Mitochondrial respiration and reactive oxygen species in C. elegans

Exposure to 6-PPD quinone causes damage on mitochondrial complex I/II associated with lifespan reduction in Caenorhabditis elegans

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6-PPDQ) is an emerging pollutant transformed from 6-PPD. However, the effect of 6-PPDQ exposure on mitochondrion and underlying mechanism remains largely unclear. Using Caenorhabditis elegans as animal model, exposed to 6-PPDQ at 0.1-10 μg/L was performed form L1 larvae to adult day-1. Exposure to 6-PPDQ (1 and 10 μg/L) could increase oxygen consumption rate and decease adenosine 5'-triphosphate (ATP) content, suggesting induction of mitochondrial dysfunction. Activities of NADH dehydrogenase (complex I) and succinate dehydrogenase (complex II) were inhibited, accompanied by a decrease in expressions of gas-1, nuo-1, and mev-1. RNAi of gas-1 and mev-1 enhanced mitochondrial dysfunction and reduced lifespan of 6-PPDQ exposed nematodes. GAS-1 and MEV-1 functioned in parallel to regulate 6-PPDQ toxicity to reduce the lifespan. Insulin peptides and the insulin signaling pathway acted downstream of GAS-1 and MEV-1 to control the 6-PPDQ toxicity on longevity. Moreover, RNAi of sod-2 and sod-3, targeted genes of daf-16, caused susceptibility to 6-PPDQ toxicity in reducing lifespan and in causing reactive oxygen species (ROS) production. Therefore, 6-PPDQ at environmentally relevant concentrations (ERCs) potentially caused mitochondrial dysfunction by affecting mitochondrial complexes I and II, which was associated with lifespan reduction by affecting insulin signaling in organisms.

Flavonoids from the mung bean coat promote longevity and fitness in Caenorhabditis elegans

Mung beans possess health benefits related to their bioactive ingredients, mainly flavonoids, which are highly concentrated in the coat. However, the anti-aging effects of mung beans are rarely reported. In this work, we found that mung bean coat extract (MBCE), rich in vitexin and isovitexin, extended the lifespan and promoted the health of Caenorhabditis elegans (C. elegans) without any disadvantages. Moreover, MBCE enhanced the resistance to heat and oxidation of C. elegans by reducing the accumulation of intracellular reactive oxygen species and up-regulating the expression of stress-resistant genes or proteins. Further studies demonstrated that MBCE improved longevity, stress-resistance and fitness by mediating the mitochondrial function, mimicking calorie restriction, and altering histone modification. These findings provide direct evidence for the anti-aging effects of mung beans and new insights into the innovations and applications of mung beans for the healthcare industry.

C. elegans electrotaxis behavior is modulated by heat shock response and unfolded protein response signaling pathways

The nematode C. elegans is a leading model to investigate the mechanisms of stress-induced behavioral changes coupled with biochemical mechanisms. Our group has previously characterized C. elegans behavior using a microfluidic-based electrotaxis device, and showed that worms display directional motion in the presence of a mild electric field. In this study, we describe the effects of various forms of genetic and environmental stress on the electrotactic movement of animals. Using exposure to chemicals, such as paraquat and tunicamycin, as well as mitochondrial and endoplasmic reticulum (ER) unfolded protein response (UPR) mutants, we demonstrate that chronic stress causes abnormal movement. Additionally, we report that pqe-1 (human RNA exonuclease 1 homolog) is necessary for the maintenance of multiple stress response signaling and electrotaxis behavior of animals. Further, exposure of C. elegans to several environmental stress-inducing conditions revealed that while chronic heat and dietary restriction caused electrotaxis speed deficits due to prolonged stress, daily exercise had a beneficial effect on the animals, likely due to improved muscle health and transient activation of UPR. Overall, these data demonstrate that the electrotaxis behavior of worms is susceptible to cytosolic, mitochondrial, and ER stress, and that multiple stress response pathways contribute to its preservation in the face of stressful stimuli.

