Queuine as a potential multi-target drug for alzheimer's disease: insights from protein dynamics.

Alzheimer's disease (AD) is a neurodegenerative disorder with a complex pathogenesis. One promising approach to treating AD is simultaneously targeting multiple aspects of the disease using a multi-target drug (MTD). In this study, multi-target drug (MTD) potential of the nutraceutical molecule Queuine was explored using molecular docking and molecular dynamics (MD) simulations with five different protein targets engaged in AD: AChE, beta-site amyloid precursor protein cleaving enzyme-1 (BACE-1), N-methyl-D-aspartate receptor (NMDAR), monoamine oxidase A (MAO-A), and Synapsin III. Queuine revealed significant binding affinities, the docking scores being -10.1, -5.97, -5.63, -8.40, and -10.56 kcal/mol for AChE, BACE-1, NMDAR, MAO-A, and Synapsin III, respectively. MD simulations showed that Queuine formed stable complexes and preserved its stability throughout the simulation, the backbone fluctuations remaining within 2.5 Å specifically in the case of the BACE-1. Elastic network model simulations and principal component analysis were carried out to illustrate the dynamics of the protein systems. Significant hinge-bending and twisting-type motions that may be relevant to function were observed around the dimerization interfaces or binding sites. Structural clustering based on PCA analysis and cross-correlation maps demonstrated that Queuine binding altered the protein dynamics more drastically in the case of highly mobile proteins NMDAR and MAO-A. We propose that the neuroprotective effect of Queuine may stem from its prominent inhibitory action on enzymes BACE-1 and AChE. Our results suggest that Queuine may serve as a promising MTD candidate for the treatment of AD.Communicated by Ramaswamy H. Sarma.

Identifying the beta-site amyloid precursor protein cleaving enzyme 1 interactome through the proximity-dependent biotin identification assay.

Beta-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) is a key drug target against Alzheimer's Disease however, due to its promiscuous proteolytic activity, little is known about its physiological functions. Previous studies have analysed BACE1 cleavage products to examine BACE1 interactions and determine substrates, but these studies cannot establish non-enzymatic (and potentially functional) associations. This study used the biotin identification proximity assay to establish the BACE1 interactome in healthy neuronal cells and identified interactions involved in BACE1 trafficking, post-translational modification and substrates. Furthermore, this method has identified a putative novel role for BACE1 in sex hormone signalling and haem regulation through interaction with the progesterone receptor membrane component 2 (PGRC2). Data are available via ProteomeXchange with identifier PXD021464.

Penetrating Ballistic-Like Brain Injury Leads to MicroRNA Dysregulation, BACE1 Upregulation, and Amyloid Precursor Protein Loss in Lesioned Rat Brain Tissues.

Severe traumatic brain injury (TBI) is a risk factor for neurodegenerative diseases. Yet, the molecular events involving dysregulated miRNAs that may be associated with protein degradation in the brain remains elusive. Quantitation of more than 800 miRNAs was conducted using rat ipsilateral coronal brain tissues collected 1, 3, or 7 days after penetrating ballistic-like brain injury (PBBI). As a control for each time-point, Sham-operated animals received craniotomy alone. Microarray and systems biology analysis indicated that the amplitude and complexity of miRNAs affected were greatest 7 day after PBBI. Arrays and Q-PCR inferred that dysregulation of miR-135a, miR-328, miR-29c, and miR-21 were associated with altered levels of beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), PSEN1, PSEN2, and amyloid precursor protein (APP) genes. These events were followed by increased levels of mature BACE1 protein and concomitant loss of full length APP within 3-7 days, then elevation of amyloid beta (Aß)-40 7 days after PBBI. This study indicates that miRNA arrays, coupled with systems biology, may be used to guide study design prior validation of miRNA dysregulation. Associative analysis of miRNAs, mRNAs, and proteins within a proposed pathway are poised for further validation as biomarkers and therapeutic targets relevant to TBI-induced APP loss and subsequent Aß peptide generation during neurodegeneration.

The correlation between accumulation of amyloid beta with enhanced neuroinflammation and cognitive impairment after intraventricular hemorrhage.

