title: Retigeric acid B-induced mitophagy by oxidative stress attenuates cell death against prostate cancer cells in vitro.
abstract: OBJECTIVE
  Retigeric acid B (RAB), a pentacyclic triterpenic acid from Lobaria kurokawae Yoshim, has been found to induce apoptosis in prostate cancer cells. The aim of this study was to investigate the roles of mitochondrial damage-caused mitophagy in RAB-induced prostate cancer cell death in vitro.
  
  
  METHODS
  Human prostate cancer PC3 and LNCaP cells were tested. Cell viability was analyzed with MTT assay. Cell apoptosis, ROS level and mitochondrial transmembrane potential (mtΔψ) were measured with flow cytometry. Autophagy- and apoptosis-related proteins were studied using Western blotting. GFP-LC3B puncta, mitochondrial swelling and mitophagy were examined morphologically. Quantitative RT-PCR was used to measure LC3B mRNA level, and siRNA was used to knock down LC3BII.
  
  
  RESULTS
  In both PC3 and LNCaP cells, RAB (15 μmol/L) increased ROS accumulation and decreased mtΔψ in a time-dependent manner. Furthermore, RAB induced mitochondrial swelling and mitophagy, significantly increased LC3B expression and conversion of LC3BI to LC3BII, and the elimination of mitochondria by LC3BII-containing autophagolysosomes. In addition, RAB suppressed the PI3K/Akt/mTOR pathway activation. Pretreatment of PC3 cells with autophagy inhibitor 3-MA (5 mmol/L) or the lysosomal protease inhibitor CQ (10 μmol/L) significantly increased RAB-induced apoptosis. Similar results were obtained in RAB-treated PC3 cells with LC3B knocked down.
  
  
  CONCLUSIONS
  RAB induces mitochondrial damage and mitophagy that attenuates RAB-induced prostate cancer cell death. Thus, suppression of mitophagy might be a potential strategy for improving the chemotherapeutic effects of RAB.
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Medicine, Shandong University, Ji-nan 250012, China.
authors.forename: Yong-qing
authors.initials: YQ
authors.lastname: Liu
authors.forename: Yuan
authors.initials: Y
authors.lastname: Ji
authors.forename: Xian-zhe
authors.initials: XZ
authors.lastname: Li
authors.forename: Ke-li
authors.initials: KL
authors.lastname: Tian
authors.forename: Charles Y F
authors.initials: CY
authors.lastname: Young
authors.forename: Hong-xiang
authors.initials: HX
authors.lastname: Lou
authors.forename: Hui-qing
authors.initials: HQ
authors.lastname: Yuan
mesh_terms: D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D006801:Humans; D008297:Male; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D063306:Mitophagy / Q000187:drug effects* / Q000502:physiology; D018384:Oxidative Stress / Q000187:drug effects* / Q000502:physiology; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000378:metabolism; D014315:Triterpenes / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D014315:Triterpenes; C540615:retigeric acid B
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