OXIDATIVE STRESS

There is normally a balance between pro-oxidants and anti-oxidants in the body. 'Oxidative stress' is a situation where this balance is displaced. The result can be accumulation of oxidation damage.

Oxidative stress arises if there is an increase in reactive oxygen that the antioxidant defences are not able to deal with.

• Antioxidant defence is not 100% efficient.
• Increased free radical formation is often referred to as oxidative stress
• Increased exposure to reactive oxygen species (ROS) eg. superoxide anion (•O₂^-), hydrogen peroxide (H₂O₂) and hydroxyl radical (•OH) leads to oxidative stress

Increase in pro-oxidants is caused by:
-too high endogenous production
-increased uptake from the environment

Too low level of anti-oxidants may be caused by:
-too low endogenoud production
-reduced intake in the diet

Oxidative stress is modulated by many factors:

• Smoking, alcohol, radiation and environmental pollutants may enhance level of ROS and free radicals.
• Diet; antioxidants such as vitamin C and carotenoids may decrease oxidative stress.
• Exercise; an acute burst of exercise can lead to oxidation damage.
• Infection, inflammation; the inflammatory response of macrophages involves release of reactive oxygen.
• Disease; diabetes, rheumatoid diseases and many others are associated with oxidative stress – which means the conditions may be caused by oxidative stress and/or the conditions may increase oxidative stress.
• Pharmaceutical and recreational drugs

Cellular response to oxidative stress:

• Cells may detoxify ROS by enzymes eg. superoxide dismutase, peroxidase or catalase
• Bacteria, yeast and some cells may induce expression of genes encoding antioxidant defence when exposed to ROS
• Transcription factors are sensitive to oxidation and contain redox-reactive cysteine/methionine residues, or metal or heme cofactors

See measurement of oxidative stress in the menu.