Memory impairment induced by brain iron overload is accompanied by reduced H3K9 acetylation and ameliorated by sodium butyrate

Transferrin Immobilized Graphene Oxide Nanocomposite for Targeted Cancer Chemodynamic Therapy via Increasing Intracellular Labile Fe2+ Concentration

Recently, different alternative regulated cell death (RCD) pathways, viz., necroptosis, pyroptosis, ferroptosis, cuproptosis etc., have been explored as important targets for the development of cancer medications in recent years, as these can change the immunogenicity of the tumor microenvironment (TME) and will finally lead to the inhibition of cancer progression and metastasis. Here, we report the development of transferrin immobilized graphene oxide (Tfn@GOAPTES) nanocomposite as a therapeutic strategy toward cancer cell killing. The electrostatic immobilization of Tfn on the GOAPTES surface was confirmed by different spectroscopy and microscopy techniques. The Tfn immobilization was found to be ∼74 ± 4%, whereas the stability of the protein on the GO surface suggested a robust nature of the nanocomposite. The MTT assay suggested that Tfn@GOAPTES exhibited cytotoxicity toward HeLa cells via increased lipid peroxidation and DNA damage. Western blot studies resulted in decreased expression of acetylation on lysine 40 of α-tubulin and increased expression of LC3a/b for Tfn@GOAPTES treated HeLa cells, suggesting autophagy to be the main cause of the cell death mechanism. Overall, we predict that the present approach can be used as a therapeutic strategy for cancer cell killing via selective induction of a high concentration of intracellular iron.

Heavy metals toxicity on epigenetic modifications in the pathogenesis of Alzheimer's disease (AD)

Alzheimer's disease (AD) is a progressive decline in cognitive ability and behavior which eventually disrupts daily activities. AD has no cure and the progression rate varies unlikely. Among various causative factors, heavy metals are reported to be a significant hazard in AD pathogenesis. Metal-induced neurodegeneration has been focused globally with thorough research to unravel the mechanistic insights in AD. Recently, heavy metals suggested to play an important role in epigenetic alterations which might provide evidential results on AD pathology. Epigenetic modifications are known to play towards novel therapeutic approaches in treating AD. Though many studies focus on epigenetics and heavy metal implications in AD, there is a lack of research on heavy metal influence on epigenetic toxicity in neurological disorders. The current review aims to elucidate the plausible role of cadmium (Cd), iron (Fe), arsenic (As), copper (Cu), and lithium (Li) metals on epigenetic factors and the increase in amyloid beta and tau phosphorylation in AD. Also, the review discusses the common methods of heavy metal detection to implicate in AD pathogenesis. Hence, from this review, we can extend the need for future research on identifying the mechanistic behavior of heavy metals on epigenetic toxicity and to develop diagnostic and therapeutic markers in AD.

Brain Iron Homeostasis and Mental Disorders

Iron plays an essential role in various physiological processes. A disruption in iron homeostasis can lead to severe consequences, including impaired neurodevelopment, neurodegenerative disorders, stroke, and cancer. Interestingly, the link between mental health disorders and iron homeostasis has not received significant attention. Therefore, our understanding of iron metabolism in the context of psychological diseases is incomplete. In this review, we aim to discuss the pathologies and potential mechanisms that relate to iron homeostasis in associated mental disorders. We propose the hypothesis that maintaining brain iron homeostasis can support neuronal physiological functions by impacting key enzymatic activities during neurotransmission, redox balance, and myelination. In conclusion, our review highlights the importance of investigating the relationship between trace element nutrition and the pathological process of mental disorders, focusing on iron. This nutritional perspective can offer valuable insights for the clinical treatment of mental disorders.

Potential Role of Oxidative Stress in the Effects of Chronic Administration of Iron on Affective and Cognitive Behavior on Male Wistar Rat

In this work, we studied the impact of chronic iron exposure, in the form of iron sulfate (FeSo4), on affective and cognitive disorders and oxidative stress in the male Wistar rat. The treatment was carried out for 8 weeks, the rats received an intraperitoneal injection of iron at different doses: 0.25, 0.5, and 1 mg/kg. Affective and cognitive disorders are assessed in open field test (OFT), elevated plus maze (EPM), forced swimming test (FST), Morris water maze (MWM), and Y-maze. The hippocampus and prefrontal cortex of each animal were taken for biochemical examination. Our results show that iron exerts anxiogenic and depressogenic effects, which were observed first at the dose of 0.5 mg/kg and continued in a dose-dependent manner up to the maximum tested dose of 1 mg/kg. According to results from the MWM and Y-maze tests, continuous exposure to iron induces cognitive disorders that are defined by the disturbance of working memory and influences spatial learning performance causing a deficit of spatial memory retention. We noted that chronic exposure to iron can be associated with the appearance of a state of oxidative stress in the hippocampus and the prefrontal cortex demonstrated by an increase in lipid peroxidation, an increase in nitric oxide, and also by disturbances in the antioxidant defense systems following a determination of the concentrations of catalase. In conclusion, we can deduce from this work that chronic iron exposure can be related to the induction of cognitive and affective disorders and oxidative stress.

Beneficial effects of butyrate on brain functions: A view of epigenetic

Brain functions are influenced by the presence, activity, and metabolism of the gut microbiota through the gut-microbiota-brain (GMB) axis. The consumption of a fiber-rich diet increases the content of short-chain fatty acids (SCFAs) from bacterial fermentation in the colon. Among SCFAs, butyrate stands out because of its wide array of biological functions, such as ability to influence brain functions. Pharmacologically, sodium butyrate (NaB) regulates gene expression in the brain, where it has several beneficial effects ranging from neurodegenerative diseases to behavioral disorders through inhibitors of histone deacetylases (HDACis). In this context, we review the mechanisms of action of the two types of butyrate on brain functions, with an emphasis on the epigenetic approach. Both types of butyrate are potentially interesting for the prevention and adjuvant therapy of neurological and psychological disorders due to their neuroprotective functions. However, further studies are needed to investigate the possible neuroepigenetic effects of butyrate derived from bacterial fermentation.

