Β-site Amyloid Precursor Protein-cleaving Enzyme Research Articles

Association of Neurogranin and BACE1 With Clinical Cognitive Decline in Individuals With Subjective Cognitive Decline.

CSF biomarkers have immense diagnostic and prognostic potential for Alzheimer disease (AD). However, AD is still diagnosed relatively late in the disease process, sometimes even years after the initial manifestation of cognitive symptoms. Thus, further identification of biomarkers is required to detect related pathology in the preclinical stage and predict cognitive decline. Our study aimed to assess the association of neurogranin and β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) with cognitive decline in individuals with subjective cognitive decline (SCD). We enrolled participants with available neurogranin and BACE1 measurements in CSF from the DELCODE (DZNE-Longitudinal Cognitive Impairment and Dementia, Germany) cohort. The longitudinal change of Preclinical Alzheimer's Cognitive Composite score was assessed as the primary outcome in participants with SCD and controls. The secondary outcome was defined as conversion of SCD to mild cognitive impairment (MCI) during follow-up. Levels of neurogranin, BACE1, and neurogranin/BACE1 ratio across groups were compared by analysis of covariance after adjustment for demographics. The linear mixed-effects model and Cox regression analysis were applied to evaluate their association with cognitive decline and progression of SCD to MCI, respectively. A total of 530 participants (mean age: 70.76 ± 6.01 years, 48.7% female) were analyzed in the study. The rate of cognitive decline was faster in individuals with SCD with higher neurogranin and neurogranin/BACE1 ratio (β = -0.138, SE = 0.065, p = 0.037, and β = -0.293, SE = 0.115, p = 0.013). Higher baseline neurogranin and neurogranin/BACE1 ratio were associated with an increased rate of conversion from SCD to MCI (hazard ratio [HR] 1.35 per SD, 95% CI 1.03-1.77, p = 0.028, and HR 1.53 per SD, 95% CI 1.13-2.07, p = 0.007). In addition, the impact of higher neurogranin levels on accelerating the rate of cognitive decline was more pronounced in the SCD group than in cognitively unimpaired controls (β = -0.077, SE = 0.033, p = 0.020). Our findings suggest that CSF neurogranin and BACE1 begin to change in the preclinical stage of AD and they are associated with clinical progression in individuals with SCD.

The alteration and role of glycoconjugates in Alzheimer's disease.

Alzheimer's disease (AD) is a prevalent neurodegenerative disorder characterized by abnormal protein deposition. With an alarming 30 million people affected worldwide, AD poses a significant public health concern. While inhibiting key enzymes such as β-site amyloid precursor protein-cleaving enzyme 1 and γ-secretase or enhancing amyloid-β clearance, has been considered the reasonable strategy for AD treatment, their efficacy has been compromised by ineffectiveness. Furthermore, our understanding of AD pathogenesis remains incomplete. Normal aging is associated with a decline in glucose uptake in the brain, a process exacerbated in patients with AD, leading to significant impairment of a critical post-translational modification: glycosylation. Glycosylation, a finely regulated mechanism of intracellular secondary protein processing, plays a pivotal role in regulating essential functions such as synaptogenesis, neurogenesis, axon guidance, as well as learning and memory within the central nervous system. Advanced glycomic analysis has unveiled that abnormal glycosylation of key AD-related proteins closely correlates with the onset and progression of the disease. In this context, we aimed to delve into the intricate role and underlying mechanisms of glycosylation in the etiopathology and pathogenesis of AD. By highlighting the potential of targeting glycosylation as a promising and alternative therapeutic avenue for managing AD, we strive to contribute to the advancement of treatment strategies for this debilitating condition.

Unravelling the Untapped Pharmacological Potential of Plant Molecules as Inhibitors of BACE1: In Silico Explorations for Alzheimer's Disease.

