Accumulation of amyloid precursor protein C-terminal fragments triggers mitochondrial structure, function, and mitophagy defects in Alzheimer's disease models and human brains

AAV-aMTD-Parkin, a therapeutic gene delivery cargo, enhances motor and cognitive functions in Parkinson's and Alzheimer's diseases

Neurodegenerative disorders, such as Parkinson's disease (PD) and Alzheimer's disease (AD), have a global prevalence and profoundly impact both motor and cognitive functions. Although adeno-associated virus (AAV)-based gene therapy has shown promise, its application for treating central nervous system (CNS) diseases faces several challenges, including effective delivery of AAV vectors across the blood-brain barrier, determining optimal dosages, and achieving targeted distribution. To address these challenges, we have developed a fusion delivery therapeutic cargo called AAV-aMTD-Parkin, which combines a hydrophobic cell-penetrating peptide sequence with the DNA sequences of AAV and Parkin. By employing this fusion delivery platform at lower dosages compared to zolgensma, we have achieved significant enhancements in cell and tissue permeability, while reducing the occurrence of common pathological protein aggregates. Consequently, motor and cognitive functions were restored in animal models of PD and AD. With its dual functionality in addressing PD and AD, AAV-aMTD-Parkin holds immense potential as a novel class of therapeutic biologics for prevalent CNS diseases.

MAMs and Mitochondrial Quality Control: Overview and Their Role in Alzheimer's Disease

Alzheimer's disease (AD) represents the most widespread neurodegenerative disorder, distinguished by a gradual onset and slow progression, presenting a substantial challenge to global public health. The mitochondrial-associated membrane (MAMs) functions as a crucial center for signal transduction and material transport between mitochondria and the endoplasmic reticulum, playing a pivotal role in various pathological mechanisms of AD. The dysregulation of mitochondrial quality control systems is considered a fundamental factor in the development of AD, leading to mitochondrial dysfunction and subsequent neurodegenerative events. Recent studies have emphasized the role of MAMs in regulating mitochondrial quality control. This review will delve into the molecular mechanisms underlying the imbalance in mitochondrial quality control in AD and provide a comprehensive overview of the role of MAMs in regulating mitochondrial quality control.

Pathophysiologic abnormalities in transgenic mice carrying the Alzheimer disease PSEN1 Δ440 mutation

Mutations in PSEN1 were first discovered as a cause of Alzheimer's disease (AD) in 1995, yet the mechanism(s) by which the mutations cause disease still remains unknown. The generation of novel mouse models assessing the effects of different mutations could aid in this endeavor. Here we report on transgenic mouse lines made with the Δ440 PSEN1 mutation that causes AD with parkinsonism:- two expressing the un-tagged human protein and two expressing a HA-tagged version. Detailed characterization of these lines showed that Line 305 in particular, which expresses the untagged protein, develops age-dependent memory deficits and pathologic features, many of which are consistent with features found in AD. Key behavioral and physiological alterations found in the novel 305 line included an age-dependent deficit in spontaneous alternations in the Y-maze, a decrease in exploration of the center of an open field box, a decrease in the latency to fall on a rotarod, a reduction in synaptic strength and pair-pulse facilitation by electrophysiology, and profound alterations to cerebral blood flow regulation. The pathologic alterations found in the line included, significant neuronal loss in the hippocampus and cortex, astrogliosis, and changes in several proteins involved in synaptic and mitochondrial function, Ca2+ regulation, and autophagy. Taken together, these findings suggest that the transgenic lines will be useful for the investigation of AD pathogenesis.

Autophagy-lysosomal-associated neuronal death in neurodegenerative disease

Autophagy, the major lysosomal pathway for degrading damaged or obsolete constituents, protects neurons by eliminating toxic organelles and peptides, restoring nutrient and energy homeostasis, and inhibiting apoptosis. These functions are especially vital in neurons, which are postmitotic and must survive for many decades while confronting mounting challenges of cell aging. Autophagy failure, especially related to the declining lysosomal ("phagy") functions, heightens the neuron's vulnerability to genetic and environmental factors underlying Alzheimer's disease (AD) and other late-age onset neurodegenerative diseases. Components of the global autophagy-lysosomal pathway and the closely integrated endolysosomal system are increasingly implicated as primary targets of these disorders. In AD, an imbalance between heightened autophagy induction and diminished lysosomal function in highly vulnerable pyramidal neuron populations yields an intracellular lysosomal build-up of undegraded substrates, including APP-βCTF, an inhibitor of lysosomal acidification, and membrane-damaging Aβ peptide. In the most compromised of these neurons, β-amyloid accumulates intraneuronally in plaque-like aggregates that become extracellular senile plaques when these neurons die, reflecting an "inside-out" origin of amyloid plaques seen in human AD brain and in mouse models of AD pathology. In this review, the author describes the importance of lysosomal-dependent neuronal cell death in AD associated with uniquely extreme autophagy pathology (PANTHOS) which is described as triggered by lysosomal membrane permeability during the earliest "intraneuronal" stage of AD. Effectors of other cell death cascades, notably calcium-activated calpains and protein kinases, contribute to lysosomal injury that induces leakage of cathepsins and activation of additional death cascades. Subsequent events in AD, such as microglial invasion and neuroinflammation, induce further cytotoxicity. In major neurodegenerative disease models, neuronal death and ensuing neuropathologies are substantially remediable by reversing underlying primary lysosomal deficits, thus implicating lysosomal failure and autophagy dysfunction as primary triggers of lysosomal-dependent cell death and AD pathogenesis and as promising therapeutic targets.

Mitochondrial dysfunction induced by ambient fine particulate matter and potential mechanisms

Air pollution is one of the major environmental threats contributing to the global burden of disease. Among diverse air pollutants, fine particulate matter (PM2.5) poses a significant adverse health impact and causes multi-system damage. As a highly dynamic organelle, mitochondria are essential for cellular energy metabolism and vital for cellular homeostasis and body fitness. Moreover, mitochondria are vulnerable to external insults and common targets for PM2.5-induced cellular damage. The resultant impairment of mitochondrial structure and function initiates the pathogenesis of diverse human diseases. This review mainly summarizes the in vivo and in vitro findings of PM2.5-induced mitochondrial dysfunction and its implication in PM2.5-induced health effects. Furthermore, recent advances toward the underlying mechanisms of PM2.5 and its components-induced mitochondrial dysfunction are also discussed, with an attempt to provide insights into the toxicity of PM2.5 and basic information for devising appropriate intervention strategies.

The reciprocal relationship between amyloid precursor protein and mitochondrial function

Amyloid precursor protein (APP), secretase enzymes, and amyloid beta (Aβ) have been extensively studied in the context of Alzheimer's disease (AD). Despite this, the function of these proteins and their metabolism is not understood. APP, secretase enzymes, and APP processing products (Aβ and C-terminal fragments) localize to endosomes, mitochondria, endoplasmic reticulum (ER), and mitochondrial/ER contact sites. Studies implicate significant relationships between APP, secretase enzyme function, APP metabolism, and mitochondrial function. Mitochondrial dysfunction is a key pathological hallmark of AD and is intricately linked to proteostasis. Here, we review studies examining potential functions of APP, secretase enzymes, and APP metabolites in the context of mitochondrial function and bioenergetics. We discuss implications and limitations of studies and highlight knowledge gaps that remain in the field.