A Delicate Balance between Bacterial Iron and Reactive Oxygen Species Supports Optimal C. elegans Development

Iron is an essential micronutrient for all forms of life; low levels of iron cause human disease, while too much iron is toxic. Low iron levels induce reactive oxygen species (ROS) by disruption of the heme and iron-sulfur cluster-dependent electron transport chain (ETC). To identify bacterial metabolites that affect development, we screened the Keio Escherichia coli collection and uncovered 244 gene deletion mutants that slow Caenorhabditis elegans development. Several of these genes encode members of the ETC cytochrome bo oxidase complex, as well as iron importers. Surprisingly, either iron or anti-oxidant supplementation reversed the developmental delay. This suggests that low bacterial iron results in high bacterial ROS and vice versa, which causes oxidative stress in C. elegans that subsequently impairs mitochondrial function and delays development. Our data indicate that the bacterial diets of C. elegans provide precisely tailored amounts of iron to support proper development.

Transcriptional response of Caenorhabditis elegans when exposed to Shigella flexneri

In recent years, researchers have begun to use Caenorhabditis elegans as a potential animal model to study Shigella pathogenesis. This study aims to further develop this model using RNA-sequencing to understand which pathways/cellular characteristics are affected and potentially cause death in Shigella-exposed worms. We identified 1631 differentially expressed genes in Shigella-exposed worms (6 h exposure). A number of these genes encode proteins involved in fatty-acid β-oxidation (FAO), antioxidant defense and autophagy. The down-regulation of acyl-CoA dehydrogenases would impede FAO, reducing the overall energy to combat Shigella in the worm's intestinal tract. This is potentially coupled with the production of reactive oxygen species (ROS) that may not be fully quenched by antioxidant defense proteins, leading to damaged cellular organelles in the worm's intestinal cells. These cells may undergo autophagy to remove the mounting damage, but may eventually undergo cell death.

Knockdown of LMW-PTP enhances stress resistance in Caenorhabditis elegans

Low molecular weight protein tyrosine phosphatase (LMW-PTP) is highly conserved across almost all living organisms and is involved in the modulation of a number of cellular proteins related to important signaling pathways. In this study, we isolated lmwptp (Y94H6A.7) of Caenorhabditis elegans, the homolog of human ACP1, and set up an effective feeding-based RNA interference (RNAi) knockdown against this gene. We found that knockdown of lmwptp decreased damage associated with heat shock, oxidative stress and UV irradiation in wild-type worms, however, its deficiency didn't further reduce the stress resistance of daf-16 or hsf-1 mutants and didn't further increase the stress sensitivity associated with age-1, akt-1 or akt-2 mutants, but it enhanced the stress resistance of daf-2 mutants. Further studies demonstrated that this stress tolerance could be attributed to increased daf-16 nuclear accumulation and enhanced expression of both superoxide dismutase-3 protein (SOD-3) and heat shock protein-16.2 (HSP-16.2) in response to stress. Additionally, quantitative real-time PCR results showed that the expression of hsf-1 and its target genes were up-regulated in lmwptp-knockdown worms under stress conditions. Together these results indicated that lmwptp is related to stress resistance of worms, and it is likely associated with the insulin/IGF-1-like signaling (IIS) pathway.

Recombinant buckwheat glutaredoxin intake increases lifespan and stress resistance via hsf-1 upregulation in Caenorhabditis elegans

Glutaredoxin (Grx) is a polypeptide with low molecular weight, which has been extracted from buckwheat and has been suggested to have multiple functions revolving around oxidative stress responses and cell signaling. Here, we report the antioxidant activity of recombinant buckwheat Grx (rbGrx) to reduce aging effects in Caenorhabditis elegans (C. elegans) as well as the mechanism involved. Our results showed that rbGrx beneficially affected the health span of C. elegans, including pharyngeal-pumping rate, locomotion, and lipofuscin accumulation. Furthermore, stress assay showed that rbGrx could extend the lifespan under both oxidative and heat stress. Further studies indicated that the longevity-extending effects of rbGrx could be attributed to its in vitro and in vivo antioxidant activities. After treatment with rbGrx, SOD activity, CAT activity, GSH content, and GSH/GSSG ratio were increased, while MDA content was decreased, which led to low intracellular levels of reactive oxygen species in C. elegans. Moreover, rbGrx up-regulated hsf-1 mRNA level and could not expand the lifespan of the hsf-1 mutant C. elegans (sy441); however, this had no effect on the transcription of daf-16 and skn-1 and could expand the lifespan of both daf-16 and skn-1 mutants. These results suggested dependency of the rbGrx effect on the heat shock transcription factor (HSF-1) and independency on both DAF-16 and SKN-1. In summary, our results demonstrated the anti-aging activity of rbGrx, which increased resistance to cellular stress and improved the health span of C. elegans. These results are very important for the use of rbGrx in anti-aging research.

