Increased cerebral glucose-6-phosphate dehydrogenase activity in Alzheimer's disease may reflect oxidative stress

Delineation of the role of G6PD in Alzheimer's disease and potential enhancement through microfluidic and nanoparticle approaches

Alzheimer's disease (AD) is a neurodegenerative pathologic entity characterized by the abnormal presence of tau and macromolecular Aβ deposition that leads to the degeneration or death of neurons. In addition to that, glucose-6-phosphate dehydrogenase (G6PD) has a multifaceted role in the process of AD development, where it can be used as both a marker and a target. G6PD activity is dysregulated due to its contribution to oxidative stress, neuroinflammation, and neuronal death. In this context, the current review presents a vivid depiction of recent findings on the relationship between AD progression and changes in the expression or activity of G6PD. The efficacy of the proposed G6PD-based therapeutics has been demonstrated in multiple studies using AD mouse models as representative animal model systems for cognitive decline and neurodegeneration associated with this disease. Innovative therapeutic insights are made for the boosting of G6PD activity via novel innovative nanotechnology and microfluidics tools in drug administration technology. Such approaches provide innovative methods of surpassing the blood-brain barrier, targeting step-by-step specific neural pathways, and overcoming biochemical disturbances that accompany AD. Using different nanoparticles loaded with G6DP to target specific organs, e.g., G6DP-loaded liposomes, enhances BBB penetration and brain distribution of G6DP. Many nanoparticles, which are used for different purposes, are briefly discussed in the paper. Such methods to mimic BBB on organs on-chip offer precise disease modeling and drug testing using microfluidic chips, requiring lower sample amounts and producing faster findings compared to conventional techniques. There are other contributions to microfluid in AD that are discussed briefly. However, there are some limitations accompanying microfluidics that need to be worked on to be used for AD. This study aims to bridge the gap in understanding AD with the synergistic use of promising technologies; microfluid and nanotechnology for future advancements.

Current biomarkers and treatment strategies in Alzheimer disease: An overview and future perspectives

Alzheimer's disease (AD), a progressive degenerative disorder first identified by Alois Alzheimer in 1907, poses a significant public health challenge. Despite its prevalence and impact, there is currently no definitive ante mortem diagnosis for AD pathogenesis. By 2050, the United States may face a staggering 13.8 million AD patients. This review provides a concise summary of current AD biomarkers, available treatments, and potential future therapeutic approaches. The review begins by outlining existing drug targets and mechanisms in AD, along with a discussion of current treatment options. We explore various approaches targeting Amyloid β (Aβ), Tau Protein aggregation, Tau Kinases, Glycogen Synthase kinase-3β, CDK-5 inhibitors, Heat Shock Proteins (HSP), oxidative stress, inflammation, metals, Apolipoprotein E (ApoE) modulators, and Notch signaling. Additionally, we examine the historical use of Estradiol (E2) as an AD therapy, as well as the outcomes of Randomized Controlled Trials (RCTs) that evaluated antioxidants (e.g., vitamin E) and omega-3 polyunsaturated fatty acids as alternative treatment options. Notably, positive effects of docosahexaenoic acid nutriment in older adults with cognitive impairment or AD are highlighted. Furthermore, this review offers insights into ongoing clinical trials and potential therapies, shedding light on the dynamic research landscape in AD treatment.

Network pharmacology and in vivo studies reveal the neuroprotective effects of paeoniflorin on Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease that has still not been effectively treated. Paeoniflorin is a traditional Chinese medicine with potential neuroprotective effects against brain injury; however, the beneficial effects and mechanisms of action in AD have not been clarified. We aimed to explore the mechanisms of action of paeoniflorin in AD using network pharmacology and experimental validation. Network pharmacology analysis revealed 30 candidate targets through the intersection of the targets of paeoniflorin and related genes in AD, which were mainly enriched in oxidative stress and inflammation. Moreover, key targets of paeoniflorin against AD, namely Nrf2 (encoded by NFE2L2) and TLR4, were screened and found to be closely related to oxidative stress and inflammation. Subsequent in vivo experiments revealed that paeoniflorin treatment improved the cognition of APP/PS1 mice by ameliorating oxidative stress and neuroinflammation, which were associated with the upregulation of Nrf2 and HO1, and the downregulation of TLR4. Collectively, the present study demonstrates that paeoniflorin alleviates cognitive impairment in AD by regulating oxidative stress and neuroinflammation, and that Nrf2, HO1, and TLR4 could be key targets.

Roles of Oxidative Stress in Synaptic Dysfunction and Neuronal Cell Death in Alzheimer's Disease

Alzheimer's disease (AD) is a brain disorder that progressively undermines memory and thinking skills by affecting the hippocampus and entorhinal cortex. The main histopathological hallmarks of AD are the presence of abnormal protein aggregates (Aβ and tau), synaptic dysfunction, aberrant proteostasis, cytoskeletal abnormalities, altered energy homeostasis, DNA and RNA defects, inflammation, and neuronal cell death. However, oxidative stress or oxidative damage is also evident and commonly overlooked or considered a consequence of the advancement of dementia symptoms. The control or onset of oxidative stress is linked to the activity of the amyloid-β peptide, which may serve as both antioxidant and pro-oxidant molecules. Furthermore, oxidative stress is correlated with oxidative damage to proteins, nucleic acids, and lipids in vulnerable cell populations, which ultimately lead to neuronal death through different molecular mechanisms. By recognizing oxidative stress as an integral feature of AD, alternative therapeutic or preventive interventions are developed and tested as potential or complementary therapies for this devastating neurodegenerative disease.

Chronic treatment with baicalein alleviates behavioural disorders and improves cerebral blood flow via reverting metabolic abnormalities in a J20 transgenic mouse model of Alzheimer's disease

Baicalein (BE) has both antioxidant and anti-inflammatory effects. It has also been reported able to improve cerebral blood circulation in brain ischemic injury. However, its chronic efficacy and metabolomics in Alzheimer's disease (AD) remain unknown. In this study, BE at 80 mg/kg was administrated through the oral route in J20 AD transgenic mice aged from aged 4 months to aged 10 months. Metabolic- and neurobehavioural phenotyping was done before and after 6 months' treatment to evaluate the drug efficacy and the relevant mechanisms. Meanwhile, molecular docking was used to study the binding affinity of BE and poly (ADP-ribose) polymerase-1 (PARP-1) which is related to neuronal injury. The open field test showed that BE could suppress hyperactivity in J20 mice and increase the frequency of the target quadrant crossing in the Morris Water Maze test. More importantly, BE restored cerebral blood flow back to the normal level after the chronic treatment. A ¹H NMR-based metabolomics study showed that BE treatment could restore the tricarboxylic acid cycle in plasma. And such a treatment could suppress oxidative stress, inhibit neuroinflammation, alleviate mitochondrial dysfunction, improve neurotransmission, and restore amino homeostasis via starch and sucrose metabolism and glycolipid metabolism in the cortex and hippocampus, which could affect the behavioural and cerebral blood flow. These findings showed that BE is a potential therapeutic agent for AD.

Homocysteine thiolactone and H2 O2 induce amino acid modifications and alter the fibrillation propensity of the Aβ25-35 peptide

Of the proteinaceous β-sheet-rich amyloid fibrillar structures, the Aβ_25-35 peptide, a component of the full-length Aβ involved in Alzheimer's disease, has similar toxicity to the parent peptide. In this study, the effects of homocysteine thiolactone (HCTL) and hydrogen peroxide (H₂ O₂ ) on the conformation and fibrillation propensity of the Aβ_25-35 peptide were investigated. Both HCTL and H₂ O₂ induced amino acid modifications along with alteration in aggregation propensity. Methionine (Met)-35 was oxidized by H₂ O₂ and aggregation was attenuated following the increased hydrophilicity of the peptide due to sulfoxide/sulfone formation. The HCTL-modified lysine (Lys-28) residue destabilizes the structure of the peptide, which leads to fibrillation. Our studies provide important information regarding the relationship between amino acid modifications and the amyloid fibrillation process.

