Mitochondrial bioenergetic deficit precedes Alzheimer's pathology in female mouse model of Alzheimer's disease. Proc Natl Acad Sci U S A. 2009;106:14670-14675. [PMID: 19667196 DOI: 10.1073/pnas.0903563106]

Qifu-yin activates the Keap1/Nrf2/ARE signaling and ameliorates synaptic injury and oxidative stress in APP/PS1 mice

ETHNOPHARMACOLOGICAL RELEVANCE

The traditional medicinal formulation, Qifu-yin (QFY), has been widely prescribed for Alzheimer's disease (AD) treatment in China, yet the comprehensive mechanisms through which QFY mitigates AD pathology remain to be fully delineated.

AIM OF THE STUDY

This study aimed to explore the therapeutic implications of QFY on the synaptic injury and oxidative stress in the hippocampus of APPswe/PS1dE9 (APP/PS1) mice, with a concerted effort to elucidate the molecular mechanisms related to synaptic preservation and memory improvement.

MATERIALS AND METHODS

The components of QFY were identified by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The neuroprotective effects of QFY was evaluated using six-month-old male APP/PS1 mice. Subsequent to a 15 days of QFY regimen, spatial memory was assessed utilizing the Morris water maze (MWM) test. Amyloid-beta (Aβ) aggregation was detected via immunostaining, while the quantification of Aβ1-40 and Aβ1-42 was achieved through enzyme-linked immunosorbent assay (ELISA). Transmission electron microscopy (TEM) was used to investigate the synaptic structure and mitochondrial morphology. Golgi staining was applied to examine dendritic spine density. Reactive oxygen species (ROS), 3-nitrotyrosine (3-NT) and 4-hydroxy-nonenal (4-HNE) assays were employed to assess oxidative stress. The expression profiles of Aβ metabolism-associated enzymes and the Keap1/Nrf2/ARE signaling pathway were determined by Western blot.

RESULTS

A total of 20 principal compounds in QFY were identified. QFY mitigated memory deficits of APP/PS1 mice, including reducing escape latency and search distance and increasing the time and distance spent in the target quadrant. In addition, QFY increased platform crossings of APP/PS1 mice in the probe trial of MWM tests. TEM analysis showed that QFY increased synapse number in the CA1 region of APP/PS1 mice. Further studies indicated that QFY elevated the expression levels of Post synaptic density protein 95 (PSD95) and synaptophysin, and mitigated the loss of dendritic spine density in the hippocampus of APP/PS1 mice. QFY has been shown to ameliorated the structural abnormalities of mitochondria, including mitochondrial dissolution and degradation, up-regulate ATP synthesis and membrane potential in the hippocampus of APP/PS1 mice. Moreover, QFY activated the Keap1/Nrf2/ARE signaling pathway in the hippocampus of APP/PS1 mice, which might contribute to the neuroprotective effects of QFY.

CONCLUSION

QFY activates the Keap1/Nrf2/ARE signaling, and protects against synaptic and mitochondrial dysfunction in APP/PS1 mice, proposing a potential alternative therapeutic strategy for AD management.

Diabetes mellitus and Alzheimer's disease: Understanding disease mechanisms, their correlation, and promising dual activity of selected herbs

ETHNOPHARMACOLOGICAL RELEVANCE

This review explores the link between Type 2 Diabetes Mellitus (T2DM) and diabetes-induced Alzheimer's disease (AD). It emphasizes the shared pathophysiological links and mechanisms between the two conditions, focusing on reduced insulin levels and receptors, impaired glucose metabolism, insulin resistance, mitochondrial dysfunction, and oxidative damage in AD-affected brains-paralleling aspects of T2DM. The review suggests AD as a "diabetes of the brain," supported by cognitive enhancement through antidiabetic interventions. It focuses on the traditionally used Indian herbs as a means to manage both conditions while addressing developmental challenges.

AIM OF THE STUDY

This study explores the DM-AD connection, reviewing medicinal herbs with protective potential for both ailments, considering traditional uses and developmental challenges.

MATERIALS AND METHODS

Studied research, reviews, and ethnobotanical and scientific data from electronic databases and traditional books.

RESULTS

The study analyzes the pathophysiological links between DM and AD, emphasizing their interconnected factors. Eight Ayurvedic plants with dual protective effects against T2DM and AD are thoroughly reviewed with preclinical/clinical evidence. Historical context, phytoconstituents, and traditional applications are explored. Innovative formulations using these plants are examined. Challenges stemming from phytoconstituents' physicochemical properties are highlighted, prompting novel formulation development, including nanotechnology-based delivery systems. The study uncovers obstacles in formulating treatments for these diseases.

CONCLUSION

The review showcases the dual potential of chosen medicinal herbs against both diseases, along with their traditional applications, endorsing their use. It addresses formulation obstacles, proposing innovative delivery technologies for herbal therapies, while acknowledging their constraints. The review suggests the need for heightened investment and research in this area.

Inhibiting mtDNA transcript translation alters Alzheimer's disease-associated biology

INTRODUCTION

Alzheimer's disease (AD) features changes in mitochondrial structure and function. Investigators debate where to position mitochondrial pathology within the chronology and context of other AD features.

METHODS

To address whether mitochondrial dysfunction alters AD-implicated genes and proteins, we treated SH-SY5Y cells and induced pluripotent stem cell (iPSC)-derived neurons with chloramphenicol, an antibiotic that inhibits mtDNA-generated transcript translation. We characterized adaptive, AD-associated gene, and AD-associated protein responses.

RESULTS

SH-SY5Y cells and iPSC neurons responded to mtDNA transcript translation inhibition by increasing mtDNA copy number and transcription. Nuclear-expressed respiratory chain mRNA and protein levels also changed. There were AD-consistent concordant and model-specific changes in amyloid precursor protein, beta amyloid, apolipoprotein E, tau, and α-synuclein biology.

DISCUSSION

Primary mitochondrial dysfunction induces compensatory organelle responses, changes nuclear gene expression, and alters the biology of AD-associated genes and proteins in ways that may recapitulate brain aging and AD molecular phenomena.

HIGHLIGHTS

In AD, mitochondrial dysfunction could represent a disease cause or consequence. We inhibited mitochondrial translation in human neuronal cells and neurons. Mitochondrial and nuclear gene expression shifted in adaptive-consistent patterns. APP, Aβ, APOE, tau, and α-synuclein biology changed in AD-consistent patterns. Mitochondrial stress creates an environment that promotes AD pathology.

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.

Exploring complexities of Alzheimer's disease: New insights into molecular and cellular mechanisms of neurodegeneration and targeted therapeutic interventions

Alzheimer's disease (AD), the common form of dementia globally, is a complex condition including neurodegeneration; shares incompletely known pathogenesis. Signal transduction and biological activities, including cell metabolism, growth, and death are regulated by different signaling pathways including AKT/MAPK, Wnt, Leptin, mTOR, ubiquitin, Sirt1, and insulin. Absolute evidence linking specific molecular pathways with the genesis and/or progression of AD is still lacking. Changes in gut microbiota and blood-brain barrier also cause amyloid β aggregation in AD. The current review reports significant characteristics of various signaling pathways, their relationship with each other, and how they interact in disease genesis and/or progression. Nevertheless, due to the enormous complexity of the brain and numerous chemical linkages between these pathways, the use of signaling pathways as possible targets for drug development against AD is minimal. Currently, there is no permanent cure for AD, and there is no way to stop brain cell loss. This review also aimed to draw attention to the role of a novel group of signaling pathways, which can be collectively dubbed "anti-AD pathways", in multi-target therapy for AD, where cellular metabolic functions are severely impaired. Thus, different hypotheses have been formulated and elaborated to explain the genesis of AD, which can be further explored for drug development too.

Crocetin Delays Brain and Body Aging by Increasing Cellular Energy Levels in Aged C57BL/6J Mice

Aging is usually accompanied by mitochondrial dysfunction, reduced energy levels, and cell death in the brain and other tissues. Mitochondria play a crucial role in maintaining cellular energy through oxidative phosphorylation (OXPHOS). However, OXPHOS is impaired as the mitochondrial oxygen supply decreases with age. We explored whether pharmacologically increased oxygen diffusion by crocetin can restore OXPHOS and help delay the aging of the brain and other vital organs. We found that aged mice treated with crocetin for four months displayed significantly improved memory behavior, neuromuscular coordination, and ATP and NAD+ levels in the brain and other vital organs, leading to an increased median life span. The transcriptomic analysis of hippocampi from crocetin-treated mice revealed that enhanced brain energy level was caused by the upregulation of genes linked to OXPHOS, and their expression was close to that in young mice. The chronic treatment of aged astrocytes also showed improved mitochondrial membrane potential and energy state of the cells. Moreover, chronic treatment with crocetin did not cause any oxidative stress. Our data suggest that restoring OXPHOS and the normal energy state of the cell can delay aging and enhance longevity. Therefore, molecules such as crocetin should be further explored to treat age-related diseases.

