Melatonin Protects Intervertebral Disc from Degeneration by Improving Cell Survival and Function via Activation of the ERK1/2 Signaling Pathway

Figure 3

Melatonin, via the ERK pathway, regulates NPCs. (a–c) Melatonin significantly increased ERK1/2 activity above the concentration of 1 μm. A slight inhibition of phosphorylated NF-κB protein expression was detected at 1 μM. A decrease in phosphorylation level of NF-κB was also found at high concentrations of melatonin. No obvious change was observed in JNK activity after melatonin treatment. (d) Melatonin increased the proportion of cells in the S-phase and decreased that of cells in the G0/G1 phase. With U0126, the effects on cell cycle distribution were reduced. (e) Similarly, the expression of the cell cycle-related proteins was reduced in NPCs treated with melatonin and U0126. (f) Quantified analysis of cell cycle-related protein Western blot result. (g, h) The inhibition of apoptosis by melatonin was also reversed upon addition of U0126. (i) Quantified analysis of apoptosis-related protein Western blot result. (j) Western blot analysis also showed that, after addition of U0126, U0126 had a significant weakened role on melatonin in the downregulation of collagen X expression and there is no more positive effect from melatonin on aggrecan and collagen II expression in the NPCs. (k) Quantified analysis of cell matrix protein Western blot result ().

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