Translocator protein (TSPO) ligands attenuate mitophagy deficits in the SH-SY5Y cellular model of Alzheimer's disease via the autophagy adaptor P62

Mitochondrial dysfunction has been widely implicated in the pathogenesis of Alzheimer's disease (AD), with accumulation of damaged and dysfunctional mitochondria occurring early in the disease. Mitophagy, which governs mitochondrial turnover and quality control, is impaired in the AD brain, and strategies aimed at enhancing mitophagy have been identified as promising therapeutic targets. The translocator protein (TSPO) is an outer mitochondrial membrane protein that is upregulated in AD, and ligands targeting TSPO have been shown to exert neuroprotective effects in mouse models of AD. However, whether TSPO ligands modulate mitophagy in AD has not been explored. Here, we provide evidence that the TSPO-specific ligands Ro5-4864 and XBD173 attenuate mitophagy deficits and mitochondrial fragmentation in a cellular model of AD overexpressing the human amyloid precursor protein (APP). Ro5-4864 and XBD173 appear to enhance mitophagy via modulation of the autophagic cargo receptor P62/SQSTM1, in the absence of an effect on PARK2, PINK1, or LC3 level. Taken together, these findings indicate that TSPO ligands may be promising therapeutic agents for ameliorating mitophagy deficits in AD.

Unraveling mitochondrial dysfunction: comprehensive perspectives on its impact on neurodegenerative diseases

Neurodegenerative diseases represent a significant challenge to modern medicine, with their complex etiology and progressive nature posing hurdles to effective treatment strategies. Among the various contributing factors, mitochondrial dysfunction has emerged as a pivotal player in the pathogenesis of several neurodegenerative disorders. This review paper provides a comprehensive overview of how mitochondrial impairment contributes to the development of neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis, driven by bioenergetic defects, biogenesis impairment, alterations in mitochondrial dynamics (such as fusion or fission), disruptions in calcium buffering, lipid metabolism dysregulation and mitophagy dysfunction. It also covers current therapeutic interventions targeting mitochondrial dysfunction in these diseases.

Mechanisms of autophagy-lysosome dysfunction in neurodegenerative diseases

Autophagy is a lysosome-based degradative process used to recycle obsolete cellular constituents and eliminate damaged organelles and aggregate-prone proteins. Their postmitotic nature and extremely polarized morphologies make neurons particularly vulnerable to disruptions caused by autophagy-lysosomal defects, especially as the brain ages. Consequently, mutations in genes regulating autophagy and lysosomal functions cause a wide range of neurodegenerative diseases. Here, we review the role of autophagy and lysosomes in neurodegenerative diseases such as Alzheimer disease, Parkinson disease and frontotemporal dementia. We also consider the strong impact of cellular ageing on lysosomes and autophagy as a tipping point for the late-age emergence of related neurodegenerative disorders. Many of these diseases have primary defects in autophagy, for example affecting autophagosome formation, and in lysosomal functions, especially pH regulation and calcium homeostasis. We have aimed to provide an integrative framework for understanding the central importance of autophagic-lysosomal function in neuronal health and disease.

Mutation of TRPML1 Channel and Pathogenesis of Neurodegeneration in Haimeria

Neurodegenerative diseases, a group of debilitating disorders, have garnered increasing attention due to their escalating prevalence, particularly among aging populations. Alzheimer's disease (AD) reigns as a prominent exemplar within this category, distinguished by its relentless progression of cognitive impairment and the accumulation of aberrant protein aggregates within the intricate landscape of the brain. While the intricate pathogenesis of neurodegenerative diseases has been the subject of extensive investigation, recent scientific inquiry has unveiled a novel player in this complex scenario-transient receptor potential mucolipin 1 (TRPML1) channels. This comprehensive review embarks on an exploration of the intricate interplay between TRPML1 channels and neurodegenerative diseases, with an explicit spotlight on Alzheimer's disease. It immerses itself in the intricate molecular mechanisms governing TRPML1 channel functionality and elucidates their profound implications for the well-being of neurons. Furthermore, the review ventures into the realm of therapeutic potential, pondering the possibilities and challenges associated with targeting TRPML1 channels as a promising avenue for the amelioration of neurodegenerative disorders. As we traverse this multifaceted terrain of neurodegeneration and the enigmatic role of TRPML1 channels, we embark on a journey that not only broadens our understanding of the intricate machinery governing neuronal health but also holds promise for the development of innovative therapeutic interventions in the relentless battle against neurodegenerative diseases.

Alterations of human CSF and serum-based mitophagy biomarkers in the continuum of Alzheimer disease

Defective mitophagy is consistently found in postmortem brain and iPSC-derived neurons from Alzheimer disease (AD) patients. However, there is a lack of extensive examination of mitophagy status in serum or cerebrospinal fluid (CSF), and the clinical potential of mitophagy biomarkers has not been tested. We quantified biomarkers of mitophagy/autophagy and lysosomal degradation (PINK1, BNIP3L and TFEB) in CSF and serum from 246 individuals, covering mild cognitive impairment due to AD (MCI-AD, n = 100), dementia due to AD (AD-dementia, n = 100), and cognitively unimpaired individuals (CU, n = 46), recruited from the Czech Brain Aging Study. Cognitive function and brain atrophy were also assessed. Our data show that serum and CSF PINK1 and serum BNIP3L were higher, and serum TFEB was lower in individuals with AD than in corresponding CU individuals. Additionally, the magnitude of mitophagy impairment correlated with the severity of clinical indicators in AD patients. Specifically, levels of PINK1 positively correlated with phosphorylated (p)-MAPT/tau (181), total (t)-MAPT/tau, NEFL (neurofilament light chain), and NRGN (neurogranin) levels in CSF and negatively with memory, executive function, and language domain. Serum TFEB levels negatively correlated with NEFL and positively with executive function and language. This study reveals mitophagy impairment reflected in biofluid biomarkers of individuals with AD and associated with more advanced AD pathology.Abbreviation: Aβ: amyloid beta; AD: Alzheimer disease; AVs: autophagic vacuoles; BNIP3L: BCL2 interacting protein 3 like; CU: cognitively unimpaired; CSF: cerebrospinal fluid; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MCI: mild cognitive impairment; NRGN: neurogranin; NEFL: neurofilament light chain; p-MAPT/tau: phosphorylated microtubule associated protein tau; PINK1: PTEN induced kinase 1; t-MAPT/tau: total microtubule associated protein tau; TFEB: transcription factor EB; TMT: Trail Making Test.

Gastrodin ameliorates synaptic impairment, mitochondrial dysfunction and oxidative stress in N2a/APP cells

Alzheimer's disease is characterized by abnormal β-amyloid and tau accumulation, mitochondrial dysfunction, oxidative stress, and synaptic dysfunction. Here, we aimed to assess the mechanisms and signalling pathways in the neuroprotective effect of gastrodin, a phenolic glycoside, on murine neuroblastoma N2a cells expressing human Swedish mutant APP (N2a/APP). We found that gastrodin increased the levels of presynaptic-SNAP, synaptophysin, and postsynaptic-PSD95 and reduced phospho-tau Ser396, APP and Aβ1-42 levels in N2a/APP cells. Gastrodin treatment reduced reactive oxygen species generation, lipid peroxidation, mitochondrial fragmentation and DNA oxidation; restored mitochondrial membrane potential and intracellular ATP production. Upregulated phospho-GSK-3β and reduced phospho-ERK and phospho-JNK were involved in the protective effect of gastrodin. In conclusion, we demonstrated the neuroprotective effect of gastrodin in the N2a/APP cell line by ameliorating the impairment on synaptic and mitochondrial function, reducing tau phosphorylation, Aβ1-42 levels as well as reactive oxygen species generation. These results provide new mechanistic insights into the potential effect of gastrodin in the treatment of Alzheimer's disease.

