Senescence-associated Research Articles

Divergent regulation of long non-coding RNAs H19 and PURPL affects cell senescence in human dermal fibroblasts.

Cellular senescence is a permanent cell growth arrest that occurs in response to various intrinsic and extrinsic stimuli and is associated with cellular and molecular changes. Long non-coding RNAs (lncRNAs) are key regulators of cellular senescence by affecting the expression of many important genes involved in senescence-associated pathways and processes. Here, we evaluated a panel of lncRNAs associated with senescence for their differential expression between young and senescent human dermal fibroblasts (NHDFs) and studied the effect of a known senomorphic compound, resveratrol, on the expression of lncRNAs in senescent NHDFs. As markers of senescence, we evaluated cell growth, senescence-associated (SA)-β-Gal staining, and the expression of p21, Lamin B1 and γH2AX. We found that H19 and PURPL were the most altered lncRNAs in replicative, in doxorubicin (DOXO) and ionising radiation (IR)-induced senescence models. We then investigated the function of H19 and PURPL in cell senescence by siRNA-mediated silencing in young and senescent fibroblasts, respectively. Our results showed that H19 knockdown reduced cell viability and induced cell senescence and autophagy of NHDFs through the regulation of the PI3K/AKT/mTOR pathway; conversely, PURPL silencing reversed senescence by reducing (SA)-β-Gal staining, recovering cell proliferation with an increase of S-phase cells, and reducing the p53-dependent DNA damage response. Overall, our data highlighted the role of H19 and PURPL in the senescent phenotype and suggested that these lncRNAs may have important implications in senescence-related diseases.

Contribution of impaired autophagy, mitochondrial dysfunction and abnormal lipolysis to epididymal aging in mice

With the increase of the aged population in modern society, research on aging and aging-related diseases has attracted increasing attention. Unlike women, men experience changes gradually in the reproductive system during aging. The epididymis is an important organ for sperm maturation and storage, but less study has been conducted to investigate cellular senescence in aging epididymis and the corresponding influences on sperm. This study aims to explore cellular and molecular mechanisms underlying aging changes in epididymal tissues. Cellular senescence in the epididymis of 18-month-old C57BL/6 J mice was evaluated with SA (senescence-associated)-β-galactosidase staining and molecular markers such as P21 and Lamin B, compared to the 2-month-old young group. Western blot analysis and immunofluorescence staining were performed to examine the proteins expressions involved in AMPKα/SIRT1 pathway, autophagy/mitophagy, mitochondrial dynamics and lipolysis. The results showed that in old mice AMPKα/ SIRT1 pathway was downregulated with increased acetylation in the epididymal tissues. Reduced expressions of autophagy related genes and PINK1/PARK2 were detected as well as increased P62 protein level and decreased colocalization of LC3 and LAMP2, which indicated deficient autophagy and mitophagy occurred in aging epididymal tissues. Significant decreased expressions of MFN1, MFN2, p-DRP1(Ser637) and FIS1 showed an imbalance in mitochondrial dynamics in aging epididymal tissues. Additionally, intracellular lipid droplets accumulation occurred in epididymal epithelial cells in old mice, with reduced expressions of the lipolysis enzymes ATGL, HSL and Ascl4. Lipophagy impairment was further detected by minimal colocalization of lipid droplets with either LC3 or LAMP2 in the epididymal ductal epithelial cells of old mice. Our study provides new insights into the molecular mechanisms of impaired autophagy, imbalanced mitochondrial dynamics and disrupted lipolysis, which together contribute to senescent changes and may be detrimental to the epididymal function during aging.

Alpha-ketoglutarate ameliorates age-related and surgery induced temporomandibular joint osteoarthritis via regulating IKK/NF-κB signaling.

Recent studies have shed light on the important role of aging in the pathogenesis of joint degenerative diseases and the anti-aging effect of alpha-ketoglutarate (αKG). However, whether αKG has any effect on temporomandibular joint osteoarthritis (TMJOA) is unknown. Here, we demonstrate that αKG administration improves condylar cartilage health of middle-aged/aged mice, and ameliorates pathological changes in a rat model of partial discectomy (PDE) induced TMJOA. Invitro, αKG reverses IL-1β-induced/H2O2-induced decrease of chondrogenic markers (Col2, Acan and Sox9), and inhibited IL-1β-induced/ H2O2-induced elevation of cartilage catabolic markers (ADAMTS5 and MMP13) in condylar chondrocytes. In addition, αKG downregulates senescence-associated (SA) hallmarks of aged chondrocytes, including the mRNA/protein level of SA genes (p16 and p53), markers of nuclear disorders (Lamin A/C) and SA-β-gal activities. Mechanically, αKG decreases the expressions of p-IKK and p-NF-κB, protecting TMJ from inflammation and senescence-related damage by regulating the NF-κB signaling. Collectively, our findings illuminate that αKG can ameliorate age-related TMJOA and PDE-induced TMJOA, maintain the homeostasis of cartilage matrix, and exert anti-aging effects in chondrocytes, with a promising therapeutic potential in TMJOA, especially age-related TMJOA.

