Senescence-associated Secretory Phenotype Proteins Research Articles

Associations between biomarkers of cellular senescence and physical function in humans: observations from the lifestyle interventions for elders (LIFE) study

Cellular senescence is a plausible mediator of age-associated declines in physical performance. To test this premise, we examined cross-sectional associations between circulating components of the senescence-associated secretory phenotype (SASP) and measures of physical function and muscle strength in 1377 older adults. We showed significant associations between multiple SASP proteins and the short physical performance battery (SPPB), its subcomponents (gait speed, balance, chair rise time), and 400-m walk time. Activin A, ICAM1, MMP7, VEGFA, and eotaxin showed strong associations based on gradient boost machine learning (GBM), and, when combined with other proteins, effectively identified participants at the greatest risk for mobility disability (SPPB score le 7). Senescence biomarkers were also associated with lower grip strength, and GBM identified PARC, ADAMTS13, and RANTES as top candidates in females, and MMP2, SOST, and MCP1 in males. These findings highlight an association between senescence biomarkers and physical performance in older adults. ClinicalTrials.gov Identifier: NCT01072500.

Deletion of the Lmna gene in fibroblasts causes senescence-associated dilated cardiomyopathy by activating the double-stranded DNA damage response and induction of senescence-associated secretory phenotype

Introduction:Mutations in the LMNA gene, encoding Lamin A/C (LMNA), are established causes of dilated cardiomyopathy (DCM). The phenotype is typically characterized by progressive cardiac conduction defects, arrhythmias, heart failure, and premature death. DCM is primarily considered a disease of cardiac myocytes. However, LMNA is also expressed in other cardiac cell types, including fibroblasts.Aim:The purpose of the study was to determine the contribution of the fibroblasts to DCM caused by LMNA deficiency.Methods and Results:The Lmna gene was deleted by crossing the platelet-derived growth factor receptor α-Cre recombinase (Pdgfra-Cre) and floxed Lmna (LmnaF/F) mice. The LMNA protein was nearly absent in ~80% of the cardiac fibroblasts and ~25% of cardiac myocytes in the Pdgfra-Cre:LmnaF/F mice. The Pdgfra-Cre:LmnaF/F mice showed an early phenotype characterized by cardiac conduction defects, arrhythmias, cardiac dysfunction, myocardial fibrosis, apoptosis, and premature death within the first six weeks of life. The Pdgfra-Cre:Lmnawild type/F (LmnaW/F) mice also showed a similar but slowly evolving phenotype that was expressed within one year of age. RNA sequencing of LMNA-deficient and wild-type cardiac fibroblasts identified differential expression of ~410 genes, which predicted activation of the TP53 and TNFA/NFκB and suppression of the cell cycle pathways. In agreement with these findings, levels of phospho-H2AFX, ATM, phospho-TP53, and CDKN1A, markers of the DNA damage response (DDR) pathway, were increased in the Pdgfra-Cre:LmnaF/F mouse hearts. Moreover, expression of senescence-associated beta-galactosidase was induced and levels of the senescence-associated secretory phenotype (SASP) proteins TGFβ1, CTGF (CCN2), and LGLAS3 were increased as well as the transcript levels of additional genes encoding SASP proteins in the Pdgfra-Cre:LmnaF/F mouse hearts. Finally, expression of pH2AFX, a bonafide marker of the double-stranded DNA breaks, was increased in cardiac fibroblasts isolated from the Pdgfra-Cre:LmnaF/F mouse hearts.Conclusion:Deletion of the Lmna gene in fibroblasts partially recapitulates the phenotype of the LMNA-associated DCM, likely through induction of double-stranded DNA breaks, activation of the DDR pathway, and induction of expression of the SASP proteins. The findings indicate that the phenotype in the LMNA-associated DCM is the aggregate consequence of the LMNA deficiency in multiple cardiac cells, including cardiac fibroblasts.

GH and Senescence: A New Understanding of Adult GH Action.

