bims-senagi Biomed News
on Senescence and aging
Issue of 2021‒10‒03
33 papers selected by
Maria Grazia Vizioli
Mayo Clinic

  1. Aging Cell. 2021 Sep 29. e13483
      The senescence-associated secretory phenotype (SASP) is a striking characteristic of senescence. Accumulation of SASP factors causes a pro-inflammatory response linked to chronic disease. Suppressing senescence and SASP represents a strategy to prevent or control senescence-associated diseases. Here, we identified a small molecule SR9009 as a potent SASP suppressor in therapy-induced senescence (TIS) and oncogene-induced senescence (OIS). The mechanism studies revealed that SR9009 inhibits the SASP and full DNA damage response (DDR) activation through the activation of the NRF2 pathway, thereby decreasing the ROS level by regulating the expression of antioxidant enzymes. We further identified that SR9009 effectively prevents cellular senescence and suppresses the SASP in the livers of both radiation-induced and oncogene-induced senescence mouse models, leading to alleviation of immune cell infiltration. Taken together, our findings suggested that SR9009 prevents cellular senescence via the NRF2 pathway in vitro and in vivo, and activation of NRF2 may be a novel therapeutic strategy for preventing cellular senescence.
    Keywords:  DNA damage; NRF2; ROS; SASP; SR9009; cellular senescence
  2. Chembiochem. 2021 Sep 27.
      Cellular senescence, a stable form of cell cycle arrest, facilitates protection from tumorigenesis and aids in tissue repair as they accumulate in the body at an early age. However, long-term retention of senescent cells causes inflammation, aging of the tissue, and progression of deadly diseases such as obesity, diabetes, and atherosclerosis. Various attempts have been made to achieve selective elimination of senescent cells from the body, yet little has been explored in designing the mitochondria-targeted senolytic agent. Many characteristics of senescence are associated with mitochondria. Here we have designed a library of alkyl-monoquaternary ammonium-triphenyl phosphine (TPP) and alkyl-diquaternary ammo-nium-TPP of varying alkyl chain lengths, which target the mitochondria; we also studied their senolytic properties. It was observed that the alkyl-diquaternary ammonium-TPP with the longest chain length induces apoptosis to senescent cells selectively via an increase of reactive oxygen species (ROS) and mitochondrial membrane disruption. This study demonstrated that mitochondria could be a potential target for designing new small molecules as senolytic agents for the treatment of a variety of dysfunctions associated with pathological aging.
    Keywords:  alkyl-quaternary ammonium-TPP * mitochondria * membrane disruption * senescence * Macula retina mouse model
  3. Cancers (Basel). 2021 Sep 11. pii: 4561. [Epub ahead of print]13(18):
      Senescence is a dynamic, multistep program that results in permanent cell cycle arrest and is triggered by developmental or environmental, oncogenic or therapy-induced stress signals. Senescence is considered as a tumor suppressor mechanism that prevents the risk of neoplastic transformation by restricting the proliferation of damaged cells. Cells undergoing senescence sustain important morphological changes, chromatin remodeling and metabolic reprogramming, and secrete pro-inflammatory factors termed senescence-associated secretory phenotype (SASP). SASP activation is required for the clearance of senescent cells by innate immunity. Therefore, escape from senescence and the associated immune editing would be a prerequisite for tumor initiation and progression as well as therapeutic resistance. One of the possible mechanisms for overcoming senescence could be the acquisition of cellular plasticity resulting from the accumulation of genomic alterations and genetic and epigenetic reprogramming. The modified composition of the SASP produced by these reprogrammed cancer cells would create a permissive environment, allowing their immune evasion. Additionally, the SASP produced by cancer cells could enhance the cellular plasticity of neighboring cells, thus hindering their recognition by the immune system. Here, we propose a comprehensive review of the literature, highlighting the role of cellular plasticity in the pro-tumoral activity of senescence in normal cells and in the cancer context.
    Keywords:  cellular plasticity; epithelial-mesenchymal transition; immune evasion; reprogramming; senescence
  4. Biomater Sci. 2021 Sep 28. 9(19): 6461-6473
      Cellular senescence, an irreversible proliferation arrested but viable cellular state, has been implicated in the progression of several age-associated pathologies. A vast amount of information about senescence has been acquired in cultured cells; however, senescence in living organisms (in vivo) remains poorly understood, mainly because of technical limitations. Furthermore, it is now widely recognized that three-dimensional (3D) culture systems are a better mimic of the in vivo physiology. Herein, senescence was induced in HeLa cells by irradiation. Non-senescent or senescent cells were cultured in soft 3D polymer scaffolds and compared with cells in conventional two-dimensional (2D) culture. This work shows that the morphology of the senescent cells markedly varies between substrates/culture platforms, driving the differences in the cytoskeletal organization, cellular division, and nanomechanical properties. One characteristic feature of senescent cells on 2D culture systems is the enlarged and flattened morphology; however, such drastic changes are not seen in vivo. This is an artificial effect of the substrate, which renders such non-physiological morphology to senescent cells. In the 3D scaffolds, this artifact is reduced. Hence, it serves as a better mimic of tissues, leading to reduced expression of senescence-associated genes, implying that the 3D scaffolds suppress the senescence in cells.
