A forkhead in the road to longevity: the molecular basis of lifespan becomes clearer

SIRT1 overexpression by melatonin and resveratrol combined treatment attenuates premature ovarian failure through activation of SIRT1/FOXO3a/BCL2 pathway

AIM

To evaluate the synergistic effect of combined treatment with melatonin (MEL) and resveratrol (RES) in cisplatin (CIS)-induced premature ovarian failure (POF) model in rats and to elucidate the molecular mechanism of this therapeutic effect.

MATERIAL & METHODS

Female Sprague Dawley rats were divided into 7 experimental groups as follows; CONT (Control), CIS, MEL, RES, POF + MEL, POF + RES, and POF + MEL + RES. H&E staining was performed to evaluate follicular cell vacuolization/degeneration, vascular congestion/hemorrhage, and inflammation, by using an ordinal scale from 0 to 4 to grade the severity of observed changes (0 = normal, 1 = mild, 2 = moderate, 3 = severe, 4 = very severe). Zona pellucida integrity and connective tissue amount in the ovarian tissue were detected using PAS & Masson Trichrome staining. The immunofluorescence method was used to determine the immune localizations of pH2Ax, SIRT1, FOXO3a, and BCL2. The connective tissue amounts and immunoreactivity staining intensities were measured using ImageJ. The gene expression of SIRT1, FOXO3a, and BCL2 was determined using RT-PCR. Serum estrogen hormone levels were measured by ELISA. Statistically, Bonferroni correction was performed, and p < 0.002 were considered significant.

RESULTS

A significant difference was observed in the POF group compared to the CONT group in all parameters except tertiary follicle count and hemorrhage. The decrease in the number of atretic follicles in the POF + MEL + RES group was found significant compared to both POF + MEL and POF + RES groups. The expression of pH2Ax, SIRT1, FOXO3a, and BCL2 at the protein level and SIRT1 and BCL2 at the mRNA level were significant in the POF + MEL + RES group compared to the POF group. Between the single and combination treatment groups, the difference in protein level was found in pH2Ax, SIRT1, FOXO3a, and BCL2 expression. The POF + MEL + RES group exhibited significantly higher SIRT1 mRNA expression compared to the groups receiving single treatments.

CONCLUSION

The present study provides evidence that MEL and RES have synergistic effects in preventing the decrease in follicle reserve and increase in DNA break (pH2Ax) and follicle atresia in POF ovaries. This therapeutic effect is mediated by SIRT1 overexpression and activation of the SIRT1/FOXO3a/BCL2 pathway.

Therapeutic Effect of Melatonin in Premature Ovarian Insufficiency: Hippo Pathway Is Involved

Objective

Premature ovarian insufficiency (POI) is a female reproductive disorder of unknown etiology with no definite pathogenesis. Melatonin (MT) is an endogenous hormone synthesized mainly by pineal cells and has strong endogenous effects in regulating ovarian function. To systematically explore the pharmacological mechanism of MT on POI therapy, a literature review approach was conducted at the signaling pathways level.

Methods

Relevant literatures were searched and downloaded from databases, including PubMed and China National Knowledge Infrastructure, using the keywords “premature ovarian insufficiency,” “Hippo signaling pathways,” and “melatonin.” The search criteria were from 2010 to 2022. Text mining was also performed.

Results

MT is involved in the regulation of Hippo signaling pathway in a variety of modes and has been correlated with ovarian function.

Conclusions

The purpose of this review is to summarize the research progress of Hippo signaling pathways and significance of MT in POI, the potential crosstalk between MT and Hippo signaling pathways, and the prospective therapy.

Improving Cardiovascular Outcomes: The Era of Personalized Therapy in Atherosclerosis

Data from the European Society of Cardiology report that cardiovascular disease (CVD) is responsible for app [...].

The Tissue Renin-Angiotensin System and Its Role in the Pathogenesis of Major Human Diseases: Quo Vadis?

Evidence has arisen in recent years suggesting that a tissue renin-angiotensin system (tRAS) is involved in the progression of various human diseases. This system contains two regulatory pathways: a pathological pro-inflammatory pathway containing the Angiotensin Converting Enzyme (ACE)/Angiotensin II (AngII)/Angiotensin II receptor type 1 (AGTR1) axis and a protective anti-inflammatory pathway involving the Angiotensin II receptor type 2 (AGTR2)/ACE2/Ang1–7/MasReceptor axis. Numerous studies reported the positive effects of pathologic tRAS pathway inhibition and protective tRAS pathway stimulation on the treatment of cardiovascular, inflammatory, and autoimmune disease and the progression of neuropathic pain. Cell senescence and aging are known to be related to RAS pathways. Further, this system directly interacts with SARS-CoV 2 and seems to be an important target of interest in the COVID-19 pandemic. This review focuses on the involvement of tRAS in the progression of the mentioned diseases from an interdisciplinary clinical perspective and highlights therapeutic strategies that might be of major clinical importance in the future.

The cross-talk between signaling pathways, noncoding RNAs and DNA damage response: Emerging players in cancer progression

The DNA damage response (DDR) pathway's primary purpose is to maintain the genome structure's integrity and stability. A great deal of effort has done to understand the exact molecular mechanisms of non-coding RNAs, such as lncRNA, miRNAs, and circRNAs, in distinct cellular and genomic processes and cancer progression. In this regard, the ncRNAs possible regulatory role in DDR via modulation of key components expression and controlling repair signaling pathway activation is validated. Therefore, in this article, we will discuss the latest developments of ncRNAs contribution in different aspects of DNA repair through regulation of ATM-ATR, P53, and other regulatory signaling pathways.

Prolonged lifespan in a spontaneously hypertensive rat (stroke prone) model following intravenous infusion of mesenchymal stem cells

Intravenous infusion of mesenchymal stem cells (MSCs) has been reported to provide therapeutic efficacy via microvascular remodeling in a spontaneously hypertensive rat. In this study, we demonstrate that intravenous infusion of MSCs increased the survival rate in a spontaneously hypertensive (stroke prone) rat model in which organs including kidney, brain, heart and liver are damaged during aging due to spontaneous hypertension. Gene expression analysis indicated that infused MSCs activates transforming growth factor-β1-smad3/forkhead box O1 signaling pathway. Renal dysfunction was recovered after MSC infusion. Collectively, intravenous infusion of MSC may extend lifespan in this model system.

Marine Fungus Aspergillus chevalieri TM2-S6 Extract Protects Skin Fibroblasts from Oxidative Stress

The strain Aspergillus chevalieri TM2-S6 was isolated from the sponge Axinella and identified according to internal transcribed spacer (ITS) molecular sequence homology with Aspergillus species from the section Restricti. The strain was cultivated 9 days on potato dextrose broth (PDB), and the medium evaluated as antioxidant on primary normal human dermal fibroblasts (NHDF). The cultivation broth was submitted to sterile filtration, lyophilized and used without any further processing to give the Aspergillus chevalieri TM2-S6 cultivation broth ingredient named ACBB. ACCB contains two main compounds: tetrahydroauroglaucin and flavoglaucin. Under oxidative stress, ACCB showed a significant promotion of cell viability. To elucidate the mechanism of action, the impact on a panel of hundreds of genes involved in fibroblast physiology was evaluated. Thus, ACCB stimulates cell proliferation (VEGFA, TGFB3), antioxidant response (GPX1, SOD1, NRF2), and extracellular matrix organization (COL1A1, COL3A1, CD44, MMP14). ACCD also reduced aging (SIRT1, SIRT2, FOXO3). These findings indicate that Aspergillus chevalieri TM2-S6 cultivation broth exhibits significant in vitro skin protection of human fibroblasts under oxidative stress, making it a potential cosmetic ingredient.

