The Longevity-Associated Variant of BPIFB4 Reduces Senescence in Glioma Cells and in Patients’ Lymphocytes Favoring Chemotherapy Efficacy

Glioblastoma (GBM) is the most common primary brain cancer with the median age at diagnosis around 64 years, thus pointing to aging as an important risk factor. Indeed, aging, by increasing the senescence burden, is configured as a negative prognostic factor for GBM stage. Furthermore, several anti-GBM therapies exist, such as temozolomide (TMZ) and etoposide (ETP), that unfortunately trigger senescence and the secretion of proinflammatory senescence-associated secretory phenotype (SASP) factors that are responsible for the improper burst of (i) tumorigenesis, (ii) cancer metastasis, (iii) immunosuppression, and (iv) tissue dysfunction. Thus, adjuvant therapies that limit senescence are urgently needed. The longevity-associated variant (LAV) of the bactericidal/permeability-increasing fold-containing family B member 4 (BPIFB4) gene previously demonstrated a modulatory activity in restoring age-related immune dysfunction and in balancing the low-grade inflammatory status of elderly people. Based on the above findings, we tested LAV-BPIFB4 senotherapeutic effects on senescent glioblastoma U87-MG cells and on T cells from GBM patients. We interrogated SA-β-gal and HLA-E senescence markers, SASP factors, and proliferation and apoptosis assays. The results highlighted a LAV-BPIFB4 remodeling of the senescent phenotype of GBM cells, enhancement of their sensitivity to temozolomide and a selective reduction of the T cells’ senescence from GBM patients. Overall, these findings candidate LAV-BPIFB4 as an adjuvant therapy for GBM.

Senescent Phenotype of Astrocytes Leads to Microglia Activation and Neuronal Death

Astrocyte, the most abundant cell type in the central nervous system, is increasingly recognized and is thought to depend on curial and diverse roles in maintaining brain homeostasis, the blood-brain barrier, ion homeostasis, secrete neurotrophic factors and regulate synaptic transmission which is essential to tune individual-to-network neuronal activity. Senescence in astrocytes has been discovered to be an important contributor to several age-related neurological diseases like Alzheimer's and Parkinson's disease. However, the latest research about astrocytes from aged subjects or aged astrocytes in vitro is not yet adequate to be well elucidated on their curial process in the regulation of brain function. In this study, an in vitro cell model of aged astrocytes was constructed by serial passaging until passage 20-25, and those passages within 1-5 were used as young astrocytes. Meanwhile, oxidative induced astrocyte senescence model was also constructed by H2O2 induction. Our results indicate that after serial passaging or oxidative stress-induced astrocytes, all showed manifest changes in several established markers of cellular senescence like P53, P21, the release of inflammatory cytokine IL-6 and SA-β-gal positive cells. Results also showed mitochondrial dysfunction in the oxidative stress-induced astrocyte senescence model and treatment of berberine could reverse these alterations. What’s more interests us is that those two types of senescent astrocytes’ conditioned medium co-cultured with neuronal cells could do impact on neuron apoptosis no matter in direct or indirect ways. This study may help us better understand the fundamental role of astrocyte senescence on the regulation of normal and pathological brain aging.

CDK5RAP2 loss-of-function causes premature cell senescence via the GSK3β/β-catenin-WIP1 pathway

Developmental disorders characterized by small body size have been linked to CDK5RAP2 loss-of-function mutations, but the mechanisms underlying which remain obscure. Here, we demonstrate that knocking down CDK5RAP2 in human fibroblasts triggers premature cell senescence that is recapitulated in Cdk5rap2an/an mouse embryonic fibroblasts and embryos, which exhibit reduced body weight and size, and increased senescence-associated (SA)-β-gal staining compared to Cdk5rap2+/+ and Cdk5rap2+/an embryos. Interestingly, CDK5RAP2-knockdown human fibroblasts show increased p53 Ser15 phosphorylation that does not correlate with activation of p53 kinases, but rather correlates with decreased level of the p53 phosphatase, WIP1. Ectopic WIP1 expression reverses the senescent phenotype in CDK5RAP2-knockdown cells, indicating that senescence in these cells is linked to WIP1 downregulation. CDK5RAP2 interacts with GSK3β, causing increased inhibitory GSK3β Ser9 phosphorylation and inhibiting the activity of GSK3β, which phosphorylates β-catenin, tagging β-catenin for degradation. Thus, loss of CDK5RAP2 decreases GSK3β Ser9 phosphorylation and increases GSK3β activity, reducing nuclear β-catenin, which affects the expression of NF-κB target genes such as WIP1. Consequently, loss of CDK5RAP2 or β-catenin causes WIP1 downregulation. Inhibition of GSK3β activity restores β-catenin and WIP1 levels in CDK5RAP2-knockdown cells, reducing p53 Ser15 phosphorylation and preventing senescence in these cells. Conversely, inhibition of WIP1 activity increases p53 Ser15 phosphorylation and senescence in CDK5RAP2-depleted cells lacking GSK3β activity. These findings indicate that loss of CDK5RAP2 promotes premature cell senescence through GSK3β/β-catenin downregulation of WIP1. Premature cell senescence may contribute to reduced body size associated with CDK5RAP2 loss-of-function.

