The Antioxidant System: An Elegant Balance of Chemicals from Birth and Onward

Although hydrogen peroxide is less harmful than superoxide, it is still a toxin (Lui et al 5). Thus, another antioxidant enzyme called catalase decomposes hydrogen peroxide (H_2O_2) to water and molecular oxygen (5). A third enzyme, glutathione peroxidase, donates an electron to speed up the decomposition (5).

This process is just one simplified piece of the body’s elegantly balanced oxidant defense system, or the body’s coordinated fight against free radicals.

ROS’s are actually healthy in the correct amounts. They play a vital role in signal transduction and in the immune system (Lui et al. 2). For example, ROS’s help initiate and maintain the inflammation that causes a fever (2). However, at birth, infants’ bodies are overwhelmed with ROS’s. For example, when a baby breathes air for the first time, it is exposed to exponentially more oxygen than it has previously experienced (Tortora et al. 1188). More oxygen creates more ROS’s (1188). A healthy baby’s immune system is well equipped for this challenge, despite the fact that its oxidant defense system is much less mature than an adult’s (1188). This is amazing considering that adults rarely experience this level of oxidative stress!

In other situations, however, a baby’s brain is temporarily deprived of blood and oxygen due to injury during birth (Rallis et al. 1).  When blood finally returns to the brain, the neurons are more overwhelmed by the oxygen than if there had been no delay in oxygenation (2). This causes an increase in ROS’s, which then attack the brain tissue (2). Scientists are currently exploring treatments for neonatal brain damage (called encephalopathy) based on their study of the oxidant defense system and the elegant balance of chemicals it regulates. For example, melatonin has been administered to babies with encephalopathy because of its antioxidant properties and its ability to cross the blood-brain barrier (5). This area of research is critical because babies currently have only one FDA-approved treatment for neonatal encephalopathy; however, younger and sicker babies often cannot endure this treatment (Children’s Hospital of Philadelphia, par. 3). Although there are other possible future therapies for neonatal encephalopathy, an understanding of the antioxidant system is important to advancing neurological neonatal care.