Reactive oxygen species and redox-active free radicals (ROS)

Cellular reactive oxygen species (ROS) and redox-active free radicals are highly reactive chemical entities, including superoxide (O2•−), hydrogen peroxide (H2O2), and hydroxyl radicals (•OH), primarily generated as byproducts of mitochondrial respiration and by specialized enzymes like NADPH oxidases (PMID: 28129551). At physiological levels, ROS function as critical signaling molecules (redox signaling) that regulate cell growth, differentiation, and the immune response (PMID: 21233300). However, an imbalance known as oxidative stress occurs when ROS production exceeds the capacity of endogenous antioxidant systems, leading to oxidative damage of DNA, proteins, and lipids (PMID: 23626520). This damage is implicated in the pathogenesis of numerous conditions, including cancer, neurodegeneration (e.g., Alzheimer's), and cardiovascular disease (Source: NIH/NIEHS). Therapeutic strategies involve the use of radical scavengers like edaravone or precursors to endogenous antioxidants like N-acetylcysteine to mitigate damage (PMID: 24746911). A significant challenge in targeting ROS is the "antioxidant paradox," where non-selective removal of ROS can interfere with essential life-sustaining signaling pathways and potentially promote disease progression in certain contexts (PMID: 26845017). Furthermore, some drugs like dexrazoxane work by preventing the formation of ROS through metal chelation, particularly to prevent cardiotoxicity (PMID: 11511521). Overall, while ROS are targets for reducing oxidative damage, their dual role as both toxic byproducts and essential signaling molecules necessitates precise therapeutic modulation rather than broad elimination.

Other names

ROSFree radicalsReactive nitrogen speciesRNSOxidantsReactive oxygen intermediates

Direct chemical neutralization (scavenging) of reactive species, donation of electrons to stabilize free radicals, and enhancement of endogenous antioxidant defense systems.