Glutaredoxin1 Diminishes Amyloid Beta-Mediated Oxidation of F-Actin and Reverses Cognitive Deficits in an Alzheimer's Disease Mouse Model

Clioquinol rescues yeast cells from Aβ42 toxicity via the inhibition of oxidative damage

Alzheimer's disease (AD), the most common form of dementia, has gotten considerable attention. Previous studies have demonstrated that clioquinol (CQ) as a metal chelator is a potential drug for the treatment of AD. However, the mode of action of CQ in AD is still unclear. In our study, the antioxidant effects of CQ on yeast cells expressing Aβ42 were investigated. We found that CQ could reduce Aβ42 toxicity by alleviating reactive oxygen species (ROS) generation and lipid peroxidation level in yeast cells. These alterations were mainly attributable to the increased reduced glutathione (GSH) content and independent of activities of superoxide dismutase (SOD) and/or catalase (CAT). CQ could affect antioxidant enzyme activity by altering the transcription level of related genes. Interestingly, it was noted for the first time that CQ could combine with antioxidant enzymes to reduce their enzymatic activities by molecular docking and circular dichroism spectroscopy. In addition, CQ restored Aβ42-mediated disruption of GSH homeostasis via regulating YAP1 expression to protect cells against oxidative stress. Our findings not only improve the current understanding of the mechanism of CQ as a potential drug for AD treatment but also provide ideas for subsequent drug research and development.

Redox signaling in cell fate: Beyond damage

This review explores the nuanced role of reactive oxygen species (ROS) in cell fate, challenging the traditional view that equates ROS with cellular damage. Through significant technological advancements in detecting localized redox states and identifying oxidized cysteines, a paradigm shift has emerged: from ROS as merely damaging agents to crucial players in redox signaling. We delve into the intricacies of redox mechanisms, which, although confined, exert profound influences on cellular physiological responses. Our analysis extends to both the positive and negative impacts of these mechanisms on cell death processes, including uncontrolled and programmed pathways. By unraveling these complex interactions, we argue against the oversimplified notion of a 'stress response', advocating for a more nuanced understanding of redox signaling. This review underscores the importance of localized redox states in determining cell fate, highlighting the sophistication and subtlety of ROS functions beyond mere damage.

Role of Thioredoxin System in Regulating Cellular Redox Status in Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia and a public health problem. It exhibits significant oxidative stress and redox alterations. The antioxidant enzyme systems defend the cellular environment from oxidative stress. One of the redox systems is the thioredoxin system (TS), which exerts decisive control over the cellular redox environment. We aimed to review the protective effects of TS, which include thioredoxin (Trx), thioredoxin reductase (TrxR), and NADPH. In the following, we discussed the physiological functioning and the role of the TS in maintaining the cellular redox-homeostasis in the AD-damaged brain. Trx protects the cellular environment from oxidative stress, while TrxR is crucial for the cellular detoxification of reactive oxygen species in the brain. However, TS dysregulation increases the susceptibility to cellular death. The changes in Trx and TrxR levels are significantly associated with AD progression. Though the data from human, animal, and cellular models support the neuroprotective role of TS in the brain of AD patients, the translational potential of these findings to clinical settings is not yet applied. This review summarizes the current knowledge on the emerging role of the TrxR-Trx system in AD.

Compilation of reported protein changes in the brain in Alzheimer's disease

Proteomic studies of human Alzheimer's disease brain tissue have potential to identify protein changes that drive disease, and to identify new drug targets. Here, we analyse 38 published Alzheimer's disease proteomic studies, generating a map of protein changes in human brain tissue across thirteen brain regions, three disease stages (preclinical Alzheimer's disease, mild cognitive impairment, advanced Alzheimer's disease), and proteins enriched in amyloid plaques, neurofibrillary tangles, and cerebral amyloid angiopathy. Our dataset is compiled into a searchable database (NeuroPro). We found 848 proteins were consistently altered in 5 or more studies. Comparison of protein changes in early-stage and advanced Alzheimer's disease revealed proteins associated with synapse, vesicle, and lysosomal pathways show change early in disease, but widespread changes in mitochondrial associated protein expression change are only seen in advanced Alzheimer's disease. Protein changes were similar for brain regions considered vulnerable and regions considered resistant. This resource provides insight into Alzheimer's disease brain protein changes and highlights proteins of interest for further study.