Characterization of senescence in human cardiac fibroblasts

Abstract Funding Acknowledgements None. Background Recent studies suggest that senescence of cardiac fibroblasts (cFib) plays a significant role in cardiac aging and disease. However, senescence of cultured cFib in response to classical pro-senescent stimuli has not been characterized yet. Purpose We thoroughly studied oncogene- and stress-induced senescence, as well as replicative senescence, in primary human cFib. Methods Human cFib were isolated from specimens of right atrial appendages, collected during cardiac surgery with extracorporeal circulation. These cells were subjected to oncogene-induced senescence by overexpression of HRasV12, were exposed to ionizing radiation (IR, 5 Gy) to recapitulate stress-induced senescence, and were passaged until replicative senescence was reached (P12-P14). Senescence was assessed by staining for senescence associated (SA) β-galactosidase and EdU and by RT-PCR for CDKN1A, CDKN2A, and LamB1. Results The main results are summarized in the graphical abstract. HRasV12 overexpression, IR, and prolonged culturing consistently caused senescence of cFib: in fact, all senescent models showed a significant increase in SA-β-gal activity and CDKN1A expression and a decrease in EdU uptake and LamB1 expression over control cells. Interestingly, cFib with HRasV12 overexpression exhibited a peculiar morphological phenotype with vacuoles and showed higher levels of the typical markers of senescence compared to control and to IR-treated or extensively passaged cFib. Moreover, only cFib with HRasV12 overexpression showed a strong downregulation of CDKN2A. Conclusions Cultured primary human cFib undergo senescence in response to established inducers of senescence. HRasV12 overexpression uniquely causes vacuolization of senescent cFib, which is currently being further characterized by transmission electron microscopy.

Abstract 2065: Activation Of Cgas-sting Axis By DNA Double-strand Breaks In Atherosclerosis: A Possible Link From DNA Damage To Inflammation And Cell Senescence

Aim: Premature atherosclerosis in some progeroid syndromes suggests the involvement of DNA damage in the progression of atherosclerosis. However, causative links between DNA double-strand breaks (DSBs) and atherosclerosis have yet to be determined. The aim of this study was to elucidate the role of DSBs in atherosclerosis using mice and vascular smooth muscle cells (VSMCs) deficient in Ku80, a DSB repair protein. Methods and Results: The plaque size and DSBs were increased in the aorta of Ku80-deficient apolipoprotein E knockout mice (Ku80 +/- ApoE -/- ) compared to those of ApoE -/- control after 4 weeks of a high-fat diet. At the early stages of atherosclerosis (two-week high-fat diet), although the plaque size of Ku80 +/- ApoE -/- was similar to that of ApoE -/- control, the number of DSBs and mRNA levels of inflammatory cytokines such as IL-6 and MCP-1 were significantly increased in the Ku80 +/- ApoE -/- aortas. We further investigated molecular links between DSBs and inflammatory responses using VSMCs isolated from Ku80 +/- mice. In VSMCs from Ku80 +/- mice, IL-6 mRNA level was elevated along with increased cellular senescence markers, such as p16 mRNA and senescence-associated (SA) β-gal activity. Additionally, Ku80 +/- VSMCs showed accumulated cytosolic free DNA, an increased level of cGAMP, and activation of TBK1, interferon regulatory factor 3 (IRF3) and NF-κB, suggesting the activation of cGAS-STING axis, a cytosolic DNA sensing machinery. Activation of cGAS-STING axis was also shown in the aortae from Ku80 +/- ApoE -/- in comparison with those from ApoE -/- control. Silencing IRF3, but not NF-κB attenuated the IL-6 mRNA level in Ku80 +/- VSMCs, so did cGAS-silencing. Of interest, cGAS-silencing also attenuated DNA damage-induced SA β-gal activity in wild-type VSMCs. Furthermore, depletion of either p16 or p53 suppressed IRF3 activation by DNA damage. Conclusions: These results suggest that accumulation of cytosolic DNA induced by DNA damage accelerates atherosclerosis via the activation of cGAS-STING-IRF3 axis. cGAS-STING-IRF3 axis may play a pivotal role as a common signaling pathway that serve as a link from DNA damage to inflammatory and cell senescence response in arterial wall.

