Oestradiol or genistein rescues neurons from amyloid beta-induced cell death by inhibiting activation of p38

Genistein mitigates senescence of bone marrow mesenchymal stem cells via ERRα-mediated mitochondrial biogenesis and mitophagy in ovariectomized rats

Senescence of bone marrow mesenchymal stem cells (BMMSCs) induced by chronic oxidative stress is an important factor contributes to the postmenopausal osteoporosis (PMOP). Mitochondrial quality control takes a pivotal role in regulating oxidative stress and cell senescence. Genistein is a major isoflavone in soy products, which is best known for its ability to inhibit bone loss in both postmenopausal women and ovariectomized (OVX) rodents. Here we show that OVX-BMMSCs displayed premature senescence, elevated reactive oxygen species (ROS) level and mitochondria dysfunction, while genistein rescued these phenotypes. Using network pharmacology and molecular docking, we identified estrogen-related receptor α (ERRα) as the potential target of genistein. Knockdown of ERRα greatly abolished the anti-senescence effect of genistein on OVX-BMMSCs. Further, the mitochondrial biogenesis and mitophagy induced by genistein were inhibited by ERRα knockdown in OVX-BMMSCs. In vivo, genistein inhibited trabecular bone loss and p16INK4a expression, upregulated sirtuin 3 (SIRT3) and peroxisome proliferator-activated receptor gamma coactivator one alpha (PGC1α) expression in the trabecular bone area of proximal tibia in OVX rats. Together, this study revealed that genistein ameliorates senescence of OVX-BMMSCs through ERRα-mediated mitochondrial biogenesis and mitophagy, which provided a molecular basis for advancement and development of therapeutic strategies against PMOP.

Roles of genistein in learning and memory during aging and neurological disorders

Genistein (GEN) is a non-steroidal phytoestrogen that belongs to the isoflavone class. It is abundantly found in soy. Soy and its products are used as food components in many countries including India. The present review is focused to address roles of GEN in brain functions in the context of learning and memory as a function of aging and neurological disorders. Memory decline is one of the most disabling features observed during normal aging and age-associated neurodegenerative disorders namely Alzheimer's disease (AD) and Parkinson's disease (PD), etc. Anatomical, physiological, biochemical and molecular changes in the brain with advancement of age and pathological conditions lead to decline of cognitive functions. GEN is chemically comparable to estradiol and binds to estrogen receptors (ERs). GEN acts through ERs and mimics estrogen action. After binding to ERs, GEN regulates a plethora of brain functions including learning and memory; however detailed study still remains elusive. Due to the neuroprotective, anti-oxidative and anti-inflammatory properties, GEN is used to restore or improve memory functions in different animal models and humans. The present review may be helpful to understand roles of GEN in learning and memory during aging and neurological disorders, its direction of research and therapeutic perspectives.

Multifaceted Pharmacological Potentials of Curcumin, Genistein, and Tanshinone IIA through Proteomic Approaches: An In-Depth Review

Phytochemicals possess various intriguing pharmacological properties against diverse pathological conditions. Extensive studies are on-going to understand the structural/functional properties of phytochemicals as well as the molecular mechanisms of their therapeutic function against various disease conditions. Phytochemicals such as curcumin (Cur), genistein (Gen), and tanshinone-IIA (Tan IIA) have multifaceted therapeutic potentials and various efforts are in progress to understand the molecular dynamics of their function with different tools and technologies. Cur is an active lipophilic polyphenol with pleiotropic function, and it has been shown to possess various intriguing properties including antioxidant, anti-inflammatory, anti-microbial, anticancer, and anti-genotoxic properties besides others beneficial properties. Similarly, Gen (an isoflavone) exhibits a wide range of vital functions including antioxidant, anti-inflammatory, pro-apoptotic, anti-proliferative, anti-angiogenic activities etc. In addition, Tan IIA, a lipophilic compound, possesses antioxidant, anti-angiogenic, anti-inflammatory, anticancer activities, and so on. Over the last few decades, the field of proteomics has garnered great momentum mainly attributed to the recent advancement in mass spectrometry (MS) techniques. It is envisaged that the proteomics technology has considerably contributed to the biomedical research endeavors lately. Interestingly, they have also been explored as a reliable approach to understand the molecular intricacies related to phytochemical-based therapeutic interventions. The present review provides an overview of the proteomics studies performed to unravel the underlying molecular intricacies of various phytochemicals such as Cur, Gen, and Tan IIA. This in-depth study will help the researchers in better understanding of the pharmacological potential of the phytochemicals at the proteomics level. Certainly, this review will be highly instrumental in catalyzing the translational shift from phytochemical-based biomedical research to clinical practice in the near future.

Hormone therapy and the decreased risk of dementia in women with depression: a population-based cohort study

Background

The literature has shown depression to be associated with an increased risk of dementia. In addition, hormone therapy can be a responsive treatment option for a certain type of depression. In this study, we examined the association between hormone therapy, including lifetime oral contraceptive (OC) use, and hormone replacement therapy (HRT) after menopause with the occurrence of dementia among female patients with depression.

Methods

The South Korean national claims data from January 1, 2005, to December 31, 2018, was used. Female subjects aged 40 years or older with depression were included in the analyses. Information on hormone therapy was identified from health examination data and followed up for the occurrence of dementia during the average follow-up period of 7.72 years.

Results

Among 209,588 subjects, 23,555 were diagnosed with Alzheimer’s disease (AD) and 3023 with vascular dementia (VD). Lifetime OC usage was associated with a decreased risk of AD (OC use for < 1 year: HR, 0.92 [95% CI, 0.88–0.97]; OC use for ≥ 1 year: HR, 0.89 [95% CI, 0.84–0.94]), and HRT after menopause was associated with a decreased risk of AD (HRT for < 2 years: HR, 0.84 [95% CI, 0.79–0.89]; HRT for 2–5 years: HR, 0.80 [95% CI, 0.74–0.88]; and HRT for ≥ 5 years : HR, 0.78 [95% CI, 0.71–0.85]) and VD (HRT < 2 years: HR, 0.82 [95% CI, 0.71–0.96]; HRT for 2–5 years: HR, 0.81 [95% CI, 0.64–1.02]; and HRT for ≥ 5 years: HR, 0.61 [95% CI, 0.47–0.79]).

