Valproic Acid Inhibits Abeta Production, Neuritic Plaque Formation, and Behavioral Deficits in Alzheimer's Disease Mouse Models

The Journal of Experimental Medicine. Nov, 2008  |  Pubmed ID: 18955571

Neuritic plaques in the brains are one of the pathological hallmarks of Alzheimer's disease (AD). Amyloid beta-protein (Abeta), the central component of neuritic plaques, is derived from beta-amyloid precursor protein (APP) after beta- and gamma-secretase cleavage. The molecular mechanism underlying the pathogenesis of AD is not yet well defined, and there has been no effective treatment for AD. Valproic acid (VPA) is one of the most widely used anticonvulsant and mood-stabilizing agents for treating epilepsy and bipolar disorder. We found that VPA decreased Abeta production by inhibiting GSK-3beta-mediated gamma-secretase cleavage of APP both in vitro and in vivo. VPA treatment significantly reduced neuritic plaque formation and improved memory deficits in transgenic AD model mice. We also found that early application of VPA was important for alleviating memory deficits of AD model mice. Our study suggests that VPA may be beneficial in the prevention and treatment of AD.

Cholesteryl Glucoside Stimulates Activation of Protein Kinase B/Akt in the Motor Neuron-Derived NSC34 Cell Line

Neurobiology of Lipids. , 2008  |  Pubmed ID: 20936097

Steryl glycosides and related compounds are commonly found in the environment and have been associated with neurodegenerative changes in vulnerable individuals. However, their mechanisms of action in mammalian cells have not been well investigated. In the present study the effects of cholesterol glucoside (CG), a variant form of steryl glycoside, was investigated in the motor neuron-derived NSC34 cell line. Prolonged treatment with CG was found to induce cell death in a dose- and time-dependent manner. However, transient exposure of CG preconditioned NSC34 cells for stress from serum deprivation. To study the signaling pathways activated by CG, we employed the Kinetworks™ KPSS 1.3 Phospho-site Screen to track the phosphorylation level of at least 35 diverse signaling proteins. The survival protein kinase B (PKB/Akt) displayed a 2-fold increase in phosphorylation at its Ser-473 activation site following CG stimulation. Akt signaling was important for conferring cytoprotection against serum deprivation-induced stress. Inhibition of phosphatidylinositol 3-kinase (PI3K), which indirectly triggers Akt stimulation, completely abolished CG preconditioning against serum deprivation. Our findings revealed that there may be a PI3K-independent pathway which also mediated Akt Ser-473 phosphorylation. Improved understanding of the mechanisms of action of CG should provide insights to the how other members of the steryl glycoside family induce toxicity in the mouse model of ALS-PDC, and how cells respond to these toxins.

PARADOXICAL RESPONSES TO NEUROTOXIC STERYL GLYCOSIDES: INSIGHTS FROM A CELLULAR MODEL OF ALSPDC

Neurobiology of Lipids. Jan, 2009  |  Pubmed ID: 21869879

The causes of many sporadic neurodegenerative diseases remain unknown making prevention difficult, if not impossible. One clue comes from the study of amyotrophic lateral sclerosis-parkinsonism dementia complex (ALS-PDC) of Guam which shares many similarities with amyotrophic lateral sclerosis, Parkinson's disease, and Alzheimer's disease seen in other parts of the world. This disorder may provide a unique opportunity to study the cause and progression of neurodegenerative diseases. Epidemiological and experimental findings indicate that dietary consumption of cycad seeds is an underlying cause of ALS-PDC. Our laboratory provided evidence that a family of compounds called steryl glycosides are the active ingredients that may be responsible for producing the neurodegenerative outcome in ALS-PDC. Here, we review some of our work on the chronic toxicity of steryl glycosides in neuronal cells maintained in cell culture and in an in vivo mouse model. The current studies indicate some mechanisms about how neuronal cells respond to this class of toxins.

Loss of Activated CaMKII at the Synapse Underlies Alzheimer's Disease Memory Loss

Journal of Neurochemistry. Nov, 2011  |  Pubmed ID: 21899538

NF-κB Signaling Inhibits Ubiquitin Carboxyl-terminal Hydrolase L1 Gene Expression

Journal of Neurochemistry. Mar, 2011  |  Pubmed ID: 21210816

Ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) is a deubiquitinating enzyme that plays a regulatory role in targeting proteins for proteasomal degradation. UCH-L1 is highly expressed in neurons and has been demonstrated to promote cell viability and maintain neuronal integrity. Reduced UCH-L1 levels have been observed in various neurodegenerative diseases, and expression of UCH-L1 can rescue synaptic dysfunction and memory deficits in Alzheimer's Disease model mice. However, the mechanisms regulating UCH-L1 expression have not been determined. In this study, we cloned a 1782 bp of the 5' flanking region of the human UCH-L1 gene and identified a 43 bp fragment containing the transcription start site as the minimal region necessary for promoter activity. Sequence analysis revealed several putative regulatory elements including NF-κB, NFAT, CREB, NRSF, YY1, AP1, and STAT in the UCH-L1 promoter. A functional NF-κB response element was identified in the UCH-L1 promoter region. Expression of NF-κB suppressed UCH-L1 gene transcription. In the RelA knockout system where NF-κB activity is ablated, UCH-L1 expression was significantly increased. Furthermore, activation of NF-κB signaling by the inflammatory stimulator lipopolysaccharide and TNFα resulted in a decrease of UCH-L1 gene expression by inhibiting its transcription. As NF-κB is an important signaling module in inflammatory response, our study suggests a possibility that inflammation might compromise neuronal functions via the interaction of NF-κB and UCH-L1. A better understanding of the NF-κB-regulated UCH-L1 transcription will provide insights to the role of inflammatory responses in Alzheimer's disease and Parkinson's disease.