Amputation-induced reactive oxygen species are required for successful Xenopus tadpole tail regeneration
TL;DR: It is shown that Xenopus tadpole tail amputation induces a sustained production of reactive oxygen species (ROS) during tail regeneration, demonstrating that injury-induced ROS production is an important regulator of tissue regeneration.
Abstract: Understanding the molecular mechanisms that promote successful tissue regeneration is critical for continued advancements in regenerative medicine. Vertebrate amphibian tadpoles of the species Xenopus laevis and Xenopus tropicalis have remarkable abilities to regenerate their tails following amputation 1,2 , through the coordinated activity of numerous growth factor signalling pathways, including the Wnt, Fgf, Bmp, Notch and TGF- pathways 36 . Little is known, however, about the events that act upstream of these signalling pathways following injury. Here, we show that Xenopus tadpole tail amputation induces a sustained production of reactive oxygen species (ROS) during tail regeneration. Lowering ROS levels, using pharmacological or genetic approaches, reduces the level of cell proliferation and impairs tail regeneration. Genetic rescue experiments restored both ROS production and the initiation of the regenerative response. Sustained increased ROS levels are required for Wnt=-catenin signalling and the activation of one of its main downstream targets, fgf20 (ref. 7), which, in turn, is essential for proper tail regeneration. These ndings demonstrate that injury-induced ROS production is an
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TL;DR: This work focuses on ROS at physiological levels and their central role in redox signalling via different post-translational modifications, denoted as ‘oxidative eustress’.
Abstract: 'Reactive oxygen species' (ROS) is an umbrella term for an array of derivatives of molecular oxygen that occur as a normal attribute of aerobic life. Elevated formation of the different ROS leads to molecular damage, denoted as 'oxidative distress'. Here we focus on ROS at physiological levels and their central role in redox signalling via different post-translational modifications, denoted as 'oxidative eustress'. Two species, hydrogen peroxide (H2O2) and the superoxide anion radical (O2·-), are key redox signalling agents generated under the control of growth factors and cytokines by more than 40 enzymes, prominently including NADPH oxidases and the mitochondrial electron transport chain. At the low physiological levels in the nanomolar range, H2O2 is the major agent signalling through specific protein targets, which engage in metabolic regulation and stress responses to support cellular adaptation to a changing environment and stress. In addition, several other reactive species are involved in redox signalling, for instance nitric oxide, hydrogen sulfide and oxidized lipids. Recent methodological advances permit the assessment of molecular interactions of specific ROS molecules with specific targets in redox signalling pathways. Accordingly, major advances have occurred in understanding the role of these oxidants in physiology and disease, including the nervous, cardiovascular and immune systems, skeletal muscle and metabolic regulation as well as ageing and cancer. In the past, unspecific elimination of ROS by use of low molecular mass antioxidant compounds was not successful in counteracting disease initiation and progression in clinical trials. However, controlling specific ROS-mediated signalling pathways by selective targeting offers a perspective for a future of more refined redox medicine. This includes enzymatic defence systems such as those controlled by the stress-response transcription factors NRF2 and nuclear factor-κB, the role of trace elements such as selenium, the use of redox drugs and the modulation of environmental factors collectively known as the exposome (for example, nutrition, lifestyle and irradiation).
1,809 citations
TL;DR: The present overview focuses on recent progress on metabolic sources and sinks of H 2O2 and on the role of H2O2 in redox signaling under physiological conditions, denoted as oxidative eustress.
Abstract: Hydrogen peroxide emerged as major redox metabolite operative in redox sensing, signaling and redox regulation. Generation, transport and capture of H2O2 in biological settings as well as their biological consequences can now be addressed. The present overview focuses on recent progress on metabolic sources and sinks of H2O2 and on the role of H2O2 in redox signaling under physiological conditions (1–10 nM), denoted as oxidative eustress. Higher concentrations lead to adaptive stress responses via master switches such as Nrf2/Keap1 or NF-κB. Supraphysiological concentrations of H2O2 (>100 nM) lead to damage of biomolecules, denoted as oxidative distress. Three questions are addressed: How can H2O2 be assayed in the biological setting? What are the metabolic sources and sinks of H2O2? What is the role of H2O2 in redox signaling and oxidative stress?
