The effect of genistein on the content and activity of α- and β-secretase and protein kinase C in Aβ-injured hippocampal neurons

Unveiling the neuroprotective properties of isoflavones: current evidence, molecular mechanisms and future perspectives

Neurodegenerative diseases encompass a wide range of debilitating and incurable brain disorders characterized by the progressive deterioration of the nervous system's structure and function. Isoflavones, which are naturally occurring polyphenolic phytochemicals, have been found to regulate various cellular signaling pathways associated with the nervous system. The main objective of this comprehensive review is to explore the neuroprotective effects of isoflavones, elucidate the underlying mechanisms, and assess their potential for treating neurodegenerative disorders. Relevant data regarding isoflavones and their impact on neurodegenerative diseases were gathered from multiple library databases and electronic sources, including PubMed, Google Scholar, Web of Science, and Science Direct. Numerous isoflavones, including genistein, daidzein, biochanin A, and formononetin, have exhibited potent neuroprotective properties against various neurodegenerative diseases. These compounds have been found to modulate neurotransmitters, which in turn contributes to their ability to protect against neurodegeneration. Both in vitro and in vivo experimental studies have provided evidence of their neuroprotection mechanisms, which involve interactions with estrogenic receptors, antioxidant effects, anti-inflammatory properties, anti-apoptotic activity, and modulation of neural plasticity. This review aims to provide current insights into the neuroprotective characteristics of isoflavones and shed light on their potential therapeutic applications in future clinical scenarios.

Mechanistic insights into the potential role of dietary polyphenols and their nanoformulation in the management of Alzheimer's disease

Alzheimer's disease (AD) is a very common neurodegenerative disorder associated with memory loss and a progressive decline in cognitive activity. The two major pathophysiological factors responsible for AD are amyloid plaques (comprising amyloid-beta aggregates) and neurofibrillary tangles (consisting of hyperphosphorylated tau protein). Polyphenols, a class of naturally occurring compounds, are immensely beneficial for the treatment or management of various disorders and illnesses. Naturally occurring sources of polyphenols include plants and plant-based foods, such as fruits, herbs, tea, vegetables, coffee, red wine, and dark chocolate. Polyphenols have unique properties, such as being the major source of anti-oxidants and possessing anti-aging and anti-cancerous properties. Currently, dietary polyphenols have become a potential therapeutic approach for the management of AD, depending on various research findings. Dietary polyphenols can be an effective strategy to tackle multifactorial events that occur with AD. For instance, naturally occurring polyphenols have been reported to exhibit neuroprotection by modulating the Aβ biogenesis pathway in AD. Many nanoformulations have been established to enhance the bioavailability of polyphenols, with nanonization being the most promising. This review comprehensively provides mechanistic insights into the neuroprotective potential of dietary polyphenols in treating AD. It also reviews the usability of dietary polyphenol as nanoformulation for AD treatment.

Atrazine Toxicity: The Possible Role of Natural Products for Effective Treatment

There are various herbicides which were used in the agriculture industry. Atrazine (ATZ) is a chlorinated triazine herbicide that consists of a ring structure, known as the triazine ring, along with a chlorine atom and five nitrogen atoms. ATZ is a water-soluble herbicide, which makes it capable of easily infiltrating into majority of the aquatic ecosystems. There are reports of toxic effects of ATZ on different systems of the body but, unfortunately, majority of these scientific reports were documented in animals. The herbicide was reported to enter the body through various routes. The toxicity of the herbicide can cause deleterious effects on the respiratory, reproductive, endocrine, central nervous system, gastrointestinal, and urinary systems of the human body. Alarmingly, few studies in industrial workers showed ATZ exposure leading to cancer. We embarked on the present review to discuss the mechanism of action of ATZ toxicity for which there is no specific antidote or drug. Evidence-based published literature on the effective use of natural products such as lycopene, curcumin, Panax ginseng, Spirulina platensis, Fucoidans, vitamin C, soyabeans, quercetin, L-carnitine, Telfairia occidentalis, vitamin E, Garcinia kola, melatonin, selenium, Isatis indigotica, polyphenols, Acacia nilotica, and Zingiber officinale were discussed in detail. In the absence of any particular allopathic drug, the present review may open the doors for future drug design involving the natural products and their active compounds.

