Yuyoung Joo

Mefenamic acid shows neuroprotective effects and improves cognitive impairment in in vitro and in vivo Alzheimer's disease models.

Nonsteroidal anti-inflammatory drugs (NSAIDs) exert anti-inflammatory, analgesic, and antipyretic activities and suppress prostaglandin synthesis by inhibiting cyclooxygenase, an enzyme that catalyzes the formation of prostaglandin precursors from arachidonic acid. Epidemiological observations indicate that the long-term treatment of patients suffering from rheumatoid arthritis with NSAIDs results in reduced risk and delayed onset of Alzheimers disease. In this study, we investigated the therapeutic potential for Alzheimers disease of mefenamic acid, a commonly used NSAID that is a cyclooxygenase-1 and 2 inhibitor with only moderate anti-inflammatory properties. We found that mefenamic acid attenuates the neurotoxicities induced by amyloid β peptide (Aβ)1–42 treatment and the expression of a Swedish double mutation (KM595/596NL) of amyloid precursor protein (Swe-APP) or the C-terminal fragments of APP (APP-CTs) in neuronal cells. We also show that mefenamic acid decreases the production of the free radical nitric oxide and reduces cytochrome c release from mitochondria induced by Aβ1–42, Swe-APP, or APP-CTs in neuronal cells. In addition, mefenamic acid up-regulates expression of the antiapoptotic protein Bcl-XL. Moreover, our study demonstrates for the first time that mefenamic acid improves learning and memory impairment in an Aβ1–42-infused Alzheimers disease rat model. Taking these in vitro and in vivo results together, our study suggests that mefenamic acid could be used as a therapeutic agent in Alzheimers disease.

Intracellular domains of amyloid precursor-like protein 2 interact with CP2 transcription factor in the nucleus and induce glycogen synthase kinase-3beta expression.

Amyloid precursor protein (APP) is a member of a gene family that includes two APP-like proteins, APLP1 and 2. Recently, it has been reported that APLP1 and 2 undergo presenilin-dependent γ-secretase cleavage, as does APP, resulting in the release of an ∼6 kDa intracellular C-terminal domain (ICD), which can translocate into the nucleus. In this study, we demonstrate that the APLP2-ICDs interact with CP2/LSF/LBP1 (CP2) transcription factor in the nucleus and induce the expression of glycogen synthase kinase 3β (GSK-3β), which has broad-ranged substrates such as τ- and β-catenin. The significance of this finding is substantiated by the in vivo evidence of the increase in the immunoreactivities for the nuclear C-terminal fragments of APLP2, and for GSK-3β in the AD patients’ brain. Taken together, these results suggest that APLP2-ICDs contribute to the AD pathogenesis, by inducing GSK-3β expression through the interaction with CP2 transcription factor in the nucleus.

Swedish amyloid precursor protein mutation increases phosphorylation of eIF2α in vitro and in vivo

Swedish double mutation (KM670/671NL) of amyloid precursor protein (Swe‐APP), a prevailing cause of familial Alzheimers disease (FAD), is known to increase in Aβ production both in vitro and in vivo, but its underlying molecular basis leading to Alzheimers disease (AD) pathogenesis remains to be elucidated, especially for the early phase of disease. We have confirmed initially that the expression of Swe‐APP mutant transgene reduced cell viability via ROS production but this effect was eliminated by an anti‐oxidative agent, vitamin E. We also found that eukaryotic translation initiation factor‐2α (eIF2α), which facilitates binding of initiator tRNA to ribosomes to set on protein synthesis, was phosphorylated in cultured cells expressing Swe‐APP. This increase in phosphorylated eIF2α was also attenuated significantly by treatment with vitamin E. The finding that eIF2α became highly phosphorylated by increased production of Aβ was substantiated in brain tissues of both an AD animal model and AD patients. Although an increase in Aβ production would result in cell death eventually (in late‐phase of the disease), the altered phosphorylation state of eIF2α evoked by Aβ may account for the decreased efficacy of mRNA translation and de novo protein synthesis required for synaptic plasticity, and may consequently be one of molecular causes for impairment of cognitive functions exhibited in the early phase of AD patients.

