Oxidative damage in Alzheimer's

Natural Antioxidants: An Effective Strategy for the Treatment of Alzheimer's Disease at the Early Stage

The critical role of oxidative stress in Alzheimer's disease (AD) has been recognized by researchers recently, and natural antioxidants have been demonstrated to have anti-AD activity in animal models, such as Ginkgo biloba extract, soy isoflavones, lycopene, and so on. This paper summarized these natural antioxidants and points out that natural antioxidants always have multiple advantages which are help to deal with AD, such as clearing free radicals, regulating signal transduction, protecting mitochondrial function, and synaptic plasticity. Based on the available data, we have created a relatively complete pathway map of reactive oxygen species (ROS) and AD-related targets and concluded that oxidative stress caused by ROS is the core of AD pathogenesis. In the prospect, we introduced the concept of a combined therapeutic strategy, termed "Antioxidant-Promoting Synaptic Remodeling," highlighting the integration of antioxidant interventions with synaptic remodeling approaches as a novel avenue for therapeutic exploration.

Mitochondrial dynamics and mitochondrial autophagy: Molecular structure, orchestrating mechanism and related disorders

Mitochondrial dynamics and autophagy play essential roles in normal cellular physiological activities, while abnormal mitochondrial dynamics and mitochondrial autophagy can cause cancer and related disorders. Abnormal mitochondrial dynamics usually occur in parallel with mitochondrial autophagy. Both have been reported to have a synergistic effect and can therefore complement or inhibit each other. Progress has been made in understanding the classical mitochondrial PINK1/Parkin pathway and mitochondrial dynamical abnormalities. Still, the mechanisms and regulatory pathways underlying the interaction between mitophagy and mitochondrial dynamics remain unexplored. Like other existing reviews, we review the molecular structure of proteins involved in mitochondrial dynamics and mitochondrial autophagy, and how their abnormalities can lead to the development of related diseases. We will also review the individual or synergistic effects of abnormal mitochondrial dynamics and mitophagy leading to cellular proliferation, differentiation and invasion. In addition, we explore the mechanisms underlying mitochondrial dynamics and mitochondrial autophagy to contribute to targeted and precise regulation of mitochondrial function. Through the study of abnormal mitochondrial dynamics and mitochondrial autophagy regulation mechanisms, as well as the role of early disease development, effective targets for mitochondrial function regulation can be proposed to enable accurate diagnosis and treatment of the associated disorders.

ApoER2-Dab1 disruption as the origin of pTau-associated neurodegeneration in sporadic Alzheimer's disease

In sporadic Alzheimer's disease (sAD) specific regions, layers and neurons accumulate hyperphosphorylated Tau (pTau) and degenerate early while others remain unaffected even in advanced disease. ApoER2-Dab1 signaling suppresses Tau phosphorylation as part of a four-arm pathway that regulates lipoprotein internalization and the integrity of actin, microtubules, and synapses; however, the role of this pathway in sAD pathogenesis is not fully understood. We previously showed that multiple ApoER2-Dab1 pathway components including ApoE, Reelin, ApoER2, Dab1, pP85αTyr607, pLIMK1Thr508, pTauSer202/Thr205 and pPSD95Thr19 accumulate together within entorhinal-hippocampal terminal zones in sAD, and proposed a unifying hypothesis wherein disruption of this pathway underlies multiple aspects of sAD pathogenesis. However, it is not yet known whether ApoER2-Dab1 disruption can help explain the origin(s) and early progression of pTau pathology in sAD. In the present study, we applied in situ hybridization and immunohistochemistry (IHC) to characterize ApoER2 expression and accumulation of ApoER2-Dab1 pathway components in five regions known to develop early pTau pathology in 64 rapidly autopsied cases spanning the clinicopathological spectrum of sAD. We found that (1) these selectively vulnerable neuron populations strongly express ApoER2; and (2) multiple ApoER2-Dab1 components representing all four arms of this pathway accumulate in abnormal neurons and neuritic plaques in mild cognitive impairment (MCI) and sAD cases and correlate with histological progression and cognitive deficits. Multiplex-IHC revealed that Dab1, pP85αTyr607, pLIMK1Thr508, pTauSer202/Thr205 and pPSD95Thr19 accumulate together within many of the same ApoER2-expressing neurons and in the immediate vicinity of ApoE/ApoJ-enriched extracellular plaques. Collective findings reveal that pTau is only one of many ApoER2-Dab1 pathway components that accumulate in multiple neuroanatomical sites in the earliest stages of sAD and provide support for the concept that ApoER2-Dab1 disruption drives pTau-associated neurodegeneration in human sAD.

ApoER2-Dab1 disruption as the origin of pTau-related neurodegeneration in sporadic Alzheimer's disease

BACKGROUND

Sporadic Alzheimer's disease (sAD) is not a global brain disease. Specific regions, layers and neurons degenerate early while others remain untouched even in advanced disease. The prevailing model used to explain this selective neurodegeneration-prion-like Tau spread-has key limitations and is not easily integrated with other defining sAD features. Instead, we propose that in humans Tau hyperphosphorylation occurs locally via disruption in ApoER2-Dab1 signaling and thus the presence of ApoER2 in neuronal membranes confers vulnerability to degeneration. Further, we propose that disruption of the Reelin/ApoE/ApoJ-ApoER2-Dab1-P85α-LIMK1-Tau-PSD95 (RAAAD-P-LTP) pathway induces deficits in memory and cognition by impeding neuronal lipoprotein internalization and destabilizing actin, microtubules, and synapses. This new model is based in part on our recent finding that ApoER2-Dab1 disruption is evident in entorhinal-hippocampal terminal zones in sAD. Here, we hypothesized that neurons that degenerate in the earliest stages of sAD (1) strongly express ApoER2 and (2) show evidence of ApoER2-Dab1 disruption through co-accumulation of multiple RAAAD-P-LTP components.

METHODS

We applied in situ hybridization and immunohistochemistry to characterize ApoER2 expression and accumulation of RAAAD-P-LTP components in five regions that are prone to early pTau pathology in 64 rapidly autopsied cases spanning the clinicopathological spectrum of sAD.

RESULTS

We found that: (1) selectively vulnerable neuron populations strongly express ApoER2; (2) numerous RAAAD-P-LTP pathway components accumulate in neuritic plaques and abnormal neurons; and (3) RAAAD-P-LTP components were higher in MCI and sAD cases and correlated with histological progression and cognitive deficits. Multiplex-IHC revealed that Dab1, pP85αTyr607, pLIMK1Thr508, pTau and pPSD95Thr19 accumulated together within dystrophic dendrites and soma of ApoER2-expressing neurons in the vicinity of ApoE/ApoJ-enriched extracellular plaques. These observations provide evidence for molecular derangements that can be traced back to ApoER2-Dab1 disruption, in each of the sampled regions, layers, and neuron populations that are prone to early pTau pathology.

CONCLUSION

Findings support the RAAAD-P-LTP hypothesis, a unifying model that implicates dendritic ApoER2-Dab1 disruption as the major driver of both pTau accumulation and neurodegeneration in sAD. This model provides a new conceptual framework to explain why specific neurons degenerate and identifies RAAAD-P-LTP pathway components as potential mechanism-based biomarkers and therapeutic targets for sAD.

ApoER2-Dab1 disruption as the origin of pTau-related neurodegeneration in sporadic Alzheimer's disease

BACKGROUND

Sporadic Alzheimer's disease (sAD) is not a global brain disease. Specific regions, layers and neurons degenerate early while others remain untouched even in advanced disease. The prevailing model used to explain this selective neurodegeneration-prion-like Tau spread-has key limitations and is not easily integrated with other defining sAD features. Instead, we propose that in humans Tau hyperphosphorylation occurs locally via disruption in ApoER2-Dab1 signaling and thus the presence of ApoER2 in neuronal membranes confers vulnerability to degeneration. Further, we propose that disruption of the Reelin/ApoE/ApoJ-ApoER2-Dab1-P85α-LIMK1-Tau-PSD95 (RAAAD-P-LTP) pathway induces deficits in memory and cognition by impeding neuronal lipoprotein internalization and destabilizing actin, microtubules, and synapses. This new model is based in part on our recent finding that ApoER2-Dab1 disruption is evident in entorhinal-hippocampal terminal zones in sAD. Here, we hypothesized that neurons that degenerate in the earliest stages of sAD (1) strongly express ApoER2 and (2) show evidence of ApoER2-Dab1 disruption through co-accumulation of multiple RAAAD-P-LTP components.