Nilotinib as a Prospective Treatment for Alzheimer's Disease: Effect on Proteins Involved in Neurodegeneration and Neuronal Homeostasis

Nilotinib, a tyrosine kinase inhibitor that targets the Abelson tyrosine kinase (c-Abl) signaling pathway, is FDA-approved to treat chronic myeloid leukemia. Nilotinib has properties indicative of a possible utility in neuroprotection that have prompted exploration of repurposing the drug for the treatment of Alzheimer's disease (AD) and Parkinson's disease (PD). AD is a progressive age-related neurodegenerative disorder characterized by the deposition of extracellular amyloid-β plaques and intracellular neurofibrillary tangles. It is incurable and affects approximately 50 million patients worldwide. Nilotinib reduces c-Abl phosphorylation, amyloid-β levels, and dopaminergic neuron degeneration in preclinical AD models. This study explores the effects of nilotinib on amyloid processing and mitochondrial functioning in the SH-SY5Y human neuroblastoma cell line. SH-SY5Y cells were exposed to nilotinib (1, 5, and 10 µM). Real-time PCR and immunoblot analysis were performed to quantify the expression of genes pertaining to amyloid-β processing and neuronal health. Nilotinib did not significantly change APP, BACE1, or ADAM10 mRNA levels. However, BACE1 protein was significantly increased at 1 µM, and ADAM10 was increased at 10 µM nilotinib without affecting APP protein expression. Further, nilotinib treatment did not affect the expression of genes associated with neuronal health and mitochondrial functioning. Taken together, our findings do not support the efficacy of nilotinib treatment for neuroprotection.

A novel PDHK inhibitor restored cognitive dysfunction and limited neurodegeneration without affecting amyloid pathology in 5xFAD mouse, a model of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the most common form of dementia. Although drugs focusing on reducing amyloid β slow progression, they fail to improve cognitive function. Deficits in glucose metabolism are reflected in FDG-PET and parallel the neurodegeneration and synaptic marker loss closely preceding cognitive decline, but the role of metabolic deficits as a cause or consequence of neurodegeneration is unclear. Pyruvate dehydrogenase (PDH) is lost in AD and an important enzyme connecting glycolysis and the tricarboxylic acid (TCA) cycle by converting pyruvate into acetyl-CoA. It is negatively regulated by pyruvate dehydrogenase kinase (PDHK) through phosphorylation.

METHODS

In the present study, we assessed the in vitro/ in vivo pharmacological profile of the novel PDHK inhibitor that we discovered, Compound A. We also assessed the effects of Compound A on AD-related phenotypes including neuron loss and cognitive impairment using 5xFAD model mice.

RESULTS

Compound A inhibited human PDHK1, 2 and 3 but had no inhibitory activity on PDHK4. In primary neurons, Compound A enhanced pyruvate and lactate utilization, but did not change glucose levels. In contrast, in primary astrocytes, Compound A enhanced pyruvate and glucose utilization and enhanced lactate production. In an efficacy study using 5xFAD mice, Compound A ameliorated the cognitive dysfunction in the novel object recognition test and Morris water maze. Moreover, Compound A prevented neuron loss in the hippocampus and cerebral cortex of 5xFAD without affecting amyloid β deposits.

CONCLUSIONS

These results suggest ameliorating metabolic deficits by activating PDH by Compound A can limit neurodegeneration and is a promising therapeutic strategy for treating AD.

Human fibroblasts from sporadic Alzheimer's disease (AD) patients show mitochondrial alterations and lysosome dysfunction

Mitophagy is a mechanism that maintains mitochondrial integrity and homeostasis and is thought to promote longevity and reduce the risk of age-related neurodegenerative diseases, including Alzheimer's disease (AD). Here, we investigate the abundance of mitochondrial reactive oxygen species (ROS), mitochondrial function, and mitophagy in primary fibroblasts from patients with sporadic AD (sAD) and normal healthy controls. The results show increased levels of mitochondrial ROS, changes in mitochondrial morphology, altered bioenergetic properties, and defects in autophagy, mitophagy, and lysosome-mediated degradation pathways in sAD fibroblasts relative to control fibroblasts. Interestingly, lysosome abundance and the staining of lysosomal markers remained high, while the capacity of lysosome-dependent degradation was lower in sAD fibroblasts than in controls fibroblasts. Nicotinamide riboside supplementation decreased mitochondrial ROS, while capacity for lysosomal degradation remained unchanged in sAD fibroblasts relative to healthy control fibroblasts. These findings provide insight into molecular mechanisms involving the dysregulation of lysosome and autophagy/mitophagy pathways that may contribute significantly to clinical signs and pathological features of sAD.

Chronic corticosterone administration alters synaptic mitochondrial function within the hippocampus of C57Bl/6NTac mice

Chronic activation of the hypothalamic-pituitary-adrenal axis increases circulating corticosterone levels, causing a host of downstream behavioral, molecular, and metabolic changes. Here, we assess the effects of chronic exogenous CORT administration on changes in behavior and mitochondrial respiration in hippocampal synaptosomes of male and female mice. Adult male (n = 15) and female (n = 17) C57Bl/6NTac mice were given 35ug/mL CORT or vehicle dissolved in their drinking water for 21 consecutive days. Chronic CORT increased piloerection in males only. Although volume of CORT-containing water consumed was similar between males and females, circulating plasma and fecal corticosterone levels were only elevated in CORT-exposed males. Behavioral effects of CORT were evident in the Y-maze such that CORT caused a decrease in direct revisits in both sexes. There was no observed presentation of anxiety-like behavior following chronic CORT administration. Functional hippocampal synaptosomes were analyzed for mitochondrial respiration using Agilent's Cell Mito Stress test. Chronic CORT caused a decrease in synaptic mitochondria basal respiration, maximal respiration, proton leak, and ATP production in both sexes. Despite only observing an effect of chronic CORT on corticosterone concentrations in fecal and blood samples of males, chronic CORT induced marked changes in hippocampal synaptic mitochondrial function of both sexes. These data highlight the importance of considering effects of stress hormone exposure on neural function even in the absence of measurable peripheral elevations in females.

Targeting mitochondrial quality control: new therapeutic strategies for major diseases

Mitochondria play a crucial role in maintaining the normal physiological state of cells. Hence, ensuring mitochondrial quality control is imperative for the prevention and treatment of numerous diseases. Previous reviews on this topic have however been inconsistencies and lack of systematic organization. Therefore, this review aims to provide a comprehensive and systematic overview of mitochondrial quality control and explore the possibility of targeting the same for the treatment of major diseases. This review systematically summarizes three fundamental characteristics of mitochondrial quality control, including mitochondrial morphology and dynamics, function and metabolism, and protein expression and regulation. It also extensively examines how imbalances in mitochondrial quality are linked to major diseases, such as ischemia-hypoxia, inflammatory disorders, viral infections, metabolic dysregulations, degenerative conditions, and tumors. Additionally, the review explores innovative approaches to target mitochondrial quality control, including using small molecule drugs that regulate critical steps in maintaining mitochondrial quality, nanomolecular materials designed for precise targeting of mitochondria, and novel cellular therapies, such as vesicle therapy and mitochondrial transplantation. This review offers a novel perspective on comprehending the shared mechanisms underlying the occurrence and progression of major diseases and provides theoretical support and practical guidance for the clinical implementation of innovative therapeutic strategies that target mitochondrial quality control for treating major diseases.

Senolytic intervention improves cognition, metabolism, and adiposity in female APPNL-F/NL-F mice

Senescent cells accumulate throughout the body and brain contributing to unhealthy aging and Alzheimer's disease (AD). The APPNL-F/NL-F amyloidogenic AD mouse model exhibits increased markers of senescent cells and the senescence-associated secretory phenotype (SASP) in visceral white adipose tissue and the hippocampus before plaque accumulation and cognitive decline. We hypothesized that senolytic intervention would alleviate cellular senescence thereby improving spatial memory in APPNL-F/NL-F mice. Thus, 4-month-old male and female APPNL-F/NL-F mice were treated monthly with vehicle, 5 mg/kg dasatinib + 50 mg/kg quercetin, or 100 mg/kg fisetin. Blood glucose levels, energy metabolism, spatial memory, amyloid burden, and senescent cell markers were assayed. Dasatinib + quercetin treatment in female APPNL-F/NL-F mice increased oxygen consumption and energy expenditure resulting in decreased body mass. White adipose tissue mass was decreased along with senescence markers, SASP, blood glucose, and plasma insulin and triglycerides. Hippocampal senescence markers and SASP were reduced along with soluble and insoluble amyloid-β (Aβ)42 and senescence-associated-β-gal activity leading to improved spatial memory. Fisetin had negligible effects on these measures in female APPNL-F/NL-F mice while neither senolytic intervention altered these parameters in the male mice. Considering women have a greater risk of dementia, identifying senotherapeutics appropriate for sex and disease stage is necessary for personalized medicine.

