title: The roles of MAPKs in rabbit nucleus pulposus cell apoptosis induced by high osmolality.
abstract: BACKGROUND
  Earlier work has suggested that the p38 MAPK, JNK1/2 and ERK1/2 signal pathway existed in nucleus pulposus cells and the cell growth, differentiation and apoptosis were regulated by them. Because osmotic ﬂuctuations are inevitable in the physicochemical environment of intervertebral disc cells, high osmolality could activate p38 MAPK, JNK1/2 and ERK1/2 signal pathway. The effects of high osmolality on the catabolic program and proliferation of nucleus pulposus cells are still not clear.
  
  
  OBJECTIVE
  To explore the possible roles of MAPKs in rabbit nucleus pulposus cell apoptosis induced by high osmolality.
  
  
  METHODS
  Rabbit nucleus pulposus cells were cultured and divided into different group at random. The cells were pretreated with inhibitor for p38 MAPK, JNK1/2 and ERK1/2 signal pathway respectively. In next step, the cells were cultured in different osmolality environment for different time at 37°C in 5% carbon dioxide incubator. After treatments, ratio of apoptosis was measured by flow cytometry, and western blotting was performed to quantify the expression of the activated forms of p38 MAPK, JNK1/2 and ERK1/2. Furthermore, immunofluorescence analysis with confocal microscopy was performed to confirm the hyperosmolality effects on activation of p38 MAPK, JNK1/2 and ERK1/2 signal pathways in nucleus pulposus cells.
  
  
  RESULTS
  Our results show that in 500 and 600 mOsm/kg medium, rabbit nucleus pulposus cell apoptosis increased, and a persistent phosphorylation of p38 MAPK, JNK1/2 and ERK1/2 proteins were observed. In the same condition, the apoptotic cells death remarkably decreased when the p38 MAPK and JNK1/2 signal pathways were blocked by their inhibitors SB203580, SP600125 repectively. On the other side, the apoptotic cells death rate reraised greatly when the ERK1/2 signal pathways were blocked by its inhibitor PD98059.
  
  
  CONCLUSIONS
  High osmolality activated p38MAPK, JNK1/2 and ERK1/2 in rabbit nucleus pulposus cell, and the activated p38 MAPK and JNK1/2 induced cell apoptosis, on the contrary, the activated ERK1/2 made the cell survived.
authors.affiliation: Intensive Care Unit, The Affiliated Hospital of Qingdao University Medical College, Qingdao, China. dechun-w@163.coma.
authors.forename: Z-H
authors.initials: ZH
authors.lastname: Dong
authors.forename: D-C
authors.initials: DC
authors.lastname: Wang
authors.forename: T-T
authors.initials: TT
authors.lastname: Liu
authors.forename: F-H
authors.initials: FH
authors.lastname: Li
authors.forename: R-L
authors.initials: RL
authors.lastname: Liu
authors.forename: J-W
authors.initials: JW
authors.lastname: Wei
authors.forename: C-L
authors.initials: CL
authors.lastname: Zhou
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D002453:Cell Cycle / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation / Q000502:physiology; D005434:Flow Cytometry; D007403:Intervertebral Disc / Q000166:cytology* / Q000201:enzymology*; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009994:Osmolar Concentration; D009995:Osmosis; D010766:Phosphorylation; D011817:Rabbits
chemical_list: D020928:Mitogen-Activated Protein Kinases