ER stress and UPR in Alzheimer's disease: mechanisms, pathogenesis, treatments

Advancing Alzheimer's Therapy: Computational strategies and treatment innovations

Alzheimer's disease (AD) is a multifaceted neurodegenerative condition distinguished by the occurrence of memory impairment, cognitive deterioration, and neuronal impairment. Despite extensive research efforts, conventional treatment strategies primarily focus on symptom management, highlighting the need for innovative therapeutic approaches. This review explores the challenges of AD treatment and the integration of computational methodologies to advance therapeutic interventions. A comprehensive analysis of recent literature was conducted to elucidate the broad scope of Alzheimer's etiology and the limitations of conventional drug discovery approaches. Our findings underscore the critical role of computational models in elucidating disease mechanisms, identifying therapeutic targets, and expediting drug discovery. Through computational simulations, researchers can predict drug efficacy, optimize lead compounds, and facilitate personalized medicine approaches. Moreover, machine learning algorithms enhance early diagnosis and enable precision medicine strategies by analyzing multi-modal datasets. Case studies highlight the application of computational techniques in AD therapeutics, including the suppression of crucial proteins implicated in disease progression and the repurposing of existing drugs for AD management. Computational models elucidate the interplay between oxidative stress and neurodegeneration, offering insights into potential therapeutic interventions. Collaborative efforts between computational biologists, pharmacologists, and clinicians are essential to translate computational insights into clinically actionable interventions, ultimately improving patient outcomes and addressing the unmet medical needs of individuals affected by AD. Overall, integrating computational methodologies represents a promising paradigm shift in AD therapeutics, offering innovative solutions to overcome existing challenges and transform the landscape of AD treatment.

Licochalcone A Ameliorates Cognitive Dysfunction in an Alzheimer's Disease Model by Inhibiting Endoplasmic Reticulum Stress-Mediated Apoptosis

BackgroundEndoplasmic reticulum (ER) stress-induced neurodegeneration has been considered an underlying cause of Alzheimer disease (AD). Here, we investigated the beneficial effects of licochalcone A (Lico A), a valuable flavonoid of the root of the Glycyrrhiza species, against cognitive impairment in AD by regulating ER stress.MethodsThe triple transgenic mouse AD models were used and were administrated 5 or 15 mg/kg Lico A. Cognitive deficits, Aβ deposition, ER stress, and neuronal apoptosis were determined using Morris Water Maze test, probe trial, immunofluorescence staining, western blotting, and TUNEL staining. To investigate the mechanisms of how Lico A exerts anti-AD effects, primary hippocampal neurons were isolated from the AD model mice and treated with Lico A, salubrinal, an eIF2α phosphatase inhibitor, ML385, a Nrf2 inhibitor, or LY294002, an inhibitor of PI3K. Pharmacokinetics and toxicity of Lico A (15 mg/kg) in AD mice were evaluated.ResultsWe found that Lico A improved cognitive impairment, decreased Aβ plaques, inhibited ER stress, and reduced neuronal apoptosis in the hippocampus and cortex of AD mice. Treatment with Lico A in primary hippocampal neurons exerted the same effects as it did in vivo. Additionally, cotreatment with ML385 or LY294002 significantly impeded the effects of Lico A against ER stress. Moreover, 15 mg/kg Lico A had a good bioavailability and low toxicity in AD mice.ConclusionOur results demonstrated that Lico A ameliorates ER stress-induced neuronal apoptosis by inhibiting PERK/eIF2α/ATF4/CHOP signaling, suggesting the therapeutic potential of Lico A in AD treatment.

Loss of the APP regulator RHBDL4 preserves memory in an Alzheimer's disease mouse model

Characteristic cerebral pathological changes of Alzheimer's disease (AD) such as glucose hypometabolism or the accumulation of cleavage products of the amyloid precursor protein (APP), known as Aβ peptides, lead to sustained endoplasmic reticulum (ER) stress and neurodegeneration. To preserve ER homeostasis, cells activate their unfolded protein response (UPR). The rhomboid-like-protease 4 (RHBDL4) is an enzyme that participates in the UPR by targeting proteins for proteasomal degradation. We demonstrated previously that RHBDL4 cleaves APP in HEK293T cells, leading to decreased total APP and Aβ. More recently, we showed that RHBDL4 processes APP in mouse primary mixed cortical cultures as well. Here, we aim to examine the physiological relevance of RHBDL4 in the brain. We first found that brain samples from AD patients and an AD mouse model (APPtg) showed increased RHBDL4 mRNA and protein expression. To determine the effects of RHBDL4's absence on APP physiology in vivo, we crossed APPtg mice to a RHBDL4 knockout (R4-/-) model. RHBDL4 deficiency in APPtg mice led to increased total cerebral APP and amyloidogenic processing when compared to APPtg controls. Contrary to expectations, as assessed by cognitive tests, RHBDL4 absence rescued cognition in 5-month-old female APPtg mice. Informed by unbiased RNA-seq data, we demonstrated in vitro and in vivo that RHBDL4 absence leads to greater levels of active β-catenin due to decreased proteasomal clearance. Decreased β-catenin activity is known to underlie cognitive defects in APPtg mice and AD. Our work suggests that RHBDL4's increased expression in AD, in addition to regulating APP levels, leads to aberrant degradation of β-catenin, contributing to cognitive impairment.

Loss of ATG7 in microglia impairs UPR, triggers ferroptosis, and weakens amyloid pathology control

Microglia impact brain development, homeostasis, and pathology. One important microglial function in Alzheimer's disease (AD) is to contain proteotoxic amyloid-β (Aβ) plaques. Recent studies reported the involvement of autophagy-related (ATG) proteins in this process. Here, we found that microglia-specific deletion of Atg7 in an AD mouse model impaired microglia coverage of Aβ plaques, increasing plaque diffusion and neurotoxicity. Single-cell RNA sequencing, biochemical, and immunofluorescence analyses revealed that Atg7 deficiency reduces unfolded protein response (UPR) while increasing oxidative stress. Cellular assays demonstrated that these changes lead to lipoperoxidation and ferroptosis of microglia. In aged mice without Aβ buildup, UPR reduction and increased oxidative damage induced by Atg7 deletion did not impact microglia numbers. We conclude that reduced UPR and increased oxidative stress in Atg7-deficient microglia lead to ferroptosis when exposed to proteotoxic stress from Aβ plaques. However, these microglia can still manage misfolded protein accumulation and oxidative stress as they age.

Combined Restraint Stress and Metal Exposure Paradigms in Rats: Unravelling Behavioural and Neurochemical Perturbations

Accumulation of heavy metals (Mn and Ni) and prolonged exposure to stress are associated with adverse health outcomes. Various studies have shown the impacts of stress and metal exposures on brain function. However, no study has examined the effects of co-exposure to stress, Mn, and Ni on the brain. This study addresses this gap by evaluating oxidative and glial responses, apoptotic activity, as well as cognitive processes in a rat model. Adult Wistar rats were exposed to vehicle (control), restraint stress, 25 mg/kg of manganese (Mn) or nickel (Ni), or combined restraint stress plus Mn or Ni. Following treatment, rats were subjected to several behavioural paradigms to assess cognitive function. Enzyme activity, as well as ATPase levels, were evaluated. Thereafter, an immunohistochemical procedure was utilised to evaluate neurochemical markers of glial function, myelination, oxidative stress, and apoptosis in the hippocampus, prefrontal cortex (PFC), and striatum. Results showed that stress and metal exposure increased oxidative stress markers and reduced antioxidant levels. Further, combined stress and metal exposure reduced various forms of learning and memory ability in rats. In addition, there were alterations in Iba1 activity and Nrf2 levels, reduced Olig2 and myelin basic protein (MBP) levels, and increased caspase-3 expression. These neurotoxic outcomes were mostly exacerbated by co-exposure to stress and metals. Overall, our findings establish that stress and metal exposures impaired cognitive performance, induced oxidative stress and apoptosis, and led to demyelination effects which were worsened by combined stress and metal exposure.

Promising protective potential of MiR-103a-3p against polystyrene microplastic neurotoxicity in rats

Introduction: Microplastics are ubiquitous environmental pollutants with potential neurotoxic effects that can impair learning and memory. MicroRNAs are essential regulators of a number of physiological and pathological processes, but detailed information on the impact of miRNAs on the neurotoxic effects of microplastics is lacking. Methods: In the present study, polystyrene microplastics (PS-MPs) were administered orally and miR-103a-3p was injected intracerebroventricularly as a treatment for PS-MPs-induced neurotoxicity. Results and Discussion: Performance in the novel object discrimination Y-maze and Barnes maze tests indicated that miR-103a-3p mitigates the deleterious effects of PS-MPs on learning and memory. Oxidative stress, pyroptosis, apoptosis and inflammation induced by PS-MPs were modulated after miR- 103a-3p injection by reducing malondialdehyde, protein carbonyl, nitrite, caspase 3, caspase 1, TNFα, and NLRP3 levels in hippocampal tissue. Our results also showed that miR-103a-3p can reverse the impact of PS-MPs on astrocytic reaction and SIRT1 and BDNF levels. MiR-103a-3p alleviated PS-MPs-induced endoplasmic reticulum (ER) stress through reducing the levels of PERK, CHOP and GRP78. These findings imply that miR-103a-3p exerts a neuroprotective influence against cognitive deficits induced by exposure to PS-MPs. This is achieved by reducing inflammation, oxidative stress, apoptosis and endoplasmic reticulum stress.

