Mechanistic Study on Anti-inflammatory Agents and Autophagic Activators Inspired by Natural Products and Designed by the Electrophilicity-increasing Strategy
Author:Sun Lan Di
Both inflammation and autophagy play important roles in the occurrence and development of cancer.Chronic inflammation is closely involved in the pathogenesis of cancer.Autophagy is a lysosomal pathway to degrade cellular components for meeting metabolic demands of cells and maintaining cellular homeostasis;compared with nomal cells,cancer cells depend redundantly on autophagy due to cellular stress and/or increased metabolic demands.Therfore,inhibition of inflammation and manipulation(inhibition or activation)of autophagy can be considered as the strategies for developing anticancer reagents.Natural products,traditionally referred to as secondary metabolites produced by living organisms,represent a pre-assembled pool of biologically active molecules programmed by evolutionary processes and are often used as starting points for drug discovery.Therefore,to target pathways of inflammation and autophagy,the structurally diverse molecules inspired by piperlongumine(PL),curcumin,-shogaol and resveratrol were selected and designed based on the electrophilicity-increasing strategy,and their structural determinants and biological mechanisms were studied in this thesis.(1)Employing LPS-stimulated RAW264.7 cells as a model of inflammation,we identified PL-ON(a nitrogen-atom-lacking analog of PL)and BC2(an anlog of curcumin)as the novel and promising anti-inflammatory agents displaying higher activity than their parent molecules.Mechanistic investigation implies that they exert anti-inflammatory activity through inhibition of IKK/NF-B transduction pathway,down-regulation of MAPKs activation and impairement of proteosomal activity,thereby stabilizing the suppressor protein IKBa,interfering with the nuclear translocation of NF-κB and inhibiting the DNA-binding of NF-κB.Intersetingly,activating autophagy in an mTOR-dependent fashion contributes to anti-inflammatory activity of PL-ON.This above work highlights the feasibility in designing PL-and curcumin-inspired anti-inflammatory agents by the electrophilicity-increasing strategy and gives us useful information on how to design them.(2)To develop autophagic activators,we designed-dehydroshogaol directed by-shogaol by introducing an additional C1-C2 double bond based on the electrophilicity-increasing strategy,and a few of resveratrol analogs with a catechol moiety,such as 3,4-DHS(pro-electrophile),in view of the facility in its oxidative conversion to the corresponding o-quinone(electrophile)in cells.It was found that these analogs compared with their parent molecule manifest the increased activity in activating autophagy in human osteosarcoma U20S cells.Mechanistic investigation implies that-dehydroshogaol and 3,4-DHS could induce autophgic cell death by blocking autophagic flux and initiating autophagosome formation,respectively,and the former is directly related to the ROS(reactive oxygen species)-generation,whereas the latter is independent of the ROS-generation.