Current Pharmacotherapy and Multi-Target Approaches for Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by decreased synaptic transmission and cerebral atrophy with appearance of amyloid plaques and neurofibrillary tangles. Cognitive, functional, and behavioral alterations are commonly associated with the disease. Different pathophysiological pathways of AD have been proposed, some of which interact and influence one another. Current treatment for AD mainly involves the use of therapeutic agents to alleviate the symptoms in AD patients. The conventional single-target treatment approaches do not often cause the desired effect in the disease due to its multifactorial origin. Thus, multi-target strategies have since been undertaken, which aim to simultaneously target multiple targets involved in the development of AD. In this review, we provide an overview of the pathogenesis of AD and the current drug therapies for the disease. Additionally, rationales of the multi-target approaches and examples of multi-target drugs with pharmacological actions against AD are also discussed.

The Neuroprotective Potentiality of Flavonoids on Alzheimer's Disease

Alzheimer's disease (AD), due to its spread, has become a global health priority, and is characterized by senile dementia and progressive disability. The main cause of AD and other neurodegenerations (Huntington, Parkinson, Amyotrophic Lateral Sclerosis) are aggregated protein accumulation and oxidative damage. Recent research on secondary metabolites of plants such as polyphenols demonstrated that they may slow the progression of AD. The flavonoids' mechanism of action in AD involved the inhibition of acetylcholinesterase, butyrylcholinesterase, Tau protein aggregation, β-secretase, oxidative stress, inflammation, and apoptosis through modulation of signaling pathways which are implicated in cognitive and neuroprotective functions, such as ERK, PI3-kinase/Akt, NFKB, MAPKs, and endogenous antioxidant enzymatic systems. This review focuses on flavonoids and their role in AD, in terms of therapeutic potentiality for human health, antioxidant potential, and specific AD molecular targets.

Genistein: A focus on several neurodegenerative diseases

Neurodegenerative diseases are caused by the progressive loss of function or structure of nerve cells in the central nervous system. The most common neurodegenerative diseases include Alzheimer's disease, Huntington's disease, motor neuron disease, and Parkinson's disease. Although the physical or mental symptoms of neurodegenerative disease may be relieved by various treatment combinations, there are currently no strategies to directly slow or prevent neurodegeneration. Given the demographic evidence of a rapidly growing aging population and the associated prevalence of these common neurodegenerative diseases, it is paramount to develop safe and effective ways to protect against neurodegenerative diseases. Most neurodegenerative diseases share some common etiologies such as oxidative stress, neuroinflammation, and mitochondrial dysfunction. Genistein is an isoflavone found in soy products that have been shown to exhibit antioxidant, anti-inflammation, and estrogenic properties. Increasing evidence indicates the protective potential of genistein in neurodegenerative disorders. In this review, we aim to provide an overview of the role that genistein plays in delaying the development of neurodegenerative disease. PRACTICAL APPLICATIONS: Genistein is a naturally occurring isoflavone found mainly in soybean, but also green peas, legumes, and peanuts. Genistein is found to pass through the blood-brain barrier and possess a neuroprotective effect. In this review, we discuss studies in support of these actions and the underlying biological mechanisms. Together, these data indicate that genistein may hold neuroprotective effects in either delaying the onset or relieving the symptoms of neurodegenerative disease.

The multimodal action of genistein in Alzheimer's and other age-related diseases

Genistein is a phytoestrogen that, due to its structural similarity with estrogen, can both mimic and antagonize estrogen effects. Early analysis proved that at high concentrations, genistein inhibits breast cancer cell proliferation, thereby suggesting an anticancer activity. Since then, many discoveries have identified the genistein mechanism of action, including cell cycle arrest, apoptosis induction, as well as angiogenesis, and metastasis inhibition. In this review, we aim to discuss the multimodal action of genistein as an antioxidant, anti-inflammatory, anti-amyloid β, and autophagy promoter, which could be responsible for the genistein beneficial effect on Alzheimer's. Furthermore, we pinpoint the main signal transduction pathways that are known to be modulated by genistein. Genistein has thus several beneficial effects in several diseases, many of them associated with age, such as the above mentioned Alzheimer disease. Indeed, the beneficial effects of genistein for health promotion depend on each multimodality. In the context of geroscience, genistein has promising beneficial effects due to its multimodal action to treat age associated-diseases.