A proteomics analysis of 5xFAD mouse brain regions reveals the lysosome-associated protein Arl8b as a candidate biomarker for Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is characterized by the intra- and extracellular accumulation of amyloid-β (Aβ) peptides. How Aβ aggregates perturb the proteome in brains of patients and AD transgenic mouse models, remains largely unclear. State-of-the-art mass spectrometry (MS) methods can comprehensively detect proteomic alterations, providing relevant insights unobtainable with transcriptomics investigations. Analyses of the relationship between progressive Aβ aggregation and protein abundance changes in brains of 5xFAD transgenic mice have not been reported previously.

METHODS

We quantified progressive Aβ aggregation in hippocampus and cortex of 5xFAD mice and controls with immunohistochemistry and membrane filter assays. Protein changes in different mouse tissues were analyzed by MS-based proteomics using label-free quantification; resulting MS data were processed using an established pipeline. Results were contrasted with existing proteomic data sets from postmortem AD patient brains. Finally, abundance changes in the candidate marker Arl8b were validated in cerebrospinal fluid (CSF) from AD patients and controls using ELISAs.

RESULTS

Experiments revealed faster accumulation of Aβ42 peptides in hippocampus than in cortex of 5xFAD mice, with more protein abundance changes in hippocampus, indicating that Aβ42 aggregate deposition is associated with brain region-specific proteome perturbations. Generating time-resolved data sets, we defined Aβ aggregate-correlated and anticorrelated proteome changes, a fraction of which was conserved in postmortem AD patient brain tissue, suggesting that proteome changes in 5xFAD mice mimic disease-relevant changes in human AD. We detected a positive correlation between Aβ42 aggregate deposition in the hippocampus of 5xFAD mice and the abundance of the lysosome-associated small GTPase Arl8b, which accumulated together with axonal lysosomal membranes in close proximity of extracellular Aβ plaques in 5xFAD brains. Abnormal aggregation of Arl8b was observed in human AD brain tissue. Arl8b protein levels were significantly increased in CSF of AD patients.

CONCLUSIONS

We report a comprehensive biochemical and proteomic investigation of hippocampal and cortical brain tissue derived from 5xFAD transgenic mice, providing a valuable resource to the neuroscientific community. We identified Arl8b, with significant abundance changes in 5xFAD and AD patient brains. Arl8b might enable the measurement of progressive lysosome accumulation in AD patients and have clinical utility as a candidate biomarker.

S-nitrosylation and S-glutathionylation of GAPDH: Similarities, differences, and relationships

The aim of this work was to compare the effect of reversible post-translational modifications, S-nitrosylation and S-glutathionylation, on the properties of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and to reveal the mechanism of the relationship between these modifications. Comparison of S-nitrosylated and S-glutathionylated GAPDH showed that both modifications inactivate the enzyme and change its spatial structure, decreasing the thermal stability of the protein and increasing its sensitivity to trypsin cleavage. Both modifications are reversible in the presence of dithiothreitol, however, in the presence of reduced glutathione and glutaredoxin 1, the reactivation of S-glutathionylated GAPDH is much slower (10% in 2 h) compared to S-nitrosylated GAPDH (60% in 10 min). This suggests that S-glutathionylation is a much less reversible modification compared to S-nitrosylation. Incubation of HEK 293 T cells in the presence of H₂O₂ or with the NO donor diethylamine NONOate results in accumulation of sulfenated GAPDH (by data of Western blotting) and S-glutathionylated GAPDH (by data of immunoprecipitation with anti-GSH antibodies). Besides GAPDH, a protein of 45 kDa was found to be sulfenated and S-glutathionylated in the cells treated with H₂O₂ or NO. This protein was identified as beta-actin. The results of this study confirm the previously proposed hypothesis based on in vitro investigations, according to which S-nitrosylation of the catalytic cysteine residue (Cys152) of GAPDH with subsequent formation of cysteine sulfenic acid at Cys152 may promote its S-glutathionylation in the presence of cellular GSH. Presumably, the mechanism may be valid in the case of beta-actin.

