Caspase-3 is Involved in Aluminum-Induced Impairment of Long-Term Potentiation in Rats Through the Akt/GSK-3β Pathway

Role of aluminum exposure on Alzheimer's disease and related glycogen synthase kinase pathway

Aluminum (Al) is an environmentally abundant metal that is not essential for life. There is considerable evidence that Al as a neurotoxic xenobiotic may play a role in the pathogenesis of neurodegenerative diseases like Alzheimer's disease (AD). Exposure to aluminum has been shown to cause neuronal damage that resembles the symptoms of AD. In this review, we will summarize recent data about Al as the possible risk of incidence of AD. Then glycogen synthase kinase-3 beta (GSK3β) contributes to the hyperphosphorylation of Tau protein, the main component of neurofibrillary tangles, one of the hallmarks of AD as one of the mechanisms behind Al neurotoxicity will be covered. Overall, there is still a need for epidemiological studies and more in vivo and in vitro studies to determine the exact mechanisms of its neurotoxicity and the role of GSK3β in both Al toxic effect and AD.

The Palmitoylation/Depalmitoylation Cycle is Involved in the Inhibition of AMPA Receptor Trafficking Induced by Aluminum In Vitro

To study the effect of the palmitoylation/depalmitoylation cycle on the inhibition of ɑ-amino-3-hydroxy-5-methyl-4-isoxazolpropionic acid (AMPA) receptor trafficking induced by aluminum (Al) in vitro. Five different doses of aluminum-maltolate complex (Al(mal)₃) were administered to rat adrenal pheochromocytoma cells (PC12 cells) for three exposure time durations, and the cell activity was measured by the CCK-8 method to obtain the optimal doses and time of Al(mal)₃ exposure. Following Al(mal)₃ exposure, membrane protein (M) and total protein (T) were extracted. The expression levels of GluR1 and GluR2, which are AMPA receptor subunits, were determined by Western blot analysis, and the levels with respect to membrane and total protein were calculated. The ratio of membrane protein to total protein (M/T) was used to measure the rate of AMPA receptor transport. The palmitoylation levels of GluR1 and GluR2 were detected by immunoprecipitation-acyl-biotin exchange (IP-ABE) assay. Western blotting was performed to detect the protein expression of acyltransferase (zDHHC3) and palmitoyl protein thioesterase 1 (PPT1). Following depalmitoylation inhibitor (palmostatin B) treatment of PC12 cells, the effect of aluminum on AMPA receptor trafficking was detected through the aforementioned methods. With increasing Al(mal)₃ doses administered to PC12 cells, a gradual decrease in the trafficking of AMPA receptor subunits GluR1 and GluR2 and in the palmitoylation levels of GluR1 and GluR2 was found; the expression of zDHHC3 was decreased; and the expression of PPT1 was increased. In addition, palmostatin B reduced the effects of Al(mal)₃ on AMPA receptor palmitoylation and trafficking. Al can inhibit the trafficking of the AMPA receptor in vitro, and a decrease in the palmitoylation level of the AMPA receptor may be a mechanism of Al action. The palmitoylation/depalmitoylation cycle of the AMPA receptor is influenced by Al through the actions of zDHHC3 and PPT1.

Aluminum Oxide Nanoparticles Impair Working Memory and Neuronal Activity through the GSK3β/BDNF Signaling Pathway of Prefrontal Cortex in Rats

Studies demonstrated that alumina nanoparticles (alumina NPs) impair spatial cognition and hippocampus-dependent synaptic plasticity. Although alumina NPs accumulate in the prefrontal cortex (PFC), their effects on PFC-mediated neuronal and cognitive function have been not yet documented. Here, alumina NPs (10 or 20 μg/kg of body weight) were bilaterally injected into the medial PFC (mPFC) of adult rats, and the levels of glycogen synthase kinase 3β (GSK3β) and the brain-derived neurotrophic factor (BDNF) were detected. The PFC-dependent working memory task with one-minute or three-minute delay time was conducted. Meanwhile, the neuronal correlates of working memory performance were recorded. The specific expression of neuronal BDNF was assessed by colabeled BDNF expression with the neuronal nuclear antigen (NeuN). Whole-cell patch-clamp recordings were employed to detect neuronal excitability. Intra-mPFC alumina NP infusions significantly enhanced the expression of GSK3β but reduced the phosphorylation of GSK3β (pGSK3β) and BDNF levels more severely at a dose of 20 μg/kg. Alumina NPs acted in a dose-dependent manner to impair working memory. The neuronal expression of BDNF in the 20 μg/kg group was markedly declined compared with the 10 μg/kg group. During the delay time, the neuronal frequency of pyramidal cells but not interneurons was significantly weakened. Furthermore, both the frequency and amplitude of the excitatory postsynaptic currents (EPSCs) were descended in the mPFC slices. Additionally, the infusion of GSK3β inhibitor SB216763 or BDNF could effectively attenuate the impairments in neuronal correlate, neuronal activity, and working memory. From the perspective of the identified GSK3β/BDNF pathway, these findings demonstrated for the first time that alumina NPs exposure can be a risk factor for prefrontal neuronal and cognitive functions.