Conclusions

In this nationwide cohort study, lifetime OC use was associated with a decreased risk of AD, and HRT after menopause was associated with a decreased risk of AD and VD among female patients with depression. However, further studies are needed to establish causality.

p38 MAPK Is a Major Regulator of Amyloid Beta-Induced IL-6 Expression in Human Microglia

The accumulation of amyloid beta (Aβ) plaques in the brain is a hallmark of Alzheimer's disease (AD) pathology. Microglial activation-mediated neuroinflammation has been implicated in the pathogenesis of AD and the expression levels of interleukin-6 (IL-6) were increased in the brains of AD patients. However, the mechanisms by which IL-6 expression is regulated in human microglia are incompletely understood. Here, we show that Aβ1-40 oligomers (Aβ40) dose-dependently stimulate IL-6 expression in HMC3 human microglial cells. Treatment with Aβ40 promotes the transcription of IL-6 and tumor necrosis factor α (TNFα) mRNAs in both HMC3 and THP-1 cells. Mechanistic studies reveal that Aβ40-induced increase of IL-6 secretion is associated with the activation of p38 mitogen-activated protein kinase (p38 MAPK). Inhibition of p38 MAPK by BIRB 796 or SB202190 abrogates Aβ40-induced increase of IL-6 production. Through analyzing brain specimens, we found that the immunoreactivity for IL-6 and phosphorylated (the activated form) p38 MAPK was markedly higher in microglia of AD patients than in age-matched control subjects. Moreover, our studies identified the co-localization of IL-6 with phosphorylated p38 MAPK in microglia in the cortices of AD patients. Taken together, these results indicate that p38 MAPK is a major regulator of Aβ-induced IL-6 production in human microglia, which suggests that targeting p38 MAPK may represent a new approach to ameliorate Aβ accumulation-induced neuroinflammation in AD.

The Proper Diet and Regular Physical Activity Slow Down the Development of Parkinson Disease

From year to year, we know more about neurodegeneration and Parkinson’s disease (PD). A positive influence of various types of physical activity is more often described in the context of neuroprotection and prevention as well as the form of rehabilitation in Parkinson’s patients. Moreover, when we look at supplementation, clinical nutrition and dietetics, we will see that balancing consumed products and supplementing the vitamins or minerals is necessary. Considering the biochemical pathways in skeletal muscle, we may see that many researchers desire to identify molecular mediators that have an impact through exercise and balanced diet on human health or development of the neurodegenerative disease. Therefore, it is mandatory to study the potential mechanism(s) related to diet and factors resulted from physical activity as molecular mediators, which play a therapeutic role in PD. This review summarizes the available literature on mechanisms and specific pathways involved in diet-exercise relationship and discusses how therapy, including appropriate exercises and diet that influence molecular mediators, may significantly slow down the progress of neurodegenerative processes. We suggest that a proper diet combined with physical activity will be a good solution for psycho-muscle BALANCE not only in PD but also in other neurodegenerative diseases.

p38 MAPK-mediated loss of nuclear RNase III enzyme Drosha underlies amyloid beta-induced neuronal stress in Alzheimer's disease

MicroRNAs (miRNAs) are small noncoding RNAs ubiquitously expressed in the brain and regulate gene expression at the post‐transcriptional level. The nuclear RNase III enzyme Drosha initiates the maturation process of miRNAs in the nucleus. Strong evidence suggests that dysregulation of miRNAs is involved in many neurological disorders including Alzheimer's disease (AD). Dysfunction of miRNA biogenesis components may be involved in the processes of those diseases. However, the role of Drosha in AD remains unknown. By using immunohistochemistry, biochemistry, and subcellular fractionation methods, we show here that the level of Drosha protein was significantly lower in the postmortem brain of human AD patients as well as in the transgenic rat model of AD. Interestingly, Drosha level was specifically reduced in neurons of the cortex and hippocampus but not in the cerebellum in the AD brain samples. In primary cortical neurons, amyloid‐beta (Aβ) oligomers caused a p38 MAPK‐dependent phosphorylation of Drosha, leading to its redistribution from the nucleus to the cytoplasm and a decrease in its level. This loss of Drosha function preceded Aβ‐induced neuronal death. Importantly, inhibition of p38 MAPK activity or overexpression of Drosha protected neurons from Aβ oligomers‐induced apoptosis. Taken together, these results establish a role for p38 MAPK‐Drosha pathway in modulating neuronal viability under Aβ oligomers stress condition and implicate loss of Drosha as a key molecular change in the pathogenesis of AD.

Therapeutic Potential of Phytoconstituents in Management of Alzheimer's Disease

Since primitive times, herbs have been extensively used in conventional remedies for boosting cognitive impairment and age-associated memory loss. It is mentioned that medicinal plants have a variety of dynamic components, and they have become a prominent choice for synthetic medications for the care of cognitive and associated disorders. Herbal remedies have played a major role in the progression of medicine, and many advanced drugs have already been developed. Many studies have endorsed practicing herbal remedies with phytoconstituents, for healing Alzheimer's disease (AD). All the information in this article was collated from selected research papers from online scientific databases, such as PubMed, Web of Science, and Scopus. The aim of this article is to convey the potential of herbal remedies for the prospect management of Alzheimer's and related diseases. Herbal remedies may be useful in the discovery and advancement of drugs, thus extending new leads for neurodegenerative diseases such as AD. Nanocarriers play a significant role in delivering herbal medicaments to a specific target. Therefore, many drugs have been described for the management of age-linked complaints such as dementia, AD, and the like. Several phytochemicals are capable of managing AD, but their therapeutic claims are restricted due to their lower solubility and metabolism. These limitations of natural therapeutics can be overcome by using a targeted nanocarrier system. This article will provide the primitive remedies as well as the development of herbal remedies for AD management.

Study on the neuroprotective effects of Genistein on Alzheimer's disease

Along with the aging of the world population, the incidence rate of Alzheimer's disease (AD) has been increasing. At present, AD has become one of the most serious problems faced by modern medicine. Studies have shown that estrogen has a positive effect on AD, but estrogen has the side effect of leading to tumors. Recent in vivo studies have shown that genistein, one of the selective estrogen receptor modulators (SERMs), can improve brain function through the blood-brain barrier (BBB), antagonize the toxicity of amyloid β-protein (Aβ), that is, to inhibit neurotoxicity due to aggregation of beta amyloid protein, and have neuroprotective effects. In addition, the use of Gen can avoid the risk of endometrial cancer and breast cancer caused by estrogen therapy while exerting an estrogen-like effect, which has some potential for the delay and treatment of AD.

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.