Endoplasmic Reticulum Stress: Implications in Diseases

Endoplasmic reticulum (ER) is a specialized organelle that plays a significant role in cellular function. The major functions of ER include protein synthesis and transport, folding of proteins, biosynthesis of lipids, calcium (Ca2+) storage, and redox balance. The loss of ER integrity results in the induction of ER stress within the cell due to the accumulation of unfolded, improperly folded proteins or changes in Ca2+ metabolism and redox balance of organelle. This ER stress commences the Unfolded Protein Response (UPR) that serves to counteract the ER stress via three sensors inositol requiring protein-1 (IRE1), protein kinase RNA-like ER kinase (PERK), and activating transcription factor-6 (ATF6) that serve to establish ER homeostasis and alleviates ER stress. Severe ER dysfunction ultimately results in the induction of apoptosis. Increasing shreds of evidence suggest the implication of ER stress in the development and progression of several diseases viz. tuberculosis, malaria, Alzheimer's disease, Parkinson's disease, diabetes, and cancer. Activation of ER stress can be beneficial for treating some diseases while inhibiting the process can be useful in others. A deeper understanding of these pathways can provide key insights in designing novel therapeutics to treat these diseases.

Akt mitigates ER stress-instigated cardiac dysfunction via regulation of ferroptosis and mitochondrial integrity in a DHODH-dependent manner

ER stress evokes various types of cell death and myocardial dysfunction. This study aimed to discern the involvement of ferroptosis in chronic Akt activation-offered benefit, if any, against ER stress-triggered cardiac remodeling and contractile anomalies. Cardiac-selective expression of active mutant of Akt (AktOE) and wild-type (WT) mice were challenged with the ER stress instigator tunicamycin (1 mg/kg, 48 h) prior to assessment of cardiac morphology and function. Tunicamycin insult prompted cardiac remodeling (interstitial fibrosis), deranged echocardiographic (higher LVESD, dropped ejection fraction and fractional shortening), cardiomyocyte mechanical and intracellular Ca2+ features alongside mitochondrial injury (collapsed mitochondrial membrane potential and ultrastructural change), oxidative stress, compromised Akt-GSK3β signaling, ER stress (upregulated GRP78 and Gadd153), carbonyl formation, apoptosis and ferroptosis (decreased GPX4, SLC7A11). Intriguingly, tunicamycin-evoked anomalies (except GRP78 and Gadd153) were abrogated by Akt activation. Chronic Akt activation negated tunicamycin-induced downregulation of ferric flavin enzyme dihydroorotate dehydrogenase (DHODH), which catalyzes the fourth step of pyrimidine ab initio biosynthesis, and conversion of dihydroorotic acid to orotate. ER stress-induced myocardial anomalies were reversed by the newly identified PI3K activator triptolide, DHODH activator menaquinone-4 and pyrimidine booster coenzyme Q. In vitro experiment revealed that Akt activation- or triptolide-evoked beneficial responses against tunicamycin-induced cardiomyocyte anomalies were cancelled off by DHODH inhibitor BAY2402234 or ferroptosis inducer erastin. These findings support that chronic Akt activation rescues ER stress-evoked myocardial derangements through DHODH-dependent control of ferroptosis and mitochondrial homeostasis.

Cellular Stress Responses and Associated Diseases: A Focus on Heat Shock Proteins

Cellular stress response is the response of the cell at molecular level in order to combat various environmental stressors / viral infections. These stressors can be either intra or extracellular. In the beginning of the insult cell tries to recoup from these adverse events by various mechanism like heat shock protein response, unfolded protein response, mitochondrial stress signaling, DNA damage response etc. However, if these stressors exceed the cellular capacity to coup with it, it leads to programmed cell death and senescence. Also, chronic stress and cortisol released in response to cellular stress decreases telomerase activity which is needed to replenish telomeres which are protective casing at the end of a strand of DNA. Too low telomeres lead to cell death or cell become pro-inflammatory leading to aging process and other health associated risks like cardiovascular diseases neurodegenerative diseases, autoimmune diseases, cancers etc.

Indole-3-acetic acid and chenodeoxycholic acid attenuate TLR4/NF-κB signaling and endoplasmic reticulum stress in valproic acid-induced neurotoxicity

Valproic acid (VA) is a commonly prescribed medication for epilepsy and other neurological conditions. Although effective, VA use can lead to neurotoxicity, especially with chronic use. This study aimed to investigate the potential neuroprotective properties of indole-3-acetic acid (IAA) and chenodeoxycholic acid (CDCA) in an animal model of VA-induced brain injury. Rats received intraperitoneal injections of VA at a dose of 500 mg/kg/day for 3 weeks. Concurrently, they were orally treated with IAA (40 mg/kg/day) and/or CDCA (90 mg/kg/day). The results showed significantly increased oxidative stress and inflammation markers in the VA-exposed group indicated by the reduced levels of glutathione (GSH, P < 0.0001) and superoxide dismutase (SOD, P < 0.01) and the elevated inflammatory cytokines Interleukin-6 (IL-6, P < 0.0001) and tumor necrosis factor-alpha (TNFα, P < 0.01). VA also induced nuclear factor kappa B (NF-κB, P < 0.01), toll-like receptor 4 (TLR4, P < 0.05), and endoplasmic reticulum (ER) stress markers, as evidenced by increased immunoreactivity of GRP78 (glucose-regulated protein 78, P < 0.0001), transcription factor 6 (ATF-6, P < 0.05) and CHOP (C/EBP homologous protein, P < 0.0001). Treatment with IAA or CDCA attenuated VA-induced neurotoxicity, to a variable extent, by improving oxidative, inflammatory, and ER stress markers. This study demonstrates that IAA and CDCA exert protective effects against VA-induced neurotoxicity by mitigating oxidative stress, inflammation, and ER stress. Further investigations are recommended to validate these findings in other neurotoxicity models.

GSK-3β dysregulation in aging: Implications for tau pathology and Alzheimer's disease progression

The role of glycogen synthase kinase-3β (GSK-3β) in the pathogenesis of Alzheimer's disease (AD) is critical for linking amyloid-beta (Aβ) and Tau pathology. The activity of GSK-3β is dysregulated in the regulation of Tau hyperphosphorylation, formation of neurofibrillary tangles (NFTs), and production of Aβ by modulating amyloid precursor protein (APP) processing. This review discusses the mechanisms controlling GSK-3β dysregulation in aging and its influence on AD progression, focusing on the role of neuroinflammation, oxidative stress, and defective signaling pathways, including PI3K/Akt and Wnt. Critical analysis is presented for therapeutic strategies targeting GSK-3β using natural compounds (e.g., curcumin, geniposide) and emerging approaches such as TREM2 modulation and miRNA therapies. In preclinical models, these interventions promise to reduce Tau hyperphosphorylation and Aβ burden, along with associated neurodegeneration. Nevertheless, achieving selective GSK-3β inhibition and optimizing drug delivery are still critical barriers to clinical translation. This review underscores the central role of GSK-3β in AD pathogenesis to highlight its potential as a multifaceted therapeutic target of an innovative strategy for treating this complex neurodegenerative disease.

Mitochondria associated membranes in dilated cardiomyopathy: connecting pathogenesis and cellular dysfunction

Dilated cardiomyopathy (DCM) is a leading cause of heart failure, yet therapeutic options remain limited. While traditional research has focused on mechanisms such as energy deficits and calcium dysregulation, increasing evidence suggests that mitochondria-associated membranes (MAMs) could provide new insights into understanding and treating DCM. In this narrative review, we summarize the key role of MAMs, crucial endoplasmic reticulum (ER)-mitochondria interfaces, in regulating cellular processes such as calcium homeostasis, lipid metabolism, and mitochondrial dynamics. Disruption of MAMs function may initiate pathological cascades, including ER stress, inflammation, and cell death. These disruptions in MAM function lead to further destabilization of cellular homeostasis. Identifying MAMs as key modulators of cardiac health may provide novel insights for early diagnosis and targeted therapies in DCM.

Pharmacological landscape of endoplasmic reticulum stress: Uncovering therapeutic avenues for metabolic diseases

The endoplasmic reticulum (ER) plays a fundamental role in maintaining cellular homeostasis by ensuring proper protein folding, lipid metabolism, and calcium regulation. However, disruptions to ER function, known as ER stress, activate the unfolded protein response (UPR) to restore balance. Chronic or unresolved ER stress contributes to metabolic dysfunctions, including insulin resistance, non-alcoholic fatty liver disease (NAFLD), and neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease. Recent studies have also highlighted the importance of mitochondria-ER contact sites (MERCs) and ER-associated inflammation in disease progression. This review explores the current pharmacological landscape targeting ER stress, focusing on therapeutic strategies for rare metabolic and neurodegenerative diseases. It examines small molecules such as tauroursodeoxycholic acid (TUDCA) and 4-phenylbutyric acid (4-PBA), repurposed drugs like 17-AAG (17-N-allylamino-17demethoxygeldanamycin (tanespimycin)) and berberine, and phytochemicals such as resveratrol and hesperidin. Additionally, it discusses emerging therapeutic areas, including soluble epoxide hydrolase (sEH) inhibitors for metabolic disorders and MERCs modulation for neurological diseases. The review emphasizes challenges in translating these therapies to clinical applications, such as toxicity, off-target effects, limited bioavailability, and the lack of large-scale randomized controlled trials (RCTs). It also highlights the potential of personalized medicine approaches and pharmacogenomics in optimizing ER stress-targeting therapies.

Customizable gene sensing and response without altering endogenous coding sequences

Synthetic biology aims to modify cellular behaviors by implementing genetic circuits that respond to changes in cell state. Integrating genetic biosensors into endogenous gene coding sequences using clustered regularly interspaced short palindromic repeats and Cas9 enables interrogation of gene expression dynamics in the appropriate chromosomal context. However, embedding a biosensor into a gene coding sequence may unpredictably alter endogenous gene regulation. To address this challenge, we developed an approach to integrate genetic biosensors into endogenous genes without modifying their coding sequence by inserting into their terminator region single-guide RNAs that activate downstream circuits. Sensor dosage responses can be fine-tuned and predicted through a mathematical model. We engineered a cell stress sensor and actuator in CHO-K1 cells that conditionally activates antiapoptotic protein BCL-2 through a downstream circuit, thereby increasing cell survival under stress conditions. Our gene sensor and actuator platform has potential use for a wide range of applications that include biomanufacturing, cell fate control and cell-based therapeutics.

