Aging biology and novel targets for drug discovery

Arthrospira platensis Nanoparticles Mitigate Aging-Related Oxidative Injured Brain Induced by D-galactose in Rats Through Antioxidants, Anti-Inflammatory, and MAPK Pathways

Background

Loss of normal function is an inevitable effect of aging. Several factors contribute to the aging process, including cellular senescence and oxidative stress.

Methods

We investigate how Arthrospira platensis Nanoparticles (NSP) protect against aging injury induced by d-galactose (D-gal) in the rat. So, we subcutaneously (S/C) injected D-gal at 200 mg/kg BW to see if Arthrospira platensis Nanoparticles (NSP) might protect against the oxidative changes generated by D-gal. NSP (0.5 mg/kg body weight once daily by gastric gavage) was given to all groups apart from the control and D-gal groups. The d-gal + NSP group was supplemented with 200 mg of D-gal per kg BW once a day and NSP 0.5 mg/kg BW given orally for 45 days. Biochemical, mRNA expression, and histological investigations of brain tissues were used to evaluate the oxidative alterations caused by d-gal and the protective role of NSP.

Results

Our data demonstrated that d-gal was causing significant reductions in relative brain and body weight with increased malondialdehyde (MDA) and redox oxygen species (ROS) levels and increases in serum creatine phosphokinase (CPK) and creatine phosphokinase isoenzyme BB (CPK-BB) with marked decreases in the level of antioxidant enzyme activity in the brain and acetylcholinesterase activity augmented with a phosphorylated H2A histone family member X (γ-H2AX) level increased. The D-gal group had considerably higher phosphorylated p38 mitogen-activated protein kinases (P38MAPK) and C-Jun N-terminal (JNK) kinases. The d-gal administration stimulates the apoptotic gene expression by downregulating the brain superoxide dismutase (SOD), catalase (CAT), and nuclear factor erythroid 2-related factor 2 (Nrf2). The NSP administration saved these parameters in the direction of the control. The brain histopathologic and immunohistochemistry analysis findings support our findings on NSP's protective role.

Conclusion

The NSP may be a promising natural protective compound that can prevent aging and preserve health.

Navitoclax improves acute-on-chronic liver failure by eliminating senescent cells in mice

AIM

Acute-on-chronic liver failure (ACLF), a disease with poor prognosis, is reportedly caused by cellular senescence due to mitochondrial dysfunction. In this study, we described and analyzed the underlying mechanism of a novel approach for ACLF using ABT263/navitoclax (Navi) that selectively eliminates senescent cells.

METHODS

Irradiation-induced senescent hepatocytes were used for in vitro evaluation of the effects of Navi on ACLF (n = 6 for each group). Lipopolysaccharide- and carbon tetrachloride-induced ACLF mouse model was used for in vivo evaluation of the effects of Navi administration compared with the control using one-way or two-way analysis of variance, followed by Student's t-test or Kruskal-Wallis test. The effects on the senescence-associated secretory phenotype (n = 8 for each group) and mitochondrial functions, including adenosine triphosphate concentration and membrane potential (n = 8 for each group), were investigated using real-time polymerase chain reaction, immunohistochemistry, and enzyme analysis.

RESULTS

Navi eliminated irradiation-induced senescent hepatocytes in vitro, leading to non-senescent hepatocyte proliferation. Navi eliminated senescent cells in the liver in vivo, resulting in downregulation of mRNA expression of senescence-associated secretory phenotype factors, a decrease of liver enzymes, and upregulated proliferation of non-senescent cells in the liver. Regarding mitochondrial functional assessment in the liver, adenosine triphosphate concentration and membrane potential were upregulated after Navi administration in vitro and in vivo.

CONCLUSIONS

Navi may ameliorate ACLF damage by eliminating senescent cells in the liver, downregulating senescence-associated secretory phenotype factors, and upregulating mitochondrial functions. We believe that this novel approach using Navi will pave the way for ACLF treatment.

Potential Application of Low-Intensity Pulsed Ultrasound in Delaying Aging for Mice

INTRODUCTION

The low-intensity pulsed ultrasound (LIPUS) is one of the popular treatment modalities allowing to boost the proliferation, differentiation, and migratory activity of cells, which might be a powerful strategy for anti-aging. Seeking a novel setup for LIPUS would benefit the development of ultrasound therapeutics.

METHODS

Here, we proposed a novel underwater exposure setup of LIPUS. C57BL/6 mice were reared in the designated age-groups, which consisted of a middle-aged group (12-14 months) and an old-age group (20-23 months). The age-related changes of body composition, imbalance of energy supply and demand, imbalance of signal network maintaining internal stability, and representative phenotypes of neurodegeneration and neuroplasticity with the presence and absence of underwater LIPUS in middle-aged and aged groups were evaluated.

RESULTS

The results showed that there were obvious aging changes, imbalance of energy supply and demand, imbalance of signal network maintaining homeostasis, neurodegeneration, and damage of neural plasticity in the middle-aged and aged group with or without the LIPUS. Although middle-aged group and aged group responded differently to LIPUS, they mostly generated positive results in relieving bone loss, improving ovarian structure, regulated immune system, and enhanced endurance ability, which should have declined over age.

DISCUSSION

These findings indicate that underwater extracorporeal LIPUS exposure could be employed as single or combined anti-aging strategies that generated positive outcomes against the process of aging.

