Genistein as a neuroprotective antioxidant attenuates redox imbalance induced by β‐amyloid peptides 25–35 in PC12 cells

The roles of dietary polyphenols at crosstalk between type 2 diabetes and Alzheimer's disease in ameliorating oxidative stress and mitochondrial dysfunction via PI3K/Akt signaling pathways

Alzheimer's disease (AD) is a fatal neurodegenerative disease in which senile plaques and neurofibrillary tangles are crucially involved in its physiological and pathophysiological processes. Growing animal and clinical studies have suggested that AD is also comorbid with some metabolic diseases, including type 2 diabetes mellitus (T2DM), and therefore, it is often considered brain diabetes. AD and T2DM share multiple molecular and biochemical mechanisms, including impaired insulin signaling, oxidative stress, gut microbiota dysbiosis, and mitochondrial dysfunction. In this review article, we mainly introduce oxidative stress and mitochondrial dysfunction and explain their role and the underlying molecular mechanism in T2DM and AD pathogenesis; then, according to the current literature, we comprehensively evaluate the possibility of regulating oxidative homeostasis and mitochondrial function as therapeutics against AD. Furthermore, considering dietary polyphenols' antioxidative and antidiabetic properties, the strategies for applying them as potential therapeutical interventions in patients with AD symptoms are assessed.

Genistein Effects on Various Human Disorders Mediated via Nrf2 Signaling

Genistein is a flavonoid, mostly found in soybean extract and is widely used for its antioxidant and anti-inflammatory activities. Genistein can interact with estrogen receptors due to its structural similarities to estrogen. It also inhibits protein tyrosine kinases and affects a variety of intracellular signal transductions. Genistein attenuates oxidative stress via diverse cellular mechanisms. However, nuclear factor (erythroidderived 2)-like 2 (Nrf2), the main antioxidant regulator, potentiates genistein's antioxidant effects and reduces cell damage. Nrf2 includes of seven domains and controls the expression of the phase II antioxidant enzymes to decrease oxidative stress. In this review, we address findings related to Nrf2 signaling pathways in the context of genistein's effects on diverse human diseases.

In Vitro Human Monoamine Oxidase Inhibition and Human Dopamine D4 Receptor Antagonist Effect of Natural Flavonoids for Neuroprotection

Natural flavone and isoflavone analogs such as 3',4',7-trihydroxyflavone (1), 3',4',7-trihydroxyisoflavone (2), and calycosin (3) possess significant neuroprotective activity in Alzheimer's and Parkinson's disease. This study highlights the in vitro human monoamine oxidase (hMAO) inhibitory potential and functional effect of those natural flavonoids at dopamine and serotonin receptors for their possible role in neuroprotection. In vitro hMAO inhibition and enzyme kinetics studies were performed using a chemiluminescent assay. The functional effect of three natural flavonoids on dopamine and serotonin receptors was tested via cell-based functional assays followed by a molecular docking simulation to predict interactions between a compound and the binding site of the target protein. A forced swimming test was performed in the male C57BL/6 mouse model. Results of in vitro chemiluminescent assays and enzyme kinetics depicted 1 as a competitive inhibitor of hMAO-A with promising potency (IC50 value: 7.57 ± 0.14 μM) and 3 as a competitive inhibitor of hMAO-B with an IC50 value of 7.19 ± 0.32 μM. Likewise, GPCR functional assays in transfected cells showed 1 as a good hD4R antagonist. In docking analysis, these active flavonoids interacted with a determinant-interacting residue via hydrophilic and hydrophobic interactions, with low docking scores comparable to reference ligands. The post-oral administration of 1 to male C57BL/6 mice did not reduce the immobility time in the forced swimming test. The results of this study suggest that 1 and 3 may serve as effective regulators of the aminergic system via hMAO inhibition and the hD4R antagonist effect, respectively, for neuroprotection. The route of administration should be considered.

Oxidative stress, the blood-brain barrier and neurodegenerative diseases: The critical beneficial role of dietary antioxidants

In recent years, growing awareness of the role of oxidative stress in brain health has prompted antioxidants, especially dietary antioxidants, to receive growing attention as possible treatments strategies for patients with neurodegenerative diseases (NDs). The most widely studied dietary antioxidants include active substances such as vitamins, carotenoids, flavonoids and polyphenols. Dietary antioxidants are found in usually consumed foods such as fresh fruits, vegetables, nuts and oils and are gaining popularity due to recently growing awareness of their potential for preventive and protective agents against NDs, as well as their abundant natural sources, generally non-toxic nature, and ease of long-term consumption. This review article examines the role of oxidative stress in the development of NDs, explores the 'two-sidedness' of the blood-brain barrier (BBB) as a protective barrier to the nervous system and an impeding barrier to the use of antioxidants as drug medicinal products and/or dietary antioxidants supplements for prevention and therapy and reviews the BBB permeability of common dietary antioxidant suplements and their potential efficacy in the prevention and treatment of NDs. Finally, current challenges and future directions for the prevention and treatment of NDs using dietary antioxidants are discussed, and useful information on the prevention and treatment of NDs is provided.

Potential Roles of Anti-Inflammatory Plant-Derived Bioactive Compounds Targeting Inflammation in Microvascular Complications of Diabetes

Diabetes mellitus (DM) is a group of metabolic disorders, the characteristics of which include chronic hyperglycemia owing to defects in insulin function, insulin secretion, or both. Inflammation plays a crucial role in DM pathogenesis and innate immunity in the development of microvascular complications of diabetes. In addition, hyperglycemia and DM mediate a proinflammatory microenvironment that can result in various microvascular complications, including diabetic nephropathy (DNP), diabetic neuropathy (DN), and diabetic retinopathy (DR). DNP is a major cause of end-stage renal disease. DNP can lead to albuminuria, decreased filtration, mesangium expansion, thickening of the basement membrane, and eventually renal failure. Furthermore, inflammatory cells can accumulate in the interstitium and glomeruli to deteriorate DNP. DN is another most prevalent microvascular complication of DM and the main cause of high mortality, disability, and a poor quality of life. DNs have a wide range of clinical manifestations because of the types of fiber dysfunctions and complex structures of the peripheral nervous system. DR is also a microvascular and multifactorial disease, as well as a major cause of visual impairment globally. Pathogenesis of DR is yet to be fully revealed, however, numerous studies have already confirmed the role of inflammation in the onset and advancement of DR. Despite evidence, and better knowledge regarding the pathogenesis of these microvascular complications of diabetes, there is still a deficiency of effective therapies. Bioactive compounds are mainly derived from plants, and these molecules have promising therapeutic potential. In this review, evidence and molecular mechanisms regarding the role of inflammation in various microvascular complications of diabetes including DNP, DN, and DR, have been summarized. The therapeutic potential of several bioactive compounds derived from plants in the treatment of these microvascular complications of diabetes has also been discussed.

