Fisetin is a senotherapeutic that extends health and lifespan

Fibrates as drugs with senolytic and autophagic activity for osteoarthritis therapy

Background

Ageing-related failure of homeostasis mechanisms contributes to articular cartilage degeneration and osteoarthritis (OA), for which disease-modifying treatments are not available. Our objective was to identify molecules to prevent OA by regulating chondrocyte senescence and autophagy.

Methods

Human chondrocytes with IL-6 induced senescence and autophagy suppression and SA-β-gal as a reporter of senescence and LC3 as reporter of autophagic flux were used to screen the Prestwick Chemical Library of approved drugs. Preclinical cellular, tissue and blood from OA and blood from OA and ageing models were used to test the efficacy and relevance of activating PPARα related to cartilage degeneration.

Findings

Senotherapeutic molecules with pro-autophagic activity were identified. Fenofibrate (FN), a PPARα agonist used for dyslipidaemias in humans, reduced the number of senescent cells via apoptosis, increased autophagic flux, and protected against cartilage degradation. FN reduced both senescence and inflammation and increased autophagy in both ageing human and OA chondrocytes whereas PPARα knockdown conferred the opposite effect. Moreover, PPARα expression was reduced through both ageing and OA in mice and also in blood and cartilage from knees of OA patients. Remarkably, in a retrospective study, fibrate treatment improved OA clinical conditions in human patients from the Osteoarthritis Initiative (OAI) Cohort.

Interpretation

These results demonstrate that FDA-approved fibrate drugs targeting lipid metabolism protect against cartilage degeneration seen with ageing and OA. Thus, these drugs could have immediate clinically utility for age-related cartilage degeneration and OA treatment.

Fund

This study was supported by Instituto de Salud Carlos III- Ministerio de Ciencia, Innovación y Universidades, Spain, Plan Estatal 2013–2016 and Fondo Europeo de Desarrollo Regional (FEDER), “Una manera de hacer Europa”, PI14/01324 and PI17/02059, by Innopharma Pharmacogenomics platform applied to the validation of targets and discovery of drugs candidates to preclinical phases, Ministerio de Economía y Competitividad, by grants of the National Instiutes of Health to PDR (P01 AG043376 and U19 AG056278). We thank FOREUM Foundation for Research in Rheumatology for their support.

Emerging senolytic agents derived from natural products

Cellular senescence is a hallmark of aging, it is a permanent state of cell cycle arrest induced by cellular stresses. During the aging process, senescent cells (SCs) increasingly accumulate in tissues, causing a loss of tissue-repair capacity because of cell cycle arrest in progenitor cells and produce proinflammatory and matrix-degrading molecules which are known as the senescence-associated secretory phenotype (SASP), and thereby contribute to the development of various age-related diseases. Genetic evidence has demonstrated that clearance of SCs can delay aging and extend healthspan. Senolytics, small molecules that can selectively kill SCs, have been developed to treat various age-related diseases. In recent years, emerging natural compounds have been discovered to be effective senolytic agents, such as quercetin, fisetin, piperlongumine and the curcumin analog. Some of the compounds have been validated in animal models and have great potential to be pushed to clinical applications. In this review, we will discuss cellular senescence and its potential as a target for treating age-related diseases, and summarize the known natural compounds as senolytic agents and their applications.

Cellular Senescence and Iron Dyshomeostasis in Alzheimer's Disease

Iron dyshomeostasis is a feature of Alzheimer's disease (AD). The impact of iron on AD is attributed to its interactions with the central proteins of AD pathology (amyloid precursor protein and tau) and/or through the iron-mediated generation of prooxidant molecules (e.g., hydroxyl radicals). However, the source of iron accumulation in pathologically relevant regions of the brain and its contribution to AD remains unclear. One likely contributor to iron accumulation is the age-associated increase in tissue-resident senescent cells that drive inflammation and contribute to various pathologies associated with advanced age. Iron accumulation predisposes ageing tissue to oxidative stress that can lead to cellular dysfunction and to iron-dependent cell death modalities (e.g., ferroptosis). Further, elevated brain iron is associated with the progression of AD and cognitive decline. Elevated brain iron presents a feature of AD that may be modified pharmacologically to mitigate the effects of age/senescence-associated iron dyshomeostasis and improve disease outcome.

