Do developmental temperatures affect redox level and lifespan in C. elegans through upregulation of peroxiredoxin?

Peroxiredoxin 2 is required for the redox mediated adaptation to exercise

Exercise generates a site-specific increase in Reactive Oxygen Species (ROS) within muscle that promotes changes in gene transcription and mitochondrial biogenesis, required for the beneficial adaptive response. We demonstrate that Peroxiredoxin 2 (Prdx2), an abundant cytoplasmic 2-Cys peroxiredoxin, is required for the adaptive hormesis response to physiological levels of H₂O₂ in myoblasts and following exercise in C. elegans. A short bolus addition of H₂O₂ increases mitochondrial capacity and improves myogenesis of cultured myoblasts, this beneficial adaptive response was suppressed in myoblasts with decreased expression of cytoplasmic Prdxs. Moreover, a swimming exercise protocol in C. elegans increased mitochondrial content, fitness, survival and longevity in wild type (N2) worms. In contrast, prdx-2 mutant worms had decreased fitness, disrupted mitochondria, reduced survival and lifespan following exercise. Global proteomics following exercise identified distinct changes in the proteome of N2 and prdx-2 mutants. Furthermore, a redox proteomic approach to quantify reversible oxidation of specific Cysteine residues revealed a more reduced redox state in the non-exercised prdx-2 mutant strain that become oxidized following exercise. In contrast, specific Cys residues from regulatory proteins become more reduced in the N2 strain following exercise, establishing the key regulatory role of PRDX-2 in a redox signalling cascade following endogenous ROS generation. Our results demonstrate that conserved cytoplasmic 2-Cys Peroxiredoxins are required for the beneficial adaptive response to a physiological redox stress.

Metabolism, homeostasis, and aging

We propose a two-mode (pursuit/maintenance) model of metabolism defined by usable resource availability. Pursuit, consisting of anabolism and catabolism, dominates when usable resources are plentiful and leads to the generation of metabolic waste. In turn, maintenance of a system is activated by elevated metabolic waste during resource depletion. Interaction with the environment results in pendulum-like swings between these metabolic states in thriveless attempts to maintain the least deleterious organismal state - ephemeral homeostasis. Imperfectness of biological processes during these attempts supports the accumulation of the deleteriome, driving organismal aging. We discuss how metabolic adjustment by the environment and resource stabilization may modulate healthspan and lifespan.

Identification of the redox-stress signaling threshold (RST): Increased RST helps to delay aging in C. elegans

Reactive oxygen species (ROS) play a dual role since they can be either beneficial or harmful to living systems. With increasing ROS concentrations, the roles of ROS change from advantageous to detrimental. There seems to be a concentration threshold that determines the transition from their advantageous to detrimental effects. If we purposefully increase the threshold, that is, increase the range of ROS that plays an advantageous role, it should be beneficial for individuals. To test this hypothesis, in C. elegans, the effects of oxidative challenge induced by different concentrations of paraquat (PQ) on nematode lifespan were evaluated. We found that there is a maximum level below which redox stress has benefits and named this threshold as "Redox-stress Signaling Threshold (RST)". Furthermore, we found that starvation (or heat stress or exercise) stimuli at early stage in C. elegans could increase the RST, indicating that this value is not fixed and can be increased by the adaptive response. More intriguingly, we found that increasing RST could improve Redox-stress Response Capacity (RRC) and healthspan, suggesting that increasing the RST value through early stimulation will be an effective strategy to delay aging.

Typical 2-Cys Peroxiredoxins as a Defense Mechanism against Metal-Induced Oxidative Stress in the Solitary Ascidian Ciona robusta

Typical 2-Cys peroxiredoxins (2-Cys Prdxs) are proteins with antioxidant properties belonging to the thioredoxin peroxidase family. With their peroxidase activity, they contribute to the homeostatic control of reactive oxygen species (ROS) and, therefore, participate in various physiological functions, such as cell proliferation, differentiation, and apoptosis. Although Prdxs have been shown to be potential biomarkers for monitoring aquatic environments, minimal scientific attention has been devoted to describing their molecular architecture and function in marine invertebrates. Our study aims to clarify the protective role against stress induced by exposure to metals (Cu, Zn, and Cd) of three Prdxs (Prdx2, Prdx3, and Prdx4) in the solitary ascidian Ciona robusta, an invertebrate chordate. Here, we report a detailed pre- and post-translational regulation of the three Prdx isoforms. Data on intestinal mRNA expression, provided by qRT-PCR analyses, show a generalized increase for Prdx2, -3, and -4, which is correlated to metal accumulation. Furthermore, the increase in tissue enzyme activity observed after Zn exposure is slower than that observed with Cu and Cd. The obtained results increase our knowledge of the evolution of anti-stress proteins in invertebrates and emphasize the importance of the synthesis of Prdxs as an efficient way to face adverse environmental conditions.