Genistein and Galantamine Combinations Decrease β-Amyloid Peptide (1-42)-Induced Genotoxicity and Cell Death in SH-SY5Y Cell Line: an In Vitro and In Silico Approach for Mimic of Alzheimer's Disease

Alzheimer's disease (AD) is the primary dementia-causing disease worldwide, involving a multifactorial combination of environmental, genetic, and epigenetic factors, with essential participation of age and sex. Biochemically, AD is characterized by the presence of abnormal deposition of beta amyloid peptide (Aβ_(1-42)), which in the brain is strongly correlated with oxidative stress, inflammation, DNA damage, and cholinergic impairment. The multiple mechanisms involved in its etiology create significant difficulty in producing an effective treatment. Neuroprotective properties of genistein and galantamine have been widely demonstrated through different mechanisms; however, it is unknown a possible synergistic neuroprotective effect against Aβ_(1-42). In order to understand how genistein and galantamine combinations regulate the mechanisms of neuroprotection, we conducted a set of bioassays in vitro to evaluate cell viability, clonogenic survival, cell death, and anti-genotoxicity. Through molecular docking and therapeutic viability assays, we analyzed the inhibitory activity exerted by genistein on three major protein targets (AChE, BChE, and NMDA) involved in AD. The results showed that genistein and galantamine afforded significant protection at higher concentrations; however, combinations of sub-effective concentrations of both compounds provided marked neuroprotection when they were combined. In silico approaches showed that genistein has higher scores than the positive controls and low toxicity levels; nevertheless, the therapeutic viability indicated that unlike galantamine, genistein cannot undergo the action by P glycoprotein (PGP) and probably may be unable to cross the blood-brain barrier. In conclusion, our results show that genistein and galantamine exert neuroprotective by decreasing genotoxicity and cell death. In silico analysis, suggest that genistein modulates positively the expression of AChE, BChE, and NMDA. In this context, a combination of two or more drugs could inspire an attractive therapeutic strategy.

Special bioactive compounds and functional foods may exhibit neuroprotective effects in patients with dementia (Review)

Dementia is a failure of cognitive ability characterized by severe neurodegeneration in select neural systems, and Alzheimer's disease (AD) is the most common type of neurodegenerative disease. Although numerous studies have provided insights into the pathogenesis of AD, the underlying signaling and molecular pathways mediating the progressive decline of cognitive function remain poorly understood. Recent progress in molecular biology has provided an improved understanding of the importance of molecular pathogenesis of AD, and has proposed an association between DNA repair mechanisms and AD. In particular, the fundamental roles of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) and breast cancer gene 1 (BRCA1) tumor suppressors have been shown to regulate the pathogenesis of neurodegeneration. Consequently, onset of neurodegenerative diseases may be deferred with the use of dietary neuroprotective agents which alter the signaling mediated by the aforementioned tumor suppressors. In a healthy neuron, homeostasis of key intracellular molecules is of great importance, and preventing neuronal apoptosis is one of the primary goals of treatments designed for dementia-associated diseases. In the present review, progress into the understanding of dietary regulation for preventing or limiting development of dementia is discussed with a focus on the modulatory roles of PTEN and BRCA1 signaling.

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.

Equol Pretreatment Protection of SH-SY5Y Cells against Aβ (25-35)-Induced Cytotoxicity and Cell-Cycle Reentry via Sustaining Estrogen Receptor Alpha Expression

β-amyloid formation in the brain is one of the characteristics of Alzheimer’s disease. Exposure to this peptide may result in reentry into the cell cycle leading to cell death. The phytoestrogen equol has similar biological effects as estrogen without the side effects. This study investigated the possible mechanism of the neuron cell-protecting effect of equol during treatment with Aβ. SH-SY5Y neuroblastoma cells were treated with either 1 μM S-equol or 10 nM 17β-estradiol for 24 h prior to 1 μM Aβ (25–35) exposure. After 24 h exposure to Aβ (25–35), a significant reduction in cell survival and a reentry into the cell cycle process accompanied by increased levels of cyclin D1 were observed. The expressions of estrogen receptor alpha (ERα) and its coactivator, steroid receptor coactivator-1 (SRC-1), were also significantly downregulated by Aβ (25–35) in parallel with activated extracellular signal-regulated kinase (ERK)1/2. However, pretreatment of cells with S-equol or 17β-estradiol reversed these effects. Treatment with the ER antagonist, ICI-182,780 (1 μM), completely blocked the effects of S-equol and 17β-estradiol on cell viability, ERα, and ERK1/2 after Aβ (25–35) exposure. These data suggest that S-equol possesses a neuroprotective potential as it effectively antagonizes Aβ (25–35)-induced cell cytotoxicity and prevents cell cycle reentry in SH-SY5Y cells. The mechanism underlying S-equol neuroprotection might involve ERα-mediated pathways.

Small Molecule Natural Products and Alzheimer's Disease

Alzheimer's disease (AD) is a progressive and deadly neurodegenerative disease that is characterized by memory loss, cognitive impairment and dementia. Several hypotheses have been proposed for the pathogenesis based on the pathological changes in the brain of AD patients during the last few decades. Unfortunately, there is no effective agents/therapies to prevent or control AD at present. Currently, only a few drugs, which function as acetylcholinesterase (AChE) inhibitors or N-methyl-Daspartate (NMDA) receptor antagonists, are available to alleviate symptoms. Since many small molecule natural products have shown their functions as agonists or antagonists of receptors, as well as inhibitors of enzymes and proteins in the brain during the development of central nervous system (CNS) drugs, it is likely that natural products will play an important role in anti-AD drug development. We review recent papers on using small molecule natural products as drug candidates for the treatment of AD. These natural products possess antioxidant, anti-inflammatory, anticholinesterase, anti-amyloidogenic and neuroprotective activities. Moreover, bioactive natural products intended to be used for preventing AD, reducing the symptoms of AD and the new targets for treatment of AD are summarized.

Changes in Chemokines and Chemokine Receptors Expression in a Mouse Model of Alzheimer's Disease

The amyloid precursor protein plus presenilin-1 (APP/PS1) mice are a frequently-used model for Alzheimer's disease studies (AD). However, the data relevant to which proteins are involved in inflammatory mechanism are not sufficiently well-studied using the AD mouse model. Using behavioral studies, quantitative RT-PCR and Western-blot techniques, significant findings were determined by the expression of proteins involved in inflammation comparing APP/PS1 and Wild type mice. Increased GFAP expression could be associated with the elevation in number of reactive astrocytes. IL-3 is involved in inflammation and ABDF1 intervenes normally in the transport across cell membranes and both were found up-regulated in APP/PS1 mice compared to Wild type mice. Furthermore, CCR5 expression was decreased and both CCL3 and CCL4 chemokines were highly expressed indicating a possible gliosis and probably an increase in chemotaxis from lymphocytes and T cell generation. We also noted for the first time, a CCR8 increase expression with diminution of its CCL1 chemokine, both normally involved in protection from bacterial infection and demyelination. Control of inflammatory proteins will be the next step in understanding the progression of AD and also in determining the mechanisms that can develop in this disease.

