Impaired mitochondrial biogenesis, defective axonal transport of mitochondria, abnormal mitochondrial dynamics and synaptic degeneration in a mouse model of Alzheimer's disease

Mitophagy in Alzheimer's disease and other metabolic disorders: A focus on mitochondrial-targeted therapeutics

Mitochondria, as central regulators of cellular processes such as energy production, apoptosis, and metabolic homeostasis, are essential to cellular function and health. The maintenance of mitochondrial integrity, especially through mitophagy-the selective removal of impaired mitochondria-is crucial for cellular homeostasis. Dysregulation of mitochondrial function, dynamics, and biogenesis is linked to neurodegenerative and metabolic diseases, notably Alzheimer's disease (AD), which is increasingly recognized as a metabolic disorder due to its shared pathophysiologic features: insulin resistance, oxidative stress, and chronic inflammation. In this review, we highlight recent advancements in pharmacological interventions, focusing on agents that modulate mitophagy, mitochondrial uncouplers that reduce oxidative phosphorylation, compounds that directly scavenge reactive oxygen species to alleviate oxidative stress, and molecules that ameliorate amyloid beta plaque accumulation and phosphorylated tau pathology. Additionally, we explore dietary and lifestyle interventions-MIND and ketogenic diets, caloric restriction, physical activity, hormone modulation, and stress management-that complement pharmacological approaches and support mitochondrial health. Our review underscores mitochondria's central role in the pathogenesis and potential treatment of neurodegenerative and metabolic diseases, particularly AD. By advocating for an integrated therapeutic model that combines pharmacological and lifestyle interventions, we propose a comprehensive approach aimed at mitigating mitochondrial dysfunction and improving clinical outcomes in these complex, interrelated diseases.

Mitochondrial Alterations in Alzheimer's Disease: Insight from the 5xFAD Mouse Model

Mitochondrial dysfunction is increasingly recognized as a key factor in Alzheimer's disease (AD) pathogenesis, but the precise relationship between mitochondrial dynamics and proteinopathies in AD remains unclear. This study investigates the role of mitochondrial dynamics and function in the hippocampal tissue and peripheral blood mononuclear cells (PBMCs) of 5xFAD transgenic mice, as a model of AD. The levels of mitochondrial fusion proteins OPA1 and MFN2 and fission proteins DRP1 and phospho-DRP1 (S616) at 3, 6, and 9 months of age were assessed. Western blot analysis revealed significantly lower levels of OPA1 and MFN2 in the hippocampus of 6- and 9-month-old transgenic (TG) 5xFAD mice compared to controls (CTR), while DRP1 and pDRP1 levels were increased in 9-month-old TG mice. Additionally, MFN2 were decreased in the PBMCs of 9-month-old TG mice, indicating systemic mitochondrial alterations. Ultrastructural analysis of hippocampal tissues showed substantial alterations in mitochondrial morphology, including abnormalities in size and shape, a preponderance of teardrop-shaped mitochondria, and alterations in the somatic mitochondria-ER complex. Notably, mitochondria-associated ER contact sites were more distant in TG mice, suggesting functional impairments. Flow cytometric measurements demonstrated decreased mitochondrial membrane potential and mass, along with increased superoxide production, in the PBMCs of TG mice, particularly at 9 months, highlighting compromised mitochondrial function. Levels of key mitochondrial proteins including VDAC, TOM2O, and mitophagy-related protein PINK1 levels altered in both central and peripheral tissue of TG mice. These findings suggest that mitochondrial dysfunction and altered dynamics are early events in AD development in 5xFAD mice, manifesting in both central and peripheral tissues, and support the notion that mitochondrial abnormalities are an integral component of AD pathology. These insights might lead to the development of targeted therapies that modulate mitochondrial dynamics and function to mitigate AD progression.

Chronic Exercise Protects Against Cognitive Deficits in an Alzheimer's Disease Model by Enhancing Autophagy and Reducing Mitochondrial Abnormalities

Alzheimer's disease (AD) is characterized by amyloid-β (Aβ) accumulation, autophagic lysosomal pathway (ALP) dysfunction, mitochondrial abnormalities, and neuroinflammation. Physical exercise (PE) protects against AD, but its molecular mechanisms remain unclear. We hypothesize that PE-mediated upregulation of REV-ERBα and TFEB pathways mitigates AD-related dysfunctions. Acute effects of FK506, a calcineurin inhibitor, were assessed as a TFEB suppressor in mice subjected to aerobic exercise. Chronic treadmill training (8 weeks, 4 sessions/week) was performed in APP/PS1 mice to evaluate hippocampal adaptations through functional tests, imaging, and molecular analyses. Acute FK506 administration inhibited Ppp3ca and Ppp3r1 expression without altering Tfeb levels. Chronic PE improved aerobic capacity, strength, coordination, and memory, promoted neuronal survival, and decreased Aβ levels in APP mice. It also elevated REV-ERBα protein and Nr1 d1 expression in wild-type and APP mice, increased ALP activity, and reduced abnormal mitochondria in the hippocampus of APP mice. A positive correlation between REV-ERBα and Nr1 d1 levels was observed in the 2-min NOR test. Public RNA-seq data revealed lower NR1D1 mRNA in extracellular vesicles from the human frontal cortex of AD patients compared to controls. PE prevents cognitive decline in APP/PS1 mice, enhancing memory, physical performance, and hippocampal health. These benefits are associated with ALP activation, mitochondrial improvements, and reduced neuroinflammation. REV-ERBα may mediate these protective effects, but further studies using pharmacological and genetic models are needed to confirm its role.

A novel Dual GLP-1/CCK Receptor Agonist Improves Cognitive Performance and Synaptogenesis in the 5 × FAD Alzheimer Mouse Model

Glucagon-like peptide 1 (GLP-1) is a peptide hormone and growth factor. Cholecystokinin (CCK) is another peptide hormone, growth factor and neurotransmitter. Both peptide hormones have shown good neuroprotective effects in animal models of Alzheimer's disease (AD). In this study, we tested the effects of a dual GLP-1/CCK (25 nmol/kg ip. for 14 days) receptor agonist that had previously shown good effects in animal models of diabetes. The GLP-1 analogue Liraglutide (50 nmol/kg ip.) was used as a positive control. Memory was improved in the water maze and the Y-maze, spontaneous activity was increased, the chronic inflammation response had been reduced and levels of NLRP3, IL-10 and TNFα were brought back to physiological levels. Levels of amyloid aggregates in the brain were reduced by the drugs. The expression of proteins SIRPα and CD47 which is related to reduced inflammation levels was reduced. Importantly, growth factor signalling was much improved and growth levels of BDNF, TrkB receptor, p-CREB, and an upregulation of the PI3K-AKT signalling pathway had been observed. Post-synaptic density protein (PSD) and synaptophysin levels were reduced, too. In transmission electron microscope analysis, the synaptic cleft was found to be wider in 5xFAD mice. In Golgi stain evaluations, synapse numbers were brought back to normal levels by the drugs. In a direct comparison with Liraglutide, the dual GLP-1/CCK receptor agonist was superior in the water maze tests and in the upregulation of BDNF and TrkB levels in the brain. In other parameters, the dual agonist and Liraglutide showed comparable effects. In conclusion, the combination of GLP-1 and CCK receptor activation did not show overall improvements over single GLP-1 receptor activation.

Unraveling the mystery of citrate transporters in Alzheimer's disease: An updated review

A key molecule in cellular metabolism, citrate is essential for lipid biosynthesis, energy production, and epigenetic control. The etiology of Alzheimer's disease (AD), a progressive neurodegenerative illness marked by memory loss and cognitive decline, may be linked to dysregulated citrate transport, according to recent research. Citrate transporters, which help citrate flow both inside and outside of cells, are becoming more and more recognized as possible participants in the molecular processes underlying AD. Citrate synthase (CS), a key enzyme in the tricarboxylic acid (TCA) cycle, supports mitochondrial function and neurotransmitter synthesis, particularly acetylcholine (ACh), essential for cognition. Changes in CS activity affect citrate availability, influencing energy metabolism and neurotransmitter production. Choline, a precursor for ACh, is crucial for neuronal function. Lipid metabolism, oxidative stress reactions, and mitochondrial function can all be affected by aberrant citrate transport, and these changes are linked to dementia. Furthermore, the two main pathogenic characteristics of AD, tau hyperphosphorylation and amyloid-beta (Aβ) aggregation, may be impacted by disturbances in citrate homeostasis. The goal of this review is to clarify the complex function of citrate transporters in AD and provide insight into how they contribute to the development and course of the illness. We aim to provide an in-depth idea of which particular transporters are dysregulated in AD and clarify the functional implications of these dysregulated transporters in brain cells. To reduce neurodegenerative processes and restore metabolic equilibrium, we have also discussed the therapeutic potential of regulating citrate transport. Gaining insight into the relationship between citrate transporters and the pathogenesis of AD may help identify new indicators for early detection and creative targets for treatment. This study offers hope for more potent ways to fight this debilitating illness and is a crucial step in understanding the metabolic foundations of AD.

Mitochondria at the crossroads: Quality control mechanisms in neuronal senescence and neurodegeneration

Mitochondria play a central role in essential cellular processes, including energy metabolism, biosynthesis of metabolic substances, calcium ion storage, and regulation of cell death. Maintaining mitochondrial quality control is critical for preserving mitochondrial health and ensuring cellular function. Given their high energy demands, neurons depend on effective mitochondrial quality control to sustain their health and functionality. Neuronal senescence, characterized by a progressive decline in structural integrity and function, is a hallmark of neurodegenerative diseases. In senescent neurons, abnormal mitochondrial morphology, functional impairments, increased reactive oxygen species production and disrupted quality control mechanisms are frequently observed. Understanding the pathological changes in neuronal structure, exploring the intricate relationship between mitochondrial quality control and neuronal health, and leveraging mitochondrial quality control interventions provide a promising foundation for addressing age-related neurodegenerative diseases. This review highlights key mitochondrial quality control, including biogenesis, dynamics, the ubiquitin-proteasome system, autophagy pathways, mitochondria-derived vesicles, and inter-organelle communication, while discussing their roles in neuronal senescence and potential therapeutic strategies. These insights may pave the way for innovative treatments to mitigate neurodegenerative disorders.

