Avenanthramide-C Restores Impaired Plasticity and Cognition in Alzheimer's Disease Model Mice

An Expanded Narrative Review of Neurotransmitters on Alzheimer's Disease: The Role of Therapeutic Interventions on Neurotransmission

Alzheimer's disease (AD) is a progressive neurodegenerative disease. The accumulation of amyloid-β (Aβ) plaques and tau neurofibrillary tangles are the key players responsible for the pathogenesis of the disease. The accumulation of Aβ plaques and tau affect the balance in chemical neurotransmitters in the brain. Thus, the current review examined the role of neurotransmitters in the pathogenesis of Alzheimer's disease and discusses the alterations in the neurochemical activity and cross talk with their receptors and transporters. In the presence of Aβ plaques and neurofibrillary tangles, changes may occur in the expression of neuronal receptors which in turn triggers excessive release of glutamate into the synaptic cleft contributing to cell death and neuronal damage. The GABAergic system may also be affected by AD pathology in a similar way. In addition, decreased receptors in the cholinergic system and dysfunction in the dopamine neurotransmission of AD pathology may also contribute to the damage to cognitive function. Moreover, the presence of deficiencies in noradrenergic neurons within the locus coeruleus in AD suggests that noradrenergic stimulation could be useful in addressing its pathophysiology. The regulation of melatonin, known for its effectiveness in enhancing cognitive function and preventing Aβ accumulation, along with the involvement of the serotonergic system and histaminergic system in cognition and memory, becomes remarkable for promoting neurotransmission in AD. Additionally, nitric oxide and adenosine-based therapeutic approaches play a protective role in AD by preventing neuroinflammation. Overall, neurotransmitter-based therapeutic strategies emerge as pivotal for addressing neurotransmitter homeostasis and neurotransmission in the context of AD. This review discussed the potential for neurotransmitter-based drugs to be effective in slowing and correcting the neurodegenerative processes in AD by targeting the neurochemical imbalance in the brain. Therefore, neurotransmitter-based drugs could serve as a future therapeutic strategy to tackle AD.

Deciphering the Role of Adrenergic Receptors in Alzheimer's Disease: Paving the Way for Innovative Therapies

Neurodegenerative diseases are currently among the most devastating diseases with no effective disease-modifying drugs in the market, with Alzheimer's disease (AD) being the most prevalent. AD is a complex multifactorial neurodegenerative disorder characterized by progressive and severe cognitive impairment and memory loss. It is the most common cause of progressive memory loss (dementia) in the elderly, and to date, there is no effective treatment to cure or slow disease progression substantially. The role of adrenergic receptors in the pathogenesis of Alzheimer's disease and other tauopathies is poorly understood or investigated. Recently, some studies indicated a potential benefit of drugs acting on the adrenergic receptors for AD and dementias, although due to the heterogeneity of the drug classes used, the results on the whole remain inconclusive. The scope of this review article is to comprehensively review the literature on the possible role of adrenergic receptors in neurodegenerative diseases, stemming from the use of agonists and antagonists including antihypertensive and asthma drugs acting on the adrenergic receptors, but also from animal models and in vitro models where these receptors have been studied. Ultimately, we hope to obtain a better understanding of the role of these receptors, identify the gaps in knowledge, and explore the possibility of repurposing such drugs for AD, given their long history of use and safety.

Olive Oil Industry By-Products as a Novel Source of Biophenols with a Promising Role in Alzheimer Disease Prevention

This review explores the potential health benefits and applications of phenolic secoiridoids derived from olive oil by-products in the prevention of Alzheimer's disease (AD). As reviewed herein, polyphenols, such as epigallocatechin-3-gallate, epicatechin, and resveratrol, show in vitro and in vivo antioxidant, anti-inflammatory, and neuroprotective properties, and are particularly relevant in the context of AD, a leading cause of dementia globally. The olive oil industry, particularly in the Mediterranean region, produces significant amounts of waste, including leaves, pomace, and wastewater, which pose environmental challenges but also offer an untapped source of bioactive compounds. Despite promising in vitro and in vivo studies indicating that olive-derived polyphenols, such as oleuropein and hydroxytyrosol, may mitigate AD pathology, human clinical trials remain limited. The variability in extraction methods and the complex nature of AD further complicate research. Future studies should focus on standardizing the protocols and conducting robust clinical trials to fully assess the therapeutic potential of these compounds. This approach not only supports the development of new treatments for AD but also promotes environmental sustainability by valorizing olive oil industry waste.

