bims-senagi Biomed News
on Senescence and aging
Issue of 2020‒10‒18
23 papers selected by
Maria Grazia Vizioli
Mayo Clinic


  1. Nucleic Acids Res. 2020 Oct 12. pii: gkaa858. [Epub ahead of print]
    Guan Y, Zhang C, Lyu G, Huang X, Zhang X, Zhuang T, Jia L, Zhang L, Zhang C, Li C, Tao W.
      The three-dimensional configuration of the chromatin architecture is known to be crucial for alterations in the transcriptional network; however, the underlying mechanisms of epigenetic control of senescence-related gene expression by modulating the chromatin architecture remain unknown. Here, we demonstrate frequent chromosomal compartment switching during mouse embryonic fibroblasts (MEFs) replicative senescence as characterized by senescence-inactivated (SIAEs) and -activated enhancers (SAEs) in topologically associated domains (TADs). Mechanistically, SAEs are closely correlated with senescence-associated secretory phenotype (SASP) genes, which are a key transcriptional feature of an aging microenvironment that contributes to tumor progression, aging acceleration, and immunoinflammatory responses. Moreover, SAEs can positively regulate robust changes in SASP expression. The transcription factor CCAAT/enhancer binding protein α (C/EBPα) is capable of enhancing SAE activity, which accelerates the emergence of SAEs flanking SASPs and the secretion of downstream factors, contributing to the progression of senescence. Our results provide novel insight into the TAD-related control of SASP gene expression by revealing hierarchical roles of the chromatin architecture, transcription factors, and enhancer activity in the regulation of cellular senescence.
    DOI:  https://doi.org/10.1093/nar/gkaa858
  2. Mol Ther. 2020 Oct 01. pii: S1525-0016(20)30494-9. [Epub ahead of print]
    Hu G, Xia Y, Chen B, Zhang J, Gong L, Chen Y, Li Q, Wang Y, Deng Z.
      Tissue stem cell senescence leads to stem cell exhaustion, which results in tissue homeostasis imbalance and a decline in regeneration capacity. However, whether neural stem cell (NSC) senescence occurs and causes neurogenesis reduction during aging is unknown. In this study, mice at different ages were used to detect age-related hippocampal NSC (H-NSC) senescence, as well as the function and mechanism of embryonic stem cell-derived small extracellular vesicles (ESC-sEVs) in rejuvenating H-NSC senescence. We found a progressive cognitive impairment, as well as age-related H-NSC senescence, in mice. ESC-sEV treatment significantly alleviated H-NSC senescence, recovered compromised self-renewal and neurogenesis capacities, and reversed cognitive impairment. Transcriptome analysis revealed that myelin transcription factor 1 (MYT1) is downregulated in senescent H-NSCs but upregulated by ESC-sEV treatment. In addition, knockdown of MYT1 in young H-NSCs accelerated age-related phenotypes and impaired proliferation and differentiation capacities. Mechanistically, ESC-sEVs rejuvenated senescent H-NSCs partly by transferring SMAD family members 4 (SMAD4) and 5 (SMAD5) to activate MYT1, which downregulated egl-9 family hypoxia inducible factor 3 (Egln3), followed by activation of hypoxia inducible factor 2 subunit α (HIF-2α), nicotinamide phosphoribosyl transferase (NAMPT), and sirtuin 1 (Sirt1) successively. Taken together, our results indicated that H-NSC senescence caused cellular exhaustion, neurogenesis reduction, and cognitive impairment during aging, which can be reversed by ESC-sEVs. Thus, ESC-sEVs may be promising therapeutic candidates for age-related diseases.
    Keywords:  ESC-sEVs; MYT1; aging; hippocampal NSCs; senescence
    DOI:  https://doi.org/10.1016/j.ymthe.2020.09.037
  3. Aging Cell. 2020 Oct 17. e13261
    Bose C, Alves I, Singh P, Palade PT, Carvalho E, Børsheim E, Jun SR, Cheema A, Boerma M, Awasthi S, Singh SP.