In vitro protective effects of marine-derived Aspergillus puulaauensis TM124-S4 extract on H2O2-stressed primary human fibroblasts

Nowadays, there is a huge interest in natural products obtained from marine organisms that can promote human health.The aim of the present study is to evaluate for the first time, the in vitro effects of marine Aspergillus puulaauensis TM124-S4 extract against oxidative stress in human fibroblasts, and its potential as a cosmetic ingredient. The strain was isolated from the Mediterranean Sea star, Echinaster sepositus, and identified according to ITS molecular sequence homology as a member of Aspergillus section versicolores.To gain insight on the bioactivity underpinning the effects of TM124-S4 extract on oxidative stress, we examined a panel of a hundred genes as well as cell viability. Initially, Aspergillus puulaauensis TM124-S4 promoted cell viability.The change in gene transcripts revealed that Aspergillus puulaauensis TM124-S4 extracts exhibited skin protection properties by mediating cell proliferation (EPS8, GDF15, CASP7, VEGFA), antioxidant response (CAT, SOD1, TXN, GPX1), skin hydration (CD44, CRABP2, SERPINE) and DNA repair (PCNA, P21). The extract also modulated the expression of genes involved in skin pigmentation and aging (TYR, FOXO3).These findings indicate that Aspergillus puulaauensis TM124-S4 extract possesses significant in-vitro skin protection activity against induced oxidative stress.Furthermore, new insights are provided into the beneficial role of fungal bioactive compounds in skin related research.

Genetic and epigenetic regulation of human aging and longevity

Here we summarize the latest data on genetic and epigenetic contributions to human aging and longevity. Whereas environmental and lifestyle factors are important at younger ages, the contribution of genetics appears more important in reaching extreme old age. Genome-wide studies have implicated ~57 gene loci in lifespan. Epigenomic changes during aging profoundly affect cellular function and stress resistance. Dysregulation of transcriptional and chromatin networks is likely a crucial component of aging. Large-scale bioinformatic analyses have revealed involvement of numerous interaction networks. As the young well-differentiated cell replicates into eventual senescence there is drift in the highly regulated chromatin marks towards an entropic middle-ground between repressed and active, such that genes that were previously inactive "leak". There is a breakdown in chromatin connectivity such that topologically associated domains and their insulators weaken, and well-defined blocks of constitutive heterochromatin give way to generalized, senescence-associated heterochromatin, foci. Together, these phenomena contribute to aging.

Insulin-like growth factor-1 directly mediates expression of mitochondrial uncoupling protein 3 via forkhead box O4

OBJECTIVE

The objective of our study was to examine the direct action of insulin-like growth factor-1(IGF-1) signaling on energy homeostasis in myocytes.

DESIGN

We studied the IGF-1 stimulation of mitochondrial uncoupling protein 3 (UCP3) expression in the HEK 293 derived cell line TSA201, murine C2C12 skeletal muscle myoblasts, and rat L6 skeletal myoblasts. We also investigated the direct effect of IGF-1 on the Insulin/IGF-1 receptor (IGF-1R)/phosphatidylinositol 3 (PI3)-Akt/forkhead box O4 (FOXO4) pathway using a combination of a reporter assay, semi-quantitative polymerase chain reaction, western blotting, and animal experiments.

RESULTS

We demonstrated that IGF-1 regulates UCP3 expression via phosphorylation of FOXO4, which is a downstream signal transducer of IGF-1. UCP3 expression increased with activated FOXO4 in a dose-dependent manner. We also examined the functional FOXO4 binding site consensus sequences and identified it as the -1922 bp site in the UCP3 promoter region. UCP3 was also found to be concomitantly expressed with IGF-1 during differentiation of C2C12 myoblasts. Our animal experiments showed that high fat diet induced IGF-1 levels which likely influenced UCP3 expression in the skeletal muscle.

CONCLUSION

Our findings demonstrate that that IGF-1 directly stimulates UCP3 expression via the IGF-1/IGF-1R/PI3-Akt/FOXO4 pathway.

Loss of foxo rescues stem cell aging in Drosophila germ line

Aging stem cells lose the capacity to properly respond to injury and regenerate their residing tissues. Here, we utilized the ability of Drosophila melanogaster germline stem cells (GSCs) to survive exposure to low doses of ionizing radiation (IR) as a model of adult stem cell injury and identified a regeneration defect in aging GSCs: while aging GSCs survive exposure to IR, they fail to reenter the cell cycle and regenerate the germline in a timely manner. Mechanistically, we identify foxo and mTOR homologue, Tor as important regulators of GSC quiescence following exposure to ionizing radiation. foxo is required for entry in quiescence, while Tor is essential for cell cycle reentry. Importantly, we further show that the lack of regeneration in aging germ line stem cells after IR can be rescued by loss of foxo.

Stem cells are unspecialized cells that have the unique ability to replace dead cells and repair damaged tissues. To give rise to new cells, stem cells need to divide. This process, known as the cell cycle, includes several stages and is regulated by many different genes.

For example, in many organisms, a gene called foxo helps cells respond to stress and to regulate the cell cycle and cell death. Defects in this gene have been linked to age-related diseases, such as cancer and Alzheimer’s disease. Previous research has shown that foxo can also regulate Tor – a gene that helps cells to divide and grow.

As we age, stem cells become less efficient at regenerating tissues, especially after exposure to toxins and radiation. However, until now, it was not known how stem cells control their division after injury and during aging, and what role these two genes play in injured and aging stem cells.

Now, Artoni, Kreipke et al. used germline stem cells from fly ovaries to investigate how young and old stem cells respond to injury. In young flies, foxo paused the cell cycle of the damaged stem cells. After 24 hours, Tor was able to overcome the action of foxo, and the stem cells resumed dividing and regenerating the damaged tissue. However, in old stem cells, foxo and Tor were misregulated and the stem cells could not restart dividing or repairing tissue after injury. When the levels of foxo in old stem cells were experimentally reduced, their ability to regenerate the tissue was restored.

These discoveries provide new insights into how stem cells respond to injury and suggest that stem cell aging may be a reversible process. A next step will be to investigate why foxo and Tor are misregulated during aging and how these two genes interact with each another. In future, this could help develop new anti-aging therapies that can restore the body’s natural ability to repair itself following injury. Moreover, since cancer cells can become resistant to conventional cancer treatment by withdrawing from the cell cycle, developing new treatments that target foxo and Tor could help beat cancer and prevent its reoccurrence.

Association Analysis of FOXO3 Longevity Variants With Blood Pressure and Essential Hypertension

BACKGROUND

The minor alleles of 3 FOXO3 single nucleotide polymorphisms (SNPs)- rs2802292 , rs2253310 , and rs2802288 -are associated with human longevity. The aim of the present study was to test these SNPs for association with blood pressure (BP) and essential hypertension (EHT).

METHODS

In a primary study involving Americans of Japanese ancestry drawn from the Family Blood Pressure Program II we genotyped 411 female and 432 male subjects aged 40-79 years and tested for statistical association by contingency table analysis and generalized linear models that included logistic regression adjusting for sibling correlation in the data set. Replication of rs2802292 with EHT was attempted in Japanese SONIC study subjects and of each SNP in a meta-analysis of genome-wide association studies of BP in individuals of European ancestry.

