Monosialoanglioside improves memory deficits and relieves oxidative stress in the hippocampus of rat model of Alzheimer’s disease

Ganglioside lipids inhibit the aggregation of the Alzheimer's amyloid-β peptide

The aggregation of the amyloid-β (Aβ) peptides (Aβ42/Aβ40) into amyloid fibrils and plaques is one of the molecular hallmarks in dementia and Alzheimer's disease (AD). While the molecular mechanisms behind this aggregation process are not fully known, it has been shown that some biomolecules can accelerate this process whereas others can inhibit amyloid formation. Lipids, which are ubiquitously found in cell membranes, play a pivotal role in protein aggregation. Here, we investigate how ganglioside lipids, which are abundant in the brain and in neurons, can influence the aggregation kinetics of both Aβ42 and Aβ40. We employ a variety of biophysical assays to characterise the effect ganglioside lipids have on the aggregation of Aβ. Through kinetic analysis, we show that the primary nucleation rate is greatly affected by the addition of gangliosides and that these lipids impair Aβ42 aggregation, while completely inhibiting Aβ40 aggregation. Furthermore, we find that an Aβ-ganglioside complex is formed, which potentially disrupts the aggregation pathway and results in delayed kinetics. Taken together, our results provide a quantitative description of how lipid molecules such as gangliosides can inhibit the aggregation of Aβ and shed light on the key factors that control these processes. In view of the fact that declining levels of gangliosides in neurons have been associated with ageing, our findings could be instrumental towards establishing new approaches in the prevention of amyloid-β aggregation.

Ganglioside GM1 and the Central Nervous System

GM1 is one of the major glycosphingolipids (GSLs) on the cell surface in the central nervous system (CNS). Its expression level, distribution pattern, and lipid composition are dependent upon cell and tissue type, developmental stage, and disease state, which suggests a potentially broad spectrum of functions of GM1 in various neurological and neuropathological processes. The major focus of this review is the roles that GM1 plays in the development and activities of brains, such as cell differentiation, neuritogenesis, neuroregeneration, signal transducing, memory, and cognition, as well as the molecular basis and mechanisms for these functions. Overall, GM1 is protective for the CNS. Additionally, this review has also examined the relationships between GM1 and neurological disorders, such as Alzheimer's disease, Parkinson's disease, GM1 gangliosidosis, Huntington's disease, epilepsy and seizure, amyotrophic lateral sclerosis, depression, alcohol dependence, etc., and the functional roles and therapeutic applications of GM1 in these disorders. Finally, current obstacles that hinder more in-depth investigations and understanding of GM1 and the future directions in this field are discussed.

GM1 Ganglioside as a Disease-Modifying Therapeutic for Parkinson's Disease: A Multi-Functional Glycosphingolipid That Targets Multiple Parkinson's Disease-Relevant Pathogenic Mechanisms

Parkinson's disease (PD) is a progressive neurodegenerative disorder affecting millions of patients worldwide. Many therapeutics are available for treating PD symptoms but there is no disease-modifying therapeutic that has been unequivocally shown to slow or stop the progression of the disease. There are several factors contributing to the failure of many putative disease-modifying agents in clinical trials and these include the choice of patients and clinical trial designs for disease modification trials. Perhaps more important, however, is the choice of therapeutic, which for the most part, has not taken into account the multiple and complex pathogenic mechanisms and processes involved in PD. This paper discusses some of the factors contributing to the lack of success in PD disease-modification trials, which have mostly investigated therapeutics with a singular mechanism of action directed at one of the many PD pathogenic processes, and suggests that an alternative strategy for success may be to employ multi-functional therapeutics that target multiple PD-relevant pathogenic mechanisms. Evidence is presented that the multi-functional glycosphingolipid GM1 ganglioside may be just such a therapeutic.

The Neuroprotective Effect of GM-1 Ganglioside on the Amyloid-Beta-Induced Oxidative Stress in PC-12 Cells Mediated by Nrf-2/ARE Signaling Pathway

Alzheimer's disease (AD) is characterized by the accumulation of amyloid-β (Aβ) plaques, tau tangles, neuroinflammation, oxidative stress, and progressive memory deficits. Aβ deposition could exacerbate oxidative damage and cellular apoptosis. GM-1 ganglioside (GM-1) has previously been reported to exhibit neuroprotective effects in rodents and patients with AD. However, the substantial impacts and mechanism of GM-1 on Aβ-induced oxidative stress remain elusive. The present study used PC-12 pheochromocytoma cells treated with Aβ_25-35 peptide to construct the AD model in vitro. Aβ_25-35 administration alone inhibited cell viability and facilitated cell apoptosis in the range doses of 10 μM to 30 μM. At the same time, GM-1 supplementation promoted cell proliferation and rescued cell apoptosis in a dose-dependent fashion ranging from 5 to 30 μM. In parallel, GM-1 treatment alleviated Aβ-induced oxidative stress by increasing the level of antioxidant enzymes and decreasing the content of malondialdehyde (MDA). The nuclear factor-E2-related factor 2 (Nrf2) is a crucial mediator of antioxidant response. We reported herein that GM-1 could activate Nrf-2 in the PC-12 cells co-treated with Aβ_25-35, following with the activated expression of antioxidant response elements (ARE)-mediated antioxidant and detoxifying genes. Consistently, knock-down of Nrf-2 via siRNA abolished the beneficial decrease of Aβ-induced oxidative stress by GM-1 treatment, indicating that GM-1-improved oxidative stress was regulated by the Nrf-2 signaling pathway. Collectively, GM-1 could alleviate Aβ_25-35-induced oxidative damage mediated through the Nrf-2/ARE signaling pathway, which might be a potential agent for AD treatment.