Artemisinin alleviates astrocyte overactivation and neuroinflammation by modulating the IRE1/NF-κB signaling pathway in in vitro and in vivo Alzheimer's disease models

Recent studies have shown that neuroinflammation and heightened glial activity, particularly astrocyte overactivation, are associated with Alzheimer's disease (AD). Abnormal accumulation of amyloid-beta (Aβ) induces endoplasmic reticulum (ER) stress and activates astrocytes. Artemisinin (ART), a frontline anti-malarial drug, has been found to have neuroprotective properties. However, its impact on astrocytes remains unclear. In this study, we used Aβ1-42 induced astrocyte cultures and 3 × Tg-AD mice as in vitro and in vivo models, respectively, to investigate the effects of ART on AD related astrocyte overactivation and its underlying mechanisms. ART attenuated Aβ1-42-induced astrocyte activation, ER stress, and inflammatory responses in astrocyte cultures by inhibiting IRE1 phosphorylation and the NF-κB pathway, as evidenced by the overexpression of IRE1 WT and IRE1-K599A (kinase activity invalidated), along with application of activators and inhibitors related to ER stress. Furthermore, ART alleviated the detrimental effects and restored neurotrophic function of astrocytes on co-cultured neurons, preventing neuronal apoptosis during Aβ1-42 treatment. In 3 × Tg-AD mice, ART treatment improved cognitive function and reduced astrocyte overactivation, neuroinflammation, ER stress, and neuronal apoptosis. Moreover, ART attenuated the upregulation of IRE1/NF-κB pathway activity in AD mice. Astrocyte-specific overexpression of IRE1 via adeno-associated virus in AD mice reversed the ameliorating effects of ART. Our findings suggest that ART inhibits astrocyte overactivation and neuroinflammation in both in vitro and in vivo AD models by modulating the IRE1/NF-κB signaling pathway, thereby enhancing neuronal functions. This study underscores the therapeutic potential of ART in AD and highlights the significance of modulating the ER stress-inflammatory cycle and normalizing astrocyte-neuron communication.

Unveiling the mTOR pathway modulation by SGLT2 inhibitors: a novel approach to Alzheimer's disease in type 2 diabetes

Alzheimer's disease (AD) is a neurological condition causing cognitive deterioration, leading to severe consequences. As the global prevalence of AD increases, new treatment approaches are needed to supplement current conventional therapies, as traditional treatments are not meeting the increasing demand for alternative treatments. It is increasingly evident that treating metabolic disorders like diabetes mellitus, obesity, and AD by blocking mechanistic target of rapamycin (mTOR) signalling is advantageous. Chronic mTOR activation may cause AD's metabolic, lysosomal, and mitochondrial dysfunction, tau hyperphosphorylation, amyloid plaque development, and disruption of the blood-brain barrier through endothelial cell malfunction. Chronic glucose loss through sodium-glucose transporter 2 (SGLT2) inhibitions can restore mTOR cycling, potentially halting or slowing AD pathogenesis. Chronic activation of mTOR is implicated in pathophysiological aspects of AD, such as metabolic dysfunction, tau hyperphosphorylation, amyloid plaque formation, and disruption of the blood-brain barrier. SGLT-2 inhibitors, commonly used in treating Type 2 Diabetes, have been shown to reduce mTOR activation and restore circadian regularity, a new finding in cognitive decline and metabolic disorders. Conversely, SGLT2 inhibitors decrease oxidative damage, inflammation, insulin signaling pathways, and proliferation of endothelial cells to enhance vascular tone, flexibility, and contractility. Along with reducing the formation of plaque containing amyloid and improving brain function, neural plasticity, acetylcholinesterase (AChE) activity, damage to the brain, and cognitive decline, they also regulate the mTOR pathway in the brain. Thus, repurposing SGLT-2 inhibitors, primarily used in diabetes treatment, presents a promising avenue for changing the way that AD is managed. The purpose of this review was to focus on the mTOR signalling cascade of SGLT 2 inhibitors to AD management in Type 2 Diabetes mellitus.

Hallmarks of aging and Alzheimer's Disease pathogenesis: Paving the route for new therapeutic targets

Aging is the leading risk factor for Alzheimer's Disease (AD). Understanding the intricate interplay between biological aging and the AD pathophysiology may help to discover innovative treatments. The relationship between aging and core pathways of AD pathogenesis (amyloidopathy and tauopathy) have been extensively studied in preclinical models. However, the potential discordance between preclinical models and human pathology could represent a limitation in the identification of new therapeutic targets. This narrative review aims to gather the evidence currently available on the associations of β-Amyloid and Tau pathology with the hallmarks of aging in human studies. Briefly, our review suggests that while several hallmarks exhibit a robust association with AD pathogenesis (e.g., epigenetic alterations, chronic inflammation, dysbiosis), others (e.g., telomere attrition, cellular senescence, stem cell exhaustion) demonstrate either no relationship or weak associations. This is often due to limitations such as small sample sizes and study designs, being either cross-sectional or with short follow-up intervals, limiting the generalizability of the findings. Distinct hallmarks play varying roles in different stages of AD pathology, emphasizing the need for longitudinal studies with longer follow-up periods. Considering the intricate interconnections across the hallmarks of aging, future research on AD pathology should focus on multiple hallmarks simultaneously.

Dengzhan Shengmai capsule ameliorates cognitive impairment via inhibiting ER stress in APP/PS1 mice

ETHNOPHARMACOLOGICAL RELEVANCE

Alzheimer's disease (AD) is a common type of neurodegenerative disease with the β-amyloid plaques (Aβ) deposition. Previously, Dengzhan Shengmai capsule (DZSM) has been shown to reduce the pathology associated with AD, but the underlying mechanism is unclear.

AIM OF STUDY

This study investigated the potential mechanisms of DZSM against AD.

MATERIALS AND METHODS

The six-month-old wild-type male mice and APP/PS1 double transgenic male mice were administered 0.9 % saline or DZSM for 8 weeks by gavage. Open field test, new object recognition test, and Morris Water maze test were used to assess spatial learning and memory. Aβ plaques in brains were visualized using ThT staining. Nissl staining, TUNEL staining, and Western blot analyses were used to detect the neuronal function and apoptosis level. The superoxide dismutase (SOD), glutathione peroxidase assay kit (GSH-Px), and malondialdehyde (MDA) kits were performed to assess oxidative stress levels. Then, immunofluorescence and Western blot analysis were applied to evaluate ER stress pathway protein levels. Finally, HT22 cells were treated by Aβ1-42 with or without DZSM medicated serum. Cell viability was assessed using the CCK-8 assay, and Western blot analysis was applied to evaluate ER stress pathway protein levels.

RESULTS

Open filed test, new object recognition test and Morris Water maze test showed that DZSM restored cognitive disorders in APP/PS1 mice. Immunohistochemistry and Thioflavin T staining results indicated that DZSM reduced Aβ plaques in the brain. Deeper and denser Nissl bodies were found in APP/PS1 mice after DZSM administration. Besides, APP/PS1 mice treated with DZSM showed a lower level of TUNEL and Bax/Bcl-2 ratio. DZSM improved the acetylcholine (ACh), choline acetyltransferase (ChAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) activity while reducing acetylcholinesterase (AChE) and malondialdehyde (MDA) activity. In addition, the levels of ER stress pathway containing Phospho-PKR-like ER kinase (P-PERK), phosphorylate eukaryotic initiation factor 2 (P-eIF2α), activating transcription factor 4 (ATF4), glutamine-rich protein 1 (QRICH1), phosphorylate inositol-requiring protein 1α (P-IRE1α), the spliced form of X-box binding protein 1 (XBP1s), activating transcription factor-6 (ATF6) and C/EBP homologous binding protein (CHOP) were decreased by DZSM. CCK-8 results indicated that DZSM medicated serum played cytoprotective effects on Aβ1-42-induced HT22 cells. Western blot results suggested DZSM possibly inhibited ER stress pathways in Aβ1-42-induced HT22 cells.

CONCLUSION

The potential protective mechanism of DZSM on cognitive impairment in AD might be related to ER stress pathways.

OTULIN Interactome Reveals Immune Response and Autophagy Associated with Tauopathy in a Mouse Model

Tauopathies are neurodegenerative diseases that are pathologically characterized by accumulation of misfolded microtubule-associated protein tau aggregates in the brain. Deubiquitination, particularly by OTULIN, a unique deubiquitinase targeting methionine-1 (M1) linkages from linear ubiquitin chain assembly complex (LUBAC)), is reportedly associated with the accumulation of neurotoxic proteins in several neurodegenerative diseases, likely including tauopathies. To investigate the potential roles of OTULIN in tauopathies, we analyzed the OTULIN interactome in hippocampal tissues from PS19 transgenic (Tg) mice and their non-transgenic (nTg) littermate controls using affinity purification-mass spectrometry (AP-MS). We identified 705 and 800 proteins enriched in Tg and nTg samples, respectively, with a protein false discovery rate (FDR) of <1%. Of these, 189 and 205 proteins were classified as probable OTULIN interactors in Tg and nTg groups, respectively, based on Significance Analysis of INTeractome (SAINT) score of ≥0.80 and FDR of ≤ 5%. A total of 84 proteins were identified as OTULIN interactors in the PS19 Tg group, while 100 proteins were associated with OTULIN in the nTg controls. Functional enrichment analyses revealed that OTULIN-interacting proteins in the nTg group were enriched in pathways related to spliceosome, complement and coagulation cascades, and ribosome, whereas those in the Tg group were associated with immune response and autophagy. These findings suggest that OTULIN-interacting proteins may play a critical role in the pathogenesis of tauopathy in this mouse model.