Type 2 Diabetes and Alzheimer's Disease: The Emerging Role of Cellular Lipotoxicity

Type 2 diabetes (T2D) and Alzheimer's diseases (AD) represent major health issues that have reached alarming levels in the last decades. Although growing evidence demonstrates that AD is a significant comorbidity of T2D, and there is a ~1.4-2-fold increase in the risk of developing AD among T2D patients, the involvement of possible common triggers in the pathogenesis of these two diseases remains largely unknown. Of note, recent mechanistic insights suggest that lipotoxicity could represent the missing ring in the pathogenetic mechanisms linking T2D to AD. Indeed, obesity, which represents the main cause of lipotoxicity, has been recognized as a major risk factor for both pathological conditions. Lipotoxicity can lead to inflammation, insulin resistance, oxidative stress, ceramide and amyloid accumulation, endoplasmic reticulum stress, ferroptosis, and autophagy, which are shared biological events in the pathogenesis of T2D and AD. In the current review, we try to provide a critical and comprehensive view of the common molecular pathways activated by lipotoxicity in T2D and AD, attempting to summarize how these mechanisms can drive future research and open the way to new therapeutic perspectives.

Activity-regulated growth of motoneurons at the neuromuscular junction is mediated by NADPH oxidases

Neurons respond to changes in the levels of activity they experience in a variety of ways, including structural changes at pre- and postsynaptic terminals. An essential plasticity signal required for such activity-regulated structural adjustments are reactive oxygen species (ROS). To identify sources of activity-regulated ROS required for structural plasticity in vivo we used the Drosophila larval neuromuscular junction as a highly tractable experimental model system. For adjustments of presynaptic motor terminals, we found a requirement for both NADPH oxidases, Nox and dual oxidase (Duox), that are encoded in the Drosophila genome. This contrasts with the postsynaptic dendrites from which Nox is excluded. NADPH oxidases generate ROS to the extracellular space. Here, we show that two aquaporins, Bib and Drip, are necessary ROS conduits in the presynaptic motoneuron for activity regulated, NADPH oxidase dependent changes in presynaptic motoneuron terminal growth. Our data further suggest that different aspects of neuronal activity-regulated structural changes might be regulated by different ROS sources: changes in bouton number require both NADPH oxidases, while activity-regulated changes in the number of active zones might be modulated by other sources of ROS. Overall, our results show NADPH oxidases as important enzymes for mediating activity-regulated plasticity adjustments in neurons.

An Alternative View of Familial Alzheimer's Disease Genetics

Probabilistic and parsimony-based arguments regarding available genetics data are used to propose that Hardy and Higgin's amyloid cascade hypothesis is valid but is commonly interpreted too narrowly to support, incorrectly, the primacy of the amyloid-β peptide (Aβ) in driving Alzheimer's disease pathogenesis. Instead, increased activity of the βCTF (C99) fragment of AβPP is the critical pathogenic determinant altered by mutations in the APP gene. This model is consistent with the regulation of APP mRNA translation via its 5' iron responsive element. Similar arguments support that the pathological effects of familial Alzheimer's disease mutations in the genes PSEN1 and PSEN2 are not exerted directly via changes in AβPP cleavage to produce different ratios of Aβ length. Rather, these mutations likely act through effects on presenilin holoprotein conformation and function, and possibly the formation and stability of multimers of presenilin holoprotein and/or of the γ-secretase complex. All fAD mutations in APP, PSEN1, and PSEN2 likely find unity of pathological mechanism in their actions on endolysosomal acidification and mitochondrial function, with detrimental effects on iron homeostasis and promotion of "pseudo-hypoxia" being of central importance. Aβ production is enhanced and distorted by oxidative stress and accumulates due to decreased lysosomal function. It may act as a disease-associated molecular pattern enhancing oxidative stress-driven neuroinflammation during the cognitive phase of the disease.

Intranasally Co-administered Berberine and Curcumin Loaded in Transfersomal Vesicles Improved Inhibition of Amyloid Formation and BACE-1

Selective permeability of the blood-brain barrier restricts the treatment efficacy of neurologic diseases. Berberine (BBR) and curcumin (CUR)-loaded transferosomes (TRANS) were prepared for the effective management of Alzheimer's disease (AD). The study involved the syntheses of BBR-TRANS, CUR-TRANS, and BBR-CUR-TRANS by the film hydration method. Vesicles were characterized to ensure the formation of drug-loaded vesicles and their in vivo performance. The particle sizes of BBR-TRANS, CUR-TRANS, and BBR-CUR-TRANS were 139.2 ± 7, 143.4 ± 8, and 165.3 ± 6.5 nm, respectively. The presence of diffused rings in the SED image indicates the crystalline nature of the payload. Low surface roughness in an AFM image could be associated with the presence of a surface lipid. BBR-CUR-TRANS showed 41.03 ± 1.22 and 47.79 ± 3.67% release of BBR and 19.22 ± 1.47 and 24.67 ± 1.94% release of CUR, respectively, in phosphate buffer saline (pH 7.4) and acetate buffer (pH 4.0). Formulations showed sustained release of both loaded drugs. BBR-TRANS, CUR-TRANS, and BBR-CUR-TRANS exhibited a lower percentage of hemolysis than pure BBR and CUR, indicating the safety of the payload from delivery vesicles. Lower percentages of binding were recorded from BBR-CUR-TRANS than BBR-TRANS and CUR-TRANS. Acetylcholinesterase inhibition activity of the prepared transferosomes was greater than that of pure drugs, which are thought to have good cellular penetration. The spatial memory was improved in treated mice models. The level of malondialdehyde decreased in AD animals treated with BBR-TRANS, CUR-TRANS, and BBR-CUR-TRANS, respectively, as compared to the scopolamine-induced AD animals. BBR-CUR-TRANS-treated animals showed the highest decrease in the NO level. The catalase level was significantly restored in scopolamine-intoxicated animals treated with BBR-TRANS, CUR-TRANS, and BBR-CUR-TRANS. The immunohistochemistry result suggested that the BBR-TRANS, CUR-TRANS, and BBR-CUR-TRANS have significantly decreased the regulation of expression of BACE-1 through antioxidant activity. In conclusion, the study highlights the utility of formulated transferosomes as promising carriers for the co-delivery of drugs to the brain.

Conjugated linoleic acid downregulates Alzheimer's hallmarks in aluminum mouse model through an Nrf2-mediated adaptive response and increases brain glucose transporter levels

Mitochondrial dysfunction, oxidative stress, inflammation and glucose dysmetabolism are pathological signs of Alzheimer's disease (AD). Dietary aluminum (Al) overload is often used to induce AD in rodents and trigger the onset of oxidative-stress hallmarks resembling those of the human disease. The Nuclear factor erythroid 2-related factor 2 (Nrf2), owing to its key role in redox homeostasis, mitochondrial function and inflammation, is a promising drug target for neurological disorders, but only a few data are available on its modulatory effects on glucose transporter expression levels. While it has been found that the protective effect of Conjugated linoleic acid (CLA) occurs through the activation of an Nrf2-mediated adaptive response, its beneficial effect on the considered pathological signs in the Al-induced model has not been established yet. Thirty-five male BalbC mice were divided into 5 groups: two Al-intoxicated groups were treated for 5 weeks with low or high Al doses (8 or 100 mg/kg/day in drinking water, respectively; L or H). Two groups of animals, orally supplemented with CLA (600 mg/kg bw/day) for 7 weeks (2 preliminary weeks plus the 5-week treatment with Al; CLA + L, CLA + H) were used to investigate its protective effect, while untreated mice were used as control (Cntr). We provide evidence that mitochondrial dysfunction, Nrf2 alteration, inflammation and Acetylcholinesterase (AChE) hyperactivation can occur even from L exposure. Interestingly, animal pre-treatment with an allometric CLA dose led to significant downregulation of the toxic effects elicited by L or H, likely through the activation of an adaptive response. In conclusion, CLA ability to increase the level of glucose transporters - along with its antioxidant and anti-inflammatory effect - expands the therapeutic targets of these molecules and comes out as an intriguing suitable candidate for the treatment of multifactorial disease.

