Autofluorescent Ceroid/Lipofuscin

Autofluorescent ceroid/lipofuscin-type pigments are usually classified and defined as follows: Lipofuscin is an intracellular, age-related, fluorescent, cytoplasmic, granular pigment. It is mainly present in secondary lysosomes of post-mitotic cells, such as neurons, cardiac myocytes, and retinal pigment epithelial (RPE) cells Ceroid is a group of biopigments, also with an intralysosomal location, which are rapidly produced as a result of various pathologies and experimental conditions, such as x-irradiation, E-vitamin deficiency, starvation, and intoxication. Ceroid is probably akin to lipofuscin and may share the same mechanisms of formation, although it does not accumulate in relation to aging. It may be present in a variety of cells, e.g., in the kidney, thymus, pancreas, testis, prostate, seminal vesicles, uterus, and adrenal gland of man and animal (1 –4 ). Advanced glycation end-products (AGEs) are mainly found extracellularly in association with long-lived proteins, e.g., in the cataractic lens of the eye (5 ,6 ), and in cross-linked collagen of the skin, arteries, lungs, and kidneys (7 –9 ). They are formed during complex non-enzymatic glycation-reactions involving Maillard- and Amadori-type chemistry. AGEs may also, however, be present intracellularly, and they probably constitute a substantial part of lipofuscin and ceroid. A variety of synthetic age pigment-like fluorophores (APFs) can be produced by oxidation/peroxidation of different biological materials. Most such fluorophores are