1,242 citations
TL;DR: 13 reasons why the brain is susceptible to oxidative stress are rationalised and key reasons include inter alia unsaturated lipid enrichment, mitochondria, calcium, glutamate, modest antioxidant defence, redox active transition metals and neurotransmitter auto-oxidation.
Abstract: The human brain consumes 20% of the total basal oxygen (O2) budget to support ATP intensive neuronal activity. Without sufficient O2 to support ATP demands, neuronal activity fails, such that, even transient ischemia is neurodegenerative. While the essentiality of O2 to brain function is clear, how oxidative stress causes neurodegeneration is ambiguous. Ambiguity exists because many of the reasons why the brain is susceptible to oxidative stress remain obscure. Many are erroneously understood as the deleterious result of adventitious O2 derived free radical and non-radical species generation. To understand how many reasons underpin oxidative stress, one must first re-cast free radical and non-radical species in a positive light because their deliberate generation enables the brain to achieve critical functions (e.g. synaptic plasticity) through redox signalling (i.e. positive functionality). Using free radicals and non-radical derivatives to signal sensitises the brain to oxidative stress when redox signalling goes awry (i.e. negative functionality). To advance mechanistic understanding, we rationalise 13 reasons why the brain is susceptible to oxidative stress. Key reasons include inter alia unsaturated lipid enrichment, mitochondria, calcium, glutamate, modest antioxidant defence, redox active transition metals and neurotransmitter auto-oxidation. We review RNA oxidation as an underappreciated cause of oxidative stress. The complex interplay between each reason dictates neuronal susceptibility to oxidative stress in a dynamic context and neural identity dependent manner. Our discourse sets the stage for investigators to interrogate the biochemical basis of oxidative stress in the brain in health and disease.
626 citations
Cites background from "Amputation-induced reactive oxygen ..."
...Niethammer's and Amaya's groups have shown that H2O2 acts as a chemoattractant in wound healing and limb regeneration [201,202]....
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TL;DR: Major processes including proliferation, differentiation, tissue repair, inflammation, circadian rhythm, and aging use this low molecular weight oxygen metabolite as signaling compound, making this reactive oxygen species essential for poising the set point of the redox proteome.
559 citations
Cites background from "Amputation-induced reactive oxygen ..."
...2, where the time course and color intensity ascribed to H2O2 generation in a model of tissue injury and repair as well as proliferation are indicated (13)....
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TL;DR: A review of the history of thalidomide and its effects on the human embryo can be found in this paper, where the authors outline the mechanisms of action the drug uses including recent molecular advances and new findings.
Abstract: Nearly 60 years ago thalidomide was prescribed to treat morning sickness in pregnant women. What followed was the biggest man‐made medical disaster ever, where over 10,000 children were born with a range of severe and debilitating malformations. Despite this, the drug is now used successfully to treat a range of adult conditions, including multiple myeloma and complications of leprosy. Tragically, a new generation of thalidomide damaged children has been identified in Brazil. Yet, how thalidomide caused its devastating effects in the forming embryo remains unclear. However, studies in the past few years have greatly enhanced our understanding of the molecular mechanisms the drug. This review will look at the history of the drug, and the range and type of damage the drug caused, and outline the mechanisms of action the drug uses including recent molecular advances and new findings. Some of the remaining challenges facing thalidomide biologists are also discussed. Birth Defects Research (Part C) 105:140–156, 2015. © 2015 The Authors Birth Defects Research Part C: Embryo Today: Reviews Published by Wiley Periodicals, Inc.
547 citations
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TL;DR: Evidence that the appropriate and inappropriate production of oxidants, together with the ability of organisms to respond to oxidative stress, is intricately connected to ageing and life span is reviewed.
Abstract: Living in an oxygenated environment has required the evolution of effective cellular strategies to detect and detoxify metabolites of molecular oxygen known as reactive oxygen species. Here we review evidence that the appropriate and inappropriate production of oxidants, together with the ability of organisms to respond to oxidative stress, is intricately connected to ageing and life span.
8,665 citations
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TL;DR: Professional phagocytes generate high levels of reactive oxygen species (ROS) using a superoxide-generating NADPH oxidase as part of their armoury of microbicidal mechanisms, leading to the concept that ROS are 'intentionally' generated in these cells with distinctive cellular functions related to innate immunity, signal transduction and modification of the extracellular matrix.
