Trametinib, an anti-tumor drug, promotes oligodendrocytes generation and myelin formation.

Oligodendrocytes (OLs) are differentiated from oligodendrocyte precursor cells (OPCs) in the central nervous system (CNS). Demyelination is a common feature of many neurological diseases such as multiple sclerosis (MS) and leukodystrophies. Although spontaneous remyelination can happen after myelin injury, nevertheless, it is often insufficient and may lead to aggravated neurodegeneration and neurological disabilities. Our previous study has discovered that MEK/ERK pathway negatively regulates OPC-to-OL differentiation and remyelination in mouse models. To facilitate possible clinical evaluation, here we investigate several MEK inhibitors which have been approved by FDA for cancer therapies in both mouse and human OPC-to-OL differentiation systems. Trametinib, the first FDA approved MEK inhibitor, displays the best effect in stimulating OL generation in vitro among the four MEK inhibitors examined. Trametinib also significantly enhances remyelination in both MOG-induced EAE model and LPC-induced focal demyelination model. More exciting, trametinib facilitates the generation of MBP+ OLs from human embryonic stem cells (ESCs)-derived OPCs. Mechanism study indicates that trametinib promotes OL generation by reducing E2F1 nuclear translocation and subsequent transcriptional activity. In summary, our studies indicate a similar inhibitory role of MEK/ERK in human and mouse OL generation. Targeting the MEK/ERK pathway might help to develop new therapies or repurpose existing drugs for demyelinating diseases.

The aminosteroid U73122 promotes oligodendrocytes generation and myelin formation.

Oligodendrocytes (OLs) are glial cells that ensheath neuronal axons and form myelin in the central nervous system (CNS). OLs are differentiated from oligodendrocyte precursor cells (OPCs) during development and myelin repair, which is often insufficient in the latter case in demyelinating diseases such as multiple sclerosis (MS). Many factors have been reported to regulate OPC-to-OL differentiation, including a number of G protein-coupled receptors (GPCRs). In an effort to search pathways downstream of GPCRs that might be involved in OPC differentiation, we discover that U73122, a phosphoinositide specific phospholipase C (PI-PLC) inhibitor, dramatically promotes OPC-to-OL differentiation and myelin regeneration in experimental autoimmune encephalomyelitis model. Unexpectedly, U73343, a close analog of U73122 which lacks PI-PLC inhibitory activity also promotes OL differentiation, while another reported PI-PLC inhibitor edelfosine does not have such effect, suggesting that U73122 and U73343 enhance OPC differentiation independent of PLC. Although the structures of U73122 and U73343 closely resemble 17ß-estradiol, and both compounds do activate estrogen receptors Erα and Erß with low efficacy and potency, further study indicates that these compounds do not act through Erα and/or Erß to promote OPC differentiation. RNA-Seq and bioinformatic analysis indicate that U73122 and U73343 may regulate cholesterol biosynthesis. Further study shows both compounds increase 14-dehydrozymostenol, a steroid reported to promote OPC differentiation, in OPC culture. In conclusion, the aminosteroids U73122 and U73343 promote OPC-to-OL generation and myelin formation by regulating cholesterol biosynthesis pathway.

The orphan G protein-coupled receptor GPR149 is a negative regulator of myelination and remyelination.

Myelin sheath, formed by oligodendrocytes (OLs) in the central nervous system (CNS) and Schwann cells in periphery, plays a critical role in supporting neuronal functions. OLs, differentiated from oligodendrocyte precursor cells (OPCs), are important for myelination during development and myelin repair in CNS demyelinating disease. To identify mechanisms of myelin development and remyelination after myelin damage is of great clinical interest. Here we show that the orphan G protein-coupled receptor GPR149, enriched in OPCs, negatively regulate OPC to OL differentiation, myelination, as well as remyelination. The expression of GPR149 is downregulated during OPCs differentiation into OLs. GPR149 deficiency does not affect the number of OPCs, but promotes OPC to OL differentiation which results in earlier development of myelin. In cuprizone-induced demyelination model, GPR149 deficiency significantly enhances myelin regeneration. Further study indicates that GPR149 may regulate OL differentiation and myelin formation via MAPK/ERK pathway. Our study suggests that deleting or blocking GPR149 might be an intriguing way to promote myelin repair in demyelinating diseases.

Inhibition of MAPK/ERK pathway promotes oligodendrocytes generation and recovery of demyelinating diseases.