Importance of oxidative stress in the pathogenesis, diagnosis, and monitoring of patients with neuropsychiatric disorders, a review

Oxidative stress is defined as the persistent imbalance between the activity of toxic reactive forms of both oxygen and nitrogen and the antioxidant defense. In low concentrations, they are essential for the proper functioning of the body. Still, their excessive amount contributes to the damage of the biomolecules, consequently leading to various pathologies of the organism. Due to the lipid-rich brain structure, enormous oxygen consumption, and the lack of a sufficient antioxidant barrier make it highly susceptible to oxidative imbalance. Hence, oxidative stress has been linked to various psychiatric disorders. These diseases include all behavioral, emotional, and cognitive abnormalities associated with a significant impediment to social life. Each of the diseases in question: Alzheimer's disease, schizophrenia, depression, and bipolar disorder, is characterized by excessive oxidative stress. Considerable damages to DNA, RNA, proteins, lipids, and mitochondrial dysfunction, are observed. All conditions show increased lipid peroxidation, which appears to be typical of psychiatric disorders because the brain contains large amounts of these types of molecules. In addition, numerous abnormalities in the antioxidant defense are noted, but the results of studies on the activity of antioxidant enzymes differ significantly. The most promising biomarkers seem to be GSH in Alzheimer's disease as an early-stage marker of the disease and thioredoxin in schizophrenia as a marker for therapy monitoring. Data from the literature are consistent with the decrease in antioxidants such as vitamin C, E, uric acid, albumin, etc. Despite these numerous inconsistencies, it seems that oxidative stress is present in the course of psychiatric diseases. Still, it cannot be conclusively determined whether it is the direct cause of development, a consequence of other abnormalities at the biochemical or molecular level, or the result of the disease itself.

Inhibition of Rho Kinase by Fasudil Ameliorates Cognition Impairment in APP/PS1 Transgenic Mice via Modulation of Gut Microbiota and Metabolites

Background: Fasudil, a Rho kinase inhibitor, exerts therapeutic effects in a mouse model of Alzheimer's disease (AD), a chronic neurodegenerative disease with progressive loss of memory. However, the mechanisms remain unclear. In addition, the gut microbiota and its metabolites have been implicated in AD.

Methods: We examined the effect of fasudil on learning and memory using the Morris water-maze (MWM) test in APPswe/PSEN1dE9 transgenic (APP/PS1) mice (8 months old) treated (i.p.) with fasudil (25 mg/kg/day; ADF) or saline (ADNS) and in age- and gender-matched wild-type (WT) mice. Fecal metagenomics and metabolites were performed to identify novel biomarkers of AD and elucidate the mechanisms of fasudil induced beneficial effects in AD mice.

Results: The MWM test showed significant improvement of spatial memory in APP/PS1 mice treated with fasudil as compared to ADNS. The metagenomic analysis revealed the abundance of the dominant phyla in all the three groups, including Bacteroidetes (23.7–44%) and Firmicutes (6.4–26.6%), and the increased relative abundance ratio of Firmicutes/Bacteroidetes in ADNS (59.1%) compared to WT (31.7%). In contrast, the Firmicutes/Bacteroidetes ratio was decreased to the WT level in ADF (32.8%). Lefse analysis of metagenomics identified s_Prevotella_sp_CAG873 as an ADF potential biomarker, while s_Helicobacter_typhlonius and s_Helicobacter_sp_MIT_03-1616 as ADNS potential biomarkers. Metabolite analysis revealed the increment of various metabolites, including glutamate, hypoxanthine, thymine, hexanoyl-CoA, and leukotriene, which were relative to ADNS or ADF microbiota potential biomarkers and mainly involved in the metabolism of nucleotide, lipids and sugars, and the inflammatory pathway.

Conclusions: Memory deficit in APP/PS1 mice was correlated with the gut microbiome and metabolite status. Fasudil reversed the abnormal gut microbiota and subsequently regulated the related metabolisms to normal in the AD mice. It is believed that fasudil can be a novel strategy for the treatment of AD via remodeling of the gut microbiota and metabolites. The novel results also provide valuable references for the use of gut microbiota and metabolites as diagnostic biomarkers and/or therapeutic targets in clinical studies of AD.

Oxidative stress-A direct bridge to central nervous system homeostatic dysfunction and Alzheimer's disease

Neurologists have highly observed a frequent increasing number of elderly patients with Alzheimer's disease (AD) without any relevant evidence of any genetic or known AD-linked predisposing factors in the past few years. Those patients are characterized by continuous and irreversible neuron cells loss along with declined cognitive functions. Numerous studies have suggested that the exaggerated release of reactive oxygen species (ROS) within the brain may develop late-onset neurodegenerative disorders, especially AD-neuroinflammatory type. However, the central nervous system is vitally linked with whole-brain chemical integrity and its related healthy state, the cascade by which ROS may result in AD's development has not been highly justified or even maintained. It is widely known that the brain consumes a vast amount of oxygen and is characterized by being rich in lipid polyunsaturated fatty acids content, explaining why it is a prone region to oxidative stress (OS) and ROS damage. The formed OS-AD cytoskeletal protein aggregates can be considered a main predisposing factor for amyloid-beta (Aβ) hallmarks precipitation. Herein, this review aims to provide a detailed information on how oxidative stress can play a pathogenic role in activating damage-associated molecular patterns (DAMPs)-related toll-like receptor-4 inflammatory (TLR-4) cascades resulting in the deposition of Aβ hallmarks in brain tissues ending with irreversible cognitive dysfunction. It also explains how microglia can be activated via ROS, which may significantly release several pro-inflammatory cascades ending with general brain atrophy. Furthermore, different types of suggested antioxidant therapies will be discussed to combat AD-related pathological disorders and hallmarks.

Metabolic disorder in Alzheimer's disease

Alzheimer's disease (AD), a well known aging-induced neurodegenerative disease is related to amyloid proteinopathy. This proteinopathy occurs due to abnormalities in protein folding, structure and thereby its function in cells. The root cause of such kind of proteinopathy and its related neurodegeneration is a disorder in metabolism, rather metabolomics of the major as well as minor nutrients. Metabolomics is the most relevant "omics" platform that offers a great potential for the diagnosis and prognosis of neurodegenerative diseases as an individual's metabolome. In recent years, the research on such kinds of neurodegenerative diseases, especially aging-related disorders is broadened its scope towards metabolic function. Different neurotransmitter metabolisms are also involved with AD and its associated neurodegeneration. The genetic and epigenetic backgrounds are also noteworthy. In this review, the physiological changes of AD in relation to its corresponding biochemical, genetic and epigenetic involvements including its (AD) therapeutic aspects are discussed.

Pterostilbene Alleviates Aβ1-42 -Induced Cognitive Dysfunction via Inhibition of Oxidative Stress by Activating Nrf2 Signaling Pathway

SCOPE

In the present study, effect of pterostilbene on β-amyloid 1-42 (Aβ_1-42 ) induced cognitive impairment in mice is investigated and explored its possible mechanism of action.

METHODS AND RESULTS

The behavior results show that pterostilbene alleviated Aβ_1-42 -induces cognitive dysfunction assessed using the Y-maze test, novel object recognition task, Morris water maze test, and passive avoidance test. Pterostilbene alleviates neuron loss and accumulation of reactive oxygen species in Aβ_1-42 treated mouse brain. Additionally, pterostilbene promotes nuclear factor-E2 p45-related factor 2 (Nrf2) nuclear translocation and enhance the transcription and expression of antioxidant genes such as heme oxygenase-1 and superoxide dismutase both in vivo and in vitro. Nrf2 inhibitor ML385 reverses the antioxidant function of pterostilbene in SH-SY5Y cells. Nrf2 is the master regulator of oxidative homeostasis and can be activated by substrate adaptor sequestosome-1 (also named p62). Pterostilbene promotes the binding of Kelch-like ECH-associated protein 1 and p62, which enhanced activation of Nrf2.

