Does oxidative damage to DNA increase with age?

Causes and consequences of DNA double-stranded breaks in cardiovascular disease

The genome, whose stability is essential for survival, is incessantly exposed to internal and external stressors, which introduce an estimated 104 to 105 lesions, such as oxidation, in the nuclear genome of each mammalian cell each day. A delicate homeostatic balance between the generation and repair of DNA lesions maintains genomic stability. To initiate transcription, DNA strands unwind to form a transcription bubble and provide a template for the RNA polymerase II (RNAPII) complex to synthesize nascent RNA. The process generates DNA supercoils and introduces torsional stress. To enable RNAPII processing, the supercoils are released by topoisomerases by introducing strand breaks, including double-stranded breaks (DSBs). Thus, DSBs are intrinsic genomic features of gene expression. The breaks are quickly repaired upon processing of the transcription. DNA lesions and damaged proteins involved in transcription could impede the integrity and efficiency of RNAPII processing. The impediment, which is referred to as transcription stress, not only could lead to the generation of aberrant RNA species but also the accumulation of DSBs. The latter is particularly the case when topoisomerase processing and/or the repair mechanisms are compromised. The DSBs activate the DNA damage response (DDR) pathways to repair the damaged DNA and/or impose cell cycle arrest and cell death. In addition, the release of DSBs into the cytosol activates the cytosolic DNA-sensing proteins (CDSPs), which along with the nuclear DDR pathways induce the expression of senescence-associated secretory phenotype (SASP), cell cycle arrest, senescence, cell death, inflammation, and aging. The primary stimulus in hereditary cardiomyopathies is a mutation(s) in genes encoding the protein constituents of cardiac myocytes; however, the phenotype is the consequence of intertwined complex interactions among numerous stressors and the causal mutation(s). Increased internal DNA stressors, such as oxidation, alkylation, and cross-linking, are expected to be common in pathological conditions, including in hereditary cardiomyopathies. In addition, dysregulation of gene expression also imposes transcriptional stress and collectively with other stressors provokes the generation of DSBs. In addition, the depletion of nicotinamide adenine dinucleotide (NAD), which occurs in pathological conditions, impairs the repair mechanism and further facilitates the accumulation of DSBs. Because DSBs activate the DDR pathways, they are expected to contribute to the pathogenesis of cardiomyopathies. Thus, interventions to reduce the generation of DSBs, enhance their repair, and block the deleterious DDR pathways would be expected to impart salubrious effects not only in pathological states, as in hereditary cardiomyopathies but also aging.

'Nomadic' Hematopoietic Stem Cells Navigate the Embryonic Landscape

Hematopoietic stem cells are a unique population of tissue-resident multipotent cells with an extensive ability to self-renew and regenerate the entire lineage of differentiated blood cells. Stem cells reside in a highly specialized microenvironment with surrounding supporting cells, forming a complex and dynamic network to preserve and maintain their function. The survival, activation, and quiescence of stem cells are largely influenced by niche-derived signals, with aging niche contributing to a decline in stem cell function. Although the role of niche in regulating hematopoiesis has long been established by transplantation studies, limited methods in observing the process in vivo have eluded a detailed understanding of the various niche components. Danio rerio (zebrafish) has emerged as a solution in the past few decades, enabling discovery of cellular interactions, in addition to chemical and genetic factors regulating HSCs. This review reiterates zebrafish as a suitable model for studies on vertebrate embryonic and adult hematopoiesis, delving into this temporally and spatially dissected multi-step process. The critical role played by epigenetic regulators are discussed, along with contributions of the various physiological processes in sustaining the stem cell population. Stem cell niche transcends mere knowledge acquisition, assuring scope in cell therapy, organoid cultures, aging research, and clinical applications including bone marrow transplantation and cancer. A better understanding of the various niche components could also leverage therapeutic efforts to drive differentiation of HSCs from pluripotent progenitors, sustain stemness in laboratory cultures, and improve stem cell transplantation outcomes.

FNDC5/irisin mitigates the cardiotoxic impacts of cancer chemotherapeutics by modulating ROS-dependent and -independent mechanisms

Cardiotoxicity remains a major limiting factor in the clinical implementation of anthracycline chemotherapy. Though the etiology of doxorubicin-dependent heart damage has yet to be fully elucidated, the ability of doxorubicin to damage DNA and trigger oxidative stress have been heavily implicated in the pathogenesis of chemotherapy-associated cardiomyopathy. Here, we demonstrate that fibronectin type III domain-containing protein 5 (FNDC5), the precursor protein for myokine irisin, is depleted in the hearts of human cancer patients or mice exposed to chemotherapeutics. In cardiomyocytes, restoration of FNDC5 expression was sufficient to mitigate reactive oxygen species (ROS) accumulation and apoptosis following doxorubicin exposure, effects dependent on the irisin encoding domain of FNDC5 as well as signaling via the putative irisin integrin receptor. Intriguingly, we identified two parallel signaling cascades impacted by FNDC5 in cardiomyocytes: the ROS-driven intrinsic mitochondrial apoptosis pathway and the ROS-independent Ataxia Telangiectasia and Rad3-Related Protein (ATR)/Checkpoint Kinase 1 (Chk1) pathway. In fact, FNDC5 forms a co-precipitable complex with Chk1 alluding to possible intracellular actions for this canonically membrane-associated protein. Whereas FNDC5 overexpression in murine heart was cardioprotective, introduction of FNDC5-targeted shRNA into the myocardium was sufficient to trigger Bax up-regulation, ATR/Chk1 activation, oxidative stress, cardiac fibrosis, loss of ventricular function, and compromised animal survival. The detrimental impact of FNDC5 depletion on heart function could be mitigated via treatment with a Chk1 inhibitor identifying Chk1 hyperactivity as a causative factor in cardiac disease. Though our data point to the potential clinical utility of FNDC5/irisin-targeted agents in the treatment of chemotherapy-induced cardiotoxicity, we also found significant down regulation in FNDC5 expression in the hearts of aged mice that attenuated the cardioprotective impacts of FNDC5 overexpression following doxorubicin exposure. Together our data underscore the importance of FNDC5/irisin in maintenance of cardiac health over the lifespan.

DNA damage and its links to neuronal aging and degeneration

DNA damage is a major risk factor for the decline of neuronal functions with age and in neurodegenerative diseases. While how DNA damage causes neurodegeneration is still being investigated, innovations over the past decade have provided significant insights into this issue. Breakthroughs in next-generation sequencing methods have begun to reveal the characteristics of neuronal DNA damage hotspots and the causes of DNA damage. Chromosome conformation capture-based approaches have shown that, while DNA damage and the ensuing cellular response alter chromatin topology, chromatin organization at damage sites also affects DNA repair outcomes in neurons. Additionally, neuronal activity results in the formation of programmed DNA breaks, which could burden DNA repair mechanisms and promote neuronal dysfunction. Finally, emerging evidence implicates DNA damage-induced inflammation as an important contributor to the age-related decline in neuronal functions. Together, these discoveries have ushered in a new understanding of the significance of genome maintenance for neuronal function.

"Aging Clocks" Based on Cell-Free DNA

Aging is associated with systemic changes in the physiological and molecular parameters of the body. These changes are referred to as biomarkers of aging. Statistical models that link changes in individual biomarkers to biological age are called aging clocks. These tools facilitate a comprehensive evaluation of bodily health and permit the quantitative determination of the rate of aging. A particularly promising area for the development of aging clocks is the analysis of cell-free DNA (cfDNA), which is present in the blood and contains numerous potential biomarkers. This review explores in detail the fragmentomics, topology, and epigenetic landscape of cfDNA as possible biomarkers of aging. The review further underscores the potential of leveraging single-molecule sequencing of cfDNA in conjunction with long-read technologies to simultaneously profile multiple biomarkers, a strategy that could lead to the development of more precise aging clocks.

Mouse models used to test the role of reactive oxygen species in aging and age-related chronic diseases

With the development of the technology to generate transgenic and knockout mice in the 1990s, investigators had a powerful tool to directly test the impact of altering a specific gene on a biological process or disease. Over the past three decades, investigators have used transgenic and knockout mouse models, which have altered expression of antioxidant genes, to test the role of oxidative stress/damage in aging and age-related diseases. In this comprehensive review, we describe the studies using transgenic and knockout mouse models to test the role of oxidative stress/damage in aging (longevity) and three age-related diseases, e.g., sarcopenia, cardiac aging, and Alzheimer's Disease. While longevity was consistently altered only by one transgenic and one knockout mouse model as predicted by the Oxidative Stress Theory of Aging, the incidence/progression of the three age-related diseases (especially Alzheimer's disease) were robustly impacted when the expression of various antioxidant genes was altered using transgenic and knockout mouse models.

