Upregulation of Thioredoxin-Interacting Protein in Brain of Amyloid-β Protein Precursor/Presenilin 1 Transgenic Mice and Amyloid-β Treated Neuronal Cells

Cornuside ameliorates cognitive impairments via RAGE/TXNIP/NF-κB signaling in Aβ1-42 induced Alzheimer's disease mice

Cornuside has been discovered to improve learning and memory in AD mice, however, its underlying mechanism was not fully understood. In the present study, we established an AD mice model by intracerebroventricular injection of Aβ1-42, which were treated with cornuside (3, 10, 30 mg/kg) for 2 weeks. Cornuside significantly ameliorated cognitive function of AD mice in series of behavioral tests, including Morris water maze test, nest building test, novel object recognition test and step-down test. Additionally, cornuside could attenuate neuronal injury, and promote cholinergic synaptic transmission by restoring the level of acetylcholine (ACh) via inhibiting acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), as well as facilitating choline acetyltransferase (ChAT). Furthermore, cornuside inhibited oxidative stress levels amplified as decreased malondialdehyde (MDA), by inhibiting TXNIP expression, improving total anti-oxidative capacity (TAOC), raising activities of superoxide dismutase (SOD) and catalase (CAT). Cornuside also reduced the activation of microglia and astrocytes, decreased the level of proinflammatory factors TNF-α, IL-6, IL-1β, iNOS and COX2 via interfering RAGE-mediated IKK-IκB-NF-κB phosphorylation. Similar anti-oxidative and anti-inflammatory effects were also found in LPS-stimulated BV2 cells via hampering RAGE-mediated TXNIP activation and NF-κB nuclear translocation. Virtual docking revealed that cornuside could interact with the active pocket of RAGE V domain directly. In conclusion, cornuside could bind to the RAGE directly impeding the interaction of Aβ and RAGE, and cut down the expression of TXNIP inhibiting ROS production and oxidative stress, as well as hamper NF-κB p65 mediated the inflammation.

Cerebral organoids with chromosome 21 trisomy secrete Alzheimer's disease-related soluble aggregates detectable by single-molecule-fluorescence and super-resolution microscopy

Understanding the role of small, soluble aggregates of beta-amyloid (Aβ) and tau in Alzheimer's disease (AD) is of great importance for the rational design of preventative therapies. Here we report a set of methods for the detection, quantification, and characterisation of soluble aggregates in conditioned media of cerebral organoids derived from human iPSCs with trisomy 21, thus containing an extra copy of the amyloid precursor protein (APP) gene. We detected soluble beta-amyloid (Aβ) and tau aggregates secreted by cerebral organoids from both control and the isogenic trisomy 21 (T21) genotype. We developed a novel method to normalise measurements to the number of live neurons within organoid-conditioned media based on glucose consumption. Thus normalised, T21 organoids produced 2.5-fold more Aβ aggregates with a higher proportion of larger (300-2000 nm2) and more fibrillary-shaped aggregates than controls, along with 1.3-fold more soluble phosphorylated tau (pTau) aggregates, increased inflammasome ASC-specks, and a higher level of oxidative stress inducing thioredoxin-interacting protein (TXNIP). Importantly, all this was detectable prior to the appearance of histological amyloid plaques or intraneuronal tau-pathology in organoid slices, demonstrating the feasibility to model the initial pathogenic mechanisms for AD in-vitro using cells from live genetically pre-disposed donors before the onset of clinical disease. Then, using different iPSC clones generated from the same donor at different times in two independent experiments, we tested the reproducibility of findings in organoids. While there were differences in rates of disease progression between the experiments, the disease mechanisms were conserved. Overall, our results show that it is possible to non-invasively follow the development of pathology in organoid models of AD over time, by monitoring changes in the aggregates and proteins in the conditioned media, and open possibilities to study the time-course of the key pathogenic processes taking place.

27-Hydroxycholesterol impairs learning and memory ability via decreasing brain glucose uptake mediated by the gut microbiota

Brain glucose hypometabolism is a significant manifestation of Alzheimer's disease (AD). 27-hydroxycholesterol (27-OHC) and the gut microbiota have been recognized as factors possibly influencing the pathogenesis of AD. This study aimed to investigate the link between 27-OHC, the gut microbiota, and brain glucose uptake in AD. Here, 6-month-old male C57BL/6 J mice were treated with sterile water or antibiotic cocktails, with or without 27-OHC and/or 27-OHC synthetic enzyme CYP27A1 inhibitor anastrozole (ANS). The gut microbiota, brain glucose uptake levels, and memory ability were measured. We observed that 27-OHC altered microbiota composition, damaged brain tissue structures, decreased the 2-deoxy-2-[18 F] fluorodeoxyglucose (18F-FDG) uptake value, downregulated the gene expression of glucose transporter type 4 (GLUT4), reduced the colocalization of GLUT1/glial fibrillary acidic protein (GFAP) in the hippocampus, and impaired spatial memory. ANS reversed the effects of 27-OHC. The antibiotic-treated mice did not exhibit similar results after 27-OHC treatment. This study reveals a potential molecular mechanism wherein 27-OHC-induced memory impairment might be linked to reduced brain glucose uptake, mediated by the gut microbiota.

