N-acetylcysteine treatment attenuates the cognitive impairment and synaptic plasticity loss induced by streptozotocin

Ferroptosis: A new strategy for targeting Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by a complex pathogenesis, which involves the formation of amyloid plaques and neurofibrillary tangles. Many recent studies have revealed a close association between ferroptosis and the pathogenesis of AD. Factors such as ferroptosis-associated iron overload, lipid peroxidation, disturbances in redox homeostasis, and accumulation of reactive oxygen species have been found to contribute to the pathological progression of AD. In this review, we explore the mechanisms underlying ferroptosis, describe the link between ferroptosis and AD, and examine the reported efficacy of ferroptosis inhibitors in treating AD. Finally, we discuss the potential challenges to ferroptosis inhibitors use in the clinic, enabling their faster use in clinical treatment.

Hippocampal acetylcholinesterase activation induced by streptozotocin in mice is protected by an organotellurium compound without evidence of toxicity

The cognitive deficit, which is like Alzheimer's disease and is associated with oxidative damage, may be induced by exposure to streptozotocin. This study aimed to evaluate if the tellurium-containing organocompound, 3j, 5'-arylchalcogeno-3-aminothymidine derivative, interferes with the effects of streptozotocin, as well as to investigate its toxicity in adult mice. Cognitive deficit was induced by two doses of streptozotocin (2.25 mg/kg/day, 48 h interval) intracerebroventricularly. After, the mice were subcutaneously treated with 3j (8.62 mg/kg/day) for 25 days. The effects were assessed by evaluating hippocampal and cortical acetylcholinesterase and behavioral tasks. 3j toxicity was investigated for 10 (0, 21.55, or 43.10 mg/kg/day) and 37 (0, 4.31, or 8.62 mg/kg/day) days by assessing biometric parameters and glucose and urea levels, and alanine aminotransferase activity in blood plasma. 3j exposure did not alter the behavioral alterations induced by streptozotocin exposure. On the other hand, 3j exposure normalized hippocampus acetylcholinesterase activity, which is enhanced by streptozotocin exposure. Toxicity evaluation showed that the administration of 3j for either 10 or 37 days did not cause harmful effects on the biometric and biochemical parameters analyzed. Therefore, 3j does not present any apparent toxicity and reverts acetylcholinesterase activity increase induced by streptozotocin in young adult mice.

Impaired Insulin Signaling Alters Mediators of Hippocampal Synaptic Dynamics/Plasticity: A Possible Mechanism of Hyperglycemia-Induced Cognitive Impairment

Alzheimer's disease (AD) is a neurological condition that affects the elderly and is characterized by progressive and irreversible neurodegeneration in the cerebral cortex [...].

In silico identification of novel stilbenes analogs for potential multi-targeted drugs against Alzheimer's disease

CONTEXT

Alzheimer's disease (AD) is a chronic progressive neurodegenerative syndrome, which adversely disturbs cognitive abilities as well as intellectual processes and frequently occurs in the elderly. Inhibition of cholinesterase is a valuable approach to upsurge acetylcholine concentrations in the brain and persuades the development of multi-targeted ligands against cholinesterases.

METHODS

The current study aims to determine the binding potential accompanied by antioxidant and anti-inflammatory activities of stilbenes-designed analogs against both cholinesterases (Acetylcholinesterase and butyrylcholinesterase) and neurotrophin targets for effective AD therapeutics. Docking results have shown that the WS6 compound exhibited the least binding energy - 10.1 kcal/mol with Acetylcholinesterase and - 7.8 kcal/mol with butyrylcholinesterase. The WS6 also showed a better binding potential with neurotrophin targets that are Brain-derived Neurotrophic Factor, Neurotrophin 4, Nerve Growth Factor, and Neurotrophin 3. The tested compounds particularly WS6 revealed significant antioxidant and anti-inflammatory activities through the comparative docking analysis with Fluorouracil and Melatonin as control drugs of antioxidants while Celecoxib and Anakinra as anti-inflammatory. The bioinformatics approaches including molecular docking calculations followed by the pharmacokinetics analysis and molecular dynamic simulations were accomplished to explore the capabilities of designed stilbenes as effective and potential leads. Root mean square deviation, root mean square fluctuations, and MM-GBSA calculations were performed through molecular dynamic simulations to extract the structural and residual variations and binding free energies through the 50-ns time scale.

