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1.
The activation of oncogenes in primary cells blocks proliferation by inducing oncogene‐induced senescence (OIS), a highly potent in vivo tumor‐suppressing program. A prime example is mutant BRAF, which drives OIS in melanocytic nevi. Progression to melanoma occurs only in the context of additional alteration(s) like the suppression of PTEN, which abrogates OIS. Here, we performed a near‐genomewide short hairpin (sh)RNA screen for novel OIS regulators and identified by next generation sequencing and functional validation seven genes. While all but one were upregulated in OIS, depletion of each of them abrogated BRAFV600E‐induced arrest. With genome‐wide DNA methylation analysis, we found one of these genes, RASEF, to be hypermethylated in primary cutaneous melanomas but not nevi. Bypass of OIS by depletion of RASEF was associated with suppression of several senescence biomarkers including senescence‐associated (SA)‐β‐galactosidase activity, interleukins, and tumor suppressor p15INK4B. Restoration of RASEF expression inhibited proliferation. These results illustrate the power of shRNA OIS bypass screens and identify a potential novel melanoma suppressor gene.  相似文献   

2.
Senescent cells contribute to age‐related pathology and loss of function, and their selective removal improves physiological function and extends longevity. Rapamycin, an inhibitor of mTOR, inhibits cell senescence in vitro and increases longevity in several species. Nrf2 levels have been shown to decrease with aging and silencing Nrf2 gene induces premature senescence. Therefore, we explored whether Nrf2 is involved in the mechanism by which rapamycin delays cell senescence. In wild‐type (WT) mouse fibroblasts, rapamycin increased the levels of Nrf2, and this correlates with the activation of autophagy and a reduction in the induction of cell senescence, as measured by SA‐β‐galactosidase (β‐gal) staining, senescence‐associated secretory phenotype (SASP), and p16 and p21 molecular markers. In Nrf2KO fibroblasts, however, rapamycin still decreased β‐gal staining and the SASP, but rapamycin did not activate the autophagy pathway or decrease p16 and p21 levels. These observations were further confirmed in vivo using Nrf2KO mice, where rapamycin treatment led to a decrease in β‐gal staining and pro‐inflammatory cytokines in serum and fat tissue; however, p16 levels were not significantly decreased in fat tissue. Consistent with literature demonstrating that the Stat3 pathway is linked to the production of SASP, we found that rapamycin decreased activation of the Stat3 pathway in cells or tissue samples from both WT and Nrf2KO mice. Our data thus suggest that cell senescence is a complex process that involves at least two arms, and rapamycin uses Nrf2 to regulate cell cycle arrest, but not the production of SASP.  相似文献   

3.
Previously, we reported that persistent DNA damage accelerates ageing of the spine, but the mechanisms behind this process are not well understood. Ataxia telangiectasia mutated (ATM) is a protein kinase involved in the DNA damage response, which controls cell fate, including cell death. To test the role of ATM in the human intervertebral disc, we exposed human nucleus pulposus (hNP) cells directly to the DNA damaging agent cisplatin. Cisplatin‐treated hNP cells exhibited rapid phosphorylation of ATM and subsequent increased NF‐κB activation, aggrecanolysis, decreased total proteoglycan production and increased expression of markers of senescence, including p21, γH2AX and SA‐ß‐gal. Treating cisplatin‐exposed hNP cells with an ATM‐specific inhibitor negated these effects. In addition, genetic reduction of ATM reduced disc cellular senescence and matrix proteoglycan loss in the progeroid Ercc1?/? mouse model of accelerated ageing. These findings suggest that activation of ATM signalling under persistent genotoxic stress promotes disc cellular senescence and matrix homeostatic perturbation. Thus, the ATM signalling pathway represents a therapeutic target to delay the progression of age‐associated spine pathologies.  相似文献   