  5. Nutrients. 2021 Sep 21. pii: 3290. [Epub ahead of print]13(9):
      Calorie restriction (CR) extends lifespan and retards age-related chronic diseases in most species. There is growing evidence that the gut microbiota has a pivotal role in host health and age-related pathological conditions. Yet, it is still unclear how CR and the gut microbiota are related to healthy aging. Here, we report findings from a small longitudinal study of male C57BL/6 mice maintained on either ad libitum or mild (15%) CR diets from 21 months of age and tracked until natural death. We demonstrate that CR results in a significantly reduced rate of increase in the frailty index (FI), a well-established indicator of aging. We observed significant alterations in diversity, as well as compositional patterns of the mouse gut microbiota during the aging process. Interrogating the FI-related microbial features using machine learning techniques, we show that gut microbial signatures from 21-month-old mice can predict the healthy aging of 30-month-old mice with reasonable accuracy. This study deepens our understanding of the links between CR, gut microbiota, and frailty in the aging process of mice.
    Keywords:  calorie restriction; gut microbiota; healthy aging; machine learning; mice
  6. Antioxidants (Basel). 2021 Sep 21. pii: 1497. [Epub ahead of print]10(9):
      Age-related hearing loss (ARHL) is an increasing and gradual sensorineural hearing dysfunction. Oxidative stress is an essential factor in developing ARHL; additionally, premature senescence of auditory cells induced by oxidative stress can produce hearing loss. Hydrogen peroxide (H2O2) represents a method commonly used to generate cellular senescence in vitro. The objective of the present paper is to study H2O2-induced senescence patterns in three auditory cell lines (House Ear Institute-Organ of Corti 1, HEI-OC1; organ of Corti, OC-k3, and stria vascularis, SV-k1 cells) to elucidate the intrinsic mechanisms responsible for ARHL. The auditory cells were exposed to H2O2 at different concentrations and times. The results obtained show different responses of the hearing cells concerning cell growth, β-galactosidase activity, morphological changes, mitochondrial activation, levels of oxidative stress, and other markers of cell damage (Forkhead box O3a, FoxO3a, and 8-oxoguanine, 8-oxoG). Comparison between the responses of these auditory cells to H2O2 is a helpful method to evaluate the molecular mechanisms responsible for these auditory cells' senescence. Furthermore, this in vitro model could help develop anti-senescent therapeutic strategies for the treatment of AHRL.
    Keywords:  age-related hearing loss; auditory cell; hydrogen peroxide (H2O2); oxidative stress; senescence
  7. Aging Cell. 2021 Oct 01. e13450
      Cells expressing high levels of the cyclin-dependent kinase (CDK)4/6 inhibitor p16 (p16High ) accumulate in aging tissues and promote multiple age-related pathologies, including neurodegeneration. Here, we show that the number of p16High cells is significantly increased in the central nervous system (CNS) of 2-year-old mice. Bulk RNAseq indicated that genes expressed by p16High cells were associated with inflammation and phagocytosis. Single-cell RNAseq of brain cells indicated p16High cells were primarily microglia, and their accumulation was confirmed in brains of aged humans. Interestingly, we identified two distinct subpopulations of p16High microglia in the mouse brain, with one being age-associated and one present in young animals. Both p16High clusters significantly differed from previously described disease-associated microglia and expressed only a partial senescence signature. Taken together, our study provides evidence for the existence of two p16-expressing microglia populations, one accumulating with age and another already present in youth that could positively and negatively contribute to brain homeostasis, function, and disease.
    Keywords:  Aging; cellular senescence; neuroscience; p16; senescence
  8. Front Physiol. 2021 ;12 734976
      Mitochondria are essential organelles that generate most of the chemical energy to power the cell through ATP production, thus regulating cell homeostasis. Although mitochondria have their own independent genome, most of the mitochondrial proteins are encoded by nuclear genes. An extensive bidirectional communication network between mitochondria and the nucleus has been discovered, thus making them semi-autonomous organelles. The nucleus-to-mitochondria signaling pathway, called Anterograde Signaling Pathway can be deduced, since the majority of mitochondrial proteins are encoded in the nucleus, less is known about the opposite pathway, the so-called mitochondria-to-nucleus retrograde signaling pathway. Several studies have demonstrated that non-coding RNAs are essential "messengers" of this communication between the nucleus and the mitochondria and that they might have a central role in the coordination of important mitochondrial biological processes. In particular, the finding of numerous miRNAs in mitochondria, also known as mitomiRs, enabled insights into their role in mitochondrial gene transcription. MitomiRs could act as important mediators of this complex crosstalk between the nucleus and the mitochondria. Mitochondrial homeostasis is critical for the physiological processes of the cell. Disruption at any stage in their metabolism, dynamics and bioenergetics could lead to the production of considerable amounts of reactive oxygen species and increased mitochondrial permeability, which are among the hallmarks of cellular senescence. Extensive changes in mitomiR expression and distribution have been demonstrated in senescent cells, those could possibly lead to an alteration in mitochondrial homeostasis. Here, we discuss the emerging putative roles of mitomiRs in the bidirectional communication pathways between mitochondria and the nucleus, with a focus on the senescence-associated mitomiRs.
    Keywords:  microRNA; mitochondria; mitomiRs; mitonuclear communication; senescence
  9. Front Cell Dev Biol. 2021 ;9 735483
      The dysfunction or exhaustion of adult stem cells during aging is closely linked to tissue aging and age-related diseases. Circumventing this aging-related exhaustion of adult stem cells could significantly alleviate the functional decline of organs. Therefore, identifying small molecular compounds that could prevent the age-related decline of stem cell function is a primary goal in anti-aging research. Caffeic acid (CA), a phenolic compound synthesized in plants, offers substantial health benefits for multiple age-related diseases and aging. However, the effects of CA on adult stem cells remain largely unknown. Using the Drosophila midgut as a model, this study showed that oral administration with CA significantly delayed age-associated Drosophila gut dysplasia caused by the dysregulation of intestinal stem cells (ISCs) upon aging. Moreover, administering CA retarded the decline of intestinal functions in aged Drosophila and prevented hyperproliferation of age-associated ISC by suppressing oxidative stress-associated JNK signaling. On the other hand, CA supplementation significantly ameliorated the gut hyperplasia defect and reduced environmentally induced mortality, revealing the positive effects of CA on tolerance to stress responses. Taken together, our findings report a crucial role of CA in delaying age-related changes in ISCs of Drosophila.
