Hydrogen peroxide release by mitochondria increases during aging

Two faces of one coin: Beneficial and deleterious effects of reactive oxygen species during short-term acclimation to hypo-osmotic stress in a decapod crab

Exposure to environmental changes often results in the production of reactive oxygen species (ROS), which, if uncontrolled, leads to loss of cellular homeostasis and oxidative distress. However, at physiological levels these same ROS are known to be key players in cellular signaling and the regulation of key biological activities (oxidative eustress). While ROS are known to mediate salinity tolerance in plants, little is known for the animal kingdom. In this study, we use the Mediterranean crab Carcinus aestuarii, highly tolerant to salinity changes in its environment, as a model to test the healthy or pathological role of ROS due to exposure to diluted seawater (dSW). Crabs were injected either with an antioxidant [N-acetylcysteine (NAC), 150 mg·kg-1] or phosphate buffered saline (PBS). One hour after the first injection, animals were either maintained in seawater (SW) or transferred to dSW and injections were carried out at 12-h intervals. After ≈48 h of salinity change, all animals were sacrificed and gills dissected for analysis. NAC injections successfully inhibited ROS formation occurring due to dSW transfer. However, this induced 55% crab mortality, as well as an inhibition of the enhanced catalase defenses and mitochondrial biogenesis that occur with decreased salinity. Crab osmoregulatory capacity under dSW condition was not affected by NAC, although it induced in anterior (non-osmoregulatory) gills a 146-fold increase in Na+/K+/2Cl- expression levels, reaching values typically observed in osmoregulatory tissues. We discuss how ROS influences the physiology of anterior and posterior gills, which have two different physiological functions and strategies during hyper-osmoregulation in dSW.

Mitochondrial Dysfunction: A Roadmap for Understanding and Tackling Cardiovascular Aging

Cardiovascular aging is a progressive remodeling process constituting a variety of cellular and molecular alterations that are closely linked to mitochondrial dysfunction. Therefore, gaining a deeper understanding of the changes in mitochondrial function during cardiovascular aging is crucial for preventing cardiovascular diseases. Cardiac aging is accompanied by fibrosis, cardiomyocyte hypertrophy, metabolic changes, and infiltration of immune cells, collectively contributing to the overall remodeling of the heart. Similarly, during vascular aging, there is a profound remodeling of blood vessel structure. These remodeling present damage to endothelial cells, increased vascular stiffness, impaired formation of new blood vessels (angiogenesis), the development of arteriosclerosis, and chronic vascular inflammation. This review underscores the role of mitochondrial dysfunction in cardiac aging, exploring its impact on fibrosis and myocardial alterations, metabolic remodeling, immune response remodeling, as well as in vascular aging in the heart. Additionally, we emphasize the significance of mitochondria-targeted therapies in preventing cardiovascular diseases in the elderly.

Compartmental Differences in the Retinal Ganglion Cell Mitochondrial Proteome

Among neurons, retinal ganglion cells (RGCs) are uniquely sensitive to mitochondrial dysfunction. The RGC is highly polarized, with a somatodendritic compartment in the inner retina and an axonal compartment projecting to targets in the brain. The drastically dissimilar functions of these compartments implies that mitochondria face different bioenergetic and other physiological demands. We hypothesized that compartmental differences in mitochondrial biology would be reflected by disparities in mitochondrial protein composition. Here, we describe a protocol to isolate intact mitochondria separately from mouse RGC somatodendritic and axonal compartments by immunoprecipitating labeled mitochondria from RGC MitoTag mice. Using mass spectrometry, 471 and 357 proteins were identified in RGC somatodendritic and axonal mitochondrial immunoprecipitates, respectively. We identified 10 mitochondrial proteins exclusively in the somatodendritic compartment and 19 enriched ≥2-fold there, while 3 proteins were exclusively identified and 18 enriched in the axonal compartment. Our observation of compartment-specific enrichment of mitochondrial proteins was validated through immunofluorescence analysis of the localization and relative abundance of superoxide dismutase ( SOD2 ), sideroflexin-3 ( SFXN3 ) and trifunctional enzyme subunit alpha ( HADHA ) in retina and optic nerve specimens. The identified compartmental differences in RGC mitochondrial composition may provide promising leads for uncovering physiologically relevant pathways amenable to therapeutic intervention for optic neuropathies.

The role of oxygen tension in cell fate and regenerative medicine: implications of hypoxia/hyperoxia and free radicals

Oxygen pressure plays an integral role in regulating various aspects of cellular biology. Cell metabolism, proliferation, morphology, senescence, metastasis, and angiogenesis are some instances that are affected by different tensions of oxygen. Hyperoxia or high oxygen concentration, enforces the production of reactive oxygen species (ROS) that disturbs physiological homeostasis, and consequently, in the absence of antioxidants, cells and tissues are directed to an undesired fate. On the other side, hypoxia or low oxygen concentration, impacts cell metabolism and fate strongly through inducing changes in the expression level of specific genes. Thus, understanding the precise mechanism and the extent of the implication of oxygen tension and ROS in biological events is crucial to maintaining the desired cell and tissue function for application in regenerative medicine strategies. Herein, a comprehensive literature review has been performed to find out the impacts of oxygen tensions on the various behaviors of cells or tissues.

Therapeutic Potential of Myricetin in the Treatment of Neurological, Neuropsychiatric, and Neurodegenerative Disorders

Myricetin (MC), 3,5,7,3',4',5'-hexahydroxyflavone, chemically belongs to a flavonoid category known to confer antioxidant, antimicrobial, antidiabetic, and neuroprotective effects. MC is known to suppress the generation of Reactive Oxygen Species (ROS), lipid peroxidation (MDA), and inflammatory markers. It has been reported to improve insulin function in the human brain and periphery. Besides this, it modulates several neurochemicals including glutamate, GABA, serotonin, etc. MC has been shown to reduce the expression of the enzyme Mono Amine Oxidase (MAO), which is responsible for the metabolism of monoamines. MC treatment reduces levels of plasma corticosterone and restores hippocampal BDNF (full form) protein in stressed animals. Further, MC has shown its protective effect against amyloid-beta, MPTP, rotenone, 6-OHDA, etc. suggesting its potential role against neurodegenerative disorders. The aim of the present review is to highlight the therapeutic potential of MC in the treatment of several neurological, neuropsychiatric, and neurodegenerative disorders.

Ageing, Metabolic Dysfunction, and the Therapeutic Role of Antioxidants

The gradual ageing of the world population has been accompanied by a dramatic increase in the prevalence of obesity and metabolic diseases, especially type 2 diabetes. The adipose tissue dysfunction associated with ageing and obesity shares many common physiological features, including increased oxidative stress and inflammation. Understanding the mechanisms responsible for adipose tissue dysfunction in obesity may help elucidate the processes that contribute to the metabolic disturbances that occur with ageing. This, in turn, may help identify therapeutic targets for the treatment of obesity and age-related metabolic disorders. Because oxidative stress plays a critical role in these pathological processes, antioxidant dietary interventions could be of therapeutic value for the prevention and/or treatment of age-related diseases and obesity and their complications. In this chapter, we review the molecular and cellular mechanisms by which obesity predisposes individuals to accelerated ageing. Additionally, we critically review the potential of antioxidant dietary interventions to counteract obesity and ageing.

