Chapter 11 Lipid photooxidative damage in biological membranes: reaction mechanisms, cytotoxic consequences, and defense strategies

Abstract

Abstract Unsaturated lipids in cell membranes, including phospholipids and cholesterol, are well-known targets of oxidative modification, which can be induced by a variety of stresses, including ultraviolet A (UVA)- and visible light-induced photodynamic stress. Photodynamic lipid peroxidation has been associated with pathological conditions such as skin phototoxicity and carcinogenesis, as well as therapeutic treatments such as antitumor photodynamic therapy (PDT). Lipid hydroperoxides (LOOHs), including cholesterol hydroperoxides (ChOOHs), are important non-radical intermediates of the peroxidative process which can (i) serve as in situ reporters of type I vs. type II chemistry, (ii) undergo one-electron or two-electron reductive turnover which determines whether peroxidative injury is respectively intensified or suppressed, and (iii) mediate signaling cascades which either fortify antioxidant defenses of cells or evoke apoptotic death if oxidative pressure is too great. The purpose of this chapter is to review current understanding of photodynamic (UVA or visible light-induced) lipid peroxidation with a special focus on these aspects relating to LOOHs. Future goals in this area, many of which depend on continued development of state-of-the-art analytical techniques, will also be discussed.