METHODS

We applied in situ hybridization and immunohistochemistry to characterize ApoER2 expression and accumulation of RAAAD-P-LTP components in five regions that are prone to early pTau pathology in 64 rapidly autopsied cases spanning the clinicopathological spectrum of sAD.

RESULTS

We found that: (1) selectively vulnerable neuron populations strongly express ApoER2; (2) numerous RAAAD-P-LTP pathway components accumulate in neuritic plaques and abnormal neurons; and (3) RAAAD-P-LTP components were higher in MCI and sAD cases and correlated with histological progression and cognitive deficits. Multiplex-IHC revealed that Dab1, pP85αTyr607, pLIMK1Thr508, pTau and pPSD95Thr19 accumulated together within dystrophic dendrites and soma of ApoER2-expressing neurons in the vicinity of ApoE/ApoJ-enriched extracellular plaques. These observations provide evidence for molecular derangements that can be traced back to ApoER2-Dab1 disruption, in each of the sampled regions, layers, and neuron populations that are prone to early pTau pathology.

CONCLUSION

Findings support the RAAAD-P-LTP hypothesis, a unifying model that implicates dendritic ApoER2-Dab1 disruption as the major driver of both pTau accumulation and neurodegeneration in sAD. This model provides a new conceptual framework to explain why specific neurons degenerate and identifies RAAAD-P-LTP pathway components as potential mechanism-based biomarkers and therapeutic targets for sAD.

Oxime blot: A novel method for reliable and sensitive detection of carbonylated proteins in diverse biological systems

Oxidative stress and oxidative protein damage occur in various biological processes and diseases. The carbonyl group on amino acid side chains is the most widely used protein oxidation biomarker. Carbonyl groups are commonly detected indirectly through their reaction with 2,4-dinitrophenylhydrazine (DNPH) and subsequent labeling with an anti-DNP antibody. However, the DNPH immunoblotting method lacks protocol standardization, exhibits technical bias, and has low reliability. To overcome these shortcomings, we have developed a new blotting method in which the carbonyl group reacts with the biotin-aminooxy probe to form a chemically stable oxime bond. The reaction speed and the extent of the carbonyl group derivatization are increased by adding a p-phenylenediamine (pPDA) catalyst under neutral pH conditions. These improvements are crucial since they ensure that the carbonyl derivatization reaction reaches a plateau within hours and increases the sensitivity and robustness of protein carbonyl detection. Furthermore, derivatization under pH-neutral conditions facilitates a good SDS-PAGE protein migration pattern, avoids protein loss by acidic precipitation, and is directly compatible with protein immunoprecipitation. This work describes the new Oxime blot method and demonstrates its use in detecting protein carbonylation in complex matrices from diverse biological samples.

Natural Product Co-Metabolism and the Microbiota-Gut-Brain Axis in Age-Related Diseases

Complementary alternative medicine approaches are growing treatments of diseases to standard medicine practice. Many of these concepts are being adopted into standard practice and orthomolecular medicine. Age-related diseases, in particular neurodegenerative disorders, are particularly difficult to treat and a cure is likely a distant expectation for many of them. Shifting attention from pharmaceuticals to phytoceuticals and "bugs as drugs" represents a paradigm shift and novel approaches to intervention and management of age-related diseases and downstream effects of aging. Although they have their own unique pathologies, a growing body of evidence suggests Alzheimer's disease (AD) and vascular dementia (VaD) share common pathology and features. Moreover, normal metabolic processes contribute to detrimental aging and age-related diseases such as AD. Recognizing the role that the cerebral and cardiovascular pathways play in AD and age-related diseases represents a common denominator in their pathobiology. Understanding how prosaic foods and medications are co-metabolized with the gut microbiota (GMB) would advance personalized medicine and represents a paradigm shift in our view of human physiology and biochemistry. Extending that advance to include a new physiology for the advanced age-related diseases would provide new treatment targets for mild cognitive impairment, dementia, and neurodegeneration and may speed up medical advancements for these particularly devastating and debilitating diseases. Here, we explore selected foods and their derivatives and suggest new dementia treatment approaches for age-related diseases that focus on reexamining the role of the GMB.

The Anaphase-Promoting Complex/Cyclosome Is a Cellular Ageing Regulator

The anaphase-promoting complex/cyclosome (APC/C) is a complicated cellular component that plays significant roles in regulating the cell cycle process of eukaryotic organisms. The spatiotemporal regulation mechanisms of APC/C in distinct cell cycle transitions are no longer mysterious, and the components of this protein complex are gradually identified and characterized. Given the close relationship between the cell cycle and lifespan, it is urgent to understand the roles of APC/C in lifespan regulation, but this field still seems to have not been systematically summarized. Furthermore, although several reviews have reported the roles of APC/C in cancer, there are still gaps in the summary of its roles in other age-related diseases. In this review, we propose that the APC/C is a novel cellular ageing regulator based on its indispensable role in the regulation of lifespan and its involvement in age-associated diseases. This work provides an extensive review of aspects related to the underlying mechanisms of APC/C in lifespan regulation and how it participates in age-associated diseases. More comprehensive recognition and understanding of the relationship between APC/C and ageing and age-related diseases will increase the development of targeted strategies for human health.

Neuroprotective Effects of the Psychoactive Compound Biatractylolide (BD) in Alzheimer's Disease

Mitochondria play a central role in the survival or death of neuronal cells, and they are regulators of energy metabolism and cell death pathways. Many studies support the role of mitochondrial dysfunction and oxidative damage in the pathogenesis of Alzheimer's disease. Biatractylolide (BD) is a kind of internal symmetry double sesquiterpene novel ester compound isolated from the Chinese medicinal plant Baizhu, has neuroprotective effects in Alzheimer's disease. We developed a systematic pharmacological model based on chemical pharmacokinetic and pharmacological data to identify potential compounds and targets of Baizhu. The neuroprotective effects of BD in PC12 (rat adrenal pheochromocytoma cells) and SH-SY5Y (human bone marrow neuroblastoma cells) were evaluated by in vitro experiments. Based on the predicted results, we selected 18 active compounds, which were associated with 20 potential targets and 22 signaling pathways. Compound-target, target-disease and target-pathway networks were constructed using Cytoscape 3.2.1. And verified by in vitro experiments that BD could inhibit Aβ by reducing oxidative stress and decreasing CytC release induced mPTP opening. This study provides a theoretical basis for the development of BD as an anti-Alzheimer's disease drug.

Alleviating Neuroinflammation through Photothermal Conjugated Polymer Nanoparticles by Regulating Reactive Oxygen Species and Ca2+ Signaling

Neuroinflammation is one of the important manifestations of the amyloid β peptide (Aβ) protein-induced neurotoxic signaling pathway in which the aggregation of Aβ causes an increase in reactive oxygen species (ROS) and Ca²⁺ concentration. Here, near-infrared (NIR) photothermal-responsive conjugated polymer nanoparticles were designed to regulate ROS and Ca²⁺ signaling to alleviate neuroinflammation. Under 808 nm laser irradiation, the nanoparticles effectively penetrated the blood-brain barrier (BBB) and reduced the aggregation of Aβ and partially disaggregated the aggregates outside the cell, thereby reducing ROS content which downregulated the oxidative stress damage to cells. Meanwhile, the nanoparticles reduced the concentration of Ca²⁺ by inhibiting the transient receptor potential melastatin-related 2 (TRPM2) ion channel inside the cell. Ultimately, the concentration of inflammatory factor tumor necrosis factor-α was decreased. This study provides an effective strategy to reduce neuroinflammation by simultaneously regulating ROS and Ca²⁺ signaling.