RESULTS

In Americans of Japanese ancestry, women homozygous for the longevity-associated (minor) allele of each FOXO3 SNP had 6mm Hg lower systolic BP and 3mm Hg lower diastolic BP compared with major allele homozygotes (Bonferroni corrected P < 0.05 and >0.05, respectively). Frequencies of minor allele homozygotes were 3.3-3.9% in women with EHT compared with 9.5-9.6% in normotensive women ( P = 0.03-0.04; haplotype analysis P = 0.0002). No association with BP or EHT was evident in males. An association with EHT was seen for the minor allele of rs2802292 in the Japanese SONIC cohort ( P = 0.03), while in European subjects the minor allele of each SNP was associated with higher systolic and diastolic BP.

CONCLUSION

Longevity-associated FOXO3 variants may be associated with lower BP and EHT in Japanese women.

DNA-bound metal ions: recent developments

The affinity of metal ions for DNA is logical considering that the structure of DNA includes a phosphate backbone with a net-negative charge, a deoxyribose sugar with O atoms, and purine and pyrimidine bases that contain O and N atoms. DNA-metal ion interactions encompass a large area of research that ranges from the most fundamental characterization of DNA-metal ion binding to the role of DNA-bound metal ions in disease and human health. Alternative DNA base pairing mediated by metal binding is also being investigated and manipulated for applications in logic gates, molecular machines, and nanotechnology. This review highlights recent work aimed at understanding interactions of redox-active metal ions with DNA that provides a better understanding of the mechanisms by which various types of oxidative DNA damage (strand breakage and base modifications) occur. Antioxidants that mitigate oxidative DNA damage by coordinating metal ions that produce reactive oxygen species are addressed, as well as recent work on the effect of DNA-metal ion interactions and the efficacy of quinolone-based antibacterial drugs. Recent advances in metal-mediated base pairing that triggers conformational changes in DNA structure for use as selective metal ion sensors and novel nanotechnology applications are also included.

FOXO3: A Major Gene for Human Longevity--A Mini-Review

BACKGROUND

The gene FOXO3, encoding the transcription factor forkhead box O-3 (FoxO3), is one of only two for which genetic polymorphisms have exhibited consistent associations with longevity in diverse human populations.

OBJECTIVE

Here, we review the multitude of actions of FoxO3 that are relevant to health, and thus healthy ageing and longevity.

METHODS

The study involved a literature search for articles retrieved from PubMed using FoxO3 as keyword.

RESULTS

We review the molecular genetics of FOXO3 in longevity, then current knowledge of FoxO3 function relevant to ageing and lifespan. We describe how FoxOs are involved in energy metabolism, oxidative stress, proteostasis, apoptosis, cell cycle regulation, metabolic processes, immunity, inflammation and stem cell maintenance. The single FoxO in Hydra confers immortality to this fresh water polyp, but as more complex organisms evolved, this role has been usurped by the need for FoxO to control a broader range of specialized pathways across a wide spectrum of tissues assisted by the advent of as many as 4 FoxO subtypes in mammals. The major themes of FoxO3 are similar, but not identical, to other FoxOs and include regulation of cellular homeostasis, particularly of stem cells, and of inflammation, which is a common theme of age-related diseases. Other functions concern metabolism, cell cycle arrest, apoptosis, destruction of potentially damaging reactive oxygen species and proteostasis.

CONCLUSIONS

The mechanism by which longevity-associated alleles of FOXO3 reduce age-related mortality is currently of great clinical interest. The prospect of optimizing FoxO3 activity in humans to increase lifespan and reduce age-related diseases represents an exciting avenue of clinical investigation. Research strategies directed at developing therapeutic agents that target FoxO3, its gene and proteins in the pathway(s) FoxO3 regulates should be encouraged and supported.

C10ORF10/DEPP, a transcriptional target of FOXO3, regulates ROS-sensitivity in human neuroblastoma

Background

FOXO transcription factors control cellular levels of reactive oxygen species (ROS) which critically contribute to cell survival and cell death in neuroblastoma. In the present study we investigated the regulation of C10orf10/DEPP by the transcription factor FOXO3. As a physiological function of C10orf10/DEPP has not been described so far we analyzed its effects on cellular ROS detoxification and death sensitization in human neuroblastoma cells.

Methods

The effect of DEPP on cellular ROS was measured by catalase activity assay and live cell fluorescence microscopy using the ROS-sensitive dye reduced MitoTracker Red CM-H2XROS. The cellular localization of DEPP was determined by confocal microscopy of EYFP-tagged DEPP, fluorescent peroxisomal- and mitochondrial probes and co-immunoprecipitation of the PEX7 receptor.

Results

We report for the first time that DEPP regulates ROS detoxification and localizes to peroxisomes and mitochondria in neuroblastoma cells. FOXO3-mediated apoptosis involves a biphasic ROS accumulation. Knockdown of DEPP prevented the primary and secondary ROS wave during FOXO3 activation and attenuated FOXO3- and H₂O₂-induced apoptosis. Conditional overexpression of DEPP elevates cellular ROS levels and sensitizes to H₂O₂ and etoposide-induced cell death. In neuronal cells, cellular ROS are mainly detoxified in peroxisomes by the enzyme CAT/catalase. As DEPP contains a peroxisomal-targeting-signal-type-2 (PTS2) sequence at its N-terminus that allows binding to the PEX7 receptor and import into peroxisomes, we analyzed the effect of DEPP on cellular detoxification by measuring enzyme activity of catalase. Catalase activity was reduced in DEPP-overexpressing cells and significantly increased in DEPP-knockdown cells. DEPP directly interacts with the PEX7 receptor and localizes to the peroxisomal compartment. In parallel, the expression of the transcription factor peroxisome proliferator-activated receptor gamma (PPARG), a critical regulator of catalase enzyme activity, was strongly upregulated in DEPP-knockdown cells.

Conclusion

The combined data indicate that in neuroblastoma DEPP localizes to peroxisomes and mitochondria and impairs cellular ROS detoxification, which sensitizes tumor cells to ROS-induced cell death.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-4598-13-224) contains supplementary material, which is available to authorized users.

FoxO3a and disease progression

The Forkhead box O (FoxO) family has recently been highlighted as an important transcriptional regulator of crucial proteins associated with the many diverse functions of cells. So far, FoxO1, FoxO3a, FoxO4 and FoxO6 proteins have been identified in humans. Although each FoxO family member has its own role, unlike the other FoxO families, FoxO3a has been extensively studied because of its rather unique and pivotal regulation of cell proliferation, apoptosis, metabolism, stress management and longevity. FoxO3a alteration is closely linked to the progression of several types of cancers, fibrosis and other types of diseases. In this review, we will examine the function of FoxO3a in disease progression and also explore FoxO3a’s regulatory mechanisms. We will also discuss FoxO3a as a potential target for the treatment of several types of disease.

