Parallel findings in age-related macular degeneration and Alzheimer's disease.

Age is a common risk factor for Alzheimer's disease (AD) and age-related macular degeneration (AMD). Because of the increasing age of the population, these two age-related diseases have recently received a great deal of attention. In addition to age as a risk factor, AD and AMD have many characteristics in common. An important characteristic common to both diseases is the presence of amyloid β (Aβ) in the senile plaques of the AD brain and in the drusen of AMD patients. We have focused on the role of Aβ as a key regulator of the progression from drusen to AMD, and our results have shown that Aβ causes an imbalance of angiogenesis-related factors in the retinal pigment epithelial (RPE) cells. Mice that lack the Aβ-degrading enzyme neprilysin develop RPE degeneration, and the sub-RPE deposits that are formed have features similar to those of AMD in humans. These data suggest that a common pathogenic mechanism might exist between AMD and AD. Thus, therapeutic approaches that have targeted Aβ in patients with AD can also be applied to AMD. In this review, we summarise recent findings on the shared characteristics and perspectives between AMD and AD, beginning with the mechanism of Aβ deposition and including a discussion of Aβ-targeted therapeutic approaches for both AD and AMD.