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Ishii S, Ozaki M, Takamura N, Ogata K, Tokunaga J, Ikeda R. Influence of Endogenous Substances on Site-II to Site-I Displacement of Diclofenac Bound to Albumin in the Aqueous Humor of Patients with Cataract. Biol Pharm Bull 2024; 47:213-220. [PMID: 38057117 DOI: 10.1248/bpb.b23-00301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2023]
Abstract
Diclofenac instillation is useful in preventing intraoperative miosis and macular edema caused by postoperative inflammation in cataract surgery; however, optimum efficacy is not attained when the instilled diclofenac strongly binds to albumin in patients' aqueous humor. Therefore, a method that inhibits diclofenac binding and increases the concentration of its free fraction is needed. We conducted a basic study regarding the effects of inhibitors on the binding of instilled diclofenac to albumin and endogenous substances in aqueous humor. Aqueous humor samples from 16 patients were pooled together for analysis. The free fraction of diclofenac was measured using ultrafiltration methods in various experiments with pooled and mimic aqueous humor. Free fraction of diclofenac, a site II drug, in pooled aqueous humor was 0.363 ± 0.013. The binding of diclofenac in the presence of phenylbutazone (PB), a site I inhibitor, was significantly inhibited (free fraction = 0.496 ± 0.013); however, no significant inhibition by ibuprofen, a site II inhibitor, (free fraction = 0.379 ± 0.004), was observed. The unexpected result was due to free fatty acids (FFAs; palmitic acid (PA)) and L-tryptophan (Trp). The inhibition of diclofenac binding by PB in the mimic aqueous humor containing these endogenous substances revealed significant binding inhibition in the presence of PA and Trp. Diclofenac is strongly rebound from site II to site I in the presence of FFAs and Trp in the aqueous humor because FFAs and Trp induce a conformational change in albumin. Therefore, PB significantly inhibits the binding of diclofenac to albumin.
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Affiliation(s)
- Saya Ishii
- Department of Pharmacy, University of Miyazaki Hospital, University of Miyazaki
- Ozaki Eye Hospital
- School of Pharmaceutical Sciences, Kyushu University of Health and Welfare
| | | | - Norito Takamura
- School of Pharmaceutical Sciences, Kyushu University of Health and Welfare
| | - Kenji Ogata
- School of Pharmaceutical Sciences, Kyushu University of Health and Welfare
| | - Jin Tokunaga
- School of Pharmaceutical Sciences, Kyushu University of Health and Welfare
| | - Ryuji Ikeda
- Department of Pharmacy, University of Miyazaki Hospital, University of Miyazaki
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Kettle AJ, Ashby LV, Winterbourn CC, Dickerhof N. Superoxide: The enigmatic chemical chameleon in neutrophil biology. Immunol Rev 2023; 314:181-196. [PMID: 36609987 DOI: 10.1111/imr.13183] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The burst of superoxide produced when neutrophils phagocytose bacteria is the defining biochemical feature of these abundant immune cells. But 50 years since this discovery, the vital role superoxide plays in host defense has yet to be defined. Superoxide is neither bactericidal nor is it just a source of hydrogen peroxide. This simple free radical does, however, have remarkable chemical dexterity. Depending on its environment and reaction partners, superoxide can act as an oxidant, a reductant, a nucleophile, or an enzyme substrate. We outline the evidence that inside phagosomes where neutrophils trap, kill, and digest bacteria, superoxide will react preferentially with the enzyme myeloperoxidase, not the bacterium. By acting as a cofactor, superoxide will sustain hypochlorous acid production by myeloperoxidase. As a substrate, superoxide may give rise to other forms of reactive oxygen. We contend that these interactions hold the key to understanding the precise role superoxide plays in neutrophil biology. State-of-the-art techniques in mass spectrometry, oxidant-specific fluorescent probes, and microscopy focused on individual phagosomes are needed to identify bactericidal mechanisms driven by superoxide. This work will undoubtably lead to fascinating discoveries in host defense and give a richer understanding of superoxide's varied biology.
