Cross-talk between oxidative stress and modifications of cholinergic and glutaminergic receptors in the pathogenesis of Alzheimer's disease

An Expanded Narrative Review of Neurotransmitters on Alzheimer's Disease: The Role of Therapeutic Interventions on Neurotransmission

Alzheimer's disease (AD) is a progressive neurodegenerative disease. The accumulation of amyloid-β (Aβ) plaques and tau neurofibrillary tangles are the key players responsible for the pathogenesis of the disease. The accumulation of Aβ plaques and tau affect the balance in chemical neurotransmitters in the brain. Thus, the current review examined the role of neurotransmitters in the pathogenesis of Alzheimer's disease and discusses the alterations in the neurochemical activity and cross talk with their receptors and transporters. In the presence of Aβ plaques and neurofibrillary tangles, changes may occur in the expression of neuronal receptors which in turn triggers excessive release of glutamate into the synaptic cleft contributing to cell death and neuronal damage. The GABAergic system may also be affected by AD pathology in a similar way. In addition, decreased receptors in the cholinergic system and dysfunction in the dopamine neurotransmission of AD pathology may also contribute to the damage to cognitive function. Moreover, the presence of deficiencies in noradrenergic neurons within the locus coeruleus in AD suggests that noradrenergic stimulation could be useful in addressing its pathophysiology. The regulation of melatonin, known for its effectiveness in enhancing cognitive function and preventing Aβ accumulation, along with the involvement of the serotonergic system and histaminergic system in cognition and memory, becomes remarkable for promoting neurotransmission in AD. Additionally, nitric oxide and adenosine-based therapeutic approaches play a protective role in AD by preventing neuroinflammation. Overall, neurotransmitter-based therapeutic strategies emerge as pivotal for addressing neurotransmitter homeostasis and neurotransmission in the context of AD. This review discussed the potential for neurotransmitter-based drugs to be effective in slowing and correcting the neurodegenerative processes in AD by targeting the neurochemical imbalance in the brain. Therefore, neurotransmitter-based drugs could serve as a future therapeutic strategy to tackle AD.

The Role of Excitotoxicity, Oxidative Stress and Bioenergetics Disruption in the Neuropathology of Nonketotic Hyperglycinemia

Nonketotic hyperglycinemia (NKH) is an inherited disorder of amino acid metabolism biochemically characterized by the accumulation of glycine (Gly) predominantly in the brain. Affected patients usually manifest with neurological symptoms including hypotonia, seizures, epilepsy, lethargy, and coma, the pathophysiology of which is still not completely understood. Treatment is limited and based on lowering Gly levels aiming to reduce overstimulation of N-methyl-D-aspartate (NMDA) receptors. Mounting in vitro and in vivo animal and human evidence have recently suggested that excitotoxicity, oxidative stress, and bioenergetics disruption induced by Gly are relevant mechanisms involved in the neuropathology of NKH. This brief review gives emphasis to the deleterious effects of Gly in the brain of patients and animal models of NKH that may offer perspectives for the development of novel adjuvant treatments for this disorder.

Saffron (Crocus sativus L.) extract attenuates chronic scopolamine-induced cognitive impairment, amyloid beta, and neurofibrillary tangles accumulation in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Crocus sativus L. known as saffron, is a popular food condiment with a high aroma, deep colour, and long and thick threads (stigmas) cultivated in Iran, Morocco, Spain, Italy, China, Japan, France, Turkey, and India. In 'Ayurveda', saffron is acknowledged for its immunostimulant, aphrodisiac, cardiotonic, liver tonic, nervine tonic, carminative, diaphoretic, diuretic, emmenagogue, galactagogue, febrifuge, sedative, relaxant, and anxiolytic activities. The renowned Persian physician and philosopher, Avicenna, delineated saffron as an antidepressant, hypnotic, anti-inflammatory, hepatoprotective, bronchodilator, and aphrodisiac in his book, the Canon of Medicine. Within traditional Iranian Medicine (TIM), saffron is characterized as a mood elevator and a rejuvenator for the body and senses. Further, the ethnopharmacological evidence indicates that saffron has shown an effect against neurodegenerative disorders namely, dementia, Alzheimer's, and Parkinson's with its bioactive constituents i.e., carotenoids and apocarotenoids.

AIM

The present study aimed to investigate the potential of standardized (Kashmir Saffron, India) Crocus sativus extract (CSE) in chronic scopolamine-induced cognitive impairment, amyloid beta (Aβ) plaque, and neurofibrillary tangles (NFT) accumulation in rat brains by targeting AChE inhibition and scopolamine mechanistic effect.

METHODS

The experimental animals were divided into six groups: group 1: normal control, group 2: scopolamine, group 3,4 and 5 rivastigmine tartrate, CSE (p.o. 10 mg/kg, 15 mg/kg, and 20 mg/kg) respectively. Each treatment group received scopolamine after 20 min of dosing, till 4 weeks. The effects of different treatments on learning, acquisition, and reversal memory were performed using a Morris water maze test. In addition to behavioral assessments, biochemical parameters such as AChE, IL-6, and antioxidants were measured in isolated brains. Histological observations were also conducted to assess the presence of Aβ plaques and NFT. Furthermore, molecular docking was performed to explore the potential AChE inhibitory activity of the bioactive constituents of standardized CSE.

RESULTS

Scopolamine produces memory impairment, and its chronic administration forms Aβ plaque and NFT in rat brains. Supplementation with CSE in presence of scopolamine has shown remarkable effects on behavioural activity, special acquisition, and reversal memory. The CSE has also shown promising effects on AChE inhibition and antioxidant activity. The results of the docking study also indicate that trans-crocetin, i.e., a biologically active metabolite of Crocins, has strong AChE inhibitory activity, supported by an in vivo animal experiment.

CONCLUSION

Supplementation with CSE significantly attenuates the formation of Aβ plaque and NFT in the hippocampus at a dose of 20 mg/kg per day. In addition, CSE also counters scopolamine-induced neuroinflammation.

Neuroprotection by Polyherbal Medicine Divya-Medha-Vati Against Scopolamine-Induced Cognitive Impairment Through Modulation of Oxidative Stress, Acetylcholine Activity, and Cell Signaling

Alzheimer disease is associated with cognitive impairments and neuronal damages. In this study, Scopolamine, a model drug used for the generation of Alzheimer-like symptoms induced cognitive dysfunction in C57BL/6 mice. It also elevated acetylcholine esterase (AcHE) activity, and reduced antioxidant (superoxide dismutase and catalase) activity in cortex tissue. Scop reduced neuronal density and increased pyknotic neurons in hippocampus tissue. In mouse neuroblastoma (Neuro2a) cells, Scop triggered a dose-dependent loss of cell viability and neurite outgrowth reduction. Scop-treated Neuro2a cells showed oxidative stress and reduction in mRNA expression for brain-derived neurotrophic factor (BDNF), nerve growth factor-1 (NGF-1), and Synapsin-1 (SYN-1) genes. Mice treated with Divya-Medha-Vati (DMV), an Ayurvedic polyherbal medicine showed protection against Scop-induced cognitive impairment (Morris Water Maze Escape Latency, and Elevated Plus Maze Transfer Latency). DMV protected against Scop-induced AcHE activity, and loss of antioxidant activities in the mice brain cortex while sustaining neuronal density in the hippocampus region. In the Neuro2a cells, DMV reduced Scop-induced loss of cell viability and neurite outgrowth loss. DMV protected the cells against induction of oxidative stress and promoted mRNA expression of BDNF, NGF-1, and SYN-1 genes. Phytochemical profiling of DMV showed the presence of Withanolide A, Withanolide B, Bacopaside II, Jujubogenin, Apigenin, Gallic acid, Caffeic acid, and Quercetin that are associated with antioxidant and neurostimulatory activities. In conclusion, the study showed that Divya-Medha-Vati was capable of promoting neuronal health and inhibiting Alzheimer-like cognitive dysfunction through enhanced antioxidant activities and modulation of neuronal activities.

