Macular Pigment Carotenoids and Bisretinoid A2E.

Lutein (L), zeaxanthin (Z), and meso-zeaxanthin (MZ) are the three macular pigments (MP) carotenoids that uniquely accumulate in the macula lutea region of the human retina. L and Z are obtained by humans through dietary intake. The third MP, MZ, is rarely present in diet, and its abundance in the human fovea is due to the metabolic conversion of dietary L by the retinal pigment epithelium's RPE65 enzyme. The major functions of MP in ocular health are to filter high-intensity, phototoxic blue light and to act as effective antioxidants for scavenging free radicals. The pyridinium bisretinoid, N-retinylidene-N-retinylethanolamine (A2E), contributes to drusen formation in dry age-related macular degeneration (AMD) and to the autofluorescent flecks in autosomal recessive Stargardt disease (STGD1). Retinal carotenoids attenuate A2E formation and can directly and indirectly alleviate A2E-mediated oxidative damage. In this chapter, we review these more recently recognized interconnections between MP carotenoids and A2E bisretinoids.