LAUSR

Abstract Current data have shown that punicalagin (PUN), an ellagitannin isolated from pomegranate, possesses anti‐inflammatory and anti‐oxidant properties; however, its direct targets have not yet been reported. This is the first report that PTP1B serves as a direct target of PUN, with IC50 value of 1.04 &mgr;M. Results from NPOI further showed that the Kon and Koff of PUN‐PTP1B complex were 3.38e2 M−1 s−1 and 4.13e‐3 s−1, respectively. The active site Arg24 of PTP1B was identified as a key binding site of PUN by computation simulation and point mutation. Moreover, inhibition of PTP1B by PUN promoted an M2c‐like macrophage polarization and enhanced anti‐inflammatory cytokines expression, including IL‐10 and M‐CSF. Based on gene expression profile, we elucidated that PUN treatment significantly up‐regulated 275 genes and down‐regulated 1059 genes. M1‐like macrophage marker genes, such as Tlr4, Irf1/2, Hmgb1, and Stat1 were down‐regulated, while M2 marker genes, including Tmem171, Gpr35, Csf1, Il1rn, Cebpb, Fos, Vegf&agr;, Slc11a1, and Bhlhe40 were up‐regulated in PUN‐treated macrophages. Hmox‐1, a gene encoding HO‐1 protein, was preferentially expressed with 16‐fold change. Inhibition of HO‐1 obviously restored PUN‐induced M2 polarization and IL‐10 secretion. In addition, phosphorylation of both Akt and STAT3 contributed to PUN‐induced HO‐1 expression. This study provided new insights into the mechanisms of PUN‐mediated anti‐inflammatory and anti‐oxidant activities and provided new therapeutic strategies for inflammatory diseases. Graphical abstract Figure. No caption available. HighlightsPunicalagin is a promising PTP1B inhibitor.Arg24 acts as a key binding site in PUN‐PTP1B combination.Punicalagin promotes an M2c like macrophage polarization.Punicalagin‐induced HO‐1 expression is essential to M2 macrophages polarization.Punicalagin has great potential as a preventive strategy in inflammatory diseases.