      Age-associated mitochondrial dysfunction and oxidative damage are primary causes for multiple health problems including sarcopenia and cardiovascular disease (CVD). Though the role of Nrf2, a transcription factor that regulates cytoprotective gene expression, in myopathy remains poorly defined, it has shown beneficial properties in both sarcopenia and CVD. Sulforaphane (SFN), a natural compound Nrf2-related activator of cytoprotective genes, provides protection in several disease states including CVD and is in various stages of clinical trials, from cancer prevention to reducing insulin resistance. This study aimed to determine whether SFN may prevent age-related loss of function in the heart and skeletal muscle. Cohorts of 2-month-old and 21- to 22-month-old mice were administered regular rodent diet or diet supplemented with SFN for 12 weeks. At the completion of the study, skeletal muscle and heart function, mitochondrial function, and Nrf2 activity were measured. Our studies revealed a significant drop in Nrf2 activity and mitochondrial functions, together with a loss of skeletal muscle and cardiac function in the old control mice compared to the younger age group. In the old mice, SFN restored Nrf2 activity, mitochondrial function, cardiac function, exercise capacity, glucose tolerance, and activation/differentiation of skeletal muscle satellite cells. Our results suggest that the age-associated decline in Nrf2 signaling activity and the associated mitochondrial dysfunction might be implicated in the development of age-related disease processes. Therefore, the restoration of Nrf2 activity and endogenous cytoprotective mechanisms by SFN may be a safe and effective strategy to protect against muscle and heart dysfunction due to aging.
    Keywords:  Nrf2; Oxidative stress; Sulforaphane; cardiac functions; mitochondrial dysfunction; sarcopenia
    DOI:  https://doi.org/10.1111/acel.13261
  4. Aging Cell. 2020 Oct 13. e13166
    Moore TM, Zhou Z, Strumwasser AR, Cohn W, Lin AJ, Cory K, Whitney K, Ho T, Ho T, Lee JL, Rucker DH, Hoang AN, Widjaja K, Abrishami AD, Charugundla S, Stiles L, Whitelegge JP, Turcotte LP, Wanagat J, Hevener AL.
      Mitochondrial dysfunction is frequently associated with impairment in metabolic homeostasis and insulin action, and is thought to underlie cellular aging. However, it is unclear whether mitochondrial dysfunction is a cause or consequence of insulin resistance in humans. To determine the impact of intrinsic mitochondrial dysfunction on metabolism and insulin action, we performed comprehensive metabolic phenotyping of the polymerase gamma (PolG) D257A "mutator" mouse, a model known to accumulate supraphysiological mitochondrial DNA (mtDNA) point mutations. We utilized the heterozygous PolG mutator mouse (PolG+/mut ) because it accumulates mtDNA point mutations ~ 500-fold > wild-type mice (WT), but fails to develop an overt progeria phenotype, unlike PolGmut/mut animals. To determine whether mtDNA point mutations induce metabolic dysfunction, we examined male PolG+/mut mice at 6 and 12 months of age during normal chow feeding, after 24-hr starvation, and following high-fat diet (HFD) feeding. No marked differences were observed in glucose homeostasis, adiposity, protein/gene markers of metabolism, or oxygen consumption in muscle between WT and PolG+/mut mice during any of the conditions or ages studied. However, proteomic analyses performed on isolated mitochondria from 12-month-old PolG+/mut mouse muscle revealed alterations in the expression of mitochondrial ribosomal proteins, electron transport chain components, and oxidative stress-related factors compared with WT. These findings suggest that mtDNA point mutations at levels observed in mammalian aging are insufficient to disrupt metabolic homeostasis and insulin action in male mice.
    Keywords:  POLG; aging; insulin resistance; metabolism; mitochondria; mitochondrial DNA; obesity
    DOI:  https://doi.org/10.1111/acel.13166
  5. Cell Death Dis. 2020 Oct 14. 11(10): 854
    Peng X, Wu Y, Brouwer U, van Vliet T, Wang B, Demaria M, Barazzuol L, Coppes RP.
      Radiotherapy for head and neck cancer is associated with impairment of salivary gland function and consequent xerostomia, which has a devastating effect on the quality of life of the patients. The mechanism of radiation-induced salivary gland damage is not completely understood. Cellular senescence is a permanent state of cell cycle arrest accompanied by a secretory phenotype which contributes to inflammation and tissue deterioration. Genotoxic stresses, including radiation-induced DNA damage, are known to induce a senescence response. Here, we show that radiation induces cellular senescence preferentially in the salivary gland stem/progenitor cell niche of mouse models and patients. Similarly, salivary gland-derived organoids show increased expression of senescence markers and pro-inflammatory senescence-associated secretory phenotype (SASP) factors after radiation exposure. Clearance of senescent cells by selective removal of p16Ink4a-positive cells by the drug ganciclovir or the senolytic drug ABT263 lead to increased stem cell self-renewal capacity as measured by organoid formation efficiency. Additionally, pharmacological treatment with ABT263 in mice irradiated to the salivary glands mitigates tissue degeneration, thus preserving salivation. Our data suggest that senescence in the salivary gland stem/progenitor cell niche contributes to radiation-induced hyposalivation. Pharmacological targeting of senescent cells may represent a therapeutic strategy to prevent radiotherapy-induced xerostomia.
