GDNF protects against aluminum-induced apoptosis in rabbits by upregulating Bcl-2 and Bcl-XL and inhibiting mitochondrial Bax translocation

Increased m6A modification of BDNF mRNA via FTO promotes neuronal apoptosis following aluminum-induced oxidative stress

N6-methyladenosine (m6A) RNA modification is a new epigenetic molecular mechanism involved in various biological or pathological processes. Exposure to aluminum (Al) has been considered to promote neuronal apoptosis resulting in cognitive dysfunction, yet whether m6A modification participates in the underlying mechanism remains largely unknown. Here, rats exposed to aluminum-maltolate [Al(mal)3] for 90 days showed impaired learning and memory function and elevated apoptosis, which were related to the increased m6A level and decreased fat mass and obesity-associated protein (FTO, an m6A demethylase) in the hippocampus. Accordingly, similar results presented in PC12 cells following Al(mal)3 treatment and FTO overexpression relieved the increased apoptosis and m6A level in vitro. Next, we identified brain-derived neurotrophic factor (BDNF) as the functional downstream target of FTO in a m6A-dependent manner. Furthermore, it was found that as the onset of aluminum neurotoxicity, oxidative stress may be the upstream regulator of FTO in aluminum-induced apoptosis. Taken together, these results suggest that increased m6A modification of BDNF mRNA via FTO promotes neuronal apoptosis following aluminum-induced oxidative stress.

Electroacupuncture blocked motor dysfunction and gut barrier damage by modulating intestinal NLRP3 inflammasome in MPTP-induced Parkinson's disease mice

Parkinson's disease (PD) is a neurodegenerative disorder commonly accompanied by gut dysfunction. EA has shown anti-inflammatory and neuroprotective effects. Here, we aim to explore whether EA can treat Parkinson's disease by restoring the intestinal barrier and modulating NLRP3 inflammasome. We applied 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to establish a PD mouse model and EA at the GV16, LR3, and ST36 for 12 consecutive days. The open-field test results indicated that EA alleviated depression and behavioral defects, upregulated the expressions of tyrosine hydroxylase (TH) and brain-derived neurotrophic factor (BDNF), and blocked the accumulation of α-synuclein (α-syn) in the midbrain. Moreover, EA blocked the damage to intestinal tissues of PD mice, indicative of suppressed NLRP3 inflammasome activation and increased gut barrier integrity. Notably, the antibiotic-treated mouse experiment validated that the gut microbiota was critical in alleviating PD dyskinesia and intestinal inflammation by EA. In conclusion, this study suggested that EA exhibited a protective effect against MPTP-induced PD by alleviating behavioral defects, reversing the block of motor dysfunction, and improving the gut barrier by modulating intestinal NLRP3 inflammasome. Above all, this study could provide novel insights into the pathogenesis and therapy of PD.

New bithiophene derivative attenuated Alzheimer's disease induced by aluminum in a rat model via antioxidant activity and restoration of neuronal and synaptic transmission

BACKGROUND

One of the hypotheses that leads to an increased incidence of Alzheimer's disease (AD) is the accumulation of aluminum in the brain's frontal cortex. The present study aimed to evaluate the therapeutic role of a novel bithiophene derivative at two doses against AlCl3-induced AD in a rat model.

METHODOLOGY

Adult male rats were divided into six groups, 18 rats each. Group 1: naïve animals, group 2: animals received a daily oral administration of bithiophene dissolved in DMSO (1 mg/kg) for 30 days every other day, groups 3-6: animals received a daily oral administration of AlCl3 (100 mg/kg/day) for 45 consecutive days. Groups 4 and 5 received an oral administration of low or high dose of the bithiophene (0.5 or 1 mg/kg, respectively). Group 6; Animals were treated with a daily oral dose of memantine (20 mg/kg) for 30 consecutive days.

MAIN FINDINGS

Al disturbed the antioxidant milieu, elevated the lipid peroxidation, and depleted the antioxidants. It also disturbed the synaptic neurotransmission by elevating the activities of acetylcholine esterase and monoamine oxidase resulting in the depletion of dopamine and serotonin and accumulation of glutamate and norepinephrine. Al also deteriorated the expression of genes involved in apoptosis and the production of amyloid-β plaques as well as phosphorylation of tau. The new bithiophene at the low dose reversed most of the previous deleterious effects of aluminum in the cerebral cortex and was in many instances superior to the reference drug; memantine.

CONCLUSION

Taking together, the bithiophene modulated the AD etiology through antioxidant activity, prevention of neuronal and synaptic loss, and probably mitigating the formation of amyloid-β plaques and phosphorylation of tau.

Aluminum neurotoxicity and autophagy: a mechanistic view

It is strongly believed that aluminum is one of the insalubrious agents because of its neurotoxicity effects and influences on amyloid β (Aβ) production and tau protein hyperphosphorylation following oxidative stress, as one of the initial events in neurotoxicity. The autophagy process plays a considerable role in neurons in preserving intracellular homeostasis and recycling organelles and proteins, especially Aβ and soluble tau. Thus, autophagy is suggested to ameliorate aluminum neurotoxicity effects, and dysfunction of this process can lead to an increase in detrimental proteins. However, the relationship between aluminum neurotoxicity and autophagy dysregulation in some dimensions remains unclear. In the present review, we want to give an overview of the autophagy roles in aluminum neurotoxicity and how dysregulation of autophagy can affect aluminum neurotoxicity.

Neurotrophins and Other Growth Factors in the Pathogenesis of Alzheimer’s Disease

The involvement of the changed expression/function of neurotrophic factors in the pathogenesis of neurodegenerative diseases, including Alzheimer’s disease (AD), has been suggested. AD is one of the age-related dementias, and is characterized by cognitive impairment with decreased memory function. Developing evidence demonstrates that decreased cell survival, synaptic dysfunction, and reduced neurogenesis are involved in the pathogenesis of AD. On the other hand, it is well known that neurotrophic factors, especially brain-derived neurotrophic factor (BDNF) and its high-affinity receptor TrkB, have multiple roles in the central nervous system (CNS), including neuronal maintenance, synaptic plasticity, and neurogenesis, which are closely linked to learning and memory function. Thus, many investigations regarding therapeutic approaches to AD, and/or the screening of novel drug candidates for its treatment, focus on upregulation of the BDNF/TrkB system. Furthermore, current studies also demonstrate that GDNF, IGF1, and bFGF, which play roles in neuroprotection, are associated with AD. In this review, we introduce data demonstrating close relationships between the pathogenesis of AD, neurotrophic factors, and drug candidates, including natural compounds that upregulate the BDNF-mediated neurotrophic system.

Neurotoxic effects of aluminium exposure as a potential risk factor for Alzheimer's disease

Aluminium is one of the most widely distributed elements of the Earth's crust. Its routine use has resulted in excessive human exposure and due to the potential neurotoxic effects has attained a huge interest in recent years. Despite its ubiquitous abundance, aluminium has no crucial biological functions in the human body. Oxidative stress and neuroinflammatory effects are attributed to its neurotoxic manifestations implicated in Alzheimer's disease. In this review, we have discussed the neuroinflammatory and neurodegenerative events in the brain induced by aluminium exposure. We have highlighted the neurotoxic events caused by aluminium, such as oxidative stress, apoptosis, inflammatory events, calcium dyshomeostasis, Aβ deposition, and neurofibrillary tangle formation in the brain. In addition, the protective measures needed for prevention of aluminium-induced neuronal dysregulations have also been discussed.

