Inhibition of inducible nitric oxide synthase and cyclooxygenase-2 activity by 1,2,3,4,6-Penta-O-galloyl-β-D-glucose in murine macrophage cells

Abstract

Activated macrophages express inducible isoforms of nitric oxide synthase (iNOS) and cyclooxygenase (COX-2), and produce excessive amounts of nitric oxide (NO) and prostaglandin E₂ (PGE₂), which play key roles in the processes of inflammation and carcinogenesis. The root ofPaeonia lactiflora Pall., and the root cortex ofPaeonia suffruticosa Andr., are important Chinese crude drugs used in many traditional prescriptions. 1,2,3,4,6-penta-O-galloyl-β-D-glu-cose (PGG) is a major bioactive constituent of both crude drugs. PGG has been shown to possess potent anti-oxidant, anti-mutagenic, anti-proliferative and anti-invasive effects. In this study, we examined the inhibitory effects of 1,2,3,4,6-penta-O-galloyl-β-D-glucose (PGG) isolated from the root ofPaeonia lactiflora Pall, on the COX-2 and iNOS activity in LPS-activated Raw 264.7 cells, COX-1 in HEL cells. To investigate the structure-activity relationships of gal-late and gallic acid for the inhibition of iNOS and COX-2 activity, we also examined (-)-epigal-locatechin gallate (EGCG), gallic acid, and gallacetophenone. The results of the present study indicated that PGG, EGCG, and gallacetophenone treatment except gallic acid significantly inhibited LPS-induced NO production in LPS-activated macrophages. All of the four compounds significantly inhibited COX-2 activity in LPS-activated macrophages. Among the four compounds examined, PGG revealed the most potent in both iNOS (IC₅₀ ≈ 18 μg/mL) and COX-2 inhibitory activity (PGE₂: IC₅₀ ≈ 8 μg/mL and PGD₂: IC₅₀ ≈ 12 μg/mL), respectively. Although further studies are needed to elucidate the molecular mechanisms and structure-activity relationship by which PGG exerts its inhibitory actions, our results suggest that PGG might be a candidate for developing anti-inflammatory and cancer chemopreventive agents.