Detection of Ultraweak Photon Emission (UPE) from Cells as a Tool for Pathological Studies

OBJECTIVE

It is well-known that all living cells emit ultra-weak photon emission (UPE), which is due to byproducts of chemical reactions in cell metabolisms. It has been shown that Reactive Oxygen Species (ROS) in the cells enhances the UPE intensity. The magnitude of such UPE is extremely weak (i.e. a few to 10³ photons/ (sec.cm2²)), and the detection of such ultra-weak signals is hardly possible via sensitive instruments like photomultiplier tube (PMT) that can detect single photons.

MATERIALS AND METHODS

H₂O₂ factor with various concentrations was applied on the HT-29 cells to generate ROS. H₂O₂ concentrations were so low to be nondestructive to the cells. Then, the effect of ROS generation on UPE intensity was investigated. PMT was used to detect UPE from HT-29 cells.

RESULTS

The topical application of H₂O₂ was significantly different (P < 0.05) in comparison with HT-29 cells without H₂O₂ at a concentration of 1mM in 5 min detection time. The integrated UPE in the presence of H₂O₂ at concentration of 3mM was significantly higher (P < 0.05) than the integrated UPE in other groups at the same detection time. The difference between the concentrations of 3mM and 4mM was not significant (P > 0.01) for integrated UPE in the cell groups in the presence of H₂O₂.

CONCLUSION

The results show that the recorded UPE from HT-29 cells increased with the topical application of exogenous ROS inducer. As a result, UPE can be used as a non-invasive technique for monitoring ROS in cells.

N-acetyl-l-cysteine mimics the effect of dietary restriction on lifespan and reduces amyloid beta-induced toxicity in Caenorhabditis elegans

The effects of antioxidants on lifespan have been widely studied. Our previous study showed supplementation with N-acetyl-l-cysteine (NAC) extends the lifespan of Caenorhabditis elegans. Here we aimed to determine the lifespan-extending mechanism involved with NAC and the effect of NAC on Alzheimer's disease (AD). NAC further increased the lifespan of age-1 and clk-1 mutants, which have increased lifespan owing to reduced insulin/IGF-1-like signaling and mitochondrial function, respectively. There was no additional lifespan extension in eat-2 background, a genetic model of dietary restriction (DR), by NAC. Gene knockdown experiments revealed that the effect of NAC is not dependent on SKN-1, a protein-sensing DR status, whereas DAF-16, a transcription factor regulating stress-responsive genes, is required for lifespan extension by NAC. NAC delayed paralysis caused by amyloid beta. Our results show that NAC mimics the effect of DR on lifespan, possibly through the induction of DAF-16 nuclear localization and may retard the incidence of AD.

Application of Spontaneous Photon Emission in the Growth Ages and Varieties Screening of Fresh Chinese Herbal Medicines

Ultraweak photon emission emitted by all living organisms has been confirmed to be a noninvasive indicator for their physiological and pathological characteristics. In this study, we investigated the characteristics of spontaneous photon emission (SPE) and the contents of specific active compounds of roots and flowers buds of several fresh Chinese herbal medicines (natural medicines) with different growth ages and varieties. The results revealed that the contents of specific active compounds from same species herbs with different growth ages and varieties were significantly different, and this difference could be reflected by their SPE. Because the contents of specific bioactive constituents in Chinese herbs are closely related to their quality and curative effect, the SPE measurement technique may contribute to the quality control of Chinese herbal medicine in the future.

Mitochondrial fusion and fission are involved in stress tolerance of Candida glabrata

Background

Recently, cell tolerance toward environmental stresses has become the major problem in the development of industrial microbial fermentation. Acetoin is an important chemical that can be synthesized by microbes. Its toxicity was investigated using Candida glabrata as the model in this study.

Results

A series of physiological and biochemical experiments demonstrated that the organic solvent acetoin can inhibit cell growth by increasing intracellular reactive oxygen species (ROS) production and inducing damage to mitochondria and cell apoptosis. Integrating RT-PCR experiments, the genes fzo1 and dnm1 were overexpressed to regulate the balance between mitochondrial fusion and fission. Enhancement of mitochondrial fusion was shown to significantly increase cell tolerance toward acetoin stress by inhibiting ROS production and increasing the intracellular adenosine triphosphate (ATP) supply, which was also demonstrated by the addition of citrate.