Iron and Ferroptosis More than a Suspect: Beyond the Most Common Mechanisms of Neurodegeneration for New Therapeutic Approaches to Cognitive Decline and Dementia

Neurodegeneration is a multifactorial process that involves multiple mechanisms. Examples of neurodegenerative diseases are Parkinson's disease, multiple sclerosis, Alzheimer's disease, prion diseases such as Creutzfeldt-Jakob's disease, and amyotrophic lateral sclerosis. These are progressive and irreversible pathologies, characterized by neuron vulnerability, loss of structure or function of neurons, and even neuron demise in the brain, leading to clinical, functional, and cognitive dysfunction and movement disorders. However, iron overload can cause neurodegeneration. Dysregulation of iron metabolism associated with cellular damage and oxidative stress is reported as a common event in several neurodegenerative diseases. Uncontrolled oxidation of membrane fatty acids triggers a programmed cell death involving iron, ROS, and ferroptosis, promoting cell death. In Alzheimer's disease, the iron content in the brain is significantly increased in vulnerable regions, resulting in a lack of antioxidant defenses and mitochondrial alterations. Iron interacts with glucose metabolism reciprocally. Overall, iron metabolism and accumulation and ferroptosis play a significant role, particularly in the context of diabetes-induced cognitive decline. Iron chelators improve cognitive performance, meaning that brain iron metabolism control reduces neuronal ferroptosis, promising a novel therapeutic approach to cognitive impairment.

Critical Roles of the Cysteine-Glutathione Axis in the Production of γ-Glutamyl Peptides in the Nervous System

γ-Glutamyl moiety that is attached to the cysteine (Cys) residue in glutathione (GSH) protects it from peptidase-mediated degradation. The sulfhydryl group of the Cys residue represents most of the functions of GSH, which include electron donation to peroxidases, protection of reactive sulfhydryl in proteins via glutaredoxin, and glutathione conjugation of xenobiotics, whereas Cys-derived sulfur is also a pivotal component of some redox-responsive molecules. The amount of Cys that is available tends to restrict the capacity of GSH synthesis. In in vitro systems, cystine is the major form in the extracellular milieu, and a specific cystine transporter, xCT, is essential for survival in most lines of cells and in many primary cultivated cells as well. A reduction in the supply of Cys causes GPX4 to be inhibited due to insufficient GSH synthesis, which leads to iron-dependent necrotic cell death, ferroptosis. Cells generally cannot take up GSH without the removal of γ-glutamyl moiety by γ-glutamyl transferase (GGT) on the cell surface. Meanwhile, the Cys-GSH axis is essentially common to certain types of cells; primarily, neuronal cells that contain a unique metabolic system for intercellular communication concerning γ-glutamyl peptides. After a general description of metabolic processes concerning the Cys-GSH axis, we provide an overview and discuss the significance of GSH-related compounds in the nervous system.

Opioid induces increased DNA damage in prefrontal cortex and nucleus accumbens

Opioid use disorder (OUD) is a chronic disease characterized by compulsive opioid taking and seeking, affecting millions of people worldwide. The high relapse rate is one of the biggest challenges in treating opioid addiction. However, the cellular and molecular mechanisms underlying relapse to opioid seeking are still unclear. Recent studies have shown that DNA damage and repair processes are implicated in a broad spectrum of neurodegenerative diseases as well as in substance use disorders. In the present study, we hypothesized that DNA damage is related to relapse to heroin seeking. To test our hypothesis, we aim to examine the overall DNA damage level in prefrontal cortex (PFC) and nucleus accumbens (NAc) after heroin exposure, as well as whether manipulating DNA damage levels can alter heroin seeking. First, we observed increased DNA damage in postmortem PFC and NAc tissues from OUD individuals compared to healthy controls. Next, we found significantly increased levels of DNA damage in the dorsomedial PFC (dmPFC) and NAc from mice that underwent heroin self-administration. Moreover, increased accumulation of DNA damage persisted after prolonged abstinence in mouse dmPFC, but not in NAc. This persistent DNA damage was ameliorated by the treatment of reactive oxygen species (ROS) scavenger N-acetylcysteine, along with attenuated heroin-seeking behavior. Furthermore, intra-PFC infusions of topotecan and etoposide during abstinence, which trigger DNA single-strand breaks and double-strand breaks respectively, potentiated heroin-seeking behavior. These findings provide direct evidence that OUD is associated with the accumulation of DNA damage in the brain (especially in the PFC), which may lead to opioid relapse.

