The Effect Of Extracellular Signal-regulated Kinase On Apoptosis Of Nucleus Pulposus Cells By Hypertonic Stress

Objective:To observe the apoptosis of primary culture rabbit nucleus pulposus cells in hypertonic environment and the effect of extracellular signal-regulated kinase/ERK signal pathways in this process.Methods:After treatment with different osmotic pressure gradients and time, Flow cytometer/FCM was used to detect the apoptosis, Western blotting technology was used to analyse the expression of phospho-ERK1/2, and Immunofluorescence was done to observe the distribution of phospho-ERK1/2in the nucleus pulposus cells treated with hypertonic mediums.Results:600mOsm hypertonic mediums powerfully induced nucleus pulposus cells apoptosis compared with control groups (P=0.013), and that appeared time dependence. However, pretreatment groups with PD98059(50μM) further increased apoptosis (P=0.035). Apoptosis was not obvious in400mOsm hypertonic mediums with or without PD98059.600mOsm hypertonic mediums markedly increased the expression of phospho-ERK1/2compared with control groups (P=0.027), and the expression level was highest after3hours. While PD98059(50μM) almost blocked expression of phospho-ERK1/2. The results of immunofluorescence showed that phospho-ERK1/2dispersed throughout cytoplasm and nucleus.Conclusion:In hypertonic mediums (600mOsm) nucleus pulposus cells apoptosis obviously increased and anti-apoptosis of nucleus pulposus cells was related to activation of ERK1/2, moreover nucleus pulposus cells could adapt low-grade hypertonic environment (400mOsm).