Mass spectrometry-based ganglioside profiling provides potential insights into Alzheimer's disease development

Gangliosides are a family of glycosphingolipids which are particularly enriched in the nervous system. They play crucial roles in neuroprotection and neurological diseases. Alzheimer's disease (AD) is a neurodegenerative disease with cognitive, judgment and memory dysfunction. In this study, a mass spectrometry-based data-dependent acquisition method assisted with fragmentation characteristics screening by computer algorithm was developed for qualitative and quantitative analysis of gangliosides at low concentration. The developed method was applied to obtain detailed ganglioside species content in hippocampus of model mice (APPswe/PS1dE9 transgenic mice) with AD at 3- to 8-month-old. Up-regulated acetylated and N-acetylgalactosaminylated ganglioside species, and the down-regulated major gangliosides were observed with the development of AD from early to late stage. We speculated that deterioration of AD may be related to the acetylation/N-acetylgalactosaminylation transformation of complex gangliosides due to the inhibition of GD3 synthase activity. Moreover, the ganglioside species di-O-Ac-GT1a (d36:1), O-Ac-GD1b (d36:1) and O-Ac-GD1b (d36:0) were considered as the time-coursed biomarkers, and O-Ac-GT1a (d36:2) could be a candidate for early diagnosis of AD.

Amyloid-β peptide dimers undergo a random coil to β-sheet transition in the aqueous phase but not at the neuronal membrane

Mounting evidence suggests that the neuronal cell membrane is the main site of oligomer-mediated neuronal toxicity of amyloid-β peptides in Alzheimer's disease. To gain a detailed understanding of the mutual interference of amyloid-β oligomers and the neuronal membrane, we carried out microseconds of all-atom molecular dynamics (MD) simulations on the dimerization of amyloid-β (Aβ)42 in the aqueous phase and in the presence of a lipid bilayer mimicking the in vivo composition of neuronal membranes. The dimerization in solution is characterized by a random coil to β-sheet transition that seems on pathway to amyloid aggregation, while the interactions with the neuronal membrane decrease the order of the Aβ42 dimer by attenuating its propensity to form a β-sheet structure. The main lipid interaction partners of Aβ42 are the surface-exposed sugar groups of the gangliosides GM1. As the neurotoxic activity of amyloid oligomers increases with oligomer order, these results suggest that GM1 is neuroprotective against Aβ-mediated toxicity.

Attenuation of spatial memory in 5xFAD mice by targeting cholinesterases, oxidative stress and inflammatory signaling using 2-(hydroxyl-(2-nitrophenyl)methyl)cyclopentanone

Alzheimer's disease (AD) is classified pathologically as a progressive neurological disorder associated with memory decline. The study was designed to assess the underlying molecular signaling involved in the neuroprotective effect of the 2-(hydroxyl-(2-nitrophenyl)methyl)cyclopentanone (2NCP) as a novel therapeutic agent for AD. In this connection, in vitro cholinesterases inhibitory and antioxidant activities were investigated. In vivo studies were carried out on a well-known 5xFAD mice model in different behavioural models such as light/dark box,balance beam, rotarod, elevated plus maze (EPM),novel object recognition (NOR), paddling Y-maze, and Morris water maze (MWM) tests. Hippocampus (HC) and frontal cortex (FC) homogenates were examined for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities, 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals, glutathione S-transferase (GST), glutathione (GSH), and catalase. Further, we examined the expression of inflammatory cytokines and Nrf2 in the HC and FC through RT-PCR. Computational studies were conducted to predict the binding mode of the 2NCP with target sites of nuclear factor-κB (NF-κB) and cholinesterases. The findings of in vitro assays revealed that the IC₅₀ values of the 2NCP against AChE and BChE were 17 and 23 µg/ml respectively. DPPH antioxidant assay displayed an IC₅₀ value for the 2NCP was 62 µg/ml. Whereas, theex vivo study depicted that the activities of AChE and BChEwere significantly reduced. Moreover, free radicals load, GSH level, catalase and GST activities were significantly declined. Furthermore, in vivostudies showed that the 2NCP treated animals exhibited gradual memory improvement and improved motor functions. RT-PCR study revealed that mRNA levels of the inflammatory mediators (IL-1β, IL-6, TNF-α) were significantly reduced, while the expression of antioxidant Nrf2 was significantly increased.The molecular docking studies further confirmed that the 2NCP showed excellent binding affinities for NF-κB and cholinesterases. Taken together, the 2NCP improves spatial memory and learning, short- and long-term memory,markedly inhibits cholinesterases, reduced neuroinflammation, and mitigated oxidative stress in the 5xFAD mice; hence the 2NCP may be a potential candidate for the management of AD.