Excitotoxicity, Oxytosis/Ferroptosis, and Neurodegeneration: Emerging Insights into Mitochondrial Mechanisms

Mitochondrial dysfunction plays a pivotal role in the development of age-related diseases, particularly neurodegenerative disorders. The etiology of mitochondrial dysfunction involves a multitude of factors that remain elusive. This review centers on elucidating the role(s) of excitotoxicity, oxytosis/ferroptosis and neurodegeneration within the context of mitochondrial bioenergetics, biogenesis, mitophagy and oxidative stress and explores their intricate interplay in the pathogenesis of neurodegenerative diseases. The effective coordination of mitochondrial turnover processes, notably mitophagy and biogenesis, is assumed to be critically important for cellular resilience and longevity. However, the age-associated decrease in mitophagy impedes the elimination of dysfunctional mitochondria, consequently impairing mitochondrial biogenesis. This deleterious cascade results in the accumulation of damaged mitochondria and deterioration of cellular functions. Both excitotoxicity and oxytosis/ferroptosis have been demonstrated to contribute significantly to the pathophysiology of neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's Disease (HD), Amyotrophic Lateral Sclerosis (ALS) and Multiple Sclerosis (MS). Excitotoxicity, characterized by excessive glutamate signaling, initiates a cascade of events involving calcium dysregulation, energy depletion, and oxidative stress and is intricately linked to mitochondrial dysfunction. Furthermore, emerging concepts surrounding oxytosis/ferroptosis underscore the importance of iron-dependent lipid peroxidation and mitochondrial engagement in the pathogenesis of neurodegeneration. This review not only discusses the individual contributions of excitotoxicity and ferroptosis but also emphasizes their convergence with mitochondrial dysfunction, a key driver of neurodegenerative diseases. Understanding the intricate crosstalk between excitotoxicity, oxytosis/ferroptosis, and mitochondrial dysfunction holds potential to pave the way for mitochondrion-targeted therapeutic strategies. Such strategies, with a focus on bioenergetics, biogenesis, mitophagy, and oxidative stress, emerge as promising avenues for therapeutic intervention.

Mitochondrial plasticity and synaptic plasticity crosstalk; in health and Alzheimer's disease

Synaptic plasticity is believed to underlie the cellular and molecular basis of memory formation. Mitochondria are one of the main organelles involved in metabolism and energy maintenance as plastic organelles that change morphologically and functionally in response to cellular needs and regulate synaptic function and plasticity through multiple mechanisms, including ATP generation, calcium homeostasis, and biogenesis. An increased neuronal activity enhances synaptic efficiency, during which mitochondria's spatial distribution and morphology change significantly. These organelles build up in the pre-and postsynaptic zones to produce ATP, which is necessary for several synaptic processes like neurotransmitter release and recycling. Mitochondria also regulate calcium homeostasis by buffering intracellular calcium, which ensures proper synaptic activity. Furthermore, mitochondria in the presynaptic terminal have distinct morphological properties compared to dendritic or postsynaptic mitochondria. This specialization enables precise control of synaptic activity and plasticity. Mitochondrial dysfunction has been linked to synaptic failure in many neurodegenerative disorders, like Alzheimer's disease (AD). In AD, malfunctioning mitochondria cause delays in synaptic vesicle release and recycling, ionic gradient imbalances, and mostly synaptic failure. This review emphasizes mitochondrial plasticity's contribution to synaptic function. It also explores the profound effect of mitochondrial malfunction on neurodegenerative disorders, focusing on AD, and provides an overview of how they sustain cellular health under normal conditions and how their malfunction contributes to neurodegenerative diseases, highlighting their potential as a therapeutic target for such conditions.

Non-transgenic guinea pig strains exhibit divergent age-related changes in hippocampal mitochondrial respiration

AIM

Alzheimer's disease (AD) is the most common form of dementia. However, while 150+ animal models of AD exist, drug translation from preclinical models to humans for treatment usually fails. One factor contributing to low translation is likely the absence of neurodegenerative models that also encompass the multi-morbidities of human aging. We previously demonstrated that, in comparison to the PigmEnTed (PET) guinea pig strain which models "typical" brain aging, the Hartley strain develops hallmarks of AD like aging humans. Hartleys also exhibit age-related impairments in cartilage and skeletal muscle. Impaired mitochondrial respiration is one driver of both cellular aging and AD. In humans with cognitive decline, diminished skeletal muscle and brain respiratory control occurs in parallel. We previously reported age-related declines in skeletal muscle mitochondrial respiration in Hartleys. It is unknown if there is concomitant mitochondrial dysfunction in the brain.

METHODS

Therefore, we assessed hippocampal mitochondrial respiration in 5- and 12-month Hartley and PET guinea pigs using high-resolution respirometry.

RESULTS

At 12 months, PETs had higher complex I supported mitochondrial respiration paralleling their increase in body mass compared to 5 months PETs. Hartleys were also heavier at 12 months compared to 5 months but did not have higher complex I respiration. Compared to 5 months Hartleys, 12 months Hartleys had lower complex I mitochondrial efficiency and compensatory increases in mitochondrial proteins collectively suggesting mitochondrial dysfunction with age.

CONCLUSIONS

Therefore, Hartleys might be a relevant model to test promising therapies targeting mitochondria to slow brain aging and AD progression.

Alpha-lipoic acid alleviates cognitive deficits in transgenic APP23/PS45 mice through a mitophagy-mediated increase in ADAM10 α-secretase cleavage of APP

BACKGROUND

Alpha-lipoic acid (ALA) has a neuroprotective effect on neurodegenerative diseases. In the clinic, ALA can improve cognitive impairments in patients with Alzheimer's disease (AD) and other dementias. Animal studies have confirmed the anti-amyloidosis effect of ALA, but its underlying mechanism remains unclear. In particular, the role of ALA in amyloid-β precursor protein (APP) metabolism has not been fully elucidated.

OBJECTIVE

To investigate whether ALA can reduce the amyloidogenic effect of APP in a transgenic mouse model of AD, and to study the mechanism underlying this effect.

METHODS

ALA was infused into 2-month-old APP23/PS45 transgenic mice for 4 consecutive months and their cognitive function and AD-like pathology were then evaluated. An ALA drug concentration gradient was applied to 20E2 cells in vitro to evaluate its effect on the expression of APP proteolytic enzymes and metabolites. The mechanism by which ALA affects APP processing was studied using GI254023X, an inhibitor of A Disintegrin and Metalloproteinase 10 (ADAM10), as well as the mitochondrial toxic drug carbonyl cyanide m-chlorophenylhydrazone (CCCP).

RESULTS

Administration of ALA ameliorated amyloid plaque neuropathology in the brain tissue of APP23/PS45 mice and reduced learning and memory impairment. ALA also increased the expression of ADAM10 in 20E2 cells and the non-amyloidogenic processing of APP to produce the 83 amino acid C-terminal fragment (C83). In addition to activating autophagy, ALA also significantly promoted mitophagy. BNIP3L-knockdown reduced the mat/pro ratio of ADAM10. By using CCCP, ALA was found to regulate BNIP3L-mediated mitophagy, thereby promoting the α-cleavage of APP.

CONCLUSIONS

The enhanced α-secretase cleavage of APP by ADAM10 is the primary mechanism through which ALA ameliorates the cognitive deficits in APP23/PS45 transgenic mice. BNIP3L-mediated mitophagy contributes to the anti-amyloid properties of ALA by facilitating the maturation of ADAM10. This study provides novel experimental evidence for the treatment of AD with ALA.

Antigen-specific age-related memory CD8 T cells induce and track Alzheimer's-like neurodegeneration

Cerebral (Aβ) plaque and (pTau) tangle deposition are hallmarks of Alzheimer's disease (AD), yet are insufficient to confer complete AD-like neurodegeneration experimentally. Factors acting upstream of Aβ/pTau in AD remain unknown, but their identification could enable earlier diagnosis and more effective treatments. T cell abnormalities are emerging AD hallmarks, and CD8 T cells were recently found to mediate neurodegeneration downstream of tangle deposition in hereditary neurodegeneration models. The precise impact of T cells downstream of Aβ/pTau, however, appears to vary depending on the animal model. Our prior work suggested that antigen-specific memory CD8 T ("hiT") cells act upstream of Aβ/pTau after brain injury. Here, we examine whether hiT cells influence sporadic AD-like pathophysiology upstream of Aβ/pTau. Examining neuropathology, gene expression, and behavior in our hiT mouse model we show that CD8 T cells induce plaque and tangle-like deposition, modulate AD-related genes, and ultimately result in progressive neurodegeneration with both gross and fine features of sporadic human AD. T cells required Perforin to initiate this pathophysiology, and IFNγ for most gene expression changes and progression to more widespread neurodegenerative disease. Analogous antigen-specific memory CD8 T cells were significantly elevated in the brains of human AD patients, and their loss from blood corresponded to sporadic AD and related cognitive decline better than plasma pTau-217, a promising AD biomarker candidate. We identify an age-related factor acting upstream of Aβ/pTau to initiate AD-like pathophysiology, the mechanisms promoting its pathogenicity, and its relevance to human sporadic AD.