Therapeutic potential of glial cell line-derived neurotrophic factor and cell reprogramming for hippocampal-related neurological disorders

Hippocampus serves as a pivotal role in cognitive and emotional processes, as well as in the regulation of the hypothalamus-pituitary axis. It is known to undergo mild neurodegenerative changes during normal aging and severe atrophy in Alzheimer’s disease. Furthermore, dysregulation in the hippocampal function leads to epilepsy and mood disorders. In the first section, we summarized the most salient knowledge on the role of glial cell-line-derived neurotrophic factor and its receptors focused on aging, cognition and neurodegenerative and hippocampal-related neurological diseases mentioned above. In the second section, we reviewed the therapeutic approaches, particularly gene therapy, using glial cell-line-derived neurotrophic factor or its gene, as a key molecule in the development of neurological disorders. In the third section, we pointed at the potential of regenerative medicine, as an emerging and less explored strategy for the treatment of hippocampal disorders. We briefly reviewed the use of partial reprogramming to restore brain functions, non-neuronal cell reprogramming to generate neural stem cells, and neural progenitor cells as source-specific neuronal types to be implanted in animal models of specific neurodegenerative disorders.

High concentrations of aluminum in maternal serum and placental tissue are associated with increased risk for fetal neural tube defects

Aluminum (Al)¹ is ubiquitously present in the environment, and human exposure to Al is common. Al has been reported to be involved in various human diseases and adverse pregnancy outcomes, including neural tube defects (NTDs). This study aimed to examine the association between prenatal Al exposure and the risk for NTDs using Al concentrations in maternal serum and placental tissue. The subjects were recruited from six counties/cities in the Shanxi province of northern China from 2003 to 2016. Al concentrations in both types of specimens were assessed using inductively coupled plasma-mass spectrometry. In the maternal serum cohort (200 cases and 400 controls), compared to the lowest tertile concentration of Al, the highest Al tertile was associated with 2.42-fold (95% confidence interval, 1.23-4.87) increased risk after adjustment for confounding factors. In the placental tissue cohort (408 cases and 593 controls), the highest tertile of Al also tended to be associated with an elevated risk for NTDs [adjusted odds ratio, 1.60 (0.94-2.70)]. When analyzed by NTD subtypes, the highest Al tertile was associated with an increased risk for anencephaly in both cohorts after adjustment for confounders [odds ratio, 1.97 (1.15-3.48) in the maternal serum cohort; odds ratio, 4.75 (2.01-12.00) in the placental tissue cohort]. Taken together, using concentrations of Al in maternal serum and placental tissue as exposure markers, we found that prenatal exposure to higher levels of Al is a risk factor for fetal NTDs, especially for the anencephaly subtype.

JM-20 treatment prevents neuronal damage and memory impairment induced by aluminum chloride in rats

The number of people with dementia worldwide is estimated at 50 million by 2018 and continues to rise mainly due to increasing aging and population growth. Clinical impact of current interventions remains modest and all efforts aimed at the identification of new therapeutic approaches are therefore critical. Previously, we showed that JM-20, a dihydropyridine-benzodiazepine hybrid molecule, protected memory processes against scopolamine-induced cholinergic dysfunction. In order to gain further insight into the therapeutic potential of JM-20 on cognitive decline and Alzheimer's disease (AD) pathology, here we evaluated its neuroprotective effects after chronic aluminum chloride (AlCl3) administration to rats and assessed possible alterations in several types of episodic memory and associated pathological mechanisms. Oral administration of aluminum to rodents recapitulates several neuropathological alterations and cognitive impairment, being considered a convenient tool for testing the efficacy of new therapies for dementia. We used behavioral tasks to test spatial, emotional- associative and novel object recognition memory, as well as molecular, enzymatic and histological assays to evaluate selected biochemical parameters. Our study revealed that JM-20 prevented memory decline alongside the inhibition of AlCl3 -induced oxidative stress, increased AChE activity, TNF-α and pro-apoptotic proteins (like Bax, caspase-3, and 8) levels. JM-20 also protected against neuronal damage in the hippocampus and prefrontal cortex. Our findings expanded our understanding of the ability of JM-20 to preserve memory in rats under neurotoxic conditions and confirm its potential capacity to counteract cognitive impairment and etiological factors of AD by breaking the progression of key steps associated with neurodegeneration.

Therapeutic potential of neurotrophic factors in Alzheimer's Disease

INTRODUCTION

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia among the elderly population. AD is accompanied with the dysregulation of specific neurotrophic factors (NTFs) and their receptors, which plays a critical role in neuronal degeneration. NTFs are small proteins with therapeutic potential for human neurodegenerative diseases. These growth factors are categorized into four families: neurotrophins, neurokines, the glial cell line-derived NTF family of ligands, and the newly discovered cerebral dopamine NTF/mesencephalic astrocyte-derived NTF family. NTFs are capable of preventing cell death in degenerative conditions and can increase the neuronal growth and function in these disorders. Nevertheless, the adverse side effects of NTFs delivery and poor diffusion of these factors in the brain restrict the efficacy of NTFs therapy in clinical situations.

MATERIALS AND METHODS

In this review, we focus on the current advances in the use of NTFs to treat AD and summarize previous experimental and clinical studies for supporting the protective and therapeutic effects of these factors.

CONCLUSION

Based on reports, NTFs are considered as new and promising candidates for treating AD and AD-associated cognitive impairment.

Mechanisms of Metal-Induced Mitochondrial Dysfunction in Neurological Disorders

Metals are actively involved in multiple catalytic physiological activities. However, metal overload may result in neurotoxicity as it increases formation of reactive oxygen species (ROS) and elevates oxidative stress in the nervous system. Mitochondria are a key target of metal-induced toxicity, given their role in energy production. As the brain consumes a large amount of energy, mitochondrial dysfunction and the subsequent decrease in levels of ATP may significantly disrupt brain function, resulting in neuronal cell death and ensuing neurological disorders. Here, we address contemporary studies on metal-induced mitochondrial dysfunction and its impact on the nervous system.

Does aluminum exposure affect cognitive function? a comparative cross-sectional study

OBJECTIVES

This study assessed the cognitive function of aluminum-exposed participants from an alum mining zone, compared them with unexposed subjects, and aimed to elucidate the effect of aluminum exposure on cognition.

DESIGN

This was a comparative cross-sectional study. Univariate analyses were used to assess the differences between the aluminum-exposed and unexposed groups. Binary logistic regression models were applied to analyze the effect of aluminum exposure.

SETTING

The aluminum-exposed participants were included from an alum mining zone and the unexposed subjects were residents from another district without alum-mine-related factories.

PARTICIPANTS

We included 539 aluminum-exposed participants (254 men, 285 women) and 1720 unexposed participants (692 men, 1028 women).

RESULTS

The mean cognition score on Mini-Mental State Examination was 21.34 (± 6.81) for aluminum-exposed participants. The exposed group had 6.77 times (95% confidence interval, 5.09-9.00) more risk of cognitive impairment than the unexposed group, after adjusting for age, sex, and educational level. No statistically significant association was found between exposure duration and cognition.

CONCLUSIONS

This study demonstrated a significant association between aluminum exposure and lower cognitive function.

Geno-cytotoxicity and congenital malformations produced by relevant environmental concentrations of aluminum, diclofenac and their mixture on Cyprinus carpio. An interactions study

Several studies highlight the presence of aluminum and diclofenac in water bodies around the world and their ability to induce oxidative stress and a negative effect on biomolecules in several aquatic species. However, studies evaluating the toxic effect of mixtures of these contaminants are scarce. The objective of this work was to determine the genotoxic, cytotoxic and embryotoxic effect of the mixture of aluminum and diclofenac at environmentally relevant concentrations on Cyprinus carpio. Juveniles of Cyprinus carpio were exposed to 0.31 μg L^-1 of diclofenac, 24.45 mg L^-1 of aluminum, and a mixture of both contaminants at the same concentrations for 12, 24, 48, 72 and 96 h. After the exposure time the liver, gills and blood were extracted and the following biomarkers were evaluated: micronucleus frequency, comet assay, caspase activity and TUNEL test. On the other hand, Cyprinus carpio embryos were exposed to diclofenac (0.31 μg L^-1), aluminum (0.06 mg L^-1) and their mixture at the same concentrations and exposure time. Microscopic observation was performed to evaluate embryonic development at 12, 24, 48, 72 and 96 h. Diclofenac (0.31 μg L^-1) induces significant increases in micronucleus frequency with respect to control (p < 0.05), in all tissues. Aluminum (24.45 mg L^-1) significantly increases DNA damage index in liver and blood cells with respect to control (p < 0.05). All treatments increase caspases activity in all tissues with respect to control (p < 0.05). Diclofenac increases the percentage of TUNEL-positive cells in liver and blood; while aluminum and the mixture increases it significantly in gills and blood with respect to the control (p < 0.05). The mixture significantly delays embryonic development, while aluminum and the mixture significantly increase teratogenic index with respect to control (p < 0.05). In conclusion, exposure to environmental concentrations of aluminium, diclofenac and their mixture induces genotoxic damage, cell death by apoptosis and negative effects on the development of Cyprinus carpio and the toxic response is modified by the interaction of the xenobiotics.

