Calorie restriction up-regulates the plasma membrane redox system in brain cells and suppresses oxidative stress during aging

Nanomicellar formulation of coenzyme Q10 (Ubisol-Q10) effectively blocks ongoing neurodegeneration in the mouse 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model: potential use as an adjuvant treatment in Parkinson's disease

Although the support for the use of antioxidants, such as coenzyme Q(10) (CoQ(10)), to treat Parkinson's disease (PD) comes from the extensive scientific evidence, the results of conducted thus far clinical trials are inconclusive. It is assumed that the efficacy of CoQ(10) is hindered by insolubility, poor bioavailability, and lack of brain penetration. We have developed a nanomicellar formulation of CoQ(10) (Ubisol-Q(10)) with improved properties, including the brain penetration, and tested its effectiveness in mouse MPTP (1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine) model with the objectives to assess its potential use as an adjuvant therapy for PD. We used a subchronic MPTP model (5-daily MPTP injections), characterized by 50% loss of dopamine neurons over a period of 28 days. Ubisol-Q(10) was delivered in drinking water. Prophylactic application of Ubisol-Q(10), started 2 weeks before the MPTP exposure, significantly offset the neurotoxicity (approximately 50% neurons died in MPTP group vs. 17% in MPTP+ Ubisol-Q(10) group by day 28). Therapeutic application of Ubisol-Q(10), given after the last MPTP injection, was equally effective. At the time of intervention on day 5 nearly 25% of dopamine neurons were already lost, but the treatment saved the remaining 25% of cells, which otherwise would have died by day 28. This was confirmed by cell counts, analyses of striatal dopamine levels, and improved animals' motor skill on a beam walk test. Similar levels of neuroprotection were obtained with 3 different Ubisol-Q(10) concentrations tested, that is, 30 mg, 6 mg, or 3 mg CoQ(10)/kg body weight/day, showing clearly that high doses of CoQ(10) were not required to deliver these effects. Furthermore, the Ubisol-Q(10) treatments brought about a robust astrocytic activation in the brain parenchyma, indicating that astroglia played an active role in this neuroprotection. Thus, we have shown for the first time that Ubisol-Q(10) was capable of halting the neurodegeneration already in progress; however, to maintain it a continuous supplementation of Ubisol-Q(10) was required. The pathologic processes initiated by MPTP resumed if supplementation was withdrawn. We suggest that in addition to brain delivery of powerful antioxidants, Ubisol-Q(10) might have also supported subcellular oxidoreductase systems allowing them to maintain a favorable cellular redox status, especially in astroglia, facilitating their role in neuroprotection. Based on this data further clinical testing of this formulation in PD patients might be justifiable.

Self-immolative bioluminogenic quinone luciferins for NAD(P)H assays and reducing capacity-based cell viability assays

Highly sensitive self-cleavable trimethyl lock quinone-luciferin substrates for diaphorase were designed and synthesized to measure NAD(P)H in biological samples and monitor viable cells via NAD(P)H-dependent cellular oxidoreductase enzymes and their NAD(P)H cofactors.

Methods for the discovery of new anti-aging products--targeted approaches

INTRODUCTION

Aging is considered to be one of the most complicated and heterogeneous phenomena and is the main risk factor for most chronic diseases, disabilities and declining health. Aging cells cease to divide and drive the progression of illness through various pathways. Over the years, a number of anti-aging medicines of natural and synthetic origin have been introduced. Indeed, some studies have identified senescent cells as potential therapeutic targets in the treatment of aging and age-related diseases.

AREAS COVERED

In this review, the authors highlight and critically review the possible mechanisms of the aging process and related illnesses. The authors give particular attention to illnesses, including Alzheimer's disease, Parkinson's disease, skin aging and cardiovascular diseases.

EXPERT OPINION

Several reports have highlighted that mitochondria are a key factor in the progression of aging and neurodegenerative illnesses. This is due to their production of extra amounts of reactive oxygen species, which leads into progressive caspase-dependent apoptosis and cell death. Therefore, strategies to prevent/reduce oxidative stress-mediated aging, whether environmental, nutritional and pharmacological, need to be taken into account. Presently, Drosophila melanogaster and Caenorhabditis elegans, which focus on the evolutionary and genetic foundations of aging, have helped to establish the screening of several synthetic and natural compounds with large cohorts in a quick manner. However, there is yet to be any efficient experimental evidence to prove the exact role of senescent cells in age-related dysfunction and further studies are required to better understand these processes.

Age-dependent effect of every-other-day feeding and aerobic exercise in ubiquinone levels and related antioxidant activities in mice muscle

Aging affects many biochemical, cellular, and physiological processes in the organisms. Accumulation of damage based on oxidized macromolecules is found in many age-associated diseases. Coenzyme Q (Q) is one of the main molecules involved in metabolic and antioxidant activities in cells. Q-dependent antioxidant activities are importantly involved on the protection of cell membranes against oxidation. Many studies indicate that Q decay in most of the organs during aging. In our study, no changes in Q levels were found in old animals in comparison with young animals. On the other hand, the interventions, caloric restriction based on every-other-day feeding procedure, and physical exercise were able to increase Q levels in muscle, but only in old and not in young animals. Probably, this effect prevented the increase in lipid peroxidation found in aged animals and also protein carbonylation. Further, Q-dependent antioxidant activities such as NADH-cytochrome b5 reductase and NAD(P)H-quinone oxidoreductase 1 are also modulated by both exercise and every other day feeding. Taken together, we demonstrate that exercise and dietary restriction as every-other-day procedure can regulate endogenous synthesized Q levels and Q-dependent antioxidant activities in muscle, preventing oxidative damage in aged muscle.

Improved on-line high performance liquid chromatography method for detection of antioxidants in Eucommia ulmoides Oliver flower

Eucommia ulmoides Oliver is a traditional Chinese medicine and material for functional food with a strong antioxidant activity. To investigate antioxidants in E. ulmoides Oliver flower, an improved on-line high performance liquid chromatography method with the radical cation 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS(+)) as a stable model free radical for the detection of radical scavenging ability was developed. The radical concentration, flow rate, and length of reaction coil were optimized with rutin as a model antioxidant. Under the optimized instrumental set-up, a radical solution of 0.32 mM ABTS(+) is delivered by a pump equipped with a superloop at 0.5 mL/min through a reaction coil of 10 m × 0.25 mm. This method showed a high sensitivity since the system noise was reduced by the superloop. The minimum detecting concentration of the method was in the range of 0.03-0.10 μM for the negative peaks of rutin, quercetin, ascorbic acid, and α-tocopherol. Importantly, the method could be not only used for detection of antioxidants in plant extracts but also combined with mass spectrometry to obtain the structural messages of peaks in high performance liquid chromatography profiles. After analysis by the method, nineteen antioxidants were found in E. ulmoides Oliver flower extract, and the main active compound was identified as chlorogenic acid.

