Relationship between Oxidative Stress, Circadian Rhythms, and AMD

Figure 1

A model showing the formation of reactive oxygen species (ROS) in different organelles of the cell. Superoxide anion radical () is produced via the membrane-bound enzyme complex NADPH oxidase (nicotinamide adenine dinucleotide phosphate-oxidase) which is found embedded within the plasma membranes and membranes of various organelles such as mitochondria, chloroplasts, and phagosomes. The dismutation of is accompanied by the formation of hydrogen peroxide (H₂O₂) and then the hydroxyl radical () via the Fenton reaction. The highly reactive has the capability to oxidize all types of biomolecules such as lipids, proteins, and nucleic acids. The oxidation of biomolecules is accompanied by the formation of high-energy intermediates such as dioxetane (ROOR) and tetroxide (ROOOOR), which upon further decomposition, generate electronically excited species such as triplet excited carbonyl, singlet and triplet excited pigments, and singlet oxygen (¹O₂). From Pospišíl et al. [7] with the permission of the authors and Elsevier.