Stress And Oxidative Stress

Peroxynitrite (ONOO−) is a well known potent oxidant and nitrating agent that is formed through the interaction of (NO•) with superoxide ion (O2•-) and its production is allied to the superoxide sources (for instance mitochondrial respiratory complexes or NAD(P)H oxidases present on plasma membrane) because superoxide is a shorter lived species and also shows constrained diffusion across biological membranes whereas NO• is quite stable and extremely diffusible free radical. In vivo, the rate of production in particular organelles (such as phagocytic vacuoles in macrophages) is very high as 50–100 μM per min. The ability of peroxynitrite to cross cell membranes despite of having short half-life at physiological pH (~10 ms) suggested that peroxynitrite formed could persuade adjoining target cells within one to two cell diameters (~5–20 μm) (Denicola et al., 1998). The decomposition of peroxynitrite occur via proton-catalyzed manner to form OH• and NO2• radicals in hydrophobic phases and initiates lipid peroxidation (Radi et al., 1991; Bartesaghi et al., 2006).

With all living organisms, a process known as cell respiration is integral in order to provide the body with an essential form of energy, adenosine triphosphate (ATP). Oxygen, although an essential part of this process, can form reactants from colliding with electrons associated with carrier molecules. (pb101.rcsb.org, 2017). Hydrogen peroxide is an integral product of this reaction but is known to impose negative effects on the body if high levels are introduced. Explicitly, this reaction is caused “If oxygen runs into (one of these) carrier molecules, the electron may be accidentally transferred to it. This converts oxygen into dangerous compounds such as superoxide radicals and hydrogen peroxide, which can attack the delicate sulphur atoms and metal ions in proteins.” (pdbh101.rcb.org, 2017). Research has suggested that the hydrogen peroxide can be converted into hydroxyl radicals, known to mutate DNA, which can potentially cause bodily harm due to DNA’s role in the synthesis of proteins. These radicals can cause detrimental effects on the human body, and studies have suggested a link to ageing. Due to the harmful effects of these H2o2, it is important that the body finds a way to dispose of hydrogen peroxide before concentrations are too great.

owever Levine,R et al concluded that methionine residues are more important than cysteine residues as an antioxidant defence. Oxidants can react with methionine to produce methionine sulfoxide and when exposed on the surface can protect the cell from oxidisation. Methionine sulfoxide can be reduced back to methionine by methionine sulfoxide reductase which allows the antioxidant process to function catalytically.

Glutathione manages to act as a scavenger, neutralizing free radicals as they peruse the body. This counterbalance leads to the protection of our individual cells and thus our skin, eyes (lens, cornea, and retina), brain, heart, liver, kidneys, lungs, intestines as well as other tissues and organs from oxidative damages to ensure a better functioning,

Urate hydroperoxide is formed when urate is oxidized to a radical that subsequently adds to superoxide. It is produced by activated white blood cells called neutrophils and by enzymes that include xanthine oxidase and peroxidase. Previous studies characterized the formation of urate hydroperoxide and its oxidation of small biomolecules (1-3). My work involved optimizing urate hydroperoxide production by xanthine oxidase and lactoperoxidase, and exploring how it reacts with thiols and thiol-dependent enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH).

Your body is in a constant battle against infection, diseases and the formation of free radicals. However, there's a secret weapon that can help you fight against these things: antioxidants! Antioxidants are elements such as vitamins A, C and E that counteract the damage caused by free radicals and help protect your healthy cells. Free radicals are the molecules that contain unpaired electrons, which make them highly reactive. In this form, they can cause damage by attacking healthy cells, and when these cells grow weakened, you become more vulnerable to disease.

The catalase enzyme is so critical to our health that it is found in nearly every living organism on the planet that is exposed to oxygen. This antioxidant enzyme can catalyze the conversion of hydrogen peroxide into water and oxygen. Hydrogen peroxide is a by-product of cell metabolism, which serves some useful functions including healthy immune response. (Group, 2013) Catalase has one of the highest rates of turnover when compared to all other enzymes. In other words, one catalase enzyme can change 40 million molecules of hydrogen peroxide into water and oxygen in just one second. In fact, catalase enzymes act to protect our cells, counteracting and balancing the continual production of hydrogen peroxide. Because of its undeniable, scientifically-proven

