The PKCβ/HuR/VEGF pathway in diabetic retinopathy

We investigated whether the diabetes-related PKC beta activation affects VEGF expression through the mRNA-stabilizing human embryonic lethal abnormal vision (ELAV) protein, HuR, in the retina of streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in rats by STZ injection. Retinal tissues were processed to detect PKC beta I, PKC beta II, VEGF and HuR contents, as well as HuR phosphorylation. Immunoprecipitation coupled to RT-PCR was employed to evaluate HuR binding to VEGF mRNA in RiboNucleoProteic (RNP) complexes. Statistical analysis was performed by ANOVA followed by an appropriate post hoc comparison test. Following experimental diabetes PKC beta I and PKC beta II levels were increased compared to sham; there was also a PKC-mediated phosphorylation/activation of HuR. These effects were blunted by the in vivo co-administration of a selective PKC beta inhibitor. A specific binding between the HuR protein and the VEGF mRNA was also detected. The PKC beta/HuR activation was accompanied by enhanced VEGF protein expression that was, again, blunted by the PKC beta inhibitor. These findings first demonstrate the activation, in the retina, of the PKC beta/HuR/VEGF pathway following experimental diabetes and disclose a new potential pharmacological target to counteract pathologies implicating VEGF deregulation, such as diabetic retinopathy. (C) 2010 Elsevier Inc. All rights reserved.