Activation of protein tyrosine phosphorylation after retinal branch vein occlusion in cats

Purpose. The authors examine the effect of retinal branch vein occlusion (BVO), a common retinal vascular disorder, on protein tyrosine phosphorylation, production of angiogenic growth factors, and activation of signal proteins in the tyrosine kinase pathways in the retina. Methods. Retinal branch vein occlusion was induced in cat retina by coagulation of retinal veins with diathermy. At 2 days, 1, 3, and 6 weeks after induction of BVO, the retina was divided into three parts: a part within the distribution of the occluded vein (BVO[IN]) or a part outside the distribution of the occluded vein (BVO [OUT]). Each part of the retina was prepared for Western blot analysis of tyrosine-phosphorylated proteins, vascular endothelial growth factor clot (VEGF), basic fibroblast growth factor (bFGF), and four signal proteins in the tyrosine kinase pathways, which were phospholipase Cγ (PLCγ), C-Src, SH2-containing protein (SHC), and mitogen-activated protein kinase (MAPK). Results. Overall, tyrosine-phosphorylated proteins were increased after BVO, especially in BVO(IN) at 2 days and 1 week. The VEGF and bFGF also were increased in BVO(IN) at 1 week and 2 days, respectively. The PLCγ and MAPK were activated at these time points. The C-Src and SHC were not activated in the retina after BVO. Conclusions. The BVO increased overall protein tyrosine phosphorylation in the cat retina in association with increase of angiogenic growth factors (VEGF and bFGF) and activation of two signal proteins (PLCγ and MAPK) in the tyrosine kinase pathways. These results suggest that the protein tyrosine phosphorylation may in part play an important role in mitogenesis of vascular endothelial cells and other retinal responses after BVO.