[A study of different intracellular signal transduction pathways on phagocytosis of fibronectin by retinal pigment epithelial cells].
OBJECTIVE
To determine the phagocytosis of fibronectin (FN) by retinal pigment epithelial (RPE) cells and its related intracellular signal transduction pathways.


METHODS
Fluorescent latex beads were coated by FN and then incubated with RPE cells at 37C for 3 hours. Phagocytosis was quantified by a flow cytometric assay. Experiments were also performed in the presence of inhibitors of various intracellular signaling pathways [tyrosine kinase (TK), phosphatidylinositol 3-kinase (PI 3-K), protein kinase C (PKC)].


RESULTS
FN-coated beads produced significantly increase in the phagocytic index (P < 0.05) when compared to the uncoated control. The PKC inhibitors, phorbol 12-myristate 13-acetate (PMA, 100 nmol/L) or calphostin C (400 nmol/L), non-specifically increased the phagocytosis of both FN-coated (P < 0.01) and uncoated beads (P < 0.01). Inhibitors of TK (genistein, 100 microgram/ml) and PI 3-K (wortmannin, 5 micromol/L), significantly inhibited FN phagocytosis (P < 0.001) but did not affect the uncoated control. While a combination of different inhibitors (genistein plus wortmannin, genistein plus PMA, wortmannin plus PMA) was used, the results showed that genistein or wortmannin can counteract the effect of PMA, and that genistein plus wortmannin have an additive inhibitory effect.


CONCLUSIONS
Our results suggest that the FN phagocytosis by RPE cells appear to be regulated, at least in part, by some signal transduction pathways. The knowledge of the signaling pathways that mediate FN phagocytosis by RPE cells may provide novel therapeutic targets for molecular pharmacology of proliferative RPE disorders such as proliferative vitreoretinopathy.
Zhao
M
M
Department of Ophthalmology, People's Hospital, Beijing Medical University, Beijing 100044, China.
He
S
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Li
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D000730:Androstadienes / Q000494:pharmacology; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005333:Fetus; D005353:Fibronectins / Q000378:metabolism*; D019833:Genistein / Q000494:pharmacology; D006801:Humans; D009281:Naphthalenes / Q000494:pharmacology; D010587:Phagocytosis; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D012160:Retina; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D000077191:Wortmannin
D000730:Androstadienes; D004791:Enzyme Inhibitors; D005353:Fibronectins; D009281:Naphthalenes; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; C058819:calphostin C; D013755:Tetradecanoylphorbol Acetate; D000077191:Wortmannin