Phytochemicals targeting Alzheimer's disease via the AMP-activated protein kinase pathway, effects, and mechanisms of action

Alzheimer's disease (AD), characterized by cognitive dysfunction and other behavioral abnormalities, is a progressive neurodegenerative disease that occurs due to aging. Currently, effective drugs to mitigate or treat AD remain unavailable. AD is associated with several abnormalities in neuronal energy metabolism, such as decreased glucose uptake, mitochondrial dysfunction, and defects in cholesterol metabolism. Amp-activated protein kinase (AMPK) is an important serine/threonine protein kinase that regulates the energy status of cells. AMPK is widely present in eukaryotic cells and can sense and regulate energy metabolism to maintain energy supply and demand balance, making it a promising target for energy metabolism-based AD therapy. Therefore, this review aimed to discuss the molecular mechanism of AMPK in the pathogenesis of AD to provide a theoretical basis for the development of new anti-AD drugs. To review the mechanisms of phytochemicals in the treatment of AD via AMPK pathway regulation, we searched PubMed, Google Scholar, Web of Science, and Embase databases using specific keywords related to AD and phytochemicals in September 2023. Phytochemicals can activate AMPK or regulate the AMPK pathway to exert therapeutic effects in AD. The anti-AD mechanisms of these phytochemicals include inhibiting Aβ aggregation, preventing Tau hyperphosphorylation, inhibiting inflammatory response and glial activation, promoting autophagy, and suppressing anti-oxidative stress. Additionally, several AMPK-related pathways are involved in the anti-AD mechanism, including the AMPK/CaMKKβ/mTOR, AMPK/SIRT1/PGC-1α, AMPK/NF-κB/NLRP3, AMPK/mTOR, and PERK/eIF2α pathways. Notably, urolithin A, artemisinin, justicidin A, berberine, stigmasterol, arctigenin, and rutaecarpine are promising AMPK agonists with anti-AD effects. Several phytochemicals are effective AMPK agonists and may have potential applications in AD treatment. Overall, phytochemical-based drugs may overcome the barriers to the effective treatment of neurodegenerative diseases.

Metabolite Profiling of Allium hookeri Leaves Using UHPLC-qTOF-MS/MS and the Senomorphic Activity of Phenolamides

The plant Allium hookeri, a member of the Allium genus, has a rich history of culinary and medicinal use. Recent studies have unveiled its potent antioxidant and anti-inflammatory properties. While research on A. hookeri has demonstrated its neuroprotective and anti-neuroinflammatory effects, the specific bioactive compounds responsible for these effects remain unidentified in prior research. This study utilized an untargeted metabolomic approach, employing HRESI-qTOF MS/MS-based molecular networking, to comprehensively profile the chemical composition of metabolites in A. hookeri and identify new compounds within the plant. As a result, ten compounds, comprising one novel flavonoid (2) and nine known compounds (1 and 3-10), were isolated and identified through NMR analysis. The inhibitory effects of all isolated compounds on the senescent cell-associated secretory phenotype (SASP), which is pivotal in neuroprotective actions, were evaluated. Biological activity testing revealed N-trans-feruloyltyramine (7) to be the most potent compound, effectively inhibiting SASP markers and contributing to the senomorphic activities of A. hookeri. These findings underscore the potential of phenolamides from A. hookeri as a promising source of bioactive compounds for mitigating senescence-associated diseases.