Pathophysiological Aspects and Therapeutic Armamentarium of Alzheimer's Disease: Recent Trends and Future Development

Alzheimer's disease (AD) is the primary cause of dementia and is characterized by the death of brain cells due to the accumulation of insoluble amyloid plaques, hyperphosphorylation of tau protein, and the formation of neurofibrillary tangles within the cells. AD is also associated with other pathologies such as neuroinflammation, dysfunction of synaptic connections and circuits, disorders in mitochondrial function and energy production, epigenetic changes, and abnormalities in the vascular system. Despite extensive research conducted over the last hundred years, little is established about what causes AD or how to effectively treat it. Given the severity of the disease and the increasing number of affected individuals, there is a critical need to discover effective medications for AD. The US Food and Drug Administration (FDA) has approved several new drug molecules for AD management since 2003, but these drugs only provide temporary relief of symptoms and do not address the underlying causes of the disease. Currently, available medications focus on correcting the neurotransmitter disruption observed in AD, including cholinesterase inhibitors and an antagonist of the N-methyl-D-aspartate (NMDA) receptor, which temporarily alleviates the signs of dementia but does not prevent or reverse the course of AD. Research towards disease-modifying AD treatments is currently underway, including gene therapy, lipid nanoparticles, and dendrimer-based therapy. These innovative approaches aim to target the underlying pathological processes of AD rather than just managing the symptoms. This review discusses the novel aspects of pathogenesis involved in the causation of AD of AD and in recent developments in the therapeutic armamentarium for the treatment of AD such as gene therapy, lipid nanoparticles, and dendrimer-based therapy, and many more.

Polypeptide from Moschus Suppresses Lipopolysaccharide-Induced Inflammation by Inhibiting NF-κ B-ROS/NLRP3 Pathway

OBJECTIVE

To examine the anti-inflammatory effects and potential mechanisms of polypeptide from Moschus (PPM) in lipopolysaccharide (LPS)-induced THP-1 macrophages and BALB/c mice.

METHODS

The polypeptide was extracted from Moschus and analyzed by high-performance liquid chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Subsequently, LPS was used to induce inflammation in THP-1 macrophages and BALB/c mice. In LPS-treated or untreated THP-1 macrophages, cell viability was observed by cell counting kit 8 and lactate dehydrogenase release assays; the proinflammatory cytokines and reactive oxygen species (ROS) were measured by enzyme-linked immunosorbent assay and flow cytometry, respectively; and protein and mRNA levels were measured by Western blot and real-time quantitative polymerase chain reaction (qRT-PCR), respectively. In LPS-induced BALB/c mice, the proinflammatory cytokines were measured, and lung histology and cytokines were observed by hematoxylin and eosin (HE) and immunohistochemical (IHC) staining, respectively.

RESULTS

The SDS-PAGE results suggested that the molecular weight of purified PPM was in the range of 10-26 kD. In vitro, PPM reduced the production of interleukin 1β (IL-1β), IL-18, tumor necrosis factor α (TNF-α), IL-6 and ROS in LPS-induced THP-1 macrophages (P<0.01). Western blot analysis demonstrated that PPM inhibited LPS-induced nuclear factor κB (NF-κB) pathway and thioredoxin interacting protein (TXNIP)/nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain containing 3 (NLRP3) inflammasome pathway by reducing protein expression of phospho-NF-κB p65, phospho-inhibitors of NF-κB (Iκ Bs) kinase α/β (IKKα/β), TXNIP, NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and pro-caspase-1 (P<0.05 or P<0.01). In addition, qRT-PCR revealed the inhibitory effects of PPM on the mRNA levels of TXNIP, NLRP3, ASC, and caspase-1 (P<0.05 or P<0.01). Furthermore, in LPS-induced BALB/c mice, PPM reduced TNF-α and IL-6 levels in serum (P<0.05 or P<0.01), decreased IL-1β and IL-18 levels in the lungs (P<0.01) and alleviated pathological injury to the lungs.

CONCLUSION

PPM could attenuate LPS-induced inflammation by inhibiting the NF-κB-ROS/NLRP3 pathway, and may be a novel potential candidate drug for treating inflammation and inflammation-related diseases.

VDUP1 Deficiency Promotes the Severity of DSS-Induced Colitis in Mice by Inducing Macrophage Infiltration

The loss of vitamin D3 upregulated protein 1 (VDUP1) has been implicated in the pathogenesis of various inflammation-related diseases. Notably, reduced expression of VDUP1 has been observed in clinical specimens of ulcerative colitis (UC). However, the role of VDUP1 deficiency in colitis remains unclear. In this study, we investigated the role of VDUP1 in dextran sulfate sodium (DSS)-induced experimental colitis in mice. VDUP1-deficient mice were more susceptible to DSS-induced colitis than their wild-type (WT) littermates after 2% DSS administration. VDUP1-deficient mice exhibited an increased disease activity index (DAI) and histological scores, as well as significant colonic goblet cell loss and an increase in apoptotic cells. These changes were accompanied by a significant decrease in MUC2 mRNA expression and a marked increase in proinflammatory cytokines and chemokines within damaged tissues. Furthermore, phosphorylated NF-κB p65 expression was significantly upregulated in damaged tissues in the context of VDUP1 deficiency. VDUP1 deficiency also led to significant infiltration of macrophages into the site of ulceration. An in vitro chemotaxis assay confirmed that VDUP1 deficiency enhanced bone marrow-derived macrophage (BMDM) chemotaxis induced by CCL2. Overall, this study highlights VDUP1 as a regulator of UC pathogenesis and a potential target for the future development of therapeutic strategies.