Alzheimer's Is a Multiform Disease of Sustained Neuronal Integrated Stress Response Driven by the C99 Fragment Generated Independently of AβPP; Proteolytic Production of Aβ Is Suppressed in AD-Affected Neurons: Evolution of a Theory

The present Perspective analyzes the remarkable evolution of the Amyloid Cascade Hypothesis 2.0 (ACH2.0) theory of Alzheimer's disease (AD) since its inception a few years ago, as reflected in the diminishing role of amyloid-beta (Aβ) in the disease. In the initial iteration of the ACH2.0, Aβ-protein-precursor (AβPP)-derived intraneuronal Aβ (iAβ), accumulated to neuronal integrated stress response (ISR)-eliciting levels, triggers AD. The neuronal ISR, in turn, activates the AβPP-independent production of its C99 fragment that is processed into iAβ, which drives the disease. The second iteration of the ACH2.0 stemmed from the realization that AD is, in fact, a disease of the sustained neuronal ISR. It introduced two categories of AD-conventional and unconventional-differing mainly in the manner of their causation. The former is caused by the neuronal ISR triggered by AβPP-derived iAβ, whereas in the latter, the neuronal ISR is elicited by stressors distinct from AβPP-derived iAβ and arising from brain trauma, viral and bacterial infections, and various types of inflammation. Moreover, conventional AD always contains an unconventional component, and in both forms, the disease is driven by iAβ generated independently of AβPP. In its third, the current, iteration, the ACH2.0 posits that proteolytic production of Aβ is suppressed in AD-affected neurons and that the disease is driven by C99 generated independently of AβPP. Suppression of Aβ production in AD seems an oxymoron: Aβ is equated with AD, and the later is inconceivable without the former in an ingrained Amyloid Cascade Hypothesis (ACH)-based notion. But suppression of Aβ production in AD-affected neurons is where the logic leads, and to follow it we only need to overcome the inertia of the preexisting assumptions. Moreover, not only is the generation of Aβ suppressed, so is the production of all components of the AβPP proteolytic pathway. This assertion is not a quantum leap (unless overcoming the inertia counts as such): the global cellular protein synthesis is severely suppressed under the neuronal ISR conditions, and there is no reason for constituents of the AβPP proteolytic pathway to be exempted, and they, apparently, are not, as indicated by the empirical data. In contrast, tau protein translation persists in AD-affected neurons under ISR conditions because the human tau mRNA contains an internal ribosomal entry site in its 5'UTR. In current mouse models, iAβ derived from AβPP expressed exogenously from human transgenes elicits the neuronal ISR and thus suppresses its own production. Its levels cannot principally reach AD pathology-causing levels regardless of the number of transgenes or the types of FAD mutations that they (or additional transgenes) carry. Since the AβPP-independent C99 production pathway is inoperative in mice, the current transgenic models have no potential for developing the full spectrum of AD pathology. What they display are only effects of the AβPP-derived iAβ-elicited neuronal ISR. The paper describes strategies to construct adequate transgenic AD models. It also details the utilization of human neuronal cells as the only adequate model system currently available for conventional and unconventional AD. The final alteration of the ACH2.0, introduced in the present Perspective, is that AβPP, which supports neuronal functionality and viability, is, after all, potentially produced in AD-affected neurons, albeit not conventionally but in an ISR-driven and -compatible process. Thus, the present narrative begins with the "omnipotent" Aβ capable of both triggering and driving the disease and ends up with this peptide largely dislodged from its pedestal and retaining its central role in triggering the disease in only one, although prevalent (conventional), category of AD (and driving it in none). Among interesting inferences of the present Perspective is the determination that "sporadic AD" is not sporadic at all ("non-familial" would be a much better designation). The term has fatalistic connotations, implying that the disease can strike at random. This is patently not the case: The conventional disease affects a distinct subpopulation, and the basis for unconventional AD is well understood. Another conclusion is that, unless prevented, the occurrence of conventional AD is inevitable given a sufficiently long lifespan. This Perspective also defines therapeutic directions not to be taken as well as auspicious ways forward. The former category includes ACH-based drugs (those interfering with the proteolytic production of Aβ and/or depleting extracellular Aβ). They are legitimate (albeit inefficient) preventive agents for conventional AD. There is, however, a proverbial snowball's chance in hell of them being effective in symptomatic AD, lecanemab, donanemab, and any other "…mab" or "…stat" notwithstanding. They comprise Aβ-specific antibodies, inhibitors of beta- and gamma-secretase, and modulators of the latter. In the latter category, among ways to go are the following: (1) Depletion of iAβ, which, if sufficiently "deep", opens up a tantalizing possibility of once-in-a-lifetime preventive transient treatment for conventional AD and aging-associated cognitive decline, AACD. (2) Composite therapy comprising the degradation of C99/iAβ and concurrent inhibition of the neuronal ISR. A single transient treatment could be sufficient to arrest the progression of conventional AD and prevent its recurrence for life. Multiple recurrent treatments would achieve the same outcome in unconventional AD. Alternatively, the sustained reduction/removal of unconventional neuronal ISR-eliciting stressors through the elimination of their source would convert unconventional AD into conventional one, preventable/treatable by a single transient administration of the composite C99/iAβ depletion/ISR suppression therapy. Efficient and suitable ISR inhibitors are available, and it is explicitly clear where to look for C99/iAβ-specific targeted degradation agents-activators of BACE1 and, especially, BACE2. Directly acting C99/iAβ-specific degradation agents such as proteolysis-targeting chimeras (PROTACs) and molecular-glue degraders (MGDs) are also viable options. (3) A circumscribed shift (either upstream or downstream) of the position of transcription start site (TSS) of the human AβPP gene, or, alternatively, a gene editing-mediated excision or replacement of a small, defined segment of its portion encoding 5'-untranslated region of AβPP mRNA; targeting AβPP RNA with anti-antisense oligonucleotides is another possibility. If properly executed, these RNA-based strategies would not interfere with the protein-coding potential of AβPP mRNA, and each would be capable of both preventing and stopping the AβPP-independent generation of C99 and thus of either preventing AD or arresting the progression of the disease in its conventional and unconventional forms. The paper is interspersed with "validation" sections: every conceptually significant notion is either validated by the existing data or an experimental procedure validating it is proposed.

Collapsin Response Mediator Protein 2 (CRMP2) Modulates Mitochondrial Oxidative Metabolism in Knock-In AD Mouse Model

We explored how the phosphorylation state of collapsin response mediator protein 2 (CRMP2) influences mitochondrial functions in cultured cortical neurons and cortical synaptic mitochondria isolated from APP-SAA KI mice, a knock-in APP mouse model of Alzheimer's disease (AD). CRMP2 phosphorylation was increased at Thr 509/514 and Ser 522 in brain cortical lysates and cultured neurons from AD mice. The basal and maximal respiration of AD neurons were decreased. Mitochondria were hyperpolarized and superoxide anion production was increased in neurons from AD mice. In isolated synaptic AD mitochondria, ADP-stimulated and DNP-stimulated respiration were decreased, whereas ADP-induced mitochondrial depolarization was reduced and prolonged. We found that CRMP2 binds to the adenine nucleotide translocase (ANT) in a phosphorylation-dependent manner. The increased CRMP2 phosphorylation in AD mice correlated with CRMP2 dissociation from the ANT and decreased ANT activity in AD mitochondria. On the other hand, recombinant CRMP2 (rCRMP2), added to the ANT-reconstituted proteoliposomes, increased ANT activity. A small molecule (S)-lacosamide ((S)-LCM), which binds to CRMP2 and suppresses CRMP2 phosphorylation by Cdk5 and GSK-3β, prevented CRMP2 hyperphosphorylation, rescued CRMP2 binding to the ANT, improved ANT activity, and restored the mitochondrial membrane potential and respiratory responses to ADP and 2,4-dinitrophenol. Thus, our study highlights an important role for CRMP2 in regulating the mitochondrial oxidative metabolism in AD by modulating the ANT activity in a phosphorylation-dependent manner.

Enhancing Mitochondrial Function Through Pharmacological Modification: A Novel Approach to Mitochondrial Transplantation in a Sepsis Model

Background/Objectives: Sepsis continues to be a significant global health issue, with current treatments primarily focused on antibiotics, fluid resuscitation, vasopressors, or steroids. Recent studies have started to explore mitochondrial transplantation as a potential treatment for sepsis. This study aims to evaluate the effects of enhanced mitochondrial transplantation on sepsis. Methods: We examined various mitochondrial-targeting drugs (formoterol, metformin, CoQ10, pioglitazone, fenofibrate, and elamipretide) to improve mitochondrial function prior to transplantation. Mitochondrial function was assessed by measuring the oxygen consumption rate (OCR) and analyzing the expression of genes related to mitochondrial biogenesis. Additionally, the effects of enhanced mitochondrial transplantation on inflammation were investigated using an in vitro sepsis model with THP-1 cells. Results: Formoterol significantly increased mitochondrial biogenesis, as evidenced by enhanced oxygen consumption rates and the upregulation of mitochondrial-associated genes, including those related to biogenesis (PGC-1α: 1.56-fold, p < 0.01) and electron transport (mt-Nd6: 1.13-fold, p = 0.16; mt-Cytb: 1.57-fold, p < 0.001; and mt-Co2: 1.44-fold, p < 0.05). Furthermore, formoterol-enhanced mitochondrial transplantation demonstrated a substantial reduction in TNF-α levels in LPS-induced hyperinflammatory THP-1 cells (untreated: 915.91 ± 12.03 vs. formoterol-treated: 529.29 ± 78.23 pg/mL, p < 0.05), suggesting its potential to modulate immune responses. Conclusions: Mitochondrial transplantation using drug-enhancing mitochondrial function might be a promising strategy in sepsis.

Mitochondrial dynamics and bioenergetics in Alzheimer's induced pluripotent stem cell-derived neurons

Mitochondrial dysfunction is a hallmark of Alzheimer's disease, but the scope and severity of these specific deficits across forms of Alzheimer's disease are not well characterized. We designed a high-throughput longitudinal phenotypic assay to track mitochondrial dynamics and bioenergetics in glutamatergic induced pluripotent stem cell (iPSC)-derived human neurons possessing mutations in presenilin 1 (PSEN1), presenilin 2 (PSEN2) and the amyloid beta precursor protein (APP). Each gene set was composed of iPSC-derived neurons from an Alzheimer's disease patient in addition to two to three engineered mutations with appropriate isogenic and age-matched controls. These iPSC-derived neurons were imaged every other day, beginning at 10 days in vitro, to assess how mitochondrial length and content change over a 10 day time course using a mitochondrially targeted reporter. A second cytosolic reporter allowed for visualization of neurites. Bioenergetics assays, focusing on mitochondrial respiration and individual electron transport chain complexes, were also surveyed over this time course. Mutations in all three genes altered mitochondrial function measured by basal, ATP-linked and maximal oxygen consumption rates and by spare respiratory capacity, with PSEN1/PSEN2 alleles being more severe than APP mutations. Electron flow through Complexes I-IV was decreased in PSEN1/PSEN2 mutations but, in contrast, APP alleles had only modest impairments of complexes I and II. We measured aspects of mitochondrial dynamics, including fragmentation and neurite degeneration, both of which were dramatic in PSEN1/PSEN2 alleles, but essentially absent in APP alleles. The marked differences in mitochondrial pathology might occur from the distinct ways in which amyloids are processed into amyloid beta peptides and might be correlated with the disease severity.

