Safflower yellow ameliorates cognition deficits and reduces tau phosphorylation in APP/PS1 transgenic mice

Apicidin attenuates memory deficits by reducing the Aβ load in APP/PS1 mice

AIMS

Amyloid beta (Aβ) is an important pathological feature of Alzheimer's disease (AD). A disintegrin and metalloproteinase 10 (ADAM10) can reduce the production of toxic Aβ by activating the nonamyloidogenic pathway of amyloid precursor protein (APP). We previously found that apicidin, which is a histone deacetylase (HDAC) inhibitor, can promote the expression of ADAM10 and reduce the production of Aβ in vitro. This study was designed to determine the potential of apicidin treatment to reverse learning and memory impairments in an AD mouse model and the possible correlation of these effects with ADAM10.

METHODS

Nine-month-old APP/PS1 mice and C57 mice received intraperitoneal injections of apicidin or vehicle for 2 months. At 11 months of age, we evaluated the memory performance of mice with Morris water maze (MWM) and context fear conditioning tests. The Aβ levels were assessed in mouse brain using the immunohistochemical method and ELISA. The expression of corresponding protein involved in proteolytic processing of APP and the phosphorylation of tau were assessed by Western blotting.

RESULTS

Apicidin reversed the deficits of spatial reference memory and contextual fear memory, attenuated the formation of Aβ-enriched plaques, and decreased the levels of soluble and insoluble Aβ40/42 in APP/PS1 mice. Moreover, apicidin significantly increased the expression of ADAM10, improved the level of sAPPα, and reduced the production of sAPPβ, but did not affect the levels of phosphorylated tau in APP/PS1 mice.

CONCLUSION

Apicidin significantly improves the AD symptoms of APP/PS1 mice by regulating the expression of ADAM10, which may contribute to decreasing the levels of Aβ rather than decreasing the phosphorylation of tau.

Carthamus tinctorius L.: A natural neuroprotective source for anti-Alzheimer's disease drugs

ETHNOPHARMACOLOGICAL RELEVANCE

Alzheimer's disease (AD) is a multicausal neurodegenerative disease clinically characterized by generalized dementia. The pathogenic process of AD not only is progressive and complex but also involves multiple factors and mechanisms, including β-amyloid (Aβ) aggregation, tau protein hyperphosphorylation, oxidative stress, and neuroinflammation. As the first-line treatment for AD, cholinesterase inhibitors can, to a certain extent, relieve AD symptoms and delay AD progression. Nonetheless, the current treatment strategies for AD are far from meeting clinical expectations, and more options for AD treatment should be applied in clinical practice.

AIM OF THE REVIEW

The aim of this review was to investigate published reports of C. tinctorius L. and its active constituents in AD treatment through a literature review.

MATERIALS AND METHODS

Information was retrieved from scientific databases including Web of Science, ScienceDirect, Scopus, Google Scholar, Chemical Abstracts Services and books, PubMed, dissertations and technical reports. Keywords used for the search engines were "Honghua" or "Carthamus tinctorius L." or "safflower" in conjunction with "(native weeds OR alien invasive)"AND "Chinese herbal medicine".

RESULTS

A total of 47 literatures about C. tinctorius L. and its active constituents in AD treatment through signaling pathways, immune cells, and disease-related mediators and systematically elucidates potential mechanisms from the point of anti-Aβ aggregation, suppressing tau protein hyperphosphorylation, increasing cholinergic neurotransmitters levels, inhibiting oxidative stress, anti-neuroinflammation, ameliorating synaptic plasticity, and anti-apoptosis.

CONCLUSIONS

Chinese herbal medicine (CHM) is a treasure endowed by nature to mankind. Emerging studies have confirmed that CHM and its active constituents play a positive role in AD treatment. Carthamus tinctorius L., the most commonly used CHM, can be used with medicine and food, with the effect of activating blood circulation and eliminating blood stasis. In the paper, we have concluded that the existing therapeutic mechanisms of C. tinctorius L. and summarized the potential mechanisms of C. tinctorius L. and its active constituents in AD treatment through a literature review.

