Chronic administration of anti-stroke herbal medicine TongLuoJiuNao reduces amyloidogenic processing of amyloid precursor protein in a mouse model of Alzheimer's disease

Generation and Characterization of a Novel Knockin Mouse Model Expressing PSEN1 D385A: Implications for Investigating Herbal Drug Effects in γ-Secretase Activity

Background

Presenilin (PSEN, PS) is essential for γ-secretase function, and mutations can disrupt amyloid-β (Aβ) production in familial Alzheimer's disease. Targeting γ-secretase is complex due to its broad involvement in physiological processes.

Objective

Our aim was to create a novel knockin (KI) mouse model expressing PSEN1 D385A mutation and investigate the efficacy of a Geniposide and Ginsenoside Rg1 combination (NeuroProtect modified formula, NP-2) in restoring γ-secretase activity.

Methods

Using gene manipulation, we established the PS1 D385A KI mouse model and confirmed the mutation, mRNA, and protein levels using Southern blotting, northern blotting, and western blotting, respectively. In vitro γ-secretase assay was conducted to measure γ-secretase activity, while histological analyses examined neurogenesis effects. NP-2 administration evaluated its impact on γ-secretase activity.

Results

The PS1 D385A KI homozygotes displayed severe cerebral hemorrhage, postnatal lethality, developmental disorders, reduced proliferation of neural progenitor cells, and disrupted γ-secretase function. The mutation abolished PS1 protein self-shearing, leading to compromised γ-secretase activity. NP-2 intervention effectively restored γ-secretase activity in the heterozygous mice.

Conclusions

PS1 D385A mutant disrupted PS1 protein self-cleaving, impairing γ-secretase activity in KI mice. NP-2 restored γ-secretase function, offering potential for novel AD treatment strategies despite the challenges posed by γ-secretase's complex role in physiological processes.

NeuroProtect, a Candidate Formula From Traditional Chinese Medicine, Attenuates Amyloid-β and Restores Synaptic Structures in APP/PS1 Transgenic Mice

Background: Alzheimer's disease (AD) is the most common cause of dementia. The emerging data suggest that cognitive decline occurred in the setting of Aβ accumulation with synaptic dysfunction, which started to happen at preclinical stages. Then, presymptomatic intervention is more critical to postponing AD processing. Traditional Chinese medicine has a long history of treating and preventing dementia. Findings have shown that the decoction of Panax notoginseng and Gardenia jasminoides Ellis enhances memory functions in patients with stroke, and their main components, Panax notoginseng saponins (PNS) and geniposide (GP), improved memory abilities in experimental AD models. Since herbal medicine has advantages in protection with few side effects, we wish to extend observations of the NeuroProtect (NP) formulation for reducing amyloid-β and restoring synaptic structures in APP/PS1 transgenic mice. Methods: APP/PS1 transgenic mice and their wild-type littermates were fed with control, NP, and their components from 4 to 7 months of age. We assessed the synaptic structure by Golgi staining, analyzed the amyloid deposits by Thioflavin-S staining, and measured related protein levels by Western blot or ELISA. We used the Morris water maze and shuttle box test to evaluate cognitive functions. Results: Compared to WT mice, APP/PS1 mice are characterized by the accumulation of amyloid plaques, reducing synaptic structure richness and memory deficits. NP prevents these changes and ameliorates cognitive deficits. These effects may have been due to the contribution of its components by inhibition of insoluble amyloid-β deposition and restoration of synaptic structures. Conclusion: These findings reveal a beneficial effect of NP on AD progression under an early intervention strategy and provide a food supplement for AD prevention.

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.

