Oxidative damage and age-related functional declines

Mitochondrial superoxide anion (O(2)(-)) inducible "mev-1" animal models for aging research

Most intracellular reactive oxygen species (ROS), especially superoxide anion (O(2)(-)) that is converted from oxygen, are overproduced by excessive electron leakage from the mitochondrial respiratory chain. Intracellular oxidative stress that damages cellular components can contribute to lifestyle-related diseases such as diabetes and arteriosclerosis, and age-related diseases such as cancer and neuronal degenerative diseases. We have previously demonstrated that the excessive mitochondrial O(2)(-) production caused by SDHC mutations (G71E in C. elegans, I71E in Drosophila and V69E in mouse) results in premature death in C. elegans and Drosophila, cancer in mouse embryonic fibroblast cells and infertility in transgenic mice. SDHC is a subunit of mitochondrial complex II. In humans, it has been reported that mutations in SDHB, SDHC or SDHD often result in inherited head and neck paragangliomas (PGLs). Recently, we established Tet-mev-1 conditional transgenic mice using our uniquely developed Tet-On/Off system, which equilibrates transgene expression to endogenous levels. These mice experienced mitochondrial respiratory chain dysfunction that resulted in O(2)(-) overproduction. The mitochondrial oxidative stress caused excessive apoptosis leading to low birth weight and growth retardation in the neonatal developmental phase in Tet-mev-1 mice. Here, we briefly describe the relationships between mitochondrial O(2)(-) and aging phenomena in mev-1 animal models. [BMB reports 2011; 44(5): 298-305].

Genetics and genomics of human ageing

Ageing in humans is typified by the decline of physiological functions in various organs and tissues leading to an increased probability of death. Some individuals delay, escape or survive much of this age-related decline and live past age 100. Studies comparing centenarians to average-aged individuals have found polymorphisms in genes that are associated with long life, including APOE and FOXOA3, which have been replicated many times. However, the associations found in humans account for small percentages of the variance in lifespan and many other gene associations have not been replicated in additional populations. Therefore, ageing is probably a highly polygenic trait. In humans, it is important to also consider differences in age-related decline that occur within and among tissues. Longitudinal data of age-related traits can be used in association studies to test for polymorphisms that predict how an individual will change over time. Transcriptional and genetic association studies of different tissues have revealed common and unique pathways involved in human ageing. Genomic convergence is a method that combines multiple types of functional genomic information such as transcriptional profiling, expression quantitative trait mapping and gene association. The genomic convergence approach has been used to implicate the gene MMP20 in human kidney ageing. New human genetics technologies are continually in development and may lead to additional breakthroughs in human ageing in the near future.

Early life benefits and later life costs of a two amino acid deletion in Drosophila simulans

Linking naturally occurring genotypic variation to the organismal phenotype is critical to our understanding of, and ability to, model biological processes such as adaptation to novel environments, disease, and aging. Rarely, however, does a simple mutation cause a single simple observable trait. Rather it is more common for a mutation to elicit an entangled web of responses. Here, we employ biochemistry as the thread to link a naturally occurring two amino acid deletion in a nuclear encoded mitochondrial protein with physiological benefits and costs in the fly Drosophila simulans. This nuclear encoded gene produces a protein that is imported into the mitochondrion and forms a subunit of complex IV (cytochrome c oxidase, or cox) of the electron transport chain. We observe that flies homozygous for the deletion have an advantage when young but pay a cost later in life. These data show that the organism responds to the deletion in a complex manner that gives insight into the mechanisms that influence mitochondrial bioenergetics and aspects of organismal physiology.

A role for immature myeloid cells in immune senescence

The reduced efficiency of the mammalian immune system with aging increases host susceptibility to infectious and autoimmune diseases. However, the mechanisms responsible for these pathologic changes are not well understood. In this study, we demonstrate that the bone marrow, blood, and secondary lymphoid organs of healthy aged mice possess increased numbers of immature myeloid cells that are phenotypically similar to myeloid-derived suppressor cells found in lymphoid organs of mice with progressive tumors and other pathologic conditions associated with chronic inflammation. These cells are characterized by the presence of Gr1 and CD11b markers on their surfaces. Gr1(+)CD11b(+) cells isolated from aged mice possess an ability to suppress T cell proliferation/activation and produce heightened levels of proinflammatory cytokines, both constitutively and upon activation, including IL-12, which promotes an excessive production of IFN-γ. IFN-γ priming is essential for excessive proinflammatory cytokine production and the suppressive activities by Gr1(+)CD11b(+) cells from aged mice. These cells suppress T cell proliferation through an NO-dependent mechanism, as depletion of splenic Gr1(+) cells reduces NO levels and restores T cell proliferation. Insights into mechanisms responsible for the proinflammatory and immune suppressive activities of Gr1(+)CD11b(+) cells from aged mice have uncovered a defective PI3K-Akt signaling pathway, leading to a reduced Akt-dependent inactivation of GSK3β. Our data demonstrate that abnormal activities of the Gr1(+)CD11b(+) myeloid cell population from aged mice could play a significant role in the mechanisms responsible for immune senescence.