Circulating markers of oxidative stress and risk of incident cardiovascular events in obstructive sleep apnea

The identification of which patients with obstructive sleep apnea (OSA) are more likely to develop cardiovascular disease (CVD) remains a challenge. OSA causes oxidative stress (OS) which may contribute to CVD pathogenesis. Therefore, OS markers could be useful in risk-stratifying cardiovascular (CV) risk in OSA patients. The purpose of this pilot study was to assess whether three OS marker levels could be associated with incident CVD in suspected OSA patients. Morning plasma levels of 8-isoprostane, 8-hydroxy-2'-deoxyguanosine (8-OHdG) and superoxide dismutase (SOD) were measured in patients with suspected OSA referred for a polysomnogram (PSG). A composite outcome of CV events was defined by linkage with provincial administrative health databases. Cox proportional hazards models were used to assess the relationship between the levels of OS markers and events. 352 patients were included (mean age of 51.4 years, 68% male, median apnea hypopnea index of 16/h). Thirty-one first CV events occurred over an 8-year follow-up. In univariate or fully adjusted models, none of the OS markers were significantly associated with incident CV events (hazard ratio in adjusted models of: 1.25 (95% CI 0.56-2.80, p = 0.59), 1.15 (0.52-2.57, p = 0.73), 0.77 (0.37-1.61, p = 0.48), for 8-OHdG, 8-isoprostane and SOD; however, confidence intervals were wide. In this small preliminary study, oxidative stress markers were not significantly associated with risk of CV events. However, moderate associations between these markers and risk of CV events are possible and should be the focus of future larger studies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41105-022-00399-0.

Turn-on fluorescent sensors for Cu-rich amyloid β peptide aggregates

Protein misfolding and metal dishomeostasis are two key pathological factors of Alzheimer's disease. Previous studies have shown that Cu-mediated amyloid β (Aβ) peptide aggregation leads to the formation of neurotoxic Aβ oligomers. Herein, we report a series of picolinic acid-based Cu-activatable sensors, which can be used for the fluorescence imaging of Cu-rich Aβ aggregates.

Association of Oxidative Stress with Neurological Disorders

BACKGORUND

Oxidative stress is one of the main contributing factors involved in cerebral biochemical impairment. The higher susceptibility of the central nervous system to reactive oxygen species mediated damage could be attributed to several factors. For example, neurons use a greater quantity of oxygen, many parts of the brain have higher concentraton of iron, and neuronal mitochondria produce huge content of hydrogen peroxide. In addition, neuronal membranes have polyunsaturated fatty acids, which are predominantly vulnerable to oxidative stress (OS). OS is the imbalance between reactive oxygen species generation and cellular antioxidant potential. This may lead to various pathological conditions and diseases, especially neurodegenerative diseases such as, Parkinson's, Alzheimer's, and Huntington's diseases.

OBJECTIVES

In this study, we explored the involvement of OS in neurodegenerative diseases.

METHODS

We used different search terms like "oxidative stress and neurological disorders" "free radicals and neurodegenerative disorders" "oxidative stress, free radicals, and neurological disorders" and "association of oxidative stress with the name of disorders taken from the list of neurological disorders. We tried to summarize the source, biological effects, and physiologic functions of ROS.

RESULTS

Finally, it was noted that more than 190 neurological disorders are associated with oxidative stress.

CONCLUSION

More elaborated studies in the future will certainly help in understanding the exact mechanism involved in neurological diseases and provide insight into revelation of therapeutic targets.

Lipid Peroxidation Induced ApoE Receptor-Ligand Disruption as a Unifying Hypothesis Underlying Sporadic Alzheimer's Disease in Humans

BACKGROUND

Sporadic Alzheimer's disease (sAD) lacks a unifying hypothesis that can account for the lipid peroxidation observed early in the disease, enrichment of ApoE in the core of neuritic plaques, hallmark plaques and tangles, and selective vulnerability of entorhinal-hippocampal structures.

OBJECTIVE

We hypothesized that 1) high expression of ApoER2 (receptor for ApoE and Reelin) helps explain this anatomical vulnerability; 2) lipid peroxidation of ApoE and ApoER2 contributes to sAD pathogenesis, by disrupting neuronal ApoE delivery and Reelin-ApoER2-Dab1 signaling cascades.

METHODS

In vitro biochemical experiments; Single-marker and multiplex fluorescence-immunohistochemistry (IHC) in postmortem specimens from 26 individuals who died cognitively normal, with mild cognitive impairment or with sAD.

RESULTS

ApoE and ApoER2 peptides and proteins were susceptible to attack by reactive lipid aldehydes, generating lipid-protein adducts and crosslinked ApoE-ApoER2 complexes. Using in situ hybridization alongside IHC, we observed that: 1) ApoER2 is strongly expressed in terminal zones of the entorhinal-hippocampal 'perforant path' projections that underlie memory; 2) ApoE, lipid aldehyde-modified ApoE, Reelin, ApoER2, and the downstream Reelin-ApoER2 cascade components Dab1 and Thr19-phosphorylated PSD95 accumulated in the vicinity of neuritic plaques in perforant path terminal zones in sAD cases; 3) several ApoE/Reelin-ApoER2-Dab1 pathway markers were higher in sAD cases and positively correlated with histological progression and cognitive deficits.

CONCLUSION

Results demonstrate derangements in multiple ApoE/Reelin-ApoER2-Dab1 axis components in perforant path terminal zones in sAD and provide proof-of-concept that ApoE and ApoER2 are vulnerable to aldehyde-induced adduction and crosslinking. Findings provide the foundation for a unifying hypothesis implicating lipid peroxidation of ApoE and ApoE receptors in sAD.

A Comprehensive Survey of Phenolic Constituents Reported in Monofloral Honeys around the Globe

The aim of this review is to provide a comprehensive overview of the large variety of phenolic compounds that have to date been identified in a wide range of monofloral honeys found globally. The collated information is structured along several themes, including the botanical family and genus of the monofloral honeys for which phenolic constituents have been reported, the chemical classes the phenolic compounds can be attributed to, and the analytical method employed in compound determination as well as countries with a particular research focus on phenolic honey constituents. This review covers 130 research papers that detail the phenolic constituents of a total of 556 monofloral honeys. Based on the findings of this review, it can be concluded that most of these honeys belong to the Myrtaceae and Fabaceae families and that Robinia (Robinia pseudoacacia, Fabaceae), Manuka (Leptospermum scoparium, Myrtaceae), and Chestnut (Castanea sp., Fagaceae) honeys are to date the most studied honeys for phenolic compound determination. China, Italy, and Turkey are the major honey phenolic research hubs. To date, 161 individual phenolic compounds belonging to five major compound groups have been reported, with caffeic acid, gallic acid, ferulic acid and quercetin being the most widely reported among them. HPLC with photodiode array detection appears to be the most popular method for chemical structure identification.

Tau phosphorylation and OPA1 proteolysis are unrelated events: Implications for Alzheimer's Disease

The neuropathological hallmarks of Alzheimer's Disease are plaques and neurofibrillary tangles. Yet, Alzheimer's is a complex disease with many contributing factors, such as energy-metabolic changes, which have been documented in autopsy brains from individuals with Alzheimer's and animal disease models alike. One conceivable explanation is that the interplay of age-related extracellular and intracellular alterations pertaining to Alzheimer's, such as cerebrovascular changes, protein aggregates and inflammation, evoke a mitochondrial response. However, it is not clear if and how mitochondria can contribute to Alzheimer's pathophysiology. This study focuses on one particular aspect of this question by investigating the functional interaction between the microtubule-associated protein tau and the mitochondrial inner membrane fusion machinery, which shows alterations in Alzheimer's brains. OPA1 is an essential inner membrane-fusion protein regulated by the two membrane proteases OMA1 and YME1L1. Assessment of OPA1 proteolysis-usually found in dividing mitochondria-and posttranslational tau modifications in mouse and human neuroblastoma cells under different experimental conditions clarified the relationship between these two pathways: OPA1 hydrolysis and phosphorylation or dephosphorylation of tau may coincide, but are not causally related. OPA1 cleavage did not alter tau's phosphorylation pattern. Conversely, tau's phosphorylation state did not induce nor correlate with OPA1 proteolysis. These results irrefutably demonstrate that there is no direct functional interaction between posttranslational tau modifications and the regulation of the OMA1-OPA1 pathway, which implies a common root cause modulating both pathways in Alzheimer's.