Resveratrol up-regulates the erythrocyte plasma membrane redox system and mitigates oxidation-induced alterations in erythrocytes during aging in humans

Reactive oxygen/nitrogen species (ROS/RNS)-mediated oxidative damage followed by disturbed cellular homeostasis is involved in aging and related consequences. Lipid peroxidation, post-translational modifications of proteins, and an impaired defense system due to increased oxidative stress jeopardize cell fate and functions, resulting in cell senescence. Resveratrol, a natural stilbene, has extensively been reported to elicit a plethora of health-promoting effects. The present study carried out on 97 healthy human subjects (62 males and 35 females) of both sexes provides experimental evidence that resveratrol confers ability to up-regulate the plasma membrane redox system (PMRS) along with ascorbate free radical reductase, a compensatory system operating in the cell to maintain cellular redox state. Furthermore, resveratrol provided significant protection against lipid peroxidation and protein carbonylation and restored the cellular redox homeostasis measured in terms of glutathione (GSH) and sulfhydryl (-SH) group levels during oxidation injury in erythrocytes of different age groups in humans. Findings suggest a possible role of resveratrol in retardation of age-dependent oxidative stress.

The effects of dietary restriction on oxidative stress in rodents

Oxidative stress is observed during aging and in numerous age-related diseases. Dietary restriction (DR) is a regimen that protects against disease and extends life span in multiple species. However, it is unknown how DR mediates its protective effects. One prominent and consistent effect of DR in a number of systems is the ability to reduce oxidative stress and damage. The purpose of this review is to comprehensively examine the hypothesis that dietary restriction reduces oxidative stress in rodents by decreasing reactive oxygen species (ROS) production and increasing antioxidant enzyme activity, leading to an overall reduction of oxidative damage to macromolecules. The literature reveals that the effects of DR on oxidative stress are complex and likely influenced by a variety of factors, including sex, species, tissue examined, types of ROS and antioxidant enzymes examined, and duration of DR. Here we present a comprehensive review of the existing literature on the effect of DR on mitochondrial ROS generation, antioxidant enzymes, and oxidative damage. In a majority of studies, dietary restriction had little effect on mitochondrial ROS production or antioxidant activity. On the other hand, DR decreased oxidative damage in the majority of cases. Although the effects of DR on endogenous antioxidants are mixed, we find that glutathione levels are the most likely antioxidant to be increased by dietary restriction, which supports the emerging redox-stress hypothesis of aging.

Dietary fat modifies mitochondrial and plasma membrane apoptotic signaling in skeletal muscle of calorie-restricted mice

Calorie restriction decreases skeletal muscle apoptosis, and this phenomenon has been mechanistically linked to its protective action against sarcopenia of aging. Alterations in lipid composition of membranes have been related with the beneficial effects of calorie restriction. However, no study has been designed to date to elucidate if different dietary fat sources with calorie restriction modify apoptotic signaling in skeletal muscle. We show that a 6-month calorie restriction decreased the activity of the plasma membrane neutral sphingomyelinase, although caspase-8/10 activity was not altered, in young adult mice. Lipid hydroperoxides, Bax levels, and cytochrome c and AIF release/accumulation into the cytosol were also decreased, although caspase-9 activity was unchanged. No alterations in caspase-3 and apoptotic index (DNA fragmentation) were observed, but calorie restriction improved structural features of gastrocnemius fibers by increasing cross-sectional area and decreasing circularity of fibers in cross sections. Changing dietary fat with calorie restriction produced substantial alterations of apoptotic signaling. Fish oil augmented the protective effect of calorie restriction decreasing plasma membrane neutral sphingomyelinase, Bax levels, caspase-8/10, and -9 activities, while increasing levels of the antioxidant coenzyme Q at the plasma membrane, and potentiating the increase of cross-sectional area and the decrease of fiber circularity in cross sections. Many of these changes were not found when we used lard. Our data support that dietary fish oil with calorie restriction produces a cellular anti-apoptotic environment in skeletal muscle with a downregulation of components involved in the initial stages of apoptosis engagement, both at the plasma membrane and the mitochondria.

Oxidative stress, neurodegeneration, and the balance of protein degradation and protein synthesis

Oxidative stress occurs in a variety of disease settings and is strongly linked to the development of neuron death and neuronal dysfunction. Cells are equipped with numerous pathways to prevent the genesis, as well as the consequences, of oxidative stress in the brain. In this review we discuss the various forms and sources of oxidative stress in the brain and briefly discuss some of the complexities in detecting the presence of oxidative stress. We then focus the review on the interplay between the diverse cellular proteolytic pathways and their roles in regulating oxidative stress in the brain. Additionally, we discuss the involvement of protein synthesis in regulating the downstream effects of oxidative stress. Together, these components of the review demonstrate that the removal of damaged proteins by effective proteolysis and the synthesis of new and protective proteins are vital in the preservation of brain homeostasis during periods of increased levels of reactive oxygen species. Last, studies from our laboratory and others have demonstrated that protein synthesis is intricately linked to the rates of protein degradation, with impairment of protein degradation sufficient to decrease the rates of protein synthesis, which has important implications for successfully responding to periods of oxidative stress. Specific neurodegenerative diseases, including Alzheimer disease, Parkinson disease, amyotrophic lateral sclerosis, and stroke, are discussed in this context. Taken together, these findings add to our understanding of how oxidative stress is effectively managed in the healthy brain and help elucidate how impairments in proteolysis and/or protein synthesis contribute to the development of neurodegeneration and neuronal dysfunction in a variety of clinical settings.

Brain response to calorie restriction

Calorie restriction extends longevity and delays ageing in model organisms and mammals, opposing the onset and progression of an array of age-related diseases. These beneficial effects also extend to the maintenance of brain cognitive functions at later age and to the prevention, at least in rodents, of brain senescence and associated neurodegenerative disorders. In recent years, the molecular mechanisms underlying brain response to calorie restriction have begun to be elucidated, revealing the unanticipated role of a number of key nutrient sensors and nutrient-triggered signaling cascades in the translation of metabolic cues into cellular and molecular events that ultimately lead to increased cell resistance to stress, enhanced synaptic plasticity, and improved cognitive performance. Of note, the brain's role in CR also includes the activation of nutrient-sensitive hypothalamic circuitries and the implementation of neuroendocrine responses that impact the entire organism. The present review addresses emerging molecular themes in brain response to dietary restriction, and the implications of this knowledge for the understanding and the prevention of brain disorders associated with ageing and metabolic disease.

Beneficial effects of a 6-month dietary restriction are time-dependently abolished within 2 weeks or 6 months of refeeding-genome-wide transcriptome analysis in mouse liver

Dietary restriction (DR) has been shown to exert a number of beneficial effects including the prolongation of life span. One of the mechanisms by which DR leads to these advantages seems to be the induction of endogenous antioxidant defense and stress response mechanisms. However, little is known about the persistence of DR benefits after return to an ad libitum diet. In this study, male C57BL/6 mice were fed 75% of a normal diet for 6 months (DR) followed by 6 months of ad libitum refeeding (RF) and compared to a continuously ad libitum fed control group. To study the impact of DR and RF on the liver transcriptome, a global gene expression profile was generated using microarray technology. In comparison, the DR group showed lower body weight, lower triglyceride and cholesterol levels, reduced lipid peroxidation, and a changed hepatic fatty acid pattern. mRNA transcription and activity of antioxidant and phase II enzymes, as well as metallothionein 1 gene expression, were increased and autophagy was induced. Shifting from long-term DR to RF abolished 96% of the DR-mediated changes in differential gene expression within 2 weeks, and after 6 months of refeeding all of the previously differentially expressed genes were similar in both groups. These results indicate that DR has to be maintained continuously to keep its beneficial effects.

