Examining the potential clinical value of curcumin in the prevention and diagnosis of Alzheimer’s disease

Oligosaccharides from black ginseng innovatively prepared by low-temperature steam-heating process ameliorate cognitive impairment in Alzheimer's disease mice via the Keap-1/Nrf2 pathway

BACKGROUND

Our objective in this study was to evaluate the effectiveness of oligosaccharides extracted from black ginseng (OSBG), innovatively prepared by a low-temperature steam-heating process, in the improvement of learning and memory impairment in mice, as well as the mechanism(s).

RESULTS

Eight carbohydrates involving isomaltose and maltotetraose were detected in black gensing; monosaccharide residues including mannose and rhamnose were also discovered. OSBG-treated mice showed significant amelioration in recognition and spatial memory deficits compared to the scopolamine group. OSBG could decrease acetylcholinesterase activity in a tissue-dependent fashion but not in a dose-dependent manner. Furthermore, in contrast, OSBG administration resulted in significant upregulation superoxide dismutase, glutathione, glutathione peroxidase (GPx), and Kelch-like ECH-associated protein 1, downregulation of malondialdehyde and nuclear factor erythroid 2-related factor 2 in the tissues. Finally, at the genus level, we observed that the OSBG interventions increased the relative abundance of probiotics (e.g., Barnesiella, Staphylococcus, Clostridium_XlVb) and decreased pernicious bacteria such as Eisenbergiella and Intestinimonas, compared to the Alzheimer's disease mouse model group. Herein, our results demonstrate that OSBG restores the composition of the scopolamine-induced intestinal microbiota in mice, providing homeostasis of gut microbiota and providing evidence for microbiota-regulated therapeutic potential.

CONCLUSION

Our results showed for the first time a clear role for OSBG in improving scopolamine-induced memory impairment by inhibiting cholinergic dysfunction in a tissue-dependent manner. Additionally, OSBG administration relieved oxidative stress by activating the Keap-1/Nrf2 pathway and modulating the gut microbiota. Collectively, OSBG may be a promising target for neuroprotective antioxidants for improving memory and cognition in Alzheimer's disease patients. © 2024 Society of Chemical Industry.

Could protein phosphatase 2A and glycogen synthase kinase-3 beta be targeted by natural compounds to ameliorate Alzheimer's pathologies?

Alzheimer's disease (AD) is a progressive neurological disorder that impairs memory and cognitive abilities, primarily in the elderly. The burden of AD extends beyond patients, impacting families and caregivers due to the patients' reliance on assistance for daily tasks. The main features of the pathogenesis of AD are beta-amyloid plaques and neurofibrillary tangles (NFTs), that strongly correlate with oxidative stress and inflammation. NFTs result from misfolded and hyperphosphorylated tau proteins. Various studies have focused on tau phosphorylation, indicating protein phosphatase 2A (PP2A) as the primary tau phosphatase and glycogen synthase kinase-3 beta (GSK-3β) as the leading tau kinase. Experimental evidence suggests that inhibition of PP2A and increased GSK-3β activity contribute to neuroinflammation, oxidative stress, and cognitive impairment. Hence, targeting PP2A and GSK-3β with pharmacological approaches shows promise in treating AD. The use of natural compounds in the drug development for AD have been extensively studied for their antioxidant, anti-inflammatory, anti-cholinesterase, and neuroprotective properties, demonstrating therapeutic advantages in neurological diseases. Alongside the development of PP2A activator and GSK-3β inhibitor drugs, natural compounds are likely to have neuroprotective effects by increasing PP2A activity and decreasing GSK-3β levels. Therefore, based on the preclinical and clinical studies, the potential of PP2A and GSK-3β as therapeutic targets of natural compounds are highlighted in this review.

Review on anti-alzheimer drug development: approaches, challenges and perspectives

Alzheimer is an irreversible progressive neurodegenerative disease that causes failure of cerebral neurons and disability of the affected person to practice normal daily life activities. There is no concrete evidence to identify the exact reason behind the disease, so several relevant hypotheses emerged, highlighting many possible therapeutic targets, such as acetylcholinesterase, cholinergic receptors, N-methyl d-aspartate receptors, phosphodiesterase, amyloid β protein, protein phosphatase 2A, glycogen synthase kinase-3 beta, β-secretase, γ-secretase, α-secretase, serotonergic receptors, glutaminyl cyclase, tumor necrosis factor-α, γ-aminobutyric acid receptors, and mitochondria. All of these targets have been involved in the design of new potential drugs. An extensive number of these drugs have been studied in clinical trials. However, only galantamine, donepezil, and rivastigmine (ChEIs), memantine (NMDA antagonist), and aducanumab and lecanemab (selective anti-Aβ monoclonal antibodies) have been approved for AD treatment. Many drugs failed in the clinical trials to such an extent that questions have been posed about the significance of some of the aforementioned targets. On the contrary, the data of other drugs were promising and shed light on the significance of their targets for the development of new potent anti-alzheimer drugs.

The Effect of a Tribulus-Based Formulation in Alleviating Cholinergic System Impairment and Scopolamine-Induced Memory Loss in Zebrafish (Danio rerio): Insights from Molecular Docking and In Vitro/In Vivo Approaches

Tribulus terrestris L. (Tt) has been recently gaining attention for its pharmacological value, including its neuroprotective activities. In this study, we explore the neuroprotective effects of a Tribulus terrestris extract in a zebrafish (Danio rerio) model of scopolamine (SCOP)-induced memory impairment and brain oxidative stress. SCOP, an anticholinergic drug, was employed to replicate fundamental aspects of Alzheimer's disease (AD) in animal models. The fish were treated with ethanolic leaf extract (ELE) from Tt (1, 3, and 6 mg/L) for 15 days. SCOP (100 µM) was administered 30 min before behavioral tests were conducted. Molecular interactions of the major compounds identified via UPLC-PDA/MS in Tt fractions with the active site of acetylcholinesterase (AChE) were explored via molecular docking analyses. Terrestrosin C, protodioscin, rutin, and saponin C exhibited the most stable binding. The spatial memory performance was assessed using the Y-maze test, and memory recognition was examined using a novel object recognition (NOR) test. Tt extract treatment reversed the altered locomotion patterns that were caused by SCOP administration. Biochemical analyses also verified Tt's role in inhibiting AChE, improving antioxidant enzyme activities, and reducing oxidative stress markers. The present findings pave the way for future application of Tt as a natural alternative to treat cognitive disorders.

Demaghi, a polyherbal formulation, mitigates aluminum chloride-induced neurological impairment in mice: Insights from phytochemical analysis and behavioral assessment

Herbal products have been very popular in Pakistan for their curative significance against various disorders. Demaghi (DEMG) is a widely used herbal product claimed to own natural substances having neuroprotective potential. The current study aims to scientifically validate the chemical composition as well as its neuroprotective claims of this widely used herbal tonic. The commercially available Demaghi product was chemically characterized for its phytocomposition. The mice were treated with two doses of Demaghi (DEMG 50 mg and 100 mg/kg/day), and the effects of its prolonged exposure on animal anxiety, memory, and depression were noted through a series of behavioral tests in the AlCl3-induced memory deficient mice model. Besides that, dissected brains were biochemically analyzed for oxidative stress markers and acetylcholinesterase activity, as well as histopathological changes. The study outcomes showed that DEMG (100 mg/kg/day) has prominent anti-anxiety effects, memory-enhancing properties, and anti-depressants effects observed in the AlCl3-induced memory-deficient mice model. Biochemical assays also showed a greater decrease in oxidative stress of tested animals treated with 100 mg/kg/day of DEMG. The histopathological analysis also revealed that administration of DEMG reduced the AlCl3-induced toxicity. UPLC-MS results revealed the presence of many phytoconstituents, which showed to support cholinergic signaling in in-silico studies. The current research validates the neurological benefits of Demaghi for memory-boosting properties. The phytocompounds present in Demaghi exert neuroprotective effects, possibly by enhancing the cholinergic neurotransmission and combating the neurotoxin-induced oxidative stress.