Nur77 improves ovarian function in reproductive aging mice by activating mitophagy and inhibiting apoptosis

Reproductive aging not only affects the fertility and physical and mental health of women but also accelerates the aging process of other organs. There is an urgent need newfor novel mechanisms, targets, and drugs to break the vicious cycle of mitochondrial dysfunction, redox imbalance, and germ cell apoptosis associated with ovarian aging. Autophagy, recognized as a longevity mechanism, has recently become a focal point in anti-aging research. Although mitophagy is a type of autophagy, its role and regulatory mechanisms in ovarian aging, particularly in age-related ovarian function decline, remain unclear. Nerve growth factor inducible gene B (Nur77) is an early response gene that can be stimulated by oxidative stress, DNA damage, metabolism, and inflammation. Recent evidence recommends that decreased expression of Nur77 is associated with age-related myocardial fibrosis, renal dysfunction, and Parkinson's disease; however, its association with ovarian aging has not been studied yet. We herein identified Nur77 as a regulator of germ cell senescence, apoptosis, and mitophagy and found that overexpression of Nur77 can activate mitophagy, improve oxidative stress, reduce apoptosis, and ultimately enhance ovarian reserve in aged mice ovaries. Furthermore, we discovered an association between Nur77 and the AKT pathway through String and molecular docking analyses. Experimental confirmation revealed that the AKT/mTOR signaling pathway is involved in the regulation of Nur77 in ovarian function. In conclusion, our results suggest Nur77 as a promising target for preventing and treating ovarian function decline related to reproductive aging.

Dietary salt promotes cognitive impairment through repression of SIRT3/PINK1-mediated mitophagy and fission

Dietary salt is increasingly recognized as an independent risk factor for cognitive impairment. However, the exact mechanisms are not yet fully understood. Mitochondria, which play a crucial role in energy metabolism, are implicated in cognitive function through processes such as mitochondrial dynamics and mitophagy. While mitochondrial dysfunction is acknowledged as a significant determinant of cognitive function, the specific relationship between salt-induced cognitive impairment and mitochondrial health has yet to be fully elucidated. Here, we explored the underlying mechanism of cognitive impairment of mice and N2a cells treated with high-salt focusing on the mitochondrial homeostasis with western blotting, immunofluorescence, electron microscopy, RNA sequencing, and more. We further explored the potential role of SIRT3 in salt-induced mitochondrial dysfunction and synaptic alteration through plasmid transfection and siRNA. High salt diet significantly inhibited mitochondrial fission and blocked mitophagy, leading to dysfunctional mitochondria and impaired synaptic plasticity. Our findings demonstrated that SIRT3 not only promote mitochondrial fission by modulating phosphorylated DRP1, but also rescue mitophagy through promoting PINK1/Parkin-dependent pathway. Overall, our data for the first time indicate that mitochondrial homeostasis imbalance is a driver of impaired synaptic plasticity in a cognitive impairment phenotype that is exacerbated by a long-term high-salt diet, and highlight the protective role of SIRT3 in this process.

Huperzine A Regulates the Physiological Homeostasis of Amyloid Precursor Protein Proteolysis and Tau Protein Conformation-A Computational and Experimental Investigation

The beneficial actions of the natural compound Huperzine A (Hup A) against age-associated learning and memory deficits promote this compound as a nootropic agent. Alzheimer's disease (AD) pathophysiology is characterized by the accumulation of amyloid beta (Aβ). Toxic Aβ oligomers account for the cognitive dysfunctions much before the pathological lesions are manifested in the brain. In the present study, we investigated the effects of Hup A on amyloid precursor protein (APP) proteolysis in SH-SY5Y neuroblastoma cells. Hup A downregulated the expression of β-site amyloid precursor protein cleaving enzyme 1 (BACE1) and presenilin 1 (PS1) levels but augmented the levels of A disintegrin and metalloproteinase 10 (ADAM10) with significant decrement in the Aβ levels. We herein report for the first time an in silico molecular docking analysis that revealed that Hup A binds to the functionally active site of BACE1. We further analyzed the effect of Hup A on glycogen synthase kinase-3 β (GSK3β) and phosphorylation status of tau. In this scenario, based on the current observations, we propose that Hup A is a potent regulator of APP processing and capable of modulating tau homeostasis under physiological conditions holding immense potential in preventing and treating AD like disorders.

Interplay among Oxidative Stress, Autophagy, and the Endocannabinoid System in Neurodegenerative Diseases: Role of the Nrf2- p62/SQSTM1 Pathway and Nutraceutical Activation

The onset of neurodegenerative diseases involves a complex interplay of pathological mechanisms, including protein aggregation, oxidative stress, and impaired autophagy. This review focuses on the intricate connection between oxidative stress and autophagy in neurodegenerative disorders, highlighting autophagy as pivotal in disease pathogenesis. Reactive oxygen species (ROS) play dual roles in cellular homeostasis and autophagy regulation, with disruptions of redox signaling contributing to neurodegeneration. The activation of the Nrf2 pathway represents a critical antioxidant mechanism, while autophagy maintains cellular homeostasis by degrading altered cell components. The interaction among p62/SQSTM1, Nrf2, and Keap1 forms a regulatory pathway essential for cellular stress response, whose dysregulation leads to impaired autophagy and aggregate accumulation. Targeting the Nrf2-p62/SQSTM1 pathway holds promise for therapeutic intervention, mitigating oxidative stress and preserving cellular functions. Additionally, this review explores the potential synergy between the endocannabinoid system and Nrf2 signaling for neuroprotection. Further research is needed to elucidate the involved molecular mechanisms and develop effective therapeutic strategies against neurodegeneration.

Advances in Alzheimer's disease: A multifaceted review of potential therapies and diagnostic techniques for early detection

Alzheimer's disease (AD) remains one of the most formidable neurological disorders, affecting millions globally. This review provides a holistic overview of the therapeutic strategies, both conventional and novel, aimed at mitigating the impact of AD. Initially, we delve into the conventional approach, emphasizing the role of Acetylcholinesterase (AChE) inhibition, which has been a cornerstone in AD management. As our understanding of AD evolves, several novel potential approaches emerge. We discuss the promising roles of Butyrylcholinesterase (BChE) inhibition, Tau Protein inhibitors, COX-2 inhibition, PPAR-γ agonism, and FAHH inhibition, among others. The potential of the endocannabinoids (eCB) system, cholesterol-lowering drugs, metal chelators, and MMPs inhibitors are also explored, culminating in the exploration of the pivotal role of microRNA in AD progression. Parallel to these therapeutic insights, we shed light on the novel tools and methodologies revolutionizing AD research. From the quantitative analysis of gene expression by qRTPCR to the evaluation of mitochondrial function using induced pluripotent stem cells (iPSCs), the advances in diagnostic and research tools offer renewed hope. Moreover, we explore the current landscape of clinical trials, highlighting the leading drug interventions and their respective stages of development. This comprehensive review concludes with a look into the future perspectives, capturing the potential breakthroughs and innovations on the horizon. Through a synthesis of current knowledge and emerging research, this article aims to provide a consolidated resource for clinicians, researchers, and academicians in the realm of Alzheimer's disease.