CRISPR-Cas9 in Alzheimer's disease: Therapeutic trends, modalities, and challenges

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with no known cure, which has prompted the exploration of novel therapeutic approaches. The clustered regularly interspaced palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9) tool has generated significant interest for its potential in AD therapeutics by correcting faulty genes. Our report comprehensively reviews emerging applications for CRISPR-Cas9 in developing in vitro and in vivo models for AD research and therapeutics. We further assess its ability to identify and validate genetic markers and potential therapeutic targets for AD. Moreover, we review the current challenges and delivery strategies for the in vivo application of CRISPR-Cas9 in AD therapeutics.

Is Drp1 a link between mitochondrial dysfunction and inflammation in Alzheimer's disease?

Recent advances highlight that inflammation is critical to Alzheimer Disease (AD) pathogenesis. Indeed, several diseases characterized by inflammation are considered risk factors for AD, such as type 2 diabetes, obesity, hypertension, and traumatic brain injury. Moreover, allelic variations in genes involved in the inflammatory cascade are risk factors for AD. AD is also characterized by mitochondrial dysfunction, which affects the energy homeostasis of the brain. The role of mitochondrial dysfunction has been characterized mostly in neuronal cells. However, recent data are demonstrating that mitochondrial dysfunction occurs also in inflammatory cells, promoting inflammation and the secretion of pro-inflammatory cytokines, which in turn induce neurodegeneration. In this review, we summarize the recent finding supporting the hypothesis of the inflammatory-amyloid cascade in AD. Moreover, we describe the recent data that demonstrate the link between altered mitochondrial dysfunction and the inflammatory cascade. We focus in summarizing the role of Drp1, which is involved in mitochondrial fission, showing that altered Drp1 activation affects the mitochondrial homeostasis and leads to the activation of the NLRP3 inflammasome, promoting the inflammatory cascade, which in turn aggravates Amyloid beta (Ab) deposition and tau-induced neurodegeneration, showing the relevance of this pro-inflammatory pathway as an early event in AD.

TXNIP contributes to induction of pro-inflammatory phenotype and caspase-3 activation in astrocytes during Alzheimer's diseases

Neuroinflammation and oxidative stress have been implicated in the pathogenesis of Alzheimer's disease (AD). Neuroinflammation and oxidative stress are associated with neuronal death in AD. Astrocytes are linked to neuroinflammation during AD. Astrocytes are important contributors to AD progression. Although the role of thioredoxin-interacting protein (TXNIP) has been identified in inflammation and oxidative stress, the mechanism by which TXNIP regulates inflammation and oxidative stress in astrocytes during AD remains unclear. In the present study, we found that TXNIP gene levels were elevated in cerebral cortex of patients with AD. The protein levels of TXNIP were elevated in GFAP-positive astrocytes of cerebral cortex from patients with AD and APP/PS1 double-transgenic mouse model of AD. Our results showed that TXNIP increased expression of genes related to pro-inflammatory reactive astrocytes and pro-inflammatory cytokines and chemokines in human astrocytes. Moreover, TXNIP increased production of pro-inflammatory cytokines and chemokines in human astrocytes. TXNIP induced activation of NK-kB signaling and over-production of mitochondrial reactive oxygen species (mtROS) in human astrocytes. TXNIP also induced mitochondrial oxidative stress by reduction of mitochondrial respiration and ATP production in human astrocytes. Furthermore, elevated TXNIP levels are correlated with caspase-3 activation of GFAP-positive astrocytes in patients with AD and mouse AD. TXNIP induced mitochondria-dependent apoptosis via caspase-9 and caspase-3 activation in human astrocytes. These results suggest that TXNIP contributes to induction of pro-inflammatory phenotype and caspase-3 activation in astrocytes during AD.

Upregulation of TXNIP contributes to granulosa cell dysfunction in polycystic ovary syndrome via activation of the NLRP3 inflammasome

Polycystic ovary syndrome (PCOS) is a complex endocrine disease. Thioredoxin-interacting protein (TXNIP) promotes oxidative stress and triggers inflammation. Herein, we investigated the role and potential mechanism of TXNIP in PCOS. In a mouse model of dehydroepiandrosterone (DHEA)-induced PCOS, we found that TXNIP was upregulated in the ovaries, especially in granulosa cells (GCs). TXNIP was also upregulated in testosterone (T)-treated GCs in vitro. Knockdown of TXNIP by lentivirus-constructed shRNA attenuated T-induced GC injury and oxidative stress, as well as inflammation and the NLRP3 inflammasome. The mechanism by which TXNIP promotes inflammation may involve TXNIP dissociation from the TXNIP-TRX complex and binding to NLRP3 to form the inflammasome. Additionally, we verified that knockdown of TXNIP ameliorated ovarian injury and inflammation in mice with DHEA-induced PCOS in vivo. Collectively, we demonstrated that TXNIP is involved in GC inflammation by promoting NLRP3 inflammasome activation in PCOS.