Do serum GDNF levels correlate with severity of Alzheimer's disease?

INTRODUCTION

A growing body of evidence that glial cell line-derived neurotrophic factor (GDNF) levels are probably involved in pathogenesis and disease course of Alzheimer's disease (AD) suggested that its blood levels could potentially be used as a biomarker of AD. The aim of this study was to compare serum GDNF levels in patients with AD and age-matched controls.

METHODS

Serum concentrations of GDNF were compared in 25 AD patients and 25 healthy volunteers using a double-antibody sandwich enzyme-linked immunosorbent assay (ELISA). Severity of the disease in AD patients was assessed using Functional Assessment Staging (FAST). Cognitive assessment of the patients was done using the Mini-Mental State Examination (MMSE).

RESULTS

Mean GDNF levels were found to be 2.45 ± 0.93 ng/ml in AD patients and 4.61 ± 3.39 ng/ml in age-matched controls. There was a statistically significant difference in GDNF serum levels in patients with AD compared to age-matched controls (p = 0.001). Moreover, GDNF serum levels were significantly correlated with disease severity (p < 0.001) and cognitive impairment (p < 0.001).

CONCLUSION

This study showed that serum levels of GDNF are significantly decreased in AD patients in comparison with age-matched controls, thus suggesting a potential role of GDNF as a disease biomarker. However, a comprehensive study of changes in serum levels of multiple neurotrophic factors reflective of different neurobiological pathways in large-scale population studies is recommended.

Oroxyloside ameliorates acetaminophen-induced hepatotoxicity by inhibiting JNK related apoptosis and necroptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Oroxyloside is a natural flavonoid isolated from Scutellaria baicalensis Georgi (Lamiaceae) which is a Chinese herb widely used for liver diseases. However, its mechanisms on protecting against drug induced liver injury has not been investigated yet.

AIM OF THE STUDY

To investigate the protecting effects and the primary mechanisms of oroxyloside on acetaminophen (APAP)-induced liver injury.

MATERIALS AND METHODS

After a 12 h fasting period with free access to water, C57BL/6 mice were injected with APAP (300 mg/kg) intragastrically (i.g.) and 1 h later with oroxyloside (100 mg/kg, i.g.). When mice sacrificed, blood samples were collected from fundus venous plexus and liver tissues were collected. In addition, cells were incubated with 10 mM APAP alone and 10 mM APAP combined with 100 μM oroxyloside for 24 h. ELISA, TUNEL assay, qRT-PCR et al. were used to assess the effect of oroxyloside on ameliorating APAP-induced hepatotoxicity in vitro and in vivo. Western bolt and immunohistochemistry were used in the signaling pathway analysis.

RESULTS

Oroxyloside administration significantly decreased the accumulations of CYP2E1, CYP1A2, IL-6, IL-1β, ALT and AST induced by APAP in vivo. In addition, oroxyloside inhibited the APAP-induced JNK related apoptosis by enhancing the antioxidant defenses, reversing ER-stress and keeping the mito-balance of liver cells in vivo and in vitro. Furthermore, oroxyloside protected the liver cells from necroptosis by affecting JNK pathway.

CONCLUSION

Oroxyloside acted as a protective agent against APAP-induced liver injury through inhibiting JNK-related apoptosis and necroptosis.

Citrus Auraptene Induces Glial Cell Line-Derived Neurotrophic Factor in C6 Cells

We previously demonstrated that auraptene (AUR), a natural coumarin derived from citrus plants, exerts anti-inflammatory effects in the brain, resulting in neuroprotection in some mouse models of brain disorders. The present study showed that treatment with AUR significantly increased the release of glial cell line-derived neurotrophic factor (GDNF), in a dose- and time-dependent manner, by rat C6 glioma cells, which release was associated with increased expression of GDNF mRNA. These results suggest that AUR acted as a neuroprotective agent in the brain via not only its anti-inflammatory action but also its induction of neurotrophic factor. We also showed that (1) the AUR-induced GDNF production was inhibited by U0126, a specific inhibitor of mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) 1/2, and by H89, a specific inhibitor of protein kinase A (PKA); and (2) AUR induced the phosphorylation of cAMP response element-binding protein (CREB), a transcription factor located within the nucleus. These results suggest that AUR-stimulated gdnf gene expression was up-regulated through the PKA/ERK/CREB pathway in C6 cells.

Bacopa phospholipid complex retrieves aluminum maltolate complex-induced oxidative stress and apoptotic alterations in the brain regions of albino rat

Highly bioavailable plant phospholipid complex that can reverse aluminum maltolate (AlM)-induced toxicity is not yet reported. Hence, the present study was planned to investigate the impact of oxidative stress and apoptotic changes provoked by Al and ameliorative role of Bacopa phospholipid complex (BPC) in albino rats. The levels of antioxidant enzymes such as superoxide dismutase (SOD), catalase activity (CAT), glutathione peroxidase (GPx), and thiobarbituric acid-reactive substance (TBA-RS) were measured and immunohistochemistry analysis of apoptotic markers, Bax and Bcl-2, was done from the four brain regions such as the hippocampus, cerebral cortex, cerebellum, and medulla oblongata. The levels of antioxidant enzymes and apoptotic markers that were decreased on AlM induction showed a significant increase in their levels, almost as observed in the control, when treated with BPC and Bm. Our results indicate that both BPC and Bm showed a therapeutic effect against AlM toxicity; however, it was found that the therapeutic potential of BPC was more pronounced than Bm against AlM-induced neurotoxicity.

Metal Toxicity Links to Alzheimer's Disease and Neuroinflammation

As the median age of the population increases, the number of individuals with Alzheimer's disease (AD) and the associated socio-economic burden are predicted to worsen. While aging and inherent genetic predisposition play major roles in the onset of AD, lifestyle, physical fitness, medical condition, and social environment have emerged as relevant disease modifiers. These environmental risk factors can play a key role in accelerating or decelerating disease onset and progression. Among known environmental risk factors, chronic exposure to various metals has become more common among the public as the aggressive pace of anthropogenic activities releases excess amount of metals into the environment. As a result, we are exposed not only to essential metals, such as iron, copper, zinc and manganese, but also to toxic metals including lead, aluminum, and cadmium, which perturb metal homeostasis at the cellular and organismal levels. Herein, we review how these metals affect brain physiology and immunity, as well as their roles in the accumulation of toxic AD proteinaceous species (i.e., β-amyloid and tau). We also discuss studies that validate the disruption of immune-related pathways as an important mechanism of toxicity by which metals can contribute to AD. Our goal is to increase the awareness of metals as players in the onset and progression of AD.

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.