Effects of Different Types of Chronic Training on Bioenergetic Profile and Reactive Oxygen Species Production in LHCN-M2 Human Myoblast Cells

Human skeletal muscle contains three different types of fibers, each with a different metabolism. Exercise differently contributes to differentiation and metabolism in human myoblast cells. The aims of the present study were to investigate the effects of different types of chronic training on the human LHCN-M2 myoblast cell bioenergetic profile during differentiation in real time and on the ROS overproduction consequent to H₂O₂ injury. We demonstrated that exercise differently affects the myoblast bioenergetics: aerobic exercise induced the most efficient glycolytic and oxidative capacity and proton leak reduction compared to untrained or anaerobic trained sera-treated cells. Similarly, ROS overproduction after H₂O₂ stress was lower in cells treated with differently trained sera compared to untrained sera, indicating a cytoprotective effect of training on the reduction of oxidative stress, and thus the promotion of longevity. In conclusion, for the first time, this study has provided knowledge regarding the modifications induced by different types of chronic training on human myoblast cell bioenergetics during the differentiation process in real time, and on ROS overproduction due to stress, with positive implications in terms of longevity.

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.

Enzymatic Delivery of Magnetic Nanoparticles into Mitochondria of Live Cells

Delivering magnetic nanoparticles (MNPs) into mitochondria provide a facile approach to manipulate cell life because mitochondria play essential roles in cell survival and death. Here we report the use of enzyme-responsive peptide assemblies to deliver MNPs into mitochondria of live cells. The mitochondria-targeting peptide (Mito-Flag), as the substrate of enterokinase (ENTK), assembles with MNPs in solution. The MNPs that are encapsulated by Mito-Flag peptides selectively accumulate to the mitochondria of cancer cells, rather than normal cells. The mitochondrial localization of MNPs reduces the viability of the cancer cells, but hardly affects the survival of the normal cell. This work demonstrates a new and facile strategy to specifically transport MNPs to the mitochondria in cancer cells for exploring the applications of MNPs as the targeted drug for biomedicine and cancer therapy.

Genome-wide impact of hydrogen peroxide on maintenance DNA methylation in replicating cells

Background

Environmental factors, such as oxidative stress, have the potential to modify the epigenetic landscape of cells. We have previously shown that DNA methyltransferase (DNMT) activity can be inhibited by sublethal doses of hydrogen peroxide (H₂O₂). However, site-specific changes in DNA methylation and the reversibility of any changes have not been explored. Using bead chip array technology, differential methylation was assessed in Jurkat T-lymphoma cells following exposure to H₂O₂.

Results

Sublethal H₂O₂ exposure was associated with an initial genome-wide decrease in DNA methylation in replicating cells, which was largely corrected 72 h later. However, some alterations were conserved through subsequent cycles of cell division. Significant changes to the variability of DNA methylation were also observed both globally and at the site-specific level.

Conclusions

This research indicates that increased exposure to H₂O₂ can result in long-term alterations to DNA methylation patterns, providing a mechanism for environmental factors to have prolonged impact on gene expression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13072-021-00388-6.

Beneficial and Detrimental Effects of Reactive Oxygen Species on Lifespan: A Comprehensive Review of Comparative and Experimental Studies

Aging is the greatest risk factor for a multitude of diseases including cardiovascular disease, neurodegeneration and cancer. Despite decades of research dedicated to understanding aging, the mechanisms underlying the aging process remain incompletely understood. The widely-accepted free radical theory of aging (FRTA) proposes that the accumulation of oxidative damage caused by reactive oxygen species (ROS) is one of the primary causes of aging. To define the relationship between ROS and aging, there have been two main approaches: comparative studies that measure outcomes related to ROS across species with different lifespans, and experimental studies that modulate ROS levels within a single species using either a genetic or pharmacologic approach. Comparative studies have shown that levels of ROS and oxidative damage are inversely correlated with lifespan. While these studies in general support the FRTA, this type of experiment can only demonstrate correlation, not causation. Experimental studies involving the manipulation of ROS levels in model organisms have generally shown that interventions that increase ROS tend to decrease lifespan, while interventions that decrease ROS tend to increase lifespan. However, there are also multiple examples in which the opposite is observed: increasing ROS levels results in extended longevity, and decreasing ROS levels results in shortened lifespan. While these studies contradict the predictions of the FRTA, these experiments have been performed in a very limited number of species, all of which have a relatively short lifespan. Overall, the data suggest that the relationship between ROS and lifespan is complex, and that ROS can have both beneficial or detrimental effects on longevity depending on the species and conditions. Accordingly, the relationship between ROS and aging is difficult to generalize across the tree of life.

The Role of Oxidative Stress in Cardiovascular Aging and Cardiovascular Diseases

Aging can be seen as process characterized by accumulation of oxidative stress induced damage. Oxidative stress derives from different endogenous and exogenous processes, all of which ultimately lead to progressive loss in tissue and organ structure and functions. The oxidative stress theory of aging expresses itself in age-related diseases. Aging is in fact a primary risk factor for many diseases and in particular for cardiovascular diseases and its derived morbidity and mortality. Here we highlight the role of oxidative stress in age-related cardiovascular aging and diseases. We take into consideration the molecular mechanisms, the structural and functional alterations, and the diseases accompanied to the cardiovascular aging process.

Redox activation of ATM enhances GSNOR translation to sustain mitophagy and tolerance to oxidative stress

The denitrosylase S-nitrosoglutathione reductase (GSNOR) has been suggested to sustain mitochondrial removal by autophagy (mitophagy), functionally linking S-nitrosylation to cell senescence and aging. In this study, we provide evidence that GSNOR is induced at the translational level in response to hydrogen peroxide and mitochondrial ROS. The use of selective pharmacological inhibitors and siRNA demonstrates that GSNOR induction is an event downstream of the redox-mediated activation of ATM, which in turn phosphorylates and activates CHK2 and p53 as intermediate players of this signaling cascade. The modulation of ATM/GSNOR axis, or the expression of a redox-insensitive ATM mutant influences cell sensitivity to nitrosative and oxidative stress, impairs mitophagy and affects cell survival. Remarkably, this interplay modulates T-cell activation, supporting the conclusion that GSNOR is a key molecular effector of the antioxidant function of ATM and providing new clues to comprehend the pleiotropic effects of ATM in the context of immune function.