Glutaredoxin 1 protects lens epithelial cells from epithelial-mesenchymal transition by preventing casein kinase 1α S-glutathionylation during posterior capsular opacification

Oxidative stress drives protein S-glutathionylation, which regulates the structure and function of target proteins and is implicated in the pathogenesis of many diseases. Glutaredoxin 1 (Grx1), a cytoplasmic deglutathionylating enzyme, maintains a reducing environment within the cell under various conditions by reversing S-glutathionylation. Grx1 performs a wide range of antioxidant activities in the lens and prevents protein-thiol mixed disulfide accumulation, reducing protein-protein aggregation, insolubilization, and apoptosis of lens epithelial cells. Oxidative stress is related to epithelial-mesenchymal transition (EMT) during posterior capsular opacification (PCO). However, whether Grx1-regulated protein S-glutathionylation plays an essential role in PCO remains unclear. In this study, we revealed that Grx1 expression was decreased in mice following cataract surgery. Furthermore, the absence of Grx1 elevated oxidative stress and protein S-glutathionylation and aggravated EMT in both in vitro and in vivo models. Concurrently, these results could be reversed by Grx1 overexpression. Notably, liquid chromatography-tandem mass spectrometry results showed that casein kinase 1α (CK1α) was susceptible to S-glutathionylation under oxidative stress, and CK1α S-glutathionylation (CK1α-SSG) was mediated at Cys249. The absence of Grx1 upregulated CK1α-SSG, subsequently decreasing the CK1α-induced phosphorylation of β-catenin at Ser45. The consequential downregulation of degradative β-catenin and upregulation of its nuclear translocation activated the Wnt/β-catenin signaling pathway and aggravated EMT. In conclusion, the downregulated expression of Grx1 in mice following cataract surgery aggravated EMT by upregulating the extent of CK1α-SSG. To the best of our knowledge, our study is the first to report how S-glutathionylation regulates CK1α activity under oxidative stress.

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

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

De-glutathionylases: The resilient underdogs to keep neurodegeneration at bay

Proteins become S-glutathionylated as a result of the derivatization of their cysteine thiols with the thiolate anion derivative of glutathione; this process is frequently linked to diseases and protein misbehavior. Along with the other well-known oxidative modifications like S-nitrosylation, S-glutathionylation has quickly emerged as a major contributor to a number of diseases, with a focus on neurodegeneration. The immense clinical significance of S-glutathionylation in cell signaling and the genesis of diseases are progressively coming to light with advanced research, which is also creating new opportunities for prompt diagnostics that utilize this phenomenon. In-depth investigation in recent years has revealed other significant deglutathionylases in addition to glutaredoxin, necessitating the hunt for their specific substrates. The precise catalytic mechanisms of these enzymes must also be understood, along with how the intracellular environment affects their impact on protein conformation and function. These insights must then be extrapolated to the understanding of neurodegeneration and the introduction of novel and clever therapeutic approaches to clinics. Clarifying the importance of the functional overlap of glutaredoxin and other deglutathionylases and examining their complementary functions as defense systems in the face of stress are essential prerequisites for predicting and promoting cell survival under high oxidative/nitrosative stress.

Sex difference in evolution of cognitive decline: studies on mouse model and the Dominantly Inherited Alzheimer Network cohort