Ethanol extract of Evodia lepta Merr. ameliorates cognitive impairment through inhibiting NLRP3 inflammasome in scopolamine-treated mice

Evodia lepta Merr. (Evodia lepta) is a well-known traditional Chinese medicine, which has been widely used in herbal tea. We previously reported that the coumarin compounds from the root of Evodia lepta exhibited neuroprotective effects. However, whether Evodia lepta could inhibit NLRP3 inflammasome in dementia was still unknown. In this study, the components of the Evodia lepta extract were identified by HPLC-Q-TOF HRMS. We employed a scopolamine-treated mouse model. Evodia lepta extract (10 or 20 mg/kg) and donepezil were treated by gavage once a day for 14 consecutive days. Following the behavioral tests, oxidative stress levels were measured. Then, Western blot and immunofluorescence analysis were used to evaluate the expressions of NLRP3 inflammasome. 14 major components of the Evodia lepta extract were identified by HPLC-Q-TOF HRMS. The results of Morris water maze, object recognition task and open field test indicated that Evodia lepta extract could ameliorate cognitive impairment in scopolamine-treated mice. Evodia lepta extract improved cholinergic system. Moreover, Evodia lepta extract improved the expressions of PSD95 and BDNF. Evodia lepta extract suppressed neuronal oxidative stress and apoptosis. In addition, Evodia lepta extract inhibited NLRP3 inflammasome in the hippocampus of scopolamine-treated mice. Evodia lepta extract could protect against cognitive impairment by inhibiting NLRP3 inflammasome in scopolamine-treated mice.

A proton-inhibited DEG/ENaC ion channel maintains neuronal ionstasis and promotes neuronal survival under stress

The nervous system participates in the initiation and modulation of systemic stress. Ionstasis is of utmost importance for neuronal function. Imbalance in neuronal sodium homeostasis is associated with pathologies of the nervous system. However, the effects of stress on neuronal Na⁺ homeostasis, excitability, and survival remain unclear. We report that the DEG/ENaC family member DEL-4 assembles into a proton-inactivated sodium channel. DEL-4 operates at the neuronal membrane and synapse to modulate Caenorhabditis elegans locomotion. Heat stress and starvation alter DEL-4 expression, which in turn alters the expression and activity of key stress-response transcription factors and triggers appropriate motor adaptations. Similar to heat stress and starvation, DEL-4 deficiency causes hyperpolarization of dopaminergic neurons and affects neurotransmission. Using humanized models of neurodegenerative diseases in C. elegans, we showed that DEL-4 promotes neuronal survival. Our findings provide insights into the molecular mechanisms by which sodium channels promote neuronal function and adaptation under stress.

Patient-specific variants of NFU1/NFU-1 disrupt cholinergic signaling in a model of multiple mitochondrial dysfunctions syndrome 1

Neuromuscular dysfunction is a common feature of mitochondrial diseases and frequently presents as ataxia, spasticity and/or dystonia, all of which can severely impact individuals with mitochondrial diseases. Dystonia is one of the most common symptoms of multiple mitochondrial dysfunctions syndrome 1 (MMDS1), a disease associated with mutations in the causative gene (NFU1) that impair iron-sulfur cluster biogenesis. We have generated Caenorhabditis elegans strains that recreated patient-specific point variants in the C. elegans ortholog (nfu-1) that result in allele-specific dysfunction. Each of these mutants, Gly147Arg and Gly166Cys, have altered acetylcholine signaling at neuromuscular junctions, but opposite effects on activity and motility. We found that the Gly147Arg variant was hypersensitive to acetylcholine and that knockdown of acetylcholine release rescued nearly all neuromuscular phenotypes of this variant. In contrast, we found that the Gly166Cys variant caused predominantly postsynaptic acetylcholine hypersensitivity due to an unclear mechanism. These results are important for understanding the neuromuscular conditions of MMDS1 patients and potential avenues for therapeutic intervention.

Yuk-Gunja-Tang attenuates neuronal death and memory impairment via ERK/CREB/BDNF signaling in the hippocampi of experimental Alzheimer’s disease model

Yuk-Gunja-Tang (YG) is the Korean traditional medicine in East Asia for gastrointestinal disorders. In the present study, we determined the protective effects of YG on glutamate-induced cytotoxicity in HT22 hippocampal neuronal cells and mice with scopolamine-induced memory impairment. In vitro assessments were performed using a cell viability assay, flow cytometry, and Western blotting, while in vivo assessments were performed in C57BL/6 mice administered with YG for 7 days and injected with scopolamine (1 mg/kg) for 7 days. We assessed the memory function using the Y-maze, novel object recognition, and passive avoidance tests. Protein expression analyses and histological analyses were performed using hippocampal tissues. YG treatment significantly restored cell viability against glutamate-induced apoptosis. It significantly suppressed glutamate-induced reactive oxygen species accumulation and mitochondrial dysfunction. It also increased Bcl-2 protein expression and decreased HO-1 protein expression. It activated the extracellular signal-regulated kinase/cAMP response element binding protein (ERK/CREB) signaling pathway and increased the expression of brain-derived neurotrophic factor (BDNF) under excitotoxic conditions. In the scopolamine-injected mice, YG ameliorated memory impairment in the Y-maze, novel object recognition, and passive avoidance tests; restored dysfunction in the acetylcholine, acetylcholinesterase expression levels; reduced neuronal damage in Nissl staining; and increased BDNF and phosphorylated ERK and CREB levels in Western blotting and immunofluorescence staining. Thus, YG exerted neuroprotective effects by activating ERK/CREB/BDNF signaling in the hippocampus, indicating its potential cognition-enhancing effects, especially in Alzheimer’s disease.