Thyroid hormone signaling and homeostasis during aging

Studies in humans and in animal models show negative correlations between thyroid hormone (TH) levels and longevity. TH signaling is implicated in maintaining and integrating metabolic homeostasis at multiple levels, notably centrally in the hypothalamus but also in peripheral tissues. The question is thus raised of how TH signaling is modulated during aging in different tissues. Classically, TH actions on mitochondria and heat production are obvious candidates to link negative effects of TH to aging. Mitochondrial effects of excess TH include reactive oxygen species and DNA damage, 2 factors often considered as aging accelerators. Inversely, caloric restriction, which can retard aging from nematodes to primates, causes a rapid reduction of circulating TH, reducing metabolism in birds and mammals. However, many other factors could link TH to aging, and it is these potentially subtler and less explored areas that are highlighted here. For example, effects of TH on membrane composition, inflammatory responses, stem cell renewal and synchronization of physiological responses to light could each contribute to TH regulation of maintenance of homeostasis during aging. We propose the hypothesis that constraints on TH signaling at certain life stages, notably during maturity, are advantageous for optimal aging.

Mitochondrial function in human neuroblastoma cells is up-regulated and protected by NQO1, a plasma membrane redox enzyme

Background

Recent findings suggest that NADH-dependent enzymes of the plasma membrane redox system (PMRS) play roles in the maintenance of cell bioenergetics and oxidative state. Neurons and tumor cells exhibit differential vulnerability to oxidative and metabolic stress, with important implications for the development of therapeutic interventions that promote either cell survival (neurons) or death (cancer cells).

Methods and Findings

Here we used human neuroblastoma cells with low or high levels of the PMRS enzyme NADH-quinone oxidoreductase 1 (NQO1) to investigate how the PMRS modulates mitochondrial functions and cell survival. Cells with elevated NQO1 levels exhibited higher levels of oxygen consumption and ATP production, and lower production of reactive oxygen species. Cells overexpressing NQO1 were more resistant to being damaged by the mitochondrial toxins rotenone and antimycin A, and exhibited less oxidative/nitrative damage and less apoptotic cell death. Cells with basal levels of NQO1 resulted in increased oxidative damage to proteins and cellular vulnerability to mitochondrial toxins. Thus, mitochondrial functions are enhanced and oxidative stress is reduced as a result of elevated PMRS activity, enabling cells to maintain redox homeostasis under conditions of metabolic and energetic stress.

Conclusion

These findings suggest that NQO1 is a potential target for the development of therapeutic agents for either preventing neuronal degeneration or promoting the death of neural tumor cells.

Pomegranate (Punica granatum) peel extract provides protection against mercuric chloride-induced oxidative stress in Wistar strain rats

CONTEXT

Pomegranate [Punica granatum L. (Lythraceae)] is rich in antioxidants.

OBJECTIVE

The present work was undertaken to evaluate the protective effects of methanol extract of pomegranate peel extract (PPE) against a rat model of oxidative stress generated by treatment with mercuric chloride (HgCl(2)).

MATERIALS AND METHODS

Rats were injected with HgCl(2) (5 mg/kg body weight in 0.9% NaCl) for developing oxidative stress. The methanol extract of pomegranate peel (PPE) was suspended in 0.5% sodium carboxymethylcellulose and fed to rats at 50 mg/kg body weight/day up to 30 days after HgCl(2) treatment. Biomarkers of oxidative stress including erythrocyte plasma membrane redox system (PMRS), lipid peroxidation, advanced oxidation protein products (AOPP), intracellular glutathione, and plasma antioxidant capacity as FRAP values were measured after PPE supplementation.

RESULTS

HgCl(2)-treated rats showed increased oxidative stress as evidenced by increased activity of erythrocyte PMRS 153%, lipid peroxidation 31%, and AOPP 290%. There was a significant (p < 0.01) decrease (25%) in plasma antioxidant capacity and intracellular glutathione (75%). Supplementation with PPE protected rats from HgCl(2) induced oxidative damage. PPE supplementation to control rats increased antioxidant defense.

DISCUSSION AND CONCLUSION

The results clearly demonstrate that PPE treatment augments the antioxidant defense mechanism in mercuric chloride-induced oxidant toxicity. To the best of our knowledge this is the first report of the increase in erythrocyte PMRS activity in rats after supplementation with any kind of antioxidant supplementation. This study emphasizes the need for characterizing PPE for potential unknown antioxidant compounds.

Energy intake and exercise as determinants of brain health and vulnerability to injury and disease

Evolution favored individuals with superior cognitive and physical abilities under conditions of limited food sources, and brain function can therefore be optimized by intermittent dietary energy restriction (ER) and exercise. Such energetic challenges engage adaptive cellular stress-response signaling pathways in neurons involving neurotrophic factors, protein chaperones, DNA-repair proteins, autophagy, and mitochondrial biogenesis. By suppressing adaptive cellular stress responses, overeating and a sedentary lifestyle may increase the risk of Alzheimer's and Parkinson's diseases, stroke, and depression. Intense concerted efforts of governments, families, schools, and physicians will be required to successfully implement brain-healthy lifestyles that incorporate ER and exercise.

Beta-lapachone, a modulator of NAD metabolism, prevents health declines in aged mice

NADH-quinone oxidoreductase 1 (NQO1) modulates cellular NAD⁺/NADH ratio which has been associated with the aging and anti-aging mechanisms of calorie restriction (CR). Here, we demonstrate that the facilitation of NQO1 activity by feeding β-lapachone (βL), an exogenous NQO1 co-substrate, prevented age-dependent decline of motor and cognitive function in aged mice. βL-fed mice did not alter their food-intake or locomotor activity but did increase their energy expenditure as measured by oxygen consumption and heat generation. Mitochondrial structure and numbers were disorganized and decreased in the muscles of control diet group but those defects were less severe in βL-fed aged mice. Furthermore, for a subset of genes associated with energy metabolism, mice fed the βL-diet showed similar changes in gene expression to the CR group (fed 70% of the control diet). These results support the potentiation of NQO1 activity by a βL diet and could be an option for preventing age-related decline of muscle and brain functions.

Sirtuin activation: a role for plasma membrane in the cell growth puzzle

For more than 20 years, the observation that impermeable oxidants can stimulate cell growth has not been satisfactorily explained. The discovery of sirtuins provides a logical answer to the puzzle. The NADH-dependent transplasma membrane electron transport system, which is stimulated by growth factors and interventions such as calorie restriction, can transfer electrons to external acceptors and protect against stress-induced apoptosis. We hypothesize that the activation of plasma membrane electron transport contributes to the cytosolic NAD(+) pool required for sirtuin to activate transcription factors necessary for cell growth and survival.