APP dyshomeostasis in the pathogenesis of Alzheimer's disease: implications for current drug targets

The Amyloid precursor protein (APP) is a transmembrane glycoprotein from which amyloid-β (Aβ) peptides are generated after proteolytic cleavage. Aβ peptides are the main constituent of amyloid plaques in Alzheimer's Disease (AD). The physiological functions of APP in the human adult brain are very diverse including intracellular signaling, synaptic and neuronal plasticity, and cell adhesion, among others. There is growing evidence that APP becomes dysfunctional in AD and that this dyshomeostasis may impact several APP functions beyond Aβ generation. The vast majority of current anti-amyloid approaches in AD have focused on reducing the synthesis of Aβ or increasing the clearance of brain Aβ aggregates following a paradigm in which Aβ plays a solo in APP dyshomeostasis. A wider view places APP at the center stage in which Aβ is an important, but not the only, factor involved in APP dyshomeostasis. Under this paradigm, APP dysfunction is universal in AD, but with some differences across different subtypes. Little is known about how to approach APP dysfunction therapeutically beyond anti-Aβ strategies. In this review, we will describe the role of APP dyshomeostasis in AD beyond Aβ and the potential therapeutic strategies targeting APP.

Accumulation of APP C-terminal fragments causes endolysosomal dysfunction through the dysregulation of late endosome to lysosome-ER contact sites

Neuronal endosomal and lysosomal abnormalities are among the early changes observed in Alzheimer's disease (AD) before plaques appear. However, it is unclear whether distinct endolysosomal defects are temporally organized and how altered γ-secretase function or amyloid precursor protein (APP) metabolism contribute to these changes. Inhibiting γ-secretase chronically, in mouse embryonic fibroblast and hippocampal neurons, led to a gradual endolysosomal collapse initiated by decreased lysosomal calcium and increased cholesterol, causing downstream defects in endosomal recycling and maturation. This endolysosomal demise is γ-secretase dependent, requires membrane-tethered APP cytoplasmic domains, and is rescued by APP depletion. APP C-terminal fragments (CTFs) localized to late endosome/lysosome-endoplasmic reticulum contacts; an excess of APP-CTFs herein reduced lysosomal Ca2+ refilling from the endoplasmic reticulum, promoting cholesterol accretion. Tonic regulation by APP-CTFs provides a mechanistic explanation for their cellular toxicity: failure to timely degrade APP-CTFs sustains downstream signaling, instigating lysosomal dyshomeostasis, as observed in prodromal AD. This is the opposite of substrates such as Notch, which require intramembrane proteolysis to initiate signaling.

Mitochondrial alterations in fibroblasts from sporadic Alzheimer's disease (AD) patients correlate with AD-related clinical hallmarks

Mitochondrial dysfunctions are key features of Alzheimer's disease (AD). The occurrence of these disturbances in the peripheral cells of AD patients and their potential correlation with disease progression are underinvestigated. We studied mitochondrial structure, function and mitophagy in fibroblasts from healthy volunteers and AD patients at the prodromal (AD-MCI) or demented (AD-D) stages. We carried out correlation studies with clinical cognitive scores, namely, (i) Mini-Mental State Examination (MMSE) and (ii) Dementia Rating-Scale Sum of Boxes (CDR-SOB), and with (iii) amyloid beta (Aβ) plaque burden (PiB-PET imaging) and (iv) the accumulation of peripheral amyloid precursor protein C-terminal fragments (APP-CTFs). We revealed alterations in mitochondrial structure as well as specific mitochondrial dysfunction signatures in AD-MCI and AD-D fibroblasts and revealed that defective mitophagy and autophagy are linked to impaired lysosomal activity in AD-D fibroblasts. We reported significant correlations of a subset of these dysfunctions with cognitive decline, AD-related clinical hallmarks and peripheral APP-CTFs accumulation. This study emphasizes the potential use of peripheral cells for investigating AD pathophysiology.

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.

Mitochondrial dysfunction: mechanisms and advances in therapy

Mitochondria, with their intricate networks of functions and information processing, are pivotal in both health regulation and disease progression. Particularly, mitochondrial dysfunctions are identified in many common pathologies, including cardiovascular diseases, neurodegeneration, metabolic syndrome, and cancer. However, the multifaceted nature and elusive phenotypic threshold of mitochondrial dysfunction complicate our understanding of their contributions to diseases. Nonetheless, these complexities do not prevent mitochondria from being among the most important therapeutic targets. In recent years, strategies targeting mitochondrial dysfunction have continuously emerged and transitioned to clinical trials. Advanced intervention such as using healthy mitochondria to replenish or replace damaged mitochondria, has shown promise in preclinical trials of various diseases. Mitochondrial components, including mtDNA, mitochondria-located microRNA, and associated proteins can be potential therapeutic agents to augment mitochondrial function in immunometabolic diseases and tissue injuries. Here, we review current knowledge of mitochondrial pathophysiology in concrete examples of common diseases. We also summarize current strategies to treat mitochondrial dysfunction from the perspective of dietary supplements and targeted therapies, as well as the clinical translational situation of related pharmacology agents. Finally, this review discusses the innovations and potential applications of mitochondrial transplantation as an advanced and promising treatment.

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.

Interplay of mitochondria-associated membrane proteins and autophagy: Implications in neurodegeneration

Since the discovery of membrane contact sites between ER and mitochondria called mitochondria-associated membranes (MAMs), several pieces of evidence identified their role in the regulation of different cellular processes such as Ca2+ signalling, mitochondrial transport, and dynamics, ER stress, inflammation, glucose homeostasis, and autophagy. The integrity of these membranes was found to be essential for the maintenance of these cellular functions. Accumulating pieces of evidence suggest that MAMs serve as a platform for autophagosome formation. However, the alteration within MAMs structure is associated with the progression of neurodegenerative diseases. Dysregulated autophagy is a hallmark of neurodegeneration. Here, in this review, we highlight the present knowledge on MAMs, their structural composition, and their roles in different cellular functions. We also discuss the association of MAMs proteins with impaired autophagy and their involvement in the progression of neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease.

Another Use for a Proven Drug: Experimental Evidence for the Potential of Artemisinin and Its Derivatives to Treat Alzheimer's Disease

Plant-derived multitarget compounds may represent a promising therapeutic strategy for multifactorial diseases, such as Alzheimer's disease (AD). Artemisinin and its derivatives were indicated to beneficially modulate various aspects of AD pathology in different AD animal models through the regulation of a wide range of different cellular processes, such as energy homeostasis, apoptosis, proliferation and inflammatory pathways. In this review, we aimed to provide an up-to-date overview of the experimental evidence documenting the neuroprotective activities of artemi-sinins to underscore the potential of these already-approved drugs for treating AD also in humans and propose their consideration for carefully designed clinical trials. In particular, the benefits to the main pathological hallmarks and events in the pathological cascade throughout AD development in different animal models of AD are summarized. Moreover, dose- and context-dependent effects of artemisinins are noted.

