Longevity Papers

Hematopoietic stem cells (HSCs) ageing is a phenomenon described by reduction in self-renewal capacity, compromised homing, a bias towards myeloid differentiation, and defective reconstitution function. The molecular mechanisms of HSCs ageing have been investigated by several groups. In a broad classification, the underlying causes can be grouped into the intrinsic factors and those related to the microenvironment. Determination of the exact mechanism of HSCs ageing and detailed molecular events during its initiation and progression will help in the establishment of novel therapies for the treatment or prevention of ageing-related hematopoietic disorders. This review offers an overview of genetic and epigenetic causes of HSCs ageing. The findings of these investigations paved the way for design of novel strategies for rejuvenation of HSCs.

Senescence emerged as significant mechanism of aging and age-related diseases, offering an attractive target for clinical interventions. Senescent cells release a senescence-associated secretory phenotype (SASP), including exosomes that may act as signal transducers between distal tissues, propagating secondary or bystander senescence and signaling throughout the body. However, the composition of exosome SASP remains underexplored, presenting an opportunity for novel unbiased discovery. We present a detailed proteomic and lipidomic analysis of exosome SASP using mass spectrometry from human plasma from young and older individuals and from tissue culture of senescent primary human lung fibroblasts. We identified ~1,300 exosome proteins released by senescent cells induced by three different senescence inducers. In parallel, a human plasma cohort from young (20 to 26 years) and old (65 to 74 years) individuals revealed over 1,350 exosome proteins and 171 plasma exosome proteins were regulated when comparing old vs young individuals. Of the age-regulated plasma exosome proteins, we observed 52 exosome SASP factors that were also regulated in exosomes from the senescent fibroblasts, including serine protease inhibitors (SERPINs), Prothrombin, Coagulation factor V, Plasminogen, and Reelin. 247 lipids were identified in exosome samples. Following senescence induction, identified phosphatidylcholines, phosphatidylethanolamines, and sphingomyelins increased significantly indicating cellular membrane changes. Interestingly, significantly changed proteins were related to extracellular matrix remodeling and inflammation, both potentially detrimental pathways that can damage surrounding tissues and even induce secondary senescence. Our findings reveal mechanistic insights and potential senescence biomarkers, enabling a better approach to surveilling the senescence burden in the aging population and offering therapeutic targets for interventions.

The quest to decipher the determinants of human longevity has intensified with the rise in global life expectancy. Long-lived individuals (LLIs), who exceed the average life expectancy while delaying age-related diseases, serve as a unique model for studying human healthy aging and longevity. Longevity is a complex phenotype influenced by both genetic and non-genetic factors. This review paper delves into the genetic, epigenetic, metabolic, immune, and environmental factors underpinning the phenomenon of human longevity, with a particular focus on LLIs, such as centenarians. By integrating findings from human longevity studies, this review highlights a diverse array of factors influencing longevity, ranging from genetic polymorphisms and epigenetic modifications to the impacts of diet and physical activity. As life expectancy grows, understanding these factors is crucial for developing strategies that promote a healthier and longer life.

Memory functions are susceptible to age-related cognitive decline, making it essential to explore the underlying neurophysiological mechanisms that contribute to memory function during healthy ageing. Resting-state EEG (rsEEG) parameters, particularly the aperiodic exponent, a marker of cortical excitation-inhibition balance, and individual alpha frequency (IAF), a correlate of neural processing efficiency, have demonstrated associations with ageing and cognitive functions. This study investigated associations between these rsEEG markers and performance across multiple memory systems in healthy older adults (n = 99) aged 50-84 years, specifically the moderating and mediating effects on memory and age-memory relationships across episodic, working, and visual short-term memory systems, assessed via computerised tasks. Results revealed significant moderating effects of the aperiodic exponent on age-related performance in episodic (EM) and visual short-term memory (VSTM). Notably, for individuals with a higher exponent, age was not significantly associated with EM or VSTM performance, whereas those with average and lower exponent values showed poorer performance with older age. These findings suggest that average and lower aperiodic exponents may reflect a marker of decrement in age-related memory performance and higher exponents may index an underlying protective mechanism against age-related memory decline. This investigation extends the current understanding of cognitive ageing mechanisms by identifying the aperiodic exponent as a potential biomarker explaining individual differences in cognitive ageing trajectories in older adult populations, particularly in EM and VSTM systems, and establishes a framework for studying neuroprotective mechanisms and developing interventions to preserve cognitive function in older adults.