    DOI:  https://doi.org/10.1038/s41419-020-03074-9
  6. Molecules. 2020 Oct 12. pii: E4649. [Epub ahead of print]25(20):
    Pyo IS, Yun S, Yoon YE, Choi JW, Lee SJ.
      Aging gradually decreases cellular biological functions and increases the risk of age-related diseases. Cancer, type 2 diabetes mellitus, cardiovascular disease, and neurological disorders are commonly classified as age-related diseases that can affect the lifespan and health of individuals. Aging is a complicated and sophisticated biological process involving damage to biochemical macromolecules including DNA, proteins, and cellular organelles such as mitochondria. Aging causes multiple alterations in biological processes including energy metabolism and nutrient sensing, thus reducing cell proliferation and causing cellular senescence. Among the polyphenolic phytochemicals, resveratrol is believed to reduce the negative effects of the aging process through its multiple biological activities. Resveratrol increases the lifespan of several model organisms by regulating oxidative stress, energy metabolism, nutrient sensing, and epigenetics, primarily by activating sirtuin 1. This review summarizes the most important biological mechanisms of aging, and the ability of resveratrol to prevent age-related diseases.
    Keywords:  age-related diseases; aging; resveratrol
    DOI:  https://doi.org/10.3390/molecules25204649
  7. Front Biosci (Landmark Ed). 2021 Jan 01. 26 1-49
    Tabibzadeh S.
      Aging in mammals results in numerous age related pathologies such as diabetes, and Alzheimer's disease which ultimately lead to organ failure and the demise of the organism. Numerous cell-centric hypotheses have attributed the disorders of aging to lie downstream to age dependent cellular damage to biologic signaling pathways, bio-informational molecules, telomeres, organelles, and stem cells. Here, we review these cell-centric causes of aging that range from the disposable soma theory, to somatic mutation theory, and free radical theory, to theories that ascribe aging to DNA damage and methylation (DNAaging and DNA superaging), impairment of autophagy (GarbAging), telomeric attrition, senescence, immunoscencence and inflammaging. Others view that aging is caused by MitoAging, NutrimiRaging and miRagings to exhaustion of stem cell pool. Together, the current models of aging, show the existence of damage to different cellular compartments. However, it is not yet clear which, if any, of these cellular damages represent the most proximal cause of aging.
  8. Front Biosci (Landmark Ed). 2021 Jan 01. 26 50-96
    Tabibzadeh S.
      Aging leads to and is associated with aberrant function of multiple signaling pathways and a host of factors that maintain cellular health. Under normal conditions, the prolongevity, 5' AMP-activated protein kinase (AMPK), is dedicated to the homeostasis of metabolism and autophagy for removal of damaged cellular compartments and molecules. A host of sirtuin family of molecules, that extend life-span, regulate metabolism and repair DNA damage, and possess either mono-ADP-ribosyltransferase, or deacylase activity. Another group of pro-longevity factors, include FOX (forkhead box) proteins, a family of transcription factors that regulate the expression of genes involved in cell growth, proliferation, differentiation, and longevity. Nicotinamide phosphoribosyltransferase (NAmPRTase or Nampt) catalyzes the condensation of nicotinamide with 5-phosphoribosyl-1-pyrophosphate to yield nicotinamide mononucleotide (NMN), a requisite step for production of NAD+, which is known to increase longevity. Loss of Klotho, a transmembrane enzyme that controls the sensitivity of the organism to insulin and suppresses oxidative stress and inflammation, leads to premature aging in mice. Hydrogen sulfide and transsulfuration pathways are crucial to the long life and are required in protection of cells against damage. Aging also leads to the imbalanced activation of other pathways and factors including p53, insulin and IGF signaling, P13K/AKT, mTOR, PKA, RAS, RTK, MEK, ERK, MAPK, CRTC-1/CREB and NFkB. Such aberrant cellular functions, disturb cell metabolism, derail autophagy and other housekeeping actions, inhibit cell division, induce inflammaging and immunosenecence, cause stem cell exhaustion and induce either senescence, apoptosis or cancer.
  9. Aging (Albany NY). 2020 Oct 10. 12
    Lan F, Lin Y, Gao Z, Cacicedo JM, Weikel K, Ido Y.