    Keywords:  aging; antioxidant activity; caffeic acid; gut; intestinal stem cell
  10. Cancer Res. 2021 Sep 27. pii: canres.0752.2021. [Epub ahead of print]
      Glioblastomas (GBM) are routinely treated with ionizing radiation (IR) but inevitably recur and develop therapy resistance. During treatment, the tissue surrounding tumors is also irradiated. IR potently induces senescence, and senescent stromal cells can promote the growth of neighboring tumor cells by secreting factors that create a senescence-associated secretory phenotype (SASP). Here, we carried out transcriptomic and tumorigenicity analyses in irradiated mouse brains to elucidate how radiation-induced senescence of non-neoplastic brain cells promotes tumor growth. Following cranial irradiation, widespread senescence in the brain occurred, with the astrocytic population being particularly susceptible. Irradiated brains showed an altered transcriptomic profile characterized by upregulation of CDKN1A (p21), a key enforcer of senescence, and several SASP factors including HGF, the ligand of the receptor tyrosine kinase (RTK) Met. Pre-irradiation of mouse brains increased Met-driven growth and invasiveness of orthotopically implanted glioma cells. Importantly, irradiated p21-/- mouse brains did not exhibit senescence and consequently failed to promote tumor growth. Senescent astrocytes secreted HGF to activate Met in glioma cells and promote their migration and invasion in vitro, which could be blocked by HGF-neutralizing antibodies or the Met inhibitor crizotinib. Crizotinib also slowed the growth of glioma cells implanted in pre-irradiated brains. Treatment with the senolytic drug ABT-263 (navitoclax) selectively killed senescent astrocytes in vivo, significantly attenuating growth of glioma cells implanted in pre-irradiated brains. These results indicate that SASP factors in the irradiated tumor microenvironment drive GBM growth via RTK activation, underscoring the potential utility of adjuvant senolytic therapy for preventing GBM recurrence after radiotherapy.
  11. Nutrients. 2021 Sep 20. pii: 3279. [Epub ahead of print]13(9):
      Several lines of evidence suggest an inhibitory role of dietary nucleotides (NTs) against oxidative stress and inflammation, which promote senescence in age-associated cardiovascular diseases. We sought to test whether the dietary NTs could retard the hydrogen peroxide (H2O2)-induced senescence of human umbilical vein endothelial cells (HUVECs) and to elucidate the efficiency of different NTs as well as the potential mechanism. Senescence was induced in HUVECs by 4 h exposure to 200 µM H2O2 and was confirmed using senescence-associated-β-galactosidase staining (SA-β-gal), cell viability, and Western blot analyses of p16INK4A and p21Waf1/Cip1 after 24 h administration of growth medium. We find that NTs retards oxidative stress-induced HUVECs senescence, as shown by a lower percentage of SA-β-gal-positive cells, lower expression of p16INK4A, and p21Waf1/Cip1 as well as higher cell viability. GMP100 was the most excellent in delaying HUVECs senescence, which was followed by the NTs mixture, NMN, CMP50, and UMP50/100, while AMP retards HUVECs senescence by specifically reducing p15INK4b expression. NTs all have significant anti-inflammatory effects; AMP and CMP were more prominent in restoring mitochondrial function, GMP and CMP were more competent at eliminating ROS and MDA, while AMP and UMP were more efficient at enhancing antioxidant enzyme activity. The role of the NTs mixture in retarding HUVECs senescence is full-scaled. These results stated that the mechanisms of NTs retarding HUVECs senescence could be related to its antioxidant and anti-inflammation properties promoting cell proliferation and protecting mitochondrial function activities.
    Keywords:  HUVECs; dietary nucleotides; inflammation; mitochondrial function; oxidative stress; senescence
  12. Biomedicines. 2021 Sep 04. pii: 1162. [Epub ahead of print]9(9):
      Idiopathic pulmonary fibrosis (IPF) is a chronic disease characterised by a dense fibrosing of the lung parenchyma. An association between IPF and cellular senescence is well established and several studies now describe a higher abundance of senescent fibroblasts and epithelial cells in the lungs of IPF patients compared with age-matched controls. The cause of this abnormal accumulation of senescent cells is unknown but evidence suggests that, once established, senescence can be transferred from senescent to non-senescent cells. In this study, we investigated whether senescent human lung fibroblasts (LFs) and alveolar epithelial cells (AECs) could induce a senescent-like phenotype in "naïve" non-senescent LFs in vitro. Primary cultures of LFs from adult control donors (Ctrl-LFs) with a low baseline of senescence were exposed to conditioned medium (CM) from: (i) Ctrl-LFs induced to become senescent using H2O2 or etoposide; (ii) LFs derived from IPF patients (IPF-LFs) with a high baseline of senescence; or (iii) senescence-induced A549 cells, an AEC line. Additionally, ratios of non-senescent Ctrl-LFs and senescence-induced Ctrl-LFs (100:0, 0:100, 50:50, 90:10, 99:1) were co-cultured and their effect on induction of senescence measured. We demonstrated that exposure of naïve non-senescent Ctrl-LFs to CM from senescence-induced Ctrl-LFs and AECs and IPF-LFs increased the markers of senescence including nuclear localisation of phosphorylated-H2A histone family member X (H2AXγ) and expression of p21, IL-6 and IL-8 in Ctrl-LFs. Additionally, co-cultures of non-senescent and senescence-induced Ctrl-LFs induced a senescent-like phenotype in the non-senescent cells. These data suggest that the phenomenon of "senescence-induced senescence" can occur in vitro in primary cultures of human LFs, and provides a possible explanation for the abnormal abundance of senescent cells in the lungs of IPF patients.
