SIRT1 is downregulated by autophagy in senescence and ageing

Pterostilbene Enhances Thermogenesis and Mitochondrial Biogenesis by Activating the SIRT1/PGC-1α/SIRT3 Pathway to Prevent Western Diet-Induced Obesity

SCOPE

Sirtuin 1/peroxisome proliferator-activated receptor gamma co-activator 1 alpha (SIRT1/PGC-1α) pathway activation is known to promote thermogenesis and mitochondrial biogenesis. Pterostilbene (PSB) and pinostilbene (PIN), the methylated analogs of resveratrol, are potential candidates to enhance thermogenesis and mitochondrial biogenesis.

METHOD AND RESULTS

A model of Western diet-induced obesity in mice is designed. Either PSB or PIN is supplemented in the diet for 16 weeks. Both samples can significantly reduce body weight gain but only PSB can decrease inguinal adipose tissue weight. Besides, both samples can promote lipolysis but only PSB supplementation activates the SIRT1/PGC-1α/SIRT3 pathway to enhance mitochondrial biogenesis and thermogenesis in the inguinal adipose tissue. In addition, although both samples exert a modulatory effect on gut microbiota but significant increments in fecal isobutyric acid, valeric acid, and isovaleric acid are only observed in the PSB group, functioning as gut microbial metabolites.

CONCLUSION

Overall, these findings suggest PSB and PIN as potential candidates for the improvement of obesity and gut microbiota dysbiosis. With its higher stability, PSB exerts a greater effect than PIN by promoting thermogenesis and mitochondrial biogenesis via SIRT1 activation.

Dapagliflozin attenuates myocardial hypertrophy via activating the SIRT1/HIF-1α signaling pathway

As a sodium-glucose transporter 2 inhibitor (SGLT2i), the cardioprotective benefits of Dapagliflozin (DAPA) are now widely appreciated. However, the underlying mechanism of DAPA on angiotensin II (Ang II)-induced myocardial hypertrophy has never been evaluated. In this study, we not only investigated the effects of DAPA on Ang II-induced myocardial hypertrophy, but explored its underlying mechanisms. Mice were injected with Ang II (500 ng /kg/min) or saline solution as control, followed by intragastric administration DAPA (1.5 mg/kg/day) or saline for four weeks. DAPA treatment alleviated the condition of decrease in left ventricular ejection fraction (LVEF) and fractional shortening (LVFS) caused by Ang II. In addition, DAPA treatment significantly alleviated Ang II-induced elevation of the ratio of heart weight to tibia length, as well as cardiac injury and hypertrophy. In mice stimulated with Ang II, the degree of myocardial fibrosis and upregulation of the markers of cardiac hypertrophy (atrial natriuretic peptide, ANP and B-type natriuretic peptide, BNP) were attenuated by DAPA. What's more, DAPA partially reversed the Ang II-induced upregulation of HIF-1α and the decrease in levels of SIRT1. Taken together, activating the SIRT1/HIF-1α signaling pathway was found to confer a protective effect against experimental myocardial hypertrophy in mice induced by Ang II, demonstrating its potential as an effective therapeutic target for pathological cardiac hypertrophy.

Targeting SIRT1-regulated autophagic cell death as a novel therapeutic avenue for cancer prevention

Cellular localization and deacetylation activity of sirtuin 1 (SIRT1) has a significant role in cancer regulation. The multifactorial role of SIRT1 in autophagy regulates several cancer-associated cellular phenotypes, aiding cellular survival and cell death induction. SIRT1-mediated deacetylation of autophagy-related genes (ATGs) and associated signaling mediators control carcinogenesis. The hyperactivation of bulk autophagy, disrupted lysosomal and mitochondrial biogenesis, and excessive mitophagy are key mechanism for SIRT1-mediated autophagic cell death (ACD). In terms of the SIRT1-ACD nexus, identifying SIRT1-activating small molecules and understanding the possible mechanism triggering ACD could be a potential therapeutic avenue for cancer prevention. In this review, we provide an update on the structural and functional intricacy of SIRT1 and SIRT1-mediated autophagy activation as an alternative cell death modality for cancer prevention.

The autophagy-NAD axis in longevity and disease

Autophagy is an intracellular degradation pathway that recycles subcellular components to maintain metabolic homeostasis. NAD is an essential metabolite that participates in energy metabolism and serves as a substrate for a series of NAD+-consuming enzymes (NADases), including PARPs and SIRTs. Declining levels of autophagic activity and NAD represent features of cellular ageing, and consequently enhancing either significantly extends health/lifespan in animals and normalises metabolic activity in cells. Mechanistically, it has been shown that NADases can directly regulate autophagy and mitochondrial quality control. Conversely, autophagy has been shown to preserve NAD levels by modulating cellular stress. In this review we highlight the mechanisms underlying this bidirectional relationship between NAD and autophagy, and the potential therapeutic targets it provides for combatting age-related disease and promoting longevity.

Lipofuscin Granule Accumulation Requires Autophagy Activation

Lipofuscins are oxidized lipid and protein complexes that accumulate during cellular senescence and tissue aging, regarded as markers for cellular oxidative damage, tissue aging, and certain aging-associated diseases. Therefore, understanding their cellular biological properties is crucial for effective treatment development. Through traditional microscopy, lipofuscins are readily observed as fluorescent granules thought to accumulate in lysosomes. However, lipofuscin granule formation and accumulation in senescent cells are poorly understood. Thus, this study examined lipofuscin accumulation in human fibroblasts exposed to various stressors. Our results substantiate that in glucose-starved or replicative senescence cells, where elevated oxidative stress levels activate autophagy, lipofuscins predominately appear as granules that co-localize with autolysosomes due to lysosomal acidity or impairment. Meanwhile, autophagosome formation is attenuated in cells experiencing oxidative stress induced by a doxorubicin pulse and chase, and lipofuscin fluorescence granules seldom manifest in the cytoplasm. As Torin-1 treatment activates autophagy, granular lipofuscins intensify and dominate, indicating that autophagy activation triggers their accumulation. Our results suggest that high oxidative stress activates autophagy but fails in lipofuscin removal, leaving an abundance of lipofuscin-filled impaired autolysosomes, referred to as residual bodies. Therefore, future endeavors in treating lipofuscin pathology-associated diseases and dysfunctions through autophagy activation demand meticulous consideration.

MiR-601-induced BMSCs senescence accelerates steroid-induced osteonecrosis of the femoral head progression by targeting SIRT1

BACKGROUND

The imbalance between osteogenic and adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) is not only the primary pathological feature but also a major contributor to the pathogenesis of steroid-induced osteonecrosis of the femoral head (SONFH). Cellular senescence is one of the main causes of imbalanced BMSCs differentiation. The purpose of this study was to reveal whether cellular senescence could participate in the progression of SONFH and the related mechanisms.

METHODS

The rat SONFH model was constructed, and rat BMSCs were extracted. Aging-related indicators were detected by SA-β-Gal staining, qRT-PCR and Western Blot experiments. Using H2O2 to construct a senescent cell model, and overexpressing and knocking down miR-601 and SIRT1 in hBMSCs, the effect on BMSCs differentiation was explored by qRT-PCR, Western Blot experiment, oil red O staining (ORO), alizarin red staining (ARS), and luciferase reporter gene experiment. A rat SONFH model was established to test the effects of miR-601 and metformin in vivo.

RESULTS

The current study showed that glucocorticoids (GCs)-induced BMSCs senescence, which caused imbalanced osteogenesis and adipogenesis of BMSCs, was responsible for the SONFH progression. Further, elevated miR-601 caused by GCs was demonstrated to contribute to BMSCs senescence through targeting SIRT1. In addition, the anti-aging drug metformin was shown to be able to alleviate GCs-induced BMSCs senescence and SONFH progression.

CONCLUSIONS

Considering the role of BMSCs aging in the progression of SONFH, this provides a new idea for the prevention and treatment of SONFH.