Therapeutic potential of mangiferin in the treatment of various neuropsychiatric and neurodegenerative disorders

Xanthones are important chemical class of bioactive products that confers therapeutic benefits. Of several xanthones, mangiferin is known to be distributed widely across several fruits, vegetables and medicinal plants. Mangiferin has been shown to exert neuroprotective effects in both in-vitro and in-vivo models. Mangiferin attenuates cerebral infarction, cerebral edema, lipid peroxidation (MDA), neuronal damage, etc. Mangiferin further potentiate levels of endogenous antioxidants to confer protection against the oxidative stress inside the neurons. Mangiferin is involved in the regulation of various signaling pathways that influences the production and levels of proinflammatory cytokines in brain. Mangiferin cosunteracted the neurotoxic effect of amyloid-beta, MPTP, rotenone, 6-OHDA etc and confer protection to neurons. These evidence suggested that the mangiferin may be a potential therapeutic strategy for the treatment of various neurological disorders. The present review demonstrated the pharmacodynamics-pharmacokinetics of mangiferin and neurotherapeutic potential in several neurological disorders with underlying mechanisms.

Mechanisms of NLRP3 priming in inflammaging and age related diseases

The NLRP3 inflammasome is a vital part of the innate immune response, whilst its aberrant activation drives the progression of a number of non-communicable diseases. Thus, NLRP3 inflammasome assembly must be tightly controlled at several checkpoints. The priming step of NLRP3 inflammasome activation is associated with increased NLRP3 gene expression, as well as post-translational modifications that control NLRP3 levels and licence the NLRP3 protein for inflammasome assembly. Increasing life expectancy in modern society is accompanied by a growing percentage of elderly individuals. The process of aging is associated with chronic inflammation that drives and/or worsens a range of age related non-communicable conditions. The NLRP3 inflammasome is known to contribute to pathological inflammation in many settings, but the mechanisms that prime NLRP3 for activation throughout aging and related co-morbidities have not been extensively reviewed. Here we dissect the biochemical changes that occur during aging and the pathogenesis of age related diseases and analyse the mechanisms by which they prime the NLRP3 inflammasome, thus exacerbating inflammation.

Cross-talk between redox signalling and protein aggregation

It is well established that both an increase in reactive oxygen species (ROS: i.e. O2•-, H2O2 and OH•), as well as protein aggregation, accompany ageing and proteinopathies such as Parkinson's and Alzheimer's disease. However, it is far from clear whether there is a causal relation between the two. This review describes how protein aggregation can be affected both by redox signalling (downstream of H2O2), as well as by ROS-induced damage, and aims to give an overview of the current knowledge of how redox signalling affects protein aggregation and vice versa. Redox signalling has been shown to play roles in almost every step of protein aggregation and amyloid formation, from aggregation initiation to the rapid oligomerization of large amyloids, which tend to be less toxic than oligomeric prefibrillar aggregates. We explore the hypothesis that age-associated elevated ROS production could be part of a redox signalling-dependent-stress response in an attempt to curb protein aggregation and minimize toxicity.

MitoTEMPO provides an antiarrhythmic effect in aged-rats through attenuation of mitochondrial reactive oxygen species

The death prevalence from cardiovascular disease is significantly high in elderly-populations, while mitochondrial-aging plays an important in abnormal function of vital organs through high mitochondrial ROS production. Mitochondria have a unique mode of action by providing ATP production and modulating the cytosolic Ca²⁺-signaling and maintain the redox status of cardiomyocytes. There is an aging-associated impairment in oxidative phosphorylation which causes a marked dysregulation of mitochondrial biogenesis. Therefore, we aimed to examine whether a mitochondria-targeting antioxidant, MitoTEMPO, can directly provide a cardioprotective effect on ventricular cardiomyocyte function under in vitro conditions. The MitoTEMPO-treatment (0.1 μM for 4-h) of aged-ventricular cardiomyocytes (from 24-mo-old rats), compared to those of the adults (from 8-mo-old rats) markedly augmented not only the depressed biochemical parameters but also the ultrastructure of mitochondria. It also provided marked protective action against increased mitochondrial superoxide formation and Bnip3 overexpression, which both markedly induce depolarized mitochondrial potential, increase reactive oxygen species, mitochondrial swelling and fission, and accelerate mitochondrial turnover via autophagy. Furthermore, it provided marked protection against spontaneous action potentials, via shortening the prolonged action potential duration, at most, through recovery in depressed K⁺-channel currents. Moreover, we determined significant recovery in the depressed intracellular Ca²⁺-changes under electrical stimulation in MitoTEMPO-treated the aged-cardiomyocytes. Overall, we provided important information associated with an antiarrhythmic action, thereby controlling cytosolic and mitochondrial Ca²⁺-handling, implying its possible protective role of mitochondria-targeting antioxidant-treatment during aging.

CoQ10 and Aging

The aging process includes impairment in mitochondrial function, a reduction in anti-oxidant activity, and an increase in oxidative stress, marked by an increase in reactive oxygen species (ROS) production. Oxidative damage to macromolecules including DNA and electron transport proteins likely increases ROS production resulting in further damage. This oxidative theory of cell aging is supported by the fact that diseases associated with the aging process are marked by increased oxidative stress. Coenzyme Q10 (CoQ₁₀) levels fall with aging in the human but this is not seen in all species or all tissues. It is unknown whether lower CoQ₁₀ levels have a part to play in aging and disease or whether it is an inconsequential cellular response to aging. Despite the current lay public interest in supplementing with CoQ₁₀, there is currently not enough evidence to recommend CoQ₁₀ supplementation as an anti-aging anti-oxidant therapy.

Reactive Oxygen Species: the Dual Role in Physiological and Pathological Conditions of the Human Body

Reactive oxygen species (ROS) are well-known for playing a dual role as destructive and constructive species. Indeed, ROS are engaged in many redox-governing activities of the cells for the preservation of cellular homeostasis. However, its overproduction has been reported to result in oxidative stress, which is considered as a deleterious process, and is involved in the damage of cell structures that causes various diseased states. This review provides a concise view on some of the current research published in this topic for an improved understanding of the key roles of ROS in diverse conditions of health and disease. Previous research demonstrated that ROS perform as potential signaling molecules to control several normal physiological functions at the cellular level. Additionally, there is a growing body of evidence supporting the role of ROS in various pathological states. The binary nature of ROS with their profitable and injurious characteristics indicates the complexities of their specific roles at a biological compartment and the difficulties in establishing convenient intervention procedures to treat ROS-related diseases.

The role of melatonin, a multitasking molecule, in retarding the processes of ageing

Biological ageing is generally accompanied by a gradual loss of cellular functions and physiological integrity of organ systems, the consequential enhancement of vulnerability, senescence and finally death. Mechanisms which underlie ageing are primarily attributed to an array of diverse but related factors including free radical-induced damage, dysfunction of mitochondria, disruption of circadian rhythms, inflammaging, genomic instability, telomere attrition, loss of proteostasis, deregulated sensing of nutrients, epigenetic alterations, altered intercellular communication, and decreased capacity for tissue repair. Melatonin, a prime regulator of human chronobiological and endocrine physiology, is highly reputed as an antioxidant, immunomodulatory, antiproliferative, oncostatic, and endocrine-modulatory molecule. Interestingly, several recent reports support melatonin as an anti-ageing agent whose multifaceted functions may lessen the consequences of ageing. This review depicts four categories of melatonin's protective effects on ageing-induced molecular and structural alterations. We also summarize recent findings related to the function of melatonin during ageing in various tissues and organs.

