The shift in degradation of phospholipids in lens membrane by oxidation in cataractous lenses is considerably greater than that in the age-related normal lens aging. The interaction of lens crystallin proteins with the membrane is one of the likely mechanisms for cataractogenesis. Although several interaction studies of crystallins with membranes have been performed, the understanding of crystallin-oxidized membranes interaction is lacking. In this work, we connect the aggregation extent of αA-crystallin with the oxidation content in the human lens lipid membrane. Total lens lipids were extracted separately from the cortical and the nuclear regions from a 63-year-old donor with grade 2 cortical and grade 1 nuclear cataract. Using the iodometric assay, the concentration of lipid hydroperoxide in total cortical lipids was found to be higher than that of the total nuclear lipids. Complete supported lipid membranes from small unilamellar vesicles made of total cortical or nuclear lipids were prepared at physiological temperature (37 °C) on a clean mica disk under a fluid cell of an atomic force microscope. After confirming the complete membrane formation, αA-crystallin was incubated, and protein-membrane aggregation images were captured. The percentage of membrane area occupied by αA-crystallin in the cortical membrane was found to be smaller than that in the nuclear membrane. Similarly, the average area of the αA-crystallin aggregates in the nuclear membrane is larger than in the cortical membrane. Thus, we studied the interaction of αA crystallin with the human lens membrane and correlated it with the lipid peroxidation content in the cortical and nuclear membranes. However, the significantly higher loss of cholesterol in the nuclear membrane compared to the cortical membrane in cataractous lenses may have affected the extent of aggregation.
Akinola et al. (Sun,) studied this question.