Repurposing drugs to fight aging: The difficult path from bench to bedside

The steady rise in life expectancy occurred across all developed countries during the last century. This demographic trend is, however, not accompanied by the same healthspan extension. This is since aging is the main risk factor for all age-associated pathological conditions. Therefore, slowing the rate of aging is suggested to be more efficient in preventing or delaying age-related diseases than treat them one by one, which is the common approach in a current pharmacological disease-oriented paradigm. To date, a variety of medications designed to treat particular pathological conditions have been shown to exhibit pro-longevity effects in different experimental models. Among them, there are many commonly used prescription and over-the-counter pharmaceuticals such as metformin, rapamycin, aspirin, statins, melatonin, vitamin antioxidants, etc. All of them are being increasingly investigated in preclinical and clinical trials with the aim of determine whether they have potential for extension of human healthspan. The results from these trials are frequently inconclusive and fall short of initial expectations, suggesting that innovative research ideas and additional translational steps are required to overcome obstacles for implementation of such approaches in clinical practice. In this review, recent advances and challenges in the field of repurposing widely used conventional pharmaceuticals to target the aging process are summarized and discussed.

Targeting cellular senescence based on interorganelle communication, multilevel proteostasis, and metabolic control

Cellular senescence, a stable cell division arrest caused by severe damage and stress, is a hallmark of aging in vertebrates including humans. With progressing age, senescent cells accumulate in a variety of mammalian tissues, where they contribute to tissue aging, identifying cellular senescence as a major target to delay or prevent aging. There is an increasing demand for the discovery of new classes of small molecules that would either avoid or postpone cellular senescence by selectively eliminating senescent cells from the body (i.e., ‘senolytics’) or inactivating/switching damage‐inducing properties of senescent cells (i.e., ‘senostatics/senomorphics’), such as the senescence‐associated secretory phenotype. Whereas compounds with senolytic or senostatic activity have already been described, their efficacy and specificity has not been fully established for clinical use yet. Here, we review mechanisms of senescence that are related to mitochondria and their interorganelle communication, and the involvement of proteostasis networks and metabolic control in the senescent phenotype. These cellular functions are associated with cellular senescence in in vitro and in vivo models but have not been fully exploited for the search of new compounds to counteract senescence yet. Therefore, we explore possibilities to target these mechanisms as new opportunities to selectively eliminate and/or disable senescent cells with the aim of tissue rejuvenation. We assume that this research will provide new compounds from the chemical space which act as mimetics of caloric restriction, modulators of calcium signaling and mitochondrial physiology, or as proteostasis optimizers, bearing the potential to counteract cellular senescence, thereby allowing healthy aging.

Stress Resistance Screen in a Human Primary Cell Line Identifies Small Molecules That Affect Aging Pathways and Extend Caenorhabditis elegans' Lifespan

Increased resistance to environmental stress at the cellular level is correlated with the longevity of long-lived mutants and wild-animal species. Moreover, in experimental organisms, screens for increased stress resistance have yielded mutants that are long-lived. To find entry points for small molecules that might extend healthy longevity in humans, we screened ∼100,000 small molecules in a human primary-fibroblast cell line and identified a set that increased oxidative-stress resistance. Some of the hits fell into structurally related chemical groups, suggesting that they may act on common targets. Two small molecules increased C. elegans’ stress resistance, and at least 9 extended their lifespan by ∼10–50%. We further evaluated a chalcone that produced relatively large effects on lifespan and were able to implicate the activity of two, stress-response regulators, NRF2/skn-1 and SESN/sesn-1, in its mechanism of action. Our findings suggest that screening for increased stress resistance in human cells can enrich for compounds with promising pro-longevity effects. Further characterization of these compounds may reveal new ways to extend healthy human lifespan.

Contaminants: a dark side of food supplements?

Food supplements (FS) are often consumed as one of the strategies to fight ageing-associated pathologies, especially in the case of oxidative stress-related diseases. Despite the popularity of FS, some concerns about their quality and safety have been raised, especially regarding the presence of contaminants. This paper reviews and discusses the occurrence of contaminants in marketed samples of FS in the last two decades, considering both scientific literature and notifications registered on RASFF portal. The most relevant classes of contaminants were included namely metals, toxins, pesticides, dioxins and PCBs, as well as pharmacologically active ingredients. Variable amounts of contaminants were reported in a significant number of commercially available FS. Although the presence of contaminants does not necessarily mean that their levels exceed the regulatory limits or that the FS intake constitutes a risk to human health, it alerts for the need to further monitor FS safety. The evaluation of the risk associated to the consumption of FS, especially in the elderly population, is particularly challenging due to the frequent exposure to multiple toxicants and to different exposure sources, as well as due to possible pre-existing diseases and respective therapeutics. Therefore, improved quality control procedures and monitoring programs should be pursued in order to avoid undesirable products and assure the safety of FS.