Transmission of unfolded protein response-a regulator of disease progression, severity, and spread in virus infections

The unfolded protein response (UPR) is a cell-autonomous stress response aimed at restoring homeostasis due to the accumulation of misfolded proteins in the endoplasmic reticulum (ER). Viruses often hijack the host cell machinery, leading to an accumulation of misfolded proteins in the ER. The cell-autonomous UPR is the immediate response of an infected cell to this stress, aiming to restore normal function by halting protein translation, degrading misfolded proteins, and activating signaling pathways that increase the production of molecular chaperones. The cell-non-autonomous UPR involves the spreading of UPR signals from initially stressed cells to neighboring unstressed cells that lack the stressor. Though viruses are known modulators of cell-autonomous UPR, recent advancements have highlighted that cell-non-autonomous UPR plays a critical role in elucidating how local infections cause systemic effects, thereby contributing to disease symptoms and progression. Additionally, by utilizing cell-non-autonomous UPR, viruses have devised novel strategies to establish a pro-viral state, promoting virus spread. This review discusses examples that have broadened the understanding of the role of UPR in virus infections and disease progression by looking beyond cell-autonomous to non-autonomous processes and mechanistic details of the inducers, spreaders, and receivers of UPR signals.

Recent Insights into the Neurobiology of Alzheimer's Disease and Advanced Treatment Strategies

In recent years, significant advancements have been made in understanding Alzheimer's disease from both neurobiological and clinical perspectives. Exploring the complex systems underlying AD has unveiled insights that could potentially revolutionize therapeutic approaches. Recent investigations have highlighted intricate interactions among genetic, molecular, and environmental factors in AD. Optimism arises from neurobiological advancements and diverse treatment options, potentially slowing or halting disease progression. Amyloid-beta plaques and tau protein tangles crucially influence AD onset and progression. Emerging treatments involve diverse strategies, such as approaches targeting multiple pathways involved in AD pathogenesis, such as inflammation, oxidative stress, and synaptic dysfunction pathways. Clinical trials using humanized monoclonal antibodies, focusing on immunotherapies eliminating amyloid-beta, have shown promise. Nonpharmacological interventions such as light therapy, electrical stimulation, cognitive training, physical activity, and dietary changes have drawn attention for their potential to slow cognitive aging and enhance brain health. Precision medicine, which involves tailoring therapies to individual genetic and molecular profiles, has gained traction. Ongoing research and interdisciplinary collaboration are expected to yield more effective treatments.

Neuroprotective role of mirabegron: Targeting beta-3 adrenergic receptors to alleviate ulcerative colitis-associated cognitive impairment

While cognitive impairment has been documented in ulcerative colitic patients, the possible influence of central β3-adrenergic receptor (β3-AR) signaling on this extraintestinal manifestation remains unclear. Previously, we identified an imperative role for mirabegron (MA) as an agonist of β3-AR, in decreasing the BACE-1/beta-amyloid (Aβ) cue in the colons of UC rats. Consequently, we investigated its therapeutic potential for alleviating cognitive impairment associated with UC. To fulfil our aim, rats administered iodoacetamide were treated with the β3-AR agonist (MA) alone, with the antagonist (SR59230A) for 8 days, or kept untreated. The animals' behavior (MWM and NOR tests) and hippocampal structure were assessed. Mechanistically, necroptosis, ER stress (ERS), Aβ-amyloidosis, inflammation/oxidative burden, and gut/BBB dysfunction were analyzed. Post-administration of MA improved weight gain, colon/hippocampal structures, and memory. Additionally, it inhibited serum levels of lipopolysaccharide and Annexin-1, indicating recovered gut and BBB integrity. MA turned off the pathogenic BACE-1/Aβ axis in the hippocampus, necroptosis trajectory (TNFR-1/RIPK1/RIPK3/MLKL), and the IRE-1α/JNK signal. Moreover, MA enhanced the transcription factor PPAR-γ, decreased NF-κΒ/TNF-α inflammatory hub, and modulated the redox imbalance by decreasing malondialdehyde and increasing catalase. Notably, MA's behavioral, structural, and molecular beneficial actions were hindered by the pre-administration of SR59230A. From a novel standpoint, we recognized the β3-AR as a therapeutic target for UC-associated cognitive impairment in the hippocampus. In this context, the aptitude of MA to inhibit UC-induced hippocampal amyloidogenesis, alongside its anti-necroptotic, anti-ERS, anti-inflammatory, and antioxidant effects, contribute to these central enhancements, while also regulating permeability in both gut and BBB barriers.

Visualizing Endoplasmic Reticulum Stress and Autophagy in Alzheimer's Model Cells by a Peroxynitrite-Responsive AIEgen Fluorescent Probe

Endoplasmic reticulum (ER) stress and autophagy (ER-phagy) occurring in nerve cells are crucial physiological processes closely associated with Alzheimer's disease (AD). Visualizing the two processes is paramount to advance our understanding of AD pathologies. Among the biomarkers identified, peroxynitrite (ONOO-) emerges as a key molecule in the initiation and aggravation of ER stress and ER-phagy, highlighting its significance in the underlying mechanisms of the two processes. In this work, we designed and synthesized an innovative ONOO--responsive AIEgen-based fluorescent probe (DHQM) with the ability to monitor ER stress and ER-phagy in AD model cells. DHQM demonstrated excellent aggregation-induced emission (AIE) properties, endowing it with outstanding ability for washing-free intracellular imaging. Meanwhile, it exhibited high sensitivity, remarkable selectivity to ONOO-, and exceptional ER-targeting ability. The probe was successfully applied for fluorescence imaging of ER ONOO- fluctuations to assess the ER stress status in aluminum-induced AD model cells. Our findings revealed that aluminum-induced ferroptosis, a regulated cell death process, was pivotal in the excessive ONOO- production, which in turn activated and exacerbated ER stress. Furthermore, the aluminum-stimulated ER-phagy was observed utilizing DHQM, which might be crucial in inhibiting ferroptosis and mitigating aberrant ER stress. Overall, this study not only offers valuable insights into the pathological mechanisms of AD at the ER level but also opens new potential therapeutic avenues targeting these pathways.

Simultaneous Imaging of pH and Peroxynitrite in the Endoplasmic Reticulum and Mitochondria: Revealing Organelle Interactions in Alzheimer's Disease Pathogenesis

pH and peroxynitrite (ONOO-) are two critical biomarkers to unveil the corresponding status of endoplasmic reticulum (ER) stress and mitochondrial dysfunction, which are closely related to Alzheimer's disease (AD). Simultaneously monitoring pH and ONOO- fluctuations in the ER and mitochondria during AD progression is pivotal for clarifying the interplay between the disorders of the two organelles and revealing AD pathogenesis. Herein, we designed and synthesized a dual-channel fluorescent probe (DCFP) to visualize pH and ONOO- in the ER and mitochondria. DCFP possessed excellent sensitivity and selectivity to pH and ONOO- without spectral crosstalk and was utilized in monitoring the two analytes within AD model cells and larval zebrafish. Importantly, DCFP could preferentially target mitochondria in normal cells and be enriched in the ER after mitochondrial depolarization. With the aid of DCFP, the slower acidification rate of the ER than that of mitochondria induced by Aβ oligomers (AβOs) was first identified, which could be ascribed to the relief of the AβOs-triggered ER stress through the Ca2+ migration from the ER to mitochondria. Moreover, continuous exposure to AβOs led to mitochondrial Ca2+ overload, accelerating the acidification and ONOO- overproduction within mitochondria. As a result, intracellular oxidative stress levels were elevated, further exacerbating ER stress and aggravating ER acidification in turn. The advanced understanding of the potential interplay between the ER and mitochondria in this work may offer new insights and methodologies for studying AD pathogenesis. The DCFP developed in this work could also be employed to study other diseases related to ER stress and mitochondrial dysfunction.

COSIME: Cooperative multi-view integration and Scalable and Interpretable Model Explainer

Single-omics approaches often provide a limited view of complex biological systems, whereas multiomics integration offers a more comprehensive understanding by combining diverse data views. However, integrating heterogeneous data types and interpreting the intricate relationships between biological features-both within and across different data views-remains a bottleneck. To address these challenges, we introduce COSIME (Cooperative Multi-view Integration and Scalable Interpretable Model Explainer). COSIME uses backpropagation of Learnable Optimal Transport (LOT) to deep neural networks, enabling the learning of latent features from multiple views to predict disease phenotypes. In addition, COSIME incorporates Monte Carlo sampling to efficiently estimate Shapley values and Shapley-Taylor indices, enabling the assessment of both feature importance and their pairwise interactions-synergistically or antagonistically-in predicting disease phenotypes. We applied COSIME to both simulated data and real-world datasets, including single-cell transcriptomics, single-cell spatial transcriptomics, epigenomics, and metabolomics, specifically for Alzheimer's disease-related phenotypes. Our results demonstrate that COSIME significantly improves prediction performance while offering enhanced interpretability of feature relationships. For example, we identified that synergistic interactions between microglia and astrocyte genes associated with AD are more likely to be active at the edges of the middle temporal gyrus as indicated by spatial locations. Finally, COSIME is open-source and available for general use.