Ameliorative effects of bromelain on aluminum-induced Alzheimer's disease in rats through modulation of TXNIP pathway

Alzheimer's disease (AD) is known as "type 3 diabetes". As thioredoxin binding protein (TXNIP) has been shown to be involved in brain insulin resistance, the present study evaluated the roles of TXNIP, phospho-insulin receptor substrate 1 (P-IRS-1), and phosphatidyl inositol-3 kinase (PI3K) in the pathogenesis of AD. The potential ameliorative effect of bromelain compared to donepezil was evaluated in an aluminum chloride (AlCl3)-induced AD in rats. Behavioral tests demonstrated similar improvements in exploratory activity, cognitive and spatial memory functions, anxiety, and depression levels between rats treated with bromelain and donepezil. Donepezil was superior to bromelain in improving locomotor activity. Histopathological examinations demonstrated neuronal degeneration in the AlCl3 group that was almost normalized by bromelain and donepezil. Moreover, there was deposition of amyloid plaques in the AlCl3 group that was improved by bromelain and donepezil. Acetylcholine esterase levels were significantly increased in rats treated with AlCl3 group and significantly decreased in rats treated with bromelain and donepezil. Furthermore, AlCl3 group showed a significantly increased TXNIP and P-IRS1 and a significantly reduced PI3K levels. These effects were ameliorated by bromelain and donepezil treatment. The present study demonstrates a previously unreported modulatory effect of bromelain on the TXNIP/P-IRS-1/PI3K axis in AD model.

Hypoglycemic medicines in the treatment of Alzheimer's disease: Pathophysiological links between AD and glucose metabolism

Alzheimer's Disease (AD) is a global chronic disease in adults with beta-amyloid (Aβ) deposits and hyperphosphorylated tau protein as the pathologic characteristics. Although the exact etiology of AD is still not fully elucidated, aberrant metabolism including insulin signaling and mitochondria dysfunction plays an important role in the development of AD. Binding to insulin receptor substrates, insulin can transport through the blood-brain barrier (BBB), thus mediating insulin signaling pathways to regulate physiological functions. Impaired insulin signaling pathways, including PI3K/Akt/GSK3β and MAPK pathways, could cause damage to the brain in the pathogenesis of AD. Mitochondrial dysfunction and overexpression of TXNIP could also be causative links between AD and DM. Some antidiabetic medicines may have benefits in the treatment of AD. Metformin can be beneficial for cognition improvement in AD patients, although results from clinical trials were inconsistent. Exendin-4 may affect AD in animal models but there is a lack of clinical trials. Liraglutide and dulaglutide could also benefit AD patients in adequate clinical studies but not semaglutide. Dipeptidyl peptidase IV inhibitors (DPP4is) such as saxagliptin, vildagliptin, linagliptin, and sitagliptin could boost cognitive function in animal models. And SGLT2 inhibitors such as empagliflozin and dapagliflozin were also considerably protective against new-onset dementia in T2DM patients. Insulin therapy is a promising therapy but some studies indicated that it may increase the risk of AD. Herbal medicines are helpful for cognitive function and neuroprotection in the brain. For example, polyphenols, alkaloids, glycosides, and flavonoids have protective benefits in cognition function and glucose metabolism. Focusing on glucose metabolism, we summarized the pharmacological mechanism of hypoglycemic drugs and herbal medicines. New treatment approaches including antidiabetic synthesized drugs and herbal medicines would be provided to patients with AD. More clinical trials are needed to produce definite evidence for the effectiveness of hypoglycemic medications.

Embryonic Deletion of TXNIP in GABAergic Neurons Enhanced Oxidative Stress in PV+ Interneurons in Primary Somatosensory Cortex of Aging Mice: Relevance to Schizophrenia

The brain is susceptible to perturbations of redox balance, affecting neurogenesis and increasing the risks of psychiatric disorders. Thioredoxin-interacting protein (TXNIP) is an endogenous inhibitor of the thioredoxin antioxidant system. Its deletion or inhibition suggests protection for a brain with ischemic stroke or Alzheimer’s disease. Combined with conditional knockout mice and schizophrenia samples, we aimed to investigate the function of TXNIP in healthy brain and psychiatric disorders, which are under-studied. We found TXNIP was remarkedly expressed in the prefrontal cortex (PFC) during healthy mice’s prenatal and early postnatal periods, whereas it rapidly decreased throughout adulthood. During early life, TXNIP was primarily distributed in inhibitory and excitatory neurons. Contrary to the protective effect, the embryonic deletion of TXNIP in GABAergic (gamma-aminobutyric acid-ergic) neurons enhanced oxidative stress in PV⁺ interneurons of aging mice. The deleterious impact was brain region-specific. We also investigated the relationship between TXNIP and schizophrenia. TXNIP was significantly increased in the PFC of schizophrenia-like mice after MK801 administration, followed by oxidative stress. First episode and drug naïve schizophrenia patients with a higher level of plasma TXNIP displayed severer psychiatric symptoms than patients with a low level. We indicated a bidirectional function of TXNIP in the brain, whose high expression in the early stage is protective for development but might be harmful in a later period, associated with mental disorders.