Role of heavy metals (copper (Cu), arsenic (As), cadmium (Cd), iron (Fe) and lithium (Li)) induced neurotoxicity

Parkinson's disease (PD) is a neurodegenerative condition characterized by the dopamine (DA) neuronal loss in the substantia nigra. PD impairs motor controls symptoms such as tremor, rigidity, bradykinesia and postural imbalance gradually along with non-motor problems such as olfactory dysfunction, constipation, sleeping disorder. Though surplus of factors and mechanisms have been recognized, the precise PD etiopathogenesis is not yet implied. Reports suggest that various environmental factors play a crucial role in the causality of the PD cases. Epidemiological studies have reported that heavy metals has a role in causing defects in substantia nigra region of brain in PD. Though the reason is unknown, exposure to heavy metals is reported to be an underlying factor in PD development. Metals are classified as either essential or non-essential, and they have a role in physiological processes such protein modification, electron transport, oxygen transport, redox reactions, and cell adhesion. Excessive metal levels cause oxidative stress, protein misfolding, mitochondrial malfunction, autophagy dysregulation, and apoptosis, among other things. In this review, we check out the link between heavy metals like copper (Cu), arsenic (As), cadmium (Cd), iron (Fe), and lithium (Li) in neurodegeneration, and how it impacts the pathological conditions of PD. In conclusion, increase or decrease in heavy metals involve in regulation of neuronal functions that have an impact on neurodegeneration process. Through this review, we suggest that more research is needed in this stream to bring more novel approaches for either disease modelling or therapeutics.

Cannabidiol reverses memory impairments and activates components of the Akt/GSK3β pathway in an experimental model of estrogen depletion

Clinical and preclinical evidence has indicated that estrogen depletion leads to memory impairments and increases the susceptibility to neural damage. Here, we have sought to investigate the effects of Cannabidiol (CBD) a non-psychotomimetic compound from Cannabis sativa, on memory deficits induced by estrogen depletion in rats, and its underlying mechanisms. Adult rats were subjected to bilateral ovariectomy, an established estrogen depletion model in rodents, or sham surgery and allowed to recover for three weeks. After that, they received daily injections of CBD (10 mg/kg) for fourteen days. Rats were tested in the inhibitory avoidance task, a type of emotionally-motivated memory. After behavioral testing they were euthanized, and their hippocampi were isolated for analysis of components of the Akt/GSK3β survival pathway and the antiapoptotic protein Bcl2. Results revealed that ovariectomy impaired avoidance memory, and CBD was able to completely reverse estrogen depletion-induced memory impairment. Ovariectomy also reduced Akt/GSK3β pathway's activation by decreasing the phosphorylation levels of Akt and GSK3β and Bcl2 levels, which were ameliorated by CBD. The present results indicate that CBD leads to a functional recovery accompanied by the Akt/GSK3β survival pathway's activation, supporting its potential as a treatment for estrogen decline-induced deterioration of neural functioning and maintenance.

Bisphenol-A exposure leads to neurotoxicity through upregulating the expression of histone deacetylase 2 in vivo and in vitro

Bisphenol-A (BPA), an environmental endocrine disruptor, is toxic to the central nervous system. Although recent studies have shown BPA-induced neurotoxicity, it is far from clear what precisely epigenetic mechanisms are involved in BPA-induced cognitive deficits. In this study, pheochromocytoma (PC12) cells were treated with BPA at 1 μM for 36 h in vitro. In vivo, C57BL/6 mice were administered to BPA at a dose of 1 mg/kg/day for 10 weeks. The results showed that 1 μM BPA exposure for 36 h impaired neurite outgrowth of PC12 cells through decreasing the primary and secondary branches. Besides, BPA exposure decreased the level of Ac-H3K9 (histone H3 Lys9 acetylation) by upregulating the expression of HDAC2 (histone deacetylases 2) in PC12 cells. Furthermore, treatment of both TSA (Trichostatin A, inhibitor of the histone deacetylase) and shHDAC2 plasmid (HDAC2 knockdown construct) resulted in amelioration neurite outgrowth deficits induced by BPA. In addition, it was shown that repression of HDAC2 could markedly rescue the spine density impairment in the hippocampus and prevent the cognitive impairment caused by BPA exposure in mice. Collectively, HDAC2 plays an essential role in BPA-induced neurotoxicity, which provides a potential molecular target for medical intervention.

The G protein-coupled estrogen receptor (GPER) regulates recognition and aversively-motivated memory in male rats

Estrogens, particularly 17β-estradiol (estradiol, E₂), regulate memory formation. E2 acts through its intracellular receptors, estrogen receptors (ER) ERα and ERβ, as well as a recently identified G protein-coupled estrogen receptor (GPER). Although the effects of E2 on memory have been investigated, studies examining the effects of GPER stimulation are scarce. Selective GPER agonism improves memory in ovariectomized female rats, but little information is available regarding the effects of GPER stimulation in male rodents. The aim of the present study was to investigate the effects of the GPER agonist, G1, on consolidation and reconsolidation of inhibitory avoidance (IA) and object recognition (OR) memory in male rats. Animals received vehicle, G1 (15, 75, 150 µg/kg; i.p.), or the GPER antagonist G15 (100 µg/kg; i.p.) immediately after training, or G1 (150 µg/kg; i.p.) 3 or 6 h after training. To investigate reconsolidation, G1 was administered immediately after IA retention Test 1. Results indicated that G1 administered immediately after training at the highest dose enhanced both OR and IA memory consolidation, while GPER blockade immediately after training impaired OR. No effects of GPER stimulation were observed when G1 was given 3 or 6 h after training or after Test 1. The present findings provide evidence that GPER is involved in the early stages of memory consolidation in both neutral and emotional memory tasks in male adult rats.

Chronic restraint stress impairs cognition via modulating HDAC2 expression

Background

To investigate the effects of chronic restraint stress on cognition and the probable molecular mechanism in mice.

Methods

In the current work, a restraining tube was used as a way to induce chronic stress in mice. The protein levels were determined with ELISA and western blot. A series of behavior tests, including the Morris water maze, elevated plus maze, open field test, and novel object recognition test, were also performed to examine the anxiety and the ability of learning and memory. Moreover, murine neuroblastoma N2a cells were used to confirm the findings from mice under chronic stress.