Alzheimer's disease (AD) is an extremely complex, heterogeneous, and multifactorial neurodegenerative disease clinically characterized by progressive memory loss and progressive decline in cognitive function. There is currently no effective treatment for the onset and/or progression of the pathophysiological diseases of AD. The global prevalence of this disease has increased in recent years due to modern lifestyle. Therefore, there is an urgent need to develop a drug with significant neuroprotective potential. Since plant metabolites, especially polyphenols, have important pharmacological properties acting against β-amyloid (Aβ), Tau, neuroinflammation, and oxidative stress, such phytochemicals were selected in the present research. Using the Schrödinger tool (Maestro V.13.6), the drug potency of these metabolites was studied after installation in the highly configured workstation. Among the 120 polyphenols docked, amygdalin showed notable docking values of - 11.2638, followed by eriocitrin (- 10.9569), keracyanin (- 10.7086), and amaroswerin (- 9.48126). The prominent MM-GBSA values of these molecules were - 62.8829, - 52.1914, - 68.6307, and - 63.1074, respectively. The MM-GBSA energy values demonstrated the drug stability of these molecules for β-site amyloid precursor protein-cleaving enzyme 1 (BACE1)-causing AD. In the absorption and distribution assessment, these phytochemicals showed significantly better values than the inhibitors CNP520. The chosen phytochemicals have been demonstrated as non-hepatotoxic; however, the BACE1 inhibitor CNP520 is hepatotoxic. In both the molecular docking and ADMET assessments, these natural chemicals have shown optimism as potential drug candidates for Alzheimer's disease. However, in order to understand the detailed biological metabolism of these compounds in AD, they need to be evaluated in in vivo studies to validate its efficacy.

Sevoflurane anesthesia reduces the expression of inflammatory response genes and β-site amyloid precursor protein-cleaving enzyme in hippocampi of diabetic mice.

Diabetes and inhaled anesthesia are associated with an increased likelihood of developing postoperative cognitive dysfunction in humans and animal models, but the mechanisms are unclear. This study aimed to investigate the effect and mechanism of sevoflurane anesthesia on cognitive function in diabetic (DM) mice. Spontaneously diabetic db/db and control db/m mice were subject to sevoflurane anesthesia or allowed to breathe air, respectively. The Morris water maze test as spatial learning and novel object recognition test as recognition memory were performed. The expression of inflammatory cytokines and neurotoxicity-related genes in the hippocampus of four groups was measured using real-time PCR. The expression level of neurotoxicity and neuroprotection-related proteins in DM mice hippocampus were estimated using Western blot assay. It is found that DM mice developed cognitive impairment; however, the cognitive impairment was not exacerbated in sevoflurane-exposed mice. Sevoflurane anesthesia led to a decrease in mRNA levels of inflammatory cytokines in DM mice hippocampi, including interleukin 17 (IL-17), C-C motif chemokine (CCL20), CCL7 as well as high mobility group box 1 and beta-site amyloid-β cleaving enzyme 1; and no effect was observed on the expression of neurotoxicity genes, including amyloid precursor protein, choline O-acetyltransferase, tumor necrosis factor, alpha-induced protein 1, B-cell lymphoma 2 and estrogen receptor 2. In addition, we observed elevated phosphorylation of cAMP response element-binding protein in DM mice exposed to sevoflurane anesthesia. In conclusion, sevoflurane did not exacerbate DM-associated cognitive impairment.

Neuroprotective effect of Kurarinone against corticosterone-induced cytotoxicity on rat hippocampal neurons by targeting BACE1 to activate P13K-AKT signaling - A potential treatment in insomnia disorder.

