Expression and regulation of the ERK1/2 and p38 MAPK signaling pathways in periodontal tissue remodeling of orthodontic tooth movement

Abstract

The present study aimed to investigate the expression and regulation of extracellular signal‑regulated kinase (ERK)1/2 and p38 mitogen‑activated protein kinase (MAPK) signaling pathways in periodontal tissue remodeling of orthodontic tooth movement. Sprague Dawley rats with orthodontic tooth movement were generated. After tension stress for 1, 3, 5, 7 and 14 days, the protein and mRNA expression levels of ERK1/2 and p38 in periodontal tissue were determined by western blotting and reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR), respectively. Primary human periodontal ligament cells (hPDLCs) were separated and characterized. Following exposure to centrifugal force for 1, 2, 6, 8 and 12 h, the protein expression levels of ERK1/2 and p38 MAPK, and the mRNA expression levels of ERK1/2, p38 and osteogenesis associated‑genes [including alkaline phosphatase (ALP), osteopontin (OPN), collagen I (Col I), osteocalcin (OCN) and bone sialoprotein (BSP)] were measured. The protein expression levels of ERK1/2 and p38 MAPK in periodontal tissue and hPDLCs treated with stress were similar to those in the control groups. However, compared with the control, the phosphorylation and mRNA expression levels of the genes encoding ERK1/2 and p38 MAPK in orthodontic periodontal tissue and forced hPDLCs were elevated. These increases reached a peak at 5 days for orthodontic periodontal tissue and at 6 h for forced hPDLCs. In forced hPDLCs, the mRNA expression levels of ALP, OPN, Col I, OCN and BSP were notably and continuously upregulated in a time‑dependent manner. In addition, hPDLCs were treated with the ERK1/2 inhibitor, PD098059, and the p38 MAPK inhibitor, SB203580, and the mRNA expression levels of the osteogenesis associated‑genes were then measured using RT‑qPCR. Following treatment with the ERK1/2 inhibitor and p38 MAPK inhibitor, the mRNA expression levels of ALP, OPN, Col I, OCN and BSP were significantly downregulated. In conclusion, ERK1/2 and p38 MAPK signaling pathways may be positively and closely associated with periodontal tissue remodeling of orthodontic tooth movement.

Figure 1.

Protein expression levels of ERK1/2 and p38 in periodontal tissue following tension force. (A) Western blotting of ERK1/2, p38 MAPK, p-ERK1/2 and p-p38 MAPK. (B) Semi-quantitative densitometric analysis of p-ERK1/2 and p-p38 after 1, 3, 5, 7 and 14 days of orthodontic tooth movement. *P<0.05 vs. the control group. ERK1/2, extracellular signal-regulated kinase 1/2; MAPK, mitogen-activated protein kinase; p-, phosphorylated.

Figure 2.

mRNA expression levels of ERK1/2 and p38 at different time points in periodontal tissue after tension force, as determined by reverse transcription-quantitative polymerase chain reaction. *P<0.05 vs. the control group. ERK1/2, extracellular signal-regulated kinase 1/2.

Figure 3.

Protein expression levels of ERK1/2 and p38 in hPDLCs treated with centrifugal force. (A) Western blotting of ERK1/2, p38 MAPK, p-ERK1/2 and p-p38 MAPK. (B) Semi-quantitative densitometric analysis of p-ERK1/2 and p-p38 MAPK in the control cells, and in hPDLCs exposed to centrifugal force for various durations. *P<0.05 vs. the control group. ERK1/2, extracellular signal-regulated kinase 1/2; hPDLCs, human periodontal ligament cells; MAPK, mitogen-activated protein kinase; p-, phosphorylated.

Figure 4.

mRNA expression levels of ERK1/2 and p38 in human periodontal ligament cells following exposure to centrifugal force for different time points, as determined by reverse transcription-quantitative polymerase chain reaction. *P<0.05 vs. the control group. ERK1/2, extracellular signal-regulated kinase 1/2.

Figure 5.

mRNA expression of osteogenesis-associated genes in the control cells or human periodontal ligament cells following exposure to centrifugal force for different time points, as determined by reverse transcription-quantitative polymerase chain reaction. *P<0.05 vs. the control group. ALP, alkaline phosphatase; BSP, bone sialoprotein; Col I, collagen I; OCN, osteocalcin; OPN, osteopontin.

Figure 6.

mRNA expression levels of osteogenesis-associated genes in hPDLCs following treatment with (A) extracellular signal-regulated kinase 1/2 inhibitor (PD098059) or (B) p38 mitogen-activated protein kinase inhibitor (SB203580), as determined by reverse transcription-quantitative polymerase chain reaction. **P<0.01 vs. the control group. ALP, alkaline phosphatase; BSP, bone sialoprotein; Col I, collagen I; hPDLCs, human periodontal ligament cells; OCN, osteocalcin; OPN, osteopontin.