The protective role of squalene in alcohol damage in the chick embryo retina

Abstract

The developing CNS, and in particular the visual system, is very sensitive to the effects of alcohol. Alcohol causes lipid peroxidation. Squalene, the major olive oil hydrocarbon, is a quencher of singlet oxygen and prevents the corresponding lipid peroxidation. We presumed that squalene can protect against the alcohol-induced damage already observed during the development of the chick retina. Alcohol+squalene was administered directly into the yolk sac of the egg of White Leghorn chicks at day 6 of incubation. The lipid composition of the retina was analyzed in embryos at E7, E11, E15 and E18. The proportions of phospholipids, free and esterified cholesterol, diacylglycerides and free fatty acids were estimated using the Iatroscan TLC/FID procedure. Gas chromatography and mass spectrometry were used to determine the fatty acid composition. The morphological study was carried out at E11 using semithin sections, and by means of immunohistochemical techniques at E19. Comparing the results obtained in control embryos, the administration of alcohol+squalene reduces the effects of alcohol on the total lipid composition of the retina during development. The effects were, in fact, of less magnitude than in embryos treated only with alcohol. The major phospholipid species of alcohol+squalene-treated embryos exhibited total recuperation at E15. As far as fatty acids are concerned, no significant changes were observed with regard to control embryos during development. From a morphological point of view, the retinas of alcohol+squalene-treated embryos show at E11 fewer cellular alterations than the retinas of alcohol-treated embryos. In this respect, the retinas of alcohol+squalene-treated embryos exhibited: a columnar cell arrangement similar to that observed in control retinas; few pycnotic cells and very few alterations in ganglion cell layers and in the optic nerve fibers layer. At E19 the recuperation of the expression of myelin oligodendrocyte specific protein (MOSP) in alcohol+squalene-treated embryos was recorded. Since squalene reduces the deleterious effects caused by alcohol on the lipid composition and the structure of the retina, squalene could act as a naturally occurring agent for the prevention of damage caused by abusive alcohol ingestion during pregnancy.