Jatamansinol from Nardostachys jatamansi Ameliorates Tau-Induced Neurotoxicity in Drosophila Alzheimer's Disease Model

Nardostachys jatamansi has long been used to prepare Medhya Rasayana in traditional Indian Ayurveda medicine to treat neurological disorders and enhance memory. Jatamansinol from the N. jatamansi against Alzheimer's disease (AD) showed that it could be a multitargeted drug against AD. Drosophila is an ideal model organism for studying a progressive age-related neurodegenerative disease such as AD since its neuronal organizations and functioning are highly similar to that of humans. The current study investigates the neuroprotective properties of jatamansinol against Tau-induced neurotoxicity in the AD Drosophila model. Results indicate jatamansinol is not an antifeedant for larva and adult Drosophila. Lifespan, locomotor activity, learning and memory, Tau protein expression level, eye degeneration, oxidative stress level, and cholinesterase activities were analyzed in 10, 20, and 30-day-old control (wild type), and tauopathy flies reared on jatamansinol supplemented food or regular food without jatamansinol supplementation. Jatamansinol treatment significantly extends the lifespan, improves locomotor activity, enhances learning and memory, and reduces Tau protein levels in tauopathy flies. It boosts the antioxidant enzyme activities, prevents Tau-induced oxidative stress, ameliorates eye degeneration, and inhibits cholinesterase activities in Tau-induced AD model. This study provides the first evidence that jatamansinol protects against Tau's neurotoxic effect in the AD Drosophila model, and it can be a potential therapeutic drug candidate for AD.

The Brilliance of the Zebrafish Model: Perception on Behavior and Alzheimer’s Disease

Alzheimer’s disease (AD) has become increasingly prevalent in the elderly population across the world. It’s pathophysiological markers such as overproduction along with the accumulation of amyloid beta (Aβ) plaques and neurofibrillary tangles (NFT) are posing a serious challenge to novel drug development processes. A model which simulates the human neurodegenerative mechanism will be beneficial for rapid screening of potential drug candidates. Due to the comparable neurological network with humans, zebrafish has emerged as a promising AD model. This model has been thoroughly validated through research in aspects of neuronal pathways analogous to the human brain. The cholinergic, glutamatergic, and GABAergic pathways, which play a role in the manifested behavior of the zebrafish, are well defined. There are several behavioral models in both adult zebrafish and larvae to establish various aspects of cognitive impairment including spatial memory, associative memory, anxiety, and other such features that are manifested in AD. The zebrafish model eliminates the shortcomings of previously recognized mammalian models, in terms of expense, extensive assessment durations, and the complexity of imaging the brain to test the efficacy of therapeutic interventions. This review highlights the various models that analyze the changes in the normal behavioral patterns of the zebrafish when exposed to AD inducing agents. The mechanistic pathway adopted by drugs and novel therapeutic strategies can be explored via these behavioral models and their efficacy to slow the progression of AD can be evaluated.

Obesity-Related Brain Cholinergic System Impairment in High-Fat-Diet-Fed Rats

A link between obesity and cerebral health is receiving growing recognition. Here, we investigate in the frontal cortex and hippocampus the potential involvement of cholinergic markers in brain alterations previously reported in rats with obesity induced by diet (DIO) after long-term exposure (17 weeks) to a high-fat diet (HFD) in comparison with animals fed with a standard diet (CHOW). The obesity developed after 5 weeks of HFD. Bodyweight, systolic blood pressure, glycemia, and insulin levels were increased in DIO rats compared to the CHOW group. Measurements of malondialdehyde (MDA) provided lipid peroxidation in HFD-fed rats. Western blot and immunohistochemical techniques were performed. Our results showed a higher expression of choline acetyltransferase (ChAT) and vesicular acetylcholine transporter (VAChT) in obese rats but not the VAChT expression in the frontal cortex after 17 weeks of HFD. Furthermore, the acetylcholinesterase (AChE) enzyme was downregulated in HFD both in the frontal cortex and hippocampus. In the brain regions analyzed, it was reported a modulation of certain cholinergic receptors expressed pre- and post-synaptically (alpha7 nicotinic receptor and muscarinic receptor subtype 1). Collectively, these findings point out precise changes of cholinergic markers that can be targeted to prevent cerebral injuries related to obesity.

Actions of Klotho on hippocampal neuronal cells

Klotho gene was originally recognized as a putative aging-suppressor and its prominent age-regulating effects are mostly attributed to the modulation of mineral homeostasis in the kidney. However, recent studies link alterations in hippocampal Klotho expression with cognitive impairment and neurodegenerative diseases. This suggests that hippocampal neurons require Klotho for health and proper functionality. Klotho protects against neuronal dysfunction and regulates several intracellular signaling pathways including oxidative stress response, inflammation, DNA damage, autophagy, endoplasmic reticulum stress response, and multiple types of cell death. Specifically, this chapter covers the current knowledge as to how Klotho protein affects the hippocampal neuronal cells, with special attention paid to underlying molecular mechanisms, and thus influences hippocampal development, hippocampal-dependent cognition, behavior, and motor skills as well as mediates neurodegenerative processes.

Targeted UHPLC-ESI-MS/MS Analysis of Selected Neurotransmitters, Tryptophan and Its Metabolite Kynurenine in Tau Transgenic Rat Brain Tissue: A Pivotal Study

Neurotransmitters (NT) are widely distributed in the central nervous system. These molecules are important for many physiological processes and the function of the immune system. Imbalance of NT are linked to numerous neurological disorders and diseases, including tauopathies. Here, a targeted approach based on on-line combination of ultra-high performance liquid chromatography with tandem mass spectrometry was validated and applied to the quantitative analysis of nine NT (acetylcholine, choline, aspartic acid, asparagine, glutamic acid, glutamine, pyroglutamate, γ-aminobutyric acid, N-acetyl-L-aspartic acid), tryptophan and its metabolite kynurenine in brain tissue samples of a rat model for tauopathy. The applied analytical method was characterized by excellent validation parameters for all analytes, such as limits of detection in the range of 0.01–1.70 µg/mL, regression coefficients of the calibration curves ≥ 0.9946, intra-day and inter-day precision expressed as coefficient of variation in the range of 0.6–11.9% and 0.6–14.4%, and accuracy in the range of 87.6–107.1% and 87.2–119.6%. Our analytical approach led to the identification of increased levels of choline and γ-aminobutyric acid in pons, and elevated concentration levels of pyroglutamate in medulla oblongata. These findings indicate that NT could play a valuable role in the study and clarification of neuroinflammation and neurodegenerative diseases.

Possible Engagement of Nicotinic Acetylcholine Receptors in Pathophysiology of Brain Ischemia-Induced Cognitive Impairment

Post-stroke disabilities like cognitive impairment impose are complex conditions with great economic burdens on health care systems. For these comorbidities, no effective therapies have been identified yet. Nicotinic acetylcholine receptors (nAChRs) are multifunctional receptors participating in various behavioral and neurobiological functions. During brain ischemia, the increased glutamate accumulation leads to neuronal excitotoxicity as well as mitochondrial dysfunction. These abnormalities then cause the increased levels of oxidants, which play key roles in neuronal death and apoptosis in the infarct zone. Additionally, recall of cytokines and inflammatory factors play a prominent role in the exacerbation of ischemic injury. As well, neurotrophic factors' insufficiency results in synaptic dysfunction and cognitive impairments in ischemic brain. Of note, nAChRs through various signaling pathways can participate in therapeutic approaches such as cholinergic system's stimulation, and reduction of excitotoxicity, inflammation, apoptosis, oxidative stress, mitochondrial dysfunction, and autophagy. Moreover, the possible roles of nAChRs in neurogenesis, synaptogenesis, and stimulation of neurotrophic factors expression have been reported previously. On the other hand, the majority of the above-mentioned mechanisms were found to be common in both brain ischemia pathogenesis and cognitive function tuning. Therefore, it seems that nAChRs might be known as key regulators in the control of ischemia pathology, and their modulation could be considered as a new avenue in the multi-target treatment of post-stroke cognitive impairment.