Replicative senescence occurs due to an inability to repair DNA damage and activation of p53/p21 and p16INK4 pathways. It is considered a preventive mechanism for arresting proliferation of DNA-damaged cells. Stably senescent cells are characterized by a senescence-associated secretory phenotype (SASP), which produces and secretes cytokines, chemokines, and/or matrix metalloproteinases depending on the cell type. SASP proteins may increase cell proliferation, facilitating conversion of premalignant to malignant tumor cells, triggering DNA damage, and altering the tissue microenvironment. Further, senescent cells accumulate with age, thereby aggravating age-related tissue damage. Here, we review a heretofore unappreciated role for growth hormone (GH) as a SASP component, acting in an autocrine and paracrine fashion. In senescent cells, GH is activated by DNA-damage-induced p53 and inhibits phosphorylation of DNA repair proteins ATM, Chk2, p53, and H2AX. Somatotroph adenomas containing abundant intracellular GH exhibit increased somatic copy number alterations, indicative of DNA damage, and are associated with induced p53/p21. As this pathway restrains proliferation of DNA-damaged cells, these mechanisms may underlie the senescent phenotype and benign nature of slowly proliferating pituitary somatotroph adenomas. In highly proliferative cells, such as colon epithelial cells, GH induced in response to DNA damage suppresses p53, thereby triggering senescent cell proliferation. As senescent cells harbor unrepaired DNA damage, GH may enable senescent cells to evade senescence and reenter the cell cycle, resulting in acquisition of harmful mutations. These mechanisms, at least in part, may underlie pro-aging effects of GH observed in animal models and in patients with chronically elevated GH levels.

Abstract 12940: Shared Senescence Pathophysiology in Preeclampsia and Peripartum Cardiomyopathy

Introduction: Peripartum cardiomyopathy (PPCM) is a rare form of pregnancy-related heart failure associated with preeclampsia. Our understanding of their shared pathophysiology is limited as are treatment options. Hypothesis: We hypothesized that plasma proteomic profiling would identify deleterious circulating proteins and provide insights into shared mechanisms driving preeclampsia and PPCM. Methods: We performed serum proteomic case-control studies in women with preeclampsia or PPCM to identify biological processes common to both conditions. The top candidate was validated in independent preeclampsia (n=58) and PPCM (n=114) cohorts. Preeclamptic placenta was examined as a potential source of circulating proteins. Therapeutic targeting the top candidate was examined in an animal model of PPCM. Results: Paradoxically, we found the senescence-associated secretory phenotype (SASP), a marker of biological aging, to be the most upregulated process in relatively young women with preeclampsia (normalized enrichment score [NES]=3.3;p adj =4.0x10 -6 ) or PPCM (NES=3.2;p adj =1.9x10 -5 ). 28 circulating proteins contributed to this common signal, and were strongly enriched in preeclamptic placenta, which expressed markers of increased senescence. The TGFb family member, Activin-A, was the most highly upregulated SASP gene in preeclamptic placentas (5-fold;p<0.001). Circulating Activin-A was elevated in preeclampsia (2.9-fold) and PPCM (2.5-fold) validation cohorts (p<0.001) and correlated with impaired left ventricular global longitudinal strain (r=0.3-0.5;p<0.001). In PPCM, Activin-A increased with worsening heart failure, reflected by NYHA class and BNP levels (p<0.05), and cardiac FSTL3 expression, an indicator of Activin-A signaling, was increased (2.2-fold;p=0.005). Inhibition of Activin-A receptors with a monoclonal antibody improved systolic function and adverse cardiac remodeling in a murine PPCM model. Conclusions: These data implicate placental senescence in the increased deleterious circulating proteins seen in preeclampsia and PPCM. We identify multiple new circulating factors associated with these diseases and demonstrate that targeting SASP proteins, such as Activin-A, can mitigate PPCM in mice.

GH Is a Component of SASP in Aging Tissue

Deficient GH signaling results in lifespan extension in murine and human models, while patients with uncontrolled acromegaly and transgenic mice overexpressing GH have a shorter lifespan. Colon polyp development increases with age, and also with GH excess in acromegaly. Aging is characterized by senescent cell accumulation with p53/p21 or p16 upregulation as well as cell cycle arrest and expression of a senescence-associated secretory phenotype (SASP). Senescence is reinforced by the SASP, which comprises pro-inflammatory cytokines, chemokines, growth modulators, angiogenic factors, and matrix metalloproteinases. SASP contributes to pro-aging phenotypes, and depletion or removal of senescent cells increases lifespan by partially protecting from age-related pathologies. Senescence, triggered by genotoxic insult with DNA damage, can be reversed by p53 inactivation; senescent cells with low p53 and unrepaired DNA damage can then re-enter the cell cycle (Beausejour et al, EMBO 2003), potentially resulting in chromosomal instability. We showed GH induction in non-pituitary senescent cells leading to suppressed p53/p21 (Chesnokova PNAS 2013). We now show that, in senescent human colon cells (hNCC) and in 3-dimensional human intestinal organoids, non-pituitary GH (npGH) is a component of SASP. In response to DNA damage, npGH is expressed and secreted locally as measured by RT-PCR, WB, and ELISA. High autocrine/paracrine GH further exacerbate DNA damage and reverses senescent in colon cells, enabling them to re-enter the cell cycle, as evidenced by p53 downregulation and increased Ki67 expression. Senescent colon cells expressing high intracellular GH form colonies in soft agar, indicative of cell transformation and proliferation, while GH deletion by shRNA results in Ki67 downregulation and decreased colony formation and size. The SASP protein CXCL1, a chemo-attractant that also functions to eliminate senescent cells, dose-dependently activates GH in hNCC and in intestinal organoids. GH, in turn, suppresses CXCL1 expression. Consistent with these findings, colon CXCL1 was induced in GHRKO mice, and also in hNCC with abrogated GH signaling by shRNA. Taken together with our finding that GH accumulates in aging normal human colon tissue and co-localizes in cells expressing senescence-associated β-galactosidase, these results suggest that GH, as a SASP component, initiates senescent cell proliferation and transformation. By inhibiting CXCL1, GH also functions to attenuate immune-mediated senescent cell elimination that protects aging tissue from deleterious effects of SASP. These mechanisms may underly an initial step in age-associated epithelial polyp development.