Abstract: Professional phagocytes generate high levels of reactive oxygen species (ROS) using a superoxide-generating NADPH oxidase as part of their armoury of microbicidal mechanisms. The multicomponent phagocyte oxidase (Phox), which has been well characterized over the past three decades, includes the catalytic subunit gp91phox. Lower levels of ROS are seen in non-phagocytic cells, but are usually thought to be 'accidental' byproducts of aerobic metabolism. The discovery of a family of superoxide-generating homologues of gp91phox has led to the concept that ROS are 'intentionally' generated in these cells with distinctive cellular functions related to innate immunity, signal transduction and modification of the extracellular matrix.
2,865 citations
TL;DR: The results suggest that H2O2 may act as a signal-transducing molecule, and they suggest a potential mechanism for the cardioprotective effects of antioxidants.
Abstract: Stimulation of rat vascular smooth muscle cells (VSMCs) by platelet-derived growth factor (PDGF) transiently increased the intracellular concentration of hydrogen peroxide (H2O2). This increase could be blunted by increasing the intracellular concentration of the scavenging enzyme catalase or by the chemical antioxidant N-acetylcysteine. The response of VSMCs to PDGF, which includes tyrosine phosphorylation, mitogen-activated protein kinase stimulation, DNA synthesis, and chemotaxis, was inhibited when the growth factor-stimulated rise in H2O2 concentration was blocked. These results suggest that H2O2 may act as a signal-transducing molecule, and they suggest a potential mechanism for the cardioprotective effects of antioxidants.
2,575 citations
TL;DR: PHluorins are developed pH-sensitive mutants of green fluorescent protein by structure-directed combinatorial mutagenesis, with the aim of exploiting the acidic pH inside secretory vesicles, to monitor vesicle exocytosis and recycling.
Abstract: In neural systems, information is often carried by ensembles of cells rather than by individual units. Optical indicators provide a powerful means to reveal such distributed activity, particularly when protein-based and encodable in DNA: encodable probes can be introduced into cells, tissues, or transgenic organisms by genetic manipulation, selectively expressed in anatomically or functionally defined groups of cells, and, ideally, recorded in situ, without a requirement for exogenous cofactors. Here we describe sensors for secretion and neurotransmission that fulfil these criteria. We have developed pH-sensitive mutants of green fluorescent protein ('pHluorins') by structure-directed combinatorial mutagenesis, with the aim of exploiting the acidic pH inside secretory vesicles to monitor vesicle exocytosis and recycling. When linked to a vesicle membrane protein, pHluorins were sorted to secretory and synaptic vesicles and reported transmission at individual synaptic boutons, as well as secretion and fusion pore 'flicker' of single secretory granules.
2,472 citations
TL;DR: It is proposed that the singular phosphorylation of the amino-terminus of histone H3 may be involved in facilitating two key functions during mitosis: (1) regulate protein-protein interactions to promote binding of trans-acting factors that “drive” chromatin condensation as cells enter M-phase and (2) coordinate chromatin decondensation associated with M- phase.
Abstract: We have generated and characterized a novel site-specific antibody highly specific for the phosphorylated form of the amino-terminus of histone H3 (Ser10). In this study, we used this antibody to examine in detail the relationship between H3 phosphorylation and mitotic chromosome condensation in mammalian cells. Our results extend previous biochemical studies by demonstrating that mitotic phosphorylation of H3 initiates nonrandomly in pericentromeric heterochromatin in late G2 interphase cells. Following initiation, H3 phosphorylation appears to spread throughout the condensing chromatin and is complete in most cell lines just prior to the formation of prophase chromosomes, in which a phosphorylated, but nonmitotic, chromosomal organization is observed. In general, there is a precise spatial and temporal correlation between H3 phosphorylation and initial stages of chromatin condensation. Dephosphorylation of H3 begins in anaphase and is complete immediately prior to detectable chromosome decondensation in telophase cells. We propose that the singular phosphorylation of the amino-terminus of histone H3 may be involved in facilitating two key functions during mitosis: (1) regulate protein-protein interactions to promote binding of trans-acting factors that "drive" chromatin condensation as cells enter M-phase and (2) coordinate chromatin decondensation associated with M-phase.
1,852 citations