title: Oridonin induces apoptosis and autophagy in murine fibrosarcoma L929 cells partly via NO-ERK-p53 positive-feedback loop signaling pathway.
abstract: OBJECTIVE
  To investigate the role of nitric oxide (NO) in oridonin-induced apoptosis and autophagy in murine fibrosarcoma L929 cells and the underlying molecular mechanisms.
  
  
  METHODS
  Cell viability was measured using MTT assay. Intracellular NO level, SubG(1) cell ratio and autophagy cell ratios were analyzed with flow cytometry after diaminofluorescein-2 diacetate (DAF-2DA), propidium iodide (PI) and monodansylcadaverine (MDC) staining, respectively. Protein expression was examined using Western blot analysis.
  
  
  RESULTS
  Exposure of L929 cells to oridonin (50 μmol/L) for 24 h led to intracellular NO production. Pretreatment with NOS inhibitor 1400w or L-NAME inhibited oridonin-induced apoptosis and autophagy in L929 cells. The pretreatment decreased the apoptosis-related protein Bax translocation and cytochrome c release, increased Bcl-2 level, reversed the autophagy-associated protein Beclin 1 increase and conversion of LC3 I to LC3 II. Furthermore, pretreatment with NO scavenger DTT completely inhibited oridonin-induced apoptosis and autophagy in L929 cells. In addition, oridonin (50 μmol/L) activated ERK and p53 in L929 cells, and the interruption of ERK and p53 activation by PD 98059, pifithrin-α, or ERK siRNA decreased oridonin-induced apoptosis and autophagy. The inhibition of NO production reduced oridonin-induced ERK and p53 activation, and NO production was down-regulated by blocking ERK and p53 activation.
  
  
  CONCLUSIONS
  NO played a pivotal role in oridonin-induced apoptosis and autophagy in L929 cells. Taken together with our previous finding that ERK contributes to p53 activation, it appears that NO, ERK, and p53 form a positive feedback loop. Consequently, we suggest that oridonin-induced apoptosis and autophagy are modulated by the NO-ERK-p53 molecular signaling mechanism in L929 cells.
authors: China-Japan Research Institute of Medical and Pharmaceutical Sciences, Shenyang Pharmaceutical University, Shenyang 110016, China.
authors: Yuan-chao
authors: YC
authors: Ye
authors: Hong-ju
authors: HJ
authors: Wang
authors: Lei
authors: L
authors: Xu
authors: Wei-wei
authors: WW
authors: Liu
authors: Bin-bin
authors: BB
authors: Liu
authors: Shin-Ichi
authors: S
authors: Tashiro
authors: Satoshi
authors: S
authors: Onodera
authors: Takashi
authors: T
authors: Ikejima
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001343:Autophagy / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D045786:Diterpenes, Kaurane / Q000494:pharmacology* / Q000627:therapeutic use; D025461:Feedback, Physiological / Q000187:drug effects / Q000502:physiology*; D005354:Fibrosarcoma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D016158:Genes, p53 / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D009569:Nitric Oxide / Q000502:physiology*
chemical_list: D045786:Diterpenes, Kaurane; C011959:oridonin; D009569:Nitric Oxide