Women carry a higher burden of Alzheimer's disease (AD) compared to men, which is not accounted entirely by differences in lifespan. To identify the mechanisms underlying this effect, we investigated sex-specific differences in the progression of familial AD in humans and in APPswe/PS1ΔE9 mice. Activity dependent protein translation and associative learning and memory deficits were examined in APPswe/PS1ΔE9 mice and wild-type mice. As a human comparator group, progression of cognitive dysfunction was assessed in mutation carriers and non-carriers from DIAN (Dominantly Inherited Alzheimer Network) cohort. Female APPswe/PS1ΔE9 mice did not show recall deficits after contextual fear conditioning until 8 months of age. Further, activity dependent protein translation and Akt1-mTOR signaling at the synapse were impaired in male but not in female mice until 8 months of age. Ovariectomized APPswe/PS1ΔE9 mice displayed recall deficits at 4 months of age and these were sustained until 8 months of age. Moreover, activity dependent protein translation was also impaired in 4 months old ovariectomized APPswe/PS1ΔE9 mice compared with sham female APPswe/PS1ΔE9 mice. Progression of memory impairment differed between men and women in the DIAN cohort as analyzed using linear mixed effects model, wherein men showed steeper cognitive decline irrespective of the age of entry in the study, while women showed significantly greater performance and slower decline in immediate recall (LOGIMEM) and delayed recall (MEMUNITS) than men. However, when the performance of men and women in several cognitive tasks (such as Wechsler's logical memory) are compared with the estimated year from expected symptom onset (EYO) we found no significant differences between men and women. We conclude that in familial AD patients and mouse models, females are protected, and the onset of disease is delayed as long as estrogen levels are intact.

Advances in the Functions of Thioredoxin System in Central Nervous System Diseases

Significance: The thioredoxin system comprises thioredoxin (Trx), thioredoxin reductase (TrxR), and nicotinamide adenine dinucleotide phosphate, besides an endogenous Trx inhibitor, the thioredoxin-interacting protein (TXNIP). The Trx system plays critical roles in maintaining the redox homeostasis in the central nervous system (CNS), in which oxidative stress damage is prone to occurrence due to its high-energy demand. Recent Advances: Increasing studies have demonstrated that the expression or activity of Trx/TrxR is usually decreased and that TXNIP expression is increased in patients with CNS diseases, including neurodegenerative diseases, cerebral ischemia, traumatic brain injury, and depression, as well as in their cellular and animal models. The compromise of Trx/TrxR enhances the susceptibility of neurons to related pathological state. Increased TXNIP not only enhances the inhibition of Trx activity, but also activates the NOD-like receptor protein 3 inflammasome, resulting in neuroinflammation in the brain. Critical Issues: In this review, we highlight the sources of oxidative stress in the CNS. The expression and function of the Trx system are summarized in different CNS diseases. This review also mentions that some inducers of Trx show neuroprotection in CNS diseases. Future Directions: Accumulating evidence has demonstrated the important roles of the Trx system in CNS diseases, suggesting that the Trx system may be a promising therapeutic target for CNS diseases. Further study should aim to develop the most effective inducers of Trx and specific inhibitors of TXNIP and to apply them in the clinical trials for the treatment of CNS diseases. Antioxid. Redox Signal. 38, 425-441.

S-Glutathionylation and S-Nitrosylation in Mitochondria: Focus on Homeostasis and Neurodegenerative Diseases

Redox post-translational modifications are derived from fluctuations in the redox potential and modulate protein function, localization, activity and structure. Amongst the oxidative reversible modifications, the S-glutathionylation of proteins was the first to be characterized as a post-translational modification, which primarily protects proteins from irreversible oxidation. However, a growing body of evidence suggests that S-glutathionylation plays a key role in core cell processes, particularly in mitochondria, which are the main source of reactive oxygen species. S-nitrosylation, another post-translational modification, was identified >150 years ago, but it was re-introduced as a prototype cell-signaling mechanism only recently, one that tightly regulates core processes within the cell’s sub-compartments, especially in mitochondria. S-glutathionylation and S-nitrosylation are modulated by fluctuations in reactive oxygen and nitrogen species and, in turn, orchestrate mitochondrial bioenergetics machinery, morphology, nutrients metabolism and apoptosis. In many neurodegenerative disorders, mitochondria dysfunction and oxidative/nitrosative stresses trigger or exacerbate their pathologies. Despite the substantial amount of research for most of these disorders, there are no successful treatments, while antioxidant supplementation failed in the majority of clinical trials. Herein, we discuss how S-glutathionylation and S-nitrosylation interfere in mitochondrial homeostasis and how the deregulation of these modifications is associated with Alzheimer’s, Parkinson’s, amyotrophic lateral sclerosis and Friedreich’s ataxia.

