Regulation of TREM2 expression by transcription factor YY1 and its protective effect against Alzheimer's disease.

TREM2 encoding the transmembrane receptor protein TREM2 is a risk gene of Alzheimer's disease (AD), and the impairment of TREM2 functions in microglia due to mutations in TREM2 may significantly increase the risk of AD by promoting AD pathologies. However, how the expression of TREM2 is regulated and the transcription factors required for TREM2 expression are largely unknown. By luciferase assay, DNA pull-down, and in silico predictions, we identified Yin Yang 1(YY1) as a binding protein of the minimal promoter of the TREM2 gene, and the binding was further confirmed by EMSA and DNA pull-down assay. shRNA-mediated YY1 silencing significantly reduced the activity of the TREM2 minimal promoter and TREM2 protein levels in the microglial cell line BV2 and the neuroblastoma Neuro2A. Furthermore, we found that the levels of TREM2 and YY1 were both downregulated in lipopolysaccharide-treated BV2 cells and in the brain of AD model mice. These results demonstrated that YY1 plays a crucial role in the regulation of TREM2 expression. Our study suggests that microglial YY1 could be targeted to maintain TREM2 expression for AD prevention and therapy.

New insight into Alzheimer's disease: Light reverses Aß-obstructed interstitial fluid flow and ameliorates memory decline in APP/PS1 mice.

INTRODUCTION: Pharmacological therapies to treat Alzheimer's disease (AD) targeting "Aß" have failed for over 100 years. Low levels of laser light can disassemble Aß. In this study, we investigated the mechanisms that Aß-blocked extracellular space (ECS) induces memory disorders in APP/PS1 transgenic mice and addressed whether red light (RL) at 630 nm rescues cognitive decline by reducing Aß-disturbed flow of interstitial fluid (ISF). METHODS: We compared the heating effects on the brains of rats illuminated with laser light at 630, 680, and 810 nm for 40 minutes, respectively. Then, a light-emitting diode with red light at 630 nm (LED-RL) was selected to illuminate AD mice. The changes in the structure of ECS in the cortex were examined by fluorescent double labeling. The volumes of ECS and flow speed of ISF were quantified by magnetic resonance imaging. Spatial memory behaviors in mice were evaluated by the Morris water maze. Then, the brains were sampled for biochemical analysis. RESULTS: RL at 630 nm had the least heating effects than other wavelengths associated with ~49% penetration ratio into the brains. For the molecular mechanisms, Aß could induce formaldehyde (FA) accumulation by inactivating FA dehydrogenase. Unexpectedly, in turn, FA accelerated Aß deposition in the ECS. However, LED-RL treatment not only directly destroyed Aß assembly in vitro and in vivo but also activated FA dehydrogenase to degrade FA and attenuated FA-facilitated Aß aggregation. Subsequently, LED-RL markedly smashed Aß deposition in the ECS, recovered the flow of ISF, and rescued cognitive functions in AD mice. DISCUSSION: Aß-obstructed ISF flow is the direct reason for the failure of the developed medicine delivery from superficial into the deep brain in the treatment of AD. The phototherapy of LED-RL improves memory by reducing Aß-blocked ECS and suggests that it is a promising noninvasive approach to treat AD.

Marginal vitamin A deficiency facilitates Alzheimer's pathogenesis.

Deposition of amyloid ß protein (Aß) to form neuritic plaques in the brain is the unique pathological hallmark of Alzheimer's disease (AD). Aß is derived from amyloid ß precursor protein (APP) by ß- and γ-secretase cleavages and turned over by glia in the central nervous system (CNS). Vitamin A deficiency (VAD) has been shown to affect cognitive functions. Marginal vitamin A deficiency (MVAD) is a serious and widespread public health problem among pregnant women and children in developing countries. However, the role of MVAD in the pathogenesis of AD remains elusive. Our study showed that MVAD is approximately twofold more prevalent than VAD in the elderly, and increased cognitive decline is positively correlated with lower VA levels. We found that MVAD, mostly prenatal MVAD, promotes beta-site APP cleaving enzyme 1 (BACE1)-mediated Aß production and neuritic plaque formation, and significantly exacerbates memory deficits in AD model mice. Supplementing a therapeutic dose of VA rescued the MVAD-induced memory deficits. Taken together, our study demonstrates that MVAD facilitates AD pathogenesis and VA supplementation improves cognitive deficits. These results suggest that VA supplementation might be a potential approach for AD prevention and treatment.