      Previous reports have shown that excess calorie intake promotes p53 dependent senescence in mouse adipose tissues. The objective of the current study was to address the mechanism underlying this observation, i.e. adipocyte aging. Using cultured 3T3-L1 cells, we investigated the involvement of energy regulators Sirt1, AMPK, and LKB1 in senescence. Fifteen days post differentiation, Sirt1 knock-down increased senescence-associated beta-galactosidase (SA-β-Gal) staining by 20-40% (p<0.05, n=12) and both cyclin kinase inhibitor p21Cip and chemokine receptor IL8Rb expression by 2-4 fold. ATP and expression of mitochondria Complex 1 were also reduced by 30% and 50%, respectively (p<0.05, n=4). Such energy depletion may have caused the observed increase in AMPK activity, despite LKB1 activity downregulation. This association between Sirt1 and LKB1 activity was confirmed in vivo in mouse adipose tissue. Upregulation of LKB1 activity by expression of the Sirt1-insensitive LKB1-K48R mutant in 3T3-L1 cells completely prevented the senescence-associated changes of Sirt1 knock-down. In addition, cellular senescence, which also occurs in cultured primary human aortic endothelial cells, was largely prevented by ectopic expression of LKB1. These results suggest that LKB1 plays a pivotal role in cellular senescence occurring in adipocytes and other cell types.
    Keywords:  AMPK; LKB1; Sirt1; adipocytes; aging
    DOI:  https://doi.org/10.18632/aging.104052
  10. Mech Ageing Dev. 2020 Oct 10. pii: S0047-6374(20)30178-0. [Epub ahead of print] 111382
    Omer A, Patel D, Moran JL, Lian XJ, Di Marco S, Gallouzi IE.
      Stress granules (SGs) are membraneless organelles formed in response to insult. These granules are related to pathological granules found in age-related neurogenerative diseases such as Parkinson's and Alzheimer's. Previously, we demonstrated that senescent cells, which accumulate with age, exposed to chronic oxidative stress, are unable to form SGs. Here, we show that the inability of senescent cells to form SGs correlates with an upregulation in both the heat-shock response and autophagy pathways, both of which are well-established promoters of SG disassembly. Our data also reveals that the knockdown of HSP70 and ATG5, important components of the heat-shock response and autophagy pathways, respectively, restores the number of SGs formed in senescent cells exposed to chronic oxidative stress. Surprisingly, under these conditions, the depletion of HSP70 or ATG5 did not affect the clearance of these SGs during their recovery from chronic stress. These data reveal that senescent cells possess a unique heat-shock and autophagy-dependent ability to impair the formation of SGs in response to chronic stress, thereby expanding the existing understanding of SG dynamics in senescent cells and their potential contribution to age-related neurodegenerative diseases.
    Keywords:  Ageing; Cellular Senescence; Molecular Biology; Oxidative Stress; Stress Granules
    DOI:  https://doi.org/10.1016/j.mad.2020.111382
  11. Sci Rep. 2020 Oct 14. 10(1): 17315
    Khanh VC, Yamashita T, Ohneda K, Tokunaga C, Kato H, Osaka M, Hiramatsu Y, Ohneda O.
      Aging induces numerous cellular disorders, such as the elevation of reactive oxygen species (ROS), in a number type of cells, including mesenchymal stem cells (MSCs). However, the correlation of ROS and impaired healing abilities as well as whether or not the inhibition of elevating ROS results in the rejuvenation of elderly MSCs is unclear. The rejuvenation of aged MSCs has thus recently received attention in the field of regenerative medicine. Specifically, extracellular vesicles (EVs) act as a novel tool for stem cell rejuvenation due to their gene transfer ability with systemic effects and safety. In the present study, we examined the roles of aging-associated ROS in the function and rejuvenation of elderly MSCs by infant EVs. The data clearly showed that elderly MSCs exhibited the downregulation of superoxide dismutase (SOD)1 and SOD3, which resulted in the elevation of ROS and downregulation of the MEK/ERK pathways, which are involved in the impairment of the MSCs' ability to decrease necrotic area in the skin flap model. Furthermore, treatment with the antioxidant Edaravone or co-overexpression of SOD1 and SOD3 rescued elderly MSCs from the elevation of ROS and cellular senescence, thereby improving their functions. Of note, infant MSC-derived EVs rejuvenated elderly MSCs by inhibiting ROS production and the acceleration of cellular senescence and promoting the proliferation and in vivo functions in both type 1 and type 2 diabetic mice.
