In vitro anti-inflammatory effect of picrasmalignan A by the inhibition of iNOS and COX-2 expression in LPS-activated macrophage RAW 264.7 cells

Abstract

Picrasma quassioides (P. quassioides) has been widely used as a traditional Chinese medicine for clearing fever and detoxification. Previous phytochemical studies have identified a novel dihydrobenzofuran-type neolignan, picrasmalignan A, isolated from the stems of P. quassioides. In the present study, the in vitro anti-inflammatory effects and molecular mechanisms of picrasmalignan A have been investigated in cultured RAW 264.7 cells, a mouse macrophage-like cell line. A Griess assay was used to demonstrate the inhibitory effect of picrasmalignan A on the overproduction of nitric oxide (NO). An enzyme-linked immunosorbent assay was used to determine the levels of pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). The inhibitory effect on the enzymatic activity of cyclooxygenase 2 (COX-2) and inducible nitric oxide synthase (iNOS) was observed by colorimetric and fluorimetric assays, respectively. Western blotting was conducted to detect the expression of iNOS and COX-2. Results showed that picrasmalignan A suppressed lipopolysaccharide-stimulated NO production and pro-inflammatory cytokine secretion, including TNF-α and IL-6, in a dose-dependent manner. It also significantly inhibited the expression and enzymatic activity of iNOS and COX-2. These results may demonstrate the anti-inflammatory mechanism of picrasmalignan A.