Antioxidant treatment for lung diseases

The lung is constantly exposed to endogenous (i.e., recruitment of inflammatory cells) as well exogenous sources of oxidative stress (i.e., oxygen, air pollution and tobacco smoke and particulate matter) and, therefore, is well-equipped with multiple antioxidant mechanisms. Increased pulmonary exposure to oxidative sources and/or reduced antioxidant defences may lead to an imbalance known as oxidative stress. The pulmonary effects of this oxidant–antioxidant imbalance can vary from progressive airway remodelling to overwhelming lung injury, depending on its severity and chronicity. This review will discuss the main sources for oxidation in the lung and how they relate to pulmonary antioxidant mechanisms, together with the mechanisms by which oxidative stress leads to an amplification of the inflammatory cascade, as well as the development of antioxidant mechanisms. This section will be followed by an in-depth discussion of each class of antioxidants, including current therapeutic uses and potential clinical applications related to lung diseases. Antioxidant treatment has had limited therapeutic success even for lung disorders, in which oxidative stress is known to play an important role. Potential reasons to explain antioxidant limitations will be discussed in the Expert opinion section of this review.