Geniposide Combined With Notoginsenoside R1 Attenuates Inflammation and Apoptosis in Atherosclerosis via the AMPK/mTOR/Nrf2 Signaling Pathway

Inflammation and apoptosis of vascular endothelial cells play a key role in the occurrence and development of atherosclerosis (AS), and the AMPK/mTOR/Nrf2 signaling pathway plays an important role in alleviating the symptoms of AS. Geniposide combined with notoginsenoside R1 (GN combination) is a patented supplement for the prevention and treatment of AS. It has been proven to improve blood lipid levels and inhibit the formation of AS plaques; however, it is still unclear whether GN combination can inhibit inflammation and apoptosis in AS by regulating the AMPK/mTOR/Nrf2 signaling pathway and its downstream signals. Our results confirmed that the GN combination could improve blood lipid levels and plaque formation in ApoE^−/− mice fed with a high-fat diet (HFD), inhibit the secretion of serum inflammatory factors and oxidative stress factors. It also decreased the expression of pyrin domain containing protein 3 (NLRP3) inflammasome-related protein and Bax/Bcl2/caspase-3 pathway-related proteins. At the same time, the GN combination could also inhibit the H₂O₂-induced inflammatory response and apoptosis of human umbilical vein endothelial cells (HUVECs), which is mainly related to the activation of the AMPK/mTOR pathway by GN combination, which in turn induces the activation of Nrf2/HO-1 signal. In addition, the above phenomenon could be significantly reversed by dorsomorphin. Therefore, our experiments proved for the first time that the GN combination can effectively inhibit AS inflammation and apoptosis by activating the AMPK/mTOR/Nrf2 signaling pathway to inhibit the NLRP3 inflammasome and Bax/Bcl2/caspase-3 pathway.

Inhibition of alpha-synuclein seeded fibril formation and toxicity by herbal medicinal extracts

Background

Recent studies indicated that seeded fibril formation and toxicity of α-synuclein (α-syn) play a main role in the pathogenesis of certain diseases including Parkinson’s disease (PD), multiple system atrophy, and dementia with Lewy bodies. Therefore, examination of compounds that abolish the process of seeding is considered a key step towards therapy of several synucleinopathies.

Methods

Using biophysical, biochemical and cell-culture-based assays, assessment of eleven compounds, extracted from Chinese medicinal herbs, was performed in this study for their effect on α-syn fibril formation and toxicity caused by the seeding process.

Results

Salvianolic acid B and dihydromyricetin were the two compounds that strongly inhibited the fibril growth and neurotoxicity of α-syn. In an in-vitro cell model, these compounds decreased the insoluble phosphorylated α-syn and aggregation. Also, in primary neuronal cells, these compounds showed a reduction in α-syn aggregates. Both compounds inhibited the seeded fibril growth with dihydromyricetin having the ability to disaggregate preformed α-syn fibrils. In order to investigate the inhibitory mechanisms of these two compounds towards fibril formation, we demonstrated that salvianolic acid B binds predominantly to monomers, while dihydromyricetin binds to oligomeric species and to a lower extent to monomers. Remarkably, these two compounds stabilized the soluble non-toxic oligomers lacking β-sheet content after subjecting them to proteinase K digestion.

Conclusions

Eleven compounds were tested but only two showed inhibition of α-syn aggregation, seeded fibril formation and toxicity in vitro. These findings highlight an essential beginning for development of new molecules in the field of synucleinopathies treatment.

Therapeutic Effects of Natural Drugs on Alzheimer's Disease

Alzheimer disease (AD) is characterized as a chronic neurodegenerative disease associated with aging. The clinical manifestations of AD include latent episodes of memory and cognitive impairment, psychiatric symptoms and behavioral disorders, as well as limited activities in daily life. In developed countries, AD is now acknowledged as the third leading cause of death, following cardiovascular disease and cancer. The pathogenesis and mechanism of AD remain unclear, although some theories have been proposed to explain AD, such as the theory of β-amyloid, the theory of the abnormal metabolism of tau protein, the theory of free radical damage, the theory of the inflammatory response, the theory of cholinergic damage, etc. Effective methods to predict, prevent or reverse AD are unavailable, and thus the development of new, efficient therapeutic drugs has become a current research hot spot worldwide. The isolation and extraction of active components from natural drugs have great potential in treating AD. These drugs possess the advantages of multiple targets in multiple pathways, fewer side effects and a long duration of curative effects. This article summaries the latest research progress regarding the mechanisms of natural drugs in the treatment of AD, providing a review of the literature and a theoretical basis for improving the clinical treatment of AD.

