Nardosinanone N suppresses LPS-induced macrophage activation by modulating the Nrf2 pathway and mPGES-1

The side effects of nonsteroidal anti-inflammatory drugs (NSAIDs) in the cardiovascular system mainly result from its inhibitory effect on cyclooxygenase-2 (COX-2). Since NSAIDs are one of the most commonly used anti-inflammatory drugs in the clinic, it is necessary to identify new anti-inflammatory drugs that are safer than NSAIDs. Nardosinanone N (NAN), a compound isolated from the roots and rhizomes of Nardostachys chinensis, was evaluated for its anti-inflammatory effects using the lipopolysaccharide (LPS)-stimulated RAW264.7 cell line and rat peritoneal macrophage models. First, we found that NAN down regulated the levels of nitric oxide (NO), inducible nitric oxide synthase (iNOS) and prostaglandin E₂ (PGE₂), but not cyclooxygenase-2 (COX-2). Additionally, NAN reduced the M1 macrophage phenotype and increased the M2 macrophage phenotype. Furthermore, mechanistic studies showed that NAN activated the nuclear factor-erythroid 2 -related factor 2 (Nrf2) signaling pathway, which, in turn, increased the expression of antioxidant protein heme oxygenase-1 (HO-1) to achieve its anti-inflammatory effect. Finally, Nrf2 siRNA and the HO-1 inhibitor significantly attenuated the anti-inflammatory effect of NAN. More interestingly, we found that NAN did not affect COX-2 expression and activity but reduced the PGE₂ concentration by selective inhibition of microsomal prostaglandin E synthase-1 (mPGES-1). In conclusion, NAN may be a new anti-inflammatory drug that has fewer side effects than NSAIDs and can be a new potential Nrf2 activator and mPGES-1 inhibitor.