Specific involvement of SRC family kinase activation in the pathogenesis of retinal neovascularization.
OBJECTIVE
Src family kinases (SFKs) are membrane-attached nonreceptor protein tyrosine kinases that link a variety of extracellular cues to intracellular signal pathways. The purpose of this study was to characterize the roles of SFKs in vascular endothelial growth factor (VEGF)-mediated retinal angiogenesis.


METHODS
Primary rat retinal glial Müller cells and bovine and human retinal microvascular endothelial cells (RMECs) were used in the in vitro studies. A rat model of retinopathy of prematurity (ROP) was used in the in vivo studies.


RESULTS
In vitro, SFKs were essential for hypoxia-induced VEGF expression in Müller cells and for VEGF signaling in RMECs. However, neither process required significant further phosphorylation of the SFK activation loop Tyr416. In vivo, in a rat model of ROP, a pronounced increase of retinal SFK Tyr416 phosphorylation was observed that was specifically associated with pathologic angiogenesis. These retinas also expressed significantly higher levels of VEGF than did those in healthy controls. Immunohistochemical analysis indicated that Müller cells were the major source of the elevated level of phospho-SFK Tyr416. Intravitreous injection of a selective SFK inhibitor, PP2, significantly reduced retinal VEGF and retinopathy in the ROP model, indicating that SFKs acted as important regulators in abnormal retinal angiogenesis.


CONCLUSIONS
Together, these data suggest that SFK activation through a Tyr416-dependent mechanism may be an important factor in the pathogenesis of retinal neovascularization.
Werdich
Xiang Q
XQ
Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, 8000 Medical Center East, Nashville, TN 37232, USA.
Penn
John S
JS
D000818:Animals; D015153:Blotting, Western; D002417:Cattle; D018929:Cell Culture Techniques; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000201:enzymology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D047468:Immunoprecipitation; D007231:Infant, Newborn; D009457:Neuroglia / Q000201:enzymology; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D020318:Rats, Long-Evans; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000494:pharmacology; D015861:Retinal Neovascularization / Q000139:chemically induced / Q000201:enzymology*; D012171:Retinal Vessels / Q000166:cytology; D012178:Retinopathy of Prematurity / Q000139:chemically induced / Q000201:enzymology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism / Q000494:pharmacology; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*
D004791:Enzyme Inhibitors; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C467498:vascular endothelial growth factor A, rat; D019061:src-Family Kinases