Exploring the Mechanism of Kai-Xin-San to Improve Cognitive Deficits in AD Rats Induced by D-Gal and Aβ25-35 Based on Multi-Omics and Network Analysis

Alzheimer's disease (AD) is a common neurodegenerative disease for which there are no effective drugs. Kai-Xin-San (KXS), with definite curative effects, is widely used for the prevention and treatment of AD in China. But its mechanism is not yet fully understood. Based on our established rat model and previous pharmacodynamics study, Multi-omics (metabolomics, proteomics) and network analysis were integrated to explore the holistic mechanism of anti-AD effects of KXS. The key pathways were validated with western blot and ELISA methods. Morris water maze and Nissl staining showed that KXS could ameliorate cognitive deficits and pathological morphology of the hippocampus in AD rats. A total of nine metabolites were identified, which were related to pyrimidine metabolism, riboflavin metabolism, tyrosine metabolism, tryptophan metabolism, and glycerophospholipid metabolism. Proteomics results indicated that the improvement of cognitive deficits by KXS was closely related to the regulation of oxidative phosphorylation in mitochondria. Western blotting results showed that KXS significantly inhibited the expression of Mt-nd2 and Ndufb6 in AD rats. Integrated analysis indicated that the anti-AD targets of KXS were interrelated and KXS could exert its anti-AD effect by reducing oxidative stress, neurotoxicity, and inflammation.

Nuclear respiratory factor-1 (NRF1) induction drives mitochondrial biogenesis and attenuates amyloid beta-induced mitochondrial dysfunction and neurotoxicity

Mitochondrial dysfunction is an important driver of neurodegeneration and synaptic abnormalities in Alzheimer's disease (AD). Amyloid beta (Aβ) in mitochondria leads to increased reactive oxygen species (ROS) production, resulting in a vicious cycle of oxidative stress in coordination with a defective electron transport chain (ETC), decreasing ATP production. AD neurons exhibit impaired mitochondrial dynamics, evidenced by fusion and fission imbalances, increased fragmentation, and deficient mitochondrial biogenesis, contributing to fewer mitochondria in brains of AD patients. Nuclear respiratory factor-1 (NRF1) is a regulator of mitochondrial biogenesis through its activation of mitochondrial transcription factor A (TFAM). Our hypothesis posited that NRF1 induction in neuronal cells exposed to amyloid β1-42 (Aβ1-42) would increase de novo mitochondrial synthesis and improve mitochondrial function, restoring neuronal survival. Following NRF1 messenger RNA (mRNA) transfection of Aβ1-42-treated SH-SY5Y cells, a marked increase in mitochondrial mass was observed. Metabolic programming toward enhanced oxidative phosphorylation resulted in increased ATP production. Oxidative stress in the form of mitochondrial ROS accumulation was reduced and mitochondrial membrane potential preserved. Mitochondrial homeostasis was maintained, evidenced by balanced fusion and fission processes. Ultimately, improvement of mitochondrial function was associated with significant decreases in Aβ1-42-induced neuronal death and neurite disruption. Our findings highlight the potential of NRF1 upregulation to counteract Aβ1-42-associated mitochondrial dysfunction and neurodegenerative cell processes, opening avenues for innovative therapeutic approaches aimed at safeguarding mitochondrial health in AD neurons.

Mitochondria-targeting by small molecules against Alzheimer's disease: A mechanistic perspective

Alzheimer's disease (AD) poses a considerable worldwide health obstacle, marked by gradual cognitive deterioration and neuronal loss. While the molecular mechanisms underlying AD pathology have been elucidated to some extent, therapeutic options remain limited. Mitochondrial dysfunction has become recognized as a significant factor in the development of AD, with oxidative stress and disrupted energy metabolism being critical elements. This review explores the mechanistic aspects of small molecule targeting of mitochondria as a potential therapeutic approach for AD. The review explores the role of mitochondrial dysfunction in AD, including its involvement in the accumulation of β-amyloid plaques and neurofibrillary tangles, synaptic dysfunction, and neuronal death. Furthermore, the effects of oxidative stress on mitochondrial function were investigated, including the resulting damage to mitochondrial components. Mitochondrial-targeted therapies have attracted attention for their potential to restore mitochondrial function and reduce AD pathology. The review outlines the latest preclinical and clinical evidence supporting the effectiveness of small molecules in targeting mitochondrial dysfunction in AD. Additionally, it discusses the molecular pathways involved in mitochondrial dysfunction and examines how small molecules can intervene to address these abnormalities. By providing a comprehensive overview of the latest research in this field, this review aims to shed light on the therapeutic potential of small molecule targeting of mitochondria in AD and stimulate further research in this promising area of drug development.

Optineurin-facilitated axonal mitochondria delivery promotes neuroprotection and axon regeneration

Optineurin (OPTN) mutations are linked to amyotrophic lateral sclerosis (ALS) and normal tension glaucoma (NTG), but a relevant animal model is lacking, and the molecular mechanisms underlying neurodegeneration are unknown. We find that OPTN C-terminus truncation (OPTN∆C) causes late-onset neurodegeneration of retinal ganglion cells (RGCs), optic nerve (ON), and spinal cord motor neurons, preceded by a decrease of axonal mitochondria in mice. We discover that OPTN directly interacts with both microtubules and the mitochondrial transport complex TRAK1/KIF5B, stabilizing them for proper anterograde axonal mitochondrial transport, in a C-terminus dependent manner. Furthermore, overexpressing OPTN/TRAK1/KIF5B prevents not only OPTN truncation-induced, but also ocular hypertension-induced neurodegeneration, and promotes robust ON regeneration. Therefore, in addition to generating animal models for NTG and ALS, our results establish OPTN as a facilitator of the microtubule-dependent mitochondrial transport necessary for adequate axonal mitochondria delivery, and its loss as the likely molecular mechanism of neurodegeneration.

OAB-14 alleviates mitochondrial impairment through the SIRT3-dependent mechanism in APP/PS1 transgenic mice and N2a/APP cells

Alzheimer's disease (AD) is a progressive degenerative disease that affects a growing number of elderly individuals worldwide. OAB-14, a novel chemical compound developed by our research group, has been approved by the China Food and Drug Administration (FDA) for clinical trials in patients with AD (approval no. YD-OAB-220210). Previous studies have shown that OAB-14 enhances cognitive function in APP/PS1 transgenic mice and ameliorates abnormal mitochondrial morphology in the hippocampus. Mitochondrial dysfunction is a major risk factor for the development of AD, and maintaining healthy mitochondrial morphology and function is essential for improving the pathological changes and symptoms of AD. However, the protective effects of OAB-14 on mitochondria in AD and the underlying mechanisms remain unclear. This study aimed to investigate the protective effects of OAB-14 on the mitochondria of APP/PS1 transgenic mice and N2a/APP cells. Treatment with OAB-14 restored impaired mitochondrial function, mitochondrial dynamics, mitophagy, and mitochondrial DNA (mtDNA) in APP/PS1 transgenic mice and N2a/APP cells. In APP/PS1 transgenic mice and N2a/APP cells, OAB-14-treated elevated the expression and activity of SIRT3, decreased mitochondrial acetylation, and reduced mitochondrial reactive oxygen species (mtROS) levels. OAB-14 also attenuated mitochondrial acetylation, improved mitochondrial dynamics and mitophagy, and mitigated mtDNA damage in a SIRT3-dependent manner. In addition, OAB-14 suppressed mitochondrial Aβ accumulation in the hippocampus of APP/PS1 transgenic mice. This study provides further clarification on the potential therapeutic mechanisms of OAB-14 in the treatment of AD and lays the groundwork for future drug applications.

The Mitochondria-Targeted Micelle Inhibits Alzheimer's Disease Progression by Alleviating Neuronal Mitochondrial Dysfunction and Neuroinflammation

Mitochondrial dysfunction plays an important role in neuroinflammation and cognitive impairment in Alzheimer's disease (AD). Herein, this work designs a mitochondria-targeted micelle CsA-TK-SS-31 (CTS) to block the progression of AD by simultaneously alleviating mitochondrial dysfunction in microglia and neurons. The mitochondria-targeted peptide SS-31 drives cyclosporin A (CsA) to penetrate the blood-brain barrier (BBB) and delivers CsA to mitochondria of microglia and neurons in the brains of 5 × FAD mice. Under the high level of reactive oxygen species (ROS) environment in damaged mitochondria of microglia and neurons, the linker (thioketal, TK) between CsA and SS-31 is broken and CsA and SS-31 are released while consuming ROS in the microenvironment. The released CsA and SS-31 synergistically restore the mitochondrial membrane potential and the balance between the fission and fusion of mitochondria, which subsequently protect neurons from apoptosis and reduce the activation of microglia in the brains of 5 × FAD mice. Ultimately, the neuroinflammation and cognitive impairment of 5 × FAD mice are ameliorated. This research provides a synergistic treatment strategy for AD through alleviating mitochondrial dysfunction to reduce neuroinflammation and restore the function of neurons simultaneously.

Stabilization of mitochondria-associated endoplasmic reticulum membranes regulates Aβ generation in a three-dimensional neural model of Alzheimer's disease

INTRODUCTION

We previously demonstrated that regulating mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs) affects axonal Aβ generation in a well-characterized three-dimensional (3D) neural Alzheimer's disease (AD) model. MAMs vary in thickness and length, impacting their functions. Here, we examined the effect of MAM thickness on Aβ in our 3D neural model of AD.

METHODS

We employed fluorescence resonance energy transfer (FRET) or fluorescence-based MAM stabilizers, electron microscopy, Aβ enzyme-linked immunosorbent assay (ELISA), and live-cell imaging with kymography to assess how stabilizing MAMs of different gap widths influence Aβ production and MAM axonal mobility.

RESULTS

Stabilizing tight MAMs (∼6 nm gap width) significantly increased Aβ levels, whereas basal (∼25 nm) and loose MAMs (∼40 nm) maintained or reduced Aβ levels, respectively. Tight MAMs reduced mitochondrial axonal velocity compared to basal MAMs, while loose MAMs showed severely reduced axonal distribution.

DISCUSSION

Our findings suggest that stabilizing MAMs of specific gap widths, particularly in axons, without complete destabilization could be an effective therapeutic strategy for AD.

