SGLT2 inhibition eliminates senescent cells and alleviates pathological aging.

It has been reported that accumulation of senescent cells in various tissues contributes to pathological aging and that elimination of senescent cells (senolysis) improves age-associated pathologies. Here, we demonstrate that inhibition of sodium-glucose co-transporter 2 (SGLT2) enhances clearance of senescent cells, thereby ameliorating age-associated phenotypic changes. In a mouse model of dietary obesity, short-term treatment with the SGLT2 inhibitor canagliflozin reduced the senescence load in visceral adipose tissue and improved adipose tissue inflammation and metabolic dysfunction, but normalization of plasma glucose by insulin treatment had no effect on senescent cells. Canagliflozin extended the lifespan of mice with premature aging even when treatment was started in middle age. Metabolomic analyses revealed that short-term treatment with canagliflozin upregulated 5-aminoimidazole-4-carboxamide-1-ß-D-ribofuranoside, enhancing immune-mediated clearance of senescent cells by downregulating expression of programmed cell death-ligand 1. These findings suggest that inhibition of SGLT2 has an indirect senolytic effect by enhancing endogenous immunosurveillance of senescent cells.

Targeting cellular senescence: A promising approach in respiratory diseases.

Cellular senescence serves as a significant tumor suppression mechanism in mammals. Cellular senescence is induced in response to various stressors and acts as a safeguard against the uncontrolled proliferation of damaged cells that could lead to malignant transformation. Senescent cells also exhibit a distinctive feature known as the senescence-associated secretory phenotype (SASP), wherein they secrete a range of bioactive molecules, including pro-inflammatory cytokines, growth factors, and proteases. These SASP components have both local and systemic effects, influencing the surrounding microenvironment and distant tissues, and have been implicated in the processes of tissue aging and the development of chronic diseases. Recent studies utilizing senolysis models have shed light on the potential therapeutic implications of targeting senescent cells. The targeting of senescent cell may alleviate the detrimental effects associated with cellular senescence and its SASP components. Senolytics have shown promise in preclinical studies for treating age-related pathologies and chronic diseases, including cancer, cardiovascular disorders, and neurodegenerative conditions. Respiratory diseases have emerged as a significant global health concern, responsible for a considerable number of deaths worldwide. Extensive research conducted in both human subjects and animal models has demonstrated the involvement of cellular senescence in the pathogenesis of respiratory diseases. Chronic pulmonary conditions such as chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis have been linked to the accumulation of senescent cells. This review aims to present the findings from research on respiratory diseases that have utilized systems targeting senescent cells and to identify potential therapeutic strategies for the clinical management of these conditions. Geriatr Gerontol Int 2024; 24: 60-66.

Kinetic Analysis of the Photochemical Paths in Asymmetric Diarylethene Dimer.

An asymmetric diarylethene dimer composed of 2- and 3-thienylethene units linked by m-phenylene developed various colors upon UV irradiation via an independent photochromic reaction on each unit. The change in contents and the other photoresponses of the photogenerated four isomers were analyzed using quantum yield for all the possible photochemical paths, i. e., photoisomerization, fluorescence, energy transfer, and the other non-radiative paths. Almost all the rate constants of photochemical paths were calculated using measurable quantum yields and lifetimes. It was found that a significant contribution on photoresponse was the competition between photoisomerization and intramolecular energy transfer. The clear difference was observed in the photoresponses of the dimer and the 1 : 1 mixture solution of the model compounds. The m-phenylene spacer appropriately regulated the rate of energy transfer in the asymmetric dimer, and the spacer enabled isolation of the excited state of the dimer, making the above quantitative analysis possible.

Age-related changes in lung function in National Center for Geriatrics and Gerontology Aging Farm C57BL/6N mice.

