Aging In Organisms Research Articles

Partial cellular reprogramming stably restores the stemness of senescent epidermal stem cells.

Adult stem cell senescence and exhaustion are important drivers of organismal age. Restored stem cell self-renewal has revealed novel therapeutic targets for decreasing the incidence of age-associated diseases (AADs) and prolonging the human health span. Transient ectopic expression of the reprogramming factors Oct3/4, Sox2, Klf4 and c-Myc (collectively known as OSKM) in somatic cells can induce partial cellular reprogramming and effectively ameliorate their age-associated hallmarks. However, how this form of rejuvenation is applied to senescent stem cells remains unknown. The Integrin-α6highCD71high epidermal stem cells (ESCs) with low self-renewal ability were sorted by flow cytometry and then treated by the interrupted reprogramming induced by transient expression of OSKM. The ability of secondary clones' generation and self-proliferation in vitro, as well as stem cell marker p63, were detected to determine their self-renewal ability. Besides, gene and protein of epidermal cell markers were detected to determine whether their cell identities were retained. Finally, DNA methylation age (eAge) and DNA dehydroxymethylase/methyltransferase were analyzed to explore the alternation of their global DNA methylation pattern during this rejuvenation. The partial reprogramming restored the youthful self-renewal and proliferation in senescent ESCs, including larger secondary clone generation, higher expression of stem cell marker p63 and proliferation marker Ki67, and faster proliferation speed, in each case without abolishing epithelial cellular identity. Moreover, the rejuvenation of adult stem cells could be maintained for 2 weeks after reprogramming factor withdrawal, which was more stable than that of differentiated somatic cells. Additionally, we found that partial reprogramming counteracted the acceleration of eAge in senescent epidermal stem cells and DNA methyltransferase 1 (DNMT1) may play a crucial role in this process. Partial reprogramming has high therapeutic potential for reversing adult stem cell age, providing an advanced way to treat AADs.

The Mitochondrial Permeability Transition Pore-Current Knowledge of Its Structure, Function, and Regulation, and Optimized Methods for Evaluating Its Functional State.

The mitochondrial permeability transition pore (MPTP) is a calcium-dependent, ion non-selective membrane pore with a wide range of functions. Although the MPTP has been studied for more than 50 years, its molecular structure remains unclear. Short-term (reversible) opening of the MPTP protects cells from oxidative damage and enables the efflux of Ca2+ ions from the mitochondrial matrix and cell signaling. However, long-term (irreversible) opening induces processes leading to cell death. Ca2+ ions, reactive oxygen species, and changes in mitochondrial membrane potential regulate pore opening. The sensitivity of the pore to Ca2+ ions changes as an organism ages, and MPTP opening plays a key role in the pathogenesis of many diseases. Most studies of the MPTP have focused on elucidating its molecular structure. However, understanding the mechanisms that will inhibit the MPTP may improve the treatment of diseases associated with its opening. To evaluate the functional state of the MPTP and its inhibitors, it is therefore necessary to use appropriate methods that provide reproducible results across laboratories. This review summarizes our current knowledge of the function and regulation of the MPTP. The latter part of the review introduces two optimized methods for evaluating the functional state of the pore under standardized conditions.

The Science of Aging and Longevity

Aging is characterized by a progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death. This deterioration is the primary risk factor for major human pathologies including cancer, diabetes, cardiovascular disorders, and neurodegenerative diseases. Aging research has experienced an unprecedented advance over recent years, particularly with the discovery that the rate of aging is controlled, at least to some extent, by genetic pathways and biochemical processes conserved in evolution. This review enumerates nine tentative hallmarks that represent common denominators of aging in different organisms, with special emphasis on mammalian aging. These hallmarks are: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient-sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication. A major challenge is to dissect the interconnectedness between the candidate hallmarks and their relative contribution to aging, with the final goal of identifying pharmaceutical targets to improve human health during aging with minimal side-effects.

