Long term therapeutic effects of icariin‐loaded <scp>PLGA</scp> microspheres in an experimental model of optic nerve ischemia via modulation of <scp>CEBP</scp> ‐β/ <scp>G‐CSF</scp> /noncanonical <scp>NF‐</scp> κ <scp>B</scp> axis
Tushar Dnyaneshwar Desai, Yao‐Tseng Wen, Jayasimha Rayalu Daddam, Felice Cheng, Chia‐Ching Chen, Chien‐Lin Pan, Keh‐Liang Lin, Rong‐Kung Tsai
Abstract
An ischemic insult at optic nerve (ON) is followed by detrimental neuroinflammation that results in progressive and long-lasting retinal ganglion cell (RGC) death and vision loss. Icariin was reported to be a safe and effective natural anti-inflammatory drug. Herein, we evaluated the long-term therapeutic effects of a single intravitreal injection of poly(lactide-co-glycolide) PLGA-icariin in a rat model of anterior ischemic optic neuropathy (rAION). Treatment with PLGA microspheres of icariin preserved the visual function and RGC density for 1 month in the rAION model. In addition, ON edema and macrophage infiltration were inhibited by treating PLGA microspheres of icariin. We found that the binding complex of icariin and CCAAT enhancer binding protein beta (CEBP-β) significantly induced endogenous granulocyte colony-stimulating factor (G-CSF) expression to activate noncanonical nuclear factor kappa B (NF-κB) signaling pathway by promoting an alternative phosphorylation reaction of IKK-β. Activation of noncanonical NF-κB signaling pathway promoted the M2 microglia/macrophage polarization and AKT1 activation, which prevented neuroinflammation and RGC apoptosis after ON infarct. This study concluded that protective mechanism of icariin is a CEBP-β/G-CSF axis-induced noncanonical NF-κB activation, which provides the long-term neuroprotective effects via anti-inflammatory and antiapoptotic actions after ON ischemia.