where are reactive oxygen species produced in the body
in the mitochondria
3093520
such as cytokine production, autophagy, and granuloma formation. Reactive oxygen species are also implicated in activation, anergy and apoptosis of T cells. In aerobic organisms the energy needed to fuel biological functions is produced in the mitochondria via the electron transport chain. In addition to energy, reactive oxygen species (ROS) with the potential to cause cellular damage are produced. ROS can damage lipid, DNA, RNA, and proteins, which, in theory, contributes to the physiology of aging. ROS are produced as a normal product of cellular metabolism. In particular, one major contributor to oxidative damage is hydrogen peroxide (HO), which is
Reactive oxygen species
3093520
such as cytokine production, autophagy, and granuloma formation. Reactive oxygen species are also implicated in activation, anergy and apoptosis of T cells. In aerobic organisms the energy needed to fuel biological functions is produced in the mitochondria via the electron transport chain. In addition to energy, reactive oxygen species (ROS) with the potential to cause cellular damage are produced. ROS can damage lipid, DNA, RNA, and proteins, which, in theory, contributes to the physiology of aging. ROS are produced as a normal product of cellular metabolism. In particular, one major contributor to oxidative damage is hydrogen peroxide (HO), which is
Reactive oxygen species
2998666
including cancer, arthritis, atherosclerosis, Alzheimer's disease, and diabetes. There has been some evidence to suggest that free radicals and some reactive nitrogen species trigger and increase cell death mechanisms within the body such as apoptosis and in extreme cases necrosis. In 1972, Harman modified his original theory. In its current form, this theory proposes that reactive oxygen species that are produced in the mitochondria, causes damage to certain macromolecules including lipids, proteins and most importantly mitochondrial DNA. This damage then causes mutations which lead to an increase of ROS production and greatly enhance the accumulation of free radicals within cells.
Free-radical theory of aging
3093512
nearly all cells exposed to oxygen. In mammals and most chordates, three forms of superoxide dismutase are present. SOD1 is located primarily in the cytoplasm, SOD2 in the mitochondria and SOD3 is extracellular. The first is a dimer (consists of two units), while the others are tetramers (four subunits). SOD1 and SOD3 contain copper and zinc ions, while SOD2 has a manganese ion in its reactive centre. The genes are located on chromosomes 21, 6, and 4, respectively (21q22.1, 6q25.3 and 4p15.3-p15.1). The SOD-catalysed dismutation of superoxide may be written with the following half-reactions: where M = Cu ("n" =
Reactive oxygen species
6891954
marrow. Protein synthesis occurs in both the cytoplasm of the cell as well as in the luminal space of mitochondria, the cytoplasmic organelle responsible for producing the cell's energy. This is done through an enzymatic pathway that generates highly oxidized molecules called reactive oxygen species, for example hydrogen peroxide. Reactive oxygen species can react with and cause damage to many critical parts of the cell including membranes, proteins, and DNA. Trichothecene inhibition of protein synthesis in the mitochondria allows reactive oxygen species to build up in the cell which inevitably leads to oxidative stress and induction of the programmed cell
Trichothecene
5604269
in which oxygen supply is insufficient. In the environment, it refers to excess oxygen in a body of water or other habitat. Associated with hyperoxia is an increased level of reactive oxygen species (ROS), which are chemically reactive molecules containing oxygen. These oxygen containing molecules can damage lipids, proteins, and nucleic acids, and react with surrounding biological tissues. The human body has naturally occurring antioxidants to combat reactive molecules, but the protective antioxidant defenses can become depleted by abundant reactive oxygen species, resulting in oxidation of the tissues and organs. The symptoms produced from breathing high concentrations of oxygen for
Hyperoxia
2628496
The biochemical basis for the toxicity of oxygen is the partial reduction of oxygen by one or two electrons to form reactive oxygen species, which are natural by-products of the normal metabolism of oxygen and have important roles in cell signalling. One species produced by the body, the superoxide anion (), is possibly involved in iron acquisition. Higher than normal concentrations of oxygen lead to increased levels of reactive oxygen species. Oxygen is necessary for cell metabolism, and the blood supplies it to all parts of the body. When oxygen is breathed at high partial pressures, a hyperoxic condition will
Oxygen toxicity
15120770
reactive oxygen species (ROS), and reactive nitrogen species (RNS). Reactive oxygen species are produced by the enzyme NADPH oxidase, which transfers electrons from NADPH to oxygen, synthesizing a superoxide, which is a reactive free radical. This superoxide can react to form hydrogen peroxide and a reactive oxygen species. The enzyme NADPH oxidase is able to generate more reactive oxygen species in the presence of arsenic, due to the subunit p22phax, which is responsible for the electron transfer, being upregulated by arsenic. The reactive oxygen species are capable of stressing the endoplasmic reticulum, which increases the amount of the unfolded protein
Arsenic biochemistry
17021134
Reactive oxygen species are especially inexpensive to produce as defense chemicals, simply because they are not composed of metabolically costly elements such as carbon, nitrogen, or phosphate. Reactive oxygen species produced by phytoplankton have been linked to deaths of fish, shellfish, and protists, as well as shown to reduce the viability and growth of bacteria. In addition, a study by Marshall "et al." showed that four algal species used as bivalve feed produced significantly lower concentrations of superoxide, suggesting that ROS production by other algal species may be a way to decrease grazing by bivalves. The most direct evidence for
Reactive oxygen species production in marine microalgae
11118297
Reactive nitrogen species Reactive nitrogen species (RNS) are a family of antimicrobial molecules derived from nitric oxide (•NO) and superoxide (O) produced via the enzymatic activity of inducible nitric oxide synthase 2 (NOS2) and NADPH oxidase respectively. NOS2 is expressed primarily in macrophages after induction by cytokines and microbial products, notably interferon-gamma (IFN-γ) and lipopolysaccharide (LPS). Reactive nitrogen species act together with reactive oxygen species (ROS) to damage cells, causing nitrosative stress. Therefore, these two species are often collectively referred to as ROS/RNS. Reactive nitrogen species are also continuously produced in plants as by-products of aerobic metabolism or in response
Reactive nitrogen species
2815446
may involve mitochondrial oxygen sensors and the haem-containing cytochromes that undergo reversible one-electron reduction during oxidative-phosphorylation. Haem reversibly binds O with an affinity similar to that of the carotid body, suggesting that haem containing proteins may have a role in O, potentially this could be one of the complexes involved in oxidative-phosphorylation. This leads to increases in reactive oxygen species and rises in intracellular Ca. However, whether hypoxia leads to an increase or decrease in reactive oxygen species is unknown. The role of reactive oxygen species in hypoxia sensing is also under question. The oxygen dependent enzyme haem-oxidase has also
Carotid body
17021113
have been linked to the aging process in humans, as well as several other diseases including Alzheimer's, rheumatoid arthritis, Parkinson's, and some cancers. Their potential for damage also makes reactive oxygen species useful in direct protection from invading pathogens, as a defense response to physical injury, and as a mechanism for stopping the spread of bacteria and viruses by inducing programmed cell death. Reactive oxygen species are present in low concentrations in seawater and produced primarily through the photolysis of organic and inorganic matter. However, the biological production of ROS, generated through algal photosynthesis and subsequently 'leaked' to the environment,
Reactive oxygen species production in marine microalgae
10197616
from metabolic alterations and dependence on mitogenic and survival signaling through reactive oxygen species represents a specific vulnerability of malignant cells that can be selectively targeted by pro-oxidant non-genotoxic redox chemotherapeutics. Pro-oxidant Pro-oxidants are chemicals that induce oxidative stress, either by generating reactive oxygen species or by inhibiting antioxidant systems. The oxidative stress produced by these chemicals can damage cells and tissues, for example an overdose of the analgesic paracetamol (acetaminophen) can fatally damage the liver, partly through its production of reactive oxygen species. Some substances can serve as either antioxidants or pro-oxidants, depending on conditions. Some of the conditions
Pro-oxidant
3093514
mitochondria, cytosol, and nucleus. Another type of reactive oxygen species is singlet oxygen (O) which is produced for example as byproduct of photosynthesis in plants. In the presence of light and oxygen, photosensitizers such as chlorophyll may convert triplet (O) to singlet oxygen: Singlet oxygen is highly reactive, especially with organic compounds that contain double bonds. The resulting damage caused by singlet oxygen reduces the photosynthetic efficiency of chloroplasts. In plants exposed to excess light, the increased production of singlet oxygen can result in cell death. Various substances such as carotenoids, tocopherols and plastoquinones contained in chloroplasts quench singlet oxygen