Results

Decreased synaptic functions were impaired in chronic stress with the downregulation of PSD95, GluR-1, the neurotrophic factor BDNF, and immediate-onset genes Arc and Egr. Chronic restraint decreased the histone acetylation level in hippocampal neurons while HDAC2 was increased and was co-localized with glucocorticoid receptors. Moreover, chronic stress inhibited the PI3K/AKT signaling pathway and induced energy metabolism dysfunctions.

Conclusion

This work examining the elevated levels of HDAC2 in the hippocampus may provide new insights and targets for drug development for treating many neurodegenerative diseases.

Effects of Maternal Chewing on Prenatal Stress-Induced Cognitive Impairments in the Offspring via Multiple Molecular Pathways

We aimed to investigate the effects of maternal chewing on prenatal stress-induced cognitive impairments in the offspring and to explore the molecular pathways of maternal chewing in a mice model. Maternal chewing ameliorated spatial learning impairments in the offspring in a Morris water maze test. Immunohistochemistry and Western blot findings revealed that maternal chewing alleviated hippocampal neurogenesis impairment and increased the expression of hippocampal brain-derived neurotrophic factor in the offspring. In addition, maternal chewing increased the expression of glucocorticoid receptor (GR) and 11β-hydroxysteroid dehydrogenase isozyme 2 (11β-HSD2) and decreased the expression of 11β-HSD1 in the placenta, thereby attenuating the increase of glucocorticoid in the offspring. Furthermore, maternal chewing increased the expression of 11β-HSD2, FK506-binding protein 51 (FKBP51) and FKBP52 and decreased the expression of 11β-HSD1, thereby increasing hippocampal nuclear GR level. In addition, maternal chewing attenuated the increase in expression of DNMT1 and DNMT3a and the decrease in expression of histone H3 methylation at lysine 4, 9, 27 and histone H3 acetylation at lysine 9 induced by prenatal stress in the offspring. Our findings suggest that maternal chewing could ameliorate prenatal stress-induced cognitive impairments in the offspring at least in part by protecting placenta barrier function, alleviating hippocampal nuclear GR transport impairment and increasing the hippocampal brain-derived neurotrophic factor (BDNF) level.

[Progress on epigenetic regulation of iron homeostasis]

Iron homeostasis plays an important role for the maintenance of human health. It is known that iron metabolism is tightly regulated by several key genes, including divalent metal transport-1(DMT1), transferrin receptor 1(TFR1), transferrin receptor 2(TFR2), ferroportin(FPN), hepcidin(HAMP), hemojuvelin(HJV) and Ferritin H. Recently, it is reported that DNA methylation, histone acetylation, and microRNA (miRNA) epigenetically regulated iron homeostasis. Among these epigenetic regulators, DNA hypermethylation of the promoter region of FPN, TFR2, HAMP, HJV and bone morphogenetic protein 6 (BMP6) genes result in inhibitory effect on the expression of these iron-related gene. In addition, histone deacetylase (HADC) suppresses HAMP gene expression. On the contrary, HADC inhibitor upregulates HAMP gene expression. Additional reports showed that miRNA can also modulate iron absorption, transport, storage and utilization via downregulation of DMT1, FPN, TFR1, TFR2, Ferritin H and other genes. It is noteworthy that some key epigenetic regulatory enzymes, such as DNA demethylase TET2 and histone lysine demethylase JmjC KDMs, require iron for the enzymatic activities. In this review, we summarize the recent progress of DNA methylation, histone acetylation and miRNA in regulating iron metabolism and also discuss the future research directions.

Iron Overload Impairs Autophagy: Effects of Rapamycin in Ameliorating Iron-Related Memory Deficits

Over the years, iron accumulation in specific brain regions has been observed in normal aging and related to the pathogenesis of neurodegenerative disorders. Many neurodegenerative diseases may involve cognitive dysfunction, and we have previously shown that neonatal iron overload induces permanent cognitive deficits in adult rats and exacerbates age-associated memory decline. Autophagy is a catabolic pathway involved in the removal of toxic protein aggregates, which are a hallmark of neurodegenerative events. In the present study, we investigated whether iron accumulation would interfere with autophagy and also sought to determine the effects of rapamycin-induced stimulation of autophagy in attenuating iron-related cognitive deficits. Male Wistar rats received a single daily oral dose of vehicle or iron carbonyl (30 mg/kg) at postnatal days 12-14. In adulthood, they received daily intraperitoneal injections of vehicle or rapamycin (0.25 mg/kg) for 14 days. Results showed that iron given in the neonatal period impaired inhibitory avoidance memory and induced a decrease in proteins critically involved in the autophagy pathway, Beclin-1 and LC3, in the hippocampus. Rapamycin in the adulthood reversed iron-induced memory deficits, decreased the ratio phospho-mTOR/total mTOR, and recovered LC3 II levels in iron-treated rats. Our results suggest that iron accumulation, as observed in neurodegenerative disorders, hinders autophagy, which might play a role in iron-induced neurotoxicity. Rapamycin, by inducing authophagy, was able to ameliorate iron-induced cognitive impairments. These findings support the use of rapamycin as a potential neuroprotective treatment against the cognitive decline associated to neurodegenerative disorders.

Effects of hippocampal histone acetylation and HDAC inhibition on spatial learning and memory in the Morris water maze in rats

In recent years, it has been pointed out that epigenetic changes affect learning and memory formation. Particularly, it has been shown that histone acetylation and DNA methylation work in concert to regulate learning and memory formation. We aimed to examine whether acetylation of H2B within the rat hippocampus alters by trainings in the Morris water maze test. Male, 2-3 months old, Sprague Dawley rats were trained in Morris water maze task. Animals were given four trials per day for five consecutive days to locate a hidden platform. On the sixth day, the platform was removed and the animals were swum for 60 s. The effects of sodium butyrate, histone deacetylase inhibitor, were tested on normal and scopolamine-induced memory-impaired rats. The histone deacetylase inhibitor, sodium butyrate, increased histone H2B acetylation in normal rats. Sodium butyrate had no effect on learning and memory performance of normal rats; however, it partially ameliorated learning and memory disruption induced by scopolamine. So, the histone deacetylase inhibitors can be new treatment agent for cognitive disorders.