Mitochondrial Redox Status Regulates Glycogen Metabolism via Glycogen Phosphorylase Activity

Mitochondria and glycogen are co-distributed in skeletal muscles to regulate the metabolic status. Mitochondria are also redox centers that regulate the muscle function during exercise. However, the pathophysiological relationship between the mitochondrial redox status and glycogen metabolism in the muscle remains unclear. In the present study, we examined the pathological effects of mitochondrial dysfunction induced by mitochondrial superoxide dismutase (SOD2) depletion on glycogen metabolism. We found that muscle glycogen was significantly accumulated in association with motor dysfunction in mice with a muscle-specific SOD2 deficiency. Muscle glycogen phosphorylase (GP-M) activity, which is a key enzyme for glycogen degradation at times when energy is needed (e.g., during exercise), was significantly decreased in the mutant muscle. Moreover, the GP-M activity on normal muscle sections decreased after treatment with paraquat, a superoxide generator. In contrast, treatment with antioxidants reversed the GP-M activity and motor disturbance of the mutant mice, indicating that GP-M activity was reversibly regulated by the redox balance. These results demonstrate that the maintenance of the mitochondrial redox balance regulates glycogen metabolism via GP-M activity.

Oxidative Stress in an African Ground Squirrel, a Case of Healthy Aging and Reproduction

Oxidative stress plays a crucial role in mediating life-history processes, where it can compromise survival and reproduction through harmful alterations to DNA, lipids, and proteins. In this study, we investigated oxidative stress in Cape ground squirrels (Xerus inauris), a longer-lived African ground squirrel species with a high reproductive skew and unique life history strategies. We measured oxidative stress as total antioxidant capacity (TAC), total oxidant status (TOS), and an oxidative stress index (OSI) in blood plasma from individuals of approximately known ages. Our results reveal a distinct pattern of decreasing oxidative stress with age, consistent across both sexes. Females exhibited lower OSI and TOS levels than males. Males employing different life-history strategies, namely natal (staying at home), had significantly lower oxidative stress compared to the band (roaming male groups), likely due to variations in metabolic rate, activity, and feeding rates. However, both strategies exhibited reduced oxidative stress with age, though the underlying mechanisms require further investigation. We propose that selection pressures favoring survival contributed to the observed reduction in oxidative stress with age, potentially maximizing lifetime reproductive success in this species.

Modulation of ATM enhances DNA repair in G2/M phase of cell cycle and averts senescence in Fuchs endothelial corneal dystrophy

Fuchs Endothelial Corneal Dystrophy (FECD) is an aging disorder characterized by expedited loss of corneal endothelial cells (CEnCs) and heightened DNA damage compared to normal CEnCs. We previously established that ultraviolet-A (UVA) light causes DNA damage and leads to FECD phenotype in a non-genetic mouse model. Here, we demonstrate that acute treatment with chemical stressor, menadione, or physiological stressors, UVA, and catechol estrogen (4-OHE2), results in an early and increased activation of ATM-mediated DNA damage response in FECD compared to normal CEnCs. Acute stress with UVA and 4OHE2 causes (i) greater cell-cycle arrest and DNA repair in G2/M phase, and (ii) greater cytoprotective senescence in NQO1-/- compared to NQO1+/+ cells, which was reversed upon ATM inhibition. Chronic stress with UVA and 4OHE2 results in ATM-driven cell-cycle arrest in G0/G1 phase, reduced DNA repair, and cytotoxic senescence, due to sustained damage. Likewise, UVA-induced cell-cycle reentry, gamma-H2AX foci, and senescence-associated heterochromatin were reduced in Atm-null mice. Remarkably, inhibiting ATM activation with KU-55933 restored DNA repair in G2/M phase and attenuated senescence in chronic cellular model of FECD lacking NQO1. This study provides insights into understanding the pivotal role of ATM in regulating cell-cycle, DNA repair, and senescence, in oxidative-stress disorders like FECD.

Brown adipose tissue: a potential target for aging interventions and healthy longevity

Brown Adipose Tissue (BAT) is a type of fat tissue that can generate heat and plays an important role in regulating body temperature and energy metabolism. Enhancing BAT activity through medication, exercise and other means has become a potential effective method for treating metabolic disorders. Recently, there has been increasing evidence suggesting a link between BAT and aging. As humans age, the volume and activity of BAT decrease, which may contribute to the development of age-related diseases. Multiple organelles signaling pathways have been reported to be involved in the aging process associated with BAT. Therefore, we aimed to review the evidence related to the association between aging process and BAT decreasing, analyze the potential of BAT as a predictive marker for age-related diseases, and explore potential therapeutic strategies targeting BAT for aging interventions and healthy longevity.

In vivo DNA replication dynamics unveil aging-dependent replication stress

The genome duplication program is affected by multiple factors in vivo, including developmental cues, genotoxic stress, and aging. Here, we monitored DNA replication initiation dynamics in regenerating livers of young and old mice after partial hepatectomy to investigate the impact of aging. In young mice, the origin firing sites were well defined; the majority were located 10-50 kb upstream or downstream of expressed genes, and their position on the genome was conserved in human cells. Old mice displayed the same replication initiation sites, but origin firing was inefficient and accompanied by a replication stress response. Inhibitors of the ATR checkpoint kinase fully restored origin firing efficiency in the old mice but at the expense of an inflammatory response and without significantly enhancing the fraction of hepatocytes entering the cell cycle. These findings unveil aging-dependent replication stress and a crucial role of ATR in mitigating the stress-associated inflammation, a hallmark of aging.

Oxidative stress and aging: synergies for age related diseases

Aging is characterized by a progressive decline in physiological function and underlies several disabilities, including the increased sensitivity of cells and tissues to undergo pathological oxidative stress. In recent years, efforts have been made to better understand the relationship between age and oxidative stress and further develop therapeutic strategies to minimize the impact of both events on age-related diseases. In this work, we review the impact of the oxidant and antioxidant systems during aging and disease development and discuss the crosstalk of oxidative stress and other aging processes, with a focus on studies conducted in elderly populations.

The Influence of SARS-CoV-2 Infection on the Development of Selected Neurological Diseases

In 2024, over 775 million cases of COVID-19 were recorded, including approximately 7 million deaths, indicating its widespread and dangerous nature. The disease is caused by the SARS-CoV-2 virus, which can manifest a wide spectrum of symptoms, from mild infection to respiratory failure and even death. Neurological symptoms, such as headaches, confusion, and impaired consciousness, have also been reported in some COVID-19 patients. These observations suggest the potential of SARS-CoV-2 to invade the central nervous system and induce neuroinflammation during infection. This review specifically explores the relationship between SARS-CoV-2 infection and selected neurological diseases such as multiple sclerosis (MS), ischemic stroke (IS), and Alzheimer's disease (AD). It has been observed that the SARS-CoV-2 virus increases the production of cytokines whose action can cause the destruction of the myelin sheaths of nerve cells. Subsequently, the body may synthesize autoantibodies that attack nerve cells, resulting in damage to the brain's anatomical elements, potentially contributing to the onset of multiple sclerosis. Additionally, SARS-CoV-2 exacerbates inflammation, worsening the clinical condition in individuals already suffering from MS. Moreover, the secretion of pro-inflammatory cytokines may lead to an escalation in blood clot formation, which can result in thrombosis, obstructing blood flow to the brain and precipitating an ischemic stroke. AD is characterized by intense inflammation and heightened oxidative stress, both of which are exacerbated during SARS-CoV-2 infection. It has been observed that the SARS-CoV-2 demonstrates enhanced cell entry in the presence of both the ACE2 receptor, which is already elevated in AD and the ApoE ε4 allele. Consequently, the condition worsens and progresses more rapidly, increasing the mortality rate among AD patients. The above information underscores the numerous connections between SARS-CoV-2 infection and neurological diseases.