    Keywords:  collagen; idiopathic pulmonary fibrosis (IPF); lung fibroblasts; senescence
  13. Aging Cell. 2021 Oct 01. e13477
      Immunosenescence is a hallmark of aging and manifests as increased susceptibility to infection, autoimmunity, and cancer in the elderly. One component of immunosenescence is thymic involution, age-associated shrinkage of the thymus, observed in all vertebrates studied to date. The naked mole rat (Heterocephalus glaber) has become an attractive animal model in aging research due to its extreme longevity and resistance to disease. Here, we show that naked mole rats display no thymic involution up to 11 years of age. Furthermore, we found large ectopic cervical thymi in addition to the canonical thoracic thymus, both being identical in their cell composition. The developmental landscape in naked mole rat thymi revealed overt differences from the murine T-cell compartment, most notably a decrease of CD4+ /CD8+ double-positive cells and lower abundance of cytotoxic effector T cells. Our observations suggest that naked mole rats display a delayed immunosenescence. Therapeutic interventions aimed at reversing thymic aging remain limited, underscoring the importance of understanding the cellular and molecular mechanisms behind a sustained immune function in the naked mole rat.
    Keywords:  CD4-CD8 Ratio; T-lymphocytes; aging; immunosenescence; lymphopoiesis; naked mole rat; thymus
  14. Cells. 2021 Sep 15. pii: 2435. [Epub ahead of print]10(9):
      Although advances in preventive medicine have greatly improved prognosis, cardiovascular disease (CVD) remains the leading cause of death worldwide. This clearly indicates that there remain residual cardiovascular risks that have not been targeted by conventional therapies. The results of multiple animal studies and clinical trials clearly indicate that inflammation is the most important residual risk and a potential target for CVD prevention. The immune cell network is intricately regulated to maintain homeostasis. Ageing associated changes to the immune system occurs in both innate and adaptive immune cells, however T cells are most susceptible to this process. T-cell changes due to thymic degeneration and homeostatic proliferation, metabolic abnormalities, telomere length shortening, and epigenetic changes associated with aging and obesity may not only reduce normal immune function, but also induce inflammatory tendencies, a process referred to as immunosenescence. Since the disruption of biological homeostasis by T cell immunosenescence is closely related to the development and progression of CVD via inflammation, senescent T cells are attracting attention as a new therapeutic target. In this review, we discuss the relationship between CVD and T cell immunosenescence associated with aging and obesity.
    Keywords:  T cell; cardiovascular disease; immunosenescence; obesity
  15. Front Physiol. 2021 ;12 726345
      Maintenance of telomere length is essential to delay replicative cellular senescence. It is controversial on whether growth differentiation factor 11 (GDF11) can reverse cellular senescence, and this work aims to establish the causality between GDF11 and the telomere maintenance unequivocally. Using CRISPR/Cas9 technique and a long-term in vitro culture model of cellular senescence, we show here that in vitro genetic deletion of GDF11 causes shortening of telomere length, downregulation of telomeric reverse transcriptase (TERT) and telomeric RNA component (TERC), the key enzyme and the RNA component for extension of the telomere, and reduction of telomerase activity. In contrast, both recombinant and overexpressed GDF11 restore the transcription of TERT in GDF11KO cells to the wild-type level. Furthermore, loss of GDF11-induced telomere shortening is likely caused by enhancing the nuclear entry of SMAD2 which inhibits the transcription of TERT and TERC. Our results provide the first proof-of-cause-and-effect evidence that endogenous GDF11 plays a causal role for proliferative cells to maintain telomere length, paving the way for potential rejuvenation of the proliferative cells, tissues, and organs.
    Keywords:  Smad2; TERC; TERT; growth differentiation factor 11; replicative cellular senescence; telomerase activity; telomere length
  16. STAR Protoc. 2021 Sep 17. 2(3): 100809
      Senescent cells constantly experience stressful conditions and restrain their protein translation to cope with it. Here, we present a detailed protocol to measure the rate of global protein synthesis using L-azidohomoalanine (L-AHA)-based click chemistry in human senescent fibroblasts. We optimized several aspects of the procedure, including senescence induction, a flow cytometry analysis of senescent cells, and the duration of L-AHA incorporation. This protocol uses senescent human fibroblasts but can be applied to other types of cells or circumstances. For complete details on the use and execution of this protocol, please refer to Lee et al. (2021).