Hypometabolism, Alzheimer's Disease, and Possible Therapeutic Targets: An Overview

The brain is a highly dynamic organ that requires a constant energy source to function normally. This energy is mostly supplied by glucose, a simple sugar that serves as the brain's principal fuel source. Glucose transport across the blood-brain barrier (BBB) is primarily controlled via sodium-independent facilitated glucose transport, such as by glucose transporter 1 (GLUT1) and 3 (GLUT3). However, other glucose transporters, including GLUT4 and the sodium-dependent transporters SGLT1 and SGLT6, have been reported in vitro and in vivo. When the BBB endothelial layer is crossed, neurons and astrocytes can absorb the glucose using their GLUT1 and GLUT3 transporters. Glucose then enters the glycolytic pathway and is metabolized into adenosine triphosphate (ATP), which supplies the energy to support cellular functions. The transport and metabolism of glucose in the brain are impacted by several medical conditions, which can cause neurological and neuropsychiatric symptoms. Alzheimer's disease (AD), Parkinson's disease (PD), epilepsy, traumatic brain injury (TBI), schizophrenia, etc., are a few of the most prevalent disorders, characterized by a decline in brain metabolism or hypometabolism early in the course of the disease. Indeed, AD is considered a metabolic disorder related to decreased brain glucose metabolism, involving brain insulin resistance and age-dependent mitochondrial dysfunction. Although the conventional view is that reduced cerebral metabolism is an effect of neuronal loss and consequent brain atrophy, a growing body of evidence points to the opposite, where hypometabolism is prodromal or at least precedes the onset of brain atrophy and the manifestation of clinical symptoms. The underlying processes responsible for these glucose transport and metabolic abnormalities are complicated and remain poorly understood. This review article provides a comprehensive overview of the current understanding of hypometabolism in AD and potential therapeutic targets.

Molecular mechanisms underlying cyclophosphamide-induced cognitive impairment and strategies for neuroprotection in preclinical models

Cyclophosphamide has drastically enhanced the expectancy and quality of life of cancer patients. However, it is accompanied by diverse neurological complications which are considered a dose-limiting adverse effect. Neurotoxicity caused by cyclophosphamide can manifest in numerous manners including anxiety, depression, motor dysfunction and cognitive deficits. This review article offers an overview on cyclophosphamide-induced neurotoxicity, providing a unified point of view on the possible underlying molecular mechanisms including oxidative brain damage, neuroinflammation, apoptotic neuronal cell death as well as disruption of the balance of brain neurotransmitters and neurotrophic factors. Besides, this review sheds light on the promising protective agents that have been investigated using preclinical animal models as well as their biological targets and protection mechanisms. Despite promising results in experimental models, none of these agents has been studied in clinical trials. Thus, there is lack of evidence to advocate the use of any neuroprotective agent in the clinical setting. Furthermore, none of the protective agents has been evaluated for its effect on the anticancer activity of cyclophosphamide in tumor-bearing animals. Therefore, there is a great necessity for adequate well-designed clinical studies for evaluation of the therapeutic values of these candidates. Conclusively, this review summarizes the molecular mechanisms accounting for cyclophosphamide-induced neurotoxicity together with the potential protective strategies seeking for downgrading this neurological complication, thus enhancing the quality of life and well-being of cancer patients treated with cyclophosphamide.

Non-Enzymatic Antioxidants against Alzheimer's Disease: Prevention, Diagnosis and Therapy

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive memory loss and cognitive decline. Although substantial research has been conducted to elucidate the complex pathophysiology of AD, the therapeutic approach still has limited efficacy in clinical practice. Oxidative stress (OS) has been established as an early driver of several age-related diseases, including neurodegeneration. In AD, increased levels of reactive oxygen species mediate neuronal lipid, protein, and nucleic acid peroxidation, mitochondrial dysfunction, synaptic damage, and inflammation. Thus, the identification of novel antioxidant molecules capable of detecting, preventing, and counteracting AD onset and progression is of the utmost importance. However, although several studies have been published, comprehensive and up-to-date overviews of the principal anti-AD agents harboring antioxidant properties remain scarce. In this narrative review, we summarize the role of vitamins, minerals, flavonoids, non-flavonoids, mitochondria-targeting molecules, organosulfur compounds, and carotenoids as non-enzymatic antioxidants with AD diagnostic, preventative, and therapeutic potential, thereby offering insights into the relationship between OS and neurodegeneration.

Influence of a 12-Month Structured Exercise Program on the Micronutrient-Cognitive Fitness-Physical Association Profiles in Mild Cognitive Impairment

Background

Preventive lifestyle strategies have shown promise to slow down or prevent age-related cognitive decline. However, evidence on the reciprocal longitudinal relationships between nutrition biomarkers and cognitive and physical performance is lacking. Studying nutritional, cognitive, and physical profiles over time may help to overcome this knowledge gap.

Objective

To investigate the relationship of plasma levels of the robust nutritional- and antioxidant defense-related biomarkers carotenoids and tocopherols with both indicators of cognitive and physical performance in persons with mild cognitive impairment (MCI) participating in a structured exercise program.

Methods

Data from 40 participants with MCI of the NeuroExercise study were analyzed. Participants had undergone a blood withdrawal for the analysis of plasma concentrations of six carotenoids, two tocopherols and retinol prior to and after one-year of structured exercise. All participants had undergone a broad spectrum of cognitive and physical performance tests.

Results

Significant associations between lipophilic micronutrients and cognitive/physical measures were observed that were previously found to play a role in cognitive and physical frailty. In particular, lutein, zeaxanthin, and lycopene are confirmed as robust, reliable, and stable indicators of nutritional defense. Importantly, these micronutrients were associated with cognitive measures prior to the physical training program and to a more prominent extent with indicators of motoric function after the physical exercise program.

Conclusion

Specific profiles of lipophilic micronutrients are associated to cognitive performance measures and, especially after a structured exercise program, to indicators of physical performance.

The Antioxidative Effects of Picein and Its Neuroprotective Potential: A Review of the Literature

Neurodegenerative diseases (NDDs) are the main cause of dementia in the elderly, having no cure to date, as the currently available therapies focus on symptom remission. Most NDDs will progress despite treatment and eventually result in the death of the patient after several years of a burden on both the patient and the caregivers. Therefore, it is necessary to investigate agents that tackle the disease pathogenesis and can efficiently slow down or halt disease progression, with the hope of curing the patients and preventing further burden and mortality. Accordingly, recent research has focused on disease-modifying treatments with neuroregenerative or neuroprotective effects. For this purpose, it is necessary to understand the pathogenesis of NDDs. It has been shown that oxidative stress plays an important role in the damage to the central nervous system and the progression of neurodegenerative disorders. Furthermore, mitochondrial dysfunction and the accumulation of unfolded proteins, including beta-amyloid (Aβ), tau proteins, and α-synuclein, have been suggested. Accordingly, cellular and molecular studies have investigated the efficacy of several natural compounds (herbs and nutritional agents) for their neuroprotective and antioxidative properties. The most popular herbs suggested for the treatment and/or prevention of NDDs include Withania somnifera (ashwagandha), ginseng, curcumin, resveratrol, Baccopa monnieri, and Ginkgo biloba. In some herbs, such as ginseng, preclinical and clinical evidence are available for supporting its effectiveness; however, in some others, only cellular and animal studies are available. In line with the scant literature in terms of the effectiveness of herbal compounds on NDDs, there are also other herbal agents that have been disregarded. Picein is one of the herbal agents that has been investigated in only a few studies. Picein is the active ingredient of several herbs and can be thus extracted from different types of herbs, which makes it more available. It has shown to have anti-inflammatory properties in cellular and plant studies; however, to date, only one study has suggested its neuroprotective properties. Furthermore, some cellular studies have shown no anti-inflammatory effect of picein. Therefore, a review of the available literature is required to summarize the results of studies on picein. To date, no review study seems to have addressed this issue. Thus, in the present study, we gather the available information about the antioxidative and potential neuroprotective properties of picein and its possible effectiveness in treating NDDs. We also summarize the plants from which picein can be extracted in order to guide researchers for future investigations.