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.

Keap1 as Target of Genistein on Nrf2 Signaling Pathway Antagonizing Aβ induced Oxidative Damage of Cerebrovascular Endothelial Cells

BACKGROUND

β-amyloid peptides (Aβ) induced oxidative damage contributes to the pathogenesis of neurodegenerative diseases and cerebrovascular system is more vulnerable to oxidative stress. Our earlier study showed a clue that Genistein (Gen) might activate Nf-E2 related factor 2 (Nrf2) pathway to protect cerebrovascular cells from oxidative damage induced by Aβ, but the specific mechanisms and regulation targets are unclear.

OBJECTIVE

In this study, the anti-oxidative effects and the possible targets of Gen on regulating Nrf2 pathway in bEnd.3 cells were investigated. Cells were divided into control, Aβ25-35, Gen and Gen+Aβ25-35 groups.

METHODS

Cell viability, levels of malondialdehyde (MDA), Superoxide Dismutase (SOD) activity and nitrotyrosine were evaluated. Moreover, mRNA and/or protein expressions of Nrf2 and kelch-like ECH-associated protein 1 (Keap1) were measured. Then we transfected Keap1 over-expressed plasmid into bEnd.3 cells and measured the protein expressions of Nrf2 pathway related factors. Data showed that Gen could inhibit the over-production of MDA and nitrotyrosine and activate SOD activity. Besides we got the phenomenon that Gen could up-regulate the mRNA and protein expressions of Nrf2 and down-regulate Keap1 protein expression, the Keap1 over-expressed plasmid study indicated that the up-regulation of Nrf2 protein expression induced by pretreatment of Gen could be blocked by the transfection of Keap1 over-expressed plasmid, and the same results also occurred in Nrf2 downstream factors.

CONCLUSION

Gen could alleviate the cerebrovascular cells oxidative damage induced by Aβ25-35 through regulating Nrf2 pathway, and Keap1 might be one of the targets of Gen on activating Nrf2 pathway.

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.

Paeonol Ameliorates Cognitive Deficits in Streptozotocin Murine Model of Sporadic Alzheimer's Disease via Attenuation of Oxidative Stress, Inflammation, and Mitochondrial Dysfunction

Intracerebroventricular (ICV) microinjection of diabetogenic drug streptozotocin (STZ) in rodents consistently produces a model of sporadic Alzheimer's disease (sAD) which is characterized by tau pathology and concomitant cognitive decline, insulin resistance, neuroinflammation, oxidative stress, and mitochondrial malfunction. Paeonol is an active phenolic component in some medicinal plants like Cortex Moutan with neuroprotective efficacy via exerting anti-inflammatory and anti-oxidative effects. This study was conducted to assess beneficial effect of paeonol in amelioration of cognitive deficits in ICV STZ rat model of sAD. STZ (3 mg/kg) was microinjected into the lateral ventricles on days 0 and 2, and paeonol was given p.o. at two doses of 25 (low) or 100 (high) mg/kg from day 0 (post-surgery) till day 24 post-STZ. Cognitive performance was evaluated in different tasks, and oxidative stress- and inflammation-related parameters were measured in addition to immunohistochemical assessment of glial fibrillary acidic protein (GFAP) as a marker of astrocytes. Paeonol at the higher dose ameliorated cognitive deficits in Barnes maze, novel object recognition (NOR) task, Y maze, and passive avoidance test. In addition, paeonol partially reversed hippocampal malondialdehyde (MDA), reactive oxygen species (ROS), total antioxidant capacity (TAC), superoxide dismutase (SOD), catalase, glutathione reductase, tumor necrosis factor α (TNFα), interleukin 6 (IL-6), mitochondrial membrane potential (MMP), myeloperoxidase (MPO), and acetylcholinesterase (AChE) activity. Paeonol treatment was also associated with lower hippocampal immunoreactivity for GFAP. This study showed that paeonol can alleviate cognitive disturbances in ICV STZ rat model of sAD via ameliorating neuroinflammation, oxidative stress, mitochondrial dysfunction, and also through its attenuation of astrogliosis.

Transmucosal Solid Lipid Nanoparticles to Improve Genistein Absorption via Intestinal Lymphatic Transport

Genistein (GEN) is a soy-derived isoflavone that exhibits several biological effects, such as neuroprotective activity and the prevention of several types of cancer and cardiovascular disease. However, due to its poor water solubility and the extensive first-pass metabolism, the oral bioavailability of GEN is limited. In this work, solid lipid nanoparticles (SLN) were developed to preferentially reach the intestinal lymphatic vessels, avoiding the first-pass metabolism of GEN. GEN-loaded SLN were obtained by a hot homogenization process, and the formulation parameters were chosen based on already formulated studies. The nanoparticles were characterized, and the preliminary in vitro chylomicron formation was evaluated. The cell uptake of selected nanocarriers was studied on the Caco-2 cell line and intestinal mucosa. The SLN, characterized by a spherical shape, showed an average diameter (about 280 nm) suitable for an intestinal lymphatic uptake, good stability during the testing time, and high drug loading capacity. Furthermore, the intestinal mucosa and Caco-2 cells were found to uptake SLN. The approximately two-fold increase in particle size suggested a possible interaction between SLN and the lipid components of chylomicrons like phospholipid; therefore, the results may support the potential for these SLN to improve oral GEN bioavailability via intestinal lymphatic absorption.

Natural Products for the Treatment of Neurodegenerative Diseases

Neurodegenerative diseases are a heterogeneous group of disorders characterized by the progressive degeneration of the structure and function of the central nervous system or peripheral nervous system. Alzheimer's Disease (AD), Parkinson's Disease (PD) and Spinal Cord Injury (SCI) are the common neurodegenerative diseases, which typically occur in people over the age of 60. With the rapid development of an aged society, over 60 million people worldwide are suffering from these uncurable diseases. Therefore, the search for new drugs and therapeutic methods has become an increasingly important research topic. Natural products especially those from the Traditional Chinese Medicines (TCMs), are the most important sources of drugs, and have received extensive interest among pharmacist. In this review, in order to facilitate further chemical modification of those useful natural products by pharmacists, we will bring together recent studies in single natural compound from TCMs with neuroprotective effect.