Protective effect of olive leaves phenolic compounds against neurodegenerative disorders: Promising alternative for Alzheimer and Parkinson diseases modulation

The main objective of this work was to review literature on compounds extracted from olive tree leaves, such as simple phenols (hydroxytyrosol) and flavonoids (Apigenin, apigenin-7-O-glucoside, luteolin.) and their diverse pharmacological activities as antioxidant, antimicrobial, anti-viral, anti-obesity, anti-inflammatory and neuroprotective properties. In addition, the study discussed the key mechanisms underlying their neuroprotective effects. This study adopted an approach of collecting data through the databases provided by ScienceDirect, SCOPUS, MEDLINE, PubMed and Google Scholar. This review revealed that there was an agreement on the great impact of olive tree leaves phenolic compounds on many metabolic syndromes as well as on the most prevalent neurodegenerative diseases such as Alzheimer and Parkinson. These findings would be of great importance for the use of olive tree leaves extracts as a food supplement and/or a source of drugs for many diseases. In addition, this review would of great help to beginning researchers in the field since it would offer them a general overview of the studies undertaken in the last two decades on the topic.

Improving the genistein oral bioavailability via its formulation into the metal-organic framework MIL-100(Fe)

Despite the interesting chemopreventive, antioxidant and antiangiogenic effects of the natural bioflavonoid genistein (GEN), its low aqueous solubility and bioavailability make it necessary to administer it using a suitable drug carrier system. Nanometric porous metal-organic frameworks (nanoMOFs) are appealing systems for drug delivery. Particularly, mesoporous MIL-100(Fe) possesses a variety of interesting features related to its composition and structure, which make it an excellent candidate to be used as a drug nanocarrier (highly porous, biocompatible, can be synthesized as homogenous and stable nanoparticles (NPs), etc.). In this study, GEN was entrapped via simple impregnation in MIL-100 NPs achieving remarkable drug loading (27.1 wt%). A combination of experimental and computing techniques was used to achieve a deep understanding of the encapsulation of GEN in MIL-100 nanoMOF. Subsequently, GEN delivery studies were carried out under simulated physiological conditions, showing on the whole a sustained GEN release for 3 days. Initial pharmacokinetic and biodistribution studies were also carried out upon the oral administration of the GEN@MIL-100 NPs in a mouse model, evidencing a higher bioavailability and showing that this oral nanoformulation appears to be very promising. To the best of our knowledge, the GEN-loaded MIL-100 will be the first antitumor oral formulation based on nanoMOFs studied in vivo, and paves the way to the efficient delivery of nontoxic antitumorals via a convenient oral route.

Current Perspectives on the Beneficial Effects of Soybean Isoflavones and Their Metabolites for Humans

Soybeans are rich in proteins and lipids and have become a staple part of the human diet. Besides their nutritional excellence, they have also been shown to contain various functional components, including isoflavones, and have consequently received increasing attention as a functional food item. Isoflavones are structurally similar to 17-β-estradiol and bind to estrogen receptors (ERα and ERβ). The estrogenic activity of isoflavones ranges from a hundredth to a thousandth of that of estrogen itself. Isoflavones play a role in regulating the effects of estrogen in the human body, depending on the situation. Thus, when estrogen is insufficient, isoflavones perform the functions of estrogen, and when estrogen is excessive, isoflavones block the estrogen receptors to which estrogen binds, thus acting as an estrogen antagonist. In particular, estrogen antagonistic activity is important in the breast, endometrium, and prostate, and such antagonistic activity suppresses cancer occurrence. Genistein, an isoflavone, has cancer-suppressing effects on estrogen receptor-positive (ER+) cancers, including breast cancer. It suppresses the function of enzymes such as tyrosine protein kinase, mitogen-activated kinase, and DNA polymerase II, thus inhibiting cell proliferation and inducing apoptosis. Genistein is the most biologically active and potent isoflavone candidate for cancer prevention. Furthermore, among the various physiological functions of isoflavones, they are best known for their antioxidant activities. S-Equol, a metabolite of genistein and daidzein, has strong antioxidative effects; however, the ability to metabolize daidzein into S-equol varies based on racial and individual differences. The antioxidant activity of isoflavones may be effective in preventing dementia by inhibiting the phosphorylation of Alzheimer's-related tau proteins. Genistein also reduces allergic responses by limiting the expression of mast cell IgE receptors, which are involved in allergic responses. In addition, they have been known to prevent and treat various diseases, including cardiovascular diseases, metabolic syndromes, osteoporosis, diabetes, brain-related diseases, high blood pressure, hyperlipidemia, obesity, and inflammation. Further, it also has positive effects on menstrual irregularity in non-menopausal women and relieving menopausal symptoms in middle-aged women. Recently, soybean consumption has shown steep increasing trend in Western countries where the intake was previously only 1/20-1/50 of that in Asian countries. In this review, I have dealt with the latest research trends that have shown substantial interest in the biological efficacy of isoflavones in humans and plants, and their related mechanisms.