Reactive oxygen species
3093505
Reactive oxygen species Reactive oxygen species (ROS) are chemically reactive chemical species containing oxygen. Examples include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen. In a biological context, ROS are formed as a natural byproduct of the normal metabolism of oxygen and have important roles in cell signaling and homeostasis. However, during times of environmental stress (e.g., UV or heat exposure), ROS levels can increase dramatically. This may result in significant damage to cell structures. Cumulatively, this is known as oxidative stress. The production of ROS is strongly influenced by stress factor responses in plants, these factors that increase ROS
Reactive oxygen species
10197611
Pro-oxidant Pro-oxidants are chemicals that induce oxidative stress, either by generating reactive oxygen species or by inhibiting antioxidant systems. The oxidative stress produced by these chemicals can damage cells and tissues, for example an overdose of the analgesic paracetamol (acetaminophen) can fatally damage the liver, partly through its production of reactive oxygen species. Some substances can serve as either antioxidants or pro-oxidants, depending on conditions. Some of the conditions that are important include the concentration of the chemical and if oxygen or transition metals are present. While thermodynamically very favored, reduction of molecular oxygen or peroxide to superoxide or hydroxyl
Pro-oxidant
3093543
is beneficial for cancer patient prognosis. Moreover, high inducers of ROS such as 2-deoxy-D-glucose and carbohydrate-based inducers of cellular stress induce cancer cell death more potently because they exploit cancer cell high avidity for sugars. Reactive oxygen species Reactive oxygen species (ROS) are chemically reactive chemical species containing oxygen. Examples include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen. In a biological context, ROS are formed as a natural byproduct of the normal metabolism of oxygen and have important roles in cell signaling and homeostasis. However, during times of environmental stress (e.g., UV or heat exposure), ROS levels can increase
Reactive oxygen species
2628497
rapidly spread, with the most vascularised tissues being most vulnerable. During times of environmental stress, levels of reactive oxygen species can increase dramatically, which can damage cell structures and produce oxidative stress. While all the reaction mechanisms of these species within the body are not yet fully understood, one of the most reactive products of oxidative stress is the hydroxyl radical (·OH), which can initiate a damaging chain reaction of lipid peroxidation in the unsaturated lipids within cell membranes. High concentrations of oxygen also increase the formation of other free radicals, such as nitric oxide, peroxynitrite, and trioxidane, which harm
Oxygen toxicity
9220277
5-nitroimidazoles such as metronidazole, but it is unclear if the same mechanism can be expanded to 2-nitroimidazoles (including benznidazole). In the presence of oxygen, by contrast, any radical nitro compounds produced will be rapidly oxidized by molecular oxygen, yielding the original nitroimidazole compound and a superoxide anion in a process known as "futile cycling". In these cases, the generation of superoxide is believed to give rise to other reactive oxygen species. The degree of toxicity or mutagenicity produced by these oxygen radicals depends on cells' ability to detoxify superoxide radicals and other reactive oxygen species. In mammals, these radicals can
Benznidazole
4795090
are continuously produced by cells as byproducts of various metabolic pathways. They were mostly shown to be massively produced after the detection of PAMPs by cell-surface located receptors (e.g. FLS2 or EFR). The production of reactive oxygen species is mediated by the NADPH oxidase, and in plant immunity the subunits RbohD and RbohF have overlapping functions but are expressed in different tissues and in different levels. ROS production can be used as a readout for successful pathogen recognition via a luminol-peroxidase based assay. Respiratory burst Respiratory burst (sometimes called oxidative burst) is the rapid release of reactive oxygen species (superoxide
Respiratory burst
7432140
drugs, or from an inherited mutation (i.e. change of an internal amino acid residue). As a result, an electron from the hemoglobin is transferred to an oxygen molecule, which creates a reactive oxygen species (ROS) that can cause severe cell damage leading to premature cell lysis. Damaged cells are cleared by macrophages in the spleen, where the precipitate and damaged membrane are removed, leading to characteristic "bite cells". The denaturing process is irreversible and the continual elimination of damaged cells leads to Heinz body anemia. There are several pathways leading to the hemoglobin damage. The presence of Heinz bodies may
Heinz body
20173781
study showed that after hypoxia, an increase in intracellular zinc induced an increase in reactive oxygen species via activation of NADPH oxidase. Although reactive oxygen species are needed for some functions (such as secondary signaling), they are unstable and are commonly known to cause damage to DNA, lipids, and proteins when at high levels. During the study, the application of TPEN prevented a zinc-induced increase in reactive oxygen species. This may have implications for diseases that have hypoxic conditions, such as stroke. Additionally, another study showed that TPEN induced DNA damage in human colon cancer cells in a reactive oxygen
TPEN
3902955
with electron transfer, a process that is common to all life. Addition of one electron gives the radical cation: The radical cation is also susceptible to further reduction to the neutral [MV]: As an herbicide, paraquat acts by inhibiting photosynthesis. In light-exposed plants, it accepts electrons from photosystem I (more specifically ferredoxin, which is presented with electrons from PS I) and transfers them to molecular oxygen. In this manner, destructive reactive oxygen species are produced. In forming these reactive oxygen species, the oxidized form of paraquat is regenerated, and is again available to shunt electrons from photosystem I to restart
Paraquat
14377297
reactive oxygen species (i.e. singlet oxygen, superoxide anions, hydroperoxyl radicals, and hydroxyl radicals). Reactive oxygen species can be created during photosynthesis; further supporting the idea that MAAs provide protection from UV light. Mycosporine-glycine is a MAA that provides antioxidant protection even before Oxidative stress response genes and antioxidant enzymes are induced. MAA-glycine (mycosporine-glycine) is able to quench singlet oxygen and hydroxyl radicals very quickly and efficiently. Some oceanic microbial ecosystems are exposed to high concentrations of oxygen and intense light; these conditions are likely to generate high levels of reactive oxygen species. In these ecosystems, MAA-rich cyanobacteria may be providing
Mycosporine-like amino acid
79130
levels of reactive oxygen species will cause the hypersensitive response. The reactive oxygen species also directly kill any pathogens within the cell. Lower levels of reactive oxygen species initiate systemic acquired resistance, triggering defense-molecule production in the rest of the plant. In some plants, chloroplasts are known to move closer to the infection site and the nucleus during an infection. Chloroplasts can serve as cellular sensors. After detecting stress in a cell, which might be due to a pathogen, chloroplasts begin producing molecules like salicylic acid, jasmonic acid, nitric oxide and reactive oxygen species which can serve as defense-signals. As
Chloroplast
3093506
production include, drought, salinity, chilling, nutrient deficiency, metal toxicity and UV-B radiation. ROS are also generated by exogenous sources such as ionizing radiation. The reduction of molecular oxygen (O) produces superoxide () and is the precursor of most other reactive oxygen species: Dismutation of superoxide produces hydrogen peroxide (HO): Hydrogen peroxide in turn may be partially reduced to hydroxyl radical (OH) or fully reduced to water: Exogenous ROS can be produced from pollutants, tobacco, smoke, drugs, xenobiotics, or radiation. Ionizing radiation can generate damaging intermediates through the interaction with water, a process termed radiolysis. Since water comprises 55–60% of the
Reactive oxygen species
17021116
molecular oxygen are what are referred to as reactive oxygen species. Thus, the production of ROS is in direct proportion to the concentration of O in the system, with increases of O leading to higher production of ROS. There are three main reactive oxygen species: the superoxide anion (O), hydrogen peroxide (HO), and the hydroxyl radical (OH•). The superoxide anion is formed directly from the one-electron reduction of molecular oxygen. Hydrogen peroxide is then formed from the disproportionation of the superoxide anion. This reaction occurs very quickly in seawater. Next, the reduction of hydrogen peroxide yields the hydroxyl radical, HO↔2OH•,
Reactive oxygen species production in marine microalgae
304678
reduces oxygen to water, which is harmless, transfer of one or two electrons produces superoxide or peroxide anions, which are dangerously reactive. These reactive oxygen species and their reaction products, such as the hydroxyl radical, are very harmful to cells, as they oxidize proteins and cause mutations in DNA. This cellular damage might contribute to disease and is proposed as one cause of aging. The cytochrome c oxidase complex is highly efficient at reducing oxygen to water, and it releases very few partly reduced intermediates; however small amounts of superoxide anion and peroxide are produced by the electron transport chain.