Fas- and Mitochondria-Mediated Signaling Pathway Involved in Osteoblast Apoptosis Induced by AlCl3

Aluminum (Al) is known to induce apoptosis of osteoblasts (OBs). However, the mechanism is not yet established. To investigate the apoptotic mechanism of OBs induced by aluminum trichloride (AlCl₃), the primary OBs from the craniums of fetal Wistar rats were exposed to 0 mg/mL (control group, CG), 0.06 mg/mL (low-dose group, LG), 0.12 mg/mL (mid-dose group, MG), and 0.24 mg/mL (high-dose group, HG) AlCl₃ for 24 h, respectively. We observed that AlCl₃ induced OB apoptosis with the appearance of apoptotic morphology and increase of apoptosis rate. Additionally, AlCl₃ treatment activated mitochondrial-mediated signaling pathway, accompanied by mitochondrial membrane potential (ΔΨm) depolarization, release of cytochrome c from the mitochondria to the cytoplasm, as well as survival signal-related factor caspase-9 and caspase-3 activation. AlCl₃ exposure also activated Fas/Fas ligand signaling pathway, presented as Fas, Fas ligand, and Fas-associated death domain expression enhancement and caspase-8 activation, as well as the hydrolysis of Bid to truncated Bid, suggesting that the Fas-mediated signaling pathway might aggravate mitochondria-mediated OB apoptosis through hydrolyzing Bid. Furthermore, AlCl₃ exposure inhibited Bcl-2 protein expression and increased the expressions of Bax, Bak, and Bim in varying degrees. These results indicated that AlCl₃ exposure induced OB apoptosis through activating Fas- and mitochondria-mediated signaling pathway and disrupted B-cell lymphoma-2 family proteins.

DBA-induced caspase-3-dependent apoptosis occurs through mitochondrial translocation of cyt-c in the rat hippocampus

Dibromoacetic acid (DBA), a by-product of disinfection, develops in drinking water during chlorination or ozonation processes. Water intake is the main source of DBA exposure in humans, which is potentially neurotoxic. The present study investigated the neurotoxic effects of DBA by assessing the behavioral and biochemical characteristics of Sprague Dawley rats intragastrically treated with DBA at concentrations of 20, 50 and 125 mg kg^-1 body weight for 28 consecutive days. The results indicated that animal weight gain and food consumption were not significantly affected by DBA. However, shuttle box tests showed increases in mistake frequency and reaction latency between the control and high-dose group. We found significant changes in hippocampal neurons by histomorphological observation. Additionally, biochemical analysis indicated enhanced production of reactive oxygen species (ROS) resulting in disruption of cellular antioxidant defense systems including decreased mitochondrial superoxide dismutase (SOD) activity and release of cytochrome c (cyt-c) from mitochondria into the cytosol, which can induce neuronal apoptosis. Furthermore, the increase of cyt-c in the cytosol enhanced caspase-3 and caspase-9 activity, which was confirmed by poly ADP-ribose polymerase-1 (PARP-1) cleavage to its signature fragment of 85 kDa and decreased levels of protein kinase C-δ (PKC-δ) in the hippocampus. Meanwhile, DBA treatment caused differential modulation of apoptosis-associated proteins and mRNAs for phosphorylated apoptosis signal regulating kinase 1 (p-ASK-1), phosphorylated c-jun N-terminal kinase (p-JNK), cyt-c, Bax, Bcl-2, caspase-9 and cleaved caspase-3 accompanied by DNA damage. Taken together, these data indicate that DBA may induce neurotoxicity via caspase-3-dependent apoptosis involving mitochondrial translocation of cyt-c in the rat hippocampus.

High Concentration of Glial Cell Line-Derived Neurotrophic Factor Protects Primary Astrocytes from Apoptosis

Background: Studies have shown that astrocytes play an important role in a variety of biological processes, so damage to astrocytes can cause a series of related diseases. Glial cell line-derived neurotrophic factor (GDNF) has always been considered a protective factor for dopamine neurons. However, it remains unclear whether GDNF has a protective effect on glial cells, especially astrocytes. In this study, we put forward the hypothesis that a high concentration of GDNF in the microenvironment of astrocytes exerts an inhibitory effect on the apoptosis of astrocytes by DNA-damaging reagents. Methods: We isolated, purified, and identified primary astrocytes from neonate rats. Astrocytes were exposed to mitoxantrone (MTN, a DNA-damaging compound) for 24 h. The effects of MTN on astrocytes were tested by Hoechst 33342 staining, CCK-8 assay, and flow cytometry assay. One of the concentrations of MTN was applied to construct an apoptotic model of astrocytes. The astrocytes were then treated with GDNF together with a selected concentration of MTN for 24 h. The cell viability, cell nucleus morphology, and apoptosis ratio of the cells was assessed by Hoechst 33342 staining, CCK-8 assay, and flow cytometry assay, respectively. RNA sequencing (RNA-Seq), quantitative PCR analysis, and KEGG pathway mapping were performed to examine the genes involved in the procedure. Finally, Western blot analysis was applied to confirm the expression levels of the proteins of interest. Results: Hoechst 33342 staining revealed a one-tenth change in the percentage of Hoechst-positive cells after the addition of 500 ng/mL GDNF combined with 1,000 nM MTN for 24 h. The viability of the cells treated the same as described above was 1.4-fold that of the control group. Flow cytometry assays indicated that the apoptotic rates were 17.67, 8.67, and 4.34% for 0, 200, and 500 ng/mL GDNF, respectively. Birc2, Birc3, and Gadd45b were linked to the antiapoptotic process induced by GDNF in astrocytes. Western blot analysis confirmed the elevated expression of Birc2 and Gadd45b. Conclusions: Our studies revealed that GDNF has a noticeable antiapoptotic effect on gene-injured astrocytes. This may provide critical clues for the treatment of a series of diseases in which damaged astrocytes are involved.

Exposure to Aluminum in Daily Life and Alzheimer's Disease

Aluminum is the third most abundant element on the earth's crust and has been considered a constituent of rather inert minerals. Therefore, it has often been regarded as not having a significant health hazard. Consequently, aluminum-containing agents have been used in processing, packaging, and storage of food products and also in the treatment of drinking water as flocculants. Recently, acid rain due to environmental pollution has transported more aluminum-containing minerals into residential drinking water resources. It is therefore not surprising that aluminum burden in the human body has increased. Research data showed that aluminum is not as safe as was previously thought and that aluminum may contribute to the initial advancement of Alzheimer's disease. Aluminum-mediated neurodegeneration resulting in cognitive dysfunction has been associated with amyloidβ (Aβ) deposition, formation of intraneuronal neurofibrillary tangles (NFTs), and apoptotic neuronal death characterized histopathologically in AD. The origin of Alzheimer's disease is generally not known; its development is likely triggered by unknown environmental factors. Although it is inconsistent with the link between human exposure to aluminum in everyday life and its contribution to Alzheimer's disease, a growing body of evidence points to aluminum as being one such significant influence.

Effect of PGE2-EPs pathway on primary cultured rat neuron injury caused by aluminum

To observe the characteristic changes of PGE₂-EP_s pathway and divergent functions of PGE₂ receptor subtypes on neuronal injury. The primary cultured rat hippocampus neuron injury model was established via aluminum maltolate (100 μM). The aluminum-overload neurons were treated with the agonists of EP1 (17-phenyl trinor Prostaglandin E2 ethyl amide), EP2 (Butaprost), EP3 (Sulprostone) and EP4 (CAY10598) and antagonists of EP1 (SC-19220), EP2 (AH6809) and EP4 (L-161982) at different concentrations, respectively. The neuronal viability, lactate dehydrogenase leakage rate and PGE2 content were detected by MTT assay, lactate dehydrogenase assay kit and enzyme-linked immunosorbent assay, respectively. The mRNA and protein expressions of mPGES-1 and EPs were determined by RT-PCR and western blot, respectively. The pathomorphology was identified by hematoxylin-eosin staining. In the model group, neuronal viability significantly decreased, while lactate dehydrogenase leakage rate and PGE2 content increased. The mPGES-1, EP1, EP2 and EP4 mRNA expression, and the mPGES-1, EP1 and EP2 protein expression increased, while EP₃ level decreased. EP3 agonist exerted protective function in neuronal viability and lactate dehydrogenase leakage rate, while EP1 agonist, EP2 and EP4 antagonist exerted an opposite effect. In conclusion, aluminum-overload caused an imbalance of PGE₂-EP_1-4 pathway and activation of EP receptor may provide a viable therapeutic target in neuronal injury.