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Affiliation(s)
- Anthony J Kettle
- Department of Pathology & Biomedical Science, Mātai Hāora: Centre for Redox Biology & Medicine, University of Otago Christchurch, Christchurch, New Zealand
| | - Louisa V Ashby
- Department of Pathology & Biomedical Science, Mātai Hāora: Centre for Redox Biology & Medicine, University of Otago Christchurch, Christchurch, New Zealand
| | - Christine C Winterbourn
- Department of Pathology & Biomedical Science, Mātai Hāora: Centre for Redox Biology & Medicine, University of Otago Christchurch, Christchurch, New Zealand
| | - Nina Dickerhof
- Department of Pathology & Biomedical Science, Mātai Hāora: Centre for Redox Biology & Medicine, University of Otago Christchurch, Christchurch, New Zealand
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Hu A, Qiu R, Li WB, Zhou W, Wu Z, Zhang H, Li J. Radical recombination and antioxidants: a hypothesis on the FLASH effect mechanism. Int J Radiat Biol 2023; 99:620-628. [PMID: 35938944 DOI: 10.1080/09553002.2022.2110307] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
Abstract
PURPOSE FLASH (ultra-high dose rate) radiotherapy spares normal tissue while keeping tumor control. However, the mechanism of the FLASH effect remains unclear and may have consequences beyond the irradiated area. MATERIALS AND METHODS We reanalyze the available results of ultra-high-dose-rate-related experiments to find out the key points of the mechanism of the FLASH effect. Then, we present a hypothesis on the mechanism of the FLASH effect: FLASH beams generate a high transient concentration of peroxyl radicals leading to a high fraction of radical recombination, which results in less oxidation damage to normal tissue. For the cells containing higher concentrations of antioxidants, the fractions of radical recombination are smaller because the antioxidants compete to react with peroxyl radicals. Therefore the damages by different dose rate beams differ slightly in this condition. Since some tumors contain a higher level of antioxidants, this may be the reason for the loss of the protective effect in tumors irradiated by FLASH beams. The high concentration of antioxidants in tumors results in slight radiolytic oxygen consumption, and consequently the protective effect observed in in vitro experiment cannot be observed in in vivo experiment. To quantitatively elaborate our hypothesis, a kinetic model is implemented to simulate the reactions induced by irradiation. Two parameters are defined to abstractly study the factors affecting the reaction, such as dose rate, antioxidants, total dose and reaction rate constants. RESULTS AND CONCLUSIONS We find that the explanation of the difference between in vivo and in vitro experiments is crucial to understanding the mechanism of the FLASH effect. Our hypothesis agrees with the results of related experiments. Based on the kinetic model, the effects of these factors on the FLASH effect are quantitatively investigated.
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Affiliation(s)
- Ankang Hu
- Department of Engineering Physics, Tsinghua University, Beijing, China
- Key Laboratory of Particle & Radiation Imaging, Tsinghua University, Ministry of Education, Beijing, China
| | - Rui Qiu
- Department of Engineering Physics, Tsinghua University, Beijing, China
- Key Laboratory of Particle & Radiation Imaging, Tsinghua University, Ministry of Education, Beijing, China
| | - Wei Bo Li
- Institute of Radiation Medicine, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Neuherberg, Germany
| | - Wanyi Zhou
- Department of Engineering Physics, Tsinghua University, Beijing, China
- Key Laboratory of Particle & Radiation Imaging, Tsinghua University, Ministry of Education, Beijing, China
| | - Zhen Wu
- Department of Engineering Physics, Tsinghua University, Beijing, China
- Nuctech Company Limited, Beijing, China
| | - Hui Zhang
- Department of Engineering Physics, Tsinghua University, Beijing, China
- Key Laboratory of Particle & Radiation Imaging, Tsinghua University, Ministry of Education, Beijing, China
| | - Junli Li
- Department of Engineering Physics, Tsinghua University, Beijing, China
- Key Laboratory of Particle & Radiation Imaging, Tsinghua University, Ministry of Education, Beijing, China
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Gęgotek A, Skrzydlewska E. Antioxidative and Anti-Inflammatory Activity of Ascorbic Acid. Antioxidants (Basel) 2022; 11:1993. [PMID: 36290716 PMCID: PMC9598715 DOI: 10.3390/antiox11101993] [Citation(s) in RCA: 51] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Revised: 09/30/2022] [Accepted: 10/05/2022] [Indexed: 07/24/2023] Open
Abstract
Ascorbic acid, as a one of the basic exogenous vitamins, occurs in the body in the form of ascorbate, known for its strong antioxidant and anti-inflammatory properties. The presented review shows not only the importance of ascorbate as a free radical scavenger but also summarizes its antioxidant action based on other mechanisms, including the activation of intracellular antioxidant systems and its effect on the NFκB/TNFα pathway and apoptosis. Ascorbate interacts with small-molecule antioxidants, including tocopherol, glutathione, and thioredoxin; it can also stimulate biosynthesis and the activation of antioxidant enzymes, such as superoxide dismutase, catalase, or glutathione peroxidase. Moreover, ascorbate promotes the activity of transcription factors (Nrf2, Ref-1, AP-1), which enables the expression of genes encoding antioxidant proteins. Additionally, it supports the action of other exogenous antioxidants, mainly polyphenols. In this regard, both DNA, proteins, and lipids are protected against oxidation, leading to an inflammatory reaction and even cell death. Although ascorbate has strong antioxidant properties, it can also have pro-oxidant effects in the presence of free transition metals. However, its role in the prevention of DNA mutation, inflammation, and cell apoptosis, especially in relation to cancer cells, is controversial.