Truncated tau interferes with the autophagy and endolysosomal pathway and results in lipid accumulation

The autophagy-lysosomal pathway plays a critical role in the clearance of tau protein aggregates that deposit in the brain in tauopathies, and defects in this system are associated with disease pathogenesis. Here, we report that expression of Tau35, a tauopathy-associated carboxy-terminal fragment of tau, leads to lipid accumulation in cell lines and primary cortical neurons. Our findings suggest that this is likely due to a deleterious block of autophagic clearance and lysosomal degradative capacity by Tau35. Notably, upon induction of autophagy by Torin 1, Tau35 inhibited nuclear translocation of transcription factor EB (TFEB), a key regulator of lysosomal biogenesis. Both cell lines and primary cortical neurons expressing Tau35 also exhibited changes in endosomal protein expression. These findings implicate autophagic and endolysosomal dysfunction as key pathological mechanisms through which disease-associated tau fragments could lead to the development and progression of tauopathy.

Senolytic Intervention Improves Cognition, Metabolism, and Adiposity in Female APP NL-F/NL-F Mice

Senescent cells accumulate throughout the body and brain contributing to unhealthy aging and Alzheimer's disease (AD). The APP NL-F/NL-F amyloidogenic AD mouse model exhibits increased markers of senescent cells and the senescence-associated secretory phenotype (SASP) in visceral white adipose tissue before plaque accumulation and cognitive decline. We hypothesized that senolytic intervention would alleviate cellular senescence thereby improving spatial memory in APP NL-F/NL-F mice. Thus, four month old male and female APP NL-F/NL-F mice were treated monthly with vehicle, 5 mg/kg Dasatinib + 50 mg/kg Quercetin, or 100 mg/kg Fisetin. Blood glucose levels, energy metabolism, spatial memory, amyloid burden, and senescent cell markers were assayed. Dasatinib + Quercetin treatment in female APP NL-F/NL-F mice increased oxygen consumption and energy expenditure resulting in decreased body mass. White adipose tissue mass was decreased along with senescence markers, SASP, blood glucose, and plasma insulin and triglycerides. Hippocampal senescence markers and SASP were reduced along with soluble and insoluble amyloid-β (Aβ) 42 and senescence associated-β-gal activity leading to improved spatial memory. Fisetin had negligible effects on these measures in female APP NL-F/NL-F mice while neither senolytic intervention altered these parameters in the male mice. Considering women have a greater risk of dementia, identifying senotherapeutics appropriate for sex and disease stage is necessary for personalized medicine.

Complicated Role of Post-translational Modification and Protease-Cleaved Fragments of Tau in Alzheimer's Disease and Other Tauopathies

Tau, a microtubule-associated protein predominantly localized in neuronal axons, plays a crucial role in promoting microtubule assembly, stabilizing their structure, and participating in axonal transport. Perturbations in tau's structure and function are implicated in the pathogenesis of neurodegenerative diseases collectively known as tauopathies, the most common disorder of which is Alzheimer's disease (AD). In tauopathies, it has been found that tau has a variety of post-translational modification (PTM) abnormalities and/or tau is cleaved into a variety of fragments by some specific proteolytic enzymes; however, the precise contributions of these abnormal modifications and fragments to disease onset and progression remain incompletely understood. Herein, we provide an overview about the involvement of distinctive abnormal tau PTMs and different tau fragments in the pathogenesis of AD and other tauopathies and discuss the involvement of proteolytic enzymes such as caspases, calpains, and asparagine endopeptidase in mediating tau cleavage while also addressing the intercellular transmission role played by tau. We anticipate that further exploration into PTMs and fragmented forms of tau will yield valuable insights for diagnostic approaches and therapeutic interventions targeting AD and other related disorders.

An efficient and high-throughput method for the evaluation of mitochondrial dysfunction in frozen brain samples after traumatic brain injury

Mitochondrial function analysis is a well-established method used in preclinical and clinical investigations to assess pathophysiological changes in various disease states, including traumatic brain injury (TBI). Although there are multiple approaches to assess mitochondrial function, one common method involves respirometric assays utilizing either Clark-type oxygen electrodes or fluorescent-based Seahorse analysis (Agilent). However, these functional analysis methods are typically limited to the availability of freshly isolated tissue samples due to the compromise of the electron transport chain (ETC) upon storage, caused by freeze-thaw-mediated breakdown of mitochondrial membranes. In this study, we propose and refine a method for evaluating electron flux through the ETC, encompassing complexes I, II, and IV, in frozen homogenates or mitochondrial samples within a single well of a Seahorse plate. Initially, we demonstrate the impact of TBI on freshly isolated mitochondria using the conventional oxidative phosphorylation protocol (OxPP), followed by a comparison with ETC analysis conducted on frozen tissue samples within the context of a controlled cortical impact (CCI) model of TBI. Additionally, we explore the effects of mitochondrial isolation from fresh versus snap-frozen brain tissues and their storage at -80°C, assessing its impact on electron transport chain protocol (ETCP) activity. Our findings indicate that while both sets of samples were frozen at a single time point, mitochondria from snap-frozen tissues exhibited reduced injury effects compared to preparations from fresh tissues, which were either homogenized or isolated into mitochondria and subsequently frozen for later use. Thus, we demonstrate that the preparation of homogenates or isolated mitochondria can serve as an appropriate method for storing brain samples, allowing for later analysis of mitochondrial function, following TBI using ETCP.

Butyrate as a potential therapeutic agent for neurodegenerative disorders

Maintaining an optimum microbial community within the gastrointestinal tract is intricately linked to human metabolic, immune and brain health. Disturbance to these microbial populations perturbs the production of vital bioactive compounds synthesised by the gut microbiome, such as short-chain fatty acids (SCFAs). Of the SCFAs, butyrate is known to be a major source of energy for colonocytes and has valuable effects on the maintenance of intestinal epithelium and blood brain barrier integrity, gut motility and transit, anti-inflammatory effects, and autophagy induction. Inducing endogenous butyrate production is likely to be beneficial for gut-brain homeostasis and for optimal neuronal function. For these reasons, butyrate has gained interest as a potential therapy for not only metabolic and immunological disorders, but also conditions related to the brain, including neurodegenerative diseases. While direct and indirect sources of butyrate, including prebiotics, probiotics, butyrate pro-drugs and glucosidase inhibitors, offer a promising therapeutic avenue, their efficacy and dosage in neurodegenerative conditions remain largely unknown. Here, we review current literature on effects of butyrate relevant to neuronal function, the impact of butyrate in a range of neurodegenerative diseases and related treatments that may have potential for the treatment of neurodegenerative diseases.

Biomarker evidence of early vision and rod energy-linked pathophysiology benefits from very low dose DMSO in 5xFAD mice

Here, we test whether early visual and OCT rod energy-linked biomarkers indicating pathophysiology in nicotinamide nucleotide transhydrogenase (Nnt)-null 5xFAD mice also occur in Nnt-intact 5xFAD mice and whether these biomarkers can be pharmacologically treated. Four-month-old wild-type or 5xFAD C57BL/6 substrains with either a null (B6J) Nnt or intact Nnt gene (B6NTac) and 5xFAD B6J mice treated for one month with either R-carvedilol + vehicle or only vehicle (0.01% DMSO) were studied. The contrast sensitivity (CS), external limiting membrane-retinal pigment epithelium (ELM-RPE) thickness (a proxy for low pH-triggered water removal), profile shape of the hyperreflective band just posterior to the ELM (i.e., the mitochondrial configuration within photoreceptors per aspect ratio [MCP/AR]), and retinal laminar thickness were measured. Both wild-type substrains showed similar visual performance indices and dark-evoked ELM-RPE contraction. The lack of a light-dark change in B6NTac MCP/AR, unlike in B6J mice, is consistent with relatively greater mitochondrial efficiency. 5xFAD B6J mice, but not 5xFAD B6NTac mice, showed lower-than-WT CS. Light-adapted 5xFAD substrains both showed abnormal ELM-RPE contraction and greater-than-WT MCP/AR contraction. The inner retina and superior outer retina were thinner. Treating 5xFAD B6J mice with R-carvedilol + DMSO or DMSO alone corrected CS and ELM-RPE contraction but not supernormal MCP/AR contraction or laminar thinning. These results provide biomarker evidence for prodromal photoreceptor mitochondrial dysfunction/oxidative stress/oxidative damage, which is unrelated to visual performance, as well as the presence of the Nnt gene. This pathophysiology is druggable in 5xFAD mice.

