Mitochondrial damage is a shared hallmark of brain aging and neurodegeneration. While pathological Tau mutations disrupt mitochondrial dynamics and function, the physiological role of wild-type (WT) Tau in the maintenance of mitochondrial homeostasis remains poorly understood. Here, using Caenorhabditis elegans and mice lacking PTL-1, the nematode Tau-like homolog, and Tau respectively, we demonstrate that Tau deficiency promotes a shift toward a pro-fusion mitochondrial state associated with enhanced mitochondrial function and stress resistance. In both models, loss of Tau leads to increased mitochondrial activity and altered redox homeostasis, while it enhances resistance to heat and mitochondrial stress in C. elegans. Strikingly, loss of FZO-1, the mitofusin homolog, abolishes the beneficial phenotypes, whereas its overexpression phenocopies key aspects of Tau/PTL-1 deficiency. Together, our findings uncover a conserved role for WT Tau in restraining mitochondrial fusion and functional adaptation, highlighting its contribution to mitochondrial homeostasis and cellular stress responses.

Alzheimer's disease (AD) is associated with the aggregation of β-amyloid (Aβ) peptides and oxidative stress, two interconnected processes that contribute to neuronal dysfunction and cognitive decline. Natural polyphenols such as oleuropein and its metabolite hydroxytyrosol display antioxidant and anti-amyloidogenic properties, but oleuropein suffers from limited stability due to glycosidic hydrolysis. To develop more robust and potent oleuropein analogs, we synthesized a series of hydroxytyrosol-based esters in which the secoiridoid glucoside scaffold of oleuropein was replaced by lipophilic substituents designed to enhance molecular stability and interactions with Aβ peptide. The compounds were evaluated for their ability to interact with Aβ40 using ESI-MS, circular dichroism (CD), and thioflavin-T fluorescence (ThT), along with complementary antioxidant assays. Most of the compounds formed stable non-covalent complexes with Aβ40, inhibited early aggregation events, and prevented the peptide's conformational transition from random coil to β-sheet. To assess biological efficacy and safety in vivo, the most promising analog (3b) was evaluated in Caenorhabditis elegans models of amyloid-β toxicity. Treatment with 3b exhibited no detectable toxicity in wild-type animals, as evidenced by normal development, growth, and reproductive efficacy. Importantly, 3b rescued lifespan shortening and locomotor deficits in transgenic nematodes expressing human Aβ42 pan-neuronally, while having no effect on control strains lacking Aβ42 expression. These findings demonstrate that 3b confers functional protection against amyloid-induced toxicity in vivo. Overall, our results identify the newly synthesized hydroxytyrosol-derived esters as promising multifunctional scaffolds that combine potent anti-aggregation activity with strong antioxidant properties and in vivo neuroprotective efficacy, supporting their further development as anti-amyloidogenic agents for AD therapy.

Ageing and neurodegeneration are characterized by the progressive breakdown of organellar communication between mitochondria, the endoplasmic reticulum (ER), and lysosomes. Recent findings underline mitophagy as a central modulator of this interconnected network. Impaired mitophagy induces ER fragmentation, lysosomal dysfunction, imbalanced mitochondrial dynamics, and deregulation of calcium homeostasis, suggesting that mitochondrial turnover is essential for the maintenance of global organellar architecture. Conversely, restoring mitophagy re-establishes structural integrity and functional coordination across subcellular compartments. Notably, Urolithin A (UA) rejuvenates inter-organelle crosstalk through a defined calcium-dependent mechanism. UA promotes ER-derived calcium release via ITR-1/ITPR/InsP3R, EMC-3/EMC3, and TMCO-1/TMCO1, and enhances calcium uptake into mitochondria through MCU-1/MCU. This calcium flux activates DRP-1/DRP1-mediated mitochondrial fission, facilitating mi-tophagy initiation. In parallel, calcium-dependent activation of the UNC-43/CaMKII-SKN-1/Nrf2 axis stimulates mitochondrial biogenesis and metabolic adaptation. Furthermore, UA increases ER-mitochondrial contact sites (MAMs) and restores lysosomal activity, thereby re-establishing functional inter-organellar communication in nematodes and mammalian cells. These findings establish mitophagy as a central node of cellular and tissue homeostasis, acting through the stabilization of the organellar communication network to promote healthspan and lifespan while highlighting the need for future studies to validate these mechanisms across human tissues and disease-relevant cellular contexts.