Conclusions

Regulating mitochondrial fusion-fission may be an alternative strategy for rationally improving the growth performance of eukaryotes under high environmental stress conditions, and also expands our knowledge of the mechanisms of cell tolerance through the processes of energy-related metabolic pathways.

Natural variation in Caenorhabditis briggsae mitochondrial form and function suggests a novel model of organelle dynamics

Mitochondrial functioning and morphology are known to be connected through cycles of organelle fusion and fission that depend upon the mitochondrial membrane potential (ΔΨM); however, we lack an understanding of the features and dynamics of natural mitochondrial populations. Using data from our recent study of univariate mitochondrial phenotypic variation in Caenorhabditis briggsae nematodes, we analyzed patterns of phenotypic correlation for 24 mitochondrial traits. Our findings support a role for ΔΨM in shaping mitochondrial dynamics, but no role for mitochondrial ROS. Further, our study suggests a novel model of mitochondrial population dynamics dependent upon cellular environmental context and with implications for mitochondrial genome integrity.

Trinations aging symposium

The "Trinations Aging Symposium" was held on the campus of Guangdong Medical College in Dongguan, China from April 28 to 30, 2011. The goal was to promote interaction, collaboration, and exchange of ideas between scientists in the field of aging research from Japan, South Korea, and China. Aging research is on the rise in Asia. This represents an important development, since Korea and Japan are the two longest-lived countries in the world, and life expectancy is increasing rapidly in China and other Asian countries. The world will see a greater percentage of people over age 65 in coming years than any period in human history. Developing therapeutic approaches to increase healthspan has the potential not only to enhance quality of life, but would also help stem the looming economic crisis associated with a high percentage of elderly. The focus of the Trinations Aging Symposium was on the basic biology of aging, and topics discussed included genome maintenance, metabolism and aging, longevity genes and interventions, and new therapies for age-related diseases. The meeting finished with a commitment for another symposium next year that will include additional Asian countries and the formation of a new scientific organization, the Asian Association for Aging Research.

Genetic approaches to aging in budding and fission yeasts: new connections and new opportunities

Yeasts are powerful model systems to examine the evolutionarily conserved aspects of eukaryotic aging because they maintain many of the same core cellular signaling pathways and essential organelles as human cells. We constructed a strain of the budding yeast Saccharomyces cerevisiae that could monitor the distribution of proteins involved in heterochromatic silencing and aging, and isolated mutants that alter this distribution. The largest class of such mutants cause defects in mitochondrial function, and appear to cause changes in nuclear silencing separate from the well-known Rtg2p-dependent pathway that alters nuclear transcription in response to the loss of the mitochondrial genome. Mutants that inactivate the ATP2 gene, which encodes the ATPase subunit of the mitochondrial F(1)F(0)-ATPase, were isolated twice in our screen and identify a lifespan extending pathway in a gene that is conserved in both prokaryotes and eukaryotes. The budding yeast S. cerevisiae S. cerevisiae has been used with great success to identify other lifespan-extending pathways in screens using surrogate phenotypes such as stress resistance or silencing to identify random mutants, or in high throughput screens that utilize the deletion strain set resource. However, the direct selection of long-lived mutants from a pool of random mutants is more challenging. We have established a new chronological aging assay for the evolutionarily distant fission yeast Schizosaccharomyces pombe that recapitulates aspects of aging conserved in all eukaryotes. We have constructed a novel S. pombe S. pombe DNA insertion mutant bank, and used it to show that we can directly select for a long-lived mutant. The use of both the budding and fission yeast systems should continue to facilitate the identification and validation of lifespan extending pathways that are conserved in humans.

A potential biochemical mechanism underlying the influence of sterol deprivation stress on Caenorhabditis elegans longevity

To investigate the biochemical mechanism underlying the effect of sterol deprivation on longevity in Caenorhabditis elegans, we treated parent worms (P0) with 25-azacoprostane (Aza), which inhibits sitosterol-to-cholesterol conversion, and measured mean lifespan (MLS) in F2 worms. At 25 μM (∼EC(50)), Aza reduced total body sterol by 82.5%, confirming sterol depletion. Aza (25 μM) treatment of wild-type (N2) C. elegans grown in sitosterol (5 μg/ml) reduced MLS by 35%. Similar results were obtained for the stress-related mutants daf-16(mu86) and gas-1(fc21). Unexpectedly, Aza had essentially no effect on MLS in the stress-resistant daf-2(e1370) or mitochondrial complex II mutant mev-1(kn1) strains, indicating that Aza may target both insulin/IGF-1 signaling (IIS) and mitochondrial complex II. Aza increased reactive oxygen species (ROS) levels 2.7-fold in N2 worms, but did not affect ROS production by mev-1(kn1), suggesting a direct link between Aza treatment and mitochondrial ROS production. Moreover, expression of the stress-response transcription factor SKN-1 was decreased in amphid neurons by Aza and that of DAF-28 was increased when DAF-6 was involved, contributing to lifespan reduction.

