OBJECTIVETo investigate the role of extracellular signal-regulated kinase 1/2 on the inhibition of N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) on the proliferation and collagen synthesis of cultured rat pulmonary fibroblasts induced by platelet-derived growth factor (PDGF).

METHODSPulmonary fibroblasts were prepared from lungs of neonatal Wistar rats as described previously. Cells were divided into 4 groups: (1) control group (0.4% FBS group); (2) PDGF (10 ng/ml) stimulated group; (3) PD98059+PDGF group (25 micromol/L PD98059+10 ng/ml PDGF); (4) AcSDKP+PDGF group (10(-8) mol/L AcSDKP+10 ng/ml PDGF). All experiments were performed in the fourth passages. Metabolic activity of fibroblasts was observed by MTT, and expressions of type I and type III collagen were measured by immunocytochemistry and western blot. Expressions of phospho-ERK1/2 and ERK1/2 were detected by western blot.

RESULTSCompared with control group, exposure of pulmonary fibroblasts to 10 ng/ml PDGF increased cell metabolic activity, expression of type I and type III collagen and phosphorylation of ERK1/2. 25 micromol/L PD98059 and AcSDKP both could inhibit the metabolic activity of pulmonary fibroblasts, type I and type III collagen synthesis and phosphorylation of ERK1/ 2 induced by PDGF, with significant differences (P < 0.05). AcSDKP+PDGF group compared with PDGF stimulated group, metabolic activity of pulmonary fibroblasts decreased to 77.4%. Immunocytochemistry result showed that in AcSDKP+PDGF group, expressions of type I and type III collagen decreased to 69.3% and 67.2% compared with those of PDGF stimulated group. Western blot result showed that in AcSDKP+PDGF group, expressions of type I and type III collagen decreased to 92.4% and 78.0%, phospho-ERK1/2 decreased to 83.5% compared with those of PDGF stimulated group, with significant differences (P < 0.05).

CONCLUSIONERK1/2 plays an important role in the inhibition of AcSDKP on the proliferation and collagen synthesis of cultured rat pulmonary fibroblasts induced by PDGF.