Spontaneous DNA damage to the nuclear genome promotes senescence, redox imbalance and aging

Accumulation of senescent cells over time contributes to aging and age-related diseases. However, what drives senescence in vivo is not clear. Here we used a genetic approach to determine if spontaneous nuclear DNA damage is sufficient to initiate senescence in mammals. Ercc1-/∆ mice with reduced expression of ERCC1-XPF endonuclease have impaired capacity to repair the nuclear genome. Ercc1-/∆ mice accumulated spontaneous, oxidative DNA damage more rapidly than wild-type (WT) mice. As a consequence, senescent cells accumulated more rapidly in Ercc1-/∆ mice compared to repair-competent animals. However, the levels of DNA damage and senescent cells in Ercc1-/∆ mice never exceeded that observed in old WT mice. Surprisingly, levels of reactive oxygen species (ROS) were increased in tissues of Ercc1-/∆ mice to an extent identical to naturally-aged WT mice. Increased enzymatic production of ROS and decreased antioxidants contributed to the elevation in oxidative stress in both Ercc1-/∆ and aged WT mice. Chronic treatment of Ercc1-/∆ mice with the mitochondrial-targeted radical scavenger XJB-5-131 attenuated oxidative DNA damage, senescence and age-related pathology. Our findings indicate that nuclear genotoxic stress arises, at least in part, due to mitochondrial-derived ROS, and this spontaneous DNA damage is sufficient to drive increased levels of ROS, cellular senescence, and the consequent age-related physiological decline.

Glomerular mitochondrial changes in HIV associated renal injury

HIV-associated nephropathy (HIVAN) is an AIDs-related disease of the kidney. HIVAN is characterized by severe proteinuria, podocyte hyperplasia, collapse, glomerular, and tubulointerstitial damage. HIV-1 transgenic (Tg26) mouse is the most popular model to study the HIV manifestations that develop similar renal presentations as HIVAN. Viral proteins, including Tat, Nef, and Vpr play a significant role in renal cell damage. It has been shown that mitochondrial changes are involved in several kidney diseases, and therefore, mitochondrial dysfunction may be implicated in the pathology of HIVAN. In the present study, we investigated the changes of mitochondrial homeostasis, biogenesis, dynamics, mitophagy, and examined the role of reactive oxygen species (ROS) generation and apoptosis in the Tg26 mouse model. The Tg26 mice showed significant impairment of kidney function, which was accompanied by increased blood urea nitrogen (BUN), creatinine and protein urea level. In addition, histological, western blot and PCR analysis of the Tg26 mice kidneys showed a downregulation of NAMPT, SIRT1, and SIRT3 expressions levels. Furthermore, the kidney of the Tg26 mice showed a downregulation of PGC1α, MFN2, and PARKIN, which are coupled with decrease of mitochondrial biogenesis, imbalance of mitochondrial dynamics, and downregulation of mitophagy, respectively. Furthermore, our results indicate that mitochondrial dysfunction were associated with ER stress, ROS generation and apoptosis. These results strongly suggest that the impaired mitochondrial morphology, homeostasis, and function associated with HIVAN. These findings indicated that a new insight on pathological mechanism associated with mitochondrial changes in HIVAN and a potential therapeutic target.

The Mitochondrial Basis of Aging and Age-Related Disorders

Aging is a natural phenomenon characterized by progressive decline in tissue and organ function leading to increased risk of disease and mortality. Among diverse factors that contribute to human aging, the mitochondrial dysfunction has emerged as one of the key hallmarks of aging process and is linked to the development of numerous age-related pathologies including metabolic syndrome, neurodegenerative disorders, cardiovascular diseases and cancer. Mitochondria are central in the regulation of energy and metabolic homeostasis, and harbor a complex quality control system that limits mitochondrial damage to ensure mitochondrial integrity and function. The intricate regulatory network that balances the generation of new and removal of damaged mitochondria forms the basis of aging and longevity. Here, I will review our current understanding on how mitochondrial functional decline contributes to aging, including the role of somatic mitochondrial DNA (mtDNA) mutations, reactive oxygen species (ROS), mitochondrial dynamics and quality control pathways. I will further discuss the emerging evidence on how dysregulated mitochondrial dynamics, mitochondrial biogenesis and turnover mechanisms contribute to the pathogenesis of age-related disorders. Strategies aimed to enhance mitochondrial function by targeting mitochondrial dynamics, quality control, and mitohormesis pathways might promote healthy aging, protect against age-related diseases, and mediate longevity.

Mitochondrial-Targeted Antioxidant Maintains Blood Flow, Mitochondrial Function, and Redox Balance in Old Mice Following Prolonged Limb Ischemia

Aging is a major factor in the decline of limb blood flow with ischemia. However, the underlying mechanism remains unclear. We investigated the role of mitochondrial reactive oxygen species (ROS) with regard to limb perfusion recovery in aging during ischemia. We performed femoral artery ligation in young and old mice with or without treatment with a scavenger of mitochondrial superoxide, MitoTEMPO (180 μg/kg/day, from pre-operative day 7 to post-operative day (POD) 21) infusion using an implanted mini-pump. The recoveries of cutaneous blood flow in the ischemic hind limb were lower in old mice than in young mice but were improved in MitoTEMPO-treated old mice. Mitochondrial DNA damage appeared in ischemic aged muscles but was eliminated by MitoTEMPO treatment. For POD 2, MitoTEMPO treatment suppressed the expression of p53 and the ratio of Bax/Bcl2 and upregulated the expression of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) in ischemic aged skeletal muscles. For POD 21, MitoTEMPO treatment preserved the expression of PGC-1α in ischemic aged skeletal muscle. The ischemic soleus of old mice showed a lower mitochondrial respiratory control ratio in POD 21 compared to young mice, which was recovered in MitoTEMPO-treated old mice. Scavenging of mitochondrial superoxide attenuated mitochondrial DNA damage and preserved the mitochondrial respiration, in addition to suppression of the expression of p53 and preservation of the expression of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) in ischemic skeletal muscles with aging. Resolution of excessive mitochondrial superoxide could be an effective therapy to recover blood flow of skeletal muscle during ischemia in senescence.