Mitochondrial quality control in human health and disease

Mitochondria, the most crucial energy-generating organelles in eukaryotic cells, play a pivotal role in regulating energy metabolism. However, their significance extends beyond this, as they are also indispensable in vital life processes such as cell proliferation, differentiation, immune responses, and redox balance. In response to various physiological signals or external stimuli, a sophisticated mitochondrial quality control (MQC) mechanism has evolved, encompassing key processes like mitochondrial biogenesis, mitochondrial dynamics, and mitophagy, which have garnered increasing attention from researchers to unveil their specific molecular mechanisms. In this review, we present a comprehensive summary of the primary mechanisms and functions of key regulators involved in major components of MQC. Furthermore, the critical physiological functions regulated by MQC and its diverse roles in the progression of various systemic diseases have been described in detail. We also discuss agonists or antagonists targeting MQC, aiming to explore potential therapeutic and research prospects by enhancing MQC to stabilize mitochondrial function.

The amyloid precursor protein and its derived fragments concomitantly contribute to the alterations of mitochondrial transport machinery in Alzheimer's disease

Mitochondria dysfunctions and mitophagy failure have been associated with several Alzheimer's disease (AD) related molecular actors including amyloid beta (Aβ) and recently the amyloid precursor protein-C terminal fragments (APP-CTFs). The efficacy of the mitophagy process in neurons relies on regulated mitochondrial transport along axons involving a complex molecular machinery. The contribution of the amyloid precursor protein (APP) and its derived fragments to the mitochondrial transport machinery alterations in AD have not been investigated before. We report herein a change of the expression of mitochondrial transport proteins (SNPH and Miro1), motor adapters (TRANK1 and TRAK2), and components of the dynein and kinesin motors (i.e., IC1,2 and Kif5 (A, B, C) isoforms) by endogenous APP and by overexpression of APP carrying the familial Swedish mutation (APPswe). We show that APP-CTFs and Aβ concomitantly regulate the expression of a set of transport proteins as demonstrated in APPswe cells treated with β- and γ-secretase inhibitors and in cells Knock-down for presenilin 1 and 2. We further report the impact of APP-CTFs on the expression of transport proteins in AAV-injected C99 mice brains. Our data also indicate that both Aβ oligomers (Aβo) and APP-CTFs impair the colocalization of mitochondria and transport proteins. This has been demonstrated in differentiated SH-SY5Y naive cells treated with Aβo and in differentiated SH-SY5Y and murine primary neurons expressing APPswe and treated with the γ-secretase inhibitor. Importantly, we uncover that the expression of a set of transport proteins is modulated in a disease-dependent manner in 3xTgAD mice and in human sporadic AD brains. This study highlights molecular mechanisms underlying mitochondrial transport defects in AD that likely contribute to mitophagy failure and disease progression.

Imbalance in Glucose Metabolism Regulates the Transition of Microglia from Homeostasis to Disease-Associated Microglia Stage 1

Microglia undergo two-stage activation in neurodegenerative diseases, known as disease-associated microglia (DAM). TREM2 mediates the DAM2 stage transition, but what regulates the first DAM1 stage transition is unknown. We report that glucose dyshomeostasis inhibits DAM1 activation and PKM2 plays a role. As in tumors, PKM2 was aberrantly elevated in both male and female human AD brains, but unlike in tumors, it is expressed as active tetramers, as well as among TREM2+ microglia surrounding plaques in 5XFAD male and female mice. snRNAseq analyses of microglia without Pkm2 in 5XFAD mice revealed significant increases in DAM1 markers in a distinct metabolic cluster, which is enriched in genes for glucose metabolism, DAM1, and AD risk. 5XFAD mice incidentally exhibited a significant reduction in amyloid pathology without microglial Pkm2 Surprisingly, microglia in 5XFAD without Pkm2 exhibited increases in glycolysis and spare respiratory capacity, which correlated with restoration of mitochondrial cristae alterations. In addition, in situ spatial metabolomics of plaque-bearing microglia revealed an increase in respiratory activity. These results together suggest that it is not only glycolytic but also respiratory inputs that are critical to the development of DAM signatures in 5XFAD mice.

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.

Consequences of Amyloid-β Deficiency for the Liver

The hepatic content of amyloid beta (Aβ) decreases drastically in human and rodent cirrhosis highlighting the importance of understanding the consequences of Aβ deficiency in the liver. This is especially relevant in view of recent advances in anti-Aβ therapies for Alzheimer's disease (AD). Here, it is shown that partial hepatic loss of Aβ in transgenic AD mice immunized with Aβ antibody 3D6 and its absence in amyloid precursor protein (APP) knockout mice (APP-KO), as well as in human liver spheroids with APP knockdown upregulates classical hallmarks of fibrosis, smooth muscle alpha-actin, and collagen type I. Aβ absence in APP-KO and deficiency in immunized mice lead to strong activation of transforming growth factor-β (TGFβ), alpha secretases, NOTCH pathway, inflammation, decreased permeability of liver sinusoids, and epithelial-mesenchymal transition. Inversely, increased systemic and intrahepatic levels of Aβ42 in transgenic AD mice and neprilysin inhibitor LBQ657-treated wild-type mice protect the liver against carbon tetrachloride (CCl4)-induced injury. Transcriptomic analysis of CCl4-treated transgenic AD mouse livers uncovers the regulatory effects of Aβ42 on mitochondrial function, lipid metabolism, and its onco-suppressive effects accompanied by reduced synthesis of extracellular matrix proteins. Combined, these data reveal Aβ as an indispensable regulator of cell-cell interactions in healthy liver and a powerful protector against liver fibrosis.

The interaction between insulin resistance and Alzheimer's disease: a review article

Insulin serves multiple functions as a growth-promoting hormone in peripheral tissues. It manages glucose metabolism by promoting glucose uptake into cells and curbing the production of glucose in the liver. Beyond this, insulin fosters cell growth, drives differentiation, aids protein synthesis, and deters degradative processes like glycolysis, lipolysis, and proteolysis. Receptors for insulin and insulin-like growth factor-1 are widely expressed in the central nervous system. Their widespread presence in the brain underscores the varied and critical functions of insulin signaling there. Insulin aids in bolstering cognition, promoting neuron extension, adjusting the release and absorption of catecholamines, and controlling the expression and positioning of gamma-aminobutyric acid (GABA). Importantly, insulin can effortlessly traverse the blood-brain barrier. Furthermore, insulin resistance (IR)-induced alterations in insulin signaling might hasten brain aging, impacting its plasticity and potentially leading to neurodegeneration. Two primary pathways are responsible for insulin signal transmission: the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway, which oversees metabolic responses, and the mitogen-activated protein kinase (MAPK) pathway, which guides cell growth, survival, and gene transcription. This review aimed to explore the potential shared metabolic traits between Alzheimer's disease (AD) and IR disorders. It delves into the relationship between AD and IR disorders, their overlapping genetic markers, and shared metabolic indicators. Additionally, it addresses existing therapeutic interventions targeting these intersecting pathways.

Native-state proteomics of Parvalbumin interneurons identifies unique molecular signatures and vulnerabilities to early Alzheimer's pathology

Dysfunction in fast-spiking parvalbumin interneurons (PV-INs) may represent an early pathophysiological perturbation in Alzheimer's Disease (AD). Defining early proteomic alterations in PV-INs can provide key biological and translationally-relevant insights. We used cell-type-specific in-vivo biotinylation of proteins (CIBOP) coupled with mass spectrometry to obtain native-state PV-IN proteomes. PV-IN proteomic signatures include high metabolic and translational activity, with over-representation of AD-risk and cognitive resilience-related proteins. In bulk proteomes, PV-IN proteins were associated with cognitive decline in humans, and with progressive neuropathology in humans and the 5xFAD mouse model of Aβ pathology. PV-IN CIBOP in early stages of Aβ pathology revealed signatures of increased mitochondria and metabolism, synaptic and cytoskeletal disruption and decreased mTOR signaling, not apparent in whole-brain proteomes. Furthermore, we demonstrated pre-synaptic defects in PV-to-excitatory neurotransmission, validating our proteomic findings. Overall, in this study we present native-state proteomes of PV-INs, revealing molecular insights into their unique roles in cognitive resiliency and AD pathogenesis.

Cooperation of Various Cytoskeletal Components Orchestrates Intercellular Spread of Mitochondria between B-Lymphoma Cells through Tunnelling Nanotubes

Membrane nanotubes (NTs) are dynamic communication channels connecting spatially separated cells even over long distances and promoting the transport of different cellular cargos. NTs are also involved in the intercellular spread of different pathogens and the deterioration of some neurological disorders. Transport processes via NTs may be controlled by cytoskeletal elements. NTs are frequently observed membrane projections in numerous mammalian cell lines, including various immune cells, but their functional significance in the 'antibody factory' B cells is poorly elucidated. Here, we report that as active channels, NTs of B-lymphoma cells can mediate bidirectional mitochondrial transport, promoted by the cooperation of two different cytoskeletal motor proteins, kinesin along microtubules and myosin VI along actin, and bidirectional transport processes are also supported by the heterogeneous arrangement of the main cytoskeletal filament systems of the NTs. We revealed that despite NTs and axons being different cell extensions, the mitochondrial transport they mediate may exhibit significant similarities. Furthermore, we found that microtubules may improve the stability and lifespan of B-lymphoma-cell NTs, while F-actin strengthens NTs by providing a structural framework for them. Our results may contribute to a better understanding of the regulation of the major cells of humoral immune response to infections.