Long-term Dietary Macronutrients and Hepatic Gene Expression in Aging Mice

Nutrition influences both hepatic function and aging, but mechanisms are poorly understood. Here, the effects of lifelong, ad libitum-fed diets varying in macronutrients and energy on hepatic gene expression were studied. Gene expression was measured using Affymetrix mouse arrays in livers of 46 mice aged 15 months fed one of 25 diets varying in protein, carbohydrates, fat, and energy density from 3 weeks of age. Gene expression was almost entirely influenced by protein intake. Carbohydrate and fat intake had few effects on gene expression compared with protein. Pathways and processes associated with protein intake included those involved with mitochondrial function, metabolic signaling (PI3K-Akt, AMPK, mTOR) and metabolism of protein and amino acids. Protein intake had variable effects on genes associated with regulation of longevity and influenced by caloric restriction. Among the genes of interest with expression that were significantly associated with protein intake are Cth, Gls2, Igf1, and Nnmt, which were increased with higher protein intake, and Igf2bp2, Fgf21, Prkab2, and Mtor, which were increased with lower protein intake. Dietary protein has a powerful impact on hepatic gene expression in older mice, with some overlap with genes previously reported to be involved with regulation of longevity or caloric restriction.

Novel targets for delaying aging: The importance of the liver and advances in drug delivery

Age-related changes in liver function have a significant impact on systemic aging and susceptibility to age-related diseases. Nutrient sensing pathways have emerged as important targets for the development of drugs that delay aging and the onset age-related diseases. This supports a central role for the hepatic regulation of metabolism in the association between nutrition and aging. Recently, a role for liver sinusoidal endothelial cells (LSECs) in the relationship between aging and metabolism has also been proposed. Age-related loss of fenestrations within LSECs impairs the transfer of substrates (such as lipoproteins and insulin) between sinusoidal blood and hepatocytes, resulting in post-prandial hyperlipidemia and insulin resistance. Targeted drug delivery methods such as nanoparticles and quantum dots will facilitate the direct delivery of drugs that regulate fenestrations in LSECs, providing an innovative approach to ameliorating age-related diseases and increasing healthspan.

Implementation of longevity-promoting supplements and medications in public health practice: achievements, challenges and future perspectives

Background

Most modern societies undergo rapid population aging. The rise in life expectancy, nevertheless, is not accompanied, to date, by the same increment of healthspan. Efforts to increase healthspan by means of supplements and pharmaceuticals targeting aging-related pathologies are presently in spotlight of a new branch in geriatric medicine, geroscience, postulating that aging could be manipulated in such a way that will in parallel allow delay the onset of all age-associated chronic disorders.

Discussion

Currently, the concept of the “longevity dividend” has been developed pointed out that the extension of healthspan by slowing the rate of aging is the most efficient way to combat various aging-related chronic illnesses and disabling conditions than combating them one by one, what is the present-day approach in a generally accepted disease-based paradigm. The further elaboration of pharmaceuticals specifically targeted at age-associated disorders (commonly referred to as ‘anti-aging drugs’) is currently one of the most extensively developed fields in modern biogerontology. Some classes of chemically synthesized compounds and nutraceuticals such as calorie restriction mimetics, autophagy inductors, senolytics and others have been identified as having potential for anti-aging intervention through their possible effects on basic processes underlying aging. In modern pharmaceutical industry, development of new classes of anti-aging medicines is apparently one of the most hopeful directions since potential target group may include each adult individual.

Summary

Implementation of the geroscience-based approaches into healthcare policy and practice would increase the ratio of healthy to unhealthy population due to delaying the onset of age-associated chronic pathologies. That might result in decreasing the biological age and increasing the age of disability, thus increasing the age of retirement and enhancing income without raising taxes. Economic, social and ethical aspects of applying the healthspan- and lifespan-promoting interventions, however, have to be comprehensively debated prior to their implementation in public health practice.

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.

Life history evolution, reproduction, and the origins of sex-dependent aging and longevity

Males and females in many species differ in how they age and how long they live. These differences have motivated much research, concerning both their evolution and the underlying mechanisms that cause them. We review how differences in male and female life histories have evolved to shape patterns of aging and some of the mechanisms and pathways involved. We pay particular attention to three areas where considerable potential for synergy between mechanistic and evolutionary research exists: (1) the role of estrogens, androgens, the growth hormone/insulin-like growth factor 1 pathway, and the mechanistic target of rapamycin signaling pathway in sex-dependent growth and reproduction; (2) sexual conflict over mating rate and fertility, and how mate presence or mating can become an avenue for males and females to directly affect each other's life span; and (3) the link between dietary restriction and aging, and the emerging understanding that only the restriction of certain nutrients is involved and that this is linked to reproduction. We suggest that ideas about life histories, sex-dependent selection, and sexual conflict can inform and be informed by the ever more refined and complex understanding of the mechanisms that cause aging.

Anti-aging pharmacology: Promises and pitfalls

Life expectancy has grown dramatically in modern times. This increase, however, is not accompanied by the same increase in healthspan. Efforts to extend healthspan through pharmacological agents targeting aging-related pathological changes are now in the spotlight of geroscience, the main idea of which is that delaying of aging is far more effective than preventing the particular chronic disorders. Currently, anti-aging pharmacology is a rapidly developing discipline. It is a preventive field of health care, as opposed to conventional medicine which focuses on treating symptoms rather than root causes of illness. A number of pharmacological agents targeting basic aging pathways (i.e., calorie restriction mimetics, autophagy inducers, senolytics etc.) are now under investigation. This review summarizes the literature related to advances, perspectives and challenges in the field of anti-aging pharmacology.