Cytochrome P450-2E1 is involved in aging-related kidney damage in mice through increased nitroxidative stress

The aim of this study was to investigate the role of cytochrome P450-2E1 (CYP2E1) in aging-dependent kidney damage since it is poorly understood. Young (7 weeks) and aged female (16-17 months old) wild-type (WT) and Cyp2e1-null mice were used. Kidney histology showed that aged WT mice exhibited typical signs of kidney aging such as cell vacuolation, inflammatory cell infiltration, cellular apoptosis, glomerulonephropathy, and fibrosis, along with significantly elevated levels of renal TNF-α and serum creatinine than all other groups. Furthermore, the highest levels of renal hydrogen peroxide, protein carbonylation and nitration were observed in aged WT mice. These increases in the aged WT mice were accompanied by increased levels of iNOS and mitochondrial nitroxidative stress through altered amounts and activities of the mitochondrial complex proteins and significantly reduced levels of the antioxidant glutathione (GSH). In contrast, the aged Cyp2e1-null mice exhibited significantly higher antioxidant capacity with elevated heme oxygenase-1 and catalase activities compared to all other groups, while maintaining normal GSH levels with significantly less mitochondrial nitroxidative stress compared to the aged WT mice. Thus, CYP2E1 is important in causing aging-related kidney damage most likely through increasing nitroxidative stress and that CYP2E1 could be a potential target in preventing aging-related kidney diseases.

Hydrogen gas protects IP3Rs by reducing disulfide bridges in human keratinocytes under oxidative stress

Based on the oxidative stress theory, aging derives from the accumulation of oxidized proteins induced by reactive oxygen species (ROS) in the cytoplasm. Hydrogen peroxide (H₂O₂) elicits ROS that induces skin aging through oxidation of proteins, forming disulfide bridges with cysteine or methionine sulfhydryl groups. Decreased Ca²⁺ signaling is observed in aged cells, probably secondary to the formation of disulfide bonds among Ca²⁺ signaling-related proteins. Skin aging processes are modeled by treating keratinocytes with H₂O₂. In the present study, H₂O₂ dose-dependently impaired the adenosine triphosphate (ATP)-induced Ca²⁺ response, which was partially protected via co-treatment with β-mercaptoethanol, resulting in reduced disulfide bond formation in inositol 1, 4, 5-trisphosphate receptors (IP₃Rs). Molecular hydrogen (H₂) was found to be more effectively protected H₂O₂-induced IP₃R1 dysfunction by reducing disulfide bonds, rather than quenching ROS. In conclusion, skin aging processes may involve ROS-induced protein dysfunction due to disulfide bond formation, and H₂ can protect oxidation of this process.

Pharmacological Strategies to Retard Cardiovascular Aging

Aging is the major risk factor for cardiovascular diseases, which are the leading cause of death in the United States. Traditionally, the effort to prevent cardiovascular disease has been focused on addressing the conventional risk factors, including hypertension, hyperglycemia, hypercholesterolemia, and high circulating levels of triglycerides. However, recent preclinical studies have identified new approaches to combat cardiovascular disease. Calorie restriction has been reproducibly shown to prolong lifespan in various experimental model animals. This has led to the development of calorie restriction mimetics and other pharmacological interventions capable to delay age-related diseases. In this review, we will address the mechanistic effects of aging per se on the cardiovascular system and focus on the prolongevity benefits of various therapeutic strategies that support cardiovascular health.

Role of the mitochondrial DNA replication machinery in mitochondrial DNA mutagenesis, aging and age-related diseases

As regulators of bioenergetics in the cell and the primary source of endogenous reactive oxygen species (ROS), dysfunctional mitochondria have been implicated for decades in the process of aging and age-related diseases. Mitochondrial DNA (mtDNA) is replicated and repaired by nuclear-encoded mtDNA polymerase γ (Pol γ) and several other associated proteins, which compose the mtDNA replication machinery. Here, we review evidence that errors caused by this replication machinery and failure to repair these mtDNA errors results in mtDNA mutations. Clonal expansion of mtDNA mutations results in mitochondrial dysfunction, such as decreased electron transport chain (ETC) enzyme activity and impaired cellular respiration. We address the literature that mitochondrial dysfunction, in conjunction with altered mitochondrial dynamics, is a major driving force behind aging and age-related diseases. Additionally, interventions to improve mitochondrial function and attenuate the symptoms of aging are examined.

Mitochondrial generation of superoxide and hydrogen peroxide as the source of mitochondrial redox signaling

This review examines the generation of reactive oxygen species by mammalian mitochondria, and the status of different sites of production in redox signaling and pathology. Eleven distinct mitochondrial sites associated with substrate oxidation and oxidative phosphorylation leak electrons to oxygen to produce superoxide or hydrogen peroxide: oxoacid dehydrogenase complexes that feed electrons to NAD⁺; respiratory complexes I and III, and dehydrogenases, including complex II, that use ubiquinone as acceptor. The topologies, capacities, and substrate dependences of each site have recently clarified. Complex III and mitochondrial glycerol 3-phosphate dehydrogenase generate superoxide to the external side of the mitochondrial inner membrane as well as the matrix, the other sites generate superoxide and/or hydrogen peroxide exclusively in the matrix. These different site-specific topologies are important for redox signaling. The net rate of superoxide or hydrogen peroxide generation depends on the substrates present and the antioxidant systems active in the matrix and cytosol. The rate at each site can now be measured in complex substrate mixtures. In skeletal muscle mitochondria in media mimicking muscle cytosol at rest, four sites dominate, two in complex I and one each in complexes II and III. Specific suppressors of two sites have been identified, the outer ubiquinone-binding site in complex III (site III_Qo) and the site in complex I active during reverse electron transport (site I_Q). These suppressors prevent superoxide/hydrogen peroxide production from a specific site without affecting oxidative phosphorylation, making them excellent tools to investigate the status of the sites in redox signaling, and to suppress the sites to prevent pathologies. They allow the cellular roles of mitochondrial superoxide/hydrogen peroxide production to be investigated without catastrophic confounding bioenergetic effects. They show that sites III_Qo and I_Q are active in cells and have important roles in redox signaling (e.g. hypoxic signaling and ER-stress) and in causing oxidative damage in a variety of biological contexts.

Autophagy and Immune Senescence

With extension of the average lifespan, aging has become a heavy burden in society. Immune senescence is a key risk factor for many age-related diseases such as cancer and increased infections in the elderly, and hence has elicited much attention in recent years. As our body's guardian, the immune system maintains systemic health through removal of pathogens and damage. Autophagy is an important cellular 'clearance' process by which a cell internally delivers damaged organelles and macromolecules to lysosomes for degradation. Here, we discuss the most current knowledge of how impaired autophagy can lead to cellular and immune senescence. We also provide an overview, with examples, of the clinical potential of exploiting autophagy to delay immune senescence and/or rejuvenate immunity to treat various age-related diseases.

The Role of Oxidative Stress in Etiopathogenesis of Chemotherapy Induced Cognitive Impairment (CICI)-"Chemobrain"

Chemobrain or chemotherapy induced cognitive impairment (CICI) represents a new clinical syndrome characterised by memory, learning and motor function impairment. As numerous patients with cancer are long-term survivors, CICI represent a significant factor which may interfere with their quality of life. However, this entity CICI must be distinguished from other cognitive syndromes and addressed accordingly. At the present time, experimental and clinical research suggests that CICI could be induced by numerous factors including oxidative stress. This type of CNS injury has been previously described in cancer patients treated with common anti-neoplastic drugs such as doxorubicine, carmustine, methotrexate and cyclophosphamide. It seems that all these pharmacological factors promote neuronal death through a final common pathway represented by TNF alpha (tumour necrosis factor). However, as cancer in general is diagnosed more commonly in the aging population, the elderly oncological patient must be treated with great care since aging per se is also impacted by oxidative stress and potentiually by TNF alpha deleterious action on brain parenchyma. In this context, some patients may develop cognitive dysfunction well before the appearance of CICI. In addition, chemotherapy may worsen their cognitive function. Therefore, at the present time, there is an acute need for development of effective therapeutic methods to prevent CICI as well as new methods of early CICI diagnosis.

