Oxidised products of cholesterol: Their role in apoptosis

Oxysterols are oxygenated derivatives of cholesterol that may be formed endogenously or absorbed from the diet and are particularly found in highly processed foods of animal origin. These compounds elicit a range of biological effects such as inhibition of HMG-CoA reductase, alteration in cellular membrane properties and the induction of cell death in a number of in vitro models. Much research, to date, has focused on oxysterols and their potential role in the development of atherosclerosis due to the ability of certain oxysterols to induce apoptosis in cells of the arterial wall, a primary process in the development of atheroma. Apoptotic cell death is the culmination of a series of events centring on the cascade of caspases, which triggers downstream effects leading to DNA cleavage. Though the induction of apoptosis by oxysterols has been the topic of intense research over the last few years, the exact mechanism through which certain oxysterols induce apoptotic cell death remains to be clarified. This review focuses on the biological effects of oxysterols, with particular emphasis on oxysterol-induced apoptosis.