Protective Effect of Curcumin on D-Galactose-Induced Senescence and Oxidative Stress in LLC-PK1 and HK-2 Cells.

D-galactose has been widely used as an inducer of cellular senescence and pathophysiological processes related to aging because it induces oxidative stress. On the other hand, the consumption of antioxidants such as curcumin can be an effective strategy to prevent phenotypes related to the enhanced production of reactive oxygen species (ROS), such as aging and senescence. This study aimed to evaluate the potential protective effect of curcumin on senescence and oxidative stress and endoplasmic reticulum stress induced by D-galactose treatment in Lilly Laboratories Culture-Porcine Kidney 1 (LLC-PK1) and human kidney 2 (HK-2) proximal tubule cell lines from pig and human, respectively. For senescence induction, cells were treated with 300 mM D-galactose for 120 h and, to evaluate the protective effect of the antioxidant, cells were treated with 5 µM curcumin for 24 h and subsequently treated with curcumin + D-galactose for 120 h. In LLC-PK1 cells, curcumin treatment decreased by 20% the number of cells positive for senescence-associated (SA)-β-D-galactosidase staining and by 25% the expression of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and increased by 40% lamin B1 expression. In HK-2 cells, curcumin treatment increased by 60% the expression of proliferating cell nuclear antigen (PCNA, 50% Klotho levels, and 175% catalase activity. In both cell lines, this antioxidant decreased the production of ROS (20% decrease for LLC-PK1 and 10 to 20% for HK-2). These data suggest that curcumin treatment has a moderate protective effect on D-galactose-induced senescence in LLC-PK1 and HK-2 cells.

Whole transcriptome scanning and validation of negatively related genes in UC-MSCs

BackgroundHuman umbilical cord mesenchymal stem cells (UC-MSCs) are one of the most extensively researched stem cell types due to their potential for multi-lineage differentiation, secretion of regenerative factors, modulations of immunological activities, and the release of regenerative substances and influence immunological processes. Since UC-MSCs must be cultivated on a large scale for clinical use, selecting the appropriate storing passage, such as the usage-based passage of UC-MSCs, is critical for long-term autologous or allogeneic usage. Long-term cultivation of stem cells, on the other hand, causes them to lose their pluripotent differentiation capacity. As a result, distinguishing between high and low passages of UC-MSCs and identifying the particular variations associated with stem cells and their modes of action is essential for regenerative medicine. Therefore, we investigated the biological features and transcriptional changes of UC-MSCs over passages. MethodsUC-MSCs were isolated from the tissues of the human umbilical cord, and UC-MSCs from five passages (P1, P3, P5, P10 and P15) with three repetitions were compared and identified based on morphology, cell markers, differentiation capacity, and aging-related characteristics. It was previously assumed that the phenotype of cells before the P10 passage was stable, defined as early passage, and that culture could be continued until the 15th passage, defined as late passage. Next, the five passages of UC-MSCs were sequenced using high-throughput complete transcriptome sequencing. Fuzzy C-Means Clustering (FCM) and Weighted Gene Co-expression Network Analysis (WGCNA) were used to find hub genes, and gene silencing was performed to investigate the impact of missing genes on the stemness of UC-MSC cells. ResultsUC-MSCs of different passages displayed similar surface markers, including CD73, CD105, CD90, CD34, CD45 and HLA-DR. However, the proliferation time of late-phase UC-MSCs was longer than that of early-phase UC-MSCs, and the expression of the senescence-associated (SA)-β-gal staining marker was higher. At the same time, pluripotency markers (NANOG, OCT4, SOX2 and KIF4A) were down-regulated, and the multi-differentiation potential was reduced. Meanwhile, KIFC1 and UBE2C were down-regulated in late-phase UC-MSCs, which were involved in the maintenance of stemness. ConclusionsKIFC1 and UBE2C were highly expressed in early-UC-MSCs and showed a downward gradient trend with cell expansion in vitro. They regulated UC-MSC proliferation, colony sphere formation, multiple differentiation, stemness maintenance, and other biological manifestations. Therefore, they are anticipated to be new biomarkers for UC-MSCs quality identification in regenerative medicine applications.