Model organism life extending therapeutics modulate diverse nodes in the drug-gene-microbe tripartite human longevity interactome

Advances in antiaging drug/lead discovery in animal models constitute a large body of literature on novel senotherapeutics and geroprotectives. However, with little direct evidence or mechanism of action in humans—these drugs are utilized as nutraceuticals or repurposed supplements without proper testing directions, appropriate biomarkers, or consistent in-vivo models. In this study, we take previously identified drug candidates that have significant evidence of prolonging lifespan and promoting healthy aging in model organisms, and simulate them in human metabolic interactome networks. Screening for drug-likeness, toxicity, and KEGG network correlation scores, we generated a library of 285 safe and bioavailable compounds. We interrogated this library to present computational modeling-derived estimations of a tripartite interaction map of animal geroprotective compounds in the human molecular interactome extracted from longevity, senescence, and dietary restriction-associated genes. Our findings reflect previous studies in aging-associated metabolic disorders, and predict 25 best-connected drug interactors including Resveratrol, EGCG, Metformin, Trichostatin A, Caffeic Acid and Quercetin as direct modulators of lifespan and healthspan-associated pathways. We further clustered these compounds and the functionally enriched subnetworks therewith to identify longevity-exclusive, senescence-exclusive, pseudo-omniregulators and omniregulators within the set of interactome hub genes. Additionally, serum markers for drug-interactions, and interactions with potentially geroprotective gut microbial species distinguish the current study and present a holistic depiction of optimum gut microbial alteration by candidate drugs. These findings provide a systems level model of animal life-extending therapeutics in human systems, and act as precursors for expediting the ongoing global effort to find effective antiaging pharmacological interventions. Communicated by Ramaswamy H. Sarma

Parasites observed in urine sediments: A learning from incidental rare species

Parasitic infection becomes an unsolved problem in using of automated instruments for urinalysis. Most common parasitic infections described in literature are Trichomonas vaginalis, Schistosoma hematobium and Microfilaria. Other rare organisms are Balantidium coli and Paramecium. The main purpose of this article is to raise the awareness in pathologists and clinicians on the importance of cytological evaluation of urine. This study was done to find the associations between the age and point prevalence of organisms in our zone in the last 6 years. Identification of parasites in centrifuged deposits of urine sediment is a relatively rare occurrence in clinical practice. A fairly wide morphological spectrum of parasites may be diagnosed through microscopic examination of centrifuged urine sediment. They may present with symptoms like pyuria, hematuria, diarrhoea, burning micturition, itching and morphological awareness helps in prompt and effective management in most cases.

Oxidative stress impairs the Nur77-Sirt1 axis resulting in a decline in organism homeostasis during aging.

Sirt1 is an NAD+ -dependent deacetylase that protects against premature aging and cell senescence. Aging accompanied by oxidative stress leads to a decrease in Sirt1 levels and activity, but the regulatory mechanism that connects these events remains unclear. Here, we reported that Nur77, which shares similar biological pathways with Sirt1, was also decreased with age in multiple organs. Our in vivo and in vitro results revealed that Nur77 and Sirt1 decreased during aging and oxidative stress-induced cell senescence. Deletion of Nr4a1 shortened the lifespan and accelerated the aging process in multiple mouse tissues. Overexpression of Nr4a1 protected the Sirt1 protein from proteasomal degradation through negative transcriptional regulation of the E3 ligase MDM2. Our results showed that Nur77 deficiency markedly aggravated aging-related nephropathy and elucidated a key role for Nur77 in the stabilization of Sirt1 homeostasis during renal aging. We proposed a model wherein a reduction of Nur77 in response to oxidative stress promotes Sirt1 protein degradation through MDM2, which triggers cell senescence. This creates additional oxidative stress and provides positive feedback for premature aging by further decreasing Nur77 expression. Our findings reveal the mechanism by which oxidative stress reduces Sirt1 expression during aging and offers an attractive therapeutic strategy for targeting aging and homeostasis in organisms.

Influence of Cholesterol on the Membrane Binding and Conformation of α-Synuclein.

