Abstract
Purpose: :
We demonstrated that within the healthy retina macrophages/microglial cells (MØ) express the characteristics of suppressor macrophages (sMØ). Also, we found that the neuropeptides -melanocyte stimulating hormone (-MSH) and neuropeptide Y (NPY) in the conditioned media (CM) of retinal pigmented epithelial (RPE) eyecups mediate the induction of suppressor functionality in MØ. Therefore we assayed the role of -MSH and NPY in RPE induction of sMØ.
Methods: :
RPE eyecups were made from healthy eyes of wild type C57BL/6, retinal laser-burned C57BL/6, and POMC knocked-out mice, and were cultured for 24 hours. Their CM were collected and used in the experiments. Primary MØ from a peritoneal lavage were cultured with the CM, CM absorbed of -MSH and/or NPY, or were treated with -MSH and/or NPY both at 1 ng/ml. The treated MØ were assayed by fluorescent-staining for the expression of Arginase1, NOS2, and for TUNEL. The concentration of -MSH and NPY in the CM of healthy and laser-burned eyecups was assayed by ELISA.
Results: :
Two different types of MØ (Arginase1+ or NOS2+) were seen when the MØ were treated with RPE CM from laser-burned eyes, POMC-knocked mice, or CM of healthy RPE eyecups with -MSH or NPY absorbed. The MØ treated with NPY had enhanced NOS2 expression, and enhanced NOS2 expression when treated with -MSH. Only when treated with the combination of -MSH and NPY did we see expression of sMØ characteristics and functionality. In addition, we found that the MØ went into apoptosis if they were treated with CM from laser-burn and POMC knocked-out mice RPE eyecups, which were diminished or devoid of -MSH. We prevented apoptosis by adding -MSH back into these CM.
Keywords: immune tolerance/privilege • immunomodulation/immunoregulation • microglia