CONCLUSION

The present study reports that pterostilbene alleviated Aβ_1-42 -induces cognitive dysfunction in mice. The mechanism of pterostilbene can be associated to the inhibition of oxidative stress through the Nrf2 signaling pathway.

Metabolic Dysregulation Contributes to the Progression of Alzheimer's Disease

Alzheimer's disease (AD) is an incurable neurodegenerative disease. Numerous studies have demonstrated a critical role for dysregulated glucose metabolism in its pathogenesis. In this review, we summarize metabolic alterations in aging brain and AD-related metabolic deficits associated with glucose metabolism dysregulation, glycolysis dysfunction, tricarboxylic acid (TCA) cycle, oxidative phosphorylation (OXPHOS) deficits, and pentose phosphate pathway impairment. Additionally, we discuss recent treatment strategies targeting metabolic defects in AD, including their limitations, in an effort to encourage the development of novel therapeutic strategies.

Reductive Stress, Bioactive Compounds, Redox-Active Metals, and Dormant Tumor Cell Biology to Develop Redox-Based Tools for the Treatment of Cancer

Significance: Cancer is related to redox biology from many points of view, such as initiation and promotion, metabolism and growth, invasion and metastasis, vascularization, or through the interaction with the immune system. In addition, this extremely complex relationship depends on the redox homeostasis of each cellular compartment, which might be used to fight cancer. Recent Advances: New ways of modulating specific and little explored aspects of redox biology have been revealed, as well as new delivery methods or uses of previously known treatments against cancer. Here, we review the latest experimental evidence regarding redox biology in cancer treatment and analyze its potential impact in the development of improved and more effective antineoplastic therapies. Critical Issues: A critical issue that deserves particular attention is the understanding that both extremes of redox biology (i.e., oxidative stress [OS] and reductive stress) might be useful or harmful in relation to cancer prevention and treatment. Future Directions: Additional research is needed to understand how to selectively induce reductive or OS adequately to avoid cancer proliferation or to induce cancer cell death.

The Protective Effect of Exercise in Neurodegenerative Diseases: The Potential Role of Extracellular Vesicles

Physical activity has systemic effects on the body, affecting almost every organ. It is important not only for general health and wellbeing, but also in the prevention of diseases. The mechanisms behind the therapeutic effects of physical activity are not completely understood; however, studies indicate these benefits are not confined to simply managing energy balance and body weight. They also include systemic factors which are released into the circulation during exercise and which appear to underlie the myriad of benefits exercise can elicit. It was shown that along with a number of classical cytokines, active tissues also engage in inter-tissue communication via extracellular vesicles (EVs), specifically exosomes and other small EVs, which are able to deliver biomolecules to cells and alter their metabolism. Thus, EVs may play a role in the acute and systemic adaptations that take place during and after physical activity, and may be therapeutically useful in the treatment of a range of diseases, including metabolic disorders such as type 2 diabetes and obesity; and the focus of this review, neurological disorders such as Alzheimer's disease.

Genetic variants and functional pathways associated with resilience to Alzheimer's disease

Approximately 30% of older adults exhibit the neuropathological features of Alzheimer's disease without signs of cognitive impairment. Yet, little is known about the genetic factors that allow these potentially resilient individuals to remain cognitively unimpaired in the face of substantial neuropathology. We performed a large, genome-wide association study (GWAS) of two previously validated metrics of cognitive resilience quantified using a latent variable modelling approach and representing better-than-predicted cognitive performance for a given level of neuropathology. Data were harmonized across 5108 participants from a clinical trial of Alzheimer's disease and three longitudinal cohort studies of cognitive ageing. All analyses were run across all participants and repeated restricting the sample to individuals with unimpaired cognition to identify variants at the earliest stages of disease. As expected, all resilience metrics were genetically correlated with cognitive performance and education attainment traits (P-values < 2.5 × 10-20), and we observed novel correlations with neuropsychiatric conditions (P-values < 7.9 × 10-4). Notably, neither resilience metric was genetically correlated with clinical Alzheimer's disease (P-values > 0.42) nor associated with APOE (P-values > 0.13). In single variant analyses, we observed a genome-wide significant locus among participants with unimpaired cognition on chromosome 18 upstream of ATP8B1 (index single nucleotide polymorphism rs2571244, minor allele frequency = 0.08, P = 2.3 × 10-8). The top variant at this locus (rs2571244) was significantly associated with methylation in prefrontal cortex tissue at multiple CpG sites, including one just upstream of ATPB81 (cg19596477; P = 2 × 10-13). Overall, this comprehensive genetic analysis of resilience implicates a putative role of vascular risk, metabolism, and mental health in protection from the cognitive consequences of neuropathology, while also providing evidence for a novel resilience gene along the bile acid metabolism pathway. Furthermore, the genetic architecture of resilience appears to be distinct from that of clinical Alzheimer's disease, suggesting that a shift in focus to molecular contributors to resilience may identify novel pathways for therapeutic targets.

Role of antioxidants and a nutrient rich diet in Alzheimer's disease

The joint attack on the body by metabolic acidosis and oxidative stress suggests that treatment in degenerative diseases, including Alzheimer's disease (AD), may require a normalizing of extracellular and intracellular pH with simultaneous supplementation of an antioxidant combination cocktail at a sufficiently high dose. Evidence is also accumulating that combinations of antioxidants may be more effective, taking advantage of synergistic effects of appropriate antioxidants as well as a nutrient-rich diet to prevent and reverse AD. This review focuses on nutritional, nutraceutical and antioxidant treatments of AD, although they can also be used in other chronic degenerative and neurodegenerative diseases.

Advanced glycation end products and protein carbonyl levels in plasma reveal sex-specific differences in Parkinson's and Alzheimer's disease

Neurodegenerative diseases (NDD) such as Alzheimer's (AD) and Parkinson's disease (PD) are distinct clinical entities, however, the aggregation of key neuronal proteins, presumably leading to neuronal demise appears to represent a common mechanism. It has become evident, that advanced glycation end products (AGEs) trigger the accumulation of such modified proteins, which eventually contributes to pathological aspect of NDDs. Increased levels of AGEs are found in amyloid plaques in AD brains and in both advanced and early PD (incidental Lewy body disease). The molecular mechanisms by which AGE dependent modifications may modulate the susceptibility towards NDDs, however, remain enigmatic and it is unclear, whether AGEs may serve as biomarker of NDD. In the present study, we examined AGEs (CML: Carboxymethyllysine and CEL: Carboxyethyllysine), markers of oxidative stress and micronutrients in the plasma of PD and AD patients and controls. As compared to healthy controls, AD females displayed lower levels of CEL while higher levels of CML were found in AD and PD patients. A somewhat similar pattern was observed for protein carbonyls (PC), revealing lower values exclusively in AD females, whereas AD males displayed significantly higher values compared to healthy controls and PD. Sex-specific differences were also observed for other relevant markers such as malondialdehyde, 3-nitrotyrosine, γ -tocopherols, retinol, plasma proteins and α-carotene, while α-tocopherols, β-carotene, lutein/zeaxanthin, β-cryptoxanthin and lycopene showed no relevant association. Taken together, our study suggests yet unappreciated differences of the distribution of AGEs among the sexes in NDD. We therefore suggest to make a clear distinction between sexes when analyzing oxidative (AGEs)-related stress and carbonyl-related stress and vitamins.