Histone modifications in embryo implantation and placentation: insights from mouse models

Embryo implantation and placentation play pivotal roles in pregnancy by facilitating crucial maternal-fetal interactions. These dynamic processes involve significant alterations in gene expression profiles within the endometrium and trophoblast lineages. Epigenetics regulatory mechanisms, such as DNA methylation, histone modification, chromatin remodeling, and microRNA expression, act as regulatory switches to modulate gene activity, and have been implicated in establishing a successful pregnancy. Exploring the alterations in these epigenetic modifications can provide valuable insights for the development of therapeutic strategies targeting complications related to pregnancy. However, our current understanding of these mechanisms during key gestational stages remains incomplete. This review focuses on recent advancements in the study of histone modifications during embryo implantation and placentation, while also highlighting future research directions in this field.

Senescence of alveolar epithelial progenitor cells: a critical driver of lung fibrosis

Pulmonary fibrosis comprises a range of chronic interstitial lung diseases (ILDs) that impose a significant burden on patients and public health. Among these, idiopathic pulmonary fibrosis (IPF), a disease of aging, is the most common and most severe form of ILD and is treated largely by lung transplantation. The lack of effective treatments to stop or reverse lung fibrosis-in fact, fibrosis in most organs-has sparked the need to understand causative mechanisms with the goal of identifying critical points for potential therapeutic intervention. Findings from many groups have indicated that repeated injury to the alveolar epithelium-where gas exchange occurs-leads to stem cell exhaustion and impaired alveolar repair that, in turn, triggers the onset and progression of fibrosis. Cellular senescence of alveolar epithelial progenitors is a critical cause of stemness failure. Hence, senescence impairs repair and thus contributes significantly to fibrosis. In this review, we discuss recent evidence indicating that senescence of epithelial progenitor cells impairs alveolar homeostasis and repair creating a profibrotic environment. Moreover, we discuss the impact of senescent alveolar epithelial progenitors, alveolar type 2 (AT2) cells, and AT2-derived transitional epithelial cells in fibrosis. Emerging evidence indicates that transitional epithelial cells are prone to senescence and, hence, are a new player involved in senescence-associated lung fibrosis. Understanding the complex interplay of cell types and cellular regulatory factors contributing to alveolar epithelial progenitor senescence will be crucial to developing targeted therapies to mitigate their downstream profibrotic sequelae and to promote normal alveolar repair.NEW & NOTEWORTHY With an aging population, lung fibrotic diseases are becoming a global health burden. Dysfunctional repair of the alveolar epithelium is a key causative process that initiates lung fibrosis. Normal alveolar regeneration relies on functional progenitor cells; however, the senescence of these cells, which increases with age, hinders their ability to contribute to repair. Here, we discuss studies on the control and consequence of progenitor cell senescence in fibrosis and opportunities for research.

Histone Deacetylase 3 Inhibition Ameliorates Microglia-Mediated Neuro-Inflammation Via the SIRT1/Nrf2 Pathway After Traumatic Spinal Cord Injury

BACKGROUND

Microglial-induced inflammation plays a crucial role in the pathophysiological process of nervous system injury, however, still lacks effective therapeutic agents. Previously, we discovered that the inhibition of histone deacetylase 3 (HDAC3) exerts anti-inflammatory effects after traumatic spinal cord injury (SCI), whereas little is known about its underlying mechanism. Therefore, the present study aimed to explore the effects and potential mechanisms of HDAC3 on neuroinflammation and microglial function.

METHODS

Rats were randomized into 4 groups: sham group, SCI group, SCI + vehicle group, and SCI + RGF966 group. To examine the effect of HDAC3 on neurological deficit after SCI, we gathered data using the Basso Beattie Bresnahan locomotion scale, the inclined plane test, the blood-spinal cord barrier, junction protein expression, and Nissl staining. We also evaluated microglial activation and inflammatory factor levels. Immunofluorescence analysis, immunohistochemical analysis, western blotting, and quantitative real-time polymerase chain reaction were performed to examine the regulation of the Sirtuin 1 (SIRT1)/nuclear factor-erythroid 2-related factor 2 (Nrf2) pathway.

RESULTS

The results showed that HDAC3 inhibition significantly ameliorated Basso-Beattie-Bresnahan (BBB) permeability, brain edema, and improved neurological functions and junction protein levels. Additionally, HDAC3 inhibition significantly inhibited microglial activation, thereby reducing the levels of SCI-induced pro-inflammatory factors. Moreover, HDAC3 inhibition dramatically enhanced the expression of SIRT1 and increased both Nrf2 nuclear accumulation and transcriptional activity, thereby increasing downstream heme oxygenase-1 and NAD(P)H quinone oxidoreductase 1 expression.

CONCLUSIONS

The results of this study suggest that HDAC3 inhibition protects the spinal cord from injury following SCI by inhibiting SCI-induced microglial activation and the subsequent inflammatory response via SIRT1/Nrf2 signaling pathway, highlighting HDAC3 as a potential therapeutic target for the treatment of SCI.

Autophagy-related proteins: Potential diagnostic and prognostic biomarkers of aging-related diseases

Autophagy plays a key role in cellular, tissue and organismal homeostasis and in the production of the energy load needed at critical times during development and in response to nutrient shortage. Autophagy is generally considered as a pro-survival mechanism, although its deregulation has been linked to non-apoptotic cell death. Autophagy efficiency declines with age, thus contributing to many different pathophysiological conditions, such as cancer, cardiomyopathy, diabetes, liver disease, autoimmune diseases, infections, and neurodegeneration. Accordingly, it has been proposed that the maintenance of a proper autophagic activity contributes to the extension of the lifespan in different organisms. A better understanding of the interplay between autophagy and risk of age-related pathologies is important to propose nutritional and life-style habits favouring disease prevention as well as possible clinical applications aimed at promoting long-term health.

Severe pneumonia induces immunosenescence of T cells in the lung of mice

Severe pneumonia may induce sequelae and accelerated aging process even after the person has recovered. However, the underline mechanism is not very clear. More research is needed to fully understand the long-term effects of severe pneumonia. In this study, we found that mice recovered from severe pneumonia showed lung immunosenescence, which was characterized by a bias naive-memory balance of T lymphocytes in the lung. The reduction of naïve T cells is associated with the diminished immune response to cancer or external new antigens, which is one of the key changes that occurs with age. Our results also indicate the link between severe pneumonia and aging process, which is mediated by the disrupted T cells homeostasis in the lungs after pneumonia.

Effects of an Intervention with Selenium and Coenzyme Q10 on Five Selected Age-Related Biomarkers in Elderly Swedes Low in Selenium: Results That Point to an Anti-Ageing Effect-A Sub-Analysis of a Previous Prospective Double-Blind Placebo-Controlled Randomised Clinical Trial

Background: Ageing is associated with cardiovascular disease (CVD). As no single biomarker reflects the full ageing process, we aimed to investigate five CVD- and age-related markers and the effects of selenium and coenzyme Q10 intervention to elucidate the mechanisms that may influence the course of ageing. Methods: This is a sub-study of a previous prospective double-blind placebo-controlled randomized clinical trial that included 441 subjects low in selenium (mean age 77, 49% women). The active treatment group (n = 220) received 200 µg/day of selenium and 200 mg/day of coenzyme Q10, combined. Blood samples were collected at inclusion and after 48 months for measurements of the intercellular adhesion molecule (ICAM-1), adiponectin, leptin, stem cell factor (SCF) and osteoprotegerin (OPG), using ELISAs. Repeated measures of variance and ANCOVA evaluations were used to compare the two groups. In order to better understand and reduce the complexity of the relationship between the biomarkers and age, factor analyses and structural equation modelling (SEM) were performed, and a structural model is presented. Results: Correlation analyses of biomarker values at inclusion in relation to age, and relevant markers related to inflammation, endothelial dysfunction and fibrosis, demonstrated the biomarkers' association with these pathological processes; however, only ICAM1 and adiponectin were directly correlated with age. SEM analyses showed, however, that the biomarkers ICAM-1, adiponectin, SCF and OPG, but not leptin, all had significant associations with age and formed two independent structural factors, both significantly related to age. While no difference was observed at inclusion, the biomarkers were differently changed in the active treatment and placebo groups (decreasing and increasing levels, respectively) at 48 months (p ≤ 0.02 in all, adjusted), and in the SEM model, they showed an anti-ageing impact. Conclusions: Supplementation with selenium/Q10 influenced the analysed biomarkers in ways indicating an anti-ageing effect, and by applying SEM methodology, the interrelationships between two independent structural factors and age were validated.