Mitochondria-associated membranes (MAMs) are specialized contact sites between the endoplasmic reticulum and mitochondria, with multiple functional aspects. Here, we present a confocal microscopy-based protocol for quantifying the area of MAM-like domains in intestinal cells of the nematode Caenorhabditis elegans using organelle-specific fluorescent reporters. We describe steps for worm synchronization, microscope setup, sample preparation, and image acquisition. We then detail procedures for manual single-image analysis and scalable automated batch processing, enabling robust quantification of ER-mitochondria contacts across experimental conditions. For complete details on the use and execution of this protocol, please refer to Roussos et al.(1).

Neurodegenerative diseases, such as Alzheimer's disease (AD), pose significant socioeconomic and personal burdens due to progressive cognitive and motor decline. AD is characterized by the accumulation of amyloid-beta (Aβ) plaques and tau tangles, alongside with emerging evidence linking metabolic dysfunction to its early disease pathogenesis. Impaired mitochondrial selective autophagy (known as mitophagy) and excessive mitochondrial dysfunction have been implicated as key contributors to disease progression. To uncover the mechanistic underpinnings of AD, Caenorhabditis elegans offers a powerful model system providing a fully mapped nervous system, transparency for live imaging, and evolutionary conserved pathways mirroring human pathophysiology. Here, we employ a pan-neuronal Aβ(1-42) -expressing C. elegans strain to phenocopy early metabolic disturbances characteristic of AD. Our methodology integrates automated motility tracking with confocal microscopy, utilizing the mitochondria-targeted Rosella biosensor to assess mitophagy dynamics in vivo. This platform enables quantitative assessment of locomotion deficits and spatiotemporal monitoring of mitophagy alterations driven by Aβ(1-42)-induced toxicity. Our method provides a robust tool for screening genetic and pharmacological interventions aimed at mitigating AD-associated mitochondrial dysfunction and neurodegeneration.

High consumption of colorful fruits and vegetables correlates with low dementia risk, but the exact molecules and the underlying biological mechanisms governing their bioactive profiles are largely unknown. Using a 10-year observational cohort study coupled with an AI-driven systems pharmacology platform, we identified a natural triterpenoid compound found in colorful fruits and vegetables, α-Amyrin (αA), as a therapeutic candidate for Alzheimer's disease (AD). The efficacy of αA in treating the symptoms of AD, such as Tau tangles, damaged mitochondria, and memory loss, was examined using cross-species models; αA retained memory in AD-like animal models while also strongly inhibiting Tau pathology, especially p-Tau217, in a cellular 'Tau seeding' system and in Tau[P301S] mice, followed by validation using a human 3D microfluidic system. At molecular level, αA is a robust mitochondrial regulator, enhancing mitochondrial stress resilience and activation of mitophagy. Mechanistically, αA inhibits dual leucine zipper kinase (DLK), leading to the inhibition of DLK-Sterile Alpha and TIR Motif Containing 1 (SARM1)-dependent neurodegeneration; this inhibition frees unc-51 Like Autophagy Activating Kinase 1 (ULK1) from the ULK1-SARM1 complex, allowing it to participate in autophagy/mitophagy. αA also shows strong translational potential with a 10.1 h half-life and the ability to cross the blood-brain barrier. Our results indicate that αA may act as a mitochondrial guardian against AD via modulating the DLK-SARM1-ULK1-autophagy/mitophagy axis while further preclinical and clinical studies are warranted.