Curcumin (diferuloylmethane), which is obtained from turmeric, the rhizome of Curcuma longa (L.), inhibits many human cancer cells. However, the molecular mechanisms responsible for curcumin-induced endoplasmic reticulum stress in human hepatic cellular carcinoma J5 cells, are not yet clearly understood. J5 cells were treated with various concentrations of curcumin for different durations. The cell viability was detected by MTT assay. The protein expressions of caspase-12, ATF6, GADD153, Calnexin, Calreticulin, PDI and Ero1-Lα, which are associated with endoplasmic reticulum stress and the unfolding protein response pathway, were examined by Western blot analysis. The cell cycle was analyzed by flow cytometry. The protein expressions of TCTP, Mcl-1, Bcl-2 and Bax, which are related to mitochondrial dysfunction, were detected by Western blot analysis. We also detected the ATF6 protein location by immunocytochemistry. The results showed that curcumin inhibits the proliferation of J5 cells in a time- and dose-dependent manner. Curcumin induced the unfolding protein response by down-regulating the protein expressions of Calnexin, PDI and Ero1-Lα and up-regulating the Calreticulin expression. Curcumin induces the GADD153 expression by cleaving caspase-12 and ATF6, and then by translocating ATF6 to the nucleus. Curcumin also down-regulates the protein expressions of TCTP, Mcl-1 and Bcl-2, in order to induce mitochondrial dysfunction. Curcumin induced cell cycle arrest at the G2/M phase by decreasing the Cdc2 expression. In conclusion, the present study showed that curcumin inhibits the proliferation of J5 cells by inducing endoplasmic reticulum stress and mito-chondrial dysfunction.

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