    Keywords:  Cell Biology; Cell-based Assays; Flow Cytometry/Mass Cytometry; Molecular Biology; Molecular/Chemical Probes; Protein Biochemistry
  17. Cancers (Basel). 2021 Sep 21. pii: 4732. [Epub ahead of print]13(18):
      Cell senescence constitutes a physiological process that serves as protection from malignant transformation of cells. However, recent scientific discoveries also identify cell senescence as pivotal in hepatocellular cancer (HCC) biology. The review herein aimed to accumulate evidence on senescence as a mediator of HCC occurrence in hepatitis B (HBV), C (HCV) virus infections, and non-alcoholic fatty liver disease (NAFLD). In HBV infection, the carcinogenic HBV X protein frequently mutates during chronic infection, and subsequently exhibits different effects on senescence. In HCV infection, senescent non-functional T-cells do not effectively clear pre-malignant hepatocytes. Furthermore, the HCV Core protein inhibits the occurrence of normal stress-induced hepatocyte senescence, allowing damaged cells to maintain their proliferative potential. In NAFLD-mediated HCC, current data point towards the gut microbiome and hepatic stellate cell senescence. Additionally, senescence contributes in the development of resistance in targeted therapies, such as sorafenib. Finally, the promising role of senotherapeutics in HCC was also explored. Overall, although we may still be at a primitive stage in fully unraveling the role of senescence in cancer, it seems that understanding and harnessing senescence may have the potential to revolutionize the way we treat hepatocellular cancer.
    Keywords:  cell senescence; hepatitis; hepatocellular cancer; non-alcoholic fatty liver disease; senescence-modulating agents; senomorphics; senoptotics; senotherapeutics
  18. Ageing Res Rev. 2021 Sep 23. pii: S1568-1637(21)00215-4. [Epub ahead of print] 101468
      Autophagy, an essential cellular process that mediates degradation of proteins and organelles in lysosomes, has been tightly linked to cellular quality control for its role as part of the proteostasis network. The current interest in identifying the cellular and molecular determinants of aging, has highlighted the important contribution of malfunctioning of autophagy with age to the loss of proteostasis that characterizes all old organisms. However, the diversity of cellular functions of the different types of autophagy and the often reciprocal interactions of autophagy with other determinants of aging, is placing autophagy at the center of the aging process. In this work, we summarize evidence for the contribution of autophagy to health- and lifespan and provide examples of the bidirectional interplay between autophagic pathways and several of the so-called hallmarks of aging. This central role of autophagy in aging, and the dependence on autophagy of many geroprotective interventions, has motivated a search for direct modulators of autophagy that could be used to slow aging and extend healthspan. Here, we review some of those ongoing therapeutic efforts and comment on the potential of targeting autophagy in aging.
    Keywords:  aging; chaperones; lysosomes; organelle turnover; proteolysis; proteostasis
  19. Metabolites. 2021 Aug 31. pii: 588. [Epub ahead of print]11(9):
      Progressive accumulation of damaged cellular constituents contributes to age-related diseases. Autophagy is the main catabolic process, which recycles cellular material in a multitude of tissues and organs. Autophagy is activated upon nutrient deprivation, and oncogenic, heat or oxidative stress-induced stimuli to selectively degrade cell constituents and compartments. Specificity and accuracy of the autophagic process is maintained via the precision of interaction of autophagy receptors or adaptors and substrates by the intricate, stepwise orchestration of specialized integrating stimuli. Polymorphisms in genes regulating selective autophagy have been linked to aging and age-associated disorders. The involvement of autophagy perturbations in aging and disease indicates that pharmacological agents balancing autophagic flux may be beneficial, in these contexts. Here, we introduce the modes and mechanisms of selective autophagy, and survey recent experimental evidence of dysfunctional autophagy triggering severe pathology. We further highlight identified pharmacological targets that hold potential for developing therapeutic interventions to alleviate cellular autophagic cargo burden and associated pathologies.
    Keywords:  age-related disease; aggrephagy; aging; mitophagy; neurodegeneration; nucleophagy; pexophagy; rapamycin; selective autophagy
  20. Redox Biol. 2021 Sep 09. pii: S2213-2317(21)00287-1. [Epub ahead of print]47 102128
      Age-associated persistent ER stress is the result of declining chaperone systems of the ER that reduces cellular functions, induces apoptosis, and leads to age-related diseases. This study investigated the previously unknown regulatory mechanism of TMBIM6 during age-associated hepatic abnormalities. Wild-type (WT) and the TMBIM6 knockout (TMBIM6-/-) mice liver, human liver samples from different age groups were used to demonstrate the effect of physiological aging on liver. For TMBIM6 rescue experiments, TMBIM6-/- old mice and stable human hepatic cell lines expressing TMBIM 6 were used to study the functional role of TMBIM6 on aging-associated steatosis and its associated mechanisms. In aging humans and mice, we observed declined expression of TMBIM6 and aberrant UPR expression, which were associated with high hepatic lipid accumulation. During aging, TMBIM6-deficient mice had increased senescence than their WT counterparts. We identified redox-mediated posttranslational modifications of IRE1α such as S-nitrosylation and sulfonation were higher in TMBIM6-deficient aging mice and humans, which impaired the ER stress response signaling. Sulfonation of IRE1α enhanced regulated IRE1α-dependent decay (RIDD) activity inducing TMBIM6 decay, whereas S-nitrosylation of IRE1α inhibited XBP1 splicing enhancing the cell death. Moreover, the degradation of miR-338-3p by strong IRE1α cleavage activity enhanced the expression of PTP1B, resulting in diminishing phosphorylation of PERK. The re-expression of TMBIM6 reduced IRE1α modifications, preserved ER homeostasis, reduced senescence and senescence-associated lipid accumulation in human hepatic cells and TMBIM6-depleted mice. S-nitrosylation or sulfonation of IRE1α and its controller, the TMBIM6, might be the potential therapeutic targets for maintaining ER homeostasis in aging and aging-associated liver diseases.