Swedish Amyloid Precursor Protein Mutation Increases Cell Cycle-Related Proteins In Vitro and In Vivo

Reactivation of the cell cycle, including DNA replication, might play a major role in Alzheimers disease. In this study, we report that the expressions of Swedish double mutation of amyloid precursor protein (Swe‐APP) or of the APP intracellular domain (AICD) into nerve growth factor (NGF)‐differentiated PC12 cells or rat primary cortical neurons increased mRNA and protein levels of cyclin D1 and cyclin B1. Treatment with lithium chloride (a glycogen synthase kinase‐3β inhibitor) down‐regulated cyclin B1 induced by Swe‐APP expression but up‐regulated cyclin D1 expression induced by Swe‐APP, suggesting that glycogen synthase kinase‐3β activity is involved in these expression changes of cyclins D1 and B1. Swe‐APP, which is a prevailing cause of familial Alzheimers disease, is well known to increase amyloid beta peptide production both in vitro and in vivo, but the underlying molecular means whereby it leads to the pathogenesis of AD remains unknown. The finding that cyclin D1 and B1 expressions were up‐regulated by Swe‐APP in in vitro cultured cells was substantiated in the brain tissues of Tg2576 mice, which harbor the Swe‐APP mutation. These results suggest that some disturbances in cell cycle regulation may be involved in Swe‐APP or AICD‐induced neurodegeneration and that these contribute to the pathogenesis of AD.

Involvement of 14-3-3 in tubulin instability and impaired axon development is mediated by Tau

14‐3‐3 proteins act as adapters that exert their function by interacting with their various protein partners. 14‐3‐3 proteins have been implicated in a variety of human diseases including neurodegenerative diseases. 14‐3‐3 proteins have recently been reported to be abundant in the neurofibrillary tangles (NFTs) observed inside the neurons of brains affected by Alzheimers disease (AD). These NFTs are mainly constituted of phosphorylated Tau protein, a microtubule‐associated protein known to bind 14‐3‐3. Despite this indication of 14‐3‐3 protein involvement in the AD pathogenesis, the role of 14‐3‐3 in the Tauopathy remains to be clarified. In the present study, we shed light on the role of 14‐3‐3 proteins in the molecular pathways leading to Tauopathies. Overexpression of the 14‐3‐3ct isoform resulted in a disruption of the tubulin cytoskeleton and prevented neuritic outgrowth in neurons. NMR studies validated the phosphorylated residues pSer214 and pSer324 in Tau as the 2 primary sites for 14‐3‐3 binding, with the crystal structure of 14‐3‐3σ in complex with Tau‐pSer214 and Tau‐pSer324 revealing the molecular details of the interaction. These data suggest a rationale for a possible pharmacologic intervention of the Tau/14‐3‐3 interaction.—Joo, Y., Schumacher, B., Landrieu, I., Bartel, M., Smet‐Nocca, C., Jang, A., Choi, H. S., Jeon, N. L., Chang, K.‐A, Kim, H.‐S., Ottmann, C., Suh, Y.‐H. Involvement of 14‐3‐3 in tubulin instability and impaired axon development is mediated by Tau. FASEB J. 29, 4133‐4144 (2015). www.fasebj.org

Therapeutic potentials of neural stem cells treated with fluoxetine in Alzheimer's disease.

Recent studies have proposed that chronic treatment with antidepressants increases neurogenesis in the adult hippocampus. However, the effect of antidepressants on fetal neural stem cells (NSCs) has not been well defined. Our study shows the dose-dependent effects of fluoxetine on the proliferation and neural differentiation of NSCs. Fluoxetine, even at nanomolar concentrations, stimulated proliferation of NSCs and increased the number of βIII-tubulin (Tuj 1)- and neural nucleus marker (NeuN)-positive cells, but not glial fibrillary acidic protein (GFAP)-positive cells. These results suggest that fluoxetine can enhance neuronal differentiation. In addition, fluoxetine has protective effects against cell death induced by oligomeric amyloid beta (Aβ(42)) peptides. Taken together, these results clearly show that fluoxetine promotes both the proliferation and neuronal differentiation of NSCs and exerts protective effects against Aβ(42)-induced cytotoxicities in NSCs, which suggest that the use of fluoxetine is applicable for cell therapy for various neurodegenerative diseases, such as Alzheimers and Parkinsons diseases by its actions in NSCs.

The Therapeutic Effects of Human Adipose-Derived Stem Cells in Alzheimer's Disease Mouse Models

Alzheimers disease (AD) is an irreversible neurodegenerative disease, still lacking proper clinical treatment. Therefore, many researchers have focused on the possibility of therapeutic use of stem cells for AD. Adipose-derived stem cells (ASCs), mesenchymal stem cells (MSCs) isolated from adipose tissue, are well known for their pluripotency and their ability to differentiate into multiple tissue types and have immune modulatory properties similar to those of MSCs from other origins. Because of their biological properties, ASCs can be considered for cell therapy and neuroregeneration. Our recent results clearly showed the therapeutic potential of these cells after transplantation into Tg2576 mice (an AD mouse model). Intravenously or intracerebrally transplanted human ASCs (hASCs) greatly improved the memory impairment and the neuropathology, suggesting that hASCs have a high therapeutic potential for AD.

