Ellagic acid prevents dementia through modulation of PI3-kinase-endothelial nitric oxide synthase signalling in streptozotocin-treated rats

Upregulation of NADPH-oxidase, inducible nitric oxide synthase and apoptosis in the hippocampus following impaired insulin signaling in the rats: Development of sporadic Alzheimer's disease

NADPH-oxidase (NOX) is a multi-subunit enzyme complex. The upregulation of NOX causes massive production of superoxide (O2¯), which avidly reacts with nitric oxide (NO) and increases cellular reactive oxygen/nitrogen species (ROS/RNS). Increased ROS/RNS plays pivotal role in the sporadic Alzheimer's disease (sAD) development and brain damage following impaired insulin signaling. Hence, this study aimed to examine early-time course of changes in NOX and NOS expression, and apoptotic proteins in the rats hippocampi following insulin signaling impairment [induced by STZ injection; intraperitoneal (IP) or in cerebral ventricles (ICV)]. Early effects (1, 3, or 6 weeks) on the NOX activity, translocation of NOX subunits from cytosol to the membrane, NO-synthases [neuronal-, inducible- and endothelial-NOS; nNOS, iNOS and eNOS], The Rac-1 protein expression, levels of NO and O2¯, cytochrome c release, caspase-3 and 9 activations (cleavage) were studied. STZ injection (in both models) increased NOX activity, O2¯ production, and enhanced cytosolic subunits translocation into membrane. The iNOS but not nNOS and eNOS expression and NO levels were increased in STZ treated rats. Finally, STZ injection increased cytochrome c release, caspase-3 and 9 activations in a manner that was significantly associated with levels of O2¯ and NO in the hippocampus. ICV-STZ administration resulted in significant profound changes over the IP route. In conclusion, impairment in insulin function induces early changes in ROS/RNS contents through NOX and iNOS upregulation and neuronal apoptosis in the hippocampus. Our results could mechanistically explain the role of impaired insulin function in the development of sAD.

Pomegranate polyphenol punicalagin as a nutraceutical for mitigating mild cognitive impairment: An overview of beneficial properties

Dementia treatment has become a global research priority, driven by the increase in the aging population. Punicalagin, the primary polyphenol found in pomegranate fruit, exhibits a variety of benefits. Today, a growing body of research is showing that punicalagin is a nutraceutical for the prevention of mild cognitive impairment (MCI). However, a comprehensive review is still lacking. The aim of this paper is to provide a comprehensive review of the physicochemical properties, origin and pharmacokinetics of punicalagin, while emphasizing the significance and mechanisms of its potential role in the prevention and treatment of MCI. Preclinical and clinical studies have demonstrated that Punicalagin possesses the potential to effectively target and enhance the treatment of MCI. Potential mechanisms by which punicalagin alleviates MCI include antioxidative damage, anti-neuroinflammation, promotion of neurogenesis, and modulation of neurotransmitter interactions. Overall, punicalagin is safer and shows potential as a therapeutic compound for the prevention and treatment of MCI, although more rigorous randomized controlled trials involving large populations are required.

In Vitro and Molecular Docking Evaluation of the Anticholinesterase and Antidiabetic Effects of Compounds from Terminalia macroptera Guill. & Perr. (Combretaceae)