HIGHLIGHTS

The stabilization of MAMs exacerbates or ameliorates Aβ generation from AD neurons in a MAM gap width-dependent manner. A specific stabilization threshold within the MAM gap width spectrum shifts the amyloidogenic process to non-amyloidogenic. Tight MAMs slow down mitochondrial axonal transport compared to lose MAMs offering a quantitative method for measuring MAM stabilization.

The role of mitochondrial remodeling in neurodegenerative diseases

Neurodegenerative diseases are a group of diseases that pose a serious threat to human health, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD) and Amyotrophic Lateral Sclerosis (ALS). In recent years, it has been found that mitochondrial remodeling plays an important role in the onset and progression of neurodegenerative diseases. Mitochondrial remodeling refers to the dynamic regulatory process of mitochondrial morphology, number and function, which can affect neuronal cell function and survival by regulating mechanisms such as mitochondrial fusion, division, clearance and biosynthesis. Mitochondrial dysfunction is an important intrinsic cause of the pathogenesis of neurodegenerative diseases. Mitochondrial remodeling abnormalities are involved in energy metabolism in neurodegenerative diseases. Pathological changes in mitochondrial function and morphology, as well as interactions with other organelles, can affect the energy metabolism of dopaminergic neurons and participate in the development of neurodegenerative diseases. Since the number of patients with PD and AD has been increasing year by year in recent years, it is extremely important to take effective interventions to significantly reduce the number of morbidities and to improve people's quality of life. More and more researchers have suggested that mitochondrial remodeling and related dynamics may positively affect neurodegenerative diseases in terms of neuronal and self-adaptation to the surrounding environment. Mitochondrial remodeling mainly involves its own fission and fusion, energy metabolism, changes in channels, mitophagy, and interactions with other cellular organelles. This review will provide a systematic summary of the role of mitochondrial remodeling in neurodegenerative diseases, with the aim of providing new ideas and strategies for further research on the treatment of neurodegenerative diseases.

Inflammatory signaling pathways in Alzheimer's disease: Mechanistic insights and possible therapeutic interventions

The complex pathophysiology of Alzheimer's disease (AD) poses challenges for the development of therapies. Recently, neuroinflammation has been identified as a key pathogenic mechanism underlying AD, while inflammation has emerged as a possible target for the management and prevention of AD. Several prior studies have demonstrated that medications modulating neuroinflammation might lessen AD symptoms, mostly by controlling neuroinflammatory signaling pathways such as the NF-κB, MAPK, NLRP3, etc, and their respective signaling cascade. Moreover, targeting these inflammatory modalities with inhibitors, natural products, and metabolites has been the subject of intensive research because of their anti-inflammatory characteristics, with many studies demonstrating noteworthy pharmacological capabilities and potential clinical applications. Therefore, targeting inflammation is considered a promising strategy for treating AD. This review comprehensively elucidates the neuroinflammatory mechanisms underlying AD progression and the beneficial effects of inhibitors, natural products, and metabolites in AD treatment.

Rg1 improves Alzheimer's disease by regulating mitochondrial dynamics mediated by the AMPK/Drp1 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Alzheimer's disease (AD) is the most prevalent form of dementia, characterized by a complex pathogenesis that includes Aβ deposition, abnormal phosphorylation of tau protein, chronic neuroinflammation, and mitochondrial dysfunction. In traditional medicine, ginseng is revered as the 'king of herbs'. Ginseng has the effects of greatly tonifying vital energy, strengthening the spleen and benefiting the lungs, generating fluids and nourishing the blood, and calming the mind while enhancing intelligence. Ginsenoside Rg1 (Rg1) is a well-defined major active component found in ginseng, known for its relatively high content. It has been demonstrated to exhibit neuroprotective effects in both in vivo and in vitro models, capable of ameliorating Aβ and tau pathology, regulating synaptic function, and reducing inflammation, oxidative stress, and apoptosis. However, the potential of Rg1 to improve AD pathology through the regulation of mitochondrial dynamics is still uncertain.

AIM OF THE STUDY

Despite the active research efforts on drugs for AD, the currently available anti-AD medications can only slow disease progression and manage symptoms, yet unable to provide a cure for AD. Furthermore, some anti-AD drugs failed phase III and IV clinical trials due to significant side effects. Therefore, there is an urgent need to further investigate the pathogenesis of AD, to identify new therapeutic targets, and to explore more effective therapies. The aim of this study is to evaluate the potential therapeutic effects of Rg1 on APP/PS1 double transgenic mice and Aβ42-induced HT22 cell models, and to investigate the potential mechanisms through which it provides neuroprotective effects.

MATERIALS AND METHODS

This study investigates the effects of Rg1 in treating AD on APP/PS1 double transgenic mice and Aβ42-induced HT22 cells. In the in vivo experiments, APP/PS1 mice were divided into a model group, Rg1-L group, Rg1-H group, and donepezil group, with C57BL/6 mice serving as the control group (n = 12 per group). The Rg1-L and Rg1-H groups were administered Rg1 at doses of 5 mg/kg/d and 10 mg/kg/d, respectively, while the donepezil group received donepezil at a dose of 1.3 mg/kg/d. Both the control and model groups received an equal volume of physiological saline daily for 28 days. Learning and spatial memory were assessed by the Morris water maze (MWM) and novel object recognition (NOR) tests, and neuronal damage by Nissl staining. Aβ deposition was analyzed through immunohistochemistry and Western blot, while the expression levels of synaptic proteins PSD95 and SYN were evaluated via immunofluorescence staining and Western blot. The dendritic spines of neurons was observed by Golgi staining.The ultrastructure of neuronal mitochondria and synapses was examined by transmission electron microscopy (TEM). Mitochondrial function was assessed through measurements of Reactive oxygen species (ROS), Superoxide Dismutase (SOD), and Adenosine Triphosphate (ATP), and Western blot analysis was performed to detect the expression levels of AMPK, p-AMPK, Drp1, p-Drp1, OPA1, Mfn1, and Mfn2, thereby investigating the protective effects of Rg1 on mitochondrial dysfunction and cognitive impairment in APP/PS1 double transgenic mice. In vitro experiments, HT22 cells were treated with Aβ42 of 10 μM for 24 h to verify the therapeutic effects of Rg1. Flow cytometry was used to detect ROS and JC-1, biochemical methods were employed to measure SOD and ATP, immunofluorescence staining was used to detect the expression levels of PSD95 and SYN, and Western blot analysis was conducted to elucidate its potential mechanisms of action.

RESULTS

The findings suggest that after 28 days of Rg1 treatment, cognitive dysfunction in APP/PS1 mice was improved. Pathological and immunohistochemical analyses demonstrated that Rg1 treatment significantly reduced Aβ deposition and neuronal loss. Rg1 can improve synaptic dysfunction and mitochondrial function in APP/PS1 mice. Rg1 activated AMPK, enhanced p-AMPK expression, inhibited Drp1, and reduced p-Drp1 levels, which led to increased expression of OPA1, Mfn1, and Mfn2, thereby inhibiting mitochondrial fission and facilitating mitochondrial fusion. Additionally, Rg1 effectively reversed the decrease in mitochondrial membrane potential (MMP) and the increase in ROS production induced by Aβ42 in HT22 cells, restoring SOD and ATP levels. Furthermore, Rg1 regulated mitochondrial fission mediated by the AMPK/Drp1 signaling pathway, promoting mitochondrial fusion and improving synaptic dysfunction.

CONCLUSION

Our research provides evidence for the neuroprotective mechanisms of Rg1 in AD models. Rg1 modulates mitochondrial dynamics through the AMPK/Drp1 signaling pathway, thereby reducing synaptic and mitochondrial dysfunction in APP/PS1 mice and AD cell models.

The neuroprotective effects of cholecystokinin in the brain: antioxidant, anti-inflammatory, cognition, and synaptic plasticity

Cholecystokinin (CCK) is a major neuropeptide in the brain that functions as a neurotransmitter, hormone, and growth factor. The peptide and its receptors are widely expressed in the brain. CCK signaling modulates synaptic plasticity and can improve or impair memory formation, depending on the brain areas studies and the receptor subtype activated. Studies have shown in a series of animal models of neurodegenerative diseases that CCK receptor agonists show neuroprotective effects and can effectively alleviate oxidative stress, alleviate chronic inflammation of the central nervous system, improve neuronal synaptic plasticity, prevent neuronal loss, and improve cognitive dysfunction in Alzheimer's disease (AD) model mice and motor activity in animal models of Parkinson's disease. In addition, CCK plays important roles in the amygdala to regulate anxiety and depressive states. Activation of interneurons or inhibition of excitatory neurons can improve anxiety levels. This review summarizes the effects on memory formation and synaptic plasticity, the neuroprotective effects of cholecystokinin and its analogs in neurological diseases such as Alzheimer and Parkinson's disease, and the effects on anxiety and neuronal activity in the amygdala.

Production of Amyloid-β in the Aβ-Protein-Precursor Proteolytic Pathway Is Discontinued or Severely Suppressed in Alzheimer's Disease-Affected Neurons: Contesting the 'Obvious'

A notion of the continuous production of amyloid-β (Aβ) via the proteolysis of Aβ-protein-precursor (AβPP) in Alzheimer's disease (AD)-affected neurons constitutes both a cornerstone and an article of faith in the Alzheimer's research field. The present Perspective challenges this assumption. It analyses the relevant empirical data and reaches an unexpected conclusion, namely that in AD-afflicted neurons, the production of AβPP-derived Aβ is either discontinued or severely suppressed, a concept that, if proven, would fundamentally change our understanding of the disease. This suppression, effectively self-suppression, occurs in the context of the global inhibition of the cellular cap-dependent protein synthesis as a consequence of the neuronal integrated stress response (ISR) elicited by AβPP-derived intraneuronal Aβ (iAβ; hence self-suppression) upon reaching certain levels. Concurrently with the suppression of the AβPP proteolytic pathway, the neuronal ISR activates in human neurons, but not in mouse neurons, the powerful AD-driving pathway generating the C99 fragment of AβPP independently of AβPP. The present study describes molecular mechanisms potentially involved in these phenomena, propounds novel approaches to generate transgenic animal models of AD, advocates for the utilization of human neuronal cells-based models of the disease, makes verifiable predictions, suggests experiments designed to validate the proposed concept, and considers its potential research and therapeutic implications. Remarkably, it opens up the possibility that the conventional production of AβPP, BACE enzymes, and γ-secretase components is also suppressed under the neuronal ISR conditions in AD-affected neurons, resulting in the dyshomeostasis of AβPP. It follows that whereas conventional AD is triggered by AβPP-derived iAβ accumulated to the ISR-eliciting levels, the disease, in its both conventional and unconventional (triggered by the neuronal ISR-eliciting stressors distinct from iAβ) forms, is driven not (or not only) by iAβ produced in the AβPP-independent pathway, as we proposed previously, but mainly, possibly exclusively, by the C99 fragment generated independently of AβPP and not cleaved at the γ-site due to the neuronal ISR-caused deficiency of γ-secretase (apparently, the AD-driving "substance X" predicted in our previous study), a paradigm consistent with a dictum by George Perry that Aβ is "central but not causative" in AD. The proposed therapeutic strategies would not only deplete the driver of the disease and abrogate the AβPP-independent production of C99 but also reverse the neuronal ISR and ameliorate the AβPP dyshomeostasis, a potentially significant contributor to AD pathology.

