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

Ellagic Acid Reverses Alterations in the Expression of AMPA Receptor and Its Scaffolding Proteins in the Cerebral Cortex and Memory Decline in STZ-sporadic Alzheimer' s Disease Mouse Model

RATIONALE

Alzheimer's disease (AD), an age-dependent devastating neuropsychiatric disorder, is a leading cause of learning, memory and intellectual disabilities. Current therapeutic approaches for the amelioration of the anomalies of AD are not effective.

OBJECTIVE

In the present study, the molecular mechanisms underlying sporadic AD (sAD), the memory related behavioral analysis and neuroprotective effects of Ellagic acid (EA) were investigated.

METHOD

sAD mouse model was developed by intracerebroventricular (ICV) injection of Streptozotocin (STZ). The efficacy of EA, a naturally occurring polyphenol, in amelioration of anomalies associated with sAD was assessed. EA was administered once daily for 28 days at a dose of 75 mg/kg body weight followed by neurobehavioral, biochemical, molecular and neuronal count analysis to delineate the mode of action of EA.

RESULT

The ICV injection of STZ in mice significantly increased the expression of AD biomarkers in addition to enhanced oxidative stress. A decline in the discrimination index in Novel Object Recognition Test was observed indicating the compromise of recognition memory in AD. Studies on the expression of genes involved in synaptic plasticity reveal the dysregulation of the α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) of the glutamate and its scaffolding proteins in the postsynaptic density and thereby synaptic plasticity in AD. ICV-STZ led to significant upregulation of apoptotic markers which led to decrease in neuronal density of the cerebral cortex. EA significantly reversed the above and improved anomalies of sAD.

CONCLUSION

EA was observed to profoundly modulate the genes involved in AD pathophysiology, restored antioxidant enzymes activity, reduced lipid peroxidation and neuronal loss in the sAD brain. Further, EA was observed to effectively modulate the genes involved in apoptosis and synaptic plasticity. Therefore, EA possesses promising anti-AD properties, which may improve AD-associated anomalies by modulating synaptic plasticity via AMPAR signaling.

Update on new trends and progress of natural active ingredients in the intervention of Alzheimer's disease, based on understanding of traditional Chinese and Western relevant theories: A review

Alzheimer's disease (AD) is one of the major neurological disorders causing death in the elderly worldwide. As a neurodegenerative disease that is difficult to prevent and cure, the pathogenesis of AD is complex and there is no effective cure. A variety of natural products derived from plants have been reported to have promising anti-AD activities, including flavonoids, terpenes, phenolic acids and alkaloids, which can effectively relieve the symptoms of AD in a variety of ways. This paper mainly reviews the pharmacological activity and mechanisms of natural products against AD. Although the clinical efficacy of these plants still needs to be determined by further high-quality studies, it may also provide a basis for future researchers to study anti-AD in depth.

Ellagic Acid: A Dietary-Derived Phenolic Compound for Drug Discovery in Mild Cognitive Impairment

Ellagic acid (EA), a naturally occurring polyphenolic compound, is detected in free form or linked to polyols or sugars, constituting hydrolyzable tannins or ellagitannins in distinct fruits, nuts, and herbs. Today, a considerable number of botanicals and enriched foods containing EA are commercially available as nutraceuticals and used to prevent mild cognitive impairment (MCI) due to the excellent neuroprotective capacity of EA. Here, this study aims to provide an overview of the physicochemical properties, source, and pharmacokinetics of EA and to emphasize the importance and mechanisms of EA in the prevention and management of MCI. To date, preclinical studies of EA and its derivatives in various cell lines and animal models have advanced the idea of dietary EA as a feasible agent capable of specifically targeting and improving MCI. The molecular mechanisms of EA and its derivatives to prevent or reduce MCI are mainly through reducing neuroinflammation, oxidative stress, neuronal apoptosis, synaptic dysfunction and loss, and defective mitochondrial functions. Nevertheless, well-designed and correctly large randomized controlled trials in the human population need to be performed to reinforce the scientific facticity of the beneficial effects of EA against MCI. Synchronously, the mechanism of EA against MCI is least provided cynosure and expects more attention from the emerging research community.