4.
This study investigated whether multiple bioactivity of terrein such as anti‐inflammatory and anti‐oxidant inhibits age‐related inflammation by promoting an antioxidant response in aged human diploid fibroblast (HDF) cells. HDF cells were cultured serially for in vitro replicative senescence. To create the ageing cell phenotype, intermediate stage (PD31) HDF cells were brought to stress‐induced premature senescence (SIPS) using hydrogen peroxide (H2O2). Terrein increased cell viability even with H2O2 stress and reduced inflammatory molecules such as intracellular adhesion molecule‐1 (ICAM‐1), cyclooxygenase‐2 (COX‐2), interleukin‐1beta (IL‐1β) and tumour necrosis factor‐alpha (TNF‐α). Terrein reduced also phospho‐extracellular kinase receptor1/2 (p‐EKR1/2) signalling in aged HDF cells. SIPS cells were attenuated for age‐related biological markers including reactive oxygen species (ROS), senescence associated beta‐galactosidase (SA β‐gal.) and the aforementioned inflammatory molecules. Terrein induced the induction of anti‐oxidant molecules, copper/zinc‐superoxide defence (Cu/ZnSOD), manganese superoxide dismutase (MnSOD) and heme oxygenase‐1 (HO‐1) in SIPS cells. Terrein also alleviated reactive oxygen species formation through the Nrf2/HO‐1/p‐ERK1/2 pathway in aged cells. The results indicate that terrein has an alleviative function of age‐related inflammation characterized as an anti‐oxidant. Terrein might be a useful nutraceutical compound for anti‐ageing. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

5.
Summary: Senescence‐associated β‐galactosidase (SA‐β‐gal) activity is widely used as a marker of cellular senescence and as an indicator of organismal aging. Here, we report that SA‐β‐gal activity is present in the visceral endoderm layer of early postimplantation mouse embryos in predictable patterns that vary as the embryo progresses in development. However, determination of the mitotic index and analysis of the expression of Cdkn1a (p21), a marker of senescent cells, do not indicate cellular senescence. Instead, analysis of embryos in culture revealed the presence of SA‐β‐gal activity in apical vacuoles of visceral endoderm cells likely a reflection of acidic β‐galactosidase function in these organelles. SA‐β‐gal serves as a practical marker of the dynamics of the visceral endoderm that can be applied to developmental as well as functional studies of early mammalian embryos. genesis 52:300–308, 2014. © 2014 Wiley Periodicals, Inc.  相似文献   

6.

Objectives

Oroxylin A, a natural flavonoid isolated from Scutellaria baicalensis, has been reported to have anti‐hepatic injury effects. However, the effects of oroxylin A on alcoholic liver disease (ALD) remains unclear. The aim of this study was to elucidate the effects of oroxylin A on ALD and the potential mechanisms.

Materials and methods

Male ICR mice and human hepatocyte cell line LO2 were used. Yes‐associated protein (YAP) overexpression and knockdown were achieved using plasmid and siRNA technique. Cellular senescence was assessed by analyses of the senescence‐associated β‐galactosidase (SA‐β‐gal), senescence marker p16, p21, Hmga1, cell cycle and telomerase activity.

Results

Oroxylin A alleviated ethanol‐induced hepatocyte damage by suppressing activities of supernatant marker enzymes. We found that oroxylin A inhibited ethanol‐induced hepatocyte senescence by decreasing the number of SA‐β‐gal‐positive LO2 cells and reducing the expression of senescence markers p16, p21 and Hmga1 in vitro. Moreover, oroxylin A affected the cell cycle and telomerase activity. Of importance, we revealed that YAP pharmacological inhibitor verteporfin or YAP siRNA eliminated the effect of oroxylin A on ethanol‐induced hepatocyte senescence in vitro, and this was further supported by the evidence in vivo experiments.

Conclusion

Therefore, these aggregated data suggested that oroxylin A relieved alcoholic liver injury possibly by inhibiting the senescence of hepatocyte, which was dependent on its activation of YAP in hepatocytes.
  相似文献   