The hippocampus has been implicated in the pathogenesis of insomnia disorder (ID) and the purpose of this study was to investigate the neuroprotective mechanism of the natural flavone Kurarinone (Kur) on hippocampal neurotoxicity as a potential treatment of ID. The effect of Kur on hippocampal neuronal cell (HNC) viability and apoptosis were assessed by Cell counting kit-8 (CCK-8) assay and flow cytometry, respectively. Then, the effect of Kur on β-site amyloid precursor protein-cleaving enzyme 1 (BACE1), brain-derived neurotrophic factor (BDNF), and phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT) phosphorylation level were measured by Western blot. Further, SwissTargetPrediction analysis and molecular docking experiments were used to detect a potential target of Kur. Then, the p-chlorophenylalanine (PCPA) model was established in vivo to further study the effect of BACE1 expression on Kur and HNC. As a result, HNC viability was only significantly decreased by 2 μM of Kur. Kur reversed the impacts of corticosterone upon inhibiting viability (0.25-1 μM), PI3K (0.5-1 μM)/AKT phosphorylation, and BDNF (1 μM) level, and enhancing the apoptosis (0.25-1 μM) and BACE1 expression (1 μM) in HNCs. BACE1 was a potential target of Kur. Notably, Kur (150 mg/kg) attenuated PCPA-induced upregulation of BACE1 expression in rat hippocampal tissues as ZRAS (0.8 g/kg). The effects of Kur (1 μM) on corticosterone-treated HNCs were reversed by BACE1 overexpression. Collectively, Kur downregulates BACE1 level to activate PI3K/AKT, thereby attenuating corticosterone-induced toxicity in HNCs, indicating that Kur possibly exerted a neuroprotective effect, which providing a new perspective for the treatment of insomnia disorders.

New Highly Selective BACE1 Inhibitors and Their Effects on Dendritic Spine Density In Vivo.

β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) is considered a therapeutic target to combat Alzheimer's disease by reducing β-amyloid in the brain. To date, all clinical trials involving the inhibition of BACE1 have been discontinued due to a lack of efficacy or undesirable side effects such as cognitive worsening. The latter could have been the result of the inhibition of BACE at the synapse where it is expressed in high amounts. We have previously shown that prolonged inhibition of BACE interferes with structural synaptic plasticity, most likely due to the diminished processing of the physiological BACE substrate Seizure protein 6 (Sez6) which is exclusively processed by BACE1 and is required for dendritic spine plasticity. Given that BACE1 has significant amino acid similarity with its homolog BACE2, the inhibition of BACE2 may cause some of the side effects, as most BACE inhibitors do not discriminate between the two. In this study, we used newly developed BACE inhibitors that have a different chemotype from previously developed inhibitors and a high selectivity for BACE1 over BACE2. By using longitudinal in vivo two-photon microscopy, we investigated the effect on dendritic spine dynamics of pyramidal layer V neurons in the somatosensory cortex in mice treated with highly selective BACE1 inhibitors. Treatment with those inhibitors showed a reduction in soluble Sez6 (sSez6) levels to 27% (elenbecestat, Biogen, Eisai Co., Ltd., Tokyo, Japan), 17% (Shionogi compound 1) and 39% (Shionogi compound 2), compared to animals fed with vehicle pellets. We observed a significant decrease in the number of dendritic spines with Shionogi compound 1 after 21 days of treatment but not with Shionogi compound 2 or with elenbecestat, which did not show cognitive worsening in clinical trials. In conclusion, highly selective BACE1 inhibitors do alter dendritic spine density similar to non-selective inhibitors if soluble (sSez6) levels drop too much. Low-dose BACE1 inhibition might be reasonable if dosing is carefully adjusted to the amount of Sez6 cleavage, which can be easily monitored during the first week of treatment.

Exercise training and BDNF injections alter APP processing enzymes and improve cognition.