Nutraceutical antioxidants as novel neuroprotective agents

A variety of antioxidant compounds derived from natural products (nutraceuticals) have demonstrated neuroprotective activity in either in vitro or in vivo models of neuronal cell death or neurodegeneration, respectively. These natural antioxidants fall into several distinct groups based on their chemical structures: (1) flavonoid polyphenols like epigallocatechin 3-gallate (EGCG) from green tea and quercetin from apples; (2) non-flavonoid polyphenols such as curcumin from tumeric and resveratrol from grapes; (3) phenolic acids or phenolic diterpenes such as rosmarinic acid or carnosic acid, respectively, both from rosemary; and (4) organosulfur compounds including the isothiocyanate, L-sulforaphane, from broccoli and the thiosulfonate allicin, from garlic. All of these compounds are generally considered to be antioxidants. They may be classified this way either because they directly scavenge free radicals or they indirectly increase endogenous cellular antioxidant defenses, for example, via activation of the nuclear factor erythroid-derived 2-related factor 2 (Nrf2) transcription factor pathway. Alternative mechanisms of action have also been suggested for the neuroprotective effects of these compounds such as modulation of signal transduction cascades or effects on gene expression. Here, we review the literature pertaining to these various classes of nutraceutical antioxidants and discuss their potential therapeutic value in neurodegenerative diseases.

Protein homeostasis in models of aging and age-related conformational disease

The stability of the proteome is crucial to the health of the cell, and contributes significantly to the lifespan of the organism. Aging and many age-related diseases have in common the expression of misfolded and damaged proteins. The chronic expression of damaged proteins during disease can have devastating consequences on protein homeostasis (proteostasis), resulting in disruption ofnumerous biological processes. This chapter discusses our current understanding of the various contributors to protein misfolding, and the mechanisms by which misfolding, and accompanied aggregation/toxicity, is accelerated by stress and aging. Invertebrate models have been instrumental in studying the processes related to aggregation and toxicity of disease-associated proteins and how dysregulation ofproteostasis leads to neurodegenerative diseases of aging.

Metal-related oxidative stress in birds

Metals can cause oxidative stress by increasing the formation of reactive oxygen species (ROS), which render antioxidants incapable of defence against growing amounts of free radicals. Metal toxicity is related to their oxidative state and reactivity with other compounds. Our aim is to review the mechanisms on how metals cause oxidative stress and what is known about metal-induced oxidative stress in wildlife. Taking birds as model organisms, we summarize the mechanisms responsible for antioxidant depletion and give a view of how to detect metal-induced oxidative stress in birds by using different biomarkers. The mechanisms producing the harmful effects of oxidative stress are complex with different biomolecular mechanisms associated with ecotoxicological and ecological aspects. The majority of the studies concerning metals and ROS related to oxidative stress have focused on the biomolecular level, but little is known about the effects at the cellular level or at the level of individuals or populations.

Dietary amelioration of locomotor, neurotransmitter and mitochondrial aging

Aging degrades motivation, cognition, sensory modalities and physical capacities, essentially dimming zestful living. Bradykinesis (declining physical movement) is a highly reliable biomarker of aging and mortality risk. Mice fed a complex dietary supplement (DSP) designed to ameliorate five mechanisms associated with aging showed no loss of total daily locomotion compared with >50% decrement in old untreated mice. This was associated with boosted striatal neuropeptide Y, reversal of age-related declines in mitochondrial complex III activity in brain and amelioration of oxidative stress (brain protein carbonyls). Supplemented mice expressed ∼50% fewer mitochondrial protein carbonyls per unit of complex III activity. Reduction of free radical production by mitochondria may explain the exceptional longevity of birds and dietary restricted animals and no DSP is known to impact this mechanism. Functional benefits greatly exceeded the modest longevity increases documented for supplemented normal mice. Regardless, for aging humans maintaining zestful health and performance into later years may provide greater social and economic benefits than simply prolonging lifespan. Although identifying the role of specific ingredients and interactions remains outstanding, results provide proof of principle that complex dietary cocktails can powerfully ameliorate biomarkers of aging and modulate mechanisms considered ultimate goals for aging interventions.

Ionizing radiation and aging: rejuvenating an old idea

This paper reviews the contemporary evidence that radiation can accelerate aging, degenerative health effects and mortality. Around the 1960s, the idea that ionizing radiation caused premature aging was dismissed as the radiation-induced health effects appeared to be virtually confined to neoplasms. More recently, radiation has become associated with a much wider spectrum of age-related diseases, including cardiovascular disease; although some diseases of old age, such as diabetes, are notably absent as a radiation risk. On the basis of recent research, is there a stronger case today to be made linking radiation and aging? Comparison is made between the now-known biological mechanisms of aging and those of radiation, including oxidative stress, chromosomal damage, apoptosis, stem cell exhaustion and inflammation. The association between radiation effects and the free-radical theory of aging as the causative hypothesis seems to be more compelling than that between radiation and the nutrient-sensing TOR pathway. Premature aging has been assessed by biomarkers in calorie restriction studies; yet, biomarkers such as telomere erosion and p16(INK4a) are ambiguous for radiation-induced aging. Some animal studies suggest low dose radiation may even demonstrate hormesis health benefits. Regardless, there is virtually no support for a life span extending hypothesis for A-bomb survivors and other exposed subjects.