    Keywords:  Aging; ER stress response failure; IRE1α modifications; S-nitrosylation; Sulfonation; TMBIM6/BI-1
  21. BMC Med Genomics. 2021 Sep 29. 14(1): 237
      BACKGROUND: The componential and structural change in the meniscus with aging would increase the tissue vulnerability of the meniscus, which would induce meniscus tearing. Here, we investigated the molecular mechanism of age-related meniscus degeneration with gene expression profiling analysis, and validate pivotal genes in vivo and in vitro models.METHODS: The GSE45233 dataset, including 6 elderly meniscus samples and 6 younger meniscus samples, was downloaded from the Gene Expression Omnibus (GEO) database. To screen the differential expression of mRNAs and identify the miRNAs targeting hub genes, we completed a series of bioinformatics analyses, including functional and pathway enrichment, protein-protein interaction network, hub genes screening, and construction of a lncRNA-miRNA-mRNA network. Furthermore, crucial genes were examined in human senescent menisci, mouse senescent meniscus tissues and mouse meniscus cells stimulated by IL-1β.
    RESULTS: In total, the most significant 4 hub genes (RRM2, AURKB, CDK1, and TIMP1) and 5 miRNAs (hsa-miR-6810-5p, hsa-miR-4676-5p, hsa-miR-6877-5p, hsa-miR-8085, and hsa-miR-6133) that regulated such 4 hub genes, were finally identified. Moreover, these hub genes were decreased in meniscus cells in vitro and meniscus tissues in vivo, which indicated that hub genes were related to meniscus senescence and could serve as potential biomarkers for age-related meniscus tearing.
    CONCLUSIONS: In short, the integrated analysis of gene expression profile, co-expression network, and models detection identified pivotal genes, which elucidated the possible molecular basis underlying the senescence meniscus and also provided prognosis clues for early-onset age-related meniscus tearing.
    Keywords:  Bioinformatics analysis; Meniscus degeneration; Senescence
  22. J Neurosci. 2021 Sep 28. pii: JN-RM-0845-21. [Epub ahead of print]
      Adult-onset neurodegenerative diseases are often accompanied by evidence of a chronic inflammation that includes activation of microglial cells and altered levels of brain cytokines. Aspects of this response are likely secondary reactions to neurodegeneration, but for many illnesses the inflammation may itself be an early and even causative disease event. In such cases, the inflammation is referred to as "sterile" as it occurs in the absence of an actual bacterial or viral pathogen. A potent trigger of sterile inflammation in CNS microglia has been shown to be the presence of DNA in the cytoplasm (cytoDNA) induced either by direct DNA damage or by inhibited DNA repair. We have shown that cytoDNA comes from the cell nucleus as a result of insufficient DNA damage repair. Using wild type and Atm-/- mouse microglia, we extend these observations here by showing that its genomic origins are not random, but rather are heavily biased towards transcriptionally inactive, intergenic regions, in particular repetitive elements and AT-rich sequences. Once released from the genome, in both males and females, we show that cytoDNA is actively exported to the cytoplasm by a CRM1-dependent mechanism. In the cytoplasm, it is degraded either by a cytosolic exonuclease, Trex1, or an autophagy pathway that ends with degradation in the lysosome. Blocking the accumulation of cytoDNA prevents the emergence of the sterile inflammation reaction. These findings offer new insights into the emergence of sterile inflammation and offer novel approaches that may be of use in combatting a wide range of neurodegenerative conditions.Significance:Sterile inflammation describes a state where the defenses of the immune system are activated in the absence of a true pathogen. A potent trigger of this unorthodox response is the presence of DNA in the cytoplasm, which immune cells interpret as an invading virus or pathogen. We show that when DNA damage increases fragments of the cell's own genome are actively exported to the cytoplasm where they are normally degraded. If this degradation is incomplete an immune reaction is triggered. Both age and stress increase DNA damage, and as age-related neurodegenerative diseases are frequently accompanied by a chronic low-level inflammation, strategies that reduce the induction of cytoplasmic DNA or speed its clearance become attractive therapeutic targets.
  23. BMC Genomics. 2021 Sep 26. 22(1): 696
      BACKGROUND: Aging and inflammation are important components of Parkinson's disease (PD) pathogenesis and both are associated with changes in hematopoiesis and blood cell composition. DNA methylation (DNAm) presents a mechanism to investigate inflammation, aging, and hematopoiesis in PD, using epigenetic mitotic aging and aging clocks. Here, we aimed to define the influence of blood cell lineage on epigenetic mitotic age and then investigate mitotic age acceleration with PD, while considering epigenetic age acceleration biomarkers.RESULTS: We estimated epigenetic mitotic age using the "epiTOC" epigenetic mitotic clock in 10 different blood cell populations and in a population-based study of PD with whole-blood. Within subject analysis of the flow-sorted purified blood cell types DNAm showed a clear separation of epigenetic mitotic age by cell lineage, with the mitotic age significantly lower in myeloid versus lymphoid cells (p = 2.1e-11). PD status was strongly associated with accelerated epigenetic mitotic aging (AccelEpiTOC) after controlling for cell composition (OR = 2.11, 95 % CI = 1.56, 2.86, p = 1.6e-6). AccelEpiTOC was also positively correlated with extrinsic epigenetic age acceleration, a DNAm aging biomarker related to immune system aging (with cell composition adjustment: R = 0.27, p = 6.5e-14), and both were independently associated with PD. Among PD patients, AccelEpiTOC measured at baseline was also associated with longitudinal motor and cognitive symptom decline.
    CONCLUSIONS: The current study presents a first look at epigenetic mitotic aging in PD and our findings suggest accelerated hematopoietic cell mitosis, possibly reflecting immune pathway imbalances, in early PD that may also be related to motor and cognitive progression.