Alzheimer's disease (AD) and diabetes are non-communicable diseases with global impacts. Inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are suitable therapies for AD, while α-amylase and α-glucosidase inhibitors are employed as antidiabetic agents. Compounds were isolated from the medicinal plant Terminalia macroptera and evaluated for their AChE, BChE, α-amylase, and α-glucosidase inhibitions. From 1H and 13C NMR data, the compounds were identified as 3,3'-di-O-methyl ellagic acid (1), 3,3',4'-tri-O-methyl ellagic acid-4-O-β-D-xylopyranoside (2), 3,3',4'-tri-O-methyl ellagic acid-4-O-β-D-glucopyranoside (3), 3,3'-di-O-methyl ellagic acid-4-O-β-D-glucopyranoside (4), myricetin-3-O-rhamnoside (5), shikimic acid (6), arjungenin (7), terminolic acid (8), 24-deoxysericoside (9), arjunglucoside I (10), and chebuloside II (11). The derivatives of ellagic acid (1-4) showed moderate to good inhibition of cholinesterases, with the most potent being 3,3'-di-O-methyl ellagic acid, with IC50 values of 46.77 ± 0.90 µg/mL and 50.48 ± 1.10 µg/mL against AChE and BChE, respectively. The compounds exhibited potential inhibition of α-amylase and α-glucosidase, especially the phenolic compounds (1-5). Myricetin-3-O-rhamnoside had the highest α-amylase inhibition with an IC50 value of 65.17 ± 0.43 µg/mL compared to acarbose with an IC50 value of 32.25 ± 0.36 µg/mL. Two compounds, 3,3'-di-O-methyl ellagic acid (IC50 = 74.18 ± 0.29 µg/mL) and myricetin-3-O-rhamnoside (IC50 = 69.02 ± 0.65 µg/mL), were more active than the standard acarbose (IC50 = 87.70 ± 0.68 µg/mL) in the α-glucosidase assay. For α-glucosidase and α-amylase, the molecular docking results for 1-11 reveal that these compounds may fit well into the binding sites of the target enzymes, establishing stable complexes with negative binding energies in the range of -4.03 to -10.20 kcalmol-1. Though not all the compounds showed binding affinities with cholinesterases, some had negative binding energies, indicating that the inhibition was thermodynamically favorable.

Ameliorating the Role of Aripiprazole in Memory Deficits Induced by Intracerebroventricular Streptozotocin-Induced Dementia of Alzheimer's Type

Alzheimer's disease (AD) is a progressive neurodegenerative disorder causing immense suffering for the patients. Dopamine D2 and 5-hydroxytryptamine receptor 1A (5-HT1A) receptors' activation has been reported to play a crucial role in managing neurological outcomes in the brain and other health disorders. This study aimed to investigate the role of aripiprazole, a dopamine D2 and 5-HT1A selective receptors' activator, in the restoration of memory deficit induced by streptozotocin in mice. The cognitive functions of animals were determined using the Morris water maze. Brain sections were stained with hematoxylin and eosin and Congo red to examine the structural deviations. Brain oxidative stress (thiobarbituric acid reactive substance and glutathione), acetylcholinesterase activity, IL-6, and IL-10 were measured to assess biochemical alterations. Activation of D2 and 5-HT1A with aripiprazole attenuated STZ-induced cognitive deficit, increased brain GSH levels, reduced TBARS levels, AChE activity, IL-6 levels, and IL-10 levels and prevented STZ-induced brain anomalies in mice. Hence, the present study concluded that aripiprazole mitigated STZ-induced memory impairment and can be used as an efficacious therapeutic target for the management of AD.

Protective Mechanisms of Nootropic Herb Shankhpushpi (Convolvulus pluricaulis) against Dementia: Network Pharmacology and Computational Approach

Convolvulus pluricaulis (CP), a Medhya Rasayana (nootropic) herb, is a major ingredient in Ayurvedic and Traditional Chinese formulae indicated for neurological conditions, namely, dementia, anxiety, depression, insanity, and epilepsy. Experimental evidence suggests various neuroactive potentials of CP such as memory-enhancing, neuroprotective, and antiepileptic. However, precise mechanisms underlying the neuropharmacological effects of CP remain unclear. The study, therefore, aimed at deciphering the molecular basis of neuroprotective effects of CP phytochemicals against the pathology of dementia disorders such as Alzheimer's (AD) and Parkinson's (PD) disease. The study exploited bioinformatics tools and resources, such as Cytoscape, DAVID (Database for annotation, visualization, and integrated discovery), NetworkAnalyst, and KEGG (Kyoto Encyclopedia of Genes and Genomes) database to investigate the interaction between CP compounds and molecular targets. An in silico analysis was also employed to screen druglike compounds and validate some selective interactions. ADME (absorption, distribution, metabolism, and excretion) analysis predicted a total of five druglike phytochemicals from CP constituents, namely, scopoletin, 4-hydroxycinnamic acid, kaempferol, quercetin, and ayapanin. In network analysis, these compounds were found to interact with some molecular targets such as prostaglandin G/H synthase 1 and 2 (PTGS1 and PTGS2), endothelial nitric oxide synthase (NOS3), insulin receptor (INSR), heme oxygenase 1 (HMOX1), acetylcholinesterase (ACHE), peroxisome proliferator-activated receptor-gamma (PPARG), and monoamine oxidase A and B (MAOA and MAOB) that are associated with neuronal growth, survival, and activity. Docking simulation further confirmed interaction patterns and binding affinity of selected CP compounds with those molecular targets. Notably, scopoletin showed the highest binding affinity with PTGS1, NOS3, PPARG, ACHE, MAOA, MAOB, and TRKB, quercetin with PTGS2, 4-hydroxycinnamic acid with INSR, and ayapanin with HMOX1. The findings indicate that scopoletin, kaempferol, quercetin, 4-hydroxycinnamic acid, and ayapanin are the main active constituents of CP which might account for its memory enhancement and neuroprotective effects and that target proteins such as PTGS1, PTGS2, NOS3, PPARG, ACHE, MAOA, MAOB, INSR, HMOX1, and TRKB could be druggable targets against dementia.

