3.3. P1A3 and P2C7 Are Internalized by Macrophages
The binding of Cy5-labeled P1A3 and P2C7 peptides, or Dil-labeled LDL (−) in BMDMs is shown in Figure 3. After 15 min of incubation, 100% of the macrophages were labeled with Cy5-P1A3 and Cy5-P2C7, whereas the Dil-LDL(-) binding was slower (Figure 3B). The median fluorescence intensity (MFI) for both peptides increased over time, with a slightly higher slope for P1A3 compared to P2C7 and LDL (−) (Figure 3C). Confocal microscopy (Figure 3D–I) indicated that both Cy5-labeled peptides were internalized by BMDMs and appeared as small intracellular droplets, whereas Dil-LDL (−) were spread throughout the cytoplasm. P1A3 endocytosis by BMDMs was inhibited by Brefeldin A, cytochalasin D, dynasore, and sodium monensin, whereas P2C7 endocytosis was inhibited by Brefeldin A, dynasore, and sodium monensin (Figure 3J–L). For both peptides, Brefeldin A provided the most significant endocytosis inhibition.