Exercise reduces cognitive aging, neurodegeneration, and Alzheimer's disease (AD) risk. Acute exercise reduces the activity of beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), the rate limiting enzyme in the production of Aβ. However, mechanisms mediating these effects remain largely unknown. Work has implicated brain-derived neurotrophic factor (BDNF) in the processing of amyloid precursor protein (APP). BDNF is an exercise-induced neurotrophin known for its role in synaptic plasticity, neurite growth, and neuronal survival. Previously, our lab has shown using an ex vivo model that treatment of the prefrontal cortex with BDNF reduced BACE1 activity, highlighting a BDNF to BACE1 link. The purpose of this research was to examine whether BDNF treatments resulted in similar biochemical adaptations to APP processing as exercise training. Male C57BL6/J mice were assigned into one of four groups (n=12/group): 1) control; 2) exercise training (progressive treadmill training 5 days/week); 3) BDNF (0.5 mg/kg body mass subcutaneous injection 5 days/week); or 4) endurance training and BDNF, for an 8-week intervention. Recognition memory was measured with a novel object recognition test. Serum, the prefrontal cortex, and hippocampus were collected. BDNF improved recognition memory to a similar extent as endurance training. BDNF and exercise decreased BACE1 activity and increased ADAM10 activity in the prefrontal cortex, indicating a shift in APP processing. Our novel results indicate that BDNF exerts similar beneficial effects on cognition and APP processing as exercise. Future evidence-based preventative or therapeutic interventions that increase BDNF and reduce BACE1 will be valuable for populations at risk of AD.

Enzymatic Screening of β-Amyloid Precursor Protein-Based Substrates

We performed an enzymatic screening of synthetic peptides based on β-amyloid precursor protein substrates. The template peptide sequence was a decapeptide derived from our previous screening study, which determined several effective unnatural amino acids. In this study, new libraries containing some unnatural amino acid compounds were prepared in the solid phase and digested with the β-site amyloid precursor protein-cleaving enzyme. The reaction mixture was analyzed using high-performance liquid chromatography combined with mass spectrometry. The peptides that showed a higher cleavage than the template sequence were determined and reported.

MiR-29c-3p Attenuates β-Amyloid-Induced Neurotoxicity in Alzheimer’s Disease Through Regulating β-Site Amyloid Precursor Protein-Cleaving Enzyme 1

The aberrantly expressed microRNAs (miRNAs) including miR-29c-3p have been reported in the brains of Alzheimer's disease (AD) patients in recent researches. Nevertheless, the functional role and underlying molecular mechanism of miR-29c-3p in AD pathogenesis are still not well elucidated. The purpose of this study was to examine whether miR-29c-3p regulated β-Ameyloid (Aβ)-induced neurotoxicity by targeting β-site amyloid precursor protein-cleaving enzyme 1 (BACE1). The expressions of miR 29c 3p and BACE1 mRNA and protein levels in Aβ-treated PC12 cellular AD model were examined by qRT-PCR and western blot analyses. Luciferase reporter assay verified the potential target of miR 29c 3p. Cell viability, apoptosis, and caspase-3 activity in PC12 cells were detected by the MTT assay, flow cytometry, and caspase-3 activity assay, respectively. Our results indicated that miR-29c-3p downregulation and BACE1 upregulation existed in the cellular AD model of PC12 cells. Moreover, miR-29c-3p directly inhibited BACE1 expression. miR-29c-3p overexpression and BACE1 knockdown strengthened Aβ-induced cell apoptosis, and caspase-3 activity in PC12 cells, which was partially eliminated by over-expression of BACE1. Conversely, BACE1 knockdown reversed the miR-29c-3p inhibition- mediated inhibitory effect on Aβ-induced cell toxicity, apoptosis, and caspase-3 activity in PC12 cells. Considering, miR-29c-3p attenuated Aβ-induced neurotoxicity through targeting BACE1 in an cellular AD model of PC12, providing a potential therapeutic target for AD treatment.

Inactivation of BACE1 increases expression of endothelial nitric oxide synthase in cerebrovascular endothelium