Protein Glutathionylation and Glutaredoxin: Role in Neurodegenerative Diseases

Oxidative stress has been implicated in the pathogenesis and progression of many neurodegenerative disorders including Parkinson's disease and Alzheimer's disease. One of the major enzyme systems involved in the defense against reactive oxygen species are the tripeptide glutathione and oxidoreductase glutaredoxin. Glutathione and glutaredoxin system are very important in the brain because of the oxidative modification of protein thiols to protein glutathione mixed disulfides with the concomitant formation of oxidized glutathione during oxidative stress. Formation of Pr-SSG acts as a sink in the brain and is reduced back to protein thiols during recovery, thus restoring protein functions. This is unlike in the liver, which has a high turnover of glutathione, and formation of Pr-SSG is very minimal as liver is able to quickly quench the prooxidant species. Given the important role glutathione and glutaredoxin play in the brain, both in normal and pathologic states, it is necessary to study ways to augment the system to help maintain the protein thiol status. This review details the importance of glutathione and glutaredoxin systems in several neurodegenerative disorders and emphasizes the potential augmentation of this system as a target to effectively protect the brain during aging.

Oxidation and reduction of actin: Origin, impact in vitro and functional consequences in vivo

Actin is among the most abundant proteins in eukaryotic cells and assembles into dynamic filamentous networks regulated by many actin binding proteins. The actin cytoskeleton must be finely tuned, both in space and time, to fulfill key cellular functions such as cell division, cell shape changes, phagocytosis and cell migration. While actin oxidation by reactive oxygen species (ROS) at non-physiological levels are known for long to impact on actin polymerization and on the cellular actin cytoskeleton, growing evidence shows that direct and reversible oxidation/reduction of specific actin amino acids plays an important and physiological role in regulating the actin cytoskeleton. In this review, we describe which actin amino acid residues can be selectively oxidized and reduced in many different ways (e.g. disulfide bond formation, glutathionylation, carbonylation, nitration, nitrosylation and other oxidations), the cellular enzymes at the origin of these post-translational modifications, and the impact of actin redox modifications both in vitro and in vivo. We show that the regulated balance of oxidation and reduction of key actin amino acid residues contributes to the control of actin filament polymerization and disassembly at the subcellular scale and highlight how improper redox modifications of actin can lead to pathological conditions.

The Functions of Thioredoxin 1 in Neurodegeneration

Significance: Thioredoxin 1 (Trx1) is a ubiquitous protein that is found in organisms ranging from prokaryotes to eukaryotes. Trx1 acts as reductases in redox regulation and protects proteins from oxidative aggregation and inactivation. Trx1 helps the cells to cope with various environmental stresses and inhibits programmed cell death. It is beneficial to neuroregeneration and resistance against oxidative stress-associated neuron damage. Trx1 also plays important roles in suppressing neurodegenerative disorders. Recent Advances: Trx1 is a redox regulating protein involved in neuronal protection. According to a previous study, Trx1 expression is increased by nerve growth factor (NGF) and necessary for neurite outgrowth of PC12 cells. Trx1 has been shown to promote the growth of neurons. Trx1 knockout or knockdown has the worse impact on cell viability and survival. Critical Issues: Trx1 has functions in central nervous system. Trx1 plays the defensive roles against oxidative stress in neurodegenerative diseases. Future Directions: In this review, we focus on the structure of Trx1 and basic functions of Trx1. Trx1 plays a neuroprotective role by suppressing endoplasmic reticulum stress in Parkinson's disease. Neurodegenerative diseases have no cure and carry a high cost to the health care system and patient's families. Trx1 may be taken as a new target for neurodegenerative disorder therapy. Further studies of the Trx1 roles and mechanisms on neurodegenerative diseases are needed. Antioxid. Redox Signal. 36, 1023-1036.