Aging is an extremely complex biological process, and various models, from unicellular organisms to mammals, have been used in its research. The mouse is the most widely used model for studying human aging and diseases due to its high homology and well-established strategies for genetic manipulation. Despite these advantages, the maximum lifespan of laboratory mice is nearly three years, which makes it time-consuming to obtain animals of the desired age. To avoid this issue and efficiently conduct aging research, the National Center for Geriatrics and Gerontology operates its "Aging Farm", a system that supplies aged animals in response to researchers' requests. In the present study, as part of the Aging Farm project, we examined changes in the physiological functions of the lungs and gene expression in lung tissues of Aging Farm animals as they aged. A decline in the physiological function of the lungs was already apparent before 6 months of age, and it continued until at least 1 year of age. On the other hand, gene expression profiling by RNA sequencing showed small changes in the early stages of aging but more pronounced changes at 12 and 24 months of age than at 3 months of age. Age-related lung tissue changes are considered to be involved in the pathogenesis of various chronic respiratory diseases, and the characterization of animals as they age will ensure the quality of the Aging Farm as a resource for aging research.

Towards a Circular Economy: Study of the Mechanical, Thermal, and Electrical Properties of Recycled Polypropylene and Their Composite Materials.

This research focuses on the mechanical properties of polypropylene (PP) blended with recycled PP (rPP) at various concentrations. The rPP can be added at up to 40 wt% into the PP matrix without significantly affecting the mechanical properties. MFI of blended PP increased with increasing rPP content. Modulus and tensile strength of PP slightly decreased with increased rPP content, while the elongation at break increased to up to 30.68% with a 40 wt% increase in rPP content. This is probably caused by the interfacial adhesion of PP and rPP during the blending process. The electrical conductivity of materials was improved by adding carbon black into the rPP matrices. It has a significant effect on the mechanical and electrical properties of the composites. Stress-strain curves of composites changed from ductile to brittle behaviors. This could be caused by the poor interfacial interaction between rPP and carbon black. FTIR spectra indicate that carbon black did not have any chemical reactions with the PP chains. The obtained composites exhibited good performance in the electrical properties tested. Finally, DSC results showed that rPP and carbon black could act as nucleating agents and thus increase the degree of crystallinity of PP.

Protocol for assessing senescence-associated lung pathologies in mice.

Cellular senescence underlies tissue aging and aging-associated pathologies, as well as lung pathology. We and others have shown that elimination of senescent cells alleviates pulmonary diseases such as fibrosis and emphysema in animal models. We herein describe a protocol for assessing senescence-dependent lung phenotypes in mice. This protocol describes the use of ARF-DTR mice for semi-genetic elimination of lung senescent cells, followed by a pulmonary function test and the combination with pulmonary disease models to study lung pathologies. For complete details on the use and execution of this protocol, please refer to Hashimoto et al. (2016), Kawaguchi et al. (2021), and Mikawa et al. (2018).

Cellular senescence promotes cancer metastasis by enhancing soluble E-cadherin production.

Cellular senescence acts as a potent tumor-suppression mechanism in mammals; however, it also promotes tumor progression in a non-cell-autonomous manner. We provided insights into the mechanism underlying senescence-dependent metastatic cancer development. The elimination of senescent cells suppressed the lung metastasis of melanoma cells. Using an antibody array screening of humoral factor(s) that depend on cellular senescence, we identified soluble E-cadherin (seCad) as a potential mediator of the senescence-induced melanoma metastasis. seCad enhanced the invasive activity of melanoma cells both in vitro and in vivo, and gene expression profiling revealed that seCad induced genes associated with poor prognosis in patients with melanoma. An analysis of sera from patients revealed that serum seCad is associated with distant metastasis. Our data suggest that senescent cells promote metastatic lung cancer through seCad, and that seCad may be a potential diagnostic marker as well as a therapeutic target for metastatic lung cancer.

Effects of CREG1 on Age-Associated Metabolic Phenotypes and Renal Senescence in Mice.