Pleiotropic Effects of Isoflavones in Inflammation and Chronic Degenerative Diseases

Isoflavones are phytoestrogens of plant origin, mostly found in the members of the Fabaceae family, that exert beneficial effects in various degenerative disorders. Having high similarity to 17-β-estradiol, isoflavones can bind estrogen receptors, scavenge reactive oxygen species, activate various cellular signal transduction pathways and modulate growth and transcription factors, activities of enzymes, cytokines, and genes regulating cell proliferation and apoptosis. Due to their pleiotropic activities isoflavones might be considered as a natural alternative for the treatment of estrogen decrease-related conditions during menopause. This review will focus on the effects of isoflavones on inflammation and chronic degenerative diseases including cancer, metabolic, cardiovascular, neurodegenerative diseases, rheumatoid arthritis and adverse postmenopausal symptoms.

Nutraceuticals and their Derived Nano-formulations for the Prevention and Treatment of Alzheimer's disease

Alzheimer's disease is one of the common chronic neurological disorders and associated with cognitive dysfunction, depression and progressive dementia. Presence of β-amyloid or senile plaques, hyper-phosphorylated tau proteins, neurofibrillary tangle, oxidative-nitrative stress, mitochondrial dysfunction, endoplasmic reticulum stress, neuroinflammation and derailed neurotransmitter status are the hallmark of AD. Currently, donepezil, memantine, rivastigmine and galantamine are approved by the FDA for symptomatic management. It is well-known that these approved drugs only exert symptomatic relief and possess poor patient-compliance. Additionally, various published evidence shows the neuroprotective potential of various nutraceuticals via their antioxidant, anti-inflammatory and anti-apoptotic effects in the preclinical and clinical studies. These nutraceuticals possess a significant neuroprotective potential and hence, can be a future pharmacotherapeutic for the management and treatment of AD. However, nutraceutical suffers from certain major limitations such as poor solubility, low bioavailability, low stability, fast hepatic-metabolism and larger particle size. These pharmacokinetic attributes restrict their entry into the brain via the blood-brain barrier. Therefore, to over such issues, various nanoformulation of nutraceuticals was developed, that allows their effective delivery into brain owning to reduced particle size, increased lipophilicity increased bioavailability and avoidance of fast hepatic metabolism. Thus, in this review, we have discussed the etiology of AD, focused on the pharmacotherapeutics of nutraceuticals with preclinical and clinical evidence, discussed pharmaceutical limitation and regulatory aspects of nutraceuticals to ensure safety and efficacy. We further explored the latitude of various nanoformulation of nutraceuticals as a novel approach to overcome the existing pharmaceutical limitation and for effective delivery into the brain.

Functional Foods: An Approach to Modulate Molecular Mechanisms of Alzheimer's Disease

A new epoch is emerging with intense research on nutraceuticals, i.e., "food or food product that provides medical or health benefits including the prevention and treatment of diseases", such as Alzheimer's disease. Nutraceuticals act at different biochemical and metabolic levels and much evidence shows their neuroprotective effects; in particular, they are able to provide protection against mitochondrial damage, oxidative stress, toxicity of β-amyloid and Tau and cell death. They have been shown to influence the composition of the intestinal microbiota significantly contributing to the discovery that differential microorganisms composition is associated with the formation and aggregation of cerebral toxic proteins. Further, the routes of interaction between epigenetic mechanisms and the microbiota-gut-brain axis have been elucidated, thus establishing a modulatory role of diet-induced epigenetic changes of gut microbiota in shaping the brain. This review examines recent scientific literature addressing the beneficial effects of some natural products for which mechanistic evidence to prevent or slowdown AD are available. Even if the road is still long, the results are already exceptional.