The roles of FoxOs in modulation of aging by calorie restriction

FoxO activity and modifications, such as its phosphorylation, acetylation, and methylation, may help drive the expression of genes involved in combating oxidative stress by causing the epigenetic modifications, and thus, preserve cellular function during aging and age-related diseases, such as diabetes, cancer, and Alzheimer disease. Insulin signaling has been postulated to influence the aging process by increasing resistance to oxidative stress, and slowing the accumulation of oxidative damage. Some antioxidative effects are mediated by a conserved family of forkhead box transcription factors (FoxOs), which in the absence of insulin signaling freely bind to promoters of antioxidant enzymes, superoxide dismutase, and catalase. On the other hand, calorie restriction (CR) extends the lifespans of several species via the insulin pathway, and extends longevity and healthspan in diverse species via a conserved mechanism. CR enhances adaptive stress responses at the cellular and organism levels and extends lifespan in a FoxO-independent manner. Thus, increased modification of FoxO is modulated via the hyperinsulinemia-induced PI3K/Akt pathway during aging, and CR reverses this process. Accordingly, FoxO plays an important role in maintenance of metabolic homeostasis and removal of oxidative stress in the aging process and in the effect of CR on lifespan.

Healthy aging diets other than the Mediterranean: a focus on the Okinawan diet

The traditional diet in Okinawa is anchored by root vegetables (principally sweet potatoes), green and yellow vegetables, soybean-based foods, and medicinal plants. Marine foods, lean meats, fruit, medicinal garnishes and spices, tea, alcohol are also moderately consumed. Many characteristics of the traditional Okinawan diet are shared with other healthy dietary patterns, including the traditional Mediterranean diet, DASH diet, and Portfolio diet. All these dietary patterns are associated with reduced risk for cardiovascular disease, among other age-associated diseases. Overall, the important shared features of these healthy dietary patterns include: high intake of unrefined carbohydrates, moderate protein intake with emphasis on vegetables/legumes, fish, and lean meats as sources, and a healthy fat profile (higher in mono/polyunsaturated fats, lower in saturated fat; rich in omega-3). The healthy fat intake is likely one mechanism for reducing inflammation, optimizing cholesterol, and other risk factors. Additionally, the lower caloric density of plant-rich diets results in lower caloric intake with concomitant high intake of phytonutrients and antioxidants. Other shared features include low glycemic load, less inflammation and oxidative stress, and potential modulation of aging-related biological pathways. This may reduce risk for chronic age-associated diseases and promote healthy aging and longevity.

Caloric restriction and aging stem cells: the stick and the carrot?

Adult tissue stem cells have the ability to adjust to environmental changes and affect also the proliferation of neighboring cells, with important consequences on tissue maintenance and regeneration. Stem cell renewal and proliferation is strongly regulated during aging of the organism. Caloric restriction is the most powerful anti-aging strategy conserved throughout evolution in the animal kingdom. Recent studies relate the properties of caloric restriction to its ability in reprogramming stem-like cell states and in prolonging the capacity of stem cells to self-renew, proliferate, differentiate, and replace cells in several adult tissues. However this general paradigm presents with exceptions. The scope of this review is to highlight how caloric restriction impacts on diverse stem cell compartments and, by doing so, might differentially delay aging in the tissues of lower and higher organisms.

Alternative strategy for Alzheimer's disease: stress response triggers

Stress resistance capacity is a hallmark of longevity protection and survival throughout the plant and animal kingdoms. Latent pathway activation of protective cascades, triggered by environmental challenges to tolerate heat, oxygen deprivation, reactive oxygen species (ROS), diet restriction, and exercise provides tolerance to these stresses. Age-related changes and disease vulnerability mark an increase in damage, like damage induced by environmental challenges. An alternative approach to immunotherapy intervention in Alzheimer's Disease is the use of mimetics of stress to upregulate endogenous protective cascades to repair age damage, shift the balance of apoptosis to regeneration to promote delay of onset, and even progression of Alzheimer's disease memory dysfunction. Mimetics of environmental stress, hormetic agents, and triggers, endogenous or engineered, can “trick” activation of expression patterns of repair and rejuvenation. Examples of known candidate triggers of heat response, endogenous antioxidants, DNA repair, exercise, hibernation, and telomeres are available for AD intervention trials. Telomeres and telomerase emerge as major regulators in crossroads of senescence, cancer, and rejuvenation responsive to mimetics of telomeres. Lessons emerge from transgenic rodent models, the long-lived mole rat, clinical studies, and conserved innate pathways of stress resistance. Cross-reaction of benefits of different triggers promises intervention into seemingly otherwise unrelated diseases.

Tetrahydrocurcumin extends life span and inhibits the oxidative stress response by regulating the FOXO forkhead transcription factor

The O-type forkhead domain transcription factor (FOXO) is involved in many biological processes such as aging, the oxidative stress response, and growth regulation. FOXO activity is tightly controlled within cells. In particular, growth factor signaling pathways and the oxidative stress response can both stimulate nuclear translocation of this transcription factor. Here, we show that tetrahydrocurcumin (THC), a curcumin metabolite, regulates the oxidative stress response and aging via FOXO. In NIH3T3 cells, THC induced nuclear accumulation of FOXO4, a member of the FOXO family of transcription factors, by inhibiting phosphorylation of protein kinase B (PKB)/Akt. In Drosophila melanogaster, THC attenuated the oxidative stress response, an effect that was blocked in a foxo mutant background. THC also extended the life span of Drosophila under normal conditions, and loss of either foxo or Sir2 activity eliminated this effect. Based on these results, THC may regulate the aging process via an evolutionarily conserved signaling pathway that includes both foxo and Sir2.

Neuroprotective role of Sirt1 in mammalian models of Huntington's disease through activation of multiple Sirt1 targets

Huntington's disease is a fatal neurodegenerative disorder caused by an expanded polyglutamine repeat in huntingtin (HTT) protein. We previously showed that calorie restriction ameliorated Huntington's disease pathogenesis and slowed disease progression in mice that model Huntington's disease (Huntington's disease mice). We now report that overexpression of sirtuin 1 (Sirt1), a mediator of the beneficial metabolic effects of calorie restriction, protects neurons against mutant HTT toxicity, whereas reduction of Sirt1 exacerbates mutant HTT toxicity. Overexpression of Sirt1 improves motor function, reduces brain atrophy and attenuates mutant-HTT-mediated metabolic abnormalities in Huntington's disease mice. Further mechanistic studies suggested that Sirt1 prevents the mutant-HTT-induced decline in brain-derived neurotrophic factor (BDNF) concentrations and the signaling of its receptor, TrkB, and restores dopamine- and cAMP-regulated phosphoprotein, 32 kDa (DARPP32) concentrations in the striatum. Sirt1 deacetylase activity is required for Sirt1-mediated neuroprotection in Huntington's disease cell models. Notably, we show that mutant HTT interacts with Sirt1 and inhibits Sirt1 deacetylase activity, which results in hyperacetylation of Sirt1 substrates such as forkhead box O3A (Foxo3a), thereby inhibiting its pro-survival function. Overexpression of Sirt1 counteracts the mutant-HTT-induced deacetylase deficit, enhances the deacetylation of Foxo3a and facilitates cell survival. These findings show a neuroprotective role for Sirt1 in mammalian Huntington's disease models and open new avenues for the development of neuroprotective strategies in Huntington's disease.