Super-resolution microscopy: a closer look at synaptic dysfunction in Alzheimer disease

The synapse has emerged as a critical neuronal structure in the degenerative process of Alzheimer disease (AD), in which the pathogenic signals of two key players - amyloid-β (Aβ) and tau - converge, thereby causing synaptic dysfunction and cognitive deficits. The synapse presents a dynamic, confined microenvironment in which to explore how key molecules travel, localize, interact and assume different levels of organizational complexity, thereby affecting neuronal function. However, owing to their small size and the diffraction-limited resolution of conventional light microscopic approaches, investigating synaptic structure and dynamics has been challenging. Super-resolution microscopy (SRM) techniques have overcome the resolution barrier and are revolutionizing our quantitative understanding of biological systems in unprecedented spatio-temporal detail. Here we review critical new insights provided by SRM into the molecular architecture and dynamic organization of the synapse and, in particular, the interactions between Aβ and tau in this compartment. We further highlight how SRM can transform our understanding of the molecular pathological mechanisms that underlie AD. The application of SRM for understanding the roles of synapses in AD pathology will provide a stepping stone towards a broader understanding of dysfunction in other subcellular compartments and at cellular and circuit levels in this disease.

Prediction of Alzheimer's disease using multi-variants from a Chinese genome-wide association study

Previous genome-wide association studies have identified dozens of susceptibility loci for sporadic Alzheimer’s disease, but few of these loci have been validated in longitudinal cohorts. Establishing predictive models of Alzheimer’s disease based on these novel variants is clinically important for verifying whether they have pathological functions and provide a useful tool for screening of disease risk. In the current study, we performed a two-stage genome-wide association study of 3913 patients with Alzheimer’s disease and 7593 controls and identified four novel variants (rs3777215, rs6859823, rs234434, and rs2255835; P_combined = 3.07 × 10⁻¹⁹, 2.49 × 10⁻²³, 1.35 × 10⁻⁶⁷, and 4.81 × 10⁻⁹, respectively) as well as nine variants in the apolipoprotein E region with genome-wide significance (P < 5.0 × 10⁻⁸). Literature mining suggested that these novel single nucleotide polymorphisms are related to amyloid precursor protein transport and metabolism, antioxidation, and neurogenesis. Based on their possible roles in the development of Alzheimer’s disease, we used different combinations of these variants and the apolipoprotein E status and successively built 11 predictive models. The predictive models include relatively few single nucleotide polymorphisms useful for clinical practice, in which the maximum number was 13 and the minimum was only four. These predictive models were all significant and their peak of area under the curve reached 0.73 both in the first and second stages. Finally, these models were validated using a separate longitudinal cohort of 5474 individuals. The results showed that individuals carrying risk variants included in the models had a shorter latency and higher incidence of Alzheimer’s disease, suggesting that our models can predict Alzheimer’s disease onset in a population with genetic susceptibility. The effectiveness of the models for predicting Alzheimer’s disease onset confirmed the contributions of these identified variants to disease pathogenesis. In conclusion, this is the first study to validate genome-wide association study-based predictive models for evaluating the risk of Alzheimer’s disease onset in a large Chinese population. The clinical application of these models will be beneficial for individuals harbouring these risk variants, and particularly for young individuals seeking genetic consultation.

Thymosin β4 reverses phenotypic polarization of glial cells and cognitive impairment via negative regulation of NF-κB signaling axis in APP/PS1 mice

Background

Thymosin β4 (Tβ4) is the most abundant member of the β-thymosins and plays an important role in the control of actin polymerization in eukaryotic cells. While its effects in multiple organs and diseases are being widely investigated, the safety profile has been established in animals and humans, currently, little is known about its influence on Alzheimer’s disease (AD) and the possible mechanisms. Thus, we aimed to evaluate the effects and mechanisms of Tβ4 on glial polarization and cognitive performance in APP/PS1 transgenic mice.

Methods

Behavior tests were conducted to assess the learning and memory, anxiety and depression in APP/PS1 mice. Thioflavin S staining, Nissl staining, immunohistochemistry/immunofluorescence, ELISA, qRT-PCR, and immunoblotting were performed to explore Aβ accumulation, phenotypic polarization of glial cells, neuronal loss and function, and TLR4/NF-κB axis in APP/PS1 mice.