Protective Effects and Target Network Analysis of Ginsenoside Rg1 in Cerebral Ischemia and Reperfusion Injury: A Comprehensive Overview of Experimental Studies

Cerebral ischemia-reperfusion is a complicated pathological process. The injury and cascade reactions caused by cerebral ischemia and reperfusion are characterized by high mortality, high recurrence, and high disability. However, only a limited number of antithrombotic drugs, such as recombinant tissue plasminogen activator (r-TPA), aspirin, and heparin, are currently available for ischemic stroke, and its safety concerns is inevitable which associated with reperfusion injury and hemorrhage. Therefore, it is necessary to further explore and examine some potential neuroprotective agents with treatment for cerebral ischemia and reperfusion injury to reduce safety concerns caused by antithrombotic drugs in ischemic stroke. Ginseng Rg1 (G-Rg1) is a saponin composed of natural active ingredients and derived from the roots or stems of Panax notoginseng and ginseng in traditional Chinese medicine. Its pharmacological effects exert remarkable neurotrophic and neuroprotective effects in the central nervous system. To explore and summarize the protective effects and mechanisms of ginsenoside Rg1 against cerebral ischemia and reperfusion injury, we conducted this review, in which we searched the PubMed database to obtain and organize studies concerning the pharmacological effects and mechanisms of ginsenoside Rg1 against cerebral ischemia and reperfusion injury. This study provides a valuable reference and clues for the development of new agents to combat ischemic stroke. Our summarized review and analysis show that the pharmacological effects of and mechanisms underlying ginsenoside Rg1 activity against cerebral ischemia and reperfusion injury mainly involve 4 sets of mechanisms: anti-oxidant activity and associated apoptosis via the Akt, Nrf2/HO-1, PPARγ/HO-1, extracellular regulated protein kinases (ERK), p38, and c-Jun N-terminal kinase (JNK) pathways (or mitochondrial apoptosis pathway) and the caspase-3/ROCK1/MLC pathway; anti-inflammatory and immune stimulatory-related activities that involve apoptosis or necrosis via MAPK pathways (the JNK1/2 + ERK1/2 and PPARγ/HO-1 pathways), endoplasmic reticulum stress (ERS), high mobility group protein1 (HMGB1)-induced TLR2/4/9 and receptor for advanced glycation end products (RAGE) pathways, and the activation of NF-κB; neurological cell cycle, proliferation, differentiation, and regeneration via the MAPK pathways (JNK1/2 + ERK1/2, PI3K-Akt/mTOR, PKB/Akt and HIF-1α/VEGF pathways); and energy metabolism and the regulation of cellular ATP levels, the blood-brain barrier and other effects via N-methyl-D-aspartic acid (NMDA) receptors, ERS, and AMP/AMPK-GLUT pathways. Collectively, these mechanisms result in significant neuroprotective effects against cerebral ischemic injury. These findings will be valuable in that they should further promote the development of candidate drugs and provide more information to support the application of previous findings in stroke clinical trials.

Therapeutic Potential of Genipin in Central Neurodegenerative Diseases

Central neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD), are one of the biggest health problems worldwide. Currently, there is no cure for these diseases. The Gardenia jasminoides fruit is a common herbal medicine in traditional Chinese medicine (TCM), and a variety of preparations are used as treatments for central nervous system (CNS) diseases. Pharmacokinetic studies suggest genipin is one of the main effective ingredients of G. jasminoides fruit extract (GFE). Accumulated research data show that genipin possesses a range of key pharmacological properties, such as anti-inflammatory, neuroprotective, neurogenic, antidiabetic, and antidepressant effects. Thus, genipin shows therapeutic potential for central neurodegenerative diseases. We review the pharmacological actions of genipin for the treatment of neurodegenerative diseases of the CNS. We also describe the potential mechanisms underlying these effects.

