Anti-Stroke Chinese Herbal Medicines Inhibit Abnormal Amyloid-β Protein Precursor Processing in Alzheimer’s Disease

Background: Chinese Herbal Medicines (CHMs), as an important and integral part of a larger system of medicine practiced in China, called Traditional Chinese Medicine (TCM), have been used in stroke therapy for centuries. A large body of studies suggest that some Chinese herbs can help reverse cognitive impairment in stroke patients, while whether these herbs also exert therapeutic benefits for Alzheimer’s disease remains to be seen. Objective: To address this issue, we selected four types of CHMs that are commonly prescribed for stroke treatment in clinical practice, namely DengZhanXiXin (D1), TongLuoJiuNao (T2), QingKaiLing (Q3), and HuangQinGan (H4), and tested their effects on amyloid-β protein precursor (AβPP) processing in vitro. Methods: AβPP, β-secretase (BACE1), and 99-amino acid C-terminal fragment of AβPP (C99) stably transfected cells were used for the tests of AβPP processing. The production of Aβ, activity of BACE1, neprilysin (NEP), and γ-secretase were assessed by ELISA, RT-PCR, and western blot. Results: By upregulating BACE1 activity, D1 increased Aβ production whereas decreased the ratio of Aβ 42/Aβ 40; by downregulating BACE1 activity and modulating the expression of γ-secretase, T2 decreased Aβ production and the ratio of Aβ 42/Aβ 40; by downregulating BACE1 activity, Q3 decreased Aβ production; H4 did not change Aβ production due to the simultaneously downregulation of BACE1 and NEP activity. Conclusion: Our study indicates that these four anti-stroke CHMs regulate AβPP processing through different mechanisms. Particularly, T2 with relatively simple components and prominent effect on AβPP processing may be a promising candidate for the treatment of AD.

Caesalpinia mimosoides Leaf Extract Promotes Neurite Outgrowth and Inhibits BACE1 Activity in Mutant APP-Overexpressing Neuronal Neuro2a Cells

Alzheimer’s disease (AD) is implicated in the imbalance of several proteins, including Amyloid-β (Aβ), amyloid precursor protein (APP), and BACE1. APP overexpression interferes with neurite outgrowth, while BACE1 plays a role in Aβ generation. Medicinal herbs with effects on neurite outgrowth stimulation and BACE1 inhibition may benefit AD. This study aimed to investigate the neurite outgrowth stimulatory effect, along with BACE1 inhibition of Caesalpinia mimosoides (CM), using wild-type (Neuro2a) and APP (Swedish mutant)-overexpressing (Neuro2a/APPSwe) neurons. The methanol extract of CM leaves stimulated neurite outgrowth in wild-type and APP-overexpressing cells. After exposure to the extract, the mRNA expression of the neurite outgrowth activation genes growth-associated protein-43 (GAP-43) and teneurin-4 (Ten-4) was increased in both Neuro2a and Neuro2a/APPSwe cells, while the mRNA expression of neurite outgrowth negative regulators Nogo receptor (NgR) and Lingo-1 was reduced. Additionally, the extract suppressed BACE1 activity in the APP-overexpressing neurons. Virtual screening demonstrated that quercetin-3′-glucuronide, quercetin-3-O-glucoside, clausarinol, and theogallin were possible inhibitors of BACE1. ADMET was analyzed to predict drug-likeness properties of CM-constituents. These results suggest that CM extract promotes neurite outgrowth and inhibits BACE1 activity in APP-overexpressing neurons. Thus, CM may serve as a source of drugs for AD treatment. Additional studies for full identification of bioactive constituents and to confirm the neuritogenesis in vivo are needed for translation into clinic of the present findings.

Examination of BDNF Treatment on BACE1 Activity and Acute Exercise on Brain BDNF Signaling

Perturbations in metabolism results in the accumulation of beta-amyloid peptides, which is a pathological feature of Alzheimer’s disease. Beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) is the rate limiting enzyme responsible for beta-amyloid production. Obesogenic diets increase BACE1 while exercise reduces BACE1 activity, although the mechanisms are unknown. Brain-derived neurotropic factor (BDNF) is an exercise inducible neurotrophic factor, however, it is unknown if BDNF is related to the effects of exercise on BACE1. The purpose of this study was to determine the direct effect of BDNF on BACE1 activity and to examine neuronal pathways induced by exercise. C57BL/6J male mice were assigned to either a low (n = 36) or high fat diet (n = 36) for 10 weeks. To determine the direct effect of BDNF on BACE1, a subset of mice (low fat diet = 12 and high fat diet n = 12) were used for an explant experiment where the brain tissue was directly treated with BDNF (100 ng/ml) for 30 min. To examine neuronal pathways activated with exercise, mice remained sedentary (n = 12) or underwent an acute bout of treadmill running at 15 m/min with a 5% incline for 120 min (n = 12). The prefrontal cortex and hippocampus were collected 2-h post-exercise. Direct treatment with BDNF resulted in reductions in BACE1 activity in the prefrontal cortex (p < 0.05), but not the hippocampus. The high fat diet reduced BDNF content in the hippocampus; however, the acute bout of exercise increased BDNF in the prefrontal cortex (p < 0.05). These novel findings demonstrate the region specific differences in exercise induced BDNF in lean and obese mice and show that BDNF can reduce BACE1 activity, independent of other exercise-induced alterations. This work demonstrates a previously unknown link between BDNF and BACE1 regulation.