Protective Role of Electroacupuncture Against Cognitive Impairment in Neurological Diseases

Many neurological diseases can lead to cognitive impairment in patients, which includes dementia and mild cognitive impairment and thus create a heavy burden both to their families and public health. Due to the limited effectiveness of medications in treating cognitive impairment, it is imperative to develop alternative treatments. Electroacupuncture (EA), a required method for Traditional Chinese Medicine, has the potential treatment of cognitive impairment. However, the molecular mechanisms involved have not been fully elucidated. Considering the current research status, preclinical literature published within the ten years until October 2022 was systematically searched through PubMed, Web of Science, MEDLINE, Ovid, and Embase. By reading the titles and abstracts, a total of 56 studies were initially included. It is concluded that EA can effectively ameliorate cognitive impairment in preclinical research of neurological diseases and induce potentially beneficial changes in molecular pathways, including Alzheimer's disease, vascular cognitive impairment, chronic pain, and Parkinson's disease. Moreover, EA exerts beneficial effects through the same or diverse mechanisms for different disease types, including but not limited to neuroinflammation, neuronal apoptosis, neurogenesis, synaptic plasticity, and autophagy. However, these findings raise further questions that need to be elucidated. Overall, EA therapy for cognitive impairment is an area with great promise, even though more research regarding its detailed mechanisms is warranted.

Dietary supplementation and the role of phytochemicals against the Alzheimer's disease: Focus on polyphenolic compounds

Alzheimer's disease is a complicated, multifaceted, neurodegenerative illness that places an increasing strain on healthcare systems. Due to increasing malfunction and death of nerve cells, the person suffering from Alzheimer's disease (AD) slowly and steadily loses their memories, cognitive functions and even their personality. Although medications may temporarily enhance memory, there are currently no permanent therapies that can halt or cure this irreversible neurodegenerative process. Nonetheless, fast progress in comprehending the cellular and molecular abnormalities responsible for neuronal degeneration has increased confidence in the development of viable prevention and treatments. All FDA-approved anti-AD medications have merely symptomatic effects and cannot cure the illness. This necessitates the pursuit of alternate treatments. Accumulating data shows that systemic neuroinflammation, oxidative stress and associated mitochondrial dysfunction play crucial roles in the etiology of AD and precede its clinical presentation. Therefore, innovative therapeutic approaches targeting these pathophysiological components of Alzheimer's disease are being explored aggressively in the present scenario. Phytochemicals such as resveratrol, curcumin, quercetin, genistein and catechins are prospective therapies owing to their capacity to alter key AD pathogenetic pathways, such as oxidative stress, neuroinflammation, and mitochondrial dysfunction. The use of new phytochemical delivery strategies would certainly provide the possibility to solve several issues with standard anti-AD medicines. In this review, the roles of phytophenolic compound-based treatment strategies for AD are discussed.

Cell culture research in aging and Alzheimer's disease: The strategic use/reuse of untreated controls and savings people's tax dollars

Cell culture is an essential tool in both fundamental and translational research, particularly for understanding complex diseases like Alzheimer's disease (AD). The use of cell lines provides the advantage of genetic homogeneity, ensuring reproducible and consistent results. This article explores the application of mammalian cell cultures to model AD, focusing on the transfection of cells with key genes associated with the disease to replicate the cellular environment of AD. It explains various transfection methods and challenges related to the process. These models offer a robust platform for investigating cellular biology, molecular pathways, physiological processes, and drug discovery efforts. A range of assays, including RT-PCR, western blotting, ELISA, mitochondrial respiration, and reactive oxygen species analysis, are employed to assess the impact of genetic modifications on cellular functions and to screen potential AD therapies. Researchers often design experiments with multiple variables such as genetic modifications, chemical treatments, or time points, paired with positive and negative controls. By using a consistent control group across all conditions and under identical experimental conditions, researchers can minimize variability and enhance data reproducibility. This approach is particularly valuable in AD research, where small experimental differences can significantly influence outcomes. Using a shared control group ensures data comparability across experiments, saving time and resources by eliminating redundant control tests. This strategy not only streamlines the research process but also improves the reliability of results, making it a sensible, resource-efficient method that ultimately conserves public funding in the pursuit of AD treatments.

Cellular senescence in Alzheimer's disease: from physiology to pathology

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders, characterized by the accumulation of Aβ and abnormal tau hyperphosphorylation. Despite substantial efforts in development of drugs targeting Aβ and tau pathologies, effective therapeutic strategies for AD remain elusive. Recent attention has been paid to the significant role of cellular senescence in AD progression. Mounting evidence suggests that interventions targeting cellular senescence hold promise in improving cognitive function and ameliorating hallmark pathologies in AD. This narrative review provides a comprehensive summary and discussion of the physiological roles, characteristics, biomarkers, and commonly employed in vivo and in vitro models of cellular senescence, with a particular focus on various cell types in the brain, including astrocytes, microglia, oligodendrocyte precursor cells, neurons, and endothelial cells. The review further delves into factors influencing cellular senescence in AD and emphasizes the significance of targeting cellular senescence as a promising approach for AD treatment, which includes the utilization of senolytics and senomorphics.

The Role of Reactive Oxygen Species in Alzheimer's Disease: From Mechanism to Biomaterials Therapy

Alzheimer's disease (AD) is a chronic, insidious, and progressive neurodegenerative disease that remains a clinical challenge for society. The fully approved drug lecanemab exhibits the prospect of therapy against the pathological processes, while debatable adverse events conflict with the drug concentration required for the anticipated therapeutic effects. Reactive oxygen species (ROS) are involved in the pathological progression of AD, as has been demonstrated in much research regarding oxidative stress (OS). The contradiction between anticipated dosage and adverse event may be resolved through targeted transport by biomaterials and get therapeutic effects through pathological progression via regulation of ROS. Besides, biomaterials fix delivery issues by promoting the penetration of drugs across the blood-brain barrier (BBB), protecting the drug from peripheral degradation, and elevating bioavailability. The goal is to comprehensively understand the mechanisms of ROS in the progression of AD disease and the potential of ROS-related biomaterials in the treatment of AD. This review focuses on OS and its connection with AD and novel biomaterials in recent years against AD via OS to inspire novel biomaterial development. Revisiting these biomaterials and mechanisms associated with OS in AD via thorough investigations presents a considerable potential and bright future for improving effective interventions for AD.

Synaptic mitochondria: A crucial factor in the aged hippocampus

Aging is a multifaceted biological process characterized by progressive molecular and cellular damage accumulation. The brain hippocampus undergoes functional deterioration with age, caused by cellular deficits, decreased synaptic communication, and neuronal death, ultimately leading to memory impairment. One of the factors contributing to this dysfunction is the loss of mitochondrial function. In neurons, mitochondria are categorized into synaptic and non-synaptic pools based on their location. Synaptic mitochondria, situated at the synapses, play a crucial role in maintaining neuronal function and synaptic plasticity, whereas non-synaptic mitochondria are distributed throughout other neuronal compartments, supporting overall cellular metabolism and energy supply. The proper function of synaptic mitochondria is essential for synaptic transmission as they provide the energy required and regulate calcium homeostasis at the communication sites between neurons. Maintaining the structure and functionality of synaptic mitochondria involves intricate processes, including mitochondrial dynamics such as fission, fusion, transport, and quality control mechanisms. These processes ensure that mitochondria remain functional, replace damaged organelles, and sustain cellular homeostasis at synapses. Notably, deficiencies in these mechanisms have been increasingly associated with aging and the onset of age-related neurodegenerative diseases. Synaptic mitochondria from the hippocampus are particularly vulnerable to age-related changes, including alterations in morphology and a decline in functionality, which significantly contribute to decreased synaptic activity during aging. This review comprehensively explores the critical roles that mitochondrial dynamics and quality control mechanisms play in preserving synaptic activity and neuronal function. It emphasizes the emerging evidence linking the deterioration of synaptic mitochondria to the aging process and the development of neurodegenerative diseases, highlighting the importance of these organelles from hippocampal neurons as potential therapeutic targets for mitigating cognitive decline and synaptic degeneration associated with aging. The novelty of this review lies in its focus on the unique vulnerability of hippocampal synaptic mitochondria to aging, underscoring their importance in maintaining brain function across the lifespan.

Rab11 suppresses neuronal stress signaling by localizing dual leucine zipper kinase to axon terminals for protein turnover

Dual leucine zipper kinase (DLK) mediates multiple neuronal stress responses, and its expression levels are constantly suppressed to prevent excessive stress signaling. We found that Wallenda (Wnd), the Drosophila ortholog of DLK, is highly enriched in the axon terminals of Drosophila sensory neurons in vivo and that this subcellular localization is necessary for Highwire-mediated Wnd protein turnover under normal conditions. Our structure-function analysis found that Wnd palmitoylation is essential for its axon terminal localization. Palmitoylation-defective Wnd accumulated in neuronal cell bodies, exhibited dramatically increased protein expression levels, and triggered excessive neuronal stress responses. Defective intracellular transport is implicated in neurodegenerative conditions. Comprehensive dominant-negative Rab protein screening identified Rab11 as an essential factor for Wnd localization in axon terminals. Consequently, Rab11 loss-of-function increased the protein levels of Wnd and induced neuronal stress responses. Inhibiting Wnd activity significantly ameliorated neuronal loss and c-Jun N-terminal kinase signaling triggered by Rab11 loss-of-function. Taken together, these suggest that DLK proteins are constantly transported to axon terminals for protein turnover and a failure of such transport can lead to neuronal loss. Our study demonstrates how subcellular protein localization is coupled to protein turnover for neuronal stress signaling.