Granular detail about the location and nature of liver cell interactions and the metabolic, inflammatory and fibrogenic pathways driving progressive fibrosis in metabolic dysfunction-associated steatotic liver disease (MASLD) is needed to deliver novel therapeutic targets. Here we used spatial transcriptomic data from human MASLD liver biopsies to identify the major cell types and their potential interconnected activities within specific tissue regions across the spectrum of MASLD. Gene expression data were generated using 10X Genomics Visium technology from 33 formalin-fixed paraffin-embedded (FFPE) liver biopsy samples and overlaid with annotated anatomical regions. Differential gene expression (DEG) and pathway analyses, cellular deconvolution and ligand-receptor interactions were conducted separately for each annotated anatomical category, with specific protein expression validated using CODEX spatial proteomics (CO-Detection by Indexing) and immunohistochemistry staining. Unsupervised gene expression data grouped the annotated spots into 2 main clusters enriched for early/intermediate vs late fibrosis and transcriptome-based cellular deconvolution was well aligned with annotated histopathological features. In addition to extracellular matrix/receptor interactions and immune cell recruitment and trafficking, several genes encoding immunoglobulins (IGKC, IGHG, IGHA, IGLC) were highly upregulated in late-stage fibrosis and were spatially associated with a senescence signature. Upregulated DEGs for early/intermediate-stage fibrosis were significantly enriched for metabolic pathways, oxidative phosphorylation and fatty acid metabolism. In contrast glycolysis genes were strongly co-expressed with late stage fibrosis. MASLD progression is accompanied by a decline in normal liver metabolic function and significant reprogramming of metabolic fuel utilisation. The spatial association of a senescence signature with expression of genes encoding immunoglobulins and complement has been linked to aging and is associated with progressive fibrosis. This work provides a valuable discovery dataset spanning different stages of human liver fibrosis and identifies ligand-receptor interactions, as well as metabolic reprogramming and senescence-related genes, associated with fibrosis progression.

Emerging evidence has unveiled heterogeneity in phenotypic and transcriptional alterations at the single-cell level during oxidative stress and senescence. Despite the pivotal roles of cellular metabolism, a comprehensive elucidation of metabolomic heterogeneity in cells and its connection with cellular oxidative and senescent status remains elusive. By integrating single-cell live imaging with mass spectrometry (SCLIMS), we establish a cross-modality technique capturing both metabolome and oxidative level in individual cells. The SCLIMS demonstrates substantial metabolomic heterogeneity among cells with diverse oxidative levels. Furthermore, the single-cell metabolome predicted heterogeneous states of cells. Remarkably, the pre-existing metabolomic heterogeneity determines the divergent cellular fate upon oxidative insult. Supplementation of key metabolites screened by SCLIMS resulted in a reduction in cellular oxidative levels and an extension of C. elegans lifespan. Altogether, SCLIMS represents a potent tool for integrative metabolomics and phenotypic profiling at the single-cell level, offering innovative approaches to investigate metabolic heterogeneity in cellular processes.

Background: While studies have examined associations between changes in BMI and biological aging, the use of biological age estimates derived from omics other than DNA methylation data as well as nonlinearity and interactions in these associations are underexplored. Objective: We aimed to investigate how BMI at ages 18 and ~60, as well as changes in BMI from age 18 to ~60, relate to downstream epigenetic and proteomic aging. We also examined nonlinearity and interactions in these associations. Methods: We analyzed data from 401 Finnish participants with up to 9 self-reported or measured BMI values collected over 40 years. Olink proteomics and Illumina DNA methylation data were generated from blood samples taken at the last BMI measurement. We calculated 4 and 5 estimates of biological age from proteomic and epigenetic clocks, respectively. Changes in BMI over time were estimated using mixed-effects models. We applied generalized additive models to explore 1) nonlinearity in associations between BMI trajectories and biological aging while adjusting for chronological age and 2) smooth interactions between baseline BMI with changes in BMI and BMI at ~60 years old. Results: BMI at 18 and ~60 years old and changes in BMI were associated with increased biological aging for most aging estimates. We found statistical evidence of nonlinearity for about one-third of the significant associations, mostly observed for proteomic clocks. We identified suggestive evidence for interactions between BMI at 18 years and BMI at ~60 years in explaining variability in two proteomic clocks (p=0.07;p=0.09). Conclusion: Our study illustrates the potential of proteomic clocks in obesity research and highlights that assuming linearity in associations between BMI trajectories and biological aging is a critical oversight. Associations between BMI and biological aging are likely modulated by past BMI, which warrants validation by other studies.