    DOI:  https://doi.org/10.1038/s41598-020-74444-8
  12. Neurobiol Aging. 2020 Sep 19. pii: S0197-4580(20)30278-5. [Epub ahead of print]96 255-266
    Meng J, Liu Y, Xie Z, Qing H, Lei P, Ni J.
      Cathepsin B (CatB) leakage from the lysosome into the cytosol in senescent microglia is associated with cognitive impairment. However, whether cellular compartmental translocation of CatB is associated with brain aging remains unclear. In the present study, increased CatB was found in the nucleus of CatB-overexpressed microglia followed by L-leucyl-L-leucine methyl ester, a lysosome-destabilizing reagent, and in the nuclear fraction of the cortex and hippocampus from aged mice. Moreover, CatB enzymatic activity examination showed the nuclear CatB exhibited the proteolytic activity to cleave its specific substrates. The amount of sirtuin1 (Sirt1), Sirt6, Sirt7, and p-Sirt1 was decreased in the cortical lysates from aged mice, in parallel with increased expression of proinflammatory mediators, which were diminished by CatB deficiency. Furthermore, intralateral ventricle administration of microglia overexpressed CatB, and treatment with L-leucyl-L-leucine methyl ester induced cognitive impairment in middle-aged mice. These observations suggest that the increase and nucleus translocation of CatB in senescent microglia were involved in the degradation of nuclear Sirts, which induced proinflammatory responses, resulting in cognition impairment.
    Keywords:  Aging; Microglia; Neuroinflammation; Nucleus translocation; Sirtuins
    DOI:  https://doi.org/10.1016/j.neurobiolaging.2020.09.001
  13. Sci Adv. 2020 Oct;pii: eabb8941. [Epub ahead of print]6(42):
    Chen H, Chen H, Zhang J, Wang Y, Simoneau A, Yang H, Levine AS, Zou L, Chen Z, Lan L.
      The cyclic GMP-AMP synthase (cGAS), a sensor of cytosolic DNA, is critical for the innate immune response. Here, we show that loss of cGAS in untransformed and cancer cells results in uncontrolled DNA replication, hyperproliferation, and genomic instability. While the majority of cGAS is cytoplasmic, a fraction of cGAS associates with chromatin. cGAS interacts with replication fork proteins in a DNA binding-dependent manner, suggesting that cGAS encounters replication forks in DNA. Independent of cGAMP and STING, cGAS slows replication forks by binding to DNA in the nucleus. In the absence of cGAS, replication forks are accelerated, but fork stability is compromised. Consequently, cGAS-deficient cells are exposed to replication stress and become increasingly sensitive to radiation and chemotherapy. Thus, by acting as a decelerator of DNA replication forks, cGAS controls replication dynamics and suppresses replication-associated DNA damage, suggesting that cGAS is an attractive target for exploiting the genomic instability of cancer cells.
    DOI:  https://doi.org/10.1126/sciadv.abb8941
  14. Cancers (Basel). 2020 Oct 14. pii: E2976. [Epub ahead of print]12(10):
    Sasaki N, Gomi F, Yoshimura H, Yamamoto M, Matsuda Y, Michishita M, Hatakeyama H, Kawano Y, Toyoda M, Korc M, Ishiwata T.
      Fibroblast growth factor receptor 4 (FGFR4), one of four tyrosine kinase receptors for FGFs, is involved in diverse cellular processes. Activation of FGF19/FGFR4 signaling is closely associated with cancer development and progression. In this study, we examined the expression and roles of FGF19/FGFR4 signaling in human pancreatic ductal adenocarcinoma (PDAC). In human PDAC cases, FGFR4 expression positively correlated with larger primary tumors and more advanced stages. Among eight PDAC cell lines, FGFR4 was expressed at the highest levels in PK-1 cells, in which single-nucleotide polymorphism G388R in FGFR4 was detected. For inhibition of autocrine/paracrine FGF19/FGFR4 signaling, we used BLU9931, a highly selective FGFR4 inhibitor. Inhibition of signal transduction through ERK, AKT, and STAT3 pathways by BLU9931 reduced proliferation in FGF19/FGFR4 signaling-activated PDAC cells. By contrast, BLU9931 did not alter stemness features, including stemness marker expression, anticancer drug resistance, and sphere-forming ability. However, BLU9931 inhibited cell invasion, in part, by downregulating membrane-type matrix metalloproteinase-1 in FGF19/FGFR4 signaling-activated PDAC cells. Furthermore, downregulation of SIRT1 and SIRT6 by BLU9931 contributed to senescence induction, priming these cells for quercetin-induced death, a process termed senolysis. Thus, we propose that BLU9931 is a promising therapeutic agent in FGFR4-positive PDAC, especially when combined with senolysis (195/200).
