A PHYSIOLOGICAL-ROLE OF PLASMALOGENS - THE PROTECTION AGAINST OXIDATIVE STRESS AND IODINE EXCESS

Plasmalogens constitute a peculiar class of glycerophospholipids characterized by a unique structural feature:a vinyl ether group on the sn-1 position of glycerol instead of the usual ester function. The specific role of plasmalogens, which are especially abundant in brain and heart, has remained elusive for a long time. The ability of reactive oxygen species such as singlet oxygen to attack vinyl ether groups led to the hypothesis that plasmalogens have all antioxidant function. This is supported by the cleavage of plasmalogens during some forms of oxidative stress and by the hypersensitivity to oxidants of mutant cells deficient in plasmalogen synthesis. In a completely different research area, the main iodolipid of the thyroid gland was identified as 2-iodohexadecanal. This compound is formed via the addition of a peroxidase-generated reactive form of iodine to the vinyl ether group of plasmalogens, followed by cleavage of this group. As 2-iodohexadecanal mimicks the inhibitory, effects of iodine on adenylyl cyclase and H2O2 production in the thyroid, it is likely to represent the mediator of these well-known autoregulatory actions which prevent the development of thyrotoxicosis following: exposure to excess iodine.