Vascular cognitive impairment (VCI) is a leading cause of age-related cognitive decline, driven by cerebrovascular dysfunction and cerebral small vessel disease (CSVD). Emerging evidence suggests that cerebromicrovascular endothelial senescence plays an important role in the pathogenesis of VCI by promoting cerebral blood flow dysregulation, neurovascular uncoupling, blood-brain barrier (BBB) disruption, and the development of cerebral microhemorrhages (CMHs). This review explores the concept of cerebromicrovascular senescence as a continuum of vascular aging, linking macrovascular atherosclerosis with microvascular dysfunction. It examines the mechanisms by which endothelial senescence drives neurovascular pathology and highlights the impact of cardiovascular risk factors in accelerating these processes. We examine preclinical and clinical studies that provide compelling evidence that atherosclerosis-induced microvascular senescence exacerbates cognitive impairment. In particular, findings suggest that targeting senescent endothelial cells through senolytic therapy can restore cerebrovascular function and improve cognitive outcomes in experimental models of atherosclerosis. Given the growing recognition of microvascular senescence as a therapeutic target, further research is warranted to explore novel interventions such as senolytics, anti-inflammatory agents, and metabolic modulators. The development of circulating biomarkers of vascular senescence (e.g., senescence-associated secretory phenotype [SASP] components and endothelial-derived extracellular vesicles) could enable early detection and risk stratification in individuals at high risk for VCI. Additionally, lifestyle modifications, including the Mediterranean diet, hold promise for delaying endothelial senescence and mitigating cognitive decline. In conclusion, cerebromicrovascular senescence is a key mechanistic link between atherosclerosis and cognitive impairment. Addressing microvascular aging as a modifiable risk factor through targeted interventions offers a promising strategy for reducing the burden of VCI and preserving cognitive function in aging populations.

White matter (WM) microstructural health declines with increasing age, with evidence suggesting that improved cardiorespiratory fitness (CRF) may mitigate this decline. Specifically, higher fit older adults tend to show preserved WM microstructural integrity compared to their lower fit counterparts. However, the extent to which fitness and aging independently impact WM integrity across the adult lifespan is still an open question, as is the extent to which cerebrovascular health mediates these relationships. In a large sample (N = 125, aged 25-72), we assessed the impact of age and estimated cardiorespiratory fitness on fractional anisotropy (FA, derived using diffusion weighted imaging, dwMRI) and probed the mediating role of cerebrovascular health (derived using diffuse optical tomography of the cerebral arterial pulse, pulse-DOT) in these relationships. After orthogonalizing age and estimated fitness and computing a PCA on whole brain WM regions, we found several WM regions impacted by age that were independent from the regions impacted by estimated fitness (hindbrain areas, including brainstem and cerebellar tracts), whereas other areas showed interactive effects of age and estimated fitness (midline areas, including fornix and corpus callosum). Critically, cerebrovascular health mediated both relationships suggesting that vascular health plays a linking role between age, fitness, and brain health. Secondarily, we assessed potential sex differences in these relationships and found that, although females and males generally showed the same age-related FA declines, males exhibited somewhat steeper declines than females. Together, these results suggest that age and fitness impact specific WM regions and highlight the mediating role of cerebrovascular health in maintaining WM health across adulthood.

Sepsis-induced acute kidney injury (AKI) can lead to chronic renal dysfunction with accelerated renal aging. Activation of the mammalian target of rapamycin (mTOR) is implicated in the initiation and progression of renal injury. This study investigates the effectiveness of the mTOR inhibitor, rapamycin, in mitigating kidney injury and explores the underlying mechanisms. AKI was induced by intraperitoneal administration of a solution containing 10 mg/kg of lipopolysaccharide (LPS) in a mouse model. Two groups of endotoxemic mice received pre- and post- treatment with rapamycin. Whole-genome DNA methylation analysis was performed on renal proximal tubular epithelial cells (RPTEC). In the LPS-induced AKI mouse model, rapamycin treatment significantly reduced creatinine levels, preserved renal parenchyma, and counteracted the endothelial-to-mesenchymal transition (EndMT) by inhibiting the ERK pathway. Whole-genome DNA methylation analysis revealed that LPS induced aberrant methylation, particularly in genes associated with premature aging, including ectonucleoside triphosphate diphosphohydrolase 1 (ENTPD1/CD39) and wolframin ER transmembrane glycoprotein (WFS1). Accordingly, endotoxemic mice exhibited decreased CD39 expression and klotho down-regulation, both of which were reversed by rapamycin, suggesting an anti-aging effect in AKI. mTOR inhibition may represent a promising strategy to prevent accelerated renal aging in LPS-induced AKI and potentially slow the progression of chronic kidney disease.