Reactive Oxygen Species and Aging in Caenorhabditis elegans: Causal or Casual Relationship?

The free radical theory of aging proposes a causal relationship between reactive oxygen species (ROS) and aging. While it is clear that oxidative damage increases with age, its role in the aging process is uncertain. Testing the free radical theory of aging requires experimentally manipulating ROS production or detoxification and examining the resulting effects on lifespan. In this review, we examine the relationship between ROS and aging in the genetic model organism Caenorhabditis elegans, summarizing experiments using long-lived mutants, mutants with altered mitochondrial function, mutants with decreased antioxidant defenses, worms treated with antioxidant compounds, and worms exposed to different environmental conditions. While there is frequently a negative correlation between oxidative damage and lifespan, there are many examples in which they are uncoupled. Neither is resistance to oxidative stress sufficient for a long life nor are all long-lived mutants more resistant to oxidative stress. Similarly, sensitivity to oxidative stress does not necessarily shorten lifespan and is in fact compatible with long life. Overall, the data in C. elegans indicate that oxidative damage can be dissociated from aging in experimental situations.

Altered redox status of coenzyme Q9 reflects mitochondrial electron transport chain deficiencies in Caenorhabditis elegans

Mitochondrial disorders are often associated with primary or secondary CoQ10 decrease. In clinical practice, Coenzyme Q10 (CoQ10) levels are measured to diagnose deficiencies and to direct and monitor supplemental therapy. CoQ10 is reduced by complex I or II and oxidized by complex III in the mitochondrial respiratory chain. Therefore, the ratio between the reduced (ubiquinol) and oxidized (ubiquinone) CoQ10 may provide clinically significant information in patients with mitochondrial electron transport chain (ETC) defects. Here, we exploit mutants of Caenorhabditis elegans (C. elegans) with defined defects of the ETC to demonstrate an altered redox ratio in Coenzyme Q9 (CoQ9), the native quinone in these organisms. The percentage of reduced CoQ9 is decreased in complex I (gas-1) and complex II (mev-1) deficient animals, consistent with the diminished activity of these complexes that normally reduce CoQ9. As anticipated, reduced CoQ9 is increased in the complex III deficient mutant (isp-1), since the oxidase activity of the complex is severely defective. These data provide proof of principle of our hypothesis that an altered redox status of CoQ may be present in respiratory complex deficiencies. The assessment of CoQ10 redox status in patients with mitochondrial disorders may be a simple and useful tool to uncover and monitor specific respiratory complex defects.

Role of Drosophila alkaline ceramidase (Dacer) in Drosophila development and longevity

Ceramidases catalyze the hydrolysis of ceramides to generate sphingosine (SPH) and fatty acids, and ceramide metabolism is implicated in various biological responses in Drosophila melanogaster. Here we report the cloning, biochemical characterization, and functional analysis of a Drosophila alkaline ceramidase (Dacer). Dacer, a membrane-bound protein of 284 amino acids, shares homology with yeast and mammalian alkaline ceramidases. Overexpression of Dacer in High Five insect cells increases ceramidase activity in the alkaline pH range, indicating that Dacer is a bona fide alkaline ceramidase. Dacer mRNA is highly expressed in the midgut and at the pupal stage. An inactivation of Dacer by insertional mutagenesis increases the levels of ceramides in both Drosophila pupae and adult flies. Dacer inactivation increases Drosophila pre-adult development time, lifespan, and anti-oxidative stress capacity. Collectively, these results suggest that Dacer plays an important role in the Drosophila development and longevity by controlling the metabolism of ceramides.

