ROS-induced lipid transformations without oxygen participation.

This review presents data showing the possibility of novel pathways to be realized for free-radical transformations of glycerophospholipids and sphingolipids. These transformations include the stages of formation and subsequent decay of carbon- and nitrogen-centered radicals of the starting lipids resulting in the accumulation of signal molecules. The presence of a hydroxyl group in the polar component of lipids is a prerequisite for the implementation of these processes. This enables their structural modification and/or destruction to take place with the accumulation of biologically active products such as phosphatidic acid, ceramides, diacylglycerols and acylamides. Sphingolipids containing a free amino group, when interacting with active species of oxygen or chlorine, form aminyl radicals. These lipid radicals undergo further fragmentation, leading to the accumulation of 2-hexadecenal, which has a broad spectrum of biological activity. The presence of an amide group in the structure of sphingolipids determines the possibility of their photodestruction, which also results in the formation of 2-hexadecenal. In contrast with lipid peroxidation, which is inhibited by reducing agents, free-radical fragmentation reactions of hydroxyl-containing lipids involving carbon-centered radicals are blocked by oxidants.