Development and mechanism investigation of a new piperlongumine derivative as a potent anti-inflammatory agent.

Inflammation, especially chronic inflammation, is directly involvement in the pathogenesis of many diseases including cancer. An effective approach for managing inflammation is to employ chemicals to block activation of nuclear factor-κB (NF-κB), a key regulator for inflammatory processes. Piperlongumine (piplartine, PL), an electrophilic molecule isolated from Piper longum L., possesses excellent anti-cancer and anti-inflammatory properties. In this study, a new PL analogue (PL-0N) was designed by replacing nitrogen atom of lactam in PL with carbon atom to increase its electrophilicity and thus anti-inflammatory activity. It was found that PL-0N is more potent than the parent compound in suppressing lipopolysaccharide (LPS)-induced secretion of nitric oxide and prostaglandin E2 as well as expression of inducible nitric oxide synthase and cyclooxygenase-2 in RAW264.7 macrophages. Mechanistic investigation implies that PL-0N exerts anti-inflammatory activity through inhibition of LPS-induced NF-κB transduction pathway, down-regulation of LPS-induced MAPKs activation and impairment of proteasomal activity, but also enhancement of LPS-induced autophagy; the inhibition of NF-κB by PL-0N is achieved at various stages by: (i) preventing phosphorylation of IKKα/β, (ii) stabilizing the suppressor protein IκBα, (iii) interfering with the nuclear translocation of NF-κB, and (iv) inhibiting the DNA-binding of NF-κB. These data indicate that nitrogen-atom-lacking pattern is a successful strategy to improve anti-inflammatory property of PL, and that the novel molecule, PL-0N may be served as a promising lead for developing natural product-directed anti-inflammatory agents.