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Antioxidants and respiratory disease: the uric acid paradox
  1. Seif O Shaheen
  1. Correspondence to Professor Seif O Shaheen, Centre for Primary Care and Public Health, Blizard Institute, Barts and The London School of Medicine and Dentistry, 58 Turner Street, London E1 2AB, UK; s.shaheen{at}qmul.ac.uk

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For humble individuals like myself, there is one poor comfort, which is this, viz. that gout, unlike any other disease, kills more rich men than poor, more wise men than simple. Thomas Sydenham.

In clinical practice, high blood concentrations of uric acid (UA) are generally thought to be a bad thing—primarily because of the risk of gout, but also because individuals with high UA concentrations are at increased risk of cardiovascular disease, metabolic syndrome and hypertension1; these associations may reflect the fact that, under certain circumstances, UA can be pro-oxidant.2 Perhaps less appreciated are the potentially beneficial antioxidant properties of UA.3 UA is present in the epithelial lining fluid (ELF) of the airways and contributes, along with other endogenous antioxidants, such as reduced glutathione, and dietary antioxidants, such as ascorbic acid, to antioxidant defences.4 Oxidative stress is thought to play an important role in the pathogenesis of asthma and COPD5 and may also be involved in the pathogenesis of lung cancer by causing DNA damage.6 This raises the interesting possibility that high concentrations of UA in the ELF may, by boosting antioxidant defences, reduce oxidative stress in the airways, thereby decreasing the risk of developing obstructive pulmonary disease and lung cancer; such beneficial effects of UA (and other antioxidants in the ELF) would be expected to be greatest in individuals with a high oxidant burden in the airways, such as smokers and those exposed to high levels of pollution.

To date, epidemiological research into the possible aetiological role of antioxidants in obstructive lung disease and lung cancer has focused particularly on the antioxidant vitamins, in the hope that preventive dietary interventions might be devised. However, this hope has not been realised. For example, despite evidence implicating a low intake of vitamin C in …

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