Toll-Like Receptor 4: A Promising Therapeutic Target for Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease that primarily manifests as memory deficits and cognitive impairment and has created health challenges for patients and society. In AD, amyloid β-protein (Aβ) induces Toll-like receptor 4 (TLR4) activation in microglia. Activation of TLR4 induces downstream signaling pathways and promotes the generation of proinflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β), which also trigger the activation of astrocytes and influence amyloid-dependent neuronal death. Therefore, TLR4 may be an important molecular target for treating AD by regulating neuroinflammation. Moreover, TLR4 regulates apoptosis, autophagy, and gut microbiota and is closely related to AD. This article reviews the role of TLR4 in the pathogenesis of AD and a range of potential therapies targeting TLR4 for AD. Elucidating the regulatory mechanism of TLR4 in AD may provide valuable clues for developing new therapeutic strategies for AD.

A bibliometric analysis of the 100 most-cited articles on curcumin

Background: Extensive studies related to curcumin were carried out over the preceding several decades. Citation frequencies represent the most prominent contributions in a specific field. This research aimed to identify and analyze the 100 most-cited articles on curcumin and to highlight the most important advances in this field.

Methods: Highly cited articles were identified in the Web of Science core collection database. “curcumin*” was used as the search string to retrieve in the “Title” field. VOSviewer was applied to perform bibliometric analysis of these papers.

Results: Totally 17,645 publications on the topic of curcumin were identified. The top most-cited 100 articles were published between 1973 and 2017. Most of these papers were original (n = 62). The total citation frequency in the top 100 article ranged from 355 to 3364, with a median of 560. The United States and India were the major countries researching curcumin. The University of Texas M.D. Anderson Cancer Center was the institution with the highest contribution rate of these articles. The most frequently nominated authors were Aggarwal B. B., Kunnumakkara A. B., Prasad S., and Priyadarsini K. I. The top 100 articles were published in 68 journals. The top four journals in terms of the number of our included articles were Cancer Research (n = 7), followed by Journal of Biological Chemistry, Biochemical Pharmacology, and Cancer Letters, with 4 articles each. NF-kappa B, cancer, gene expression, apoptosis, inflammation, chemopreventive agent, and nitric oxide synthase are presumed to be the current hot topics. Bioavailability, anticancer, anti-inflammatory, and antioxidant activities were the major research directions of curcumin.

Conclusion: This study analyzed the 100 most-cited articles on curcumin and provided insights into the characteristics and research hotspots of the articles on this topic.

Deciphering the enigmatic crosstalk between prostate cancer and Alzheimer's disease: A current update on molecular mechanisms and combination therapy

Alzheimer's disease (AD) and prostate cancer (PCa) are considered the leading causes of death in elderly people worldwide. Although both these diseases have striking differences in their pathologies, a few underlying mechanisms are similar when cell survival is considered. In the current study, we employed an in-silico approach to decipher the possible role of bacterial proteins in the initiation and progression of AD and PCa. We further analyzed the molecular connections between these two life-threatening diseases. The androgen deprivation therapy used against PCa has been shown to promote castrate resistant PCa as well as AD. In addition, cell signaling pathways, such as Akt, IGF, and Wnt contribute to the progression of both AD and PCa. Besides, various proteins and genes are also common in disease progression. One such similarity is mTOR signaling. mTOR is the common downstream target for many signaling pathways and plays a vital role in both PCa and AD. Targeting mTOR can be a favorable line of treatment for both AD and PCa. However, drug resistance is one of the challenges in effective drug therapy. A few drugs that target mTOR have now become ineffective due to the development of resistance. In that regard, phytochemicals can be a rich source of novel drug candidates as they can act via multiple mechanisms. This review also presents mTOR targeting phytochemicals with promising anti-PCa, anti-AD activities, and approaches to overcome the issues associated with phytochemical-based therapies in clinical trials.

Insights into the Explicit Protective Activity of Herbals in Management of Neurodegenerative and Cerebrovascular Disorders

The longstanding progressive neurodegenerative conditions of the central nervous system arise mainly due to deterioration, degradation and eventual neuronal cell loss. As an individual ages, the irreversible neurodegenerative disorders associated with aging also begin to develop, and these have become exceedingly prominent and pose a significant burden mentally, socially and economically on both the individual and their family. These disorders express several symptoms, such as tremors, dystonia, loss of cognitive functions, impairment of motor activity leading to immobility, loss of memory and many more which worsen with time. The treatment employed in management of these debilitating neurodegenerative disorders, such as Parkinson’s disease (which mainly involves the loss of dopaminergic neurons in the nigrostriatal region), Alzheimer’s disease (which arises due to accumulation of Tau proteins causing diffusive atrophy in the brain), Huntington’s disease (which involves damage of striatal and spinal neurons, etc.), have several adverse effects, leading to exploration of several lead targets and molecules existing in herbal drugs. The current review highlights the mechanistic role of natural products in the treatment of several neurodegenerative and cerebrovascular diseases such as Parkinson’s disease, Alzheimer’s disease, ischemic stroke and depression.

Toward the Noninvasive Diagnosis of Alzheimer's Disease: Molecular Basis for the Specificity of Curcumin for Fibrillar Amyloid-β

Recent studies show that curcumin, a naturally fluorescent dye, can be used for the noninvasive optical imaging of retinal amyloid-β (Aβ) plaques. We investigated the molecular basis for curcumin's specificity for hierarchical Aβ structures using molecular dynamics simulations, with a focus on how curcumin is able to detect and discriminate different amyloid morphologies. Curcumin inhibits and breaks up β-sheet formation in Aβ monomers. With disordered Aβ structures, curcumin forms a coarse-grained composite structure. With an ordered fibril, curcumin's interaction is highly specific, and the curcumin molecules are deposited in the fibril groove. Curcumin tends to self-aggregate, which is finely balanced with its affinity for Aβ. This tendency concentrates curcumin molecules at Aβ deposition sites, potentially increasing the fluorescence signal. This is probably why curcumin is such an effective amyloid imaging agent.

Evidence for Oxidative Pathways in the Pathogenesis of PD: Are Antioxidants Candidate Drugs to Ameliorate Disease Progression?

Parkinson’s disease (PD) is a progressive neurodegenerative disorder that arises due to a complex and variable interplay between elements including age, genetic, and environmental risk factors that manifest as the loss of dopaminergic neurons. Contemporary treatments for PD do not prevent or reverse the extent of neurodegeneration that is characteristic of this disorder and accordingly, there is a strong need to develop new approaches which address the underlying disease process and provide benefit to patients with this debilitating disorder. Mitochondrial dysfunction, oxidative damage, and inflammation have been implicated as pathophysiological mechanisms underlying the selective loss of dopaminergic neurons seen in PD. However, results of studies aiming to inhibit these pathways have shown variable success, and outcomes from large-scale clinical trials are not available or report varying success for the interventions studied. Overall, the available data suggest that further development and testing of novel therapies are required to identify new potential therapies for combating PD. Herein, this review reports on the most recent development of antioxidant and anti-inflammatory approaches that have shown positive benefit in cell and animal models of disease with a focus on supplementation with natural product therapies and selected synthetic drugs.

Application of curcumin nanoformulations in Alzheimer's disease: prevention, diagnosis and treatment

Objectives: Alzheimer's disease (AD) is a serious neurodegenerative disease. Although many therapeutic strategies have been studied, their clinical applications are immature. Moreover, these methods can only alleviate symptoms rather than cure it, posing a challenge to brain health in older adults worldwide. Curcumin (CUR) is a very promising natural compound for nerve protection and treatment. It can prevent and treat AD, and on the other hand, its fluorescence properties can be used in the diagnosis of AD. However, CUR is characterized by very low water solubility, fluid instability, rapid metabolism, low bioavailability and difficulty in penetrating the biological barriers, which limit its application. Nanocarriers are a potential material to improve the biocompatibility of CUR and its ability to cross biological barriers. Therefore, delivering CUR by nanocarriers is an effective method to achieve better efficacy. Methods: In this review, the preventive, therapeutic and diagnostic effects of CUR nanoformulations on AD, as well as various patents, clinical trials and experimental research progress in this field are discussed. The aim is to provide detailed reference and practical suggestions for future research. Results: CUR has a variety of pharmacological activities in the prevention and treatment of AD, and its nanoformulation can effectively improve solubility, bioavailability and the ability to penetrate the blood-brain barrier. Significant benefits have been observed in the current study. Discussion: CUR formulations have a good prospect in the prevention, diagnosis and treatment of AD, but the safety and principle of its administration need more detailed study in the future.