Microencapsulation of Plant Phenolic Extracts Using Complex Coacervation Incorporated in Ultrafiltered Cheese Against AlCl3-Induced Neuroinflammation in Rats

Plant-derived phenolic compounds have numerous biological effects, including antioxidant, anti-inflammatory, and neuroprotective effects. However, their application is limited because they are degraded under environmental conditions. The aim of this study was to microencapsulate plant phenolic extracts using a complex coacervation method to mitigate this problem. Red beet (RB), broccoli (BR), and spinach leaf (SL) phenolic extracts were encapsulated by complex coacervation. The characteristics of complex coacervates [zeta potential, encapsulation efficiency (EE), FTIR, and morphology] were evaluated. The RB, BR, and SL complex coacervates were incorporated into an ultrafiltered (UF) cheese system. The chemical properties, pH, texture profile, microstructure, and sensory properties of UF cheese with coacervates were determined. In total, 54 male Sprague–Dawley rats were used, among which 48 rats were administered an oral dose of AlCl₃ (100 mg/kg body weight/d). Nutritional and biochemical parameters, including malondialdehyde, superoxide dismutase, catalase, reduced glutathione, nitric oxide, acetylcholinesterase, butyrylcholinesterase, dopamine, 5-hydroxytryptamine, brain-derived neurotrophic factor, and glial fibrillary acidic protein, were assessed. The RB, BR, and SL phenolic extracts were successfully encapsulated. The RB, BR, and SL complex coacervates had no impact on the chemical composition of UF cheese. The structure of the RB, BR, and SL complex coacervates in UF cheese was the most stable. The hardness of UF cheese was progressively enhanced by using the RB, BR, and SL complex coacervates. The sensory characteristics of the UF cheese samples achieved good scores and were viable for inclusion in food systems. Additionally, these microcapsules improved metabolic strategies and neurobehavioral systems and enhanced the protein biosynthesis of rat brains. Both forms failed to induce any severe side effects in any experimental group. It can be concluded that the microencapsulation of plant phenolic extracts using a complex coacervation technique protected rats against AlCl3-induced neuroinflammation. This finding might be of interest to food producers and researchers aiming to deliver natural bioactive compounds in the most acceptable manner (i.e., food).

The association between blood lymphocyte NMDAR, group I mGluRs and cognitive function changes in occupationally aluminum-exposed workers and verification in rats

BACKGROUND

Many studies have shown that occupational aluminum (Al) exposure could affect the cognitive functions of workers and cause mild cognitive impairment (MCI). Glutamate receptors (GluRs) play an important role in learning and memory functions.

METHODS

352 workers in a large Al production enterprise were investigated in this research. MMSE, CDT, DST, VFT, FOM were used to evaluate the cognitive functions of workers. Plasma Al levels as exposure indices were measured by Graphite Furnace Atomic Absorption Method (GFAAS). The expression of GluRs was measured by ELISA. Cognitive function comprehensive scores were obtained through factor analysis. Then a rat model of chronic AlCl₃ exposure was established. The detection method of Al levels and protein expression were the same as mentioned-above.

RESULTS

Compared with the Q1 group, the DST, VFT, and comprehensive cognitive function scores of the Q4 group were lower(P < 0.05). For every 1μg/L increase in plasma Al concentration, the risk of cognitive impairment increases 1.051 times (95 %CI:1.031,1.072). Both NMDAR1 and NMDAR2A protein expression level of Q1 group were higher than those of Q2, Q3, Q4 group (all P < 0.05). The mediating effect ratio of NMDAR1 between plasma Al levels and cognitive function comprehensive scores was a1*b1/c=11.30 %, and the mediating effect ratio of NMDAR2A was |a2*b2/c|=21.77 %. Compared with control group, the escape latency of rats in the high Al dose group was longer day by day (P < 0.05). With the increase of Al dose, the relative expression of NMDAR1, NMDAR2A, NMDAR2B, GluR1 and mGluR5 in cerebral cortex and lymphocytes of rats were decreased (P < 0.05). The result of correlation analysis on NMDAR1 protein expression between brain cortex and lymphocyte showed that the correlation coefficient is r = 0.646(P < 0.05).

CONCLUSION

Taking together the results from both Al exposed workers and animal, there is a certain correlation between NMDAR1 protein contents of brain cortex and peripheral lymphocytes. We propose that lymphocyte NMDAR1 could be considered as a peripheral potential marker of cognitive impairment for further observation.

Effects of a Novel Magnesium Complex on Metabolic and Cognitive Functions and the Expression of Synapse-Associated Proteins in Rats Fed a High-Fat Diet

This study was conducted to compare the effects of a novel form of magnesium, Mg picolinate (MgPic), to magnesium oxide (MgO) on metabolic and cognitive functions and the expression of genes associated with these functions in rats fed a high-fat diet (HFD). Forty-two Wistar rats were divided into six groups: control, MgO, MgPic, HFD, HFD + MgO, and HFD + MgPic. Mg was supplemented at 500 mg of elemental Mg/kg diet for 8 weeks. MgPic and MgO supplementation decreased visceral fat, serum glucose, insulin, leptin, TC, TG, FFA, testosterone, FSH, LH, SHBG, IGF-1, and MDA levels, but increased brain SOD, CAT, and GSH-Px activities in HFD rats. Inflammation and cognitive-related markers (presynaptic synapsin PSD95, postsynaptic PSD93, postsynaptic GluR1, and GluR2) were improved in HFD rats administered Mg, with more significant effects seen in the MgPic group. MgPic also decreased brain NF-κB but elevated brain Nrf2 levels, compared with the HFD group. The phosphorylation levels of Akt (Thr308), Akt (Ser473), PI3K try 458/199, and Ser9-GSK-3 in the brain were improved after Mg treatment in HFD rats, with more potent effects seen from MgPic supplementation. MgPic has a higher bioavailability and is more effective in improving metabolic parameters and enhancing memory than MgO. The pro-cognitive effects of MgO and MgPic could be mediated via modulation of the AMPA-type glutamate receptor and activation of the PI3K-Akt-GSK-3β signaling pathway. These findings further support the use of MgPic in the management of metabolic and cognitive disorders.