Potentials of incretin-based therapies in dementia and stroke in type 2 diabetes mellitus

Patients with type 2 diabetes mellitus are at risk for accelerated cognitive decline and dementia. Furthermore, their risk of stroke is increased and their outcome after stroke is worse than in those without diabetes. Incretin-based therapies are a class of antidiabetic agents that are of interest in relation to these cerebral complications of diabetes. Two classes of incretin-based therapies are currently available: the glucagon-like-peptide-1 agonists and the dipeptidyl peptidase-4 -inhibitors. Independent of their glucose-lowering effects, incretin-based therapies might also have direct or indirect beneficial effects on the brain. In the present review, we discuss the potential of incretin-based therapies in relation to dementia, in particular Alzheimer's disease, and stroke in patients with type 2 diabetes. Experimental studies on Alzheimer's disease have found beneficial effects of incretin-based therapies on cognition, synaptic plasticity and metabolism of amyloid-β and microtubule-associated protein tau. Preclinical studies on incretin-based therapies in stroke have shown an improved functional outcome, a reduction of infarct volume as well as neuroprotective and neurotrophic properties. Both with regard to the treatment of Alzheimer's disease, and with regard to prevention and treatment of stroke, randomized controlled trials in patients with or without diabetes are underway. In conclusion, experimental studies show promising results of incretin-based therapies at improving the outcome of Alzheimer's disease and stroke through glucose-independent pleiotropic effects on the brain. If these findings would indeed be confirmed in large clinical randomized controlled trials, this would have substantial impact.

Ginsenoside Rb1 inhibits fibrillation and toxicity of alpha-synuclein and disaggregates preformed fibrils

Compelling evidence indicates that α-synuclein (α-syn) aggregation plays a central role in the pathogenesis of Parkinson's disease (PD) and other synucleinopathies. Identification of compounds that inhibit or reverse the aggregation process may thus represent a viable therapeutic strategy against PD and related disorders. Ginseng is a well-known medicinal plant that has been used in East Asia for more than two thousand years to treat several conditions. It is now understood that the pharmacological properties of ginseng can be attributed to its biologically active components, the ginsenosides, which in turn have been shown to have neuroprotective properties. We therefore sought to determine for the first time, the potential of the most frequently used and studied ginsenosides, namely Rg1, Rg3 and Rb1, as anti-amyloidogenic agents. The effect of Rg1, Rg3 and Rb1 on α-syn aggregation and toxicity was determined by an array of biophysical, biochemical and cell-culture-based techniques. Among the screened ginsenosides, only Rb1 was shown to be a potent inhibitor of α-syn fibrillation and toxicity. Additionally, Rb1 exhibited a strong ability to disaggregate preformed fibrils and to inhibit the seeded polymerization of α-syn. Interestingly, Rb1 was found to stabilize soluble non-toxic oligomers with no β-sheet content, that were susceptible to proteinase K digestion, and the binding of Rb1 to those oligomers may represent a potential mechanism of action. Thus, Rb1 could represent the starting point for designing new molecules that could be utilized as drugs for the treatment of PD and related disorders.

Neuroprotective effects of geniposide in SH-SY5Y cells and primary hippocampal neurons exposed to Aβ42

Our former studies have suggested that TongLuoJiuNao (TLJN) is clinically efficacious in the treatment of dementia and improving learning and memory in AD models. When Aβ aggregated with oligomer, it is known to be able to induce cellular toxicity as well as cognitive impairment. We tested the possibility that TLJN affects the formation of Aβ oligomers. In our experiment, TLJN improved cell viability, inhibited LDH release, and promoted the outgrowth of neurites of neurons treated with Aβ. Geniposide, the main component of TLJN, could increase the cell viability of SY5Y-APP695sw cells. The cytotoxicity of pretreated Aβ with geniposide was decreased in a dose-dependent manner. SDS-PAGE and Western blotting showed that geniposide and TLJN stimulated Aβ oligomer assembly. Compared with the control, more and longer fibrils of Aβ in the presence of geniposide were observed under electron microscope though the fibrils became less sensitive to thioflavin T staining. In sum, geniposide is able to protect neurons from Aβ-induced damage by remodeling Aβ.