Targeting pro-senescence mitogen activated protein kinase (Mapk) enzymes with bioactive natural compounds

Aging is a multifactorial universal process characterized by a gradual decrease in physiological and biochemical functions. Given that life expectancy is on the rise, a better understanding of molecular mechanisms of the aging process is necessary in order to develop anti-aging interventions. Uncontrolled cellular senescence promotes persistent inflammation and accelerates the aging process by decreasing tissue renewal, repair and regeneration. Senescence of immune cells, immunesenescence, is another hallmark of aging. Targeting pro-senescent enzymes increases survival and therefore the lifespan. Although the upregulation of Mitogen Activated Protein Kinases (MAPK) enzymes in aging is still controversial, increasing evidence shows that dysregulation of those enzymes are associated with biological processes that contribute to aging such as irreversible senescence. In this manuscript components of the MAPK pathway will be summarized, including extracellular signal-regulated kinase 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK) and p38, as well as natural flavonoids, phenolic and diterpenoids with anti-senescence activity that shows positive effects on longevity and MAPK inhibition. Although more studies using additional aging models are needed, we suggest that these selected natural bioactive compounds that regulate MAPK enzymes and reduce senescent cells can be potentially used to improve longevity and prevent/treat age-related diseases.

Slowing Down Ageing: The Role of Nutrients and Microbiota in Modulation of the Epigenome

The human population is getting ageing. Both ageing and age-related diseases are correlated with an increased number of senescent cells in the organism. Senescent cells do not divide but are metabolically active and influence their environment by secreting many proteins due to a phenomenon known as senescence associated secretory phenotype (SASP). Senescent cells differ from young cells by several features. They possess more damaged DNA, more impaired mitochondria and an increased level of free radicals that cause the oxidation of macromolecules. However, not only biochemical and structural changes are related to senescence. Senescent cells have an altered chromatin structure, and in consequence, altered gene expression. With age, the level of heterochromatin decreases, and less condensed chromatin is more prone to DNA damage. On the one hand, some gene promoters are easily available for the transcriptional machinery; on the other hand, some genes are more protected (locally increased level of heterochromatin). The structure of chromatin is precisely regulated by the epigenetic modification of DNA and posttranslational modification of histones. The methylation of DNA inhibits transcription, histone methylation mostly leads to a more condensed chromatin structure (with some exceptions) and acetylation plays an opposing role. The modification of both DNA and histones is regulated by factors present in the diet. This means that compounds contained in daily food can alter gene expression and protect cells from senescence, and therefore protect the organism from ageing. An opinion prevailed for some time that compounds from the diet do not act through direct regulation of the processes in the organism but through modification of the physiology of the microbiome. In this review we try to explain the role of some food compounds, which by acting on the epigenetic level might protect the organism from age-related diseases and slow down ageing. We also try to shed some light on the role of microbiome in this process.

Senolytic therapies for healthy longevity

Clearing senescent cells with targeted drugs could combat age-associated disease

Obesity-Induced Cellular Senescence Drives Anxiety and Impairs Neurogenesis

Cellular senescence entails a stable cell-cycle arrest and a pro-inflammatory secretory phenotype, which contributes to aging and age-related diseases. Obesity is associated with increased senescent cell burden and neuropsychiatric disorders, including anxiety and depression. To investigate the role of senescence in obesity-related neuropsychiatric dysfunction, we used the INK-ATTAC mouse model, from which p16Ink4a-expressing senescent cells can be eliminated, and senolytic drugs dasatinib and quercetin. We found that obesity results in the accumulation of senescent glial cells in proximity to the lateral ventricle, a region in which adult neurogenesis occurs. Furthermore, senescent glial cells exhibit excessive fat deposits, a phenotype we termed "accumulation of lipids in senescence." Clearing senescent cells from high fat-fed or leptin receptor-deficient obese mice restored neurogenesis and alleviated anxiety-related behavior. Our study provides proof-of-concept evidence that senescent cells are major contributors to obesity-induced anxiety and that senolytics are a potential new therapeutic avenue for treating neuropsychiatric disorders.