The GSK-3β/β-Catenin Signaling-Mediated Brain-Derived Neurotrophic Factor Pathway Is Involved in Aluminum-Induced Impairment of Hippocampal LTP In Vivo

The neurotoxic effects of aluminum (Al) are associated with the impairment of synaptic plasticity, the biological basis of learning and memory, the major form of which is long-term potentiation (LTP). The canonical glycogen synthase kinase-3β (GSK-3β)/β-catenin signaling-mediated brain-derived neurotrophic factor (BDNF) pathway has been suggested to play important roles in memory. Thus, Al may affect LTP through this pathway. In this study, a Sprague-Dawley rat model of neurotoxicity was established through intracerebroventricular (i.c.v.) injection of aluminum maltol (Al(mal)₃), which was achieved by preimplantation of a cannula into the lateral ventricle. The rats in the control and Al-treated groups received a daily injection of SB216763, an inhibitor of GSK-3β. Electrophysiology and western blot analysis were used to investigate the regulatory effect of the GSK-3β/β-catenin signaling-mediated BDNF pathway on LTP impairment induced by Al(mal)₃. The results confirmed that i.c.v. injection of Al(mal)₃ significantly suppressed the field excitatory postsynaptic potential (fEPSP) amplitude, as indicated by a decrease in BDNF protein expression, which was accompanied by dose-dependent decreases in β-catenin protein expression and the phosphorylation of GSK-3β at Ser9. Rats that received SB216763, a GSK-3β inhibitor, exhibited higher fEPSP amplitudes than control rats. Furthermore, SB216763 treatment upregulated the hippocampal protein expression of BDNF and β-catenin while increasing the ratio of p-GSK-3β/GSK-3β. From the perspective of the identified β-catenin-BDNF axis, Al impairs hippocampal LTP, possibly through the GSK-3β/β-catenin signaling-mediated BDNF pathway.

miR-29a and the PTEN-GSK3β axis are involved in aluminum-induced damage to primary hippocampal neuronal networks

We previously reported that aluminum (Al) can cause a range of neurotoxic injuries including progressive irreversible synaptic structural damage and synaptic dysfunction, and eventually neuronal deaths. Mechanism of Al-induced electrophysiological and neuronal connectivity changes in neurons may indicate damage to the neuronal network. Here, mouse primary hippocampal neurons were cultured on micro-electrode array (MEA)- and high-content analysis (HCA)-related plates, showing that Al exposure significantly inhibited hippocampal neuronal electrical spike activity and neurite outgrowth characterized by a reduction in neurite branching and a decrease in the average total neurite length in relation to both Al dose and time of incubation. In recent years, miR-29a/ phosphatase and tensin homolog (PTEN) have been found to play pivotal roles in the morphogenesis of neurons, it has been confirmed in vitro and in vivo that the PTEN-Glycogen synthase kinase-3β (GSK-3β) axis regulates neurite outgrowth. The present study demonstrated that increases in Al exposure and dose gradually reduce miR-29a expression. Up-regulation of miR-29a in the hippocampal neurons by lentivirus transfection reversed the decrease in electrical spike activity and the reduction in both neurite branching and length induced by Al. Moreover, miR-29a suppressed the expression of PTEN and increased the level of phosphorylated Protein Kinase B (p-AKT) and p-GSK-3β which were inhibited by the Al treatment. This suggests that miR-29a is critically involved in the functional and structural neuronal damage induced by Al and is a potential target for Al neurotoxicity. Moreover, the reduction of neurite length and branching induced by Al exposure was regulated by miR-29a and its target neuronal PTEN-GSK3β signaling pathway, which also represents a possible mechanism of Al-induced the inhibition of the electrical activity. Collectively, Al-induced damage to the neuronal network occurred through miR-29a-mediated alterations of the PTEN-GSK3β signaling pathway.

Regulation of mGluR1 on the Expression of PKC and NMDAR in Aluminum-Exposed PC12 Cells

Aluminum demonstrates clear neurotoxicity and can cause Alzheimer's disease (AD)-like symptoms, including cognitive impairment. One toxic effect of aluminum is a decrease in synaptic plasticity, but the specific mechanism remains unclear. In this study, PC12 cells were treated with Al(mal)₃ to construct a toxic cell model. (S)-3,5-Dihydroxyphenylglycine (DHPG), α-methyl-4-carboxyphenylglycine (MCPG), and mGluR1-siRNA were used to interfere with the expression of metabotropic glutamate receptor subtype 1 (mGluR1). Polymerase chain reaction and western blotting were used to investigate the expression of mGluR1, protein kinase C (PKC), and N-methyl-D-aspartate receptor (NMDAR) subunits. ELISA was used to detect PKC enzyme activity. In PC12 cells, mRNA and protein expressions of PKC and NMDAR subunits were inhibited by Al(mal)₃. Aluminum may further regulate the expression of NMDAR1 and NMDAR2B through mGluR1 to regulate PKC enzyme activity, thereby affecting learning and memory functions. Furthermore, the results implied that the mGluR1-PKC-NMDAR signaling pathway may predominately involve positive regulation. These findings provide new targets for studying the neurotoxic mechanism of aluminum.