The effects of age and behavioral development on honey bee (Apis mellifera) flight performance

A critical but seldom-studied component of life history theory is how behavior and age affect whole-organism performance. To address this issue we compared the flight performance of honey bees (whose behavioral development and age can be assessed independently via simple manipulations of colony demographics) between distinct behavioral castes (in-hive nurse bees vs out-of-hive foragers) and across lifespan. Variable-density gases and high-speed video were used to determine the maximum hovering flight capacity and wing kinematics of age-matched nurse bees and foragers sampled from a single-cohort colony over a period of 34 days. The transition from hive work to foraging was accompanied by a 42% decrease in body mass and a proportional increase in flight capacity (defined as the minimum gas density allowing hovering flight). The lower flight capacity of hive bees was primarily due to the fact that in air they were functioning at a near-maximal wing angular velocity due to their high body masses. Foragers were lighter and when hovering in air required a much lower wing angular velocity, which they were able to increase by 32% during maximal flight performance. Flight performance of hive bees was independent of age, but in foragers the maximal wingbeat frequency and maximal average angular velocity were lowest in precocious (7-14 day old) foragers, highest in normal-aged (15-28 day old) foragers and intermediate in foragers older than 29 days. This pattern coincides with previously described age-dependent biochemical and metabolic properties of honey bee flight muscle.

Methylglyoxal: possible link between hyperglycaemia and immune suppression?

No matter the cause of diabetes, the result is always hyperglycaemia. This excess glucose metabolism drives several damage pathways and raises concentrations of the reactive dicarbonyl, methylglyoxal (MG). MG can modify the structure and function of target molecules by forming advanced glycation end-products (AGEs) that act through their receptor (RAGE) to perpetuate vascular and neuronal injury responsible for long-term complications of diabetes. Diabetes patients also suffer lower resistance to many common infections, although the cause(s) for this lower resistance remains elusive. Here, we review recent evidence concerning immune suppression in diabetes and discuss the effects of MG on components of the immune system. We suggest that MG could be a missing link between hyperglycaemia and immune suppression in diabetes.

Food level and sex shape predator-induced physiological stress: immune defence and antioxidant defence

Despite the potential impact on prey fitness and predator-prey interactions, most studies of predation risk ignore physiological responses and their dependence upon food level and sex. Therefore, we reared male and female larvae of the damselfly Lestes viridis under predator stress (dragonfly larvae) at high and low food levels, and subsequently scored for important variables of insect immune defence (i.e. phenoloxidase) and antioxidant defence [i.e. superoxide dismutase, and catalase (CAT)]. Under predation risk, larvae did not decrease growth rate or immune defence, and only slightly reduced food intake in the high food treatment, probably because of time stress, i.e. little time available to complete the larval development. However, larvae facing predator stress did show an upregulation of antioxidant enzymes. This upregulation was dependent upon food level for CAT and both food level and sex for SOD, consistent with energetic constraints and sex differences in the link between longevity and adult fitness. Our results illustrate that predator stress can influence life history, behavioural and physiological responses differentially and in a context-dependent way. This implies that non-consumptive physiological effects of predators on their prey show independent yet similar complexities in behavioural and life history response variables. In general, our results advocate that mechanistic studies on predator-prey interactions may benefit from including physiological variables.

Manipulation of Sod1 expression ubiquitously, but not in the nervous system or muscle, impacts age-related parameters in Drosophila

Superoxide dismutase 1 (SOD1) is an important antioxidant previously shown to impact life span in Drosophila. We examined the consequences of manipulating Sod1 expression throughout the body or in the nervous system or musculature on life span and age-related locomotor impairment (ARLI) in Drosophila. Ubiquitous overexpression of SOD1 extended life span but did not substantially forestall ARLI, whereas ubiquitous knock-down of Sod1 shortened life span and accelerated ARLI. Interestingly, neither overexpression of Sod1 nor expression of Sod1 RNAi in the nervous system or muscle altered life span or ARLI. Our studies suggest that the control of reactive oxygen species by SOD1 in tissues other than the nervous system and musculature support life span and ARLI in Drosophila.

Modulation of DNA glycosylase activities in mesenchymal stem cells

Adipose-tissue derived mesenchymal stem cells (AT-MSCs) are a promising tool for use in cell-based therapies. However, in vitro expansion is required to obtain clinically relevant cell numbers, and this might increase the chance of genomic instability. DNA repair is crucial for maintaining DNA integrity. Here we have compared the initial step of base excision repair in uncultured and cultured AT-MSCs by analysis of base removal activities and expression levels of relevant DNA glycosylases. Uracil, 5-hydroxyuracil and ethenoadenine removal activities were upregulated in cultured cells compared to uncultured cells. In contrast, both the 8-oxo-7,8-dihydroguanine (8-oxoG) removal activity and the concentration of 8-oxoG bases in the DNA were reduced in the cultured cells. Gene expression analysis showed no substantial changes in mRNA expression. The glycosylase activities remained stable through at least 12 passages, suggesting that DNA repair is proficient through the period required for in vitro expansion of AT-MSCs to clinically relevant numbers.

Association between serum gamma-glutamyltransferase and cardiovascular mortality varies by age: the Minnesota Heart Survey

BACKGROUND

Although serum gamma-glutamyltransferase (GGT) predicted cardiovascular diseases (CVD) in prospective studies and may be useful in risk assessment, prediction in older adults was weaker in several studies.

METHODS

We performed a nested case-control study with 5-12-year follow-up in 137 CVD deaths and 249 controls (frequency-matched on age, sex, and examination year, age range 26-85 years).

RESULTS

An age interaction of serum GGT and CVD mortality (P value for interaction=0.02) was observed. After adjusting for known CVD risk factors, compared with the lowest tertile, odds ratios (95% confidence intervals) in participants less than 70 years (half the participants) were: middle tertile: 2.17 (0.68-6.97), top tertile up to GGT less than 50 U/l: 3.54 (1.07-11.7), and GGT >/=50 U/l: 4.69 (1.16-18.9). In participants aged more than or equal to 70 years, GGT was not related to CVD. Well-known demographic and health behavior associations with serum GGT were observed only in controls among participants aged less than 70 years.