    Keywords:  FGFR4; FGFR4 inhibitor; growth; invasion; pancreatic cancer; senescence; senolytic therapy
    DOI:  https://doi.org/10.3390/cancers12102976
  15. Cell Res. 2020 Oct 13.
    Cao D, Han X, Fan X, Xu RM, Zhang X.
      Activation of cyclic GMP-AMP synthase (cGAS) through sensing cytosolic double stranded DNA (dsDNA) plays a pivotal role in innate immunity against exogenous infection as well as cellular regulation under stress. Aberrant activation of cGAS induced by self-DNA is related to autoimmune diseases. cGAS accumulates at chromosomes during mitosis or spontaneously in the nucleus. Binding of cGAS to the nucleosome competitively attenuates the dsDNA-mediated cGAS activation, but the molecular mechanism of the attenuation is still poorly understood. Here, we report two cryo-electron microscopy structures of cGAS-nucleosome complexes. The structures reveal that cGAS interacts with the nucleosome as a monomer, forming 1:1 and 2:2 complexes, respectively. cGAS contacts the nucleosomal acidic patch formed by the H2A-H2B heterodimer through the dsDNA-binding site B in both complexes, and could interact with the DNA from the other symmetrically placed nucleosome via the dsDNA-binding site C in the 2:2 complex. The bound nucleosome inhibits the activation of cGAS through blocking the interaction of cGAS with ligand dsDNA and disrupting cGAS dimerization. R236A or R255A mutation of cGAS impairs the binding between cGAS and the nucleosome, and largely relieves the nucleosome-mediated inhibition of cGAS activity. Our study provides structural insights into the inhibition of cGAS activity by the nucleosome, and advances the understanding of the mechanism by which hosts avoid the autoimmune attack caused by cGAS.
    DOI:  https://doi.org/10.1038/s41422-020-00422-4
  16. Front Cell Dev Biol. 2020 ;8 577084
    Liu Y, Shen Q, Zhang L, Xiang W.
      Extracellular vesicles (EVs), present in cell culture media and several body fluids, play a prominent role in intercellular communication under physiological and pathological conditions. We performed a systematic literature search to review evidence regarding the existence, composition, and release of different EVs, as well as the biomarkers, cargos, and separation methods. We also reviewed the potential of EVs to transport cargos and alter the function and phenotype of recipient cells associated with aging and reproductive diseases, including polycystic ovary syndrome and endometriosis. In aging, EVs promote inflammatory reactions and offsetting the occurrence of aging. In the polycystic ovary syndrome and endometriosis, EVs and their cargos are involved in the occurrence of diseases, therapeutic strategies, and perform as non-invasive biomarkers. As the study of EVs is still in the early stages, it is not surprising that most of the current literature only describes their possible roles.
    Keywords:  aging; endometriosis; extracellular vesicles; isolation; polycystic ovary syndrome
    DOI:  https://doi.org/10.3389/fcell.2020.577084
  17. Front Neurol. 2020 ;11 575953
    Bryant AG, Hu M, Carlyle BC, Arnold SE, Frosch MP, Das S, Hyman BT, Bennett RE.
      Alzheimer's Disease (AD) is associated with neuropathological changes, including aggregation of tau neurofibrillary tangles (NFTs) and amyloid-beta plaques. Mounting evidence indicates that vascular dysfunction also plays a key role in the pathogenesis and progression of AD, in part through endothelial dysfunction. Based on findings in animal models that tau pathology induces vascular abnormalities and cellular senescence, we hypothesized that tau pathology in the human AD brain leads to vascular senescence. To explore this hypothesis, we isolated intact microvessels from the dorsolateral prefrontal cortex (PFC, BA9) from 16 subjects with advanced Braak stages (Braak V/VI, B3) and 12 control subjects (Braak 0/I/II, B1), and quantified expression of 42 genes associated with senescence, cell adhesion, and various endothelial cell functions. Genes associated with endothelial senescence and leukocyte adhesion, including SERPINE1 (PAI-1), CXCL8 (IL8), CXCL1, CXCL2, ICAM-2, and TIE1, were significantly upregulated in B3 microvessels after adjusting for sex and cerebrovascular pathology. In particular, the senescence-associated secretory phenotype genes SERPINE1 and CXCL8 were upregulated by more than 2-fold in B3 microvessels after adjusting for sex, cerebrovascular pathology, and age at death. Protein quantification data from longitudinal plasma samples for a subset of 13 (n = 9 B3, n = 4 B1) subjects showed no significant differences in plasma senescence or adhesion-associated protein levels, suggesting that these changes were not associated with systemic vascular alterations. Future investigations of senescence biomarkers in both the peripheral and cortical vasculature could further elucidate links between tau pathology and vascular changes in human AD.