Adult Neural Stem Cell Migration Is Impaired in a Mouse Model of Alzheimer’s Disease

Neurogenesis in the adult brain takes place in two neurogenic niches: the ventricular-subventricular zone (V-SVZ) and the subgranular zone. After differentiation, neural precursor cells (neuroblasts) have to move to an adequate position, a process known as neuronal migration. Some studies show that in Alzheimer’s disease, the adult neurogenesis is impaired. Our main aim was to investigate some proteins involved both in the physiopathology of Alzheimer’s disease and in the neuronal migration process using the APP/PS1 Alzheimer’s mouse model. Progenitor migrating cells are accumulated in the V-SVZ of the APP/PS1 mice. Furthermore, we find an increase of Cdh1 levels and a decrease of Cdk5/p35 and cyclin B1, indicating that these cells have an alteration of the cell cycle, which triggers a senescence state. We find less cells in the rostral migratory stream and less mature neurons in the olfactory bulbs from APP/PS1 mice, leading to an impaired odour discriminatory ability compared with WT mice. Alzheimer’s disease mice present a deficit in cell migration from V-SVZ due to a senescent phenotype. Therefore, these results can contribute to a new approach of Alzheimer’s based on senolytic compounds or pro-neurogenic factors.

Cellular Senescence in Adrenocortical Biology and Its Disorders

Cellular senescence is considered a physiological process along with aging and has recently been reported to be involved in the pathogenesis of many age-related disorders. Cellular senescence was first found in human fibroblasts and gradually explored in many other organs, including endocrine organs. The adrenal cortex is essential for the maintenance of blood volume, carbohydrate metabolism, reaction to stress and the development of sexual characteristics. Recently, the adrenal cortex was reported to harbor some obvious age-dependent features. For instance, the circulating levels of aldosterone and adrenal androgen gradually descend, whereas those of cortisol increase with aging. The detailed mechanisms have remained unknown, but cellular senescence was considered to play an essential role in age-related changes of the adrenal cortex. Recent studies have demonstrated that the senescent phenotype of zona glomerulosa (ZG) acts in association with reduced aldosterone production in both physiological and pathological aldosterone-producing cells, whereas senescent cortical-producing cells seemed not to have a suppressed cortisol-producing ability. In addition, accumulated lipofuscin formation, telomere shortening and cellular atrophy in zona reticularis cells during aging may account for the age-dependent decline in adrenal androgen levels. In adrenocortical disorders, including both aldosterone-producing adenoma (APA) and cortisol-producing adenoma (CPA), different cellular subtypes of tumor cells presented divergent senescent phenotypes, whereby compact cells in both APA and CPA harbored more senescent phenotypes than clear cells. Autonomous cortisol production from CPA reinforced a local cellular senescence that was more severe than that in APA. Adrenocortical carcinoma (ACC) was also reported to harbor oncogene-induced senescence, which compensatorily follows carcinogenesis and tumor progress. Adrenocortical steroids can induce not only a local senescence but also a periphery senescence in many other tissues. Therefore, herein, we systemically review the recent advances related to cellular senescence in adrenocortical biology and its associated disorders.