G protein-coupled oestrogen receptor stimulation ameliorates iron- and ovariectomy-induced memory impairments through the cAMP/PKA/CREB signalling pathway

Iron accumulation in the brain has been associated with neurodegenerative disorders, and imaging studies in humans indicate that iron content in brain regions correlates with poor performance in cognitive tasks. In rats, iron overload impairs memory retention in a variety of memory tasks. Although the effects of iron on cognition in rodents are extensively reported, no previous study has been conducted in female rats. The incidence of certain dementias, such as Alzheimer's disease, is higher in women after menopause compared to aged-matched men. The role of oestrogen depletion in memory deficits in menopausal women is still a matter of debate. The present study aimed to characterise the effects of iron overload on memory in female rats by investigating the effects of ovariectomy (OVX, an experimental model of oestrogen depletion) in rats submitted to iron overload, as well as examining the effects of G protein-coupled oestrogen receptor (GPER) agonism on memory impairments induced by iron and OVX. Female rats received iron (30 mg kg-1 , orally) or vehicle at postnatal days 12-14 and were submitted to OVX in adulthood. Results showed that either iron or OVX impaired memory for object placement and inhibitory avoidance. The selective GPER agonist G1, administered immediately after training, reversed both iron- and OVX-induced memory impairments. G1 effects were abolished by protein kinase A (PKA) inhibition, suggesting the involvement of the cAMP/PKA/CREB signalling pathway. The search for novel oestrogen agonists with positive effects on cognition may be promising for the development of treatments for memory disorders.

Iron chelator deferiprone rescues memory deficits, hippocampal BDNF levels and antioxidant defenses in an experimental model of memory impairment

Brain-derived neurotrophic factor (BDNF) plays a key role in neural development and physiology, as well as in pathological states. Post-mortem studies demonstrate that BDNF is reduced in the brains of patients affected by neurodegenerative diseases. Iron accumulation has also been associated to the pathogenesis of neurodegenerative diseases. In rats, iron overload induces persistent memory deficits, increases oxidative stress and apoptotic markers, and decreases the expression of the synaptic marker, synaptophysin. Deferiprone (DFP) is an oral iron chelator used for the treatment of systemic iron overload disorders, and has recently been tested for Parkinson's disease. Here, we investigated the effects of iron overload on BDNF levels and on mRNA expression of genes encoding TrkB, p75^NTR, catalase (CAT) and NQO1. We also aimed at investigating the effects of DFP on iron-induced impairments. Rats received iron or vehicle at postnatal days 12-14 and when adults, received chronic DFP or water (vehicle). Recognition memory was tested 19 days after the beginning of chelation therapy. BDNF measurements and expression analyses in the hippocampus were performed 24 h after the last day of DFP treatment. DFP restored memory and increased hippocampal BDNF levels, ameliorating iron-induced effects. Iron overload in the neonatal period reduced, while treatment with DFP was able to rescue, the expression of antioxidant enzymes CAT and NQO1.

MGCD0103, a selective histone deacetylase inhibitor, coameliorates oligomeric Aβ25-35 -induced anxiety and cognitive deficits in a mouse model

AIMS

Recently, histone deacetylase (HDAC) inhibitors are considered a possible therapeutic strategy in Alzheimer's disease (AD). However, HDACi treatments exhibit diverse functions with unfavorable effects in AD. Thus, the development of selective HDACi without side effects is urgently needed.

METHODS

HDACi, namely, BML210, MGCD0103, PXD101, and Droxinostat, were screened in mouse hippocampal primary cultures incubated with oligomeric Aβ_25-35 (50 μmol/L). MGCD0103 was chosen for in vivo tests and was intraperitoneally injected into C57BL/6J mice (0.5 mg/kg, once per day) for 4 weeks following an intrahippocampal CA1 injection of oligomeric Aβ_25-35 . Brain samples were collected for pathological analyses after the behavioral analyses including open- field test (OFT), elevated plus maze (EPM), Y-maze, and Morris water maze (MWM).

RESULTS

Among the HDACi, MGCD0103 exhibited significant neuroprotection against the Aβ toxicity in primary cultures. MGCD0103 coattenuated cognitive deficits and anxiety against Aβ damage in mice. MGCD0103 further ameliorated pathological features such as the levels of acetylated histone 3 at Lys 9 site (H3K9) and α-tubulin, synaptophysin, Aβ, tau protein phosphorylation, and serotonergic neuron loss against Aβ toxicity. Furthermore, chronic MGCD0103 treatment did not show liver or kidney toxicity in mice.

CONCLUSIONS

These results reveal MGCD0103 could be a potential therapeutic agent against AD.

Administration of a Histone Deacetylase Inhibitor into the Basolateral Amygdala Enhances Memory Consolidation, Delays Extinction, and Increases Hippocampal BDNF Levels

Gene expression related to the formation and modification of memories is regulated epigenetically by chromatin remodeling through histone acetylation. Memory formation and extinction can be enhanced by treatment with inhibitors of histone deacetylases (HDACs). The basolateral amygdala (BLA) is a brain area critically involved in regulating memory for inhibitory avoidance (IA). However, previous studies have not examined the effects of HDAC inhibition in the amygdala on memory for IA. Here we show that infusion of an HDAC inhibitor (HDACi), trichostatin A (TSA), into the BLA, enhanced consolidation of IA memory in rats when given at 1.5, 3, or 6 h posttraining, but not when the drug was infused immediately after training. In addition, intra-BLA administration of TSA immediately after retrieval delayed extinction learning. Moreover, we show that intra-BLA TSA in rats given IA training increased the levels of brain-derived neurotrophic factor in the dorsal hippocampus, but not in the BLA itself. These findings reveal novel aspects of the regulation of fear memory by epigenetic mechanisms in the amygdala.