Review on anti-alzheimer drug development: approaches, challenges and perspectives

Alzheimer is an irreversible progressive neurodegenerative disease that causes failure of cerebral neurons and disability of the affected person to practice normal daily life activities. There is no concrete evidence to identify the exact reason behind the disease, so several relevant hypotheses emerged, highlighting many possible therapeutic targets, such as acetylcholinesterase, cholinergic receptors, N-methyl d-aspartate receptors, phosphodiesterase, amyloid β protein, protein phosphatase 2A, glycogen synthase kinase-3 beta, β-secretase, γ-secretase, α-secretase, serotonergic receptors, glutaminyl cyclase, tumor necrosis factor-α, γ-aminobutyric acid receptors, and mitochondria. All of these targets have been involved in the design of new potential drugs. An extensive number of these drugs have been studied in clinical trials. However, only galantamine, donepezil, and rivastigmine (ChEIs), memantine (NMDA antagonist), and aducanumab and lecanemab (selective anti-Aβ monoclonal antibodies) have been approved for AD treatment. Many drugs failed in the clinical trials to such an extent that questions have been posed about the significance of some of the aforementioned targets. On the contrary, the data of other drugs were promising and shed light on the significance of their targets for the development of new potent anti-alzheimer drugs.

Latest assessment methods for mitochondrial homeostasis in cognitive diseases

Mitochondria play an essential role in neural function, such as supporting normal energy metabolism, regulating reactive oxygen species, buffering physiological calcium loads, and maintaining the balance of morphology, subcellular distribution, and overall health through mitochondrial dynamics. Given the recent technological advances in the assessment of mitochondrial structure and functions, mitochondrial dysfunction has been regarded as the early and key pathophysiological mechanism of cognitive disorders such as Alzheimer's disease, Parkinson's disease, Huntington's disease, mild cognitive impairment, and postoperative cognitive dysfunction. This review will focus on the recent advances in mitochondrial medicine and research methodology in the field of cognitive sciences, from the perspectives of energy metabolism, oxidative stress, calcium homeostasis, and mitochondrial dynamics (including fission-fusion, transport, and mitophagy).

Olfactory Receptor OR2K2 Expression in Human Choroid Plexus as a Potential Marker in Early Sporadic Alzheimer's Disease

Epithelial cells comprising the choroid plexus (CP) form a crucial barrier between the blood and the cerebrospinal fluid, thereby assuming a central position in brain homeostasis and signaling. Mounting evidence suggests that the impairment of CP function may be a significant contributor to Alzheimer's disease (AD) pathogenesis. CP function relies on the expression of specific receptors, and the potential involvement of olfactory receptors (ORs) and taste receptors (TASRs) in chemical surveillance within the CP is being investigated. Previous studies have implicated ORs and TASRs in neurodegenerative disorders like AD, although the direct evidence of their expression in the human CP remains to be established. In this study, we conducted a transcriptomic analysis encompassing eleven ORs and TASRs in the CP, comparing samples from healthy age-matched controls to those from patients with AD spanning Braak stages I to VI. Among these receptors, a striking finding emerged-OR2K2 exhibited robust expression, with a statistically significant upregulation noted at Braak stage I. Surprisingly, at the protein level, OR2K2 showed a significant decrease in both Braak stage I and VI. Additionally, we identified CP epithelial cells as the source of OR2K2 expression, where it colocalized with autophagy markers LC3 and p62. We postulate that OR2K2 could be subjected to degradation by autophagy in the early stages of AD, triggering a compensatory mechanism that leads to increased OR2K2 mRNA transcription. This study uncovers a potential role for OR2K2 in AD pathogenesis, offering a novel perspective on the intricate dynamics at play in this neurodegenerative disorder.

The Multiple Roles of Autophagy in Neural Function and Diseases

Autophagy involves the sequestration and delivery of cytoplasmic materials to lysosomes, where proteins, lipids, and organelles are degraded and recycled. According to the way the cytoplasmic components are engulfed, autophagy can be divided into macroautophagy, microautophagy, and chaperone-mediated autophagy. Recently, many studies have found that autophagy plays an important role in neurological diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, neuronal excitotoxicity, and cerebral ischemia. Autophagy maintains cell homeostasis in the nervous system via degradation of misfolded proteins, elimination of damaged organelles, and regulation of apoptosis and inflammation. AMPK-mTOR, Beclin 1, TP53, endoplasmic reticulum stress, and other signal pathways are involved in the regulation of autophagy and can be used as potential therapeutic targets for neurological diseases. Here, we discuss the role, functions, and signal pathways of autophagy in neurological diseases, which will shed light on the pathogenic mechanisms of neurological diseases and suggest novel targets for therapies.

Altered synaptic currents, mitophagy, mitochondrial dynamics in Alzheimer's disease models and therapeutic potential of Dengzhan Shengmai capsules intervention

Emerging research suggests a potential association of progression of Alzheimer's disease (AD) with alterations in synaptic currents and mitochondrial dynamics. However, the specific associations between these pathological changes remain unclear. In this study, we utilized Aβ42-induced AD rats and primary neural cells as in vivo and in vitro models. The investigations included behavioural tests, brain magnetic resonance imaging (MRI), liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis, Nissl staining, thioflavin-S staining, enzyme-linked immunosorbent assay, Golgi-Cox staining, transmission electron microscopy (TEM), immunofluorescence staining, proteomics, adenosine triphosphate (ATP) detection, mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) assessment, mitochondrial morphology analysis, electrophysiological studies, Western blotting, and molecular docking. The results revealed changes in synaptic currents, mitophagy, and mitochondrial dynamics in the AD models. Remarkably, intervention with Dengzhan Shengmai (DZSM) capsules emerged as a pivotal element in this investigation. Aβ42-induced synaptic dysfunction was significantly mitigated by DZSM intervention, which notably amplified the frequency and amplitude of synaptic transmission. The cognitive impairment observed in AD rats was ameliorated and accompanied by robust protection against structural damage in key brain regions, including the hippocampal CA3, primary cingular cortex, prelimbic system, and dysgranular insular cortex. DZSM intervention led to increased IDE levels, augmented long-term potential (LTP) amplitude, and enhanced dendritic spine density and length. Moreover, DZSM intervention led to favourable changes in mitochondrial parameters, including ROS expression, MMP and ATP contents, and mitochondrial morphology. In conclusion, our findings delved into the realm of altered synaptic currents, mitophagy, and mitochondrial dynamics in AD, concurrently highlighting the therapeutic potential of DZSM intervention.