Avenanthramide-C Shows Potential to Alleviate Gingival Inflammation and Alveolar Bone Loss in Experimental Periodontitis

Periodontal disease is a chronic inflammatory disease that leads to the gradual destruction of the supporting structures of the teeth including gums, periodontal ligaments, alveolar bone, and root cementum. Recently, interests in alleviating symptoms of periodontitis (PD) using natural compounds is increasing. Avenanthramide-C (Avn-C) is a polyphenol found only in oats. It is known to exhibit various biological properties. To date, the effect of Avn-C on PD pathogenesis has not been confirmed. Therefore, this study aimed to verify the protective effects of Avn-C on periodontal inflammation and subsequent alveolar bone erosion in vitro and in vivo. Upregulated expression of catabolic factors, such as matrix metalloproteinase 1 (MMP1), MMP3, interleukin (IL)-6, IL-8, and COX2 induced by lipopolysaccharide and proinflammatory cytokines, IL-1β, and tumor necrosis factor α (TNF-α), was dramatically decreased by Avn-C treatment in human gingival fibroblasts and periodontal ligament cells. Moreover, alveolar bone erosion in the ligature-induced PD mouse model was ameliorated by intra-gingival injection of Avn-C. Molecular mechanism studies revealed that the inhibitory effects of Avn-C on the upregulation of catabolic factors were mediated via ERK (extracellular signal-regulated kinase) and NF-κB pathway that was activated by IL-1β or p38 MAPK and JNK signaling that was activated by TNF-α, respectively. Based on this study, we recommend that Avn-C may be a new natural compound that can be applied to PD treatment.

Overview on the Polyphenol Avenanthramide in Oats (Avena sativa Linn.) as Regulators of PI3K Signaling in the Management of Neurodegenerative Diseases

Avenanthramides (Avns) and their derivatives, a group of polyphenolic compounds found abundantly in oats (Avena sativa Linn.), have emerged as promising candidates for neuroprotection due to their immense antioxidant, anti-inflammatory, and anti-apoptotic properties. Neurodegenerative diseases (NDDs), characterized by the progressive degeneration of neurons, present a significant global health burden with limited therapeutic options. The phosphoinositide 3-kinase (PI3K) signaling pathway plays a crucial role in cell survival, growth, and metabolism, making it an attractive target for therapeutic intervention. The dysregulation of PI3K signaling has been implicated in the pathogenesis of various NDDs including Alzheimer's and Parkinson's disease. Avns have been shown to modulate PI3K/AKT signaling, leading to increased neuronal survival, reduced oxidative stress, and improved cognitive function. This review explores the potential of Avn polyphenols as modulators of the PI3K signaling pathway, focusing on their beneficial effects against NDDs. Further, we outline the need for clinical exploration to elucidate the specific mechanisms of Avn action on the PI3K/AKT pathway and its potential interactions with other signaling cascades involved in neurodegeneration. Based on the available literature, using relevant keywords from Google Scholar, PubMed, Scopus, Science Direct, and Web of Science, our review emphasizes the potential of using Avns as a therapeutic strategy for NDDs and warrants further investigation and clinical exploration.

A PAM of the α1A-Adrenergic receptor rescues biomarker, long-term potentiation, and cognitive deficits in Alzheimer's disease mouse models without effects on blood pressure

α1-Adrenergic Receptors (ARs) regulate the sympathetic nervous system by the binding of norepinephrine (NE) and epinephrine (Epi) through different subtypes (α1A, α1B, α1D). α1A-AR activation is hypothesized to be memory forming and cognitive enhancing but drug development has been stagnant due to unwanted side effects on blood pressure. We recently reported the pharmacological characterization of the first positive allosteric modulator (PAM) for the α1A-AR with predictive pro-cognitive and memory properties. In this report, we now demonstrate the in vivo characteristics of Compound 3 (Cmpd-3) in two genetically-different Alzheimer's Disease (AD) mouse models. Drug metabolism and pharmacokinetic studies indicate sufficient brain penetrance and rapid uptake into the brain with low to moderate clearance, and a favorable inhibition profile against the major cytochrome p450 enzymes. Oral administration of Cmpd-3 (3-9 mg/kg QD) can fully rescue long-term potentiation defects and AD biomarker profile (amyloid β-40, 42) within 3 months of dosing to levels that were non-significant from WT controls and which outperformed donepezil (1 mg/kg QD). There were also significant effects on paired pulse facilitation and cognitive behavior. Long-term and high-dose in vivo studies with Cmpd-3 revealed no effects on blood pressure. Our results suggest that Cmpd-3 can maintain lasting therapeutic levels and efficacy with disease modifying effects with a once per day dosing regimen in AD mouse models with no observed side effects.