Circulating factors induced by caloric restriction in the nonhuman primate Macaca mulatta activate angiogenic processes in endothelial cells

Moderate caloric restriction (CR) without malnutrition increases healthspan in virtually every species studied, including nonhuman primates. In mice, CR exerts significant microvascular protective effects resulting in increased microvascular density in the heart and the brain, which likely contribute to enhanced tolerance to ischemia and improved cardiac performance and cognitive function. Yet, the underlying mechanisms by which CR confer microvascular protection remain elusive. To test the hypothesis that circulating factors triggered by CR regulate endothelial angiogenic capacity, we treated cultured human endothelial cells with sera derived from Macaca mulatta on long-term (over 10 years) CR. Cells treated with sera derived from ad-libitum-fed control monkeys served as controls. We found that factors present in CR sera upregulate vascular endothelial growth factor (VEGF) signaling and stimulate angiogenic processes, including endothelial cell proliferation and formation of capillary-like structures. Treatment with CR sera also tended to increase cellular migration (measured by a wound-healing assay using electric cell-substrate impedance sensing [ECIS] technology) and adhesion to collagen. Collectively, we find that circulating factors induced by CR promote endothelial angiogenic processes, suggesting that increased angiogenesis may be a potential mechanism by which CR improves cardiac function and prevents vascular cognitive impairment.

NRF2 and the Phase II Response in Acute Stress Resistance Induced by Dietary Restriction

Dietary restriction (DR) as a means to increase longevity is well-established in a number of model organisms from yeast to primates. DR also improves metabolic fitness and increases resistance to acute oxidative, carcinogenic and toxicological stressors - benefits with more immediate potential for clinical translation than increased lifespan. While the detailed mechanism of DR action remains unclear, a conceptual framework involving an adaptive, or hormetic response to the stress of nutrient/energy deprivation has been proposed. A key prediction of the hormesis hypothesis of DR is that beneficial adaptations occur in response to an increase in reactive oxygen/nitrogen species (ROS). These ROS may be derived either from increased mitochondrial respiration or increased xenobiotic metabolism in the case of some DR mimetics. This review will focus on the potential role of the redox-sensing transcription factor NF-E2-related factor 2 (NRF2) and its control of the evolutionarily conserved antioxidant/redox cycling and detoxification systems, collectively known as the Phase II response, in the adaptive response to DR.

Circadian modulation of human erythrocyte plasma membrane redox system by melatonin

BACKGROUND

The pineal hormone melatonin works for the stabilization of biological rhythms, however, it also modulates several other functions such as cardioprotection, thermoregulation and immunomodulation. Melatonin also shows antioxidant activity. The erythrocyte plasma membrane redox system (PMRS) alongwith ascorbate free radical (AFR) reductase is involved in providing protection against oxidative stress. The present work is an ex vivo study addressing RBC PMRS and AFR reductase activities at two different times of the day. The in vitro modulatory effect of melatonin on PMRS and AFR reductase activities is also reported.

MATERIALS AND METHODS

The study was carried out on 61 healthy donors of both sexes (aged 20-30). Blood samples were collected at two different timings viz., 10:00 a.m. and 10:00 p.m. PMRS and AFR reductase were determined by methods already reported. The concentration-dependent effect of the melatonin was evaluated by incubating the RBCs with the hormone at different doses.

RESULTS

We present results to show that erythrocyte PMRS and AFR reductase activity are modulated by melatonin, a higher activity (p<0.05) of PMRS and AFR reductase is observed during night when the level of melatonin is high. The effect of in vitro treatment of erythrocytes with melatonin (10(-7) M to 10(-11) M final concentration) shows significant changes during day at a melatonin concentration of 10(-9)M.

CONCLUSION

To the best of our knowledge this study shows for the first time the circadian rhythmicity of erythrocyte PMRS and AFR reductase activities. The modulatory effect of melatonin on PMRS and AFR reductase opens the possibility of melatonin being used in treatment of such physiological and metabolic dysfunctions that involve photic cues in association with oxidative stress.

The plasma membrane redox enzyme NQO1 sustains cellular energetics and protects human neuroblastoma cells against metabolic and proteotoxic stress

The plasma membrane redox system (PMRS) of nicotinamide adenine dinucleotide (NADH)-related enzymes plays a key role in the maintenance of cellular energetics. During the aging process, neural cells are particularly sensitive to impaired energy metabolism and oxidative damage, but the involvement of the PMRS in these processes is unknown. Here, we used human neuroblastoma cells with either elevated or reduced levels of the PMRS enzyme NADH-quinone oxidoreductase 1 (NQO1) to investigate how the PMRS regulates neuronal stress responses. Cells with elevated NQO1 levels were more resistant to death induced by 2-deoxyglucose, potassium cyanide (energetic stress), and lactacystin (proteotoxic stress), but were not protected from being killed by H(2)O(2) and serum withdrawal. The NAD(+)(an oxidized form of NADH)/NADH ratio was maintained at a significantly higher level in cells overexpressing NQO1, consistent with enhanced levels of NQO1 activity. Levels of the neuroprotective transcription factors nuclear factor kappa-light-chain-enhancer of activated B cells and nuclear factor (erythroid-derived 2)-like 2, and the protein chaperone HSP70 were elevated in cells overexpressing NQO1. Cells in which NQO1 levels were decreased by RNA interference exhibited increased vulnerability to death induced by 2-deoxyglucose and lactacystin. Thus, a higher NAD(+)/NADH ratio and activation of adaptive stress response pathways are enhanced by the PMRS in neuroblastoma cells, enabling them to maintain redox homeostasis under conditions of energetic and proteotoxic stress. These findings have implications for the development of therapeutic interventions for neural tumors and neurodegenerative conditions.

Identification of age-specific Nrf2 binding to a novel antioxidant response element locus in the Gclc promoter: a compensatory means for the loss of glutathione synthetic capacity in the aging rat liver?

NFE2-related factor 2 (Nrf2) transcriptionally governs the cellular response to harmful electrophiles, xenobiotics, and reactive oxygen species. Its nuclear levels decline with age (Suh et al., 2004a), which in part explains the age-related loss of phase II detoxification. However, little work has yet characterized how age affects Nrf2 DNA binding or the role that alterations to the Nrf2 transcriptional apparatus plays in modulating Nrf2-mediated gene expression. In this study, we used immunoprecipitation assays to show that Nrf2 bound to the active antioxidant response element (ARE) of the catalytic subunit of glutamate cysteine ligase (GCLC) is significantly lower in hepatic chromatin from aged vs. young rats. Moreover, the activity at this ARE locus is diminished during aging because of the presence of Bach1 and the absence of CREB-binding protein (CBP), a transcriptional repressor and co-activator, respectively. Further analysis reveals that Nrf2 occupies an alternate ARE site located -2.2 kb downstream from the normally active ARE binding site in livers of old rats, indicating an age-specific adaptation to maintain gene expression. Our results, thus, show that the conversion of Nrf2 binding from an active ARE to an alternative ARE element is not adequate to maintain basal expression of hepatic Gclc in old rats, which provides a potential mechanism for the age-related loss of glutathione synthetic and other phase II enzymes.