Amyloid precursor protein binding protein-1 modulates cell cycle progression in fetal neural stem cells.

Amyloid precursor protein binding protein-1 (APP-BP1) binds to the carboxyl terminus of the amyloid precursor protein (APP) and serves as the bipartite activation enzyme for the ubiquitin-like protein, NEDD8. In the present study, we explored the physiological role of APP-BP1 in the cell cycle progression of fetal neural stem cells. Our results show that cell cycle progression of the cells is arrested at the G1 phase by depletion of APP-BP1, which results in a marked decrease in the proliferation of the cells. This action of APP-BP1 is antagonistically regulated by the interaction with APP. Consistent with the evidence that APP-BP1 function is critical for cell cycle progression, the amount of APP-BP1 varies depending upon cell cycle phase, with culminating expression at S-phase. Furthermore, our FRET experiment revealed that phosphorylation of APP at threonine 668, known to occur during the G2/M phase, is required for the interaction between APP and APP-BP1. We also found a moderate ubiquitous level of APP-BP1 mRNA in developing embryonic and early postnatal brains; however, APP-BP1 expression is reduced by P12, and only low levels of APP-BP1 were found in the adult brain. In the cerebral cortex of E16 rats, substantial expression of both APP-BP1 and APP mRNAs was observed in the ventricular zone. Collectively, these results indicate that APP-BP1 plays an important role in the cell cycle progression of fetal neural stem cells, through the interaction with APP, which is fostered by phopshorylation of threonine 668.

In vivo imaging of human adipose-derived stem cells in Alzheimer’s disease animal model

Abstract. Stem cell therapy is a promising tool for the treatment of diverse conditions, including neurodegenerative diseases such as Alzheimer’s disease (AD). To understand transplanted stem cell biology, in vivo imaging is necessary. Nanomaterial has great potential for in vivo imaging and several noninvasive methods are used, such as magnetic resonance imaging, positron emission tomography, fluorescence imaging (FI) and near-infrared FI. However, each method has limitations for in vivo imaging. To overcome these limitations, multimodal nanoprobes have been developed. In the present study, we intravenously injected human adipose-derived stem cells (hASCs) that were labeled with a multimodal nanoparticle, LEO-LIVE™-Magnoxide 675 or 797 (BITERIALS, Seoul, Korea), into Tg2576 mice, an AD mouse model. After sequential in vivo tracking using Maestro Imaging System, we found fluorescence signals up to 10 days after injection. We also found strong signals in the brains extracted from hASC-transplanted Tg2576 mice up to 12 days after injection. With these results, we suggest that in vivo imaging with this multimodal nanoparticle may provide a useful tool for stem cell tracking and understanding stem cell biology in other neurodegenerative diseases.

Plasminogen Activator Inhibitor-1 Promotes Synaptogenesis and Protects Against Aβ 1-42 -Induced Neurotoxicity in Primary Cultured Hippocampal Neurons

ABSTRACT Plasminogen activator inhibitor-1 (PAI-1) is a soluble factor that is released from astrocytes, the most abundant type of glial cell in the brain. PAI-1 was initially identified as inhibiting two types of plasminogen activators, that is, tissue-type plasminogen and urokinase activators that are known to lead to the proteolytic degradation of the extracellular matrix. Recently, PAI-1 was reported to mediate the neuroprotective activity of transforming growth factor-β1 against N-methyl-D-aspartate receptor-mediated excitotoxicity and to be involved in angiogenesis following ischemic stroke, independently of the effects via the inhibition of tissue-type plasminogen and urokinase-type plasminogen activators. In this study, we examined whether PAI-1 influences synaptogenesis and neurotoxicity induced by amyloid beta peptide1-42 (Aß1-42) in rat primary hippocampal neurons. Using immunostaining, treatment with PAI-1 for 24 h was found to significantly upregulate synaptophysin, postsynaptic density-95, and the polysialylated form of neural cell adhesion molecule, compared to treatment with vehicle alone. In addition, PAI-1 has neuroprotective effects against Aβ1-42-induced cytotoxicity in rat primary cultured hippocampal neurons. Taken together, our results suggest that PAI-1 has therapeutic potential in Alzheimers disease by promoting synaptogenesis and by demonstrating neuroprotective effects against Aβ1-42-oligomer-induced neurotoxicity in rat primary cultured hippocampal neurons.