Function of Glia in Aging and the Brain Diseases

Microglia cells during aging, neurodegeneration and neuroinflammation show different morphological and transcriptional profiles (related to axonal direction and cell adhesion). Furthermore, expressions of the receptors on the surface and actin formation compared to young are also different. This review delves into the role of glia during aging and the development of the diseases. The susceptibility of different regions of the brain to disease are linked to the overstimulation of signals related to the immune system during aging, as well as the damaging impact of these cascades on the functionality of different populations of microglia present in each region of the brain. Furthermore, a decrease in microglial phagocytosis has been related to many diseases and also has been detected during aging. In this paper we also describe the role of glia in different illness, such as AD, ALS, pain related disorders, cancer, developmental disorders and the problems produced by opening of the blood brain barrier. Future studies will clarify many points planted by this review.

Alzheimer's disease: Only prevention makes sense

Alzheimer's disease therapeutics is one of the most important endeavours in today's clinical investigation. Over more than 30 years of research, no disease-modifying treatment has been approved by either the FDA or the EMA to treat Alzheimer's disease. Recently, the evidence of pathological alterations in the brain tissue has been gathered showing that the signs of brain damage appear more than 20 years before the onset of Alzheimer's dementia. The major aim of this review is to underpin the idea that in Alzheimer's therapeutics, only prevention makes sense. It is difficult to visualise that would-be patients may be treated with endovenous administration of antibodies for several years to delay the onset of dementia. Rather, changes in lifestyle that should be specific, stratified and personalised are a likely alternative to delay the transition from asymptomatic Alzheimer's to minimal cognitive impairment and from there to dementia. These efforts are of the utmost importance. If we could delay the onset of full-blown dementia by 5 years, the number of demented patients would be almost halved. Thus, emphasis on preventive measures that can be implemented for decades must be supported. This approach, where even mild changes in cognition are of the greatest importance, cannot be underestimated in terms of both the individual and society's viewpoints.

Targeting ERK signaling pathway by polyphenols as novel therapeutic strategy for neurodegeneration

Numerous chemicals, such as phenolic compounds are strong radical scavengers, capable of alleviating oxidative stress induced neurodegeneration. Dietary antioxidants, especially flavonoids, are being considered as a promising approach to prevent or slow the pathological development of neurological illness and aging. One of the major advantage of natural products is that of their anti-amyloid effects over synthetic counterpart, however a healthy diet provides these beneficial natural substances as nutraceuticals. The extracellular-signal-regulated kinase (ERK) is one of the main pharmacological target of natural phenolic compounds, participating in several therapeutic effects. Mounting evidence revealed that numerous bioflavonoids, obtained from a variety of dietary fruits or plants as well as medicinal herbal sources, exhibit protective or therapeutic functions versus development of neurodegenerative diseases mainly through modulation of different compartments of ERK signaling pathway. Currently, there is remarkable interest in the beneficial effects of natural flavonoids to improve neural performance and prevent the onset and development of major neurodegenerative diseases. Natural products originated from medicinal plants, in particular antioxidants, have gained a great deal of attention due to their safe and non-toxic natures. Here, we summarized the effect of natural bioflavonoids on ERK signaling pathway and their molecular mechanism.

BACE1 Inhibition by Genistein: Biological Evaluation, Kinetic Analysis, and Molecular Docking Simulation

β-site amyloid precursor protein cleaving enzyme 1 (BACE1) plays a role in generating amyloid β (Aβ), thus playing a major part early in the pathogenesis of Alzheimer's disease (AD). BACE1 has emerged as a crucial therapeutic target for decreasing the Aβ concentration in the AD brain. To explore natural BACE1 inhibitors, the present study concentrated on isoflavones, including genistein, formononetin, glycitein, daidzein, and puerarin. In this study, in vitro anti-AD activities were assessed using BACE1 inhibition assays, as well as enzyme kinetic predictions. Molecular docking analysis was applied to design potential BACE1 inhibitors. Among the major isoflavones, genistein exerted a notable BACE1 inhibition through reversible noncompetitive mechanism, while other compounds were less potent against BACE1. The docking study revealed that genistein had negative binding energy (-8.5 kcal/mol) and was stably positioned in the allosteric domains of BACE1 residues. It interacted with important amino acid residues in BACE1, such as ASN37, GLN73, and TRP76, through hydrogen bonding. The results suggested that genistein may be beneficial for preventing and/or treating AD. Furthermore, it may provide potential guidelines for the design of new BACE1 inhibitors.

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.

PPAR Gamma Coactivator 1 Beta (PGC-1β) Reduces Mammalian Target of Rapamycin (mTOR) Expression via a SIRT1-Dependent Mechanism in Neurons

Mammalian target of rapamycin (mTOR) is a key regulator of metabolism, cell growth, and protein synthesis. Since decreased mTOR activity has been found to slow aging in many species, the aim of this study was to examine the activity of mTOR and its phosphorylated form in in vitro and in vivo models mimicking Alzheimer's disease (AD), and investigate the potential pathway of PGC-1β in regulating mTOR expression. Primary neurons and N2a cells were treated with Aβ25-35, while untreated cells served as controls. The expression of mTOR, p-mTOR (Ser2448), and PGC-1β was determined with Western blotting and RT-PCR assay, and the translocation of mTOR was detected using confocal microscopy. Aβ25-35 treatment stimulated the translocation of mTOR from cytoplasm to nucleus, and resulted in elevated expression of mTOR and p-mTOR (Ser2448) and reduced PGC-1β expression. In addition, overexpression of PGC-1β was found to decrease mTOR expression. The results of this study demonstrate that Aβ increases the expression of mTOR and p-mTOR at the site of Ser2448, and the stimulation of Aβ is likely to depend on sirtuin 1, PPARγ, and PGC-1β pathway in regulating mTOR expression.