From Genes to Metabolites: HSP90B1's Role in Alzheimer's Disease and Potential for Therapeutic Intervention

Alzheimer's disease (AD) is a prototypical neurodegenerative disorder, predominantly affecting individuals in the presenile and elderly populations, with an etiology that remains elusive. This investigation aimed to elucidate the alterations in anoikis-related genes (ARGs) in the AD brain, thereby expanding the repertoire of biomarkers for the disease. Using publically available gene expression data for the hippocampus from both healthy and AD subjects, differentially expressed genes (DEGs) were identified. Subsequent intersection with a comprehensive list of 575 ARGs yielded a subset for enrichment analysis. Machine learning algorithms were employed to identify potential biomarker, which was validated in an AD animal model. Additionally, gene set enrichment analysis was conducted on the biomarker and its interacting genes and microRNAs were predicted through online databases. To assess its biological functions, the expression of the marker was suppressed in an in vitro model to examine cell viability and inflammation-related indicators. Furthermore, following treatment with the inhibitor, the dysregulated metabolites in the hippocampus of the model mice were evaluated. Forty-seven ARGs were ultimately identified, with HSP90B1 emerging as a central marker. HSP90B1 was found to be significantly up-regulated in AD hippocampal samples and its inhibition conferred increased cell viability and reduced levels of inflammatory factors in amyloid β-protein (Aβ)-treated cells. A total of 24 differentially expressed metabolites were confidently identified between model mice and those with low HSP90B1 expression, with bioinformatics analysis shedding light on the molecular underpinnings of HSP90B1's involvement in AD. Collectively, these findings may inform novel insights into the pathogenesis, mechanisms, or therapeutic strategies for AD.

TOR and heat shock response pathways regulate peroxisome biogenesis during proteotoxic stress

Peroxisomes are versatile organelles mediating energy homeostasis and redox balance. While peroxisome dysfunction is linked to numerous diseases, the molecular mechanisms and signaling pathways regulating peroxisomes during cellular stress remain elusive. Using yeast, we show that perturbations disrupting protein homeostasis including loss of ER or cytosolic chaperone function, impairments in ER protein translocation, blocking ER N-glycosylation, or reductive stress, cause peroxisome proliferation. This proliferation is driven by increased de novo biogenesis from the ER as well as increased fission of pre-existing peroxisomes, rather than impaired pexophagy. Notably, peroxisome biogenesis is essential for cellular recovery from proteotoxic stress. Through comprehensive testing of major signaling pathways, we determine this response to be mediated by activation of the heat shock response and inhibition of Target of Rapamycin (TOR) signaling. Finally, the effects of proteotoxic stress and TOR inhibition on peroxisomes are also captured in human fibroblasts. Overall, our findings reveal a critical and conserved role of peroxisomes in cellular response to proteotoxic stress.

Remodelling of Cellular Protein Homeostasis by Enhanced ER-Mitochondrial Tethering

Alterations of endoplasmic reticulum (ER)-mitochondrial interaction have been associated with different pathological conditions, including neurodegenerative diseases, characterized by dysregulation of protein homeostasis. However, little is known about how enhanced ER-mitochondrial tethering affects cellular proteostatic machinery. Here, we transiently overexpressed synthetic ER-mitochondrial linkers (EMLs), stabilizing the ER-mitochondrial distance at ≤5 nm (denominated as 5 nm-EML) and ∼10 nm (10 nm-EML), in HeLa cells. No alterations were found in cell growth, although metabolic activity and total ATP were significantly reduced. In EML-expressing cells, global protein synthesis was significantly reduced, accompanied by a reduction of total PERK and eIF2α protein levels, but increased p-eIF2α. Unfolded protein response (UPR) markers ATF4 and ATF6 were upregulated, suggesting that enhanced ER-mitochondrial tethering deranges protein synthesis and induces a low-grade ER stress/UPR. To further investigate ER-mitochondrial tethering-induced protein dyshomeostasis, we performed shotgun mass spectrometry proteomics followed by bioinformatic analysis. Analysis of highly changed proteins and the most significantly overrepresented gene ontology (GO) terms revealed that ≤5 nm tethering preferentially affected the expression of proteins involved in RNA processing and splicing and proteasomal protein degradation, while ∼10 nm tethering preferentially affected protein translation. Both EMLs affected expression of proteins involved in mitochondrial bioenergetics and metabolism, defense against oxidative stress, ER protein homeostasis, signaling and secretion. Finally, lipidomic analysis suggests that 5 nm-EML and 10 nm-EML differentially affect lipid homeostasis. Altogether, our results suggest that enhanced ER-mitochondrial tethering leads to a profound remodeling of cellular protein homeostasis, which may play a key role in pathogenesis of Alzheimer's and other neurodegenerative diseases.

ADNP is essential for sex-dependent hippocampal neurogenesis, through male unfolded protein response and female mitochondrial gene regulation

Essential for brain formation and protective against tauopathy, activity-dependent neuroprotective protein (ADNP) is critical for neurogenesis and cognitive functions, while regulating steroid hormone biogenesis. As such, de novo mutations in ADNP lead to syndromic autism and somatic ADNP mutations parallel Alzheimer's disease progression. Furthermore, clinical trials with the ADNP fragment NAP (the investigational drug davunetide) showed efficacy in women suffering from the tauopathy progressive supranuclear palsy and differentially boosted memory in men (spatial) and women (verbal), exhibiting prodromal Alzheimer's disease. While autism is more prevalent in boys and Alzheimer's disease in women, both involve impaired neurogenesis. Here, we asked whether ADNP sex-dependently regulates neurogenesis. Using bromodeoxyuridine (BrdU) as a marker of neurogenesis, we identified two-fold higher labeling in the hippocampal sub-ventricular zone of ADNP-intact male versus female mice. Adnp haplo-insufficient (Adnp+/-) mice or mice CRSIPR/Cas9-edited to present the most prevalent neurodevelopmental ADNP syndrome mutation, p.Tyr718* (Tyr) showed dramatic reductions in male BrdU incorporation, resulting in mutated females presenting higher labeling than males. Treatment with NAP compensated for the male reduction of BrdU labeling. Mechanistically, hippocampal RNAseq revealed male-specific Tyr down-regulation of endoplasmic reticulum unfolded protein response genes critical for sex-dependent organogenesis. Newly discovered mitochondrial accessibility of ADNP was inhibited by the Tyr718* mutation further revealing female-specific Tyr downregulation of mitochondrial ATP6. NAP moderated much of the differential expression caused by p.Tyr718*, accompanied by the down-regulation of neurotoxic, pro-inflammatory and pro-apoptotic genes. Thus, ADNP is a key regulator of sex-dependent neurogenesis that acts by controlling canonical pathways, with NAP compensating for fundamental ADNP deficiencies, striding toward clinical development targeting the ADNP syndrome and related neurodevelopmental/neurodegenerative diseases.

The UFMylation pathway is impaired in Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is characterized by the presence of neurofibrillary tangles made of hyperphosphorylated tau and senile plaques composed of beta-amyloid. These pathognomonic deposits have been implicated in the pathogenesis, although the molecular mechanisms and consequences remain undetermined. UFM1 is an important, but understudied ubiquitin-like protein that is covalently attached to substrates. UFMylation has recently been identified as major modifier of tau aggregation upon seeding in experimental models. However, potential alterations of the UFM1 pathway in human AD brain have not been investigated yet.

METHODS

Here we used frontal and temporal cortex samples from individuals with or without AD to measure the protein levels of the UFMylation pathway in human brain. We used multivariable regression analyses followed by Bonferroni correction for multiple testing to analyze associations of the UFMylation pathway with neuropathological characteristics, primary biochemical measurements of tau and additional biochemical markers from the same cases. We further studied associations of the UFMylation cascade with cellular stress pathways using Spearman correlations with bulk RNAseq expression data and functionally validated these interactions using gene-edited neurons that were generated by CRISPR-Cas9.

RESULTS

Compared to controls, human AD brain had increased protein levels of UFM1. Our data further indicates that this increase mainly reflects conjugated UFM1 indicating hyperUFMylation in AD. UFMylation was strongly correlated with pathological tau in both AD-affected brain regions. In addition, we found that the levels of conjugated UFM1 were negatively correlated with soluble levels of the deUFMylation enzyme UFSP2. Functional analysis of UFM1 and/or UFSP2 knockout neurons revealed that the DNA damage response as well as the unfolded protein response are perturbed by changes in neuronal UFM1 signaling.

CONCLUSIONS

There are marked changes in the UFMylation pathway in human AD brain. These changes are significantly associated with pathological tau, supporting the idea that the UFMylation cascade might indeed act as a modifier of tau pathology in human brain. Our study further nominates UFSP2 as an attractive target to reduce the hyperUFMylation observed in AD brain but also underscores the critical need to identify risks and benefits of manipulating the UFMylation pathway as potential therapeutic avenue for AD.

The mechanisms, hallmarks, and therapies for brain aging and age-related dementia

Age-related cognitive decline and dementia are significant manifestations of brain aging. As the elderly population grows rapidly, the health and socio-economic impacts of cognitive dysfunction have become increasingly significant. Although clinical treatment of dementia has faced considerable challenges over the past few decades, with limited breakthroughs in slowing its progression, there has been substantial progress in understanding the molecular mechanisms and hallmarks of age-related dementia (ARD). This progress brings new hope for the intervention and treatment of this disease. In this review, we categorize the latest findings in ARD biomarkers into four stages based on disease progression: Healthy brain, pre-clinical, mild cognitive impairment, and dementia. We then systematically summarize the most promising therapeutic approaches to prevent or slow ARD at four levels: Genome and epigenome, organelle, cell, and organ and organism. We emphasize the importance of early prevention and detection, along with the implementation of combined treatments as multimodal intervention strategies, to address brain aging and ARD in the future.