The ability of p53 to regulate metabolism is also associated with the ability to regulate cellular ROS levels. As previously mentioned, p53 can either remove damaged cells that have suffered sustained oxidative stress, or limit levels of ROS in order to lower oxidative stress and consequently, potential cell damage. Through the regulation of carbohydrate and lipid metabolism, p53 is able to influence the response to ROS accordingly. By driving the expression of TIGAR and promoting PPP activity, p53 can increase the production of NAPDH, which can be used to generate the cellular antioxidant GSH (Bensaad 2006). Moreover, at the expense of nucleotide synthesis, p53 can also promote GSH synthesis following serine starvation, thereby lowering ROS

Alveolar type II (ATII) cells have a highly oxidative phenotype and numerous mitochondria (1). They are heavily dependent on mitochondrial function for energy generation required for pulmonary surfactant production, fluid transport and transdifferentation to alveolar type I cells to restore the epithelium after damage (2, 3). Cigarette smoking (CS) induces oxidative stress and is one of the most common causes of ATII cell injury and pulmonary emphysema. DJ-1 serves as a sensor of redox status and protect cells from oxidative stress (4). It is localized in the mitochondria, cytoplasm and nucleus. The oxidation of cysteine at position 106 (Cys106) to a sulfinate enhances DJ-1’s cytoprotective activity. We found further oxidized DJ-1 to

Catalase is an enzyme that converts hydrogen peroxide into oxygen and water. Catalase is most commonly found in the liver of animals. Catalase is essential because peroxide is toxic to our

The intracellular redox state is a dynamic system which may modify on many factors. Mitochondria are essential to sustain life and the main intracellular source for fuel generation; moreover engaged in the regulation of many intracellular functions such as redox homeostasis and cell fate. The mitochondrial dynamics have changed and reactive oxygen species (ROS) generation could encourage the induction of oxidative DNA damage, inactivation of phosphatases and transcription factors. Moreover the mitochondrial dysfunction may constantly accompanied and contributed for a broad range of human diseases. Mitochondrial disrepair will result in oxidative stress, which is one of the underlying causal factors for a variety of diseases. High levels of

The importance of ROS in ageing is well illustrated by studies involving overexpression of antioxidant enzymes. Study on overexpression of manganese superoxide dismutase (MnSOD) in Drosophila resulted in prolonged lifespan [100]. Overexpression of catalase increased the

Deponte, M. (2017). The incomplete glutathione puzzle: Just guessing at numbers and figures?. Antioxidants & Redox Signaling, Doi: 10.1089/ars.2017.7123.

Catalase is an enzyme that destroys harmful substances inside the body and is found is nearly all living organisms (Dominic Corsini, 2011). The enzyme, catalase, brings about the reaction by which hydrogen peroxide is decomposed to water and oxygen. This can be found in organisms that live in the presence of oxygen. Catalase protects cellular organelles and tissues from the damage that could be inflicted from hydrogen peroxide. With mammals, catalase is found only in the liver (The Editors of Encyclopaedia Britannica,

However, an imbalance in the production and elimination of ROS is associated with human diseases (68). ROS molecules are produced by the host enzyme NADPH oxidase (NOX). Seven NOX homologues are encoded in the human genome. NOX2 (otherwise known as gp91Phox) is the best-characterized family member in terms of its regulation. Gp91Phox is the catalytic unit of this multicomponent oxidase whereas p22Phox, p40Phox, p47Phox, p67Phox and the small GTPase RAC are regulatory subunits. Exposure of cells to pathogens triggers the assembly of cytosolic regulatory subunit (p40Phox, p47Phox, p67Phox and RAC) with transmembrane protein complex formed by gp91Phox and p22Phox (47). NOX2 mediates the transfer of an electron from NADPH to O2, forming the superoxide radical (O2̇ ˉ) (47). The superoxide radical is converted to hydrogen peroxide by superoxide dismutase. In the phagolysosome of neutrophils, myeloperoxidase (MPO) catalyzes the generation of hypochlorite (HOCl) from hydrogen peroxide. HOCl dramatically enhances the microbicidal activity of hydrogen peroxide (92). Pro-inflammatory cytokines such as IL-1 and TNF-α upregulate the expression of inducible nitric oxide synthase (iNOS), which produces nitric oxide from the amino acid L-arginine. Nitric oxide reacts with superoxide to generate peroxynitrite (OONO-), a potent nitrating agent and oxidant (Figure 2D) (31). Both RNS and ROS