CONCLUSION

Our findings suggest that serum GGT within its normal range can predict CVD mortality in those aged less than 70 years, but may have limited usefulness for risk assessment in older adults.

Expression patterns of Neil3 during embryonic brain development and neoplasia

Background

The base excision repair pathway is responsible for repairing small DNA base lesions caused by endogenous and exogenous damaging agents. Repair is initiated by DNA glycosylases that recognize and remove the lesions. NEIL3 is one of 11 mammalian DNA glycosylases identified to date and it was discovered on the basis of sequence homology to the E. coli Fpg and Nei glycosylases. Difficulties in purifying the protein have limited its biochemical characterization and in contrast to the other glycosylases, its function remains unclear.

Results

In this study we describe the expression pattern of Neil3 during mouse embryonic development with special focus on brain development. We have also looked at the expression of NEIL3 in several normal and tumor tissues. Quantitative real-time PCR and in situ hybridization revealed that Neil3 was highly expressed at embryonic days 12–13, when neurogenesis starts. The expression decreased during development and in the adult brain,Neil3 could not be detected in any of the brain areas examined by quantitative real-time PCR. During embryogenesis and in newborn mice specific expression was observed in areas known to harbour neural stem and progenitor cells such as the subventricular zone and the dentate gyrus. Finally, NEIL3 expression was higher in tumors compared to normal tissues, except for testis and pancreas.

Conclusion

Our findings indicate that mammalian NEIL3 is specifically expressed in brain areas where neurogenesis takes place during development and that its expression is tightly regulated both temporally and spatially. In addition, NEIL3 seems to be upregulated in tumor tissues compared to normal tissues. Altogether, mammalian NEIL3 seems to be highly expressed in cells with high proliferative potential.

Confronting challenges in intervention research with ethnically diverse older adults: the USC Well Elderly II Trial

BACKGROUND

Community-dwelling older adults are at risk for declines in physical health, cognition, and psychosocial well-being. However, their enactment of active and health-promoting lifestyles can reduce such declines.

PURPOSE

The purpose of this article is to describe the USC Well Elderly II study, a randomized clinical trial designed to test the effectiveness of a healthy lifestyle program for elders, and document how various methodological challenges were addressed during the course of the trial.

METHODS

In the study, 460 ethnically diverse elders recruited from a variety of sites in the urban Los Angeles area were enrolled in a randomized experiment involving a crossover design component. Within either the first or second 6-month phase of their study involvement, each elder received a lifestyle intervention designed to improve a variety of aging outcomes. At 4-5 time points over an 18-24 month interval, the research participants were assessed on measures of healthy activity, coping, social support, perceived control, stress-related biomarkers, perceived physical health, psychosocial well-being, and cognitive functioning to test the effectiveness of the intervention and document the process mechanisms responsible for its effects.

RESULTS

The study protocol was successfully implemented, including the enrollment of study sites, the recruitment of 460 older adults, administration of the intervention, adherence to the plan for assessment, and establishment of a large computerized data base.

LIMITATIONS

Methodological challenges were encountered in the areas of site recruitment, participant recruitment, testing, and intervention delivery.

CONCLUSIONS

The completion of clinical trials involving elders from numerous local sites requires careful oversight and anticipation of threats to the study design that stem from: (a) social situations that are particular to specific study sites; and (b) physical, functional, and social challenges pertaining to the elder population.

The absence of a mitochondrial genome in rho0 yeast cells extends lifespan independently of retrograde regulation

The absence of mtDNA in rho0 yeast cells affects both respiration and mitochondrial-nuclear communication (e.g., retrograde regulation, intergenomic signaling, or pleiotropic drug resistance). Previously, it has been reported that some rho0 strains have increased replicative lifespans, attributable to the lack of respiration and retrograde regulation. Here, we have been able to confirm that rho0 cells exhibit increased replicative lifespans but have found that this is not associated with the lack of respiration or reduced oxidative stress but instead, is related to the lack of mtDNA per se in rho0 cells. Also, we find no correlation between the strength of retrograde regulation and lifespan. Furthermore, we find that pdr3- or rtg2- mutations are not responsible for lifespan extension in rho0 cells, ruling out a specific role for PDR3-pleiotropic drug resistance or RGT2-retrograde regulation pathways in the extended lifespans of rho0 cells. Surprisingly, Rtg3p, which acts downstream of Rtg2p, is required for lifespan increase in rho0 cells. Together, these findings indicate that the loss of mtDNA per se and not the lack of respiration lead to extended longevity in rho0 cells. They also suggest that Rtg3p, acting independently of retrograde regulation, mediates this effect, possibly via intergenomic signaling.

Antioxidant and antiapoptotic activities of deprenyl and estradiol co-administration in aged rat kidney

Aging is a progressive degeneration process in living organisms. Deprenyl is an irreversible monoamine-oxidase B inhibitor which has antioxidant, antiapoptotic and neuroprotective effects. Estradiol is also a neuroprotective and antioxidant hormone. The objective of this study was to determine whether the antioxidative effects of deprenyl can suppress apoptotic activity, with or without estradiol, in aged female rat kidney. Wistar Albino female rats were divided into six groups as follows; young (3 months old) control, aged (24 months old) control, aged deprenyl treated, aged estradiol treated, aged deprenyl plus estradiol treated and sham. All rats except for the sham group were injected for 21 days. Determination of oxidative stress parameter was performed spectrophotometrically. To detect apoptotic cells, TUNEL staining and caspase-3 immunohistochemistry were performed. Deprenyl and estradiol administration, alone or in combination, decreased significantly the levels of lipid peroxidation relative to aged control and sham-injected rats. The number of TUNEL positive cells decreased significantly in deprenyl and estradiol-treated rats compared with aged control and sham rats. Deprenyl and estradiol replacement attenuated age-related changes in renal morphology. The results indicate that deprenyl treatment alone, or in combination with estradiol, may modulate age-related apoptotic changes in rat kidney by decreasing oxidative stress.