7.
Unlike various model organisms, cellular responses to stress have not been related to human longevity. We investigated cellular responses to stress in skin fibroblasts that were isolated from young and very old subjects, and from offspring of nonagenarian siblings and their partners, representatives of the general population. Fibroblasts were exposed to rotenone and hyperglycemia and assessed for senescence‐associated β‐galactosidase (SA‐β‐gal) activity by flow cytometry. Apoptosis/cell death was measured with the Annexin‐V/PI assay and cell‐cycle analysis (Sub‐G1 content) and growth potential was determined by the colony formation assay. Compared with fibroblasts from young subjects, baseline SA‐β‐gal activity was higher in fibroblasts from old subjects (P = 0.004) as were stress‐induced increases (rotenone: P < 0.001, hyperglycemia: P = 0.027). For measures of apoptosis/cell death, fibroblasts from old subjects showed higher baseline levels (Annexin V+/PI+ cells: P = 0.040, Sub‐G1: P = 0.014) and lower stress‐induced increases (Sub‐G1: P = 0.018) than fibroblasts from young subjects. Numbers and total size of colonies under nonstressed conditions were higher for fibroblasts from young subjects (P = 0.017 and 0.006, respectively). Baseline levels of SA‐β‐gal activity and apoptosis/cell death were not different between fibroblasts from offspring and partner. Stress‐induced increases were lower for SA‐β‐gal activity (rotenone: P = 0.064, hyperglycemia: P < 0.001) and higher for apoptosis/cell death (Annexin V+/PI? cells: P = 0.041, Annexin V+/PI+ cells: P = 0.008). Numbers and total size of colonies under nonstressed conditions were higher for fibroblasts from offspring (P = 0.001 and 0.024, respectively) whereas rotenone‐induced decreases were lower (P = 0.008 and 0.004, respectively). These data provide strong support for the hypothesis that in vitro cellular responses to stress reflect the propensity for human longevity.  相似文献   

8.

Background

Cellular senescence is a permanent growth arrest that occurs in response to cellular stressors, such as telomere shortening or activation of oncogenes. Although the process of senescence growth arrest is somewhat conserved between mouse and human cells, there are some critical differences in the molecular pathways of senescence between these two species. Recent studies in human fibroblasts have defined a cell signaling pathway that is initiated by repression of a specific Wnt ligand, Wnt2. This, in turn, activates a histone chaperone HIRA, and culminates in formation of specialized punctate domains of facultative heterochromatin, called Senescence-Associated Heterochromatin Foci (SAHF), that are enriched in the histone variant, macroH2A. SAHF are thought to repress expression of proliferation-promoting genes, thereby contributing to senescence-associated proliferation arrest. We asked whether this Wnt2-HIRA-SAHF pathway is conserved in mouse fibroblasts.

Results

We show that mouse embryo fibroblasts (MEFs) and mouse skin fibroblasts, do not form robust punctate SAHF in response to an activated Ras oncogene or shortened telomeres. However, senescent MEFs do exhibit elevated levels of macroH2A staining throughout the nucleus as a whole. Consistent with their failure to fully activate the SAHF assembly pathway, the Wnt2-HIRA signaling axis is not overtly regulated between proliferating and senescent mouse cells.

Conclusions

In addition to the previously defined differences between mouse and human cells in the mechanisms and phenotypes associated with senescence, we conclude that senescent mouse and human fibroblasts also differ at the level of chromatin and the signaling pathways used to regulate chromatin. These differences between human and mouse senescence may contribute to the increased propensity of mouse fibroblasts (and perhaps other mouse cell types) to become immortalized and transformed, compared to human cells.  相似文献   

9.
Wnt proteins are thought to bind to their receptors on the cell surfaces of neighboring cells. Wnt8 likely substitutes for the dorsal determinants in Xenopus embryos to dorsalize early embryos via the Wnt/β‐catenin pathway. Here, we show that Wnt8 can dorsalize Xenopus embryos working cell autonomously. Wnt8 mRNA was injected into a cleavage‐stage blastomere, and the subcellular distribution of Wnt8 protein was analyzed. Wnt8 protein was predominantly found in the endoplasmic reticulum (ER) and resided at the periphery of the cells; however, this protein was restricted to the mRNA‐injected cellular region as shown by lineage tracing. A mutant Wnt8 that contained an ER retention signal (Wnt8‐KDEL) could dorsalize Xenopus embryos. Finally, Wnt8‐induced dorsalization occurred only in cells injected with Wnt8 mRNA. These experiments suggest that the Wnt8 protein acts within the cell, likely in the ER or on the cell surface in an autocrine manner for dorsalization.  相似文献   