Ellagic Acid Modulates Uninduced as well as Mutation and Metal-Induced Aggregation of α-Synuclein: Implications for Parkinson's Disease

α-Synuclein (αS) is an intrinsically disordered protein whose aggregation and deposition in Lewy bodies is involved in the progression of Parkinson's disease (PD) and other related disorders. The aggregation process of αS is also triggered by mutations like A53T and E46K in the SNCA gene and disruption in metal-ion homeostasis. Currently, there is no obviating therapy available in the market that could effectively prevent the progression of the disease. In this backdrop, there exists an emerging need to consider naturally occurring polyphenols and flavonoids as potential therapeutic agents against PD. In this study, we demonstrate the modulatory effect of ellagic acid (EA) against wild-type as well as mutation and metal-induced aggregation of αS. Thioflavin T (ThT) fluorescence assay suggests that EA acts on the nucleation phase of αS fibrillization, thereby increasing the lag phase from 21.33 ± 3.01 to 48.20 ± 5.05 h and reducing the fibrils growth rate from 4.60 ± 2.06 to 0.890 ± 0.36 h^-1. 8-Anilino-1-naphthalene sulfonic acid (ANS), Congo red (CR), and intrinsic fluorescence studies indicate that the interaction of EA with αS facilitates the structural changes in the protein that lead to inhibition of fibril formation. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) images illustrate that the size of fibrils diminishes up to 100 nm in the presence of EA. Dot blot and seeding experiments put forward that EA directs the αS aggregation toward off-pathway fibrillization. Our 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay deciphers the role of EA in minimizing the αS fibril-induced toxicity, thereupon leading to an increase in cell viability. Also, EA attenuates both mutations as well as metal-induced αS fibrillization and disaggregates the preexisting fibrils. Additionally, computational studies elucidate that EA preferentially interacts with the N-terminal and NAC domain of αS. Hence, this work reveals the aggregation inhibition mechanism of EA and provides considerable therapeutic interventions against PD and related disorders.

Treadmill Running Improves Spatial Learning Memory Through Inactivation of Nuclear Factor Kappa B/Mitogen-Activated Protein Kinase Signaling Pathway in Amyloid-β-Induced Alzheimer Disease Rats

PURPOSE

Exercise is known to reduce proinflammatory cytokines production and apoptosis. We investigated the effect of treadmill running on spatial learning memory in terms of activation of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathway in Alzheimer disease (AD) rats. We also evaluated the effect of treadmill running on proinflammatory cytokine production and apoptosis.

METHODS

Using the stereotaxic frame, amyloid-β (Aβ) was injected into the lateral ventricle of the brain. The rats belong to treadmill running groups were forced to run on a motorized treadmill for 30 minutes per a day during 4 weeks, starting 3 days after Aβ injection. Morris water maze task was done for the determination of spatial learning memory. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, immunohistochemistry for cleaved caspase-3, and western blot for NF-κB, inhibitory protein of NF-κB (IκB), MAPK signaling pathway, tumor necrosis factor (TNF)-α, interleukin (IL)-1β were done.

RESULTS

Induction of AD increased proinflammatory cytokine secretion by activating the NF-κB/MAPK signaling pathway. These changes induced apoptosis in the hippocampus and reduced spatial learning memory. In contrast, treadmill running inactivated the NF-κB/MAPK signaling pathway and suppressed proinflammatory cytokine production. These changes inhibited apoptosis and improved spatial learning memory.

CONCLUSION

Current results showed that treadmill running promoted spatial learning memory through suppressing proinflammatory cytokine production and apoptosis via inactivation of NF-κB/MAPK signaling pathway. Treadmill exercise can be considered an effective intervention for symptom relieve of AD.