The α-Synuclein (α-Syn) plays an important role in the pathology of Parkinson's disease (PD), and its oligomers and fibrils are toxic to the nervous system. As organisms age, the cholesterol content in biological membranes increases, which is a potential cause of PD. Cholesterol may affect the membrane binding of α-Syn and its abnormal aggregation, but the mechanism remains unclear. Here, we present our molecular dynamics simulation studies on the interaction between α-Syn and lipid membranes, with or without cholesterol. It is demonstrated that cholesterol provides additional hydrogen bond interaction with α-Syn; however, the coulomb interaction and hydrophobic interaction between α-Syn and lipid membranes could be weakened by cholesterol. In addition, cholesterol leads to the shrinking of lipid packing defects and the decrease of lipid fluidity, thereby shortening the membrane binding region of α-Syn. Under these multifaceted effects of cholesterol, membrane-bound α-Syn shows signs of forming a β-sheet structure, which may further induce the formation of abnormal α-Syn fibrils. These results provide important information for the understanding of membrane binding of α-Syn, and they are expected to promote the bridging between cholesterol and the pathological aggregation of α-Syn.

Genome-wide analysis reveals novel regulators of synaptic maintenance in Drosophila.

Maintaining synaptic communication is required to preserve nervous system function as an organism ages. While much work has been accomplished to understand synapse formation and development, we understand relatively little regarding maintaining synaptic integrity throughout aging. To better understand the mechanisms responsible for maintaining synaptic structure and function, we performed an unbiased forward genetic screen to identify genes required for synapse maintenance of adult Drosophila neuromuscular junctions. Using flight behavior as a screening tool, we evaluated flight ability in 198 lines from the Drosophila Genetic Reference Panel to identify single nucleotide polymorphisms (SNPs) that are associated with a progressive loss of flight ability with age. Among the many candidate genes identified from this screen, we focus here on 10 genes with clear human homologs harboring SNPs that are most highly associated with synaptic maintenance. Functional validation of these genes using mutant alleles revealed a progressive loss of synaptic structural integrity. Tissue-specific knockdown of these genes using RNA interference (RNAi) uncovered important roles for these genes in either presynaptic motor neurons, postsynaptic muscles, or associated glial cells, highlighting the importance of each component of tripartite synapses. These results offer greater insight into the mechanisms responsible for maintaining structural and functional integrity of synapses with age.

DNA methylation entropy as a measure of stem cell replication and aging

BackgroundEpigenetic marks are encoded by DNA methylation and accumulate errors as organisms age. This drift correlates with lifespan, but the biology of how this occurs is still unexplained. We analyze DNA methylation with age in mouse intestinal stem cells and compare them to nonstem cells.ResultsAge-related changes in DNA methylation are identical in stem and nonstem cells, affect most prominently CpG islands and correlate weakly with gene expression. Age-related DNA methylation entropy, measured by the Jensen-Shannon Distribution, affects up to 25% of the detectable CpG sites and is a better measure of aging than individual CpG methylation. We analyze this entropy as a function of age in seven other tissues (heart, kidney, skeletal muscle, lung, liver, spleen, and blood) and it correlates strikingly with tissue-specific stem cell division rates. Thus, DNA methylation drift and increased entropy with age are primarily caused by and are sensors for, stem cell replication in adult tissues.ConclusionsThese data have implications for the mechanisms of tissue-specific functional declines with aging and for the development of DNA-methylation-based biological clocks.

Systematic estimation of biological age of in vitro cell culture systems by an age-associated marker panel.

Aging is a process that affects almost all multicellular organisms and since our population ages with increasing prevalence of age-related diseases, it is important to study basic processes involved in aging. Many studies have been published so far using different and often single age markers to estimate the biological age of organisms or different cell culture systems. However, comparability of studies is often hampered by the lack of a uniform panel of age markers. Consequently, we here suggest an easy-to-use biomarker-based panel of classical age markers to estimate the biological age of cell culture systems that can be used in standard cell culture laboratories. This panel is shown to be sensitive in a variety of aging conditions. We used primary human skin fibroblasts of different donor ages and additionally induced either replicative senescence or artificial aging by progerin overexpression. Using this panel, highest biological age was found for artificial aging by progerin overexpression. Our data display that aging varies depending on cell line and aging model and even from individual to individual showing the need for comprehensive analyses.