Effect of exogenous hydrogen peroxide on biophoton emission from radish root cells

Biophotons spontaneously emitted from radish root cells were detected using highly sensitive photomultiplier tube. Freshly isolated radish root cells exhibited spontaneous photon emission of about 4 counts s(-1). Addition of hydrogen peroxide to the cells caused significant enhancement in biophoton emission to about 500 counts s(-1). Removal of molecular oxygen using glucose/glucose oxidase system and scavengering of reactive oxygen species by reducing agents such are sodium ascorbate and cysteine completely diminished biophoton emission. Spectral analysis of the hydrogen peroxide-induced biophoton emission indicates that biophotons are emitted mainly in green-red region of the spectra. The data provided by electron paramagnetic resonance spin-trapping technique showed that formation of singlet oxygen observed after addition of H2O2 correlates with enhancement in biophoton emission. These observations provide direct evidence that singlet oxygen is involved in biophoton emission from radish root cells.

Insulin and Insulin-Sensitizing Drugs in Neurodegeneration: Mitochondria as Therapeutic Targets

Insulin, besides its glucose lowering effects, is involved in the modulation of lifespan, aging and memory and learning processes. As the population ages, neurodegenerative disorders become epidemic and a connection between insulin signaling dysregulation, cognitive decline and dementia has been established. Mitochondria are intracellular organelles that despite playing a critical role in cellular metabolism are also one of the major sources of reactive oxygen species. Mitochondrial dysfunction, oxidative stress and neuroinflammation, hallmarks of neurodegeneration, can result from impaired insulin signaling. Insulin-sensitizing drugs such as the thiazolidinediones are a new class of synthetic compounds that potentiate insulin action in the target tissues and act as specific agonists of the peroxisome proliferator-activated receptor gamma (PPAR-γ). Recently, several PPAR agonists have been proposed as novel and possible therapeutic agents for neurodegenerative disorders. Indeed, the literature shows that these agents are able to protect against mitochondrial dysfunction, oxidative damage, inflammation and apoptosis. This review discusses the role of mitochondria and insulin signaling in normal brain function and in neurodegeneration. Furthermore, the potential protective role of insulin and insulin sensitizers in Alzheimer´s, Parkinson´s and Huntington´s diseases and amyotrophic lateral sclerosis will be also discussed.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

A Measurable increase in oxidative damage due to reduction in superoxide detoxification fails to shorten the life span of long-lived mitochondrial mutants of Caenorhabditis elegans

SOD-1 and SOD-2 detoxify superoxide in the cytoplasm and mitochondria. We find that, although several long-lived mutants of Caenorhabditis elegans have increased SOD levels, this phenomenon does not correlate with life span or growth rate. Furthermore, although disruption of sod-1 or -2 expression produces numerous phenotypes, including increased sensitivity to paraquat and increased oxidative damage to proteins (except in daf-2 mutants), this fails to shorten the life span of these long-lived mutants. In fact, sod-1(RNAi) increases the life span of daf-2 mutants and sod-2(RNAi) that of clk-1 mutants. Our results suggest that increased superoxide detoxification and low oxidative damage are not crucial for the longevity of the mutants examined, with the possible exception of daf-2, where our results are inconclusive. These results are surprising because several of the long-lived mutants that we examined specifically affect mitochondrial electron transport, a process whose involvement in life-span determination is believed to be related to superoxide generation. We discuss the significance of our findings in light of the oxidative stress theory of aging.

Glyoxalase-1 prevents mitochondrial protein modification and enhances lifespan in Caenorhabditis elegans

Studies of mutations affecting lifespan in Caenorhabditis elegans show that mitochondrial generation of reactive oxygen species (ROS) plays a major causative role in organismal aging. Here, we describe a novel mechanism for regulating mitochondrial ROS production and lifespan in C. elegans: progressive mitochondrial protein modification by the glycolysis-derived dicarbonyl metabolite methylglyoxal (MG). We demonstrate that the activity of glyoxalase-1, an enzyme detoxifying MG, is markedly reduced with age despite unchanged levels of glyoxalase-1 mRNA. The decrease in enzymatic activity promotes accumulation of MG-derived adducts and oxidative stress markers, which cause further inhibition of glyoxalase-1 expression. Over-expression of the C. elegans glyoxalase-1 orthologue CeGly decreases MG modifications of mitochondrial proteins and mitochondrial ROS production, and prolongs C. elegans lifespan. In contrast, knock-down of CeGly increases MG modifications of mitochondrial proteins and mitochondrial ROS production, and decreases C. elegans lifespan.