Interactions of Amyloid-β with Membrane Proteins

In developing and developed countries, an increasing elderly population is observed. This affects the growing percentage of people struggling with neurodegenerative diseases, including Alzheimer's disease. Nevertheless, the pathomechanism of this disease is still unknown. This contributes to problems with early diagnosis of the disease as well as with treatment. One of the most popular hypotheses of Alzheimer's disease is related to the pathological deposition of amyloid-β (Aβ) in the brain of ill people. In this paper, we discuss issues related to Aβ and its relationship in the development of Alzheimer's disease. The structure of Aβ and its interaction with the cell membrane are discussed. Not only do the extracellular plaques affect nerve cells, but other forms of this peptide as well.

The significance of sialylation on the pathogenesis of Alzheimer's disease

Sialylation, one of the most common and complex modes of glycosylation, corresponds with the development of the infant brain and nervous system. The most prevalent neurodegenerative disease is Alzheimer's disease (AD), which is mainly characterized by cognitive decline and behavioral disorders. However, the relationship between sialylation and AD occurrence is poorly understood. In this article, we reviewed the role of sialylation on the occurrence and development of AD, then discussed the value of sialylation modification for AD diagnosis and treatment.

Ganglioside GM1 Targets Astrocytes to Stimulate Cerebral Energy Metabolism

Gangliosides are major constituents of the plasma membrane and are known to promote a number of physiological actions in the brain, including synaptic plasticity and neuroprotection. In particular, the ganglioside GM1 was found to have a wide range of preclinical and clinical benefits in brain diseases such as spinal cord injury, Huntington’s disease and Parkinson’s disease. However, little is known about the underlying cellular and molecular mechanisms of GM1 in the brain. In the present study, we show that GM1 exerts its actions through the promotion of glycolysis in astrocytes, which leads to glucose uptake and lactate release by these cells. In astrocytes, GM1 stimulates the expression of several genes involved in the regulation of glucose metabolism. GM1 also enhances neuronal mitochondrial activity and triggers the expression of neuroprotection genes when neurons are cultured in the presence of astrocytes. Finally, GM1 leads to a neuroprotective effect in astrocyte-neuron co-culture. Together, these data identify a previously unrecognized mechanism mediated by astrocytes by which GM1 exerts its metabolic and neuroprotective effects.

Implications of Glycosylation in Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia, affecting millions of people worldwide, and no cure is currently available. The major pathological hallmarks of AD are considered to be amyloid beta plaques and neurofibrillary tangles, generated by respectively APP processing and Tau phosphorylation. Recent evidence imply that glycosylation of these proteins, and a number of other AD-related molecules is altered in AD, suggesting a potential implication of this process in disease pathology. In this review we summarize the understanding of glycans in AD pathogenesis, and discuss how glycobiology can contribute to early diagnosis and treatment of AD, serving as potential biomarkers and therapeutic targets. Furthermore, we look into the potential link between the emerging topic neuroinflammation and glycosylation, combining two interesting, and until recent years, understudied topics in the scope of AD. Lastly, we discuss how new model platforms such as induced pluripotent stem cells can be exploited and contribute to a better understanding of a rather unexplored area in AD.

Glycosphingolipids

Glycosphingolipids are amphiphilic plasma membrane components formed by a glycan linked to a specific lipid moiety. In this chapter we report on these compounds, on their role played in our cells to maintain the correct cell biology.In detail, we report on their structure, on their metabolic processes, on their interaction with proteins and from this, their property to modulate positively in health and negatively in disease, the cell signaling and cell biology.

Gangliosides in the Brain: Physiology, Pathophysiology and Therapeutic Applications

Gangliosides are glycosphingolipids highly abundant in the nervous system, and carry most of the sialic acid residues in the brain. Gangliosides are enriched in cell membrane microdomains ("lipid rafts") and play important roles in the modulation of membrane proteins and ion channels, in cell signaling and in the communication among cells. The importance of gangliosides in the brain is highlighted by the fact that loss of function mutations in ganglioside biosynthetic enzymes result in severe neurodegenerative disorders, often characterized by very early or childhood onset. In addition, changes in the ganglioside profile (i.e., in the relative abundance of specific gangliosides) were reported in healthy aging and in common neurological conditions, including Huntington's disease (HD), Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), stroke, multiple sclerosis and epilepsy. At least in HD, PD and in some forms of epilepsy, experimental evidence strongly suggests a potential role of gangliosides in disease pathogenesis and potential treatment. In this review, we will summarize ganglioside functions that are crucial to maintain brain health, we will review changes in ganglioside levels that occur in major neurological conditions and we will discuss their contribution to cellular dysfunctions and disease pathogenesis. Finally, we will review evidence of the beneficial roles exerted by gangliosides, GM1 in particular, in disease models and in clinical trials.

The Role of Lipid Environment in Ganglioside GM1-Induced Amyloid β Aggregation

Ganglioside GM1 is the most common brain ganglioside enriched in plasma membrane regions known as lipid rafts or membrane microdomains. GM1 participates in many modulatory and communication functions associated with the development, differentiation, and protection of neuronal tissue. It has, however, been demonstrated that GM1 plays a negative role in the pathophysiology of Alzheimer's disease (AD). The two features of AD are the formation of intracellular neurofibrillary bodies and the accumulation of extracellular amyloid β (Aβ). Aβ is a peptide characterized by intrinsic conformational flexibility. Depending on its partners, Aβ can adopt different spatial arrangements. GM1 has been shown to induce specific changes in the spatial organization of Aβ, which lead to enhanced peptide accumulation and deleterious effect especially on neuronal membranes containing clusters of this ganglioside. Changes in GM1 levels and distribution during the development of AD may contribute to the aggravation of the disease.