Oxidative phosphorylation
17021140
iron to a usable form. Similarly, lower ROS production would suggest that the intracellular iron is at sufficiently high levels for cellular function. Reactive oxygen species production in marine microalgae All living cells produce reactive oxygen species (ROS) as a byproduct of metabolism. ROS are reduced oxygen intermediates that include the superoxide radical (O) and the hydroxyl radical (OH•), as well as the non-radical species hydrogen peroxide (HO). These ROS are important in the normal functioning of cells, playing a role in signal transduction and the expression of transcription factors. However, when present in excess, ROS can cause damage to
Reactive oxygen species production in marine microalgae
17021112
Reactive oxygen species production in marine microalgae All living cells produce reactive oxygen species (ROS) as a byproduct of metabolism. ROS are reduced oxygen intermediates that include the superoxide radical (O) and the hydroxyl radical (OH•), as well as the non-radical species hydrogen peroxide (HO). These ROS are important in the normal functioning of cells, playing a role in signal transduction and the expression of transcription factors. However, when present in excess, ROS can cause damage to proteins, lipids and DNA by reacting with these biomolecules to modify or destroy their intended function. As an example, the occurrence of ROS
Reactive oxygen species production in marine microalgae
9017142
light causes damage more efficiently than strong light. The mechanism(s) of photoinhibition are under debate, several mechanisms have been suggested. Reactive oxygen species, especially singlet oxygen, have a role in the acceptor-side, singlet oxygen and low-light mechanisms. In the manganese mechanism and the donor side mechanism, reactive oxygen species do not play a direct role. Photoinhibited PSII produces singlet oxygen, and reactive oxygen species inhibit the repair cycle of PSII by inhibiting protein synthesis in the chloroplast. Strong light causes the reduction of the plastoquinone pool, which leads to protonation and double reduction (and double protonation) of the Q electron
Photoinhibition
305252
metazoa, oxygen was thought to be a requirement for all complex life. Reactive oxygen species, such as superoxide ion () and hydrogen peroxide (), are reactive by-products of oxygen use in organisms. Parts of the immune system of higher organisms create peroxide, superoxide, and singlet oxygen to destroy invading microbes. Reactive oxygen species also play an important role in the hypersensitive response of plants against pathogen attack. Oxygen is damaging to obligately anaerobic organisms, which were the dominant form of early life on Earth until began to accumulate in the atmosphere about 2.5 billion years ago during the Great Oxygenation
Oxygen
15120771
response signals. This leads to inflammation, cell proliferation, and eventually to cell death. Another mechanism in which reactive oxygen species cause cell death would be through the cytoskeleton rearrangement, which affects the contractile proteins. The reactive nitrogen species arise once the reactive oxygen species destroy the mitochondria. This leads to the formation of the reactive nitrogen species, which are responsible for damaging DNA in arsenic poisoning. Mitochondrial damage is known to cause the release of reactive nitrogen species, due to the reaction between superoxides and nitric oxide (NO). Nitric oxide (NO) is a part of cell regulation, including cellular metabolism,
Arsenic biochemistry
11118298
to stress. RNS are produced in animals starting with the reaction of nitric oxide (•NO) with superoxide (O) to form peroxynitrite (ONOO): Superoxide anion (O) is a reactive oxygen species that reacts quickly with nitric oxide (NO) in the vasculature. The reaction produces peroxynitrite and depletes the bioactivity of NO. This is important because NO is a key mediator in many important vascular functions including regulation of smooth muscle tone and blood pressure, platelet activation, and vascular cell signaling. Peroxynitrite itself is a highly reactive species which can directly react with various biological targets and components of the cell including
Reactive nitrogen species
17021125
of 4.5 nm). Thus, direct effects to organisms of externally generated hydroxyl radicals are expected to be minimal. Indirectly, the hydroxyl radical can result in significant biogeochemical changes in marine systems by influencing the cycling of dissolved organic matter and trace metal speciation. Both intracellular and extracellular reactive oxygen species can be removed from the environment by antioxidants produced biologically as a defense mechanism. Many phytoplankton, for instance, have been found to have numerous superoxide-scavenging (superoxide dismutase) and hydrogen peroxide-scavenging enzymes (catalase, ascorbate peroxidase, and glutathione peroxidase). The antioxidant superoxide dismutase catalyses the formation of hydrogen peroxide from the superoxide
Reactive oxygen species production in marine microalgae
274425
to try to eliminate microbes. Meconium perhaps leads to chemical pneumonitis as it is a potent activator of inflammatory mediators which include cytokines, complement, prostaglandins and reactive oxygen species. Meconium is a source of pro-inflammatory cytokines, including tumour necrosis factor (TNF) and interleukins (IL-1, IL-6, IL-8), and mediators produced by neutrophils, macrophages and epithelial cells that may injure the lung tissue directly or indirectly. For example, proteolytic enzymes are released from neutrophilic granules and these may damage the lung membrane and surfactant proteins. Additionally, activated leukocytes and cytokines generate reactive nitrogen and oxygen species which have cytotoxic effects. Oxidative stress
Meconium aspiration syndrome
3132045
damages tissue enough to cause a wound. In prolonged ischemia (60 minutes or more), hypoxanthine is formed as a breakdown product of ATP metabolism. The enzyme "xanthine dehydrogenase" acts in reverse, that is as a "xanthine oxidase" as a result of the higher availability of oxygen. This oxidation results in molecular oxygen being converted into highly reactive superoxide and hydroxyl radicals. Xanthine oxidase also produces uric acid, which may act as both a prooxidant and as a scavenger of reactive species such as peroxynitrite. Excessive nitric oxide produced during reperfusion reacts with superoxide to produce the potent reactive species peroxynitrite.