Caloric Restriction Does Not Offset Age-Associated Changes in the Biophysical Properties of Motoneurons

Age-associated changes in neuromuscular function may be due to a loss of motor neurons as well as changes in their biophysical properties. Neuronal damage imposed by reactive oxygen species may contribute to age-related deficits in CNS function. Thus we hypothesized that aging would alter the functional properties of motoneurons and that caloric-restriction would offset these changes. Intracellular recordings were made from lumbar motoneurons of old Fisher Brown Norway (FBN) fed ad libitum (oldAL, 30.8 ± 1.3 mo) or on a fortified calorie-restricted diet from 14 wk of age (oldCR, 31.0 ± 1.8 mo). Basic and rhythmic firing properties recorded from these aged motoneurons (MNs) were compared with properties recorded from young FBN controls (young, 8.4 ± 4.6 mo). Compared with young MNs, old MNs had a 104% greater ( P < 0.001) afterhyperpolarization potential (AHP), a 21.1% longer AHP half-decay time ( P < 0.05), 28.7% lower rheobase ( P < 0.001), 49.7% greater ( P < 0.001) input resistance, 21.1% ( P < 0.0001) less spike frequency adaptation, lower minimal (30.2%, P < 0.0001) and maximal (16.7%, P < 0.0001) steady-state firing frequencies, a lower (35.5%, P < 0.0001) frequency-current slope, and an increased incidence of persistent inward current. Because basic properties became more diverse in old MNs and the slope of the frequency-current relationship, which is normally similar for high- and low-threshold MNs, was lower in the old group, we conclude that aging alters the biophysical properties of MNs in a fashion that cannot be simply attributed to a loss of high-threshold MNs. Surprisingly, caloric restriction, which is known to attenuate aging-associated changes in hindlimb muscles, had no effect on the progress of aging in the innervating MNs.

Oxidative stress as a mediator of life history trade-offs: mechanisms, measurements and interpretation

The concept of trade-offs is central to our understanding of life-history evolution. The underlying mechanisms, however, have been little studied. Oxidative stress results from a mismatch between the production of damaging reactive oxygen species (ROS) and the organism's capacity to mitigate their damaging effects. Managing oxidative stress is likely to be a major determinant of life histories, as virtually all activities generate ROS. There is a recent burgeoning of interest in how oxidative stress is related to different components of animal performance. The emphasis to date has been on immediate or short-term effects, but there is an increasing realization that oxidative stress will influence life histories over longer time scales. The concept of oxidative stress is currently used somewhat loosely by many ecologists, and the erroneous assumption often made that dietary antioxidants are necessarily the major line of defence against ROS-induced damage. We summarize current knowledge on how oxidative stress occurs and the different methods for measuring it, and highlight where ecologists can be too simplistic in their approach. We critically review the potential role of oxidative stress in mediating life-history trade-offs, and present a framework for formulating appropriate hypotheses and guiding experimental design. We indicate throughout potentially fruitful areas for further research.

Short-period hypoxia increases mouse embryonic stem cell proliferation through cooperation of arachidonic acid and PI3K/Akt signalling pathways

Hypoxia plays important roles in some early stages of mammalian embryonic development and in various physiological functions. This study examined the effect of arachidonic acid on short-period hypoxia-induced regulation of G(1) phase cell-cycle progression and inter-relationships among possible signalling molecules in mouse embryonic stem cells. Hypoxia increased the level of hypoxia-inducible factor-1alpha (HIF-1alpha) expression and H2O2 generation in a time-dependent manner. In addition, hypoxia increased the levels of cell-cycle regulatory proteins (cyclin D(1), cyclin E, cyclin-dependent kinase 2 (CDK2) and CDK4). Maximum increases in the level of these proteins and retinoblastoma phosphorylation were observed after 12-24 h of exposure to hypoxic conditions, and then decreased. Alternatively, the level of the CDK inhibitors, p21(Cip1) and p27(Kip1) were decreased. These results were consistent with the results of [3H]-thymidine incorporation and cell counting. Hypoxia also increased the level of [3H]-arachidonic acid release and inhibition of cPLA(2) reduced hypoxia-induced increase in levels of the cell-cycle regulatory proteins and [3H]-thymidine incorporation. The level of cyclooxygenase-2 (COX-2) was also increased by hypoxia and inhibition of COX-2 decreased the levels of cell-cycle regulatory proteins and [3H]-thymidine incorporation. Indeed, the percentage of cells in S phase, levels of cell cycle regulatory proteins, and [3H]-thymidine incorporation were further increased in hypoxic conditions with arachidonic acid treatment compared to normoxic conditions. Hypoxia-induced Akt and mitogen-activated protein kinase (MAPK) phosphorylation was inhibited by vitamin C (antioxidant, 10(-3) M). In addition, hypoxia-induced increase of cell-cycle regulatory protein expression and [(3)H]-thymidine incorporation were attenuated by LY294002 (PI3K inhibitor, 10(-6) M), Akt inhibitor (10(-6) M), rapamycin (mTOR inhibitor, 10(-9) M), PD98059 (p44/42 inhibitor, 10(-5) M), and SB203580 (p38 MAPK inhibitor, 10(-6) M). Furthermore, hypoxia-induced increase of [(3)H]-arachidonic acid release was blocked by PD98059 or SB203580, but not by LY294002 or Akt inhibitor. In conclusion, arachidonic acid up-regulates short time-period hypoxia-induced G(1) phase cyclins D(1) and E, and CDK 2 and 4, in mouse embryonic stem cells through the cooperation of PI3K/Akt/mTOR, MAPK and cPLA(2)-mediated signal pathways.

