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.

Pyrus pashia fruit extract and its major phytometabolite chrysin prevent hippocampal apoptosis and memory impairment in PTZ-kindled mice.

OBJECTIVES: Epilepsy is a chronic neurological condition with recurrent seizures. One-third of epilepsy patients experience unacceptable side effects from antiepileptic drugs. Pyrus pashia is a deciduous tree from southern Asia. Ethnomedicinally, Malakand tribes use its fruits for epilepsy treatment. Our prior research demonstrated the anticonvulsive properties of ethanolic extract of Pyrus pashia (EPP) and its bioactive compound chrysin in acute seizure tests. This study aims to investigate the impact of EPP and chrysin on cognitive impairment in a PTZ-induced kindling mice model of epilepsy. METHODS: Swiss albino male mice were equally divided into four groups. The first group received 0.5% carboxy methyl cellulose dissolved in normal saline while the other three groups were pre-treated with Diazepam (DZP) (1 mg/kg, i.p.), EPP (200 mg/kg, p.o.) and chrysin (5 mg/kg, p.o.). After 30 min, all groups were administered PTZ (35 mg/kg, i.p.) and evaluated for seizure severity, cognitive function, and neuronal apoptosis. Western blot analysis was conducted to analyze the expressions of apoptosis biomarkers and memory-related genes, including cAMP response element-binding protein (CREB) and Brain Derived Neurotrophic Factor (BDNF). RESULTS: The therapeutic effects of EPP and Chrysin were comparable to DZP in terms of reducing seizure severity, but unlike DZP, they prevented PTZ-induced memory impairment in experimental animals. Additionally, they increased the levels of BDNF and CREB while reducing apoptotic biomarkers in the hippocampus of experimental animals. CONCLUSIONS: Based on the leads offered by this study EPP and its major bioactive constituent, could be developed as the treatment option for epilepsy.

Hippocampal chromatin-modifying enzymes are pivotal for scopolamine-induced synaptic plasticity gene expression changes and memory impairment.

The amnesic potential of scopolamine is well manifested through synaptic plasticity gene expression changes and behavioral paradigms of memory impairment. However, the underlying mechanism remains obscure and consequently ideal therapeutic target is lacking. In this context, chromatin-modifying enzymes, which regulate memory gene expression changes, deserve major attention. Therefore, we analyzed the expression of chromatin-modifying enzymes and recovery potential of enzyme modulators in scopolamine-induced amnesia. Scopolamine administration drastically up-regulated DNA methyltransferases (DNMT1) and HDAC2 expression while CREB-binding protein (CBP), DNMT3a and DNMT3b remained unaffected. HDAC inhibitor sodium butyrate and DNMT inhibitor Aza-2'deoxycytidine recovered scopolamine-impaired hippocampal-dependent memory consolidation with concomitant increase in the expression of synaptic plasticity genes Brain-derived neurotrophic factor (BDNF) and Arc and level of histone H3K9 and H3K14 acetylation and decrease in DNA methylation level. Sodium butyrate showed more pronounced effect than Aza-2'deoxycytidine and their co-administration did not exhibit synergistic effect on gene expression. Taken together, we showed for the first time that scopolamine-induced up-regulation of chromatin-modifying enzymes, HDAC2 and DNMT1, leads to gene expression changes and consequent decline in memory consolidation. Our findings on the action of scopolamine as an epigenetic modulator can pave a path for ideal therapeutic targets. We propose the following putative pathway for scopolamine-mediated memory impairment; scopolamine up-regulates hippocampal DNMT1 and HDAC2 expression, induces methylation and deacetylation of BDNF and Arc promoter, represses gene expression and eventually impairs memory consolidation. On the other hand, Aza-2 and NaB inhibit DNMT1 and HDAC2 respectively, up-regulate BDNF and Arc expression and recover memory consolidation. We elucidate the action of scopolamine as an epigenetic modulator and hope that DNMT1 and HDAC2 would be ideal therapeutic targets for memory disorders.

Reduced recognition memory is correlated with decrease in DNA methyltransferase1 and increase in histone deacetylase2 protein expression in old male mice.

Chromatin modifying enzymes DNA methyltransferases (DNMTs), histone deacetylase (HDAC) 2 and CREB binding protein (CBP) play a crucial role in memory, particularly during consolidation process which declines with advancing age. However, the expression of these enzymes and their effect on memory consolidation during aging are not clearly understood. In the present study, novel object recognition test was used to assess the memory consolidation followed by expression analysis of DNMTs, HDAC2 and CBP in the cerebral cortex and hippocampus of young, adult and old male mice. Object recognition memory was reduced in old as compared to young and adult. DNMT1 protein expression was high in the cerebral cortex and hippocampus of young male mice, but declined gradually with age. On the other hand, HDAC2 mRNA and protein expression increased in the hippocampus of old male mice as compared to young and adult. Alteration in the expression of these enzymes is correlated with reduced recognition memory in old.

Therapeutic effects of mirodenafil, a phosphodiesterase 5 inhibitor, on stroke models in rats.