Melatonin reverses cognitive deficits in streptozotocin-induced type 1 diabetes in the rat through attenuation of oxidative stress and inflammation

Uncontrolled diabetes mellitus (DM) is linked to attentional deficits and cognition deterioration. The neurohormone melatonin is an endogenous synchronizer of circadian rhythms with multiple protective properties. This research was designed to assess its effect against learning and memory decline in streptozotocin (STZ)-induced diabetic rats. Rats were assigned to control, melatonin-treated control, diabetic, and melatonin-treated diabetic groups. Melatonin was administered i.p. at a dose of 10 mg/kg/day for 47 days. Treatment of diabetic rats with melatonin reversed decline of spatial recognition memory in Y maze, performance of rats in novel object discrimination, and retention and recall in passive avoidance tasks. Furthermore, melatonin appropriately attenuated hippocampal malondialdehyde (MDA) and reactive oxygen species (ROS) and improved superoxide dismutase (SOD) activity and improved mitochondrial membrane potential (MMP) and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) with no significant effect on nitrite, glutathione (GSH) and catalase activity. Besides, hippocampal level of acetylcholinesterase (AChE), glial fibrillary acidic protein (GFAP), nuclear factor-kappaB (NF-κB), interleukin 6 (IL-6) and tumor necrosis factor α (TNFα) decreased following melatonin treatment. There was also a reduction of dendritic spines of pyramidal neurons of hippocampal CA1 area in diabetic group that was significantly alleviated upon melatonin treatment. Melatonin could ameliorate learning and memory disturbances in diabetic rats through mitigation of cholinesterase activity, astrocytes, oxidative stress and inflammation and also via upregulation of some antioxidants in addition to its prevention of dendritic spine loss.

Transcription factor NRF2 as a promising therapeutic target for Alzheimer's disease

Oxidative stress is considered as one of the pathogenesis of Alzheimer's disease (AD) and plays an important role in the occurrence and development of AD. Nuclear factor erythroid 2 related factor 2 (NRF2) is a key regulatory of oxidative stress defence. There is growing evidence indicating the relationship between NRF2 and AD. NRF2 activation mitigates multiple pathogenic processes involved in AD by upregulating antioxidative defense, inhibiting neuroinflammation, improving mitochondrial function, maintaining proteostasis, and inhibiting ferroptosis. In addition, several NRF2 activators are currently being evaluated as AD therapeutic agents in clinical trials. Thus, targeting NRF2 has been the focus of a new strategy for prevention and treatment of AD. In this review, the role of NRF2 in AD and the NRF2 activators advanced into clinical and preclinical studies will be summarized.

Genistein inhibits amyloid peptide 25-35-induced neuronal death by modulating estrogen receptors, choline acetyltransferase and glutamate receptors

PURPOSE

To explore genistein, the most active component of soy isoflavones, on viability, expression of estrogen receptor (ER) subtypes, choline acetyltransferase (ChAT), and glutamate receptor subunits in amyloid peptide 25-35-induced hippocampal neurons, providing valuable data and basic information for neuroprotective effect of genistein in Aβ_25-35-induced neuronal injury.

METHODS

We established an in vitro model of Alzheimer's disease by exposing primary hippocampal neurons of newborn rats to amyloid peptide 25-35 (20 μM) for 24 h and observing the effects of genistein (10 μM, 3 h) on viability, expression of ER subtypes, ChAT, NMDA receptor subunit NR2B and AMPA receptor subunit GluR2 in Aβ_25-35-induced hippocampal neurons.

RESULTS

We found that amyloid peptide 25-35 exposure reduced the viability of hippocampal neurons. Meanwhile, amyloid peptide 25-35 exposure decreased the expression of ER subtypes, ChAT and GluR2, and increased the expression of NR2B. Genistein at least partially reversed the effects of amyloid peptide 25-35 in hippocampal neurons.

CONCLUSION

Genistein could increase the expression of ChAT as a consequence of activating estrogen receptor subtypes, modulating the expression of NR2B and GluR2, and thereby ameliorating the status of hippocampal neurons and exerting neuroprotective effects against amyloid peptide 25-35. Our data suggest that genistein might represent a potential cell-targeted therapy which could be a promising approach to treating AD.

Genistein attenuates amyloid-beta-induced cognitive impairment in rats by modulation of hippocampal synaptotoxicity and hyperphosphorylation of Tau

Alzheimer's disease is a progressive neurodegenerative disorder characterized by extracellular accumulation of amyloid-beta (Aβ) peptide, which induces synaptic dysfunction, alteration of intracellular signaling pathways, hyperphosphorylation of the Tau protein, and cognitive impairment. Genistein, one of the major isoflavones present in soy and soy products, has been shown to modulate some of the pathogenic events associated with the neurodegeneration process. However, its underlying mechanisms remain to be clarified. Therefore, the objectives of the present study were to evaluate the ability of genistein to protect against Aβ_1-42-induced cognitive impairment in rats and to elucidate some of the possible mechanisms involved in its neuroprotective effects in the hippocampus. Male Wistar rats received bilateral intracerebroventricular infusions of Aβ_1-42 (2 nmol) and genistein 10 mg/kg orally for 10 days. The Aβ-infused animals showed significant impairment of memory, which was accompanied by the following neurochemical alterations in the hippocampus: decreased levels of the synaptic proteins synaptophysin and postsynaptic density protein 95 (PSD-95), hyperphosphorylation of Tau with increased activation of glycogen synthase kinase-3β and c-Jun N-terminal kinase, and inactivation of ERK. Treatment with genistein improved Aβ-induced cognitive impairment by attenuation of synaptotoxicity, hyperphosphorylation of Tau, and inactivation of ERK. Furthermore, treatment with this soy isoflavone did not cause systemic toxicity. These findings provide further evidence of the neuroprotective effect of genistein in an in vivo model of Aβ toxicity and, importantly, extend the current knowledge concerning the mechanisms associated with the neuroprotective effects of this compound in the hippocampus.