Gene transcripts associated with BMI in the motor cortex and caudate nucleus of calorie restricted rhesus monkeys

Obesity affects over 500 million people worldwide, and has far reaching negative health effects. Given that high body mass index (BMI) and insulin resistance are associated with alterations in many regions of brain and that physical activity can decrease obesity, we hypothesized that in Rhesus monkeys (Macaca mulatta) fed a high fat diet and who subsequently received reduced calories BMI would be associated with a unique gene expression signature in motor regions of the brain implicated in neurodegenerative disorders. In the motor cortex with increased BMI we saw the upregulation of genes involved in apoptosis, altered gene expression in metabolic pathways, and the downregulation of pERK1/2 (MAPK1), a protein involved in cellular survival. In the caudate nucleus with increased BMI we saw the upregulation of known obesity related genes (the insulin receptor (INSR) and the glucagon-like peptide-2 receptor (GLP2R)), apoptosis related genes, and altered expression of genes involved in various metabolic processes. These studies suggest that the effects of high BMI on the brain transcriptome persist regardless of two months of calorie restriction. We hypothesize that active lifestyles with low BMIs together create a brain homeostasis more conducive to brain resiliency and neuronal survival.

The visinin-like proteins VILIP-1 and VILIP-3 in Alzheimer's disease-old wine in new bottles

The neuronal Ca²⁺-sensor (NCS) proteins VILIP-1 and VILIP-3 have been implicated in the etiology of Alzheimer's disease (AD). Genome-wide association studies (GWAS) show association of genetic variants of VILIP-1 (VSNL1) and VILIP-3 (HPCAL1) with AD+P (+psychosis) and late onset AD (LOAD), respectively. In AD brains the expression of VILIP-1 and VILIP-3 protein and mRNA is down-regulated in cortical and limbic areas. In the hippocampus, for instance, reduced VILIP-1 mRNA levels correlate with the content of neurofibrillary tangles (NFT) and amyloid plaques, the pathological characteristics of AD, and with the mini mental state exam (MMSE), a test for cognitive impairment. More recently, VILIP-1 was evaluated as a cerebrospinal fluid (CSF) biomarker and a prognostic marker for cognitive decline in AD. In CSF increased VILIP-1 levels correlate with levels of Aβ, tau, ApoE4, and reduced MMSE scores. These findings tie in with previous results showing that VILIP-1 is involved in pathological mechanisms of altered Ca²⁺-homeostasis leading to neuronal loss. In PC12 cells, depending on co-expression with the neuroprotective Ca²⁺-buffer calbindin D28K, VILIP-1 enhanced tau phosphorylation and cell death. On the other hand, VILIP-1 affects processes, such as cyclic nucleotide signaling and dendritic growth, as well as nicotinergic modulation of neuronal network activity, both of which regulate synaptic plasticity and cognition. Similar to VILIP-1, its interaction partner α4β2 nicotinic acetylcholine receptor (nAChR) is severely reduced in AD, causing severe cognitive deficits. Comparatively little is known about VILIP-3, but its interaction with cytochrome b5, which is part of an antioxidative system impaired in AD, hint toward a role in neuroprotection. A current hypothesis is that the reduced expression of visinin-like protein (VSNLs) in AD is caused by selective vulnerability of subpopulations of neurons, leading to the death of these VILIP-1-expressing neurons, explaining its increased CSF levels. While the Ca²⁺-sensor appears to be a good biomarker for the detrimental effects of Aβ in AD, its early, possibly Aβ-induced, down-regulation of expression may additionally attenuate neuronal signal pathways regulating the functions of dendrites and neuroplasticity, and as a consequence, this may contribute to cognitive decline in early AD.

Oxidative stress

Oxidative stress is defined by an imbalance between increased levels of reactive oxygen species (ROS) and a low activity of antioxidant mechanisms. An increased oxidative stress can induce damage to the cellular structure and potentially destroy tissues. However, ROS are needed for adequate cell function, including the production of energy by the mitochondria. Increased oxidative stress has been incriminated in physiological conditions, such as aging and exercise, and in several pathological conditions, including cancer, neurodegenerative diseases, cardiovascular diseases, diabetes, inflammatory diseases, and intoxications. However, prevention by antioxidants has been mostly inefficient. Therefore, a rigorous scientific evaluation in well-defined conditions is mandatory to define the appropriate place for manipulations of the oxidative pathways in human medicine.

Recruiting adaptive cellular stress responses for successful brain ageing

Successful ageing is determined in part by genetic background, but also by experiential factors associated with lifestyle and culture. Dietary, behavioural and pharmacological interventions have been identified as potential means to slow brain ageing and forestall neurodegenerative disease. Many of these interventions recruit adaptive cellular stress responses to strengthen neuronal networks and enhance plasticity. In this Science and Society article, we describe several determinants of healthy and pathological brain ageing, with insights into how these processes are accelerated or prevented. We also describe the mechanisms underlying the neuroprotective actions of exercise and nutritional interventions, with the goal of recruiting these molecular targets for the treatment and prevention of neurodegenerative disease.

A defect in Nrf2 signaling constitutes a mechanism for cellular stress hypersensitivity in a genetic rat model of type 2 diabetes

Nrf2 regulates the expression and coordinated induction of a battery of antioxidant phase 2 genes that protect cells against the cumulative damaging effects of oxidative stress (OS), a major contributor in the development of chronic diabetic complications. Using cultured dermal fibroblasts from rats with type 2 diabetes (DFs), we investigated the intracellular redox status and the adaptive response to OS, in which Nrf2 plays a central role. Our data confirmed that the generation of superoxide by NADPH oxidase and the mitochondria was enhanced in DFs compared with corresponding controls. This was associated with a decrease in the antioxidant capacity and an increase in the sensitivity of these DFs to hydrogen peroxide-induced necrotic cell death. Nrf2 levels in total cell extracts were diminished, and this abnormality appears to stem from a diabetes-related decrease in Nrf2 protein stability. Endogenous (oligomycin) and exogenous (tert-butylhydroquinone) induction of OS enhanced the nuclear translocation of Nrf2 and increased the mRNA expression of Nrf2-sensitive genes in control but not DFs. The activity of the GSK-3β/Fyn axis was increased markedly in DFs when compared with the corresponding controls. Chemical inhibition of GSK-3β mitigated the diabetes-related suppression of the OS-induced nuclear accumulation of Nrf2 and the transcriptional activation of the genes downstream of Nrf2. Overall, these findings suggest that an augmentation in GSK-3β/Fyn signaling during diabetes contributes to a deficit in both the cellular redox state and the Nrf2-based adaptive response to OS. Moreover, they may also offer a new perspective in the understanding and treatment of nonhealing diabetic wounds.

Impact of caloric and dietary restriction regimens on markers of health and longevity in humans and animals: a summary of available findings

Considerable interest has been shown in the ability of caloric restriction (CR) to improve multiple parameters of health and to extend lifespan. CR is the reduction of caloric intake - typically by 20 - 40% of ad libitum consumption - while maintaining adequate nutrient intake. Several alternatives to CR exist. CR combined with exercise (CE) consists of both decreased caloric intake and increased caloric expenditure. Alternate-day fasting (ADF) consists of two interchanging days; one day, subjects may consume food ad libitum (sometimes equaling twice the normal intake); on the other day, food is reduced or withheld altogether. Dietary restriction (DR) - restriction of one or more components of intake (typically macronutrients) with minimal to no reduction in total caloric intake - is another alternative to CR. Many religions incorporate one or more forms of food restriction. The following religious fasting periods are featured in this review: 1) Islamic Ramadan; 2) the three principal fasting periods of Greek Orthodox Christianity (Nativity, Lent, and the Assumption); and 3) the Biblical-based Daniel Fast. This review provides a summary of the current state of knowledge related to CR and DR. A specific section is provided that illustrates related work pertaining to religious forms of food restriction. Where available, studies involving both humans and animals are presented. The review includes suggestions for future research pertaining to the topics of discussion.