Impact of high iron intake on cognition and neurodegeneration in humans and in animal models: a systematic review

Context

Accumulation of brain iron is linked to aging and protein-misfolding neurodegenerative diseases. High iron intake may influence important brain health outcomes in later life.

Objective

The aim of this systematic review was to examine evidence from animal and human studies of the effects of high iron intake or peripheral iron status on adult cognition, brain aging, and neurodegeneration.

Data Sources

MEDLINE, Scopus, CAB Abstracts, the Cochrane Central Register of Clinical Trials, and OpenGrey databases were searched.

Study Selection

Studies investigating the effect of elevated iron intake at all postnatal life stages in mammalian models and humans on measures of adult brain health were included.

Data Extraction

Data were extracted and evaluated by two authors independently, with discrepancies resolved by discussion. Neurodegenerative disease diagnosis and/or behavioral/cognitive, biochemical, and brain morphologic findings were used to study the effects of iron intake or peripheral iron status on brain health. Risk of bias was assessed for animal and human studies. PRISMA guidelines for reporting systematic reviews were followed.

Results

Thirty-four preclinical and 14 clinical studies were identified from database searches. Thirty-three preclinical studies provided evidence supporting an adverse effect of nutritionally relevant high iron intake in neonates on brain-health-related outcomes in adults. Human studies varied considerably in design, quality, and findings; none investigated the effects of high iron intake in neonates/infants.

Conclusions

Human studies are needed to verify whether dietary iron intake levels used in neonates/infants to prevent iron deficiency have effects on brain aging and neurodegenerative disease outcomes.

TXNIP mediates the differential responses of A549 cells to sodium butyrate and sodium 4-phenylbutyrate treatment

Sodium butyrate (NaBu) and sodium 4-phenylbutyrate (4PBA) have promising futures in cancer treatment; however, their underlying molecular mechanisms are not clearly understood. Here, we show A549 cell death induced by NaBu and 4PBA are not the same. NaBu treatment induces a significantly higher level of A549 cell death than 4PBA. A gene expression microarray identified more than 5000 transcripts that were altered (>1.5-fold) in NaBu-treated A549 cells, but fewer than 2000 transcripts that were altered in 4PBA. Moreover, more than 100 cell cycle-associated genes were greatly repressed by NaBu, but slightly repressed by 4PBA; few genes were significantly upregulated only in 4PBA-treated cells. Gene expression was further validated by other experiments. Additionally, A549 cells that were treated with these showed changes in glucose consumption, caspase 3/7 activation and histone modifications, as well as enhanced mitochondrial superoxide production. TXNIP was strongly induced by NaBu (30- to 40-fold mRNA) but was only slightly induced by 4PBA (two to fivefold) in A549 cells. TXNIP knockdown by shRNA in A549 cells significantly attenuated caspase 3/7 activation and restored cell viability, while TXNIP overexpression significantly increased caspase 3/7 activation and cell death only in NaBu-treated cells. Moreover, TXNIP also regulated NaBu- but not 4PBA-induced H4K5 acetylation and H3K4 trimethylation, possibly by increasing WDR5 expression. Finally, we demonstrated that 4PBA induced a mitochondrial superoxide-associated cell death, while NaBu did so mainly through a TXNIP-mediated pathway. The above data might benefit the future clinic application.

Accelerated reduction of serum thyroxine and hippocampal histone acetylation links to exacerbation of spatial memory impairment in aged CD-1 mice pubertally exposed to bisphenol-a

Age-related cognitive decline has been associated with changes in endogenous hormones and epigenetic modification of chromatin, including histone acetylation. Developmental exposure to endocrine disrupting chemicals, such as bisphenol-A (BPA) that produces endocrine disruption and epigenetic changes, may be a risk factor for accelerating cognitive deficits during aging. Thus, we exposed CD-1 mice to BPA (0, 1, and 100 mg/l BPA in the drinking water) orally during puberty (from postnatal days 28 to 56) and investigated whether pubertal BPA exposure exacerbates the age-related impairment of spatial cognition in old age (18 months old) and whether serum sex and thyroid hormones or hippocampal histone acetylation (H3K9ac and H4K8ac) are associated with cognitive effects. A young control group (6 months old) was added to analyze the age effect. Results showed untreated aged mice had marked decline of spatial learning and memory in the novel location recognition and radial six-arm water maze tasks, with decreased levels of these hormones and hippocampal H3K9ac and H4K8ac compared to young controls. The BPA treatment exacerbated age-related spatial cognitive impairment and accelerated the reduction of free thyroxine (FT4), H3K9ac, and H4K8ac, and the 100 mg/l BPA group showed more significant impact. Additionally, correlation analyses revealed that lower levels of FT4, H3K9ac, and H4K8ac were accompanied by decreased spatial memory abilities. We concluded that accelerated reduction of serum FT4 and hippocampal H3K9ac and H4K8ac might be linked to exacerbation of age-related spatial cognitive impairment due to pubertal BPA exposure.

Treadmill exercise induces selective changes in hippocampal histone acetylation during the aging process in rats

Physical exercise and the aging process have been shown to induce opposite effects on epigenetic marks, such as histone acetylation. The impact of exercise on hippocampal histone acetylation on specific lysine residues, especially during the aging process, is rarely studied. The aim of this study was to investigate the effect of treadmill exercise (20min/day during 2 weeks) on H3K9, H4K5 and H4K12 acetylation levels in hippocampi of young adult and aged rats. Male Wistar rats aged 3 or 20-21 months were assigned to sedentary and exercise groups. Single-trial step-down inhibitory avoidance conditioning was employed as an aversive memory paradigm. Hippocampal H3K9, H4K5 and H4K12 acetylation was determined by Western blotting. The daily moderate exercise protocol improved the aversive memory performance and increased hipocampal H4K12 acetylation levels in both tested ages. Exercise was also able to increase H3K9 acetylation levels in aged rats. An age-related decline in memory performance was observed, without any effect of the aging process on histone acetylation state. Our data suggest that treadmill exercise can impact hippocampal the histone acetylation profile in an age- and lysine-dependent manner. In addition, higher hippocampal H4K12 acetylation levels at both ages may be related to improvement of aversive memory performance.