Novel chrysin derivatives as hidden multifunctional agents for anti-Alzheimer's disease: design, synthesis and in vitro evaluation

Alzheimer's disease (AD) is the most common type of dementia, the exact etiology of the disease has not been known yet. The use of single-target drugs limits the efficacy of drugs and has certain side effects. In this study, the 'hidden' multi-target strategy was used in combination with chrysin's metal chelating site and rivastigmine's anti-cholinesterase pharmacophore to form an ester, which improves the hydrophobicity and protects the phenolic hydroxyl group at the same time. Four derivatives (1-4) were synthesized as the hidden multifunctional agents for AD therapy. Most of the compounds displayed good activities of anti-cholinesterase, antioxidant, appropriate blood brain barrier (BBB) penetration and certain inhibitory activity of β-amyloid (Aβ) aggregation. Compound 3 was demonstrated as the highest selective butyrylcholinesterase (BuChE) inhibitor and targeted both the catalytic active site (CAS) and the peripheral anion site (PAS). And it could be hydrolyzed by BuChE to release chrysin with good ability to chelate Cu²⁺ and Fe²⁺. At the same time, phenol fragment can exert its good antioxidant effect. Overall, these findings demonstrated that compound 3 might be considered as a potential hidden multifunctional candidate in the therapy 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.

Disentangling Mitochondria in Alzheimer's Disease

Alzheimer's disease (AD) is a major cause of dementia in older adults and is fast becoming a major societal and economic burden due to an increase in life expectancy. Age seems to be the major factor driving AD, and currently, only symptomatic treatments are available. AD has a complex etiology, although mitochondrial dysfunction, oxidative stress, inflammation, and metabolic abnormalities have been widely and deeply investigated as plausible mechanisms for its neuropathology. Aβ plaques and hyperphosphorylated tau aggregates, along with cognitive deficits and behavioral problems, are the hallmarks of the disease. Restoration of mitochondrial bioenergetics, prevention of oxidative stress, and diet and exercise seem to be effective in reducing Aβ and in ameliorating learning and memory problems. Many mitochondria-targeted antioxidants have been tested in AD and are currently in development. However, larger streamlined clinical studies are needed to provide hard evidence of benefits in AD. This review discusses the causative factors, as well as potential therapeutics employed in the treatment of AD.

A Review of Oxidative Stress Products and Related Genes in Early Alzheimer's Disease

Oxidative stress is associated with the progression of Alzheimer’s disease (AD). Reactive oxygen species can modify lipids, DNA, RNA, and proteins in the brain. The products of their peroxidation and oxidation are readily detectable at incipient stages of disease. Based on these oxidation products, various biomarker-based strategies have been developed to identify oxidative stress levels in AD. Known oxidative stress-related biomarkers include lipid peroxidation products F2-isoprostanes, as well as malondialdehyde and 4-hydroxynonenal which both conjugate to specific amino acids to modify proteins, and DNA or RNA oxidation products 8-hydroxy-2’-deoxyguanosine (8-OHdG) and 8-hydroxyguanosine (8-OHG), respectively. The inducible enzyme heme oxygenase type 1 (HO-1) is found to be upregulated in response to oxidative stress-related events in the AD brain. While these global biomarkers for oxidative stress are associated with early-stage AD, they generally poorly differentiate from other neurodegenerative disorders that also coincide with oxidative stress. Redox proteomics approaches provided specificity of oxidative stress-associated biomarkers to AD pathology by the identification of oxidatively damaged pathology-specific proteins. In this review, we discuss the potential combined diagnostic value of these reported biomarkers in the context of AD and discuss eight oxidative stress-related mRNA biomarkers in AD that we newly identified using a transcriptomics approach. We review these genes in the context of their reported involvement in oxidative stress regulation and specificity for AD. Further research is warranted to establish the protein levels and their functionalities as well as the molecular mechanisms by which these potential biomarkers are involved in regulation of oxidative stress levels and their potential for determination of oxidative stress and disease status of AD patients.

Defective mitophagy and synaptic degeneration in Alzheimer's disease: Focus on aging, mitochondria and synapse

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by memory loss and multiple cognitive impairments. AD is marked by multiple cellular changes, including deregulation of microRNAs, activation of glia and astrocytes, hormonal imbalance, defective mitophagy, synaptic degeneration, in addition to extracellular neuritic amyloid-beta (Aβ) plaques, phosphorylated tau (P-tau), and intracellular neurofibrillary tangles (NFTs). Recent research in AD revealed that defective synaptic mitophagy leads to synaptic degeneration and cognitive dysfunction in AD neurons. Our critical analyses of mitochondria and Aβ and P-tau revealed that increased levels of Aβ and P-Tau, and abnormal interactions between Aβ and Drp1, P-Tau and Drp1 induced increased mitochondrial fragmentation and proliferation of dysfunctional mitochondria in AD neurons and depleted Parkin and PINK1 levels. These events ultimately lead to impaired clearance of dead and/or dying mitochondria in AD neurons. The purpose of our article is to highlight the recent research on mitochondria and synapses in relation to Aβ and P-tau, focusing on recent developments.

Sex Differences in Locus Coeruleus: A Heuristic Approach That May Explain the Increased Risk of Alzheimer's Disease in Females

This article aims to reevaluate our approach to female vulnerability to Alzheimer's disease (AD) and put forth a new hypothesis considering how sex differences in the locus coeruleus-noradrenaline (LC-NA) structure and function could account for why females are more likely to develop AD. We specifically focus our attention on locus coeruleus (LC) morphology, the paucity of estrogens, neuroinflammation, blood-brain barrier permeability, apolipoprotein ɛ4 polymorphism (APOEɛ4), and cognitive reserve. The role of the LC-NA system and sex differences are two of the most rapidly emerging topics in AD research. Current literature either investigates the LC due to it being one of the first brain areas to develop AD pathology or acknowledges the neuroprotective effects of estrogens and how the loss of these female hormones have the capacity to contribute to the sex differences seen in AD; however, existing research has neglected to concurrently examine these two rationales and therefore leaving our hypothesis undetermined. Collectively, this article should assist in alleviating current challenges surrounding female AD by providing thought-provoking connections into the interrelationship between the disruption of the female LC-NA system, the decline of estrogens, and AD vulnerability. It is therefore likely that treatment for this heterogeneous disease may need to be distinctly developed for females and males separately, and may require a precision medicine approach.

Improved quality and fertilizability of cryopreserved buffalo spermatozoa with the supplementation of methionine sulfoxide reductase A

BACKGROUND

The excessive reactive oxygen species produced during semen-freezing and -thawing damage the macromolecules resulting in impairment of cellular functions. Proteins are the primary targets of oxidative damage, wherein methionine residues are more prone to oxidation and get converted into methionine sulfoxide, thus affecting the protein function. The methionine sulfoxide reductase A (MsrA) catalyzes the conversion of methionine sulfoxide to methionine and restores the functionality of defective proteins.

OBJECTIVES

To establish the expression of MsrA in male reproductive organs, including semen and its effect on quality of cryopreserved semen upon exogenous supplementation, taking buffalo semen as a model.

MATERIALS AND METHODS

The expression of MsrA was established by immunohistochemistry, PCR, and Western blots. Further, the effect of recombinant MsrA (rMsrA) supplementation on the quality of cryopreserved spermatozoa was assessed in three treatment groups containing 1.0, 1.5, and 2.0 µg of rMsrA/50 million spermatozoa in egg yolk glycerol extender along with a control group; wherein the post-thaw progressive motility, viability, membrane integrity, and zona binding ability of cryopreserved spermatozoa were studied.

RESULTS

The MsrA was expressed in buffalo testis, epididymis, accessory sex glands, and spermatozoa except in seminal plasma. In group 2, the supplementation has resulted in a significant (p < 0.05) improvement as compared to the control group in mean progressive motility (47.50 ± 2.50 vs. 36.25 ± 2.63), viability (56.47 ± 1.85 vs. 48.05 ± 2.42), HOST (50.76 ± 1.73 vs. 44.29 ± 1.29), and zona binding ability of spermatozoa (149.50 ± 8.39 vs. 29.50 ± 2.85).

DISCUSSION AND CONCLUSION

In the absence of native MsrA of seminal plasma, the supplementations of rMsrA may repair the oxidatively damaged seminal plasma proteins and exposed sperm plasma membrane proteins resulting in better quality with a fivefold increase in fertilizability of frozen-thawed spermatozoa. The findings can be extended to other species to improve the semen quality with the variation in the amounts of rMsrA supplementation.