TXNIP: A Double-Edged Sword in Disease and Therapeutic Outlook

Thioredoxin-interacting protein (TXNIP) was originally named vitamin D₃ upregulated protein-1 (VDUP1) because of its ability to bind to thioredoxin (TRX) and inhibit TRX function and expression. TXNIP is an alpha-arrestin protein that is essential for redox homeostasis in the human body. TXNIP may act as a double-edged sword in the cell. The balance of TXNIP is crucial. A study has shown that TXNIP can travel between diverse intracellular locations and bind to different proteins to play different roles under oxidative stress. The primary function of TXNIP is to induce apoptosis or pyroptosis under oxidative stress. TXNIP also inhibits proliferation and migration in cancer cells, although TXNIP levels decrease, and function diminishes in various cancers. In this review, we summarized the main structure, binding proteins, pathways, and the role of TXNIP in diseases, aiming to explore the double-edged sword role of TXNIP, and expect it to be helpful for future treatment using TXNIP as a therapeutic target.

AGE-TXNIP axis drives inflammation in Alzheimer's by targeting Aβ to mitochondria in microglia

Alzheimer's disease (AD) is the most common form of dementia characterized by progressive memory loss and cognitive decline. Although neuroinflammation and oxidative stress are well-recognized features of AD, their correlations with the early molecular events characterizing the pathology are not yet well clarified. Here, we characterize the role of RAGE-TXNIP axis in neuroinflammation in relation to amyloid-beta (Aβ) burden in both in vivo and in vitro models. In the hippocampus of 5xFAD mice microglial activation, cytokine secretion, and glial fibrillary acidic protein-enhanced expression are paralleled with increased TXNIP expression. TXNIP silencing or its pharmacological inhibition prevents neuroinflammation in those mice. TXNIP is also associated with RAGE and Aβ. In particular, RAGE-TXNIP axis is required for targeting Aβ in mitochondria, leading to mitochondrial dysfunction and oxidative stress. Silencing of TXNIP or inhibition of RAGE activation reduces Aβ transport from the cellular surface to mitochondria, restores mitochondrial functionality, and mitigates Aβ toxicity. Furthermore, Aβ shuttling into mitochondria promotes Drp1 activation and exacerbates mitochondrial dysfunction, which induces NLRP3 inflammasome activation, leading to secretion of IL-1β and activation of the pyroptosis-associated protein Gasdermin D (GSDMD). Downregulation of RAGE-TXNIP axis inhibits Aβ-induced mitochondria dysfunction, inflammation, and induction of GSDMD. Herein we unveil a new pathway driven by TXNIP that links the mitochondrial transport of Aβ to the activation of Drp1 and the NLRP3 inflammasome, promoting the secretion of IL-1β and the pyroptosis pathway associated with GSDMD cleavage. Altogether these data shed new light on a novel mechanism of action of RAGE-TXNIP axis in microglia, which is intertwined with Aβ and ultimately causes mitochondria dysfunction and NLRP3 inflammasome cascade activation, suggesting TXNIP as a druggable target to be better deepened for AD.

Localization of Thioredoxin-Interacting Protein in Aging and Alzheimer’s Disease Brains

Thioredoxin-Interacting Protein (TXNIP) has been shown to have significant pathogenic roles in many human diseases, particularly those associated with diabetes and hyperglycemia. Its main mode of action is to sequester thioredoxins, resulting in enhanced oxidative stress. The aim of this study was to identify if cellular expression of TXNIP in human aged and Alzheimer’s disease (AD) brains correlated with pathological structures. This study employed fixed tissue sections and protein extracts of temporal cortex from AD and aged control brains. Studies employed light and fluorescent immunohistochemical techniques using the monoclonal antibody JY2 to TXNIP to identify cellular structures. Immunoblots were used to quantify relative amounts of TXNIP in brain protein extracts. The major finding was the identification of TXNIP immunoreactivity in selective neuronal populations and structures, particularly in non-AD brains. In AD brains, less neuronal TXNIP but increased numbers of TXNIP-positive plaque-associated microglia were observed. Immunoblot analyses showed no significant increase in levels of TXNIP protein in the AD samples tested. In conclusion, this study identified altered patterns of expression of TXNIP in human brains with progression of AD pathology.

Role of Thioredoxin-1 and its inducers in human health and diseases

Thioredoxin-1 (Trx-1) is a small redox-active protein normally found in mammalian cells that responds to the changing redox environment by contributing electrons or regulating related proteins. There is growing evidence that Trx-1 has multiple functions, including cytoprotective, anti-apoptotic, antioxidant and anti-inflammatory effects. To date, researchers have found that Trx-1 deficiency leads to severe damage in various disease models, such as atherosclerosis, cerebral ischemia, diabetes and tumors. Conversely, activation of Trx-1 has a protective effect against these diseases. Accordingly, a variety of Trx-1 inducers have been widely used in the clinic with significant therapeutic value. In this paper, we summarize the pathogenesis of Trx-1 involvement in the above-mentioned diseases and describe the protective effects of Trx-1 inducers on them.

