Figure 4. Effects of berberine (BBR) on nuclear factor kappa B (NF-κB) signaling pathway activation were shown. Human retinal endothelial cells (HRECs) were pretreated with 5, 25, or 50 μM berberine for 12 h before being exposed to high glucose for 24 h. A: Representative results of western blot were shown. Berberine inhibited high-glucose-induced (B) accumulation of nuclear factor kappa B (NF-κB) p65 expression in the nucleus and (C) increased p65 expression in the cytoplasm. D–E: Berberine inhibited high-glucose-induced phosphorylation of a key enzyme involved in activation of NF-κB (nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha; IκB-α) and the degradation of IκB-α, resulting in (F) a significant effect on the p-IκB-α/IκB-α ratio. The results are representative of three independent experiments, and are summarized graphically in B–F. The density of each band was measured and compared to that of the internal control, β–actin. * indicates a significant difference (p<0.05) in band density between low- and high-glucose-treated cells; ^† indicates a significant difference (p<0.05) in band density between berberine-treated and non-treated cells cultured in high glucose.