10.
E.Y. Moon  H.S. Kim  Y.S. Im 《Life sciences》2010,86(17-18):683-690
AimsWe evaluated Gi-protein inhibitor, guanosine 5′-O-(2-thiodiphosphate)(GOT)-induced senescence-associated(SA)-β-galactosidase(Gal) positive cell formation to determine if it occurred through phosphorylation of cyclic AMP-dependent response element binding protein (CREB).Main methodsIMR-90 human lung fibroblast cells were used. SA-β-Gal positive cells and senescence-associated heterochromatic foci (SAHF) were determined by assessing blue color formation of substrate, X-gal inside cells and DAPI staining, respectively. Cell cycle and hypodiploid cell formation were assessed by flow cytometry analysis. CREB phosphorylation and molecular changes were analyzed by western blot.Key findingsGOT treatment led to SA-β-Gal positive cell formation and SAHF. CREB phosphorylation increased in response to GOT treatment but then decreased over 24 h. SA-β-Gal positive cell formation increased in response to transient transfection of pS6-RSV-CREB and no changes were detected following CREB knockdown with CREB-siRNA. In addition, CREB phosphorylation was delayed by treatment with the anti-cellular senescence agents, clitocybins which also reduced the number of SA-β-Gal positive cells. Collectively, our data showed that GOT-induced CREB phosphorylation initiated SA-β-Gal positive cell formation after which decreased in SA-β-Gal positive cells.SignificanceThese findings suggest for the first time that CREB phosphorylation by GOT could induce cellular senescence as judged by SA-β-Gal positive cell formation.  相似文献   

11.
Phenyl‐2‐pyridyl ketoxime (PPKO) was found to be one of the small molecules enriched in the extracellular matrix of near‐senescent human diploid fibroblasts (HDFs). Treatment of young HDFs with PPKO reduced the viability of young HDFs in a dose‐ and time‐dependent manner and resulted in senescence‐associated β‐galactosidase (SA‐β‐gal) staining and G2/M cell cycle arrest. In addition, the levels of some senescence‐associated proteins, such as phosphorylated ERK1/2, caveolin‐1, p53, p16ink4a, and p21waf1, were elevated in PPKO‐treated cells. To monitor the effect of PPKO on cell stress responses, reactive oxygen species (ROS) production was examined by flow cytometry. After PPKO treatment, ROS levels transiently increased at 30 min but then returned to baseline at 60 min. The levels of some antioxidant enzymes, such as catalase, peroxiredoxin II and glutathione peroxidase I, were transiently induced by PPKO treatment. SOD II levels increased gradually, whereas the SOD I and III levels were biphasic during the experimental periods after PPKO treatment. Cellular senescence induced by PPKO was suppressed by chemical antioxidants, such as N‐acetylcysteine, 2,2,6,6‐tetramethylpiperidinyloxy, and L‐buthionine‐(S,R)‐sulfoximine. Furthermore, PPKO increased nitric oxide (NO) production via inducible NO synthase (iNOS) in HDFs. In the presence of NOS inhibitors, such as L‐NG‐nitroarginine methyl ester and L‐NG‐monomethylarginine, PPKO‐induced transient NO production and SA‐β‐gal staining were abrogated. Taken together, these results suggest that PPKO induces cellular senescence in association with transient ROS and NO production and the subsequent induction of senescence‐associated proteins .  相似文献   

