gms | German Medical Science

Background: Enhanced complement activation may support pathologic processes underlying AMD. Further, retinal pigment epithelial (RPE)-cells are impaired. Therefore the effects of fully activated complement and isolated C5a on RPE cells were examined in this study.

Methods: Confluent ARPE-19 cells as model for RPE were incubated with increasing concentrations of human complement serum (HCS) or recombinant C5a. C5b-9 as terminal complement complex was stained by immunocytochemistry. Development of reactive oxygen species (ROS) was determined by a nitroblue tetrazolium assay. ELISA was used to quantify vascular endothelial growth factor (VEGF) in cell culture supernatants. Experiments were also performed with polarised cells grown on transwell inserts.

Results: Strong staining for C5b-9 was detected after low amounts of HCS but was not observed in C5a-treated cells. Incubation with HCS clearly increased the amount of ROS while C5a caused only a small rise. C5a only induced minor changes in the VEGF production whereas HCS generated a strong increase. VEGF was mainly secreted towards the basal side. The effects of HCS were seen after 24 hours, prolonged time of incubation could not provoke stronger changes due to C5a.

Conclusions: C5a was previously reported to enhance the cytokine secretion of subconfluent ARPE-19 cells. In this study ARPE-19 cells appear to be relatively resistant against C5a while HCS induced clear effects. The effect of C5a may also be more transient. For new therapeutic interventions in AMD the inhibition of the complete complement cascade may be more efficient than the inhibition of single emerging components.