title: Involvement of the mitochondrion-dependent and the endoplasmic reticulum stress-signaling pathways in isoliquiritigenin-induced apoptosis of HeLa cell.
abstract: OBJECTIVE
  Isoliquiritigenin (ISL), a licorice chalconoid, is considered to be a bioactive agent with chemopreventive potential. This study investigates the mechanisms involved in ISL-induced apoptosis in human cervical carcinoma HeLa cells.
  
  
  METHODS
  Cell viability was evaluated using a 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) assay. Apoptosis was determined by flow cytometry using an Annexin V-FITC Apoptosis Detection Kit. The intracellular ROS levels were assessed using a 2, 7-dichlorofluorescein probe assay. The mitochondrial membrane potential was measured with the dual-emission potential-sensitive probe 5, 5', 6, 6'-tetra-chloro-1, 1', 3, 3'-tetraethyl-imidacarbocyanine iodide (JC-1). The degradation of poly-ADP-ribose polymerase (PARP) protein, the phosphorylation of PKR-like ER kinase (PERK), the phosphorylation of the α-subunit of eukaryotic initiation factor 2 (eIF2α), the expression of the 78 kD glucose-regulated protein (GRP 78), and the activation of caspase-12 were analyzed via western blot analysis.
  
  
  RESULTS
  ISL significantly inhibited the proliferation, the increase in ROS levels and apoptotic rates of HeLa cells in a concentration-dependent manner. Moreover, ISL induced mitochondrial dysfunction, caspase activation, and PARP cleavage, which displayed features of mitochondria dependent on apoptotic signals. Besides, exposure of HeLa cells to ISL triggered endoplasmic reticulum (ER) stress, as indicated by the increase in p-eIF2α and GRP78 expression, ER stress-dependent apoptosis is caused by the activation of ER-specific caspase-12.
  
  
  CONCLUSIONS
  The findings from our study suggest that ISL-induced oxidative stress causes HeLa cell apoptosis via the mitochondrion-dependent and the ER stress-triggered signaling pathways.
authors.affiliation: Lanzhou University Second Hospital, Lanzhou University, Lanzhou 730000, Gansu, China.
authors.forename: Xuan
authors.initials: X
authors.lastname: Yuan
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.forename: Lu
authors.initials: L
authors.lastname: Gan
authors.forename: Zhen Hua
authors.initials: ZH
authors.lastname: Wang
authors.forename: Ba Cui
authors.initials: BC
authors.lastname: Yu
authors.forename: Liang Liang
authors.initials: LL
authors.lastname: Liu
authors.forename: Qiu Sheng
authors.initials: QS
authors.lastname: Zheng
authors.forename: Zhi Ping
authors.initials: ZP
authors.lastname: Wang
mesh_terms: D000449:Aldehyde Reductase / Q000037:antagonists & inhibitors*; D017209:Apoptosis / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D047188:Chalcones / Q000494:pharmacology* / Q000627:therapeutic use; D018890:Chemoprevention; D004354:Drug Screening Assays, Antitumor; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D006367:HeLa Cells; D006801:Humans; D008928:Mitochondria / Q000187:drug effects*; D009369:Neoplasms / Q000517:prevention & control*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D047188:Chalcones; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D017382:Reactive Oxygen Species; C040920:isoliquiritigenin; D000449:Aldehyde Reductase
keywords: Apoptosis; ER stress; HeLa cells; ISL; Mitochondria; ROS