Forest Biomass as a Promising Source of Bioactive Essential Oil and Phenolic Compounds for Alzheimer's Disease Therapy

Alzheimer’s disease (AD) is the most common neurodegenerative disorder affecting elderly people worldwide. Currently, there are no effective treatments for AD able to prevent disease progression, highlighting the urgency of finding new therapeutic strategies to stop or delay this pathology. Several plants exhibit potential as source of safe and multi-target new therapeutic molecules for AD treatment. Meanwhile, Eucalyptus globulus extracts revealed important pharmacological activities, namely antioxidant and anti-inflammatory properties, which can contribute to the reported neuroprotective effects. This review summarizes the chemical composition of essential oil (EO) and phenolic extracts obtained from Eucalyptus globulus leaves, disclosing major compounds and their effects on AD-relevant pathological features, including deposition of amyloid-β (Aβ) in senile plaques and hyperphosphorylated tau in neurofibrillary tangles (NFTs), abnormalities in GABAergic, cholinergic and glutamatergic neurotransmission, inflammation, and oxidative stress. In general, 1,8-cineole is the major compound identified in EO, and ellagic acid, quercetin, and rutin were described as main compounds in phenolic extracts from Eucalyptus globulus leaves. EO and phenolic extracts, and especially their major compounds, were found to prevent several pathological cellular processes and to improve cognitive function in AD animal models. Therefore, Eucalyptus globulus leaves are a relevant source of biological active and safe molecules that could be used as raw material for nutraceuticals and plant-based medicinal products useful for AD prevention and treatment.

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.

Implications of Phosphoinositide 3-Kinase-Akt (PI3K-Akt) Pathway in the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is the foremost type of dementia that afflicts considerable morbidity and mortality in aged population. Several transcription molecules, pathways, and molecular mechanisms such as oxidative stress, inflammation, autophagy, and immune system interact in a multifaceted way that disrupt physiological processes (cell growth, differentiation, survival, lipid and energy metabolism, endocytosis) leading to apoptosis, tauopathy, β-amyloidopathy, neuron, and synapse loss, which play an important role in AD pathophysiology. Despite of stupendous advancements in pathogenic mechanisms, treatment of AD is still a nightmare in the field of medicine. There is compelling urgency to find not only symptomatic but effective disease-modifying therapies. Recently, phosphoinositide 3-kinase (PI3K) and Akt are identified as a pathway triggered by diverse stimuli, including insulin, growth factors, cytokines, and cellular stress, that link amyloid-β, neurofibrillary tangles, and brain atrophy. The present review aims to explore and analyze the role of PI3K-Akt pathway in AD and agents which may modulate Akt and have therapeutic prospects in AD. The literature was researched using keywords "PI3K-Akt" and "Alzheimer's disease" from PubMed, Web of Science, Bentham, Science Direct, Springer Nature, Scopus, and Google Scholar databases including books. Articles published from 1992 to 2021 were prioritized and analyzed for their strengths and limitations, and most appropriate ones were selected for the purpose of review. PI3K-Akt pathway regulates various biological processes such as cell proliferation, motility, growth, survival, and metabolic functions, and inhibits many neurotoxic mechanisms. Furthermore, experimental data indicate that PI3K-Akt signaling might be an important therapeutic target in treatment of AD.