Cellular senescence in the lung across the age spectrum

Cellular senescence results in cell cycle arrest with secretion of cytokines, chemokines, growth factors, and remodeling proteins (senescence-associated secretory phenotype; SASP) that have autocrine and paracrine effects on the tissue microenvironment. SASP can promote remodeling, inflammation, infectious susceptibility, angiogenesis, and proliferation, while hindering tissue repair and regeneration. While the role of senescence and the contributions of senescent cells are increasingly recognized in the context of aging and a variety of disease states, relatively less is known regarding the portfolio and influences of senescent cells in normal lung growth and aging per se or in the induction or progression of lung diseases across the age spectrum such as bronchopulmonary dysplasia, asthma, chronic obstructive pulmonary disease, or pulmonary fibrosis. In this review, we introduce concepts of cellular senescence, the mechanisms involved in the induction of senescence, and the SASP portfolio that are relevant to lung cells, presenting the potential contribution of senescent cells and SASP to inflammation, hypercontractility, and remodeling/fibrosis: aspects critical to a range of lung diseases. The potential to blunt lung disease by targeting senescent cells using a novel class of drugs (senolytics) is discussed. Potential areas for future research on cellular senescence in the lung are identified.

Will Biotechnology Stop Aging?

Could biotechnology stop aging? The answer may be yes, no, or something in between, depending on who is being asked and what it means to "stop" aging. For those at one end of the spectrum- life extension seekers (including some deep-pocketed Silicon Valley investors)-the answer is "yes." They believe biotechnology will lengthen human life spans to range anywhere from 1,000 years to forever. But for most, the answer is more nuanced and in- volves a dream of extended healthspan, rather than immortality. They imagine a future in which people over the age of 65 years are healthy, active, independent, and not burdened by disease, and that this is the norm rather than the exception. "Healthspanners" believe that one day, science will delay the onset of aging-related conditions and, as a side-effect, modestly extend life. Aging as we know it-and dread it-could become ancient history.

Drugs that target aging: how do we discover them?

INTRODUCTION

Biology of aging is focused on elucidating the biochemical and genetic pathways that contribute to cellular damage accumulation over time. Thirty years of research are beginning to bear fruit as the first pharmacological interventions based on biology of aging go through clinical trials. Evolutionary theories of aging suggest that naturally selected traits believed to impart fitness in young organisms may be damaging in later life. Three major areas of focus in biology of aging are lifespan, healthspan, and rejuvenation. Areas covered: Aging research has produced several validated pharmacological interventions currently in clinical trials. Herein, the authors consider two representative case studies: 1) rapamycin analogs and their effect on the mTORC1 pathway, and 2) small molecules that target and kill senescent cells. The authors also provide their expert current and future perspectives on aging targeting drug discovery. Expert opinion: Aging-related therapeutic interventions will continue to emerge at an accelerating pace, both from research in biology of aging, as well as from coordinated biomedical research in aging-related chronic conditions.

The Role of Curcumin in the Modulation of Ageing

It is believed that postponing ageing is more effective and less expensive than the treatment of particular age-related diseases. Compounds which could delay symptoms of ageing, especially natural products present in a daily diet, are intensively studied. One of them is curcumin. It causes the elongation of the lifespan of model organisms, alleviates ageing symptoms and postpones the progression of age-related diseases in which cellular senescence is directly involved. It has been demonstrated that the elimination of senescent cells significantly improves the quality of life of mice. There is a continuous search for compounds, named senolytic drugs, that selectively eliminate senescent cells from organisms. In this paper, we endeavor to review the current knowledge about the anti-ageing role of curcumin and discuss its senolytic potential.

Senolytics and senostatics as adjuvant tumour therapy

Cell senescence is a driver of ageing, frailty, age-associated disease and functional decline. In oncology, tumour cell senescence may contribute to the effect of adjuvant therapies, as it blocks tumour growth. However, this is frequently incomplete, and tumour cells that recover from senescence may gain a more stem-like state with increased proliferative potential. This might be exaggerated by the induction of senescence in the surrounding niche cells. Finally, senescence will spread through bystander effects, possibly overwhelming the capacity of the immune system to ablate senescent cells. This induces a persistent system-wide senescent cell accumulation, which we hypothesize is the cause for the premature frailty, multi-morbidity and increased mortality in cancer survivors. Senolytics, drugs that selectively kill senescent cells, have been developed recently and have been proposed as second-line adjuvant tumour therapy. Similarly, by blocking accelerated senescence following therapy, senolytics might prevent and potentially even revert premature frailty in cancer survivors. Adjuvant senostatic interventions, which suppress senescence-associated bystander signalling, might also have therapeutic potential. This becomes pertinent because treatments that are senostatic in vitro (e.g. dietary restriction mimetics) persistently reduce numbers of senescent cells in vivo, i.e. act as net senolytics in immunocompetent hosts.

