Induction of Nrf2-mediated genes by Antrodia salmonea inhibits ROS generation and inflammatory effects in lipopolysaccharide-stimulated RAW264.7 macrophages
Antrodia salmonea (AS), a well-known medicinal mushroom in Taiwan, has been reported to exhibit anti-oxidant, anti-angiogenic, anti-atherogenic, and anti-inflammatory effects. In the present study, we investigated the activation of Nrf2-mediated antioxidant genes in RAW264.7 macrophages by the fermented culture broth of AS, studied the resulting protection against lipopolysaccharide (LPS)-stimulated inflammation, and revealed the molecular mechanisms underlying these protective effects. We found that non-cytotoxic concentrations of AS (25–100 μg mL−1) protected macrophages from LPS-induced cell death and ROS generation in a dose-dependent manner. The antioxidant potential of AS was directly correlated with the increased expression of the antioxidant genes HO-1, NQO-1, and γ-GCLC, as well as the level of intracellular GSH followed by an increase in the nuclear translocation and transcriptional activation of the Nrf2–ARE pathway. Furthermore, Nrf2 knockdown diminished the protective effects of AS, as evidenced by the increased production of pro-inflammatory cytokines and chemokines, including PGE2, NO, TNF-α, and IL-1β, in LPS-stimulated macrophages. Notably, AS treatment significantly inhibited LPS-induced ICAM-1 expression in macrophages. Our data suggest that the anti-inflammatory potential of Antrodia salmonea is mediated by the activation of Nrf2-dependent antioxidant defense mechanisms. Results support the traditional usage of this beneficial mushroom for the treatment of free radical-related diseases and inflammation.