Reperfusion injury
1880598
formation of a phagosome into which reactive oxygen species and hydrolytic enzymes are secreted. The consumption of oxygen during the generation of reactive oxygen species has been termed the "respiratory burst", although unrelated to respiration or energy production. The respiratory burst involves the activation of the enzyme NADPH oxidase, which produces large quantities of superoxide, a reactive oxygen species. Superoxide decays spontaneously or is broken down via enzymes known as superoxide dismutases (Cu/ZnSOD and MnSOD), to hydrogen peroxide, which is then converted to hypochlorous acid (HClO), by the green heme enzyme myeloperoxidase. It is thought that the bactericidal properties of
Neutrophil
9847351
primary mechanisms is formation of free radicals. All liquids are subject to radiation damage, with few exotic exceptions; e.g. molten sodium, where there are no chemical bonds to be disrupted, and liquid hydrogen fluoride, which produces gaseous hydrogen and fluorine, which spontaneously react back to hydrogen fluoride. Water subjected to ionizing radiation forms free radicals of hydrogen and hydroxyl, which can recombine to form gaseous hydrogen, oxygen, hydrogen peroxide, hydroxyl radicals, and peroxide radicals. In living organisms, which are composed mostly of water, majority of the damage is caused by the reactive oxygen species, free radicals produced from water. The
Radiation damage
17021117
which can then get reduced to the hydroxyl ion and water. However, the presence of reactive oxygen species in marine systems is hard to detect and measure accurately, for a number of reasons. First, ROS concentrations are generally low (nanomoles) in seawater. Second, they may react with other hard to identify molecules that occur in low quantities, resulting in unknown products. Finally, they are (for the most part) transient intermediates, having lifetimes as little as microseconds. According to Blough & Zepp, superoxide is one of the hardest reactive oxygen species to quantify because it is present in low concentrations: 2×10
Reactive oxygen species production in marine microalgae
17021127
only produce reactive oxygen species under normal conditions but to increase production of these compounds under stressful situations. In particular, ROS levels have been shown to be influenced by cell size, cell density, growth stage, light intensity, temperature, and nutrient availability. Oda "et al." found that differences in the production of ROS were due to the size of the cell. By comparing four species of flagellates, they showed that the larger species Ichatonella produced the most superoxide and hydrogen peroxide per cell than "Heterosigma akashiwo", "Olisthodiscus luteus", and "Fibrocapsa japonica". In a comparison of 37 species of marine microalgae, including
Reactive oxygen species production in marine microalgae
16117736
and vagus nerves carry sensory nerve fibres into the brain and central nervous system. Through studies using mammalian model organisms, there are two main hypotheses for the location of oxygen sensing in chemoreceptor cells: the membrane hypothesis and the mitochondrial hypothesis. The membrane hypothesis was proposed for the carotid body in mice, and it predicts that oxygen sensing is an ion balance initiated process. The mitochondrial hypothesis was also proposed for the carotid body of mice, but it relies on the levels of oxidative phosphorylation and/or reactive oxygen species (ROS) production as a cue for hypoxia. Specifically, the oxygen sensitive
Hypoxia in fish
5437712
E) may increase mortality risk (although studies more prone to bias reported the reverse). The USDA removed the table showing the Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods Release 2 (2010) table due to the lack of evidence that the antioxidant level present in a food translated into a related antioxidant effect in the body. Metals such as iron, copper, chromium, vanadium, and cobalt are capable of redox cycling in which a single electron may be accepted or donated by the metal. This action catalyzes production of reactive radicals and reactive oxygen species. The presence of such metals in
Oxidative stress
11934048
studied the isotopic composition of atmospheric and dissolved oxygen in the composition of dissolved gases, where he discovered the biochemical oxygen demand and the intake in the ocean mixed layer. Craig determined that the element, Pb measurement is an indication of a particle-reactive species that concludes that another reactive particle would have the same effects in the ocean. In 1970, Craig teamed up with colleagues at Scripps, Columbia University's Lamont–Doherty Earth Observatory and the Woods Hole Oceanographic Institution to direct the GEOSECS Programme (geochemical ocean sections study) to investigate the chemical and isotopic properties of the world's oceans. GEOSECS produced
Harmon Craig
11315646
in enhancing athletic performance while minimizing fatigue. Glisodin Glisodin is the registered trademark of a nutritional supplement based on two constituents: As oxygen metabolizes in the body, potentially harmful reactive oxygen species (ROS) are created. The human body implements an antioxidant defense system to protect against ROS. In the event that these defenses are overpowered by the ROS, cell damage results (which is a major cause of aging in the body). Superoxide dismutase (SOD) helps to slow the creation of ROS, ultimately playing a key role in the defense against cell damage. However, due to a very fragile molecular structure,
Glisodin
11315644
Glisodin Glisodin is the registered trademark of a nutritional supplement based on two constituents: As oxygen metabolizes in the body, potentially harmful reactive oxygen species (ROS) are created. The human body implements an antioxidant defense system to protect against ROS. In the event that these defenses are overpowered by the ROS, cell damage results (which is a major cause of aging in the body). Superoxide dismutase (SOD) helps to slow the creation of ROS, ultimately playing a key role in the defense against cell damage. However, due to a very fragile molecular structure, it is particularly prone to damage from
Glisodin
18997665
of kaolinite and montmorillonite, and this may proceed via the formation of reactive oxygen species at the surface of these clay minerals. Indeed, reactive oxygen species have been observed when soil surfaces are exposed to sunlight. The ability of irradiated soil to generate singlet oxygen was found to be independent of the organic matter content, and both the mineral and organic components of soil appear to contribute to this process. Indirect photolysis in soil has been observed to occur at depths of up to 2 mm due to migration of reactive species; in contrast, direct photolysis (in which the degraded
Photogeochemistry
326584
Plasma ashing In semiconductor manufacturing plasma ashing is the process of removing the photoresist (light sensitive coating) from an etched wafer. Using a plasma source, a monatomic (single atom) substance known as a reactive species is generated. Oxygen or fluorine are the most common reactive species. The reactive species combines with the photoresist to form ash which is removed with a vacuum pump. Typically, monatomic oxygen plasma is created by exposing oxygen gas at a low pressure (O) to high power radio waves, which ionise it. This process is done under vacuum in order to create a plasma. As the
Plasma ashing
11447757
38 ATP molecules are formed from one molecule of glucose). The simplified version of this reaction is: Reactive oxygen species are dangerous by-products that sometimes result from the use of oxygen in organisms. Important examples include; oxygen free radicals such as the highly-dangerous superoxide O, and the less harmful hydrogen peroxide (HO). The body uses superoxide dismutase to reduce superoxide radicals to hydrogen peroxide. Glutathione peroxidase and similar enzymes then convert the HO to water and dioxygen. Parts of the immune system of higher organisms, however, create peroxide, superoxide, and singlet oxygen to destroy invading microbes. Recently, singlet oxygen has
Dioxygen in biological reactions
20545653
The ketoamide adduct formation blocks the lysine residues of histones from binding to acetylation proteins thus decreasing gene transcription. DNA hypermethylation is seen in the genome with DNA breaks at a gene-specific basis, such as promoters of regulatory genes, but the global methylation of the genome shows a hypomethylation pattern during the period of reactive oxygen species stress. DNA damage induced by reactive oxygen species results in increased gene methylation and ultimately gene silencing. Reactive oxygen species modify the mechanism of epigenetic methylation by inducing DNA breaks which are later repaired and then methylated by DNMTs. DNA damage response genes,
Biological effects of radiation on the epigenome
