Brassinin, a brassica-derived phytochemical, regulates monocyte-to-macrophage differentiation and inflammatory responses in human monocytes and murine macrophages.

OBJECTIVES: The effects and molecular mechanisms of brassinin (BR), an indole phytoalexin from cruciferous vegetables, on monocyte-to-macrophage differentiation and inflammatory responses were investigated in this study. METHODS: Inflammatory responses from RAW264.7 cells and THP-1 were stimulated by lipopolysaccharide (1 µg/ml), and monocyte-to-macrophage differentiation of THP-1 was induced by phorbol myristate acetate (50 ng/ml). The production of inflammatory mediators was determined by ELISA, Western blot or real-time PCR. Reactive oxygen species were examined by DCFH-DA assay. KEY FINDINGS: Brassinin at 50 µm suppressed lipopolysaccharide-induced production of nitric oxide synthase, cyclooxygenase-2, prostaglandin E2 and reactive oxygen species by 90%, 69%, 52% and 41%, respectively, in RAW264.7 cells. In THP-1 cells, BR inhibited phorbol myristate acetate-induced monocyte-to-macrophage differentiation by suppressing cluster of differentiation molecule ß and CD36. In addition, BR suppressed translocation of nuclear factor 'kappa-light-chain-enhancer' of activated B cells (NF-κB) into the nucleus. However, BR activated the nuclear factor erythroid-derived 2-like 2 (Nrf2) and its target molecules hemoxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO1), with an increase in nuclear translocation of Nrf2. CONCLUSIONS: Brassinin suppressed monocyte-to-macrophage differentiation and inflammatory responses by differentially regulating Nrf2 and NF-κB signallings.

Brassinin, a phytoalexin in cruciferous vegetables, suppresses obesity-induced inflammatory responses through the Nrf2-HO-1 signaling pathway in an adipocyte-macrophage co-culture system.

The aim of this study was to investigate the effect of brassinin (BR), a phytoalexin found in plants belonging to the Brassicaceae family, on the obesity-induced inflammatory response and its molecular mechanism in co-culture of 3T3-L1 adipocytes and RAW264.7 macrophages. BR effectively suppressed lipid accumulation by down-regulating the expression of adipogenic factors, which in turn, were regulated by early adipogenic factors such as CCAAT-enhancer-binding protein-ß and Kruppel-like factor 2. Production of inflammatory cytokines and reactive oxygen species, induced by adipocyte-conditioned medium, was significantly decreased in BR-treated cells. This effect of BR was more prominent in contact co-culture of adipocytes and macrophages with a 90% and 34% reduction in IL-6 and MCP-1 levels, respectively. BR also restored adiponectin expression, which was significantly reduced by culturing adipocytes in macrophage-conditioned medium. In the transwell system, BR increased the protein levels of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and its target molecule, hemoxygenase-1 (HO-1), by 55%-93% and 45%-48%, respectively, and also increased Nrf2 translocation into the nucleus. However, knockdown of Nrf2 or HO-1 in RAW264.7 cells restored this BR-mediated inhibition of IL-6 and MCP-1 production. These results indicated that BR inhibited obesity-induced inflammation via the Nrf2-HO-1 pathway.