Regulatory role of cathepsin L in induction of nuclear laminopathy in Alzheimer's disease

Experimental and clinical therapies in the field of Alzheimer's disease (AD) have focused on elimination of extracellular amyloid beta aggregates or prevention of cytoplasmic neuronal fibrillary tangles formation, yet these approaches have been generally ineffective. Interruption of nuclear lamina integrity, or laminopathy, is a newly identified concept in AD pathophysiology. Unraveling the molecular players in the induction of nuclear lamina damage may lead to identification of new therapies. Here, using 3xTg and APP/PS1 mouse models of AD, and in vitro model of amyloid beta42 (Aβ42) toxicity in primary neuronal cultures and SH‐SY5Y neuroblastoma cells, we have uncovered a key role for cathepsin L in the induction of nuclear lamina damage. The applicability of our findings to AD pathophysiology was validated in brain autopsy samples from patients. We report that upregulation of cathepsin L is an important process in the induction of nuclear lamina damage, shown by lamin B1 cleavage, and is associated with epigenetic modifications in AD pathophysiology. More importantly, pharmacological targeting and genetic knock out of cathepsin L mitigated Aβ42 induced lamin B1 degradation and downstream structural and molecular changes. Affirming these findings, overexpression of cathepsin L alone was sufficient to induce lamin B1 cleavage. The proteolytic activity of cathepsin L on lamin B1 was confirmed using mass spectrometry. Our research identifies cathepsin L as a newly identified lamin B1 protease and mediator of laminopathy observed in AD. These results uncover a new aspect in the pathophysiology of AD that can be pharmacologically prevented, raising hope for potential therapeutic interventions.

Application of CRISPR/Cas9 in Alzheimer's Disease

Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disorder clinically characterized by cognitive impairment, abnormal behavior, and social deficits, which is intimately linked with excessive β-amyloid (Aβ) protein deposition along with many other misfolded proteins, neurofibrillary tangles formed by hyperphosphorylated tau protein aggregates, and mitochondrial damage in neurons, leading to neuron loss. Currently, research on the pathological mechanism of AD has been elucidated for decades, still no effective treatment for this complex disease was developed, and the existing therapeutic strategies are extremely erratic, thereby leading to irreversible and progressive cognitive decline in AD patients. Due to gradually mental dyscapacitating of AD patients, AD not only brings serious physical and psychological suffering to patients themselves, but also imposes huge economic burdens on family and society. Accordingly, it is very imperative to recapitulate the progress of gene editing-based precision medicine in the emerging fields. In this review, we will mainly focus on the application of CRISPR/Cas9 technique in the fields of AD research and gene therapy, and summarize the application of CRISPR/Cas9 in the aspects of AD model construction, screening of pathogenic genes, and target therapy. Finally, the development of delivery systems, which is a major challenge that hinders the clinical application of CRISPR/Cas9 technology will also be discussed.

The Emerging Role of Metabolism in Brain-Heart Axis: New Challenge for the Therapy and Prevention of Alzheimer Disease. May Thioredoxin Interacting Protein (TXNIP) Play a Role?

Alzheimer disease (AD) is the most frequent cause of dementia and up to now there is not an effective therapy to cure AD. In addition, AD onset occurs decades before the diagnosis, affecting the possibility to set up appropriate therapeutic strategies. For this reason, it is necessary to investigate the effects of risk factors, such as cardiovascular diseases, in promoting AD. AD shows not only brain dysfunction, but also alterations in peripheral tissues/organs. Indeed, it exists a reciprocal connection between brain and heart, where cardiovascular alterations participate to AD as well as AD seem to promote cardiovascular dysfunction. In addition, metabolic dysfunction promotes both cardiovascular diseases and AD. In this review, we summarize the pathways involved in the regulation of the brain-heart axis and the effect of metabolism on these pathways. We also present the studies showing the role of the gut microbiota on the brain-heart axis. Herein, we propose recent evidences of the function of Thioredoxin Interacting protein (TXNIP) in mediating the role of metabolism on the brain-heart axis. TXNIP is a key regulator of metabolism at both cellular and body level and it exerts also a pathological function in several cardiovascular diseases as well as in AD.

A Fluorine-19 Magnetic Resonance Probe, Shiga-Y5, Downregulates Thioredoxin-Interacting Protein Expression in the Brain of a Mouse Model of Alzheimer's Disease