Decoding Cancer through Silencing the Mitochondrial Gatekeeper VDAC1

Mitochondria serve as central hubs for regulating numerous cellular processes that include metabolism, apoptosis, cell cycle progression, proliferation, differentiation, epigenetics, immune signaling, and aging. The voltage-dependent anion channel 1 (VDAC1) functions as a crucial mitochondrial gatekeeper, controlling the flow of ions, such as Ca2+, nucleotides, and metabolites across the outer mitochondrial membrane, and is also integral to mitochondria-mediated apoptosis. VDAC1 functions in regulating ATP production, Ca2+ homeostasis, and apoptosis, which are essential for maintaining mitochondrial function and overall cellular health. Most cancer cells undergo metabolic reprogramming, often referred to as the "Warburg effect", supplying tumors with energy and precursors for the biosynthesis of nucleic acids, phospholipids, fatty acids, cholesterol, and porphyrins. Given its multifunctional nature and overexpression in many cancers, VDAC1 presents an attractive target for therapeutic intervention. Our research has demonstrated that silencing VDAC1 expression using specific siRNA in various tumor types leads to a metabolic rewiring of the malignant cancer phenotype. This results in a reversal of oncogenic properties that include reduced tumor growth, invasiveness, stemness, epithelial-mesenchymal transition. Additionally, VDAC1 depletion alters the tumor microenvironment by reducing angiogenesis and modifying the expression of extracellular matrix- and structure-related genes, such as collagens and glycoproteins. Furthermore, VDAC1 depletion affects several epigenetic-related enzymes and substrates, including the acetylation-related enzymes SIRT1, SIRT6, and HDAC2, which in turn modify the acetylation and methylation profiles of histone 3 and histone 4. These epigenetic changes can explain the altered expression levels of approximately 4000 genes that are associated with reversing cancer cells oncogenic properties. Given VDAC1's critical role in regulating metabolic and energy processes, targeting it offers a promising strategy for anti-cancer therapy. We also highlight the role of VDAC1 expression in various disease pathologies, including cardiovascular, neurodegenerative, and viral and bacterial infections, as explored through siRNA targeting VDAC1. Thus, this review underscores the potential of targeting VDAC1 as a strategy for addressing high-energy-demand cancers. By thoroughly understanding VDAC1's diverse roles in metabolism, energy regulation, mitochondrial functions, and other cellular processes, silencing VDAC1 emerges as a novel and strategic approach to combat cancer.

Withania somnifera (Ashwagandha) Improves Spatial Memory, Anxiety and Depressive-like Behavior in the 5xFAD Mouse Model of Alzheimer's Disease

Withania somnifera (WS), also known as ashwagandha, is a popular botanical supplement used to treat various conditions including memory loss, anxiety and depression. Previous studies from our group showed an aqueous extract of WS root (WSAq) enhances cognition and alleviates markers for depression in Drosophila. Here, we sought to confirm these effects in the 5xFAD mouse model of β-amyloid (Aβ) accumulation. Six- to seven-month-old male and female 5xFAD mice were treated with WSAq in their drinking water at 0 mg/mL, 0.5 mg/mL or 2.5 mg/mL for four weeks. In the fourth week of treatment, spatial memory, anxiety and depressive-like symptoms were evaluated. At the conclusion of behavioral testing, brain tissue was harvested, immunohistochemistry was performed, and the cortical expression of antioxidant response genes was evaluated. Both concentrations of WSAq improved spatial memory and reduced depressive and anxiety-related behavior. These improvements were accompanied by a reduction in Aβ plaque burden in the hippocampus and cortex and an attenuation of activation of microglia and astrocytes. Antioxidant response genes were upregulated in the cortex of WSAq-treated mice. Oral WSAq treatment could be beneficial as a therapeutic option in AD for improving disease pathology and behavioral symptoms. Future studies focused on dose optimization of WSAq administration and further assessment of the mechanisms by which WSAq elicits its beneficial effects will help inform the clinical potential of this promising botanical therapy.

Quintessential Synergy: Concurrent Transient Administration of Integrated Stress Response Inhibitors and BACE1 and/or BACE2 Activators as the Optimal Therapeutic Strategy for Alzheimer's Disease

The present study analyzes two potential therapeutic approaches for Alzheimer's disease (AD). One is the suppression of the neuronal integrated stress response (ISR). Another is the targeted degradation of intraneuronal amyloid-beta (iAβ) via the activation of BACE1 (Beta-site Aβ-protein-precursor Cleaving Enzyme) and/or BACE2. Both approaches are rational. Both are promising. Both have substantial intrinsic limitations. However, when combined in a carefully orchestrated manner into a composite therapy they display a prototypical synergy and constitute the apparently optimal, potentially most effective therapeutic strategy for AD.

Alzheimer's Disease Pathology and Assistive Nanotheranostic Approaches for Its Therapeutic Interventions

Alzheimer's disease (AD) still prevails and continues to increase indiscriminately throughout the 21st century, and is thus responsible for the depreciating quality of health and associated sectors. AD is a progressive neurodegenerative disorder marked by a significant amassment of beta-amyloid plaques and neurofibrillary tangles near the hippocampus, leading to the consequent loss of cognitive abilities. Conventionally, amyloid and tau hypotheses have been established as the most prominent in providing detailed insight into the disease pathogenesis and revealing the associative biomarkers intricately involved in AD progression. Nanotheranostic deliberates rational thought toward designing efficacious nanosystems and strategic endeavors for AD diagnosis and therapeutic implications. The exceeding advancements in this field enable the scientific community to envisage and conceptualize pharmacokinetic monitoring of the drug, sustained and targeted drug delivery responses, fabrication of anti-amyloid therapeutics, and enhanced accumulation of the targeted drug across the blood-brain barrier (BBB), thus giving an optimistic approach towards personalized and precision medicine. Current methods idealized on the design and bioengineering of an array of nanoparticulate systems offer higher affinity towards neurocapillary endothelial cells and the BBB. They have recently attracted intriguing attention to the early diagnostic and therapeutic measures taken to manage the progression of the disease. In this article, we tend to furnish a comprehensive outlook, the detailed mechanism of conventional AD pathogenesis, and new findings. We also summarize the shortcomings in diagnostic, prognostic, and therapeutic approaches undertaken to alleviate AD, thus providing a unique window towards nanotheranostic advancements without disregarding potential drawbacks, side effects, and safety concerns.

SS-31 mitigates oxidative stress and restores mitochondrial function in cigarette smoke-damaged oral epithelial cells via PINK1-mediated mitophagy

Smoking is a well-established risk factor for several oral diseases, including oral cancer, oral leukoplakia and periodontitis, primarily related to reactive oxygen species (ROS). SS-31, a mitochondria-targeting tetrapeptide, has exhibited demonstrable efficacy in medical conditions by attenuating mitochondrial ROS production. However, its potential in the treatment of oral diseases remains underexplored. The aim of this study was to investigate the therapeutic potential of SS-31 in mitigating smoking-induced oral epithelial injury. Through in vitro experiments, our results indicate that SS-31 plays a protective role against cigarette smoke extract (CSE) by reducing oxidative stress, attenuating inflammatory response, and restoring mitochondrial function. Furthermore, we found that mitophagy, regulated by PINK1 (PTEN-induced putative kinase 1)/Parkin (Parkin RBR E3 ubiquitin-protein ligase), was critical for the protective role of SS-31. Our findings offer valuable insights into SS-31's therapeutic potential in mitigating CSE-induced oxidative stress, inflammatory response, and mitochondrial dysfunction in oral epithelial cells. This study provides novel intervention targets for smoking-related oral diseases.

Regulation of DNA damage response by RNA/DNA-binding proteins: Implications for neurological disorders and aging

RNA-binding proteins (RBPs) are evolutionarily conserved across most forms of life, with an estimated 1500 RBPs in humans. Traditionally associated with post-transcriptional gene regulation, RBPs contribute to nearly every known aspect of RNA biology, including RNA splicing, transport, and decay. In recent years, an increasing subset of RBPs have been recognized for their DNA binding properties and involvement in DNA transactions. We refer to these RBPs with well-characterized DNA binding activity as RNA/DNA binding proteins (RDBPs), many of which are linked to neurological diseases. RDBPs are associated with both nuclear and mitochondrial DNA repair. Furthermore, the presence of intrinsically disordered domains in RDBPs appears to be critical for regulating their diverse interactions and plays a key role in controlling protein aggregation, which is implicated in neurodegeneration. In this review, we discuss the emerging roles of common RDBPs from the heterogeneous nuclear ribonucleoprotein (hnRNP) family, such as TAR DNA binding protein-43 (TDP43) and fused in sarcoma (FUS) in controlling DNA damage response (DDR). We also explore the implications of RDBP pathology in aging and neurodegenerative diseases and provide a prospective on the therapeutic potential of targeting RDBP pathology mediated DDR defects for motor neuron diseases and aging.

The potential benefits of PGC-1α in treating Alzheimer's disease are dependent on the integrity of the LLKYL L3 motif: Effect of regulating mitochondrial axonal transportation

Mitochondrial dysfunction is a prominent hallmark of Alzheimer's disease (AD). The transcriptional coactivator PPARγ coactivator 1 (PGC-1a) has been identified as a key regulator of mitochondrial biogenesis and function. However, the precise structure/function relationship between PGC-1a and mitochondrial quality control remains incompletely understood. In this study, we investigated the impact of PGC-1a on AD pathology and its underlying mechanisms with a specific focus on mitochondrial axonal transport. Additionally, we generated two PGC-1α mutants by substituting leucine residues at positions 148 and 149 within the LKKLL motif or at positions 209 and 210 within the LLKYL motif with alanine. Subsequently, we examined the effects of these mutants on mutAPP-induced abnormalities in anterograde and retrograde axonal transport, disrupted mitochondrial distribution, and impaired mitophagy. Mutagenesis studies revealed that the LLKYL motif at amino acid position 209-210 within PGC-1α plays an essential role in its interaction with estrogen-related receptors (ERRα), which is necessary for restoring normal mitochondrial anterograde axonal transport, maintaining proper mitochondrial distribution, and ultimately preventing neuronal apoptosis. Furthermore, it was found that the Leu-rich motif at amino acids 209-210 within PGC-1α is crucial for rescuing mutAPP-induced impairment in mitophagy and loss of membrane potential by restoring normal mitochondrial retrograde axonal transport. Conversely, mutation of residues 148 and 149 in the LKKLL motif does not compromise the effectiveness of PGC-1α. These findings provide valuable insights into the molecular determinants governing specificity of action for PGC-1α involved in regulating mutAPP-induced deficits in mitochondrial axonal trafficking. Moreover, they suggest a potential therapeutic target for addressing Alzheimer's disease.