Metal ions influx is a double edged sword for the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a common form of dementia in aged people, which is defined by two pathological characteristics: β-amyloid protein (Aβ) deposition and tau hyperphosphorylation. Although the mechanisms of AD development are still being debated, a series of evidence supports the idea that metals, such as copper, iron, zinc, magnesium and aluminium, are involved in the pathogenesis of the disease. In particular, the processes of Aβ deposition in senile plaques (SP) and the inclusion of phosphorylated tau in neurofibrillary tangles (NFTs) are markedly influenced by alterations in the homeostasis of the aforementioned metal ions. Moreover, the mechanisms of oxidative stress, synaptic plasticity, neurotoxicity, autophagy and apoptosis mediate the effects of metal ions-induced the aggregation state of Aβ and phosphorylated tau on AD development. More importantly, imbalance of these mechanisms finally caused cognitive decline in different experiment models. Collectively, reconstructing the signaling network that regulates AD progression by metal ions may provide novel insights for developing chelators specific for metal ions to combat AD.

Activated Microglia Induce Bone Marrow Mesenchymal Stem Cells to Produce Glial Cell-Derived Neurotrophic Factor and Protect Neurons Against Oxygen-Glucose Deprivation Injury

In this study, we investigated interactions among microglia (MG), bone marrow mesenchymal stem cells (BMSCs) and neurons in cerebral ischemia and the potential mechanisms using an in vitro oxygen-glucose deprivation (OGD) model. Rat BMSCs were incubated with conditioned medium (CM) from in vitro cultures of OGD-activated rat MG and murine BV2 MG cells. Effects of glial cell-derived neurotrophic factor (GDNF) on rat neuron viability, apoptosis, lactate dehydrogenase (LDH) leakage and mitochondrial membrane potential (MMP) were analyzed in this model. OGD-activated MG promoted GDNF production by BMSCs (P < 0.01). Tumor necrosis factor-α (TNFα), but not interleukin-6 (IL6) or interleukin 1β (IL1β), promoted GDNF production by BMSCs (P < 0.001). GDNF or CM pre-treated BMSCs elevated neuronal viability and suppressed apoptosis (P < 0.05 or P < 0.01); these effects were inhibited by the RET antibody. GDNF activated MEK/ERK and phosphoinositide-3-kinase (PI3K)/AKT signaling but not JNK/c-JUN. Furthermore, GDNF upregulated B cell lymphoma 2 (BCL2) and heat shock 60 kDa protein 1 (HSP60) levels, suppressed LDH leakage, and promoted MMP. Thus, activated MG produce TNFα to stimulate GDNF production by BMSCs, which prevents and repairs OGD-induced neuronal injury, possibly via regulating MEK/ERK and PI3K/AKT signaling. These findings will facilitate the prevention and treatment of neuronal injury by cerebral ischemia.

Pumping the Brakes: Neurotrophic Factors for the Prevention of Cognitive Impairment and Dementia after Traumatic Brain Injury

Traumatic brain injury (TBI) is the leading cause of disability and death worldwide, affecting as many as 54,000,000-60,000,000 people annually. TBI is associated with significant impairments in brain function, impacting cognitive, emotional, behavioral, and physical functioning. Although much previous research has focused on the impairment immediately following injury, TBI may have much longer-lasting consequences, including neuropsychiatric disorders and cognitive impairment. TBI, even mild brain injury, has also been recognized as a significant risk factor for the later development of dementia and Alzheimer's disease. Although the link between TBI and dementia is currently unknown, several proposed mechanisms have been put forward, including alterations in glucose metabolism, excitotoxicity, calcium influx, mitochondrial dysfunction, oxidative stress, and neuroinflammation. A treatment for the devastating long-term consequences of TBI is desperately needed. Unfortunately, however, no such treatment is currently available, making this a major area of unmet medical need. Increasing the level of neurotrophic factor expression in key brain areas may be one potential therapeutic strategy. Of the neurotrophic factors, granulocyte-colony stimulating factor (G-CSF) may be particularly effective for preventing the emergence of long-term complications of TBI, including dementia, because of its ability to reduce apoptosis, stimulate neurogenesis, and increase neuroplasticity.

Potential therapeutic action of natural products from traditional Chinese medicine on Alzheimer's disease animal models targeting neurotrophic factors

Alzheimer's disease (AD) is a neurodegenerative disorder in which the death of brain cells leads to memory loss and cognitive decline. To reduce the death rate and improve the biological activity of neurocytes, neurotrophic factors (NTFs) exhibit therapeutic effect on AD. However, therapeutic application of exogenous NTFs in treatment of AD is largely limited due to short half-life, poor stability, etc. Various extracts of traditional Chinese medicine (TCM) have been shown to exhibit therapeutic effects on AD, and some of these effects are associated with regulation on the expression of nerve growth factor, brain-derived neurotrophic factor (BDNF), and glial cell line-derived neurotrophic factor (GDNF) and their associated receptors. This article reviews the progress on promotion of Panax ginseng, Rehmannia glutinosa Libosch., Epimedium, Polygala tenuifolia Willd, and seven other TCMs on secretion of NTFs during AD, with a view to preparation development and clinical application of these TCMs on AD.

Multifaceted effects of aluminium in neurodegenerative diseases: A review

Aluminium (Al) is the most common metal and widely distributed in our environment. Al was first isolated as an element in 1827, and its use began only after 1886. Al is widely used for industrial applications and consumer products. Apart from these it is also used in cooking utensils and in pharmacological agents, including antacids and antiperspirants from which the element usually enters into the human body. Evidence for the neurotoxicity of Al is described in various studies, but still the exact mechanism of Al toxicity is not known. However, the evidence suggests that the Al can potentiate oxidative stress and inflammatory events and finally leads to cell death. Al is considered as a well-established neurotoxin and have a link between the exposure and development of neurodegenerative diseases, including Amyotrophic Lateral Sclerosis (ALS), Alzheimer's disease (AD), dementia, Gulf war syndrome and Parkinsonism. Here, we review the detailed possible pathogenesis of Al neurotoxicity. This review summarizes Al induced events likewise oxidative stress, cell mediated toxicity, apoptosis, inflammatory events in the brain, glutamate toxicity, effects on calcium homeostasis, gene expression and Al induced Neurofibrillary tangle (NFT) formation. Apart from these we also discussed animal models that are commonly used for Al induced neurotoxicity and neurodegeneration studies. These models help to find out a better way to treat and prevent the progression in Al induced neurodegenerative diseases.

The involvement of BDNF, NGF and GDNF in aging and Alzheimer's disease

Aging is a normal physiological process accompanied by cognitive decline. This aging process has been the primary risk factor for development of aging-related diseases such as Alzheimer's disease (AD). Cognitive deficit is related to alterations of neurotrophic factors level such as brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF) and glial cell-derived neurotrophic factor (GDNF). These strong relationship between aging and AD is important to investigate the time which they overlap, as well as, the pathophysiological mechanism in each event. Considering that aging and AD are related to cognitive impairment, here we discuss the involving these neurotrophic factors in the aging process and AD.