Many countries face an unprecedented challenge in aging demographics. This has led to an exponential growth in research of aging, which, coupled to a massive financial influx of funding in the private and public sectors, has resulted in seminal insights into the underpinnings of this biological process. However, critical validation in humans have been hampered by the limited translatability of results obtained in model organisms, additionally confined by the need for extremely time-consuming clinical studies in the ostensible absence of robust biomarkers that would allow monitoring in shorter time frames. In the future, molecular parameters might hold great promise in this regard. In contrast, biomarkers centered on function, resilience and frailty are available at the present time, with proven predictive value for morbidity and mortality. In this review, the current knowledge of molecular and physiological aspects of human aging, potential anti-aging strategies, and the basis, evidence, and potential application of physiological biomarkers in human aging are discussed.

As aging progresses, the structures and functions of immune organs such as the thymus and spleen deteriorate, leading to impaired immune function and immune senescence. This study investigated the potential of umbilical cord mesenchymal stem cells (UC-MSCs) to mitigate D-galactose-induced immune senescence by enhancing the structural and functional integrity of aging immune organs and regulating the gut microbiota. The findings show that UC-MSCs treatment significantly delayed thymus and spleen atrophy and reduced the number of senescence-associated β-galactosidase (SA-β-gal) positive cells. At the molecular level, UC-MSCs treatment downregulated the expression of aging-related genes, including p16, p53, p21, and RB. It also boosted antioxidant enzyme activity, increasing the levels of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px), while decreasing serum malondialdehyde (MDA) levels by activating the Nrf2/HO-1 pathway. Additionally, UC-MSCs treatment restored the balance of the gut microbiota. These results demonstrate that UC-MSCs significantly improve the structural and functional integrity of immune organs and enhance the composition of the gut microbiome, offering a potential strategy for delaying immune senescence.

Psychosocial stressors accelerate telomere attrition, a biomarker of cell aging, whereas good sleep is hypothesized to be a mitigating factor. However, methodological aspects - particularly underpowered studies, inconsistent findings, and multiple approaches to assessing sleep - demonstrate the need for a meta-analysis. After PROSPERO registration, we conducted a systematical search of the following databases until June 2024 to identify studies examining the relationship between sleep quality and telomere length in adult humans: CINAHL, Cochrane Library, MEDLINE, PsychINFO, PubMed, Web of Science, and Google Scholar. In total, 29 studies met inclusion criteria for the systematic review according to the preferred reporting items for systematic reviews and meta-analysis guidelines (PRISMA), 19 of which provided data that was appropriate for meta-analytic calculations. We identified the Pittsburgh sleep quality index (PSQI) global score (odds ratio (OR) 1.24, CI 95 % [1.03; 1.50], p = 0.02), sleep-related daytime impairments (OR 1.01 [1.00; 1.02], p = 0.04), and wake after sleep onset (WASO) time (OR 1.28 [1.12; 1.47], p < 0.01) as to be significantly associated with telomere attrition. Thus, the subtle telomere attrition-mitigating role of sleep has been demonstrated based on a sufficiently large body of data and defined aspects of sleep quality.

Our previous transcriptomic analysis revealed an up-regulation of the antiapoptotic protein B cell lymphoma-extra large (Bcl-xL) in centenarians relative to octogenarians or younger cohorts. In this study, we used Bcl-xL-overexpressing mice to assess its impact on successful aging. Our findings indicate that Bcl-xL overexpression modifies T cell subsets and improves their metabolism, apoptosis resistance, macroautophagy, and cytokine production during aging. This more resilient immune system reduces inflammation and preserves mitochondrial integrity and function in muscle tissue, thereby retarding the onset of frailty. These results underscore the important contribution of Bcl-xL to healthy aging, a phenomenon that is conserved across mammalian species.