Resveratrol, by modulating RNA processing factor levels, can influence the alternative splicing of pre-mRNAs

Alternative pre-mRNA splicing defects can contribute to, or result from, various diseases, including cancer. Aberrant mRNAs, splicing factors and other RNA processing factors have therefore become targets for new therapeutic interventions. Here we report that the natural polyphenol resveratrol can modulate alternative splicing in a target-specific manner. We transfected minigenes of several alternatively spliceable primary mRNAs into HEK293 cells in the presence or absence of 1, 5, 20 and 50 µM resveratrol and measured exon levels by semi-quantitative PCR after separation by agarose gel electrophoresis. We found that 20 µg/ml and 50 µg/ml of resveratrol affected exon inclusion of SRp20 and SMN2 pre-mRNAs, but not CD44v5 or tau pre-mRNAs. By Western blotting and immunofluorescence we showed that this effect may be due to the ability of resveratrol to change the protein level but not the localization of several RNA processing factors. The processing factors that increased significantly were ASF/SF2, hnRNPA1 and HuR, but resveratrol did not change the levels of RBM4, PTBP1 and U2AF35. By means of siRNA-mediated knockdown we depleted cells of SIRT1, regarded as a major target of resveratrol, and showed that the effect on splicing was not dependent on SIRT1. Our results suggest that resveratrol might be an attractive small molecule to treat diseases in which aberrant splicing has been implicated, and justify more extensive research on the effects of resveratrol on the splicing machinery.

Effects of Longevinex (modified resveratrol) on cardioprotection and its mechanisms of action

Although resveratrol has been proven to possess diverse health benefits, several recent reports have demonstrated conflicting results on some aspects of its effects, including its anti-aging properties. Considerable debate appears to exist on the dose and bioavailability of resveratrol, leading to the controversies on its effectiveness. To resolve the problem, we designed a study with a resveratrol formulation that contained resveratrol supplemented with 5% quercetin and 5% rice bran phytate (commercially known as Longevinex). These ingredients were micronized to increase the bioavailability. Sprague-Dawley rats were gavaged with either Longevinex or vehicle (5% quercetin plus 5% rice bran phytate), and rats were sacrificed after 1 or 3 months, when isolated working hearts were subjected to 30 min ischemia followed by 2 h of reperfusion. Longevinex-treated hearts, irrespective of the duration of treatments, revealed superior cardiac performance, reduced infarct size, and induction of survival signals as evidenced by increased Bcl2/Bax ratio and enhanced Akt phosphorylation. In contrast, LC3-II and Beclin were enhanced significantly after 3 months of Longevinex treatment, suggesting that autophagy occurred only after feeding Longevinex to rats for a prolonged period of time. Corroborating with the results of autophagy, Sirt1 and Sirt3 increased significantly only after 3 months of Longevinex treatment, suggesting that enhanced expression of Sirts correlated with induction of autophagy. In concert, Longevinex caused phosphorylation and nuclear translocation of FoxO1, FoxO3a, and FoxO4, indicating involvement of FoxOs with autophagy. Since Sirts and FoxOs are reliable markers of longevity, the results appear to suggest that Longevinex induces longevity after prolonged feeding via induction of autophagy, while it converts death signals into survival signals and provides cardioprotection within a relatively shorter period of time.

Synaptic activity and nuclear calcium signaling protect hippocampal neurons from death signal-associated nuclear translocation of FoxO3a induced by extrasynaptic N-methyl-D-aspartate receptors

Synaptic activity and the generation of nuclear calcium signals promote neuronal survival through a transcription-dependent process that is not fully understood. Here we show that one mechanism of activity-induced acquired neuroprotection involves the Forkhead transcription factor, FoxO3a, which is known to induce genomic death responses upon translocation from the cytosol to the nucleus. Depletion of endogenous FoxO3a using RNA interference renders hippocampal neurons more resistant to excitotoxic cell death. Using a FoxO3a-green fluorescent protein (GFP) fusion protein to monitor in real time the localization of FoxO3a in hippocampal neurons, we found that several cell death inducing stimuli, including the stimulation of extrasynaptic N-methyl-D-aspartate receptors, growth factor withdrawal, and oxygen-glucose deprivation, caused a swift translocation of FoxO3a-GFP from the cytosol to the cell nucleus. This translocation was inhibited in hippocampal neurons that had undergone prolonged periods of synaptic activity before exposure to cell death-inducing conditions. The activity-dependent protection from death signal-induced FoxO3a-GFP nuclear translocation required synaptic N-methyl-D-aspartate receptor activation and was dependent on nuclear calcium signaling and calcium/calmodulin-dependent protein kinase IV. The modulation of nucleo-cytoplasmic shuttling of FoxO3a may represent one mechanism through which nuclear calcium-induced genomic responses affect cell death processes.

Genome-wide analysis of binding sites and direct target genes of the orphan nuclear receptor NR2F1/COUP-TFI

Background

Identification of bona fide direct nuclear receptor gene targets has been challenging but essential for understanding regulation of organismal physiological processes.

Results

We describe a methodology to identify transcription factor binding sites and target genes in vivo by intersecting microarray data, computational binding site queries, and evolutionary conservation. We provide detailed experimental validation of each step and, as a proof of principle, utilize the methodology to identify novel direct targets of the orphan nuclear receptor NR2F1 (COUP-TFI). The first step involved validation of microarray gene expression profiles obtained from wild-type and COUP-TFI^−/− inner ear tissues. Secondly, we developed a bioinformatic tool to search for COUP-TFI DNA binding sites in genomes, using a classification-type Hidden Markov Model trained with 49 published COUP-TF response elements. We next obtained a ranked list of candidate in vivo direct COUP-TFI targets by integrating the microarray and bioinformatics analyses according to the degree of binding site evolutionary conservation and microarray statistical significance. Lastly, as proof-of-concept, 5 specific genes were validated for direct regulation. For example, the fatty acid binding protein 7 (Fabp7) gene is a direct COUP-TFI target in vivo because: i) we identified 2 conserved COUP-TFI binding sites in the Fabp7 promoter; ii) Fapb7 transcript and protein levels are significantly reduced in COUP-TFI^−/− tissues and in MEFs; iii) chromatin immunoprecipitation demonstrates that COUP-TFI is recruited to the Fabp7 promoter in vitro and in vivo and iv) it is associated with active chromatin having increased H3K9 acetylation and enrichment for CBP and SRC-1 binding in the newborn brain.

Conclusion

We have developed and validated a methodology to identify in vivo direct nuclear receptor target genes. This bioinformatics tool can be modified to scan for response elements of transcription factors, cis-regulatory modules, or any flexible DNA pattern.

The molecular basis of longevity, and clinical implications

The determinants of length of life are multifactorial and involve complex processes, most of which are not as yet understood completely. Tremendous advances have, however, been made in recent times in understanding some of the key molecular mechanisms that influence ageing and lifespan. Herein we highlight many of the more important findings and their potential clinical implications. Most of the intracellular factors involved in the ageing process, such as members of the sirtuin family, as well as insulin and insulin-like growth factor-I and their genes, are part of interconnected pathways. The manipulation of these and other genes in animal models can increase or decrease lifespan. Transcriptional and post-transcriptional regulatory mechanisms, some of which involve microRNAs, as well as modifications to chromatin and histones, can influence longevity. A decline in the function of stem cells might also be responsible for some aspects of mammalian ageing. Calorie restriction, polyphenols such as resveratrol, rapamycin, spermidine and angiotensin I converting enzyme inhibitor, are able to increase lifespan by modulation of branches of the longevity pathways. Molecular genetic studies of long-lived subjects have identified several potential candidate genes, but genetic research on ageing is in its infancy. Large genome-wide association studies should provide insights. Although new biomarkers for ageing and health, such as ones that might reveal telomere dysfunction, have been described, advances in the genetics and molecular biology of longevity will require interdisciplinary approaches if the much-hoped for success in alleviating the diseases of ageing, and an extension of both lifespan and healthspan is to be achieved.