Neuroprotective Effects of Higenamine Against the Alzheimer's Disease Via Amelioration of Cognitive Impairment, A Burden, Apoptosis and Regulation of Akt/GSK3β Signaling Pathway

The present investigation was envisaged to elucidate the neuroprotective effect of Higenamine (HGN) against aluminum chloride (AlCl₃) triggered experimental Alzheimer's disease (AD) rat model. Thirty-six male albino Wister rats were randomized and divided in 6 groups and subjected to experimentation for 6 weeks. Control group, AlCl₃ (100 mg/kg orally), HGN (50 mg/kg orally), HGN25, HGN50, HGN75 (HGN 25, 50 and 75 mg/kg respectively and AlCl₃ 100 mg/kg orally). After completion of 42 days protocol, the animals were subjected to passive avoidance test. The animals were then anesthetized by intramuscularly injecting ketamine hydrochloride (24 mg/kg body weight) and euthanized by cervical amputation. Cortical and hippocampal tissues were carefully removed and were employed for quantification of aluminum and acetylcholinesterase. The tissues were quantified using Western blotting and detection kits for APP, Aβ_1-42, β and γ secretases, Bax, Bad, caspases-9, cyto-c, pAkt and pGSK-3β, and oxidative markers. HGN significantly protected AlCl₃ induced memory and learning impairments, Al overload, AChE hyperactivity, amyloid β (Aβ) burden and apoptosis in brain tissues via activating Akt/GSK3β pathway. HGN attenuated oxidative damage induced by Al by modulation of oxidative markers. Our findings advocate the neuroprotective effect of HGN in AlCl₃ induced AD rat model.

Effects of Chronic Aluminum Lactate Exposure on Neuronal Apoptosis and Hippocampal Synaptic Plasticity in Rats

This study investigated the effects of chronic aluminum exposure on apoptosis of hippocampal neurons, and synaptic plasticity in the hippocampus in rats. Rats were divided into the control, low-dose (L-Al), mid-dose (M-Al), and high-dose (H-Al) groups. After chronic exposure of aluminum, the Morris water maze (MWM) and open-field (OF) tests were performed to assess the behavioral performance. Electrophysiological measurements were conducted. Flow cytometry was used to assess the apoptotic processes. Quantitative real-time PCR and ELISA were performed to measure mRNA and protein expression levels of caspases. After 90 days of aluminum exposure, the aluminum contents in the brain of the rats were increased, with the increasing exposure dose. The MWM and OF tests showed that chronic exposure of aluminum significantly impaired the neurobehavior of rats. Moreover, after high-frequency stimulation (HFS), the average amplitudes of field excitatory postsynaptic potentials (fEPSPs) for the M-Al and H-Al groups were lower than the control group at 10, 20, 30, 40, 50, and 60 min. Furthermore, the apoptotic rates in the M-Al and H-Al groups were significantly higher than the control group. The qRT-PCR and ELISA showed that, compared with the control group, the mRNA and protein expression levels of caspases-3, -8, and -9 were significantly increased in the aluminum-treated groups compared with the control group. Long-term exposure to aluminum could induce the apoptosis of hippocampal neurons, damage the synaptic plasticity, and impair the learning and memory functions in rats. There might be a close relationship between the neuronal apoptosis and synaptic plasticity damage.

Effects of regulating miR-132 mediated GSK-3β on learning and memory function in mice

The aimf of this study was to explore effects of miR-132 and glycogen synthase kinase-3β (GSK-3β) on learning and memory in mice. miR-132 inhibitor GSK-3β overexpression agent (sh-GSK-3β) and normal saline (negative control group) were injected into the hippocampus of adult mice, and healthy adult mice were taken as the unrelated control group. The expression of miR-132 and GSK-3β in the hippocampus of adult and elderly mice was detected using reverse transcription-quantitative PCR (RT-qPCR) and western blot analysis. Morris water maze test was employed to detect learning and memory function in mice. The dual luciferase reporter was adopted to determine the relationship between miR-132 and GSK-3β. Compared with the adult group, the expression of miR-132 was significantly downregulated in the hippocampus in the elderly group, while the expression of GSK-3β was upregulated. Injecting miR-132 inhibitor into the hippocampus of adult mice led to a significant increase in escape latency and a significant decrease in the number of times of crossing platforms. The injection of GSK-3β overexpression agent into the hippocampus of adult mice resulted in a marked increase in escape latency and a significant decrease in the number of times of crossing platforms in the water maze test. It was also found that downregulation of GSK-3β reversed the decline in learning and memory in mice caused by downregulation of miR-132 expression. The dual luciferase report identified a targeted regulatory relationship between miR-132 and GSK-3β. Overexpression of miR-132 can inhibit the expression of GSK-3β in mouse learning and memory ability, which provides some inspiration for understanding the occurrence of learning and memory disorders and future treatment methods.