MicroRNA-206 as a potential cholesterol-lowering drug is superior to statins in mice

Hypercholesterolemia is frequently intertwined with hepatosteatosis, hypertriglyceridemia, and hyperglycemia. This study is designed to assess the therapeutic efficacy of miR-206 in contrast to statins in the context of managing hypercholesterolemia in mice. We previously showed that miR-206 is a potent inhibitor of de novo lipogenesis (DNL), cholesterol synthesis, and gluconeogenesis in mice. Given that these processes occur within hepatocytes, we employed a mini-circle (MC) system to deliver miR-206 specifically to hepatocytes (designated as MC-miR-206). A single intravenous injection of MC-miR-206 maintained high levels of miR-206 in the liver for at least two weeks, thereby maintaining suppression of hepatic DNL, cholesterol synthesis, and gluconeogenesis. MC-miR-206 significantly reduced DNA damage, endoplasmic reticulum and oxidative stress, and hepatic toxicity. Therapeutically, both MC-miR-206 and statins significantly reduced total serum cholesterol and triglycerides as well as LDL cholesterol and VLDL cholesterol in mice maintained on the normal chow and high-fat high-cholesterol diet. MC-miR-206 reduced liver weight, hepatic triglycerides and cholesterol, and blood glucose, while statins slightly increased hepatic cholesterol and blood glucose and failed to affect levels of liver weight and hepatic triglycerides. Mechanistically, miR-206 alleviated hypercholesterolemia by inhibiting hepatic cholesterol synthesis, while statins increased HMGCR activity, hepatic cholesterol synthesis, and fecal-neutral steroid excretion. MiR-206 facilitates the regression of hypercholesterolemia, hypertriglyceridemia, hyperglycemia, and hepatosteatosis. MiR-206 outperforms statins by reducing hyperglycemia, hepatic cholesterol levels, and hepatic toxicity.

Decreasing Intracellular Entropy by Increasing Mitochondrial Efficiency and Reducing ROS Formation-The Effect on the Ageing Process and Age-Related Damage

A hypothesis is presented to explain how the ageing process might be influenced by optimizing mitochondrial efficiency to reduce intracellular entropy. Research-based quantifications of entropy are scarce. Non-equilibrium metabolic reactions and compartmentalization were found to contribute most to lowering entropy in the cells. Like the cells, mitochondria are thermodynamically open systems exchanging matter and energy with their surroundings-the rest of the cell. Based on the calculations from cancer cells, glycolysis was reported to produce less entropy than mitochondrial oxidative phosphorylation. However, these estimations depended on the CO2 concentration so that at slightly increased CO2, it was oxidative phosphorylation that produced less entropy. Also, the thermodynamic efficiency of mitochondrial respiratory complexes varies depending on the respiratory state and oxidant/antioxidant balance. Therefore, in spite of long-standing theoretical and practical efforts, more measurements, also in isolated mitochondria, with intact and suboptimal respiration, are needed to resolve the issue. Entropy increases in ageing while mitochondrial efficiency of energy conversion, quality control, and turnover mechanisms deteriorate. Optimally functioning mitochondria are necessary to meet energy demands for cellular defence and repair processes to attenuate ageing. The intuitive approach of simply supplying more metabolic fuels (more nutrients) often has the opposite effect, namely a decrease in energy production in the case of nutrient overload. Excessive nutrient intake and obesity accelerate ageing, while calorie restriction without malnutrition can prolong life. Balanced nutrient intake adapted to needs/activity-based high ATP requirement increases mitochondrial respiratory efficiency and leads to multiple alterations in gene expression and metabolic adaptations. Therefore, rather than overfeeding, it is necessary to fine-tune energy production by optimizing mitochondrial function and reducing oxidative stress; the evidence is discussed in this paper.

Nutritional approaches targeting mitochondria for the prevention of sarcopenia

A decline in function and loss of mass, a condition known as sarcopenia, is observed in the skeletal muscles with aging. Sarcopenia has a negative effect on the quality of life of elderly. Individuals with sarcopenia are at particular risk for adverse outcomes, such as reduced mobility, fall-related injuries, and type 2 diabetes mellitus. Although the pathogenesis of sarcopenia is multifaceted, mitochondrial dysfunction is regarded as a major contributor for muscle aging. Hence, the development of preventive and therapeutic strategies to improve mitochondrial function during aging is imperative for sarcopenia treatment. However, effective and specific drugs that can be used for the treatment are not yet approved. Instead studies on the relationship between food intake and muscle aging have suggested that nutritional intake or dietary control could be an alternative approach for the amelioration of muscle aging. This narrative review approaches various nutritional components and diets as a treatment for sarcopenia by modulating mitochondrial homeostasis and improving mitochondria. Age-related changes in mitochondrial function and the molecular mechanisms that help improve mitochondrial homeostasis are discussed, and the nutritional components and diet that modulate these molecular mechanisms are addressed.

Drug-Induced Liver Injury in the Elderly: Consensus Statements and Recommendations from the IQ-DILI Initiative

The elderly demographic is the fastest-growing segment of the world's population and is projected to exceed 1.5 billion people by 2050. With multimorbidity, polypharmacy, susceptibility to drug-drug interactions, and frailty as distinct risk factors, elderly patients are especially vulnerable to developing potentially life-threatening safety events such as serious forms of drug-induced liver injury (DILI). It has been a longstanding shortcoming that elderly individuals are often a vulnerable population underrepresented in clinical trials. As such, an improved understanding of DILI in the elderly is a high-priority, unmet need. This challenge is underscored by recent documents put forward by the U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA) that encourage data collection in the elderly and recommend improved practices that will facilitate a more inclusive approach. To establish what is already known about DILI in the elderly and pinpoint key gaps of knowledge in this arena, a working definition of "elderly" is required that accounts for both chronologic and biologic ages and varying states of frailty. In addition, it is critical to characterize the biological role of aging on liver function, as well as the different epidemiological factors such as polypharmacy and inappropriate prescribing that are common practices. While data may not show that elderly people are more susceptible to DILI, DILI due to specific drugs might be more common in this population. Improved characterization of DILI in the elderly may enhance diagnostic and prognostic capabilities and improve the way in which liver safety is monitored during clinical trials. This summary of the published literature provides a framework to understand and evaluate the risk of DILI in the elderly. Consensus statements and recommendations can help to optimize medical care and catalyze collaborations between academic clinicians, drug manufacturers, and regulatory scientists to enable the generation of high-quality research data relevant to the elderly population.

Long-term suboptimal dietary trace element supply does not affect trace element homeostasis in murine cerebellum

The ageing process is associated with alterations of systemic trace element (TE) homeostasis increasing the risk, e.g. neurodegenerative diseases. Here, the impact of long-term modulation of dietary intake of copper, iron, selenium, and zinc was investigated in murine cerebellum. Four- and 40-wk-old mice of both sexes were supplied with different amounts of those TEs for 26 wk. In an adequate supply group, TE concentrations were in accordance with recommendations for laboratory mice while suboptimally supplied animals received only limited amounts of copper, iron, selenium, and zinc. An additional age-adjusted group was fed selenium and zinc in amounts exceeding recommendations. Cerebellar TE concentrations were measured by inductively coupled plasma-tandem mass spectrometry. Furthermore, the expression of genes involved in TE transport, DNA damage response, and DNA repair as well as selected markers of genomic stability [8-oxoguanine, incision efficiency toward 8-oxoguanine, 5-hydroxyuracil, and apurinic/apyrimidinic sites and global DNA (hydroxy)methylation] were analysed. Ageing resulted in a mild increase of iron and copper concentrations in the cerebellum, which was most pronounced in the suboptimally supplied groups. Thus, TE changes in the cerebellum were predominantly driven by age and less by nutritional intervention. Interestingly, deviation from adequate TE supply resulted in higher manganese concentrations of female mice even though the manganese supply itself was not modulated. Parameters of genomic stability were neither affected by age, sex, nor diet. Overall, this study revealed that suboptimal dietary TE supply does not substantially affect TE homeostasis in the murine cerebellum.

ELF5: A Molecular Clock for Breast Aging and Cancer Susceptibility

Breast cancer is predominantly an age-related disease, with aging serving as the most significant risk factor, compounded by germline mutations in high-risk genes like BRCA1/2. Aging induces architectural changes in breast tissue, particularly affecting luminal epithelial cells by diminishing lineage-specific molecular profiles and adopting myoepithelial-like characteristics. ELF5 is an important transcription factor for both normal breast and breast cancer development. This review focuses on the role of ELF5 in normal breast development, its altered expression throughout aging, and its implications in cancer. It discusses the lineage-specific expression of ELF5, its regulatory mechanisms, and its potential as a biomarker for breast-specific biological age and cancer risk.

