Background & Objectives Diabetic retinopathy is the most frequent cause of blindness among working-age adults in the industrialized world and, among Qataris over the age of 40 with diabetes, has a prevalence of 31.8%. Diabetic retinopathy begins when metabolic changes and alterations in vascular perfusion cause capillary leakage and closure, due to dropout of pericytes, cells that stabilizes microvessels. Annexin A2 (A2), a Ca2+- dependent phospholipid-binding protein that is expressed on endothelial cells. In the presence of S100 A10 (protein p11), A2 forms a stable heterotetramer that binds plasminogen (Plg) as well as its activator, tissue plasminogen activator (tPA) to enable tPA-dependent activation of Plg to plasmin and thus promotes angiogenesis. Thus inhibition of A2/p11 system is considered a promising therapeutic intervention in diabetic retinopathy. MicroRNAs are small (~22 nucleotide), noncoding single- strand RNAs that modulates both physiological and pathological pathways, by selectively inhibiting the expression of a set of target genes. MicroRNA target prediction programs reveal that both Annexin A2 and p11 3'-UTR region harbor distinct microRNA binding sites. However, the regulation of Annexin A2/p11 system by microRNAs remains unknown. Methods We performed microarray analysis to assess the microRNAs profile of isolated CD31+ mouse retinal endothelial cells. Second, Luciferase based assays were carried out to validate predicated microRNA binding sites using renilla Luciferase plasmid constructs containing human Annexin A2 and p11 3'UTR sequence, respectively. Moreover, Annexin A2 and p11 gene expression and protein levels were evaluated in human umbilical vein endothelial cells (HUVEC) in absence and presence of microRNA mimics or antisense-inhibitors. Results Global assessment of microRNA expression profile revealed miR-425 as the most highly expressed microRNA that is predicted to target Annexin A2. Indeed, validation of the cognate binding site confirmed that miR-425 specifically binds human Annexin A2 3'-UTR and inhibits its expression. Accordingly, ectopic expression of miR-425 significantly attenuated Annexin A2 expression in HUVEC cells. In addition, we found that human miR-767-3p as predicted specifically interacts with p11-3'UTR for inhibition. Conclusion Our current studies identified human miR-425 and miR-767-3p as two potent inhibitors of the Annexin A2/p11 system, thereby providing new insight into how Annexin A2/p11 system might be regulated at the posttranscriptional level. Further ongoing studies will elucidate the role of miR-425 and miR-767-3p and the underlying mechanism that contribute to angiogenesis in pathologic setting of diabetic retinopathy.


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