Protection against β-amyloid-induced neurotoxicity by naturally occurring Z-ligustilide through the concurrent regulation of p38 and PI3-K/Akt pathways

Alzheimer's disease (AD) is primarily characterized by the progressive loss of functional neurons in the brain. Therefore, compounds with neuroprotective property may have therapeutic value in treating AD. Z-ligustilide (Z-LIG) is an essential oil originally isolated from umbelliferous plants. In the current study, the neuroprotective effects and underlying mechanisms of Z-LIG against fibrillar aggregates of Aβ_25-35 and Aβ_1-42-induced neurotoxicity were investigated in both SH-SY5Y cells and differentiated PC12 cells. Z-LIG at 1-30 μM provided an effective neuroprotection, as evidenced by the increase in cell viability, as well as the decrease in LDH release and intracellular accumulation of reactive oxygen species. Additionally, Z-LIG markedly blocked Aβ fibrils-induced condensed nuclei and sub-G1 accumulation suggestive of apoptosis. Furthermore, Z-LIG substantially reversed the activation of phosphorylated p38 and the inhibition of phosphorylated Akt caused by Aβ_25-35. LY294002, the specific inhibitor of PI3-K, significantly abrogated the protein expression of up-regulated phosphorylated Akt offered by Z-LIG. Most importantly, siRNA-mediated knockdown of PI3-K and p38 significantly abolished the neuroprotective effects of Z-LIG. The results taken together indicate that Z-LIG protects against Aβ fibrils-induced neurotoxicity possibly through the inhibition of p38 and activation of PI3-K/Akt signaling pathways concurrently. Z-LIG might be a potential candidate for further preclinical study aimed at the prevention and treatment of AD.

Neurodegenerative diseases: From available treatments to prospective herbal therapy

Neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease and many others represent a relevant health problem with age worldwide. Efforts have been made in recent years to discover the mechanism of neurodegenerative diseases and prospective therapy that can help to slow down the effects of the aging and prevent these diseases. Since pathogenesis of these diseases involves multiple factors therefore the important task for neuroscientists is to identify such multiple factors and prevent age-associated neurodegenerative diseases. For these neurodegenerative diseases yet we have only palliative therapies and none of them significantly capable to slow down or halt the underlying pathology. Polyphenolic compounds such as flavonoids present in vegetables and fruits are believed to have anti-aging properties and reduce the risk of neurodegenerative diseases. Despite their abundance, investigations into the benefits of these polyphenolic compounds in human health have only recently begun. Preclinical and clinical studies have demonstrated the potential beneficial effects of flavonoids in neurons. Although clinical trials on the effectiveness of dietary flavonoids to treat human diseases are limited but various animal models and cell culture studies have shown a great promise in developing these compounds as suitable therapeutic targets. In this review, we elaborate the neuroprotective properties of flavonoids especially their applications in prevention and intervention of different neurodegenerative diseases. Their multi-target properties may allow them to be potential dietary supplement in prevention and treatment of the age-associated neurodegenerative diseases.

Effects of Ranolazine on Astrocytes and Neurons in Primary Culture

Ranolazine (Rn) is an antianginal agent used for the treatment of chronic angina pectoris when angina is not adequately controlled by other drugs. Rn also acts in the central nervous system and it has been proposed for the treatment of pain and epileptic disorders. Under the hypothesis that ranolazine could act as a neuroprotective drug, we studied its effects on astrocytes and neurons in primary culture. We incubated rat astrocytes and neurons in primary cultures for 24 hours with Rn (10-7, 10-6 and 10-5 M). Cell viability and proliferation were measured using trypan blue exclusion assay, MTT conversion assay and LDH release assay. Apoptosis was determined by Caspase 3 activity assay. The effects of Rn on pro-inflammatory mediators IL-β and TNF-α was determined by ELISA technique, and protein expression levels of Smac/Diablo, PPAR-γ, Mn-SOD and Cu/Zn-SOD by western blot technique. In cultured astrocytes, Rn significantly increased cell viability and proliferation at any concentration tested, and decreased LDH leakage, Smac/Diablo expression and Caspase 3 activity indicating less cell death. Rn also increased anti-inflammatory PPAR-γ protein expression and reduced pro-inflammatory proteins IL-1 β and TNFα levels. Furthermore, antioxidant proteins Cu/Zn-SOD and Mn-SOD significantly increased after Rn addition in cultured astrocytes. Conversely, Rn did not exert any effect on cultured neurons. In conclusion, Rn could act as a neuroprotective drug in the central nervous system by promoting astrocyte viability, preventing necrosis and apoptosis, inhibiting inflammatory phenomena and inducing anti-inflammatory and antioxidant agents.

Protective Mechanisms of Flavonoids in Parkinson's Disease

Parkinson's disease is a chronic, debilitating neurodegenerative movement disorder characterized by progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta region in human midbrain. To date, oxidative stress is the well accepted concept in the etiology and progression of Parkinson's disease. Hence, the therapeutic agent is targeted against suppressing and alleviating the oxidative stress-induced cellular damage. Within the past decades, an explosion of research discoveries has reported on the protective mechanisms of flavonoids, which are plant-based polyphenols, in the treatment of neurodegenerative disease using both in vitro and in vivo models. In this paper, we have reviewed the literature on the neuroprotective mechanisms of flavonoids in protecting the dopaminergic neurons hence reducing the symptoms of this movement disorder. The mechanism reviewed includes effect of flavonoids in activation of endogenous antioxidant enzymes, suppressing the lipid peroxidation, inhibition of inflammatory mediators, flavonoids as a mitochondrial target therapy, and modulation of gene expression in neuronal cells.

WIN 55,212-2, agonist of cannabinoid receptors, prevents amyloid β1-42 effects on astrocytes in primary culture

Alzheimer´s disease (AD), a neurodegenerative illness involving synaptic dysfunction with extracellular accumulation of Aβ_1-42 toxic peptide, glial activation, inflammatory response and oxidative stress, can lead to neuronal death. Endogenous cannabinoid system is implicated in physiological and physiopathological events in central nervous system (CNS), and changes in this system are related to many human diseases, including AD. However, studies on the effects of cannabinoids on astrocytes functions are scarce. In primary cultured astrocytes we studied cellular viability using MTT assay. Inflammatory and oxidative stress mediators were determined by ELISA and Western-blot techniques both in the presence and absence of Aβ_1-42 peptide. Effects of WIN 55,212-2 (a synthetic cannabinoid) on cell viability, inflammatory mediators and oxidative stress were also determined. Aβ_1-42 diminished astrocytes viability, increased TNF-α and IL-1β levels and p-65, COX-2 and iNOS protein expression while decreased PPAR-γ and antioxidant enzyme Cu/Zn SOD. WIN 55,212-2 pretreatment prevents all effects elicited by Aβ_1-42. Furthermore, cannabinoid WIN 55,212-2 also increased cell viability and PPAR-γ expression in control astrocytes. In conclusion cannabinoid WIN 55,212-2 increases cell viability and anti-inflammatory response in cultured astrocytes. Moreover, WIN 55,212-2 increases expression of anti-oxidant Cu/Zn SOD and is able to prevent inflammation induced by Aβ_1-42 in cultured astrocytes. Further studies would be needed to assess the possible beneficial effects of cannabinoids in Alzheimer's disease patients.