The immunity and redox clocks in mice, markers of lifespan

Immune function and redox markers are used for estimating the aging rate, namely biological age (BA). However, it is unknown if this BA and its changes can be reflected in longevity. Thus, we must quantify BA in experimental animals. In peritoneal immune cells of 202 female mice (ICR/CD1) in different ages, 10 immune and 6 redox parameters were evaluated to construct two mathematical models for BA quantification in mice by multiple linear regression. Immune and redox parameters were selected as independent variables and chronological age as dependent, developing two models: the Immunity and the Redox Clocks, reaching both an adjusted R2 of 80.9% and a standard error of 6.38 and 8.57 weeks, respectively. Both models were validated in a different group of healthy mice obtaining a Pearson's correlation coefficient of 0.844 and 0.800 (p < 0.001) between chronological and BA. Furthermore, they were applied to adult prematurely aging mice, which showed a higher BA than non-prematurely aging mice. Moreover, after positive and negative lifestyle interventions, mice showed a lower and higher BA, respectively, than their age-matched controls. In conclusion, the Immunity and Redox Clocks allow BA quantification in mice and both the ImmunolAge and RedoxAge in mice relate to lifespan.

Mitochondria-induced formation of neutrophil extracellular traps is enhanced in the elderly via Toll-like receptor 9

Neutrophil extracellular traps are potent antimicrobial weapons; however, their formation during sterile inflammation is detrimental, and the mechanism of induction is still unclear. Since advanced age is the primary clinical risk factor for poor outcomes in inflammatory diseases, we hypothesized that sterile stimuli, represented by mitochondria, would induce neutrophil extracellular trap formation in an age-dependent manner. Therefore, we analyzed induction of neutrophil extracellular traps in patients grouped according to age or immune status and observed that neutrophils from elderly patients responded to the presence of mitochondria with enhanced neutrophil extracellular trap formation. These neutrophil extracellular traps were also found to be more oxidized and exhibited higher resistance to DNase I degradation. Additionally, a higher concentration of residual neutrophil extracellular traps was detected in the plasma of the elderly. This plasma was capable of priming neutrophils through TLR9-mediated signaling, leading to further neutrophil extracellular trap formation, which was successfully inhibited with chloroquine. Finally, in a mouse model of mitochondria-induced acute lung injury, we observed that neutrophils from aged mice displayed impaired chemotactic activity but exhibited a trend of higher neutrophil extracellular trap formation. Thus, we propose that residual neutrophil extracellular traps circulating in the elderly preactivate neutrophils, making them more prone to enhanced neutrophil extracellular trap formation when exposed to mitochondria during sterile inflammation. Further investigation is needed to determine whether this vicious circle could be a suitable therapeutic target.

Subcutaneous Infusion of DNA-Aptamer Raised against Advanced Glycation End Products Prevents Loss of Skeletal Muscle Mass and Strength in Accelerated-Aging Mice

We have developed DNA aptamers that can inhibit the toxic effects of advanced glycation end products (AGE-Apts). We herein evaluated the effects of AGE-Apts on muscle mass and strength in senescence-accelerated mouse prone 8 (SAMP8) mice. Eight-month-old male SAMP8 mice received subcutaneous infusion of control DNA aptamers (CTR-Apts) or AGE-Apts. Mice in an age-matched senescence-accelerated mouse resistant strain 1 (SAMR1) group were treated with CTR-Apts as controls. The soleus muscles were collected after the 8-week intervention for weight measurement and histological, RT-PCR, and immunofluorescence analyses. Grip strength was measured before and after the 8-week intervention. AGE-Apt treatment inhibited the progressive decrease in the grip strength of SAMP8 mice. SAMP8 mice had lower soleus muscle weight and fiber size than SAMR1 mice, which was partly restored by AGE-Apt treatment. Furthermore, AGE-Apt-treated SAMP8 mice had a lower interstitial fibrosis area of the soleus muscle than CTR-Apt-treated SAMP8 mice. The soleus muscle levels of AGEs, oxidative stress, receptor for AGEs, and muscle ring-finger protein-1 were increased in the CTR-Apt-treated mice, all of which, except for AGEs, were inhibited by AGE-Apt treatment. Our present findings suggest that the subcutaneous delivery of AGE-Apts may be a novel therapeutic strategy for aging-related decrease in skeletal muscle mass and strength.

Oxidative stress associated with spatial memory impairment and social olfactory deterioration in female mice reveals premature aging aroused by perinatal protein malnutrition

Early-life adversity, like perinatal protein malnutrition, increases the vulnerability to develop long-term alterations in brain structures and function. This study aimed to determine whether perinatal protein malnutrition predisposes to premature aging in a murine model and to assess the cellular and molecular mechanisms involved. To this end, mouse dams were fed either with a normal (NP, casein 20%) or a low-protein diet (LP, casein 8%) during gestation and lactation. Female offspring were evaluated at 2, 7 and 12 months of age. Positron emission tomography analysis showed alterations in the hippocampal CA3 region and the accessory olfactory bulb of LP mice during aging. Protein malnutrition impaired spatial memory, coinciding with higher levels of reactive oxygen species in the hippocampus and sirt7 upregulation. Protein malnutrition also led to higher senescence-associated β-galactosidase activity and p21 expression. LP-12-month-old mice showed a higher number of newborn neurons that did not complete the maturation process. The social-odor discrimination in LP mice was impaired along life. In the olfactory bulb of LP mice, the senescence marker p21 was upregulated, coinciding with a downregulation of Sirt2 and Sirt7. Also, LP-12-month-old mice showed a downregulation of catalase and glutathione peroxidase, and LP-2-month-old mice showed a higher number of newborn neurons in the subventricular zone, which then returned to normal values. Our results show that perinatal protein malnutrition causes long-term impairment in cognitive and olfactory skills through an accelerated senescence phenotype accompanied by an increase in oxidative stress and altered sirtuin expression in the hippocampus and olfactory bulb.

The Association of Tryptophan and Its Metabolites With Incident Hip Fractures, Mortality, and Prevalent Frailty in Older Adults: The Cardiovascular Health Study

Amino acids are the building blocks of proteins, and sufficient protein intake is important for skeletal health. We utilized stored serum from the Cardiovascular Health Study in 1992-1993 to examine the relationship between levels of the essential amino acid tryptophan (trp) and its oxidized and nonoxidized metabolites to risk for incident hip fractures and mortality over 12 years of follow-up. We included 131 persons who sustained a hip fracture during this time period and 131 without a hip fracture over these same 12 years of follow-up; 58% female and 95% White. Weighted multivariable Cox hazards models were used to estimate the hazard ratios (HR) and 95% confidence intervals (CI) of incident hip fracture associated with a one standard deviation (SD) higher trp or its metabolites exposure. Relative risk regression was used to evaluate the cross-sectional association of trp and its metabolites with frailty. Higher serum levels of trp were significantly associated with lower risk of incident hip fractures (HR = 0.75 per SD of trp (95% CI 0.57-0.99) but were not significantly associated with mortality or frailty status by Freid's frailty index. There were no statistically significant associations between any of the oxidized or nonoxidized products of trp with incident hip fractures (p ≥ 0.64), mortality (p ≥ 0.20), or cross-sectional frailty status (p ≥ 0.13) after multiple testing adjustment. Randomized clinical trials examining whether increasing trp intake is beneficial for osteoporosis are needed. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Discerning the Prospects of miRNAs as a Multi-Target Therapeutic and Diagnostic for Alzheimer's Disease

Although over the last few decades, numerous attempts have been made to halt Alzheimer's disease (AD) progression and mitigate its symptoms, only a few have been proven beneficial. Most medications available, still only cater to the symptoms of the disease rather than fixing the cause at the root level. A novel approach involving the use of miRNAs, which work on the principle of gene silencing, is being explored by scientists. Naturally present miRNAs in the biological system help to regulate various genes than may be implicated in AD-like BACE-1 and APP. One miRNA thus, holds the power to keep a check on several genes, conferring it the ability to be used as a multi-target therapeutic. With aging and the onset of diseased pathology, dysregulation of these miRNAs is observed. This flawed miRNA expression is responsible for the unusual buildup of amyloid proteins, fibrillation of tau proteins in the brain, neuronal death and other hallmarks leading to AD. The use of miRNA mimics and miRNA inhibitors provides an attractive perspective for fixing the upregulation and downregulation of miRNAs that led to abnormal cellular activities. Furthermore, the detection of miRNAs in the CSF and serum of diseased patients might be considered an earlier biomarker for the disease. While most of the therapies designed around AD have not succeeded completely, the targeting of dysregulated miRNAs in AD patients might give a new direction to scholars to develop an effective treatment for Alzheimer's disease.