Cerebrovascular effects of β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) inactivation have not been systematically studied. In the present study we employed cultured human brain microvascular endothelial cells (BMECs), BACE1-knockout (BACE1−/−) mice and conditional (tamoxifen-induced) endothelium-specific BACE1-knockout (eBACE1−/−) mice to determine effect of BACE1 inhibition on expression and function of endothelial nitric oxide synthase (eNOS). Deletion of BACE1 caused upregulation of eNOS and glypican-1 (GPC1) in human BMECs treated with BACE1-siRNA, and cerebral microvessels of male BACE1−/− mice and male eBACE1−/− mice. In addition, BACE1siRNA treatment increased NO production in human BMECs. These effects appeared to be independent of amyloid β-peptide production. Furthermore, adenoviral-mediated overexpression of BACE1 in human BMECs down-regulated GPC1 and eNOS. Treatment of human BMECs with GPC1siRNA suppressed mRNA and protein levels of eNOS. In basilar arteries of male eBACE1−/− mice, endothelium-dependent relaxations to acetylcholine and endothelium-independent relaxations to NO donor, DEA-NONOate, were not affected, consistent with unchanged expression of eNOS and phosphorylation of eNOS at Ser1177 in large cerebral arteries. In aggregate, our findings suggest that under physiological conditions, inactivation of endothelial BACE1 increases expression of eNOS in cerebral microvessels but not in large brain arteries. This effect appears to be mediated by increased GPC1 expression.

Chinese Prescription Kangen-karyu as Potential Anti-Alzheimer’s Disease Therapeutic: Analyses of BACE1 and GSK-3b Inhibitory Activities

Inhibition of β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) or glycogen synthase kinase-3β (GSK-3β) is estimated to be the central therapeutic approach for Alzheimer’s disease (AD). In this study, water extract of Kangenkaryu, its crude drug and chemical composition used in oriental medicine were evaluated regarding their BACE1 and GSK-3β inhibitory activities.Fluorescence resonance energy transfer was used to characterize the BACE1 inhibitory effect of Kangen-karyu, its crude drug and chemical composition.GSK-3β activity was determined using the Kinase-Glo Luminescent Kinase Assay Platform. The water extract of Kangen-karyu inhibited BACE1 and GSK-3β in concentration-dependent manners when compared with reference drugs, quercetin and luteolin. Among six components of Kangen-karyu, the water extracts of Salviae Miltiorrhizae Radix or Cyperi Rhizoma exhibited significant inhibitory effects on BACE1 and GSK-3β. Among the constituents of Salviae Miltiorrhizae Radix extract, salvianolic acid C, salvianolic acid A, rosmarinic acid, and magnesium lithospermate B significantly inhibited BACE1. In addition, they inhibited GSK-3β with an IC50 value range of 6.97 to 135.35 μM. From these results, one of the effectiveness and its mechanisms of action of Kangen-karyu against AD may be the inhibition of BACE1 and GSK-3β, and one of the active ingredients of Kangen-karyu is Salviae Miltiorrhizae Radix and its constituents.

Self-Assembly of Superquenched Gold Nanoparticle Nanosensors for Lighting up BACE-1 in Live Cells.

The β-site amyloid precursor protein-cleaving enzyme 1 (BACE-1) plays a key role in Alzheimer's disease (AD) pathogenesis and is regarded as a valuable biomarker for AD diagnosis and treatment. The reported BACE-1 assay often suffers from laborious procedures, large sample consumption, and unsatisfactory sensitivity with high background signals. Herein, we report the self-assembly of superquenched gold nanoparticle (AuNP) nanosensors for lighting up the BACE-1 in live cells. Through the self-assembly of both fluorophore-labeled peptide probes and quencher-labeled assistant DNAs on the surface of a single AuNP, a superquenched AuNP nanoprobe is obtained with a high quenching efficiency of 98.37% and a near-zero background fluorescence. The presence of target BACE-1 induces a distinct fluorescence signal as a result of the BACE-1-catalyzed cleavage of peptide probe and the subsequent release of abundant fluorophore moieties from the AuNP nanoprobe. The fluorescence signal can be directly visualized by single-molecule imaging and easily quantified by single-molecule counting. This nanosensor involves only a single nanoprobe for the one-step homogeneous detection of the BACE-1 activity without the requirements of any antibodies and separation steps, and it possesses good selectivity and high sensitivity with a low detection limit of 26.48 pM. Moreover, it can be employed to screen BACE-1 inhibitors and analyze kinetic parameters. Especially, this nanoprobe possesses good stability and can be easily transferred into live cells for the real-time imaging of cellular BACE-1 activity, providing a new platform for BACE-1-associated research and early diagnosis of Alzheimer's disease.