Non-mitochondrial coenzyme Q

The key role of coenzyme Q (ubiquinone or Q) is in mitochondrial and prokaryotic energetics. Less well investigated is the basis for its presence in eukaryotic membrane locations other than mitochondria and in plasma where both antioxidant and potentially more targeted roles are indicated. Included in the latter is that of a lipid-soluble electron transfer intermediate that serves as the transmembrane component of plasma membrane and Golgi apparatus electron transport, which regulates cytosolic NAD(+) /NADH ratios and is involved in vectorial membrane displacements and in the regulation of cell growth. Important protective effects on circulating lipoproteins and in the prevention of coronary artery disease ensue not only from the antioxidant role of CoQ(10) but also from its ability to directly block protein oxidation and superoxide generation of the TM-9 family of membrane proteins known as age-related NADH oxidase or arNOX (ENOX3) and their shed forms that appear after age 30 and some of which associate specifically with low-density lipoprotein particles to catalyze protein oxidation and crosslinking.

Energy restriction negates NMDA receptor antagonist efficacy in ischemic stroke

Preclinical evaluation of drugs for neurological disorders is usually performed on overfed rodents, without consideration of how metabolic state might affect drug efficacy. Using a widely employed mouse model of focal ischemic stroke, we found that that the NMDA receptor antagonist dizocilpine (MK-801) reduces brain damage and improves functional outcome in mice on the usual ad libitum diet, but exhibits little or no therapeutic efficacy in mice maintained on an energy-restricted diet. Thus, NMDA receptor activation plays a central role in the mechanism by which a high dietary energy intake exacerbates ischemic brain injury. These findings suggest that inclusion of subjects with a wide range of energy intakes in clinical trials for stroke may mask a drug benefit in the overfed/obese subpopulation of subjects.

Trans-plasma membrane electron transport in mammals: functional significance in health and disease

Trans-plasma membrane electron transport (t-PMET) has been established since the 1960s, but it has only been subject to more intensive research in the last decade. The discovery and characterization at the molecular level of its novel components has increased our understanding of how t-PMET regulates distinct cellular functions. This review will give an update on t-PMET, with particular emphasis on how its malfunction relates to some diseases, such as cancer, abnormal cell death, cardiovascular diseases, aging, obesity, neurodegenerative diseases, pulmonary fibrosis, asthma, and genetically linked pathologies. Understanding these relationships may provide novel therapeutic approaches for pathologies associated with unbalanced redox state.

Lifelong caloric restriction prevents age-induced oxidative stress in the sympathoadrenal system of Fischer 344 x Brown Norway rats

Aging is associated with oxidative damage and an imbalance in redox signaling in a variety of tissues, yet little is known about the extent of age-induced oxidative stress in the sympathoadrenal system. Lifelong caloric restriction has been shown to lower levels of oxidative stress and slow the aging process. Therefore, the aims of this study were twofold: (1) to investigate the effect of aging on oxidative stress in the adrenal medulla and hypothalamus and (2) determine if lifelong 40% caloric restriction (CR) reverses the adverse effects of age-induced oxidative stress in the sympathetic adrenomedullary system. Adult (18months) and very old (38months) male Fischer 344 x Brown Norway rats were divided into ad libitum or 40% CR groups and parameters of oxidative stress were analyzed in the adrenal medulla and the hypothalamus. A significant age-dependent increase in lipid peroxidation (+20%, P<0.05) and tyrosine nitration (+111%, P<0.001) were observed in the adrenal medulla while age resulted in a reduction in the protein expression of key antioxidant enzymes, CuZnSOD (-27%, P<0.01) and catalase (-27%, P<0.05) in the hypothalamus. Lifelong CR completely prevented the age-induced increase in lipid peroxidation in the adrenal medulla and restored the age-related decline in antioxidant enzymes in the hypothalamus. These data indicate that aging results in a significant increase in oxidative stress in the sympathoadrenal system. Importantly, lifelong CR restored the age-related changes in oxidative stress in the adrenal medulla and hypothalamus. Caloric restriction could be a potential non-pharmacological intervention to prevent increased oxidative stress in the sympathetic adrenomedullary system with age.

Impaired adaptive cellular responses to oxidative stress and the pathogenesis of Alzheimer's disease

As is generally true with other age-related diseases, Alzheimer's disease (AD) involves oxidative damage to cellular components in the affected tissue, in this case the brain. The causes and consequences of oxidative stress in neurons in AD are not fully understood, but considerable evidence points to important roles for accumulation of amyloid β-peptide upstream of oxidative stress and perturbed cellular Ca(2+) homeostasis and energy metabolism downstream of oxidative stress. The identification of mutations in the β-amyloid precursor protein and presenilin-1 as causes of some cases of early onset inherited AD, and the development of cell culture and animal models based on these mutations has greatly enhanced our understanding of the AD process, and has greatly expanded opportunities for preclinical testing of potential therapeutic interventions. In this regard, and of particular interest to us, is the elucidation of adaptive cellular stress response pathways (ACSRP) that can counteract multiple steps in the AD neurodegenerative cascades, thereby limiting oxidative damage and preserving cognitive function. ACSRP can be activated by factors ranging from exercise and dietary energy restriction, to drugs and phytochemicals. In this article we provide an overview of oxidative stress and AD, with a focus on ACSRP and their potential for preventing and treating AD.

Calorie restriction modulates hippocampal NMDA receptors in diet-induced obese rats

Calorie restriction (CR) has attracted increased interest since CR enhances lifespan and alters age-related decline in hippocampal-dependent cognitive functions. Obesity is associated with poor neurocognitive outcome including impaired hippocampal synaptic plasticity and cognitive abilities such as learning and memory. N-Methyl-D-aspartate receptors (NMDARs) are linked to hippocampal-dependent learning and memory, which may be stabilized by CR. In the present study, we aimed to establish the effects of CR on NMDARs in CA1 region of hippocampus in obese and non-obese rats. In addition, malondialdehyde (MDA) levels were determined as a marker for lipid peroxidation (LPO) in hippocampus. Four groups were constituted as control group (C, n = 9), obese group (OB, n = 10), obese calorie-restricted group (OCR, n = 9), and non-obese calorie-restricted group (NCR, n = 10). OCR and NCR were fed with a 60% CR diet for 10 weeks. After 10 weeks of CR, the MDA levels significantly decreased in the calorie-restricted groups. Obesity caused significant decreases in NR2A and NR2B subunit expressions in the hippocampus. The hippocampal NR2A and NR2B levels significantly increased in the OCR group compared with the OB group (P < 0.05). In contrast, the hippocampal NR2A and NR2B levels significantly decreased in the NCR group compared with the C group (P < 0.05). Oxidative stress can be prevented by CR, and these data may provide a molecular and cellular mechanism by which CR may regulate NMDAR-mediated response against obesity-induced changes in the hippocampus.