Protection against APOE4-associated aging phenotypes with a longevity-promoting intervention

Two of the primary risk factors for late onset Alzheimer’s Disease (AD) are aging and APOE genotype. While the causal relationship between aging and AD is not well defined, there are strong leads from shared phenotypes such as decreased metabolic function and increased inflammation. APOE genotype may be linked to AD phenotypes through the regulation of aging processes. The NIA Interventions Testing Program (ITP) recently found that 17α-estradiol (17αE2) treatment increases rodent lifespan. Since 17αE2 acts upon systemic and neural pathways associated with AD pathology, we propose that 17αE2 may be a pleiotropic intervention strategy. Further, because APOE4 is associated with a senescent phenotype, 17αE2 may have APOE genotype-specific effects. Using 10-month-old APOE3 or APOE4 targeted replacement male mice maintained on normal chow with and without 14.4 ppm 17aE2 for 20 weeks, our initial results indicate genotype differences in the efficacy of 17αE2 across multiple outcomes. APOE4 mice exhibited an aged phenotype compared to APOE3, with APOE4 mice having a higher frailty index; however, 17αE2 treatment reduced the frailty index most strongly in APOE4 mice. APOE4 mice were impaired across multiple metabolic measures including body weight, plasma leptin, and hepatic steatosis. 17αE2 significantly attenuated the APOE4 metabolic phenotype. These data confirm and extend prior findings that APOE4 is linked to progeroid effects both peripheral and neural outcomes associated with AD risk. Importantly, 17αE2 significantly improved a range of measures, but showed the strongest effects in the APOE4 genotype. This research was funded by the Cure Alzheimer's Fund.

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.

Influence of Glucocorticoids on Cellular Senescence Hallmarks in Osteoarthritic Fibroblast-like Synoviocytes

Osteoarthritis (OA) is recognized as being a cellular senescence-linked disease. Intra-articular injections of glucocorticoids (GC) are frequently used in knee OA to treat synovial effusion but face controversies about toxicity. We investigated the influence of GC on cellular senescence hallmarks and senescence induction in fibroblast-like synoviocytes (FLS) from OA patients and mesenchymal stem cells (MSC). Methods: Cellular senescence was assessed via the proliferation rate, β-galactosidase staining, DNA damage and CKI expression (p21, p16INK4A). Experimental senescence was induced by irradiation. Results: The GC prednisolone did not induce an apparent senescence phenotype in FLS, with even higher proliferation, no accumulation of β-galactosidase-positive cells nor DNA damage and reduction in p21mRNA, only showing the enhancement of p16INK4A. Prednisolone did not modify experimental senescence induction in FLS, with no modulation of any senescence parameters. Moreover, prednisolone did not induce a senescence phenotype in MSC: despite high β-galactosidase-positive cells, no reduction in proliferation, no DNA damage and no CKI enhancement was observed. Conclusions: We provide reassuring in vitro data about the use of GC regarding cellular senescence involvement in OA: the GC prednisolone did not induce a senescent phenotype in OA FLS (the proliferation ratio was even higher) and in MSC and did not worsen cellular senescence establishment.

BCL-Xl Driven Accumulation of Dysfunctional Mitochondria in Aged Stromal Cells Impairs the Haematopoietic Stem Cell Response to Stress