Maternal inflammation linearly exacerbates offspring age-related changes of spatial learning and memory, and neurobiology until senectitude

Maternal inflammation during pregnancy can elevate the risk of neurodegenerative disorders in offspring. However, how it affects age-related impairments of spatial learning and memory and changes in the neurobiological indictors in the offspring in later adulthood is still elusive. In this study, the CD-1 mice with maternal gestational inflammation due to receiving lipopolysaccharide (LPS, i.p. 50 or 25μg/kg) were divided into 3-, 12-, 18-, and 22-month-old groups. The spatial learning and memory were evaluated using a six-radial arm water maze and the levels of presynaptic proteins (synaptotagmin-1 and syntaxin-1) and histone acetylation (H3K9ac and H4K8ac) in the dorsal hippocampus were detected using the immunohistochemical method. The results indicated that there were significant age-related impairments of spatial learning and memory, decreased levels of H4K8ac, H3K9ac, and syntaxin-1, and increased levels of synaptotagmin-1 in the offspring mice from 12 months old to 22 months old compared to the same-age controls. Maternal LPS treatment significantly exacerbated the offspring impairments of spatial learning and memory, the reduction of H3K9ac, H4K8ac, and syntaxin-1, and the increment of synaptotagmin-1 from 12 months old to 22 months old compared to the same-age control groups. The changes in the neurobiological indicators significantly correlated with the impairments of spatial learning and memory. Furthermore, this correlation, besides the age and LPS-treatment effects, also showed a dose-dependent effect. Our results suggest that maternal inflammation during pregnancy could exacerbate age-related impairments of spatial learning and memory, and neurobiochemical indicators in the offspring CD-1 mice from midlife to senectitude.

Butyrate, neuroepigenetics and the gut microbiome: Can a high fiber diet improve brain health?

As interest in the gut microbiome has grown in recent years, attention has turned to the impact of our diet on our brain. The benefits of a high fiber diet in the colon have been well documented in epidemiological studies, but its potential impact on the brain has largely been understudied. Here, we will review evidence that butyrate, a short-chain fatty acid (SCFA) produced by bacterial fermentation of fiber in the colon, can improve brain health. Butyrate has been extensively studied as a histone deacetylase (HDAC) inhibitor but also functions as a ligand for a subset of G protein-coupled receptors and as an energy metabolite. These diverse modes of action make it well suited for solving the wide array of imbalances frequently encountered in neurological disorders. In this review, we will integrate evidence from the disparate fields of gastroenterology and neuroscience to hypothesize that the metabolism of a high fiber diet in the gut can alter gene expression in the brain to prevent neurodegeneration and promote regeneration.

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.

Neonatal isoflurane exposure induces neurocognitive impairment and abnormal hippocampal histone acetylation in mice

Background

Neonatal exposure to isoflurane may induce long-term memory impairment in mice. Histone acetylation is an important form of chromatin modification that regulates the transcription of genes required for memory formation. This study investigated whether neonatal isoflurane exposure-induced neurocognitive impairment is related to dysregulated histone acetylation in the hippocampus and whether it can be attenuated by the histone deacetylase (HDAC) inhibitor trichostatin A (TSA).

Methods

C57BL/6 mice were exposed to 0.75% isoflurane three times (each for 4 h) at postnatal days 7, 8, and 9. Contextual fear conditioning (CFC) was tested at 3 months after anesthesia administration. TSA was intraperitoneally injected 2 h before CFC training. Hippocampal histone acetylation levels were analyzed following CFC training. Levels of the neuronal activation and synaptic plasticity marker c-Fos were investigated at the same time point.

Results

Mice that were neonatally exposed to isoflurane showed significant memory impairment on CFC testing. These mice also exhibited dysregulated hippocampal H4K12 acetylation and decreased c-Fos expression following CFC training. TSA attenuated isoflurane-induced memory impairment and simultaneously increased histone acetylation and c-Fos levels in the hippocampal cornu ammonis (CA)1 area 1 h after CFC training.

Conclusions

Memory impairment induced by repeated neonatal exposure to isoflurane is associated with dysregulated histone H4K12 acetylation in the hippocampus, which probably affects downstream c-Fos gene expression following CFC training. The HDAC inhibitor TSA successfully rescued impaired contextual fear memory, presumably by promoting histone acetylation and histone acetylation-mediated gene expression.

Noradrenergic-Dopaminergic Interactions Due to DSP-4-MPTP Neurotoxin Treatments: Iron Connection

The investigations of noradrenergic lesions and dopaminergic lesions have established particular profiles of functional deficits and accompanying alterations of biomarkers in brain regions and circuits. In the present account, the focus of these lesions is directed toward the effects upon dopaminergic neurotransmission and expression that are associated with the movement disorders and psychosis-like behavior. In this context, it was established that noradrenergic denervation, through administration of the selective noradrenaline (NA) neurotoxin, DSP-4, should be performed prior to the depletion of dopamine (DA) with the selective neurotoxin, MPTP. Employing this regime, it was shown that (i) following DSP-4 (50 mg/kg) pretreatment of C57/Bl6 mice, both the functional and neurochemical (DA loss) effects of MPTP (2 × 20 and 2 × 40 mg/kg) were markedly exacerbated, and (ii) following postnatal iron (Fe(2+), 7.5 mg/kg, on postnatal days 19-12), pretreatment with DSP-4 followed by the lower 2 × 20 mg/kg MPTP dose induced even greater losses of motor behavior and striatal DA. As yet, the combination of NA-DA depletions, and even more so Fe(2+)-NA-DA depletion, has been considered to present a movement disorder aspect although studies exploring cognitive domains are lacking. With intrusion of iron overload into this formula, the likelihood of neuropsychiatric disorder, as well, unfolds.

Sodium butyrate, a histone deacetylase Inhibitor, ameliorates SIRT2-induced memory impairment, reduction of cell proliferation, and neuroblast differentiation in the dentate gyrus

OBJECTIVES

Histone deacetylases (HDACs) play a key role in synaptic plasticity and learning and memory. Sirtuin 2 (SIRT2), a class III HDAC, is abundantly expressed in neurons and functions as a mitotic exit regulator in dividing cells. In this study, we investigated the role of SIRT2 in cell proliferation and neuroblast differentiation in the mouse dentate gyrus.