Box A of HMGB1 Maintains the DNA Gap and Prevents DDR-induced Kidney Injury in D-galactose Induction Rats.

Disability and mortality rates for renal failure are still increasing. DNA damage and oxidative stress intoxication from body metabolism, high blood glucose, or the environment cause significant kidney damage. Recently, we reported that Box A of HMGB1 (Box A) acts as molecular scissors, producing DNA gaps that prevent DNA damage in kidney cell lines and ultimately reverse aging phenotypes in aging rat models. The present study aimed to demonstrate the potency of Box A in preventing D-galactose (D-gal)-induced kidney injury. A Box A expression plasmid was constructed and administered to a rat model. D-gal was injected subcutaneously for eight weeks. Serum was collected to study renal function, and white blood cells were collected for DNA gap measurement. Kidney tissue was also collected for γ-H2AX and NF-κB immunostaining; Senescence-associated (SA)-beta-gal staining; and analysis of the mRNA expression of p16INK4A, TNF-α, and IL-6. Moreover, histopathology analysis was performed using hematoxylin & eosin and Masson trichome staining. Pretreatment with Box A administration prevented the reduction of DNA gaps and the consequences of the DNA damage response, which include elevated serum creatinine; high serum BUN; an increased positive SA-beta-gal staining area; overexpression of p16INK4A, NF-κB and senescence-associated secretory phenotype molecules, including IL-6, TNF-α; and histological alterations, including tubular dilation and collagen accumulation. Box A effectively prevents DNA gap reduction and all D-gal-induced kidney pathological changes at the molecular, histological, and physiological levels. Therefore, Box A administration is a promising novel therapeutic strategy to prevent DNA-damaging agent-induced kidney failure.

A preliminary study of sirtuin-1 on angiotensin II-induced senescence and inflammation in abdominal aortic aneurysms.

Recent evidence suggests the involvement of senescence and inflammation in abdominal aortic aneurysm (AAA). Considering the role of sirtuin-1 (SIRT1) in delaying senescence, we aimed to preliminarily investigate the potential mechanism underlying the effects of SIRT1 in senescence and inflammation during AAA. A cell AAA model was established using angiotensin II (Ang II) as the inducer, which was applied to treat human aortic vascular smooth muscle cells (HASMCs). The senescence and cell cycle of treated HASMCs were evaluated based on senescence-associated (SA)-b-galactosidase (b-gal) assay and flow cytometry, respectively. The levels of inflammatory cytokines and proteins related to senescence-associated secretory phenotype (SASP), along with nuclear factor-kappa B (NF-kB) and mitogen-activated protein kinases (MAPK) pathways, as well as SIRT1, were gauged. The correlation between SIRT1 and NF-kB and MAPK pathway-related proteins was further estimated. In Ang II-treated HASMCs, reduced SIRT1 and B-cell lymphoma-2 levels yet increased levels of SASP-related proteins P16 and P21, inflammatory cytokines, as well as Bax and caspases were all visible. In the meantime, Ang II exposure enhanced the number of b-gal-positive HASMCs and promoted cell cycle arrest. SIRT1 was also repressed following Ang II treatment and negatively correlated with NF-kB and MAPK pathway-related proteins (P < 0.05). Furthermore, the overexpression of SIRT1 diminished the levels of SASP-related proteins and reduced the phosphorylation of extracellular regulated kinase 1/2 and P65 in Ang II-treated HASMCs (P < 0.05). Taken together, our results indicate that SIRT1 overexpression attenuates the inflammatory and senescent responses of HASMCs in the Ang II-induced AAA cell model. This finding suggests that SIRT1 can be a highly promising target for clinical treatment of AAA.

Autophagy in homocysteine‑induced HUVEC senescence.