An elt-3/elt-5/elt-6 GATA transcription circuit guides aging in C. elegans

To define the C. elegans aging process at the molecular level, we used DNA microarray experiments to identify a set of 1294 age-regulated genes and found that the GATA transcription factors ELT-3, ELT-5, and ELT-6 are responsible for age regulation of a large fraction of these genes. Expression of elt-5 and elt-6 increases during normal aging, and both of these GATA factors repress expression of elt-3, which shows a corresponding decrease in expression in old worms. elt-3 regulates a large number of downstream genes that change expression in old age, including ugt-9, col-144, and sod-3. elt-5(RNAi) and elt-6(RNAi) worms have extended longevity, indicating that elt-3, elt-5, and elt-6 play an important functional role in the aging process. These results identify a transcriptional circuit that guides the rapid aging process in C. elegans and indicate that this circuit is driven by drift of developmental pathways rather than accumulation of damage.

The effects of age on radiation resistance and oxidative stress in adult Drosophila melanogaster

Drosophila melanogaster (fruit fly) is a well-established model organism for genetic studies of development and aging. We examined the effects of lethal ionizing radiation on male and female adult Drosophila of different ages, using doses of radiation from 200 to 1500 Gy. Fifty percent lethality 2 days postirradiation (LD(50/2)) in wild-type 1-day-old adult fruit flies was approximately 1238 Gy for males and 1339 Gy for females. We observed a significant age-dependent decline in the radiation resistance of both males and females. Radiation damage is postulated to occur by the generation of oxygen radicals. An age-related decline in the ability of flies to resist an agent that induces oxygen radicals, paraquat, was observed when comparing 10- and 20-day adults. Female flies are more resistant to paraquat than male flies. Oxidative stress mediated by paraquat was additive with sublethal exposures to radiation in young adults. Therefore, the ability to repair the damage caused by oxygen radicals seems to decline with the age of the flies. Because Drosophila adults are largely post-mitotic, our data suggest that adult Drosophila melanogaster can serve as an excellent model to study the factors responsible for radiation resistance in post-mitotic tissue and age-dependent changes in this resistance.

Reversion of age-related recognition memory impairment by iron chelation in rats

It is now generally accepted that iron accumulates in the brain during the ageing process. Increasing evidence demonstrate that iron accumulation in selective regions of the brain may generate free radicals, thereby possessing implications for the etiology of neurodegenerative disorders. In a previous study we have reported that aged rats present recognition memory deficits. The aim of the present study was to evaluate the effect of desferoxamine (DFO), an iron chelator agent, on age-induced memory impairment. Aged Wistar rats received intraperitoneal injections of saline or DFO (300mg/kg) for 2 weeks. The animals were submitted to a novel object recognition task 24h after the last injection. DFO-treated rats showed normal recognition memory while the saline group showed long-term recognition memory deficits. The results show that DFO is able to reverse age-induced recognition memory deficits. We also demonstrated that DFO reduced the oxidative damage to proteins in cortex and hippocampus. Thus, the present findings provide the first evidence that iron chelators might prevent age-related memory dysfunction.

Chronic exposure to 50Hz magnetic fields causes a significant weakening of antioxidant defence systems in aged rat brain

Several studies suggest that extremely low-frequency magnetic fields (ELF-MFs) may enhance the free radical endogenous production. It is also well known that one of the unavoidable consequences of ageing is an overall oxidative stress-based decline in several physiological functions and in the general resistance to stressors. On the basis of these assumptions, the aim of this study was to establish whether the ageing process can increase susceptibility towards widely present ELF-MF-mediated pro-oxidative challenges. To this end, female Sprague-Dawley rats were continuously exposed to a sinusoidal 50 Hz, 0.1 mT magnetic field for 10 days. Treatment-induced changes in the major antioxidant protection systems and in the neurotrophic support were investigated, as a function of the age of the subjects. All analyses were performed in brain cortices, due to the high susceptibility of neuronal cells to oxidative injury. Our results indicated that ELF-MF exposure significantly affects anti-oxidative capability, both in young and aged animals, although in opposite ways. Indeed, exposed young individuals enhanced their neurotrophic signalling and anti-oxidative enzymatic defence against a possible ELF-MF-mediated increase in oxygen radical species. In contrast, aged subjects were not capable of increasing their defences in response to ELF-MF treatment but, on the contrary, they underwent a significant decrease in the major antioxidant enzymatic activities. In conclusion, our data seem to suggest that the exposure to ELF-MFs may act as a risk factor for the occurrence of oxidative stress-based nervous system pathologies associated with ageing.