Design and various in silico studies of the novel curcumin derivatives as potential candidates against COVID-19 -associated main enzymes

The novel coronavirus disease (COVID-19) is a highly contagious disease caused by the SARS-CoV-2 virus, leading severe acute respiratory syndrome in patients. Although various antiviral drugs and their combinations have been tried so far against SARS-CoV-2 and they have shown some effectiveness, there is still a need for safe and cost-effective binding inhibitors in the fight against COVID-19. Therefore, phytochemicals in nature can be a quick solution due to their wide therapeutic spectrum and strong antiviral, anti-inflammatory, and antioxidant properties. In this context, the low toxicity, and high pharmacokinetic properties of curcumin, which is a natural phytochemical, as well as the easy synthesizing of its derivatives reveal the need for investigation of its various derivatives as inhibitors against coronaviruses. The present study focused on curcumin derivatives with reliable ADME profile and high molecular binding potency to different SARS-CoV-2 target enzymes (3CLPro, PLpro, NSP7/8/12, NSP7/8/12 +RNA, NSP15, NSP16, Spike, Spike+ACE). In the molecular docking studies, the best binding scores for the 22 proposed curcumin derivatives were obtained for the PLpro protein. Furthermore, MD simulations were performed for high-affinity ligand-PLpro protein complexes and subsequently, Lys157, Glu161, Asp164, Arg166, Glu167, Met208, Pro247, Pro248, Tyr264, Tyr273 and Asp302 residues of PLpro was determined to play key role for ligand binding by Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) analysis. The results of the study promise that the proposed curcumin derivatives can be potent inhibitors against SARS-CoV-2 and be converted into pharmaceutical drugs. It is also expected that the findings may provide guiding insights to future design studies for synthesizing different antiviral derivatives of phytochemicals.

Curcumin protects against manganese-induced neurotoxicity in rat by regulating oxidative stress-related gene expression via H3K27 acetylation

Long-term manganese exposure causes a neurodegenerative disorder referred to as manganese poisoning, but the mechanism remains unclear and no specific treatment is available. Oxidative stress is widely recognised as one of the main causes of manganese-induced neurotoxicity. In recent years, the role of histone acetylation in neurodegenerative diseases has been widely concerned. curcumin is a natural polyphenol compound extracted from the rhizome of turmeric and exhibits both antioxidant and neuroprotective properties. Therefore, we aimed to investigate whether and how curcumin protects against manganese-induced neurotoxicity from the perspective of histone acetylation, based on the reversibility of histone acetylation modification. In this study, rats were treated with or without curcumin and subjected to long-term manganese exposure. Results that treatment of manganese decreased the protein expression of H3K18 acetylation and H3K27 acetylation at the promoters of oxidative stress-related genes and inhibited the expression of these genes. Nevertheless, curcumin increased the H3K27 acetylation level at the manganese superoxide dismutase (SOD2) gene promoter and promoted the expression of SOD2 gene. Oxidative damage in the rat striatum as well as learning and memory dysfunction were ameliorated after curcumin treatment. Taken together, our results suggest that the regulation of oxidative stress by histone acetylation may be a key mechanism of manganese-induced neurotoxicity. In addition, curcumin ameliorates Mn-induced neurotoxicity may be due to alleviation of oxidative damage mediated by increased activation of H3K27 acetylation at the SOD2 gene promoter.

Nutraceuticals in HIV and COVID-19-Related Neurological Complications: Opportunity to Use Extracellular Vesicles as Drug Delivery Modality

Simple Summary

In this review, we discuss the potential use of extracellular vesicles (EVs) to deliver dietary supplements to the brain to reduce brain complications associated with HIV, COVID-19, and other brain disorders. Brain-related complications affect people with HIV and COVID-19 alike. Moreover, since HIV patients are at a higher risk of contracting COVID-19, their neurological problems can be exacerbated by COVID-19. The use of dietary supplements together with available treatment options has been shown to reduce the severity of infections. However, these treatments are not chemically compatible with the body’s blood–brain barrier defense mechanism. Therefore, a viable delivery method is needed to deliver drugs and nutraceuticals to the brain in HIV and COVID-19 comorbid patients.

Abstract

People living with HIV/AIDS (PLWHA) are at an increased risk of severe and critical COVID-19 infection. There is a steady increase in neurological complications associated with COVID-19 infection, exacerbating HIV-associated neurocognitive disorders (HAND) in PLWHA. Nutraceuticals, such as phytochemicals from medicinal plants and dietary supplements, have been used as adjunct therapies for many disease conditions, including viral infections. Appropriate use of these adjunct therapies with antiviral proprieties may be beneficial in treating and/or prophylaxis of neurological complications associated with these co-infections. However, most of these nutraceuticals have poor bioavailability and cannot cross the blood–brain barrier (BBB). To overcome this challenge, extracellular vesicles (EVs), biological nanovesicles, can be used. Due to their intrinsic features of biocompatibility, stability, and their ability to cross BBB, as well as inherent homing capabilities, EVs hold immense promise for therapeutic drug delivery to the brain. Therefore, in this review, we summarize the potential role of different nutraceuticals in reducing HIV- and COVID-19-associated neurological complications and the use of EVs as nutraceutical/drug delivery vehicles to treat HIV, COVID-19, and other brain disorders.

Curcumin Attenuates the PERK-eIF2α Signaling to Relieve Acrylamide-Induced Neurotoxicity in SH‑SY5Y Neuroblastoma Cells

Curcumin is a natural polyphenolic compound with neuroprotective and antioxidant properties. Acrylamide (ACR) is a by-product of food processing that produces neurotoxicity in humans and animals. The pancreatic endoplasmic reticulum kinase (PERK)-eukaryotic initiation factor-2α (eIF2α) signaling is involved in the occurrence of neurotoxicities. This study is aimed to investigate the protective effect of curcumin on ACR-induced cytotoxicity and explore the role of PERK-eIF2α signaling in this process. ACR exposure at 2.5 mM for 24 h caused oxidative stress as revealed by the distinct increase in cellular reactive oxygen species (ROS) and malondialdehyde (MDA) level, and a significant decrease in glutathione (GSH) content. ACR induced phosphorylated tau aggregation, phosphorylated cAMP response elements binding protein (CREB) reduction, and Bax/Bcl-2 ratio up-regulation in SH-SY5Y cells. ACR also activated the PERK-eIF2α signaling in SH-SY5Y cells and triggered the activation of glycogen synthase kinase-3β (GSK-3β), up-regulated activating transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP). Curcumin pretreatment significantly attenuated ACR-induced neuronal toxicity as revealed by the ameliorated cell viability, mitigated intracellular ROS and MDA level, and elevated GSH content. Moreover, curcumin pretreatment inhibited PERK-dependent eIF2α phosphorylation, further suppressed GSK-3β and ATF4 function, and abolished abnormal tau phosphorylation, P-CREB reduction, and CHOP-induced apoptosis in SH-SY5Y cells. These results provided empirical evidence between curcumin and PERK-eIF2α signaling in ACR-induced neurotoxicity.

Effect of Whey-Derived Lactopeptide β-Lactolin on Memory in Healthy Adults: An Integrated Analysis of Data from Randomized Controlled Trials

CONTEXT

Epidemiological studies have shown that consumption of dairy products reduces the risk of dementia and cognitive decline in older individuals. Tryptophan-tyrosine-related β-lactopeptides and their representative β-lactolin of glycine-threonine-tryptophan-tyrosine tetra-peptide have been identified as agents in dairy products, which improve cognitive function as well as memory function via the activation of the dopaminergic system in a mouse model of amnesia. Previous clinical trials have shown that supplementation with β-lactolin improves memory retrieval in healthy older adults. Specifically, β-lactolin improved the scores in some neuropsychological tests. However, the effects of β-lactolin on memory function have not been clarified.