Neuroprotection: Targeting Multiple Pathways by Naturally Occurring Phytochemicals

With the increase in the expectancy of the life span of humans, neurodegenerative diseases (NDs) have imposed a considerable burden on the family, society, and nation. In defiance of the breakthroughs in the knowledge of the pathogenesis and underlying mechanisms of various NDs, very little success has been achieved in developing effective therapies. This review draws a bead on the availability of the nutraceuticals to date for various NDs (Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, Huntington's disease, vascular cognitive impairment, Prion disease, Spinocerebellar ataxia, Spinal muscular atrophy, Frontotemporal dementia, and Pick's disease) focusing on their various mechanisms of action in various in vivo and in vitro models of NDs. This review is distinctive in its compilation to critically review preclinical and clinical studies of the maximum phytochemicals in amelioration and prevention of almost all kinds of neurodegenerative diseases and address their possible mechanism of action. PubMed, Embase, and Cochrane Library searches were used for preclinical studies, while ClinicalTrials.gov and PubMed were searched for clinical updates. The results from preclinical studies demonstrate the efficacious effects of the phytochemicals in various NDs while clinical reports showing mixed results with promise for phytochemical use as an adjunct to the conventional treatment in various NDs. These studies together suggest that phytochemicals can significantly act upon different mechanisms of disease such as oxidative stress, inflammation, apoptotic pathways, and gene regulation. However, further clinical studies are needed that should include the appropriate biomarkers of NDs and the effect of phytochemicals on them as well as targeting the appropriate population.

Current Status of Drug Targets and Emerging Therapeutic Strategies in the Management of Alzheimer's Disease

Alzheimer's disease (AD) is a chronic neurodegenerative disease affecting the elderly. AD is associated with a progressive decline in memory and cognitive abilities, drastic changes in behavioural patterns and other psychiatric manifestations. It leads to a significant decline in the quality of life at personal, household as well as national level. Although AD was described about hundred years back and multiple theories have been proposed, its exact pathophysiology is unknown. There is no cure for AD and the life expectancy of AD patients remains low at 3-9 years. An accurate understanding of the molecular mechanism(s) involved in the pathogenesis of AD is imperative to devise a successful treatment strategy. This review explains and summarises the current understanding of different therapeutic strategies based on various molecular pathways known to date. Different strategies based on anti-amyloid pathology, glutamatergic pathway, anti-tau, neuroprotection through neurotrophic factors and cholinergic neurotransmission have been discussed. Further, the use of anti-inflammatory drugs, nutraceuticals, and dietary interventions has also been explained in the management of AD. It further describes different pharmacological and dietary interventions being used in treating and/or managing AD. Additionally, this article provides a thorough review of the literature for improving the therapeutic paradigm of AD.

Emerging Signal Regulating Potential of Genistein Against Alzheimer's Disease: A Promising Molecule of Interest

Alzheimer’s disease (AD) is a progressive, irreversible brain disorder characterized by pathological aggregation of the amyloid-β peptide (Aβ) and tau protein; both of these are toxic to neurons. Currently, natural products are regarded as an alternative approach to discover novel multipotent drugs against AD. Dietary soy isoflavone genistein is one of the examples of such agents that occurs naturally and is known to exert a number of beneficial health effects. It has been observed that genistein has the capacity to improve the impairments triggered by Aβ and also it possesses the antioxidant potential to scavenge the AD-mediated generation of free radicals. Furthermore, genistein can interact directly with the targeted signaling proteins and also can stabilize their activity to combat AD. In order to advance the development of AD treatment, a better comprehension of the direct interactions of target proteins and genistein might prove beneficial. Therefore, this article focuses on the therapeutic effects and molecular targets of genistein, which has been found to target directly the Aβ and tau to control the intracellular signaling pathways responsible for neurons death in the AD brain.

Increasing protective activity of genistein by loading into transfersomes: A new potential adjuvant in the oxidative stress-related neurodegenerative diseases?

BACKGROUND

Genistein is a soy-derived isoflavone and phytoestrogen with antioxidant and neuroprotective activity. Genistein has intrinsically low oral bioavailability that affects its dose-response activities.

PURPOSE

Nanotechnologies were used to obtain the delivery of genistein to the brain: lipid-based nanovesicles, transfersomes, loaded with the phytoestrogen were developed as potential therapeutic or preventive strategy against neurodegenerative diseases by intranasal administration.

METHODS

Phosphatidylcholine from soybean and different edge activators were used to prepare transfersomes. The effect of selected nanovesicles on the oxidative damage was studied in PC12 cell line.