Cellular repressor of E1A-stimulated genes 1 (CREG1) is a secreted glycoprotein that accelerates p16-dependent cellular senescence in vitro. We recently reported the ability of CREG1 to stimulate brown adipogenesis using adipocyte P2-CREG1-transgenic (Tg) mice; however, little is known about the effect of CREG1 on aging-associated phenotypes. In this study, we investigated the effects of CREG1 on age-related obesity and renal dysfunction in Tg mice. Increased brown fat formation was detected in aged Tg mice, in which age-associated metabolic phenotypes such as body weight gain and increases in blood glucose were improved compared with those in wild-type (WT) mice. Blood CREG1 levels increased significantly in WT mice with age, whereas the age-related increase was suppressed, and its levels were reduced, in the livers and kidneys of Tg mice relative to those in WT mice at 25 months. Intriguingly, the mRNA levels of Ink4a, Arf, and senescence-associated secretory phenotype (SASP)-related genes and p38MAPK activity were significantly lowered in the aged kidneys of Tg mice, in which the morphological abnormalities of glomeruli as well as filtering function seen in WT kidneys were alleviated. These results suggest the involvement of CREG1 in kidney aging and its potential as a target for improving age-related renal dysfunction.

An antioxidant suppressed lung cellular senescence and enhanced pulmonary function in aged mice.

Oxidative stress is one of the major causes of cellular senescence in mammalian cells. The excess amount of reactive oxygen species generated by oxygen metabolism is pathogenic and facilitates tissue aging. Lung tissue is more susceptible to oxidative stress than other organs because it is directly exposed to environmental stresses. The aging of lung tissues increases the risk of chronic diseases. Senescent cells accumulate in tissues during aging and contribute to aging-associated morbidity; however, the roles of cellular senescence in lung aging and diseases have not yet been elucidated in detail. To clarify the physiological role of oxidative stress-induced cellular senescence in aging-associated declines in pulmonary function, we herein investigated the effects of the antioxidant N-acetyl-L-cysteine (NAC) on lung cellular senescence and aging in mice. The administration of NAC to 1-year-old mice reduced the expression of senescence-associated genes in lung tissue. Pulmonary function and lung morphology were partly restored in mice administered NAC. Collectively, these results suggest that oxidative stress is a major inducer of cellular senescence in vivo and that the control of oxidative stress may prevent lung aging and diseases.

Senolysis by glutaminolysis inhibition ameliorates various age-associated disorders.

Removal of senescent cells (senolysis) has been proposed to be beneficial for improving age-associated pathologies, but the molecular pathways for such senolytic activity have not yet emerged. Here, we identified glutaminase 1 (GLS1) as an essential gene for the survival of human senescent cells. The intracellular pH in senescent cells was lowered by lysosomal membrane damage, and this lowered pH induced kidney-type glutaminase (KGA) expression. The resulting enhanced glutaminolysis induced ammonia production, which neutralized the lower pH and improved survival of the senescent cells. Inhibition of KGA-dependent glutaminolysis in aged mice eliminated senescent cells specifically and ameliorated age-associated organ dysfunction. Our results suggest that senescent cells rely on glutaminolysis, and its inhibition offers a promising strategy for inducing senolysis in vivo.

Senolytic vaccination improves normal and pathological age-related phenotypes and increases lifespan in progeroid mice.

Elimination of senescent cells (senolysis) was recently reported to improve normal and pathological changes associated with aging in mice1,2. However, most senolytic agents inhibit antiapoptotic pathways3, raising the possibility of off-target effects in normal tissues. Identification of alternative senolytic approaches is therefore warranted. Here we identify glycoprotein nonmetastatic melanoma protein B (GPNMB) as a molecular target for senolytic therapy. Analysis of transcriptome data from senescent vascular endothelial cells revealed that GPNMB was a molecule with a transmembrane domain that was enriched in senescent cells (seno-antigen). GPNMB expression was upregulated in vascular endothelial cells and/or leukocytes of patients and mice with atherosclerosis. Genetic ablation of Gpnmb-positive cells attenuated senescence in adipose tissue and improved systemic metabolic abnormalities in mice fed a high-fat diet, and reduced atherosclerotic burden in apolipoprotein E knockout mice on a high-fat diet. We then immunized mice against Gpnmb and found a reduction in Gpnmb-positive cells. Senolytic vaccination also improved normal and pathological phenotypes associated with aging, and extended the male lifespan of progeroid mice. Our results suggest that vaccination targeting seno-antigens could be a potential strategy for new senolytic therapies.

Caveolin-1 Promotes Cellular Senescence in Exchange for Blocking Subretinal Fibrosis in Age-Related Macular Degeneration.