Permissive underfeeding and intensive insulin therapy in critically ill patients: a randomized controlled trial

BACKGROUND

Nutritional support has been recognized as an essential part of intensive care unit management. However, the appropriate caloric intake for critically ill patients remains ill defined.

OBJECTIVE

We examined the effect of permissive underfeeding compared with that of target feeding and of intensive insulin therapy (IIT) compared with that of conventional insulin therapy (CIT) on the outcomes of critically ill patients.

DESIGN

This study had a 2 × 2 factorial, randomized, controlled design. Eligible patients were randomly assigned to permissive underfeeding or target feeding groups (caloric goal: 60-70% compared with 90-100% of calculated requirement, respectively) with either IIT or CIT (target blood glucose: 4.4-6.1 compared with 10-11.1 mmol/L, respectively).

RESULTS

Twenty-eight-day all-cause mortality was 18.3% in the permissive underfeeding group compared with 23.3% in the target feeding group (relative risk: 0.79; 95% CI: 0.48, 1.29; P = 0.34). Hospital mortality was lower in the permissive underfeeding group than in the target group (30.0% compared with 42.5%; relative risk: 0.71; 95% CI: 0.50, 0.99; P = 0.04). No significant differences in outcomes were observed between the IIT and CIT groups.

CONCLUSION

In critically ill patients, permissive underfeeding may be associated with lower mortality rates than target feeding. This trial was registered at controlled-trials.com as ISRCTN96294863.

E3 ligase STUB1/CHIP regulates NAD(P)H:quinone oxidoreductase 1 (NQO1) accumulation in aged brain, a process impaired in certain Alzheimer disease patients

NAD(P)H:quinone oxidoreductase 1 (NQO1) is a flavoenzyme that is important in maintaining the cellular redox state and regulating protein degradation. The NQO1 polymorphism C609T has been associated with increased susceptibility to various age-related pathologies. We show here that NQO1 protein level is regulated by the E3 ligase STUB1/CHIP (C terminus of Hsc70-interacting protein). NQO1 binds STUB1 via the Hsc70-interacting domain (tetratricopeptide repeat domain) and undergoes ubiquitination and degradation. We demonstrate here that the product of the C609T polymorphism (P187S) is a stronger STUB1 interactor with increased susceptibility to ubiquitination by the E3 ligase STUB1. Furthermore, age-dependent decrease of STUB1 correlates with increased NQO1 accumulation. Remarkably, examination of hippocampi from Alzheimer disease patients revealed that in half of the cases examined the NQO1 protein level was undetectable due to C609T polymorphism, suggesting that the age-dependent accumulation of NQO1 is impaired in certain Alzheimer disease patients.

Disrupted energy metabolism and neuronal circuit dysfunction in cognitive impairment and Alzheimer's disease

Epidemiological, neuropathological, and functional neuroimaging evidence implicates global and regional disruptions in brain metabolism and energetics in the pathogenesis of cognitive impairment. Nerve cell microcircuits are modified by excitatory and inhibitory synaptic activity and neurotrophic factors. Ageing and Alzheimer's disease cause perturbations in cellular energy metabolism, level of excitation or inhibition, and neurotrophic factor release, which overwhelm compensatory mechanisms and result in dysfunction of neuronal microcircuits and brain networks. A prolonged positive energy balance impairs the ability of neurons to adapt to oxidative and metabolic stress. Results from experimental studies in animals show how disruptions caused by chronic positive energy balance, such as diabetes, lead to accelerated cognitive ageing and Alzheimer's disease. Therapeutic interventions to allay cognitive dysfunction that target energy metabolism and adaptive stress responses (such as neurotrophin signalling) have been effective in animal models and in preliminary studies in humans.

Cellular stress responses, the hormesis paradigm, and vitagenes: novel targets for therapeutic intervention in neurodegenerative disorders

Despite the capacity of chaperones and other homeostatic components to restore folding equilibrium, cells appear poorly adapted for chronic oxidative stress that increases in cancer and in metabolic and neurodegenerative diseases. Modulation of endogenous cellular defense mechanisms represents an innovative approach to therapeutic intervention in diseases causing chronic tissue damage, such as in neurodegeneration. This article introduces the concept of hormesis and its applications to the field of neuroprotection. It is argued that the hormetic dose response provides the central underpinning of neuroprotective responses, providing a framework for explaining the common quantitative features of their dose-response relationships, their mechanistic foundations, and their relationship to the concept of biological plasticity, as well as providing a key insight for improving the accuracy of the therapeutic dose of pharmaceutical agents within the highly heterogeneous human population. This article describes in mechanistic detail how hormetic dose responses are mediated for endogenous cellular defense pathways, including sirtuin and Nrf2 and related pathways that integrate adaptive stress responses in the prevention of neurodegenerative diseases. Particular attention is given to the emerging role of nitric oxide, carbon monoxide, and hydrogen sulfide gases in hormetic-based neuroprotection and their relationship to membrane radical dynamics and mitochondrial redox signaling.

NRF2, cancer and calorie restriction

The transcription factor NF-E2-related factor (NRF2) is a key regulator of several enzymatic pathways, including cytoprotective enzymes in highly metabolic organs. In this review, we summarize the ongoing research related to NRF2 activity in cancer development, focusing on in vivo studies using NRF2 knockout (KO) mice, which have helped in defining the crucial role of NRF2 in chemoprevention. The lower cancer protection observed in NRF2 KO mice under calorie restriction (CR) suggests that most of the beneficial effects of CR on the carcinogenesis process are likely mediated by NRF2. We propose that future interventions in cancer treatment would be carried out through the activation of NRF2 in somatic cells, which will lead to a delay or prevention of the onset of some forms of human cancers, and subsequently an extension of health- and lifespan.

Energy metabolism in adult neural stem cell fate

The adult mammalian brain contains a population of neural stem cells that can give rise to neurons, astrocytes, and oligodendrocytes and are thought to be involved in certain forms of memory, behavior, and brain injury repair. Neural stem cell properties, such as self-renewal and multipotency, are modulated by both cell-intrinsic and cell-extrinsic factors. Emerging evidence suggests that energy metabolism is an important regulator of neural stem cell function. Molecules and signaling pathways that sense and influence energy metabolism, including insulin/insulin-like growth factor I (IGF-1)-FoxO and insulin/IGF-1-mTOR signaling, AMP-activated protein kinase (AMPK), SIRT1, and hypoxia-inducible factors, are now implicated in neural stem cell biology. Furthermore, these signaling modules are likely to cooperate with other pathways involved in stem cell maintenance and differentiation. This review summarizes the current understanding of how cellular and systemic energy metabolism regulate neural stem cell fate. The known consequences of dietary restriction, exercise, aging, and pathologies with deregulated energy metabolism for neural stem cells and their differentiated progeny will also be discussed. A better understanding of how neural stem cells are influenced by changes in energy availability will help unravel the complex nature of neural stem cell biology in both the normal and diseased state.