5437714
transition metals with proteins oxidated by Reactive Oxygen Species or Reactive Nitrogen Species can yield reactive products that accumulate and contribute to aging and disease. For example, in Alzheimer's patients, peroxidized lipids and proteins accumulate in lysosomes of the brain cells. Certain organic compounds in addition to metal redox catalysts can also produce reactive oxygen species. One of the most important classes of these are the quinones. Quinones can redox cycle with their conjugate semiquinones and hydroquinones, in some cases catalyzing the production of superoxide from dioxygen or hydrogen peroxide from superoxide. The immune system uses the lethal effects of
Oxidative stress
11569363
cause damage to living cells that come in contact with them. The molecule that originally absorbs the UV-photon is called a "chromophore". Bimolecular reactions can occur either between the excited chromophore and DNA or between the excited chromophore and another species, to produce free radicals and reactive oxygen species. These reactive chemical species can reach DNA by diffusion and the bimolecular reaction damages the DNA (oxidative stress). It is important to note that indirect DNA damage does not result in any warning signal or pain in the human body. The bimolecular reactions that cause the indirect DNA damage are illustrated
Indirect DNA damage
3093507
human body, the probability of radiolysis is quite high under the presence of ionizing radiation. In the process, water loses an electron and becomes highly reactive. Then through a three-step chain reaction, water is sequentially converted to hydroxyl radical (OH), hydrogen peroxide (HO), superoxide radical (), and ultimately oxygen (O). The hydroxyl radical is extremely reactive and immediately removes electrons from any molecule in its path, turning that molecule into a free radical and thus propagating a chain reaction. However, hydrogen peroxide is actually more damaging to DNA than the hydroxyl radical, since the lower reactivity of hydrogen peroxide provides
Reactive oxygen species
33560
Earth requires oxygen for its existence, oxygen is a highly reactive molecule that damages living organisms by producing reactive oxygen species. Consequently, organisms contain a complex network of antioxidant metabolites and enzymes that work together to prevent oxidative damage to cellular components such as DNA, proteins and lipids. In general, antioxidant systems either prevent these reactive species from being formed, or remove them before they can damage vital components of the cell. However, reactive oxygen species also have useful cellular functions, such as redox signaling. Thus, the function of antioxidant systems is not to remove oxidants entirely, but instead to
Antioxidant
3093515
and protect against its toxic effects. In addition to direct toxicity, singlet oxygen acts a signaling molecule. Oxidized products of β-carotene arising from the presence of singlet oxygen act as second messengers that can either protect against singlet oxygen induced toxicity or initiate programmed cell death. Levels of jasmonate play a key role in the decision between cell acclimation or cell death in response to elevated levels of this reactive oxygen species. Effects of ROS on cell metabolism are well documented in a variety of species. These include not only roles in apoptosis (programmed cell death) but also positive effects
Reactive oxygen species
27651
is directly neurotoxic in humans. However, large doses of amphetamine may indirectly cause dopaminergic neurotoxicity as a result of hyperpyrexia, the excessive formation of reactive oxygen species, and increased autoxidation of dopamine. Animal models of neurotoxicity from high-dose amphetamine exposure indicate that the occurrence of hyperpyrexia (i.e., core body temperature ≥ 40 °C) is necessary for the development of amphetamine-induced neurotoxicity. Prolonged elevations of brain temperature above 40 °C likely promote the development of amphetamine-induced neurotoxicity in laboratory animals by facilitating the production of reactive oxygen species, disrupting cellular protein function, and transiently increasing blood–brain barrier permeability. A severe amphetamine
Amphetamine
1800123
workers can be exposed to arising from grain decomposing in silos; chronic exposure can lead to lung damage in a condition called "Silo-filler's disease". Historically, nitrogen dioxide was also produced by atmospheric nuclear tests, and was responsible for the reddish colour of mushroom clouds. Gaseous diffuses into the epithelial lining fluid (ELF) of the respiratory epithelium and dissolves, and chemically reacts with antioxidant and lipid molecules in the ELF; 's health effects are caused by the reaction products or their metabolites, which are reactive nitrogen species and reactive oxygen species that can drive bronchoconstriction, inflammation, reduced immune response, and may
Nitrogen dioxide
305234
oxygen is so magnetic that, in laboratory demonstrations, a bridge of liquid oxygen may be supported against its own weight between the poles of a powerful magnet. Singlet oxygen is a name given to several higher-energy species of molecular in which all the electron spins are paired. It is much more reactive with common organic molecules than is molecular oxygen per se. In nature, singlet oxygen is commonly formed from water during photosynthesis, using the energy of sunlight. It is also produced in the troposphere by the photolysis of ozone by light of short wavelength, and by the immune system
Oxygen
326587
large portion of the active species is lost to recombination, process times may take longer. To some extent, these longer process times can be mitigated by increasing the temperature of the reaction area. Plasma ashing In semiconductor manufacturing plasma ashing is the process of removing the photoresist (light sensitive coating) from an etched wafer. Using a plasma source, a monatomic (single atom) substance known as a reactive species is generated. Oxygen or fluorine are the most common reactive species. The reactive species combines with the photoresist to form ash which is removed with a vacuum pump. Typically, monatomic oxygen plasma
Plasma ashing
17945155
Diallyl trisulfide Diallyl trisulfide (DATS), also known as Allitridin, is an organosulfur compound with the formula S(SCHCH=CH). It is one of several produced by the hydrolysis of allicin, including diallyl disulfide and diallyl tetrasulfide, DATS is one of the most potent. Many health benefits of garlic are attributed in part to DATS. These benefits include anti-cancer effects, platelet aggregation, blood pressure reduction, decreases in cholesterol levels, and increases in levels of reactive oxygen species. DATS has been shown to selectively kill cancerous cells in the prostate and breast, leaving healthy cells unharmed. This effect is attributed to increased reactive oxygen
Diallyl trisulfide
4306462
irradiation free radicals, mainly superoxide/hydroperoxyl (O/HO), and other reactive species (ROS/RNS) are produced, that can react with the ketoamines (Amadori products) and other intermediates of the Maillard reaction. This leads to autoxidationradical chain reactions of the ketoamines, which cause a dramatic increase in the radical injury of the skin. This can be suppressed by antioxidants, which shows involvement of reactive oxygen species (ROS). The ketoamines were shown to cause DNA strand breaks and to act as mutagens. The free radicals are due to the action of UV light on AGE (Advanced Glycation End-products) as a result of the reaction of
Erythrulose
11144219
PINK1/parkin pathway. In addition to mitochondrial fission, PINK1 has been implicated in mitochondrial motility. The accumulation of PINK1 and recruitment of parkin targets a mitochondria for degradation, and PINK1 may serve to enhance degradation rates by arresting mitochondrial motility. Over-expression of PINK1 produced similar effects to silencing Miro, a protein closely associated with mitochondrial migration. Another mechanism of mitochondrial quality control may arise through mitochondria-derived vesicles. Oxidative stress in mitochondria can produce potentially harmful compounds including improperly folded proteins or reactive oxygen species. PINK1 has been shown to facilitate the creation of mitochondria-derived vesicles which can separate reactive oxygen species
PINK1
2013831
energy it becomes excited, then transfers the excited electrons to the chlorophyll for photosynthesis. The triplet-triplet transfer is a higher energy state and is essential in photoprotection. Both light and oxygen produce damaging species during photosynthesis, with the most damaging being reactive oxygen species (ROS). As these high energy ROS are produced in the chlorophyll the energy is transferred to the carotenoid’s polyene tail and undergoes a series of reactions in which electrons are moved between the carotenoid bonds in order find the most balanced state (lowest energy state) for the carotenoid. The length of carotenoids also has a role