Avenanthramide-C Activates Nrf2/ARE Pathway and Inhibiting Ferroptosis Pathway to Improve Cognitive Dysfunction in Aging Rats

Postoperative neurocognitive impairment (POCD) is a common complication after surgery and anesthesia, especially in elderly patients. Avenanthramide-C (AVC) test is a vascular endothelial cell adhesion molecule inhibitor with strong anti-inflammatory and antioxidant effects. The aim of this study was to investigate the effect and mechanism of AVC on POCD in aged rats to clarify the effect of AVC on POCD in aged rats. The aging rat model was established by continuous 200 mg/kg propofol anesthesia. Repeated propofol anesthesia could severely impair spatial learning ability, memory and cognitive function, and could promote hippocampal apoptosis, oxidative stress injury, neuroinflammation and ferroptosis in aging rats. In addition, AVC not only improved cognitive dysfunction, but also significantly inhibited apoptosis, neuroinflammatory response, ferroptosis and oxidative stress level in the hippocampus of aging rats induced by repeated anesthesia. Further mechanistic studies manifested that the above protective effects of AVC on aging rats induced by repeated propofol anesthesia may be achieved by activating Nrf2/ARE pathway activity. AVC pretreatment has a preventive effect on cognitive dysfunction induced by repeated propofol anesthesia in aging rats, and the preventive effect of AVC may be realized by activating the Nrf2/ARE signaling pathway activity. Our results demonstrate that AVC preconditioning reduces postoperative neuronal loss and neuroinflammation, activates the Nrf2/ARE pathway, reduces oxidative stress injury, and improves POCD in aged rats.

Coarse cereals modulating chronic low-grade inflammation: review

Chronic low-grade inflammation (CLGI) is closely associated with various chronic diseases. Researchers have paid attention to the comprehensive application and development of food materials with potential anti-inflammatory activity. Owing to their abundant nutrients and biological activities, coarse cereals have emerged as an important component of human diet. Increasing evidence has revealed their potential protective effects against CLGI in chronic conditions. However, this property has not been systematically discussed and summarized. In the present work, numerous published reports were reviewed to systematically analyze and summarize the protective effects of coarse cereals and their main active ingredients against CLGI. Their current utilization state was investigated. The future prospects, such as the synergistic effects among the active compounds in coarse cereals and the biomarker signatures of CLGI, were also discussed. Coarse cereals show promise as food diet resources for preventing CLGI in diseased individuals. Their active ingredients, including β-glucan, resistant starch, arabinoxylan, phenolic acids, flavonoids, phytosterols and lignans, function against CLGI through multiple possible intracellular signaling pathways and immunomodulatory effects. Therefore, coarse cereals play a crucial role in the food industry due to their health effects on chronic diseases and are worthy of further development for possible application in modulating chronic inflammation.