Thioredoxin-interacting protein (TXNIP) is involved in multiple disease-associated functions related to oxidative stress, especially by inhibiting the anti-oxidant- and thiol-reducing activity of thioredoxin (TXN). Shiga-Y5 (SY5), a fluorine-19 magnetic resonance probe for detecting amyloid-β deposition in the brain, previously showed therapeutic effects in a mouse model of Alzheimer's disease; however, the mechanism of action of SY5 remains unclear. SY5 passes the blood-brain barrier and then undergoes hydrolysis to produce a derivative, Shiga-Y6 (SY6), which is a TXNIP-negative regulator. Therefore, this study investigates the therapeutic role of SY5 as the prodrug of SY6 in the thioredoxin system in the brain of a mouse model of Alzheimer's disease. The intraperitoneal injection of SY5 significantly inhibited TXNIP mRNA (p = 0.0072) and protein expression (p = 0.0143) induced in the brain of APP/PS1 mice. In contrast, the levels of TXN mRNA (p = 0.0285) and protein (p = 0.0039) in the brain of APP/PS1 mice were increased after the injection of SY5. The ratio of TXN to TXNIP, which was decreased (p = 0.0131) in the brain of APP/PS1 mice, was significantly increased (p = 0.0072) after the injection of SY5. These results suggest that SY5 acts as a prodrug of SY6 in targeting the thioredoxin system and could be a potential therapeutic compound in oxidative stress-related diseases in the brain.

ER stress associated TXNIP-NLRP3 inflammasome activation in hippocampus of human Alzheimer's disease

Although the exact etiology of Alzheimer's disease (AD) is poorly understood, experimental and clinical evidences suggest the contribution of neuroinflammation in the pathogenesis of AD. Pathologically, AD brain is characterized by an imbalance in redox status, elevated endoplasmic reticulum (ER) stress, synaptic dysfunction, inflammation, and progressive neurodegeneration. It has been noted that continuous accumulation of amyloid-beta (Aβ) and intracellular neurofibrillary tangles (NFTs) in AD brain trigger ER stress, which contributes to neurodegeneration. Similarly, experimental evidences supports the hypothesis that thioredoxin-interacting protein (TXNIP), an endogenous regulator of redox regulator thioredoxin (TRX), is activated by ER stress and contributes to activation of NLRP3 (NOD-like receptor protein 3) inflammatory cascade in hippocampus of the AD brain. Hippocampus of postmortem human AD and aged matched non-AD controls were analyzed for the expression ER stress markers and TXNIP-NLRP3 inflammasome at cellular and molecular levels. We found higher expression of TXNIP at protein and transcript levels in close association with pathological markers of AD such as Aβ and NFTs in AD hippocampus. In addition, our results demonstrated that TXNIP was co-localized in neurons and microglia. Moreover, expression of binding immunoglobulin protein (BiP), activated eukaryotic initiation factor-2α (eIf2α) and C/EBP homology protein (CHOP), proteins involved the development of ER stress, were elevated in AD hippocampus. Further, elevated expression of effector molecules of NLRP3 inflammasome activation such as apoptosis associated speck-like protein (ASC), cleaved caspase-1 and cleaved interleukin-1β were observed in the AD hippocampus. The study suggests that TXNIP could be a link that connect ER stress with neuroinflammation. Thus, TXNIP can be a possible therapeutic target to mitigate the progression of neuroinflammation in the pathogenesis of AD.

PKC Delta Activation Promotes Endoplasmic Reticulum Stress (ERS) and NLR Family Pyrin Domain-Containing 3 (NLRP3) Inflammasome Activation Subsequent to Asynuclein-Induced Microglial Activation: Involvement of Thioredoxin-Interacting Protein (TXNIP)/Thioredoxin (Trx) Redoxisome Pathway

A classical hallmark of Parkinson's disease (PD) pathogenesis is the accumulation of misfolded alpha-synuclein (αSyn) within Lewy bodies and Lewy neurites, although its role in microglial dysfunction and resultant dopaminergic (DAergic) neurotoxicity is still elusive. Previously, we identified that protein kinase C delta (PKCδ) is activated in post mortem PD brains and experimental Parkinsonism and that it participates in reactive microgliosis; however, the relationship between PKCδ activation, endoplasmic reticulum stress (ERS) and the reactive microglial activation state in the context of α-synucleinopathy is largely unknown. Herein, we show that oxidative stress, mitochondrial dysfunction, NLR family pyrin domain containing 3 (NLRP3) inflammasome activation, and PKCδ activation increased concomitantly with ERS markers, including the activating transcription factor 4 (ATF-4), serine/threonine-protein kinase/endoribonuclease inositol-requiring enzyme 1α (p-IRE1α), p-eukaryotic initiation factor 2 (eIF2α) as well as increased generation of neurotoxic cytokines, including IL-1β in aggregated αSyn_agg-stimulated primary microglia. Importantly, in mouse primary microglia-treated with αSyn_agg we observed increased expression of Thioredoxin-interacting protein (TXNIP), an endogenous inhibitor of the thioredoxin (Trx) pathway, a major antioxidant protein system. Additionally, αSyn_agg promoted interaction between NLRP3 and TXNIP in these cells. In vitro knockdown of PKCδ using siRNA reduced ERS and led to reduced expression of TXNIP and the NLRP3 activation response in αSyn_agg-stimulated mouse microglial cells (MMCs). Additionally, attenuation of mitochondrial reactive oxygen species (mitoROS) via mito-apocynin and amelioration of ERS via the eIF2α inhibitor salubrinal (SAL) reduced the induction of the ERS/TXNIP/NLRP3 signaling axis, suggesting that mitochondrial dysfunction and ERS may act in concert to promote the αSyn_agg-induced microglial activation response. Likewise, knockdown of TXNIP by siRNA attenuated the αSyn_agg-induced NLRP3 inflammasome activation response. Finally, unilateral injection of αSyn preformed fibrils (αSyn_PFF) into the striatum of wild-type mice induced a significant increase in the expression of nigral p-PKCδ, ERS markers, and upregulation of the TXNIP/NLRP3 inflammasome signaling axis prior to delayed loss of TH⁺ neurons. Together, our results suggest that inhibition of ERS and its downstream signaling mediators TXNIP and NLRP3 might represent novel therapeutic avenues for ameliorating microglia-mediated neuroinflammation in PD and other synucleinopathies.

