Longevity Papers

Stresses occurring transiently and early in life can have long-standing consequences for health, even long after the stress has resolved. Many environmental stressors converge on activating the integrated stress response (ISR), whose major effector is ATF4. However, it remains unknown whether transient ATF4-ISR activation early in life is a mediator of life and healthspan. Here we used inducible, reversible ATF4 gain-of-function in Drosophila to determine how the timing, duration and tissue of ATF4 activation determine ageing outcomes. We found that ATF4 induction confined to early adulthood extended healthspan, reducing mortality risk by approximately 50% across all ages and improving neuromuscular function in aged flies. Multi-organ transcriptomics showed that the acute ATF4 transcriptional response was transient, as expected, but replaced by a distinct, secondary transcriptional programme of metabolic remodelling that was associated with decreased total body protein content. By using tissue-specific ATF4 induction, we found that transient ATF4 activation in neurons was sufficient to extend lifespan, slow age-related locomotor decline and increase starvation resistance in old age. This neuron-restricted activation prevented the costs to body weight and fecundity induced by ubiquitous ATF4 activation. Transient neuronal ATF4 left a lasting non-autonomous imprint on the fat body at old age: induction of heterochromatin genes, reduced transposable element expression, and increased mitochondrial respiratory capacity. These findings show that the duration and tissue of ISR-ATF4 activation are the key determinants of ATF4 actions that promote healthy ageing, while revealing a brain-to-fat body axis initiated by neuronal ATF4 that results in lasting systemic adaptation.

How progenitor cells couple their metabolic state to the regulation of fate and differentiation remains a fundamental question in tissue development and regeneration. Here, we identify a nutrient-responsive circuit that links progenitor anabolism to differentiation in the Drosophila midgut. We show that the mTORC1 downstream effector PWP1 is necessary and sufficient for differentiation of intestinal stem cell progeny toward the absorptive lineage in fed animals. In progenitors with high mTORC1 activity, PWP1 controls gene expression to promote Hedgehog (Hh) signaling, which cell autonomously drives progenitor differentiation into enterocytes. This circuit is constrained by feedback regulation, as elevated Hh activity inhibits mTORC1 and consequently excludes PWP1 from the nucleus. Disruption of the mTORC1-PWP1-Hh axis causes a progressive failure of enterocyte turnover during aging and reduced lifespan. While the aged midguts retain their barrier function, defective renewal leads to aging-associated deregulation of intestinal metabolism. Collectively, these observations support the concept of growth-dependent licensing of differentiation, whereby the nutrient-responsive anabolic state of a progenitor cell controls its lineage progression, consequently enabling organ renewal.

Iron accumulation is a conserved hallmark of cellular as well as organismal aging, yet its mechanistic role in senescence remains largely elusive. Here we show that the accumulation of ferrous iron (Fe

One influential proposal holds that DNA damage drives aging by degrading the epigenome, so that a cell loses the information that specifies what it is. We test that specific proposed driver, not the broader idea that aging involves a loss of epigenetic information. Cell-type-unique CpGs are a direct place to test it. They are the sites where a cell's methylome differs most from every other cell type, so they are where its identity information can be accurately measured. We built such a panel for human skin fibroblasts against twenty primary cell types, and found that most of its 9,150 CpGs behave as a record of proliferation rather than identity. Their methylation state in fibroblasts is shared with continuously proliferating cell lines, consistent with the bulk hypomethylation of late-replicating chromatin that accumulates in culture, and this layer must be separated from identity marks before identity loss can be tested. We then expressed every perturbation as the fraction of the panel's identity information lost beyond baseline-matched background CpGs, using a Bernoulli cross-entropy between the fibroblast code and a generic comparator cell. In 24 matched fibroblast cultures, replicative exhaustion cost 24.3% of the identity information (95% CI 20.2 to 28.7) and RAS activation cost 5.4% (4.6 to 6.1), both at p = 1.2 X 10^-7;. A senescence-inducing dose of X-rays cost nothing: -0.5% (-0.7 to -0.2), with identity CpGs if anything moving slightly further from other cell types than matched background did. The design could detect a loss of 0.4%, about one sixtieth of the exhaustion effect, so the X-ray result is a bounded negative rather than an absence of power. Doxorubicin-induced and irradiation-induced senescence did not move the panel either. Clones that kept dividing after irradiation moved further from other cell types rather than collapsing toward them. In human fibroblasts, loss of identity information tracks prolonged division, not acute DNA damage.

