Ikuo Mikuni

Acceleration of calcium-induced aggregation of rat lens soluble protein by photosensitization with 8-methoxypsoralen and 3-Hydroxy-l-kynurenine O-β-glucoside

Abstract The present investigation shows a relationship between near ultraviolet light and calcium-induced aggregation of rat lens protein. Ca-induced aggregation of rat lens soluble protein was accelerated by 8-methoxypsoralen plus near ultraviolet light. This photosensitization effect increased with concentration of 8-methoxypsoralen and with light irradiation time. 3-Hydroxy- l -Kynurenine O -β-glucoside also had a similar photosensitizing action as 8-methoxypsoralen on the Ca-induced aggregation of the lens protein. Furthermore, it was found that acceleration of the Ca-induced protein aggregation by photosensitization was inhibited by glutathione, and that the Ca-induced aggregation of the lens protein was not reversed when calcium ion was removed from the protein solution with dialysis.

Calcium-induced lens protein aggregation accelerated by reactive oxygen species photosensitized in the presence of hydroxykynurenines.

Photo-oxidation with 3-OH L-kynurenine O-beta-glucoside or 3-OH L-kynurenine accelerates the aggregation of water-soluble protein in the rat lens due to the presence of calcium ion. The present report demonstrates that hydrogen peroxide and superoxide anion mediate a large part of the photodynamic acceleration with hydroxykynurenine compounds. In addition, 3-OH L-kynurenine O-beta-glucoside seems to photosensitize more of the two reactive oxygen species than 3-OH L-kynurenine. The findings are discussed together with other photodynamic effects of hydroxykynurenine compounds.