OBJECTIVE: Intraventricular hemorrhage (IVH) is found in approximately 40% of intracerebral hemorrhages and is associated with increased mortality and poor functional outcome. Cognitive impairment is one of the complications and occurs due to various pathological changes. Amyloid beta (Aß) accumulation and neuroinflammation, and the Alzheimer disease-like pathology, may contribute to cognitive impairment. Iron, the degradation product of hemoglobin, correlates with Aß. In this study, the authors investigated the correlation between Aß accumulation with enhanced neuroinflammation and cognitive impairment in a rat model of IVH. METHODS: Nine male Sprague-Dawley rats underwent an intraventricular injection of autologous blood. Another 9 rats served as controls. Cognitive function was assessed by the Morris water maze and T-maze rewarded alternation tests. Biomarkers of Aß accumulation, neuroinflammation, and c-Jun N-terminal kinase (JNK) activation were examined. RESULTS: Cognitive function was impaired in the autologous blood injection group compared with the control group. In the blood injection group, Aß accumulation was observed, with a co-located correlation between iron storage protein ferritin and Aß. Beta-site amyloid precursor protein cleaving enzyme-1 (BACE1) activity was elevated. Microgliosis and astrogliosis were observed in hippocampal CA1, CA2, CA3, and dentate gyrus areas, with elevated proinflammatory cytokines tumor necrosis factor-α and interleukin-1. Protein levels of phosphorylated JNK were increased after blood injection. CONCLUSIONS: Aß accumulation and enhanced neuroinflammation have a role in cognitive impairment after IVH. A potential therapeutic method requires further investigation.

Beta secretase activity in peripheral nerve regeneration.

While the peripheral nervous system has the capacity to regenerate following a nerve injury, it is often at a slow rate and results in unsatisfactory recovery, leaving patients with reduced function. Many regeneration associated genes have been identified over the years, which may shed some insight into how we can manipulate this intrinsic regenerative ability to enhance repair following peripheral nerve injuries. Our lab has identified the membrane bound protease beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1), or beta secretase, as a potential negative regulator of peripheral nerve regeneration. When beta secretase activity levels are abolished via a null mutation in mice, peripheral regeneration is enhanced following a sciatic nerve crush injury. Conversely, when activity levels are greatly increased by overexpressing beta secretase in mice, nerve regeneration and functional recovery are impaired after a sciatic nerve crush injury. In addition to our work, many substrates of beta secretase have been found to be involved in regulating neurite outgrowth and some have even been identified as regeneration associated genes. In this review, we set out to discuss BACE1 and its substrates with respect to axonal regeneration and speculate on the possibility of utilizing BACE1 inhibitors to enhance regeneration following acute nerve injury and potential uses in peripheral neuropathies.

PPAR-α agonist regulates amyloid-ß generation via inhibiting BACE-1 activity in human neuroblastoma SH-SY5Y cells transfected with APPswe gene.

Alzheimer's disease is a neuroinflammatory disease and is the most common cause of dementia in the elderly. Studies have shown the beneficial effects of the peroxisome proliferator-activated receptor alpha (PPAR-α) agonists on the treatment of neuroinflammatory diseases. The aim of the present study is to examine the ability of GW7647 (a PPAR-α agonist) to regulate amyloid precursor protein (APP) amyloidogenic processing in human neuroblastoma SH-SY5Y cells transfected with APPswe gene. After administration of GW7647 for 24 h, the levels of APP, soluble APPß (sAPPß), and presenilin 1 (PS-1) were assessed by Western blot. Cellular culture medium levels of amyloid-ß 42 (Aß42) were analyzed by ELISA, and the activity of beta-site APP cleaving enzyme 1 (BACE-1) was measured by fluorometric assay. We found that GW7647 decreased the expression of sAPPß and the activity of BACE-1, and also reduced Aß42 release. However, GW7647 did not modify the levels of APP and PS-1. Furthermore, LY294002, the phosphoinositide 3-kinase (PI3-K) inhibitor, reversed the effects of GW7647 on the BACE-1 activity and the levels of sAPPß and Aß42. Our data demonstrate that GW7647 may reduce Aß production via inhibiting BACE-1 activity, and this may involve in PI3-K pathway.

Fenofibrate reduces amyloidogenic processing of APP in APP/PS1 transgenic mice via PPAR-α/PI3-K pathway.

The peroxisome proliferator-activated receptor alpha (PPAR-α), a member of the family of ligand-activated nuclear hormone receptors, plays a relevant role in the development of Alzheimer's disease (AD). To better understand the role of PPAR-α in AD, we examined the ability of fenofibrate (a PPAR-α agonist) to regulate amyloid precursor protein (APP) processing in APP/PS1 transgenic mice. After intragastric administration of fenofibrate into 3-month-old APP/PS1 transgenic mice for 6 months, and the levels of relative proteins were quantified by quantitative reverse transcription-PCR, Western blotting and ELISA. We found that fenofibrate increased the expression of PPAR-α, and decreased beta-site amyloid precursor protein cleaving enzyme 1 (BACE-1) mRNA and protein levels, and also reduced soluble APPß (sAPPß) and amyloid-ß 42 (Aß42) releases. However. fenofibrate did not modify the levels of APP and presenilin 1 (PS1). Furthermore, LY294002, the phosphoinositide 3-kinase (PI3-K) inhibitor, suppressed the effects of fenofibrate on BACE-1, sAPPß, and Aß42, but not PPAR-α. Our data suggest that fenofibrate may reduce the amyloidogenic processing of APP in APP/PS1 transgenic mice via PPAR-α/PI3-K pathway.