Assessing and validating circulating biomarkers is essential for developing preclinical measures of biological aging in mice. However, comprehensive serum proteomics are limited by technical challenges and low sample volumes. Here we present a quantitative nanoparticle-based enrichment workflow coupled with data-independent acquisition mass spectrometry for deep proteomic profiling of low-volume mouse serum. This approach increased proteomic coverage by 3-6-fold with median coefficient of variation <10%. In 30 mice aged 12, 24 and 30 months, we uncovered 3,992 protein groups from 20 µl of serum and revealed age- and sex-specific changes, and capturing senescence-associated circulating proteins. With 1 µl additional serum,the proximity extension assay quantified 43 cytokines not detected by mass spectrometry. Comparison with plasma proteomics from the Baltimore Longitudinal Study of Aging identified conserved age-associated circulating proteins, several of which were linked to frailty in humans, notably COL6A3. These results establish a scalable approach for discovering aging biomarkers in sample-limited mouse studies with translational relevance to human health.

When subject to damage or stress, cells develop responses in order to maintain tissue homeostasis. Two such responses are ferroptosis and cellular senescence, but how cells decide between these outcomes remains unclear. Here, we show that senescent cells increase import and membrane levels of multiple polyunsaturated fatty acids (PUFAs), but a specific intermediate PUFA, dihomo-gamma-linolenic acid (DGLA, 20:3ω-6), is reduced. Exogenous repletion of DGLA instead results in cell death by ferroptosis. Senescent cells manifest additional features associated with ferroptosis, including labile iron and expression of lipoxygenases as well as low-level membrane peroxidation. Oral DGLA supplementation lowers markers of senescence in aged mice and improves age-related functional outcomes. Finally, obese humans with lowered DGLA desaturation rates have lower markers of adipose tissue senescence. Together, our data implicate shifts in PUFA metabolism as a driver of decisions between senescence and ferroptosis.

Chromatin stability and nuclear architectural integrity constitute the primary defense against cellular senescence. Their collapse precipitates genomic disarray, epigenetic misregulation, and functional decline in stem cells. Although TOP2A is conventionally known for resolving DNA topological stress, its role in aging remains largely unexplored. Here, we found that TOP2A expression progressively decreased in senescent mesenchymal stem cells (MSCs), and its depletion initiated a catastrophic nuclear remodeling process characterized by the loss of Lamin B1, heterochromatin erosion, and senescence-associated phenotypes. Mechanistically, TOP2A directly regulated the expression of Lamin B1 to maintain nuclear architecture. TOP2A depletion set off a domino effect involving nuclear membrane rupture, loss of heterochromatin-associated factors (H3K9me3, KAP1, and LAP2), deterioration of cellular functions and acceleration of senescence. Notably, overexpression of TOP2A restored Lamin B1 levels, mitigated nuclear protein loss, preserved nuclear integrity, and counteracted cellular senescence. The in vivo relevance of these findings was further underscored by TOP2A inhibitor-induced brain aging in murine models. Our study establishes TOP2A as a novel modulator of cellular senescence, which stabilizes heterochromatin and nuclear structure, and provides new perspectives for targeting chromatin-based mechanisms in aging.

Our body is continuously exposed to endogenous and exogenous sources of oxidative stress arising from physiological metabolism and environmental factors such as ultraviolet (UV) radiation. These stresses generate reactive oxygen species (ROS) that can induce genotoxicity through oxidative DNA damage. To evaluate the contribution of NRF2, which is a master transcription factor regulating cellular antioxidant responses, to the suppression of oxidative stress-induced genotoxicity in the skin, we examined Nrf2-deficient mice regarding mutagenic responses to two separate biological situations: acute UVB exposures and the chronic process of aging. Analyses were performed using transgenic mice carrying the bacterial lacZ gene as a mutational reporter. No significant differences were detected between Nrf2-deficient and wild-type mice in mutagenicity, induced mutation spectrum, and mutation distribution within the reporter gene after acute UVB exposure, whereas the dose-response kinetics of UVB-induced mutation in the phase called "mutation induction suppression" (MIS) differed significantly between genotypes, with a more pronounced MIS response observed in the Nrf2-/- epidermis. Little contribution of ROS to genotoxicity was observed after the acute exposure. Notably, however, the age-dependent accumulation of mutations was significantly elevated in the Nrf2-deficient epidermis compared to the wild-type. These findings indicate that NRF2 plays a protective role for the skin, not by directly preventing genotoxicity, but by promoting tissue recovery after acute UVB damage and, more importantly, by suppressing the genotoxic effects of physiologically produced ROS in a chronic aging process.