Purpose: To determine whether caveolin-1 (i) prevents epithelial-mesenchymal transition in the RPE and laser-induced subretinal fibrosis and (ii) promotes or inhibits cellular senescence in the RPE. Methods: We examined laser-induced subretinal fibrosis and RPE cell contraction in wild-type and Caveolin-1 knockout (Cav-1-/-) mice treated with or without cavtratin, a cell-permeable peptide of caveolin-1. The senescence marker p16INK4a was measured in RPE tissues from patients with geographic atrophy and aged mice, laser-induced subretinal fibrosis, and primary human RPE cells. Human RPE was examined by TUNEL staining, reactive oxygen species generation, cell viability, and senescence-associated ß-galactosidase staining. Results: The volume of subretinal fibrosis was significantly smaller in cavtratin-injected eyes from wild-type mice than in control eyes from wild-type, P = 0.0062, and Cav-1-/- mice, P = 0.0095. Cavtratin treatment produced significant improvements in primary RPE cell contraction in wild-type, P = 0.04, and Cav-1-/- mice, P = 0.01. p16INK4a expression in the RPE was higher in patients with than without geographic atrophy. p16INK4a was expressed in 18-month-old but not 2-month-old wild-type mouse eyes. p16INK4a and collagen type I antibodies showed co-localization in subretinal fibrosis. Cavtratin did not affect RPE cell apoptosis or reactive oxygen species generation, but decreased cell viability and increased senescence-associated ß-galactosidase-positive cells. Conclusions: Enhanced expression of caveolin-1 successfully blocked epithelial-mesenchymal transition of RPE and the reduction of subretinal fibrosis in mice. Nevertheless, in exchange for blocking subretinal fibrosis, caveolin-1 promotes RPE cellular senescence and might affect the progression of geographic atrophy in AMD.

Lamivudine Inhibits Alu RNA-induced Retinal Pigment Epithelium Degeneration via Anti-inflammatory and Anti-senescence Activities.

Purpose: Accumulation of the long noncoding Alu element RNA activates the NLRP3 inflammasome and leads to retinal pigment epithelium (RPE) cell death, a key event in the pathogenesis of geographic atrophy during late-stage age-related macular degeneration. Lamivudine (3TC) is a nucleoside analog reverse transcriptase inhibitor known to inhibit the NLRP3 inflammasome. Currently, the intracellular response of the senescence marker p16Ink4a to the long noncoding RNA is being actively studied. The present study aimed to assess the efficacy of 3TC against Alu RNA-induced RPE inflammation and senescence by evaluating changes in expression of the proinflammatory cytokines IL-18 and IL-1ß and of p16INK4a in RPE cells. Methods: Cultured human RPE cells and in vivo mouse RPE cells were transfected with an in vitro-transcribed Alu RNA, and changes in IL-18, IL-1ß, and p16Ink4a expression measured in the presences of 3TC or 3,4-(M)CA as a negative control. Results: Treatment with 3TC markedly reduced Alu RNA-induced expression of IL-18 and IL-1ß in human and mouse RPE cells compared with the negative control. Further, Alu RNA-induced p16INK4a expression was suppressed by 3TC in human RPE cells. Conclusions: Our data suggest that Alu RNA accumulation contributes to RPE cell senescence in age-related macular degeneration and that this pathogenic process can be suppressed by 3TC. Translational Relevance: Further verifying this study leads to potential targets for age-related macular degeneration therapy.

p19Arf Exacerbates Cigarette Smoke-Induced Pulmonary Dysfunction.

Senescent cells accumulate in tissues during aging or pathological settings. The semi-genetic or pharmacological targeting of senescent cells revealed that cellular senescence underlies many aspects of the aging-associated phenotype and diseases. We previously reported that cellular senescence contributes to aging- and disease-associated pulmonary dysfunction. We herein report that the elimination of Arf-expressing cells ameliorates cigarette smoke-induced lung pathologies in mice. Cigarette smoke induced the expression of Ink4a and Arf in lung tissue with concomitant increases in lung tissue compliance and alveolar airspace. The elimination of Arf-expressing cells prior to cigarette smoke exposure protected against these changes. Furthermore, the administration of cigarette smoke extract lead to pulmonary dysfunction, which was ameliorated by subsequent senescent cell elimination. Collectively, these results suggest that senescent cells are a potential therapeutic target for cigarette smoking-associated lung disease.