The senescence of vascular endothelial cells (VECs) drives the occurrence and development of cardiovascular disease (CVD). Homocysteine (HCY) is a general risk factor for age-associated CVDs. Autophagy, an evolutionarily conserved lysosomal protein degradation pathway, serves a part in VEC senescence. The purpose of this study was to investigate the role of autophagy in HCY-induced endothelial cell senescence and explore novel mechanisms and therapeutic approaches for related CVDs. Human umbilical vein endothelial cells (HUVECs) were isolated from fresh umbilical cords of healthy pregnancies. Cell Counting Kit-8, flow cytometry and senescence-associated (SA) β-galactosidase (Gal) staining demonstrated that HCY induced HUVEC senescence by decreasing cell proliferation, arresting cell cycle and increasing the number of SA-β-Gal-positive cells. Stub-RFP-Sens-GFP-LC3 autophagy-related double fluorescence lentivirus revealed that HCY increased autophagic flux. Further, inhibition of autophagy using 3-methyladenine increased HCY-induced HUVEC senescence. By contrast, the induction of autophagy via rapamycin alleviated HCY-induced HUVEC senescence. Finally, the detection of reactive oxygen species (ROS) with ROS kit showed that HCY increased intracellular ROS, whereas induction of autophagy reduced intracellular ROS. In conclusion, HCY increased HUVEC senescence and upregulated autophagy; moderate autophagy could reverse HCY-induced cell senescence. Autophagy may alleviate HCY-induced cell senescence by decreasing intracellular ROS. This provides insight into the underlying mechanism of HCY-induced VEC senescence and potential treatments for age-associated CVDs.

Involvement of lncRNA TUG1 in HIV-1 Tat-Induced Astrocyte Senescence.

HIV-1 infection in the era of combined antiretroviral therapy has been associated with premature aging. Among the various features of HIV-1 associated neurocognitive disorders, astrocyte senescence has been surmised as a potential cause contributing to HIV-1-induced brain aging and neurocognitive impairments. Recently, lncRNAs have also been implicated to play essential roles in the onset of cellular senescence. Herein, using human primary astrocytes (HPAs), we investigated the role of lncRNA TUG1 in HIV-1 Tat-mediated onset of astrocyte senescence. We found that HPAs exposed to HIV-1 Tat resulted in significant upregulation of lncRNA TUG1 expression that was accompanied by elevated expression of p16 and p21, respectively. Additionally, HIV-1 Tat-exposed HPAs demonstrated increased expression of senescence-associated (SA) markers-SA-β-galactosidase (SA-β-gal) activity and SA-heterochromatin foci-cell-cycle arrest, and increased production of reactive oxygen species and proinflammatory cytokines. Intriguingly, gene silencing of lncRNA TUG1 in HPAs also reversed HIV-1 Tat-induced upregulation of p21, p16, SA-β gal activity, cellular activation, and proinflammatory cytokines. Furthermore, increased expression of astrocytic p16 and p21, lncRNA TUG1, and proinflammatory cytokines were observed in the prefrontal cortices of HIV-1 transgenic rats, thereby suggesting the occurrence of senescence activation in vivo. Overall, our data indicate that HIV-1 Tat-induced astrocyte senescence involves the lncRNA TUG1 and could serve as a potential therapeutic target for dampening accelerated aging associated with HIV-1/HIV-1 proteins.

Priming of adipose-derived stem cells with curcumin prior to cryopreservation preserves their functional potency: Towards an ‘Off-the-shelf’ therapy for burns

Stem cells-based treatment for burn wounds require frozen cells as an off-the-shelf therapy; however, cryopreservation-induced oxidative stress resulted in post-thaw cell death or loss of cell functions, thus arrested their clinical practicality. Although antioxidant priming to stem cells increase their resistant to oxidative stress, but this strategy is still unexplored on cryopreserved cells. Herein, we investigated whether curcumin priming before cryopreservation could preserve the therapeutic potency of thawed stem cells. For this, unprimed and curcumin-primed adipose-derived stem cells (ASCs) were cryopreserved for one month. Post-thawing, cells were assessed for viability by trypan blue assay; metabolic activity by MTT assay; senescence by senescence-associated (SA)‐β‐galactosidase activity staining assay; migration by scratch healing assay and; mRNA expression by real-time PCR. Subsequently, the healing potential was examined by injecting cells around the wound periphery of acidic burn in rats. Post-healing, skin architecture was histologically examined. Results demonstrated that, curcumin-primed frozen cells (Cryo/Cur-ASCs) showed better post-thaw viability, metabolic activity, migration ability and lower percent of senescence comparative to unprimed frozen cells (Cryo/ASCs). Curcumin priming alleviated the oxidative damage by activating the ROS-reducing cellular antioxidant system as shown by the evident increase in GSH levels and upregulated mRNA expression of glutathione peroxidase (GPx), superoxide dismutases (SOD1, SOD2), and catalase (CAT). Further, invivo findings revealed that Cryo/Cur-ASCs-treated wounds exhibited earlier wound closure with an improved architecture comparative to Cryo/ASCs and depicted healing capacity almost similar to Fresh/ASCs. Our findings suggested that curcumin priming could be effective to alleviate the cryo-induced oxidative stress in post-thawed cells.