Inhibition of miR-494-3p alleviates oxidative stress-induced cell senescence and inflammation in the primary epithelial cells of COPD patients

BackgroundChronic obstructive pulmonary disease (COPD) is a disease associated with accelerated aging that threatens the lives of people worldwide and imposes heavy social and economic burdens. Cellular senescence is commonly observed in COPD and contributes to aging-related diseases. PurposeTo identify the possible molecular pathways modulating cellular senescence in COPD. MethodsMiR-494-3p expression levels in COPD tissues, small airway epithelial cells (SAECs) and BEAS-2B cells were detected by qRT-PCR. After transfection with miR-494-3p mimic or inhibitor in COPD SAECs, miR-494-3p modulation of senescence markers and senescence-associated secretory phenotype (SASP) proteins was detected. A luciferase assay was employed to verify the direct binding of SIRT3 and miR-494-3p. VX745 and c-myc siRNA were used to investigate the regulation of p38MAPK and c-myc by miR-494-3p. ResultsAs a result of oxidative stress, MiR-494-3p was increased via the p38MAPK-c-myc signaling pathway in the lung tissues and cells of patients with COPD, and the increase in miR-494-3p was accompanied by increases in senescence markers (p27, p21 and p16) and SASP proteins (IL-1β, TNF-α, MMP2 and MMP9). MiR-494-3p was directly bound to SIRT3 in SAECs and was involved in cellular senescence. The upregulation of miR-494-3p decreased SIRT3 expression while increasing p27 expression in SAECs. Inhibition of miR-494-3p in SAECs from COPD patients reduced cell cycle arrest and the expression of SASP proteins (IL-1β, TNF-α, MMP2 and MMP9). ConclusionMiR-494-3p expression can be induced by oxidative stress via the p38MAPK-c-myc signaling pathway, and miR-494-3p can directly bind to SIRT3 to reduce its expression, leading to increased cellular senescence and thereby contributing to COPD progression.

Molecular Aspects of Senescence and Organismal Ageing—DNA Damage Response, Telomeres, Inflammation and Chromatin

Cells can become senescent in response to stress. Senescence is a process characterised by a stable proliferative arrest. Sometimes it can be beneficial—for example, it can suppress tumour development or take part in tissue repair. On the other hand, studies show that it is also involved in the ageing process. DNA damage response (DDR) is triggered by DNA damage or telomere shortening during cell division. When left unresolved, it may lead to the activation of senescence. Senescent cells secrete certain proteins in larger quantities. This phenomenon is referred to as senescence-associated secretory phenotype (SASP). SASP can induce senescence in other cells; evidence suggests that overabundance of senescent cells contributes to ageing. SASP proteins include proinflammatory cytokines and metalloproteinases, which degrade the extracellular matrix. Shortening of telomeres is another feature associated with organismal ageing. Older organisms have shorter telomeres. Restoring telomerase activity in mice not only slowed but also partially reversed the symptoms of ageing. Changes in chromatin structure during senescence include heterochromatin formation or decondensation and loss of H1 histones. During organismal ageing, cells can experience heterochromatin loss, DNA demethylation and global histone loss. Cellular and organismal ageing are both complex processes with many aspects that are often related. The purpose of this review is to bring some of these aspects forward and provide details regarding them.

The senescence-associated secretome as an indicator of age and medical risk.

