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.
Keywords: Autophagy; Inflammation; MAPK; Mechanism; NF-κB; Piperlongumine; Piperlongumine (PubChem CID: 637858).
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