Single-cell transcriptomic and neuropathologic analysis reveals dysregulation of the integrated stress response in progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a sporadic neurodegenerative tauopathy variably affecting brainstem and cortical structures, and characterized by tau inclusions in neurons and glia. The precise mechanism whereby these protein aggregates lead to cell death remains unclear. To investigate the contribution of these different cellular abnormalities to PSP pathogenesis, we performed single-nucleus RNA sequencing (snRNA-seq) and analyzed 50,708 high quality nuclei targeting the diencephalon, including the subthalamic nucleus and adjacent structures, from human post-mortem PSP brains with varying degrees of pathology compared to controls. Cell-type-specific differential expression and pathway analysis identified both common and discrete changes in numerous pathways previously implicated in PSP and other neurodegenerative disorders. This included EIF2 signaling, an adaptive pathway activated in response to diverse stressors, which was activated in multiple vulnerable cell types and validated in independent snRNA-seq and bulk RNA-seq datasets. Using immunohistochemistry, we found that activated eIF2α was positively correlated with tau pathology burden in vulnerable brain regions. Multiplex immunofluorescence localized activated eIF2α positivity to hyperphosphorylated tau (p-tau) positive neurons and ALDH1L1-positive astrocytes, supporting the increased transcriptomic EIF2 activation observed in these vulnerable cell types. In conclusion, these data provide insights into cell-type-specific pathological changes in PSP and support the hypothesis that failure of adaptive stress pathways play a mechanistic role in the pathogenesis and progression of PSP.

Plasticity of Human Microglia and Brain Perivascular Macrophages in Aging and Alzheimer's Disease

The complex roles of myeloid cells, including microglia and perivascular macrophages, are central to the neurobiology of Alzheimer's disease (AD), yet they remain incompletely understood. Here, we profiled 832,505 human myeloid cells from the prefrontal cortex of 1,607 unique donors covering the human lifespan and varying degrees of AD neuropathology. We delineated 13 transcriptionally distinct myeloid subtypes organized into 6 subclasses and identified AD-associated adaptive changes in myeloid cells over aging and disease progression. The GPNMB subtype, linked to phagocytosis, increased significantly with AD burden and correlated with polygenic AD risk scores. By organizing AD-risk genes into a regulatory hierarchy, we identified and validated MITF as an upstream transcriptional activator of GPNMB, critical for maintaining phagocytosis. Through cell-to-cell interaction networks, we prioritized APOE-SORL1 and APOE-TREM2 ligand-receptor pairs, associated with AD progression. In both human and mouse models, TREM2 deficiency disrupted GPNMB expansion and reduced phagocytic function, suggesting that GPNMB's role in neuroprotection was TREM2-dependent. Our findings clarify myeloid subtypes implicated in aging and AD, advancing the mechanistic understanding of their role in AD and aiding therapeutic discovery.

Oleanonic acid ameliorates mutant Aβ precursor protein-induced oxidative stress, autophagy deficits, ferroptosis, mitochondrial damage, and ER stress in vitro

Accumulation in the brain of amyloid-β (Aβ), derived from cleavage of Aβ precursor protein (APP), is a hallmark of Alzheimer's disease (AD). Oleanonic acid (OA), a phytochemical from several plants, has proven anti-inflammatory effects, but its role in AD remains unknown. Here we found that OA reduced APP expression and inhibited oxidative stress via Nrf2/HO-1 signaling in SH-SY5Y neuroblastoma cells stably overexpressing APP. OA suppressed phosphorylated mTOR but increased autophagy markers ATG5 and LC3-II. Moreover, OA rescued ferroptosis-related factors GPX4, NCOA, and COX2 and ER stress markers GRP78, CHOP, and three main induction pathways of ER stress including IRE1/XBP1s, PERK/EIF2α, and ATF6. OA alleviated mitochondrial damage through MFN1, MFN2, OPA1, FIS1, and DRP1. Furthermore, OA upregulated GDF11 expression and downregulated phosphorylation of ErbB4 and TrkB without affecting BDNF levels. Thus, OA might protect neurons from APP-induced neurotoxicity by inhibiting oxidative stress, autophagy deficits, ferroptosis, mitochondrial damage, and ER stress in AD, providing a new promising therapeutic strategy in patients with AD.

Network-based identification and mechanism exploration of active ingredients against Alzheimer's disease via targeting endoplasmic reticulum stress from traditional chinese medicine

Alzheimer's disease is a neurodegenerative disease that leads to dementia and poses a serious threat to the health of the elderly. Traditional Chinese medicine (TCM) presents as a promising novel therapeutic therapy for preventing and treating dementia. Studies have shown that natural products derived from kidney-tonifying herbs can effectively inhibit AD. Furthermore, endoplasmic reticulum (ER) stress is a critical factor in the pathology of AD. Regulation of ER stress is a crucial approach to prevent and treat AD. Thus, in this study, we first collected kidney-tonifying herbs, integrated chemical ingredients from multiple TCM databases, and constructed a comprehensive drug-target network. Subsequently, we employed the endophenotype network (network proximity) method to identify potential active ingredients in kidney-tonifying herbs that prevented AD via regulating ER stress. By combining the predicted outcomes, we discovered that 32 natural products could ameliorate AD pathology via regulating ER stress. After a comprehensive evaluation of the multi-network model and systematic pharmacological analyses, we further selected several promising compounds for in vitro testing in the APP-SH-SY5Y cell model. Experimental results showed that echinacoside and danthron were able to effectively reduce ER stress-mediated neuronal apoptosis by inhibiting the expression levels of BIP, p-PERK, ATF6, and CHOP in APP-SH-SY5Y cells. Overall, this study utilized the endophenotype network to preliminarily decipher the effective material basis and potential molecular mechanism of kidney-tonifying Chinese medicine for prevention and treatment of AD.

Long noncoding RNAs in ubiquitination, protein degradation, and human diseases

Protein stability and turnover is critical in normal cellular and physiological process and their misregulation may contribute to accumulation of unwanted proteins causing cellular malfunction, neurodegeneration, mitochondrial malfunction, and disrupted metabolism. Signaling mechanism associated with protein degradation is complex and is extensively studied. Many protein and enzyme machineries have been implicated in regulation of protein degradation. Despite these insights, our understanding of protein degradation mechanisms remains limited. Emerging studies suggest that long non-coding RNAs (lncRNAs) play critical roles in various cellular and physiological processes including metabolism, cellular homeostasis, and protein turnover. LncRNAs, being large nucleic acids (>200 nt long) can interact with various proteins and other nucleic acids and modulate protein structure and function leading to regulation of cell signaling processes. LncRNAs are widely distributed across cell types and may exhibit tissue specific expression. They are detected in body fluids including blood and urine. Their expressions are also altered in various human diseases including cancer, neurological disorders, immune disorder, and others. LncRNAs are being recognized as novel biomarkers and therapeutic targets. This review article focuses on the emerging role of noncoding RNAs (ncRNAs), particularly long noncoding RNAs (lncRNAs), in the regulation of protein polyubiquitination and proteasomal degradation.

Enhancing mitochondrial one-carbon metabolism is neuroprotective in Alzheimer's disease models

Alzheimer's disease (AD) is the most common form of age-related dementia. In AD, the death of neurons in the central nervous system is associated with the accumulation of toxic amyloid β peptide (Aβ) and mitochondrial dysfunction. Mitochondria are signal transducers of metabolic and biochemical information, and their impairment can compromise cellular function. Mitochondria compartmentalise several pathways, including folate-dependent one-carbon (1C) metabolism and electron transport by respiratory complexes. Mitochondrial 1C metabolism is linked to electron transport through complex I of the respiratory chain. Here, we analysed the proteomic changes in a fly model of AD by overexpressing a toxic form of Aβ (Aβ-Arc). We found that expressing Aβ-Arc caused alterations in components of both complex I and mitochondrial 1C metabolism. Genetically enhancing mitochondrial 1C metabolism through Nmdmc improved mitochondrial function and was neuroprotective in fly models of AD. We also found that exogenous supplementation with the 1C donor folinic acid improved mitochondrial health in both mammalian cells and fly models of AD. We found that genetic variations in MTHFD2L, the human orthologue of Nmdmc, were linked to AD risk. Additionally, Mendelian randomisation showed that increased folate intake decreased the risk of developing AD. Overall, our data suggest enhancement of folate-dependent 1C metabolism as a viable strategy to delay the progression and attenuate the severity of AD.

The Mechanistic Link Between Tau-Driven Proteotoxic Stress and Cellular Senescence in Alzheimer's Disease

In Alzheimer's disease (AD), tau dissociates from microtubules (MTs) due to hyperphosphorylation and misfolding. It is degraded by various mechanisms, including the 20S proteasome, chaperone-mediated autophagy (CMA), 26S proteasome, macroautophagy, and aggrephagy. Neurofibrillary tangles (NFTs) form upon the impairment of aggrephagy, and eventually, the ubiquitin chaperone valosin-containing protein (VCP) and heat shock 70 kDa protein (HSP70) are recruited to the sites of NFTs for the extraction of tau for the ubiquitin-proteasome system (UPS)-mediated degradation. However, the impairment of tau degradation in neurons allows tau to be secreted into the extracellular space. Secreted tau can be monomers, oligomers, and paired helical filaments (PHFs), which are seeding competent pathological tau that can be endocytosed/phagocytosed by healthy neurons, microglia, astrocytes, oligodendrocyte progenitor cells (OPCs), and oligodendrocytes, often causing proteotoxic stress and eventually triggers senescence. Senescent cells secrete various senescence-associated secretory phenotype (SASP) factors, which trigger cellular atrophy, causing decreased brain volume in human AD. However, the molecular mechanisms of proteotoxic stress and cellular senescence are not entirely understood and are an emerging area of research. Therefore, this comprehensive review summarizes pertinent studies that provided evidence for the sequential tau degradation, failure, and the mechanistic link between tau-driven proteotoxic stress and cellular senescence in AD.