Transcriptomic and Network Analysis Identifies Shared and Unique Pathways across Dementia Spectrum Disorders

Background: Dementia is a growing public health concern with an estimated prevalence of 50 million people worldwide. Alzheimer’s disease (AD) and vascular and frontotemporal dementias (VaD, FTD), share many clinical, genetical, and pathological features making the diagnosis difficult. Methods: In this study, we compared the transcriptome from the frontal cortex of patients with AD, VaD, and FTD to identify dysregulated pathways. Results: Upregulated genes in AD were enriched in adherens and tight junctions, mitogen-activated protein kinase, and phosphatidylinositol 3-kinase and protein kinase B/Akt signaling pathways, whereas downregulated genes associated with calcium signaling. Upregulated genes in VaD were centered on infectious diseases and nuclear factor kappa beta signaling, whereas downregulated genes are involved in biosynthesis of amino acids and the pentose phosphate pathway. Upregulated genes in FTD were associated with ECM receptor interactions and the lysosome, whereas downregulated genes were involved in glutamatergic synapse and MAPK signaling. The transcription factor KFL4 was shared among the 3 types of dementia. Conclusions: Collectively, we identified similarities and differences in dysregulated pathways and transcription factors among the dementias. The shared pathways and transcription factors may indicate a potential common etiology, whereas the differences may be useful for distinguishing dementias.

Role of Oxidative Stress and Metal Toxicity in the Progression of Alzheimer's Disease

Alzheimer's disease (AD) is one of the life-threatening neurodegenerative disorders in the elderly (>60 years) and incurable across the globe to date. AD is caused by the involvement of various genetic, environmental and lifestyle factors that affect neuronal cells to degenerate over the period of time. The oxidative stress is engaged in the pathogenesis of various disorders and its key role is also linked to the etiology of AD. AD is attributed by neuronal loss, abnormal accumulation of Amyloid-β (Aβ) and neurofibrillary tangles (NFTs) with severe memory impairments and other cognitive dysfunctions which lead to the loss of synapses and neuronal death and eventual demise of the individual. Increased production of reactive oxygen species (ROS), loss of mitochondrial function, altered metal homeostasis, aberrant accumulation of senile plaque and mitigated antioxidant defense mechanism all are indulged in the progression of AD. In spite of recent advances in biomedical research, the underlying mechanism of disruption of redox balance and the actual source of oxidative stress is still obscure. This review highlights the generation of ROS through different mechanisms, the role of some important metals in the progression of AD and free radical scavenging by endogenous molecule and supplementation of nutrients in AD.

Oxidative stress, dysfunctional glucose metabolism and Alzheimer disease

Alzheimer disease (AD) is a major cause of age-related dementia. We do not fully understand AD aetiology and pathogenesis, but oxidative damage is a key component. The brain mostly uses glucose for energy, but in AD and amnestic mild cognitive impairment glucose metabolism is dramatically decreased, probably owing, at least in part, to oxidative damage to enzymes involved in glycolysis, the tricarboxylic acid cycle and ATP biosynthesis. Consequently, ATP-requiring processes for cognitive function are impaired, and synaptic dysfunction and neuronal death result, with ensuing thinning of key brain areas. We summarize current research on the interplay and sequence of these processes and suggest potential pharmacological interventions to retard AD progression.

Examining the homeostatic distribution of metals and Zn isotopes in Göttingen minipigs

The role of metals in biologic systems is manifold, and understanding their behaviour in bodily processes, especially those relating to neurodegenerative diseases, is at the forefront of medical science. The function(s) of metals - such as the transition metals - and their utility in both the diagnosis and treatment of diseases in human beings, is often examined via the characterization of their distribution in animal models, with porcine models considered exceptional proxies for human physiology. To this end, we have investigated the homeostatic distribution of numerous metals (Mg, K, Ca, Mn, Fe, Cu, Zn, Rb and Mo), the non-metal P, and Zn isotopes in the organs and blood (red blood cells, plasma) of Göttingen minipigs. These results represent the first set of data outlining the homeostatic distribution of metals and Zn isotopes in Göttingen minipigs, and indicate a relatively homogeneous distribution of alkali/alkaline earth metals and P among the organs, with generally lower levels in the blood, while indicating more heterogeneous and systematic abundance patterns for transition metals. In general, the distribution of all elements analysed is similar to that found in humans. Our elemental abundance data, together with data reported for humans in the literature, suggest that element-to-element ratios, e.g. Cu/Mg, show potential as simple diagnostics for diseases such as Alzheimer's. Isotopic data indicate a heterogeneous distribution of Zn isotopes among the organs and blood, with the liver, heart and brain being the most depleted in heavy Zn isotopes, and the blood the most enriched, consistent with observations in other animal models and humans. The Zn isotopic composition of Göttingen minipigs displays a systematic offset towards lighter δ66Zn values relative to mice and sheep models, suggesting physiology that is more closely aligned with that of humans. Cumulatively, these observations strongly suggest that Göttingen minipigs are an excellent animal model for translational research involving metals, and these data provide a strong foundation for future research.

Neuroprotection by glucose-6-phosphate dehydrogenase and the pentose phosphate pathway

Glucose-6-phosphate dehydrogenase (G6PD), the rate limiting enzyme that channels glucose catabolism from glycolysis into the pentose phosphate pathway (PPP), is vital for the production of reduced nicotinamide adenine dinucleotide phosphate (NADPH) in cells. NADPH is in turn a substrate for glutathione reductase, which reduces oxidized glutathione disulfide to sulfhydryl glutathione. Best known for inherited deficiencies underlying acute hemolytic anemia due to elevated oxidative stress by food or medication, G6PD, and PPP activation have been associated with neuroprotection. Recent works have now provided more definitive evidence for G6PD's protective role in ischemic brain injury and strengthened its links to neurodegeneration. In Drosophila models, improved proteostasis and lifespan extension result from an increased PPP flux due to G6PD induction, which is phenocopied by transgenic overexpression of G6PD in neurons. Moderate transgenic expression of G6PD was also shown to improve healthspan in mouse. Here, the deciphered and implicated roles of G6PD and PPP in protection against brain injury, neurodegenerative diseases, and in healthspan/lifespan extensions are discussed together with an important caveat, namely NADPH oxidase (NOX) activity and the oxidative stress generated by the latter. Activation of G6PD with selective inhibition of NOX activity could be a viable neuroprotective strategy for brain injury, disease, and aging.

Reactive oxygen species regulate activity-dependent neuronal plasticity in Drosophila

Reactive oxygen species (ROS) have been extensively studied as damaging agents associated with ageing and neurodegenerative conditions. Their role in the nervous system under non-pathological conditions has remained poorly understood. Working with the Drosophila larval locomotor network, we show that in neurons ROS act as obligate signals required for neuronal activity-dependent structural plasticity, of both pre- and postsynaptic terminals. ROS signaling is also necessary for maintaining evoked synaptic transmission at the neuromuscular junction, and for activity-regulated homeostatic adjustment of motor network output, as measured by larval crawling behavior. We identified the highly conserved Parkinson’s disease-linked protein DJ-1β as a redox sensor in neurons where it regulates structural plasticity, in part via modulation of the PTEN-PI3Kinase pathway. This study provides a new conceptual framework of neuronal ROS as second messengers required for neuronal plasticity and for network tuning, whose dysregulation in the ageing brain and under neurodegenerative conditions may contribute to synaptic dysfunction.

Dysregulation of Neuronal Iron Homeostasis as an Alternative Unifying Effect of Mutations Causing Familial Alzheimer's Disease

The overwhelming majority of dominant mutations causing early onset familial Alzheimer’s disease (EOfAD) occur in only three genes, PSEN1, PSEN2, and APP. An effect-in-common of these mutations is alteration of production of the APP-derived peptide, amyloid β (Aβ). It is this key fact that underlies the authority of the Amyloid Hypothesis that has informed Alzheimer’s disease research for over two decades. Any challenge to this authority must offer an alternative explanation for the relationship between the PSEN genes and APP. In this paper, we explore one possible alternative relationship – the dysregulation of cellular iron homeostasis as a common effect of EOfAD mutations in these genes. This idea is attractive since it provides clear connections between EOfAD mutations and major characteristics of Alzheimer’s disease such as dysfunctional mitochondria, vascular risk factors/hypoxia, energy metabolism, and inflammation. We combine our ideas with observations by others to describe a “Stress Threshold Change of State” model of Alzheimer’s disease that may begin to explain the existence of both EOfAD and late onset sporadic (LOsAD) forms of the disease. Directing research to investigate the role of dysregulation of iron homeostasis in EOfAD may be a profitable way forward in our struggle to understand this form of dementia.

