Effect of Lecithin-Bound Iodine Treatment on Inherited Retinal Degeneration in Mice

PURPOSE: Although lecithin-bound iodine (LBI) has been administered orally for retinal diseases, a lack of clinical studies and obscure action mechanism of LBI hinder its large-scale prescription. LBI treatment suppresses chemokine (C-C motif) ligand 2 (CCL2) secretion from retinal pigment epithelial cells in vitro. Herein, we assessed the in vivo effect of LBI treatment on retinal degeneration (RD) in mice. METHODS: Mertk(−/−)Cx3cr1(GFP/+)Ccr2(RFP/+) mice—a model for RD—demonstrate fluorescein-labeled microglia/macrophage to facilitate visualization of CX3CR1-green fluorescent protein (GFP) and CCR2-red fluorescent protein (RFP). An LBI-containing mouse diet was provided to Mertk(−/−)Cx3cr1(GFP/+)Ccr2(RFP/+) mice ad libitum from postnatal day (POD) 28. CX3CR1-GFP and CCR2-RFP expression was assessed at POD 56 using retinal sectioning and flat mounting. RD severity was assessed at POD 84. Retinal RNA was extracted from the mice of each group to measure chemokine expression. Electroretinography was performed to assess retinal function. RESULTS: CCR2-RFP expression in the retina and retinal pigment epithelial cells was suppressed by LBI treatment compared with that in the control at POD 56. The number of outer nuclear layer nuclei was higher in the group fed with LBI-containing diet than in the control mice at POD 84. Ccl2 and Ccr2 RNA expression was suppressed by LBI intake. Electroretinography showed the LBI-treated group to have a high b-wave amplitude compared with the control group. CONCLUSIONS: Suppressing CCR2-RFP–positive macrophage invasion into the retina and CCL2 and CCR2 expression is a potential mechanism underlying LBI-mediated attenuation of RD. TRANSLATIONAL RELEVANCE: Life-long LBI administration may become a candidate for treating RD.