Counteracting role of nuclear factor erythroid 2-related factor 2 pathway in Alzheimer's disease

A salient pathological features in Alzheimer's disease includes redox impairment and neuroinflammation. Nuclear factor erythroid 2-related factor 2 (Nrf2) and Nuclear factor kappa B (NF-ҡB) are the two key transcription factors that regulate cellular responses to redox impairment and neuroinflammation respectively. An effective way to confer neuroprotection in central nervous system (CNS) is the activation of a transcription factor i.e Nuclear factor erythroid 2-related factor 2 (Nrf2). An enhancer element known as Antioxidant Response Element (ARE) mediates the expression of phase II detoxification enzymes. Nrf2 is a nuclear transcription factor that binds to ARE thereby transcribing expression of several antioxidant genes. Kelch ECH associating protein-1 (Keap1), a culin 3-based E3 ligase, polyubiquitinates Nrf2 and targets it for its degradation. Disruption in the interaction between Keap1/Nrf2 can increase the brain's endogenous antioxidant capacity and thereby responsible for cell defence against oxidative stress and neuroinflammation in Alzheimer's disease (AD). The current review discusses about Keap1-Nrf2-ARE structure and function with special emphasis on the various pathways involved in positive and negative modulation of Nrf2, namely Phosphoinositide 3- kinase (PI3K), Glycogen synthase kinase-3β (GSK-3β), Nuclear factor kappa-b (NF-ҡb), Janus kinase/signal transducer and activator of transcription (JAK-STAT),Tumour Necrosis Factor- α (TNF-α), p38Mitogen-activated protein kinases (p38MAPK), Cyclic AMP response element binding protein (CREB) and intrinsic & extrinsic apoptotic pathway. Furthermore, this review highlights the miscellaneous Nrf2 activators as promising therapeutic agents for slowingdown the progression of AD.

Impact of Antioxidant Natural Compounds on the Thyroid Gland and Implication of the Keap1/Nrf2 Signaling Pathway

BACKGROUND

Natural compounds with potential antioxidant properties have been used in the form of food supplements or extracts with the intent to prevent or treat various diseases. Many of these compounds can activate the cytoprotective Nrf2 pathway. Besides, some of them are known to impact the thyroid gland, often with potential side-effects, but in other instances, with potential utility in the treatment of thyroid disorders.

OBJECTIVE

In view of recent data regarding the multiple roles of Nrf2 in the thyroid, this review summarizes the current bibliography on natural compounds that can have an effect on thyroid gland physiology and pathophysiology, and it discusses the potential implication of the Nrf2 system in the respective mechanisms.

METHODS & RESULTS

Literature searches for articles from 1950 to 2018 were performed in PubMed and Google Scholar using relevant keywords about phytochemicals, Nrf2 and thyroid. Natural substances were categorized into phenolic compounds, sulfur-containing compounds, quinones, terpenoids, or under the general category of plant extracts. For individual compounds in each category, respective data were summarized, as derived from in vitro (cell lines), preclinical (animal models) and clinical studies. The main emerging themes were as follows: phenolic compounds often showed potential to affect the production of thyroid hormones; sulfur-containing compounds impacted the pathogenesis of goiter and the proliferation of thyroid cancer cells; while quinones and terpenoids modified Nrf2 signaling in thyroid cell lines.

CONCLUSION

Natural compounds that modify the activity of the Nrf2 pathway should be evaluated carefully, not only for their potential to be used as therapeutic agents for thyroid disorders, but also for their thyroidal safety when used for the prevention and treatment of non-thyroidal diseases.

Genistein protects against amyloid-beta-induced toxicity in SH-SY5Y cells by regulation of Akt and Tau phosphorylation

Alzheimer's disease is a neurodegenerative disorder characterized by extracellular deposition of amyloid-β (Aβ) peptide and hyperphosphorylation of Tau protein, which ultimately leads to the formation of intracellular neurofibrillary tangles and cell death. Increasing evidence indicates that genistein, a soy isoflavone, has neuroprotective effects against Aβ-induced toxicity. However, the molecular mechanisms involved in its neuroprotection are not well understood. In this study, we have established a neuronal damage model using retinoic-acid differentiated SH-SY5Y cells treated with different concentrations of Aβ_25-35 to investigate the effect of genistein against Aβ-induced cell death and the possible involvement of protein kinase B (PKB, also termed Akt), glycogen synthase kinase 3β (GSK-3β), and Tau as an underlying mechanism to this neuroprotection. Differentiated SH-SY5Y cells were pre-treated for 24 hr with genistein (1 and 10 nM) and exposed to Aβ_25-35 (25 μM), and we found that genistein partially inhibited Aβ induced cell death, primarily apoptosis. Furthermore, the protective effect of genistein was associated with the inhibition of Aβ-induced Akt inactivation and Tau hyperphosphorylation. These findings reinforce the neuroprotective effects of genistein against Aβ toxicity and provide evidence that its mechanism may involve regulation of Akt and Tau proteins.

Safranal, an active ingredient of saffron, attenuates cognitive deficits in amyloid β-induced rat model of Alzheimer's disease: underlying mechanisms

Alzheimer's disease (AD) is the most prevalent neurodegenerative amyloid disorder with progressive deterioration of cognitive and memory skills. Despite many efforts, no decisive therapy yet exists for AD. Safranal is the active constituent of saffron essential oil with antioxidant, anti-inflammatory, and anti-apoptotic properties. In this study, the possible beneficial effect of safranal on cognitive deficits was evaluated in a rat model of AD induced by intrahippocampal amyloid beta (Aβ_1-40). Safranal was daily given p.o. (0.025, 0.1, and 0.2 ml/kg) post-surgery for 1 week and finally learning and memory were evaluated in addition to assessment of the involvement of oxidative stress, inflammation, and apoptosis. Findings showed that safranal treatment of amyloid β-microinjected rats dose-dependently improved cognition in Y-maze, novel-object discrimination, passive avoidance, and 8-arm radial arm maze tasks. Besides, safranal attenuated hippocampal level of malondialdehyde (MDA), reactive oxygen species (ROS), protein carbonyl, interleukin 1β (IL-1β), interleukin 6 (IL-6), tumor necrosis factor α (TNFα), nuclear factor-kappa B (NF-kB), apoptotic biomarkers including caspase 3 and DNA fragmentation, glial fibrillary acidic protein (GFAP), myeloperoxidase (MPO), and acetylcholinesterase (AChE) activity and improved superoxide dismutase (SOD) activity and mitochondrial membrane potential (MMP) with no significant effect on nitrite, catalase activity, and glutathione (GSH). Furthermore, safranal prevented CA1 neuronal loss due to amyloid β_1-40. In summary, safranal treatment of intrahippocampal amyloid beta_1-40-microinjected rats could prevent learning and memory decline via neuronal protection and at a molecular level through amelioration of apoptosis, oxidative stress, inflammation, cholinesterase activity, neutrophil infiltration, and also by preservation of mitochondrial integrity.