    Keywords:  DNA methylation; Epigenetics; Mitotic Age; Parkinson’s Disease; Progression
  24. Aging Cell. 2021 Sep 30. e13474
      Glucocorticoid (GC)-induced osteoporosis is a widespread health problem that is accompanied with increased fracture risk. Detrimental effects of anti-inflammatory GC therapy on bone have been ascribed to the excess in GC exposure, but it is unknown whether there is also a role for disruption of the endogenous GC rhythm that is inherent to GC therapy. To investigate this, we implanted female C57Bl/6J mice with slow-release corticosterone (CORT) pellets to blunt the rhythm in CORT levels without inducing hypercortisolism. Flattening of CORT rhythm reduced cortical and trabecular bone volume and thickness, whilst bone structure was maintained in mice injected with supraphysiologic CORT at the time of their endogenous GC peak. Mechanistically, mice with a flattened CORT rhythm showed disrupted circadian gene expression patterns in bone, along with changes in circulating bone turnover markers indicative of a negative balance in bone remodelling. Indeed, double calcein labelling of bone in vivo revealed a reduced bone formation in mice with a flattened CORT rhythm. Collectively, these perturbations in bone turnover and structure decreased bone strength and stiffness, as determined by mechanical testing. In conclusion, we demonstrate for the first time that flattening of the GC rhythm disrupts the circadian clock in bone and results in an osteoporotic phenotype in mice. Our findings indicate that at least part of the fracture risk associated with GC therapy may be the consequence of a disturbed GC rhythm, rather than excess GC exposure alone, and that a dampened GC rhythm may contribute to the age-related risk of osteoporosis.
    Keywords:  bone health; circadian rhythm; corticosteroids; fracture risk; osteoporosis
  25. Cell Rep. 2021 Sep 28. pii: S2211-1247(21)01219-5. [Epub ahead of print]36(13): 109765
      Gut microbial diversity decreases with aging, but existing studies have used stool samples, which do not represent the entire gut. We analyzed the duodenal microbiome in 251 subjects aged 18-35 (n = 32), 36-50 (n = 41), 51-65 (n = 96), and 66-80 (n = 82). Decreased duodenal microbial diversity in older subjects is associated with combinations of chronological age, number of concomitant diseases, and number of medications used, and also correlated with increasing coliform numbers (p < 0.0001). Relative abundance (RA) of phylum Proteobacteria increases in older subjects, with increased RA of family Enterobacteriaceae and coliform genera Escherichia and Klebsiella, and is associated with alterations in the RA of other duodenal microbial taxa and decreased microbial diversity. Increased RA of specific genera are associated with chronological age only (Escherichia, Lactobacillus, and Enterococcus), number of medications only (Klebsiella), or number of concomitant diseases only (Clostridium and Bilophila). These findings indicate the small intestinal microbiome changes significantly with age and the aging process.
    Keywords:  Escherichia; Lactobacillus; Proteobacteria; age; aging; coliforms; concomitant diseases; duodenal microbiome; medication use; small intestinal microbiome
  26. Aging Cell. 2021 Sep 30. e13485
      Atherosclerosis is a serious age-related disease, which has a tremendous impact on health care globally. Macrophage inflammation is crucial for the initiation and progression of atherosclerosis, and microRNAs (miRNAs) recently have emerged as potent modulators of inflammation, while the underlying mechanisms of its involvement in homocysteine (Hcy)-mediated macrophage inflammation of atherosclerosis remain largely unknown. Here, we demonstrated that elevated Hcy inhibits the expression of miR-195-3p, which in turn enhances IL-31 expression and thereby causes the secretion of macrophages pro-inflammatory factors IL-1β, IL-6 and TNF-α and accelerate atherosclerosis. Furthermore, we identified that Hcy can induce DNA hypermethylation and H3K9 deacetylation of miR-195-3p promoter due to the increased the binding of DNMT3a and HDAC11 at its promoter. More importantly, Sp1 interacts with DNMT3a suppressed the binding of HDAC11 at miR-195-3p promoter and promoted its transcription. In summary, our results revealed a novel mechanism that transcriptional and epigenetic regulation of miR-195-3p inhibits macrophage inflammation through targeting IL-31, which provides a candidate diagnostic marker and novel therapeutic target in cardiovascular diseases induced by Hcy.
    Keywords:  DNA methylation; H3K9 acetylation; homocysteine; inflammation; miR-195-3p
  27. Front Cell Dev Biol. 2021 ;9 725606
      The outcomes of Coronavirus disease-2019 (COVID-19) vary depending on the age, health status and sex of an individual, ranging from asymptomatic to lethal. From an immunologic viewpoint, the final severe lung damage observed in COVID-19 should be caused by cytokine storm, driven mainly by interleukin-6 and other pro-inflammatory cytokines. However, which immunopathogenic status precedes this "cytokine storm" and why the male older population is more severely affected, are currently unanswered questions. The aging of the immune system, i.e., immunosenescence, closely associated with a low-grade inflammatory status called "inflammageing," should play a key role. The remodeling of both innate and adaptive immune response observed with aging can partly explain the age gradient in severity and mortality of COVID-19. This review discusses how aging impacts the immune response to the virus, focusing on possible strategies to rejuvenate the immune system with stem cell-based therapies. Indeed, due to immunomodulatory and anti-inflammatory properties, multipotent mesenchymal stem cells (MSCs) are a worth-considering option against COVID-19 adverse outcomes.