The burden of infections is known to increase with age. Not only is ageing associated with greater susceptibility to infections but also an increase in subsequent morbidity and mortality. The bone marrow (BM) niche is essential for the body's response to infection. Haematopoietic stem and progenitor cells (HSPCs) heavily rely on their supporting BM microenvironment to effectively expand and differentiate in response to stress and infection (1). The role of senescent cells has been explored in a number of age-related diseases including acute myeloid leukaemia (2). Here we explore the role of senescence during natural ageing in the BM microenvironment, the mechanism which drives this and how this impacts on the metabolic health of HSPCs. BM was isolated from aged (18-24 months) and young (8-12 weeks) C57Bl/6 mice and flow cytometry was used to compare mitochondrial membrane potential (ΔΨm) and mitochondrial ROS in HSPCs. Results show that HSPCs from aged animals increase in numbers and accumulate mitochondria with low membrane potential with lower mitochondrial ROS. Next, young and aged mice were treated with lipopolycaccharide (LPS). Metabolic analysis revealed that HSPCs from young mice increase metabolism of mitochondrial TCA cycle substrates in response to LPS whereas aged HSPCs continued to rely on glycolysis. When HSPCs from aged C57Bl/6 mice (CD45.2+) were FACS purified and adoptively transferred into young PepCboy (CD45.1+) mice, thus removing them from the aged BM microenvironment, they were able to recover their mitochondrial health and showed an improved metabolic response to treatment with LPS. Furthermore, qRT-PCR analysis of p16 and p21 expression in HSPCs and mesenchymal stromal cells (MSC) showed that MSCs, but not HSPCs, acquire a senescent phenotype in aged mice, and depletion of senescent cells in the p16-3MR mouse model (3) allowed recovery of HSPC mitochondrial function and response to LPS. Mechanistically, we found a significant upregulation of the anti-apoptotic protein BCL-XL in MSCs of aged mice. This has previously been described to drive the senescent phenotype and prevent apoptosis in senescent cells. By over-expressing GFP-tagged BCL-XL in MSCs and then co-culturing them with LSKs we were able to show that BCL-XL is transferred from MSCs to HSPCs in vitro. Finally, we demonstrated that targeting BCL-XL in vivo, using the senolytic drug ABT-263, in aged mice can restore the HSPC metabolic response to stress resulting in upregulation of TCA cycle metabolism. In conclusion, we show that the aged BM microenvironment is responsible for the HSPC metabolic shortfall resulting in impaired response to stress. Targeting the senescent cells in the environment restored the HSPC metabolic function and their response to infection in aged mice. This suggests that manipulation of the ageing BM microenvironment can help to improve the body's response to infection. 1. Mistry JJ, Marlein CR, Moore JA, Hellmich C, Wojtowicz EE, Smith JGW, et al. ROS-mediated PI3K activation drives mitochondrial transfer from stromal cells to hematopoietic stem cells in response to infection. Proc Natl Acad Sci U S A. 2019;116(49):24610-9. 2. Abdul-Aziz AM, Sun Y, Hellmich C, Marlein CR, Mistry J, Forde E, et al. Acute myeloid leukemia induces protumoral p16INK4a-driven senescence in the bone marrow microenvironment. Blood. 2019;133(5):446-56. 3. Demaria M, Ohtani N, Youssef SA, Rodier F, Toussaint W, Mitchell JR, et al. An essential role for senescent cells in optimal wound healing through secretion of PDGF-AA. Dev Cell. 2014;31(6):722-33. Disclosures No relevant conflicts of interest to declare.

Senescence as a trade-off between successful land colonisation and longevity: critical review and analysis of a hypothesis

Background Most common terrestrial animal clades exhibit senescence, suggesting strong adaptive value of this trait. However, there is little support for senescence correlated with specific adaptations. Nevertheless, insects, mammals, and birds, which are the most common terrestrial animal clades that show symptoms of senescence, evolved from clades that predominantly did not show symptoms of senescence. Thus, we aimed to examine senescence in the context of the ecology and life histories of the main clades of animals, including humans, and to formulate hypotheses to explain the causes and origin of senescence in the major clades of terrestrial animals. Methodology We reviewed literature from 1950 to 2020 concerning life expectancy, the existence of senescence, and the adaptive characteristics of the major groups of animals. We then proposed a relationship between senescence and environmental factors, considering the biology of these groups of animals. We constructed a model showing the phylogenetic relationships between animal clades in the context of the major stages of evolution, distinguishing between senescent and biologically ‘immortal’ clades of animals. Finally, we synthesised current data on senescence with the most important concepts and theories explaining the origin and mechanisms of senescence. Although this categorisation into different senescent phenotypes may be simplistic, we used this to propose a framework for understanding senescence. Results We found that terrestrial mammals, insects, and birds show senescence, even though they likely evolved from non-senescent ancestors. Moreover, secondarily aquatic animals show lower rate of senescence than their terrestrial counterparts. Based on the possible life histories of these groups and the analysis of the most important factors affecting the transition from a non-senescent to senescent phenotype, we conclude that aging has evolved, not as a direct effect, but as a correlated response of selection on developmental strategies, and that this occurred separately within each clade. Adoption of specific life history strategies could thus have far-reaching effects in terms of senescence and lifespan. Conclusions Our analysis strongly suggests that senescence may have emerged as a side effect of the evolution of adaptive features that allowed the colonisation of land. Senescence in mammals may be a compromise between land colonisation and longevity. This hypothesis, is supported by palaeobiological and ecological evidence. We hope that the development of new research methodologies and the availability of more data could be used to test this hypothesis and shed greater light on the evolution of senescence.