The impact of low-protein high-carbohydrate diets on aging and lifespan

Most research on nutritional effects on aging has focussed on the impact of manipulating single dietary factors such as total calorie intake or each of the macronutrients individually. More recent studies using a nutritional geometric approach called the Geometric Framework have facilitated an understanding of how aging is influenced across a landscape of diets that vary orthogonally in macronutrient and total energy content. Such studies have been performed using ad libitum feeding regimes, thus taking into account compensatory feeding responses that are inevitable in a non-constrained environment. Geometric Framework studies on insects and mice have revealed that diets low in protein and high in carbohydrates generate longest lifespans in ad libitum-fed animals while low total energy intake (caloric restriction by dietary dilution) has minimal effect. These conclusions are supported indirectly by observational studies in humans and a heterogeneous group of other types of interventional studies in insects and rodents. Due to compensatory feeding for protein dilution, low-protein, high-carbohydrate diets are often associated with increased food intake and body fat, a phenomenon called protein leverage. This could potentially be mitigated by supplementing these diets with interventions that influence body weight through physical activity and ambient temperature.

Clearance of senescent cells by ABT263 rejuvenates aged hematopoietic stem cells in mice

Senescent cells (SCs) accumulate with age and after genotoxic stress, such as total-body irradiation (TBI). Clearance of SCs in a progeroid mouse model using a transgenic approach delays several age-associated disorders, suggesting that SCs play a causative role in certain age-related pathologies. Thus, a 'senolytic' pharmacological agent that can selectively kill SCs holds promise for rejuvenating tissue stem cells and extending health span. To test this idea, we screened a collection of compounds and identified ABT263 (a specific inhibitor of the anti-apoptotic proteins BCL-2 and BCL-xL) as a potent senolytic drug. We show that ABT263 selectively kills SCs in culture in a cell type- and species-independent manner by inducing apoptosis. Oral administration of ABT263 to either sublethally irradiated or normally aged mice effectively depleted SCs, including senescent bone marrow hematopoietic stem cells (HSCs) and senescent muscle stem cells (MuSCs). Notably, this depletion mitigated TBI-induced premature aging of the hematopoietic system and rejuvenated the aged HSCs and MuSCs in normally aged mice. Our results demonstrate that selective clearance of SCs by a pharmacological agent is beneficial in part through its rejuvenation of aged tissue stem cells. Thus, senolytic drugs may represent a new class of radiation mitigators and anti-aging agents.

Classifying aging as a disease in the context of ICD-11

Aging is a complex continuous multifactorial process leading to loss of function and crystalizing into the many age-related diseases. Here, we explore the arguments for classifying aging as a disease in the context of the upcoming World Health Organization's 11th International Statistical Classification of Diseases and Related Health Problems (ICD-11), expected to be finalized in 2018. We hypothesize that classifying aging as a disease with a "non-garbage" set of codes will result in new approaches and business models for addressing aging as a treatable condition, which will lead to both economic and healthcare benefits for all stakeholders. Actionable classification of aging as a disease may lead to more efficient allocation of resources by enabling funding bodies and other stakeholders to use quality-adjusted life years (QALYs) and healthy-years equivalent (HYE) as metrics when evaluating both research and clinical programs. We propose forming a Task Force to interface the WHO in order to develop a multidisciplinary framework for classifying aging as a disease with multiple disease codes facilitating for therapeutic interventions and preventative strategies.

Whole-organism screening for modulators of fasting metabolism using transgenic zebrafish

Organismal energy homeostasis is maintained by complex interorgan communications making the discovery of novel drugs against metabolic diseases challenging using traditional high-throughput approaches in vitro. Here, we describe a method that rapidly identifies small molecules with an impact on organismal energy balance in vivo. Specifically, we developed a whole-organism screen for modulators of fasting metabolism using transgenic bioluminescence-reporter zebrafish for the gluconeogenic gene phosphoenolpyruvate-carboxykinase 1 (pck1).

Genetics and pharmacology of longevity: the road to therapeutics for healthy aging

Aging can be defined as the progressive decline in tissue and organismal function and the ability to respond to stress that occurs in association with homeostatic failure and the accumulation of molecular damage. Aging is the biggest risk factor for human disease and results in a wide range of aging pathologies. Although we do not completely understand the underlying molecular basis that drives the aging process, we have gained exceptional insights into the plasticity of life span and healthspan from the use of model organisms such as the worm Caenorhabditis elegans and the fruit fly Drosophila melanogaster. Single-gene mutations in key cellular pathways that regulate environmental sensing, and the response to stress, have been identified that prolong life span across evolution from yeast to mammals. These genetic manipulations also correlate with a delay in the onset of tissue and organismal dysfunction. While the molecular genetics of aging will remain a prosperous and attractive area of research in biogerontology, we are moving towards an era defined by the search for therapeutic drugs that promote healthy aging. Translational biogerontology will require incorporation of both therapeutic and pharmacological concepts. The use of model organisms will remain central to the quest for drug discovery, but as we uncover molecular processes regulated by repurposed drugs and polypharmacy, studies of pharmacodynamics and pharmacokinetics, drug-drug interactions, drug toxicity, and therapeutic index will slowly become more prevalent in aging research. As we move from genetics to pharmacology and therapeutics, studies will not only require demonstration of life span extension and an underlying molecular mechanism, but also the translational relevance for human health and disease prevention.