Phikud navakot extract acts as an ER stress inhibitor to ameliorate ER stress and neuroinflammation

The prevalence of neurological disorders (NDs) such as Alzheimer's disease (AD) is increasing globally, and the lack of effective pharmacological interventions presents a significant health risk. Multiple mechanisms including the activation of oxidative stress, amyloid pathway, ER stress, and neuroinflammation have been implicated in AD; therefore, multi-targeted agents against these mechanisms may be preferable to single-target agents. Phikud Navakot (PN), a Thai traditional medicine combining nine herbs, has been shown to reduce oxidative stress and neuroinflammation of neuronal and microglia cells and the coculture between them, indicating the promising role of PN extract as anti-AD. This study evaluated the neuroprotective effects of PN extract against oxidative stress, amyloid pathway, endoplasmic reticulum stress (ER stress), and neuroinflammation using neuronal and microglia cells, as well as in a Drosophila model of AD. Results showed that PN extract reduced oxidative stress, lipid peroxidation, pro-inflammatory cytokines, amyloid pathway, and ER stress induced by aluminum chloride (AlCl3, AD-induced agent) or thapsigargin (TG, an ER stress activator) in both neurons and microglia cells. PN extract also reduced oxidative stress, ER-stress-related genes, and neurotoxic peptides (amyloid beta) in a Drosophila model of AD. Data indicated that PN extract may function as an anti-AD agent by targeting multiple mechanisms as described. This research also revealed for the first time that PN extract acted as an ER stress inhibitor.

Astaxanthin inhibits apoptosis in a cell model of tauopathy by attenuating endoplasmic reticulum stress and unfolded protein response

The accumulation of misfolded proteins is a common pathological characteristic shared by many neurodegenerative diseases including Alzheimer's disease and Parkinson's disease. The disruption of proteostasis triggers endoplasmic reticulum (ER) stress, during which the unfolded protein response (UPR) is initiated by the activation of protein kinase R-like ER kinase (PERK), inositol-requiring enzyme 1 (IRE1) and activating transcription factor 6 (ATF6). These three branches of UPR signals act in concert to reduce the levels of abnormal proteins and restore ER homeostasis. However, the overactivation of UPR impairs cell function and induces apoptosis, which has been implicated in neurodegeneration. Astaxanthin is a xanthophyll carotenoid which has been shown to have neuroprotective effects in both cell and animal models; however, its effects on ER stress and UPR induced by disrupted proteostasis remain unclear. In this study, the effects of astaxanthin on ER stress and cytotoxicity were investigated in N2a cells stably expressing the pro-aggregant tau repeat domain carrying FTDP-17 mutation ΔK280 (Tau4RDΔK280). The results demonstrated that astaxanthin significantly inhibited Tau4RDΔK280-induced loss of cell viability and apoptosis, attenuating Tau4RDΔK280-induced caspase-3 activation and decrease of Bcl-2. Further studies revealed that astaxanthin treatment alleviated Tau4RDΔK280-induced ER stress and suppressed the activation of PERK, IRE1 and ATF6 signaling pathways. These findings suggested that astaxanthin might inhibit Tau4RDΔK280-induced cytotoxicity by attenuating UPR and ER stress. In addition, astaxanthin treatment resulted in a great reduction in the production of intracellular reactive oxygen species and a significant decrease in calcium influx induced by Tau4RDΔK280, which also contributed to the protective effects of astaxanthin against Tau4RDΔK280-induced cytotoxicity.

Mitochondrial Quality Control in Alzheimer's Disease: Insights from Caenorhabditis elegans Models

Alzheimer's disease (AD) is a complex neurodegenerative disorder that is classically defined by the extracellular deposition of senile plaques rich in amyloid-beta (Aβ) protein and the intracellular accumulation of neurofibrillary tangles (NFTs) that are rich in aberrantly modified tau protein. In addition to aggregative and proteostatic abnormalities, neurons affected by AD also frequently possess dysfunctional mitochondria and disrupted mitochondrial maintenance, such as the inability to eliminate damaged mitochondria via mitophagy. Decades have been spent interrogating the etiopathogenesis of AD, and contributions from model organism research have aided in developing a more fundamental understanding of molecular dysfunction caused by Aβ and toxic tau aggregates. The soil nematode C. elegans is a genetic model organism that has been widely used for interrogating neurodegenerative mechanisms including AD. In this review, we discuss the advantages and limitations of the many C. elegans AD models, with a special focus and discussion on how mitochondrial quality control pathways (namely mitophagy) may contribute to AD development. We also summarize evidence on how targeting mitophagy has been therapeutically beneficial in AD. Lastly, we delineate possible mechanisms that can work alone or in concert to ultimately lead to mitophagy impairment in neurons and may contribute to AD etiopathology.

trans-chalcone ameliorates CCl4-induced acute liver injury by suppressing endoplasmic reticulum stress, oxidative stress and inflammation

BACKGROUND

Acute liver injury serves as a crucial marker for detecting liver damage due to toxic, viral, metabolic, and autoimmune exposures. Due to the response to adverse external stimuli and various cellular homeostasis, Endoplasmic reticulum stress (ERS), Oxidative stress, and Inflammation have great potential for treating liver injury. Trans-chalcones (TC) is a polyphenolic compound derived from a natural plant with anti-oxidative and anti-inflammatory abilities. Here, TC was aimed to attenuate liver injury by triggering ER stress, oxidative stress, inflammation, and apoptosis. A single dose of carbon tetrachloride (CCl4) 1 mL/kg was administered intraperitoneally into C57BL6 mice to construct an in vivo NAFLD model, whereas AML12 cells were treated with lipopolysaccharides (LPS) to construct an in vitro NAFLD model. The mice used in the experiment were randomly assigned to two groups: a 12-hour set and a 24-hour set. Forty-nine mice were randomly divided into seven groups, the control group (Group I), TC group (Group II) 10 mg/kg TC, negative control group (Group III) CCl4, TC + CCl4 groups (Groups IV-VI), mice were subcutaneously treated with (5, 10, and 20) mg/kg of TC for three consecutive days before the CCl4 injection and the positive control group (Group VII) received 10 mg/kg Silymarin. After the experiment, serum transaminase, liver histological pathology, hepatic expression levels ERS, oxidative stress, and inflammation-related markers were assessed. TC pre-treatment significantly alleviates the expression of ER stress, oxidative stress, inflammatory cytokines, and apoptosis in both in vivo and in vitro models of liver injury. TC treatment significantly reduced serum transaminase levels (ALT and AST), and improved liver histopathological scores. TC administration also led to a reduction in MDA levels and the suppression of ROS generated by CCl4 in hepatic tissue, which contributed to an increase in GSH levels. The protective effect of TC on the liver injury mouse model was achieved by inhibiting hepatocyte apoptosis. Moreover, TC pre-treatment dramatically decreased the protein levels of ER stress indicators such as CHOP, Bip, Ero-Lα, IRE1α, PERK, Calnexin, and PDI when compared to the CCl4-only treated group. TC exerts hepatoprotective effects against CCl4-induced acute liver injuries in mice by modulating ERS, oxidative stress, and inflammation. These results suggest that TC pre-treatment at a dose of (20 mg/kg BW) was as effective as silymarin (10 mg/kg) in preventing CCl4-induced acute liver injury. Further investigations are necessary to elucidate the precise molecular mechanisms underlying the hepatoprotective effects of TC and to explore its therapeutic potential in clinical trials.

Bacopa monnieri confers neuroprotection by influencing signaling pathways associated with interleukin 4, 13 and extracellular matrix organization in Alzheimer's disease: A proteomics-based perspective

Alzheimer's disease, a prevalent neurodegenerative disorder in the elderly, is characterized by the accumulation of senile plaques and neurofibrillary tangles, triggering oxidative stress, neuroinflammation, and neuronal apoptosis. Current therapies focus on symptomatic treatment rather than targeting the underlying disease-modifying molecular mechanisms and are often associated with significant side effects. Bacopa monnieri, a traditional Indian herb with nootropic properties, has shown promise in neurological disorder treatment from ancient times. However, its mechanisms of action in Alzheimer's disease remain elusive. In this study, a cellular model for Alzheimer's disease was created by treating differentiated IMR-32 cells with beta-amyloid, 1-42 peptide (Aβ42). Additionally, a recovery model was established through co-treatment with Bacopa monnieri to explore its protective mechanism. Co-treatment with Bacopa monnieri extract recovered Aβ42 induced damage as evidenced by the decreased apoptosis and reduced reactive oxygen species production. Mass spectrometry-based quantitative proteomic analysis identified 21,674 peptides, corresponding to 3626 proteins from the Alzheimer's disease model. The proteins dysregulated by Aβ42 were implicated in cellular functions, such as negative regulation of cell proliferation and microtubule cytoskeleton organization. The enriched pathways include extracellular matrix organization and interleukin-4 and interleukin-13 signaling. Bacopa monnieri co-treatment showed remarkable restoration of Aβ42 altered proteins, including FOSL1, and TDO2. The protein-protein interaction network analysis of Bacopa monnieri restored proteins identified the hub gene involved in Alzheimer's disease. The findings from this study may open up new avenues for creating innovative therapeutic approaches for Alzheimer's disease.

Beyond Wolfram Syndrome 1: The WFS1 Gene's Role in Alzheimer's Disease and Sleep Disorders

The WFS1 gene was first identified in Wolfram Syndrome 1 (WS1), a rare autosomal recessive genetic disorder characterized by severe and progressive neurodegenerative changes. WFS1's role in various cellular mechanisms, particularly in calcium homeostasis and the modulation of endoplasmic reticulum (ER) stress, suggests its potential involvement in the pathogenesis of Alzheimer's disease (AD) and sleep disorders. Because it is involved in maintaining ER balance, calcium signaling, and stress responses, WFS1 plays a multifaceted role in neuronal health. Numerous studies have shown that the absence or improper expression of WFS1 disrupts these cellular processes, leading to neurodegeneration and making neurons more vulnerable. In AD, WFS1 dysfunction is thought to contribute to the accumulation of amyloid-β (Aβ) plaques and tau tangles, thereby accelerating disease progression. Additionally, WFS1 plays an essential role in sleep regulation by influencing neuronal excitability and neurotransmitter release, which may explain the sleep disturbances frequently observed in neurodegenerative diseases. Due to its involvement in the pathological mechanisms of AD and sleep disorders, WFS1 is regarded as a potential early diagnostic marker for these diseases. Further research is required to fully elucidate WFS1's role in the cellular pathway, perhaps facilitating the development of new therapeutic strategies for Alzheimer's disease and sleep disorders.