Cognitive impairments in type 1 diabetes mellitus model mice are associated with synaptic protein disorders

An association between type 1 diabetes mellitus (T1DM) and cognitive impairment was recently reported. However, the mechanisms by which T1DM induces cognitive impairment are still unknown. Here, we confirmed that T1DM mice induced by streptozotocin (STZ) injection had impaired working memory and spatial memory. We observed long-term potentiation (LTP) induction defects and synaptic loss in mice 20 weeks after STZ injection. We also found decreased levels of synaptic proteins, including the N-methyl-D-aspartic acid receptor (NMDAR) subunit NR2A, synaptophysin (SYP), and postsynaptic density 95 (PSD95), in the hippocampus and prefrontal cortex, revealing similarities in the alteration patterns of these synaptic proteins in aged Alzheimer's disease (AD) APP/PS1 mice and T1DM mice. Taken together, these findings expand our understanding of the mechanisms underlying T1DM-induced cognitive impairment.

Ferroptosis, a Potential Therapeutic Target in Alzheimer's Disease

Cell death is a common phenomenon in the progression of Alzheimer’s disease (AD). However, the mechanism of triggering the death of neuronal cells remains unclear. Ferroptosis is an iron-dependent lipid peroxidation-driven cell death and emerging evidences have demonstrated the involvement of ferroptosis in the pathological process of AD. Moreover, several hallmarks of AD pathogenesis were consistent with the characteristics of ferroptosis, such as excess iron accumulation, elevated lipid peroxides, and reactive oxygen species (ROS), reduced glutathione (GSH), and glutathione peroxidase 4 (GPX4) levels. Besides, some ferroptosis inhibitors can relieve AD-related pathological symptoms in AD mice and exhibit potential clinical benefits in AD patients. Therefore, ferroptosis is gradually being considered as a distinct cell death mechanism in the pathogenesis of AD. However, direct evidence is still lacking. In this review, we summarize the features of ferroptosis in AD, its underlying mechanisms in AD pathology, and review the application of ferroptosis inhibitors in both AD clinical trials and mice/cell models, to provide valuable information for future treatment and prevention of this devastating disease.

N-Acetyl Cysteine and Catechin-Derived Polyphenols: A Path Toward Multi-Target Compounds Against Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is a multifactorial disease, that involves neuroinflammatory processes in which microglial cells respond to "damage signals". The latter includes oligomeric tau, iron, oxidative free radicals, and other molecules that promotes neuroinflammation in the brain, promoting neuronal death and cognitive impairment. Since AD is the first cause of dementia in the elderly, and its pharmacotherapy has limited efficacy, novel treatments are critical to improve the quality of life of AD patients. Multitarget therapy based on nutraceuticals has been proposed as a promising intervention based on evidence from clinical trials. Several studies have shown that epicatechin-derived polyphenols from tea improve cognitive performance; also, the polyphenol molecule N-acetylcysteine (NAC) promotes neuroprotection.

OBJECTIVE

To develop an approach for a rational design of leading compounds against AD, based on specific semisynthetic epicatechin and catechin derivatives.

METHODS

We evaluated tau aggregation in vitro and neuritogenesis by confocal microscopy in mouse neuroblastoma cells (N2a), after exposing cells to either epicatechin-pyrogallol (EPIC-PYR), catechin-pyrogallol (CAT-PYR), catechin-phloroglucinol (CAT-PhG), and NAC.

RESULTS

We found that EPIC-PYR, CAT-PYR, and CAT-PhG inhibit human tau aggregation and significantly increase neuritogenesis in a dose-dependent manner. Interestingly, modification with a phloroglucinol group yielded the most potent molecule of those evaluated, suggesting that the phloroglucinol group may enhance neuroprotective activity of the catechin-derived compounds. Also, as observed with cathechins, NAC promotes neuritogenesis and inhibits tau self-aggregation, possibly through a different pathway.