Autophagy enables microglia to engage amyloid plaques and prevents microglial senescence

Dysfunctional autophagy has been implicated in the pathogenesis of Alzheimer's disease (AD). Previous evidence suggested disruptions of multiple stages of the autophagy-lysosomal pathway in affected neurons. However, whether and how deregulated autophagy in microglia, a cell type with an important link to AD, contributes to AD progression remains elusive. Here we report that autophagy is activated in microglia, particularly of disease-associated microglia surrounding amyloid plaques in AD mouse models. Inhibition of microglial autophagy causes disengagement of microglia from amyloid plaques, suppression of disease-associated microglia, and aggravation of neuropathology in AD mice. Mechanistically, autophagy deficiency promotes senescence-associated microglia as evidenced by reduced proliferation, increased Cdkn1a/p21Cip1, dystrophic morphologies and senescence-associated secretory phenotype. Pharmacological treatment removes autophagy-deficient senescent microglia and alleviates neuropathology in AD mice. Our study demonstrates the protective role of microglial autophagy in regulating the homeostasis of amyloid plaques and preventing senescence; removal of senescent microglia is a promising therapeutic strategy.

Atg4b Overexpression Extends Lifespan and Healthspan in Drosophila melanogaster

Autophagy plays important but complex roles in aging, affecting health and longevity. We found that, in the general population, the levels of ATG4B and ATG4D decreased during aging, yet they are upregulated in centenarians, suggesting that overexpression of ATG4 members could be positive for healthspan and lifespan. We therefore analyzed the effect of overexpressing Atg4b (a homolog of human ATG4D) in Drosophila, and found that, indeed, Atg4b overexpression increased resistance to oxidative stress, desiccation stress and fitness as measured by climbing ability. The overexpression induced since mid-life increased lifespan. Transcriptome analysis of Drosophila subjected to desiccation stress revealed that Atg4b overexpression increased stress response pathways. In addition, overexpression of ATG4B delayed cellular senescence, and improved cell proliferation. These results suggest that ATG4B have contributed to a slowdown in cellular senescence, and in Drosophila, Atg4b overexpression may have led to improved healthspan and lifespan by promoting a stronger stress response. Overall, our study suggests that ATG4D and ATG4B have the potential to become targets for health and lifespan interventions.

A miRNome analysis at the early postmortem interval

The postmortem interval (PMI) is the time elapsing since the death of an individual until the body is examined. Different molecules have been analyzed to better estimate the PMI with variable results. The miRNAs draw attention in the forensic field to estimate the PMI as they can better support degradation. In the present work, we analyzed the miRNome at early PMI in rats' skeletal muscle using the Affymetrix GeneChip™ miRNA 4.0 microarrays. We found 156 dysregulated miRNAs in rats' skeletal muscle at 24 h of PMI, out of which 84 were downregulated, and 72 upregulated. The miRNA most significantly downregulated was miR-139-5p (FC = -160, p = 9.97 × 10^-11), while the most upregulated was rno-miR-92b-5p (FC = 241.18, p = 2.39 × 10^-6). Regarding the targets of these dysregulated miRNAs, the rno-miR-125b-5p and rno-miR-138-5p were the miRNAs with more mRNA targets. The mRNA targets that we found in the present study participate in several biological processes such as interleukin secretion regulation, translation regulation, cell growth, or low oxygen response. In addition, we found a downregulation of SIRT1 mRNA and an upregulation of TGFBR2 mRNA at 24 h of PMI. These results suggest there is an active participation of miRNAs at early PMI which could be further explored to identify potential biomarkers for PMI estimation.

SIRT1 ubiquitination is regulated by opposing activities of APC/C-Cdh1 and AROS during stress-induced premature senescence

SIRT1, a member of the mammalian sirtuin family, is a nicotinamide adenosine dinucleotide (NAD)-dependent deacetylase with key roles in aging-related diseases and cellular senescence. However, the mechanism by which SIRT1 protein homeostasis is controlled under senescent conditions remains elusive. Here, we revealed that SIRT1 protein is significantly downregulated due to ubiquitin-mediated proteasomal degradation during stress-induced premature senescence (SIPS) and that SIRT1 physically associates with anaphase-promoting complex/cyclosome (APC/C), a multisubunit E3 ubiquitin ligase. Ubiquitin-dependent SIRT1 degradation is stimulated by the APC/C coactivator Cdh1 and not by the coactivator Cdc20. We found that Cdh1 depletion impaired the SIPS-promoted downregulation of SIRT1 expression and reduced cellular senescence, likely through SIRT1-driven p53 inactivation. In contrast, AROS, a SIRT1 activator, reversed the SIRT1 degradation induced by diverse stressors and antagonized Cdh1 function through competitive interactions with SIRT1. Furthermore, our data indicate opposite roles for Cdh1 and AROS in the epigenetic regulation of the senescence-associated secretory phenotype genes IL-6 and IL-8. Finally, we demonstrated that pinosylvin restores downregulated AROS (and SIRT1) expression levels in bleomycin-induced mouse pulmonary senescent tissue while repressing bleomycin-promoted Cdh1 expression. Overall, our study provides the first evidence of the reciprocal regulation of SIRT1 stability by APC/C-Cdh1 and AROS during stress-induced premature senescence, and our findings suggest pinosylvin as a potential senolytic agent for pulmonary fibrosis.

Autophagy inhibition signals through senescence to promote tumor suppression

Macroautophagy/autophagy, a stress-responsive cellular survival mechanism, plays important and context-dependent roles in cancer, and its inhibition has been implicated as a promising cancer therapeutic approach. The detailed mechanisms underlying the function of autophagy in cancer have not been fully understood. In this study, we show that autophagy inhibition promotes both the efficacy of chemotherapy for the treatment of glioblastoma (GBM) and therapy-induced senescence of GBM cells. As a specific cell fate characterized by permanent cell cycle arrest, senescence is also associated with the expression of a panel of specific secreted protein factors known as senescence-associated secretory phenotype (SASP). Intriguingly, we found that autophagy inhibition not only quantitatively enhanced GBM cell senescence but also qualitatively altered the spectrum of SASP. The altered SASP had increased potent activity to induce paracrine senescence of neighboring GBM cells, to skew macrophage polarization toward the anti-tumor M1 state, and to block the recruitment of pro-tumor neutrophils to GBM tumor tissues. Taken together, this study reveals novel functional communication between autophagy and senescence and suggests cancer therapeutic approaches harnessing autophagy blockage in inducing senescence-mediated antitumor immunity.

Ginsenoside Rh4 delays skeletal muscle aging through SIRT1 pathway

BACKGROUND

The aging of skeletal muscle is the leading cause of physical disability in older adults, currently effective treatment methods are lacking. Ginsenoside Rh4, an active component extracted from ginseng, possesses beneficial anti-inflammatory and anti-oxidative effects.

PURPOSE

The aim of this study was to elucidate the antioxidant effect of ginsenoside Rh4 on aging skeletal muscle and its molecular mechanism of anti-aging of skeletal muscle.

STUDY DESIGN

In this study, we employed a D-galactose-induced model of skeletal muscle aging to investigate whether ginsenoside Rh4 can delay the process of skeletal muscle senescence.

METHODS

The effects of ginsenoside Rh4 on oxidative damage and inflammation in aging skeletal muscle were analyzed using immunofluorescence, immunohistochemistry, ELISA kits, H&E staining, flow cytometry, and protein immunoblotting. The changes of ginsenoside Rh4 on mitochondrial morphology were observed by transmission electron microscopy, and ELISA kits and protein immunoblotting analyzed the effects of ginsenoside Rh4 on mitochondrial homeostasis in skeletal muscle cells. The influence of ginsenoside Rh4 on the SIRT1 signaling pathway in aging skeletal muscle were investigated by protein immunoblotting, immunofluorescence, and β-galactosidase staining.

RESULTS

Our results showed that Rh4 improved the morphology of muscle fibers and produced an anti-inflammatory response. Furthermore, in vitro experiments indicated that ginsenosides reduced the production of senescent cells, while Rh4 effectively alleviated oxidative damage in skeletal muscle and restored mitochondrial balance. Transcriptome analysis and molecular docking showed that Rh4 improved mitochondrial homeostasis and delayed skeletal muscle aging by regulating the PGC-1α-TFAM and HIF-1α-c-Myc pathways via targeting SIRT1.