Impaired Iron Homeostasis and Haematopoiesis Impacts Inflammation in the Ageing Process in Down Syndrome Dementia

Down syndrome (DS) subjects are more likely to develop the clinical features of Alzheimer's disease (AD) very early in the disease process due to the additional impact of neuroinflammation and because of activation of innate immunity. Many factors involved in the neuropathology of AD in DS, including epigenetic factors, innate immunity and impaired haematopoiesis, contribute significantly towards the pathophysiology and the enhanced ageing processes seen in DS and as a consequence of the triplication of genes RUNX1, S100β and OLIG2, together with the influence of proteins that collectively protect from cellular defects and inflammation, which include hepcidin, ferritin, IL-6 and TREM2. This study is aimed at determining whether genetic variants and inflammatory proteins are involved in haematopoiesis and cellular processes in DS compared with age-matched control participants, particularly with respect to neuroinflammation and accelerated ageing. Serum protein levels from DS, AD and control participants were measured by enzyme-linked immunosorbent assay (ELISA). Blood smears and post-mortem brain samples from AD and DS subjects were analysed by immunohistochemistry. RUNX1 mRNA expression was analysed by RT-PCR and in situ hybridisation in mouse tissues. Our results suggest that hepcidin, S100β and TREM2 play a critical role in survival and proliferation of glial cells through a common shared pathway. Blood smear analysis showed the presence of RUNX1 in megakaryocytes and platelets, implying participation in myeloid cell development. In contrast, hepcidin was expressed in erythrocytes and in platelets, suggesting a means of possible entry into the brain parenchyma via the choroid plexus (CP). The gene product of RUNX1 and hepcidin both play a critical role in haematopoiesis in DS. We propose that soluble TREM2, S100β and hepcidin can migrate from the periphery via the CP, modulate the blood-brain immune axis in DS and could form an important and hitherto neglected avenue for possible therapeutic interventions to reduce plaque formation.

Amyloids: The History of Toxicity and Functionality

Proteins can perform their specific function due to their molecular structure. Partial or complete unfolding of the polypeptide chain may lead to the misfolding and aggregation of proteins in turn, resulting in the formation of different structures such as amyloid aggregates. Amyloids are rigid protein aggregates with the cross-β structure, resistant to most solvents and proteases. Because of their resistance to proteolysis, amyloid aggregates formed in the organism accumulate in tissues, promoting the development of various diseases called amyloidosis, for instance Alzheimer's diseases (AD). According to the main hypothesis, it is considered that the cause of AD is the formation and accumulation of amyloid plaques of Aβ. That is why Aβ-amyloid is the most studied representative of amyloids. Therefore, in this review, special attention is paid to the history of Aβ-amyloid toxicity. We note the main problems with anti-amyloid therapy and write about new views on amyloids that can play positive roles in the different organisms including humans.

The role of mitophagy in the regulation of mitochondrial energetic status in neurons

Mitochondria are the main cellular energy powerhouses and supply most of the energy in the form of ATP to fuel essential neuronal functions through oxidative phosphorylation (OXPHOS). In Alzheimer disease (AD), metabolic and mitochondrial disruptions are an early feature preceding any histopathological and clinical manifestations. Mitochondrial malfunction is also linked to synaptic defects in early AD. Mitophagy serves as a key cellular quality control mechanism involving sequestration of damaged mitochondria within autophagosomes and their subsequent degradation in lysosomes. However, it remains largely unknown whether mitophagy is involved in the regulation of energy metabolism in neurons, and if so, whether metabolic deficiency in AD is attributed to mitophagy dysfunction. Here we reveal that mitophagy is broadly activated in metabolically enhanced neurons upon OXPHOS stimulation, which sustains high energetic activity by increasing mitochondrial turnover and hence facilitating mitochondrial maintenance. Unexpectedly, in AD-related mutant HsAPP Tg mouse brains, early stimulation of OXPHOS activity fails to correct energy deficits but exacerbates synapse loss as a consequence of mitophagy failure. Excitingly, lysosomal enhancement in AD neurons restores impaired metabolic function by promoting elimination of damaged mitochondria, protecting against synaptic damage in AD mouse brains. Taken together, we propose a new mechanism by which mitophagy controls bioenergetic status in neurons, furthering our understanding of the direct impact of mitophagy defects on AD-linked metabolic deficits and shedding light on the development of novel therapeutic strategies to treat AD by the early stimulation of mitochondrial metabolism combined with elevation of lysosomal proteolytic activity.

Knock-Down of HDAC2 in Human Induced Pluripotent Stem Cell Derived Neurons Improves Neuronal Mitochondrial Dynamics, Neuronal Maturation and Reduces Amyloid Beta Peptides

Histone deacetylase 2 (HDAC2) is a major HDAC protein in the adult brain and has been shown to regulate many neuronal genes. The aberrant expression of HDAC2 and subsequent dysregulation of neuronal gene expression is implicated in neurodegeneration and brain aging. Human induced pluripotent stem cell-derived neurons (hiPSC-Ns) are widely used models for studying neurodegenerative disease mechanisms, but the role of HDAC2 in hiPSC-N differentiation and maturation has not been explored. In this study, we show that levels of HDAC2 progressively decrease as hiPSCs are differentiated towards neurons. This suppression of HDAC2 inversely corresponds to an increase in neuron-specific isoforms of Endophilin-B1, a multifunctional protein involved in mitochondrial dynamics. Expression of neuron-specific isoforms of Endophilin-B1 is accompanied by concomitant expression of a neuron-specific alternative splicing factor, SRRM4. Manipulation of HDAC2 and Endophilin-B1 using lentiviral approaches shows that the knock-down of HDAC2 or the overexpression of a neuron-specific Endophilin-B1 isoform promotes mitochondrial elongation and protects against cytotoxic stress in hiPSC-Ns, while HDAC2 knock-down specifically influences genes regulating mitochondrial dynamics and synaptogenesis. Furthermore, HDAC2 knock-down promotes enhanced mitochondrial respiration and reduces levels of neurotoxic amyloid beta peptides. Collectively, our study demonstrates a role for HDAC2 in hiPSC-neuronal differentiation, highlights neuron-specific isoforms of Endophilin-B1 as a marker of differentiating hiPSC-Ns and demonstrates that HDAC2 regulates key neuronal and mitochondrial pathways in hiPSC-Ns.

Mitochondria and early-life adversity

Early-life adversity (ELA), which includes maltreatment, neglect, or severe trauma in childhood, increases the life-long risk for negative health outcomes. Mitochondria play a key role in the stress response and may be an important mechanism by which stress is transduced into biological risk for disease. By responding to cues from stress-signaling pathways, mitochondria interact dynamically with physiological stress responses coordinated by the central nervous, endocrine, and immune systems. Preclinical evidence suggests that alterations in mitochondrial function and structure are linked to both early stress and systemic biological dysfunction. Early clinical studies support that increased mitochondrial DNA content and altered cellular energy demands may be present in individuals with a history of ELA. Further research should investigate mitochondria as a potential therapeutic target following ELA.

A review on α-mangostin as a potential multi-target-directed ligand for Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disease characterized by progressive memory loss, declining language skills and other cognitive disorders. AD has brought great mental and economic burden to patients, families and society. However due to the complexity of AD's pathology, drugs developed for the treatment of AD often fail in clinical or experimental trials. The main problems of current anti-AD drugs are low efficacy due to mono-target method or side effects, especially high hepatotoxicity. To tackle these two main problems, multi-target-directed ligand (MTDL) based on "one molecule, multiple targets" has been studied. MTDLs can regulate multiple biological targets at the same time, so it has shown higher efficacy, better safety. As a natural active small molecule, α-mangostin (α-M) has shown potential multi-factor anti-AD activities in a series of studies, furthermore it also has a certain hepatoprotective effect. The good availability of α-M also provides support for its application in clinical research. In this work, multiple activities of α-M related to AD therapy were reviewed, which included anti-cholinesterase, anti-amyloid-cascade, anti-inflammation, anti-oxidative stress, low toxicity, hepatoprotective effects and drug formulation. It shows that α-M is a promising candidate for the treatment of AD.