The Expression Changes of Inflammasomes in the Aging Rat Kidneys

The mechanisms of kidney aging are not yet clear. Studies have shown that immunological inflammation is related to kidney aging. Inflammasomes are important components of innate immune system in the body. However, the function of inflammasomes and their underlying mechanisms in renal aging remain unclear. In this study, for the first time, we systematically investigated the role of the inflammasomes and the inflammatory responses activated by inflammasomes during kidney aging. We found that during kidney aging, the expression levels of the molecules associated with the activation of inflammasomes, including toll-like receptor-4 and interleukin-1 receptor (IL-1R), were significantly increased; their downstream signaling pathway molecule interleukin-1 receptor-associated kinase-4 (IRAK4) was markedly activated (Phospho-IRAK4 was obviously increased); the nuclear factor-κB (NF-κB) signaling pathway was activated (the activated NF-κB pathway molecules Phospho-IKKβ, Phospho-IκBα, and Phospho-NF-κBp65 were significantly elevated); the levels of the inflammasome components NOD-like receptor P3 (NLRP3), NLRC4, and pro-caspase-1 were prominently upregulated; and the proinflammatory cytokines IL-1β and IL-18 were notably increased in the kidneys of 24-month-old (elderly group) rats. These results showed that inflammasomes are markedly activated during the renal aging process and might induce inflamm-aging by promoting the maturation and secretion of the proinflammatory cytokines IL-1β and IL-18.

Macronutrients and caloric intake in health and longevity

Both lifespan and healthspan are influenced by nutrition, with nutritional interventions proving to be robust across a wide range of species. However, the relationship between nutrition, health and aging is still not fully understood. Caloric restriction is the most studied dietary intervention known to extend life in many organisms, but recently the balance of macronutrients has been shown to play a critical role. In this review, we discuss the current understanding regarding the impact of calories and macronutrient balance in mammalian health and longevity, and highlight the key nutrient-sensing pathways that mediate the effects of nutrition on health and ageing.

Dietary Protein to Carbohydrate Ratio and Caloric Restriction: Comparing Metabolic Outcomes in Mice

Both caloric restriction (CR) and low-protein, high-carbohydrate (LPHC) ad-libitum-fed diets increase lifespan and improve metabolic parameters such as insulin, glucose, and blood lipids. Severe CR, however, is unsustainable for most people; therefore, it is important to determine whether manipulating macronutrient ratios in ad-libitum-fed conditions can generate similar health outcomes. We present the results of a short-term (8 week) dietary manipulation on metabolic outcomes in mice. We compared three diets varying in protein to carbohydrate ratio under both CR and ad libitum conditions. Ad libitum LPHC diets delivered similar benefits to CR in terms of levels of insulin, glucose, lipids, and HOMA, despite increased energy intake. CR on LPHC diets did not provide additional benefits relative to ad libitum LPHC. We show that LPHC diets under ad-libitum-fed conditions generate the metabolic benefits of CR without a 40% reduction in total caloric intake.

Rapamycin reverses paraquat-induced acute lung injury in a rat model through inhibition of NFκB activation

OBJECTIVE

To evaluate the role of rapamycin (RAPA) in paraquat (PQ)-induced acute lung injury.

METHODS

Lung tissues were stained with HE and lung histology was observed. Mortality rate, and neutrophil and leukocyte count in blood and bronchoalveolar lavage fluid (BALF) were recorded. Protein content in BALF was determined by Coomassie blue staining. Malondialdehyde (MDA) content, glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) activity in blood were determined by thiobarbituric acid (TBA) assay, pyrogallol autoxidation method, and modified Haefman method, respectively. The NF-κB activity was measured by gel electrophoretic mobility shift assay (EMSA). Carbon dioxide partial pressure (PaCO2), partial pressure of oxygen (PaO2) and pH values were measured by automated blood gas analyzer.

RESULTS

HE staining results demonstrated RAPA alleviated pathological changes of acute alveolitis in SD rats. Trend of protein content in BALF was PQ group>RAPA treatment group>control group (P<0.05). Neutrophil and leukocyte count in RAPA treatment group was significantly lower than PQ group at 3, 5, and 7 days after injection (P<0.05). Trend of MDA content was RAPA treatment group>PQ group>control group (P<0.05). Trend of GSH-Px and SOD activity was control group>RAPA treatment group>PQ group (P<0.05). Compared with PQ group, PaO2 in RAPA treatment group was markedly higher and PaCO2 was lower (P<0.05).

CONCLUSION

PQ-induced acute lung injury was effectively reversed with RAPA, through inhibition of NF-κB activation.

NaDC3 Induces Premature Cellular Senescence by Promoting Transport of Krebs Cycle Intermediates, Increasing NADH, and Exacerbating Oxidative Damage

High-affinity sodium-dependent dicarboxylate cotransporter 3 (NaDC3) is a key metabolism-regulating membrane protein responsible for transport of Krebs cycle intermediates. NaDC3 is upregulated as organs age, but knowledge regarding the underlying mechanisms by which NaDC3 modulates mammalian aging is limited. In this study, we showed that NaDC3 overexpression accelerated cellular senescence in young human diploid cells (MRC-5 and WI-38) and primary renal tubular cells, leading to cell cycle arrest in G1 phase and increased expression of senescent biomarkers, senescence-associated β-galactosidase and p16. Intracellular levels of reactive oxygen species, 8-hydroxy-2'-deoxyguanosine, malondialdehyde, and carbonyl were significantly enhanced, and activities of respiratory complexes I and III and ATP level were significantly decreased in NaDC3-infected cells. Stressful premature senescent phenotypes induced by NaDC3 were markedly ameliorated via treatment with the antioxidants Tiron and Tempol. High expression of NaDC3 caused a prominent increase in intracellular levels of Krebs cycle intermediates and NADH. Exogenous NADH and NAD(+) may aggravate and attenuate the aging phenotypes induced by NaDC3, respectively. These results suggest that NaDC3 can induce premature cellular senescence by promoting the transport of Krebs cycle intermediates, increasing generation of NADH and reactive oxygen species and leading to oxidative damage. Our results clarify the aging signaling pathway regulated by NaDC3.