Length doesn't matter-telomere damage triggers cellular senescence in the ageing heart

Telomere shortening induces cellular senescence in proliferative cells. Yet, it is presently unclear how it is triggered in post‐mitotic cells such as cardiac myocytes. A new study by Anderson et al (2019 ) reports that during ageing of the heart, cellular senescence develops independently of telomere length, but is evoked by DNA damage, which preferentially accumulates at the telomere. Removal of senescent cells using senolytic drugs ameliorated cardiac hypertrophy and fibrosis and may inform novel approaches to improve the conditions for the ageing heart.

Inflammation, infection and atherosclerosis

Atherosclerotic cardiovascular disease is a leading cause of death in much of the world. Adoption of a healthy lifestyle and cholesterol lowering are the key measures used to prevent major complications of atherosclerosis. Recent data have identified a critical role for inflammation mediated through activation of both innate and adaptive immune pathways in the pathophysiology of atherosclerosis opening up opportunities for development of anti-inflammatory interventions that could supplement risk factor modification and lipid lowering as an approach to further reducing the burden of atherosclerotic cardiovascular disease.

Senolytics in idiopathic pulmonary fibrosis: Results from a first-in-human, open-label, pilot study

Background

Cellular senescence is a key mechanism that drives age-related diseases, but has yet to be targeted therapeutically in humans. Idiopathic pulmonary fibrosis (IPF) is a progressive, fatal cellular senescence-associated disease. Selectively ablating senescent cells using dasatinib plus quercetin (DQ) alleviates IPF-related dysfunction in bleomycin-administered mice.

Methods

A two-center, open-label study of intermittent DQ (D:100 mg/day, Q:1250 mg/day, three-days/week over three-weeks) was conducted in participants with IPF (n = 14) to evaluate feasibility of implementing a senolytic intervention. The primary endpoints were retention rates and completion rates for planned clinical assessments. Secondary endpoints were safety and change in functional and reported health measures. Associations with the senescence-associated secretory phenotype (SASP) were explored.

Findings

Fourteen patients with stable IPF were recruited. The retention rate was 100% with no DQ discontinuation; planned clinical assessments were complete in 13/14 participants. One serious adverse event was reported. Non-serious events were primarily mild-moderate, with respiratory symptoms (n = 16 total events), skin irritation/bruising (n = 14), and gastrointestinal discomfort (n = 12) being most frequent. Physical function evaluated as 6-min walk distance, 4-m gait speed, and chair-stands time was significantly and clinically-meaningfully improved (p < .05). Pulmonary function, clinical chemistries, frailty index (FI-LAB), and reported health were unchanged. DQ effects on circulat.ing SASP factors were inconclusive, but correlations were observed between change in function and change in SASP-related matrix-remodeling proteins, microRNAs, and pro-inflammatory cytokines (23/48 markers r ≥ 0.50).

Interpretation

Our first-in-humans open-label pilot supports study feasibility and provides initial evidence that senolytics may alleviate physical dysfunction in IPF, warranting evaluation of DQ in larger randomized controlled trials for senescence-related diseases.

ClinicalTrials.gov identifier: NCT02874989 (posted 2016–2018).

Senescent cell clearance by the immune system: Emerging therapeutic opportunities

Senescent cells (SCs) arise from normal cells in multiple organs due to inflammatory, metabolic, DNA damage, or tissue damage signals. SCs are non-proliferating but metabolically active cells that can secrete a range of pro-inflammatory and proteolytic factors as part of the senescence-associated secretory phenotype (SASP). Senescent cell anti-apoptotic pathways (SCAPs) protect SCs from their own pro-apoptotic SASP. SCs can chemo-attract immune cells and are usually cleared by these immune cells. During aging and in multiple chronic diseases, SCs can accumulate in dysfunctional tissues. SCs can impede innate and adaptive immune responses. Whether immune system loss of capacity to clear SCs promotes immune system dysfunction, or conversely whether immune dysfunction permits SC accumulation, are important issues that are not yet fully resolved. SCs may be able to assume distinct states that interact differentially with immune cells, thereby promoting or inhibiting SC clearance, establishing a chronically pro-senescent and pro-inflammatory environment, leading to modulation of the SASP by the immune cells recruited and activated by the SASP. Therapies that enhance immune cell-mediated clearance of SCs could provide a lever for reducing SC burden. Such therapies could include vaccines, small molecule immunomodulators, or other approaches. Senolytics, drugs that selectively eliminate SCs by transiently disabling their SCAPs, may prove to alleviate immune dysfunction in older individuals and thereby accelerate immune-mediated clearance of SCs. The more that can be understood about the interplay between SCs and the immune system, the faster new interventions may be developed to delay, prevent, or treat age-related dysfunction and the multiple senescence-associated chronic diseases and disorders.