Mimetics of hormetic agents: stress-resistance triggers

Mimetics of hormetic agents offer a novel approach to adjust dose to minimize the risk of toxic response, and maximize the benefit of induction of at least partial physiological conditioning. Nature selected and preserved those organisms and triggers that promote tolerance to stress. The induced tolerance can serve to resist that challenge and can repair previous age, disease, and trauma damage as well to provide a more youthful response to other stresses. The associated physiological conditioning may include youthful restoration of DNA repair, resistance to oxidizing pollutants, protein structure and function repair, improved immunity, tissue remodeling, adjustments in central and peripheral nervous systems, and altered metabolism. By elucidating common pathways activated by hormetic agent's mimetics, new strategies for intervention in aging, disease, and trauma emerge. Intervention potential in cancer, diabetes, age-related diseases, infectious diseases, cardiovascular diseases, and Alzheimer's disease are possible. Some hormetic mimetics exist in pathways in primitive organisms and are active or latent in humans. Peptides, oligonucleotides, and hormones are among the mimetics that activate latent resistance to radiation, physical endurance, strength, and immunity to physiological condition tolerance to stress. Co-activators may be required for expression of the desired physiological conditioning health and rejuvenation benefits.

Overexpression of FOXO1 in skeletal muscle does not alter longevity in mice

Caloric restriction (CR) is the most robust and reproducible intervention that can extend lifespan in rodents. Studies in invertebrates have led to the identification of genes that regulate lifespan, some of which encode components of the insulin or insulin-like signaling pathway, including DAF-16 (C. elegans) and dFOXO (Drosophila). Mice subjected to CR for 8 weeks showed an increase in FOXO1 mRNA and other longevity-related genes: Gadd 45alpha, glutamine synthase, and catalase in skeletal muscle. To investigate whether FOXO1 expression affects longevity in mammals, transgenic mice were studied that over-express FOXO1 in their skeletal muscle (FOXO1 mice), and in which muscle atrophy occurs. FOXO1 mice showed increases in Gadd 45alpha, and glutamine synthase proteins in skeletal muscle. In FOXO1 mice, the phosphorylation/dephosphorylation state of the p70 S6K and 4E-BP1 proteins were not altered, suggesting that translation initiation of protein synthesis might not be suppressed. The lifespan of FOXO1 mice was similar to their wild-type littermates. FOXO1 overexpression could not prevent aging-induced reduction in catalase, CuZu-SOD, and Mn-SOD mRNA in skeletal muscle. These data suggest that an increase in FOXO1 protein and its activation in skeletal muscle does not extend lifespan in mice.

Lifestyle-induced metabolic inflexibility and accelerated ageing syndrome: insulin resistance, friend or foe?

The metabolic syndrome may have its origins in thriftiness, insulin resistance and one of the most ancient of all signalling systems, redox. Thriftiness results from an evolutionarily-driven propensity to minimise energy expenditure. This has to be balanced with the need to resist the oxidative stress from cellular signalling and pathogen resistance, giving rise to something we call 'redox-thriftiness'. This is based on the notion that mitochondria may be able to both amplify membrane-derived redox growth signals as well as negatively regulate them, resulting in an increased ATP/ROS ratio. We suggest that 'redox-thriftiness' leads to insulin resistance, which has the effect of both protecting the individual cell from excessive growth/inflammatory stress, while ensuring energy is channelled to the brain, the immune system, and for storage. We also suggest that fine tuning of redox-thriftiness is achieved by hormetic (mild stress) signals that stimulate mitochondrial biogenesis and resistance to oxidative stress, which improves metabolic flexibility. However, in a non-hormetic environment with excessive calories, the protective nature of this system may lead to escalating insulin resistance and rising oxidative stress due to metabolic inflexibility and mitochondrial overload. Thus, the mitochondrially-associated resistance to oxidative stress (and metabolic flexibility) may determine insulin resistance. Genetically and environmentally determined mitochondrial function may define a 'tipping point' where protective insulin resistance tips over to inflammatory insulin resistance. Many hormetic factors may induce mild mitochondrial stress and biogenesis, including exercise, fasting, temperature extremes, unsaturated fats, polyphenols, alcohol, and even metformin and statins. Without hormesis, a proposed redox-thriftiness tipping point might lead to a feed forward insulin resistance cycle in the presence of excess calories. We therefore suggest that as oxidative stress determines functional longevity, a rather more descriptive term for the metabolic syndrome is the 'lifestyle-induced metabolic inflexibility and accelerated ageing syndrome'. Ultimately, thriftiness is good for us as long as we have hormetic stimuli; unfortunately, mankind is attempting to remove all hormetic (stressful) stimuli from his environment.

Role of sirtuin histone deacetylase SIRT1 in prostate cancer. A target for prostate cancer management via its inhibition?

Prostate cancer (PCa) is a major age-related malignancy, and according to estimates from the American Cancer Society, a man's chance of developing this cancer significantly increases with increasing age, from 1 in 10,149 by age 39 to 1 in 38 by age 59 to 1 in 7 by age 70. Therefore, it is important to identify the causal connection between mechanisms of aging and PCa. Employing in vitro and in vivo approaches, in this study, we tested the hypothesis that SIRT1, which belongs to the Sir2 (silent information regulator 2) family of sirtuin class III histone deacetylases, is overexpressed in PCa, and its inhibition will have antiproliferative effects in human PCa cells. Our data demonstrated that SIRT1 was significantly overexpressed in human PCa cells (DU145, LNCaP, 22Rnu1, and PC3) compared with normal prostate epithelial cells (PrEC) at protein, mRNA, and enzymatic activity levels. SIRT1 was also found to be overexpressed in human PCa tissues compared with adjacent normal prostate tissue. Interestingly, our data demonstrated that SIRT1 inhibition via nicotinamide and sirtinol (at the activity level) as well as via short hairpin RNA-mediated RNA interference (at the genetic level) resulted in a significant inhibition in the growth and viability of human PCa cells while having no effect on normal prostate epithelial cells. Further, we found that inhibition of SIRT1 caused an increase in FOXO1 acetylation and transcriptional activation in PCa cells. Our data suggested that SIRT1, via inhibiting FOXO1 activation, could contribute to the development of PCa. We suggest that SIRT1 could serve as a target toward developing novel strategies for PCa management.

Role of sirtuin histone deacetylase SIRT1 in prostate cancer. A target for prostate cancer management via its inhibition?

Prostate cancer (PCa) is a major age-related malignancy, and according to estimates from the American Cancer Society, a man's chance of developing this cancer significantly increases with increasing age, from 1 in 10,149 by age 39 to 1 in 38 by age 59 to 1 in 7 by age 70. Therefore, it is important to identify the causal connection between mechanisms of aging and PCa. Employing in vitro and in vivo approaches, in this study, we tested the hypothesis that SIRT1, which belongs to the Sir2 (silent information regulator 2) family of sirtuin class III histone deacetylases, is overexpressed in PCa, and its inhibition will have antiproliferative effects in human PCa cells. Our data demonstrated that SIRT1 was significantly overexpressed in human PCa cells (DU145, LNCaP, 22Rnu1, and PC3) compared with normal prostate epithelial cells (PrEC) at protein, mRNA, and enzymatic activity levels. SIRT1 was also found to be overexpressed in human PCa tissues compared with adjacent normal prostate tissue. Interestingly, our data demonstrated that SIRT1 inhibition via nicotinamide and sirtinol (at the activity level) as well as via short hairpin RNA-mediated RNA interference (at the genetic level) resulted in a significant inhibition in the growth and viability of human PCa cells while having no effect on normal prostate epithelial cells. Further, we found that inhibition of SIRT1 caused an increase in FOXO1 acetylation and transcriptional activation in PCa cells. Our data suggested that SIRT1, via inhibiting FOXO1 activation, could contribute to the development of PCa. We suggest that SIRT1 could serve as a target toward developing novel strategies for PCa management.

