Figure 1.Diagram
illustrating the progression of early age related macular degeneration
(AMD) into 2 divergent late stages and the potential role of BMP4 as a
switch between these pathways. Chronic stressors such as oxidative stress
can promote the expression of BMP4 in the retinal pigment epithelium (RPE)
and induce RPE senescence as part of the phenotype of early AMD. If BMP4
expression is sustained, it could lead to RPE apoptosis and geographic
atrophy. In other individuals, activation of the senescence activated
secretory pathway and expression of pro-inflammatory mediators could result
in increased expression of interleukin (IL)-8, decreased expression of BMP4
and increased expression of vascular endothelial growth factor (VEGF)
resulting in neovascular AMD with choroidal angiogenesis.
