Reactive oxygen intermediates
Under certain conditions, oxygen can undergo chemical modification into highly reactive substances with the potential to damage cellular molecules and inhibit functional properties in pathogens or host cells. Three of the most important oxygen intermediates are (1) the superoxide anion, (2) hydrogen peroxide, and (3) the hydroxyl radical:
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superoxide anion |
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superoxide dismutase catalyzes anions to form hydrogen peroxide |
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hydroxyl anion and hydroxyl radical |
Oxygen metabolites triggered by immune responses and generated by leukocytes, especially neutrophils and macrophages, are the most important source of free radicals during inflammation. A wide variety of stimuli can trigger leukocyte oxygen metabolism, including
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innate triggers, such as LPS or fMLP
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adaptive effectors, such as complement-fixing antibodies or certain cytokines produced by activated T lymphocytes
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other chemical mediator systems, such as C5a, PAF, and leukotrienes
Reactive oxygen intermediates can also be generated as part of noninflammatory cellular biochemical processes, especially by electron transport in the mitochondria, detoxification of certain chemicals, or interactions with environmental light or radiation. These reactive intermediates are highly toxic to living pathogens and damage pathogenic mediators such as exotoxins and lipids.
Excerpted from BCSC 2020-2021 series: Section 9 - Uveitis and Ocular Inflammation. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.