Costunolide inhibits production of tumor necrosis factor-alpha and interleukin-6 by inducing heme oxygenase-1 in RAW264.7 macrophages.

Heme oxygenase (HO)-1 expression via nuclear factor-erythroid 2-related factor 2 (Nrf2) activation has an ability to inhibit tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 production. Costunolide has been reported to inhibit IL-1 production, but whether other cytokines could be inhibited remains to be confirmed. We investigated the effects of costunolide and its components (alpha-methylene-gamma-butyrolactone; CH2-BL, alpha-methyl-gamma-butyrolactone; CH3-BL, and gamma-butyrolactone; BL) on HO-1 expression as well as TNF-alpha and IL-6 production in RAW264.7 macrophages. HO-1 expression and Nrf2 nuclear accumulation were analyzed by Western blot analysis. The production of TNF-alpha and IL-6 in RAW264.7 macrophages stimulated with lipopolysaccharide (LPS) was assayed by ELISA. Costunolide and CH2-BL induced HO-1 expression and Nrf2 nuclear accumulation, whereas CH3-BL and BL did not. Pre-incubation with costunolide inhibited LPS-induced production of TNF-alpha and IL-6. The inhibitory effects of costunolide on TNF-alpha and IL-6 production were abrogated by tin protoporphyrin, an HO inhibitor. Costunolide is an effective HO-1 inducer capable of inhibiting macrophage-derived pro-inflammatory cytokines. CH2-BL moiety of costunolide is essential for Nrf2 activation leading to HO-1 expression.