Produced by senescent cells, the senescence-associated secretory phenotype (SASP) is a potential driver of age-related dysfunction. We tested whether circulating concentrations of SASP proteins reflect age and medical risk in humans. We first screened senescent endothelial cells, fibroblasts, preadipocytes, epithelial cells, and myoblasts to identify candidates for human profiling. We then tested associations between circulating SASP proteins and clinical data from individuals throughout the life span and older adults undergoing surgery for prevalent but distinct age-related diseases. A community-based sample of people aged 20-90 years (retrospective cross-sectional) was studied to test associations between circulating SASP factors and chronological age. A subset of this cohort aged 60-90 years and separate cohorts of older adults undergoing surgery for severe aortic stenosis (prospective longitudinal) or ovarian cancer (prospective case-control) were studied to assess relationships between circulating concentrations of SASP proteins and biological age (determined by the accumulation of age-related health deficits) and/or postsurgical outcomes. We showed that SASP proteins were positively associated with age, frailty, and adverse postsurgery outcomes. A panel of 7 SASP factors composed of growth differentiation factor 15 (GDF15), TNF receptor superfamily member 6 (FAS), osteopontin (OPN), TNF receptor 1 (TNFR1), ACTIVIN A, chemokine (C-C motif) ligand 3 (CCL3), and IL-15 predicted adverse events markedly better than a single SASP protein or age. Our findings suggest that the circulating SASP may serve as a clinically useful candidate biomarker of age-related health and a powerful tool for interventional human studies.

TMIC-20. ELIMINATION OF SENESCENT ASTROCYTES IN THE BRAIN TUMOR MICROENVIRONMENT ATTENUATES GLIOBLASTOMA RECURRENCE AFTER RADIOTHERAPY

Abstract Glioblastomas (GBM) are treated with high doses of ionizing radiation (IR) yet these tumors inevitably recur, and the recurrent tumors are highly therapy resistant. During GBM therapy, the surrounding brain tissue is irradiated along with the tumor. IR induces senescence in multiple cell types, and senescent stromal cells are known to promote the growth of neighboring tumor cells by secreting cytokines which create a senescence-associated secretory phenotype (SASP). We hypothesize that IR-induced senescence of normal brain cells in the tumor microenvironment is a powerful driver of GBM recurrence. We intra-cranially irradiated C57BL/6J mice, and found evidence of widespread senescence, with the astrocytic population being highly susceptible. Genomic analyses of irradiated brains revealed an altered transcriptomic profile which included upregulation of CDKN1A (p21), a key enforcer of senescence, and increased expression of SASP proteins including HGF, the ligand for the RTK Met. We orthotopically implanted mock-irradiated or irradiated mice with a limiting number of syngeneic glioma cells. Pre-irradiation of mouse brains resulted in a striking increase in tumor growth and invasion driven by Met activation in the tumor cells. Importantly, irradiated p21-/- mouse brains did not exhibit SASP and failed to promote tumor growth. Irradiated primary astrocytes underwent senescence in vitro and promoted the migration of glioma cells, and this could be attenuated with HGF-neutralizing antibodies or by the Met inhibitor Crizotinib. These findings indicate that SASP factors (like HGF) in the irradiated brain microenvironment could drive GBM recurrence after radiotherapy via the activation of RTKs (like MET) in the tumor cells. Significantly, we found that senolytic drugs can selectively kill senescent astrocytes both in vitro and in vivo resulting in attenuated growth of glioma cells. These results are of great translational significance as they indicate that adjuvant therapy with senolytic drugs might attenuate GBM recurrence after radiotherapy.

SENESCENCE SECRETOME: BIOMARKERS OF BIOLOGICAL AGING AND POSTOPERATIVE OUTCOMES

Senescent cells drive age-related tissue dysfunction through their potent secretome, termed the senescence associated secretory phenotype (SASP). Circulating concentrations of SASP factors may reflect biological age and serve as clinically useful biomarkers of surgical risk and ultimately, surrogate endpoints in clinical trials. However, they remain largely uncharacterized. We tested associations between circulating concentrations of SASP proteins and biological age, as determined by the accumulation of age-related health deficits, and/or postoperative outcomes in a sample of residents in Olmstead County, MN, age 60-90 years (n = 115) and cohorts of older adults undergoing surgery for severe aortic stenosis (prospective; n = 97) or ovarian cancer (case-control; n = 36). Circulating concentrations of SASP factors were associated with biological age and adverse postoperative outcomes, including risk of any adverse event or rehospitalization within the year following surgery (aortic stenosis group) or admission to an intensive care unit within 30 days of hospital discharge (ovarian cancer group). Gradient boosting machine modeling revealed a panel of SASP factors that predicted adverse outcomes across both surgical groups better than biological age or chronological age and sex. This suggests that the circulating SASP is a robust indicator of age-related health status and may help guide clinical decision making. Furthermore, circulating SASP factors may be harnessed as a readily quantifiable biomarkers in senescence-targeting interventional human studies.