Exogenous GM1 Ganglioside Attenuates Ketamine-Induced Neurocognitive Impairment in the Developing Rat Brain

BACKGROUND

A prolonged exposure to ketamine triggers significant neurodegeneration and long-term neurocognitive deficits in the developing brain. Monosialotetrahexosylganglioside (GM1) can limit the neuronal damage from necrosis and apoptosis in neurodegenerative conditions. We aimed to assess whether GM1 can prevent ketamine-induced developmental neurotoxicity.

METHODS

Postnatal day 7 (P7) rat pups received 5 doses of intraperitoneal ketamine (20 mg/kg per dose) at 90-minute intervals for 6 hours. Cognitive functions, determined by using Morris water maze (MWM) including escape latency (at P32-36) and platform crossing (at P37), were compared among the ketamine-exposed pups treated with or without exogenous GM1 (30 mg/kg; n = 12/group). The effect of GM1 on apoptosis in hippocampus was determined by terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick end labeling (TUNEL) staining and activated caspase 3 measurement. The hippocampal expression of brain-derived neurotrophic factor (BDNF), along with the phosphorylation of protein kinase B (AKT) and extracellular signal-related kinases 1 and 2 (ERK1/2), was detected by western blotting (n = 6/group). Anti-BDNF antibody (2 μg per rat) administered before GM1 treatment was applied to determine the neuroprotective mechanisms of GM1.

RESULTS

The rats receiving ketamine exposure experinced cognitive impairment in MWM test compared to the control rats, indicated by prolonged escape latency at P34 (P = .006), P35 (P = .002), and P36 (P = .005). However, in GM1-pretreated rats, ketamine exposure did not induce prolonged escape latency. The exogenous GM1 increased the platform-crossing times at P37 (3.00 ± 2.22 times vs 5.40 ± 1.53 times, mean ± standard deviation; P = .041) and reduced the hippocampal TUNEL-positive cells and cleaved-caspase 3 expression in ketamine-exposed young rats. Ketamine decreased BDNF expression and phosphorylation of AKT and ERK in the hippocampus, whereas exogenous GM1 blocked these ketamine-caused effects. However, for the ketamine-exposed rat pups receiving exogenous GM1, compared to immunoglobulin Y (IgY) isotype control, the BDNF-neutralizing antibody treatment counteracted the exogenous GM1-induced improvement of the escape latency at P36 (41.32 ± 12.37 seconds vs 25.14 ± 8.97 seconds, mean ± standard deviation; P = .036), platform-crossing times at P37 (2.16 ± 1.12 times vs 3.92 ± 1.97 times, mean ± standard deviation; P < .036), apoptotic activity, as well as AKT and ERK1/2 phosphorylation in the hippocampus of ketamine-challenged young rats.

CONCLUSIONS

Our data suggest that the exogenous GM1 acts on BDNF signaling pathway to ameliorate the cognitive impairment and hippocampal apoptosis induced by ketamine in young rats. Our study may indicate a potential use of GM1 in preventing the cognitive deficits induced by ketamine in the young per se.

Aβ-ganglioside interactions in the pathogenesis of Alzheimer's disease

It is widely accepted that the abnormal self-association of amyloid β-protein (Aβ) is central to the pathogenesis of Alzheimer's disease, the most common form of dementia. Accumulating evidence, both in vivo and in vitro, suggests that the binding of Aβ to gangliosides, especially monosialoganglioside GM1, plays an important role in the aggregation of Aβ. This review summarizes the molecular details of the binding of Aβ to ganglioside-containing membranes and subsequent structural changes, as revealed by liposomal and cellular studies. Furthermore, mechanisms of cytotoxicity by aggregated Aβ are also discussed.

Lipids and Alzheimer's Disease

Lipids, as the basic component of cell membranes, play an important role in human health as well as brain function. The brain is highly enriched in lipids, and disruption of lipid homeostasis is related to neurologic disorders as well as neurodegenerative diseases such as Alzheimer’s disease (AD). Aging is associated with changes in lipid composition. Alterations of fatty acids at the level of lipid rafts and cerebral lipid peroxidation were found in the early stage of AD. Genetic and environmental factors such as apolipoprotein and lipid transporter carrying status and dietary lipid content are associated with AD. Insight into the connection between lipids and AD is crucial to unraveling the metabolic aspects of this puzzling disease. Recent advances in lipid analytical methodology have led us to gain an in-depth understanding on lipids. As a result, lipidomics have becoming a hot topic of investigation in AD, in order to find biomarkers for disease prediction, diagnosis, and prevention, with the ultimate goal of discovering novel therapeutics.