Carotenoid
33562
repair mechanisms, while damage to proteins causes enzyme inhibition, denaturation and protein degradation. The use of oxygen as part of the process for generating metabolic energy produces reactive oxygen species. In this process, the superoxide anion is produced as a by-product of several steps in the electron transport chain. Particularly important is the reduction of coenzyme Q in complex III, since a highly reactive free radical is formed as an intermediate (Q·). This unstable intermediate can lead to electron "leakage", when electrons jump directly to oxygen and form the superoxide anion, instead of moving through the normal series of well-controlled
Antioxidant
11109840
where it converts mitochondrial-generated reactive oxygen species from the respiratory chain to H2. Alternate transcriptional splice variants, encoding different isoforms, have been characterized. As a member of the iron/manganese superoxide dismutase family, this protein transforms toxic superoxide, a byproduct of the mitochondrial electron transport chain, into hydrogen peroxide and diatomic oxygen. This function allows SOD2 to clear mitochondrial reactive oxygen species (ROS) and, as a result, confer protection against cell death. As a result, this protein plays an antiapoptotic role against oxidative stress, ionizing radiation, and inflammatory cytokines. The SOD2 enzyme is an important constituent in apoptotic signaling and oxidative
SOD2
1302030
aerobic conditions, approximately 4% of the oxygen metabolized by mitochondria is converted to superoxide ion, which can subsequently be converted to hydrogen peroxide, hydroxyl radical and eventually other reactive species including other peroxides and singlet oxygen, which can, in turn, generate free radicals capable of damaging structural proteins and DNA. Certain metal ions found in the body, such as copper and iron, may participate in the process. (In Wilson's disease, a hereditary defect that causes the body to retain copper, some of the symptoms resemble accelerated senescence.) These processes termed oxidative stress are linked to the potential benefits of dietary
Senescence
3093326
This enzyme oxidizes NADPH and reduces molecular oxygen to produce superoxide anions, a reactive oxygen species. Superoxide is then disproportionated into peroxide and molecular oxygen by superoxide dismutase. Finally, peroxide is used by myeloperoxidase to oxidize chloride ions into hypochlorite (the active component of bleach), which is toxic to bacteria. Thus, NADPH oxidase is critical for phagocyte killing of bacteria through reactive oxygen species. Defects in one of the four essential subunits of phagocyte NADPH oxidase (PHOX) can all cause CGD of varying severity, dependent on the defect. There are over 410 known possible defects in the PHOX enzyme complex
Chronic granulomatous disease
19755125
(hirsutism), irregular periods, anovulation and subfertility. Obesity in PCOS sufferers amplifies hormonal and metabolic decline, therefore damaging fertility and oocyte quality in women. PCOS can also have an effect if conception is successful through assisted reproductive technology (ART) in obese patients, leading to an increase in miscarriage rates. PCOS is a very common endocrine disorder among women who are reproductively active. Hyperandrogenism is a medical condition where there are excessive levels of androgens in the body. It is associated with PCOS. Studies have shown that hyperandrogenism could be caused by a reaction between ovarian theca cells and reactive oxygen species.
Obesity and fertility
10663283
or chronic exposure in comparison to the other compounds. In a similar study, nitenpyram was shown to have adverse effects on the DNA of Zebrafish. Enzymes inhibiting the formation of reactive oxygen species (ROS) were severely affected, causing oxidative DNA damage increasing with chronic exposure. The oxford university chemical safety data documents an LD50 toxicology test on rats, both male and female, where doses are recorded as 1680 mg and 1575 mg per kg body weight respectively. As such, the overdose limit for humans and animals are quite high, reaching into grams, and the compound is seen as safe for
Nitenpyram
2859277
(BH4), which then moves from the plasma membrane into the cytoplasm. As a final step, NOS is dephosphorylated yielding nitric oxide (NO), which accumulates in the brain, increasing its oxidative stress. There are several ROS, including superoxide, hydrogen peroxide and hydroxyl, all of which lead to neurotoxicity. Naturally, the body utilizes a defensive mechanism to diminish the fatal effects of the reactive species by employing certain enzymes to break down the ROS into small, benign molecules of simple oxygen and water. However, this breakdown of the ROS is not completely efficient; some reactive residues are left in the brain to
Neurotoxicity
5437708
in age-related development of cancer. The reactive species produced in oxidative stress can cause direct damage to the DNA and are therefore mutagenic, and it may also suppress apoptosis and promote proliferation, invasiveness and metastasis. Infection by "Helicobacter pylori" which increases the production of reactive oxygen and nitrogen species in human stomach is also thought to be important in the development of gastric cancer. The use of antioxidants to prevent some diseases is controversial. In a high-risk group like smokers, high doses of beta carotene increased the rate of lung cancer since high doses of beta-carotene in conjunction of high
Oxidative stress
5109905
low light and with high C-PC levels. Hydroxyl radicals are found at inflamed parts of the body. C-PC, being an anti-oxidant, scavenges these damage-inducing radicals, hence being an anti-inflammation agent. Excess oxygen in the brain generates Reactive Oxygen Species (ROS). ROS causes damages to brain neurons, leading to strokes. C-phycocyanin scavenges hydrogen peroxide, a type of ROS species, from the inside of astrocyte, reducing oxidative stress. Astrocytes also increase the production of growth factors like BDNF and NDF, therefore, enhance nerve regeneration. C-PC also prevents astrogliosis and glial inflammation. C-phycocyanin is found to have hepatotoxicity protection. Vadiraja et al. (1998)
Phycocyanin
789234
include prostaglandins, inflammatory cytokines such as IL-1β, TNF-α, IL-6 and IL-15 and chemokines such as IL-8 and GRO-alpha. These inflammatory mediators, and others, orchestrate an environment that fosters proliferation and survival. Inflammation also causes DNA damages due to the induction of reactive oxygen species (ROS) by various intracellular inflammatory mediators. In addition, leukocytes and other phagocytic cells attracted to the site of inflammation induce DNA damages in proliferating cells through their generation of ROS and reactive nitrogen species (RNS). ROS and RNS are normally produced by these cells to fight infection. ROS, alone, cause more than 20 types of DNA
Inflammation
1973261
and its significant concentrations within mitochondria, a number of authors have indicated that melatonin has an important physiological function as a mitochondrial antioxidant. The melatonin metabolites produced via the reaction of melatonin with reactive oxygen species or reactive nitrogen species also react with and reduce free radicals. Melatonin metabolites generated from redox reactions include cyclic 3-hydroxymelatonin, N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK), and N1-acetyl-5-methoxykynuramine (AMK). While it is known that melatonin interacts with the immune system, the details of those interactions are unclear. Antiinflammatory effect seems to be the most relevant and most documented in the literature. There have been few trials designed to
Melatonin
437582
was considered not harmful or less harmful than UVB, but today it is known to contribute to skin cancer via indirect DNA damage (free radicals such as reactive oxygen species). UVA can generate highly reactive chemical intermediates, such as hydroxyl and oxygen radicals, which in turn can damage DNA. The DNA damage caused indirectly to skin by UVA consists mostly of single-strand breaks in DNA, while the damage caused by UVB includes direct formation of thymine dimers or other pyrimidine dimers and double-strand DNA breakage. UVA is immunosuppressive for the entire body (accounting for a large part of the immunosuppressive
Ultraviolet
4154129
the step in which a fatty acid radical is produced. The most notable initiators in living cells are reactive oxygen species (ROS), such as OH· and HOO·, which combines with a hydrogen atom to make water and a fatty acid radical. The fatty acid radical is not a very stable molecule, so it reacts readily with molecular oxygen, thereby creating a peroxyl-fatty acid radical. This radical is also an unstable species that reacts with another free fatty acid, producing a different fatty acid radical and a lipid peroxide, or a cyclic peroxide if it had reacted with itself. This cycle
