title: Biological autoxidation. II. Cholesterol esters as inert barrier antioxidants. Self-assembly of porous membrane sacs. An hypothesis.
abstract: The antioxidation defenses recognized thus far appear too weak. Needed are inert barriers to encapsulate foci of activated oxygen (FAOs) and contain their spreading. These capsules must: 1. self-assemble nonenzymatically and spontaneously in face of adversity; 2. resist oxidation and dissolution in water; and 3. be moderately fluid and elastic enough to withstand flexing by tissues. Evidence shows activated oxygen: a. is produced by common cholesterolester (CE)-raising agents; b. boosts accumulation of CEs; and c. splits low-density lipoproteins (LDL), thus releasing CE-rich coalescence-prone lipid micelles. I am proposing that CEs, combined with polar lipids, are uniquely suited to form inert-lipid antioxidation barriers (ILABs). Porous ILAB capsules self-assemble from lipid micelles released by oxidatively degraded LDL. The capsules are thermodynamically unstable but elastic, durable and capable of self-repair through oxidation of ambient LDL. All capsules tend to contract into spheres. Enclosed needle-like "foreign bodies", such as asbestos, puncture the contracting capsules. Hence the odd bulbous architecture of asbestos bodies. ILABs protect from--and their failure initiates and promotes--carcinogenesis and atherosclerosis. ILABs may be mediators of membrane biogenesis. The loss of arterial flexibility in atherosclerosis protects ILAB capsules from breakage.
mesh_terms: D000975:Antioxidants; D001161:Arteriosclerosis / Q000209:etiology; D055598:Chemical Phenomena; D002621:Chemistry; D002784:Cholesterol / Q000172:deficiency / Q000502:physiology; D002788:Cholesterol Esters / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D003094:Collagen / Q000502:physiology; D004548:Elasticity; D005547:Foreign Bodies / Q000150:complications; D006801:Humans; D050356:Lipid Metabolism; D008055:Lipids / Q000502:physiology*; D008247:Lysosomes / Q000502:physiology; D008566:Membranes / Q000502:physiology; D009369:Neoplasms / Q000209:etiology; D010084:Oxidation-Reduction
chemical_list: D000975:Antioxidants; D002788:Cholesterol Esters; D008055:Lipids; D003094:Collagen; D002784:Cholesterol