GM1 Ganglioside Is A Key Factor in Maintaining the Mammalian Neuronal Functions Avoiding Neurodegeneration

Many species of ganglioside GM1, differing for the sialic acid and ceramide content, have been characterized and their physico-chemical properties have been studied in detail since 1963. Scientists were immediately attracted to the GM1 molecule and have carried on an ever-increasing number of studies to understand its binding properties and its neurotrophic and neuroprotective role. GM1 displays a well balanced amphiphilic behavior that allows to establish strong both hydrophobic and hydrophilic interactions. The peculiar structure of GM1 reduces the fluidity of the plasma membrane which implies a retention and enrichment of the ganglioside in specific membrane domains called lipid rafts. The dynamism of the GM1 oligosaccharide head allows it to assume different conformations and, in this way, to interact through hydrogen or ionic bonds with a wide range of membrane receptors as well as with extracellular ligands. After more than 60 years of studies, it is a milestone that GM1 is one of the main actors in determining the neuronal functions that allows humans to have an intellectual life. The progressive reduction of its biosynthesis along the lifespan is being considered as one of the causes underlying neuronal loss in aged people and severe neuronal decline in neurodegenerative diseases. In this review, we report on the main knowledge on ganglioside GM1, with an emphasis on the recent discoveries about its bioactive component.

A Systematic Review of Interleukin-1β in Post-Traumatic Stress Disorder: Evidence from Human and Animal Studies

Pro-inflammatory cytokines, such as interleukin (IL)-1β, have been implicated as underlying pathophysiological mechanisms and potential biomarkers of post-traumatic stress disorder (PTSD). This systematic review examines data regarding IL-1β production/concentration in human and animal studies of PTSD. In accordance with PRISMA guidelines, relevant articles from PubMed were reviewed from inception until July 10, 2017. Nineteen studies were eligible for inclusion. Animal studies demonstrated increased hippocampal IL-1β in rodent models of PTSD. Several immunomodulatory drugs were shown to reduce elevated IL-1β levels and anxiety-like behaviors in animals. Human cross-sectional studies showed contradictory results; serum and plasma IL-1β concentrations in PTSD patients were either elevated or did not differ from control groups. In vitro IL-1β production by stimulated cells demonstrated no difference between PTSD and control participants, although spontaneous in vitro production of IL-1β was increased in the PTSD group. The findings from 2 longitudinal studies were inconsistent. Given the conflicting findings, it is premature to consider IL-1β as a biomarker of PTSD. Anti-inflammatory agents may reduce IL-1β, and be a potential basis for future therapeutic agents in PTSD treatment. More longitudinal research is needed to better understand the role of IL-1β in the development and/or maintenance of PTSD.

Gangliosides: Treatment Avenues in Neurodegenerative Disease

Gangliosides are cell membrane components, most abundantly in the central nervous system (CNS) where they exert among others neuro-protective and -restorative functions. Clinical development of ganglioside replacement therapy for several neurodegenerative diseases was impeded by the BSE crisis in Europe during the 1990s. Nowadays, gangliosides are produced bovine-free and new pre-clinical and clinical data justify a reevaluation of their therapeutic potential in neurodegenerative diseases. Clinical experience is greatest with monosialo-tetrahexosyl-ganglioside (GM1) in the treatment of stroke. Fourteen randomized controlled trials (RCTs) in overall >2,000 patients revealed no difference in survival, but consistently superior neurological outcomes vs. placebo. GM1 was shown to attenuate ischemic neuronal injuries in diabetes patients by suppression of ERK1/2 phosphorylation and reduction of stress to the endoplasmic reticulum. There is level-I evidence from 5 RCTs of a significantly faster recovery with GM1 vs. placebo in patients with acute and chronic spinal cord injury (SCI), disturbance of consciousness after subarachnoid hemorrhage, or craniocerebral injuries due to closed head trauma. In Parkinson's disease (PD), two RCTs provided evidence of GM1 to be superior to placebo in improving motor symptoms and long-term to result in a slower than expected symptom progression, suggesting disease-modifying potential. In Alzheimer's disease (AD), the role of gangliosides has been controversial, with some studies suggesting a "seeding" role for GM1 in amyloid β polymerization into toxic forms, and others more recently suggesting a rather protective role in vivo. In Huntington's disease (HD), no clinical trials have been conducted yet. However, low GM1 levels observed in HD cells were shown to increase cell susceptibility to apoptosis. Accordingly, treatment with GM1 increased survival of HD cells in vitro and consistently ameliorated pathological phenotypes in several murine HD models, with effects seen at molecular, cellular, and behavioral level. Given that in none of the clinical trials using GM1 any clinically relevant safety issues have occurred to date, current data supports expanding GM1 clinical research, particularly to conditions with high, unmet medical need.

Dissociation of HKII in retinal epithelial cells induces oxidative stress injury in the retina

The retina is sensitive to injury resulting from oxidative stress (OS) due to its high oxygen consumption. Patients with retinitis pigmentosa suffer from excessive OS. N‑acetylcysteine (NAC) is used as a mucolytic agent for the clinical treatment of disorders, such as chronic bronchitis and other pulmonary diseases. The aim of the present study was to investigate the role of hexokinase 2 (HKII) in retinal OS injury. Amyloid β (Aβ)1‑40 was used to establish a cellular model of OS. Cell viability was measured with a Cell Counting Kit‑8 assay, and the apoptosis, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) of cells were analyzed via flow cytometry with corresponding kits. The mRNA and protein levels were detected by reverse transcription‑quantitative PCR and western blot analyses, respectively. It was observed that Aβ1‑40 reduced the expression of HKII in the mitochondria of retinal pigment epithelial ARPE cells and impaired mitochondrial antioxidant functions. Additionally, knockdown of HKII promoted apoptosis, and increased ROS levels and the MMP. NAC attenuated the inhibition of mitochondrial functions induced by Aβ1‑40. The knockdown of HKII was revealed to decrease the levels of Bcl‑2, manganese superoxide dismutase (SOD) and copper‑zinc‑SOD, and increase the levels of cleaved caspase‑3, Bax and cytochrome c. The present findings suggested that the dissociation of HKII induced by OS induces apoptosis and mitochondrial damage. This study provided improved understanding of the mechanisms underlying the effects of OS on retinal epithelial cells.