Lacidipine Prevents Scopolamine-Induced Memory Impairment by Reducing Brain Oxido-nitrosative Stress in Mice

Cholinergic deficits and oxido-nitrosative stress are consistently associated with Alzheimer's disease (AD). Previous findings indicate that acetylcholine subdues Ca²⁺ current in the brain. Cholinergic antagonists (e.g., scopolamine) can instigate Ca²⁺-induced redox imbalance, inflammation, and cell-death pathways leading to AD-type memory impairment. Earlier, several Ca²⁺-channel blockers (CCB, e.g., dihydropyridine type) or cholinergic enhancers showed promising results in animal models of AD. In the present research, pretreatment effects of lacidipine (L-type CCB) on learning and memory functions were investigated using the scopolamine mouse model of AD. Swiss albino mice (20-25 g) were administered lacidipine (1 and 3 mg/kg) for 14 days. Scopolamine, an anti-muscarinic drug, was given (1 mg/kg) from days 8 to 14. The mice were subjected to elevated plus maze (EPM) and passive-avoidance (PA) paradigms. Bay-K8644 (a Ca²⁺-channel agonist) was administered before behavioral studies on days 13 and 14. Biochemical parameters of oxidative stress and acetylcholinesterase (AChE) activity were quantified using the whole brain. Behavioral studies showed an increase in transfer latency (TL) in the EPM test and a decrease in step-through latency (STL) in the PA test in scopolamine-administered mice. Scopolamine enhanced the AChE activity and oxidative stress in the brain of mice which resulted in memory impairment. Lacidipine prevented the amnesia against scopolamine and reduced the oxidative stress and AChE activity in the brain of mice. Bay-K8644 attenuated the lacidipine-induced improvement in memory and redox balance in scopolamine-administered mice. Lacidipine can prevent the oxidative stress and improve the cholinergic function in the brain. These properties of lacidipine can mitigate the pathogenesis of AD-type dementia.

Arthrophytum scoparium Extract Improves Memory Impairment and Affects Acetylcholinesterase Activity In Mice Brain

BACKGROUND

Arthrophytum scoparium (Pomel) Iljin (Amaranthaceae family) has been widely used in traditional Tunisian medicine to treat many disorders such as migraine, headache, and neurological disorders. This study investigates the effect of Arthrophytum scoparium Aqueous Extract (ASAE) on cognitive impairments and oxidative injury induced by galactose (10%) in a mouse model.

MATERIALS AND METHODS

The mice were divided randomly into 4 experimental groups, including the control group (saline water 9 ‰), Galactose group, Scop group (300 mg/kg/d), and Scop+Gal group (300 mg/kg/d). Mice received the corresponding solutions by intraperitoneal injection (i.p.) for 7 days before the Y-maze active tests. Galactose 10% was given to all groups except control and Scop groups, 30 min before the trial. Levels of Acetylcholinesterase Activity (AChE), Ascorbic Acid (AA), Gluthatione (GSH) and Malondialdehyde (MDA) in mice brains were examined.

RESULTS

Chronic administration of galactose significantly impaired cognitive performance in Y maze, caused marked oxidative damages and a significant increase in the acetylcholinesterase activity as compared to other groups. On the contrary, ASAE (300 mg/kg) treatment suppressed galactoseinduced oxidative damage by ameliorating the increased levels of GSH and AA. Moreover, ASAE treatment reduced brain AChE activities in the galactose-induced model.

CONCLUSION

These findings suggest that ASAE exerts potent anti-amnesic effects via the modulation of cholinergic and antioxidant activities. The observed pharmacological activities should be further evaluated by detailed experimental studies and validated by clinical trials.

Simultaneous exposure to noise and carbon monoxide increases the risk of Alzheimer's disease: a literature review

Dementia is a syndrome of cognitive and functional decline, commonly occurring in later life as a result of neurodegenerative and cerebrovascular processes beginning earlier in the life course. An excess of free radicals has an essential role in neurodegenerative diseases and aging. This paper aims to review the effects of noise and carbon monoxide as a risk factor in Alzheimer's disease as well as the role of free radicals in the progress of Alzheimer's disease. Articles included in this review were identified through a search of the databases PubMed, Scopus, and Google Scholar using the search terms Alzheimer's disease, dementia, noise, reactive oxygen species, and Carbon Monoxide. The literature search was restricted to the years 1982 to 2020 and articles published in the English language. The metabolism rate of the body is very high when exposed to noise and carbon monoxide; this leads to overproduction of reactive oxygen species and oxidative stress conditions. Oxidative stress has an essential role in the mechanisms concerned in Alzheimer's disease. In addition to the consequences of noise and a chemical substance on the auditory system, they also have non-auditory effects that affect the brain and induced neurodegenerative disease.

Win 55,212-2, atenolol and subdiaphragmatic vagotomy prevent acceleration of gastric emptying induced by cachexia via Yoshida-AH-130 cells in rats

The aim of this study was to investigate the effect of cachexia induced by AH-130 cells on gastrointestinal motility in rats. We evaluated food intake, body weight variation, cachexia index, gastric emptying and in vitro gastric responsiveness of control or cachexia rats. In addition, we evaluated the effect of pretreatment with atenolol (20 mg/kg, p.o.), win 55,212-2 (2 mg/kg, s.c.) or subdiaphragmatic vagotomy on the effects found. Atenolol prevented (P < 0.05) the acceleration of gastric emptying (area under the curve, AUC, 20360.17 ± 1970.9 vs. 12579.2 ± 785.4 μg/min/ml), and increased gastric responsiveness to carbachol (CCh) stimulation in cachectic rats compared to control groups (CCh-6M: 63.2 ± 5.5% vs. 46.5 ± 5.7%). Vagotomy prevented (P < 0.05) increase in gastric emptying acceleration (AUC 20360.17 ± 1970.9 vs. 13414.0 ± 1112.9 μg/min/ml) and caused greater in vitro gastric responsiveness of cachectic compared to control rats (CCh-6M: 63.2 ± 5.5% vs. 31.2 ± 4.7%). Win 55,212-2 attenuated the cachexia index (38.5 ± 2.1% vs. 25.8 ± 2.7%), as well as significantly (P < 0.05) preventing increase in gastric emptying (AUC 20360.17 ± 1970.9 vs. 10965.4 ± 1392.3 μg/min/ml) and gastric responsiveness compared to control groups (CCh-6M: 63.2 ± 5.5% vs. 38.2 ± 3.9%). Cachexia accelerated gastric emptying and increased gastric responsiveness in vitro. These phenomena were prevented by subdiaphragmatic vagotomy and by atenolol and win 55,212-2 treatments, showing vagal involvement of β₁-adrenergic and cannabinoid CB₁/CB₂ receptors.

