Influence of Nicotine and Cotinine on Retinal Phospholipase A2 and its Significance to Macular Function

ABSTRACT The macula is a constituent of the sensory retina that is necessary for sharp contrast and color vision. A significant relationship has been found between tobacco smoking and age-related macular degeneration. Opsin, rhodopsin and phospholipase A2 (PLA2) are located in excitable membranes of retina which are enriched with polyunsaturated fatty acids (PUFA). A question may arise as to whether nicotine and its major metabolite cotinine influence PLA2 so that arachidonic acid (AA) and pro-inflammatory prostaglandins (PG) are produced in the retina. Therefore, the effects of nicotine and cotinine on the retinal PLA2 were studied. PLA2 activity of rat retinal sonicates was assayed using 1-palmitoyl-2[1-14C]arachidonyl-Phosphatidylethanolamine (PE, 2.2 nmol) as a substrate in Tris buffer (10 mM, pH 7.4) at 37°C with and without nicotine or cotinine in the assay medium. These studies gave the following results: (1) Rat retinal PLA2 activity was 4.2 ± 0.8 pmol PE hydrolyzed/100 ng protein/hr. (2) Nicotine...