GM1 Ameliorates Lead-Induced Cognitive Deficits and Brain Damage Through Activating the SIRT1/CREB/BDNF Pathway in the Developing Male Rat Hippocampus

Developmental lead (Pb) exposure involves various serious consequences, especially leading to neurotoxicity. In this study, we examined the possible role of monosialoganglioside (GM1) in lead-induced nervous impairment in the developing rat. Newborn male Sprague-Dawley rat pups were exposed to lead from birth for 30 days and then subjected to GM1 administration (0.4, 2, or 10 mg/kg; i.p.) or 0.9% saline. The results showed that developmental lead exposure significantly impaired spatial learning and memory in the Morris water maze test, reduced GM1 content, induced oxidative stress, and weakened the antioxidative systems in the hippocampus. However, co-treatment with GM1 reversed these effects. Moreover, GM1 counteracted lead-induced apoptosis by decreasing the expression of Bax, cleaved caspase-3, and by increasing the level of Bcl-2 in a dose-dependent manner. Furthermore, we found that GM1 upregulated the expression of SIRT1, CREB phosphorylation, and BDNF, which underlie learning and memory in the lead-treated developing rat hippocampus. In conclusion, our study demonstrated that GM1 exerts a protective effect on lead-induced cognitive deficits via antioxidant activity, preventing apoptosis, and activating SIRT1/CREB/BDNF in the developing rat hippocampus, implying a novel potential assistant therapy for lead poisoning.

Ganglioside GM1 protects against high altitude cerebral edema in rats by suppressing the oxidative stress and inflammatory response via the PI3K/AKT-Nrf2 pathway

High altitude cerebral edema (HACE) is a severe type of acute mountain sickness (AMS) that occurs in response to a high altitude hypobaric hypoxic (HH) environment. GM1 monosialoganglioside can alleviate brain injury under adverse conditions including amyloid-β-peptide, ischemia and trauma. However, its role in HACE-induced brain damage remains poorly elucidated. In this study, GM1 supplementation dose-dependently attenuated increase in rat brain water content (BWC) induced by hypobaric chamber (7600 m) exposurefor 24 h. Compared with the HH-treated group, rats injected with GM1 exhibited less brain vascular leakage, lower aquaporin-4 and higher occludin expression, but they also showed increase in Na+/K+-ATPase pump activities. Importantly, HH-incurred consciousness impairment and coordination loss also were ameliorated following GM1 administration. Furthermore, the increased oxidative stress and decrease in anti-oxidant stress system under the HH condition were also reversely abrogated by GM1 treatment via suppressing accumulation of ROS, MDA and elevating the levels of SOD and GSH. Simultaneously, GM1 administration also counteracted the enhanced inflammation in HH-exposed rats by muting pro-inflammatory cytokines IL-1β, TNF-α, and IL-6 levels in serum and brain tissues. Subsequently, GM1 potentiated the activation of the PI3K/AKT-Nrf2 pathway. Cessation of this pathway by LY294002 reversed GM1-mediated inhibitory effects on oxidative stress and inflammation, and ultimately abrogated the protective role of GM1 in abating brain edema, cognitive and motor dysfunction. Overall, GM1 may afford a protective intervention in HACE by suppressing oxidative stress and inflammatory response via activating the PI3K/AKT-Nrf2 pathway, implying a promising agent for the treatment of HACE.

The Pathogenic Role of Ganglioside Metabolism in Alzheimer's Disease-Cholinergic Neuron-Specific Gangliosides and Neurogenesis

Alzheimer's disease (AD) is the most common type of dementia with clinical symptoms that include deficits in memory, judgment, thinking, and behavior. Gangliosides are present on the outer surface of plasma membranes and are especially abundant in the nervous tissues of vertebrates. Ganglioside metabolism, especially the cholinergic neuron-specific gangliosides, GQ1bα and GT1aα, is altered in mouse model of AD and patients with AD. Thus, alterations in ganglioside metabolism may participate in several events related to the pathogenesis of AD. Increased expressions of GT1aα may reflect cholinergic neurogenesis. Most changes in ganglioside metabolism occur in the specific brain areas and their lipid rafts. Targeting ganglioside metabolism in lipid rafts may represent an underexploited opportunity to design novel therapeutic strategies for AD.

Baseline Oxidative Stress Is Associated with Memory Changes in Omega-3 Fatty Acid Treated Coronary Artery Disease Patients

Objective

This study investigated whether pretreatment oxidative stress, measured by lipid hydroperoxides (LPH), 4-hydroxy-2-nonenal (4-HNE), 8-isoprostane (8-ISO), and malondialdehyde (MDA), was associated with improvement in immediate recall among n-3 PUFA-treated coronary artery disease patients.