Intranasal glyphosate-based herbicide administration alters the redox balance and the cholinergic system in the mouse brain

Pesticide exposure is associated with cognitive and psychomotor disorders. Glyphosate-based herbicides (GlyBH) are among the most used agrochemicals, and inhalation of GlyBH sprays may arise from frequent aerial pulverizations. Previously, we described that intranasal (IN) administration of GlyBH in mice decreases locomotor activity, increases anxiety, and impairs recognition memory. Then, the aim of the present study was to investigate the mechanisms involved in GlyBH neurotoxicity after IN administration. Adult male CF-1 mice were exposed to GlyBH IN administration (equivalent to 50 mg/kg/day of Gly acid, 3 days a week, during 4 weeks). Total thiol content and the activity of the enzymes catalase, acetylcholinesterase and transaminases were evaluated in different brain areas. In addition, markers of the cholinergic and the nigrostriatal pathways, as well as of astrocytes were evaluated by fluorescence microscopy in coronal brain sections. The brain areas chosen for analysis were those seen to be affected in our previous study. GlyBH IN administration impaired the redox balance of the brain and modified the activities of enzymes involved in cholinergic and glutamatergic pathways. Moreover, GlyBH treatment decreased the number of cholinergic neurons in the medial septum as well as the expression of the α7-acetylcholine receptor in the hippocampus. Also, the number of astrocytes increased in the anterior olfactory nucleus of the exposed mice. Taken together, these disturbances may contribute to the neurobehavioural impairments reported previously by us after IN GlyBH administration in mice.

Stimulation of SIRT1 Attenuates the Level of Oxidative Stress in the Brains of APP/PS1 Double Transgenic Mice and in Primary Neurons Exposed to Oligomers of the Amyloid-β Peptide

In the study, we examined whether the silent information regulator 1 (SIRT1) can attenuate oxidative stress in the brains of mice carrying the APP/PS1 double mutation and/or in primary neonatal rat neurons exposed to oligomers of amyloid-β peptide (AβOs). Starting at 4 or 8 months of age, the transgenic mice were treated with resveratrol (RSV, a stimulator of SIRT1) or suramin (an inhibitor) (each 20 mg/kg BW/day) for two months. The primary neurons were exposed to AβOs (0.5 μM) for 48 h and thereafter RSV (20 μM) or suramin (300 mg/ml) for 24 h. Cell viability was assessed by the CCK-8 assay; SIRT1 protein and mRNA determined by western blotting and real-time PCR, respectively; senile plaques examined immunohistochemically; ROS monitored by flow cytometry; and the contents of OH-, H2O2, O2·-, and MDA, and the activities of SOD and GSH-Px measured by standard biochemical procedures. In comparison to wild-type mice or untreated primary neurons, the expression of SIRT1 was significantly lower in the brains of APP/PS1 mice or neurons exposed to AβOs. In these same systems, increased numbers of senile plaques and a high level of oxidative stress were apparent. Interestingly, these two latter changes were attenuated by treatment with RSV, but enhanced by suramin. These findings indicate that SIRT1 may be neuroprotective.

Vitis vinifera acts as anti-Alzheimer's agent by modulating biochemical parameters implicated in cognition and memory

Background

Aluminum a known neuro and cholinotoxin has been implicated in the pathogenesis of Alzheimer’s disease. Its exposure is associated with impairment of the memory and cognition.

Objective

The present study was undertaken to evaluate the anti-Alzheimer’s activity of Vitis vinifera in aluminum induced Alzheimer’s disease.

Materials and methods

In this study, we investigated the behavioral and biochemical effects of aluminum in Sprague-Dawley rats. Animals were exposed to aluminum chloride (100 mg/kg/day) orally for a period of 8 weeks. Vitis was given in doses of 250 mg/kg and 500 mg/kg for 16 weeks and the possible effects of Vitis vinifera on the expression of Tau and amyloid precursor protein were evaluated by PCR analysis and the possible activities of lipid peroxidation, inflammation and anti-cholinesterase activity were evaluated.

Results

Aluminum intoxication was associated with significant impairment in learning and memory in Morris water maze test. A significant improvement was observed with Vitis vinifera in a dose dependent manner.

Conclusion

The findings of the present study revealed the significant neuroprotective actions of Vitis vinifera by modifying the biochemical parameters and inhibited the mRNA expression of Amyloid Precursor Protein and Tau, which are the key pathological hallmarks of Alzheimer’s disease, which was further confirmed by histopathological observations.

Design, synthesis and biological evaluation of LX2343 derivatives as neuroprotective agents for the treatment of Alzheimer's disease

A series of LX2343 derivatives were designed, synthesized and evaluated as neuroprotective agents for Alzheimer's disease (AD) in vitro. Most of the compounds displayed potent neuroprotective activities. Especially for compound A6, exhibited a remarkable EC₅₀ value of 0.22 μM. Further investigation demonstrated that compound A6 can significantly reduce Aβ production and increase Aβ clearance, and alleviate Tau hyperphosphorylation. Most importantly, compound A6 could ameliorate learning and memory impairments in APP/PS1 transgenic mice. The present study evidently showed that compound A6 is a potent neuroprotective agent and might serve as a promising lead candidate for the treatment of Alzheimer's disease.

LX2343 alleviates cognitive impairments in AD model rats by inhibiting oxidative stress-induced neuronal apoptosis and tauopathy

Alzheimer's disease (AD) is a progressive neurodegenerative disease leading to the irreversible loss of brain neurons and cognitive abilities, and the vicious interplay between oxidative stress (OS) and tauopathy is believed to be one of the major players in AD development. Here, we demonstrated the capability of the small molecule N-(1,3-benzodioxol-5-yl)-2-[5-chloro-2-methoxy(phenylsulfonyl)anilino]acetamide (LX2343) to ameliorate the cognitive dysfunction of AD model rats by inhibiting OS-induced neuronal apoptosis and tauopathy. Streptozotocin (STZ) was used to induce OS in neuronal cells in vitro and in AD model rats that were made by intracerebroventricular injection of STZ (3 mg/kg, bilaterally), and Morris water maze test was used to evaluate the cognitive dysfunction in ICV-STZ rats. Treatment with LX2343 (5-20 μmol/L) significantly attenuated STZ-induced apoptosis in SH-SY5Y cells and mouse primary cortical neurons by alleviating OS and inhibiting the JNK/p38 and pro-apoptotic pathways. LX2343 was able to restore the integrity of mitochondrial function and morphology, increase ATP biosynthesis, and reduce ROS accumulation in the neuronal cells. In addition, LX2343 was found to be a non-ATP competitive GSK-3β inhibitor with IC₅₀ of 1.84±0.07 μmol/L, and it potently inhibited tau hyperphosphorylation in the neuronal cells. In ICV-STZ rats, administration of LX2343 (7, 21 mg·kg^-1·d^-1, ip, for 5 weeks) efficiently improved their cognitive deficits. LX2343 ameliorates the cognitive dysfunction in the AD model rats by suppressing OS-induced neuronal apoptosis and tauopathy, thus highlighting the potential of LX2343 for the treatment of AD.