The mitochondrial bc1 complex catalyzes the oxidation of ubiquinol by reducing cytochrome c. Cytochrome b, the catalytic core of bc1, generates superoxide during the oxidation of ubiquinol. Excessive superoxide production is known to accelerate aging and neurodegeneration. Songbirds (oscine, Passeri) exhibit lower production of mitochondrial ROS and greatly accelerated evolution of cytochrome b, relative to all other modern birds, suggesting adaptive selection for lower generation of ROS. Here we identified songbirds-specific substitutions in modern bird's cytochrome b amino-acids sequences and examined the high-resolution structures of the chicken bc1 complex in an effort to predict the effect of these substitutions on the function of bc1. Many of the songbirds-specific substitution cluster around sites that are critical for the function of bc1. One cluster of substitutions interacts with heme BH. A second cluster of substitutions interacts with residues in the ubiquinone reduction site, Qi. Both groups of substitution may affect the rate of reduction of ubiquinone at the Qi site. Another cluster of cytochrome b substitutions interacts with the hinge region of the Rieske protein that transfers electron from cytochrome b to cytochrome c1. These songbirds-specific substitutions appear to be selected to modulate the rate of both ubiquinol oxidation at the Qo site and ubiquinone reduction at the Qi site thereby modulating the rate of superoxide production. These findings are compatible with the hypothesis that cytochrome b evolution in songbirds was driven by selection of substitutions that reduce the rate of superoxide production thereby increasing songbird lifespan and cognitive abilities.

Cellular senescence is an irreversible form of cell-cycle arrest caused by excessive stress or damage. While various biomarkers of cellular senescence have been proposed, there are currently no universal, stand-alone indicators of this condition. The field largely relies on the combined detection of multiple biomarkers to differentiate senescent cells from non-senescent cells. Here we introduce a new approach: unbiased cell culture selections to identify senescent cell-specific folded DNA aptamers from vast libraries of trillions of random DNAs. Senescent mouse adult fibroblasts and their non-senescent counterparts were employed for selection. We demonstrate aptamer specificity for senescent mouse cells in culture, identify a form of fibronectin as the molecular target of two selected aptamers, show increased aptamer staining in naturally aged mouse tissues, and demonstrate decreased aptamer staining when p16 expressing cells are removed in a transgenic INK-ATTAC mouse model. This work demonstrates the value of unbiased cell-based selections to identify new senescence-specific DNA reagents.

The allostatic load (AL) concept measures physiological dysregulation in response to internal and external stressors that accumulate across the life course. AL has been consistently linked to chronic disease risk across studies. However, there is considerable variation in its operationalization. In the present study, DNA methylation (DNAm) data (using the Illumina Infinium MethylationEPIC BeadChip (EPIC) array) from the Swiss Kidney Project on Genes in Hypertension (SKIPOGH) cohort, a Swiss-based family cohort study, were used in a discovery epigenome-wide association study (EWAS) to identify CpG sites associated with phenotypic measures of AL. Elastic net linear regression models were used to estimate an epigenetic signature of AL (methAL), including an Illumina HumanMethylation450K (HM450K) assay-compatible signature (methALT). The methALT signature was validated in the 1936 Lothian Birth Cohort (LBC1936), population-based prospective cohort study. We found that the methAL signature was positively associated with the clinical phenotype of AL in both the SKIPOGH (R2= 0.59) and LBC1936 (R2=0.16) cohorts. In the validation cohort, a one SD increase in methALT signature was associated with 25% higher odds of reported history of CVD (OR=1.25, 95% CI=1.05-1.50), and a nearly two-fold increase in all-cause mortality rate at the beginning of follow-up (HR= 1.68, 95% CI= 1.33-2.13) when adjusting for all potential confounders. In conclusion, the epigenetic signature for AL not only correlated well with phenotype-based AL scores, but also exhibited a stronger association with history of CVD and all-cause mortality compared to AL scores. The methAL signature could help assuage issues of comparison across studies.

Regeneration of hair cells is a primary target of gene therapy aimed at restoring vestibular and cochlear functions. Indeed, vestibular dysfunction constitutes a major medical concern, as one of its manifestation, dizziness, affects 15-35% of the general population, with a prevalence rate of 85% for those over 80 of age. Age-related alterations of both vestibular function and the integrity of vestibular hair cells has been reported in humans. However, direct comparisons between structural pathology and vestibular dysfunctions quantifications are lacking in humans and rather limited in animal models, representing a significant gap in current knowledge. Thus far, therapeutic trials in animal models targeting vestibular loss associated with genetic diseases have yielded varied and partial results, and the functional identity and quantity of hair cells sufficient to restore minimal or normal vestibular function remain undefined. Here, we further develop an innovative methodology to bridge the gap between hair cells integrity and functional vestibular loss in individuals. Gradual vestibular deficits were induced through a dose-dependent ototoxic compound, quantified with canal or utricular-specific vestibulo-ocular reflex tests, and were then correlated in all individuals with the loss of type I and type II hair cells in different regions of ampulla and macula. Our findings reveal that the structure-function relationship is nonlinear, with lower bound of approximately 50% of hair cells necessary to retain minimal vestibular function, and threshold exceeding 80% to preserve normal function, thus shedding light on population-coding mechanisms for vestibular response. Our data further support the decisive role of type I, rather than type II, HC in the tested VOR functions.