Methods

This was a secondary analysis of the CAROTID trial (NCT00981383). Composite immediate recall, measured using the California Verbal Learning Test, Second Edition, and the Brief Visuospatial Memory Test-Revised, was assessed. LPH, 4-HNE, 8-ISO, MDA, and n-3 PUFA concentrations were analysed from fasting blood. Patients then received either n-3 PUFA treatment or placebo for 12 weeks, after which composite immediate recall was reassessed. Linear regression was used to investigate relationships between lipid peroxidation markers and changes in composite immediate recall in each treatment group.

Results

Eighty-five patients (age = 61.1 ± 8.5, 77% male, mean years of education = 15.3 ± 3.4) were included (n = 46 placebo, n = 39 n-3 PUFA). After adjusting for multiple comparisons and potential confounders, greater baseline concentrations of LPH (β = 0.45, p = .002) and 4-HNE (β = 0.38, p = .005) were associated with greater improvement in composite immediate recall among n-3 PUFA-treated patients. No other associations were observed.

Conclusions

N-3 PUFA treatment may be more likely to improve immediate recall in patients with greater oxidative stress.

Impact of GM1 on Membrane-Mediated Aggregation/Oligomerization of β-Amyloid: Unifying View

In this perspective we summarize current knowledge of the effect of monosialoganglioside GM₁ on the membrane-mediated aggregation of the β-amyloid (Aβ) peptide. GM₁ has been suggested to be actively involved in the development of Alzheimer's disease due to its ability to seed the aggregation of Aβ. However, GM₁ is known to be neuroprotective against Aβ-induced toxicity. Here we suggest that the two scenarios are not mutually exclusive but rather complementary, and might depend on the organization of GM₁ in membranes. Improving our understanding of the molecular details behind the role of gangliosides in neurodegenerative amyloidoses might help in developing disease-modifying treatments.

Comparative study of the transfection efficiency of commonly used viral vectors in rhesus monkey (Macaca mulatta) brains

Viral vector transfection systems are among the simplest of biological agents with the ability to transfer genes into the central nervous system. In brain research, a series of powerful and novel gene editing technologies are based on these systems. Although many viral vectors are used in rodents, their full application has been limited in non-human primates. To identify viral vectors that can stably and effectively express exogenous genes within non-human primates, eleven commonly used recombinant adeno-associated viral and lentiviral vectors, each carrying a gene to express green or red fluorescence, were injected into the parietal cortex of four rhesus monkeys. The expression of fluorescent cells was used to quantify transfection efficiency. Histological results revealed that recombinant adeno-associated viral vectors, especially the serotype 2/9 coupled with the cytomegalovirus, human synapsin I, or Ca2+/calmodulin-dependent protein kinase II promoters, and lentiviral vector coupled with the human ubiquitin C promoter, induced higher expression of fluorescent cells, representing high transfection efficiency. This is the first comparison of transfection efficiencies of different viral vectors carrying different promoters and serotypes in non-human primates (NHPs). These results can be used as an aid to select optimal vectors to transfer exogenous genes into the central nervous system of non-human primates.

Endo-lysosomal and autophagic dysfunction: a driving factor in Alzheimer's disease?

Alzheimer's disease (AD) is the most common cause of dementia, and its prevalence will increase significantly in the coming decades. Although important progress has been made, fundamental pathogenic mechanisms as well as most hereditary contributions to the sporadic form of the disease remain unknown. In this review, we examine the now substantial links between AD pathogenesis and lysosomal biology. The lysosome hydrolyses and processes cargo delivered by multiple pathways, including endocytosis and autophagy. The endo-lysosomal and autophagic networks are central to clearance of cellular macromolecules, which is important given there is a deficit in clearance of amyloid-β in AD. Numerous studies show prominent lysosomal dysfunction in AD, including perturbed trafficking of lysosomal enzymes and accumulation of the same substrates that accumulate in lysosomal storage disorders. Examination of the brain in lysosomal storage disorders shows the accumulation of amyloid precursor protein metabolites, which further links lysosomal dysfunction with AD. This and other evidence leads us to hypothesise that genetic variation in lysosomal genes modifies the disease course of sporadic AD.

GM1 Ganglioside Inhibits β-Amyloid Oligomerization Induced by Sphingomyelin

β-Amyloid (Aβ) oligomers are neurotoxic and implicated in Alzheimer's disease. Neuronal plasma membranes may mediate formation of Aβ oligomers in vivo. Membrane components sphingomyelin and GM1 have been shown to promote aggregation of Aβ; however, these studies were performed under extreme, non-physiological conditions. We demonstrate that physiological levels of GM1 , organized in nanodomains do not seed oligomerization of Aβ40 monomers. We show that sphingomyelin triggers oligomerization of Aβ40 and that GM1 is counteractive thus preventing oligomerization. We propose a molecular explanation that is supported by all-atom molecular dynamics simulations. The preventive role of GM1 in the oligomerization of Aβ40 suggests that decreasing levels of GM1 in the brain, for example, due to aging, could reduce protection against Aβ oligomerization and contribute to the onset of Alzheimer's disease.

Antidepressant-Like Effects of GM1 Ganglioside Involving the BDNF Signaling Cascade in Mice

BACKGROUND

Depression is a serious psychiatric disorder that easily causes physical impairments and a high suicide rate. Monosialotetrahexosylganglioside is a crucial ganglioside for the central nervous system and has been reported to affect the function of the brain derived neurotrophic factor system. This study is aimed to evaluate whether monosialotetrahexosylganglioside has antidepressant-like effects.