Impact of COVID-19 on Mitochondrial-Based Immunity in Aging and Age-Related Diseases

The coronavirus disease 2019 (COVID-19) has become a deadly pandemic with surging mortality rates and no cure. COVID-19 is caused by the severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) with a range of clinical symptoms, including cough, fever, chills, headache, shortness of breath, difficulty breathing, muscle pain, and a loss of smell or taste. Aged individuals with compromised immunity are highly susceptible to COVID-19 and the likelihood of mortality increases with age and the presence of comorbidities such as hypertension, diabetes mellitus, cardiovascular disease, or chronic obstructive pulmonary disease. Emerging evidence suggests that COVID-19 highjacks mitochondria of immune cells, replicates within mitochondrial structures, and impairs mitochondrial dynamics leading to cell death. Mitochondria are the powerhouses of the cell and are largely involved in maintaining cell immunity, homeostasis, and cell survival/death. Increasing evidence suggests that mitochondria from COVID-19 infected cells are highly vulnerable, and vulnerability increases with age. The purpose of our article is to summarize the role of various age-related comorbidities such as diabetes, obesity, and neurological diseases in increasing mortality rates amongst the elderly with COVID-19. Our article also highlights the interaction between coronavirus and mitochondrial dynamics in immune cells. We also highlight the current treatments, lifestyles, and safety measures that can help protect against COVID-19. Further research is urgently needed to understand the molecular mechanisms between the mitochondrial virus and disease progression in COVID-19 patients.

Nicotine Prevents Oxidative Stress-Induced Hippocampal Neuronal Injury Through α7-nAChR/Erk1/2 Signaling Pathway

Oxidative stress-induced neuronal damage has been implicated to play a dominant role in neurodegenerative disorders, such as Alzheimer’s disease (AD). Nicotine, a principal additive compound for tobacco users, is thought as a candidate to attenuate amyloid-β-mediated neurotoxicity and NMDA-induced excitotoxicity. Previous studies demonstrated that nicotine exerted this neuroprotective action on oxidative stress. However, the mechanisms underlying how nicotine contributes on oxidative injury in immortalized hippocampal HT-22 cells remain largely unknown. Therefore, in this study we investigated that the potential effects of nicotine on hydrogen peroxide (H₂O₂)-induced oxidative injury and underlying mechanisms in HT-22 cells. We found that pretreatment with nicotine at low concentrations markedly recovered the cell cycle that was arrested at the G2/M phase in the presence of H₂O₂ through reduced intracellular ROS generation. Moreover, nicotine attenuated H₂O₂-induced mitochondrial dysfunctions. Mechanistically, the application of nicotine significantly upregulated the levels of phosphorylated Erk1/2. The neuroprotective effects of nicotine, in turn, were abolished by PD0325901, a selective Erk1/2 inhibitor. Further obtained investigation showed that nicotine exerted its neuroprotective effects via specifically activating α7 nicotinic acetylcholine receptors (α7-nAChRs). A selective inhibitor of α7-nAChRs, methyllycaconitine citrate (MLA), not only completely prevented nicotine-mediated antioxidation but also abolished expression of p-Erk1/2. Taken together, our findings suggest that nicotine suppresses H₂O₂-induced HT-22 cell injury through activating the α7-nAChR/Erk1/2 signaling pathway, which indicates that nicotine may be a novel strategy for the treatment of neurodegenerative disorders.

Relationships between Mitochondrial Dysfunction and Neurotransmission Failure in Alzheimer's Disease

Besides extracellular deposition of amyloid beta and formation of phosphorylated tau in the brains of patients with Alzheimer's disease (AD), the pathogenesis of AD is also thought to involve mitochondrial dysfunctions and altered neurotransmission systems. However, none of these components can describe the diverse cognitive, behavioural, and psychiatric symptoms of AD without the pathologies interacting with one another. The purpose of this review is to understand the relationships between mitochondrial and neurotransmission dysfunctions in terms of (1) how mitochondrial alterations affect cholinergic and monoaminergic systems via disruption of energy metabolism, oxidative stress, and apoptosis; and (2) how different neurotransmission systems drive mitochondrial dysfunction via increasing amyloid beta internalisation, oxidative stress, disruption of mitochondrial permeabilisation, and mitochondrial trafficking. All these interactions are separately discussed in terms of neurotransmission systems. The association of mitochondrial dysfunctions with alterations in dopamine, norepinephrine, and histamine is the prospective goal in this research field. By unfolding the complex interactions surrounding mitochondrial dysfunction in AD, we can better develop potential treatments to delay, prevent, or cure this devastating disease.

Neuroprotective Effects of the Amylin Analog, Pramlintide, on Alzheimer's Disease Are Associated with Oxidative Stress Regulation Mechanisms

Administration of the recombinant analog of the pancreatic amyloid amylin, Pramlintide, has shown therapeutic benefits in aging and Alzheimer's disease (AD) models, both on cognition and amyloid-β (Aβ) pathology. However, the neuroprotective mechanisms underlying the benefits of Pramlintide remain unclear. Given the early and critical role of oxidative stress in AD pathogenesis and the known reactive oxygen species (ROS) modulating function of amyloids, we sought to determine whether Pramlintide's neuroprotective effects involve regulation of oxidative stress mechanisms. To address this, we treated APP/PS1 transgenic mice with Pramlintide for 3 months, starting at 5.5 months prior to widespread AD pathology onset, and measured cognition (Morris Water Maze), AD pathology, and oxidative stress-related markers and enzymes in vivo. In vitro, we determined the ability of Pramlintide to modulate H2O2-induced oxidative stress levels. Our data show that Pramlintide improved cognitive function, altered amyloid-processing enzymes, reduced plaque burden in the hippocampus, and regulated endogenous antioxidant enzymes (MnSOD and GPx1) and the stress marker HO-1 in a location specific manner. In vitro, Pramlintide treatment in neuronal models reduced H2O2-induced endogenous ROS production and lipid peroxidation in a dose-dependent manner. Together, these results indicate that Pramlintide's benefits on cognitive function and pathology may involve antioxidant-like properties of this compound.

Increased basal antioxidant levels in RCAN1 - deficient mice lowers oxidative injury after acute paraquat insult

RCAN1 is an inhibitor of the phosphatase calcineurin, which is involved in the regulation of oxidative stress and apoptosis, among other important cell processes. Here we have used RCAN1 deficient mice (RCAN1^-/-) to elucidate its role after an acute oxidative insult such as paraquat injection. We have observed that RCAN1^-/- mice show less oxidative damage than wildtype (WT) mice after treatment. Under basal conditions, RCAN1^-/- animals express more calcineurin, heme oxygenase-1, Nrf2, and catalase compared to WT mice (controls). This may explain the less severe effect of paraquat treatment on RCAN1^-/- mice compared to WT. We showed that oxidative stress is involved in the early stages of apoptosis, thus we determined the apoptotic effector BAD and found that decreases in RCAN1^-/- mice after treatment with paraquat compared with WT in similar experimental conditions. Our results suggest that RCAN1 may be involved in the balance between oxidant and antioxidant species production in vivo.

Chemistry and Antioxidant Potential of Phytoconstituents from Aegle Marmelos Fruit-Shell

BACKGROUND

Oxidative stress is among the main causes of metabolic disorders. Hence, there is a need to discover potent antioxidants for therapeutic applications.

OBJECTIVE

The objective of this study has been to investigate the phytoconstituents of the methanolic extract of the hard shell of Aegle marmelos fruit and their antioxidant potential.

METHODS

Methanolic extract was fractionated using different solvents by liquid-liquid extraction. Characterization of the phytoconstituents was done by using phytochemical tests and GC-MS analysis. The free radical scavenging activity, total reducing power, lipid peroxidation inhibition and cell protection assays against oxidative stress were performed with methanolic extract and its fractions.

RESULTS

Therapeutically significant class of compounds, for example, polyphenols, glycosides and sterols were revealed in the hard-shell extract. Differential separation of compounds was achieved by liquid-liquid extraction using different solvents. Six compounds: 4-Hydroxybenzeneacetic acid; 5-Oxo-pyrrolidine-2-carboxylic acid methyl ester; 1-[3-Methyl-3-Butenyl] Pyrrolidine; Trans-sinapyl alcohol; 5-[Hydroxymethyl]-2-furaldehyde and 2,4- Dihydroxy-2,5-dimethyl-3[2H]-furan-3-one, identified in the fruit-shell extract, are being reported for the first time from this plant. Strong antioxidant potential of the extract was evident from efficient scavenging of free radicals. The extract also conferred protection to yeast cells against oxidative damage.