Emerging Anti-Aging Strategies - Scientific Basis and Efficacy

The prevalence of age-related diseases is in an upward trend due to increased life expectancy in humans. Age-related conditions are among the leading causes of morbidity and death worldwide currently. Therefore, there is an urgent need to find apt interventions that slow down aging and reduce or postpone the incidence of debilitating age-related diseases. This review discusses the efficacy of emerging anti-aging approaches for maintaining better health in old age. There are many anti-aging strategies in development, which include procedures such as augmentation of autophagy, elimination of senescent cells, transfusion of plasma from young blood, intermittent fasting, enhancement of adult neurogenesis, physical exercise, antioxidant intake, and stem cell therapy. Multiple pre-clinical studies suggest that administration of autophagy enhancers, senolytic drugs, plasma from young blood, drugs that enhance neurogenesis and BDNF are promising approaches to sustain normal health during aging and also to postpone age-related neurodegenerative diseases such as Alzheimer's disease. Stem cell therapy has also shown promise for improving regeneration and function of the aged or Alzheimer's disease brain. Several of these approaches are awaiting critical appraisal in clinical trials to determine their long-term efficacy and possible adverse effects. On the other hand, procedures such as intermittent fasting, physical exercise, intake of antioxidants such as resveratrol and curcumin have shown considerable promise for improving function in aging, some of which are ready for large-scale clinical trials, as they are non-invasive, and seem to have minimal side effects. In summary, several approaches are at the forefront of becoming mainstream therapies for combating aging and postponing age-related diseases in the coming years.

Advances and challenges in geroscience research: An update

Aging remains the most pervasive risk factor for a wide range of chronic diseases that afflict modern societies. In the United States alone, incidence of age-related diseases (e.g., cardiovascular disease, stroke, Alzheimer's disease, vascular cognitive impairment and dementia, cancer, hypertension, type-2 diabetes, chronic obstructive pulmonary disease, and osteoarthritis) is on the rise, posing an unsustainable socioeconomic burden even for the most developed countries. Tackling each and every age-related disease alone is proving to be costly and ineffective. The emerging field of geroscience has posed itself as an interdisciplinary approach that aims to understand the relationship between the biology of aging and the pathophysiology of chronic age-related diseases. According to the geroscience concept, aging is the single major risk factor that underlies several age-related chronic diseases, and manipulation of cellular and systemic aging processes can delay the manifestation and/or severity of these age-related chronic pathologies. The goal of this endeavor is to achieve health improvements by preventing/delaying the pathogenesis of several age-related diseases simultaneously in the elderly population by targeting key cellular and molecular processes of aging instead of managing diseases of aging as they arise individually. In this review, we discuss recent advances in the field of geroscience, highlighting their implications for potential future therapeutic targets and the associated scientific challenges and opportunities that lay ahead.

The senescent cell epigenome

A critical hallmark of aging is cellular senescence, a state of growth arrest and inflammatory cytokine release in cells, caused by a variety of stresses. Recent work has convincingly linked the accumulation of senescent cells in aged tissues to a decline in health and a limit of lifespan, primarily through "inflammaging". Importantly, interventions that clear senescent cells have achieved marked improvements in healthspan and lifespan in mice. A growing list of studies show that environmental stimuli can affect aging and longevity through conserved pathways which, in turn, modulate chromatin states. This review consolidates key findings of chromatin state changes in senescence including histone modifications, histone variants, DNA methylation and changes in three-dimensional genome organization. This information will facilitate the identification of mechanisms and discovery of potential epigenetic targets for therapeutic interventions in aging and age-related disease.