Role of mGluR 1 in synaptic plasticity impairment induced by maltol aluminium in rats

The main symptoms of Alzheimer's disease (AD) is the loss of learning and memory ability, of which biological basis is synaptic plasticity. Aluminium has been found to cause changes in synaptic plasticity, but its molecular mechanism was unclear. In this study, Sprague-Dawley rats were injected with aluminium maltol (Al(mal)₃) through the lateral ventricle to establish an AD-like model. Y-maze, electrophysiological measurements, Golgi staining, scanning electron microscopy, quantitative real-time polymerase chain reaction, and western blot techniques were used to investigate regulation of the metabolic glutamate receptor 1 (mGluR1) in synaptic plasticity impairment induced by Al(mal)₃. The results showed that Al(mal)₃ inhibited the induction and maintenance of long-term potentiation in the hippocampal CA1 region. During this process, the expression of mGluR1 was up-regulated and it inhibited the expression and phosphorylation of the N-methyl-D-aspartic acid receptors (NMDARs). This mainly affected NMDAR1 and NMDAR2B but did not affect protein kinase C expression.

Aluminium-induced synaptic plasticity injury via the PHF8-H3K9me2-BDNF signalling pathway

Aluminium is an environmental neurotoxin that comes extensively in contact with human being. The molecular mechanism of aluminium toxicity remains unclear. A number of studies have indicated that exposure to aluminium can impair learning and memory function. The purpose of this study was to investigate the mechanism of long-term potentiation(LTP) injury and the related signalling pathway activated by aluminium exposure. The results showed that aluminium treatment produced dose-dependent inhibition of LTP and reduced the activity of Histone H3K9 demethylation (H3K9me2) demethylase and the expression of the PHD (plant homeodomain) finger protein 8 (PHF8). Interestingly, there was no statistically significant difference in the expression of the PHF8 gene, suggesting that aluminium exposure only affects the translation process. Decrease in brain-derived neurotrophic factor (BDNF) expression may be related to the effect of aluminium. With correlation analysis between the hippocampal standardised field excitatory postsynaptic potential (fEPSP) amplitude and the expression of various proteins in the aluminium-exposed rat, the hippocampal standardised fEPSP amplitude was positively correlated with the expression of hippocampal PHF8 and BDNF proteins, and negatively correlated with the expression of hippocampal H3K9me2 protein. The correlation between H3K9me2 and BDNF was also considered negative. The results suggest that changes in synaptic plasticity might be related to changes in these proteins, which were induced by aluminium exposure. In conclusion, chronic aluminium exposure may inhibit PHF8 and prevent it from functioning as a demethylase. This may block H3K9me2 demethylation, decrease BDNF protein expression, and lead to LTP impairment.

Aluminum-Induced Synaptic Plasticity Impairment via PI3K-Akt-mTOR Signaling Pathway

Aluminum (Al) is an environmental neurotoxin with extensive exposure by humans, but the molecular mechanism of its toxicity is still unclear. Several studies have indicated that exposure to aluminum can impair learning and memory function. The purpose of this study was to investigate the mechanism of LTP injury and the effect of aluminum exposure on related signal pathways. The results showed that the axonal dendrites of neurons in the hippocampal CA1 area of rats exposed to maltol aluminum showed neuritic beading and the dendritic spines were reduced. This resulted in dose-dependent LTP inhibition and led to impaired learning and memory function in rats. The PI3K-Akt-mTOR pathway may play a crucial role in this process.

Aluminum-induced "mixed" cell death in mice cerebral tissue and potential intervention

The brain is one of organs vulnerable to aluminum insult. Aluminum toxicity is involved in neurobehavioral deficit, neuronal cell dysfunction, and death. The aim of this study are as follows: (1) to evaluate the repairing efficiency of Necrostatin-1 (Nec-1), a cell death inhibitor, and Z-VAD-FMK, a pan-caspase inhibitor, on Al-induced neurobehavioral deficit and neuronal cell death, in order to evidence the cell death inducing ability of aluminum, and (2) to primarily explore the possibility of treating neuronal cell loss-related disease, such as Alzheimer's disease, with Nec-1 and Z-VAD in Al-induced dementia animal model. We found Nec-1 and Z-VAD-FMK alone or in combination could reduce aluminum-induced learning and memory impairment in mice. Pathohistological results indicated that Nec-1 and Z-VAD-FMK can decrease Al-induced neuronal death cell. In addition, some cell death-associated proteins in cell death signal pathway were inhibited by Nec-1 and Z-VAD-FMK in Al-exposed mice. In conclusions, Nec-1 and Z-VAD-FMK can repair the injury of learning and memory induced by aluminum in mice. Furthermore, Nec-1 was more obvious to repair the injury of learning and memory function compared with Z-VAD-FMK. Nec-1 and Z-VAD-FMK can repair the Al-induced morphological injury of cell and reduce the amounts of dead cell, and repairing effects were more significant at higher doses. The effect of Nec-1 was stronger than Z-VAD-FMK, though their mechanism was different. The combination of them had the strongest effect. Our study evidenced Al-induced neuronal necroptosis and apoptosis existing in animal model and suggested potential therapeutic effects of Nec-1 and Z-VAD-FMK on neuronal cell death in neurodegenerative diseases.