CONCLUSION

Results showed that the hard shell of the Aegle marmelos fruit was a potent source for antioxidant compounds, which can be developed for therapeutic applications in the control and management of metabolic diseases.

Interplay between Oxidative Stress, Inflammation, and Amyloidosis in the Anterior Segment of the Eye; Its Pathological Implications

There are different pathologies associated with amyloidogenic processes caused by the increase of reactive oxygen species (ROS) and the overactivation of inflammatory responses. These alterations are present in different regions of the anterior segment of the eye, and they have been associated with the development and progression of ocular pathologies, such as glaucoma, dry eye syndrome, keratitis, and cataracts among other pathologies. Aim. To discuss briefly the anatomical characteristics of the anterior segment of the eye and describe the interaction between oxidative stress (OS) and inflammatory responses, emphasizing the misfolding of several proteins leading to amyloidogenic processes occurring in the anterior segment and their implications in the development of ocular diseases. We performed a search on PubMed, CINAHL, and Embase using the MeSH terms “eye,” “anterior segment”, “inflammation”, “oxidative stress”, and “amyloidosis”. The search encompassed manuscripts published up to April 2019. A hundred forty-four published studies met the inclusion criteria. We present the current knowledge regarding the interaction between OS and the activation of inflammatory processes and how both can cause conformational changes in several peptides and proteins in each compartment of the anterior segment. However, we found that there is no consensus about which factor is the first to cause amyloidosis. Our conclusions suggest that there is an interplay among these factors forming a vicious cycle that leads to the loss of protein structure in ocular pathologies, and multifactorial therapies should be developed to avoid protein misfolding and to stop the progression of ocular pathologies.

Purification, characterization and antioxidant activities in vitro of polysaccharides from Amaranthus hybridus L

Background

Amaranthus hybridus L. is an annual, erect or less commonly ascending herb that is a member of the Amaranthaceae family. Polysaccharides extracted from traditional Chinese medicines may be effective substances with antioxidant activity.

Methods

In this study, we isolated crude polysaccharides from A. hybridus (AHP-M) using microwave-assisted extraction. Then, the AHP-M was purified by chromatography with DEAE-32 cellulose, and two fractions, AHP-M-1 and AHP-M-2, were obtained. The structural characteristics of AHP-M-1 and AHP-M-2 were investigated, and their antioxidant activities were analyzed in vitro.

Results

We found that the monosaccharide composition of AHP-M-1 was different from that of AHP-M-2. The molecular weights of AHP-M-1 and AHP-M-2 were 77.625 kDa and 93.325 kDa, respectively. The results showed that the antioxidant activity of AHP-M-2 was better than that of AHP-M-1. For AHP-M-2, the DPPH radical scavenging rate at a concentration of 2 mg/mL was 78.87%, the hydroxyl radical scavenging rate was 39.34%, the superoxide anion radical scavenging rate was 80.2%, and the reduction ability of Fe³⁺ was approximately 0.90. The total antioxidant capacity per milligram of AHP-M-2 was 6.42, which was higher than that of Vitamin C (Vc).

Conclusion

The in vitro test indicated that AHP-M-1 and AHP-M-2 have good antioxidant activity, demonstrating that A. hybridus L. polysaccharide has immense potential as a natural antioxidants.

A Preliminary Study of Cu Exposure Effects upon Alzheimer's Amyloid Pathology

A large body of evidence indicates that dysregulation of cerebral biometals (Fe, Cu, Zn) and their interactions with amyloid precursor protein (APP) and Aβ amyloid may contribute to the Alzheimer's disease (AD) Aβ amyloid pathology. However, the molecular underpinnings associated with the interactions are still not fully understood. Herein we have further validated the exacerbation of Aβ oligomerization by Cu and H2O2 in vitro. We have also reported that Cu enhanced APP translations via its 5' untranslated region (5'UTR) of mRNA in SH-SY5Y cells, and increased Aβ amyloidosis and expression of associated pro-inflammatory cytokines such as MCP-5 in Alzheimer's APP/PS1 doubly transgenic mice. This preliminary study may further unravel the pathogenic role of Cu in Alzheimer's Aβ amyloid pathogenesis, warranting further investigation.

In-vitro antioxidant, antimutagenic and cancer cell growth inhibition activities of Rhododendron arboreum leaves and flowers

In the current investigation, the active principles of the methanol extracts of Rhododendron arboreum leaves (MEL) and flowers (MEF) were investigated with the help of ultra-high performance liquid chromatography (UHPLC), amino acid analyzer and gas chromatography mass spectrometry (GC-MS). UHPLC revealed different polyphenols present in the extracts. GC-MS identified 20 phytochemicals in leaves and 17 in the flowers, whereas, amino acid analyzer confirmed 11 amino acids in leaves and 10 in the flowers. The extracts were subjected to the investigation of biological activity through analysis of antioxidant activity in different in vitro assays, antimutagenic activity in Ames assay and cancer cell growth inhibition activity by MTT (3-4,5 dimethylthiazol-2,5 diphenyltetrazolium bromide) assay. MEL showed higher antioxidant activity in lipid peroxidation inhibition assay (95.32 ± 0.37%) than MEF (77.09 ± 4.17%) with IC₅₀103.6 µg/ml for MEL and 271.17 µg/ml for MEF. In nitric oxide scavenging assay, an activity of 94.46 ± 0.32% (IC₅₀ 150.13) was observed in MEF followed by 83.71 ± 0.74% (IC₅₀ 179.52) in MEL. The antimutagenic activity of both the extracts was evaluated against sodium azide, 4-nitro-O-phenylenediamine and 2-aminofluorene mutagens in TA-98 and TA-100 strains of Salmonella typhimurium. The analysis was carried out using pre- and co-incubation modes. However, both extracts were observed to possess considerable antimutagenic activity against different known mutagens, flowers came out to be more effective than the leaves in terms of % inhibition. The extracts also exhibited significant cancer cell growth inhibition activity, when tested against 3 cancer cell lines namely, Human cervical cancer cell line (HeLa), Breast cancer cell line (MCF7) and Lung cancer cell line (A549). In case of HeLa and A549, MEL showed higher activity of 64.62 ± 2.65 and 75.08 ± 1.68% as compared to 53.11 ± 2.84 and 45.92 ± 2.43% in MEL, respectively. The EC₅₀ values for MEL in HeLa and A549 were noted to be 232.76 and 155.38 µg/ml, respectively, whereas, MEF had EC₅₀ of 395.50 µg/ml in HeLa and 660.26 µg/ml in A549. Further, MEF showed higher cytotoxicity in MCF7 cell line (84.93 ± 1.17%) followed by the MEL (73.57 ± 1.27%) with EC₅₀ value of 95.16 µg/ml for MEF followed by 172.19 µg/ml for MEL. The biological activities of the extracts can be attributed to the phyto-constituents identified by sophisticated instruments.

The biological activities of the extracts can be attributed to the active principles identified by sophisticated instruments.

Nrf2 activation through the PI3K/GSK-3 axis protects neuronal cells from Aβ-mediated oxidative and metabolic damage

Background

Mounting evidence points to a crucial role of amyloid-β (Aβ) in the pathophysiology of Alzheimer’s disease (AD), a disorder in which brain glucose hypometabolism, downregulation of central elements of phosphorylation pathways, reduced ATP levels, and enhanced oxidative damage coexist, and sometimes precede, synaptic alterations and clinical manifestations. Since the brain has limited energy storage capacity, mitochondria play essential roles in maintaining the high levels of energy demand, but, as major consumers of oxygen, these organelles are also the most important generators of reactive oxygen species (ROS). Thus, it is not surprising that mitochondrial dysfunction is tightly linked to synaptic loss and AD pathophysiology. In spite of their relevance, the mechanistic links among ROS homeostasis, metabolic alterations, and cell bioenergetics, particularly in relation to Aβ, still remain elusive.

Methods

We have used classic biochemical and immunocytochemical approaches together with the evaluation of real-time changes in global energy metabolism in a Seahorse Metabolic Analyzer to provide insights into the detrimental role of oligAβ in SH-SY5Y and primary neurons testing their pharmacologic protection by small molecules.