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.

Soy isoflavones protect against oxidative stress and diminish apoptosis in ovary of middle-aged female rats

Ovarian aging is characterized by declines in follicular reserve and oocyte quality due, in part, to increased oxidative stress and apoptosis. Soy isoflavones (ISOs) have been shown to improve ovarian lifespan by acting as antioxidant and antiapoptotic agents. We aimed at evaluating whether ISOs could modulate oxidative stress and reduce apoptosis and improve ovarian follicle survival in middle-aged female rats. Twelve ovary-intact female Wistar rats (12-month-old) were divided into groups: control (CTRL) and ISO, daily treated by gavage with vehicle or soy-ISO extract (150 mg/kg b.w), respectively. After 8 weeks, rats were euthanized and their ovaries removed for histomorphometric (% follicles) and apoptosis (cleaved-caspase-3/BCL2 immunostaining) evaluations, or subjected to biochemical assays to survey reactive oxygen species (ROS) and lipid peroxidation levels and total antioxidant capacity (TAC). The frequency of atretic follicles and number of cleaved-caspase-3-positive cells, as well as the ROS and lipid peroxidation levels, were significantly lower in ISO group compared to CTRL. A significantly higher number of BCL2-positive cells and TAC levels were also observed in ISO group. In conclusion, soy ISOs could decrease follicular atresia, apoptosis and oxidative stress, as well as increase the TAC in ovaries of female rats.

Trigonelline protects hippocampus against intracerebral Aβ(1-40) as a model of Alzheimer's disease in the rat: insights into underlying mechanisms

Alzheimer's disease (AD) is a chronic neurodegenerative disorder and the most common phenotype of dementia. Trigonelline is an alkaloid found in medicinal plants such as fenugreek seeds and coffee beans with neuroprotective potential and according to existing evidences, a favorable agent for treatment of neurodegenerative disorders. In this study, the possible protective effect of trigonelline against intracerebral Aβ(1-40) as a model of AD in the rat was investigated. For induction of AD, aggregated A(1-40) (10 μg/2 휇l for each side) was bilaterally microinjected into the hippocampal CA1 area. Trigonelline was administered p.o. at a dose of 100 mg/kg. The results showed that trigonelline pretreatment of Aβ-microinjected rats significantly improves spatial recognition memory in Y maze and performance in novel object recognition (NOR) task, mitigates hippocampal malondialdehyde (MDA), protein carbonyl, lactate dehydrogenase (LDH), and improves mitochondrial membrane potential (MMP), glutathione (GSH), and superoxide dismutase (SOD) with no significant change of catalase activity, nitrite level, caspase 3 activity, and DNA fragmentation. Additionally, trigonelline ameliorated hippocampal levels of glial fibrillary acidic protein (GFAP), S100b, cyclooxygenase 2 (Cox2), tumor necrosis factor α (TNFα), and interleukin 6 (IL-6) with no significant alteration of inducible nitric oxide synthase (iNOS). In addition, trigonelline pretreatment prevented loss of hippocampal CA1 neurons in Aβ-microinjected group. Therefore, our results suggest that trigonelline pretreatment in Aβ model of AD could improve cognition and is capable to alleviate neuronal loss through suppressing oxidative stress, astrocyte activity, and inflammation and also through preservation of mitochondrial integrity.

Genistein inhibits Aβ25-35 -induced SH-SY5Y cell damage by modulating the expression of apoptosis-related proteins and Ca2+ influx through ionotropic glutamate receptors

In this study, we investigated the protective effects of genistein against SH-SY5Y cell damage induced by β-amyloid 25-35 peptide (Aβ_25-35 ) and the underlying mechanisms. Aβ-induced neuronal death, apoptosis, glutamate receptor subunit expression, Ca²⁺ ion concentration, amino acid transmitter concentration, and apoptosis-related factor expression were evaluated to determine the effects of genistein on Aβ-induced neuronal death and apoptosis. The results showed that genistein increased the survival of SH-SY5Y cells and decreased the level of apoptosis induced by Aβ_25-35 . In addition, genistein reversed the Aβ_25-35 -induced changes in amino acid transmitters, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors, and N-methyl-d-aspartate (NMDA) receptor subunits in SH-SY5Y cells. Aβ_25-35 -induced changes in Ca²⁺ and B-cell lymphoma-2 (Bcl-2) and Bcl-2-associated X (Bax) protein and gene levels in cells were also reversed by genistein. Our data suggest that genistein protects against Aβ_25-35 -induced damage in SH-SY5Y cells, possibly by regulating the expression of apoptosis-related proteins and Ca²⁺ influx through ionotropic glutamate receptors.

Hesperetin, a citrus flavonoid, attenuates testicular damage in diabetic rats via inhibition of oxidative stress, inflammation, and apoptosis

AIM

This study was designed to assess the beneficial effect of hesperetin on diabetes-associated testicular injury in the rat.

MAIN METHODS

Oral treatment with hesperetin started 10 days after diabetes induction by streptozotocin (60 mg/kg, i.p.) for 46 days. Testicular damage was evaluated by histological evaluation of seminiferous tubules in addition to assessment of epididymal sperm count, motility, and viability. In addition, testicular biomarkers of apoptosis, inflammation, and oxidative stress were also determined.

KEY FINDINGS

Hesperetin treatment of diabetic group prevented body weight loss and reduced serum glucose in addition to improvement of serum testosterone. Additionally, hesperetin-treated diabetic group had lower levels of malondialdehyde (MDA), reactive oxygen species (ROS), protein carbonyl, DNA fragmentation, and caspase 3 activity as specific biomarkers of oxidative stress and/or apoptosis. Furthermore, hesperetin augmented testicular antioxidant system as shown by higher levels of glutathione (GSH), mitochondrial membrane potential (MMP), and ferric reducing antioxidant power (FRAP) in addition to improvement of superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx). Moreover, hesperetin administration to diabetic rats attenuated testicular indices of inflammation consisting of tumor necrosis factor α (TNFα) and interleukin 17 (IL-17) and prevented damage of seminiferous tubules as revealed by higher levels of sperm count, motility, and viability in diabetic rats.