CONCLUSION

Ginsenoside Rh4 improves oxidative stress and inflammation in skeletal muscle by activating SIRT1, deacetylating Nrf2, regulating PGC-1α-TFAM and HIF-1α-c-Myc pathways, and enhancing mitochondrial homeostasis, thus achieving the effect of delaying skeletal muscle aging.

The impact of metabolic stressors on mitochondrial homeostasis in a renal epithelial cell model of methylmalonic aciduria

Methylmalonic aciduria (MMA-uria) is caused by deficiency of the mitochondrial enzyme methylmalonyl-CoA mutase (MUT). MUT deficiency hampers energy generation from specific amino acids, odd-chain fatty acids and cholesterol. Chronic kidney disease (CKD) is a well-known long-term complication. We exposed human renal epithelial cells from healthy controls and MMA-uria patients to different culture conditions (normal treatment (NT), high protein (HP) and isoleucine/valine (I/V)) to test the effect of metabolic stressors on renal mitochondrial energy metabolism. Creatinine levels were increased and antioxidant stress defense was severely comprised in MMA-uria cells. Alterations in mitochondrial homeostasis were observed. Changes in tricarboxylic acid cycle metabolites and impaired energy generation from fatty acid oxidation were detected. Methylcitrate as potentially toxic, disease-specific metabolite was increased by HP and I/V load. Mitophagy was disabled in MMA-uria cells, while autophagy was highly active particularly under HP and I/V conditions. Mitochondrial dynamics were shifted towards fission. Sirtuin1, a stress-resistance protein, was down-regulated by HP and I/V exposure in MMA-uria cells. Taken together, both interventions aggravated metabolic fingerprints observed in MMA-uria cells at baseline. The results point to protein toxicity in MMA-uria and lead to a better understanding, how the accumulating, potentially toxic organic acids might trigger CKD.

Oxidative stress: A common pathological state in a high-risk population for osteoporosis

Osteoporosis is becoming a major concern in the field of public health. The process of bone loss is insidious and does not directly induce obvious symptoms. Complications indicate an irreversible decrease in bone mass. The high-risk populations of osteoporosis, including postmenopausal women, elderly men, diabetic patients and obese individuals need regular bone mineral density testing and appropriate preventive treatment. However, the primary changes in these populations are different, increasing the difficulty of effective treatment of osteoporosis. Determining the core pathogenesis of osteoporosis helps improve the efficiency and efficacy of treatment among these populations. Oxidative stress is a common pathological state secondary to estrogen deficiency, aging, hyperglycemia and hyperlipemia. In this review, we divided oxidative stress into the direct effect of reactive oxygen species (ROS) and the reduction of antioxidant enzyme activity to discuss their roles in the development of osteoporosis. ROS initiated mitochondrial apoptotic signaling and suppressed osteogenic marker expression to weaken osteogenesis. MAPK and NF-κB signaling pathways mediated the positive effect of ROS on osteoclast differentiation. Antioxidant enzymes not only eliminate the negative effects of ROS, but also directly participate in the regulation of bone metabolism. Additionally, we also described the roles of proinflammatory factors and HIF-1α under the pathophysiological changes of inflammation and hypoxia, which provided a supplement of oxidative stress-induced osteoporosis. In conclusion, our review showed that oxidative stress was a common pathological state in a high-risk population for osteoporosis. Targeted oxidative stress treatment would greatly optimize the therapeutic schedule of various osteoporosis treatments.

SIRT1/FOXO3-mediated autophagy signaling involved in manganese-induced neuroinflammation in microglia

Manganese (Mn), as one of the environmental risk factors for Parkinson's disease (PD), has been widely studied. Though autophagy dysfunction and neuroinflammation mainly are responsible for the causative issue of Mn neurotoxicity, the molecular mechanism of parkinsonism caused by Mn has not been explored clearly. The results of in vivo and in vitro experiments showed that overexposure to Mn caused neuroinflammation impairment and autophagy dysfunction, accompanied by the increase of IL-1β, IL-6, and TNF-α mRNA expression, and nerve cell apoptosis, microglia cell activation, NF-κB activation, poor neurobehavior performance. This is due to Mn-induced the downregulation of SIRT1. Upregulation of SIRT1 in vivo and in vitro could alleviate Mn-induced autophagy dysfunction and neuroinflammation, yet these beneficial effects were abolished following 3-MA administration. Furthermore, we found that Mn interfered with the acetylation of FOXO3 by SIRT1 in BV2 cells, leading to a decrease in the nuclear translocation of FOXO3, and its binding of LC3B promoter and transcription activity. This could be antagonized by the upregulation of SIRT1. Finally, it is proved that SIRT1/FOXO3-LC3B autophagy signaling involves in Mn-induced neuroinflammation impairment.

Cellular senescence and the blood-brain barrier: Implications for aging and age-related diseases

The blood-brain barrier (BBB) is a critical physiochemical interface that regulates communication between the brain and blood. It is comprised of brain endothelial cells which regulate the BBB's barrier and interface properties and is surrounded by supportive brain cell types including pericytes and astrocytes. Recent reports have suggested that the BBB undergoes dysfunction during normative aging and in disease. In this review, we consider the effect of cellular senescence, one of the nine hallmarks of aging, on the BBB. We first characterize known normative age-related changes at the BBB, and then evaluate changes in neurodegenerative diseases, with an emphasis on if/how cellular senescence is influencing these changes. We then discuss what insight has been gained from in vitro and in vivo studies of cellular senescence at the BBB. Finally, we evaluate mechanisms by which cellular senescence in peripheral pathologies can indirectly or directly affect BBB function.

The Critical Role of Sirt1 in Subarachnoid Hemorrhages: Mechanism and Therapeutic Considerations

The subarachnoid hemorrhage (SAH) is an important cause of death and long-term disability worldwide. As a nicotinamide adenine dinucleotide-dependent deacetylase, silent information regulator 1 (Sirt1) is a multipotent molecule involved in many pathophysiological processes. A growing number of studies have demonstrated that Sirt1 activation may exert positive effects on SAHs by regulating inflammation, oxidative stress, apoptosis, autophagy, and ferroptosis. Thus, Sirt1 agonists may serve as potential therapeutic drugs for SAHs. In this review, we summarized the current state of our knowledge on the relationship between Sirt1 and SAHs and provided an updated overview of the downstream molecules of Sirt1 in SAHs.

Metabolic landscape in cardiac aging: insights into molecular biology and therapeutic implications

Cardiac aging is evident by a reduction in function which subsequently contributes to heart failure. The metabolic microenvironment has been identified as a hallmark of malignancy, but recent studies have shed light on its role in cardiovascular diseases (CVDs). Various metabolic pathways in cardiomyocytes and noncardiomyocytes determine cellular senescence in the aging heart. Metabolic alteration is a common process throughout cardiac degeneration. Importantly, the involvement of cellular senescence in cardiac injuries, including heart failure and myocardial ischemia and infarction, has been reported. However, metabolic complexity among human aging hearts hinders the development of strategies that targets metabolic susceptibility. Advances over the past decade have linked cellular senescence and function with their metabolic reprogramming pathway in cardiac aging, including autophagy, oxidative stress, epigenetic modifications, chronic inflammation, and myocyte systolic phenotype regulation. In addition, metabolic status is involved in crucial aspects of myocardial biology, from fibrosis to hypertrophy and chronic inflammation. However, further elucidation of the metabolism involvement in cardiac degeneration is still needed. Thus, deciphering the mechanisms underlying how metabolic reprogramming impacts cardiac aging is thought to contribute to the novel interventions to protect or even restore cardiac function in aging hearts. Here, we summarize emerging concepts about metabolic landscapes of cardiac aging, with specific focuses on why metabolic profile alters during cardiac degeneration and how we could utilize the current knowledge to improve the management of cardiac aging.