METHODS

To facilitate the delivery of SIRT2 into neurons, we constructed a PEP-1-SIRT2 fusion protein. Mice were divided into three groups: vehicle (PEP-1), SIRT2, and SIRT2 with sodium butyrate (an HDAC inhibitor). PEP-1 or PEP-1-SIRT2 fusion protein was administered intraperitoneally to 7-week-old mice once a day for 3 weeks, and the mice were killed 2 h after the last administration. Sodium butyrate, an HDAC inhibitor, was subcutaneously administered in parallel with PEP-1-SIRT2 once a day for 3 weeks.

RESULTS

The administration of PEP-1-SIRT2 alone significantly reduced the time spent exploring a new object in the novel object recognition test, whereas treatment with sodium butyrate increased the time spent exploring a new object. RESULTS of Ki67 and doublecortin immunohistochemistry revealed that the administration of PEP-1-SIRT2 significantly reduced cell proliferation and neuroblast differentiation, respectively, in the dentate gyrus. However, the administration of sodium butyrate significantly ameliorated the SIRT2-induced reduction in cell proliferation and neuroblast differentiation.

CONCLUSION

This result suggests that histone acetylation and deacetylation are key factors modulating hippocampal functions such as memory formation, cell proliferation, and neuroblast differentiation in the dentate gyrus.

Altered brain iron homeostasis and dopaminergic function in Restless Legs Syndrome (Willis-Ekbom Disease)

Restless legs syndrome (RLS), also known as Willis-Ekbom Disease (WED), is a sensorimotor disorder for which the exact pathophysiology remains unclear. Brain iron insufficiency and altered dopaminergic function appear to play important roles in the etiology of the disorder. This concept is based partly on extensive research studies using cerebrospinal fluid (CSF), autopsy material, and brain imaging indicating reduced regional brain iron and on the clinical efficacy of dopamine receptor agonists for alleviating RLS symptoms. Finding causal relations, linking low brain iron to altered dopaminergic function in RLS, has required however the use of animal models. These models have provided insights into how alterations in brain iron homeostasis and dopaminergic system may be involved in RLS. The results of animal models of RLS and biochemical, postmortem, and imaging studies in patients with the disease suggest that disruptions in brain iron trafficking lead to disturbances in striatal dopamine neurotransmission for at least some patients with RLS. This review examines the data supporting an iron deficiency-dopamine metabolic theory of RLS by relating the results from animal model investigations of the influence of brain iron deficiency on dopaminergic systems to data from clinical studies in patients with RLS.

Repression of contexual fear memory induced by isoflurane is accompanied by reduction in histone acetylation and rescued by sodium butyrate

BACKGROUND

Isoflurane produces amnesia in mice during contextual fear conditioning (CFC) trials. Histone acetylation is a form of chromatin modification involved in the transcriptional regulation underlying memory formation. We investigated whether isoflurane-induced repression of contextual fear memory is related to altered histone acetylation in the hippocampus, and whether it can be rescued by the histone deacetylases inhibitor sodium butyrate (SB).

METHODS

Adult C57BL/6 mice were chronically given intraperitoneal injections of SB or vehicle for 28 days. Immediately before CFC training, the mice were exposed to isoflurane or air for 30 min and CFC testing was performed the next day. Hippocampal histone acetylation was analysed 1 h after CFC training. c-Fos, an immediate early gene (IEG) suggested to participate in learning and memory formation, was also investigated at the same timepoint.

RESULTS

Mice exposed to isoflurane showed a reduction in freezing time during the CFC test. These mice also exhibited reduced hippocampal H3K14, H4K5, and H4K12 acetylation 1 h after CFC training, and also decreased c-Fos expression. All of these changes were attenuated in isoflurane-exposed mice that were chronically treated with SB.

CONCLUSIONS

Isoflurane suppresses histone acetylation and down-regulates c-Fos gene expression in CA1 of the hippocampus after CFC training. These changes are associated with isoflurane-induced amnesia. The HDAC inhibitor SB prevented repressed contextual fear memory, presumably by promoting histone acetylation and histone acetylation-mediated gene expression in response to CFC training.

Differential effects of modafinil on memory in naïve and memory-impaired rats

Modafinil is a wake-promoting drug and has been approved for the treatment of excessive daytime sleepiness in narcolepsy and obstructive sleep apnea. Modafinil was shown to improve learning and memory in rodents, and to reverse memory deficits induced by sleep deprivation or stress. However, depending on the memory paradigm used, modafinil might also impair memory. We aimed to investigate the effects of modafinil on memory consolidation and retrieval for object recognition and inhibitory avoidance in naïve adult rats. We also investigated whether acute or chronic administration of modafinil would reverse memory deficits induced by iron overload, a model of memory impairment related to neurodegenerative disorders. Adult naïve rats received modafinil (0.0, 0.75, 7.5 or 75 mg/kg) either immediately after training or 1 h prior to testing in object recognition or inhibitory avoidance. Iron-treated rats received modafinil immediately after training in object recognition. In order to investigate the effects of chronic modafinil, iron-treated rats received daily injections of modafinil for 17 days, and 24 h later they were trained in object recognition or inhibitory avoidance. Acute modafinil does not affect memory consolidation or retrieval in naive rats. A single injection of modafinil at the highest dose was able to recover recognition memory in iron-treated rats. Chronic modafinil completely recovered iron-induced recognition memory and emotional memory deficits. Additional preclinical and clinical studies are necessary in order to support the applicability of modafinil in recovering memory impairment associated with neurodegenerative disorders.