Results

We demonstrated that Tβ4 protein level elevated in all APP/PS1 mice. Over-expression of Tβ4 alone alleviated AD-like phenotypes of APP/PS1 mice, showed less brain Aβ accumulation and more Insulin-degrading enzyme (IDE), reversed phenotypic polarization of microglia and astrocyte to a healthy state, improved neuronal function and cognitive behavior performance, and accidentally displayed antidepressant-like effect. Besides, Tβ4 could downregulate both TLR4/MyD88/NF-κB p65 and p52-dependent inflammatory pathways in the APP/PS1 mice. While combination drug of TLR4 antagonist TAK242 or NF-κB p65 inhibitor PDTC exerted no further effects.

Conclusions

These results suggest that Tβ4 may exert its function by regulating both classical and non-canonical NF-κB signaling and is restoring its function as a potential therapeutic target against AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02166-3.

Actin-Binding Proteins as Potential Biomarkers for Chronic Inflammation-Induced Cancer Diagnosis and Therapy

Actin-binding proteins (ABPs), by interacting with actin, regulate the polymerization, depolymerization, bundling, and cross-linking of actin filaments, directly or indirectly, thereby mediating the maintenance of cell morphology, cell movement, and many other biological functions. Consequently, these functions of ABPs help regulate cancer cell invasion and metastasis when cancer occurs. In recent years, a variety of ABPs have been found to be abnormally expressed in various cancers, indicating that the detection and interventions of unusual ABP expression to alter this are available for the treatment of cancer. The early stages of most cancer development involve long-term chronic inflammation or repeated stimulation. This is the case for breast cancer, gastric cancer, lung cancer, prostate cancer, liver cancer, esophageal cancer, pancreatic cancer, melanoma, and colorectal cancer. This article discusses the relationship between chronic inflammation and the above-mentioned cancers, emphatically introduces relevant research on the abnormal expression of ABPs in chronic inflammatory diseases, and reviews research on the expression of different ABPs in the above-mentioned cancers. Furthermore, there is a close relationship between ABP-induced inflammation and cancer. In simple terms, abnormal expression of ABPs contributes to the chronic inflammation developing into cancer. Finally, we provide our viewpoint regarding these unusual ABPs serving as potential biomarkers for chronic inflammation-induced cancer diagnosis and therapy, and interventions to reverse the abnormal expression of ABPs represent a potential approach to preventing or treating the corresponding cancers.

Glutaredoxin: Discovery, redox defense and much more

Glutaredoxin, Grx, is a small protein containing an active site cysteine pair and was discovered in 1976 by Arne Holmgren. The Grx system, comprised of Grx, glutathione, glutathione reductase, and NADPH, was first described as an electron donor for Ribonucleotide Reductase but, from the first discovery in E.coli, the Grx family has impressively grown, particularly in the last two decades. Several isoforms have been described in different organisms (from bacteria to humans) and with different functions.

The unique characteristic of Grxs is their ability to catalyse glutathione-dependent redox regulation via glutathionylation, the conjugation of glutathione to a substrate, and its reverse reaction, deglutathionylation. Grxs have also recently been enrolled in iron sulphur cluster formation. These functions have been implied in various physiological and pathological conditions, from immune defense to neurodegeneration and cancer development thus making Grx a possible drug target.

This review aims to give an overview on Grxs, starting by a phylogenetic analysis of vertebrate Grxs, followed by an analysis of the mechanisms of action, the specific characteristics of the different human isoforms and a discussion on aspects related to human physiology and diseases.

Oxidative Stress Boosts the Uptake of Cerium Oxide Nanoparticles by Changing Brain Endothelium Microvilli Pattern