Age-associated impairment of Akt phosphorylation in primary rat hepatocytes is remediated by alpha-lipoic acid through PI3 kinase, PTEN, and PP2A

Akt is a highly regulated serine/threonine kinase involved in stress response and cell survival. Stress response pathways must cope with increasing chronic stress susceptibility with age. We found an age-related lesion in Akt activity via loss of phosphorylation on Ser473. In hepatocytes from old rats, basal phospho-Ser473 Akt is 30% lower when compared to young, but basal phospho-Thr308 Akt is unchanged. (R)-alpha-lipoic acid (LA), a dithiol compound with antioxidant properties, is effective against age-related increases in oxidative stress and has been used to improve glucose utilization through insulin receptor (IR) pathway-mediated Akt phosphorylation. Treatment with physiologically relevant doses of LA (50 microM) provided a 30% increase in phospho-Ser473. Furthermore, two phosphatases that antagonize Akt, PTEN and PP2A, were both partially inhibited by LA. Thus, LA may be a nutritive agent that can remediate loss of function in the Akt pathway and aid in the survival of liver cells.

The forkhead transcription factor FOXO4 sensitizes cancer cells to doxorubicin-mediated cytotoxicity

The forkhead superfamily of transcription factors, which play major roles in control of cellular proliferation, oxidative stress and apoptosis, are becoming more and more considered as crucial therapeutic targets in cancer. In this study, we addressed the contribution of class O of forkhead box transcription factor (FOXO) 4 transcription factor, a forkhead superfamily member, to cytotoxicity mediated by the anthracyclic drug doxorubicin. FOXO4 can be phosphorylated by phosphatidylinositol-3-kinase/AKT signaling resulting in its inactivation and nuclear exclusion. Under stress conditions, FOXO4 can be phosphorylated via jun N-terminal kinase (JNK) leading to increased transcriptional activation of the transcription factor. Our results show that doxorubicin incubation led to phosphorylation of AKT and concomitantly to AKT-dependent inactivation and nuclear exclusion of the tumor suppressor FOXO4 in Hct-116 cells. We found that inhibition of FOXO4 nuclear exclusion by blockage of AKT phosphorylation following overexpression of dominant-negative AKT enhanced doxorubicin-mediated cytotoxicity. Overexpression of wild-type FOXO4 led to an increase in doxorubicin-mediated cytotoxicity, which was further exacerbated by overexpression of a solely nuclear-localized FOXO4 mutant. In contrast, though doxorubicin resulted in JNK activation, modulation of JNK-dependent regulation of FOXO4 was of no effect to doxorubicin cytotoxicity. These results show for the first time that in Hct-116 cells sustained nuclear localization of FOXO4 seems to be one crucial point enhancing doxorubicin-induced cytotoxicity and apoptosis. Targeting FOXO4 or AKT may lead to new chances in sensitizing cancer cells to cytostatic drugs thereby allowing use of lower drug concentrations and minimizing drug-induced adverse effects in patients.

Regulation and function of foxe3 during early zebrafish development

In this article, we investigate the expression, regulation, and function of the zebrafish forkhead gene foxe3. In wild type embryos, foxe3 is first expressed in a crescent-shaped area at the anterior end of the prechordal plate, corresponding to the polster. At later stages, the hatching gland, the lens, and the anterior pituitary express this gene. Using morpholinos against the zinc finger Kruppel-like factor 4 (KLF4) we show that foxe3 is regulated differently in the polster and in the lens. In the absence of KLF4, expression of foxe3 in the polster is not activated, whereas in the lens placode the expression of KLF4 is not required for the transcription of foxe3. The expression of foxe3 is also regulated by the hedgehog and nodal signaling pathways. foxe3 expression is altered in the hedgehog pathway mutants iguana and you-too and the nodal pathway mutant cyclops. foxe3 function is necessary for the execution of lens-specific gene expression and lens morphogenesis, as the knockdown of foxe3 results in a loss of platelet-derived growth factor receptor alpha (pdgfralpha) expression and in the vacuolization of the lens.

Forkhead class O transcription factor 3a activation and Sirtuin1 overexpression in the hypertrophied myocardium of the diabetic Goto-Kakizaki rat

BACKGROUND

Ventricular remodeling in type 2 diabetes predisposes to fatal coronary heart disease. The proapoptotic forkhead class O transcription factor 3a (FOXO3a) and its modulator, the cardioprotective longevity factor and class III histone deacetylase Sirtuin1 (Sirt1), have been implicated in the regulation of the cardiomyocyte lifespan and hypertrophy.

OBJECTIVE

To examine whether FOXO3a-Sirt1 activation is involved in diabetes-induced cardiomyocyte apoptosis and ventricular hypertrophy.

METHODS

The blood pressure, cardiac functions, cardiomyocyte size, neurohumoral markers, cardiomyocyte apoptosis, nuclear binding of FOXO3a, and Sirt1 expression were determined for 12-week-old spontaneously diabetic Goto-Kakizaki rats and the nondiabetic Wistar control rats.

RESULTS

Goto-Kakizaki rats showed a modest increase in blood pressure, pronounced cardiac hypertrophy, impaired systolic function, and increased plasma brain natriuretic peptide level without changes in plasma renin activity, serum aldosterone or urinary noradrenaline excretion. The cardiomyocyte cross-sectional area was increased by 22%. Phosphorylation of FOXO3a was decreased with a concomitant increase in its nuclear translocation. The myocardial expression of the antiapoptotic FOXO3a modulator Sirt1 was increased two-fold. Acetylation of p53 at the Sirt1-specific lysine 373/382 site was markedly decreased. Myocardial caspase-3 and Bax expression were increased, indicating increased apoptotic signaling; however, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling staining did not reveal any significant increase in cardiomyocyte apoptosis.

CONCLUSIONS

Diabetes-induced cardiac remodeling in Goto-Kakizaki rats is associated with cardiac hypertrophy, systolic dysfunction, increased apoptotic signaling and activation of the FOXO3a pathway. The present study also suggests that antiapoptotic Sirt1 protects against cardiomyocyte apoptosis and acts as a novel regulator of cardiomyocyte growth.

