Oxidized Sterols
Oxysterols are oxygenated derivatives of sterols that are found in animal tissues. Many oxysterols have been linked to vital functions in animals or as short-lived intermediates in the catabolic pathway of cholesterol or steroid hormones, including bile acids. Oxysterols are typically found in trace amounts in biological membranes and lipoproteins. Sterols are oxidized via several specific oxygenases, but may also be oxidized via non-enzymatic oxidation (autoxidation) of cholesterol and cholesteryl esters in tissues with high concentrations of different oxygenated species. Typically, enzymatic oxidation is used to produce oxidation products of the sterol ring system and non-enzymatic oxidation produces oxidation of the side chain; however, there are exceptions. Oxidized sterols have a variety of roles related to cholesterol homeostasis and maybe in signaling. Pathologies related to oxysterols include brain pathologies due to cholesterol homeostasis, atherosclerosis, cytotoxicity, inflammation, immunosuppression, phospholipidosis, and gallstone formation.