p75 neurotrophin receptor participates in the choroidal antiangiogenic and apoptotic effects of T-lymphocyte-derived microparticles.
OBJECTIVE
Choroidal neovascularization (CNV) is a major cause of vision loss in which choroidal vessels penetrate the RPE-an important source of growth factors, including nerve growth factor (NGF), whose activation via the p75NTR receptor promotes apoptosis and inhibits angiogenesis. We demonstrated previously that human T-lymphocyte-derived microparticles (LMPs) significantly inhibit angiogenesis in several models of ocular neovascularization. We investigated how LMPs modulate pro- and antiangiogenic microenvironments during choroidal angiogenesis.


METHODS
Antiangiogenic effects of LMPs were investigated using a rat model of choroidal angiogenesis. The impact of LMPs on expression of major angiogenic factors was assessed by real-time quantitative PCR (qPCR). To determine whether p75NTR signalling was implicated in LMPs-induced activities, we used a specific antibody and short hairpin RNA (shRNA) targeting p75NTR. Cellular apoptosis was determined via evaluation of activated caspase-3 and annexin V binding.


RESULTS
The LMPs time-dependently inhibited choroidal angiogenesis by more than 64% after 48 hours of treatment. Removal of the RPE from choroidal explants abolished the antiangiogenic effects of LMPs. The mRNA levels of pigment epithelium-derived factor (PEDF) and NGF were increased significantly following LMPs treatment of intact, but not RPE-removed choroids. Downregulation of PEDF and p75NTR significantly blocked the antiangiogenic effects of LMPs. Finally, induction of choroidal endothelial cell apoptosis by LMPs was dependent on p75NTR.


CONCLUSIONS
We demonstrate for the first time to our knowledge that LMPs markedly inhibit choroidal angiogenesis via mechanisms that are dependent on the integrity of the RPE, and that are mediated largely by the PEDF and proapoptotic activities of p75NTR.
Department of Pharmacology, Faculty of Medicine, Université de Montréal, Montréal, Quebec, Canada.
Houda
H
Tahiri
Chun
C
Yang
François
F
Duhamel
Samy
S
Omri
Emilie
E
Picard
Sylvain
S
Chemtob
Pierre
P
Hardy
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D002478:Cells, Cultured; D020256:Choroidal Neovascularization / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D018507:Gene Expression Regulation, Developmental; D009419:Nerve Tissue Proteins; D012313:RNA / Q000235:genetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D017978:Receptors, Growth Factor; D017475:Receptors, Nerve Growth Factor / Q000096:biosynthesis / Q000235:genetics*; D013601:T-Lymphocytes / Q000378:metabolism*
D009419:Nerve Tissue Proteins; D017978:Receptors, Growth Factor; D017475:Receptors, Nerve Growth Factor; C068313:Ngfr protein, rat; D012313:RNA
PEDF; choroidal neovascularization; lymphocytic microparticles; neurotrophins; p75NTR