Phosphatidate phosphatase Lipin1 involves in diabetic encephalopathy pathogenesis via regulating synaptic mitochondrial dynamics

Diabetic encephalopathy (DE) is a common central nervous system complication of diabetes mellitus without effective therapy currently. Recent studies have highlighted synaptic mitochondrial damages as a possible pathological basis for DE, but the underlying mechanisms remain unclear. Our previous work has revealed that phosphatidate phosphatase Lipin1, a critical enzyme involved with phospholipid synthesis, is closely related to the pathogenesis of DE. Here, we demonstrate that Lipin1 is significantly down-regulated in rat hippocampus of DE. Knock-down of Lipin1 within hippocampus of normal rats induces dysregulation of homeostasis in synaptic mitochondrial dynamics with an increase of mitochondrial fission and a decrease of fusion, then causes synaptic mitochondrial dysfunction, synaptic plasticity deficits as well as cognitive impairments, similar to that observed in response to chronic hyperglycemia exposure. In contrast, an up-regulation of Lipin1 within hippocampus in the DE model ameliorates this cascade of dysfunction. We also find that the effect of Lipin1 that regulating mitochondrial dynamics results from maintaining appropriate phospholipid components in the mitochondrial membrane. In conclusion, alterations in hippocampal Lipin1 contribute to hippocampal synaptic mitochondrial dysfunction and cognitive deficits observed in DE. Targeting Lipin1 might be a potential therapeutic strategy for the clinical treatment of DE.

Network pharmacology-based analysis of Jin-Si-Wei on the treatment of Alzheimer's disease

ETHNOPHARMACOLOGICAL RELEVANCE

Jin-Si-Wei (JSW), a traditional Chinese medicine (TCM) formula, have cognitive enhancing effect and delay the memory decline in an animal model of AD， which has been reported. However, the therapeutic mechanism of JSW in the treatment of AD remains unclear.

AIM OF THE STUDY

This study aimed to verify the pharmacodynamics of JSW in the treatment of AD, and to explore its potential mechanism based on network pharmacology, molecular docking and experimental validation both in vitro and in vivo.

MATERIALS AND METHODS

In this study, the underlying mechanism of JSW against AD was investigated by the integration of network pharmacology. Then, the core pathways and biological process of JSW were verified by experiment, including behavioral test and pathological and biochemical assays with 6-month-old APPswe/PS1ΔE9 transgenic (APP/PS1) mice in vivo and verified with Aβ1-42-stimulated SH-SY5Y cells in vitro. At last, molecular docking was used to show the binding activity of each active ingredient to the core genes of JSW treatment in AD.

RESULTS

A Drug-Ingredient-Target network was established, which included 363 ingredients and 116 targets related to the JSW treatment of AD. The main metabolic pathway of JSW treatment for AD is neuroactive ligand-receptor interaction pathway, and biological processes are mainly involved in Aβ metabolic process. In vivo experiments, compared with APP/PS1 mice, the cognitive and memory ability of mice was significantly improved after JSW administration. In brain tissue of APP/PS1 mice, JSW could increase the contents of low-density lipoprotein receptor-related protein 1 (LRP-1), enkephalinase (NEP) and Acetyl choline (ACh), and decrease the contents of Aβ1-42, amyloid precursor protein (APP) and receptor for advanced glycation end products (RAGE), decrease the vitality of cholinesterase (AChE) and choline acetyltransferase (ChAT). Besides, JSW could increase α-secretase expression and decrease β/γ-secretase expression, and improve the number and morphology of synapses in CA1 region of the hippocampus of APP/PS1 mice. In vitro experiments, Drug-Containing Serum (JSW-serum) has a neuroprotective effect by reducing the apoptosis on Aβ1-42-stimulated SH-SY5Y cells. Molecular docking results showed that 2-Isopropyl-8-methylphenanthrene-3,4-dione had strong binding activity with PTGS2, which maybe a potential ingredient for the treatment of AD.

CONCLUSIONS

JSW improves AD in APP/PS1 mice, and this therapeutic effect may be achieved in part by altering the neuroactive ligand-receptor interaction pathway.

Monotropein induces autophagy through activation of the NRF2/PINK axis, thereby alleviating sepsis-induced colonic injury

Sepsis is a systemic inflammatory disease that is caused by a dysregulated host response to infection and is a life-threatening organ dysfunction that affects many organs, which includes the colon. Mounting evidence suggests that sepsis-induced colonic damage is a major contributor to organ failure and cellular dysfunction. Monotropein (MON) is the major natural compound in the iris glycoside that is extracted from Morendae officinalis radix, which possesses the potent pharmacological activities of anti-inflammatory and antioxidant properties. This research evaluated whether MON is able to alleviate septic colonic injury in mice by cecal ligation and puncture. Colonic tissues were analyzed using histopathology, immunofluorescence, quantitative real-time polymerase chain reaction, and Western blot methods. It was initially discovered that MON reduced colonic damage in infected mice, in addition to inflammation, apoptosis, and oxidative stress in colonic tissues, while it activated autophagy, with the NRF2/keap1 and PINK1/Parkin pathways also being activated. Through the stimulation of NCM460 cells with lipopolysaccharides, an in vitro model of sepsis was created as a means of further elucidating the potential mechanisms of MON. In the in vitro model, it was found that MON could still activate the NRF2/keap1, PINK1/Parkin, and autophagy pathways. However, when MON was paired with the NRF2 inhibitor ML385, it counteracted MON-induced activation of PINK1/Parkin and autophagy, while also promoting inflammatory response and apoptosis in NCM460 cells. Therefore, the data implies that MON could play a therapeutic role through the activation of the NFR2/PINK pathway as a means of inducing autophagy to alleviate the oxidative stress in colonic tissues that is induced by sepsis, which will improve inflammation and apoptosis in colonic tissues.

Research Progress of Mitophagy in Alzheimer's Disease

The prevalence of Alzheimer's disease (AD) is increasing as the elderly population, which hurts elderly people's cognition and capacity for self-care. The process of mitophagy involves the selective clearance of ageing and impaired mitochondria, which is required to preserve intracellular homeostasis and energy metabolism. Currently, it has been discovered that mitophagy abnormalities are intimately linked to the beginning and progression of AD. This article discusses the mechanism of mitophagy, abnormal mitophagy, and therapeutic effects in AD. The purpose is to offer fresh perspectives on the causes and remedies of AD.

Mutant NOTCH3ECD Triggers Defects in Mitochondrial Function and Mitophagy in CADASIL Cell Models

Background

Cerebral autosomal-dominant arteriopathy with subcortical infarction and leukoencephalopathy (CADASIL) is an inherited small-vessel disease that affects the white matter of the brain. Recent studies have confirmed that the deposition of NOTCH3ECD is the main pathological basis of CADASIL; however, whether different mutations present the same pathological characteristics remains to be further studied. Some studies have found that mitochondrial dysfunction is related to CADASIL; however, the specific effects of NOTCH3ECD on mitochondrial remain to be determined.

Objective

We aimed to explore the role of mitochondrial dysfunction in CADASIL.

Methods

We established transgenic human embryonic kidney-293T cell models (involving alterations in cysteine and non-cysteine residues) via lentiviral transfection. Mitochondrial function and structure were assessed using flow cytometry and transmission electron microscopy, respectively. Mitophagy was assessed using western blotting and immunofluorescence.

Results

We demonstrated that NOTCH3ECD deposition affects mitochondrial morphology and function, and that its protein levels are significantly correlated with mitochondrial quality and can directly bind to mitochondria. Moreover, NOTCH3ECD deposition promoted the induction of autophagy and mitophagy. However, these processes were impaired, leading to abnormal mitochondrial accumulation.

Conclusions

This study revealed a common pathological feature of NOTCH3ECD deposition caused by different NOTCH3 mutations and provided new insights into the role of NOTCH3ECD in mitochondrial dysfunction and mitophagy.