Mitochondrial Dysfunction: A Key Player in Brain Aging and Diseases

Mitochondria are thought to have become incorporated within the eukaryotic cell approximately 2 billion years ago and play a role in a variety of cellular processes, such as energy production, calcium buffering and homeostasis, steroid synthesis, cell growth, and apoptosis, as well as inflammation and ROS production. Considering that mitochondria are involved in a multitude of cellular processes, mitochondrial dysfunction has been shown to play a role within several age-related diseases, including cancers, diabetes (type 2), and neurodegenerative diseases, although the underlying mechanisms are not entirely understood. The significant increase in lifespan and increased incidence of age-related diseases over recent decades has confirmed the necessity to understand the mechanisms by which mitochondrial dysfunction impacts the process of aging and age-related diseases. In this review, we will offer a brief overview of mitochondria, along with structure and function of this important organelle. We will then discuss the cause and consequence of mitochondrial dysfunction in the aging process, with a particular focus on its role in inflammation, cognitive decline, and neurodegenerative diseases, such as Huntington's disease, Parkinson's disease, and Alzheimer's disease. We will offer insight into therapies and interventions currently used to preserve or restore mitochondrial functioning during aging and neurodegeneration.

Mitochondria Dysfunction and Neuroinflammation in Neurodegeneration: Who Comes First?

Neurodegenerative diseases (NDs) encompass an assorted array of disorders such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, each characterised by distinct clinical manifestations and underlying pathological mechanisms. While some cases have a genetic basis, many NDs occur sporadically. Despite their differences, these diseases commonly feature chronic neuroinflammation as a hallmark. Consensus has recently been reached on the possibility that mitochondria dysfunction and protein aggregation can mutually contribute to the activation of neuroinflammatory response and thus to the onset and progression of these disorders. In the present review, we discuss the contribution of mitochondria dysfunction and neuroinflammation to the aetiology and progression of NDs, highlighting the possibility that new potential therapeutic targets can be identified to tackle neurodegenerative processes and alleviate the progression of these pathologies.

CoQ10 and Mitochondrial Dysfunction in Alzheimer's Disease

The progress in understanding the pathogenesis and treatment of Alzheimer's disease (AD) is based on the recognition of the primary causes of the disease, which can be deduced from the knowledge of risk factors and biomarkers measurable in the early stages of the disease. Insights into the risk factors and the time course of biomarker abnormalities point to a role for the connection of amyloid beta (Aβ) pathology, tau pathology, mitochondrial dysfunction, and oxidative stress in the onset and development of AD. Coenzyme Q10 (CoQ10) is a lipid antioxidant and electron transporter in the mitochondrial electron transport system. The availability and activity of CoQ10 is crucial for proper mitochondrial function and cellular bioenergetics. Based on the mitochondrial hypothesis of AD and the hypothesis of oxidative stress, the regulation of the efficiency of the oxidative phosphorylation system by means of CoQ10 can be considered promising in restoring the mitochondrial function impaired in AD, or in preventing the onset of mitochondrial dysfunction and the development of amyloid and tau pathology in AD. This review summarizes the knowledge on the pathophysiology of AD, in which CoQ10 may play a significant role, with the aim of evaluating the perspective of the pharmacotherapy of AD with CoQ10 and its analogues.

Trazodone rescues dysregulated synaptic and mitochondrial nascent proteomes in prion neurodegeneration

The unfolded protein response (UPR) is rapidly gaining momentum as a therapeutic target for protein misfolding neurodegenerative diseases, in which its overactivation results in sustained translational repression leading to synapse loss and neurodegeneration. In mouse models of these disorders, from Alzheimer's to prion disease, modulation of the pathway-including by the licensed drug, trazodone-restores global protein synthesis rates with profound neuroprotective effects. However, the precise nature of the translational impairment, in particular the specific proteins affected in disease, and their response to therapeutic UPR modulation are poorly understood. We used non-canonical amino acid tagging (NCAT) to measure de novo protein synthesis in the brains of prion-diseased mice with and without trazodone treatment, in both whole hippocampus and cell-specifically. During disease the predominant nascent proteome changes occur in synaptic, cytoskeletal and mitochondrial proteins in both hippocampal neurons and astrocytes. Remarkably, trazodone treatment for just 2 weeks largely restored the whole disease nascent proteome in the hippocampus to that of healthy, uninfected mice, predominantly with recovery of proteins involved in synaptic and mitochondrial function. In parallel, trazodone treatment restored the disease-associated decline in synapses and mitochondria and their function to wild-type levels. In conclusion, this study increases our understanding of how translational repression contributes to neurodegeneration through synaptic and mitochondrial toxicity via depletion of key proteins essential for their function. Further, it provides new insights into the neuroprotective mechanisms of trazodone through reversal of this toxicity, relevant for the treatment of neurodegenerative diseases via translational modulation.

Mitophagy in Alzheimer's Disease: A Bibliometric Analysis from 2007 to 2022

Background

The investigation of mitophagy in Alzheimer's disease (AD) remains relatively underexplored in bibliometric analysis.

Objective

To delve into the progress of mitophagy, offering a comprehensive overview of research trends and frontiers for researchers.

Methods

Basic bibliometric information, targets, and target-drug-clinical trial-disease extracted from publications identified in the Web of Science Core Collection from 2007 to 2022 were assessed using bibliometric software.

Results

The study encompassed 5,146 publications, displaying a consistent 16-year upward trajectory. The United States emerged as the foremost contributor in publications, with the Journal of Alzheimer's Disease being the most prolific journal. P. Hemachandra Reddy, George Perry, and Xiongwei Zhu are the top 3 most prolific authors. PINK1 and Parkin exhibited an upward trend in the last 6 years. Keywords (e.g., insulin, aging, epilepsy, tauopathy, and mitochondrial quality control) have recently emerged as focal points of interest within the past 3 years. "Mitochondrial dysfunction" is among the top terms in disease clustering. The top 10 drugs/molecules (e.g., curcumin, insulin, and melatonin) were summarized, accompanied by their clinical trials and related targets.

Conclusions

This study presents a comprehensive overview of the mitophagy research landscape in AD over the past 16 years, underscoring mitophagy as an emerging molecular mechanism and a crucial focal point for potential drug in AD. This study pioneers the inclusion of targets and their correlations with drugs, clinical trials, and diseases in bibliometric analysis, providing valuable insights and inspiration for scholars and readers of JADR interested in understanding the potential mechanisms and clinical trials in AD.

Antigen-specific age-related memory CD8 T cells induce and track Alzheimer's-like neurodegeneration

Cerebral (Aβ) plaque and (pTau) tangle deposition are hallmarks of Alzheimer's disease (AD), yet are insufficient to confer complete AD-like neurodegeneration experimentally. Factors acting upstream of Aβ/pTau in AD remain unknown, but their identification could enable earlier diagnosis and more effective treatments. T cell abnormalities are emerging AD hallmarks, and CD8 T cells were recently found to mediate neurodegeneration downstream of tangle deposition in hereditary neurodegeneration models. The precise impact of T cells downstream of Aβ/fibrillar pTau, however, appears to vary depending on the animal model used. Our prior work suggested that antigen-specific memory CD8 T (" hi T") cells act upstream of Aβ/pTau after brain injury. Here we examine whether hi T cells influence sporadic AD-like pathophysiology upstream of Aβ/pTau. Examining neuropathology, gene expression, and behavior in our hi T mouse model we show that CD8 T cells induce plaque and tangle-like deposition, modulate AD-related genes, and ultimately result in progressive neurodegeneration with both gross and fine features of sporadic human AD. T cells required Perforin to initiate this pathophysiology, and IFNγ for most gene expression changes and progression to more widespread neurodegenerative disease. Analogous antigen-specific memory CD8 T cells were significantly elevated in the brains of human AD patients, and their loss from blood corresponded to sporadic AD and related cognitive decline better than plasma pTau-217, a promising AD biomarker candidate. Our work is the first to identify an age-related factor acting upstream of Aβ/pTau to initiate AD-like pathophysiology, the mechanisms promoting its pathogenicity, and its relevance to human sporadic AD.

Significance Statement

This study changes our view of Alzheimer's Disease (AD) initiation and progression. Mutations promoting cerebral beta-amyloid (Aβ) deposition guarantee rare genetic forms of AD. Thus, the prevailing hypothesis has been that Aβ is central to initiation and progression of all AD, despite contrary animal and patient evidence. We show that age-related T cells generate neurodegeneration with compelling features of AD in mice, with distinct T cell functions required for pathological initiation and neurodegenerative progression. Knowledge from these mice was applied to successfully predict previously unknown features of human AD and generate novel tools for its clinical management.