The accumulation of senescent cells contributes to aging and related diseases; therefore, discovering safe senolytic agents-compounds that selectively eliminate senescent cells-is a critical priority. Heat shock protein 90 (HSP90) inhibitors (HSP90i), traditionally investigated for cancer treatment, have shown potential as senolytic agents. However, inhibitors face formulation, toxicity, and cost challenges. To overcome these limitations, we employed a virtual screening approach combining structure-based prefiltering with a ligand-based pharmacophore model to identify novel, potentially safe HSP90 alpha isoform inhibitors exhibiting senolytic properties. This strategy identified 14 candidate molecules evaluated for senolytic activity in primary human fetal pulmonary fibroblasts. Four compounds exhibited significant HSP90i and senolytic activity, including two novel compounds, namely K4 and K5. The latter, 1-benzyl-3-(2-methylphenyl)-3,7-dihydro-1H-purine-2,6-dione, structurally related to the xanthinic family, emerged as a promising, well-tolerated senolytic agent. K5 demonstrated senolytic activity across various cellular senescence models, including human fibroblasts, mesenchymal stem cells, and breast cancer cells. It was also effective in vivo, extending lifespan in Drosophila and reducing senescence markers in geriatric mice. Additionally, the xanthinic nature of K5 implicates a multimodal action, now including the inhibition of HSP90α, that might enhance its efficacy and selectivity towards senescent cells, Senolytic index SI > 1320 for IMR90 cells, and SI > 770 for WI38 cells, underscoring its therapeutic potential. These findings advance senolytic therapy research, opening new avenues for safer interventions to combat age-related inflammaging and diseases, including cancer, and possibly extend a healthy lifespan.

Cardiovascular-kidney-metabolic (CKM) syndrome, characterized by pathophysiological interactions among metabolic risk factors, chronic kidney disease and the cardiovascular system, is a significant global health concern, particularly in populations with adverse social determinants of health (SDOH). However, the influence of CKM syndrome and the joint effects of SDOH on the risk of developing incident dementia has not been fully elucidated. Here, we examined these associations among 382569 individuals from the UK Biobank. We found that unfavorable SDOH and advanced CKM syndrome (stage 3-4) are independently associated with increased risks of incident all-cause dementia, Alzheimer's disease and vascular dementia. Additionally, joint associations of CKM syndrome stages and SODH with incident dementia were observed. Individuals with [≥]3 unfavorable SDOH and in CKM syndrome stage 4 exhibited the highest dementia risk, even after adjusting for APOE {varepsilon}4 status. Our findings highlighted the importance of maintaining optimal CKM health and addressing unfavorable SODH in cognitive aging.

Ubiquitin (Ub), a central regulator of protein turnover, can be phosphorylated by PINK1 (PTEN-induced putative kinase 1) to generate S65-phosphorylated ubiquitin (pUb). Elevated pUb levels have been observed in aged human brains and in Parkinson's disease, but the mechanistic link between pUb elevation and neurodegeneration remains unclear. Here, we demonstrate that pUb elevation is a common feature under neurodegenerative conditions, including Alzheimer's disease, aging, and ischemic injury. We show that impaired proteasomal activity leads to the accumulation of sPINK1, the cytosolic form of PINK1 that is normally proteasome-degraded rapidly. This accumulation increases ubiquitin phosphorylation, which then inhibits ubiquitin-dependent proteasomal activity by interfering with both ubiquitin chain elongation and proteasome-substrate interactions. Specific expression of sPINK1 in mouse hippocampal neurons induced progressive pUb accumulation, accompanied by protein aggregation, proteostasis disruption, neuronal injury, neuroinflammation, and cognitive decline. Conversely, pink1 knockout mitigated protein aggregation in both mouse brains and HEK293 cells. Furthermore, the detrimental effects of sPINK1 could be counteracted by co-expressing Ub/S65A phospho-null mutant but exacerbated by over-expressing Ub/S65E phospho-mimic mutant. Together, these findings reveal that pUb elevation, triggered by reduced proteasomal activity, inhibits proteasomal activity and forms a feedforward loop that drives progressive neurodegeneration.