Ellagic acid prevents 3-nitropropionic acid induced symptoms of Huntington's disease

Mitochondrial abnormalities and redox imbalance are major pathogenic factors in progression of Huntington's disease (HD), manifested clinically by affective, motor, cognitive, and psychiatric incompetence. Antioxidants behold much promise in mitigation of several pathological facets in HD. Ellagic acid (EA) is a naturally derived polyphenol acknowledged for potent neuroprotective abilities that enabled its significance amongst popular brain tonics. The present study is aimed to examine the outcome of EA pre-treatment in 3-nitropropionic acid (3-NP) rat prototype of HD. Separate rat groups were pre-treated with EA (25, 50, and 100 mg/kg, p.o.) for 21 days and 3-NP (10 mg/kg, i.p.) was given for 14 days alongside to induce symptoms of HD. The physical/motor functions (narrow beam paradigm, footprint study, hanging-wire assessment) and cognitive abilities using elevated plus maze and novel object recognition task were evaluated. Entire brain was isolated and succinate dehydrogenase activity and parameters of oxido-nitrosative stress were assessed in mitochondrial fraction. 3-NP accrued oxido-nitrosative stress and significant decrease in succinate dehydrogenase activity caused motor and cognitive deficits in rats. EA pre-treatment resurrected succinate dehydrogenase activity in 3-NP treated rats that indicated preservation of mitochondrial function. A significant decrease in thiobarbituric acid reactive substances and nitrite levels and increase in glutathione and catalase activity by EA in 3-NP treated rats was noted. EA protected the rats against 3-NP triggered cognitive insufficiency and motor disturbances. It can be inferred that ellagic acid protects against 3-NP induced mitochondrial dysfunction and oxido-nitrosative stress in the brain. EA supplements or nutraceuticals might possess protective potential against symptoms of HD.

Neuroprotective Potential of Ellagic Acid: A Critical Review

Ellagic acid (EA) is a dietary polyphenol present in various fruits, vegetables, herbs, and nuts. It exists either independently or as part of complex structures, such as ellagitannins, which release EA and several other metabolites including urolithins following absorption. During the past few decades, EA has drawn considerable attention because of its vast range of biological activities as well as its numerous molecular targets. Several studies have reported that the oxidative stress-lowering potential of EA accounts for its broad-spectrum pharmacological attributes. At the biochemical level, several mechanisms have also been associated with its therapeutic action, including its efficacy in normalizing lipid metabolism and lipidemic profile, regulating proinflammatory mediators, such as IL-6, IL-1β, and TNF-α, upregulating nuclear factor erythroid 2-related factor 2 and inhibiting NF-κB action. EA exerts appreciable neuroprotective activity by its free radical-scavenging action, iron chelation, initiation of several cell signaling pathways, and alleviation of mitochondrial dysfunction. Numerous in vivo studies have also explored the neuroprotective attribute of EA against various neurotoxins in animal models. Despite the increasing number of publications with experimental evidence, a critical analysis of available literature to understand the full neuroprotective potential of EA has not been performed. The present review provides up-to-date, comprehensive, and critical information regarding the natural sources of EA, its bioavailability, metabolism, neuroprotective activities, and underlying mechanisms of action in order to encourage further studies to define the clinical usefulness of EA for the management of neurological disorders.

Ellagic acid protects mice against sleep deprivation-induced memory impairment and anxiety by inhibiting TLR4 and activating Nrf2

Sleep disorder has become a prevalent issue in current society and is connected with the deterioration of neurobehaviors such as mood, cognition and memory. Ellagic acid (EA) is a phenolic phytoconstituent extracted from grains and fruits that has potent neuroprotective properties. This research aimed to study the alleviative effect and mechanism of EA on memory impairment and anxiety caused by sleep deprivation (SD). EA ameliorated behavioral abnormalities in SD mice, associated with increased dendritic spine density, and reduced shrinkage and loss of hippocampal neurons. EA reduced the inflammatory response and oxidative stress injury caused by SD, which may be related to activation of the Nrf2/HO-1 pathway and mitigation of the TLR4-induced inflammatory response. In addition, EA significantly reduced the mortality and ROS levels in glutamate (Glu)-induced hippocampal neuron injury, and these effects of EA were enhanced in TLR4 siRNA-transfected neurons. However, knockdown of Nrf2 dramatically restrained the protective impact of EA on Glu-induced toxicity. Taken together, EA alleviated memory impairment and anxiety in sleep-deprived mice potentially by inhibiting TLR4 and activating Nrf2. Our findings suggested that EA may be a promising nutraceutical ingredient to prevent cognitive impairment and anxiety caused by sleep loss.

