Inhibition of Emodin on LPS-induced Nitric Oxide Generation by Suppressing PLC-γ Phosphorylation in Rat Peritoneal Macrophages

Objective To investigate the inhibitory mechanism of emodin on lipopolysaccharide (LPS)-induced nitric oxide (NO) generation in rat peritoneal macrophages. Methods NO production and iNOS expression were measured through nitrite assay and Western blotting assay, respectively. NF-κB activity and nuclei P65 expression were estimated by dual-luciferase and Western blotting assay, respectively. Intracellular free Ca2+ ([Ca2+]i) was detected using the ratiometric fluorescent calcium indicator dye, Fura-2, and a microspectrofluorometer. PLC-γ phosporylation was analyzed by Western blotting assay. Results First, emodin was found playing active roles in suppressing LPS-induced NF-κB activation in rat peritoneal macrophages. Second, emodin down-regulated transient [Ca2+]i and could increase in NF-κB upstream signal. Finally, emodin suppressed phosphorylation of PLC-γ by LPS stimulation in the upstream of [Ca2+]i. Conclusion Suppression of PLC-γ phosphorylation is involved in emodin inhibiting NO generation by LPS stimulation in rat peritoneal macrophages.