Genetic deletion of Nrf2 promotes immortalization and decreases life span of murine embryonic fibroblasts

Nuclear factor E2-related factor-2 (Nrf2) transcription factor is one of the main regulators of intracellular redox balance and a sensor of oxidative and electrophilic stress. Low Nrf2 activity is usually associated with carcinogenesis, but Nrf2 is also considered as an oncogene because it increases survival of transformed cells. Because intracellular redox balance alterations are involved in both senescence and tumorigenesis, we investigated the impact of Nrf2 genetic deletion on cellular immortalization and life span of murine embryonic fibroblasts. We report that Nrf2 genetic deletion promotes immortalization due to an early loss of p53-dependent gene expression. However, compared with control cells, immortalized Nrf2-/- murine embryonic fibroblasts exhibited decreased growth, lower cyclin E levels, and impaired expression of NQO1 and cytochrome b₅ reductase. Moreover, SirT1 was also significantly reduced in immortalized Nrf2-/- murine embryonic fibroblasts, and these cells exhibited shorter life span. Our results underscore the dual role of Nrf2 in protection against carcinogenesis and in the delay of cellular aging.

Aberrant subcellular neuronal calcium regulation in aging and Alzheimer's disease

In this mini-review/opinion article we describe evidence that multiple cellular and molecular alterations in Alzheimer's disease (AD) pathogenesis involve perturbed cellular calcium regulation, and that alterations in synaptic calcium handling may be early and pivotal events in the disease process. With advancing age neurons encounter increased oxidative stress and impaired energy metabolism, which compromise the function of proteins that control membrane excitability and subcellular calcium dynamics. Altered proteolytic cleavage of the β-amyloid precursor protein (APP) in response to the aging process in combination with genetic and environmental factors results in the production and accumulation of neurotoxic forms of amyloid β-peptide (Aβ). Aβ undergoes a self-aggregation process and concomitantly generates reactive oxygen species that can trigger membrane-associated oxidative stress which, in turn, impairs the functions of ion-motive ATPases and glutamate and glucose transporters thereby rendering neurons vulnerable to excitotoxicity and apoptosis. Mutations in presenilin-1 that cause early-onset AD increase Aβ production, but also result in an abnormal increase in the size of endoplasmic reticulum calcium stores. Some of the events in the neurodegenerative cascade can be counteracted in animal models by manipulations that stabilize neuronal calcium homeostasis including dietary energy restriction, agonists of glucagon-like peptide 1 receptors and drugs that activate mitochondrial potassium channels. Emerging knowledge of the actions of calcium upstream and downstream of Aβ provides opportunities to develop novel preventative and therapeutic interventions for AD. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.

Ecological processes in a hormetic framework

There is increasing evidence that some non-essential substances or environmental stressors can have stimulatory or beneficial effects at low exposure levels while being toxic at higher levels, and that environmental 'priming' of certain physiological processes can result in their improved functioning in later life. These kinds of nonlinear dose-response relationships are referred to as hormetic responses and have been described across a wide range of organisms (from bacteria to vertebrates), in response to exposure to at least 1000 different chemical and environmental stressors. Although most work in this area has been in the fields of toxicology and human health, the concept of hormesis also has general applicability in ecology and evolutionary biology as it provides an important conceptual link between environmental conditions and organism function - both at the time of initial exposure to stressors and later in life. In this review, we discuss and clarify the different ways in which the term hormesis is used and provide a framework that we hope will be useful for ecologists interested in the fitness consequences of exposure to stressors. By using ecologically relevant examples from the existing literature, we show that hormesis is connected with both acclimation and phenotypic plasticity, and may play an important role in allowing animals to adjust to changing environments.

The role of polyphenolic antioxidants in health, disease, and aging

Polyphenolic antioxidants from dietary sources are frequently a topic of interest due to widespread scientific agreement that they may help lower the incidence of certain cancers, cardiovascular and neurodegenerative diseases, and DNA damage and even may have antiaging properties. On the other hand, questions still remain as to whether some antioxidants could be potentially harmful to health, because an increase in glycation-mediated protein damage (carbonyl stress) has been reported in some cases. Nevertheless, the quest for healthy aging has led to the extensive use of phytochemically derived antioxidants to disrupt age-associated deterioration in physiological function and to prevent many age-related diseases. Although a diet rich in the polyphenolic forms of antioxidants does seem to offer hope in delaying the onset of age-related disorders, it is still too early to define their exact clinical benefit for treating age-related disease. This review critically examines polyphenolic antioxidants, such as flavonoids, curcumene, and resveratrol in health, disease, and aging with the hope that a better understanding of the many mechanisms involved with these diverse compounds may lead to better health and novel treatment approaches for age-related diseases.

Chemical probes for analysis of carbonylated proteins: a review

Protein carbonylation is a major form of protein oxidation and is widely used as an indicator of oxidative stress. Carbonyl groups do not have distinguishing UV or visible, spectrophotometric absorbance/fluorescence characteristics and thus their detection and quantification can only be achieved using specific chemical probes. In this paper, we review the advantages and disadvantages of several chemical probes that have been and are still being used for protein carbonyl analysis. These probes include 2,4-dinitrophenylhydazine (DNPH), tritiated sodium borohydride ([(3)H]NaBH(4)), biotin-containing probes, and fluorescence probes. As our discussions lean toward gel-based approaches, utilizations of these probes in 2D gel-based proteomic analysis of carbonylated proteins are illustrated where applicable. Analysis of carbonylated proteins by ELISA, immunofluorescent imaging, near infrared fluorescence detection, and gel-free proteomic approaches are also discussed where appropriate. Additionally, potential applications of blue native gel electrophoresis as a tool for first dimensional separation in 2D gel-based analysis of carbonylated proteins are discussed as well.

The plasma membrane redox system is impaired by amyloid β-peptide and in the hippocampus and cerebral cortex of 3xTgAD mice

Membrane-associated oxidative stress has been implicated in the synaptic dysfunction and neuronal degeneration that occurs in Alzheimer's disease (AD), but the underlying mechanisms are unknown. Enzymes of the plasma membrane redox system (PMRS) provide electrons for energy metabolism and recycling of antioxidants. Here, we show that activities of several PMRS enzymes are selectively decreased in plasma membranes from the hippocampus and cerebral cortex of 3xTgAD mice, an animal model of AD. Our results that indicate the decreased PMRS enzyme activities are associated with decreased levels of coenzyme Q(10) and increased levels of oxidative stress markers. Neurons overexpressing the PMRS enzymes (NQO1 or cytochrome b5 reductase) exhibit increased resistance to amyloid β-peptide (Aβ). If and to what extent Aβ is the cause of the impaired PMRS enzymes in the 3xTgAD mice is unknown. Because these mice also express mutant tau and presenilin-1, it is possible that one or more of the PMRS could be adversely affected by these mutations. Nevertheless, the results of our cell culture studies clearly show that exposure of neurons to Aβ1-42 is sufficient to impair PMRS enzymes. The impairment of the PMRS in an animal model of AD, and the ability of PMRS enzyme activities to protect neurons against Aβ-toxicity, suggest enhancement PMRS function as a novel approach for protecting neurons against oxidative damage in AD and related disorders.