Exploration of the shared gene signatures and molecular mechanisms between Alzheimer's disease and intracranial aneurysm

Although Alzheimer's disease (AD) and intracranial aneurysm (IA) were two different types of diseases that occurred in the brain, ruptured IA (RIA) survivors may experience varying degrees of cognitive dysfunction. Neither AD nor IA is easily recognizable by an early onset so that the incidence of adverse clinical outcomes would be on the rise. Therefore, we focused on the exploration of the shared genes and molecular mechanisms between AD and IA, which would be significant for the efficiency of co-screening and co-diagnosis. Two GEO datasets were selected for the weighted gene co-expression network analysis (WGCNA) and differentially expressed gene screening, obtaining 78 overlapped genes. Next, 9 hub genes were identified by the protein-protein interaction network, including PIK3CA, GAB1, IGF1R, PLCB1, PGR, PDGFRB, PLCE1, FGFR3, and SYNJ1. The interactions among the hub genes, miRNA, and TFs were also explored. Meanwhile, we performed GO and KEGG pathway enrichment analyses for the results of WGCNA and hub genes, which showed that the Ras signaling and Rap1 signaling were the main shared pathogenesis. In conclusion, the present bioinformatics analysis revealed that AD and IA had the shared genes and molecular mechanisms, and these outcomes were associated with inflammation and calcium homeostasis, which could provide research clues for further studies.

Increased expression of mesencephalic astrocyte-derived neurotrophic factor (MANF) contributes to synapse loss in Alzheimer's disease

BACKGROUND

The activation of endoplasmic reticulum (ER) stress is an early pathological hallmark of Alzheimer's disease (AD) brain, but how ER stress contributes to the onset and development of AD remains poorly characterized. Mesencephalic astrocyte-derived neurotrophic factor (MANF) is a non-canonical neurotrophic factor and an ER stress inducible protein. Previous studies reported that MANF is increased in the brains of both pre-symptomatic and symptomatic AD patients, but the consequence of the early rise in MANF protein is unknown.

METHODS

We examined the expression of MANF in the brain of AD mouse models at different pathological stages. Through behavioral, electrophysiological, and neuropathological analyses, we assessed the level of synaptic dysfunctions in the MANF transgenic mouse model which overexpresses MANF in the brain and in wild type (WT) mice with MANF overexpression in the hippocampus. Using proteomic and transcriptomic screening, we identified and validated the molecular mechanism underlying the effects of MANF on synaptic function.

RESULTS

We found that increased expression of MANF correlates with synapse loss in the hippocampus of AD mice. The ectopic expression of MANF in mice via transgenic or viral approaches causes synapse loss and defects in learning and memory. We also identified that MANF interacts with ELAV like RNA-binding protein 2 (ELAVL2) and affects its binding to RNA transcripts that are involved in synaptic functions. Increasing or decreasing MANF expression in the hippocampus of AD mice exacerbates or ameliorates the behavioral deficits and synaptic pathology, respectively.

CONCLUSIONS

Our study established MANF as a mechanistic link between ER stress and synapse loss in AD and hinted at MANF as a therapeutic target in AD treatment.

Effects of treadmill exercise on endoplasmic reticulum protein folding and endoplasmic reticulum-associated protein degradation pathways in APP/PS1 mice

A hallmark of Alzheimer's disease (AD) is the disruption of protein homeostasis (proteostasis), manifested by the misfolding and aggregation of proteins. Molecular chaperones and the endoplasmic reticulum (ER)-associated protein degradation (ERAD) pathway in the ER are essential for correct protein folding and degradation of misfolded proteins respectively, thus contributing to the maintenance of proteostasis. The present study aimed to investigate whether the beneficial effects of exercise in an AD mice model is associated with changes in ER protein folding and ERAD. APP/PS1 transgenic and wild-type mice were subjected to treadmill exercise for three months. The levels of molecular chaperones, specifically protein disulfide isomerases (PDIs) and heat shock proteins (HSPs), as well as ERAD-associated molecules were analyzed in the hippocampus. The result revealed a decrease in mRNA levels of PDIA2, PDIA3, PDIA4, PDIA5, PDIA6, HSPA1B, HSPA8, HSP90B1, DNAJB2, CRYAB, and CNX, an increase in mRNA levels of HSPA5 and HSPH1, an increase in protein levels of HERPUD1, and a decrease in protein levels of VCP in APP/PS1 mice. However, following a 3-month treadmill exercise regimen, an increase in mRNA levels of PDIA2, PDIA4, PDIA6, HSPA1A, HSPA8, HSP90AB1, and DNAJB2, as well as an increase in protein levels of VCP and DERL2, and a decrease in protein levels of HERPUD1 were noted. Overall, our findings indicate that disruptions in hippocampal ER protein folding and ERAD pathways may be implicated in AD, with exercise serving as a regulator of these pathways.

Transcriptome and proteome profiling reveals TREM2-dependent and -independent glial response and metabolic perturbation in an Alzheimer's mouse model

Elucidating the intricate molecular mechanisms of Alzheimer's disease (AD) requires a multidimensional analysis incorporating various omics data. In this study, we employed transcriptome and proteome profiling of AppNL-G-F, a human APP knock-in model of amyloidosis, at the early and mid-stages of amyloid-beta (Aβ) pathology to delineate the impacts of Aβ deposition on brain cells. By contrasting AppNL-G-F mice with TREM2 (Triggering receptor expressed on myeloid cells 2) knockout models, our study further investigates the role of TREM2, a well-known AD risk gene, in influencing microglial responses to Aβ pathology. Our results highlight altered microglial states as a central feature of Aβ pathology, characterized by the significant upregulation of microglia-specific genes related to immune responses such as complement system and antigen presentation, and catabolic pathways such as phagosome formation and lysosome biogenesis. The absence of TREM2 markedly diminishes the induction of these genes, impairs Aβ clearance, and exacerbates dystrophic neurite formation. Importantly, TREM2 is required for the microglial engagement with Aβ plaques and the formation of compact Aβ plaque cores. Furthermore, this study reveals substantial disruptions in energy metabolism and protein synthesis, signaling a shift from anabolism to catabolism in response to Aβ deposition. This metabolic alteration, coupled with a decrease in synaptic protein abundance, occurs independently of TREM2, suggesting the direct effects of Aβ deposition on synaptic integrity and plasticity. In summary, our findings demonstrate altered microglial states and metabolic disruption following Aβ deposition, offering mechanistic insights into Aβ pathology and highlighting the potential of targeting these pathways in AD therapy.

ERO1A inhibition mitigates neuronal ER stress and ameliorates UBQLN2ALS phenotypes in Drosophila melanogaster

Modulating the ER stress pathway holds therapeutic promise for neurodegenerative diseases; however, identifying optimal targets remains challenging. In this study, we conducted an unbiased screening to systematically search for commonly up-regulated proteins in ER stress-related neurodegenerative conditions, with endoplasmic reticulum oxidoreductase 1 alpha (ERO1A) emerging as a significant hit. Further experiments conducted in the model organism Drosophila melanogaster demonstrated that elevated levels of Drosophila ERO1A (ERO1L) were indeed detrimental to neurons. Conversely, genetic suppression or pharmacological inhibition of ERO1L activity provided neuroprotection under ER stress and extended the lifespan of flies. To translate these findings, we performed a genetic modifier screening and underscored significant neuroprotective effects against UBQLN2ALS pathology. Additionally, administration of the chemical probe inhibitor of ERO1A, known as EN460, enhanced locomotive functions and neuromuscular junction (NMJ) morphology in Drosophila UBQLN2ALS model. Mechanistically, targeting ERO1L during environmental or pathological ER stress mitigated proteotoxic stress by lowering either the PERK or IRE1 branches of the unfolded protein response (UPR). These findings suggest ERO1A as a promising therapeutic target in UBQLN2ALS and other ER stress-related conditions.

Refined diet consumption increases neuroinflammatory signalling through bile acid dysmetabolism

Over recent decades, dietary patterns have changed significantly due to the increasing availability of convenient, ultra-processed refined foods. Refined foods are commonly depleted of key bioactive compounds, which have been associated with several deleterious health conditions. As the gut microbiome can influence the brain through a bidirectional communication system known as the 'microbiota-gut-brain axis', the consumption of refined foods has the potential to affect cognitive health. In this study, multi-omics approaches were employed to assess the effect of a refined diet on the microbiota-gut-brain axis, with a particular focus on bile acid metabolism. Mice maintained on a refined low-fat diet (rLFD), consisting of high sucrose, processed carbohydrates and low fibre content, for eight weeks displayed significant gut microbial dysbiosis, as indicated by diminished alpha diversity metrics (p < 0.05) and altered beta diversity (p < 0.05) when compared to mice receiving a chow diet. Changes in gut microbiota composition paralleled modulation of the metabolome, including a significant reduction in short-chain fatty acids (acetate, propionate and n-butyrate; p < 0.001) and alterations in bile acid concentrations. Interestingly, the rLFD led to dysregulated bile acid concentrations across both the colon (p < 0.05) and the brain (p < 0.05) which coincided with altered neuroinflammatory gene expression. In particular, the concentration of TCA, TDCA and T-α-MCA was inversely correlated with the expression of NF-κB1, a key transcription factor in neuroinflammation. Overall, our results suggest a novel link between a refined low-fat diet and detrimental neuronal processes, likely in part through modulation of the microbiota-gut-brain axis and bile acid dysmetabolism.