Deoxyshikonin inhibited rotavirus replication by regulating autophagy and oxidative stress through SIRT1/FoxO1/Rab7 axis

BACKGROUND

Rotavirus (RV) is a double-stranded RNA virus. RV prevention and treatment remain a major public health problem due to the lack of clinically specific drugs. Deoxyshikonin is a natural compound isolated from the root of Lithospermum erythrorhizon and one of the shikonin derivatives which owns remarkable therapeutic effects on multiple diseases. The purpose of this research was to inquire Deoxyshikonin's role and mechanism in RV infection.

METHODS

Deoxyshikonin's function in RV was estimated using Cell Counting Kit-8 analysis, cytopathic effect inhibition assay, virus titer determination, quantitative real-time PCR, enzyme linked-immunosorbent assay, Western blot, immunofluorescence, and glutathione levels detection. Also, Deoxyshikonin's mechanism in RV was appraised with Western blot, virus titer determination, and glutathione levels detection. Moreover, Deoxyshikonin's function in RV in vivo was determined using animal models, and diarrhea score analysis.

RESULTS

Deoxyshikonin owned anti-RV activity and repressed RV replication in Caco-2 cells. Furthermore, Deoxyshikonin reduced autophagy and oxidative stress caused by RV. Mechanistically, Deoxyshikonin induced low protein levels of SIRT1, ac-Foxo1, Rab7, VP6, low levels of RV titers, low autophagy and oxidative stress. SIRT1 overexpression abolished the effects of Deoxyshikonin on RV-treated Caco-2 cells. Meanwhile, in vivo research affirmed that Deoxyshikonin also possessed anti-RV function, and this was reflected in increased survival rate, body weight, GSH levels, and decreased diarrhea score, RV virus antigen, LC-3II/LC3-I.

CONCLUSION

Deoxyshikonin reduced RV replication through mediating autophagy and oxidative stress via SIRT1/FoxO1/Rab7 pathway.

Phosphoglycerate dehydrogenase activates PKM2 to phosphorylate histone H3T11 and attenuate cellular senescence

Vascular endothelial cells (ECs) senescence correlates with the increase of cardiovascular diseases in ageing population. Although ECs rely on glycolysis for energy production, little is known about the role of glycolysis in ECs senescence. Here, we report a critical role for glycolysis-derived serine biosynthesis in preventing ECs senescence. During senescence, the expression of serine biosynthetic enzyme PHGDH is significantly reduced due to decreased transcription of the activating transcription factor ATF4, which leads to reduction of intracellular serine. PHGDH prevents premature senescence primarily by enhancing the stability and activity of pyruvate kinase M2 (PKM2). Mechanistically, PHGDH interacts with PKM2, which prevents PCAF-catalyzed PKM2 K305 acetylation and subsequent degradation by autophagy. In addition, PHGDH facilitates p300-catalyzed PKM2 K433 acetylation, which promotes PKM2 nuclear translocation and stimulates its activity to phosphorylate H3T11 and regulate the transcription of senescence-associated genes. Vascular endothelium-targeted expression of PHGDH and PKM2 ameliorates ageing in mice. Our findings reveal that enhancing serine biosynthesis could become a therapy to promote healthy ageing.

Ceria Nanoparticles Alleviated Osteoarthritis through Attenuating Senescence and Senescence-Associated Secretory Phenotype in Synoviocytes

Accumulation of senescent cells is the prominent risk factor for osteoarthritis (OA), accelerating the progression of OA through a senescence-associated secretory phenotype (SASP). Recent studies emphasized the existence of senescent synoviocytes in OA and the therapeutic effect of removing senescent synoviocytes. Ceria nanoparticles (CeNP) have exhibited therapeutic effects in multiple age-related diseases due to their unique capability of ROS scavenging. However, the role of CeNP in OA remains unknown. Our results revealed that CeNP could inhibit the expression of senescence and SASP biomarkers in multiple passaged and hydrogen-peroxide-treated synoviocytes by removing ROS. In vivo, the concentration of ROS in the synovial tissue was remarkably suppressed after the intra-articular injection of CeNP. Likewise, CeNP reduced the expression of senescence and SASP biomarkers as determined by immunohistochemistry analysis. The mechanistic study showed that CeNP inactivated the NFκB pathway in senescent synoviocytes. Finally, safranin O-fast green staining showed milder destruction of articular cartilage in the CeNP-treated group compared with the OA group. Overall, our study suggested that CeNP attenuated senescence and protected cartilage from degeneration via scavenging ROS and inactivating the NFκB signaling pathway. This study has potentially significant implications in the field of OA as it provides a novel strategy for OA treatment.

An AMP Kinase-pathway dependent integrated stress response regulates ageing and longevity

The purpose of this article is to investigate the role of the AMP-kinase pathway (AMPK pathway) in the induction of a concomitant set of health benefits by exercise, numerous drugs, and health ingredients, all of which are adversely affected by ageing. Despite the AMPK pathway being frequently mentioned in relation to both these health effects and ageing, it appears challenging to understand how the activation of a single biochemical pathway by various treatments can produce such a diverse range of concurrent health benefits, involving so many organs. We discovered that the AMPK pathway functions as an integrated stress response system because of the presence of a feedback loop in it. This evolutionary conserved stress response system detects changes in AMP/ATP and NAD/NADH ratios, as well as the presence of potential toxins, and responds by activating a common protective transcriptional response that protects against aging and promotes longevity. The inactivation of the AMPK pathway with age most likely explains why ageing has a negative impact on the above-mentioned set of health benefits. We conclude that the presence of a feedback loop in the AMP-kinase pathway positions this pathway as an AMPK-ISR (AMP Kinase-dependent integrated stress response) system that responds to almost any type of (moderate) environmental stress by inducing various age-related health benefits and longevity.

Therapeutic potential of natural molecules against Alzheimer's disease via SIRT1 modulation

Alzheimer's disease (AD) is a neurodegenerative disease mainly characterized by progressive cognitive dysfunction and memory impairment. Recent studies have shown that regulating silent information regulator 1 (SIRT1) expression has a significant neuroprotective effect, and SIRT1 may become a new therapeutic target for AD. Natural molecules are an important source of drug development for use in AD therapy and may regulate a wide range of biological events by regulating SIRT1 as well as other SIRT1-mediated signaling pathways. This review aims to summarize the correlation between SIRT1 and AD and to identify in vivo and in vitro studies investigating the anti-AD properties of natural molecules as modulators of SIRT1 and SIRT1-mediated signaling pathways. A literature search was conducted for studies published between January 2000 and October 2022 using various literature databases, including Web of Science, PubMed, Google Scholar, Science Direct, and EMBASE. Natural molecules, such as resveratrol, quercetin, icariin, bisdemethoxycurcumin, dihydromyricetin, salidroside, patchouli, sesamin, rhein, ligustilide, tetramethoxyflavanone, 1-theanine, schisandrin, curcumin, betaine, pterostilbene, ampelopsin, schisanhenol, and eriodictyol, have the potential to modulate SIRT1 and SIRT1 signaling pathways, thereby combating AD. The natural molecules modulating SIRT1 discussed in this review provide a potentially novel multi-mechanistic therapeutic strategy for AD. However, future clinical trials need to be conducted to further investigate their beneficial properties and to determine the safety and efficacy of SIRT1 natural activators against AD.

