Melanization and phagocytosis: Implications for age relatedmacular degeneration

[摘要] Signaling pathways that upregulate melanization in the retinalpigment epithelium (RPE) may also be implicated in the downregulation ofrod outer segment (ROS) phagocytosis by the RPE. Melanization activatingpathways may also modulate oxygen consumption by the photoreceptors,apolipoprotein E4 levels, and the rate of photoisomerization events suchthat the net effect may be a reduction in drusen and/or lipofuscinaccumulation. An increase in melanin at the apical microvilli of the RPEmay shield ROS from light thereby contributing in part to the decreasein the rate of ROS phagocytosis. This decrease in ROS phagocytosis bythe RPE may serve to maintain a balance between ingestion anddegradation/recycling thereby avoiding an increase to its alreadysubstantial metabolic load. Several experimental drugs for age relatedmacular degeneration (ARMD) coincidentally are also capable ofdecreasing the rate of ROS phagocytosis. This review attempts toidentify the signaling pathways that may link the upregulation ofmelanization to the downregulation of ROS phagocytosis. Phagocyticpathways that are modulated by melanization need to be studied inisolation to determine what role, if any, they possess in amelioratingthe onset and progression of ARMD. Many more empirical studies areneeded to unravel specific pathways and mechanisms that seem to linkmelanization with ARMD.

[学科分类] 生物化学/生物物理