OBJECTIVES

The aim of this study was to evaluate the effect of β-lactolin on memory function using statistical methods.

DATA SOURCES

We searched the Web of Science, Cochrane Library, and JDream III until November 2021 to identify relevant randomized controlled trials for integrated analysis.

DATA SYNTHESIS

Three randomized controlled trials evaluating the effect of β-lactolin on memory in healthy adults were selected for the integrated analysis. The results showed that the score of cued recall among the neuropsychological tests in the β-lactolin group was significantly higher than that in the placebo group (g=0.33; 95% CI: 0.10, 0.55). In addition, the total memory score was higher but this difference was not significant (g=0.17; 95% CI: -0.09, 0.43).

CONCLUSIONS

Taken together, these results suggest that supplementation with β-lactolin improves cued recall in healthy older adults.

An overview on therapeutic role of Diferuloylmethane (Curcumin) in Azheimer’s disease and sleep disorders

Curcumin is widely used in spices in Asia. It has been widely explored for various diseases as therapeutic agent. Alzheimer’s disease (AD) is a neurodegenerative disease associated with dementia and cognitive disabilities. With the progression of disease, various changes appear in the brain cells that greatly affect the daily routine of the patient including sleep-wake disturbances. In the last few decades, extensive research has been carried out on this disease suggesting the development of non-steroidal anti-inflammatory drugs for its treatment. Since long, turmeric has been used in Asian countries as a home remedy for treating various ailments. Curcumin is an active ingredient isolated from the turmeric plant and is composed of curcuminoids. Because of its anti-inflammatory, antioxidant, anti-apoptotic and neuroprotective properties, curcumin can be safely administered to stop the progression of dementia and can be used for the development of such drugs that can reverse the neurotic damage caused by AD. This review article provides a comprehensive overview on the research carried out for AD using curcumin as active model drug.

Amyotrophic Lateral Sclerosis: A Diet Review

Amyotrophic lateral sclerosis (ALS) is a fatal disease related to upper and lower motor neurons degeneration. Although the environmental and genetic causes of this disease are still unclear, some factors involved in ALS onset such as oxidative stress may be influenced by diet. A higher risk of ALS has been correlated with a high fat and glutamate intake and β-methylamino-L-alanine. On the contrary, a diet based on antioxidant and anti-inflammatory compounds, such as curcumin, creatine, coenzyme Q10, vitamin E, vitamin A, vitamin C, and phytochemicals could reduce the risk of ALS. However, data are controversial as there is a discrepancy among different studies due to a limited number of samples and the many variables that are involved. In addition, an improper diet could lead to an altered microbiota and consequently to an altered metabolism that could predispose to the ALS onset. In this review we summarized some research that involve aspects related to ALS such as the epidemiology, the diet, the eating behaviour, the microbiota, and the metabolic diseases. Further research is needed to better comprehend the role of diet and the metabolic diseases in the mechanisms leading to ALS onset and progression.

Nanoparticle-Guided Brain Drug Delivery: Expanding the Therapeutic Approach to Neurodegenerative Diseases

Neurodegenerative diseases (NDs) represent a heterogeneous group of aging-related disorders featured by progressive impairment of motor and/or cognitive functions, often accompanied by psychiatric disorders. NDs are denoted as 'protein misfolding' diseases or proteinopathies, and are classified according to their known genetic mechanisms and/or the main protein involved in disease onset and progression. Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease (HD) are included under this nosographic umbrella, sharing histopathologically salient features, including deposition of insoluble proteins, activation of glial cells, loss of neuronal cells and synaptic connectivity. To date, there are no effective cures or disease-modifying therapies for these NDs. Several compounds have not shown efficacy in clinical trials, since they generally fail to cross the blood-brain barrier (BBB), a tightly packed layer of endothelial cells that greatly limits the brain internalization of endogenous substances. By engineering materials of a size usually within 1-100 nm, nanotechnology offers an alternative approach for promising and innovative therapeutic solutions in NDs. Nanoparticles can cross the BBB and release active molecules at target sites in the brain, minimizing side effects. This review focuses on the state-of-the-art of nanoengineered delivery systems for brain targeting in the treatment of AD, PD and HD.

Improving Curcumin Bioavailability: Current Strategies and Future Perspectives

Curcumin possesses a plethora of interesting pharmacological effects. Unfortunately, it is also characterized by problematic drug delivery and scarce bioavailability, representing the main problem related to the use of this compound. Poor absorption, fast metabolism, and rapid systemic clearance are the most important factors contributing to low curcumin levels in plasma and tissues. Accordingly, to overcome these issues, numerous strategies have been proposed and are investigated in this article. Due to advances in the drug delivery field, we describe here the most promising strategies for increasing curcumin bioavailability, including the use of adjuvant, complexed/encapsulated curcumin, specific curcumin formulations, and curcumin nanoparticles. We analyze current strategies, already available in the market, and the most advanced technologies that can offer a future perspective for effective curcumin formulations. We focus the attention on the effectiveness of curcumin-based formulations in clinical trials, providing a comprehensive summary. Clinical trial results, employing various delivery methods for curcumin, showed that improved bioavailability corresponds to increased therapeutic efficacy. Furthermore, advances in the field of nanoparticles hold great promise for developing curcumin-based complexes as effective therapeutic agents. Summarizing, suitable delivery methods for this polyphenol will ensure the possibility of using curcumin-derived formulations in clinical practice as preventive and disease-modifying therapeutics.

Effects of Curcumin and Boric Acid Against Neurodegenerative Damage Induced by Amyloid Beta (1-42)

Synaptosomes are used as an ex vivo model in the investigation of neuronal transmission and neurodegenerative processes. In this study, we aimed to determine the protective effects of boric acid (BA) and curcumin, which have antioxidant and anti-inflammatory properties, on Aβ1-42 induced neurodegenerative damage. Synaptosomes obtained from the rat cerebral cortex were divided into five groups: control, 10 μM Aβ1-42, 10 μM Aβ1-42 + 25 mM BA, 10 μM Aβ1-42 + 10 μM curcumin, and 10 μM Aβ1-42 + 25 mM BA+10 μM curcumin. Synaptosomes treated with Aβ1-42 caused a significant decline in synaptophysin levels and increase in malondialdehyde (MDA) levels, acetylcholinesterase (AChE) activities, DNA fragmentation values, and nitric oxide (NO) levels compared with the control group (P < 0.01). Synaptosomes treated with BA showed a significant reduction in MDA and NO levels against Aβ1-42 exposure (P < 0.01). In addition, curcumin treatment has been found to cause a significant reduction in AChE activities and MDA levels in synaptosomes (P < 0.05). Co-administration of BA and curcumin on synaptosomes exposed to Aβ1-42 resulted in a significant decrease in DNA fragmentation values, MDA levels, and AChE activities. Curcumin and BA + curcumin combination showed an enhancement in synaptophysin levels of Aβ1-42-induced synaptosomes (P < 0.01). The results showed that BA and curcumin had protective effects on rat brain synaptosomes against Aβ1-42 exposure. BA and curcumin treatment can have abilities to prevent the alterations of the cholinergic system and inhibit oxidative stress in the cerebral cortex synapses of Aβ1-42 exposed.

The clinical use of curcumin on neurological disorders: An updated systematic review of clinical trials

Neuroprotective effects of curcumin have been shown in previous studies. This updated systematic review of clinical trials aimed to investigate the effect of curcumin on neurological disorders. Databases including PubMed, Scopus, Web of Science, and Google Scholar were systematically searched to identify clinical trials investigating the effects of curcumin/turmeric supplements alone, or in combination with other ingredients, on neurological diseases. Nineteen studies comprising 1,130 patients met the inclusion criteria. Generally, intervention and study outcomes were heterogeneous. In most of the studies, curcumin had a favorable effect on oxidative stress and inflammation. However, with the exception of AD, curcumin supplementation either alone, or in combination with other ingredients, had beneficial effects on clinical outcomes for the other aforementioned neurodegenerative diseases. For example, the frequency, severity, and duration of migraine attacks, scores on the revised ALS functional rating scale, and the occurrence of motor complications in PD were all significantly improved with curcumin supplementation either alone or in combination with other ingredients. However, in three studies, several adverse side effects (mostly gastrointestinal in nature) were reported. Curcumin supplementation may have favorable effects on inflammatory status and clinical outcomes of patients with neurological disease, although the results were not consistent.