Rab11 suppresses neuronal stress signaling by localizing Dual leucine zipper kinase to axon terminals for protein turnover

Dual Leucine Zipper Kinase (DLK) mediates multiple neuronal stress responses, and its expression levels are constantly suppressed to prevent excessive stress signaling. We found that Wallenda (Wnd), the Drosophila ortholog of DLK, is highly enriched in the axon terminals of Drosophila sensory neurons in vivo and that this subcellular localization is necessary for Highwire-mediated Wnd protein turnover under normal conditions. Our structure-function analysis found that Wnd palmitoylation is essential for its axon terminal localization. Palmitoylation-defective Wnd accumulated in neuronal cell bodies, exhibited dramatically increased protein expression levels, and triggered excessive neuronal stress responses. Defective intracellular transport is implicated in neurodegenerative conditions. Comprehensive dominant-negative Rab protein screening identified Rab11 as an essential factor for Wnd localization in axon terminals. Consequently, Rab11 loss-of-function increased the protein levels of Wnd and induced neuronal stress responses. Inhibiting Wnd activity significantly ameliorated neuronal loss and c-Jun N-terminal kinase signaling triggered by Rab11 loss-of-function. Taken together, these suggest that DLK proteins are constantly transported to axon terminals for protein turnover and a failure of such transport can lead to neuronal loss. Our study demonstrates how subcellular protein localization is coupled to protein turnover for neuronal stress signaling.

Highlights

Wnd is highly enriched in axon terminals.Wnd protein turnover by Hiw is restricted in the axon terminals.Protein palmitoylation of Wnd and Rab11 activity is essential for Wnd axonal localization. Rab11 mutations and defective Wnd palmitoylation impair Wnd protein turnover leading to increased Wnd protein levels and neuronal loss. Inhibiting Wnd activity mitigates neuronal stress response caused by Rab11 loss-of-function.

Dendrimers-Novel Therapeutic Approaches for Alzheimer's Disease

Dendrimers are covalently bonded globular nanostructures that may be used in the treatment of Alzheimer's disease (AD). Nowadays, AD therapies are focused on improving cognitive functioning and not causal treatment. However, this may change with the use of dendrimers, which are being investigated as a drug-delivery system or as a drug per se. With their ability to inhibit amyloid formation and their anti-tau properties, they are a promising therapeutic option for AD patients. Studies have shown that dendrimers may inhibit amyloid formation in at least two ways: by blocking fibril growth and by breaking already existing fibrils. Neurofibrillary tangles (NFTs) are abnormal filaments built by tau proteins that can be accumulated in the cell, which leads to the loss of cytoskeletal microtubules and tubulin-associated proteins. Cationic phosphorus dendrimers, with their anti-tau properties, can induce the aggregation of tau into amorphous structures. Drug delivery to mitochondria is difficult due to poor transport across biological barriers, such as the inner mitochondrial membrane, which is highly negatively polarized. Dendrimers may be potential nanocarriers and increase mitochondria targeting. Another considered use of dendrimers in AD treatment is as a drug-delivery system, for example, carbamazepine (CBZ) or tacrine. They can also be used to transport siRNA into neuronal tissue and to carry antioxidants and anti-inflammatory drugs to act protectively on the nervous system.

Protective effects of 2,4-dinitrophenol in okadaic acid-induced cellular model of Alzheimer's disease

Alzheimer's disease (AD) research started several decades ago and despite the many efforts employed to develop new treatments or approaches to slow and/or revert disease progression, AD treatment remains an unsolved issue. Knowing that mitochondria loss of function is a central hub for many AD-associated pathophysiological processes, there has been renewed interest in exploring mitochondria as targets for intervention. In this perspective, the present study was aimed to investigate the possible beneficial effects of 2,4 dinitrophenol (DNP), a mitochondrial uncoupler agent, in an in vitro model of AD. Retinoic acid-induced differentiated SH-SY5Y cells were incubated with okadaic acid (OA), a neurotoxin often used as an AD experimental model, and/or with DNP. OA caused a decrease in neuronal cells viability, induced multiple mitochondrial anomalies including increased levels of reactive oxygen species, decreased bioenergetics and mitochondria content markers, and an altered mitochondria morphology. OA-treated cells also presented increased lipid peroxidation levels, and overactivation of tau related kinases (GSK3β, ERK1/2 and AMPK) alongside with a significant augment in tau protein phosphorylation levels. Interestingly, DNP co-treatment ameliorated and rescued OA-induced detrimental effects not only on mitochondria but also but also reinstated signaling pathways homeostasis and ameliorated tau pathology. Overall, our results show for the first time that DNP has the potential to preserve mitochondria homeostasis under a toxic insult, like OA exposure, as well as to reestablish cellular signaling homeostasis. These observations foster the idea that DNP, as a mitochondrial modulator, might represent a new avenue for treatment of AD.

Progress in mitochondrial and omics studies in Alzheimer's disease research: from molecular mechanisms to therapeutic interventions

Alzheimer's disease (Alzheimer's disease, AD) is a progressive neurological disorder characterized by memory loss and cognitive impairment. It is characterized by the formation of tau protein neurofibrillary tangles and β-amyloid plaques. Recent studies have found that mitochondria in neuronal cells of AD patients exhibit various dysfunctions, including reduced numbers, ultrastructural changes, reduced enzyme activity, and abnormal kinetics. These abnormal mitochondria not only lead to the loss of normal neuronal cell function, but are also a major driver of AD progression. In this review, we will focus on the advances of mitochondria and their multi-omics in AD research, with particular emphasis on how mitochondrial dysfunction in AD drives disease progression. At the same time, we will focus on summarizing how mitochondrial genomics technologies have revealed specific details of these dysfunctions and how therapeutic strategies targeting mitochondria may provide new directions for future AD treatments. By delving into the key mechanisms of mitochondria in AD related to energy metabolism, altered kinetics, regulation of cell death, and dysregulation of calcium-ion homeostasis, and how mitochondrial multi-omics technologies can be utilized to provide us with a better understanding of these processes. In the future, mitochondria-centered therapeutic strategies will be a key idea in the treatment of AD.

Peroxiredoxin 1 inhibits streptozotocin-induced Alzheimer's disease-like pathology in hippocampal neuronal cells via the blocking of Ca2+/Calpain/Cdk5-mediated mitochondrial fragmentation

Oxidative stress plays an essential role in the progression of Alzheimer's disease (AD), the most common age-related neurodegenerative disorder. Streptozotocin (STZ)-induced abnormal brain insulin signaling and oxidative stress play crucial roles in the progression of Alzheimer's disease (AD)-like pathology. Peroxiredoxins (Prxs) are associated with protection from neuronal death induced by oxidative stress. However, the molecular mechanisms underlying Prxs on STZ-induced progression of AD in the hippocampal neurons are not yet fully understood. Here, we evaluated whether Peroxiredoxin 1 (Prx1) affects STZ-induced AD-like pathology and cellular toxicity. Prx1 expression was increased by STZ treatment in the hippocampus cell line, HT-22 cells. We evaluated whether Prx1 affects STZ-induced HT-22 cells using overexpression. Prx1 successfully protected the forms of STZ-induced AD-like pathology, such as neuronal apoptosis, synaptic loss, and tau phosphorylation. Moreover, Prx1 suppressed the STZ-induced increase of mitochondrial dysfunction and fragmentation by down-regulating Drp1 phosphorylation and mitochondrial location. Prx1 plays a role in an upstream signal pathway of Drp1 phosphorylation, cyclin-dependent kinase 5 (Cdk5) by inhibiting the STZ-induced conversion of p35 to p25. We found that STZ-induced of intracellular Ca2+ accumulation was an important modulator of AD-like pathology progression by regulating Ca2+-mediated Calpain activation, and Prx1 down-regulated STZ-induced intracellular Ca2+ accumulation and Ca2+-mediated Calpain activation. Finally, we identified that Prx1 antioxidant capacity affected Ca2+/Calpain/Cdk5-mediated AD-like pathology progress. Therefore, these findings demonstrated that Prx1 is a key factor in STZ-induced hippocampal neuronal death through inhibition of Ca2+/Calpain/Cdk5-mediated mitochondrial dysfunction by protecting against oxidative stress.

Genomic stress and impaired DNA repair in Alzheimer disease

Alzheimer disease (AD) is the most prominent form of dementia and has received considerable attention due to its growing burden on economic, healthcare and basic societal infrastructures. The two major neuropathological hallmarks of AD, i.e., extracellular amyloid beta (Aβ) peptide plaques and intracellular hyperphosphorylated Tau neurofibrillary tangles, have been the focus of much research, with an eye on understanding underlying disease mechanisms and identifying novel therapeutic avenues. One often overlooked aspect of AD is how Aβ and Tau may, through indirect and direct mechanisms, affect genome integrity. Herein, we review evidence that Aβ and Tau abnormalities induce excessive genomic stress and impair genome maintenance mechanisms, events that can promote DNA damage-induced neuronal cell loss and associated brain atrophy.

ACH2.0/E, the Consolidated Theory of Conventional and Unconventional Alzheimer's Disease: Origins, Progression, and Therapeutic Strategies

The centrality of amyloid-beta (Aβ) is an indisputable tenet of Alzheimer's disease (AD). It was initially indicated by the detection (1991) of a mutation within Aβ protein precursor (AβPP) segregating with the disease, which served as a basis for the long-standing Amyloid Cascade Hypothesis (ACH) theory of AD. In the intervening three decades, this notion was affirmed and substantiated by the discovery of numerous AD-causing and AD-protective mutations with all, without an exception, affecting the structure, production, and intraneuronal degradation of Aβ. The ACH postulated that the disease is caused and driven by extracellular Aβ. When it became clear that this is not the case, and the ACH was largely discredited, a new theory of AD, dubbed ACH2.0 to re-emphasize the centrality of Aβ, was formulated. In the ACH2.0, AD is caused by physiologically accumulated intraneuronal Aβ (iAβ) derived from AβPP. Upon reaching the critical threshold, it triggers activation of the autonomous AβPP-independent iAβ generation pathway; its output is retained intraneuronally and drives the AD pathology. The bridge between iAβ derived from AβPP and that generated independently of AβPP is the neuronal integrated stress response (ISR) elicited by the former. The ISR severely suppresses cellular protein synthesis; concurrently, it activates the production of a small subset of proteins, which apparently includes components necessary for operation of the AβPP-independent iAβ generation pathway that are absent under regular circumstances. The above sequence of events defines "conventional" AD, which is both caused and driven by differentially derived iAβ. Since the ISR can be elicited by a multitude of stressors, the logic of the ACH2.0 mandates that another class of AD, referred to as "unconventional", has to occur. Unconventional AD is defined as a disease where a stressor distinct from AβPP-derived iAβ elicits the neuronal ISR. Thus, the essence of both, conventional and unconventional, forms of AD is one and the same, namely autonomous, self-sustainable, AβPP-independent production of iAβ. What distinguishes them is the manner of activation of this pathway, i.e., the mode of causation of the disease. In unconventional AD, processes occurring at locations as distant from and seemingly as unrelated to the brain as, say, the knee can potentially trigger the disease. The present study asserts that these processes include traumatic brain injury (TBI), chronic traumatic encephalopathy, viral and bacterial infections, and a wide array of inflammatory conditions. It considers the pathways which are common to all these occurrences and culminate in the elicitation of the neuronal ISR, analyzes the dynamics of conventional versus unconventional AD, shows how the former can morph into the latter, explains how a single TBI can hasten the occurrence of AD and why it takes multiple TBIs to trigger the disease, and proposes the appropriate therapeutic strategies. It posits that yet another class of unconventional AD may occur where the autonomous AβPP-independent iAβ production pathway is initiated by an ISR-unrelated activator, and consolidates the above notions in a theory of AD, designated ACH2.0/E (for expanded ACH2.0), which incorporates the ACH2.0 as its special case and retains the centrality of iAβ produced independently of AβPP as the driving agent of the disease.