Ageing-associated phenotypes in mice

Ageing is a continuous process in life featuring progressive damage accumulation that leads to physiological decline, functional deterioration and ultimately death of an organism. Based on the relatively close anatomical and physiological similarity to humans, the mouse has been proven as a valuable model organism in ageing research over the last decades. In this review, we survey methods and tools currently in use to assess ageing phenotypes in mice. We summarize a range of ageing-associated alterations detectable at two major levels of analysis: (1) physiology and pathophysiology and (2) molecular biomarkers. Age-sensitive phenotypes provided in this article may serve to inform future studies targeting various aspects of organismal ageing in mice. In addition, we discuss conceptual and technical challenges faced by previous ageing studies in mice and, where possible, provide recommendations on how to resolve some of these issues.

Exploring the therapeutic potential of the mitochondrial transfer-associated enzymatic machinery in brain degeneration

Mitochondrial dysfunction is a central event in the pathogenesis of several degenerative brain disorders. It entails fission and fusion dynamics disruption, progressive decline in mitochondrial clearance, and uncontrolled oxidative stress. Many therapeutic strategies have been formulated to reverse these alterations, including replacing damaged mitochondria with healthy ones. Spontaneous mitochondrial transfer is a naturally occurring process with different biological functions. It comprises mitochondrial donation from one cell to another, carried out through different pathways, such as the formation and stabilization of tunneling nanotubules and Gap junctions and the release of extracellular vesicles with mitochondrial cargoes. Even though many aspects of regulating these mechanisms still need to be discovered, some key enzymatic regulators have been identified. This review summarizes the current knowledge on mitochondrial dysfunction in different neurodegenerative disorders. Besides, we analyzed the usage of mitochondrial transfer as an endogenous revitalization tool, emphasizing the enzyme regulators that govern this mechanism. Going deeper into this matter would be helpful to take advantage of the therapeutic potential of mitochondrial transfer.

Taurine deficiency as a driver of aging

Aging is associated with changes in circulating levels of various molecules, some of which remain undefined. We find that concentrations of circulating taurine decline with aging in mice, monkeys, and humans. A reversal of this decline through taurine supplementation increased the health span (the period of healthy living) and life span in mice and health span in monkeys. Mechanistically, taurine reduced cellular senescence, protected against telomerase deficiency, suppressed mitochondrial dysfunction, decreased DNA damage, and attenuated inflammaging. In humans, lower taurine concentrations correlated with several age-related diseases and taurine concentrations increased after acute endurance exercise. Thus, taurine deficiency may be a driver of aging because its reversal increases health span in worms, rodents, and primates and life span in worms and rodents. Clinical trials in humans seem warranted to test whether taurine deficiency might drive aging in humans.

DNA damage-induced stalling of transcription drives aging through gene expression imbalance

Age-related changes in gene expression have long been examined to understand the biology of aging. The hallmarks of aging are biological processes known to be associated with aging, but whether there is a unifying driver of these attributes, is not well understood. With the advent of technology over the last few years, it is quite clear that aging leads to global decline in transcription. In this Perspective, we highlight a new study in Nature Genetics that aimed to determine why global transcription rate reduces with age and how this phenomenon is the driver that interconnects multiple hallmarks of aging. This study recognizes that age-related accumulation of DNA damage, particularly transcription-blocking lesions, stalls RNA polymerase. This phenomenon affects longer genes leading to a gradual loss of transcription and skewing the transcriptome. In order to design a successful aging intervention, future work will be needed to test how some promising therapies in pre-clinical trials target affect transcriptional rate.

Hematopoietic Stem Cells and the Immune System in Development and Aging

Hematopoietic stem cells (HSCs) support haematopoiesis throughout life and give rise to the whole variety of cells of the immune system. Developing in the early embryo, passing through the precursor stage, and maturing into the first HSCs, they undergo a fairly large number of divisions while maintaining a high regenerative potential due to high repair activity. This potential is greatly reduced in adult HSCs. They go into a state of dormancy and anaerobic metabolism to maintain their stemness throughout life. However, with age, changes occur in the pool of HSCs that negatively affect haematopoiesis and the effectiveness of immunity. Niche aging and accumulation of mutations with age reduces the ability of HSCs to self-renew and changes their differentiation potential. This is accompanied by a decrease in clonal diversity and a disturbance of lymphopoiesis (decrease in the formation of naive T- and B-cells) and the predominance of myeloid haematopoiesis. Aging also affects mature cells, regardless of HSC, therefore, phagocytic activity and the intensity of the oxidative burst decrease, and the efficiency of processing and presentation of antigens by myeloid cells is impaired. Aging cells of innate and adaptive immunity produce factors that form a chronic inflammatory background. All these processes have a serious negative impact on the protective properties of the immune system, increasing inflammation, the risk of developing autoimmune, oncological, and cardiovascular diseases with age. Understanding the mechanisms of reducing the regenerative potential in a comparative analysis of embryonic and aging HSCs, the features of inflammatory aging will allow us to get closer to deciphering the programs for the development, aging, regeneration and rejuvenation of HSCs and the immune system.

Cellular mechanisms in brain aging: Focus on physiological and pathological aging

Aging is a natural phenomenon characterized by accumulation of cellular damage and debris. Oxidative stress, cellular senescence, sustained inflammation, and DNA damage are the main cellular processes characteristic of aging associated with morphological and functional decline. These effects tend to be more pronounced in tissues with high metabolic rates such as the brain, mainly in regions such as the prefrontal cortex, hippocampus, and amygdala. These regions are highly related to cognitive behavior, and therefore their atrophy usually leads to decline in processes such as memory and learning. These cognitive declines can occur in physiological aging and are exacerbated in pathological aging. In this article, we review the cellular processes that underlie the triggers of aging and how they relate to one another, causing the atrophy of nerve tissue that is typical of aging. The main topic of this review to determine the central factor that triggers all the cellular processes that lead to cellular aging and discriminate between normal and pathological aging. Finally, we review how the use of supplements with antioxidant and anti-inflammatory properties reduces the cognitive decline typical of aging, which reinforces the hypothesis of oxidative stress and cellular damage as contributors of physiological atrophy of aging. Moreover, cumulative evidence suggests their possible use as therapies, which improve the aging population's quality of life.

A Chemoptogenetic Tool for Spatiotemporal Induction of Oxidative DNA Lesions In Vivo

Oxidative nuclear DNA damage increases in all tissues with age in multiple animal models, as well as in humans. However, the increase in DNA oxidation varies from tissue to tissue, suggesting that certain cells/tissues may be more vulnerable to DNA damage than others. The lack of a tool that can control dosage and spatiotemporal induction of oxidative DNA damage, which accumulates with age, has severely limited our ability to understand how DNA damage drives aging and age-related diseases. To overcome this, here we developed a chemoptogenetic tool that produces 8-oxoguanine (8-oxoG) at DNA in a whole organism, Caenorhabditis elegans. This tool uses di-iodinated malachite green (MG-2I) photosensitizer dye that generates singlet oxygen, 1O2, upon fluorogen activating peptide (FAP) binding and excitation with far-red light. Using our chemoptogenetic tool, we are able to control generation of singlet oxygen ubiquitously or in a tissue-specific manner, including in neurons and muscle cells. To induce oxidative DNA damage, we targeted our chemoptogenetic tool to histone, his-72, that is expressed in all cell types. Our results show that a single exposure to dye and light is able to induce DNA damage, promote embryonic lethality, lead to developmental delay, and significantly reduce lifespan. Our chemoptogenetic tool will now allow us to assess the cell autonomous versus non-cell autonomous role of DNA damage in aging, at an organismal level.