SIGNIFICANCE

Collectively, hesperetin could alleviate testicular damage in DM, at least through inhibition of apoptosis, oxidative stress, and inflammation in addition to its up-regulation of endogenous enzymatic and non-enzymatic antioxidants.

Effect of Genistein on the Transgenic Drosophila Model of Parkinson's Disease

Parkinson's disease (PD) is the second-most common neurodegenerative disorder and is characterized by the degeneration of dopaminergic neurons in the substantia nigra pars compacta. Oxidative stress has also been linked with the progression of PD, hence the involvement of a natural plant product could offer neuroprotection. The present study deals with the effect of genistein on the transgenic flies expressing normal human alpha synuclein panneurally. The PD flies were exposed to 10, 20, 30, and 40 µM of genistein (mixed in diet) for 24 days. A significant dose-dependent increase in the life span and delay in the loss of climbing ability were observed in the PD flies exposed to genistein (p < .05). A significant dose-dependent decrease in oxidative stress markers and increase in dopamine content were observed in PD flies exposed to genistein. However, the exposure of genistein did not inhibit the expression of α-synuclein in the brains of PD flies.

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: is the multifarious botanical a natural anthelmintic too?

Genistein (4',5,7-trihydroxyisoflavone) is naturally present in plants of the soy family and is known to have various pharmacological activities, such as anti-cancer, anti-diabetic, anti-oxidant, etc. The phytoestrogen is one of the major isoflavones found in some medicinal plants having anthelmintic properties. This review describes the putative role of genistein as an anthelmintic, which has been tested on some helminth parasites in vitro. Genistein has been shown to cause paralysis and alterations in the tegument and tegumental enzymes (acid phosphatase, alkaline phosphatase, adenosine triphosphatase, and 5'-nucleotidase) of helminth parasites. Alterations in the activities of several enzymes associated with the coordination system (specifically non-specific esterases, acetylcholine esterase, and nitric oxide synthase), and changes in the concentration of nitric oxide, cGMP, free amino acid pool, and tissue ammonia are observed in helminth parasites treated with genistein. The phytoestrogen also affects the carbohydrate metabolism by altering the activities of key enzymes involved in glycogen- and glucose-metabolism of a cestode parasite. Considering the significance of phosphoenolpyruvate carboxykinase (PEPCK) in glycolysis of the cestode parasite, Ki of the phytoestrogen for PEPCK in the parasite has been determined, and molecular docking of genistein into the active site of the enzyme has also been described. The potential beneficial role of genistein as a natural alternative in management of helminth parasites needs to be further explored, particularly considering its in vivo efficacy and pharmacokinetics.

Genistein promotes the metabolic transformation of acetaminophen to glucuronic acid in human L-O2, HepG2 and Hep3b cells via the Nrf2/Keap1 pathway

This study aimed to explore the effects of genistein on regulating the activation of UGTs via the Nrf2/Keap1 pathway and to elucidate the underlying mechanisms of detoxification and hepatic protection. Experiments monitoring genistein-induced protection against acetaminophen-induced cell damage were performed in L-02, HepG2 and Hep3b cells. The results of the MTT, AST, ALT, LDH, GSH and GSSG assays showed that genistein evidently protected the cells from acetaminophen-induced injury in a dose-dependent manner. The control cells were treated with 10 mM acetaminophen without genistein to compare with the effects of the combination of acetaminophen and genistein on the expression of UGT1A1, 1A6 and 1A9, Nrf2 and Keap1 mRNAs, as well as the expression of Nrf2 and Keap1 proteins, which were tested by western blotting. The results showed that the expression of the Nrf2 mRNA and protein increased; in contrast, the expression levels of the Keap1 mRNA and protein were obviously reduced by genistein in a dose-dependent manner. Meanwhile, the expression of the UGT mRNA was increased, and UGT1A9 exhibited the highest expression among the three UGTs. Accordingly, the residual acetaminophen content was obviously reduced and acetaminophen glucuronidation increased after 24 hours of treatment with genistein in a dose-dependent manner.

Neuroprotective Effects of Acetylcholinesterase Inhibitory Peptides from Anchovy (Coilia mystus) against Glutamate-Induced Toxicity in PC12 Cells

Ameliorations of cholinergic system dysfunction and oxidative stress in neurodegenerative diseases were main approaches to improve memory disorder. Our previous investigation showed that anchovy protein hydrolysate (APH) could attenuate scopolamine-induced memory deficits in mice by regulating acetylcholinesterase (AChE) activity. Therefore, peptides with AChE inhibitory activity in APH were explored and identified in this study, and their possible neuroprotective mechanisms on glutamate induced apoptosis in PC12 were also elucidated. Two peptides with strong AChE inhibitory capacity were identified as Pro-Ala-Tyr-Cys-Ser (PAYCS) and Cys-Val-Gly-Ser-Tyr (CVGSY) by ultraperformance liquid chromatography coupled with tandem mass spectrometry. The AChE inhibitory was 23.68 ± 0.97% and 6.08 ± 0.41%, respectively. Treatment with PAYCS and CVGSY could significantly (p < 0.05) increase cells viability, reduce lactate dehydrogenase release, reactive oxygen species (ROS) production, malondialdehyde content, and the ratio of Bax/Bcl-2 of glutamate-induced apoptosis PC12 cells (82.78 ± 6.58 and 109.94 ± 7.16% of control, respectively) as well as increase superoxide dismutase and GSH-px activities. In addition, both the peptides could inhibit Ca²⁺ influx but have no effects on mitochondrial membrane potential. Results indicated that AChE inhibitory peptides (PAYCS and CVGSY) possibly protected the PC12 cells against glutamate-induced apoptosis via inhibiting ROS production and Ca²⁺ influx. PAYCS and CVGSY might be considered as nutraceuticals for alleviating memory deficits.