Exendin-4 antagonizes Aβ1-42-induced attenuation of spatial learning and memory ability

β-amyloid protein (Aβ) accumulation in cerebral centers involved in cognition and memory is a pivotal pathological feature of Alzheimer's disease (AD). The onset process of type 2 diabetes mellitus (T2DM) has a number of similarities compared with AD. Thus, it is hypothesized that the pharmacological therapy employed for the treatment of T2DM may help to prevent and ameliorate the symptoms of AD. This study demonstrated that Exendin-4, which is a glucagon-like peptide-1 analogue which is used as a therapeutic drug for T2DM, markedly antagonized Aβ fragment-induced attenuation of spatial learning and memory ability, as indicated by a Morris water maze experiment. In addition, we investigated the potential underlying electrophysiological and molecular mechanisms. The results indicate that Exendin-4 rescued long-term potentiation from Aβ1-42-induced damage in the rat hippocampal CA1 region in vivo, and antagonized Aβ1-42-induced reduction of cyclic adenosine monophosphate and phosphorylated-cAMP response element-binding protein in rat hippocampal tissue using ELISA and western blot analysis, respectively. Thus, the results of the present study provide theoretical support for the application of Exendin-4 for improving AD.

LPS-Induced Macrophage Activation and Plasma Membrane Fluidity Changes are Inhibited Under Oxidative Stress

Macrophage activation is essential for a correct and efficient response of innate immunity. During oxidative stress membrane receptors and/or membrane lipid dynamics can be altered, leading to dysfunctional cell responses. Our aim is to analyze membrane fluidity modifications and cell function under oxidative stress in LPS-activated macrophages. Membrane fluidity of individual living THP-1 macrophages was evaluated by the technique two-photon microscopy. LPS-activated macrophage function was determined by TNFα secretion. It was shown that LPS activation causes fluidification of macrophage plasma membrane and production of TNFα. However, oxidative stress induces rigidification of macrophage plasma membrane and inhibition of cell activation, which is evidenced by a decrease of TNFα secretion. Thus, under oxidative conditions macrophage proinflammatory response might develop in an inefficient manner.

Small molecule LX2343 ameliorates cognitive deficits in AD model mice by targeting both amyloid β production and clearance

AIM

Streptozotocin (STZ) is widely used to induce oxidative damage and to impair glucose metabolism, apoptosis, and tau/Aβ pathology, eventually leading to cognitive deficits in both in vitro and in vivo models of Alzheimer's disease (AD). In this study, we constructed a cell-based platform using STZ to induce stress conditions mimicking the complicated pathologies of AD in vitro, and evaluated the anti-amyloid effects of a small molecule, N-(1,3-benzodioxol-5-yl)-2-[5-chloro-2-methoxy(phenylsulfonyl)anilino]acetamide (LX2343) in the amelioration of cognitive deficits in AD model mice.

METHODS

Cell-based assays for screening anti-amyloid compounds were established by assessing Aβ accumulation in HEK293-APPsw and CHO-APP cells, and Aβ clearance in primary astrocytes and SH-SY5Y cells after the cells were treated with STZ in the presence of the test compounds. Autophagic flux was observed using confocal laser scanning microscopy. APP/PS1 transgenic mice were administered LX2343 (10 mg·kg-1·d-1, ip) for 100 d. After LX2343 administration, cognitive ability of the mice was evaluated using Morris water maze test, and senile plaques in the brains were detected using Thioflavine S staining. ELISA assay was used to evaluate Aβ and sAPPβ levels, while Western blot analysis was used to measure the signaling proteins in both cell and animal brains.

RESULTS

LX2343 (5-20 μmol/L) dose-dependently decreased Aβ accumulation in HEK293-APPsw and CHO-APP cells, and promoted Aβ clearance in SH-SY5Y cells and primary astrocytes. The anti-amyloid effects of LX2343 were attributed to suppressing JNK-mediated APPThr668 phosphorylation, thus inhibiting APP cleavage on one hand, and inhibiting BACE1 enzymatic activity with an IC50 value of 11.43±0.36 μmol/L, on the other hand. Furthermore, LX2343 acted as a non-ATP competitive PI3K inhibitor to negatively regulate AKT/mTOR signaling, thus promoting autophagy, and increasing Aβ clearance. Administration of LX2343 in APP/PS1 transgenic mice significantly ameliorated cognitive deficits and markedly ameliorated the Aβ pathology in their brains.

CONCLUSION

LX2343 ameliorates cognitive dysfunction in APP/PS1 transgenic mice via both Aβ production inhibition and clearance promotion, which highlights the potential of LX2343 in the treatment of AD.

Original Research: Influence of okadaic acid on hyperphosphorylation of tau and nicotinic acetylcholine receptors in primary neurons

The aim of the study was to investigate the influence of hyperphosphorylation of tau induced by okadaic acid on the expression of nicotinic acetylcholine receptors and the neurotoxicity of β-amyloid peptide. Primary cultures of neurons isolated from the hippocampus of the brains of neonatal rats were exposed to okadaic acid or/and Aβ1-42 Tau phosphorylated at Ser404 and Ser202, and the protein expressions of α7, α4 and α3 nAChR subunits were quantified by Western blotting, and their corresponding mRNAs by real-time PCR. Superoxide dismutase activity was assayed biochemically and malondialdehyde by thiobarbituric acid-reactive substance. As compared to controls, phosphorylations of tau at Ser404 and Ser202 in the neurons were elevated by exposure to 20 nM okadaic acid for 48 h but not by 1 or 2 µM Aβ1-42 Treatment with 20 nM okadaic acid or 1 µM Aβ1-42 for 48 h resulted in the reduced α7, α4 and α3 proteins, and α4 and α3 mRNAs, as well as the decreased activity of superoxide dismutase and the increased malondialdehyde. Okadaic acid and Aβ1-42 together caused more pronounced changes in the expressions of α7 and α4, superoxide dismutase activity and lipid peroxidation than either alone. When pre-treatment with vitamin E or lovastatin, the neurotoxicity induced by okadaic acid was significantly attenuated. These findings indicate that hyperphosphorylation of tau induced by okadaic acid inhibits the expression of nicotinic acetylcholine receptors at both the protein and mRNA levels, as well as enhances the neurotoxicity of β-amyloid peptide.

Aβ regulation-based multitarget strategy for drug discovery against Alzheimer’s disease

Alzheimer’s disease (AD) is a progressively neurodegenerative disease that eventually leads to the irreversible loss of neurons and intellectual abilities, including cognition and memory. AD has become the most common cause of dementia in aged people, and the ill-defined pathogenesis of AD is seriously impeding the current drug discovery against this disease. To date, there is still a lack of etiologically therapeutic drugs for AD, although some symptomatic treatments have been successfully developed. The β-amyloid (Aβ)-induced neurodegeneration is determined as the main pathogenesis of AD, and by targeting the regulation of Aβ in production inhibition or clearance promotion, many active agents have been designed potentially for AD treatment, but no drug has yet been approved in clinical use. Actually, AD has a complex pathogenic mechanism that involves multiple aberrant signaling genes and pathways, and the idea of ‘single target’ for anti-AD drug research is thus full of challenges. Recently, with a deep understanding of AD pathogeneses and the development of advanced pharmacological techniques, ‘multiple target’-based strategy has been widely applied for the drug discovery against this disease, and many promising results have been achieved. Here, we review the recent multitarget strategies for the drug discovery in the treatment of AD by focusing on the involvement of Aβ regulation.