Subacute ruminal acidosis downregulates FOXA2, changes oxidative status, and induces autophagy in the livers of dairy cows fed a high-concentrate diet

The purpose of this experiment was to investigate high-concentrate feeding-induced changed status of oxidative and autophagy in the livers of dairy cows. Hepatocyte nuclear factor 3β (FOXA2) was reported in cases of liver fibrosis, glucolipid metabolism, and hepatocyte differentiation, but not in cases liver damage in cows fed a high-concentrate diet. Therefore, we also aimed to explore the potential role of FOXA2 in SARA-induced liver damage. We divided 12 mid-lactating Holstein cows into 2 groups and fed them a high-concentrate (HC group, forage:concentrate = 4:6) and a low-concentrate (forage:concentrate = 6:4) diet. After a 2-wk adaptation period and a 3-wk experimental period, peripheral blood was collected for determination of antioxidant enzyme activity, and liver tissue was collected to examine genes and proteins. On d 20 and 21 of the experiment, rumen fluid was collected, and the pH was measured. A significant difference in rumen fluid pH was found between the 2 groups (low-concentrate: 6.10 ± 0.07 vs. HC: 5.59 ± 0.09). The rumen fluid pH in the HC group was less than 5.6 at 2 time points, indicating that SARA was successfully induced. Lipopolysaccharide (0.24 ± 0.10 vs. 0.42 ± 0.12) and malondialdehyde (1.46 ± 0.25 vs. 2.94 ± 0.65) increased, whereas superoxide dismutase (14.06 ± 0.63 vs. 11.71 ± 0.64), reduced glutathione (14.48 ± 2.25 vs. 6.82 ± 0.67), and the total antioxidant capacity (0.43 ± 0.03 vs. 0.30 ± 0.03) decreased in the peripheral blood of the HC group. Moreover, in liver tissue from the HC group, catalase (0.71 ± 0.03 vs. 0.49 ± 0.03) and superoxide dismutase (27.46 ± 1.90 vs. 20.32 ± 1.54) were decreased, whereas malondialdehyde (0.21 ± 0.03 vs. 0.28 ± 0.03) was elevated. Meanwhile, we observed lower gene expression of CAT (1.00 ± 0.15 vs. 0.64 ± 0.17), NAD(P)H quinone dehydrogenase 1 (NQO1; 1.00 ± 0.09 vs. 0.47 ± 0.14), glutathione peroxidase 1 (GPX1; 1.03 ± 0.27 vs. 0.55 ± 0.09), SOD1 (1.01 ± 0.17 vs. 0.76 ± 0.17), and SOD3 (1.02 ± 0.21 vs. 0.55 ± 0.16) in the liver tissue of the HC group. Furthermore, western blot analysis showed that high-concentrate feeding led to decreased sirtuin-1 (SIRT1) (1.00 ± 0.10 vs. 0.62 ± 0.15) and FOXA2 (1.02 ± 0.19 vs. 0.68 ± 0.18), elevated autophagy-related protein microtubule associated protein 1 light chain 3 II (MAP1LC3-II; 1.00 ± 0.32 vs. 1.98 ± 0.83) and autophagy related 5 (ATG5; 1.00 ± 0.30 vs. 1.80 ± 0.27), and suppressed antioxidant signaling pathway-related protein nuclear factor erythroid 2-like 2 (NFE2L2; 1.00 ± 0.18 vs. 0.61 ± 0.30) and heme oxygenase 1 (HMOX1; 1.00 ± 0.48 vs. 0.38 ± 0.25) in liver tissue. Overall, these data indicated that SARA elevated systematic oxidative status and enhanced autophagy in the liver, and suppressed SIRT1 and FOXA2 may mediate enhanced oxidative damage and autophagy in the livers of dairy cows fed a high-concentrate diet.

Regulation of telomere silencing by the core histones-autophagy-Sir2 axis

Telomeres contain compacted heterochromatin, and genes adjacent to telomeres are subjected to transcription silencing. Maintaining telomere structure integrity and transcription silencing is important to prevent the occurrence of premature aging and aging-related diseases. How telomere silencing is regulated during aging is not well understood. Here, we find that the four core histones are reduced during yeast chronological aging, leading to compromised telomere silencing. Mechanistically, histone loss promotes the nuclear export of Sir2 and its degradation by autophagy. Meanwhile, reducing core histones enhances the autophagy pathway, which further accelerates autophagy-mediated Sir2 degradation. By screening the histone mutant library, we identify eight histone mutants and one histone modification (histone methyltransferase Set1-catalyzed H3K4 trimethylation) that regulate telomere silencing by modulating the core histones-autophagy-Sir2 axis. Overall, our findings reveal core histones and autophagy as causes of aging-coupled loss of telomere silencing and shed light on dynamic regulation of telomere structure during aging.

SIRT1 as a Potential Therapeutic Target for Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a common, preventable, and treatable disease characterized by irreversible airflow obstruction and lung function decline. It is well established that COPD represents a major cause of morbidity and mortality globally. Due to the substantial economic and social burdens associated with COPD, it is necessary to discover new targets and develop novel beneficial therapies. Although the pathogenesis of COPD is complex and remains to be robustly elucidated, numerous studies have shown that oxidative stress, inflammatory responses, cell apoptosis, autophagy, and aging are involved in the pathogenesis of COPD. Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase belonging to the silent information regulator 2 (Sir2) family. Multiple studies have indicated that SIRT1 plays an important role in oxidative stress, apoptosis, inflammation, autophagy, and cellular senescence, which contributes to the pathogenesis and development of COPD. This review aimed to discuss the functions and mechanisms of SIRT1 in the progression of COPD and concluded that SIRT1 activation might be a potential therapeutic strategy for COPD.

Sirtuins and their influence on autophagy

Sirtuins and autophagy are well-characterized agents that can promote longevity and protect individual organisms from age-associated diseases like neurodegenerative disorders. In recent years, more and more data has been obtained that discerned potential overlaps and crosstalk between Sirtuin proteins and autophagic activity. This review aims to summarize the advances within the field for each individual Sirtuin in mammalian systems. In brief, most Sirtuins have been implicated in promoting autophagy, with Sirtuin 1 and Sirtuin 6 showing the highest immediate involvement, while Sirtuin 4 and Sirtuin 5 only demonstrate occasional influence. The way Sirtuins regulate autophagy, however, is very diverse, as they have been shown to regulate gene expression of autophagy-associated genes and posttranslational modifications of proteins, with consequences for the activity and cellular localization of these proteins. They have also been shown to determine specific proteins for autophagic degradation. Overall, much data has been accumulated over recent years, yet many open questions remain. Especially although the dynamic between Sirtuin proteins and the immediate regulation of autophagic players like Light Chain 3B has been confirmed, many of these proteins have various orthologues in mammalian systems, and research so far has not exceeded the bona fide components of autophagy.

CRISPR-based DNA methylation editing of NNT rescues the cisplatin resistance of lung cancer cells by reducing autophagy

Cisplatin is recommended as a first-line chemotherapeutic agent against advanced non-small cell lung cancer (NSCLC), but acquired resistance substantially limits its clinical efficacy. Recently, DNA methylation has been identified as an essential contributor to chemoresistance. However, the precise DNA methylation regulatory mechanism of cisplatin resistance remains unclear. Here, we found that nicotinamide nucleotide transhydrogenase (NNT) was silenced by DNA hypermethylation in cisplatin resistance A549 (A549/DDP) cells. Also, the DNA hypermethylation of NNT was positively correlated to poor prognosis in NSCLC patients. Overexpression of NNT in A549/DDP cells could reduce their cisplatin resistance, and also suppressed their tumor malignancy such as cell proliferation and clone formation. However, NNT enhanced sensitivity of A549/DDP cells to cisplatin had little to do with its function in mediating NADPH and ROS level, but was mainly because NNT could inhibit protective autophagy in A549/DDP cells. Further investigation revealed that NNT could decrease NAD⁺ level, thereby inactivate SIRT1 and block the autophagy pathway, while re-activation of SIRT1 through NAD⁺ precursor supplementation could antagonize this effect. In addition, targeted demethylation of NNT CpG island via CRISPR/dCas9-Tet1 system significantly reduced its DNA methylation level and inhibited the autophagy and cisplatin resistance in A549/DDP cells. Thus, our study found a novel chemoresistance target gene NNT, which played important roles in cisplatin resistance of lung cancer cells. Our findings also suggested that CRISPR-based DNA methylation editing of NNT could be a potential therapeutics method in cisplatin resistance of lung cancer.

PUS7 promotes the proliferation of colorectal cancer cells by directly stabilizing SIRT1 to activate the Wnt/β-catenin pathway

Pseudouridine synthase 7 (PUS7) may play key roles in cancer development. However, few studies have been conducted in this area. In the present study, we explored the function and potential mechanisms of PUS7 in colorectal cancer (CRC) progression. We found that PUS7 had higher expression in CRC tissues and cell lines. Clinically, high expression of PUS7 was associated with an unfavorable prognosis for CRC patients. Functionally, knockdown of PUS7 suppressed the proliferation of CRC cells in vitro and inhibited tumorigenicity in vivo. Mechanistically, RNA sequencing and coimmunoprecipitation (Co-IP) indicated that PUS7 exhibited oncogenic functions through the interaction of Sirtuin 1 (SIRT1) and activated the Wnt/β-catenin signaling pathway. Thus, our findings suggest that PUS7 promotes the proliferation of CRC cells by directly stabilizing SIRT1 to activate the Wnt/β-catenin pathway.