Cannabidiol normalizes caspase 3, synaptophysin, and mitochondrial fission protein DNM1L expression levels in rats with brain iron overload: implications for neuroprotection

We have recently shown that chronic treatment with cannabidiol (CBD) was able to recover memory deficits induced by brain iron loading in a dose-dependent manner in rats. Brain iron accumulation is implicated in the pathogenesis of neurodegenerative diseases, including Parkinson's and Alzheimer's, and has been related to cognitive deficits in animals and human subjects. Deficits in synaptic energy supply have been linked to neurodegenerative diseases, evidencing the key role played by mitochondria in maintaining viable neural cells and functional circuits. It has also been shown that brains of patients suffering from neurodegenerative diseases have increased expression of apoptosisrelated proteins and specific DNA fragmentation. Here, we have analyzed the expression level of brain proteins involved with mitochondrial fusion and fission mechanisms (DNM1L and OPA1), the main integral transmembrane protein of synaptic vesicles (synaptophysin), and caspase 3, an apoptosis-related protein, to gain a better understanding of the potential of CBD in restoring the damage caused by iron loading in rats. We found that CBD rescued iron-induced effects, bringing hippocampal DNM1L, caspase 3, and synaptophysin levels back to values comparable to the control group. Our results suggest that iron affects mitochondrial dynamics, possibly trigging synaptic loss and apoptotic cell death and indicate that CBD should be considered as a potential molecule with memory-rescuing and neuroprotective properties to be used in the treatment of cognitive deficits observed in neurodegenerative disorders.

Acetate reduces PGE2 release and modulates phospholipase and cyclooxygenase levels in neuroglia stimulated with lipopolysaccharide

Acetate supplementation attenuates neuroglial activation, increases histone and non-histone protein acetylation, reduces pro-inflammatory cytokine expression, and increases IL-4 transcription in rat models of neuroinflammation and Lyme's neuroborreliosis. Because eicosanoid signaling is involved in neuroinflammation, we measured the effect acetate treatment had on phospholipase, cyclooxygenase, and prostaglandin E2 (PGE2) levels in BV-2 microglia and primary astrocytes stimulated with lipopolysaccharide (LPS). In BV-2 microglia, we found that LPS increased the phosphorylation-state of cytosolic phospholipase A2 (cPLA2), reduced the levels of phospholipase C (PLC) β1, and increased the levels of cyclooxygenase (Cox)-1 and -2. Acetate treatment returned PLCβ1 and Cox-1 levels to normal, attenuated the increase in Cox-2, but had no effect on cPLA2 phosphorylation. In primary astrocytes, LPS increased the phosphorylation of cPLA2 and increased the levels of Cox-1 and Cox-2. Acetate treatment in these cells reduced secretory PLA2 IIA and PLCβ1 levels as compared to LPS-treatment groups, reversed the increase in cPLA2 phosphorylation, and returned Cox-1 levels to normal. Acetate treatment reduced PGE2 release in astrocytes stimulated with LPS to control levels, but did not alter PGE2 levels in BV-2 microglia. The amount of acetylated H3K9 bound to the promoter regions of Cox-1, Cox-2, IL-1β and NF-κB p65 genes, but not IL-4 in were increased in BV-2 microglia treated with acetate. These data suggest that acetate treatment can disrupt eicosanoid signaling in neuroglia that may, in part, be the result of altering gene expression due chromatin remodeling as a result of increasing H3K9 acetylation.

Modulation of inflammatory cytokines and mitogen-activated protein kinases by acetate in primary astrocytes

Acetate supplementation attenuates neuroglia activation in a rat model of neuroinflammation by a mechanism associated with an increase in brain acetyl-CoA, an alteration in histone acetylation, and reduction of interleukin (IL)-1β expression. We propose that reduced astroglial activation occurs by disrupting astrocyte-derived inflammatory signaling and cytokine release. Using primary astroglial cultures, we found that LPS (0-25 ng/ml, 4 h) increased tumor necrosis factor (TNF-α) and IL-1β in a concentration-dependent manner, which was reduced by treatment with sodium acetate (12 mM). LPS did not alter H3K9 acetylation or IL-6 levels, whereas acetate treatment increased H3K9 acetylation by 2-fold and decreased basal levels of IL-6 by 2-fold. Acetate treatment attenuated the LPS-induced increase in TNF-α mRNA, but did not reverse the mRNA levels of other pro-inflammatory cytokines. By contrast, LPS decreased TGF-β1 and IL-4 protein and TGF-β1 mRNA, all of which was reversed with acetate treatment. Further, we found that acetate treatment completely reversed LPS-induced phosphorylation of MAPK p38 and decreased basal levels of phosphorylated extracellular signal-regulated kinases1/2 (ERK1/2) by 2-fold. Acetate treatment also reversed LPS-elevated NF-κB p65, CCAAT/enhancer-binding protein beta protein levels, and reduced basal levels of phosphorylated NF-κB p65 at serine 536. These results suggest that acetate treatment has a net anti-inflammatory effect in LPS-stimulated astrocytes that is largely associated with a disruption in MAPK and NF-κB signaling.

Acetate reduces microglia inflammatory signaling in vitro

Acetate supplementation increases brain acetyl-CoA and histone acetylation and reduces lipopolysaccharide (LPS)-induced neuroglial activation and interleukin (IL)-1β expression in vivo. To determine how acetate imparts these properties, we tested the hypothesis that acetate metabolism reduces inflammatory signaling in microglia. To test this, we measured the effect acetate treatment had on cytokine expression, mitogen-activated protein kinase (MAPK) signaling, histone H3 at lysine 9 acetylation, and alterations of nuclear factor-kappa B (NF-κB) in primary and BV-2 cultured microglia. We found that treatment induced H3K9 hyperacetylation and reversed LPS-induced H3K9 hypoacetylation similar to that found in vivo. LPS also increased IL-1β, IL-6, and tumor necrosis factor-alpha (TNF-α) mRNA and protein, whereas treatment returned the protein to control levels and only partially attenuated IL-6 mRNA. In contrast, treatment increased mRNA levels of transforming growth factor-β1 (TGF-β1) and both IL-4 mRNA and protein. LPS increased p38 MAPK and JNK phosphorylation at 4 and 2-4 h, respectively, whereas treatment reduced p38 MAPK and JNK phosphorylation only at 2 h. In addition, treatment reversed the LPS-induced elevation of NF-κB p65 protein and phosphorylation at serine 468 and induced acetylation at lysine 310. These data suggest that acetate metabolism reduces inflammatory signaling and alters histone and non-histone protein acetylation.