BACTERIOLOGY AND ANTIMICROBIAL SUSCEPTIBILITY OF OSTEOARTICULAR INFECTIONS AT A REGIONAL PAEDIATRIC UNIT IN SOUTH AFRICA

Osteoarticular infections (OAI) are a common cause of morbidity in children, and as opposed to adults is usually caused by haematogenous spread. The bacteriology of OAI in children is not well described in the South African context, therefore this study was designed to determine the bacteriology of OAI in our population.All patients that underwent surgery for the treatment of OAI over a 3-year period were identified and those with positive cultures where organisms were identified from tissue, pus, fluid or blood were included. Duplicate cultures from the same patient were excluded if the organism and antibiotic susceptibility profile was the same. Patients were categorised according to age and class of infection (Septic arthritis, acute osteomyelitis, fracture related infection, post-operative sepsis and chronic osteomyelitis) and organisms were stratified according to these categories.We identified 132 organisms from 123 samples collected from 86 patients. Most cultured organisms were from children older than 3-years with acute haematogenous septic arthritis, osteomyelitis, or both. Methicillin sensitive Staphylococcus aureus accounted for 56% (74/132) of organisms cultured. There were no cases of MRSA. The Enterobacterales accounted for 17% (22/132) of organisms cultured, mostly in the fracture related and post-operative infection groups. Of these, 6 each were extended spectrum B-lactamase producers and AmpC producers. There were no carbapenemase producing Enterobacterales. Kingella kingae was not isolated in any patient.Methicillin sensitive S. aureus is the most common infecting organism in paediatric OAI and an anti-staphylococcal penicillin such as cloxacillin or flucloxacillin is the most appropriate empiric treatment for haematogenous OAI in our environment. In fracture related or post-operative infections, Enterobacterales were more frequently cultured, and treatment should be guided by culture and susceptibility results.

Exosome Release Delays Senescence by Disposing of Obsolete Biomolecules.

Accumulation of obsolete biomolecules can accelerate cell senescence and organism aging. The two efficient intracellular systems, namely the ubiquitin-proteasome system and the autophagy-lysosome system, play important roles in dealing with cellular wastes. However, how multicellular organisms orchestrate the processing of obsolete molecules and delay aging remains unclear. Herein, it is shown that prevention of exosome release by GW4869 or Rab27a-/- accelerated senescence in various cells and mice, while stimulating exosome release by nutrient restriction delays aging. Interestingly, exosomes isolate from serum-deprived cells or diet-restricted human plasma, enriched with garbage biomolecules, including misfolded proteins, oxidized lipids, and proteins. These cellular wastes can be englobed by macrophages, eventually, for disintegration in vivo. Inhibition of nutrient-sensing mTORC1 signaling increases exosome release and delays senescence, while constitutive activation of mTORC1 reduces exosome secretion and exacerbates senescence in vitro and in mice. Notably, inhibition of exosome release attenuates nutrient restriction- or rapamycin-delayed senescence, supporting a key role for exosome secretion in this process. This study reveals a potential mechanism by which stimulated exosome release delays aging in multicellular organisms, by orchestrating the harmful biomolecules disposal via exosomes and macrophages.

Spt4 promotes cellular senescence by activating non-coding RNA transcription in ribosomal RNA gene clusters

Genome instability can drive aging in many organisms. The ribosomal RNA gene (rDNA) cluster is one of the most unstable regions in the genome and the stability of this region impacts replicative lifespan in budding yeast. To understand the underlying mechanism, we search for yeast mutants with stabler rDNA and longer lifespans than wild-type cells. We show that absence of a transcription elongation factor, Spt4, results in increased rDNA stability, reduced levels of non-coding RNA transcripts from the regulatory E-pro promoter in the rDNA, and extended replicative lifespan in a SIR2-dependent manner. Spt4-dependent lifespan restriction is abolished in the absence of non-coding RNA transcription at the E-pro locus. The amount of Spt4 increases and its function becomes more important as cells age. These findings suggest that Spt4 is a promising aging factor that accelerates cellular senescence through rDNA instability driven by non-coding RNA transcription.