Dietary flavonoid fisetin regulates aluminium chloride-induced neuronal apoptosis in cortex and hippocampus of mice brain

Dietary flavonoids have been suggested to promote brain health by protecting brain parenchymal cells. Recently, understanding the possible mechanism underlying neuroprotective efficacy of flavonoids is of great interest. Given that fisetin exerts neuroprotection, we have examined the mechanisms underlying fisetin in regulating Aβ aggregation and neuronal apoptosis induced by aluminium chloride (AlCl3) administration in vivo. Male Swiss albino mice were induced orally with AlCl3 (200 mg/kg. b.wt./day/8 weeks). Fisetin (15 mg/Kg. b.wt. orally) was administered for 4 weeks before AlCl3-induction and administered simultaneously for 8 weeks during AlCl3-induction. We found aggregation of Amyloid beta (Aβ 40-42), elevated expressions of Apoptosis stimulating kinase (ASK-1), p-JNK (c-Jun N-terminal Kinase), p53, cytochrome c, caspases-9 and 3, with altered Bax/Bcl-2 ratio in favour of apoptosis in cortex and hippocampus of AlCl3-administered mice. Furthermore, TUNEL and fluoro-jade C staining demonstrate neurodegeneration in cortex and hippocampus. Notably, treatment with fisetin significantly (P<0.05) reduced Aβ aggregation, ASK-1, p-JNK, p53, cytochrome c, caspase-9 and 3 protein expressions and modulated Bax/Bcl-2 ratio. TUNEL-positive and fluoro-jade C stained cells were also significantly reduced upon fisetin treatment. We have identified the involvement of fisetin in regulating ASK-1 and p-JNK as possible mediator of Aβ aggregation and subsequent neuronal apoptosis during AlCl3-induced neurodegeneration. These findings define the possibility that fisetin may slow or prevent neurodegneration and can be utilised as neuroprotective agent against Alzheimer's and Parkinson's disease.

Gas1 Knockdown Increases the Neuroprotective Effect of Glial Cell-Derived Neurotrophic Factor Against Glutamate-Induced Cell Injury in Human SH-SY5Y Neuroblastoma Cells

Growth arrest-specific 1 (Gas1) protein acts as an inhibitor of cell growth and a mediator of cell death in nervous system during development and is also re-expressed in adult neurons during excitotoxic insult. Due to its structural similarity to the glial cell-derived neurotrophic factor family receptors α (GFRα), Gas1 is likely to interfere with the neuroprotective effect of GDNF. In the present study, we investigated the expression profile of Gas1 during glutamate insults in human SH-SY5Y neuroblastoma cells as well as the influence of Gas1 inhibition on the protective effect of GDNF against glutamate-induced cell injury. Our data showed that Gas1 expression was significantly increased with the treatment of glutamate in SH-SY5Y cells. The silencing of Gas1 by small interfering RNA promoted the protective effect of GDNF against glutamate-induced cytotoxicity as well as cell apoptosis, which effect was likely mediated through activating Akt/PI3 K-dependent cell survival signaling pathway and inhibiting mitochondrial-dependent cell apoptosis signaling pathway via Bad dephosphorylation blockade. In summary, this study showed the synergistic effect of Gas1 inhibition and GDNF against glutamate-induced cell injury in human SH-SY5Y neuroblastoma cells, which information might significantly contribute to better understanding the function of Gas1 in neuronal cells and form the basis of the therapeutic development of GDNF in treating human neurodegenerative diseases in the future.

Sesamol, a lipid lowering agent, ameliorates aluminium chloride induced behavioral and biochemical alterations in rats

Background:

Sesame oil from the seeds of Sesamum indicum Linn. (Pedaliaceae) has been used traditionally in Indian medical practice of Ayurveda in the treatment of central nervous system disorders and insomnia. A few published reports favor the anti-dementia effect of sesamol (SML), an active constituent of sesame oil.

Objective:

Thus, the present study was aimed to explore the anti-dementia effect and possible mechanism (s) of SML in aluminium chloride (AlCl₃)-induced cognitive dysfunction model in rodents with special emphasis on memory centers viz., hippocampus and frontal cortex.

Methods:

Male Wistar rats were exposed to AlCl₃ (175 mg/kg p.o.) for 60 days. SML (10 and 20 mg/kg) and rivastigmine (1 mg/kg) were administered orally 45 min before administration of AlCl₃ for 60 days. Spatial memory was assessed using Morris water maze test. After 60 days of treatment animals were sacrificed, hippocampus and frontal cortex were collected and analyzed for acetylcholinesterase (AChE) activity, tumor necrosis factor (TNF-α) level, antioxidant enzymes (Glutathione, catalase), lipid peroxidation, and nitrite level. The circulating triglycerides, total cholesterol, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) levels were also analyzed.

Results:

SML significantly prevented behavioral impairments in aluminium-exposed rats. Treatment with SML reversed the increased cholesterol, triglycerides and LDL while raised the HDL levels. SML significantly corrected the effect of AlCl₃ on AChE activity. Further, SML reversed the elevated nitric oxide, TNF-α and reduced antioxidant enzymes in hippocampus and frontal cortex.

Conclusion:

The present study suggests the neuro-protection by SML against cognitive dysfunction induced by environmental toxin (AlCl₃) in hippocampus and frontal cortex.

Modulatory role of simvastatin against aluminium chloride-induced behavioural and biochemical changes in rats

Objectives. Aluminium, a neurotoxic agent in humans, has been implicated in the pathogenesis of neurodegenerative disorders. In this study, we examined the behavioral and biochemical effects of aluminium in rats with special emphasis on memory centres, namely, hippocampus and frontal cortex. Further, the effect of simvastatin treatment on aluminium intoxication was evaluated. Methods. Rats were exposed to aluminium chloride (AlCl₃) for 60 days. Simvastatin (10 mg/kg/p.o.) and rivastigmine (1 mg/kg/p.o.) were administered daily prior to AlCl₃. Behavioral parameters were assessed using Morris water maze test and actophotometer followed by biochemical investigations, namely, acetylcholinesterase (AChE) activity, TNF-α level, antioxidant enzymes (GSH, catalase), lipid peroxidation, and nitrite level in hippocampus and frontal cortex. Triglycerides, total cholesterol, LDL, and HDL levels in serum were also determined. Key Findings. Simvastatin treatment improved cognitive function and locomotor activity in rats. Simvastatin reversed hyperlipidemia and significantly rectified the deleterious effect of AlCl₃ on AChE activity. Further, in hippocampus and frontal cortex, aluminium-induced elevation in nitrite and TNF-α and reduction in antioxidant enzymes were inhibited by simvastatin. Conclusion. To conclude, the present study suggests that simvastatin per se protects the neurons in hippocampus and frontal cortex from AlCl₃, an environmental toxin.

Neuroprotective effects of GDNF-expressing human amniotic fluid cells

Brain injury continues to be one of the leading causes of disability worldwide. Despite decades of research, there is currently no pharmacologically effective treatment for preventing neuronal loss and repairing the brain. As a result, novel therapeutic approaches, such as cell-based therapies, are being actively pursued to repair tissue damage and restore neurological function after injury. In this study, we examined the neuroprotective potential of amniotic fluid (AF) single cell clones, engineered to secrete glial cell derived neurotrophic factor (AF-GDNF), both in vitro and in a surgically induced model of brain injury. Our results show that pre-treatment with GDNF significantly increases cell survival in cultures of AF cells or cortical neurons exposed to hydrogen peroxide. Since improving the efficacy of cell transplantation depends on enhanced graft cell survival, we investigated whether AF-GDNF cells seeded on polyglycolic acid (PGA) scaffolds could enhance graft survival following implantation into the lesion cavity. Encouragingly, the AF-GDNF cells survived longer than control AF cells in serum-free conditions and continued to secrete GDNF both in vitro and following implantation into the injured motor cortex. AF-GDNF implantation in the acute period following injury was sufficient to activate the MAPK/ERK signaling pathway in host neural cells in the peri-lesion area, potentially boosting endogenous neuroprotective pathways. These results were complemented with promising trends in beam walk tasks in AF-GDNF/PGA animals during the 7 day timeframe. Further investigation is required to determine whether significant behavioural improvement can be achieved at a longer timeframe.