Mirodenafil is a phosphodiesterase 5 (PDE5) inhibitor with high specificity for its target and good blood-brain barrier permeability. The drug, which is currently used for treatment of erectile dysfunction, reduces Aß and pTau levels and improves cognitive function in mouse models of Alzheimer's disease. In the present study, we investigated the effect of mirodenafil in the transient and permanent middle cerebral artery occlusion (tMCAO and pMCAO) models of stroke in rats. Starting 24 â€‹h after cerebral artery occlusion, mirodenafil was administered subcutaneously at doses of 0.5, 1, and 2 â€‹mg/kg per day for 9 days in the tMCAO model and for 28 days in the pMCAO model. Mirodenafil significantly increased sensorimotor and cognitive recovery of tMCAO and pMCAO rats compared to saline control rats, and significantly decreased the amount of degenerative cells and cleaved caspase-3 and cleaved PARP immunoreactive cells. Effects were seen in a dose-dependent manner up to 1 â€‹mg/kg mirodenafil. The benefits of mirodenafil treatment increased with longer treatment duration, and the largest improvements over control were typically observed on the last assessment day. There was no effect of mirodenafil on infarct volume in both tMCAO and pMCAO rats. In an experiment to determine the treatment window for mirodenafil effects, a protective effect was observed when treatment was delayed 72 â€‹h after MCAO, although the most improvement was observed with shorter treatment windows. Using pMCAO and tMCAO rat models of stroke, we determined that mirodenafil improves the recovery of sensorimotor and cognitive functions after MCAO and protects cortical cells from apoptosis and degeneration. Greater benefit was observed with longer duration of treatment, and improvement was seen even when treatment was delayed.

Neuromodulating roles of estrogen and phytoestrogens in cognitive therapeutics through epigenetic modifications during aging.

Estrogen (E2) plays important role in regulating hippocampal learning and memory. The decline of E2 after menopause affects learning and memory and increases the risk of neurodegenerative diseases like Alzheimer's disease (AD). Additionally, from the estrogen receptor (ER) mediated gene regulation; E2 also regulates gene expression at the transcriptional and posttranscriptional levels through epigenetic modifications. E2 recruits a number of proteins called co-regulators at the promoter region of genes. These co-regulators act as chromatin modifiers, alter DNA and histone modifications and regulate gene expression. Several studies show that E2 regulates learning and memory by altering chromatin at the promoters of memory-linked genes. Due to structural similarities with E2 and low side effects, phytoestrogens are now used as neuroprotective agents to recover learning and memory in animal models as well as human subjects during aging and different neurological disorders. Growing evidence suggests that apart from anti-oxidative and anti-inflammatory properties, phytoestrogens also act as epigenetic modifiers and regulate gene expression through epigenetic modifications. The epigenetic modifying properties of phytoestrogens are mostly studied in cancer cells but very little is known regarding the regulation of synaptic plasticity genes, learning and memory, and neurological disorders. In this article, we discuss the epigenetic modifying properties of E2 and the roles of phytoestrogens as epigenetic modifiers in the brain to recover and maintain cognitive functions.

Oxidative stress-mediated memory impairment during aging and its therapeutic intervention by natural bioactive compounds.

Aging and associated neurodegenerative diseases are accompanied by the decline of several brain functions including cognitive abilities. Progressive deleterious changes at biochemical and physiological levels lead to the generation of oxidative stress, accumulation of protein aggregates, mitochondrial dysfunctions, loss of synaptic connections, and ultimately neurodegeneration and cognitive decline during aging. Oxidative stress that arises due to an imbalance between the rates of production and elimination of free radicles is the key factor for age-associated neurodegeneration and cognitive decline. Due to high energy demand, the brain is more susceptible to free radicals-mediated damages as they oxidize lipids, proteins, and nucleic acids, thereby causing an imbalance in the homeostasis of the aging brain. Animal, as well as human subject studies, showed that with almost no or few side effects, dietary interventions and plant-derived bioactive compounds could be beneficial to recovering the memory or delaying the onset of memory impairment. As the plant-derived bioactive compounds have antioxidative properties, several of them were used to recover the oxidative stress-mediated changes in the aging brain. In the present article, we review different aspects of oxidative stress-mediated cognitive change during aging and its therapeutic intervention by natural bioactive compounds.

Role of nutraceuticals in cognition during aging and related disorders.

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

Histone Deacetylase 2 Inhibition Attenuates Downregulation of Hippocampal Plasticity Gene Expression during Aging.