Emerging role of aging in the progression of NAFLD to HCC

With the aging of global population, the incidence of nonalcoholic fatty liver disease (NAFLD) has surged in recent decades. NAFLD is a multifactorial disease that follows a progressive course, ranging from simple fatty liver, nonalcoholic steatohepatitis (NASH) to liver cirrhosis and hepatocellular carcinoma (HCC). It is well established that aging induces pathological changes in liver and potentiates the occurrence and progression of NAFLD, HCC and other age-related liver diseases. Studies of senescent cells also indicate a pivotal engagement in the development of NAFLD via diverse mechanisms. Moreover, nicotinamide adenine dinucleotide (NAD⁺), silence information regulator protein family (sirtuins), and mechanistic target of rapamycin (mTOR) are three vital and broadly studied targets involved in aging process and NAFLD. Nevertheless, the crucial role of these aging-associated factors in aging-related NAFLD remains underestimated. Here, we reviewed the current research on the roles of aging, cellular senescence and three aging-related factors in the evolution of NAFLD to HCC, aiming at inspiring promising therapeutic targets for aging-related NAFLD and its progression.

PBX1-SIRT1 Positive Feedback Loop Attenuates ROS-Mediated HF-MSC Senescence and Apoptosis

Stem cell senescence and depletion are major causes of aging and aging-related diseases. The NAD (Nicotinamide adenine dinucleotide) - SIRT1 (Silent Information Regulator 1) - PARP1 (Poly (ADP-ribose) polymerase-1) axis has gained interest owing to its significant role in regulating stem cell senescence and organismal aging. A recent study from our lab showed that pre-B-cell leukemia transcription factor1 (PBX1) overexpression attenuates hair follicle-derived mesenchymal stem cells (HF-MSCs) senescence and apoptosis by regulating ROS-mediated DNA damage via PARP1 downregulation; thus, suggesting that PARP1 downregulation is a common manifestation of the roles of both PBX1 and SIRT1 in HF-MSCs senescence attenuation, and implying a potential link between PBX1 and SIRT1. To this end, HF-MSCs overexpressing PBX1, overexpressing both PBX1 and PARP1, downregulating SIRT1, and overexpressing PBX1 as well as downregulating SIRT1 were generated, and senescence, apoptosis, DNA damage, and repair biomarkers were analyzed. Our results showed that (1) PBX1 overexpression alleviated HF-MSCs senescence and apoptosis accompanied by SIRT1 upregulation, PARP1 downregulation, and increased intracellular NAD and ATP levels. (2) SIRT1 knockdown enhanced cellular senescence and apoptosis, accompanied by increased ROS accumulation, DNA damage aggravation, and decreased intracellular NAD and ATP levels. (3) PBX1 overexpression rescued HF-MSCs senescence and apoptosis induced by SIRT1 knockdown. (4) PBX1 rescued PARP1 overexpression-mediated ATP and NAD depletion, accompanied by increased SIRT1 expression. Collectively, our results revealed that a positive interaction feedback loop exists between PBX1 and SIRT1. To the best of our knowledge we are the first to report that there is a PBX1-SIRT1-PARP1 axis that plays a critical role in alleviating HF-MSCs senescence and apoptosis. We provide a new perspective on the mechanisms underlying stem cell senescence as well as age-related disease prevention and treatment.

New Insights into the Genetics and Epigenetics of Aging Plasticity

Biological aging is characterized by irreversible cell cycle blockade, a decreased capacity for tissue regeneration, and an increased risk of age-related diseases and mortality. A variety of genetic and epigenetic factors regulate aging, including the abnormal expression of aging-related genes, increased DNA methylation levels, altered histone modifications, and unbalanced protein translation homeostasis. The epitranscriptome is also closely associated with aging. Aging is regulated by both genetic and epigenetic factors, with significant variability, heterogeneity, and plasticity. Understanding the complex genetic and epigenetic mechanisms of aging will aid the identification of aging-related markers, which may in turn aid the development of effective interventions against this process. This review summarizes the latest research in the field of aging from a genetic and epigenetic perspective. We analyze the relationships between aging-related genes, examine the possibility of reversing the aging process by altering epigenetic age.

Comparative analysis of markers for H2O2-induced senescence in renal tubular cells

To address what marker(s) is/are most suitable for determining renal cell senescence, cell area, granularity, cycle shift/arrest, SA-β-Gal, SIRT1 and p16 were evaluated after inducing senescence in HK-2 cells with 0.2-0.8 mM H₂O₂. Only cell area and granularity concentration-dependently increased at all time-points, whereas SA-β-Gal, SIRT1 and p16 showed significant coefficient of determination (R²) at two time-points. Cell granularity had significant correlation coefficient (R) with other six, whereas SA-β-Gal had significant R with five, and cell area, SIRT1 and p16 had significant R with four others. Comparing to SA-β-Gal, other markers had significantly lower fold-changes only at 72-h with 0.8 mM H₂O₂, whereas p16 provided greater fold-changes at 48-h with 0.4 and 0.8 mM H₂O₂. Therefore, cell area, granularity, SA-β-Gal and p16 may serve as the most suitable markers for determining H₂O₂-induced senescence in HK-2 renal cells, whereas other markers can be also used but with inferior quantitative precision.

Sirtuins in osteoarthritis: current understanding

Osteoarthritis (OA) is a common disease characterized by severe chronic joint pain, that imposes a large burden on elderly people. OA is a highly heterogeneous disease, and multiple etiologies contribute to its progression. Sirtuins (SIRTs) are Class III histone deacetylases (HDACs) that regulate a comprehensive range of biological processes such as gene expression, cell differentiation, and organism development, and lifespan. Over the past three decades, increasing evidence has revealed that SIRTs are not only important energy sensors but also protectors against metabolic stresses and aging, and an increasing number of studies have focused on the functions of SIRTs in OA pathogenesis. In this review, we illustrate the biological functions of SIRTs in OA pathogenesis from the perspectives of energy metabolism, inflammation, autophagy and cellular senescence. Moreover, we offer insights into the role played by SIRTs in regulating circadian rhythm, which has recently been recognized to be crucial in OA development. Here, we provide the current understanding of SIRTs in OA to guide a new direction for OA treatment exploration.

Adenovirus-mediated SIRT1 protects cochlear strial marginal cells in a D-gal-induced senescent model in vitro

BACKGROUND

A primary obstacle in age-related hearing loss (ARHL) study is the lack of accelerated senescent models in vitro that explore the precise underlying mechanism in different types of ARHL. The damage to strial marginal cells (SMCs) is a subset of strial presbycusis-associated pathological changes. We aimed to establish a D-galactose (D-gal)-induced SMCs senescent model and study the effect of deacetylase sirtuin 1 (SIRT1) on presbycusis in vitro.

METHODS

SMCs from C57BL/6J neonatal mice were cultured and treated with D-gal to establish accelerated senescent models. And then D-gal-induced SMCs were transfected with adenovirus (Ad)-SIRT1-GFP or Ad-GFP. Oxidative stress and mitochondrial DNA (mtDNA) damage were determined by histological analysis or RT-PCR. Western blotting (WB) and RT-PCR were used to evaluate protein and mRNA levels of superoxide dismutase 2 (SOD2) and SIRT1, respectively. Additionally, apoptosis was investigated by WB and TUNEL staining.

RESULTS

D-gal-induced SMCs exhibited several characteristics of senescence, including increased the level of 8-hydroxy-2'-deoxyguanosine, which is a marker of DNA oxidative damage, and elevated the amount of mtDNA 3860-bp deletion, which is a common type of mtDNA damage in the auditory system of mice. SIRT1 overexpression effectively inhibited these changes by upregulating the level of SOD2, thereby inhibiting cytochrome c translocation from mitochondria to cytoplasm, inhibiting cell apoptosis, and ultimately delaying aging in the D-gal-induced senescent SMCs.

CONCLUSIONS

Altogether, the evidence suggests that the D-gal-induced SMCs accelerated aging model is successfully established, and SIRT1 overexpression protects SMCs against oxidative stress by enhancing SOD2 expression in ARHL.

