Retinal pigment epithelium melanin granule (RPE melanin granule)

Retinal pigment epithelium (RPE) melanin granules, also known as melanosomes, are specialized organelles within the RPE cell layer that contain the pigment melanin. They play a critical role in ocular health by absorbing stray light to prevent reflections, scavenging reactive oxygen species (ROS), and sequestering toxic metal ions and xenobiotics [2, 8, 16]. In the context of pharmacology, these granules serve as a significant reservoir for various drugs, particularly basic and lipophilic compounds like chloroquine, which can lead to prolonged drug retention and potential retinal toxicity [3, 6, 7]. Melanin is also the primary target for therapeutic lasers used in treating retinal disorders, where it acts as a chromophore to convert light energy into localized heat [11]. With age, RPE melanin undergoes oxidative degradation and fuses with lipofuscin to form melanolipofuscin, a process linked to the pathogenesis of age-related macular degeneration (AMD) [18]. Emerging therapies also explore melanin-based nanotechnology and radionuclide delivery systems that specifically target these pigmented structures [1, 4, 8].

Other names

MelanosomeRPE pigment granuleMelanin pigmentRetinal melaninUveal melanin