Purpose:
This study investigates the reaction of RPE cells to inflammatory assault from activated T cells.
Methods:
T cells were purified from freshly tapped human blood, and placed in Transwell inserts with activating CD3/CD28 antibodies, either in an empty well, or over 6-12 week old ARPE-19 cell cultures. After co-culture for 12-48 hours, RNA was purified separately from the two cell types, labeled, and hybridized to commercial microarrays quantifying 440 genes related to immunology and hematology.
Results:
Out of the 440 genes quantified, 27 genes were identified as upregulated >500%, when RPE cells were co-cultured with activated T cells for 12, 24, or 48 hours, as compared to expression in RPE cells cultured alone. Among these 27 genes were 3 complement factors: Factor B (CFB), Component 3 (C3), and Component 4A (C4A). The expression of Factor H (CFH) was also significantly upregulated, but to a lesser extent (283% +/- 59%). The upregulated genes furthermore included 19 proteins mediating immune cell chemotaxis, activation, and extravasation, as well as genes involved in angiogenesis, IFNγ signal transduction, and other inflammatory markers, respectively. The T cells showed no significant differential expression of the 440 genes when cultured with or without RPE cells.
Conclusions:
This study shows that cultured RPE cells respond to inflammatory assault from activated T cells by upregulating the expression of many proinflammatory genes, including 4 complement factors. There have been many indications that inflammation in general, and complement activation in particular, play a role in the pathogenesis of age-related macular degeneration (AMD), and these results may help increase our understanding of the ethiology of AMD. These preliminary data suggest that an initial inflammatory insult to the retinal pigment epithelium (RPE) may cause the RPE itself to increase retinal inflammation, including complement activation. Thereby the RPE may add inflammatory stress to the oxidative and ischemic stress the RPE cells already face, leading to increased risk of RPE cell death.
Keywords: age-related macular degeneration • retinal pigment epithelium • inflammation