THE ROLE OF THE ENDOPLASMIC RETICULUM UNFOLDED PROTEIN STRESS RESPONSES IN A C. ELEGANS MODEL OF QUIESCENCE

Abstract Cells devote extraordinary energy to translate and fold approximately 20,000 proteins encoded by the human genome. About one third of these proteins are transmembrane proteins—correctly folded in the endoplasmic reticulum (ER). The ER Unfolded Protein Response (UPRER) is a response to disturbances at the ER. As an organism ages, cells lose the ability to activate the UPRER. Our lab uses C. elegans—a microscopic roundworm—as a model organism to determine how loss of ER function can contribute to aging. The UPRER plays a key role in maintenance of functional quiescence. Quiescent cells exist in a reversible state of dormancy and can receive specific environmental cues to proliferate. The developmental state known as L1 arrest resembles the same features as quiescent cells. IRE-1 is required for worms to exit their quiescent state after starvation. Understanding the genetic pathways that are best at suppressing ire-1 terminal L1 arrest could indicate ways to improve functional quiescence. We forced the worms into an L1 arrest state; The unfolded protein response in the endoplasmic reticulum maintains functional quiescence within the cell. The worm’s ability to develop once they exit this quiescent stage effectively, indicated the ability of the worm to maintain protein homeostasis despite non-ideal conditions. It was found that all tested mutations were unable to demonstrate improvement in ability to maintain development when arrested long-term. Our data indicates that our worms were counted prematurely. In the future, we will allow for a longer growth period as well as larger quantities of food.

HDL-localized plasma ceramides support body temperature regulation

Abstract As organisms age, the balance of energy expenditure is disrupted. One of the major ways in which this disruption is observed is in an inability to maintain body temperature. Our lab is interested in understanding the signals that regulate this energy balance, and we focus on lipids as energy substrates and signaling molecules to regulate this process. During cold exposure, plasma lipids produced by peripheral tissues are required to fuel and activate heat production in the brown adipose tissue. One of the lipid classes that increases with cold exposure is plasma ceramides. Beyond cold exposure, ceramide lipids are also elevated in aged individuals and are associated with increased cardiovascular disease risk and age-related diseases such as Alzheimer’s disease where they are thought to signal inflammation. However, the functions of ceramides in non-disease states are unknown. To address this gap in knowledge, we have shown that ceramide production in 12-week-old C57Bl6/J mice is required for body temperature maintenance in the cold. Moreover, plasma ceramide levels in 2-year-old mice are unchanged in the cold, and these mice are unable to maintain their body temperature. In disease states, ceramides are transported through the plasma in LDL, but ceramides are enriched in the HDL plasma fraction in the cold. This differential plasma lipid transport suggests dynamic modes of lipid uptake and tissue targeting to regulate energy expenditure. This work will identify molecular mechanisms governing ceramide function in the mammalian response to cold and better our understanding of the systemic lipid metabolism dysregulated in disease.

Variable rate of ageing within species: insights from Darwin’s frogs

AbstractActuarial senescence, the increase in adult mortality risk with increasing age, is a widespread phenomenon across the animal kingdom. Although between-species variation in the rate of increase in mortality as organisms age (i.e. ageing rate) is now well documented, the occurrence of variation in ageing rate within a given species remains much more debatable. We evaluated the level of within-species variation in ageing rate in four populations of the southern Darwin’s frog (Rhinoderma darwinii) from Chile. Our results revealed strong among-population variation in ageing rates, and these were correlated with the population-specific generation time. A higher ageing rate occurred in populations where individuals exhibited a faster pace of life. Our results, along with recent studies in evolutionarily distant amphibian species, indicate that there can be substantial within-species variation in the rate of ageing, highlighting amphibians as emerging models to study the patterns and mechanisms of intraspecific variation in ageing rate.

Modalities of aging in organisms with different strategies of resource allocation.

