodes a lysosomal enzyme called glucocerebrosidase (GCase), are the most common genetic risk factor for Parkinson's disease (PD). The pathogenesis of PD results from the death of dopaminergic neurons in the substantia nigra of the brain, which is associated with the aggregation of α-synuclein protein. However, not all GBA1 mutation carriers develop PD during their lifetime. The aim of this study was to evaluate GCase activity and α-synuclein levels in CD45+ blood cells of patients with PD associated with GBA1 mutations (GBА1-PD), asymptomatic carriers of GBA1 mutations (GBА1-carriers), and patients with sporadic PD (sPD), as well as correlation between the study parameters in the study groups. Materials and methods. The study included patients with GBА1-PD (n = 25) and sPD (n = 147), and GBА1-carriers (n = 16). A control group included healthy volunteers (n = 154). The level of α-synuclein in CD45+ cells was measured by enzyme-linked immunosorbent assay, and GCase activity in dried blood spots was detected by high-performance liquid chromatography with tandem mass spectrometry. Results. Increased level of α-synuclein protein was detected in CD45+ blood cells of patients with GBA1-PD, sPD, and GBA1-carriers compared to controls (p = 0.0043; p = 0.0002; p = 0.032, respectively). Decreased GCase activity was reported in GBA1-PD patients and GBA1-carriers compared to sPD patients (p = 0.0003; p = 0.003, respectively) and controls (p 0.0001; p 0.0001, respectively). However, negative correlation between α-synuclein levels and GCase activity was observed only in GBA1-PD patients, but not in GBA1-carriers. Conclusion. Our data suggest a possible functional relationship between the activity of GCase and the metabolism of α-synuclein in PD associated with GBA1 mutations.

В настоящем исследовании проведена оценка уровня мРНК и белка генов SNCA, DNMT1, а также степени метилирования интрона 1 гена SNCA в CD45+ клетках периферической крови пациентов со спорадической болезнью Паркинсона (БП) и индивидуумов контрольной группы. Впервые было выявлено снижение концентрации белка DNMT1 в CD45+ клетках периферической крови пациентов с БП по сравнению с группой контроля. Обнаружено увеличение уровня мРНК гена DNMT1 у пациентов с БП по сравнению с контролем. Не выявлено статистически значимых различий при сравнении степени метилирования интрона 1 гена SNCA в CD45+ клетках периферической крови пациентов с БП и контроля. В группе контроля выявлена обратная корреляция степени метилирования отдельных CpG островков с концентрацией белка альфа-синуклеина и уровнем мРНК гена SNCA. Проведенное исследование позволяет предположить участие гена DNMT1 в патогенезе БП и отсутствие ассоциации степени метилирования интрона 1 гена SNCA с БП. The aim of this study was to assess the level of mRNA and protein of the SNCA, DNMT1 genes, as well as intron 1 methylation of the SNCA gene in CD45 + peripheral blood cells of patients with sporadic PD and control individuals. For the first time, a decrease in the concentration of DNMT1 protein in CD45 + peripheral blood cells from PD patients compare to controls was revealed. An increase in DNMT1 gene expression in PD patients compare to controls was found. No differences in intron 1 methylation of the SNCA gene in CD45 + peripheral blood cells was found between PD patients and controls. An inverse correlations between methylation level of 21, 22 CpG island in intron1 of SNCA gene and mRNA SNCA gene and alpha-synuclein protein level were found. The study suggests the involvement of DNMT1 in the pathogenesis of PD and the lack of association of PD with intron 1 methylation of the SNCA gene.

To date, we and others have demonstrated that GBA1-associated Parkinson’s disease (GBA1-PD) exhibits hyperactivation of mTOR and impairment of mTOR-regulated autophagy. Our previous study showed that the degree of autophagy impairment depends on the type of GBA1 mutation in peripheral blood mononuclear cell (PBMC)-derived macrophages. Moreover, the type of GBA1 mutation (“mild”—e.g., p.N370S or “severe”—e.g., p.L444P) correlates with PD severity and may influence therapeutic response. Here, we investigated the dose-dependent effects of GCase inhibition by conduritol β-epoxide (CBE) in SH-SY5Y cells on mTOR signaling, as well as the effects of mTOR inhibition by Torin 1 on mTOR-dependent autophagy-related proteins, lysosomal morphology, and lysosomal hydrolase activities in PBMC-derived macrophages from PD patients carrying GBA1-L444P or GBA1-N370S mutations. CBE induced dose-dependent activation of mTOR signaling in SH-SY5Y, as evidenced by dose-dependent accumulation of p-RPS6 (Ser235/236). mTOR inhibition decreased Beclin-1 protein levels while increasing the LC3B-II/LC3B-I ratio, LC3B–lysosome colocalization, and lysosome number regardless of mutation type in PBMC-derived macrophages. However, Torin1 reduced p62 levels in GBA1-N370S-PD, whereas lysosomal size decreased in GBA1-L444P-PD. Interestingly, Torin 1 increased GCase activity in both patient groups. These findings suggest that mTOR inhibition restores GCase function and autophagy and may represent a potential therapeutic strategy for GBA1-PD.

Mutations in the GBA1 gene, encoding lysosomal β-glucocerebrosidase (GCase), cause Gaucher disease (GD) and represent the most common genetic risk factor for Parkinson’s disease (PD). To target this pathway, therapeutic approaches for both GD and PD are actively being developed, focusing on two main drug classes: pharmacological chaperones (e.g., ambroxol) and allosteric GCase activators. Here, we characterize a novel allosteric GCase activator, N2, a derivative of the non-inhibitory chaperone NCGC607, and evaluate its therapeutic potential using computational, in vitro, and in vivo approaches. Molecular docking and molecular dynamics simulations indicated that N2 binds within the allosteric site of the mutant p.N370S GCase structure. In patient-derived cells (peripheral blood mononuclear cell-derived macrophages and induced pluripotent stem cell-derived dopaminergic neurons from GD and GBA1-PD patients), N2 enhanced GCase lysosomal translocation, modulated its enzymatic activity and protein level, and reduced substrate accumulation. Furthermore, we demonstrate for the first time that N2 exerts robust neuroprotective effects in an in vivo 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model of PD. Specifically, N2 treatment attenuated MPTP-induced hexosylsphingosine accumulation in the prefrontal cortex, and ameliorated both tyrosine hydroxylase-positive neuronal loss in the substantia nigra and dopamine depletion in the striatum. Our findings first demonstrated the neuroprotective properties of a GCase allosteric activator on an MPTP-induced mouse model of PD and supported the emerging perspectives of such compounds for the treatment of GCase-related disorders.