Inhibition of Nitric Oxide Production by Ethyl Digallates Isolated from Gal la Rhois in RAW 264.7 Macrophages

Galla Rhois and its components are known to possess anti-inflammatory properties. In the present study, we prepared equilibrium mixture of ethyl m-digallate and ethyl p-digallate isomers (EDG) from Galla Rhois and examined its effect on nitric oxide (NO) production in murine macrophage cell line. Treatment of RAW264.7 macrophages with EDG significantly inhibited NO production and inducible nitric oxide synthase (iNOS) expression stimulated by LPS, as assessed by Western blot and quantitative RTPCR analyses. We also demonstrated that EDG treatment led to an increase in heme oxygenase-1 (H0-1) mRNA and protein expression. EDG treatment also enhanced expression level of nuclear factor-erythroid 2-related factor 2 (Nrf2) in nucleus, which is critical for transcriptional induction of HO-1. Treatment with SnPP (tin protoporphyrin IX), a selective HO-1 inhibitor, reversed EDG-mediated inhibition of nitrite production, suggesting that HO-1 plays an important role in the suppression of NO production by EDG. Taken together, these results indicate that EDG isolated from Galla Rhois suppresses LPS-stimulated NO production in RAW 264,7 macrophages via HO-1 induction.