Antipsychotic induced alteration of growth and proteome of rat neural stem cells

Proteomic Analysis of Plasma Markers in Patients Maintained on Antipsychotics: Comparison to Patients Off Antipsychotics and Normal Controls

BACKGROUND

Schizophrenia (SZ) and bipolar disorder (BD) share many features: overlap in mood and psychotic symptoms, common genetic predisposition, treatment with antipsychotics (APs), and similar metabolic comorbidities. The pathophysiology of both is still not well defined, and no biomarkers can be used clinically for diagnosis and management. This study aimed to assess the plasma proteomics profile of patients with SZ and BD maintained on APs compared to those who had been off APs for 6 months and to healthy controls (HCs).

METHODS

We analyzed the data using functional enrichment, random forest modeling to identify potential biomarkers, and multivariate regression for the associations with metabolic abnormalities.

RESULTS

We identified several proteins known to play roles in the differentiation of the nervous system like NTRK2, CNTN1, ROBO2, and PLXNC1, which were downregulated in AP-free SZ and BD patients but were "normalized" in those on APs. Other proteins (like NCAM1 and TNFRSF17) were "normal" in AP-free patients but downregulated in patients on APs, suggesting that these changes are related to medication's effects. We found significant enrichment of proteins involved in neuronal plasticity, mainly in SZ patients on APs. Most of the proteins associated with metabolic abnormalities were more related to APs use than having SZ or BD. The biomarkers identification showed specific and sensitive results for schizophrenia, where two proteins (PRL and MRC2) produced adequate results.

CONCLUSIONS

Our results confirmed the utility of blood samples to identify protein signatures and mechanisms involved in the pathophysiology and treatment of SZ and BD.

Proteome Analysis of PC12 Cells Reveals Alterations in Translation Regulation and Actin Signaling Induced by Clozapine

Although antipsychotics are routinely used in the treatment of schizophrenia for the last decades, their precise mechanism of action is still unclear. In this study, we investigated changes in the PC12 cells’ proteome under the influence of clozapine, risperidone, and haloperidol to identify protein pathways regulated by antipsychotics. Analysis of the protein profiles in two time points: after 12 and 24 h of incubation with drugs revealed significant alterations in 510 proteins. Further canonical pathway analysis revealed an inhibition of ciliary trophic factor signaling after treatment with haloperidol and showed a decrease in acute phase response signaling in the risperidone group. Interestingly, all tested drugs have caused changes in PC12 proteome which correspond to inhibition of cytokines: tumor necrosis factor (TNF) and transforming growth factor beta 1 (TGF-β1). We also found that the 12-h incubation with clozapine caused up-regulation of protein kinase A signaling and translation machinery. After 24 h of treatment with clozapine, the inhibition of the actin cytoskeleton signaling and Rho proteins signaling was revealed. The obtained results suggest that the mammalian target of rapamycin complex 1 (mTORC1) and 2 (mTORC2) play a central role in the signal transduction of clozapine.

Exposure of Rat Neural Stem Cells to Ethanol Affects Cell Numbers and Alters Expression of 28 Proteins

Developing brain cells express many proteins but little is known of how their protein composition responds to chronic exposure to alcohol and/or how such changes might relate to alcohol toxicity. We used cultures derived from embryonic rat brain (previously shown to contain mostly neural stem cells; rat NSC, rNSC), exposed them to ethanol (25-100 mM) for up to 96 h and studied how they reacted. Ethanol (50 and 100 mM) reduced cell numbers indicating either compromised cell proliferation, cytotoxicity or both. Increased lipid peroxidation was consistent with the presence of oxidative stress accompanying alcohol-induced cytotoxicity. Proteomics revealed 28 proteins as altered by ethanol (50 mM for 96 h). Some were constituents of cytoskeleton, others were involved in transcription/translation, signal transduction and oxidative stress. Nucleophosmin (NPM1) and dead-end protein homolog 1 (DND1) were further studied by immunological techniques in cultured neurons and astrocytes (derived from brain tissue at embryonic ages E15 and E20, respectively). In the case of DND1 (but not NPM1) ethanol induced similar pattern of changes in both types of cells. Given the critical role of the protein NPM1 in cell proliferation and differentiation, its reduced expression in the ethanol-exposed rNSC could, in part, explain the lower cells numbers. We conclude that chronic ethanol profoundly alters protein composition of rNSC to the extent that their functioning-including proliferation and survival-would be seriously compromised. Translated to humans, such changes could point the way towards mechanisms underlying the fetal alcohol spectrum disorder and/or alcoholism later in life.