Lipid peroxidation
10132668
TBARS Thiobarbituric acid reactive substances (TBARS) are formed as a byproduct of lipid peroxidation (i.e. as degradation products of fats) which can be detected by the TBARS assay using thiobarbituric acid as a reagent. TBARS can be upregulated, for example, by heart attack or by certain kinds of stroke. Because reactive oxygen species (ROS) have extremely short half-lives, they are difficult to measure directly. Instead, what can be measured are several products of the damage produced by oxidative stress, such as TBARS. Assay of TBARS measures malondialdehyde (MDA) present in the sample, as well as malondialdehyde generated from lipid hydroperoxides
TBARS
4795089
peroxide to produce hypochlorous acid. Many vascular stimuli, including all those known to lead to insulin resistance, activate NADPH oxidase via both increased gene expression and complex activation mechanisms. To combat infections, immune cells use NADPH oxidase to reduce O to oxygen free radical and then HO. Neutrophils and monocytes utilize myeloperoxidase to further combine HO with Cl to produce hypochlorite, which plays a role in destroying bacteria. Absence of NADPH oxidase will prevent the formation of reactive oxygen species and will result in chronic granulomatous disease. Reactive oxygen species (ROS) in plants are important in various signaling cascades and
Respiratory burst
11603038
by the interaction of reactive oxygen species (ROS) with the guanine base in DNA under conditions of oxidative stress. The possible role of oxidative stress in aging and male infertility, using 8-oxoguanine as a measure of such stress, is described in the wikipedia article reactive oxygen species. 8-Oxoguanine 8-Oxoguanine (8-hydroxyguanine, 8-oxo-Gua, or OHGua) is one of the most common DNA lesions resulting from reactive oxygen species and can result in a mismatched pairing with adenine resulting in G to T and C to A substitutions in the genome. In humans, it is primarily repaired by DNA glycosylase OGG1. It can
8-Oxoguanine
7679726
sulfur occurs predominantly in the chloroplast. Glutathione is directly involved in the reduction and assimilation of selenite into selenocysteine. Furthermore, glutathione is of great significance in the protection of plants against oxidative and environmental stress and it depresses/scavenges the formation of toxic reactive oxygen species, e.g. superoxide, hydrogen peroxide and lipid hydroperoxides. Glutathione functions as reductant in the enzymatic detoxification of reactive oxygen species in the glutathione-ascorbate cycle and as thiol buffer in the protection of proteins via direct reaction with reactive oxygen species or by the formation of mixed disulfides. The potential of glutathione as protectant is related to
Sulfur assimilation
1638443
to visible energies, have been proven to result in formation of reactive oxygen species in skin, which cause indirect damage since these are electronically excited molecules which can inflict reactive damage, although they do not cause sunburn (erythema). Like ionization-damage, all these effects in skin are beyond those produced by simple thermal effects. Neutrons have zero electrical charge and thus often do not "directly" cause ionization in a single step or interaction with matter. However, fast neutrons will interact with the protons in hydrogen via LET, and this mechanism scatters the nuclei of the materials in the target area, causing
Ionizing radiation
7855078
containing a damaged site, it may inaccurately bypass the damage and, as a consequence, introduce an incorrect base leading to a mutation. Experimentally, mutation rates increase substantially in cells defective in DNA mismatch repair or in Homologous recombinational repair (HRR). In both prokaryotes and eukaryotes, DNA genomes are vulnerable to attack by reactive chemicals naturally produced in the intracellular environment and by agents from external sources. An important internal source of DNA damage in both prokaryotes and eukaryotes is reactive oxygen species (ROS) formed as byproducts of normal aerobic metabolism. For eukaryotes, oxidative reactions are a major source of DNA
Cell damage
29977
reactive oxygen species generated by the photosensitiser, such as hydroxyl radicals, singlet oxygen or superoxide ion. These reactive photochemical intermediates are generated in what are known as Type I, Type II, and Type III processes, respectively. These various alternative processes and reactions can be controlled by choice of specific reaction conditions, leading to a wide range of different products. A common example is the [4+2]-cycloaddition of singlet oxygen with a diene such as cyclopentadiene to yield an endoperoxide: Another example is the Schenck ene reaction, in which singlet oxygen reacts with an allylic structure to give a transposed allyl peroxide:
Alkene
5135050
by either removing excess light energy from chlorophyll molecules or quenching the singlet oxygen molecules directly. In mammalian biology, singlet oxygen is one of the reactive oxygen species, which is linked to oxidation of LDL cholesterol and resultant cardiovascular effects. Polyphenol antioxidants can scavenge and reduce concentrations of reactive oxygen species and may prevent such deleterious oxidative effects. Ingestion of pigments capable of producing singlet oxygen with activation by light can produce severe photosensitivity of skin (see phototoxicity, photosensitivity in humans, photodermatitis, phytophotodermatitis). This is especially a concern in herbivorous animals (see Photosensitivity in animals). Singlet oxygen is the active
Singlet oxygen
15281316
there is greater production of reactive oxygen species and therefore greater chance of mutation. Furthermore, sperm are exposed to reactive oxygen species from leukocytes in the epididymis during transit. Additionally, quality control of spermatozoa is much worse than for the ovum, as many sperm are released whereas only one dominant follicle is released per cycle. This competitive selection helps to ensure the most 'fit' ova are selected for fertilisation. Oocyte activation may be artificially facilitated by calcium ionophores, something that is speculated to be useful in case of fertilization failure, such as still occurs in 1–5% of intracytoplasmic sperm injection
Oocyte activation
1880605
unequal subpopulations of neutrophils were identified on the basis of different levels of their reactive oxygen metabolite generation, membrane permeability, activity of enzyme system, and ability to be inactivated. The cells of one subpopulation with high membrane permeability (neutrophil-killers) intensively generate reactive oxygen metabolites and are inactivated in consequence of interaction with the substrate, whereas cells of another subpopulation (neutrophil-cagers) produce reactive oxygen species less intensively, don't adhere to substrate and preserve their activity. Neutrophils display highly directional amoeboid motility in infected footpad and phalanges. Intravital imaging was performed in the footpad path of LysM-eGFP mice 20 minutes after infection
Neutrophil
33564
to prevent the production of reactive oxygen species. Antioxidants are classified into two broad divisions, depending on whether they are soluble in water (hydrophilic) or in lipids (lipophilic). In general, water-soluble antioxidants react with oxidants in the cell cytosol and the blood plasma, while lipid-soluble antioxidants protect cell membranes from lipid peroxidation. These compounds may be synthesized in the body or obtained from the diet. The different antioxidants are present at a wide range of concentrations in body fluids and tissues, with some such as glutathione or ubiquinone mostly present within cells, while others such as uric acid are more
Antioxidant
11139540
the pancreas islets appear to be the major if not only site where ALOX12 is expressed in these patients. The studies propose that in the islets of Langerhans ALOX12 and its 12("S")-HETE product cause excessive production of reactive oxygen species and inflammation which lead to losses in insulin-secreting beta cells and thereby types 1 and 2 diabetes and that in adipose tissue the excess in AlOX12, 12("S")-HETE, reactive oxygen species, and inflammation lead to fat cell dysfunction (also see 12-HETE#Inflammation and inflammatory diseases and 12-HETE#Diabetes). Indeed, in one study a Single-nucleotide polymorphism, rs2073438, located in an intron region of the
ALOX12
5424056