RESULTS

Suitable nanovesicles as carrier of genistein were obtained; their composition affects deformability, drug permeation behavior and cytotoxicity. In particular, the formulation containing Span 80, GEN-TF2, showed efficiency of internalization into the cell and it was able to attenuate ROS formation and to reduce the amount of apoptotic cells generated by H₂O₂ treatment compared to genistein.

CONCLUSION

GEN-TF2 was able to reduce the oxidative damage suggesting a possible antioxidant role of this drug delivery system. These obtained data confer to GEN-TF2 a potential antioxidant activity and then it could be used as adjuvant therapy in oxidative stress-related neurodegenerative diseases.

Computational Studies Applied to Flavonoids against Alzheimer's and Parkinson's Diseases

Neurodegenerative diseases, such as Parkinson's and Alzheimer's, are understood as occurring through genetic, cellular, and multifactor pathophysiological mechanisms. Several natural products such as flavonoids have been reported in the literature for having the capacity to cross the blood-brain barrier and slow the progression of such diseases. The present article reports on in silico enzymatic target studies and natural products as inhibitors for the treatment of Parkinson's and Alzheimer's diseases. In this study we evaluated 39 flavonoids using prediction of molecular properties and in silico docking studies, while comparing against 7 standard reference compounds: 4 for Parkinson's and 3 for Alzheimer's. Osiris analysis revealed that most of the flavonoids presented no toxicity and good absorption parameters. The Parkinson's docking results using selected flavonoids as compared to the standards with four proteins revealed similar binding energies, indicating that the compounds 8-prenylnaringenin, europinidin, epicatechin gallate, homoeriodictyol, capensinidin, and rosinidin are potential leads with the necessary pharmacological and structural properties to be drug candidates. The Alzheimer's docking results suggested that seven of the 39 flavonoids studied, being those with the best molecular docking results, presenting no toxicity risks, and having good absorption rates (8-prenylnaringenin, europinidin, epicatechin gallate, homoeriodictyol, aspalathin, butin, and norartocarpetin) for the targets analyzed, are the flavonoids which possess the most adequate pharmacological profiles.

Phytoconstituents and their Possible Mechanistic Profile for Alzheimer's Disease - A Literature Review

Memory is an associated part of life without which livelihood of a human being becomes miserable. As the global aged population is increasing tremendously, time has come to concentrate on tail end life stage diseases. Alzheimer's disease (AD) is one of such diseases whose origin is enigmatic, having an impact on later stage of life drastically due to irreparable damage of cognition, characterised by the presence of neurotoxic amyloid-beta (Aβ) plaques and hyper phosphorylated Tau protein as fibrillary tangles. Existing therapeutic regimen mainly focuses on symptomatic relief by targeting neurotransmitters that are secondary to AD pathology. Plant derived licensed drugs, Galantamine and Huperzine-A were studied extensively due to their AChE inhibitory action for mild to moderate cases of AD. Although many studies have proved the efficacy of AChEIs as a preferable symptom reliever, they cannot offer long term protection. The future generation drugs of AD is expected to alter various factors that underlie the disease course with a symptomatic benefit promise. As AD involves complex pathology, it is essential to consider several molecular divergent factors apart from the events that result in the production of toxic plaques and neurofibrillary tangles. Even though several herbals have shown neuroprotective actions, we have mentioned about the phytoconstituents that have been tested experimentally against different Alzheimer's pathology models. These phytoconstituents need to be considered by the researchers for further drug development process to make them viable clinically, which is currently a lacuna.

Role of Plant-Derived Flavonoids and Their Mechanism in Attenuation of Alzheimer's and Parkinson's Diseases: An Update of Recent Data

Neurodegeneration is a progressive loss of neuronal cells in certain regions of the brain. Most of the neurodegenerative disorders (NDDs) share the communal characteristic such as damage or reduction of various cell types typically including astrocytes and microglial activity. Several compounds are being trialed to treat NDDs but they possess solitary symptomatic advantages along with copious side effects. The finding of more enthralling and captivating compounds to suspend and standstill the pathology of NDDs will be considered as a hallmark of present times. Phytochemicals possess the potential to alternate the synthetic line of therapy against NDDs. The present review explores the potential efficacy of plant-derived flavonoids against most common NDDs including Alzheimer's disease (AD) and Parkinson's disease (PD). Flavonoids are biologically active phytochemicals which possess potential pharmacological effects, including antiviral, anti-allergic, antiplatelet, anti-inflammatory, anti-tumor, anti-apoptotic and anti-oxidant effects and are able to attenuate the pathology of various NDDs through down-regulating the nitric oxide (NO) production, by reducing the tumor necrosis factor-α (TNF-α), by reducing the excitotoxicity of superoxide as well as acting as tyrosine kinase (TK) and monoamine oxidase (MAO) inhibiting enzyme.