Role of Thioredoxin-Interacting Protein in Diseases and Its Therapeutic Outlook

Thioredoxin-interacting protein (TXNIP), widely known as thioredoxin-binding protein 2 (TBP2), is a major binding mediator in the thioredoxin (TXN) antioxidant system, which involves a reduction-oxidation (redox) signaling complex and is pivotal for the pathophysiology of some diseases. TXNIP increases reactive oxygen species production and oxidative stress and thereby contributes to apoptosis. Recent studies indicate an evolving role of TXNIP in the pathogenesis of complex diseases such as metabolic disorders, neurological disorders, and inflammatory illnesses. In addition, TXNIP has gained significant attention due to its wide range of functions in energy metabolism, insulin sensitivity, improved insulin secretion, and also in the regulation of glucose and tumor suppressor activities in various cancers. This review aims to highlight the roles of TXNIP in the field of diabetology, neurodegenerative diseases, and inflammation. TXNIP is found to be a promising novel therapeutic target in the current review, not only in the aforementioned diseases but also in prolonged microvascular and macrovascular diseases. Therefore, TXNIP inhibitors hold promise for preventing the growing incidence of complications in relevant diseases.

An immunoblot assay for cysteine oxidation by reactive oxygen species allows detection of novel thioprotective efficacy of black tea extracts

INTRODUCTION

While cysteine thiol groups help to maintain the redox status of many proteins, they can be very susceptible to damaging oxidants. Despite broad interest in their antioxidant properties, whether tea polyphenols protect against protein thiol damage of this kind is unclear. This study sought to develop a simple immunoassay for use in screening tea extracts and other antioxidants for thioprotective efficacy at protein thiol groups.

METHODS

Fresh aqueous extracts were prepared from commercially sourced green, white, black and red teas. Traut's reagent (2-iminothiolane) was used to prepare surface-thiolated bovine serum albumin for use as assay substrate in the protein oxidation assay. Oxidative damage was induced during a 15 min incubation with hydrogen peroxide (H₂O₂) in the presence of tea extracts and reference antioxidants. The substrate protein was then derivatised with dimedone before samples were loaded onto a nitrocellulose membrane housed within a Slot-Blot apparatus. After blocking nonspecific protein binding a commercially available antibody was used to detect dimedone-labelled groups.

RESULTS

While the total phenol content of tea extracts typically correlated with their activity in lipid peroxidation and galvinoxyl radical-trapping assays, the former did not fully predict their abilities to suppress H₂O₂-induced cysteine oxidation, with black tea extracts displaying greater activity than the other teas and an apparent ability to reverse pre-existing cysteine oxidation. Among the model antioxidants tested, quercetin displayed a heightened ability to suppress cysteine oxidation.

DISCUSSION

This slot-blot immunoassay is a convenient method that facilitates standardised comparisons between the thioprotective properties of structurally- and constitutively-diverse antioxidants.

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.

Thioredoxin-Interacting Protein (TXNIP) with Focus on Brain and Neurodegenerative Diseases

The development of new therapeutic approaches to diseases relies on the identification of key molecular targets involved in amplifying disease processes. One such molecule is thioredoxin-interacting protein (TXNIP), also designated thioredoxin-binding protein-2 (TBP-2), a member of the α-arrestin family of proteins and a central regulator of glucose and lipid metabolism, involved in diabetes-associated vascular endothelial dysfunction and inflammation. TXNIP sequesters reduced thioredoxin (TRX), inhibiting its function, resulting in increased oxidative stress. Many different cellular stress factors regulate TXNIP expression, including high glucose, endoplasmic reticulum stress, free radicals, hypoxia, nitric oxide, insulin, and adenosine-containing molecules. TXNIP is also directly involved in inflammatory activation through its interaction with the nucleotide-binding domain, leucine-rich-containing family, and pyrin domain-containing-3 (NLRP3) inflammasome complex. Neurodegenerative diseases such as Alzheimer’s disease have significant pathologies associated with increased oxidative stress, inflammation, and vascular dysfunctions. In addition, as dysfunctions in glucose and cellular metabolism have been associated with such brain diseases, a role for TXNIP in neurodegeneration has actively been investigated. In this review, we will focus on the current state of the understanding of possible normal and pathological functions of TXNIP in the central nervous system from studies of in vitro neural cells and the brains of humans and experimental animals with reference to other studies. As TXNIP can be expressed by neurons, microglia, astrocytes, and endothelial cells, a complex pattern of regulation and function in the brain is suggested. We will examine data suggesting TXNIP as a therapeutic target for neurodegenerative diseases where further research is needed.