Biomarkers of lipid peroxidation, airway inflammation and asthma.

Oxidative stress, specifically lipid peroxidation, is believed to contribute to the pathophysiology of asthma. This review highlights the pathways through which reactive oxygen species (ROS) may lead to lipid peroxidation. The potential of both the innate and acquired immune systems to activate inflammatory cells and release ROS that may overwhelm the host antioxidant defences and cause lipid peroxidation, accompanied by detrimental pathophysiological effects, are discussed. Despite the evidence demonstrating the importance of lipid peroxidation, systematic characterisation of oxidative stress and antioxidant defences has not been undertaken, largely due to the lack of appropriate biomarkers. This review discusses the emergence of isoprostanes (specifically 8-iso-prostaglandin F2alpha) as reliable, in vivo markers of lipid peroxidation, which provides an appropriate tool for studying oxidative stress. Furthermore, the development of techniques to study induced sputum and breath condensate, derived directly from the airway surface, enables the site of oxidative damage to be closely assessed. Evidence suggests that dietary changes that have occurred over recent years have increased susceptibility to lipid peroxidation, due to reduced antioxidant defences. To date, the limited number of long-term (>1 week) supplementation trials have been promising. However, the development of techniques to study isoprostanes in airway-lining fluid pave the way for further studies investigating the potential for antioxidant supplements to be used as routine therapy in asthma.