Paullinia cupana seed extract ameliorated methotrexate-induced testicular dysfunction through the regulation of antioxidants, inflammatory, apoptosis/anti-apoptosis, and steroidogenesis-associated genes

Methotrexate (MXT) is a medication used for cancer and rheumatoid treatment with severe organs toxicity as a side effect. Paullinia cupana (Guarana) is a plant with pleiotropic functions used to overcome the side effects of some chemotherapeutic medications. Current study aimed to examine the possible protective effect of guarana against oxidative stress induced by a single dose of MTX in testis. Forty male mice were divided into 4 groups (8 weeks old; 30 g weight), 1st group is negative control. The 2nd group is positive intoxicated group, received a single dose of MTX intraperitoneally (IP; 20 mg/kg BW in saline) on day 7. The 3rd group received guarana seed extract orally (300 mg/kg BW daily) for 12 days. The protective group was given guarana seed extract orally for 1 week, then on day 7 injected with MTX, and continued with guarana for extra 5 days. Blood was taken for biochemical measurement (hormones, antioxidants, cytokines, and oxidative stress biomarkers). Testicular tissues were taken for gene quantification (qRT-PCR), testicular oxidative stress activity (malondialdehyde; MDA, and SOD) and comet assay (sperm DNA damage), and histopathological changes at the end of experimental design. MTX intoxication caused a decrease in testicular SOD, GSH, and catalase and an increase in serum and tissue levels of MDA. Biomarkers of oxidative stress were increased by MTX intoxication, and were ameliorated by guarana administration to MTX-intoxicated mice. Guarana prevented the increase in IL-1β and IL-6 levels compared to mice intoxicated with MTX alone. MTX upregulated the expression of caspase-3 and downregulated Bcl-2 expression using qRT-PCR analysis. These negative impacts of MTX were protected by guarana pre-administration. MTX decreased reproductive hormones and altered spermogram parameters (sperm concentration and motility, and percentage of live and dead sperms). In addition, the mRNA expression of steroidogenesis-associated genes, such cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc), and 17β hydroxyl steroid dehydrogenase (17β-HSD) was downregulated in the MTX-treated group, all were prevented by guarana administration. The sperm DNA damage revealed by a comet assay was increased in MTX group and was reversed to control levels by guarana supplementation. Finally, testis histology of MTX-group showed marked spermatocytes vacuolization and a decrease in spermatogenesis. Guarana administration abrogated histopathological changes reported in the Leydig cells and testicular tissues. In conclusion, guarana has the potential as a supplement medication to antagonize testicular oxidative stress induced by methotrexate.

Links between COVID-19 and Alzheimer's Disease-What Do We Already Know?

Alzheimer's disease (AD) is a life-changing condition whose etiology is explained by several hypotheses. Recently, a new virus contributed to the evidence of viral involvement in AD: the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes the COVID-19 coronavirus disease. AD was found to be one of the most common COVID-19 comorbidities, and it was found to increase mortality from this disease as well. Moreover, AD patients were observed to present with the distinct clinical features of COVID-19, with delirium being prevalent in this group. The SARS-CoV-2 virus enters host cells through the angiotensin-converting enzyme 2 (ACE2) receptor. ACE2 is overexpressed in brains with AD, which thus increases the viral invasion. Furthermore, the inhibition of the ACE2 receptor by the SARS-CoV-2 virus may also decrease the brain-derived neurotrophic factor (BDNF), contributing to neurodegeneration. The ApoE ε4 allele, which increases the risk of AD, was found to facilitate the SARS-CoV-2 entry into cells. Furthermore, the neuroinflammation and oxidative stress existing in AD patients enhance the inflammatory response associated with COVID-19. Moreover, pandemic and associated social distancing measures negatively affected the mental health, cognitive function, and neuro-psychiatric symptoms of AD patients. This review comprehensively covers the links between COVID-19 and Alzheimer's disease, including clinical presentation, molecular mechanisms, and the effects of social distancing.

Role of primary aging hallmarks in Alzheimer´s disease

Alzheimer's disease (AD) is the most common neurodegenerative disease, which severely threatens the health of the elderly and causes significant economic and social burdens. The causes of AD are complex and include heritable but mostly aging-related factors. The primary aging hallmarks include genomic instability, telomere wear, epigenetic changes, and loss of protein stability, which play a dominant role in the aging process. Although AD is closely associated with the aging process, the underlying mechanisms involved in AD pathogenesis have not been well characterized. This review summarizes the available literature about primary aging hallmarks and their roles in AD pathogenesis. By analyzing published literature, we attempted to uncover the possible mechanisms of aberrant epigenetic markers with related enzymes, transcription factors, and loss of proteostasis in AD. In particular, the importance of oxidative stress-induced DNA methylation and DNA methylation-directed histone modifications and proteostasis are highlighted. A molecular network of gene regulatory elements that undergoes a dynamic change with age may underlie age-dependent AD pathogenesis, and can be used as a new drug target to treat AD.

Association of buccal micronucleus cytome assay (BMNCyt) biomarkers with inorganic element concentration and genetic polymorphisms in welders

Welding fumes are classified as carcinogenic to humans. The aim of the present study was to measure buccal micronucleus cytome assay biomarkers and to evaluate their association with inorganic elements and genetic polymorphisms (XRCC1, OGG1, XRCC3, GSTM1, and GSTT1) in welders (n = 98) and control individuals (n = 100). Higher levels of DNA damage and cell death were observed in the exposed group. Also, a significant correlation between the frequency of micronuclei and Na, Si, Cl, Ti, Cr, Zn and Mg concentrations. The formation of micronuclei, binucleated cells, cell death was associated with polymorphisms in repair pathways. The OGG1Ser326Cys and XRCC3 241Thr/Met genotypes were associated with cell death. Individuals with GSTM1 null genotype had a higher frequency of micronuclei. These results demonstrate that the deleterious effects of exposure to welding fumes are exacerbated by lifestyle habits, and genetic polymorphisms can influence DNA damage and cell death.

Natural Compounds That Enhance Motor Function in a Mouse Model of Muscle Fatigue

Musculoskeletal disease can be a serious condition associated with aging that may lead to fractures and a bedridden state due to decreased motor function. In addition to exercise training to increase muscle mass, increasing muscle function with the intake of functional foods is an effective treatment strategy for musculoskeletal disease. Muscle-specific SOD2-deficient mice (muscle-Sod2^-/-) show a severe disturbance in exercise in association with increased mitochondrial reactive oxygen species, as well as mitochondrial dysfunction and muscle damage. In the present study, to develop a therapeutic strategy for musculoskeletal disease, we searched for substances that enhanced motor function among functional compounds by in vivo screening using muscle-Sod2^-/- mice as a muscle fatigue model. We administered 96 compounds, including antioxidants, to muscle-Sod2^-/- mice and assessed their effects on treadmill performance. Among the administered compounds, gossypin, genistein, kaempferol, taxifolin, fumaric acid, β-hydroxy-β-methylbutyrate Ca, and astaxanthin, which are dietary functional food factors, increased forced running time in muscle-Sod2^-/- mice. In addition, troglitazone, tempol, trolox, and MnTE-2-PyP, which are antioxidants, also significantly increased the running ability of muscle-Sod2^-/- mice. These results suggest that the intake of functional foods with antioxidant activity can improve motor function. Muscle-Sod2^-/- mice, as a muscle fatigue model, are suitable for the in vivo screening of functional substances that promote improvements in exercise and muscle performance.

Pathological Nuclear Hallmarks in Dentate Granule Cells of Alzheimer’s Patients: A Biphasic Regulation of Neurogenesis

The dentate gyrus (DG) of the human hippocampus is a complex and dynamic structure harboring mature and immature granular neurons in diverse proliferative states. While most mammals show persistent neurogenesis through adulthood, human neurogenesis is still under debate. We found nuclear alterations in granular cells in autopsied human brains, detected by immunohistochemistry. These alterations differ from those reported in pyramidal neurons of the hippocampal circuit. Aging and early AD chromatin were clearly differentiated by the increased epigenetic markers H3K9me3 (heterochromatin suppressive mark) and H3K4me3 (transcriptional euchromatin mark). At early AD stages, lamin B2 was redistributed to the nucleoplasm, indicating cell-cycle reactivation, probably induced by hippocampal nuclear pathology. At intermediate and late AD stages, higher lamin B2 immunopositivity in the perinucleus suggests fewer immature neurons, less neurogenesis, and fewer adaptation resources to environmental factors. In addition, senile samples showed increased nuclear Tau interacting with aged chromatin, likely favoring DNA repair and maintaining genomic stability. However, at late AD stages, the progressive disappearance of phosphorylated Tau forms in the nucleus, increased chromatin disorganization, and increased nuclear autophagy support a model of biphasic neurogenesis in AD. Therefore, designing therapies to alleviate the neuronal nuclear pathology might be the only pathway to a true rejuvenation of brain circuits.

