Ros S et al. (2004) European Worm Meeting "GENETIC ANALYSIS OF GENES INVOLVED FE-S CLUSTERS BIOGENESIS IN CAENORHABDITIS ELEGANS"

Ros S, Palau F, Gonzalez-Cabo P, Vazquez-Manrique R

[European Worm Meeting, 2004]

Iron-sulfur clusters (ISC) are co-factors of numerous proteins with important functions in metabolism, electron transport and regulation of gene expression. Biosynthesis of these proteins is a complex process involving numerous components. In eukaryote cells, this process is accomplished inside mitochondria. The mitochondrial ISC machinery is responsible for biogenesis iron-sulfur proteins both within and outside the organelle. Fe/S cluster biosynthesis for the model eukaryote Saccharomyces cerevisiae is initiated by the abstration of sulfur from cysteine in a reaction catalysed by cysteine desulfurase (Nfs1). For this reduction electrons are needed that are transferred by an electron transport chain encompassing the adrenodoxin reductase Arh1p and ferredoxin Yah1p. Fe/S assembly is mediated by protein Isu1/Isu2, Isa1/Isa2 and Nfu1. Maturation of the latter proteins involves the ABC transporter Atm1p which presumably exports iron-sulfur clusters from the mitochondria towards cytosol. We are addressing the analysis of ISC metabolism in mitochondria by genetic studies in C. elegans. Genes orthologues of the proteins involved in the ISC biogenesis of were searched in C.elegans for homology to the genes already described in S.cerevisiae. These genes are Y45F10D.4, Y39B6A.3, R10H10.1, Y73F8A.27, B0205.6, Y62E10A.6 and Y74C10AM.1 that show homology to the genes of S.cerevisiae Isu1/Isu2, Isa1/Isa2, Nfu1, Yah1, Nfs1, Arh1 and Atm1 respectively. Transient knock-down experiments by RNAi produce a specific phenotype in worms of the F1 generation. All knock-down mutants have a common phenotype: embryonic lethality or/and larva arrest (Lva) and slow growth (Gro). Moreover, some knock-down mutans of R10H10.1 and Y74C10AM.1 were able to get the size of adult worm. In this case it was possible to measure defecation rhythm and life span. Knock-down mutant of R10H10.1 shows life span longer (p<0.05) than in wild-type. Knock-down mutant of Y74C10AM.1 has a high reduction of the defecation rhythm (p<0.05) and the life span is increased (p<0.05).

Doser, Rachel L et al. (2022) MicroPubl Biol

Hoerndli, Frederic J, Doser, Rachel L

[MicroPubl Biol, 2022]

Reactive oxygen species (ROS) are chemically reactive molecules normally produced during cellular respiration. High ROS levels negatively impact forms of synaptic plasticity that rely on changes in the number of ionotropic glutamate receptors (iGluRs) at synapses. More recently, we have shown that physiological increases in ROS reduce iGluR transport to synapses by acting on activity-dependent calcium signaling. Here, we show that decreasing mitochondria-derived ROS decrease iGluR transport albeit in a calcium-independent manner. These data demonstrate differential regulatory mechanisms by elevated or diminished ROS levels which further support a physiological signaling role for ROS in regulating iGluR transport to synapses.

Van Raamsdonk JM (2015) Worm "Levels and location are crucial in determining the effect of ROS on lifespan."

Van Raamsdonk JM

[Worm, 2015]

Reactive oxygen species (ROS) cause molecular damage that accumulates with age and have been proposed to be one of the primary causes of aging. However, recent work indicates that ROS have beneficial roles in an organism and that the relationship between ROS and aging is complex. We have shown that increasing ROS levels or oxidative damage does not necessarily lead to decreased lifespan. We have also shown that in some cases increasing ROS can promote longevity. Further investigation of the factors that determine the effect of ROS on lifespan demonstrate that both the levels and location of ROS are important in predicting the impact of ROS on longevity. Increasing superoxide levels in the cytoplasm results in decreased lifespan, while increasing superoxide levels in the mitochondria leads to increased lifespan. Within the mitochondria, mild elevation of superoxide levels promote longevity, while high levels of superoxide are toxic. Thus, a new paradigm is emerging in which ROS are neither good nor bad but levels and location makes it so.

Hwang AB et al. (2014) Proc Natl Acad Sci U S A "Feedback regulation via AMPK and HIF-1 mediates ROS-dependent longevity in Caenorhabditis elegans."