Cytochrome P450-2E1 promotes aging-related hepatic steatosis, apoptosis and fibrosis through increased nitroxidative stress

The role of ethanol-inducible cytochrome P450-2E1 (CYP2E1) in promoting aging-dependent hepatic disease is unknown and thus was investigated in this study. Young (7 weeks) and aged female (16 months old) wild-type (WT) and Cyp2e1-null mice were used in this study to evaluate age-dependent changes in liver histology, steatosis, apoptosis, fibrosis and many nitroxidative stress parameters. Liver histology showed that aged WT mice exhibited markedly elevated hepatocyte vacuolation, ballooning degeneration, and inflammatory cell infiltration compared to all other groups. These changes were accompanied with significantly higher hepatic triglyceride and serum cholesterol in aged WT mice although serum ALT and insulin resistance were not significantly altered. Aged WT mice showed the highest rates of hepatocyte apoptosis and hepatic fibrosis. Further, the highest levels of hepatic hydrogen peroxide, lipid peroxidation, protein carbonylation, nitration, and oxidative DNA damage were observed in aged WT mice. These increases in the aged WT mice were accompanied by increased levels of mitochondrial nitroxidative stress and alteration of mitochondrial complex III and IV proteins in aged WT mice, although hepatic ATP levels seems to be unchanged. In contrast, the aging-related nitroxidative changes were very low in aged Cyp2e1-null mice. These results suggest that CYP2E1 is important in causing aging-dependent hepatic steatosis, apoptosis and fibrosis possibly through increasing nitroxidative stress and that CYP2E1 could be a potential target for translational research in preventing aging-related liver disease.

Saussurea involucrata: A review of the botany, phytochemistry and ethnopharmacology of a rare traditional herbal medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Saussurea involucrata Matsum. & Koidz. is an endangered species of the Asteraceae family, growing in the high mountains of central Asia. It has been, and is, widely used in traditional Uyghur, Mongolian and Kazakhstan medicine as well as in Traditional Chinese Medicine as Tianshan Snow Lotus (Chinese: ). In traditional medical theory, S. involucrata can promote blood circulation, thereby alleviating all symptoms associated with poor circulation. It also reputedly eliminates cold and dampness from the body, diminishes inflammation, invigorates, and strengthens Yin and Yang. It has long been used to treat rheumatoid arthritis, cough with cold, stomach ache, dysmenorrhea, and altitude sickness in Uyghur and Chinese medicine.

AIM OF THE REVIEW

To comprehensively summarize the miscellaneous research that has been done regarding the botany, ethnopharmacology, phytochemistry, biological activity, and toxicology of S. involucrata.

METHOD

An extensive review of the literature was carried out. Apart from different electronic databases including SciFinder, Chinese National Knowledge Infrastructure (CNKI), ScienceDirect that were sourced for information, abstracts, full-text articles and books written in English and Chinese, including those traditional records tracing back to the Qing Dynasty. Pharmacopoeia of China and other local herbal records in Uighur, Mongolian and Kazakhstan ethnomedicines were investigated and compared for pertinent information.

RESULTS

The phytochemistry of S. involucrata has been comprehensively investigated. More than 70 compounds have been isolated and identified; they include phenylpropanoids, flavonoids, coumarins, lignans, sesquiterpenes, steroids, ceramides, polysaccharides. Scientific studies on the biological activity of S. involucrata are equally numerous. The herb has been shown to have anti-neoplastic, anti-inflammatory, analgesic, anti-oxidative, anti-fatigue, anti-aging, anti-hypoxic, neuroprotective and immunomodulating effects. Many have shown correlations to the traditional clinical applications in Traditional Chinese Medicine and medicines. The possible mechanisms of S. involucrata in treating various cancers are revealed in the article, these include inhibition of cancer cells by affecting their growth, adhesion, migration, aggregation and invasion, inhibition of epidermal growth factor receptor signaling in cancer cells, hindrance of cancer cell proliferation, causing cytotoxicity to cancer cells and promoting expression of tumor suppressor genes. Dosage efficacy is found to be generally concentration- and time-dependent. However, studies on the correlation between particular chemical constituents and specific bioactivities are limited.

CONCLUSION

In this review, we have documented the existing traditional uses of S. involucrata and summarized recent research into the phytochemistry and pharmacology of S. involucrata. Many of the traditional uses have been validated by phytochemical and modern pharmacological studies but there are still some areas where the current knowledge could be improved. Although studies have confirmed that S. involucrata has a broad range of bioactivities, further in-depth studies on the exact bioactive molecules and the mechanism of action are expected. Whether we should use this herb independently or in combination deserves to be clarified. The exact quality control as well as the toxicology studies is necessary to guarantee the stability and safety of the clinic use. The sustainable use of this endangered resource was also addressed. In conclusion, this review was anticipated to highlight the importance of S. involucrata and provides some directions for the future development of this plant.

Mitochondrial physiology in the major arbovirus vector Aedes aegypti: substrate preferences and sexual differences define respiratory capacity and superoxide production

Adult females of Aedes aegypti are facultative blood sucking insects and vectors of Dengue and yellow fever viruses. Insect dispersal plays a central role in disease transmission and the extremely high energy demand posed by flight is accomplished by a very efficient oxidative phosphorylation process, which take place within flight muscle mitochondria. These organelles play a central role in energy metabolism, interconnecting nutrient oxidation to ATP synthesis, but also represent an important site of cellular superoxide production. Given the importance of mitochondria to cell physiology, and the potential contributions of this organelle for A. aegypti biology and vectorial capacity, here, we conducted a systematic assessment of mitochondrial physiology in flight muscle of young adult A. aegypti fed exclusively with sugar. This was carried out by determining the activities of mitochondrial enzymes, the substrate preferences to sustain respiration, the mitochondrial bioenergetic efficiency and capacity, in both mitochondria-enriched preparations and mechanically permeabilized flight muscle in both sexes. We also determined the substrates preferences to promote mitochondrial superoxide generation and the main sites where it is produced within this organelle. We observed that respiration in A. aegypti mitochondria was essentially driven by complex I and glycerol 3 phosphate dehydrogenase substrates, which promoted distinct mitochondrial bioenergetic capacities, but with preserved efficiencies. Respiration mediated by proline oxidation in female mitochondria was strikingly higher than in males. Mitochondrial superoxide production was essentially mediated through proline and glycerol 3 phosphate oxidation, which took place at sites other than complex I. Finally, differences in mitochondrial superoxide production among sexes were only observed in male oxidizing glycerol 3 phosphate, exhibiting higher rates than in female. Together, these data represent a significant step towards the understanding of fundamental mitochondrial processes in A. aegypti, with potential implications for its physiology and vectorial capacity.