Effect of MK-801 and Clozapine on the Proteome of Cultured Human Oligodendrocytes

Separate lines of evidence have demonstrated the involvement of N-methyl-D-aspartate (NMDA) receptor and oligodendrocyte dysfunctions in schizophrenia. Here, we have carried out shotgun mass spectrometry proteome analysis of oligodendrocytes treated with the NMDA receptor antagonist MK-801 to gain potential insights into these effects at the molecular level. The MK-801 treatment led to alterations in the levels of 68 proteins, which are associated with seven distinct biological processes. Most of these proteins are involved in energy metabolism and many have been found to be dysregulated in previous proteomic studies of post-mortem brain tissues from schizophrenia patients. Finally, addition of the antipsychotic clozapine to MK-801-treated oligodendrocyte cultures resulted in changes in the levels of 45 proteins and treatment with clozapine alone altered 122 proteins and many of these showed opposite changes to the MK-801 effects. Therefore, these proteins and the associated energy metabolism pathways should be explored as potential biomarkers of antipsychotic efficacy. In conclusion, MK-801 treatment of oligodendrocytes may provide a useful model for testing the efficacy of novel treatment approaches.

Employing proteomics to unravel the molecular effects of antipsychotics and their role in schizophrenia

Schizophrenia is an incurable neuropsychiatric disorder managed mostly by treatment of the patients with antipsychotics. However, the efficacy of these drugs has remained only low to moderate despite intensive research efforts since the early 1950s when chlorpromazine, the first antipsychotic, was synthesized. In addition, antipsychotic treatment can produce often undesired severe side effects in the patients and addressing these remains a large unmet clinical need. One of the reasons for the low effectiveness of these drugs is the limited knowledge about the molecular mechanisms of schizophrenia, which impairs the development of new and more effective treatments. Recently, proteomic studies of clinical and preclinical samples have identified changes in the levels of specific proteins in response to antipsychotic treatment, which have converged on molecular pathways such as cell communication and signaling, inflammation and cellular growth, and maintenance. The findings of these studies are summarized and discussed in this review and we suggest that this provides validation of proteomics as a useful tool for mining drug mechanisms of action and potentially for pinpointing novel molecular targets that may enable development of more effective medications.

Stathmin reduction and cytoskeleton rearrangement in rat nucleus accumbens in response to clozapine and risperidone treatment - Comparative proteomic study

The complex network of anatomical connections of the nucleus accumbens (NAc) makes it an interface responsible for the selection and integration of cognitive and affective information to modulate appetitive or aversively motivated behaviour. There is evidence for NAc dysfunction in schizophrenia. NAc also seems to be important for antipsychotic drug action, but the biochemical characteristics of drug-induced alterations within NAc remain incompletely characterized. In this study, a comprehensive proteomic analysis was performed to describe the differences in the mechanisms of action of clozapine (CLO) and risperidone (RIS) in the rat NAc. Both antipsychotics influenced the level of microtubule-regulating proteins, i.e., stathmin, and proteins of the collapsin response mediator protein family (CRMPs), and only CLO affected NAD-dependent protein deacetylase sirtuin-2 and septin 6. Both antipsychotics induced changes in levels of other cytoskeleton-related proteins. CLO exclusively up-regulated proteins involved in neuroprotection, such as glutathione synthetase, heat-shock 70-kDa protein 8 and mitochondrial heat-shock protein 75. RIS tuned cell function by changing the pattern of post-translational modifications of some proteins: it down-regulated the phosphorylated forms of stathmin and dopamine and the cyclic AMP-regulated phosphoprotein (DARPP-32) isoform but up-regulated cyclin-dependent kinase 5 (Cdk5). RIS modulated the level and phosphorylation state of synaptic proteins: synapsin-2, synaptotagmin-1 and adaptor-related protein-2 (AP-2) complex.

Proteome effects of antipsychotic drugs: Learning from preclinical models

Proteome-wide expression analyses are performed in the brain of schizophrenia patients to understand the biological basis of the disease and discover molecular paths for new clinical interventions. A major issue with postmortem analysis is the lack of tools to discern molecular modulation related to the disease from dysregulation due to medications. We review available proteome-wide analysis of antipsychotic treatment in rodents, highlighting shared dysregulated pathways that may contribute to an extended view of molecular processes underlying their pharmacological activity. Fourteen proteomic studies conducted with typical and atypical antipsychotic treatments were examined; hypothesis-based approaches are also briefly discussed. Treatment with antipsychotics mainly affects proteins belonging to metabolic pathways involved in energy generation, both in glycolytic and oxidative phosphorylation pathways, suggesting antipsychotics-induced impairments in metabolism. Nevertheless, schizophrenic patients show impaired glucose metabolism and mitochondrial dysfunctions independent of therapy. Other antipsychotics-induced changes shared by different studies implicate cytoskeletal and synaptic function proteins. The mechanism can be related to the reorganization of dendritic spines resulting from neural plasticity events induced by treatments affecting neurotransmitter circuitry. However, metabolic and plasticity pathways activated by antipsychotics can also play an authentic role in the etiopathological basis of schizophrenia.