The brain undergoes several anatomical, biochemical, and molecular changes during aging, which subsequently result in downregulation of synaptic plasticity genes and decline of memory. However, the regulation of these genes during aging is not clearly understood. Previously, we reported that the expression of histone deacetylase (HDAC)2 was upregulated in the hippocampus of old mice and negatively correlated with the decline in recognition memory. As HDAC2 regulates key synaptic plasticity neuronal immediate early genes (IEGs), we have examined their expression and epigenetic regulation. We noted that the expression of neuronal IEGs decreased both at mRNA and protein level in the hippocampus of old mice. To explore the underlying regulation, we analyzed the binding of HDAC2 and level of histone acetylation at the promoter of neuronal IEGs. While the binding of HDAC2 was higher, H3K9 and H3K14 acetylation level was lower at the promoter of these genes in old as compared to young and adult mice. Further, we inhibited HDAC2 non-specifically by sodium butyrate and specifically by antisense oligonucleotide to recover epigenetic modification, expression of neuronal IEGs, and memory in old mice. Inhibition of HDAC2 increased histone H3K9 and H3K14 acetylation level at the promoter of neuronal IEGs, their expression, and recognition memory in old mice as compared to control. Thus, inhibition of HDAC2 can be used as a therapeutic target to recover decline in memory due to aging and associated neurological disorders.

Epigenetic Regulation of Memory-Therapeutic Potential for Disorders.

BACKGROUND: Memory is a vital function which declines in different physiological and pathological conditions such as aging and neurodegenerative diseases. Research in the past has reported that memory formation and consolidation require the precise expression of synaptic plasticity genes. However, little is known about the regulation of these genes. Epigenetic modification is now a well established mechanism that regulates synaptic plasticity genes and neuronal functions including memory. Therefore, we have reviewed the epigenetic regulation of memory and its therapeutic potential for memory dysfunction during aging and neurological disorders. METHOD: Research reports and online contents relevant to epigenetic regulation of memory during physiological and pathological conditions have been compiled and discussed. RESULTS: Epigenetic modifications include mainly DNA methylation and hydroxymethylation, histone acetylation and methylation which involve chromatin modifying enzymes. These epigenetic marks change during memory formation and impairment due to dementia, aging and neurodegeneration. As the epigenetic modifications are reversible, they can be modulated by enzyme inhibitors leading to the recovery of memory. CONCLUSION: Epigenetic modifications could be exploited as a potential therapeutic target to recover memory disorders during aging and pathological conditions.

Age-associated Cognitive Decline: Insights into Molecular Switches and Recovery Avenues.

Age-associated cognitive decline is an inevitable phenomenon that predisposes individuals for neurological and psychiatric disorders eventually affecting the quality of life. Scientists have endeavored to identify the key molecular switches that drive cognitive decline with advancing age. These newly identified molecules are then targeted as recovery of cognitive aging and related disorders. Cognitive decline during aging is multi-factorial and amongst several factors influencing this trajectory, gene expression changes are pivotal. Identifying these genes would elucidate the neurobiological underpinnings as well as offer clues that make certain individuals resilient to withstand the inevitable age-related deteriorations. Our laboratory has focused on this aspect and investigated a wide spectrum of genes involved in crucial brain functions that attribute to senescence induced cognitive deficits. We have recently identified master switches in the epigenome regulating gene expression alteration during brain aging. Interestingly, these factors when manipulated by chemical or genetic strategies successfully reverse the age-related cognitive impairments. In the present article, we review findings from our laboratory and others combined with supporting literary evidences on molecular switches of brain aging and their potential as recovery targets.

Social isolation mediated anxiety like behavior is associated with enhanced expression and regulation of BDNF in the female mouse brain.

Adverse early life experience is prominent risk factors for numerous psychiatric illnesses, including mood and anxiety disorders. It imposes serious long-term costs on the individual as well as health and social systems. Hence, developing therapies that prevent the long-term consequences of early life stress is of utmost importance, and necessitates a better understanding of the mechanisms by which early life stress triggers long-lasting alterations in gene expression and behavior. Post-weaning isolation rearing of rodents models the behavioral consequences of adverse early life experiences in humans and it is reported to cause anxiety like behavior which is more common in case of females. Therefore, in the present study, we have studied the impact of social isolation of young female mice for 8weeks on the anxiety like behavior and the underlying molecular mechanism. Elevated plus maze and open field test revealed that social isolation caused anxiety like behavior. BDNF, a well-known molecule implicated in the anxiety like behavior, was up-regulated both at the message and protein level in cerebral cortex by social isolation. CREB-1 and CBP, which play a crucial role in BDNF transcription, were up-regulated at mRNA level in cerebral cortex by social isolation. HDAC-2, which negatively regulates BDNF expression, was down-regulated at mRNA and protein level in cerebral cortex by social isolation. Furthermore, BDNF acts in concert with Limk-1, miRNA-132 and miRNA-134 for the regulation of structural and morphological plasticity. Social isolation resulted in up-regulation of Limk-1 mRNA and miRNA-132 expression in the cerebral cortex. MiRNA-134, which inhibits the translation of Limk-1, was decreased in cerebral cortex by social isolation. Taken together, our study suggests that social isolation mediated anxiety like behavior is associated with up-regulation of BDNF expression and concomitant increase in the expression of CBP, CREB-1, Limk-1 and miRNA-132, and decrease in the expression of HDAC-2 and miRNA-134 in the cerebral cortex.