Effects of simulated weightlessness on the kinase activity of MEK1 induced by bone morphogenetic protein-2 in rat osteosarcoma cells

Bing WANG; Xinsheng CAO; Yanhong WU; Shu ZHANG

ABSTRACT

BACKGROUND:

The mRNA expression of α1 chain of type I collagen (COL- Iα1)in rat osteosarcoma (ROS17/2.8) induced by bone morphogenetic protein-2(BMP-2)was reduced under simulated weightlessness. The protein kinase MEK1 in the signal pathway of mitogen-activated protein kinase (MAPK) plays an important role in the expression of COL- I αl mRNA regulated by BMP-2. But there was no report on the kinase activity of MEK1 under simulated weightlessness.

OBJECTIVE:

To investigate the effects of simulated weightlessness on the activity of MEK1 induced by BMP-2 in ROS17/2.8 cells.

DESIGN:

A non-randomly control study was conducted.

SETTING:

Department of Aerospace Biodynamics, Fourth Military Medical University of Chinese PLAMATERIALS Rat osteosarcoma osteoblast-like cell

METHODS:

This experiment was conducted at the Laboratory of Aerospace cells and Molecular Biology Laboratory , Institute of Space Medico-Engineering between August 2002 and January 2003. ROS17/2.8 cells were cultured in 1 G control and rotating clinostat simulated weightlessness for 24 hours, 48 hours and 72 hours. The cells were divided into 7 groups as follows Group 1 was blank control group in which ROS17/2.8 cells were cultured in 1 G condition without BMP2; Group 2, cells were cultured in 1 G for 24 hours;Group 3,in weightlessness for 24 hours; Group 4, in 1 G for 48 hours; Group 5, in weightlessness for 48 hours;Group 6,in 1 G for 72 hours;Group 7,in weightlessness for 72 hours. Cells in Group 2 to Group 7 were all cultured with BMP-2. BMP-2 (500 mg/L) was added into the medium 1 hou before the culture ended. Then the total protein of cells was extracted and the kinase activity of MEK1 was detected by means of Western Blotting.MAIN OUTCOME

MEASURES:

The content of total ERK1/2 and phosphated-ERK1/2 (p-ERK1/2) protein in the cells

RESULTS:

①Total ERK1/2 expression induced by BMP-2 in ROS17/2.8 cells under simulated weightlessness The total ERK1/2 expression induced by BMP-2 in cells in all the groups showed no significant differences ② Phosphated-ERK1/2 expression induced by BMP-2 in ROS17/2.8 .cells under simulated weightlessness There was little protein of p-ERK1/2 in ROS17/2.8 cells in Group 1 cultured without BMP-2 in 1 G for 24 hours. The content of p-ERK1/2 in ROS17/2.8 cells in Group 2 cultured with BMP-2 in 1 G for 24 hours was much more than that in Group 1 (P ＜ 0.01). The level of p-ERK1/2 was much lower in simulated weightlessness groups than that in 1 G control groups at the same time point. In other words, the content of p-ERK1/2 in Groups 3, 5 and 7 was respectively lower than that in Groups 2, 4 and 6 (P ＜ 0.01).The expression of p-ERK1/2 showed-a tendency of gradually decreasing in Groups 3, 5 and 7 with the prolongation of time of simulated weightlessness(P ＜ 0.01 ).

CONCLUSION:

The kinase activity of MEK1 in MAPK signal pathway induced by BMP-2 is reduced under simulated weightlessness.