Recent evidence implicates that the oxidative stress plays a role in the etiology of Age-Related Cataract, and suggests that aged lens cells are prone to this damage due to reduced expression of antioxidants. Because ocular lens is constantly exposed to environmental stress, it continuously generates reactive oxygen species (ROS), if not removed, increased formation and local accumulation of ROS in the cellular microenvironment causes lens cell damage-by initiating wide-spectrum of deleterious signaling and if this situation prolongs may lead to cataractogenesis. Peroxiredoxin 6 (PRDX6), a 'moonlighting protein'with both GSH peroxidase and aiPLA2 (acidic Ca2+independent phospholipase A2) activities, is highly expressed in lens. Our studies have shown diminution of PRDX6 expression and higher intracellular ROS levels in lens cells during aging. Using targeted inactivation of Prdx6 gene in mice, we found that Prdx6-depleted lenses and/or lens epithelial cells (LECs) contain elevated levels of ROS and bio-activeTGF21;exhibit phenotypic changes with overmodulation of TGF21 inducible genes such as 1-SM-actin and 2ig-h3, and these genes are implicated in pathophysiology of cataractogenesis. We envisage a vicious feed-forward-process (ROS?? TGF?1??ROS = overmodulation of genes??) taking place within the local microenvironment of aging LECs or LECs facing oxidative stress, and therefore, we hypothesized that by blocking ROS mediated deleterious signaling should reduce progression of cataractogenesis, by interrupting the vicious cycle initiated by locally high levels of ROS and activated TGF21 within cellular microenvironment. We believe that these events are causally related, i.e., that the environmental stress and age-related reduction in PRDX6 in lens tissues leads to ROS-induced damage of membrane or cytosolic factors, as a consequence of this damage, cell homeostatic system fails. The over all goal of this proposal, therefore, is to unveil the roles of oxidative stress in pathophisiology of cataract formation and to show PRDX6 ability in treating/delaying cataractogenesis through three specific aims: 1) Understand the functional significance of PRDX6 and its regulatory role during oxidative stress and aging. 2) Assess the antioxidant potential of PRDX6 in protecting cells facing oxidative stress in vitro and in vivo using TAT-HA- PRDX6 to cargoing PRDX6 protein in Prdx6-/- depleted mice and mice with Paraquat-induced oxidative stress as well as Shumiya cataract rat (SCR), and assess whether cataract progression is slowed by PRDX6. 3) Investigate the regulatory mechanisms of PRDX6 in normal and aging LECs and cells under oxidative stress and define role(s) of downstream redox signaling in controlling its gene transcription. These studies should provide novel insights into the role of oxidative stress in cataract formation and will provide a foundation for rational use of antioxidant based therapeutics for treating or preventing/delaying cataractogenesis. A common disorder of the eye, Age-Related Cataract (ARC) is among the leading causes of blindness. Although evidence suggests a role for reactive oxygen species-driven oxidative stress in the progression and etiology of age-related degenerative diseases including ARC, the mechanism of oxidative stress-induced deleterious signaling, a cause of cellular damage that leads to the disease state, is not clear. Thus clinical application of antioxidant therapy or combination of therapies has been at best equivocal. Using eye lens as a model for age-associated disorders, we will unveil the underlying mechanism involved in the pathophysiology of tissues/organs during oxidative stress or aging. The proposed studies will provide a sound scientific basis for developing an antioxidant-based therapy or combination of therapies for preventing cataractogenesis and age-associated degenerative diseases in general.