Pharmacological inhibition of BACE1 suppresses glioblastoma growth by stimulating macrophage phagocytosis of tumor cells.

Glioblastoma (GBM) contains abundant tumor-associated macrophages (TAMs). The majority of TAMs are tumor-promoting macrophages (pTAMs), while tumor-suppressive macrophages (sTAMs) are the minority. Thus, reprograming pTAMs into sTAMs represents an attractive therapeutic strategy. By screening a collection of small molecule compounds, we find that inhibiting the β-site amyloid precursor protein cleaving enzyme 1 (BACE1) by MK-8931 potently reprograms pTAMs into sTAMs and promotes macrophage phagocytosis of glioma cells; moreover, low-dose radiation markedly enhances TAM infiltration and synergizes with MK-8931 treatment to suppress malignant growth. BACE1 is preferentially expressed by pTAMs in human GBMs and is required for maintaining pTAM polarization through trans-IL-6-sIL-6R-STAT3 signaling. Because MK-8931 and other BACE1 inhibitors have been developed for Alzheimer's disease, and have been shown to be safe for humans in clinical trials, these inhibitors could be potentially streamlined for cancer therapy. Collectively, this study offers a promising therapeutic approach to enhance macrophage-based therapy for malignant tumors.

Discovery of Extremely Selective Fused Pyridine-Derived β-Site Amyloid Precursor Protein-Cleaving Enzyme (BACE1) Inhibitors with High In Vivo Efficacy through 10s Loop Interactions.

β-Site amyloid precursor protein-cleaving enzyme 1 (BACE1) is considered to be a promising target for treating Alzheimer's disease. However, all clinical BACE1 inhibitors have failed due to lack of efficacy, and some have even led to cognitive worsening. Recent evidence points to the importance of avoiding BACE2 inhibition along with careful dose titration. In this study, we focused on the fact that the 10s loop lining the S3 pocket in BACE1 can form both "open (up)" and "closed (down)" conformations, whereas in BACE2, it prefers to adopt a "closed" form; thus, more space is available in BACE1. By leveraging the difference, we designed fused pyridine analogues that could reach the 10s loop, leading to 6 with high selectivity and significant Aβ reduction. The cocrystal structures confirmed that 6 significantly increased B-factors of the 10s loop in BACE2 relative to those in BACE1. Thus, the destabilization of BACE2 seems to offer structural insights into the reduced BACE2 potency of 6, explaining the significant improvement in BACE1 selectivity.

Apigenin Ameliorates Scopolamine-Induced Cognitive Dysfunction and Neuronal Damage in Mice.

We investigated the protective effect and mechanisms of apigenin against cognitive impairments in a scopolamine-injected mouse model. Our results showed that intraperitoneal (i.p.) injection of scopolamine leads to learning and memory dysfunction, whereas the administration of apigenin (synthetic compound, 100 and 200 mg/kg/day) improved cognitive ability, which was confirmed by behavioral tests such as the T-maze test, novel objective recognition test, and Morris water maze test in mice. In addition, scopolamine-induced lipid peroxidation in the brain was attenuated by administration of apigenin. To further evaluate the protective mechanisms of apigenin on cognitive and memory function, Western blot analysis was carried out. Administration of apigenin decreased the B-cell lymphoma 2-associated X/B-cell lymphoma 2 (Bax/Bcl-2) ratio and suppressed caspase-3 and poly ADP ribose polymerase cleavage. Furthermore, apigenin down-regulated the β-site amyloid precursor protein-cleaving enzyme, along with presenilin 1 (PS1) and PS2 protein levels. Apigenin-administered mice showed lower protein levels of a receptor for advanced glycation end-products, whereas insulin-degrading enzyme, brain-derived neurotrophic factor (BDNF), and tropomyosin receptor kinase B (TrkB) expression were promoted by treatment with apigenin. Therefore, this study demonstrated that apigenin is an active substance that can improve cognitive and memory functions by regulating apoptosis, amyloidogenesis, and BDNF/TrkB signaling pathways.

