Oxidative stress and microglial response in retinitis pigmentosa

An imbalance between the production of reactive oxygen species (ROS) and anti-oxidant capacity results in oxidative injury to cellular components and molecules, which in turn disturbs the homeostasis of cells and organs. Although retinitis pigmentosa (RP) is a hereditary disease, non-genetic biological factors including oxidative stress also modulate or contribute to the disease progression. In animal models of RP, the degenerating retina exhibits marked oxidative damage in the nucleic acids, proteins, and lipids, and anti-oxidant treatments substantially suppress photoreceptor cell death and microgliosis. Although the mechanisms by which oxidative stress mediates retinal degeneration have not been fully elucidated, our group has shown that oxidative DNA damage and its defense system are key regulators of microglial activation and photoreceptor degeneration in RP. In this review, we summarize the current evidence regarding oxidative stress in animal models and patients with RP. The clinical efficacy of anti-oxidant treatments for RP has not been fully established. Nevertheless, elucidating key biological processes that underlie oxidative damage in RP will be pivotal to understanding the pathology and developing a potent anti-oxidant strategy that targets specific cell types or molecules under oxidative stress.