Reactive oxygen species induced by hydrogen peroxide (H
2O
2) change the oxidant/antioxidant balance in the aqueous humor. Reactive oxygen species decrease antioxidant levels in the lens, and accelerate the damage to the lens epithelial cells (LECs), resulting in subsequent cataract development.
14–16 When the lens is exposed to H
2O
2, a vast amount of ROS, which exceeds the self-scavenging ability of the lens, is adequately generated, resulting in oxidative stress and DNA damage.
17 Glutathione (GSH) functions as an important intracellular radical scavenger, and protects cells against ROS. Under normal conditions, the lens contains high levels of reduced GSH,
18 which is likely to have an important role in defending the lens against oxidative stress. The levels of GSH in the LECs of patients with pseudoexfoliation syndrome were significantly lower than those in the LECs of nonpseudoexfoliation patients.
19 Glutathione also functions as a coenzyme in glutathione S-transferases (GSTs).
20–22 Glutathione S-transferases belong to an almost universal superfamily of enzymes that is present and has evolved in all aerobic organisms,
23,24 and are considered major players in the phase II detoxification of endogenous oxidative stress products and exogenous electrophilic chemical compounds. Glutathione S-transferases are a family of detoxification enzymes classified as α, μ, π, σ, or θ according to their sequence homologies and substrate specificities.
23 Certain types of GSTs have a key role in regulating mitogen-activated protein kinase pathways involved in the cellular response to oxidative stress. It is believed that GSTs are involved in the transport and biosynthesis of endogenous compounds and cellular defense mechanisms against xenobiotics and oxidative damage by catalyzing the conjugation of reduced glutathione through its cysteine thiol.
24 Cellular detoxification mechanisms are of critical importance in maintaining health by providing protection against numerous noxious agents in the environment. They also allow the cell to withstand harmful endogenously produced substances, such as ROS that arise through normal metabolic processes.
25 The GSTs activity was detected in the central cortex; however, there was no measurable activity in the nucleus.
26 Thus, supplementation with antioxidant nutrients is one reasonable approach to prevent cataract development.