Diabetes and Alzheimer's Disease: Might Mitochondrial Dysfunction Help Deciphering the Common Path?

A growing number of clinical and epidemiological studies support the hypothesis of a tight correlation between type 2 diabetes mellitus (T2DM) and the development risk of Alzheimer's disease (AD). Indeed, the proposed definition of Alzheimer's disease as type 3 diabetes (T3D) underlines the key role played by deranged insulin signaling to accumulation of aggregated amyloid beta (Aβ) peptides in the senile plaques of the brain. Metabolic disturbances such as hyperglycemia, peripheral hyperinsulinemia, dysregulated lipid metabolism, and chronic inflammation associated with T2DM are responsible for an inefficient transport of insulin to the brain, producing a neuronal insulin resistance that triggers an enhanced production and deposition of Aβ and concomitantly contributes to impairment in the micro-tubule-associated protein Tau, leading to neural degeneration and cognitive decline. Furthermore, the reduced antioxidant capacity observed in T2DM patients, together with the impairment of cerebral glucose metabolism and the decreased performance of mitochondrial activity, suggests the existence of a relationship between oxidative damage, mitochondrial impairment, and cognitive dysfunction that could further reinforce the common pathophysiology of T2DM and AD. In this review, we discuss the molecular mechanisms by which insulin-signaling dysregulation in T2DM can contribute to the pathogenesis and progression of AD, deepening the analysis of complex mechanisms involved in reactive oxygen species (ROS) production under oxidative stress and their possible influence in AD and T2DM. In addition, the role of current therapies as tools for prevention or treatment of damage induced by oxidative stress in T2DM and AD will be debated.

Applications of Radiolabelled Curcumin and Its Derivatives in Medicinal Chemistry

Curcumin is a natural occurring molecule that has aroused much interest among researchers over the years due to its pleiotropic set of biological properties. In the nuclear medicine field, radiolabelled curcumin and curcumin derivatives have been studied as potential radiotracers for the early diagnosis of Alzheimer’s disease and cancer. In the present review, the synthetic pathways, labelling methods and the preclinical investigations involving these radioactive compounds are treated. The studies entailed chemical modifications for enhancing curcumin stability, as well as its functionalisation for the labelling with several radiohalogens or metal radionuclides (fluorine-18, technetium-99m, gallium-68, etc.). Although some drawbacks have yet to be addressed, and none of the radiolabelled curcuminoids have so far achieved clinical application, the studies performed hitherto provide useful insights and lay the foundation for further developments.

Effect of high-frequency low-intensity pulsed electric field on protecting SH-SY5Y cells against hydrogen peroxide and β-amyloid-induced cell injury via ERK pathway

As the most common type of neurodegenerative diseases (NDDs), Alzheimer's disease (AD) is thought to be caused mainly by the excessive aggregation of β-amyloid protein (Aβ). However, a growing number of studies have found that reactive oxygen species (ROS) play a key role in the onset and progression of AD. The present study aimed to probe the neuroprotective effect of high-frequency low-intensity pulsed electric field (H-LIPEF) for SH-SY5Y cells against hydrogen peroxide (H2O2) and Aβ-induced cytotoxicity. By looking in a systematic way into the frequency- and amplitude-dependent neuroprotective effect of pulsed electric field (PEF), the study finds that H-LIPEF at 200 Hz produces the optimal protective effect for SH-SY5Y cells. The underlying mechanisms were confirmed to be due to the activation of extracellular signal-regulated kinase (ERK) pathway and the downstream prosurvival and antioxidant proteins. Because the electric field can be modified to focus on specific area in a non-contact manner, the study suggests that H-LIPEF holds great potential for treating NDDs, whose effect can be further augmented with the administering of drugs or natural compounds at the same time.

Curcumin activates Nrf2 through PKCδ-mediated p62 phosphorylation at Ser351

Curcumin, a phytochemical extracted from Curcuma longa rhizomes, is known to be protective in neurons via activation of Nrf2, a master regulator of endogenous defense against oxidative stress in cells. However, the exact mechanism by which curcumin activates Nrf2 remains controversial. Here, we observed that curcumin induced the expression of genes downstream of Nrf2 such as HO-1, NQO1, and GST-mu1 in neuronal cells, and increased the level of Nrf2 protein. Notably, the level of p62 phosphorylation at S351 (S349 in human) was significantly increased in cells treated with curcumin. Additionally, curcumin-induced Nrf2 activation was abrogated in p62 knockout (−/−) MEFs, indicating that p62 phosphorylation at S351 played a crucial role in curcumin-induced Nrf2 activation. Among the kinases involved in p62 phosphorylation at S351, PKCδ was activated in curcumin-treated cells. The phosphorylation of p62 at S351 was enhanced by transfection of PKCδ expression plasmid; in contrast, it was inhibited in cells treated with PKCδ-specific siRNA. Together, these results suggest that PKCδ is mainly involved in curcumin-induced p62 phosphorylation and Nrf2 activation. Accordingly, we demonstrate for the first time that curcumin activates Nrf2 through PKCδ-mediated p62 phosphorylation at S351.

Permeability of Hypogymnia physodes Extract Component-Physodic Acid through the Blood-Brain Barrier as an Important Argument for Its Anticancer and Neuroprotective Activity within the Central Nervous System

Simple Summary

Central nervous system (CNS) diseases, including tumors such as glioblastomas and neurodegenerative diseases, such as Alzheimer’s disease, are some of the greatest challenges of modern medicine. Therefore, our study aimed to evaluate the anticancer and neuroprotective activity of the extract from a common European lichen Hypogymnia physodes and of its compound-physodic acid. The examined substances were cytotoxic against the glioblastoma cell lines A-172, T98G, and U-138 MG. Both substances strongly inhibited hyaluronidase, and diminished cyclooxygenase-2 activity (H. physodes extract), enzymes expressed in patients with malignant glioma. Furthermore, H. physodes extract inhibited tyrosinase activity, the enzyme linked to neurodegenerative diseases. The tested substances exhibited antioxidant activity, however, acetylcholinesterase and butyrylcholinesterase inhibitory activity were not high. We proved that physodic acid can cross the blood–brain barrier. We conclude that physodic acid and H. physodes extract should be regarded as promising agents with anticancer, chemopreventive, and neuroprotective activities, especially concerning CNS.

Abstract

Lichen secondary metabolites are characterized by huge pharmacological potential. Our research focused on assessing the anticancer and neuroprotective activity of Hypogymnia physodes acetone extract (HP extract) and physodic acid, its major component. The antitumor properties were evaluated by cytotoxicity analysis using A-172, T98G, and U-138 MG glioblastoma cell lines and by hyaluronidase and cyclooxygenase-2 (COX-2) inhibition. The neuroprotective potential was examined using COX-2, tyrosinase, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) activity tests. Moreover, the antioxidant potential of the tested substances was examined, and the chemical composition of the extract was analyzed. For physodic acid, the permeability through the blood–brain barrier using Parallel Artificial Membrane Permeability Assay for the Blood–Brain Barrier assay (PAMPA-BBB) was assessed. Our study shows that the tested substances strongly inhibited glioblastoma cell proliferation and hyaluronidase activity. Besides, HP extract diminished COX-2 and tyrosinase activity. However, the AChE and BChE inhibitory activity of HP extract and physodic acid were mild. The examined substances exhibited strong antioxidant activity. Importantly, we proved that physodic acid crosses the blood–brain barrier. We conclude that physodic acid and H. physodes should be regarded as promising agents with anticancer, chemopreventive, and neuroprotective activities, especially regarding the central nervous system diseases.