GH replacement reduces increased lipid peroxidation in GH-deficient adults

BACKGROUND

GH replacement improves numerous metabolic abnormalities in GH-deficient patients; increased lipid peroxidation (LPO) has been observed in GH-deficient patients; however, it is unknown if LPO is influenced by GH replacement.

AIM AND METHODS

To evaluate the extent to which GH replacement might reverse the increased LPO in GH-deficient adults and to analyse if this phenomenon might be involved in the improvement of metabolic disturbances due to GH treatment. Serum concentrations of malondialdehyde + 4-hydroxyalkenals (MDA + 4-HDA), as an index of LPO, were measured at baseline, and after 12 and 24 months of GH replacement in 40 adult patients with severe GH deficiency (both in adult- and childhood-onset) and in 40 healthy volunteers, matched for sex, age and body mass index (BMI). Correlations were evaluated between LPO and lipids, IGF-I, metalloproteinase-2 and -9 (MMP-2, -9), vascular endothelial growth factor (VEGF), BMI and GH dose.

RESULTS

LPO values in GH-deficient patients were several-fold higher than in controls [55.36 +/- 2.27 vs. 4.19 +/- 0.42 nmol/mg protein (mean +/- SEM), P < 0.0001] and decreased significantly over time with GH replacement to 38.61 +/- 2.15 nmol/mg protein (i.e. by approximately 30%), though still remaining markedly elevated compared with controls (P < 0.0001). The proatherogenic lipid profile parameters correlated positively with LPO in the childhood-onset subgroup before GH replacement. GH replacement restored the positive correlation between LPO and age in male patients (r = 0.57, P = 0.013; r = 0.8, P < 0.001, at 12 and 24 months of GH replacement, respectively).

CONCLUSIONS

GH replacement partially reverses the grossly abnormal LPO in GH-deficient adults. It is highly probable, therefore, that oxidative mechanisms are involved in the overall improvement of metabolic changes due to GH replacement.

Long flights and age affect oxidative status of homing pigeons (Columba livia)

Flying is an energy demanding activity that imposes several physiological challenges on birds, such as increase in energy expenditure. Evidence from sports medicine shows that exhausting exercise may cause oxidative stress. Studies on avian flight have so far considered several blood parameters, such as uric acid, corticosteroids, or circulating free fatty acids, but only one study has analysed markers of oxidative stress in flying birds. In this study, we evaluated, for the first time, how different flight efforts affect the oxidative status using homing pigeons (Columba livia) as a model species. Two groups of pigeons flew for around 60 and 200 km, respectively. Pigeons that flew for 200 km had a 54% increase in oxidative damage as measured by serum reactive oxygen metabolites (ROMs), a 19% drop in total serum antioxidant capacity (OXY) and an 86% increase of oxidative stress (ROMs/OXYx1000). Older pigeons depleted more serum antioxidants regardless of the release distance. Among pigeons that flew the longer distance, heavier ones depleted less serum antioxidants. The results of the study suggest that long flights may cause oxidative stress, and that older individuals may experience higher physiological demands.

Stem cells for cardiovascular repair - the challenges of the aging heart

The discovery of extracardiac progenitor cells and resident cardiac stem cells in recent years has led to a great deal of interest in the development of therapeutic strategies that target these endogenous cell sources for promotion of cardiovascular repair mechanisms in the diseased heart. Cardiovascular risk increases with age and among many factors, the age-associated decline in cardiac and vascular regenerative capacity may contribute to the progressive deterioration of cardiovascular health. Thus, understanding the mechanisms which underlie the dysregulation of cardiac stem and progenitor cells may lead to the identification of novel targets and approaches to reverse this decline. In this review, we outline the current knowledge about cardiac stem and progenitor cells, their contribution to cardiovascular regenerative processes and factors that may affect their decreased function in aging individuals. Moreover, we describe the therapeutic strategies that are currently being tested in clinical trials as well as potential new avenues of investigation for the future.

Age and natural metabolically-intensive behavior affect oxidative stress and antioxidant mechanisms

Flying honey bees have among the highest mass-specific metabolic rates ever measured, suggesting that their flight muscles may experience high levels of oxidative stress during normal daily activities. We measured parameters of oxidative stress and antioxidant capacity in highly metabolic flight muscle and less active head tissue in cohorts of age-matched nurse bees, which rarely fly, and foragers, which fly several hours per a day. Naturally occurring foraging flight elicited an increase in flight muscle Hsp70 content in both young and old foragers; however catalase and total antioxidant capacity increased only in young flight muscle. Surprisingly, young nurse bees also showed a modest daily increase in Hsp70, catalase levels and antioxidant capacity, and these effects were likely due to collecting the young nurses soon after orientation flights. There were no differences in flight muscle carbonyl content over the course of daily activity and few differences in Hsp70, catalase, total antioxidant capacity and protein carbonyl levels in head tissue regardless of age or activity. In summary, honey bee flight likely produces high levels of reactive oxygen species in flight muscle that, when coupled with age-related decreases in antioxidant activity may be responsible for behavioral senescence and reduced longevity.