A Human MSH6 Germline Variant Associated With Systemic Lupus Erythematosus Induces Lupus-like Disease in Mice

OBJECTIVE

To determine if single-nucleotide polymorphisms (SNPs) in DNA repair genes are enriched in individuals with systemic lupus erythematosus (SLE) and if they are sufficient to confer a disease phenotype in a mouse model.

METHODS

Human exome chip data of 2499 patients with SLE and 1230 healthy controls were analyzed to determine if variants in 10 different mismatch repair genes (MSH4, EXO1, MSH2, MSH6, MLH1, MSH3, POLH, PMS2, ML3, and APEX2) were enriched in individuals with SLE. A mouse model of the MSH6 SNP, which was found to be enriched in individuals with SLE, was created using CRISPR/Cas9 gene targeting. Wildtype mice and mice heterozygous and homozygous for the MSH6 variant were then monitored for 2 years for the development of autoimmune phenotypes, including the presence of high levels of antinuclear antibodies (ANA). Additionally, somatic hypermutation frequencies and spectra of the intronic region downstream of the VH J558-rearranged JH4 immunoglobulin gene was characterized from Peyer's patches.

RESULTS

Based on the human exome chip data, the MSH6 variant (rs63750897, p.Ser503Cys) is enriched among patients with SLE versus controls after we corrected for ancestry (odds ratio = 8.39, P = 0.0398). Mice homozygous for the MSH6 variant (Msh6S502C/S502C ) harbor significantly increased levels of ANA. Additionally, the Msh6S502C/S502C mice display a significant increase in the infiltration of CD68+ cells (a marker for monocytes and macrophages) into the lung alveolar space as well as apoptotic cells. Furthermore, characterization of somatic hypermutation in these mice reveals an increase in the DNA polymerase η mutational signature.

CONCLUSION

An MSH6 mutation that is enriched in humans diagnosed with lupus was identified. Mice harboring this Msh6 mutation develop increased autoantibodies and an inflammatory lung disease. These results suggest that the human MSH6 variant is linked to the development of SLE.

Downregulating Mitochondrial DNA Polymerase γ in the Muscle Stimulated Autophagy, Apoptosis, and Muscle Aging-Related Phenotypes in Drosophila Adults

Reactive oxygen species, generated as by-products of mitochondrial electron transport, can induce damage to mitochondrial DNA (mtDNA) and proteins. Here, we investigated whether the moderate accumulation of mtDNA damage in adult muscles resulted in accelerated aging-related phenotypes in Drosophila. DNA polymerase γ (Polγ) is the sole mitochondrial DNA polymerase. The muscle-specific silencing of the genes encoding the polymerase subunits resulted in the partial accumulation of mtDNA with oxidative damage and a reduction in the mtDNA copy number. This subsequently resulted in the production of abnormal mitochondria with reduced membrane potential and, consequently, a partially reduced ATP quantity in the adult muscle. Immunostaining indicated a moderate increase in autophagy and mitophagy in adults with RNA interference of Polγ (PolγRNAi) muscle cells with abnormal mitochondria. In adult muscles showing continuous silencing of Polγ, malformation of both myofibrils and mitochondria was frequently observed. This was associated with the partially enhanced activation of pro-apoptotic caspases in the muscle. Adults with muscle-specific PolγRNAi exhibited a shortened lifespan, accelerated age-dependent impairment of locomotor activity, and disturbed circadian rhythms. Our findings in this Drosophila model contribute to understanding how the accumulation of mtDNA damage results in impaired mitochondrial activity and how this contributes to muscle aging.

Oxidative Stress, Mitochondrial Dysfunction, and Premature Ageing in Severe Acute Malnutrition in Under-Five Children

OBJECTIVES

To assess oxidative stress, mitochondrial dysfunction, and premature ageing in children with severe acute malnutrition (SAM).

METHODS

This cross-sectional study was conducted in children (1 mo-5 y) with SAM (defined as per WHO criteria) presenting to Pediatrics inpatient department. Oxidative stress, mitochondrial dysfunction, and premature ageing were assessed by measuring and comparing total antioxidant status (TAOS), mitochondrial DNA (mtDNA) content, and telomere length (TL), respectively in 40 under-five children with SAM and 40 age- and sex-matched non-malnourished controls.

RESULTS

Oxidative stress was significantly increased in children with SAM, reflected by lower median (IQR) TAOS in cases as compared to controls [10.78 (9.08, 12.3) vs. 16.63 (15.20, 18.03) mM Trolox, p < 0.001]. Median (IQR) mtDNA content was significantly increased in children with SAM [188.7 (105.2, 398.9) vs. 116.2 (67.2, 154.6), p < 0.001]. There was no significant difference in telomere length between cases and controls [1184.5 (894, 1408) vs.1082.6 (823.3, 1479), p = 0.747].

CONCLUSION

Children with SAM had significantly increased oxidative stress that possibly caused mitochondrial dysfunction but no premature ageing.

3,3'-Diindolylmethane Supplementation Maintains Oocyte Quality by Reducing Oxidative Stress and CEP-1/p53-Mediated Regulation of Germ Cells in a Reproductively Aged Caenorhabditis elegans Model

In recent decades, maternal age at first birth has increased, as has the risk of infertility due to rapidly declining oocyte quality with age. Therefore, an understanding of female reproductive aging and the development of potential modulators to control oocyte quality are required. In this study, we investigated the effects of 3,3'-diindolylmethane (DIM), a natural metabolite of indole-3-cabinol found in cruciferous vegetables, on fertility in a Caenorhabditis elegans model. C. elegans fed DIM showed decreased mitochondrial dysfunction, oxidative stress, and chromosomal aberrations in aged oocytes, and thus reduced embryonic lethality, suggesting that DIM, a dietary natural antioxidant, improves oocyte quality. Furthermore, DIM supplementation maintained germ cell apoptosis (GCA) and germ cell proliferation (GCP) in a CEP-1/p53-dependent manner in a reproductively aged C. elegans germ line. DIM-induced GCA was mediated by the CEP-1-EGL-1 pathway without HUS-1 activation, suggesting that DIM-induced GCA is different from DNA damage-induced GCA in the C. elegans germ line. Taken together, we propose that DIM supplementation delays the onset of reproductive aging by maintaining the levels of GCP and GCA and oocyte quality in a reproductively aged C. elegans.

Long-term effects of melatonin and resveratrol on aging rats: A multi-biomarker approach

Aging-related impaired body structure and functions may be, at least partially, caused by elevated oxidative stress. Melatonin (MEL) and resveratrol (RSV) may act as antioxidant and anti-aging compounds, but these actions in experimental animals and humans are controversial. Herein, a rat model of aging was used to study the long-term sex-related effects of MEL and RSV treatment on body mass and blood/plasma parameters of DNA damage, oxidative status (glutathione and malondialdehyde levels), and concentrations of sex hormones. Starting from the age of 3mo, for the next 9mo or 21mo male and female Wistar rats (n = 4-7 per group) were given water to drink (controls) or 0.1 % ethanol in water (vehicle), or MEL or RSV (each 10 mg/L vehicle). DNA damage in whole blood cells was tested by comet assay, whereas in plasma, glutathione, malondialdehyde, and sex hormones were determined by established methods. Using statistical analysis of data by ANOVA/Scheffe post hoc, we observed a similar sex- and aging-dependent rise of body mass in both sexes and drop of plasma testosterone in control and vehicle-treated male rats, whose pattern remained unaffected by MEL and RSV treatment. Compared with controls, all other parameters remained largely unchanged in aging and differently treated male and female rats. We concluded that the sex- and aging-related pattern of growth and various blood parameters in rats were not affected by the long-term treatment with MEL and RSV at the estimated daily doses (300-400 μg/kg b.m.) that exceed usual moderate consumption in humans.