Shared cerebral metabolic pathology in non-transgenic animal models of Alzheimer's and Parkinson's disease

Parkinson's disease (PD) and Alzheimer's disease (AD) are the most common chronic neurodegenerative disorders, characterized by motoric dysfunction or cognitive decline in the early stage, respectively, but often by both symptoms in the advanced stage. Among underlying molecular pathologies that PD and AD patients have in common, more attention is recently paid to the central metabolic dysfunction presented as insulin resistant brain state (IRBS) and altered cerebral glucose metabolism, both also explored in animal models of these diseases. This review aims to compare IRBS and alterations in cerebral glucose metabolism in representative non-transgenic animal PD and AD models. The comparison is based on the selectivity of the neurotoxins which cause experimental PD and AD, towards the cellular membrane and intracellular molecular targets as well as towards the selective neurons/non-neuronal cells, and the particular brain regions. Mitochondrial damage and co-expression of insulin receptors, glucose transporter-2 and dopamine transporter on the membrane of particular neurons as well as astrocytes seem to be the key points which are further discussed in a context of alterations in insulin signalling in the brain and its interaction with dopaminergic transmission, particularly regarding the time frame of the experimental AD/PD pathology appearance and the correlation with cognitive and motor symptoms. Such a perspective provides evidence on IRBS being a common underlying metabolic pathology and a contributor to neurodegenerative processes in representative non-transgenic animal PD and AD models, instead of being a direct cause of a particular neurodegenerative disorder.

Lacidipine attenuates caffeine-induced anxiety-like symptoms in mice: Role of calcium-induced oxido-nitrosative stress

BACKGROUND

Anxiety is a disorder of multi-factorial pathogenesis involving interrelated pathways of neurotransmitters, oxidative stress and metamorphosed calcium-signaling that negatively affects brain functions. Modulation of Ca2+-channels outlines a promising strategy to curb the progression of anxiety-like disorders through attenuation of redox-imbalance. The current research scheme was designed to explore the anxiolytic effects of lacidipine (L-type Ca2+-channel blocker; LCD) pretreatment in caffeine-induced anxiety-like symptom model in mice.

METHODS

Forty-two Swiss albino mice (25-30 g) were distributed to 7 groups (n = 6): Vehicle control, caffeine, alprazolam + caffeine, lacidipine(0.3, 1 and 3 mg/kg, ip)+caffeine and Bay-K8644+LCD(3)+caffeine. Caffeine (25 mg/kg, ip) was administered from day 8 to 14 to induce anxiety-like symptoms in mice. Lacidipine (0.3, 1 and 3 mg/kg, ip) and alprazolam (0.25 mg/kg, ip) were administered from day 1 to 14 in separate groups. Bay-K8644 (Ca2+-channel agonist) was injected on day 14 to delineate the role of Ca2+ in anti-anxiety effect of LCD in caffeine-treated mice. Elevated zero maze and mirror chamber test were employed to assess anxiety-like behavior. Afterwards, the mice were sacrificed and whole brains were harvested for estimation of biomarkers of oxido-nitrosative stress, such as TBARS, GSH, SOD, catalase and total nitrite content.

RESULTS

An increase in brain oxido-nitrosative stress and anxiety-like behavior was observed in caffeine treated mice. LCD pretreatment attenuated the brain oxido-nitrosative stress and anxiety-like behavior in mice in caffeine treated mice. Anxiolytic effect of LCD was attenuated by Bay-K8644 (0.5 mg/kg) in caffeine treated mice.

CONCLUSION

LCD (L-type Ca2+-channel antagonist) pretreatment attenuated caffeine-induced oxido-nitrosative stress and anxiety-like behavior.