Kabir MH, Mair WB, Lee SS, Chang HW, Lee SJ, Ryu EA, Yang JS, Kim S, Lee D, Nam HJ, Hwang AB, Lee C, Artan M

[Proc Natl Acad Sci U S A, 2014]

Mild inhibition of mitochondrial respiration extends the lifespan of many species. In Caenorhabditis elegans, reactive oxygen species (ROS) promote longevity by activating hypoxia-inducible factor 1 (HIF-1) in response to reduced mitochondrial respiration. However, the physiological role and mechanism of ROS-induced longevity are poorly understood. Here, we show that a modest increase in ROS increases the immunity and lifespan of C. elegans through feedback regulation by HIF-1 and AMP-activated protein kinase (AMPK). We found that activation of AMPK as well as HIF-1 mediates the longevity response to ROS. We further showed that AMPK reduces internal levels of ROS, whereas HIF-1 amplifies the levels of internal ROS under conditions that increase ROS. Moreover, mitochondrial ROS increase resistance to various pathogenic bacteria, suggesting a possible association between immunity and long lifespan. Thus, AMPK and HIF-1 may control immunity and longevity tightly by acting as feedback regulators of ROS.

Hwang, Ara B. et al. (2013) International Worm Meeting "Mitochondrial ROS promote longevity and innate immunity via a feedback loop involving HIF-1 and AMPK."

Mair, William, Artan, Murat, Lee, Seung-Jae, Hwang, Ara B., Ryu, Eun-A

[International Worm Meeting, 2013]

Mild inhibition of mitochondrial respiration promotes longevity across phyla. Recently we reported that reduced respiration lengthens lifespan by increasing reactive oxygen species (ROS) that activate the hypoxia-inducible factor 1 (HIF-1) in C. elegans. Here we elucidated a feedback-regulatory mechanism and functional significance of the ROS-induced longevity. We initially found that mutations in aak-2 (catalytic a subunit of AMP-activated protein kinase [AMPK]) suppressed the longevity induced by an ROS-generating chemical, paraquat (0.25 mM). In addition, we showed that mitochondrial ROS activated AMPK, and that paraquat did not further increase the longevity of gain-of-function AAK-2 transgenic animals. These data suggest that AMPK mediates the longevity induced by mitochondrial ROS. We then investigated the mechanisms by which AMPK contributes to the ROS-induced longevity. We demonstrated that AMPK acts as a negative feedback regulator of internal ROS levels, because aak-2 mutants were hyper-sensitive to ROS and contained increased ROS levels upon paraquat treatment. In contrast, HIF-1 was required for increasing internal ROS levels, suggesting that HIF-1 acts as a positive regulator of ROS. These data imply that feedback regulation by AMPK and HIF-1 ensures balance between the benefit and toxicity of ROS. Next, we determined the relationship between the ROS-induced longevity and innate immunity, because infection by E. coli is the major cause of death of aged C. elegans in laboratory. We found that feeding non-pathogenic bacteria increased the lifespan of wild type but not that of the long-lived mitochondrial isp-1 mutants, which display high levels of ROS. Moreover, isp-1 mutants were resistant to several pathogens, and both aak-2 and hif-1 were required for the enhanced pathogen resistance. Taken together, we propose that the feedback circuit involving AMPK and HIF-1 regulates ROS levels to maintain an optimal immunity and longevity.

Zarse K et al. (2012) Cell Metab "Impaired insulin/IGF1 signaling extends life span by promoting mitochondrial L-proline catabolism to induce a transient ROS signal."

Guthke R, Platzer M, Kahn CR, Groth M, Priebe S, Ristow M, Beuster G, Zarse K, Schmeisser S, Kuhlow D

[Cell Metab, 2012]

Impaired insulin and IGF-1 signaling (iIIS) in C.elegans daf-2 mutants extends life span more than 2-fold. Constitutively, iIIS increases mitochondrial activity and reduces reactive oxygen species (ROS) levels. By contrast, acute impairment of daf-2 in adult C.elegans reduces glucose uptake and transiently increases ROS. Consistent with the concept ofmitohormesis, this ROS signal causes an adaptive response by inducing ROS defense enzymes (SOD, catalase), culminating in ultimately reduced ROS levels despite increased mitochondrial activity. Inhibition of this ROS signal by antioxidants reduces iIIS-mediated longevity by up to 60%. Induction of the ROS signal requires AAK-2 (AMPK), while PMK-1 (p38) and SKN-1 (NRF-2) are needed for the retrograde response. IIIS upregulates mitochondrial L-proline catabolism, and impairment of the latter impairs the life span-extending capacity of iIIS while L-proline supplementation extends C.elegans life span. Taken together, iIIS promotes L-proline metabolism to generate a ROS signal for the adaptive induction of endogenous stress defense to extend life span.

Van Raamsdonk, Jeremy et al. (2015) International Worm Meeting "The complex relationship between reactive oxygen species and aging: levels and location determine the effect of superoxide on lifespan."