Royalactin extends lifespan of Caenorhabditis elegans through epidermal growth factor signaling

Royalactin is a glycoprotein essential for the development of long-lived queen honeybees. Only larvae fed with royal jelly, containing royalactin, develop into queens. Royalactin plays a central role in this process by switching on the epidermal growth factor (EGF) receptor signaling pathway which ultimately leads to epigenetic changes and a long-lived queen phenotype. Recently it was shown that royalactin by itself also extends lifespan in Drosophila melanogaster. Yet, the mechanism by which royalactin promotes longevity remains largely unknown. We set out to characterize the effects of royalactin on Caenorhabditis elegans lifespan, and clarify the possible involvement of EGF signaling in this process. We demonstrate that royalactin extends lifespan of this nematode and that both EGF (LIN-3) and its receptor (LET-23) are essential to this process. To our knowledge, this is the first report of royalactin-mediated lifespan extension in a non-insect species. Additionally, we show that royalactin enhances locomotion in adult nematodes, implying that royalactin also influences healthspan. Our results suggest that royalactin is an important lifespan-extending factor in royal jelly and acts by promoting EGF signaling in C. elegans. Further work will now be needed to clarify which (secondary) signaling pathways are activated by royalactin, and how this ultimately translates into an extended health- and lifespan.

Testing efficacy of administration of the antiaging drug rapamycin in a nonhuman primate, the common marmoset

This report is the first description of dosing procedures, pharmacokinetics, biochemical action, and general tolerability of the antiaging drug rapamycin in the common marmoset, a small and short-lived monkey. Eudragit-encapsulated rapamycin was given orally to trained marmosets in a short-term (3 weeks) and a long-term (14 months) study. Circulating trough rapamycin levels (mean = 5.2 ng/mL; 1.93-10.73 ng/mL) achieved at roughly 1.0 mg/kg/day was comparable to those reported in studies of rodents and within the therapeutic range for humans. Long-term treated animals (6/8) indicated a reduction in mammalian target of rapamycin complex 1 signaling as noted by a decrease in the phospho rpS6 to total rpS6 ratio after 2 weeks of treatment. All long-term treated subjects had detectable concentrations of rapamycin in liver (4.7-19.9 pg/mg) and adipose tissue (2.2-32.8 pg/mg) with reduced mammalian target of rapamycin signaling in these tissues. There was no evidence of clinical anemia, fibrotic lung changes, or mouth ulcers. The observed death rate in the long-term study was as expected given the animals' ages. The ability to rapidly and reliably dose socially housed marmosets with an oral form of rapamycin that is well tolerated and that demonstrates a suppression of the mammalian target of rapamycin pathway leads us to conclude that this species offers a viable model for rapamycin testing to establish safety and efficacy for long-term antiaging intervention.

Rapamycin reduces Drosophila longevity under low nutrition

Rapamycin treatment is considered a pharmacological intervention with the potential to mimic the longevity benefits of dietary manipulations. However, how rapamycin interacts with nutrition is not fully understood. Here we studied the effect of rapamycin on the longevity of Drosophila under a range of dietary conditions. In diets low in nutrients, rapamycin reduced longevity in a dosage-dependent manner. This dosage effect requires some nutrients as rapamycin has no impact on survival under starvation conditions. Under a balanced diet of yeast and sugar, rapamycin had no repeatable beneficial effect on organismal longevity. These results show that the effect of rapamycin on longevity is sensitive to the nutritional environment and it can reduce lifespan when nutrients are limited.

Lifespan extension of rotifers by treatment with red algal extracts

Aging results from an accumulation of damage to macromolecules inhibiting cellular replication, repair, and other necessary functions. Damage may be due to environmental stressors such as metal toxicity, oxidative stress caused by imperfections in electron transfer reactions, or other metabolic processes. In an effort to discover medical treatments that counteract this damage, we initiated a search for small molecule drugs from natural sources using life table experiments which, through their unbiased approach, present the opportunity to discover first-in-class molecules. We have identified marine red algae as a source of natural products that slow aging of the invertebrate rotifer Brachionus manjavacas. Rotifers are a promising model organism for life extension studies as they maintain a short, measurable lifespan while also having an extensive literature related to aging. Rotifer lifespan was increased 9-14% by exposure to three of a total of 200 screened red algal extracts. Bioassay guided fractionation led to semi-purified extracts composed primarily of lipids responsible for rotifer life extension. The life extending mixture from the red alga Acanthophora spicifera contained eicosanoic, octadecanoic, and hexadecanoic acids as well as several unidentified unsaturated fatty acids. The life extending effects of these small molecule mixtures are not a result of their direct antioxidant capacity; other unknown mechanisms of action are likely involved. An understanding of how these natural products interact with their molecular targets could lead to selective and effective treatments for slowing aging and reducing age related diseases.