Safety and efficacy of valproic acid treatment in SCA3/MJD patients.

BACKGROUND: Spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD) is one of 10 known polyglutamine (polyQ) diseases. In Drosophila and rat models of polyQ diseases, histone deacetylation (HDAC) inhibitors improved locomotor function and survival time by increasing histone acetylation levels and modulating gene expression. Valproic acid (VPA) is a pan-HDAC inhibitor used clinically to treat bipolar and seizure disorders. We evaluated the clinical safety and efficacy of VPA treatment for SCA3/MJD patients. METHODS: First, a randomized, open-label, dose-escalation method was used to evaluate tolerance to single-dose VPA administration in 12 SCA3/MJD patients. Patients were randomly assigned to three groups of four subjects, each with an oral dosage of 400 mg, 600 mg, or 800 mg (twice daily (bid) for one day). VPA was well-tolerated for one-dose by all patient groups. Second, a randomized, double-blind, placebo-controlled, dose-controlled study evaluated the safety and efficacy of multi-dose VPA (oral administration, twice daily (bid) for 12 weeks) in 36 SCA3/MJD patients. Patients received either low-dose VPA (800 mg/day), high-dose VPA (1200 mg/day), or placebo (n = 12 subjects per group). Symptoms were evaluated using the Scale for Assessment and Rating of Ataxia (SARA). RESULTS: Multi-dose VPA treatment improved SARA measures of locomotor function. Major adverse effects included dizziness and loss of appetite. CONCLUSIONS: VPA is a potentially beneficial agent for the treatment of SCA3/MJD. These results also provide insight into possible future therapeutics for polyQ diseases.

Lys(203) and Lys(382) are essential for the proteasomal degradation of BACE1.

Amyloid ß protein (Aß) is the primary component of senile plaques in Alzheimer's disease brains and its aggregate form is neurotoxic. Aß is generated through proteolysis of ß-amyloid precursor protein (APP) by two proteases: ß-secretase and γ-secretase. BACE1, the ß-secretase in vivo and the key rate-limiting enzyme that initiates the formation of Aß, is an attractive drug target for AD therapy. Our previous study demonstrated that BACE1 is ubiquitinated and its degradation and effect on APP cleaving process are mediated by the ubiquitin-proteasome pathway. However, the specific underlying mechanism is still not well defined. In present study, we determined the specific binding sites responsible for the proteasomal degradation of BACE1. Ten fragments of human BACE1 cDNA with each of them containing 1 to 3 Lys codons were cloned, and HEK293 cells transfected with these recombinant plasmids were treated with specific proteasome inhibitor lactacystin. The protein levels of fragment-3 (Pro(149)-Leu(180)), -4 (IIe(179)-Ser(230)) and -8 (Met(349)-Arg(400)) were significantly increased by lactacystin treatment, and immunocytochemical staining results showed that fragment-3, -4 and -8 proteins were colocalized with ubiquitin. Site-directed mutagenesis at Lys(203) and Lys(382) of BACE1 abolished the proteasomal degradation of BACE1 and affected APP processing at ß site and Aß production. Taken together, our study demonstrated that BACE1 Lys(203) and Lys(382) are essential for its proteasomal degradation, and the results may advance our understanding of regulation of BACE1 and APP processing by the ubiquitin proteasome system in AD pathogenesis and shed new insights on its pharmaceutical potential.