Rheum tanguticum Alleviates Cognitive Impairment in APP/PS1 Mice by Regulating Drug-Responsive Bacteria and Their Corresponding Microbial Metabolites

Drugs targeting intestinal bacteria have shown great efficacy for alleviating symptoms of Alzheimer’s disease (AD), and microbial metabolites are important messengers. Our previous work indicated that Rheum tanguticum effectively improved cognitive function and reshaped the gut microbial homeostasis in AD rats. However, its therapeutic mechanisms remain unclear. Herein, this study aimed to elaborate the mechanisms of rhubarb for the treatment of AD by identifying effective metabolites associated with rhubarb-responsive bacteria. The results found that rhubarb reduced hippocampal inflammation and neuronal damage in APP/PS1 transgenic (Tg) mice. 16S rRNA sequencing and metabolomic analysis revealed that gut microbiota and their metabolism in Tg mice were disturbed in an age-dependent manner. Rhubarb-responsive bacteria were further identified by real-time polymerase chain reaction (RT-PCR) sequencing. Four different metabolites reversed by rhubarb were found in the position of the important nodes on rhubarb-responsive bacteria and their corresponding metabolites combined with pathological indicators co-network. Furthermore, in vitro experiments demonstrated o-tyrosine not only inhibited the viabilities of primary neurons as well as BV-2 cells, but also increased the levels of intracellular reactive oxygen species and nitric oxide. In the end, the results suggest that rhubarb ameliorates cognitive impairment in Tg mice through decreasing the abundance of o-tyrosine in the gut owing to the regulation of rhubarb-responsive bacteria. Our study provides a promising strategy for elaborating therapeutic mechanisms of bacteria-targeted drugs for AD.

Pharmacological relevance of CDK inhibitors in Alzheimer's disease

Evidence suggests that cell cycle activation plays a role in the pathophysiology of neurodegenerative diseases. Alzheimer's disease is a progressive, terminal neurodegenerative disease that affects memory and other important mental functions. Intracellular deposition of Tau protein, a hyperphosphorylated form of a microtubule-associated protein, and extracellular aggregation of Amyloid β protein, which manifests as neurofibrillary tangles (NFT) and senile plaques, respectively, characterize this condition. In recent years, however, several studies have concluded that cell cycle re-entry is one of the key causes of neuronal death in the pathogenesis of Alzheimer's disease. The eukaryotic cell cycle is well-coordinated machinery that performs critical functions in cell replenishment, such as DNA replication, cell creation, repair, and the birth of new daughter cells from the mother cell. The complex interplay between the levels of various cyclins and cyclin-dependent kinases (CDKs) at different checkpoints is needed for cell cycle synchronization. CDKIs (cyclin-dependent kinase inhibitors) prevent cyclin degradation and CDK inactivation. Different external and internal factors regulate them differently, and they have different tissue expression and developmental functions. The checkpoints ensure that the previous step is completed correctly before starting the new cell cycle phase, and they protect against the transfer of defects to the daughter cells. Due to the development of more selective and potent ATP-competitive CDK inhibitors, CDK inhibitors appear to be on the verge of having a clinical impact. This avenue is likely to yield new and effective medicines for the treatment of cancer and other neurodegenerative diseases. These new methods for recognizing CDK inhibitors may be used to create non-ATP-competitive agents that target CDK4, CDK5, and other CDKs that have been recognized as important therapeutic targets in Alzheimer's disease treatment.