In Vivo Imaging with Genetically Encoded Redox Biosensors

Redox reactions are of high fundamental and practical interest since they are involved in both normal physiology and the pathogenesis of various diseases. However, this area of research has always been a relatively problematic field in the context of analytical approaches, mostly because of the unstable nature of the compounds that are measured. Genetically encoded sensors allow for the registration of highly reactive molecules in real-time mode and, therefore, they began a new era in redox biology. Their strongest points manifest most brightly in in vivo experiments and pave the way for the non-invasive investigation of biochemical pathways that proceed in organisms from different systematic groups. In the first part of the review, we briefly describe the redox sensors that were used in vivo as well as summarize the model systems to which they were applied. Next, we thoroughly discuss the biological results obtained in these studies in regard to animals, plants, as well as unicellular eukaryotes and prokaryotes. We hope that this work reflects the amazing power of this technology and can serve as a useful guide for biologists and chemists who work in the field of redox processes.

Yes-associated protein reduces neuroinflammation through upregulation of Sirt3 and inhibition of JNK signaling pathway

Objective: Neuroinflammation is linked to a series of neurodegenerative diseases through the unknown mechanisms.Aim: The aim of this study was to investigate the role of Yes-associated protein (Yap) in the regulation of neuroinflammation.Methods: BV-2 neuroglia cells were treated with TNFα in vitro. Then, western blots, qPCR, immunofluorescence, and ELISA were used to verify the influence of Yap in BV-2 cells neuroinflammation response.Results: After exposure to TNFα, viability of BV-2 cells decreased whereas apoptosis index was increased. Of note, Yap expression in BV-2 cells was significantly reduced, when compared to the normal cells. Interestingly, adenovirus-induced Yap overexpression was capable to reverse cell viability and thus reduce apoptotic index in TNFα-treated BV-2 cells. Molecular investigation demonstrated that Yap overexpression was linked to Sirt3 upregulation. Increased Sirt3 reduced endoplasmic reticulum (ER) stress, attenuated mitochondrial damage, and blocked JNK pro-apoptotic pathway. Interestingly, loss of Sirt3 abolished the protective effects induced by Yap overexpression in TNFα-treated BV-2 cells.Conclusions: Altogether, our results demonstrated that neuroinflammation could be caused by Yap downregulation, possible driven through Sirt3 inhibition and JNK activation. However, overexpression of Yap could protect BV-2 cells against TNFα-mediated apoptosis through modulating Sirt3-JNK signaling pathways.

Ripk3 mediates cardiomyocyte necrosis through targeting mitochondria and the JNK-Bnip3 pathway under hypoxia-reoxygenation injury

Context: Cardiomyocyte necrosis following myocardial infarction drastically the progression of heart failure.Objective: In the current study, we explored the upstream mediator for cardiomyocytes necrosis induced by hypoxia-reoxygenation (HR) injury with a focus on mitochondrial function and JNK-Bnip3 pathway.Materials and methods: Cell necrosis was determined via MTT assay, TUNEL staining and PI staining. siRNA transfection was performed to inhibit Ripk3 activation in response to HR injury. Pathway blocker was applied to prevent JNK activation.Results: Ripk3 was rapidly increased in HR-treated cardiomyocytes and correlated with the necrosis of cardiomyocytes. Interestingly, silencing of Ripk3 attenuated HR-mediated cardiomyocytes necrosis. At the molecular levels, Ripk3 deletion sustained mitochondrial bioenergetics and stabilized mitochondrial glucose metabolism. Besides, Ripk3 deletion also reduced mitochondrial oxidative stress and inhibited mPTP opening. To the end, we found Ripk3 activation was along with JNK pathway activation and Bnip3 upregulation. Interestingly, blockade of JNK pathway abolished the harmful effects of HR injury on mitochondrial function, energy metabolism and redox balance. Moreover, overexpression of Bnip3 abrogated the protection action played by Ripk3 deletion on cardiomyocytes survival.Conclusions: Taken together, these data may identify Ripk3 upregulation, mitochondrial dysfunction and JNK-Bnip3 axis activation as the novel mechanisms underlying cardiomyocytes necrosis achieved by HR injury. Thereby, approaches targeted to the Ripk3-JNK-Bnip3-mitochondria cascade have the potential to ameliorate the progression of HR-related cardiomyocytes necrosis in the clinical practice.