Age-related deficits in episodic memory and mnemonic discrimination are associated with an increased risk of neurodegenerative diseases, such as Alzheimer\'s disease (AD) (Stark et al., 2013). While much research has focused on hippocampal contributions to these age-related changes (Stark et al., 2019), less is known about the role of posterior cingulate cortex (PCC) especially reduced inhibition in episodic memory deficit. PCC has connections to the medial temporal lobe and is linked to memory declines (Greicius et al., 2004). It is also one of the most vulnerable regions to amyloid deposition in AD (Yokoi et al., 2018). This study hypothesized and found that age-related declines in GABAergic function (brain\'s major inhibitory neurotransmitter) within the PCC contributes to individual differences in memory performance in healthy older adults. Using Magnetic Resonance Spectroscopy, we measured GABA levels in the PCC in 22 healthy younger and 30 older adults. We assessed episodic memory using Rey Delayed Auditory Verbal Learning Test (RAVLT) and Mnemonic Similarity Task (MST). We found that both raw GABA levels and episodic memory performance are lower in older adults compared to young. This reduction in GABA levels is subserved by age-related changes in tissue-composition as evidenced by no age-group differences in corrected GABA levels. More importantly, lower GABA levels (independent of tissue-correction) were associated with poorer episodic performance including delayed recall and mnemonic discrimination. This research suggests that therapeutically targeting posterior cingulate GABA levels might help slow or alleviate memory decline.

Organismal aging is accompanied by the accumulation of senescent cells in the body, which drives tissue dysfunction. Senescent cells have a distinctive profile, including proliferation arrest, resistance to apoptosis, altered gene expression, and high inflammation. Despite global signaling and metabolic dysregulation during senescence, the underlying reasons for changes in signaling remain unclear. GPCRs are pivotal in cellular signaling, dynamically mediating the complex interplay between cells and their surrounding environment to maintain cellular homeostasis. The chemokine receptor CXCR4 plays a crucial role in modulating immune responses and inflammation. It has been shown that the expression of CXCR4 increases in cells undergoing senescence, which enhances inflammation postactivation. Here, we examine CXCR4 signaling in deeply senescent cells (aged cells), where cholesterol and its oxidized derivatives, oxysterols, affect receptor function. We report elevated oxysterol levels in senescent cells, which altered classical CXCL12-mediated CXCR4 signaling. Tail-oxidized sterols disrupted signaling more than ring-oxidized counterparts. Molecular dynamics simulations revealed that 27-hydroxycholesterol displaces cholesterol and binds strongly to alter the conformation of critical signaling residues, modifying the sterol-CXCR4 interaction landscape. Our study provides a molecular view of the observed mitigated GPCR signaling in the presence of oxysterols, which switched G-protein signaling from Gα

Accumulation of senescent hepatocytes is universal in chronic liver disease (CLD). This study investigates an association between hepatocyte senescence and hepatocellular carcinoma (HCC) and explores the therapeutic role of sirolimus. Background liver biopsies from 15 patients with cirrhosis and HCC and 45 patients with cirrhosis were stained for p16, a marker of cell senescence. STAM™ mice were randomized into 3 groups of 5 at 4 weeks of age and administered vehicle ± sirolimus intraperitoneally, thrice weekly, from 4 to 18 weeks of age. Placebo group was an administered vehicle, early sirolimus group was an administered vehicle with sirolimus, late sirolimus group was an administered vehicle from 4 to 12 weeks then vehicle with sirolimus from 12 to 18 weeks. The primary outcome was HCC nodule development. Senescent hepatocyte burden and senescence-associated secretory phenotype (SASP) factors were assessed in mice livers. In the human study, age (OR 1.282, 95% CI 1.086-1.513, p = 0.003) and p16 (OR 1.429, 95% CI 1.112-1.838, p = 0.005) were independently associated with HCC. In the animal study, all three groups exhibited similar MASLD activity scores (p = 0.39) and fibrosis area (p = 0.92). The number and the maximum diameter of HCC nodules were significantly lower in the early sirolimus group compared to placebo and late sirolimus group. The gene expression of SASP factors was similar in all groups. Protein levels of some SASP factors (TNFα, IL1β, IL-2, CXCL15) were significantly lower in sirolimus administered groups compared to placebo group. The study demonstrates an independent association between senescent hepatocyte burden and HCC. It indicates a potential chemoprophylactic role for sirolimus through SASP factor inhibition. These early results could inform a future human clinical trial.