hydrogen peroxide that undergoes further reactions to generate other reactive oxygen species (ROS) like hypochlorous acid (the reactive agent in bleach). It may also inactivate critical metabolic enzymes, initiate lipid peroxidation, damage iron-sulphur clusters, and liberate redox-active iron, which allows the generation of indiscriminate oxidants such as the hydroxyl radical. Careful regulation of NADPH oxidase activity is crucial to maintain a healthy level of ROS in the body. The enzyme is dormant in resting cells but becomes rapidly activated by several stimuli, including bacterial products and cytokines. Vascular NADPH oxidases are regulated by a variety of hormones and factors known
NADPH oxidase
4154131
is vitamin C. Other anti-oxidants made within the body include the enzymes superoxide dismutase, catalase, and peroxidase. The end products of lipid peroxidation are reactive aldehydes, such as malondialdehyde (MDA) and 4-hydroxynonenal (HNE), the second one being known also as "second messenger of free radicals" and major bioactive marker of lipid peroxidation, due to its numerous biological activities resembling activities of reactive oxygen species. If not terminated fast enough, there will be damage to the cell membrane, which consists mainly of lipids. Phototherapy may cause hemolysis by rupturing red blood cell cell membranes in this way. In addition, end-products of
Lipid peroxidation
3093517
in both animals and humans. ROS are also implicated in mediation of apoptosis or programmed cell death and ischaemic injury. Specific examples include stroke and heart attack. In general, harmful effects of reactive oxygen species on the cell are most often: When a plant recognizes an attacking pathogen, one of the first induced reactions is to rapidly produce superoxide () or hydrogen peroxide () to strengthen the cell wall. This prevents the spread of the pathogen to other parts of the plant, essentially forming a net around the pathogen to restrict movement and reproduction. In the mammalian host, ROS is
Reactive oxygen species
4204786
DNA damages are the likely cause of lung cancer due to smoking. UV light from solar radiation causes DNA damage that is important in melanoma. "Helicobacter pylori" infection produces high levels of reactive oxygen species that damage DNA and contributes to gastric cancer. Bile acids, at high levels in the colons of humans eating a high fat diet, also cause DNA damage and contribute to colon cancer. Katsurano et al. indicated that macrophages and neutrophils in an inflamed colonic epithelium are the source of reactive oxygen species causing the DNA damages that initiate colonic tumorigenesis. Some sources of DNA damage
Neoplasm
18658969
Superoxide dismutase mimetics Superoxide dismutase (SOD) mimetics are synthetic compounds that mimic the native superoxide dismutase enzyme. SOD mimetics effectively convert the superoxide anion (O), a reactive oxygen species, into hydrogen peroxide, which is further converted into water by catalase. Reactive oxygen species are natural byproducts of cellular respiration and cause oxidative stress and cell damage, which has been linked to causing cancers, neurodegeneration, age-related declines in health, and inflammatory diseases. SOD mimetics are a prime interest in therapeutic treatment of oxidative stress because of their smaller size, longer half-life, and similarity in function to the native enzyme. The chemical
Superoxide dismutase mimetics
17169319
Mitochondrial ROS Mitochondrial ROS (mtROS or mROS) are reactive oxygen species (ROS) that are produced by mitochondria. Generation of mitochondrial ROS mainly takes place at the electron transport chain located on the inner mitochondrial membrane during the process of oxidative phosphorylation (OXPHOS). Leakage of electrons at complex I and complex III from electron transport chains leads to partial reduction of oxygen to form superoxide. Subsequently, superoxide is quickly dismutated to hydrogen peroxide by two dismutases including superoxide dismutase 2 (SOD2) in mitochondrial matrix and superoxide dismutase 1 (SOD1) in mitochondrial intermembrane space. Collectively, both superoxide and hydrogen peroxide generated in
Mitochondrial ROS
2786068
N-methoxy oxygen and the carbonyl oxygen, which forms a tetrahedral intermediate that collapses upon acidic work up. Organolithium reagents can also react with carbon dioxide to form carboxylic acids. In the case of enone substrates, where two sites of nucleophilic addition are possible (1,2 addition to the carbonyl carbon or 1,4 conjugate addition to the β carbon), most highly reactive organolithium species favor the 1,2 addition, however, there are several ways to propel organolithium reagents to undergo conjugate addition. First, since the 1,4 adduct is the likely to be the more thermodynamically favorable species, conjugate addition can be achieved through
Organolithium reagent
9472302
synthesis. Proposed functions of TRAP include osteopontin /bone sialoprotein dephosphorylation, the generation of reactive oxygen species (ROS), iron transport, and as a cell growth and differentiation factor. It has been shown that osteopontin and bone sialoprotein, bone matrix phosphoproteins, are highly efficient "in vitro" TRAP substrates, which bind to osteoclasts when phosphorylated. Upon partial dephosphorylation, both osteopontin and bone sialoprotein are incapable of binding to osteoclasts. From this effect, it has been hypothesized that TRAP is secreted from the ruffled border, dephosphorylates osteopontin and allows osteoclast migration, and further resorption to occur. Reactive oxygen species (ROS) are generated in macrophages
Tartrate-resistant acid phosphatase
18658976
treatment also rescued age-related cognitive impairment. These findings suggest that oxidative stress is an important determinant of life-span. Superoxide dismutase mimetics Superoxide dismutase (SOD) mimetics are synthetic compounds that mimic the native superoxide dismutase enzyme. SOD mimetics effectively convert the superoxide anion (O), a reactive oxygen species, into hydrogen peroxide, which is further converted into water by catalase. Reactive oxygen species are natural byproducts of cellular respiration and cause oxidative stress and cell damage, which has been linked to causing cancers, neurodegeneration, age-related declines in health, and inflammatory diseases. SOD mimetics are a prime interest in therapeutic treatment of oxidative
Superoxide dismutase mimetics
69349
The rates of reaction for the chlorine oxyanions increases as the oxidation state of chlorine decreases. The strengths of the chlorine oxyacids increase very quickly as the oxidation state of chlorine increases due to the increasing delocalisation of charge over more and more oxygen atoms in their conjugate bases. Most of the chlorine oxoacids may be produced by exploiting these disproportionation reactions. Hypochlorous acid (HOCl) is highly reactive and quite unstable; its salts are mostly used for their bleaching and sterilising abilities. They are very strong oxidising agents, transferring an oxygen atom to most inorganic species. Chlorous acid (HOClO) is
Chlorine
13226068
matrix which provides structural support to the skin. However, with constant UVA exposure, the size of the dermis layer will be reduced, thereby causing the epidermis to start drooping off the body. Due to the presence of blood vessels in the dermis, UVA rays can lead to dilated or broken blood vessels which are most commonly visible on the nose and cheeks. UVA can also damage DNA indirectly through the generation of reactive oxygen species (ROS), which include superoxide anion, peroxide and singlet oxygen. These ROS damage cellular DNA as well as lipids and proteins. UV exposure can also lead
Photoaging
3980899
lipid bilayer, where the hydrophobic tails are usually found. It is very structurally similar to ubiquinone, or Coenzyme Q10, differing by the length of the isoprenyl side chain, replacement of the methoxy groups with methyl groups, and removal of the methyl group in the 2 position on the quinone. Like ubiquinone, it can come in several redox states, plastoquinone, plastosemiquinone (unstable), and plastoquinol, which differs from plastoquinone by having two hydroxyl groups instead of two carbonyl groups. Plastoquinol, the reduced form, also functions as an antioxidant by reducing reactive oxygen species, some produced from the photosynthetic reactions, that could harm
Plastoquinone
2788736
A and vitamin C. Beta-Carotene is required to synthesize vitamin A and vitamin A is needed to synthesize retinol. A lack of retinol-binding protein is due to a lack of retinol which is required to trigger its production. The damaging effects of porphyrins interacting with iron, absorbing photons to then emit reactive oxygen species is the mechanism of action that results in the itchy, painful blisters that are common with PCT. The reactive oxygen species that are formed interact with and exhaust the antioxidants in the skin, primarily those of beta-Carotene, vitamin E, and vitamin C. Supplementation of these three
Porphyria cutanea tarda