Objective: To investigate the effect of epidermal growth factor (EGF) on the expression of Matrix metalloproteinase-9 (MMP-9) and the signalling pathways involved in the trophoblast cell line JEG-3.
Methods: The JEG-3 trophoblast cell line was used in this study. (1) JEG-3 cells were cultured with various concentrations of EGF (0, 1, 10, 20 ng/ml) for 24 hours and the expression of MMP-9 was tested by western blotting and reverse transcription PCR (RT-PCR). (2) Western blotting and RT-PCR were also used to investigate the expression of MMP-9 expression after incubation for 0, 4, 12 and 24 hours with EGF treatment (10 ng/ml) in JEG-3 cells. (3) According to the different added ingredients, JEG-3 cells were divided into some groups: control group (without EGF), EGF group (exposure to 10 ng/ml EGF), EGF+ inhibitors group (exposure to 10 ng/ml EGF+ 20 ng/ml SB203580 or exposure to 10 ng/ml EGF+ 10 ng/ml U0126), inhibitors group (exposure to 20 ng/ml SB203580 or exposure to 10 ng/ml U0126). Western blotting were used to investigate the expression levels of MMP-9, nuclear factor kappa B (NF-κB), p38MAPK, phospho-p38MAPK (p-p38MAPK), extracellular-signal regulated kinase (ERK) and phospho-ERK (p-ERK) protein in JEG-3 cells after incubation for 24 hours.
Results: (1) The profiles of MMP-9 mRNA were increased by various concentrations of EGF (0, 1, 10, 20 ng/ml) in JEG-3 cells after 24 h-culture. The expression of MMP-9 mRNA in JEG-3 cells exposure at 1 ng/ml of EGF (0.567±0.056), 10 ng/ml of EGF (1.392±0.133), 20 ng/ml of EGF (1.971±0.067) were significantly higher respectively (P<0.05), compared with 0 ng/ml of EGF treatment (0.166±0.015). Similarly, MMP-9 mRNAs were also increased with the increasing incubation time. Compared to EGF (10 ng/ml) stimulation for 0 h (0.253±0.044), the MMP-9 mRNA profiles were 0.470±0.026, 1.061±0.115, 1.453±0.180 for 4, 12 and 24 hours, respectively (P<0.05). (2) In accordance to the mRNA profiles, the expression of MMP-9 protein was also increased by different concentrations of EGF (0, 1, 10, 20 ng/ml) in JEG-3 cells after 24 h-culture. The abundance of MMP-9 protein in the three groups was 0.043±0.012, 0.085±0.008, 0.142±0.015, with a significantly higher expression, compared with 0 ng/ml of EGF treatment (0.004±0.001, P<0.05) respectively. Similarly, MMP-9 proteins were also increased with the increasing incubation time. Compared to EGF (10 ng/ml) stimulation for 0 h (0.030±0.009), the profiles of MMP-9 protein were 0.137±0.010, 0.240±0.010, 1.240±0.061 for 4, 12 and 24 hours, respectively (P<0.05). (3) Both p38MAPK and ERK signalling pathways were activated by EGF in JEG-3 cells. The expression of p-p38MAPK was significantly higher (without or with 10 ng/ml EGF, 234.1±4.1 vs. 260.9±2.5, P<0.05), however, the p38MAPK inhibitor SB203580 markedly suppressed the increase in p-p38MAPK content induced by EGF (227.9±2.4 vs. 260.9±2.5, P<0.05). Similarly, the expression of p-ERK was significantly higher with EGF treatment (812.2±3.5) vs. without EGF group (453.4±5.8) (P<0.05), while the ERK inhibitor U0126 significantly inhibited the increased p-ERK content in response to EGF treatment (71.0±1.2 vs. 812.2±3.5, P<0.05). (4) The p38MAPK inhibitor SB203580 significantly reduced the expression of EGF-induced MMP-9 (0.645±0.270 vs. 1.476±0.452, P<0.05) and NF-κB (0.530±0.026 vs. 0.959±0.017, P<0.05). (5) The ERK inhibitor U0126 also significantly reduced the expression of EGF-induced MMP-9 (0.623±0.030 vs. 2.112±0.056, P<0.05) and NF-κB (0.325±0.082 vs. 0.939±0.153, P<0.05).
Conclusion: EGF induced the expression of MMP-9 in a time and dose-dependant manner in JEG-3 cells. EGF enhanced MMP-9 expression through the activation of p38MAPK and ERK signalling pathways in JEG-3 cells.