Preventive and Therapeutic Strategies in Alzheimer's Disease: Focus on Oxidative Stress, Redox Metals, and Ferroptosis

Significance: Alzheimer's disease (AD) is the most common cause of dementia in the elderly. AD is currently ranked as the sixth leading cause of death, but some sources put it as third, after heart disease and cancer. Currently, there are no effective therapeutic approaches to treat or slow the progression of chronic neurodegeneration. In addition to the accumulation of amyloid-β (Aβ) and tau, AD patients show progressive neuronal loss and neuronal death, also high oxidative stress that correlates with abnormal levels or overload of brain metals. Recent Advances: Several promising compounds targeting oxidative stress, redox metals, and neuronal death are under preclinical or clinical evaluation as an alternative or complementary therapeutic strategy in mild cognitive impairment and AD. Here, we present a general analysis and overview, discuss limitations, and suggest potential directions for these treatments for AD and related dementia. Critical Issues: Most of the disease-modifying therapeutic strategies for AD under evaluation in clinical trials have focused on components of the amyloid cascade, including antibodies to reduce levels of Aβ and tau, as well as inhibitors of secretases. Unfortunately, several of the amyloid-focused therapeutics have failed the clinical outcomes or presented side effects, and numerous clinical trials of compounds have been halted, reducing realistic options for the development of effective AD treatments. Future Directions: The focus of research on AD and related dementias is shifting to alternative or innovative areas, such as ApoE, lipids, synapses, oxidative stress, cell death mechanisms, neuroimmunology, and neuroinflammation, as well as brain metabolism and bioenergetics.

Role of natural products for the treatment of Alzheimer's disease

Negative psychological and physiological consequences of neurodegenerative disorders represent a high social and health cost. Among the neurodegenerative disorders Alzheimer's disease (AD) is recognized as a leading neurodegenerative condition and a primary cause of dementia in the elderlys. AD is considered as neurodegenerative disorder that progressively impairs cognitive function and memory. According to current epidemiological data, about 50 milLion people worldwide are suffering from AD. The primary symptoms of AD are almost inappreciable and usually comprise forgetfulness of recent events. Numerous processes are involved in the development of AD, for example oxidative stress (OS) mainly due to mitochondrial dysfunction, intracellular the accumulation of hyperphosphorylated tau (τ) proteins in the form of neurofibrillary tangles, excessive the accumulation of extracellular plaques of beta-amyloid (Aβ), genetic and environmental factors. Running treatments only attenuate symptoms and temporarily reduce the rate of cognitive progression associated with AD. This means that most treatments focus only on controlLing symptoms, particularly in the initial stages of the disease. In the past, the first choice of treatment was based on natural ingredients. In this sense, diverse natural products (NPs) are capable to decrease the symptoms and alleviate the development of several diseases including AD attracting the attention of the scientific community and the pharmaceutical industry. Specifically, numerous NPs including flavonoids, gingerols, tannins, anthocyanins, triterpenes and alkaloids have been shown anti-inflammatory, antioxidant, anti-amyloidogenic, and anti-choLinesterase properties. This review provide a summary of the pathogenesis and the therapeutic goals of AD. It also discusses the available data on various plants and isolated natural compounds used to prevent and diminish the symptoms of AD.

Beneficial Effects of Epigallocatechin-3-O-Gallate, Chlorogenic Acid, Resveratrol, and Curcumin on Neurodegenerative Diseases

Many observational and clinical studies have shown that consumption of diets rich in plant polyphenols have beneficial effects on various diseases such as cancer, obesity, diabetes, cardiovascular diseases, and neurodegenerative diseases (NDDs). Animal and cellular studies have indicated that these polyphenolic compounds contribute to such effects. The representative polyphenols are epigallocatechin-3-O-gallate in tea, chlorogenic acids in coffee, resveratrol in wine, and curcumin in curry. The results of human studies have suggested the beneficial effects of consumption of these foods on NDDs including Alzheimer's and Parkinson's diseases, and cellular animal experiments have provided molecular basis to indicate contribution of these representative polyphenols to these effects. This article provides updated information on the effects of these foods and their polyphenols on NDDs with discussions on mechanistic aspects of their actions mainly based on the findings derived from basic experiments.

Curcumin and Its Derivatives as Theranostic Agents in Alzheimer's Disease: The Implication of Nanotechnology

Curcumin is a polyphenolic natural compound with diverse and attractive biological properties, which may prevent or ameliorate pathological processes underlying age-related cognitive decline, Alzheimer's disease (AD), dementia, or mode disorders. AD is a chronic neurodegenerative disorder that is known as one of the rapidly growing diseases, especially in the elderly population. Moreover, being the eminent cause of dementia, posing problems for families, societies as well a severe burden on the economy. There are no effective drugs to cure AD. Although curcumin and its derivatives have shown properties that can be considered useful in inhibiting the hallmarks of AD, however, they have low bioavailability. Furthermore, to combat diagnostic and therapeutic limitations, various nanoformulations have also been recognized as theranostic agents that can also enhance the pharmacokinetic properties of curcumin and other bioactive compounds. Nanocarriers have shown beneficial properties to deliver curcumin and other nutritional compounds against the blood-brain barrier to efficiently distribute them in the brain. This review spotlights the role and effectiveness of curcumin and its derivatives in AD. Besides, the gut metabolism of curcumin and the effects of nanoparticles and their possible activity as diagnostic and therapeutic agents in AD also discussed.

Role of nutraceuticals in cognition during aging and related disorders

Cognitive abilities are compromised with advancing age posing a great risk for the development of dementia and other related brain disorders. Genetic susceptibility as well as environmental exposures determine the fate of cognitive aging and its transition to pathological states. Emerging epidemiological and observational studies have revealed the importance of lifestyle factors including dietary patterns and nutritional intake in the maintenance of cognitive health and reducing the risk of neurodegenerative disorders. In this context, nutraceutical interventions have gained considerable attention in preventing age-related cognitive deficits and counteracting pathological processes. Nutraceuticals include dietary plants and derivatives, food supplements and processed foods with nutritional and pharmaceutical values. The present review highlights the importance of nutraceuticals in attenuating cognitive aging and its progression to dementia, with specific emphasis on chemical constituents, neurocognitive properties and mechanism of action.

Curcumin prevents cognitive deficits in the bile duct ligated rats

RATIONALE

Bile duct ligation (BDL) in rodents can cause impaired liver function and cognition deficits. Curcumin has shown a preventive and therapeutic role in memory impairment.

OBJECTIVES

Therefore, this study aimed to explore the effect of curcumin on the performance of male adult Wistar rats that underwent BDL, a model of hepatic encephalopathy (HE) in the Morris water maze (MWM).

METHODS

Four weeks after surgery, sham (manipulation of common bile duct without ligation) and BDL rats underwent the MWM test.

RESULTS

The representative data showed that BDL rats exhibited impairments in spatial learning and reference memory in the MWM compared with the sham rats. Treatment of BDL rats with curcumin (40 mg/kg, i.p., for 4 weeks) prevented these impairments, while it did not affect spatial learning and memory in the sham rats, by itself. Curcumin increased expression levels of the pro-survival B cell lymphoma extra-large (Bcl-xL) gene and two genes involved in mitochondrial function, peroxisome proliferative-activated receptor-γ co-activator 1α (PGC-1α) and mitochondrial transcription factor A (TFAM), in the hippocampus of BDL rats compared with the vehicle-treated sham or BDL rats, while it decreased the pro-apoptotic Bcl-2-associated X protein (Bax) gene expression level. BDL up-regulated Bax and down-regulated TFAM, by itself. Furthermore, curcumin reduced the mRNA level of Bax, while it increased Bcl-2 and TFAM mRNA levels.

CONCLUSIONS

These findings demonstrate the beneficial effect of curcumin on cognitive function in BDL rats of the HE model. The curcumin effect may be related to mitochondrial function improvement in the HE.

The effects of caloric restriction and its mimetics in Alzheimer's disease through autophagy pathways

Alzheimer's disease (AD) is a neurodegenerative disorder that commonly occurs among older individuals. Increasing evidence suggests that a low-caloric diet might be a promising adjuvant therapeutic strategy for slowing or preventing the pathogenesis and progression of AD through the induction of autophagy. Several intracellular pathways have been implicated in caloric restriction (CR)-induced autophagy. In this review, we summarized the efficacy of CR as well as its mimetics (resveratrol, spermidine, aspirin, rapamycin, metformin, and curcumin) in improving cognitive function of rodent models of AD. On the basis of recent in vitro and animal studies, the beneficial effects of CR- or caloric restriction mimetics-induced autophagy in alleviating amyloid burden and tau pathology of AD were also discussed.