FOXO1 locus and acetylcholinesterase inhibitors in elderly patients with Alzheimer's disease

Objective

Acetylcholinesterase inhibitors (AChEIs) may reduce the oxidative stress in brain of Alzheimer’s disease (AD) patients. Forkhead box O1 (FOXO1) protein has been reported as the link between oxidative stress and AD. We evaluated a potential association between FOXO1 gene locus and the response to AChEI treatment in patients with sporadic AD.

Methods

In this prospective study, 109 Caucasian AD patients were treated with standard doses of donepezil, galantamine, or rivastigmine for 6 months. Functional and cognitive status were evaluated at baseline and after treatment. Response to therapy was defined according to the National Institute for Health and Clinical Excellence criteria. Genotype analyses, including the APOE polymorphism, were made in blinded fashion.

Results

A significantly higher frequency of FOXO1 rs7981045 G/G genotype was observed in nonresponders compared with responders (17.14% versus 2.70%, P=0.010). Age, sex, and APOE-adjusted logistic regression analysis confirmed that patients with the G/G genotype had a significantly higher risk of poor response to AChEI treatment (odds ratio =10.310; 95% confidence interval, 1.510–70.362). Haplotype analysis revealed significant differences in haplotype frequency distribution between these groups.

Conclusion

FOXO1 may influence the clinical response to AChEIs in AD patients.

Pretreatment of SH-SY5Y cells with dicaffeoylquinic acids attenuates the reduced expression of nicotinic receptors, elevated level of oxidative stress and enhanced apoptosis caused by β-amyloid peptide

Objectives

This in vitro investigation was designed to examine potential neuroprotection by dicaffeoylquinic acids (diCQAs) extracted from a traditional Chinese medicinal herb herba erigerontis and their effects against the toxicity induced by β-amyloid peptide (Aβ25–35).

Methods

The neuroblastoma SH-SY5Y cell line was treated with Aβ or 3, 4-diCQA, 3, 5-diCQA or 4, 5-diCQA. 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) reduction was assayed by spectrophotometrical method, lipid peroxidation (malondialdehyde) on the basis of the level of thiobarbituric acid-reactive substance, the activity of superoxide dismutase by the xanthine oxidase procedure, the frequency of apoptosis by flow cytometry, and the levels of α3 and α7 nicotinic acetylcholine receptor (nAChR) subunit proteins by Western blotting.

Key findings

When the cells were exposed to Aβ25–35, MTT reduction declined, oxidative stress and apoptosis were enhanced, and the expression of α3 and α7 nAChR subunit proteins was lowered. Expression of the α7 nAChR subunit protein was increased by all three diCQAs, and the level of α3 was increased by 3, 5-diCQA and 4, 5-diCQA. Significantly, pretreatment with diCQAs attenuated the neurotoxic effects of Aβ25–35, a neuroprotective effect in which the upregulation of α7 and α3 nAChR may be involved.

Conclusion

The diCQAs exert a protective effect on Aβ-induced neurotoxicity in SH-SY5Y cells and a potential underlying mechanism involving stimulation of nAChRs.

Activation of muscarinic receptors inhibits glutamate-induced GSK-3β overactivation in PC12 cells

AIM

To investigate the actions of the muscarinic agonist carbachol on glutamate-induced neurotoxicity in PC12 cells, and the underlying mechanisms.

METHODS

PC12 cells were treated with different concentrations of glutamate for 24 or 48 h. The cell viability was measured using MTT assay, and the expression and activation of GSK-3β were detected with Western blot. β-Catenin translocation was detected using immunofluorescence. Luciferase reporter assay and real-time PCR were used to analyze the transcriptional activity of β-catenin.

RESULTS

Glutamate (1, 3, and 10 mmol/L) induced PC12 cell death in a dose-dependent manner. Moreover, treatment of the cells with glutamate (1 mmol/L) caused significant overactivation of GSK-3β and prevented β-catenin translocation to the nucleus. Pretreatment with carbachol (0.01 μmol/L) blocked glutamate-induced cell death and GSK-3β overactivation, and markedly enhanced β-catenin transcriptional activity.

CONCLUSION

Activation of muscarinic receptors exerts neuroprotection in PC12 cells by attenuating glutamate-induced GSK-3β overactivation, suggesting potential benefits of muscarinic agonists for Alzheimer's disease.

Granulocyte colony stimulating factor (GCSF) improves memory and neurobehavior in an amyloid-β induced experimental model of Alzheimer's disease

GCSF is an endogenous neuronal hematopoietic factor that displays robust in vitro and in vivo neuroprotective activity. The present study aimed to evaluate the effect of GCSF on Aβ-induced memory loss in an Alzheimer's disease model of rats. A total of 42 male adult Wistar rats weighing 200-250 g were used in the study and were divided into 7 experimental groups. Animals were subjected to intracerebroventricular (ICV) injection stereotaxically at day 0 to instill amyloid-β(1-42) (Aβ(1-42)) or PBS (sham operated group) at 10 μl (5 μl bilaterally). GCSF treatment was given from day 7 to 12 of Aβ injection. On day 21, behavioral tests (short term memory, exploratory behavior and motor coordination) in all groups were evaluated. Biochemical parameters and RNA expression were measured to ensure the efficacy of GCSF. GCSF (35 and 70 μg/kg, s.c.) showed statistically significant improvement in memory as compared to control and sham operated groups (p<0.05). Mean time spent in the platform placed quadrant was found to be significantly increased in the GCSF (70 μg/kg, s.c.) as compared to GCSF (35 μg/kg, s.c.) and GCSF (10 μg/kg, s.c.) groups (p<0.001). GCSF (35 and 70 μg/kg, s.c.) also improved motor coordination and exploratory behavior significantly as compared to naïve sham operated and GCSF (10 μg/kg, s.c.) groups (p<0.05). Improvement in memory by GCSF (35 and 70 μg/kg, s.c.) was coupled with marked reduction of lipid peroxidation, acetylcholinesterase levels and a significant increase in antioxidant enzymes as well as total RNA expression in the brain. Additionally, GCSF (35 and 70 μg/kg, s.c.) significantly increased progenitor cells (iPSCs) and surface marker CD34+ in the brain and hence induced neurogenesis. The present findings demonstrate an improvement of memory and neurobehavioral function with GCSF in Aβ-induced Alzheimer's disease model in rats.