Genistein: mechanisms of action for a pleiotropic neuroprotective agent in stroke

Genistein is a plant estrogen promoted as an alternative to post-menopausal hormone therapy because of a good safety profile and its promotion as a natural product. Several preclinical studies of cerebral ischemia and other models of brain injury support a beneficial role for genistein in protecting the brain from injury whether administered chronically or acutely. Like estrogen, genistein is a pleiotropic molecule that engages several different mechanisms to enhance brain health, including reduction of oxidative stress, promotion of growth factor signaling, and immune suppression. These actions occur in endothelial, glial, and neuronal cells to provide a coordinated beneficial action to ischemic challenge. Though many of these protective actions are associated with estrogen-like actions of genistein, additional activities on other receptors and intracellular targets suggest that genistein is more than a mere estrogen-mimic. Importantly, genistein lacks some of the detrimental effects associated with post-menopausal estrogen treatment and may provide an alternative to hormone therapy in those patients at risk for ischemic events.

Genistein protects against Aβ25-35 induced apoptosis of PC12 cells through JNK signaling and modulation of Bcl-2 family messengers

Background

Deposition of aggregated amyloid beta (Aβ) protein is hallmark of Alzheimer’s disease, leading to dysfunction and apoptosis of neurons. The isoflavone phytoestrogen compound genistein (Gen) exerts a significant protective effect against Aβ_25–35 induced neurotoxicity and mitochondrial damage in rat pheochromocytoma (PC12) cells. However, the mechanisms underlying Gen’s rescue remain elusive. Therefore we endeavored to research further the molecular mechanisms underlying Gen’s inhibition of Aβ_25–35 induced apoptosis of neurons.

Results

We found that Gen dramatically suppressed the activation by Aβ_25–35 of p-c-Jun N-terminal kinase (p-JNK), and also inhibited the JNK-dependent decreased of Bcl-w and increased of Bim. Furthermore, Gen significantly reduced the cytoplasmic concentrations of cytochrome c and Smac protein as well as caspase-3 activity. Additionally, pretreatment with JNK inhibitor SP600125 effectively suppressed Aβ_25–35 induced PC12 cell cytotoxicity.

Conclusion

Taken together, the results suggested that Gen protects PC12 cells from Aβ_25–35 induced neurotoxicity by interfering with p-JNK activation, thus attenuating the JNK-dependent apoptosis through the mitochondrial pathway. These findings constitute novel insights into the pathway for Aβ_25–35 toxicity, and the neuroprotective action of Gen.

Electronic supplementary material

The online version of this article (doi:10.1186/s12868-016-0329-9) contains supplementary material, which is available to authorized users.

Molecular and Therapeutic Targets of Genistein in Alzheimer's Disease

Alzheimer's disease (AD) is a devastating brain disorder characterized by an increased level of amyloid-beta (Aβ) peptide deposition and neuronal cell death leading to an impairment of learning and thinking skills. The Aβ deposition is a key factor in senile plaques of the AD brain which cause the elevation of intracellular calcium ions and the production of formidable free radicals, both of which greatly contribute to the AD-associated cascade, leading to unstoppable neuronal loss in the hippocampal region of the brain. Natural products are currently considered as an alternative strategy for the discovery of novel multipotent drugs against AD. They include the naturally occurring dietary soy isoflavone genistein which has been recognized to possess several health-promoting effects. Genistein has been mainly focused because of its potential on amelioration of Aβ-induced impairment and its antioxidant capacity to scavenge the free radicals produced in AD. It can also directly interact with the targeted signaling proteins and stabilize their activity to prevent AD. An improved understanding of the direct interactions between genistein and target proteins would contribute to the further development of AD treatment. This review mainly focuses on molecular targets and the therapeutic effects regulated by genistein, which has the ability to directly target the Aβ peptide and to control its activity involved in intracellular signaling pathways, which otherwise would lead to neuronal death in the hippocampal region of the AD brain.