Emodin inhibits aggregation of amyloid-β peptide 1-42 and improves cognitive deficits in Alzheimer's disease transgenic mice

Aggregation of amyloid-β peptide 1-42 (Aβ42) initiates the onset of Alzheimer's disease (AD), and all the drugs designed to attenuate AD have failed in clinical trials. Emodin reduces levels of β-amyloid, tau aggregation, oxidative stress, and inflammatory response, demonstrating AD therapeutic potential, whereas its effect on the accumulation of the amyloid-β protein is not well understood. In this work, we investigated emodin activity on Aβ aggregation using a range of biochemical, biophysical, and cell-based approaches. We provide evidence to suggest that emodin blocks Aβ42 fibrillogenesis and Aβ-induced cytotoxicity, displaying a greater effect than that of curcumin. Through adopting three short peptides (Aβ1-16, Aβ17-33, and Aβ28-42), it was proven that emodin interacts with the Leu17-Gly33 sequence. Furthermore, our findings indicated that Val18 and Phe19 in Aβ42 are the target residues with which emodin interacts according amino acid mutation experiments. When fed to 8-month-old B6C3-Tg mice for 2 months, high-dose emodin ameliorates cognitive impairment by 60%-70%. Pathological results revealed that levels of Aβ deposition in the brains of AD mice treated with a high dose of emodin decreased by 50%-70%. Therefore, our study indicates that emodin may represent a promising drug for AD treatment.

Turmeric and Its Major Compound Curcumin on Health: Bioactive Effects and Safety Profiles for Food, Pharmaceutical, Biotechnological and Medicinal Applications

Curcumin, a yellow polyphenolic pigment from the Curcuma longa L. (turmeric) rhizome, has been used for centuries for culinary and food coloring purposes, and as an ingredient for various medicinal preparations, widely used in Ayurveda and Chinese medicine. In recent decades, their biological activities have been extensively studied. Thus, this review aims to offer an in-depth discussion of curcumin applications for food and biotechnological industries, and on health promotion and disease prevention, with particular emphasis on its antioxidant, anti-inflammatory, neuroprotective, anticancer, hepatoprotective, and cardioprotective effects. Bioavailability, bioefficacy and safety features, side effects, and quality parameters of curcumin are also addressed. Finally, curcumin's multidimensional applications, food attractiveness optimization, agro-industrial procedures to offset its instability and low bioavailability, health concerns, and upcoming strategies for clinical application are also covered.

Impact of nano-conjugate on Drosophila for early diagnosis of Alzheimer's disease

Alzheimer's disease (AD) is an irreversible neurodegenerative disease. Recent identification of AD biomarkers has led to the diagnosis of AD before the onset of dementia. It has been shown that Drosophila melanogaster is a valuable model for studying human neurodegeneration, including AD. According to its properties, curcumin shows promising potential for the diagnosis of AD. In order to improve its use, new formulations, including nanotechnology-based delivery systems, have been applied. The current study aims to diagnose AD by detecting the accumulation of amyloid beta-peptide via carbon-dot-curcumin nanoparticle conjugation in Drosophila. The accumulation of amyloid beta-peptide has been detected via the conjugate using the fluorescence imaging technique. These results suggest that carbon-dot-curcumin nanoparticle conjugation could be used as a diagnostic tool for AD.

The anti-apoptotic, antioxidant and anti-inflammatory effects of curcumin on acrylamide-induced neurotoxicity in rats

Background

Acrylamide (ACR) formed during heating of tobacco and carbohydrate-rich food as well as widely applied in industries has been known as a well-established neurotoxic pollutant. Although the precise mechanism is unclear, enhanced apoptosis, oxidative stress and inflammation have been demonstrated to contribute to the ACR-induced neurotoxicity. In this study, we assessed the possible anti-apoptotic, antioxidant and anti-inflammatory effects of curcumin, the most active component in a popular spice known as turmeric, on the neurotoxicity caused by ACR in rats.

Methods

Curcumin at the dose of 50 and 100 mg/kg was orally given to ACR- intoxicated Sprague-Dawley rats exposed by ACR at 40 mg/kg for 4 weeks. All rats were subjected to behavioral analysis. The HE staining and terminal deoxynucleotidyl transferase mediated dUTP nick end labelling (TUNEL) staining were used to detect histopathological changes and apoptotic cells, respectively. The mRNA and protein expressions of apoptosis-related molecule telomerase reverse transcriptase (TERT) were detected using real-time PCR and immunohistochemistry, respectively. The contents of malondialdehyde (MDA) and glutathione (GSH) as well as the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were measured as the indicators for evaluating the level of oxidative stress in brain. The levels of pro-inflammatory cytokinestumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in the cerebral homogenates were detected using ELISA assay.

Results

ACR-induced weigh loss, deficits in motor function as well as pathological alterations in brains were significantly improved in rats administrated with 50 and 100 mg/kg curcumin. TUNEL-positive apoptotic cells in curcumin-treated ACR intoxicated brains were less than those in the ACR model group. Curcumin administration especially at the dose of 100 mg/kg upregulated the TERT mRNA expression and enhanced the number of TERT-positive cells in ACR-intoxicated cortex tissues. Moreover, curcumin treatment reduced the concentrations of TNF-α, IL-1β and MDA, while increased the GSH contents as well as the SOD and GSH-Px activities in the cerebral homogenates, in comparison to ACR control group.

Conclusions

These data suggested the anti-apoptotic, antioxidant and anti-inflammatory effects of curcumin on ACR-induced neurotoxicity in rats. Maintaining TERT-related anti-apoptotic function might be one mechanism underlying the protective effect of curcumin on ACR-intoxicated brains.

Recent Advances in Nanoencapsulation of Phytochemicals to Combat Obesity and Its Comorbidities

An increasing epidemic of obesity has become a serious public health concern primarily because it contributes to pathogenesis of many chronic diseases including type 2 diabetes, cardiovascular disease, hepatobiliary disease, obstructive sleep apnea, kidney disease, some types of cancer, among others. Consumption of a variety of phytochemicals has emerged as a promising potential for combating obesity and its comorbidities. However, the generally low aqueous solubility, stability, bioavailability, and target specificity of phytochemicals, along with their side-effects and toxicity seen when used at high doses, have restricted their clinical applications. As a solution, phytochemicals can be encapsulated into nanoparticles to increase their stability and solubility, enhance their bioavailability, protect them from premature degradation in the body, prolong their circulation time, and thus enhance their antiobesity activity. In this perspective, we summarize the problems and limitations of the prominent phytochemicals (epigallocatechin gallate, trans-resveratrol, curcumin, and quercetin), the major biocompatible and biodegradable nanoparticles, and the efficacy of nanoencapsulated forms of these phytochemicals in combating obesity and its comorbidities.

Targeting Amyloidogenic Processing of APP in Alzheimer's Disease

Alzheimer's disease (AD) is the most common type of senile dementia, characterized by neurofibrillary tangle and amyloid plaque in brain pathology. Major efforts in AD drug were devoted to the interference with the production and accumulation of amyloid-β peptide (Aβ), which plays a causal role in the pathogenesis of AD. Aβ is generated from amyloid precursor protein (APP), by consecutive cleavage by β-secretase and γ-secretase. Therefore, β-secretase and γ-secretase inhibition have been the focus for AD drug discovery efforts for amyloid reduction. Here, we review β-secretase inhibitors and γ-secretase inhibitors/modulators, and their efficacies in clinical trials. In addition, we discussed the novel concept of specifically targeting the γ-secretase substrate APP. Targeting amyloidogenic processing of APP is still a fundamentally sound strategy to develop disease-modifying AD therapies and recent advance in γ-secretase/APP complex structure provides new opportunities in designing selective inhibitors/modulators for AD.