FOXO transcription factors are mechanosensitive and their regulation is altered with aging in the respiratory pump

The mechanical regulation of the forkhead box O (FOXO) subclass of transcription factors in the respiratory pump and its implication in aging are completely unknown. We investigated the effects of diaphragm stretch on three FOXO isoforms, Foxo1, Foxo3a, and Foxo4, in normal mice at different ages. We tested the hypotheses that 1) FOXO activities are regulated in response to diaphragm stretch and 2) mechanical properties of aging diaphragm are altered, leading to altered regulation of FOXO with aging. Our results showed that stretch downregulated FOXO DNA-binding activity by a mechanism that required Akt and IKK activation in young mice but that these pathways lost their mechanosensitivity with age. This aberrant regulation of FOXO with aging was associated with altered viscoelasticity, compliance, and extensibility of the aged diaphragm. Curiously, the dramatic decrease of the nuclear content of Foxo1 and Foxo3a, the two isoforms associated with muscle atrophy, with aging correlated with higher basal activation of Akt and IKK signaling in diaphragms of old mice. In contrast, the stability of Foxo4 in the nucleus became dependent on JNK, which is strongly activated in aged diaphragm. This finding suggests that Foxo4 was responsible for the FOXO-dependent transcriptional activity in aging diaphragm. Our data support the hypothesis that aging alters the mechanical properties of the respiratory pump, leading to altered mechanical regulation of the stretch-induced signaling pathways controlling FOXO activities. Our study supports a mechanosensitive signaling mechanism that is responsible for regulation of the FOXO transcription factors by aging.

A combination of genomic approaches reveals the role of FOXO1a in regulating an oxidative stress response pathway

BACKGROUND

While many of the phenotypic differences between human and chimpanzee may result from changes in gene regulation, only a handful of functionally important regulatory differences are currently known. As a first step towards identifying transcriptional pathways that have been remodeled in the human lineage, we focused on a transcription factor, FOXO1a, which we had previously found to be up-regulated in the human liver compared to that of three other primate species. We concentrated on this gene because of its known role in the regulation of metabolism and in longevity.

METHODOLOGY

Using a combination of expression profiling following siRNA knockdown and chromatin immunoprecipitation in a human liver cell line, we identified eight novel direct transcriptional targets of FOXO1a. This set includes the gene for thioredoxin-interacting protein (TXNIP), the expression of which is directly repressed by FOXO1a. The thioredoxin-interacting protein is known to inhibit the reducing activity of thioredoxin (TRX), thereby hindering the cellular response to oxidative stress and affecting life span.

CONCLUSIONS

Our results provide an explanation for the repeated observations that differences in the regulation of FOXO transcription factors affect longevity. Moreover, we found that TXNIP is down-regulated in human compared to chimpanzee, consistent with the up-regulation of its direct repressor FOXO1a in humans, and with differences in longevity between the two species.

FoxO transcription factors activate Akt and attenuate insulin signaling in heart by inhibiting protein phosphatases

Insulin resistance and metabolic syndrome are rapidly expanding public health problems. Acting through the PI3K/Akt pathway, insulin and insulin-like growth factor-1 (IGF-1) inactivate FoxO transcription factors, a class of highly conserved proteins important in numerous physiological functions. However, even as FoxO is a downstream target of insulin, FoxO factors also control upstream signaling elements governing insulin sensitivity and glucose metabolism. Here, we report that sustained activation of either FoxO1 or FoxO3 in cardiac myocytes increases basal levels of Akt phosphorylation and kinase activity. FoxO-activated Akt directly interacts with and phosphorylates FoxO, providing feedback inhibition. We reported previously that FoxO factors attenuate cardiomyocyte calcineurin (PP2B) activity. We now show that calcineurin forms a complex with Akt and inhibition of calcineurin enhances Akt phosphorylation. In addition, FoxO activity suppresses protein phosphatase 2A (PP2A) and disrupts Akt-PP2A and Akt-calcineurin interactions. Repression of Akt-PP2A/B interactions and phosphatase activities contributes, at least in part, to FoxO-dependent increases in Akt phosphorylation and kinase activity. Resveratrol, an activator of Sirt1, increases the transcriptional activity of FoxO1 and triggers Akt phosphorylation in heart. Importantly, FoxO-mediated increases in Akt activity diminish insulin signaling, as manifested by reduced Akt phosphorylation, reduced membrane translocation of Glut4, and decreased insulin-triggered glucose uptake. Also, inactivation of the gene coding for FoxO3 enhances insulin-dependent Akt phosphorylation. Taken together, this study demonstrates that changes in FoxO activity have a dose-responsive repressive effect on insulin signaling in cardiomyocytes through inhibition of protein phosphatases, which leads to altered Akt activation, reduced insulin sensitivity, and impaired glucose metabolism.

Colon Cancer and Physical Activity: A Content Analysis of Reciprocal Relationship

Background

Colon cancer is among the leading causes of cancer mortality and its incidence is increasing worldwide. This is true in spite of broad basic research into colon cancer while, concurrently, physical activity has been shown to offer significant preventive potential. This background led to the formulation of the following research questions: • Why is physical activity so effective in decreasing the incidence of colon cancer? • Is there a common denominator to colon cancer and physical activity, which has a reciprocal function? • Knowing the potential for public health impact of physical activity on colon cancer, has physical activity-colon cancer relationship been in the forefront of research efforts?

Methods

Content analysis of archival literature has been carried out on census of 32,822 message units, extracted from the National Library of Medicine and its PubMed database. The following search terms were used: colon cancer, physical activity, melatonin, age/genetics, diet (obesity, vitamin D, calcium), immunity/inflammation, and bioactive substances incorporating insulin-like growth factor 1, interleukins, and prostaglandins. The research timeframe for each category began with the first article published and ended with the last one printed in 2005.

Results/Conclusions

The effectiveness of physical activity in decreasing the incidence of colon cancer is likely the result of its biologic activity within not one or two but all of the major known colon cancer etiologies, demonstrating a powerful reciprocal relationship. Melatonin is identified as a plausible common denominator of colon cancer and physical activity. The greatest volume of publications deals with colon cancer and genetics. A significant societal health care impact could be achieved by adopting physical activity as a major cancer control strategy.

Syntheses of nicotinamide riboside and derivatives: effective agents for increasing nicotinamide adenine dinucleotide concentrations in mammalian cells

A new two-step methodology achieves stereoselective synthesis of beta-nicotinamide riboside and a series of related amide, ester, and acid nucleosides. Compounds were prepared through a triacetylated-nicotinate ester nucleoside, via coupling of either ethylnicotinate or phenylnicotinate with 1,2,3,5-tetra-O-acetyl-beta-D-ribofuranose. Nicotinamide riboside, nicotinic acid riboside, O-ethylnicotinate riboside, O-methylnicotinate riboside, and several N-alkyl derivatives increased NAD+ concentrations from 1.2-2.7-fold in several mammalian cell lines. These findings establish bioavailability and potent effects of these nucleosides in stimulating the increase of NAD+ concentrations in mammalian cells.

FOXO and insulin signaling regulate sensitivity of the circadian clock to oxidative stress

Circadian rhythms can be regulated by many environmental and endogenous factors. We show here a sensitivity of circadian clock function to oxidative stress that is revealed in flies lacking the foxo gene product. When exposed to oxidative stress, wild-type flies showed attenuated clock gene cycling in peripheral tissues, whereas foxo mutants also lost behavioral rhythms driven by the central clock. FOXO is expressed predominantly in the fat body, and transgenic expression in this tissue rescued the mutant behavioral phenotype, suggesting that foxo has non-cell-autonomous effects on central circadian clock function. Overexpression of signaling molecules that affect FOXO activity, such as the insulin receptor or Akt, in the fat body also increased susceptibility of the central clock to oxidative stress. Finally, foxo mutants showed a rapid decline in rest:activity rhythms with age, supporting the idea that the increase of oxidative stress contributes to age-associated degeneration of behavioral rhythms and indicating the importance of FOXO in mitigating this deterioration. Together these data demonstrate that metabolism affects central clock function and provide a link among insulin signaling, oxidative stress, aging, and circadian rhythms.