The Effect of Particle Shapes on the Field-Dependent Rheological Properties of Magnetorheological Greases.

The transient response of magnetorheological (MR) materials, in general, is very important for design consideration in MR-based devices. Better response to magnetic fields is beneficial for a better response rate to the electrical current applied in the electromagnetic coil. As a result, MR-based devices would have a high response to external stimuli. In this work, the principal characteristics of magnetorheological greases (MRGs) which have two different particle shapes are experimentally investigated. One type of particle distributed in the grease medium is conventional spherical-shaped carbonyl iron (CI) particles, while the other is plate-like CI particles made using a high-energy rotary ball mill from spherical CI particles. A set of bidisperse MRG samples are firstly prepared by adjusting the weight percentage of the plate-like CI particles and mixing with the spherical CI particles. Subsequently, three important properties of MRGs in terms of their practical application are measured and compared between the two different particle shapes. The field-dependent apparent viscoelastic properties of the prepared MRG samples are measured, followed by the field-dependent storage and loss moduli using an oscillatory shear rheometer. In addition, the transient response time, which indicates the speed in the actuating period of MRGs, is measured by changing the strain amplitude. Then, a comparative assessment on the three properties are undertaken between two different particle shapes by presenting the corresponding results in the same plot. It is shown that the bidisperse MRG with plate-like CI particles exhibits an increase in the initial apparent viscosity as well as stiffness property compared to the MRG with spherical particles only.

Age-associated alterations in murine dermis through inflammatory response with mitochondrial DNA deletions.

AIM: Skin aging is caused by intrinsic and extrinsic mechanisms. Because it is difficult to distinguish intrinsic mechanisms from extrinsic skin aging, the mechanisms of intrinsic skin aging remain unclear. The present study aimed to characterize age-associated alterations in murine skin and investigate the mechanisms of intrinsic skin aging. METHODS: We measured morphological changes in dorsal skin from young (aged 2 months) and old (aged 22-24 months) mice by histological analysis. Age-associated alteration of gene expression patterns was determined by quantitative polymerase chain reaction and immunohistochemistry. Reactive oxygen species production in mouse dorsal skin was detected by confocal laser scanning microscopy. Mitochondrial DNA deletions were detected by conventional polymerase chain reaction and quantitative polymerase chain reaction analyses. RESULTS: Chronologically aged skin had dermal atrophy caused by increased matrix-degrading enzymes and decreased collagen synthesis. Chronologically aged skin samples also had increased senescence-associated secretory phenotype factors, elevated reactive oxygen species production and a higher frequency of the mitochondrial DNA common deletion. CONCLUSIONS: These observations suggest that chronological skin aging is associated with increased frequency of the mitochondrial DNA common deletion and chronic inflammation through the reactive oxygen species-senescence-associated secretory phenotype axis. Geriatr Gerontol Int 2019; 19: 451-457.

Elimination of p19ARF -expressing cells protects against pulmonary emphysema in mice.

Senescent cells accumulate in tissues during aging and are considered to underlie several aging-associated phenotypes and diseases. We recently reported that the elimination of p19ARF -expressing senescent cells from lung tissue restored tissue function and gene expression in middle-aged (12-month-old) mice. The aging of lung tissue increases the risk of pulmonary diseases such as emphysema, and cellular senescence is accelerated in emphysema patients. However, there is currently no direct evidence to show that cellular senescence promotes the pathology of emphysema, and the involvement of senescence in the development of this disease has yet to be clarified. We herein demonstrated that p19ARF facilitated the development of pulmonary emphysema in mice. The elimination of p19ARF -expressing cells prevented lung tissue from elastase-induced lung dysfunction. These effects appeared to depend on reduced pulmonary inflammation, which is enhanced after elastase stimulation. Furthermore, the administration of a senolytic drug that selectively kills senescent cells attenuated emphysema-associated pathologies. These results strongly suggest the potential of senescent cells as therapeutic/preventive targets for pulmonary emphysema.