12.
Cellular senescence, an irreversible proliferation arrest evoked by stresses such as oncogene activation, telomere dysfunction, or diverse genotoxic insults, has been implicated in tumor suppression and aging. Primary human fibroblasts undergoing oncogene-induced or replicative senescence are known to form senescence-associated heterochromatin foci (SAHF), nuclear DNA domains stained densely by DAPI and enriched for histone modifications including lysine9-trimethylated histone H3. While cellular senescence occurs also in premalignant human lesions, it is unclear how universal is SAHF formation among various cell types, under diverse stresses, and whether SAHF occur in vivo. Here, we report that human primary fibroblasts (BJ and MRC-5) and primary keratinocytes undergoing replicative senescence, or premature senescence induced by oncogenic H-Ras, diverse chemotherapeutics and bacterial cytolethal distending toxin, show differential capacity to form SAHF. Whereas all tested cell types formed SAHF in response to activated H-Ras, only MRC-5, but not BJ fibroblasts or keratinocytes, formed SAHF under senescence induced by etoposide, doxorubicin, hydroxyurea, bacterial intoxication or telomere attrition. In addition, DAPI-defined SAHF were detected on paraffin sections of Ras-transformed cultured fibroblasts, but not human lesions at various stages of tumorigenesis. Overall, our results indicate that unlike the widely present DNA damage response marker γH2AX, SAHF is not a common feature of cellular senescence. Whereas SAHF formation is shared by diverse cultured cell types under oncogenic stress, SAHF are cell-type-restricted under genotoxin-induced and replicative senescence. Furthermore, while the DNA/DAPI-defined SAHF formation in cultured cells parallels enhanced expression of p16ink4a, such ‘prototypic’ SAHF are not observed in tissues, including premalignant lesions, irrespective of enhanced p16ink4a and other features of cellular senescence.  相似文献   

13.
Cells undergo replicative senescence during in vitro expansion, which is induced by the accumulation of cellular damage caused by excessive reactive oxygen species. In this study, we investigated whether long‐term‐cultured human bone marrow mesenchymal stromal cells (MSCs) are insensitive to apoptotic stimulation. To examine this, we established replicative senescent cells from long‐term cultures of human bone marrow MSCs. Senescent cells were identified based on declining population doublings, increased expression of senescence markers p16 and p53 and increased senescence‐associated β‐gal activity. In cell viability assays, replicative senescent MSCs in late passages (i.e. 15–19 passages) resisted damage induced by oxidative stress more than those in early passages did (i.e. 7–10 passages). This resistance occurred via caspase‐9 and caspase‐3 rather than via caspase‐8. The senescent cells are gradually accumulated during long‐term expansion. The oxidative stress‐sensitive proteins ataxia‐telangiectasia mutated and p53 were phosphorylated, and the expression of apoptosis molecules Bax increased, and Bcl‐2 decreased in early passage MSCs; however, the expression of the apoptotic molecules did less change in response to apoptotic stimulation in late‐passage MSCs, suggesting that the intrinsic apoptotic signalling pathway was not induced by oxidative stress in long‐term‐cultured MSCs. Based on these results, we propose that some replicative senescent cells may avoid apoptosis signalling via impairment of signalling molecules and accumulation during long‐term expansion. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

14.
The present study was designed to investigate the effect of hydrogen sulfide on cellular senescence of human umbilical vascular endothelial cells (HUVECs CC-2517) and its underlying mechanism. The premature senescence-like phenotype HUVECs (the fourth passage) was induced by treatment with nicotinamide (NAM, an inhibitor of SIRT1, 5 mmol/L, 12 h). Cells were cultured with sodium hydrosulfide (NaHS, 12.5, 25, 50 and 100 μmol/L) for 48 h in premature senescence-like phenotype HUVECs. The fourth passage of HUVECs was considered as young group. Senescence-associated (SA)-β-galactosidase activities were detected to evaluate cell senescence, and the expression of SA heterochromatin foci (SAHF) was visualized by DAPI DNA staining. The mRNA and protein levels of SIRT1 were detected using RT-PCR and western blotting analysis, respectively. The results showed that β-galactosidase positive cells and the formation of SAHF were markedly increased after treatment with NAM (5 mmol/L) for 12 h. We also found that NaHS (12.5 μmol/L) had no effect on the percentage of SA β-gal positive cells and the expression of SAHF, and the hallmarks decreased at the concentration of 25 and 50 μmol/L, reaching the minimum at 50 μmol/L, while the percentage of SA β-gal positive cells and the expression of SAHF increased at the concentration of 100 μmol/L. Furthermore, we found that both on protein and mRNA levels of SIRT1 in the Y+N+S50 group was significantly increased compared with that in Y+N group. In conclusion, NaHS delays senescence of HUVECs induced by NAM via upregulation of SIRT1 expression.  相似文献   

