Neuroprotective Activity of Icariin Against Hypoxic-ischemic Brain Injury in Neonatal Rats

Effect of icariin in a rat model of colchicine-induced cognitive deficit: role of βamyloid proteolytic enzymes

ABSTRACTThe deposition of β-amyloid plaques, either due to their over-production or insufficient clearance, is an important pathological process in cognitive impairment and dementia. Icariin (ICA), a flavonoid compound extracted from Epimedium, has recently gained attention for numerous age-related diseases, such as neurodegenerative diseases. We aimed to explore the possible neuro-protective effect of ICA supplementation in colchicine-induced cognitive deficit rat model and exploring its effect on the β-amyloid proteolytic enzymes. The study included four groups (10 rats each): normal control, untreated colchicine, colchicine + 10 mg/kg ICA, and colchicine + 30 mg/ kg ICA. Results revealed that intra-cerebro-ventricular colchicine injection produced neuronal morphological damage, β amyloid deposition, and evident cognitive impairment in the behavioral assessment. Icariin supplementation in the two doses for 21 days attenuated neuronal death, reduced the β amyloid levels, and improved memory consolidation. This was associated with modulation of the proteolytic enzymes (Neprilysin, Matrix Metalloproteinase-2, and insulin-degrading enzyme) concluding that β-amyloid enzymatic degradation may be the possible therapeutic target for ICA.

Long term therapeutic effects of icariin‐loaded PLGA microspheres in an experimental model of optic nerve ischemia via modulation of CEBP ‐β/ G‐CSF /noncanonical NF‐ κ B axis

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.