Flavonoid-based therapies in the early management of neurodegenerative diseases

During the past several years, there has been enormous progress in the understanding of the causative factors that initiate neuronal damage in various neurodegenerative diseases, including Alzheimer disease, Parkinson disease, multiple sclerosis, amyotrophic lateral sclerosis, and Huntington disease. Preventing neuronal damage and neuronal death will have a huge clinical benefit. However, despite major advances in causative factors that trigger these neurodegenerative diseases, to date there have been no therapies available that benefit patients who suffer from these diseases. Because most neurodegenerative diseases are late-onset and remain asymptomatic for most of the phases, the therapies initiated in advanced stages of the disease have limited value to patients. It may be possible to prevent or halt the disease progression to a great extent if therapies start at the initial stage of the disease. Such therapies may restore neuronal function by reducing or even eliminating the primary stressor. Flavonoids are key compounds for the development of a new generation of therapeutic agents that are clinically effective in treating neurodegenerative diseases. Regular consumption of flavonoids has been associated with a reduced risk of neurodegenerative diseases. In addition to their antioxidant properties, these polyphenolic compounds exhibit neuroprotective properties by their interaction with cellular signaling pathways followed by transcription and translation that mediate cell function under both normal and pathologic conditions. This review focuses on human intervention studies as well as animal studies on the role of various flavonoids in the prevention of neurodegenerative diseases.

Astrocytes protect neurons from Aβ1-42 peptide-induced neurotoxicity increasing TFAM and PGC-1 and decreasing PPAR-γ and SIRT-1

One of the earliest neuropathological events in Alzheimer's disease is accumulation of astrocytes at sites of Aβ1-42 depositions. Our results indicate that Aβ1-42 toxic peptide increases lipid peroxidation, apoptosis and cell death in neurons but not in astrocytes in primary culture. Aβ1-42-induced deleterious neuronal effects are not present when neurons and astrocytes are mixed cultured. Stimulation of astrocytes with toxic Aβ1-42 peptide increased p-65 and decreased IκB resulting in inflammatory process. In astrocytes Aβ1-42 decreases protein expressions of sirtuin 1 (SIRT-1) and peroxisome proliferator-activated receptor γ (PPAR-γ) and over-expresses peroxisome proliferator-activated receptor γ coactivator 1 (PGC-1) and mitochondrial transcription factor A (TFAM), protecting mitochondria against Aβ1-42-induced damage and promoting mitochondrial biogenesis. In summary our data suggest that astrocytes may have a key role in protecting neurons, increasing neural viability and mitochondrial biogenesis, acquiring better oxidative stress protection and perhaps modulating inflammatory processes against Aβ1-42 toxic peptide. This might be a sign of a complex epigenetic process in Alzheimer's disease development.

The neuroprotective actions of oestradiol and oestrogen receptors

Hormones regulate homeostasis by communicating through the bloodstream to the body's organs, including the brain. As homeostatic regulators of brain function, some hormones exert neuroprotective actions. This is the case for the ovarian hormone 17β-oestradiol, which signals through oestrogen receptors (ERs) that are widely distributed in the male and female brain. Recent discoveries have shown that oestradiol is not only a reproductive hormone but also a brain-derived neuroprotective factor in males and females and that ERs coordinate multiple signalling mechanisms that protect the brain from neurodegenerative diseases, affective disorders and cognitive decline.

Melatonin and oestrogen treatments were able to improve neuroinflammation and apoptotic processes in dentate gyrus of old ovariectomized female rats

The aim of this study was to determine the outcomes of oestrogen and melatonin treatments following long-term ovarian hormone depletion on neuroinflammation and apoptotic processes in dentate gyrus of hippocampi. Forty-six female Wistar rats of 22 months of age were used. Twelve of them remained intact, and the other 34 were ovariectomized at 12 months of age. Ovariectomized animals were divided into three groups and treated for 10 weeks with oestrogens, melatonin or saline. All rats were killed by decapitation at 24 months of age, and dentate gyri were collected. A group of 2 month-old intact female rats was used as young control. The levels of pro-inflammatory cytokines and heat shock protein 70 (HSP 70) were analysed by ELISA. The expressions of TNFα, IL1β, GFAP, nNOS, iNOS, HO-1, NFκB, Bax, Bad, AIF, Bcl2 and SIRT1 genes were detected by real-time (RT)-PCR. Western blots were used to measure the protein expression of NFκB p65, NFκB p50/105, IκBα, IκBβ, p38 MAPK, MAP-2 and synapsin I. We have assessed the ability of 17β-oestradiol and melatonin administration to downregulate markers of neuroinflammation in the dentate gyrus of ovariectomized female rats. Results indicated that 17β-oestradiol and melatonin treatments were able to significantly decrease expression of pro-inflammatory cytokines, iNOS and HO-1 in the hippocampus when compared to non-treated animals. A similar age- and long-term ovarian hormone depletion- related increase in GFAP was also attenuated after both melatonin and oestradiol treatments. In a similar way to oestradiol, melatonin decreased the activation of p38 MAPK and NFκB pathways. The treatments enhanced the levels of synaptic molecules synapsin I and MAP-2 and have been shown to modulate the pro-antiapoptotic ratio favouring the second and to increase SIRT1 expression. These findings support the potential therapeutic role of melatonin and oestradiol as protective anti-inflammatory agents for the central nervous system during menopause.

Neuroprotective effects of diarylpropionitrile against β-amyloid peptide-induced neurotoxicity in rat cultured cortical neurons

Alzheimer's disease is a major cause of dementia in the elderly that involves a β-amyloid peptide (Aβ)-induced cascade of an increase in oxidative damage and inflammation. The present study demonstrated the neuroprotective effects of diarylpropionitrile (DPN), a non-steroidal estrogen receptor β selective ligand, against 10 μM Aβ1-42-induced oxidative stress and inflammation in primary rat cortical cell culture. Pre-treatment with 1-100 nM DPN significantly decreased neuronal cell death by increasing cell viability through a significant attenuation in the reactive oxygen species level, downregulation of pro-apoptotic activated caspase-3 and Bax, and upregulation of anti-apoptotic Bcl-2, thereby mitigating apoptotic morphological alterations. DPN pre-treatment decreased the expression levels of pro-inflammatory cytokines IL-1β and IL-6 through attenuation of Aβ1-42-induced phosphorylation of mitogen-activated protein kinases JNK and p38. In addition, DPN enhanced ERK1/2 and Akt phosphorylation depressed by Aβ1-42. These findings suggest that DPN protects neurons from Aβ1-42-induced neurotoxicity through a variety of mechanisms, ranging from anti-oxidation, anti-apoptosis, through to anti-inflammation.