    Keywords:  Alzheimer's disease; endothelial senescence; gene expression; neurofibrillary tangles; plasma biomarkers; tau pathology; vascular dysfunction
    DOI:  https://doi.org/10.3389/fneur.2020.575953
  18. Hepatology. 2020 Oct 14.
    Ravichandra A, Filliol A, Schwabe RF.
      During chronic liver injury, hepatic stellate cells (HSC) differentiate from lipid-storing pericytes into extracellular matrix (ECM)-producing fibroblasts. While we tend to view these activated HSC as a homogenous fibrogenic cell population that accumulates in the fibrotic liver, this oversimplifies the dynamic nature of fibrogenesis, the different functional states of HSC and their ultimate fate. In parallel to their activation, HSC also undergo massive expansion under stimulation of cytokines such as platelet-derived growth factor beta, leading to their accumulation within fibrotic septa and ultimately HSC senescence. In a recent paper published in Nature, Amor et al. establish chimeric antigen receptor (CAR) T cells as new and powerful method for clearing senescent-cells and demonstrate that removal of senescent HSC ameliorates liver fibrosis (1).
    DOI:  https://doi.org/10.1002/hep.31596
  19. Front Endocrinol (Lausanne). 2020 ;11 573032
    Berlanga-Acosta JA, Guillén-Nieto GE, Rodríguez-Rodríguez N, Mendoza-Mari Y, Bringas-Vega ML, Berlanga-Saez JO, García Del Barco Herrera D, Martinez-Jimenez I, Hernandez-Gutierrez S, Valdés-Sosa PA.
      Diabetes is constantly increasing at a rate that outpaces genetic variation and approaches to pandemic magnitude. Skin cells physiology and the cutaneous healing response are progressively undermined in diabetes which predisposes to lower limb ulceration, recidivism, and subsequent lower extremities amputation as a frightened complication. The molecular operators whereby diabetes reduces tissues resilience and hampers the repair mechanisms remain elusive. We have accrued the notion that diabetic environment embraces preconditioning factors that definitively propel premature cellular senescence, and that ulcer cells senescence impair the healing response. Hyperglycemia/oxidative stress/mitochondrial and DNA damage may act as major drivers sculpturing the senescent phenotype. We review here historical and recent evidences that substantiate the hypothesis that diabetic foot ulcers healing trajectory, is definitively impinged by a self-expanding and self-perpetuative senescent cells society that drives wound chronicity. This society may be fostered by a diabetic archetypal secretome that induces replicative senescence in dermal fibroblasts, endothelial cells, and keratinocytes. Mesenchymal stem cells are also susceptible to major diabetic senescence drivers, which accounts for the inability of these cells to appropriately assist in diabetics wound healing. Thus, the use of autologous stem cells has not translated in significant clinical outcomes. Novel and multifaceted therapeutic approaches are required to pharmacologically mitigate the diabetic cellular senescence operators and reduce the secondary multi-organs complications. The senescent cells society and its adjunctive secretome could be an ideal local target to manipulate diabetic ulcers and prevent wound chronification and acute recidivism. This futuristic goal demands harnessing the diabetic wound chronicity epigenomic signature.
    Keywords:  aging; chronic wounds; diabetic ulcers; proliferative senescence; senescence
    DOI:  https://doi.org/10.3389/fendo.2020.573032
  20. Int J Mol Sci. 2020 Oct 14. pii: E7580. [Epub ahead of print]21(20):
    Webb M, Sideris DP.
      Mitochondrial dysfunction is associated with ageing, but the detailed causal relationship between the two is still unclear. We review the major phenomenological manifestations of mitochondrial age-related dysfunction including biochemical, regulatory and energetic features. We conclude that the complexity of these processes and their inter-relationships are still not fully understood and at this point it seems unlikely that a single linear cause and effect relationship between any specific aspect of mitochondrial biology and ageing can be established in either direction.
