Allergic asthma is a worldwide chronic inflammatory disease characterized
by cycles of airway obstruction due to recurrent episodes of respiratory smooth muscle
contraction and bronchoconstriction. Public awareness of asthma has increased over the
past few decades due to higher prevalence, especially among younger generations.
Many research efforts are dedicated to the understanding of this complex disorder and
the role of genetic and environmental factors. Emerging evidence from animal studies
and clinical trials has identified oxidative stress (OS) as an important factor contributing
to asthma pathogenesis. In addition, observational epidemiologic studies suggest a
possible correlation between impaired intake of antioxidants and increased prevalence
of allergic asthma. The imbalance between antioxidants and oxidants in the respiratory
airway due to overproduction of reactive oxygen species (ROS) or overwhelmed
antioxidant system indicates a strong association between ROS and asthma. Although
physiological levels of ROS are essential for the modulation of cell signaling pathway,
excessive ROS production can lead to worsened physiological conditions, including
increased airway hyperresponsiveness, epithelial shedding, vascular permeability,
mucus secretion, as well as other inflammatory responses through the upregulation of
proinflammatory mediators. In particular, the exposure to sources such as allergens, air
pollution, and tobacco smoke, not only triggers airway inflammation, but also provides
exogenous ROS. Simultaneously, overreacted immune responses exacerbate ROS
formation, which furthers the inflammation. Redox therapeutics has become a potential
approach in alleviating OS and restoring oxidant-antioxidant balance. However, redox
therapeutics is limited by ineffective measurement of lung redox status due to the lack
of standard biomarkers of OS and antioxidant capacity. Moreover, the responses to
antioxidants are largely dependent on the stage of the disease, genetic susceptibility, and
external sources of OS. These aspects also pose a great challenge to the redox
therapeutics. The antioxidants, either antioxidant enzymes or non-enzymatic
antioxidants, are frequently used in the treatment for multiple diseases, including neurodegenerative, cardiovascular, skin, and liver diseases. Particularly, the intake of
antioxidant supplements, such as vitamin C, and dietary changes are proposed to
decrease asthma prevalence and enhance asthma control. However, limited data has
displayed their beneficial effects on asthma subjects clinically. The exact mechanism by
which ROS influence the lung tissue remains unclear. Future studies may be focused on
the molecular mechanisms of redox processes as well as the development of treatments
in allergic asthma.
In this chapter, we will discuss the specific antioxidants from supplement and diet that
are potential agents for the treatment and prevention of asthma. The pathogenesis of
allergic asthma and its correlation with inflammation and ROS/OS will be presented.
The development of potential biomarkers of OS and effective therapeutic redox
intervention will be discussed in this chapter.
Keywords: Airway hyperresponsiveness, allergen, allergic asthma, antioxidant,
FENO, inflammation, inhaled corticosteroids, oxidative stress, reactive oxygen
species, vitamin.
