Potential role of andrographolide in the proliferation of osteoblasts mediated by the ERK signaling pathway.

ABSTRACT

The aim of the present study was to explore the effects of andrographolide (AG) and the ERK signaling pathway on the proliferation of osteoblasts (OBs) in vitro. The calvarial OBs from Sprague Dawley (SD) rats were collected and treated at different concentrations of AG and U0126. The concentrations of AG were measured by colorimetry. Based on different treatment methods, the cells were separated into four groups control group, U0126 group, AG group, and AG+U0126 group. The cells were cultured for 24h, 48h and 72h. An inverted phase contrast microscope was used to observe the morphologies of treated OBs. The MTT assay was performed to plot OB proliferation curves, and to measure the changes in alkaline phosphatase and hydroxyproline contents after U0126 treatments. The expressions of proliferating cell nuclear antigen (PCNA), Ki67, core binding factor alpha-1 (Cbfa1), type I collagen (Col I), osterix (OSX), p38, extracellular signal regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) were measured by fluorescent quantitative polymerase chain reaction (PCR) and Western blotting. In different cell groups, the in vitro proliferation rates of OBs reached the highest at an AG concentration of 20µmol/L, and the amounts of alkaline phosphatase, hydroxyproline, PCNA, Ki67, Cbfa1, Col I, OSX, and ERK were significantly higher than at other concentrations (all P<0.05). U0126 intervention significantly decreased the expressions of these factors (all P<0.05). At the meantime, p38 and JNK were not affected by AG and were only inhibited by U0126. In conclusion, ERK played an important role in mediating the functions of AG in the proliferation of OBs, indicating that the ERK signaling pathway may be the main pathway through which AG exerts its effects.