Anti-inflammatory effect of Ruta graveolens L. in murine macrophage cells

Ruta graveolens L. (Rutaceae) is used for several therapeutic purposes worldwide. The present study is designed to investigate the effect of plant extract of Ruta graveolens on murine macrophage cells (J-774) challenged with lipopolysaccharide (LPS). LPS induces inflammatory response by stimulating the production of nitric oxide and other mediators. Significant inhibition (p=0.01 to p<0.002) of the LPS-induced nitric oxide production was observed in cells treated with plant extract in a concentration dependent manner. The inhibition observed for the extract was significantly higher than that observed for rutin, a flavonoid constituent of the plant. At 40 microM rutin, a comparable concentration of this flavonoid in the highest concentration (500 microg/ml) of plant extract was used in this study; a 20% inhibition (p=0.058) was observed. Inhibition in inducible nitric oxide synthase (inos) gene expression in the cells treated with the plant extract suggests an inhibition at the transcription level. Interestingly, a concomitant decrease in transcription of cyclooxygenase-2 (COX-2) gene has also been observed in cells treated with the plant extract and this inhibition is significantly higher than that observed with the highest concentration of rutin (80 microM) used in the study. As an inflammatory response, upregulation of nitric oxide synthase (iNOS) and COX-2 enzymes leads to production of pro-inflammatory mediators, namely nitric oxide and prostaglandins, respectively. Hence, the significant inhibitory effects on both of these inflammatory mediators unravel a novel anti-inflammatory action of this plant.