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F. Drago, C. Bucolo, A. Pascale, M. L. Amadio; PKCβII/HuR/VEGF Cascade in Experimental Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2009;50(13):80.
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The existence of PKCβII/HuR/VEGF molecular cascade operating in retinal bovine pericytes has been demonstrated in our lab (Amadio et al., Pharmacol. Res. 2008). We investigated whether PKCβII could control VEGF levels via the mRNA stabilizing human embryonic lethal abnormal vision (ELAV)-like protein, HuR, in retina of streptozotocin(STZ)-induced diabetic rat.
Retinal tissues, collected after 10 days from STZ-injected rats, were processed for western blotting and preparation of mRNP (ribonucleoproteic complexes). Anti-PKCβI mouse monoclonal antibody, anti-PKCβII rabbit polyclonal antibody, anti-HuR mouse monoclonal antibody, anti-VEGF rabbit polyclonal antibody and anti--tubulin rat monoclonal antibody were used for western blot analysis. Samples were processed for immunoprecipitation using anti-HuR antibody, and VEGF mRNA was detected by real-time quantitative PCR. Statistical analysis was performed by ANOVA by and an appropriate post hoc comparison test using GraphPad (San Diego, CA).
PKCβI and PKCβII were increased in the retina of STZ injected rats compared to sham (+160% +113%, respectively). We showed a PKC-mediated phosphorylation of HuR in the retina from diabetic rats. HuR protein levels increased in STZ-treated rats (+62% vs. sham), and this was accompanied by an higher phosphorylation in serine residues (+209% vs. sham). These effects were blunted by selective PKCβ inhibitor treatment. A specific binding between HuR protein and VEGF mRNA in the retina was shown. We also demontrated that the PKCβ/HuR activation is accompanied by enhanced VEGF protein expression VEGF protein content significantly increased in STZ-rats (+256% vs. sham), and this effect was attenuated by PKCβ inhibitor.
These findings demonstrated the existence of PKC/HuR/VEGF pathway in experimental diabetic retinopathy. A better dissection of this cascade in diabetic conditions may help to disclose new potential pharmacological targets useful to counteract the development and progression of diabetic retinopathy and offer novel clues to study other pathologies implicating VEGF.
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