The cGAS-STING pathway mediates the innate immune response to cytosolic DNA, contributing to surveillance against microbial invasion or cellular damage. Once activated, STING recruits TBK1 at the trans-Golgi network (TGN), which in turn phosphorylates IRF3 to induce type I interferon (IFN-I) expression. In contrast to STING, little is known about how TBK1 is transported to the TGN for activation. Here, we show that multiple TGN tethering factors, a group of proteins involved in vesicle capturing, are indispensable for STING-IFN-I signaling. Deletion of TBC1D23, a recently reported tethering factor, in mice impairs the STING-IFN-I signaling, but with insignificant effect on STING-NF-κB signaling. Mechanistically, TBC1D23 interacts with TBK1 via the WASH complex subunit FAM21 and promotes its endosome-to-TGN translocation. Furthermore, multiple TGN tethering factors were reduced in aged mice and senescent fibroblasts. In summary, our study uncovers that TGN tethering factors are key regulators of the STING-IFN-I signaling and suggests that their reduction in senescence may produce aberrant STING signaling.

Epigenetics, the study of heritable changes in gene expression that do not involve alterations to the deoxyribonucleic acid (DNA) sequence, plays a pivotal role in cellular function, development, and aging. This review explores key epigenetic mechanisms, including DNA methylation (DNAm), histone modifications, chromatin remodeling, RNA-based regulation, and long-distance chromosomal interactions. These modifications contribute to cellular differentiation and function, mediating the dynamic interplay between the genome and environmental factors. Epigenetic clocks, biomarkers based on DNAm patterns, have emerged as powerful tools to measure biological age and predict health span. This article highlights the evolution of epigenetic clocks, from first-generation models such as Horvath's multi-tissue clock to advanced second- and third-generation clocks such as DNAGrimAge and DunedinPACE, which incorporate biological parameters and clinical biomarkers for precise age estimation. Moreover, the role of epigenetics in aging and age-related diseases is discussed, emphasizing its impact on genomic stability, transcriptional regulation, and cellular senescence. Epigenetic dysregulation is implicated in cancer, genetic disorders, and neurodegenerative diseases, making it a promising target for therapeutic interventions. The reversibility of epigenetic modifications offers hope for mitigating age acceleration and enhancing health span through lifestyle changes and pharmacological approaches.

Epigenetic clocks have emerged as novel measures of biological aging and potential predictors of mortality. We examined all-cause, cardiovascular, and cancer mortality prediction by epigenetic age acceleration (EAA) estimated using different epigenetic clocks. Among 2105 participants to the 1999-2002 National Health and Nutrition Examination Survey aged ≥ 50 years old and followed for mortality through 2019, we calculated EAAs from the residuals of nine epigenetic clocks regressed on chronological age. We assessed the association of EAAs and pace of aging with mortality adjusting for covariates. During 17.5 years of median follow-up, 998 deaths occurred, including 272 from cardiovascular disease and 209 from cancer. Overall mortality was most significantly predicted by Grim EAA (P < 0.0001) followed by Hannum (P = 0.005), Pheno (P = 0.004), Horvath (P = 0.03), and Vidal-Bralo (P = 0.04) EAAs. Grim EAA predicted cardiovascular mortality (P < 0.0001), whereas Hannum (P = 0.006), Horvath (P = 0.009), and Grim (P = 0.01) EAAs predicted cancer mortality. Overall mortality prediction differed by race/ethnicity between non-Hispanic White and White participants for Horvath (P

The traditional view of aging as a gradual, progressive process is increasingly being challenged. A growing body of evidence suggests the existence of abrupt transitions in the aging process, marked by sudden molecular shifts. Interestingly, the data indicates that such transitions occur not only in late life but also throughout the entire lifespan. Further research on the nature of such events could enhance our understanding of aging and pave the way for novel therapeutic strategies, including personalized medicine. We propose that these abrupt molecular shifts could serve as biomarkers, dividing the lifespan into distinct stages and providing the foundation for a much-needed staging system for aging. Furthermore, we argue that the sudden changes may be the hallmarks of aging tipping points, that is, points in time where aging processes are quickly amplified after surpassing critical biological thresholds.