Dietary Phenolic Acids and Their Major Food Sources Are Associated with Cognitive Status in Older Italian Adults

BACKGROUND

Life expectancy is increasing along with the rising prevalence of cognitive disorders. Among the factors that may contribute to their prevalence, modifiable risk factors such as diet may be of primary importance. Unarguably, plant-based diets rich in bioactive compounds, such as polyphenols, showed their potential in decreasing risk of neurodegenerative disorders. Therefore, the aim of the present study is to investigate whether exposure to components of plant-based diets, namely phenolic acids, may affect cognitive status in older Italian adults.

METHODS

The demographic, lifestyle and dietary habits of a sample of individuals living in southern Italy were analyzed. Dietary intake was assessed through food frequency questionnaires (FFQs). Data on the phenolic acids content in foods were estimated using the Phenol-Explorer database. Cognitive status was evaluated using The Short Portable Mental Status Questionnaire. Multivariate logistic regression analyses were used to assess the associations.

RESULTS

The mean intake of phenolic acids was 346.6 mg/d. After adjustment for potential confounding factors, individuals in the highest quartile of total phenolic acid intake were less likely to have impaired cognitive status (OR = 0.36 (95% CI: 0.14, 0.92)); similarly, the analysis for subclasses of phenolic acids showed the beneficial effect toward cognitive status of greater intake of hydroxycinnamic acids (OR = 0.35 (95% CI: 0.13, 0.91)). Among individual compounds, only higher intake of caffeic acid was inversely associated with impaired cognitive status (OR = 0.32 (95% CI: 0.11, 0.93)); notably, the association with ferulic acid intake was significant only when adjusting for background characteristics, and not for adherence to the Mediterranean diet.

CONCLUSIONS

This study revealed that greater intakes of dietary phenolic acids were significantly inversely associated with impaired cognition, emphasizing the possible role of phenolic acids in the prevention of cognitive disorders.

Bioaccessible Raspberry Extracts Enriched in Ellagitannins and Ellagic Acid Derivatives Have Anti-Neuroinflammatory Properties

Chronic neuroinflammation associated with neurodegenerative disorders has been reported to be prevented by dietary components. Particularly, dietary (poly)phenols have been identified as having anti-inflammatory and neuroprotective actions, and their ingestion is considered a major preventive factor for such disorders. To assess the relation between (poly)phenol classes and their bioactivity, we used five different raspberry genotypes, which were markedly different in their (poly)phenol profiles within a similar matrix. In addition, gastro-intestinal bio-accessible fractions were produced, which simulate the (poly)phenol metabolites that may be absorbed after digestion, and evaluated for anti-inflammatory potential using LPS-stimulated microglia. Interestingly, the fraction from genotype 2J19 enriched in ellagitannins, their degradation products and ellagic acid, attenuated pro-inflammatory markers and mediators CD40, NO, TNF-α, and intracellular superoxide via NF-κB, MAPK and NFAT pathways. Importantly, it also increased the release of the anti-inflammatory cytokine IL-10. These effects contrasted with fractions richer in anthocyanins, suggesting that ellagitannins and its derivatives are major anti-inflammatory (poly)phenols and promising compounds to alleviate neuroinflammation.

Ellagic Acid Inhibits Neuroinflammation and Cognitive Impairment Induced by Lipopolysaccharides

Neuroinflammation is a predisposing factor for the development of cognitive impairment and dementia. Among the new molecules that are currently being studied, ellagic acid (EA) has stood out for its neuroprotective properties. The present study investigated the effects of ellagic acid in the object recognition test, oxidative stress, cholinergic neurotransmission, glial cell expression, and phosphorylated Tau protein expression. For this, 32 male Wistar rats received an intraperitoneal (IP) application of lipopolysaccharides (LPS) at a dose of 250 µg/kg or 0.9% saline solution (SAL) for 8 days. Two hours after the IP injections, the animals received 100 mg/kg of EA or SAL via intragastric gavage. Behavioral parameters (open field test and object recognition) were performed on days 5, 6, and 7 of the experimental periods. The results showed that the treatment with EA in the LPS group was able to inhibit cognitive impairment, modulate the immune system response by significantly reducing glial cell expression, attenuating phosphorylated Tau and oxidative damage with consequent improvement in the antioxidant system, as well as preventing the increase of acetylcholinesterase activity. Thus, the neuroprotective effects of EA and its therapeutic potential in cognitive disorders secondary to neuroinflammation were demonstrated.