Development of Nasal Lipid Nanocarriers Containing Curcumin for Brain Targeting

BACKGROUND

Curcumin (CUR) has properties that can be useful for the treatment of Alzheimer's disease. Such properties are the inhibition of amyloid-β-protein (Aβ) aggregation, Aβ-induced inflammation, and activities of β-secretase and acetylcholinesterase. However, previous studies have revealed that CUR exhibited low bioavailability and difficulties in reaching the brain.

OBJECTIVE

To overcome such drawbacks, this study aims at developing nasal lipid nanocarriers loaded with CUR to effectively target the brain.

METHODS

The lipid nanocarriers (NE) were prepared using the hot solvent diffusion associated with the phase inversion temperature methods. Physico-chemical and morphological characterizations and in vitro drug release of the nanocarriers were carried out. The CUR permeation/retention was analyzed in Franz-type diffusion cell using porcine nasal mucosa. Confocal laser scan and histopathological studies were also performed.

RESULTS

The results showed that the NE sizes ranged between 18 nm and 44 nm with negative zeta potential. The CUR content ranged from 0.24 to 1.50 mg/mL with an encapsulation efficiency of 99%. The profiles of CUR release indicated a biphasic kinetics. CUR-NE permeation across the porcine nasal mucosa was higher when compared to free CUR. These results have also been validated through an analysis on a confocal microscopy. In addition, no toxicity on the nasal mucosa has been observed in a histopathological analysis.

CONCLUSION

These results suggest that it is possible to develop NEs with a high content of CUR and small particle size. Such an encapsulation increases the potential of CUR permeation across the porcine nasal mucosa.

The Link between Type 2 Diabetes and Neurodegeneration: Roles for Amyloid-β, Amylin, and Tau Proteins

A wealth of evidence indicates a strong link between type 2 diabetes (T2D) and neurodegenerative diseases such as Alzheimer's disease (AD). Although the precise mechanism remains unclear, T2D can exacerbate neurodegenerative processes. Brain atrophy, reduced cerebral glucose metabolism, and central nervous system insulin resistance are features of both AD and T2D. The T2D phenotype (glucose dyshomeostasis, insulin resistance, impaired insulin signaling) also promotes AD pathology, namely accumulation of amyloid-β (Aβ) and hyperphosphorylated tau and can induce other aspects of neuronal degeneration including inflammatory and oxidative processes. Aβ and hyperphosphorylated tau may also have roles in pancreatic β-cell dysfunction and in reducing insulin sensitivity and glucose uptake by peripheral tissues such as liver, skeletal muscle, and adipose tissue. This suggests a role for these AD-related proteins in promoting T2D. The accumulation of the islet amyloid polypeptide (IAPP, or amylin) within islet β-cells is a major pathological feature of the pancreas in patients with chronic T2D. Co-secreted with insulin, amylin accumulates over time and contributes to β-cell toxicity, ultimately leading to reduced insulin secretion and onset of overt (insulin dependent) diabetes. Recent evidence also suggests that this protein accumulates in the brain of AD patients and may interact with Aβ to exacerbate the neurodegenerative process. In this review, we highlight evidence indicating T2D in promoting Aβ and tau mediated neurodegeneration and the potential contributions of Aβ and tau in promoting a diabetic phenotype that could further exacerbate neurodegeneration. We also discuss underlying mechanisms by which amylin can contribute to the neurodegenerative processes.

Regulation of neuronal development and function by ROS

Reactive oxygen species (ROS) have long been studied as destructive agents in the context of nervous system ageing, disease and degeneration. Their roles as signalling molecules under normal physiological conditions is less well understood. Recent studies have provided ample evidence of ROS-regulating neuronal development and function, from the establishment of neuronal polarity to growth cone pathfinding; from the regulation of connectivity and synaptic transmission to the tuning of neuronal networks. Appreciation of the varied processes that are subject to regulation by ROS might help us understand how changes in ROS metabolism and buffering could progressively impact on neuronal networks with age and disease.

Antimicrobial activity of apple cider vinegar against Escherichia coli, Staphylococcus aureus and Candida albicans; downregulating cytokine and microbial protein expression

The global escalation in antibiotic resistance cases means alternative antimicrobials are essential. The aim of this study was to investigate the antimicrobial capacity of apple cider vinegar (ACV) against E. coli, S. aureus and C. albicans. The minimum dilution of ACV required for growth inhibition varied for each microbial species. For C. albicans, a 1/2 ACV had the strongest effect, S. aureus, a 1/25 dilution ACV was required, whereas for E-coli cultures, a 1/50 ACV dilution was required (p < 0.05). Monocyte co-culture with microbes alongside ACV resulted in dose dependent downregulation of inflammatory cytokines (TNFα, IL-6). Results are expressed as percentage decreases in cytokine secretion comparing ACV treated with non-ACV treated monocytes cultured with E-coli (TNFα, 99.2%; IL-6, 98%), S. aureus (TNFα, 90%; IL-6, 83%) and C. albicans (TNFα, 83.3%; IL-6, 90.1%) respectively. Proteomic analyses of microbes demonstrated that ACV impaired cell integrity, organelles and protein expression. ACV treatment resulted in an absence in expression of DNA starvation protein, citrate synthase, isocitrate and malate dehydrogenases in E-coli; chaperone protein DNak and ftsz in S. aureus and pyruvate kinase, 6-phosphogluconate dehydrogenase, fructose bisphosphate were among the enzymes absent in C.albican cultures. The results demonstrate ACV has multiple antimicrobial potential with clinical therapeutic implications.

Alzheimer's Disease: A Journey from Amyloid Peptides and Oxidative Stress, to Biomarker Technologies and Disease Prevention Strategies-Gains from AIBL and DIAN Cohort Studies

Worldwide there are over 46 million people living with dementia, and this number is expected to double every 20 years reaching about 131 million by 2050. The cost to the community and government health systems, as well as the stress on families and carers is incalculable. Over three decades of research into this disease have been undertaken by several research groups in Australia, including work by our original research group in Western Australia which was involved in the discovery and sequencing of the amyloid-β peptide (also known as Aβ or A4 peptide) extracted from cerebral amyloid plaques. This review discusses the journey from the discovery of the Aβ peptide in Alzheimer's disease (AD) brain to the establishment of pre-clinical AD using PET amyloid tracers, a method now serving as the gold standard for developing peripheral diagnostic approaches in the blood and the eye. The latter developments for early diagnosis have been largely achieved through the establishment of the Australian Imaging Biomarker and Lifestyle research group that has followed 1,100 Australians for 11 years. AIBL has also been instrumental in providing insight into the role of the major genetic risk factor apolipoprotein E ɛ4, as well as better understanding the role of lifestyle factors particularly diet, physical activity and sleep to cognitive decline and the accumulation of cerebral Aβ.