Therapeutic contribution of melatonin to the treatment of septic cardiomyopathy: A novel mechanism linking Ripk3-modified mitochondrial performance and endoplasmic reticulum function

The basic pathophysiological mechanisms underlying septic cardiomyopathy have not yet been completely clarified. Disease-specific treatments are lacking, and care is still based on supportive modalities. The aim of our study was to assess the protective effects of melatonin on septic cardiomyopathy, with a focus on the interactions between receptor-interacting protein kinase 3 (Ripk3), the mitochondria, endoplasmic reticulum (ER) and cytoskeletal degradation in cardiomyocytes. Ripk3 expression was increased in heart samples challenged with LPS, followed by myocardial inflammation, cardiac dysfunction, myocardial breakdown and cardiomyocyte death. The melatonin treatment attenuated septic myocardial injury in a comparable manner to the genetic depletion of Ripk3. Molecular investigations revealed that Ripk3 intimately regulated mitochondrial function, ER stress, cytoskeletal homeostasis and cardioprotective signaling pathways. Melatonin-mediated inhibition of Ripk3 improved mitochondrial bioenergetics, reduced mitochondria-initiated oxidative damage, sustained mitochondrial dynamics, ameliorated ER stress, normalized calcium recycling, and activated cardioprotective signaling pathways (including AKT, ERK and AMPK) in cardiomyocytes. Interestingly, Ripk3 overexpression mediated resistance to melatonin therapy following the infection of LPS-treated hearts with an adenovirus expressing Ripk3. Altogether, our findings identify Ripk3 upregulation as a novel risk factor for the development of sepsis-related myocardial injury, and melatonin restores the physiological functions of the mitochondria, ER, contractile cytoskeleton and cardioprotective signaling pathways. Additionally, our data also reveal a new, potentially therapeutic mechanism by which melatonin protects the heart from sepsis-mediated dysfunction, possibly by targeting Ripk3.

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LPS-activated Ripk3 disturbs mitochondrial bioenergetics and promotes mitochondrial dynamics disorder.

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The inhibitory effect of melatonin on Ripk3 sustains heart function in LPS-mediated septic cardiomyopathy.

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LPS-mediated degradation of the cardiomyocyte contractile cytoskeleton could be reversed by melatonin.

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Melatonin modulates mitochondrial dynamics, ER stress, and cardioprotective signals by repressing Ripk3 expression.

TrxR2 overexpression alleviates inflammation-mediated neuronal death via reducing the oxidative stress and activating the Akt-Parkin pathway

Neuronal death caused by inflammatory cytokine-mediated neuroinflammation is being extensively explored. Thioredoxin reductase (TrxR) 2 is a novel mediator of inflammation response. In the current study, we focus on the mechanisms of TrxR2 overexpression in inflammation-mediated neuronal death. LPS was used to induce neuroinflammation in N2a cells in vitro. Adenovirus-loaded TrxR2 was transfected into N2a cells to up-regulate TrxR2 expression. Then, cell viability was determined via MTT assay and TUNEL assay. Apoptosis was measured via western blotting and ELISA. Oxidative stress was detected via ELISA and flow cytometry. A pathway inhibitor was used to verify the role of the Akt-Parkin pathway in the LPS-mediated N2a cell death in the presence of TrxR2 overexpression. With the help of immunofluorescence assay and western blotting, we found that TrxR2 expression was significantly reduced in response to LPS treatment, and this effect was associated with N2a cell death via apoptosis. At the molecular level, TrxR2 overexpression elevated the activity of the Akt-Parkin pathway, as evidenced by the increased expression of p-Akt and Parkin. Interestingly, inhibition of the Akt-Parkin pathway abolished the regulatory effect of TrxR2 on LPS-treated N2a cells, as evidenced by the decreased cell viability and increased apoptotic ratio. Besides, TrxR2 overexpression also reduced oxidative stress, inflammation factor transcription and mitochondrial apoptosis. However, inhibition of Akt-Parkin axis abrogated the protective effects of TrxR2 on redox balance, mitochondrial performance and cell survival. LPS-mediated neuronal death was linked to a drop in TrxR2 overexpression and the inactivation of the Akt-Parkin pathway. Overexpression of TrxR2 sustained mitochondrial function, inhibited oxidative stress, repressed inflammation response, and blocked mitochondrial apoptosis, finally sending a pro-survival signal for the N2a cells in the setting of LPS-mediated inflammation environment.

Genetic ablation of TAZ induces HepG2 liver cancer cell apoptosis through activating the CaMKII/MIEF1 signaling pathway

Background and objective

Transcriptional coactivator with PDZ-binding motif (TAZ) has been found to be associated with tumor progression. Mitochondrial homeostasis regulates cancer cell viability and metastasis. However, the roles of TAZ and mitochondrial homeostasis in liver cancer viability have not been explored. The aim of our study was to investigate the influence of TAZ on HepG2 liver cancer cell apoptosis.

Materials and methods

HepG2 liver cancer cell was used in the present study, and shRNA against TAZ was transfected into HepG2 cell to knockdown TAZ expression. Mitochondrial function was analyzed using Western blotting, immunofluorescence assay, and flow cytometry. Pathway blocker was used to confirm the role of CaMKII pathway in TAZ-mediated cancer cell death.

