Lipofuscinogenesis in a model system of cultured cardiac myocytes.

Lipofuscin, or age pigment, is a yellowish-brown, autofluorescent, protein, and lipid containing pigment that accumulates in the lysosomal vacuome of a variety of post-mitotic cells in man and animals during aging. Lipofuscin seems to be an end product of peroxidation, fragmentation and polymerization of proteins and lipids. Protein and lipid containing materials are regularly sequestered to the lysosomal system by means of endocytosis and autophagocytosis. Lysosomes and acidified endosomes constitute cellular compartments where iron for short periods of time may exist in reactive form allowing for peroxidative processes. The importance was demonstrated in model systems of cultured cells subjected to oxidative stress and augmented amounts of FeCl3 in the culture medium. This combination was considered to result in increased intracellular, mainly mitochondrial, production of hydrogen peroxide as well as increased intralysosomal concentration of iron. One of the results of this situation was dramatically increased lipofuscinogenesis.