The Gut-Brain Axis in Alzheimer's and Parkinson's Diseases: The Catalytic Role of Mitochondria

Accumulating evidence suggests that gut inflammation is implicated in neuroinflammation in Alzheimer's and Parkinson's diseases. Despite the numerous connections it remains unclear how the gut and the brain communicate and whether gut dysbiosis is the cause or consequence of these pathologies. Importantly, several reports highlight the importance of mitochondria in the gut-brain axis, as well as in mechanisms like gut epithelium self-renewal, differentiation, and homeostasis. Herein we comprehensively address the important role of mitochondria as a cellular hub in infection and inflammation and as a link between inflammation and neurodegeneration in the gut-brain axis. The role of mitochondria in gut homeostasis and as well the crosstalk between mitochondria and gut microbiota is discussed. Significantly, we also review studies highlighting how gut microbiota can ultimately affect the central nervous system. Overall, this review summarizes novel findings regarding this cross-talk where the mitochondria has a main role in the pathophysiology of both Alzheimer's and Parkinson's disease strengthen by cellular, animal and clinical studies.

Multiomics Blood-Based Biomarkers Predict Alzheimer's Predementia with High Specificity in a Multicentric Cohort Study

BACKGROUND

The primary criteria for diagnosing mild cognitive impairment (MCI) due to Alzheimer's Disease (AD) or probable mild AD dementia rely partly on cognitive assessments and the presence of amyloid plaques. Although these criteria exhibit high sensitivity in predicting AD among cognitively impaired patients, their specificity remains limited. Notably, up to 25% of non-demented patients with amyloid plaques may be misdiagnosed with MCI due to AD, when in fact they suffer from a different brain disorder. The introduction of anti-amyloid antibodies complicates this scenario. Physicians must prioritize which amyloid-positive MCI patients receive these treatments, as not all are suitable candidates. Specifically, those with non-AD amyloid pathologies are not primary targets for amyloid-modifying therapies. Consequently, there is an escalating medical necessity for highly specific blood biomarkers that can accurately detect pre-dementia AD, thus optimizing amyloid antibody prescription.

OBJECTIVES

The objective of this study was to evaluate a predictive model based on peripheral biomarkers to identify MCI and mild dementia patients who will develop AD dementia symptoms in cognitively impaired population with high specificity.

DESIGN

Peripheral biomarkers were identified in a gene transfer-based animal model of AD and then validated during a retrospective multi-center clinical study.

SETTING

Participants from 7 retrospective cohorts (US, EU and Australia).

PARTICIPANTS

This study followed 345 cognitively impaired individuals over up to 13 years, including 193 with MCI and 152 with mild dementia, starting from their initial visits. The final diagnoses, established during their last assessments, classified 249 participants as AD patients and 96 as having non-AD brain disorders, based on the specific diagnostic criteria for each disorder subtype. Amyloid status, assessed at baseline, was available for 82.9% of the participants, with 61.9% testing positive for amyloid. Both amyloid-positive and negative individuals were represented in each clinical group. Some of the AD patients had co-morbidities such as metabolic disorders, chronic diseases, or cardiovascular pathologies.

MEASUREMENTS

We developed targeted mass spectrometry assays for 81 blood-based biomarkers, encompassing 45 proteins and 36 metabolites previously identified in AAV-AD rats.

METHODS

We analyzed blood samples from study participants for the 81 biomarkers. The B-HEALED test, a machine learning-based diagnostic tool, was developed to differentiate AD patients, including 123 with Prodromal AD and 126 with mild AD dementia, from 96 individuals with non-AD brain disorders. The model was trained using 70% of the data, selecting relevant biomarkers, calibrating the algorithm, and establishing cutoff values. The remaining 30% served as an external test dataset for blind validation of the predictive accuracy.

RESULTS

Integrating a combination of 19 blood biomarkers and participant age, the B-HEALED model successfully distinguished participants that will develop AD dementia symptoms (82 with Prodromal AD and 83 with AD dementia) from non-AD subjects (71 individuals) with a specificity of 93.0% and sensitivity of 65.4% (AUROC=81.9%, p<0.001) during internal validation. When the amyloid status (derived from CSF or PET scans) and the B-HEALED model were applied in association, with individuals being categorized as AD if they tested positive in both tests, we achieved 100% specificity and 52.8% sensitivity. This performance was consistent in blind external validation, underscoring the model's reliability on independent datasets.

CONCLUSIONS

The B-HEALED test, utilizing multiomics blood-based biomarkers, demonstrates high predictive specificity in identifying AD patients within the cognitively impaired population, minimizing false positives. When used alongside amyloid screening, it effectively identifies a nearly pure prodromal AD cohort. These results bear significant implications for refining clinical trial inclusion criteria, facilitating drug development and validation, and accurately identifying patients who will benefit the most from disease-modifying AD treatments.

Intermittent fasting and Alzheimer's disease-Targeting ketone bodies as a potential strategy for brain energy rescue

Alzheimer's disease (AD) lacks effective clinical treatments. As the disease progresses, the cerebral glucose hypometabolism that appears in the preclinical phase of AD gradually worsens, leading to increasingly severe brain energy disorders. This review analyzes the brain energy deficit in AD and its etiology, brain energy rescue strategies based on ketone intervention, the effects and mechanisms of IF, the differences in efficacy between IF and ketogenic diet and the duality of IF. The evidence suggests that brain energy deficits lead to the development and progression of AD pathology. IF, which improves brain energy impairments by promoting ketone metabolism, thus has good therapeutic potential for AD.

Selective induction of Rab9-dependent alternative mitophagy using a synthetic derivative of isoquinoline alleviates mitochondrial dysfunction and cognitive deficits in Alzheimer's disease models

Rationale: Promotion of mitophagy is considered a promising strategy for the treatment of neurodegenerative diseases including Alzheimer's disease (AD). The development of mitophagy-specific inducers with low toxicity and defined molecular mechanisms is essential for the clinical application of mitophagy-based therapy. The aim of this study was to investigate the potential of a novel small-molecule mitophagy inducer, ALT001, as a treatment for AD. Methods: ALT001 was developed through chemical optimization of an isoquinolium scaffold, which was identified from a chemical library screening using a mitophagy reporter system. In vitro and in vivo experiments were conducted to evaluate the potential of ALT001 as a mitophagy-targeting therapeutic agent and to investigate the molecular mechanisms underlying ALT001-induced mitophagy. The therapeutic effect of ALT001 was assessed in SH-SY5Y cells expressing mutant APP and mouse models of AD (5×FAD and PS2APP) by analyzing mitochondrial dysfunction and cognitive defects. Results: ALT001 specifically induces mitophagy both in vitro and in vivo but is nontoxic to mitochondria. Interestingly, we found that ALT001 induces mitophagy through the ULK1-Rab9-dependent alternative mitophagy pathway independent of canonical mitophagy pathway regulators such as ATG7 and PINK1. Importantly, ALT001 reverses mitochondrial dysfunction in SH-SY5Y cells expressing mutant APP in a mitophagy-dependent manner. ALT001 induces alternative mitophagy in mice and restores the decreased mitophagy level in a 5×FAD AD model mouse. In addition, ALT001 reverses mitochondrial dysfunction and cognitive defects in the PS2APP and 5×FAD AD mouse models. AAV-mediated silencing of Rab9 in the hippocampus further confirmed that ALT001 exerts its therapeutic effect through alternative mitophagy. Conclusion: Our results highlight the therapeutic potential of ALT001 for AD via alleviation of mitochondrial dysfunction and indicate the usefulness of the ULK1-Rab9 alternative mitophagy pathway as a therapeutic target.

Micropeptides: origins, identification, and potential role in metabolism-related diseases

With the development of modern sequencing techniques and bioinformatics, genomes that were once thought to be noncoding have been found to encode abundant functional micropeptides (miPs), a kind of small polypeptides. Although miPs are difficult to analyze and identify, a number of studies have begun to focus on them. More and more miPs have been revealed as essential for energy metabolism homeostasis, immune regulation, and tumor growth and development. Many reports have shown that miPs are especially essential for regulating glucose and lipid metabolism and regulating mitochondrial function. MiPs are also involved in the progression of related diseases. This paper reviews the sources and identification of miPs, as well as the functional significance of miPs for metabolism-related diseases, with the aim of revealing their potential clinical applications.