Although the progress of aging research relies heavily on a theoretical framework, today there is no consensus on many critical questions in aging biology. I hypothesize that a systematic analysis of the intersection of different evolutionary mechanisms of aging with diverse resource allocation strategies in different organisms may reconcile aging hypotheses. The application of disposable soma, mutation accumulation, antagonistic pleiotropy, and life-history theory is considered across organisms with asexual reproduction, organisms with sexual reproduction and indeterminate growth in different conditions of extrinsic mortality, and organisms with determinate growth, with endotherms/homeotherms as a subgroup. This review demonstrates that different aging mechanisms are complementary to each other, and in organisms with different resource allocation strategies they form aging modalities ranging from immortality to suicidal programs. It also revamps the role of growth arrest in aging. Growth arrest evolved in many different groups of organisms as a result of resource reallocation from growth to reproduction (e.g., semelparous animals, holometabolic insects), or from growth to nutrient storage (endotherms/homeotherms). Growth arrest in different animal lineages has similar molecular mechanisms and similar consequences for longevity due to the conflict between growth-promoting and growth-suppressing programs and suppression of regenerative capacity.

Measurements of damage and repair of binary health attributes in aging mice and humans reveal that robustness and resilience decrease with age, operate over broad timescales, and are affected differently by interventions.

As an organism ages, its health-state is determined by a balance between the processes of damage and repair. Measuring these processes requires longitudinal data. We extract damage and repair transition rates from repeated observations of binary health attributes in mice and humans to explore robustness and resilience, which respectively represent resisting or recovering from damage. We assess differences in robustness and resilience using changes in damage rates and repair rates of binary health attributes. We find a conserved decline with age in robustness and resilience in mice and humans, implying that both contribute to worsening aging health - as assessed by the frailty index (FI). A decline in robustness, however, has a greater effect than a decline in resilience on the accelerated increase of the FI with age, and a greater association with reduced survival. We also find that deficits are damaged and repaired over a wide range of timescales ranging from the shortest measurement scales toward organismal lifetime timescales. We explore the effect of systemic interventions that have been shown to improve health, including the angiotensin-converting enzyme inhibitor enalapril and voluntary exercise for mice. We have also explored the correlations with household wealth for humans. We find that these interventions and factors affect both damage and repair rates, and hence robustness and resilience, in age and sex-dependent manners.

Mammalian Target of Rapamycin (mTOR) Signaling at the Crossroad of Muscle Fiber Fate in Sarcopenia.

The mammalian target of rapamycin (mTOR) is a major regulator of skeletal myocyte viability. The signaling pathways triggered by mTOR vary according to the type of endogenous and exogenous factors (e.g., redox balance, nutrient availability, physical activity) as well as organismal age. Here, we provide an overview of mTOR signaling in skeletal muscle, with a special focus on the role played by mTOR in the development of sarcopenia. Intervention strategies targeting mTOR in sarcopenia (e.g., supplementation of plant extracts, hormones, inorganic ions, calorie restriction, and exercise) have also been discussed.

Экстракт черноплодной рябины (×Sorbaronia mitschurinii ) замедляет возрастное нарушение целостности интестинального барьера Drosophila melanogaster

Chokeberry contains a wide range of biologically active substances with potential geroprotective activity. An ethanolic extract of chokeberry ×Sorbaronia mitschurinii (ABE) has previously been found to have a positive effect on the lifespan of Drosophila melanogaster individuals in short-term exposure (two weeks). The present study evaluated the effects of ABE on the integrity of the D. melanogaster intestinal barrier. This indicator is a marker of aging in many model organisms (nematodes, fish, and flies) and its appearance correlates with the risk of age-dependent death. Brilliant Blue FCF, a synthetic blue food coloring, was used as an indicator of intestinal barrier permeability. It was found that ABE applied before the age of 2 weeks did not significantly affect the integrity of the intestinal barrier in D. melanogaster males and females. However, treatment with ABE at the age of 4-5 weeks resulted in a 3-fold reduction (p < 0.05) in females with compromised intestinal barrier integrity at 8 weeks of age compared to untreated females of the same age. Thus, the use of chokeberry fruit extract in middle age leads to a delay in the onset of age-dependent defects of the integrity of the D. melanogaster intestinal barrier.