    Keywords:  COVID-19; cytokine storm; immunopathology; immunosenescence; stem cell transplantation
  28. Nature. 2021 Sep 29.
    Keywords:  Ageing; Metabolism; Nutrition; Physiology
  29. Biomolecules. 2021 Aug 28. pii: 1286. [Epub ahead of print]11(9):
      Gut microbiota modulate age-associated changes in metabolism, innate immune responses, and cognitive function. However, the involvement of host factors in the regulation of age-dependent gut microbial structure and intestinal inflammation is largely unknown. Lipocalin 2 (Lcn2) has previously been identified as an adipocytokine and characterized as an important regulator of diet-induced obesity and inflammation. Previous studies have shown that Lcn2 plays a role in high fat diet-induced reshaping of gut microbiota and intestinal inflammation. However, the role of Lcn2 in the regulation of aging-related reshaping of gut microbiota is unclear. Herein, we demonstrate that fecal levels of Lcn2 are reduced during aging. Age reshaped gut microbiota composition in wild-type (WT) mice. Interestingly, Lcn2 deficiency diminished this effect of aging in Lcn2 knockout (LKO) mice, leading to decreased bacterial diversity and increased Firmicutes to Bacteroidetes (F to B) ratio. Specifically, we identified 16 bacteria at the family level that were differentially abundant between WT and LKO mice at old age. Several health-promoting bacteria, including SCFA-producing bacteria, were significantly less prevalent in old LKO mice compared to WT mice, indicating that Lcn2 deficiency shifts the aging-related gut microbial community towards an unhealthy population and lowers microbial butyrate production. Our results provide a line of evidence that Lcn2 plays a role in the control of aging-related reshaping of gut microbiota composition and metabolites.
    Keywords:  aging; gut microbiota; inflammation; lipocalin 2
  30. J Nutr. 2021 Sep 29. pii: nxab309. [Epub ahead of print]
      Cellular increases in oxidative stress (OxS) and decline in mitochondrial function are identified as key defects in aging, but underlying mechanisms are poorly understood and interventions are lacking. Defects linked to OxS and impaired mitochondrial fuel oxidation, such as inflammation, insulin resistance, endothelial dysfunction, and aging hallmarks, are present in older humans and are associated with declining strength and cognition, as well as the development of sarcopenic obesity. Investigations on the origins of elevated OxS and mitochondrial dysfunction in older humans led to the discovery that deficiencies of the antioxidant tripeptide glutathione (GSH) and its precursor amino acids glycine and cysteine may be contributory. Supplementation with GlyNAC (combination of glycine and N-acetylcysteine as a cysteine precursor) was found to improve/correct cellular glycine, cysteine, and GSH deficiencies; lower OxS; and improve mitochondrial function, inflammation, insulin resistance, endothelial dysfunction, genotoxicity, and multiple aging hallmarks; and improve muscle strength, exercise capacity, cognition, and body composition. This review discusses evidence from published rodent studies and human clinical trials to provide a detailed summary of available knowledge regarding the effects of GlyNAC supplementation on age-associated defects and aging hallmarks, as well as discussing why GlyNAC supplementation could be effective in promoting healthy aging. It is particularly exciting that GlyNAC supplementation appears to reverse multiple aging hallmarks, and if confirmed in a randomized clinical trial, it could introduce a transformative paradigm shift in aging and geriatrics. GlyNAC supplementation could be a novel nutritional approach to improve age-associated defects and promote healthy aging, and existing data strongly support the need for additional studies to explore the role and impact of GlyNAC supplementation in aging.
    Keywords:  GlyNAC; aging hallmarks; cognition; glutathione; inflammation; insulin resistance; mitochondrial function; oxidative stress; strength
  31. Neurobiol Aging. 2021 Aug 18. pii: S0197-4580(21)00260-8. [Epub ahead of print]
      DNA methylation is a well-characterized epigenetic modification involved in numerous molecular and cellular functions. Methylation patterns have also been associated with aging mechanisms. However, how DNA methylation patterns change within key brain regions involved in memory formation in an age- and sex-specific manner remains unclear. Here, we performed reduced representation bisulfite sequencing (RRBS) from mouse dorsal hippocampus - which is necessary for the formation and consolidation of specific types of memories - in young and aging mice of both sexes. Overall, our findings demonstrate that methylation levels within the dorsal hippocampus are divergent between sexes during aging in genomic features correlating to mRNA functionality, transcription factor binding sites, and gene regulatory elements. These results define age-related changes in the methylome across genomic features and build a foundation for investigating potential target genes regulated by DNA methylation in an age- and sex-specific manner.
    Keywords:  Aging; DNA methylation; Dorsal hippocampus; Lifespan; Tissue-specific
  32. EMBO J. 2021 Sep 29. e108234
      DNA methylation is a fundamental epigenetic modification, important across biological processes. The maintenance methyltransferase DNMT1 is essential for lineage differentiation during development, but its functions in tissue homeostasis are incompletely understood. We show that epidermis-specific DNMT1 deletion severely disrupts epidermal structure and homeostasis, initiating a massive innate immune response and infiltration of immune cells. Mechanistically, DNA hypomethylation in keratinocytes triggered transposon derepression, mitotic defects, and formation of micronuclei. DNA release into the cytosol of DNMT1-deficient keratinocytes activated signaling through cGAS and STING, thus triggering inflammation. Our findings show that disruption of a key epigenetic mark directly impacts immune and tissue homeostasis, and potentially impacts our understanding of autoinflammatory diseases and cancer immunotherapy.
    Keywords:  DNA methylation; autoinflammation; cytosolic DNA; epigenetics; innate immune system