The role of hydrogen therapy in Alzheimer's disease management: Insights into mechanisms, administration routes, and future challenges

Alzheimer's disease (AD) is a progressive neurodegenerative disorder predominantly affecting the elderly. While conventional pharmacological therapies remain the primary treatment for AD, their efficacy is limited effectiveness and often associated with significant side effects. This underscores the urgent need to explore alternative, non-pharmacological interventions. Oxidative stress has been identified as a central player in AD pathology, influencing various aspects including amyloid-beta metabolism, tau phosphorylation, autophagy, neuroinflammation, mitochondrial dysfunction, and synaptic dysfunction. Among the emerging non-drug approaches, hydrogen therapy has garnered attention for its potential in mitigating these pathological conditions. This review provides a comprehensively overview of the therapeutic potential of hydrogen in AD. We delve into its mechanisms of action, administration routes, and discuss the current challenges and future prospects, with the aim of providing valuable insights to facilitate the clinical application of hydrogen-based therapies in AD management.

The Natural Alkaloid Palmatine Selectively Induces Mitophagy and Restores Mitochondrial Function in an Alzheimer's Disease Mouse Model

Palmatine, a natural alkaloid found in various plants, has been reported to have diverse pharmacological and biological effects, including anti-inflammatory, antioxidant, and cardiovascular effects. However, the role of palmatine in mitophagy, a fundamental process crucial for maintaining mitochondrial function, remains elusive. In this study, we found that palmatine efficiently induces mitophagy in various human cell lines. Palmatine specifically induces mitophagy and subsequently stimulates mitochondrial biogenesis. Palmatine did not interfere with mitochondrial function, similar to CCCP, suggesting that palmatine is not toxic to mitochondria. Importantly, palmatine treatment alleviated mitochondrial dysfunction in PINK1-knockout MEFs. Moreover, the administration of palmatine resulted in significant improvements in cognitive function and restored mitochondrial function in an Alzheimer's disease mouse model. This study identifies palmatine as a novel inducer of selective mitophagy. Our results suggest that palmatine-mediated mitophagy induction could be a potential strategy for Alzheimer's disease treatment and that natural alkaloids are potential sources of mitophagy inducers.

Breast cancer therapies reduce risk of Alzheimer's disease and promote estrogenic pathways and action in brain

Worldwide, an ever-increasing number of women are prescribed estrogen-modulating therapies (EMTs) for the treatment of breast cancer. In parallel, aging of the global population of women will contribute to risk of both breast cancer and Alzheimer's disease. To address the impact of anti-estrogen therapies on risk of Alzheimer's and neural function, we conducted medical informatic and molecular pharmacology analyses to determine the impact of EMTs on risk of Alzheimer's followed by determination of EMT estrogenic mechanisms of action in neurons. Collectively, these data provide both clinical and mechanistic data indicating that select EMTs exert estrogenic agonist action in neural tissue that are associated with reduced risk of Alzheimer's disease while simultaneously acting as effective estrogen receptor antagonists in breast.

Mitochondrial Complex I and β-Amyloid Peptide Interplay in Alzheimer's Disease: A Critical Review of New and Old Little Regarded Findings

Alzheimer's disease (AD) is the most common neurodegenerative disorder and the main cause of dementia which is characterized by a progressive cognitive decline that severely interferes with daily activities of personal life. At a pathological level, it is characterized by the accumulation of abnormal protein structures in the brain-β-amyloid (Aβ) plaques and Tau tangles-which interfere with communication between neurons and lead to their dysfunction and death. In recent years, research on AD has highlighted the critical involvement of mitochondria-the primary energy suppliers for our cells-in the onset and progression of the disease, since mitochondrial bioenergetic deficits precede the beginning of the disease and mitochondria are very sensitive to Aβ toxicity. On the other hand, if it is true that the accumulation of Aβ in the mitochondria leads to mitochondrial malfunctions, it is otherwise proven that mitochondrial dysfunction, through the generation of reactive oxygen species, causes an increase in Aβ production, by initiating a vicious cycle: there is therefore a bidirectional relationship between Aβ aggregation and mitochondrial dysfunction. Here, we focus on the latest news-but also on neglected evidence from the past-concerning the interplay between dysfunctional mitochondrial complex I, oxidative stress, and Aβ, in order to understand how their interplay is implicated in the pathogenesis of the disease.

Exercise mitigates age-related metabolic diseases by improving mitochondrial dysfunction

The benefits of regular physical activity are related to delaying and reversing the onset of ageing and age-related disorders, including cardiomyopathy, neurodegenerative diseases, cancer, obesity, diabetes, and fatty liver diseases. However, the molecular mechanisms of the benefits of exercise or physical activity on ageing and age-related disorders remain poorly understood. Mitochondrial dysfunction is implicated in the pathogenesis of ageing and age-related metabolic diseases. Mitochondrial health is an important mediator of cellular function. Therefore, exercise alleviates metabolic diseases in individuals with advancing ageing and age-related diseases by the remarkable promotion of mitochondrial biogenesis and function. Exerkines are identified as signaling moieties released in response to exercise. Exerkines released by exercise have potential roles in improving mitochondrial dysfunction in response to age-related disorders. This review comprehensive summarizes the benefits of exercise in metabolic diseases, linking mitochondrial dysfunction to the onset of age-related diseases. Using relevant examples utilizing this approach, the possibility of designing therapeutic interventions based on these molecular mechanisms is addressed.

Mitochondrial DNA and Inflammation in Alzheimer's Disease

Mitochondrial dysfunction and neuroinflammation are implicated in the pathogenesis of most neurodegenerative diseases, such as Alzheimer's disease (AD). In fact, although a growing number of studies show crosstalk between these two processes, there remain numerous gaps in our knowledge of the mechanisms involved, which requires further clarification. On the one hand, mitochondrial dysfunction may lead to the release of mitochondrial damage-associated molecular patterns (mtDAMPs) which are recognized by microglial immune receptors and contribute to neuroinflammation progression. On the other hand, inflammatory molecules released by glial cells can influence and regulate mitochondrial function. A deeper understanding of these mechanisms may help identify biomarkers and molecular targets useful for the treatment of neurodegenerative diseases. This review of works published in recent years is focused on the description of the mitochondrial contribution to neuroinflammation and neurodegeneration, with particular attention to mitochondrial DNA (mtDNA) and AD.

Scorpion venom heat-resistant peptide alleviates mitochondrial dynamics imbalance induced by PM2.5 exposure by downregulating the PGC-1α/SIRT3 signaling pathway

Background

Epidemiological inquiry reveals that neuroinflammation and mitochondrial dysfunction caused by PM2.5 exposure are associated with Alzheimer's disease. Nevertheless, the molecular mechanisms of mitochondrial dynamics and neuroinflammation induced by PM2.5 exposure remain elusive. In this study, our objective was to explore the impact of PM2.5 on mitochondrial dynamics and neuroinflammation, while also examining the reparative potential of scorpion venom heat-resistant synthetic peptide (SVHRSP).

Methods

Western blot and quantitative reverse transcription polymerase chain reaction (RT-qPCR) were employed to ascertain the protein and gene levels of IL-1β, IL-6, and TNF-α in BV2 cells. The concentration of IL-6 in the supernatant of the BV2 cell culture was measured by enzyme-linked immunosorbent assay. For the assessment of mitochondrial homeostasis, western blot, RT-qPCR, and cellular immunohistochemistry methods were utilized to investigate the protein and gene levels of DRP1 and MFN-2 in HT22 cells. In the context of signal pathway analyses, western blot, RT-qPCR, and immunofluorescence techniques were employed to detect the protein and gene expressions of PGC-1α and SIRT3 in HT22 cells, respectively. Following the transfection with siPGC-1αRNA, downstream proteins of PGC-1α/SIRT3 pathway in HT22 cells were investigated by Western blot and RT-qPCR.

Results

The experimental findings demonstrated that exposure to PM2.5 exacerbated neuroinflammation, resulting in elevated levels of IL-1β, IL-6, and TNF-α. Furthermore, it perturbed mitochondrial dynamics, as evidenced by increased DRP1 expression and decreased MFN-2 expression. Additionally, dysfunction was observed in the PGC-1α/SIRT3 signal pathway. However, intervention with SVHRSP ameliorated the cellular damage induced by PM2.5 exposure.

Conclusions

SVHRSP alleviated neuroinflammation and mitochondrial dynamics imbalance induced by PM2.5 exposure by downregulating the PGC-1α/SIRT3 signaling pathway.

Mitochondria in health, disease, and aging

Mitochondria are well known as organelles responsible for the maintenance of cellular bioenergetics through the production of ATP. Although oxidative phosphorylation may be their most important function, mitochondria are also integral for the synthesis of metabolic precursors, calcium regulation, the production of reactive oxygen species, immune signaling, and apoptosis. Considering the breadth of their responsibilities, mitochondria are fundamental for cellular metabolism and homeostasis. Appreciating this significance, translational medicine has begun to investigate how mitochondrial dysfunction can represent a harbinger of disease. In this review, we provide a detailed overview of mitochondrial metabolism, cellular bioenergetics, mitochondrial dynamics, autophagy, mitochondrial damage-associated molecular patterns, mitochondria-mediated cell death pathways, and how mitochondrial dysfunction at any of these levels is associated with disease pathogenesis. Mitochondria-dependent pathways may thereby represent an attractive therapeutic target for ameliorating human disease.