Pigment epithelial growth factor suppresses inflammation by modulating macrophage activation.
OBJECTIVE
To study the contribution of murine retinal pigment epithelial (RPE) cells to the innate immune-privilege status of the subretinal space as determined by the ability of pigment epithelial-derived factor (PEDF) and somatostatin (SOM), produced by RPE, to regulate macrophage-mediated inflammation.


METHODS
Serum-free medium was added to RPE eyecups (a healthy monolayer of RPE resting on choroid and sclera) and the supernatants were removed after 24 hours (RPE SN). The RPE SN was assayed for the presence of PEDF and SOM and for its ability to regulate interleukin (IL)-12, IL-10, and nitric oxide (NO) production by resting and activated macrophages. A group of mice received intradermal injection of lipopolysaccharide (LPS) and PEDF in one ear and LPS alone in the other ear. Ear thickness was measured before- and 24 hours after ear injections.


RESULTS
Soluble factors present in the RPE SN inhibited IL-12 production and substantially increased IL-10 while having minimal effects on NO production by activated macrophages. The message for PEDF, SOM, and IL-10 was detected in RPE cells, and the protein for these factors was found in the RPE SN. The stimulation of IL-10 and suppression of IL-12 production by RPE-SN-treated macrophages was neutralized by anti-PEDF antibodies. Neutralization of SOM in the RPE SN, suppressed NO production by activated macrophages. Intradermal injection of PEDF substantially inhibited LPS-induced inflammatory response.


CONCLUSIONS
PEDF inhibits LPS-driven macrophage activation in vitro and in vivo. By producing PEDF, the RPE contributes to innate immune privilege of the eye.
Zamiri
Parisa
P
Department of Dermatology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
Masli
Sharmila
S
Streilein
J Wayne
JW
Taylor
Andrew W
AW
D000818:Animals; D018929:Cell Culture Techniques; D004797:Enzyme-Linked Immunosorbent Assay; D005136:Eye Proteins / Q000378:metabolism / Q000494:pharmacology*; D015151:Immunoblotting; D007249:Inflammation / Q000517:prevention & control*; D016753:Interleukin-10 / Q000378:metabolism; D018664:Interleukin-12 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008262:Macrophage Activation / Q000187:drug effects*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009414:Nerve Growth Factors / Q000378:metabolism / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism; D010857:Pigment Epithelium of Eye / Q000187:drug effects* / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015843:Serpins / Q000378:metabolism / Q000494:pharmacology*; D013004:Somatostatin / Q000378:metabolism; D000099174:Pigment Epithelium-Derived Factor
D005136:Eye Proteins; D016753:Interleukin-10; D018664:Interleukin-12; D008070:Lipopolysaccharides; D009414:Nerve Growth Factors; D009569:Nitric Oxide; D011994:Recombinant Proteins; D015843:Serpins; D013004:Somatostatin; D000099174:Pigment Epithelium-Derived Factor