CSIG-04. BMP4 INDUCTION OF A SENESCENCE-LIKE PHENOTYPE IN HUMAN GLIOBLASTOMA CELLS IS PARTIALLY DEPENDENT ON P21

Abstract Bone morphogenetic protein 4 (BMP4) was initially suggested as a potential differentiation-inducing factor to be used in the therapy of glioblastoma. We and others have however demonstrated that the response is reversible, variable among patient samples, and heterogeneous within the same cell line. To deepen our knowledge on how BMP4 affects different types of glioblastoma cells, we treated phenotypically different clones from the same patient tumor—a multitherapy-sensitive/proneural-like (SENS/PN) clone and a multitherapy-resistant/mesenchymal-like (RES/MES) clone—with BMP4. In the SENS/PN clone, BMP4 turned on a mesenchymal-related gene program, whereas this response was less prominent in the RES/MES clone. Untreated SENS/PN cells were smaller than RES/MES cells, but both clones responded to BMP4 by cell size enlargement. Increase in cell size has been suggested to precede senescence; young cells are smaller than old cells that eventually enter replicative senescence. BMP4 induced a senescence-like phenotype in a subpopulation of cells, demonstrated by induction of senescence-associated (SA)-β-gal, p21 up-regulation, lamin B1 down-regulation, as well as increased lysosomal mass and granularity. This was more pronounced in the RES/MES clone than in the SENS/PN clone, and it was dependent on canonical SMAD signaling. Senolytic treatment ablated the SA-β-gal positive cells and reduced the p21 level at the population level. Targeted deletion of p21 abolished BMP4-induced SA-β-gal and increase in cell growth, while lamin B1 down-regulation remained, demonstrating that p21 signaling is crucial for one part of the senescence induction by BMP4. We are currently further investigating a connection between cell size, mesenchymality and senescence. We hypothesize that large mesenchymal-like cells are closer to senescence than smaller proneural cells within the cell culture. A combination of senescence-induction and senolytic treatment may open treatment opportunities to target therapy-resistant glioblastoma cells.

Abstract 14719: Erk5 S496 Phosphorylation, but Not Erk5 Kinase Activation, Promotes Senescence-Associated Cell Growth (sacg) and Inflammation of Myeloid Cells and Atherosclerosis via Upregulating Sumoylation at a Novel Site (k518) on Nrf2 and Aryl Hydrocarbon Receptor

Senescence induced by various stresses reprograms cancer cells to acquire senescence-associated (SA) cell growth (SACG), which allows them to escape senescence-induced cell cycle arrest with enhanced growth potential. ERK5 is a dual kinase-transcription factor, containing an N-terminal kinase domain and transactivation domains in the C-terminal half. Recent data have raised questions regarding the functional role of ERK5 kinase inhibitors in cancer and inflammatory diseases. We aimed to investigate how ERK5 reprograms myeloid cells (MC) to the SA secretory phenotype (SASP) and SACG, consequently leading to atherosclerosis (AthS). AthS was inhibited in ERK5 S496A knock-in (KI) mice. Single-cell analysis of p53 and Ki67 with imaging mass cytometry revealed three groups of MCs with different p53 and Ki67 expression patterns in the plaque. One group showed that p53 and Ki67 were co-expressed lineally, suggesting that this group of cells escaped from the growth-suppression effects of p53, which is also known as a senescence marker. The % of ERK5 S496A KI cells in this group was significantly lower than in wild-type (WT). Also, we found an increase of SA β-gal (SAβ-gal) + Ki67 + and 53BP1 + Ki67 + cells in bone narrow-derived macrophage (BMDMs) isolated from hypercholesterolemia (H-chol) WT mice, suggesting H-chol-induced MC SACG. MC SACG were significantly inhibited in ERK5 S496A KI mice, supporting the role of ERK5 S496 phosphorylation on SACG. RNA sequencing analysis identified the ERK5 S496 phosphorylation-dependent AHR induction by H-chol, and AHR depletion significantly inhibited SACG. We also discovered a critical effect of ERK5 S496 phosphorylation on SUMOylation at a novel site of NRF2 (i.e., K518), which inhibited NRF2 transcriptional activity without affecting ERK5 kinase activity and antagonized oxidized LDL (oxLDL)-induced SASP. Specific ERK5 kinase inhibitors (AX15836 and XMD8-92) inhibited oxLDL-induced ERK5 S496 phosphorylation, suggesting that ERK5 S496 phosphorylation was involved at least in part of the effects of these inhibitors. We have discovered a novel mechanism in which ERK5 S496 phosphorylation directly inhibits NRF2 activity by upregulating NRF2 K518 SUMOylation and AHR induction, subsequently inducing SACG and AthS.