Flavonoids of Kudzu Root Fermented by Eurtotium cristatum Protected Rat Pheochromocytoma Line 12 (PC12) Cells against H₂O₂-Induced Apoptosis

Novel bioactive components have greatly attracted attention as they demonstrate health benefits. Reversed-phase high performance liquid chromatography (RP-HPLC) showed that isoflavonoid compounds of kudzu root (Pueraria lobata) fermented by Eurtotium cristatum and extracted using de-ionized water were higher active compared with non-fermented. A model of H₂O₂-inducd cell damage was built using rat pheochromocytoma line 12 (PC12) cell to observe the protective effect of non-fermented kudzu root (Pueraria lobata) (NFK) and fermented kudzu root (Pueraria lobata) (FK). Cell viability and apoptosis were analyzed through inverted microscopy and flow cytometry. The level of lactate dehydrogenase, catalase activity, superoxide dismutase, glutathione, and reactive oxygen species (ROS) were evaluated. Results showed that NFK and FK could significantly protect PC12 cell against damage caused by H₂O₂-induced oxidative stress. The intracellular antioxidant system was increased, protected the cell membrane inhibit H₂O₂-induced apoptosis by scavenging of ROS. Moreover, NFK and FK regulated the cell cycle to prevent cell apoptosis. Isoflavonoid from the kudzu root especially fermented kudzu root with E. cristatum are potentially therapeutic drugs against diseases induced by oxidative damage.

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.

Exploring the oxidative stress response mechanism triggered by environmental water samples

Environmental waters can contain a wide range of micropollutants. Bioanalytical test batteries using assays indicative of different stages of cellular toxicity pathways, such as adaptive stress responses, have been applied to a range of water samples. Oxidative stress response assays have proven to be sensitive tools, but the mechanism by which water samples are inducing the oxidative stress response remains unclear because both electrophiles and reactive oxygen species (ROS) may activate the Nrf2-antioxidant response element (ARE) pathway. The current study aimed to explore the underlying mechanisms of the oxidative stress response triggered by exposure to surface water extracts previously shown to be active in the ARE GeneBLAzer oxidative stress response assay. ROS formation and changes in glutathione (GSH) concentration were assessed in human liver cells exposed to water extracts from a large river in addition to individual chemicals that were detected in these water extracts and reported to be active in the ARE GeneBLAzer assay in a previous study. Many of the surface water samples induced ROS formation and decreased the GSH to glutathione disulfide (GSSG) ratio, suggesting that the formation of ROS is an important mechanism. However, some of the most responsive samples in the ARE GeneBLAzer assay, as well as the individual chemicals, did not have a significant effect on either ROS formation or the GSH/GSSG ratio, suggesting a different mechanism. Antioxidants can also induce the Nrf2-ARE pathway and the ARE GeneBLAzer assay may also detect compounds that activate ARE by Nrf2-independent mechanisms, thus further research is required to characterise active chemicals in oxidative stress response assays. However, these tests are still useful for quantifying the integrated cellular response to multiple molecular initiating events and can be used complementary to assays indicative of specific effects, such as receptor-mediated assays.

Genistein inhibits hypoxia, ischemic-induced death, and apoptosis in PC12 cells

A hypoxia/ischemia neuronal model was established in PC12 cells using oxygen-glucose deprivation (OGD). OGD-induced neuronal death, apoptosis, glutamate receptor subunit GluR2 expression, and potassium channel currents were evaluated in the present study to determine the effects of genistein in mediating the neuronal death and apoptosis induced by hypoxia and ischemia, as well as its underlying mechanism. OGD exposure reduced the cell viability, increased apoptosis, decreased the GluR2 expression, and decreased the voltage-activated potassium currents. Genistein partially reversed the effects induced by OGD. Therefore, genistein may prevent hypoxia/ischemic-induced neuronal apoptosis that is mediated by alterations in GluR2 expression and voltage-activated potassium currents.

Dietary Phytochemicals and Cancer Chemoprevention: A Perspective on Oxidative Stress, Inflammation, and Epigenetics

Oxidative stress occurs when cellular reactive oxygen species levels exceed the self-antioxidant capacity of the body. Oxidative stress induces many pathological changes, including inflammation and cancer. Chronic inflammation is believed to be strongly associated with the major stages of carcinogenesis. The nuclear factor erythroid 2-related factor 2 (Nrf2) pathway plays a crucial role in regulating oxidative stress and inflammation by manipulating key antioxidant and detoxification enzyme genes via the antioxidant response element. Many dietary phytochemicals with cancer chemopreventive properties, such as polyphenols, isothiocyanates, and triterpenoids, exert antioxidant and anti-inflammatory functions by activating the Nrf2 pathway. Furthermore, epigenetic changes, including DNA methylation, histone post-translational modifications, and miRNA-mediated post-transcriptional alterations, also lead to various carcinogenesis processes by suppressing cancer repressor gene transcription. Using epigenetic research tools, including next-generation sequencing technologies, many dietary phytochemicals are shown to modify and reverse aberrant epigenetic/epigenome changes, potentially leading to cancer prevention/treatment. Thus, the beneficial effects of dietary phytochemicals on cancer development warrant further investigation to provide additional impetus for clinical translational studies.

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.

Cognitive Effects of Soy Isoflavones in Patients with Alzheimer's Disease

BACKGROUND

In a previous trial, treatment with soy isoflavones was associated with improved nonverbal memory, construction abilities, verbal fluency, and speeded dexterity compared to treatment with placebo in cognitively healthy older adults.

OBJECTIVE

The current trial aimed to examine the potential cognitive benefits of soy isoflavones in patients with Alzheimer's disease.

METHODS

Sixty-five men and women over the age of 60 were treated with 100 mg/day soy isoflavones, or matching placebo capsules for six months. APOE genotype was determined for all participants. Cognitive outcomes and plasma isoflavone levels were measured at baseline, and at two additional time points: three and six months after baseline.

RESULTS

Of the sixty-five participants enrolled, thirty-four (52.3% ) were women, and 31 (47.7% ) were APOEɛ4 positive. Average age was 76.3 (SD = 7.2) years. Fifty-nine (90.8% ) subjects completed all study visits. Plasma isoflavone levels increased in subjects treated with soy isoflavones compared to baseline and to placebo, although intersubject variability in plasma levels was large. No significant differences in treatment effects for cognition emerged between treatment groups or genders. Exploratory analyses of associations between changes in cognition and plasma isoflavone levels revealed an association between equol levels, and speeded dexterity and verbal fluency.

CONCLUSIONS

Six months of 100 mg/day treatment with soy isoflavones did not benefit cognition in older men and women with Alzheimer's disease. However, our results suggest the need to examine the role of isoflavone metabolism, i.e., the ability to effectively metabolize soy isoflavones by converting daidzen to equol when attempting to fully clarify the cognitive effects of isoflavones.