Results

Our findings indicate that oligomeric Aβ induces a dramatic increase in ROS production and severely affects neuronal metabolism and bioenergetics. Assessment of global energy metabolism in real time demonstrated Aβ-mediated reduction in oxygen consumption affecting basal and maximal respiration and causing decreased ATP production. Pharmacologic targeting of Aβ-challenged neurons with a set of small molecules of known antioxidant and cytoprotective activity prevented the metabolic/bioenergetic changes induced by the peptide, fully restoring mitochondrial function while inducing an antioxidant response that counterbalanced the ROS production. Search for a mechanistic link among the protective small molecules tested identified the transcription factor Nrf2—compromised by age and downregulated in AD and transgenic models—as their main target and the PI3K/GSK-3 axis as the central pathway through which the compounds elicit their Aβ protective action.

Conclusions

Our study provides insights into the complex molecular mechanisms triggered by oligAβ which profoundly affect mitochondrial performance and argues for the inclusion of small molecules targeting the PI3K/GSK-3 axis and Nrf2-mediated pathways as part of the current or future combinatorial therapies.

Mitophagy in Alzheimer's Disease and Other Age-Related Neurodegenerative Diseases

Mitochondrial dysfunction is a central aspect of aging and neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease. Mitochondria are the main cellular energy powerhouses, supplying most of ATP by oxidative phosphorylation, which is required to fuel essential neuronal functions. Efficient removal of aged and dysfunctional mitochondria through mitophagy, a cargo-selective autophagy, is crucial for mitochondrial maintenance and neuronal health. Mechanistic studies into mitophagy have highlighted an integrated and elaborate cellular network that can regulate mitochondrial turnover. In this review, we provide an updated overview of the recent discoveries and advancements on the mitophagy pathways and discuss the molecular mechanisms underlying mitophagy defects in Alzheimer's disease and other age-related neurodegenerative diseases, as well as the therapeutic potential of mitophagy-enhancing strategies to combat these disorders.

Interplay Between MicroRNAs and Oxidative Stress in Ovarian Conditions with a Focus on Ovarian Cancer and Endometriosis

Ovarian cancer and endometriosis are two distinct gynaecological conditions that share many biological aspects incuding proliferation, invasion of surrounding tissue, inflammation, inhibition of apoptosis, deregulation of angiogenesis and the ability to spread at a distance. miRNAs are small non-coding RNAs (19–22 nt) that act as post-transcriptional modulators of gene expression and are involved in several of the aforementioned processes. In addition, a growing body of evidence supports the contribution of oxidative stress (OS) to these gynaecological diseases: increased peritoneal OS due to the decomposition of retrograde menstruation blood facilitates both endometriotic lesion development and fallopian tube malignant transformation leading to high-grade serous ovarian cancer (HGSOC). Furthermore, as HGSOC develops, increased OS levels are associated with chemoresistance. Finally, continued bleeding within ovarian endometrioma raises OS levels and contributes to the development of endometriosis-associated ovarian cancer (EAOC). Therefore, this review aims to address the need for a better understanding of the dialogue between miRNAs and oxidative stress in the pathophysiology of ovarian conditions: endometriosis, EAOC and HGSOC.

Copper Ion Uptake by Chitosan in the Presence of Amyloid-β and Histidine

Alzheimer's disease (AD) is related to the anomalous binding that occurs between amyloid-β peptide (Aβ) and copper ion, through imidazole ring of histidine (His), as stated in the literature. It is also known that high-affinity metal ion chelators can be pharmacologically used as a possible therapeutic approach. In this work, we tested the ability "in vitro" of chitosan (Chi) to reduce Aβ aggregation and Thioflavin T binding assay indicated that chitosan has affinity for Aβ and interferes in its aggregation. We also tested the ability of Chi to uptake copper ions in the presence of Aβ or His. Equilibrium data reveals that chitosan acted as an effective chelating agent competing with Aβ and histidine for copper binding. The addition of histidine or Aβ in the system promotes an unfolding of chitosan chains, as verified by small-angle X-ray scattering. Extended X-ray absorption fine structure and XPS spectra show that new copper interactions with groups containing nitrogen in the presence of histidine may occur. These results can help understanding fundamental chemical interactions among species detected in AD and biopolymers, opening up possibilities for new treatment approaches for this disease.

AOPs-SVM: A Sequence-Based Classifier of Antioxidant Proteins Using a Support Vector Machine

Antioxidant proteins play important roles in countering oxidative damage in organisms. Because it is time-consuming and has a high cost, the accurate identification of antioxidant proteins using biological experiments is a challenging task. For these reasons, we proposed a model using machine-learning algorithms that we named AOPs-SVM, which was developed based on sequence features and a support vector machine. Using a testing dataset, we conducted a jackknife cross-validation test with the proposed AOPs-SVM classifier and obtained 0.68 in sensitivity, 0.985 in specificity, 0.942 in average accuracy, 0.741 in MCC, and 0.832 in AUC. This outperformed existing classifiers. The experiment results demonstrate that the AOPs-SVM is an effective classifier and contributes to the research related to antioxidant proteins. A web server was built at http://server.malab.cn/AOPs-SVM/index.jsp to provide open access.

Metabolic Dysfunction in Alzheimer's Disease: From Basic Neurobiology to Clinical Approaches

Clinical trials have extensively failed to find effective treatments for Alzheimer's disease (AD) so far. Even after decades of AD research, there are still limited options for treating dementia. Mounting evidence has indicated that AD patients develop central and peripheral metabolic dysfunction, and the underpinnings of such events have recently begun to emerge. Basic and preclinical studies have unveiled key pathophysiological mechanisms that include aberrant brain stress signaling, inflammation, and impaired insulin sensitivity. These findings are in accordance with clinical and neuropathological data suggesting that AD patients undergo central and peripheral metabolic deregulation. Here, we review recent basic and clinical findings indicating that metabolic defects are central to AD pathophysiology. We further propose a view for future therapeutics that incorporates metabolic defects as a core feature of AD pathogenesis. This approach could improve disease understanding and therapy development through drug repurposing and/or identification of novel metabolic targets.

Synergistic Protective Effects of Mitochondrial Division Inhibitor 1 and Mitochondria-Targeted Small Peptide SS31 in Alzheimer's Disease

The purpose of our study was to determine the synergistic protective effects of mitochondria-targeted antioxidant SS31 and mitochondria division inhibitor 1 (Mdivi1) in Alzheimer's disease (AD). Using biochemical methods, we assessed mitochondrial function by measuring the levels of hydrogen peroxide, lipid peroxidation, cytochrome c oxidase activity, mitochondrial ATP, and GTPase Drp1 enzymatic activity in mutant AβPP cells. Using biochemical methods, we also measured cell survival and apoptotic cell death. Amyloid-β (Aβ) levels were measured using sandwich ELISA, and using real-time quantitative RT-PCR, we assessed mtDNA (mtDNA) copy number in relation to nuclear DNA (nDNA) in all groups of cells. We found significantly reduced levels of Aβ40 and Aβ42 in mutant AβPP cells treated with SS31, Mdivi1, and SS31+Mdivi1, and the reduction of Aβ42 levels were much higher in SS31+Mdivi1 treated cells than individual treatments of SS31 and Mdivi1. The levels of mtDNA copy number and cell survival were significantly increased in SS31, Mdivi1, and SS31+Mdivi1 treated mutant AβPP cells; however, the increased levels of mtDNA copy number and cell survival were much higher in SS31+Mdivi1 treated cells than individual treatments of SS31 and Mdivi1. Mitochondrial dysfunction is significantly reduced in SS31, Mdivi1, and SS31+Mdivi1 treated mutant AβPP cells; however, the reduction is much higher in cells treated with both SS31+Mdvi1. Similarly, GTPase Drp1 activity is reduced in all treatments, but reduced much higher in SS31+Mdivi1 treated cells. These observations strongly suggest that combined treatment of SS31+Mdivi1 is effective than individual treatments of SS31 and Mdivi1. Therefore, we propose that combined treatment of SS31+Mdivi1 is a better therapeutic strategy for AD. Ours is the first study to investigate combined treatment of mitochondria-targeted antioxidant SS31 and mitochondrial division inhibitor 1 in AD neurons.