Inhibitory effect of curcumin on inflammatory responses induced by LPS in human retinal pigment epithelial cells

Abstract:

Objective：To explore the inhibitory effect of curcumin on inflammatory responses induced by lipopolysaccharide （LPS） in retinal pigment epithelial（RPE） cells. Methods：ARPE-19 cells were cultured in vitro. Before being stimulated with or without LPS （5 μg/mL），ARPE-19 cells were pre-incubated with different concentrations of curcumin（5，10，20，30，40 ?滋mol/L）. The optimum con－centration of curcumin was detected by CCK-8 assay. The mRNA level of IL-6 and IL-8 was measured by real-time polymerase chain reaction（RT-PCR） and their protein expression was detected by enzyme-linked immunosorbent assay（ELISA）. Protein expres－sion levels of IκB-α and p-IκB-α were examined by Western blot. Results：The CCK-8 results showed that the activities of ARPE-19 cells were not affected by different concentrations of curcumin（P5 ?滋mol/L=0.998，P10 ?滋mol/L=1.000，P20 ?滋mol/L=0.124，P30 ?滋mol/L=0.092，P40 ?滋mol/L=0.078）. Curcumin was indicated to be able to protect ARPE-19 cells since pre-treatment with different concentrations of curcumin following by LPS administration. This protection resulted with a maximal protective effect at 20 μmol/L（P=0.041）. The RT-PCR results indicated that the relative mRNA level of IL-8 in curcumin+LPS group（4.965±3.863） was significantly lower than that in LPS group（106.331±37.314）（P=0.000） and the relative mRNA level of IL-6 in curcumin+LPS group（0.992±0.374） was significantly lower than that in LPS group（2.175±0.560）（P=0.005）. The ELISA results showed that protein expression of IL-8 in curcumin+LPS group[（191.600±18.773） pg/mL] was significantly lower than that in LPS group[（589.025±38.880） pg/mL]（P=0.000） and protein expression of IL-6 in curcumin+LPS group[（113.906±27.947） pg/mL] was significantly lower than that in LPS group[（243.380±38.001）pg/mL]（P=0.000）. Meanwhile，the Western blot results indicated that pre-treatment with curcumin inhibit－ed the phosphorylation of IκB-α（P=0.001） mediated by LPS stimulation. Conclusion：Curcumin inhibits the inflammatory responses induced by LPS via suppression NF-κB activity and protects retinal pigment epithelial cells.