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.

Call to action to properly utilize electron microscopy to measure organelles to monitor disease

This review provides an overview of the current methods for quantifying mitochondrial ultrastructure, including cristae morphology, mitochondrial contact sites, and recycling machinery and a guide to utilizing electron microscopy to effectively measure these organelles. Quantitative analysis of mitochondrial ultrastructure is essential for understanding mitochondrial biology and developing therapeutic strategies for mitochondrial-related diseases. Techniques such as transmission electron microscopy (TEM) and serial block face-scanning electron microscopy, as well as how they can be combined with other techniques including confocal microscopy, super-resolution microscopy, and correlative light and electron microscopy are discussed. Beyond their limitations and challenges, we also offer specific magnifications that may be best suited for TEM analysis of mitochondrial, endoplasmic reticulum, and recycling machinery. Finally, perspectives on future quantification methods are offered.

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.

Reduction of alcohol-induced mitochondrial damage with ginsenoside Rg1 studied by atomic force microscopy

The quantification of mitochondrial morphology and mechanical properties is useful for the diagnosis and treatment of mitochondrial and alcoholic liver disease. In this study, the effects of ginsenoside Rg1 (G-Rg1) on the morphology and mechanical properties of mitochondria that had suffered alcohol-induced damage were investigated under near-physiological conditions. Additionally, the morphological and mechanical properties of mitochondria were quantified through atomic force microscopy. Atomic force microscopy revealed that alcohol-induced significant morphological changes in mitochondria. Compared with that of the mitochondria of normal hepatocytes, the average surface area of the damaged mitochondria was found to have increased significantly under the influence of alcohol. Furthermore, the mitochondrial area tended to be normal under the action of G-Rg1, whilst other parameters (length, width and perimeter) were significantly different from those of the mitochondria with the alcohol-induced damage. Simultaneously, alcohol significantly reduced the adhesion and elastic modulus of mitochondria, whilst the adhesion and elastic modulus of mitochondria in the G-Rg1 treatment group were closer to the values of normal mitochondria. This study overall showed that G-Rg1 could effectively alleviate the swelling and anomalous mechanical properties of mitochondria induced by alcohol.

Unveiling the Molecular Footprint: Proteome-Based Biomarkers for Alzheimer's Disease

Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by progressive cognitive decline and memory loss. Early and accurate diagnosis of AD is crucial for implementing timely interventions and developing effective therapeutic strategies. Proteome-based biomarkers have emerged as promising tools for AD diagnosis and prognosis due to their ability to reflect disease-specific molecular alterations. There is of great significance for biomarkers in AD diagnosis and management. It emphasizes the limitations of existing diagnostic approaches and the need for reliable and accessible biomarkers. Proteomics, a field that comprehensively analyzes the entire protein complement of cells, tissues, or bio fluids, is presented as a powerful tool for identifying AD biomarkers. There is a diverse range of proteomic approaches employed in AD research, including mass spectrometry, two-dimensional gel electrophoresis, and protein microarrays. The challenges associated with identifying reliable biomarkers, such as sample heterogeneity and the dynamic nature of the disease. There are well-known proteins implicated in AD pathogenesis, such as amyloid-beta peptides, tau protein, Apo lipoprotein E, and clusterin, as well as inflammatory markers and complement proteins. Validation and clinical utility of proteome-based biomarkers are addressing the challenges involved in validation studies and the diagnostic accuracy of these biomarkers. There is great potential in monitoring disease progression and response to treatment, thereby aiding in personalized medicine approaches for AD patients. There is a great role for bioinformatics and data analysis in proteomics for AD biomarker research and the importance of data preprocessing, statistical analysis, pathway analysis, and integration of multi-omics data for a comprehensive understanding of AD pathophysiology. In conclusion, proteome-based biomarkers hold great promise in the field of AD research. They provide valuable insights into disease mechanisms, aid in early diagnosis, and facilitate personalized treatment strategies. However, further research and validation studies are necessary to harness the full potential of proteome-based biomarkers in clinical practice.

APP-BACE1 Interaction and Intracellular Localization Regulate Aβ Production in iPSC-Derived Cortical Neurons

Alzheimer's disease (AD) is characterized pathologically by amyloid β (Aβ)-containing plaques. Generation of Aβ from amyloid precursor protein (APP) by two enzymes, β- and γ-secretase, has therefore been in the AD research spotlight for decades. Despite this, how the physical interaction of APP with the secretases influences APP processing is not fully understood. Herein, we compared two genetically identical human iPSC-derived neuronal cell types: low Aβ-secreting neuroprogenitor cells (NPCs) and high Aβ-secreting mature neurons, as models of low versus high Aβ production. We investigated levels of substrate, enzymes and products of APP amyloidogenic processing and correlated them with the proximity of APP to β- and γ-secretase in endo-lysosomal organelles. In mature neurons, increased colocalization of full-length APP with the β-secretase BACE1 correlated with increased β-cleavage product sAPPβ. Increased flAPP/BACE1 colocalization was mainly found in early endosomes. In the same way, increased colocalization of APP-derived C-terminal fragment (CTF) with presenilin-1 (PSEN1), the catalytic subunit of γ-secretase, was seen in neurons as compared to NPCs. Furthermore, most of the interaction of APP with BACE1 in low Aβ-secreting NPCs seemed to derive from CTF, the remaining APP part after BACE1 cleavage, indicating a possible novel product-enzyme inhibition. In conclusion, our results suggest that interaction of APP and APP cleavage products with their secretases can regulate Aβ production both positively and negatively. β- and γ-Secretases are difficult targets for AD treatment due to their ubiquitous nature and wide range of substrates. Therefore, targeting APP-secretase interactions could be a novel treatment strategy for AD. Colocalization of APP species with BACE1 in a novel model of low- versus high-Aβ secretion-Two genetically identical human iPSC-derived neuronal cell types: low Aβ-secreting neuroprogenitor cells (NPCs) and high Aβ secreting mature neurons, were compared. Increased full-length APP (flAPP)/BACE1 colocalization in early endosomes was seen in neurons, while APP-CTF/BACE1 colocalization was much higher than flAPP/BACE1 colocalization in NPCs, although the cellular location was not determined.

Amyloid Precursor Protein and Alzheimer's Disease

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders associated with age or inherited mutations. It is characterized by severe dementia in the late stages that affect memory, cognitive functions, and daily life overall. AD progression is linked to the accumulation of cytotoxic amyloid beta (Aβ) and hyperphosphorylated tau protein combined with other pathological features such as synaptic loss, defective energy metabolism, imbalances in protein, and metal homeostasis. Several treatment options for AD are under investigation, including antibody-based therapy and stem cell transplantation. Amyloid precursor protein (APP) is a membrane protein considered to play a main role in AD pathology. It is known that APP in physiological conditions follows a non-amyloidogenic pathway; however, it can proceed to an amyloidogenic scenario, which leads to the generation of extracellular deleterious Aβ plaques. Not all steps of APP biogenesis are clear so far, and these questions should be addressed in future studies. AD is a complex chronic disease with many factors that contribute to disease progression.