Aging synaptic mitochondria exhibit dynamic proteomic changes while maintaining bioenergetic function

Aging correlates with a progressive impairment of mitochondrial homeostasis and is an influential factor for several forms of neurodegeneration. However, the mechanisms underlying age-related alterations in synaptosomal mitochondria, a neuronal mitochondria population highly susceptible to insults and critical for brain function, remain incompletely understood. Therefore this study investigates the synaptic mitochondrial proteomic and bioenergetic alterations that occur with age. The utilization of a state of the art quantitative proteomics approach allowed for the comparison of protein expression levels in synaptic mitochondria isolated from 5 (mature), 12 (old), and 24 (aged) month old mice. During the process of aging we find that dynamic proteomic alterations occur in synaptic mitochondria. Despite direct (mitochondrial DNA deletions) and indirect (increased antioxidant protein levels) signs of mitochondrial damage in the aged mice, there was an overall maintenance of mitochondrial function. Therefore the synaptic mitochondrial proteomic changes that occur with aging correlate with preservation of synaptic mitochondrial function.

Upregulation of Hsp72 mediates anoxia/reoxygenation neuroprotection in the freshwater turtle via modulation of ROS

The neuroprotective role of Hsp72 has been demonstrated in several ischemic/stroke models to occur primarily through mediation of apoptotic pathways, and a number of heat shock proteins are upregulated in animal models capable of extended anoxic survival. In the present study, we investigated the role of Hsp72 on cell death and apoptotic regulators in one anoxia tolerant model system, the freshwater turtle Trachemys scripta. Since Hsp72 is known to regulate apoptosis through interactions with Bcl-2, we manipulated the levels of Hsp72 and Bcl-2 with siRNA in neuronally enriched primary cell cultures and examined downstream effects. The knockdown of either Hsp72 or Bcl-2 induced cell death during anoxia and reoxygenation. Knockdown of Bcl-2 resulted in increases in apoptotic markers and increased ROS levels 2-fold. However, significant knockdown of Hsp72 did not have any effect on the expression of key mitochondrial apoptotic regulators such as Cytochrome c and caspase-3. Hsp72 knockdown however significantly increased apoptosis inducing factor in both anoxia and reoxygenation and resulted in a six-fold induction of hydrogen peroxide levels. These findings suggest that the neuroprotection offered by Hsp72 in the anoxia/reoxygenation tolerant turtle is through the mediation of ROS levels and not through modulation of caspase-dependent pathways.

Causes and Consequences of Age-Related Changes in DNA Methylation: A Role for ROS?

Recent genome-wide analysis of C-phosphate-G (CpG) sites has shown that the DNA methylome changes with increasing age, giving rise to genome-wide hypomethylation with site‑specific incidences of hypermethylation. This notion has received a lot of attention, as it potentially explains why aged organisms generally have a higher risk of age-related diseases. However, very little is known about the mechanisms that could cause the occurrence of these changes. Moreover, there does not appear to be a clear link between popular theories of aging and alterations in the methylome. Some of the most fruitful of these theories attribute an important role to reactive oxygen species, which seem to be responsible for an increase in oxidative damage to macromolecules, such as DNA, during the lifetime of an organism. In this review, the connection between changes in DNA methylation and these reactive oxygen species is discussed, as well as the effect of these changes on health. Deeper insights into the nature, causes and consequences of the aging methylome might provide a deeper understanding of the molecular mechanisms of aging and eventually contribute to the development of new diagnostic and therapeutic tools.

VMP1-deficient Chlamydomonas exhibits severely aberrant cell morphology and disrupted cytokinesis

BACKGROUND

The versatile Vacuole Membrane Protein 1 (VMP1) has been previously investigated in six species. It has been shown to be essential in macroautophagy, where it takes part in autophagy initiation. In addition, VMP1 has been implicated in organellar biogenesis; endo-, exo- and phagocytosis, and protein secretion; apoptosis; and cell adhesion. These roles underly its proven involvement in pancreatitis, diabetes and cancer in humans.

RESULTS

In this study we analyzed a VMP1 homologue from the green alga Chlamydomonas reinhardtii. CrVMP1 knockdown lines showed severe phenotypes, mainly affecting cell division as well as the morphology of cells and organelles. We also provide several pieces of evidence for its involvement in macroautophagy.

CONCLUSION

Our study adds a novel role to VMP1's repertoire, namely the regulation of cytokinesis. Though the directness of the observed effects and the mechanisms underlying them remain to be defined, the protein's involvement in macroautophagy in Chlamydomonas, as found by us, suggests that CrVMP1 shares molecular characteristics with its animal and protist counterparts.

Protein carbonylation and heat shock proteins in human skeletal muscle: relationships to age and sarcopenia

Aging is associated with a gradual loss of muscle mass termed sarcopenia, which has significant impact on quality-of-life. Because oxidative stress is proposed to negatively impact upon musculoskeletal aging, we investigated links between human aging and markers of oxidative stress, and relationships to muscle mass and strength in young and old nonsarcopenic and sarcopenic adults. Sixteen young and 16 old males (further subdivided into “old” and “old sarcopenic”) were studied. The abundance of protein carbonyl adducts within skeletal muscle sarcoplasmic, myofibrillar, and mitochondrial protein subfractions from musculus vastus lateralis biopsies were determined using Oxyblot immunoblotting techniques. In addition, concentrations of recognized cytoprotective proteins (eg, heat shock proteins [HSP], αβ-crystallin) were also assayed. Aging was associated with increased mitochondrial (but not myofibrillar or sarcoplasmic) protein carbonyl adducts, independently of (stage-I) sarcopenia. Correlation analyses of all subjects revealed that mitochondrial protein carbonyl abundance negatively correlated with muscle strength ([1-repetition maximum], p = .02, r² = −.16), but not muscle mass (p = .13, r² = −.08). Abundance of cytoprotective proteins, including various HSPs (HSP 27 and 70), were unaffected by aging/sarcopenia. To conclude, these data reveal that mitochondrial protein carbonylation increases moderately with age, and that this increase may impact upon skeletal muscle function, but is not a hallmark of (stage-I) sarcopenia, per se.

Dietary antiaging phytochemicals and mechanisms associated with prolonged survival

Aging is well-known an inevitable process that is influenced by genetic, lifestyle and environmental factors. However, the exact mechanisms underlying the aging process are not well understood. Increasing evidence shows that aging is highly associated with chronic increase in reactive oxygen species (ROS), accumulation of a low-grade proinflammatory phenotype and reduction in age-related autophagy, suggesting that these factors may play important roles in promoting aging. Indeed, reduction of ROS and low-grade inflammation and promotion of autophagy by calorie restriction or other dietary manipulation can extend lifespan in a wide spectrum of model organisms. Interestingly, recent studies show that some food-derived small molecules, also called phytochemicals, can extend lifespan in various animal species. In this paper, we review several recently identified potential antiaging phytochemicals that have been studied in cells, animals and humans and further highlight the cellular and molecular mechanisms underlying the antiaging actions by these molecules.