Can we catch the second loach employing BACE1 inhibition, even as the first one might be escaping?

Obesity, diabetes, and Alzheimer's disease (AD) are becoming increasingly common, especially in the aging population, and are adversely affecting quality of life for patients and their families. These conditions have been shown to be interrelated, and AD has recently been referred to as type 3 diabetes, because neuronal insulin resistance underlies the pathophysiology of AD. Based on the amyloid-beta hypothesis, BACE1 (β-site amyloid precursor protein-cleaving enzyme 1) is the most promising drug target for AD. BACE1 is a β-secretase that processes the amyloid precursor protein (APP) to generate amyloid β-42 (Aβ42).

Development of Simultaneous Analysis Method for Multi-Compounds Content of New Shilajit Using HPLC-UV and the Cognitive Enhancing Effect: Mongolian Shilajit

Shilajit has a longstanding use as an anti-aging and memory enhancing drug. It is known to have excellent anti-bacterial effects and is believed to be effective for cognitive enhancement, but is difficult to standardize because of the lack of quality control standards. This study, for the first time, proposes a quality control standard using a simultaneous analytical method for the drug’s multi-compound content using high-performance liquid chromatography-ultraviolet detection (HPLC-UV) as an aid for the internationalization of Mongolian Shilajit. Phenolic compounds 1-6 were isolated from Mongolian Shilajit extract using bioassay-guided isolation, and the isolated compounds were evaluated for cognitive-related anti-Alzheimer’s disease (AD) activities using 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging, acetylcholinesterase (AChE), butyrylcholinesterase (BChE), β-site amyloid precursor protein-cleaving enzyme 1 (BACE1), and advanced glycation end-product (AGE) formation assays. The isolated compounds showed good effects for each activity. In addition, the isolated compounds were successfully quantified using a validated quantitative HPLC analysis method. As a result, the isolated compounds were suggested as standard marker compounds for Mongolian Shilajit. Also, we proved that the original material of Mongolian Shilajit is a lichen named Xanthoparmelia somloensis (Gyel.) Hale using HPLC-UV, ultra-high-performance liquid chromatography-electrospray ionization/hybrid linear trap-quadruple-orbitrap-high-resolution mass spectrometry (UHPLC-ESI/LTQ-HRMS).

Beta-Secretase 1 Underlies Reactive Astrocytes and Endothelial Disruption in Neurodegeneration.

Dysfunction in the neurovascular unit (NVU) is a key component in the progressive deterioration of Alzheimer’s disease (AD) and is critical in vascular dementia. Recent studies have shown that inflammation plays early and perhaps causal roles in the pathogenesis of AD related to NVU damage, possibly in part by overactivating the aspartic acid protease activity of β-site amyloid precursor protein-cleaving enzyme 1 (BACE1), which until now has almost solely been studied in the context of the β-amyloid cascade. In this study, we analyzed the relationship of BACE1 with astrocytes and blood vessels in human brains with sporadic and familial dementia [Autosomal dominant cerebral arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), sporadic Alzheimer’s disease (SAD), and familial Alzheimer’s disease (FAD)] and how BACE1 inhibition affects astrocytes and endothelial cells under conditions of glutamate toxicity. Our results show increased BACE1, PHF (Paired helical filaments)-tau and GFAP (Glial Fibrillary Acid Protein) immunoreactivity (IR) in the CA1 hippocampal regions of FAD and SAD brains. Furthermore, BACE1 immunoprecipitated with GFAP in tissue samples from all study cases, but their immunofluorescence close to (10 μm3) or overlapping blood vessels was only increased in FAD and SAD brains, and PHF-tau was present around the vessels mainly in FAD brains. Interestingly, the increased BACE1 levels were associated with reactive astrocytes, characterized by morphological changes and upregulation of GFAP under pathological and stressful conditions, and endothelial disruption by glutamate excitotoxicity, and these effects were reversed by BACE1 inhibition; further, BACE1-inhibited astrocytes protected endothelial cell integrity by preserving zonula occludens-1 (ZO-1) distribution and decreasing the expression of inflammatory markers. Taken together, these findings suggest that BACE1 dysregulation in astrocytes may have a role in the alterations in NVU integrity implicated in neurodegeneration.