15.
Cellular senescence is an irreversible proliferation arrest of primary cells and an important tumor suppression process. Senescence is often characterized by domains of facultative heterochromatin, called senescence-associated heterochromatin foci (SAHF), which repress expression of proliferation-promoting genes. Formation of SAHF is driven by a complex of histone chaperones, HIRA and ASF1a, and depends upon prior localization of HIRA to PML nuclear bodies. However, how the SAHF assembly pathway is activated in senescent cells is not known. Here we show that expression of the canonical Wnt2 ligand and downstream canonical Wnt signals are repressed in senescent human cells. Repression of Wnt2 occurs early in senescence and independently of the pRB and p53 tumor suppressor proteins and drives relocalization of HIRA to PML bodies, formation of SAHF and senescence, likely through GSK3beta-mediated phosphorylation of HIRA. These results have major implications for our understanding of both Wnt signaling and senescence in tissue homeostasis and cancer progression.  相似文献   

16.
Systemic inflammation is central to aging‐related conditions. However, the intrinsic factors that induce inflammation are not well understood. We previously identified a cell‐autonomous pathway through which damaged nuclear DNA is trafficked to the cytosol where it activates innate cytosolic DNA sensors that trigger inflammation. These results led us to hypothesize that DNA released after cumulative damage contributes to persistent inflammation in aging cells through a similar mechanism. Consistent with this notion, we found that older cells harbored higher levels of extranuclear DNA compared to younger cells. Extranuclear DNA was exported by a leptomycin B‐sensitive process, degraded through the autophagosome–lysosomal pathway and triggered innate immune responses through the DNA‐sensing cGAS‐STING pathway. Patient cells from the aging diseases ataxia and progeria also displayed extranuclear DNA accumulation, increased pIRF3 and pTBK1, and STING‐dependent p16 expression. Removing extranuclear DNA in old cells using DNASE2A reduced innate immune responses and senescence‐associated (SA) β‐gal enzyme activity. Cells and tissues of Dnase2a?/? mice with defective DNA degradation exhibited slower growth, higher activity of β‐gal, or increased expression of HP‐1β and p16 proteins, while Dnase2a?/?;Sting?/? cells and tissues were rescued from these phenotypes, supporting a role for extranuclear DNA in senescence. We hypothesize a direct role for excess DNA in aging‐related inflammation and in replicative senescence, and propose DNA degradation as a therapeutic approach to remove intrinsic DNA and revert inflammation associated with aging.  相似文献   

17.
18.
The blind mole rat (Spalax) is a wild, long‐lived rodent that has evolved mechanisms to tolerate hypoxia and resist cancer. Previously, we demonstrated high DNA repair capacity and low DNA damage in Spalax fibroblasts following genotoxic stress compared with rats. Since the acquisition of senescence‐associated secretory phenotype (SASP) is a consequence of persistent DNA damage, we investigated whether cellular senescence in Spalax is accompanied by an inflammatory response. Spalax fibroblasts undergo replicative senescence (RS) and etoposide‐induced senescence (EIS), evidenced by an increased activity of senescence‐associated beta‐galactosidase (SA‐β‐Gal), growth arrest, and overexpression of p21, p16, and p53 mRNAs. Yet, unlike mouse and human fibroblasts, RS and EIS Spalax cells showed undetectable or decreased expression of the well‐known SASP factors: interleukin‐6 (IL6), IL8, IL1α, growth‐related oncogene alpha (GROα), SerpinB2, and intercellular adhesion molecule (ICAM‐1). Apparently, due to the efficient DNA repair in Spalax, senescent cells did not accumulate the DNA damage necessary for SASP activation. Conversely, Spalax can maintain DNA integrity during replicative or moderate genotoxic stress and limit pro‐inflammatory secretion. However, exposure to the conditioned medium of breast cancer cells MDA‐MB‐231 resulted in an increase in DNA damage, activation of the nuclear factor κB (NF‐κB) through nuclear translocation, and expression of inflammatory mediators in RS Spalax cells. Evaluation of SASP in aging Spalax brain and intestine confirmed downregulation of inflammatory‐related genes. These findings suggest a natural mechanism for alleviating the inflammatory response during cellular senescence and aging in Spalax, which can prevent age‐related chronic inflammation supporting healthy aging and longevity.  相似文献   

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