Apolipoprotein D takes center stage in the stress response of the aging and degenerative brain

Apolipoprotein D (ApoD) is an ancient member of the lipocalin family with a high degree of sequence conservation from insects to mammals. It is not structurally related to other major apolipoproteins and has been known as a small, soluble carrier protein of lipophilic molecules that is mostly expressed in neurons and glial cells within the central and peripheral nervous system. Recent data indicate that ApoD not only supplies cells with lipophilic molecules, but also controls the fate of these ligands by modulating their stability and oxidation status. Of particular interest is the binding of ApoD to arachidonic acid and its derivatives, which play a central role in healthy brain function. ApoD has been shown to act as a catalyst in the reduction of peroxidized eicosanoids and to attenuate lipid peroxidation in the brain. Manipulating its expression level in fruit flies and mice has demonstrated that ApoD has a favorable effect on both stress resistance and life span. The APOD gene is the gene that is upregulated the most in the aging human brain. Furthermore, ApoD levels in the nervous system are elevated in a large number of neurologic disorders including Alzheimer's disease, schizophrenia, and stroke. There is increasing evidence for a prominent neuroprotective role of ApoD because of its antioxidant and anti-inflammatory activity. ApoD emerges as an evolutionarily conserved anti-stress protein that is induced by oxidative stress and inflammation and may prove to be an effective therapeutic agent against a variety of neuropathologies, and even against aging.

The impact of early nutrition on the ageing trajectory

Epidemiological studies, including those in identical twins, and in individuals in utero during periods of famine have provided robust evidence of strong correlations between low birth-weight and subsequent risk of disease in later life, including type 2 diabetes (T2D), CVD, and metabolic syndrome. These and studies in animal models have suggested that the early environment, especially early nutrition, plays an important role in mediating these associations. The concept of early life programming is therefore widely accepted; however the molecular mechanisms by which early environmental insults can have long-term effects on a cell and consequently the metabolism of an organism in later life, are relatively unclear. So far, these mechanisms include permanent structural changes to the organ caused by suboptimal levels of an important factor during a critical developmental period, changes in gene expression caused by epigenetic modifications (including DNA methylation, histone modification and microRNA) and permanent changes in cellular ageing. Many of the conditions associated with early-life nutrition are also those which have an age-associated aetiology. Recently, a common molecular mechanism in animal models of developmental programming and epidemiological studies has been development of oxidative stress and macromolecule damage, specifically DNA damage and telomere shortening. These are phenotypes common to accelerated cellular ageing. Thus, this review will encompass epidemiological and animal models of developmental programming with specific emphasis on cellular ageing and how these could lead to potential therapeutic interventions and strategies which could combat the burden of common age-associated disease, such as T2D and CVD.

Redox proteomics and the dynamic molecular landscape of the aging brain

It is well established that the risk to develop neurodegenerative disorders increases with chronological aging. Accumulating studies contributed to characterize the age-dependent changes either at gene and protein expression level which, taken together, show that aging of the human brain results from the combination of the normal decline of multiple biological functions with environmental factors that contribute to defining disease risk of late-life brain disorders. Finding the "way out" of the labyrinth of such complex molecular interactions may help to fill the gap between "normal" brain aging and development of age-dependent diseases. To this purpose, proteomics studies are a powerful tool to better understand where to set the boundary line of healthy aging and age-related disease by analyzing the variation of protein expression levels and the major post translational modifications that determine "protein" physio/pathological fate. Increasing attention has been focused on oxidative modifications due to the crucial role of oxidative stress in aging, in addition to the fact that this type of modification is irreversible and may alter protein function. Redox proteomics studies contributed to decipher the complexity of brain aging by identifying the proteins that were increasingly oxidized and eventually dysfunctional as a function of age. The purpose of this review is to summarize the most important findings obtained by applying proteomics approaches to murine models of aging with also a brief overview of some human studies, in particular those related to dementia.

Mechanisms of skeletal muscle aging: insights from Drosophila and mammalian models

A characteristic feature of aged humans and other mammals is the debilitating, progressive loss of skeletal muscle function and mass that is known as sarcopenia. Age-related muscle dysfunction occurs to an even greater extent during the relatively short lifespan of the fruit fly Drosophila melanogaster. Studies in model organisms indicate that sarcopenia is driven by a combination of muscle tissue extrinsic and intrinsic factors, and that it fundamentally differs from the rapid atrophy of muscles observed following disuse and fasting. Extrinsic changes in innervation, stem cell function and endocrine regulation of muscle homeostasis contribute to muscle aging. In addition, organelle dysfunction and compromised protein homeostasis are among the primary intrinsic causes. Some of these age-related changes can in turn contribute to the induction of compensatory stress responses that have a protective role during muscle aging. In this Review, we outline how studies in Drosophila and mammalian model organisms can each provide distinct advantages to facilitate the understanding of this complex multifactorial condition and how they can be used to identify suitable therapies.

Active transcriptomic and proteomic reprogramming in the C. elegans nucleotide excision repair mutant xpa-1

Oxidative stress promotes human aging and contributes to common neurodegenerative diseases. Endogenous DNA damage induced by oxidative stress is believed to be an important promoter of neurodegenerative diseases. Although a large amount of evidence correlates a reduced DNA repair capacity with aging and neurodegenerative disease, there is little direct evidence of causality. Moreover, the contribution of oxidative DNA damage to the aging process is poorly understood. We have used the nematode Caenorhabditis elegans to study the contribution of oxidative DNA damage and repair to aging. C. elegans is particularly well suited to tackle this problem because it has a minimum complexity DNA repair system, which enables us to circumvent the important limitation presented by the extensive redundancy of DNA repair enzymes in mammals.

Role of autophagy in aging

Constitutive autophagy is important for the control of the quality of proteins and organelles to maintain cell function. Damaged proteins and organelles accumulate in aged organs. The level of autophagic activity decreases with aging. Autophagic activity is regulated by many factors, such as the insulin receptor-signaling pathway, the TOR pathway, Sirt1, and caloric restriction. Autophagy-related genes are known to be essential for the lifespan extension of flies, nematodes, and mice. The inhibition of autophagy decreases the lifespan, and on the other hand, the induction of autophagy can prolong the lifespan. Pharmacological intervention to extend the lifespan has demonstrated a crucial role for autophagy. Heart failure is an age-related disease, as the incidence increases with age. The autophagic activity of the heart decreases during aging. Cardiac-specific autophagy-deficient mice have shown no obvious phenotype up to 10 weeks of age. However, these mice began to die after the age of 6 months, with a significant increase in the left ventricular dimensions and a decrease in the fractional shortening of the left ventricle compared with control mice. This indicates that continuous constitutive autophagy during aging has a crucial role in maintaining cardiac structure and function.