Systematic review of potential health risks posed by pharmaceutical, occupational and consumer exposures to metallic and nanoscale aluminum, aluminum oxides, aluminum hydroxide and its soluble salts

Abstract Aluminum (Al) is a ubiquitous substance encountered both naturally (as the third most abundant element) and intentionally (used in water, foods, pharmaceuticals, and vaccines); it is also present in ambient and occupational airborne particulates. Existing data underscore the importance of Al physical and chemical forms in relation to its uptake, accumulation, and systemic bioavailability. The present review represents a systematic examination of the peer-reviewed literature on the adverse health effects of Al materials published since a previous critical evaluation compiled by Krewski et al. (2007) . Challenges encountered in carrying out the present review reflected the experimental use of different physical and chemical Al forms, different routes of administration, and different target organs in relation to the magnitude, frequency, and duration of exposure. Wide variations in diet can result in Al intakes that are often higher than the World Health Organization provisional tolerable weekly intake (PTWI), which is based on studies with Al citrate. Comparing daily dietary Al exposures on the basis of "total Al"assumes that gastrointestinal bioavailability for all dietary Al forms is equivalent to that for Al citrate, an approach that requires validation. Current occupational exposure limits (OELs) for identical Al substances vary as much as 15-fold. The toxicity of different Al forms depends in large measure on their physical behavior and relative solubility in water. The toxicity of soluble Al forms depends upon the delivered dose of Al(+3) to target tissues. Trivalent Al reacts with water to produce bidentate superoxide coordination spheres [Al(O2)(H2O4)(+2) and Al(H2O)6 (+3)] that after complexation with O2(•-), generate Al superoxides [Al(O2(•))](H2O5)](+2). Semireduced AlO2(•) radicals deplete mitochondrial Fe and promote generation of H2O2, O2 (•-) and OH(•). Thus, it is the Al(+3)-induced formation of oxygen radicals that accounts for the oxidative damage that leads to intrinsic apoptosis. In contrast, the toxicity of the insoluble Al oxides depends primarily on their behavior as particulates. Aluminum has been held responsible for human morbidity and mortality, but there is no consistent and convincing evidence to associate the Al found in food and drinking water at the doses and chemical forms presently consumed by people living in North America and Western Europe with increased risk for Alzheimer's disease (AD). Neither is there clear evidence to show use of Al-containing underarm antiperspirants or cosmetics increases the risk of AD or breast cancer. Metallic Al, its oxides, and common Al salts have not been shown to be either genotoxic or carcinogenic. Aluminum exposures during neonatal and pediatric parenteral nutrition (PN) can impair bone mineralization and delay neurological development. Adverse effects to vaccines with Al adjuvants have occurred; however, recent controlled trials found that the immunologic response to certain vaccines with Al adjuvants was no greater, and in some cases less than, that after identical vaccination without Al adjuvants. The scientific literature on the adverse health effects of Al is extensive. Health risk assessments for Al must take into account individual co-factors (e.g., age, renal function, diet, gastric pH). Conclusions from the current review point to the need for refinement of the PTWI, reduction of Al contamination in PN solutions, justification for routine addition of Al to vaccines, and harmonization of OELs for Al substances.

Lenti-GDNF gene therapy protects against Alzheimer's disease-like neuropathology in 3xTg-AD mice and MC65 cells

AIMS

Glial cell-derived neurotrophic factor (GDNF) is emerging as a potent neurotrophic factor with therapeutic potential against a range of neurodegenerative conditions including Alzheimer's disease (AD). We assayed the effects of GDNF treatment in AD experimental models through gene-therapy procedures.

METHODS

Recombinant lentiviral vectors were used to overexpress GDNF gene in hippocampal astrocytes of 3xTg-AD mice in vivo, and also in the MC65 human neuroblastoma that conditionally overexpresses the 99-residue carboxyl-terminal (C99) fragment of the amyloid precursor protein.

RESULTS

After 6 months of overexpressing GDNF, 10-month-old 3xTg-AD mice showed preserved learning and memory, while their counterparts transduced with a green fluorescent protein vector showed cognitive loss. GDNF therapy did not significantly reduce amyloid and tau pathology, but rather, induced a potent upregulation of brain-derived neurotrophic factor that may act in concert with GDNF to protect neurons from atrophy and degeneration. MC65 cells overexpressing GDNF showed an abolishment of oxidative stress and cell death that was at least partially mediated by a reduced presence of intracellular C99 and derived amyloid β oligomers.

CONCLUSIONS

GDNF induced neuroprotection in the AD experimental models used. Lentiviral vectors engineered to overexpress GDNF showed to be safe and effective, both as a potential gene therapy and as a tool to uncover the mechanisms of GDNF neuroprotection, including cross talk between astrocytes and neurons in the injured brain.

Effects of CDNF on 6-OHDA-induced apoptosis in PC12 cells via modulation of Bcl-2/Bax and caspase-3 activation

Progressive dopamine neuron degeneration in the substantia nigra pars compacta is considered the most prominent pathological characteristic of Parkinson's disease (PD). Currently, there is no cure, but only the capability to relieve the symptoms of PD. The conserved dopamine neurotrophic factor (CDNF) protects and rescues dopamine neurons in vivo. However, the molecular function of CDNF in PD remains unclear. In present study, we investigated the role and intrinsic mechanism of CDNF in preventing and reversing rat pheochromocytoma (PC12) cells from apoptosis induced by 6-hydroxydopamine (6-OHDA). We demonstrate that 6-OHDA induces cell death in PC12 cells, but that CDNF attenuates this effect in a dose-dependent manner. Further study shows that upregulation of the Bcl-2/Bax ratio and downregulation of caspase-3 activity are observed in a dose-dependent manner upon pre-treatment or post-treatment with CDNF, suggesting a pathway of regulation of apoptosis by CDNF. These data demonstrate that CDNF prevents the apoptosis of PC12 cells induced by 6-OHDA by modulating Bcl-2/Bax and caspase-3 activation.

Oxidative stress and mitochondrial dysfunction in aluminium neurotoxicity and its amelioration: a review

Aluminium is light weight and toxic metal present ubiquitously on earth which has gained considerable attention due to its neurotoxic effects. The widespread use of products made from or containing aluminium is ensuring its presence in our body. There is prolonged retention of a fraction of aluminium that enters the brain, suggesting its potential for accumulation with repeated exposures. There is no known biological role for aluminium within the body but adverse physiological effects of this metal have been observed in mammals. The generation of oxidative stress may be attributed to its toxic consequences in animals and humans. The oxidative stress has been implicated in pathogenesis of various neurodegenerative conditions including Alzheimer's disease and Parkinson's disease. Though it remains unclear whether oxidative stress is a major cause or merely a consequence of cellular dysfunction associated with neurodegenerative diseases, an accumulating body of evidence implicates that impaired mitochondrial energy production and increased mitochondrial oxidative damage is associated with the pathogenesis of neurodegenerative disorders. Being involved in the production of reactive oxygen species, aluminium may impair mitochondrial bioenergetics and may lead to the generation of oxidative stress. In this review, we have discussed the oxidative stress and mitochondrial dysfunctions occurring in Al neurotoxicity. In addition, the ameliorative measures undertaken in aluminium induced oxidative stress and mitochondrial dysfunctions have also been highlighted.

Epidural application of spinal instrumentation particulate wear debris: a comprehensive evaluation of neurotoxicity using an in vivo animal model

Object

The introduction and utilization of motion-preserving implant systems for spinal reconstruction served as the impetus for this basic scientific investigation. The effect of unintended wear particulate debris resulting from micromotion at spinal implant interconnections and bearing surfaces remains a clinical concern. Using an in vivo rabbit model, the current study quantified the neural and systemic histopathological responses following epidural application of 11 different types of medical-grade particulate wear debris produced from spinal instrumentation.