Nanoformulated ellagic acid ameliorates pentylenetetrazol-induced experimental epileptic seizures by modulating oxidative stress, inflammatory cytokines and apoptosis in the brains of male mice

The present study evaluated the neuroprotective and antiepileptic efficacy of ellagic acid (EA) encapsulated in calcium-alginate nanoparticles (Ca²⁺-ALG NPs) in pentylenetetrazol (PTZ)-induced seizures in male mice. EA was encapsulated in ALG NPs using a nanospray drying method followed by ionotropic crosslinking with Ca²⁺. Characterization of the developed Ca²⁺-crosslinked EA-ALG NPs showed spherical, high stability NPs; successful loading of EA within crosslinked ALG NPs; and sustained release of EA. Male Swiss albino mice were divided into ten groups as follows; Group I- (control), Group II (50 mg EA /kg) - (EA), Group III polyethylene glycol (PEG), Group IV EA NPs (50 mg/kg) - (EA NP), Group (50 mg/kg alginate) V void V NPs - (void NPs), Group VI: (37.5 PTZ mg/kg) -(PTZ), Group VII: PTZ and EA - (PTZ-EA). Group VIII: animals received PTZ and PEG concurrently (PTZ-PEG). Group IX; animals received PTZ and void NPs concurrently - (PTZ-void). Group X: animals received PTZ and EA NPs concurrently (PTZ-EA NPs). PTZ was used to induce experimental epilepsy. Ca²⁺-ALG NPs prevented seizures throughout the experimental period and had a more prominent effect than free EA did. Ca²⁺-ALG NPs prevented increased glutamate, decreased GABA concentrations and ameliorated increased amyloid-β and homocysteine levels in the serum and brain. Ca²⁺-EA-ALG NPs were superior to free EA in improving increased IL-6 and TNF-α. Ca²⁺-ALG NPs ameliorated PTZ-induced oxidative stress, as evidenced by decreased 4HNE levels and enhanced GSH, GR and GPx levels in the brain. These changes were accompanied by amelioration of apoptosis and its regulating proteins, including Cytochrome C, P53, Bax, Bcl2 and caspase-3 and caspase-9, and protected against DNA damage. Histological examination of the hippocampus confirmed that the neuroprotective effect of Ca²⁺-EA-ALG NPs was superior and more effective than that of free EA.

The Rho kinase inhibitor fasudil attenuates Aβ1-42-induced apoptosis via the ASK1/JNK signal pathway in primary cultures of hippocampal neurons

Alzheimer's disease (AD), a chronic, progressive, neurodegenerative disorder, is the most common type of dementia. Beta amyloid (Aβ) peptide aggregation and phosphorylated tau protein accumulation are considered as one of the causes for AD. Our previous studies have demonstrated the neuroprotective effect of the Rho kinase inhibitor fasudil, but the mechanism remains elucidated. In the present study, we examined the effects of fasudil on Aβ_1-42 aggregation and apoptosis and identified the intracellular signaling pathways involved in these actions in primary cultures of mouse hippocampal neurons. The results showed that fasudil increased neurite outgrowth (52.84%), decreased Aβ burden (46.65%), Tau phosphorylation (96.84%), and ROCK-II expression. In addition, fasudil reversed Aβ_1-42-induced decreased expression of Bcl-2 and increases in caspase-3, cleaved-PARP, phospho-JNK(Thr183/Tyr185), and phospho-ASK1(Ser966). Further, fasudil decreased mitochondrial membrane potential and intracellular calcium overload in the neurons treated with Aβ_1-42. These results suggest that inhibition of Rho kinase by fasudil reverses Aβ_1-42-induced neuronal apoptosis via the ASK1/JNK signal pathway, calcium ions, and mitochondrial membrane potential. Fasudil could be a drug of choice for treatment of Alzheimer's disease.