Novel action of metformin in the prevention of haloperidol-induced catalepsy in mice: Potential in the treatment of Parkinson's disease?

Metformin is widely used to treat type II diabetes and other metabolic syndromes. In addition, it has been shown to increase neurogenesis, spatial memory formation and reduce the risk of Parkinson's disease. On this basis, the aim of the present study was the investigation of the protective potential of metformin in the haloperidol-induced catalepsy model of Parkinson's disease in mice. The effect of metformin (20 - 100mg/kg, p.o) on motor coordination was assessed using rotarod and forced swimming tests (FST), while the effect on memory function was evaluated using the Y-maze test. The neuroprotective activity was investigated in acute/chronic (21days) haloperidol-induced catalepsy in mice. On the 21st day, biochemical estimation of nitrosative and oxidative stress parameters was carried out. Metformin (50 or 100mg/kg, p.o.) did not affect motor coordination in rotarod test and FST but significantly reversed haloperidol-induced memory deficit (+35.50%) at 100mg/kg. Importantly, metformin significantly reduced the duration of catalepsy score during acute and chronic catalepsy tests as compared to trihexylphenidyl (reference standard). Intraperitoneal chronic injection of haloperidol (1mg/kg) significantly increased malondialdehyde and nitrite levels, while it significantly attenuated the activity of reduced glutathione, catalase and superoxide dismutase. Moreover, oral chronic administration of metformin significantly attenuated the haloperidol-induced increase of malondialdehyde and nitrite, as well as the deficit of glutathione and catalase. These findings suggest that metformin protects against haloperidol-induced catalepsy through inhibition of oxidative/nitrosative stress and has the potential for adjuvant action in the management of Parkinson's disease.

Recent advances in quantitative neuroproteomics

The field of proteomics is undergoing rapid development in a number of different areas including improvements in mass spectrometric platforms, peptide identification algorithms and bioinformatics. In particular, new and/or improved approaches have established robust methods that not only allow for in-depth and accurate peptide and protein identification and modification, but also allow for sensitive measurement of relative or absolute quantitation. These methods are beginning to be applied to the area of neuroproteomics, but the central nervous system poses many specific challenges in terms of quantitative proteomics, given the large number of different neuronal cell types that are intermixed and that exhibit distinct patterns of gene and protein expression. This review highlights the recent advances that have been made in quantitative neuroproteomics, with a focus on work published over the last five years that applies emerging methods to normal brain function as well as to various neuropsychiatric disorders including schizophrenia and drug addiction as well as of neurodegenerative diseases including Parkinson's disease and Alzheimer's disease. While older methods such as two-dimensional polyacrylamide electrophoresis continued to be used, a variety of more in-depth MS-based approaches including both label (ICAT, iTRAQ, TMT, SILAC, SILAM), label-free (label-free, MRM, SWATH) and absolute quantification methods, are rapidly being applied to neurobiological investigations of normal and diseased brain tissue as well as of cerebrospinal fluid (CSF). While the biological implications of many of these studies remain to be clearly established, that there is a clear need for standardization of experimental design and data analysis, and that the analysis of protein changes in specific neuronal cell types in the central nervous system remains a serious challenge, it appears that the quality and depth of the more recent quantitative proteomics studies is beginning to shed light on a number of aspects of neuroscience that relates to normal brain function as well as of the changes in protein expression and regulation that occurs in neuropsychiatric and neurodegenerative disorders.

Translational strategies to schizophrenia from a proteomic perspective

There is an urgent necessity of designing translational strategies to schizophrenia, a mental disorder that affects 30 million people worldwide. Proteomic studies have been providing data enough to pave the way for that, but these need to be connected in a concise manner in order to translate laboratorial findings to real improvements in the lives of the patients.

Translational strategies to schizophrenia from a proteomic perspective

There is an urgent necessity of designing translational strategies to schizophrenia, a mental disorder that affects 30 million people worldwide. Proteomic studies have been providing data enough to pave the way for that, but these need to be connected in a concise manner in order to translate laboratorial findings to real improvements in the lives of the patients.