Oat Extract Avenanthramide-C Reverses Hippocampal Long-Term Potentiation Decline in Tg2576 Mice

Memory deterioration in Alzheimer’s disease (AD) is thought to be underpinned by aberrant amyloid β (Aβ) accumulation, which contributes to synaptic plasticity impairment. Avenanthramide-C (Avn-C), a polyphenol compound found predominantly in oats, has a range of biological properties. Herein, we performed methanolic extraction of the Avns-rich fraction (Fr. 2) from germinated oats using column chromatography, and examined the effects of Avn-C on synaptic correlates of memory in a mouse model of AD. Avn-C was identified in Fr. 2 based on ¹H-NMR analysis. Electrophysiological recordings were performed to examine the effects of Avn-C on the hippocampal long-term potentiation (LTP) in a Tg2576 mouse model of AD. Avn-C from germinated oats restored impaired LTP in Tg2576 mouse hippocampal slices. Furthermore, Avn-C-facilitated LTP was associated with changes in the protein levels of phospho-glycogen synthase kinase-3β (p-GSK3β-S9) and cleaved caspase 3, which are involved in Aβ-induced synaptic impairment. Our findings suggest that the Avn-C extract from germinated oats may be beneficial for AD-related synaptic plasticity impairment and memory decline.

Effects and mechanisms of natural products on Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia in elderly people with a high incidence rate and complicated pathogenesis, and causes progressive cognitive deficit and memory impairment. Some natural products and bioactive compounds from natural sources show great potential in the prevention and treatment of AD, such as apple, blueberries, grapes, chili pepper, Monsonia angustifolia, cruciferous vegetables, Herba epimedii, Angelica tenuissima, Embelia ribes, sea cucumber, Cucumaria frondosa, green tea, Puer tea, Amanita caesarea and Inonotus obliquus, via reducing amyloid beta (Aβ) deposition, decreasing Tau hyperphosphorylation, regulating cholinergic system, reducing oxidative stress, inhibiting apoptosis and ameliorating inflammation. This review mainly summarizes the effects of some natural products and their bioactive compounds on AD with the potential molecular mechanisms.

Alzheimer's Disease Animal Models: Elucidation of Biomarkers and Therapeutic Approaches for Cognitive Impairment

Alzheimer's disease (AD) is an age-related and progressive neurodegenerative disorder. It is widely accepted that AD is mainly caused by the accumulation of extracellular amyloid β (Aβ) and intracellular neurofibrillary tau tangles. Aβ begins to accumulate years before the onset of cognitive impairment, suggesting that the benefit of currently available interventions would be greater if they were initiated in the early phases of AD. To understand the mechanisms of AD pathogenesis, various transgenic mouse models with an accelerated accumulation of Aβ and tau tangles have been developed. However, none of these models exhibit all pathologies present in human AD. To overcome these undesirable phenotypes, APP knock-in mice, which were presented with touchscreen-based tasks, were developed to better evaluate the efficacy of candidate therapeutics in mouse models of early-stage AD. This review assesses several AD mouse models from the aspect of biomarkers and cognitive impairment and discusses their potential as tools to provide novel AD therapeutic approaches.

Avenanthramide C Suppresses Matrix Metalloproteinase-9 Expression and Migration Through the MAPK/NF- κB Signaling Pathway in TNF-α-Activated HASMC Cells

In oat ingredients, flavonoids and phenolic acids are known to be the most important phenolic compounds. In phenolic compounds, wide-ranging biological responses, including antioxidative, anti-inflammatory, anti-allergic, and anti-cancer properties, were reported. Avenanthramide C (Avn C), a component of the phenolic compound of oats, has been reported to be highly antioxidant and anti-inflammatory, but its role in an anti-atherosclerosis response is unknown. The aim of this research was to assess the effect of Avn C on expression of MMP-9 on TNF-α-activated human arterial smooth-muscle cells (HASMC) and signaling involved in its anti-atherosclerosis activity. HASMC cells are known to produce inflammatory cytokines involving IL-6, IL-1β, and TNF-α during arteriosclerosis activity. Avn C specifically reduced IL-6 secretion in HASMC cells. Furthermore, we investigated whether Avn C could inhibit NF-κB nuclear protein translocation. Avn C suppressed nuclear protein translocation of NF-κB in TNF-α-stimulated HASMCs. The MMP-9 enzyme activity and expression are controlled through the MAPKs signaling path during the Avn C treatment. We confirmed that the levels of wound healing (p-value = 0.013, *p < 0.05) and migration (p-value = 0.007, **p < 0.01) are inhibited by 100 ng/ml TNF-α and 100 μM Avn C co-treated. Accordingly, Avn C inhibited the expression of MMP-9 and cell migration through the MAPK/NF-κB signaling pathway in TNF-α-activated HASMC. Therefore, Avn C can be identified and serve as disease prevention material and remedy for atherosclerosis.