Schaar, Claire, Van Raamsdonk, Jeremy, Cooper, Jason, Senchuk, Megan, Dues, Dylan, Spielbauer, Katie, Machiela, Emily

[International Worm Meeting, 2015]

The accumulation of oxidative damage caused by reactive oxygen species (ROS) has been proposed to be one of the main causes of aging. However, recent work indicates that low levels of ROS can be beneficial and promote longevity. We have shown that while mild elevation of ROS levels causes increased lifespan, high levels of ROS are toxic. To further explore the relationship between ROS and aging, we determined how the subcellular location of ROS impacts the effect of ROS on lifespan. We used a genetic approach to decrease the levels of the antioxidant enzyme superoxide dismutase (SOD) in specific compartments of the cell. Since superoxide is unable to cross membranes, this results in elevated levels of superoxide in the part of the cell in which SOD expression was decreased. To increase our ability to observe an effect of ROS on lifespan, we performed these experiments in clk-1 mitochondrial mutants, which are sensitized to ROS. We generated clk-1 double mutants with each of the five C. elegans sod genes and examined the resulting effect on lifespan. We found that increasing superoxide levels in the mitochondria, through the deletion of sod-2, markedly increased the lifespan of clk-1 worms. In contrast, increasing the levels of superoxide in the cytoplasm, through deletion of either sod-1 or sod-5, resulted in decreased lifespan. This indicates that mitochondrial and cytoplasmic ROS have opposing effects on lifespan. To determine if mitochondrial and cytoplasmic ROS act independently to affect lifespan, we increased mitochondrial ROS in clk-1;sod-1 worms through treatment with the superoxide-generator paraquat (PQ). We found that increasing mitochondrial ROS, through treatment with PQ, still increased clk-1;sod-1 lifespan. Similarly, we found that increasing cytoplasmic ROS, through deletion of sod-1, decreased the lifespan of clk-1;sod-2 worms, thereby indicating that mitochondrial and cytoplasmic ROS act independently to influence longevity. Finally, we show that the effect of ROS on stress resistance and physiologic rates is also dependent on the location of ROS within the cell, but that both can be experimentally dissociated from lifespan. Overall, this work demonstrates that the relationship between ROS and aging is complex, and that both the levels and location of ROS are crucial in determining the effect of ROS on lifespan.

Senchuk MM et al. (2017) Bio Protoc "Measuring Oxidative Stress in Caenorhabditis elegans: Paraquat and Juglone Sensitivity Assays."

Van Raamsdonk JM, Senchuk MM, Dues DJ

[Bio Protoc, 2017]

Oxidative stress has been proposed to be one of the main causes of aging and has been implicated in the pathogenesis of many diseases. Sensitivity to oxidative stress can be measured by quantifying survival following exposure to a reactive oxygen species (ROS)-generating compound such as paraquat or juglone. Sensitivity to oxidative stress is a balance between basal levels of ROS, the ability to detoxify ROS, and the ability to repair ROS-mediated damage.

Chung YM et al. (2008) J Biol Chem "Replicative senescence induced by Romo1-derived reactive oxygen species."

Yoo YD, Chung JS, Kim HJ, Lee SB, Chung YM, Kim JJ, Park SH

[J Biol Chem, 2008]

Persistent accumulation of DNA damage induced by reactive oxygen species (ROS) is proposed to be a major contributor toward the aging process. Furthermore, an increase in age-associated ROS is strongly correlated with aging in various species, including humans. Here we showed that the enforced expression of the ROS modulator 1 (Romo1) triggered premature senescence by ROS production, and this also contributed toward induction of DNA damage. Romo1-derived ROS was found to originate in the mitochondrial electron transport chain. Romo1 expression gradually increased in proportion to population doublings of IMR-90 human fibroblasts. An increase in ROS production in these cells with high population doubling was blocked by the Romo1 knockdown using Romo1 small interfering RNA. Romo1 knockdown also inhibited the progression of replicative senescence. Based on these results, we suggest that age-related ROS levels increase, and this contributes to replicative senescence, which is directly associated with Romo1 expression.

Na AR et al. (2008) Biochem Biophys Res Commun "A critical role for Romo1-derived ROS in cell proliferation."

Na AR, Lee SB, Lee MS, Yoo YD, Park SH, Chung YM

[Biochem Biophys Res Commun, 2008]

Low levels of endogenous reactive oxygen species (ROS) originating from NADPH oxidase have been implicated in various signaling pathways induced by growth factors and mediated by cytokines. However, the main source of ROS is known to be the mitochondria, and increased levels of ROS from the mitochondria have been observed in many cancer cells. Thus far, the mechanism of ROS production in cancer cell proliferation in the mitochondria is not well-understood. We recently identified a novel protein, ROS modulator 1 (Romo1), and reported that increased expression of Romo1-triggered ROS production in the mitochondria. The experiments conducted in the present study showed that Romo1-derived ROS were indispensable for the proliferation of both normal and cancer cells. Furthermore, whilst cell growth was inhibited by blocking the ERK pathway in cells transfected with siRNA directed against Romo1, the cell growth was recovered by addition of exogenous hydrogen peroxide. The results of this study suggest that Romo1-induced ROS may play an important role in redox signaling in cancer cells.