Novel Role of the SIRT1 in Endocrine and Metabolic Diseases

Silent information regulator 1 (SIRT1), a highly conserved NAD⁺-dependent deacetylase, is a cellular regulator that has received extensive attention in recent years and regarded as a sensor of cellular energy and metabolism. The accumulated evidence suggests that SIRT1 is involved in the development of endocrine and metabolic diseases. In a variety of organisms, SIRT1 regulates gene expression through the deacetylation of histone, transcription factors, and lysine residues of other modified proteins including several metabolic and endocrine signal transcription factors, thereby enhancing the therapeutic effects of endocrine and metabolic diseases. These evidences indicate that targeting SIRT1 has promising applications in the treatment of endocrine and metabolic diseases. This review focuses on the role of SIRT1 in endocrine and metabolic diseases. First, we describe the background and structure of SIRT1. Then, we outline the role of SIRT1 in endocrine and metabolic diseases such as hyperuricemia, diabetes, hypertension, hyperlipidemia, osteoporosis, and polycystic ovarian syndrome. Subsequently, the SIRT1 agonists and inhibitors in the above diseases are summarized and future research directions are proposed. Overall, the information presents here may highlight the potential of SIRT1 as a future biomarker and therapeutic target for endocrine and metabolic diseases.

Mitophagy in ototoxicity

Mitochondrial dysfunction is associated with ototoxicity, which is caused by external factors. Mitophagy plays a key role in maintaining mitochondrial homeostasis and function and is regulated by a series of key mitophagy regulatory proteins and signaling pathways. The results of ototoxicity models indicate the importance of this process in the etiology of ototoxicity. A number of recent investigations of the control of cell fate by mitophagy have enhanced our understanding of the mechanisms by which mitophagy regulates ototoxicity and other hearing-related diseases, providing opportunities for targeting mitochondria to treat ototoxicity.

Role of autophagy in aging: The good, the bad, and the ugly

Autophagy (self-eating) is a conserved catabolic homeostatic process required for cellular metabolic demands by removal of the damaged molecules and organelles and for alleviation of stress initiated by pathology and infection. By such actions, autophagy is essential for the prevention of aging, disease, and cancer. Genetic defects of autophagy genes lead to a host of developmental, metabolic, and pathological aberrations. Similarly, the age-induced decline in autophagy leads to the loss of cellular homeostatic control. Paradoxically, such a valuable mechanism is hijacked by diseases, during tumor progression and by senescence, presumably due to high levels of metabolic demand. Here, we review both the role of autophagy in preventing cellular decline in aging by fulfillment of cellular bioenergetic demands and its contribution to the maintenance of the senescent state and SASP by acting on energy and nutritional sensors and diverse signaling pathways.

USP5-Beclin 1 axis overrides p53-dependent senescence and drives Kras-induced tumorigenicity

Non-small cell lung cancers (NSCLC) frequently contain KRAS mutation but retain wild-type TP53. Abundant senescent cells are observed in premalignant but not in malignant tumors derived from the Kras-driven mouse model, suggesting that KRAS oncogenic signaling would have to overcome the intrinsic senescence burden for cancer progression. Here, we show that the nuclear Beclin 1-mediated inhibition of p53-dependent senescence drives Kras-mediated tumorigenesis. KRAS activates USP5 to stabilize nuclear Beclin 1, leading to MDM2-mediated p53 protein instability. KrasG12D mice lacking Beclin 1 display retarded lung tumor growth. Knockdown of USP5 or knockout of Becn1 leads to increased senescence and reduced autophagy. Mechanistically, KRAS elevates ROS to induce USP5 homodimer formation by forming the C195 disulfide bond, resulting in stabilization and activation of USP5. Together, these results demonstrate that activation of the USP5-Beclin 1 axis is pivotal in overriding intrinsic p53-dependent senescence in Kras-driven lung cancer development.

O-GlcNAcylation of SIRT1 Protects against Cold Stress-Induced Skeletal Muscle Damage via Amelioration of Mitochondrial Homeostasis

Cold stress disturbs cellular metabolic and energy homeostasis, which is one of the causes of stress-induced illnesses. O-GlcNAcylation is a nutrient-sensing pathway involved in a myriad of cellular processes. It plays a key role in metabolic homeostasis. Nevertheless, a specific sensing mechanism linking skeletal muscle to O-GlcNAcylation in cold stress is unknown. In this study, O-GlcNAcylation of SIRT1 was targeted to explore the mechanism of skeletal muscle adaptation to cold stress. Ogt mKO aggravated skeletal muscle fibrosis induced by cold stress. At the same time, Ogt gene deletion accelerated the homeostasis imbalance and oxidative stress of skeletal muscle mitochondria induced by cold stress. In vitro results showed that inhibition of SIRT1's O-GlcNAcylation accelerated mild hypothermia induced mitochondrial homeostasis in mouse myogenic cells (C2C12 cells). However, overexpression of SIRT1's O-GlcNAcylation improved the above phenomena. Thus, these results reveal a protective role of OGT-SIRT1 in skeletal muscle's adaptation to cold stress, and our findings will provide new avenues to combat stress-induced diseases.

The role of SIRT1 in the process of Toxoplasma gondii infection of RAW 264.7 macrophages

Toxoplasma gondii is an opportunistic pathogenic protozoan that can infect almost all kinds of warm-blooded animals, including humans. T. gondii can evade the host's immune response, a process known as immune evasion. Our main objective was to evaluate the role played by Sirtuin1 (SIRT1) [one of the sirtuins (SIRTs) that are a family of nicotinamide adenine dinucleotide (NAD)-dependent histone deacetylases (HDACs)] in the T. gondii infection of RAW264.7 macrophages. In this study, we evaluated and observed alterations in the activity, expression, and localization of SIRT1 and assessed its involvement in the CD154/IFN-γ (CD40 ligand/interferon gamma) killing pathway and in autophagy during T. gondii infection. The inhibition of SIRT1 in host cells effectively reduced the number of intracellular tachyzoites, and the mechanism behind this effect might be the upregulation of IRGM1 [murine ortholog of IRGM (immunity-related GTPase family M)] and the initiation of autophagy. To the best of our knowledge, our study is the first to prove that T. gondii infection upregulates SIRT1 in RAW264.7 cells and that the inhibition of SIRT1 reduces the number of intracellular tachyzoites. Moreover, the upregulation of IRGM1 and the activation of autophagy may contribute to the intracellular inhibition of T. gondii caused by SIRT1 inhibition.

Mechanism of Mitochondrial Homeostasis Controlling Ovarian Physiology

Ovarian cells, including oocytes, granulosa/cumulus cells, theca cells, and stromal cells, contain abundant mitochondria, which play indispensable roles in the processes of ovarian follicle development. Ovarian function is closely controlled by mitochondrial proteostasis and mitostasis. While mitochondrial proteostasis and mitostasis are disturbed by several factors, leading to dysfunction of ovarian function and initiating the mitochondrial unfolded protein response (UPRmt) and mitophagy to maintain or recover ovarian function and mitochondrial function, clear interactions between the 2 pathways in the ovary have not been fully elucidated. Here, we comprehensively summarize the molecular networks or regulatory mechanisms behind further mitochondrial research in the ovary. This review provides novel insights into the interactions between the UPRmt and mitophagy in ovarian functions.

Emerging degrader technologies engaging lysosomal pathways

Targeted protein degradation (TPD) provides unprecedented opportunities for drug discovery. While the proteolysis-targeting chimera (PROTAC) technology has already entered clinical trials and changed the landscape of small-molecule drugs, new degrader technologies harnessing alternative degradation machineries, especially lysosomal pathways, have emerged and broadened the spectrum of degradable targets. We have recently proposed the concept of autophagy-tethering compounds (ATTECs) that hijack the autophagy protein microtubule-associated protein 1A/1B light chain 3 (LC3) for targeted degradation. Other groups also reported degrader technologies engaging lysosomal pathways through different mechanisms including AUTACs, AUTOTACs, LYTACs and MoDE-As. In this review, we analyse and discuss ATTECs along with other lysosomal-relevant degrader technologies. Finally, we will briefly summarize the current status of these degrader technologies and envision possible future studies.