Vascular oxidative stress is considered a worsening factor in the progression of Alzheimer's disease (AD). Increased reactive oxygen species (ROS) levels promote the accumulation of amyloid-β peptide (Aβ), one of the main hallmarks of AD. In turn, Aβ is a potent inducer of oxidative stress. In early stages of AD, the concomitant action of oxidative stress and Aβ on brain capillary endothelial cells was observed to compromise the blood-brain barrier functionality. In this context, antioxidant compounds might provide therapeutic benefits. To this aim, we investigated the antioxidant activity of cerium oxide nanoparticles (CNP) in human cerebral microvascular endothelial cells (hCMEC/D3) exposed to Aβ oligomers. Treatment with CNP (13.9 ± 0.7 nm in diameter) restored basal ROS levels in hCMEC/D3 cells, both after acute or prolonged exposure to Aβ. Moreover, we found that the extent of CNP uptake by hCMEC/D3 was +43% higher in the presence of Aβ. Scanning electron microscopy and western blot analysis suggested that changes in microvilli structures on the cell surface, under pro-oxidant stimuli (Aβ or H₂O₂), might be involved in the enhancement of CNP uptake. This finding opens the possibility to exploit the modulation of endothelial microvilli pattern to improve the uptake of anti-oxidant particles designed to counteract ROS-mediated cerebrovascular dysfunctions.

The Potential Roles of Redox Enzymes in Alzheimer's Disease: Focus on Thioredoxin

Alzheimer's disease (AD) is the most common neurodegenerative diseases. Increasing studies have demonstrated the critical importance for redox proteins mediating neuronal protection in models of AD. This review briefly describes some of the risk factors contributing to AD, specifically highlighting the important roles of oxidative stress in the pathology of AD. Then this article concisely introduces the dysregulation and functions of two main redox enzymes, peroxiredoxins and glutaredoxins, in AD models. This review emphasizes the neuroprotective role of the third redox enzyme thioredoxin (Trx), an important multifunctional protein regulating cellular redox status. This commentary not only summarizes the alterations of Trx expression in AD patients and models, but also reviews the potential effects and mechanisms of Trx, Trx-related molecules and Trx-inducing compounds against AD. In conclusion, Trx has a potential neuroprotection in AD and may be very promising for clinical therapy of AD in the future.

Redox-dependent regulation of end-binding protein 1 activity by glutathionylation

Cytoskeletal proteins are susceptible to glutathionylation under oxidizing conditions, and oxidative damage has been implicated in several neurodegenerative diseases. End-binding protein 1 (EB1) is a master regulator of microtubule plus-end tracking proteins (+TIPs) and is critically involved in the control of microtubule dynamics and cellular processes. However, the impact of glutathionylation on EB1 functions remains unknown. Here we reveal that glutathionylation is important for controlling EB1 activity and protecting EB1 from irreversible oxidation. In vitro biochemical and cellular assays reveal that EB1 is glutathionylated. Diamide, a mild oxidizing reagent, reduces EB1 comet number and length in cells, indicating the impairment of microtubule dynamics. Three cysteine residues of EB1 are glutathionylated, with mutations of these three cysteines to serines attenuating microtubule dynamics but buffering diamide-induced decrease in microtubule dynamics. In addition, glutaredoxin 1 (Grx1) deglutathionylates EB1, and Grx1 depletion suppresses microtubule dynamics and leads to defects in cell division orientation and cell migration, suggesting a critical role of Grx1-mediated deglutathionylation in maintaining EB1 activity. Collectively, these data reveal that EB1 glutathionylation is an important protective mechanism for the regulation of microtubule dynamics and microtubule-based cellular activities.

Synaptosome as a tool in Alzheimer's disease research

Synapse dysfunction is an integral feature of Alzheimer's disease (AD) pathophysiology. In fact, prodromal manifestation of structural and functional deficits in synapses much prior to appearance of overt pathological hallmarks of the disease indicates that AD might be considered as a degenerative disorder of the synapses. Several research instruments and techniques have allowed us to study synaptic function and plasticity and their alterations in pathological conditions, such as AD. One such tool is the biochemically isolated preparations of detached and resealed synaptic terminals, the "synaptosomes". Because of the preservation of many of the physiological processes such as metabolic and enzymatic activities, synaptosomes have proved to be an indispensable ex vivo model system to study synapse physiology both when isolated from fresh or cryopreserved tissues, and from animal or human post-mortem tissues. This model system has been tremendously successful in the case of post-mortem tissues because of their accessibility relative to acute brain slices or cultures. The current review details the use of synaptosomes in AD research and its potential as a valuable tool in furthering our understanding of the pathogenesis and in devising and testing of therapeutic strategies for the disease.