title: The cytoprotective effects of 7,8-dihydroxyflavone against oxidative stress are mediated by the upregulation of Nrf2-dependent HO-1 expression through the activation of the PI3K/Akt and ERK pathways in C2C12 myoblasts.
abstract: Recent studies have demonstrated that 7,8-dihydroxyflavone (7,8-DHF), a newly identified tyrosine kinase receptor B agonist, is a potent antioxidant agent. The present study was designed to confirm the cytoprotective effects of 7,8-DHF against oxidative stress-induced cellular damage and to further elucidate the underlying mechanisms in C2C12 myoblasts. We found that 7,8-DHF attenuated hydrogen peroxide (H2O2)-induced growth inhibition and exhibited scavenging activity against intracellular reactive oxygen species (ROS) that were induced by H2O2. We also observed that 7,8-DHF significantly attenuated H2O2-induced comet tail formation, and decreased the phosphorylation levels of the histone, H2AX, as well as the number of Annexin V-positive cells, suggesting that 7,8-DHF prevents H2O2-induced DNA damage and cell apoptosis. Furthermore, 7,8-DHF increased the levels of heme oxygenase-1 (HO-1), which is a potent antioxidant enzyme associated with the induction and phosphorylation of nuclear factor-erythroid 2-related factor 2 (Nrf2), as well as the translocation of Nrf2 from the cytosol to the nucleus. However, the protective effects of 7,8-DHF against H2O2 -induced ROS generation and growth inhibition were significantly diminished by zinc protoporphyrin IX, an HO-1 competitive inhibitor. Moreover, the potential of 7,8-DHF to mediate HO-1 induction and protect the cells against H2O2 -mediated growth inhibition was abrogated by transient transfection with Nrf2-specific small interfering RNA (siRNA). In addition, 7,8-DHF induced the activation of Akt, a downstream target of phosphatidylinositol 3-kinase (PI3K), and also that of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK), while specific inhibitors of PI3K and ERK, but not a p38 MAPK inhibitor, abolished the 7,8-DHF induced HO-1 upregulation and Nrf2 induction and phosphorylation. Collectively, these results demonstrate that 7,8-DHF augments the cellular antioxidant defense capacity through activation of the Nrf2/HO-1 pathway, which also involves the activation of the PI3K/Akt and ERK pathways, thereby protecting C2C12 myoblasts from H2O2-induced oxidative cytotoxicity.
authors.affiliation: Blue-Bio Industry RIC and Anti-Aging Research Center, Dongeui University, Busan 614-714, Republic of Korea.
authors.forename: Ji Sook
authors.initials: JS
authors.lastname: Kang
authors.affiliation: Department of Microbiology, College of Medicine, Inje University, Busan 608-756, Republic of Korea.
authors.forename: Il-Whan
authors.initials: IW
authors.lastname: Choi
authors.affiliation: Blue-Bio Industry RIC and Anti-Aging Research Center, Dongeui University, Busan 614-714, Republic of Korea.
authors.forename: Min Ho
authors.initials: MH
authors.lastname: Han
authors.affiliation: Laboratory of Immunobiology, Department of Marine Life Sciences, Jeju National University, Jeju 690-756, Republic of Korea.
authors.forename: Gi-Young
authors.initials: GY
authors.lastname: Kim
authors.affiliation: Department of Biochemistry, Dongeui University College of Korean Medicine, Busan 614-052, Republic of Korea.
authors.forename: Su Hyun
authors.initials: SH
authors.lastname: Hong
authors.affiliation: Department of Molecular Biology, College of Natural Sciences and Human Ecology, Dongeui University, Busan 614-714, Republic of Korea.
authors.forename: Cheol
authors.initials: C
authors.lastname: Park
authors.affiliation: Blue-Bio Industry RIC and Anti-Aging Research Center, Dongeui University, Busan 614-714, Republic of Korea.
authors.forename: Hye Jin
authors.initials: HJ
authors.lastname: Hwang
authors.affiliation: Department of Biochemistry, Busan National University College of Medicine, Yangsan, Gyeongsangnam-do 626-870, Republic of Korea.
authors.forename: Cheol Min
authors.initials: CM
authors.lastname: Kim
authors.affiliation: Blue-Bio Industry RIC and Anti-Aging Research Center, Dongeui University, Busan 614-714, Republic of Korea.
authors.forename: Byung Woo
authors.initials: BW
authors.lastname: Kim
authors.affiliation: Blue-Bio Industry RIC and Anti-Aging Research Center, Dongeui University, Busan 614-714, Republic of Korea.
authors.forename: Yung Hyun
authors.initials: YH
authors.lastname: Choi
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection / Q000187:drug effects*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D047309:Flavones / Q000494:pharmacology*; D051547:Heme Oxygenase-1 / Q000235:genetics; D051379:Mice; D032446:Myoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism; D020011:Protective Agents / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: C485383:6,7-dihydroxyflavone; D000975:Antioxidants; D047309:Flavones; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D020011:Protective Agents; D017382:Reactive Oxygen Species; D051547:Heme Oxygenase-1; D058539:Phosphatidylinositol 3-Kinase; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases