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AIM: To examine the potency of 1,2,3,4,6-penta-O-galloyl-β-D-glucose (PGG) as a hepatic heme oxygenase-1 (HO-1) inducer and its regulation in HepG2 cells.METHODS: Expression of HO-1 and NF-E2-related factor 2 (Nrf2) and activation of mitogen-activated protein (MAP) kinases were analyzed by West blot, immunofluorescence assay, and flow cytometry. Transfections of HO-1 gene, small interfering RNAs for HO-1 and Nrf2,and dominant-negative gene for MAP/extracellular signalregulated kinase (ERK) were carried out to dissect the signaling pathways leading to HO-1 expression in HepG 2 cells.RESULTS: PGG up-regulated HO-1 expression and this expression conferred cytoprotection against oxidative injury induced by t-butyl hydroperoxide. Moreover, PGG induced Nrf2 nuclear translocation, which was found to be an upstream step of PGG-induced HO-1 expression, and ERK activation, of which pathway was involved in PGG-induced Nrf2 nuclear translocation, HO-1 expression and cytoprotection.CONCLUSION: PGG up-regulates HO-1 expression by stimulating Nrf2 nuclear translocation in an ERK-dependent manner, and HO-1 expression by PGG may serve as one of the important mechanisms for its hepatoprotective effects.