Inferring the effective TOR-dependent network: a computational study in yeast

Background

Calorie restriction (CR) is one of the most conserved non-genetic interventions that extends healthspan in evolutionarily distant species, ranging from yeast to mammals. The target of rapamycin (TOR) has been shown to play a key role in mediating healthspan extension in response to CR by integrating different signals that monitor nutrient-availability and orchestrating various components of cellular machinery in response. Both genetic and pharmacological interventions that inhibit the TOR pathway exhibit a similar phenotype, which is not further amplified by CR.

Results

In this paper, we present the first comprehensive, computationally derived map of TOR downstream effectors, with the objective of discovering key lifespan mediators, their crosstalk, and high-level organization. We adopt a systematic approach for tracing information flow from the TOR complex and use it to identify relevant signaling elements. By constructing a high-level functional map of TOR downstream effectors, we show that our approach is not only capable of recapturing previously known pathways, but also suggests potential targets for future studies.

Information flow scores provide an aggregate ranking of relevance of proteins with respect to the TOR signaling pathway. These rankings must be normalized for degree bias, appropriately interpreted, and mapped to associated roles in pathways. We propose a novel statistical framework for integrating information flow scores, the set of differentially expressed genes in response to rapamycin treatment, and the transcriptional regulatory network. We use this framework to identify the most relevant transcription factors in mediating the observed transcriptional response, and to construct the effective response network of the TOR pathway. This network is hypothesized to mediate life-span extension in response to TOR inhibition.

Conclusions

Our approach, unlike experimental methods, is not limited to specific aspects of cellular response. Rather, it predicts transcriptional changes and post-translational modifications in response to TOR inhibition. The constructed effective response network greatly enhances understanding of the mechanisms underlying the aging process and helps in identifying new targets for further investigation of anti-aging regimes. It also allows us to identify potential network biomarkers for diagnosis and prognosis of age-related pathologies.

Decreased levels of proapoptotic factors and increased key regulators of mitochondrial biogenesis constitute new potential beneficial features of long-lived growth hormone receptor gene-disrupted mice

Decreased somatotrophic signaling is among the most important mechanisms associated with extended longevity. Mice homozygous for the targeted disruption of the growth hormone (GH) receptor gene (GH receptor knockout; GHRKO) are obese and dwarf, are characterized by a reduced weight and body size, undetectable levels of GH receptor, high concentration of serum GH, and greatly reduced plasma levels of insulin and insulin-like growth factor-I, and are remarkably long lived. Recent results suggest new features of GHRKO mice that may positively affect longevity-decreased levels of proapoptotic factors and increased levels of key regulators of mitochondrial biogenesis. The alterations in levels of the proapoptotic factors and key regulators of mitochondrial biogenesis were not further improved by two other potential life-extending interventions-calorie restriction and visceral fat removal. This may attribute the primary role to GH resistance in the regulation of apoptosis and mitochondrial biogenesis in GHRKO mice in terms of increased life span.

Inhibition of phosphodiesterase-5 rescues age-related impairment of synaptic plasticity and memory

Aging is characterized by a progressive cognitive decline that leads to memory impairment. Because the cyclic nucleotide cascade is essential for the integrity of synaptic function and memory, and it is down-regulated during aging and in neurodegenerative disorders, we investigated whether an increase in cGMP levels might rescue age-related synaptic and memory deficits in mice. We demonstrated that acute perfusion with the phosphodiesterase-5 inhibitor sildenafil (50 nM) ameliorated long-term potentiation in hippocampal slices from 26-30-month-old mice. Moreover, chronic intraperitoneal injection of sildenafil (3mg/kg for 3 weeks) improved age-related spatial learning and reference memory as tested by the Morris Water Maze, and recognition memory as tested by the Object Recognition Test. Finally, sildenafil restored central cAMP responsive element-binding protein (CREB) phosphorylation, which is crucial for synaptic plasticity and memory. Our data suggest that inhibition of phosphodiesterase-5 may be beneficial to treat age-related cognitive dysfunction in a physiological mouse model of aging.

DNA damage, NF-κB and accelerated aging

The aging process is the major risk factor for disease and disability yet the cellular mechanisms for aging are uncertain. By studying transgenic mice with altered expression of the DNA repair enzyme, ERCC1, it was concluded that DNA damage is an important, if not the primary mechanism for aging. Moreover it was established that altered activity of the transcription factor, NF-κB (nuclear factor kappa B) mediates the effects of DNA damage on aging. Therefore inhibition of NF-κB might have a role in delaying aging.

Are sirtuins viable targets for improving healthspan and lifespan?

Although the increased lifespan of our populations illustrates the success of modern medicine, the risk of developing many diseases increases exponentially with old age. Caloric restriction is known to retard ageing and delay functional decline as well as the onset of disease in most organisms. Studies have implicated the sirtuins (SIRT1-SIRT7) as mediators of key effects of caloric restriction during ageing. Two unrelated molecules that have been shown to increase SIRT1 activity in some settings, resveratrol and SRT1720, are excellent protectors against metabolic stress in mammals, making SIRT1 a potentially appealing target for therapeutic interventions. This Review covers the current status and controversies surrounding the potential of sirtuins as novel pharmacological targets, with a focus on SIRT1.