Modulation of infection-induced inflammation and locomotive deficit and longevity in senescence-accelerated mice-prone (SAMP8) model by the oligomerized polyphenol Oligonol

Oligonol is produced from the oligomerization of polyphenols (typically proanthocyanidin from a variety of fruits such as lychees, grapes, apples, persimmons, etc.) and contains catechin-type monomers and oligomers of proanthocyanidins. The ability of Oligonol to affect infection-dependent eye inflammation, locomotion and longevity in senescence-accelerated prone mice (SAMP8) (a model of senescence acceleration and geriatric disorders with increased oxidative stress and neuronal deficit) was investigated. Oligonol (60mg/kg) significantly modulated the extent of inflammation scores in the eye of SAMP8 mice. Examination of the mice indicated infection with mouse hepatitis virus and pinworm (Syphacia obvelata) in both males and females and with the intestinal protozoa (trichomonad) in males. A comparison of the two groups (using log-rank test) and the difference in the mean life span between groups (using Student's t-test) indicated significant differences in survival (p=0.043) and the mean life span (p=0.033) in male SAMP8 mice. Oligonol increased the mean life span and this was statistically significant. In the open-field locomotive test, the 7-week-old SAMP8 mice crossed more than 40 partitioned lines in 1min. At 48-week-old control untreated male SAMP8 crossed 2 lines. The Oligonol-treated 48-week-old male SAMP8 mice crossed 17 lines however. The improved locomotive activity was statistically significant even after 36weeks in the Oligonol-treated male SAMP8 but this was not the case throughout the time course of the study in the Oligonol-treated female SAMP8. Thus Oligonol treatment to SAMP8 mice modulated the severity of infection-dependent inflammation, prolonged life-span and significantly improved locomotive activity indicating potential benefit to aging-associated diseases such as Alzheimer's or Parkinson's diseases. This presents potential for further research to define infection-dependent inflammation associated with degenerative conditions and the molecular mechanism of dietary antioxidant protection.

Age-related changes in climbing behavior and neural circuit physiology in Drosophila

Identifying the cellular and molecular basis for functional decline remains key to understanding aging. To this end, we have characterized age-dependent changes in climbing and the electrophysiology of the giant fiber circuitry in wild type (Wt) and mutant flies with altered lifespan (methuselah and fragile-X). Our data demonstrate a gradual decline in climbing in Wt and methuselah flies aged 5-45 days. In contrast, fragile-X flies climbed poorly even at 5 days and failed completely at 45 days. We then examined whether synaptic transmission to indirect flight muscles along the giant fiber circuit was altered with aging. At 5 days, the dorsal longitudinal muscle (DLM) in Wt flies followed high frequency stimulation well (at 130 Hz or above). At 35 and 45 days, these flies only followed 60-80 Hz. Methuselah flies did not follow stimuli as well as the Wt flies did at 5 and 25 days, but they were similar to Wt flies at older ages. Fragile-X flies responded poorly even at 5 days (40 Hz) and worsened at 35 days (30 Hz). Unlike DLMs, the tergotrochanteral muscle followed high frequency stimuli relatively well in all genotypes, suggesting that the peripheral interneuron along the DLM pathway or the DLM muscular synapse is prone to age-dependent functional decline. These studies reveal subcellular structures as potential targets of aging, indicating that the giant fiber pathway can be used as a model circuit for quantitative studies of aging in flies as well as fly models of age-related human neurological disorders.

The capacity to remove 8-oxoG is enhanced in newborn neural stem/progenitor cells and decreases in juvenile mice and upon cell differentiation

In mammalian cells, 8-oxoguanine DNA glycosylase-1 (OGG1) is the main DNA glycosylase for the removal of 8-oxoguanine (8-oxoG). 8-oxoG, one of the most common products of the oxidative attack of DNA, is a premutagenic lesion that accumulates spontaneously at high frequencies in the genome. In this study, Ogg1 mRNA expression was detected throughout embryonic development in mice. In situ hybridization showed that in the neonatal brain, Ogg1 expression was detected in a distinct layer of cells in the medial wall of the lateral ventricle, which may correspond to ependymal cells, and in some scattered cells in the subventricular zone (SVZ), a brain region rich in neural stem/progenitor cells. Using neurospheres as a model for the study of neural stem/progenitor cells, we found that both the expression and activity of Ogg1 were high in neurospheres derived from newborn mice and decreased in adults and upon induction of cell differentiation. Furthermore, Ogg1 was shown to be the major DNA glycosylase initiating 8-oxoG repair in neurospheres. Our results strongly indicate that enhanced DNA repair capacity is an important mechanism by which neural stem/progenitor cells maintain their genome.

Memantine reduces oxidative damage and enhances long-term recognition memory in aged rats

Many neurodegenerative diseases, including Alzheimer's (AD), Parkinson's (PD) and Huntington's diseases (HD), are caused by different mechanisms but may share a common pathway to neuronal injury as a result of the overstimulation of glutamate receptors. It has been suggested that this pathway can be involved in generation of cognitive deficits associated with normal aging. Previous studies performed in our laboratory have demonstrated that aged rats presented recognition memory deficits. The aim of the present study was to evaluate the effect of memantine, a low-affinity N-methyl-D-aspartate (NMDA) receptor antagonist, on age-induced recognition memory deficits. Additionally, parameters of oxidative damage in cerebral regions related to memory formation were evaluated. In order to do that, male Wistar rats (24 months old) received daily injections of saline solution or memantine (20 mg/kg i.p.) during 21 days. The animals were submitted to a novel object recognition task 1 week after the last injection. Memantine-treated rats showed normal recognition memory while the saline group showed long-term recognition memory deficits. The results show that memantine is able to reverse age-induced recognition memory deficits. We also demonstrated that memantine reduced the oxidative damage to proteins in cortex and hippocampus, two important brain regions involved in memory formation. Thus, the present findings suggest that, at least in part, age-induced cognitive deficits are related to oxidative damage promoted by NMDA receptor overactivation.