Glucose 6 phosphatase dehydrogenase (G6PD) and neurodegenerative disorders: Mapping diagnostic and therapeutic opportunities

Glucose 6 phosphate dehydrogenase (G6PD) is a key and rate limiting enzyme in the pentose phosphate pathway (PPP). The physiological significance of enzyme is providing reduced energy to specific cells like erythrocyte by maintaining co-enzyme nicotinamide adenine dinucleotide phosphate (NADPH). There are preponderance research findings that demonstrate the enzyme (G6PD) role in the energy balance, and it is associated with blood-related diseases and disorders, primarily the anemia resulted from G6PD deficiency. The X-linked genetic deficiency of G6PD and associated non-immune hemolytic anemia have been studied widely across the globe. Recent advancement in biology, more precisely neuroscience has revealed that G6PD is centrally involved in many neurological and neurodegenerative disorders. The neuroprotective role of the enzyme (G6PD) has also been established, as well as the potential of G6PD in oxidative damage and the Reactive Oxygen Species (ROS) produced in cerebral ischemia. Though G6PD deficiency remains a global health issue, however, a paradigm shift in research focusing the potential of the enzyme in neurological and neurodegenerative disorders will surely open a new avenue in diagnostics and enzyme therapeutics. Here, in this study, more emphasis was made on exploring the role of G6PD in neurological and inflammatory disorders as well as non-immune hemolytic anemia, thus providing diagnostic and therapeutic opportunities.

Apolipoprotein E4 and Insulin Resistance Interact to Impair Cognition and Alter the Epigenome and Metabolome

Apolipoprotein E4 (E4) and type 2 diabetes are major risk factors for cognitive decline and late onset Alzheimer's disease (AD). E4-associated phenotypes and insulin resistance (IR) share several features and appear to interact in driving cognitive dysfunction. However, shared mechanisms that could explain their overlapping pathophysiology have yet to be found. We hypothesized that, compared to E3 mice, E4 mice would be more susceptible to the harmful cognitive effects of high fat diet (HFD)-induced IR due to apoE isoform-specific differences in brain metabolism. While both E3 and E4 mice fed HFD displayed impairments in peripheral metabolism and cognition, deficits in hippocampal-dependent spatial learning and memory were exaggerated in E4 mice. Combining genome-wide measures of DNA hydroxymethylation with comprehensive untargeted metabolomics, we identified novel alterations in purine metabolism, glutamate metabolism, and the pentose phosphate pathway. Finally, in E4 mice, the metabolic and cognitive deficiencies caused by HFD were rescued by switching to a low fat diet for one month, suggesting a functional role was associated with reversal of the same metabolic pathways described above. These results suggest a susceptibility of E4 carriers to metabolic impairments brought on by IR, and may guide development of novel therapies for cognitive decline and dementia.

Glucose-6-phosphate dehydrogenase a novel hope on a blood-based diagnosis of Alzheimer's disease

Alzheimer's disease (AD) is a multi-factorial neurodegenerative disorder that numerous factors have key properties in the development of this proteopathy. Glucose-6-phosphate dehydrogenase (G6PD) is the most common form of enzymopathy. We have examined G6PD enzyme activity levels in the serum of newly diagnosed AD patients compared with control subjects without dementia from the both sexes. Serum G6PD levels were found to be significantly higher (approximately two times) in AD patients compared to control geriatric subjects in both sexes. We have concluded that G6PD seems to play an integral role in the progress and/or prevention of AD.

Low-level laser therapy for beta amyloid toxicity in rat hippocampus

Beta amyloid (Aβ) is well accepted to play a central role in the pathogenesis of Alzheimer's disease (AD). The present work evaluated the therapeutic effects of low-level laser irradiation (LLI) on Aβ-induced neurotoxicity in rat hippocampus. Aβ 1-42 was injected bilaterally to the hippocampus CA1 region of adult male rats, and 2-minute daily LLI treatment was applied transcranially after Aβ injection for 5 consecutive days. LLI treatment suppressed Aβ-induced hippocampal neurodegeneration and long-term spatial and recognition memory impairments. Molecular studies revealed that LLI treatment: (1) restored mitochondrial dynamics, by altering fission and fusion protein levels thereby suppressing Aβ-induced extensive fragmentation; (2) suppressed Aβ-induced collapse of mitochondrial membrane potential; (3) reduced oxidized mitochondrial DNA and excessive mitophagy; (4) facilitated mitochondrial homeostasis via modulation of the Bcl-2-associated X protein/B-cell lymphoma 2 ratio and of mitochondrial antioxidant expression; (5) promoted cytochrome c oxidase activity and adenosine triphosphate synthesis; (6) suppressed Aβ-induced glucose-6-phosphate dehydrogenase and nicotinamide adenine dinucleotide phosphate oxidase activity; (7) enhanced the total antioxidant capacity of hippocampal CA1 neurons, whereas reduced the oxidative damage; and (8) suppressed Aβ-induced reactive gliosis, inflammation, and tau hyperphosphorylation. Although development of AD treatments has focused on reducing cerebral Aβ levels, by the time the clinical diagnosis of AD or mild cognitive impairment is made, the brain is likely to have already been exposed to years of elevated Aβ levels with dire consequences for multiple cellular pathways. By alleviating a broad spectrum of Aβ-induced pathology that includes mitochondrial dysfunction, oxidative stress, neuroinflammation, neuronal apoptosis, and tau pathology, LLI could represent a new promising therapeutic strategy for AD.

Oxidative Stress in Neurodegenerative Diseases

The pathophysiologies of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), and Alzheimer's disease (AD), are far from being fully explained. Oxidative stress (OS) has been proposed as one factor that plays a potential role in the pathogenesis of neurodegenerative disorders. Clinical and preclinical studies indicate that neurodegenerative diseases are characterized by higher levels of OS biomarkers and by lower levels of antioxidant defense biomarkers in the brain and peripheral tissues. In this article, we review the current knowledge regarding the involvement of OS in neurodegenerative diseases, based on clinical trials and animal studies. In addition, we analyze the effects of the drug-induced modulation of oxidative balance, and we explore pharmacotherapeutic strategies for OS reduction.

Possible peripheral markers for chronic aluminium toxicity in Wistar rats

This investigation gives detailed analysis of peripheral marker enzymes as well as neurobehavioral tests following chronic aluminium (Al) exposure (10 mg/kg b.w. for 12 weeks intragastrically). We observed a significant decrease in the levels of serum cholinesterase after toxicity. The enzymatic activity of cytochrome oxidase (CO), the terminal enzyme of the electron transport chain, was significantly diminished and that of glucose-6-phosphate dehydrogenase (G-6-PD) was significantly enhanced. Neuromuscular co-ordination was assessed using motor and memory function tests. Deficits were observed suggesting a probable model for chronic Al neurotoxicity.

Simultaneous activation of Nrf2 and elevation of antioxidant compounds for reducing oxidative stress and chronic inflammation in human Alzheimer's disease

Despite extensive research, neither the incidence nor the rate of progression of Alzheimer's disease (AD) has significantly changed. Some biochemical and genetic defects that initiate and promote AD include: (a) increased oxidative stress, (b) chronic inflammation (c) mitochondrial dysfunction, (d) Aß1-42 peptides generated from the amyloid precursor protein (APP), (e) proteasome inhibition, and (f) mutations in APP, presenilin-1 and presenilin-2 genes. Increased oxidative stress appears to precede other biochemical and genetic defects. Oxidative damage induces chronic inflammation. Therefore, reducing these defects simultaneously may reduce the development and progression of AD. Previous studies with individual antioxidants produced consistent benefits in animal models of AD; however, a similar approach produced inconsistent results in human AD. This review proposes a hypothesis that simultaneous elevation of the levels of antioxidant enzymes and antioxidant compounds is necessary for optimally reducing oxidative stress and chronic inflammation in human AD. Supplementation can enhance the levels of antioxidant compounds; but elevation of antioxidant enzymes requires activation of Nrf2. This review discusses activation and regulation of Nrf2. The need for multi- antioxidants that can affect multi-targets has been proposed without specific recommendations. This review proposes a micronutrient mixture that would simultaneously enhance the levels of antioxidant enzymes and antioxidant compounds in human AD.