Oligodendrocytes (OLs) are the myelinating glia of the central nervous system. Injury to OLs causes myelin loss. In demyelinating diseases, such as multiple sclerosis, the remyelination is hindered principally due to a failure of the oligodendrocyte precursor cells (OPCs) to differentiate into mature OLs. To identify inducers of OPC to OL differentiation, a high-throughput screening based on myelin basic protein expression using neural progenitor cells-derived OPCs has been performed and, PD0325901-an MEK (MAPK kinase) inhibitor-is found to significantly enhance OPC to OL differentiation in a dose- and time-dependent manner. Other MEK inhibitors also display similar effect, indicating blockade of MAPK-ERK signaling is sufficient to induce OPC differentiation into OLs. PD0325901 facilitates the formation of myelin sheaths in OPC-neuron co-culture in vitro. And in experimental autoimmune encephalomyelitis model and cuprizone-induced demyelination model, PD0325901 displays significant therapeutic effect by promoting myelin regeneration. Our results suggest that targeting the MAPK-ERK pathway might be an intriguing way to develop new therapies for demyelinating diseases.

Donepezil, a drug for Alzheimer's disease, promotes oligodendrocyte generation and remyelination.

Myelin sheaths play important roles in neuronal functions. In the central nervous system (CNS), the myelin is formed by oligodendrocytes (OLs), which are differentiated from oligodendrocyte precursor cells (OPCs). In CNS demyelinating disorders such as multiple sclerosis (MS), the myelin sheaths are damaged and the remyelination process is hindered. Small molecule drugs that promote OPC to OL differentiation and remyelination may provide a new way to treat these demyelinating diseases. Here we report that donepezil, an acetylcholinesterase inhibitor (AChEI) developed for the treatment of Alzheimer's disease (AD), significantly promotes OPC to OL differentiation. Interestingly, other AChEIs, including huperzine A, rivastigmine, and tacrine, have no such effect, indicating that donepezil's effect in promoting OPC differentiation is not dependent on the inhibition of AChE. Donepezil also facilitates the formation of myelin sheaths in OPC-DRG neuron co-culture. More interestingly, donepezil also promotes the repair of the myelin sheaths in vivo and provides significant therapeutic effect in a cuprizone-mediated demyelination animal model. Donepezil is a drug that has been used to treat AD safely for many years; our findings suggest that it might be repurposed to treat CNS demyelinating diseases such as MS by promoting OPC to OL differentiation and remyelination.

Vitamin C promotes oligodendrocytes generation and remyelination.

Oligodendrocyte-formed myelin sheaths play important roles in the neuronal functions in the central nervous system. In demyelinating diseases, such as Multiple Sclerosis, the myelin sheaths are damaged and the remyelinating process is somehow hindered. Restoration of the myelin sheaths requires the differentiation of the oligodendrocyte precursor cells (OPCs) into mature oligodendrocytes (OLs). To discover small molecule compounds that might promote the OPC to OL differentiation, a high-throughput screening system is established and L-ascorbyl-2-phosphate (As-2P), a stable form of Vitamin C (Vc), is found to greatly enhance the OPC to OL differentiation. As-2P promotes gradual expression of OL lineage markers, including O4, CNPase and MBP, in a dose- and time-dependent manner. It also facilitates the formation of myelin sheaths in OPC-neuron co-culture. As-2P also promotes the repair of the myelin sheaths in vivo and provides significant therapeutic effect in a cuprizone-mediated demyelination animal model. Interestingly, As-2P's function in promoting OPC differentiation is not related to its antioxidant activity. And an intracellular rather than an extracellular mechanism might be involved. Considering the safe use of Vc as a dietary supplement for many years, it might also be used as an alternative medicine for CNS demyelinating diseases.

Development and characterization of 110 novel EST-SSR markers for Dendrobium officinale (Orchidaceae).

PREMISE OF THE STUDY: Expressed sequence tag (EST)-derived simple sequence repeat (SSR) markers were developed in Dendrobium officinale by screening a cDNA library. The loci were verified by sequencing and explored for polymorphism among 19 genotypes and transferability among 30 other distantly related Dendrobium species. • METHODS AND RESULTS: One hundred ten EST-SSRs were developed, and a set of 20 amplified two to six nucleotide repeats with a mean number of 2.5 alleles per locus and with an observed heterozygosity and polymorphism information content per locus ranging from 0.3463 to 0.9003 and 0.0997 to 0.6537 in 19 D. officinale genotypes, respectively. Furthermore, 92 of these markers have cross-taxa transferability, ranging from 6.45% to 100% among 30 other distantly related Dendrobium species. • CONCLUSIONS: The developed markers have potential for application in germplasm appraisal, genetic diversity study, genetic mapping, and molecular breeding in D. officinale and other congeneric species.