Neuroprotective Effects of Biochanin A against β-Amyloid-Induced Neurotoxicity in PC12 Cells via a Mitochondrial-Dependent Apoptosis Pathway

Alzheimer's disease is considered one of the major neurodegenerative diseases and is characterized by the production of β-amyloid (Aβ) proteins and progressive loss of neurons. Biochanin A, a phytoestrogen compound found mainly in Trifolium pratense, was used in the present study as a potential alternative to estrogen replacement therapy via the investigation of its neuroprotective effects against Aβ25-35-induced toxicity, as well as of its potential mechanisms of action in PC12 cells. Exposure of these cells to the Aβ25-35 protein significantly increased cell viability loss and apoptosis. However, the effects induced by Aβ25-35 were markedly reversed in the present of biochanin A. Pretreatment with biochanin A attenuated the cytotoxic effect of the Aβ25-35 protein by decreasing viability loss, LDH release, and caspase activity in cells. Moreover, we found that expression of cytochrome c and Puma were reduced, alongside with the restoration of Bcl-2/Bax and Bcl-xL/Bax ratio in the presence of biochanin A, which led to a decrease in the apoptotic rate. These data demonstrate that mitochondria are involved in the protective effect of biochanin A against Aβ25-35 and that this drug attenuated Aβ25-35-induced PC12 cell injury and apoptosis by preventing mitochondrial dysfunction. Thus, biochanin A might raise a possibility as a potential therapeutic agent for Alzheimer's disease and other related neurodegenerative diseases.

Effects of equol on H2O2-induced oxidative stress in primary chicken intestinal epithelial cells

This experiment investigated the antioxidant effects of equol on oxidative stress induced by H2O2 in chicken intestinal epithelial cells (IEC). IEC, from Lingnan yellow broiler chick embryos at embryonic day 18, were cultured in Dulbecco's modified Eagle's medium/F12. Cells were pretreated with 0, 10, 100, or 500 nM equol for 24 h before exposure to 300 μM H2O2 during a further 24 h. Oxidative damage was assessed by photomicrographs of cells, measuring cell proliferation, malondialdehyde (MDA) content, and antioxidative capacity from cellular total superoxide dismutase (T-SOD) activity, as well as the relative expressions of Nrf2, Bcl-2, SOD-1, GSH-Px3, Claudin-1 Treatment with 300 μM H2O2 caused serious damage to cells, with fewer normal intestinal epithelial cells, revealed by photomicroscopy. Treatment with 300 μM H2O2 significantly decreased live cell numbers compared with controls and prior treatment with equol had no effect in offsetting this action of H2O2 (P > 0.05). Compared with the cells treated just with H2O2, pre-treatment with 10, 100 and 500 nM equol significantly enhanced T-SOD activity (P < 0.05), while 10 and 100 nM equol before H2O2 significantly enhanced T-SOD activity compared with the untreated controls (P < 0.05). In cells pre-treated with 100 nM equol, the relative abundance of Nrf2 transcripts increased from the controls (P < 0.05) but expressions of Bcl-2, GSH-Px3, or SOD-1 were unaffected (P > 0.05). Pre-treatment with 10 and 100 nM equol significantly increased the transcript abundance of Claudin-1 (P < 0.05). Equol is shown here to protect IECs from oxidative damage by promoting the expression of antioxidant genes, increasing the activities of antioxidant enzymes, and by enhancing antioxidant capacity; 100 nM equol appeared to be the most effective concentration.

Genistein alleviates lead-induced neurotoxicity in vitro and in vivo: Involvement of multiple signaling pathways

Lead (Pb) is a ubiquitous environmental and industrial pollutant. It induces neurotoxicity and cell death by disrupting the pro- and anti-oxidative balance; however, the mechanisms of its toxicity have yet to be fully understood. The soy-derived isoflavonoid, genistein (GEN), was reported to possess neuroprotective and antioxidative properties. The present study investigated the molecular mechanisms of Pb-induced neurotoxicity in vivo and in vitro, addressing the efficacy of GEN in protecting against Pb-induced toxicity. Pb exposure was associated with reduction of cell viability and cell apoptosis, concomitant with reactive oxygen species (ROS) generation in vitro, and pre-treatment with GEN markedly ameliorated the Pb-induced oxidative injury by increasing the expression of key antioxidant enzymes and the antioxidant transcription factor, nuclear factor erythroid 2 p45-related factor 2 (Nrf2). Next, PKC-α activation was found after Pb exposure in vitro and pretreatment with GEN attenuated Pb-induced ROS generation by PKC-α inhibition. MAPK-NF-κB activation triggered by Pb was also inhibited by GEN. In summary, our study establishes that GEN alleviates Pb-induced impairment in spatial memory, and reduces cell apoptosis caused by Pb exposure and GEN protects neurons from Pb-induced neurotoxicity by downstream activation of antioxidant and anti-apoptotic pathways via regulation of Nrf2 and MAPK-NF-κB signaling.

Genistein alleviates β-amyloid-induced inflammatory damage through regulating Toll-like receptor 4/nuclear factor κB

Genistein (GEN), a major soybean isoflavone (SIF), might possess neuroprotective properties through its anti-inflammatory activity. We hypothesized that GEN could prevent the inflammatory damage detected in C6 cells induced by β-amyloid peptides 25-35 (Aβ25-35). Accordingly, we evaluated the inflammatory damage induced by Aβ25-35 and the protective effect of GEN against Aβ25-35 in C6 cells. In our study, the C6 glial cells (rats glioma cell lines) were preincubated with or without GEN for 2 h following incubation with Aβ25-35 for another 24 h. Then, methylthiazolyl tetrazolium (MTT) assay was used to assess the cell viability. Immunofluorescence staining was used to identify the C6 cells. Inflammatory factors tumor necrosis factor (TNF)-α and interleukin (IL)-1β were analyzed by using enzyme-linked immunosorbent assay (ELISA). Western blot analysis and reverse transcription-polymerase chain reaction analysis were performed to assess the expression of Toll-like receptors 4 (TLR4), inhibitor of kappaB-alpha (IκB-α). The current results showed that GEN could alleviate Aβ25-35-induced cell apoptosis and prevent Aβ25-35-induced TNF-α and IL-1β release from C6 cells. In addition, GEN prevented Aβ25-35-induced upregulation of the gene and protein expression of TLR4, and GEN significantly upregulated the expression of IκB-α in C6 cells damaged by Aβ25-35. These results suggest that GEN can alleviate the inflammatory stress caused by Aβ25-35 treatment, which might be associated with the neuroprotective effect of GEN regulating the TLR4/NFκB signaling pathway.