Tau Related Pathways as a Connecting Link between Epilepsy and Alzheimer's Disease

Emerging findings point toward an important interconnection between epilepsy and Alzheimer's disease (AD) pathogenesis. Patients with epilepsy (PWE) commonly exhibit cognitive impairment similar to AD patients, who in turn are at a higher risk of developing epilepsy compared to age-matched controls. To date, no disease-modifying treatment strategy is available for either epilepsy or AD, reflecting an immediate need for exploring common molecular targets, which can delineate a possible mechanistic link between epilepsy and AD. This review attempts to disentangle the interconnectivity between epilepsy and AD pathogenesis via the crucial contribution of Tau protein. Tau protein is a microtubule-associated protein (MAP) that has been implicated in the pathophysiology of both epilepsy and AD. Hyperphosphorylation of Tau contributes to the different forms of human epilepsy and inhibition of the same exerted seizure inhibitions and altered disease progression in a range of animal models. Moreover, Tau-protein-mediated therapy has demonstrated promising outcomes in experimental models of AD. In this review, we discuss how Tau-related mechanisms might present a link between the cause of seizures in epilepsy and cognitive disruption in AD. Untangling this interconnection might be instrumental in designing novel therapies that can minimize epileptic seizures and cognitive deficits in patients with epilepsy and AD.

Cognitive impairment of workers in a large-scale aluminium factory in China: a cross-sectional study

OBJECTIVES

To investigate the prevalence of mild cognitive impairment and the relationship with plasma aluminium among aluminium workers.

DESIGN

This was a cross-sectional case-control study in the SH Aluminium Factory, China.

SETTING

The university and affiliated hospital cooperated in the study.

PARTICIPANTS

There were 910 aluminium workers on duty, among whom 853 participated in our study. Participants, such as those with cerebral vascular disease, epilepsy, brain trauma, Parkinson's and mental diseases, aluminium-containing drug and mental drug use, and any family history of dementia in first-degree relatives were excluded.

PRIMARY AND SECONDARY OUTCOME MEASURES

Blood samples were collected, and plasma aluminium was measured by inductively coupled plasma-mass spectrometry. For each case, four age-matched controls were evaluated to determine the relationship between aluminium exposure and mild cognitive impairment. Conditional logistic regression was used to explore influential factors in mild cognitive impairment.

RESULTS

Among 910 workers, 93.74% participated in stage 1; 53 cases were finally diagnosed. The crude prevalence of mild cognitive impairment among aluminium workers on duty was 6.21%. There was a significant difference in plasma aluminium concentration between the two groups. In the multivariate analysis, we found that a higher level of plasma aluminium was associated with a high risk of cognitive impairment when compared with a lower aluminium level (AOR=2.24, 95% CI=1.17 to 4.26), and a high education level was a protective factor (AOR=0.36, 95% CI=0.18 to 0.70). No other factor was statistically significant.

CONCLUSIONS

Mild cognitive impairment is no longer a disease specific to elderly people. High plasma aluminium exposure might be associated with an increased risk of cognitive impairment, but a reduced risk was observed with a high education level. The cognitive function of aluminium workers on duty must be considered seriously.

Aluminum-Induced Electrophysiological Variation, Synaptic Plasticity Impairment, and Related Mechanism

Aluminum, an environmentally abundant non-redox trivalent cation, has long been reported to alter blood-brain barrier and gets deposited in different regions of the brain. Many reports strongly indicated that Al had an adverse impact on the central nervous system (CNS), particularly on cognitive ability. Until now, studies in animal models and cell cultures have revealed that Al exposure results in altered behavioral performance and memory damage. The present paper reviews the scientific literature linking aluminum and the impairment of electrophysiological variation and synaptic plasticity. The focus is on the changes of electrical excitability, voltage-operated ion channels, and synaptic plasticity induced by aluminum. A detailed mechanism of the role of aluminum in hippocampal LTP which is the most widely studied example of synaptic plasticity is highlighted. Evidence revealed that glutamate-NO-cGMP, PLC, Ca²⁺-CaM-CaMKII, MAPK, and Wnt pathway may be important in the mechanism underlying Al-induced long-term memory impairment. Further studies are required to establish the upstream activators and downstream effectors of these cascades and to answer how so many signaling cascades relate to the other signaling processes that might be involved in the Al-induced inhibition of synaptic plasticity.

RETRACTED: Osthole decreases tau protein phosphorylation via PI3K/AKT/GSK-3β signaling pathway in Alzheimer's disease

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of Editor-in-Chief. The corresponding author notified the journal of image duplications within the published article and requested a corrigendum. Specifically, the ‘APP/PS1’ plot in Figure 1A had appeared in a previous publication [Panaxadiol inhibits synaptic dysfunction in Alzheimer's disease and targets the Fyn protein in APP/PS1 mice and APP-SH-SY5Y cells, Life Sciences (DOI: 10.1016/j.lfs.2019.03.070)], as the ‘TG’ plot in Figure 2A. In addition, several image duplications were identified within the panels of Figure 2. These issues, and others relating to unusual characteristics within the western blots, have been detailed here: https://pubpeer.com/publications/892AF7E4913255548C1446247FC65A#. As per journal policy when considering corrigendum requests, the journal requested the authors to provide explanations and source data relating to these affected figures. Upon receipt of additional source data, the editorial team noticed additional suspected image duplications. In relation to Figure 1A, the corresponding author stated that “…we mistakenly used the same Morris Water Maze data”, and a corrected figure was submitted. In relation to the image duplications within Figure 2, the corresponding author stated “…we mistakenly used the copy-and-paste tool instead of a color adjustment tool” during image post-processing. The corresponding author was unable to produce original unaltered and uncropped western blot source data. The editorial team have concerns about the provenance of the data and therefore the Editor-in-Chief decided to retract the article.

