Singlet oxygen species and systemic lupus erythematosus: a brief review.

Reactive oxygen species (ROS) are implicated in inflammatory, autoimmune, and neurodegenerative diseases. The activation, proliferation, and apoptosis of immune cells are dependent on the controlled production and elimination of ROS. However, under chronic inflammatory conditions, large amounts of ROS generated are a major cause of many human diseases. The electronically excited molecular oxygen species known as singlet oxygen (1O2) is a form of ROS and is one of the major cytotoxic species in eukaryotic cells. ROS are known to cause DNA damage leading to strand breaks, base damage, and conformational changes. The 1O2, being one of the most potent ROS, is generated by photoexcitation or by chemiexcitation and is known to selectively react with the deoxyguanosine moiety in DNA. The biological consequences of 1O2-induced damage causes loss of transforming activity as well as mutagenicity and genotoxicity and may lead to the formation of neo-epitopes in native DNA and generation of pathogenic anti-DNA antibodies. The excessive production of ROS may be one of the factors responsible for the induction of autoimmune response in diseases such as cancer and systemic lupus erythematosus. Abbreviations: Singlet oxygen: 1O2; Superoxide anion: O2-.; Hydroxyl radical: OH; Hydrogen peroxide: H2O2.