Bioactive peptides in the pancreatin-hydrolysates of whey protein support cell proliferation and scavenge reactive oxygen species

ABSTRACT Whey protein (WP) in milk shows physiologically active functions such as cholesterol control and immune system strengthening. In this study, we performed hydrolysis and peptide polarity fractionation to enhance the efficacy and diversity of its physiological activities, using the digesting enzyme, pancreatin. Our results indicate that hydrolysis significantly increased the cell proliferation of the WP fractions, with the lower-polarity fractions showing greater efficacy in this regard. Our results indicate that hydrolysis significantly increases cell proliferation of the WP fractions. Additionally, we confirmed differences in the antioxidant activity of the WP fractions as a function of polarity was confirmed via scavenging 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay in vitro. WP itself did not show anti-inflammatory efficacy. However, all the hydrolyzed fractions downregulated the mRNA expression levels of inflammatory cytokines in all treated cell lines and, based on a senescence-associated (SA)-β-galactosidase assay, the fraction with the lowest polarity (F6) inhibited cellular senescence to the greatest extent. Furthermore, we identified the peptide sequences with various physiological activities from whey protein hydrolysates through mass spectrometry. Taken together, our results indicate that the fractionation of WP via hydrolysis generates novel functions including promoting cellular cell proliferation, anti-inflammatory effects, and enhancing antioxidant and anti-cellular senescence.

Cis interaction of CD153 with TCR/CD3 is crucial for the pathogenic activation of senescence-associated Tcells.

With age, senescence-associated (SA) CD4+ Tcells that are refractory to Tcell receptor (TCR) stimulation are increased along with spontaneous germinal center (Spt-GC) development prone to autoantibody production. We demonstrate that CD153 and its receptor CD30 are expressed in SA-T and Spt-GC B cells, respectively, and deficiency of either CD153 or CD30 results in the compromised increase of both cell types. CD153 engagement on SA-T cells upon TCR stimulation causes association of CD153 with the TCR/CD3 complex and restores TCR signaling, whereas CD30 engagement on GC B cells induces their expansion. Administration of an anti-CD153 antibody blocking the interaction with CD30 suppresses the increase in both SA-T and Spt-GC B cells with age and ameliorates lupus in lupus-prone mice. These results suggest that the molecular interaction of CD153 and CD30 plays a central role in the reciprocal activation of SA-T and Spt-GC B cells, leading to immunosenescent phenotypes and autoimmunity.

Transcriptional Heterogeneity of Cellular Senescence in Cancer.

Cellular senescence plays a paradoxical role in tumorigenesis through the expression of diverse senescence-associated (SA) secretory phenotypes (SASPs). The heterogeneity of SA gene expression in cancer cells not only promotes cancer stemness but also protects these cells from chemotherapy. Despite the potential correlation between cancer and SA biomarkers, many transcriptional changes across distinct cell populations remain largely unknown. During the past decade, single-cell RNA sequencing (scRNA-seq) technologies have emerged as powerful experimental and analytical tools to dissect such diverse senescence-derived transcriptional changes. Here, we review the recent sequencing efforts that successfully characterized scRNA-seq data obtained from diverse cancer cells and elucidated the role of senescent cells in tumor malignancy. We further highlight the functional implications of SA genes expressed specifically in cancer and stromal cell populations in the tumor microenvironment. Translational research leveraging scRNA-seq profiling of SA genes will facilitate the identification of novel expression patterns underlying cancer susceptibility, providing new therapeutic opportunities in the era of precision medicine.

In Vitro Characterization of Doxorubicin-Mediated Stress-Induced Premature Senescence in Human Chondrocytes.