Results

Our results indicated that TAZ deletion induced death in HepG2 cell via apoptosis. Biological analysis demonstrated that mitochondrial stress, including mitochondrial bioenergetics disorder, mitochondrial oxidative stress, and mitochondrial apoptosis, were activated by TAZ deletion. Furthermore, we found that TAZ affected mitochondrial stress by triggering mitochondrial elongation factor 1 (MIEF1)-related mitochondrial dysfunction. The loss of MIEF1 sustained mitochondrial function and promoted cancer cell survival. Molecular investigation illustrated that TAZ regulated MIEF1 expression via the CaMKII signaling pathway. Blockade of the CaMKII pathway prevented TAZ-mediated MIEF1 upregulation and improved cancer cell survival.

Conclusion

Taken together, our results highlight the key role of TAZ as a master regulator of HepG2 liver cancer cell viability via the modulation of MIEF1-related mitochondrial stress and the CaMKII signaling pathway. These findings define TAZ and MIEF1-related mitochondrial dysfunction as tumor suppressors that act by promoting cancer apoptosis via the CaMKII signaling pathway, with potential implications for new approaches to liver cancer therapy.

The glutathione system and the related thiol network in Caenorhabditis elegans

Advances in the field of redox biology have contributed to the understanding of the complexity of the thiol-based system in mediating signal transduction. The redox environment is the overall spatiotemporal balance of oxidation-reduction systems within the integrated compartments of the cell, tissues and whole organisms. The ratio of the reduced to disulfide glutathione redox couple (GSH:GSSG) is a key indicator of the redox environment and its associated cellular health. The reaction mechanisms of glutathione-dependent and related thiol-based enzymes play a fundamental role in the function of GSH as a redox regulator. Glutathione homeostasis is maintained by the balance of GSH synthesis (de novo and salvage pathways) and its utilization through its detoxification, thiol signalling, and antioxidant defence functions via GSH-dependent enzymes and free radical scavenging. As such, GSH acts in concert with the entire redox network to maintain reducing conditions in the cell. Caenorhabditis elegans offers a simple model to facilitate further understanding at the multicellular level of the physiological functions of GSH and the GSH-dependent redox network. This review discusses the C. elegans studies that have investigated glutathione and related systems of the redox network including; orthologs to the protein-encoding genes of GSH synthesis; glutathione peroxidases; glutathione-S-transferases; and the glutaredoxin, thioredoxin and peroxiredoxin systems.

Cytoplasmic and Mitochondrial NADPH-Coupled Redox Systems in the Regulation of Aging

The reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) protects against redox stress by providing reducing equivalents to antioxidants such as glutathione and thioredoxin. NADPH levels decline with aging in several tissues, but whether this is a major driving force for the aging process has not been well established. Global or neural overexpression of several cytoplasmic enzymes that synthesize NADPH have been shown to extend lifespan in model organisms such as Drosophila suggesting a positive relationship between cytoplasmic NADPH levels and longevity. Mitochondrial NADPH plays an important role in the protection against redox stress and cell death and mitochondrial NADPH-utilizing thioredoxin reductase 2 levels correlate with species longevity in cells from rodents and primates. Mitochondrial NADPH shuttles allow for some NADPH flux between the cytoplasm and mitochondria. Since a decline of nicotinamide adenine dinucleotide (NAD⁺) is linked with aging and because NADP⁺ is exclusively synthesized from NAD⁺ by cytoplasmic and mitochondrial NAD⁺ kinases, a decline in the cytoplasmic or mitochondrial NADPH pool may also contribute to the aging process. Therefore pro-longevity therapies should aim to maintain the levels of both NAD⁺ and NADPH in aging tissues.

Beyond ROS clearance: Peroxiredoxins in stress signaling and aging

Antioxidants were long predicted to have lifespan-promoting effects, but in general this prediction has not been well supported. While some antioxidants do seem to have a clear effect on longevity, this may not be primarily as a result of their role in the removal of reactive oxygen species, but rather mediated by other mechanisms such as the modulation of intracellular signaling. In this review we discuss peroxiredoxins, a class of proteinaceous antioxidants with redox signaling and chaperone functions, and their involvement in regulating longevity and stress resistance. Peroxiredoxins have a clear role in the regulation of lifespan and survival of many model organisms, including the mouse, Caenorhabditis elegans and Drosophila melanogaster. Recent research on peroxiredoxins - in these models and beyond - has revealed surprising new insights regarding the interplay between peroxiredoxins and longevity signaling, which will be discussed here in detail. As redox signaling is emerging as a potentially important player in the regulation of longevity and aging, increased knowledge of these fascinating antioxidants and their mode(s) of action is paramount.