Brain region-specific changes in oxidative stress and neurotrophin levels in autism spectrum disorders (ASD)

Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders characterized by social and language deficits, stereotypic behavior, and abnormalities in motor functions. The particular set of behavioral impairments expressed in any given individual is variable across the spectrum. These behavioral abnormalities are consistent with our current understanding of the neuropathology of ASD which suggests abnormalities in the amygdala, temporal and frontal cortexes, hippocampus, and cerebellum. However, regions unrelated to these behavioral deficits appear largely intact. Both genetic predisposition and environmental toxins and toxicants have been implicated in the etiology of autism; the impact of these environmental triggers is associated with increases in oxidative stress, and is further exacerbated when combined with genetic susceptibility. We have previously reported increased levels of 3-nitrotyrosine (3-NT), a marker of oxidative stress, in ASD cerebella. We have also shown that this increase was associated with an elevation in neurotrophin-3 (NT-3) levels. The objectives of the current study were to determine whether the increase in oxidative stress in ASD is brain region-specific, to identify the specific brain regions affected by oxidative stress, and to compare brain region-specific NT-3 expression between ASD and control cases. The levels of 3-NT and NT-3 were measured with specific ELISAs in individual brain regions of two autistic and age- and postmortem interval (PMI)--matched control donors. In the control brain, the levels of 3-NT were uniformly low in all brain regions examined ranging from 1.6 to 12.0 pmol/g. On the other hand, there was a great variation in 3-NT levels between individual brain regions of the autistic brains ranging from 1.7 to 281.2 pmol/g. The particular brain regions with the increased 3-NT and the magnitude of the increase were both different in the two autistic cases. In the older autistic case, the brain regions with highest levels of 3-NT included the orbitofrontal cortex (214.5 pmol/g), Wernicke's area (171.7 pmol/g), cerebellar vermis (81.2 pmol/g), cerebellar hemisphere (37.2 pmol/g), and pons (13.6 pmol/g); these brain areas are associated with the speech processing, sensory and motor coordination, emotional and social behavior, and memory. Brain regions that showed 3-NT increase in both autistic cases included the cerebellar hemispheres and putamen. Consistent with our earlier report, we found an increase in NT-3 levels in the cerebellar hemisphere in both autistic cases. We also detected an increase in NT-3 level in the dorsolateral prefrontal cortex (BA46) in the older autistic case and in the Wernicke's area and cingulate gyrus in the younger case. These preliminary results reveal, for the first time, brain region-specific changes in oxidative stress marker 3-NT and neurotrophin-3 levels in ASD.

Basal metallothionein-I/II protects against NMDA-mediated oxidative injury in cortical neuron/astrocyte cultures

N-Methyl-D-aspartate (NMDA) receptor overactivation-mediated oxidative stress has been proposed to contribute to brain injury. Metallothionein-I/II (MT-I/II), a member of cysteine-rich metalloproteins, has been found to express in the central nervous system primarily in cortical tissues and be upregulated following brain injury. To address the role of MT-I/II on NMDA-mediated oxidative injury, we established primary cortical neuron/astrocyte cultures from neonatal MT-I/II deficient (MT⁻/⁻) and wild type (MT+/+) mice to test whether basal MT-I/II protects cortical cultures against NMDA-mediated injury. We found that MT-I/II expression was increased by NMDA in MT+/+ cultures but was not detectable in MT⁻/⁻ cultures. NMDA concentration-dependently induced oxidative injury in both MT+/+ and MT⁻/⁻ cultures as evidenced by decrease of cell viability, increases of lipid peroxidation and DNA damage. However, these toxic effects were greater in MT⁻/⁻ than MT+/+ cultures. NMDA significantly increased reactive oxygen species (ROS) generation and disrupted mitochondrial membrane potential in neurons in MT+/+ cultures, and these effects were exaggerated in MT⁻/⁻ cultures. Our findings clearly show that basal MT-I/II provides protection against NMDA-mediated oxidative injury in cortical neuron/astrocyte cultures, and suggest that the protective effects are possibly associated with inhibition of ROS generation and preservation of mitochondrial membrane potential.

Brain redox imaging

Nitroxyl contrast agents (nitroxyl radicals, also known as nitroxide) are paramagnetic species, which can react with reactive oxygen species (ROS) to lose paramagnetism to be diamagnetic species. The paramagnetic nitroxyl radical forms can be detected by using electron paramagnetic resonance imaging (EPRI), Overhauser MRI (OMRI), or MRI. The time course of in vivo image intensity induced by paramagnetic redox-sensitive contrast agent can give tissue redox information, which is the so-called redox imaging technique. The redox imaging technique employing a blood-brain barrier permeable nitroxyl contrast agent can be applied to analyze the pathophysiological functions in the brain. A brief theory of redox imaging techniques is described, and applications of redox imaging techniques to brain are introduced.

Amyloid precursor protein gene mutated at Swedish 670/671 sites in vitro induces changed expression of nicotinic acetylcholine receptors and neurotoxicity

In order to investigate the influence of amyloid precursor protein (APP) over-expression on the levels of nicotinic acetylcholine receptors (nAChRs), the pCDNA 3.0 carrying the Swedish 670/671 APP double mutation (APP(SWE)) gene was transfected into human neuroblastoma (SH-SY5Y) cells and primary culture of rat hippocampal neurons. The mRNA level of APP, and nAChR α3, α4 and α7 subunits were detected by real-time PCR, and their corresponding proteins as well as α-secreted APP (αAPPs) by Western blotting. [3H]Epibatidine binding sites were measured by the receptor binding assay. The results showed that significantly concomitant increases in mRNA and protein levels of SH-SY5Y cells and primary cultured neurons transfected with APP(SWE) were observed. Interestingly, a decreased αAPPs level was detected in both cells treated with APP(SWE) transfection. In addition, decreases in mRNA and protein levels of α3 nAChR subunit in SH-SY5Y cells or α4 subunit in primary cultured neurons with APP(SWE) transfection were observed. For α7 nAChR, the increased protein and mRNA levels were found in SH-SY5Y cells and primary cultured neurons with APP(SWE) transfection. The number of cholinergic receptor binding site of [3H]epibatidine was decreased in the SH-SY5Y cells transfected with APP(SWE). Elevations in the activities of AChE and BuChE and in the level of lipid peroxidation were detected in both types of cultured cells transfected with APP(SWE). These results indicated that the over-expression of APP(SWE) gene can influence the expression of nAChRs and resulted in neurotoxicity, in which this process might play an important role in the pathogenesis of Alzheimer's disease.

Baicalin attenuates oxygen-glucose deprivation-induced injury by inhibiting oxidative stress-mediated 5-lipoxygenase activation in PC12 cells

AIM

To determine whether the flavonoid baicalin attenuates oxygen-glucose deprivation (OGD)-induced injury by inhibiting oxidative stress-mediated 5-lipoxygenase (5-LOX) activation in PC12 cells.

METHODS

The effects of baicalin and the 5-LOX inhibitor zileuton on the changes induced by OGD/recovery or H(2)O(2) (an exogenous reactive oxygen species [ROS]) in green fluorescent protein-5-LOX-transfected PC12 cells were compared.

RESULTS

Both baicalin and zileuton attenuated OGD/recovery- and H(2)O(2)-induced injury and inhibited OGD/recovery-induced production of 5-LOX metabolites (cysteinyl leukotrienes) in a concentration-dependent manner. However, baicalin did not reduce baseline cysteinyl leukotriene levels. Baicalin also reduced OGD/recovery-induced ROS production and inhibited 5-LOX translocation to the nuclear envelope and p38 phosphorylation induced by OGD/recovery and H(2)O(2). In contrast, zileuton did not show these effects.

CONCLUSION

Baicalin can inhibit 5-LOX activation after ischemic injury, which may partly result from inhibition of the ROS/p38 mitogen-activated protein kinase pathway.