Epigenetic Changes and Its Intervention in Age-Related Neurodegenerative Diseases

Epigenetic mechanisms involving the modulation of gene activity without modifying the DNA bases are reported to have lifelong effects on mature neurons in addition to their impact on synaptic plasticity and cognition. Histone methylation and acetylation are involved in synchronizing gene expression and protein function in neuronal cells. Studies have demonstrated in experimental models of neurodegenerative disorders that manipulations of these two mechanisms influence the susceptibility of neurons to degeneration and apoptosis. In Alzheimer's disease (AD), the expression of presenilin 1 (PSEN1) is markedly increased due to decreased methylation at CpG sites, thus promoting the accumulation of toxic amyloid-β (Aβ) peptide. In Parkinson's disease (PD), dysregulation of α-synuclein (SNCA) expression is presumed to occur via aberrant methylation at CpG sites, which controls the activation or suppression of protein expression. Mutant Huntingtin (mtHTT) alters the activity of histone acetyltransferases (HATs), causing the dysregulation of transcription observed in most Huntington's disease (HD) cases. Folate, vitamin B6, vitamin B12, and S-adenosylmethionine (SAM) are vital cofactors involved in DNA methylation modification; 5-azacytidine (AZA) is the most widely studied DNA methyltransferase (DNMT) inhibitor, and dietary polyphenols are DNMT inhibitors in vitro. Drug intervention is believed to reverse the epigenetic mechanisms to serve as a regulator in neuronal diseases. Nevertheless, the biochemical effect of the drugs on brain function and the underlying mechanisms are not well understood. This review focuses on further discussion of therapeutic targets, emphasizing the potential role of epigenetic factors including histone and DNA modifications in the diseases.

The oxidatively damaged DNA and amyloid-β oligomer hypothesis of Alzheimer's disease

The amyloid-β (Aβ) oligomer hypothesis of Alzheimer's disease (AD) still dominates the field, yet the clinical trial evidence does not robustly support it. A falsifiable prediction of the hypothesis is that Aβ oligomer levels should be elevated in the brain regions and at the disease stages where and when neuron death and synaptic protein loss begin and are the most severe, but we review previous evidence to demonstrate that this is not consistently the case. To rescue the Aβ oligomer hypothesis from falsification, we propose the novel ad-hoc hypothesis that the exceptionally vulnerable hippocampus may normally produce Aβ peptides even in healthily aging individuals, and hippocampal oxidatively damaged DNA, pathogen DNA, and metal ions such as zinc may initiate and drive Aβ peptide aggregation into oligomers and spreading, neuron death, synaptic dysfunction, and other aspects of AD neurodegeneration. We highlight additional evidence consistent with the underwhelming efficacy of Aβ oligomer-lowering agents, such as aducanumab, and of antioxidants, such as vitamin E, versus the so far isolated case report that DNase-I treatment for 2 months resulted in a severe AD patient's Mini-Mental State Exam score increasing from 3 to 18, reversing his diagnosis to moderate AD, according to the Mini-Mental State Exam.

Effects of prenatal testosterone on cumulative markers of oxidative damage to organs of young adult zebra finches (Taeniopygia guttata)

We tested the hypothesis that exposure of avian embryos to androgens in ovo entails long-term costs in the form of oxidative damage to vital cells and organs in adulthood. We injected zebra finch eggs with testosterone (T), monitored postnatal growth, and analyzed markers of oxidative damage in heart and liver in mature birds. We measured 8-oxo-2'-deoxyguanosine and isoprostanes, markers of oxidative damage to DNA and membrane lipids, respectively. T treatment (1) reduced growth rates of female but not male nestlings vs. controls; (2) resulted in less accumulation of 8-oxo-dG, but not IsoPs, in liver tissue of 60-day-old females, but not males; and (3) a trend toward elevated 8-oxo-dG levels in heart tissue of males and females at 60 and 180 days old combined. These results generally support the testosterone oxidative damage hypothesis, in that embryonic exposure to higher T resulted in damage to DNA of heart tissue in both sexes. They also suggest that sex-specific effects of androgens on early growth rates may carry over as differences in some forms of oxidative damage in adults. This supports a basic tenet of evolutionary aging theory that developmental influences early in life can be linked to costs later on.

Cisd2 slows down liver aging and attenuates age-related metabolic dysfunction in male mice

The liver plays a pivotal role in mammalian aging. However, the mechanisms underlying liver aging remain unclear. Cisd2 is a pro‐longevity gene in mice. Cisd2 mediates lifespan and healthspan via regulation of calcium homeostasis and mitochondrial functioning. Intriguingly, the protein level of Cisd2 is significantly decreased by about 50% in the livers of old male mice. This down‐regulation of Cisd2 may result in the aging liver exhibiting non‐alcoholic fatty liver disease (NAFLD) phenotype. Here, we use Cisd2 transgenic mice to investigate whether maintaining Cisd2 protein at a persistently high level is able to slow down liver aging. Our study identifies four major discoveries. Firstly, that Cisd2 expression attenuates age‐related dysregulation of lipid metabolism and other pathological abnormalities. Secondly, revealed by RNA sequencing analysis, the livers of old male mice undergo extensive transcriptomic alterations, and these are associated with steatosis, hepatitis, fibrosis, and xenobiotic detoxification. Intriguingly, a youthful transcriptomic profile, like that of young 3‐month‐old mice, was found in old Cisd2 transgenic male mice at 26 months old. Thirdly, Cisd2 suppresses the age‐associated dysregulation of various transcription regulators (Nrf2, IL‐6, and Hnf4a), which keeps the transcriptional network in a normal pattern. Finally, a high level of Cisd2 protein protects the liver from oxidative stress, and this is associated with a reduction in mitochondrial DNA deletions. These findings demonstrate that Cisd2 is a promising target for the development of therapeutic agents that, by bringing about an effective enhancement of Cisd2 expression, will slow down liver aging.

Redox Dysregulation in Aging and COPD: Role of NOX Enzymes and Implications for Antioxidant Strategies

With a rapidly growing elderly human population, the incidence of age-related lung diseases such as chronic obstructive pulmonary disease (COPD) continues to rise. It is widely believed that reactive oxygen species (ROS) play an important role in ageing and in age-related disease, and approaches of antioxidant supplementation have been touted as useful strategies to mitigate age-related disease progression, although success of such strategies has been very limited to date. Involvement of ROS in ageing is largely attributed to mitochondrial dysfunction and impaired adaptive antioxidant responses. NADPH oxidase (NOX) enzymes represent an important enzyme family that generates ROS in a regulated fashion for purposes of oxidative host defense and redox-based signalling, however, the associations of NOX enzymes with lung ageing or age-related lung disease have to date only been minimally addressed. The present review will focus on our current understanding of the impact of ageing on NOX biology and its consequences for age-related lung disease, particularly COPD, and will also discuss the implications of altered NOX biology for current and future antioxidant-based strategies aimed at treating these diseases.

Senescent cells in 3D culture show suppressed senescence signatures

Cellular senescence, an irreversible proliferation arrested but viable cellular state, has been implicated in the progression of several age-associated pathologies. A vast amount of information about senescence has been acquired in cultured cells; however, senescence in living organisms (in vivo) remains poorly understood, mainly because of technical limitations. Furthermore, it is now widely recognized that three-dimensional (3D) culture systems are a better mimic of the in vivo physiology. Herein, senescence was induced in HeLa cells by irradiation. Non-senescent or senescent cells were cultured in soft 3D polymer scaffolds and compared with cells in conventional two-dimensional (2D) culture. This work shows that the morphology of the senescent cells markedly varies between substrates/culture platforms, driving the differences in the cytoskeletal organization, cellular division, and nanomechanical properties. One characteristic feature of senescent cells on 2D culture systems is the enlarged and flattened morphology; however, such drastic changes are not seen in vivo. This is an artificial effect of the substrate, which renders such non-physiological morphology to senescent cells. In the 3D scaffolds, this artifact is reduced. Hence, it serves as a better mimic of tissues, leading to reduced expression of senescence-associated genes, implying that the 3D scaffolds suppress the senescence in cells.

Phospho-Tau and Chromatin Landscapes in Early and Late Alzheimer's Disease

Cellular identity is determined through complex patterns of gene expression. Chromatin, the dynamic structure containing genetic information, is regulated through epigenetic modulators, mainly by the histone code. One of the main challenges for the cell is maintaining functionality and identity, despite the accumulation of DNA damage throughout the aging process. Replicative cells can remain in a senescent state or develop a malign cancer phenotype. In contrast, post-mitotic cells such as pyramidal neurons maintain extraordinary functionality despite advanced age, but they lose their identity. This review focuses on tau, a protein that protects DNA, organizes chromatin, and plays a crucial role in genomic stability. In contrast, tau cytosolic aggregates are considered hallmarks of Alzheimer´s disease (AD) and other neurodegenerative disorders called tauopathies. Here, we explain AD as a phenomenon of chromatin dysregulation directly involving the epigenetic histone code and a progressive destabilization of the tau–chromatin interaction, leading to the consequent dysregulation of gene expression. Although this destabilization could be lethal for post-mitotic neurons, tau protein mediates profound cellular transformations that allow for their temporal survival.