Potential Herb-Drug Interactions in the Management of Age-Related Cognitive Dysfunction

Late-life mild cognitive impairment and dementia represent a significant burden on healthcare systems and a unique challenge to medicine due to the currently limited treatment options. Plant phytochemicals have been considered in alternative, or complementary, prevention and treatment strategies. Herbals are consumed as such, or as food supplements, whose consumption has recently increased. However, these products are not exempt from adverse effects and pharmacological interactions, presenting a special risk in aged, polymedicated individuals. Understanding pharmacokinetic and pharmacodynamic interactions is warranted to avoid undesirable adverse drug reactions, which may result in unwanted side-effects or therapeutic failure. The present study reviews the potential interactions between selected bioactive compounds (170) used by seniors for cognitive enhancement and representative drugs of 10 pharmacotherapeutic classes commonly prescribed to the middle-aged adults, often multimorbid and polymedicated, to anticipate and prevent risks arising from their co-administration. A literature review was conducted to identify mutual targets affected (inhibition/induction/substrate), the frequency of which was taken as a measure of potential interaction. Although a limited number of drugs were studied, from this work, interaction with other drugs affecting the same targets may be anticipated and prevented, constituting a valuable tool for healthcare professionals in clinical practice.

Phenolamides: Plant specialized metabolites with a wide range of promising pharmacological and health-promoting interests

Phenolamides constitute a family of metabolites, widely represented in the plant kingdom, that can be found in all plant organs with a predominance in flowers and pollen grains. They represent a large and structurally diverse family, resulting from the association of phenolic acids with aliphatic or aromatic amines. Initially revealed as active compounds in several medicinal plant extracts, phenolamides have been extensively studied for their health-promoting and pharmacological properties. Indeed, phenolamides have been shown to exhibit antioxidant, anti-inflammatory, anti-cancer and antimicrobial properties, but also protective effects against metabolic syndrome and neurodegenerative diseases. The purpose of this review is to summarise this large body of literature, including in vitro and in vivo studies, by describing the diversity of their biological properties and our actual knowledge of the molecular mechanisms behind them. With regard to their considerable pharmacological interest, the question of industrial production is also tackled through chemical and biological syntheses in engineered microorganisms. The diversity of biological activities already described, together with the active discovery of the broad structural diversity of this metabolite family, make phenolamides a promising source of new active compounds on which future studies should be focused.

The Chemistry and Health Benefits of Dietary Phenolamides

Phenolamides, also known as hydroxycinnamic acid amides or phenylamides, have been reported throughout the plant kingdom, while a few of these amine-conjugated hydroxycinnamic acids are unique in foods. The current knowledge of their specific functions in plant development and defense is readily available as is their biosynthesis; however, their functionality in humans is still largely unknown. Of the currently known phenolamides, the most common are avenanthramides, which are unique in oats and similar to the well-known drug Tranilast, which possess anti-inflammatory, antioxidant, anti-itch, and antiatherogenic activities. While recent data have brought to light more information regarding the other known phenolamides, such as hordatines, dimers of agmatine conjugated to hydroxycinnamic acid, and kukoamines, spermine-derived phenolamides, the information is still severely limited, leaving their potential health benefits to speculation. Herein, to highlight the importance of dietary phenolamides to human health, we review and summarize the four major subgroups of phenolamides, including their chemical structures, dietary sources, and reported health benefits. We believe that the studies on phenolamides are still in the infancy stage and additional health benefits of these phenolamides may yet be identified.