Safflower Yellow Improves the Synaptic Structural Plasticity by Ameliorating the Disorder of Glutamate Circulation in Aβ1-42-induced AD Model Rats

Safflower yellow (SY) is the main effective component of Carthamus tinctorius L., and Hydroxysafflor yellow A (HSYA) is the single active component with the highest content in SY. SY and HSYA have been shown to have neuroprotective effects in several AD models. In this study, we aimed to clarify whether the effects of SY and HSYA on the learning and memory abilities of Aβ_1-42-induced AD model rats are related to the enhancement of synaptic structural plasticity in brain tissues and the amelioration of disorder of glutamate circulation. We used rats injected with Aβ_1-42 into the bilateral hippocampus as a model of AD. After treatment with SY and HSYA, the learning and memory abilities of the Aβ_1-42-induced AD model rats were enhanced, Aβ deposition in the AD model rats was decreased, structural damage to dendritic spines and the loss of synaptic-associated proteins were alleviated, and the disorder of glutamate circulation was ameliorated. The results indicated that SY and HSYA improve synaptic structural plasticity by ameliorating the disorder of glutamate circulation in Aβ_1-42-induced AD model rats.

Safflower yellow attenuates learning and memory deficits in amyloid β-induced Alzheimer's disease rats by inhibiting neuroglia cell activation and inflammatory signaling pathways

Safflower yellow (SY) is an aqueous extract of natural safflower. Our laboratory has reported protective effects of alleviating memory impairment with SY in a transgentic mouse model of Alzheimer's disease. The possible beneficial effects of SY on amyloid-β-induced neuroinflammation in dementia remain unclarified. This study we hypothesize that astrocytes and microglia may cause amyloid-β deposition and produce a neuroinflammatory response, aims to explain the role and mechanism of SY in regulating glial activation and reducing Aβ deposition in Aβ_1-42 induced rat model. Wistar rats were treated with SY for one month after bilateral hippocampal injection of aggregated Aβ_1-42; behavioral tests were performed to demonstrate the amelioration of cognitive function. After that, the contents of iNOS, IL-1β, IL-6, and TNF-α in AD brain was detected. Western blot and real-time PCR were used to detect the M1 and M2-associated markers to demonstrate the activation of microglia. The conducted experiments have revealed that SY could strengthen spatial learning and memory ability of dementia rats, decrease the contents of iNOS, IL-1β, IL-6, and TNF-α and depress the activation of glial cells. Moreover, the SY treatment inhibited the M1 release of pro-inflammatory cytokines (iNOS and CD86), increased the expression of arginase-1, CD206, and YM-1 thereby reduced inflammation in model rats. Thus our results indicated that SY has very important theoretical and clinical value for the research and development of Chinese medicine for the treatment of AD.

Ellagic acid ameliorates learning and memory impairment in APP/PS1 transgenic mice via inhibition of β-amyloid production and tau hyperphosphorylation

β-amyloid (Aβ) aggregation and tau hyperphosphorylation are considered to be the primary pathological hallmarks of Alzheimer's disease (AD). Targeted inhibition of these pathological processes may provide effective treatments for AD. Accumulating evidence has demonstrated that ellagic acid (EA) exerts neuroprotective effects in several diseases. The present study investigated the effects of EA on AD-associated learning and memory deficits on APP/PS1 double transgenic mice and the underlying mechanisms. APP/PS1 mice or wild-type C57BL/6 mice were intragastrically administered EA (50 mg/kg/day) or vehicle for 60 consecutive days. The learning and memory abilities of mice were investigated using the Morris water maze test. Hippocampal regions were examined for the presence of amyloid plaques, neuronal apoptosis and tau phosphorylation. Expression levels of APP, Aβ, RAC-αserine/threonine-protein kinase and glycogen synthase kinase (GSK)3β in the hippocampus were determined by western blot analysis and ELISA. The results demonstrated that EA treatment ameliorated spatial learning and memory impairment in APP/PS1 mice and significantly reduced neuronal apoptosis and Aβ deposition in the hippocampus (P<0.05 and P<0.01). In addition, EA significantly inhibited the hyperphosphorylation of tau and significantly decreased the activity of glycogen synthase kinase (GSK)3β (P<0.01), which is involved in tau phosphorylation. Overall, these findings indicated that the beneficial effects of EA on AD-associated cognitive impairments may be attributed to the inhibition of Aβ production and tau hyperphosphorylation, and its beneficial action may be mediated in part, by the RAC-α serine/threonine-protein kinase/GSK3β signaling pathway.