Accumulation of senescent chondrocytes is thought to drive inflammatory processes and subsequent cartilage degeneration in age-related as well as posttraumatic osteoarthritis (OA). However, the underlying mechanisms of senescence and consequences on cartilage homeostasis are not completely understood so far. Therefore, suitable in vitro models are needed to study chondrocyte senescence. In this study, we established and evaluated a doxorubicin (Doxo)-based model of stress-induced premature senescence (SIPS) in human articular chondrocytes (hAC). Cellular senescence was determined by the investigation of various senescence associated (SA) hallmarks including β-galactosidase activity, expression of p16, p21, and SA secretory phenotype (SASP) markers (IL-6, IL-8, MMP-13), the presence of urokinase-type plasminogen activator receptor (uPAR), and cell cycle arrest. After seven days, Doxo-treated hAC displayed a SIPS-like phenotype, characterized by excessive secretion of SASP factors, enhanced uPAR-positivity, decreased proliferation rate, and increased β-galactosidase activity. This phenotype was proven to be stable seven days after the removal of Doxo. Moreover, Doxo-treated hAC exhibited increased granularity and flattened or fibroblast-like morphology. Further analysis implies that Doxo-mediated SIPS was driven by oxidative stress as demonstrated by increased ROS levels and NO release. Overall, we provide novel insights into chondrocyte senescence and present a suitable in vitro model for further studies.

Olive phenols preserve lamin B1 expression reducing cGAS/STING/NFκB-mediated SASP in ionizing radiation-induced senescence.

Senescence occurs upon critical telomere shortening, or following DNA damage, oncogenic activation, hypoxia and oxidative stress, overall referred to stress‐induced premature senescence (SIPS). In response to DNA damage, senescent cells release cytoplasmic chromatin fragments (CCFs), and express an altered secretome, the senescence‐associated secretory phenotype (SASP), which contributes to generate a pro‐inflammatory and pro‐tumoral extracellular milieu. Polyphenols have gained significant attention owing to their anti‐inflammatory and anti‐tumour activities. Here, we studied the effect of oleuropein aglycone (OLE) and hydroxytyrosol (HT) on DNA damage, CCF appearance and SASP in a model of irradiation‐induced senescence. Neonatal human dermal fibroblasts (NHDFs) were γ‐irradiated and incubated with OLE, 5 µM and HT, 1 µM. Cell growth and senescence‐associated (SA)‐β‐Gal‐staining were used as senescence markers. DNA damage was evaluated by Comet assay, lamin B1 expression, release of CCFs, cyclic GMP‐AMP Synthase (cGAS) activation. IL‐6, IL‐8, MCP‐1 and RANTES were measured by ELISA assay. Our results showed that OLE and HT exerted a protective effect on 8 Gy irradiation‐induced senescence, preserving lamin B1 expression and reducing cGAS/STING/NFκB‐mediated SASP. The ability of OLE and HT to mitigate DNA damage, senescence status and the related SASP in normal cells can be exploited to improve the efficacy and safety of cancer radiotherapy.

Targeting IKKε in Androgen-Independent Prostate Cancer Causes Phenotypic Senescence and Genomic Instability.

Advanced prostate cancer will often progress to a lethal, castration-resistant state. We previously demonstrated that IKKε expression correlated with the aggressiveness of prostate cancer disease. Here, we address the potential of IKKε as a therapeutic target in prostate cancer. We examined cell fate decisions (proliferation, cell death, and senescence) in IKKε-depleted PC-3 cells, which exhibited delayed cell proliferation and a senescent phenotype, but did not undergo cell death. Using IKKε/TBK1 inhibitors, BX795 and Amlexanox, we measured their effects on cell fate decisions in androgen-sensitive prostate cancer and androgen-independent prostate cancer cell lines. Cell-cycle analyses revealed a G2-M cell-cycle arrest and a higher proportion of cells with 8N DNA content in androgen-independent prostate cancer cells only. Androgen-independent prostate cancer cells also displayed increased senescence-associated (SA)-β-galactosidase activity; increased γH2AX foci; genomic instability; and altered p15, p16, and p21 expression. In our mouse model, IKKε inhibitors also decreased tumor growth of androgen-independent prostate cancer xenografts but not 22Rv1 androgen-sensitive prostate cancer xenografts. Our study suggests that targeting IKKε with BX795 or Amlexanox in androgen-independent prostate cancer cells induces a senescence phenotype and demonstrates in vivo antitumor activity. These results strengthen the potential of exploiting IKKε as a therapeutic target.