Hydrogen sulfide improves spatial memory impairment and decreases production of Aß in APP/PS1 transgenic mice.

Alzheimer's disease (AD) is defined both by its progressive cognitive deterioration and hallmark increase in neuronal Aß plaque formation. However, many of the underlying neurobiological facets of this disease are still being elucidated. Previous research has demonstrated that production of neuronal hydrogen sulfide (H2S) is significantly decreased in patients with AD. Moreover, systemic plasma H2S levels are negatively correlated with its severity. However, how a decrease in H2S production might be correlated with either the etiology or pathophysiology of AD remains unknown. To better understand the role of H2S in AD, we examined both levels of H2S and the expression and activity H2S-synthesizing enzyme (cystathionine beta synthase or CBS) in an APP/PS1 transgenic mouse line at 3, 6, 9 and 12 months. After intraperitoneal (i.p.) administration of an H2S donor (NaHS) into APP/PS1 mice, application of exogenous H2S resulted in improved spatial learning and memory acquisition in APP/PS1 mice. H2S administration also led to significant decrease in extracellular levels of Aß40 and Aß42, the expression of BACE1 and PS1, and a significant increase of ADAM17 expression. Similarly, an increase in non-amyloidogenic C83 fragment generation and a decrease in amyloidogenic C99 fragment generation were also observed. Thus, NaHS application resulted in a shift from the plaque-forming beta pathway to the non-plaque forming alpha pathway of APP cleavage in 6 and 12 month APP/PS1 mice. These results indicate the importance of H2S to AD severity and that administration of exogenous H2S can promote a non-amyloidogenic processing of APP.

The effects of serum uric acid on expression of APP and BACE1 in rats / 中国神经精神疾病杂志

Objective To observe the effects of the different serum uric acid levels on expression of Alzheimer’s disease biomarkers (APP and BACE1) in rats. Methods Intraperitoneal injection of oxygen of oxazine acid potassium was used to produce HUA models in rats. H&E staining was used to detect the morphological changes of the hippocampus. Western blot was used to detect the protein levels of APP and BACE1 of the hippocampus. Results Compared with nor-mal control group, the serum uric acid and the protein levels of APP and BACE1 in the hippocampus was obviously in-creased at OAPS treatment group (P0.05). Conclusion The higher level of serum uric acid may be a protective factor of AD. The higher serum uric acid levels, the lower the risk of AD.

Divalent cation tolerance protein binds to ß-secretase and inhibits the processing of amyloid precursor protein.

The deposition of amyloid-beta is a pathological hallmark of Alzheimer's disease. Amyloid-beta is derived from amyloid precursor protein through sequential proteolytic cleavages by ß-secretase (beta-site amyloid precursor protein-cleaving enzyme 1) and γ-secretase. To further elucidate the roles of beta-site amyloid precursor protein-cleaving enzyme 1 in the development of Alzheimer's disease, a yeast two-hybrid system was used to screen a human embryonic brain cDNA library for proteins directly interacting with the intracellular domain of beta-site amyloid precursor protein-cleaving enzyme 1. A potential beta-site amyloid precursor protein-cleaving enzyme 1-interacting protein identified from the positive clones was divalent cation tolerance protein. Immunoprecipitation studies in the neuroblastoma cell line N2a showed that exogenous divalent cation tolerance protein interacts with endogenous beta-site amyloid precursor protein-cleaving enzyme 1. The overexpression of divalent cation tolerance protein did not affect beta-site amyloid precursor protein-cleaving enzyme 1 protein levels, but led to increased amyloid precursor protein levels in N2a/APP695 cells, with a concomitant reduction in the processing product amyloid precursor protein C-terminal fragment, indicating that divalent cation tolerance protein inhibits the processing of amyloid precursor protein. Our experimental findings suggest that divalent cation tolerance protein negatively regulates the function of beta-site amyloid precursor protein-cleaving enzyme 1. Thus, divalent cation tolerance protein could play a protective role in Alzheimer's disease.