METHODS

Antidepressant-like effects of monosialotetrahexosylganglioside were assessed in the chronic social defeat stress model of depression, and various behavioral tests were performed. Changes in the brain derived neurotrophic factor signaling pathway after chronic social defeat stress and monosialotetrahexosylganglioside treatment were also investigated. A tryptophan hydroxylase inhibitor and brain derived neurotrophic factor signaling inhibitors were used to determine the antidepressant mechanisms of monosialotetrahexosylganglioside.

RESULTS

Monosialotetrahexosylganglioside administration significantly reversed the chronic social defeat stress-induced reduction of sucrose preference and social interaction in mice and also prevented the increased immobility time in the forced swim test and tail suspension test. In addition, monosialotetrahexosylganglioside completely ameliorated the stress-induced dysfunction of brain derived neurotrophic factor signaling cascade in the hippocampus and medial prefrontal cortex, 2 regions closely involved in the pathophysiology of depression. Furthermore, the usage of brain derived neurotrophic factor signaling cascade inhibitors, K252a and anti-brain derived neurotrophic factor antibody, each abolished the antidepressant-like effects of monosialotetrahexosylganglioside, while the usage of a serotonin system inhibitor did not.

CONCLUSIONS

Taken together, our findings suggest that monosialotetrahexosylganglioside indeed has antidepressant-like effects, and these effects were mediated through the activation of brain derived neurotrophic factor signaling cascade.

The role of gangliosides in neurodevelopment

Gangliosides are important components of neuronal cell membranes and it is widely accepted that they play a critical role in neuronal and brain development. They are functionally involved in neurotransmission and are thought to support the formation and stabilization of functional synapses and neural circuits required as the structural basis of memory and learning. Available evidence, as reviewed herein, suggests that dietary gangliosides may impact positively on cognitive functions, particularly in the early postnatal period when the brain is still growing. Further, new evidence suggests that the mechanism of action may be through an effect on the neuroplasticity of the brain, mediated through enhanced synaptic plasticity in the hippocampus and nigro-striatal dopaminergic pathway.

Cattle encephalon glycoside and ignotin injection improves cognitive impairment in APPswe/PS1dE9 mice used as multitarget anti-Alzheimer's drug candidates

BACKGROUND

Cattle encephalon glycoside and ignotin injection (CEGI), a multitargeted neurotrophic drug, has been widely used in the treatment of central and peripheral nerve injuries, such as stroke, hypoxic ischemic encephalopathy, and diabetic neuropathy in the People's Republic of China. However, data regarding the effect of CEGI on Alzheimer's disease (AD) remain scarce. The present study aimed to investigate the effect of CEGI on learning and memory in an APPswe/PS1dE9 double-transgenic mouse model, a suitable animal model of AD, and elucidate its possible mechanisms.

MATERIALS AND METHODS

Five-month-old APP/PS1 mice were intraperitoneally administered 6.6 mL/kg or 13.2 mL/kg of CEGI for 1 month. After 1 month of administration, all mice received Morris water maze training and a probe test. Mouse brain sections were detected by standard biochemical and immunohistochemical measures.

RESULTS

CEGI treatment significantly improved the spatial learning and memory deficits and decreased cerebral amyloid-β42 levels in brain homogenates of APP/PS1 mice. CEGI treatment elevated the activities of superoxide dismutase, and reduced the levels of malondialdehyde. CEGI attenuated neuronal damage in the hippocampus of APP/PS1 mice and upregulated protein and gene expression of Bcl-2 and the ratio of Bcl-2/Bax. CEGI treatment decreased the number of Iba1(+) activated microglia in the cortex of the APP/PS1 mice.

CONCLUSION

Our results showed that CEGI prevents memory impairment, possibly by decreasing the amyloid-β42 levels in APP/PS1 mice and inhibiting oxidative stress, apoptosis, and inflammation, making CEGI a promising therapeutic agent for AD.

Pharmacogenomics of Alzheimer's disease: novel therapeutic strategies for drug development

Alzheimer's disease (AD) is a major problem of health and disability, with a relevant economic impact on our society. Despite important advances in pathogenesis, diagnosis, and treatment, its primary causes still remain elusive, accurate biomarkers are not well characterized, and the available pharmacological treatments are not cost-effective. As a complex disorder, AD is a polygenic and multifactorial clinical entity in which hundreds of defective genes distributed across the human genome may contribute to its pathogenesis. Diverse environmental factors, cerebrovascular dysfunction, and epigenetic phenomena, together with structural and functional genomic dysfunctions, lead to amyloid deposition, neurofibrillary tangle formation, and premature neuronal death, the major neuropathological hallmarks of AD. Future perspectives for the global management of AD predict that genomics and proteomics may help in the search for reliable biomarkers. In practical terms, the therapeutic response to conventional drugs (cholinesterase inhibitors, multifactorial strategies) is genotype-specific. Genomic factors potentially involved in AD pharmacogenomics include at least five categories of gene clusters: (1) genes associated with disease pathogenesis; (2) genes associated with the mechanism of action of drugs; (3) genes associated with drug metabolism (phase I and II reactions); (4) genes associated with drug transporters; and (5) pleiotropic genes involved in multifaceted cascades and metabolic reactions. The implementation of pharmacogenomic strategies will contribute to optimize drug development and therapeutics in AD and related disorders.