Developmental perfluorooctane sulfonate exposure inhibits long-term potentiation by affecting AMPA receptor trafficking

Both animal study and epidemiological survey revealed the associations between defects of cognitive function and the developmental exposure to perfluorooctane sulfonate (PFOS), while the mechanism is not well known. The SD rats were exposed PFOS at 1.7, 5 and 15 mg/L by drinking water from gestation to the adulthood of the pups for evaluating the effects of PFOS exposure on long-term potentiation (LTP) and the role of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors trafficking. Whole-life exposure of PFOS beginning in utero to adulthood significantly inhibited the induction and expression of LTP, and the input/output curve (I/O) and paired-pulse facilitation (PPF) were moderately suppressed, suggesting that PFOS might affect the synaptic transmission and plasticity both in pre- and post-synaptic cells. Meanwhile, PFOS decreased the mRNA levels of AMPA receptor subunits GluA1 and GluA2, and the protein amounts in the membrane, with the total GluA1 and GluA2 protein amounts increased, indicating the internalization of AMPA receptors. Furthermore, tests in the primary hippocampal neurons also support the decreased mRNA levels of GluA1 and GluA2 induced by PFOS. After the pretreatment of AMPA antagonist (NBQX), PFOS decreased the expression of GluA1 and GluA2 and increased internal cellular calcium at much lower levels than that in the neurons without NBQX treatment. The results provide electrophysiological evidence for the impaired cognitive function induced by PFOS exposure and revealed the critical role of AMPA receptor involved.

Chlorogenic acid protects against aluminum toxicity via MAPK/Akt signaling pathway in murine RAW264.7 macrophages

Aluminum (Al), which may bring about damage to the macrophages, has been implicated in the development of immunological diseases. It has been reported that chlorogenic acid (CGA, 5‑caffeoylquinic acid, chemical formula: C₁₆H₁₈O₉) is a natural antioxidant and chelating agent with the capacity against Al (III)-induced biotoxicity. The present study was carried out to investigate whether CGA could reduce AlCl₃-induced cellular damage in RAW264.7 cells. After treatment with AlCl₃, the inhibition rate of viability and phagocytic activity of RAW264.7 cells was 54.5% and 27.6%, respectively. Administration of CGA significantly improved the integrity and phagocytic activity, and attenuated the accumulation of intracellular Al(III) level and oxidative stress in Al(III)-treated cells. Furthermore, CGA significantly inhibited Al(III)-induced increase of phospho-Jun N-terminal kinase (p-JNK), a pro-apoptotic Bcl-2 family protein (Bad), cytochrome c and decrease of extracellular regulated protein kinases (ERK1/2), protein kinase B (Akt) protein expressions. These results showed that CGA has a protective effect against Al(III)-induced cytotoxicity through mitogen-activated protein kinase (MAPK)/Akt-mediated caspase pathways in RAW264.7 cells.

Differential Expression Pattern of Exosome Long Non-Coding RNAs (lncRNAs) and MicroRNAs (miRNAs) in Vascular Endothelial Cells Under Heat Stroke

BACKGROUND Heat stroke is a life-threatening disease which is characterized by a high body temperature and multiple organ dysfunction syndrome. Vascular endothelial cell injury is a main feature of heat stroke. Little is known about the long noncoding RNA (lncRNA) and microRNA (miRNA) expression alternation in endothelial cell exosomes related to heat stroke. The aim of this study was to explore the changes of lncRNAs and miRNAs expression pattern in exosomes derived from vascular endothelial cells under heat stroke temperature conditions. MATERIAL AND METHODS Cultured medium exosomes from HUVECs (human vascular endothelial cells) either under normal temperature or heat stroke temperature conditions were harvested; then RNA was extracted and the lncRNAs and miRNAs were analyzed by high throughput sequencing. RESULTS Ten significantly upregulated and 10 downregulated lncRNAs were identified in exosomes derived from heat stroke temperature treated cells. Furthermore, GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analyses were used to evaluate the signaling pathway of differential expressions in lncRNAs. Finally, the interaction network of lncRNAs-miRNAs-mRNA was uncovered using ceRNA (competing endogenous RNA) principle via prediction software. CONCLUSIONS These results indicate that the identified lncRNAs and miRNAs in endothelial cell exosomes might serve as non-invasive biomarkers for heat stroke.

Physiological functions of non-apoptotic caspase activity in the nervous system

Caspases are cysteine proteases that play important and well-defined roles in apoptosis and inflammation. Increasing evidence point to alternative functions of caspases where restricted and localized caspase activation within neurons allows for a variety of non-apoptotic and non-inflammatory processes required for brain development and function. In this review, we highlight sublethal caspase functions in axon and dendrite pruning, neurite outgrowth and dendrite branches formation, as well as in long-term depression and synaptic plasticity. Importantly, as non-apoptotic activity of caspases is often confined in space and time in neurons, we also discuss the mechanisms that restrict caspase activity in order to maintain the neuronal networks in a healthy and functional state.

