Christina Ploumi

Metabolic homeostasis is a key determinant of stress resilience and healthy ageing. Pomegranate juice (PGJ) and its characteristic ellagitannin punicalagin (PUN) have been associated with beneficial metabolic effects, but the mechanisms through which they influence metabolic adaptation and healthspan, and whether they act through shared or distinct pathways, remain poorly defined. We investigated the effects of lyophilized PGJ (50, 100, and 200 μg/mL) and PUN (25, 50, and 100 μM) on metabolic regulation and stress resilience in Caenorhabditis elegans. Nuclear magnetic resonance spectroscopy was employed for metabolic profiling of PGJ, whereas ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry enabled the quantification of PUN at 2.4 ± 0.127 µg/mg lyophilized juice. Under glucose-enriched conditions, PGJ (200 μg/mL) and PUN (100 μM) reduced normalised Nile Red fluorescence to 0.53 and 0.59 of vehicle levels. On day 10 of adulthood, both treatments increased mean survival under oxidative stress by 1.73- and 1.50-fold, respectively. Both treatments increased MDT-15 reporter response (1.13- and 1.44-fold, respectively), whereas PGJ preferentially increased AAK-2- and FAT-6-associated responses and PUN elevated NHR-49- and FAT-7 expression. PUN also improved locomotor performance under amyloid-β-induced proteotoxic stress. Overall, PGJ and PUN elicited partially overlapping metabolic responses in C. elegans, with NHR-49 and MDT-15 emerging as treatment-responsive regulators associated with lipid homeostasis.

Defective mitophagy is emerging as a key contributor to Alzheimer’s disease (AD), but the neuronal pathways governing mitochondrial clearance and their contribution to disease progression remain poorly understood. Here, we identify BNIP3L/NIX-dependent mitophagy as a conserved neuronal quality control pathway that maintains mitochondrial fitness and constrains AD-associated proteotoxicity. Loss of BNIP3L/NIX or its C. elegans orthologue DCT-1 impaired basal and stressed-induced mitophagy, disrupted mitochondrial homeostasis, enhanced Tau and Aβ pathology and compromised neuronal network, synaptic and behavioral function across human neuronal and in vivo models. Conversely, restoring BNIP3L/NIX and DCT-1 activity improved neuronal function under proteotoxic stress in vivo , reduced disease-associated Tau phosphorylation in human neurons and markedly suppressed seeded Tau aggregation in primary mouse neurons. Together, these findings identify BNIP3L/NIX-mediated mitophagy as a mechanistic link between mitochondrial quality control, proteostasis and neuronal function, and establish its restoration as a potential strategy for counteracting AD-associated pathology.

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.

Mitochondrial dysfunction and impaired mitophagy are hallmarks of aging and age-related pathologies. Disrupted inter-organellar communication among mitochondria, endoplasmic reticulum (ER), and lysosomes, further contributes to cellular dysfunction. While mitophagy has emerged as a promising target for neuroprotection and geroprotection, its potential to restore age-associated defects in organellar crosstalk remains unclear. Here, we show that mitophagy deficiency deregulates the morphology and homeostasis of mitochondria, ER and lysosomes, mirroring age-related alterations. In contrast, urolithin A (UA), a gut-derived metabolite and potent mitophagy inducer, restores inter-organellar communication via calcium signaling, thereby, promoting mitophagy, healthspan and longevity. Our multi-omic analyses reveal that UA reorganizes ER, mitochondrial and lysosomal networks, linking inter-organellar dynamics to mitochondrial quality control. In C. elegans, UA induces calcium release from the ER, enhances lysosomal activity, and drives DRP-1/DNM1L/DRP1-mediated mitochondrial fission, culminating in efficient mitophagy. Calcium chelation abolishes UA-induced mitophagy, blocking its beneficial impact on muscle function and lifespan, underscoring the critical role of calcium signaling in UA's geroprotective effects. Furthermore, UA-induced calcium elevation activates mitochondrial biogenesis via UNC-43/CAMK2D and SKN-1/NFE2L2/Nrf2 pathways, which are both essential for healthspan and lifespan extension. Similarly, in mammalian cells, UA increases intracellular calcium, enhances mitophagy and mitochondrial metabolism, and mitigates stress-induced senescence in a calcium-dependent manner. Our findings uncover a conserved mechanism by which UA-induced mitophagy restores inter-organellar communication, supporting cellular homeostasis and organismal health.

Preserving mitochondrial homeostasis is vital, particularly for the energetically demanding and metabolically active nerve cells. Mitophagy, the selective autophagic removal of mitochondria, stands out as a prominent mechanism for efficient mitochondrial turnover, which is crucial for proper neuronal development and function. Dysfunctional mitochondria and disrupted mitophagy pathways have been linked to a diverse array of neurological disorders. The nematode Caenorhabditis elegans, with its well-defined nervous system, serves as an excellent model to unravel the intricate involvement of mitophagy in developing neurons. This chapter describes the use of Rosella biosensor in C. elegans to monitor neuronal mitophagy, providing a user-friendly platform for screening genes and drugs affecting mitophagic pathways under physiological conditions or in the context of neurodevelopmental pathologies.

N⁶-methyladenine (6mA) in the DNA is a conserved epigenetic mark with various cellular, physiological and developmental functions. Although the presence of 6mA was discovered a few years ago in the nuclear genome of distantly related animal taxa and just recently in mammalian mitochondrial DNA (mtDNA), accumulating evidence at present seriously questions the presence of N⁶-adenine methylation in these genetic systems, attributing it to methodological errors. In this paper, we present a reliable, PCR-based method to determine accurately the relative 6mA levels in the mtDNA of Caenorhabditis elegans, Drosophila melanogaster and dogs, and show that these levels gradually increase with age. Furthermore, daf-2(−)-mutant worms, which are defective for insulin/IGF-1 (insulin-like growth factor) signaling and live twice as long as the wild type, display a half rate at which 6mA progressively accumulates in the mtDNA as compared to normal values. Together, these results suggest a fundamental role for mtDNA N⁶-adenine methylation in aging and reveal an efficient diagnostic technique to determine age using DNA.

One-carbon metabolism (OCM) is a network of biochemical reactions delivering one-carbon units to various biosynthetic pathways. The folate cycle and methionine cycle are the two key modules of this network that regulate purine and thymidine synthesis, amino acid homeostasis, and epigenetic mechanisms. Intersection with the transsulfuration pathway supports glutathione production and regulation of the cellular redox state. Dietary intake of micronutrients, such as folates and amino acids, directly contributes to OCM, thereby adapting the cellular metabolic state to environmental inputs. The contribution of OCM to cellular proliferation during development and in adult proliferative tissues is well established. Nevertheless, accumulating evidence reveals the pivotal role of OCM in cellular homeostasis of non-proliferative tissues and in coordination of signaling cascades that regulate energy homeostasis and longevity. In this review, we summarize the current knowledge on OCM and related pathways and discuss how this metabolic network may impact longevity and neurodegeneration across species.

The elimination of abnormal and dysfunctional cellular constituents is an essential prerequisite for nerve cells to maintain their homeostasis and proper function. This is mainly achieved through autophagy, a process that eliminates abnormal and dysfunctional cellular components, including misfolded proteins and damaged organelles. Several studies suggest that age-related decline of autophagy impedes neuronal homeostasis and, subsequently, leads to the progression of neurodegenerative disorders due to the accumulation of toxic protein aggregates in neurons. Here, we discuss the involvement of autophagy perturbation in neurodegeneration and present evidence indicating that upregulation of autophagy holds potential for the development of therapeutic interventions towards confronting neurodegenerative diseases in humans.