Hydrogen-rich pure water prevents cigarette smoke-induced pulmonary emphysema in SMP30 knockout mice.

Chronic obstructive pulmonary disease (COPD) is predominantly a cigarette smoke (CS)-triggered disease with features of chronic systemic inflammation. Oxidants derived from CS can induce DNA damage and stress-induced premature cellular senescence in the respiratory system, which play significant roles in COPD. Therefore, antioxidants should provide benefits for the treatment of COPD; however, their therapeutic potential remains limited owing to the complexity of this disease. Recently, molecular hydrogen (H2) has been reported as a preventive and therapeutic antioxidant. Molecular H2 can selectively reduce hydroxyl radical accumulation with no known side effects, showing potential applications in managing oxidative stress, inflammation, apoptosis, and lipid metabolism. However, there have been no reports on the efficacy of molecular H2 in COPD patients. In the present study, we used a mouse model of COPD to investigate whether CS-induced histological damage in the lungs could be attenuated by administration of molecular H2. We administered H2-rich pure water to senescence marker protein 30 knockout (SMP30-KO) mice exposed to CS for 8 weeks. Administration of H2-rich water attenuated the CS-induced lung damage in the SMP30-KO mice and reduced the mean linear intercept and destructive index of the lungs. Moreover, H2-rich water significantly restored the static lung compliance in the CS-exposed mice compared with that in the CS-exposed H2-untreated mice. Moreover, treatment with H2-rich water decreased the levels of oxidative DNA damage markers such as phosphorylated histone H2AX and 8-hydroxy-2'-deoxyguanosine, and senescence markers such as cyclin-dependent kinase inhibitor 2A, cyclin-dependent kinase inhibitor 1, and ß-galactosidase in the CS-exposed mice. These results demonstrated that H2-rich pure water attenuated CS-induced emphysema in SMP30-KO mice by reducing CS-induced oxidative DNA damage and premature cell senescence in the lungs. Our study suggests that administration of molecular H2 may be a novel preventive and therapeutic strategy for COPD.

Elimination of p19ARF-expressing cells enhances pulmonary function in mice.

Senescent cells accumulate in many tissues as animals age and are considered to underlie several aging-associated pathologies. The tumor suppressors p19ARF and p16INK4a, both of which are encoded in the CDKN2A locus, play critical roles in inducing and maintaining permanent cell cycle arrest during cellular senescence. Although the elimination of p16INK4a-expressing cells extends the life span of the mouse, it is unclear whether tissue function is restored by the elimination of senescent cells in aged animals and whether and how p19ARF contributes to tissue aging. The aging-associated decline in lung function is characterized by an increase in compliance as well as pathogenic susceptibility to pulmonary diseases. We herein demonstrated that pulmonary function in 12-month-old mice was reversibly restored by the elimination of p19ARF-expressing cells. The ablation of p19ARF-expressing cells using a toxin receptor-mediated cell knockout system ameliorated aging-associated lung hypofunction. Furthermore, the aging-associated gene expression profile was reversed after the elimination of p19ARF. Our results indicate that the aging-associated decline in lung function was, at least partly, attributed to p19ARF and was recovered by eliminating p19ARF-expressing cells.

ATM Regulates Adipocyte Differentiation and Contributes to Glucose Homeostasis.

Ataxia-telangiectasia (A-T) patients occasionally develop diabetes mellitus. However, only limited attempts have been made to gain insight into the molecular mechanism of diabetes mellitus development in A-T patients. We found that Atm-/- mice were insulin resistant and possessed less subcutaneous adipose tissue as well as a lower level of serum adiponectin than Atm+/+ mice. Furthermore, in vitro studies revealed impaired adipocyte differentiation in Atm-/- cells caused by the lack of induction of C/EBPα and PPARγ, crucial transcription factors involved in adipocyte differentiation. Interestingly, ATM was activated by stimuli that induced differentiation, and the binding of ATM to C/EBPß and p300 was involved in the transcriptional regulation of C/EBPα and adipocyte differentiation. Thus, our study sheds light on the poorly understood role of ATM in the pathogenesis of glucose intolerance in A-T patients and provides insight into the role of ATM in glucose metabolism.