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Gebicki JM, Nauser T. Initiation and Prevention of Biological Damage by Radiation-Generated Protein Radicals. Int J Mol Sci 2021; 23:ijms23010396. [PMID: 35008823 PMCID: PMC8745036 DOI: 10.3390/ijms23010396] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Revised: 12/27/2021] [Accepted: 12/27/2021] [Indexed: 12/23/2022] Open
Abstract
Ionizing radiations cause chemical damage to proteins. In aerobic aqueous solutions, the damage is commonly mediated by the hydroxyl free radicals generated from water, resulting in formation of protein radicals. Protein damage is especially significant in biological systems, because proteins are the most abundant targets of the radiation-generated radicals, the hydroxyl radical-protein reaction is fast, and the damage usually results in loss of their biological function. Under physiological conditions, proteins are initially oxidized to carbon-centered radicals, which can propagate the damage to other molecules. The most effective endogenous antioxidants, ascorbate, GSH, and urate, are unable to prevent all of the damage under the common condition of oxidative stress. In a promising development, recent work demonstrates the potential of polyphenols, their metabolites, and other aromatic compounds to repair protein radicals by the fast formation of less damaging radical adducts, thus potentially preventing the formation of a cascade of new reactive species.
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Affiliation(s)
- Janusz M. Gebicki
- Department of Biological Sciences, Macquarie University, Sydney 2109, Australia
- Correspondence:
| | - Thomas Nauser
- Departement für Chemie und Angewandte Biowissenschaften, Eidgenössische Technische Hochschule, 8093 Zurich, Switzerland;
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Fast Antioxidant Reaction of Polyphenols and Their Metabolites. Antioxidants (Basel) 2021; 10:antiox10081297. [PMID: 34439545 PMCID: PMC8389220 DOI: 10.3390/antiox10081297] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Revised: 08/01/2021] [Accepted: 08/11/2021] [Indexed: 12/12/2022] Open
Abstract
The negative correlation between diets rich in fruits and vegetables and the occurrence of cardiovascular disease, stroke, cancer, atherosclerosis, cognitive impairment and other deleterious conditions is well established, with flavonoids and other polyphenols held to be partly responsible for the beneficial effects. Initially, these effects were explained by their antioxidant ability, but the low concentrations of polyphenols in tissues and relatively slow reaction with free radicals suggested that, instead, they act by regulating cell signalling pathways. Here we summarise results demonstrating that the abandonment of an antioxidant role for food polyphenols is based on incomplete knowledge of the mechanism of the polyphenol-free radical reaction. New kinetic measurements show that the reaction is up to 1000 times faster than previously reported and lowers the damaging potential of the radicals. The results also show that the antioxidant action does not require phenolic groups, but only a carbon-centred free radical and an aromatic molecule. Thus, not only food polyphenols but also many of their metabolites are effective antioxidants, significantly increasing the antioxidant protection of cells and tissues. By restoring an important antioxidant role for food polyphenols, the new findings provide experimental support for the advocacy of diets rich in plant-derived food.
