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Congxiao Zhang, Arvydas Maminishkis, Tina Banzon, Sheldon Miller; Pro-Inflammatory Cytokine Mixture Selectively Elevates miR-155 and Modulates RPE Physiology. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1184.
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It has been shown that miR-155 plays a critical role in the regulation of inflammation in several disease conditions, for example in cancer, cystic fibrosis, and arthritis. miR-155 is particularly important in mediating innate immune responses and, as with all microRNAs, exhibits distinct functions in distinct cells. It is therefore of interest in RPE whose polarized secretion of cytokines is likely to be important in retinal degenerative diseases. As a first step, we sought to understand how miR-155 might regulate human fetal RPE (hfRPE) physiology.
A fully-differentiated monolayer of cultured hfRPE cells was used as previously described. A pro-inflammatory cytokine mixture (ICM) that contains TNF-alpha, IL-1beta and IFN-gamma was added to the control Ringer bathing either the apical or basolateral membranes of hfRPE. The relative levels of miRNA were quantified by qRT-PCR using TaqMan® microRNA assay. Oligonucleotide of either miR-155 mimic or inhibitor was transfected using Dharmafect 4 reagents. A modified Üssing chamber with capacitance probes was used to measure steady-state fluid transport (Jν) across RPE. Concomitantly, transepithelial potential (TEP) and total tissue resistance (TER) were measured to asses transport capacity and monolayer integrity.
Using confluent monolayers, ICM was added to the Ringer bathing either the apical or basolateral membranes. Out of 13,000 confirmed or putative miRNAs, ICM significantly increased only two human miRNAs - hsa miR-155 and miR-146a. At 24 hrs, the level of ICM - induced increase in miR-155 was significantly greater than that of miR-146a. Of the two microRNAs, only miR-155 mimic lowers TER. Anti-miR-155 partially reversed the ICM-induced TER decrease. miR-155 mimic increased fluid absorption (Jν). The induced Jν increase is abrogated by anti-miR-155. CFTR inhibitors block the miR-155 mimic induced Jν increase, indicating a role for CFTR in miR-155 mediated Jν increase.
miR-155 modulates inflammatory signals that regulate CFTR-mediated fluid absorption across the hfRPE. This finding suggests that in situ, miR-155 and its targets may serve to modulate cytokine activity in the subretinal space or the choroid.
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