Relationship Between Alzheimer’s Disease and Retinal Choroidal Thickness: A Cross-Sectional Study

Background: The choroid is involved directly or indirectly in many pathological conditions such as Alzheimer’s disease (AD), Parkinson’s disease (PD), and multiple sclerosis (MS). Objective: The objective of this study was to investigate the association between retinal choroidal properties and the pathology of AD by determining choroidal thickness, hippocampus volume, cognitive functions, and plasma BACE1 activity. Methods: In this cross-sectional study, 37 patients with AD and 34 age-matched controls were included. Retinal choroidal thickness was measured via enhanced depth imaging optical coherence tomography. Hippocampal volume was measured via 3.0T MRI. Cognitive functions were evaluated using the Mini-Mental State Examination (MMSE) and Alzheimer’s Disease Assessment Scale-cognitive subscale (ADAS-Cog). Plasma BACE1 activity was analyzed using a fluorescence substrate-based plasma assay, and regression model were to analyze the data. Results: Retinal choroidal thickness was significantly thinner in the AD group than in the control group [(114.81±81.30) μm versus (233.79±38.29) μm, p < 0.05]. Multivariable regression analysis indicated that the ADAS-cog scores (β=–0.772, p = 0.000) and age (β=–0.176, p = 0.015) were independently associated with choroidal thickness. The logistic regression model revealed that the subfoveal choroidal thickness was a significant predictor for AD (OR = 0.984, 95% CI: 0.972–0.997). Conclusion: There was a general tendency of choroid thinning as the cognitive function declined. Although choroidal thickness was not a potential indicator for early stage AD, it was valuable in monitoring AD progression.

Traditional Chinese Medicine for Stroke Treatment Inhibits Abnormal Amyloid Precursor Processing in Alzheimer’s Disease

Ethnopharmacological relevance: Traditional Chinese Medicine (TCM) has a long history in oriental countries for its therapeutic benefits with stroke therapy, and improves cognitive deficits in those patients, but the potential impact on Alzheimer’s disease therapy remains unknown. Objective: To address this issue, in vitro, we have examined the effects of four types of TCMs selected from the ginsenoside family of drugs that are currently used in clinical stroke therapy on APP processing, DengZhanXiXin (D1), TongLuoJiuNao (T2), QingKaiLing (Q3) and HuangQinGan (H4). Materials and methods: APP, BACE1 and C99 stable transfected cells have been used to test the APP processing. The Aβ production, BACE1, NEP and γ-secretase activity were assessed by ELISA, RT-PCR and Western blot analysis. Results: In this study, D1 increases Aβ production but reduces the ratio of Aβ42/Aβ40 by up-regulating BACE1 activity; T2 reduces Aβ production and Aβ42/Aβ40 ratio by down-regulating BACE1 activity and modulating γ-secretase expression; Q3 reduces Aβ production by down-regulating BACE1 activity; H4 does not change Aβ production by the compromising effects on down-regulating BACE1 and NEP activity. Conclusion: These studies suggest that these four anti-stroke TCMs show different mechanisms on APP processing, and have the potential to be used in Aβ clearance; particularly, T2 with relatively simple components and evident effects in APP processing may be a promising candidate for the treatment of AD.

Increased blood BACE1 activity as a potential common pathogenic factor of vascular dementia and late onset Alzheimer's disease

Late onset Alzheimer disease (LOAD) is traditionally considered as a separate disease from vascular dementia (VAD). However, growing evidence suggests that β-amyloid (Aβ) accumulation, that initiates LOAD-related neurodegeneration, is preceded by vascular events. Previous in vitro studies showed that β-secretase 1 (BACE1), the key-enzyme of amyloidogenesis, is upregulated by cerebrovascular insult; moreover, its activity is increased both in brain and serum of LOAD patients. We aimed to investigate whether BACE1 serum activity is altered also in dementias related, or not, to cerebrovascular disease. Thus, we evaluated serum BACE1 activity in a sample of individuals, including patients with LOAD (n. 175), VAD (n. 40), MIXED (LOAD/VAD) dementia (n. 123), other types of dementia (n. 56), and healthy Controls (n. 204). We found that BACE1 was significantly higher not only in LOAD (+ 30%), but also in VAD (+ 35%) and MIXED dementia (+ 22%) (p < 0.001 for all), but not in the other types of dementia (+ 10%). Diagnostic accuracy was 77% for LOAD, 83% for VAD, and 77% for MIXED dementia. In conclusion, we showed for the first time that the increase in peripheral BACE1 activity is a common feature of LOAD and VAD, thus underlying a further pathogenic link between these two forms of dementia.

The Investigation on Cholinesterases and BACE1 Inhibitory Activities in Various Tea Infusions

Alzheimer’s disease (AD) is a chronic neurological disease related to the decline in brain and nervous system functions. At present, inhibitions of cholinesterases (ChEs) including acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) to enhance neurotransmitters and retardation of b-amyloid formation through b-secretase (BACE1) inhibition are 2 hypotheses for AD prevention and treatment. Hence, this study aims to investigate inhibitory activities against ChEs of various tea varieties of Camellia sinensis and herbal teas. At this step, the screening methodology for ChEs inhibitory activities in various tea varieties in order to provide a fast, inexpensive and convenient method for the detection of anti-cholinesterase activity was optimized. Then, selected tea with high ChEs was further examined regarding its BACE1 activity. As results, all tea samples displayed both anti-AChE and -BChE activities with the broad ranges of 6 - 85 % and 0 - 72 % inhibitory activities, respectively. Interestingly, C. sinensis teas exhibited higher ChEs inhibitory activities than herbal teas, in exception of Pandanus amaryllifolius (pandan) tea, which exhibited comparable inhibitory activities as C. sinensis teas. Pandan leaves were found to exhibit anti-BACE1 activity with 98 % inhibition. Besides, preliminary in vivo study showed that pandan leaves extract was able to rescue climbing defect observed in AD Drosophila melanogaster model, indicating the potential roles of pandan leaves in AD prevention.