Formation of a new class of aging pigments in human lens

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Previous studies on cataractous and normal lenses have revealed the age-related accumulation of fluorogens in the human lens. Although some fluorescent compounds such as beta-carboline derivatives, anthranilic acid and 3,3'-bityrosine have been identified in human lens, most of fluorescent compounds in human lens have not been identified. In this investigation, we found four fluorescent compounds as new fluorogens in lens and investigated the age-related accumulation of these compounds. The presence of these compounds in lens have not been reported and these four compounds are structurally a family of heterocyclic amines. Later, these heterocyclic amines were found to be carcinogenic glutamic acid pyrolysis products products (Glu-P-1, Glu-P-2) and carcinogenic tryptophan pyrolysis products (Trp-P-1, Trp-P-2) which had been reported to be present as carcinogens in cooked foodstuffs. these carcinogenic heterocyclic amines are strong fluorescent compounds and their contents in denatured lens proteins are significantly higher than those in carcinogenic tryptophan pyrolysis products may be formed in lens under the certain conditions. These results suggest that the carcinogenic heterocyclic amines are present as aging pigments in human lens, but also might open new vistas about the determination of the relationship between aging and carcinogenesis.