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Antioxidants and radical damage in a hydrophilic environment: chemical reactions and concepts. Essays Biochem 2019; 64:67-74. [DOI: 10.1042/ebc20190063] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 11/14/2019] [Accepted: 11/18/2019] [Indexed: 12/29/2022]
Abstract
AbstractKnown endogenous antioxidants are unlikely to prevent radical damage due to oxidative stress or achieve complete repair by established reaction mechanisms. While near complete prevention seems very unrealistic, some of the initial damage can be repaired. Depending on tissue, this may be even a large fraction. Antioxidants, however, will efficiently break radical reaction chains and, therefore, certainly limit the damage caused by radicals. It is not clear if chemical antioxidant action is strictly limited to electron-transfer processes or if additional reaction mechanisms may contribute.
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Nauser T, Gebicki JM. Fast reaction of carbon free radicals with flavonoids and other aromatic compounds. Arch Biochem Biophys 2019; 674:108107. [DOI: 10.1016/j.abb.2019.108107] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 08/27/2019] [Accepted: 09/13/2019] [Indexed: 12/26/2022]
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Affiliation(s)
- Kazuo Kobayashi
- The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan
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Molecular Mechanisms Involved in Oxidative Stress-Associated Liver Injury Induced by Chinese Herbal Medicine: An Experimental Evidence-Based Literature Review and Network Pharmacology Study. Int J Mol Sci 2018; 19:ijms19092745. [PMID: 30217028 PMCID: PMC6165031 DOI: 10.3390/ijms19092745] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Revised: 09/08/2018] [Accepted: 09/10/2018] [Indexed: 12/20/2022] Open
Abstract
Oxidative stress, defined as a disequilibrium between pro-oxidants and antioxidants, can result in histopathological lesions with a broad spectrum, ranging from asymptomatic hepatitis to hepatocellular carcinoma in an orchestrated manner. Although cells are equipped with sophisticated strategies to maintain the redox biology under normal conditions, the abundance of redox-sensitive xenobiotics, such as medicinal ingredients originated from herbs or animals, can dramatically invoke oxidative stress. Growing evidence has documented that the hepatotoxicity can be triggered by traditional Chinese medicine (TCM) during treating various diseases. Meanwhile, TCM-dependent hepatic disorder represents a strong correlation with oxidative stress, especially the persistent accumulation of intracellular reactive oxygen species. Of note, since TCM-derived compounds with their modulated targets are greatly diversified among themselves, it is complicated to elaborate the potential pathological mechanism. In this regard, data mining approaches, including network pharmacology and bioinformatics enrichment analysis have been utilized to scientifically disclose the underlying pathogenesis. Herein, top 10 principal TCM-modulated targets for oxidative hepatotoxicity including superoxide dismutases (SOD), malondialdehyde (MDA), glutathione (GSH), reactive oxygen species (ROS), glutathione peroxidase (GPx), Bax, caspase-3, Bcl-2, nuclear factor (erythroid-derived 2)-like 2 (Nrf2), and nitric oxide (NO) have been identified. Furthermore, hepatic metabolic dysregulation may be the predominant pathological mechanism involved in TCM-induced hepatotoxic impairment.
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Nauser T, Gebicki JM. Reaction rates of glutathione and ascorbate with alkyl radicals are too slow for protection against protein peroxidation in vivo. Arch Biochem Biophys 2017; 633:118-123. [PMID: 28939102 DOI: 10.1016/j.abb.2017.09.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 09/15/2017] [Accepted: 09/18/2017] [Indexed: 11/19/2022]
Abstract
Reaction kinetics of amino acid and peptide alkyl radicals with GSH and ascorbate, the two most abundant endogenous antioxidants, were investigated by pulse radiolysis. Rate constants in the order of 106 M-1s-1 were found. Alkyl radicals react at almost diffusion controlled rates and irreversibly with oxygen to form peroxyl radicals, and competition with this reaction is the benchmark for efficient repair in vivo. We consider repair of protein radicals and assume comparable rate constants for the reactions of GSH/ascorbate with peptide alkyl radicals and with alkyl radicals on a protein surface. Given physiological concentrations of oxygen, GSH and ascorbate, protein peroxyl radicals will always be a major product of protein alkyl radicals in vivo. Therefore, if they are formed by oxidative stress, protein alkyl radicals are a probable cause for biological damage.
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Affiliation(s)
- Thomas Nauser
- Laboratorium für Anorganische Chemie, Departement für Chemie und Angewandte Biowissenschaften, Eidgenössische Technische Hochschule (ETH) Zürich, CH - 8093 Zürich, Switzerland.
| | - Janusz M Gebicki
- Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia
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