One size may not fit all: anti-aging therapies and sarcopenia

Sarcopenia refers to age-related loss of muscle mass and function. Several age-related changes occur in skeletal muscle including a decrease in myofiber size and number and a diminished ability of satellite cells to activate and proliferate upon injury leading to impaired muscle remodeling. Although the molecular mechanisms underlying sarcopenia are unknown, it is tempting to hypothesize that interplay between biological and environmental factors cooperate in a positive feedback cycle contributing to the progression of sarcopenia. Indeed many essential biological mechanisms such as apoptosis and autophagy and critical signaling pathways involved in skeletal muscle homeostasis are altered during aging and have been linked to loss of muscle mass. Moreover, the environmental effects of the sedentary lifestyle of older people further promote and contribute the loss of muscle mass. There are currently no widely accepted therapeutic strategies to halt or reverse the progression of sarcopenia. Caloric restriction has been shown to be beneficial as a sarcopenia and aging antagonist. Such results have made the search for caloric restriction mimetics (CRM) a priority. However given the mechanisms of action, some of the currently investigated CRMs may not combat sarcopenia. Thus, sarcopenia may represent a unique phenotypic feature of aging that requires specific and individually tailored therapeutic strategies.

Testosterone improves the regeneration of old and young mouse skeletal muscle

Aging is associated with loss of muscle mass and strength, reduced satellite cell number, and lower regenerative potential. Testosterone increases muscle mass, strength, and satellite cell number in humans; however, the effects of testosterone on the regenerative potential of skeletal muscle are unclear. Here, we investigated the effect of testosterone on the skeletal muscle regeneration of young (2-month-old) and aged (24-month-old) male mice. We show that testosterone increases the number of proliferating satellite cells in regenerating "tibialis anterior" muscle of young and aged castrated mice 2 and 4 days postinjury. Testosterone supplementation increases the number and the cross-sectional area of regenerating fibers in both classes of age 4 days postinjury. Testosterone increases satellite cell activation and proliferation and the regeneration of both young and aged mouse muscle. These data suggest prospective application of androgens to improve the regenerating potential of the aged human skeletal muscle.

Genomics and successful aging: grounds for renewed optimism?

BACKGROUND

Successful aging depends in part on delaying age-related disease onsets until later in life. Conditions including coronary artery disease, Alzheimer's disease, prostate cancer, and type 2 diabetes are moderately heritable. Genome-wide association studies have identified many risk associated single-nucleotide polymorphisms for these conditions, but much heritability remains unaccounted for. Nevertheless, a great deal is being learned.

METHODS

Here, we review age-related disease associated single-nucleotide polymorphisms and identify key underlying pathways including lipid handling, specific immune processes, early tissue development, and cell cycle control.

RESULTS

Most age-related disease associated single-nucleotide polymorphisms do not affect coding regions of genes or protein makeup but instead influence regulation of gene expression. Recent evidence indicates that evolution of gene regulatory sites is fundamental to interspecies differences. Animal models relevant to human aging may therefore need to focus more on gene regulation rather than testing major disruptions to fundamental pathway genes. Recent larger scale human studies of in vivo genome-wide expression (notably from the InCHIANTI aging study) have identified changes in splicing, the "fine tuning" of protein sequences, as a potentially important factor in decline of cellular function with age. Studies of expression with muscle strength and cognition have shown striking concordance with certain mice models of muscle repair and beta-amyloid phagocytosis respectively.

CONCLUSIONS

The emerging clearer picture of the genetic architecture of age-related diseases in humans is providing new insights into the underlying pathophysiological pathways involved. Translation of genomics into new approaches to prevention, tests and treatments to extend successful aging is therefore likely in the coming decades.

Antioxidants can extend lifespan of Brachionus manjavacas (Rotifera), but only in a few combinations

Animal cells are protected from oxidative damage by an antioxidant network operating as a coordinated system, with strong synergistic interactions. Lifespan studies with whole animals are expensive and laborious, so there has been little investigation of which antioxidant interactions might be useful for life extension. Animals in the phylum Rotifera are particularly promising models for aging studies because they are small (0.1-1 mm), have short, two-week lifespan, display typical patterns of animal aging, and have well characterized, easy to measure phenotypes of aging and senescence. One class of interventions that has consistently produced significant rotifer life extension is antioxidants. Although the mechanism of antioxidant effects on animal aging remains controversial, the ability of some antioxidant supplements to extend rotifer lifespan was unequivocal. We found that exposing rotifers to certain combinations of antioxidant supplements can produce up to about 20% longer lifespan, but that most antioxidants have no effect. We performed life table tests with 20 single antioxidants and none yielded significant rotifer life extension. We tested 60 two-way combinations of selected antioxidants and only seven (12%) produced significant rotifer life extension. None of the 20 three- and four-way antioxidant combinations tested yielded significant rotifer life extension. These observations suggest that dietary exposure of antioxidants can extend rotifer lifespan, but most antioxidants do not. We observed significant rotifer life extension only when antioxidants were paired with trolox, N-acetyl cysteine, L: -carnosine, or EUK-8. This illustrates that antioxidant treatments capable of rotifer life extension are patchily distributed in the parameter space, so large regions must be searched to find them. It furthermore underscores the value of the rotifer model to conduct rapid, facile life table experiments with many treatments, which makes such a search feasible. Although some antioxidants extended rotifer lifespan, they likely did so by another mechanism than direct antioxidation.