Non-feminizing estrogens: a novel neuroprotective therapy

While the conflict between basic science evidence for estrogen neuroprotection and the lack of effectiveness in clinical trials is only now being resolved, it is clear that strategies for estrogen neuroprotection that avoid activation of ERs have the potential for clinical application. Herein we review the evidence from both in vitro and in vivo studies that describe high potency neuroprotection with non-feminizing estrogens. We have characterized many of the essential chemical features of non-feminizing estrogens that eliminate or reduce ER binding while maintaining or enhancing neuroprotection. Additionally, we provide evidence that these non-feminizing estrogens have efficacy in protecting the brain from AD neuropathology and traumatic brain injury. In conclusion, it appears that the non-feminizing estrogen strategy for neuroprotection is a viable option to achieve the beneficial neuroprotective effects of estrogens while eliminating the toxic off-target effects of chronic estrogen administration.

Sugammadex, a neuromuscular blockade reversal agent, causes neuronal apoptosis in primary cultures

Sugammadex, a γ-cyclodextrin that encapsulates selectively steroidal neuromuscular blocking agents, such as rocuronium or vecuronium, has changed the face of clinical neuromuscular pharmacology. Sugammadex allows a rapid reversal of muscle paralysis. Sugammadex appears to be safe and well tolerated. Its blood-brain barrier penetration is poor (< 3% in rats), and thus no relevant central nervous toxicity is expected. However the blood brain barrier permeability can be altered under different conditions (i.e. neurodegenerative diseases, trauma, ischemia, infections, or immature nervous system). Using MTT, confocal microscopy, caspase-3 activity, cholesterol quantification and Western-blot we determine toxicity of Sugammadex in neurons in primary culture. Here we show that clinically relevant sugammadex concentrations cause apoptotic/necrosis neuron death in primary cultures. Studies on the underlying mechanism revealed that sugammadex-induced activation of mitochondria-dependent apoptosis associates with depletion of neuronal cholesterol levels. Furthermore SUG increase CytC, AIF, Smac/Diablo and CASP-3 protein expression in cells in culture. Potential association of SUG-induced alteration in cholesterol homeostasis with oxidative stress and apoptosis activation occurs. Furthermore, resistance/sensitivity to oxidative stress differs between neuronal cell types.

Genistein inhibits Aβ₂₅₋₃₅ -induced neurotoxicity in PC12 cells via PKC signaling pathway

Protein kinase C (PKC) signaling pathway is recognized as an important molecular mechanism of Alzheimer's disease (AD) in the regulation of neuronal plasticity and survival. Genistein, the most active molecule of soy isoflavones, exerts neuroprotective roles in AD. However, the detailed mechanism has not been fully understood yet. The present study aimed to investigate whether the neuroprotective effects of genistein against amyloid β (Aβ)-induced toxicity in cultured rat pheochromocytoma (PC12) cells is involved in PKC signaling pathway. PC12 cells were pretreated with genistein for 2 h following incubation with Aβ(25-35) for additional 24 h. Cell viability was assessed by MTT. Hoechst33342/PI staining was applied to determine the apoptotic cells. PKC activity, intracellular calcium level and caspase-3 activity were analyzed by assay kits. The results showed that pretreatment with genistein significantly increased cell viability and PKC activity, decreased the levels of intracellular calcium, attenuated Hoechst/PI staining and blocked caspase-3 activity in Aβ(25-35)-treated PC12 cells. Pretreatment of Myr, a general PKC inhibitor, significantly attenuated the neuroprotective effect of genistein against Aβ(25-35)-treated PC12 cells. The present study indicates that PKC signaling pathway is involved in the neuroprotective action of genistein against Aβ(25-35)-induced toxicity in PC12 cells.

Anti-amyloidogenic effects of soybean isoflavones in vitro: Fluorescence spectroscopy demonstrating direct binding to Aβ monomers, oligomers and fibrils

Alzheimer's disease is characterized by the presence of extracellular deposits of amyloid, primarily composed of the amyloid β-protein (Aβ). A growing body of evidence indicates that oligomeric forms of Aβ play a critical role in disease causation. Soybean isoflavones are flavonoids with an isoflavone backbone. Isoflavones have been reported to protect against Aβ-induced neurotoxicity in cultured cell systems, the molecular mechanisms remain unclear. Our previous studies demonstrated that red wine-related flavonoids with a flavone backbone are able to inhibit Aβ assembly and destabilize preformed Aβ aggregates. Here, we show that isoflavones, especially glycitein and genistein, have anti-fibrillization, anti-oligomerization and fibril-destabilizing effects on Aβ(1-40) and Aβ(1-42)in vitro at physiological pH and temperature, by using nucleation-dependent polymerization monitored by thioflavin T fluorescence, atomic force microscopy, electron microscopy, and photo-induced cross-linking of unmodified proteins followed by SDS-PAGE. Our three-dimensional fluorescence spectroscopic analyses demonstrated that glycitein interacted with Aβ monomers, oligomers and fibrils, indicating specific binding of glycitein to these Aβ species. Glycitein also interacted with different Aβ fragments (Aβ(1-42), Aβ(1-40), Aβ(1-16) and Aβ(25-35)), exhibiting the highest fluorescence enhancement with Aβ(25-35). We speculated that glycitein's anti-amyloidogenic properties are specifically mediated by its binding to Aβ monomers, oligomers and fibrils. Isoflavones may hold promise as a treatment option for preventative strategies targeting amyloid formation in Alzheimer's disease.

Intermittent hypoxia conditioning protects mitochondrial cytochrome c oxidase of rat cerebellum from ethanol withdrawal stress

Intermittent hypoxia (IH) conditioning minimizes neurocognitive impairment and stabilizes brain mitochondrial integrity during ethanol withdrawal (EW) in rats, but the mitoprotective mechanism is unclear. We investigated whether IH conditioning protects a key mitochondrial enzyme, cytochrome c oxidase (COX), from EW stress by inhibiting mitochondrially directed apoptotic pathways involving cytochrome c, Bax, or phosphor-P38 (pP38). Male rats completed two cycles of a 4-wk ethanol diet (6.5%) and 3 wk of EW. An IH program consisting of 5-10 bouts of 5-8 min of mild hypoxia (9.5-10% inspired O(2)) and 4 min of reoxygenation for 20 consecutive days began 3 days before the first EW period. For some animals, vitamin E replaced IH conditioning to test the contributions of antioxidant mechanisms to IH's mitoprotection. During the second EW, cerebellar-related motor function was evaluated by measuring latency of fall from a rotating rod (Rotarod test). After the second EW, COX activity in cerebellar mitochondria was measured by spectrophotometry, and COX, cytochrome c, Bax, and pP38 content were analyzed by immunoblot. Mitochondrial protein oxidation was detected by measuring carbonyl contents and by immunochemistry. Earlier IH conditioning prevented motor impairment, COX inactivation, depletion of COX subunit 4, protein carbonylation, and P38 phosphorylation during EW. IH did not prevent cytochrome c depletion during EW, and Bax content was unaffected by EW ± IH. Vitamin E treatment recapitulated IH protection of COX, and P38 inhibition attenuated protein oxidation during EW. Thus IH protects COX and improves cerebellar function during EW by limiting P38-dependent oxidative damage.