Methods

A total of 120 New Zealand White rabbits were equally randomized into 12 groups based on implant treatment: 1) sham (control), 2) stainless steel, 3) titanium alloy, 4) cobalt chromium alloy, 5) ultra–high molecular weight polyethylene (UHMWPe), 6) ceramic, 7) polytetrafluoroethylene, 8) polycarbonate urethane, 9) silicone, 10) polyethylene terephthalate, 11) polyester, and 12) polyetheretherketone. The surgical procedure consisted of a midline posterior approach followed by resection of the L-6 spinous process and L5–6 ligamentum flavum, permitting interlaminar exposure of the dural sac. Four milligrams of the appropriate treatment material (Groups 2–12) was then implanted onto the dura in a dry, sterile format. All particles (average size range 0.1–50 μm in diameter) were verified to be endotoxin free prior to implantation. Five animals from each treatment group were sacrificed at 3 months and 5 were sacrificed at 6 months postoperatively. Postmortem analysis included epidural cultures and histopathological assessment of local and systemic tissue samples. Immunocytochemical analysis of the spinal cord and overlying epidural fibrosis quantified the extent of proinflammatory cytokines (tumor necrosis factor–α, tumor necrosis factor–β, interleukin [IL]–1α, IL-1β, and IL-6) and activated macrophages.

Results

Epidural cultures were negative for nearly all cases, and there was no evidence of particulate debris or significant histopathological changes in the systemic tissues. Gross histopathological examination demonstrated increased levels of epidural fibrosis in the experimental treatment groups compared with the control group. Histopathological evaluation of the epidural fibrous tissues showed evidence of a histiocytic reaction containing phagocytized inert particles and foci of local inflammatory reactions. At 3 months, immunohistochemical examination of the spinal cord and epidural tissues demonstrated upregulation of IL-6 in the groups in which metallic and UHMWPe debris were implanted (p < 0.05), while macrophage activity levels were greatest in the stainless-steel and UHMWPe groups (p < 0.05). By 6 months, the levels of activated cytokines and macrophages in nearly all experimental cases were downregulated and not significantly different from those of the operative controls (p > 0.05). The spinal cord had no evidence of lesions or neuropathology. However, multiple treatments in the metallic groups exhibited a mild, chronic macrophage response to particulate debris, which had diffused intrathecally.

Conclusions

Epidural application of spinal instrumentation particulate wear debris elicits a chronic histiocytic reaction localized primarily within the epidural fibrosis. Particles have the capacity to diffuse intrathecally, eliciting a transient upregulation in macrophage/cytokine activity response within the epidural fibrosis. Overall, based on the time periods evaluated, there was no evidence of an acute neural or systemic histopathological response to the materials included in the current project.

''70th Birthday Professor Riederer'' induction of glial cell line-derived and brain-derived neurotrophic factors by rasagiline and (-)deprenyl: a way to a disease-modifying therapy?

Neuroprotection has been proposed in neurodegenerative disorders, such as Parkinson's and Alzheimer's diseases, to delay or halt disease progression or reverse neuronal deterioration. The inhibitors of type B monoamine oxidase (MAO), rasagiline and (-)deprenyl, prevent neuronal loss in cellular and animal models of neurodegenerative disorders by intervening in the death signal pathway in mitochondria. In addition, rasagiline and (-)deprenyl increase the expression of anti-apoptotic Bcl-2 protein family and neurotrophic factors. Neurotrophic factors, especially glial cell line-derived neurotrophic factor (GDNF) and brain-derived derived neurotrophic factor (BDNF), are required not only for growth and maintenance of developing neurons, but also for function and plasticity of distinct population of adult neurons. GDNF and BDNF have been reported to reduce Parkinson and Alzheimer's diseases, respectively. GDNF protects the nigra-striatal dopamine neurons in animal models of Parkinson's disease, and its administration has been tried as a disease-modifying therapy for parkinsonian patients. However, the results of clinical trials have not been fully conclusive and more practical ways to enhance GDNF levels in the targeted neurons are essentially required for future clinical application. Rasagiline and (-)deprenyl induced preferentially GDNF and BDNF in cellular and non-human primate experiments, and (-)deprenyl increased BDNF level in the cerebrospinal fluid of parkinsonian patients. In this paper, we review the induction of GDNF and BDNF by these MAO inhibitors as a strategy of neuroprotective therapy. The induction of prosurvival genes is discussed in relation to a possible disease-modifying therapy with MAO inhibitors in neurodegenerative disorders.

Current challenges for the advancement of neural stem cell biology and transplantation research

Transplantation of neural stem cells (NSC) is hoped to become a promising primary or secondary therapy for the treatment of various neurodegenerative disorders of the central nervous system (CNS), as demonstrated by multiple pre-clinical animal studies in which functional recovery has already been demonstrated. However, for NSC therapy to be successful, the first challenge will be to define a transplantable cell population. In the first part of this review, we will briefly discuss the main features of ex vivo culture and characterisation of NSC. Next, NSC grafting itself may not only result in the regeneration of lost tissue, but more importantly has the potential to improve functional outcome through many bystander mechanisms. In the second part of this review, we will briefly discuss several pre-clinical studies that contributed to a better understanding of the therapeutic potential of NSC grafts in vivo. However, while many pre-clinical animal studies mainly report on the clinical benefit of NSC grafting, little is known about the actual in vivo fate of grafted NSC. Therefore, the third part of this review will focus on non-invasive imaging techniques for monitoring cellular grafts in the brain under in vivo conditions. Finally, as NSC transplantation research has evolved during the past decade, it has become clear that the host micro-environment itself, either in healthy or injured condition, is an important player in defining success of NSC grafting. The final part of this review will focus on the host environmental influence on survival, migration and differentiation of grafted NSC.

Link between Aluminum and the Pathogenesis of Alzheimer's Disease: The Integration of the Aluminum and Amyloid Cascade Hypotheses

Whilst being environmentally abundant, aluminum is not essential for life. On the contrary, aluminum is a widely recognized neurotoxin that inhibits more than 200 biologically important functions and causes various adverse effects in plants, animals, and humans. The relationship between aluminum exposure and neurodegenerative diseases, including dialysis encephalopathy, amyotrophic lateral sclerosis and Parkinsonism dementia in the Kii Peninsula and Guam, and Alzheimer's disease (AD) has been suggested. In particular, the link between aluminum and Alzheimer's disease has been the subject of scientific debate for several decades. However, the complex characteristics of aluminum bioavailability make it difficult to evaluate its toxicity and therefore, the relationship remains to be established. Mounting evidence has suggested that significance of oligomerization of β-amyloid protein and neurotoxicity in the molecular mechanism of AD pathogenesis. Aluminum may play crucial roles as a cross-linker in β-amyloid oligomerization. Here, we review the detailed characteristics of aluminum neurotoxicity based on our own studies and the recent literatures. Our aim is to revisit the link between aluminum and AD and to integrate aluminum and amyloid cascade hypotheses in the context of β-amyloid oligomerization and the interactions with other metals.

Oral silicon supplementation: an effective therapy for preventing oral aluminum absorption and retention in mammals

Silicon is an essential element for some lower forms of life. However, it is not generally considered an essential nutrient for mammals and the mechanisms underlying its potential essentiality remain partially unknown. In recent years, a possible association between the aluminum and silicon levels in drinking water and Alzheimer's disease (AD) has been suggested. It has been reported that silicon might have a protective effect for limiting oral aluminum absorption. This review is focused primarily on the potential role of silicon in preventing oral aluminum absorption and retention in mammals. The results of a number of studies suggest that dietary silicon supplementation could be of therapeutic value for preventing chronic aluminum accumulation in the brain, and hence, be a potential therapy for AD. However, it must be noted that controversy remains about whether aluminum accumulation in the brain is a cause or a consequence of AD. It is suggested that further investigation of this issue is warranted.