Hyperforin attenuates aluminum-induced Aβ production and Tau phosphorylation via regulating Akt/GSK-3β signaling pathway in PC12 cells

Aluminum (Al) is a neurotoxicant and cause β-amyloid (Aβ) peptides aggregation and tau hyperphosphorylation. Hyperforin (HF) is one of the major active constituents of the extracts of St. John's Wort (Hypericum perforatum), can treat Alzheimer's disease (AD) and other diseases involving peptide accumulation and cognition impairment. To determine the effects of HF on Al-induced Aβ formation and tau hyperphosphorylation, PC12 cells were cultured and treated with Al-malt (500μM) and/or HF (1μM). The results showed that HF treatment significantly attenuated Al-malt-induced Aβ_1-42 production by reducing the expressions of APP, BACE1 and PS1, while increasing the expressions of sAPPα, ADAM9/10/17, and tau phosphorylation in PC12 cells. In addition, HF treatment also increased phosphorylation of AKT (Ser473) and inhibited GSK-3β activity by increasing phosphorylation of GSK-3β (Ser9). These results indicated that HF may exert the protection via regulating the AKT/GSK-3β signaling to reduce Aβ production and tau phosphorylation in PC12 cells. Furthermore, these results could lead a possible therapeutics for the management of Al neurotoxicity.

Tannoid principles of Emblica officinalis attenuated aluminum chloride induced apoptosis by suppressing oxidative stress and tau pathology via Akt/GSK-3βsignaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Fruits of Phyllanthus emblica Linn. or Emblica officinalis Gaertn. (Phyllanthaceae) are used in Ayurveda, Siddha, Unani, Arabic, Tibetan and various other folk medicinal systems to promote intelligence and memory. Recent study from our lab indicated the neuroprotective effect of tannoids principles of Emblica officinalis (EoT) against memory loss caused by aluminum chloride (AlCl₃) intoxication through attenuating acetylcholine esterase activity and the expression of amyloid β protein biosynthesis related markers. However the molecular mechanism of EoT has not yet been fully elucidated.

AIM OF THE STUDY

The aim of the present study was to further investigate the neuroprotective mechanisms of EoT against AlCl₃-induced cognitive deficits, tau hyperphosphorylation, oxidative stress and apoptosis.

MATERIALS AND METHODS

Rats were treated with AlCl₃ for 60 days to induce biochemical and physiological abnormalities similar to AD patients. AD rats were treated with EoT (100mg/kg., bw. oral) for 60 days. For the examination of neuroprotective effect of EoT, behavior analysis, biochemical estimations and western blot were performed in the hippocampus and cortex of control, EoT treated and untreated AD rats.

RESULTS

Intraperitoneal injections of AlCl₃ (100mg/kg., b.w.) for 60 days enhanced the learning and memory deficits, levels of TBARS and diminished the levels of reduced glutathione and activities of enzymatic antioxidants as compared to control group. Moreover toxicity of AlCl₃ is accompanied by the enhanced expressions of Bax, caspases-3,-9, cytosolic cytochrome c (cyto c), and pTau along with diminished expressions of Bcl-2, mitochondrial cyto c, pGSK-3β and pAkt. Coadministration of EoT nullified the cognitive deficits, biochemical abnormalities and apoptosis induced by AlCl₃ treatment. Moreover EoT prevents tau hyperphosphorylation by targeting the GSK-3β/Akt signaling pathway.

CONCLUSIONS

This study confirms that EoT would be used as a potential drug candidate for AD and other tau pathology-related neuronal degenerative diseases.

Fenugreek Seed Powder Nullified Aluminium Chloride Induced Memory Loss, Biochemical Changes, Aβ Burden and Apoptosis via Regulating Akt/GSK3β Signaling Pathway

Alzheimer's disease (AD) is the most common form of dementia that mainly affects the cognitive functions of the aged populations. Trigonella foenum-graecum (L.) (fenugreek), a traditionally well utilized medicinal plant ubiquitously used as one of the main food additive worldwide, is known to have numerous beneficial health effects. Fenugreek seed extract could be able to inhibit the activity of acetylcholinesterase (AChE), a key enzyme involved in the pathogenesis of AD, and further shown to have anti-parkinsonic effect. The present study was aimed to explore the neuroprotective effect of fenugreek seed powder (FSP) against aluminium chloride (AlCl₃) induced experimental AD model. Administration of germinated FSP (2.5, 5 and 10% mixed with ground standard rat feed) protected AlCl₃ induced memory and learning impairments, Al overload, AChE hyperactivity, amyloid β (Aβ) burden and apoptosis via activating Akt/GSK3β pathway. Our present data could confirm the neuroprotective effect of fenugreek seeds. Further these results could lead a possible therapeutics for the management of neurodegenerative diseases including AD in future.

Natural and synthetic bioactive inhibitors of glycogen synthase kinase

Glycogen synthase kinase-3 is a multi-functional serine-threonine kinase and is involved in diverse physiological processes, including metabolism, cell cycle, and gene expression by regulating a wide variety of known substrates like glycogen synthase, tau-protein and β-catenin. Aberrant GSK-3 has been involved in diabetes, inflammation, cancer, Alzheimer's and bipolar disorder. In this review, we present an overview of the involvement of GSK-3 in various signalling pathways, resulting in a number of adverse pathologies due to its dysregulation. In addition, a detailed description of the small molecule inhibitors of GSK-3 with different mode of action discovered or specifically developed for GSK-3 has been presented. Furthermore, some clues for the future optimization of these promising molecules to develop specific drugs inhibiting GSK-3, for the treatment of associated disease conditions have also been discussed.