Neurotoxic β-amyloid oligomers cause mitochondrial dysfunction-the trigger for PANoptosis in neurons

As the global population ages, the incidence of elderly patients with dementia, represented by Alzheimer's disease (AD), will continue to increase. Previous studies have suggested that β-amyloid protein (Aβ) deposition is a key factor leading to AD. However, the clinical efficacy of treating AD with anti-Aβ protein antibodies is not satisfactory, suggesting that Aβ amyloidosis may be a pathological change rather than a key factor leading to AD. Identification of the causes of AD and development of corresponding prevention and treatment strategies is an important goal of current research. Following the discovery of soluble oligomeric forms of Aβ (AβO) in 1998, scientists began to focus on the neurotoxicity of AβOs. As an endogenous neurotoxin, the active growth of AβOs can lead to neuronal death, which is believed to occur before plaque formation, suggesting that AβOs are the key factors leading to AD. PANoptosis, a newly proposed concept of cell death that includes known modes of pyroptosis, apoptosis, and necroptosis, is a form of cell death regulated by the PANoptosome complex. Neuronal survival depends on proper mitochondrial function. Under conditions of AβO interference, mitochondrial dysfunction occurs, releasing lethal contents as potential upstream effectors of the PANoptosome. Considering the critical role of neurons in cognitive function and the development of AD as well as the regulatory role of mitochondrial function in neuronal survival, investigation of the potential mechanisms leading to neuronal PANoptosis is crucial. This review describes the disruption of neuronal mitochondrial function by AβOs and elucidates how AβOs may activate neuronal PANoptosis by causing mitochondrial dysfunction during the development of AD, providing guidance for the development of targeted neuronal treatment strategies.

New cyclophilin D inhibitor rescues mitochondrial and cognitive function in Alzheimer's disease

Mitochondrial dysfunction is an early pathological feature of Alzheimer disease and plays a crucial role in the development and progression of Alzheimer's disease. Strategies to rescue mitochondrial function and cognition remain to be explored. Cyclophilin D (CypD), the peptidylprolyl isomerase F (PPIase), is a key component in opening the mitochondrial membrane permeability transition pore, leading to mitochondrial dysfunction and cell death. Blocking membrane permeability transition pore opening by inhibiting CypD activity is a promising therapeutic approach for Alzheimer's disease. However, there is currently no effective CypD inhibitor for Alzheimer's disease, with previous candidates demonstrating high toxicity, poor ability to cross the blood-brain barrier, compromised biocompatibility and low selectivity. Here, we report a new class of non-toxic and biocompatible CypD inhibitor, ebselen, using a conventional PPIase assay to screen a library of ∼2000 FDA-approved drugs with crystallographic analysis of the CypD-ebselen crystal structure (PDB code: 8EJX). More importantly, we assessed the effects of genetic and pharmacological blockade of CypD on Alzheimer's disease mitochondrial and glycolytic bioenergetics in Alzheimer's disease-derived mitochondrial cybrid cells, an ex vivo human sporadic Alzheimer's disease mitochondrial model, and on synaptic function, inflammatory response and learning and memory in Alzheimer's disease mouse models. Inhibition of CypD by ebselen protects against sporadic Alzheimer's disease- and amyloid-β-induced mitochondrial and glycolytic perturbation, synaptic and cognitive dysfunction, together with suppressing neuroinflammation in the brain of Alzheimer's disease mouse models, which is linked to CypD-related membrane permeability transition pore formation. Thus, CypD inhibitors have the potential to slow the progression of neurodegenerative diseases, including Alzheimer's disease, by boosting mitochondrial bioenergetics and improving synaptic and cognitive function.

Focusing on mitochondria in the brain: from biology to therapeutics

Mitochondria have multiple functions such as supplying energy, regulating the redox status, and producing proteins encoded by an independent genome. They are closely related to the physiology and pathology of many organs and tissues, among which the brain is particularly prominent. The brain demands 20% of the resting metabolic rate and holds highly active mitochondrial activities. Considerable research shows that mitochondria are closely related to brain function, while mitochondrial defects induce or exacerbate pathology in the brain. In this review, we provide comprehensive research advances of mitochondrial biology involved in brain functions, as well as the mitochondria-dependent cellular events in brain physiology and pathology. Furthermore, various perspectives are explored to better identify the mitochondrial roles in neurological diseases and the neurophenotypes of mitochondrial diseases. Finally, mitochondrial therapies are discussed. Mitochondrial-targeting therapeutics are showing great potentials in the treatment of brain diseases.

GSDMD/Drp1 signaling pathway mediates hippocampal synaptic damage and neural oscillation abnormalities in a mouse model of sepsis-associated encephalopathy

BACKGROUND

Gasdermin D (GSDMD)-mediated pyroptotic cell death is implicated in the pathogenesis of cognitive deficits in sepsis-associated encephalopathy (SAE), yet the underlying mechanisms remain largely unclear. Dynamin-related protein 1 (Drp1) facilitates mitochondrial fission and ensures quality control to maintain cellular homeostasis during infection. This study aimed to investigate the potential role of the GSDMD/Drp1 signaling pathway in cognitive impairments in a mouse model of SAE.

METHODS

C57BL/6 male mice were subjected to cecal ligation and puncture (CLP) to establish an animal model of SAE. In the interventional study, mice were treated with the GSDMD inhibitor necrosulfonamide (NSA) or the Drp1 inhibitor mitochondrial division inhibitor-1 (Mdivi-1). Surviving mice underwent behavioral tests, and hippocampal tissues were harvested for histological analysis and biochemical assays at corresponding time points. Haematoxylin-eosin staining and TUNEL assays were used to evaluate neuronal damage. Golgi staining was used to detect synaptic dendritic spine density. Additionally, transmission electron microscopy was performed to assess mitochondrial and synaptic morphology in the hippocampus. Local field potential recordings were conducted to detect network oscillations in the hippocampus.

RESULTS

CLP induced the activation of GSDMD, an upregulation of Drp1, leading to associated mitochondrial impairment, neuroinflammation, as well as neuronal and synaptic damage. Consequently, these effects resulted in a reduction in neural oscillations in the hippocampus and significant learning and memory deficits in the mice. Notably, treatment with NSA or Mdivi-1 effectively prevented these GSDMD-mediated abnormalities.

CONCLUSIONS

Our data indicate that the GSDMD/Drp1 signaling pathway is involved in cognitive deficits in a mouse model of SAE. Inhibiting GSDMD or Drp1 emerges as a potential therapeutic strategy to alleviate the observed synaptic damages and network oscillations abnormalities in the hippocampus of SAE mice.

Optineurin-facilitated axonal mitochondria delivery promotes neuroprotection and axon regeneration

Optineurin (OPTN) mutations are linked to amyotrophic lateral sclerosis (ALS) and normal tension glaucoma (NTG), but a relevant animal model is lacking, and the molecular mechanisms underlying neurodegeneration are unknown. We found that OPTN C-terminus truncation (OPTN∆C) causes late-onset neurodegeneration of retinal ganglion cells (RGCs), optic nerve (ON), and spinal cord motor neurons, preceded by a striking decrease of axonal mitochondria. Surprisingly, we discover that OPTN directly interacts with both microtubules and the mitochondrial transport complex TRAK1/KIF5B, stabilizing them for proper anterograde axonal mitochondrial transport, in a C-terminus dependent manner. Encouragingly, overexpressing OPTN/TRAK1/KIF5B reverses not only OPTN truncation-induced, but also ocular hypertension-induced neurodegeneration, and promotes striking ON regeneration. Therefore, in addition to generating new animal models for NTG and ALS, our results establish OPTN as a novel facilitator of the microtubule-dependent mitochondrial transport necessary for adequate axonal mitochondria delivery, and its loss as the likely molecular mechanism of neurodegeneration.

Redox changes and cellular senescence in Alzheimer's disease

The redox process and cellular senescence are involved in a range of essential physiological functions. However, they are also implicated in pathological processes underlying age-related neurodegenerative disorders, including Alzheimer's disease (AD). Elevated levels of reactive oxygen species (ROS) are generated as a result of abnormal accumulation of beta-amyloid peptide (Aβ), tau protein, and heme dyshomeostasis and is further aggravated by mitochondria dysfunction and endoplasmic reticulum (ER) stress. Excessive ROS damages vital cellular components such as proteins, DNA and lipids. Such damage eventually leads to impaired neuronal function and cell death. Heightened oxidative stress can also induce cellular senescence via activation of the senescence-associated secretory phenotype to further exacerbate inflammation and tissue dysfunction. In this review, we focus on how changes in the redox system and cellular senescence contribute to AD and how they are affected by perturbations in heme metabolism and mitochondrial function. While potential therapeutic strategies targeting such changes have received some attention, more research is necessary to bring them into clinical application.

hnRNP R regulates mitochondrial movement and membrane potential in axons of motoneurons

Axonal mitochondria defects are early events in the pathogenesis of motoneuron disorders such as spinal muscular atrophy and amyotrophic lateral sclerosis. The RNA-binding protein hnRNP R interacts with different motoneuron disease-related proteins such as SMN and TDP-43 and has important roles in axons of motoneurons, including axonal mRNA transport. However, whether hnRNP R also modulates axonal mitochondria is currently unknown. Here, we show that axonal mitochondria exhibit altered function and motility in hnRNP R-deficient motoneurons. Motoneurons lacking hnRNP R show decreased anterograde and increased retrograde transport of mitochondria in axons. Furthermore, hnRNP R-deficiency leads to mitochondrial hyperpolarization, caused by decreased complex I and reversed complex V activity within the respiratory chain. Taken together, our data indicate a role for hnRNP R in regulating transport and maintaining functionality of axonal mitochondria in motoneurons.