CONCLUSION

EPIC-PYR, CAT-PYR, CAT-PhG, and NAC increased the number of neurites in Na2 cell line and inhibits tau-self aggregation in vitro.

Apelin-13 Suppresses Neuroinflammation Against Cognitive Deficit in a Streptozotocin-Induced Rat Model of Alzheimer's Disease Through Activation of BDNF-TrkB Signaling Pathway

Alzheimer’s disease (AD), a progressive neurodegenerative disease characterized by impairments of cognitive function as a result of synaptic deficits and neuronal loss, is associated with inflammation. Apelin-13, a predominant neuropeptide with inhibiting effect on inflammation, has beneficial effects on cognition memory and neuronal damage. However, whether apelin-13 can protect neurons to ameliorate cognitive deficits in AD by inhibiting the inflammatory response remains largely unknown. To test this hypothesis, rats were intracerebroventricularly (ICV) injected with streptozotocin (3 mg/kg) alone or in combination with apelin-13 (2 μg). And tyrosine receptor kinase B (TrkB) blocker K252a (200 nM) was administrated 10 min before apelin injection. Furthermore, cognitive performance was assessed by new object recognition (NOR) and Y-maze tests. Protein expression of apelin, APJ, microglial marker (IBA1), astroglia marker (GFAP), interleukin 1 beta (IL-1β), tumor necrosis factor-α (TNF-α), synaptophysin (SYP), brain-derived neurotrophic factor (BDNF), TrkB, phospho-TrkB (p-TrkB) in the hippocampus were examined by western blotting or immunohistochemistry. And the gene expression of IBA1, GFAP, IL-1β, TNF-α, and SYP were detected by real-time quantitative polymerase chain reaction (PCR). Inflammatory disorder in the hippocampus was tested by hematoxylin and eosin (H&E) staining. The enzyme-linked immunosorbent assay (ELISA) was used to study the expression level of acetylcholine. And the activity of acetylcholinesterase was detected by Acetylcholinesterase Assay Kit. We observed that apelin/APJ signaling was downregulated in the hippocampus of rats administrated with STZ. Apelin-13 was found to significantly ameliorate STZ-induced AD-like phenotypes including congnitive deficit, cholinergic disfunction and the damage of neuron and synaptic plasticity. Moreover, apelin-13 inhibited microglia and astrocyte activation, reduced IL-1β and TNF-α expression and hippocampal BDNF/TrkB expression deficit in AD rats. Finally, apelin-13-mediated effects were blocked by TrkB receptor antagonist K252a. These results suggest that apelin-13 upregulates BDNF/TrkB pathway against cognitive deficit in a STZ-induced rat model of sporadic AD by attenuating inflammation.

Overview on the Effects of N-Acetylcysteine in Neurodegenerative Diseases

N-acetylcysteine (NAC), which is an acetylated cysteine compound, has aroused scientific interest for decades due to its important medical applications. It also represents a nutritional supplement in the human diet. NAC is a glutathione precursor and shows antioxidant and anti-inflammatory activities. In addition to the uses quoted in the literature, NAC may be considered helpful in therapies to counteract neurodegenerative and mental health diseases. Furthermore, this compound has been evaluated for its neuroprotective potential in the prevention of cognitive aging dementia. NAC is inexpensive, commercially available and no relevant side effects were observed after its administration. The purpose of this paper is to give an overview on the effects and applications of NAC in Parkinson's and Alzheimer's disorders and in neuropathic pain and stroke.

N-acetylcysteine protects hepatocytes from hypoxia-related cell injury

Aim of the study

Hepatocyte transplantation has been discussed as an alternative to liver transplantation in selected cases of acute and chronic liver failure and metabolic diseases. Immediately after infusion of hepatocytes, hypoxia-related cell injury is inevitable. N-acetylcysteine (NAC) has been suggested to attenuate hypoxic damage. This study’s objective was to evaluate NAC’s protective effect in a model of hypoxia-related hepatocyte injury.