The Ames dwarf mutation attenuates Alzheimer's disease phenotype of APP/PS1 mice

APP/PS1 double transgenic mice expressing human mutant amyloid precursor protein (APP) and presenilin-1 (PS1) demonstrate robust brain amyloid beta (Aβ) peptide containing plaque deposition, increased markers of oxidative stress, behavioral dysfunction, and proinflammatory gliosis. On the other hand, lack of growth hormone, prolactin, and thyroid-stimulating hormone due to a recessive mutation in the Prop 1 gene (Prop1df) in Ames dwarf mice results in a phenotype characterized by potentiated antioxidant mechanisms, improved learning and memory, and significantly increased longevity in homozygous mice. Based on this, we hypothesized that a similar hormone deficiency might attenuate disease changes in the brains of APP/PS1 mice. To test this idea, APP/PS1 mice were crossed to the Ames dwarf mouse line. APP/PS1, wild-type, df/+, df/df, df/+/APP/PS1, and df/df/APP/PS1 mice were compared at 6 months of age through behavioral testing and assessing amyloid burden, reactive gliosis, and brain cytokine levels. df/df mice demonstrated lower brain growth hormone and insulin-like growth factor 1 concentrations. This correlated with decreased astrogliosis and microgliosis in the df/df/APP/PS1 mice and, surprisingly, reduced Aβ plaque deposition and Aβ 1-40 and Aβ 1-42 concentrations. The df/df/APP/PS1 mice also demonstrated significantly elevated brain levels of multiple cytokines in spite of the attenuated gliosis. These data indicate that the df/df/APP/PS1 line is a unique resource in which to study aging and resistance to disease and suggest that the affected pituitary hormones may have a role in regulating disease progression.

Examining the potential clinical value of curcumin in the prevention and diagnosis of Alzheimer’s disease

Curcumin derived from turmeric is well documented for its anti-carcinogenic, antioxidant and anti-inflammatory properties. Recent studies show that curcumin also possesses neuroprotective and cognitive-enhancing properties that may help delay or prevent neurodegenerative diseases, including Alzheimer’s disease (AD). Currently, clinical diagnosis of AD is onerous, and it is primarily based on the exclusion of other causes of dementia. In addition, phase III clinical trials of potential treatments have mostly failed, leaving disease-modifying interventions elusive. AD can be characterised neuropathologically by the deposition of extracellular β amyloid (Aβ) plaques and intracellular accumulation of tau-containing neurofibrillary tangles. Disruptions in Aβ metabolism/clearance contribute to AD pathogenesis. In vitro studies have shown that Aβ metabolism is altered by curcumin, and animal studies report that curcumin may influence brain function and the development of dementia, because of its antioxidant and anti-inflammatory properties, as well as its ability to influence Aβ metabolism. However, clinical studies of curcumin have revealed limited effects to date, most likely because of curcumin’s relatively low solubility and bioavailability, and because of selection of cohorts with diagnosed AD, in whom there is already major neuropathology. However, the fresh approach of targeting early AD pathology (by treating healthy, pre-clinical and mild cognitive impairment-stage cohorts) combined with new curcumin formulations that increase bioavailability is renewing optimism concerning curcumin-based therapy. The aim of this paper is to review the current evidence supporting an association between curcumin and modulation of AD pathology, including in vitro and in vivo studies. We also review the use of curcumin in emerging retinal imaging technology, as a fluorochrome for AD diagnostics.

Inflammation and Oxidative Stress: The Molecular Connectivity between Insulin Resistance, Obesity, and Alzheimer's Disease

Type 2 diabetes (T2DM), Alzheimer's disease (AD), and insulin resistance are age-related conditions and increased prevalence is of public concern. Recent research has provided evidence that insulin resistance and impaired insulin signalling may be a contributory factor to the progression of diabetes, dementia, and other neurological disorders. Alzheimer's disease (AD) is the most common subtype of dementia. Reduced release (for T2DM) and decreased action of insulin are central to the development and progression of both T2DM and AD. A literature search was conducted to identify molecular commonalities between obesity, diabetes, and AD. Insulin resistance affects many tissues and organs, either through impaired insulin signalling or through aberrant changes in both glucose and lipid (cholesterol and triacylglycerol) metabolism and concentrations in the blood. Although epidemiological and biological evidence has highlighted an increased incidence of cognitive decline and AD in patients with T2DM, the common molecular basis of cell and tissue dysfunction is rapidly gaining recognition. As a cause or consequence, the chronic inflammatory response and oxidative stress associated with T2DM, amyloid-β (Aβ) protein accumulation, and mitochondrial dysfunction link T2DM and AD.

The role of type 2 diabetes in neurodegeneration

A growing body of evidence links type-2 diabetes (T2D) with dementia and neurodegenerative diseases such as Alzheimer's disease (AD). AD is the most common form of dementia and is characterised neuropathologically by the accumulation of extracellular beta amyloid (Aβ) peptide aggregates and intracellular hyper-phosphorylated tau protein, which are thought to drive and/or accelerate inflammatory and oxidative stress processes leading to neurodegeneration. Although the precise mechanism remains unclear, T2D can exacerbate these neurodegenerative processes. Brain atrophy, reduced cerebral glucose metabolism and CNS insulin resistance are features of both AD and T2D. Cell culture and animal studies have indicated that the early accumulation of Aβ may play a role in CNS insulin resistance and impaired insulin signalling. From the viewpoint of insulin resistance and impaired insulin signalling in the brain, these are also believed to initiate other aspects of brain injury, including inflammatory and oxidative stress processes. Here we review the clinical and experimental pieces of evidence that link these two chronic diseases of ageing, and discuss underlying mechanisms. The evaluation of treatments for the management of diabetes in preclinical, and clinical studies and trials for AD will also be discussed.

Alzheimer's disease-related peptide PS2V plays ancient, conserved roles in suppression of the unfolded protein response under hypoxia and stimulation of γ-secretase activity

The PRESENILIN1 and PRESENILIN2 genes encode structurally related proteases essential for γ-secretase activity. Of nearly 200 PRESENILIN mutations causing early onset, familial Alzheimer's disease (FAD) only the K115Efx10 mutation of PSEN2 causes truncation of the open reading frame. If translated, the truncated product would resemble a naturally occurring isoform of PSEN2 named PS2V that is induced by hypoxia and found at elevated levels in late onset Alzheimer's disease (AD) brains. The function of PS2V is largely unexplored. We show that zebrafish possess a PS2V-like isoform, PS1IV, produced from the fish's PSEN1 rather than PSEN2 orthologous gene. The molecular mechanism controlling formation of PS2V/PS1IV was probably present in the ancient common ancestor of the PSEN1 and PSEN2 genes. Human PS2V and zebrafish PS1IV have highly divergent structures but conserved abilities to stimulate γ-secretase activity and to suppress the unfolded protein response (UPR) under hypoxia. The putative protein truncation caused by K115Efx10 resembles PS2V in its ability to increase γ-secretase activity and suppress the UPR. This supports increased Aβ levels as a common link between K115Efx10 early onset AD and sporadic, late onset AD. The ability of mutant variants of PS2V to stimulate γ-secretase activity partially correlates with their ability to suppress the UPR. The cytosolic, transmembrane and luminal domains of PS2V are all critical to its γ-secretase and UPR-suppression activities. Our data support a model in which chronic hypoxia in aged brains promotes excessive Notch signalling and accumulation of Aβ that contribute to AD pathogenesis.

Pentose-phosphate pathway disruption in the pathogenesis of Parkinson’s disease

Oxidative stress is known to be a key factor in the pathogenesis of Parkinson’s disease (PD). Neuronal redox status is maintained by glucose metabolism via the pentose-phosphate pathway and it is known that disruption of glucose metabolism is damaging to neurons. Accumulating evidence supports the idea that glucose metabolism is altered in PD and dysregulation of the pentose-phosphate pathway in this disease has recently been shown. In this review, we present an overview of the literature regarding neuronal glucose metabolism and PD, and discuss the implications of these findings for PD pathogenesis and possible future therapeutic avenues.