    Keywords:  ROS; ageing; energetics; gene regulation; mitochondria
    DOI:  https://doi.org/10.3390/ijms21207580
  21. Cell Death Dis. 2020 Oct 11. 11(10): 844
    Jin C, Li Y, Su Y, Guo Z, Wang X, Wang S, Zhang F, Zhang Z, Shao J, Zheng S.
      Related research has recognized the vital role of methionine cycle metabolism in cancers. However, the role and mechanism of methionine cycle metabolism in hepatocellular carcinoma are still unknown. In this study, we found that [Cu(ttpy-tpp)Br2]Br (Referred to as CTB) could induce hepatocellular carcinoma cells senescence, which is a new copper complex synthesized by our research group. Interestingly, CTB induces senescence by inhibiting the methionine cycle metabolism of HCC cells. Furthermore, the inhibitory effect of CTB on the methionine cycle depends on mitochondrial carrier protein SLC25A26, which was also required for CTB-induced HCC cells senescence. Importantly, we found that CTB-induced upregulation of SLC25A26 could cause abnormal methylation of TERT and inhibited TERT expression, which is considered to be an essential cause of cell senescence. The same results were also obtained in vivo, CTB inhibits the growth of subcutaneously implanted tumors in nude mice and promoted the expression of senescence markers in tumor tissues, and interference with SLC25A26 partially offset the antitumor effect of CTB.
    DOI:  https://doi.org/10.1038/s41419-020-03048-x
  22. Cancers (Basel). 2020 Oct 09. pii: E2899. [Epub ahead of print]12(10):
    Purohit S, Zhi W, Ferris DG, Alverez M, Tran LKH, Tran PMH, Dun B, Hopkins D, Santos BD, Ghamande S, She JX.
      Molecular biomarkers that can predict survival and therapeutic outcome are still lacking for cervical cancer. Here we measured a panel of 19 serum proteins in sera from 565 patients with stage II or III cervical cancer and identified 10 proteins that have an impact on disease specific survival (DSS) (Hazzard's ratio; HR = 1.51-2.1). Surprisingly, all ten proteins are implicated in senescence-associated secreted phenotype (SASP), a hallmark of cellular senescence. Machine learning using Ridge regression of these SASP proteins can robustly stratify patients with high SASP, which is associated with poor survival, and patients with low SASP associated with good survival (HR = 3.09-4.52). Furthermore, brachytherapy, an effective therapy for cervical cancer, greatly improves survival in SASP-high patients (HR = 3.3, p < 5 × 10-5) but has little impact on survival of SASP-low patients (HR = 1.5, p = 0.31). These results demonstrate that cellular senescence is a major determining factor for survival and therapeutic response in cervical cancer and suggest that senescence reduction therapy may be an efficacious strategy to improve the therapeutic outcome of cervical cancer.
    Keywords:  biomarkers; cervical neoplasia; gynecologic cancers; prognosis; proteomics; radiation therapy; serum proteins
    DOI:  https://doi.org/10.3390/cancers12102899
  23. Curr Opin Clin Nutr Metab Care. 2020 Oct 13.
    Ruocco C, Segala A, Valerio A, Nisoli E.
      PURPOSE OF REVIEW: Both restriction and supplementation of specific amino acids or branched-chain amino acids (BCAAs) are described to improve metabolic homeostasis, energy balance, and health span. This review will discuss the recent findings of the role of amino acid supplements in the regulation of mitochondrial health.RECENT FINDINGS: A mixture of essential amino acids (EAAs), BCAA enriched mixture, was found to extend healthy life span in elderly mice and prevent multiple diseases associated with an energy deficit, similarly to caloric restriction or fasting-mimicking diets. A growing body of evidence highlights mitochondria as the central target of this supplement: it promotes mitochondrial biogenesis and the activation of antioxidant defence systems in different physiological (e.g., exercise or ageing) or pathological conditions (e.g., sarcopenia, muscular dystrophy, liver steatosis, or impaired cognition). Based on these results, new formulas have been created enriched with Krebs cycle substrates, behaving more efficiently than BCAA enriched mixture.
    SUMMARY: EAA-BCAA balanced supplements might be valuable not only for healthy individuals undergoing to energy deficit (e.g., athletes or military personnel) during strenuous exercise or training but also against diseases characterized by a dysregulated catabolic state or mitochondrial dysfunction, such as age-related disorders. The associated mechanistic processes should be identified as potential pharmacological targets.
    DOI:  https://doi.org/10.1097/MCO.0000000000000704