Material and methods

HepG2 cells were used as a model for hepatocytes and were cultured under standardized hypoxia or normoxia for 24 hours with or without NAC. Growth kinetics were monitored using trypan blue staining. The activation of apoptotic pathways was measured using quantitative real-time PCR for Bcl-2/Bax and p53. The proportions of vital, apoptotic and necrotic cells were verified by fluorescence activated cell sorting using annexin V-labelling. The expression of hypoxia inducible factor 1 (HIF-1) was measured indirectly using its downstream target vascular endothelial growth factor A (VEGF-A).

Results

After NAC, cell proliferation increased under both hypoxia and normoxia by 528% and 320% (p < 0.05), while VEGF-A expression decreased under normoxia by 67% and 37% (p < 0.05). Compared to cells treated without NAC under hypoxia, the Bcl-2/Bax ratio increased significantly in cells treated with NAC. This finding was confirmed by an increased number of vital cells in FACS analysis.

Conclusions

NAC protects hepatocytes from hypoxic injury and ultimately activates anti-apoptotic pathways.

Neuroprotective effects of Bergenia ciliata on NMDA induced injury in SH-SY5Y cells and attenuation of cognitive deficits in scopolamine induced amnesia in rats

Bergenia ciliata (Haw) Sternb. possess immunomodulatory, anti-inflammatory, antioxidant, anti-urolithiatic, wound healing, anti-malarial, anti-diabetic and anti-cancer properties. Moreover, the methanolic extracts of the rhizomes of the plant were found to demonstrate beneficial neuroprotective effects in the intracerebroventricular streptozotocin-induced model in rats. Thus, the present study was undertaken to further explore the neuroprotective potential of the aqueous (BA) and methanolic extracts (BM) of B. ciliata through various in-vitro and in-vivo studies. Both the extracts at all tested concentrations i.e. 50-50,000 ng/mL did not cause any significant reduction of cell viability of SH-SY5Y cells when tested for 48 h when assessed through MTT and resazurin metabolism- based cell viability assays. The pre-treatment with the extracts could confer significant (p < 0.001) and dose-dependent protective effects against NMDA induced injury in SH-SY5Y cells. BM [IC₅₀: 5.7 and 5.19 μg/mL for acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) respectively] led to more potent inhibition of both the enzymes as compared to BA (IC₅₀: 227.12 and 23.25 μg/mL for AChE and BuChE respectively). BM also proved to be a 1.85-fold better scavenger of the DPPH free radicals as compared to BA. Thus, BM was taken further for the evaluation of the beneficial effects of 14-day pre-treatment in rats in the scopolamine (2 mg/kg, i.p.) induced amnesia model at 125, 250 and 500 mg/kg, p.o. BM pre-treatment at 250 and 500 mg/kg could significantly ameliorate the cognitive impairment (p < 0.001), inhibit AChE (p < 0.001) and BuChE (p < 0.05) activity, restore GSH levels (p < 0.05) in serum and brain homogenates and recover the morphology of hippocampal neurons back to normal. Moreover, the BM administration at 500 mg/kg also showed beneficial effects through the significant (p < 0.05) reduction of Aβ_1-42, phosphorylated tau (p-tau) and GSK-3β immunoreactivity in the brain homogenates of the intracerebroventricularly streptozotocin (ICV STZ) injected rats as observed from the results of the ELISA assays. The outcomes of the study unveiled that BM exerts its beneficial effects through prevention of NMDA induced excitotoxic cell death, dual cholinesterase inhibition, antioxidant activity coupled with the reduction of the immunoreactivity for the Aβ_1-42, p-tau and GSK-3β indicating its potential to be screened further for various other models to determine the exact mechanism of action.

