title: Grp94 acts as a mediator of curcumin-induced antioxidant defence in myogenic cells.
abstract: Curcumin is a non-toxic polyphenol with pleiotropic activities and limited bioavailability. We investigated whether a brief exposure to low doses of curcumin would induce in the myogenic C2C12 cell line an endoplasmic reticulum (ER) stress response and protect against oxidative stress. A 3-hr curcumin administration (5-10 microM) increased protein levels of the ER chaperone Grp94, without affecting those of Grp78, calreticulin and haeme-oxygenase-1 (HO-1). Exposure of cells to hydrogen peroxide 24 hrs after the curcumin treatment decreased caspase-12 activation, total protein oxidation and translocation of NF-kappaB to the nucleus, compared with untreated cells. Grp94 overexpression, achieved by means of either stable or transient trasfection, induced comparable cytoprotective effects to hydrogen peroxide. The delayed cytoprotection induced by curcumin acted through Grp94, because the curcumin-induced increase in Grp94 expression was hampered by either stable or transient transfection with antisense cDNA; in these latter cells, the extent of total protein oxidation, as well as the translocation of NF-kappaB to the nucleus, and the percentage of apoptotic cells were comparable to those observed in both curcumin-untreated wild-type and empty vector transfected cells. Defining the mechanism(s) by which Grp94 exerts its antioxidant defence, the determination of cytosolic calcium levels in C2C12 cells by fura-2 showed a significantly reduced amount of releasable calcium from intracellular stores, both in conditions of Grp94 overexpression and after curcumin pre-treatment. Therefore, a brief exposure to curcumin induces a delayed cytoprotection against oxidative stress in myogenic cells by increasing Grp94 protein level, which acts as a regulator of calcium homeostasis.
authors.affiliation: Department of Biomedical Sciences, University of Padova, Padova, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Pizzo
authors.forename: Cristina
authors.initials: C
authors.lastname: Scapin
authors.forename: Maurizio
authors.initials: M
authors.lastname: Vitadello
authors.forename: Cristina
authors.initials: C
authors.lastname: Florean
authors.forename: Luisa
authors.initials: L
authors.lastname: Gorza
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D053454:Caspase 12 / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003474:Curcumin / Q000494:pharmacology*; D019610:Cytoprotection / Q000187:drug effects; D018076:DNA, Complementary / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D032446:Myoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D013312:Stress, Physiological / Q000187:drug effects; D014162:Transfection
chemical_list: D000975:Antioxidants; D018076:DNA, Complementary; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D008565:Membrane Proteins; D016328:NF-kappa B; C018551:glucose-regulated proteins; D006861:Hydrogen Peroxide; D053454:Caspase 12; D003474:Curcumin; D002118:Calcium