BDNF increases the phagocytic activity in cultured iris pigment epithelial cells

To investigate the effect of brain derived neurotrophic factor (BDNF) on the phagocytic activity in iris pigment epithelial (IPE) cells, purified porcine photoreceptor outer segments (POS) were applied to cultured IPE cells for three hours. To measure phagocytic activities, bound and total POS were differentially stained using a double immunofluorescence staining method. BDNF increased the binding of POS in IPE cells in a dose-dependent manner. Ingestion of POS, however, was not affected throughout the concentrations used in this study. To investigate the signal transduction pathways of BDNF, a phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002, and MAPK/ERK kinase (MEK) inhibitor, PD98059, were used for this study. LY294002 had no effect on the binding and ingestion of POS in BDNF-treated IPE cells. On the other hand, PD98059 completely inhibited the increase of POS binding in BDNF-treated cells and also decreased the ingestion of POS. These results indicate that increased POS binding activity by BDNF and the decreased ingestion of POS were mediated through the MAPK pathway.