The improvement of spatial memory deficits in APP/V717I transgenic mice by chronic anti-stroke herb treatment

In China, herbal medicine has an extensive history for the treatment of cerebrovascular diseases. Clinical studies have shown that stroke patients are more likely to experience significant memory decline in comparison to their healthy counterparts. Cognition is improved in stroke patients treated with herbal medicine active components, Geniposide (GP) and Geniposide Rg1 (GRg1) (together, called TLJN). However, the effect of TLJN in Alzheimer disease remains unknown. Therefore, we investigated the behavioral effect of TLJN in male and female APP/V717I transgenic (Tg) mice. We conducted two different treatment strategies: (1) pretreatment strategy: medically treated at the age of 3 months which lasted for 3 months; (2) early treatment strategy: medically treated at the age of 6 months which lasted for 4 months. In open field test, locomotor activity and anxiety-like behavior were not affected after TLJN administration in Tg mice. In Morris Water Maze test, spatial learning processes in both genders were improved by TLJN treatments. Furthermore, retrieval processes were significantly improved in the pretreatment strategy for only male mice, which also showed a trend for improved retrieval processes with early treatment. In the inhibitory avoidance test, TLJN enhanced learning processes. In addition, gender differences were found in Tg mice exposed to TLJN treatments. In Tg male mice, significant efficacy was seen at high and middle doses, and in Tg female mice, a low dose was more effective.

Pharmacogenomics of Alzheimer's disease: novel therapeutic strategies for drug development

Alzheimer's disease (AD) is a major problem of health and disability, with a relevant economic impact on our society. Despite important advances in pathogenesis, diagnosis, and treatment, its primary causes still remain elusive, accurate biomarkers are not well characterized, and the available pharmacological treatments are not cost-effective. As a complex disorder, AD is a polygenic and multifactorial clinical entity in which hundreds of defective genes distributed across the human genome may contribute to its pathogenesis. Diverse environmental factors, cerebrovascular dysfunction, and epigenetic phenomena, together with structural and functional genomic dysfunctions, lead to amyloid deposition, neurofibrillary tangle formation, and premature neuronal death, the major neuropathological hallmarks of AD. Future perspectives for the global management of AD predict that genomics and proteomics may help in the search for reliable biomarkers. In practical terms, the therapeutic response to conventional drugs (cholinesterase inhibitors, multifactorial strategies) is genotype-specific. Genomic factors potentially involved in AD pharmacogenomics include at least five categories of gene clusters: (1) genes associated with disease pathogenesis; (2) genes associated with the mechanism of action of drugs; (3) genes associated with drug metabolism (phase I and II reactions); (4) genes associated with drug transporters; and (5) pleiotropic genes involved in multifaceted cascades and metabolic reactions. The implementation of pharmacogenomic strategies will contribute to optimize drug development and therapeutics in AD and related disorders.

β-Secretase: its biology as a therapeutic target in diseases

β-Secretase (BACE1, β-site APP cleaving enzyme 1) is an aspartic proteinase that has multiple functions in various physiological processes, such as cell differentiation, immunoregulation, and cell death. There is increasing evidence that changes in BACE1 activity are involved in many diseases, such as Alzheimer's disease (AD), schizophrenia, epileptic behavior, and others. However, a deeper understanding of the molecular biology of BACE1 is necessary for further exploration of cell development, immunological regulation, and disease pathogenesis. Here, we review the molecular and cellular biology of BACE1, including its enzymatic properties, structure, biosynthesis, and physiological functions to provide a new perspective and rational assessment of drugability. Lastly, we discuss proposed strategies to control BACE1 activity for possible therapeutic application.