Neuroprotective effects of bergenin in Alzheimer's disease: Investigation through molecular docking, in vitro and in vivo studies

Alzheimer's disease (AD) is an enervating and chronic progressive neurodegenerative disorder, occurring frequently in the elderly and adversely affecting intellectual capabilities and the cognitive processes. Bergenin possesses efficacious antioxidant, antiulcerogenic, anti-HIV, hepatoprotective, neuroprotective, anti-inflammatory and immunomodulatory activity along with antinociceptive effect and wound healing properties. Previous studies have shown that bergenin has in vitro bovine adrenal tyrosine hydroxylase inhibitory activity, mushroom tyrosinase inhibitory activities, β-secretase (BACE-1) enzyme inhibitory activity and prevented neuronal death in the primary culture of rat cortical neurons. Protein tyrosine phosphatase-1B (PTP1B) is an intriguing target for anticancer and antidiabetic drugs and has recently been implicated to act as a positive regulator of neuroinflammation. Bergenin is also found to inhibit human protein tyrosine phosphatase-1B (hPTP1B) in vitro. Thus, bergenin was screened by molecular docking study using GOLD suite (version 5.2), CCDC for predicting its activity against targets of AD management like acetylcholinesterase (AChE) (1B41), butyrylcholinesterase (BuChE) (1P0I), Tau protein kinase 1 (GSK-3β) (1J1B), BACE-1 (1FKN) wherein the GOLD score and fitness of bergenin were comparable to those of standard drugs like donepezil, galanthamine, physostigmine, etc. Bergenin demonstrated dose-dependent inhibition of both AChE and BuChE in vitro and found to be safe up to 50 μM when screened in vitro on SH-SY5Y cell lines by cytotoxicity studies using MTT and Alamar blue assays. It also led to dose-dependent prevention of NMDA induced toxicity in these cells. Pretreatment with bergenin (14 days) in rats at three dose levels (20, 40 and 80 mg/kg; p.o.) significantly (p < 0.01) and dose-dependently alleviated amnesia induced by scopolamine (2 mg/kg, i.p.). The therapeutic effect of bergenin supplementation for 28 days, at three dose levels, was also evaluated in streptozotocin (3 mg/kg, ICV, unilateral) induced AD model in Wistar rats using Morris water maze and Y maze on 7th, 14th, 21st and 28th days. STZ caused significant (p < 0.001) cognitive impairment and cholinergic deficit and increased oxidative stress in rats. Bergenin could significantly ameliorate STZ induced behavioral deficits, inhibit the AChE and BuChE activity in parallel with an increase in the diminished GSH levels in a dose-dependent fashion. The histopathological investigations were also supportive of this datum. The bergenin treatment at 80 mg/kg led to significant (p < 0.05) abatement of the raised Aβ-_1-42 levels and alleviated the perturbed p- tau levels leading to significantly low (p < 0.01) levels of p-tau in brain homogenates of rats as compared to ICV STZ injected rats. In conclusion, the observed effects might be attributed to the cholinesterase inhibitory activity of bergenin coupled with its antioxidant effect, anti-inflammatory activity and reduction of Aβ-_1-42 and p-tau levels which could have collectively helped in the attenuation of cognitive deficits. The current findings of the study are indicative of the promising preventive and ameliorative potential of bergenin in the management of AD through multiple targets.

Behavioral and biochemical evidences for nootropic activity of boldine in young and aged mice

Boldine, a bioactive compound, has been reported to be neuroprotective, but its effect on learning and memory has not been explored. So, the present study was aimed to study the effect of boldine on the learning and memory of the Swiss albino male young and aged mice. Boldine (1.5, 3 and 6mg/kg, po) and physostigmine salicylate (0.1mg/kg, ip) were administered to separate groups of mice for 7 successive days. Morris water maze was utilized as a behavioural model to study the effect of drugs on learning and memory of mice. Boldine and physostigmine significantly improved learning and memory of young as well as aged mice, as indicated by decrease in escape latency time during training session and increase in time spent in target quadrant during retrieval session. No significant effect on locomotor activities of mice was observed due to drug treatments. Memory-enhancing activity of boldine (3mg/kg) was found to be comparable to physostigmine. Boldine significantly reversed scopolamine-, sodium nitrite- and aging-induced amnesia in mice. Moreover, boldine attenuated oxidative stress, as shown by a significant decrease in brain malondialdehyde as well as brain nitrite levels and a significant increase in brain GSH level of young as well as aged mice. Brain acetylcholinesterase activity was also significantly inhibited by boldine in young as well as aged mice. In conclusion boldine administered for 7 successive days exhibited significant improvement of learning and memory of young and aged mice possibly through inhibition of brain acetylcholinesterase activity and alleviation of brain oxidative stress.