Genistein suppresses the mitochondrial apoptotic pathway in hippocampal neurons in rats with Alzheimer's disease

Genistein is effective against amyloid-β toxicity, but the underlying mechanisms are unclear. We hypothesized that genistein may protect neurons by inhibiting the mitochondrial apoptotic pathway, and thereby play a role in the prevention of Alzheimer’s disease. A rat model of Alzheimer’s disease was established by intraperitoneal injection of D-galactose and intracerebral injection of amyloid-β peptide (25–35). In the genistein treatment groups, a 7-day pretreatment with genistein (10, 30, 90 mg/kg) was given prior to establishing Alzheimer’s disease model, for 49 consecutive days. Terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling assay demonstrated a reduction in apoptosis in the hippocampus of rats treated with genistein. Western blot analysis showed that expression levels of capase-3, Bax and cytochrome c were decreased compared with the model group. Furthermore, immunohistochemical staining revealed reductions in cytochrome c and Bax immunoreactivity in these rats. Morris water maze revealed a substantial shortening of escape latency by genistein in Alzheimer’s disease rats. These findings suggest that genistein decreases neuronal loss in the hippocampus, and improves learning and memory ability. The neuroprotective effects of genistein are associated with the inhibition of the mitochondrial apoptotic pathway, as shown by its ability to reduce levels of caspase-3, Bax and cytochrome c.

Genistein Inhibits Aβ25-35-Induced Synaptic Toxicity and Regulates CaMKII/CREB Pathway in SH-SY5Y Cells

Genistein (Gen), as a functional food in human diet, has shown many beneficial effects on neurodegenerative diseases such as Alzheimer's disease (AD). But the neuroprotective mechanism of Gen is not clear. Because synaptic failure is considered as the earliest phase in the pathogenesis of AD, we try to validate our hypothesis that synapse may be one target of Gen on protecting neurons. In this study, SH-SY5Y cells were pre-incubated with or without Gen for 2 h followed by the incubation with Aβ25-35 (25 μmol/L) for another 24 h. Flow cytometry, Western Blots, and RT-PCR analysis were used to test the synaptic factors. The data showed that Gen pre-treatment could reverse the Aβ25-35-induced down-regulation of synaptophysin and postsynaptic marker postsynaptic density-95. In addition, the down-regulation of NR1 and NR2B induced by Aβ25-35 which are subunits of N-methyl-D-aspartate receptor also could be antagonized by pre-treatment of Gen. Moreover, the factors of CaMKII/CREB signaling pathway were detected. The results showed that mRNA and protein expressions of (Ca(2+))/calmodulin(CaM), CaMKII/pCaMKII, and CREB/pCREB were significantly down-regulated by Aβ25-35, but they were all restored by the pre-treatment of Gen. Furthermore, Gen also maintained the intracellular Ca(2+) concentration which was disturbed by Aβ25-35. In conclusion, these results suggested that Gen could protect synaptic dysfunction induced by Aβ, and the mechanism might be associated with the regulation of synaptic markers and Ca(2+) level through activating CaM/CaMK/CREB signaling pathway.

Ginsenoside Rd attenuates Aβ25-35-induced oxidative stress and apoptosis in primary cultured hippocampal neurons

One of the most common pathological changes in Alzheimer's disease (AD) brain is the large number of amyloid β (Aβ) peptides accumulating in lesion areas. Ginsenosides are the most active components extracted from ginseng. Ginsenoside Rd (GRd) is a newly discovered saponin that has a stronger pharmacological activity than other ginsenosides, especially in neuroprotection. Here we examined the neuroprotective effects of GRd against neuronal insults induced by Aβ25-35 in primary cultured hippocampal neurons. A 10μM GRd treatment significantly prevented the loss of hippocampal neurons induced by Aβ25-35. In addition, GRd significantly ameliorated Aβ25-35-induced oxidative stress by decreasing the reactive oxygen species (ROS) production and malondialdehyde (MDA) level, and increasing the levels of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px); which is similar in treatments with 10μM of probucol (PB) and 100μM of edaravone (EDA). Moreover, our present study demonstrated that GRd significantly enhanced the expression of Bcl-2 mRNA, and decreased the expressions of Bax mRNA and Cyt c mRNA. GRd also downregulated the protein level of cleaved Caspase-3 compared to controls. These results highlighted the neuroprotective effects of GRd against Aβ25-35-induced oxidative stress and neuronal apoptosis, suggesting that this may be a promising therapeutics against AD.