The Distinguish Effects And Underlying Mechanisms Of Antipsychotic Drugs On Differentiation And Myelination Of Oligodendroglia

Myelin sheaths, formed by oligodendrocytes (OLs), play essential roles in the centralnervous system (CNS), on facilitating neural transmission, maintaining insulation shieldingand providing nutrition for neuron axons. The myelin-forming OLs derive from theoligodendrocyte progenitor cells (OPCs) and undergo a series of developmental processes,including myelin-specific gene expression and the essential morphological transformation,prior to attaining its mature myelinating phenotype, i.e., myelin sheet formation. Recentstudies demonstrated that impaired OPC development and/or inhibition of re-myelination mayresult in demyelinating diseases as well as neural disorders. Thus, facilitating oligodendrocytefunction in myelination has been hypothesized to be a potential therapeutic approach in thetreatment against myelin-related neural disorders, such as schizophrenia.Currently, antipsychotic medication is widely used as first-line clinical treatmentapproach. The first-generation (aka typical) antipsychotic drugs, such as haloperidol (HAL),play different role versus the second-generation (aka atypical) antipsychotics, such asquetiapine (QUE), in the progress of spontaneous remyeliantion. Here, we demonstrated forthe first time that these two categories of antipsychotics have distinguished effects on thedifferentiation of OPCs, i.e., QUE promotes while HAL inhibits differentiation of OPCs albeitthe underlying mechanism remains largely unclear.Recently, the crucial manipulatory roles of transcriptional regulation in the generation ofoligodendroglial lineage cells and in the processes of OPCs differentiate into maturemyelin-forming OLs have been evaluated. In particular, the basic helix-loop-helixtranscription factor, Olig1, was identified to play essential roles in the terminal maturation ofoligodendrocytes while the molecular basis for Olig1function keeps unknown. In our study,we found that treatment of QUE promotes OPC differentiation and Olig1translocalization,evidenced by that Olig1translocation into the cytosol highly correlates with thedifferentiation of oligodendrocytes. Further, we illustrated for the first time that phosphorylation of Olig1play a novel role in the morphological transformation ofoligodendroglia. The phosphorylated Olig1localizes in cytosol that promotes processoutgrowth and myelination, whereas the non-phosphorylated Olig1enriches in nuclei tofacilitate expression of MBP.This investigation is composed of four parts:Part1: Establishment of a highly efficient and economical culture approach forenrichment of purified OPCsWe developed a simplified highly efficient approach to produce a high yield of purifiedOPCs at a low expense with following features:1. B104-conditioned medium, combined with adopted culture paradigm, was used as amitogenic source for OPC propagation,2. Two modified media were used for enriching OPCs at an early-stage of the mixed glialcultures and for promoting cell detach in isolation.3. A two-step chemical-based isolation procedure was used to increase the yield ofpurified OPCs.Part2: Comparative study of two kinds of antipsychotics on the development ofOligodendrogliaThis part aims to clarify the effects of two kinds of antipsychotic drugs, HAL and QUE,on the development of oligodendroglia by using animal development models, in vitro pureOPC culture as well as co-culture models. We found that:1. HAL promotes the proliferation but inhibits the differentiation and process outgrowthof OPC.2. QUE specifically promotes the differentiation and myelination of OPC, but has noeffect on the OPC proliferation.These results revealed that different kinds of antipsychotic drugs play distinguish roles indevelopment of oligodendroglia. QUE can specifically enhance the potential capacity ofmyelination, and may become a novel therapeutic target for treatment in re-myelination. Part3: Mechanisms underlying the promotive effect of QUE on differentiation andmyelination of oligodendrogliaIn this part, we performed micro array and bioinformatics analysis and screened geneexpression changes on transcription factors after QUE treatment, in both in vivo and in vitromodels, to investigate the effect of QUE on the regulation of Olig1. We found that:1. QUE up-regulates the expression level of Olig1.2. QUE promotes the translocalization of Olig1.These results suggest that QUE promote OPC differentiation might via activation ofMAPK (ERK1/2) pathway and translocalization of Olig1.Part4: Phosphorylation of transcription factor Olig1regulates differentiation andmyelination of oligodendrogliaWe evaluate the process, in both in vivo and in vitro models, by which Olig1translocatesto cytosol and this process-related Olig1function in the differentiation and myelination ofoligodendrocyte. We showed:1. The phosphorylation status of Olig1is correlated with its subcellular localization.2. The phosphorylation status of Serine-138determines its subcellular localization ofOlig1and specifies function of oligodendrocyte.3. The nuclear Olig1facilitates the myelin gene expression while cytosolic Olig1contributes to the membrane expansion and process outgrowth.These results revealed a novel role of phosphorylated cytosolic Olig1in membraneexpansion and maturation of oligodendrocytes; it also provided potential new therapeuticapproaches to promote remyelination after injury and/or disease.In summary, we have identified the different roles of two kinds of antipsychoticdrugs, QUE and HAL, on the development of OLs. We demonstrated that atypicalantipsychotic drug QUE promotes the phosphorylation and subcellular trans-localization ofOlig1, then consequently facilitates the membrane expansion and maturation ofoligodendrocytes. The novel effect and underlying mechanism of QUE on the development ofoligodendroglia revealed in our study provides a new insight into the pathogenesis ofschizophrenia therapeutic that may lead to a new therapeutic strategy against demyelination disease.