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Ahmed Elsherbini, Sadanand Fulzele, Saif Ahmad, Rajini Sangani, Suraporn Matragoon, Azza B El-Remessy, Gregory Liou; The micro-RNA miR-146b-3p controls diabetic retinal inflammation by suppressing adenosine deaminase-2. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1046.
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In Diabetic retinopathy (DR), activated retinal microglia and infiltrated monocytes contribute to retinal inflammation that causes losses of blood-retinal barrier function and retinal neurons. Because tissue damage can become irreversible by the time these losses become demonstrable, early detection and intervention of DR is greatly needed. We aim to identify an event that can detect DR during its early stage.
A microwave oven-based technique for immunohistochemisrty staining of fixed tissues was used to doubly label human eye sections with antibodies. The ADA2 assay is based on the enzymatic deamination of adenosine to inosine at pH6 in the presence of ADA1-specific inhibitor. The human monocyte cell line U937 is cultured in ATCC-formulated RPMI-1640 Medium and conditions. Cells were differentiated into macrophages and transfected using a Nucleofector electroporation system.
ADA2 gene is up-regulated in the activated microglia or monocytes in the diabetic retina. ADA2 expression is inversely correlated with miR-146b-3p in diabetes. Ectopic expression of miR-146b-3p reduces ADA2 expression through a direct interaction between each other during macrophage activation. Using a Secrete-Pair Dual Luminescence assay system, The results suggest that miR-146b-3p suppresses ADA2 expression by binding to the 3′-UTR, and that ADA2 is a direct target of miR-146b-3p. MiR-146b-3p gene expression is promoted by pro-inflammatory cytokines. This suggests that miR-146b-3p negatively regulates ADA2 as a feedback mechanism to prevent further inflammation.
We have demonstrated that ADA2 has a causal role in microglial activation and retinal inflammation in early diabetes. Because increased adenosine production and ADA2 activity occur at specific pathological sites, inhibition of ADA2 activity may represent a mechanism to selectively enhance the actions of adenosine at specific tissue sites. Inhibition of ADA2 is, therefore, potentially with limited side-effects, and is of highly translational impact.
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