Mechanistic insights into the role of herpes simplex virus 1 in Alzheimer's disease

Alzheimer's Disease (AD) is an aging-associated neurodegenerative disorder, threatening millions of people worldwide. The onset and progression of AD can be accelerated by environmental risk factors, such as bacterial and viral infections. Human herpesviruses are ubiquitous infectious agents that underpin numerous inflammatory disorders including neurodegenerative diseases. Published studies concerning human herpesviruses in AD imply an active role HSV-1 in the pathogenesis of AD. This review will summarize the current understanding of HSV-1 infection in AD and highlight some barriers to advance this emerging field.

Maternal exposure to sunlight-irradiated graphene oxide induces neurodegeneration-like symptoms in zebrafish offspring through intergenerational translocation and genomic DNA methylation alterations

The physiochemical properties of graphene oxide may be affected by sunlight irradiation. However, the underlying mechanisms that alter the properties and subsequent intergenerational effects are not sufficiently investigate. Epigenetics is an early sensitive marker for the intergenerational effects of nanomaterial exposure due to the epigenetic memory. In this study, we investigate changes in the physicochemical properties and the intergenerational effects of maternal exposure to simulated sunlight-irradiated polyethyleneimine-functionalized graphene oxide (SL-PEI-GO). Results show that the physicochemical properties of polyethyleneimine-functionalized graphene oxide (PEI-GO) can be altered significantly by the oxidation of carbon atoms with unpaired electrons present in the defects and on the edges of PEI-GO by sunlight. First, the positive charges, sharp edges, defects and disordered structures of SL-PEI-GO make it translocate from maternal zebrafish to offspring, thus catalyzing the production of reactive oxygen species and damaging mitochondria directly. In addition, changes in DNA methylation reduce the expression of protocadherin1a, protocadherin19 and cadherin4, thus destroying cell membrane integrity, cell adhesion and Ca2+ binding. The alteration of DNA methylation induced by maternal exposure activates the Ca2+-CaMKK-brsk2a pathway, which catalyzes the phosphorylation of Tau and eventually results in the appearance of neurodegeneration-like symptoms, including the loss of neurons and neurobehavioral disorders. This study demonstrates that maternal exposure to SL-PEI-GO induces clear neurodegeneration-like symptoms in offspring through both the intergenerational translocation of nanomaterials and differential DNA methylation. These findings may provide new insights into the health risks of nanomaterials altered by nature conditions.

A novel peptidoglycan isolated from Semiaquilegia adoxoides inhibits Aβ42 production via activating autophagy

The accumulation of amyloid β (Aβ) containing senile plaques is one of the key histopathological hallmarks of Alzheimer's disease (AD). Increasing evidences demonstrated the important role of autophagy in Aβ clearance. Recent studies implied that extracts from Semiaquilegia adoxoides (DC.) Makino could ameliorate the memory of D-galactose induced aging mice. However, the bioactive substance and underlying mechanism remains unknown. Thus, the present study sought to explore the effects of a novel homogenous peptidoglycan on Aβ42 secretion and the underlying mechanism. Briefly, we extracted a novel peptidoglycan named SA02C using hot water extraction and alcohol precipitation with the Mw of 13.72 kDa. SA02C contains 73.33% carbohydrate and 27.83% protein. The structure characterization revealed that its glycan part might mainly composed of galacturonic acid with minor rhamnose in backbone, and branched with glucose, galactose, arabinose, xylose and galacturonic acid. The protein or peptide moiety in SA02C was bonded to the polysaccharide via threonine. Bioactivities test showed that SA02C could reduce Aβ42 production in a dose dependent manner with no obvious cytotoxicity. Mechanism study demonstrated that SA02C could modulate APP processing by upregulating the expression of ADAM10, sAPPα and downregulating BACE1, sAPPβ. Furthermore, SA02C also could stimulate autophagy by promoting the expression of the markers of autophagy such as LC3B and ATG5, resulting in the promotion of Aβ42 phagocytosis.

Astrocytic AT1R deficiency ameliorates Aβ-induced cognitive deficits and synaptotoxicity through β-arrestin2 signaling

Alzheimer's disease (AD) seriously influences human health, and there is no effective treatment to prevent or cure AD. Recent studies have shown that angiotensin II type 1 receptor (AT1R) blockers significantly reduce the prevalence of AD, while the precise role and mechanism of AT1R in AD remain obscure. In this study, for the first time, we identified that astrocytic but not neuronal AT1R levels were significantly increased in AD model rats and found that astrocyte-specific knockout of AT1R significantly ameliorated amyloid β (Aβ)-induced cognitive deficits and synaptotoxicity. Pretreating astrocytes with an AT1R blocker also alleviated Aβ-induced synaptotoxicity in the coculture system of hippocampal neurons and astrocytes. Moreover, AT1R could directly bind to Aβ1-42 and activate the astrocytic β-arrestin2 pathway in a biased manner, and biased inhibition of the astrocytic AT1R/β-arrestin2 pathway relieved Aβ-induced neurotoxicity. Furthermore, we demonstrated that astrocytic AT1R/β-arrestin2 pathway-mediated synaptotoxicity was associated with the aggregation of autophagosomes, which triggered the disordered degradation of Aβ. Our findings reveal a novel molecular mechanism of astrocytic AT1R in Aβ-induced neurodegeneration and might contribute to establishing new targets for AD prevention and therapy.

Emerging concepts towards a translational framework in Alzheimer's disease

Over the past decades, significant efforts have been made to understand the precise mechanisms underlying the pathogenesis of Alzheimer's disease (AD), the most common cause of dementia. However, clinical trials targeting AD pathological hallmarks have consistently failed. Refinement of AD conceptualization, modeling, and assessment is key to developing successful therapies. Here, we review critical findings and discuss emerging ideas to integrate molecular mechanisms and clinical approaches in AD. We further propose a refined workflow for animal studies incorporating multimodal biomarkers used in clinical studies - delineating critical paths for drug discovery and translation. Addressing unresolved questions with the proposed conceptual and experimental framework may accelerate the development of effective disease-modifying strategies for AD.

Mitochondrial heterogeneity in diseases

As key organelles involved in cellular metabolism, mitochondria frequently undergo adaptive changes in morphology, components and functions in response to various environmental stresses and cellular demands. Previous studies of mitochondria research have gradually evolved, from focusing on morphological change analysis to systematic multiomics, thereby revealing the mitochondrial variation between cells or within the mitochondrial population within a single cell. The phenomenon of mitochondrial variation features is defined as mitochondrial heterogeneity. Moreover, mitochondrial heterogeneity has been reported to influence a variety of physiological processes, including tissue homeostasis, tissue repair, immunoregulation, and tumor progression. Here, we comprehensively review the mitochondrial heterogeneity in different tissues under pathological states, involving variant features of mitochondrial DNA, RNA, protein and lipid components. Then, the mechanisms that contribute to mitochondrial heterogeneity are also summarized, such as the mutation of the mitochondrial genome and the import of mitochondrial proteins that result in the heterogeneity of mitochondrial DNA and protein components. Additionally, multiple perspectives are investigated to better comprehend the mysteries of mitochondrial heterogeneity between cells. Finally, we summarize the prospective mitochondrial heterogeneity-targeting therapies in terms of alleviating mitochondrial oxidative damage, reducing mitochondrial carbon stress and enhancing mitochondrial biogenesis to relieve various pathological conditions. The possibility of recent technological advances in targeted mitochondrial gene editing is also discussed.