SILAC Analysis Reveals Increased Secretion of Hemostasis-Related Factors by Senescent Cells

SUMMARYCellular senescence irreversibly arrests cell proliferation, accompanied by a multi-component senescence-associated secretory phenotype (SASP) that participates in several age-related diseases. Using stable isotope labeling with amino acids (SILACs) and cultured cells, we identify 343 SASP proteins that senescent human fibroblasts secrete at 2-fold or higher levels compared with quiescent cell counterparts. Bioinformatic analysis reveals that 44 of these proteins participate in hemostasis, a process not previously linked with cellular senescence. We validated the expression of some of these SASP factors in cultured cells and in vivo. Mice treated with the chemotherapeutic agent doxorubicin, which induces widespread cellular senescence in vivo, show increased blood clotting. Conversely, selective removal of senescent cells using transgenic p163MR mice showed that clearing senescent cells attenuates the increased clotting caused by doxorubicin. Our study provides an in-depth, unbiased analysis of the SASP and unveils a function for cellular senescence in hemostasis.

Molecular Senescence Is Associated With White Matter Microstructural Damage in Late-Life Depression

ObjectivesThe authors aim to investigate the association between white matter integrity and accelerated brain aging in late-life depression. MethodsThe authors measured senescence-associated secretory phenotype (SASP) index proteins, cognitive performance, and MRI diffusion tensor imaging (DTI) measures of fractional anisotropy and mean diffusivity-based indices of white matter microstructure measures in 56 older adults with remitted late-life depression. ResultsHigher SASP index was significantly correlated with older age (r = 0.42, p = 0.001) and worse executive function performance (r = −0.27, p = 0.04). After controlling for the effect of age, overall cognitive performance, and white matter hyperintensities, the association between SASP and left and right cingulate bundle mean diffusivity remained statistically significant. ConclusionsOur data suggest that, in the context of late-life depression, SASP proteins are associated with microstructural abnormalities in white matter tracts in brain and worse executive function performance.

Epstein-Barr virus Rta promotes invasion of bystander tumor cells through paracrine of matrix metalloproteinase 9

Clinical studies suggest a positive association between malignant progression of nasopharyngeal carcinoma (NPC) and Rta, a transcription factor of Epstein-Barr virus (EBV). However, Rta induces cellular senescence in vitro. To provide an underlying mechanism integrating these clues, we adapted a concept of senescence-associated secretory phenotype (SASP), based on which senescent cells facilitate tumor progression through paracrine. First, Rta-expressing NPC cells themselves show reduced invasiveness but promote invasion of Rta-negative tumor cells through secreted factors. Secretion of matrix metalloproteinase 9 (MMP9), an SASP protein, is increased by Rta, which requires the C-terminus of Rta and Rta-induced activation of E2F. Furthermore, the Rta-induced, paracrine-mediated pro-invasive effect is blocked upon knockdown of MMP9 expression or treatment with an MMP9 inhibitor. This study not only indicates that Rta can contribute to NPC progression through paracrine but also supports that MMP9 is a potential therapeutic target to prevent NPC metastasis.

SILAC Analysis Reveals a Role for the Senescence-Associated Secretory Phenotype in Hemostasis

Cellular senescence irreversibly arrests cell proliferation, accompanied by a multi-component senescence-associated secretory phenotype (SASP) that participates in several age-related diseases. Using stable isotope labeling with amino acids in cell culture (SILAC), we identify 343 SASP proteins that senescent human fibroblasts secrete at 2-fold or higher levels compared to quiescent cell counterparts. Bioinformatic analysis revealed that 44 of these SASP factors are involved in hemostasis, a process not previously linked with cellular senescence. We validate the expression of some of these SASP factors in cell culture and in vivo. Mice treated with the chemotherapeutic agent doxorubicin, which induces widespread cellular senescence in vivo, show increased blood clotting. Conversely, use of a transgene that permits the selective removal of senescent cells shows that senescent cell clearance attenuates the increased clotting shown by doxorubicin-treated mice. Together, our study characterizes a SASP profile using SILAC, unveiling a novel function for cellular senescence in hemostasis.