Epigallocatechin-3-Gallate Provides Protection Against Alzheimer's Disease-Induced Learning and Memory Impairments in Rats.

PurposeRecent evidence has highlighted the anti-inflammatory properties of the constituent of Green Tea Polyphenols (GTP), epigallocatechin-3-gallate (EGCG) which has been suggested to exert a neuroprotective effect on Alzheimer’s disease (AD). The current study aimed to elucidate the effect of EGCG on memory function in rats with AD.MethodsAD rat models were initially established through an injection with Aβ 25–35 solution, followed by gavage with EGCG at varying doses to determine the effect of EGCG on learning and cognitive deficits in AD. Morris water maze test was conducted to evaluate the spatial memory function of the rats. Immunohistochemistry and Western blot analysis were performed to identify Tau phosphorylation. The expression of β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) mRNA and protein in rat hippocampus was measured by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis. Acetylcholinesterase (AchE) activity, Aβ1-42 expression and Ach content were all detected using enzyme-linked immunosorbent assay (ELISA).ResultsEGCG intervention brought about a decrease in the escape latency period while increasing the time at the target quadrant among the AD rats. EGCG decreased the hyperphosphorylation of Tau in hippocampus. BACE1 expression and activity as well as the expression of Aβ1-42 were suppressed by EGCG. Moreover, EGCG promoted Ach content by diminishing the activity of AchE.ConclusionThe current study demonstrates that EGCG may diminish the hyperphosphorylation of the Tau protein, downregulate BACE1 and Aβ1-42 expression to improve the antioxidant system and learning and memory function of rats with AD.

Protection against Alzheimer's disease by luteolin: Role of brain glucose regulation, anti-inflammatory activity, and the gut microbiota-liver-brain axis.

Luteolin is a widely distributed flavone herbs and vegetables. It has anti-oxidant and anti-inflammatory activities and improves glucose metabolism by potentiating insulin sensitivity and improving β-cell function and mass. Alzheimer's disease (AD) is induced by the deposition of amyloid-beta (Aβ) in the hippocampus and the formation of neurotoxic Aβ plaques. The Aβ deposition is associated with increased formation of Aβ from amyloid precursor protein by up-regulation of β-secretase and β-site amyloid precursor protein-cleaving enzyme 1 (BACE1). Furthermore, Aβ accumulation is increased by brain insulin resistance. The impairment of insulin/IGF-1 signaling mainly in the hippocampus and brain insulin resistance is connected to signals originating in the liver and gut microbiota, known as the gut microbiota-liver-brain axis. This indicates that the changes in the production of short-chain fatty acids by the gut microbiota and pro-inflammatory cytokines can alter insulin resistance in the liver and brain. Luteolin is detected in the brain tissues after passing through the blood-brain barrier, where it can directly influence neuroinflammation and brain insulin resistance and modulate Aβ deposition. Luteolin (10-70 mg/kg bw for rodents) can modulate the systemic and brain insulin resistance, and it suppresses AD development directly, and it influences Aβ deposition by activation of the gut microbiota-liver-brain axis. In this review, we evaluate the potential of luteolin to mitigate two potential causes of AD, neuroinflammatory processes, and disruption of glucose metabolism in the brain. This review suggests that luteolin intake can enhance brain insulin resistance and neuroinflammation, directly and indirectly, to protect against the development of Alzheimer's-like disease, and the gut microbiota-liver-brain axis is mainly involved in the indirect pathway. However, most studies have been conducted in animal studies, and human clinical trials are needed.