Amyloid-β toxicity and tau hyperphosphorylation are linked via RCAN1 in Alzheimer's disease

Amyloid-β peptide (Aβ) toxicity and tau hyperphosphorylation are hallmarks of Alzheimer's disease (AD). How their molecular relationships may affect the etiology, progression, and severity of the disease, however, has not been elucidated. We now report that incubation of fetal rat cortical neurons with Aβ upregulates expression of the Regulator of Calcineurin gene RCAN1, and this is mediated by Aβ-induced oxidative stress. Calcineurin (PPP3CA) is a serine-threonine phosphatase that dephosphorylates tau. RCAN1 proteins inhibit this phosphatase activity of calcineurin. Increased expression of RCAN1 also causes upregulation of glycogen synthase kinase-3β (GSK3β), a tau kinase. Thus, increased RCAN1 expression might be expected to decrease phospho-tau dephosphorylation (via calcineurin inhibition) and increase tau phosphorylation (via increased GSK3β activity). Indeed, we find that incubation of primary cortical neurons with Aβ results in increased phosphorylation of tau, unless RCAN1 gene expression is silenced, or antioxidants are added. Thus we propose a mechanism to link Aβ toxicity and tau hyperphosphorylation in AD: In our hypothesis, Aβ causes mitochondrial oxidative stress and increases production of reactive oxygen species, which result in an upregulation of RCAN1 gene expression. RCAN1 proteins then both inhibit calcineurin and induce expression of GSK3β. Both mechanisms shift tau to a hyperphosphorylated state. We also find that lymphocytes from persons whose ApoE genotype is ε4/ε4 (with high risk of developing AD) show higher levels of RCAN1 and phospho-tau than those carrying the ApoE ε3/ε3 or ε3/ε4 genotypes. Thus upregulation of RCAN1 may be a valuable biomarker for AD risk.

IGF-I receptor signaling pathway is involved in the neuroprotective effect of genistein in the neuroblastoma SK-N-SH cells

Genistein, an isoflavone naturally found in soy products, displays estrogenic properties. Our previous study clearly demonstrated that genistein can activate the insulin-like growth factor-I receptor (IGF-IR) signaling pathway in human breast cancer MCF-7 cells. The present study aims to test the hypothesis that the IGF-I receptor signaling pathway is involved in the neuroprotective effects of genistein in neuroblastoma SK-N-SH cells. Our results revealed that pretreatment with genistein resulted in an enhancement in the survival of human neuroblastoma SK-N-SH cells against 6-hydroxydopamine (6-OHDA)-induced neurotoxicity. 6-OHDA arrested the cells at G(0)G(1) phase and prevented S phase entry. Genistein pretreatment could reverse the cytostatic effect of 6-OHDA on cell cycle. The decreased mitochondrial membrane potential induced by 6-OHDA could be also reversed by genistein pretreatment. These effects could be completely blocked by co-treatment with JB-1, which is the specific antagonist of the IGF-I receptor. Furthermore, genistein pretreatment restored the 6-OHDA-induced up-regulation of Bax and down-regulation of Bcl-2 mRNA and protein expression. Genistein treatment alone could significantly increase the phosphorylation level of MEK and induce ERE luciferase activity. Co-treatment with IGF-I could enhance the effect of genistein on cell proliferation and MEK phosphorylation. This study provides the first evidence that genistein has neuroprotective effects against 6-OHDA-induced neurotoxicity in SK-N-SH cells and activation of the IGF-I receptor signaling pathway might be involved in actions of genistein.

Protective Action of Neurotrophic Factors and Estrogen against Oxidative Stress-Mediated Neurodegeneration

Oxidative stress is involved in the pathogenesis of neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, and Huntington's disease. Low levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) are important for maintenance of neuronal function, though elevated levels lead to neuronal cell death. A complex series of events including excitotoxicity, Ca(2+) overload, and mitochondrial dysfunction contributes to oxidative stress-mediated neurodegeneration. As expected, many antioxidants like phytochemicals and vitamins are known to reduce oxidative toxicity. Additionally, growing evidence indicates that neurotrophic factors such as brain-derived neurotrophic factor (BDNF) and estrogens significantly prevent neuronal damage caused by oxidative stress. Here, we review and discuss recent studies addressing the protective mechanisms of neurotrophic factors and estrogen within this system.

Resveratrol interacts with estrogen receptor-β to inhibit cell replicative growth and enhance stress resistance by upregulating mitochondrial superoxide dismutase

trans-Resveratrol (RES) is one of a number of dietary polyphenols that have been reported to beneficially affect human physiology. Although numerous studies have attributed this to direct interactions between RES and histone deacetylases, recently the reliability of these results has been questioned. We have shown that the mitochondrial superoxide dismutase (MnSOD) is substantially upregulated in RES-treated cells. Here we explore the mechanisms underlying this, showing that two of RES's more interesting effects, inhibition of replication and enhancement of stress resistance, are mediated by MnSOD upregulation in three cell lines: MRC5 human lung fibroblasts, C2C12 mouse myoblasts, and SHSY5Y human neuroblastoma cells. When small interfering RNA was used to prevent induction of MnSOD expression, the effects of RES on population doubling time of cells in culture, and resistance to cell death after exposure to hydrogen peroxide or paraquat, were abolished. Interestingly, the RES-induced upregulation of MnSOD levels could be prevented by the estrogen receptor antagonist ICI 182780. RES's effects also could be reproduced using estradiol or the estrogen receptor-β agonist diarylpropionitrile, but not using the estrogen receptor-α agonist propylpyrazole triol. Thus, we suggest that RES interacts with estrogen receptor-β to induce the upregulation of MnSOD, which affects cell cycle progression and stress resistance. These results have important implications for our understanding of RES's biological activities and potential applications to human health.